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Sample records for silicate earth bse

  1. Calcium Isotopic Composition of Bulk Silicate Earth

    Science.gov (United States)

    Kang, J.; Ionov, D. A.; Liu, F.; Zhang, C.; Zhang, Z.; Huang, F.

    2016-12-01

    Ca isotopes are used to study the accretion history of the Earth and terrestrial planets, but, Ca isotopic composition of the Bulk Silicate Earth (BSE) remains poorly constrained [1]. To better understand the Ca isotopic composition of BSE, we analyzed 22 well studied peridotite xenoliths from Tariat (Mongolia), Vitim (southern Siberia) and Udachnaya (Siberian Craton). These samples include both fertile and highly depleted garnet and spinel peridotites that show no or only minor post-melting metasomatism or alteration. Ca isotope measurements were done on a Triton-TIMS using double spike method at the Guangzhou Institute of Geochemistry, CAS. The data are reported as δ44/40Ca (relative to NIST SRM 915a). Results for geostandards are consistent with those from other laboratories. 2 standard deviations of SRM 915a analyses are 0.13‰ (n=48). δ44/40Ca of both and fertile and refractory peridotites range from 0.79 to 1.07‰ producing an average of 0.93±0.12‰ (2SD). This value defines the Ca isotopic composition of the BSE, which is consistent with the average δ44/40Ca of oceanic basalts ( 0.90‰)[2,3]. [1] Huang et al (2010) EPSL 292; [2] Valdes et al (2014) EPSL 394; [3]DePaolo (2004) RMG 55.

  2. New silicates of rare earths and calcium

    International Nuclear Information System (INIS)

    Andreev, I.F.; Shevyakov, A.M.; Smorodina, T.P.; Semenov, N.E.

    1975-01-01

    The complex silicates of the third subgroup elements of lanthanides and calcium were synthesized: Ca 3 Er 2 Si 6 O 18 , Ca 3 Lu 2 Si 6 O 18 and Ca 3 Yb 2 Si 6 O 18 . To specify these compounds their physical and chemical properties were studied by means of roentgenographic, IR spectroscopic and crystaloptical methods. The values of Ng, Np,Δn,m,p were determined, the elementary cell parameters: a,b,c,α,β,γ were computed. Existence of such compounds and their analogy in ternary systems MeO-Ln 2 O 3 -SiO 2 were forcasted

  3. Mineralogy and trace element chemistry of the Siliceous Earth of ...

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    We report the presence of a 3–5 cm thick loose fragmental layer in the Siliceous Earth at Matti ka. Gol in the Barmer basin of Rajasthan. Petrographic, chemical and mineralogical study reveals the presence of abundant volcanic debris such as glass shards, agglutinates, hollow spheroids, kinked biotites, feldspars showing ...

  4. Effects of Mixed Alkaline Earth Oxides in Potash Silicate Glass ...

    African Journals Online (AJOL)

    The aim of this work is to investigate the effects of mixed alkaline earth oxide in potash silicate glasses with regards to their physical properties. More recently; there has been an increase in the demand for light weight glasses which retains their physical and chemical properties for both domestic and industrial applications.

  5. Deep-Earth Equilibration between Molten Iron and Solid Silicates

    Science.gov (United States)

    Brennan, M.; Zurkowski, C. C.; Chidester, B.; Campbell, A.

    2017-12-01

    Elemental partitioning between iron-rich metals and silicate minerals influences the properties of Earth's deep interior, and is ultimately responsible for the nature of the core-mantle boundary. These interactions between molten iron and solid silicates were influential during planetary accretion, and persist today between the mantle and liquid outer core. Here we report the results of diamond anvil cell experiments at lower mantle conditions (40 GPa, >2500 K) aimed at examining systems containing a mixture of metals (iron or Fe-16Si alloy) and silicates (peridotite). The experiments were conducted at pressure-temperature conditions above the metallic liquidus but below the silicate solidus, and the recovered samples were analyzed by FIB/SEM with EDS to record the compositions of the coexisting phases. Each sample formed a three-phase equilibrium between bridgmanite, Fe-rich metallic melt, and an oxide. In one experiment, using pure Fe, the quenched metal contained 6 weight percent O, and the coexisting oxide was ferropericlase. The second experiment, using Fe-Si alloy, was highly reducing; its metal contained 10 wt% Si, and the coexisting mineral was stishovite. The distinct mineralogies of the two experiments derived from their different starting metals. These results imply that metallic composition is an important factor in determining the products of mixed phase iron-silicate reactions. The properties of deep-Earth interfaces such as the core-mantle boundary could be strongly affected by their metallic components.

  6. Polymer Derived Rare Earth Silicate Nanocomposite Protective Coatings for Nuclear Thermal Propulsion Systems, Phase II

    Data.gov (United States)

    National Aeronautics and Space Administration — Leveraging a rapidly evolving state-of-the-art technical base empowered by Phase I NASA SBIR funding, NanoSonic's polymer derived rare earth silicate EBCs will...

  7. Polymer Derived Rare Earth Silicate Nanocomposite Protective Coatings for Nuclear Thermal Propulsion Systems, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — The objective of this Phase I SBIR program is to develop polymer derived rare earth silicate nanocomposite environmental barrier coatings (EBC) for providing...

  8. Tin isotope fractionation during magmatic processes and the isotope composition of the bulk silicate Earth

    Science.gov (United States)

    Wang, Xueying; Amet, Quentin; Fitoussi, Caroline; Bourdon, Bernard

    2018-05-01

    Tin is a moderately volatile element whose isotope composition can be used to investigate Earth and planet differentiation and the early history of the Solar System. Although the Sn stable isotope composition of several geological and archaeological samples has been reported, there is currently scarce information about the effect of igneous processes on Sn isotopes. In this study, high-precision Sn isotope measurements of peridotites and basalts were obtained by MC-ICP-MS with a double-spike technique. The basalt samples display small variations in δ124/116Sn ranging from -0.01 ± 0.11 to 0.27 ± 0.11‰ (2 s.d.) relative to NIST SRM 3161a standard solution, while peridotites have more dispersed and more negative δ124Sn values ranging from -1.04 ± 0.11 to -0.07 ± 0.11‰ (2 s.d.). Overall, basalts are enriched in heavy Sn isotopes relative to peridotites. In addition, δ124Sn in peridotites become more negative with increasing degrees of melt depletion. These results can be explained by different partitioning behavior of Sn4+ and Sn2+ during partial melting. Sn4+ is overall more incompatible than Sn2+ during partial melting, resulting in Sn4+-rich silicate melt and Sn2+-rich residue. As Sn4+ has been shown experimentally to be enriched in heavy isotopes relative to Sn2+, the effect of melting is to enrich residual peridotites in relatively more compatible Sn2+, which results in isotopically lighter peridotites and isotopically heavier mantle-derived melts. This picture can be disturbed partly by the effect of refertilization. Similarly, the presence of enriched components such as recycled oceanic crust or sediments could explain part of the variations in Sn isotopes in oceanic basalts. The most primitive peridotite analyzed in this study was used for estimating the Sn isotope composition of the BSE, with δ124Sn = -0.08 ± 0.11‰ (2 s.d.) relative to the Sn NIST SRM 3161a standard solution. Altogether, this suggests that Sn isotopes may be a powerful probe of

  9. Heterogeneous Delivery of Silicate and Metal to the Earth via Large Planetesimals

    Science.gov (United States)

    Marchi, S.; Canup, R. M.; Walker, R. J.

    2017-12-01

    Earth's mantle abundances of at least some highly siderophile elements, (HSE; Re, Os, Ir, Ru, Pt, Rh, Pd, and Au), are much higher than would result from metal-silicate equilibration during terrestrial core formation, and can be better explained as a result of late accretion of a minimum of 0.5% Earth's masses after core formation was complete. Traditional models assume that HSEs delivered by late projectiles completely mixed and chemically equilibrated with the Earth's mantle. This appears likely for undifferentiated, well-mixed projectiles, or for relatively small, differentiated projectiles. However several arguments suggest that late projectiles may have been large (> 1500 km in diameter) and differentiated, and in this case, portions of the projectile's core may merge with the Earth's core, rather than being mixed into the Earth's mantle. We investigate projectile mixing with a suite of SPH simulations of differentiated planetesimal colliding with the Earth. A range of outcomes emerge from our simulations suggesting that for large impactors (>1500 km), the delivery of HSE to the Earth's mantle may be disproportionate with the overall delivery of mass. For impacts with impact angles 60°, most of the impactor core escapes for moderate impact speeds. An implication is that the late accreted mass inferred from terrestrial HSE abundances may be a substantial underestimate, by a factor 2-5. In addition, partial mixing of projectiles result in an enrichment in mantle vs core material delivered to the bulk silicate Earth, implying substantial compositional variations in the accreted mass. Such variations could produce initially localized domains in Earth's mantle with distinct, mass independent isotopic signatures, given the isotopic variability resulting from nucleosynthetic heterogeneities among genetically diverse meteorites. In general we find that larger, low angle collisions would be more likely to produce initial mantle domains of anomalous composition

  10. Making Earth's earliest continental crust - an analogue from voluminous Neogene silicic volcanism in NE-Iceland

    Science.gov (United States)

    Berg, Sylvia E.; Troll, Valentin R.; Burchardt, Steffi; Riishuus, Morten S.; Deegan, Frances M.; Harris, Chris; Whitehouse, Martin J.; Gústafsson, Ludvik E.

    2014-05-01

    Borgarfjörður Eystri in NE-Iceland represents the second-most voluminous exposure of silicic eruptive rocks in Iceland and is a superb example of bimodal volcanism (Bunsen-Daly gap), which represents a long-standing controversy that touches on the problem of crustal growth in early Earth. The silicic rocks in NE-Iceland approach 25 % of the exposed rock mass in the region (Gústafsson et al., 1989), thus they significantly exceed the usual ≤ 12 % in Iceland as a whole (e.g. Walker, 1966; Jonasson, 2007). The origin, significance, and duration of the voluminous (> 300 km3) and dominantly explosive silicic activity in Borgarfjörður Eystri is not yet constrained (c.f. Gústafsson, 1992), leaving us unclear as to what causes silicic volcanism in otherwise basaltic provinces. Here we report SIMS zircon U-Pb ages and δ18O values from the region, which record the commencement of silicic igneous activity with rhyolite lavas at 13.5 to 12.8 Ma, closely followed by large caldera-forming ignimbrite eruptions from the Breiðavik and Dyrfjöll central volcanoes (12.4 Ma). Silicic activity ended abruptly with dacite lava at 12.1 Ma, defining a ≤ 1 Myr long window of silicic volcanism. Magma δ18O values estimated from zircon range from 3.1 to 5.5 (± 0.3; n = 170) and indicate up to 45 % assimilation of a low-δ18O component (e.g. typically δ18O = 0 ‰, Bindeman et al., 2012). A Neogene rift relocation (Martin et al., 2011) or the birth of an off-rift zone to the east of the mature rift associated with a thermal/chemical pulse in the Iceland plume (Óskarsson & Riishuus, 2013), likely brought mantle-derived magma into contact with fertile hydrothermally-altered basaltic crust. The resulting interaction triggered large-scale crustal melting and generated mixed-origin silicic melts. Such rapid formation of silicic magmas from sustained basaltic volcanism may serve as an analogue for generating continental crust in a subduction-free early Earth (e.g. ≥ 3 Ga, Kamber et

  11. Relations between structure and material properties in earth alkaline silicate basing phosphors; Struktureigenschaftsbeziehungen in Erdalkalisilikat basierenden Leuchtstoffen

    Energy Technology Data Exchange (ETDEWEB)

    Hempel, Wolfgang

    2008-03-19

    This work is basing on the relation between structure and luminescence of Eu{sup 2+} doped Earth-Alkaline-Silicates. After an overview of Earth-Alkaline-Silicates silicates with an additional cation (Li{sup +}, Al{sup 3+}) and an additional anion (Cl{sup -}, N{sup 3-}) are examined in chapter 4 and 5. Basing on this data an relation between structural influence - like ion-radii, anion and coordination polyeder - and phosphor luminescence is set up. The ability of using as an industrial phosphor is made in the final chapter. (orig.)

  12. BSE in the UK

    DEFF Research Database (Denmark)

    Jensen, Karsten Klint

    2004-01-01

    assessment by the Southwood Working Party. This lack of transparency ensured that the working party's risk characterization and recommendations were ambiguous and thus hard to interpret. It also meant that uncertainties were not addressed in a satisfactory way. In the recommendations, the attitude...... to uncertainty was implicit rather than explicit. The risk communication based on the report amplified these flaws. Most importantly, it did not address the uncertainty at all. Apparently, the reason for this was fear of overreaction by the public. However, the result was counter-productive, because the risk....... There seemed to be little faith in the public's ability to reach a balanced judgment regarding the uncertainties. In the concluding section of the paper, this analysis is compared with the food standards agency's (FSA's) approach to BSE. The intervention of this agency was seen as one of the more important...

  13. Recent developments in the MOCVD and ALD of rare earth oxides and silicates

    International Nuclear Information System (INIS)

    Jones, Anthony C.; Aspinall, Helen C.; Chalker, Paul R.; Potter, Richard J.; Kukli, Kaupo; Rahtu, Antti; Ritala, Mikko; Leskelae, Markku

    2005-01-01

    Lanthanide, or rare-earth oxides are currently being investigated as alternatives to SiO 2 as the dielectric insulating layer in sub-0.1 μm CMOS technology. Metalorganic chemical vapour deposition (MOCVD) and atomic layer deposition (ALD) are promising techniques for the deposition of these high-κ dielectric oxides and in this paper some of our recent research into the MOCVD and ALD of PrO x , La 2 O 3 , Gd 2 O 3 , Nd 2 O 3 and their related silicates are reviewed

  14. Effect of the addition of Na2O on the thermal stability of alumino silicated glasses rich in rare earths

    International Nuclear Information System (INIS)

    Lassalle-Herraud, Olivier; Matecki, Marc; Glorieux, Benoit; Sadiki, Najim; Montoullout, Valerie; Dussossoy, Jean-Luc

    2006-01-01

    Alumino silicated glasses rich in rare earths have been prepared by concentrated solar way. Their recrystallization, the structural and microstructural properties as well as the mechanical and thermal properties of these glasses have been studied. The results show the effect of sodium addition on the thermal stability of the materials, the vitreous transition temperature and the recrystallization temperature. A heat treatment has allowed to reveal the formation of sodium apatite micro-crystallites and of lanthanum silicate in the glasses. (O.M.)

  15. Metal-silicate Partitioning and Its Role in Core Formation and Composition on Super-Earths

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, Laura; Petaev, M. I.; Sasselov, Dimitar D. [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Jacobsen, Stein B.; Remo, John L., E-mail: lschaefer@asu.edu [Harvard University, Department of Earth and Planetary Sciences, 20 Oxford St., Cambridge, MA 02138 (United States)

    2017-02-01

    We use a thermodynamic framework for silicate-metal partitioning to determine the possible compositions of metallic cores on super-Earths. We compare results using literature values of the partition coefficients of Si and Ni, as well as new partition coefficients calculated using results from laser shock-induced melting of powdered metal-dunite targets at pressures up to 276 GPa, which approaches those found within the deep mantles of super-Earths. We find that larger planets may have little to no light elements in their cores because the Si partition coefficient decreases at high pressures. The planet mass at which this occurs will depend on the metal-silicate equilibration depth. We also extrapolate the equations of state (EOS) of FeO and FeSi alloys to high pressures, and present mass–radius diagrams using self-consistent planet compositions assuming equilibrated mantles and cores. We confirm the results of previous studies that the distribution of elements between mantle and core will not be detectable from mass and radius measurements alone. While observations may be insensitive to interior structure, further modeling is sensitive to compositionally dependent properties, such as mantle viscosity and core freeze-out properties. We therefore emphasize the need for additional high pressure measurements of partitioning as well as EOSs, and highlight the utility of the Sandia Z-facilities for this type of work.

  16. The neodymium stable isotope composition of the silicate Earth and chondrites

    Science.gov (United States)

    McCoy-West, Alex J.; Millet, Marc-Alban; Burton, Kevin W.

    2017-12-01

    The non-chondritic neodymium (Nd) 142Nd/144Nd ratio of the silicate Earth potentially provides a key constraint on the accretion and early evolution of the Earth. Yet, it is debated whether this offset is due to the Earth being formed from material enriched in s-process Nd isotopes or results from an early differentiation process such as the segregation of a late sulfide matte during core formation, collisional erosion or a some combination of these processes. Neodymium stable isotopes are potentially sensitive to early sulfide segregation into Earth's core, a process that cannot be resolved using their radiogenic counterparts. This study presents the first comprehensive Nd stable isotope data for chondritic meteorites and terrestrial rocks. Stable Nd measurements were made using a double spike technique coupled with thermal ionisation mass spectrometry. All three of the major classes of chondritic meteorites, carbonaceous, enstatite and ordinary chondrites have broadly similar isotopic compositions allowing calculation of a chondritic mean of δ146/144Nd = -0.025 ± 0.025‰ (±2 s.d.; n = 39). Enstatite chondrites yield the most uniform stable isotope composition (Δ146/144Nd = 26 ppm), with considerably more variability observed within ordinary (Δ146/144Nd = 72 ppm) and carbonaceous meteorites (Δ146/144Nd = 143 ppm). Terrestrial weathering, nucleosynthetic variations and parent body thermal metamorphism appear to have little measurable effect on δ146/144Nd in chondrites. The small variations observed between ordinary chondrite groups most likely reflect inherited compositional differences between parent bodies, with the larger variations observed in carbonaceous chondrites being linked to varying modal proportions of calcium-aluminium rich inclusions. The terrestrial samples analysed here include rocks ranging from basaltic to rhyolitic in composition, MORB glasses and residual mantle lithologies. All of these terrestrial rocks possess a broadly similar Nd

  17. REDOX BEHAVIOR AND DIFFUSIVITY OF ANTIMONY AND CERIUM ION IN ALKALI ALKALINE EARTH SILICATE GLASS MELTS

    Directory of Open Access Journals (Sweden)

    K. D. Kim

    2010-03-01

    Full Text Available Redox behavior and diffusivity of antimony and cerium ion in alkali alkaline earth silicate CRT (Cathode Ray Tube model glass melts were studied by means of square wave voltammetry under the frequency range of 5-1000 Hz and in the temperature range of 800-1400°C. According to voltammogram, peaks due to Sb³⁺/Sb⁰ were positioned in the negative potential region while peaks due to Sb⁵⁺/Sb³⁺ and Ce⁴⁺/Ce³⁺ were found in the positive potential region. By using some equations, correlation for peak potential versus temperature and peak current versus reciprocal frequency was examined, respectively. Their correlation showed a linear relation in the applied temperature and frequency range. Based on the linear relationship, thermodynamic and kinetic properties for each redox reaction were suggested.

  18. Fluorescence yield in rare-earth-doped sol-gel silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Silversmith, A.J., E-mail: asilvers@hamilton.ed [Physics Department, Hamilton College, 198 College Hill Road, Clinton, NY 13323 (United States); Nguyen, Nguyen T.T.; Campbell, D.L. [Physics Department, Hamilton College, 198 College Hill Road, Clinton, NY 13323 (United States); Boye, D.M.; Ortiz, C.P. [Davidson College, Davidson, NC 28035 (United States); Hoffman, K.R. [Whitman College, Walla Walla, WA 99362 (United States)

    2009-12-15

    We have used trivalent terbium to investigate the mechanism behind fluorescence enhancement by Al{sup 3+} co-doping. Our results indicate that rare-earth (RE) ions cluster together in aluminum-rich regions of the glass, and behave as if they were dispersed uniformly throughout these regions when the ratio of Al to RE is {approx}10 or greater. We also studied the effects of adding chemical drying agents to the precursor solution for the synthesis of sol-gel-derived silicate glasses. Such glasses can be treated at significantly higher annealing temperatures without degradation of optical quality, and have the density of melt glass. Fluorescence yield from doped RE ions improves markedly with the addition of the drying agents, and the denser glasses are not subject to rehydration.

  19. Relationship with BSE (Mad Cow Disease)

    Science.gov (United States)

    ... Disease (CWD) Prion Diseases Relationship with BSE (Mad Cow Disease) Evidence Recommend on Facebook Tweet Share Compartir ... macaque monkeys inoculated with brain tissue obtained from cattle with BSE had clinical and neuropathological features strikingly ...

  20. Syntheses and characterizations of rare earth doped phospho-silicated apatites: application to nuclear waste confinement

    International Nuclear Information System (INIS)

    Boyer, Laurent

    1998-01-01

    Apatite matrices have been developed for the conditioning of actinides from spent fuels of PWR reactors. Silicated apatites (britholites) containing actinides and lanthanides have been discovered in the natural environment. Synthetic analogues of these britholites can be obtained by solid-solid reaction at high temperature. The compounds of the solid solution of fluorinated britholites are synthesized by the double substitution of (Ca 2+ , PO 4 3- ) by (Ln 3+ , SiO 4 4- ). Trivalent lanthanides are chemical analogues of trivalent actinides. The synthesis was performed with La, Nd and Eu. This study allows to demonstrate that the chemical immobilization comes from the fixation of rare earths at the atomic scale, thanks to their participation to the mineral structure. In part 1, the criteria for the formulation of a matrix for the conditioning of separate radionuclides are given. The structure and the different methods of apatite preparation are shown. Part 2 treats of the study of the solid solution, of the elaboration of the Ca 9 Nd 1 (SiO 4 ) 5 F 2 ceramic and of its physico chemical characterization. The last part deals with the localization of rare earths in the apatite structure, determined by europium luminescence and X-ray diffraction on monocrystal. (J.S.) [fr

  1. Crystallographic and spectroscopic investigations on nine metal-rare-earth silicates with the apatite structure type

    International Nuclear Information System (INIS)

    Wierzbicka-Wieczorek, Maria; Goeckeritz, Martin; Kolitsch, Uwe; Lenz, Christoph; Giester, Gerald

    2015-01-01

    Nine silicates with the apatite structure type (space group P6 3 /m) containing both rare-earth elements (REEs: Pr, Nd, Sm, Tb, Ho and Er) and various metals (K, Sr, Ba and Cd) were synthesised by high-temperature flux-growth techniques and characterised by single-crystal X-ray diffraction, scanning electron microscopy, Raman spectroscopy and laser-induced photoluminescence spectroscopy. In all of the compounds, the 6h Wyckoff position is predominantly or solely occupied by REE 3+ cations, whereas the cations shows a mixed occupancy at the larger, nine-coordinate 4f site with 55-75 % of REE 3+ cations and 45-25 % of other metal cations. The O4 (''free'' oxygen) site is fully occupied by O 2- anions, except for a Ba-Pr member with full occupancy by F - anions. The refined formulas are Cd 2 Er 8 (SiO 4 ) 6 O 2 , Cd 2 Tb 8 (SiO 4 ) 6 O 2 , KHo 9 (SiO 4 ) 6 O 2 , KTb 9 (SiO 4 ) 6 O 2 , KSm 9 (SiO 4 ) 6 O 2 , Sr 2 Nd 8 (SiO 4 ) 6 O 2 , Ba 2 Nd 8 (SiO 4 ) 6 O 2 , Ba 2 Sm 8 (SiO 4 ) 6 O 2 and Ba 4 Pr 6 (SiO 4 ) 6 F 2 . Changes in the metaprism twist angle (φ) and correlations between the unit-cell parameters, average cationic radii (of M + /M 2+ -REE 3+ pairs) and the chemistry of both the synthesised M + /M 2+ -REE 3+ silicate apatites and those reported previously are evaluated. Photoluminescence measurements of undoped samples yielded emission bands in the visible region from green to red; therefore, these compounds are potential candidates for luminescent materials. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  2. Physical mineralogy of (Ca,Al)-rich silicate phases of the Earth's mantle. Geodynamic implications

    International Nuclear Information System (INIS)

    Gautron, Laurent

    2008-01-01

    Mineral physics could provide answers to many questions we asked about mineral phases present in the Earth's mantle, their characteristics, their crystal structure, their phase transitions. In the second part of the twentieth century, high pressure and high temperature experiments could give essential data about materials from the deep Earth: these data could then be combined to those obtained by seismology measurements, geochemistry analyses, experimental and theoretical geodynamics, for a better understanding of the deep parts of our planet. Many former studies revealed that silicate phases bearing calcium and/or aluminium could display very interesting characteristics and properties, with important geodynamics implications. The combination of calcium and aluminium is know to be very useful for mineral phases: indeed, calcium is able to be substituted by atoms which display large cations, while aluminium when replacing silicon atoms could allow the eventual charge compensation required by the substitution of calcium. Moreover, there is an increasing amount of data which reveal the existence of many new (Ca,Al)-rich silicate phases at (P,T) conditions of the Earth's mantle: these phase are found to display very original structure and properties. In this thesis manuscript, we report the main results obtained about the aluminous calcium perovskite, Al-CaSiO 3 , which is one of the three main mineral phases present in the lower mantle. We show that this phase is able to incorporate huge amount of natural actinides uranium and thorium which provide the main part of the heat produced in our planet, by radioactive decay. Then the Al-rich Ca-perovskite bearing U and Th could be the thermal engine of the Earth's lower mantle. These results obtained by mineral physics experiments and methodology are presented with the objective to better constrain the recent geodynamics models. Here, we propose that the (U,Th)-Al-CaSiO 3 perovskite alone is able to provide the entire

  3. Thermal Cycling and High-Temperature Corrosion Tests of Rare Earth Silicate Environmental Barrier Coatings

    Science.gov (United States)

    Darthout, Émilien; Gitzhofer, François

    2017-12-01

    Lutetium and yttrium silicates, enriched with an additional secondary zirconia phase, environmental barrier coatings were synthesized by the solution precursor plasma spraying process on silicon carbide substrates. A custom-made oven was designed for thermal cycling and water vapor corrosion testing. The oven can test four specimens simultaneously and allows to evaluate environmental barrier performances under similar corrosion kinetics compared to turbine engines. Coatings structural evolution has been observed by SEM on the polished cross sections, and phase composition has been analyzed by XRD. All coatings have been thermally cycled between 1300 °C and the ambient temperature, without spallation, due to their porosity and the presence of additional secondary phase which increases the thermal cycling resistance. During water vapor exposure at 1200 °C, rare earth disilicates showed a good stability, which is contradictory with the literature, due to impurities—such as Si- and Al-hydroxides—in the water vapor jets. The presence of vertical cracks allowed the water vapor to reach the substrate and then to corrode it. It has been observed that thin vertical cracks induced some spallation after 24 h of corrosion.

  4. The adsorption kinetics of metal ions onto different microalgae and siliceous earth.

    Science.gov (United States)

    Schmitt, D; Müller, A; Csögör, Z; Frimmel, F H; Posten, C

    2001-03-01

    In the present work the adsorption kinetics of the six metal ions aluminum, zinc, mercury, lead, copper, and cadmium onto living microalgae were measured. The freshwater green microalga Scenedesmus subspicatus, the brackish water diatom Cyclotella cryptica, the seawater diatom Phaeodactylum tricornutum, and the seawater red alga Porphyridium purpureum were the subject of investigation. In most cases the adsorption rate of the metals could be well described by using the equation of the Langmuir adsorption rate expression. Inverse parameter estimation allowed the determination of the rate constants of the adsorption process and the maximum metal content of the algae. The highest values for the rate constant were obtained for Porphyridium purpureum followed by Phaeodactylum tricornutum. High values for the maximum content were obtained for Cyclotella cryptica and Scenedesmus subspicatus. The maximum rate constant was 24.21 h-1 for the adsorption of Hg to Porphyridium purpureum whereas the maximum metal content (0.243 g g-1) was obtained for Zn on Cyclotella cryptica. A comparison of these values with those obtained for the mineral siliceous earth exhibiting low maximum content and high adsorption rates reveals that the mechanism of adsorption onto the algae is a mixture of adsorption and accumulation.

  5. Valence determination of rare earth elements in lanthanide silicates by L 3-XANES spectroscopy

    International Nuclear Information System (INIS)

    Kravtsova, Antonina N; Guda, Alexander A; Soldatov, Alexander V; Goettlicher, Joerg; Taroev, Vladimir K; Suvorova, Lyudmila F; Tauson, Vladimir L; Kashaev, Anvar A

    2016-01-01

    Lanthanide silicates have been hydrothermally synthesized using Cu and Ni containers. Chemical formulae of the synthesized compounds correspond to K 3 Eu[Si 6 O 15 ] 2H 2 O, HK 6 Eu[Si 10 O 25 ], K 7 Sm 3 [Si 12 O 32 ], K 2 Sm[AlSi 4 O 12 ] 0.375H 2 O, K 4 Yb 2 [Si 8 O 21 ], K 4 Ce 2 [Al 2 Si 8 O 24 ]. The oxidation state of lanthanides (Eu, Ce, Tb, Sm, Yb) in these silicates has been determined using XANES spectroscopy at the Eu, Ce, Tb, Sm, Yb, L 3 - edges. The experimental XANES spectra were recorded using the synchrotron radiation source ANKA (Karlsruhe Institute of Technology) and the X-ray laboratory spectrometer Rigaku R- XAS. By comparing the absorption edge energies and white line intensities of the silicates with the ones of reference spectra the oxidation state of lanthanides Eu, Ce, Tb, Sm, Yb has been found to be equal to +3 in all investigated silicates except of the Ce-containing silicate from the run in Cu container where the cerium oxidation state ranges from +3 (Ce in silicate apatite and in a KCe silicate with Si 12 O 32 layers) to +4 (starting CeO 2 or oxidized Ce 2 O 3 ). (paper)

  6. BSE Practice and BSE Self-Efficacy among Nursing Students in Aceh, Indonesia

    Directory of Open Access Journals (Sweden)

    Juanita Juanita

    2013-01-01

    Full Text Available Purpose: To survey the level of BSE practice among female nursing students in Aceh, and the degree of self-efficacy in those who did practice it.Method: Seventy-six nursing students from the Public Nursing College, Syiah Kuala University in Aceh who met the inclusion criteria were recruited. Stratified proportionate random sampling was used to determine the required number of first, second, and third year students. BSE self-efficacy of the students was measured by the BSE Self-Efficacy Questionnaire which was modified from an existing tool developed by Khatun (2010. In addition, the students’ doing BSE or not was measured by BSE Practice Questionnaire which was developed by the researcher. The data were analyzed by using descriptive statistics.Result: Only 39.5% of the students practiced BSE with more than half of the students saying they did not practice BSE (60.5%. The main factors that influenced the students’ performing BSE were not having a family history of breast cancer, single, and no history of breast illness. Among the thirty students who practiced BSE, most of them did not practice it routinely (70%, nor at the correct time (86.7%, and their confidence in performing BSE was at a moderate level overall, with a high level for BSE procedural efficacy and moderate level for barrier management efficacy.Conclusion: A majority of the Acehnese nursing students did not practice BSE, and those who did had only a moderate level of BSE self-efficacy. Therefore, the results of this study suggest emphasizing the need to teach nursing students about BSE in their undergraduate courses, with future follow-up research regarding the success of the educational program.Keywords: practice, self-efficacy, breast self-examination (BSE, nursing students

  7. The Carbonate-Silicate Cycle on Earth-like Planets Near The End Of Their Habitable Lifetimes

    Science.gov (United States)

    Rushby, A. J.; Mills, B.; Johnson, M.; Claire, M.

    2016-12-01

    The terrestrial cycle of silicate weathering and metamorphic outgassing buffers atmospheric CO2 and global climate over geological time on Earth. To first order, the operation of this cycle is assumed to occur on Earth-like planets in the orbit of other main-sequence stars in the galaxy that exhibit similar continent/ocean configurations. This has important implications for studies of planetary habitability, atmospheric and climatic evolution, and our understanding of the potential distribution of life in the Universe. We present results from a simple biogeochemical carbon cycle model developed to investigate the operation of the carbonate-silicate cycle under conditions of differing planet mass and position within the radiative habitable zone. An active carbonate-silicate cycle does extend the length of a planet's habitable period through the regulation of the CO2 greenhouse. However, the breakdown of the negative feedback between temperature, pCO2, and weathering rates towards the end of a planet's habitable lifespan results in a transitory regime of `carbon starvation' that would inhibit the ability of oxygenic photoautotrophs to metabolize, and result in the collapse of any putative biosphere supported by these organisms, suggesting an earlier limit for the initiation of inhabitable conditions than when considering temperature alone. This conclusion stresses the importance of considering the full suite of planetary properties when determining potential habitability. A small sample of exoplanets was tested using this model, and the length of their habitable periods were found to be significantly longer than that of the Earth, primarily as a function of the differential rates of stellar evolution expected from their host stars. Furthermore, we carried out statistical analysis of a series of model input parameters, determining that both the mass of the planet and the sensitivity of seafloor weathering processes to dissolved CO2 exhibit significant controls on the

  8. A major genetic component of BSE susceptibility

    Science.gov (United States)

    Juling, Katrin; Schwarzenbacher, Hermann; Williams, John L; Fries, Ruedi

    2006-01-01

    Background Coding variants of the prion protein gene (PRNP) have been shown to be major determinants for the susceptibility to transmitted prion diseases in humans, mice and sheep. However, to date, the effects of polymorphisms in the coding and regulatory regions of bovine PRNP on bovine spongiform encephalopathy (BSE) susceptibility have been considered marginal or non-existent. Here we analysed two insertion/deletion (indel) polymorphisms in the regulatory region of bovine PRNP in BSE affected animals and controls of four independent cattle populations from UK and Germany. Results In the present report, we show that two previously reported 23- and 12-bp insertion/deletion (indel) polymorphisms in the regulatory region of bovine PRNP are strongly associated with BSE incidence in cattle. Genotyping of BSE-affected and control animals of UK Holstein, German Holstein, German Brown and German Fleckvieh breeds revealed a significant overrepresentation of the deletion alleles at both polymorphic sites in diseased animals (P = 2.01 × 10-3 and P = 8.66 × 10-5, respectively). The main effect on susceptibility is associated with the 12-bp indel polymorphism. Compared with non-carriers, heterozygous and homozygous carriers of the 12-bp deletion allele possess relatively higher risks of having BSE, ranging from 1.32 to 4.01 and 1.74 to 3.65 in the different breeds. These values correspond to population attributable risks ranging from 35% to 53%. Conclusion Our results demonstrate a substantial genetic PRNP associated component for BSE susceptibility in cattle. Although the BSE risk conferred by the deletion allele of the 12-bp indel in the regulatory region of PRNP is substantial, the main risk factor for BSE in cattle is environmental, i.e. exposure to feedstuffs contaminated with the infectious agent. PMID:17014722

  9. A major genetic component of BSE susceptibility

    Directory of Open Access Journals (Sweden)

    Williams John L

    2006-10-01

    Full Text Available Abstract Background Coding variants of the prion protein gene (PRNP have been shown to be major determinants for the susceptibility to transmitted prion diseases in humans, mice and sheep. However, to date, the effects of polymorphisms in the coding and regulatory regions of bovine PRNP on bovine spongiform encephalopathy (BSE susceptibility have been considered marginal or non-existent. Here we analysed two insertion/deletion (indel polymorphisms in the regulatory region of bovine PRNP in BSE affected animals and controls of four independent cattle populations from UK and Germany. Results In the present report, we show that two previously reported 23- and 12-bp insertion/deletion (indel polymorphisms in the regulatory region of bovine PRNP are strongly associated with BSE incidence in cattle. Genotyping of BSE-affected and control animals of UK Holstein, German Holstein, German Brown and German Fleckvieh breeds revealed a significant overrepresentation of the deletion alleles at both polymorphic sites in diseased animals (P = 2.01 × 10-3 and P = 8.66 × 10-5, respectively. The main effect on susceptibility is associated with the 12-bp indel polymorphism. Compared with non-carriers, heterozygous and homozygous carriers of the 12-bp deletion allele possess relatively higher risks of having BSE, ranging from 1.32 to 4.01 and 1.74 to 3.65 in the different breeds. These values correspond to population attributable risks ranging from 35% to 53%. Conclusion Our results demonstrate a substantial genetic PRNP associated component for BSE susceptibility in cattle. Although the BSE risk conferred by the deletion allele of the 12-bp indel in the regulatory region of PRNP is substantial, the main risk factor for BSE in cattle is environmental, i.e. exposure to feedstuffs contaminated with the infectious agent.

  10. Emergence of silicic continents as the lower crust peels off on a hot plate-tectonic Earth

    Science.gov (United States)

    Chowdhury, Priyadarshi; Gerya, Taras; Chakraborty, Sumit

    2017-09-01

    The rock record and geochemical evidence indicate that continental recycling has been occurring since the early history of the Earth. The stabilization of felsic continents in place of Earth's early mafic crust about 3.0 to 2.0 billion years ago, perhaps due to the initiation of plate tectonics, implies widespread destruction of mafic crust during this time interval. However, the physical mechanisms of such intense recycling on a hotter, (late) Archaean and presumably plate-tectonic Earth remain largely unknown. Here we use thermomechanical modelling to show that extensive recycling via lower crustal peeling-off (delamination but not eclogitic dripping) during continent-continent convergence was near ubiquitous during the late Archaean to early Proterozoic. We propose that such destruction of the early mafic crust, together with felsic magmatism, may have caused both the emergence of silicic continents and their subsequent isostatic rise, possibly above the sea level. Such changes in the continental character have been proposed to influence the Great Oxidation Event and, therefore, peeling-off plate tectonics could be the geodynamic trigger for this event. A transition to the slab break-off controlled syn-orogenic recycling occurred as the Earth aged and cooled, leading to reduced recycling and enhanced preservation of the continental crust of present-day composition.

  11. Mechanical properties of silicate glasses exposed to a low-Earth orbit

    Science.gov (United States)

    Wiedlocher, David E.; Tucker, Dennis S.; Nichols, Ron; Kinser, Donald L.

    1992-01-01

    The effects of a 5.8 year exposure to low earth orbit environment upon the mechanical properties of commercial optical fused silica, low iron soda-lime-silica, Pyrex 7740, Vycor 7913, BK-7, and the glass ceramic Zerodur were examined. Mechanical testing employed the ASTM-F-394 piston on 3-ball method in a liquid nitrogen environment. Samples were exposed on the Long Duration Exposure Facility (LDEF) in two locations. Impacts were observed on all specimens except Vycor. Weibull analysis as well as a standard statistical evaluation were conducted. The Weibull analysis revealed no differences between control samples and the two exposed samples. We thus concluded that radiation components of the Earth orbital environment did not degrade the mechanical strength of the samples examined within the limits of experimental error. The upper bound of strength degradation for meteorite impacted samples based upon statistical analysis and observation was 50 percent.

  12. Does the Amazon suffer from BSE prevention?

    NARCIS (Netherlands)

    Elferink, E.V.; Nonhebel, S.; Schoot Uiterkamp, A.J.M.

    In the last decade, large-scale production of soybeans has been a major driver of the enhanced deforestation in the Brazilian Amazon. We show that these soybeans are mainly exported to the EU to substitute for the BSE related banned meat and bone meal in livestock feed. This strongly suggests a link

  13. Review on the epidemiology and dynamics of BSE epidemics

    NARCIS (Netherlands)

    Ducrot, C.; Calavas, D.; Arnold, M.; Koeijer, de A.A.; Heim, D.

    2008-01-01

    The paper describes how the comprehensive surveillance of bovine spongiform encephalopathy (BSE) and studies carried out on these data has enhanced our knowledge of the epidemiology of BSE. Around 7 000 BSE cases were detected through the screening of about 50 million cattle with rapid tests in

  14. High modulus rare earth and beryllium containing silicate glass compositions. [for glass reinforcing fibers

    Science.gov (United States)

    Bacon, J. F. (Inventor)

    1976-01-01

    Glass compositions having a Young's modulus of at least 16 million psi and a specific modulus of at least 110 million inches consisting essentially of approximately, by weight, 20 to 43% SiO2, 8 to 21% Al2O3, 4 to 10% BeO, 27 to 58% of at least one oxide selected from a first group consisting of Y2O3, La2O3, Nd2O3, Ce2O3, Ce2O3, and the mixed rare earth oxides, and 3 to 12% of at least one oxide selected from a second group consisting of MgO, ZrO2, ZnO and CaO are described. The molar ratio of BeO to the total content of the first group oxides is from 1.0 to 3.0.

  15. Carbon substituting for oxygen in silicates: A novel mechanism for carbon incorporation in the deep Earth

    Science.gov (United States)

    Armentrout, M. M.; Tavakoli, A.; Ionescu, E.; Mera, G.; Riedel, R.; Navrotsky, A.

    2013-12-01

    Traditionally, carbon in the deep Earth has been thought of in terms of either carbonate at high oxygen fugacities or graphite or diamond under more reducing conditions. However, material science studies of amorphous Si-O-C polymer derived ceramics have demonstrated that carbon can be accommodated as an anion substituting for oxygen in mixed silica tetrahedra. Furthermore these structures are energetically favorable relative to a mixture of crystalline silica, silicon carbide, and graphite by ten or more kJ/g.atom. Thermodynamic stability suggests that these nano-structured composites are a potentially important storage mechanism for carbon under moderately reducing conditions. Here we expand the scope of the previous work by examining the compositional effect of geologically relevant cations (calcium and magnesium) on the thermodynamic stability, nanostructure, and ability to accommodate carbon of these composites. Silicon oxy-carbides doped with magnesium, magnesium and calcium or undoped resisted crystallization at 1100 C under inert atmosphere. 29Si NMR of the samples shows a similar distribution of silicon between end-member and mixed sites (Table 1). Results are presented from studies utilizing NMR, high temperature solution calorimetry, and microprobe. Table 1. Percentages of Si species in each material as determined by 29Si NMR.

  16. Quantum efficiency of silica-coated rare-earth doped yttrium silicate

    International Nuclear Information System (INIS)

    Cervantes-Vásquez, D.; Contreras, O.E.; Hirata, G.A.

    2013-01-01

    The photoluminescent properties of rare earth-activated white-emitting Y 2 SiO 5 :Ce,Tb nanocrystalline phosphor prepared by two different methods, pressure-assisted combustion synthesis and sol–gel, were studied. The synthesized phosphor samples were post-annealed at 1373 K and 1623 K in order to obtain the X1-Y 2 SiO 5 and X2-Y 2 SiO 5 phases, respectively, which were confirmed by X-ray diffraction measurements. Photoluminescence analysis showed the contribution of two blue-emission bands within the 380–450 nm region originating from 5d–4f transitions in Ce 3+ ions and a well-defined green emission of Tb 3+ ions located at 545 nm corresponding to 5 D 4 → 7 F 5 electronic transitions. Thereafter, Y 2 SiO 5 :Ce,Tb powders were coated with colloidal silica in order to investigate the effect of silica coatings on their luminescent properties. Absolute fluorescence quantum efficiency measurements were carefully performed, which revealed an increase of 12% of efficiency in coated compared with bare-Y 2 SiO 5 :Ce,Tb phosphor. -- Highlights: • Y 2 SiO 5 :Ce,Tb phosphor powders were successfully coated with colloidal silica. • Post-annealing treatments improved the quantum efficiency of silica-coated Y 2 SiO 5 :Ce,Tb phosphors. • Absolute fluorescence quantum efficiency measurements showed an increase of 12%

  17. Impact of BSE on livestock production system.

    Science.gov (United States)

    Nardone, A

    2003-09-01

    The small number of BSE cases diagnosed in Italy from January 2001 to 12 September 2001 (a total of 28, one every 9000 head) does not allow for a statistical analysis of the relationship between this disease and the livestock systems. However, some indications can be noted: (a) only dairy cattle, which represent three-quarters of the cattle raised in Italy, are involved; (b) 58% of the cases belong to medium-large farms that breed 27% of all head; (c) 13 out of 28 cases are 5-year-old animals and 26 out of 28 are between 5 and 7 years of age; (d) 15 of 28 cases come from Lombardia, where 27% of Italian dairy cattle are raised. The following factors may have affected the livestock system: (1) trends of beef meat consumption; (2) changes in livestock management; (3) changes in animal feeding; (4) possible effects on selection. A strong decline in beef meat consumption (4 kg/year) has been observed in the UK and other European countries since 1996 (the year of the discovery of the relationship between BSE and nvCJD). In Italy, from January 2001 the consumption of beef meat has declined as well as slaughter: a drop of 31% in the total slaughtered head in the period January-February, a drop of 14% in January-May. A fall in the price of calves has promoted, in some dairy farms, the start of the production of light beef less than one year old (advantages in the marketing of meat favour this initiative), a phenomenon which is not yet well established. Traceability and certification of meat have improved, thanks to breeders' associations and interprofessional agreements. The breeders associations have also started insurance initiatives against BSE risks. In Italy the employment of plant protein meals would increase the total feedstuff consumption by about 7%. Direct effects of BSE could slow down the genetic progress (GP) of cattle populations within breed and country. Indirect effects on GP may also happen as a consequence of an increase in the replacement rate (rr). This

  18. Quantum efficiency of silica-coated rare-earth doped yttrium silicate

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes-Vásquez, D., E-mail: dcervant@cnyn.unam.mx [Centro de Investigación Científica y de Educación Superior de Ensenada, Carretera Ensenada-Tijuana No. 3918, Zona Playitas, C.P. 22860 Ensenada, B.C., México (Mexico); Contreras, O.E.; Hirata, G.A. [Centro de Nanociencias y Nanotecnología, Universidad Nacional Autónoma de México, Km. 107 Carretera Tijuana-Ensenada, C.P. 22800 Ensenada, B.C., México (Mexico)

    2013-11-15

    The photoluminescent properties of rare earth-activated white-emitting Y{sub 2}SiO{sub 5}:Ce,Tb nanocrystalline phosphor prepared by two different methods, pressure-assisted combustion synthesis and sol–gel, were studied. The synthesized phosphor samples were post-annealed at 1373 K and 1623 K in order to obtain the X1-Y{sub 2}SiO{sub 5} and X2-Y{sub 2}SiO{sub 5} phases, respectively, which were confirmed by X-ray diffraction measurements. Photoluminescence analysis showed the contribution of two blue-emission bands within the 380–450 nm region originating from 5d–4f transitions in Ce{sup 3+} ions and a well-defined green emission of Tb{sup 3+} ions located at 545 nm corresponding to {sup 5}D{sub 4}→{sup 7}F{sub 5} electronic transitions. Thereafter, Y{sub 2}SiO{sub 5}:Ce,Tb powders were coated with colloidal silica in order to investigate the effect of silica coatings on their luminescent properties. Absolute fluorescence quantum efficiency measurements were carefully performed, which revealed an increase of 12% of efficiency in coated compared with bare-Y{sub 2}SiO{sub 5}:Ce,Tb phosphor. -- Highlights: • Y{sub 2}SiO{sub 5}:Ce,Tb phosphor powders were successfully coated with colloidal silica. • Post-annealing treatments improved the quantum efficiency of silica-coated Y{sub 2}SiO{sub 5}:Ce,Tb phosphors. • Absolute fluorescence quantum efficiency measurements showed an increase of 12%.

  19. A volatile topic: Parsing out the details of Earth's formation through experimental metal-silicate partitioning of volatile and moderately volatile elements

    Science.gov (United States)

    Mahan, B. M.; Siebert, J.; Blanchard, I.; Badro, J.; Sossi, P.; Moynier, F.

    2017-12-01

    Volatile and moderately volatile elements display different volatilities and siderophilities, as well as varying sensitivity to thermodynamic controls (X, P, T, fO2) during metal-silicate differentiation. The experimental determination of the metal-silicate partitioning of these elements permits us to evaluate processes controlling the distribution of these elements in Earth. In this work, we have combined metal-silicate partitioning data and results for S, Sn, Zn and Cu, and input these characterizations into Earth formation models. Model parameters such as source material, timing of volatile delivery, fO2 path, and degree of impactor equilibration were varied to encompass an array of possible formation scenarios. These models were then assessed to discern plausible sets of conditions that can produce current observed element-to-element ratios (e.g. S/Zn) in the Earth's present-day mantle, while also satisfying current estimates on the S content of the core, at no more than 2 wt%. The results of our models indicate two modes of accretion that can maintain chondritic element-to-element ratios for the bulk Earth and can arrive at present-day mantle abundances of these elements. The first mode requires the late addition of Earth's entire inventory of these elements (assuming a CI-chondritic composition) and late-stage accretion that is marked by partial equilibration of large impactors. The second, possibly more intuitive mode, requires that Earth accreted - at least initially - from volatile poor material preferentially depleted in S relative to Sn, Zn, and Cu. From a chemical standpoint, this source material is most similar to type I chondrule rich (and S poor) materials (Hewins and Herzberg, 1996; Mahan et al., 2017; Amsellem et al., 2017), such as the metal-bearing carbonaceous chondrites.

  20. How much uranium is in the Earth? Predictions for geoneutrinos at KamLAND

    International Nuclear Information System (INIS)

    Fiorentini, Gianni; Lissia, Marcello; Mantovani, Fabio; Vannucci, Riccardo

    2005-01-01

    Geo-neutrino detection can determine the amount of long-lived radioactive elements within our planet, thus providing a direct test of the bulk silicate Earth (BSE) model and fixing the radiogenic contribution to the terrestrial heat. We present a prediction for the geo-neutrino signal at KamLAND as a function of the uranium mass in the Earth. The prediction is based on global mass balance, supplemented by a detailed geochemical and geophysical study of the region near the detector. The prediction is weakly dependent on mantle modeling. If BSE is correct, uranium geo-neutrinos will produce between 25 and 35 events per year and 10 32 protons at Kamioka

  1. [Basic research on BSE transmission to people].

    Science.gov (United States)

    Bodemer, W; Kaup, F J

    2002-08-01

    Prion diseases of animal and man belong to neurological diseases with amyloidal deposition of the respective proteins. As to prion disease, the cellular prionprotein is in its abnormal isoform(s) an essential component of prionprotein aggregates found in affected tissue. In contrast to all neurodegenerative diseases like Morbus Alzheimer or Huntington's disease, prion diseases are transmissible. Therefore, prion diseases were designated Transmissible Spongiform Encephalopathies (TSE). The diseases are well known since decades. Scrapie was first described around 1750, a BSE case was reported in the 1850, most likely a misdiagnosis, and in 1920/1930 the human Creutzfeldt-Jakob disease (CJD) had been described. Transmission of CJD i.e. Kuru had been suspected in the early 1950s and erronously classified as slow virus disease. The CJD transmission posed a problem to humans when transplants from CJD cases were used for treatment. Fortunately, these iatrogenic transmissions remained limited. But with the advent of BSE and appearance of variant CJD cases in the UK and some places in Europe scientists suspected that transmission from cattle to man could have happened. From animal models we know of successful transmission via several routes. Species barriers do not completely prevent transmission. Rather transmission barriers might exist controlling individual susceptibility against prions. Modes of transmission, susceptibility for transmission, identification of receptor molecules as well as molecular mechanisms of the transmission process are intensely investigated. Current knowledge let us to assume that inapparent stages of prion infection pretend a (not existing) species barrier. This inapparent infection preceeds overt disease and, thus, most re-search focuses on the development of highly sensitive assay systems for detection of minute amounts of pathological prionprotein in suspected cases. Inapparence also should warn us to underestimate BSE or human vCJD cases; at

  2. Ag Isotopic Evolution of the Mantle During Accretion: New Constraints from Pd and Ag Metal-Silicate Partitioning

    Science.gov (United States)

    Righter, K.; Schonbachler, M.

    2018-01-01

    Decay of (sup 107) Pd to (sup 107) Ag has a half-life of 6.5 times 10 (sup 6) mega-annums. Because these elements are siderophile but also volatile, they offer potential constraints on the timing of core formation as well as volatile addition. Initial modelling has shown that the Ag isotopic composition of the bulk silicate Earth (BSE) can be explained if accretion occurs with late volatile addition. These arguments were tested for sensitivity for pre-cursor Pd/Ag contents, and for a fixed Pd/Ag ratio of the BSE of 0.1. New Ag and Pd partitioning data has allowed a better understanding of the partitioning behavior of Pd and Ag during core formation. The effects of S, C and Si, and the effect of high temperature and pressure has been evaluated. We can now calculate D(Ag) and D(Pd) over the wide range of PT conditions and variable metallic liquid compositions that are known during accretion. We then use this new partitioning information to revisit the Ag isotopic composition of the BSE during accretion.

  3. Bovine Spongiform Encephalopathy (BSE, Mad Cow Disease

    Directory of Open Access Journals (Sweden)

    G. K. Bruckner

    1997-07-01

    Full Text Available Mad Cow Disease or BSE (Bovine Spongiform Encephalopathy became a household name internationally and also in South Africa. International hysteria resulted following reports of a possible link between a disease diagnosed in cattle in Britain and a variant of the disease diagnosed in humans after the presumed ingestion or contact with meat from infected cattle. The European Union instituted a ban on the importation of beef from the United Kingdom during March 1996 that had a severe effect on the beef industry in the UK and also resulted in a world wide consumer resistance against beef consumption.

  4. Stable chromium isotopic composition of meteorites and metal-silicate experiments: Implications for fractionation during core formation

    Science.gov (United States)

    Bonnand, P.; Williams, H. M.; Parkinson, I. J.; Wood, B. J.; Halliday, A. N.

    2016-02-01

    We present new mass independent and mass dependent Cr isotope compositions for meteorites measured by double spike thermal ionisation mass spectrometry. Small differences in both mass independent 53Cr and 54Cr relative to the Bulk Silicate Earth are reported and are very similar to previously published values. Carbonaceous chondrites are characterised by an excess in 54Cr compared to ordinary and enstatite chondrites which make mass independent Cr isotopes a useful tool for distinguishing between meteoritic groups. Mass dependent stable Cr isotope compositions for the same samples are also reported. Carbonaceous and ordinary chondrites are identical within uncertainty with average δ53 Cr values of - 0.118 ± 0.040 ‰ and - 0.143 ± 0.074 ‰ respectively. The heaviest isotope compositions are recorded by an enstatite chondrite and a CO carbonaceous chondrite, both of which have relatively reduced chemical compositions implying some stable Cr isotope fractionation related to redox processes in the circumstellar disk. The average δ53 Cr values for chondrites are within error of the estimate for the Bulk Silicate Earth (BSE) also determined by double spiking. The lack of isotopic difference between chondritic material and the BSE provides evidence that Cr isotopes were not fractionated during core formation on Earth. A series of high-pressure experiments was also carried out to investigate stable Cr isotope fractionation between metal and silicate and no demonstrable fractionation was observed, consistent with our meteorites data. Mass dependent Cr isotope data for achondrites suggest that Cr isotopes are fractionated during magmatic differentiation and therefore further work is required to constrain the Cr isotopic compositions of the mantles of Vesta and Mars.

  5. Tracing metal–silicate segregation and late veneer in the Earth and the ureilite parent body with palladium stable isotopes

    DEFF Research Database (Denmark)

    Creech, J. B.; Moynier, F.; Bizzarro, Martin

    2017-01-01

    Stable isotope studies of highly siderophile elements (HSE) have the potential to yield valuable insights into a range of geological processes. In particular, the strong partitioning of these elements into metal over silicates may lead to stable isotope fractionation during metal......–silicate segregation, making them sensitive tracers of planetary differentiation processes. We present the first techniques for the precise determination of palladium stable isotopes by MC-ICPMS using a 106Pd–110Pd double-spike to correct for instrumental mass fractionation. Results are expressed as the per mil...... (‰) difference in the 106Pd/105Pd ratio (δ106Pd) relative to an in-house solution standard (Pd_IPGP) in the absence of a certified Pd isotopic standard. Repeated analyses of the Pd isotopic composition of the chondrite Allende demonstrate the external reproducibility of the technique of ±0.032‰ on δ106Pd. Using...

  6. Thermochemical properties of some alkaline-earth silicates and zirconates. Fission product behaviour during molten core-concrete interactions

    Energy Technology Data Exchange (ETDEWEB)

    Huntelaar, M.E.

    1996-06-19

    This thesis aims to make a contribution to a better understanding of the chemical processes occurring during an ex-vessel MCCI accident with a western-type of nuclear reactor. Chosen is for a detailed thermochemical study of the silicates and zirconates of barium and strontium. In Chapter one a short introduction in the history of (research in) nuclear safety is given, followed by the state-of-the-art of molten core-concrete interactions in Chapter two. In both Chapters the role of chemical thermodynamics on this particular subject is dealt with. The experimental work on the silicates and zirconates of barium and strontium performed for this thesis, is described in the Chapters three, four, five, six, and parts of eight. In Chapter three the basis for all thermochemical measurements, the sample preparation is given. Because the sample preparation effects the accuracy of the thermodynamic measurements, a great deal of effort is spent in optimizing the synthesis of the silicates which resulted in the TEOS-method widely employed here. In the next Chapters the different thermochemical techniques used, are described: The low-temperature heat capacity measurements and the enthalpy increment measurements in Chapter four, the enthalpy-of-solution measurements in Chapter five, and measurements to determine the crystal structures in Chapter six. (orig.).

  7. Thermochemical properties of some alkaline-earth silicates and zirconates. Fission product behaviour during molten core-concrete interactions

    International Nuclear Information System (INIS)

    Huntelaar, M.E.

    1996-01-01

    This thesis aims to make a contribution to a better understanding of the chemical processes occurring during an ex-vessel MCCI accident with a western-type of nuclear reactor. Chosen is for a detailed thermochemical study of the silicates and zirconates of barium and strontium. In Chapter one a short introduction in the history of (research in) nuclear safety is given, followed by the state-of-the-art of molten core-concrete interactions in Chapter two. In both Chapters the role of chemical thermodynamics on this particular subject is dealt with. The experimental work on the silicates and zirconates of barium and strontium performed for this thesis, is described in the Chapters three, four, five, six, and parts of eight. In Chapter three the basis for all thermochemical measurements, the sample preparation is given. Because the sample preparation effects the accuracy of the thermodynamic measurements, a great deal of effort is spent in optimizing the synthesis of the silicates which resulted in the TEOS-method widely employed here. In the next Chapters the different thermochemical techniques used, are described: The low-temperature heat capacity measurements and the enthalpy increment measurements in Chapter four, the enthalpy-of-solution measurements in Chapter five, and measurements to determine the crystal structures in Chapter six. (orig.)

  8. Tracing metal-silicate segregation and late veneer in the Earth and the ureilite parent body with palladium stable isotopes

    Science.gov (United States)

    Creech, J. B.; Moynier, F.; Bizzarro, M.

    2017-11-01

    Stable isotope studies of highly siderophile elements (HSE) have the potential to yield valuable insights into a range of geological processes. In particular, the strong partitioning of these elements into metal over silicates may lead to stable isotope fractionation during metal-silicate segregation, making them sensitive tracers of planetary differentiation processes. We present the first techniques for the precise determination of palladium stable isotopes by MC-ICPMS using a 106Pd-110Pd double-spike to correct for instrumental mass fractionation. Results are expressed as the per mil (‰) difference in the 106Pd/105Pd ratio (δ106Pd) relative to an in-house solution standard (Pd_IPGP) in the absence of a certified Pd isotopic standard. Repeated analyses of the Pd isotopic composition of the chondrite Allende demonstrate the external reproducibility of the technique of ±0.032‰ on δ106Pd. Using these techniques, we have analysed Pd stable isotopes from a range of terrestrial and extraterrestrial samples. We find that chondrites define a mean δ106Pdchondrite = -0.19 ± 0.05‰. Ureilites reveal a weak trend towards heavier δ106Pd with decreasing Pd content, similar to recent findings based on Pt stable isotopes (Creech et al., 2017), although fractionation of Pd isotopes is significantly less than for Pt, possibly related to its weaker metal-silicate partitioning behaviour and the limited field shift effect. Terrestrial mantle samples have a mean δ106Pdmantle = -0.182 ± 0.130‰, which is consistent with a late-veneer of chondritic material after core formation.

  9. Silicate diagenesis in deep-sea sediments from the Tonga fore-arc (SW Pacific): a strontium and rare earth elements signature

    International Nuclear Information System (INIS)

    Vitali, F.; Stille, P.; Blanc, G.; Toulkeridis, T.

    2000-01-01

    87 Sr/ 86 Sr isotopic ratios, strontium and Rare Earth Element concentrations obtained on volcano-sedimentary rocks and separated clay mineral and zeolite fractions reveal a formation by pore water-volcanic rock interaction for most of the hydrous silicate minerals of the Site 841 ODP collected from the Tonga fore-arc. Unusual strontium concentrations and isotopic ratios recorded in the Miocene tuffs associated with specific REE patterns indicate that the formation of these hydrous silicates does not follow a simple burial diagenesis model, but was related to the cooling of intruding basaltic sills in the Miocene volcano-sedimentary series. Migration of strontium into the pore water in response to the heat flow induced the formation of Sr-bearing zeolites such as clinoptilolite, heulandite and chabazite. No evidence of any influence of a further thermal pulse in the Eocene rhyolitic tuffs could be found. As recorded by the chemistry of their clay mineral fraction, the rhyolitic tuffs developed a polyphasic diagenetic process, which might have been influenced by a possible circulation of a fluid into structurally weak areas. (authors)

  10. Understanding the pattern of the BSE Sensex

    Science.gov (United States)

    Mukherjee, I.; Chatterjee, Soumya; Giri, A.; Barat, P.

    2017-09-01

    An attempt is made to understand the pattern of behaviour of the BSE Sensex by analysing the tick-by-tick Sensex data for the years 2006 to 2012 on yearly as well as cumulative basis using Principal Component Analysis (PCA) and its nonlinear variant Kernel Principal Component Analysis (KPCA). The latter technique ensures that the nonlinear character of the interactions present in the system gets captured in the analysis. The analysis is carried out by constructing vector spaces of varying dimensions. The size of the data set ranges from a minimum of 360,000 for one year to a maximum of 2,520,000 for seven years. In all cases the prices appear to be highly correlated and restricted to a very low dimensional subspace of the original vector space. An external perturbation is added to the system in the form of noise. It is observed that while standard PCA is unable to distinguish the behaviour of the noise-mixed data from that of the original, KPCA clearly identifies the effect of the noise. The exercise is extended in case of daily data of other stock markets and similar results are obtained.

  11. Bovine Spongiform Encephalopathy (BSE), or Mad Cow Disease

    Science.gov (United States)

    ... the CDC Bovine Spongiform Encephalopathy (BSE), or Mad Cow Disease Note: Javascript is disabled or is not ... spongiform encephalopathy) is a progressive neurological disorder of cattle that results from infection by an unusual transmissible ...

  12. Group separation of rare earth elements by liquid-liquid extraction for the neutron activation analysis of silicate rocks

    International Nuclear Information System (INIS)

    Wyttenbach, A.; Bajo, S.; Tobler, L.

    1983-01-01

    Rare earth elements are isolated as a group from neutron activated rock samples by a new radiochemical procedure based on extraction with thenoyltrifluoracetone/phenanthroline in CHCl 3 . The procedure consists of three extraction steps, obviates the use of inactive carriers and gives practically quantitative chemical yields, thereby avoiding fractionation of the individual rare earths. Details of the dissolution, chemical separations. and counting procedure are given together with an analysis of BCR-1. (author)

  13. Boson peak of alkali and alkaline earth silicate glasses: influence of the nature and size of the network-modifying cation.

    Science.gov (United States)

    Richet, Nicolas F

    2012-01-21

    The influence of the size of the alkaline earth cation on the boson peak of binary metasilicate glasses, MSiO(3) (M = Mg, Ca, Sr, Ba), has been investigated from vibrational densities of states determined by inversion of low-temperature heat capacities. As given both by C(p)/T(3) and g(ω)/ω(2), the intensity of the boson peak undergoes a 7-fold increase from Mg to Ba, whereas its temperature and frequency correlatively decrease from 18 to 10 K and from 100 to 20 cm(-1), respectively. The boson peak results from a combination of librations of SiO(4) tetrahedra and localized vibrations of network-modifying cations with non-bridging oxygens whose contribution increases markedly with the ionic radius of the alkaline earth. As a function of ionic radii, the intensity for Sr and Ba varies in the same way as previously found for alkali metasilicate glasses. The localized vibrations involving alkali and heavy alkaline earth cations appear to be insensitive to the overall glass structure. Although the new data are coherent with an almost linear relationship between the temperature of the boson peak and transverse sound velocity, pure SiO(2) and SiO(2)-rich glasses make marked exceptions to this trend because of the weak transverse character of SiO(4) librations. Finally, the universality of the calorimetric boson peak is again borne out because all data for silicate glasses collapse on the same master curve when plotted in a reduced form (C(P)∕/T(3))/(C(P)/T(3))(b) vs. T/T(b). © 2012 American Institute of Physics

  14. [Effects of BSE on consumer attitudes and behavior].

    Science.gov (United States)

    von Alvenisleben, R

    2002-08-01

    The extremely high media emphasis of the BSE issue during the period December 2000 to February 2001 has caused considerable short term public concern. A significant amount of this concern was due to an intensive communication of pictures. Pictures are "fast shots into the brain" (Kroeber-Riel). Pictured stimuli run under the cognitive control of the recipients effecting the consumer below the threshold of consciousness. However, the issue has fallen into oblivion very soon. In summer 2001 the public concern was not higher than before the BSE crisis. The perception of product quality regained a "normal level". The public concern has caused a considerable decline of the demand for beef and an increase of demand for substitutes and organic meat. When the media emphasis of the BSE issue diminished, the beef demand recovered but did not reach the pre-crisis level again. However, the BSE crisis has intensified animal welfare concerns, polarized public opinion about food and agriculture and had big effects in the political sphere. Furthermore, the BSE crisis has led to additional--politically supported--activities of the organic food suppliers causing a further growth of this market segment.

  15. Silicates in Alien Asteroids

    Science.gov (United States)

    2009-01-01

    This plot of data from NASA's Spitzer Space Telescopes shows that asteroid dust around a dead 'white dwarf' star contains silicates a common mineral on Earth. The data were taken primarily by Spitzer's infrared spectrograph, an instrument that breaks light apart into its basic constituents. The yellow dots show averaged data from the spectrograph, while the orange triangles show older data from Spitzer's infrared array camera. The white dwarf is called GD 40.

  16. High-precision Mg isotope measurements of terrestrial and extraterrestrial material by HR-MC-ICPMS—implications for the relative and absolute Mg isotope composition of the bulk silicate Earth

    DEFF Research Database (Denmark)

    Bizzarro, Martin; Paton, Chad; Larsen, Kirsten Kolbjørn

    2011-01-01

    -isotope composition for Earth’s mantle – and hence that of the bulk silicate Earth – to be 25Mg/24Mg 1/4 0.126896 ¿ 0.000025 and 26Mg/24Mg 1/4 0.139652 ¿ 0.000033. Given the restricted range of m25Mg obtained for bulk planetary material by the sample-standard bracketing technique and the excellent agreement between...

  17. Review on the epidemiology and dynamics of BSE epidemics.

    Science.gov (United States)

    Ducrot, Christian; Arnold, Mark; de Koeijer, Aline; Heim, Dagmar; Calavas, Didier

    2008-01-01

    The paper describes how the comprehensive surveillance of bovine spongiform encephalopathy (BSE) and studies carried out on these data has enhanced our knowledge of the epidemiology of BSE. Around 7, 000 BSE cases were detected through the screening of about 50 million cattle with rapid tests in Europe. It confirmed that the clinical surveillance had a poor capacity to detect cases, and also showed the discrepancy of this passive surveillance efficiency between regions and production types (dairy/beef). Other risk factors for BSE were being in a dairy herd (three times more than beef), having a young age at first calving (for dairy cattle), being autumn-born (dairy and beef), and being in a herd with a very high milk yield. These findings focus the risk on the feeding regimen of calves/heifers. Several epidemiological studies across countries suggest that the feedborne source related to meat and bone meal (MBM) is the only substantiated route of infection - even after the feed ban -, while it is not possible to exclude maternal transmission or milk replacers as a source of some infections. In most European countries, the average age of the cases is increasing over time and the prevalence decreasing, which reflects the effectiveness of control measures. Consistent results on the trend of the epidemic were obtained using back-calculation modelling, the R(0) approach and Age-Period-Cohort models. Furthermore, active surveillance also resulted in the finding of atypical cases. These are distinct from previously found BSE and classified in two different forms based on biochemical characteristics; their prevalence is very low (36 cases up to 1st September 2007), affected animals were old and some of them displayed clinical signs. The origin and possibility of natural transmission is unknown.

  18. Rare Earth Element Behavior During Incongruent Weathering and Varying Discharge Conditions in Silicate Dominated River Systems: The Australian Victorian Alps

    Science.gov (United States)

    Hagedorn, K. B.; Cartwright, I.

    2008-12-01

    The distribution of rare earth elements (REE) and trace elements was measured by ICP-MS on fresh, slightly weathered and weathered granite and surface water samples from a network of 11 pristine rivers draining the Australian Victorian Alps during (i) high and (ii) low discharge conditions. River water REE concentrations are largely derived from atmospheric precipitation (rain, snow), as indicated by similar Chondrite normalized REE patterns (higher LREE over HREE; negative Ce anomalies, positive Eu anomalies) and similar total REE concentrations during both dry and wet seasons. Calculations based on the covariance between REE and Cl concentrations and oxygen and hydrogen isotopes indicate precipitation input coupled with subsequent evaporation may account for 30% o 100% of dissolved REE in stream waters. The dissolved contribution to the granitic substratum to stream water comes mainly from the transformation of plagioclase to smectite, kaolinite and gibbsite and minor apatite dissolution. However, since most REE of the regional granite are present in accessory minerals (titanite, zircon, etc.) they do not significantly contribute to the river REE pool. REE concentrations drop sharply downstream as a result of dilution and chemical attenuation. A trend of downstream enrichment of the heavier REE is due to selective partitioning of the lighter REE (as both free REE or REECO3 complexes) to hydrous oxides of suspended Al which, in turn, is controlled by a downstream increase of pH to values > 6.1 (for free REE) and > 7.3 (for REECO3 complexes). Although most circumneutral waters were supersaturated with REE phosphate compounds, precipitation of LnPO4 is not believed to have been a dominant process because the predicted phosphate fractionation pattern is inconsistent with the observed trends. Negative saturation indices of hydrous ferric oxides also militate against surface complexation onto goethite. Instead, REE attenuation most likely resulted from adsorption onto

  19. Rare earth silicate (Ce, La, Nd, Ca, Th) SiO4 and cheralite (Th, Ca, Ce, La) (Psi)O4 are the responsible minerals for the anomalies of Morro de Ferro

    International Nuclear Information System (INIS)

    Fujimori, K.

    1982-01-01

    The Rare Earth silicate (La, Ce, Nd, Ca, Th)SiO 4 and cheralite (identified by Prof. Freeborn on a sample prepared from drilling core) were recognized as the most probable radioactive minerals that gave origin to high radioactive anomaly at Morro do Ferro hill together with coffinite, thorite, pyrochlore, apatite, etc., that are found in small quantity. The acids produced by decomposition of pyrite and fluorite have etched these radioactive minerals giving the high radioactive anomaly caracterized by high grade desiquilibrium of 232 Th serie. (Author) [pt

  20. Silicate glasses

    International Nuclear Information System (INIS)

    Lutze, W.

    1988-01-01

    Vitrification of liquid high-level radioactive wastes has received the greatest attention, world-wide, compared to any other HLW solidification process. The waste form is a borosilicate-based glass. The production of phosphate-based glass has been abandoned in the western world. Only in the Soviet Union are phosphate-based glasses still being developed. Vitrification techniques, equipment and processes and their remote operation have been developed and studied for almost thirty years and have reached a high degree of technical maturity. Industrial demonstration of the vitrification process has been in progress since 1978. This chapter is a survey of world-wide research and development efforts in nuclear waste glasses and its production technology. The principal glasses considered are silicate glasses which contain boron, i.e., borosilicate glasses

  1. SOA and Web Technology for Building BSE Market Map

    Directory of Open Access Journals (Sweden)

    Claudiu VINTE

    2012-01-01

    Full Text Available Visual representation as a map of the stock market data can offer access, in a quick and rele-vant manner for human participants, to the overall state of the market at a given point in time. The purpose of this paper is to present the results of our academic research upon building the market map for Bucharest Stock Exchange (BSE. We will focus on the algorithm for generat-ing the market map, the system architecture, and web technology employed for capturing the required data and making the map publicly available through the portal www.bursa.ase.ro. Mathematics Subject Classification: 68M14 (Distributed Systems

  2. Bankruptcy Risk in IFRS Era. Case Study on BSE Companies

    Directory of Open Access Journals (Sweden)

    Valentin BURCA

    2013-12-01

    Full Text Available The path of international accounting convergence is, unanimously accepted by all decision makers of the international financial reporting environment, as being the best solution towards reducing differences in international accounting. The idea of core standards is embraced by our country, too, the proof being the last legislative changes in Romanian accounting framework. This study aims to highlight a small part of the economic consequences of the decision to extend the mandatory use of IFRS standards to the statutory financial statements, also. More exactly we will underline the changes registered at the level of bankruptcy risk measureson a samples of companies listed on BSE.

  3. CNS histopathology on 203 bovines with clinical suspicion of BSE in Denmark 2001 to 2016

    DEFF Research Database (Denmark)

    Jensen, Tim Kåre

    2017-01-01

    During 2001 to 2016 a total of 203 bovines were submitted to the instutute with clinical suspicion of having BSE. In two cases BSE was confirmed. The most common differential diagnosis was listeriosis, found in 54% of the cases. Listeriosis was characterized by multifocal, necrotizing, non-suppur...

  4. CNS histopathology on bovines with clinical suspicion of BSE in Denmark 2001 to 2011

    DEFF Research Database (Denmark)

    Jensen, Tim Kåre

    During2001 to 2011 a total of 195 bovines were submitted to the instutute with clinical suspicion of having BSE. In two cases BSE was confirmed. The most common differential diagnosis was listeriosis, found in 54% of the cases. Listeriosis was characterized by multifocal, necrotizing, non-suppura...

  5. Modelling BSE trend over time in Europe, a risk assessment perspective

    NARCIS (Netherlands)

    Ducrot, C.; Sala, C.; Ru, G.; Koeijer, de A.A.; Sheridan, H.; Saegerman, C.; Selhorst, T.; Arnold, M.; Polak, M.P.; Calavas, D.

    2010-01-01

    BSE is a zoonotic disease that caused the emergence of variant Creuzfeldt-Jakob disease in the mid 1990s. The trend of the BSE epidemic in seven European countries was assessed and compared, using Age-Period-Cohort and Reproduction Ratio modelling applied to surveillance data 2001-2007. A strong

  6. Monitoring and analysis of bovine spongiform encephalopathy (BSE) testing in Denmark using statistical models

    DEFF Research Database (Denmark)

    Paisley, Larry

    2002-01-01

    The evolution of monitoring and surveillance for bovine spongiform encephalopathy (BSE) from the phase of passive surveillance that began in the United Kingdom in 1988 until the present is described. Currently, surveillance for BSE in Europe consists of mass testing of cattle slaughtered for human...

  7. Modelling BSE trend over time in Europe, a risk assessment perspective.

    Science.gov (United States)

    Ducrot, Christian; Sala, Carole; Ru, Giuseppe; de Koeijer, Aline; Sheridan, Hazel; Saegerman, Claude; Selhorst, Thomas; Arnold, Mark; Polak, Miroslaw P; Calavas, Didier

    2010-06-01

    BSE is a zoonotic disease that caused the emergence of variant Creuzfeldt-Jakob disease in the mid 1990s. The trend of the BSE epidemic in seven European countries was assessed and compared, using Age-Period-Cohort and Reproduction Ratio modelling applied to surveillance data 2001-2007. A strong decline in BSE risk was observed for all countries that applied control measures during the 1990s, starting at different points in time in the different countries. Results were compared with the type and date of the BSE control measures implemented between 1990 and 2001 in each country. Results show that a ban on the feeding of meat and bone meal (MBM) to cattle alone was not sufficient to eliminate BSE. The fading out of the epidemic started shortly after the complementary measures targeted at controlling the risk in MBM. Given the long incubation period, it is still too early to estimate the additional effect of the ban on the feeding of animal protein to all farm animals that started in 2001. These results provide new insights in the risk assessment of BSE for cattle and Humans, which will especially be useful in the context of possible relaxing BSE surveillance and control measures.

  8. The price of the precautionary principle: cost-effectiveness of BSE intervention strategies in The Netherlands.

    Science.gov (United States)

    Benedictus, A; Hogeveen, H; Berends, B R

    2009-06-01

    Since 1996, bovine spongiform encephalopathy (BSE) in cattle has been linked to a new variant of Creutzfeldt-Jakob disease (vCJD), a fatal brain disease in man. This paper assessed the cost-effectiveness of BSE control strategies instituted by the European Commission. In a Monte Carlo simulation model, a non-intervention baseline scenario was compared to three intervention strategies: removal of specified risk materials from slaughter animals, post-mortem testing for BSE and the culling of feed and age cohorts of BSE cases. The food risk in the baseline scenario ranged from 16.98 lost life years in 2002 to 2.69 lost life years in 2005. Removing specified risk materials removal practices, post-mortem testing and post-mortem testing plus cohort culling reduced this risk with 93%, 82.7% and 83.1%. The estimated cost-effectiveness of all BSE measures in The Netherlands ranged from 4.3 million euros per life year saved in 2002 to 17.7 million euros in 2005. It was discussed that the cost-effectiveness of BSE control strategies will further deviate from regular health economics thresholds as BSE prevalence and incidence declines.

  9. Chondritic Mn/Na ratio and limited post-nebular volatile loss of the Earth

    Science.gov (United States)

    Siebert, Julien; Sossi, Paolo A.; Blanchard, Ingrid; Mahan, Brandon; Badro, James; Moynier, Frédéric

    2018-03-01

    The depletion pattern of volatile elements on Earth and other differentiated terrestrial bodies provides a unique insight as to the nature and origin of planetary building blocks. The processes responsible for the depletion of volatile elements range from the early incomplete condensation in the solar nebula to the late de-volatilization induced by heating and impacting during planetary accretion after the dispersion of the H2-rich nebular gas. Furthermore, as many volatile elements are also siderophile (metal-loving), it is often difficult to deconvolve the effect of volatility from core formation. With the notable exception of the Earth, all the differentiated terrestrial bodies for which we have samples have non-chondritic Mn/Na ratios, taken as a signature of post-nebular volatilization. The bulk silicate Earth (BSE) is unique in that its Mn/Na ratio is chondritic, which points to a nebular origin for the depletion; unless the Mn/Na in the BSE is not that of the bulk Earth (BE), and has been affected by core formation through the partitioning of Mn in Earth's core. Here we quantify the metal-silicate partitioning behavior of Mn at deep magma ocean pressure and temperature conditions directly applicable to core formation. The experiments show that Mn becomes more siderophile with increasing pressure and temperature. Modeling the partitioning of Mn during core formation by combining our results with previous data at lower P-T conditions, we show that the core likely contains a significant fraction (20 to 35%) of Earth's Mn budget. However, we show that the derived Mn/Na value of the bulk Earth still lies on the volatile-depleted end of a trend defined by chondritic meteorites in a Mn/Na vs Mn/Mg plot, which tend to higher Mn/Na with increasing volatile depletion. This suggests that the material that formed the Earth recorded similar chemical fractionation processes for moderately volatile elements as chondrites in the solar nebula, and experienced limited post

  10. Evaluation of the cumulative evidence for freedom from BSE in birth cohorts

    DEFF Research Database (Denmark)

    Böhning, Dankmar; Greiner, Matthias

    2006-01-01

    Substantial resources are used for surveillance of bovine spongiform encephalopathy (BSE) despite an extremely low detection rate, especially in healthy slaughtered cattle. We have developed a method based on the geometric waiting time distribution to establish and update the statistical evidence...... for BSE-freedom for defined birth cohorts using continued surveillance data. The results suggest that currently (data included till September 2004) a birth cohort of Danish cattle born after March 1999 is free from BSE with probability (power) of 0.8746 or 0.8509, depending on the choice of a model...

  11. A Cesium Rare-Earth Silicate Cs3 RESi6 O15 (RE=Dy-Lu, Y, In): The Parent of an Unusual Structural Class Featuring a Remarkable 57 Å Unit Cell Axis.

    Science.gov (United States)

    Terry, Rylan; Vinton, Daniel; McMillen, Colin D; Kolis, Joseph W

    2018-02-19

    The structure of Cs 3 RESi 6 O 15 , where RE=Dy-Lu, Y, In, is unusual in that it contains octahedrally coordinated rare-earth ions; their relative orientation dictates the structure, as they rotate about the c-axis supported by the cyclic Si 6 O 15 framework. The repeat unit of the rotation is eight units generating a very long (ca. 57 Å) unit cell axis. This unusual repeat unit is created by the structural flexibility of the hexasilicate ring, which is in turn affected by the size of the rare earth ion as well as the size of alkali ion residing within the silicate layers. Previous work showed for the smaller Sc 3+ ion, the rotation of the octahedra is not sufficient to achieve closure at an integral repeat unit and an incommensurate structure results. The products are prepared as large, high quality single crystals using a high-temperature (650 °C) hydrothermal method with CsOH and F - mineralizers. The presence of fluoride is essential to the formation of the product. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. A cesium rare-earth silicate Cs{sub 3}RESi{sub 6}O{sub 15} (RE = Dy-Lu, Y, In). The parent of an unusual structural class featuring a remarkable 57 Aa unit cell axis

    Energy Technology Data Exchange (ETDEWEB)

    Terry, Rylan; Vinton, Daniel; McMillen, Colin D.; Kolis, Joseph W. [Department of Chemistry and Center for Optical Materials Science and Engineering Technologies (COMSET), Clemson University, H.L. Hunter Laboratories (United States)

    2018-02-19

    The structure of Cs{sub 3}RESi{sub 6}O{sub 15}, where RE = Dy-Lu, Y, In, is unusual in that it contains octahedrally coordinated rare-earth ions; their relative orientation dictates the structure, as they rotate about the c-axis supported by the cyclic Si{sub 6}O{sub 15} framework. The repeat unit of the rotation is eight units generating a very long (ca. 57 Aa) unit cell axis. This unusual repeat unit is created by the structural flexibility of the hexasilicate ring, which is in turn affected by the size of the rare earth ion as well as the size of alkali ion residing within the silicate layers. Previous work showed for the smaller Sc{sup 3+} ion, the rotation of the octahedra is not sufficient to achieve closure at an integral repeat unit and an incommensurate structure results. The products are prepared as large, high quality single crystals using a high-temperature (650 C) hydrothermal method with CsOH and F{sup -} mineralizers. The presence of fluoride is essential to the formation of the product. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. Pruritus is a common feature in sheep infected with the BSE agent.

    Science.gov (United States)

    Konold, Timm; Bone, Gemma; Vidal-Diez, Alberto; Tortosa, Raul; Davis, Andrew; Dexter, Glenda; Hill, Peter; Jeffrey, Martin; Simmons, Marion M; Chaplin, Melanie J; Bellworthy, Susan J; Berthelin-Baker, Christine

    2008-04-29

    The variability in the clinical or pathological presentation of transmissible spongiform encephalopathies (TSEs) in sheep, such as scrapie and bovine spongiform encephalopathy (BSE), has been attributed to prion protein genotype, strain, breed, clinical duration, dose, route and type of inoculum and the age at infection. The study aimed to describe the clinical signs in sheep infected with the BSE agent throughout its clinical course to determine whether the clinical signs were as variable as described for classical scrapie in sheep. The clinical signs were compared to BSE-negative sheep to assess if disease-specific clinical markers exist. Forty-seven (34%) of 139 sheep, which comprised 123 challenged sheep and 16 undosed controls, were positive for BSE. Affected sheep belonged to five different breeds and three different genotypes (ARQ/ARQ, VRQ/VRQ and AHQ/AHQ). None of the controls or BSE exposed sheep with ARR alleles were positive. Pruritus was present in 41 (87%) BSE positive sheep; the remaining six were judged to be pre-clinically infected. Testing of the response to scratching along the dorsum of a sheep proved to be a good indicator of clinical disease with a test sensitivity of 85% and specificity of 98% and usually coincided with weight loss. Clinical signs that were displayed significantly earlier in BSE positive cases compared to negative cases were behavioural changes, pruritic behaviour, a positive scratch test, alopecia, skin lesions, teeth grinding, tremor, ataxia, loss of weight and loss of body condition. The frequency and severity of each specific clinical sign usually increased with the progression of disease over a period of 16-20 weeks. Our results suggest that BSE in sheep presents with relatively uniform clinical signs, with pruritus of increased severity and abnormalities in behaviour or movement as the disease progressed. Based on the studied sheep, these clinical features appear to be independent of breed, affected genotype, dose, route

  14. Pruritus is a common feature in sheep infected with the BSE agent

    Directory of Open Access Journals (Sweden)

    Jeffrey Martin

    2008-04-01

    Full Text Available Abstract Background The variability in the clinical or pathological presentation of transmissible spongiform encephalopathies (TSEs in sheep, such as scrapie and bovine spongiform encephalopathy (BSE, has been attributed to prion protein genotype, strain, breed, clinical duration, dose, route and type of inoculum and the age at infection. The study aimed to describe the clinical signs in sheep infected with the BSE agent throughout its clinical course to determine whether the clinical signs were as variable as described for classical scrapie in sheep. The clinical signs were compared to BSE-negative sheep to assess if disease-specific clinical markers exist. Results Forty-seven (34% of 139 sheep, which comprised 123 challenged sheep and 16 undosed controls, were positive for BSE. Affected sheep belonged to five different breeds and three different genotypes (ARQ/ARQ, VRQ/VRQ and AHQ/AHQ. None of the controls or BSE exposed sheep with ARR alleles were positive. Pruritus was present in 41 (87% BSE positive sheep; the remaining six were judged to be pre-clinically infected. Testing of the response to scratching along the dorsum of a sheep proved to be a good indicator of clinical disease with a test sensitivity of 85% and specificity of 98% and usually coincided with weight loss. Clinical signs that were displayed significantly earlier in BSE positive cases compared to negative cases were behavioural changes, pruritic behaviour, a positive scratch test, alopecia, skin lesions, teeth grinding, tremor, ataxia, loss of weight and loss of body condition. The frequency and severity of each specific clinical sign usually increased with the progression of disease over a period of 16–20 weeks. Conclusion Our results suggest that BSE in sheep presents with relatively uniform clinical signs, with pruritus of increased severity and abnormalities in behaviour or movement as the disease progressed. Based on the studied sheep, these clinical features appear to

  15. Generation of a persistently infected MDBK cell line with natural bovine spongiform encephalopathy (BSE.

    Directory of Open Access Journals (Sweden)

    Dongseob Tark

    Full Text Available Bovine spongiform encephalopathy (BSE is a zoonotic transmissible spongiform encephalopathy (TSE thought to be caused by the same prion strain as variant Creutzfeldt-Jakob disease (vCJD. Unlike scrapie and chronic wasting disease there is no cell culture model allowing the replication of proteinase K resistant BSE (PrPBSE and the further in vitro study of this disease. We have generated a cell line based on the Madin-Darby Bovine Kidney (MDBK cell line over-expressing the bovine prion protein. After exposure to naturally BSE-infected bovine brain homogenate this cell line has shown to replicate and accumulate PrPBSE and maintain infection up to passage 83 after initial challenge. Collectively, we demonstrate, for the first time, that the BSE agent can infect cell lines over-expressing the bovine prion protein similar to other prion diseases. These BSE infected cells will provide a useful tool to facilitate the study of potential therapeutic agents and the diagnosis of BSE.

  16. Origin of convex tetrads in rare earth element patterns of hydrothermally altered siliceous igneous rocks from the Zinnwald Sn–W deposit, Germany

    OpenAIRE

    T. Monecke; Peter Dulski; U. Kempe

    2007-01-01

    The chondrite-normalized rare earth element (REE) patterns of whole rock samples from evolved granitic systems hosting rare metal deposits sometimes show a split into four consecutive curved segments, referred to as tetrads. In the present contribution, a rigorous statistical method is proposed that can be used to test whether geological significance should be attributed to tetrads that are only of limited size. The method involves a detailed evaluation of element and sample specific random a...

  17. The Development of a Cultural-Based Educational Program to Enhance Breast Self-Examination (BSE Self-Efficacy

    Directory of Open Access Journals (Sweden)

    Juanita Juanita

    2012-08-01

    Full Text Available Purpose: To develop the educational program which is appropriate with Islamic culture in order to enhance BSE self-efficacy of nursing students and thus promote BSE practice. Method: This study is a development research study which is consisting of three phases including: 1 reviewing several existing BSE educational programs; 2 program design based on SCT and Islamic culture; and 3 program validation by three experts. Result: Based on previous studies, the most appropriate theory to enhance self-efficacy was Social Cognitive Theory (SCT because this theory provides several strategies to increase the self-efficacy. Further, the program that used Islamic culture was more appropriate to increase BSE practice among Muslim women. As a result, the newly developed program was developed used SCT and Islamic culture. This program was comprised of four sessions including: 1 exploring Islamic mandate on prevention and individual responsibility in health promotion, and culture-related beliefs toward BSE, 2 health education by conducting lecturing session and watching a video about BSE procedures, 3 BSE training activities including BSE demonstration and return demonstration, 4 follow-up by conducting a meeting. Conclusion: The cultural-based educational program for enhancing BSE self-efficacy and promoting BSE is a program using multifaceted methods. It designed based on a review of the literature from previous studies and were supported by research findings on experimental studies in other population. Keywords: Cultural, Educational program development, Breast self-examination, Self-efficacy.

  18. Earth

    CERN Document Server

    Carter, Jason

    2017-01-01

    This curriculum-based, easy-to-follow book teaches young readers about Earth as one of the eight planets in our solar system in astronomical terms. With accessible text, it provides the fundamental information any student needs to begin their studies in astronomy, such as how Earth spins and revolves around the Sun, why it's uniquely suitable for life, its physical features, atmosphere, biosphere, moon, its past, future, and more. To enhance the learning experience, many of the images come directly from NASA. This straightforward title offers the fundamental information any student needs to sp

  19. Olivine/melt transition metal partitioning, melt composition, and melt structure—Melt polymerization and Qn-speciation in alkaline earth silicate systems

    Science.gov (United States)

    Mysen, Bjorn O.

    2008-10-01

    govern their solubility behavior in silicate melts.

  20. Thermodynamics and Kinetics of Silicate Vaporization

    Science.gov (United States)

    Jacobson, Nathan S.; Costa, Gustavo C. C.

    2015-01-01

    Silicates are a common class of materials that are often exposed to high temperatures. The behavior of these materials needs to be understood for applications as high temperature coatings in material science as well as the constituents of lava for geological considerations. The vaporization behavior of these materials is an important aspect of their high temperature behavior and it also provides fundamental thermodynamic data. The application of Knudsen effusion mass spectrometry (KEMS) to silicates is discussed. There are several special considerations for silicates. The first is selection of an appropriate cell material, which is either nearly inert or has well-understood interactions with the silicate. The second consideration is proper measurement of the low vapor pressures. This can be circumvented by using a reducing agent to boost the vapor pressure without changing the solid composition or by working at very high temperatures. The third consideration deals with kinetic barriers to vaporization. The measurement of these barriers, as encompassed in a vaporization coefficient, is discussed. Current measured data of rare earth silicates for high temperature coating applications are discussed. In addition, data on magnesium-iron-silicates (olivine) are presented and discussed.

  1. Lattice thermal conductivity of silicate glasses at high pressures

    Science.gov (United States)

    Chang, Y. Y.; Hsieh, W. P.

    2016-12-01

    Knowledge of the thermodynamic and transport properties of magma holds the key to understanding the thermal evolution and chemical differentiation of Earth. The discovery of the remnant of a deep magma ocean above the core mantle boundary (CMB) from seismic observations suggest that the CMB heat flux would strongly depend on the thermal conductivity, including lattice (klat) and radiative (krad) components, of dense silicate melts and major constituent minerals around the region. Recent measurements on the krad of dense silicate glasses and lower-mantle minerals show that krad of dense silicate glasses could be significantly smaller than krad of the surrounding solid mantle phases, and therefore the dense silicate melts would act as a thermal insulator in deep lower mantle. This conclusion, however, remains uncertain due to the lack of direct measurements on the lattice thermal conductivity of silicate melts under relevant pressure-temperature conditions. Besides the CMB, magmas exist in different circumstances beneath the surface of the Earth. Chemical compositions of silicate melts vary with geological and geodynamic settings of the melts and have strong influences on their thermal properties. In order to have a better view of heat transport within the Earth, it is important to study compositional and pressure dependences of thermal properties of silicate melts. Here we report experimental results on lattice thermal conductivities of silicate glasses with basaltic and rhyolitic compositions up to Earth's lower mantle pressures using time-domain thermoreflectance coupled with diamond-anvil cell techniques. This study not only provides new data for the thermal conductivity of silicate melts in the Earth's deep interior, but is crucial for further understanding of the evolution of Earth's complex internal structure.

  2. Nanostructured silicate polymer concrete

    Directory of Open Access Journals (Sweden)

    Figovskiy Oleg L'vovich

    2014-03-01

    Full Text Available It has been known that acid-resistant concretes on the liquid glass basis have high porosity (up to 18~20 %, low strength and insufficient water resistance. Significant increasing of silicate matrix strength and density was carried out by incorporation of special liquid organic alkali-soluble silicate additives, which block superficial pores and reduce concrete shrinkage deformation. It was demonstrated that introduction of tetrafurfuryloxisilane additive sharply increases strength, durability and shock resistance of silicate polymer concrete in aggressive media. The experiments showed, that the strength and density of silicate polymer concrete increase in case of decreasing liquid glass content. The authors obtained optimal content of silicate polymer concrete, which possesses increased strength, durability, density and crack-resistance. Diffusive permeability of concrete and its chemical resistance has been investigated in various corroding media.

  3. Rapid and discriminatory diagnosis of scrapie and BSE in retro-pharyngeal lymph nodes of sheep

    Directory of Open Access Journals (Sweden)

    van Zijderveld Fred G

    2006-06-01

    Full Text Available Abstract Background Diagnosis based on prion detection in lymph nodes of sheep and goats can improve active surveillance for scrapie and, if it were circulating, for bovine spongiform encephalopathy (BSE. With sizes that allow repetitive testing and a location that is easily accessible at slaughter, retropharyngeal lymph nodes (RLN are considered suitable organs for testing. Western blotting (WB of brain homogenates is, in principle, a technique well suited to both detect and discriminate between scrapie and BSE. In this report, WB is developed for rapid diagnosis in RLN and to study biochemical characteristics of PrPres. Results Optimal PrPres detection in RLN by WB was achieved by proper tissue processing, antibody choice and inclusion of a step for PrPresconcentration. The analyses were performed on three different sheep sources. Firstly, in a study with preclinical scrapie cases, WB of RLN from infected sheep of VRQ/VRQ genotype – VRQ represents, respectively, polymorphic PrP amino acids 136, 154, and 171 – allowed a diagnosis 14 mo earlier compared to WB of brain stem. Secondly, samples collected from sheep with confirmed scrapie in the course of passive and active surveillance programmes in the period 2002–2003 yielded positive results depending on genotype: all sheep with genotypes ARH/VRQ, VRQ/VRQ, and ARQ/VRQ scored positive for PrPres, but ARQ/ARQ and ARR/VRQ were not all positive. Thirdly, in an experimental BSE study, detection of PrPres in all 11 ARQ/ARQ sheep, including 7 preclinical cases, was possible. In all instances, WB and IHC were almost as sensitive. Moreover, BSE infection could be discriminated from scrapie infection by faster electrophoretic migration of the PrPres bands. Using dual antibody staining with selected monoclonal antibodies like 12B2 and L42, these differences in migration could be employed for an unequivocal differentiation between BSE and scrapie. With respect to glycosylation of PrPres, BSE cases

  4. Causality and correlations between BSE and NYSE indexes: A Janus faced relationship

    Science.gov (United States)

    Neeraj; Panigrahi, Prasanta K.

    2017-09-01

    We study the multi-scale temporal correlations and causality connections between the New York Stock Exchange (NYSE) and Bombay Stock Exchange (BSE) monthly average closing price indexes for a period of 300 months, encompassing the time period of the liberalisation of the Indian economy and its gradual global exposure. In multi-scale analysis; clearly identifiable 1, 2 and 3 year non-stationary periodic modulations in NYSE and BSE have been observed, with NYSE commensurating changes in BSE at 3 years scale. Interestingly, at one year time scale, the two exchanges are phase locked only during the turbulent times, while at the scale of three year, in-phase nature is observed for a much longer time frame. The two year time period, having characteristics of both one and three year variations, acts as the transition regime. The normalised NYSE's stock value is found to Granger cause those of BSE, with a time lag of 9 months. Surprisingly, observed Granger causality of high frequency variations reveals BSE behaviour getting reflected in the NYSE index fluctuations, after a smaller time lag. This Janus faced relationship, shows that smaller stock exchanges may provide a natural setting for simulating market fluctuations of much bigger exchanges. This possibly arises due to the fact that high frequency fluctuations form an universal part of the financial time series, and are expected to exhibit similar characteristics in open market economies.

  5. Experimental sheep BSE prions generate the vCJD phenotype when serially passaged in transgenic mice expressing human prion protein.

    Science.gov (United States)

    Joiner, Susan; Asante, Emmanuel A; Linehan, Jacqueline M; Brock, Lara; Brandner, Sebastian; Bellworthy, Susan J; Simmons, Marion M; Hope, James; Collinge, John; Wadsworth, Jonathan D F

    2018-03-15

    The epizootic prion disease of cattle, bovine spongiform encephalopathy (BSE), causes variant Creutzfeldt-Jakob disease (vCJD) in humans following dietary exposure. While it is assumed that all cases of vCJD attributed to a dietary aetiology are related to cattle BSE, sheep and goats are susceptible to experimental oral challenge with cattle BSE prions and farmed animals in the UK were undoubtedly exposed to BSE-contaminated meat and bone meal during the late 1980s and early 1990s. Although no natural field cases of sheep BSE have been identified, it cannot be excluded that some BSE-infected sheep might have entered the European human food chain. Evaluation of the zoonotic potential of sheep BSE prions has been addressed by examining the transmission properties of experimental brain isolates in transgenic mice that express human prion protein, however to-date there have been relatively few studies. Here we report that serial passage of experimental sheep BSE prions in transgenic mice expressing human prion protein with methionine at residue 129 produces the vCJD phenotype that mirrors that seen when the same mice are challenged with vCJD prions from patient brain. These findings are congruent with those reported previously by another laboratory, and thereby strongly reinforce the view that sheep BSE prions could have acted as a causal agent of vCJD within Europe. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

  6. Origin of convex tetrads in rare earth element patterns of hydrothermally altered siliceous igneous rocks from the Zinnwald Sn W deposit, Germany

    Science.gov (United States)

    Monecke, T.; Dulski, P.; Kempe, U.

    2007-01-01

    The chondrite-normalized rare earth element (REE) patterns of whole rock samples from evolved granitic systems hosting rare metal deposits sometimes show a split into four consecutive curved segments, referred to as tetrads. In the present contribution, a rigorous statistical method is proposed that can be used to test whether geological significance should be attributed to tetrads that are only of limited size. The method involves a detailed evaluation of element and sample specific random and systematic errors that are constrained on the basis of independent repeated preparations and analyses of sample and reference materials. Application of the proposed method to samples from the granite-hosted Zinnwald Sn-W deposit, Germany, revealed that at least two tetrads in normalized whole rock REE patterns have to be analytically significant to rule out that fractional crystallization led to the unusual behavior of the REEs. Based on the analysis of altered albite granite and greisen samples from the endocontact of the Zinnwald granite massif, it is demonstrated that the lanthanide tetrad effect is responsible for the formation of the convex tetrads. Geological and petrological evidence suggests that the tetrads in the samples developed prior to greisenization and related cassiterite precipitation. In contrast to the endocontact samples, the rhyolitic wall rocks are typified by normalized REE patterns having tetrads that are variable in size and frequently close to the limit of analytical significance. The sizes of the tetrads apparently correlate with the intensity of albitization, but show no relation to subsequent alteration processes including greisenization and low-temperature argillization. This observation proves that curved segments in normalized whole rock REE patterns can be introduced during hydrothermal fluid-rock interaction.

  7. Factors affecting the accuracy of urine-based biomarkers of BSE

    Directory of Open Access Journals (Sweden)

    Ruddat Viola

    2011-02-01

    Full Text Available Abstract Background Transmissible spongiform encephalopathy diseases are untreatable, uniformly fatal degenerative syndromes of the central nervous system that can be transmitted both within as well as between species. The bovine spongiform encephalopathy (BSE epidemic and the emergence of a new human variant of Creutzfeldt-Jakob disease (vCJD, have profoundly influenced beef production processes as well as blood donation and surgical procedures. Simple, robust and cost effective diagnostic screening and surveillance tools are needed for both the preclinical and clinical stages of TSE disease in order to minimize both the economic costs and zoonotic risk of BSE and to further reduce the risk of secondary vCJD. Objective Urine is well suited as the matrix for an ante-mortem test for TSE diseases because it would permit non-invasive and repeated sampling. In this study urine samples collected from BSE infected and age matched control cattle were screened for the presence of individual proteins that exhibited disease specific changes in abundance in response to BSE infection that might form the basis of such an ante-mortem test. Results Two-dimensional differential gel electrophoresis (2D-DIGE was used to identify proteins exhibiting differential abundance in two sets of cattle. The known set consisted of BSE infected steers and age matched controls throughout the course of the disease. The blinded unknown set was composed of BSE infected and control samples of both genders, a wide range of ages and two different breeds. Multivariate analyses of individual protein abundance data generated classifiers comprised of the proteins best able to discriminate between the samples based on disease state, breed, age and gender. Conclusion Despite the presence of confounding factors, the disease specific changes in abundance exhibited by a panel of urine proteins permitted the creation of classifiers able to discriminate between control and infected cattle

  8. EFSA BIOHAZ Panel (EFSA Panel on Biological Hazards), 2014. Scientific Opinion on BSE risk in bovine intestines and mesentery

    DEFF Research Database (Denmark)

    Hald, Tine; Baggesen, Dorte Lau

    infected cattle entering undetected in the food and feed chain yearly. A model named TSEi was developed to estimates the BSE infectious load in tissues from infected animals at different ages and the total yearly infectious load that could enter the food and feed chain in the EU27. In BSE infected cattle...

  9. Improvement of goat TSE discriminative diagnosis and susceptibility based assessment of BSE infectivity in goat milk and meat

    NARCIS (Netherlands)

    Bossers, A.; Langeveld, J.P.M.

    2012-01-01

    In light of the known ability of the BSE agent to cross the animal/human species barrier, the evidence establishing the presence of BSE in goat is especially alarming, as it represents a potential risk of food-born contamination to human consumers of goat milk and meat products. The main objective

  10. The BSE Risk of Processing Meat and Bone Meal in Nonruminant Feed: A Quantitative Assessment for the Netherlands

    NARCIS (Netherlands)

    Vos, de C.J.; Heres, L.

    2009-01-01

    The total ban on use of meat and bone meal (MBM) in livestock feed has been very successful in reducing bovine spongiform encephalopathy (BSE) spread, but also implies a waste of high-quality proteins resulting in economic and ecological loss. Now that the BSE epidemic is fading out, a partial

  11. The kinetic fragility of natural silicate melts

    International Nuclear Information System (INIS)

    Giordano, Daniele; Dingwell, Donald B

    2003-01-01

    Newtonian viscosities of 19 multicomponent natural and synthetic silicate liquids, with variable contents of SiO 2 (41-79 wt%), Al 2 O 3 (10-19 wt%), TiO 2 (0-3 wt%), FeO tot (0-11 wt%); alkali oxides (5-17 wt%), alkaline-earth oxides (0-35 wt%), and minor oxides, obtained at ambient pressure using the high-temperature concentric cylinder, the low-temperature micropenetration, and the parallel plates techniques, have been analysed. For each silicate liquid, regression of the experimentally determined viscosities using the well known Vogel-Fulcher-Tammann (VFT) equation allowed the viscosity of all these silicates to be accurately described. The results of these fits, which provide the basis for the subsequent analysis here, permit qualitative and quantitative correlations to be made between the VFT adjustable parameters (A VFT , B VFT , and T 0 ). The values of B VFT and T 0 , calibrated via the VFT equation, are highly correlated. Kinetic fragility appears to be correlated with the number of non-bridging oxygens per tetrahedrally coordinated cation (NBO/T). This is taken to infer that melt polymerization controls melt fragility in liquid silicates. Thus NBO/T might form an useful ingredient of a structure-based model of non-Arrhenian viscosity in multicomponent silicate melts

  12. Light tetraquarks and mesons in a DSE/BSE approach

    Energy Technology Data Exchange (ETDEWEB)

    Heupel, Walter

    2015-07-01

    quark propagator and it's dressing functions. This enables one to derive closed expressions for the interaction kernel beyond the rainbow-ladder approximation. This technique is very general, and in principle applicable to any vertex that is given in terms of quark dressing functions. As an improvement over previous approaches this technique allows one to determine not only the masses of the bound-states but also their Bethe-Salpeter wave functions. As examples, this technique was applied to two type of vertices, the Ball-Chiu vertex and the Munczek vertex that both respect the constraints due to the vector Ward-Takahashi identity but contain additional structures related to spin-orbit forces. Upon solving the BSE for pseudo-scalar, scalar, vector and axial-vector mesons it was found that these structures alone are not sufficient to generate a physical spectrum of light mesons while keeping the pion properties intact.

  13. Bovine spongiform encephalopathy: is it time to relax BSE-related measures in the context of international trade?

    Science.gov (United States)

    Matthews, D; Adkin, A

    2011-04-01

    Bovine spongiform encephalopathy (BSE) has presented serious challenges to both the World Organisation for Animal Health and national governments, in defining and implementing appropriate national control measures, and in agreeing trade rules that permit safe trade in cattle and bovine products. Precautionary trade rules were initially necessary, based upon the science of sheep scrapie, but research into BSE later enabled BSE-specific trade rules to be developed. As a result, current rules on trade are underpinned by a sound body of knowledge on BSE. Declining epidemics in most affected countries confirm the appropriateness of current precautions. Nevertheless, risk is primarily dependent on the prevalence of infection with BSE. In the face of low prevalence scenarios, certain precautionary measures in the Terrestrial Animal Health Code may now be considered excessive. A thorough review is therefore deemed appropriate.

  14. 9 CFR 93.436 - Ruminants from regions of minimal risk for BSE.

    Science.gov (United States)

    2010-01-01

    ... each animal's right hip, high on the tail-head (over the junction of the sacral and first cocygeal... 9 Animals and Animal Products 1 2010-01-01 2010-01-01 false Ruminants from regions of minimal risk for BSE. 93.436 Section 93.436 Animals and Animal Products ANIMAL AND PLANT HEALTH INSPECTION SERVICE...

  15. PCR-RFLP Using BseDI Enzyme for Pork Authentication in Sausage and Nugget Products

    Directory of Open Access Journals (Sweden)

    Y. Erwanto

    2011-04-01

    Full Text Available A polymerase chain reaction–restriction fragment length polymorphism (PCR–RFLP using BseDI restriction enzyme had been applied for identifying the presence of pork in processed meat (beef sausage and chicken nugget including before and after frying. Pork sample in various levels (1%, 3%, 5%, 10%, and 25 % was prepared in a mixture with beef and chicken meats and processed for sausage and nugget. The primers CYTb1 and CYTb2 were designed in the mitochondrial cytochrome b (cyt b gene and PCR successfully amplified fragments of 359 bp. To distinguish existence of porcine species, the amplified PCR products of mitochondrial DNA were cut by BseDI restriction enzyme. The result showed pig mitochondrial DNA was cut into 131 and 228 bp fragments. The PCR-RFLP species identification assay yielded excellent results for identification of porcine species. It is a potentially reliable technique for pork detection in animal food processed products for Halal authentication.

  16. Development of Neutron Interferometer with Wide-Gapped ''BSE''s for Precision Measurements

    International Nuclear Information System (INIS)

    Seki, Y.; Kitaguchi, M.; Hino, M.; Funahashi, H.; Taketani, K.; Otake, Y.; Shimizu, H. M.

    2007-01-01

    We are developing large-dimensional cold-neutron interferometers with multilayer mirrors in order to investigate small interactions. In particular Jamin type interferometers composed of wide-gapped 'BSE's, which divide the beam completely, can realize the precision measurement of topological Aharonov-Casher effect. We have made a prototype with 200 μm gapped BSEs and confirmed the spatial separation of its two paths at monochromatic cold-neutron beamline MINE2 on JRR-3M reactor in JAEA

  17. THE EVALUATION OF BSE BAHASA INGGRIS FOR GRADE VII: WHEN ENGLISH RINGS A BELL

    OpenAIRE

    Doddy Dwi Wahyuwono; I Gusti Ngurah Aditya Liem Aria; Tandya Anggergian

    2017-01-01

    Coursebooks are core parts of any curriculum as the unique contributors to content learning (Demir & Ertas, 2014). Currently, in Indonesian curriculum, K13, the government develops coursebooks that can be used by students nationally. The developed coursebooks, Buku Sekolah Elektronik (BSE), vary for different level of education, starting from elementary schools up to senior and vocational high schools. In developing the coursebooks, the government needs to implement the coursebooks to the rea...

  18. ANALISIS SOAL JENJANG KOGNITIF TAKSONOMI BLOOM REVISI PADA BUKU SEKOLAH ELEKTRONIK (BSE BIOLOGI SMA

    Directory of Open Access Journals (Sweden)

    Aa Juhanda

    2016-11-01

    Penelitian ini bertujuan untuk menganalisis kemunculan soal jenjang kognitif Bloom Revisi pada Buku Sekolah Elektronik (BSE Biologi SMA. Subjek penelitian adalah 1.650 soal yang terdapat pada BSE Edisi 2009. Instrumen yang digunakan adalah lembar analisis dokumen yang di dalamnya memuat informasi seperti kode soal, soal, dan jenis tingkatan kognitif taksonomi Bloom Revisi. Analisis data dilakukan secara kuantitatif dan kualitatif. Hasil penelitian menunjukkan bahwa rerata persentase kemunculan cukup tinggi diperoleh pada soal yang mengembangkan keterampilan berpikir tingkat rendah (Lower-Order Thinking Skills yaitu soal C1 (mengingat sebesar 46,60% dan C2 (memahami sebesar 47,99%, meskipun untuk C3 (menerapkan persentasenya masih rendah (0,28%. Rerata persentase kemunculan soal yang mengembangkan keterampilan tingkat tinggi (Higher-Order Thinking Skills mulai dari soal C4 (menganalisis sampai dengan C6 (mencipta memiliki rerata persentase yang rendah. Oleh karena itu, kemunculan soal jenjang kognitif Bloom Revisi pada BSE khususnya yang mengembangkan Higher-Order Thinking Skills masih perlu untuk ditingkatkan.

  19. High Pressure/Temperature Metal Silicate Partitioning of Tungsten

    Science.gov (United States)

    Shofner, G. A.; Danielson, L.; Righter, K.; Campbell, A. J.

    2010-01-01

    The behavior of chemical elements during metal/silicate segregation and their resulting distribution in Earth's mantle and core provide insight into core formation processes. Experimental determination of partition coefficients allows calculations of element distributions that can be compared to accepted values of element abundances in the silicate (mantle) and metallic (core) portions of the Earth. Tungsten (W) is a moderately siderophile element and thus preferentially partitions into metal versus silicate under many planetary conditions. The partitioning behavior has been shown to vary with temperature, silicate composition, oxygen fugacity, and pressure. Most of the previous work on W partitioning has been conducted at 1-bar conditions or at relatively low pressures, i.e. pressure. Predictions based on extrapolation of existing data and parameterizations suggest an increased pressured dependence on metal/ silicate partitioning of W at higher pressures 5. However, the dependence on pressure is not as well constrained as T, fO2, and silicate composition. This poses a problem because proposed equilibration pressures for core formation range from 27 to 50 GPa, falling well outside the experimental range, therefore requiring exptrapolation of a parametereized model. Higher pressure data are needed to improve our understanding of W partitioning at these more extreme conditions.

  20. The BSE risk of processing meat and bone meal in nonruminant feed: a quantitative assessment for the Netherlands.

    Science.gov (United States)

    de Vos, Clazien J; Heres, Lourens

    2009-04-01

    The total ban on use of meat and bone meal (MBM) in livestock feed has been very successful in reducing bovine spongiform encephalopathy (BSE) spread, but also implies a waste of high-quality proteins resulting in economic and ecological loss. Now that the BSE epidemic is fading out, a partial lifting of the MBM ban might be considered. The objective of this study was to assess the BSE risk for the Netherlands if MBM derived from animals fit for human consumption, i.e., category 3 MBM, would be used in nonruminant feed. A stochastic simulation model was constructed that calculates (1) the probability that infectivity of undetected BSE-infected cows ends up with calves and (2) the quantity of infectivity (Q(inf)) consumed by calves in case of such an incident. Three pathways were considered via which infectivity can reach cattle: (1) cross-contamination in the feed mill, (2) cross-contamination on the primary farm, and (3) pasture contamination. Model calculations indicate that the overall probability that infectivity ends up with calves is 3.2%. In most such incidents the Q(inf) is extremely small (median = 6.5 x 10(-12) ID(50); mean = 1.8 x 10(-4) ID(50)), corresponding to an average probability of 1.3 x 10(-4) that an incident results in >or=1 new BSE infections. Cross-contamination in the feed mill is the most risky pathway. Combining model results with Dutch BSE prevalence estimates for the coming years, it can be concluded that the BSE risk of using category 3 MBM derived from Dutch cattle in nonruminant feed is very low.

  1. Vesuvianite–wollastonite–grossular-bearing calc-silicate rock near ...

    Indian Academy of Sciences (India)

    Felsic layers are white in colour, whereas mafic layers range from green, brown to grey colour depending on the modal abundance of different mafic minerals. Layers rich in diopside are green coloured and those rich in garnet are brown. Keywords. Vesuvianite; wollastonite; grossular; diopside; calc-silicate rock. J. Earth ...

  2. 21 CFR 573.260 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 573.260 Section 573.260 Food and... Listing § 573.260 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely used as an anticaking agent in animal feed, provided that the amount of calcium silicate does not...

  3. Biological and therapeutic effects of ortho-silicic acid and some ortho-silicic acid-releasing compounds: New perspectives for therapy

    Directory of Open Access Journals (Sweden)

    Jurkić Lela Munjas

    2013-01-01

    Full Text Available Abstract Silicon (Si is the most abundant element present in the Earth's crust besides oxygen. However, the exact biological roles of silicon remain unknown. Moreover, the ortho-silicic acid (H4SiO4, as a major form of bioavailable silicon for both humans and animals, has not been given adequate attention so far. Silicon has already been associated with bone mineralization, collagen synthesis, skin, hair and nails health atherosclerosis, Alzheimer disease, immune system enhancement, and with some other disorders or pharmacological effects. Beside the ortho-silicic acid and its stabilized formulations such as choline chloride-stabilized ortho-silicic acid and sodium or potassium silicates (e.g. M2SiO3; M= Na,K, the most important sources that release ortho-silicic acid as a bioavailable form of silicon are: colloidal silicic acid (hydrated silica gel, silica gel (amorphous silicon dioxide, and zeolites. Although all these compounds are characterized by substantial water insolubility, they release small, but significant, equilibrium concentration of ortho-silicic acid (H4SiO4 in contact with water and physiological fluids. Even though certain pharmacological effects of these compounds might be attributed to specific structural characteristics that result in profound adsorption and absorption properties, they all exhibit similar pharmacological profiles readily comparable to ortho-silicic acid effects. The most unusual ortho-silicic acid-releasing agents are certain types of zeolites, a class of aluminosilicates with well described ion(cation-exchange properties. Numerous biological activities of some types of zeolites documented so far might probably be attributable to the ortho-silicic acid-releasing property. In this review, we therefore discuss biological and potential therapeutic effects of ortho-silicic acid and ortho-silicic acid -releasing silicon compounds as its major natural sources.

  4. The stable Cr isotopic compositions of chondrites and silicate planetary reservoirs

    Science.gov (United States)

    Schoenberg, Ronny; Merdian, Alexandra; Holmden, Chris; Kleinhanns, Ilka C.; Haßler, Kathrin; Wille, Martin; Reitter, Elmar

    2016-06-01

    The depletion of chromium in Earth's mantle (∼2700 ppm) in comparison to chondrites (∼4400 ppm) indicates significant incorporation of chromium into the core during our planet's metal-silicate differentiation, assuming that there was no significant escape of the moderately volatile element chromium during the accretionary phase of Earth. Stable Cr isotope compositions - expressed as the ‰-difference in 53Cr/52Cr from the terrestrial reference material SRM979 (δ53/52CrSRM979 values) - of planetary silicate reservoirs might thus yield information about the conditions of planetary metal segregation processes when compared to chondrites. The stable Cr isotopic compositions of 7 carbonaceous chondrites, 11 ordinary chondrites, 5 HED achondrites and 2 martian meteorites determined by a double spike MC-ICP-MS method are within uncertainties indistinguishable from each other and from the previously determined δ53/52CrSRM979 value of -0.124 ± 0.101‰ for the igneous silicate Earth. Extensive quality tests support the accuracy of the stable Cr isotope determinations of various meteorites and terrestrial silicates reported here. The uniformity in stable Cr isotope compositions of samples from planetary silicate mantles and undifferentiated meteorites indicates that metal-silicate differentiation of Earth, Mars and the HED parent body did not cause measurable stable Cr isotope fractionation between these two reservoirs. Our results also imply that the accretionary disc, at least in the inner solar system, was homogeneous in its stable Cr isotopic composition and that potential volatility loss of chromium during accretion of the terrestrial planets was not accompanied by measurable stable isotopic fractionation. Small but reproducible variations in δ53/52CrSRM979 values of terrestrial magmatic rocks point to natural stable Cr isotope variations within Earth's silicate reservoirs. Further and more detailed studies are required to investigate whether silicate

  5. Risk, science and policy: definitional struggles, information management, the media and BSE.

    Science.gov (United States)

    Miller, D

    1999-11-01

    This article examines the role of definitional struggles in the science policy interface using the example of the cattle disease bovine spongiform encephalopathy (BSE) or mad cow disease in the UK. A central contention is that an explicit focus on definition illuminates the processes by which scientific judgements are made, promoted, communicated, assessed and judged and gives an improved picture of policy making. Neglected areas such as the role of secrecy, public relations and the mass media in the science-policy interface are brought into sharper focus as an intrinsic part of the wider operation of definitional struggles. The focus on definitional struggles also sheds light on some current work on risk in social theory. It is argued that the neglect of questions of agency which are central to definitional struggles has led to some theorists presenting risks as inevitable concomitants of technological and cultural developments leaving them in the grip of political quietism.

  6. [Animal feeding and feed legislation after the detection of the first indigenous BSE cases in Germany].

    Science.gov (United States)

    Kamphues, J

    2002-08-01

    In Great Britain, even the earliest tangible signs indicating the epidemiologic significance of meat and bone meal in the spreading of BSE soon gave rise to increasingly rigorous legislative measures regulating animal feedstuffs. In 1994 a ban on the feeding of animal proteins to ruminants was implemented throughout the entire EU. But until the first BSE cases were actually confirmed in locally raised cattle (November 2000), feeding practice and legislation more or less in Germany remained unaffected by the efforts undertaken in Great Britain. This situation was suddenly changed on 1 December, 2000, when the so-called "Verfütterungsverbot" was put into effect, a law which drastically extended bans regarding the feedstuffs (including fishmeal and animal fats) as well as the species concerned (all animals used in food production). In 2001 the "contamination" phenomenon (ingredients of animal origin were detected in mixed feeds) became a vital issue for the feed industry; through the media, the subject "feedstuff safety" gained a previously unseen level of public awareness. Those circles concerned with mixed feed production and animal husbandry were increasingly confronted with the consequences of the "Verfütterungsverbot" (availability and pricing of substitute ingredients; the demand for amino acids and inorganic sources of phosphorus; problems finding adequate substitutes for animal fats; poor digestibility of alternative components such as indigenous legumes or vegetable fats in calf diets; lower utilization rate of original phosphorus in mixed feeds with negative consequences for skeletal development). With the conditional approval of fishmeal (except in feeds for ruminants) the situation has eased again to a certain degree; on the EU level there are increasing signals pointing toward a political intention to reinstate the utilization of by-products of slaughtered animals qualified for human consumption (with the exception of fallen/dead animals and specific

  7. Silicate glasses. Chapter 1

    International Nuclear Information System (INIS)

    Lutze, W.

    1988-01-01

    This chapter is a survey of world-wide research and development efforts in nuclear waste glasses and its production technology. The principal glasses considered are silicate glasses which contain boron, i.e. borosilicate glass. A historical overview of waste form development programs in nine countries is followed by a summary of the design criteria for borosilicate glass compositions glass compositions. In the sections on glass properties the waste form is characterized in terms of potential alterations under the influence of heat, thermal gradients, radiation, aqueous solutions and combinations thereof. The topics are phase transformations, mechanical properties, radiation effects and chemical durability. The results from studies of volcanic glasses, as natural analogues for borosilicate nuclear waste glasses in order to verify predictions obtained from short-term tests in the laboratory, have been compiled in a special section on natural analogues. A special section on advanced vitrification techniques summarizes the various actual and potential processing schemes and describes the facilities. The literature has been considered until 1985. (author). 430 refs.; 68 figs.; 29 tabs

  8. Radioanalysis of siliceous materials

    International Nuclear Information System (INIS)

    Das, H.A.

    2003-01-01

    Both natural and induced radioactivity as well as man-made radiotracers may be applied to assess quality and its maintenance a widely varying range of siliceous materials. One example of industrial application is given for each of these three branches. Natural Radioactivity: The measurement of 222-Rn emanation from building material components serves the determination of the internal diffusion and thus of the effective porosity as well as the usual environmental control. Radiotracers: The specific surface area of silica components can be obtained from measurements of the chemisorptions of fluoride and its kinetics, using acid fluoride solutions and carrier-free 18-F, Tl/2 = 110 min, as the radiotracer. This also enables the determination of fluoride in drinking water at the (sub-) ppm level by spiking isotope dilution and substoichiometric adsorption to small glass beads. Neutron activation analysis (NAA): Concentration profiles down to the micro m-range of trace elements in small electronic components of irregular shape are derived from combination of NAA with controlled sequential etching flux in dilute HF-solutions. The cases of Na, Mn, Co and Se by instrumental NAA and that of W by chemical isolation from the reagent solution are considered. (author)

  9. Correlation between the Insertion/Deletion Mutations of Prion Protein Gene and BSE Susceptibility and Milk Performance in Dairy Cows

    Directory of Open Access Journals (Sweden)

    Hu Shen-rong

    2013-12-01

    Full Text Available Objective To investigate the 23 bp and 12 bp insertion/deletion (indel mutations within the bovine prion protein (PRNP gene in Chinese dairy cows, and to detect the associations of two indel mutations with BSE susceptibility and milk performance.

  10. ESEM-BSE coupled with rapid nano-scratching for micro-physicochemical analysis of marine exposed concrete

    NARCIS (Netherlands)

    Palin, D.; Thijssen, A.; Wiktor, V.; Jonkers, H.M.; Schlangen, H.E.J.G.

    2015-01-01

    Ordinary Portland cement (OPC) mortar specimens submerged in sea-water were analysed through environmental scanning electron microscopy (ESEM) in back scattered electron (BSE) mode and nano-scratching. Results from both sets of analysis show the presence of distinct phases associated with aragonite,

  11. Environmental silicate nano-biocomposites

    CERN Document Server

    Pollet, Eric

    2012-01-01

    Environmental Silicate Nano-Biocomposites focuses on nano-biocomposites, which are obtained by the association of silicates such as bioclays with biopolymers. By highlighting recent developments and findings, green and biodegradable nano-composites from both renewable and biodegradable polymers are explored. This includes coverage of potential markets such as packaging, agricultures, leisure and the fast food industry. The knowledge and experience of more than twenty international experts in diverse fields, from chemical and biochemical engineering to applications, is brought together in four different sections covering: Biodegradable polymers and Silicates, Clay/Polyesters Nano-biocomposites, Clay/Agropolymers Nano-biocomposites, and Applications and biodegradation of Nano-biocomposites. By exploring the relationships between the biopolymer structures, the processes, and the final properties Environmental Silicate Nano-Biocomposites explains how to design nano-materials to develop new, valuable, environmenta...

  12. Poly-γ-glutamic acid productivity of Bacillus subtilis BsE1 has positive function in motility and biocontrol against Fusarium graminearum.

    Science.gov (United States)

    Wang, Luyao; Wang, Ning; Mi, Dandan; Luo, Yuming; Guo, Jianhua

    2017-07-01

    In this study, we investigate the relationship between γ-PGA productivity and biocontrol capacity of Bacillus subtilis BsE1; one bacterial isolate displayed 62.14% biocontrol efficacy against Fusarium root rot. The γ-PGA yield assay, motility assay, wheat root colonization assay, and biological control assay were analysed in different γ-PGA yield mutants of BsE1. The pgsB (PGA-synthase-CapB gene) deleted mutant of BsE1 reduced γ-PGA yield and exhibited apparent decline of in vitro motile ability. Deletion of pgsB impaired colonizing capacity of BsE1 on wheat root in 30 days, also lowered biocontrol efficacies from 62.08% (wild type BsE1) to 14.22% in greenhouse experiment against Fusarium root rot. The knockout of pgdS and ggt (genes relate to two γ-PGA degrading enzymes) on BsE1, leads to a considerable improvement in polymer yield and biocontrol efficacy, which attains higher level compared with wild type BsE1. Compared with ΔpgsB mutant, defense genes related to reactive oxygen species (ROS) and phytoalexin expressed changes by notable levels on wheat roots treated with BsE1, demonstrating the functional role γ-PGA plays in biocontrol against Fusarium root rot. γ-PGA is not only important to the motile and plant root colonization ability of BsE1, but also essential to the biological control performed by BsE1 against Fusarium root rot. Our goal in this study is to reveals a new perspective of BCAs screening on bacterial isolates, without good performance during pre-assays of antagonism ability.

  13. 21 CFR 172.410 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 172.410 Section 172.410 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR HUMAN... Agents § 172.410 Calcium silicate. Calcium silicate, including synthetic calcium silicate, may be safely...

  14. A spatio-temporal analysis of BSE cases born before and after the reinforced feed ban in France.

    Science.gov (United States)

    Ducrot, Christian; Abrial, David; Calavas, Didier; Carpenter, Tim

    2005-01-01

    A spatio-temporal analysis was carried out to see how the risk distribution of bovine spongiform encephalopathy (BSE) in France changed depending on the period of birth. The data concerned the 539 BSE cases born in France after the ban (BAB) of meat and bone meal (MBM) in 1990 and detected between July 1, 2001 and December 31, 2003, when the surveillance of BSE was comprehensive. Seventy-two of these cases were born after the reinforced (second) ban (BASB) in 1996, which involved the removal of BSE-risk materials and cadavers from the processing of MBM. The Ederer-Myers-Mantel (EMM) time and space cluster test was applied, after classifying the cases by trimester and region of birth, BAB or BASB status, and dairy or beef status. Then disease mapping was performed for four successive birth periods, three for the BAB cases (January 1991 through June 1994, July 1994 through June 1995, July 1995 through June 1996), and one for the BASB (July 1996 through October 1998). It was elaborated with the Bayesian graphical modelling methods and based on a Poisson distribution with spatial smoothing. The parameters were estimated by a Markov Chain Monte Carlo (MCMC) simulation method. The main finding was that the areas with the highest risk of BSE changed largely from one birth period to another; from the west, it reached the east of France for birth cohort 1994-1995 and the southwest for birth cohort 1995-1996. The EMM test identified a peak risk in this region both for dairy and beef cattle in the fall 1995. The spatial distribution of the risk for the BASB cases matched the spatial pattern of risk for the preceding BAB birth cohort quite well; this was in favour of a common origin of the infection of the BAB and BASB cases, despite the complementary control measures.

  15. Thermochemistry of dense hydrous magnesium silicates

    Science.gov (United States)

    Bose, Kunal; Burnley, Pamela; Navrotsky, Alexandra

    1994-01-01

    Recent experimental investigations under mantle conditions have identified a suite of dense hydrous magnesium silicate (DHMS) phases that could be conduits to transport water to at least the 660 km discontinuity via mature, relatively cold, subducting slabs. Water released from successive dehydration of these phases during subduction could be responsible for deep focus earthquakes, mantle metasomatism and a host of other physico-chemical processes central to our understanding of the earth's deep interior. In order to construct a thermodynamic data base that can delineate and predict the stability ranges for DHMS phases, reliable thermochemical and thermophysical data are required. One of the major obstacles in calorimetric studies of phases synthesized under high pressure conditions has been limitation due to the small (less than 5 mg) sample mass. Our refinement of calorimeter techniques now allow precise determination of enthalpies of solution of less than 5 mg samples of hydrous magnesium silicates. For example, high temperature solution calorimetry of natural talc (Mg(0.99) Fe(0.01)Si4O10(OH)2), periclase (MgO) and quartz (SiO2) yield enthalpies of drop solution at 1044 K to be 592.2 (2.2), 52.01 (0.12) and 45.76 (0.4) kJ/mol respectively. The corresponding enthalpy of formation from oxides at 298 K for talc is minus 5908.2 kJ/mol agreeing within 0.1 percent to literature values.

  16. Control methods for cattle feedstuffs aimed at prevention of Bovine spongiform encephalopathy (BSE

    Directory of Open Access Journals (Sweden)

    Nešić Ksenija

    2006-01-01

    Full Text Available In the course of the last decades of the twentieth century, more than 30 new diseases were determined for the first time in history. Bovine spongiform encephalopathy (BSE, or "mad cow disease" is one of them. The disease implies the subacute neurodegenerative transmission of spongiform encephalopathy and it was diagnosed and described for the first time in Great Britain in 1986. A theory has been established that BSE is spread through feedstuffs, more precisely, meat-bone flour which contains infective proteins of ruminants, and legislature has been passed throughout the world with the objective of preventing the entry of meat-bone flour into the food chain. The complete ban of the use of meat-bone flour for all farm animals (with the exception of fish flour for non-ruminants and an adequate thermal treatment in the production of meat-bone flour (133ºC, 3 bar, 20 min are the elements on which the European Union (EU legislature is based. The regulations in our country include a ban on the use of meat-bone flour in cattle feedstuffs and a ban on imports of beef proteins. The implementation of this legislature throughout the world requires the corresponding analytical means. At the present time, there are several available possibilities: optic microscopy, PCR, immunoprobes, spectroscopic methods, and several others which are still being examined for use for this purpose. All the analytical methods are being applied with the objective of controlling the implementation of the current regulations, but also in order to discover possible cross contamination that could take place in factories of animal feedstuffs, during transportation, storage, or on farms, in particular when there are no separate lines for feedstuffs that contains meat-bone flour and others in which even its traces are banned. In order to secure the successful control and prevention of bovine spongiform encephalopathy in our country, as well as to secure the unhindered continuation of

  17. Polymer-Layer Silicate Nanocomposites

    DEFF Research Database (Denmark)

    Potarniche, Catalina-Gabriela

    Nowadays, some of the material challenges arise from a performance point of view as well as from recycling and biodegradability. Concerning these aspects, the development of polymer layered silicate nanocomposites can provide possible solutions. This study investigates how to obtain polymer layered...... with a spectacular improvement up to 300 % in impact strength were obtained. In the second part of this study, layered silicate bio-nanomaterials were obtained starting from natural compounds and taking into consideration their biocompatibility properties. These new materials may be used for drug delivery systems...... and as biomaterials due to their high biocompatible properties, and because they have the advantage of being biodegradable. The intercalation process of natural compounds within silicate platelets was investigated. By uniform dispersing of binary nanohybrids in a collagen matrix, nanocomposites with intercalated...

  18. On crystallochemistry of uranil silicates

    International Nuclear Information System (INIS)

    Sidorenko, G.A.; Moroz, I.Kh.; Zhil'tsova, I.G.

    1975-01-01

    A crystallochemical analysis has been made of uranil silicates. It is shown that on crystallochemical grounds it is justified to distinguish among them uranophane-kasolite, soddyite and viksite groups differing in the uranil-anion [SiO 4 ] -4 ratio and, as a consequence, in their crystallochemical structures. Widespread silicates of the uranophane-kasolite group is the formation of polytype modifications where, depending on the interlaminar cation, crystalline structures are formed with various packing of single-type uranil-anion layers. It has been shown experimentally that silicates of the uranophanekasolite group contain no oxonium ion in their crystalline structures. Minerals of the viksite group belong to a group of isostructural (homeotypic) laminated formation apt to form phases of different degrees of hydration. Phases with a smaller interlaminar cation form hydrates with a greater number of water molecules in the formulas unit

  19. NON-AUTOCLAVE SILICATE BRICK

    Directory of Open Access Journals (Sweden)

    V. N. Yaglov

    2015-01-01

    Full Text Available The paper proposes a technology for obtaining bricks on the basis of lime-silica mixtures where chemical interactions are practically completely realized in dispersive state at the stage of preparation of binding contact maturing and raw mixture as a whole. The role of forming operation (moulding is changed in principle because in this case conversion of dispersive system into a rock-like solid occurs and due to this the solid obtains complete water-resistance in contact with water immediately after forming operation. Theoretical basis for the developed technology is capability of silicate dispersive substances (hydrated calcium silicate to transit in non-stable state, to form a rock-like water-resistant solid in the moment of mechanical load application during forming process. Specific feature of the proposed method is an exclusion of additional operations for autoclaving of products from the process of obtaining a silicate brick.Synthetic hydrated calcium silicate in contrast to natural ones are more uniform in composition and structure, they contain less impurities and they are characterized by dispersive composition and due to the mentioned advantages they find wider practical application. Contact-condensation binders permit to manipulate product properties on their basis and ensure maximum correspondence to the requirements of the concrete application. Raw material sources for obtaining synthetic hydrated calcium silicates are practically un-limited because calcium-silicon containing substances are found as in various technogenic wastes so in natural compounds as well. So the problem for obtaining hydrated calcium silicates having contact-condensation ability for structure formation becomes more and more actual one. This transition is considered as dependent principally on arrangement rate of substance particles which determined the level of its instability.

  20. A country that never had a BSE crisis: consensus and tensions in transforming the Norwegian food system.

    Science.gov (United States)

    Terragni, Laura

    2006-09-01

    Norway is often described as a country where the safety of domestically produced food is not questioned and where there is a prevailing consensus about the division of responsibility for food safety. For this reason it was surprising to find that Norwegian consumers trust the safety of their meat less than do their British counterparts. This result is particularly interesting, as Norway is one of the few countries that has never experienced BSE, while Britain has been the country most affected by it. The data discussed in the article suggest that not having to cope with a BSE crisis meant that some problems within the Norwegian food safety system remained unresolved. This in turn has affected patterns of consumer trust. The article is based on the data collected for a comparative study on European consumers' confidence in food safety.

  1. THE EVALUATION OF BSE BAHASA INGGRIS FOR GRADE VII: WHEN ENGLISH RINGS A BELL

    Directory of Open Access Journals (Sweden)

    Doddy Dwi Wahyuwono

    2017-12-01

    Full Text Available Coursebooks are core parts of any curriculum as the unique contributors to content learning (Demir & Ertas, 2014. Currently, in Indonesian curriculum, K13, the government develops coursebooks that can be used by students nationally. The developed coursebooks, Buku Sekolah Elektronik (BSE, vary for different level of education, starting from elementary schools up to senior and vocational high schools. In developing the coursebooks, the government needs to implement the coursebooks to the real life situation and also evaluate them. In this paper, the researchers try to evaluate a coursebook used in English class for Junior High School students grade VII. The evaluation is done through two ways, the theory-based analysis and checklist-based analysis. The used evaluative theories are made by Cunningsworth and the Checklist is made by Mukundan, Nimehchisalem, and Hajimohammadi. The findings show that the coursebook has met the requirements of learners‘ needs stated in the K13; however, there are still some aspects that can use some further improvement, such as the design, materials‘ authenticity, and so on. Ergo, in corresponding to the findings, the suggestions can be given to two parties, the developers and the teachers. The developers are hoped to take the evaluation results into account as the crucial points for future improvement and the teachers are hoped to not solely depend on the coursebook itself, but creatively look for extra materials.

  2. Health communication and consumer behavior on meat in Belgium: from BSE until dioxin.

    Science.gov (United States)

    Verbeke, W; Viaene, J; Guiot, O

    1999-01-01

    This article focuses on the impact of mass media meat-health information on consumer perception, attitude, and behavior toward fresh meat in Belgium. In a situation similar to that which occurred in most other European countries, Belgian fresh meat consumption fell considerably during 1995-1999. A multitude of messages linking meat consumption to human health risks were reported by mass media. Bovine Spongiform Encephalopathy (BSE) since 1996 and dioxin in 1999 constituted the major issues. Empirical research, conducted in April 1998, revealed the tremendous negative impact of mass media coverage of meat-health issues on consumer risk perception, health concern, and attitude and behavior toward fresh meat. Oppositely, personal communication through butchers had only a small effect on consumer decision-making in this era dominated by alarming meat-health press. Implications are threefold. First, mass media should be aware of its social responsibilities, which include spreading reliable and correct information to the society. This is especially the case as human health risks are involved. Second, the meat industry urgently needs to reorient itself toward quality, safety, and transparency. Finally, future communication dealing with similar crises situations requires cooperation across the meat chain, government, and those who are responsible for public health promotion and communication.

  3. Poultry, pig and the risk of BSE following the feed ban in France--a spatial analysis.

    Science.gov (United States)

    Abrial, David; Calavas, Didier; Jarrige, Nathalie; Ducrot, Christian

    2005-01-01

    A spatial analysis was carried out in order to analyse the reason why the risk of Bovine Spongiform Encephalopathy (BSE) was spatially heterogeneous in France, during the period following the feed ban of Meat and Bone Meal to cattle. The hypothesis of cross-contamination between cattle feedstuff and monogastric feedstuff, which was strongly suggested from previous investigations, was assessed, with the assumption that the higher the pig or poultry density is in a given area, the higher the risk of cross-contamination and cattle infection might be. The data concerned the 467 BSE cases born in France after the ban of meat and bone meal (July 1990) and detected between July 1st, 2001 and December 31, 2003, when the surveillance system was optimal and not spatially biased. The disease mapping models were elaborated with the Bayesian graphical modelling methods and based on a Poisson distribution with spatial smoothing (hierarchical approach) and covariates. The parameters were estimated by a Markov Chain Monte Carlo simulation method. The main result was that the poultry density did not significantly influence the risk of BSE whereas the pig density was significantly associated with an increase in the risk of 2.4% per 10 000 pigs. The areas with a significant pig effect were located in regions with a high pig density as well as a high ratio of pigs to cattle. Despite the absence of a global effect of poultry density on the BSE risk, some areas had a significant poultry effect and the risk was better explained in some others when considering both pig and poultry densities. These findings were in agreement with the hypothesis of cross-contamination, which could take place at the feedstuff factory, during the shipment of food or on the farm. Further studies are needed to more precisely explore how the cross-contamination happened.

  4. Rare earth germanates

    International Nuclear Information System (INIS)

    Bondar', I.A.; Vinogradova, N.V.; Dem'yanets, L.N.

    1983-01-01

    From the viewpoint of structural chemistry and general regularities controlling formation reactions of compounds and phases in melts, solid and gaseous states, recent achievements in the chemistry of rare earth germanates are generalized. Methods of synthesizing germanates, systems on the base of germanium oxides and rare earths are considered. The data on crystallochemical characteristics are tabulated. Individual compounds of scandium germanate are also characterized. Processes of germanate formation using the data of IR-spectroscopy, X-ray phase analysis are studied. The structure and morphotropic series of rare earth germanates and silicates are determined. Fields of their present and possible future application are considered

  5. Evidence for more cost-effective surveillance options for bovine spongiform encephalopathy (BSE) and scrapie in Great Britain.

    Science.gov (United States)

    Wall, Ben A; Arnold, Mark E; Radia, Devi; Gilbert, Will; Ortiz-Pelaez, Angel; Stärk, Katharina Dc; Van Klink, Ed; Guitian, Javier

    2017-08-10

    Transmissible spongiform encephalopathies (TSEs) are an important public health concern. Since the emergence of bovine spongiform encephalopathy (BSE) during the 1980s and its link with human Creutzfeldt-Jakob disease, active surveillance has been a key element of the European Union's TSE control strategy. Success of this strategy means that now, very few cases are detected compared with the number of animals tested. Refining surveillance strategies would enable resources to be redirected towards other public health priorities. Cost-effectiveness analysis was performed on several alternative strategies involving reducing the number of animals tested for BSE and scrapie in Great Britain and, for scrapie, varying the ratio of sheep sampled in the abattoir to fallen stock (which died on the farm). The most cost-effective strategy modelled for BSE involved reducing the proportion of fallen stock tested from 100% to 75%, producing a cost saving of ca GBP 700,000 per annum. If 50% of fallen stock were tested, a saving of ca GBP 1.4 million per annum could be achieved. However, these reductions are predicted to increase the period before surveillance can detect an outbreak. For scrapie, reducing the proportion of abattoir samples was the most cost-effective strategy modelled, with limited impact on surveillance effectiveness. This article is copyright of The Authors, 2017.

  6. Antibacterial Activity of Silicate Bioceramics

    Institute of Scientific and Technical Information of China (English)

    HU Sheng; NING Congqin; ZHOU Yue; CHEN Lei; LIN Kaili; CHANG Jiang

    2011-01-01

    Four kinds of pure silicate ceramic particles, CaSiO3, Ca3SiO5, bredigite and akermanite were prepared and their bactericidal effects were systematically investigated. The phase compositions of these silicate ceramics were characterized by XRD. The ionic concentration meas urement revealed that the Calcium (Ca) ion concentration were relatively higher in Ca3SiO5 and bredigite, and much lower in CaSiO3 and akermanite. Accordingly, the pH values of the four silicate ceramics extracts showed a positive correlation with the particle concentrations. Meanwhile, by decreasing the particle size, higher Ca ion concentrations can be achieved, leading to the increase of aqueous pH value as well. In summary, all of the four silicate ceramics tested in our study showed antibacterial effect in a dose-dependent manner. Generally, the order of their antibacterial activity against E.coli from strong to weak is Ca3SiO5, bredigite, CaSiO3 and akermanite.

  7. Amended Silicated for Mercury Control

    Energy Technology Data Exchange (ETDEWEB)

    James Butz; Thomas Broderick; Craig Turchi

    2006-12-31

    Amended Silicates{trademark}, a powdered, noncarbon mercury-control sorbent, was tested at Duke Energy's Miami Fort Station, Unit 6 during the first quarter of 2006. Unit 6 is a 175-MW boiler with a cold-side electrostatic precipitator (ESP). The plant burns run-of-the-river eastern bituminous coal with typical ash contents ranging from 8-15% and sulfur contents from 1.6-2.6% on an as-received basis. The performance of the Amended Silicates sorbent was compared with that for powdered activated carbon (PAC). The trial began with a period of baseline monitoring during which no sorbent was injected. Sampling during this and subsequent periods indicated mercury capture by the native fly ash was less than 10%. After the baseline period, Amended Silicates sorbent was injected at several different ratios, followed by a 30-day trial at a fixed injection ratio of 5-6 lb/MMACF. After this period, PAC was injected to provide a comparison. Approximately 40% mercury control was achieved for both the Amended Silicates sorbent and PAC at injection ratios of 5-6 lbs/MMACF. Higher injection ratios did not achieve significantly increased removal. Similar removal efficiencies have been reported for PAC injection trials at other plants with cold-side ESPs, most notably for plants using medium to high sulfur coal. Sorbent injection did not detrimentally impact plant operations and testing confirmed that the use of Amended Silicates sorbent does not degrade fly ash quality (unlike PAC). The cost for mercury control using either PAC or Amended Silicates sorbent was estimated to be equivalent if fly ash sales are not a consideration. However, if the plant did sell fly ash, the effective cost for mercury control could more than double if those sales were no longer possible, due to lost by-product sales and additional cost for waste disposal. Accordingly, the use of Amended Silicates sorbent could reduce the overall cost of mercury control by 50% or more versus PAC for locations where

  8. Sulfur Saturation Limits in Silicate Melts and their Implications for Core Formation Scenarios for Terrestrial Planets

    Science.gov (United States)

    Holzheid, Astrid; Grove, Timothy L.

    2002-01-01

    This study explores the controls of temperature, pressure, and silicate melt composition on S solubility in silicate liquids. The solubility of S in FeO-containing silicate melts in equilibrium with metal sulfide increases significantly with increasing temperature but decreases with increasing pressure. The silicate melt structure also exercises a control on S solubility. Increasing the degree of polymerization of the silicate melt structure lowers the S solubility in the silicate liquid. The new set of experimental data is used to expand the model of Mavrogenes and O'Neill(1999) for S solubility in silicate liquids by incorporating the influence of the silicate melt structure. The expected S solubility in the ascending magma is calculated using the expanded model. Because the negative pressure dependence of S solubility is more influential than the positive temperature dependence, decompression and adiabatic ascent of a formerly S-saturated silicate magma will lead to S undersaturation. A primitive magma that is S-saturated in its source region will, therefore, become S-undersaturated as it ascends to shallower depth. In order to precipitate magmatic sulfides, the magma must first cool and undergo fractional crystallization to reach S saturation. The S content in a metallic liquid that is in equilibrium with a magma ocean that contains approx. 200 ppm S (i.e., Earth's bulk mantle S content) ranges from 5.5 to 12 wt% S. This range of S values encompasses the amount of S (9 to 12 wt%) that would be present in the outer core if S is the light element. Thus, the Earth's proto-mantle could be in equilibrium (in terms of the preserved S abundance) with a core-forming metallic phase.

  9. 21 CFR 182.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium silicate. 182.2227 Section 182.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

  10. 21 CFR 582.2227 - Calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium silicate. 582.2227 Section 582.2227 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium silicate. (a) Product. Calcium silicate. (b) Tolerance. 2 percent and 5 percent. (c) Limitations...

  11. Chemistry of the subalkalic silicic obsidians

    Science.gov (United States)

    MacDonald, Ray; Smith, Robert L.; Thomas, John E.

    1992-01-01

    Nonhydrated obsidians are quenched magmatic liquids that record in their chemical compositions details of the tectonic environment of formation and of the differentiation mechanisms that affected their subsequent evolution. This study attempts to analyze, in terms of geologic processes, the compositional variations in the subalkalic silicic obsidians (Si02≥70 percent by weight, molecular (Na2O+K20)>Al2O3). New major- and trace-element determinations of 241 samples and a compilation of 130 published major-element analyses are reported and interpreted. Obsidians from five different tectonic settings are recognized: (1) primitive island arcs, (2) mature island arcs, (3) continental margins, (4) continental interiors, and (5) oceanic extensional zones. Tectonomagmatic discrimination between these groups is successfully made on Nb-Ta, Nb-FeOt and Th-Hf-Ta plots, and compositional ranges and averages for each group are presented. The chemical differences between groups are related to the type of crust in which magmas were generated. With increasingly sialic (continental type) crust, the obsidians show overall enrichment in F, Be, Li, Mo, Nb, Rb, Sn, Ta, U, W, Zn, and the rare-earth elements, and depletion in Mg, Ca, Ba, Co, Sc, Sr, and Zr. They become more potassic, have higher Fe/Mg and F/Cl ratios, and lower Zr/Hf, Nb/Ta, and Th/U ratios. Higher values of total rare-earth elements are accompanied by light rare-earth-element enrichment and pronounced negative Eu anomalies. An attempt is made to link obsidian chemistry to genetic mechanlism. Two broad groups of rocks are distinguished: one generated where crystal-liquid processes dominated (CLPD types), which are the products of crustal anatexis, possibly under conditions of low halogen fugacity, ± crystal fractionation ± magma mixing; and a second group represented by rocks formed in the upper parts of large magma chambers by interplays of crystal fractionation, volatile transfer, magma mixing, and possibly various

  12. Turbulent Mixing of Metal and Silicate during Planet Accretion – and interpretation of the Hf-W chronometer

    DEFF Research Database (Denmark)

    Dahl, Tais Wittchen; Stevenson, David

    2010-01-01

    is enhanced if most of the accreting metal cores deform into thin structures during descent through the Earth's mantle. Yet, only 1–20% of Earth's corewould equilibrate with silicate during Earth's accretion. The initial speed of the impactor is of little importance. We proceed to evaluate the mixing......In the current view of planet formation, the final assembly of the Earth involved giant collisions between protoplanets (N1000 kmradius), with theMoon formed as a result of one such impact.At this stage the colliding bodies had likely differentiated into a metallic core surrounded by a silicate...... mantle. During the Moon-forming impact, nearly all metal sank into the Earth's core. Weinvestigate towhat extent large self-gravitating iron cores can mix with surrounding silicate and howthis influences the short-lived chronometer, Hf–W, used to infer the age of the Moon. We present fluid dynamical...

  13. Modifying Silicates for Better Dispersion in Nanocomposites

    Science.gov (United States)

    Campbell, Sandi

    2005-01-01

    An improved chemical modification has been developed to enhance the dispersion of layered silicate particles in the formulation of a polymer/silicate nanocomposite material. The modification involves, among other things, the co-exchange of an alkyl ammonium ion and a monoprotonated diamine with interlayer cations of the silicate. The net overall effects of the improved chemical modification are to improve processability of the nanocomposite and maximize the benefits of dispersing the silicate particles into the polymer. Some background discussion is necessary to give meaning to a description of this development. Polymer/silicate nanocomposites are also denoted polymer/clay composites because the silicate particles in them are typically derived from clay particles. Particles of clay comprise layers of silicate platelets separated by gaps called "galleries." The platelet thickness is 1 nm. The length varies from 30 nm to 1 m, depending on the silicate. In order to fully realize the benefits of polymer/silicate nanocomposites, it is necessary to ensure that the platelets become dispersed in the polymer matrices. Proper dispersion can impart physical and chemical properties that make nanocomposites attractive for a variety of applications. In order to achieve nanometer-level dispersion of a layered silicate into a polymer matrix, it is typically necessary to modify the interlayer silicate surfaces by attaching organic functional groups. This modification can be achieved easily by ion exchange between the interlayer metal cations found naturally in the silicate and protonated organic cations - typically protonated amines. Long-chain alkyl ammonium ions are commonly chosen as the ion-exchange materials because they effectively lower the surface energies of the silicates and ease the incorporation of organic monomers or polymers into the silicate galleries. This completes the background discussion. In the present improved modification of the interlayer silicate surfaces

  14. Properties of Tricalcium Silicate Sealers.

    Science.gov (United States)

    Khalil, Issam; Naaman, Alfred; Camilleri, Josette

    2016-10-01

    Sealers based on tricalcium silicate cement aim at an interaction of the sealer with the root canal wall, alkalinity with potential antimicrobial activity, and the ability to set in a wet field. The aim of this study was to characterize and investigate the properties of a new tricalcium silicate-based sealer and verify its compliance to ISO 6876 (2012). A new tricalcium silicate-based sealer (Bio MM; St Joseph University, Beirut, Lebanon), BioRoot RCS (Septodont, St Maure de Fosses, France), and AH Plus (Dentsply, DeTrey, Konstanz, Germany) were investigated. Characterization using scanning electron microscopy, energy-dispersive spectroscopy, and X-ray diffraction analysis was performed. Furthermore, sealer setting time, flow, film thickness, and radiopacity were performed following ISO specifications. pH and ion leaching in solution were assessed by pH analysis and inductively coupled plasma. Bio MM and BioRoot RCS were both composed of tricalcium silicate and tantalum oxide in Bio MM and zirconium oxide in BioRoot RCS. In addition, the Bio MM contained calcium carbonate and a phosphate phase. The inorganic components of AH Plus were calcium tungstate and zirconium oxide. AH Plus complied with the ISO norms for both flow and film thickness. BioRoot RCS and Bio MM exhibited a lower flow and a higher film thickness than that specified for sealer cements in ISO 6876. All test sealers exhibited adequate radiopacity. Bio MM interacted with physiologic solution, thus showing potential for bioactivity. Sealer properties were acceptable and comparable with other sealers available clinically. Copyright © 2016 American Association of Endodontists. Published by Elsevier Inc. All rights reserved.

  15. Silicate enamel for alloyed steel

    International Nuclear Information System (INIS)

    Ket'ko, K.K.

    1976-01-01

    The use of silicate enamels in the metallurgical industry is discussed. Presented are the composition and the physico-chemical properties of the silicate enamel developed at the factory 'Krasnyj Oktyabr'. This enamel can be used in the working conditions both in the liquid and the solid state. In so doing the enamel is melted at 1250 to 1300 deg C, granulated and then reduced to a fraction of 0.3 to 0.5 mm. The greatest homogeneity is afforded by a granulated enamel. The trials have shown that the conversion of the test ingots melted under a layer of enamel leads to the smaller number of the ingots rejected for surface defect reasons and the lower metal consumption for slab cleaning. The cost of the silicate enamel is somewhat higher than that of synthetic slags but its application to the melting of stainless steels is still economically beneficial and technologically reasonable. Preliminary calculations only for steel EhI4IEh have revealed that the use of this enamel saves annually over 360000 roubles [ru

  16. Absence of Evidence for a Causal Link between Bovine Spongiform Encephalopathy Strain Variant L-BSE and Known Forms of Sporadic Creutzfeldt-Jakob Disease in Human PrP Transgenic Mice.

    Science.gov (United States)

    Jaumain, Emilie; Quadrio, Isabelle; Herzog, Laetitia; Reine, Fabienne; Rezaei, Human; Andréoletti, Olivier; Laude, Hubert; Perret-Liaudet, Armand; Haïk, Stéphane; Béringue, Vincent

    2016-12-01

    Prions are proteinaceous pathogens responsible for subacute spongiform encephalopathies in animals and humans. The prions responsible for bovine spongiform encephalopathy (BSE) are zoonotic agents, causing variant Creutzfeldt-Jakob disease (CJD) in humans. The transfer of prions between species is limited by a species barrier, which is thought to reflect structural incompatibilities between the host cellular prion protein (PrP C ) and the infecting pathological PrP assemblies (PrP Sc ) constituting the prion. A BSE strain variant, designated L-BSE and responsible for atypical, supposedly spontaneous forms of prion diseases in aged cattle, demonstrates zoonotic potential, as evidenced by its capacity to propagate more easily than classical BSE in transgenic mice expressing human PrP C and in nonhuman primates. In humanized mice, L-BSE propagates without any apparent species barrier and shares similar biochemical PrP Sc signatures with the CJD subtype designated MM2-cortical, thus opening the possibility that certain CJD cases classified as sporadic may actually originate from L-type BSE cross-transmission. To address this issue, we compared the biological properties of L-BSE and those of a panel of CJD subtypes representative of the human prion strain diversity using standard strain-typing criteria in human PrP transgenic mice. We found no evidence that L-BSE causes a known form of sporadic CJD. Since the quasi-extinction of classical BSE, atypical BSE forms are the sole BSE variants circulating in cattle worldwide. They are observed in rare cases of old cattle, making them difficult to detect. Extrapolation of our results suggests that L-BSE may propagate in humans as an unrecognized form of CJD, and we urge both the continued utilization of precautionary measures to eliminate these agents from the human food chain and active surveillance for CJD phenotypes in the general population. Copyright © 2016, American Society for Microbiology. All Rights Reserved.

  17. 21 CFR 573.340 - Diatomaceous earth.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Diatomaceous earth. 573.340 Section 573.340 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additive Listing § 573.340 Diatomaceous earth. (a) Identity. The additive consists of siliceous skeletal...

  18. Calcium and magnesium silicate hydrates

    International Nuclear Information System (INIS)

    Lothenbach, B.; L'Hopital, E.; Nied, D.; Achiedo, G.; Dauzeres, A.

    2015-01-01

    Deep geological disposals are planed to discard long-lived intermediate-level and high-level radioactive wastes. Clay-based geological barriers are expected to limit the ingress of groundwater and to reduce the mobility of radioelements. In the interaction zone between the cement and the clay based material alteration can occur. Magnesium silicate hydrates (M-S-H) have been observed due to the reaction of magnesium sulfate containing groundwater with cements or in the interaction zone between low-pH type cement and clays. M-S-H samples synthesized in the laboratory showed that M-S-H has a variable composition within 0.7 ≤ Mg/Si ≤ 1.5. TEM/EDS analyses show an homogeneous gel with no defined structure. IR and 29 Si NMR data reveal a higher polymerization degree of the silica network in M-S-H compared to calcium silicate hydrates (C-S-H). The presence of mainly Q 3 silicate tetrahedrons in M-S-H indicates a sheet like or a triple-chain silica structure while C-S-H is characterised by single chain-structure. The clear difference in the silica structure and the larger ionic radius of Ca 2+ (1.1 Angstrom) compared to Mg 2+ (0.8 Angstrom) make the formation of an extended solid solution between M-S-H and C-S-H gel improbable. In fact, the analyses of synthetic samples containing both magnesium and calcium in various ratios indicate the formation of separate M-S-H and C-S-H gels with no or very little uptake of magnesium in CS-H or calcium in M-S-H

  19. High-temperature silicate volcanism on Jupiter's moon Io

    Science.gov (United States)

    McEwen, A.S.; Keszthelyi, L.; Spencer, J.R.; Schubert, G.; Matson, D.L.; Lopes-Gautier, R.; Klaasen, K.P.; Johnson, T.V.; Head, J.W.; Geissler, P.; Fagents, S.; Davies, A.G.; Carr, M.H.; Breneman, H.H.; Belton, M.J.S.

    1998-01-01

    Infrared wavelength observations of Io by the Galileo spacecraft show that at last 12 different vents are erupting lavas that are probably hotter than the highest temperature basaltic eruptions on Earth today. In at least one case, the eruption near Pillan Patea, two independent instruments on Galileo show that the lava temperature must have exceeded 1700 kelvin and may have reached 2000 kelvin. The most likely explanation is that these lavas are ultramafic (magnesium-rich) silicates, and this idea is supported by the tentative identification of magnesium-rich orthopyroxene in lava flows associated with thse high-temperature hot spots.

  20. Decomposition of silicate sample by fusion with potassium hydroxide and potassium nitrate

    International Nuclear Information System (INIS)

    Yang Tongzai; Wang Xiaolin; Liu Yinong; Chen Yinliang; Sun Ying; Li Yuqian

    1995-01-01

    The decomposition method of silicate sample by fusion with KOH and KNO 3 recounted. The decomposed sample can be used to separate and purify the rare earth nuclides. The advantage of this method is that it can decompose larger amount of sample under lower decomposition temperature

  1. Reduction-induced inward diffusion and crystal growth on the surfaces of iron-bearing silicate glasses

    DEFF Research Database (Denmark)

    Liu, S.J.; Tao, H.Z.; Zhang, Y.F.

    2015-01-01

    We investigate the sodium inward diffusion (i.e., sodium diffusion from surface toward interior) in iron containing alkaline earth silicate glasses under reducing conditions around Tg and the induced surface crystallization. The surface crystallization is caused by formation of a silicate-gel lay......+ ions have stronger bonds to oxygen and lower coordination number (4~5) than Ca2+, Sr2+ and Ba2+ ions. In contrast, a cristobalite layer forms in Ca-, Sr- and Ba-containing glasses....

  2. Silicate bonded ceramics of laterites

    International Nuclear Information System (INIS)

    Wagh, A.S.; Douse, V.

    1989-05-01

    Sodium silicate is vacuum impregnated in bauxite waste (red mud) at room temperature to develop ceramics of mechanical properties comparable to the sintered ceramics. For a concentration up to 10% the fracture toughness increases from 0.12 MNm -3/2 to 0.9 MNm -3/2 , and the compressive strength from 7 MNm -2 to 30 MNm -2 . The mechanical properties do not deteriorate, when soaked in water for an entire week. The viscosity and the concentration of the silicate solution are crucial, both for the success of the fabrication and the economics of the process. Similar successful results have been obtained for bauxite and lime stone, even though the latter has poor weathering properties. With scanning electron microscopy and energy dispersive analysis, an attempt is made to identify the crystals formed in the composite, which are responsible for the strength. The process is an economic alternative to the sintered ceramics in the construction industry in the tropical countries, rich in lateritic soils and poor in energy. Also the process has all the potential for further development in arid regions abundant in limestone. (author). 6 refs, 20 figs, 3 tabs

  3. Radiation effects in silicate glasses

    International Nuclear Information System (INIS)

    Bibler, N.E.; Howitt, D.G.

    1988-01-01

    The study of radiation effects in complex silicate glasses has received renewed attention because of their use in special applications such as high level nuclear waste immobilization and fiber optics. Radiation changes the properties of these glasses by altering their electronic and atomic configurations. These alterations or defects may cause dilatations or microscopic phase changes along with absorption centers that limit the optical application of the glasses. Atomic displacements induced in the already disordered structure of the glasses may affect their use where heavy irradiating particles such as alpha particles, alpha recoils, fission fragments, or accelerated ions are present. Large changes (up to 1%) in density may result. In some cases the radiation damage may be severe enough to affect the durability of the glass in aqueous solutions. In the paper, the authors review the literature concerning radiation effects on density, durability, stored energy, microstructure and optical properties of silicate glasses. Both simple glasses and complex glasses used for immobilization of nuclear waste are considered

  4. Silicates materials of high vacuum technology

    CERN Document Server

    Espe, Werner

    2013-01-01

    Materials of High Vacuum Technology, Volume 2: Silicates covers silicate insulators of special importance to vacuum technology. The book discusses the manufacture, composition, and physical and chemical properties of technical glasses, quartz glass, quartzware, vycor glass, ceramic materials, mica, and asbestos.

  5. Mesoporous Silicate Materials in Sensing

    Directory of Open Access Journals (Sweden)

    Paul T. Charles

    2008-08-01

    Full Text Available Mesoporous silicas, especially those exhibiting ordered pore systems and uniform pore diameters, have shown great potential for sensing applications in recent years. Morphological control grants them versatility in the method of deployment whether as bulk powders, monoliths, thin films, or embedded in coatings. High surface areas and pore sizes greater than 2 nm make them effective as adsorbent coatings for humidity sensors. The pore networks also provide the potential for immobilization of enzymes within the materials. Functionalization of materials by silane grafting or through cocondensation of silicate precursors can be used to provide mesoporous materials with a variety of fluorescent probes as well as surface properties that aid in selective detection of specific analytes. This review will illustrate how mesoporous silicas have been applied to sensing changes in relative humidity, changes in pH, metal cations, toxic industrial compounds, volatile organic compounds, small molecules and ions, nitroenergetic compounds, and biologically relevant molecules.

  6. Inheritance of silicate differentiation during lunar origin by giant impact

    Science.gov (United States)

    Warren, Paul H.

    1992-01-01

    It is pointed out that the implication of the popular giant impact model of lunar origin (e.g., Hartmann and Davis, 1975; Cameron and Ward, 1976; Stevenson, 1987) is that any depth-related silicate differentiation within the impactor (and/or the earth) at the time of the impact must be partly inherited by the preferentially peripheral matter that forms the moon. This paper presents calculations of the magnitude of the net differentiation of the protolunar matter for a variety of elements and scenarios, with different assumptions regarding the geometries of the 'sampled' peripheral zones, the relative proportions of the earth-derived to impactor-derived matter in the final moon, and the degree to which the impactor mantle had crystallized prior to the giant impact. It is shown that these differention effects constrain the overall plausibility of the giant impact hypothesis.

  7. REM-containing silicate concentrates

    International Nuclear Information System (INIS)

    Pavlov, V F; Shabanova, O V; Pavlov, I V; Pavlov, M V; Shabanov, A V

    2016-01-01

    A new method of advanced complex processing of ores containing rare-earth elements (REE) is proposed to obtain porous X-ray amorphous aluminosilicate material with a stable chemical composition which concentrates oxides of rare-earth metals (REM). The ferromanganese oxide ores of Chuktukon deposit (Krasnoyarsk Region, RF) were used for the experiment. The obtained aluminosilicate material is appropriate for treatment with 5 - 15% solutions of mineral acids to leach REM. (paper)

  8. REM-containing silicate concentrates

    Science.gov (United States)

    Pavlov, V. F.; Shabanova, O. V.; Pavlov, I. V.; Pavlov, M. V.; Shabanov, A. V.

    2016-01-01

    A new method of advanced complex processing of ores containing rare-earth elements (REE) is proposed to obtain porous X-ray amorphous aluminosilicate material with a stable chemical composition which concentrates oxides of rare-earth metals (REM). The ferromanganese oxide ores of Chuktukon deposit (Krasnoyarsk Region, RF) were used for the experiment. The obtained aluminosilicate material is appropriate for treatment with 5 - 15% solutions of mineral acids to leach REM.

  9. Melting in super-earths.

    Science.gov (United States)

    Stixrude, Lars

    2014-04-28

    We examine the possible extent of melting in rock-iron super-earths, focusing on those in the habitable zone. We consider the energetics of accretion and core formation, the timescale of cooling and its dependence on viscosity and partial melting, thermal regulation via the temperature dependence of viscosity, and the melting curves of rock and iron components at the ultra-high pressures characteristic of super-earths. We find that the efficiency of kinetic energy deposition during accretion increases with planetary mass; considering the likely role of giant impacts and core formation, we find that super-earths probably complete their accretionary phase in an entirely molten state. Considerations of thermal regulation lead us to propose model temperature profiles of super-earths that are controlled by silicate melting. We estimate melting curves of iron and rock components up to the extreme pressures characteristic of super-earth interiors based on existing experimental and ab initio results and scaling laws. We construct super-earth thermal models by solving the equations of mass conservation and hydrostatic equilibrium, together with equations of state of rock and iron components. We set the potential temperature at the core-mantle boundary and at the surface to the local silicate melting temperature. We find that ancient (∼4 Gyr) super-earths may be partially molten at the top and bottom of their mantles, and that mantle convection is sufficiently vigorous to sustain dynamo action over the whole range of super-earth masses.

  10. Evaluation of the effectiveness of selected measures against Bovine Spongiform Encephalopathy (BSE) in Switzerland by use of the basic reproduction ratio R0

    NARCIS (Netherlands)

    Schwermer, H.; Brülisauer, F.; Koeijer, de A.A.; Heim, D.

    2007-01-01

    The effectiveness of two measures against Bovine Spongiform Encephalopathy (BSE), the compulsory processing of animal by products to meat and bone mea (MBM) at 133 °C under 3 bars of pressure for 20 minutes in February 1993 and the exclusion offallen stock, heads with eyes and spinal cord of cattle

  11. SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

    Energy Technology Data Exchange (ETDEWEB)

    Fogerty, S.; Forrest, W.; Watson, D. M.; Koch, I. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Sargent, B. A., E-mail: sfogerty@pas.rochester.edu [Center for Imaging Science and Laboratory for Multiwavelength Astrophysics, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States)

    2016-10-20

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. An analysis of the well-known 9.7 μ m feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

  12. SILICATE COMPOSITION OF THE INTERSTELLAR MEDIUM

    International Nuclear Information System (INIS)

    Fogerty, S.; Forrest, W.; Watson, D. M.; Koch, I.; Sargent, B. A.

    2016-01-01

    The composition of silicate dust in the diffuse interstellar medium and in protoplanetary disks around young stars informs our understanding of the processing and evolution of the dust grains leading up to planet formation. An analysis of the well-known 9.7 μ m feature indicates that small amorphous silicate grains represent a significant fraction of interstellar dust and are also major components of protoplanetary disks. However, this feature is typically modeled assuming amorphous silicate dust of olivine and pyroxene stoichiometries. Here, we analyze interstellar dust with models of silicate dust that include non-stoichiometric amorphous silicate grains. Modeling the optical depth along lines of sight toward the extinguished objects Cyg OB2 No. 12 and ζ Ophiuchi, we find evidence for interstellar amorphous silicate dust with stoichiometry intermediate between olivine and pyroxene, which we simply refer to as “polivene.” Finally, we compare these results to models of silicate emission from the Trapezium and protoplanetary disks in Taurus.

  13. Titanium stable isotope investigation of magmatic processes on the Earth and Moon

    Science.gov (United States)

    Millet, Marc-Alban; Dauphas, Nicolas; Greber, Nicolas D.; Burton, Kevin W.; Dale, Chris W.; Debret, Baptiste; Macpherson, Colin G.; Nowell, Geoffrey M.; Williams, Helen M.

    2016-09-01

    We present titanium stable isotope measurements of terrestrial magmatic samples and lunar mare basalts with the aims of constraining the composition of the lunar and terrestrial mantles and evaluating the potential of Ti stable isotopes for understanding magmatic processes. Relative to the OL-Ti isotope standard, the δ49Ti values of terrestrial samples vary from -0.05 to +0.55‰, whereas those of lunar mare basalts vary from -0.01 to +0.03‰ (the precisions of the double spike Ti isotope measurements are ca. ±0.02‰ at 95% confidence). The Ti stable isotope compositions of differentiated terrestrial magmas define a well-defined positive correlation with SiO2 content, which appears to result from the fractional crystallisation of Ti-bearing oxides with an inferred isotope fractionation factor of ΔTi49oxide-melt = - 0.23 ‰ ×106 /T2. Primitive terrestrial basalts show no resolvable Ti isotope variations and display similar values to mantle-derived samples (peridotite and serpentinites), indicating that partial melting does not fractionate Ti stable isotopes and that the Earth's mantle has a homogeneous δ49Ti composition of +0.005 ± 0.005 (95% c.i., n = 29). Eclogites also display similar Ti stable isotope compositions, suggesting that Ti is immobile during dehydration of subducted oceanic lithosphere. Lunar basalts have variable δ49Ti values; low-Ti mare basalts have δ49Ti values similar to that of the bulk silicate Earth (BSE) while high-Ti lunar basalts display small enrichment in the heavy Ti isotopes. This is best interpreted in terms of source heterogeneity resulting from Ti stable isotope fractionation associated with ilmenite-melt equilibrium during the generation of the mantle source of high-Ti lunar mare basalts. The similarity in δ49Ti between terrestrial samples and low-Ti lunar basalts provides strong evidence that the Earth and Moon have identical stable Ti isotope compositions.

  14. Factors related to the practice of breast self examination (BSE and Pap smear screening among Malaysian women workers in selected electronics factories

    Directory of Open Access Journals (Sweden)

    Shamsuddin K

    2003-05-01

    Full Text Available Abstract Background The Malaysian Ministry of Health promotes breast self-examination (BSE for all women, and Pap smear screening every three years for all sexually active women ages 20 years and above. The objectives of this paper were to examine the practice of these two screening tests among women production workers in electronics factories, and to identify factors related to practice. Methods This was a cross-sectional survey of women production workers from ten electronics factories. Data was collected by a self-administered questionnaire from a total of 1,720 women. The chi-square test, odds ratio and binomial logistic regression were used in bivariate and multivariate analysis. Results Prevalence rates were 24.4% for BSE once a month, and 18.4% for Pap smear examination within the last three years. Women who were significantly more likely to perform BSE every month were 30 years and older, Malays, with upper secondary education and above, answered the BSE question correctly, and had a Pap smear within the last three years. The proportion of women who had a Pap smear within the last three years were significantly higher among those who were older, married, with young children, on the contraceptive pill or intra-uterine device, had a medical examination within the last five years, answered the Pap smear question correctly, and performed BSE monthly. Conclusion Screening practice rates in this study were low when compared to national rates. Socio-demographic and health care factors significantly associated with screening practice are indicative of barriers which should be further understood so that more effective educational and promotional strategies could be developed.

  15. Physical ageing of silicate glasses

    Energy Technology Data Exchange (ETDEWEB)

    Nemilov, S.V. [S. I. Vavilov State Optical Inst., St. Petersburg (Russian Federation)

    2003-02-01

    The presented review has been devoted to the problem of volume-determined properties relaxation of silicate glasses at room temperature. It is shown that the experimental data are described by the simple Debye exponential law or by a superposition of two exponents. Their parameters are calculated and systematized. A molecular-kinetic model is proposed for these ageing processes. It proceeds from the possibility of volume relaxation due to the cooperative β-relaxation mechanism with no change in the system's topology. The characteristic ageing times can be calculated according to equations obtained based on the viscosity data in the glass transition range. The precision of the calculations is about {+-} 15% at the time variations from a few weeks up to about 15 years. The system of calculated parameters is proposed which characterizes the completeness of ageing and its rate at any glass age. Optical and thermometric glasses have been ranked by their tendency to ageing. The scheme of future investigations predetermined by practice is defined. (orig.)

  16. Magnetic properties of sheet silicates

    International Nuclear Information System (INIS)

    Ballet, O.; Coey, J.M.D.

    1982-01-01

    Susceptibility, magnetisation and Moessbauer measurements are reported for a representative selection of 2:1 layer phyllosilicates. Eight samples from the mica, vermiculite and smectite groups include examples diluted in iron which are paramagnetic at all temperatures, as well as iron-rich silicates which order magnetically below 10 K. Anisotropic susceptibility of crystals of muscovite, biotite and vermiculite is quantitatively explained with a model where the Fe 2+ ions lie in sites of effective trigonal symmetry, the trigonal axis lying normal to the sheets. The ferrous ground state is an orbital singlet. Ferric iron gives an isotropic contribution to the susceptibility. Fe 2+ -Fe 2+ exchange interactions are ferromagnetic with Gapprox. equal to2 K, whereas Fe 3+ -Fe 3+ coupling is antiferromagnetic in the purely ferric minerals. A positive paramagnetic Curie temperature for glauconite may be attributable to Fe 2+ → Fe 3+ charge transfer. Magnetic order was found to set in inhomogeneously for glauconite at 1-7 K. One biotite sample showed an antiferromagnetic transition at Tsub(N) = 7 K marked by a well-defined susceptibility maximum. Its magnetic structure, consisting of ferromagnetic sheets with moments in their planes coupled antiferromagnetically by other, weak interactions, resembles that found earlier for the 1:1 mineral greenalite. (orig.)

  17. Adsorption of aqueous silicate on hematite

    International Nuclear Information System (INIS)

    Taylor, P.; Ticknor, K.V.

    1997-08-01

    During radioisotope sorption studies, adsorption of silicate from synthetic groundwaters by synthetic hematite was observed. To further investigate this observation, the adsorption of silicate onto hematite (α-Fe 2 O 3 ) powder from a neutral, aqueous NaC1 solution (0.1 mol/dm 3 ), containing 2.56 x 10 -4 mol/dm 3 of Si added as Na 2 SiO 3 ·9H 2 O, was measured at ∼21 deg C. Equilibrium adsorption of silicate amounted to ∼1.93 μmol/m 2 (one Si(O,OH) 4 moiety per 86 A 2 ). It is important to take this adsorption into account when evaluating the ability of iron oxides to adsorb other species, especially anions, from groundwaters. Silicate adsorption is known to diminish the ability of iron oxides to adsorb other anions. (author)

  18. Experimental evidence for Mo isotope fractionation between metal and silicate liquids

    Science.gov (United States)

    Hin, Remco C.; Burkhardt, Christoph; Schmidt, Max W.; Bourdon, Bernard; Kleine, Thorsten

    2013-10-01

    Stable isotope fractionation of siderophile elements may inform on the conditions and chemical consequences of core-mantle differentiation in planetary objects. The extent to which Mo isotopes fractionate during such metal-silicate segregation, however, is so far unexplored. We have therefore investigated equilibrium fractionation of Mo isotopes between liquid metal and liquid silicate to evaluate the potential of Mo isotopes as a new tool to study core formation. We have performed experiments at 1400 and 1600 °C in a centrifuging piston cylinder. Tin was used to lower the melting temperature of the Fe-based metal alloys to double spike technique. In experiments performed at 1400 °C, the 98Mo/95Mo ratio of silicate is 0.19±0.03‰ (95% confidence interval) heavier than that of metal. This fractionation is not significantly affected by the presence or absence of carbon. Molybdenum isotope fractionation is furthermore independent of oxygen fugacity in the range IW -1.79 to IW +0.47, which are plausible values for core formation. Experiments at 1600 °C show that, at equilibrium, the 98Mo/95Mo ratio of silicate is 0.12±0.02‰ heavier than that of metal and that the presence or absence of Sn does not affect this fractionation. Equilibrium Mo isotope fractionation between liquid metal and liquid silicate as a function of temperature can therefore be described as ΔMoMetal-Silicate98/95=-4.70(±0.59)×105/T2. Our experiments show that Mo isotope fractionation may be resolvable up to metal-silicate equilibration temperatures of about 2500 °C, rendering Mo isotopes a novel tool to investigate the conditions of core formation in objects ranging from planetesimals to Earth sized bodies.

  19. Q-Speciation and Network Structure Evolution in Invert Calcium Silicate Glasses.

    Science.gov (United States)

    Kaseman, Derrick C; Retsinas, A; Kalampounias, A G; Papatheodorou, G N; Sen, S

    2015-07-02

    Binary silicate glasses in the system CaO-SiO2 are synthesized over an extended composition range (42 mol % ≤ CaO ≤ 61 mol %), using container-less aerodynamic levitation techniques and CO2-laser heating. The compositional evolution of Q speciation in these glasses is quantified using (29)Si and (17)O magic angle spinning nuclear magnetic resonance spectroscopy. The results indicate progressive depolymerization of the silicate network upon addition of CaO and significant deviation of the Q speciation from the binary model. The equilibrium constants for the various Q species disproportionation reactions for these glasses are found to be similar to (much smaller than) those characteristic of Li (Mg)-silicate glasses, consistent with the corresponding trends in the field strengths of these modifier cations. Increasing CaO concentration results in an increase in the packing density and structural rigidity of these glasses and consequently in their glass transition temperature Tg. This apparent role reversal of conventional network-modifying cations in invert alkaline-earth silicate glasses are compared and contrasted with that in their alkali silicate counterparts.

  20. Pore solution in alkali-activated slag cement pastes. Relation to the composition and structure of calcium silicate hydrate

    International Nuclear Information System (INIS)

    Puertas, F.; Fernandez-Jimenez, A.; Blanco-Varela, M.T.

    2004-01-01

    In this work, the relationship between the composition of pore solution in alkali-activated slag cement (AAS) pastes activated with different alkaline activator, and the composition and structure of the main reaction products, has been studied. Pore solution was extracted from hardened AAS pastes. The analysis of the liquids was performed through different techniques: Na, Mg and Al by atomic absorption (AA), Ca ions by ionic chromatography (IC) and Si by colorimetry; pH was also determined. The solid phases were analysed by XRD, FTIR, solid-state 29 Si and 27 Al NMR and BSE/EDX. The most significant changes in the ionic composition of the pore solution of the AAS pastes activated with waterglass take place between 3 and 24 h of reaction. These changes are due to the decrease of the Na content and mainly to the Si content. Results of 29 Si MAS NMR and FTIR confirm that the activation process takes place with more intensity after 3 h (although at this age, Q 2 units already exist). The pore solution of the AAS pastes activated with NaOH shows a different evolution to this of pastes activated with waterglass. The decrease of Na and Si contents progresses with time. The nature of the alkaline activator influences the structure and composition of the calcium silicate hydrate formed as a consequence of the alkaline activation of the slag. The characteristic of calcium silicate hydrate in AAS pastes activated with waterglass is characterised by a low structural order with a low Ca/Si ratio. Besides, in this paste, Q 3 units are detected. The calcium silicate hydrate formed in the pastes activated with NaOH has a higher structural order (higher crystallinity) and contains more Al in its structure and a higher Ca/Si ratio than those obtained with waterglass

  1. Wear and chemistry of zirconium-silicate, aluminium-silicate and zirconium-aluminium-silicate glasses in alkaline medium

    International Nuclear Information System (INIS)

    Rouse, C.G.; Lemos Guenaga, C.M. de

    1984-01-01

    A study of the chemical durability, in alkaline solutions, of zirconium silicate, aluminium silicate, zirconium/aluminium silicate glasses as a function of glass composition is carried out. The glasses were tested using standard DIN-52322 method, where the glass samples are prepared in small polished pieces and attacked for 3 hours in a 800 ml solution of 1N (NaOH + NA 2 CO 3 ) at 97 0 C. The results show that the presence of ZrO 2 in the glass composition increases its chemical durability to alkaline attack. Glasses of the aluminium/zirconium silicate series were melted with and without TiO 2 . It was shown experimentally that for this series of glasses, the presence of both TiO 2 and ZrO 2 gave better chemical durability results. However, the best overall results were obtained from the simpler zirconium silicate glasses, where it was possible to make glasses with higher values of ZrO 2 . (Author) [pt

  2. A study of redox kinetic in silicate melt

    International Nuclear Information System (INIS)

    Magnien, V.

    2005-12-01

    The aim of this thesis is to understand better iron redox reactions and mechanisms in silicate glasses and melts. Particular interest has been paid to the influence of temperature and chemical composition. For this purpose, the influence of alkali element content, iron content and network formers on the kinetics of redox reactions has been determined through XANES and Raman spectroscopy experiments performed either near the glass transition or above the liquidus temperature. As a complement, electrical conductivity and RBS spectroscopy experiments have been made to characterize the diffusivity of the species that transport electrical charges and the reaction morphology, respectively. Temperature and composition variations can induce changes in the dominating redox mechanism. At a given temperature, the parameters that exert the strongest influence on redox mechanisms are the presence or lack of divalent cations and the existing decoupling between the mobility of network former and modifier elements. Near Tg, the diffusion of divalent cations, when present in the melt, controls the kinetics of iron redox reactions along with a flux of electron holes. Composition, through the degree of polymerization and the silicate network structure, influences the kinetics and the nature of the involved cations, but not the mechanisms of the reaction. Without alkaline earth elements, the kinetics of redox reactions are controlled by the diffusion of oxygen species. With increasing temperatures, the diffusivities of all ionic species tend to become similar. The decoupling between ionic fluxes then is reduced so that several mechanisms become kinetically equivalent and can thus coexist. (author)

  3. Siliceous Shrubs in Yellowstone's Hot Springs: Implications for Exobiological Investigations

    Science.gov (United States)

    Guidry, S. A.; Chafetz, H. S.

    2003-01-01

    Potential relict hot springs have been identified on Mars and, using the Earth as an analog, Martian hot springs are postulated to be an optimal locality for recognizing preserved evidence of extraterrestrial life. Distinctive organic and inorganic biomarkers are necessary to recognize preserved evidence of life in terrestrial and extraterrestrial hot spring accumulations. Hot springs in Yellowstone National Park, Wyoming, U.S.A., contain a wealth of information about primitive microbial life and associated biosignatures that may be useful for future exobiological investigations. Numerous siliceous hot springs in Yellowstone contain abundant, centimeter-scale, spinose precipitates of opaline silica (opal-A). Although areally extensive in siliceous hot spring discharge channel facies, these spinose forms have largely escaped attention. These precipitates referred to as shrubs, consist of porous aggregates of spinose opaline silica that superficially resemble miniature woody plants, i.e., the term shrubs. Shrubs in carbonate precipitating systems have received considerable attention, and represent naturally occurring biotically induced precipitates. As such, shrubs have great potential as hot spring environmental indicators and, more importantly, proxies for pre-existing microbial life.

  4. Multiple Stage Ore Formation in the Chadormalu Iron Deposit, Bafq Metallogenic Province, Central Iran: Evidence from BSE Imaging and Apatite EPMA and LA-ICP-MS U-Pb Geochronology

    Directory of Open Access Journals (Sweden)

    Hassan Heidarian

    2018-02-01

    Full Text Available The Chadormalu magnetite-apatite deposit in Bafq metallogenic province, Central Iran, is hosted in the late Precambrian-lower Cambrian volcano-sedimentary rocks with sodic, calcic, and potassic alterations characteristic of iron oxide copper-gold (IOCG and iron oxide-apatite (IOA ore systems. Apatite occurs as scattered irregular veinlets and disseminated grains, respectively, within and in the marginal parts of the main ore-body, as well as apatite-magnetite veins in altered wall rocks. Textural evidence (SEM-BSE images of these apatites shows primary bright, and secondary dark areas with inclusions of monazite/xenotime. The primary, monazite-free fluorapatite contains higher concentrations of Na, Si, S, and light rare earth elements (LREE. The apatite was altered by hydrothermal events that led to leaching of Na, Si, and REE + Y, and development of the dark apatite. The bright apatite yielded two U-Pb age populations, an older dominant age of 490 ± 21 Ma, similar to other iron deposits in the Bafq district and associated intrusions, and a younger age of 246 ± 17 Ma. The dark apatite yielded a U-Pb age of 437 ± 12 Ma. Our data suggest that hydrothermal magmatic fluids contributed to formation of the primary fluorapatite, and sodic and calcic alterations. The primary apatite reequilibrated with basinal brines in at least two regional extensions and basin developments in Silurian and Triassic in Central Iran.

  5. A study of redox kinetic in silicate melt; Etude cinetique des reactions d'oxydoreduction dans les silicates

    Energy Technology Data Exchange (ETDEWEB)

    Magnien, V

    2005-12-15

    The aim of this thesis is to understand better iron redox reactions and mechanisms in silicate glasses and melts. Particular interest has been paid to the influence of temperature and chemical composition. For this purpose, the influence of alkali element content, iron content and network formers on the kinetics of redox reactions has been determined through XANES and Raman spectroscopy experiments performed either near the glass transition or above the liquidus temperature. As a complement, electrical conductivity and RBS spectroscopy experiments have been made to characterize the diffusivity of the species that transport electrical charges and the reaction morphology, respectively. Temperature and composition variations can induce changes in the dominating redox mechanism. At a given temperature, the parameters that exert the strongest influence on redox mechanisms are the presence or lack of divalent cations and the existing decoupling between the mobility of network former and modifier elements. Near Tg, the diffusion of divalent cations, when present in the melt, controls the kinetics of iron redox reactions along with a flux of electron holes. Composition, through the degree of polymerization and the silicate network structure, influences the kinetics and the nature of the involved cations, but not the mechanisms of the reaction. Without alkaline earth elements, the kinetics of redox reactions are controlled by the diffusion of oxygen species. With increasing temperatures, the diffusivities of all ionic species tend to become similar. The decoupling between ionic fluxes then is reduced so that several mechanisms become kinetically equivalent and can thus coexist. (author)

  6. A study of redox kinetic in silicate melt; Etude cinetique des reactions d'oxydoreduction dans les silicates

    Energy Technology Data Exchange (ETDEWEB)

    Magnien, V

    2005-12-15

    The aim of this thesis is to understand better iron redox reactions and mechanisms in silicate glasses and melts. Particular interest has been paid to the influence of temperature and chemical composition. For this purpose, the influence of alkali element content, iron content and network formers on the kinetics of redox reactions has been determined through XANES and Raman spectroscopy experiments performed either near the glass transition or above the liquidus temperature. As a complement, electrical conductivity and RBS spectroscopy experiments have been made to characterize the diffusivity of the species that transport electrical charges and the reaction morphology, respectively. Temperature and composition variations can induce changes in the dominating redox mechanism. At a given temperature, the parameters that exert the strongest influence on redox mechanisms are the presence or lack of divalent cations and the existing decoupling between the mobility of network former and modifier elements. Near Tg, the diffusion of divalent cations, when present in the melt, controls the kinetics of iron redox reactions along with a flux of electron holes. Composition, through the degree of polymerization and the silicate network structure, influences the kinetics and the nature of the involved cations, but not the mechanisms of the reaction. Without alkaline earth elements, the kinetics of redox reactions are controlled by the diffusion of oxygen species. With increasing temperatures, the diffusivities of all ionic species tend to become similar. The decoupling between ionic fluxes then is reduced so that several mechanisms become kinetically equivalent and can thus coexist. (author)

  7. About Fundamental Problems of Hydrosphere and Silicate Karst

    Directory of Open Access Journals (Sweden)

    A. Ya. Gayev

    2017-09-01

    Full Text Available Rationale of hydrosphere model with two regions of supply and discharge reveals regularities of ground water formation reflecting the special features of system water – rock – gas – living material and character of interaction of hydrosphere with the other spheres of the Earth. It is necessary to concentrate the development of endogenous hy-drogeology fundamentals with the study of silicate karst on investigation of “white and black smokers”, the structure and isotope composition of water in different phase condi-tions, and on modeling of situation in hydrometagenese zone. It will support the development of geotechnology and providing the humanity with mineral and energetic resources in future.

  8. How do US and Canadian consumers value credence attributes associated with beef labels after the North American BSE crisis of 2003?

    DEFF Research Database (Denmark)

    Steiner, Bodo; Yang, Jun

    2010-01-01

    A consumer survey conducted in 2006 (n = 419), and therefore after the first confirmed bovine spongiform encephalopathy (BSE) cases in North America in 2003, employs attribute-based choice experiments for a cross-country comparison of consumers' valuation of credence attributes associated with be....... Effective supply-chain responses to consumers' valuation of credence attributes, for example, in the form of labelling, should therefore take consumers' heterogeneity into account.......A consumer survey conducted in 2006 (n = 419), and therefore after the first confirmed bovine spongiform encephalopathy (BSE) cases in North America in 2003, employs attribute-based choice experiments for a cross-country comparison of consumers' valuation of credence attributes associated with beef...

  9. Experimental determination of the Mo isotope fractionation factor between metal and silicate liquids

    Science.gov (United States)

    Hin, R. C.; Burkhardt, C.; Schmidt, M. W.; Bourdon, B.

    2011-12-01

    The conditions and chemical consequences of core formation have mainly been reconstructed from experimentally determined element partition coefficients between metal and silicate liquids. However, first order questions such as the mode of core formation or the nature of the light element(s) in the Earth's core are still debated [1]. In addition, the geocentric design of most experimental studies leaves the conditions of core formation on other terrestrial planets and asteroids even more uncertain than for Earth. Through mass spectrometry, records of mass-dependent stable isotope fractionation during high-temperature processes such as metal-silicate segregation are detectable. Stable isotope fractionation may thus yield additional constrains on core formation conditions and its consequences for the chemical evolution of planetary objects. Experimental investigations of equilibrium mass-dependent stable isotope fractionation have shown that Si isotopes fractionate between metal and silicate liquids at temperatures of 1800°C and pressures of 1 GPa, while Fe isotopes leave no resolvable traces of core formation processes [2,3]. Molybdenum is a refractory and siderophile trace element in the Earth, and thus much less prone to complications arising from mass balancing core and mantle and from potential volatile behaviour than other elements. To determine equilibrium mass-dependent Mo isotope fractionation during metal-silicate segregation, we have designed piston cylinder experiments with a basaltic silicate composition and an iron based metal with ~8 wt% Mo, using both graphite and MgO capsules. Metal and silicate phases are completely segregated by the use of a centrifuging piston cylinder at ETH Zurich, thus preventing analysis of mixed metal and silicate signatures. Molybdenum isotope compositions were measured using a Nu Instruments 1700 MC-ICP-MS at ETH Zurich. To ensure an accurate correction of analytical mass fractionation a 100Mo-97Mo double spike was admixed

  10. The Trade-Off between Phosphorus Recycling and Health Protection during the BSE Crisis in Switzerland. A “Disposal Dilemma”

    OpenAIRE

    Lamprecht, Heinz; Lang, Daniel J.; Binder, Claudia R.; Scholz, Roland W.

    2011-01-01

    Phosphorus (P) is an essential, finite resource whose geological, economic, and geopolitical accessibility may become critical in the future. Because P losses from agriculture, sewage and waste have serious environmental impacts such as eutrophication, it would be desirable to close P cycles. However, there may arise dilemmas due to trade-offs with other issues. For instance, recycling of animal bones – containing relatively high amounts of P – was prohibited in Switzerland after the BSE cris...

  11. Electronic structures and optical properties of wurtzite type LiBSe2 (B=Al, Ga, In): A first-principles study

    International Nuclear Information System (INIS)

    Li Longhua; Li Junqian; Wu Liming

    2008-01-01

    The electronic structures of three wurtzite type isostructural compounds LiBSe 2 (B=Al, Ga, In) are studied by the density functional theory (DFT). The results reveal that the presence of Li cations has direct influence on neither the band gaps (Eg) nor the bonding levels, but plays an important role in the stabilization of the structures. The band structures and densities of states (DOS) are analyzed in detail, and the band gaps of LiBSe 2 adhere to the following trend Eg (LiAlSe2) >Eg (LiGaSe2) >Eg (LiInSe2) , which is in agreement with the decrease of the bond energy of the corresponding Se 4p-B s antibonding orbitals. The role of the active s electrons of B element on the band gaps is also discussed. Finally, the optical properties are predicted, and the results would be a guide to understand the experiments. - Graphical abstract: The electronic structures and optical properties of wurtzite type LiBSe 2 (B=Al, Ga, In) have been studied by the DFT calculations. And the correlation of the electronegative of B element and the band gap decrease-trend are discussed. The comparison between different calculation methods and the experimental results is presented

  12. Silicic magma generation at Askja volcano, Iceland

    Science.gov (United States)

    Sigmarsson, O.

    2009-04-01

    Rate of magma differentiation is an important parameter for hazard assessment at active volcanoes. However, estimates of these rates depend on proper understanding of the underlying magmatic processes and magma generation. Differences in isotope ratios of O, Th and B between silicic and in contemporaneous basaltic magmas have been used to emphasize their origin by partial melting of hydrothermally altered metabasaltic crust in the rift-zones favoured by a strong geothermal gradient. An alternative model for the origin of silicic magmas in the Iceland has been proposed based on U-series results. Young mantle-derived mafic protolith is thought to be metasomatized and partially melted to form the silicic end-member. However, this model underestimates the compositional variations of the hydrothermally-altered basaltic crust. New data on U-Th disequilibria and O-isotopes in basalts and dacites from Askja volcano reveal a strong correlation between (230Th/232Th) and delta 18O. The 1875 AD dacite has the lowest Th- and O isotope ratios (0.94 and -0.24 per mille, respectively) whereas tephra of evolved basaltic composition, erupted 2 months earlier, has significantly higher values (1.03 and 2.8 per mille, respectively). Highest values are observed in the most recent basalts (erupted in 1920 and 1961) inside the Askja caldera complex and out on the associated fissure swarm (Sveinagja basalt). This correlation also holds for older magma such as an early Holocene dacites, which eruption may have been provoked by rapid glacier thinning. Silicic magmas at Askja volcano thus bear geochemical signatures that are best explained by partial melting of extensively hydrothermally altered crust and that the silicic magma source has remained constant during the Holocene at least. Once these silicic magmas are formed they appear to erupt rapidly rather than mixing and mingling with the incoming basalt heat-source that explains lack of icelandites and the bi-modal volcanism at Askja

  13. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.; Chae, S. R.; Benmore, C. J.; Wenk, H. R.; Monteiro, P. J. M.

    2010-01-01

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  14. Nanostructure of Calcium Silicate Hydrates in Cements

    KAUST Repository

    Skinner, L. B.

    2010-05-11

    Calcium silicate hydrate (CSH) is the major volume phase in the matrix of Portland cement concrete. Total x-ray scattering measurements with synchrotron x rays on synthetic CSH(I) shows nanocrystalline ordering with a particle diameter of 3.5(5) nm, similar to a size-broadened 1.1 nm tobermorite crystal structure. The CSH component in hydrated tricalcium silicate is found to be similar to CSH(I). Only a slight bend and additional disorder within the CaO sheets is required to explain its nanocrystalline structure. © 2010 The American Physical Society.

  15. Combustion synthesis and photoluminescence study of silicate ...

    Indian Academy of Sciences (India)

    sorbable and durable materials for orthopaedic and dental implants, that are capable of bearing high stress ... Other studies showed that these silicate ceramics also possess good in vivo bioactivity (Hench 1998; ... ceramic powders without the intermediate decomposition and/or calcining steps has attracted a good deal of ...

  16. Synthesis of non-siliceous mesoporous oxides.

    Science.gov (United States)

    Gu, Dong; Schüth, Ferdi

    2014-01-07

    Mesoporous non-siliceous oxides have attracted great interest due to their unique properties and potential applications. Since the discovery of mesoporous silicates in 1990s, organic-inorganic assembly processes by using surfactants or block copolymers as soft templates have been considered as a feasible path for creating mesopores in metal oxides. However, the harsh sol-gel conditions and low thermal stabilities have limited the expansion of this method to various metal oxide species. Nanocasting, using ordered mesoporous silica or carbon as a hard template, has provided possibilities for preparing novel mesoporous materials with new structures, compositions and high thermal stabilities. This review concerns the synthesis, composition, and parameter control of mesoporous non-siliceous oxides. Four synthesis routes, i.e. soft-templating (surfactants or block copolymers as templates), hard-templating (mesoporous silicas or carbons as sacrificial templates), colloidal crystal templating (3-D ordered colloidal particles as a template), and super lattice routes, are summarized in this review. Mesoporous metal oxides with different compositions have different properties. Non-siliceous mesoporous oxides are comprehensively described, including a discussion of constituting elements, synthesis, and structures. General aspects concerning pore size control, atomic scale crystallinity, and phase control are also reviewed.

  17. Dielectric properties of plasma sprayed silicates

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Neufuss, Karel; Dubský, Jiří; Chráska, Pavel

    -, č. 31 (2005), s. 315-321 ISSN 0272-8842 R&D Projects: GA ČR(CZ) GA202/03/0708 Institutional research plan: CEZ:AV0Z20430508 Keywords : Optical microscopy * electrical properties * silicates * insulators * plasma spraying Subject RIV: JH - Ceramics, Fire-Resistant Materials and Glass Impact factor: 0.702, year: 2005

  18. Selective silicate-directed motility in diatoms

    DEFF Research Database (Denmark)

    Bondoc, Karen Grace V.; Heuschele, Jan; Gillard, Jeroen

    2016-01-01

    the major sink in the global Si cycle. Dissolved silicic acid (dSi) availability frequently limits diatom productivity and influences species composition of communities. We show that benthic diatoms selectively perceive and behaviourally react to gradients of dSi. Cell speed increases under d...

  19. The importance of the Maillard-metal complexes and their silicates in astrobiology

    Science.gov (United States)

    Liesch, Patrick J.; Kolb, Vera M.

    2007-09-01

    The Maillard reaction occurs when sugars and amino acids are mixed together in the solid state or in the aqueous solution. Since both amino acids and sugar-like compounds are found on meteorites, we hypothesized that they would also undergo the Maillard reaction. Our recent work supports this idea. We have shown previously that the water-insoluble Maillard products have substantial similarities with the insoluble organic materials from the meteorites. The Maillard organic materials are also part of the desert varnish on Earth, which is a dark, shiny, hard rock coating that contains iron and manganese and is glazed in silicate. Rocks that are similar in appearance to the desert varnish have been observed on the Martian surface. They may also contain the organic materials. We have undertaken study of the interactions between the Maillard products, iron and other metals, and silicates, to elucidate the role of the Maillard products in the chemistry of desert varnish and meteorites. Specifically, we have synthesized a series of the Maillard-metal complexes, and have tested their reactivity towards silicates. We have studied the properties of these Maillard-metal-silicate products by the IR spectroscopy. The astrobiological potential of the Maillard-metal complexes is assessed.

  20. 21 CFR 582.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Aluminum calcium silicate. 582.2122 Section 582.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  1. 21 CFR 182.2122 - Aluminum calcium silicate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Aluminum calcium silicate. 182.2122 Section 182.2122 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED....2122 Aluminum calcium silicate. (a) Product. Aluminum calcium silicate. (b) Tolerance. 2 percent. (c...

  2. Suppressive effects of a polymer sodium silicate solution on ...

    African Journals Online (AJOL)

    Sodium silicate was dissolved in water in either a monomer form or polymer form; the effects of both forms of sodium silicate aqueous solution on rose powdery mildew and root rot diseases of miniature rose were examined. Both forms of sodium silicate aqueous solution were applied to the roots of the miniature rose.

  3. 40 CFR 721.9513 - Modified magnesium silicate polymer (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Modified magnesium silicate polymer... Specific Chemical Substances § 721.9513 Modified magnesium silicate polymer (generic). (a) Chemical... as modified magnesium silicate polymer (PMN P-98-604) is subject to reporting under this section for...

  4. Rare earth element patterns of the Central Indian Basin sediments related to their lithology

    Digital Repository Service at National Institute of Oceanography (India)

    Nath, B.N.; Roelandts, I.; Sudhakar, M.; Pluger, W.L.

    Rare earth element (REE) concentration have been determined in terrigenous, siliceous (nodule barren and nodule bearing), calcareous, and red clay from the Central Indian Basin. The bulk distribution of REE, and in particular the relative cerium...

  5. Final report on the safety assessment of potassium silicate, sodium metasilicate, and sodium silicate.

    Science.gov (United States)

    Elmore, Amy R

    2005-01-01

    Potassium Silicate, Sodium Metasilicate, and Sodium Silicate combine metal cations with silica to form inorganic salts used as corrosion inhibitors in cosmetics. Sodium Metasilicate also functions as a chelating agent and Sodium Silicate as a buffering and pH adjuster. Sodium Metasilicate is currently used in 168 formulations at concentrations ranging from 13% to 18%. Sodium Silicate is currently used in 24 formulations at concentrations ranging from 0.3% to 55%. Potassium Silicate and Sodium Silicate have been reported as being used in industrial cleaners and detergents. Sodium Metasilicate is a GRAS (generally regarded as safe) food ingredient. Aqueous solutions of Sodium Silicate species are a part of a chemical continuum of silicates based on an equilibrium of alkali, water, and silica. pH determines the solubility of silica and, together with concentration, determines the degree of polymerization. Sodium Silicate administered orally is readily absorbed from the alimentary canal and excreted in the urine. The toxicity of these silicates has been related to the molar ratio of SiO2/Na2O and the concentration being used. The Sodium Metasilicate acute oral LD50 ranged from 847 mg/kg in male rats to 1349.3 mg/kg in female rats and from 770 mg/kg in female mice to 820 mg/kg in male mice. Gross lesions of variable severity were found in the oral cavity, pharynx, esophagus, stomach, larynx, lungs, and kidneys of dogs receiving 0.25 g/kg or more of a commercial detergent containing Sodium Metasilicate; similar lesions were also seen in pigs administered the same detergent and dose. Male rats orally administered 464 mg/kg of a 20% solution containing either 2.0 or 2.4 to 1.0 ratio of sodium oxide showed no signs of toxicity, whereas doses of 1000 and 2150 mg/kg produced gasping, dypsnea, and acute depression. Dogs fed 2.4 g/kg/day of Sodium Silicate for 4 weeks had gross renal lesions but no impairment of renal function. Dermal irritation of Potassium Silicate, Sodium

  6. Insight into silicate-glass corrosion mechanisms

    Energy Technology Data Exchange (ETDEWEB)

    Cailleteau, C; Angeli, F; Gin, S; Jollivet, P [CEA VALRHO, DEN, Lab Etude Comportement Long Terme, F-30207 Bagnols Sur Ceze, (France); Devreux, F [Ecole Polytech, CNRS, Lab Phys Mat Condensee, F-91128 Palaiseau, (France); Jestin, J [CEA, CNRS, Lab Leon Brillouin, F-91191 Gif Sur Yvette, (France); Spalla, O [CEA, DSM, Lab Interdisciplinaire Org Nanometr et Supramol, F-91191 Gif Sur Yvette, (France)

    2008-07-01

    The remarkable chemical durability of silicate glass makes it suitable for a wide range of applications. The slowdown of the aqueous glass corrosion kinetics that is frequently observed at long time is generally attributed to chemical affinity effects (saturation of the solution with respect to silica). Here, we demonstrate a new mechanism and highlight the impact of morphological transformations in the alteration layer on the leaching kinetics. A direct correlation between structure and reactivity is revealed by coupling the results of several structure-sensitive experiments with numerical simulations at mesoscopic scale. The sharp drop in the corrosion rate is shown to arise from densification of the outer layers of the alteration film, leading to pore closure. The presence of insoluble elements in the glass can inhibit the film restructuring responsible for this effect. This mechanism may be more broadly applicable to silicate minerals. (authors)

  7. Sorption of Europium in zirconium silicate

    International Nuclear Information System (INIS)

    Garcia R, G.

    2004-01-01

    Some minerals have the property of sipping radioactive metals in solution, that it takes advantage to manufacture contention barriers that are placed in the repositories of nuclear wastes. The more recent investigations are focused in the development of new technologies guided to the sorption of alpha emissors on minerals which avoid their dispersion in the environment. In an effort to contribute to the understanding of this type of properties, some studies of sorption of Europium III are presented like homologous of the americium, on the surface of zirconium silicate (ZrSiO 4 ). In this work the results of sorption experiences are presented as well as the interpretation of the phenomena of the formation of species in the surface of the zirconium silicate. (Author)

  8. Effects of ionization on silicate glasses

    International Nuclear Information System (INIS)

    Primak, W.

    1982-02-01

    This evaluation of radiation effects in silicate glasses caused by ionization is based on our own investigations, on material collected in our files (reports, articles, and notes), and on a computer literature search through recent issues of Physics Abstracts and Chemical Abstracts (and the apparently pertinent references which appeared). Some of our recent results, available heretofore only in internal correspondence, are presented in some detail. It is concluded that research into the behavior of silicate glasses generally will be required before the specific effects in the radioactive waste storage glasses can be properly understood and evaluated. Two particular neglected areas of investigation are targeted for immediate concern: a kinetic analysis of annealing data and the acquisition of data on effects of irradiation at controlled elevated temperatures

  9. Stability constants for silicate adsorbed to ferrihydrite

    DEFF Research Database (Denmark)

    Hansen, Hans Christian Bruun; Wetche, T.P.; Raulund-Rasmussen, Karsten

    1994-01-01

    Intrinsic surface acidity constants (K(a1)intr, K(a2)intr) and surface complexation constant for adsorption of orthosilicate onto synthetic ferrihydrite (K(Si) for the complex = FeOSi(OH)3) have been determined from acid/base titrations in 0.001-0.1 m NaClO4 electrolytes and silicate adsorption...... experiments in 0.01 m NaNO3 electrolyte (pH 3-6). The surface equilibrium constants were calculated according to the two-layer model by Dzombak & Morel (1990). Near equilibrium between protons/hydroxyls in solution and the ferrihydrite surface was obtained within minutes while equilibration with silicate...

  10. SILICATE EVOLUTION IN BROWN DWARF DISKS

    International Nuclear Information System (INIS)

    Riaz, B.

    2009-01-01

    We present a compositional analysis of the 10 μm silicate spectra for brown dwarf disks in the Taurus and Upper Scorpius (UppSco) star-forming regions, using archival Spitzer/Infrared Spectrograph observations. A variety in the silicate features is observed, ranging from a narrow profile with a peak at 9.8 μm, to nearly flat, low-contrast features. For most objects, we find nearly equal fractions for the large-grain and crystalline mass fractions, indicating both processes to be active in these disks. The median crystalline mass fraction for the Taurus brown dwarfs is found to be 20%, a factor of ∼2 higher than the median reported for the higher mass stars in Taurus. The large-grain mass fractions are found to increase with an increasing strength in the X-ray emission, while the opposite trend is observed for the crystalline mass fractions. A small 5% of the Taurus brown dwarfs are still found to be dominated by pristine interstellar medium-like dust, with an amorphous submicron grain mass fraction of ∼87%. For 15% of the objects, we find a negligible large-grain mass fraction, but a >60% small amorphous silicate fraction. These may be the cases where substantial grain growth and dust sedimentation have occurred in the disks, resulting in a high fraction of amorphous submicron grains in the disk surface. Among the UppSco brown dwarfs, only usd161939 has a signal-to-noise ratio high enough to properly model its silicate spectrum. We find a 74% small amorphous grain and a ∼26% crystalline mass fraction for this object.

  11. Adsorption of dimeric surfactants in lamellar silicates

    Energy Technology Data Exchange (ETDEWEB)

    Balcerzak, Mateusz; Pietralik, Zuzanna [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland); Domka, Ludwik [Department of Metalorganic Chemistry, Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Poznań (Poland); Skrzypczak, Andrzej [Institute of Chemical Technology, Poznań University of Technology, Berdychowo 4, 60-965 Poznań (Poland); Kozak, Maciej, E-mail: mkozak@amu.edu.pl [Department of Macromolecular Physics, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Poznań (Poland)

    2015-12-01

    Highlights: • The intercalation of dimeric surfactants changed the morphology of MMT samples. • XRD indicated structures formed by surfactant molecules in interlayer space. • The four-step thermal decomposition of dimeric surfactant, confirms intercalation. - Abstract: The adsorption of different types of cationic surfactants in lamellar silicates changes their surface character from hydrophilic to hydrophobic. This study was undertaken to obtain lamellar silicates modified by a series of novel dimeric (gemini) surfactants of different length alkyl chains and to characterise these organophilised materials. Synthetic sodium montmorillonite SOMASIF® ME 100 (M) and enriched bentonite of natural origin (Nanoclay – hydrophilic bentonite®) were organophilised with dimeric (gemini) surfactants (1,1′-(1,4-butanediyl)bis(alkoxymethyl)imidazolium dichlorides). As a result of surfactant molecule adsorption in interlamellar space, the d-spacing (d{sub 001}) increased from 0.97 nm (for the anhydrous structure) to 2.04 nm. A Fourier transform infrared spectroscopy (FTIR) analysis of the modified systems reveals bands assigned to the stretching vibrations of the CH{sub 2} and CH{sub 3} groups and the scissoring vibrations of the NH group from the structure of the dimeric surfactants. Thermogravimetric (TG) and derivative thermogravimetric (DTG) studies imply a four-stage process of surfactant decomposition. Scanning electron microscopy (SEM) images provide information on the influence of dimeric surfactant intercalation into the silicate structures. Particles of the modified systems show a tendency toward the formation of irregularly shaped agglomerates.

  12. Lead-silicate glass optical microbubble resonator

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Pengfei, E-mail: pengfei.wang@dit.ie [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland); Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Ward, Jonathan; Yang, Yong; Chormaic, Síle Nic [Light-Matter Interactions Unit, OIST Graduate University, 1919-1 Tancha, Onna-son, Okinawa 904-0495 (Japan); Feng, Xian; Brambilla, Gilberto [Optoelectronics Research Centre, University of Southampton, Southampton SO17 1BJ (United Kingdom); Farrell, Gerald [Photonics Research Centre, Dublin Institute of Technology, Kevin Street, Dublin 8 (Ireland)

    2015-02-09

    Microbubble whispering gallery resonators have the potential to become key components in a variety of active and passive photonic circuit devices by offering a range of significant functionalities. Here, we report on the fabrication, optical characterization, and theoretical analysis of lead-silicate glass and optical microbubble resonators. Evanescent field coupling to the microbubbles was achieved using a 1 μm diameter, silica microfiber at a wavelength of circa 775 nm. High Q-factor modes were efficiently excited in both single-stem and two-stem, lead-silicate glass, and microbubble resonators, with bubble diameters of 38 μm (single-stem) and 48 μm (two-stem). Whispering gallery mode resonances with Q-factors as high as 2.3 × 10{sup 5} (single-stem) and 7 × 10{sup 6} (two-stem) were observed. By exploiting the high-nonlinearity of the lead-silicate glass, this work will act as a catalyst for studying a range of nonlinear optical effects in microbubbles, such as Raman scattering and four-wave mixing, at low optical powers.

  13. Congruency within rural social networks as an indicator of interpersonal influence on risk judgments: the great stir caused by BSE in a village in northern Germany.

    Science.gov (United States)

    Lehmkuhl, Markus J

    2008-10-01

    In the following survey, congruency within a sample of 150 rural social networks ascertained by comparing independently gathered data is used as an indicator of interpersonal influence concerning BSE-related current knowledge and consumption habits. Our findings suggest that friends, relatives and acquaintances mutually orientated each other about what was worth knowing about BSE. Concerning the behavioral dimension of risk judgments, our findings indicate that social networks obtained within the village explored have activated collective resistance against fear. This is explained by the character of the risk source. Positive attitudes towards conventional farming obviously contributed to the social identity of villagers. The devaluation of conventional farming as a source of societal threat by the mass media touched on an integral part of the self-definitions of villagers and activated resistance within their social networks. It is argued that a central point in explaining the role of interpersonal influence in risk judgments is not only the dimension of risk judgments but the character of the risk source. If attitudes concerning a risk source contribute positively to one's identity, the devaluation of the risk source by mass media coverage may enhance the probability of collective resistance against fear.

  14. Behaviour of Rare Earth Elements during the Earth's core formation

    Science.gov (United States)

    Faure, Pierre; Bouhifd, Mohamed Ali; Boyet, Maud; Hammouda, Tahar; Manthilake, Geeth

    2017-04-01

    Rare Earth Elements (REE) are classified in the refractory group, which means that they have a high temperature condensation and their volatility-controlled fractionation is limited to high-temperature processes. Anomalies have been measured for Eu, Yb and Sm, which are the REE with the lowest condensation temperatures in CAIs and chondrules (e.g. [1]). REE are particularly abundant in the sulfides of enstatite chondrites, 100 to 1000 times the CI value [e.g. 2,3], proving that these elements are not strictly lithophile under extremely reducing conditions. However by investigating experimentally the impact of Earth's core formation on the behavior of Sm and Nd, we have shown the absence of fractionation between Sm and Nd during the segregation of the metallic phase [4]. Recently, Wohlers and Wood [5] proposed that Nd and Sm could be fractionated in presence of a S-rich alloy phase. However, their results were obtained at pressure and temperature conditions below the plausible conditions of the Earth's core formation. Clearly, large pressure range needs to be covered before well-constrained model can be expected. Furthermore, our preliminary metal-silicate partitioning results show that Ce and Eu have higher metal/silicate partition coefficients than their neighboring elements, and that the presence of sulphur enhances the relative difference between partition coefficients. In this presentation, we will present and discuss new metal-silicate partition coefficients of all REE at a deep magma ocean at pressures ranging from those of the uppermost upper mantle ( 5 GPa) to a maximum pressure expected in the range of 20 GPa, temperatures ranging from 2500 to about 3000 K, and oxygen fugacities within IW-1 to IW-5 (1 to 5 orders of magnitude lower than the iron-wüstite buffer). We will discuss the effect of S, as well as the effect of H2O on the behaviour of REE during the Earth's core formation: recent models suggest that contrary to currently accepted beliefs, the

  15. Regularities in Low-Temperature Phosphatization of Silicates

    Science.gov (United States)

    Savenko, A. V.

    2018-01-01

    The regularities in low-temperature phosphatization of silicates are defined from long-term experiments on the interaction between different silicate minerals and phosphate-bearing solutions in a wide range of medium acidity. It is shown that the parameters of the reaction of phosphatization of hornblende, orthoclase, and labradorite have the same values as for clayey minerals (kaolinite and montmorillonite). This effect may appear, if phosphotization proceeds, not after silicate minerals with a different structure and composition, but after a secondary silicate phase formed upon interaction between silicates and water and stable in a certain pH range. Variation in the parameters of the reaction of phosphatization at pH ≈ 1.8 is due to the stability of the silicate phase different from that at higher pH values.

  16. Testing Urey's carbonate-silicate cycle using the calcium isotopic composition of sedimentary carbonates

    Science.gov (United States)

    Blättler, Clara L.; Higgins, John A.

    2017-12-01

    Carbonate minerals constitute a major component of the sedimentary geological record and an archive of a fraction of the carbon and calcium cycled through the Earth's surface reservoirs for over three billion years. For calcium, carbonate minerals constitute the ultimate sink for almost all calcium liberated during continental and submarine weathering of silicate minerals. This study presents >500 stable isotope ratios of calcium in Precambrian carbonate sediments, both limestones and dolomites, in an attempt to characterize the isotope mass balance of the sedimentary carbonate reservoir through time. The mean of the dataset is indistinguishable from estimates of the calcium isotope ratio of bulk silicate Earth, consistent with the Urey cycle being the dominant mechanism exchanging calcium among surface reservoirs. The variability in bulk sediment calcium isotope ratios within each geological unit does not reflect changes in the global calcium cycle, but rather highlights the importance of local mineralogical and/or diagenetic effects in the carbonate record. This dataset demonstrates the potential for calcium isotope ratios to help assess these local effects, such as the former presence of aragonite, even in rocks with a history of neomorphism and recrystallization. Additionally, 29 calcium isotope measurements are presented from ODP (Ocean Drilling Program) Site 801 that contribute to the characterization of altered oceanic crust as an additional sink for calcium, and whose distinct isotopic signature places a limit on the importance of this subduction flux over Earth history.

  17. What can the Hf–W System tell Us About the Mechanism and Timing of Earth's Core Formation?

    Science.gov (United States)

    Fischer, R. A.; Nimmo, F.; O'Brien, D. P.

    2018-05-01

    Strong tradeoff between effects of depth and extent of metal-silicate equilibration and formation timescale on the Hf-W system. Whole mantle equilibration requires k = 0.4. Later formation times require less equilibration to match Earth's anomaly.

  18. Tribo-exoemission from some silicate materials

    International Nuclear Information System (INIS)

    Holzapfel, G.; Lesz, J.; Otto, W.

    1983-01-01

    The tribo-exoemission from some minerals has been investigated in view of applications in the porcelain industries. Milling and sample preparation were performed under defined (liquid and solvent free) conditions. Quartz and the members of the alumo-silicate family feldspar, kaolin, and pegmatite are characterised by a strongly overlapped TSEE-peak between 100 0 C and 200 0 C, growing strongly with the mechanical dispersion of the powders. Thermal (TSEE) as well as optical (OSEE) stimulation reveal pegmatite as the strongest emitter with a very low fading of the tribo-signal at room temperature. (author)

  19. Structure peculiarities of mixed alkali silicate glasses

    International Nuclear Information System (INIS)

    Bershtein, V.A.; Gorbachev, V.V.; Egorov, V.

    1980-01-01

    The thermal porperties and structure of alkali and mixed alkali (Li, Na, K) silicate glasses by means of differential scanning calorimetry (DSC), the positron annihilation method, X-ray fluorescence and infrared (300-30 cm -1 ) spectroscopy were studied. Introduction of different alkali cations in glass results in nonadditive change in their electron structure (bond covalence degree growth) and the thermal behaviour. The different manifestations of mixed alkali effect can be explained by the lessening of long distance Coulomb interactions and strengthening the short-range forces in the mixed alkali glasses. (orig.)

  20. LABORATORY INVESTIGATIONS OF SILICATE MUD CONTAMINATION WITH CALCIUM

    Directory of Open Access Journals (Sweden)

    Nediljka Gaurina-Međimurec

    2004-12-01

    Full Text Available The silicate-based drilling fluid is a low solids KCl/polymer system with the addition of soluble sodium or potassium silicate to enhance inhibition and wellbore stability. Silicate-based drilling fluids exhibit remarkable shale and chalk stabilizing properties, resulting in gauge hole and the formation of firm cuttings when drilling reactive shales and soft chalks. Silicates protect shales by in-situ gellation when exposed to the neutral pore fluid and precipitation, which occurs on contact with divalent ions present at the surface of the shale. Also, silicates prevent the dispersion and washouts when drilling soft chalk by reacting with the Ca2+ ions present on chalk surfaces of cutting and wellbore to form a protective film. The silicate-based drilling fluid can be used during drilling hole section through shale interbeded anhydrite formations because of its superior shale stabilizing characteristics. However, drilling through the anhydrite can decrease the silicate concentration and change rheological and filtration fluid properties. So, the critical concentration of calcium ions should be investigated by lab tests. This paper details the mechanism of shale inhibition using silicate-based drilling fluid, and presents results of lab tests conducted to ascertain the effect of Ca2+ ions on silicate level in the fluid and the fluid properties.

  1. Location of silicic caldera formation in arc settings

    Energy Technology Data Exchange (ETDEWEB)

    Hughes, Gwyneth R; Mahood, Gail A [Department of Geological and Environmental Sciences, Stanford University, 450 Serra, Mall, Building 320, Stanford, CA 94305-2115 (United States)

    2008-10-01

    Silicic calderas are the surface expressions of silicic magma chambers, and thus their study may yield information about what tectonic and crustal features favor the generation of evolved magma. The goal of this study is to determine whether silicic calderas in arc settings are preferentially located behind the volcanic front. After a global analysis of young, arc-related calderas, we find that silicic calderas at continental margins do form over a wide area behind the front, as compared to other types of arc volcanoes.

  2. Incorporation of bitumen and calcium silicate in cement and lime stabilized soil blocks

    Science.gov (United States)

    Kwan, W. H.; Cheah, C. B.; Ramli, M.; Al-Sakkaf, Y. K.

    2017-04-01

    Providing affordable housing is the most critical problem in many of the developing countries. Using earth materials in building construction is one of the feasible methods to address this issue and it can be a way towards sustainable construction as well. However, the published information on the stabilized soil blocks is limited. Therefore, the present study is conducted to examine the characterization of the soils and engineering properties of the stabilized soil blocks. Four types of stabilizer were used in the study, namely; cement, slaked lime, bitumen emulsion and calcium silicate. Cement and slaked lime were added at different percentages in the range of 5% to 15%, with interval of 2.5%. The percentage was determined based on weight of soil. Meanwhile, bitumen emulsion and calcium silicate were incorporated at various percentages together with 10% of cement. Dosage of bitumen emulsion is in the range of 2% to 10% at interval of 2% while calcium silicate was incorporated at 0.50%, 0.75%, 1.00%, 1.25%, 1.50% and 2.00%. Results show that cement is the most viable stabilizer for the soil block among all stabilizers in this study. The bulk density, optimum moisture content and compressive strengths were increased with the increasing cement content. The most suitable cement content was 10% added at moisture content of 12%. Lime, bitumen and calcium contents were recommended at 5.0%, 6.0% and 1.25%, respectively.

  3. Tip-induced nanoreactor for silicate

    Science.gov (United States)

    Gao, Ming; Ma, Liran; Liang, Yong; Gao, Yuan; Luo, Jianbin

    2015-09-01

    Nanoscale scientific issues have attracted an increasing amount of research interest due to their specific size-effect and novel structure-property. From macro to nano, materials present some unique chemical reactivity that bulk materials do not own. Here we introduce a facile method to generate silicate with nanoscale control based on the establishment of a confined space between a meso/nanoscale tungsten tip and a smooth silica/silicon substrate. During the process, local water-like droplets deposition can be obviously observed in the confinement between the Si/SiO2 surfaces and the KOH-modified tungsten tip. By the combination of in-situ optical microscopy and Raman spectroscopy, we were able to take a deep insight of both the product composition and the underlying mechanism of such phenomena. It was indicated that such nanoreactor for silicate could be quite efficient as a result of the local capillarity and electric field effect, with implications at both nano and meso scales.

  4. Evidence for seismogenic fracture of silicic magma.

    Science.gov (United States)

    Tuffen, Hugh; Smith, Rosanna; Sammonds, Peter R

    2008-05-22

    It has long been assumed that seismogenic faulting is confined to cool, brittle rocks, with a temperature upper limit of approximately 600 degrees C (ref. 1). This thinking underpins our understanding of volcanic earthquakes, which are assumed to occur in cold rocks surrounding moving magma. However, the recent discovery of abundant brittle-ductile fault textures in silicic lavas has led to the counter-intuitive hypothesis that seismic events may be triggered by fracture and faulting within the erupting magma itself. This hypothesis is supported by recent observations of growing lava domes, where microearthquake swarms have coincided with the emplacement of gouge-covered lava spines, leading to models of seismogenic stick-slip along shallow shear zones in the magma. But can fracturing or faulting in high-temperature, eruptible magma really generate measurable seismic events? Here we deform high-temperature silica-rich magmas under simulated volcanic conditions in order to test the hypothesis that high-temperature magma fracture is seismogenic. The acoustic emissions recorded during experiments show that seismogenic rupture may occur in both crystal-rich and crystal-free silicic magmas at eruptive temperatures, extending the range of known conditions for seismogenic faulting.

  5. Magnetic mineralogy and rock magnetic properties of silicate and carbonatite rocks from Oldoinyo Lengai volcano (Tanzania)

    Science.gov (United States)

    Mattsson, H. B.; Balashova, A.; Almqvist, B. S. G.; Bosshard-Stadlin, S. A.; Weidendorfer, D.

    2018-06-01

    Oldoinyo Lengai, a stratovolcano in northern Tanzania, is most famous for being the only currently active carbonatite volcano on Earth. The bulk of the volcanic edifice is dominated by eruptive products produced by silica-undersaturated, peralkaline, silicate magmas (effusive, explosive and/or as cumulates at depth). The recent (2007-2008) explosive eruption produced the first ever recorded pyroclastic flows at this volcano and the accidental lithics incorporated into the pyroclastic flows represent a broad variety of different rock types, comprising both extrusive and intrusive varieties, in addition to various types of cumulates. This mix of different accidental lithics provides a unique insight into the inner workings of the world's only active carbonatite volcano. Here, we focus on the magnetic mineralogy and the rock magnetic properties of a wide selection of samples spanning the spectrum of Oldoinyo Lengai rock types compositionally, as well from a textural point of view. Here we show that the magnetic properties of most extrusive silicate rocks are dominated by magnetite-ulvöspinel solid solutions, and that pyrrhotite plays a larger role in the magnetic properties of the intrusive silicate rocks. The natrocarbonatitic lavas, for which the volcano is best known for, show distinctly different magnetic properties in comparison with the silicate rocks. This discrepancy may be explained by abundant alabandite crystals/blebs in the groundmass of the natrocarbonatitic lavas. A detailed combination of petrological/mineralogical studies with geophysical investigations is an absolute necessity in order to understand, and to better constrain, the overall architecture and inner workings of the subvolcanic plumbing system. The results presented here may also have implications for the quest in order to explain the genesis of the uniquely natrocarbonatitic magmas characteristic of Oldoinyo Lengai.

  6. Journal of Earth System Science | Indian Academy of Sciences

    Indian Academy of Sciences (India)

    We report the presence of a 3-5 cm thick loose fragmental layer in the Siliceous Earth at Matti ka Gol in the Barmer basin of Rajasthan. Petrographic, chemical and mineralogical study reveals the presence of abundant volcanic debris such as glass shards, agglutinates, hollow spheroids, kinked biotites, feldspars showing ...

  7. Spectral properties of porphyrins in the systems with layered silicates

    International Nuclear Information System (INIS)

    Ceklovsky, A.

    2009-03-01

    This work is focused on investigation of hybrid materials based on layered silicates, representing host inorganic component, and porphyrin dyes as organic guest. Aqueous colloidal dispersions, as well as thin solid films of layered silicate/porphyrin systems were studied. Modification of photophysical properties, such as absorption and fluorescence of molecules, adsorbed or incorporated in layered silicate hosts, were studied mainly to spread the knowledge about the environments suitable for incorporating aromatic compounds, providing photoactive properties of potential technological interest. TMPyP cations interact with the surfaces of layered silicates via electrostatic interactions. The extent of dye adsorption on colloidal particles of the silicates is influenced by the CEC values and swelling ability of silicates. Interaction of porphyrins with layered silicate hosts leads to significant changes of dye spectral properties. One of the key parameters that has a crucial impact on this interaction is the layer charge of silicate template. Other factors influence the resulting spectral properties of hybrid systems, such as the method of hybrid material preparation, the material's type (colloid, film), and the modification of the silicate host. Molecular orientation studies using linearly-polarized spectroscopies in VIS and IR regions revealed that TMPyP molecules were oriented in almost parallel fashion with respect to the silicate surface plane. Slightly higher values of the orientation angle of TMPyP transition moment were observed for the TMPyP/FHT system. Thus, flattening of the guest TMPyP molecules is the next important factor (mainly in the systems with lower layer charge), influencing its spectral properties upon the interaction with layered silicates. Fluorescence was effectively quenched in the systems based on solid films prepared from the high concentration of the dye (10-3 mol.dm-3). The quenching is most probably related to the structure of the

  8. Stress-corrosion mechanisms in silicate glasses

    International Nuclear Information System (INIS)

    Ciccotti, Matteo

    2009-01-01

    The present review is intended to revisit the advances and debates in the comprehension of the mechanisms of subcritical crack propagation in silicate glasses almost a century after its initial developments. Glass has inspired the initial insights of Griffith into the origin of brittleness and the ensuing development of modern fracture mechanics. Yet, through the decades the real nature of the fundamental mechanisms of crack propagation in glass has escaped a clear comprehension which could gather general agreement on subtle problems such as the role of plasticity, the role of the glass composition, the environmental condition at the crack tip and its relation to the complex mechanisms of corrosion and leaching. The different processes are analysed here with a special focus on their relevant space and time scales in order to question their domain of action and their contribution in both the kinetic laws and the energetic aspects.

  9. Cesium titanium silicate and method of making

    Science.gov (United States)

    Balmer, Mari L.

    1997-01-01

    The invention is the new material, a ternary compound of cesium, silica, and titania, together with a method of making the ternary compound, cesium titanium silicate pollucite. More specifically, the invention is Cs.sub.2 Ti.sub.2 Si.sub.4 O.sub.13 pollucite which is a new crystalline phase representing a novel class of Ti-containing zeolites. Compositions contain relatively high Cs.sub.2 O and TiO.sub.2 loadings and are durable glass and ceramic materials. The amount of TiO.sub.2 and Cs.sub.2 that can be incorporated into these glasses and crystalline ceramics far exceeds the limits set for the borosilicate high level waste glass.

  10. Radiation effects on lead silicate glass surfaces

    International Nuclear Information System (INIS)

    Wang, P.W.; Zhang, L.P.; Borgen, N.; Pannell, K.

    1996-01-01

    Radiation-induced changes in the microstructure of lead silicate glass were investigated in situ under Mg K α irradiation in an ultra-high vacuum (UHV) environment by X-ray photoelectron spectroscopy (XPS). Lead-oxygen bond breaking resulting in the formation of pure lead was observed. The segregation, growth kinetics and the structural relaxation of the lead, with corresponding changes in the oxygen and silicon on the glass surfaces were studied by measuring the time-dependent changes in concentration, binding energy shifts, and the full width at half maximum. A bimodal distribution of the oxygen XPS signal, caused by bridging and non-bridging oxygens, was found during the relaxation process. All experimental data indicate a reduction of the oxygen concentration, a phase separation of the lead from the glass matrix, and the metallization of the lead occurred during and after the X-ray irradiation. (author)

  11. Redox kinetics and mechanism in silicate melts

    International Nuclear Information System (INIS)

    Cochain, B.

    2009-12-01

    This work contributes to better understand iron redox reactions and mechanisms in silicate melts. It was conducted on compositions in both Na 2 O-B 2 O 3 -SiO 2 -FeO and Na 2 O-Al 2 O 3 -SiO 2 -FeO systems. The influence of boron-sodium and aluminum-sodium substitutions and iron content on properties and structure of glasses and on the iron redox kinetics has been studied by Raman, Moessbauer and XANES spectroscopies at the B and Fe K-edges. In borosilicate glasses, an increase in iron content or in the Fe 3+ /ΣFe redox state implies a structural rearrangement of the BO 4 species in the glass network whereas the BO 3 and BO 4 relative proportions remain nearly constant. In all studied glasses and melts, Fe 3+ is a network former in tetrahedral coordination, unless for aluminosilicates of ratio Al/Na≥1 where Fe 3+ is a network modifier in five-fold coordination. Near Tg, diffusion of network modifying cations controls the iron redox kinetics along with a flux of electron holes. At liquidus temperatures, oxygen diffusion is considered to be the mechanism that governs redox reactions. This study shows the role played by the silicate network polymerization on the redox kinetics. In borosilicate melts, iron redox kinetics depends on the boron speciation between BO 3 and BO 4 that depends itself on the sodium content. Furthermore, an increase in the network-former/network-modifier ratio implies a decrease in oxygen diffusion that results in a slowing down of the redox kinetics. The obtained results allow a description of the iron redox kinetics for more complex compositions as natural lavas or nuclear waste model glasses. (author)

  12. X-ray photoemission spectroscopy (XPS) and extended x-ray absorption fine structure (EXAFS) studies of silicate based glasses

    International Nuclear Information System (INIS)

    Karim, D.; Lam, D.J.

    1979-01-01

    The application of the x-ray photoemission spectroscopy (XPS) technique to study the electronic structure and bonding of heavy metal oxides in alkali- and alkali-earth-silicate glasses had been demonstrated. The bonding characteristics of the iron oxide and uranium oxide in sodium silicate glasses were deduced from the changes in the oxygen 1s levels and the heavy metal core levels. It is reasonable to expect that the effect of leaching on the heavy metal ions can be monitored using the appropriate core levels of these ions. To study the effect of leaching on the glass forming network, the valence band structure of the bridging and nonbridging oxygens in sodium silicate glasses were investigated. The measurement of extended x-ray absorption fine-structure (EXAFS) is a relatively new analytical technique for obtaining short range (<5 A) structural information around atoms of a selected species in both solid and fluid systems. Experiments have recently begun to establish the feasibility of using EXAFS to study the bonding of actinides in silicate glasses. Because of the ability of EXAFS to yield specific structural data even in complex multicomponent systems, it could prove to be an invaluable tool in understanding glass structure

  13. Ab-initio structure determination of novel strontium-containing layered silicate AES-18 synthesized using mechanochemical reaction

    Energy Technology Data Exchange (ETDEWEB)

    Ikeda, Takuji [AIST Tohoku, Sendai (Japan). Research Center for Compact Chemical System; Ideta, Chiaki; Yamamoto, Katsutoshi [Kitakyushu Univ. (Japan). Faculty of Environmental Engineering

    2013-07-01

    A new strontium-containing layered silicate, alkaline earth-containing silicate (AES)-18 [chemical composition: Si{sub 16}O{sub 24}(OH){sub 16} . {Sr(OH)_2}{sub 8} . (KOH){sub 2}], was synthesized utilizing a mechanochemical reaction in which an admixture of strontium hydroxide, which unfavorably precipitates in conventional syntheses, and a fumed silica (Aerosil) was allowed to react in the solid phase. The crystal structure of AES-18 was elucidated by the charge-flipping method using powder X-ray diffraction data, and the obtained structure was refined by a combination with the Rietveld method and the maximum entropy method (MEM). The structure analyses showed a tetragonal symmetry with a = 0.912738(3) nm, c = 1.628120(8) nm, and the space group P4{sub 2}/mnc. Two silicate layers composed of Q{sup 3} local structure [(-SiO){sub 3}Si-OH], 7-coordinated Sr{sup 2+} cations, and K{sup +} cations were included in a unit cell, and a Sr{sub 4}(OH){sub 17} cluster was formed between adjacent silicate layers. The framework topology of AES-18 containing 4- and 8-Si-membered rings was similar to that of paracelsian.

  14. The Teles Pires volcanic province: A paleogeoproterozoic silicic-dominated large igneous province in southwest Amazon craton and tectonic implications

    International Nuclear Information System (INIS)

    Leite, Jayme Alfredo Dexheimer; Saes, Gerson Souza; Macambira, Moacir Jose Buenano

    2001-01-01

    Large Igneous Provinces (LIPs) are important features of the Earth history especially recognized during Paleo to Mezosoic times when they are related to the break up of supercontinents (Coffin and Eldhom, 1994). These provinces occur in several different tectonic settings such as volcanic passive margins, submarine ridges and continental and oceanic plateaux. Mafic-dominanted provinces are the most well known among the LIPs and the best examples are the Karoo, Kerguelem and Ontong-Java. LIPs including an important silicic component have been described in some basaltic provinces of southern Africa (Milner et al. 1992). More recently, silicic-dominated LIPs have been recognized in eastern Australia (Bryan et al., 2000), in southern South America (Pankhurst et al. 1998) and in Antartica Penninsula (Riley and Leat, 1999). The common characteristics of this kind of LIP include: 1) large volume of silicic rocks with dominance of ignimbrites, 2) active over 40 to 50 m.y.; and 3) spatially and temporally associated with plate break up. In this paper we present the main geologic and geochronologic characteristics of the Teles Pires volcanic province from southwest Amazon Craton, which allow its classification as a Paleoprotorozoic silicic-dominated LIP. Geologic implications of this suggestion includes the existence of a large cratonic plate as old as 1.81Ga for the Amazon Craton, therefore the proposed 1.85-1.55 Ga magmatic arc of Rio Negro-Juruena Province should be reviewed (au)

  15. Rare earths

    Energy Technology Data Exchange (ETDEWEB)

    Cranstone, D A

    1979-01-01

    Rare earth elements are commonly extracted from the minerals monazite, bastnaesite, and xenotine. New uses for these elements are constantly developing; they have found applications in glass polishing, television tube phosphors, high-strength low-alloy steels, magnets, catalysts, refractory ceramics, and hydrogen sponge alloys. In Canada, rare earths have been produced as byproducts of the uranium mining industry, but there was no production of rare earths in 1978 or 1979. The world sources of and markets for the rare earth elements are discussed.

  16. Water-bearing, high-pressure Ca-silicates

    Science.gov (United States)

    Németh, Péter; Leinenweber, Kurt; Ohfuji, Hiroaki; Groy, Thomas; Domanik, Kenneth J.; Kovács, István J.; Kovács, Judit S.; Buseck, Peter R.

    2017-07-01

    Water-bearing minerals provide fundamental knowledge regarding the water budget of the mantle and are geophysically significant through their influence on the rheological and seismic properties of Earth's interior. Here we investigate the CaO-SiO2-H2O system at 17 GPa and 1773 K, corresponding to mantle transition-zone condition, report new high-pressure (HP) water-bearing Ca-silicates and reveal the structural complexity of these phases. We document the HP polymorph of hartrurite (Ca3SiO5), post-hartrurite, which is tetragonal with space group P4/ncc, a = 6.820 (5), c = 10.243 (8) Å, V = 476.4 (8) Å3, and Z = 4, and is isostructural with Sr3SiO5. Post-hartrurite occurs in hydrous and anhydrous forms and coexists with larnite (Ca2SiO4), which we find also has a hydrous counterpart. Si is 4-coordinated in both post-hartrurite and larnite. In their hydrous forms, H substitutes for Si (4H for each Si; hydrogrossular substitution). Fourier transform infrared (FTIR) spectroscopy shows broad hydroxyl absorption bands at ∼3550 cm-1 and at 3500-3550 cm-1 for hydrous post-hartrurite and hydrous larnite, respectively. Hydrous post-hartrurite has a defect composition of Ca2.663Si0.826O5H1.370 (5.84 weight % H2O) according to electron-probe microanalysis (EPMA), and the Si deficiency relative to Ca is also observed in the single-crystal data. Hydrous larnite has average composition of Ca1.924Si0.851O4H0.748 (4.06 weight % H2O) according to EPMA, and it is in agreement with the Si occupancy obtained using X-ray data collected on a single crystal. Superlattice reflections occur in electron-diffraction patterns of the hydrous larnite and could indicate crystallographic ordering of the hydroxyl groups and their associated cation defects. Although textural and EPMA-based compositional evidence suggests that hydrous perovskite may occur in high-Ca-containing (or low silica-activity) systems, the FTIR measurement does not show a well-defined hydroxyl absorption band for this

  17. Viscosity of Heterogeneous Silicate Melts: A Non-Newtonian Model

    Science.gov (United States)

    Liu, Zhuangzhuang; Blanpain, Bart; Guo, Muxing

    2017-12-01

    The recently published viscosity data of heterogeneous silicate melts with well-documented structure and experimental conditions are critically re-analyzed and tabulated. By using these data, a non-Newtonian viscosity model incorporating solid fraction, solid shape, and shear rate is proposed on the basis of the power-law equation. This model allows calculating the viscosity of the heterogeneous silicate melts with solid fraction up to 34 vol pct. The error between the calculated and measured data is evaluated to be 32 pct, which is acceptable considering the large error in viscosity measurement of the completely liquid silicate melt.

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

    Science.gov (United States)

    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-poor melt compositions. From our experimental data we present an model that combines

  19. A case of the tail wagging the dog? Reverse weathering and Earth's CO2 thermostat.

    Science.gov (United States)

    Higgins, J. A.

    2017-12-01

    Feedbacks between climate, the global carbon cycle, and the chemistry of seawater stabilize Earth's surface temperature on geologic timescales and are likely responsible for its habitability over billions of years of Earth history. The most important component of the geologic carbon cycle is the precipitation and burial of carbonate sediments. The amount of carbonate sediment produced depends, in turn, on the alkalinity generated during silicate weathering less the amount consumed during the formation of secondary clay minerals both on the continents and in the ocean. In marine enviroments this process, often referred to as reverse weathering, consumes seawater alkalinity (and cations) via reaction with degraded Al-silicate minerals. Because these reactions constitute a sink of seawater alkalinity, changes in the amount of reverse weathering will lead to imbalances between alkalinity sources and sinks. The net effect is that on timescales greater than the timescale of carbonate compensation (< 10 kyr), changes in reverse weathering will lead to changes in the rate of continental silicate weathering through the dependence of continental silicate weathering on atmospheric CO2 and climate. This mechanism is capable of changing rates of continental silicate weathering without changing either the rate of volcanic outgassing or the rate constant for continental silicate weathering (i.e. through mountain-building or the exposure of different rock types) and as a result represents a unique way of modulating the global carbon cycle and Earth's climate on geologic timescales.

  20. Interstellar silicate analogs for grain-surface reaction experiments: Gas-phase condensation and characterization of the silicate dust grains

    Energy Technology Data Exchange (ETDEWEB)

    Sabri, T.; Jäger, C. [Laboratory Astrophysics Group of the Max Planck Institute for Astronomy at the Friedrich Schiller University Jena Institute of Solid State Physics, Helmholtzweg 3, D-07743 Jena (Germany); Gavilan, L.; Lemaire, J. L.; Vidali, G. [Observatoire de Paris/Université de Cergy-Pontoise, 5 mail Gay Lussac, F-95000 Cergy-Pontoise (France); Mutschke, H. [Laboratory Astrophysics Group of the Astrophysical Institute and University Observatory, Friedrich Schiller University Jena Schillergässchen 3, D-07743 Jena (Germany); Henning, T., E-mail: tolou.sabri@uni-jena.de [Max Planck Institute for Astronomy Königstuhl 17, D-69117 Heidelberg (Germany)

    2014-01-10

    Amorphous, astrophysically relevant silicates were prepared by laser ablation of siliceous targets and subsequent quenching of the evaporated atoms and clusters in a helium/oxygen gas atmosphere. The described gas-phase condensation method can be used to synthesize homogeneous and astrophysically relevant silicates with different compositions ranging from nonstoichiometric magnesium iron silicates to pyroxene- and olivine-type stoichiometry. Analytical tools have been used to characterize the morphology, composition, and spectral properties of the condensates. The nanometer-sized silicate condensates represent a new family of cosmic dust analogs that can generally be used for laboratory studies of cosmic processes related to condensation, processing, and destruction of cosmic dust in different astrophysical environments. The well-characterized silicates comprising amorphous Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4}, as well as the corresponding crystalline silicates forsterite and fayalite, produced by thermal annealing of the amorphous condensates, have been used as real grain surfaces for H{sub 2} formation experiments. A specifically developed ultra-high vacuum apparatus has been used for the investigation of molecule formation experiments. The results of these molecular formation experiments on differently structured Mg{sub 2}SiO{sub 4} and Fe{sub 2}SiO{sub 4} described in this paper will be the topic of the next paper of this series.

  1. Silicate melts density, buoyancy relations and the dynamics of magmatic processes in the upper mantle

    Science.gov (United States)

    Sanchez-Valle, Carmen; Malfait, Wim J.

    2016-04-01

    Although silicate melts comprise only a minor volume fraction of the present day Earth, they play a critical role on the Earth's geochemical and geodynamical evolution. Their physical properties, namely the density, are a key control on many magmatic processes, including magma chamber dynamics and volcanic eruptions, melt extraction from residual rocks during partial melting, as well as crystal settling and melt migration. However, the quantitative modeling of these processes has been long limited by the scarcity of data on the density and compressibility of volatile-bearing silicate melts at relevant pressure and temperature conditions. In the last decade, new experimental designs namely combining large volume presses and synchrotron-based techniques have opened the possibility for determining in situ the density of a wide range of dry and volatile-bearing (H2O and CO2) silicate melt compositions at high pressure-high temperature conditions. In this contribution we will illustrate some of these progresses with focus on recent results on the density of dry and hydrous felsic and intermediate melt compositions (rhyolite, phonolite and andesite melts) at crustal and upper mantle conditions (up to 4 GPa and 2000 K). The new data on felsic-intermediate melts has been combined with in situ data on (ultra)mafic systems and ambient pressure dilatometry and sound velocity data to calibrate a continuous, predictive density model for hydrous and CO2-bearing silicate melts with applications to magmatic processes down to the conditions of the mantle transition zone (up to 2773 K and 22 GPa). The calibration dataset consist of more than 370 density measurements on high-pressure and/or water-and CO2-bearing melts and it is formulated in terms of the partial molar properties of the oxide components. The model predicts the density of volatile-bearing liquids to within 42 kg/m3 in the calibration interval and the model extrapolations up to 3000 K and 100 GPa are in good agreement

  2. Rare earths

    International Nuclear Information System (INIS)

    1984-01-01

    The conference was held from September 12 to 13, 1984 in Jetrichovice, Czechoslovakia. The participants heard 16 papers of which 4 were inputted in INIS. These papers dealt with industrial separation processes of rare earths, the use of chemical methods of separation from the concentrate of apatite and bastnesite, the effect of the relative permittivity of solvents in the elution of rare earth elements from a cation exchanger, and the determination of the content of different rare earth elements using X-ray fluorescence analysis and atomic absorption spectroscopy. (E.S.)

  3. Electronic structure calculations of calcium silicate hydrates

    International Nuclear Information System (INIS)

    Sterne, P.A.; Meike, A.

    1995-11-01

    Many phases in the calcium-silicate-hydrate system can develop in cement exposed over long periods of time to temperatures above 25 C. As a consequence, chemical reactions involving these phases can affect the relative humidity and water chemistry of a radioactive waste repository that contains significant amounts of cement. In order to predict and simulate these chemical reactions, the authors are developing an internally consistent database of crystalline Ca-Si-hydrate structures. The results of first principles electronic structure calculations on two such phases, wollastonite (CaSiO 3 ) and xonotlite (Ca 6 Si 6 O 17 (OH) 2 ), are reported here. The calculated ground state properties are in very good agreement with experiment, providing equilibrium lattice parameters within about 1--1.4% of the experimentally reported values. The roles of the different types of oxygen atoms, which are fundamental to understanding the energetics of crystalline Ca-Si-hydrates are briefly discussed in terms of their electronic state densities. The good agreement with experiment for the lattice parameters and the consistency of the electronic density of states features for the two structures demonstrate the applicability of these electronic structure methods in calculating the fundamental properties of these phases

  4. Suppressive effects of a polymer sodium silicate solution on ...

    African Journals Online (AJOL)

    Mohsen

    2015-10-21

    Oct 21, 2015 ... suppressive effects of sodium silicate in the polymer form were confirmed against powdery mildew and ... crops (such as rice) controls diseases and could reduce ... negative charge and sodium ions with a positive charge.

  5. Conversion of rice hull ash into soluble sodium silicate

    Directory of Open Access Journals (Sweden)

    Edson Luiz Foletto

    2006-09-01

    Full Text Available Sodium silicate is used as raw material for several purposes: silica gel production, preparation of catalysts, inks, load for medicines, concrete hardening accelerator, component of detergents and soaps, refractory constituent and deflocculant in clay slurries. In this work sodium silicate was produced by reacting rice hull ash (RHA and aqueous sodium hydroxide, in open and closed reaction systems. The studied process variables were time, temperature of reaction and composition of the reaction mixture (expressed in terms of molar ratios NaOH/SiO2 and H2O/SiO2. About 90% silica conversion contained in the RHA into sodium silicate was achieved in closed system at 200 °C. The results showed that sodium silicate production from RHA can generate aggregate value to this residue.

  6. Synthesis of the Tube Silicate Litidionite and Structural Relationships between It and Some Other Silicates.

    Science.gov (United States)

    1982-02-17

    CuSi4015 Others are agrellite, NaCa2Si4O0oF, 1 6 narsarsukite, Na2TiSi4O 1 7 miserite, KCa5 i2 07 Si601 5 (OH)F,18 and probably canasite , Na4K2Ca 5...and canasite are rare. Litidionite is apparently very rare, the only reported occurrence of it being in the crater of Mt. Vesuvius. Both litidionite1...narsarsukite, miserite, and probably canasite contain, like 13-19 lititionite, tube silicate ions. The first three contain ions that are the same as that in

  7. Thermal properties and application of potential lithium silicate breeder materials

    International Nuclear Information System (INIS)

    Skokan, A.; Wedemeyer, H.; Vollath, D.; Gunther, E.

    1987-01-01

    Phase relations, thermal stability and preparation methods of the Li 2 O-rich silicates Li 8 SiO 6 and ''Li 6 SiO 5 '' have been investigated experimentally, the application of these compounds as solid breeder materials is discussed. In the second part of this contribution, the results of thermal expansion measurements on the silicates Li 2 SiO 3 , Li 4 SiO 4 and Li 8 SiO 6 are presented

  8. Thermal properties and application of potential lithium silicate breeder materials

    International Nuclear Information System (INIS)

    Skokan, A.; Wedemeyer, H.; Vollath, D.; Guenther, E.

    1986-01-01

    Phase relations, thermal stability and preparation methods of the Li 2 O-rich silicates Li 8 SiO 6 and 'Li 6 SiO 5 ' have been investigated experimentally, the application of these compounds as solid breeder materials is discussed. In the second part of this contribution, the results of thermal expansion measurements on the silicates Li 2 SiO 3 , Li 4 SiO 4 and Li 8 SiO 6 are presented. (author)

  9. Comparison of silicon nanoparticles and silicate treatments in fenugreek.

    Science.gov (United States)

    Nazaralian, Sanam; Majd, Ahmad; Irian, Saeed; Najafi, Farzaneh; Ghahremaninejad, Farrokh; Landberg, Tommy; Greger, Maria

    2017-06-01

    Silicon (Si) fertilization improves crop cultivation and is commonly added in the form of soluble silicates. However, most natural plant-available Si originates from plant formed amorphous SiO 2 particles, phytoliths, similar to SiO 2 -nanoparticles (SiNP). In this work we, therefore, compared the effect by sodium silicate and that of SiNP on Si accumulation, activity of antioxidative stress enzymes catalase, peroxidase, superoxide dismutase, lignification of xylem cell walls and activity of phenylalanine ammonia-lyase (PAL) as well as expression of genes for the putative silicon transporter (PST), defensive (Tfgd 1) and phosphoenolpyruvate carboxykinase (PEPCK) and protein in fenugreek (Trigonella foenum-graecum L.) grown in hydroponics. The results showed that Si was taken up from both silicate and SiNP treatments and increasing sodium silicate addition increased the translocation of Si to the shoot, while this was not shown with increasing SiNP addition. The silicon transporter PST was upregulated at a greater level when sodium silicate was added compared with SiNP addition. There were no differences in effects between sodium silicate and SiNP treatments on the other parameters measured. Both treatments increased the uptake and accumulation of Si, xylem cell wall lignification, cell wall thickness, PAL activity and protein concentration in seedlings, while there was no effect on antioxidative enzyme activity. Tfgd 1 expression was strongly downregulated in leaves at Si addition. The similarity in effects by silicate and SiNP would be due to that SiNP releases silicate, which may be taken up, shown by a decrease in SiNP particle size with time in the medium. Copyright © 2017 Elsevier Masson SAS. All rights reserved.

  10. PETROLOGY AND GEOCHEMISTRY OF CALC-SILICATE SCHISTS ...

    African Journals Online (AJOL)

    DR OKONKOWO

    2012-02-29

    silicate reaction bands have higher contents of CaO and Sr and lower concentrations of K2O, Rb, Ni, and Ba relative to the calc-silicate schists; and relatively higher SiO2, TiO2, Al2O3, Fe2O3, MgO, Na2O, K2O and P2O5 and lower ...

  11. PETROLOGIC CONSTRAINTS ON AMORPHOUS AND CRYSTALLINE MAGNESIUM SILICATES: DUST FORMATION AND EVOLUTION IN SELECTED HERBIG Ae/Be SYSTEMS

    Energy Technology Data Exchange (ETDEWEB)

    Rietmeijer, Frans J. M. [Department of Earth and Planetary Sciences, MSC 03 2040, 1-University of New Mexico, Albuquerque, NM 87131-001 (United States); Nuth, Joseph A., E-mail: fransjmr@unm.edu [Astrochemistry Laboratory, Solar System Exploration Division, Code 691, NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

    2013-07-01

    The Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory surveys provided a wealth of data on the Mg-silicate minerals (forsterite, enstatite), silica, and ''amorphous silicates with olivine and pyroxene stoichiometry'' around Herbig Ae/Be stars. These incredible findings do not resonate with the mainstream Earth Sciences because of (1) disconnecting ''astronomical nomenclature'' and the long existing mineralogical and petrologic terminology of minerals and amorphous materials, and (2) the fact that Earth scientists (formerly geologists) are bound by the ''Principle of Actualism'' that was put forward by James Hutton (1726-1797). This principle takes a process-oriented approach to understanding mineral and rock formation and evolution. This paper will (1) review and summarize the results of laboratory-based vapor phase condensation and thermal annealing experiments, (2) present the pathways of magnesiosilica condensates to Mg-silicate mineral (forsterite, enstatite) formation and processing, and (3) present mineralogical and petrologic implications of the properties and compositions of the infrared-observed crystalline and amorphous dust for the state of circumstellar disk evolution. That is, the IR-observation of smectite layer silicates in HD142527 suggests the break-up of asteroid-like parent bodies that had experienced aqueous alteration. We discuss the persistence of amorphous dust around some young stars and an ultrafast amorphous to crystalline dust transition in HD 163296 that leads to forsterite grains with numerous silica inclusions. These dust evolution processes to form forsterite, enstatite {+-} tridymite could occur due to amorphous magnesiosilica dust precursors with a serpentine- or smectite-dehydroxylate composition.

  12. PETROLOGIC CONSTRAINTS ON AMORPHOUS AND CRYSTALLINE MAGNESIUM SILICATES: DUST FORMATION AND EVOLUTION IN SELECTED HERBIG Ae/Be SYSTEMS

    International Nuclear Information System (INIS)

    Rietmeijer, Frans J. M.; Nuth, Joseph A.

    2013-01-01

    The Infrared Space Observatory, Spitzer Space Telescope, and Herschel Space Observatory surveys provided a wealth of data on the Mg-silicate minerals (forsterite, enstatite), silica, and ''amorphous silicates with olivine and pyroxene stoichiometry'' around Herbig Ae/Be stars. These incredible findings do not resonate with the mainstream Earth Sciences because of (1) disconnecting ''astronomical nomenclature'' and the long existing mineralogical and petrologic terminology of minerals and amorphous materials, and (2) the fact that Earth scientists (formerly geologists) are bound by the ''Principle of Actualism'' that was put forward by James Hutton (1726-1797). This principle takes a process-oriented approach to understanding mineral and rock formation and evolution. This paper will (1) review and summarize the results of laboratory-based vapor phase condensation and thermal annealing experiments, (2) present the pathways of magnesiosilica condensates to Mg-silicate mineral (forsterite, enstatite) formation and processing, and (3) present mineralogical and petrologic implications of the properties and compositions of the infrared-observed crystalline and amorphous dust for the state of circumstellar disk evolution. That is, the IR-observation of smectite layer silicates in HD142527 suggests the break-up of asteroid-like parent bodies that had experienced aqueous alteration. We discuss the persistence of amorphous dust around some young stars and an ultrafast amorphous to crystalline dust transition in HD 163296 that leads to forsterite grains with numerous silica inclusions. These dust evolution processes to form forsterite, enstatite ± tridymite could occur due to amorphous magnesiosilica dust precursors with a serpentine- or smectite-dehydroxylate composition.

  13. The application of silicon and silicates in dentistry: a review.

    Science.gov (United States)

    Lührs, A-K; Geurtsen, Werner

    2009-01-01

    Silicates and silicate-based compounds are frequently used materials in dentistry. One of their major applications is their use as fillers in different dental filling materials such as glass-ionomer cements, compomers, composites, and adhesive systems. In these materials, the fillers react with acids during the setting process or they improve the mechanical properties by increasing physical resistance, thermal expansion coefficient and radiopacity in acrylic filling materials. They also reduce polymerization shrinkage, and increase esthetics as well as handling properties. Furthermore, silicates are used for the tribochemical silication of different surfaces such as ceramics or alloys. The silicate layer formed in this process is the chemical basis for silanes that form a bond between this layer and the organic composite matrix. It also provides a micromechanical bond between the surface of the material and the composite matrix. Silicates are also a component of dental ceramics, which are frequently used in dentistry, for instance for veneers, inlays, and onlays, for denture teeth, and for full-ceramic crowns or as crown veneering materials.

  14. Earth Rotation

    Science.gov (United States)

    Dickey, Jean O.

    1995-01-01

    The study of the Earth's rotation in space (encompassing Universal Time (UT1), length of day, polar motion, and the phenomena of precession and nutation) addresses the complex nature of Earth orientation changes, the mechanisms of excitation of these changes and their geophysical implications in a broad variety of areas. In the absence of internal sources of energy or interactions with astronomical objects, the Earth would move as a rigid body with its various parts (the crust, mantle, inner and outer cores, atmosphere and oceans) rotating together at a constant fixed rate. In reality, the world is considerably more complicated, as is schematically illustrated. The rotation rate of the Earth's crust is not constant, but exhibits complicated fluctuations in speed amounting to several parts in 10(exp 8) [corresponding to a variation of several milliseconds (ms) in the Length Of the Day (LOD) and about one part in 10(exp 6) in the orientation of the rotation axis relative to the solid Earth's axis of figure (polar motion). These changes occur over a broad spectrum of time scales, ranging from hours to centuries and longer, reflecting the fact that they are produced by a wide variety of geophysical and astronomical processes. Geodetic observations of Earth rotation changes thus provide insights into the geophysical processes illustrated, which are often difficult to obtain by other means. In addition, these measurements are required for engineering purposes. Theoretical studies of Earth rotation variations are based on the application of Euler's dynamical equations to the problem of finding the response of slightly deformable solid Earth to variety of surface and internal stresses.

  15. Effect of moisture and chitosan layered silicate on morphology and properties of chitosan/layered silicates films

    International Nuclear Information System (INIS)

    Silva, J.R.M.B. da; Santos, B.F.F. dos; Leite, I.F.

    2014-01-01

    Thin chitosan films have been for some time an object of practical assessments. However, to obtain biopolymers capable of competing with common polymers a significant improvement in their properties is required. Currently, the technology of obtaining polymer/layered silicates nanocomposites has proven to be a good alternative. This work aims to evaluate the effect of chitosan content (CS) and layered silicates (AN) on the morphology and properties of chitosan/ layered silicate films. CS/AN bionanocomposites were prepared by the intercalation by solution in the proportion 1:1 and 5:1. Then were characterized by infrared spectroscopy (FTIR), diffraction (XRD) and X-ray thermogravimetry (TG). It is expected from the acquisition of films, based on different levels of chitosan and layered silicates, choose the best composition to serve as a matrix for packaging drugs and thus be used for future research. (author)

  16. Potassium silicate and calcium silicate on the resistance of soybean to Phakopsora pachyrhizi infection

    Directory of Open Access Journals (Sweden)

    Maria Fernanda Cruz

    2013-01-01

    Full Text Available The control of Asian Soybean Rust (ASR, caused by Phakopsora pachyrhizi, has been difficult due to the aggressiveness of the pathogen and the lack of resistant cultivars. The objective of this study was to evaluate the effects of spray of potassium silicate (PS and soil amendment with calcium silicate (CS on soybean resistance to ASR. The PS solution was sprayed to leaves 24 hours prior to fungal inoculation while CS was amended to the soil at thirty-five days before sowing. The infection process of P. pachyrhizi was investigated by scanning electron microscopy. The uredia on leaves of plants sprayed with PS were smaller and more compact than those observed on the leaves of plants grown in soil amended with CS or in soil non-amended with CS (control treatment. On leaves of plants from the control treatment, uredia produced many urediniospores at 9 days after inoculation, and the ASR severity was 15, 8 and 9%, respectively, for plants from control, PS and CS treatments. In conclusion, the spray of PS contributed to reduce the number of uredia per cm² of leaf area and both PS spray and CS resulted in lower ASR symptoms.

  17. Giant siliceous spicules from the deep-sea glass sponge Monorhaphis chuni.

    Science.gov (United States)

    Wang, Xiaohong; Schröder, Heinz C; Müller, Werner E G

    2009-01-01

    Only 13 years after realizing, during a repair of a telegraph cable pulled out from the deep sea, that the depth of the ocean is plentifully populated with a highly diverse fauna and flora, the Challenger expedition (1873-1876) treasured up a rich collection of vitreous sponges (Hexactinellida). They had been described by Schulze and represent the phylogenetically oldest class of siliceous sponges (phylum Porifera); they are eye-catching because of their distinct body plan, which relies on a filigree skeleton. It is constructed by an array of morphologically determined elements, the spicules. Soon after, during the German Deep Sea Expedition "Valdivia" (1898-1899), Schulze could describe the largest siliceous hexactinellid sponge on Earth, the up to 3-m high Monorhaphis chuni, which develops the equally largest bio-silica structure, the giant basal spicules (3 mx10 mm). Using these spicules as a model, basic knowledge on the morphology, formation, and development of the skeletal elements could be achieved. They are formed by a proteinaceous scaffold (composed of a 27-kDa protein), which mediates the formation of the siliceous lamellae, into which the proteins are encased. The high number of 800 of 5-10 microm thick lamellae is concentrically arranged around the axial canal. The silica matrix is composed of almost pure silicon oxide, providing it with unusually optophysical properties, which are superior to those of man-made waveguides. Experiments might suggest that the spicules function in vivo as a nonocular photoreception system. In addition, the spicules have exceptional mechanical properties, combining mechanical stability with strength and stiffness. Like demosponges, also the hexactinellids synthesize their silica enzymatically, via the enzyme silicatein (27-kDa protein). It is suggested that these basic insights will surely contribute to a further applied utilization and exploration of silica in bio-material/biomedical science.

  18. Fine-grained sheet silicate rocks

    International Nuclear Information System (INIS)

    Weaver, C.E.

    1977-09-01

    Considerable interest has been shown in the possibility of using shales as repositories for radioactive waste and a variety of other waste products, and it appears that over the next few years much money and effort will be expended to investigate and test a wide variety of shales. If shales are to be studied in detail by a large number of investigators, it is important that all concerned have the same concept of what constitutes a shale. The term shale and other terms for fine-grained rocks have been used for many years and have been continually redefined. Most definitions predate the development of modern instrumentation and are based on field observations and intuition; however, the main problem is the diversity of definitions. An attempt is made here to develop a simple, rational classification of fine-grained sediments, and it is hoped that this classification will eliminate some of the present ambiguity. In order that the classification be pertinent, mineral composition and textural data were compiled and evaluated. The data on unconsolidated and consolidated sediments were contrasted and the effects of burial diagenesis assessed. It was found necessary to introduce a new term, physil, to describe all sheet silicate minerals. In contrast to the term clay mineral, the term physil has no size connotation. A simple classification is proposed that is based on the percentage of physils and grain size. In Part II the fine-grained physil rocks are classified on the basis of physil type, non-physil minerals, and texture. Formations are listed which have the mineral and textural characteristics of the most important rock types volumetrically. Selected rock types, and the formations in which they can be found, are recommended for laboratory study to determine their suitability for the storage of high-level radioactive waste

  19. The electrorheological properties of nano-sized SiO2 particle materials doped with rare earths

    International Nuclear Information System (INIS)

    Liu Yang; Liao Fuhui; Li Junran; Zhang Shaohua; Chen Shumei; Wei Chenguan; Gao Song

    2006-01-01

    Electrorheological (ER) materials of pure SiO 2 and SiO 2 doped with rare earths (RE = Ce, Gd, Y) (non-metallic glasses (silicates)) were prepared using Na 2 SiO 3 and RECl 3 as starting materials. The electrorheological properties are not enhanced by all rare earth additions. The material doped with Ce exhibits the best ER performance

  20. COMPARISON OF SOL-GEL SILICATE COATINGS ON Ti SUBSTRATE

    Directory of Open Access Journals (Sweden)

    DIANA HORKAVCOVÁ

    2012-12-01

    Full Text Available The objective of the submitted work was to prepare and to characterize two types of silicate coatings prepared by the sol-gel method using the dip-coating technique on a titanium substrate. Efforts have been made to use mechanical properties of bio-inert titanium and bioactive properties of a silicate layer enriched with an admixture of compounds identified below. The first group consisted of silicate coatings containing silver, brushite and monetite. The other group of silicate coatings contained calcium nitrate and triethyl phosphate. Mechanically and chemically treated titanium substrates were dipped into sols and dried and fired. Silicate coatings from the first group were also chemically treated in 10 mol.l-1 solution of sodium hydroxide. All coatings were measured to determine their adhesive and bioactive properties and furthermore the antibacterial properties were tested in the case of first group. Surfaces of the coated substrates were investigated after the firing and after the individual tests with optical and electron microscopy and X-ray microdiffraction. A tape test demonstrated excellent adhesive property of all coatings to the substrate, classified with degree 5. A static in vitro test demonstrated bioactivity of nearly all the coatings. The basic silicate coating from the first group and one type of coating from the second group were identified as inert. Antibacterial properties of silicate coatings containing silver showed to be different when tested against Escherichia coli bacteria. A complete inhibition of the growth of bacteria under our experimental conditions was observed for the coating containing silver and monetite and a partial inhibition of the growth of bacteria for coatings containing silver and silver in combination with brushite.

  1. A subsurface Fe-silicate weathering microbiome

    Science.gov (United States)

    Napieralski, S. A.; Buss, H. L.; Roden, E. E.

    2017-12-01

    Traditional models of microbially mediated weathering of primary Fe-bearing minerals often invoke organic ligands (e.g. siderophores) used for nutrient acquisition. However, it is well known that the oxidation of Fe(II) governs the overall rate of Fe-silicate mineral dissolution. Recent work has demonstrated the ability of lithtrophic iron oxidizing bacteria (FeOB) to grow via the oxidation of structural Fe(II) in biotite as a source of metabolic energy with evidence suggesting a direct enzymatic attack on the mineral surface. This process necessitates the involvement of dedicated outer membrane proteins that interact with insoluble mineral phases in a process known as extracellular electron transfer (EET). To investigate the potential role FeOB in a terrestrial subsurface weathering system, samples were obtained from the bedrock-saprolite interface (785 cm depth) within the Rio Icacos Watershed of the Luquillo Mountains in Puerto Rico. Prior geochemical evidence suggests the flux of Fe(II) from the weathering bedrock supports a robust lithotrophic microbial community at depth. Current work confirms the activity of microorganism in situ, with a marked increase in ATP near the bedrock-saprolite interface. Regolith recovered from the interface was used as inoculum to establish enrichment cultures with powderized Fe(II)-bearing minerals serving as the sole energy source. Monitoring of the Fe(II)/Fe(total) ratio and ATP generation suggests growth of microorganisms coupled to the oxidation of mineral bound Fe(II). Analysis of 16S rRNA gene and shotgun metagenomic libraries from in situ and enrichment culture samples lends further support to FeOB involvement in the weathering process. Multiple metagenomic bins related to known FeOB, including Betaproteobacteria genera, contain homologs to model EET systems, including Cyc2 and MtoAB. Our approach combining geochemistry and metagenomics with ongoing microbiological and genomic characterization of novel isolates obtained

  2. High-Temperature Thermal Diffusivity Measurements of Silicate Glasses

    Science.gov (United States)

    Pertermann, M.; Hofmeister, A. M.; Whittington, A. G.; Spera, F. J.; Zayac, J.

    2005-12-01

    Transport of heat in geologically relevant materials is of great interest because of its key role in heat transport, magmatism and volcanic activity on Earth. To better understand the thermal properties of magmatic materials at high temperatures, we measured the thermal diffusivity of four synthetic end-member silicate glasses with the following compositions: albite (NaAlSi3O8), orthoclase (KAlSi3O8), anorthite (CaAl2Si2O8), and diopside (CaMgSi2O6). Thermal diffusivity measurements were conducted with the laser-flash technique and data were acquired from room temperature to a maximum temperature near 1100°C, depending on the glass transition temperature. The presence of sub-mm sized bubbles in one of the orthoclase samples had no discernable effect on measured diffusivities. At room temperature, the three feldspar-type glasses have thermal diffusivity (D) values of 0.58-0.61 mm2/s, whereas the diopside glass has 0.52 mm2/s. With increasing temperature, D decreases by 5-10% (relative) for all samples and becomes virtually constant at intermediate temperatures. At higher temperatures, the anorthite and diopside glasses exhibit significant drops in thermal diffusivity over a 50-100°C interval, correlating with previously published heat capacity changes near the glass transition for these compositions. For anorthite, D (in mm2/s) decreases from 0.48 at 750-860°C to 0.36 at 975-1075°C; for diopside, D changes from 0.42 at 630-750°C to 0.30 at 850-910°C, corresponding to relative drops of 24 and 29%, respectively. Albite and orthoclase glasses do not exhibit this change and also lack significant changes in heat capacity near the glass transition. Instead, D is constant at 400-800°C for albite, and for orthoclase values go through a minimum at 500-600°C before increasing slightly towards 1100°C but it never exceeds the room temperature D. Our data on thermal diffusivity correlate closely with other thermophysical properties. Thus, at least in case of simple

  3. The Effect of Al on the Compressibility of Silicate Perovskite

    Science.gov (United States)

    Walter, M. J.; Kubo, A.; Yoshino, T.; Koga, K. T.; Ohishi, Y.

    2003-12-01

    Experimental data on compressibility of aluminous silicate perovskite show widely disparate results. Several studies show that Al causes a dramatic increase in compressibility1-3, while another study indicates a mild decrease in compressibility4. Here we report new results for the effect of Al on the room-temperature compressibility of perovskite using in situ X-ray diffraction in the diamond anvil cell from 30 to 100 GPa. We studied compressibility of perovskite in the system MgSiO3-Al2O3 in compositions with 0 to 25 mol% Al. Perovskite was synthesized from starting glasses using laser-heating in the DAC, with KBr as a pressure medium. Diffraction patterns were obtained using monochromatic radiation and an imaging plate detector at beamline BL10XU, SPring8, Japan. Addition of Al into the perovskite structure causes systematic increases in orthorhombic distortion and unit cell volume at ambient conditions (V0). Compression of the perovskite unit cell is anisotropic, with the a axis about 25% and 3% more compressive than the b and c axes, respectively. The magnitude of orthorhombic distortion increases with pressure, but aluminous perovskite remains stable to at least 100 GPa. Our results show that Al causes only a mild increase in compressibility, with the bulk modulus (K0) decreasing at a rate of 0.7 GPa/0.01 XAl. This increase in compressibility is consistent with recent ab initio calculations if Al mixes into both the 6- and 8-coordinated sites by coupled substitution5, where 2 Al3+ = Mg2+ + Si4+. Our results together with those of [4] indicate that this substitution mechanism predominates throughout the lower mantle. Previous mineralogic models indicating the upper and lower mantle are compositionally similar in terms of major elements remain effectively unchanged because solution of 5 mol% Al into perovskite has a minor effect on density. 1. Zhang & Weidner (1999). Science 284, 782-784. 2. Kubo et al. (2000) Proc. Jap. Acad. 76B, 103-107. 3. Daniel et al

  4. Digital Earth - A sustainable Earth

    Science.gov (United States)

    Mahavir

    2014-02-01

    All life, particularly human, cannot be sustainable, unless complimented with shelter, poverty reduction, provision of basic infrastructure and services, equal opportunities and social justice. Yet, in the context of cities, it is believed that they can accommodate more and more people, endlessly, regardless to their carrying capacity and increasing ecological footprint. The 'inclusion', for bringing more and more people in the purview of development is often limited to social and economic inclusion rather than spatial and ecological inclusion. Economic investment decisions are also not always supported with spatial planning decisions. Most planning for a sustainable Earth, be at a level of rural settlement, city, region, national or Global, fail on the capacity and capability fronts. In India, for example, out of some 8,000 towns and cities, Master Plans exist for only about 1,800. A chapter on sustainability or environment is neither statutorily compulsory nor a norm for these Master Plans. Geospatial technologies including Remote Sensing, GIS, Indian National Spatial Data Infrastructure (NSDI), Indian National Urban Information Systems (NUIS), Indian Environmental Information System (ENVIS), and Indian National GIS (NGIS), etc. have potential to map, analyse, visualize and take sustainable developmental decisions based on participatory social, economic and social inclusion. Sustainable Earth, at all scales, is a logical and natural outcome of a digitally mapped, conceived and planned Earth. Digital Earth, in fact, itself offers a platform to dovetail the ecological, social and economic considerations in transforming it into a sustainable Earth.

  5. Trace element partitioning between aqueous fluids and silicate melts measured with a proton microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Adam, J.; Green, T.H. [Macquarie Univ., North Ryde, NSW (Australia). School of Earth Sciences; Sie, S.H. [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1996-12-31

    A series of experiments were performed to examine the capacity of H{sub 2}O-fluids to concentrate and transport incompatible elements through peridotitic mantle and metamorphosed (eclogitic) ocean crust. Two naturally occurring rock compositions, trondhjemitic and basanitic, were used in experiments. The proton microprobe was used to determine the trace element concentrations in the solutes from H{sub 2}O-fluids equilibrated at 900-1100 degree C, 2.0 GPa with water saturated melts of trondhjemitic and basanitic compositions. Partitioning data for H{sub 2}O-fluids and silicate melts show that H{sub 2}O-fluids equilibrated with mantle peridotites will not be strongly enriched in trace elements relative to their wallrocks, and thus they melts do not strongly concentrate alkaline earths Th and U, relative to high-field strength elements. 3 refs., 1 tab., 2 figs.

  6. The carbonate-silicate cycle and CO2/climate feedbacks on tidally locked terrestrial planets.

    Science.gov (United States)

    Edson, Adam R; Kasting, James F; Pollard, David; Lee, Sukyoung; Bannon, Peter R

    2012-06-01

    Atmospheric gaseous constituents play an important role in determining the surface temperatures and habitability of a planet. Using a global climate model and a parameterization of the carbonate-silicate cycle, we explored the effect of the location of the substellar point on the atmospheric CO(2) concentration and temperatures of a tidally locked terrestrial planet, using the present Earth continental distribution as an example. We found that the substellar point's location relative to the continents is an important factor in determining weathering and the equilibrium atmospheric CO(2) level. Placing the substellar point over the Atlantic Ocean results in an atmospheric CO(2) concentration of 7 ppmv and a global mean surface air temperature of 247 K, making ∼30% of the planet's surface habitable, whereas placing it over the Pacific Ocean results in a CO(2) concentration of 60,311 ppmv and a global temperature of 282 K, making ∼55% of the surface habitable.

  7. Trace element partitioning between aqueous fluids and silicate melts measured with a proton microprobe

    Energy Technology Data Exchange (ETDEWEB)

    Adam, J; Green, T H [Macquarie Univ., North Ryde, NSW (Australia). School of Earth Sciences; Sie, S H [Commonwealth Scientific and Industrial Research Organisation (CSIRO), North Ryde, NSW (Australia). Div. of Exploration Geoscience

    1997-12-31

    A series of experiments were performed to examine the capacity of H{sub 2}O-fluids to concentrate and transport incompatible elements through peridotitic mantle and metamorphosed (eclogitic) ocean crust. Two naturally occurring rock compositions, trondhjemitic and basanitic, were used in experiments. The proton microprobe was used to determine the trace element concentrations in the solutes from H{sub 2}O-fluids equilibrated at 900-1100 degree C, 2.0 GPa with water saturated melts of trondhjemitic and basanitic compositions. Partitioning data for H{sub 2}O-fluids and silicate melts show that H{sub 2}O-fluids equilibrated with mantle peridotites will not be strongly enriched in trace elements relative to their wallrocks, and thus they melts do not strongly concentrate alkaline earths Th and U, relative to high-field strength elements. 3 refs., 1 tab., 2 figs.

  8. Dependence of Hardness of Silicate Glasses on Composition and Thermal History

    DEFF Research Database (Denmark)

    Jensen, Martin; Smedskjær, Morten Mattrup; Yue, Yuanzheng

    composition on hardness of silicate glasses. E-glasses of different compositions are subjected to various degrees of annealing to obtain various fictive temperatures in the glasses. It is found that hardness decreases with the fictive temperature. Addition of Na2O to a SiO2-Al2O3-Na2O glass system causes......The prediction of hardness is possible for crystalline materials, but so far not possible for glasses. In this work, several important factors that should be used for predicting the hardness of glasses are discussed. To do so, we have studied the influences of thermal history and chemical...... a decrease in hardness. However, hardness cannot solely be determined from the degree of polymerisation of the glass network. It is also determined by the effect of ionic radius on hardness. However, this effect has opposite trend for alkali and alkaline earth ions. The hardness increases with ionic radius...

  9. Heterogeneous nucleation of protein crystals on fluorinated layered silicate.

    Directory of Open Access Journals (Sweden)

    Keita Ino

    Full Text Available Here, we describe an improved system for protein crystallization based on heterogeneous nucleation using fluorinated layered silicate. In addition, we also investigated the mechanism of nucleation on the silicate surface. Crystallization of lysozyme using silicates with different chemical compositions indicated that fluorosilicates promoted nucleation whereas the silicates without fluorine did not. The use of synthesized saponites for lysozyme crystallization confirmed that the substitution of hydroxyl groups contained in the lamellae structure for fluorine atoms is responsible for the nucleation-inducing property of the nucleant. Crystallization of twelve proteins with a wide range of pI values revealed that the nucleation promoting effect of the saponites tended to increase with increased substitution rate. Furthermore, the saponite with the highest fluorine content promoted nucleation in all the test proteins regardless of their overall net charge. Adsorption experiments of proteins on the saponites confirmed that the density of adsorbed molecules increased according to the substitution rate, thereby explaining the heterogeneous nucleation on the silicate surface.

  10. Relationships between mineralization and silicic volcanism in the central Andes

    Energy Technology Data Exchange (ETDEWEB)

    Francis, P.W.; Halls, C.; Baker, M.C.W.

    1983-10-01

    Studies of late Tertiary silicic volcanic centers in the Western and Eastern Cordilleras of the Central Andes show that three volcanic environments are appropriate sites for mineralization: (1) ring-fracture extrusions post-dating large calderas; (2) similar extrusions within ignimbrite shields; and (3) isolated, small silicic volcanoes. Subvolcanic tin mineralization in the Eastern Cordillera is located in silicic stocks and associated breccias of Miocene age. The Cerro Rico stock, Potosi, Bolivia, contains tin and silver mineralization and has an intrusion age apparently millions of years younger than that of the associated Kari Kari caldera. Similar age relationships between mineralization and caldera formation have been described from the San Juan province, Colorado. The vein deposits of Chocaya, southern Bolivia, were emplaced in the lower part of an ignimbrite shield, a type of volcanic edifice as yet unrecognized in comparable areas of silicic volcanism. The El Salvador porphyry copper deposit, Chile, is related to silicic stocks which may have been intruded along a caldera ring fracture. Existing models for the genesis of porphyry copper deposits suggest that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. The dome of La Soufriere, Guadeloupe is proposed as a modern analog for the surface expression of subvolcanic mineralization processes, the phreatic eruptions there suggesting the formation of hydrothermal breccia bodies in depth.

  11. [Influence of cations on the laser Raman spectra of silicate glasses].

    Science.gov (United States)

    Xiong, Yi; Zhao, Hong-xia; Gan, Fu-xi

    2012-04-01

    Na2O(K2O)-CaO(MgO)-SiO2, Na2O(K2O)-Al2O3-SiO2, Na2O(K2O)-B2O3-SiO2, Na2O(K2O)-PbO-SiO2 and PbO-BaO-SiO2 glass systems were investigated using laser Raman spectroscopic technique. The modification of short-range structure of glass caused by network modifier cations will influence Raman signature. Alkali and alkali-earth ions can weaken the bridging oxygen bond, thus lower the frequency of Si-O(b)-Si anti-symmetric stretching vibration. When coordina ted by oxygen ions, B3+ can form [BO4] tetrahedron and enter the silicon-oxygen network, but this effect had little impact on the frequency of Raman peaks located in the high-frequency region. Al3+ can also be coordinated by oxygen ions to form [AlO4] tetrahedron. [AlO4] will increase the disorder degree of network while entering network. Ba2+ can increase the density of electron cloud along the Si-O(nb) bond when it bonds with non-bridging oxygen, which will lead to a higher peak intensity of O-Si-O stretching vibration. The Raman peaks of alkli- and alkali-earth silicate glasses are mainly distributed in the region of 400 - 1 200 cm(-1), while in the spectrum of Na2O(K2O)-PbO-SiO2 glass system a 131 cm(-1) peak existed. The authors assigned it to the Pb-O symmetric stretching vibration. Some of the samples were produced in the laboratory according to the average compositions of ancient glasses, so this research is very significant to discriminating ancient silicate glasses of different systems by Laser Raman spectroscopic technique.

  12. Investigations on fabricating strategies and utilization of rare earth based multicomponent oxide powders in radiation detection

    International Nuclear Information System (INIS)

    Shinde, Seema; Pitale, S.S.; Banthia, S.; Ghosh, M.; Tyagi, M.; Sen, S.; Gadkari, S.C.

    2014-01-01

    Materials containing rare earths demonstrate a broad field of applications as high energy radiation detectors, mainly due to their fascinating optical properties. Currently, Ce 3+ -doped rare earth silicates and garnets dominate the scintillator market because they show a high light yield, fast decay time, and high chemical stability. Moreover, the emission wavelength of silicates (410-440 nm) matches the wavelength sensitivity of conventional PMTs while, Si-photo-detector readouts are possible with garnets (emission near 550 nm). The composition, structure and phase of rare earth silicates are rather complex. For example, there are many phases like oxyorthosilicate R 2 SiO 5 , disilicate R 2 Si 2 O 7 , hexagonal R x (SiO 4 ) 6 O 2 oxyapatite etc (where R= Rare earth element). The controlled synthesis of single phase rare earth silicates and garnets nanomaterials is not easy and can only be reached with precisely controlled experimental conditions. In this work, we provide a broad overview of our recent scientific developments linked to a few aspects of synthesizing cerium activated rare earth based silicates and garnet materials, namely Gd 2 SiO 5 :Ce 3+ , Gd 4.67 (SiO 4 ) 3 O, Gd 2 Si 2 O 7 :Ce 3+ and Gd 3 Al x Ga 1-x O 12 :Ce 3+ (where 0≤x≤5) exploiting the advantages of solution combustion, chemical co-precipitation and hydrothermal techniques. A brief summary of results based on synthesis strategy adopted, composition, size shape and corresponding luminescence features of Gd based compounds are tabulated. The room temperature photoluminescence (PL) features of compounds listed. Efforts towards finding new properties and new materials will be continued and several applications, in particular energy-conversion and scintillator detectors, will benefit from these rare earth materials

  13. Steam based conversion coating on AA6060 alloy: Effect of sodium silicate chemistry and corrosion performance

    Science.gov (United States)

    Din, Rameez Ud; Bordo, Kirill; Tabrizian, Naja; Jellesen, Morten Stendahl; Ambat, Rajan

    2017-11-01

    Surface treatment of aluminium alloy AA6060 using an industrially applicable pilot steam jet system with and without silicate chemistry has been investigated. Treatment using steam alone and steam with silicate, resulted in an oxide layer formation with thickness ∼425 nm and ∼160 nm, respectively. Moreover, the use of sodium silicate resulted in the formation of distinct microstructure and incorporation of silicate into the oxide film. These oxide films reduced the anodic activity 4 times, while the corrosion protection by silicate containing oxide was the function of its concentration. Further, in acid salt spray and filiform corrosion tests, oxide layer containing silicate exhibited two times higher corrosion resistance.

  14. Rubber curing chemistry governing the orientation of layered silicate

    Directory of Open Access Journals (Sweden)

    2007-11-01

    Full Text Available The effect of curing systems on the orientation and the dispersion of the layered silicates in acrylonitrile butadiene rubber nanocomposite is reported. Significant differences in X-ray diffraction pattern between peroxide curing and sulfur curing was observed. Intense X-ray scattering values in the XRD experiments from peroxide cured vulcanizates indicate an orientation of the layers in a preferred direction as evinced by transmission electron micrographs. However, sulfur cured vulcanizates show no preferential orientation of the silicate particles. Nevertheless, a closer inspection of transmission electron microscopy (TEM images of peroxide and sulfur cured samples shows exfoliated silicate layers in the acrylonitrile butadiene rubber (NBR matrix. It was revealed in the prevailing study that the use of an excess amount of stearic acid in the formulation of the sulfur curing package leads to almost exfoliated type X-ray scattering pattern.

  15. Crystallochemical characteristics of alkali calcium silicates from charoitites

    International Nuclear Information System (INIS)

    Rozhdestvenskaya, I.V.; Nikishova, L.V.

    2002-01-01

    The characteristic features of the crystal structures of alkali calcium silicates from various deposits are considered. The structures of these minerals, which were established by single-crystal X-ray diffraction methods, are described as the combinations of large construction modules, including the alternating layers of alkali cations and tubular silicate radicals (in canasite, frankamenite, miserite, and agrellite) and bent ribbons linked through hydrogen bonds in the layers (in tinaksite and tokkoite). The incorporation of impurities and the different ways of ordering them have different effects on the structures of these minerals and give rise to the formation of superstructures accompanied by a change of the space group (frankamenite-canasite), leading, in turn, to different mutual arrangements of the layers of silicate tubes and the formation of pseudopolytypes (agrellites), structure deformation, and changes in the unit-cell parameters (tinaksite-tokkoite)

  16. Petrophysical Analysis of Siliceous Ooze Sediments, Ormen Lange Field, Norway

    DEFF Research Database (Denmark)

    Awedalkarim, Ahmed; Fabricius, Ida Lykke

    , but apparent porosity indications in any other lithology, such as siliceous ooze, are wrong and they should be corrected. The apparent bulk density log should be influenced by the hydrogen in opal as also the neutron porosity tools because they are sensitive to the amount of hydrogen in a formation...... present in the solid. Some minerals of siliceous ooze, such as opal, have hydrogen in their structures which influences the measured hydrogen index (HI). The neutron tool obtains the combined signal of the HI of the solid phase and of the water that occupies the true porosity. The HI is equal to true...... to interpret lithology and the unusual physical properties of the studied intervals. The integration of all these data revealed that the studied siliceous ooze is a mixture of opal and non-opal (shale). Our results proved to be reasonably consistent. The studied intervals apparently do not contain hydrocarbons....

  17. Energetic Processing of Interstellar Silicate Grains by Cosmic Rays

    Energy Technology Data Exchange (ETDEWEB)

    Bringa, E M; Kucheyev, S O; Loeffler, M J; Baragiola, R A; Tielens, A G Q M; Dai, Z R; Graham, G; Bajt, S; Bradley, J; Dukes, C A; Felter, T E; Torres, D F; van Breugel, W

    2007-03-28

    While a significant fraction of silicate dust in stellar winds has a crystalline structure, in the interstellar medium nearly all of it is amorphous. One possible explanation for this observation is the amorphization of crystalline silicates by relatively 'low' energy, heavy ion cosmic rays. Here we present the results of multiple laboratory experiments showing that single-crystal synthetic forsterite (Mg{sub 2}SiO{sub 4}) amorphizes when irradiated by 10 MeV Xe{sup ++} ions at large enough fluences. Using modeling, we extrapolate these results to show that 0.1-5.0 GeV heavy ion cosmic rays can rapidly ({approx}70 Million yrs) amorphize crystalline silicate grains ejected by stars into the interstellar medium.

  18. Synthesis and luminescence properties of erbium silicate thin films

    International Nuclear Information System (INIS)

    Miritello, Maria; Lo Savio, Roberto; Iacona, Fabio; Franzo, Giorgia; Bongiorno, Corrado; Priolo, Francesco

    2008-01-01

    We have studied the structure and the room temperature luminescence of erbium silicate thin films deposited by rf magnetron sputtering. Films deposited on silicon oxide layers are characterized by good structural properties and excellent stability. The optical properties of these films are strongly improved by rapid thermal annealing processes performed in the range of temperature 800-1250 deg. C. In fact through the reduction of the defect density of the material, a very efficient room temperature photoluminescence at 1535 nm is obtained. We have also investigated the influence of the annealing ambient, by finding that treatments in O 2 atmosphere are significantly more efficient in improving the optical properties of the material with respect to processes in N 2 . Upconversion effects become effective only when erbium silicate is excited with high pump powers. The evidence that all Er atoms (about 10 22 cm -3 ) in erbium silicate films are optically active suggests interesting perspectives for optoelectronic applications of this material

  19. Potassium Silicate Foliar Fertilizer Grade from Geothermal Sludge and Pyrophyllite

    Directory of Open Access Journals (Sweden)

    Muljani Srie

    2016-01-01

    Full Text Available Potassium silicate fertilizer grade were successfully produced by direct fusion of silica (SiO2 and potasium (KOH and K2CO3 in furnaces at temperatures up to melting point of mixture. The geothermal sludge (98% SiO2 and the pyrophyllite (95% SiO2 were used as silica sources. The purposes of the study was to synthesise potassium silicate fertilizer grade having solids concentrations in the range of 31-37% K2O, and silica in the range of 48-54% SiO2. The weight ratio of silicon dioxide/potasium solid being 1:1 to 5:1. Silica from geothermal sludge is amorphous, whereas pyrophylite is crystalline phase. The results showed that the amount of raw materials needed to get the appropriate molar ratio of potassium silicate fertilizer grade are different, as well as the fusion temperature of the furnace. Potassium silicate prepared from potassium hydroxide and geothermal sludge produced a low molar ratio (2.5: 1 to 3: 1. The potassium required quite small (4:1 in weight ratio, and on a fusion temperature of about 900 °C. Meanwhile, the potassium silicate prepared from pyrophyllite produced a high molar ratio (1.4 - 9.4 and on a fusion temperature of about 1350 °C, so that potassium needed large enough to meet the required molar ratio for the fertilizer grade. The product potassium silicate solid is amorphous with a little trace of crystalline.

  20. Early Earth(s) Across Time and Space

    Science.gov (United States)

    Mojzsis, S.

    2014-04-01

    The geochemical and cosmochemical record of our solar system is the baseline for exploring the question: "when could life appear on a world similar to our own?" Data arising from direct analysis of the oldest terrestrial rocks and minerals from the first 500 Myr of Earth history - termed the Hadean Eon - inform us about the timing for the establishment of a habitable silicate world. Liquid water is the key medium for life. The origin of water, and its interaction with the crust as revealed in the geologic record, guides our exploration for a cosmochemically Earth-like planets. From the time of primary planetary accretion to the start of the continuous rock record on Earth at ca. 3850 million years ago, our planet experienced a waning bolide flux that partially or entirely wiped out surface rocks, vaporized oceans, and created transient serpentinizing atmospheres. Arguably, "Early Earths" across the galaxy may start off as ice planets due to feeble insolation from their young stars, occasionally punctuated by steam atmospheres generated by cataclysmic impacts. Alternatively, early global environments conducive to life spanned from a benign surface zone to deep into crustal rocks and sediments. In some scenarios, nascent biospheres benefit from the exogenous delivery of essential bio-elements via leftovers of accretion, and the subsequent establishment of planetary-scale hydrothermal systems. If what is now known about the early dynamical regime of the Earth serves as any measure of the potential habitability of worlds across space and time, several key boundary conditions emerge. These are: (i) availability and long-term stability of liquid water; (ii) presence of energy resources; (iii) accessibility of organic raw materials; (iv) adequate inventory of radioisotopes to drive internal heating; (v) gross compositional parameters such as mantle/core mass ratio, and (vi) P-T conditions at or near the surface suitable for sustaining biological activity. Life could

  1. Leaf application of silicic acid to upland rice and corn

    Directory of Open Access Journals (Sweden)

    Carlos Alexandre Costa Crusciol

    2013-12-01

    Full Text Available This study aimed to evaluate the effect of Si (stabilized silicic acid, Silamol® leaf application on mineral nutrition and yield in upland rice and corn crops. The treatments were the control (without Si and Si foliar split spraying using 2 L ha-1 of the Silamol® commercial product, with 0.8% soluble Si as concentrated stabilized silicic acid. Silicon leaf application increased the concentrations of K, Ca and Si in rice and corn leaves, the number of panicles per m2 of rice and the number of grains per ear of corn; accordingly, the Si leaf application provided a higher grain yield in both crops.

  2. Earth thermics

    Energy Technology Data Exchange (ETDEWEB)

    Ueda, M

    1960-01-01

    The thermodynamics of the Earth are described, including terrestrial heat flow, internal temperatures and thermal history. The value of the geothermal gradient has been considered to be 3/sup 0/C/100 m but measured values are slightly different. The values of terrestrial heat flow are relatively constant and are calculated be about 2.3 x 10 to the minus 6 cal/cm/sup 2/ sec (2.3 HFU). The Earth's internal temperature can be calculated from the adiabatic temperature gradient of adiabatic expansion. Using Simon's equation No. 9, a value of 2100-2500/sup 0/C is obtained, this is much lower than it was previously thought to be. The value of 2.3 HFU can easily be obtained from this internal temperature figure.

  3. Earth's Paleomagnetosphere and Planetary Habitability

    Science.gov (United States)

    Tarduno, J. A.; Blackman, E. G.; Oda, H.; Bono, R. K.; Carroll-Nellenback, J.; Cottrell, R. D.; Nimmo, F.

    2017-12-01

    The geodynamo is thought to play an important role in protecting Earth's hydrosphere, vital for life as we know it, from loss due to the erosive potential of the solar wind. Here we consider the mechanisms and history of this shielding. A larger core dynamo magnetic field strength provides more pressure to abate the solar wind dynamic pressure, increasing the magnetopause radius. However, the larger magnetopause also implies a larger collecting area for solar wind flux during phases of magnetic reconnection. The important variable is not mass capture but energy transfer, which does not scale linearly with magnetosphere size. Moreover, the ordered field provides the magnetic topology for recapturing atmospheric components in the opposite hemisphere such that the net global loss might not be greatly affected. While a net protection role for magnetospheres is suggested, forcing by the solar wind will change with stellar age. Paleomagnetism utilizing the single silicate crystal approach, defines a relatively strong field some 3.45 billion years ago (the Paleoarchean), but with a reduced magnetopause of 5 Earth radii, implying the potential for some atmospheric loss. Terrestrial zircons from the Jack Hills (Western Australia) and other localities host magnetic inclusions, whose magnetization has now been recorded by a new generation of ultra-sensitive 3-component SQUID magnetometer (U. Rochester) and SQUID microscope (GSJ/AIST). Paleointensity data suggest the presence of a terrestrial dynamo and magnetic shielding for Eoarchean to Hadean times, at ages as old as 4.2 billion years ago. However, the magnetic data suggest that for intervals >100,000 years long, magnetopause standoff distances may have reached 3 to 4 Earth radii or less. The early inception of the geodynamo, which probably occurred shortly after the lunar-forming impact, its continuity, and an early robust hydrosphere, appear to be key ingredients for Earth's long-term habitability.

  4. Obtainment and characterization of pure and doped gadolinium oxy ortho silicates with terbium III, precursor of luminescent silicates with sulphur

    International Nuclear Information System (INIS)

    Simoneti, J.A.

    1992-01-01

    Silicate and sulfide lattices are uniquely efficient luminescent materials to excitation by cathodic rays and furthermore the cathodoluminescence study of these compounds have been few investigated. In this work it has been prepared, characterized and investigated some spectroscopic properties of pure and Tb a+ - activated Gd 2 Si O 3 system and it has been tried to substitute oxygen by sulphur in order to obtain this or sulfide-silicate lattices. Products were characterized by vibrational infrared spectroscopy, powder X-ray diffraction patterns and electronic emission in UV-VIS region. (author)

  5. Non-conservative controls on distribution of dissolved silicate in Cochin Backwaters

    Digital Repository Service at National Institute of Oceanography (India)

    Balachandran, K.K.; Sankaranarayanan, V.N.; Joseph, T.; Nair, M.

    Cochin backwater system was studied with regard to dissolved silicate (DSi) to understand its seasonal distribution and behaviour during estuarine mixing. Silicate had a linear relationship with salinity during the high river discharge period...

  6. Wind-Eroded Silicate as a Source of Hydrogen Peroxide on Mars

    Science.gov (United States)

    Bak, E. N.; Merrison, J. P.; Jensen, S. K.; Nørnberg, P.; Finster, K.

    2014-07-01

    Laboratory simulations show that wind-eroded silicate can be a source of hydrogen peroxide. The ubiquitous, fine-grained silicate dust might thus explain the oxidizing properties of the martian soil and affect the preservation of organic compounds.

  7. SILICATE TECHNOLOGY CORPORATION'S SOLIDIFICATION/ STABILIZATION TECHNOLOGY FOR ORGANIC AND INORGANIC CONTAMINANTS IN SOILS - APPLICATIONS ANALYSIS REPORT

    Science.gov (United States)

    This Applications Analysis Report evaluates the solidification/stabilization treatment process of Silicate Technology Corporation (STC) for the on-site treatment of hazardous waste. The STC immobilization technology utilizes a proprietary product (FMS Silicate) to chemically stab...

  8. E-Beam-Cured Layered-Silicate and Spherical Silica Epoxy Nanocomposites (Preprint)

    National Research Council Canada - National Science Library

    Chen, Chenggang; Anderson, David P

    2007-01-01

    .... The nanofillers can be two dimensional (layered-silicate) and zero dimensional (spherical silica). Both the spherical silica epoxy nanocomposite and the layered-silicate epoxy nanocomposite can be cured to a high degree of curing...

  9. Thermodynamics of the Earth

    International Nuclear Information System (INIS)

    Stacey, Frank D

    2010-01-01

    Applications of elementary thermodynamic principles to the dynamics of the Earth lead to robust, quantitative conclusions about the tectonic effects that arise from convection. The grand pattern of motion conveys deep heat to the surface, generating mechanical energy with a thermodynamic efficiency corresponding to that of a Carnot engine operating over the adiabatic temperature gradient between the heat source and sink. Referred to the total heat flux derived from the Earth's silicate mantle, the efficiency is 24% and the power generated, 7.7 x 10 12 W, causes all the material deformation apparent as plate tectonics and the consequent geological processes. About 3.5% of this is released in seismic zones but little more than 0.2% as seismic waves. Even major earthquakes are only localized hiccups in this motion. Complications that arise from mineral phase transitions can be used to illuminate details of the motion. There are two superimposed patterns of convection, plate subduction and deep mantle plumes, driven by sources of buoyancy, negative and positive respectively, at the top and bottom of the mantle. The patterns of motion are controlled by the viscosity contrasts (>10 4 : 1) at these boundaries and are self-selected as the least dissipative mechanisms of heat transfer for convection in a body with very strong viscosity variation. Both are subjects of the thermodynamic efficiency argument. Convection also drives the motion in the fluid outer core that generates the geomagnetic field, although in that case there is an important energy contribution by compositional separation, as light solute is rejected by the solidifying inner core and mixed into the outer core, a process referred to as compositional convection. Uncertainty persists over the core energy balance because thermal conduction is a drain on core energy that has been a subject of diverse estimates, with attendant debate over the need for radiogenic heat in the core. The geophysical approach to

  10. Dielectric properties of plasma sprayed silicates subjected to additional annealing

    Czech Academy of Sciences Publication Activity Database

    Ctibor, Pavel; Sedláček, J.; Nevrlá, Barbara; Neufuss, Karel

    2017-01-01

    Roč. 10, č. 2 (2017), s. 105-114 ISSN 2008-2134 Institutional support: RVO:61389021 Keywords : Annealing * Dielectric properties * Plasma spraying * Silicates * Electrical properties * Insulators Subject RIV: JK - Corrosion ; Surface Treatment of Materials OBOR OECD: Coating and films http://pccc.icrc.ac.ir/Articles/1/18/990/

  11. Decreased water flowing from a forest amended with calcium silicate

    Science.gov (United States)

    Mark B. Green; Amey S. Bailey; Scott W. Bailey; John J. Battles; John L. Campbell; Charles T. Driscoll; Timothy J. Fahey; Lucie C. Lepine; Gene E. Likens; Scott V. Ollinger; Paul G. Schaberg

    2013-01-01

    Acid deposition during the 20th century caused widespread depletion of available soil calcium (Ca) throughout much of the industrialized world. To better understand how forest ecosystems respond to changes in a component of acidification stress, an 11.8-ha watershed was amended with wollastonite, a calcium silicate mineral, to restore available soil Ca to preindustrial...

  12. Preparation of β-belite using liquid alkali silicates

    International Nuclear Information System (INIS)

    Koutník, P.

    2017-01-01

    The aim of this study is the preparation of β-belite by a solid-state reaction using powdered limestone, amorphous silica and liquid alkali silicates. The raw materials were blended, the mixtures were agglomerated and then burnt. The resulting samples were characterized by X-ray diffraction analysis and scanning electron microscopy. Free lime content in the β-belite samples was also determined. The effects of CaO/SiO2 ratio (1.6–2.1), burning temperature (800–1400 °C), utilization of different raw materials (silica fume, synthetic silica, potassium silicate, sodium silicate, potassium hydroxide) and burning time (0.5–16 h) on free lime content and mineralogical composition were investigated. The purest ?-belite samples were prepared from a mixture of powdered limestone, silica fume and liquid potassium silicate with a ratio CaO/SiO2 = 2 by burning at temperatures between 1100 and 1300 °C for more than 2 h. Decreasing of the CaO/SiO2 ratio led to rankinite formation and lower a burning temperature led to the formation of wollastonite. [es

  13. Silicon K-edge XANES spectra of silicate minerals

    Science.gov (United States)

    Li, Dien; Bancroft, G. M.; Fleet, M. E.; Feng, X. H.

    1995-03-01

    Silicon K-edge x-ray absorption near-edge structure (XANES) spectra of a selection of silicate and aluminosilicate minerals have been measured using synchrotron radiation (SR). The spectra are qualitatively interpreted based on MO calculation of the tetrahedral SiO{4/4-}cluster. The Si K-edge generally shifts to higher energy with increased polymerization of silicates by about 1.3 eV, but with considerable overlap for silicates of different polymerization types. The substitution of Al for Si shifts the Si K-edge to lower energy. The chemical shift of Si K-edge is also sensitive to cations in more distant atom shells; for example, the Si K-edge shifts to lower energy with the substitution of Al for Mg in octahedral sites. The shifts of the Si K-edge show weak correlation with average Si-O bond distance (dSi-O), Si-O bond valence (sSi-O) and distortion of SiO4 tetrahedra, due to the crystal structure complexity of silicate minerals and multiple factors effecting the x-ray absorption processes.

  14. Preparation and characterization of magnesium–aluminium–silicate ...

    Indian Academy of Sciences (India)

    A three-stage heating schedule involving calcination, nucleation and crystallization, has been evolved for the preparation of magnesium aluminium silicate (MAS) glass ceramic with MgF2 as a nucleating agent. The effect of sintering temperature on the density of compacted material was studied. Microstructure and ...

  15. Effect of antioxidants and silicates on peroxides in povidone.

    Science.gov (United States)

    Narang, Ajit S; Rao, Venkatramana M; Desai, Divyakant S

    2012-01-01

    Reactive peroxides in povidone often lead to degradation of oxidation-labile drugs. To reduce peroxide concentration in povidone, the roles of storage conditions, antioxidants, and silicates were investigated. Povidone alone and its physical mixtures with ascorbic acid, propyl gallate, sodium sulfite, butylated hydroxyanisole (BHA), or butylated hydroxytoluene (BHT) were stored at 25 °C and 40 °C, at 11%, 32%, and 50% relative humidity. In addition, povidone solution in methanol was equilibrated with silicates (silica gel and molecular sieves), followed by solvent evaporation to recover povidone powder. Peroxide concentrations in povidone were measured. The concentration of peroxides in povidone increased under very-low-humidity storage conditions. Among the antioxidants, ascorbic acid, propyl gallate, and sodium sulfite reduced the peroxide concentration in povidone, whereas BHA and BHT did not. Water solubility appeared to determine the effectiveness of antioxidants. Also, some silicates significantly reduced peroxide concentration in povidone without affecting its functionality as a tablet binder. Porosity of silicates was critical to their ability to reduce the peroxide concentration in povidone. A combination of these approaches can reduce the initial peroxide concentration in povidone and minimize peroxide growth under routine storage conditions. Copyright © 2011 Wiley-Liss, Inc.

  16. Small angle X-ray scattering from hydrating tricalcium silicate

    International Nuclear Information System (INIS)

    Vollet, D.

    1983-01-01

    The small-angle X-ray scattering technique was used to study the structural evolution of hydrated tricalcium silicate at room temperature. The changes in specific area of the associated porosity and the evolution of density fluctuations in the solid hydrated phase were deduced from the scattering data. A correlation of these variations with the hydration mechanism is tried. (Author) [pt

  17. In vitro bioactivity and cytocompatibility of tricalcium silicate

    Indian Academy of Sciences (India)

    tricalcium silicate powder showed that it could induce bone- like apatite formation after ... ated by soaking them in SBF, cell adhesion and MTT assay, respectively. 2. .... tibility, which might be used as one of the bioactive coating materials and ...

  18. Determination of reactivity rates of silicate particle-size fractions

    Directory of Open Access Journals (Sweden)

    Angélica Cristina Fernandes Deus

    2014-04-01

    Full Text Available The efficiency of sources used for soil acidity correction depends on reactivity rate (RR and neutralization power (NP, indicated by effective calcium carbonate (ECC. Few studies establish relative efficiency of reactivity (RER for silicate particle-size fractions, therefore, the RER applied for lime are used. This study aimed to evaluate the reactivity of silicate materials affected by particle size throughout incubation periods in comparison to lime, and to calculate the RER for silicate particle-size fractions. Six correction sources were evaluated: three slags from distinct origins, dolomitic and calcitic lime separated into four particle-size fractions (2, 0.84, 0.30 and <0.30-mm sieves, and wollastonite, as an additional treatment. The treatments were applied to three soils with different texture classes. The dose of neutralizing material (calcium and magnesium oxides was applied at equal quantities, and the only variation was the particle-size material. After a 90-day incubation period, the RER was calculated for each particle-size fraction, as well as the RR and ECC of each source. The neutralization of soil acidity of the same particle-size fraction for different sources showed distinct solubility and a distinct reaction between silicates and lime. The RER for slag were higher than the limits established by Brazilian legislation, indicating that the method used for limes should not be used for the slags studied here.

  19. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina; Yamauchi, Kazuo; Li, Zongjin; Zhang, Xixiang; Ma, Hongyan; Ge, Shenguang

    2017-01-01

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10

  20. Role of elastic deformation in determining the mixed alkaline earth effect of hardness in silicate glasses

    DEFF Research Database (Denmark)

    Kjeldsen, Jonas; Smedskjær, Morten Mattrup; Potuzak, M.

    2015-01-01

    been investigated previously, but the link between the resistance to elastic deformation and hardness has not yet been studied. In this work, we investigate the link between elastic deformation during indentation and Vickers hardness in a series of mixed magnesium-barium boroaluminosilicate glasses. We...

  1. Spray-drying and fabrication of superionic conducting sodium rare-earth silicates

    International Nuclear Information System (INIS)

    Yamashita, Kimihiro; Nicholson, P.S.

    1985-01-01

    Fine precursor powders of particle diameter of 0.50-7 μm and high surface area (9 m 2 /g) for superionic conducting Na 5 RESi 4 O 12 (RE = Gd, Y) were successfully produced by spray-drying and an optimised calcination procedure. Using these powders, dense sinters (>98% of theoretical) with f(NGS) or f(NYS) = 1.0 (the proposed parameter for purity) were obtained under normal sintering conditions. 300 0 C ionic resistivities were calculated from ac impedance and had values of 5.6 Ω cm with an activation energy for conduction of 4.5 kcal/mol for Na 5 GdSi 4 O 12 and 7.7 Ω cm and 5.9 kcal/mol for Na 5 YSi 4 O 12 . These values were dependent on the f(NGS) or f(NYS). (orig.)

  2. Decomposition of pre calcined aluminium silicate ores of Afghanistan by hydrochloric acid

    International Nuclear Information System (INIS)

    Khomidi, A.K.; Mamatov, E.D.

    2015-01-01

    Present article is devoted to decomposition of pre calcined aluminium silicate ores of Afghanistan by hydrochloric acid. The physicochemical properties of initial aluminium silicate ores were studied by means of X-ray phase, differential thermal and silicate analysis. The chemical composition of aluminium containing ores was determined. The optimal conditions of interaction of initial and pre calcined siallites with hydrochloric acid were defined. The kinetics of acid decomposition of aluminium silicate ores was studied as well.

  3. Silicate Dispersion and Mechanical Reinforcement in Polysiloxane/Layered Silicate Nanocomposites

    KAUST Repository

    Schmidt, Daniel F.

    2010-01-12

    We report the first in-depth comparison of the mechanical properties and equilibrium solvent uptake of a range of polysiloxane nanocomposites based on treated and untreated montmorillonite and fumed silica nanofillers. We demonstrate the ability of equilibrium solvent uptake data (and, thus, overall physical and chemical cross-link density) to serve as a proxy for modulus (combining rubber elasticity and Flory-Rehner theory), hardness (via the theory of Boussinesq), and elongation at break, despite the nonideal nature of these networks. In contrast, we find that tensile and tear strength are not well-correlated with solvent uptake. Interfacial strength seems to dominate equilibrium solvent uptake and the mechanical properties it predicts. In the montmorillonite systems in particular, this results in the surprising consequence that equilibrium solvent uptake and mechanical properties are independent of dispersion state. We conclude that edge interactions play a more significant role than degree of exfoliation, a result unique in the field of polymer nanocomposites. This demonstrates that even a combination of polymer/nanofiller compatibility and thermodynamically stable nanofiller dispersion levels may not give rise to reinforcement. These findings provide an important caveat when attempting to connect structure and properties in polymer nanocomposites, and useful guidance in the design of optimized polymer/layered silicate nanocomposites in particular. © 2009 American Chemical Society.

  4. Transition metal ions in silicate melts. I. Manganese in sodium silicate melts

    Energy Technology Data Exchange (ETDEWEB)

    Nelson, C; White, W B

    1980-01-01

    Optical absorption spectra obtained on glasses quenched from sodium silicate melts show Mn/sup 3 +/ to be the dominant species for melts heated in air and Mn/sup 2 +/ to be the dominant species for melts heated at P/sub O/sub 2// = 10/sup -17/ bar. The absorption spectrum of Mn/sup 3 +/ consists of an intense band at 20,000 cm/sup -1/ with a 15,000 cm/sup -1/ satellite possibly arising from the Jahn-Teller effect. The independence of the spectrum from melt composition and the high band intensity is offered as evidence for a distinct Mn/sup 3 +/ complex in the melt. The spectrum of Mn/sup 2 +/ is weak and many expected bands are not observed. A two-band luminescence spectrum from Mn/sup 2 +/ has been tentatively interpreted as due to Mn/sup 2 +/ in interstitial sites in the network and Mn/sup 2 +/ coordiated by non-bridging oxygens.

  5. Lunar oxygen and metal for use in near-Earth space: Magma electrolysis

    Science.gov (United States)

    Colson, Russell O.; Haskin, Larry A.

    1990-01-01

    Because it is energetically easier to get material from the Moon to Earth orbit than from the Earth itself, the Moon is a potentially valuable source of materials for use in space. The unique conditions on the Moon, such as vacuum, absence of many reagents common on the Earth, and the presence of very nontraditional ores suggest that a unique and nontraditional process for extracting materials from the ores may prove the most practical. With this in mind, an investigation of unfluxed silicate electrolysis as a method for extracting oxygen, iron, and silicon from lunar regolith was initiated and is discussed. The advantages of the process include simplicity of concept, absence of need to supply reagents from Earth, and low power and mass requirements for the processing plant. Disadvantages include the need for uninterrupted high temperature and the highly corrosive nature of the high-temperature silicate melts which has made identifying suitable electrode and container materials difficult.

  6. Irradiations effects on the structure of boro-silicated glasses: long term behaviour of nuclear waste glassy matrices

    International Nuclear Information System (INIS)

    Bonfils, J. de

    2007-09-01

    This work deals with the long term behaviour of R7T7-type nuclear waste glasses and more particularly of non-active boro-silicated glasses made up of 3 or 5 oxides. Radioactivity of active glasses is simulated by multi energies ions implantations which reproduce the same defects. The damages due to the alpha particles are simulated by helium ions implantations and those corresponding to the recoil nucleus are obtained with gold ions ones. Minor actinides, stemming from the used fuel, is simulated by trivalent rare-earths (Eu 3+ and Nd 3+ ). In a first part, we have shown by macroscopic experiments (Vickers hardness - swelling) and optical spectroscopies (Raman - ATR-IR) that the structure of the glassy matrices is modified under implantations until a dose of 2,3.10 13 at.cm -2 , which corresponds to a R7T7 storage time estimated at 300 years. Beyond this dose, no additional modifications have been observed. The second part concerns the local environment of the rare-earth ions in glasses. Two different environments were found and identified as follows: one is a silicate rich one and the other is attributed to a borate rich one. (author)

  7. Energetics of silicate melts from thermal diffusion studies. Final report

    International Nuclear Information System (INIS)

    Walker, D.

    1997-01-01

    Initially this project was directed towards exploiting Soret diffusion of silicate liquids to learn about the internal energetics of the constituents of the liquids. During the course of this project this goal was realized at the same time a series of intellectual and technical developments expanded the scope of the undertaking. Briefly recapping some of the highlights, the project was initiated after the discovery that silicate liquids were strongly Soret-active. It was possible to observe the development of strong diffusive gradients in silicate liquid composition in response to laboratory-imposed thermal gradients. The character of the chemical separations was a direct window into the internal speciation of the liquids; the rise time of the separation was a useful entree to quantitatively measuring chemical diffusivity; and the steady state magnitude of the separation proved to be an excellent determinant of the constituents' mixing energies. A comprehensive program was initiated to measure the separations, rise times, and mixing energies of a range of geologically and technically interesting silicate liquids. An additional track of activities in the DOE project has run in parallel to the Soret investigation of single-phase liquids in a thermal gradient. This additional track is the study of liquid-plus-crystal systems in a thermal gradient. In these studies solubility-driven diffusion introduced many useful effects, some quite surprising. In partially molten silicate liquids the authors applied their experiments to understanding magmatic cumulate rocks. They have also applied their understanding of these systems to aspects of evaporite deposits in the geological record. They also undertook studies of this sort in systems with retrograde solubility in order to form the basis for understanding remediation for brine migration problems in evaporite-hosted nuclear waste repositories such as the WIPP

  8. Wastewater reuse in liquid sodium silicate manufacturing in alexandria, egypt.

    Science.gov (United States)

    Ismail, Gaber A; Abd El-Salam, Magda M; Arafa, Anwar K

    2009-01-01

    Soluble sodium silicates (waterglass) are liquids containing dissolved glass which have some water like properties. They are widely used in industry as sealants, binders, deflocculants, emulsifiers and buffers. Their most common applications in Egypt are in the pulp and paper industry (where they improve the brightness and efficiency of peroxide bleaching) and the detergent industry, in which they improve the action of the detergent and lower the viscosity of liquid soaps. The survey results showed that the production was carried out batch-wise, in an autoclave (dissolver). Sodium silicate in the state of crushed glass was charged in an autoclave (dissolver) with sodium hydroxide and water. The product is filtered through a press. The left over sludge (mud and silicates impurities) is emptied into the local sewer system. Also, sludge (silica gel) was discharged from the neutralization process of the generated alkaline wastewater and consequently clogging the sewerage system. So this study was carried out to modify the current wastewater management system which eliminates sludge formation, the discharge of higher pH wastewater to the sewer system, and to assess its environmental and economic benefits. To assess the characteristics of wastewater to be reused, physico-chemical parameters of 12 samples were tested using standard methods. The survey results showed that a total capacity of the selected enterprise was 540 tons of liquid sodium silicates monthly. The total amount of wastewater being discharged was 335 m3/month. Reusing of wastewater as feed autoclave water reduced water consumption of 32.1% and reduced wastewater discharge/month that constitutes 89.6% as well as saving in final product of 6 ton/month. It was concluded that reusing of wastewater generated from liquid sodium silicate manufacturing process resulted in cheaper and environmental-friendly product.

  9. Silicate Phases on the Surfaces of Trojan Asteroids

    Science.gov (United States)

    Martin, Audrey; Emery, Joshua P.; Lindsay, Sean S.

    2017-10-01

    Determining the origin of asteroids provides an effective means of constraining the solar system’s dynamic past. Jupiter Trojan asteroids (hereafter Trojans) may help in determining the amount of radial mixing that occurred during giant planet migration. Previous studies aimed at characterizing surface composition show that Trojans have low albedo surfaces and are spectrally featureless in the near infrared. The thermal infrared (TIR) wavelength range has advantages for detecting silicates on low albedo asteroids such as Trojans. The 10 μm region exhibits strong features due to the Si-O fundamental molecular vibrations. Silicates that formed in the inner solar system likely underwent thermal annealing, and thus are crystalline, whereas silicates that accreted in the outer solar system experienced less thermal processing, and therefore are more likely to have remained in an amorphous phase. We hypothesize that the Trojans formed in the outer solar system (i.e., the Kuiper Belt), and therefore will have a more dominant amorphous spectral silicate component. With TIR spectra from the Spitzer Space Telescope, we identify mineralogical features from the surface of 11 Trojan asteroids. Fine-grain mixtures of crystalline pyroxene and olivine exhibit a 10 μm feature with sharp cutoffs between about 9 μm and 12 μm, which create a broad flat plateau. Amorphous phases, when present, smooth the sharp emission features, resulting in a dome-like shape. Preliminary results indicate that the surfaces of analyzed Trojans contain primarily amorphous silicates. Emissivity spectra of asteroids 1986 WD and 4709 Ennomos include small peaks in the 10 μm region, diagnostic of small amounts of crystalline olivine. One explanation is that Trojans formed in the same region as Kuiper Belt objects, and when giant planet migration ensued, they were swept into Jupiter’s stable Lagrange points where they are found today. As such, it is possible that an ancestral group of Kuiper Belt

  10. Qualitative microanalysis of rare earths (ceric and yttric), of thorium and uranium in minerals

    International Nuclear Information System (INIS)

    Agrinier, H.

    1955-01-01

    We propose in this study to give a general method of attack of the niobio-titanates, niobio-tantalates, oxides, phosphates or silicates containing rare earths (ceric or yttric), uranium or thorium, and to put in evidence these different elements by microchemical reactions giving crystallization or the characteristic colorations. (M.B.) [fr

  11. Experimental weathering rates of aluminium silicates

    International Nuclear Information System (INIS)

    Gudbrandsson, Snorri

    2013-01-01

    80 C as a function of fluid saturation state. Analyses of the solids demonstrate that gibbsite precipitation occurred in all experiments. The comparison of gibbsite precipitation to the dissolution rates of plagioclase at pH 11 shows that the rates are close to equal. The precipitation rates of gibbsite, however, decrease faster with decreasing pH than plagioclase dissolution rates. As such it seem likely that plagioclase dissolution is faster than gibbsite precipitation at near to neutral pH, and the relatively slow rate of gibbsite precipitation influences plagioclase weathering in many Earth surface systems. Kaolinite is commonly the second secondary mineral formed during low temperature dissolution of plagioclase. Kaolinite precipitation rates were measured in mixed flow reactors as a function of fluid saturation state at pH=4 and 25 C. In total eight long-term precipitation experiments were performed in fluids mildly supersaturated with respect to kaolinite, together with a known quantity of cleaned low defect Georgia Kaolinite as seeds. Measured kaolinite precipitation rates are relatively slow compared with plagioclase dissolution rates. This observation suggests that kaolinite formation during weathering is limited by its precipitation rates rather than by the availability of aqueous species sourced from plagioclase dissolution. Taken together the results of this study provide some of the fundamental scientific basic for predicting the rates and consequences of crystalline basalt and plagioclase dissolution at both the Earth's surface and during the near surface injection of CO 2 as part of carbon storage efforts. Results indicate that although gibbsite precipitation rates are relatively rapid, the relatively slow precipitation rates of kaolinite may be the process controlling the formation of this mineral at the Earth's surface. (author)

  12. Effect of silicate module of water glass on rheological parameters of poly(sodium acrylate)/sodium silicate hydrogels

    Science.gov (United States)

    Mastalska-Popiawska, J.; Izak, P.

    2017-01-01

    The poly(sodium acrylate)/sodium silicate hydrogels were synthesized in the presence of sodium thiosulphate and potassium persulphate as the redox initiators and N,N’-methylene-bisacrylamide as the cross-linking monomer. 20 wt% aqueous solution of sodium acrylate was polymerized together with water glass with different silicate modules (M) from 1.74 to 2.29, in three mass ratio of the monomer solution to the water glass 2:1, 1:1 and 1:2. Such obtained hybrid composites were rheologically tested using the oscillation method. It allowed to designate the crossover point during polymerization, as well as to define the viscoelastic properties of the casted hydrogel samples one week after the reaction. The obtained results of the oscillation measurements showed that cross-linking reaction proceeds very quickly and the lower the silicate module is, the process starts faster. After the completion of the reaction the silicate-polymer hydrogels are strongly elastic materials and the highest elasticity characterizes systems with the mass ratio 1:2, i.e. with the highest water glass content.

  13. Suspension hydration of tricalcium silicate at constant pH. I. Variation of particle size and tricalcium silicate content

    NARCIS (Netherlands)

    McCurdy, K.G.; Stein, H.N.

    1973-01-01

    Calcium and silicate ion concentrations during suspension hydration of C3S indicate that at pH 11.5 an equilibrium is established between one of the hydrates and the solution during about 80 minutes. The concentrations found in this period are indipendent of the particle size of the C3S and (within

  14. A quantitative assessment of the BSE risk associated with fly ash and slag from the incineration of meat-and-bone meal in a gas-fired power plant in Denmark

    DEFF Research Database (Denmark)

    Paisley, Larry; Hostrup-Pedersen, J.

    2005-01-01

    and slag are incorporated into the cement or concrete. Our goal was to assess with a Monte Carlo simulation model the bovine spongiform, encephalopathy (BSE) risk to cattle and humans posed by the ash and slag. The results will be used by decision makers to evaluate the need for disposal of the fly ash......It has been recommended that meat-and-bone meal (MBM) be incinerated at 850 degrees C for at least 2 s and the ashes and slag disposed of in controlled landfills, to dispose of animal-derived proteins. Most commonly, the MBM is incinerated in cement works or coal-fired power plants and the ashes...

  15. Hadean silicate differentiation revealed by anomalous 142Nd in the Réunion hotspot source

    Science.gov (United States)

    Peters, B. J.; Carlson, R.; Day, J. M.; Horan, M.

    2017-12-01

    Geochemical and geophysical data show that volcanic hotspots can tap ancient domains sequestered in Earth's deep mantle. Evidence from stable and long-lived radiogenic isotope systems has demonstrated that many of these domains result from tectonic and differentiation processes that occurred more than two billion years ago. Recent advances in the analysis of short-lived radiogenic isotopes have further shown that some hotspot sources preserve evidence for metal-silicate differentiation occurring within the first one percent of Earth's history. Despite these discoveries, efforts to detect variability in the lithophile 146Sm-142Nd (t1/2 = 103 Ma) system in Phanerozoic hotspot lavas have not yet detected significant global variation. We report 142Nd/144Nd ratios in Réunion Island basalts that are statistically distinct from the terrestrial Nd standard ranging to both higher and lower 142Nd/144Nd. Variations in 142Nd/144Nd, which total nearly 15 ppm on Réunion, are correlated with 3He/4He among both anomalous and non-anomalous samples. Such behavior implies that there were analogous changes in Sm/Nd and (U+Th)/3He that occurred during a Hadean silicate differentiation event and were not completely overprinted by the depleted mantle. Variations in the 142Nd-143Nd compositions of Réunion basalts can be explained by a single Hadean melting event producing enriched and depleted domains that partially re-mixed after 146Sm was no longer extant. Assuming differentiation occurred at pressures where perovskite is stable, anomalies of the magnitude observed in Réunion basalts require melting of at least 50% across a wide depth range, and up to 90% for melting at pressures near those of the deepest mantle. Models with best fits to Nd isotope data suggest this differentiation occurred around 4.40 Ga and mixing occurred after 4 Ga. This two-stage differentiation process nearly erased the ancient, anomalous 142Nd composition of the Réunion source and produced the relatively

  16. Stagnant lid tectonics: Perspectives from silicate planets, dwarf planets, large moons, and large asteroids

    Directory of Open Access Journals (Sweden)

    Robert J. Stern

    2018-01-01

    Full Text Available To better understand Earth's present tectonic style–plate tectonics–and how it may have evolved from single plate (stagnant lid tectonics, it is instructive to consider how common it is among similar bodies in the Solar System. Plate tectonics is a style of convection for an active planetoid where lid fragment (plate motions reflect sinking of dense lithosphere in subduction zones, causing upwelling of asthenosphere at divergent plate boundaries and accompanied by focused upwellings, or mantle plumes; any other tectonic style is usefully called “stagnant lid” or “fragmented lid”. In 2015 humanity completed a 50+ year effort to survey the 30 largest planets, asteroids, satellites, and inner Kuiper Belt objects, which we informally call “planetoids” and use especially images of these bodies to infer their tectonic activity. The four largest planetoids are enveloped in gas and ice (Jupiter, Saturn, Uranus, and Neptune and are not considered. The other 26 planetoids range in mass over 5 orders of magnitude and in diameter over 2 orders of magnitude, from massive Earth down to tiny Proteus; these bodies also range widely in density, from 1000 to 5500 kg/m3. A gap separates 8 silicate planetoids with ρ = 3000 kg/m3 or greater from 20 icy planetoids (including the gaseous and icy giant planets with ρ = 2200 kg/m3 or less. We define the “Tectonic Activity Index” (TAI, scoring each body from 0 to 3 based on evidence for recent volcanism, deformation, and resurfacing (inferred from impact crater density. Nine planetoids with TAI = 2 or greater are interpreted to be tectonically and convectively active whereas 17 with TAI <2 are inferred to be tectonically dead. We further infer that active planetoids have lithospheres or icy shells overlying asthenosphere or water/weak ice. TAI of silicate (rocky planetoids positively correlates with their inferred Rayleigh number. We conclude that some type of stagnant lid tectonics is

  17. Coordinated HArd Sphere Model (CHASM): A Simplified Model for Silicate and Oxide Liquids at Mantle Conditions

    Science.gov (United States)

    Wolf, A. S.; Asimow, P. D.; Stevenson, D. J.

    2013-12-01

    Recent first-principles theoretical calculations (Stixrude 2009) and experimental shock-wave investigations (Mosenfelder 2009) indicate that melting perovskite requires significantly less energy than previously thought, supporting the idea of a deep-mantle magma ocean early in Earth's history. The modern-day solid Earth is thus likely the result of crystallization from an early predominantly molten state, a process that is primarily controlled by the poorly understood behavior of silicate melts at extreme pressures and temperatures. Probing liquid thermodynamics at mantle conditions is difficult for both theory and experiment, and further challenges are posed by the large relevant compositional space including at least MgO, SiO2, and FeO. First-principles molecular dynamics has been used with great success to determine the high P-T properties of a small set of fixed composition silicate-oxide liquids including MgO (Karki 2006), SiO2 (Karki 2007), Mg2SiO4 (de Koker 2008), MgSiO3 (Stixrude 2005), and Fe2SiO4 (Ramo 2012). While extremely powerful, this approach has limitations including high computational cost, lower bounds on temperature due to relaxation constraints, as well as restrictions to length scales and time scales that are many orders of magnitude smaller than those relevant to the Earth or experimental methods. As a compliment to accurate first-principles calculations, we have developed the Coordinated HArd Sphere Model (CHASM). We extend the standard hard sphere mixture model, recently applied to silicate liquids by Jing (2011), by accounting for the range of oxygen coordination states available to liquid cations. Utilizing approximate analytic expressions for the hard sphere model, the method can predict complex liquid structure and thermodynamics while remaining computationally efficient. Requiring only minutes on standard desktop computers rather than months on supercomputers, the CHASM approach is well-suited to providing an approximate thermodynamic

  18. Addressing Rare-Earth Element Criticality: An Example from the Aviation Industry

    Science.gov (United States)

    Ku, Anthony Y.; Dosch, Christopher; Grossman, Theodore R.; Herzog, Joseph L.; Maricocchi, Antonio F.; Polli, Drew; Lipkin, Don M.

    2014-11-01

    Rare-earth (RE) elements are enablers for a wide range of technologies, including high-strength permanent magnets, energy-efficient lighting, high-temperature thermal barrier coatings, and catalysts. While direct material substitution is difficult in many of these applications because of the specific electronic, optical, or electrochemical properties imparted by the individual rare-earth elements, we describe an example from the aviation industry where supply chain optimization may be an option. Ceramic matrix composite engine components require environmental barrier coatings (EBCs) to protect them from extreme temperatures and adverse reactions with water vapor in the hot gas path. EBC systems based on rare-earth silicates offer a unique combination of environmental resistance, thermal expansion matching, thermal conductivity, and thermal stability across the service temperature window. Several pure rare-earth silicates and solid solutions have been demonstrated in EBC applications. However, all rely on heavy rare-earth elements (HREEs) for phase stability. This article considers the possibility of using separation tailings containing a mixture of HREEs as a source material in lieu of using the high-purity HREE oxides. This option arises because the desired properties of RE-silicate EBCs derive from the average cation size rather than the electronic properties of the individual rare-earth cations. Because separation tailings have not incurred the costs associated with the final stages of separation, they offer an economical alternative to high-purity oxides for this emerging application.

  19. Sulfur Earth

    Science.gov (United States)

    de Jong, B. H.

    2007-12-01

    Variations in surface tension affect the buoyancy of objects floating in a liquid. Thus an object floating in water will sink deeper in the presence of dishwater fluid. This is a very minor but measurable effect. It causes for instance ducks to drown in aqueous solutions with added surfactant. The surface tension of liquid iron is very strongly affected by the presence of sulfur which acts as a surfactant in this system varying between 1.9 and 0.4 N/m at 10 mass percent Sulfur (Lee & Morita (2002), This last value is inferred to be the maximum value for Sulfur inferred to be present in the liquid outer core. Venting of Sulfur from the liquid core manifests itself on the Earth surface by the 105 to 106 ton of sulfur vented into the atmosphere annually (Wedepohl, 1984). Inspection of surface Sulfur emission indicates that venting is non-homogeneously distributed over the Earth's surface. The implication of such large variation in surface tension in the liquid outer core are that at locally low Sulfur concentration, the liquid outer core does not wet the predominantly MgSiO3 matrix with which it is in contact. However at a local high in Sulfur, the liquid outer core wets this matrix which in the fluid state has a surface tension of 0.4 N/m (Bansal & Doremus, 1986), couples with it, and causes it to sink. This differential and diapiric movement is transmitted through the essentially brittle mantle (1024 Pa.s, Lambeck & Johnson, 1998; the maximum value for ice being about 1030 Pa.s at 0 K, in all likely hood representing an upper bound of viscosity for all materials) and manifests itself on the surface by the roughly 20 km differentiation, about 0.1 % of the total mantle thickness, between topographical heights and lows with concomitant lateral movement in the crust and upper mantle resulting in thin skin tectonics. The brittle nature of the medium though which this movement is transmitted suggests that the extremes in topography of the D" layer are similar in range to

  20. Evidence of denser MgSiO3 glass above 133 gigapascal (GPa) and implications for remnants of ultradense silicate melt from a deep magma ocean.

    Science.gov (United States)

    Murakami, Motohiko; Bass, Jay D

    2011-10-18

    Ultralow velocity zones are the largest seismic anomalies in the mantle, with 10-30% seismic velocity reduction observed in thin layers less than 20-40 km thick, just above the Earth's core-mantle boundary (CMB). The presence of silicate melts, possibly a remnant of a deep magma ocean in the early Earth, have been proposed to explain ultralow velocity zones. It is, however, still an open question as to whether such silicate melts are gravitationally stable at the pressure conditions above the CMB. Fe enrichment is usually invoked to explain why melts would remain at the CMB, but this has not been substantiated experimentally. Here we report in situ high-pressure acoustic velocity measurements that suggest a new transformation to a denser structure of MgSiO(3) glass at pressures close to those of the CMB. The result suggests that MgSiO(3) melt is likely to become denser than crystalline MgSiO(3) above the CMB. The presence of negatively buoyant and gravitationally stable silicate melts at the bottom of the mantle, would provide a mechanism for observed ultralow seismic velocities above the CMB without enrichment of Fe in the melt. An ultradense melt phase and its geochemical inventory would be isolated from overlying convective flow over geologic time.

  1. Wind-eroded silicate as a source of hydrogen peroxide on Mars

    DEFF Research Database (Denmark)

    Bak, Ebbe Norskov; Merrison, Jonathan P.; Jensen, Svend Knak

    -sists of silicates [4] that due to wind erosion has a very fine grained texture. Based on the composition of the surface material and investigations showing that crushing of silicates can give rise to reactive oxygen species [5], we hypothesized that wind erosion of silicates can explain the reactivity of Martian...... soil. Wind-erosion of silicate could thus be one of several causes of the soil’s reactivity. As our experiments show, the globally distributed wind eroded silicate dust can lead to the production of hydrogen peroxide which might explain the reactivity of the Martian soil. The reactivity of eroded...

  2. Calc-silicate mineralization in active geothermal systems

    Energy Technology Data Exchange (ETDEWEB)

    Bird, D.K.; Schiffman, P.; Elders, W.A.; Williams, A.E.; McDowell, S.D.

    1983-01-01

    The detailed study of calc-silicate mineral zones and coexisting phase relations in the Cerro Prieto geothermal system were used as examples for thermodynamic evaluation of phase relations among minerals of variable composition and to calculate the chemical characteristics of hydrothermal solutions compatible with the observed calc-silicate assemblages. In general there is a close correlation between calculated and observed fluid compositions. Calculated fugacities of O{sub 2} at about 320{degrees}C in the Cerro Prieto geothermal system are about five orders of magnitude less than that at the nearby Salton Sea geothermal system. This observation is consistent with the occurrence of Fe{sup 3+} rich epidotes in the latter system and the presence of prehnite at Cerro Prieto.

  3. Charge trapping and dielectric breakdown in lead silicate glasses

    International Nuclear Information System (INIS)

    Weeks, R.A.; Kinser, D.L.; Lee, J.M.

    1976-01-01

    When irradiated with beams of energetic electrons or gamma rays, many insulating glasses and plastics exhibit a spontaneous electrical discharge producing permanent patterns in the materials (Lichtenberg figures). In the case of inorganic glasses, this effect is not observed in pure silicate, germanate, or phosphate glasses nor in their crystalline forms and has only been reported in mixed-oxide glasses with low alkali content. In a series of lead silicate glasses of composition [PbO]/sub (x)/[SiO 2 ]/sub [1-(x)]/, the effect is observed only for 0 less than x less than or equal to 0.40. Changes in electrical properties are related to structural changes in these glasses. Electron microscopy of these glasses confirms the existence of microphase separation in the range 0.2 less than or equal to x less than or equal to 0.5

  4. Chemical bonding and structural ordering of cations in silicate glasses

    International Nuclear Information System (INIS)

    Calas, G.; Cormier, L.; Galoisy, L.; Ramos, A.; Rossano, St.

    1997-01-01

    The specific surrounding of cations in multicomponent silicate glasses is briefly presented. Information about interatomic distances and site geometry may be gained by using spectroscopic methods among which x-ray absorption spectroscopy may be used for the largest number of glass components. Scattering of x-rays and neutrons may also be used to determine the importance of medium range order around specific cations. All the existing data show that cations occur in sites with a well-defined geometry, which are in most cases connected to the silicate polymeric network. Medium range order has been detected around cations such as Ti, Ca and Ni, indicating that these elements have an heterogeneous distribution within the glassy matrix. (authors)

  5. Silica from triethylammonium tris (oxalato) silicate (IV) thermal decomposition

    International Nuclear Information System (INIS)

    Ferracin, L.C.; Ionashiro, M.; Davolos, M.R.

    1990-01-01

    Silica can be obtained from differents precursors by differents methods. In this paper it has been investigated the thermal decomposition of triethylammonium tris (oxalato) silicate (IV) to render silica. Among the trisoxalato-complexes of silicon preparation methods reviewed it has been used the Bessler's one with the reflux adaptaded in microwave oven. Thermal decomposition analysis of the compound has been made by TG-DTG and DTA curves. Silica powders obtained and heated between 300 to 900 0 C in a oven were characterized by infrared vibrational spectroscopy, X-ray powder difraction and nitrogen adsorption isotherm (BET). The triethylammonium tris (oxalato) silicate (IV) thermal decomposition takes place at 300 0 C and the silica powder obtained is non cristalline with impurities that are eliminated with heating at 400 0 C. (author) [pt

  6. Crystal structure study of new lanthanide silicates with silico-carnotite structure

    International Nuclear Information System (INIS)

    Piccinelli, F.; Lausi, A.; Speghini, A.; Bettinelli, M.

    2012-01-01

    The crystal structures of new rare earth-based silicate compounds (Ca 3 Eu 2 Si 3 O 12 , Ca 3 Gd 2 Si 3 O 12 , Ca 3 Dy 2 Si 3 O 12 , Ca 3 Er 2 Si 3 O 12 and Ca 3 Lu 2 Si 3 O 12 ) have been determined using powder X-ray diffraction. From Rietveld refinement calculations on the collected powder patterns we observe a different distribution of the rare earth ions on the three available crystal sites characterized by different coordination numbers, depending on the ionic radius of the rare earth ion. The reasons of the instability of the silico-carnotite structure for lanthanide ions larger than Eu 3+ have been deduced. In addition, in order to detect crystal phase transitions, the powder patterns of Ca 3 Eu 2 Si 3 O 12 and Ca 3 Sm 2 Si 3 O 12 samples have been collected as a function of the temperature (RT-1000 °C range), but no phase transitions have been observed. - Graphical abstract: Synchrotron X-ray diffraction allows us the accurate determination of the RE 3+ ions distribution on the three available crystal sites of the silico-carnotite structure. Highlights: ► The structure of the Ca 3 M 2 Si 3 O 12 (M=Eu, Gd, Dy, Er and Lu) was determined. ► Different distribution of RE 3+ ions on the three available crystal sites was observed. ► The instability of the silico-carnotite structure for RE=La→Sm was discussed.

  7. An optical fibre-type silicate glass thermoluminescent detector

    International Nuclear Information System (INIS)

    Zheng Zheng; Dai Honggui; Hu Shangze; Liu Jian; Fang Jie

    1991-01-01

    A description of dosimetric properties and the preparation method of an optical fibre-type silicate glass thermoluminescent detector (TLD) is presented. Results showed that this new phosphor is a good one which could be used as a routine dosimeter in the range 10 -1 -10 3 Gy. The preparation method is a new one which differs greatly from all previous ones. Furthermore this kind of detector is small and of low weight. (orig.)

  8. Cracking phenomena in lithium-di-silicate glass ceramics

    Indian Academy of Sciences (India)

    Unknown

    Abstract. Lithium-di-silicate glass ceramic (Li2O, SiO2) with uniformly oriented crystals was placed on a. Vickers indentation with extrusion axis horizontally parallel to the base axis. The material was rotated through. 0°– 90° and at each angle a 20 N load was applied to ascertain the crack path. It was observed that the crack.

  9. Strength and impermeability recovery of siliceous mudstone from complete failure

    International Nuclear Information System (INIS)

    Sugita, Yutaka; Sanada, Masanori; Fujita, Tomoo; Hashiba, Kimihiro; Fukui, Katsunori; Okubo, Seisuke

    2013-01-01

    Radionuclide migration can be undesirably increased by weakening the mechanical properties of a rock mass in the excavated disturbed zone (EDZ) around the tunnels of a geological disposal facility for high level radioactive waste. Laboratory testing of loading stress and loading time on failed siliceous mudstone specimens has identified the potential for the long-term recovery of the strength and impermeability of the rock mass in the EDZ. (author)

  10. Structure change of soda-silicate glass by mechanical milling

    International Nuclear Information System (INIS)

    Iwao, M; Okuno, M

    2010-01-01

    Structure change of ground soda-silicate glass (SiO 2 -Na 2 O binary systems) was investigated using X-ray diffraction (XRD) and infrared spectroscopy. The measurement results were discussed comparison to that of SiO 2 glass. With increasing Na 2 O concentrations, the XRD intensity around 2θ = 22 0 decreased and the intensity around 32 0 increased. The intensity around 22 0 and 32 0 maybe attributed to SiO 2 glass structure unit and soda-silicate glass unit, respectively. The peaks of Na 2 CO 3 crystal for 2SiO 2 -Na 2 O glass were observed with increasing milling time. This crystallization was suggested that Na + ion on 2SiO 2 -Na 2 O glass surface connected CO 2 in air. The intensity around 22 0 and 32 0 decreased and the intensity around 30 0 increased with increasing milling time. These may indicate that SiO 2 glass structure unit and soda-silicate glass structure unit were mixed by milling. In addition, IR absorption band near v = 1100 cm -1 was separated to two bands near 940 cm -1 and 1070 cm -1 with increasing Na 2 O concentrations. The band near 940 cm -1 decreased and the band near 1070 cm -1 increased with increasing milling time. These spectra changes were suggested due to decrease of Na 2 O concentrations in 2SiO 2 -Na 2 O glass with Na 2 CO 3 crystallization.

  11. Development of Li+ alumino-silicate ion source

    International Nuclear Information System (INIS)

    Roy, P.K.; Seidl, P.A.; Waldron, W.; Greenway, W.; Lidia, S.; Anders, A.; Kwan, J.

    2009-01-01

    To uniformly heat targets to electron-volt temperatures for the study of warm dense matter, one strategy is to deposit most of the ion energy at the peak of energy loss (dE/dx) with a low (E < 5 MeV) kinetic energy beam and a thin target. Lower mass ions have a peak dE/dx at a lower kinetic energy. To this end, a small lithium (Li+) alumino-silicate source has been fabricated, and its emission limit has been measured. These surface ionization sources are heated to 1000-1150 C where they preferentially emit singly ionized alkali ions. Alumino-silicates sources of K+ and Cs+ have been used extensively in beam experiments, but there are additional challenges for the preparation of high-quality Li+ sources: There are tighter tolerances in preparing and sintering the alumino-silicate to the substrate to produce an emitter that gives uniform ion emission, sufficient current density and low beam emittance. We report on recent measurements ofhigh ( up to 35 mA/cm2) current density from a Li+ source. Ion species identification of possible contaminants is being verified with a Wien (E x B) filter, and via time-of-flight.

  12. Mechanical properties of zirconia reinforced lithium silicate glass-ceramic.

    Science.gov (United States)

    Elsaka, Shaymaa E; Elnaghy, Amr M

    2016-07-01

    The aim of this study was to assess the mechanical properties of recently introduced zirconia reinforced lithium silicate glass-ceramic. Two types of CAD/CAM glass-ceramics (Vita Suprinity (VS); zirconia reinforced lithium silicate and IPS e.max CAD (IC); lithium disilicate) were used. Fracture toughness, flexural strength, elastic modulus, hardness, brittleness index, and microstructures were evaluated. Data were analyzed using independent t tests. Weibull analysis of flexural strength data was also performed. VS had significantly higher fracture toughness (2.31±0.17MPam(0.5)), flexural strength (443.63±38.90MPa), elastic modulus (70.44±1.97GPa), and hardness (6.53±0.49GPa) than IC (Pglass-ceramic revealed significantly a higher brittleness index (2.84±0.26μm(-1/2)) (lower machinability) than IC glass-ceramic (Pglass-ceramic revealed a lower probability of failure and a higher strength than IC glass-ceramic according to Weibull analysis. The VS zirconia reinforced lithium silicate glass-ceramic revealed higher mechanical properties compared with IC lithium disilicate glass-ceramic. Copyright © 2016 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  13. The thermodynamic activity of ZnO in silicate melts

    Science.gov (United States)

    Reyes, R. A.; Gaskell, D. R.

    1983-12-01

    The activity of ZnO in ZnO-SiO2 and CaO-ZnO-SiO2 melts has been measured at 1560 °C using a transpiration technique with CO-CO2 mixtures as the carrier gas. The activities of ZnO in dilute solution in 42 wt pct SiO2-38 wt pct CaO-20 wt pct A12O3 in the range 1400° to 1550 °C and in 62 wt pct SiO2-23.3 wt pct CaO-14.7 wt pct A12O3 at 1550 °C have also been measured. The measured free energies of formation of ZnO-SiO2 melts are significantly more negative than published estimated values and this, together with the behavior observed in the system CaO-Al2O3-SiO2, indicate that ZnO is a relatively basic oxide. The results are discussed in terms of the polymerization model of binary silicate melts and ideal silicate mixing in ternary silicate melts. The behavior of ZnO in dilute solution in CaO-Al2O3-SiO2 melts is discussed in terms of the possibility of the fluxing of ZnO by iron blast furnace slags.

  14. Proton tunneling in low dimensional cesium silicate LDS-1

    Science.gov (United States)

    Matsui, Hiroshi; Iwamoto, Kei; Mochizuki, Dai; Osada, Shimon; Asakura, Yusuke; Kuroda, Kazuyuki

    2015-07-01

    In low dimensional cesium silicate LDS-1 (monoclinic phase of CsHSi2O5), anomalous infrared absorption bands observed at 93, 155, 1210, and 1220 cm-1 are assigned to the vibrational mode of protons, which contribute to the strong hydrogen bonding between terminal oxygen atoms of silicate chain (O-O distance = 2.45 Å). The integrated absorbance (oscillator strength) for those modes is drastically enhanced at low temperatures. The analysis of integrated absorbance employing two different anharmonic double-minimum potentials makes clear that proton tunneling through the potential barrier yields an energy splitting of the ground state. The absorption bands at 93 and 155 cm-1, which correspond to the different vibrational modes of protons, are attributed to the optical transition between the splitting levels (excitation from the ground state (n = 0) to the first excited state (n = 1)). Moreover, the absorption bands at 1210 and 1220 cm-1 are identified as the optical transition from the ground state (n = 0) to the third excited state (n = 3). Weak Coulomb interactions in between the adjacent protons generate two types of vibrational modes: symmetric mode (93 and 1210 cm-1) and asymmetric mode (155 and 1220 cm-1). The broad absorption at 100-600 cm-1 reveals an emergence of collective mode due to the vibration of silicate chain coupled not only with the local oscillation of Cs+ but also with the proton oscillation relevant to the second excited state (n = 2).

  15. Silicate bonding properties: Investigation through thermal conductivity measurements

    Energy Technology Data Exchange (ETDEWEB)

    Lorenzini, M; Cesarini, E; Cagnoli, G; Campagna, E; Losurdo, G; Martelli, F; Piergiovanni, F; Vetrano, F [INFN, Istituto Nazionale di Fisica Nucleare, Sez. di Firenze, via G. Sansone 1, 50019 Sesto Fiorentino (Italy); Haughian, K; Hough, J; Martin, I; Reid, S; Rowan, S; Veggel, A A van, E-mail: lorenzini@fi.infn.i [SUPA, University of Glasgow, Department of Physics and Astronomy, Kelvin Building G12 8QQ Glasgow, Scotland (United Kingdom)

    2010-05-01

    A direct approach to reduce the thermal noise contribution to the sensitivity limit of a GW interferometric detector is the cryogenic cooling of the mirrors and mirrors suspensions. Future generations of detectors are foreseen to implement this solution. Silicon has been proposed as a candidate material, thanks to its very low intrinsic loss angle at low temperatures and due to its very high thermal conductivity, allowing the heat deposited in the mirrors by high power lasers to be efficiently extracted. To accomplish such a scheme, both mirror masses and suspension elements must be made of silicon, then bonded together forming a quasi-monolithic stage. Elements can be assembled using hydroxide-catalysis silicate bonding, as for silica monolithic joints. The effect of Si to Si bonding on suspension thermal conductance has therefore to be experimentally studied. A measurement of the effect of silicate bonding on thermal conductance carried out on 1 inch thick silicon bonded samples, from room temperature down to 77 K, is reported. In the explored temperature range, the silicate bonding does not seem to affect in a relevant way the sample conductance.

  16. Lithium concentration dependence of implanted helium retention in lithium silicates

    Energy Technology Data Exchange (ETDEWEB)

    Szocs, D.E., E-mail: szocsd@rmki.kfki.h [KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, P.O. Box 49 (Hungary); Szilagyi, E.; Bogdan, Cs.; Kotai, E. [KFKI Research Institute for Particle and Nuclear Physics, H-1525 Budapest, P.O. Box 49 (Hungary); Horvath, Z.E. [Research Institute for Technical Physics and Materials Science, H-1525 Budapest, P.O. Box 49 (Hungary)

    2010-06-15

    Helium ions of 500 keV were implanted with a fluence of 1.4 x 10{sup 17} ion/cm{sup 2} into various lithium silicates to investigate whether a threshold level of helium retention exists in Li-containing silicate ceramics similar to that found in SiO{sub x} in previous work. The composition and phases of the as prepared lithium silicates were determined by proton backscattering spectrometry (p-BS) and X-ray diffraction (XRD) methods with an average error of {+-}10%. Electrostatic charging of the samples was successfully eliminated by wrapping the samples in Al foil. The amounts of the retained helium within the samples were determined by subtracting the non-implanted spectra from the implanted ones. The experimental results show a threshold in helium retention depending on the Li concentration. Under 20 at.% all He is able to escape from the material; at around 30 at.% nearly half of the He, while over 65 at.% all implanted He is retained. With compositions expressed in SiO{sub 2} volume percentages, a trend similar to those reported of SiO{sub x} previously is found.

  17. Nitrogen partitioning during Earth's accretion and core-mantle differentiation

    Science.gov (United States)

    Speelmanns, I. M.; Schmidt, M. W.; Liebske, C.

    2017-12-01

    On present day Earth, N is one of the key constituents of our atmosphere and forms the basis of life. However, the deep Earth geochemistry of N, i.e. its distribution and isotopic fractionation between Earth's deep reservoirs is not well constrained. This study investigates nitrogen partitioning between metal and silicate melts as relevant for core segregation during the accretion of planetesimals into the Earth. We have determined N-partitioning coefficients over a wide range of temperatures (1250-2000 °C), pressures (15-35 kbar) and oxygen fugacity's, the latter in the relevant range of core segregation (IW-5 to IW). Centrifuging piston cylinders were used to equilibrate and then gravitationally separate metal-silicate melt pairs. Separation of the two melts is necessary to avoid micro nugget contamination in the silicate melt at reducing conditions double capsule technique in all experiments, using an outer metallic (Pt) and inner non-metallic capsule (graphite or Al2O3), minimizes N-loss over the course of the experiments compared to single non-metallic capsules. The two quenched melts were cut apart mechanically, cleaned at the outside, their N concentrations were then analysed on bulk samples by an elemental analyser, the low abslute masses requiring careful development of analytical routines. Despite these difficulties, we were able to determine a DNmetal/silicate of 13±0.3 at IW-1 decreasing to 2.0±0.2 at IW-5.5, at 1250°C and 15 kbar, N partitioning into the core forming metal. Increasing temperature dramatically lowers the DNmetal/silicate to e.g. 0.5±0.15 at IW-4, during early core formation N was hence mildly incompatible in the metal. The results suggest that under magma ocean conditions (> 2000 oC and fO2 IW-2.5), N-partition coefficents were within a factor of 2 of unity. Hence, N did not partition into the core, which should contain negliligible quantities of N. The few available literature data [1],[2],[3] support N changing compatibility with

  18. Formation and Evolution of the Continental Lithospheric Mantle: Perspectives From Radiogenic Isotopes of Silicate and Sulfide Inclusions in Macrodiamonds

    Science.gov (United States)

    Shirey, S. B.; Richardson, S. H.

    2007-12-01

    Silicate and sulfide inclusions that occur in diamonds comprise the oldest (>3 Ga), deepest (>140 km) samples of mantle-derived minerals available for study. Their relevance to the evolution of the continental lithosphere is clear because terrestrial macrodiamonds are confined to regions of the Earth with continental lithospheric mantle keels. The goals of analytical work on inclusions in diamond are to obtain paragenesis constraints, radiogenic ages, and initial isotopic compositions. The purpose is to place diamond formation episodes into the broader framework of the geological processes that create and modify the continental lithosphere and to relate the source of the C and N in diamond-forming fluids to understanding the Earth's C and N cycles in the Archean. Although sulfide and silicate inclusions rarely occur in the same diamond, they both can be grouped according to their geochemical similarity with the chief rock types that comprise the mantle keel: peridotite and eclogite. Silicate inclusions are classified as harzburgitic (depleted; olivine > Fo91, garnet Cr2O3 > 3 wt% and CaO from 0 to 5 wt%), lherzolitic (fertile), or eclogitic (basaltic; garnet Cr2O3 14 wt%; Os > 2 ppm) versus eclogitic (Ni bearing kimberlites, and the generosity of mining companies because of the extreme rarity of inclusions in suites of mostly gem-quality diamonds. Most isotopic work has been on the Kaapvaal-Zimbabwe craton with lesser work on the Slave, Siberian, and Australian cratons. Sm-Nd ages on silicate suites and Re-Os ages on sulfide suites confirm diamond formation from the Mesoarchean though the Neoproterozoic. Most important are the systematics across cratons in the context of crustal geology that lead to generalities about craton evolution. Inclusion suites date mantle keels as Mesoarchean and clearly point to subduction as the major process to form the earliest continental nuclei and to amalgamate the cratons in their present form. This is evident from the elevated

  19. Silicate melt metasomatism in the lithospheric mantle beneath SW Poland

    Science.gov (United States)

    Puziewicz, Jacek; Matusiak-Małek, Magdalena; Ntaflos, Theodoros; Grégoire, Michel; Kukuła, Anna

    2014-05-01

    The xenoliths of peridotites representing the subcontinental lithospheric mantle (SCLM) beneath SW Poland and adjacent parts of Germany occur in the Cenozoic alkaline volcanic rocks. Our study is based on detailed characterization of xenoliths occurring in 7 locations (Steinberg in Upper Lusatia, Księginki, Pilchowice, Krzeniów, Wilcza Góra, Winna Góra and Lutynia in Lower Silesia). One of the two major lithologies occurring in the xenoliths, which we call the "B" lithology, comprises peridotites (typically harzburgites) with olivine containing from 90.5 to 84.0 mole % of forsterite. The harzburgites contain no clinopyroxene or are poor in that mineral (eg. in Krzeniów the group "B" harzburgites contain pfu in ortho-, and pfu in clinopyroxene). The exception are xenoliths from Księginki, which contain pyroxenes characterised by negative correlation between mg# and Al. The REE patterns of both ortho- and clinopyroxene in the group "B" peridotites suggest equilibration with silicate melt. The rocks of "B" lithology were formed due to alkaline silicate melt percolation in the depleted peridotitic protolith. The basaltic melts formed at high pressure are usually undersaturated in both ortho- and clinopyroxene at lower pressures (Kelemen et al. 1992). Because of cooling and dissolution of ortho- and clinopyroxene the melts change their composition and become saturated in one or both of those phases. Experimental results (e.g. Tursack & Liang 2012 and references therein) show that the same refers to alkaline basaltic silicate melts and that its reactive percolation in the peridotitic host leads to decrease of Mg/(Mg+Fe) ratios of olivine and pyroxenes. Thus, the variation of relative volumes of olivine and orthopyroxene as well as the decrease of mg# of rock-forming silicates is well explained by reactive melt percolation in the peridotitic protolith consisting of high mg# olivine and pyroxenes (in the area studied by us that protolith was characterised by olivine

  20. Does Silicate Weathering of Loess Affect Atmospheric CO2?

    Science.gov (United States)

    Anderson, S. P.

    2002-12-01

    Weathering of glacial loess may be a significant, yet unrecognized, component of the carbon cycle. Glaciers produce fine-grained sediment, exposing vast amounts of mineral surface area to weathering processes, yet silicate mineral weathering rates at glacier beds and of glacial till are not high. Thus, despite the tremendous potential for glaciers to influence global weathering rates and atmospheric CO2 levels, this effect has not been demonstrated. Loess, comprised of silt-clay sizes, may be the key glacial deposit in which silicate weathering rates are high. Loess is transported by wind off braid plains of rivers, and deposited broadly (order 100 km from the source) in vegetated areas. Both the fine grain size, and hence large mineral surface area, and presence of vegetation should render loess deposits highly susceptible to silicate weathering. These deposits effectively extend the geochemical impact of glaciation in time and space, and bring rock flour into conditions conducive to chemical weathering. A simple 1-d model of silicate weathering fluxes from a soil profile demonstrates the potential of loess deposition to enhance CO2 consumption. At each time step, computed mineral dissolution (using anorthite and field-based rate constants) modifies the size of mineral grains within the soil. In the case of a stable soil surface, this results in a gradual decline in weathering fluxes and CO2 consumption through time, as finer grain sizes dissolve away. Computed weathering fluxes for a typical loess, with an initial mean grain size of 25 μm, are an order of magnitude greater than fluxes from a non-loess soil that differs only in having a mean grain size of 320 μm. High weathering fluxes are maintained through time if loess is continually deposited. Deposition rates as low as 0.01 mm/yr (one loess grain thickness per year) can lead to a doubling of CO2 consumption rates within 5 ka. These results suggest that even modest loess deposition rates can significantly

  1. Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates

    International Nuclear Information System (INIS)

    Krishnan, N. M. Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan

    2016-01-01

    Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C–S–H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C–S–H shows a sudden increase when the CaO/SiO_2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C–S–H’s nanostructure. We identify that confinement is dictated by the topology of the C–S–H’s atomic network. Altogether, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

  2. Confined Water in Layered Silicates: The Origin of Anomalous Thermal Expansion Behavior in Calcium-Silicate-Hydrates.

    Science.gov (United States)

    Krishnan, N M Anoop; Wang, Bu; Falzone, Gabriel; Le Pape, Yann; Neithalath, Narayanan; Pilon, Laurent; Bauchy, Mathieu; Sant, Gaurav

    2016-12-28

    Water, under conditions of nanoscale confinement, exhibits anomalous dynamics, and enhanced thermal deformations, which may be further enhanced when such water is in contact with hydrophilic surfaces. Such heightened thermal deformations of water could control the volume stability of hydrated materials containing nanoconfined structural water. Understanding and predicting the thermal deformation coefficient (TDC, often referred to as the CTE, coefficient of thermal expansion), which represents volume changes induced in materials under conditions of changing temperature, is of critical importance for hydrated solids including: hydrogels, biological tissues, and calcium silicate hydrates, as changes in their volume can result in stress development, and cracking. By pioneering atomistic simulations, we examine the physical origin of thermal expansion in calcium-silicate-hydrates (C-S-H), the binding agent in concrete that is formed by the reaction of cement with water. We report that the TDC of C-S-H shows a sudden increase when the CaO/SiO 2 (molar ratio; abbreviated as Ca/Si) exceeds 1.5. This anomalous behavior arises from a notable increase in the confinement of water contained in the C-S-H's nanostructure. We identify that confinement is dictated by the topology of the C-S-H's atomic network. Taken together, the results suggest that thermal deformations of hydrated silicates can be altered by inducing compositional changes, which in turn alter the atomic topology and the resultant volume stability of the solids.

  3. An Earth-sized exoplanet with a Mercury-like composition

    Science.gov (United States)

    Santerne, A.; Brugger, B.; Armstrong, D. J.; Adibekyan, V.; Lillo-Box, J.; Gosselin, H.; Aguichine, A.; Almenara, J.-M.; Barrado, D.; Barros, S. C. C.; Bayliss, D.; Boisse, I.; Bonomo, A. S.; Bouchy, F.; Brown, D. J. A.; Deleuil, M.; Delgado Mena, E.; Demangeon, O.; Díaz, R. F.; Doyle, A.; Dumusque, X.; Faedi, F.; Faria, J. P.; Figueira, P.; Foxell, E.; Giles, H.; Hébrard, G.; Hojjatpanah, S.; Hobson, M.; Jackman, J.; King, G.; Kirk, J.; Lam, K. W. F.; Ligi, R.; Lovis, C.; Louden, T.; McCormac, J.; Mousis, O.; Neal, J. J.; Osborn, H. P.; Pepe, F.; Pollacco, D.; Santos, N. C.; Sousa, S. G.; Udry, S.; Vigan, A.

    2018-05-01

    Earth, Venus, Mars and some extrasolar terrestrial planets1 have a mass and radius that is consistent with a mass fraction of about 30% metallic core and 70% silicate mantle2. At the inner frontier of the Solar System, Mercury has a completely different composition, with a mass fraction of about 70% metallic core and 30% silicate mantle3. Several formation or evolution scenarios are proposed to explain this metal-rich composition, such as a giant impact4, mantle evaporation5 or the depletion of silicate at the inner edge of the protoplanetary disk6. These scenarios are still strongly debated. Here, we report the discovery of a multiple transiting planetary system (K2-229) in which the inner planet has a radius of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth masses. This Earth-sized planet thus has a core-mass fraction that is compatible with that of Mercury, although it was expected to be similar to that of Earth based on host-star chemistry7. This larger Mercury analogue either formed with a very peculiar composition or has evolved, for example, by losing part of its mantle. Further characterization of Mercury-like exoplanets such as K2-229 b will help to put the detailed in situ observations of Mercury (with MESSENGER and BepiColombo8) into the global context of the formation and evolution of solar and extrasolar terrestrial planets.

  4. An Earth-sized exoplanet with a Mercury-like composition

    Science.gov (United States)

    Santerne, A.; Brugger, B.; Armstrong, D. J.; Adibekyan, V.; Lillo-Box, J.; Gosselin, H.; Aguichine, A.; Almenara, J.-M.; Barrado, D.; Barros, S. C. C.; Bayliss, D.; Boisse, I.; Bonomo, A. S.; Bouchy, F.; Brown, D. J. A.; Deleuil, M.; Delgado Mena, E.; Demangeon, O.; Díaz, R. F.; Doyle, A.; Dumusque, X.; Faedi, F.; Faria, J. P.; Figueira, P.; Foxell, E.; Giles, H.; Hébrard, G.; Hojjatpanah, S.; Hobson, M.; Jackman, J.; King, G.; Kirk, J.; Lam, K. W. F.; Ligi, R.; Lovis, C.; Louden, T.; McCormac, J.; Mousis, O.; Neal, J. J.; Osborn, H. P.; Pepe, F.; Pollacco, D.; Santos, N. C.; Sousa, S. G.; Udry, S.; Vigan, A.

    2018-03-01

    Earth, Venus, Mars and some extrasolar terrestrial planets1 have a mass and radius that is consistent with a mass fraction of about 30% metallic core and 70% silicate mantle2. At the inner frontier of the Solar System, Mercury has a completely different composition, with a mass fraction of about 70% metallic core and 30% silicate mantle3. Several formation or evolution scenarios are proposed to explain this metal-rich composition, such as a giant impact4, mantle evaporation5 or the depletion of silicate at the inner edge of the protoplanetary disk6. These scenarios are still strongly debated. Here, we report the discovery of a multiple transiting planetary system (K2-229) in which the inner planet has a radius of 1.165 ± 0.066 Earth radii and a mass of 2.59 ± 0.43 Earth masses. This Earth-sized planet thus has a core-mass fraction that is compatible with that of Mercury, although it was expected to be similar to that of Earth based on host-star chemistry7. This larger Mercury analogue either formed with a very peculiar composition or has evolved, for example, by losing part of its mantle. Further characterization of Mercury-like exoplanets such as K2-229 b will help to put the detailed in situ observations of Mercury (with MESSENGER and BepiColombo8) into the global context of the formation and evolution of solar and extrasolar terrestrial planets.

  5. The partitioning of barium and lead between silicate melts and aqueous fluids at high pressures and temperatures

    International Nuclear Information System (INIS)

    Bureau, Helene; Menez, Benedicte; Khodja, Hicham; Daudin, Laurent; Gallien, Jean-Paul; Massare, Dominique; Shaw, Cliff; Metrich, Nicole

    2003-01-01

    The origin of subduction-related magmas is still a matter of debate in the Earth Sciences. These magmas are characterised by their distinctive trace element compositions compared to magmas from other tectonic settings, e.g. mid-ocean ridges or rifts. The distinct trace element composition of these magmas is generally attributed to alteration of the source region by a contaminating agent: either a silicate melt or a hydrous fluid, possibly chlorine-enriched. In this study, we have used μPIXE (proton induced X-ray emission) to analyse synthetic samples obtained from a micro-experimental petrology study that aims to determine the partitioning behaviour of two key elements, Ba and Pb, between silicate melt and both pure water and saline fluids. Our experiments were performed at high-pressure (>0.34-1.53 GPa) and high-temperature (697-1082 deg. C) in a hydrothermal diamond anvil cell, that was used as a transparent rapid quench autoclave. We observed that at high pressure and temperature, in the presence of pure water, Ba and Pb are not strongly fractionated into one phase or the other. The partition coefficient of Pb is ranging from 0.46 to 1.28. Results from one experiment performed at 0.83 GPa and 847 deg. C, in the presence of a saline fluid indicate that the presence of Cl induces strong fractionation of Pb and moderate fractionation of Ba both into the silicate melt. In addition, our data indicate that Cl is strongly partitioned into the fluid phase

  6. Metal/silicate partitioning of Pt and the origin of the "late veneer"

    Science.gov (United States)

    Ertel, W.; Walter, M. J.; Drake, M. J.; Sylvester, P. J.

    2002-12-01

    Highly siderophile elements (HSEs) are perfect tools for investigating core forming processes in planetary bodies due to their Fe-loving (siderophile) geochemical behavior. Tremendous scientific effort was invested into this field during the past 10 years - mostly in 1 atm experiments. However, little is known about their high-pressure geochemistry and partitioning behavior between core and mantle forming phases. This knowledge is essential to distinguish between equilibrium (Magma Ocean) and non-equilibrium (heterogeneous accretion, late veneer) models for the accretion history for the early Earth. We therefore chose to investigate the partitioning behavior of Pt up to pressures of 140 kbar (14 GPa) and temperatures of 1950°C. The used melt composition - identical to melt systems used in 1 atm experiments - is the eutectic composition of Anorthite-Diopside (AnDi), a pseudo-basalt. A series of runs were performed which were internaly buffered by the piston cylinder apparatus, and were followed by duplicate experiments buffered in the AnDi-C-CO2 system. These experiments constitute reversals since they approach equilibrium from an initially higher and lower Pt solubility (8 ppm in the non-buffered runs, and essentially Pt free in the buffered runs). Experimental charges were encapsulated in Pt capsules which served as source for Pt. Experiments up to 20 kbar were performed in a Quickpress piston cylinder apparatus, while experiments at higher pressures were performed in a Walker-type (Tucson, AZ) and a Kawai-type (Misasa, Japan) multi anvil apparatus. Time series experiments were performed in piston-cylinder runs to determine minimum run durations for the achievement of equilibrium, and to guarantee high-quality partitioning data. 6 hours was found to be sufficient to obtain equilibrium. In practice, all experiments exceeded 12 hours to assure equilibrium. In a second set of runs the temperature dependence of the partitioning behavior of Pt was investigated between

  7. Lattice-dynamical estimation of atomic thermal parameters for silicates: Forsterite. alpha. -Mg sub 2 SiO sub 4

    Energy Technology Data Exchange (ETDEWEB)

    Pilati, T.; Bianchi, R. (Consiglio Nazionale delle Ricerche, Milan (Italy). Centro per lo Studio delle Relazioni tra Struttura e Reattivita' Chimica); Gramaccioli, C.M. (Milan Univ. (Italy). Dipt. di Scienze della Terra)

    1990-06-01

    As an example of extending harmonic lattice-dynamical procedures to silicates, the atomic thermal parameters for forsterite Mg{sub 2}SiO{sub 4}, an important constituent of earth's crust, have been calculated on this basis. For this purpose, Iishi's rigid-ion model was used, with slight modifications. Although such potentials were derived exclusively from fitting IR and Raman-active frequencies, the reproduction of the phonon-dispersion curves is good, and the calculation of thermodynamic functions such as entropy provides values which are near to calorimetric estimates. The calculated atomic thermal parameters are in good agreement with the experimental values reported by most authors. The calculations at various temperatures show the effect of zero-point motion very clearly: its contribution to temperature factors is about half of the total at room temperature. Bond-length corrections for thermal libration can be applied using the general-case formula: these amount to 0.003 A for the Si-O bonds at room temperature. Although the thermal parameters in the SiO{sub 4} group fit a rigid-body model, the correction obtained using the Schomaker-Trueblood procedure gives a significantly different result: this is essentially due to the weak librational character of the motion of silicate groups in the structure. (orig.).

  8. Lattice-dynamical estimation of atomic thermal parameters for silicates: Forsterite α-Mg2SiO4

    International Nuclear Information System (INIS)

    Pilati, T.; Bianchi, R.; Gramaccioli, C.M.

    1990-01-01

    As an example of extending harmonic lattice-dynamical procedures to silicates, the atomic thermal parameters for forsterite Mg 2 SiO 4 , an important constituent of earth's crust, have been calculated on this basis. For this purpose, Iishi's rigid-ion model was used, with slight modifications. Although such potentials were derived exclusively from fitting IR and Raman-active frequencies, the reproduction of the phonon-dispersion curves is good, and the calculation of thermodynamic functions such as entropy provides values which are near to calorimetric estimates. The calculated atomic thermal parameters are in good agreement with the experimental values reported by most authors. The calculations at various temperatures show the effect of zero-point motion very clearly: its contribution to temperature factors is about half of the total at room temperature. Bond-length corrections for thermal libration can be applied using the general-case formula: these amount to 0.003 A for the Si-O bonds at room temperature. Although the thermal parameters in the SiO 4 group fit a rigid-body model, the correction obtained using the Schomaker-Trueblood procedure gives a significantly different result: this is essentially due to the weak librational character of the motion of silicate groups in the structure. (orig.)

  9. Steam based conversion coating on AA6060 alloy: Effect of sodium silicate chemistry and corrosion performance

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Bordo, Kirill; Tabrizian, Naja

    2017-01-01

    . Moreover, the use of sodium silicate resulted in the formation of distinct microstructure and incorporation of silicate into the oxide film. These oxide films reduced the anodic activity 4 times, while the corrosion protection by silicate containing oxide was the function of its concentration. Further......Surface treatment of aluminium alloy AA6060 using an industrially applicable pilot steam jet system with and without silicate chemistry has been investigated. Treatment using steam alone and steam with silicate, resulted in an oxide layer formation with thickness ∼425 nm and ∼160 nm, respectively......, in acid salt spray and filiform corrosion tests, oxide layer containing silicate exhibited two times higher corrosion resistance....

  10. Presentation, calibration and validation of the low-order, DCESS Earth System Model

    DEFF Research Database (Denmark)

    Shaffer, G.; Olsen, S. Malskaer; Pedersen, Jens Olaf Pepke

    2008-01-01

    A new, low-order Earth system model is described, calibrated and tested against Earth system data. The model features modules for the atmosphere, ocean, ocean sediment, land biosphere and lithosphere and has been designed to simulate global change on time scales of years to millions of years...... remineralization. The lithosphere module considers outgassing, weathering of carbonate and silicate rocks and weathering of rocks containing old organic carbon and phosphorus. Weathering rates are related to mean atmospheric temperatures. A pre-industrial, steady state calibration to Earth system data is carried...

  11. Redox dependent behaviour of molybdenum during magmatic processes in the terrestrial and lunar mantle: Implications for the Mo/W of the bulk silicate Moon

    Science.gov (United States)

    Leitzke, F. P.; Fonseca, R. O. C.; Sprung, P.; Mallmann, G.; Lagos, M.; Michely, L. T.; Münker, C.

    2017-09-01

    We present results of high-temperature olivine-melt, pyroxene-melt and plagioclase-melt partitioning experiments aimed at investigating the redox transition of Mo in silicate systems. Data for a series of other minor and trace elements (Sc, Ba, Sr, Cr, REE, Y, HFSE, U, Th and W) were also acquired to constrain the incorporation of Mo in silicate minerals. All experiments were carried out in vertical tube furnaces at 1 bar and temperatures ranging from ca. 1220 to 1300 °C. Oxygen fugacity was controlled via CO-CO2 gas mixtures and varied systematically from 5.5 log units below to 1.9 log units above the fayalite-magnetite-quartz (FMQ) redox buffer thereby covering the range in oxygen fugacities of terrestrial and lunar basalt genesis. Molybdenum is shown to be volatile at oxygen fugacities above FMQ and that its compatibility in pyroxene and olivine increases three orders of magnitude towards the more reducing conditions covered in this study. The partitioning results show that Mo is dominantly tetravalent at redox conditions below FMQ-4 and dominantly hexavalent at redox conditions above FMQ. Given the differences in oxidation states of the terrestrial (oxidized) and lunar (reduced) mantles, molybdenum will behave significantly differently during basalt genesis in the Earth (i.e. highly incompatible; average DMoperidotite/melt ∼ 0.008) and Moon (i.e. moderately incompatible/compatible; average DMoperidotite/melt ∼ 0.6). Thus, it is expected that Mo will strongly fractionate from W during partial melting in the lunar mantle, given that W is broadly incompatible at FMQ-5. Moreover, the depletion of Mo and the Mo/W range in lunar samples can be reproduced by simply assuming a primitive Earth-like Mo/W for the bulk silicate Moon. Such a lunar composition is in striking agreement with the Moon being derived from the primitive terrestrial mantle after core formation on Earth.

  12. Structure and properties of polymer-silicate nanocomposites based on polytetrafluoroethylene

    Energy Technology Data Exchange (ETDEWEB)

    Sleptsova, Sardana A.; Okhlopkova, Aitalina A. [North-Eastern Federal University, Yakutsk (Russian Federation)

    2011-07-01

    The results of physicomechanical, tribological , and structural investigation of polytetrafluoroethylene based polymers and natural layered silicates are reported. It is shown that the tribological behaviour of the composites can be significantly improved by introducing a small amount of activated silicates. The results of structural examination of the composite friction surfaces by scanning-probe microscopy and IR spectroscopy are discussed. Key words: polytetrafluoroethylene, layered silicates, wear resistance, friction coefficient, structure, IR-spectrum.

  13. Application of Sodium Silicate Enhances Cucumber Resistance to Fusarium Wilt and Alters Soil Microbial Communities

    Directory of Open Access Journals (Sweden)

    Xingang Zhou

    2018-05-01

    Full Text Available Exogenous silicates can enhance plant resistance to pathogens and change soil microbial communities. However, the relationship between changes in soil microbial communities and enhanced plant resistance remains unclear. Here, effects of exogenous sodium silicate on cucumber (Cucumis sativus L. seedling resistance to Fusarium wilt caused by the soil-borne pathogen Fusarium oxysporum f.sp. cucumerinum Owen (FOC were investigated by drenching soil with 2 mM sodium silicate. Soil bacterial and fungal community abundances and compositions were estimated by real-time PCR and high-throughput amplicon sequencing; then, feedback effects of changes in soil biota on cucumber seedling resistance to FOC were assessed. Moreover, effects of sodium silicate on the growth of FOC and Streptomyces DHV3-2, an antagonistic bacterium to FOC, were investigated both in vitro and in the soil environment. Results showed that exogenous sodium silicate enhanced cucumber seedling growth and resistance to FOC. In bare soil, sodium silicate increased bacterial and fungal community abundances and diversities. In cucumber-cultivated soil, sodium silicate increased bacterial community abundances, but decreased fungal community abundances and diversities. Sodium silicate also changed soil bacterial and fungal communality compositions, and especially, decreased the relative abundances of microbial taxa containing plant pathogens but increased these with plant-beneficial potentials. Moreover, sodium silicate increased the abundance of Streptomyces DHV3-2 in soil. Soil biota from cucumber-cultivated soil treated with sodium silicate decreased cucumber seedling Fusarium wilt disease index, and enhanced cucumber seedling growth and defense-related enzyme activities in roots. Sodium silicate at pH 9.85 inhibited FOC abundance in vitro, but did not affect FOC abundance in soil. Overall, our results suggested that, in cucumber-cultivated soil, sodium silicate increased cucumber seedling

  14. Conduction mechanism in bismuth silicate glasses containing titanium

    International Nuclear Information System (INIS)

    Dult, Meenakshi; Kundu, R.S.; Murugavel, S.; Punia, R.; Kishore, N.

    2014-01-01

    Bismuth silicate glasses mixed with different concentrations of titanium dioxide having compositions xTiO 2 –(60−x)Bi 2 O 3 –40SiO 2 with x=0, 5, 10, 15 and 20 were prepared by the normal melt quench technique. The frequency dependence of the ac electrical conductivity of different compositions of titanium bismuth silicate glasses has been studied in the frequency range 10 −1 Hz to 10 MHz and in the temperature range 623–703 K. The temperature and frequency dependent conductivity is found to obey Jonscher's universal power law for all the compositions of titanium bismuth silicate glass system. The dc conductivity (σ dc ), so called crossover frequency (ω H ), and frequency exponent (s) have been estimated from the fitting of experimental data of ac conductivity with Jonscher's universal power law. Enthalpy to dissociate the cation from its original site next to a charge compensating center (H f ) and enthalpy of migration (H m ) have also been estimated. The conductivity data have been analyzed in terms of different theoretical models to determine the possible conduction mechanism. Analysis of the conductivity data and the frequency exponent shows that the correlated barrier hopping of electrons between Ti 3+ and Ti 4+ ions in the glasses is the most favorable mechanism for ac conduction. The temperature dependent dc conductivity has been analyzed in the framework of theoretical variable range hopping model (VRH) proposed by Mott which describe the hopping conduction in disordered semiconducting systems. The various polaron hopping parameters have also been deduced. Mott's VRH model is found to be in good agreement with experimental data and the values of inverse localization length of s-like wave function (α) obtained by this model with modifications suggested by Punia et al. are close to the ones reported for a number of oxide glasses

  15. New candidates for carbon stars with silicate features

    Science.gov (United States)

    Chan, S. J.; Kwok, Sun

    1991-01-01

    All stars in the General Catalog of Cool Galactic Carbon Stars with IRAS 12-micron fluxes greater than 10 Jy were searched for Low-Resolution-Spectrometer (LRS) spectra in the IRAS LRS data base. Out of the 532 spectra examined, 11 were found to show the 9.7-micron silicate emission feature. Four of these are identified for the first time. This group of carbon stars may represent transition objects between oxygen-rich and carbon-rich stars on the asymptotic giant branch.

  16. VISION: a Versatile and Innovative SIlicOn tracking system

    CERN Document Server

    Lietti, Daniela; Vallazza, Erik

    This thesis work focuses on the study of the performance of different tracking and profilometry systems (the so-called INSULAB, INSUbria LABoratory, and VISION, Versatile and Innovative SIlicON, Telescopes) used in the last years by the NTA-HCCC, the COHERENT (COHERENT effects in crystals for the physics of accelerators), ICE-RAD (Interaction in Crystals for Emission of RADiation) and CHANEL (CHAnneling of NEgative Leptons) experiments, four collaborations of the INFN (Istituto Nazionale di Fisica Nucleare) dedicated to the research in the crystals physics field.

  17. Minerals ontology: application in the environmental field to silicates

    International Nuclear Information System (INIS)

    Galan Saulnier, A.; Garcia Gimenez, R.

    2010-01-01

    The aim of this paper is to describe the application of an ontology, or up-to-date computerized tool, developed in the field of artificial intelligence and in particular of knowledge engineering, to inert elements, in this case the silicate class, which are minerals of scientific, technical and economic interest. The importance of applying ontology to minerals lies in the fact that these substances are capable of causing negative environmental impacts upon other variables in the natural environment, such as the atmosphere and the hydrosphere, and possible subsequent effects on human health. (Author) 37 refs.

  18. The Evolution of Land Plants and the Silicate Weathering Feedback

    Science.gov (United States)

    Ibarra, D. E.; Caves Rugenstein, J. K.; Bachan, A.; Baresch, A.; Lau, K. V.; Thomas, D.; Lee, J. E.; Boyce, C. K.; Chamberlain, C. P.

    2017-12-01

    It has long been recognized that the advent of vascular plants in the Paleozoic must have changed silicate weathering and fundamentally altered the long-term carbon cycle. Efforts to quantify these effects have been formulated in carbon cycle models that are, in part, calibrated by weathering studies of modern plant communities. In models of the long-term carbon cycle, plants play a key role in controlling atmospheric CO2, particularly in the late Paleozoic. We test the impact of some established and recent theories regarding plant-enhanced weathering by coupling a one-dimensional vapor transport model to a reactive transport model of silicate weathering. In this coupled model, we evaluate consequences of plant evolutionary innovation that have not been mechanistically incorporated into most existing models: 1) the role of evolutionary shifts in plant transpiration in enhancing silicate weathering by increasing downwind transport and recycling of water vapor to continental interiors; 2) the importance of deeply-rooted plants and their associated microbial communities in increasing soil CO2 and weathering zone length scales; and, 3) the cumulative effect of these processes. Our modeling approach is framed by energy/supply constraints calibrated for minimally vegetated-, vascular plant forested-, and angiosperm-worlds. We find that the emergence of widespread transpiration and associated inland vapor recycling approximately doubles weathering solute concentrations when deep-rooted vascular plants (Devonian-Carboniferous) fully replace a minimally vegetated (pre-Devonian) world. The later evolution of angiosperms (Cretaceous and Cenozoic) and subsequent increase in transpiration fluxes increase weathering solute concentrations by approximately an additional 20%. Our estimates of the changes in weatherability caused by land plant evolution are of a similar magnitude, but explained with new process-based mechanisms, than those used in existing carbon cycle models. We

  19. Theoretical and practical aspects of aqueous solution sodium silicate modifying

    Directory of Open Access Journals (Sweden)

    Mizuryaev Sergey

    2016-01-01

    Full Text Available This research deals with the use of liquid glass in industry particularly for porous filler production. The aim of this paper is to show the necessity liquid glass modification for the purpose of its rheological characteristics change for raw granules formation and providing given structure after porization. Data on chemical liquid glass modification are provided by adding sodium chloride. Moreover, inert mineral additives influence on porous filler properties are shown in this paper. The basic principles of light concrete composition selection are specified. Test results of light concrete on the developed porous sodium silicate filler are given.

  20. Infrared Spectroscopy and Stable Isotope Geochemistry of Hydrous Silicate Glasses

    Energy Technology Data Exchange (ETDEWEB)

    Stolper, Edward

    2007-03-05

    The focus of this DOE-funded project has been the study of volatile components in magmas and the atmosphere. Over the twenty-one year period of this project, we have used experimental petrology and stable isotope geochemistry to study the behavior and properties of volatile components dissolved in silicate minerals and melts and glasses. More recently, we have also studied the concentration and isotopic composition of CO2 in the atmosphere, especially in relation to air quality issues in the Los Angeles basin.

  1. Surface charges and Np(V) sorption on amorphous Al- and Fe- silicates

    International Nuclear Information System (INIS)

    Del Nero, M.; Assada, A.; Barillon, R.; Duplatre, G.; Made, B.

    2005-01-01

    Full text of publication follows: Sorption onto Si-rich alteration layers of crystalline minerals and nuclear glasses, and onto amorphous secondary silicates of rocks and soils, are expected to retard the migration of actinides in the near- and far-field of HLW repositories. We present experimental and modeling studies on the effects of silicate structure and bulk chemistry, and of solution chemistry, on charges and adsorption of neptunyl ions at surfaces of synthetic, amorphous or poorly ordered silica, Al-silicates and Fe-silicates. The Al-silicates display similar pH-dependent surface charges characterized by predominant Si-O - Si sites, and similar surface affinities for neptunyl ions, irrespective to their Si/Al molar ratio (varying from 10 to 4.3). Such experimental features are explained by incorporation of Al atoms in tetrahedral position in the silicate lattice, leading to only trace amounts of high-affinity Al-OH surface groups due to octahedral Al. By contrast, the structure of the Fe-silicates ensures the occurrence of high-affinity Fe-OH surface groups, whose concentration is shown by proton adsorption measurements to increase with decreasing of the silicate Si/Fe molar ratio (from 10 to 2.3). Nevertheless, experimental data of the adsorption of neptunyl and electrolyte ions show unexpectedly weak effect of the Si/Fe ratio, and suggest predominant Si-OH surface groups. A possible explanation is that aqueous silicate anions, released by dissolution, adsorb at OH Fe - surface groups and / or precipitate as silica gel coatings, because experimental solutions were found at near-equilibrium with respect to amorphous silica. Therefore, the environmental sorption of Np(V) onto Si-rich, amorphous or poorly ordered Al-silicates may primarily depend on pH and silicate specific surface areas, given the low overall chemical affinity of such phases for dissolved metals. By contrast, the sorption of Np(V) on natural, amorphous or poorly ordered Fe-silicates may be a

  2. New findings for diatomite (Diatomaceous earth) between the villages of manastir and Bešište (Mariovo)

    OpenAIRE

    Spasovski, Orce; Sijakova-Ivanova, Tena; Doneva, Blagica; Spasovski, Daniel

    2016-01-01

    Diatomaceous earth as porous, fine granular siliceous sedimentary rock, due to their specific physical-chemical properties, often attracted attention to the study of professional and scientific aspect. For diatomaceous earth from the Manastir–Bešište deposit in geological literature very little has been written, especially its mineralogical and chemical composition. In the paper will be present the latest research and results obtained on samples taken from the surface of the ground from...

  3. Modifier cation effects on (29)Si nuclear shielding anisotropies in silicate glasses.

    Science.gov (United States)

    Baltisberger, Jay H; Florian, Pierre; Keeler, Eric G; Phyo, Pyae A; Sanders, Kevin J; Grandinetti, Philip J

    2016-07-01

    We have examined variations in the (29)Si nuclear shielding tensor parameters of SiO4 tetrahedra in a series of seven alkali and alkaline earth silicate glass compositions, Cs2O·4.81 SiO2, Rb2O·3.96 SiO2, Rb2O·2.25 SiO2, K2O·4.48 SiO2, Na2O·4.74 SiO2, BaO·2.64 SiO2, and SrO·2.36 SiO2, using natural abundance (29)Si two-dimensional magic-angle flipping (MAF) experiments. Our analyses of these 2D spectra reveal a linear dependence of the (29)Si nuclear shielding anisotropy of Q((3)) sites on the Si-non-bridging oxygen bond length, which in turn depends on the cation potential and coordination of modifier cations to the non-bridging oxygen. We also demonstrate how a combination of Cu(2+) as a paramagnetic dopant combined with echo train acquisition can reduce the total experiment time of (29)Si 2D NMR measurements by two orders of magnitude, enabling higher throughput 2D NMR studies of glass structure. Copyright © 2016 Elsevier Inc. All rights reserved.

  4. Modifier cation effects on 29Si nuclear shielding anisotropies in silicate glasses

    Science.gov (United States)

    Baltisberger, Jay H.; Florian, Pierre; Keeler, Eric G.; Phyo, Pyae A.; Sanders, Kevin J.; Grandinetti, Philip J.

    2016-07-01

    We have examined variations in the 29Si nuclear shielding tensor parameters of SiO4 tetrahedra in a series of seven alkali and alkaline earth silicate glass compositions, Cs2O · 4.81 SiO2, Rb2O · 3.96 SiO2, Rb2O · 2.25 SiO2, K2O · 4.48 SiO2, Na2O · 4.74 SiO2, BaO · 2.64 SiO2, and SrO · 2.36 SiO2, using natural abundance 29Si two-dimensional magic-angle flipping (MAF) experiments. Our analyses of these 2D spectra reveal a linear dependence of the 29Si nuclear shielding anisotropy of Q(3) sites on the Si-non-bridging oxygen bond length, which in turn depends on the cation potential and coordination of modifier cations to the non-bridging oxygen. We also demonstrate how a combination of Cu2+ as a paramagnetic dopant combined with echo train acquisition can reduce the total experiment time of 29Si 2D NMR measurements by two orders of magnitude, enabling higher throughput 2D NMR studies of glass structure.

  5. Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

    Energy Technology Data Exchange (ETDEWEB)

    Cochain, B; Neuville, D R; Roux, J; Strukelj, E; Richet, P [Physique des Mineraux et Magmas, Geochimie-Cosmochimie, CNRS-IPGP, 4 place Jussieu, 75005 Paris (France); Ligny, D de [Universite Claude Bernard Lyon 1, LPCML, F-69622 Villeurbanne (France); Baudelet, F, E-mail: cochain@ipgp.jussieu.f [Synchrotron SOLEIL, L' Orme des Merisiers, Saint Aubin (France)

    2009-11-15

    In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe{sup 2+} and Fe{sup 3+}, but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

  6. Kinetics of iron redox reaction in silicate melts: A high temperature Xanes study on an alkali basalt

    International Nuclear Information System (INIS)

    Cochain, B; Neuville, D R; Roux, J; Strukelj, E; Richet, P; Ligny, D de; Baudelet, F

    2009-01-01

    In Earth and Materials sciences, iron is the most important transition element. Glass and melt properties are strongly affected by iron content and redox state with the consequence that some properties (i.e. viscosity, heat capacity, crystallization...) depend not only on the amounts of Fe 2+ and Fe 3+ , but also on the coordination state of these ions. In this work we investigate iron redox reactions through XANES experiments at the K-edge of iron. Using a high-temperature heating device, pre-edge of XANES spectra exhibits definite advantages to make in-situ measurements and to determine the evolution of redox state with time, temperature and composition of synthetic silicate melts. In this study, new kinetics measurements are presented for a basalt melt from the 31,000-BC eruption of the Puy de Lemptegy Volcano in France. These measurements have been made between 773 K and at superliquidus temperatures up to 1923 K.

  7. Sulfur in Earth's Mantle and Its Behavior During Core Formation

    Science.gov (United States)

    Chabot, Nancy L.; Righter,Kevin

    2006-01-01

    The density of Earth's outer core requires that about 5-10% of the outer core be composed of elements lighter than Fe-Ni; proposed choices for the "light element" component of Earth's core include H, C, O, Si, S, and combinations of these elements [e.g. 1]. Though samples of Earth's core are not available, mantle samples contain elemental signatures left behind from the formation of Earth's core. The abundances of siderophile (metal-loving) elements in Earth's mantle have been used to gain insight into the early accretion and differentiation history of Earth, the process by which the core and mantle formed, and the composition of the core [e.g. 2-4]. Similarly, the abundance of potential light elements in Earth's mantle could also provide constraints on Earth's evolution and core composition. The S abundance in Earth's mantle is 250 ( 50) ppm [5]. It has been suggested that 250 ppm S is too high to be due to equilibrium core formation in a high pressure, high temperature magma ocean on early Earth and that the addition of S to the mantle from the subsequent accretion of a late veneer is consequently required [6]. However, this earlier work of Li and Agee [6] did not parameterize the metalsilicate partitioning behavior of S as a function of thermodynamic variables, limiting the different pressure and temperature conditions during core formation that could be explored. Here, the question of explaining the mantle abundance of S is revisited, through parameterizing existing metal-silicate partitioning data for S and applying the parameterization to core formation in Earth.

  8. Earth mortars and earth-lime renders

    Directory of Open Access Journals (Sweden)

    Maria Fernandes

    2008-01-01

    Full Text Available Earth surface coatings play a decorative architectural role, apart from their function as wall protection. In Portuguese vernacular architecture, earth mortars were usually applied on stone masonry, while earth renders and plasters were used on indoors surface coatings. Limestone exists only in certain areas of the country and consequently lime was not easily available everywhere, especially on granite and schist regions where stone masonry was a current building technique. In the central west coast of Portugal, the lime slaking procedure entailed slaking the quicklime mixed with earth (sandy soil, in a pit; the resulting mixture would then be combined in a mortar or plaster. This was also the procedure for manufactured adobes stabilized with lime. Adobe buildings with earth-lime renderings and plasters were also traditional in the same region, using lime putty and lime wash for final coat and decoration. Classic decoration on earth architecture from the 18th-19th century was in many countries a consequence of the François Cointeraux (1740-1830 manuals - Les Cahiers d'Architecture Rurale" (1793 - a French guide for earth architecture and building construction. This manual arrived to Portugal in the beginning of XIX century, but was never translated to Portuguese. References about decoration for earth houses were explained on this manual, as well as procedures about earth-lime renders and ornamentation of earth walls; in fact, these procedures are exactly the same as the ones used in adobe buildings in this Portuguese region. The specific purpose of the present paper is to show some cases of earth mortars, renders and plasters on stone buildings in Portugal and to explain the methods of producing earth-lime renders, and also to show some examples of rendering and coating with earth-lime in Portuguese adobe vernacular architecture.

  9. Why Earth Science?

    Science.gov (United States)

    Smith, Michael J.

    2004-01-01

    This article briefly describes Earth science. The study of Earth science provides the foundation for an understanding of the Earth, its processes, its resources, and its environment. Earth science is the study of the planet in its entirety, how its lithosphere, atmosphere, hydrosphere, and biosphere work together as systems and how they affect…

  10. Ab Initio Predictions of K, He and Ar Partitioning Between Silicate Melt and Liquid Iron Under High Pressure

    Science.gov (United States)

    Xiong, Z.; Tsuchiya, T.

    2017-12-01

    Element partitioning is an important property in recording geochemical processes during the core-mantle differentiation. However, experimental measurements of element partitioning coefficients under extreme temperature and pressure condition are still challenging. Theoretical modeling is also not easy, because it requires estimation of high temperature Gibbs free energy, which is not directly accessible by the standard molecular dynamics method. We recently developed an original technique to simulate Gibbs free energy based on the thermodynamics integration method[1]. We apply it to element partitioning of geochemical intriguing trace elements between molten silicate and liquid iron such as potassium, helium and argon as starting examples. Radiogenic potassium in the core can provide energy for Earth's magnetic field, convection in the mantle and outer core[2]. However, its partitioning behavior between silicate and iron remains unclear under high pressure[3,4]. Our calculations suggest that a clear positive temperature dependence of the partitioning coefficient but an insignificant pressure effect. Unlike sulfur and silicon, oxygen dissolved in the metals considerably enhances potassium solubility. Calculated electronic structures reveal alkali-metallic feature of potassium in liquid iron, favoring oxygen with strong electron affinity. Our results suggest that 40K could serve as a potential radiogenic heat source in the outer core if oxygen is the major light element therein.­­ We now further extend our technique to partitioning behaviors of other elements, helium and argon, to get insides into the `helium paradox' and `missing argon' problems. References [1] T. Taniuchi, and T. Tsuchiya, Phys.Rev.B. In press [2] B.A. Buffett, H.E. Huppert, J.R. Lister, and A.W. Woods, Geophys.Res.Lett. 29 (1996) 7989-8006. [3] V.R. Murthy, W. Westrenen, and Y. Fei, Nature. 426 (2003) 163-165. [4] A. Corgne, S.Keshav, Y. Fei, and W.F. McDonough, Earth.Planet.Sci.Lett. 256 (2007

  11. Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO2 degassing

    International Nuclear Information System (INIS)

    Kadoya, S.; Tajika, E.

    2014-01-01

    Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO 2 degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO 2 degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowball climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO 2 degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.

  12. NMR study of hydrated calcium silicates; Etude par RMN de la structure des silicates de calcium hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Klur, I

    1996-02-26

    Radioactive wastes storage methods are developed by the CEA. As cements are important materials as well for hours living radioisotopes than for years living radioisotopes, a better knowledge of this material will allow to anticipate its behaviour and to obtain safer storage methods. The structure of calcium silicates (C-S-H) (main constituent of cements) have then been determined in this thesis by nuclear magnetic resonance. This method has allow to explain in structural terms, the different calcium rates that can be measured in the C-S-H too. (O.M.) 101 refs.

  13. Polymer-Layered Silicate Nanocomposites for Cryotank Applications

    Science.gov (United States)

    Miller, Sandi G.; Meador, Michael A.

    2007-01-01

    Previous composite cryotank designs have relied on the use of conventional composite materials to reduce microcracking and permeability. However, revolutionary advances in nanotechnology derived materials may enable the production of ultra-lightweight cryotanks with significantly enhanced durability and damage tolerance, as well as reduced propellant permeability. Layered silicate nanocomposites are especially attractive in cryogenic storage tanks based on results that have been reported for epoxy nanocomposite systems. These materials often exhibit an order of magnitude reduction in gas permeability when compared to the base resin. In addition, polymer-silicate nanocomposites have been shown to yield improved dimensional stability, strength, and toughness. The enhancement in material performance of these systems occurs without property trade-offs which are often observed in conventionally filled polymer composites. Research efforts at NASA Glenn Research Center have led to the development of epoxy-clay nanocomposites with 70% lower hydrogen permeability than the base epoxy resin. Filament wound carbon fiber reinforced tanks made with this nanocomposite had a five-fold lower helium leak rate than the corresponding tanks made without clay. The pronounced reduction observed with the tank may be due to flow induced alignment of the clay layers during processing. Additionally, the nanocomposites showed CTE reductions of up to 30%, as well as a 100% increase in toughness.

  14. Diblock Copolymer/Layered Silicate Nanocomposite Thin Film Stability

    Science.gov (United States)

    Limary, Ratchana; Green, Peter

    2000-03-01

    The stability of thin film symmetric diblock copolymers blended with layered silicate nanocomposites were examined using a combination of optical microscopy, atomic force microscopy (AFM), and X-ray diffraction (XRD). Two cases were examined PS-b-PMMA (polystyrene-b-polymethylacrylate) blended with montmorillonite stoichiometrically loaded with alkyl ammonium ions, OLS(S), and PS-b-PMMA blended with montmorillonite loaded with excess alkyl ammonium ions, OLS(E). XRD spectra show an increase in the gallery spacing of the OLSs, indicating that the copolymer chains have intercalated the layered silicates. AFM images reveal a distinct difference between the two nanocomposite thin films: regions in the vicinity of OLS(S) aggregates were depleted of material, while in the vicinity of OLS(E) aggregates, dewetting of the substrate occurred. We show that the stability of the copolymer/OLS nanocomposite films is determined by the enthalpic driving force associated with intercalation of the copolymer chains into the galleries of the modified OLS layers and by the substrate/organic modifier interactions.

  15. Ultrafast Carbon Dioxide Sorption Kinetics Using Lithium Silicate Nanowires.

    Science.gov (United States)

    Nambo, Apolo; He, Juan; Nguyen, Tu Quang; Atla, Veerendra; Druffel, Thad; Sunkara, Mahendra

    2017-06-14

    In this paper, the Li 4 SiO 4 nanowires (NWs) were shown to be promising for CO 2 capture with ultrafast kinetics. Specifically, the nanowire powders exhibited an uptake of 0.35 g g -1 of CO 2 at an ultrafast adsorption rate of 0.22 g g -1 min -1 at 650-700 °C. Lithium silicate (Li 4 SiO 4 ) nanowires and nanopowders were synthesized using a "solvo-plasma" technique involving plasma oxidation of silicon precursors mixed with lithium hydroxide. The kinetic parameter values (k) extracted from sorption kinetics obtained using NW powders are 1 order of magnitude higher than those previously reported for the Li 4 SiO 4 -CO 2 reaction system. The time scales for CO 2 sorption using nanowires are approximately 3 min and two orders magnitude faster compared to those obtained using lithium silicate powders with spherical morphologies and aggregates. Furthermore, Li 4 SiO 4 nanowire powders showed reversibility through sorption-desorption cycles indicating their suitability for CO 2 capture applications. All of the morphologies of Li 4 SiO 4 powders exhibited a double exponential behavior in the adsorption kinetics indicating two distinct time constants for kinetic and the mass transfer limited regimes.

  16. In vitro bioactivity of a tricalcium silicate cement

    Energy Technology Data Exchange (ETDEWEB)

    Morejon-Alonso, L.; Bareiro, O.; Santos, L.A. dos, E-mail: loreley.morejon@ufrgs.b [Universidade Federal do Rio Grande do Sul (UFRG), Porto Alegre, RS (Brazil). Escola de Engenharia. Dep. de Materiais; Carrodeguas R, Garcia [Consejo Superior de Investigaciones Cientificas (CSIC), Madrid (Spain). Inst. de Ceramica y Vidrio. Dept. de Ceramica

    2009-07-01

    Tricalcium silicate is the major constituent of Portland cement and the responsible for their mechanical strength at early stages. In order to be used as and additive of conventional calcium phosphate cement (CPC), in vitro bioactivity of a calcium silicate cement (CSC) after soaking in simulated body fluid (SBF) for 14 days was study. The cement was obtained by mixing Ca{sub 3}SiO{sub 5}, obtained by sol-gel process, and a Na{sub 2}HPO{sub 4} solution. The morphological and structural changes of the material before and after soaking were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed the formation of a layer of a Hydroxyapatite (HA) onto the CSC cement after soaking for 1h in SBF that became denser with the increase of soaking time. The study suggests that Ca{sub 3}SiO{sub 5} would be an effective additive to improve the bioactivity and long term strength of conventional CPC. (author)

  17. The structure of alkali silicate gel by total scattering methods

    KAUST Repository

    Benmore, C.J.

    2010-06-01

    The structure of the alkali silicate gel (ASR) collected from the galleries of Furnas Dam in Brazil was determined by a pair distribution function (PDF) analysis of high energy X-ray diffraction data. Since this method is relatively new to concrete structure analysis a detailed introduction on the PDF method is given for glassy SiO2. The bulk amorphous structure of the dam material is confirmed as no Bragg peaks are observed in the scattered intensity. The real space results show that the local structure of the amorphous material is similar to kanemite (KHSi2O5:3H2O) however the long range layer structure of the crystal is broken up in the amorphous state, so that ordering only persists of the length scale of a few polyhedra. The silicate layer structure is a much more disordered than predicted by molecular dynamics models. The X-ray results are consistent with the molecular dynamics model of Kirkpatrick et al. (2005) [1] which predicts that most of the water resides in pores within the amorphous network rather than in layers. The total scattering data provide a rigorous basis against which other models may also be tested. © 2010.

  18. The structure of alkali silicate gel by total scattering methods

    KAUST Repository

    Benmore, C.J.; Monteiro, Paulo J.M.

    2010-01-01

    The structure of the alkali silicate gel (ASR) collected from the galleries of Furnas Dam in Brazil was determined by a pair distribution function (PDF) analysis of high energy X-ray diffraction data. Since this method is relatively new to concrete structure analysis a detailed introduction on the PDF method is given for glassy SiO2. The bulk amorphous structure of the dam material is confirmed as no Bragg peaks are observed in the scattered intensity. The real space results show that the local structure of the amorphous material is similar to kanemite (KHSi2O5:3H2O) however the long range layer structure of the crystal is broken up in the amorphous state, so that ordering only persists of the length scale of a few polyhedra. The silicate layer structure is a much more disordered than predicted by molecular dynamics models. The X-ray results are consistent with the molecular dynamics model of Kirkpatrick et al. (2005) [1] which predicts that most of the water resides in pores within the amorphous network rather than in layers. The total scattering data provide a rigorous basis against which other models may also be tested. © 2010.

  19. Formation mechanisms of colloidal silica via sodium silicate

    International Nuclear Information System (INIS)

    Tsai, M.-S.; Huang, P.Y.; Yang, C.-H.

    2006-01-01

    Colloidal silica is formed by titrating active silicic acid into a heated KOH with seed solution. The colloidal silica formation mechanisms are investigated by sampling the heated solution during titration. In the initial stage, the added seeds were dissolved. This might due to the dilution of seed concentration, the addition of potassium hydroxide (KOH) and the heating at 100 deg. C. Homogenous nucleation and surface growth occur simultaneously in the second stage of colloidal silica formation. Homogenous nucleation is more important when the seed concentration is relatively low. On the other hand, surface growth plays an important role when the seed concentration is increased. In the middle seed concentration, the seed particles grow up and some new small particles are born by the homogenous nucleation process to form a bimodal size distribution product. As the titrating volume of active silicic acid exceeds a specific value in the last stage the particle size increases rapidly and the particle number decreases, which may be caused by the aggregation of particles. The intervals between each stage were varied with the seed concentration. Increasing the seed concentration led to the formation of uniform particle size colloidal silica

  20. Anionic silicate organic frameworks constructed from hexacoordinate silicon centres

    Science.gov (United States)

    Roeser, Jérôme; Prill, Dragica; Bojdys, Michael J.; Fayon, Pierre; Trewin, Abbie; Fitch, Andrew N.; Schmidt, Martin U.; Thomas, Arne

    2017-10-01

    Crystalline frameworks composed of hexacoordinate silicon species have thus far only been observed in a few high pressure silicate phases. By implementing reversible Si-O chemistry for the crystallization of covalent organic frameworks, we demonstrate the simple one-pot synthesis of silicate organic frameworks based on octahedral dianionic SiO6 building units. Clear evidence of the hexacoordinate environment around the silicon atoms is given by 29Si nuclear magnetic resonance analysis. Characterization by high-resolution powder X-ray diffraction, density functional theory calculation and analysis of the pair-distribution function showed that those anionic frameworks—M2[Si(C16H10O4)1.5], where M = Li, Na, K and C16H10O4 is 9,10-dimethylanthracene-2,3,6,7-tetraolate—crystallize as two-dimensional hexagonal layers stabilized in a fully eclipsed stacking arrangement with pronounced disorder in the stacking direction. Permanent microporosity with high surface area (up to 1,276 m2 g-1) was evidenced by gas-sorption measurements. The negatively charged backbone balanced with extra-framework cations and the permanent microporosity are characteristics that are shared with zeolites.

  1. Laser ablation of silicate glasses doped with transuranic actinides

    International Nuclear Information System (INIS)

    Gibson, J.K.; Haire, R.G.

    1998-01-01

    Direct sampling laser ablation plasma mass spectrometry (DS-LAMS) was applied to silica glasses doped with 237 Np, 242 Pu or 241 Am using a unique instrument recently installed into a transuranic glovebox. The primary goal was to assess the utility of mass spectrometry of directly ablated ions for facile evaluation of actinide (An) constituents of silicate glass immobilization matrices used for encapsulation of radionuclides. The instrument and general procedures have been described elsewhere. Three high-purity silicate glasses prepared by a sol-gel process (SG) and one conventional high-temperature (HT; melting point ∼ 1,450 C) borosilicate glass were studied. These glasses comprised the following constituents, with compositions expressed in mass percentages: Np-HT ∼ 30% SiO 2 + 6% B 2 O 3 + 3% BaO + 13% Al 2 O 3 + 10% PbO + 30% La 2 O 3 + 8% 237 NpO 2 ; Np-SG ∼ 70% SiO 2 + 30% 237 NpO 2 ; Pu-SG ∼ 70% SiO 2 + 30% 242 PuO 2 ; Am-SG ∼ 85% SiO 2 + 15% 241 AmO 2

  2. Development of alumino-silicate refractories in Ghana

    International Nuclear Information System (INIS)

    Kisiedu, A. K.; Tetteh, D.M.B.; Obiri, H. A.; Brenya, E. F.; Ayensu, A.

    2008-01-01

    Alumino-silicate (bauxite), andalusite, kaolin and clay were investigated for suitability in production of alumina, mullite and fireclay brick refractories. The raw materials were characterized by X-ray diffraction, differential thermal and silicate analyses. The x-ray diffraction analysis of alumina and mullite refractories fired at 1450 0 C, and fireclay bricks fired at 1350 0 C, indicated presence of corundum and alpha-alumina crystals. The values of thermal (fired) shrinkage, crushing, strength, porosity, water absorption and bulk density determined were 31.1%, 2.3 x 10 3 kg/m 3 , 4.86 x 10 6 N/m 2 and 13.2 % for mullite; 30.2%, 2.4 x 10 3 kg/m 3 , 3.20 x 10 6 N/m 2 and W = 12.8 % for alumina; and 25.2 %, 2.1 x 10 3 kg/m 3 , 2.61 x 10 6 N/m 2 and W = 11.8% for fireclay, respectively. Bauxite, andalusite and special kaolin were identified as potential raw materials for developing alumina and mullite refractories for construction of high temperature kilns and furnaces operating at 1350 0 C. The clay and kaolin minerals could be used to produce fireclay refractories for construction of incinerators operating at maximum temperatures of about 1000 0 C. The performance of the refractories was demonstrated by producing bricks to construct kilns and incinerators for the ceramic industry and hospitals. (au)

  3. Novel understanding of calcium silicate hydrate from dilute hydration

    KAUST Repository

    Zhang, Lina

    2017-05-13

    The perspective of calcium silicate hydrate (C-S-H) is still confronting various debates due to its intrinsic complicated structure and properties after decades of studies. In this study, hydration at dilute suspension of w/s equaling to 10 was conducted for tricalcium silicate (C3S) to interpret long-term hydration process and investigate the formation, structure and properties of C-S-H. Based on results from XRD, IR, SEM, NMR and so forth, loose and dense clusters of C-S-H with analogous C/S ratio were obtained along with the corresponding chemical formulae proposed as Ca5Si4O13∙6.2H2O. Crystalline structure inside C-S-H was observed by TEM, which was allocated at the foil-like proportion as well as the edge of wrinkles of the product. The long-term hydration process of C3S in dilute suspension could be sketchily described as migration of calcium hydroxide and in-situ growth of C-S-H with equilibrium silicon in aqueous solution relatively constant and calcium varied.

  4. 6Li-doped silicate glass for thermal neutron shielding

    International Nuclear Information System (INIS)

    Stone, C.A.; Blackburn, D.H.; Kauffman, D.A.; Cranmer, D.C.; Olmez, I.

    1994-01-01

    Glass formulations are described that contain high concentrations of 6 Li and are suitable for use as thermal neutron shielding. One formulation contained 31 mol% of 6 Li 2 O and 69 mol% of SiO 2 . Studies were performed on a second formulation that contained as much as 37 mol% of 6 Li 2 O and 59 mol% of SiO 2 , with 4 mol% Al 2 O 3 added to prevent crystallization at such high 6 Li 2 O concentrations. These lithium silicate glasses can be formed into a variety of shapes using conventional glass fabrication techniques. Examples include flat plates, disks, hollow cylinders, and other more complex geometries. Both in-beam and in-core experiments have been performed to study the use and durability of Li silicate glasses. In-core experiments show the glass can withstand the intense radiation fields near the core of a reactor. The neutron attenuation of the glasses used in these studies was 90%/mm. In-beam studies show that the glass is effective for reducing the gamma-ray and neutron fields near experiments. ((orig.))

  5. Interaction of dispersed polyvynil acetate with silicate in finishing materials

    Directory of Open Access Journals (Sweden)

    Runova, R. F.

    1996-12-01

    Full Text Available This article focuses on the processes of interaction between calcium silicate hydrates and dispersed polyvinyl acetate in tight films with the aim of developing compounds meant for restoration and finishing works. The basis of this development relies on the concept concerning the determining role of the crystal-chemical factor of the silicate phase in the formation of organic-mineral compounds of increased durability. The characteristics of dispersed calcium silicate hydrates are portrayed. The preparation conditions, accounting for the synthesis of the product of submicrocrystalline structure, conforming with the stoichiometry CaO∙SiO2 =0.8-2.0 have been determined. The interaction has been studied for compounds achieved by mixing ingredients in a rapid whirling mixer, and subjected to hardening at T=20+2 T. With the aid of XRD, DTA and Infra-Red Spectrometry methods the formation process of the sophisticated polymer silicate phase in the material was observed for a period of 90 days. The properties of the film were investigated and its high resistance against the influence of external factors was established. On this basis a conclusion concerning the quite high effectiveness of substituting portland cement with dispersed calcium silicate hydrate in polymer cement compounds has been made. White colour and other various special properties determine the suitability for repair and finishing works on facades of buildings.

    Este artículo está orientado a estudiar los procesos de interacción entre los silicatos cálcicos hidratados y el acetato de polivinilo disperso en capas impermeables, con el objeto de desarrollar compuestos destinados para la restauración. El fundamento de estos estudios es determinar el papel que los factores cristaloquímicos de las fases silicato tienen en la formación de compuestos órganominerales de elevada durabilidad. Se han descrito las características de los silicatos cálcicos hidratados

  6. [Isotope tracer studies of diffusion in silicates and of geological transport processes using actinide elements

    International Nuclear Information System (INIS)

    Wasserburg, G.J.

    1991-01-01

    This report consists of sections entitled resonance ionization mass spectrometry of Os, Mg self-diffusion in spinel and silicate melts, neotectonics: U-Th ages of solitary corals from the California coast, uranium-series evidence on diagenesis and hydrology of carbonates of Barbados, diffusion of H 2 O molecules in silicate glasses, and development of an extremely high abundance sensitivity mass spectrometer

  7. FT-IR and 29 Si-NMR for evaluating aluminium silicate precursors for geopolymers

    NARCIS (Netherlands)

    Valcke, S.L.A.; Pipilikaki, P.; Fischer, H.R.; Verkuijlen, M.H.W.; Eck, E.R.H.

    2014-01-01

    Geopolymers are systems of inorganic binders that can be used for sustainable, cementless concrete and are formed by alkali activation of an aluminium–silicate precursor (often secondary resources like fly ash or slag). The type of aluminium– silicate precursor and its potential variations within

  8. EFFECT OF SILICATE ON GRAM STAINING AND VIABILITY OF PNEUMOCOCCI AND OTHER BACTERIA

    Science.gov (United States)

    MacLeod, Colin M.; Roe, Amy S.

    1956-01-01

    Application of silicate solutions to living or heat-killed pneumococci and to certain "viridans" streptococci causes their conversion from a Gram-positive to a Gram-negative state. The original staining properties can be restored by suspending the silicate-treated bacteria in alkaline solutions of various salts but not by simple washing in water. Living pneumococci and the strains of streptococci whose staining properties are similarly affected are killed when suspended in silicate solutions. In other Gram-positive species silicate causes conversion to Gram negativity but restoration to positivity occurs upon washing in water. In a third group of Gram-positive organisms silicate has no effect on the Gram reaction. The viability of organisms in these two groups is unaffected by silicate under the conditions employed. No effect on staining or viability of Gram-negative bacteria has been observed. The effects of silicate on staining and viability are inhibited by nutrient broth or whole serum but not by purified serum albumin. Lecithin, choline, and other substituted ammonium compounds also inhibit the effects of silicate on pneumococci. PMID:13306854

  9. KINETICS OF A SILICATE COMPOSITION GELATION IN PRESENCE OF REACTION RATE REGULATING COMPOUNDS

    Directory of Open Access Journals (Sweden)

    Olga Titova

    2013-12-01

    Full Text Available The influence of organic and inorganic additions on the formation rate of the silicate gels standard systems – sodium silicate solution in model fresh water was studied. As a result of the experiments were selected optimum concentrations of additives - gelation time regulators

  10. Impact of Micro Silica Surface Hydroxyl Groups on the Properties of Calcium Silicate Products

    DEFF Research Database (Denmark)

    Haastrup, Sonja; Jørgensen, Bianca; Yu, Donghong

    2017-01-01

    Porous calcium silicates are widely used in insulating systems for high temperature applications. In the production of porous calcium silicates, quicklime and micro silica have been utilized as key raw materials. In the reaction between SiO2 and CaO, the dissolution of SiO2 has been proven...

  11. Controlled structure and properties of silicate nanoparticle networks for incorporation of biosystem components

    International Nuclear Information System (INIS)

    Sakai-Kato, Kumiko; Kawanishi, Toru; Hasegawa, Toshiaki; Takaoka, Akio; Kato, Masaru; Toyo'oka, Toshimasa; Utsunomiya-Tate, Naoko

    2011-01-01

    Inorganic nanoparticles are of technological interest in many fields. We created silicate nanoparticle hydrogels that effectively incorporated biomolecules that are unstable and involved in complicated reactions. The size of the silicate nanoparticles strongly affected both the physical characteristics of the resulting hydrogel and the activity of biomolecules incorporated within the hydrogel. We used high-resolution transmission electron microscopy (TEM) to analyze in detail the hydrogel network patterns formed by the silicate nanoparticles. We obtained clear nanostructured images of biomolecule-nanoparticle composite hydrogels. The TEM images also showed that larger silicate nanoparticles (22 nm) formed more loosely associated silicate networks than did smaller silicate nanoparticles (7 nm). The loosely associated networks formed from larger silicate nanoparticles might facilitate substrate diffusion through the network, thus promoting the observed increased activity of the entrapped biomolecules. This doubled the activity of the incorporated biosystems compared with that of biosystems prepared by our own previously reported method. We propose a reaction scheme to explain the formation of the silicate nanoparticle networks. The successful incorporation of biomolecules into the nanoparticle hydrogels, along with the high level of activity exhibited by the biomolecules required for complicated reaction within the gels, demonstrates the nanocomposites' potential for use in medical applications.

  12. Sodium Silicate Behavior in Porous Media Applied for In-Depth Profile Modifications

    Directory of Open Access Journals (Sweden)

    Hossein A. Akhlaghi Amiri

    2014-03-01

    Full Text Available This paper addresses alkaline sodium silicate (Na-silicate behavior in porous media. One of the advantages of the Na-silicate system is its water-like injectivity during the placement stage. Mixing Na-silicate with saline water results in metal silicate precipitation as well as immediate gelation. This work demonstrated that low salinity water (LSW, sea water diluted 25 times could be used as a pre-flush in flooding operations. A water override phenomenon was observed during gel formation which is caused by gravity segregation. Dynamic adsorption tests in the sand-packed tubes showed inconsiderable adsorbed silicon density (about 8.5 × 10−10 kg/cm3 for a solution with 33 mg/L silicon content, which is less than the estimated mono-layer adsorption density of 1.4 × 10−8 kg/cm3. Na-silicate enhanced water sweep efficiency after application in a dual-permeability sand-pack system, without leak off into the oil-bearing low permeability (LP zone. Field-scale numerical sensitivity studies in a layered reservoir demonstrated that higher permeability and viscosity contrasts and lower vertical/horizontal permeability ratio result in lower Na-silicate leakoff into the matrix. The length of the mixing zone between reservoir water and the injected Na-silicate solution, which is formed by low salinity pre-flush, acts as a buffer zone.

  13. LUMINESCENT PROPERTIES OF SILICATE GLASSES WITH CERIUM IONS AND ANTIMONY

    Directory of Open Access Journals (Sweden)

    A. M. Klykova

    2014-05-01

    Full Text Available The paper deals with the results of an experimental study of luminescence excitation spectra and luminescence of silicate glasses containing cerium ions and antimony. The aim of this work was to study the features of the luminescence and the effect of UV irradiation and heat treatment on luminescence and the state of cerium ions and antimony in glass. We investigated glass system Na2O-ZnO-Al2O3-SiO2-NaF-NaBr with additives CeO2 and Sb2O3. Synthesis was carried out in platinum crucibles in the air at 14500C. The samples were polished glass plates with a thickness of 0.5-1 mm. UV irradiation was carried out with a mercury lamp having a wide range of radiation in the spectral range 240-390 nm. It was conducted in a Nabertherm muffle furnaces. Luminescence spectra and excitation spectra were measured using a spectrofluorimeter MPF-44A (PerkinElmer at the room temperature. Measured luminescence spectra were corrected in view of the spectral sensitivity of the photodetector for spectrofluorimeter. Adjustment of the excitation spectra for the spectral dependence of the intensity of the excitation source was not carried out. During the experiments it was found that in silicate glasses Sb3+ ions can exist in two energy states, which corresponds to a different environment with oxygen ions. Heat treatment of these glasses in an oxidizing atmosphere leads to an increase in ion concentration of Sb3+ ions with a greater amount of oxygen in the environment. In glasses containing antimony and cerium ions, ultraviolet irradiation causes a change in the valence of cerium ions and antimony, which is accompanied by luminescence quenching. Subsequent heat treatment of glass leads to the inverse processes and restore luminescence excitation spectra. The study of fluorescent properties of silicate glasses with cerium and antimony ions led to the conclusion of the practical significance of this work. Promising multifunctional materials can be created on the basis of

  14. Silicate reduces cadmium uptake into cells of wheat

    International Nuclear Information System (INIS)

    Greger, Maria; Kabir, Ahmad H.; Landberg, Tommy; Maity, Pooja J.; Lindberg, Sylvia

    2016-01-01

    Cadmium (Cd) is a health threat all over the world and high Cd content in wheat causes high Cd intake. Silicon (Si) decreases cadmium content in wheat grains and shoot. This work investigates whether and how silicate (Si) influences cadmium (Cd) uptake at the cellular level in wheat. Wheat seedlings were grown in the presence or absence of Si with or without Cd. Cadmium, Si, and iron (Fe) accumulation in roots and shoots was analysed. Leaf protoplasts from plants grown without Cd were investigated for Cd uptake in the presence or absence of Si using the fluorescent dye, Leadmium Green AM. Roots and shoots of plants subjected to all four treatments were investigated regarding the expression of genes involved in the Cd uptake across the plasma membrane (i.e. LCT1) and efflux of Cd into apoplasm or vacuole from the cytosol (i.e. HMA2). In addition, phytochelatin (PC) content and PC gene (PCS1) expression were analysed. Expression of iron and metal transporter genes (IRT1 and NRAMP1) were also analysed. Results indicated that Si reduced Cd accumulation in plants, especially in shoot. Si reduced Cd transport into the cytoplasm when Si was added both directly during the uptake measurements and to the growth medium. Silicate downregulated LCT1 and HMA2 and upregulated PCS1. In addition, Si enhanced PC formation when Cd was present. The IRT1 gene, which was downregulated by Cd was upregulated by Si in root and shoot facilitating Fe transport in wheat. NRAMP1 was similarly expressed, though the effect was limited to roots. This work is the first to show how Si influences Cd uptake on the cellular level. - Highlights: • Si decreases accumulation and translocation of Cd in plants at tissue level. • This work is the first to show how Si influences Cd uptake. • Si decreases Cd uptake into cell and downregulates heavy metal transporter LCT1. • Si downregulates HMA2 transporter, which regulates Cd transport from root to shoot. • Si increases phytochelatin formation

  15. The Lifeworld Earth and a Modelled Earth

    Science.gov (United States)

    Juuti, Kalle

    2014-01-01

    The goal of this paper is to study the question of whether a phenomenological view of the Earth could be empirically endorsed. The phenomenological way of thinking considers the Earth as a material entity, but not as an object as viewed in science. In the learning science tradition, tracking the process of the conceptual change of the shape of the…

  16. Rare earth sulfates

    International Nuclear Information System (INIS)

    Komissarova, L.N.; Shatskij, V.M.; Pokrovskij, A.N.; Chizhov, S.M.; Bal'kina, T.I.; Suponitskij, Yu.L.

    1986-01-01

    Results of experimental works on the study of synthesis conditions, structure and physico-chemical properties of rare earth, scandium and yttrium sulfates, have been generalized. Phase diagrams of solubility and fusibility, thermodynamic and crystallochemical characteristics, thermal stability of hydrates and anhydrous sulfates of rare earths, including normal, double (with cations of alkali and alkaline-earth metals), ternary and anion-mixed sulfates of rare earths, as well as their adducts, are considered. The state of ions of rare earths, scandium and yttrium in aqueous sulfuric acid solutions is discussed. Data on the use of rare earth sulfates are given

  17. Rare earth germanates

    International Nuclear Information System (INIS)

    Bondar', I.A.; Vinogradova, N.V.; Dem'yanets, L.N.

    1983-01-01

    Rare earth germanates attract close attention both as an independent class of compounds and analogues of a widely spread class of natural and synthetic minerals. The methods of rare earth germanate synthesis (solid-phase, hydrothermal) are considered. Systems on the basis of germanium and rare earth oxides, phase diagrams, phase transformations are studied. Using different chemical analysese the processes of rare earth germanate formation are investigated. IR spectra of alkali and rare earth metal germanates are presented, their comparative analysis being carried out. Crystal structures of the compounds, lattice parameters are studied. Fields of possible application of rare earth germanates are shown

  18. The mitochondrial activation of silicate and its role in silicosis, black lung disease and lung cancer.

    Science.gov (United States)

    Hadler, H I; Cook, G L

    1979-01-01

    Silicate substitutes for phosphate in the transitory uncoupling of rat liver mitochondria induced by hydrazine when beta-hydroxy-butyrate is the substrate. Uncoupling is blocked by rutamycin. Just as in the case when phosphate is combined with hydrazine, ATP, ADP, PPi, and Mg++ protect against hydrazine when silicate is combined with hydrazine. A high level of ADP in the absence of added phosphate, but in the presence of silicate, induces a pseudo state three of the mitochondria. Silicate, like sulfate and arsenate which have been reported previously, is activated by the enzymes which mediate oxidative phosphorylation. These results serve to explain a role for silicate in silicosis, black lung disease, and cancer. In addition, since there is suggestive evidence in the literature that lung tissue solubilizes asbestos fibers, these results not only expand the confluence between oxidative phosphorylation and chemical carcinogenesis but are correlated with the synergistic carcinogenicity of asbestos and smoking observed by epidemiologists.

  19. SOFT X-RAY IRRADIATION OF SILICATES: IMPLICATIONS FOR DUST EVOLUTION IN PROTOPLANETARY DISKS

    Energy Technology Data Exchange (ETDEWEB)

    Ciaravella, A.; Cecchi-Pestellini, C.; Jiménez-Escobar, A. [INAF—Osservatorio Astronomico di Palermo, P.za Parlamento 1, I-90134 Palermo (Italy); Chen, Y.-J.; Huang, C.-H. [Department of Physics, National Central University, Jhongli City, Taoyuan County 32054, Taiwan (China); Muñoz Caro, G. M. [Centro de Astrobiología (INTA-CSIC), Carretera de Ajalvir, km 4, Torrejón de Ardoz, E-28850 Madrid (Spain); Venezia, A. M., E-mail: aciaravella@astropa.unipa.it [ISMN—CNR, Via Ugo La Malfa 153, I-90146 Palermo (Italy)

    2016-09-01

    The processing of energetic photons on bare silicate grains was simulated experimentally on silicate films submitted to soft X-rays of energies up to 1.25 keV. The silicate material was prepared by means of a microwave assisted sol–gel technique. Its chemical composition reflects the Mg{sub 2}SiO{sub 4} stoichiometry with residual impurities due to the synthesis method. The experiments were performed using the spherical grating monochromator beamline at the National Synchrotron Radiation Research Center in Taiwan. We found that soft X-ray irradiation induces structural changes that can be interpreted as an amorphization of the processed silicate material. The present results may have relevant implications in the evolution of silicate materials in X-ray-irradiated protoplanetary disks.

  20. Identification of an Extremely 180-Rich Presolar Silicate Grain in Acfer 094

    Science.gov (United States)

    Nguyen, A. N.; Messenger, S.

    2009-01-01

    Presolar silicate grains have been abundantly identified since their first discovery less than a decade ago [1,2,3]. The O isotopic compositions of both silicate and oxide stardust indicate the vast majority (>90%) condensed around Orich asymptotic giant branch (AGB) stars. Though both presolar phases have average sizes of 300 nm, grains larger than 1 m are extremely uncommon for presolar silicates. Thus, while numerous isotopic systems have been measured in presolar oxide grains [4], very few isotopic analyses for presolar silicates exist outside of O and Si [2,5]. And still, these measurements suffer from isotopic dilution with surrounding matrix material [6]. We conduct a search for presolar silicates in the primitive carbonaceous chondrite Acfer 094 and in some cases obtain high spatial resolution, high precision isotopic ratios.

  1. Effect of temperature on hydration kinetics and polymerization of tricalcium silicate in stirred suspensions of CaO-saturated solutions

    International Nuclear Information System (INIS)

    Grant, Steven A.; Boitnott, Ginger E.; Korhonen, Charles J.; Sletten, Ronald S.

    2006-01-01

    Tricalcium silicate was hydrated at 274, 278, 283, 298, and 313 K in stirred suspensions of saturated CaO solutions under a nitrogen-gas atmosphere until the end of deceleratory period. The suspension conductivities and energy flows were measured continuously. The individual reaction rates for tricalcium silicate dissolution, calcium silicate hydrate precipitation, and calcium hydroxide precipitation were calculated from these measurements. The results suggest that the proportion of tricalcium silicate dissolved was determined by the rate of tricalcium silicate dissolution and the time to very rapid calcium hydroxide precipitation. The time to very rapid calcium hydroxide precipitation was more sensitive to changes in temperature than was the rate of tricalcium silicate dissolution, so that the proportion of tricalcium silicate hydration dissolved by the deceleratory period increased with decreasing temperature. The average chain length of the calcium silicate hydrate ascertained by magic-angle spinning nuclear magnetic resonance spectroscopy increased with increasing temperature

  2. Role of organically modified layered silicate both as an active interfacial modifier and nanofiller for immiscible polymer blends.

    CSIR Research Space (South Africa)

    Ray, SS

    2007-05-01

    Full Text Available ) revealed efficient mixing of the polymers in the presence of organically modified layered silicate. X-ray diffraction (XRD) patterns and transmission electron microscopic (TEM) observations showed that silicate layers were either intercalated or exfoliated...

  3. TECHNOLOGY EVALUATION REPORT: SILICATE TECHNOLOGY CORPORATION - SOLIDIFICATION/STABILIZATION OF PCP AND INORGANIC CONTAMINANTS IN SOILS - SELMA, CA

    Science.gov (United States)

    This Technolgy Evaluation Report evaluates the solidification/stabilization process of Silicate Technology Corporation (STC) for the on-site treatment of contaminated soil The STC immobilization technology uses a proprietary product (FMS Silicate) to chemically stabilize and ...

  4. Lunar oxygen and metal for use in near-earth space - Magma electrolysis

    Science.gov (United States)

    Colson, Russell O.; Haskin, Larry A.

    1990-01-01

    The unique conditions on the moon, such as vacuum, absence of many reagents common on the earth, and presence of very nontraditional 'ores', suggest that a unique and nontraditional process for extracting materials from the ores may prove the most practical. An investigation has begun into unfluxed silicate electrolysis as a method for extracting oxygen, Fe, and Si from lunar regolith. The advantages of the process include simplicity of concept, absence of need to supply reagents from the earth, and low power and mass requirements for the processing plant. Disadvantages include the need for uninterrupted high temperature and the highly corrosive nature of the high-temperature silicate melts, which has made identifying suitable electrode and container materials difficult.

  5. Measurement of the efficacy of calcium silicate for the protection and repair of dental enamel.

    Science.gov (United States)

    Parker, Alexander S; Patel, Anisha N; Al Botros, Rehab; Snowden, Michael E; McKelvey, Kim; Unwin, Patrick R; Ashcroft, Alexander T; Carvell, Mel; Joiner, Andrew; Peruffo, Massimo

    2014-06-01

    To investigate the formation of hydroxyapatite (HAP) from calcium silicate and the deposition of calcium silicate onto sound and acid eroded enamel surfaces in order to investigate its repair and protective properties. Calcium silicate was mixed with phosphate buffer for seven days and the resulting solids analysed for crystalline phases by Raman spectroscopy. Deposition studies were conducted on bovine enamel surfaces. Acid etched regions were produced on the enamel surfaces using scanning electrochemical cell microscopy (SECCM) with acid filled pipettes and varying contact times. Following treatment with calcium silicate, the deposition was visualised with FE-SEM and etch pit volumes were measured by AFM. A second set of bovine enamel specimens were pre-treated with calcium silicate and fluoride, before acid exposure with the SECCM. The volumes of the resultant acid etched pits were measured using AFM and the intrinsic rate constant for calcium loss was calculated. Raman spectroscopy confirmed that HAP was formed from calcium silicate. Deposition studies demonstrated greater delivery of calcium silicate to acid eroded than sound enamel and that the volume of acid etched enamel pits was significantly reduced following one treatment (penamel was 0.092 ± 0.008 cm/s. This was significantly reduced, 0.056 ± 0.005 cm/s, for the calcium silicate treatments (penamel surfaces. Calcium silicate can provide significant protection of sound enamel from acid challenges. Calcium silicate is a material that has potential for a new approach to the repair of demineralised enamel and the protection of enamel from acid attacks, leading to significant dental hard tissue benefits. © 2014 Elsevier Ltd. All rights reserved.

  6. Structural relaxation dynamics and annealing effects of sodium silicate glass.

    Science.gov (United States)

    Naji, Mohamed; Piazza, Francesco; Guimbretière, Guillaume; Canizarès, Aurélien; Vaills, Yann

    2013-05-09

    Here we report high-precision measurements of structural relaxation dynamics in the glass transition range at the intermediate and short length scale for a strong sodium silicate glass during long annealing times. We evidence for the first time the heterogeneous dynamics at the intermediate range order by probing the acoustic longitudinal frequency in the GHz region by Brillouin light scattering spectroscopy. Or, from in-situ Raman measurements, we show that relaxation is indeed homogeneous at the interatomic length scale. Our results show that the dynamics at the intermediate range order contains two distinct relaxation time scales, a fast and a slow component, differing by about a 10-fold factor below Tg and approaching to one another past the glass transition. The slow relaxation time agrees with the shear relaxation time, proving that Si-O bond breaking constitutes the primary control of structural relaxation at the intermediate range order.

  7. Tribological properties of silicate materials on nano and microscale

    International Nuclear Information System (INIS)

    Tordjeman, Ph.; Morel, N.; Ramonda, M.

    2009-01-01

    We studied the friction properties of four model silicate materials at the nanoscale and microscale. From nanotribology, we characterized the tribological properties at single asperity contact scale and from microtribology, we characterized the tribological properties at multi asperity contact scale. First, for each material we measured chemical composition by XPS, Young's modulus by acoustical microscopy and roughness σ by atomic force microscopy (AFM). Second, we measured the nanofriction coefficients with an AFM and the microfriction coefficients with a ball probe tribometer, for three hardnesses of the ball probe. We identified one friction mechanism at the nanoscale (sliding friction) and two friction mechanisms at the microscale (sliding friction and yielding friction). Comparison of the nano and microfriction coefficients at the same sliding friction regime shown, that the tribological properties of these materials didn't depend on roughness.

  8. Discrete element modeling of calcium-silicate-hydrate

    International Nuclear Information System (INIS)

    Chandler, Mei Qiang; Peters, John F; Pelessone, Daniele

    2013-01-01

    The discrete element method (DEM) was used to model calcium-silicate-hydrate (C-S-H) at the nanoscale. The C-S-H nanoparticles were modeled as spherical particles with diameters of approximately 5 nm. Interparticle forces included traditional mechanical contact forces, van der Waals forces and ionic correlation forces due to negatively charged C-S-H nanoparticles and ion species in the nanopores. Previous work by the authors demonstrated the DEM method was feasible in studying the properties of the C-S-H nanostructures. In this work, the simulations were performed to look into the effects of nanoparticle packing, nanoparticle morphology, interparticle forces and nanoparticle properties on the deformation mechanisms and mechanical properties of the C-S-H matrix. This work will provide insights into possible ways to improve the properties of the C-S-H matrix. (paper)

  9. Beneficiation studies of an uranium siliceous - phosphate ore

    International Nuclear Information System (INIS)

    Bruno, J.B.; Santos, A.T.; Santos Benedetto, J. dos

    1980-01-01

    The consolidation of the beneficiation studies of a low-grade uranium siliceous - phosphate ore (11% P 2 O 5 ) from Itataia region in the Northeast of Brazil, owned by Empresas Nucleares Brasileiras S.A. - NUCLEBRAS, are presented. Laboratory studies using froth flotation technique and applying statistical methods for data evaluation were made. Pilot plant tests in a 120 Kg/h scale were conducted as a consequence of the bench scale tests. The developed process using tall-oil as collector and starch as depressant gave a total yield of 80% for the P 2 O 5 and 71% the U 3 O 8 , for a 33% P 2 O 5 phosphate concentrate. (Author) [pt

  10. COMPACTION OF LITHIUM-SILICATE CERAMICS USING SPARK PLASMA SINTERING

    Directory of Open Access Journals (Sweden)

    Tomas Frantisek Kubatik

    2016-12-01

    Full Text Available This paper deals with the compaction of ceramics based on lithium-silicate by spark plasma sintering (SPS. The initial powder was prepared by calcination in a resistance furnace at a temperature of 1300 °C with the ratio of Li/Si = 1. Compacting by SPS was carried out at temperatures of 800 - 1000 °C with a maximum pressure of 80 MPa. Samples with open porosity of less than 1 % were prepared at the temperature of 1000 °C. According to the quantitative Rietveld refinement of x-ray diffraction data, the dominant phases in all samples were Li₂Si₂O₅ and Li₂SiO₃, together representing over 80 wt. % of the sintered material.

  11. Calcium silicate-based cements: composition, properties, and clinical applications.

    Science.gov (United States)

    Dawood, Alaa E; Parashos, Peter; Wong, Rebecca H K; Reynolds, Eric C; Manton, David J

    2017-05-01

    Mineral trioxide aggregate (MTA) is a calcium silicate-based cement (CSC) commonly used in endodontic procedures involving pulpal regeneration and hard tissue repair, such as pulp capping, pulpotomy, apexogenesis, apexification, perforation repair, and root-end filling. Despite the superior laboratory and clinical performance of MTA in comparison with previous endodontic repair cements, such as Ca(OH) 2 , MTA has poor handling properties and a long setting time. New CSC have been commercially launched and marketed to overcome the limitations of MTA. The aim of the present review was to explore the available literature on new CSC products, and to give evidence-based recommendations for the clinical use of these materials. Within the limitations of the available data in the literature regarding the properties and performance of the new CSC, the newer products could be promising alternatives to MTA; however, further research is required to support this assumption. © 2015 Wiley Publishing Asia Pty Ltd.

  12. High-dose dosimetry using natural silicate minerals

    International Nuclear Information System (INIS)

    Carmo, Lucas S. do; Mendes, Leticia; Watanabe, Shigueo; Rao, Gundu; Lucas, Natasha; Sato, Karina; Barbosa, Renata F.

    2015-01-01

    In the present study, certain natural silicate minerals such as aquamarine (AB), morganite (PB), goshenite (WB), white jadeite (JW), green jadeite (JG), pink tourmaline (PT) and two varieties of jadeite-like quartz, denoted here by JQ1 and JQ2, were investigated using the thermoluminescence technique to evaluate their potential for use as very-high- and high-dose dosimeters. These minerals respond to high doses of γ-rays of up to 1000 kGy and often to very high doses of up to 3000 kGy. The TL response of these minerals may be considered to be satisfactory for applications in high-dose dosimetry. Investigations of electron paramagnetic resonance and optically stimulated luminescence dosimetry are in progress. (author)

  13. Predicting the dissolution kinetics of silicate glasses using machine learning

    Science.gov (United States)

    Anoop Krishnan, N. M.; Mangalathu, Sujith; Smedskjaer, Morten M.; Tandia, Adama; Burton, Henry; Bauchy, Mathieu

    2018-05-01

    Predicting the dissolution rates of silicate glasses in aqueous conditions is a complex task as the underlying mechanism(s) remain poorly understood and the dissolution kinetics can depend on a large number of intrinsic and extrinsic factors. Here, we assess the potential of data-driven models based on machine learning to predict the dissolution rates of various aluminosilicate glasses exposed to a wide range of solution pH values, from acidic to caustic conditions. Four classes of machine learning methods are investigated, namely, linear regression, support vector machine regression, random forest, and artificial neural network. We observe that, although linear methods all fail to describe the dissolution kinetics, the artificial neural network approach offers excellent predictions, thanks to its inherent ability to handle non-linear data. Overall, we suggest that a more extensive use of machine learning approaches could significantly accelerate the design of novel glasses with tailored properties.

  14. Determination of phosphorus in silicate rocks by activation analysis

    International Nuclear Information System (INIS)

    Khalil, S.O.

    1974-01-01

    A neutron activation method for the determination of phosphorus from ammonium phosphomolibdate precipitate is applied to silicate rocks. Ammonium phosphate is added as carrier to the irradiated rock powder and the phosphorus is recovered as ammonium phosphomolibdate, which is precipitated several times in the presence of appropriate holdback carriers to ensure its radiochemical purity and then finally dissolved and reprecipitated as AgTlPO 4 for weighing and counting. The samples were irradiated for 3 1/2 days in a thermal flux of 2.10 10 n.s -1 .cm -2 and the β-activities were measured by an end-window Geiger-Mueller counter. The results for rock standards granite G-1 and diabase W-1 are given. (K.A.)

  15. Calorimetric signature of structural heterogeneity in a ternary silicate glass

    DEFF Research Database (Denmark)

    Zhang, Yanfei; Yang, G.; Yue, Yuanzheng

    2013-01-01

    We investigate the structural heterogeneity in a silicate glass by hyperquenching–annealing–calorimetry approach. The results show a striking phenomenon: two separated sub-Tg relaxation peaks appear on the calorimetric curve of the hyperquenched CaO–MgO–SiO2 glass, implying the existence of two...... distinct structural domains of higher and lower potential energies, respectively. The higher energy domains in nanoscale are so unstable that they become ordered during hyperquenching. This is verified by the high-resolution transmission electron microscopy image exhibiting nanoordered domains in the glass...... matrix. The higher energy domains relax similar to a strong glass phase, whereas the lower energy domains do similar to a fragile one....

  16. High-dose dosimetry using natural silicate minerals

    Energy Technology Data Exchange (ETDEWEB)

    Carmo, Lucas S. do; Mendes, Leticia, E-mail: isatiro@usp.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Watanabe, Shigueo; Rao, Gundu; Lucas, Natasha; Sato, Karina, E-mail: lacifid@if.usp.br [Universidade de Sao Paulo (USP), Sao Paulo, SP (Brazil). Instituto de Fisica. Departamento de Fisica Nuclear; Barbosa, Renata F., E-mail: profcelta@hotmail.com [Universidade Federal de Sao Paulo (UNIFESP), Santos, SP (Brazil). Departamento de Ciencias do Mar

    2015-07-01

    In the present study, certain natural silicate minerals such as aquamarine (AB), morganite (PB), goshenite (WB), white jadeite (JW), green jadeite (JG), pink tourmaline (PT) and two varieties of jadeite-like quartz, denoted here by JQ1 and JQ2, were investigated using the thermoluminescence technique to evaluate their potential for use as very-high- and high-dose dosimeters. These minerals respond to high doses of γ-rays of up to 1000 kGy and often to very high doses of up to 3000 kGy. The TL response of these minerals may be considered to be satisfactory for applications in high-dose dosimetry. Investigations of electron paramagnetic resonance and optically stimulated luminescence dosimetry are in progress. (author)

  17. The role of silicate surfaces on calcite precipitation kinetics

    DEFF Research Database (Denmark)

    Stockmann, Gabrielle J.; Wolff-Boenisch, Domenik; Bovet, Nicolas Emile

    2014-01-01

    The aim of this study is to illuminate how calcite precipitation depends on the identity and structure of the growth substrate. Calcite was precipitated at 25°C from supersaturated aqueous solutions in the presence of seeds of either calcite or one of six silicate materials: augite, enstatite......, labradorite, olivine, basaltic glass and peridotite rock. Calcite saturation was achieved by mixing a CaCl2-rich aqueous solution with a NaHCO3-Na2CO3 aqueous buffer in mixed-flow reactors containing 0.5-2g of mineral, rock, or glass seeds. This led to an inlet fluid calcite saturation index of 0.6 and a p...

  18. Formation of siliceous sediments in brandy after diatomite filtration.

    Science.gov (United States)

    Gómez, J; Gil, M L A; de la Rosa-Fox, N; Alguacil, M

    2015-03-01

    Brandy is quite a stable spirit but sometimes light sediment appears. This sediment was separated and analysed by IR and SEM-EDX. It was revealed that the sediment is composed mostly of silica and residual organic matter. Silica was present as an amorphous phase and as microparticles. In an attempt to reproduce the formation of the sediment, a diatomite extract was prepared with an ethanol/water mixture (36% vol.) and a calcined diatomite similar to that used in brandy filtration. This extract was added to unfiltered brandy in different amounts. After 1 month, the Si concentration decreased in all samples and sediments with similar compositions and features to those found in the unstable brandy appeared. The amounts of sediment obtained were directly related to the decrease in Si concentration in solution. Consequently, it can be concluded that siliceous sediment in brandy originates from Si released during diatomite filtration. Copyright © 2014 Elsevier Ltd. All rights reserved.

  19. High-performance polymer/layered silicate nanocomposites

    Science.gov (United States)

    Heidecker, Matthew J.

    High-performance layered-silicate nanocomposites of Polycarbonate (PC), poly(ethylene terephthalate) (PET), and their blends were produced via conventional melt-blending techniques. The focus of this thesis was on the fundamentals of dispersion, control of thermal stability, maintenance of melt-blending processing conditions, and on optimization of the composites' mechanical properties via the design of controlled and thermodynamically favorable nano-filler dispersions within the polymer matrices. PET and PC require high temperatures for melt-processing, rendering impractical the use of conventional/commercial organically-modified layered-silicates, since the thermal degradation temperatures of their ammonium surfactants lies below the typical processing temperatures. Thus, different surfactant chemistries must be employed in order to develop melt-processable nanocomposites, also accounting for polymer matrix degradation due to water (PET) or amine compounds (PC). Novel high thermal-stability surfactants were developed and employed in montmorillonite nanocomposites of PET, PC, and PC/PET blends, and were compared to the respective nanocomposites based on conventional quaternary-ammonium modified montmorillonites. Favorable dispersion was achieved in all cases, however, the overall material behavior -- i.e., the combination of crystallization, mechanical properties, and thermal degradation -- was better for the nanocomposites based on the thermally-stable surfactant fillers. Studies were also done to trace, and ultimately limit, the matrix degradation of Polycarbonate/montmorillonite nanocomposites, through varying the montmorillonite surfactant chemistry, processing conditions, and processing additives. Molecular weight degradation was, maybe surprisingly, better controlled in the conventional quaternary ammonium based nanocomposites -- even though the thermal stability of the organically modified montmorillonites was in most cases the lowest. Dependence of the

  20. The Effect of Pressure on Iron Speciation in Silicate Melts at a Fixed Oxygen Fugacity: The Possibility of a Redox Profile Through a Terrestrial Magma Ocean

    Science.gov (United States)

    Armstrong, K.; Frost, D. J.; McCammon, C. A.; Rubie, D. C.; Boffa Ballaran, T.

    2017-12-01

    As terrestrial planets accreted, mantle silicates equilibrated with core-forming metallic iron, which would have imposed a mantle oxygen fugacity below the iron-wüstite oxygen buffer. Throughout Earth's history, however, the oxygen fugacity of at least the accessible portions of the upper mantle has been 4-5 orders of magnitude higher. The process that caused the rapid increase in the redox state of the mantle soon after core formation is unclear. Here we test the possibility that pressure stabilises ferric iron in silicate melts, as has been observed in silicate minerals. A deep magma ocean, which would have likely existed towards the end of accretion, could then develop a gradient in oxygen fugacity for a fixed ferric-ferrous ratio as a result of pressure. We have equilibrated an andesitic melt with a Ru-RuO2 buffer in a multianvil press between 5 and 24 GPa. Further experiments were performed on the same melt in equilibrium with iron metal. The recovered melts were then analysed using Mössbauer spectroscopy to determine the ferric/ferrous ratio. The results show that for the Ru-RuO2 buffer at lower pressures, the ferric iron content decreases with pressure, due to a positive volume change of the reaction FeO + 1/4O2 = FeO1.5. Ferric iron content also appears to be sensitive to water content at lower pressures. However, above 15 GPa this trend apparently reverses and the ferric iron content increases with pressure. This reversal in pressure dependence would drive the oxygen fugacity of a deep magma ocean with a fixed ferric/ferrous ratio down with increasing depth. This would create a redox gradient, where the magma ocean could potentially be in equilibrium with metallic iron at its base but more oxidised in its shallower regions. Crystallisation of this magma ocean could render an upper mantle oxygen fugacity similar to that in the Earth's accessible mantle today.

  1. Hydration behaviors of calcium silicate-based biomaterials.

    Science.gov (United States)

    Lee, Yuan-Ling; Wang, Wen-Hsi; Lin, Feng-Huie; Lin, Chun-Pin

    2017-06-01

    Calcium silicate (CS)-based biomaterials, such as mineral trioxide aggregate (MTA), have become the most popular and convincing material used in restorative endodontic treatments. However, the commercially available CS-based biomaterials all contain different minor additives, which may affect their hydration behaviors and material properties. The purpose of this study was to evaluate the hydration behavior of CS-based biomaterials with/without minor additives. A novel CS-based biomaterial with a simplified composition, without mineral oxides as minor additives, was produced. The characteristics of this biomaterial during hydration were investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FTIR) spectrometry. The hydration behaviors of commercially available gray and white MTAs with mineral oxide as minor additives were also evaluated for reference. For all three test materials, the XRD analysis revealed similar diffraction patterns after hydration, but MTAs presented a significant decrease in the intensities of Bi 2 O 3 -related peaks. SEM results demonstrated similar porous microstructures with some hexagonal and facetted crystals on the outer surfaces. In addition, compared to CS with a simplified composition, the FTIR plot indicated that hydrated MTAs with mineral oxides were better for the polymerization of calcium silicate hydrate (CSH), presenting Si-O band shifting to higher wave numbers, and contained more water crystals within CSH, presenting sharper bands for O-H bending. Mineral oxides might not result in significant changes in the crystal phases or microstructures during the hydration of CS-based biomaterials, but these compounds affected the hydration behavior at the molecular level. Copyright © 2016. Published by Elsevier B.V.

  2. Modified tricalcium silicate cement formulations with added zirconium oxide.

    Science.gov (United States)

    Li, Xin; Yoshihara, Kumiko; De Munck, Jan; Cokic, Stevan; Pongprueksa, Pong; Putzeys, Eveline; Pedano, Mariano; Chen, Zhi; Van Landuyt, Kirsten; Van Meerbeek, Bart

    2017-04-01

    This study aims to investigate the effect of modifying tricalcium silicate (TCS) cements on three key properties by adding ZrO 2 . TCS powders were prepared by adding ZrO 2 at six different concentrations. The powders were mixed with 1 M CaCl 2 solution at a 3:1 weight ratio. Biodentine (contains 5 wt.% ZrO 2 ) served as control. To evaluate the potential effect on mechanical properties, the mini-fracture toughness (mini-FT) was measured. Regarding bioactivity, Ca release was assessed using ICP-AES. The component distribution within the cement matrix was evaluated by Feg-SEM/EPMA. Cytotoxicity was assessed using an XTT assay. Adding ZrO 2 to TCS did not alter the mini-FT (p = 0.52), which remained in range of that of Biodentine (p = 0.31). Ca release from TSC cements was slightly lower than that from Biodentine at 1 day (p > 0.05). After 1 week, Ca release from TCS 30 and TCS 50 increased to a level that was significantly higher than that from Biodentine (p  0.05). EPMA revealed a more even distribution of ZrO 2 within the TCS cements. Particles with an un-reacted core were surrounded by a hydration zone. The 24-, 48-, and 72-h extracts of TCS 50 were the least cytotoxic. ZrO 2 can be added to TCS without affecting the mini-FT; Ca release was reduced initially, to reach a prolonged release thereafter; adding ZrO 2 made TCS cements more biocompatible. TCS 50 is a promising cement formulation to serve as a biocompatible hydraulic calcium silicate cement.

  3. Trace element analysis of silicate rocks by XRF. Pt. 2

    International Nuclear Information System (INIS)

    Orihashi, Yuji; Yuhara, Masaki; Kagami, Hiroo; Honma, Hiroji

    1993-01-01

    Quantitative X-ray fluorescence analysis of six trace elements (Ce, Ba, Ga, Co, Cr, V) in silicate rocks has been investigated, using pressed powder pellets. Ga analysis was performed using a Cr tube, whereas a Au tube was used for the remaining five elements. Corrections were made for the interference of BaKα on CeKα, FeKβ on CoKα, CrKα on VKβ and VKα on TiKβ. Mass absorption functions were estimated from background intensities at 2θ=35.5deg and that of FeKα at wavelengths longer than the iron absorption edge for a Au tube, and from the value of net intensity/background one for a Cr tube. Calibration lines were constructed using twenty-four U.S. Geological Survey and Geological Survey of Japan igneous rock reference samples. For each line, the correction coefficient is greater than 0.993 except for Ga and Ce (>0.985), indicating that the correction and calibration procedures are appropriate for accurate analysis over a wide compositional range. Analytical results for igneous, sedimentary and metamorphic reference samples (U. S. Geological Survey, Institute of Geophysical and Geochemical Exploration, South-African Bureau of Standards) accord well with recommended or proposed values, respectively. The results of this study and those of Orihashi et al. (1993) show Ce, Ba, Nb, Zr, Y, Sr, Rb, Th, Ga, Zn, Cu, Ni, Co, Cr and V in silicate rocks can be quantitatively determined by XRF at ISEI. (author)

  4. Formation of Silicate and Titanium Clouds on Hot Jupiters

    Science.gov (United States)

    Powell, Diana; Zhang, Xi; Gao, Peter; Parmentier, Vivien

    2018-06-01

    We present the first application of a bin-scheme microphysical and vertical transport model to determine the size distribution of titanium and silicate cloud particles in the atmospheres of hot Jupiters. We predict particle size distributions from first principles for a grid of planets at four representative equatorial longitudes, and investigate how observed cloud properties depend on the atmospheric thermal structure and vertical mixing. The predicted size distributions are frequently bimodal and irregular in shape. There is a negative correlation between the total cloud mass and equilibrium temperature as well as a positive correlation between the total cloud mass and atmospheric mixing. The cloud properties on the east and west limbs show distinct differences that increase with increasing equilibrium temperature. Cloud opacities are roughly constant across a broad wavelength range, with the exception of features in the mid-infrared. Forward-scattering is found to be important across the same wavelength range. Using the fully resolved size distribution of cloud particles as opposed to a mean particle size has a distinct impact on the resultant cloud opacities. The particle size that contributes the most to the cloud opacity depends strongly on the cloud particle size distribution. We predict that it is unlikely that silicate or titanium clouds are responsible for the optical Rayleigh scattering slope seen in many hot Jupiters. We suggest that cloud opacities in emission may serve as sensitive tracers of the thermal state of a planet’s deep interior through the existence or lack of a cold trap in the deep atmosphere.

  5. Evaluation of apatite silicates as solid oxide fuel cell electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Marrero-Lopez, D. [Dpto. de Fisica Aplicada I, Laboratorio de Materiales y Superficies (Unidad Asociada al C.S.I.C.), Universidad de Malaga, 29071 Malaga (Spain); Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Martin-Sedeno, M.C.; Aranda, M.A.G. [Dpto. de Quimica Inorganica, Universidad Malaga, 29071 Malaga (Spain); Pena-Martinez, J. [Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Instituto de Energias Renovables, Parque Tecnologico, Universidad de Castilla La Mancha, 02006 Albacete (Spain); Ruiz-Morales, J.C.; Nunez, P. [Dpto. de Quimica Inorganica, Universidad de La Laguna, 38200 La Laguna, Tenerife (Spain); Ramos-Barrado, J.R. [Dpto. de Fisica Aplicada I, Laboratorio de Materiales y Superficies (Unidad Asociada al C.S.I.C.), Universidad de Malaga, 29071 Malaga (Spain)

    2010-05-01

    Apatite-type silicates have been considered as promising electrolytes for Solid Oxide Fuel Cells (SOFC); however studies on the potential use of these materials in SOFC devices have received relatively little attention. The lanthanum silicate with composition La{sub 10}Si{sub 5.5}Al{sub 0.5}O{sub 26.75} has been evaluated as electrolyte with the electrode materials commonly used in SOFC, i.e. manganite, ferrite and cobaltite as cathode materials and NiO-CGO composite, chromium-manganite and Sr{sub 2}MgMoO{sub 6} as anode materials. Chemical compatibility, area-specific resistance and fuel cell studies have been performed. X-ray powder diffraction (XRPD) analysis did not reveal any trace of reaction products between the apatite electrolyte and most of the aforementioned electrode materials. However, the area-specific polarisation resistance (ASR) of these electrodes in contact with apatite electrolyte increased significantly with the sintering temperature, indicating reactivity at the electrolyte/electrode interface. On the other hand, the ASR values are significantly improved using a ceria buffer layer between the electrolyte and electrode materials to prevent reactivity. Maximum power densities of 195 and 65 mWcm{sup -2} were obtained at 850 and 700 C, respectively in H{sub 2} fuel, using an 1 mm-thick electrolyte, a NiO-Ce{sub 0.8}Gd{sub 0.2}O{sub 1.9} composite as anode and La{sub 0.6}Sr{sub 0.4}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} as cathode materials. This fuel cell was tested for 100 h in 5%H{sub 2}-Ar atmosphere showing stable performance. (author)

  6. Calcium isotope fractionation in a silicate dominated Cenozoic aquifer system

    Science.gov (United States)

    Li, Junxia; DePaolo, Donald J.; Wang, Yanxin; Xie, Xianjun

    2018-04-01

    To understand the characteristics of Ca isotope composition and fractionation in silicate-dominated Quaternary aquifer system, hydrochemical and isotope studies (87Sr/86Sr, 13CDIC and 44/40Ca) were conducted on groundwater, sediment and rock samples from the Datong basin, China. Along the groundwater flow path from the basin margin to the center, groundwater hydrochemical type evolves from Ca-HCO3 to Na-HCO3/Na-Cl type, which results from aluminosilicate hydrolysis, vertical mixing, cation exchange between CaX2 and NaX, and calcite/dolomite precipitation. These processes cause the decrease in groundwater Ca concentration and the associated modest fractionation of groundwater Ca isotopes along the flowpath. The groundwater δ44/40Ca value varies from -0.11 to 0.49‰. The elevated δ44/40Ca ratios in shallow groundwater are attributed to vertical mixing involving addition of irrigation water, which had the average δ44/40Ca ratio of 0.595‰. Chemical weathering of silicate minerals and carbonate generates depleted δ44/40Ca signatures in groundwater from Heng Mountain (east area) and Huanghua Uplift (west area), respectively. Along the groundwater flow path from Heng Mountain to central area of east area, cation exchange between CaX2 and NaX on clay mineral results in the enrichment of heavier Ca isotope in groundwater. All groundwater samples are oversaturated with respect to calcite and dolomite. The groundwater environment rich in organic matter promotes the precipitation of carbonate minerals via the biodegradation of organic carbon, thereby further promoting the elevation of groundwater δ44/40Ca ratios.

  7. A-thermal elastic behavior of silicate glasses.

    Science.gov (United States)

    Rabia, Mohammed Kamel; Degioanni, Simon; Martinet, Christine; Le Brusq, Jacques; Champagnon, Bernard; Vouagner, Dominique

    2016-02-24

    Depending on the composition of silicate glasses, their elastic moduli can increase or decrease as function of the temperature. Studying the Brillouin frequency shift of these glasses versus temperature allows the a-thermal composition corresponding to an intermediate glass to be determined. In an intermediate glass, the elastic moduli are independent of the temperature over a large temperature range. For sodium alumino-silicate glasses, the a-thermal composition is close to the albite glass (NaAlSi3O8). The structural origin of this property is studied by in situ high temperature Raman scattering. The structure of the intermediate albite glass and of silica are compared at different temperatures between room temperature and 600 °C. When the temperature increases, it is shown that the high frequency shift of the main band at 440 cm(-1) in silica is a consequence of the cristobalite-like alpha-beta transformation of 6-membered rings. This effect is stronger in silica than bond elongation (anharmonic effects). As a consequence, the elastic moduli of silica increase as the temperature increases. In the albite glass, the substitution of 25% of Si(4+) ions by Al(3+) and Na(+) ions decreases the proportion of SiO2 6-membered rings responsible for the silica anomaly. The effects of the silica anomaly balance the anharmonicity in albite glass and give rise to an intermediate a-thermal glass. Different networks, formers or modifiers, can be added to produce different a-thermal glasses with useful mechanical or chemical properties.

  8. Evidence of yttrium silicate inclusions in YSZ-porcelain veneers.

    Science.gov (United States)

    Stoner, Brian R; Griggs, Jason A; Neidigh, John; Piascik, Jeffrey R

    2014-04-01

    This report introduces the discovery of crystalline defects that can form in the porcelain veneering layer when in contact with yttria-stabilized zirconia (YSZ). The focus was on dental prostheses and understanding the defects that form in the YSZ/porcelain system; however the data reported herein may have broader implications toward the use and stability of YSZ-based ceramics in general. Specimens were cut from fully sintered YSZ plates and veneering porcelain was applied (X-ray (EDAX) was used for microstructural and elemental analysis. EDAX, for chemical analysis and transmission electron diffraction (TED) for structural analysis were both performed in the transmission electron microscope (TEM). Additionally, in order to spatially resolve Y-rich precipitates, micro-CT scans were conducted at varying depths within the porcelain veneer. Local EDAX (SEM) was performed in the regions of visible inclusions and showed significant increases in yttrium concentration. TEM specimens also showed apparent inclusions in the porcelain and selected area electron diffraction was performed on these regions and found the inclusions to be crystalline and identified as either yttrium-silicate (Y2 SiO5 ) or yttrium-disilicate (Y2 Si2 O7 ). Micro-CT data showed that yttrium-silicate precipitates were distributed throughout the thickness of the porcelain veneer. Future studies are needed to determine whether many of the premature failures associated with this materials system may be the result of crystalline flaws that form as a result of high temperature yttrium diffusion near the surfaces of YSZ. © 2013 Wiley Periodicals, Inc.

  9. Crystallisation mechanism of a multicomponent lithium alumino-silicate glass

    International Nuclear Information System (INIS)

    Wurth, R.; Pascual, M.J.; Mather, G.C.; Pablos-Martín, A.; Muñoz, F.; Durán, A.; Cuello, G.J.; Rüssel, C.

    2012-01-01

    A base glass of composition 3.5 Li 2 O∙0.15 Na 2 O∙0.2 K 2 O∙1.15 MgO∙0.8 BaO∙1.5 ZnO∙20 Al 2 O 3 ∙67.2 SiO 2 ∙2.6 TiO 2 ∙1.7 ZrO 2 ∙1.2 As 2 O 3 (in wt.%), melted and provided by SCHOTT AG (Mainz), was used to study the crystallisation mechanism of lithium alumino-silicate glass employing X-ray diffraction combined with neutron diffraction and non-isothermal differential scanning calorimetry (DSC). A high-quartz solid solution of LiAlSi 2 O 6 with nanoscaled crystals forms at 750 °C. Quantitative Rietveld refinement of samples annealed at 750 °C for 8 h determined a crystallised fraction of around 59 wt.%. The room temperature crystallised phase adopts an ordered, β-eucryptite-like structure (2 × 2 × 2 cell) with Li ordered in the structural channels. The Avrami parameter (n ∼ 4), calculated from DSC data using different theoretical approaches, indicates that bulk crystallisation occurs and that the number of nuclei increases during annealing. The activation energy of the crystallisation is 531 ± 20 kJ mol −1 . - Highlights: ► Nanoscaled high-quartz crystals from a multicomponent lithium alumino-silicate glass. ► Combined X-ray and neutron diffraction structural refinement. ► β-Eucryptite-like structure (2 × 2×2 cell) with Li ordered in the structural channels. ► 3-Dimensional bulk crystallisation mechanism with an increasing number of nuclei. ► Usage and validation of an alternative approach to calculate the Avrami parameter.

  10. NASA Earth Exchange (NEX)

    Data.gov (United States)

    National Aeronautics and Space Administration — The NASA Earth Exchange (NEX) represents a new platform for the Earth science community that provides a mechanism for scientific collaboration and knowledge sharing....

  11. The problem of iron partition between Earth and Moon during simultaneous formation as a double planet system

    Science.gov (United States)

    Cassidy, W. A.

    1984-01-01

    A planetary model is described which requires fractional vapor/liquid condensation, planet accumulation during condensation, a late start for accumulation of the Moon, and volatile accretion to the surfaces of each planet only near the end of the accumulation process. In the model, initial accumulation of small objects is helped if the agglomerating particles are somewhat sticky. Assuming that growth proceeds through this range, agglomeration continues. If the reservoir of vapor is being preferentially depleted in iron by fractional condensation, an iron-rich planetary core forms. As the temperature decreases, condensing material becomes progressively richer in silicates and poorer in iron, forming the silicate-rich mantle of an already differentiated Earth. A second center of agglomeration successfully forms near the growing Earth after most of the iron in the reservoir has been used up. The bulk composition of the Moon then is similar to the outer mantle of the accumulating Earth.

  12. Element Abundances in Meteorites and the Earth: Implication for the Accretion of Planetary Bodies

    Science.gov (United States)

    Mezger, K.; Vollstaedt, H.; Maltese, A.

    2017-12-01

    Essentially all known inner solar system materials show near chondritic relative abundances of refractory elements and depletion in volatile elements. To a first approximation volatile element depletion correlates with the respective condensation temperature (TC) of the elements. Possible mechanisms for this depletion are incomplete condensation and partial loss by evaporation caused by heating prior to or during the planetesimal accretion. The stable isotope compositions of almost all moderately volatile elements in different meteorite classes show only minor, or no evidence for a Rayleigh-type fractionation that could be attributed to partial condensation or evaporation. The different classes of meteorites also show that the degree of depletion in their parent bodies (i.e. mostly planetesimals) is quite variable, but nevertheless systematic. For primitive and least disturbed carbonaceous chondrites the element depletion pattern is a smooth function of TC. The accessible silicate Earth also shows this general depletion pattern, but in detail it is highly complex and requires differentiation processes that are not solely controlled by TC. If only highly lithophile elements are considered the depletion pattern of the silicate Earth reveals a step function that shows that moderately volatile lithophile elements have abundances that are ca. 0.1 times the chondritic value, irrespective of their TC. This element pattern observed for bulk silicate Earth can be modelled as a mixture of two distinct components: ca. 90% of a strongly reduced planetary body that is depleted in highly volatile elements and ca. 10% of a more volatile element rich and oxidized component. This mixture can account for the apparent Pb- paradox observed in melts derived from the silicate Earth and provides a time constraint for the mixing event, which is ca. 70 My after the beginning of the solar system. This event corresponds to the giant impact that also formed the Moon.

  13. Rare-earth elements

    Science.gov (United States)

    Van Gosen, Bradley S.; Verplanck, Philip L.; Seal, Robert R.; Long, Keith R.; Gambogi, Joseph; Schulz, Klaus J.; DeYoung,, John H.; Seal, Robert R.; Bradley, Dwight C.

    2017-12-19

    The rare-earth elements (REEs) are 15 elements that range in atomic number from 57 (lanthanum) to 71 (lutetium); they are commonly referred to as the “lanthanides.” Yttrium (atomic number 39) is also commonly regarded as an REE because it shares chemical and physical similarities and has affinities with the lanthanides. Although REEs are not rare in terms of average crustal abundance, the concentrated deposits of REEs are limited in number.Because of their unusual physical and chemical properties, the REEs have diverse defense, energy, industrial, and military technology applications. The glass industry is the leading consumer of REE raw materials, which are used for glass polishing and as additives that provide color and special optical properties to the glass. Lanthanum-based catalysts are used in petroleum refining, and cerium-based catalysts are used in automotive catalytic converters. The use of REEs in magnets is a rapidly increasing application. Neodymium-iron-boron magnets, which are the strongest known type of magnets, are used when space and weight are restrictions. Nickel-metal hydride batteries use anodes made of a lanthanum-based alloys.China, which has led the world production of REEs for decades, accounted for more than 90 percent of global production and supply, on average, during the past decade. Citing a need to retain its limited REE resources to meet domestic requirements as well as concerns about the environmental effects of mining, China began placing restrictions on the supply of REEs in 2010 through the imposition of quotas, licenses, and taxes. As a result, the global rare-earth industry has increased its stockpiling of REEs; explored for deposits outside of China; and promoted new efforts to conserve, recycle, and substitute for REEs. New mine production began at Mount Weld in Western Australia, and numerous other exploration and development projects noted in this chapter are ongoing throughout the world.The REE-bearing minerals are

  14. Relationships between CO2, thermodynamic limits on silicate weathering, and the strength of the silicate weathering feedback

    Science.gov (United States)

    Winnick, Matthew J.; Maher, Kate

    2018-03-01

    Recent studies have suggested that thermodynamic limitations on chemical weathering rates exert a first-order control on riverine solute fluxes and by extension, global chemical weathering rates. As such, these limitations may play a prominent role in the regulation of carbon dioxide levels (pCO2) over geologic timescales by constraining the maximum global weathering flux. In this study, we develop a theoretical scaling relationship between equilibrium solute concentrations and pCO2 based on equilibrium constants and reaction stoichiometry relating primary mineral dissolution and secondary mineral precipitation. We test this theoretical scaling relationship against reactive transport simulations of chemical weathering profiles under open- and closed-system conditions, representing partially and fully water-saturated regolith, respectively. Under open-system conditions, equilibrium bicarbonate concentrations vary as a power-law function of pCO2 (y = kxn) where n is dependent on reaction stoichiometry and k is dependent on both reaction stoichiometry and the equilibrium constant. Under closed-system conditions, bicarbonate concentrations vary linearly with pCO2 at low values and approach open-system scaling at high pCO2. To describe the potential role of thermodynamic limitations in the global silicate weathering feedback, we develop a new mathematical framework to assess weathering feedback strength in terms of both (1) steady-state atmospheric pCO2 concentrations, and (2) susceptibility to secular changes in degassing rates and transient carbon cycle perturbations, which we term 1st and 2nd order feedback strength, respectively. Finally, we discuss the implications of these results for the effects of vascular land plant evolution on feedback strength, the potential role of vegetation in controlling modern solute fluxes, and the application of these frameworks to a more complete functional description of the silicate weathering feedback. Most notably, the dependence

  15. On the Relation of Silicates and SiO Maser in Evolved Stars

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jiaming; Jiang, Biwei, E-mail: bjiang@bnu.edu.cn [Department of Astronomy, Beijing Normal University, Beijing 100875 (China)

    2017-04-01

    The SiO molecule is one of the candidates for the seed of silicate dust in the circumstellar envelope of evolved stars, but this opinion is challenged. In this work we investigate the relation of the SiO maser emission power and the silicate dust emission power. With both our own observation by using the PMO/Delingha 13.7 m telescope and archive data, a sample is assembled of 21 SiO v  = 1, J  = 2 − 1 sources and 28 SiO v  = 1, J  = 1 − 0 sources that exhibit silicate emission features in the ISO /SWS spectrum as well. The analysis of their SiO maser and silicate emission power indicates a clear correlation, which is not against the hypothesis that the SiO molecules are the seed nuclei of silicate dust. On the other hand, no correlation is found between SiO maser and silicate crystallinity, which may imply that silicate crystallinity does not correlate with mass-loss rate.

  16. Evaluation of the effect of sodium silicate addition to mine backfill, Gelfill − Part 1

    Directory of Open Access Journals (Sweden)

    M. Kermani

    2015-06-01

    Full Text Available In this paper, the mechanical properties of sodium silicate-fortified backfill, called Gelfill, were investigated by conducting a series of laboratory experiments. Two configurations were tested, i.e. Gelfill and cemented hydraulic fill (CHF. The Gelfill has an alkali activator such as sodium silicate in its materials in addition to primary materials of mine backfill which are tailings, water and binders. Large numbers of samples of Gelfill and CHF with various mixture designs were cast and cured for over 28 d. The mechanical properties of samples were investigated using uniaxial compression test, and the results were compared with those of reference samples made without sodium silicate. The test results indicated that the addition of an appropriate amount of an alkali activator such as sodium silicate can enhance the mechanical (uniaxial compressive strength and physical (water retention properties of backfill. The microstructure analysis conducted by mercury intrusion porosimetry (MIP revealed that the addition of sodium silicate can modify the pore size distribution and total porosity of Gelfill, which can contribute to the better mechanical properties of Gelfill. It was also shown that the time and rate of drainage in the Gelfill specimens are less than those in CHF specimens made without sodium silicate. Finally, the study showed that the addition of sodium silicate can reduce the required setting time of mine backfill, which can contribute to increase mine production in accordance with the mine safety.

  17. Synthesis and characterization of silica gel from siliceous sands of southern Tunisia

    Directory of Open Access Journals (Sweden)

    Ali Sdiri

    2014-09-01

    Full Text Available The present work aimed to achieve valorization of Albian sands for the preparation of sodium silicates that are commonly used as a precursor to prepare silica gel. A siliceous sand sample was mixed with sodium carbonate and heated at a high temperature (1060 °C to prepare sodium silicates. The sodium silicates were dissolved in distilled water to obtain high quality sodium silicate solution. Hydrochloric acid was then slowly added to the hydrated sodium silicates to obtain silica gel. The collected raw siliceous sands, as well as the prepared silica gels, were characterized by different techniques, such as X-ray fluorescence (XRF, X-ray diffraction (XRD, scanning electron microscopy (SEM and thermal analysis (DSC. XRF confirmed that the detrital sand deposits of southern Tunisia contain high amounts of silica, with content ranging from 88.8% to 97.5%. The internal porosity varied between 17% and 22%, and the specific surface area was less than 5 m2/g. After the treatment described above, it was observed that the porosity of the obtained silica gel reached 57% and the specific surface area exceeded 340 m2/g. Nitrogen adsorption isotherms showed that the prepared silica gels are microporous and mesoporous materials with high adsorption capacities. These results suggest that the obtained silica gels are promising materials for numerous environmental applications.

  18. Evolution of silicate dust in interstellar, circumstellar and cometary environments: the role of irradiation and temperature

    International Nuclear Information System (INIS)

    Davoisne, Carine

    2006-01-01

    Due to the development of observational and analytical tools, our knowledge of the silicate dust has considerably increased these last years. Dust is formed around evolved stars and injected in the interstellar medium (ISM) in which it travels. Dust is then incorporated in the proto-planetary disks around young stars. During its life cycle, the silicate dust is subjected by numerous processes. The aim of this PhD work is firstly to study the chemical and morphological modifications of silicate dust in supernovae shock waves then to indicate its evolution when it is incorporated around young stars. We have developed low energy ion irradiations in situ in a photoelectron spectrometer (XPS). The chemical and morphological changes have been measured respectively by XPS and atomic force microscopy. We have also carried out thermal annealing under controlled atmosphere of amorphous silicates. The structural and chemical modifications have been observed by analytical transmission electron microscopy. We have shown that ion irradiation induces chemical and morphological changes in silicate. In the ISM, supernovae shock waves are thus a major process which could affect the silicate dust evolution. The microstructure obtained after thermal annealing strongly depends on oxygen fugacity. They often offer a good comparison with those observed in primitive materials present in our solar system. The recrystallization of amorphous interstellar precursors in the inner accretion disk is thus an efficient process to form crystalline silicates which are furthermore incorporated in small parent bodies (asteroids or comets). (author) [fr

  19. Mission to Planet Earth

    Science.gov (United States)

    Tilford, Shelby G.; Asrar, Ghassem; Backlund, Peter W.

    1994-01-01

    Mission to Planet Earth (MTPE) is NASA's concept for an international science program to produce the understanding needed to predict changes in the Earth's environment. NASA and its interagency and international partners will place satellites carrying advanced sensors in strategic Earth orbits to gather multidisciplinary data. A sophisticated data system will process and archive an unprecedented amount of information about the Earth and how it works as a system. Increased understanding of the Earth system is a basic human responsibility, a prerequisite to informed management of the planet's resources and to the preservation of the global environment.

  20. Mission to Planet Earth

    International Nuclear Information System (INIS)

    Wilson, G.S.; Backlund, P.W.

    1992-01-01

    Mission to Planet Earth (MTPE) is NASA's concept for an international science program to produce the understanding needed to predict changes in the earth's environment. NASA and its interagency and international partners will place satellites carrying advanced sensors in strategic earth orbits to gather multidisciplinary data. A sophisticated data system will process and archive an unprecedented amount of information about the earth and how it works as a system. Increased understanding of the earth system is a basic human responsibility, a prerequisite to informed management of the planet's resources and to the preservation of the global environment. 8 refs

  1. Carbonate formation in non-aqueous environments by solid-gas carbonation of silicates

    Science.gov (United States)

    Day, S. J.; Thompson, S. P.; Evans, A.; Parker, J. E.

    2012-02-01

    We have produced synthetic analogues of cosmic silicates using the Sol Gel method, producing amorphous silicates of composition Mg(x)Ca(1-x)SiO3. Using synchrotron X-ray powder diffraction on Beamline I11 at the Diamond Light Source, together with a newly-commissioned gas cell, real-time powder diffraction scans have been taken of a range of silicates exposed to CO2 under non-ambient conditions. The SXPD is complemented by other techniques including Raman and Infrared Spectroscopy and SEM imaging.

  2. New Silicate Phosphors for a White LED(Electronic Displays)

    OpenAIRE

    Toda, Kenji; Kawakami, Yoshitaka; Kousaka, Shin-ichiro; Ito, Yutaka; Komeno, Akira; Uematsu, Kazuyoshi; Sato, Mineo

    2006-01-01

    We focus on the development of new silicate phosphors for a white LED. In the europium doped silicate system, four LED phosphor candidates-Li_2SrSiO_4:Eu^, Ba_9Sc_2Si_6O_:Eu^, Ca_3Si_2O_7:Eu^ and Ba_2MgSi_2O_7:Eu^ were found. Luminescent properties under near UV and visible excitation were investigated for the new Eu^ doped LED silicate phosphors. These new phosphors have a relatively strong absorption band in a long wavelength region.

  3. USE OF LOCAL NATURAL SILICEOUS RAW MATERIAL AND WASTES FOR PRODUCTION OF HEAT-INSULATING FOAMCONCRETE

    Directory of Open Access Journals (Sweden)

    V. U. Matsapulin

    2015-01-01

    Full Text Available The article analyzes the resource base, reserves and the use of siliceous rocks, their economic feasibility of the use for production of building materials of new generation with low-energy and other costs. Presented are the results of laboratory research and testing technology of production of insulating foam from a composition based on an aqueous solution of sodium silicate obtained from the local siliceous rocks (diatomite and the liquid alkali component - soapstock, hardener from ferrochrome slag and waste carbonate rock able to harden at a low temperature processing ( 100-110 ° C.

  4. Pressure effect on Fe3+/FeT in silicate melts and applications to magma redox, particularly in magma oceans

    Science.gov (United States)

    Zhang, H.; Hirschmann, M. M.

    2014-12-01

    The proportions of Fe3+ and Fe2+ in magmas reflect the redox conditions of their origin and influence the chemical and physical properties of natural silicate liquids, but the relationship between Fe3+/FeT and oxygen fugacity depends on pressure owing to different molar volumes and compressibilities of Fe3+ and Fe2+ in silicates. An important case where the effect of pressure effect may be important is in magma oceans, where well mixed (and therefore potentially uniform Fe3+/FeT) experiencses a wide range of pressures, and therefore can impart different ƒO2 at different depths, influencing magma ocean degassing and early atmospheres, as well as chemical gradients within magma oceans. To investigate the effect of pressure on magmatic Fe3+/FeT we conducted high pressure expeirments on ƒO2-buffered andestic liquids. Quenched glasses were analyzed by Mössbauer spectroscopy. To verify the accuracy of Mössbauer determinations of Fe3+/FeT in glasses, we also conducted low temperature Mössbauer studies to determine differences in the recoilless fraction (ƒ) of Fe2+ and Fe3. These indicate that room temperature Mössbauer determinations of on Fe3+/FeT glasses are systematically high by 4% compared to recoilless-fraction corrected ratios. Up to 7 GPa, pressure decreases Fe3+/FeT, at fixed ƒO2 relative to metal-oxide buffers, meaning that an isochemical magma will become more reduced with decreasing pressure. Consequently, for small planetary bodies such as the Moon or Mercury, atmospheres overlying their MO will be highly reducing, consisting chiefly of H2 and CO. The same may also be true for Mars. The trend may reverse at higher pressure, as is the case for solid peridotite, and so for Earth, Venus, and possibly Mars, more oxidized atmospheres above MO are possible. Diamond anvil experiments are underway to examine this hypothesis.

  5. Noble gas solubility in silicate melts:a review of experimentation and theory, and implications regarding magma degassing processes

    Directory of Open Access Journals (Sweden)

    A. Paonita

    2005-06-01

    Full Text Available Noble gas solubility in silicate melts and glasses has gained a crucial role in Earth Sciences investigations and in the studies of non-crystalline materials on a micro to a macro-scale. Due to their special geochemical features, noble gases are in fact ideal tracers of magma degassing. Their inert nature also allows them to be used to probe the structure of silicate melts. Owing to the development of modern high pressure and temperature technologies, a large number of experimental investigations have been performed on this subject in recent times. This paper reviews the related literature, and tries to define our present state of knowledge, the problems encountered in the experimental procedures and the theoretical questions which remain unresolved. Throughout the manuscript I will also try to show how the thermodynamic and structural interpretations of the growing experimental dataset are greatly improving our understanding of the dissolution mechanisms, although there are still several points under discussion. Our improved capability of predicting noble gas solubilities in conditions closer to those found in magma has allowed scientists to develop quantitative models of magma degassing, which provide constraints on a number of questions of geological impact. Despite these recent improvements, noble gas solubility in more complex systems involving the main volatiles in magmas, is poorly known and a lot of work must be done. Expertise from other fields would be extremely valuable to upcoming research, thus focus should be placed on the structural aspects and the practical and commercial interests of the study of noble gas solubility.

  6. Na, Rb and Cs partitioning between metal, silicate and sulfide: Implications for volatile depletion in terrestrial planets

    Science.gov (United States)

    Boujibar, A.; Fei, Y.; Du, Z.; Righter, K.; Bullock, E. S.

    2017-12-01

    Inner Solar System materials are known for their depletion in volatile elements, including the moderately volatile alkalis: Na, K, Rb, and Cs. The origin of this depletion is still uncertain, as several processes could have been involved, during the nebular condensation or planetary accretion. Volatile depletion is commonly estimated through comparison of alkali concentrations relatively to those of chondrites, assuming they remain in planetary mantles during core segregation. However, experimental studies show that substantial K can partition into metals that are enriched in sulfur and oxygen. Several models have also suggested that sulfides may have played an important role during episodes of sulfide segregation from a crystallizing magma ocean (sulfide matte) or accretion of S-rich planetary embryos. For Mercury, a sulfide layer could be present between core and mantle, due to immiscibility between Si-rich and S-rich metals. Therefore, here we investigate whether alkali elements (Na, Cs and Rb) could be partly sequestered in planetary cores during their differentiation. We conducted experiments at high pressure and temperature (1 to 5 GPa and up to 1900 °C) to determine partition coefficients of Na, Rb and Cs between metal and silicate. Our results show that pressure, temperature, sulfur and oxygen in metals enhance the partitioning of Na, Rb and Cs into metals, as previously found for K. For all three investigated alkalis (Na, Rb and Cs), we found a maximum partition coefficient of 1 between sulfides containing 13 wt% O and silicate melt. Therefore, S-rich cores or sulfide layers formed due to immiscibility in Fe-S-O systems could have acted as important geochemical reservoirs for alkali elements. Using our experimental data and different assumptions on initial bulk abundances, we evaluate volatile depletion in terrestrial planets, by comparing resulting mantle alkali concentrations after core segregation, with actual concentrations in the Earth's mantle.

  7. Radiation response of cubic mesoporous silicate and borosilicate thin films

    Science.gov (United States)

    Manzini, Ayelén; Alurralde, Martín; Luca, Vittorio

    2018-01-01

    The radiation response has been studied of cubic mesoporous silicate and borosilicate thin films having different boron contents prepared using the block copolymer template Brij 58 and the dip coating technique. The degree of pore ordering of the films was analysed using low-angle X-ray diffraction and film thickness measured by X-ray reflectivity. For films calcined at 350 °C, the incorporation of boron resulted in a reproducible oscillatory variation in the d-spacing and intensity of the primary reflection as a function of boron content. A clear peak was observed in the d-spacing at 5-10 mol% boron incorporation. For borosilicate films of a given composition an overall suppression of d-spacing was observed as a function of aging time relative to films that did not contain boron. This was ascribed to a slow condensation process. The films were irradiated in pile with neutrons and with iodine ions at energies of 180 keV and 70 MeV. Neutron irradiation of the silicate thin films for periods up to 30 days and aged for 400 days resulted in little reduction in either d-spacing or intensity of the primary low-angle X-ray reflection indicating that the films retained their mesopore ordering. In contrast borosilicate films for which the B (n, α) reaction was expected to result in enhanced displacement damage showed much larger variations in X-ray parameters. For these films short irradiation times resulted in a reduction of the d-spacing and intensity of the primary reflections considerably beyond that observed through aging. It is concluded that prolonged neutron irradiation and internal α irradiation have only a small, although measurable, impact on mesoporous borosilicate thin films increasing the degree of condensation and increasing unit cell contraction. When these borosilicate films were irradiated with iodine ions, more profound changes occurred. The pore ordering of the films was significantly degraded when low energy ions were used. In some cases the degree

  8. Crystallisation mechanism of a multicomponent lithium alumino-silicate glass

    Energy Technology Data Exchange (ETDEWEB)

    Wurth, R. [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany); Pascual, M.J., E-mail: mpascual@icv.csic.es [Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Mather, G.C.; Pablos-Martin, A.; Munoz, F.; Duran, A. [Instituto de Ceramica y Vidrio, CSIC, Kelsen 5, 28049 Madrid (Spain); Cuello, G.J. [Institut Laue-Langevin, Boite Postale 156, 38042 Grenoble Cedex 9 (France); Ruessel, C. [Otto-Schott-Institut, Jena University, Fraunhoferstr. 6, 07743 Jena (Germany)

    2012-06-15

    A base glass of composition 3.5 Li{sub 2}O Bullet-Operator 0.15 Na{sub 2}O Bullet-Operator 0.2 K{sub 2}O Bullet-Operator 1.15 MgO Bullet-Operator 0.8 BaO Bullet-Operator 1.5 ZnO Bullet-Operator 20 Al{sub 2}O{sub 3} Bullet-Operator 67.2 SiO{sub 2} Bullet-Operator 2.6 TiO{sub 2} Bullet-Operator 1.7 ZrO{sub 2} Bullet-Operator 1.2 As{sub 2}O{sub 3} (in wt.%), melted and provided by SCHOTT AG (Mainz), was used to study the crystallisation mechanism of lithium alumino-silicate glass employing X-ray diffraction combined with neutron diffraction and non-isothermal differential scanning calorimetry (DSC). A high-quartz solid solution of LiAlSi{sub 2}O{sub 6} with nanoscaled crystals forms at 750 Degree-Sign C. Quantitative Rietveld refinement of samples annealed at 750 Degree-Sign C for 8 h determined a crystallised fraction of around 59 wt.%. The room temperature crystallised phase adopts an ordered, {beta}-eucryptite-like structure (2 Multiplication-Sign 2 Multiplication-Sign 2 cell) with Li ordered in the structural channels. The Avrami parameter (n {approx} 4), calculated from DSC data using different theoretical approaches, indicates that bulk crystallisation occurs and that the number of nuclei increases during annealing. The activation energy of the crystallisation is 531 {+-} 20 kJ mol{sup -1}. - Highlights: Black-Right-Pointing-Pointer Nanoscaled high-quartz crystals from a multicomponent lithium alumino-silicate glass. Black-Right-Pointing-Pointer Combined X-ray and neutron diffraction structural refinement. Black-Right-Pointing-Pointer {beta}-Eucryptite-like structure (2 Multiplication-Sign 2 Multiplication-Sign 2 cell) with Li ordered in the structural channels. Black-Right-Pointing-Pointer 3-Dimensional bulk crystallisation mechanism with an increasing number of nuclei. Black-Right-Pointing-Pointer Usage and validation of an alternative approach to calculate the Avrami parameter.

  9. Influence of the type of aqueous sodium silicate on the stabilization and rheology of kaolin clay suspensions

    Science.gov (United States)

    Izak, Piotr; Ogłaza, Longin; Mozgawa, Włodzimierz; Mastalska-Popławska, Joanna; Stempkowska, Agata

    2018-05-01

    To avoid agglomeration and sedimentation of grains, ceramic slurries should be modified by stabilizers in order to increase the electrostatic interactions between the dispersed particles. In this study we present the spectral analysis of aqueous sodium silicates obtained by different synthesis methods and their influence on the rheological properties of kaolin based slurries. Infrared and Raman spectra can be used to describe the structure of silicate structural units present in aqueous sodium silicates. It was confirmed that the best stabilization results possess aqueous sodium silicates of the silicate moduli of about 2 and the optimal concentration of the used fluidizer is 0.3 wt% to the kaolin clay dry mass. One of the most important conclusions is that the synthesis method of the fluidizer has no significant effect on its stabilization properties but used medium does create adequate stabilization mechanism depending on the silicate structures present in the sodium silicate solution.

  10. Natural penetrating radiation inside silicate dwellings in Chengdu and recommendation on permissible limits for radioactivity of building material made of silicate cinders

    International Nuclear Information System (INIS)

    Li Guangzao

    1984-01-01

    This paper reports the results of external exposure rate of penetrating radiation inside silicate dwellings in Chengdu. The average exposure rate was 24.3+-3.5 R/h. It was evidently higher than of red brick dwellings. The average effective equivalent of the population in silicate dwellings was 123.4+-10.4 mrem/y and the average additional dose was 29.5+-12.5 mrem/y. The permissible limits recommended for silicate building material would be 6 pCi/g, 7 pCi/g and 102 pCi/g for 226 Ra, 232 Th and 40 K, respectively. The total activity must fulfill the formula of Csub(Ra)/6 + Csub(Th)/7 + Csub(k)/102 1. Under ordinary condition the exposure rate (10+background) R/h of penetrating radiation from the surface of dry building material might be taken as the permissible limit for dwellings and other public buildings

  11. Digital Earth – A sustainable Earth

    International Nuclear Information System (INIS)

    Mahavir

    2014-01-01

    All life, particularly human, cannot be sustainable, unless complimented with shelter, poverty reduction, provision of basic infrastructure and services, equal opportunities and social justice. Yet, in the context of cities, it is believed that they can accommodate more and more people, endlessly, regardless to their carrying capacity and increasing ecological footprint. The 'inclusion', for bringing more and more people in the purview of development is often limited to social and economic inclusion rather than spatial and ecological inclusion. Economic investment decisions are also not always supported with spatial planning decisions. Most planning for a sustainable Earth, be at a level of rural settlement, city, region, national or Global, fail on the capacity and capability fronts. In India, for example, out of some 8,000 towns and cities, Master Plans exist for only about 1,800. A chapter on sustainability or environment is neither statutorily compulsory nor a norm for these Master Plans. Geospatial technologies including Remote Sensing, GIS, Indian National Spatial Data Infrastructure (NSDI), Indian National Urban Information Systems (NUIS), Indian Environmental Information System (ENVIS), and Indian National GIS (NGIS), etc. have potential to map, analyse, visualize and take sustainable developmental decisions based on participatory social, economic and social inclusion. Sustainable Earth, at all scales, is a logical and natural outcome of a digitally mapped, conceived and planned Earth. Digital Earth, in fact, itself offers a platform to dovetail the ecological, social and economic considerations in transforming it into a sustainable Earth

  12. Immobilisation of active concrete debris using soluble sodium silicates

    International Nuclear Information System (INIS)

    Field, S.N.; Jull, S.P.

    1991-01-01

    Demolition of concrete biological shields will generate large quantities of active demolition debris. The size distribution of such concrete may range from pieces of size less than one tonne down to dust. Handling and disposal methods for this material are still the subject of current research. Although the literature indicates that the mechanisms of silicate/concrete interaction are not well understood, successful setting of the smaller size fraction of concrete demolition debris can be achieved at laboratory scale. Hardened properties of the set slurry are also acceptable. A study of the full scale process has resulted in an outline design for a suitable on-site plant. Estimated capital costs of the equipment are of the order of pounds 1.1M. The project has shown that the material of less than 5mm particle size can be set by this technique. Whilst this meets the original objectives of immobilising dust, it had been hoped that the 10mm size material, (which will require removal from the larger debris before grouting can take place) could also be disposed of by the slurry setting technique. Co-disposal of slurry and large active items in the same container is unlikely to be worthwhile. 14 tabs., 5 figs., 30 refs

  13. Zeta potentials in the flotation of oxide and silicate minerals.

    Science.gov (United States)

    Fuerstenau, D W; Pradip

    2005-06-30

    Adsorption of collectors and modifying reagents in the flotation of oxide and silicate minerals is controlled by the electrical double layer at the mineral-water interface. In systems where the collector is physically adsorbed, flotation with anionic or cationic collectors depends on the mineral surface being charged oppositely. Adjusting the pH of the system can enhance or prevent the flotation of a mineral. Thus, the point of zero charge (PZC) of the mineral is the most important property of a mineral in such systems. The length of the hydrocarbon chain of the collector is important because of chain-chain association enhances the adsorption once the surfactant ions aggregate to form hemimicelles at the surface. Strongly chemisorbing collectors are able to induce flotation even when collector and the mineral surface are charged similarly, but raising the pH sufficiently above the PZC can repel chemisorbing collectors from the mineral surface. Zeta potentials can be used to delineate interfacial phenomena in these various systems.

  14. Silicate grout curtains behaviour for the protection of coastal aquifers

    International Nuclear Information System (INIS)

    Elektorowicz, M.; Chifrina, R.; Hesnawi, R.

    1997-01-01

    Tests were performed to evaluate the behaviour of silicate grout with different reagents (ethylacetate - formamide SA and calcium chloride SC) in pure silica sand and natural soils from coastal areas containing organic matter, clayey soil and silica sand. The grouted specimens were tested with simulated fresh and salt water. The setting process during chemical grouting in the soil and sand was studied. The grouting of soil and sand with SA caused a transfer to the environment of some compounds: sodium formate, sodium acetate, ammonia and part of the initial ethylacetate and formamide. This process had a tendency to decrease for approximately 4 months. The stability of specimens was low. The grouting of soil and sand with SC caused no significant contamination of the environment. The increase of pH of environmental water was even less than with SA grouting. Also, the stability of specimens is higher in comparison with SA grouting. Salt water protected the specimens grouted with SA and SC from destruction and prevented contamination

  15. Fabrication of large diameter alumino-silicate K+ sources

    International Nuclear Information System (INIS)

    Baca, D.; Chacon-Golcher, E.; Kwan, J.W.; Wu, J.K.

    2003-01-01

    Alumino-silicate K + sources have been used in HIF experiments for many years. For example the Neutralized Transport Expt. (NTX) and the High Current Transport Expt. (HCX) are now using this type of ion source with diameters of 2.54 cm and 10 cm respectively. These sources have demonstrated ion currents of 80 mA and 700 mA, for typical HIF pulse lengths of 5-10 (micro)s. The corresponding current density is ∼ 10-15 mA/cm 2 , but much higher current density has been observed using smaller size sources. Recently we have improved our fabrication techniques and, therefore, are able to reliably produce large diameter ion sources with high quality emitter surface without defects. This note provides a detailed description of the procedures employed in the fabrication process. The variables in the processing steps affecting surface quality, such as substrate porosity, powder size distribution, coating technique on large area concave surfaces, drying, and heat firing temperature have been investigated

  16. Mechanical behavior of a composite interface: Calcium-silicate-hydrates

    Energy Technology Data Exchange (ETDEWEB)

    Palkovic, Steven D.; Moeini, Sina; Büyüköztürk, Oral, E-mail: obuyuk@mit.edu [Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States); Yip, Sidney [Department of Nuclear Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)

    2015-07-21

    The generalized stacking fault (GSF) is a conceptual procedure historically used to assess shear behavior of defect-free crystalline structures through molecular dynamics or density functional theory simulations. We apply the GSF technique to the spatially and chemically complex quasi-layered structure of calcium-silicate-hydrates (C-S-H), the fundamental nanoscale binder within cementitious materials. A failure plane is enforced to calculate the shear traction-displacement response along a composite interface containing highly confined water molecules, hydroxyl groups, and calcium ions. GSF simulations are compared with affine (homogeneous) shear simulations, which allow strain to localize naturally in response to the local atomic environment. Comparison of strength and deformation behavior for the two loading methods shows the composite interface controls bulk shear deformation. Both models indicate the maximum shear strength of C-S-H exhibits a normal-stress dependency typical of cohesive-frictional materials. These findings suggest the applicability of GSF techniques to inhomogeneous structures and bonding environments, including other layered systems such as biological materials containing organic and inorganic interfaces.

  17. A New Biphasic Dicalcium Silicate Bone Cement Implant

    Directory of Open Access Journals (Sweden)

    Fausto Zuleta

    2017-07-01

    Full Text Available This study aimed to investigate the processing parameters and biocompatibility of a novel biphasic dicalcium silicate (C2S cement. Biphasic α´L + β-C2Sss was synthesized by solid-state processing, and was used as a raw material to prepare the cement. In vitro bioactivity and biocompatibility studies were assessed by soaking the cement samples in simulated body fluid (SBF and human adipose stem cell cultures. Two critical-sized defects of 6 mm Ø were created in 15 NZ tibias. A porous cement made of the high temperature forms of C2S, with a low phosphorous substitution level, was produced. An apatite-like layer covered the cement’s surface after soaking in SBF. The cell attachment test showed that α´L + β-C2Sss supported cells sticking and spreading after 24 h of culture. The cement paste (55.86 ± 0.23 obtained higher bone-to-implant contact (BIC percentage values (better quality, closer contact in the histomorphometric analysis, and defect closure was significant compared to the control group (plastic. The residual material volume of the porous cement was 35.42 ± 2.08% of the initial value. The highest BIC and bone formation percentages were obtained on day 60. These results suggest that the cement paste is advantageous for initial bone regeneration.

  18. Relationships between mineralization and silicic volcanism in the central Andes

    Science.gov (United States)

    Francis, P. W.; Halls, C.; Baker, M. C. W.

    1983-01-01

    Existing models for the genesis of porphyry copper deposits indicate that they formed in granodioritic stocks located in the infrastructure of andesitic stratovolcanoes. It is noted that sites of porphyry-type subvolcanic tin mineralization in the Eastern Cordillera of Bolivia are distinguished by the absence of such andesitic structures. The surface expression of a typical subvolcanic porphyry tin deposit is thought to be an extrusive dome of quartz latite porphyry, sometimes related to a larger caldera structure. Evidence from the El Salvador porphyry copper deposit in the Eocene magmatic belt in Chile indicates that it too may be more closely related to a silicic volcanic structure than to an andesitic stratovolcano. The dome of La Soufriere, Guadeloupe is offered as a modern analog for the surface expression of subvolcanic mineralization processes, with the phreatic eruptions there indicating the formation of hydrothermal breccia bodies in depths. It is pointed out that the occurrence of mineralized porphyries, millions of years after caldera formation, does not necessarily indicate that tin intrusions and mineralization are not genetically related to the subcaldera pluton, but may be a consequence of the long thermal histories (1-10 million years) of the lowermost parts of large plutons.

  19. Chemical interactions and configurational disorder in silicate melts

    Directory of Open Access Journals (Sweden)

    G. Ottonello

    2005-06-01

    Full Text Available The Thermodynamics of quasi-chemical and polymeric models are briefly reviewed. It is shown that the two classes are mutually consistent, and that opportune conversion of the existing quasi-chemical parameterization of binary interactions in MO-SiO2 joins to polymeric models may be afforded without substantial loss of precision. It is then shown that polymeric models are extremely useful in deciphering the structural and reactive properties of silicate melts and glasses. They not only allow the Lux-Flood character of the dissolved oxides to be established, but also discriminate subordinate strain energy contributions to the Gibbs free energy of mixing from the dominant chemical interaction terms. This discrimination means that important information on the short-, medium- and long-range periodicity of this class of substances can be retrieved from thermodynamic analysis. Lastly, it is suggested that an important step forward in deciphering the complex topology of the inhomogeneity ranges observed at high SiO2 content can be performed by applying SCMF theory and, particularly, Matsen-Schick spectral analysis, hitherto applied only to rubberlike materials.

  20. Edge dislocations in dicalcium silicates: Experimental observations and atomistic analysis

    International Nuclear Information System (INIS)

    Shahsavari, Rouzbeh; Chen, Lu; Tao, Lei

    2016-01-01

    Understanding defects and influence of dislocations on dicalcium silicates (Ca 2 SiO 4 ) is a challenge in cement science. We report a high-resolution transmission electron microscopy image of edge dislocations in Ca 2 SiO 4 , followed by developing a deep atomic understanding of the edge dislocation-mediated properties of five Ca 2 SiO 4 polymorphs. By decoding the interplay between core dislocation energies, core structures, and nucleation rate of reactivity, we find that γ-C2S and α-C2S polymorphs are the most favorable polymorphs for dislocations in Ca 2 SiO 4 , mainly due to their large pore channels which take away majority of the distortions imposed by edge dislocations. Furthermore, in the context of edge dislocation, while α-C2S represents the most active polymorph for reactivity and crystal growth, β-C2S represents the most brittle polymorph suitable for grinding. This work is the first report on the atomistic-scale analysis of edge dislocation-mediated properties of Ca 2 SiO 4 and may open up new opportunities for tuning fracture and reactivity processes of Ca 2 SiO 4 and other cement components.

  1. Structural and hydration properties of amorphous tricalcium silicate

    International Nuclear Information System (INIS)

    Mori, K.; Fukunaga, T.; Shiraishi, Y.; Iwase, K.; Xu, Q.; Oishi, K.; Yatsuyanagi, K.; Yonemura, M.; Itoh, K.; Sugiyama, M.; Ishigaki, T.; Kamiyama, T.; Kawai, M.

    2006-01-01

    Mechanical milling was carried out to synthesize amorphous tricalcium silicate (Ca 3 SiO 5 ) sample, where Ca 3 SiO 5 is the most principal component of Portland cement. The partial phase transformation from the crystalline to the amorphous state was observed by X-ray and neutron diffractions. Moreover, it was found that the structural distortion on the Ca-O correlation exists in the milled Ca 3 SiO 5 . The hydration of the milled Ca 3 SiO 5 with D 2 O proceeds as follows: the formation of hydration products such as Ca(OD) 2 rapidly occurs in the early hydration stage, and then proceeds slowly after about 15 h. The induction time for the hydration of the milled Ca 3 SiO 5 is approximately one half shorter than that for the hydration of the unmilled one. This result means that the mechanical milling brings about the chemical activity of Ca 3 SiO 5 for hydration, and may be particularly useful for increasing the reactivity in the early hydration stage

  2. Intraplate mantle oxidation by volatile-rich silicic magmas

    Energy Technology Data Exchange (ETDEWEB)

    Martin, Audrey M.; Médard, Etienne; Righter, Kevin; Lanzirotti, Antonio

    2017-11-01

    The upper subcontinental lithospheric mantle below the French Massif Central is more oxidized than the average continental lithosphere, although the origin of this anomaly remains unknown. Using iron oxidation analysis in clinopyroxene, oxybarometry, and melt inclusions in mantle xenoliths, we show that widespread infiltration of volatile (HCSO)-rich silicic melts played a major role in this oxidation. We propose the first comprehensive model of magmatism and mantle oxidation at an intraplate setting. Two oxidizing events occurred: (1) a 365–286 Ma old magmatic episode that produced alkaline vaugnerites, potassic lamprophyres, and K-rich calc-alkaline granitoids, related to the N–S Rhenohercynian subduction, and (2) < 30 Ma old magmatism related to W–E extension, producing carbonatites and hydrous potassic trachytes. These melts were capable of locally increasing the subcontinental lithospheric mantle fO2 to FMQ + 2.4. Both events originate from the melting of a metasomatized lithosphere containing carbonate + phlogopite ± amphibole. The persistence of this volatile-rich lithospheric source implies the potential for new episodes of volatile-rich magmatism. Similarities with worldwide magmatism also show that the importance of volatiles and the oxidation of the mantle in intraplate regions is underestimated.

  3. Nanoporous Calcium Silicate and PLGA Bio composite for Bone Repair

    International Nuclear Information System (INIS)

    Su, J.; Wang, Z.; Wu, Y.; Cao, L.; Ma, Y.; Yu, B.; Li, M.; Yan, Y.

    2010-01-01

    Nanoporous calcium silicate (n-CS) with high surface area was synthesized using the mixed surfactants of EO20PO70EO20 (polyethylene oxide)20(polypropylene oxide)70(polyethylene oxide)20, P123) and hexadecyltrimethyl ammonium bromide (CTAB) as templates, and its composite with poly(lactic acid-co-glycolic acid) (PLGA) were fabricated. The results showed that the n-CS/PLGA composite (n-CPC) with 20 wt% n-CS could induce a dense and continuous layer of apatite on its surface after soaking in simulated body fluid (SBF) for 1 week, suggesting the excellent in vitro bioactivity. The n-CPC could promote cell attachment on its surfaces. In addition, the proliferation ratio of MG63 cells on n-CPC was significantly higher than PLGA; the results demonstrated that n-CPC had excellent cytocompatibility. We prepared n-CPC scaffolds that contained open and interconnected macroporous ranging in size from 200 to 500 μ m. The n-CPC scaffolds were implanted in femur bone defect of rabbits, and the in vivo biocompatibility and osteogenicity of the scaffolds were investigated. The results indicated that n-CPC scaffolds exhibited good biocompatibility, degradability, and osteogenesis in vivo. Collectively, these results suggested that the incorporation of n-CS in PLGA produced biocomposites with improved bioactivity and biocompatibility.

  4. Mid-Infrared Silicate Dust Features in Seyfert 1 Spectra

    Science.gov (United States)

    Thompson, Grant D.; Levenson, N. A.; Sirocky, M. M.; Uddin, S.

    2007-12-01

    Silicate dust emission dominates the mid-infrared spectra of galaxies, and the dust produces two spectral features, at 10 and 18 μm. These features' strengths (in emission or absorption) and peak wavelengths reveal the geometry of the dust distribution, and they are sensitive to the dust composition. We examine mid-infrared spectra of 32 Seyfert 1 active galactic nuclei (AGN), observed with the Infrared Spectrograph aboard the Spitzer Space Telescope. In the spectra, we typically find the shorter-wavelength feature in emission, at an average peak wavelength of 10.0 μm, although it is known historically as the "9.7 μm" feature. In addition, peak wavelength increases with feature strength. The 10 and 18 μm feature strengths together are sensitive to the dust geometry surrounding the central heating engine. Numerical calculations of radiative transfer distinguish between clumpy and smooth distributions, and we find that the surroundings of these AGN (the obscuring "tori" of unified AGN schemes) are clumpy. Polycyclic aromatic hydrocarbon (PAH) features are associated with star formation, and we find strong PAH emission (luminosity ≥ 1042 erg/s) in only four sources, three of which show independent evidence for starbursts. We will explore the effects of luminosity on dust geometry and chemistry in a comparison sample of quasars. We acknowledge work supported by the NSF under grant number 0237291.

  5. Conditions for oceans on Earth-like planets orbiting within the habitable zone: importance of volcanic CO{sub 2} degassing

    Energy Technology Data Exchange (ETDEWEB)

    Kadoya, S. [Department of Earth and Planetary Science, The University of Tokyo, Kiban Bldg. 408, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan); Tajika, E., E-mail: kadoya@astrobio.k.u-tokyo.ac.jp, E-mail: tajika@astrobio.k.u-tokyo.ac.jp [Department of Complexity Science and Engineering, The University of Tokyo, Kiban Bldg. 409, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8561 (Japan)

    2014-08-01

    Earth-like planets in the habitable zone (HZ) have been considered to have warm climates and liquid water on their surfaces if the carbonate-silicate geochemical cycle is working as on Earth. However, it is known that even the present Earth may be globally ice-covered when the rate of CO{sub 2} degassing via volcanism becomes low. Here we discuss the climates of Earth-like planets in which the carbonate-silicate geochemical cycle is working, with focusing particularly on insolation and the CO{sub 2} degassing rate. The climate of Earth-like planets within the HZ can be classified into three climate modes (hot, warm, and snowball climate modes). We found that the conditions for the existence of liquid water should be largely restricted even when the planet is orbiting within the HZ and the carbonate-silicate geochemical cycle is working. We show that these conditions should depend strongly on the rate of CO{sub 2} degassing via volcanism. It is, therefore, suggested that thermal evolution of the planetary interiors will be a controlling factor for Earth-like planets to have liquid water on their surface.

  6. Geotechnical properties of two siliceous cores from the central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Khadge, N.H.

    Physical properties of the siliceous sediments from the Central Indian Basin are measured on two short cores. The properties such as water content, Atterberg limits, porosity specific gravity, wet density show the medium to high plastic sediment...

  7. Dynamic shear stiffness and damping ratio of marine calcareous and siliceous sands

    Science.gov (United States)

    Javdanian, Hamed; Jafarian, Yaser

    2018-03-01

    Shear stiffness and damping ratio of two marine calcareous and siliceous sands were evaluated through an experimental program. Resonant column and cyclic triaxial experiments were conducted to measure the dynamic properties of the sands in small and large shear strain amplitudes. The tests were conducted under various initial stress-density conditions. The influence of effective confining pressure on the dynamic properties of the sands was assessed and compared in a preceding paper. It was shown that the calcareous sand has higher shear stiffness and lower damping ratio in comparison to the siliceous sand. In this note, the results are presented in more details and the dynamic behavior curves of the studied sands are compared with some available models, mostly developed based on the laboratory data of siliceous sands. This comparative study reveals that the previous models predict the dynamic properties of the calcareous sand in less precision than those of the siliceous sand.

  8. Carbonation of metal silicates for long-term CO.sub.2 sequestration

    Energy Technology Data Exchange (ETDEWEB)

    Blencoe, James G.; Palmer, Donald A.; Anovitz, Lawrence M.; Beard, James S.

    2017-08-01

    In a preferred embodiment, the invention relates to a process of sequestering carbon dioxide. The process comprises the steps of: (a) reacting a metal silicate with a caustic alkali-metal hydroxide to produce a hydroxide of the metal formerly contained in the silicate; (b) reacting carbon dioxide with at least one of a caustic alkali-metal hydroxide and an alkali-metal silicate to produce at least one of an alkali-metal carbonate and an alkali-metal bicarbonate; and (c) reacting the metal hydroxide product of step (a) with at least one of the alkali-metal carbonate and the alkali-metal bicarbonate produced in step (b) to produce a carbonate of the metal formerly contained in the metal silicate of step (a).

  9. Imaging the Oxygen-Rich Disk Toward the Silicate Carbon Star EU Andromedae

    National Research Council Canada - National Science Library

    Ohnaka, K; Boboltz, D. A

    2007-01-01

    .... We present multi-epoch, high-angular resolution observations of 22 GHz H2O masers toward the silicate carbon star EU And to probe the spatio-kinematic distribution of oxygen-rich material. Methods...

  10. Some observations on use of siliceous mineral waters in reduction of corrosion in RCC structures

    Digital Repository Service at National Institute of Oceanography (India)

    Venugopal, C.

    The corrosion-resisting characteristics of reinforcement in cement blended with siliceous mineral wastes viz. gold tailing and flyash have been evaluated by using an accelerated corrosion technique. The additions of these mineral admixtures...

  11. Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

    Energy Technology Data Exchange (ETDEWEB)

    Blander, M. (Argonne National Lab., IL (United States)); Pelton, A.; Eriksson, G. (Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Metallurgy and Materials Engineering)

    1992-01-01

    Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.

  12. Analyses and predictions of the thermodynamic properties and phase diagrams of silicate systems

    Energy Technology Data Exchange (ETDEWEB)

    Blander, M. [Argonne National Lab., IL (United States); Pelton, A.; Eriksson, G. [Ecole Polytechnique, Montreal, PQ (Canada). Dept. of Metallurgy and Materials Engineering

    1992-07-01

    Molten silicates are ordered solutions which can not be well represented by the usual polynomial representation of deviations from ideal solution behavior (i.e. excess free energies of mixing). An adaptation of quasichemical theory which is capable of describing the properties of ordered solutions represents the measured properties of binary silicates over broad ranges of composition and temperature. For simple silicates such as the MgO-FeO-SiO{sub 2} ternary system, in which silica is the only acid component, a combining rule generally leads to good predictions of ternary solutions from those of the binaries. In basic solutions, these predictions are consistent with those of the conformal ionic solution theory. Our results indicate that our approach could provide a potentially powerful tool for representing and predicting the properties of multicomponent molten silicates.

  13. Polymer Derived Yttrium Silicate Ablative TPS Materials for Next-Generation Exploration Missions, Phase I

    Data.gov (United States)

    National Aeronautics and Space Administration — Through the proposed NASA SBIR program, NanoSonic will optimize its HybridSil® derived yttrium silicates to serve as next-generation reinforcement for carbon and...

  14. Solidification of low-level radioactive liquid waste using a cement-silicate process

    International Nuclear Information System (INIS)

    Grandlund, R.W.; Hayes, J.F.

    1979-01-01

    Extensive use has been made of silicate and Portland cement for the solidification of industrial waste and recently this method has been successfully used to solidify a variety of low level radioactive wastes. The types of wastes processed to date include fuel fabrication sludges, power reactor waste, decontamination solution, and university laboratory waste. The cement-silicate process produces a stable solid with a minimal increase in volume and the chemicals are relatively inexpensive and readily available. The method is adaptable to either batch or continuous processing and the equipment is simple. The solid has leaching characteristics similar to or better than plain Portland cement mixtures and the leaching can be further reduced by the use of ion-exchange additives. The cement-silicate process has been used to solidify waste containing high levels of boric acid, oils, and organic solvents. The experience of handling the various types of liquid waste with a cement-silicate system is described

  15. Mid-infrared spectra of cometary dust: the evasion of its silicate mineralogy

    Science.gov (United States)

    Kimura, H.; Chigai, T.; Yamamoto, T.

    2008-04-01

    Infrared spectra of dust in cometary comae provide a way to identify its silicate constituents, and this is crucial for correctly understanding the condition under which our planetary system is formed. Recent studies assign a newly detected peak at a wavelength of 9.3 μm to pyroxenes and regard them as the most abundant silicate minerals in comets. Here we dispense with this pyroxene hypothesis to numerically reproduce the infrared features of cometary dust in the framework of our interstellar dust models. Presolar interstellar dust in a comet is modeled as fluffy aggregates consisting of submicrometer-sized organic grains with an amorphous-silicate core that undergoes nonthermal crystallization in a coma. We assert that forsterite (Mg2SiO4) is the carrier of all the observed features, including the 9.3 μm peak and that the major phase of iron is sulfides rather than iron-rich silicates.

  16. Observations on the morphological diversity and distribution of two siliceous nannoplankton genera, Hyalolithus and Petasaria

    DEFF Research Database (Denmark)

    Jordan, Richard W.; Abe, Kent; Cruz, Jarret

    2016-01-01

    Scale-bearing siliceous nannoplankton are occasionally encountered in surface seawater samples, but are rarely identified or illustrated. In this study, the morphological diversity of the haptophyte Hyalolithus neolepis and the enigmatic Petasaria heterolepis are investigated in scanning...

  17. Himalayan sedimentary pulses recorded by silicate detritus within a ferromanganese crust from the Central Indian Ocean

    Digital Repository Service at National Institute of Oceanography (India)

    Banakar, V.K.; Galy, A.; Sukumaran, N.P.; Parthiban, G.; Volvaiker, A.Y.

    A Central Indian Ocean deep-water seamount hydrogenous ferromanganese crust (SS663-Crust) contains variable (7-23%) amounts of detrital material (silicate-detritus). Taking into account the growth rate of the authigenic component, the accumulation...

  18. Nanoporous layered silicate AMH-3/cellulose acetate nanocomposite membranes for gas separations

    KAUST Repository

    Kim, Wun-gwi; Lee, Jong Suk; Bucknall, David G.; Koros, William J.; Nair, Sankar

    2013-01-01

    Nanoporous layered silicate/polymer composite membranes are of interest because they can exploit the high aspect ratio of exfoliated selective flakes/layers to enhance molecular sieving and create a highly tortuous transport path for the slower

  19. X-ray emission spectroscopy study of iron silicate catalyst FeZSM-5

    International Nuclear Information System (INIS)

    Csencsits, R.; Lyman, C.E.; Gronsky, R.

    1988-03-01

    Iron silicate analogs of the zeolite ZMS-5 may be directly synthesized from iron silicate gels in a manner which differs slightly from the alumino-silicate ZSM-5. The resultant white, crystalline iron silicate is referred to as FeZSM-5 in the as-synthesized form. Thermal treatment removes the organic crystal-directing agent and moves some of the framework iron into non-framework sites producing the calcined form of the molecular sieve FeZSM-5. Homogeneity in the distribution of catalytic iron throughout the particles is desired in an optimal catalyst. Distribution of the iron throughout the framework in the as-synthesized forms would affect the final distribution of catalytic iron in the calcined and steamed forms; thus, the iron distribution throughout the as-synthesized and calcined forms of FeZSM-5 were studied using the high spatial resolution on the analytical electron microscope. 7 refs., 3 figs

  20. Microstructure engineering of Portland cement pastes and mortars through addition of ultrafine layer silicates

    DEFF Research Database (Denmark)

    Lindgreen, Holger; Geiker, Mette; Krøyer, Hanne

    2008-01-01

    Pozzolanic submicron-sized silica fume and the non-pozzolanic micron- and nano-sized layer silicates (clay minerals) kaolinite, smectite and palygorskite have been used as additives in Portland cement pastes and mortars. These layer silicates have different particle shape (needles and plates......), surface charge, and size (micron and nano). The structure of the resulting cement pastes and mortars has been investigated by atomic force microscopy (AFM), helium porosimetry, nitrogen adsorption (specific surface area and porosity), low-temperature calorimetry (LTC) and thermal analysis. The main result...... is that the cement paste structure and porosity can be engineered by addition of selected layer silicates having specific particle shapes and surface properties (e.g., charge and specific surface area). This seems to be due to the growth of calcium-silicate hydrates (C-S-H) on the clay particle surfaces...

  1. Methylated silicates may explain the release of chlorinated methane from Martian soil

    Science.gov (United States)

    Bak, Ebbe N.; Jensen, Svend J. Knak; Nørnberg, Per; Finster, Kai

    2016-01-01

    The only organic compounds that have been detected in the Martian soil are simple chlorinated compounds released from heated surface material. However, the sources of the organic carbon are in dispute. Wind abraded silicates, which are widespread on the Martian surface, can sequester atmospheric methane which generates methylated silicates and thus could provide a mechanism for accumulation of reduced carbon in the surface soil. In this study we show that thermal volatilization of methylated silicates in the presence of perchlorate leads to the production of chlorinated methane. Thus, methylated silicates could be a source of the organic carbon released as chlorinated methane upon thermal volatilization of Martian soil samples. Further, our experiments show that the ratio of the different chlorinated compounds produced is dependent on the mass ratio of perchlorate to organic carbon in the soil.

  2. Swelling, Functionalization, and Structural Changes of the Nanoporous Layered Silicates AMH-3 and MCM-22

    KAUST Repository

    Kim, Wun-gwi; Choi, Sunho; Nair, Sankar

    2011-01-01

    Nanoporous layered silicate materials contain 2D-planar sheets of nanoscopic thickness and ordered porous structure. In comparison to porous 3D-framework materials such as zeolites, they have advantages such as significantly increased surface area

  3. Carbonation of metal silicates for long-term CO2 sequestration

    Science.gov (United States)

    Blencoe, James G; Palmer, Donald A; Anovitz, Lawrence M; Beard, James S

    2014-03-18

    In a preferred embodiment, the invention relates to a process of sequestering carbon dioxide. The process comprises the steps of: (a) reacting a metal silicate with a caustic alkali-metal hydroxide to produce a hydroxide of the metal formerly contained in the silicate; (b) reacting carbon dioxide with at least one of a caustic alkali-metal hydroxide and an alkali-metal silicate to produce at least one of an alkali-metal carbonate and an alkali-metal bicarbonate; and (c) reacting the metal hydroxide product of step (a) with at least one of the alkali-metal carbonate and the alkali-metal bicarbonate produced in step (b) to produce a carbonate of the metal formerly contained in the metal silicate of step (a).

  4. Carbonation of metal silicates for long-term CO.sub.2 sequestration

    Science.gov (United States)

    Blencoe, James G [Harriman, TN; Palmer, Donald A [Oliver Springs, TN; Anovitz, Lawrence M [Knoxville, TN; Beard, James S [Martinsville, VA

    2012-02-14

    In a preferred embodiment, the invention relates to a process of sequestering carbon dioxide. The process comprises the steps of: (a) reacting a metal silicate with a caustic alkali-metal hydroxide to produce a hydroxide of the metal formerly contained in the silicate; (b) reacting carbon dioxide with at least one of a caustic alkali-metal hydroxide and an alkali-metal silicate to produce at least one of an alkali-metal carbonate and an alkali-metal bicarbonate; and (c) reacting the metal hydroxide product of step (a) with at least one of the alkali-metal carbonate and the alkali-metal bicarbonate produced in step (b) to produce a carbonate of the metal formerly contained in the metal silicate of step (a).

  5. Non-Topotactic Transformation of Silicate Nanolayers into Mesostructured MFI Zeolite Frameworks During Crystallization.

    Science.gov (United States)

    Berkson, Zachariah J; Messinger, Robert J; Na, Kyungsu; Seo, Yongbeom; Ryoo, Ryong; Chmelka, Bradley F

    2017-05-02

    Mesostructured MFI zeolite nanosheets are established to crystallize non-topotactically through a nanolayered silicate intermediate during hydrothermal synthesis. Solid-state 2D NMR analyses, with sensitivity enhanced by dynamic nuclear polarization (DNP), provide direct evidence of shared covalent 29 Si-O- 29 Si bonds between intermediate nanolayered silicate moieties and the crystallizing MFI zeolite nanosheet framework. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Synthesis of yttrium silicate luminescent materials by sol-gel method

    International Nuclear Information System (INIS)

    Arkhipov, D.V.; Vasina, O.Yu.; Popovich, N.V.; Galaktionov, S.S.; Soshchin, N.P.

    1996-01-01

    Several yttrium-silicate composition with Y 2 O 3 content within 44-56% have been synthesized. it is ascertained that employment of sol-gel technique permits preparation of luminescent materials on yttrium silicate basis, which compare favourably with bath-produced specimens. The influence of phase composition of sol-gel phosphors on basic performance indices: intensity and luminescence spectrum, has been analyzed

  7. Multiple ways of producing intermediate and silicic rocks within Thingmúli and other Icelandic volcanoes

    DEFF Research Database (Denmark)

    Charreteur, Gilles; Tegner, Christian; Haase, Karsten

    2013-01-01

    Major and trace element compositions of rocks and coexisting phenocrysts of the ThingmA(0)li volcano suggest a revision of the existing models for the formation of intermediate and silicic melts in Iceland. The new data define two compositional tholeiitic trends with a significant gap between the...... between the compositions of intermediate and silicic rocks and plate tectonic setting, therefore, should be avoided....

  8. Spectroscopic study of silicate glass structure. Application to the case of iron and magnesium

    International Nuclear Information System (INIS)

    Rossano, Stephanie

    2008-01-01

    During the last 10 years, I focused my research topics on silicate glass structure. More specifically I have been interested by two main components of natural and technological silicate glasses, Fe and Mg. Using solid state spectroscopic methods adapted to the disordered nature of glass coupled to molecular dynamics simulation and modeling or ab initio calculation, I have studied the environment of iron and magnesium and their impact on glass properties. Information on the distribution of environments in glasses have been extracted. (author)

  9. Radiation Shielding Properties Comparison of Pb-Based Silicate, Borate, and Phosphate Glass Matrices

    OpenAIRE

    Ruengsri, Suwimon

    2014-01-01

    Theoretical calculations of mass attenuation coefficients, partial interactions, atomic cross-section, and effective atomic numbers of PbO-based silicate, borate, and phosphate glass systems have been investigated at 662 keV. PbO-based silicate glass has been found with the highest total mass attenuation coefficient and then phosphate and borate glasses, respectively. Compton scattering has been the dominate interaction contributed to the different total attenuation coefficients in each of th...

  10. The earth's gravitational field

    Digital Repository Service at National Institute of Oceanography (India)

    Ramprasad, T.

    . But to say that gravity acts downwards is not correct. Gravity acts down, no matter where you stand on the Earth. It is better to say that on Earth gravity pulls objects towards the centre of the Earth. So no matter where you are on Earth all objects fall... pull than objects at the poles. In combination, the equatorial bulge and the effects of centrifugal force mean that sea-level gravitational acceleration increases from about 9.780 m/s² at the equator to about 9.832 m/s² at the poles, so an object...

  11. Geomagnetic field of earth

    International Nuclear Information System (INIS)

    Delipetrev, Marjan; Delipetrev, Blagoj; Panovska, Sanja

    2008-01-01

    In this paper is introduced the theory of geomagnetic field of the Earth. A homogenous and isotropic sphere is taken for a model of Earth with a bar magnet at its center as a magnetic potential. The understanding of the real origin of geomagnetic field produced from differential rotation of inner core with respect to the outer core of Earth is here presented. Special attention is given to the latest observed data of the established net of geomagnetic repeat stations in the Republic of Macedonia. Finally, the maps of elements of geomagnetic field and the equation for calculation of normal magnetic field of Earth are provided. (Author)

  12. Rare earth octacyanomolybdates(4)

    International Nuclear Information System (INIS)

    Zubritskaya, D.I.; Sergeeva, A.N.; Pisak, Yu.V.

    1980-01-01

    Optimal conditions for synthesis of rare-earth octacyanomolybdates(4) of the Ln 4 [Mo(CN) 8 ] 3 xnH 2 O composition (where Ln is a rare-earth element, other than Pr, Pm, Lu, Tb) have been worked out. The synthesis has been accomplished by neutralization with octacianomolybdic acid with rare-earth carbonates. The composition and structure of the compounds synthesized have been studied by infrared-spectroscopy. It has been established that rare-earth octacyanomolybdates(4) form three isostructural groups

  13. Capturing near-Earth asteroids around Earth

    Science.gov (United States)

    Hasnain, Zaki; Lamb, Christopher A.; Ross, Shane D.

    2012-12-01

    The list of detected near-Earth asteroids (NEAs) is constantly growing. NEAs are likely targets for resources to support space industrialization, as they may be the least expensive source of certain needed raw materials. The limited supply of precious metals and semiconducting elements on Earth may be supplemented or even replaced by the reserves floating in the form of asteroids around the solar system. Precious metals make up a significant fraction NEAs by mass, and even one metallic asteroid of ˜1km size and fair enrichment in platinum-group metals would contain twice the tonnage of such metals already harvested on Earth. There are ˜1000 NEAs with a diameter of greater than 1 km. Capturing these asteroids around the Earth would expand the mining industry into an entirely new dimension. Having such resources within easy reach in Earth's orbit could provide an off-world environmentally friendly remedy for impending terrestrial shortages, especially given the need for raw materials in developing nations. In this paper, we develop and implement a conceptually simple algorithm to determine trajectory characteristics necessary to move NEAs into capture orbits around the Earth. Altered trajectories of asteroids are calculated using an ephemeris model. Only asteroids of eccentricity less than 0.1 have been studied and the model is restricted to the ecliptic plane for simplicity. We constrain the time of retrieval to be 10 years or less, based on considerations of the time to return on investment. For the heliocentric phase, constant acceleration is assumed. The acceleration required for transporting these asteroids from their undisturbed orbits to the sphere of influence of the Earth is the primary output, along with the impulse or acceleration necessary to effect capture to a bound orbit once the Earth's sphere of influence is reached. The initial guess for the constant acceleration is provided by a new estimation method, similar in spirit to Edelbaum's. Based on the

  14. AC electrical breakdown phenomena of epoxy/layered silicate nanocomposite in needle-plate electrodes.

    Science.gov (United States)

    Park, Jae-Jun; Lee, Jae-Young

    2013-05-01

    Epoxy/layered silicate nanocomposite for the insulation of heavy electric equipments were prepared by dispersing 1 wt% of a layered silicate into an epoxy matrix with a homogenizing mixer and then AC electrical treeing and breakdown tests were carried out. Wide-angle X-ray diffraction (WAXD) analysis and transmission electron microscopy (TEM) observation showed that nano-sized monolayers were exfoliated from a multilayered silicate in the epoxy matrix. When the nano-sized silicate layers were incorporated into the epoxy matrix, the breakdown rate in needle-plate electrode geometry was 10.6 times lowered than that of the neat epoxy resin under the applied electrical field of 520.9 kV/mm at 30 degrees C, and electrical tree propagated with much more branches in the epoxy/layered silicate nanocomposite. These results showed that well-dispersed nano-sized silicate layers retarded the electrical tree growth rate. The effects of applied voltage and ambient temperature on the tree initiation, growth, and breakdown rate were also studied, and it was found that the breakdown rate was largely increased, as the applied voltage and ambient temperature increased.

  15. Uranium-thorium silicates, with specific reference to the species in the Witwatersrand reefs

    International Nuclear Information System (INIS)

    Smits, G.

    1987-01-01

    (U,Th)-silicates form two complete series of anhydrous and hydrated species with general formulae (U,Th)SiO 4 and (U,Th)SiO 4 .nH 2 O respectively. The end-members of the anhydrous series are anhydrous coffinite and thorite, and those of the hydrated series, coffinite and thorogummite. Although the silicates are relatively rare in nature, coffinite is a common ore mineral in uranium deposits of the sandstone type. In the Witwatersrand reefs, (U,Th)-silicates are extremely rare in most reefs, except for the Elsburg Reefs on the West Rand Goldfield and the Dominion Reef. In these reefs detrital uraninite has been partly or entirely transformed to (U,Th)-silicates of coffinite composition, but thorite and thorogummite of detrital origin are also found in the Dominion Reef. In leaching tests on polished sections of rock samples containing (U,Th)-silicates, a dilute sulphuric acid solution, to which ferric iron had been added, was used as the lixiviant. It appeared that the dissolution of coffinite is less rapid than that of uraninite and uraniferous leucoxene. However, the reaction of silicates of high thorium content is much slower, and was not completed during the tests

  16. Revisiting classical silicate dissolution rate laws under hydrothermal conditions

    Science.gov (United States)

    Pollet-Villard, Marion; Daval, Damien; Saldi, Giuseppe; Knauss, Kevin; Wild, Bastien; Fritz, Bertrand

    2015-04-01

    apparent modification of silicate dissolution rate over time. In addition, we evidenced that the relation between K-spar dissolution rate and ΔG depends on the crystallographic orientation of the altered surface, and differs from the transition state theory currently implemented into geochemical codes. Importantly, this theoretical curve overestimates the dissolution rates measured in close-to-equilibrium conditions. Taken together, the new findings show promise as a means for improving the accuracy of geochemical simulations. [1] Schott, J., Pokrovsky, O. S., and Oelkers, E. H., 2009. The Link Between Mineral Dissolution/Precipitation Kinetics and Solution Chemistry. Rev Mineral Geochem 70, 207-258. [2] Daval, D., Hellmann, R., Saldi, G. D., Wirth, R., and Knauss, K. G., 2013. Linking nm-scale measurements of the anisotropy of silicate surface reactivity to macroscopic dissolution rate laws: New insights based on diopside. Geochim Cosmochim Acta 107, 121-134.

  17. Sodium silicate solutions from dissolution of glasswastes. Statistical analysis

    Directory of Open Access Journals (Sweden)

    Torres-Carrasco, M.

    2014-05-01

    Full Text Available It has studied the solubility process of four different waste glasses (with different particle sizes, 125 µm in alkaline solutions (NaOH and NaOH/Na₂CO₃ and water as a reference and under different conditions of solubility (at room temperature, at 80°C and a mechano-chemical process. Have established the optimal conditions of solubility and generation of sodium silicates solutions, and these were: the smaller particle size (Se ha estudiado el proceso de solubilidad de cuatro diferentes residuos vítreos (con distintas granulometrías, 125 µm en disoluciones alcalinas de NaOH y NaOH/Na₂CO₃ y agua como medio de referencia y bajo distintas condiciones de solubilidad (a temperatura ambiente, a 80°C y con un proceso mecano-químico. Se han establecido las condiciones óptimas de solubilidad y generación de disoluciones de silicato sódico, y estas son: menor tamaño de partícula del residuo vítreo (inferior a 45 µm, con la disolución de NaOH/Na₂CO₃ y tratamiento térmico a 80°C durante 6 horas de agitación. El análisis estadístico realizado a los resultados obtenidos da importancia a las variables estudiadas y a las interacciones de las mismas. A través de ²⁹Si RMN MAS se ha confirmado la formación, tras los procesos de disolución, de un silicato monomérico, apto para su utilización como activador en la preparación de cementos y hormigones alcalinos.

  18. Modeling Silicate Weathering for Elevated CO2 and Temperature

    Science.gov (United States)

    Bolton, E. W.

    2016-12-01

    A reactive transport model (RTM) is used to assess CO2 drawdown by silicate weathering over a wide range of temperature, pCO2, and infiltration rates for basalts and granites. Although RTM's have been used extensively to model weathering of basalts and granites for present-day conditions, we extend such modeling to higher CO2 that could have existed during the Archean and Proterozoic. We also consider a wide range of surface temperatures and infiltration rates. We consider several model basalt and granite compositions. We normally impose CO2 in equilibrium with the various atmospheric ranges modeled and CO2 is delivered to the weathering zone by aqueous transport. We also consider models with fixed CO2 (aq) throughout the weathering zone as could occur in soils with partial water saturation or with plant respiration, which can strongly influence pH and mineral dissolution rates. For the modeling, we use Kinflow: a model developed at Yale that includes mineral dissolution and precipitation under kinetic control, aqueous speciation, surface erosion, dynamic porosity, permeability, and mineral surface areas via sub-grid-scale grain models, and exchange of volatiles at the surface. Most of the modeling is done in 1D, but some comparisons to 2D domains with heterogeneous permeability are made. We find that when CO2 is fixed only at the surface, the pH tends toward higher values for basalts than granites, in large part due to the presence of more divalent than monovalent cations in the primary minerals, tending to decrease rates of mineral dissolution. Weathering rates increase (as expected) with increasing CO2 and temperature. This modeling is done with the support of the Virtual Planetary Laboratory.

  19. EARTH FROM SPACE

    Indian Academy of Sciences (India)

    Table of contents. EARTH FROM SPACE · Slide 2 · Earth System · Slide 4 · Global water cycle · Slide 6 · Slide 7 · Direct Observations of Recent Climate Change · Slide 9 · Slide 10 · Snow cover and Arctic sea ice are decreasing · Polar Melting & Global Heat Transport · Antarctica: Melting and Thickening · Slide 14 · Slide 15.

  20. Earth and Universe

    Energy Technology Data Exchange (ETDEWEB)

    Kosygin, Yu A

    1986-12-01

    Rocks, the age of which according to certain data exceeds considerably the recognized age of the Earth and approximates the age of the Universe, have been detected on the Earth. There is a necessity to coordinate the geological data with cosmological structures.

  1. Hands On Earth Science.

    Science.gov (United States)

    Weisgarber, Sherry L.; Van Doren, Lisa; Hackathorn, Merrianne; Hannibal, Joseph T.; Hansgen, Richard

    This publication is a collection of 13 hands-on activities that focus on earth science-related activities and involve students in learning about growing crystals, tectonics, fossils, rock and minerals, modeling Ohio geology, geologic time, determining true north, and constructing scale-models of the Earth-moon system. Each activity contains…

  2. Introducing Earth's Orbital Eccentricity

    Science.gov (United States)

    Oostra, Benjamin

    2015-01-01

    Most students know that planetary orbits, including Earth's, are elliptical; that is Kepler's first law, and it is found in many science textbooks. But quite a few are mistaken about the details, thinking that the orbit is very eccentric, or that this effect is somehow responsible for the seasons. In fact, the Earth's orbital eccentricity is…

  3. Earth System Science Project

    Science.gov (United States)

    Rutherford, Sandra; Coffman, Margaret

    2004-01-01

    For several decades, science teachers have used bottles for classroom projects designed to teach students about biology. Bottle projects do not have to just focus on biology, however. These projects can also be used to engage students in Earth science topics. This article describes the Earth System Science Project, which was adapted and developed…

  4. Aluminosilicate Dissolution and Silicate Carbonation during Geologic CO2 Sequestration

    Science.gov (United States)

    Min, Yujia

    Geologic CO2 sequestration (GCS) is considered a promising method to reduce anthropogenic CO2 emission. Assessing the supercritical CO2 (scCO2) gas or liquid phase water (g, l)-mineral interactions is critical to evaluating the viability of GCS processes. This work contributes to our understanding of geochemical reactions at CO 2-water (g, l)-mineral interfaces, by investigating the dissolution of aluminosilicates in CO2-acidified water (l). Plagioclase and biotite were chosen as model minerals in reservoir rock and caprock, respectively. To elucidate the effects of brine chemistry, first, the influences of cations in brine including Na, Ca, and K, have been investigated. In addition to the cations, the effects of abundant anions including sulfate and oxalate were also examined. Besides the reactions in aqueous phase, we also examine the carbonation of silicates in water (g)-bearing supercritical CO2 (scCO2) under conditions relevant to GCS. For the metal carbonation, in particular, the effects of particle sizes, water, temperature, and pressure on the carbonation of wollastonite were systematically examined. For understanding the cations effects in brine, the impacts of Na concentrations up to 4 M on the dissolution of plagioclase and biotite were examined. High concentrations of Na significantly inhibited plagioclase dissolution by competing adsorption with proton and suppressing proton-promoted dissolution. Ca has a similar effect to Na, and their effects did not suppress each other when Na and Ca co-existed. For biotite, the inhibition effects of Na coupled with an enhancing effect due to ion exchange reaction between Na and interlayer K, which cracked the basal surfaces of biotite. The K in aqueous phase significantly inhibited the dissolution. If the biotite is equilibrated with NaCl solutions initially, the biotite dissolved faster than the original biotite and the dissolution was inhibited by Na and K in brine. The outcomes improve our current knowledge of

  5. Atmospheres of partially differentiated super-Earth exoplanets

    Science.gov (United States)

    Schaefer, Laura; Sasselov, Dimitar

    2015-11-01

    Terrestrial exoplanets have been discovered in a range of sizes, densities and orbital locations that defy our expectations based upon the Solar System. Planets discovered to date with radii less than ~1.5-1.6 Earth radii all seem to fall on an iso-density curve with the Earth [1]. However, mass and radius determinations, which depend on the known properties of the host star, are not accurate enough to distinguish between a fully differentiated three-layer planet (core, mantle, ocean/atmosphere) and an incompletely differentiated planet [2]. Full differentiation of a planet will depend upon the conditions at the time of accretion, including the abundance of short-lived radioisotopes, which will vary from system to system, as well as the number of giant impacts the planet experiences. Furthermore, separation of metal and silicates at the much larger pressures found inside super-Earths will depend on how the chemistry of these materials change at high pressures. There are therefore hints emerging that not all super-Earths will be fully differentiated. Incomplete differentiation will result in a more reduced mantle oxidation state and may have implications for the composition of an outgassed atmosphere. Here we will present the first results from a chemical equilibrium model of the composition of such an outgassed atmosphere and discuss the possibility of distinguishing between fully and incompletely differentiated planets through atmospheric observations.[1] Rogers, L. 2015. ApJ, 801, 41. [2] Zeng, L. & Sasselov, D. 2013. PASP, 125, 227.

  6. Two Earth-sized planets orbiting Kepler-20.

    Science.gov (United States)

    Fressin, Francois; Torres, Guillermo; Rowe, Jason F; Charbonneau, David; Rogers, Leslie A; Ballard, Sarah; Batalha, Natalie M; Borucki, William J; Bryson, Stephen T; Buchhave, Lars A; Ciardi, David R; Désert, Jean-Michel; Dressing, Courtney D; Fabrycky, Daniel C; Ford, Eric B; Gautier, Thomas N; Henze, Christopher E; Holman, Matthew J; Howard, Andrew; Howell, Steve B; Jenkins, Jon M; Koch, David G; Latham, David W; Lissauer, Jack J; Marcy, Geoffrey W; Quinn, Samuel N; Ragozzine, Darin; Sasselov, Dimitar D; Seager, Sara; Barclay, Thomas; Mullally, Fergal; Seader, Shawn E; Still, Martin; Twicken, Joseph D; Thompson, Susan E; Uddin, Kamal

    2011-12-20

    Since the discovery of the first extrasolar giant planets around Sun-like stars, evolving observational capabilities have brought us closer to the detection of true Earth analogues. The size of an exoplanet can be determined when it periodically passes in front of (transits) its parent star, causing a decrease in starlight proportional to its radius. The smallest exoplanet hitherto discovered has a radius 1.42 times that of the Earth's radius (R(⊕)), and hence has 2.9 times its volume. Here we report the discovery of two planets, one Earth-sized (1.03R(⊕)) and the other smaller than the Earth (0.87R(⊕)), orbiting the star Kepler-20, which is already known to host three other, larger, transiting planets. The gravitational pull of the new planets on the parent star is too small to measure with current instrumentation. We apply a statistical method to show that the likelihood of the planetary interpretation of the transit signals is more than three orders of magnitude larger than that of the alternative hypothesis that the signals result from an eclipsing binary star. Theoretical considerations imply that these planets are rocky, with a composition of iron and silicate. The outer planet could have developed a thick water vapour atmosphere.

  7. Generation of Silicic Melts in the Early Izu-Bonin Arc Recorded by Detrital Zircons in Proximal Arc Volcaniclastic Rocks From the Philippine Sea

    Science.gov (United States)

    Barth, A. P.; Tani, K.; Meffre, S.; Wooden, J. L.; Coble, M. A.; Arculus, R. J.; Ishizuka, O.; Shukle, J. T.

    2017-10-01

    A 1.2 km thick Paleogene volcaniclastic section at International Ocean Discovery Program Site 351-U1438 preserves the deep-marine, proximal record of Izu-Bonin oceanic arc initiation, and volcano evolution along the Kyushu-Palau Ridge (KPR). Pb/U ages and trace element compositions of zircons recovered from volcaniclastic sandstones preserve a remarkable temporal record of juvenile island arc evolution. Pb/U ages ranging from 43 to 27 Ma are compatible with provenance in one or more active arc edifices of the northern KPR. The abundances of selected trace elements with high concentrations provide insight into the genesis of U1438 detrital zircon host melts, and represent useful indicators of both short and long-term variations in melt compositions in arc settings. The Site U1438 zircons span the compositional range between zircons from mid-ocean ridge gabbros and zircons from relatively enriched continental arcs, as predicted for melts in a primitive oceanic arc setting derived from a highly depleted mantle source. Melt zircon saturation temperatures and Ti-in-zircon thermometry suggest a provenance in relatively cool and silicic melts that evolved toward more Th and U-rich compositions with time. Th, U, and light rare earth element enrichments beginning about 35 Ma are consistent with detrital zircons recording development of regional arc asymmetry and selective trace element-enriched rear arc silicic melts as the juvenile Izu-Bonin arc evolved.

  8. Polymer/Silicate Nanocomposites Used to Manufacture Gas Storage Tanks With Reduced Permeability

    Science.gov (United States)

    Campbell, Sandi G.; Johnston, Chris

    2004-01-01

    Over the past decade, there has been considerable research in the area of polymer-layered silicate nanocomposites. This research has shown that the dispersion of small amounts of an organically modified layered silicate improves the polymer strength, modulus, thermal stability, and barrier properties. There have been several reports on the dispersion of layered silicates in an epoxy matrix. Potential enhancements to the barrier properties of epoxy/silicate nanocomposites make this material attractive for low permeability tankage. Polymer matrix composites (PMCs) have several advantages for cryogenic storage tanks. They are lightweight, strong, and stiff; therefore, a smaller fraction of a vehicle's potential payload capacity is used for propellant storage. Unfortunately, the resins typically used to make PMC tanks have higher gas permeability than metals. This can lead to hydrogen loss through the body of the tank instead of just at welds and fittings. One approach to eliminate this problem is to build composite tanks with thin metal liners. However, although these tanks provide good permeability performance, they suffer from a substantial mismatch in the coefficient of thermal expansion, which can lead to failure of the bond between the liner and the body of the tank. Both problems could be addressed with polymersilicate nanocomposites, which exhibit reduced hydrogen permeability, making them potential candidates for linerless PMC tanks. Through collaboration with Northrop Grumman and Michigan State University, nanocomposite test tanks were manufactured for the NASA Glenn Research Center, and the helium permeability was measured. An organically modified silicate was prepared at Michigan State University and dispersed in an epoxy matrix (EPON 826/JeffamineD230). The epoxy/silicate nanocomposites contained either 0 or 5 wt% of the organically modified silicate. The tanks were made by filament winding carbon fibers with the nanocomposite resin. Helium permeability

  9. EXPERIMENTAL INVESTIGATION OF IRRADIATION-DRIVEN HYDROGEN ISOTOPE FRACTIONATION IN ANALOGS OF PROTOPLANETARY HYDROUS SILICATE DUST

    Energy Technology Data Exchange (ETDEWEB)

    Roskosz, Mathieu; Remusat, Laurent [IMPMC, CNRS UMR 7590, Sorbonne Universités, Université Pierre et Marie Curie, IRD, Muséum National d’Histoire Naturelle, CP 52, 57 rue Cuvier, Paris F-75231 (France); Laurent, Boris; Leroux, Hugues, E-mail: mathieu.roskosz@mnhn.fr [Unité Matériaux et Transformations, Université Lille 1, CNRS UMR 8207, Bâtiment C6, F-59655 Villeneuve d’Ascq (France)

    2016-11-20

    The origin of hydrogen in chondritic components is poorly understood. Their isotopic composition is heavier than the solar nebula gas. In addition, in most meteorites, hydrous silicates are found to be lighter than the coexisting organic matter. Ionizing irradiation recently emerged as an efficient hydrogen fractionating process in organics, but its effect on H-bearing silicates remains essentially unknown. We report the evolution of the D/H of hydrous silicates experimentally irradiated by electrons. Thin films of amorphous silica, amorphous “serpentine,” and pellets of crystalline muscovite were irradiated at 4 and 30 keV. For all samples, irradiation leads to a large hydrogen loss correlated with a moderate deuterium enrichment of the solid residue. The entire data set can be described by a Rayleigh distillation. The calculated fractionation factor is consistent with a kinetically controlled fractionation during the loss of hydrogen. Furthermore, for a given ionizing condition, the deuteration of the silicate residues is much lower than the deuteration measured on irradiated organic macromolecules. These results provide firm evidence of the limitations of ionizing irradiation as a driving mechanism for D-enrichment of silicate materials. The isotopic composition of the silicate dust cannot rise from a protosolar to a chondritic signature during solar irradiations. More importantly, these results imply that irradiation of the disk naturally induces a strong decoupling of the isotopic signatures of coexisting organics and silicates. This decoupling is consistent with the systematic difference observed between the heavy organic matter and the lighter water typically associated with minerals in the matrix of most carbonaceous chondrites.

  10. Electrical conductivity studies of nanocrystalline lanthanum silicate synthesized by sol-gel route

    International Nuclear Information System (INIS)

    Nallamuthu, N.; Prakash, I.; Satyanarayana, N.; Venkateswarlu, M.

    2011-01-01

    Research highlights: → Nanocrystalline La 10 Si 6 O 27 material was synthesized by sol-gel method. → TG/DTA curves predicted the thermal behavior of the material. → FTIR spectra confirmed the formation of SiO 4 and La-O network in the La 10 Si 6 O 27 . → XRD patterns confirmed the formation of pure crystalline La 10 Si 6 O 27 phase. → The grain interior and the grain boundary conductivities are evaluated. - Abstract: Nanocrystalline apatite type structured lanthanum silicate (La 10 Si 6 O 27 ) sample was synthesized by sol-gel process. Thermal behavior of the dried gel of lanthanum silicate sample was studied using TG/DTA. The structural coordination of the dried gel of lanthanum silicate, calcined at various temperatures, was identified from the observed FTIR spectral results. The observed XRD patterns of the calcined dried gel were compared with the ICDD data and confirmed the formation of crystalline lanthanum silicate phase. The average crystalline size of La 10 Si 6 O 27 was calculated using the Scherrer formula and it is found to be ∼80 nm. The observed SEM images of the lanthanum silicate indicate the formation of the spherical particles and the existence of O, Si and La in the lanthanum silicate are confirmed from the SEM-EDX spectrum. The grain and grain boundary conductivities are evaluated by analyzing the measured impedance data, using winfit software, obtained at different temperatures, of La 10 Si 6 O 27 sample. Also, the observed grain and grain boundary conductivity behaviors of the La 10 Si 6 O 27 sample are analysed using brick layer model. The electrical permittivity and electrical modulus were calculated from the measured impedance data and were analyzed by fitting through the Havriliak and Negami function to describe the dielectric relaxation behavior of the nanocrystalline lanthanum silicate.

  11. Isotopes as clues to the origin and earliest differentiation history of the Earth.

    Science.gov (United States)

    Jacobsen, Stein B; Ranen, Michael C; Petaev, Michael I; Remo, John L; O'Connell, Richard J; Sasselov, Dimitar D

    2008-11-28

    Measurable variations in (182)W/(183)W, (142)Nd/(144)Nd, (129)Xe/(130)Xe and (136)XePu/(130)Xe in the Earth and meteorites provide a record of accretion and formation of the core, early crust and atmosphere. These variations are due to the decay of the now extinct nuclides (182)Hf, (146)Sm, (129)I and (244)Pu. The (l82)Hf-(182)W system is the best accretion and core-formation chronometer, which yields a mean time of Earth's formation of 10Myr, and a total time scale of 30Myr. New laser shock data at conditions comparable with those in the Earth's deep mantle subsequent to the giant Moon-forming impact suggest that metal-silicate equilibration was rapid enough for the Hf-W chronometer to reliably record this time scale. The coupled (146)Sm-(147)Sm chronometer is the best system for determining the initial silicate differentiation (magma ocean crystallization and proto-crust formation), which took place at ca 4.47Ga or perhaps even earlier. The presence of a large (129)Xe excess in the deep Earth is consistent with a very early atmosphere formation (as early as 30Myr); however, the interpretation is complicated by the fact that most of the atmospheric Xe may be from a volatile-rich late veneer.

  12. Earth as art three

    Science.gov (United States)

    ,

    2010-01-01

    For most of us, deserts, mountains, river valleys, coastlines even dry lakebeds are relatively familiar features of the Earth's terrestrial environment. For earth scientists, they are the focus of considerable scientific research. Viewed from a unique and unconventional perspective, Earth's geographic attributes can also be a surprising source of awe-inspiring art. That unique perspective is space. The artists for the Earth as Art Three exhibit are the Landsat 5 and Landsat 7 satellites, which orbit approximately 705 kilometers (438 miles) above the Earth's surface. While studying the images these satellites beam down daily, researchers are often struck by the sheer beauty of the scenes. Such images inspire the imagination and go beyond scientific value to remind us how stunning, intricate, and simply amazing our planet's features can be. Instead of paint, the medium for these works of art is light. But Landsat satellite sensors don't see light as human eyes do; instead, they see radiant energy reflected from Earth's surface in certain wavelengths, or bands, of red, green, blue, and infrared light. When these different bands are combined into a single image, remarkable patterns, colors, and shapes emerge. The Earth as Art Three exhibit provides fresh and inspiring glimpses of different parts of our planet's complex surface. The images in this collection were chosen solely based on their aesthetic appeal. Many of the images have been manipulated to enhance color variations or details. They are not intended for scientific interpretation only for your viewing pleasure. Enjoy!

  13. Earth Science Informatics - Overview

    Science.gov (United States)

    Ramapriyan, H. K.

    2017-01-01

    Over the last 10-15 years, significant advances have been made in information management, there are an increasing number of individuals entering the field of information management as it applies to Geoscience and Remote Sensing data, and the field of informatics has come to its own. Informatics is the science and technology of applying computers and computational methods to the systematic analysis, management, interchange, and representation of science data, information, and knowledge. Informatics also includes the use of computers and computational methods to support decision making and applications. Earth Science Informatics (ESI, a.k.a. geoinformatics) is the application of informatics in the Earth science domain. ESI is a rapidly developing discipline integrating computer science, information science, and Earth science. Major national and international research and infrastructure projects in ESI have been carried out or are on-going. Notable among these are: the Global Earth Observation System of Systems (GEOSS), the European Commissions INSPIRE, the U.S. NSDI and Geospatial One-Stop, the NASA EOSDIS, and the NSF DataONE, EarthCube and Cyberinfrastructure for Geoinformatics. More than 18 departments and agencies in the U.S. federal government have been active in Earth science informatics. All major space agencies in the world, have been involved in ESI research and application activities. In the United States, the Federation of Earth Science Information Partners (ESIP), whose membership includes over 180 organizations (government, academic and commercial) dedicated to managing, delivering and applying Earth science data, has been working on many ESI topics since 1998. The Committee on Earth Observation Satellites (CEOS)s Working Group on Information Systems and Services (WGISS) has been actively coordinating the ESI activities among the space agencies.The talk will present an overview of current efforts in ESI, the role members of IEEE GRSS play, and discuss

  14. Creep of Sylramic-iBN Fiber Tows at Elevated Temperature in Air and in Silicic Acid-Saturated Steam

    Science.gov (United States)

    2015-06-01

    CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM ...protection in the United States. AFIT-ENY-15-J-46 CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM ...DISTRIBUTION UNLIMITED. AFIT-ENY-15-J-46 CREEP OF SYLRAMIC-iBN FIBER TOWS AT ELEVATED TEMPERATURE IN AIR AND IN SILICIC ACID-SATURATED STEAM

  15. Origin and mixing timescale of Earth's late veneer

    Science.gov (United States)

    Prescher, C.; Allu Peddinti, D.; Bell, E. A.; Bello, L.; Cernok, A.; Ghosh, N.; Tucker, J.; Wielicki, M. M.; Zahnle, K. J.

    2012-12-01

    Experimental studies on the partitioning behavior of highly siderophile elements (HSE) between silicate and metallic melts imply that the Earth's mantle should have been highly depleted in these elements by core formation in an early magma ocean. However, present HSE contents of the Earth's mantle are ~3 orders of magnitude higher than that expected by experiments. The apparent over-abundance of HSE has commonly been explained by the addition of meteoritic material in the "late veneer" which describes the exogenous mass addition following the moon forming impact and concluding with the late heavy bombardment at ~3.8-3.9 Ga. The strongest evidence for this theory is that the platinum group element (PGE) contents in today's mantle are present in chondritic relative abundances, as opposed to a fractionated pattern expected with metal-silicate partitioning. Archean komatiites indicate that the PGE content of the Earth's mantle increased from about half their present abundances at 3.5 Ga to their present abundances at 2.9 Ga. This secular increase in PGE content suggests a progressive mixing of the late veneer material into the Earth's mantle. However, this time scale also implies that the whole mantle was relatively well mixed by 2.9 Ga. We use a compilation of existing isotopic and trace element data in order to constrain the origin and composition of the late veneer. We use PGE abundances, W abundances and W isotopic compositions in chondritic meteorites and the primitive upper mantle to compute the amount of mass delivered during the late veneer and find the late veneer mass to be ~0.6 % the mass of the bulk silicate Earth (consistent with earlier estimates). We also use the 187Re-187Os and 190Pt-186Os systems to constrain the composition and timing of delivery of the impacting population. We model the efficiency of mantle mixing in this time frame by using 3-dimensional numerical geodynamical simulations and geochemical constraints. Initial parameters include the

  16. Project Earth Science

    CERN Document Server

    Holt, Geoff

    2011-01-01

    Project Earth Science: Astronomy, Revised 2nd Edition, involves students in activities that focus on Earth's position in our solar system. How do we measure astronomical distances? How can we look back in time as we gaze across vast distances in space? How would our planet be different without its particular atmosphere and distance to our star? What are the geometries among Earth, the Moon, and the Sun that yield lunar phases and seasons? Students explore these concepts and others in 11 teacher-tested activities.

  17. Earth formation porosity log

    International Nuclear Information System (INIS)

    Smith, H.D.; Smith, M.P.; Schultz, W.E.

    1977-01-01

    A method for determining the porosity of earth formations in the vicinity of a cased well borehole is described, comprising the steps of: irradiating the earth formations in the vicinity of the cased well borehole with fast neutrons from a source of fast neutrons passed into the borehole; and generating a signal representative of the fast neutron population present in the well borehole at a location in the borehole, the signal is functionally related to the porosity of the earth formations in the vicinity of the borehole

  18. Earth before life.

    Science.gov (United States)

    Marzban, Caren; Viswanathan, Raju; Yurtsever, Ulvi

    2014-01-09

    A recent study argued, based on data on functional genome size of major phyla, that there is evidence life may have originated significantly prior to the formation of the Earth. Here a more refined regression analysis is performed in which 1) measurement error is systematically taken into account, and 2) interval estimates (e.g., confidence or prediction intervals) are produced. It is shown that such models for which the interval estimate for the time origin of the genome includes the age of the Earth are consistent with observed data. The appearance of life after the formation of the Earth is consistent with the data set under examination.

  19. Hydration water and microstructure in calcium silicate and aluminate hydrates

    International Nuclear Information System (INIS)

    Fratini, Emiliano; Ridi, Francesca; Chen, Sow-Hsin; Baglioni, Piero

    2006-01-01

    Understanding the state of the hydration water and the microstructure development in a cement paste is likely to be the key for the improvement of its ultimate strength and durability. In order to distinguish and characterize the reacted and unreacted water, the single-particle dynamics of water molecules in hydrated calcium silicates (C 3 S, C 2 S) and aluminates (C 3 A, C 4 AF) were studied by quasi-elastic neutron scattering, QENS. The time evolution of the immobile fraction represents the hydration kinetics and the mobile fraction follows a non-Debye relaxation. Less sophisticated, but more accessible and cheaper techniques, like differential scanning calorimetry, DSC, and near-infrared spectroscopy, NIR, were validated through QENS results and they allow one to easily and quantitatively follow the cement hydration kinetics and can be widely applied on a laboratory scale to understand the effect of additives (i.e., superplasticizers, cellulosic derivatives, etc) on the thermodynamics of the hydration process. DSC provides information on the free water index and on the activation energy involved in the hydration process while the NIR band at 7000 cm -1 monitors, at a molecular level, the increase of the surface-interacting water. We report as an example the effect of two classes of additives widely used in the cement industry: superplasticizers, SPs, and cellulose derivatives. SPs interact at the solid surface, leading to a consistent increment of the activation energy for the processes of nucleation and growth of the hydrated phases. In contrast, the cellulosic additives do not affect the nucleation and growth activation energy, but cause a significant increment in the water availability: in other words the hydration process is more efficient without any modification of the solid/liquid interaction, as also evidenced by the 1 H-NMR. Additional information is obtained by scanning electron microscopy (SEM), ultra small angle neutron scattering (USANS) and wide

  20. Sulfur concentration at sulfide saturation (SCSS) in magmatic silicate melts

    Science.gov (United States)

    Liu, Yanan; Samaha, Naji-Tom; Baker, Don R.

    2007-04-01

    The sulfur concentration in silicate melts at sulfide saturation (SCSS) was experimentally investigated in a temperature range from 1150 to 1450 °C and a pressure range from 500 MPa to 1 GPa in a piston-cylinder apparatus. The investigated melt compositions varied from rhyolitic to basaltic and water concentrations varied from 0 to ˜9 wt%. All experiments were saturated with FeS melt or pyrrhotite crystals. Temperature was confirmed to have a positive effect on the SCSS. Experimental oxygen fugacities were either near the carbon-carbon monoxide buffer or one log unit above the nickel-nickel oxide buffer, and found to positively affect the SCSS. Combining our results with data from the literature we constructed a model to predict the SCSS in melts ranging in composition from komatiitic to rhyolitic, with water concentrations from 0 to 9 wt%, at pressures from 1 bar to 9 GPa and oxygen fugacities between ˜2 log units below the fayalite-magnetite-quartz buffer to ˜2 log units above it. The coefficients were obtained by multiple linear regression of experimental data and the best model found for the prediction of the SCSS is: ln(Sinppm)=11.35251-{4454.6}/{T}-0.03190{P}/{T}+0.71006ln(MFM)-1.98063[(MFM)(XO)]+0.21867ln(XO)+0.36192lnX where P is in bar, T is in K, MFM is a compositional parameter describing the melt based upon cation mole fractions: MFM={Na+K+2(Ca+Mg+Fe)}/{Si×(Al+Fe)}, XO is the mole fraction of water in the melt, and X is the mole fraction of FeO in the melt. This model was independently tested against experiments performed on anhydrous and hydrous melts in the temperature range from 800 to 1800 °C and 1-9 GPa. The model typically predicts the measured values of the natural log of the SCSS (in ppm) for komatiitic to rhyolitic (˜42 to ˜74 wt% SiO 2) melts to within 5% relative, but is less accurate for high-silica (>76 wt% SiO 2) rhyolites, especially those with molar ratios of iron to sulfur below 2. We demonstrate how this model can be used with