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Sample records for subordinate calcite calcium

  1. Atomistic simulations of calcium uranyl(VI) carbonate adsorption on calcite and stepped-calcite surfaces.

    Science.gov (United States)

    Doudou, Slimane; Vaughan, David J; Livens, Francis R; Burton, Neil A

    2012-07-17

    Adsorption of actinyl ions onto mineral surfaces is one of the main mechanisms that control the migration of these ions in environmental systems. Here, we present computational classical molecular dynamics (MD) simulations to investigate the behavior of U(VI) in contact with different calcite surfaces. The calcium-uranyl-carbonate [Ca(2)UO(2)(CO(3))(3)] species is shown to display both inner- and outer-sphere adsorption to the flat {101̅4} and the stepped {314̅8} and {31̅2̅16} planes of calcite. Free energy calculations, using the umbrella sampling method, are employed to simulate adsorption paths of the same uranyl species on the different calcite surfaces under aqueous condition. Outer-sphere adsorption is found to dominate over inner-sphere adsorption because of the high free energy barrier of removing a uranyl-carbonate interaction and replacing it with a new uranyl-surface interaction. An important binding mode is proposed involving a single vicinal water monolayer between the surface and the sorbed complex. From the free energy profiles of the different calcite surfaces, the uranyl complex was also found to adsorb preferentially on the acute-stepped {314̅8} face of calcite, in agreement with experiment.

  2. Evaluation of Various Synthesis Methods for Calcite-Precipitated Calcium Carbonate (PCC) Formation

    Energy Technology Data Exchange (ETDEWEB)

    Ramakrishna, Chilakala [Hanil Cement Corporation, Danyang (Korea, Republic of); Thenepalli, Thriveni; Ahn, Ji Whan [Korea Institute of Geoscience and Mineral Resources, Daejeon (Korea, Republic of)

    2017-06-15

    This review paper evaluates different kinds of synthesis methods for calcite precipitated calcium carbonates by using different materials. The various processing routes of calcite with different compositions are reported and the possible optimum conditions required to synthesize a desired particle sizes of calcite are predicted. This paper mainly focuses on that the calcite morphology and size of the particles by carbonation process using loop reactors. In this regard, we have investigated various parameters such as CO{sub 2} flow rate, Ca (OH){sub 2} concentration, temperature, pH effect, reaction time and loop reactor mechanism with orifice diameter. The research results illustrate the formation of well-defined and pure calcite crystals with controlled crystal growth and particle size, without additives or organic solvents. The crystal growth and particle size can be controlled, and smaller sizes are obtained by decreasing the Ca (OH){sub 2} concentration and increasing the CO{sub 2} flow rate at lower temperatures with suitable pH. The crystal structure of obtained calcite was characterized by using X-ray diffraction method and the morphology by scanning electron microscope (SEM). The result of x-ray diffraction recognized that the calcite phase of calcium carbonate was the dominating crystalline structure.

  3. Incorporation of Mg and Sr in calcite of cultured benthic foraminifera: impact of calcium concentration and associated calcite saturation state

    Directory of Open Access Journals (Sweden)

    M. Raitzsch

    2010-03-01

    Full Text Available We investigated the effect of the calcium concentration in seawater and thereby the calcite saturation state (Ω on the magnesium and strontium incorporation into benthic foraminiferal calcite under laboratory conditions. For this purpose individuals of the shallow-water species Heterostegina depressa (precipitating high-Mg calcite, symbiont-bearing and Ammonia tepida (low-Mg calcite, symbiont-barren were cultured in media under a range of [Ca2+], but similar Mg/Ca ratios. Trace element/Ca ratios of newly formed calcite were analysed with Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS and normalized to the seawater elemental composition using the equation DTE=(TE/Cacalcite/(TE/Caseawater. The culturing study shows that DMg of A. tepida significantly decreases with increasing Ω at a gradient of −4.3×10−5 per Ω unit. The DSr value of A. tepida does not change with Ω, suggesting that fossil Sr/Ca in this species may be a potential tool to reconstruct past variations in seawater Sr/Ca. Conversely, DMg of H. depressa shows only a minor decrease with increasing Ω, while DSr increases considerably with Ω at a gradient of 0.009 per Ω unit. The different responses to seawater chemistry of the two species may be explained by a difference in the calcification pathway that is, at the same time, responsible for the variation in the total Mg incorporation between the two species. Since the Mg/Ca ratio in H. depressa is 50–100 times higher than that of A. tepida, it is suggested that the latter exhibits a mechanism that decreases the Mg/Ca ratio of the calcification fluid, while the high-Mg calcite forming species may not have this physiological tool. If the dependency of Mg incorporation on seawater [Ca2+] is also valid for deep

  4. Modeling results of calcium-containing minerals precipitation in the alkaline hydrotherms of Baikal Rift Zone: calcite and dolomite

    Science.gov (United States)

    Tokarenko, O. G.; Zippa, E. V.

    2015-11-01

    The calculation modeling results of the nitric hydrotherms saturation in Baikal Rift Zone with calcite and dolomite are presented. The calcite and dolomite make the carbonate barrier to thermal waters equilibrium with primary minerals of igneous rocks. In the research territory, there are three main types of geochemical thermal waters which are characterized by the saturation degree with the calcite and dolomite and the proportion of precipitating minerals phases. It has been established that nitric thermal waters-rock system has equilibrium with these minerals, which leads to bonding migrated from the rocks calcium and magnesium by the secondary formed minerals - calcite and dolomite.

  5. Sea Urchin Spine Calcite Forms via a Transient Amorphous Calcium Carbonate Phase

    Science.gov (United States)

    Politi, Yael; Arad, Talmon; Klein, Eugenia; Weiner, Steve; Addadi, Lia

    2004-11-01

    The skeletons of adult echinoderms comprise large single crystals of calcite with smooth convoluted fenestrated morphologies, raising many questions about how they form. By using water etching, infrared spectroscopy, electron diffraction, and environmental scanning electron microscopy, we show that sea urchin spine regeneration proceeds via the initial deposition of amorphous calcium carbonate. Because most echinoderms produce the same type of skeletal material, they probably all use this same mechanism. Deposition of transient amorphous phases as a strategy for producing single crystals with complex morphology may have interesting implications for the development of sophisticated materials.

  6. Calcite growth rates as a function of aqueous calcium-to-carbonate ratio, saturation index and strontium concentration

    Energy Technology Data Exchange (ETDEWEB)

    Bracco, Jacquelyn N [ORNL; Grantham, Ms. Meg [Georgia Institute of Technology; Stack, Andrew G [ORNL

    2012-01-01

    Using in situ atomic force microscopy, the growth rates of the obtuse and acute step orientations on the calcite surface were measured at two saturation indices as a function of the aqueous calcium-to-carbonate ratio and aqueous strontium concentration. The amount of strontium required to inhibit growth was found to correlate with the aqueous calcium concentration, but did not correlate with carbonate. This suggests that strontium inhibits attachment of calcium ions to the reactive sites on the calcite surface. Strontium/calcium cation exchange selectivity coefficients for those sites, Kex, of 1.09 0.09 and 1.44 0.19 are estimated for the obtuse and acute step orientations, respectively. The implication of this finding is that to avoid poisoning calcite growth, the concentration of calcium should be higher than the quotient of the strontium concentration and Kex, regardless of saturation state. Additionally, analytical models of nucleation and propagation of steps are expanded from previous work to capture growth rates of these steps at multiple saturation indices and the effect of strontium. This work will have broader implications for naturally occurring or engineered calcite growth, such as to sequester subsurface strontium contamination.

  7. Nanoscale observations of the effect of citrate on calcium oxalate precipitation on calcite surfaces.

    Science.gov (United States)

    Burgos-Cara, Alejandro; Ruiz-Agudo, Encarnacion; Putnis, Christine V.

    2016-04-01

    Calcium oxalate (CaC2O4ṡxH2O) minerals are naturally occurring minerals found in fossils, plants, kidney stones and is a by-product in some processes such as paper, food and beverage production [1,2]. In particular, calcium oxalate monohydrate phase (COM) also known as whewellite (CaC2O4ṡH2O), is the most frequently reported mineral phase found in urinary and kidney stones together with phosphates. Organic additives are well known to play a key role in the formation of minerals in both biotic and abiotic systems, either facilitating their precipitation or hindering it. In this regard, recent studies have provided direct evidence demonstrating that citrate species could enhance dissolution of COM and inhibit their precipitation. [3,4] The present work aims at evauate the influence of pH, citrate and oxalic acid concentrations in calcium oxalate precipitation on calcite surfaces (Island Spar, Chihuahua, Mexico) through in-situ nanoscale observation using in situ atomic force microscopy (AFM, Multimode, Bruker) in flow-through experiments. Changes in calcium oxalate morphologies and precipitated phases were observed, as well as the inhibitory effect of citrate on calcium oxalate precipitation, which also lead to stabilization an the amorphous calcium oxalate phase. [1] K.D. Demadis, M. Öner, Inhibitory effects of "green"additives on the crystal growth of sparingly soluble salts, in: J.T. Pearlman (Ed.), Green Chemistry Research Trends, Nova Science Publishers Inc., New York, 2009, pp. 265-287. [2] M. Masár, M. Zuborová, D. Kaniansky, B. Stanislawski, Determination of oxalate in beer by zone electrophoresis on a chip with conductivity detection, J. Sep. Sci. 26 (2003) 647-652. [3] Chutipongtanate S, Chaiyarit S, Thongboonkerd V. Citrate, not phosphate, can dissolve calcium oxalate monohydrate crystals and detach these crystals from renal tubular cells. Eur J Pharmacol 2012;689:219-25. [4] Weaver ML, Qiu SR, Hoyer JR, Casey WH, Nancollas GH, De Yoreo JJ

  8. Altervalent substitution of sodium for calcium in biogenic calcite and aragonite

    Science.gov (United States)

    Yoshimura, Toshihiro; Tamenori, Yusuke; Suzuki, Atsushi; Kawahata, Hodaka; Iwasaki, Nozomu; Hasegawa, Hiroshi; Nguyen, Luan T.; Kuroyanagi, Azumi; Yamazaki, Toshitsugu; Kuroda, Junichiro; Ohkouchi, Naohiko

    2017-04-01

    Sodium concentrations in biogenic CaCO3 are several thousands of parts per million, and, on a molar basis, Na is among the most abundant constituent minor element in these carbonates. Nevertheless, the chemical form of Na in CaCO3 is not well constrained. We used synchrotron X-ray spectroscopy to identify the dominant molecular host sites for Na in biogenic calcite and aragonite precipitated by corals, bivalves, and foraminifera. We also used the K-edge X-ray absorption near-edge structure to investigate the chemical environment of Na in biogenic calcium carbonates and identify the altervalent substitution of Na into Ca sites in the lattice structures of calcite and aragonite. Minor cation and anion concentrations in biogenic CaCO3 suggest that the principal substitution mechanism involves charge compensation through the creation of CO32- vacancies. The mostly homogeneous Na concentrations in the skeletal microstructures of the various biota we examined indicate that environmental and biological controls, such as temperature, skeletal microstructure, and calcification rates, have only minor influences on skeletal Na concentrations. A decrease of Na:Ca ratios with increasing age of foraminiferal shells picked from a Quaternary sediment core, indicates progressive release of Na, which suggests that structurally-substituted Na in biogenic CaCO3 is readily leached during burial diagenesis. Whereas the sediment that undergo diagenesis release some Na back to the water column, sodium co-precipitation in biogenic CaCO3 serves as a potential sink of Na for the ocean.

  9. Stable calcium isotope composition of a pedogenic carbonate in forested ecosystem: the case of the needle fibre calcite (NFC).

    Science.gov (United States)

    Milliere, Laure; Verrecchia, Eric; Gussone, Nikolaus

    2014-05-01

    Calcium (Ca), carbon (C) and oxygen (O) are important elements in terrestrial environment, as their biogeochemical cycles are directly related to the storage of atmospheric carbon. Nevertheless, contrarily to C and O, Ca isotope composition has been only poorly studied in the terrestrial carbonates. Needle Fibre Calcite (NFC) is one of the most common pedogenic carbonates, unless its origin is still under debate. Recent studies explain its formation by precipitation inside fungal hyphae. Due to this possible biogenic origin, NFC can be considered as a potential bridge between the biochemistry (precipitation inside organic structure) and geochemistry (pedogenic carbonate related to soil conditions) of the Ca. Thus, the study of the Ca isotope composition of NFC seem to be of first interest in order to shed light on the behaviour of Ca in terrestrial environment, especially when precipitation of secondary carbonates is involved. The sampling site is situated in the Swiss Jura Mountains and has been chosen due to a previous complete study of the C and O isotope composition of NFC in relation to the ecosystem, which represent a good precondition for the understanding of the NFC Ca isotope signatures in this context. In this study, the implication of the fungi in the origin of NFC is investigated, by comparing the Ca isotope composition of NFC and a purely physicochemical calcite cement (LCC), both precipitated in the same environment. The δ44Ca signature of NFC and LCC crystals were used to determine possible differences of the precipitation rate during their formation. NFC and LCC have similar δ18O composition and are supposed to precipitate at the same temperature (Milliere et al., 2011a). Thus the study of Ca isotope composition of NFC seems to demonstrate that the elongated shape of the calcite needle can be explained by different precipitation processes than the rhombohedric calcite crystals precipitated in the same environment; and more precisely, the specific

  10. Calcium and strontium isotope fractionation in aqueous solutions as a function of temperature and reaction rate; I. Calcite

    Science.gov (United States)

    AlKhatib, Mahmoud; Eisenhauer, Anton

    2017-07-01

    In order to study Strontium (Sr) partitioning and isotope fractionation of Sr and Calcium (Ca) in calcite we performed precipitation (T) experiments decoupling temperature and precipitation rate (R∗). Calcite was precipitated at 12.5, 25.0 and 37.5 °C by diffusing NH3 and CO2 gases into aqueous solutions closely following the experimental setup of Lemarchand et al. (2004). The precipitation rate (R∗) for every sample was determined applying the initial rate method and from the specific surface area of almost all samples for each reaction. The order of reaction with respect to Ca2+ ions was determined to be one and independent of T. However, the order of reaction with respect to HCO3- changed from three to one as temperature increases from 12.5, 25 °C and 37.5 °C. Strontium incorporated into calcite (expressed as DSr = [Sr/Ca]calcite/[Sr/Ca]solution) was found to be R∗ and T dependent. As a function of increasing R∗ the Δ88/86Sr-values become more negative and as temperature increases the Δ88/86Sr values also increase at constant R∗. The DSr and Δ88/86Sr-values are correlated to a high degree and depend only on R∗ being independent of temperature, complexation and varying initial ratios. Latter observation may have important implications for the study of diagenesis, the paleo-sciences and the reconstruction of past environmental conditions. Calcium isotope fractionation (Δ44/40Ca) was also found to be R∗ and T dependent. For 12.5 and 25.0 °C we observe a general increase of the Δ44/40Ca values as a function of R∗ (Lemarchand et al. type behavior, Lemarchand et al. (2004)). Whereas at 37.5 °C a significant decreasing Δ44/40Ca is observed relative to increasing R∗ (Tang et al. type behavior, Tang et al. (2008)). In order to reconcile the discrepant observations we suggest that the temperature triggered change from a Ca2+-NH3-aquacomplex covalent controlled bonding to a Ca2+-H2O-aquacomplex van-der-Waals controlled bonding caused the change

  11. Modeling results of calcium-containing minerals precipitation in the alkaline hydrotherms of Baikal Rift Zone: calcite and dolomite

    OpenAIRE

    Tokarenko, Olga Grigorievna; Zippa, E. V.

    2015-01-01

    The calculation modeling results of the nitric hydrotherms saturation in Baikal Rift Zone with calcite and dolomite are presented. The calcite and dolomite make the carbonate barrier to thermal waters equilibrium with primary minerals of igneous rocks. In the research territory, there are three main types of geochemical thermal waters which are characterized by the saturation degree with the calcite and dolomite and the proportion of precipitating minerals phases. It has been established that...

  12. Ternary iron, magnesium, calcium carbonates; a thermodynamic model for dolomite as an ordered derivative of calcite-structure solutions

    National Research Council Canada - National Science Library

    Davidson, Paula M

    1994-01-01

      The simplest solution model that can account for dolomite as an ordered derivative structure of the disordered calcite structure solution, based on a ternary extension of the generalized point approximation given by C...

  13. Investigating the Basis of Biogenic Calcium Carbonate Formation from an Amorphous Precursor: Nature of the Transformation to Calcite on Hydroxyl Functionalized Surfaces

    Science.gov (United States)

    Wang, D.; Lee, J. R.; Talley, C. E.; Murphy, K. E.; Han, T. Y.; Deyoreo, J. J.; Dove, P. M.

    2006-12-01

    Calcium carbonate biominerals are particularly significant because of their direct role in regulating the global carbon cycle, as well as their ubiquitous occurrence across earth environments. Biogenic carbonates are further distinguished by their broad phlyogenetic distribution; hence it has been suggested that unrelated eukaryotes must have used similar biochemical strategies to control mineralization. Recent studies have shown that an amorphous calcium carbonate (ACC) phase potentially plays a key role in the initial formation of carbonate minerals and in "shaping" them into complex morphologies widely seen in biominerals. Echinoderms, mollusks, and possibly many other organisms use ACC as a precursor phase that is first nucleated in cellularly controlled environments such as vesicles and subsequently transforms into a fully crystalline material. Recent studies on sea urchin embryos have shown that during transformation ACC develops short range that resembles calcite before fully crystallizing and serve as inspiration for our studies in synthetic systems. Self-assembled monolayers (SAM) on gold and silver have been used as simple model systems that approximate biological surfaces. Many studies have shown that thiol monolayers with hydroxyl termination stabilize a transitory ACC film that with prolonged exposure to aqueous solution transforms into calcite nucleated on {104} faces. Using Near Edge X-ray Absorption Fine Structure (NEXAFS) we studied SAM/mineral interactions with well ordered mercaptophenol monolayers showed that when these films are first exposed to calcium carbonate solutions, they become disordered and remain so after subsequent deposition of an ACC over-layer. Yet calcite nucleates and grows from the surface bound ACC with predominantly {104} orientation, which suggests a dynamic structural relationship between the SAMs and the mineral phase. While the monolayer/mineral phase interaction has been characterized, the mechanism for nucleating

  14. Atomic Resolution of Calcium and Oxygen Sublattices of Calcite in Ambient Conditions by Atomic Force Microscopy Using qPlus Sensors with Sapphire Tips.

    Science.gov (United States)

    Wastl, Daniel S; Judmann, Michael; Weymouth, Alfred J; Giessibl, Franz J

    2015-01-01

    Characterization and imaging at the atomic scale with atomic force microscopy in biocompatible environments is an ongoing challenge. We demonstrate atomically resolved imaging of the calcite (101̅4) surface plane using stiff quartz cantilevers ("qPlus sensors", stiffness k = 1280 N/m) equipped with sapphire tips in ambient conditions without any surface preparation. With 10 atoms in one surface unit cell, calcite has a highly complex surface structure comprising three different chemical elements (Ca, C, and O). We obtain true atomic resolution of calcite in air at relative humidity ranging from 20% to 40%, imaging atomic steps and single atomic defects. We observe a great durability of sapphire tips with their Mohs hardness of 9, only one step below diamond. Depending on the state of the sapphire tip, we resolve either the calcium or the oxygen sublattice. We determine the tip termination by comparing the experimental images with simulations and discuss the possibility of chemical tip identification in air. The main challenges for imaging arise from the presence of water layers, which form on almost all surfaces and have the potential to dissolve the crystal surface. Frequency shift versus distance spectra show the presence of at least three ordered hydration layers. The measured height of the first hydration layer corresponds well to X-ray diffraction data and molecular dynamic simulations, namely, ∼220 pm. For the following hydration layers we measure ∼380 pm for the second and third layer, ending up in a total hydration layer thickness of at least 1 nm. Understanding the influence of water layers and their structure is important for surface segregation, surface reactions including reconstructions, healing of defects, and corrosion.

  15. The subordinate's predicaments.

    Science.gov (United States)

    Neilsen, E H; Gypen, J

    1979-01-01

    How can subordinates improve relations with their superiors? And how can superiors help their subordinates feel comfortable in what is often a tense relationship? These questions have usually been dealt with only indirectly in management circles. Yet the relationship is so threatening to many subordinates that they react in ways that are damaging to themselves and their ogranizations. Drawing heavily on the work of psychologist Erik Erikson, the authors present dilemmas that commonly confront the subordinate. They point out that being aware of these dilemmas can make them more manageable and then offer advice to superiors to aid subordinates in handling such situations.

  16. INVERSE STABLE SUBORDINATORS.

    Science.gov (United States)

    Meerschaert, Mark M; Straka, Peter

    2013-01-01

    The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled.

  17. INVERSE STABLE SUBORDINATORS

    Science.gov (United States)

    MEERSCHAERT, MARK M.; STRAKA, PETER

    2013-01-01

    The inverse stable subordinator provides a probability model for time-fractional differential equations, and leads to explicit solution formulae. This paper reviews properties of the inverse stable subordinator, and applications to a variety of problems in mathematics and physics. Several different governing equations for the inverse stable subordinator have been proposed in the literature. This paper also shows how these equations can be reconciled. PMID:25045216

  18. Subordinates as Threats to Leaders

    OpenAIRE

    Glazer, Amihai; Segendorff, Björn

    2001-01-01

    A leader of an organization may view a subordinate as threatening or weakening the leader's position. The threat may increase with the subordinate's ability and reduce the rents the leader wins. In particular, a leader who trains his subordinate reduces the cost to the owner of a firm in replacing the leader, and so reduces the leader's bargaining power. The leader therefore provides inefficiently low training for the subordinate.

  19. Subordination by convex functions

    Directory of Open Access Journals (Sweden)

    Rosihan M. Ali

    2006-01-01

    Full Text Available For a fixed analytic function g(z=z+∑n=2∞gnzn defined on the open unit disk and γ<1, let Tg(γ denote the class of all analytic functions f(z=z+∑n=2∞anzn satisfying ∑n=2∞|angn|≤1−γ. For functions in Tg(γ, a subordination result is derived involving the convolution with a normalized convex function. Our result includes as special cases several earlier works.

  20. Calcite growth-rate inhibition by fulvic acid and magnesium ion—Possible influence on biogenic calcite formation

    Science.gov (United States)

    Reddy, Michael M.

    2012-08-01

    Increases in ocean surface water dissolved carbon dioxide (CO2) concentrations retard biocalcification by reducing calcite supersaturation (Ωc). Reduced calcification rates may influence growth-rate dependent magnesium ion (Mg) incorporation into biogenic calcite modifying the use of calcifying organisms as paleoclimate proxies. Fulvic acid (FA) at biocalcification sites may further reduce calcification rates. Calcite growth-rate inhibition by FA and Mg, two common constituents of seawater and soil water involved in the formation of biogenic calcite, was measured separately and in combination under identical, highly reproducible experimental conditions. Calcite growth rates (pH=8.5 and Ωc=4.5) are reduced by FA (0.5 mg/L) to 47% and by Mg (10-4 M) to 38%, compared to control experiments containing no added growth-rate inhibitor. Humic acid (HA) is twice as effective a calcite growth-rate inhibitor as FA. Calcite growth rate in the presence of both FA (0.5 mg/L) and Mg (10-4 M) is reduced to 5% of the control rate. Mg inhibits calcite growth rates by substitution for calcium ion at the growth site. In contrast, FA inhibits calcite growth rates by binding multiple carboxylate groups on the calcite surface. FA and Mg together have an increased affinity for the calcite growth sites reducing calcite growth rates.

  1. Calcite Biohybrids as Microenvironment for Stem Cells

    Directory of Open Access Journals (Sweden)

    Razi Vago

    2012-04-01

    Full Text Available A new type of composite 3D biomaterial that provides extracellular cues that govern the differentiation processes of mesenchymal stem cells (MSCs has been developed. In the present study, we evaluated the chondrogenecity of a biohybrid composed of a calcium carbonate scaffold in its calcite polymorph and hyaluronic acid (HA. The source of the calcite scaffolding is an exoskeleton of a sea barnacle Tetraclita rifotincta (T. rifotincta, Pilsbry (1916. The combination of a calcium carbonate-based bioactive scaffold with a natural polymeric hydrogel is designed to mimic the organic-mineral composite of developing bone by providing a fine-tuned microenvironment. The results indicate that the calcite-HA interface creates a suitable microenvironment for the chondrogenic differentiation of MSCs, and therefore, the biohybrid may provide a tool for tissue-engineered cartilage.

  2. SUBORDINATE GAPS IN MANDARIN CHINESE

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    Ting-Chi Wei

    2011-06-01

    Full Text Available The existence of subordinate gaps in Mandarin Chinese casts doubt on analyses built on canonical coordinate gapping. We observe that the minimality of contrastive focus and the type of subordinate clause determine the acceptability of a missing gap in subordinate structure. Along this vein, we propose that a semantic-based deletion account can be used to interpret gapping in Mandarin. Such account relies on two violable constraints, AvoidF and Focus condition on gapping (Schwarzchild 1999, Merchant 2001 to compute the acceptability of a gap.

  3. High surface area calcite

    Science.gov (United States)

    Schultz, L. N.; Andersson, M. P.; Dalby, K. N.; Müter, D.; Okhrimenko, D. V.; Fordsmand, H.; Stipp, S. L. S.

    2013-05-01

    Calcite (CaCO3) is important in many fields—in nature, because it is a component of aquifers, oil reservoirs and prospective CO2 storage sites, and in industry, where it is used in products as diverse as paper, toothpaste, paint, plastic and aspirin. It is difficult to obtain high purity calcite with a high surface area but such material is necessary for industrial applications and for fundamental calcite research. Commercial powder is nearly always contaminated with growth inhibitors such as sugars, citrate or pectin and most laboratory synthesis methods deliver large precipitates, often containing vaterite or aragonite. To address this problem, we (i) adapted the method of carbonating a Ca(OH)2 slurry with CO2 gas to develop the first simple, cheap, safe and reproducible procedure using common laboratory equipment, to obtain calcite that reproducibly had a surface area of 14-17 m2/g and (ii) conducted a thorough characterization of the product. Scanning electron microscopy (SEM) revealed nanometer scale, rhombohedral crystals. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and infrared spectroscopy (IR) confirmed highly crystalline, pure calcite that more closely resembles the dimensions of the biogenic calcite produced by algae in coccoliths than other methods for synthesizing calcite. We suggest that this calcite is useful when purity and high surface area are important.

  4. Calcium

    Science.gov (United States)

    ... Turn to calcium-fortified (or "calcium-set") tofu, soy milk, tempeh, soy yogurt, and cooked soybeans (edamame). Calcium-fortified foods. Look for calcium-fortified orange juice, soy or rice milk, breads, and cereal. Beans. You can get decent ...

  5. Immobilization of nanoparticles by occlusion into microbial calcite

    DEFF Research Database (Denmark)

    Skuce, Rebecca L.; Tobler, Dominique Jeanette; MacLaren, Ian

    2017-01-01

    systems. In this study, the ureolytic bacteria Sporosarcina pasteurii was used to induce calcium carbonate precipitation in the presence of organo-metallic manufactured nanoparticles. As calcite crystals grew the nanoparticles in the solution became trapped inside these crystals. Capture of NPs within...... not influence calcite precipitation at the concentrations used here. Overall, these findings demonstrate that microbially driven mineral precipitation has potential to immobilize nanoparticles in the environment via occlusion....

  6. Why European Subordinates Trust their Managers

    Directory of Open Access Journals (Sweden)

    Andersen Jon Aarum

    2012-11-01

    Full Text Available This article addresses the problem of why subordinates trust their managers based on the responses from 108 subordinates of seven Slovenian managers and from 138 subordinates of eight Swedish managers. The subordinates of these managers responded to a 20-item instrument tested for reliability and validity. In both samples the managers enjoyed different degrees of trust. The level of trust vested in Slovenian managers was higher than in Swedish ones. The kinds of managers’ actions that enhanced trust were similar amongst Swedish and Slovenian subordinates. Different socio-cultural contexts may theoretically explain why some other kinds of actions had contrasting effects between the samples. On the whole, the actions of managers explain trust in both countries. Subordinates’ trust in managers declines with the increasing hierarchical distance in both national samples. Managers need to show in action that they trust their subordinates, promote their interests, demonstrate appreciation of their subordinates, and solve problems.

  7. Elastic constants of calcite

    Science.gov (United States)

    Peselnick, L.; Robie, R.A.

    1962-01-01

    The recent measurements of the elastic constants of calcite by Reddy and Subrahmanyam (1960) disagree with the values obtained independently by Voigt (1910) and Bhimasenachar (1945). The present authors, using an ultrasonic pulse technique at 3 Mc and 25??C, determined the elastic constants of calcite using the exact equations governing the wave velocities in the single crystal. The results are C11=13.7, C33=8.11, C44=3.50, C12=4.82, C13=5.68, and C14=-2.00, in units of 1011 dyncm2. Independent checks of several of the elastic constants were made employing other directions and polarizations of the wave velocities. With the exception of C13, these values substantially agree with the data of Voigt and Bhimasenachar. ?? 1962 The American Institute of Physics.

  8. Calcium

    Science.gov (United States)

    ... and blood vessels contract and expand, to secrete hormones and enzymes and to send messages through the nervous system. It is important to get plenty of calcium in the foods you eat. Foods rich in calcium include Dairy products such as milk, cheese, and yogurt Leafy, green vegetables Fish with ...

  9. Biocementation of Concrete Pavements Using Microbially Induced Calcite Precipitation.

    Science.gov (United States)

    Jeong, Jin-Hoon; Jo, Yoon-Soo; Park, Chang-Seon; Kang, Chang-Ho; So, Jae-Seong

    2017-07-28

    In this study, the feasibility of introducing calcite-forming bacteria into concrete pavements to improve their mechanical performance was investigated. Lysinibacillus sphaericus WJ-8, which was isolated in a previous study and is capable of exhibiting high urease activity and calcite production, was used. When analyzed via scanning electron microscopy (SEM) and X-ray diffraction, WJ-8 showed a significant amount of calcite precipitation. The compressive strength of cement mortar mixed with WJ-8 cells and nutrient medium (urea with calcium lactate) increased by 10% compared with that of the controls. Energy dispersive x-ray spectroscopy analyses confirmed that the increase in strength was due to the calcite formed by the WJ-8 cells.

  10. Calcium

    Science.gov (United States)

    ... from dietary supplements are linked to a greater risk of kidney stones, especially among older adults. But calcium from foods does not appear to cause kidney stones. For most people, other factors (such as not drinking enough fluids) probably have ...

  11. Subordination stress: behavioral, brain, and neuroendocrine correlates.

    Science.gov (United States)

    Blanchard, D C; Sakai, R R; McEwen, B; Weiss, S M; Blanchard, R J

    1993-12-20

    In mixed-sex rat groups consistent asymmetries in offensive and defensive behaviors of male dyads are associated with the development of dominance hierarchies. Subordinate males can be differentiated from dominants on the basis of both agonistic and non-agonistic behaviors, wound patterns, weight changes. Their behavior changes suggest chronic defensiveness and are also broadly isomorphic to many of the symptoms of depression; their voluntary alcohol consumption increases, and their life-spans are shortened. Both subordinate and dominant males tend to show organ change compared to non-grouped controls, with adrenal and spleen enlargement and thymus reduction. However, these changes appear to be more marked in subordinates, and only subordinates show reduced testes weights. Basal corticosterone (CORT) levels were sharply higher, and plasma testosterone (T) sharply lower, in subordinates compared to both dominants and controls, and reduced corticosterone binding globulin further enhanced free CORT for subordinates particularly. Many subordinates failed to show a normal CORT response to restraint stress. Subordinates also appear to show widespread changes in serotonin systems, with increased 5-HIAA/5-HT ratios in a number of brain areas, and alterations of 5-HT1A receptor binding at some sites. These changes suggest that subordination, a common and consistent feature of life for many animals living in social groups, may be a particularly relevant model for investigating the behavioral, neural and endocrine correlates of chronic stress.

  12. Relationship Patterns Between Leader-Subordinate Similarity and Subordinate Satisfaction: a Case Study

    OpenAIRE

    Mat Zin, Razali bin; Fahd, King

    2006-01-01

    The leadership literature is voluminous. This study adopted the contingency model to explain the relationship between the leader-subordinate similarity and subordinate satisfaction. The effects of selected intervening variables namely age, educational level, race and sex were also analyzed. The findings showed that there is a significant relationship between leader-subordinate similarity and subordinates' satisfaction. However, this significance was determined only after accounting for the de...

  13. The moderating role of subordinate political skill on supervisors' impressions of subordinate ingratiation and ratings of subordinate interpersonal facilitation.

    Science.gov (United States)

    Treadway, Darren C; Ferris, Gerald R; Duke, Allison B; Adams, Garry L; Thatcher, Jason B

    2007-05-01

    Nearly 2 decades ago, social influence theorists called for a new stream of research that would investigate why and how influence tactics are effective. The present study proposed that political skill affects the style of execution of influence attempts. It utilized balance theory to explain the moderating effect of employee political skill on the relationships between self- and supervisor-reported ingratiation. Additionally, supervisor reports of subordinate ingratiation were hypothesized to be negatively related to supervisor ratings of subordinate interpersonal facilitation. Results from a combined sample of 2 retail service organizations provided evidence that subordinates with high political skill were less likely than those low in political skill to have their demonstrated ingratiation behavior perceived by targets as a manipulative influence attempt. Also, when subordinates were perceived by their supervisors to engage in more ingratiation behavior, the subordinates were rated lower on interpersonal facilitation. Implications of these findings, limitations, and future research directions are provided. 2007 APA, all rights reserved

  14. Subordination in Cholón

    NARCIS (Netherlands)

    Alexander-Bakkerus, A.; van Gijn, R.; Haude, K.; Muysken, P.

    2011-01-01

    In Cholón, an indigenous language from northern Peru, subordinate clauses are formed by means of nominalizers or subordinators. Most of these markers attach to reduced verb forms, but some nominalizers are attached to a fully inflected form. Nominalizers can be followed by a case marker or by a

  15. Neptunium(V) coprecipitation with calcite.

    Science.gov (United States)

    Heberling, Frank; Denecke, Melissa A; Bosbach, Dirk

    2008-01-15

    Coprecipitation experiments of Np(V) and U(VI) with calcite were performed in mixed-flow reactors under steady state conditions at room temperature for up to 400 h at precipitation rates of 1.0 x 10(-8) to 6.8 x 10(-8) mol/(m2 s). The saturation index with respect to calcite varied between 0.04 and 0.95. Initial Np(V) or U(VI) concentrations were 1 micromol/L, 0.01 mol/L NaCl was used as background electrolyte, and pH ranged from 7.8 to 12.8. Partition coefficients for Np(V) were in the range of 0.5-10.3, compared to 0.02 for U(VI). Np L(III) and U L(III) EXAFS were used to characterize the local structural environment of the incorporated actinides. In the case of U(VI), the structural environment is not unambiguously characterized. Our data suggest that Np(V) ions occupy calcium lattice sites. The two axial oxygen atoms of the linear neptunyl moiety substitute two calcite carbonate groups in the first coordination sphere. Thus, four carbonate groups coordinate the neptunyl-ion in a monodentate fashion with four equatorial oxygen atoms (Oeq) at 2.4 A and associated carbon atoms (C) at 3.2 A. The interatomic distances indicate slight structural relaxation of the carbonate groups from their ideal sites. A similar structural model has been reported for U(VI) incorporated into natural calcite.

  16. in situ Calcite Precipitation for Contaminant Immobilization

    Energy Technology Data Exchange (ETDEWEB)

    Yoshiko Fujita; Robert W. Smith

    2009-08-01

    in situ Calcite Precipitation for Contaminant Immobilization Yoshiko Fujita (Yoshiko.fujita@inl.gov) (Idaho National Laboratory, Idaho Falls, Idaho, USA) Robert W. Smith (University of Idaho-Idaho Falls, Idaho Falls, Idaho, USA) Subsurface radionuclide and trace metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE’s greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent trace ions, such as the short-lived radionuclide strontium-90, is co-precipitation in calcite. Calcite, a common mineral in the arid western U.S., can form solid solutions with trace metals. The rate of trace metal incorporation is susceptible to manipulation using either abiotic or biotic means. We have previously demonstrated that increasing the calcite precipitation rate by stimulating the activity of urea hydrolyzing microorganisms can result in significantly enhanced Sr uptake. Urea hydrolysis causes the acceleration of calcium carbonate precipitation (and trace metal co-precipitation) by increasing pH and alkalinity, and also by liberating the reactive cations from the aquifer matrix via exchange reactions involving the ammonium ion derived from urea: H2NCONH2 + 3H2O ? 2NH4+ + HCO3- + OH- urea hydrolysis >X:2Ca + 2NH4+ ? 2>X:NH4 + Ca2+ ion exchange Ca2+ + HCO3- + OH- ? CaCO3(s) + H2O calcite precipitation where >X: is a cation exchange site on the aquifer matrix. This contaminant immobilization approach has several attractive features. Urea hydrolysis is catalyzed by the urease enzyme, which is produced by many indigenous subsurface microorganisms. Addition of foreign microbes is unnecessary. In turn the involvement of the native microbes and the consequent in situ generation of reactive components in the aqueous phase (e.g., carbonate and Ca or Sr) can allow dissemination of the reaction over a larger volume and/or farther away from an amendment injection point, as compared to direct addition of the reactants at

  17. Defluoridation of drinking water by boiling with brushite and calcite.

    Science.gov (United States)

    Larsen, M J; Pearce, E I F

    2002-01-01

    Existing methods for defluoridating drinking water involve expensive high technology or are slow, inefficient and/or unhygienic. A new method is now suggested, encompassing brushite and calcite suspension followed by boiling. Our aim was to examine the efficiency of the method and the chemical reactions involved. Brushite, 0.3-0.5 g, and an equal weight of calcite were suspended in 1 litre water containing 5-20 ppm fluoride. The suspensions were boiled in an electric kettle, left to cool and the calcium salts to sediment. Solution ion concentrations were determined and sediments were examined by X-ray diffraction. In distilled water initially containing 5, 10 and 20 ppm fluoride the concentration was reduced to 0.06, 0.4 and 5.9 ppm, respectively. Using Aarhus tap water which contained 2.6 mmol/l calcium the final concentrations were 1.2, 2.5 and 7.7 ppm, respectively, and runs without calcite gave results similar to those with calcite. Without boiling the fluoride concentration remained unaltered, as did the brushite and calcite salts, despite occasional agitation by hand. All solutions were supersaturated with respect to fluorapatite and hydroxyapatite and close to saturation with respect to brushite. Boiling produced well-crystallised apatite and traces of calcite, while boiling of brushite alone left a poorly crystallised apatite. We conclude that boiling a brushite/calcite suspension rapidly converts the two salts to apatite which incorporates fluoride if present in solution, and that this process may be exploited to defluoridate drinking water. Copyright 2002 S. Karger AG, Basel

  18. Arsenic uptake in bacterial calcite

    Science.gov (United States)

    Catelani, Tiziano; Perito, Brunella; Bellucci, Francesco; Lee, Sang Soo; Fenter, Paul; Newville, Matthew; Rimondi, Valentina; Pratesi, Giovanni; Costagliola, Pilario

    2018-02-01

    Bio-mediated processes for arsenic (As) uptake in calcite were investigated by means of X-ray Diffraction (XRD) and X-ray Absorption Spectroscopy (XAS) coupled with X-ray Fluorescence measurements. The environmental bacterial strain Bacillus licheniformis BD5, sampled at the Bullicame Hot Springs (Viterbo, Central Italy), was used to synthesize calcite from As-enriched growth media. Both liquid and solid cultures were applied to simulate planktonic and biofilm community environments, respectively. Bacterial calcite samples cultured in liquid media had an As enrichment factor (Kd) 50 times higher than that from solid media. The XRD analysis revealed an elongation of the crystal lattice along the c axis (by 0.03 Å) for biogenic calcite, which likely resulted from the substitution of larger arsenate for carbonate in the crystal. The XAS data also showed a clear difference in the oxidation state of sorbed As between bacterial and abiotic calcite. Abiotic chemical processes yielded predominantly As(V) uptake whereas bacterial precipitation processes led to the uptake of both As(III) and As(V). The presence of As(III) in bacterial calcite is proposed to result from subsequent reduction of arsenate to arsenite by bacterial activities. To the best of our knowledge, this is the first experimental observation of the incorporation of As(III) in the calcite crystal lattice, revealing a critical role of biochemical processes for the As cycling in nature.

  19. Arsenic uptake in bacterial calcite

    Energy Technology Data Exchange (ETDEWEB)

    Catelani, Tiziano; Perito, Brunella; Bellucci, Francesco; Lee, Sang Soo; Fenter, Paul; Newville, Matthew G.; Rimondi, Valentina; Pratesi, Giovanni; Costagliola, Pilario

    2018-02-01

    Bio-mediated processes for arsenic (As) uptake in calcite were investigated by means of X-ray Diffraction (XRD) and Xray Absorption Spectroscopy (XAS) coupled with X-ray Fluorescence measurements. The environmental bacterial strain Bacillus licheniformis BD5, sampled at the Bullicame Hot Springs (Viterbo, Central Italy), was used to synthesize calcite from As-enriched growth media. Both liquid and solid cultures were applied to simulate planktonic and biofilm community environments, respectively. Bacterial calcite samples cultured in liquid media had an As enrichment factor (Kd) 50 times higher than that from solid media. The XRD analysis revealed an elongation of the crystal lattice along the c axis (by 0.03Å) for biogenic calcite, which likely resulted from the substitution of larger arsenate for carbonate in the crystal. The XAS data also showed a clear difference in the oxidation state of sorbed As between bacterial and abiotic calcite. Abiotic chemical processes yielded predominantly As(V) uptake whereas bacterial precipitation processes led to the uptake of both As(III) and As(V). The presence of As(III) in bacterial calcite is proposed to result from subsequent reduction of arsenate to arsenite by bacterial activities. To the best of our knowledge, this is the first experimental observation of the incorporation of As(III) in the calcite crystal lattice, revealing a critical role of biochemical processes for the As cycling in nature.

  20. Superior-subordinate relations as organizational processes

    DEFF Research Database (Denmark)

    Asmuss, Birte; Aggerholm, Helle Kryger; Oshima, Sae

    -subordinate relations and thus for organizing an institution. References Fletcher, C. (2001). Performance appraisal and management: The developing research agenda. Journal of Occupational and Organizational Psychology, 74:473-487. Cooren, F., Taylor, J.R., & Van Every, E.J. (Eds.) (2006). Communication as organizing...... on organizational practices relates closely to an increased focus on communication as being constitutive of the organization in general and the superior-subordinate relationship in specific. The current study aims to contribute to this line of research by investigating micro-practices involved in establishing...... superior-subordinate relations in a specific institutionalized setting: performance appraisal interviews (PAIs). While one main task of PAIs is to manage and integrate organizational and employee performance (Fletcher, 2001:473), PAIs are also organizational practices where superior-subordinate relations...

  1. Fabrication of Single-Crystalline Calcite Needle-Like Particles Using the Aragonite–Calcite Phase Transition

    Directory of Open Access Journals (Sweden)

    Yuki Kezuka

    2017-08-01

    Full Text Available Calcium carbonate (CaCO3 occurs in two major polymorphs: rhombohedral calcite and orthorhombic aragonite, the latter is thermodynamically metastable. In this study, we first prepared aragonite needle-like particles by introducing CO2-containing gas into Ca(OH2 aqueous slurry. Then, the resulted aragonite particles were heat treated at 500 °C for 1 h, in order to induce the aragonite–calcite phase transition. Particle structures before and after the heat treatment were characterized mainly by powder X-ray diffractometry (XRD, field emission-scanning electron microscopy (FE-SEM and transmission electron microscopy (TEM. We found that single-crystalline calcite needle-like particles with zigzag surface structures can be fabricated using the phase transition.

  2. Utilization of calcite produced in Turkey for paper coating

    Directory of Open Access Journals (Sweden)

    Hüdaverdi Eroğlu

    2002-03-01

    Full Text Available Calcium carbonate is one of the coating pigments widely used in paper industry. Especially, in recent years calcium carbonate filler has gained high importance in alkaline pulping. In Turkey industry actually imports calcium carbonate; whereas, there are rich calcite reservoirs in the country. In this study two different types of domestic ground (GCC calcite samples were used. Physical and chemical properties of calcite samples were tested firstly. CaCO3 percentages of both samples were 97.3 % and 97.6 % (min. 95 % CaCO3. MgCO3 and Fe2O3 percentages were within the desired limits. Brightness values were 95.5 % and 94.5 % and yellowness 1.1 % and 1.5 % elrepho. These values also were within the requested limits. Under 2 microns particle size and over 10 microns particle size fractions were 95 % and 89 % (min. 80 and 1 % and 2 % (max. 2 respectively. Dry matter rates were between 40 %-65 %, for the pilot plant-coating machine. During the preparation of coating color calcium carbonate has been used together with kaolin. The ratios of calcium carbonate to kaolin were 30/70, 40/60, 50/50, 60/40, 70/30, 100/0. In coating color preparation latex was used as a binder because of its wide applications. Latex percentages were 11, 12, and 13 %. Coated papers were glossed and physically tested. As a result, both calcium carbonate samples were found suitable for using in coating color preparation. By the utilization of domestic calcium carbonate in coated paper production, there will be foreign currencies saving.

  3. Calcite Dissolution Kinetics

    Science.gov (United States)

    Berelson, W.; Subhas, A.; Dong, S.; Naviaux, J.; Adkins, J. F.

    2016-12-01

    A geological buffer for high atmospheric CO2 concentrations is neutralization via reaction with CaCO3. We have been studying the dissolution kinetics of carbonate minerals using labeled 13C calcite and Picarro-based measurements of 13C enrichments in solution DIC. This methodology has greatly facilitated our investigation of dissolution kinetics as a function of water carbonate chemistry, temperature and pressure. One can adjust the saturation state Omega by changing the ion activity product (e.g. adjusting carbonate ion concentration), or by changing the solubility product (e.g. adjusting temperature or pressure). The canonical formulation of dissolution rate vs. omega has been refined (Subhas et al. 2015) and shows distinct non-linear behavior near equilibrium and rates in sea water of 1-3 e-6 g/cm2day at omega = 0.8. Carbonic anhydrase (CA), an enzyme that catalyzes the hydration of dissolved CO2 to carbonic acid, was shown (in concentrations rate at low degrees of undersaturation by >500x. This result points to the importance of carbonic acid in enhancing dissolution at low degrees of undersaturation. CA activity and abundance in nature must be considered regarding the role it plays in catalyzing dissolution. We also have been investigating the role of temperature on dissolution kinetics. An increase of 16C yields an order of magnitude increase in dissolution rate. Temperature (and P) also change Omega critical, the saturation state where dissolution rates change substantially. Increasing pressure (achieved in a pressure reaction chamber we built) also shifts Omega critical closer to equilibrium and small pressure increases have large impact on dissolution kinetics. Dissolution rates are enhanced by an order of magnitude for a change in pressure of 1500 psi relative to the dissolution rate achieved by water chemistry effects alone for an omega of 0.8. We've shown that the thermodynamic determination of saturation state does not adequately describe the kinetics

  4. Rate of radiocarbon retention onto calcite by isotope exchange

    Energy Technology Data Exchange (ETDEWEB)

    Lempinen, Janne; Lehto, Jukka [Helsinki Univ. (Finland). Lab. of Radiochemistry

    2016-11-01

    Radiocarbon ({sup 14}C) is a top priority class radionuclide associated with the long-term safety of spent nuclear fuel disposal. Dissolved inorganic radiocarbon can be retained in bedrock via isotope exchange with calcite (CaCO{sub 3}) at solubility equilibrium with groundwater. In the present study, the rate of the isotope exchange process was investigated on synthetic calcite using batch experiments. Experiments were performed in solutions with a calcium concentration of 0.0002-0.1 M, including two synthetic reference groundwaters. The radiocarbon activity in the solutions decreased exponentially as a function of time, thus following first-order kinetics. The rate of isotope exchange was quantified from an exponential fit to the activity data over time. The rate of radiocarbon retention increased as a function of the calcium activity. The isotope exchange half-life was only 4.3 days at calcium ion activities over 0.01. This half-life is very much shorter than the half-life of {sup 14}C or the time scale of groundwater movements; consequently calcite can effectively retain radiocarbon from brackish and saline groundwaters.

  5. The potential for phosphorus pollution remediation by calcite precipitation in UK freshwaters

    Directory of Open Access Journals (Sweden)

    C. Neal

    2001-01-01

    Full Text Available This paper examines the potential for calcium carbonate to reduce phosphate pollution in freshwaters by co-precipitation, a process known as a "self cleansing mechanism". Calcium carbonate saturation levels and phosphate concentrations (SRP - soluble reactive phosphate across the major eastern UK river basins are examined to test for solubility controls. The study shows that calcite saturation varies for each catchment as a function of flow and biological activity rather than by direct regulation by SRP. Indeed, there is no evidence, for any of the rivers studied, that calcite solubility controls hold. However, for groundwater and groundwater-fed springs in the Chalk of the Thames basin, calcite saturation is observed with associated low SRP levels. A self-cleansing mechanism may well be operative within the Chalk due to two factors. Firstly, there is a high potential for nucleation on the calcite micro-crystals in the aquifer. Secondly, there are within aquifer reactions that remove the calcite nucleating inhibitors (SRP and dissolved organic carbon, DOC to levels lower than those occurring within the rivers do. These inhibitors enter the catchment at very high concentrations in association with agricultural pollution (fertilizer application and animal slurry and household contamination (e.g. sewage sources from septic tanks. Under low flow conditions, when the saturation index for calcite is at its highest, so too is the concentration of the nucleation inhibitor SRP. Companion work shows that calcite precipitation can occur at the water-sediment interface of the river and this may involve SRP removal. The data, as a whole, define an apparent bound for calcite solubility control where in the presence of nucleating centres, SRP must be less than 4 mM-P l-1 and DOC must be less than 150 mM-C l-1: a condition that does not seem to pertain within most UK rivers. Keywords: calcite, calcium carbonate, phosphate, soluble reactive phosphate, dissolved

  6. Meta-Times and Extended Subordination

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole; Pedersen, Jan

    The problem of defining subordination of a homogeneous Lévy basis by a non-negative homogeneous Lévy basis is discussed. An explicit construction, generalizing the usual one-dimensional case, is given. This construction involves certain random meta-time changes.......The problem of defining subordination of a homogeneous Lévy basis by a non-negative homogeneous Lévy basis is discussed. An explicit construction, generalizing the usual one-dimensional case, is given. This construction involves certain random meta-time changes....

  7. Calcium carbonate precipitation in the Cueva di Watapana on Bonaire, Netherlands Antilles

    NARCIS (Netherlands)

    Meer Mohr, van der C.G.

    1978-01-01

    Calcium carbonate precipitates as low Mg-calcite and aragonite in slightly brackish water in a cave in the Pleistocene Middle Terrace of southern Bonaire. The calcium carbonate precipitates at the atmosphere-water interface forming floating calcite scales (calcite ice). Aragonite crystals frequently

  8. Enhancing Supervisor and Subordinate Communication in Diversity ...

    African Journals Online (AJOL)

    provides for the institutionalisation of diversity management by integrating it with the organisation's management practices. This article proposes that communication between supervisors and subordinates in the public service must be strengthened to enhance diversity management. It argues that diversity management is an ...

  9. Matrix subordinators and related Upsilon transformations

    DEFF Research Database (Denmark)

    Barndorff-Nielsen, Ole Eiler; Pérez-Abreu, V.

    2008-01-01

    A class of upsilon transformations of Lévy measures for matrix subordinators is introduced. Some regularizing properties of these transformations are derived, such as absolute continuity and complete monotonicity. The class of Lévy measures with completely monotone matrix densities is characterized....... Examples of infinitely divisible nonnegative definite random matrices are constructed using an upsilon transformation....

  10. subordination across ghanaian and british newspaper editorials

    African Journals Online (AJOL)

    Empirical research in this area is scanty, though this theoretical argumentation is not without contention, especially cross-culturally. Empirical investigation is therefore ... Frimpong: Subordination Across Ghanaian and British Newspaper Editorials: A Register. Perspective. 78. Figure 1: The Components in a register analysis.

  11. Trichomes of tobacco excrete zinc as zinc-substituted calcium carbonate and other zinc-containing compounds.

    Science.gov (United States)

    Sarret, Géraldine; Harada, Emiko; Choi, Yong-Eui; Isaure, Marie-Pierre; Geoffroy, Nicolas; Fakra, Sirine; Marcus, Matthew A; Birschwilks, Mandy; Clemens, Stephan; Manceau, Alain

    2006-07-01

    Tobacco (Nicotiana tabacum L. cv Xanthi) plants were exposed to toxic levels of zinc (Zn). Zn exposure resulted in toxicity signs in plants, and these damages were partly reduced by a calcium (Ca) supplement. Confocal imaging of intracellular Zn using Zinquin showed that Zn was preferentially accumulated in trichomes. Exposure to Zn and Zn + Ca increased the trichome density and induced the production of Ca/Zn mineral grains on the head cells of trichomes. These grains were aggregates of submicrometer-sized crystals and poorly crystalline material and contained Ca as major element, along with subordinate amounts of Zn, manganese, potassium, chlorine, phosphorus, silicon, and magnesium. Micro x-ray diffraction revealed that the large majority of the grains were composed essentially of metal-substituted calcite (CaCO3). CaCO3 polymorphs (aragonite and vaterite) and CaC2O4 (Ca oxalate) mono- and dihydrate also were identified, either as an admixture to calcite or in separate grains. Some grains did not diffract, although they contained Ca, suggesting the presence of amorphous form of Ca. The presence of Zn-substituted calcite was confirmed by Zn K-edge micro-extended x-ray absorption fine structure spectroscopy. Zn bound to organic compounds and Zn-containing silica and phosphate were also identified by this technique. The proportion of Zn-substituted calcite relative to the other species increased with Ca exposure. The production of Zn-containing biogenic calcite and other Zn compounds through the trichomes is a novel mechanism involved in Zn detoxification. This study illustrates the potential of laterally resolved x-ray synchrotron radiation techniques to study biomineralization and metal homeostasis processes in plants.

  12. Attitudes Of Subordinates Toward Women In Leadership Position ...

    African Journals Online (AJOL)

    The t-test of independent sample was used to analyse the research data. The findings revealed that: (a) Male subordinates have negative attitude toward women leader; (b) Subordinates with higher educational qualification have positive attitude towards women leaders; (c) Young subordinates have negative attitudes ...

  13. Managers can drive their subordinates mad.

    Science.gov (United States)

    Kets de Vries, M F

    1979-01-01

    This article explores the phenomenon of "folie à deux"--an aberrant relationship between manager and subordinates that is characterized by shared delusions. Though most visible among public figures like Adolf Hitler, J. Edgar Hoover and Jim Jones, the problem also surfaces among private managers and their associates with dangerous implications for the firm. In folie à deux, the unusual behavior patterns of a manager in an isolated setting become mirrored by dependent subordinates, and the organization loses touch with its original goals and strategies. The author describes the dynamics of this phenomenon and details steps to remedy the situation. Once recognized, he suggests that the manager establish a trusting relationship with the instigator as a prelude to altering the behavior patterns, then transfer the subordinates and reorient the work climate so that independence and responsibility are encouraged. If the instigator is a powerful executive, the author suggests enlisting the support of a countervailing force, such as the government or a union, to guide the organization away from possible self-destructive adventures.

  14. Calcite/aragonite-biocoated artificial coral reefs for marine parks

    Directory of Open Access Journals (Sweden)

    Volodymyr Ivanov

    2017-08-01

    Full Text Available Natural formation of the coral reefs is complicated by slow biomediated precipitation of calcium carbonate from seawater. Therefore, manufactured artificial coral reefs can be used for the formation of “underwater gardens” in marine parks for the recreational fishing and diving that will protect natural coral reefs from negative anthropogenic effects. Additionally, the coating of the concrete, plastic or wooden surfaces of artificial coral reef with calcium carbonate layer could promote attachment and growth of coral larvae and photosynthetic epibiota on these surfaces. Three methods of biotechnological coating of the artificial coral reefs have been tested: (1 microbially induced calcium carbonate precipitation from concentrated calcium chloride solution using live bacterial culture of Bacillus sp. VS1 or dead but urease-active cells of Yaniella sp. VS8; (2 precipitation from calcium bicarbonate solution; (3 precipitation using aerobic oxidation of calcium acetate by bacteria Bacillus ginsengi strain VSA1. The thickness of biotechnologically produced calcium carbonate coating layer was from 0.3 to 3 mm. Biocoating using calcium salt and urea produced calcite in fresh water and aragonite in seawater. The calcium carbonate-coated surfaces were colonized in aquarium with seawater and hard corals as inoculum or in aquarium with fresh water using cyanobacteria Chlorella sorokiana as inoculum. The biofilm on the light-exposed side of calcium carbonate-coated surfaces was formed after six weeks of incubation and developed up to the average thickness of 250 µm in seawater and about 150 µm in fresh water after six weeks of incubation. The biotechnological manufacturing of calcium carbonate-coated concrete, plastic, or wooden surfaces of the structures imitating natural coral reef is technologically feasible. It could be commercially attractive solution for the introduction of aesthetically pleasant artificial coral reefs in marine parks and

  15. Seawater-softening process through formation of calcite ooids

    Directory of Open Access Journals (Sweden)

    A.A. Bakr

    2015-03-01

    Full Text Available Conventional water-softening processes usually involve the exchange of Na+ ions for Ca2+ and Mg2+ using commercial or synthesized ion exchangers. The differences in chemical compositions of the ooids can be attributed to the formation in different environments. In this paper, ooid grains form inside assembled semi-pilot softening unit through a continuous chemical process involving reaction between bicarbonate ions and added lime using natural seawater. Our sample of Mediterranean seawater has low Mg2+/Ca2+ ratio (1.98% within the range chemically favorable for precipitation of low-Mg calcite ooids. Precipitation of calcite occurs around pure quartz sand grains which act as nucleation points (the bed required for sand vessel is 1.65 l. The shape of the sand grains controls the overall external morphology of the resulting ooids; they vary in size from 0.5 to 3.0 mm and have a high degree of polish due to surface abrasion caused by continuous agitation inside the softening system. Calcite ooid grains (1.53 kg formed within the seawater-softening unit every 18 days have many of the ooid features formed in marine environments. Ooids grow to a significant size, at a rate of about 0.17 mm of one layer thickness per day inside the softening unit. The average weight percent of calcite precipitate is 35.48% after 18 days, at 10 °C, 60 l/min and pH 9.0. The pellets comprise mainly CaCO3 and SiO2 and some metal ions which may substitute for calcium ions in calcite are present only in trace amounts of the total composition.

  16. Biogenic calcite particles from microalgae-Coccoliths as a potential raw material.

    Science.gov (United States)

    Jakob, Ioanna; Chairopoulou, Makrina Artemis; Vučak, Marijan; Posten, Clemens; Teipel, Ulrich

    2017-06-01

    Synthetic calcite (CaCO3) particles are found in a broad range of applications. The geometry of particles produced from limestone or precipitation are versatile but limited to basic shapes. The microalga Emiliania huxleyi produces micro-structured calcite platelets, called coccoliths. This article presents the results of an application-orientated study, which includes characteristic values also used in the calcite industry for particle evaluation. It is demonstrated that coccoliths are significantly different from all industrial particles produced so far. Coccoliths are porous particles, mainly consisted of calcium carbonate, with further elements such as Mg, Si, Sr, and Fe often embedded in their structure. Their structure is extremely sophisticated, while the overall particle morphology and particle size distribution are homogeneous. This study gives a first inside into the potential of these exceptional objects and may set further impulses for their utilization in specific calcite particle applications.

  17. Atomic modifications by synchrotron radiation at the calcite-ethanol interface

    DEFF Research Database (Denmark)

    Pasarín, I. S.; Bovet, Nicolas Emile; Glyvradal, Magni

    2012-01-01

    -mineral interfaces where the polar OH group, as present in ethanol, plays a key role in their molecular structure and bonding. Also, the chemical evolution observed in the interface provides new insight into the behavior of some complex organic molecules involved in biomineralization processes.......This article reports on studies of the chemical alterations induced by synchrotron radiation at the calcite-ethanol interface, a simple model system for interfaces between minerals and more complex organic molecules containing OH groups. A combination of X-ray reflectivity and X-ray photoelectron...... spectroscopy of natural calcite, cleaved in distilled ethanol to obtain new clean interfaces, indicated that, during a 5 h period, the two top atomic layers of calcite, CaCO3, transform into calcium oxide, CaO, by releasing CO2. Also, the occupation of the first ordered layer of ethanol attached to calcite...

  18. Effect of inorganic anions on the morphology and structure of magnesium calcite.

    Science.gov (United States)

    Kralj, Damir; Kontrec, Jasminka; Brecević, Ljerka; Falini, Giuseppe; Nöthig-Laslo, Vesna

    2004-04-02

    Calcium carbonate was precipitated from calcium hydroxide and carbonic acid solutions at 25 degrees C, with and without addition of different magnesium (MgSO(4), Mg(NO(3))(2) and MgCl(2)) and sodium salts (Na(2)SO(4), NaNO(3) and NaCl) of identical anions, in order to study the mode of incorporation of magnesium and inorganic anions and their effect on the morphology of calcite crystals over a range of initial reactant concentrations and limited c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios. The morphology, crystal size distribution, composition, structure, and specific surface area of the precipitated crystals, as well as the mode of cation and anion incorporation into the calcite crystal lattice, were studied by a combination of optical and scanning electron microscopy (SEM), electronic counting, a multiple BET method, thermogravimetry, FT-IR spectroscopy, X-ray diffraction (XRD), and electron paramagnetic resonance (EPR) spectroscopy. In the systems of high initial relative supersaturation, precipitation of an amorphous precursor phase preceded the formation of calcite, whereas in those of lower supersaturation calcite was the first and only polymorphic modification of calcium carbonate that appeared in the system. The magnesium content in calcite increased with the magnesium concentration in solution and was correlated with the type of magnesium salt used. Mg incorporation caused the formation of crystals elongated along the calcite c axis and, in some cases, the appearance of new [011] faces. Polycrystalline aggregates were formed when the c(i)(Mg(2+))/c(i)(Ca(2+)) molar ratios in solution were increased. Addition of sulfate ions, alone, caused formation of spherical calcite polycrystalline aggregates.

  19. Lebanon in the Middle East Subordinate System.

    Science.gov (United States)

    1983-06-03

    the land of Aram;4 the "people of the sea," became the Philistines ; and the Hebrews created their kingdom under the scepter of King David), the ...legislative. Before sunrise, they were taken to an ancient fort at Rashaya to be . held in separate cells. On the same day, M. Helleu, French delegate...R AD-138 031 LEBANON IN THE MIDDLE EAST SUBORDINATE SYSTEM(U) RRMY 1/3, COMMRAND AND GENERAL STAFF COLL FORT LEAVENWORTH KS N S EID 03 JUN 83 SBI-AD

  20. Influence of calcium sources on microbially induced calcium carbonate precipitation by Bacillus sp. CR2.

    Science.gov (United States)

    Achal, Varenyam; Pan, Xiangliang

    2014-05-01

    Stimulation of microbially induced calcium carbonate precipitation (MICCP) is likely to be influenced by calcium sources. In order to study such influences, we performed MICCP using Bacillus sp. CR2 in nutrient broth containing urea, supplemented with different calcium sources (calcium chloride, calcium oxide, calcium acetate and calcium nitrate). The experiment lasted 7 days, during which bacterial growth, urease activity, calcite production and pH were measured. Our results showed that calcium chloride is the better calcium source for MICCP process, since it provides higher urease activity and more calcite production. The influences of calcium sources on MICCP were further studied using Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. These analyses confirmed that the precipitate formed was CaCO3 and composed of predominantly calcite crystals with a little amount of aragonite and vaterite crystals. The maximum yield of calcite precipitation was achievable with calcium chloride followed by calcium nitrate as a calcium source. The results of present study may be applicable to media preparation during efficient MICCP process.

  1. Controlling the size and morphology of precipitated calcite particles by the selection of solvent composition

    Science.gov (United States)

    Konopacka-Łyskawa, Donata; Kościelska, Barbara; Karczewski, Jakub

    2017-11-01

    Precipitated calcium carbonate is used as an additive in the manufacture of many products. Particles with specific characteristics can be obtained by the selection of precipitation conditions, including temperature and the composition of solvent. In this work, calcium carbonate particles were obtained in the reaction of calcium hydroxide with carbon dioxide at 65 °C. Initial Ca(OH)2 suspensions were prepared in pure water and aqueous solutions of ethylene glycol or glycerol of the concentration range up to 20% (vol.). The course of reaction was monitored by conductivity measurements. Precipitated solids were analyzed by FTIR, XRD, SEM and the particles size distribution was determined by a laser diffraction method. The adsorption of ethylene glycol or glycerol on the surface of scalenohedral and rhombohedral calcite was testes by a normal-phase high-performance liquid chromatography. The addition of organic solvents changed the viscosity of reaction mixtures, the rate of carbon dioxide absorption and the solubility of inorganic components and therefore influence calcium carbonate precipitation conditions. All synthesized calcium carbonate products were in a calcite form. Scalenohedral calcite crystals were produced when water was a liquid phase, whereas addition of organic solvents resulted in the formation of rhombo-scalenohedral particles. The increase in organic compounds concentration resulted in the decrease of mean particles size from 2.4 μm to 1.7 μm in ethylene glycol solutions and to 1.4 μm in glycerol solutions. On the basis of adsorption tests, it was confirm that calcite surface interact stronger with glycerol than ethylene glycol. The interaction between scalenohedral calcite and used organic additives was higher in comparison to the pure rhombohedral form applied as a stationary phase.

  2. Paternity of subordinates raises cooperative effort in cichlids.

    Directory of Open Access Journals (Sweden)

    Rick Bruintjes

    Full Text Available In cooperative breeders, subordinates generally help a dominant breeding pair to raise offspring. Parentage studies have shown that in several species subordinates can participate in reproduction. This suggests an important role of direct fitness benefits for cooperation, particularly where groups contain unrelated subordinates. In this situation parentage should influence levels of cooperation. Here we combine parentage analyses and detailed behavioural observations in the field to study whether in the highly social cichlid Neolamprologus pulcher subordinates participate in reproduction and if so, whether and how this affects their cooperative care, controlling for the effect of kinship.We show that: (i male subordinates gained paternity in 27.8% of all clutches and (ii if they participated in reproduction, they sired on average 11.8% of young. Subordinate males sharing in reproduction showed more defence against experimentally presented egg predators compared to subordinates not participating in reproduction, and they tended to stay closer to the breeding shelter. No effects of relatedness between subordinates and dominants (to mid-parent, dominant female or dominant male were detected on parentage and on helping behaviour.This is the first evidence in a cooperatively breeding fish species that the helping effort of male subordinates may depend on obtained paternity, which stresses the need to consider direct fitness benefits in evolutionary studies of helping behaviour.

  3. Paternity of subordinates raises cooperative effort in cichlids.

    Science.gov (United States)

    Bruintjes, Rick; Bonfils, Danielle; Heg, Dik; Taborsky, Michael

    2011-01-01

    In cooperative breeders, subordinates generally help a dominant breeding pair to raise offspring. Parentage studies have shown that in several species subordinates can participate in reproduction. This suggests an important role of direct fitness benefits for cooperation, particularly where groups contain unrelated subordinates. In this situation parentage should influence levels of cooperation. Here we combine parentage analyses and detailed behavioural observations in the field to study whether in the highly social cichlid Neolamprologus pulcher subordinates participate in reproduction and if so, whether and how this affects their cooperative care, controlling for the effect of kinship. We show that: (i) male subordinates gained paternity in 27.8% of all clutches and (ii) if they participated in reproduction, they sired on average 11.8% of young. Subordinate males sharing in reproduction showed more defence against experimentally presented egg predators compared to subordinates not participating in reproduction, and they tended to stay closer to the breeding shelter. No effects of relatedness between subordinates and dominants (to mid-parent, dominant female or dominant male) were detected on parentage and on helping behaviour. This is the first evidence in a cooperatively breeding fish species that the helping effort of male subordinates may depend on obtained paternity, which stresses the need to consider direct fitness benefits in evolutionary studies of helping behaviour.

  4. Monitoring of Calcite Precipitation in Hardwater Lakes with Multi-Spectral Remote Sensing Archives

    Directory of Open Access Journals (Sweden)

    Iris Heine

    2017-01-01

    Full Text Available Calcite precipitation is a common phenomenon in calcium-rich hardwater lakes during spring and summer, but the number and spatial distribution of lakes with calcite precipitation is unknown. This paper presents a remote sensing based method to observe calcite precipitation over large areas, which are an important prerequisite for a systematic monitoring and evaluation of restoration measurements. We use globally archived satellite remote sensing data for a retrospective systematic assessment of past multi-temporal calcite precipitation events. The database of this study consists of 205 data sets that comprise freely available Landsat and Sentinel 2 data acquired between 1998 and 2015 covering the Northeast German Plain. Calcite precipitation is automatically identified using the green spectra and the metric BGR area, the triangular area between the blue, green and red reflectance value. The validation is based on field measurements of CaCO3 concentrations at three selected lakes, Feldberger Haussee, Breiter Luzin and Schmaler Luzin. The classification accuracy (0.88 is highest for calcite concentrations ≥0.7 mg/L. False negative results are caused by the choice of a conservative classification threshold. False positive results can be explained by already increased calcite concentrations. We successfully transferred the developed method to 21 other hardwater lakes in Northeast Germany. The average duration of lakes with regular calcite precipitation is 37 days. The frequency of calcite precipitation reaches from single time detections up to detections nearly every year. False negative classification results and gaps in Landsat time series reduce the accuracy of frequency and duration monitoring, but in future the image density will increase by acquisitions of Sentinel-2a (and 2b. Our study tested successfully the transfer of the classification approach to Sentinel-2 images. Our study shows that 15 of the 24 lakes have at least one phase of

  5. Utilization of microbial induced calcite precipitation for sand consolidation and mortar crack remediation

    Directory of Open Access Journals (Sweden)

    S.A. Abo-El-Enein

    2012-12-01

    Full Text Available The microbes can hydrolyze urea by urease enzyme to produce ammonium as well as carbonate ions and in the presence of calcium ions which can precipitate calcium carbonate; this process is called “biocalcification” or microbial induced calcite precipitation (MICP.This technology is environmentally friendly not only because it gives strength to sand body, but also it allows water to penetrate to sand body, which is unlike silicate cement that will destroy the ecosystem of the earth. Calcium carbonate precipitated by bacteria acts as a binding material to sand particles, so incompact sand will be consolidated. Calcium chloride, calcium acetate and calcium nitrate (1 M as calcium sources were tested for their ability to consolidate sand by mixing with urea (1 M and bacteria cells (one optical density, 1 OD. The key point of this study aimed to choose the suitable calcium source which produces higher compressive strength and lower water absorption. The results showed that the degree of crystallinity and amount of precipitated calcium carbonate, as well as the consequent increase in strength of consolidated sand, in case of calcium chloride medium are higher than those precipitated in case of calcium acetate as well as calcium nitrate media. In addition, consolidated sand by calcium chloride was also used for cement mortar crack remediation.

  6. Helpful female subordinate cichlids are more likely to reproduce.

    Directory of Open Access Journals (Sweden)

    Dik Heg

    Full Text Available BACKGROUND: In many cooperatively breeding vertebrates, subordinates assist a dominant pair to raise the dominants' offspring. Previously, it has been suggested that subordinates may help in payment for continued residency on the territory (the 'pay-to-stay hypothesis', but payment might also be reciprocated or might allow subordinates access to reproductive opportunities. METHODOLOGY/PRINCIPAL FINDINGS: We measured dominant and subordinate female alloparental brood care and reproductive success in four separate experiments and show that unrelated female dominant and subordinate cichlid fish care for each other's broods (alloparental brood care, but that there is no evidence for reciprocal 'altruism' (no correlation between alloparental care received and given. Instead, subordinate females appear to pay with alloparental care for own direct reproduction. CONCLUSIONS/SIGNIFICANCE: Our results suggest subordinate females pay with alloparental care to ensure access to the breeding substrate and thereby increase their opportunities to lay their own clutches. Subordinates' eggs are laid, on average, five days after the dominant female has produced her first brood. We suggest that immediate reproductive benefits need to be considered in tests of the pay-to-stay hypothesis.

  7. 46 CFR 67.243 - Requirements for instruments subordinating mortgages.

    Science.gov (United States)

    2010-10-01

    ... 46 Shipping 2 2010-10-01 2010-10-01 false Requirements for instruments subordinating mortgages. 67... MEASUREMENT OF VESSELS DOCUMENTATION OF VESSELS Filing and Recording of Instruments-Mortgages, Preferred Mortgages, and Related Instruments § 67.243 Requirements for instruments subordinating mortgages. An...

  8. Gender, Leadership Style, and Subordinate Satisfaction: An Experiment

    Science.gov (United States)

    Kushell, Elliot; Newton, Rae

    1986-01-01

    Reports on an experiment that analyzed the effects of gender and leadership style on subordinate satisfaction. While subjects were more satisfied in democratically led groups, gender of leader did not significantly affect satisfaction. Female subordinates were more dissatisfied than males in autocratically led groups. (KH)

  9. Leaders' achievement goals and their reactions to subordinates' creative input

    NARCIS (Netherlands)

    Sijbom, R.B.L.; Janssen, O.; van Yperen, N.W.

    2010-01-01

    The present experimental research examined the impact of leaders' achievement goals on their reactions to creative input provided by their subordinates. In Experiment 1, performance goal leaders were found to be less receptive to subordinates' creative input than mastery goal leaders. In Experiment

  10. Calcite biomineralization in coccoliths: Evidence from atomic force microscopy (AFM)

    DEFF Research Database (Denmark)

    Henriksen, Karen; Stipp, S.L.S.

    2002-01-01

    geochemistry, crystal orientation, coccolith function, biomineralization, biological calcite, atomic force microscopy......geochemistry, crystal orientation, coccolith function, biomineralization, biological calcite, atomic force microscopy...

  11. Analysis of gender stereotypic characteristics in leaders and subordinates

    Directory of Open Access Journals (Sweden)

    María Laura Lupano Perugini

    2013-08-01

    Full Text Available An investigation was realized to analyze the way leaders and subordinates describe themselves in relation to perceived gender stereotypic characteristics and, to verify if exists differences in these characteristics according position (leader/ subordinate. Participate 612 individuals, 329 male (54% y 283 female (46%, age average = 37,54 years (DE=11,88. 59 % of the participants occupied executive positions and the rest were subordinates. It was utilized and abbreviate version of the Bem Sex Roles (Bem, 1974 to data recollection. The obtained results show that male leaders describe themselves mainly with agentic-masculine attributes (e.g. dominant, compared with subordinates who describe themselves with communal- feminine characteristics (e.g. submission. On the other hand, the female leaders describe themselves mainly with androgyny attributes combining qualities of both genders (e.g. dominant and sensible to the needs of others; however the female subordinates show communal attributes (e.g. submission

  12. Study of Factors Related to Magnetic Treatment of Calcium Carbonate Saturated Water

    National Research Council Canada - National Science Library

    Lambert, Kevin

    1998-01-01

    ..., calcium carbonate concentration and number of magnetic device attached. XRD of crystals gave relative proportions of calcite and aragonite present and XRF measured transition metals and elements known to substitute for calcium in scale...

  13. Manganese-calcium intermixing facilitates heteroepitaxial growth at the 101¯4 calcite-water interface

    Energy Technology Data Exchange (ETDEWEB)

    Xu, Man; Riechers, Shawn L.; Ilton, Eugene S.; Du, Yingge; Kovarik, Libor; Varga, Tamas; Arey, Bruce W.; Qafoku, Odeta; Kerisit, Sebastien

    2017-10-01

    In situ atomic force microscopy (AFM) measurements were performed to probe surface precipitates that formed on the (10-14) surface of calcite (CaCO3) single crystals following reaction with Mn2+-bearing aqueous solutions with a range of initial concentrations. Three-dimensional epitaxial islands were observed to precipitate and grow on the surfaces and in situ time-sequenced measurements demonstrated that their growth rates were commensurate with those obtained for epitaxial islands formed on calcite crystals reacted with Cd2+-bearing aqueous solutions of the same range in supersaturation with respect to the pure metal carbonate phase. This finding was unexpected as rhodochrosite (MnCO3) and calcite display a 10% lattice mismatch, based on the area of their (10-14) surface unit cells, whereas the lattice mismatch is only 4% for otavite (CdCO3) and calcite. Coatings of varying thicknesses were therefore synthesized by reacting calcite single crystals with calcite-equilibrated aqueous solutions with concentrations of up to 250 µM MnCl2 and analyzed to determine the composition of the surface precipitates. Ex situ X-ray photoelectron spectroscopy (XPS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), X-ray reflectivity (XRR), and AFM measurements of the reacted crystals demonstrated the formation of an epitaxial (Mn,Ca)CO3 solid solution with a spatially complex composition atop the calcite surface, whereby the first few nanometers were rich in Ca and the Mn content increased with distance from the original calcite surface, culminating in a topmost region of almost pure MnCO3 for the thickest coatings. These findings explain the measured growth rates (the effective lattice mismatch was much smaller than nominal mismatch) and highlight the strong influence played by the substrate on the composition of surface precipitates in aqueous conditions.

  14. Structure and reactivity of the calcite-water interface.

    Science.gov (United States)

    Heberling, Frank; Trainor, Thomas P; Lützenkirchen, Johannes; Eng, Peter; Denecke, Melissa A; Bosbach, Dirk

    2011-02-15

    The zetapotential of calcite in contact with aqueous solutions of varying composition is determined for pre-equilibrated suspensions by means of electrophoretic measurements and for non-equilibrium solutions by means of streaming potential measurements. Carbonate and calcium are identified as charge determining ions. Studies of the equilibrium solutions show a shift of isoelectric point with changing CO(2) partial pressure. Changes in pH have only a weak effect in non-equilibrium solutions. The surface structure of (104)-faces of single crystal calcite in contact to solutions corresponding to those of the zetapotential investigations is determined from surface diffraction measurements. The results reveal no direct indication of calcium or carbonate inner-sphere surface species. The surface ions are found to relax only slightly from their bulk positions; the most significant relaxation is a ∼4° tilt of the surface carbonate ions towards the surface. Two ordered layers of water molecules are identified, the first at 2.35±0.05Å above surface calcium ions and the second layer at 3.24±0.06Å above the surface associated with surface carbonate ions. A Basic-Stern surface complexation model is developed to model observed zetapotentials, while only considering outer-sphere complexes of ions other than protons and hydroxide. The Basic-Stern SCM successfully reproduces the zetapotential data and gives reasonable values for the inner Helmholtz capacitance, which are in line with the Stern layer thickness estimated from surface diffraction results. Copyright © 2010 Elsevier Inc. All rights reserved.

  15. Structure of the (1014) Surfaces of Calcite, Dolomite, and Magnesite under Wet and Dry Conditions

    Energy Technology Data Exchange (ETDEWEB)

    WRIGHT,KATE; CYGAN,RANDALL T.; SLATER,BEN

    2000-06-12

    Atomistic computer simulation methods have been employed to model the structure of the (10{bar 1}4) surfaces of calcite, dolomite and magnesite. The authors calculations show that under vacuum conditions, calcite undergoes the greatest degree of surface relaxation with rotation and distortion of the carbonate group accompanied by movement of the calcium ion. The magnesite surface is the least distorted of the three carbonates, with dolomite being intermediate to the two end members. When water molecules are placed on the surface to produce complete monolayer coverage, the calcite surface is stabilized and the amount of relaxation is substantially reduced. In contrast, the dolomite and magnesite surfaces are destabilized by hydration as indicated by a significant increase in the surface energies relative to the dry surface.

  16. 'Bioethics' is subordinate to morality in Japan.

    Science.gov (United States)

    Tanida, Noritoshi

    1996-07-01

    Disputes over brain death and euthanasia are used to illuminate the question whether there really is a Japanese way of thinking in bioethics. In Japanese thought, a person does not exist as an individual but as a member of the family, community or society. I describe these features of Japanese society as 'mutual dependency'. In this society, an act is 'good' and 'right' when it is commonly done, and it is 'bad' and 'wrong' when nobody else does it. Thus, outsiders to this ring of mutual dependency encounter ostracism. One feature of this society is a lack of open discussion which leads to the existence of multiple standards. This Japanese morality even prevails over written laws. In Japan, there is a public stance that euthanasia does not exist. On the other hand, there are certain decisions which have permitted euthanasia. Similarly, organ transplants were performed from brain dead donors, while that procedure was not accepted officially by the medical profession. In this situation, there is a danger that human rights will be neglected. So far bioethical approaches have not helped to work out these problems. This may be because Japanese think that bioethics is subordinate to morality. The current dispute over brain death involves a struggle for the establishment of a rational society in Japan. Overcoming mutual dependency and ostracism is essential to resolve this struggle and to lead Japan into a society of mutual respect where all individuals, families and communities are esteemed.

  17. Calcite as a bone substitute. Comparison with hydroxyapatite and tricalcium phosphate with regard to the osteoblastic activity

    Energy Technology Data Exchange (ETDEWEB)

    Monchau, F., E-mail: Francine.monchau@univ-artois.fr [Laboratoire Genie Civil et geo-Environnement (EA 4515, Universite Lille Nord de France), Equipe Biomateriaux Artois (Universite d' Artois), IUT/GMP, 1230, rue de l' Universite, BP 819, 62408 Bethune cedex (France); Hivart, Ph.; Genestie, B. [Laboratoire Genie Civil et geo-Environnement (EA 4515, Universite Lille Nord de France), Equipe Biomateriaux Artois (Universite d' Artois), IUT/GMP, 1230, rue de l' Universite, BP 819, 62408 Bethune cedex (France); Chai, F. [Laboratoire Medicaments et Biomateriaux a Liberation Controlee (INSERM U 1008, Universite Lille Nord de France), Groupe de Recherche sur les Biomateriaux (Universite Lille-2), Faculte de Medecine, 1, place de Verdun, 59045 Lille cedex (France); and others

    2013-01-01

    Close to the bone mineral phase, the calcic bioceramics, such as hydroxyapatite (HA) and {beta}-tricalcium phosphate ({beta}-TCP), are commonly used as substitutes or filling materials in bone surgery. Besides, calcium carbonate (CaCO{sub 3}) is also used for their excellent biocompatibility and bioactivity. However, the problem with the animal-origin aragonite demands the new technique to synthesize pure calcite capable of forming 3D bone implant. This study aims to manufacture and evaluate a highly-pure synthetic crystalline calcite with good cytocompatibility regarding to the osteoblasts, comparing to that of HA and {beta}-TCP. After the manufacture of macroporous bioceramic scaffolds with the identical internal architecture, their cytocompatibility is studied through MC3T3-E1 osteoblasts with the tests of cell viability, proliferation, vitality, etc. The results confirmed that the studied process is able to form a macroporous material with a controlled internal architecture, and this synthesized calcite is non-cytotoxic and facilitate the cell proliferation. Indeed requiring further improvement, the studied calcite is definitely an interesting alternative not only to coralline aragonite but also to calcium phosphate ceramics, particularly in bone sites with the large bone remodelling. Highlights: Black-Right-Pointing-Pointer Macroporous calcite manufacturing with controlled architecture as bone substitute Black-Right-Pointing-Pointer Cytotoxicity: adaptation of the colony-forming method with the target cells: MC3T3-E1 osteoblasts Black-Right-Pointing-Pointer Study of osteoblast proliferation and activity on calcite, HA and TCP.

  18. Interaction of alcohols with the calcite surface

    DEFF Research Database (Denmark)

    Bovet, Nicolas Emile; Yang, Mingjun; Javadi, Meshkat Sadat

    2015-01-01

    A clearer understanding of calcite interactions with organic molecules would contribute to a range of fields including harnessing the secrets of biomineralisation where organisms produce hard parts, increasing oil production from spent reservoirs, remediating contaminated soils and drinking water...... aquifers and improving manufacturing methods for industrial products such as pigments, soft abrasives, building materials and optical devices. Biomineralisation by some species of blue green algae produces beautifully elaborate platelets of calcite where the individual crystals are of nanometer scale...

  19. From Subordinate Marker to Discourse Marker: que in Andean Spanish

    Directory of Open Access Journals (Sweden)

    Anna María Escobar

    2005-06-01

    Full Text Available This paper proposes an analysis of a redundant use of que ('that' found in Andean Spanish as an expression which has undergone a grammaticalization process. Evidence suggests that the function of que as subordinate marker is much more generalized in this variety than in other dialects of Spanish. que is found to be used as a marker introducing both nominal and adjectival clauses, suggesting that adjectival subordinates behave as nominal subordinates in this variety of Spanish. An intrusive que appears in restricted syntactic and semantic contexts with clauses that have nominal and adjectival functions, and even appears replacing adverbial expressions in some adverbial subordinates (temporal, spatial, and manner. Furthermore, it is found to be sensitive to the degree of the argument’s thematic/semantic function in the subordinate clause. In particular, it seems to occur more often with low-agency arguments in adjectival and nominal contexts, and, in nominal subordinates, tends to appear with a restricted set of epistemic and evidential main verbs (e.g. creer 'to believe', saber 'to know', decir 'to say'. The analysis suggests that que has developed a new function in this variety of Spanish, namely, one of indicating that the information contained in the subordinate clause does not constitute background information (as would be expected in non-contact varieties of Spanish but instead contains information relevant to the discourse.

  20. Diffusion of Ca and Mg in Calcite

    Energy Technology Data Exchange (ETDEWEB)

    Cygan, R.T.; Fisler, D.K.

    1999-02-10

    The self-diffusion of Ca and the tracer diffusion of Mg in calcite have been experimentally measured using isotopic tracers of {sup 25}Mg and {sup 44}Ca. Natural single crystals of calcite were coated with a thermally-sputtered oxide thin film and then annealed in a CO{sub 2} gas at one atmosphere total pressure and temperatures from 550 to 800 C. Diffusion coefficient values were derived from the depth profiles obtained by ion microprobe analysis. The resultant activation energies for Mg tracer diffusion and Ca self-diffusion are respectively: E{sub a}(Mg) = 284 {+-} 74 kJ/mol and E{sub a}(Ca) = 271 {+-} 80 kJ/mol. For the temperature ranges in these experiments, the diffusion of Mg is faster than Ca. The results are generally consistent in magnitude with divalent cation diffusion rates obtained in previous studies and provide a means of interpreting the thermal histories of carbonate minerals, the mechanism of dolomitization, and other diffusion-controlled processes. The results indicate that cation diffusion in calcite is relatively slow and cations are the rate-limiting diffusing species for the deformation of calcite and carbonate rocks. Application of the calcite-dolomite geothermometer to metamorphic assemblages will be constrained by cation diffusion and cooling rates. The direct measurement of Mg tracer diffusion in calcite indicates that dolomitization is unlikely to be accomplished by Mg diffusion in the solid state but by a recrystallization process.

  1. V2 word order in subordinate clauses in spoken Danish

    DEFF Research Database (Denmark)

    Jensen, Torben Juel; Christensen, Tanya Karoli

    studies of two age cohorts of speakers in Copenhagen, recorded in the 1980s and again in 2005-07, and on recent recordings with two age cohorts of speakers from the western part of Jutland. This makes it possible to study variation and change with respect to word order in subordinate clauses in both real...... and apparent time, as well as geographical variation. The results show that V2 word order in subordinate clauses is much more frequent than commonly assumed. Furthermore, they indicate that the most decisive factors predicting word order in subordinate clauses are the syntactic function of the clause...

  2. Principles of calcite dissolution in human and artificial otoconia.

    Directory of Open Access Journals (Sweden)

    Leif Erik Walther

    Full Text Available Human otoconia provide mechanical stimuli to deflect hair cells of the vestibular sensory epithelium for purposes of detecting linear acceleration and head tilts. During lifetime, the volume and number of otoconia are gradually reduced. In a process of degeneration morphological changes occur. Structural changes in human otoconia are assumed to cause vertigo and balance disorders such as benign paroxysmal positional vertigo (BPPV. The aim of this study was to investigate the main principles of morphological changes in human otoconia in dissolution experiments by exposure to hydrochloric acid, EDTA, demineralized water and completely purified water respectively. For comparison reasons artificial (biomimetic otoconia (calcite gelatin nanocomposits and natural calcite were used. Morphological changes were detected in time steps by the use of environmental scanning electron microscopy (ESEM. Under in vitro conditions three main dissolution mechanisms were identified as causing characteristic morphological changes of the specimen under consideration: pH drops in the acidic range, complex formation with calcium ions and changes of ion concentrations in the vicinity of otoconia. Shifts in pH cause a more uniform reduction of otoconia size (isotropic dissolution whereas complexation reactions and changes of the ionic concentrations within the surrounding medium bring about preferred attacks at specific areas (anisotropic dissolution of human and artificial otoconia. Owing to successive reduction of material, all the dissolution mechanisms finally produce fragments and remnants of otoconia. It can be assumed that the organic component of otoconia is not significantly attacked under the given conditions. Artificial otoconia serve as a suitable model system mimicking chemical attacks on biogenic specimens. The underlying principles of calcite dissolution under in vitro conditions may play a role in otoconia degeneration processes such as BPPV.

  3. Mechanism of Calcite Co-Orientation in the Sea Urchin Tooth

    Energy Technology Data Exchange (ETDEWEB)

    Killian, Christopher; Metzler, Rebecca; Gong, Y. U. T.; Olson, Ian; Aizenberg, Joanna; Politi, Yael; Wilt, Fred; Scholl, Andreas; Young, Anthony; Doran, Andrew; Kunz, Martin; Tamura, Nobumichi; Coppersmith, Susan; Gilbert, P. U. P. A.

    2009-12-01

    Sea urchin teeth are remarkable and complex calcite structures, continuously growing at the forming end and self-sharpening at the mature grinding tip. The calcite (CaCO{sub 3}) crystals of tooth components, plates, fibers, and a high-Mg polycrystalline matrix, have highly co-oriented crystallographic axes. This ability to co-orient calcite in a mineralized structure is shared by all echinoderms. However, the physico-chemical mechanism by which calcite crystals become co-oriented in echinoderms remains enigmatic. Here, we show differences in calcite c-axis orientations in the tooth of the purple sea urchin (Strongylocentrotus purpuratus), using high-resolution X-ray photoelectron emission spectromicroscopy (X-PEEM) and microbeam X-ray diffraction ({mu}XRD). All plates share one crystal orientation, propagated through pillar bridges, while fibers and polycrystalline matrix share another orientation. Furthermore, in the forming end of the tooth, we observe that CaCO{sub 3} is present as amorphous calcium carbonate (ACC). We demonstrate that co-orientation of the nanoparticles in the polycrystalline matrix occurs via solid-state secondary nucleation, propagating out from the previously formed fibers and plates, into the amorphous precursor nanoparticles. Because amorphous precursors were observed in diverse biominerals, solid-state secondary nucleation is likely to be a general mechanism for the co-orientation of biomineral components in organisms from different phyla.

  4. Influence of calcite on uranium(VI) reactive transport in the groundwater-river mixing zone.

    Science.gov (United States)

    Ma, Rui; Liu, Chongxuan; Greskowiak, Janek; Prommer, Henning; Zachara, John; Zheng, Chunmiao

    2014-01-01

    Calcite is an important, relatively soluble mineral phase that can affect uranium reactive transport in subsurface sediments. This study was conducted to investigate the distribution of calcite and its influence on uranium adsorption and reactive transport in the groundwater-river mixing zone of the Hanford 300A site, Washington State. Simulations using a two-dimensional (2D) reactive transport model under field-relevant hydrological and hydrogeochemical conditions revealed the development of a calcite reaction front through the mixing zone as a result of dynamic groundwater-river interactions. The calcite concentration distribution, in turn, affected the concentrations of aqueous carbonate and calcium, and pH through dissolution, as river waters intruded and receded from the site at different velocities in response to stage changes. The composition variations in groundwater subsequently influenced uranium mobility and discharge rates into the river in a complex fashion. The results implied that calcite distribution and concentration are important variables that need to be quantified for accurate reactive transport predictions of uranium, especially in dynamic groundwater-river mixing zones. © 2013.

  5. On Certain Subclasses of Analytic Functions Defined by Differential Subordination

    Directory of Open Access Journals (Sweden)

    Hesam Mahzoon

    2011-01-01

    Full Text Available We introduce and study certain subclasses of analytic functions which are defined by differential subordination. Coefficient inequalities, some properties of neighborhoods, distortion and covering theorems, radius of starlikeness, and convexity for these subclasses are given.

  6. Supervisor's HEXACO personality traits and subordinate perceptions of abusive supervision

    NARCIS (Netherlands)

    Breevaart, Kimberley; de Vries, Reinout Everhard

    2017-01-01

    Abusive supervision is detrimental to both subordinates and organizations. Knowledge about individual differences in personality related to abusive supervision may improve personnel selection and potentially reduce the harmful effects of this type of leadership. Using the HEXACO personality

  7. Rehabilitation Agency Leadership Style: Impact on Subordinates' Job Satisfaction.

    Science.gov (United States)

    Packard, Susan H.; Kauppi, Dwight R.

    1999-01-01

    One hundred five rehabilitation employees were surveyed on the effect of leadership style on subordinates' perceptions of their work environment and on their job satisfaction. Findings suggest that leadership style affects service delivery. (Author/MKA)

  8. Superiors' Argumentativeness and Verbal Agressiveness as Predictors of Subordinates' Satisfaction.

    Science.gov (United States)

    Infante, Dominic A.; Gorden, William I.

    1985-01-01

    Supported the hypothesis that the more employees perceive their supervisors as high in argumentativeness and low in verbal aggressiveness, the more the subordinates also will be argumentative (i.e., assertive) and have job satisfaction. (PD)

  9. 32 CFR 776.54 - Responsibilities of a subordinate attorney.

    Science.gov (United States)

    2010-07-01

    ... part or the duty of a judge advocate to exercise independent professional judgment as to the best interest of an individual client. (3) A subordinate covered attorney does not violate this part if that...

  10. A taxonomy of supervisor–subordinate exchanges across cultures

    Directory of Open Access Journals (Sweden)

    Naresh Khatri

    2011-06-01

    Full Text Available Major concerns, both theoretical and methodological, have been raised about the adequacy of the leader-member exchange (LMX theory, the existing model on supervisor–subordinate exchanges. This paper seeks to overcome three main theoretical shortcomings of the LMX theory as documented in past research. First, that the LMX theory does not describe the exchange process sufficiently, and second, that it does not capture the cross-cultural influences on supervisor–subordinate exchanges. This paper deals with these weaknesses by providing a comprehensive description of supervisor–subordinate exchanges across cultures using two theoretical frameworks, Fiske’s relational theory and Triandis’s cultural syndromes. A third problem with the LMX theory is that it assumes all close relationships between supervisors and subordinates to be beneficial for the organisation. However, a stream of research has emerged that documents the downside of close relationships between supervisors and their subordinates. Utilising a recent cross-cultural framework on cronyism, this paper sheds light on the dysfunctional organisational consequences of close relationships between supervisors and their subordinates across cultures.

  11. Do organic ligands affect calcite dissolution rates?

    Science.gov (United States)

    Oelkers, Eric H.; Golubev, Sergey V.; Pokrovsky, Oleg S.; Bénézeth, Pascale

    2011-04-01

    Steady state Iceland-spar calcite dissolution rates were measured at 25 °C in aqueous solutions containing 0.1 M NaCl and up to 0.05 M dissolved bicarbonate at pH from 7.9 to 9.1 in the presence of 13 distinct dissolved organic ligands in mixed-flow reactors. The organic ligands considered in this study include those most likely to be present in either (1) aquifers at the conditions pertinent to CO 2 sequestration or (2) soil/early diagenetic environments: acetate, phthalate, citrate, EDTA 4-, succinate, D-glucosaminate, L-glutamate, D-gluconate, 2,4-dihydroxybenzoate, 3,4-dihydroxybenzoate, fumarate, malonate, and gallate. Results show that the presence of exopolysaccharides, and analogs of microbial cell envelopes: alginate, lichen extract, humic acid, pectin, and gum xanthan. In no case did the presence of <100 ppm of these organics change calcite dissolution rates by more than a factor of 2.5. Results obtained in this study suggest that the presence of aqueous organic anions negligibly affects calcite forward dissolution rates in most natural environments. Some effect on calcite reactivity may be observed, however, by the presence of organic anions if they change substantially the chemical affinity of the fluid with respect to calcite.

  12. EFFECT OF MAGNESIUM AS SUBSTITUTE MATERIAL IN ENZYME MEDIATED CALCITE PRECIPITATION (EMCP) FOR SOIL IMPROVEMENT TECHNIQUE

    OpenAIRE

    Heriansyah ePutra; Heriansyah ePutra; Hideaki eYasuhara; Naoki eKinoshita; Debendra eNeupane

    2016-01-01

    The optimization of enzyme-mediated calcite precipitation (EMCP) was evaluated as a soil improvement technique. In our previous works, purified urease was utilized to bio-catalyze the hydrolysis of urea, which causes the supplied Ca2+ to precipitate with CO32- as calcium carbonate. In the present work, magnesium chloride was newly added to the injecting solutions to delay the reaction rate and to enhance the amount of carbonate precipitation. Soil specimens were prepared in PVC cylinders and ...

  13. Structure and dynamics of microbe-exuded polymers and their interactions with calcite surfaces.

    Energy Technology Data Exchange (ETDEWEB)

    Cygan, Randall Timothy; Mitchell, Ralph (Harvard University, Cambridge, MA); Perry, Thomas D. (Harvard University, Cambridge, MA)

    2005-12-01

    Cation binding by polysaccharides is observed in many environments and is important for predictive environmental modeling, and numerous industrial and food technology applications. The complexities of these organo-cation interactions are well suited to predictive molecular modeling studies for investigating the roles of conformation and configuration of polysaccharides on cation binding. In this study, alginic acid was chosen as a model polymer and representative disaccharide and polysaccharide subunits were modeled. The ability of disaccharide subunits to bind calcium and to associate with the surface of calcite was investigated. The findings were extended to modeling polymer interactions with calcium ions.

  14. Two-phase flow and calcite deposition

    Energy Technology Data Exchange (ETDEWEB)

    Gudmudsson, J.S.; Granadso-G, E.; Ortiz-R, J.

    1984-04-01

    The literature on two-phase flow in geothermal wells shows that the Orkiszewski method has found wide application in state-of-the-art wellbore simulators. Such a simulator was developed and then used for the problem of wellbore deposition of calcite in the Miravalles geothermal field in Costa Rica. The output of wells suffering calcite deposition decreases slowly at early time but rapidly at late time. The simulator was also used to estimate the deliverability curve for a large diameter well in the Svartsengi geothemal field in Iceland. The view is presented that more accurate wellbore simulators will make new reservoir engineering studies possible in geothermal fields.

  15. Acidization of shales with calcite cemented fractures

    Science.gov (United States)

    Kwiatkowski, Kamil; Szymczak, Piotr; Jarosiński, Marek

    2017-04-01

    Investigation of cores drilled from shale formations reveals a relatively large number of calcite-cemented fractures. Usually such fractures are reactivated during fracking and can contribute considerably to the permeability of the resulting fracture network. However, calcite coating on their surfaces effectively excludes them from production. Dissolution of the calcite cement by acidic fluids is investigated numerically with focus on the evolution of fracture morphology. Available surface area, breakthrough time, and reactant penetration length are calculated. Natural fractures in cores from Pomeranian shale formation (northern Poland) were analyzed and classified. Representative fractures are relatively thin (0.1 mm), flat and completely sealed with calcite. Next, the morphology evolution of reactivated natural fractures treated with low-pH fluids has been simulated numerically under various operating conditions. Depth-averaged equations for fracture flow and reactant transport has been solved by finite-difference method coupled with sparse-matrix solver. Transport-limited dissolution has been considered, which corresponds to the treatment with strong acids, such as HCl. Calcite coating in reactivated natural fractures dissolves in a highly non-homogeneous manner - a positive feedback between fluid transport and calcite dissolution leads to the spontaneous formation of wormhole-like patterns, in which most of the flow is focused. The wormholes carry reactive fluids deeper inside the system, which dramatically increases the range of the treatment. Non-uniformity of the dissolution patterns provides a way of retaining the fracture permeability even in the absence of the proppant, since the less dissolved regions will act as supports to keep more dissolved regions open. Evolution of fracture morphology is shown to depend strongly on the thickness of calcite layer - the thicker the coating the more pronounced wormholes are observed. However the interaction between

  16. A fully subordinated linear flow model for hillslope subsurface stormflow

    Science.gov (United States)

    Zhang, Yong; Baeumer, Boris; Chen, Li; Reeves, Donald M.; Sun, HongGuang

    2017-04-01

    Hillslope subsurface stormflow exhibits complex patterns when natural soils with multiscale heterogeneity impart a spatiotemporally nonlocal memory on flow dynamics. To efficiently quantify such nonlocal flow responses, this technical note proposes a fully subordinated flow (FSF) equation where the time- and flow-subordination capture the temporal and spatial memory, respectively. Results show that the time-subordination component of the FSF model captures a wide range of delayed flow response due to various degrees of soil heterogeneity (especially for low-conductivity zones), while the model's flow-subordination term accounts for the rapid flow responses along preferential flow paths. In the FSF model, parameters defining spatiotemporal memory functions may be related to soil properties, while other parameters such as scalar factors controlling the overall advection and diffusion are difficult to predict and can be estimated from subsurface stormflow hydrographs. These parameters can be constants at the hillslope scale because the spatiotemporal subordination, an upscaling technique, can capture the impact of system heterogeneity on flow dynamics, leading to a linear FSF model that might be applicable for various slopes. Valid scale, limitation and extension of the FSF model, and modification of the model for other complex hydrological dynamics are also discussed.

  17. Morphology and formation mechanism in precipitation of calcite induced by Curvibacter lanceolatus strain HJ-1

    Science.gov (United States)

    Zhang, Chonghong; Li, Fuchun; Lv, Jiejie

    2017-11-01

    Precipitation of calcium carbobate induced by microbial activities is common occurrence in controlled solution, but the formation mechanism and morphology in precipitation of calcite in solution systems is unclear, and the role of microbes is disputed. Here, culture experiment was performed for 50 days using the Curvibacter lanceolatus strain HJ-1 in a M2 culture medium, and the phase composition and morphology of the precipitates were characterized by the X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and scanning electron microscopy (SEM) techniques. We show that the precipitation processes in our experiment lead to unusual morphologies of crystals corresponding to different growth stages, and the morphologies of the precipitated crystal aggregates ranging from the main rod-, cross-, star-, cauliflower-like morphologies to spherulitic structure. The complex and unusual morphologies of the precipitated calcite by strain HJ-1 may provide a reference point for better understanding the biomineralization mechanism of calcite, moreover, morphological transition of minerals revealed that the multi-ply crystals-aggregation mechanism for calcite growth in crystallisation media.

  18. Unusual biogenic calcite structures in two shallow lakes, James Ross Island, Antarctica

    Science.gov (United States)

    Elster, J.; Nedbalová, L.; Vodrážka, R.; Láska, K.; Haloda, J.; Komárek, J.

    2016-01-01

    The floors of two shallow endorheic lakes, located on volcanic surfaces on James Ross Island, are covered with calcareous organosedimentary structures. Their biological and chemical composition, lake water characteristics, and seasonal variability of the thermal regime are introduced. The lakes are frozen down to the bottom for 8-9 months a year and their water chemistry is characterised by low conductivity and neutral to slightly alkaline pH. The photosynthetic microbial mat is composed of filamentous cyanobacteria and microalgae that are considered to be Antarctic endemic species. The mucilaginous black biofilm is covered by green spots formed by a green microalga and the macroscopic structures are packed together with fine material. Thin sections consist of rock substrate, soft biofilm, calcite spicules and mineral grains originating from different sources. The morphology of the spicules is typical of calcium carbonate monocrystals having a layered structure and specific surface texture, which reflect growth and degradation processes. The spicules' chemical composition and structure correspond to pure calcite. The lakes' age, altitude, morphometry, geomorphological and hydrological stability, including low sedimentation rates, together with thermal regime predispose the existence of this community. We hypothesise that the precipitation of calcite is connected with the photosynthetic activity of the green microalgae that were not recorded in any other lake in the region. This study has shown that the unique community producing biogenic calcite spicules is quite different to any yet described.

  19. Calcite dissolution kinetics at the interface between a calcite-rich simulated sediment and natural seawater.

    Science.gov (United States)

    Sulpis, O.; Lix, C.; Mucci, A.; Boudreau, B. P.

    2016-12-01

    Over the past decades, numerous studies of CaCO3 mineral dissolution kinetics have been performed in seawater. Despite this continuous effort, the mechanisms controlling the dissolution are still poorly understood and large discrepancies exist between results of in-situ and laboratory studies, most of which have been carried out under conditions (e.g., mineral suspensions) that are not representative of processes taking place at the seafloor. In this study, we addressed this issue by using a synthetic sediment disk composed of a mixture of calcite and montmorillonite, in a thermostated, stirred-flow reactor over a range of seawater undersaturations in an attempt to simulate conditions encountered at the seafloor. We show that, unlike the higher reaction orders reported in previous studies, the dissolution kinetics of calcite are almost linearly dependent on the seawater undersaturation with respect to calcite when normalized to the exposed surface area of the disks, with a rate constant similar to that derived by Keir (1983) using reagent calcite. Even under quiescent conditions, the calcite dissolution appears to extend well below the sediment-water interface of our synthetic sediment disks. When normalized to the geometric surface area of calcite within the apparent reaction volume, the dissolution kinetics are also nearly linear, with a dissolution rate constant whose value is orders of magnitude lower than previously reported. Keir, R. S. (1983), Variation in the carbonate reactivity of deep-sea sediments: determination from flux experiments, Deep Sea Res., Part A, 30, 279-296.

  20. A Subordination Principle on Wright Functions and Regularized Resolvent Families

    Directory of Open Access Journals (Sweden)

    Luciano Abadias

    2015-01-01

    Full Text Available We obtain a vector-valued subordination principle for gα,gβ-regularized resolvent families which unified and improves various previous results in the literature. As a consequence, we establish new relations between solutions of different fractional Cauchy problems. To do that, we consider scaled Wright functions which are related to Mittag-Leffler functions, the fractional calculus, and stable Lévy processes. We study some interesting properties of these functions such as subordination (in the sense of Bochner, convolution properties, and their Laplace transforms. Finally we present some examples where we apply these results.

  1. Calcite growth kinetics: Modeling the effect of solution stoichiometry

    NARCIS (Netherlands)

    Wolthers, M.; Nehrke, G.; Gustafsson, J.P.; Van Cappellen, P.

    2012-01-01

    Until recently the influence of solution stoichiometry on calcite crystal growth kinetics has attracted little attention, despite the fact that in most aqueous environments calcite precipitates from non-stoichiometric solution. In order to account for the dependence of the calcite crystal growth

  2. High-Magnesian Calcite Mesocrystals : A Coordination Chemistry Approach

    NARCIS (Netherlands)

    Lenders, Jos J. M.; Dey, Archan; Bomans, Paul H. H.; Spielmann, Jan; Hendrix, Marco M. R. M.; de With, Gijsbertus; Meldrum, Fiona C.; Harder, Sjoerd; Sommerdijk, Nico A. J. M.

    2012-01-01

    While biogenic calcites frequently contain appreciable levels of magnesium, the pathways leading to such high concentrations remain unclear. The production of high-magnesian calcites in vitro is highly challenging, because Mg-free aragonite, rather than calcite, is the favored product in the

  3. Patriarchy and the subordination of women among the Abagusii of ...

    African Journals Online (AJOL)

    The paper discusses the role of private patriarchy in the subordination of women among the Abagusii of western Kenya. It identifies customs and practices governing marriage such as the payment of dowry, circumcision, the gender division of labour within the household and polygamy as the main factors contributing to the ...

  4. Supervisors' and subordinates' perception of the Impact of Botswana ...

    African Journals Online (AJOL)

    This study was a descriptive survey, which ascertained supervisors and subordinates perception of the impact of Botswana College of Agriculture training programme on graduates' job behaviour. The study was carried out in the Ministry of Agriculture, Gaborone, Botswana, which is composed of six departments. All BCA ...

  5. Stable Lévy motion with inverse Gaussian subordinator

    Science.gov (United States)

    Kumar, A.; Wyłomańska, A.; Gajda, J.

    2017-09-01

    In this paper we study the stable Lévy motion subordinated by the so-called inverse Gaussian process. This process extends the well known normal inverse Gaussian (NIG) process introduced by Barndorff-Nielsen, which arises by subordinating ordinary Brownian motion (with drift) with inverse Gaussian process. The NIG process found many interesting applications, especially in financial data description. We discuss here the main features of the introduced subordinated process, such as distributional properties, existence of fractional order moments and asymptotic tail behavior. We show the connection of the process with continuous time random walk. Further, the governing fractional partial differential equations for the probability density function is also obtained. Moreover, we discuss the asymptotic distribution of sample mean square displacement, the main tool in detection of anomalous diffusion phenomena (Metzler et al., 2014). In order to apply the stable Lévy motion time-changed by inverse Gaussian subordinator we propose a step-by-step procedure of parameters estimation. At the end, we show how the examined process can be useful to model financial time series.

  6. Health care managers learning by listening to subordinates' dialogue training.

    Science.gov (United States)

    Grill, C; Ahlborg, G; Wikström, E

    2014-01-01

    Middle managers in health care today are expected to continuously and efficiently decide and act in administration, finance, care quality, and work environment, and strategic communication has become paramount. Since dialogical communication is considered to promote a healthy work environment, the purpose of this paper is to investigate the ways in which health care managers experienced observing subordinates' dialogue training. A qualitative study using semi-structured interviews and documents from eight middle managers in a dialogue programme intervention conducted by dialogue trainers. Focus was on fostering and assisting workplace dialogue. Conventional qualitative content analysis was used. Managers' experiences were both enriching and demanding, and consisted of becoming aware of communication, meaning perceiving interaction between subordinates as well as own silent interaction with subordinates and trainer; Discovering communicative actions for leadership, by gaining self-knowledge and recognizing relational leadership models from trainers--such as acting democratically and pedagogically--and converting theory into practice, signifying practising dialogue-promoting conversation behaviour with subordinates, peers, and superiors. Only eight managers participated in the intervention, but data afforded a basis for further research. Findings stressed the importance of listening, and of support from superiors, for well-functioning leadership communication at work. Studies focusing on health care managers' communication and dialogue are few. This study contributes to knowledge about these activities in managerial leadership.

  7. On a differential subordination of some certain subclass of Univalent ...

    African Journals Online (AJOL)

    convex functions using Briot-Bouquet differential subordination method. Journal of the Nigerian Association of Mathematical Physics Vol. 10 2006: pp. 181-184. http://dx.doi.org/10.4314/jonamp.v10i1.40124 · AJOL African Journals Online.

  8. Children's Communication of Basic Level and Subordinate Level Semantic Contrasts.

    Science.gov (United States)

    Kossan, Nancy E.

    Developmental differences in preschool children's abilities to communicate about basic and subordinate level semantic contrasts were examined in a referential communication situation. Twenty-four three, four, and five-year-old children communicated with children of the same age and adults about pictures' referents. Speakers talked about one…

  9. Relative wettability alteration of calcite surfaces

    Science.gov (United States)

    Prabhakar, Sanjay; Liu, Jian; Pantelides, Sokrates

    Enhancement of crude oil recovery from calcite reservoirs remains a major challenge in the oil industry. Crude oil recovery can be enhanced by modifying the relative wettability of calcite reservoirs by injecting sea water. In this work, we consider acetic acid as a model component of crude oil and use the changes of adsorption energies of oil and water molecules induced by additives as a measure of relative wettability alteration of the calcite surface. More specifically, we investigate the influence of Na+, Mg2+, Ca2+, SO42- and Cl- ions on the adsorption energies of water and acetic acid. It is expected that crude oil recovery is enhanced if the modified acetic acid molecule binds weaker than acetic acid. We use density functional theory calculations and show that the presence of Na+ ions reduces oil recovery whereas the presence of Mg and SO4 ions enhance oil recovery. Additionally, we propose a novel possibility of lifting two oil molecules by one Mg2+ ion, which yields enhanced oil recovery, as observed. We also found that Cl merely binds to the surface and has no effect on the adsorption energy of acetic acid, which means that Cl has no effect on oil recovery. This work was supported by a Grant from the Petroleum Institute of Abu Dhabi.

  10. Common Ion Effects In Zeoponic Substrates: Dissolution And Cation Exchange Variations Due to Additions of Calcite, Dolomite and Wollastonite

    Science.gov (United States)

    Beiersdorfer, R. E.; Ming, D. W.; Galindo, C., Jr.

    2003-01-01

    c1inoptilolite-rich tuff-hydroxyapatite mixture (zeoponic substrate) has the potential to serve as a synthetic soil-additive for plant growth. Essential plant macro-nutrients such as calcium, phosphorous, magnesium, ammonium and potassium are released into solution via dissolution of the hydroxyapatite and cation exchange on zeolite charged sites. Plant growth experiments resulting in low yield for wheat have been attributed to a Ca deficiency caused by a high degree of cation exchange by the zeolite. Batch-equilibration experiments were performed in order to determine if the Ca deficiency can be remedied by the addition of a second Ca-bearing, soluble, mineral such as calcite, dolomite or wollastonite. Variations in the amount of calcite, dolomite or wollastonite resulted in systematic changes in the concentrations of Ca and P. The addition of calcite, dolomite or wollastonite to the zeoponic substrate resulted in an exponential decrease in the phosphorous concentration in solution. The exponential rate of decay was greatest for calcite (5.60 wt. % -I), intermediate for wollastonite (2.85 wt.% -I) and least for dolomite (1.58 wt.% -I). Additions of the three minerals resulted in linear increases in the calcium concentration in solution. The rate of increase was greatest for calcite (3.64), intermediate for wollastonite (2.41) and least for dolomite (0.61). The observed changes in P and Ca concentration are consistent with the solubilities of calcite, dolomite and wollastonite and with changes expected from a common ion effect with Ca. Keywords: zeolite, zeoponics, common-ion effect, clinoptilolite, hydroxyapatite

  11. The influence of mineralization pathways on the Mg content and fractionation patterns in calcite

    Science.gov (United States)

    Dove, P. M.; Wang, D.; DeYoreo, J.

    2011-12-01

    Chemical proxy models are based upon the long-standing assumption that the uptake of minor and trace elements into a growing mineral reflects equilibrium fractionation processes. This picture is rooted in fundamental assumptions from BCF crystal growth theory- the thermodynamic-based model that was derived for step growth at very near equilibrium conditions. However, the original assumptions of this theory have been lost. Moreover, the applicability of step growth processes to biomineralization is being called into question with the realization that many carbonate biominerals form by non-classical processes. Here, mineralization begins with the accumulation of an amorphous calcium carbonate (ACC) in a localized environment that subsequently transforms to the complex mesocrystal/organic composites we know as skeletal structures. This study investigates the Mg content of calcites that form from ACC over a range of Mg/Ca ratios. At low Mg/Ca levels where Mg content is insufficient to inhibit step growth, the ACC transforms into crystallites of Mg calcites with 0-20 mol % MgCO3. These calcites exhibit the expected linear fractionation with Mg/Ca of the initial solution. In contrast, when initial Mg levels are above the threshold where step growth is prohibited, ACC transforms to nanoparticle aggregates of very high Mg calcite (30-50 mol% MgCO3). The Mg content of calcites formed by this process is approximately independent of solution composition- without evidence of fractionation. Mineralization is biased to this alternative pathway when the Mg content of the local environment is too high for calcite growth and saturation increases rapidly to reach ACC solubility before aragonite precipitation can occur. The pathway is allowed because high levels of supersaturation render thermodynamic barriers to nucleation less significant than kinetic barriers, which are apparently larger for the crystalline phases. Thus, the alternative pathway is a consequence of interplays

  12. Impact of amorphous precursor phases on magnesium isotope signatures of Mg-calcite

    Science.gov (United States)

    Mavromatis, Vasileios; Purgstaller, Bettina; Dietzel, Martin; Buhl, Dieter; Immenhauser, Adrian; Schott, Jacques

    2017-04-01

    Various marine calcifiers form exoskeletons via an amorphous calcium carbonate (ACC) precursor phase and magnesium plays an important role in the temporary stabilization of this metastable phase. Thus, the use of Mg isotope ratios of marine biogenic carbonates as a proxy to reconstruct past seawater chemistry calls for a detailed understanding of the mechanisms controlling Mg isotope signatures during the formation and transformation of ACC to the final crystalline carbonate mineral. For this purpose we have investigated the Mg isotope fractionation between (Ca,Mg)CO3 solids and aqueous fluids at 25 °C and pH = 8.3 during (i) the direct precipitation of crystalline Mg-calcite and (ii) the formation of Mg-rich ACC (Mg-ACC) and its transformation to Mg-calcite. The outcome documents that the small Mg isotope fractionation between Mg-ACC and reactive fluid (ΔMg26ACC-fluid = - 1.0 ± 0.1 ‰) is not preserved during the transformation of the ACCs into Mg-calcite. Following a pronounced isotopic shift accompanying the transformation of Mg-ACC into Mg-calcite, Δ26Mgcalcite-fluid progressively decreases with reaction progress from ∼ - 3.0 ‰ to - 3.6 ‰, reflecting both the approach of isotopic equilibrium and the increase of calcite Mg content (to near 20 mol % Mg). In contrast the crystalline Mg-calcite precipitated directly from the reacting fluid, i.e. lacking a discernable formation of an amorphous precursor, exhibits only small temporal variations in Δ26Mgcalcite-fluid which overall is affected by the precipitation kinetics. The values found in this study at the onset of Mg-ACC precipitation for Mg isotope fractionation between Mg-ACC and the fluid (ΔMg26ACC-fluid = - 1.0 ‰) and between Mg-ACC and Mg2+(aq) (Δ (aq) 26Mg ACC-Mg2+ = + 2.0 ‰) are consistent with the formation of a hydrated Ca nanoporous solid accommodating Mg bicarbonate/carbonate species in combination with hydrated magnesium. This material crossed by percolating channels filled with the

  13. Abusive Supervision and Subordinate Performance : Instrumentality Considerations in the Emergence and Consequences of Abusive Supervision

    NARCIS (Netherlands)

    Walter, Frank; Lam, Catherine K.; van der Vegt, Geert; Huang, X.; Miao, Q.

    Drawing from moral exclusion theory, this article examines outcome dependence and interpersonal liking as key boundary conditions for the linkage between perceived subordinate performance and abusive supervision. Moreover, it investigates the role of abusive supervision for subordinates' subsequent,

  14. Growing spherulitic calcite grains in saline, hyperalkaline lakes: experimental evaluation of the effects of Mg-clays and organic acids

    Science.gov (United States)

    Mercedes-Martín, R.; Rogerson, M. R.; Brasier, A. T.; Vonhof, H. B.; Prior, T. J.; Fellows, S. M.; Reijmer, J. J. G.; Billing, I.; Pedley, H. M.

    2016-04-01

    The origin of spherical-radial calcite bodies - spherulites - in sublacustrine, hyperalkaline and saline systems is unclear, and therefore their palaeoenvironmental significance as allochems is disputed. Here, we experimentally investigate two hypotheses concerning the origin of spherulites. The first is that spherulites precipitate from solutions super-saturated with respect to magnesium-silicate clays, such as stevensite. The second is that spherulite precipitation happens in the presence of dissolved, organic acid molecules. In both cases, experiments were performed under sterile conditions using large batches of a synthetic and cell-free solution replicating waters found in hyperalkaline, saline lakes (such as Mono Lake, California). Our experimental results show that a highly alkaline and highly saline solution supersaturated with respect to calcite (control solution) will precipitate euhedral to subhedral rhombic and trigonal bladed calcite crystals. The same solution supersaturated with respect to stevensite precipitates sheet-like stevensite crystals rather than a gel, and calcite precipitation is reduced by ~ 50% compared to the control solution, producing a mixture of patchy prismatic subhedral to euhedral, and minor needle-like, calcite crystals. Enhanced magnesium concentration in solution is the likely the cause of decreased volumes of calcite precipitation, as this raised equilibrium ion activity ratio in the solution. On the other hand, when alginic acid was present then the result was widespread development of micron-size calcium carbonate spherulite bodies. With further growth time, but falling supersaturation, these spherules fused into botryoidal-topped crusts made of micron-size fibro-radial calcite crystals. We conclude that the simplest tested mechanism to deposit significant spherical-radial calcite bodies is to begin with a strongly supersaturated solution that contains specific but environmentally-common organic acids. Furthermore, we found

  15. Three-dimensional hydration layer mapping on the (10.4) surface of calcite using amplitude modulation atomic force microscopy

    Science.gov (United States)

    Marutschke, Christoph; Walters, Deron; Cleveland, Jason; Hermes, Ilka; Bechstein, Ralf; Kühnle, Angelika

    2014-08-01

    Calcite, the most stable modification of calcium carbonate, is a major mineral in nature. It is, therefore, highly relevant in a broad range of fields such as biomineralization, sea water desalination and oil production. Knowledge of the surface structure and reactivity of the most stable cleavage plane, calcite (10.4), is pivotal for understanding the role of calcite in these diverse areas. Given the fact that most biological processes and technical applications take place in an aqueous environment, perhaps the most basic—yet decisive—question addresses the interaction of water molecules with the calcite (10.4) surface. In this work, amplitude modulation atomic force microscopy is used for three-dimensional (3D) mapping of the surface structure and the hydration layers above the surface. An easy-to-use scanning protocol is implemented for collecting reliable 3D data. We carefully discuss a comprehensible criterion for identifying the solid-liquid interface within our data. In our data three hydration layers form a characteristic pattern that is commensurate with the underlying calcite surface.

  16. Iodate in calcite and vaterite: Insights from synchrotron X-ray absorption spectroscopy and first-principles calculations

    Science.gov (United States)

    Podder, J.; Lin, J.; Sun, W.; Botis, S. M.; Tse, J.; Chen, N.; Hu, Y.; Li, D.; Seaman, J.; Pan, Y.

    2017-02-01

    Calcium carbonates such as calcite are the dominant hosts of inorganic iodine in nature and are potentially important for the retention and removal of radioactive iodine isotopes (129I and 131I) in contaminated water. However, little is known about the structural environment of iodine in carbonates. In this study, iodate (IO3-) doped calcite and vaterite have been synthesized using the gel-diffusion method at three NaIO3 concentrations (0.002; 0.004; 0.008 M) and a pH value of 9.0, under ambient temperature and pressure. Inductively coupled plasma mass spectrometry (ICP-MS) analyses show that iodine is preferentially incorporated into calcite over vaterite. Synchrotron iodine K-edge X-ray absorption near-edge structure (XANES) spectra confirm that IO3- is the dominant iodine species in synthetic calcite and vaterite. Analyses of iodine K-edge extended X-ray absorption fine structure (EXAFS) data, complemented by periodic first-principles calculations at the density functional theory (DFT) levels, demonstrate that the I5+ ion of the IO3- group in calcite and vaterite is bonded by three and two additional O atoms (i.e., coordination numbers = 6 and 5), respectively, and is incorporated via the charged coupled substitution I5+ + Na+ ↔ C4+ + Ca2+, with the Na+ cation at a nearest Ca2+ site being the most energetically favorable configuration.

  17. The Perceived Leader Support Behavior for Subordinate's Creativity: The Moderating Effect of Trust

    OpenAIRE

    Kuo-Hsiung Chen; Jui-Mei Yien; Chien-Jung Huang

    2011-01-01

    Problem statement: The main goal behind this study tries to figure out whether or not the leaders supportive behavior will influence subordinates creativity and is there any affection of trust between leaders supportive behavior and subordinates creativity? Approach: This study was conducted to examine the relationships between leader support behavior and subordinate creativity and the moderating effect of trust on subordinates' creativity under the leader support behavior...

  18. Cross-Situational Specificity in Managers' Perceptions of Subordinate Performance, Attributions, and Leader Behaviors.

    Science.gov (United States)

    James, Lawrence R.; White, John F.

    1983-01-01

    Examined managers' perceptions of subordinates' performance, causes (attributions) of subordinates' performance, and the leader behaviors they employed toward subordinates from the standpoint of cross-situational consistency versus cross-situational specificity. Empirical results for 377 Navy managers provided strong support for cross-situational…

  19. Zinc isotope fractionation during adsorption on calcite

    Science.gov (United States)

    Dong, S.; Wasylenki, L. E.

    2013-12-01

    Zinc is an important element as a nutrient in the marine biosphere. However, our understanding of its biogeochemical cycling in the oceans is relatively limited. The Zn stable isotope system holds the promise of providing novel insights, since published Zn isotopic values for various natural samples reveal significant fractionations in the marine environment. Surface seawater, basalts, shales, deep-sea clay sediments, sediment trap material, bulk plankton and zooplankton samples, and eolian dust fall within a tight range (δ66/64Zn from -0.1 to 0.5‰), but modern ferromanganese crusts (δ66/64Zn from 0.5 to 1.2‰), as well as carbonates (δ66/64Zn from 0.3 to 1.4‰), are notably enriched in heavy Zn isotopes [1-4]. In this study we seek to constrain the mechanism by which carbonates are enriched in heavier isotopes. In particular, we have conducted experiments to quantify isotope fractionation during adsorption of Zn onto the surfaces of calcite crystals that are in equilibrium with solution. The adsorption experiments were carried out in a series of small-volume batch reactions in a clean laboratory environment, using high-purity reagents and calcite seed crystals. The calcite was equilibrated with the solution prior to addition of Zn at atmospheric CO2 pressure (i.e., in air) for 5 days until a stable pH of 8.3 was reached. Later, a small aliquot of dissolved ZnCl2 was added such that the solution remained undersaturated with respect to hydrozincite. Experimental duration varied among the replicates from 6 to 144 hours, and then all solids and solutions were separated by filtration, purified by ion exchange chromatography, and analyzed by MC-ICP-MS. Zn adsorbed on calcite is isotopically heavier than in the co-existing solutions, with Δ68/66Zncalcite-solution of approximately 0.3‰. The variation of Δ68/66Zncalcite-solution beyond 24 hours is insignificant, so we infer that isotopic equilibrium is reached by this time. Previous work strongly suggests that a

  20. Fracture calcites at Olkiluoto. Evidence from quaternary infills for palaeohydrogeology

    Energy Technology Data Exchange (ETDEWEB)

    Gehoer, S.; Kaerki, A.; Taikina-aho, O. [Kivitieto Oy (Finland); Karhu, J. [Helsinki Univ. (Finland); Loefman, J. [VTT Processes, Espoo (Finland); Pitkaenen, P. [VTT Building and Transport, Espoo (Finland); Ruotsalainen, P. [TUKES, Helsinki (Finland)

    2002-02-01

    Recently formed secondary minerals, predominantly calcite, occur in varying amounts as fracture infills, and the calcite types, their chemical compositions and isotope ratios reflect the compositions and physicochemical factors of the groundwater system in which they were formed. Fluid inclusions trapped in calcites give direct evidence of trapping temperatures and past salinities and of the chemical compositions of the palaeo fluids. A wide range of mineralogical and geochemical examinations were carried out within the EQUIP project to examine features of this kind. The fracture calcites at the Olkiluoto site are of various origins and represent several textural types. The exact number of calcite-producing events is unknown, but the duration of the period that was appropriate for the precipitation of low temperature calcite is estimated to have exceeded 1000 Ma. Thus the number of genetically related calcite units is assumed to be considerable. This study was focused on the petrogenesis of calcites crystallized in fractures of high water conductivity during the latest stages of geological evolution. The majority of these late stage calcites form physically homogeneous, scaly layers, and in a few cases thin layers composed of idiomorphic crystals. Chemically these are almost stoichiometric calcites (CaCO{sub 3}). The MnO content may exceed 1%, while the amounts of other elements present are minor, although the trace element concentrations, particularly those of large ionic trace elements, can be used as distinguishing features for the recognition of individual precipitates representing different calcite generations. Evidence from fluid inclusions, or more correctly from the absence of these in the late stage calcites, can be interpreted as an indication of slow rates of crystallization under cool conditions. Many chemical variables, e.g. oxygen isotope ratios, demonstrate an equilibrium between the latest calcites and water similar to the present groundwater. Older

  1. Cone-Parameter Convolution Semigroups and Their Subordination

    OpenAIRE

    Pedersen, Jan; Sato, Ken-iti

    2003-01-01

    Convolution semigroups of probability measures with parameter in a cone in a Euclidean space generalize usual convolution semigroups with parameter in $[0,\\infty)$. A characterization of such semigroups is given and examples are studied. Subordination of cone-parameter convolution semigroups by cone-valued cone-parameter convolution semigroups is introduced. Its general description is given and inheritance properties are shown. In the study the distinction between cones with an...

  2. Calcium carbonate precipitation by different bacterial strains ...

    African Journals Online (AJOL)

    Bacteria are capable of performing metabolic activities which thereby promote precipitation of calcium carbonate in the form of calcite. In this study, it is shown that microbial mineral precipitation was a result of metabolic activities of some specific microorganisms. Concrete microorganisms were used to improve the overall ...

  3. Calcite-forming bacteria for compressive strength improvement in mortar.

    Science.gov (United States)

    Park, Sung-Jin; Park, Yu-Mi; Chun, Woo-Young; Kim, Wha-Jung; Ghim, Sa-Youl

    2010-04-01

    Microbiological calcium carbonate precipitation (MCP) has been investigated for its ability to improve the compressive strength of concrete mortar. However, very few studies have been conducted on the use of calcite-forming bacteria (CFB) to improve compressive strength. In this study, we discovered new bacterial genera that are capable of improving the compressive strength of concrete mortar. We isolated 4 CFB from 7 environmental concrete structures. Using sequence analysis of the 16S rRNA genes, the CFB could be partially identified as Sporosarcina soli KNUC401, Bacillus massiliensis KNUC402, Arthrobacter crystallopoietes KNUC403, and Lysinibacillus fusiformis KNUC404. Crystal aggregates were apparent in the bacterial colonies grown on an agar medium. Stereomicroscopy, scanning electron microscopy, and x-ray diffraction analyses illustrated both the crystal growth and the crystalline structure of the CaCO3 crystals. We used the isolates to improve the compressive strength of concrete mortar cubes and found that KNUC403 offered the best improvement in compressive strength.

  4. Subordinated diffusion and continuous time random walk asymptotics.

    Science.gov (United States)

    Dybiec, Bartłomiej; Gudowska-Nowak, Ewa

    2010-12-01

    Anomalous transport is usually described either by models of continuous time random walks (CTRWs) or, otherwise, by fractional Fokker-Planck equations (FFPEs). The asymptotic relation between properly scaled CTRW and fractional diffusion process has been worked out via various approaches widely discussed in literature. Here, we focus on a correspondence between CTRWs and time and space fractional diffusion equation stemming from two different methods aimed to accurately approximate anomalous diffusion processes. One of them is the Monte Carlo simulation of uncoupled CTRW with a Lévy α-stable distribution of jumps in space and a one-parameter Mittag-Leffler distribution of waiting times. The other is based on a discretized form of a subordinated Langevin equation in which the physical time defined via the number of subsequent steps of motion is itself a random variable. Both approaches are tested for their numerical performance and verified with known analytical solutions for the Green function of a space-time fractional diffusion equation. The comparison demonstrates a trade off between precision of constructed solutions and computational costs. The method based on the subordinated Langevin equation leads to a higher accuracy of results, while the CTRW framework with a Mittag-Leffler distribution of waiting times provides efficiently an approximate fundamental solution to the FFPE and converges to the probability density function of the subordinated process in a long-time limit. © 2010 American Institute of Physics.

  5. The origin of carbon isotope vital effects in coccolith calcite

    Science.gov (United States)

    McClelland, H. L. O.; Bruggeman, J.; Hermoso, M.; Rickaby, R. E. M.

    2017-03-01

    Calcite microfossils are widely used to study climate and oceanography in Earth's geological past. Coccoliths, readily preserved calcite plates produced by a group of single-celled surface-ocean dwelling algae called coccolithophores, have formed a significant fraction of marine sediments since the Late Triassic. However, unlike the shells of foraminifera, their zooplankton counterparts, coccoliths remain underused in palaeo-reconstructions. Precipitated in an intracellular chemical and isotopic microenvironment, coccolith calcite exhibits large and enigmatic departures from the isotopic composition of abiogenic calcite, known as vital effects. Here we show that the calcification to carbon fixation ratio determines whether coccolith calcite is isotopically heavier or lighter than abiogenic calcite, and that the size of the deviation is determined by the degree of carbon utilization. We discuss the theoretical potential for, and current limitations of, coccolith-based CO2 paleobarometry, that may eventually facilitate use of the ubiquitous and geologically extensive sedimentary archive.

  6. A High-Pressure Phase Transition of Calcite-III

    Science.gov (United States)

    Catalli, K. C.; Williams, Q.

    2005-12-01

    We document the presence of a high-pressure phase transition in metastable calcite-III using infrared spectroscopy. The post-calcite-III transition initiates at a pressure of 15.5 (±2) GPa, and is completed between 25 and 30 GPa. The transition is particularly apparent in the ν4-in-plane bending vibration of the carbonate group, in which two new peaks gradually supplant the doublet associated with calcite-III. Furthermore, both the ν3-asymmetric and ν1-symmetric stretches of the carbonate group in the high-pressure phase appear at considerably lower frequencies than the extrapolated positions of the corresponding calcite-III peaks. The geometry of the carbonate unit within the high-pressure phase is likely closer to trigonal symmetry than in the calcite-III structure, and the C-O bond is probably longer than in the lower pressure calcite-III phase.

  7. Origin of calcite in the glacigenic Virttaankangas complex

    Directory of Open Access Journals (Sweden)

    Nina M. Kortelainen

    2007-01-01

    Full Text Available Groundwaters of the glacigenic Virttaankangas complex in southern Finland are characterized by high pH values ranging up to 9.5. These values are significantly higher than those observed in silicate-rich shallow groundwater formations in crystalline bedrock areas. TheVirttaankangas sediments were discovered to contain small amounts of fine grained, dispersed calcite, which has a high tendency to increase the pH of local groundwaters. The primary goal of this study was to determine the mode of occurrence of calcite and to identifyits sources. The mineralogy of the glacigenic Virttaankangas complex was studied using material from 21 sediment drill cores. Fine-grained calcite is present in trace amounts (<< 1.4 % in the glaciofluvial and glaciolacustrine depositional units of the Virttaankangas complex. The topmost littoral sands were practically devoid of calcite. The isotope records of carbon and oxygen, the angular morphology of the grains and the uniform dispersion of calcite in the complex suggest a clastic origin for calcite, with no evidence for in-situ precipitation. In order to constrain the source of calcite, the isotopic composition of carbon and oxygen in five calcite samples was compared to the isotopic data from five carbonate rock erratics and eight crystalline bedrock samples from the region. Based on carbon and oxygen isotope ratios and chemical compositions, the dispersed calcite grains of the Virttaankangas complex appear to have been derived from the Mesoproterozoic Satakunta Formation, some 30 km NW from the Virttaankangas area. In sandstone, calcite is predominantly present as diagenetic cement in grain interspaces, concretions and interlayers. The source of detrital calcite was unexpected, as prior to this study the Satakunta sandstone hasnot been known to contain calcite.

  8. Effect of Magnesium as Substitute Material in Enzyme-Mediated Calcite Precipitation for Soil-Improvement Technique

    OpenAIRE

    Putra, Heriansyah; Yasuhara, Hideaki; Kinoshita, Naoki; Neupane, Debendra; Lu, Chih-Wei

    2016-01-01

    The optimization of enzyme-mediated calcite precipitation was evaluated as a soil-improvement technique. In our previous works, purified urease was utilized to bio-catalyze the hydrolysis of urea, which causes the supplied Ca2+ to precipitate with C O 3 2 ? as calcium carbonate. In the present work, magnesium chloride was newly added to the injecting solutions to delay the reaction rate and to enhance the amount of carbonate precipitation. Soil specimens were prepared in PVC cylinders and tre...

  9. Mechanisms of Subcritical Cracking in Calcite

    Science.gov (United States)

    Royne, A.; Dysthe, D. K.; Bisschop, J.

    2008-12-01

    Brittle materials are characterized by a critical stress intensity factor above which they will fail catastrophically by dynamic cracking. However, it has been observed that materials can also fail at much lower stresses, through slow crack growth, often referred to as subcritical cracking. This phenomenon can take place even in vacuum, but is greatly enhanced by water and other reactive species in the environment. For a given material and environmental condition there is a systematic relationship between the crack tip velocity and the stress intensity factor. The presence of a lower stress limit to subcritical cracking has been predicted from thermodynamics but has not been firmly demonstrated experimentally. This parameter would control the long- term strength of geological materials. Subcritical cracking must necessarily be important in controlling the rock strength in near-surface processes where water and other active species are present and the displacements and stresses are low. Weathering is one example of such a process. Modelling has shown that fracture networks generated by a high degree of subcritical cracking will percolate at much lower fracture densities than purely stochastical fracture networks. This has important implications for how water can move through the crust. Understanding the mechanisms for subcritical crack growth in geological materials is also important in assessing the stability and long term performance of sequestration reservoirs for CO2 or nuclear waste. The mechanism for stress corrosion is well known for glasses and quartz. For carbonate minerals, the mechanism for subcritical crack growth has not been identified, and the only experimental studies on calcitic materials have been on polycrystalline rocks such as marble. Suggested mechanisms include stress corrosion (weakening reactions at the crack tip), preferential dissolution at the crack tip with rapid removal of dissolved species, and environmentally controlled

  10. Neptunium(V) adsorption to calcite.

    Science.gov (United States)

    Heberling, Frank; Brendebach, Boris; Bosbach, Dirk

    2008-12-12

    The migration behavior of the actinyl ions U(VI)O2(2+), Np(V)O2+ and Pu(V,VI)O2(+,2+) in the geosphere is to a large extend controlled by sorption reactions (inner- or outer-sphere adsorption, ion-exchange, coprecipitation/structural incorporation) with minerals. Here NpO2+ adsorption onto calcite is studied in batch type experiments over a wide range of pH (6.0-9.4) and concentration (0.4 microM-40 microM) conditions. pH is adjusted by variation of CO2 partial pressure. Adsorption is found to be pH dependent with maximal adsorption at pH 8.3 decreasing with increasing and decreasing pH. pH dependence of adsorption decreases with increasing Np(V) concentration. EXAFS data of neptunyl adsorbed to calcite and neptunyl in the supernatant shows differences in the Np(V)-O-yl distance, 1.85+/-0.01 angstroms for the adsorbed and 1.82+/-0.01 angstroms for the solution species. The equatorial environment of the neptunyl in solution shows about 5 oxygen neighbours at 2.45+/-0.02 angstroms. For adsorbed neptunyl there are also about 5 oxygen neighbours at 2.46+/-0.01 angstroms. An additional feature in the adsorbed species' R-space spectrum can be related to carbonate neighbours, 3 to 6 carbon backscatterers (C-eq) at 3.05+/-0.03 angstroms and 3 to 6 oxygen backscatterers (O-eq2) at 3.31+/-0.02 angstroms. The differences in the Np(V)-O-yl distance and the C-eq and O-eq2 backscatterers which are only present for the adsorbed species indicate inner-sphere bonding of the adsorbed neptunyl species to the calcite surface. Experiments on adsorption kinetics indicate that after a fast surface adsorption process a continuous slow uptake occurs which may be explained by incorporation via surface dissolution and reprecipitation processes. This is also indicated by the part irreversibility of the adsorption as shown by increased KD values after desorption compared to adsorption.

  11. Calcium - urine

    Science.gov (United States)

    Urinary Ca+2; Kidney stones - calcium in urine; Renal calculi - calcium in your urine; Parathyroid - calcium in urine ... Urine calcium level can help your provider: Decide on the best treatment for the most common type of kidney ...

  12. On the Fractional Poisson Process and the Discretized Stable Subordinator

    Directory of Open Access Journals (Sweden)

    Rudolf Gorenflo

    2015-08-01

    Full Text Available We consider the renewal counting number process N = N(t as a forward march over the non-negative integers with independent identically distributed waiting times. We embed the values of the counting numbers N in a “pseudo-spatial” non-negative half-line x ≥ 0 and observe that for physical time likewise we have t ≥ 0. Thus we apply the Laplace transform with respect to both variables x and t. Applying then a modification of the Montroll-Weiss-Cox formalism of continuous time random walk we obtain the essential characteristics of a renewal process in the transform domain and, if we are lucky, also in the physical domain. The process t = t(N of accumulation of waiting times is inverse to the counting number process, in honour of the Danish mathematician and telecommunication engineer A.K. Erlang we call it the Erlang process. It yields the probability of exactly n renewal events in the interval (0; t]. We apply our Laplace-Laplace formalism to the fractional Poisson process whose waiting times are of Mittag-Leffler type and to a renewal process whose waiting times are of Wright type. The process of Mittag-Leffler type includes as a limiting case the classical Poisson process, the process of Wright type represents the discretized stable subordinator and a re-scaled version of it was used in our method of parametric subordination of time-space fractional diffusion processes. Properly rescaling the counting number process N(t and the Erlang process t(N yields as diffusion limits the inverse stable and the stable subordinator, respectively.

  13. Calcite-impregnated defluidization structures in littoral sands of mono lake, california.

    Science.gov (United States)

    Cloud, P; Lajoie, K R

    1980-11-28

    Associated locally with well-known tufa mounds and towers of Mono Lake, California, are subvertical, concretionary sand structures through which fresh calcium-containing artesian waters moved up to sites of calcium carbonate precipitation beneath and adjacent to the lake. The structures include closely spaced calcite-impregnated columns, tubes, and other configurations with subcylindrical to bizarre cross sections and predominantly vertical orientation in coarse, barely coherent pumice sands along the south shore of the lake. Many structures terminate upward in extensive calcareous layers of caliche and tufa. Locally they enter the bases of tufa mounds and towers. A common form superficially resembles root casts and animal burrows except that branching is mostly up instead of down. Similar defluidization structures in ancient sedimentary rocks have been mistakenly interpreted as fossil burrows.

  14. Phase transitions in biogenic amorphous calcium carbonate

    Science.gov (United States)

    Gong, Yutao

    Geological calcium carbonate exists in both crystalline phases and amorphous phases. Compared with crystalline calcium carbonate, such as calcite, aragonite and vaterite, the amorphous calcium carbonate (ACC) is unstable. Unlike geological calcium carbonate crystals, crystalline sea urchin spicules (99.9 wt % calcium carbonate and 0.1 wt % proteins) do not present facets. To explain this property, crystal formation via amorphous precursors was proposed in theory. And previous research reported experimental evidence of ACC on the surface of forming sea urchin spicules. By using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), we studied cross-sections of fresh sea urchin spicules at different stages (36h, 48h and 72h after fertilization) and observed the transition sequence of three mineral phases: hydrated ACC → dehydrated ACC → biogenic calcite. In addition, we unexpectedly found hydrated ACC nanoparticles that are surrounded by biogenic calcite. This observation indicates the dehydration from hydrated ACC to dehydrated ACC is inhibited, resulting in stabilization of hydrated ACC nanoparticles. We thought that the dehydration was inhibited by protein matrix components occluded within the biomineral, and we designed an in vitro assay to test the hypothesis. By utilizing XANES-PEEM, we found that SM50, the most abundant occluded matrix protein in sea urchin spicules, has the function to stabilize hydrated ACC in vitro.

  15. Timescale for hygroscopic conversion of calcite mineral particles through heterogeneous reaction with nitric acid.

    Science.gov (United States)

    Sullivan, Ryan C; Moore, Meagan J K; Petters, Markus D; Kreidenweis, Sonia M; Roberts, Greg C; Prather, Kimberly A

    2009-09-28

    Atmospheric heterogeneous reactions can potentially change the hygroscopicity of atmospheric aerosols as they undergo chemical aging processes in the atmosphere. A particle's hygroscopicity influences its cloud condensation nuclei (CCN) properties with potential impacts on cloud formation and climate. In this study, size-selected calcite mineral particles were reacted with controlled amounts of nitric acid vapour over a wide range of relative humidities in an aerosol flow tube to study the conversion of insoluble and thus apparently non-hygroscopic calcium carbonate into soluble and hygroscopic calcium nitrate. The rate of hygroscopic change particles undergo during a heterogeneous reaction is derived from experimental measurements for the first time. The chemistry of the reacted particles was determined using an ultrafine aerosol time-of-flight mass spectrometer (UF-ATOFMS) while the particles' hygroscopicity was determined through measuring CCN activation curves fit to a single parameter of hygroscopicity, kappa. The reaction is rapid, corresponding to atmospheric timescales of hours. At low to moderate HNO3 exposures, the increase in the hygroscopicity of the particles is a linear function of the HNO3(g) exposure. The experimentally observed conversion rate was used to constrain a simple but accurate kinetic model. This model predicts that calcite particles will be rapidly converted into hygroscopic particles (kappa>0.1) within 4 h for low HNO3 mixing ratios (10 pptv) and in less than 3 min for 1000 pptv HNO3. This suggests that the hygroscopic conversion of the calcite component of atmospheric mineral dust aerosol will be controlled by the availability of nitric acid and similar reactants, and not by the atmospheric residence time.

  16. Calcite surface structure and reactivity: molecular dynamics simulations and macroscopic surface modelling of the calcite-water interface

    NARCIS (Netherlands)

    Wolthers, M.; Di Tommaso, D.; Du, Z.; de Leeuw, N.H.

    2012-01-01

    Calcite–water interactions are important not only in carbon sequestration and the global carbon cycle, but also in contaminant behaviour in calcite-bearing host rock and in many industrial applications. Here we quantify the effect of variations in surface structure on calcite surface reactivity.

  17. Understanding of subordinate clauses in the language of dysphasic children

    Directory of Open Access Journals (Sweden)

    Lazarević Emilija

    2007-01-01

    Full Text Available This paper presents the results of the research of peculiarities of syntactic development, as an element of language structure on the grammatical level of children suffering from developmental dysphasia, after the completed speech pathology treatment of many years. Syntactic level at younger school age was studied by assessing language competence in the accomplishment of communicative sentence with subordinate clause. The research was performed on the samples of children at school age in regular primary schools in Belgrade. The sample comprised 160 respondents who were divided in two groups: target and comparative. The target group consisted of 60 respondents (children suffering from developmental dysphasia after the completed speech pathology treatment of many years, and the comparative group consisted of 100 respondents from regular primary school "Gavrilo Princip" in Zemun. Research results show that grammatical development of children suffering from developmental dysphasia takes place at a considerably slower rate and entails substantially more difficulties in accomplishing predication in subordinate clauses. This paper discusses the consequences which the difficulties in grammatical development can have on school achievement.

  18. Mitochondrial function in the brain links anxiety with social subordination

    Science.gov (United States)

    Hollis, Fiona; van der Kooij, Michael A.; Zanoletti, Olivia; Lozano, Laura; Cantó, Carles; Sandi, Carmen

    2015-01-01

    Dominance hierarchies are integral aspects of social groups, yet whether personality traits may predispose individuals to a particular rank remains unclear. Here we show that trait anxiety directly influences social dominance in male outbred rats and identify an important mediating role for mitochondrial function in the nucleus accumbens. High-anxious animals that are prone to become subordinate during a social encounter with a low-anxious rat exhibit reduced mitochondrial complex I and II proteins and respiratory capacity as well as decreased ATP and increased ROS production in the nucleus accumbens. A causal link for these findings is indicated by pharmacological approaches. In a dyadic contest between anxiety-matched animals, microinfusion of specific mitochondrial complex I or II inhibitors into the nucleus accumbens reduced social rank, mimicking the low probability to become dominant observed in high-anxious animals. Conversely, intraaccumbal infusion of nicotinamide, an amide form of vitamin B3 known to enhance brain energy metabolism, prevented the development of a subordinate status in high-anxious individuals. We conclude that mitochondrial function in the nucleus accumbens is crucial for social hierarchy establishment and is critically involved in the low social competitiveness associated with high anxiety. Our findings highlight a key role for brain energy metabolism in social behavior and point to mitochondrial function in the nucleus accumbens as a potential marker and avenue of treatment for anxiety-related social disorders. PMID:26621716

  19. Does main clause word order affect attention to change in subordinate clauses?

    DEFF Research Database (Denmark)

    Christensen, Marie Herget; Christensen, Tanya Karoli; Jensen, Torben Juel

    2018-01-01

    is that a subordinate clause with Verb>Adverb word order will attract more attention than a clause with Adverb>Verb word order. To test this, we conducted an experiment under the text change paradigm. 59 students each read 24 constructions twice, each containing a subordinate clause with either Verb>Adverb or Adverb......>Verb word order. Half of the subordinate clauses were governed by a semifactive predicate (open to both word orders) and the other half by a semantically secondary sentence (in itself strongly favoring Verb>Adverb word order). Attention to the subordinate clause was tested by measuring how disinclined...... the participants were to notice change of a word in the subordinate clause when re-reading it. Results showed significantly more attention to Verb>Adverb clauses than to Adverb>Verb clauses under semifactive predicates, and more attention to subordinate clauses under semantically secondary than semifactive...

  20. A quantitative analysis of microbially-induced calcite precipitation employing artificial and naturally-occurring sediments

    Science.gov (United States)

    Lokier, Stephen; Krieg Dosier, Ginger

    2013-04-01

    Microbially-induced calcite precipitation is a strong candidate for the production of sustainable construction materials. The process employs the microbe Sporosarcina pasteurii as an agent to microbially mediate the precipitation of calcium carbonate to bind unconsolidated sediment. As this process can be achieved under ambient temperature conditions and can utilise a wide variety of easily-available sediments, potentially including waste materials, it is envisioned that this procedure could significantly reduce carbon-dioxide emissions in the construction industry. This study describes and quantifies the precipitation of calcite cement in a range of naturally-occurring sediments compared with a control matrix. The study establishes the optimum treatment time for effective cement precipitation in order to produce a material that meets the standards required for construction whilst keeping economic and environmental outlays at a minimum. The 'control sediment' employed industrial-grade glass beads with a grain size range of 595-1180 microns (16-30 US mesh). Sporosarcina pasteurii were mixed in a solution of urea and calcium chloride and then inoculated into the control sediment. The microbes attach to the surface of the sediment grains and employ urea as a source of energy to produce ammonia and carbon dioxide. By so doing, they increase the pH of the solution allowing calcium carbonate to precipitate at the cell walls to act as nucleation points facilitating the precipitation of cements as a grain-coating and biocementing the unconsolidated sediment. The solution treatment was repeated at eight hour intervals with samples removed for detailed analysis after each every five consecutive treatments (i.e. 40 hours). The process was repeated to produce 20 samples with treatment times between 40 and 800 hours. Cemented samples were impregnated with blue epoxy and examined petrographically to monitor cement development. Modal analysis was undertaken on each cemented

  1. Subordinate plant species moderate drought effects on earthworms communities in grasslands

    OpenAIRE

    Mariotte Pierre; Le Bayon Renee-Claire; Eisenhauer Nico; Guenat Claire; Buttler Alexandre

    2016-01-01

    Loss of plant diversity resulting from forecasted drought events is likely to alter soil functioning and affect earthworm communities. Plant soil interactions are expected to play an important role in mediating climate change effects on soil decomposers. In this study we test above belowground linkages after drought by focusing on the effects of subordinate plant species on earthworm communities. Using a combination of subordinate species removal and experimental drought we show that subordin...

  2. Influence of solution chemistry on the boron content in inorganic calcite grown in artificial seawater

    Science.gov (United States)

    Uchikawa, Joji; Harper, Dustin T.; Penman, Donald E.; Zachos, James C.; Zeebe, Richard E.

    2017-12-01

    The ratio of boron to calcium (B/Ca) in marine biogenic carbonates has been proposed as a proxy for properties of seawater carbonate chemistry. Applying this proxy to planktic foraminifera residing in the surface seawater largely in equilibrium with the atmosphere may provide a valuable handle on past atmospheric CO2 concentrations. However, precise controls on B/Ca in planktic foraminifera remain enigmatic because it has been shown to depend on multiple physicochemical seawater properties. To help establish a firm inorganic basis for interpreting the B/Ca records, we examined the effect of a suite of chemical parameters ([Ca2+], pH, [DIC], salinity and [PO43-]) on B/Ca in inorganic calcite precipitated in artificial seawater. These parameters were primarily varied individually while keeping all others constant, but we also tested the influence of pH and [DIC] at a constant calcite precipitation rate (R) by concurrent [Ca2+] adjustments. In the simple [Ca2+], pH and [DIC] experiments, both R and B/Ca increased with these parameters. In the pH-[Ca2+] and [DIC]-[Ca2+] experiments at constant R, on the other hand, B/Ca was invariant at different pH and decreased with [DIC], respectively. These patterns agree with the behavior of solution [BTotal/DIC] ratio such that, at a fixed [BTotal], it is independent of pH but decreases with [DIC]. Based on these results, R and [BTotal/DIC] ratio appear to be the primary controls on B/Ca in inorganic calcite, suggesting that both B(OH)4- and B(OH)3 are possibly involved in B incorporation. Moreover, B/Ca modestly increased with salinity and [PO43-]. Inorganic calcite precipitated at higher R and in the presence of oxyanions such as SO42- and PO43- in growth solutions often undergoes surface roughening due to formation of crystallographic defects, vacancies and, occasionally, amorphous/hydrous CaCO3. These non-lattice sites may provide additional space for B, particularly B(OH)3. Consequently, besides the macroscopic influence of

  3. Investigating the Physical Basis of Amorphous Precursor Transformation to Calcite Using Patterned Alkanethiol Surfaces

    Science.gov (United States)

    Wang, D.; Wallace, A.; Han, T. Y.; Lee, J. R.; Hailey, P. D.; de Yoreo, J. J.; Dove, P. M.

    2007-12-01

    Increasing evidence from X-ray Absorption Spectroscopy and Environmental Scanning Electron Microscopy (ESEM) studies of biominerals extracted from calcifying organisms show that amorphous calcium carbonate (ACC) plays a key role in the initial formation of carbonate minerals and in shaping them into complex morphologies. Echinoderms and possibly a wide variety of other organisms, use ACC as a precursor phase. The ACC is first formed within spatial and temporally controlled environments such as vesicles, followed by a subsequent onset of mineralization that transforms the precursor into a fully crystalline material. Recent studies on sea urchin embryos have shown that during this transformation, ACC develops short-range order that resembles calcite before fully crystallizing. While this "non-traditional" process is recognized, the mechanisms and factors that govern this transformation remain poorly understood. Of particular interest are the roles of water, and the functional group chemistry of surfaces and macromolecules within mineralization environments. To investigate these questions, we have developed an experimental approach using ESEM that allows us to control impurity concentration, surface functionality and water content through the degree of water condensation. Patterned self-assembled monolayers (SAM) of hydrophilic moieties with domains of approximately 25 microns in diameter are used to form an array of micro-reactors. ACC particles with known composition are then deposited on the patterns. Condensing water in the ESEM initializes the transformation of ACC to calcite. Our results show that in saturated water vapor, ACC swells, but no obvious faceting of the material occurs. It is only in bulk water, via dissolution/crystallization, where the calcite grown on carboxyl-terminated surfaces is found with the often-observed \\{013\\} nucleation face. We use this insight to understand the role of the different chemical moieties on ACC to calcite transformation

  4. Fleet leaders' attitudes about subordinates' use of mental health services.

    Science.gov (United States)

    Westphal, Richard J

    2007-11-01

    Mental disorders are a significant source of medical and occupational morbidity for sailors. Stigma, fear of negative career impact, and subordinates concern about leaders' attitudes are significant barriers to the use of mental health services. Semistructured interviews and military policies were data sources used to analyze the language, knowledge, and attitudes of Navy surface fleet leaders about mental illness and mental health treatment using Foucault's concept of discourse analysis. A discourse is a system of knowledge that influences language, perceptions, values, and social practices. The results showed that leaders' concerns about sailors' mental combat readiness, not mental illness stigma, was the dominant discourse about mental illness and mental health services use. In particular, organizational differences between the surface warfare and the mental health communities may influence leaders' attitudes more than stigma. This study provides an elaborated view of mental health knowledge and power within a Navy community.

  5. Subordination Principle for a Class of Fractional Order Differential Equations

    Directory of Open Access Journals (Sweden)

    Emilia Bazhlekova

    2015-05-01

    Full Text Available The fractional order differential equation \\(u'(t=Au(t+\\gamma D_t^{\\alpha} Au(t+f(t, \\ t>0\\, \\(u(0=a\\in X\\ is studied, where \\(A\\ is an operator generating a strongly continuous one-parameter semigroup on a Banach space \\(X\\, \\(D_t^{\\alpha}\\ is the Riemann–Liouville fractional derivative of order \\(\\alpha \\in (0,1\\, \\(\\gamma>0\\ and \\(f\\ is an \\(X\\-valued function. Equations of this type appear in the modeling of unidirectional viscoelastic flows. Well-posedness is proven, and a subordination identity is obtained relating the solution operator of the considered problem and the \\(C_{0}\\-semigroup, generated by the operator \\(A\\. As an example, the Rayleigh–Stokes problem for a generalized second-grade fluid is considered.

  6. Socially transmitted diffusion of a novel behavior from subordinate chimpanzees

    DEFF Research Database (Denmark)

    Watson, Stuart K; Reamer, Lisa A; Mareno, Mary Catherine

    2017-01-01

    Chimpanzees (Pan troglodytes) demonstrate much cultural diversity in the wild, yet a majority of novel behaviors do not become group-wide traditions. Since many such novel behaviors are introduced by low-ranking individuals, a bias toward copying dominant individuals ("rank-bias") has been proposed...... as an explanation for their limited diffusion. Previous experimental work showed that chimpanzees (Pan troglodytes) preferentially copy dominant over low-rank models. We investigated whether low ranking individuals may nevertheless successfully seed a beneficial behavior as a tradition if there are no "competing....... Finally, we report an innovation by a subordinate individual that built cumulatively on existing methods of opening the puzzle-box and was subsequently copied by a dominant observer. These findings illustrate that chimpanzees are motivated to copy rewarding novel behaviors that are demonstrated...

  7. First-principles study of boron speciation in calcite and aragonite

    Science.gov (United States)

    Balan, Etienne; Pietrucci, Fabio; Gervais, Christel; Blanchard, Marc; Schott, Jacques; Gaillardet, Jérome

    2016-11-01

    Despite the importance of boron as a proxy of past ocean pH, the crystal-chemical factors controlling its incorporation in the structure of calcium carbonates are still poorly understood. This is partly linked to an imperfect knowledge of the coordination, protonation state and local environment of boron species in these minerals. In the present study, we use first-principles quantum mechanical tools to model selected trigonal and tetragonal boron species in calcite and aragonite. The stable geometry of the models is obtained from standard energy minimization schemes or using a more advanced metadynamics exploration of their configurational space. The computation of 11B NMR chemical shifts and quadrupolar coupling parameters enables a straightforward comparison of the models to existing experimental NMR data. The results show that B in calcium carbonates does occur as structural species substituted for CO32- anions. The B speciation depends on the polymorph considered. In calcite, structural boron is present as partially deprotonated trigonal BO2(OH)2- species coexisting with a fraction of substituted B(OH)4- groups. In aragonite, the B(OH)4- substitution for CO32- anions is dominant. Different species, including entrapped B(OH)3 molecules and substituted BO33- groups also occur in biogenic samples. The diversity of B speciation reflects a diversity of B incorporation mechanisms and sheds light on previous studies confronting B isotopic composition determination with NMR observations. The mechanisms of boron incorporation in calcium carbonates are probably more complex than usually assumed in the literature using boron isotopes as a proxy of paleo-atmospheric CO2 reconstructions. Although not invalidating the empirical paleo-pH proxy, these results call for a better understanding of the fundamental mechanisms of boron incorporation in carbonates.

  8. MicroRaman, PXRD, EDS and microscopic investigation of magnesium calcite biomineral phases. The case of sea urchin biominerals

    Science.gov (United States)

    Borzęcka-Prokop, B.; Wesełucha-Birczyńska, A.; Koszowska, E.

    2007-02-01

    This study concerns Mg-calcite characterization (and in particular molecular structure and microstructural studies of mineral phases) of a sea urchin mineralised test and spines. Sea urchins are spiny sea animals (kingdom Animalia, phylum Echinodermata, class Echinoidea). Microscopic observations, SEM, EDS, PXRD and spectroscopic microRaman methods have been applied to characterize the biomineral parts of the sea urchin. The latter technique is very useful in research of biological systems and especially suitable for monitoring differences within biomineral phases exhibiting varieties of morphological forms. Crystalline magnesium calcium carbonate, Mg xCa 1- xCO 3 (magnesian calcite; space group R-3 cH; a = 4.9594(8) Å, c = 16.886(6) Å), has been identified as the predominant biomineral component.

  9. Molecular ordering of ethanol at the calcite surface

    DEFF Research Database (Denmark)

    Pasarín, I. S.; Yang, M.; Bovet, Nicolas Emile

    2012-01-01

    dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH 3-CH2-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol...... molecules stand up perpendicularly at the interface or nearly so. As a consequence, the fatty, CH3 ends form a new surface, about 6 Å from the termination of the bulk calcite, and beyond that, there is a thin gap where ethanol density is low. Following is a more disordered layer that is two to three...... ethanol molecules thick, about 14 Å, where density more resembles that of bulk liquid ethanol. The good agreement between theory and experiment gives confidence that a theoretical approach can offer information about behavior in more complex systems. © 2012 American Chemical Society....

  10. 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

    , 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...

  11. Calcium Carbonate

    Science.gov (United States)

    Calcium carbonate is a dietary supplement used when the amount of calcium taken in the diet is not ... for healthy bones, muscles, nervous system, and heart. Calcium carbonate also is used as an antacid to relieve ...

  12. Calcium supplements

    Science.gov (United States)

    ... this page: //medlineplus.gov/ency/article/007477.htm Calcium supplements To use the sharing features on this page, please enable JavaScript. WHO SHOULD TAKE CALCIUM SUPPLEMENTS? Calcium is an important mineral for the ...

  13. Selective Flotation of Calcite from Fluorite: A Novel Reagent Schedule

    Directory of Open Access Journals (Sweden)

    Zhiyong Gao

    2016-10-01

    Full Text Available Fluorite is an important strategic mineral. In general, fluorite ores will contain a certain amount of calcite gangue mineral. Thus, they need to be separated from each other. For an economic separation, a reverse flotation process is used to float calcite gangue from fluorite. However, little information on the separation is available. In this study, a novel reagent schedule using citric acid (CA as the depressant, sodium fluoride (NaF as the regulator and sulfoleic acid (SOA as the collector, was developed to separate calcite from fluorite. The results demonstrated a high selectivity for the flotation of calcite from fluorite using this new reagent schedule. The best selective separation for a single mineral and mixed binary minerals was obtained when 200 mg/L of NaF, 50 mg/L of CA, and 6 mg/L of SOA were used at pH 9. In addition, a batch flotation experiment was carried out using a run-of-mine feed material. Selective separation was achieved with 85.18% calcite removal while only 11.2% of fluorite was lost. An attempt was made to understand the effect of the new reagent schedule on the flotation of calcite. The results from both microflotation and bench scale flotation demonstrated a great potential for industrial application using this novel reagent schedule to upgrade fluorite ore.

  14. Susceptibility or resilience? Prenatal stress predisposes male rats to social subordination, but facilitates adaptation to subordinate status.

    Science.gov (United States)

    Scott, Karen A; de Kloet, Annette D; Smeltzer, Michael D; Krause, Eric G; Flak, Jonathan N; Melhorn, Susan J; Foster, Michelle T; Tamashiro, Kellie L K; Sakai, Randall R

    2017-09-01

    Mood disorders such as major depressive disorder (MDD) affect a significant proportion of the population. Although progress has been made in the development of therapeutics, a large number of individuals do not attain full remission of symptoms and adverse side effects affect treatment compliance for some. In order to develop new therapies, there is a push for new models that better reflect the multiple risk factors that likely contribute to the development of depressive illness. We hypothesized that early life stress would exacerbate the depressive-like phenotype that we have previously observed in socially subordinate (SUB) adult male rats in the visible burrow system (VBS), a semi-natural, ethologically relevant environment in which males in a colony form a dominance hierarchy. Dams were exposed to chronic variable stress (CVS) during the last week of gestation, resulting in a robust and non-habituating glucocorticoid response that did not alter maternal food intake, body weight or litter size and weight. As adults, one prenatal CVS (PCVS) and one non-stressed (NS) male were housed in the VBS with adult females. Although there were no overt differences between PCVS and NS male offspring prior to VBS housing, a greater percentage of PCVS males became SUB. However, the depressive-like phenotype of SUB males was not exacerbated in PCVS males; rather, they appeared to better cope with SUB status than NS SUB males. They had lower basal plasma corticosterone than NS SUB males at the end of VBS housing. In situ hybridization for CRH in the PVN and CeA did not reveal any prenatal treatment or status effects, while NPY expression was higher within the MeA of dominant and subordinate males exposed to the VBS in comparison with controls, but with no effect of prenatal treatment. These data suggest that prenatal chronic variable stress may confer resilience to offspring when exposed to social stress in adulthood. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. 29 CFR 780.202 - Subordination to farming operations is necessary for exemption.

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 3 2010-07-01 2010-07-01 false Subordination to farming operations is necessary for... Operations § 780.202 Subordination to farming operations is necessary for exemption. While section 3(f) speaks of practices performed “in conjunction with” as well as “incident to” farming operations, it would...

  16. Subordinators and Supradialectal Formulas in the Dialectal Inscriptions from Mainland Greece (Excluding Attica)

    Science.gov (United States)

    Minamimoto, Toru

    2017-01-01

    In this dissertation, I investigated the usage of subordinators in Ancient Greek dialectal inscriptions and their interactions with supradialectal formulas, i.e., relatively fixed expressions shared across dialectal borders. Subordinators are grammatical elements and therefore are expected to behave in a systematic manner; supradialectal formulas…

  17. Aspects of Subordination in English Syntax and its Use Among Bette ...

    African Journals Online (AJOL)

    Bette is a language widely spoken in the north-eastern part of Cross River State, Nigeria. The need for this study arises from an observation of serious interference of Bette system of subordination in Bette bilinguals with that of English. I examined subordination in the two systems through a contrastive linguistic analysis to ...

  18. 7 CFR 1717.858 - Lien subordination for rural development investments.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 11 2010-01-01 2010-01-01 false Lien subordination for rural development investments... Lien subordination for rural development investments. (a) Policy. RUS encourages borrowers to consider... financial risks and the revenues and costs of the rural development enterprise from those of the borrower's...

  19. Involuntary Subordination and Its Relation to Personality, Mood, and Submissive Behavior

    Science.gov (United States)

    Sturman, Edward D.

    2011-01-01

    According to social rank theory, involuntary subordination may be adaptive in species that compete for resources as a mechanism to switch off fighting behaviors when loss is imminent (thus saving an organism from injury). In humans, major depression is thought to occur when involuntary subordination becomes prolonged. The present study sought to…

  20. 12 CFR 563.81 - Inclusion of subordinated debt securities and mandatorily redeemable preferred stock as...

    Science.gov (United States)

    2010-01-01

    ... 12 Banks and Banking 5 2010-01-01 2010-01-01 false Inclusion of subordinated debt securities and... Borrowings § 563.81 Inclusion of subordinated debt securities and mandatorily redeemable preferred stock as..., subpart A seeking OTS approval of, or non-objection to, the inclusion of covered securities in...

  1. Participation with Supervisor and Subordinate Authoritarianism: A Path-Goal Theory Reconciliation

    Science.gov (United States)

    Schuler, Randall S.

    1976-01-01

    Tested the hypothesis that participation would be satisfying to low-authoritarian subordinates regardless of the degree of task repetitiveness but would be satisfying to high-authoritarian subordinates only on tasks with low repetitiveness and that highly repetitive tasks would be less conducive to ego involvement than low-repetitive tasks.…

  2. Charismatic, Ideological, and Pragmatic Leaders' Influence on Subordinate Creative Performance across the Creative Process

    Science.gov (United States)

    Lovelace, Jeffrey B.; Hunter, Samuel T.

    2013-01-01

    Using the charismatic, ideological, and pragmatic (CIP) model of leadership as a framework, 2 primary research questions were examined. First, when engaging in different tasks along the creative process, does leadership style influence the creative performance of subordinates? Second, how does the level of stress, to which subordinates are…

  3. Calcite Farming at Hollow Ridge Cave: Calibrating Net Rainfall and Cave Microclimate to Dripwater and Calcite Chemical Variability

    Science.gov (United States)

    Tremaine, D. M.; Kilgore, B. P.; Froelich, P. N.

    2012-04-01

    Stable isotope (δ18O and δ13C) and trace element records in cave speleothems are often interpreted as climate changes in rainfall amount or source, cave air temperature, overlying vegetation and atmospheric pCO2. However, these records are difficult to verify without in situ calibration of changes in cave microclimate (e.g., net rainfall, interior ventilation changes) to contemporaneous variations in dripwater and speleothem chemistry. In this study at Hollow Ridge Cave (HRC) in Marianna, Florida (USA), cave dripwater, bedrock, and modern calcite (farmed in situ) were collected in conjunction with continuous cave air pCO2, temperature, barometric pressure, relative humidity, radon-222 activity, airflow velocity and direction, rainfall amount, and drip rate data [1]. We analyzed rain and dripwater δD and δ18O, dripwater Ca2+, pH, δ13C and TCO2, cave air pCO2 and δ13C, and farmed calcite δ18O and δ13C to examine the relationships among rainwater isotopic composition, cave air ventilation, cave air temperature, calcite growth rate and seasonal timing, and calcite isotopic composition. Farmed calcite δ13C decreases linearly with distance from the front entrance to the interior of the cave during all seasons, with a maximum entrance-to-interior gradient of Δδ13C = -7‰ . A whole-cave "Hendy test" at distributed contemporaneous farming sites reveals that ventilation induces a +1.9 ± 0.96‰ δ13C offset between calcite precipitated in a ventilation flow path and out of flow paths. Farmed calcite δ18O exhibits a +0.82 ± 0.24‰ offset from values predicted by both theoretical calcite-water calculations and by laboratory-grown calcite [2]. Unlike calcite δ13C, oxygen isotopes show no ventilation effects and are a function only of temperature. Combining our data with other speleothem studies, we find a new empirical relationship for cave-specific water-calcite oxygen isotope fractionation across a range of temperatures and cave environments: 1000 ln α = 16

  4. Controls on the precipitation of barite (BaSO 4) crystals in calcite travertine at Twitya Spring, a warm sulphur spring in Canada's Northwest Territories

    Science.gov (United States)

    Bonny, Sandy M.; Jones, Brian

    2008-01-01

    Twitya Spring discharges warm (24 °C), anoxic, sulphide-, calcium- (65 ppm) and barium- (≥ 0.78 ppm) rich spring water to a steep flow path that is inhabited by streamer and mat-forming microbes ( Thiothrix, Beggiatoa, Oscillatoria, Spirulina, diatoms, rod shaped bacteria). Oxidation and CO 2 degassing drive precipitation of elemental sulphur, barite, opaline silica, and calcite. A mound of travertine at the base of the flow path, dominantly composed of bedded barium-enriched crystallographic and noncrystallographic dendritic calcite crystals and calcite cements, hosts three types of barite crystals: type 1 (T1) intergrown tabular crystals that formed in solution, type 2 (T2) tabular and rhombic crystals that nucleated on calcite, and type 3 (T3) subhedral and anhedral microcrystals that nucleated on microbial cell surfaces and in microbial extracellular polymeric substances. The formation and distribution of T1, T2, and T3 barite in the Twitya Spring flow path are controlled by physiochemical gradients, calcite precipitation rates, and adsorption of barium to microbial biomass, all of which vary seasonally and episodically at Twitya Spring. The complex physiochemical and biological controls on barite formation at Twitya Spring both suggest that the classification of biogenic or inorganic sedimentary barite on the basis of crystal size and morphology may be oversimplified. There is also the potential that primary and authigenic barite crystals hosted in carbonates may yield information about the microbial ecology and ambient physiochemistry of their depositional environments.

  5. Relationships between leaders' and subordinates' emotion regulation and satisfaction and affect at work.

    Science.gov (United States)

    Kafetsios, Konstantinos; Nezlek, John B; Vassilakou, Thanai

    2012-01-01

    The study examined relationships between leaders' emotion regulation and leaders' and subordinates' work-related outcomes. Fifty-one school directors and 281 teachers reported on their strategies of emotion regulation (reappraisal, suppression), job satisfaction, and affect at work. For subordinates, suppression was negatively related to job satisfaction and was positively related to negative affect and emotional exhaustion, and reappraisal was positively related to job satisfaction and negatively to negativ affect. In contrast, multilevel analyses found that directors' use of reappraisal was neg atively related to subordinates' job satisfaction, and directors' use of suppression wa positively related to subordinates' positive affect. Leaders' suppression interacted wit group cohesion to predict subordinates' negative affect. This is one of the first studies to find evidence for the possible tension between leaders' emotion regulation competencie and organizational-role interests.

  6. The role of leadership perception as a mediator between managers' self-monitoring and subordinate attitudes.

    Science.gov (United States)

    Özalp Türetgen, Ilknur; Unsal, Pinar; Dural, Uzay

    2017-01-01

    Although the role of social cognition in leadership perception has been emphasized frequently in recent years, research using this approach in an organizational context is rare. This study investigated subordinates' perceptions of their managers as leaders (that is, to what extent they perceive their manager as a leader) as a potential mediating factor explaining the relationship between managers' self-monitoring and their subordinates' attitudes toward their organizations. The study was carried out with middle-level managers (N = 64) and their subordinates (N = 210) from various business organizations in Turkey. Results indicate that subordinates' leadership perceptions of their managers mediate the relationship between managers' self-monitoring and their subordinates' affective and normative organizational commitment. These results provide insight into some of the antecedents and outcomes of leadership perception.

  7. Photoinduced synthesis of single-digit micrometer-size spheroidal calcite composites in the presence of partially hydrolyzed poly(vinyl alcohol)

    Science.gov (United States)

    Nishio, Takashi; Naka, Kensuke

    2015-06-01

    Photoinduced crystallization of calcium carbonate (CaCO3), which was based on the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphyenyl)propionic acid) under alkaline conditions of pH 8.4 and 10 was studied for preparation of CaCO3 composite particles in single-digit micrometer-sizes. In this method, a homogeneous solution comprising KP, calcium chloride, ammonia, and partially hydrolyzed poly(vinyl alcohol) (PVAPS, degree of saponification: 86.5-89.0 mol%) was used as a precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. After the UV irradiation for 50 min, calcite spheroids in single-digit micrometer-sizes were obtained as major products at pH 8.4. The obtained calcite spheroids contained organic components of about 10 wt%. The comparison of the characteristics of the CaCO3 obtained at pH 8.4 and 10 suggests that the nucleation and crystallization of both vaterite and calcite continuously took place in a moderated supersaturation owing to the CO2 hydration equilibrium as long as the photodecarboxylation of KP continued. Consequently, the aggregation-based crystal growth in the presence of PVAPS seemed to enable the formation of the spheroidal composites of calcite in single-digit micrometer-sizes.

  8. Characterization of urease and carbonic anhydrase producing bacteria and their role in calcite precipitation.

    Science.gov (United States)

    Achal, Varenyam; Pan, Xiangliang

    2011-03-01

    Urease and carbonic anhydrase (CA) are key enzymes in the chemical reaction of living organisms and have been found to be associated with calcification in a number of microorganisms and invertebrates. Three bacterial strains designated as AP4, AP6, and AP9 were isolated from highly alkaline soil samples using the enrichment culture technique. On the basis of various physiological tests and 16S rRNA sequence analysis, these three bacteria were identified as Bacillus sp., B. megaterium, and B. simplex. Further, these Bacillus species have been characterized for the production of urease and CA in the process of biocalcification. One of the isolates, AP6 produced 553 U/ml of urease and 5.61 EU/ml CA. All the strains were able to produce significant amount of exopolymeric substances and biofilm. Further, efficacy of these strains was tested for calcite production ability and results were correlated with urease and CA. Isolate AP6 precipitated 2.26 mg calcite/cell dry mass (mg). Our observations strongly suggest that it is not only urease but CA also plays an important role in microbially induced calcium carbonate precipitation process. The current work demonstrates that urease and CA producing microbes can be utilized in biocalcification as a sealing agent for filling the gaps or cracks and fissures in constructed facilities and natural formations alike.

  9. Study on effect of Microbial Induced Calcite Precipitates on strength of fine grained soils

    Directory of Open Access Journals (Sweden)

    Animesh Sharma

    2016-09-01

    Full Text Available For construction purposes, it is very essential to provide a strong foundation for the structure. If required, the suitability of soil has to be improved; this process of improving properties of soil is called Soil Stabilisation. This study intends to experimentally analyse the effectiveness of use of an unorthodox liquid soil stabiliser, Microbial Induced Calcite Precipitates (MICP for improving the shear strength parameters of two different types of fine grained soils. For this process, a species of Bacillus group, B. pastuerii was used to activate and catalyse the calcite precipitation caused by reaction between urea and calcium chloride. Two types of soils, i.e. intermediate compressible clay and highly compressible clay were used for the study. Parameters included concentration of B. pasteurii, concentration of the cementation reagent and duration of treatment. These parameters were applied on both the soils in a specified range in order to optimise their usage. The results proved that with the use of MICP, there was a noticeable improvement (1.5–2.9 times in the unconfined compressive strength of both type of soils. It was also found that the strength increased with an increase in duration of treatment. Based on this study, optimum quantity and concentration of liquid additive to be added for different soil types for better strength increments were established.

  10. On the complex conductivity signatures of calcite precipitation

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Yuxin; Hubbard, Susan; Williams, Kenneth Hurst; Ajo-Franklin, Jonathan

    2009-11-01

    Calcite is a mineral phase that frequently precipitates during subsurface remediation or geotechnical engineering processes. This precipitation can lead to changes in the overall behavior of the system, such as flow alternation and soil strengthening. Because induced calcite precipitation is typically quite variable in space and time, monitoring its distribution in the subsurface is a challenge. In this research, we conducted a laboratory column experiment to investigate the potential of complex conductivity as a mean to remotely monitor calcite precipitation. Calcite precipitation was induced in a glass bead (3 mm) packed column through abiotic mixing of CaCl{sub 2} and Na{sub 2}CO{sub 3} solutions. The experiment continued for 12 days with a constant precipitation rate of {approx}0.6 milimole/d. Visual observations and scanning electron microscopy imaging revealed two distinct phases of precipitation: an earlier phase dominated by well distributed, discrete precipitates and a later phase characterized by localized precipitate aggregation and associated pore clogging. Complex conductivity measurements exhibited polarization signals that were characteristic of both phases of calcite precipitation, with the precipitation volume and crystal size controlling the overall polarization magnitude and relaxation time constant. We attribute the observed responses to polarization at the electrical double layer surrounding calcite crystals. Our experiment illustrates the potential of electrical methods for characterizing the distribution and aggregation state of nonconductive minerals like calcite. Advancing our ability to quantify geochemical transformations using such noninvasive methods is expected to facilitate our understanding of complex processes associated with natural subsurface systems as well as processes induced through engineered treatments (such as environmental remediation and carbon sequestration).

  11. Nanometer-Scale Chemistry of a Calcite Biomineralization Template: Implications for Skeletal Composition and Nucleation

    Energy Technology Data Exchange (ETDEWEB)

    Branson, Oscar; Bonnin, Elisa A.; Perea, Daniel E.; Spero, Howard J.; Zhu, Zihua; Winters, Maria; Hönisch, Bärbel; Russell, Ann D.; Fehrenbacher, Jennifer S.; Gagnon, Alexander C.

    2016-10-28

    Biomineralizing organisms exhibit exquisite control over skeletal morphology and composition. The promise of understanding and harnessing this feat of natural engineering has motivated an intense search for the mechanisms that direct in vivo mineral self-assembly. We used atom probe tomography, a sub-nanometer 3D chemical mapping technique, to examine the chemistry of a buried organic-mineral interface in biomineral calcite from a marine foraminifer. The chemical patterns at this interface capture the processes of early biomineralization, when the shape, mineralogy, and orientation of skeletal growth are initially established. Sodium is enriched by a factor of nine on the organic side of the interface. Based on this pattern, we suggest that sodium plays an integral role in early biomineralization, potentially altering interfacial energy to promote crystal nucleation, and that interactions between organic surfaces and electrolytes other than calcium or carbonate could be a crucial aspect of CaCO3 biomineralization.

  12. A Raman spectroscopic comparison of calcite and dolomite.

    Science.gov (United States)

    Sun, Junmin; Wu, Zeguang; Cheng, Hongfei; Zhang, Zhanjun; Frost, Ray L

    2014-01-03

    Raman spectroscopy was used to characterize and differentiate the two minerals calcite and dolomite and the bands related to the mineral structure. The (CO3)(2-) group is characterized by four prominent Raman vibrational modes: (a) the symmetric stretching, (b) the asymmetric deformation, (c) asymmetric stretching and (d) symmetric deformation. These vibrational modes of the calcite and dolomite were observed at 1440, 1088, 715 and 278 cm(-1). The significant differences between the minerals calcite and dolomite are observed by Raman spectroscopy. Calcite shows the typical bands observed at 1361, 1047, 715 and 157 cm(-1), and the special bands at 1393, 1098, 1069, 1019, 299, 258 and 176 cm(-1) for dolomite are observed. The difference is explained on the basis of the structure variation of the two minerals. Calcite has a trigonal structure with two molecules per unit cell, and dolomite has a hexagonal structure. This is more likely to cause the splitting and distorting of the carbonate groups. Another cause for the difference is the cation substituting for Mg in the dolomite mineral. Copyright © 2013 Elsevier B.V. All rights reserved.

  13. Nuclear anomalies in the buccal cells of calcite factory workers.

    Science.gov (United States)

    Diler, Songül Budak; Ergene, Serap

    2010-04-01

    The micronucleus (MN) assay on exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans. To determine the genotoxic effects of calcite dust that forms during processing, MN assay was carried out in exfoliated buccal cells of 50 (25 smokers and 25 non-smokers) calcite factory workers and 50 (25 smokers and 25 non-smokers) age- and sex-matched control subjects. Frequencies of nuclear abnormalities (NA) other than micronuclei, such as binucleates, karyorrhexis, karyolysis and 'broken eggs', were also evaluated. Micronuclei and the other aforementioned anomalies were analysed by two way analysis of covariance. The linear correlations between the types of micronucleus and nuclear abnormalities were determined by Spearman's Rho. There was a positive correlation between micronuclei and other types of nuclear abnormalities in accordance with the Spearman's Rho test. Results showed statistically significant difference between calcite fabric workers and control groups. MN and NA frequencies in calcite fabric workers were significantly higher than those in control groups (p < 0.05). The results of this study indicate that calcite fabric workers are under risk of significant cytogenetic damage.

  14. Nuclear anomalies in the buccal cells of calcite factory workers

    Directory of Open Access Journals (Sweden)

    Songül Budak Diler

    2010-01-01

    Full Text Available The micronucleus (MN assay on exfoliated buccal cells is a useful and minimally invasive method for monitoring genetic damage in humans. To determine the genotoxic effects of calcite dust that forms during processing, MN assay was carried out in exfoliated buccal cells of 50 (25 smokers and 25 non-smokers calcite factory workers and 50 (25 smokers and 25 non-smokers age- and sex-matched control subjects. Frequencies of nuclear abnormalities (NA other than micronuclei, such as binucleates, karyorrhexis, karyolysis and 'broken eggs', were also evaluated. Micronuclei and the other aforementioned anomalies were analysed by two way analysis of covariance. The linear correlations between the types of micronucleus and nuclear abnormalities were determined by Spearman's Rho. There was a positive correlation between micronuclei and other types of nuclear abnormalities in accordance with the Spearman's Rho test. Results showed statistically significant difference between calcite fabric workers and control groups. MN and NA frequencies in calcite fabric workers were significantly higher than those in control groups (p < 0.05. The results of this study indicate that calcite fabric workers are under risk of significant cytogenetic damage.

  15. Psychological characteristics of the rules of subordination within the cultural and historical analysis

    Directory of Open Access Journals (Sweden)

    Budyakova T.P.,

    2016-01-01

    Full Text Available The article examines the psychology of submission. Given psychological characteristic standards of submission historically embodied in the moral codes and legal sources. The subject of analysis are historical regulations XII—XX centuries, the customs, in which the fixed rate of submission, as well as the memoir literature. There are four basic psychological lines of development in the history of the rules of subordination, in particular: a special regulation of the rules of subordination and increasing social importance of the role of subordinate. It is proved that psychological acceptance of a subordinate role and the satisfaction of its implementation includes the requirement of special rules regulating authority and emphasis on the social importance of the role of subordinate. It was established that one of the reasons that the job satisfaction of employees of state structures higher than employees of private companies, a large schema definition of relations with management. Hierarchical role is considered in terms of two components: the role of attributes and rules, rules of conduct. The article focuses on the fact that the individual external signs, locking status subordination, increase the level of self-esteem of subordinate.

  16. Empowerment and performance of managers and subordinates in elderly care: A longitudinal and multilevel study.

    Science.gov (United States)

    Hagerman, Heidi; Högberg, Hans; Skytt, Bernice; Wadensten, Barbro; Engström, Maria

    2017-11-01

    To investigate relationships between first-line managers' ratings of structural and psychological empowerment, and the subordinates' ratings of structural empowerment, as well as their ratings of the managers' leadership-management performance. Work situations in elderly care are complex. To date, few studies have used a longitudinal, correlational and multilevel design to study the working life of subordinates and managers. In five Swedish municipalities, questionnaires were answered twice during 2010-12 by 56 first-line managers and 769 subordinates working in nursing homes or home-help services. First-line managers' empowerment at Time 1 partially predicted subordinate's structural empowerment and ratings of their managers' leadership-management performance at Time 2. Changes over time partially revealed that the more access managers had to structural empowerment, i.e. increase over time, the higher the ratings were for structural empowerment and managerial leadership-management performance among subordinates. Findings strengthen research and theoretical suggestions linking first-line managers' structural empowerment to their subordinates' structural empowerment and ratings of their manager's leadership-management performance. Managers with high access to structural empowerment are more likely to provide subordinates access to structural empowerment. © 2017 The Authors. Journal of Nursing Management Published by John Wiley & Sons Ltd.

  17. Social subordination impairs hypothalamic-pituitary-adrenal function in female rhesus monkeys.

    Science.gov (United States)

    Michopoulos, Vasiliki; Reding, Katherine M; Wilson, Mark E; Toufexis, Donna

    2012-09-01

    Linear dominance hierarchies organize and maintain stability in female rhesus macaque (Macaca mulatta) social groups regardless of group size. As a consequence of their low social status, subordinate females suffer from an array of adverse outcomes including reproductive compromise, impaired immune function, and poor cardiovascular health. However, data that differentiate limbic-hypothalamic-pituitary-adrenal axis (LHPA) parameters between dominant from subordinate female monkeys are inconsistent, bringing into question whether social subordination alters the LHPA axis in female macaques. One difficulty in examining LHPA function in macaques may be the confounding effects of cycling ovarian steroids that are known to modulate LHPA activity. The current study used ovariectomized dominant and subordinate female rhesus monkeys to examine the effect that social subordination has on LHPA function by measuring morning and diurnal serum cortisol levels, dexamethasone (Dex) suppression of cortisol, metabolic clearance of Dex, and ACTH stimulation of adrenal cortisol release and cortisol response following exposure to acute social isolation. Compared to dominant females, subordinate females showed diminished morning peak cortisol secretion, weakened glucocorticoid negative feedback, and decreased adrenal cortisol response to an ACTH challenge as well as a restrained cortisol response following social isolation. However, the metabolism of Dex did not account for differences in Dex suppression between dominant and subordinate females. These results indicate that the ability to mount and limit glucocorticoid release is significantly reduced by psychosocial stress in female rhesus macaques, suggesting a hyporesponsive LHPA phenotype which resembles that observed in several human psychopathologies. Copyright © 2012 Elsevier Inc. All rights reserved.

  18. Caspartin and calprismin, two proteins of the shell calcitic prisms of the Mediterranean fan mussel Pinna nobilis.

    Science.gov (United States)

    Marin, Frédéric; Amons, Reinout; Guichard, Nathalie; Stigter, Martin; Hecker, Arnaud; Luquet, Gilles; Layrolle, Pierre; Alcaraz, Gérard; Riondet, Christophe; Westbroek, Peter

    2005-10-07

    We used the combination of preparative electrophoresis and immunological detection to isolate two new proteins from the shell calcitic prisms of Pinna nobilis, the Mediterranean fan mussel. The amino acid composition of these proteins was determined. Both proteins are soluble, intracrystalline, and acidic. The 38-kDa protein is glycosylated; the 17-kDa one is not. Ala, Asx, Thr, and Pro represent the dominant residues of the 38-kDa protein, named calprismin. An N-terminal sequence was obtained from calprismin. This sequence, which comprises a pattern of 4 cysteine residues, is not related to any known protein. The second protein, named caspartin, exhibits an unusual amino acid composition, since Asx constitutes by far the main amino acid residue. Preliminary sequencing surprisingly suggests that the first 75 N-terminal residues are all Asp. Caspartin self-aggregates spontaneously into multimers. In vitro tests show that it inhibits the precipitation of calcium carbonate. Furthermore, it strongly interferes with the growth of calcite crystals. A polyclonal antiserum raised against caspartin was used to localize this protein in the shell by immunogold. The immunolocalization demonstrates that caspartin is distributed within the prisms and makes a continuous film at the interface between the prisms and the surrounding insoluble sheets. Our finding emphasizes the prominent role of aspartic acid-rich proteins for the building of calcitic prisms among molluscs.

  19. Calcium carbonate polyamorphism and its role in biomineralization: how many amorphous calcium carbonates are there?

    Science.gov (United States)

    Cartwright, Julyan H E; Checa, Antonio G; Gale, Julian D; Gebauer, Denis; Sainz-Díaz, C Ignacio

    2012-11-26

    Although the polymorphism of calcium carbonate is well known, and its polymorphs--calcite, aragonite, and vaterite--have been highly studied in the context of biomineralization, polyamorphism is a much more recently discovered phenomenon, and the existence of more than one amorphous phase of calcium carbonate in biominerals has only very recently been understood. Here we summarize what is known about polyamorphism in calcium carbonate as well as what is understood about the role of amorphous calcium carbonate in biominerals. We show that consideration of the amorphous forms of calcium carbonate within the physical notion of polyamorphism leads to new insights when it comes to the mechanisms by which polymorphic structures can evolve in the first place. This not only has implications for our understanding of biomineralization, but also of the means by which crystallization may be controlled in medical, pharmaceutical, and industrial contexts. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. CRACK2. Modelling calcium carbonate deposition from bicarbonate solutions in cracks in concrete

    OpenAIRE

    Brodersen, Knud Erik

    2003-01-01

    The numerical CRACK2 model simulates precipitation of calcite from calcium bicarbonate solution (e.g. groundwater) passing through cracks in concrete or other cementitious materials. A summary of experimental work is followed by a detailed description ofthe model. Hydroxyl ions are transported by diffusion in pore systems in columns of cementitious materials. The hydroxyl is precipitating calcite from a flow of bicarbonate solution in a crack connecting the ends of a row of such columns. Thec...

  1. Catalysis and chemical mechanisms of calcite dissolution in seawater.

    Science.gov (United States)

    Subhas, Adam V; Adkins, Jess F; Rollins, Nick E; Naviaux, John; Erez, Jonathan; Berelson, William M

    2017-07-18

    Near-equilibrium calcite dissolution in seawater contributes significantly to the regulation of atmospheric [Formula: see text] on 1,000-y timescales. Despite many studies on far-from-equilibrium dissolution, little is known about the detailed mechanisms responsible for calcite dissolution in seawater. In this paper, we dissolve (13)C-labeled calcites in natural seawater. We show that the time-evolving enrichment of [Formula: see text] in solution is a direct measure of both dissolution and precipitation reactions across a large range of saturation states. Secondary Ion Mass Spectrometer profiles into the (13)C-labeled solids confirm the presence of precipitated material even in undersaturated conditions. The close balance of precipitation and dissolution near equilibrium can alter the chemical composition of calcite deeper than one monolayer into the crystal. This balance of dissolution-precipitation shifts significantly toward a dissolution-dominated mechanism below about [Formula: see text] Finally, we show that the enzyme carbonic anhydrase (CA) increases the dissolution rate across all saturation states, and the effect is most pronounced close to equilibrium. This finding suggests that the rate of hydration of [Formula: see text] is a rate-limiting step for calcite dissolution in seawater. We then interpret our dissolution data in a framework that incorporates both solution chemistry and geometric constraints on the calcite solid. Near equilibrium, this framework demonstrates a lowered free energy barrier at the solid-solution interface in the presence of CA. This framework also indicates a significant change in dissolution mechanism at [Formula: see text], which we interpret as the onset of homogeneous etch pit nucleation.

  2. ARTICLE Evolution Mechanism of Calcium Carbonate in Solution

    Science.gov (United States)

    Guo, Ya-ping; Tang, Hai-xiong; Zhou, Yu; Jia, De-chang; Ning, Cong-qin; Guo, Ya-jun

    2010-12-01

    Calcium carbonate was synthesized in a CaCl2/NaCO3 mixed solution by using ethylenediaminetetraacetic acid (EDTA) as an additive. The thermodynamics and kinetics analyses indicate that although the driving force of amorphous calcium carbonate (ACC) precipitation is always less than that of calcite and vaterite precipitation, the nucleation rate of ACC is greater than that of calcite and vaterite at the initial stage of the precipitation reaction. With the increasing incubation time, vaterite and calcite particles nucleate heterogeneously by using the as-formed particles as active sites. Scanning electron microscopy images indicate that the transformation mechanism of ACC and vaterite to calcite is the dissolution-recrystallisation reaction. The presence of EDTA not only improves the stabilities of ACC and vaterite, but also leads to forming enlongated, connected rhombohedral calcite crystals after incubation 7 days in solutions. The ACC and vaterite are stabler in air than in solutions at room temperature, although the dissolution-recrystallisation reaction occurs on the surface.

  3. Calcium and calcium magnesium carbonate specimens submitted as urinary tract stones.

    Science.gov (United States)

    Gault, M H; Chafe, L; Longerich, L; Mason, R A

    1993-02-01

    Of 8,129 specimens submitted as urinary stones from 6,095 patients, 67 from 15 patients were predominantly calcium carbonate or calcium magnesium carbonate (dolomite) by infrared analysis. Detailed study of 1 man and 4 women who submitted 3 or more such specimens showed that all were of aragonite calcium carbonate crystal form in 2 women and all calcite in the man. All 3 patients had a long history of nephrolithiasis preceding submission of calcium carbonate stones. There was frequent and often painful spontaneous passage of many small stones. Medullary sponge kidney was reported in 2 patients. Specimens submitted by the other 2 women included dolomite and quartz artifacts. Of the other 10 patients 4 had calcite and 1 had aragonite (possibly true stones). Five patients had artifacts with dolomite in 3 and mixed specimens in 2. True calcium carbonate kidney stones and calcium carbonate artifacts may be difficult to distinguish, and dolomite and quartz artifacts may require x-ray diffraction for clear-cut diagnosis.

  4. Formation of a ternary neptunyl(V) biscarbonato inner-sphere sorption complex inhibits calcite growth rate.

    Science.gov (United States)

    Heberling, Frank; Scheinost, Andreas C; Bosbach, Dirk

    2011-06-01

    Neptunyl, Np(V)O(2)(+), along with the other actinyl ions U(VI)O(2)(2+) and Pu(V,VI)O(2)((+,2+)), is considered to be highly mobile in the geosphere, while interaction with mineral surfaces (inner- or outer-sphere adsorption, ion-exchange, and coprecipitation/structural incorporation) may retard its migration. Detailed information about the exact interaction mechanisms including the structure and stoichiometry of the adsorption complexes is crucial to predict the retention behavior in diverse geochemical environments. Here, we investigated the structure of the neptunyl adsorption complex at the calcite-water interface at pH 8.3 in equilibrium with air by means of low-temperature (15K) EXAFS spectroscopy at the Np-L(III) edge. The coordination environment of neptunyl consists of two axial oxygen atoms at 1.87(±0.01)Å, and an equatorial oxygen shell of six atoms at 2.51(±0.01)Å. Two oxygen backscatterers at 3.50(±0.04)Å along with calcium backscatterers at 3.95(±0.03)Å suggest that neptunyl is linked to the calcite surface through two monodentate bonds towards carbonate groups of the calcite surface. Two additional carbon backscatterers at 2.94(±0.02)Å are attributed to two carbonate ions in bidentate coordination. This structural environment is conclusively interpreted as a ternary surface complex, where a neptunyl biscarbonato complex sorbs through two monodentate carbonate bonds to steps at the calcite (104) face, while the two bidentately coordinated carbonate groups point away from the surface. This structural information is further supported by Mixed Flow Reactor (MFR) experiments. They show a significant decrease of the calcite growth rate in the presence of neptunyl(V), in line with blockage of the most active crystal growth sites, step and kink sites, by adsorption of neptunyl. Formation of this sorption complex constitutes an important retention mechanism for neptunyl in calcite-rich environments. Copyright © 2011 Elsevier B.V. All rights

  5. Cretaceous joints in southeastern Canada: dating calcite-filled fractures

    Science.gov (United States)

    Schneider, David; Spalding, Jennifer; Gautheron, Cécile; Sarda, Philippe; Davis, Donald; Petts, Duane

    2017-04-01

    To resolve the timing of brittle tectonism is a challenge since the classical chronometers required for analyses are not often in equilibrium with the surrounding material or simply absent. In this study, we propose to couple LA-ICP-MS U-Pb and (U-Th)/He dating with geochemical proxies in vein calcite to tackle this dilemma. We examined intracratonic Middle Ordovician limestone bedrock that overlies Mesoproterozoic crystalline basement, which are cut by NE-trending fault zones that have historic M4-5 earthquakes along their trace. E-W to NE-SW vertical joint sets, the relatively youngest stress recorded in the bedrock, possess 1-7 mm thick calcite veins that seal fractures or coat fracture surfaces. The veins possess intragranular calcite that are lined with fine-grained calcite along the vein margin and can exhibit µm- to mm-scale offset (e.g. displaced fossil fragments in host rock). Calcite d18O and d13C values are analogous to the bulk composition of Middle to Late Ordovician limestones, and suggest vein formation from a source dominated by connate fluids. The calcite contain trails of fluid inclusions commonly along fractures, and 3He/4He analyses indicate a primitive, deep fluid signature (R/Ra: 0.5-2.7). Trace element geochemistry of the calcite is highly variable, generally following the elevated HREE and lower LREE of continental crust trends but individual crystals from a single vein may vary by three orders of magnitude. LA-ICP-MS geochemical traverse across veins show elevated concentrations along (sub)grain boundaries and the vein-host rock contact. Despite abundant helium concentrations, (U-Th)/He dating was unsuccessful yielding highly dispersed dates likely from excess helium derived from the fluid inclusions. However, LA-ICP-MS U-Pb dating on calcite separated from the veins yielded model ages of 110.7 ± 6.8 Ma (MSWD: 0.53; n: 16) to 81.4 ± 8.3 Ma (MSWD: 2.6; n: 17). Since all veins are from the same ENE-trend, we regressed all the calcite dates

  6. IMPRISONMENT AS A RESULT OF WOMEN SUBORDINATION 194 REFLECTED IN MAYA ANGELOU‘S POEMS

    Directory of Open Access Journals (Sweden)

    Fatikha Amalina

    2017-12-01

    Full Text Available This research is aimed to describe the imprisonment of African American people, especially women, in the case of patriarchy and women subordination through Maya Angelou‘s selected poems entitled ―Caged Bird‖, ―Still I Rise‖ and ―Woman Work‖. This research discusses the meaning behind the poems that reflected Maya Angelou‘s life experience relating to women subordination and freedom. Feminism approach is applied to analyze the concept of freedom in women subordination and patriarchy in this research. The paper points to how the concept of gender intertwines with labor, ethnics, kinship and gender domination. Without aiming to paint a detailed picture of feminism, the paper explores how ideas developed in these inquiries question the taken-for-granted assumption about the universality of women‘s subordination and challenge the emancipation prerequisite of feminist agenda.

  7. Genetic sorting of subordinate species in grassland modulated by intraspecific variation in dominant species.

    Directory of Open Access Journals (Sweden)

    Danny J Gustafson

    Full Text Available Genetic variation in a single species can have predictable and heritable effects on associated communities and ecosystem processes, however little is known about how genetic variation of a dominant species affects plant community assembly. We characterized the genetic structure of a dominant grass (Sorghastrum nutans and two subordinate species (Chamaecrista fasciculata, Silphium integrifolium, during the third growing season in grassland communities established with genetically distinct (cultivated varieties or local ecotypes seed sources of the dominant grasses. There were genetic differences between subordinate species growing in the cultivar versus local ecotype communities, indicating that intraspecific genetic variation in the dominant grasses affected the genetic composition of subordinate species during community assembly. A positive association between genetic diversity of S. nutans, C. fasciculata, and S. integrifolium and species diversity established the role of an intraspecific biotic filter during community assembly. Our results show that intraspecific variation in dominant species can significantly modulate the genetic composition of subordinate species.

  8. Synthesis and characterization of CaCO3 (calcite) nano particles from cockle shells (Anadara granosa Linn) by precipitation method

    Science.gov (United States)

    Widyastuti, Sri; Intan Ayu Kusuma, P.

    2017-06-01

    Calcium supplements can reduce the risk of osteoporosis, but they are not automatically absorbed in the gastrointestinal tract. Nanotechnology is presumed to have a capacity in resolving this problem. The preparation and characterization of calcium carbonate nano particle to improve the solubility was performed. Calcium carbonate nano particles were synthesized using precipitation method from cockle shells (Anadara granosa Linn). Samples of the cockle shells were dried in an oven at temperature of 50°C for 7 (seven) days and subsequently they were crushed and blended into fine powder that was sieved through 125-μm sieve. The synthesis of calcium carbonate nanocrystals was done by extracting using hydro chloride acid and various concentrations of sodium hydroxide were used to precipitate the calcium carbonate nano particles. The size of the nano particles was determined by SEM, XRD data, and Fourier transform infrared spectroscopy (FT-IR). The results of XRD indicated that the overall crystalline structure and phase purity of the typical calcite phase CaCO3 particles were approximately 300 nm in size. The method to find potential applications in industry to yield the large scale synthesis of aragonite nano particles by a low cost but abundant natural resource such as cockle shells is required.

  9. Calcium carbonates: induced biomineralization with controlled macromorphology

    Science.gov (United States)

    Meier, Aileen; Kastner, Anne; Harries, Dennis; Wierzbicka-Wieczorek, Maria; Majzlan, Juraj; Büchel, Georg; Kothe, Erika

    2017-11-01

    Biomineralization of (magnesium) calcite and vaterite by bacterial isolates has been known for quite some time. However, the extracellular precipitation has hardly ever been linked to different morphologies of the minerals that are observed. Here, isolates from limestone-associated groundwater, rock and soil were shown to form calcite, magnesium calcite or vaterite. More than 92 % of isolates were indeed able to form carbonates, while abiotic controls failed to form minerals. The crystal morphologies varied, including rhombohedra, prisms and pyramid-like macromorphologies. Different conditions like varying temperature, pH or media components, but also cocultivation to test for collaborative effects of sympatric bacteria, were used to differentiate between mechanisms of calcium carbonate formation. Single crystallites were cemented with bacterial cells; these may have served as nucleation sites by providing a basic pH at short distance from the cells. A calculation of potential calcite formation of up to 2 g L-1 of solution made it possible to link the microbial activity to geological processes.

  10. Copper incorporation in foraminiferal calcite: results from culturing experiments

    NARCIS (Netherlands)

    Nooijer, L.J. de; Reichart, G.-J.; Dueñas Bohórquez, A.D.B.; Wolthers, M.; Ernst, S.R.; Mason, P.R.D.; Zwaan, G.J. van der

    2007-01-01

    A partition coefficient for copper (DCu) in foraminiferal calcite has been determined by culturing individuals of two benthic species under controlled laboratory conditions. The partition coefficient of a trace element (TE) is an emperically determined relation between the TE/Ca ratio in seawater

  11. NMR spectroscopic study of organic phosphate esters coprecipitated with calcite

    Science.gov (United States)

    Phillips, Brian L.; Zhang, Zelong; Kubista, Laura; Frisia, Silvia; Borsato, Andrea

    2016-06-01

    Organic phosphorus incorporated in calcite during laboratory precipitation experiments and in natural cave deposits was investigated by solid-state NMR spectroscopy. For calcite precipitated in the presence of organic phosphoesters of varying size and functionality, solid-state 31P{1H} CP/MAS NMR shows that the phosphoesters were incorporated intact into the solid. Systematic changes in the 31P NMR chemical shift of the phosphate group were observed between the solid phosphoester and that incorporated in the solid precipitate, yielding 31P NMR chemical shifts of the coprecipitates in the range of +1.8 to -2.2 ppm. These chemical shifts are distinct from that of similarly prepared calcite coprecipitated with inorganic phosphate, 3.5 ppm. Only minor changes were noted in the phosphoester 31P chemical shift anisotropy (CSA) which suggests no significant change in the local structure of the phosphate group, which is dominated by C-O-P bonding. Close spatial proximity of the organic phosphate group to calcite structural components was revealed by 31P/13C rotational echo double resonance (REDOR) experiments for coprecipitates prepared with 13C-labeled carbonate. All coprecipitates showed significant 31P dephasing effects upon 13C-irradiation, signaling atomic-scale proximity to carbonate carbon. The dephasing rate for smaller organophosphate molecules is similar to that observed for inorganic phosphate, whereas much slower dephasing was observed for larger molecules having long and/or bulky side-chains. This result suggests that small organic molecules can be tightly enclosed within the calcite structure, whereas significant structural disruption required to accommodate the larger organic molecules leads to longer phosphate-carbonate distances. Comparison of 31P NMR spectroscopic data from the synthetic coprecipitates with those from calcite moonmilk speleothems indicates that phosphorus occurs mainly as inorganic orthophosphate in the natural deposits, although small

  12. Temperature limits for preservation of primary calcite clumped isotope paleotemperatures

    Science.gov (United States)

    Henkes, Gregory A.; Passey, Benjamin H.; Grossman, Ethan L.; Shenton, Brock J.; Pérez-Huerta, Alberto; Yancey, Thomas E.

    2014-08-01

    Solid-state reordering of C-O bonds in the calcite lattice can alter the clumped isotope composition of paleotemperature archives such as fossil brachiopod shells without inducing significant changes in shell microstructure and trace element concentrations, metrics commonly used to gauge preservation quality. To correctly interpret the paleoenvironmental significance of clumped isotope-derived paleotemperatures, it is necessary to understand the temperature-time domain in which solid-state C-O bond reordering is important. We address this question using a combination of laboratory and natural geological experiments on Paleozoic brachiopod shells. The laboratory experiments involve heating fossil brachiopod calcite at different temperatures and times to directly observe rates of 13C-18O bond reordering. The resulting Arrhenius parameters are indistinguishable from values previously determined for an optical calcite with similar trace element compositions. We develop an alternative kinetic model for reordering that accounts for non-first-order reaction progress observed during the initial several hundred minutes of laboratory heating experiments, and show that the simplified first-order approximation model (Passey and Henkes, 2012) predicts reaction progress equally well for temperatures and timescales relevant to sedimentary basins. We evaluate our laboratory-based rate predictions by studying brachiopod calcite from several sedimentary basins with independently constrained burial temperature histories. Specifically, we use the laboratory-derived Arrhenius parameters to predict the evolution of brachiopod calcite clumped isotope compositions during successive one million-year time steps reflecting the burial and exhumation temperature paths of each basin. While this exercise is limited by the relatively large uncertainties in the temperature histories of these basins, we find general correspondence, within error, between predicted and observed clumped isotope values

  13. Uranium Isotope Fractionation During Coprecipitation with Aragonite and Calcite

    Science.gov (United States)

    Chen, X.; Romaniello, S. J.; Herrmann, A. D.; Wasylenki, L. E.; Anbar, A. D.

    2014-12-01

    Natural variations in the 238U/235U ratio of marine carbonates may provide a useful way of constraining past variations in ocean redox conditions. However, before applying this novel redox proxy, it is essential to explore possible isotopic fractionation during U coprecipitation with aragonite and calcite. We investigated these effects in laboratory experiments. Aragonite and calcite coprecipitation experiments were conducted at pH 8.5±0.1 using a constant addition method [1]. More than 90% of the U was incorporated into the solid phase at the end of each experiment. Samples were purified using UTEVA chemistry and δ238/235U was measured using 233U-236U double-spike MC-ICP-MS with a precision of ±0.10‰ [2]. The aragonite experiment demonstrated a 238U/235U Rayleigh fractionation factor of α=1.00008±0.00002 with the 238U preferentially incorporated. In contrast, the calcite experiment demonstrated no resolvable U isotope fractionation (α=1.00001±0.00003). To determine if U isotopes are affected during the early diagenetic conversion of aragonite to calcite, natural carbonate samples were collected along an aragonite-calcite transition across a single coral head in the Key Largo limestone, and characterized for U concentration and δ238/235U [3]. We found that the mean δ238/235U in aragonite (-0.33±0.07‰ 2se) was slightly heavier than that in calcite (-0.37±0.02‰ 2se). Further work is needed to address the mechanisms leading to differential isotopic fractionation of U(VI) during incorporation into aragonite and calcite. Possible drivers include differences in coordination in the crystal structure or equilibrium isotopic fractionation between various aqueous U(VI) species prior to incorporation. [1] Reeder et al. (2001) GCA 65, 3491-3503. [2] Weyer et al., (2008) GCA 72, 345-359. [3] Gill et al., (2008) GCA 72, 4699-4722.

  14. Molecular ordering of ethanol at the calcite surface.

    Science.gov (United States)

    Pasarín, I S; Yang, M; Bovet, N; Glyvradal, M; Nielsen, M M; Bohr, J; Feidenhans'l, R; Stipp, S L S

    2012-02-07

    To produce biominerals, such as shells, bones, and teeth, living beings create organic compounds that control the growth of the solid phase. Investigating the atomic scale behavior of individual functional groups at the mineral-fluid interface provides fundamental information that is useful for constructing accurate predictive models for natural systems. Previous investigations of the activity of coccolith-associated polysaccharides (CAP) on calcite, using atomic force microscopy (AFM) [Henriksen, K., Young, J. R., Bown, P. R., and Stipp, S. L. S. Palentology 2004, 43 (Part 3), 725-743] and molecular dynamics (MD) modeling [Yang, M., Stipp, S. L. S., and Harding, J. H. Cryst. Growth Des. 2008, 8 (11), 4066-4074], have suggested that OH functional groups control polysaccharide attachment. The purpose of this work was to characterize, using X-ray reflectivity (XR) combined with molecular dynamics (MD) simulations, the structuring on calcite of a layer of the simplest carbon chain molecule that contains an OH group, ethanol (CH(3)-CH(2)-OH). We found evidence that EtOH forms a highly ordered structure at the calcite surface, where the first layer molecules bond with calcite. The ethanol molecules stand up perpendicularly at the interface or nearly so. As a consequence, the fatty, CH(3) ends form a new surface, about 6 Å from the termination of the bulk calcite, and beyond that, there is a thin gap where ethanol density is low. Following is a more disordered layer that is two to three ethanol molecules thick, about 14 Å, where density more resembles that of bulk liquid ethanol. The good agreement between theory and experiment gives confidence that a theoretical approach can offer information about behavior in more complex systems.

  15. EFFECT OF MAGNESIUM AS SUBSTITUTE MATERIAL IN ENZYME MEDIATED CALCITE PRECIPITATION (EMCP FOR SOIL IMPROVEMENT TECHNIQUE

    Directory of Open Access Journals (Sweden)

    Heriansyah ePutra

    2016-05-01

    Full Text Available The optimization of enzyme-mediated calcite precipitation (EMCP was evaluated as a soil improvement technique. In our previous works, purified urease was utilized to bio-catalyze the hydrolysis of urea, which causes the supplied Ca2+ to precipitate with CO32- as calcium carbonate. In the present work, magnesium chloride was newly added to the injecting solutions to delay the reaction rate and to enhance the amount of carbonate precipitation. Soil specimens were prepared in PVC cylinders and treated with concentration-controlled solutions composed of urea, urease, calcium, and magnesium chloride. The mechanical properties of the treated soil specimens were examined through unconfined compressive strength (UCS tests. A precipitation ratio of the carbonate up to 90% of the maximum theoretical precipitation was achieved by adding a small amount of magnesium chloride. Adding magnesium chloride as a delaying agent was indeed found to reduce the reaction rate of the precipitation, which may increase the volume of the treated soil if used in real fields because of the slower precipitation rate and the resulting higher injectivity. A mineralogical analysis revealed that magnesium chloride decreases the crystal size of the precipitated materials and that another carbonate of aragonite is newly formed. Mechanical test results indicated that carbonate precipitates within the soils and brings about a significant improvement in strength. A maximum UCS of 0.6 MPa was obtained from the treated samples.

  16. Avian embryonic development does not change the stable isotope composition of the calcite eggshell.

    Science.gov (United States)

    Maurer, G; Portugal, S J; Boomer, I; Cassey, P

    2011-01-01

    The avian embryo resorbs most of the calcium for bone formation from the calcite eggshell but the exact mechanisms of the resorption are unknown. The present study tested whether this process results in variable fractionation of the oxygen and carbon isotopes in shell calcium carbonate, which could provide a detailed insight into the temporal and spatial use of the eggshell by the developing embryo. Despite the uncertainty regarding changes in stable isotope composition of the eggshell across developmental stages or regions of the shell, eggshells are a popular resource for the analysis of historic and extant trophic relationships. To clarify how the stable isotope composition varies with embryonic development, the δ(13)C and δ(18)O content of the carbonate fraction in shells of black-headed gull (Larus ridibundus) eggs were sampled at four different stages of embryonic development and at five eggshell regions. No consistent relationship between the stable isotope composition of the eggshell and embryonic development, shell region or maculation was observed, although shell thickness decreased with development in all shell regions. By contrast, individual eggs differed significantly in isotope composition. These results establish that eggshells can be used to investigate a species' carbon and oxygen sources, regardless of the egg's developmental stage.

  17. Morphological Investigation of Calcium Carbonate during Ammonification-Carbonization Process of Low Concentration Calcium Solution

    Directory of Open Access Journals (Sweden)

    Huaigang Cheng

    2014-01-01

    Full Text Available Ultrafine calcium carbonate is a widely used cheap additive. The research is conducted in low degree supersaturation solution in order to study the polymorphic phases’ change and its factors of the calcium carbonate precipitate in the ammonification-carbonization process of the solution with calcium. Fine particles of calcium carbonate are made in the solution containing 0.015 mol/L of Ca2+. Over 98% of the calcium carbonate precipitate without ammonification resembles the morphology of calcite, while the introduction of ammonia can benefit the formation of vaterite. It was inferred that the main cause should be serious partial oversaturation or steric effects. Ammonia also helps to form the twin spherical calcium carbonate. However, particles formed in the process of ammonification-carbonization in solution with low concentration degree of calcium are not even with a scale of the particle diameter from 5 to 12 μm. Inorganic salts, alcohol, or organic acid salts have significant controlling effect on the particle diameter of calcium carbonate and can help to decrease the particle diameter to about 3 μm. Anionic surfactants can prevent the conglobation of calcium carbonate particles and shrink its diameter to 500 nm–1 μm.

  18. Supervisors' upward exchange relationships and subordinate outcomes: testing the multilevel mediation role of empowerment.

    Science.gov (United States)

    Zhou, Le; Wang, Mo; Chen, Gilad; Shi, Junqi

    2012-05-01

    This study empirically examined the proposition that supervisors' exchange relationships with their own supervisors (i.e., leader-leader exchange, or LLX) are related to their subordinates' work-related outcomes through 3 mechanisms: (a) leaders modeling their LLX to develop and maintain their exchange relationships with their subordinates (i.e., leader-member exchange, or LMX), (b) motivating the team and its members, captured by team and individual empowerment, and (c) facilitating the relationships between LMX and individual outcomes. Analyses of multisource and lagged data from 104 team supervisors and 577 subordinates showed that LMX mediated the positive relationship of LLX on subordinates' individual empowerment. Furthermore, team empowerment and individual empowerment sequentially mediated the positive relationships between LLX and subordinates' job satisfaction and job performance. The authors also found that the indirect relationships of LMX with job satisfaction and job performance via individual empowerment were stronger when LLX was higher. Theoretical and practical implications of these findings are discussed. (PsycINFO Database Record (c) 2012 APA, all rights reserved).

  19. Surface tension alteration on calcite, induced by ion substitution

    DEFF Research Database (Denmark)

    Sakuma, Hiroshi; Andersson, Martin Peter; Bechgaard, Klaus

    2014-01-01

    The interaction of water and organic molecules with mineral surfaces controls many processes in nature and industry. The thermodynamic property, surface tension, is usually determined from the contact angle between phases, but how does one understand the concept of surface tension at the nanoscale...... in the pore water. Incorporation of MgSO4 into calcite, which is energetically favored, decreases surface tension and releases polar oil compounds......., where particles are smaller than the smallest droplet? We investigated the energy required to exchange Mg2+ and SO4 2- from aqueous solution into calcite {10.4} surfaces using density functional theory. Mg2+ substitution for Ca2+ is favored but only when SO4 2- is also present and MgSO4 incorporates...

  20. Copper incorporation in foraminiferal calcite: results from culturing experiments

    Directory of Open Access Journals (Sweden)

    G. J. van der Zwaan

    2007-07-01

    Full Text Available A partition coefficient for copper (DCu in foraminiferal calcite has been determined by culturing individuals of two benthic species under controlled laboratory conditions. The partition coefficient of a trace element (TE is an emperically determined relation between the TE/Ca ratio in seawater and the TE/Ca ratio in foraminiferal calcite and has been established for many divalent cations. Despite its potential to act as a tracer of human-induced, heavy metal pollution, data is not yet available for copper. Since partition coefficients are usually a function of multiple factors (seawater temperature, pH, salinity, metabolic activity of the organism, etc., we chose to analyze calcite from specimens cultured under controlled laboratory conditions. They were subjected to different concentrations of Cu2+ (0.1–20 µmol/l and constant temperature (10 and 20°C, seawater salinity and pH. We monitored the growth of new calcite in specimens of the temperate, shallow-water foraminifer Ammonia tepida and in the tropical, symbiont-bearing Heterostegina depressa. Newly formed chambers were analyzed for Cu/Ca ratios by laser ablation-ICP-MS. The estimated partition coefficient (0.1–0.4 was constant to within experimental error over a large range of (Cu/Caseawater ratios and was remarkably similar for both species. Neither did the presence or absence of symbionts affect the DCu, nor did we find a significant effect of temperature or salinity on Cu-uptake.

  1. Effect of Mica and Hematite (001 Surfaces on the Precipitation of Calcite

    Directory of Open Access Journals (Sweden)

    Huifang Xu

    2018-01-01

    Full Text Available The substrate effect of mica and hematite on the nucleation and crystallization of calcite was investigated using scanning electron microscope (SEM, X-ray diffraction (XRD, and electron backscatter diffraction (EBSD methods. On mica, we found, in the absence of Mg2+, the substrates’ (001 surfaces with hexagonal and pseudo-hexagonal two-dimensional (2-D structure can affect the orientation of calcite nucleation with calcite (001 ~// mica (001 and calcite (010 ~// mica (010 to be the major interfacial relationship. On hematite, we did not observe frequent twinning relationship between adjacent calcite gains, but often saw preferentially nucleation of calcite at surface steps on hematite substrate. We suggest that calcite crystals initially nucleate from the Ca2+ layers adsorbed on the surfaces. The pseudo-hexagonal symmetry on mica (001 surface also leads to the observed calcite (001 twinning. A second and less common orientation between calcite {104} and mica (001 was detected but could be due to local structure damage of the mica surface. Results in the presence of Mg2+ show that the substrate surfaces can weaken Mg toxicity to calcite nucleation and lead to a higher level of Mg incorporation into calcite lattice.

  2. Saudi Arabian Woman's Marriage Life in Girls of Riyadh, a Novel by Rajaa Alsanea: Subordination and Struggle

    OpenAIRE

    THALIB, AMIRAH ANIS

    2013-01-01

    This article argues that implementation of Pre-Islamic tradition and culture emerges subordination toward woman in Saudi Arabia. They face subordination in many aspects of life. This phenomenon can be found in Girls of Riyadh novel. In this novel, Rajaa Alsanea, a Saudi Arabian woman writer tells how women live under male domination. In analyzing the phenomena, the writer used feminist approach by applying feminism theory which is combined with Islamic references to reveal subordination and s...

  3. Leadership predictors of innovation and task performance : Subordinates self-esteem and self-presentation as moderators

    OpenAIRE

    Rank, Johannes; Nelson, Nicole E.; Allen, Tammy D.; Xu, Xian

    2008-01-01

    This study examined self-related subordinate variables as moderators of relationships between supervisors leadership behaviours (transformational as well as activecorrective transactional leadership) and subordinates innovative behaviour and task performance. Based on behavioural plasticity and self-monitoring theory, we hypothesized that these associations would be moderated by subordinates organization-based self-esteem and by their propensity to modify self-presentation, a major facet o...

  4. Is bicarbonate stable in and on the calcite surface?

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Rodriguez Blanco, Juan Diego; Stipp, Susan Louise Svane

    2016-01-01

    We have used density functional theory with the COSMO-RS implicit solvent model to predict the pKa for the deprotonation of bicarbonate to carbonate, i.e. HCO3− CO32− + H+, when HCO3− is included in, and adsorbed on, a calcite surface. We have used cluster models (80–100 atoms) to represent...... the flat {10.4} surface, acute steps, obtuse steps, two types of kinks on the acute step and two types of kinks on the obtuse steps. Based on the predicted pKa values, which range from −6.0 to 2.4 depending on the surface site, we conclude that bicarbonate deprotonates to carbonate when it is in calcite...... even when pH in solution is very low. This is true for all surface sites, even for solutions where 2.4 bicarbonate is adsorbed on calcite, the predicted pKa for deprotonation is 7.5, which is ∼3 pH units lower than in aqueous solution...

  5. Rheological characterization of the influence of PVOH on calcite suspensions.

    Science.gov (United States)

    Eriksson, Rasmus; Kokko, Annaleena; Rosenholm, Jarl B

    2010-06-01

    Flow properties of the calcite/poly(vinyl alcohol) (PVOH) system were studied and related to the microstructure of the suspension. Adsorption of PVOH on calcite was confirmed, and it results in a shift of the slipping plane out from the surface. The charge density at the surface is assumed to remain unchanged. Since the PVOH used is only partially hydrolyzed, the most likely adsorption conformation consists of residual acetate groups adsorbed to the surface and vinylalcohol groups extending outward from the surface as loops and tails. The microstructure and flow properties of the calcite/PVOH system was found to go through several different stages as a function of PVOH concentration. At low PVOH concentrations a gradual weakening of the initially formed floc network is observed as a function of PVOH concentration. Further addition of PVOH eventually leads to breakdown of the flocs which results in a sterically stabilized suspension with a very low viscosity. This state persists for a narrow concentration range of PVOH, and increasing the PVOH concentration over a certain limit leads to a second gradual increase in viscosity. The system is believed not to undergo reflocculation at high PVOH concentrations as judged from the nonelastic nature of the suspensions. Instead, the polymers form a viscous matrix in the solution while the particles remain well-dispersed. At high enough PVOH concentration, the free volume available for the particles is greatly reduced, and the viscosity increases sharply.

  6. Amorphous calcium carbonate controls avian eggshell mineralization: A new paradigm for understanding rapid eggshell calcification.

    Science.gov (United States)

    Rodríguez-Navarro, Alejandro B; Marie, Pauline; Nys, Yves; Hincke, Maxwell T; Gautron, Joel

    2015-06-01

    Avian eggshell mineralization is the fastest biogenic calcification process known in nature. How this is achieved while producing a highly crystalline material composed of large calcite columnar single crystals remains largely unknown. Here we report that eggshell mineral originates from the accumulation of flat disk-shaped amorphous calcium carbonate (ACC) particles on specific organic sites on the eggshell membrane, which are rich in proteins and sulfated proteoglycans. These structures known as mammillary cores promote the nucleation and stabilization of a amorphous calcium carbonate with calcitic short range order which predetermine the calcite composition of the mature eggshell. The amorphous nature of the precursor phase was confirmed by the diffuse scattering of X-rays and electrons. The nascent calcitic short-range order of this transient mineral phase was revealed by infrared spectroscopy and HRTEM. The ACC mineral deposited around the mammillary core sites progressively transforms directly into calcite crystals without the occurrence of any intermediate phase. Ionic speciation data suggest that the uterine fluid is equilibrated with amorphous calcium carbonate, throughout the duration of eggshell mineralization process, supporting that this mineral phase is constantly forming at the shell mineralization front. On the other hand, the transient amorphous calcium carbonate mineral deposits, as well as the calcite crystals into which they are converted, form by the ordered aggregation of nanoparticles that support the rapid mineralization of the eggshell. The results of this study alter our current understanding of avian eggshell calcification and provide new insights into the genesis and formation of calcium carbonate biominerals in vertebrates. Copyright © 2015 Elsevier Inc. All rights reserved.

  7. Similarity and Dissimilarity between Superiors and Subordinates and Their Implications for Dyadic Relationship Quality

    Directory of Open Access Journals (Sweden)

    Nereida Salette Paulo da Silveira

    2009-01-01

    Full Text Available Although literature advocates the advantages of work force diversification, studies based on the Similarity- Attraction Paradigm indicate that people are more disposed to feel attraction to those who are similar to them. A field study with the comparative data of 89 dyads investigated the effect of the actual and perceived similarity in the quality of the relationship between superiors and subordinates within the Leader-Member Exchange [LMX] perspective. The investigated characteristics were: gender, age and work-family conflict. The data indicate the influence only of perceived similarity in the quality of the relationship between superiors and subordinates. This effect broadens when the subordinate feels satisfied with the quality and frequency of contact with his/her superior. The methodological procedures included factorial analysis and validation of two scales (EIFT and LMX-7, the correlations analysis and hierarchic regressions. Finally, the implications of some results and directions for future research in diversity are discussed.

  8. PVC mixtures’ mechanical properties with the addition of modified calcite as filler

    Directory of Open Access Journals (Sweden)

    Vučinić Dušica R.

    2012-01-01

    Full Text Available In this study mechanical properties of PVC mixtures (PVC, stabilizer, lubricant, filler such as tensile strength, tensile elongation, breaking strength, and breaking elongation were investigated. Unmodified calcite, as well as calcite modified by stearic acid, were used as fillers in wet and dry processes. The PVC mixtures containing the calcite modified by wet procedure have better mechanical properties compared to those with the calcite modified by the dry process. Tensile and breaking strength of the PVC mixture containing the calcite modified with 1.5% stearic acid using wet process, are higher for 2.8% and 5.2%, respectively, compared to the PVC mixture containing the calcite modified with the same amount of acid used in the dry process. The tensile strength difference between the mixtures increases with the increase of the concentration of used stearic acid up to 3%. The strength of PVC mixture with the calcite modified by wet process is 3.1% higher compared to the mixture containing calcite modified by dry process. The results showed that the bonding strength between calcite and the adsorbed organic component affected tensile strength, tensile elongation and breaking strength of the PVC mixtures. The best filler was obtained by wet modification using 1.5% stearic acid solution that provided the formation of a stearate monolayer chemisorbed on calcite. The PVC mixtures containing the calcite modified by wet process using 1.5% stearic acid solution exhibited the best mechanical properties. This calcite was completely hydrophobic with dominant chemically adsorbed surfactant, which means that stearate chemisorbed on calcite provided stronger interaction in the calcite-stearic acid-PVC system.

  9. Novel Determination of the Orientation of Calcite on Mineral Substrates

    Science.gov (United States)

    Zhao, L.; Ji, X.; Teng, H.

    2016-12-01

    In the threat of global warming, the transformation from CO2 to stable carbonate minerals is significant to geological CO2 sequestration in the long term.Previous efforts have found that when carbonate minerals nucleate on some mineral substrates ,the time of carbon capture can be shorted .Many efforts have been focused on the dynamics when carbonate minerals nucleate on mineral substrates, but few have studied the orientation of carbonate minerals on mineral substrates. In our experiment, we mainly focused on the orientation of calcite on mineral substrates.We mixed NaHCO3 and CaCl2 to nucleate when mineral substrates were added and a multi-parameter analyzer was used to monitor in real time to determine the induction time for nucleation. On the basis of classical nucleation theory, we got a brand new formula to decide the orientation of calcite on mineral substrates. lntind=(2-cosθ+cos3θ)*16πγ3vm2(12*(kBT)3*(lnS)2)+ln(1/N0v)+ ΔEa/(kBT)where θ is the angle between the substrate and the nuclei, tind is the induction time for nucleation, γ is he average surface free energy, N0 is the total number of particles per unit volume of solution, ΔEa is the activation energy for molecular motion across the embryo-matrix interface, S is the supersaturation index ,kB is the Boltzmann constant. Using the new formula above , when biotite was used as substrate mineral ,we found that the angle between the biotite and the nuclei was 119°. Angle measured on SEM images also supported our conclusion above. Combined with SEM and Debye ring analysed by Rigaku 2D data processing software, we only found one point of (006) in Debye ring, unlike (104)(many points in one ring and it meant that the orientation of (104) is random ). That meant (001) of calcite was first formed on biotite (001). In that case we inferred that 119° was formed by (001) of botite and (012) of calcite for the intersection angle of (001) and (012) was 120°. Future research will focus on the orientation of

  10. Ruin Time and Severity for a Lévy Subordinator Claim Process: A Simple Approach

    Directory of Open Access Journals (Sweden)

    Claude Lefèvre

    2013-12-01

    Full Text Available This paper is concerned with an insurance risk model whose claim process is described by a Lévy subordinator process. Lévy-type risk models have been the object of much research in recent years. Our purpose is to present, in the case of a subordinator, a simple and direct method for determining the finite time (and ultimate ruin probabilities, the distribution of the ruin severity, the reserves prior to ruin, and the Laplace transform of the ruin time. Interestingly, the usual net profit condition will be essentially relaxed. Most results generalize those known for the compound Poisson claim process.

  11. Subject of Subordinate Clause as Object with Verbs of Perception, Thought, and Communication in Old Russian

    Directory of Open Access Journals (Sweden)

    Anna A. Pichkhadze

    2012-08-01

    Full Text Available This paper describes the Old Russian construction involving verbs of perception, thought, and communication. In this construction, a single semantic argument corresponds to two syntactic constituents: a direct object and a finite subordinate clause, the subject of which is coreferential with the direct object of the main clause. The Old Russian construction is seen as an instantiation of a cross-linguistic option in the argument structure of these verbs (above all, of the perception verbs, that is, to take the subject of the subordinate clause as the direct object.

  12. Absorption mechanism study of benzoic acid on calcite. Influence on the wettability; Etude du mecanisme d`absorption de l`acide benzoique sur la calcite. Incidence sur la mouillabilite

    Energy Technology Data Exchange (ETDEWEB)

    Legens, Ch.

    1997-12-03

    A pure carbonate rock is strongly water-wet whereas oil accumulations study shows that most of carbonate reservoirs are oil-wet or of mixed-wettability. This is one of the main difficulties to extract crude oil. This change of behavior is due to the adsorption of some crude oil compounds on the mineral surface. We have mainly studied the interactions between acid molecules by adsorption on a calcite powder in an organic phase (benzoic acid and lauric acid) and in an aqueous phase (benzoic acid and lauric sodium salt). The technics which enabled us to define and characterize adsorption are thermogravimetry infrared diffuse reflection and thermal analysis with controlled kinetic linked to a mass spectrometer. Molecular modelling calculations have completed these analysis. It has been showed that when crude oil fills the biggest pores of the reservoir rock, the aqueous film is unstable and acids adsorb via ionic bonds on mineral calcium ions. Wettability is evaluated thanks to contact angle measurements of a water droplet deposited on a compacted powder pellet. Calcite wettability changes were all the greater as hydro-carbonated chains were longer, as it confers molecule hydrophobia. It has been also investigated acid molecules diffusion from the organic to the aqueous phase which saturates the smallest pores. Molecules which are able to diffuse from the first to the second medium do not adsorb on the surface. As a consequence, carbonate rock wettability changes require a direct contact between crude oil and mineral that involves aqueous film instability. (author) 128 refs.

  13. Zircon-quartz-calcite segregations in carbonate-alkaline metasomatic rocks of the western Baikal region and their petrogenetic implications

    Science.gov (United States)

    Savelyeva, V. B.; Bazarova, E. P.; Sharygin, V. V.; Karmanov, N. S.

    2015-12-01

    Fine-grained segregations up to 5 mm in size composed of graphic intergrowths of zircon, quartz, calcite and containing up to 0.8 wt % SrO have been found in albite-riebeckite and dolomite-biotite metasomatic rocks formed after alaskite granite. They contain magnetite, titanomagnetite (25.4 wt % TiO2), cerite-(Ce,Nd), rutile (up to 1.2 wt % Nb2O5), as well as rare micrograins of monazite-(Ce), bastnaesite-(Ce), and barite (up to 5.7 wt % SrO). The fine-grained structure of mineral aggregates suggests a metacolloidal nature. It is assumed that the zircon-quartz-calcite assemblage was formed due to exchange decomposition reaction between the salt phase of hydrothermal solution with predominant Na2CO3, elevated Zr and, to a lesser extent, Fe, Ti, LREE, Nb contents and dissolved calcium and silica compounds of a Na2SiO3 type.

  14. Supervisor-Subordinate Relationship, Differentiation, and Employee Creativity: A Self-Categorization Perspective

    Science.gov (United States)

    Zhao, Hongdan; Kessel, Maura; Kratzer, Jan

    2014-01-01

    This study seeks to explore the effect of the quality of supervisor-subordinate relationship (i.e., leader-member exchange; LMX) on employee creativity by examining a moderated-mediation model. The model focuses on the mediating role of perceived insider status and the moderating role of perceived LMX differentiation in influencing the mediation.…

  15. Impact of different-sized herbivores on recruiment opportunities for subordinate herbs in grasslands

    NARCIS (Netherlands)

    Bakker, E.S.; Olff, H.

    2003-01-01

    Potential effects of herbivores on plant species diversity depend on herbivore size, species and density. In this study we examine the effect of different-sized herbivores (cattle and rabbits) on recruitment of subordinate herbs in grasslands. We show that in a grazed floodplain, grassland plant

  16. Impact of different-sized herbivores on recruitment opportunities for subordinate herbs in grasslands

    NARCIS (Netherlands)

    Bakker, Elisabeth S.; Olff, Han

    2003-01-01

    Potential effects of herbivores on plant species diversity depend on herbivore size, species and density. In this study we examine the effect of different-sized herbivores (cattle and rabbits) on recruitment of subordinate herbs in grasslands. We show that in a grazed floodplain, grassland plant

  17. Analysis of Subordination Errors in Students' Writings: A Study of Selected Teacher Training Colleges in Ghana

    Science.gov (United States)

    Adjei, Amma Abrafi

    2015-01-01

    This study is aimed at examining how students of selected Teacher Training Colleges handle one important aspect of sentence structure, i.e. "subordination". Data were collected from written scripts, and tests responded to by 150 participants from three selected colleges. These were analyzed by identifying both correct and incorrect uses…

  18. Sex of leader, sex of subordinate and leader behaviour type as ...

    African Journals Online (AJOL)

    Sex of leader, sex of subordinate and leader behaviour type as predictors of task performance. Jackson I Osu. Abstract. No Abstract Available African Journal for the Psychological Study of Social Issues Vol.4(2) 1999: 245-258. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL ...

  19. Perceptions of Leadership Style: Superior and Subordinate Descriptions of Decision-Making Behavior

    Science.gov (United States)

    Jago, Arthur G.; Vroom, Victor H.

    1975-01-01

    This research concerns the level of agreement among subordinates reporting to the same leader in their descriptions of his behavior. (Available from the Comparative Administration Research Institute, Graduate School of Business Administration, Kent State University, Kent, OH 44242; $12.00 annually) (Author/MLF)

  20. The subordinate concept ‘marketing’ in the contemporary business English discourse

    Directory of Open Access Journals (Sweden)

    Liudmyla Naumenko

    2015-05-01

    Full Text Available The paper considers architectonics of the concept ‘marketing’ as a subordinate one to the concept ‘market’ which, alongside with other concepts, organizes the conceptual sphere of the basic concept ‘trade’. The notional, sense (sense centres, and schematic (dynamic frame components are researched, the model of the concept inner structure is developed

  1. On differential subordinations for a class of analytic functions defined by a linear operator

    Directory of Open Access Journals (Sweden)

    V. Ravichandran

    2004-01-01

    Full Text Available We obtain several results concerning the differential subordination between analytic functions and a linear operator defined for a certain family of analytic functions which are introduced here by means of these linear operators. Also, some special cases are considered.

  2. A Study of Relationship between Leader Behaviors and Subordinate Job Expectancies: A Path-Goal Approach

    Directory of Open Access Journals (Sweden)

    Sikandar Hayyat Malik

    2012-12-01

    Full Text Available This study investigates relationship between leader behavior (directive, supportive, participative and achievement-oriented of corporate managers and subordinates’ job expectancies using House (1974 Path-goal model of leadership. The results reveal thatleader behavior affects subordinates’ job expectancies. The situational factors (task structure, role ambiguity, stress, need for autonomy, locus of control, need for achievement and perception about abilities affect subordinates’ job expectancies (I&II.While subordinates’ attributes/characteristics (age, gender, qualification, rank, experience and length of service under the current supervisor do not affect job expectancies (I&II except for rank/position and expectancy-II. Path goal theory predicts that directive leader behavior will be more effective for the subordinates with high need for achievement because directive leader through clarifying path guides subordinates. Similarly, participative leader behavior is also effective as heconsults with subordinates in setting, clarifying and achieving goals. The results of this study reveal that there is an inverse relationship between subordinates’ job expectancy (I&II. According to Yukl (2006, for subordinates with high need for autonomy,participative leader behavior will increase the intrinsic valence of work.

  3. Some subordination and superordination results for the generalized hypergeometric functions associated with Ruscheweyh derivative

    Directory of Open Access Journals (Sweden)

    Abdul Rahman S. Juma

    2014-10-01

    Full Text Available Our purpose in this paper is to define a linear operator  F_{p,q,s}[\\alpha_{1},m], then applying it to obtain some results on subordination and superordination preserving properties of holomorphic multivalent functions in the  open unit disc. And sandwich-type result for these holomorphic multivalent functions is also considered.

  4. The (Biological or Cultural Essence of Essentialism: Implications for Policy Support among Dominant and Subordinated Groups

    Directory of Open Access Journals (Sweden)

    Nur Soylu Yalcinkaya

    2017-05-01

    Full Text Available Most research links (racial essentialism to negative intergroup outcomes. We propose that this conclusion reflects both a narrow conceptual focus on biological/genetic essence and a narrow research focus from the perspective of racially dominant groups. We distinguished between beliefs in biological and cultural essences, and we investigated the implications of this distinction for support of social justice policies (e.g., affirmative action among people with dominant (White and subordinated (e.g., Black, Latino racial identities in the United States. Whereas, endorsement of biological essentialism may have similarly negative implications for social justice policies across racial categories, we investigated the hypothesis that endorsement of cultural essentialism would have different implications across racial categories. In Studies 1a and 1b, we assessed the properties of a cultural essentialism measure we developed using two samples with different racial/ethnic compositions. In Study 2, we collected data from 170 participants using an online questionnaire to test the implications of essentialist beliefs for policy support. Consistent with previous research, we found that belief in biological essentialism was negatively related to policy support for participants from both dominant and subordinated categories. In contrast, the relationship between cultural essentialism and policy support varied across identity categories in the hypothesized way: negative for participants from the dominant category but positive for participants from subordinated categories. Results suggest that cultural essentialism may provide a way of identification that subordinated communities use to mobilize support for social justice.

  5. Supervisors' Responses to Subordinate Performance: Effect of Personal-Control Orientation and Situational Control.

    Science.gov (United States)

    Ashkanasy, Neal M.

    1991-01-01

    Presents a study extending a model of leadership response based on attribution theories to include measures of locus of control and situational control. Describes a procedure by which subjects responded to descriptions of subordinate performance. Concludes that supervisors with an external locus of control were less sensitive to subordinate…

  6. Task Structure as Moderator of College Principals' Leadership Behavior and Their Subordinates' Outcomes

    Science.gov (United States)

    Awan, Riffat-Un-Nisa; Zaidi, Nayyar Raza; Naz, Anjum; Noureen, Ghazala

    2011-01-01

    This research article intended to investigate the moderating effect of structured task on the relationship of leadership behavior of degree college principals and their subordinates' job satisfaction, job expectancies and acceptance of leader. Data was collected from 640 college faculty members and 170 principals of degree colleges situated in 34…

  7. Leader reliance on subordinates across nations that differ in development and climate

    NARCIS (Netherlands)

    Van de Vliert, E; Smith, P B

    How, where, and why do leaders follow the people they lead? An 84-nation analysis of survey responses from 19,525 managers shows that their reliance on subordinates depends on the level of wealth and development, and the harshness of cold or hot climates. In support of the thermal demands-resources

  8. Peering is not a formal indicator of subordination in bonobos (Pan paniscus)

    NARCIS (Netherlands)

    Stevens, J.M.G.; Vervaecke, H.; Vries, Han de; Elsacker, L. van

    2005-01-01

    It has been suggested that peering behavior in bonobos is a formal signal acknowledging social dominance status. We investigated whether peering meets the published criteria for a formal signal of subordination in five captive groups of bonobos. The degree of linearity in the set of peering

  9. Leaders' achievement goals and their integrative management of creative ideas voiced by subordinates or superiors

    NARCIS (Netherlands)

    Sijbom, Roy B. L.; Janssen, Onne; Van Yperen, Nico W.

    2016-01-01

    The purpose of this research was to examine the joint impact of leader achievement goals and hierarchical position of the voicer of creative ideas (subordinate vs. superior) on the extent to which leaders (intent to) integrate these voiced creative ideas with their own ideas (integrative idea

  10. Leaders’ achievement goals and their integrative management of creative ideas voiced by subordinates or superiors

    NARCIS (Netherlands)

    Sijbom, R.B.L.; Janssen, O.; van Yperen, N.W.

    2016-01-01

    The purpose of this research was to examine the joint impact of leader achievement goals and hierarchical position of the voicer of creative ideas (subordinate vs. superior) on the extent to which leaders (intent to) integrate these voiced creative ideas with their own ideas (integrative idea

  11. Leader motives, charismatic leadership and subordinates' work attitude in the profit and voluntary sector

    NARCIS (Netherlands)

    de Hoogh, A.H.B.; den Hartog, D.N.; Koopman, P.L.; Thierry, Hk.; van den Berg, P.T.; van der Weide, J.G.; Wilderom, C.P.M.

    2005-01-01

    This multimethod study examined leaders' motives, charismatic leader behavior, and subordinates' work attitude for CEOs (N=73) of small and medium-sized organizations in two sectors, namely, the profit and voluntary sector. Interviews with CEOs were coded for motive imagery. Direct reports rated CEO

  12. Production supervisor impacts on subordinates' safety outcomes: an investigation of leader-member exchange and safety communication

    Science.gov (United States)

    Judd H. Michael; Zhen George Guo; Janice K. Wiedenbeck; Charles D. Ray

    2006-01-01

    Problem: Supervisors are increasingly important to the functioning of manufacturing operations, in large part due to their role as leaders. While supervisors' relations and communication with their subordinates are known to be important in influencing subordinates' behavior, little is known about how these two factors will impact...

  13. The sensitized luminescence of manganese-activated calcite

    Science.gov (United States)

    Schulman, J.H.; Evans, L.W.; Ginther, R.J.; Murata, K.J.

    1947-01-01

    Synthetic manganese-activated calcites are shown to be practically inert to ultraviolet excitation in the range 2000-3500A, while they are luminescent under cathode-ray excitation. The incorporation of small amounts of an auxiliary impurity along with the manganese produces the strong response to ultraviolet radiation hitherto ascribed to CaCO3:Mn itself. Three such impurities have been studied: lead, thallium, and cerium. The first two induce excitation in the neighborhood of the mercury resonance line, while the cerium introduces a response principally to longer wave ultraviolet. The strong response to 2537A excitation shown by some natural calcites is likewise found to be due to the presence of lead along with the manganese, rather than to the manganese alone. The data do not warrant ascribing the longer wave-length ultraviolet-excited luminescence of all natural calcites to the action of an auxiliary impurity. The essential identity of the cathode-ray excited luminescence spectra of CaCO 3:Mn, CaCO3: (Pb+Mn), CaCO3:(Tl+Mn), and CaCO3:(Ce+Mn) with the 2537A-excited spectra of the latter three is evidence that the luminescent center in all cases is the manganese ion or the MnO6 group. It is shown that a "cascade" mechanism for the action of the auxiliary impurities, lead, thallium, and cerium, is incorrect; and that the phenomenon must be considered as a case of sensitized luminescence. Owing to the nature of cathode-ray excitation, the manganese activator can be excited by this agent even in the absence of a second impurity. For optical excitation, however, an absorption band for the ultraviolet must be established by building into the CaCO3:Mn a second impurity or "sensitizer.".

  14. Calcite production by coccolithophores in the south east Pacific Ocean

    Directory of Open Access Journals (Sweden)

    L. Beaufort

    2008-08-01

    Full Text Available BIOSOPE cruise covered an oceanographic transect through the centre of the South Pacific Gyre (SPG from the Marquesas archipelago to the Peru-Chile upwelling (PCU. Water samples from 6 depths in the euphotic zone were collected at 20 stations. The concentrations of suspended calcite particles, coccolithophores cells and detached coccoliths were estimated together with size and weight using an automatic polarizing microscope, a digital camera, and a collection of softwares performing morphometry and pattern recognition. Some of these softwares are new and described here for the first time. The coccolithophores standing stocks were usually low and reached maxima west of the PCU. The coccoliths of Emiliania huxleyi, Gephyrocapsa spp. and Crenalithus spp. (Order Isochrysidales represented more than 30% of all the suspended calcite particles detected in the size range 0.1–46 μm (22% of PIC in term of calcite weight. These species grew preferentially in the Chlorophyll maximum zone. In the SPG their maximum cell concentrations were recorded between depth of 150 and 200 m, which is unusually deep for these taxa. The weight of coccoliths and coccospheres were correlated to their size. Large and heavy coccoliths and coccospheres were found in regions with relatively high fertility in the Marquises Island and in the PCU. Small and light coccoliths and coccospheres were found west of the PCU. This distribution is strongly related to ocean chemistry in particular to alkalinity and to carbonate ions concentration. The biotic (coccolithophores production influence on calcification is mainly driven at the local scale (depth whereas the abiotic (carbonate chemistry plays its most important role at the regional (horizontal level. Here 94% of the variability of coccolith and coccosphere weight can be explained by a change in 7 environmental variables.

  15. Adsorption of polar aromatic hydrocarbons on synthetic calcite

    DEFF Research Database (Denmark)

    Madsen, Lene; Grahl-Madsen, Laila; Grøn, Christian

    1996-01-01

    The wettability of hydrocarbon reservoirs depends on how and to what extent the organic compounds are adsorbed onto the surfaces of calcite, quartz and clay. A model system of synthetic call cite, cyclohexane and the three probe molecules: benzoic acid, benzyl alcohol and benzylamine, have been...... studied by adsorption experiments. The results clearly demonstrate the differences in the adsorption behaviour between probes with different functional groups of varying polarity and acidity. The maximum adsorption decreases in the order: benzoic acid, benzyl alcohol and benzylamine. The order...

  16. Incorporation of Eu(III) into calcite under recrystallization conditions

    Energy Technology Data Exchange (ETDEWEB)

    Hellebrandt, S.E. [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Inst. of Resource Ecology; Jordan, Norbert [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Surface Processes; Barkleit, Astrid [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Chemistry of the F-Elements; Schmidt, Moritz [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). HGF Young Investigator Group; Hofmann, S.

    2017-06-01

    The interaction of three calcite powders with Eu(III) under recrystallization conditions was studied on the molecular level using site-selective time-resolved laser fluorescence spectroscopy (TRLFS). Batch contact studies with reaction times from 1 week up to 3 years revealed that the speciation differs from that observed previously in co-precipitation experiments and is dominated by a newly identified species ''γ''. The speed of formation of this species was found to depend greatly on the recrystallization rate of the studied minerals.

  17. Gallium isotope fractionation during Ga adsorption on calcite and goethite

    Science.gov (United States)

    Yuan, Wei; Saldi, Giuseppe D.; Chen, JiuBin; Vetuschi Zuccolini, Marino; Birck, Jean-Louis; Liu, Yujie; Schott, Jacques

    2018-02-01

    Gallium (Ga) isotopic fractionation during its adsorption on calcite and goethite was investigated at 20 °C as a function of the solution pH, Ga aqueous concentration and speciation, and the solid to solution ratio. In all experiments Ga was found to be enriched in light isotopes at the solid surface with isotope fractionation △71Gasolid-solution up to -1.27‰ and -0.89‰ for calcite and goethite, respectively. Comparison of Ga isotopic data of this study with predictions for 'closed system' equilibrium and 'Rayleigh fractionation' models indicates that the experimental data are consistent with a 'closed system' equilibrium exchange between the fluid and the solid. The results of this study can be interpreted based on Ga aqueous speciation and the structure of Ga complexes formed at the solid surfaces. For calcite, Ga isotope fractionation is mainly triggered by increased Ga coordination and Ga-O bond length, which vary respectively from 4 and 1.84 Å in Ga(OH)4- to 6 and 1.94 Å in the >Ca-O-GaOH(OH2)4+ surface complex. For goethite, despite the formation of Ga hexa-coordinated >FeOGa(OH)20 surface complexes (Ga-O distances of 1.96-1.98 Å) both at acid and alkaline pH, a similar extent of isotope fractionation was found at acid and alkaline pH, suggesting that Ga(OH)4- is preferentially adsorbed on goethite for all investigated pH conditions. In addition, the observed decrease of Ga isotope fractionation magnitude observed with increasing Ga surface coverage for both calcite and goethite is likely related to the formation of Ga surface polymers and/or hydroxides with reduced Ga-O distances. This first study of Ga isotope fractionation during solid-fluid interactions suggests that the adsorption of Ga by oxides, carbonates or clay minerals could yield significant Ga isotope fractionation between secondary minerals and surficial fluids including seawater. Ga isotopes thus should help to better characterize the surficial biogeochemical cycles of gallium and its

  18. Characterization of Calcium Compounds in Opuntia ficus indica as a Source of Calcium for Human Diet

    Directory of Open Access Journals (Sweden)

    Isela Rojas-Molina

    2015-01-01

    Full Text Available Analyses of calcium compounds in cladodes, soluble dietary fiber (SDF, and insoluble dietary fiber (IDF of Opuntia ficus indica are reported. The characterization of calcium compounds was performed by using Scanning Electron Microscopy, Energy Dispersive Spectrometry, X-ray diffraction, and infrared spectroscopy. Atomic Absorption Spectroscopy and titrimetric methods were used for quantification of total calcium and calcium compounds. Whewellite (CaC2O4·H2O, weddellite (CaC2O4·(H2O2.375, and calcite (CaCO3 were identified in all samples. Significant differences (P≤0.05 in the total calcium contents were detected between samples. CaC2O4·H2O content in cladodes and IDF was significantly higher (P≤0.05 in comparison to that observed in SDF, whereas minimum concentration of CaCO3 was detected in IDF with regard to CaCO3 contents observed in cladodes and SDF. Additionally, molar ratio oxalate : Ca2+ in all samples changed in a range from 0.03 to 0.23. These results support that calcium bioavailability in O. ficus indica modifies according to calcium compounds distribution.

  19. Calcium carbonate phase transformations during the carbonation reaction of calcium heavy alkylbenzene sulfonate overbased nanodetergents preparation.

    Science.gov (United States)

    Chen, Zhaocong; Xiao, Shan; Chen, Feng; Chen, Dongzhong; Fang, Jianglin; Zhao, Min

    2011-07-01

    The preparation and application of overbased nanodetergents with excess alkaline calcium carbonate is a good example of nanotechnology in practice. The phase transformation of calcium carbonate is of extensive concern since CaCO(3) serves both as an important industrial filling material and as the most abundant biomineral in nature. Industrially valuable overbased nanodetergents have been prepared based on calcium salts of heavy alkylbenzene sulfonate by a one-step process under ambient pressure, the carbonation reaction has been monitored by the instantaneous temperature changes and total base number (TBN). A number of analytical techniques such as TGA, DLS, SLS, TEM, FTIR, and XRD have been utilized to explore the carbonation reaction process and phase transformation mechanism of calcium carbonate. An enhanced understanding on the phase transformation of calcium carbonate involved in calcium sulfonate nanodetergents has been achieved and it has been unambiguously demonstrated that amorphous calcium carbonate (ACC) transforms into the vaterite polymorph rather than calcite, which would be of crucial importance for the preparation and quality control of lubricant additives and greases. Our results also show that a certain amount of residual Ca(OH)(2) prevents the phase transformation from ACC to crystalline polymorphs. Moreover, a vaterite nanodetergent has been prepared for the first time with low viscosity, high base number, and uniform particle size, nevertheless a notable improvement on its thermal stability is required for potential applications. Copyright © 2011 Elsevier Inc. All rights reserved.

  20. Factors regulating the Great Calcite Belt in the Southern Ocean and its biogeochemical significance

    Science.gov (United States)

    Balch, William M.; Bates, Nicholas R.; Lam, Phoebe J.; Twining, Benjamin S.; Rosengard, Sarah Z.; Bowler, Bruce C.; Drapeau, Dave T.; Garley, Rebecca; Lubelczyk, Laura C.; Mitchell, Catherine; Rauschenberg, Sara

    2016-08-01

    The Great Calcite Belt (GCB) is a region of elevated surface reflectance in the Southern Ocean (SO) covering 16% of the global ocean and is thought to result from elevated, seasonal concentrations of coccolithophores. Here we describe field observations and experiments from two cruises that crossed the GCB in the Atlantic and Indian sectors of the SO. We confirm the presence of coccolithophores, their coccoliths, and associated optical scattering, located primarily in the region of the subtropical, Agulhas, and Subantarctic frontal regions. Coccolithophore-rich regions were typically associated with high-velocity frontal regions with higher seawater partial pressures of CO2 (pCO2) than the atmosphere, sufficient to reverse the direction of gas exchange to a CO2 source. There was no calcium carbonate (CaCO3) enhancement of particulate organic carbon (POC) export, but there were increased POC transfer efficiencies in high-flux particulate inorganic carbon regions. Contemporaneous observations are synthesized with results of trace-metal incubation experiments, 234Th-based flux estimates, and remotely sensed observations to generate a mandala that summarizes our understanding about the factors that regulate the location of the GCB.

  1. Influence of substrate mineralogy on bacterial mineralization of calcium carbonate: implications for stone conservation.

    Science.gov (United States)

    Rodriguez-Navarro, Carlos; Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnación; González-Muñoz, María Teresa

    2012-06-01

    The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed.

  2. Adaptive changes in zebrafish brain in dominant-subordinate behavioral context.

    Science.gov (United States)

    Pavlidis, Michail; Sundvik, Maria; Chen, Yu-Chia; Panula, Pertti

    2011-12-01

    Male zebrafish were held in dyadic social stress situation for a period of 5 days, to characterize stress coping styles and to investigate the role of the underlying neuroendocrine mechanisms in establishing dominant-subordinate relationships. A strong consistent dominant-subordinate relationship was formed in ten out of the sixteen pairs of fish (62.5%). Both dominant (DOM) and subordinate (SUB) individuals showed statistically significant higher trunk cortisol concentration than controls. Expression of genes encoding proteins involved in the functioning of the hypothalamus-hypophysis-interrenal axis (corticotropin releasing factor, CRF; glucocorticoid receptor, GR; mineralocorticoid receptor, MR); arginine vasotocin, AVT), in the biosynthesis and catabolism of catecholamines (tyrosine hydroxylase, TH1 and TH2; DOPA decarboxylase, DDC), dopamine β-hydroxylase, DBH; catechol-O-methyl transferase, COMT), in the biosynthesis of histamine (histidine decarboxylase, HDC) and in the general stress response (galanin, GAL; hypocretin/orexin, Hcrt) was examined. The MR/GR ratio was higher in dominant and subordinate fish than in controls (P=0.016). The mRNA levels of TH2 and HDC were up-regulated in DOM, of AVT in SUB, while COMT mRNA levels were down-regulated in both DOM and SUB compared to control fish. In addition, mRNA levels of hypocretin/orexin (Hcrt) were up-regulated in dominant compared to subordinate and control males. There was a statistically significant correlation between mRNA expression levels of TH2, HDC, Hcrt, GR, MR and CRF genes. The obtained results provide new evidences for the use of zebrafish as an animal model to study social stress and allostasis in vertebrates. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. Calcium Electroporation

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gibot, Laure; Madi, Moinecha

    2015-01-01

    BACKGROUND: Calcium electroporation describes the use of high voltage electric pulses to introduce supraphysiological calcium concentrations into cells. This promising method is currently in clinical trial as an anti-cancer treatment. One very important issue is the relation between tumor cell kill...... efficacy-and normal cell sensitivity. METHODS: Using a 3D spheroid cell culture model we have tested the effect of calcium electroporation and electrochemotherapy using bleomycin on three different human cancer cell lines: a colorectal adenocarcinoma (HT29), a bladder transitional cell carcinoma (SW780......), and a breast adenocarcinoma (MDA-MB231), as well as on primary normal human dermal fibroblasts (HDF-n). RESULTS: The results showed a clear reduction in spheroid size in all three cancer cell spheroids three days after treatment with respectively calcium electroporation (p

  4. Sorption of phosphate onto calcite; results from batch experiments and surface complexation modeling

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus

    2011-01-01

    . Generally the model captures the variation in phosphate adsorption onto calcite as a function of solution composition, though it was necessary to include two types of sorption sites (strong and weak) in the model to reproduce the convex shape of the sorption isotherms.......The adsorption of phosphate onto calcite was studied in a series of batch experiments. To avoid the precipitation of phosphate-containing minerals the experiments were conducted using a short reaction time (3h) and low concentrations of phosphate (⩽50μM). Sorption of phosphate on calcite...... was studied in 11 different calcite-equilibrated solutions that varied in pH, PCO2, ionic strength and activity of Ca2+, CO32- and HCO3-. Our results show strong sorption of phosphate onto calcite. The kinetics of phosphate sorption onto calcite are fast; adsorption is complete within 2–3h while desorption...

  5. Review: geological and experimental evidence for secular variation in seawater Mg/Ca (calcite-aragonite seas and its effects on marine biological calcification

    Directory of Open Access Journals (Sweden)

    J. B. Ries

    2010-09-01

    production increased along with calcification within the bryopsidalean and coccolithophorid algae in mineralogically favorable seawater is consistent with the hypothesis that calcification promotes photosynthesis within some species of these algae through the liberation of CO2.

    The experiments also revealed that aragonite-secreting bryopsidalean algae and scleractinian corals, and bacterial biofilms that secrete a mixture of aragonite and high Mg calcite, began secreting an increased proportion of their calcium carbonate as the calcite polymorph in the lower-Mg/Ca experimental seawaters. Furthermore, the Mg/Ca ratio of calcite secreted by the coccolithophores, coralline red algae, reef-dwelling animals (crustacea, urchins, calcareous tube worms, bacterial biofilms, scleractinian corals, and bryopsidalean algae declined with reductions in seawater Mg/Ca. Notably, Mg fractionation in autotrophic organisms was more strongly influenced by changes in seawater Mg/Ca than in heterotrophic organisms, a probable consequence of autotrophic organisms inducing a less controlled mode of calcification simply through the removal of CO2 via photosynthesis.

    These results indicate that biomineralogical control can be partially overridden by ambient seawater Mg/Ca and suggest that modern aragonite-secreting organisms may have secreted a mixture of aragonite and low Mg calcite, and that modern high Mg calcite-secreting organisms probably secreted low Mg calcite, in calcite seas of the past. These effects of seawater Mg/Ca on the polymorph mineralogy and calcite Mg/Ca ratio of calcareous skeletons should be accounted for in thermal-chemical reconstructions of seawater that are based upon skeletal Mg/Ca.

    Lastly, by identifying how marine calcifiers respond to changes in seawater Mg/Ca and absolute Ca2+ concentration, this work should enhance our interpretation of parallel studies investigating the effects of anthropogenic CO2

  6. Strong kinetic effects on Sr/Ca ratios in the calcitic bivalve

    OpenAIRE

    Lorrain, Anne; Gillikin, David Paul; Paulet, Yves-Marie; Chauvaud, L.; Le Mercier, Alain; Navez, Jacques; André, Luc

    2005-01-01

    International audience; Although Sr/Ca ratios in abiogenic calcite are strongly controlled by precipitation rates, such a kinetic effect has never been demonstrated in calcitic bivalve shells. Therefore, we report Sr/Ca ratios together with daily growth rates in the calcitic shells of 4 individuals of the bivalve Pecten maximus (age class I). Ratios of Sr/Ca were found to be variable among individuals that grew at the same location, illustrating that vital effects dominate over environmental ...

  7. Prediction of calcite Cement Distribution in Shallow Marine Sandstone Reservoirs using Seismic Data

    Energy Technology Data Exchange (ETDEWEB)

    Bakke, N.E.

    1996-12-31

    This doctoral thesis investigates how calcite cemented layers can be detected by reflection seismic data and how seismic data combined with other methods can be used to predict lateral variation in calcite cementation in shallow marine sandstone reservoirs. Focus is on the geophysical aspects. Sequence stratigraphy and stochastic modelling aspects are only covered superficially. Possible sources of calcite in shallow marine sandstone are grouped into internal and external sources depending on their location relative to the presently cemented rock. Well data and seismic data from the Troll Field in the Norwegian North Sea have been analysed. Tuning amplitudes from stacks of thin calcite cemented layers are analysed. Tuning effects are constructive or destructive interference of pulses resulting from two or more closely spaced reflectors. The zero-offset tuning amplitude is shown to depend on calcite content in the stack and vertical stack size. The relationship is found by regression analysis based on extensive seismic modelling. The results are used to predict calcite distribution in a synthetic and a real data example. It is found that describing calcite cemented beds in shallow marine sandstone reservoirs is not a deterministic problem. Hence seismic inversion and sequence stratigraphy interpretation of well data have been combined in a probabilistic approach to produce models of calcite cemented barriers constrained by a maximum amount of information. It is concluded that seismic data can provide valuable information on distribution of calcite cemented beds in reservoirs where the background sandstones are relatively homogeneous. 63 refs., 78 figs., 10 tabs.

  8. Isotopic analysis for degradation diagnosis of calcite matrix in mortar.

    Science.gov (United States)

    Dotsika, E; Psomiadis, D; Poutoukis, D; Raco, B; Gamaletsos, P

    2009-12-01

    Mortar that was used in building as well as in conservation and restoration works of wall paintings have been analysed isotopically (delta(13)C and delta(18)O) in order to evaluate the setting environments and secondary processes, to distinguish the structural components used and to determine the exact causes that incurred the degradation phenomena. The material undergoes weathering and decay on a large proportion of its surface and in depth, due to the infiltration of water through the structural blocks. Mineralogical analysis indicated signs of sulphation and dissolution/recrystallisation processes taking place on the material, whereas stable isotopes provided information relative to the origin of the CO(2) and water during calcite formation and degradation processes. Isotopic change of the initial delta(13)C and delta(18)O in carbonate matrix was caused by alteration of the primary source of CO(2) and H(2)O in mortar over time, particularly by recrystallisation of calcite with porewater, evaporated or re-condensed water, and CO(2) from various sources of atmospheric and biogenic origin. Human influence (surface treatment) and biological growth (e.g. fungus) are major exogenic processes which may alter delta(18)O and delta(13)C in lime mortar.

  9. Alternative origins for nannobacteria-like objects in calcite

    Science.gov (United States)

    Kirkland, Brenda L.; Lynch, F. Leo; Rahnis, Michael A.; Folk, Robert L.; Molineux, Ian J.; McLean, Robert J. C.

    1999-04-01

    More than 40 calcite-precipitation experiments were performed under sterile conditions in order to investigate the origins of 25 300 nm spherical-, rod-, and ovoid-shaped objects that have been widely interpreted as evidence of nanometer-scale life (i.e., nannobacteria). Individual experiments included the addition of soluble organic compounds, common species of eubacteria, or phage-induced eubacterial lysates. These experiments indicate that many of the nanometer-scale objects have inorganic or nonnannobacterial origins. In the precipitation experiments, calcite formed euhedral crystals 50 800 nm in diameter and smaller (Bacterial fragments occur as rounded to irregularly shaped particles that included cell-wall fragments, expulsed cytoplasm, and relict capsules that also closely resembled nannobacteria. Acid etching of the large euhedral crystals produced in the precipitation experiments also resulted in the formation of nanometer-scale features that resembled nannobacteria in natural carbonates. The shapes of the etching artifacts vary as a function of the strength of the acid and the duration of etching. Much caution is advisable in interpreting the origin of rounded features <50 nm.

  10. Direct observation of microbial inhibition of calcite dissolution.

    Science.gov (United States)

    Lüttge, Andreas; Conrad, Pamela G

    2004-03-01

    Vertical scanning interferometry (VSI) provides a method for quantification of surface topography at the angstrom to nanometer level. Time-dependent VSI measurements can be used to study the surface-normal retreat across crystal and other solid surfaces during dissolution or corrosion processes. Therefore, VSI can be used to directly and nondestructively measure mineral dissolution rates with high precision. We have used this method to compare the abiotic dissolution behavior of a representative calcite (CaCO(3)) cleavage face with that observed upon addition of an environmental microbe, Shewanella oneidensis MR-1, to the crystal surface. From our direct observations, we have concluded that the presence of the microbes results in a significant inhibition of the rate of calcite dissolution. This inhibition appears to be a 2nd-order effect that is related to the formation of etch pits. The opening of etch pits was greatly inhibited in the presence of added bacteria, suggesting that the bacterial cells exert their effect by inhibiting the formation of etch pits at high-energy sites at the crystal surface caused by lattice defects, e.g., screw or point dislocations. The experimental methodology thus provides a nondestructive, directly quantifiable, and easily visualized view of the interactions of microbes and minerals during weathering (or corrosion) processes or during mineral precipitation.

  11. Angle-dependent rotation of calcite in elliptically polarized light

    Science.gov (United States)

    Herne, Catherine M.; Cartwright, Natalie A.; Cattani, Matthew T.; Tracy, Lucas A.

    2017-08-01

    Calcite crystals trapped in an elliptically polarized laser field exhibit intriguing rotational motion. In this paper, we show measurements of the angle-dependent motion, and discuss how the motion of birefringent calcite can be used to develop a reliable and efficient process for determining the polarization ellipticity and orientation of a laser mode. The crystals experience torque in two ways: from the transfer of spin angular momentum (SAM) from the circular polarization component of the light, and from a torque due to the linear polarization component of the light that acts to align the optic axis of the crystal with the polarization axis of the light. These torques alternatingly compete with and amplify each other, creating an oscillating rotational crystal velocity. We model the behavior as a rigid body in an angle-dependent torque. We experimentally demonstrate the dependence of the rotational velocity on the angular orientation of the crystal by placing the crystals in a sample solution in our trapping region, and observing their behavior under different polarization modes. Measurements are made by acquiring information simultaneously from a quadrant photodiode collecting the driving light after it passes through the sample region, and by imaging the crystal motion onto a camera. We finish by illustrating how to use this model to predict the ellipticity of a laser mode from rotational motion of birefringent crystals.

  12. Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications

    DEFF Research Database (Denmark)

    Douglas, Timothy E L; Łapa, Agata; Samal, Sangram Keshari

    2017-01-01

    Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration. Calcium carbonate (CaCO3 ) has been successfully applied as a bone regeneration material, but hydrogel-CaCO3 composites have received less attention. Magnesium (Mg) has...... enzymatically with CaCO3 , Mg-enriched CaCO3 and magnesium carbonate to generate composite biomaterials for bone regeneration. Hydrogels loaded with the enzyme urease were mineralized by incubation in mineralization media containing urea and different ratios of calcium and magnesium ions. Increasing...... the magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite was formed. Hydromagnesite (Mg5 (CO3 )4 (OH)2 .4H2 O) formed at high magnesium concentration in the absence of calcium. The amount of mineral formed...

  13. The influence of leadership style on subordinates' attachment to the leader.

    Science.gov (United States)

    Molero, Fernando; Moriano, Juan A; Shaver, Phillip R

    2013-01-01

    The aim of this research is to explore the extent to which employees establish attachment bonds with their leaders and the effects these bonds have on organizational outcomes. A sample of 225 participants reported on their supervisor's leadership style (transformational, transactional, or passive-avoidant), their attachment bonds to this supervisor (anxious or avoidant), and four organizational variables (subordinate's satisfaction, identification with the organization, extra effort, and perceived leadership effectiveness). Results, analyzed using a Partial Least Squares (PLS) approach, indicated that (a) transformational leadership was negatively associated with employees' insecure (anxious or avoidant) attachment to their leader; (b) passive/avoidant leadership was positively associated with subordinates' insecure attachment to their leader; (c) transactional leadership was positively associated with employee's anxious attachment but not with their avoidant attachment; (d) avoidant, but not anxious, attachment to the leader was negatively associated with employee satisfaction, perceived leader effectiveness, employee's extra effort, and organizational identification.

  14. Principal-subordinate hierarchical multi-objective programming model of initial water rights allocation

    Directory of Open Access Journals (Sweden)

    Dan WU

    2009-06-01

    Full Text Available The principal-subordinate hierarchical multi-objective programming model of initial water rights allocation was developed based on the principle of coordinated and sustainable development of different regions and water sectors within a basin. With the precondition of strictly controlling maximum emissions rights, initial water rights were allocated between the first and the second levels of the hierarchy in order to promote fair and coordinated development across different regions of the basin and coordinated and efficient water use across different water sectors, realize the maximum comprehensive benefits to the basin, promote the unity of quantity and quality of initial water rights allocation, and eliminate water conflict across different regions and water sectors. According to interactive decision-making theory, a principal-subordinate hierarchical interactive iterative algorithm based on the satisfaction degree was developed and used to solve the initial water rights allocation model. A case study verified the validity of the model.

  15. Context-Specific Dimensions of Trust in Manager, Subordinate and Co-Worker in Organizations

    Directory of Open Access Journals (Sweden)

    Ferda Erdem

    2014-10-01

    Full Text Available The purpose of this study is to determine the dimensions of trust relationship among managers, subordinates and the co-workers in organizations. Using an original trust questionnaire data has been collected from 550 middle-level managers from organizations operating in different regions of Turkey. Results from both qualitative and quantitative research methods indicate that the dimensions of trust vary in organizational relationships between managers and subordinates and between co-workers and furthermore, that a culture-specific meaning is attributed to its content. This study contributes to trust literature developing three original sub-scales and also it indicates that the meaning of trust in organizational relationships is influenced by cultural context.

  16. Psychosocial predictors of supervisor-, peer-, subordinate-, and service-provider-targeted aggression.

    Science.gov (United States)

    Inness, Michelle; Leblanc, Manon Mireille; Barling, Julian

    2008-11-01

    The authors investigate whether known person predictors (trait anger, trait aggression) and situational predictors (perceived interpersonal mistreatment, perceived organizational sanctions against aggression) of supervisor-targeted aggression also predict employee's aggression toward other workplace targets, namely peers, subordinates, and customers' aggression toward service providers. The authors also investigate the moderating impact of situational factors on the relationship between person factors and aggression. Participants (N = 308) were asked whether they had a conflict with their supervisor, a subordinate, a work peer, and/or a service provider in the past 6 months. Different patterns of main and interaction effects emerged across the 4 targets, suggesting the importance of accounting for the target of aggression in workplace aggression research.

  17. Study on monitoring achievement of performance indicators in the subordinate local companies in Romania

    Directory of Open Access Journals (Sweden)

    Gheorghe Neamţiu

    2011-12-01

    Full Text Available This paper deals with the pursuit of economic indicators which are calculated in local subordinate companies. These indicators are imposed by the Board employee manager contract term. Accounting provides enough information to calculate them but we put the issue of prevention of the ability to stay within budget, projected revenues and expenses, before closing operations of an accounting period (month, quarter, semester, year.

  18. Manager-subordinate exchange relationships : investigation of a manager behavior model

    OpenAIRE

    Carter, Marta L.

    1993-01-01

    This field study investigated the relationship among behavioral and perceptual measures of the Leader-Member Exchange (LMX) relationship and organizational outcome variables. The major purposes of this study were to determine: (1) the extent to which the dyad is the appropriate level of analysis for the examination of manager-subordinate relationships, (2) which objectively observed managerr behaviors are important in defining negotiating latitude, the most commonly us...

  19. Calling Where It Counts: Subordinate Pied Babblers Target the Audience of Their Vocal Advertisements.

    Science.gov (United States)

    Humphries, David J; Finch, Fiona M; Bell, Matthew B V; Ridley, Amanda R

    2015-01-01

    For territorial group-living species, opportunities to reproduce on the natal territory can be limited by a number of factors including the availability of resources within a territory, access to unrelated individuals, and monopolies on reproduction by dominant group members. Individuals looking to reproduce are therefore faced with the options of either waiting for a breeding opportunity to arise in the natal territory, or searching for reproductive opportunities in non-natal groups. In the cooperatively breeding Southern pied babbler, Turdoides bicolor, most individuals who achieve reproductive success do so through taking up dominant breeding positions within non-natal groups. For subordinate pied babblers therefore, searching for breeding opportunities in non-natal groups is of primary importance as this represents the major route to reproductive success. However, prospecting (where individuals leave the group to search for reproductive opportunities within other groups) is costly and individuals rapidly lose weight when not part of a group. Here we demonstrate that subordinate pied babblers adopt an alternative strategy for mate attraction by vocal advertisement from within their natal territories. We show that subordinates focus their calling efforts on the edges of their territory, and specifically near boundaries with neighbouring groups that have potential breeding partners (unrelated individuals of the opposite sex). In contrast to prospecting, calling individuals showed no body mass loss associated with this behaviour, suggesting that calling from within the group may provide a 'cheap' advertisement strategy. Additionally, we show that subordinates use information regarding the composition of neighbouring groups to target the greatest number of potential mating partners.

  20. Stress coping style does not determine social status, but influences the consequences of social subordination stress.

    Science.gov (United States)

    Boersma, Gretha J; Smeltzer, Michael D; Scott, Karen A; Scheurink, Anton J; Tamashiro, Kellie L; Sakai, Randall R

    2017-09-01

    Chronic stress exposure may have negative consequences for health. One of the most common sources of chronic stress is stress associated with social interaction. In rodents, the effects of social stress can be studied in a naturalistic way using the visual burrow system (VBS). The way an individual copes with stress, their "stress coping style", may influence the consequences of social stress. In the current study we tested the hypothesis that stress coping style may modulate social status and influence the consequences of having a lower social status. We formed 7 VBS colonies, with 1 proactive coping male, 1 passive coping male, and 4 female rats per colony to assess whether a rat's coping style prior to colony formation could predict whether that individual is more likely to become socially dominant. The rats remained in their respective colonies for 14days and the physiological and behavioral consequences of social stress were assessed. Our study shows that stress coping style does not predict social status. However, stress coping style may influence the consequences of having a lower social status. Subordinate passive and proactive rats had distinctly different wound patterns; proactive rats had more wounds on the front of their bodies. Behavioral analysis confirmed that proactive subordinate rats engaged in more offensive interactions. Furthermore, subordinate rats with a proactive stress coping style had larger adrenals, and increased stress responsivity to a novel acute stressor (restraint stress) compared to passive subordinate rats or dominant rats, suggesting that the allostatic load may have been larger in this group. Copyright © 2017 Elsevier Inc. All rights reserved.

  1. Biotic control of skeletal growth by scleractinian corals in aragonite-calcite seas.

    Directory of Open Access Journals (Sweden)

    Tomihiko Higuchi

    Full Text Available Modern scleractinian coral skeletons are commonly composed of aragonite, the orthorhombic form of CaCO3. Under certain conditions, modern corals produce calcite as a secondary precipitate to fill pore space. However, coral construction of primary skeletons from calcite has yet to be demonstrated. We report a calcitic primary skeleton produced by the modern scleractinian coral Acropora tenuis. When uncalcified juveniles were incubated from the larval stage in seawater with low mMg/Ca levels, the juveniles constructed calcitic crystals in parts of the primary skeleton such as the septa; the deposits were observable under Raman microscopy. Using scanning electron microscopy, we observed different crystal morphologies of aragonite and calcite in a single juvenile skeleton. Quantitative analysis using X-ray diffraction showed that the majority of the skeleton was composed of aragonite even though we had exposed the juveniles to manipulated seawater before their initial crystal nucleation and growth processes. Our results indicate that the modern scleractinian coral Acropora mainly produces aragonite skeletons in both aragonite and calcite seas, but also has the ability to use calcite for part of its skeletal growth when incubated in calcite seas.

  2. Ion beam modifications of defect sub-structure of calcite cleavages

    Indian Academy of Sciences (India)

    WINTEC

    Planar plastic anisotropy has been studied on irradiated calcite cleavages by measurement of micro- hardness. Keywords. Calcite crystals; ion-bombardment; optical microscopy; ... in the near surface composition (Arnold and Peercy 1980). The ultimate physical properties depend on the inherent defects together with those ...

  3. Removal of Pb(II from aqueous solution by natural and synthetic calcites

    Directory of Open Access Journals (Sweden)

    Ayomadewa Mercy Adesola

    2012-08-01

    Full Text Available A comparative evaluation of the adsorption capacity and kinetics of Pb(II uptake by both synthetic and natural calcites has been undertaken using batch equilibration technique. The originality of the calcite materials was confirmed by XRD and elemental composition by XRF. The point of zero charge values of 9.57 and 8.20 were obtained by mass titration method for synthetic and natural calcite, respectively. The maximum adsorption capacities of 200 mg/g and 150 mg/g Pb(II of synthetic calcite and natural calcite were obtained at initial lead loading of 1200 mg/L at 25±2 °C, respectively. The study showed a very slight dependence of sorption capacity on the ionic strength and pH, but a strong dependence on the particle size and contact time. The sorption data results fitted better the Langmuir than the Freundlich isotherms. The kinetic data fitted well to pseudo-first order sorption kinetic model with a regression coefficient value of 0.96 and 0.94 for synthetic and natural calcites, respectively. Desorption of Pb(II from calcite surface was achieved with efficiency of 95% using 4 M HNO3. The extent of reversibility of sorption reaction was a function of the equilibrium pH of calcite-Pb(II solution suspension.DOI: http://dx.doi.org/10.4314/bcse.v26i2.4

  4. Extra-territorial movements differ between territory holders and subordinates in a large, monogamous rodent.

    Science.gov (United States)

    Mayer, Martin; Zedrosser, Andreas; Rosell, Frank

    2017-11-10

    Territorial animals carry out extra-territorial movements (forays) to obtain pre-dispersal information or to increase reproductive success via extra-pair copulation. However, little is known about other purposes and spatial movement patterns of forays. In this study, we GPS-tagged 54 Eurasian beavers (Castor fiber), a year-round territorial, monogamous mammal, during the non-mating season. We investigated forays in territory-holding breeders (dominants) and non-breeding (subordinate) family members. Twenty of 46 dominant individuals (44%), and 6 of 10 subordinates (60%) conducted forays. Generally, beavers spent between 0 and 11% of their active time on forays, travelled faster and spend more time in water when on forays compared to intra-territorial movements, suggesting that forays are energetically costly. Further, beavers in smaller territories conducted more forays. Possibly, smaller territories might not have sufficient resources and thus dominant individuals might conduct forays to assess possibilities for territory expansion, and potentially for foraging. Generally, besides territory advertisement (e.g. via scent-marking), forays might serve as an additional mechanism for territory owners to assess neighbours. Subordinates spent more time on forays, moved greater distances and intruded into more territories than dominant individuals did, suggesting that they prospected to gain information on the population density and available mates before dispersal.

  5. Get Enough Calcium

    Science.gov (United States)

    ... Calcium Print This Topic En español Get Enough Calcium Browse Sections The Basics Overview Foods and Vitamins ... women, don't get enough calcium. How much calcium do I need every day? Women: If you ...

  6. Calcium carbonate overdose

    Science.gov (United States)

    Tums overdose; Calcium overdose ... Calcium carbonate can be dangerous in large amounts. ... Some products that contain calcium carbonate are certain: ... and mineral supplements Other products may also contain calcium ...

  7. The quantitative determination of calcite associated with the carbonate-bearing apatites

    Science.gov (United States)

    Silverman, Sol R.; Fuyat, Ruth K.; Weiser, Jeanne D.

    1951-01-01

    The CO2 combined as calcite in carbonate-bearing apatites as been distinguished from that combined as carbonate-apatite, or present in some form other than calcite, by use of X-ray powder patterns, differential thermal analyses, and differential solubility tests. These methods were applied to several pure apatite minerals, to one fossil bone, and to a group of phosphorites from the Phosphoria formation of Permian age from Trail Canyon and the Conda mine, Idaho, and the Laketown district, Utah. With the exceptions of pure fluorapatite, pure carbonate-flueorapatite, and one phosphorite from Trail Canyon, these substances contain varying amounts of calcite, but in all the samples an appreciable part of the carbonite content is not present as calcite. The results of solubility tests, in which the particle size of sample and the length of solution time were varied, imply that the carbonate content is not due to shielded calcite entrapped along an internal network of surfaces.

  8. The surface reactivity of chalk (biogenic calcite) with hydrophilic and hydrophobic functional groups

    Science.gov (United States)

    Okhrimenko, D. V.; Dalby, K. N.; Skovbjerg, L. L.; Bovet, N.; Christensen, J. H.; Stipp, S. L. S.

    2014-03-01

    The surface properties of calcium carbonate minerals play an important role in a number of industrial and biological processes. Properties such as wettability and adsorption control liquid-solid interface behaviour and thus have a strong influence on processes such as biomineralisation, remediation of aquifers and oil recovery. We investigated how two model molecules of different polarity, namely water and ethanol, interact with reservoir and outcrop chalk samples and we compared their behaviour with that of pure, inorganically precipitated calcite. Thermodynamic quantities, such as the work of wetting, surface energy and isosteric adsorption enthalpy, were determined from vapour adsorption isotherms. The chalks were studied fresh and after extraction of organic residues that were originally present in these samples. The work of wetting correlates with the amount of organic matter present in the chalk samples but we observed a fundamental difference between the adsorption properties of chalk and pure, inorganically precipitated calcite toward the less polar, ethanol molecule. Further analysis of the chemical composition of the organic matter extracted from the chalk samples was made by gas chromatography (GC-MS). Monitoring surface composition by X-ray photoelectron spectroscopy (XPS) before and after extraction of the organic material, and with atomic force microscopy (AFM), showed that nanometer sized clay crystals observed on the chalk particle surfaces could be an important part of the reason for the differences. Removal of the extractable portion of the hydrocarbons liberates adsorption sites that have different wetting properties than the rest of the chalk and these have an energy distribution that is similar to clays. Thus, the results exemplify the complexity of biogenic calcite adsorption behaviour and demonstrate that chalk wetting in drinking water aquifers as well as oil reservoirs is controlled partly by the nanoparticles of clay that have grown on the

  9. Composite Magnetite and Protein Containing CaCO3 Crystals. External Manipulation and Vaterite → Calcite Recrystallization-Mediated Release Performance.

    Science.gov (United States)

    Sergeeva, Alena; Sergeev, Roman; Lengert, Ekaterina; Zakharevich, Andrey; Parakhonskiy, Bogdan; Gorin, Dmitry; Sergeev, Sergey; Volodkin, Dmitry

    2015-09-30

    Biocompatibility and high loading capacity of mesoporous CaCO3 vaterite crystals give an option to utilize the polycrystals for a wide range of (bio)applications. Formation and transformations of calcium carbonate polymorphs have been studied for decades, aimed at both basic and applied research interests. Here, composite multilayer-coated calcium carbonate polycrystals containing Fe3O4 magnetite nanoparticles and model protein lysozyme are fabricated. The structure of the composite polycrystals and vaterite → calcite recrystallization kinetics are studied. The recrystallization results in release of both loaded protein and Fe3O4 nanoparticles (magnetic manipulation is thus lost). Fe3O4 nanoparticles enhance the recrystallization that can be induced by reduction of the local pH with citric acid and reduction of the polycrystal crystallinity. Oppositely, the layer-by-layer assembled poly(allylamine hydrochloride)/poly(sodium styrenesulfonate) polyelectrolyte coating significantly inhibits the vaterite → calcite recrystallization (from hours to days) most likely due to suppression of the ion exchange giving an option to easily tune the release kinetics for a wide time scale, for example, for prolonged release. Moreover, the recrystallization of the coated crystals results in formulation of multilayer capsules keeping the feature of external manipulation. This study can help to design multifunctional microstructures with tailor-made characteristics for loading and controlled release as well as for external manipulation.

  10. Investigating calcite growth rates using a quartz crystal microbalance with dissipation (QCM-D)

    Science.gov (United States)

    Cao, Bo; Stack, Andrew G.; Steefel, Carl I.; DePaolo, Donald J.; Lammers, Laura N.; Hu, Yandi

    2018-02-01

    Calcite precipitation plays a significant role in processes such as geological carbon sequestration and toxic metal sequestration and, yet, the rates and mechanisms of calcite growth under close to equilibrium conditions are far from well understood. In this study, a quartz crystal microbalance with dissipation (QCM-D) was used for the first time to measure macroscopic calcite growth rates. Calcite seed crystals were first nucleated and grown on sensors, then growth rates of calcite seed crystals were measured in real-time under close to equilibrium conditions (saturation index, SI = log ({Ca2+}/{CO32-}/Ksp) = 0.01-0.7, where {i} represent ion activities and Ksp = 10-8.48 is the calcite thermodynamic solubility constant). At the end of the experiments, total masses of calcite crystals on sensors measured by QCM-D and inductively coupled plasma mass spectrometry (ICP-MS) were consistent, validating the QCM-D measurements. Calcite growth rates measured by QCM-D were compared with reported macroscopic growth rates measured with auto-titration, ICP-MS, and microbalance. Calcite growth rates measured by QCM-D were also compared with microscopic growth rates measured by atomic force microscopy (AFM) and with rates predicted by two process-based crystal growth models. The discrepancies in growth rates among AFM measurements and model predictions appear to mainly arise from differences in step densities, and the step velocities were consistent among the AFM measurements as well as with both model predictions. Using the predicted steady-state step velocity and the measured step densities, both models predict well the growth rates measured using QCM-D and AFM. This study provides valuable insights into the effects of reactive site densities on calcite growth rate, which may help design future growth models to predict transient-state step densities.

  11. The Paradox of Power Sharing: Participative Charismatic Leaders have Subordinates with more instead of less Need for Leadership

    NARCIS (Netherlands)

    de Vries, R.E.; Pathak, R.D.; Paquin, A.R.

    2011-01-01

    Although charismatic and participative leaders have been noted for their positive effects on criteria such as performance, job satisfaction, and commitment, few studies have looked at the relations with subordinates' leadership needs. In this study, the relations between charismatic and

  12. Infrared spectroscopy and density functional theory investigation of calcite, chalk, and coccoliths-do we observe the mineral surface?

    DEFF Research Database (Denmark)

    Andersson, Martin Peter; Hem, Caroline Piper; Schultz, Logan Nicholas

    2014-01-01

    We have measured infrared spectra from several types of calcite: chalk, freshly cultured coccoliths produced by three species of algae, natural calcite (Iceland Spar), and two types of synthetic calcite. The most intense infrared band, the asymmetric carbonate stretch vibration, is clearly asymme...

  13. Controls on Calcium Isotope Fractionation in Cultured Foraminifera

    Science.gov (United States)

    Kisakurek, B.; Boehm, F.; Eisenhauer, A.; Hathorne, E.; Garbe-Schoenberg, D.; Erez, J.

    2008-12-01

    Calcium isotopes have recently emerged as an important tool to study the biomineralization pathways and processes in foraminifera. We analyzed calcium isotopes in planktonic and benthic foraminifera grown under controlled laboratory conditions at different salinity, temperature and pH values. Our results indicate that calcium isotope fractionation in foraminifera is controlled by more than one environmental parameter, requiring a common mechanism to explain the observed trends. There is a significant negative correlation between calcium isotope fractionation and the distribution coefficient of strontium in planktonic foraminifera, which has the same slope (within error) as that in inorganic calcite (Tang et al, 2008). In analogy to these inorganic experiments, calcium isotopic fractionation and Sr/Ca ratios in planktonic foraminifera appear to be mainly controlled by the precipitation rate. However, the two regressions (inorganic vs. foraminiferal) have a small but constant offset from each other by about 0.2 permil in delta(44Ca/40Ca) for a given D(Sr). This offset is presumably due to a vital effect that can be modeled via Rayleigh distillation from an internal biomineralization reservoir (Elderfield et al., 1996). Our preliminary results suggest that such a reservoir behaves as a semi-open system, wherein only less than 25 percent of the calcium taken up from seawater is being utilized for calcification. Elderfield, H., Bertram, C.J., Erez, J. 1996. A biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate. Earth Planet. Sci. Lett., 142:409-423. Tang J., Dietzel M., Boehm F., Koehler S.J., Eisenhauer A. 2008. Sr2+/Ca2+ and 44Ca/40Ca fractionation during inorganic calcite formation: II. Ca isotopes. Geochim. Cosmochim. Acta, 72:3733-3745.

  14. Calcium paradox and calcium entry blockers

    NARCIS (Netherlands)

    Ruigrok, T.J.C.; Slade, A.M.; Nayler, W.G.; Meijler, F.L.

    1984-01-01

    Reperfusion of isolated hearts with calcium-containing solution after a short period of calcium-free perfusion results in irreversible cell damage (calcium paradox). This phenomenon is characterized by an excessive influx of calcium into the cells, the rapid onset of myocardial contracture,

  15. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum.

    Science.gov (United States)

    Offeddu, Francesco Giancarlo; Cama, Jordi; Soler, Josep Maria; Putnis, Christine V

    2014-01-01

    In-situ atomic force microscopy (AFM) experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite) and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C). The dissolution of the carbonate minerals took place at the (104) cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours.

  16. Direct nanoscale observations of the coupled dissolution of calcite and dolomite and the precipitation of gypsum

    Directory of Open Access Journals (Sweden)

    Francesco G. Offeddu

    2014-08-01

    Full Text Available In-situ atomic force microscopy (AFM experiments were performed to study the overall process of dissolution of common carbonate minerals (calcite and dolomite and precipitation of gypsum in Na2SO4 and CaSO4 solutions with pH values ranging from 2 to 6 at room temperature (23 ± 1 °C. The dissolution of the carbonate minerals took place at the (104 cleavage surfaces in sulfate-rich solutions undersaturated with respect to gypsum, by the formation of characteristic rhombohedral-shaped etch pits. Rounding of the etch pit corners was observed as solutions approached close-to-equilibrium conditions with respect to calcite. The calculated dissolution rates of calcite at pH 4.8 and 5.6 agreed with the values reported in the literature. When using solutions previously equilibrated with respect to gypsum, gypsum precipitation coupled with calcite dissolution showed short gypsum nucleation induction times. The gypsum precipitate quickly coated the calcite surface, forming arrow-like forms parallel to the crystallographic orientations of the calcite etch pits. Gypsum precipitation coupled with dolomite dissolution was slower than that of calcite, indicating the dissolution rate to be the rate-controlling step. The resulting gypsum coating partially covered the surface during the experimental duration of a few hours.

  17. Fabrication of porous calcite using chopped nylon fiber and its evaluation using rats.

    Science.gov (United States)

    Ishikawa, Kunio; Tram, Nguyen Xuan Thanh; Tsuru, Kanji; Toita, Riki

    2015-02-01

    Although porous calcite has attracted attention as bone substitutes, limited studies have been made so far. In the present study, porous calcite block was fabricated by introducing chopped nylon fiber as porogen. Ca(OH)2 powder containing 10 wt% chopped nylon fiber was compacted at 150 MPa, and sintered to burn out the fiber and to carbonate the Ca(OH)2 under stream of 1:2 O2-CO2. Sintering of Ca(OH)2 at 750 °C or lower temperature resulted in incomplete burning out of the fiber whereas sintering at 800 °C or higher temperature resulted in the formation of CaO due to the thermal decomposition of Ca(OH)2. However, sintering at 770 °C resulted in complete burning out of the fiber and complete carbonation of Ca(OH)2 to calcite without forming CaO. Macro- and micro-porosities of the porous calcite were approximately 23 and 16%, respectively. Diameter of the macropores was approximately 100 μm which is suitable for bone tissue penetration. Porous calcite block fabricated by this method exhibited good tissue response when implanted in the bone defect in femur of 12-weeks-old rat. Four weeks after implantation, bone bonded on the surface of calcite. Furthermore, bone tissue penetrated interior to the macropore at 8 weeks. These results demonstrated the good potential value of porous calcite as artificial bone substitutes.

  18. Reconciling disparate views of template-directed nucleation through measurement of calcite nucleation kinetics and binding energies.

    Science.gov (United States)

    Hamm, Laura M; Giuffre, Anthony J; Han, Nizhou; Tao, Jinhui; Wang, Debin; De Yoreo, James J; Dove, Patricia M

    2014-01-28

    The physical basis for how macromolecules regulate the onset of mineral formation in calcifying tissues is not well established. A popular conceptual model assumes the organic matrix provides a stereochemical match during cooperative organization of solute ions. In contrast, another uses simple binding assays to identify good promoters of nucleation. Here, we reconcile these two views and provide a mechanistic explanation for template-directed nucleation by correlating heterogeneous nucleation barriers with crystal-substrate-binding free energies. We first measure the kinetics of calcite nucleation onto model substrates that present different functional group chemistries (carboxyl, thiol, phosphate, and hydroxyl) and conformations (C11 and C16 chain lengths). We find rates are substrate-specific and obey predictions of classical nucleation theory at supersaturations that extend above the solubility of amorphous calcium carbonate. Analysis of the kinetic data shows the thermodynamic barrier to nucleation is reduced by minimizing the interfacial free energy of the system, γ. We then use dynamic force spectroscopy to independently measure calcite-substrate-binding free energies, ΔGb. Moreover, we show that within the classical theory of nucleation, γ and ΔGb should be linearly related. The results bear out this prediction and demonstrate that low-energy barriers to nucleation correlate with strong crystal-substrate binding. This relationship is general to all functional group chemistries and conformations. These findings provide a physical model that reconciles the long-standing concept of templated nucleation through stereochemical matching with the conventional wisdom that good binders are good nucleators. The alternative perspectives become internally consistent when viewed through the lens of crystal-substrate binding.

  19. Measuring Carbon and Oxygen Isotope Uptake into Inorganic Calcite using Crystal Growth Experiments

    Science.gov (United States)

    Baker, E. B.; Watkins, J. M.

    2014-12-01

    Carbon and oxygen isotopes measured on natural calcite crystals provide a record of paleo-environment conditions. Despite the importance of measuring stable isotopes in calcite for paleo-environment reconstructions, there is neither a general theory nor an experimental data set that fully separates the effects of pH, temperature, and precipitation rate on isotope discrimination during calcite growth. Many stable isotope studies of calcite have focused on either carbon or oxygen isotope compositions individually, but few have measured both carbon and oxygen isotope uptake in the same set of crystals. We are precipitating inorganic calcite across a range in temperature, pH, and precipitation rate to guide the development of a general theory for combined carbon and oxygen isotope uptake into calcite crystals grown on laboratory timescales. In our experiments, dissolved inorganic carbon (DIC) is added to an aqueous solution (15 mM CaCl2 + 5 mM NH4Cl) by CO2 bubbling. Once a critical supersaturation is reached, calcite crystals nucleate spontaneously and grow on the beaker walls. A key aspect of this experimental approach is that the δ13C of DIC is relatively constant throughout the crystal growth period, because there is a continuous supply of DIC from the CO2-bearing bubbles. Carbonic anhydrase, an enzyme promoting rapid equilibration of isotopes between DIC and water, was added to ensure that the solution remained isotopically equilibrated during calcite growth. We have conducted experiments at T = 25°C and pH = 8.3 - 9.0. We observe that the fractionation of oxygen isotopes between calcite and water decreases with increasing pH, consistent with available data from experiments in which the enzyme carbonic anhydrase was used. Our results for carbon isotopes extend the available data set, which previously ranged from pH 6.62 to 7.75, to higher pH. At pH 8.3, we observe that calcite is isotopically heavier than DIC with respect to carbon isotopes by about 0.25‰. At

  20. 88Sr/86Sr fractionation and calcite accumulation rate in the Sea of Galilee

    Science.gov (United States)

    Fruchter, N.; Lazar, B.; Nishri, A.; Almogi-Labin, A.; Eisenhauer, A.; Be'eri Shlevin, Y.; Stein, M.

    2017-10-01

    This study used the Sea of Galilee (Lake Kinneret, northern Israel) as a ;natural laboratory; to investigate the fractionation of the stable Sr isotope ratio (88Sr/86Sr) during precipitation of inorganic (primary) calcite from the lake's water. It was found that the absolute value of the 88Sr/86Sr fractionation factor, Δ88/86Sr, increases as a function of calcite accumulation rate (Δ88/86Sr [‰] = -0.05 to 0.042·log(R) [μmol·m-2·d-1], where R is the accumulation rate). Furthermore, the 87Sr/86Sr and 88Sr/86Sr ratios in the freshwater and brines that enter the lake were used to calculate the contributions of these sources to the lake Sr budget. The 87Sr/86Sr and 88Sr/86Sr ratios were measured in primary calcite, aragonite shells of live Melanopsis, lake water and various water sources to the lake. While the lake's 87Sr/86Sr ratios are determined by the mixture of freshwater of the Jordan River and saline springs, the 88Sr/86Sr ratios of the lake reflect a more complex mass balance that includes the effect of isotopic fractionation associated with the precipitation of primary calcite. Data analysis suggests that long-term accumulation of inorganic calcite depleted in the heavy isotope 88Sr, results in an increase of the δ88/86Sr value of the lake water by 0.05‰. In contrast to the primary inorganic calcite, biogenic aragonite of the Melanopsis shells show a rather constant 88Sr/86Sr water-CaCO3 fractionation of Δ88/86Sr = -0.21‰. Similar Δ88/86Sr values were reported for the precipitation of coralline and inorganic aragonite from seawater and the precipitation of inorganic calcite from various continental waters. The Δ88/86Sr value of inorganic calcite is modulated by the rate of carbonate precipitation, as noted above and shown by precipitation experiments. Massive precipitation of primary calcite with a wide spread of accumulation rates occurs during the spring phytoplankton bloom in Lake Kinneret. The bloom dictates the degree of calcite saturation

  1. Subordinate clause comprehension and tense/agreement inconsistency in children with specific language impairment.

    Science.gov (United States)

    Souto, Sofía M; Leonard, Laurence B; Deevy, Patricia; Fey, Marc E; Bredin-Oja, Shelley L

    2016-01-01

    Several recent studies have suggested that the production errors of children with specific language impairment (SLI) such as The girl singing may be explained by a misinterpretation of grammatical adult input containing a similar structure (e.g., The boy hears the girl singing). Thirteen children with SLI and 13 younger typically developing children with comparable sentence comprehension test scores (TD-COMP) completed a comprehension task to assess their understanding of sentences involving a nonfinite subject-verb sequence in a subordinate clause such as The dad sees the boy running. TD-COMP children were more accurate on subordinate clause items than children with SLI despite similar performance on simple transitive (e.g., The horse sees the cow) and simple progressive (e.g., The cow is eating) items. However, no relationship was found between the SLI group's specific subordinate clause comprehension level and their specific level of auxiliary is production, casting some doubt on this type of structure as a source for inconsistent use of auxiliary is. The reader will learn that children with specific language impairment (SLI): (1) have difficulty understanding complex sentences that include nonfinite subject-verb sequences; (2) that this difficulty is apparent in comparison to younger typically developing peers who have similar scores not only on a sentence comprehension test, but also on simple sentences that correspond to the component parts of the complex sentences; and (3) that this weakness is concurrent with these children's inconsistent use of auxiliary is in production. Although novel verb studies show a clear connection between how children with SLI hear new verbs and how they use them, we do not yet have evidence that this connection is tied to a poor understanding of the input sentences that house the verbs. Copyright © 2016 Elsevier Inc. All rights reserved.

  2. Final report for DOE Grant No. DE-SC0006609 - Persistence of Microbially Facilitated Calcite Precipitation as an in situ Treatment for Strontium-90

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W. [Univ. of Idaho, Idaho Falls, ID (United States); Fujita, Yoshiko [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hubbard, Susan S. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)

    2013-11-15

    Subsurface radionuclide and metal contaminants throughout the U.S. Department of Energy (DOE) complex pose one of DOE's greatest challenges for long-term stewardship. One promising stabilization mechanism for divalent ions, such as the short-lived radionuclide 90Sr, is co-precipitation in calcite. We have previously found that nutrient addition can stimulate microbial ureolytic activity, that this activity accelerates calcite precipitation and co-precipitation of Sr, and that higher calcite precipitation rates can result in increased Sr partitioning. We have conducted integrated field, laboratory, and computational research to evaluate the relationships between ureolysis and calcite precipitation rates and trace metal partitioning under environmentally relevant conditions, and investigated the coupling between flow/flux manipulations and precipitate distribution. A field experimental campaign conducted at the Integrated Field Research Challenge (IFRC) site located at Rifle, CO was based on a continuous recirculation design; water extracted from a down-gradient well was amended with urea and molasses (a carbon and electron donor) and re-injected into an up-gradient well. The goal of the recirculation design and simultaneous injection of urea and molasses was to uniformly accelerate the hydrolysis of urea and calcite precipitation over the entire inter-wellbore zone. The urea-molasses recirculation phase lasted, with brief interruptions for geophysical surveys, for 12 days and was followed by long-term monitoring which continued for 13 months. A post experiment core located within the inter-wellbore zone was collected on day 321 and characterized with respect to cation exchange capacity, mineral carbonate content, urease activity, ureC gene abundance, extractable ammonium (a urea hydrolysis product) content, and the 13C isotopic composition of solid carbonates. It was also subjected to selective extractions for strontium and uranium. Result

  3. Effect of fluid salinity on subcritical crack propagation in calcite

    Science.gov (United States)

    Rostom, Fatma; Røyne, Anja; Dysthe, Dag Kristian; Renard, François

    2013-01-01

    The slow propagation of cracks, also called subcritical crack growth, is a mechanism of fracturing responsible for a ductile deformation of rocks under crustal conditions. In the present study, the double-torsion technique was used to measure the effect of fluid chemistry on the slow propagation of cracks in calcite single crystals at room temperature. Time-lapse images and measurements of force and load-point displacement allowed accurate characterization of crack velocities in a range of 10- 8 to 10- 4 m/s. Velocity curves as a function of energy-release rates were obtained for different fluid compositions, varying NH4Cl and NaCl concentrations. Our results show the presence of a threshold in fluid composition, separating two regimes: weakening conditions where the crack propagation is favored, and strengthening conditions where crack propagation slows down. We suggest that electrostatic surface forces that modify the repulsion forces between the two surfaces of the crack may be responsible for this behavior.

  4. Calcium phosphate mineralization is widely applied in crustacean mandibles.

    Science.gov (United States)

    Bentov, Shmuel; Aflalo, Eliahu D; Tynyakov, Jenny; Glazer, Lilah; Sagi, Amir

    2016-02-24

    Crustaceans, like most mineralized invertebrates, adopted calcium carbonate mineralization for bulk skeleton reinforcement. Here, we show that a major part of the crustacean class Malacostraca (which includes lobsters, crayfishes, prawns and shrimps) shifted toward the formation of calcium phosphate as the main mineral at specified locations of the mandibular teeth. In these structures, calcium phosphate is not merely co-precipitated with the bulk calcium carbonate but rather creates specialized structures in which a layer of calcium phosphate, frequently in the form of crystalline fluorapatite, is mounted over a calcareous "jaw". From a functional perspective, the co-existence of carbonate and phosphate mineralization demonstrates a biomineralization system that provides a versatile route to control the physico-chemical properties of skeletal elements. This system enables the deposition of amorphous calcium carbonate, amorphous calcium phosphate, calcite and apatite at various skeletal locations, as well as combinations of these minerals, to form graded composites materials. This study demonstrates the widespread occurrence of the dual mineralization strategy in the Malacostraca, suggesting that in terms of evolution, this feature of phosphatic teeth did not evolve independently in the different groups but rather represents an early common trait.

  5. Chronic subordination stress induces hyperphagia and disrupts eating behavior in mice modeling binge-eating-like disorder

    Directory of Open Access Journals (Sweden)

    Maria eRazzoli

    2015-01-01

    Full Text Available Background: Eating disorders are associated with physical morbidity and appear to have causal factors like stressful life events and negative affect. Binge eating disorder (BED is characterized by eating in a discrete period of time a larger than normal amount of food, a sense of lack of control over eating, and marked distress. There are still unmet needs for the identification of mechanisms regulating excessive eating, which is in part due to the lack of appropriate animal models. We developed a naturalistic murine model of subordination stress induced hyperphagia associated with the development of obesity. Here we tested the hypotheses that the eating responses of subordinate mice recapitulate the BED and that limiting hyperphagia could prevent stress-associated metabolic changes. Methods: Adult male mice were exposed to a model of chronic subordination stress associated with the automated acquisition of food intake and we performed a detailed meal pattern analysis. Additionally, using a pair-feeding protocol was test the hypothesis that the manifestation of obesity and the metabolic syndrome could be prevented by limiting hyperphagia. Results: The architecture of feeding of subordinate mice was disrupted during the stress protocol due to disproportionate amount of food ingested at higher rate and with shorter satiety ratio than control mice. Subordinate mice hyperphagia was further exacerbated in response to either hunger or to the acute application of a social defeat. Notably, the obese phenotype but not the fasting hyperglycemia of subordinate mice was abrogated by preventing hyperphagia in a pair feeding paradigm. Conclusion: Overall these results support the validity of our chronic subordination stress to model binge eating disorder allowing for the determination of the underlying molecular mechanisms and the generation of testable predictions for innovative therapies, based on the understanding of the regulation and the control of food

  6. Chronic subordination stress induces hyperphagia and disrupts eating behavior in mice modeling binge-eating-like disorder.

    Science.gov (United States)

    Razzoli, Maria; Sanghez, Valentina; Bartolomucci, Alessandro

    Eating disorders are associated with physical morbidity and appear to have causal factors like stressful life events and negative affect. Binge eating disorder (BED) is characterized by eating in a discrete period of time a larger than normal amount of food, a sense of lack of control over eating, and marked distress. There are still unmet needs for the identification of mechanisms regulating excessive eating, which is in part due to the lack of appropriate animal models. We developed a naturalistic murine model of subordination stress induced hyperphagia associated with the development of obesity. Here we tested the hypotheses that the eating responses of subordinate mice recapitulate the BED and that limiting hyperphagia could prevent stress-associated metabolic changes. Adult male mice were exposed to a model of chronic subordination stress associated with the automated acquisition of food intake and we performed a detailed meal pattern analysis. Additionally, using a pair-feeding protocol was test the hypothesis that the manifestation of obesity and the metabolic syndrome could be prevented by limiting hyperphagia. The architecture of feeding of subordinate mice was disrupted during the stress protocol due to disproportionate amount of food ingested at higher rate and with shorter satiety ratio than control mice. Subordinate mice hyperphagia was further exacerbated in response to either hunger or to the acute application of a social defeat. Notably, the obese phenotype but not the fasting hyperglycemia of subordinate mice was abrogated by preventing hyperphagia in a pair feeding paradigm. Overall these results support the validity of our chronic subordination stress to model binge eating disorder allowing for the determination of the underlying molecular mechanisms and the generation of testable predictions for innovative therapies, based on the understanding of the regulation and the control of food intake.

  7. Fractionation behavior of chromium isotopes during coprecipitation with calcium carbonate

    DEFF Research Database (Denmark)

    Rodler, Alexandra; Sánchez-Pastor, Nuria; Fernández-Díaz, Lurdes

    2015-01-01

    Interest in chromium (Cr) isotope incorporation into carbonates arises from the observation that Cr isotopic composition of carbonates could be used as a paleoclimate proxy to elucidate past fluctuations of oxygen contents in atmosphere and hydrosphere. The use of Cr isotopes to track....... The fractionation of Cr isotopes during calcium carbonate coprecipitation was assumed to be small, based on previously published data of modern seawater and modern non-skeletal marine carbonates. However, results from this study for rapidly precipitated calcium carbonate in the presence of chromate show a tendency...... showed the presence of vaterite. Calcium carbonate crystals were also precipitated in a double diffusion silica hydrogel over a longer period of time resulting in samples consisting of micrometric-millimetric calcite crystals, which were again significantly enriched in heavy Cr isotopes compared...

  8. Coronary Calcium Scan

    Science.gov (United States)

    ... Back To Health Topics / Coronary Calcium Scan Coronary Calcium Scan Also known as Calcium Scan Test A coronary calcium scan is a CT scan of your heart that detects and measures the amount of calcium in the walls of your coronary arteries. Overview ...

  9. The chemical transformation of calcium in Shenhua coal during combustion in a muffle furnace

    Energy Technology Data Exchange (ETDEWEB)

    Tian, Sida [North China Electric Power Univ., Beijing (China). School of Energy, Power and Mechanical Engineering; Ministry of Education, Beijing (China). Key Lab. of Condition Monitoring and Control for Power Plant Equipment; Zhuo, Yuqun; Chen, Changhe [Tsinghua Univ., Beijing (China). Dept. of Thermal Engineering; Ministry of Education, Beijing (China). Key Lab. for Thermal Science and Power Engineering; Shu, Xinqian [China Univ. of Mining and Technology, Beijing (China). School of Chemical and Environmental Engineering

    2013-07-01

    The chemical reaction characteristics of calcium in three samples of Shenhua coal, i.e. raw sample, hydrochloric acid washed sample and hydrochloric acid washed light fraction, during combustion in a muffle furnace have been investigated in this paper. Ca is bound by calcite and organic matter in Shenhua coal. X ray diffraction (XRD) phase analysis has been conducted to these samples' combustion products obtained by heating at different temperatures. It has been found that the organically-bound calcium could easily react with clays and transform into gehlenite and anorthite partially if combusted under 815 C, whilst the excluded minerals promoted the conversion of gehlenite to anorthite. Calcite in Shenhua coal decomposed into calcium oxide and partially transformed into calcium sulfate under 815 C, and formed gehlenite and anorthite under 1,050 C. Calcite and other HCl-dissolved minerals in Shenhua coal were responsible mainly for the characteristic that the clay minerals in Shenhua coal hardly became mullite during combustion.

  10. The effect of the Ca2+ to CO32- activity ratio on spiral growth at the calcite {1014} surface

    DEFF Research Database (Denmark)

    Larsen, Kirsten Kolbjørn; Bechgaard, Klaus; Stipp, Susan Louise Svane

    2010-01-01

    Variation in the Ca2+ to CO 2¿ activity ratio of natural waters is rarely considered in models intended to describe calcite 3 growth. Atomic force microscopy (AFM) and differential interference contrast (DIC) microscopy were used to examine spiral growth on calcite f10¿14g surfaces from solutions...... steps grow faster 3 than acute steps but this trend reverses at low activity ratios. This is reflected in the morphology of growth pyramids. The reversal in the inequivalent step growth velocity indicates that the hydrated carbonate ion preferentially incorporates at kink sites along the more...... structurally open obtuse step edges, whereas the hydrated calcium ion is more easily accommodated at the more confined acute step kink sites. Furthermore, the experimental data demonstrate that velocity is maximum for obtuse steps when the activities of Ca2+ and CO 2¿ are equal, whereas maximum acute step...

  11. Ocean acidification: Towards a better understanding of calcite dissolution

    Science.gov (United States)

    Wilhelmus, Monica M.; Adkins, Jess; Menemenlis, Dimitris

    2016-11-01

    The drastic increase of anthropogenic CO2 emissions over the past two centuries has altered the chemical structure of the ocean, acidifying upper ocean waters. The net impact of this pH decrease on marine ecosystems is still unclear, given the unprecedented rate at which CO2 is being released into the atmosphere. As part of the carbon cycle, calcium carbonate dissolution in sediments neutralizes CO2: phytoplankton at the surface produce carbonate minerals, which sink and reach the seafloor after the organisms die. On time scales of thousands of years, the calcium carbonate in these shells ultimately reacts with CO2 in seawater. Research in this field has been extensive; nevertheless, the dissolution rate law, the impact of boundary layer transport, and the feedback with the global ocean carbon cycle remain controversial. Here, we (i) develop a comprehensive numerical framework via 1D modeling of carbonate dissolution in sediments, (ii) approximate its impact on water column properties by implementing a polynomial approximation to the system's response into a global ocean biogeochemistry general circulation model (OBGCM), and (iii) examine the OBGCM sensitivity response to different formulations of sediment boundary layer properties. We find that, even though the burial equilibration time scales of calcium carbonate are in the order of thousands of years, the formulation of a bottom sediment model along with an improved description of the dissolution rate law can have consequences on multi-year to decadal time scales.

  12. Polymorph-selective crystallization of calcium carbonate inspired by biomineralization

    Science.gov (United States)

    Kim, Il Won

    This dissertation primarily examines bioinspired mineralization, focusing on the polymorph-selective crystallization of calcium carbonate. (1) The effect of epitaxy on the polymorphic control of calcium carbonate was studied with aragonite-type inorganic substrates. The critical epitaxial mismatch for aragonite growth, when conditions disfavor aragonite, seems to be less than 7.1%. Larger epitaxial strain appeared to prohibit aragonite formation even though the substrates had the same crystal structure. The epitaxy required for aragonite nucleation seems to be more precise than that often suggested for biological systems. (2) Polymers of different aqueous-solution properties were tested to observe the effect on the crystallization of calcium carbonate. Near exclusive formation of aragonite was attained through the inhibition of more stable calcite with poly(vinyl alcohol). The contributing characteristics of poly(vinyl alcohol) seemed to be its ability to hydrogen bond and its tendency to adsorb non-specifically onto solid surfaces. Similar inhibition activity is suggested for various biomacromolecules involved in biogenic aragonite formation of mollusks, with the biomacromolecules acting in the same way as poly(vinyl alcohol). (3) Polymer surfaces imprinted by aragonite-type crystals (strontium carbonate) were studied as substrates for the crystallization of calcium carbonate. Only calcite formed under vaterite-, aragonite-, and calcite-favorable conditions. This result seemed to arise from the nature of functional groups, rather than from the molecular structure of the imprint. Interaction between the functional groups and calcium carbonate is suggested to have enhanced the crystallization rate, resulting in the rapid formation of the thermodynamically stable calcite irrespective of the bulk crystallization conditions. (4) A catechol-based monomer was synthesized in the course of developing a dental adhesive, which mimics the functionalities of mussel adhesive

  13. The sixteenth century Alderney crystal: a calcite as an efficient reference optical compass?

    National Research Council Canada - National Science Library

    Albert Le Floch; Guy Ropars; Jacques Lucas; Steve Wright; Trevor Davenport; Michael Corfield; Michael Harrisson

    2013-01-01

    ... the crystal by inducing roughness of its surface. Although both phenomena have reduced the transparency of the Alderney calcite crystal, we demonstrate that Alderney-like crystals could really have been used as an accurate optical sun compass...

  14. Machine learning approach for predicting the effect of CO2 solubility on dissolution rate of calcite

    Science.gov (United States)

    Nomeli, Mohammad

    2017-11-01

    A machine learning-assisted model is developed to predict the dissolution rate of calcite in saline solutions that are imbibed with dissolved CO2 over a broad range of both subcritical and supercritical conditions. This study focuses on determining the rate of calcite dissolution within a temperature range of 50-100 C and pressures up to 600 bar, relevant for CO2 sequestration in saline aquifers. A general reaction kinetic model is used that is based on the extension of the standard Arrhenius equation with an added, solubility dependent, pH term to account for the saturated concentration of dissolved CO2. The kinetic model helps to obtain a predictive rate equation using machine learning methods to determine the dissolution of calcite as a function of temperature, pressure and salinity. The new rate equation helps us obtain good agreement with experimental data, and it is applied to study the geochemically induced alterations of fracture geometry due to calcite dissolution.

  15. Total alignment of calcite at acidic polydiacetylene films: cooperativity at the organic-inorganic interface.

    Science.gov (United States)

    Berman, A; Ahn, D J; Lio, A; Salmeron, M; Reichert, A; Charych, D

    1995-07-28

    Biological matrices can direct the absolute alignment of inorganic crystals such as calcite. Cooperative effects at an organic-inorganic interface resulted in similar co-alignment of calcite at polymeric Langmuir-Schaefer films of 10,12-pentacosadiynoic acid (p-PDA). The films nucleated calcite at the (012) face, and the crystals were co-aligned with respect to the polymer's conjugated backbone. At the same time, the p-PDA alkyl side chains reorganized to optimize the stereochemical fit to the calcite structure, as visualized by changes in the optical spectrum of the polymer. These results indicate the kinds of interactions that may occur in biological systems where large arrays of crystals are co-aligned.

  16. Kinetic and thermodynamic factors controlling the distribution of SO 32- and Na + in calcites and selected aragonites

    Science.gov (United States)

    Busenberg, Eurybiades; Niel Plummer, L.

    1985-03-01

    Significant amounts of SO 42-, Na +, and OH - are incorporated in marine biogenic calcites. Biogenic high Mg-calcites average about 1 mole percent SO 42-. Aragonites and most biogenic low Mg-calcites contain significant amounts of Na +, but very low concentrations of SO 42-. The SO 42- content of non-biogenic calcites and aragonites investigated was below 100 ppm. The presence of Na + and SO 42- increases the unit cell size of calcites. The solid-solutions show a solubility minimum at about 0.5 mole percent SO 42- beyond which the solubility rapidly increases. The solubility product of calcites containing 3 mole percent SO 42- is the same as that of aragonite. Na + appears to have very little effect on the solubility product of calcites. The amounts of Na + and SO 42- incorporated in calcites vary as a function of the rate of crystal growth. The variation of the distribution coefficient ( D) of SO 42- in calcite at 25.0°C and 0.50 molal NaCl is described by the equation D = k 0 + k 1R where k 0 and k 1 are constants equal to 6.16 × 10 -6 and 3.941 × 10 -6, respectively, and R is the rate of crystal growth of calcite in mg·min -1·g -1 of seed. The data on Na + are consistent with the hypothesis that a significant amount of Na + occupies interstitial positions in the calcite structure. The distribution of Na + follows a Freundlich isotherm and not the Berthelot-Nernst distribution law. The numerical value of the Na + distribution coefficient in calcite is probably dependent on the number of defects in the calcite structure. The Na + contents of calcites are not very accurate indicators of environmental salinities.

  17. Discrimination between dominant and subordinate groups: the positive-negative asymmetry effect and normative processes.

    Science.gov (United States)

    Amiot, Catherine E; Bourhis, Richard Y

    2005-06-01

    Research using the minimal group paradigm (MGP) demonstrates that categorization and in-group identification can suffice to foster intergroup discrimination. However, the positive- negative asymmetry effect (PNAE) shows that less discrimination occurs when negative than when positive outcomes are distributed between group members. Combining the polarization paradigm and the MGP, this study investigated the discriminatory behaviour of dominant and subordinate group members ( N = 197) on positive and negative outcome distributions. During private outcome distributions at pre-consensus, dominant groups discriminated more than subordinate groups while the PNAE was not replicated. Positive/negative outcome distributions were sought during intragroup discussion in the consensus phase, while post-consensus involved private outcome distributions. The PNAE emerged in both consensus and post-consensus phases: group members discriminated less on salary cuts than on salary increases, whereas the power effect disappeared in those phases. The emergence of in-group norms during face-to-face discussions at consensus as well as social identity processes help account for the results obtained in this study.

  18. The mechanical and microstructural behaviour of calcite-dolomite composites: An experimental investigation

    OpenAIRE

    Kushnir, Alexandra R. l.; Kennedy, L. A.; Misra, Santanu; Benson, Philip; White, J. C.

    2015-01-01

    The styles and mechanisms of deformation associated with many variably dolomitized limestone shear systems are strongly controlled by strain partitioning between dolomite and calcite. Here, we present experimental results from the deformation of four composite materials designed to address the role of dolomite on the strength of limestone. Composites were synthesized by hot isostatic pressing mixtures of dolomite (Dm) and calcite powders (% Dm: 25%-Dm, 35%-Dm, 51%-Dm, and 75%-Dm). In all comp...

  19. Precipitation of Calcite during the Deposition of Paleogene Sangkarewang Oil Shale, Ombilin Basin, West Sumatra, Indonesia

    Directory of Open Access Journals (Sweden)

    Agus Haris Widayat

    2015-09-01

    Full Text Available DOI: 10.17014/ijog.2.3.185-197Geochemical and petrographical analyses were carried out to investigate the occurrence of calcite in theformer Ombilin lacustrine lake. The study involves eight samples taken from a 56 m long drill core of Sangkarewangoil shale. Geochemical investigation showed that the samples consist of varied terrigenous input represented by Si, Al, K, and Ti, and autochthonous input represented by S, total organic carbon (TOC, and d13C of bulk organic matter. Along the drill core profile the abundance of autochthonous input decreases upwards, while that of terrigenous input oppositely increases upwards. Petrographical analysis revealed that calcite is a major mineral in the samples. In this study, the abundance of calcite could be represented by the abundance of Ca, as calcite is the only significant Ca containing mineral. Ca is abundant in the samples (8.4% in average and its concentration varies similarly with those of S, TOC, and d13C, suggesting that the element as well as calcite incorporates the autochthonous input. Thevariation of calcite abundance in the drill core profile is considered to be related with primary productivity changes during the development of the former lake. Higher primary productivity represented by more positive of d13C value(-24.8‰ during the deposition of the lower part of the drill core profile promoted the higher amount of deposited organic matter. In such environment, the supersaturation of carbonate ion in lake water was also reached and significant precipitation of authigenic calcite occurred. As the lake developed, the primary productivity decreased as indicated by more negative of d13C value (eventually -26.8‰. This condition led to the decreases of deposited organic matterand calcite in the lake sediments.

  20. Calcium-magnesium carbonate solid solutions from Holocene conglomerate cements and travertines in the Coast Range of California

    Science.gov (United States)

    Barnes, I.; O'Neil, J.R.

    1971-01-01

    Two calcium-magnesium carbonate solid solutions form Holocene travertines and conglomerate cements in fresh water stream channels of the Coast Range of California. Calcite does not yield the {015} diffraction maximum. The {006} diffraction maximum is lacking over most of the range of composition of calcite. Calcite has compositions from CaCO3 to Ca0.5Mg0.5CO3. Dolomite yields both the {006} and {015} diffraction maxima over its entire composition range, Ca0.6Mg0.4CO3 to Ca0.5Mg0.5CO3. The Ca-Mg carbonates form in isotopic equilibrium and thermodynamic disequilibrium from dispersion of Ca2+-rich water into CO32--rich water within the alluvium. The stable isotope data suggest that all the Mg-rich carbonates are primary precipitates and not a result of Mg-substitution in precursor CaCO3. There is a correlation between ??C13 and Mg content of the carbonates which predicts a 5%. fractionation of C13 between dolomite and calcite at sedimentary temperatures. C14 is incorporated in Ca-Mg carbonates forming from C13-poor meteoric waters and C13-rich waters from Cretaceous sediments. C14 ages of the Ca-Mg carbonates are apparent, and cannot be corrected to absolute values. Solution rates of calcite decrease with increasing MgCO3 content; dolomite dissolves slower than any calcite. ?? 1971.

  1. Sociality and oxytocin and vasopressin in the brain of male and female dominant and subordinate mandarin voles.

    Science.gov (United States)

    Qiao, Xufeng; Yan, Yating; Wu, Ruiyong; Tai, Fadao; Hao, Ping; Cao, Yan; Wang, Jianli

    2014-02-01

    The dominant-subordinate hierarchy in animals often needs to be established via agonistic encounters and consequently affects reproduction and survival. Differences in brain neuropeptides and sociality among dominant and subordinate males and females remain poorly understood. Here we explore neuropeptide levels and sociality during agonistic encounter tests in mandarin voles. We found that dominant mandarin voles engaged in higher levels of approaching, investigating, self-grooming and exploring behavior than subordinates. Dominant males habituated better to a stimulus vole than dominant females. Dominant males displayed significantly less oxytocin-immunoreactive neurons in the paraventricular nuclei and more vasopressin-immunoreactive neurons in the paraventricular nuclei, supraoptic nuclei, and the lateral and anterior hypothalamus than subordinates. Dominant females displayed significantly more vasopressin-immunoreactive neurons in the lateral hypothalamus and anterior hypothalamus than subordinates. Sex differences were found in the level of oxytocin and vasopressin. These results indicate that distinct parameters related to central nervous oxytocin and vasopressin are associated with behaviors during agonistic encounters in a sex-specific manner in mandarin voles.

  2. The need for power, need for influence, sense of power, and directiveness in female and male superiors and subordinates

    Directory of Open Access Journals (Sweden)

    Dagna Kocur

    2017-12-01

    Full Text Available Background The purpose of the study was to examine the phenomenon of power within an organisation from the vantage point of gender, the occupied position, earnings, and the number of subordinates. Participants and procedure The sample group comprised 107 female and 98 male participants. The mean age was 42.14 years (SD = 11.73. The study covered 100 superiors and 105 subordinates. The research tools were: the Need for Power and Influence Questionnaire (Bennett, 1988, the Personal Sense of Power Scale (Anderson, John, & Keltner, 2012, and the Directiveness Scale SD (Ray, 1976. Results The superiors scored significantly higher on the need for power, need for influence, and directiveness. They also scored higher in terms of the need for power in relations with other people, with colleagues, and in superior-subordinate relations. The number of male leaders was conspicuously greater than the number of female leaders. Furthermore, women had fewer subordinates than men and earned less than men. Female participants scored lower on the sense of power and the need for power scales. Conclusions Occupying either an executive or subordinate position differentiates between women and men in terms of sense of power in interpersonal relationships. The findings on sense of power in the professional context may be applied in organisational psychology in order to increase employees’ competence and qualifications.

  3. Chromium isotopic fractionation in aquatic systems and foraminiferal calcite

    Science.gov (United States)

    Wang, X.; Wu, W.; Reinhard, C. T.; Planavsky, N.

    2016-12-01

    The stable chromium (Cr) isotope system is an emerging proxy for studying the reduction/oxidation (redox) state of the early earth. However, the distribution and isotopic composition of Cr in many modern environments is still poorly known. For this reason, Cr isotope fractionation during biological processes, in rivers, estuaries, seawaters, and modern sediments need to be constrained to calibrate this potentially very useful paleoredox proxy. Here we report concentrations and isotope systematics of dissolved and suspended Cr in the Connecticut River system, and from core-top planktonic foraminiferal calcite from the global ocean. In the Connecticut River system, soil profile samples are unfractionated from bulk silicate Earth (BSE) values. River waters range from -0.2‰ to 0.9‰ (δ53Cr expressed as 53Cr/52Cr relative to NIST SRM 979 standard), with some, but not all tributaries showing seasonal differences. Suspended particulate samples range from -0.1 to 0‰ in autumn and from 0 to 0.1‰ in spring. Modern planktonic foraminifera show a wide range of δ53Cr values, from 0.2‰ to 2.2‰. Such variability seems to be controlled by both seawater heterogeneity and biological fractionation. In summary, weathering environments studied so far suggest wide variability of δ53Cr in rivers and weathered rocks, but with indiscernible correlation with climate types (temperate vs. tropical). In addition, large spatial variability has been detected in the modern seawater and large biological fractionation has been observed during marine biological calcification. These observations provide important guidelines for interpreting the ancient Cr isotope record.

  4. Transformation and Crystallization Energetics of Synthetic and Biogenic Amorphous Calcium Carbonate

    Energy Technology Data Exchange (ETDEWEB)

    Radha, A. V. [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States); Forbes, Tori Z. [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States); Killian, Christopher E. [Univ. of Wisconsin, Madison, WI (United States); Gilbert, P.U.P.A [Univ. of Wisconsin, Madison, WI (United States); Navrotsky, Alexandra [Peter A. Rock Thermochemistry Lab. and Nanomaterials in the Environment, Agriculture, and Technology Organized Research Unit (NEAT ORU), Univ. of California, Davis, CA (United States)

    2010-01-01

    Amorphous calcium carbonate (ACC) is a metastable phase often observed during low temperature inorganic synthesis and biomineralization. ACC transforms with aging or heating into a less hydrated form, and with time crystallizes to calcite or aragonite. The energetics of transformation and crystallization of synthetic and biogenic (extracted from California purple sea urchin larval spicules, Strongylocentrotus purpuratus) ACC were studied using isothermal acid solution calorimetry and differential scanning calorimetry. Transformation and crystallization of ACC can follow an energetically downhill sequence: more metastable hydrated ACC → less metastable hydrated ACC→anhydrous ACC ~ biogenic anhydrous ACC→vaterite → aragonite → calcite. In a given reaction sequence, not all these phases need to occur. The transformations involve a series of ordering, dehydration, and crystallization processes, each lowering the enthalpy (and free energy) of the system, with crystallization of the dehydrated amorphous material lowering the enthalpy the most. ACC is much more metastable with respect to calcite than the crystalline polymorphs vaterite or aragonite. The anhydrous ACC is less metastable than the hydrated, implying that the structural reorganization during dehydration is exothermic and irreversible. Dehydrated synthetic and anhydrous biogenic ACC are similar in enthalpy. The transformation sequence observed in biomineralization could be mainly energetically driven; the first phase deposited is hydrated ACC, which then converts to anhydrous ACC, and finally crystallizes to calcite. The initial formation of ACC may be a first step in the precipitation of calcite under a wide variety of conditions, including geological CO₂ sequestration.

  5. Calcium source (image)

    Science.gov (United States)

    Getting enough calcium to keep bones from thinning throughout a person's life may be made more difficult if that person has ... as a tendency toward kidney stones, for avoiding calcium-rich food sources. Calcium deficiency also effects the ...

  6. Calcium and bones (image)

    Science.gov (United States)

    Calcium is one of the most important minerals for the growth, maintenance, and reproduction of the human ... body, are continually being re-formed and incorporate calcium into their structure. Calcium is essential for the ...

  7. Calcium hydroxide poisoning

    Science.gov (United States)

    Hydrate - calcium; Lime milk; Slaked lime ... Calcium hydroxide ... These products contain calcium hydroxide: Cement Limewater Many industrial solvents and cleaners (hundreds to thousands of construction products, flooring strippers, brick cleaners, cement ...

  8. Calcium Pyrophosphate Deposition (CPPD)

    Science.gov (United States)

    ... Patient / Caregiver Diseases & Conditions Calcium Pyrophosphate Deposition (CPPD) Calcium Pyrophosphate Deposition (CPPD) Fast Facts The risk of ... young people, too. Proper diagnosis depends on detecting calcium pyrophosphate crystals in the fluid of an affected ...

  9. Calcium blood test

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/003477.htm Calcium blood test To use the sharing features on this page, please enable JavaScript. The calcium blood test measures the level of calcium in the blood. ...

  10. Improvement of calcium mineral separation contrast using anionic reagents: electrokinetics properties and flotation

    Science.gov (United States)

    Lafhaj, Z.; Filippov, L. O.; Filippova, I. V.

    2017-07-01

    The flotation separation of salt type calcium minerals is problematic, due to the similarities in their same active Ca2+ related site for interaction with anionic collectors and similar physicochemical characteristics such as solubility, zero-point charge, surface speciation and Ca-site density. The work was performed to achieve effective and selective separation of the calcium-minerals using pure minerals samples: orange calcite with Mg impurities, optic calcite with impurities level and an apatite. The pure samples surface was examined using techniques sensitive near-surface like infrared spectroscopy (FTIR) and chemical composition was obtained by ICPMS. The isoelectric point (IEP) and point of zero charge (PZC) in electrolyte were recorded using electrophoresis method at different ionic strengths of the solution. Mechanisms of charge development at the mineral-water interface are discussed. The time of contact as important parameter for the charge equilibrium was deduced from kinetics study and fixed to 30 minutes. The difference in the values obtained between IEP and PZSE can be explained by the presence of a specific adsorption of cations and anions on the surface. The effect of pure anionic collectors such as oleic and linoleic acid were studied. At low pH, both collectors lead to a good recovery for the calcites. The flotation recovery of optic calcite at pH 9 with sodium oleate is higher than with sodium linoleate. At alkaline pH, apatite showed a better recovery with sodium linoleate.

  11. Nanoparticle tracers in calcium carbonate porous media

    KAUST Repository

    Li, Yan Vivian

    2014-07-15

    Tracers are perhaps the most direct way of diagnosing subsurface fluid flow pathways for ground water decontamination and for natural gas and oil production. Nanoparticle tracers could be particularly effective because they do not diffuse away from the fractures or channels where flow occurs and thus take much less time to travel between two points. In combination with a chemical tracer they can measure the degree of flow concentration. A prerequisite for tracer applications is that the particles are not retained in the porous media as the result of aggregation or sticking to mineral surfaces. By screening eight nanoparticles (3-100 nm in diameter) for retention when passed through calcium carbonate packed laboratory columns in artificial oil field brine solutions of variable ionic strength we show that the nanoparticles with the least retention are 3 nm in diameter, nearly uncharged, and decorated with highly hydrophilic polymeric ligands. The details of these column experiments and the tri-modal distribution of zeta potential of the calcite sand particles in the brine used in our tests suggests that parts of the calcite surface have positive zeta potential and the retention of negatively charged nanoparticles occurs at these sites. Only neutral nanoparticles are immune to at least some retention. © 2014 Springer Science+Business Media.

  12. Effect of pH on the precipitation of synthetic CaCO3 polymorphs and determination of Mg/Ca ratios in synthetic low-magnesium calcite: An experimental investigation

    Science.gov (United States)

    Gabitov, R. I.; Weremeichik, J. M.; Novak, A.; Sadekov, A.; Thirumalai, R. V. K. G.

    2016-02-01

    The intent of the work presented is to determine the effect which the Mg/Ca ratio in fluid has on the Mg partition coefficient (KMg) between synthetically precipitated low-magnesium calcite and solution. In nature, planktonic foraminifera produce low-magnesium calcite with distinct Mg/Ca that is typically found to be within the range of 1.4 to 10 mmol/mol (e.g. Regenberg et al., 2009; Sadekov et al., 2009). Our intent was to replicate Mg/Ca found in foraminifera by conducting experiments where low-Mg calcite was grown inorganically at a near-constant salinity and temperature. Synthetic low-Mg calcite was precipitated using a continuous pumping method whereby NaHCO3 and Mg-doped CaCl2 solutions were pumped into a NaCl solution. Continuous pumping allows for delivery of solutions to a reaction vessel at a constant rate while simultaneously maintaining fluid volume by removing fluid at a constant rate equal to the delivery rate. In order to vary the Mg/Ca ratio while keeping salinity near-constant, magnesium and calcium molar concentrations were varied but the sum of the concentrations was kept equal to the concentration of NaHCO3 or Na2CO3. Optical microscopy analysis of samples showed that the use of Na2CO3 as the carbonate ion source in experiments precipitated predominately aragonite with needle-like crystals whereas use of NaHCO3 yielded calcite with rhombohedral crystals. Powder XRD analysis of a sample collected from one of the Na2CO3 experiments confirmed that the dominant CaCO3 polymorph precipitated was aragonite. This suggests that aragonite is being produced at higher pH values using Na2CO3 and calcite is being produced at lower values of pH using NaHCO3. We intend use XRD, AAS, and ICP-MS to confirm that rhombohedral crystals are calcite and determine Mg/Ca of fluid and those crystals. ReferencesRegenberg et al. (2009) Earth Planet. Sci. Lett., 278, doi: 10.1016/j.epsl.2008.12.019. Sadekov et al. (2009) Paleoceanography, 24, doi: 10.1029/2008PA001664.

  13. Study of calcium carbonate and sulfate co-precipitation

    KAUST Repository

    Zarga, Y.

    2013-06-01

    Co-precipitation of mineral based salts in scaling is still not well understood and/or thermodynamically well defined in the water industry. This study focuses on investigating calcium carbonate (CaCO3) and sulfate mixed precipitation in scaling which is commonly observed in industrial water treatment processes including seawater desalination either by thermal-based or membrane-based processes. Co-precipitation kinetics were studied carefully by monitoring several parameters simultaneously measured, including: pH, calcium and alkalinity concentrations as well as quartz microbalance responses. The CaCO3 germination in mixed precipitation was found to be different than that of simple precipitation. Indeed, the co-precipitation of CaCO3 germination time was not anymore related to supersaturation as in a simple homogenous precipitation, but was significantly reduced when the gypsum crystals appeared first. On the other hand, the calcium sulfate crystals appear to reduce the energetic barrier of CaCO3 nucleation and lead to its precipitation by activating heterogeneous germination. However, the presence of CaCO3 crystals does not seem to have any significant effect on gypsum precipitation. IR spectroscopy and the Scanning Electronic Microscopy (SEM) were used to identify the nature of scales structures. Gypsum was found to be the dominant precipitate while calcite and especially vaterite were found at lower proportions. These analyses showed also that gypsum crystals promote calcite crystallization to the detriment of other forms. © 2013 Elsevier Ltd.

  14. Chemical and physical evolution of dolomite precipitation at 180°C and 220°C from calcite and aragonite seeds

    Science.gov (United States)

    Kell-Duivestein, Isaac; Dietzel, Martin; Mavromatis, Vasileios

    2016-04-01

    In this present study an experimental approach is taken to gain a better understanding of secondary dolomite formation under diagenetic hydrothermal conditions. A series of 60 experiments were set up in closed bomb reactors with Teflon inserts to simulate exposure of calcium carbonate materials of (i) aragonite and (ii) calcite to hydrothermal conditions. 30 reactors were prepared using calcite as a seed material and 30 using aragonite. In each experiment 330mg of the seed calcium carbonate was placed in 30mL of 0.2M MgCl2 solution along with 252mg NaHCO3 to balance charges. 15 of each the calcite and aragonite prepared reactors were placed in an oven at 180°C and 15 of each at 220°C. Samples were then progressively removed from the ovens beginning in short time intervals and increasing the time apart as the phase transformations became less rapid (ie. after 3, 6, 13, 21, 31, 56 days *ongoing*). Samples were separated into fluid and solid phases by filtration for separate analysis. Fluids were analysed by titration for alkalinity and ICP-OES for elemental concentrations of major cations to determine the migration of major cations between the calcium carbonate seed material and the reaction fluid. Solid samples were analysed with FTIR-spectroscopy and X-ray diffraction of powdered smears on glass loading slides to identify the present mineral phases. Rietveld analysis was conducted on the XRD patterns to quantify the mineral phases and to determine the stoichiometry and the superstructure of the formed magnesite and dolomite. Although experiments are still running, several trends have been identified. Transformation of the aragonite seed material occurs at a much faster rate than transformation of the calcite seed material, with each precursor material first transforming into a Ca-rich magnesite. With increased reaction time the Ca-rich magnesite recrystallizes to purer phases of magnesite, the Ca concentration of the fluid increases as the Ca is liberated into

  15. Chronic Subordination Stress Induces Hyperphagia and Disrupts Eating Behavior in Mice Modeling Binge-Eating-Like Disorder

    Science.gov (United States)

    Razzoli, Maria; Sanghez, Valentina; Bartolomucci, Alessandro

    2015-01-01

    Background: Eating disorders are associated with physical morbidity and appear to have causal factors like stressful life events and negative affect. Binge-eating disorder (BED) is characterized by eating in a discrete period of time a larger than normal amount of food, a sense of lack of control over eating, and marked distress. There are still unmet needs for the identification of mechanisms regulating excessive eating, which is in part due to the lack of appropriate animal models. We developed a naturalistic murine model of subordination stress-induced hyperphagia associated with the development of obesity. Here, we tested the hypotheses that the eating responses of subordinate mice recapitulate the BED and that limiting hyperphagia could prevent stress-associated metabolic changes. Methods: Adult male mice were exposed to a model of chronic subordination stress (CSS) associated with the automated acquisition of food intake and we performed a detailed meal pattern analysis. Additionally, using a pair-feeding protocol we tested the hypothesis that the manifestation of obesity and the metabolic syndrome could be prevented by limiting hyperphagia. Results: The architecture of feeding of subordinate mice was disrupted during the stress protocol due to disproportionate amount of food ingested at higher rate and with shorter satiety ratio than control mice. Subordinate mice hyperphagia was further exacerbated in response to either hunger or to the acute application of a social defeat. Notably, the obese phenotype but not the fasting hyperglycemia of subordinate mice was abrogated by preventing hyperphagia in a pair-feeding paradigm. Conclusion: Overall, these results support the validity of our CSS to model BED allowing for the determination of the underlying molecular mechanisms and the generation of testable predictions for innovative therapies, based on the understanding of the regulation and the control of food intake. PMID:25621284

  16. Fire disturbance disrupts an acacia ant-plant mutualism in favor of a subordinate ant species.

    Science.gov (United States)

    Sensenig, Ryan L; Kimuyu, Duncan K; Ruiz Guajardo, Juan C; Veblen, Kari E; Riginos, Corinna; Young, Truman P

    2017-05-01

    Although disturbance theory has been recognized as a useful framework in examining the stability of ant-plant mutualisms, very few studies have examined the effects of fire disturbance on these mutualisms. In myrmecophyte-dominated savannas, fire and herbivory are key drivers that could influence ant-plant mutualisms by causing complete colony mortality and/or decreasing colony size, which potentially could alter dominance hierarchies if subordinate species are more fire resilient. We used a large-scale, replicated fire experiment to examine long-term effects of fire on acacia-ant community composition. To determine if fire shifted ant occupancy from a competitive dominant to a subordinate ant species, we surveyed the acacia-ant community in 6-7 yr old burn sites and examined how the spatial scale of these burns influenced ant community responses. We then used two short-term fire experiments to explore possible mechanisms for the shifts in community patterns observed. Because survival of ant colonies is largely dependent on their ability to detect and escape an approaching fire, we first tested the evacuation response of all four ant species when exposed to smoke (fire signal). Then to better understand how fire and its interaction with large mammal herbivory affect the density of ants per tree, we quantified ant worker density in small prescribed burns within herbivore exclusion plots. We found clear evidence suggesting that fire disturbance favored the subordinate ant Crematogaster nigriceps more than the dominant and strong mutualist ant C. mimosae, whereby C. nigriceps (1) was the only species to occupy a greater proportion of trees in 6-7 yr old burn sites compared to unburned sites, (2) had higher burn/unburn tree ratios with increasing burn size, and (3) evacuated significantly faster than C. mimosae in the presence of smoke. Fire and herbivory had opposite effects on ant density per meter of branch for both C. nigriceps and C. mimosae, with fire

  17. Calcium carbonate precipitation by heterotrophic bacteria isolated from biofilms formed on deteriorated ignimbrite stones: influence of calcium on EPS production and biofilm formation by these isolates.

    Science.gov (United States)

    López-Moreno, Angélica; Sepúlveda-Sánchez, José David; Mercedes Alonso Guzmán, Elia Mercedes; Le Borgne, Sylvie

    2014-01-01

    Heterotrophic CaCO3-precipitating bacteria were isolated from biofilms on deteriorated ignimbrites, siliceous acidic rocks, from Morelia Cathedral (Mexico) and identified as Enterobacter cancerogenus (22e), Bacillus sp. (32a) and Bacillus subtilis (52g). In solid medium, 22e and 32a precipitated calcite and vaterite while 52g produced calcite. Urease activity was detected in these isolates and CaCO3 precipitation increased in the presence of urea in the liquid medium. In the presence of calcium, EPS production decreased in 22e and 32a and increased in 52g. Under laboratory conditions, ignimbrite colonization by these isolates only occurred in the presence of calcium and no CaCO3 was precipitated. Calcium may therefore be important for biofilm formation on stones. The importance of the type of stone, here a siliceous stone, on biological colonization is emphasized. This calcium effect has not been reported on calcareous materials. The importance of the effect of calcium on EPS production and biofilm formation is discussed in relation to other applications of CaCO3 precipitation by bacteria.

  18. Chicken eggshells (Gallus gallus domesticus) as carbonate calcium source for biomaterials production; Casca de ovo de galinha caipira (gallus gallus domesticus), como fonte de carbonato de calcio para producao de biomateriais

    Energy Technology Data Exchange (ETDEWEB)

    Junior, E.A. de O.; Bastos, J.S.B.; Silva, R.C. de S.; Macedo, H.R.A.; Macedo, M. O.C.; Bradim, A.S., E-mail: angelcassiasasilva@gmail.com [Instituto Federal de Educacao, Ciencia e Tecnologia do Piaui (FIPI), PI (Brazil)

    2016-07-01

    The eggshells present high levels of calcium carbonate. Calcium carbonate obtained from eggshells has been used in the production of biomaterials with applications in bone regeneration, since it is biocompatible. In this work, calcium carbonate was obtained from eggshells to prepare a composite biomaterial. The presence of calcium carbonate bands was observed through spectrometry in the infrared region. Scanning electron microscopy showed the presence of calcium carbonate particles with different sizes and shapes. Carbonate predominance in the form of calcite was also observed through the X-ray diffraction.

  19. The subjunctive, a marker of 'subordinance'? A comparison between German and Spanish

    Directory of Open Access Journals (Sweden)

    Hans Jörg Busch

    2014-05-01

    Full Text Available Moods as inflectional paradigms can only have a very general value and function, similar to other verbal categories such as tense and aspect. A comparison with German shows that the subjunctive functions as a marker of subordination and signals that the proposition in which it stands is incomplete and must be interpreted with the help of other contextual elements, for example the meaning of the main or matrix verb, a characteristic that has also been called procedural. Therefore only the indicative can be used to express independent statements. All the communicative functions of the subjunctive, for example to express politeness, will be explained as a result of its procedural character. The article clarifies why the subjunctive is also used with factual propositions, for example after verbs of emotions and ‘aunque’. (37,402 characters with spaces

  20. From Ambiguity to Deceptiveness: the Case of Hybrid since- Subordinates in English

    Directory of Open Access Journals (Sweden)

    Bénédicte GUILLAUME

    2012-03-01

    Full Text Available Lorsqu’il est utilisé en tant que subordonnant, since peut introduire une subordonnée circonstancielle de temps ou bien de cause. Cet article s’intéresse aux cas dans lesquels une telle polysémie au niveau du subordonnant déclenche une ambiguïté quant à la nature temporelle ou causale de l’utilisation de la subordonnée. En plus du recours au contexte endophorique ou exophorique, nous proposons des critères syntaxiques de désambigüisation, mis au jour grâce à l’étude d’un corpus de près de cinq cent exemples pris dans le British National Corpus, un corpus d’anglais contemporain de cent millions de mots. En dépit de tout cela, une petite minorité d’exemples reste inclassable, remplissant ainsi les conditions pour être considérés comme « hybrides » en fonction de la définition que nous en proposons, à savoir des subordonnées permettant de remettre en cause la division traditionnelle entre les catégories de subordonnées en anglais, dans la mesure où ils possèdent au moins une caractéristique déviante par rapport à la catégorie à laquelle ils semblent appartenir en fonction de tous leurs autres traits. De tels phénomènes rendent nécessaires la prise en compte d’un « reste », selon la terminologie de Jean-Jacques Lecercle, dans la grammaire d’une langue donnée.When since is used as a subordinator,it can introduce either a temporal adverbial clause or a causal one. My purpose in this paper is to study cases in which such a polysemy at the level of the subordinator results in the production of subordinates whose meaning proves to be ambiguous between the categories of time and cause. In addition to the taking into account of the context, whether exophoric or endophoric, I put forward a series of syntactic criteria which should help disambiguate between the two possible interpretations. These are based on the study of the characteristics of nearly five-hundred examples of since- clauses taken

  1. Brownian yet Non-Gaussian Diffusion: From Superstatistics to Subordination of Diffusing Diffusivities

    Directory of Open Access Journals (Sweden)

    Aleksei V. Chechkin

    2017-04-01

    Full Text Available A growing number of biological, soft, and active matter systems are observed to exhibit normal diffusive dynamics with a linear growth of the mean-squared displacement, yet with a non-Gaussian distribution of increments. Based on the Chubinsky-Slater idea of a diffusing diffusivity, we here establish and analyze a minimal model framework of diffusion processes with fluctuating diffusivity. In particular, we demonstrate the equivalence of the diffusing diffusivity process with a superstatistical approach with a distribution of diffusivities, at times shorter than the diffusivity correlation time. At longer times, a crossover to a Gaussian distribution with an effective diffusivity emerges. Specifically, we establish a subordination picture of Brownian but non-Gaussian diffusion processes, which can be used for a wide class of diffusivity fluctuation statistics. Our results are shown to be in excellent agreement with simulations and numerical evaluations.

  2. Detecting Microbially Induced Calcite Precipitation in a Model Well-Bore Using Downhole Low-Field NMR.

    Science.gov (United States)

    Kirkland, Catherine M; Zanetti, Sam; Grunewald, Elliot; Walsh, David O; Codd, Sarah L; Phillips, Adrienne J

    2017-02-07

    Microbially induced calcite precipitation (MICP) has been widely researched recently due to its relevance for subsurface engineering applications including sealing leakage pathways and permeability modification. These applications of MICP are inherently difficult to monitor nondestructively in time and space. Nuclear magnetic resonance (NMR) can characterize the pore size distributions, porosity, and permeability of subsurface formations. This investigation used a low-field NMR well-logging probe to monitor MICP in a sand-filled bioreactor, measuring NMR signal amplitude and T2 relaxation over an 8 day experimental period. Following inoculation with the ureolytic bacteria, Sporosarcina pasteurii, and pulsed injections of urea and calcium substrate, the NMR measured water content in the reactor decreased to 76% of its initial value. T2 relaxation distributions bifurcated from a single mode centered about approximately 650 ms into a fast decaying population (T2 less than 10 ms) and a larger population with T2 greater than 1000 ms. The combination of changes in pore volume and surface minerology accounts for the changes in the T2 distributions. Destructive sampling confirmed final porosity was approximately 88% of the original value. These results indicate the low-field NMR well-logging probe is sensitive to the physical and chemical changes caused by MICP in a laboratory bioreactor.

  3. Microbial dissolution of calcite at T = 28 °C and ambient pCO 2

    Science.gov (United States)

    Jacobson, Andrew D.; Wu, Lingling

    2009-04-01

    This study used batch reactors to quantify the mechanisms and rates of calcite dissolution in the presence and absence of a single heterotrophic bacterial species ( Burkholderia fungorum). Experiments were conducted at T = 28°C and ambient pCO 2 over time periods spanning either 21 or 35 days. Bacteria were supplied with minimal growth media containing either glucose or lactate as a C source, NH 4+ as an N source, and H 2PO 4- as a P source. Combining stoichiometric equations for microbial growth with an equilibrium mass-balance model of the H 2O-CO 2-CaCO 3 system demonstrates that B. fungorum affected calcite dissolution by modifying pH and alkalinity during utilization of ionic N and C species. Uptake of NH 4+ decreased pH and alkalinity, whereas utilization of lactate, a negatively charged organic anion, increased pH and alkalinity. Calcite in biotic glucose-bearing reactors dissolved by simultaneous reaction with H 2CO 3 generated by dissolution of atmospheric CO 2 (H 2CO 3 + CaCO 3 → Ca 2+ + 2HCO 3-) and H + released during NH 4+ uptake (H + + CaCO 3 → Ca 2+ + HCO 3-). Reaction with H 2CO 3 and H + supplied ˜45% and 55% of the total Ca 2+ and ˜60% and 40% of the total HCO 3-, respectively. The net rate of microbial calcite dissolution in the presence of glucose and NH 4+ was ˜2-fold higher than that observed for abiotic control experiments where calcite dissolved only by reaction with H 2CO 3. In lactate bearing reactors, most H + generated by NH 4+ uptake reacted with HCO 3- produced by lactate oxidation to yield CO 2 and H 2O. Hence, calcite in biotic lactate-bearing reactors dissolved by reaction with H 2CO 3 at a net rate equivalent to that calculated for abiotic control experiments. This study suggests that conventional carbonate equilibria models can satisfactorily predict the bulk fluid chemistry resulting from microbe-calcite interactions, provided that the ionic forms and extent of utilization of N and C sources can be constrained. Because

  4. The Influence of Kinetic Growth Factors on the Clumped Isotope Composition of Calcite

    Science.gov (United States)

    Hunt, J. D.; Watkins, J. M.; Tripati, A.; Ryerson, F. J.; DePaolo, D. J.

    2014-12-01

    Clumped isotope paleothermometry is based on the association of 13C and 18O within carbonate minerals. Although the influence of temperature on equilibrium 13C-18O bond ordering has been studied, recent oxygen isotope studies of inorganic calcite demonstrate that calcite grown in laboratory experiments and in many natural settings does not form in equilibrium with water. It is therefore likely that the carbon and clumped isotope composition of these calcite crystals are not representative of true thermodynamic equilibrium. To isolate kinetic clumped isotope effects that arise at the mineral-solution interface, clumped isotopic equilibrium of DIC species must be maintained. This can be accomplished by dissolving the enzyme carbonic anhydrase (CA) into the solution, thereby reducing the time required for isotopic equilibration of DIC species by approximately two orders of magnitude between pH 7.7 and 9.3. We conduct calcite growth experiments aimed specifically at measuring the pH-dependence of kinetic clumped isotope effects during non-equilibrium precipitation of calcite. We precipitated calcite from aqueous solution at a constant pH and controlled supersaturation over the pH range 7.7-9.3 in the presence of CA. For each experiment, a gas mixture of N2 and CO2 is bubbled through a beaker of solution without seed crystals. As CO2 from the gas dissolves into solution, calcite crystals grow on the beaker walls. The pH of the solution is maintained by use of an autotitrator with NaOH as the titrant. We control the temperature, pH, the pCO2 of the gas inflow, and the gas inflow rate, and monitor the total alkalinity, the pCO2 of the gas outflow, and the amount of NaOH added. A constant crystal growth rate of ~1.6 mmol/m2/hr is maintained over all experiments. Results from these experiments are compared to predictions from a recently-developed isotopic ion-by-ion growth model of calcite. The model describes the rate, temperature and pH dependence of oxygen isotope uptake

  5. 88Sr/86Sr fractionation and calcite accumulation rate in the Sea of Galilee

    Science.gov (United States)

    Fruchter, Noa; Lazar, Boaz; Nishri, Aminadav; Almogi-Labin, Ahuva; Eisenhauer, Anton; Beeri-Shlevin, Yaron; Stein, Mordechai

    2017-04-01

    This study uses Lake Kinneret (Sea of Galilee, northern Israel) as a natural laboratory to investigate the fractionation of the stable Sr isotope ratio (88Sr/86Sr) during precipitation of authigenic calcite in the water column, and evaluates the dependence of the fractionation 87Sr/86Sr and 88Sr/86Sr ratios in the freshwater and brines that enter the lake are used to calculate the relative contributions of these sources to the Sr budget of the modern lake. The 87Sr/86Sr and 88Sr/86Sr ratios were measured in authigenic calcite, living Melanopsis shells, lake water and various water sources to the lake. While the lake's 87Sr/86Sr ratios are determined by the mixture of freshwater supplied mainly by the Jordan River and saline springs, the 88Sr/86Sr ratios of the lake reflect a more complex mass balance that includes the effect of isotopic fractionation during the precipitation of authigenic calcite. The data show a significant long-term effect of calcite accumulation on the stable Sr isotope ratio of the lake, increasing the 88Sr/86Sr of the water by 0.04 ‰. In contrast to the authigenic calcite, biogenic aragonite shells are shown to have a rather constant 88Sr/86Sr water-CaCO3 fractionation of precipitation of coralline and chemical aragonite from seawater and the precipitation of authigenic calcite from various continental waters. The field data of the present study suggests that the fractionation of 88Sr/86Sr in authigenic calcite represents a kinetic fractionation that varies with precipitation rate, in addition to the constant thermodynamic property. Massive precipitation of authigenic calcite occurs in Lake Kinneret during the spring phytoplankton bloom as the latter increases considerably the degree of calcite saturation. The correlation between accumulation rate can be therefore used as a tool to reconstruct paleo-environmental variations by analyzing the 88Sr/86Sr ratio in authigenic CaCO3 in core sections.

  6. Strong kinetic effects on Sr/Ca ratios in the calcitic bivalve Pecten maximus

    OpenAIRE

    A. Lorrain; Gillikin, D. P.; Paulet, Y.-M.; Chauvaud, L.; Le Mercier, A.; Navez, J.; André, L.

    2005-01-01

    Although Sr/Ca ratios in abiogenic calcite are strongly controlled by precipitation rates, such a kinetic effect has never been demonstrated in calcitic bivalve shells. Therefore, we report Sr/Ca ratios together with daily growth rates in the calcitic shells of four individuals of the bivalve Pecten maximus (age class I). Ratios of Sr/Ca were found to be variable among individuals that grew at the same location, illustrating that vital effects dominate over environmental controls. Although da...

  7. Oxygen isotope fractionation processes in the water-calcite-aragonite system

    Science.gov (United States)

    Fohlmeister, Jens; Spötl, Christoph; Plessen, Birgit; Tjallingii, Rik; Schröder-Ritzrau, Andrea; Frank, Norbert; Arps, Jennifer; Leutz, Kathrin; Vollweiler, Nicole; Trüssel, Martin

    2017-04-01

    The O isotopic composition of speleothems in their pure calcite or pure aragonite polymorphs provides valuable insight into past climate variability. However, robust climatic interpretations become difficult when both polymorphs are present either in different growth layers or as intergrown fabrics. Experimental studies show that the O isotope fractionation between the dissolved carbonate species and CaCO3 is about 0.75‰ (at 10°C) larger for aragonite than for calcite (e.g., Kim et al., 2007, Kim and O'Neil, 1997). The temperature dependence of this offset is negligible for temperature variations typical of most cave systems. However, cave analogue experiments examining this offset are still lacking. Here, we present stable O isotope measurements of a Holocene speleothem from the Swiss Alps, which shows exactly one calcite-aragonite transition along individual growth layers. Oxygen isotope measurements along 'Hendy test'-like traverses across those transitions provide insight into the fractionation behavior of the water-calcite vs. water-aragonite system. We observed a fractionation offset smaller than predicted by laboratory experiments that varies by at least a factor of two. In addition, the observed variations correlate positively with growth rate and negatively with the isotopic composition of the calcite precipitating at the growth axis. The reason for this behavior is still unclear. Trace element analyses across the transitions of growth layers are planned to help understanding this pattern.

  8. Strong kinetic effects on Sr/Ca ratios in the calcitic bivalve Pecten maximus

    Science.gov (United States)

    Lorrain, Anne; Gillikin, David P.; Paulet, Yves-Marie; Chauvaud, Laurent; Le Mercier, Alain; Navez, Jacques; André, Luc

    2005-12-01

    Although Sr/Ca ratios in abiogenic calcite are strongly controlled by precipitation rates, such a kinetic effect has never been demonstrated in calcitic bivalve shells. Therefore, we report Sr/Ca ratios together with daily growth rates in the calcitic shells of four individuals of the bivalve Pecten maximus (age class I). Ratios of Sr/Ca were found to be variable among individuals that grew at the same location, illustrating that vital effects dominate over environmental controls. Although daily growth rate was correlated with shell Sr/Ca ratios, it explained only half of the Sr/Ca variations. However, daily shell surface area increment, an estimation of the total quantity of carbonate precipitated for a given time, explained 74% of the Sr/Ca variability in the shells of P. maximus. This proves, for the first time in a calcitic bivalve, that shell Sr/Ca partitioning is mainly controlled by kinetic effects. The Sr/Ca ratio should therefore be tested as a potential proxy of calcification rate in modern or fossil calcitic biocarbonates.

  9. Selective Separation of Fluorite, Barite and Calcite with Valonea Extract and Sodium Fluosilicate as Depressants

    Directory of Open Access Journals (Sweden)

    Zijie Ren

    2017-02-01

    Full Text Available Fluorite, barite and calcite are important industry minerals. However, they often co-exist, presenting difficulty in selectively separating them due to their similar surface properties. In this study, valonea extract and sodium fluosilicate were used as depressants to selectively separate them by flotation, with sodium oleate as the collector. The single mineral flotation results showed that valonea extract displayed the strongest depression on calcite, while sodium fluosilicate displayed the strongest depression on barite. These two depressants allowed selective separation of the three minerals through sequential flotation. The flotation of mixed minerals showed that 94% of the calcite was successfully depressed by the valonea extract, and 95% recovery of the fluorite was achieved in the subsequent flotation with sodium fluosilicate depressing barite. The different depressant–mineral interactions were investigated via electro-kinetic studies and molecular dynamics (MD simulations using the Materials Studio 6.0 program. The valonea extract exhibited the strongest adsorption on the calcite surface, and sodium fluosilicate exhibited the strongest adsorption on the barite surface, which prevented oleate species from reacting with Ca2+ or Ba2+ surface sites. This study provides useful guidance for how to process fluorite, barite and calcite resources.

  10. 29 CFR 408.6 - Amendments to the Labor Organization Information Report filed by or on behalf of the subordinate...

    Science.gov (United States)

    2010-07-01

    ... 29 Labor 2 2010-07-01 2010-07-01 false Amendments to the Labor Organization Information Report filed by or on behalf of the subordinate labor organization. 408.6 Section 408.6 Labor Regulations... LABOR ORGANIZATION TRUSTEESHIP REPORTS § 408.6 Amendments to the Labor Organization Information Report...

  11. Chronic social subordination stress modulates glutamic acid decarboxylase (GAD) 67 mRNA expression in central stress circuits

    Science.gov (United States)

    Makinson, Ryan; Lundgren, Kerstin H.; Seroogy, Kim B.; Herman, James P.

    2015-01-01

    Chronic social subordination is a well-known precipitant of numerous psychiatric and physiological health concerns. In this study, we examine the effects of chronic social stress in the visible burrow system (VBS) on the expression of glutamic acid decarboxylase (GAD) 67 and brain-derived neurotropic factor (BDNF) mRNA in forebrain stress circuitry. Male rats in the VBS system form a dominance hierarchy, whereby subordinate males exhibit neuroendocrine and physiological profiles characteristic of chronic exposure to stress. We found that social subordination decreases GAD67 mRNA in the peri-paraventricular nucleus region of the hypothalamus and the interfascicular nucleus of the bed nucleus of the stria terminalis (BNST), and increases in GAD67 mRNA in the hippocampus, medial prefrontal cortex, and dorsal medial hypothalamus. Expression of BDNF mRNA increased in the dorsal region of the BNST, but remained unchanged in all other regions examined. Results from this study indicate that social subordination is associated with several region-specific alterations in GAD67 mRNA expression in central stress circuits, whereas changes in the expression of BDNF mRNA are limited to the BNST. PMID:26066725

  12. Forum: Interpersonal Communication in Instructional Settings. The Instructor-Student Relationship as an Alternative Form of Superior-Subordinate Relationship

    Science.gov (United States)

    Myers, Scott A.

    2017-01-01

    In this brief forum article, the author suggests studying the instructor-student relationship as a superior-subordinate relationship offers an alternative way to view how student learning occurs in the college classroom, and can provide instructional communication researchers with the opportunity to explore how structural and institutional…

  13. The Development of Subordinate Clauses in German and Swedish as L2s: A Theoretical and Methodological Camparison

    Science.gov (United States)

    Baten, Kristof; Håkansson, Gisela

    2015-01-01

    In this article, we aim to contribute to the debate about the use of subordination as a measure of language proficiency. We compare two theories of SLA--specifically, processability theory (PT; Pienemann, 1998) and dynamic systems theory (DST; de Bot, Lowie, & Verspoor, 2007)--and, more particularly, how they address the development of…

  14. Responses of biotic interactions of dominant and subordinate species to decadal warming and simulated rotational grazing in Tibetan alpine meadow.

    Science.gov (United States)

    Li, Xin'e; Zhu, Xiaoxue; Wang, Shiping; Cui, Shujuan; Luo, Caiyun; Zhang, Zhenhua; Zhang, Lirong; Jiang, Lili; Lü, Wangwang

    2018-01-18

    Warming increases competition among plant species in alpine communities by ameliorating harsh environmental conditions, such as low temperatures. Grazing, as the main human activity, may mitigate the effect of warming, as previously reported. However, it is critical to refine the effects of warming on biotic interactions among species, for example, by taking the competitive ability of species into consideration. Based on a 10-year warming and grazing experiment in a Tibetan alpine meadow, we evaluated interspecific biotic interactions of dominant and subordinate species, using the approach of interspecific spatial associations. Warming significantly increased competition between subordinate and dominant species as well as among subordinate species, but not among dominant species. Moreover, facilitation of dominant-subordinate species also increased under warming. Simulated rotational grazing had similar effects to warming, with increasing interspecific competition. Our results show that, when studying the effects of warming on biotic interactions among species, it is necessary to characterize different species pairs relative to their competitive ability, and that simulated rotational grazing does not mitigate the effects of warming in the long term. Our results also provide evidence that the spatial pattern of species is a critical mechanism in species coexistence.

  15. How to get radical creative ideas into a leader's mind? Leader's achievement goals and subordinates' voice of creative ideas

    NARCIS (Netherlands)

    Sijbom, Roy B.L.; Janssen, Onne; Van Yperen, Nico W.

    2015-01-01

    In the present research we investigated when and why leaders tend to oppose or adopt radical creative ideas voiced by their subordinates. In a field study (Study 1, N=127) we showed that leaders' performance goals were positively related to their tendency to oppose radical creative ideas, whereas

  16. THE SUBORDINATION OF THE EMPLOYEE TO THE EMPLOYER – THE FUNDAMENTAL LEGAL CHARACTERISTIC OF THE INDIVIDUAL EMPLOYMENT CONTRACT AND ITS CONSEQUENCES ON LABOR LAW

    OpenAIRE

    Brindusa VARTOLOMEI

    2014-01-01

    Fundamental legal feature of the labor contract is the subordination of the employee to the employer. This is evidenced, during the execution of the labor contract of the employer rights granted much higher in comparison with those of the employee. Economic dependency is the objective support legal subordination of the employee to the employer.

  17. An intraovarian mechanism that enhances the effect of an FSH surge on recovery of subordinate follicles in heifers.

    Science.gov (United States)

    Ginther, O J; Siddiqui, M A R; Baldrighi, J M; Araujo, E R

    2017-04-01

    The effect of the future dominant follicle (DF), corpus luteum (CL), and side (left ovary [LO] and right ovary [RO]) on FSH-induced recovery (increase in diameter) of regressing subordinate follicles was studied in heifers. The DF of wave 2 and the largest subordinate follicle remained intact (controls, n = 14 heifers) or were ablated (n = 14 heifers) on a mean of 13 d postovulation when the DF was ∼10 mm (hour 0). Concentration of FSH (P < 0.0004) and diameter of subordinate follicles (P < 0.0002) decreased between hours -48 to 0 combined for the control and ablation groups. Thereafter, follicle diameter continued to decrease in the controls. Concentration of FSH increased (P < 0.05) and diameter of subordinates began to increase at hour 12 in the ablation group. Follicle-stimulating hormone increased to hour 24 and then returned to the hour 0 concentration by hour 72, completing the induced FSH surge. Concentration of LH began to increase at hour 0 in each group and at a similar rate between groups. Follicle recovery in the ablation group was compared among 8 subgroups as defined by the 2 sides and 4 intraovarian patterns (DF-CL pattern, both structures in same ovary; DF pattern, DF alone; CL pattern, CL alone; and devoid pattern, both structures absent). Follicle diameter increased (P < 0.05) between hours 24 and 48, and diameter at hours 24, 48, 72, and 96 involved a 3-way interaction (P < 0.0001) of pattern, side, and hour. The interaction was similar when diameter of the DF that originated from a recovered subordinate was either included or excluded in the analysis. Diameter of subordinate follicles in the ablation group at hour 96 was greater (P < 0.05) in the DF-CL/RO and DF/RO subgroups than that in the devoid/LO, devoid/RO, and CL/LO subgroups. The DF-CL/LO and CL/RO subgroups were intermediate. For follicles that decreased in diameter before hour 0, a greater (P < 0.05) percentage increased after hour 0 when the ovary contained a DF and was in

  18. Biomimetic synthesis of hollow calcium carbonate with the existence of the agar matrix and bovine serum albumin

    Energy Technology Data Exchange (ETDEWEB)

    Feng, Jianhua, E-mail: fjh2008@126.com; Wu, Gang; Qing, Chengsong

    2016-01-01

    Proteins play important roles in the process of biomineralization. Vaterite and calcite have been synthesized by the reaction of Na{sub 2}CO{sub 3} and CaCl{sub 2} in the bovine serum albumin (BSA) and agar system. The samples have been characterized by Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The shape of CaCO{sub 3} crystal has been analyzed by scanning electronic microscopy (SEM). The results show that calcite is a single product in the absence of BSA, but the product is a mixture of calcite and vaterite in the presence of BSA. The spheral shell of CaCO{sub 3} crystal was obtained when the concentration of BSA increased to 9.0 mg/mL. - Highlights: • Biomimetic synthesis of hollow calcium carbonate • Calcification mechanisms in the presence of both protein and polysaccharides • Biomineralization under the action of protein and polysaccharides.

  19. Green technological approach to synthesis hydrophobic stable crystalline calcite particles with one-pot synthesis for oil-water separation during oil spill cleanup.

    Science.gov (United States)

    Wu, Min-Nan; Maity, Jyoti Prakash; Bundschuh, Jochen; Li, Che-Feng; Lee, Chin-Rong; Hsu, Chun-Mei; Lee, Wen-Chien; Huang, Chung-Ho; Chen, Chien-Yen

    2017-10-15

    The process of separating oil and water from oil/water mixtures is an attractive strategy to answer the menace caused by industrial oil spills and oily wastewater. In addition, water coproduced during hydrocarbon exploitation, which can be an economic burden and risk for freshwater resources, can become an important freshwater source after suitable water-oil separation. For oil-water separation purposes, considerable attention has been paid to the preparation of hydrophobic-oleophilic materials with modified surface roughness. However, due to issues of thermodynamic instability, costly and complex methods as well as lack of ecofriendly compounds, most of hydrophobic surface modified particles are of limited practical application. The study presents a facile procedure, to synthesize crystalline particles of calcite, which is the most stable polymorph of CaCO 3 from industrial CaCO 3 using oleic acid as an additive in a one-pot synthesis method. The XRD results show that the synthesized particles were a well-crystallized form of calcite. The FTIR results reflect the appearance of the alkyl groups from the oleic acid in synthesized particles which promotes the production of calcite with 'rice shape' (1.64 μm) (aggregated by spherical nanoparticle of 19.56 nm) morphology with concomitant changes in its surface wettability from hydrophilic to hydrophobic. The synthesized particles exhibited near to super hydrophobicity with ∼99% active ratio and a contact angle of 143.8°. The synthesized hydrophobic calcite particles had an oleophilic nature where waste diesel oil adsorption capacity of synthesized calcium carbonate (HCF) showed a very high (>99%) and fast (7 s) oil removal from oil-water mixture. The functional group of long alkyl chain including of CO bounds may play critical roles for adsorption of diesel oils. Moreover, the thermodynamically stable crystalline polymorph calcite (compared to vaterite) exhibited excellent recyclability. The isothermal study

  20. Experimental and simulated scattering matrices of small calcite particles at 647nm

    Science.gov (United States)

    Dabrowska, D. D.; Muñoz, O.; Moreno, F.; Nousiainen, T.; Zubko, E.; Marra, A. C.

    2013-07-01

    We present measurements of the complete scattering matrix as a function of the scattering angle of a sample of calcite particles. The measurements are performed at 647nm in the scattering angle range from 3° to 177°. To facilitate the use of the experimental data we present a synthetic scattering matrix based on the measurements and defined in the full range from 0° to 180°. The scattering matrix of the calcite sample is modeled using the discrete-dipole approximation. Two sets of shapes, flake-like and rhomboid-like particles giving a total of 15 different targets are considered since both types of shapes have been found in our calcite sample. In our computations we use the measured size distribution of the calcite sample truncated at 1.2μm. We present a theoretical study of the impact of birefringence on the computed scattering matrix elements for both sets of shapes. Four different cases regarding the composition of the calcite particles are considered: two isotropic cases corresponding to the ordinary and extraordinary refractive index of calcite, respectively; one equivalent isotropic case analogous to internal mixing; and birefringence fully accounted for. Numerical simulations are compared with the experimental data. We find that birefringence has little impact on the calculated phase functions but it has a significant effect on the polarization-related elements of the scattering matrix. Moreover, we conclude that the shape of the targets (flakes or irregular rhomboids) has a much stronger effect on the computed scattering matrix elements than birefringence.

  1. Experimental fractionation of stable carbon isotopes during degassing of carbon dioxide and precipitation of calcite from aqueous solutions

    Science.gov (United States)

    Müller, K.; Winde, V.; Escher, P.; von Geldern, R.; Böttcher, M. E.

    2012-04-01

    Processes in the carbonate system of surface waters are in particular sensitive to variations of boundary conditions as, for instance, the partial pressure of carbon dioxide in the atmosphere and the aqueous solution. Examples range from streams, rivers, to coastal marine waters. The flux of carbon dioxide from continental flowing waters was recently included into calculations of the global carbon budget (Butman & Raymond, 2011, Nature Geo.). These solutions, are often supersaturated in carbon dioxide with respect to the atmosphere. The degassing of carbon dioxide is associated with a kinetically controlled fractionation of the stable carbon isotopes, which has to be considered in balancing water-air carbon dioxide fluxes. The degassing process additionally leads to the super-saturation of the aqueous solution with respect to calcium carbonate. Stable isotope fractionation is of particular value to identify and quantify processes at the water-gas phase interface and link these non-equilibrium processes to the formation mechanisms of calcite and the hydrodynamics of surface waters. Experiments were carried out with or without inert N2 gas flow to degas carbon dioxide from initially supersaturated solutions. Natural solutions used are from different stations of the Elbe estuary, the Jade Bay, the backbarrier tidal area of Spiekeroog Island, carbonate springs of Rügen Island, and the Baltic Sea coastline. Results are compared experiments using bottled mineral waters. By following the (physico) chemical changes in the solutions (pH, TA, Ca PHREEQC modeling) it was found, that two evolutionary stages can be differentiated. Reaction progress led to the preferential liberation of carbon dioxide containing the light carbon isotope, following a Rayleigh-type process. After an induction period, where only degassing of carbon dioxide took place, a second stage was observed where calcite began to form from the highly supersaturated solutions. In this stage the carbonate

  2. A facile magnesium-containing calcium carbonate biomaterial as potential bone graft.

    Science.gov (United States)

    He, Fupo; Zhang, Jing; Tian, Xiumei; Wu, Shanghua; Chen, Xiaoming

    2015-12-01

    The calcium carbonate is the main composition of coral which has been widely used as bone graft in clinic. Herein, we readily prepared novel magnesium-containing calcium carbonate biomaterials (MCCs) under the low-temperature conditions based on the dissolution-recrystallization reaction between unstable amorphous calcium carbonate (ACC) and metastable vaterite-type calcium carbonate with water involved. The content of magnesium in MCCs was tailored by adjusting the proportion of ACC starting material that was prepared using magnesium as stabilizer. The phase composition of MCCs with various amounts of magnesium was composed of one, two or three kinds of calcium carbonates (calcite, aragonite, and/or magnesian calcite). The different MCCs differed in topography. The in vitro degradation of MCCs accelerated with increasing amount of introduced magnesium. The MCCs with a certain amount of magnesium not only acquired higher compressive strength, but also promoted in vitro cell proliferation and osteogenic differentiation. Taken together, the facile MCCs shed light on their potential as bone graft. Copyright © 2015 Elsevier B.V. All rights reserved.

  3. Calcium carbonate mineralization: involvement of extracellular polymeric materials isolated from calcifying bacteria.

    Science.gov (United States)

    Ercole, Claudia; Bozzelli, Paola; Altieri, Fabio; Cacchio, Paola; Del Gallo, Maddalena

    2012-08-01

    This study highlights the role of specific outer bacterial structures, such as the glycocalix, in calcium carbonate crystallization in vitro. We describe the formation of calcite crystals by extracellular polymeric materials, such as exopolysaccharides (EPS) and capsular polysaccharides (CPS) isolated from Bacillus firmus and Nocardia calcarea. Organic matrices were isolated from calcifying bacteria grown on synthetic medium--in the presence or absence of calcium ions--and their effect on calcite precipitation was assessed. Scanning electron microscopy observations and energy dispersive X-ray spectrometry analysis showed that CPS and EPS fractions were involved in calcium carbonate precipitation, not only serving as nucleation sites but also through a direct role in crystal formation. The utilization of different synthetic media, with and without addition of calcium ions, influenced the biofilm production and protein profile of extracellular polymeric materials. Proteins of CPS fractions with a molecular mass between 25 and 70 kDa were overexpressed when calcium ions were present in the medium. This higher level of protein synthesis could be related to the active process of bioprecipitation.

  4. Ubiquitylation functions in the calcium carbonate biomineralization in the extracellular matrix.

    Science.gov (United States)

    Fang, Dong; Pan, Cong; Lin, Huijuan; Lin, Ya; Xu, Guangrui; Zhang, Guiyou; Wang, Hongzhong; Xie, Liping; Zhang, Rongqing

    2012-01-01

    Mollusks shell formation is mediated by matrix proteins and many of these proteins have been identified and characterized. However, the mechanisms of protein control remain unknown. Here, we report the ubiquitylation of matrix proteins in the prismatic layer of the pearl oyster, Pinctada fucata. The presence of ubiquitylated proteins in the prismatic layer of the shell was detected with a combination of western blot and immunogold assays. The coupled ubiquitins were separated and identified by Edman degradation and liquid chromatography/mass spectrometry (LC/MS). Antibody injection in vivo resulted in large amounts of calcium carbonate randomly accumulating on the surface of the nacreous layer. These ubiquitylated proteins could bind to specific faces of calcite and aragonite, which are the two main mineral components of the shell. In the in vitro calcium carbonate crystallization assay, they could reduce the rate of calcium carbonate precipitation and induce the calcite formation. Furthermore, when the attached ubiquitins were removed, the functions of the EDTA-soluble matrix of the prismatic layer were changed. Their potency to inhibit precipitation of calcium carbonate was decreased and their influence on the morphology of calcium carbonate crystals was changed. Taken together, ubiquitylation is involved in shell formation. Although the ubiquitylation is supposed to be involved in every aspect of biophysical processes, our work connected the biomineralization-related proteins and the ubiquitylation mechanism in the extracellular matrix for the first time. This would promote our understanding of the shell biomineralization and the ubiquitylation processes.

  5. Characteristics of a calcite "limestone"-marble from Macedonia, used as flux material

    Directory of Open Access Journals (Sweden)

    Hristova E.

    2003-01-01

    Full Text Available The phase characteristics of calcite "limestone"-marble from Banjany area village (near Skopje, Macedonia were examined by means of XRD, SEM microscope in polarizing and reflected lights, chemical, DT/TG-analyses. It was concluded as follows: - calcite (CaCO3 is a major mineral component (cca 80-90 % prevailing in the marble over the other minerals - dolomite is generally of minor importance (cca 10-20 % in the rock - quartz, micas graphite, pyrite represent typical accessories. As result of the mentioned phase characteristics, this raw materials was for a long time (more than 30 years used as flux in the iron and steel metallurgy in Macedonia.

  6. Thickness and structure of the water film deposited from vapour on calcite surfaces

    DEFF Research Database (Denmark)

    Bohr, Jakob; Wogelius, Roy A.; Morris, Peter M.

    2010-01-01

    Synchrotron X-ray reflectivity (SXR) was used to measure the thickness of the water film that adsorbs on a {10¯14} cleavage surface of calcite (CaCO3) in a sample chamber where relative humidity could be controlled within the range from......Synchrotron X-ray reflectivity (SXR) was used to measure the thickness of the water film that adsorbs on a {10¯14} cleavage surface of calcite (CaCO3) in a sample chamber where relative humidity could be controlled within the range from...

  7. Field Experiment to Stimulate Microbial Urease Activity in Groundwater for in situ Calcite Precipitation

    Science.gov (United States)

    Fujita, Y.; Taylor, J. L.; Tyler, T. L.; Banta, A. B.; Reysenbach, A. L.; Delwiche, M. E.; McLing, T. L.; Colwell, F. S.; Smith, R. W.

    2003-12-01

    Groundwater contamination by radionuclides and metals from past weapons processing activities is a significant problem for the United States Department of Energy. Removal of these pollutants from the subsurface can be prohibitively expensive and result in worker exposure, and therefore in situ containment and stabilization is an attractive remediation alternative. One potential approach for the immobilization of certain radionuclides and metals (e.g., 90Sr, 60Co, Pb, Cd) is to induce geochemical conditions that promote co-precipitation in calcite. Many aquifers in the arid western US are calcite-saturated, and calcite precipitated under an engineered remediation scheme in such aquifers should remain stable even after return to ambient conditions. We have proposed that an effective way to promote calcite precipitation is to utilize native microorganisms that hydrolyze urea. Urea hydrolysis results in carbonate and ammonium production, and an increase in pH. The increased carbonate alkalinity favors calcite precipitation, and the ammonium serves the additional role of promoting desorption of sorbed metal ions from the aquifer matrix by ion exchange. The desorbed metals are then accessible to co-precipitation in calcite, which can be a longer-term immobilization mechanism than sorption. The ability to hydrolyze urea is common among environmental microorganisms, and we have shown in the laboratory that microbial urea hydrolysis can be linked to calcite precipitation and co-precipitation of the trace metal strontium. As a next step in the development of our remediation approach, we aimed to demonstrate that we can stimulate the native microbial community to express urease in the field. In 2002 we conducted a preliminary field trial of our approach, using a well in the Eastern Snake River Plain Aquifer in Idaho Falls, Idaho, USA. A dilute molasses solution (0.00075%) was injected to promote overall biological growth, and then urea (50 mM) was added to the aquifer

  8. New Shocked Calcite and Fe Grains from Noerdlingen Ries Impact Crater

    Science.gov (United States)

    Miura, Y.

    1995-09-01

    Shocked minerals with simple chemical composition of silica, carbon or iron material reveal high-pressure phase during compression process [1]. As calcite mineral shows high-pressure phase of aragonite it should have the "shocked phase" formed from high-pressure phase mixed with quenched materials of gas-melt reaction [2,3,4]. The main purposes of this paper are (1) to discuss new shocked materials of calcite found in the Noerdlingen Ries impact crater. Germany and artificial impact phases. and (2) to show new findings of fine Fe-grains and anomalous plagioclase in suevite. Single grains of anomalous calcite for X-ray analysis were selected from limestone with wormy or bubble-included texture in Buschelberg Ries impact crater (sample R8) [3 4]. Powdered and single grain samples of anomalous calcites show low X-ray intensity and high Bragg angle shift. compared with standard calcite of Akiyoshi limestone as listed in Table 1 [2.3.4]. The unit-cell dimensions of the single grain measured with the four-axes X-ray diffractometer in Yamaguchi University were determined by the least square calculation from the "highest X-ray intensity peak" of each crystal plane which is the same data of the powdered X-ray diffraction sample as an average structure . Both powdered and single grain data reveal high density of 2.76 g/cm^3 (between aragonite of density: rho=2.8g/cm^3, and normal calcite: rho=2.71g/cm^3) of the calcite cell which is the same characters of shocked phases of quartz or graphite [1,2,3,4] (Table 1). Anomalous calcite contains minor amount of Si Fe Ti, though major cation is Ca of 99.4% in cation content. These foreign elements are mixed with during the formation in vapor plume [5]. Table 1, showing the x-ray density and unit-cell parameters of anomalous shocked calcite with high density from Ries and artificial impact craters, appears here in the hard copy. Two types of shocked calcites are found in artificial impact experiments of railgun of the ISAS. Japan. (a

  9. Substitutions in Calcium Aluminates and Calcium Aluminoferrites.

    Science.gov (United States)

    ALUMINUM COMPOUNDS, *CEMENTS, * CALCIUM COMPOUNDS, * FERRITES , *SCIENTIFIC RESEARCH, INFRARED SPECTROSCOPY, X RAY DIFFRACTION, CHEMICAL COMPOSITION, SUBSTITUTES, CHEMICAL ANALYSIS, ALKALI METAL COMPOUNDS.

  10. Synthesis of calcium carbonate using extract components of croaker gill as morphology and polymorph adjust control agent.

    Science.gov (United States)

    Chen, Hao; Qing, Chengsong; Zheng, Jiaoling; Liu, Yuxi; Wu, Gang

    2016-06-01

    Biomimetic synthesis of calcium carbonate with various polymorphs, sizes and morphologies by using organic substrates has become an interesting topic for the last years. Calcium carbonate has been synthesized by the reaction of Na2CO3 and CaCl2 in the presence of extract components of croaker gill. The products were characterized by powder X-ray diffraction (PXRD) and Fourier transform infrared (FT-IR) spectrum, and particle morphologies were observed by scanning electron microscope (SEM). The results show that at lower concentration yellow croaker gill extract has no effect on calcium carbonate crystal polymorph. Calcite was obtained only. But the morphologies of calcite particle change with the increase of the concentration. The corners of the particle change from angular to curved. However, with the further increase of the concentration of yellow croaker gill extract, the calcium carbonate obtained is a mixture of calcite and vaterite. The vaterite component in the mixture rises with increasing concentration of extract solution, indicating that the proteins from the yellow croaker gill during growth play a crucial role in stabilizing and directing the crystal growth. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Epitaxial Relationships between Calcium Carbonate and Inorganic Substrates

    Directory of Open Access Journals (Sweden)

    Taewook Yang

    2014-09-01

    Full Text Available The polymorph-selective crystallization of calcium carbonate has been studied in terms of epitaxial relationship between the inorganic substrates and the aragonite/calcite polymorphs with implication in bioinspired mineralization. EpiCalc software was employed to assess the previously published experimental results on two different groups of inorganic substrates: aragonitic carbonate crystals (SrCO3, PbCO3, and BaCO3 and a hexagonal crystal family (α-Al2O3, α-SiO2, and LiNbO3. The maximum size of the overlayer (aragonite or calcite was calculated for each substrate based on a threshold value of the dimensionless potential to estimate the relative nucleation preference of the polymorphs of calcium carbonate. The results were in good agreement with previous experimental observations, although stereochemical effects between the overlayer and substrate should be separately considered when existed. In assessing the polymorph-selective nucleation, the current method appeared to provide a better tool than the oversimplified mismatch parameters without invoking time-consuming molecular simulation.

  12. Protein mapping of calcium carbonate biominerals by immunogold.

    Science.gov (United States)

    Marin, Frédéric; Pokroy, Boaz; Luquet, Gilles; Layrolle, Pierre; De Groot, Klaas

    2007-05-01

    The construction of metazoan calcium carbonate skeletons is finely regulated by a proteinaceous extracellular matrix, which remains embedded within the exoskeleton. In spite of numerous biochemical studies, the precise localization of skeletal proteins has remained for a long time as an elusive goal. In this paper, we describe a technique for visualizing shell matrix proteins on the surface of calcium carbonate crystals or within the biominerals. The technique is as follows: freshly broken pieces of biominerals or NaOCl then EDTA-etched polished surfaces are incubated with an antibody elicited against one matrix protein, then with a secondary gold-coupled antibody. After silver enhancement, the samples are subsequently observed with scanning electron microscopy by using back-scattered electron mode. In the present case, the technique is applied to a particular example, the calcitic prisms that compose the outer shell layer of the mediterranean fan mussel Pinna nobilis. One major soluble protein, caspartin, which was identified recently, was partly de novo sequenced after enzymatic digestions. A polyclonal antibody raised against caspartin was used for its localization within and on the prisms. The immunogold localization indicated that caspartin surrounds the calcitic prisms, but is also dispersed within the biominerals. This example illustrates the deep impact of the technique on the definition of intracrystalline versus intercrystalline matrix proteins. Furthermore, it is an important tool for assigning a putative function to a matrix protein of interest.

  13. Effects of increased pCO2 and geographic origin on purple sea urchin (Strongylocentrotus purpuratus) calcite elemental composition

    Science.gov (United States)

    LaVigne, M.; Hill, T. M.; Sanford, E.; Gaylord, B.; Russell, A. D.; Lenz, E. A.; Hosfelt, J. D.; Young, M. K.

    2012-12-01

    Ocean acidification will likely have negative impacts on invertebrates producing skeletons composed of calcium carbonate. Skeletal solubility is partly controlled by the incorporation of "foreign" ions (such as Mg and Sr) into the crystal lattice of these skeletal structures, a process that is sensitive to a variety of biological and environmental factors. Here we explore the effects of life stage, oceanographic region of origin, and changes in the partial pressure of carbon dioxide in seawater (pCO2) on trace elemental composition in the purple sea urchin (Strongylocentrotus purpuratus). We show that, similar to other urchin taxa, adult purple sea urchins have the ability to precipitate skeleton composed of a range of biominerals spanning low to high magnesium calcites. Mg/Ca and Sr/Ca ratios were substantially lower in adult spines compared to adult tests. On the other hand, trace elemental composition was invariant among adults collected from four oceanographically distinct regions along the US west coast (Oregon, Northern California, Central California, and Southern California). Skeletons of newly settled juvenile urchins that originated from adults from the four regions exhibited intermediate Mg/Ca and Sr/Ca between adult spine and test endmembers, indicating that skeleton precipitated during early life stages is more soluble than adult spines and less soluble than adult tests. Mean skeletal Mg/Ca or Sr/Ca of juvenile skeleton did not vary with source region when larvae were reared under present-day, global-average seawater carbonate conditions (400 ppm; pH = 8.02 ± 0.03 1 SD; Ωcalcite = 3.3 ± 0.2 1 SD). However, when reared under elevated CO2 (900 ppm; pH = 7.72 ± 0.03; Ωcalcite = 1.8 ± 0.1), skeletal Sr/Ca in juveniles exhibited increased variance across the four regions. Although larvae from the northern populations (Oregon, Northern California, Central California) did not exhibit differences in Mg or Sr incorporation under elevated CO2 (Sr/Ca = 2

  14. Calcium carbonate nucleation in an alkaline lake surface water, Pyramid Lake, Nevada, USA

    Science.gov (United States)

    Reddy, Michael M.; Hoch, Anthony

    2012-01-01

    Calcium concentration and calcite supersaturation (Ω) needed for calcium carbonate nucleation and crystal growth in Pyramid Lake (PL) surface water were determined during August of 1997, 2000, and 2001. PL surface water has Ω values of 10-16. Notwithstanding high Ω, calcium carbonate growth did not occur on aragonite single crystals suspended PL surface water for several months. However, calcium solution addition to PL surface-water samples caused reproducible calcium carbonate mineral nucleation and crystal growth. Mean PL surface-water calcium concentration at nucleation was 2.33 mM (n = 10), a value about nine times higher than the ambient PL surface-water calcium concentration (0.26 mM); mean Ω at nucleation (109 with a standard deviation of 8) is about eight times the PL surface-water Ω. Calcium concentration and Ω regulated the calcium carbonate formation in PL nucleation experiments and surface water. Unfiltered samples nucleated at lower Ω than filtered samples. Calcium concentration and Ω at nucleation for experiments in the presence of added particles were within one standard deviation of the mean for all samples. Calcium carbonate formation rates followed a simple rate expression of the form, rate (mM/min) = A (Ω) + B. The best fit rate equation "Rate (Δ mM/Δ min) = -0.0026 Ω + 0.0175 (r = 0.904, n = 10)" was statistically significant at greater than the 0.01 confidence level and gives, after rearrangement, Ω at zero rate of 6.7. Nucleation in PL surface water and morphology of calcium carbonate particles formed in PL nucleation experiments and in PL surface-water samples suggest crystal growth inhibition by multiple substances present in PL surface water mediates PL calcium carbonate formation, but there is insufficient information to determine the chemical nature of all inhibitors.

  15. Interactions of the Calcite {10.4} Surface with Organic Compounds: Structure and Behaviour at Mineral – Organic Interfaces

    DEFF Research Database (Denmark)

    Hakim, S. S.; Olsson, M. H. M.; Sørensen, H. O.

    2017-01-01

    that control crystal growth with organic macromolecules. Carbonate rocks, composed almost exclusively of calcite, host drinking water aquifers and oil reservoirs. In this study, we examined the ordering behaviour of several organic compounds and the thickness of the adsorbed layers formed on calcite {10...

  16. Supervisor-subordinate communication relationships, role ambiguity, autonomy and affective commitment for nurses.

    Science.gov (United States)

    Brunetto, Yvonne; Farr-Wharton, Rod; Shacklock, Kate

    2011-10-01

    This paper examine nurses' levels of satisfaction with their supervisor-subordinate communication relationships on their level of role ambiguity (in relation to their supervisors) and their resultant perceptions of autonomy and in turn, affective commitment. A survey of 900 nurses working in private sector hospitals in Australia was used to collect data. The combined effects of supervisor-nurse communication relationships, nurses' role ambiguity in relation to their supervisors plus nurses' resultant perceptions of autonomy, definitely influenced nurses' level of affective commitment. Also, nurses were somewhat dissatisfied with their communication relationships with their supervisors, experienced role ambiguity, reported being only a little autonomous, and were subsequently only somewhat committed to their hospitals. Contribution: The findings contribute to addressing nurse retention challenges by identifying factors affecting nurses' organisational commitment. Not only will nurses be more productive (with less supervisor ambiguity), but high quality Nurse Unit Manager-nurse communication relationships are also likely to enhance perceptions of autonomy and thereby, encourage nurses' commitment to their organisation and intention to remain. These results raise the question as to whether the present management practices are ideal for retaining nurses who are in short supply in many Organisation for Economic Co-operation and Development countries.

  17. A closer look at the subordinate population within the visible burrow system.

    Science.gov (United States)

    Melhorn, Susan J; Elfers, Clinton T; Scott, Karen A; Sakai, Randall R

    2017-09-01

    The visible burrow system (VBS) utilizes the natural social behavior of rodents to model chronic social stress. Classically, when male and female rats are housed together in the VBS a dominance hierarchy rapidly forms with one dominant (DOM) and three subordinate (SUB) males. SUB animals show signs of chronic social stress, including loss of body weight and elevated basal corticosterone. This study furthered examined differences among the SUB population. Quantitative observations across numerous VBS colonies within the Sakai Lab suggest that there is variability in the effects of stress on the SUB population, specifically that some animals may experience more severe effects of chronic social stress than others. To further examine this observation, SUB animals were classified as OMEGA if they received a disproportionate amount of their colonies' wounds. OMEGA animals received more wounds to their body compared to SUB (PVBS-housed animals (group×time interaction PVBS housing it was determined the OMGEA also lost lean body mass (PVBS colony and represents the variability of the effects of chronic social stress. Copyright © 2017 Elsevier Inc. All rights reserved.

  18. [The effects of planning leadership behavior on the subordinates' person perception].

    Science.gov (United States)

    Arima, Y

    1989-10-01

    According to the two factor theory of leadership, leaders were instructed to behave both gently and strictly. However, how can be achieved such behavior? Here, a solution to this problem is suggested by an analysis of subordinates' person perception. Yamada (1987) analyzed the data of PM leadership surveys, and found three factors; Maintenance [M.] (corresponds to "Consideration" in the Ohio Study) Planning (Initiating Structure), and Pressure (Production Emphasis). It was found that High Planning supported the independence of M. from Pressure. The purpose of this experimental study was to test the effect of Planning behavior on cognitive structure. Sixty-four female subjects performed a maze task using computer simulation. In the high Planning condition, the leader displayed direction signs, whereas no sign was displayed in the low Planning condition. Each condition was further subdivided into two Pressure conditions (High or low) by the amount of linguistic behavior. The result of the survey data was supported. M. cognition decreased by increasing Pressure cognition in the low Planning condition, but no correlation was found between M. and Pressure in the High Planning condition.

  19. Chronic clomipramine treatment reverses core symptom of depression in subordinate tree shrews.

    Directory of Open Access Journals (Sweden)

    Jing Wang

    Full Text Available Chronic stress is the major cause of clinical depression. The behavioral signs of depression, including anhedonia, learning and memory deficits, and sleep disruption, result from the damaging effects of stress hormones on specific neural pathways. The Chinese tree shrew (Tupaia belangeri chinensis is an aggressive non-human primate with a hierarchical social structure that has become a well-established model of the behavioral, endocrine, and neurobiological changes associated with stress-induced depression. The tricyclic antidepressant clomipramine treats many of the core symptoms of depression in humans. To further test the validity of the tree shrew model of depression, we examined the effects of clomipramine on depression-like behaviors and physiological stress responses induced by social defeat in subordinate tree shrews. Social defeat led to weight loss, anhedonia (as measured by sucrose preference, unstable fluctuations in locomotor activity, sustained urinary cortisol elevation, irregular cortisol rhythms, and deficient hippocampal long-term potentiation (LTP. Clomipramine ameliorated anhedonia and irregular locomotor activity, and partially rescued the irregular cortisol rhythm. In contrast, weight loss increased, cortisol levels were even higher, and in vitro LTP was still impaired in the clomipramine treatment group. These results demonstrate the unique advantage of the tree shrew social defeat model of depression.

  20. The downside of goal-focused leadership: the role of personality in subordinate exhaustion.

    Science.gov (United States)

    Perry, Sara Jansen; Witt, L A; Penney, Lisa M; Atwater, Leanne

    2010-11-01

    Exhaustion has a significant impact on employees and organizations, and leader behavior may affect it. We applied conservation of resources theory to test propositions regarding the joint effects of goal-focused leadership (GFL) and personality on employee exhaustion. We proposed that the relationship between GFL and exhaustion depends on employees' standing on both conscientiousness and emotional stability. Specifically, we expected that high-conscientiousness subordinates experience greater compatibility with a goal-focused leader because of their predisposition to direct resources toward achievement and goal setting, resulting in lower exhaustion under such a leader than among low-conscientiousness employees. Furthermore, high emotional stability may compensate for GFL incompatibility among low-conscientiousness employees by providing additional resources to manage GFL. In contrast, employees low on both traits likely experience greater exhaustion under a goal-focused leader compared with other employees. Results revealed a 3-way interaction in 2 independent samples and were generally supportive of our predictions. GFL was associated with heightened exhaustion among individuals in the low-emotional-stability, low-conscientiousness group but not among workers having any other trait combination. (c) 2010 APA, all rights reserved.

  1. Chronic subordinate colony housing paradigm: A mouse model to characterize the consequences of insufficient glucocorticoid signalling

    Directory of Open Access Journals (Sweden)

    Dominik eLanggartner

    2015-02-01

    Full Text Available Chronic, in particular chronic psychosocial, stress is a burden of modern societies and known to be a risk factor for numerous somatic and affective disorders (in detail referenced below. However, based on the limited existence of appropriate, and clinically-relevant, animal models for studying the effects of chronic stress, the detailed behavioural, physiological, neuronal, and immunological mechanisms linking stress and such disorders are insufficiently understood. To date, most chronic stress studies in animals employ intermittent exposure to the same (homotypic or to different (heterotypic stressors of varying duration and intensity. Such models are only of limited value, since they do not adequately reflect the chronic, and continuous, situation that humans typically experience. Furthermore, application of different physical or psychological stimuli renders comparisons to the mainly psychosocial stressors faced by humans, as well as between the different stress studies almost impossible. In contrast, rodent models of chronic psychosocial stress represent situations more akin to those faced by humans and consequently seem to hold more clinical relevance. Our laboratory has developed a model in which mice are exposed to social stress for 19 continuous days, namely the chronic subordinate colony housing (CSC paradigm, which bridges this gap. The main aim of the current review article is to provide a detailed summary of the behavioural, physiological, neuronal and immunological consequences of the CSC paradigm, and wherever possible relate the findings to other stress models and to those from human studies.

  2. Comparison for Chinese subordinates as a motivation approach: Scale Development and Psychometric Properties

    Directory of Open Access Journals (Sweden)

    Jingjing Ge

    2015-11-01

    Full Text Available Purpose: Chinese people are motivated by social comparison and temporal comparison. Based on this finding, we conceptualized lateral comparison and vertical comparison as two distinct constructs that represent individual self-enhancement toward the nature of social comparison with others and temporal comparison with self over time. We hypothesized that as stable individual psychological difference, lateral comparison and vertical comparison would have differential effects on people’s working behavior in the Chinese organizational context. Design/methodology/approach: Based on a conceptualization approach to Chinese management research, we conducted three studies to develop and validate a two-factor comparison scale which includes three-item lateral comparison and a three-item vertical comparison. Findings: Results from qualitative data in Study 1 provide evidence of convergent and discriminate validity of the scale, while Study 2 demonstrates the scale’s predictive validity. Furthermore, in Study two, a field survey in multiple Chinese organizations showed that lateral comparison and vertical comparison had differential effects on employee task performance and organizational citizenship behavior. Research implications: The theoretical and practical implications of this study are discussed in the working context in Chinese organizations and beyond. Originality/value: This finding integrates insights from previous research in social comparison and temporal comparison into a motivation approach that supervisors use toward subordinates in the Chinese organizational context.

  3. Inhibition of calcium carbonate crystal growth by organic additives using the constant composition method in conditions of recirculating cooling circuits

    Science.gov (United States)

    Chhim, Norinda; Kharbachi, Chams; Neveux, Thibaut; Bouteleux, Céline; Teychené, Sébastien; Biscans, Béatrice

    2017-08-01

    The cooling circuits used in power plants are subject to mineral crystallization which can cause scaling on the surfaces of equipment and construction materials reducing their heat exchange efficiency. Precipitated calcium carbonate is the predominant mineral scale commonly observed in cooling systems. Supersaturation is the key parameter controlling the nucleation and growth of calcite in these systems. The present work focuses on the precipitation of calcite using the constant composition method at constant supersaturation, through controlled addition of reactants to a semi-batch crystallizer, in order to maintain constant solution pH. The determination of the thermodynamic driving force (supersaturation) was based on the relevant chemical equilibria, total alkalinity and calculation of the activity coefficients. Calcite crystallization rates were derived from the experiments performed at supersaturation levels similar to those found in industrial station cooling circuits. Several types of seeds particles were added into the aqueous solution to mimic natural river water conditions in terms of suspended particulate matters content, typically: calcite, silica or illite particles. The effect of citric and copolycarboxylic additive inhibitors added to the aqueous solution was studied. The calcium carbonate growth rate was reduced by 38.6% in the presence of the citric additive and a reduction of 92.7% was observed when the copolycarboxylic additive was used under identical experimental conditions. These results are explained by the location of the adsorbed inhibitor at the crystal surface and by the degree of chemical bonding to the surface.

  4. Calcium channel blocker overdose

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/002580.htm Calcium-channel blocker overdose To use the sharing features on this page, please enable JavaScript. Calcium-channel blockers are a type of medicine used to ...

  5. Fenoprofen calcium overdose

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/article/002649.htm Fenoprofen calcium overdose To use the sharing features on this page, please enable JavaScript. Fenoprofen calcium is a type of medicine called a nonsteroidal ...

  6. Binding of ethanol on calcite: the role of the OH bond and its relevance to biomineralization

    DEFF Research Database (Denmark)

    Sand, K K; Yang, M; Makovicky, E

    2010-01-01

    The interaction of OH-containing compounds with calcite, CaCO(3), such as is required for the processes that control biomineralization, has been investigated in a low-water solution. We used ethanol (EtOH) as a simple, model, OH-containing organic compound, and observed the strength of its...

  7. Simple, simultaneous gravimetric determination of calcite and dolomite in calcareous soils

    Science.gov (United States)

    Literature pertaining to determination of calcite and dolomite is not modern and describes slow methods that require expensive specialized apparatus. The objective of this paper was to describe a new method that requires no specialized equipment. Linear regressions and correlation coefficients for...

  8. Impacts of pH and [CO32-] on the incorporation of Zn in foraminiferal calcite

    NARCIS (Netherlands)

    van Dijk, Inge; de Nooijer, Lennart J.; Wolthers, Mariëtte; Reichart, Gert-Jan

    2017-01-01

    The trace elemental composition of foraminiferal shell calcite is known to reflect the environment in which the shell was precipitated. Whereas conservative elements incorporated in foraminiferal shell carbonate reflect factors such as temperature (Mg), carbonate chemistry (B) and salinity (Na), the

  9. Fulvic acid-like organic compounds control nucleation of marine calcite under suboxic conditions

    NARCIS (Netherlands)

    Neuweiler, F.; D'Orazio, M.; Immenhauser, A.M.; Geipel, G.; Heise, K.H.; Cocozza, C.; Miano, T.M.

    2003-01-01

    Intracrystalline organic compounds, enclosed within in situprecipitated marine microcrystalline calcite (automicrite), might represent either an inclusion or the catalyst of such precipitation. We use evidence from a Lower Cretaceous deep-water carbonate mound to show (1) the original source, (2)

  10. Binding of ethanol on calcite: the role of the OH bond and its relevance to biomineralization.

    Science.gov (United States)

    Sand, K K; Yang, M; Makovicky, E; Cooke, D J; Hassenkam, T; Bechgaard, K; Stipp, S L S

    2010-10-05

    The interaction of OH-containing compounds with calcite, CaCO(3), such as is required for the processes that control biomineralization, has been investigated in a low-water solution. We used ethanol (EtOH) as a simple, model, OH-containing organic compound, and observed the strength of its adsorption on calcite relative to OH from water and the consequences of the differences in interaction on crystal growth and dissolution. A combination of atomic force microscopy (AFM) and molecular dynamics (MD) simulations showed that EtOH attachment on calcite is stronger than HOH binding and that the first adsorbed layer of ethanol is highly ordered. The strong ordering of the ethanol molecules has important implications for mineral growth and dissolution because it produces a hydrophobic layer. Ethanol ordering is disturbed along steps and at defect sites, providing a bridge from the bulk solution to the surface. The strong influence of calcite in structuring ethanol extends further into the liquid than expected from electrical double-layer theory. This suggests that in fluids where water activity is low, such as in biological systems optimized for biomineralization, organic molecules can control ion transport to and from the mineral surface, confining it to specific locations, thus providing the organism with control for biomineral morphology.

  11. DC CONDUCTIVITY OF CERAMICS WITH CALCITE WASTE IN THE TEMPERATURE RANGE 20 - 1050C

    Directory of Open Access Journals (Sweden)

    Jan Ondruska

    2015-06-01

    Full Text Available The temperature dependences of the electrical DC conductivity of calcite waste, kaolinite and illite based ceramics were measured in the temperature range of 20 - 1050oC. The ceramic mass that was used was a mixture of 60 wt. % kaolinitic-illitic clay, 20 - 40 wt. % of this clay was fired at 1000oC for 90 min and 0, 10 and 20 wt. % of calcite waste. During heating, several processes take place - the release of the physically bound water, the burning of organic impurities, the dehydroxylation of kaolinite and illite, the decomposition of calcite, and the creation of anorthite and mullite. All of these processes were checked by means of differential thermal analysis (DTA, derivative thermogravimetry (DTG and thermodilatometry (TDA. At low temperatures (20 - 200oC, due to the release and decomposition of physically bound water, H+ and OH- are dominant charge carriers. After completion of release of physically bound water, up to the start of dehydroxylation at the temperature of ~ 450oC, the DC conductivity is dominated by a transport of Na+, K+, and Ca2+ ions. During dehydroxylation, H+ and OH- ions, which are released from kaolinite and illite lattices, contribute to the DC conductivity. Decomposition of calcite runs between ~ 700oC and 900oC. The glassy phase has a dominant influence on the DC conductivity in the fired ceramics. Its high conductivity is determined by the high mobility of Na+, K+, and Ca2+ ions.

  12. Ethanol adsorption on the {10(1)over-bar4} calcite surface

    DEFF Research Database (Denmark)

    Sand, Karina Krarup; Stipp, Susan Louise Svane; Hassenkam, Tue

    2008-01-01

    Preliminary atomic force microscopy investigations of the {10 (1) over bar4} calcite Surface cleaved in ethanol indicate a different surface behaviour than that of the {10 (1) over bar4} surface cleaved in air. The results are consistent with recent theoretical studies and suggest strong ordering...

  13. A generalised chemical precipitation modelling approach in wastewater treatment applied to calcite

    DEFF Research Database (Denmark)

    Mbamba, Christian Kazadi; Batstone, Damien J.; Flores Alsina, Xavier

    2015-01-01

    , the present study aims to identify a broadly applicable precipitation modelling approach. The study uses two experimental platforms applied to calcite precipitating from synthetic aqueous solutions to identify and validate the model approach. Firstly, dynamic pH titration tests are performed to define...

  14. Calcium and Mitosis

    Science.gov (United States)

    Hepler, P.

    1983-01-01

    Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

  15. Carbonates in thrust faults: High temperature investigations into deformation processes in calcite-dolomite systems

    Science.gov (United States)

    Kushnir, A.; Kennedy, L.; Misra, S.; Benson, P.

    2012-04-01

    The role of dolomite on the strength and evolution of calcite-dolomite fold and thrust belts and nappes (as observed in the Canadian Rockies, the Swiss Alps, the Italian Apennines, and the Naukluft Nappe Complex) is largely unknown. Field investigations indicate that strain in natural systems is localized in calcite, resulting in a ductile response, while dolomite deforms in a dominantly brittle manner. To date, experimental studies on polymineralic carbonate systems are limited to homogeneous, fine-grained, calcite-dolomite composites of relatively low dolomite content. The effect of dolomite on limestone rheology, the onset of crystal-plastic deformation in dolomite in composites, and the potential for strain localization in composites have not yet been fully quantified. Constant displacement rate (3x10-4 s-1and 10-4 s-1), high confining pressure (300 MPa) and high temperature (750° C and 800° C) torsion experiments were conducted to address the role of dolomite on the strength of calcite-dolomite composites. Experiments were performed on samples produced by hot isostatic pressing (HIP) amalgams of a natural, pure dolomite and a reagent, pure calcite. We performed experiments on the following mixtures (given as dolomite%): 25%, 35%, 50%, and 75%. These synthetic HIP products eliminated concerns of mineralogical impurities and textural anomalies due to porosity, structural fabrics (e.g., foliation) and fossil content. The samples were deformed up to a maximum finite shear strain of 5.0 and the experimental set up was unvented to inhibit sample decarbonation. Mechanical data shows a considerable increase in sample yield strength with increasing dolomite content. Experimental products with low starting dolomite content (dol%: 25% and 35%) display macroscopic strain localization along compositionally defined foliation. Experimental products with high dolomite content (dol%: 50% and 75%) demonstrate no macroscopic foliation. Post-deformation microstructure analysis

  16. Tracing formation and durability of calcite in a Punic-Roman cistern mortar (Pantelleria Island, Italy).

    Science.gov (United States)

    Dietzel, Martin; Schön, Frerich; Heinrichs, Jens; Deditius, Artur P; Leis, Albrecht

    2016-01-01

    Ancient hydraulic lime mortar preserves chemical and isotopic signatures that provide important information about historical processing and its durability. The distribution and isotopic composition of calcite in a mortar of a well-preserved Punic-Roman cistern at Pantelleria Island (Italy) was used to trace the formation conditions, durability, and individual processing periods of the cistern mortar. The analyses of stable carbon and oxygen isotopes of calcite revealed four individual horizons, D, E, B-1 and B-2, of mortar from the top to the bottom of the cistern floor. Volcanic and ceramic aggregates were used for the production of the mortar of horizons E/D and B-1/B-2, respectively. All horizons comprise hydraulic lime mortar characterized by a mean cementation index of 1.5 ± 1, and a constant binder to aggregate ratio of 0.31 ± 0.01. This suggests standardized and highly effective processing of the cistern. The high durability of calcite formed during carbonation of slaked lime within the matrix of the ancient mortar, and thus the excellent resistance of the hydraulic lime mortar against water, was documented by (i) a distinct positive correlation of δ(18)Ocalcite and δ(13)Ccalcite; typical for carbonation through a mortar horizon, (ii) a characteristic evolution of δ(18)Ocalcite and δ(13)Ccalcite through each of the four mortar horizons; lighter follow heavier isotopic values from upper to lower part of the cistern floor, and (iii) δ(18)Ocalcite varying from -10 to -5 ‰ Vienna Pee Dee belemnite (VPDB). The range of δ(18)Ocalcite values rule out recrystallization and/or neoformation of calcite through chemical attack of water stored in cistern. The combined studies of the chemical composition of the binder and the isotopic composition of the calcite in an ancient mortar provide powerful tools for elucidating the ancient techniques and processing periods. This approach helps to evaluate the durability of primary calcite and demonstrates the

  17. Calcium en cardioplegie

    NARCIS (Netherlands)

    Ruigrok, T.J.C.; Meijler, F.L.

    1985-01-01

    Coronary perfusion with a calcium-free solution, followed by reperfusion with a calcium containing solution, may result in acute myocardial cell death and in irreversible loss of the e1ectrical and mechanical activity of the heart. This phenomenon is known as the calcium paradox. A number of

  18. Enzymatic, urease-mediated mineralization of gellan gum hydrogel with calcium carbonate, magnesium-enriched calcium carbonate and magnesium carbonate for bone regeneration applications

    DEFF Research Database (Denmark)

    Douglas, Timothy; Lapa, Agata; Samal, Sangram K.

    Introduction: Mineralization of hydrogel biomaterials is considered desirable to improve their suitability as materials for bone regeneration[1],[2]. Hydrogels have been most commonly mineralized with calcium phosphate (CaP), but hydrogel-CaCO3 composites have received less attention. Magnesium (Mg......) has been added to CaP to stimulate cell adhesion and proliferation and bone regeneration in vivo, but its effect as a component of carbonate-based biomaterials remains uninvestigated. In this study, gellan gum (GG) hydrogels were mineralized enzymatically with (CaCO3), Mg-enriched CaCO3 and magnesium...... and subjected to physiochemical, mechanical and cell biological characterization. Results: FTIR, SEM, TGA and XRD analysis revealed that increasing magnesium concentration decreased mineral crystallinity. At low magnesium concentrations calcite was formed, while at higher concentrations magnesian calcite...

  19. Review of aragonite and calcite crystal morphogenesis in thermal spring systems

    Science.gov (United States)

    Jones, Brian

    2017-06-01

    Aragonite and calcite crystals are the fundamental building blocks of calcareous thermal spring deposits. The diverse array of crystal morphologies found in these deposits, which includes monocrystals, mesocrystals, skeletal crystals, dendrites, and spherulites, are commonly precipitated under far-from-equilibrium conditions. Such crystals form through both abiotic and biotic processes. Many crystals develop through non-classical crystal growth models that involve the arrangement of nanocrystals in a precisely controlled crystallographic register. Calcite crystal morphogenesis has commonly been linked to a ;driving force;, which is a conceptual measure of the distance of the growth conditions from equilibrium conditions. Essentially, this scheme indicates that increasing levels of supersaturation and various other parameters that produce a progressive change from monocrystals and mesocrystals to skeletal crystals to crystallographic and non-crystallographic dendrites, to dumbbells, to spherulites. Despite the vast amount of information available from laboratory experiments and natural spring systems, the precise factors that control the driving force are open to debate. The fact that calcite crystal morphogenesis is still poorly understood is largely a reflection of the complexity of the factors that influence aragonite and calcite precipitation. Available information indicates that variations in calcite crystal morphogenesis can be attributed to physical and chemical parameters of the parent water, the presence of impurities, the addition of organic or inorganic additives to the water, the rate of crystal growth, and/or the presence of microbes and their associated biofilms. The problems in trying to relate crystal morphogenesis to specific environmental parameters arise because it is generally impossible to disentangle the controlling factor(s) from the vast array of potential parameters that may act alone or in unison with each other.

  20. Impact of trace metals on the water structure at the calcite surface

    Science.gov (United States)

    Wolthers, Mariette; Di Tommaso, Devis; De Leeuw, Nora

    2014-05-01

    Carbonate minerals play an important role in regulating the chemistry of aquatic environments, including the oceans, aquifers, hydrothermal systems, soils and sediments. Through mineral surface processes such as dissolution, precipitation and sorption, carbonate minerals affect the biogeochemical cycles of not only the constituent elements of carbonates, such as Ca, Mg, Fe and C, but also H, P and trace elements. Surface charging of the calcite mineral-water interface, and its reactivity towards foreign ions can be quantified using a surface structural model that includes, among others, the water structure at the interface (i.e. hydrogen bridging) [1,2] in accordance with the CD-MUSIC formalism [3]. Here we will show the impact of foreign metals such as Mg and Sr on the water structure around different surface sites present in etch pits and on growth terraces at the calcite (10-14) surface. We have performed Molecular Dynamics simulations of metal-doped calcite surfaces, using different interatomic water potentials. Results show that the local environment around the structurally distinct sites differs depending on metal presence, suggesting that metal substitutions in calcite affect its reactivity. The information obtained in this study will help in improving existing macroscopic surface model for the reactivity of calcite [2] and give more general insight in mineral surface reactivity in relation to crystal composition. [1] Wolthers, Charlet, & Van Cappellen (2008). Am. J. Sci., 308, 905-941. [2] Wolthers, Di Tommaso, Du, & de Leeuw (2012). Phys. Chem. Chem. Phys. 14, 15145-15157. [3] Hiemstra and Van Riemsdijk (1996) J. Colloid Interf. Sci. 179, 488-508.

  1. Leadership behavior changes following a theory-based leadership development intervention: A longitudinal study of subordinates' and leaders' evaluations.

    Science.gov (United States)

    Larsson, Gerry; Sandahl, Christer; Söderhjelm, Teresa; Sjövold, Endre; Zander, Ann

    2017-02-01

    The aim was to evaluate effects of leadership courses based on the developmental leadership model at the leadership behavioral level. A longitudinal design was employed with assessments before, one and six months after the leadership courses. The sample consisted of 59 leaders who made self-ratings and were rated by at least three subordinates on each occasion. Leadership behaviors were measured with the Developmental Leadership Questionnaire (DLQ). A limited increase of favorable leadership behaviors and a significant reduction of unfavorable leadership behaviors were found, particularly according to the subordinates' ratings. A cluster analysis yielded three meaningful leader profiles and showed that this pattern was found in all three profiles, irrespective of how favorably they were rated before the onset of the intervention. © 2016 Scandinavian Psychological Associations and John Wiley & Sons Ltd.

  2. Supplementation of pig diets in the growth and termination phases with different calcium sources.

    Science.gov (United States)

    Santana, Ana Lúcia Almeida; de Oliveira Carvalho, Paulo Levi; Cristofori, Eliseu Carlos; da Silva Chambo, Poliana Caroline; Barbizan, Mariana; Nunes, Ricardo Vianna; Gregory, Cristine Regina; Genova, Jansller Luiz

    2017-11-07

    The aim of this study was to evaluate the effect of supplementation of pig diets in the growth and termination phases with different calcium sources. In experiment I, 36 whole males were distributed in randomized blocks in six groups, with six replications. A basal diet was formulated to meet the animals' nutritional requirements except for calcium (0.09%), and the sources evaluated (calcitic limestone, monodicalcium phosphate, calcinated bone flour, and oyster flour) replaced the basal diet to provide 0.59% of total calcium. To determine the endogenous calcium, a diet containing low calcium (0.019%) was given simultaneously to another group of animals. Feces and urine were collected for determination the coefficients of apparent and true digestibility. In experiment II, 160 piglets were distributed in randomized blocks in four treatments, with five replications and four animals per experimental unit. Carcass and performance parameters, calcium concentration in bone and serum, and bone parameters were evaluated. The data were submitted to analysis of variance and factorial. The calcium source did not influence the digestibility coefficients determined by total collection (P > 0.05). The digestibility of Ca from oyster flour estimated by collection with an indicator was higher than that from the other sources (P Calcium sources did not interfere in the evaluated parameters (P > 0.05). The sources studied in this work can be used to supplement growing pigs' diets.

  3. Effects of calcium source on biochemical properties of microbial CaCO3 precipitation

    Directory of Open Access Journals (Sweden)

    Jing eXu

    2015-12-01

    Full Text Available The biochemical properties of CaCO3 precipitation induced by Sporosarcina pasteurii, an ureolytic type microorganism, were investigated. Effects of calcium source on the precipitation process were examined, since calcium source plays a key role in microbiologically-induced mineralization. Regardless of the calcium source type, three distinct stages in the precipitation process were identified by Ca2+, NH4+, pH and cell density monitoring. Compared with stage 1 and 3, stage 2 was considered as the most critical part since biotic CaCO3 precipitation occurs during this stage. Kinetics studies showed that the microbial CaCO3 precipitation rate for calcium lactate was over twice of that for calcium nitrate, indicating that calcium lactate is more beneficial for the cell activity, which in turn determines urease production and CaCO3 precipitation. X-ray diffraction analysis confirmed the CaCO3 crystal as calcite, although scanning electron microscopy revealed a difference in crystal size and morphology if calcium source was different. The findings of this paper further suggest a promising application of microbiologically-induced CaCO3 precipitation in remediation of surface and cracks of porous media, e.g. cement-based composites, particularly by using organic source of calcium lactate.

  4. The Paradox of Power Sharing: Participative Charismatic Leaders have Subordinates with more instead of less Need for Leadership

    OpenAIRE

    de Vries, R.E.; Pathak, R.D.; Paquin, A.R.

    2011-01-01

    Although charismatic and participative leaders have been noted for their positive effects on criteria such as performance, job satisfaction, and commitment, few studies have looked at the relations with subordinates' leadership needs. In this study, the relations between charismatic and participative leadership, team outcomes, and a team's need for leadership were investigated. The sample consisted of South Pacific CEOs and their top-level management teams from Fiji, Tonga, Samoa, Vanuatu, an...

  5. Bed site selection by a subordinate predator: an example with the cougar (Puma concolor) in the Greater Yellowstone Ecosystem.

    Science.gov (United States)

    Kusler, Anna; Elbroch, L Mark; Quigley, Howard; Grigione, Melissa

    2017-01-01

    As technology has improved, our ability to study cryptic animal behavior has increased. Bed site selection is one such example. Among prey species, bed site selection provides thermoregulatory benefits and mitigates predation risk, and may directly influence survival. We conducted research to test whether a subordinate carnivore also selected beds with similar characteristics in an ecosystem supporting a multi-species guild of competing predators. We employed a model comparison approach in which we tested whether cougar (Puma concolor) bed site attributes supported the thermoregulatory versus the predator avoidance hypotheses, or exhibited characteristics supporting both hypotheses. Between 2012-2016, we investigated 599 cougar bed sites in the Greater Yellowstone Ecosystem and examined attributes at two scales: the landscape (second-order, n = 599) and the microsite (fourth order, n = 140). At the landscape scale, cougars selected bed sites in winter that supported both the thermoregulatory and predator avoidance hypotheses: bed sites were on steeper slopes but at lower elevations, closer to the forest edge, away from sagebrush and meadow habitat types, and on southern, eastern, and western-facing slopes. In the summer, bed attributes supported the predator avoidance hypothesis over the thermoregulation hypothesis: beds were closer to forest edges, away from sagebrush and meadow habitat classes, and on steeper slopes. At the microsite scale, cougar bed attributes in both the winter and summer supported both the predator avoidance and thermoregulatory hypotheses: they selected bed sites with high canopy cover, high vegetative concealment, and in a rugged habitat class characterized by cliff bands and talus fields. We found that just like prey species, a subordinate predator selected bed sites that facilitated both thermoregulatory and anti-predator functions. In conclusion, we believe that measuring bed site attributes may provide a novel means of measuring the

  6. Bed site selection by a subordinate predator: an example with the cougar (Puma concolor in the Greater Yellowstone Ecosystem

    Directory of Open Access Journals (Sweden)

    Anna Kusler

    2017-11-01

    Full Text Available As technology has improved, our ability to study cryptic animal behavior has increased. Bed site selection is one such example. Among prey species, bed site selection provides thermoregulatory benefits and mitigates predation risk, and may directly influence survival. We conducted research to test whether a subordinate carnivore also selected beds with similar characteristics in an ecosystem supporting a multi-species guild of competing predators. We employed a model comparison approach in which we tested whether cougar (Puma concolor bed site attributes supported the thermoregulatory versus the predator avoidance hypotheses, or exhibited characteristics supporting both hypotheses. Between 2012–2016, we investigated 599 cougar bed sites in the Greater Yellowstone Ecosystem and examined attributes at two scales: the landscape (second-order, n = 599 and the microsite (fourth order, n = 140. At the landscape scale, cougars selected bed sites in winter that supported both the thermoregulatory and predator avoidance hypotheses: bed sites were on steeper slopes but at lower elevations, closer to the forest edge, away from sagebrush and meadow habitat types, and on southern, eastern, and western-facing slopes. In the summer, bed attributes supported the predator avoidance hypothesis over the thermoregulation hypothesis: beds were closer to forest edges, away from sagebrush and meadow habitat classes, and on steeper slopes. At the microsite scale, cougar bed attributes in both the winter and summer supported both the predator avoidance and thermoregulatory hypotheses: they selected bed sites with high canopy cover, high vegetative concealment, and in a rugged habitat class characterized by cliff bands and talus fields. We found that just like prey species, a subordinate predator selected bed sites that facilitated both thermoregulatory and anti-predator functions. In conclusion, we believe that measuring bed site attributes may provide a novel

  7. Calcium Carbonate Formation by Genetically Engineered Inorganic Binding Peptides

    Science.gov (United States)

    Gresswell, Carolyn Gayle

    Understanding how organisms are capable of forming (synthesize, crystallize, and organize) solid minerals into complex architectures has been a fundamental question of biomimetic materials chemistry and biomineralization for decades. This study utilizes short peptides selected using a cell surface display library for the specific polymorphs of calcium carbonate, i.e., aragonite and calcite, to identify two sets of sequences which can then be used to examine their effects in the formation, crystal structure, morphology of the CaCO3 minerals. A procedure of counter selection, along with fluorescence microscopy (FM) characterization, was adapted to insure that the sequences on the cells were specific to their respective substrate, i.e., aragonite or calcite. From the resulting two sets of sequences selected, five distinct strong binders were identified with a variety of biochemical characteristics and synthesized for further study. Protein derived peptides, using the known sequences of the proteins that are associated with calcite or aragonite, were also designed using a bioinformatics-based similarity analysis of the two sets of binders. In particular, an aragonite binding protein segment, AP7, a protein found in nacre, was chosen for this design and the resulting effects of the designed peptides and the AP7 were examined. Specifically, the binding affinities of the selected and the protein derived peptides off the cells were then tested using FM; these studies resulted in different binding characteristics of the synthesized and cellular bound peptides. Two of the peptides that displayed strong binding on the cells bound to neither of the CaCO 3 substrates and both the high and low similarity protein-derived peptides bound to both polymorphs. However, two of the peptides were found to only bind to their respective polymorph showing; these results are significant in that with this study it is demonstrated that the designed peptides based on experimental library

  8. Production supervisor impacts on subordinates' safety outcomes: an investigation of leader-member exchange and safety communication.

    Science.gov (United States)

    Michael, Judd H; Guo, Zhen George; Wiedenbeck, Janice K; Ray, Charles D

    2006-01-01

    Supervisors are increasingly important to the functioning of manufacturing operations, in large part due to their role as leaders. While supervisors' relations and communication with their subordinates are known to be important in influencing subordinates' behavior, little is known about how these two factors will impact subordinates' safety. This study investigated how much each factor contributes to safety-related outcomes for blue-collar production employees. Production employees at five Pennsylvania wood manufacturers completed a survey during their work shift. Five hundred and ninety eight employees provided data on leader-member exchange (LMX), safety communication, and safety-related events. Archival data on OSHA recordables were also obtained from the producers' human resources database. Analyses found that the influence of LMX was greater than that of safety communication in predicting safety-related events. Neither LMX nor safety communication was significantly related to OSHA recordables. Results also demonstrated that employee job satisfaction and demographic variables such as gender and age have safety implications. Results from this study further emphasize the importance of production supervisors and illustrate the potential role of leader-member exchange in enhancing workplace safety. Specifically, organizations should foster positive social exchange between their employees and supervisors and enhance the leadership qualities of supervisors to help reduce workplace injuries.

  9. Relationship between nurses and physicians in terms of organizational culture: who is responsible for subordination of nurses?

    Science.gov (United States)

    Skela Savic, Brigita; Pagon, Milan

    2008-06-01

    To investigate how nurses and physicians perceive organizational culture, their integration into the organizational processes, and relations within a health care team. We performed a cross-sectional study that included 106 physicians and 558 nurses from 14 Slovenian hospitals in December 2005. The hospitals were randomly selected. We distributed the questionnaires on the same day to physicians and nurses during a morning shift. The total number of distributed questionnaires represented a 20% of each personnel category at each hospital. The following variables were studied: organizational culture, integration of nurses and physicians in hospital processes, and subordination of nurses to physicians. Physicians and nurses favored a culture of internal focus, stability, and control. Both groups estimated that they had a low level of personal involvement in their organizations and indicated insufficient involvement in work teams, while nurses also felt that they were subordinated (mean+/-standard deviation, 3.6+/-0.9 on a scale from 1 to 5) to physicians (2.7+/-1.0; Porientation correlated positively with the subordination of nurses (PPmarket culture, level of personal involvement, and the level of education. Our research showed that the professional growth of nurses was mainly threatened by organizational factors such as hierarchy, control orientation, a lack of cooperation and team building between physicians and nurses, as well as insufficient inclusion of both physicians and nurses into change implementation activities.

  10. Third-Order Differential Subordination and Superordination Results for Meromorphically Multivalent Functions Associated with the Liu-Srivastava Operator

    Directory of Open Access Journals (Sweden)

    Huo Tang

    2014-01-01

    Full Text Available There are many articles in the literature dealing with the first-order and the second-order differential subordination and superordination problems for analytic functions in the unit disk, but only a few articles are dealing with the above problems in the third-order case (see, e.g., Antonino and Miller (2011 and Ponnusamy et al. (1992. The concept of the third-order differential subordination in the unit disk was introduced by Antonino and Miller in (2011. Let Ω be a set in the complex plane C. Also let p be analytic in the unit disk U=z:z∈C  and  z<1 and suppose that ψ:C4×U→C. In this paper, we investigate the problem of determining properties of functions p(z that satisfy the following third-order differential superordination: Ω⊂ψpz,zp′z,z2p′′z,z3p′′′z;z:z∈U. As applications, we derive some third-order differential subordination and superordination results for meromorphically multivalent functions, which are defined by a family of convolution operators involving the Liu-Srivastava operator. The results are obtained by considering suitable classes of admissible functions.

  11. Organizational environment factors associated with corporate social responsibility: effects on communication and guanxi relationship between supervisors and subordinates in SMEs

    Directory of Open Access Journals (Sweden)

    Edward WONG SEK KHIN

    2016-09-01

    Full Text Available Effective communication within an organization as part of CSR benchmarking factor that helps align employee expectations facilitates problem solving, builds cooperative relationships and channels employee efforts to achieve common goals. This paper seeks to determine how CSR benchmarking factors of the organizational environment (such as management style, organizational structure and workplace culture affect the effectiveness of intra-organizational communication and to examine the moderating effect of supervisor – subordinate guanxi. Data for the study was collected using self-administered questionnaires from working respondents in Kuala Lumpur in Selangor State, Malaysia. This study found that a more participative management style, less formalized organizational structure of SMEs and a healthier workplace culture are positively related to intra-organizational communication effectiveness. It was also discovered that the supervisor – subordinate relationship known as guanxi, has a positive moderating effect on all three relationships between management style, organizational structure and workplace culture with intra-organizational communication effectiveness. This study concludes that an organization’s management attitude towards employee participation, formalization of structure and healthiness of culture play important roles in encouraging effective communication and close supervisor – subordinate guanxi and further promotes communication, in addition to the mentioned environmental conditions.

  12. Petrography, mineralogy, and chemistry of calcite-silica deposits at Exile Hill, Nevada, compared with local spring deposits

    Energy Technology Data Exchange (ETDEWEB)

    Vaniman, D.T.; Chipera, S.J.; Bish, D.L.

    1995-12-01

    Chemical, mineralogic, and petrographic analyses of siliceous calcretes from Exile Hill east of Yucca Mountain, Nevada, indicate that pedogenic processes alone account for the formation of the calcretes. These calcretes have been interpreted by some observers as evidence of seismically triggered eruptions of deep water. Such an origin could have important consequences if Yucca Mountain is developed as an unsaturated site for the disposal of high-level nuclear waste. At odds with this hypothesis are the absence of features that should be present at fault-fed springs (e.g., fissure-ridge mounds with microterraces) and the preservation within root casts of delicate pedogenic microfossils, such as calcified filaments and needle-fiber calcites. Mineral-chemical evidence of pedogenic origin is found in heavy-mineral concentrations, reflected in Fe and Sc enrichments. These concentrations, which occur in the most massive of the vein calcretes, require derivation of detritus from a mixture of weathered and eolian materials that occur in the overlying B soil horizons, as opposed to direct incorporation of adjacent unweathered bedrock. Carbonate and silica abundances and accumulation rates are well within the scope of pedogenic processes. Calcium is derived from rainwater or eolian sources, whereas silica is derived in part by dissolution of local volcanic glasses or from dissolution of unstable silica minerals that are abundant in the local tuffs. In contrast with local deposits that are of spring or seep origin, the siliceous calcretes at Yucca Mountain are pedogenic in origin as well as evolution and provide no evidence in support of conjectured spring activity.

  13. Olfactory cues are subordinate to visual stimuli in a neotropical generalist weevil.

    Directory of Open Access Journals (Sweden)

    Fernando Otálora-Luna

    Full Text Available The tropical root weevil Diaprepes abbreviatus is a major pest of multiple crops in the Caribbean Islands and has become a serious constraint to citrus production in the United States. Recent work has identified host and conspecific volatiles that mediate host- and mate-finding by D. abbreviatus. The interaction of light, color, and odors has not been studied in this species. The responses of male and female D. abbreviatus to narrow bandwidths of visible light emitted by LEDs offered alone and in combination with olfactory stimuli were studied in a specially-designed multiple choice arena combined with a locomotion compensator. Weevils were more attracted to wavelengths close to green and yellow compared with blue or ultraviolet, but preferred red and darkness over green. Additionally, dim green light was preferred over brighter green. Adult weevils were also attracted to the odor of its citrus host + conspecifics. However, the attractiveness of citrus + conspecific odors disappeared in the presence of a green light. Photic stimulation induced males but not females to increase their speed. In the presence of light emitted by LEDs, turning speed decreased and path straightness increased, indicating that weevils tended to walk less tortuously. Diaprepes abbreviatus showed a hierarchy between chemo- and photo-taxis in the series of experiments presented herein, where the presence of the green light abolished upwind anemotaxis elicited by the pheromone + host plant odor. Insight into the strong responses to visual stimuli of chemically stimulated insects may be provided when the amount of information supplied by vision and olfaction is compared, as the information transmission capacity of compound eyes is estimated to be several orders of magnitude higher compared with the olfactory system. Subordination of olfactory responses by photic stimuli should be considered in the design of strategies aimed at management of such insects.

  14. Chronic subordinate colony housing (CSC as a model of chronic psychosocial stress in male rats.

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    Kewir D Nyuyki

    Full Text Available Chronic subordinate colony housing (CSC is an adequate and reliable mouse model of chronic psychosocial stress, resulting in reduced body weight gain, reduced thymus and increased adrenal weight, long-lasting anxiety-like behaviour, and spontaneous colitis. Furthermore, CSC mice show increased corticotrophin (ACTH responsiveness to acute heterotypic stressors, suggesting a general mechanism which allows a chronically-stressed organism to adequately respond to a novel threat. Therefore, the aim of the present study was to extend the CSC model to another rodent species, namely male Wistar rats, and to characterize relevant physiological, immunological, and behavioural consequences; placing particular emphasis on changes in hypothalamo-pituitary-adrenal (HPA axis responsiveness to an acute heterotypic stressor. In line with previous mouse data, exposure of Wistar rats to 19 days of CSC resulted in a decrease in body weight gain and absolute thymus mass, mild colonic barrier defects and intestinal immune activation. Moreover, no changes in stress-coping behaviour or social preference were seen; again in agreement with the mouse paradigm. Most importantly, CSC rats showed an increased plasma corticosterone response to an acute heterotypic stressor (open arm, 5 min despite displaying similar basal levels and similar basal and stressor-induced plasma ACTH levels. In contrast to CSC mice, anxiety-related behaviour and absolute, as well as relative adrenal weights remained unchanged in CSC rats. In summary, the CSC paradigm could be established as an adequate model of chronic psychosocial stress in male rats. Our data further support the initial hypothesis that adrenal hyper-responsiveness to ACTH during acute heterotypic stressors represents a general adaptation, which enables a chronically-stressed organism to adequately respond to novel challenges.

  15. Olfactory Cues Are Subordinate to Visual Stimuli in a Neotropical Generalist Weevil

    Science.gov (United States)

    Otálora-Luna, Fernando; Lapointe, Stephen L.; Dickens, Joseph C.

    2013-01-01

    The tropical root weevil Diaprepes abbreviatus is a major pest of multiple crops in the Caribbean Islands and has become a serious constraint to citrus production in the United States. Recent work has identified host and conspecific volatiles that mediate host- and mate-finding by D. abbreviatus. The interaction of light, color, and odors has not been studied in this species. The responses of male and female D. abbreviatus to narrow bandwidths of visible light emitted by LEDs offered alone and in combination with olfactory stimuli were studied in a specially-designed multiple choice arena combined with a locomotion compensator. Weevils were more attracted to wavelengths close to green and yellow compared with blue or ultraviolet, but preferred red and darkness over green. Additionally, dim green light was preferred over brighter green. Adult weevils were also attracted to the odor of its citrus host + conspecifics. However, the attractiveness of citrus + conspecific odors disappeared in the presence of a green light. Photic stimulation induced males but not females to increase their speed. In the presence of light emitted by LEDs, turning speed decreased and path straightness increased, indicating that weevils tended to walk less tortuously. Diaprepes abbreviatus showed a hierarchy between chemo- and photo-taxis in the series of experiments presented herein, where the presence of the green light abolished upwind anemotaxis elicited by the pheromone + host plant odor. Insight into the strong responses to visual stimuli of chemically stimulated insects may be provided when the amount of information supplied by vision and olfaction is compared, as the information transmission capacity of compound eyes is estimated to be several orders of magnitude higher compared with the olfactory system. Subordination of olfactory responses by photic stimuli should be considered in the design of strategies aimed at management of such insects. PMID:23341926

  16. Calcite dissolution by Brevibacterium sp. SOTI06: A futuristic approach for the reclamation of calcareous sodic soils

    Directory of Open Access Journals (Sweden)

    Tamilselvi S.M

    2016-12-01

    Full Text Available Assessing the ability of soil microorganisms to dissolute poorly soluble native calcite to supply Ca2+ is a new area to be explored in reclaiming sodic soils by supplying adequate Ca2+ and reducing the recurrent sodicity. Hence, the present study aimed to isolate a calcite dissolving bacteria (CDB from calcareous sodic soils and to understand the mechanism of calcite dissolution. Of the thirty three CDB isolates recovered from the calcareous sodic soils of Tamil Nadu (Coimbatore, Ramnad and Trichy, eleven isolates were screened for calcite dissolution based on titratable acidity. 16S rRNA gene sequence analysis of the three best isolates viz., SORI09, SOTI05 and SOTI06 revealed 99 % similarity to Bacillus aryabhattai, 100 % to B. megaterium and 93 % to Brevibacterium sp., respectively. Among them, Brevibacterium sp. SOTI06 released more Ca2+ (3.6 g.l-1 by dissolving 18.6 % of the native calcite. The spectral data of FTIR also showed reduction in the intensity of calcite (55.36 to 41.27 by the isolate at a wave number of 1636 cm-1 which confirmed the dissolution. Besides producing organic acids (gluconic acid and acetic acid, Brevibacterium sp. SOTI06 also produced siderophore (91.6 % and extracellular polysaccharides (EPS, 13.3 µg. ml-1 which might have enhanced the calcite dissolution.

  17. Calcite Dissolution by Brevibacterium sp. SOTI06: A Futuristic Approach for the Reclamation of Calcareous Sodic Soils.

    Science.gov (United States)

    Tamilselvi, S M; Thiyagarajan, Chitdeshwari; Uthandi, Sivakumar

    2016-01-01

    Assessing the ability of soil microorganisms to dissolute poorly soluble native calcite to supply Ca2+ is a new area to be explored in reclaiming sodic soils by supplying adequate Ca2+ and reducing the recurrent sodicity. Hence, the present study aimed to isolate a calcite dissolving bacteria (CDB) from calcareous sodic soils and to understand the mechanism of calcite dissolution. Of the 33 CDB isolates recovered from the calcareous sodic soils of Tamil Nadu (Coimbatore, Ramnad, and Trichy), 11 isolates were screened for calcite dissolution based on titratable acidity. 16S rRNA gene sequence analysis of the three best isolates viz., SORI09, SOTI05, and SOTI06 revealed 99% similarity to Bacillus aryabhattai, 100% to B. megaterium, and 93% to Brevibacterium sp., respectively. Among them, Brevibacterium sp. SOTI06 released more Ca2+ (3.6 g.l-1) by dissolving 18.6% of the native calcite. The spectral data of FTIR also showed reduction in the intensity of calcite (55.36-41.27) by the isolate at a wave number of 1636 cm-1 which confirmed the dissolution. Besides producing organic acids (gluconic acid and acetic acid), Brevibacterium sp. SOTI06 also produced siderophore (91.6%) and extracellular polysaccharides (EPS, 13.3 μg. ml-1) which might have enhanced the calcite dissolution.

  18. Brain levels of arginine-vasotocin and isotocin in dominant and subordinate males of a cichlid fish.

    Science.gov (United States)

    Almeida, Olinda; Gozdowska, Magdalena; Kulczykowska, Ewa; Oliveira, Rui F

    2012-02-01

    The nonapeptides arginine-vasotocin (AVT) and isotocin (IT), which are the teleost homologues of arginine-vasopressin and oxytocin in mammals, have well established peripheral effects on osmoregulation and stress response, and central effects on social behavior. However, all studies that have looked so far into the relationship between these nonapeptides and social behavior have used indirect measures of AVT/IT activity (i.e. immunohistochemistry of AVT/IT immunoreactive neurons, or AVT/IT or their receptors mRNA expression with in situ hybridization or qPCR) and therefore direct measures of peptide levels in relation to social behavior are still lacking. Here we use a recently developed high-performance liquid chromatography analysis with fluorescence detection (HPLC-FL) method to quantify the levels of both AVT and IT in macro-dissected brain areas [i.e. olfactory bulbs, telencephalon, diencephalon, optic tectum, cerebellum, and hindbrain (= rhombencephalon minus cerebellum)] and pituitary of dominant and subordinate male cichlid fish (Oreochromis mossambicus). The pituitary shows higher levels of both peptides than any of the brain macroareas, and the olfactory bulbs have the highest AVT among all brain areas. Except for IT in the telencephalon there is a lack of correlations between central levels and pituitary peptide levels, suggesting an independent control of hypophysial and CNS nonapeptide secretion. There were also no correlations between AVT and IT levels either for each brain region or for the pituitary gland, suggesting a decoupled activity of the AVT and IT systems at the CNS level. Subordinate AVT pituitary levels are significantly higher than those of dominants, and dominant hindbrain IT levels are significantly higher than those of subordinates, suggesting a potential involvement of AVT in social stress in subordinate fish and of IT in the regulation of dominant behavior at the level of the hindbrain. Since in this species dominant males use urine

  19. Influence of water on clumped-isotope bond reordering kinetics in calcite

    Science.gov (United States)

    Brenner, Dana C.; Passey, Benjamin H.; Stolper, Daniel A.

    2018-03-01

    Oxygen self-diffusion in calcite and many other minerals is considerably faster under wet conditions relative to dry conditions. Here we investigate whether this "water effect" also holds true for solid-state isotope exchange reactions that alter the abundance of carbonate groups with multiple rare isotopes ('clumped' isotope groups) via the process of solid-state bond reordering. We present clumped-isotope reordering rates for optical calcite heated under wet, high-pressure (100 MPa) conditions. We observe only modest increases in reordering rates under such conditions compared with rates for the same material reacted in dry CO2 under low-pressure conditions. Activation energies under wet, high-pressure conditions are indistinguishable from those for dry, low-pressure conditions, while rate constants are resolvably higher (up to ∼3 times) for wet, high-pressure relative to dry, low-pressure conditions in most of our interpretations of experimental results. This contrasts with the water effect for oxygen self-diffusion in calcite, which is associated with lower activation energies, and diffusion coefficients that are ≥103 times higher compared with dry (pure CO2) conditions in the temperature range of this study (385-450 °C). The water effect for clumped-isotopes leads to calculated apparent equilibrium temperatures ("blocking temperatures") for typical geological cooling rates that are only a few degrees higher than those for dry conditions, while O self-diffusion blocking temperatures in calcite grains are ∼150-200 °C lower in wet conditions compared with dry conditions. Since clumped-isotope reordering is a distributed process that occurs throughout the mineral volume, our clumped-isotope results support the suggestion of Labotka et al. (2011) that the water effect in calcite does not involve major changes in bulk (volume) diffusivity, but rather is primarily a surface phenomenon that facilitates oxygen exchange between the calcite surface and external

  20. Microstructure of calcite deformed by high-pressure torsion: An X-ray line profile study

    Science.gov (United States)

    Schuster, Roman; Schafler, Erhard; Schell, Norbert; Kunz, Martin; Abart, Rainer

    2017-11-01

    Calcite aggregates were deformed to high strain using high-pressure torsion and applying confining pressures of 1-6 GPa and temperatures between room temperature and 450 °C. The run products were characterized by X-ray diffraction, and key microstructural parameters were extracted employing X-ray line profile analysis. The dominant slip system was determined as r { 10 1 bar 4 } ⟨ 2 bar 021 ⟩ with edge dislocation character. The resulting dislocation density and the size of the coherently scattering domains (CSD) exhibit a systematic dependence on the P-T conditions of deformation. While high pressure generally impedes recovery through reducing point defect mobility, the picture is complicated by pressure-induced phase transformations in the CaCO3 system. Transition from the calcite stability field to those of the high-pressure polymorphs CaCO3-II, CaCO3-III and CaCO3-IIIb leads to a change of the microstructural evolution with deformation. At 450 °C and pressures within the calcite stability field, dislocation densities and CSD sizes saturate at shear strains exceeding 10 in agreement with earlier studies at lower pressures. In the stability field of CaCO3-II, the dislocation density exhibits a more complex behavior. Furthermore, at a given strain and strain rate, the dislocation density increases and the CSD size decreases with increasing pressure within the stability fields of either calcite or of the high-pressure polymorphs. There is, however, a jump from high dislocation densities and small CSDs in the upper pressure region of the calcite stability field to lower dislocation densities and larger CSDs in the low-pressure region of the CaCO3-II stability field. This jump is more pronounced at higher temperatures and less so at room temperature. The pressure influence on the deformation-induced evolution of dislocation densities implies that pressure variations may change the rheology of carbonate rocks. In particular, a weakening is expected to occur at

  1. 3D Mapping of calcite and a demonstration of its relevance to permeability evolution in reactive fractures

    Science.gov (United States)

    Ellis, Brian R.; Peters, Catherine A.

    2016-09-01

    There is a need to better understand reaction-induced changes in fluid transport in fractured shales, caprocks and reservoirs, especially in the context of emerging energy technologies, including geologic carbon sequestration, unconventional natural gas, and enhanced geothermal systems. We developed a method for 3D calcite mapping in rock specimens. Such information is critical in reactive transport modeling, which relies on information about the locations and accessible surface area of reactive minerals. We focused on calcite because it is a mineral whose dissolution could lead to substantial pathway alteration because of its high solubility, fast reactivity, and abundance in sedimentary rocks. Our approach combines X-ray computed tomography (XCT) and scanning electron microscopy. The method was developed and demonstrated for a fractured limestone core containing about 50% calcite, which was 2.5 cm in diameter and 3.5 cm in length and had been scanned using XCT. The core was subsequently sectioned and energy dispersive X-ray spectroscopy was used to determine elemental signatures for mineral identification and mapping. Back-scattered electron microscopy was used to identify features for co-location. Finally, image analysis resulted in characteristic grayscale intensities of X-ray attenuation that identify calcite. This attenuation mapping ultimately produced a binary segmented 3D image of the spatial distribution of calcite in the entire core. To demonstrate the value of this information, permeability changes were investigated for hypothetical fractures created by eroding calcite from 2D rock surfaces. Fluid flow was simulated using a 2D steady state model. The resulting increases in permeability were profoundly influenced by the degree to which calcite is contiguous along the flow path. If there are bands of less reactive minerals perpendicular to the direction of flow, fracture permeability may be an order of magnitude smaller than when calcite is contiguous

  2. Preparation of calcium carbonate as nanoparticles from inorganic precursors and sucrose as additive with potential application as biomaterial

    Energy Technology Data Exchange (ETDEWEB)

    Takabaita, F.; Mahtout, L.; Perez Villarejo, L.; Carrasco Hurtado, B.; Sanchez Soto, P.J.

    2016-07-01

    In this communication, it is reported the first relevant results on a broad study on the preparation of calcium carbonate as precipitated nanoparticles of the polymorphs vaterite and calcite. The inorganic precursors are calcium nitrate tetrahydrate and sodium hydrogencarbonate, and the organic additive is sucrose in aqueous solution. The crystalline phases are studied by X-Ray powder diffraction, using a quantitative method, and the particle morphologies using scanning electron microscopy. When the organic additive is not used, calcite as the most thermodynamically stable polymorph is precipitated as nanocrystalline predominant phase (83%) mixed with vaterite. Using a high concentration of the organic additive (67%), vaterite is precipitated as the nanocrystalline predominant phase (>98%). Using the additive in variable proportion produces the precipitation of the 2 polymorphs, being vaterite always the predominant phase. The morphology of the precipitated calcium carbonate shows nanospherical uniform particles with irregular contourns of vaterite and characteristic rhomboedral particles of calcite when this phase is present. According to the biocompatibility, this material shows interest in applications as biomaterial in bone implants. (Author)

  3. Effects of the job stress education for supervisors on psychological distress and job performance among their immediate subordinates: a supervisor-based randomized controlled trial.

    Science.gov (United States)

    Takao, Soshi; Tsutsumi, Akizumi; Nishiuchi, Kyoko; Mineyama, Sachiko; Kawakami, Norito

    2006-11-01

    As job stress is now one of the biggest health-related problems in the workplace, several education programs for supervisors have been conducted to reduce job stress. We conducted a supervisor-based randomized controlled trial to evaluate the effects of an education program on their subordinates' psychological distress and job performance. The subjects were 301 employees (46 supervisors and 255 subordinates) in a Japanese sake brewery. First, we randomly allocated supervisors to the education group (24 supervisors) and the waiting-list group (22 supervisors). Then, for the allocated supervisors we introduced a single-session, 60-min education program according to the guidelines for employee mental health promotion along with training that provided consulting skills combined with role-playing exercises. We conducted pre- and post-intervention (after 3 months) surveys for all subordinates to examine psychological distress and job performance. We defined the intervention group as those subordinates whose immediate supervisors received the education, and the control group was defined as those subordinates whose supervisors did not. To evaluate the effects, we employed a repeated measures analysis of variance (ANOVA). Overall, the intervention effects (time x group) were not significant for psychological distress or job performance among both male (p=0.456 and 0.252) and female (p=0.714 and 0.106) subordinates. However, young male subordinates engaged in white-collar occupations showed significant intervention effects for psychological distress (p=0.012) and job performance (p=0.029). In conclusion, our study indicated a possible beneficial effect of supervisor education on the psychological distress and job performance of subordinates. This effect may vary according to specific groups.

  4. Thermodynamics of magnesian calcite solid-solutions at 25°C and 1 atm total pressure

    Science.gov (United States)

    Busenberg, Eurybiades; Plummer, L. Niel

    1989-01-01

    The stability of magnesian calcites was reexamined, and new results are presented for 28 natural inorganic, 12 biogenic, and 32 synthetic magnesian calcites. The magnesian calcite solid-solutions were separated into two groups on the basis of differences in stoichiometric solubility and other physical and chemical properties. Group I consists of solids of mainly metamorphic and hydrothermal origin, synthetic calcites prepared at high temperatures and pressures, and synthetic solids prepared at low temperature and very low calcite supersaturations () from artificial sea water or NaClMgCl2CaCl2solutions. Group I solids are essentially binary s of CaCO2 and MgCO2, and are thought to be relatively free of structural defects. Group II solid-solutions are of either biogenic origin or are synthetic magnesian calcites and protodolomites (0–20 and ∼ 45 mole percent MgCO3) prepared at high calcite supersaturations () from NaClNa2SO4MgCl2CaCl2 or NaClMgCl2CaCl2 solutions. Group II solid-solutions are treated as massively defective solids. The defects include substitution foreign ions (Na+ and SO42−) in the magnesian calcite lattice (point defects) and dislocations (~2 · 109 cm−2). Within each group, the excess free energy of mixing, GE, is described by the mixing model , where x is the mole fraction of the end-member Ca0.5Mg0.5CO3 in the solid-solution. The values of A0and A1 for Group I and II solids were evaluated at 25°C. The equilibrium constants of all the solids are closely described by the equation ln , where KC and KD are the equilibrium constants of calcite and Ca0.5Mg0.5CO3. Group I magnesian calcites were modeled as sub-regular solid-solutions between calcite and dolomite, and between calcite and “disordered dolomite”. Both models yield almost identical equilibrium constants for these magnesian calcites. The Group II magnesian calcites were modeled as sub-regular solid-solutions between defective calcite and

  5. Uranium immobilization by sulfate-reducing biofilms grown on hematite, dolomite, and calcite.

    Science.gov (United States)

    Marsili, Enrico; Beyenal, Haluk; Di Palma, Luca; Merli, Carlo; Dohnalkova, Alice; Amonette, James E; Lewandowski, Zbigniew

    2007-12-15

    Biofilms of sulfate-reducing bacteria Desulfovibrio desulfuricans G20 were used to reduce dissolved U(VI) and subsequently immobilize U(IV) in the presence of uranium-complexing carbonates. The biofilms were grown in three identically operated fixed bed reactors, filled with three types of minerals: one noncarbonate-bearing mineral (hematite) and two carbonate-bearing minerals (calcite and dolomite). The source of carbonates in the reactors filled with calcite and dolomite were the minerals, while in the reactor filled with hematite it was a 10 mM carbonate buffer, pH 7.2, which we added to the growth medium. Our five-month study demonstrated that the sulfate-reducing biofilms grown in all reactors were able to immobilize/reduce uranium efficiently, despite the presence of uranium-complexing carbonates.

  6. Geochemistry of speleothems affected by aragonite to calcite recrystallization - Potential inheritance from the precursor mineral

    Science.gov (United States)

    Domínguez-Villar, David; Krklec, Kristina; Pelicon, Primož; Fairchild, Ian J.; Cheng, Hai; Edwards, Lawrence R.

    2017-03-01

    Formerly aragonite speleothems recrystallized to calcite result from solutions subsaturated in aragonite and supersaturated in calcite that infiltrate into the speleothem through the interconnected porosity. In most cases, the crystal replacement takes place through a thin solution film. This diagenetic process can occur under open or semi-closed geochemical conditions. Thus, secondary calcite crystals record the composition of the fluid at the time of diagenesis affected by calcite partition coefficients and fractionation factors (open system) or partly inherit the composition of the primary aragonite (semi-closed system). So, whether or not recrystallized aragonite speleothems can record reliable geochemical signals from the time of speleothem primary deposition still is an open debate. We studied a stalagmite from Eagle Cave (Spain) predominantly composed of secondary calcite that replaced aragonite, although a core of primary aragonite extending 45 mm along the growth direction was preserved at the base of the sample. We obtained Mg and Sr compositional maps, paired U-Th dating and δ18O and δ13C profiles across the diagenetic front. Additionally, two parallel isotope records were obtained along the speleothem growth direction in the aragonite and calcite sectors. Our results support that recrystallization of this speleothem took place in open system conditions for δ18O, δ13C, Mg and Sr, but in semi-closed system conditions for U and Th. The recrystallization of this sample took place during one or several events, likely after the Younger Dryas as a result of climate change influencing drip water composition. Based on compositional zoned patterns, we suggest that the advance of diagenetic fronts in this speleothem had an average rate of 50 ± 45 μm/yr. Such recrystallization rate can transform any aragonite speleothem into calcite within a few centuries. We suggest that the volume of water interacting with the speleothem at the time of recrystallization is

  7. Strain-relief by single dislocation loops in calcite crystals grown on self-assembled monolayers.

    Science.gov (United States)

    Ihli, Johannes; Clark, Jesse N; Côté, Alexander S; Kim, Yi-Yeoun; Schenk, Anna S; Kulak, Alexander N; Comyn, Timothy P; Chammas, Oliver; Harder, Ross J; Duffy, Dorothy M; Robinson, Ian K; Meldrum, Fiona C

    2016-06-15

    Most of our knowledge of dislocation-mediated stress relaxation during epitaxial crystal growth comes from the study of inorganic heterostructures. Here we use Bragg coherent diffraction imaging to investigate a contrasting system, the epitaxial growth of calcite (CaCO3) crystals on organic self-assembled monolayers, where these are widely used as a model for biomineralization processes. The calcite crystals are imaged to simultaneously visualize the crystal morphology and internal strain fields. Our data reveal that each crystal possesses a single dislocation loop that occupies a common position in every crystal. The loops exhibit entirely different geometries to misfit dislocations generated in conventional epitaxial thin films and are suggested to form in response to the stress field, arising from interfacial defects and the nanoscale roughness of the substrate. This work provides unique insight into how self-assembled monolayers control the growth of inorganic crystals and demonstrates important differences as compared with inorganic substrates.

  8. Calcite and dolomite in intrusive carbonatites. II. Trace-element variations

    Science.gov (United States)

    Chakhmouradian, Anton R.; Reguir, Ekaterina P.; Couëslan, Christopher; Yang, Panseok

    2016-04-01

    The composition of calcite and dolomite from several carbonatite complexes (including a large set of petrographically diverse samples from the Aley complex in Canada) was studied by electron-microprobe analysis and laser-ablation inductively-coupled-plasma mass-spectrometry to identify the extent of substitution of rare-earth and other trace elements in these minerals and the effects of different igneous and postmagmatic processes on their composition. Analysis of the newly acquired and published data shows that the contents of rare-earth elements (REE) and certain REE ratios in magmatic calcite and dolomite are controlled by crystal fractionation of fluorapatite, monazite and, possibly, other minerals. Enrichment in REE observed in some samples (up to ~2000 ppm in calcite) cannot be accounted for by coupled substitutions involving Na, P or As. At Aley, the REE abundances and chondrite-normalized (La/Yb)cn ratios in carbonates decrease with progressive fractionation. Sequestration of heavy REE from carbonatitic magma by calcic garnet may be responsible for a steeply sloping "exponential" pattern and lowered Ce/Ce* ratios of calcite from Magnet Cove (USA) and other localities. Alternatively, the low levels of Ce and Mn in these samples could result from preferential removal of these elements by Ce4+- and Mn3+-bearing minerals (such as cerianite and spinels) at increasing f(O2) in the magma. The distribution of large-ion lithophile elements (LILE = Sr, Ba and Pb) in rock-forming carbonates also shows trends indicative of crystal fractionation effects (e.g., concomitant depletion in Ba + Pb at Aley, or Sr + Ba at Kerimasi), although the phases responsible for these variations cannot be identified unambiguously at present. Overall, element ratios sensitive to the redox state of the magma and its complexing characteristics (Eu/Eu*, Ce/Ce* and Y/Ho) are least variable and in both primary calcite and dolomite, approach the average chondritic values. In consanguineous

  9. The kinetics of the ordering of 13C-18O bonds in calcite and apatite

    Science.gov (United States)

    Stolper, D. A.; Halevy, I.; Eiler, J. M.

    2011-12-01

    Eiler and Schauble (2004) showed that the isotopes of C and O are not randomly distributed within single phases such as CO2 gas and carbonates, and in particular, that heavy isotopes of C and O tend to bond preferentially (clump) at lower temperatures. Consequently, the measurement of the deviation from a random distribution of C and O isotope distributions in a single phase can be used as a thermometer. As with other geothermometers based on homogeneous or heterogeneous equilibria, the clumped-isotope thermometer is susceptible to resetting (e.g., if the phase is reheated or experiences slow cooling). Thus, clumped-isotope "temperatures" of phases that have experienced complex thermal histories may, in fact, be closure temperatures, the interpretation of which requires quantification of the kinetics of redistribution of C and O isotopes as a function of temperature. These kinetics have received increasing attention (Dennis and Schrag, 2010; Passey 2010), and are likely to be critical for understanding clumped-isotope temperatures of samples that have been buried for long periods of time. To better constrain these kinetics we performed experiments on natural optical calcite from Mexico and carbonate-bearing apatite from the Siilinjarvi carbonatite (Finland). For each experiment, multiple single crystal grains (~2 mm in diameter) of calcite or apatite were loaded in open Pt capsules, pressurized with Ar gas, and held at 400-700 °C, 550 bars using a rapid quench TZM apparatus for 5 min to 520 hrs. After quenching, 13C-18O clumping was measured in the samples; the change from the initial Δ47 with time for each phase at each temperature was fit to simple mechanistic models of isotope exchange between sites in these phases. One conclusion of the experimental study is that resetting the internal ordering of carbonate groups proceeds more rapidly in calcites than in apatites. For example, heating apatite at 400 °C results in no change in clumping over a 24 hr period

  10. A calcite permeable reactive barrier for the remediation of Fluoride from spent potliner (SPL) contaminated groundwater

    DEFF Research Database (Denmark)

    Turner, B.D.; Binning, Philip John; Sloan, S.W.

    2008-01-01

    . The paper focuses on two issues in the implementation of calcite permeable reactive barriers for remediating fluoride contaminated water: the impact of the groundwater chemical matrix and CO2 addition on fluoride removal. Column tests comparing pure NaF solutions, synthetic SPL solutions, and actual SPL......The use of calcite (CaCO3) as a substrate for a permeable reactive barrier (PRB) for removing fluoride from contaminated groundwater is proposed and is illustrated by application to groundwater contaminated by spent potliner leachate (SPL), a waste derived from the aluminium smelting process...... leachate indicate that the complex chemical matrix of the SPL leachate can impact fluoride removal significantly. For SPL contaminant mixtures, fluoride removal is initially less than expected from idealized, pure, solutions. However, with time, the effect of other contaminants on fluoride removal...

  11. Calcium channel blocker poisoning

    Directory of Open Access Journals (Sweden)

    Miran Brvar

    2005-04-01

    Full Text Available Background: Calcium channel blockers act at L-type calcium channels in cardiac and vascular smooth muscles by preventing calcium influx into cells with resultant decrease in vascular tone and cardiac inotropy, chronotropy and dromotropy. Poisoning with calcium channel blockers results in reduced cardiac output, bradycardia, atrioventricular block, hypotension and shock. The findings of hypotension and bradycardia should suggest poisoning with calcium channel blockers.Conclusions: Treatment includes immediate gastric lavage and whole-bowel irrigation in case of ingestion of sustainedrelease products. All patients should receive an activated charcoal orally. Specific treatment includes calcium, glucagone and insulin, which proved especially useful in shocked patients. Supportive care including the use of catecholamines is not always effective. In the setting of failure of pharmacological therapy transvenous pacing, balloon pump and cardiopulmonary by-pass may be necessary.

  12. The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

    KAUST Repository

    Li, Yan Vivian

    2016-03-02

    A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl2, and MgCl2) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl2 and MgCl2 solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl2 and MgCl2 solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.

  13. Aragonite→calcite transformation studied by EPR of Mn 2+ ions

    Science.gov (United States)

    Lech, J.; Śl|zak, A.

    1989-05-01

    The irreversible transformation aragonite→calcite has been studied both at different fixed heating rates (5, 10, 15 and 20 K/min) and at different fixed temperatures. Apparent progression rates of the transformation were observed above 685 K. At 730 K the transformation became sudden and violent. Time developments of the transformation at fixed temperatures have been discussed in terms of Avrami-Lichti's approach to transitions involving nucleation processes.

  14. Coccolithophore responses to environmental variability in the South China Sea: species composition and calcite content

    OpenAIRE

    Jin, Xiaobo; Liu, Chuanlian; Poulton, Alex J.; Dai, Minhan; Guo, Xianghui

    2016-01-01

    Coccolithophore contributions to the global marine carbon cycle are regulated by the calcite content of their scales (coccoliths) and the relative cellular levels of photosynthesis and calcification rates. All three of these factors vary between coccolithophore species and with response to the growth environment. Here, water samples were collected in the northern basin of the South China Sea (SCS) during summer 2014 in order to examine how environmental variability influence...

  15. Epr of Mn2+ Impurities in Calcite: A Detailed Study Pertinent to Marble Provenance Determination

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters...... having the correct signs as well as magnitudes. We present data that determine the sign of the axial anisotropy parameter and thereby facilitate future quantum mechanical characterizations of marble electron paramagnetic resonance spectra that supplement provenance determination...

  16. EPR OF Mn2+ IMPURITIES IN CALCITE: A DETAILED STUDY PERTINENT TO MARBLE PROVENANCE DETERMINATION

    DEFF Research Database (Denmark)

    Weihe, H.; Piligkos, S.; Barra, A.L.

    2009-01-01

    We demonstrate that the electron paramagnetic resonance spectrum of Mn2+ impurities in calcite, and therefore also in marble, may be accurately reproduced by a traditional spin Hamiltonian formalism. The success of such a treatment, however, very much depends on the spin Hamiltonian parameters...... having the correct signs as well as magnitudes. We present data that determine the sign of the axial anisotropy parameter and thereby facilitate future quantum mechanical characterizations of marble electron paramagnetic resonance spectra that supplement provenance determination....

  17. An efficient phosphorus scavenging from aqueous solution using magnesiothermally modified bio-calcite.

    Science.gov (United States)

    Ahmad, Munir; Ahmad, Mahtab; Usman, Adel R A; Al-Faraj, Abdullah S; Ok, Yong Sik; Hussain, Qaiser; Abduljabbar, Adel S; Al-Wabel, Mohammad I

    2017-06-09

    Bio-calcite (BC) derived from waste hen eggshell was subjected to thermal treatments (calcined bio-calcite (CBC)). The BC and CBC were further modified via magnesiothermal treatments to produce modified bio-calcite (MBC) and modified calcined bio-calcite (MCBC), respectively, and evaluated as a novel green sorbent for P removal from aqueous solutions in the batch experiments. Modified BC exhibited improved structural and chemical properties, such as porosity, surface area, thermal stability, mineralogy and functional groups, than pristine material. Langmuir and Freundlich models well described the P sorption onto both thermally and magnesiothermally sorbents, respectively, suggesting mono- and multi-layer sorption. Langmuir predicted highest P sorption capacities were in the order of: MCBC (43.33 mg g -1 ) > MBC (35.63 mg g- 1 ) > CBC (34.38 mg g -1 ) > BC (30.68 mg g -1 ). The MBC and MCBC removed 100% P up to 50 mg P L -1 , which reduced to 35.43 and 39.96%, respectively, when P concentration was increased up to 1000 mg L -1 . Dynamics of P sorption was well explained by the pseudo-second-order rate equation, with the highest sorption rate of 4.32 mg g -1  min -1 for the MCBC. Hydroxylapatite [Ca 10 (PO 4 ) 6 (OH) 2 ] and brushite [CaH(PO 4 )·2H 2 O] were detected after P sorption onto the modified sorbents by X-ray diffraction analysis, suggesting chemisorption as the operating sorption mechanism.

  18. Quantitative laboratory measurements of biogeochemical processes controlling biogenic calcite carbon sequestration.

    Energy Technology Data Exchange (ETDEWEB)

    Zendejas, Frank; Lane, Todd W.; Lane, Pamela D.

    2011-01-01

    The purpose of this LDRD was to generate data that could be used to populate and thereby reduce the uncertainty in global carbon cycle models. These efforts were focused on developing a system for determining the dissolution rate of biogenic calcite under oceanic pressure and temperature conditions and on carrying out a digital transcriptomic analysis of gene expression in response to changes in pCO2, and the consequent acidification of the growth medium.

  19. The surface interactions of a near-neutral carbon nanoparticle tracer with calcite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Yan Vivian, E-mail: yan.li@colostate.edu [Colorado State University, Department of Design and Merchandising (United States); Cathles, Lawrence M., E-mail: lmc19@cornell.edu [Cornell University, Earth and Atmospheric Sciences (United States)

    2016-03-15

    A new class of nearly charge-neutral carbon-cored nanoparticle tracers are remarkably non-interactive with solid surfaces and could provide a valuable baseline for diverse hydrological and environmental studies of subsurface flow and particle transport. We investigate the causes of inertness by studying the interactions with calcite of a nanoparticle of this class synthesized from malic acid and ethanolamine (M-dots) dispersed in brine (NaCl, CaCl{sub 2}, and MgCl{sub 2}) solutions. None of the M-dots are retained in calcite sand-packed columns when dispersed in DI water. Dispersed in the NaCl and mixed brine solutions, 5.6 % of and 7.3 % of the M-dots are initially retained, but 65 and 13 % of these retained particles are subsequently released when the column is flushed with DI water. When dispersed in the CaCl{sub 2} and MgCl{sub 2} solutions, 65 and 54 % of the M-dots are initially retained, and 28 and 26 % subsequently released in the DI water flush. The M-dots have a small negative zeta potential in all solutions, but the calcite zeta potential changes from strongly negative to strongly positive across the solution series, and the particle retention tracks this change. Derjaguin–Landau–Verwey–Overbeek (DLVO) modeling of the force between a calcite probe and an M-dot coated surface shows that hydration forces repel the particles in the DI water, NaCl, and mixed solutions, but not in the CaCl{sub 2} and MgCl{sub 2} solutions. These results show that near-zero charge and strongly hydrophilic decoration are the causes of the remarkable inertness of carbon-cored nanoparticles, and also suggest that nanoparticles could be useful in solute-surface interaction studies.Graphical Abstract.

  20. Smaller calcite lattice deformation caused by occluded organic material in coccoliths than in mollusk shell

    DEFF Research Database (Denmark)

    Frølich, Simon; Sørensen, Henning Osholm; Hakim, Sepideh Sadat

    2015-01-01

    The growth and nucleation of biominerals are directed and affected by associated biological molecules. In this paper, we investigate the influence of occluded biomolecules on biogenic calcite from the coccolithophorid Pleurochrysis carterae and from chalk, a rock composed predominantly of fossil...... and the coccolithophorids. These differences were reflected in lattice deformation (macrostrain), structure (microstrain), and atomic disorder distributions (δorganic). The influence of the biological macromolecules on the inorganic phase was consistently smaller in the P. carterae compared to P. nobilis...

  1. Fluid inclusion studies of calcite veins from Yucca Mountain, Nevada, Tuffs: Environment of formation

    Energy Technology Data Exchange (ETDEWEB)

    Roedder, E. [Harvard Univ., Cambridge, MA (United States); Whelan, J.F. [Geological Survey, Denver, CO (United States); Vaniman, D.T. [Los Alamos National Lab., NM (United States)

    1994-12-31

    Calcite vein and vug fillings at four depths (130-314m), all above the present water table in USW G-1 bore hole at Yucca Mountain, Nevada, contain primary fluid inclusions with variable vapor/liquid raitos: Most of these inclusions are either full of liquid or full of vapor. The liquid-filled inclusions show that most of the host calcite crystallized from fluids at <100{degrees}C. The vapor-filled inclusions provide evidence that a separate vapor phase was present in the fluid during crystallization. Studies of these vapor-filled inclusions on the microscope crushing stage were interpreted in an earlier paper as indicating trapping of an air-water-CO{sub 2} vapor phase at ``<100{degrees}C``. Our new studies reveal the additional presence of major methane in the vapor-filled inclusion, indicating even lower temperatures of trapping, perhaps at near-surface temperatures. They also show that the host calcite crystals grew from a flowing film of water on the walls of fractures open to the atmosphere, the vapor-filled inclusions representing bubbles that exsolved from this film onto the crystal surface.

  2. Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface

    Science.gov (United States)

    Ylikantola, A.; Linnanto, J.; Knuutinen, J.; Oravilahti, A.; Toivakka, M.

    2013-07-01

    The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree-Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate polymers influence the interactions between the calcite surface and the polymer. The force field applied, and also water molecules, were found to have an impact on all systems studied. Ab initio Hartree-Fock calculations indicated that there are two types of coordination between sodium atoms and carboxylate groups of the sodium polyacrylate polymer, inter- and intra-carboxylate group coordination. In addition, ab initio Hartree-Fock calculations of the structure of the sodium polyacrylate polymer produced important information regarding interactions between the polymers and carboxylated styrene-butadiene latex particles.

  3. Molecular modeling studies of interactions between sodium polyacrylate polymer and calcite surface

    Energy Technology Data Exchange (ETDEWEB)

    Ylikantola, A. [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); Linnanto, J., E-mail: juha.m.linnanto@gmail.com [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); University of Tartu, Institute of Physics, Riia 142, EE-51014 Tartu (Estonia); Knuutinen, J.; Oravilahti, A. [University of Jyväskylä, Department of Chemistry, P.O. Box 35, University of Jyväskylä, FI-40014 (Finland); Toivakka, M. [Åbo Akademi University, Laboratory of Paper Coating and Converting and Center for Functional Materials, FI-20500 Turku/Åbo (Finland)

    2013-07-01

    The interactions between calcite pigment and sodium polyacrylate dispersing agent, widely used in papermaking as paper coating components, were investigated using classical force field and quantum chemical approaches. The objective was to understand interactions between the calcite surface and sodium polyacrylate polymer at 300 K using molecular dynamics simulations. A quantum mechanical ab initio Hartree–Fock method was also used to obtain detailed information about the sodium polyacrylate polymer structure. The effect of water molecules (moisture) on the interactions was also examined. Calculations showed that molecular weight, branching and the orientation of sodium polyacrylate polymers influence the interactions between the calcite surface and the polymer. The force field applied, and also water molecules, were found to have an impact on all systems studied. Ab initio Hartree–Fock calculations indicated that there are two types of coordination between sodium atoms and carboxylate groups of the sodium polyacrylate polymer, inter- and intra-carboxylate group coordination. In addition, ab initio Hartree–Fock calculations of the structure of the sodium polyacrylate polymer produced important information regarding interactions between the polymers and carboxylated styrene-butadiene latex particles.

  4. Intermediate-scale tests of sodium interactions with calcite and dolomite aggregate concretes. [LMFBR

    Energy Technology Data Exchange (ETDEWEB)

    Randich, E.; Acton, R.U.

    1983-09-01

    Two intermediate-scale tests were performed to compare the behavior of calcite and dolomite aggregate concretes when attacked by molten sodium. The tests were performed as part of an interlaboratory comparison between Sandia National Laboratories and Hanford Engineering Development Laboratories. Results of the tests at Sandia National Laboratories are reported here. The results show that both concretes exhibit similar exothermic reactions with molten sodium. The large difference in reaction vigor suggested by thermodynamic considerations of CO/sub 2/ release from calcite and dolomite was not realized. Penetration rates of 1.4 to 1.7 mm/min were observed for short periods of time with reaction zone temperatures in excess of 800/sup 0/C during the energetic attack. The penetration was not uniform over the entire sodium-concrete contact area. Rapid attack may be localized due to inhomogeneities in the concrete. The chemical reaction zone is less then one cm thick for the calcite concrete but is about seven cm thick for the dolomite concrete.

  5. Sulfur in foraminiferal calcite as a potential proxy for seawater carbonate ion concentration

    Science.gov (United States)

    van Dijk, I.; de Nooijer, L. J.; Boer, W.; Reichart, G.-J.

    2017-07-01

    Sulfur (S) incorporation in foraminiferal shells is hypothesized to change with carbonate ion concentration [CO32-], due to substitution of sulfate for carbonate ions in the calcite crystal lattice. Hence S/Ca values of foraminiferal carbonate shells are expected to reflect sea water carbonate chemistry. To generate a proxy calibration linking the incorporation of S into foraminiferal calcite to carbonate chemistry, we cultured juvenile clones of the larger benthic species Amphistegina gibbosa and Sorites marginalis over a 350-1200 ppm range of pCO2 values, corresponding to a range in [CO32-] of 93 to 211 μmol/kg. We also investigated the potential effect of salinity on S incorporation by culturing juvenile Amphistegina lessonii over a large salinity gradient (25-45). Results show S/CaCALCITE is not impacted by salinity, but increases with increasing pCO2 (and thus decreasing [CO32-] and pH), indicating S incorporation may be used as a proxy for [CO32-]. Higher S incorporation in high-Mg species S. marginalis suggests a superimposed biomineralization effect on the incorporation of S. Microprobe imaging reveals co-occurring banding of Mg and S in Amphistegina lessonii, which is in line with a strong biological control and might explain higher S incorporation in high Mg species. Provided a species-specific calibration is available, foraminiferal S/Ca values might add a valuable new tool for reconstructing past ocean carbonate chemistry.

  6. Adsorption Behavior and Mechanism of SCA-1 on a Calcite Surface: A Molecular Dynamics Study.

    Science.gov (United States)

    Xue, Zhengyang; Shen, Qiying; Liang, Lijun; Shen, Jia-Wei; Wang, Qi

    2017-10-24

    The crystallization mechanism for natural mineral, especially the role of biological molecules in biomineralization, is still under debate. Protein adsorption on material surfaces plays a key role in biomineralization. In this article, molecular dynamics (MD) simulations were performed to systematically investigate the adsorption behavior of struthio camelus eggshell protein struthiocalcin-1 (SCA-1) on the calcite (104) surface with several different starting orientations in an explicit water environment. For each binding configuration, detailed adsorption behaviors and a mechanism were presented with the analysis of interaction energy, binding residues, hydrogen bonding, and structures (such as DSSP, dipole moment, and the electrostatic potential calculation). The results indicate that the positively charged and polar residues are the dominant residues for protein adsorption on the calcite (104) surface, and the strong electrostatic interaction drives the binding of model protein to the surface. The hydrogen bond bridge was found to play an important role in surface interactions as well. These results also demonstrate that SCA-1 is relatively rigid in spite of strong adsorption with few structural changes in α-helix and β-sheet contents. The results of the orientation calculation suggest that the dipole moment of the protein tends to remain parallel to calcite in most stable cases, which was confirmed by electrostatic potential isosurfaces analysis.

  7. The co-effect of collagen and magnesium ions on calcium carbonate biomineralization

    Energy Technology Data Exchange (ETDEWEB)

    Jiao Yunfeng [Department of Materials Science and Engineering, Biomaterials Laboratory, Tsinghua University, Beijing 100084 (China); Feng Qingling [Department of Materials Science and Engineering, Biomaterials Laboratory, Tsinghua University, Beijing 100084 (China)]. E-mail: biomater@mail.tsinghua.edu.cn; Li Xiaoming [Department of Materials Science and Engineering, Biomaterials Laboratory, Tsinghua University, Beijing 100084 (China)

    2006-05-15

    The process of calcium carbonate biomineralization in the solution containing collagen and magnesium ions was studied in this paper. The results were characterized by using powder X-ray diffraction (XRD) and scanning electron microscopy (SEM). The effect rules were obtained by the cooperation of collagen and magnesium ions in different concentration. The experiment results showed that in the presence of both collagen and magnesium ions, aragonite and vaterite were precipitated at low Mg/Ca ion concentration ratio, while only aragonite with regular spherical morphology was precipitated at high Mg/Ca ion concentration ratio. It indicated that collagen has a promotional effect on magnesium ions in controlling the polymorph of calcium carbonate crystal. A much wider range of calcium carbonate morphologies was observed in the presence of both collagen and magnesium ions. The experiments suggested that collagen acts in combination with magnesium ions to inhibit calcite crystal growth, while favoring the formation of aragonite crystals.

  8. Constant-distance mode scanning potentiometry. 1. Visualization of calcium carbonate dissolution in aqueous solution.

    Science.gov (United States)

    Etienne, Mathieu; Schulte, Albert; Mann, Stefan; Jordan, Guntram; Dietzel, Irmgard D; Schuhmann, Wolfgang

    2004-07-01

    Constant-distance mode scanning potentiometry was established by integrating potentiometric microsensors as ion-selective scanning probes into a SECM setup that was equipped with a piezoelectric shear force-based tip-to-sample distance control. The combination of specially designed micrometer-sized potentiometric tips with an advanced system for tip positioning allowed simultaneous acquisition of both topographic and potentiometric information at solid/liquid interfaces with high spatial resolution. The performance of the approach was evaluated by applying Ca(2+)-selective constant-distance mode potentiometry to monitor the dissolution of calcium carbonate occurring either at the (104) surface of calcite crystals or in proximity to the more complex surface of cross sections of a calcium carbonate shell of Mya arenaria exposed to slightly acidic aqueous solutions. Micrometer-scale heterogeneities in the apparent calcium activity profiles have successfully been resolved for both samples.

  9. Effect of some organic solvent-water mixtures composition on precipitated calcium carbonate in carbonation process

    Science.gov (United States)

    Konopacka-Łyskawa, Donata; Kościelska, Barbara; Karczewski, Jakub

    2015-05-01

    Precipitated calcium carbonate particles were obtained during carbonation of calcium hydroxide slurry with carbon dioxide. Aqueous solutions of isopropyl alcohol, n-butanol and glycerol were used as solvents. Concentration of organic additives in the reactive mixture was from 0% to 20% (vol). Precipitation process were performed in a stirred tank reactor equipped with gas distributor. Multimodal courses of particles size distribution were determined for produced CaCO3 particles. Calcium carbonate as calcite was precipitated in all experiments. The mean Sauter diameter of CaCO3 particles decreased when the concentration of all used organic additives increased. The amount of small particle fraction in the product increased with the increasing concentration of organic solvents. Similar physical properties of used liquid phase resulted in the similar characteristics of obtained particles.

  10. Differential early diagenetic low-Mg calcite cementation and rhythmic hardground development in Campanian-Maastrichtian chalk

    DEFF Research Database (Denmark)

    Molenaar, Nicolaas; J.J.P., Zijlstra

    1997-01-01

    calcite cementation is proposed, in which early calcite cementation occurred within the sediment at some distance below the seafloor as a result of organic matter degradation and internal redistribution of bioclastic carbonate. Bacterial organic matter degradation caused dissolution of relatively unstable...... older burrowed sediment with a more advanced stage of organic matter degradation, in particular iron reduction. Cementation also occurred when redox boundaries repeatedly moved through the same layers during periods with low nett sedimentation and increased storm activity and erosion. The differences...... in the degree of early diagenetic calcite cementation were further enhanced during Paleocene karstification and development of secondary porosity by dissolution of remaining unstable carbonate grains and by associated meteoric water calcite cementation....

  11. Growing spherulitic calcite grains in saline, hyperalkaline lakes: Experimental evaluation of the effects of Mg-clays and organic acids

    NARCIS (Netherlands)

    Mercedes-Martín, R.; Rogerson, M.R.; Brasier, A.T.; Vonhof, H.B.; Prior, T.; Fellows, S.M.; Reijmer, J.J.G.; Billing, I.; Pedley, H.M.

    2016-01-01

    The origin of spherical-radial calcite bodies - spherulites - in sublacustrine, hyperalkaline and saline systems is unclear, and therefore their palaeoenvironmental significance as allochems is disputed. Here, we experimentally investigate two hypotheses concerning the origin of spherulites. The

  12. Adsorption of arsenic and phosphate onto the surface of calcite as revealed by batch experiments and surface complexation modelling

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt

    is complete after 1 and 2-3 hours, respectively). Also desorption is fast and complete for both ions within 0.5 h. The reversibility of the sorption process indicates that neither arsenate nor phosphate is readily incorporated into the calcite crystal lattice under our experimental conditions. The phosphate....... The primary effect of the ionic strength on phosphate sorption onto calcite is its influence on the activity of the different aqueous phosphate species. For the adsorption of arsenate onto calcite, the effect of the ionic strength is more pronounced and cannot fully be accounted for by changes in the aqueous...... and sequential addition (3 hours apart) yields the same reduction in adsorption, underlining the high reversibility of the system. The reduction in adsorption of both arsenate and phosphate is most likely due to competition for the same sorption sites at the calcite surface, considering the similarity...

  13. [Does carbonate originate from carbonate-calcium crystal component of the human urinary calculus?].

    Science.gov (United States)

    Yuzawa, Masayuki; Nakano, Kazuhiko; Kumamaru, Takatoshi; Nukui, Akinori; Ikeda, Hitoshi; Suzuki, Kazumi; Kobayashi, Minoru; Sugaya, Yasuhiro; Morita, Tatsuo

    2008-09-01

    It gives important information in selecting the appropriate treatment for urolithiasis to confirm the component of urinary calculus. Presently component analysis of the urinary calculus is generally performed by infrared spectroscopy which is employed by companies providing laboratory testing services in Japan. The infrared spectroscopy determines the molecular components from the absorption spectra in consequence of atomic vibrations. It has the drawback that an accurate crystal structure cannot be analyzed compared with the X-ray diffraction method which analyzes the crystal constituent based on the diffraction of X-rays on crystal lattice. The components of the urinary calculus including carbonate are carbonate apatite and calcium carbonate such as calcite. Although the latter is reported to be very rare component in human urinary calculus, the results by infrared spectroscopy often show that calcium carbonate is included in calculus. The infrared spectroscopy can confirm the existence of carbonate but cannot determine whether carbonate is originated from carbonate apatite or calcium carbonate. Thus, it is not clear whether calcium carbonate is included in human urinary calculus component in Japan. In this study, we examined human urinary calculus including carbonate by use of X-ray structural analysis in order to elucidate the origin of carbonate in human urinary calculus. We examined 17 human calculi which were reported to contain calcium carbonate by infrared spectroscopy performed in the clinical laboratory. Fifteen calculi were obtained from urinary tract, and two were from gall bladder. The stones were analyzed by X-ray powder method after crushed finely. The reports from the clinical laboratory showed that all urinary culculi consisted of calcium carbonate and calcium phosphate, while the gallstones consisted of calcium carbonate. But the components of all urinary calculi were revealed to be carbonate apatite by X-ray diffraction. The components of

  14. Competitive adsorption of arsenate and phosphate onto calcite; experimental results and modeling with CCM and CD-MUSIC

    DEFF Research Database (Denmark)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus

    2012-01-01

    that adsorption of arsenate onto calcite is of minor importance in most groundwater aquifers, as phosphate is often present at concentration levels sufficient to significantly reduce arsenate adsorption. The CD-MUSIC model for calcite was used successfully to model adsorption of arsenate and phosphate separately....... This study clearly shows the importance of performing competitive adsorption studies for validation of multi-component models and for estimating the mobility of an ion in the environment....

  15. Mn and Zn incorporation into calcite as a function of chloride aqueous concentration

    Science.gov (United States)

    Temmam, M.; Paquette, J.; Vali, H.

    2000-07-01

    During spiral growth of the calcite rhombohedron {10 overline14}, divalent metals substituting for Ca 2+ are differentially incorporated due to steric differences inherent to the asymmetric kink sites exposed at nonequivalent growth steps. Hence, ions "larger" than Ca 2+ (e.g., Sr 2+ and Ba 2+) exhibit an incorporation trend opposite to that of "smaller" ions (e.g., Mn 2+ and Co 2+). However, Zn 2+ exhibits the same incorporation trend as large ions in coprecipitation experiments conducted from strong NH 4Cl electrolytes. In this study we compared the incorporation trends of Zn and Mn from solutions with various chloride content to test the possibility that the adsorption of "large" ZnCl n2-n aqueous complexes influences the site preference of Zn. The incorporation trends of Mn and Zn were opposite at the symmetrically nonequivalent growth steps. From a 0.4 M NH 4Cl solution, where Zn aqueous speciation was thermodynamically dominated by the "free" aquo ion, Zn maintained its site preference for the geometrically less constrained surface sites. Thus, Zn exhibits a particular interaction with surface sites and its incorporation trend is not controlled by the prevalence of ZnCl n2-n complexes. Other factors like the electronic configuration must be considered. The surface microtopography of calcite was found to be sensitive to changes in the aqueous concentrations of NH 4Cl and Zn. Decreases in NH 4Cl concentration resulted in an increase of the density of growth hillocks. The strong adsorbing behaviour of Zn increased the surface roughness, decreased the rate of growth, perturbed the spiral growth mechanism, and triggered the nucleation of discrete surface precipitates (˜0.2 μm) along macrosteps. An increase of Cl incorporation, despite the decrease of its aqueous concentration by dilutions of the parent solution, suggests that surface roughness at the calcite-solution interface is another factor involved in the nonequilibrium process of impurity element

  16. Clumped isotope thermometry of calcite and dolomite in a contact metamorphic environment

    Science.gov (United States)

    Lloyd, Max K.; Eiler, John M.; Nabelek, Peter I.

    2017-01-01

    Clumped isotope compositions of slowly-cooled calcite and dolomite marbles record apparent equilibrium temperatures of roughly 150-200 °C and 300-350 °C, respectively. Because clumped isotope compositions are sensitive to the details of T-t path within these intervals, measurements of the Δ47 values of coexisting calcite and dolomite can place new constraints on thermal history of low-grade metamorphic rocks over a large portion of the upper crust (from ∼5 to ∼15 km depth). We studied the clumped isotope geochemistry of coexisting calcite and dolomite in marbles from the Notch Peak contact metamorphic aureole, Utah. Here, flat-lying limestones were intruded by a pluton, producing a regular, zoned metamorphic aureole. Calcite Δ47 temperatures are uniform, 156 ± 12 °C (2σ s.e.), across rocks varying from high-grade marbles that exceeded 500 °C to nominally unmetamorphosed limestones >5 km from the intrusion. This result appears to require that the temperature far from the pluton was close to this value; an ambient temperature just 20 °C lower would not have permitted substantial re-equilibration, and should have preserved depositional or early diagenetic Δ47 values several km from the pluton. Combining this result with depth constraints from overlying strata suggests the country rock here had an average regional geotherm of 22.3-27.4 °C/km from the late Jurassic Period until at least the middle Paleogene Period. Dolomite Δ47 in all samples above the talc + tremolite-in isograd record apparent equilibrium temperatures of 328-12+13 °C (1σ s.e.), consistent with the apparent equilibrium blocking temperature we expect for cooling from peak metamorphic conditions. At greater distances, dolomite Δ47 records temperatures of peak (anchi)metamorphism or pre-metamorphic diagenetic conditions. The interface between these domains is the location of the 330 °C isotherm associated with intrusion. Multiple-phase clumped isotope measurements are complemented by

  17. Bulk and Surface Aqueous Speciation of Calcite: Implications for Low-Salinity Waterflooding of Carbonate Reservoirs

    KAUST Repository

    Yutkin, Maxim P.

    2017-08-25

    Low-salinity waterflooding (LSW) is ineffective when reservoir rock is strongly water-wet or when crude oil is not asphaltenic. Success of LSW relies heavily on the ability of injected brine to alter surface chemistry of reservoir crude-oil brine/rock (COBR) interfaces. Implementation of LSW in carbonate reservoirs is especially challenging because of high reservoir-brine salinity and, more importantly, because of high reactivity of the rock minerals. Both features complicate understanding of the COBR surface chemistries pertinent to successful LSW. Here, we tackle the complex physicochemical processes in chemically active carbonates flooded with diluted brine that is saturated with atmospheric carbon dioxide (CO2) and possibly supplemented with additional ionic species, such as sulfates or phosphates. When waterflooding carbonate reservoirs, rock equilibrates with the injected brine over short distances. Injected-brine ion speciation is shifted substantially in the presence of reactive carbonate rock. Our new calculations demonstrate that rock-equilibrated aqueous pH is slightly alkaline quite independent of injected-brine pH. We establish, for the first time, that CO2 content of a carbonate reservoir, originating from CO2-rich crude oil and gas, plays a dominant role in setting aqueous pH and rock-surface speciation. A simple ion-complexing model predicts the calcite-surface charge as a function of composition of reservoir brine. The surface charge of calcite may be positive or negative, depending on speciation of reservoir brine in contact with the calcite. There is no single point of zero charge; all dissolved aqueous species are charge determining. Rock-equilibrated aqueous composition controls the calcite-surface ion-exchange behavior, not the injected-brine composition. At high ionic strength, the electrical double layer collapses and is no longer diffuse. All surface charges are located directly in the inner and outer Helmholtz planes. Our evaluation of

  18. Simulated oxygen isotopes in cave drip water and speleothem calcite in European caves

    Directory of Open Access Journals (Sweden)

    A. Wackerbarth

    2012-11-01

    Full Text Available Interpreting stable oxygen isotope (δ18O records from stalagmites is still one of the complex tasks in speleothem research. Here, we present a novel model-based approach, where we force a model describing the processes and modifications of δ18O from rain water to speleothem calcite (Oxygen isotope Drip water and Stalagmite Model – ODSM with the results of a state-of-the-art atmospheric general circulation model enhanced by explicit isotope diagnostics (ECHAM5-wiso. The approach is neither climate nor cave-specific and allows an integrated assessment of the influence of different varying climate variables, e.g. temperature and precipitation amount, on the isotopic composition of drip water and speleothem calcite.

    First, we apply and evaluate this new approach under present-day climate conditions using observational data from seven caves from different geographical regions in Europe. Each of these caves provides measured δ18O values of drip water and speleothem calcite to which we compare our simulated isotope values. For six of the seven caves modeled δ18O values of drip water and speleothem calcite are in good agreement with observed values. The mismatch of the remaining caves might be caused by the complexity of the cave system, beyond the parameterizations included in our cave model.

    We then examine the response of the cave system to mid-Holocene (6000 yr before present, 6 ka climate conditions by forcing the ODSM with ECHAM5-wiso results from 6 ka simulations. For a set of twelve European caves, we compare the modeled mid-Holocene-to-modern difference in speleothem calcite δ18O to available measurements. We show that the general European changes are simulated well. However, local discrepancies are found, and might be explained either by a too low model resolution, complex local soil-atmosphere interactions affecting evapotranspiration or by cave specific factors

  19. Interaction of europium and nickel with calcite studied by Rutherford Backscattering Spectrometry and Time-Resolved Laser Fluorescence Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Sabau, A. [Agence Nationale pour la gestion des Déchets RAdioactifs, 1-7 rue J. Monnet, Parc de la Croix Blanche, 92298 Châtenay-Malabry Cedex (France); Université de Nice Sophia Antipolis, Ecosystèmes Côtiers Marins et Réponses aux Stress (ECOMERS), 28 avenue Valrose, 06108 Nice Cedex 2 (France); Pipon, Y., E-mail: pipon@ipnl.in2p3.fr [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); Institut Universitaire de Technologie (IUT) Lyon-1, Université Claude Bernard Lyon 1, 69 622 Villeurbanne Cedex (France); Toulhoat, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); CEA/DEN, Saclay, 91191 Gif sur Yvette (France); Lomenech, C. [Université de Nice Sophia Antipolis, Ecosystèmes Côtiers Marins et Réponses aux Stress (ECOMERS), 28 avenue Valrose, 06108 Nice Cedex 2 (France); Jordan, N. [Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology (IRE) (Germany); Moncoffre, N. [Institut de Physique Nucléaire de Lyon (IPNL), Université Lyon 1, CNRS/IN2P3, 4 rue Enrico Fermi, 69 622 Villeurbanne Cedex (France); Barkleit, A. [Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Resource Ecology (IRE) (Germany); and others

    2014-08-01

    This study aims at elucidating the mechanisms regulating the interaction of Eu and Ni with calcite (CaCO{sub 3}). Calcite powders or single crystals (some mm sized) were put into contact with Eu or Ni solutions at concentrations ranging from 10{sup −3} to 10{sup −5} mol L{sup −1} for Eu and 10{sup −3} mol L{sup −1} for Ni. The sorption durations ranged from 1 week to 1 month. Rutherford Backscattering Spectrometry (RBS) well adapted to discriminate incorporation processes such as: (i) adsorption or co precipitation at the mineral surfaces or, (ii) incorporation into the mineral structure (through diffusion for instance), has been carried out. Moreover, using the fluorescence properties of europium, the results have been compared to those obtained by Time-Resolved Laser Fluorescence Spectroscopy (TRLFS) on calcite powders. For the single crystals, complementary SEM observations of the mineral surfaces at low voltage were also performed. Results showed that Ni accumulates at the calcite surface whereas Eu is also incorporated at a greater depth. Eu seems therefore to be incorporated into two different states in calcite: (i) heterogeneous surface accumulation and (ii) incorporation at depth greater than 160 nm after 1 month of sorption. Ni was found to accumulate at the surface of calcite without incorporation.

  20. Trace Metals in Groundwater and Vadose Zone Calcite: In Situ Containment and Stabilization of Stronthium-90 and Other Divalent Metals and Radionuclides at Arid Western DOE Sites: Final Report for Award Number DE-FG07-02ER63486 to the University of Idaho (RW Smith) Environmental Management Science Program Project Number 87016

    Energy Technology Data Exchange (ETDEWEB)

    Smith, Robert W.; Fujita, Yoshiko

    2007-11-07

    Radionuclide and metal contaminants are present in the vadose zone and groundwater throughout the U.S. Department of Energy (DOE) energy research and weapons complex. In situ containment and stabilization of these contaminants represents a cost-effective treatment strategy that minimizes workers’ exposure to hazardous substances, does not require removal or transport of contaminants, and generally does not generate a secondary waste stream. We have investigated an in situ bioremediation approach that immobilizes radionuclides or contaminant metals (e.g., strontium-90) by their microbially facilitated co-precipitation with calcium carbonate in groundwater and vadose zone systems. Calcite, a common mineral in many aquifers and vadose zones in the arid west, can incorporate divalent metals such as strontium, cadmium, lead, and cobalt into its crystal structure by the formation of a solid solution. Collaborative research undertaken by the Idaho National Laboratory (INL), University of Idaho, and University of Toronto as part of this Environmental Management Science Program project has focused on in situ microbially-catalyzed urea hydrolysis, which results in an increase in pH, carbonate alkalinity, ammonium, calcite precipitation, and co-precipitation of divalent cations. In calcite-saturated aquifers, microbially facilitated co-precipitation with calcium carbonate represents a potential long-term contaminant sequestration mechanism. Key results of the project include: **Demonstrating the linkage between urea hydrolysis and calcite precipitation in field and laboratory experiments **Observing strontium incorporation into calcite precipitate by urea hydrolyzers with higher distribution coefficient than in abiotic **Developing and applying molecular methods for characterizing microbial urease activity in groundwater including a quantitative PCR method for enumerating ureolytic bacteria **Applying the suite of developed molecular methods to assess the feasibility of the

  1. Surface kinetic model for isotopic and trace element fractionation during precipitation of calcite from aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    DePaolo, D.

    2010-10-15

    A surface reaction kinetic model is developed for predicting Ca isotope fractionation and metal/Ca ratios of calcite as a function of rate of precipitation from aqueous solution. The model is based on the requirements for dynamic equilibrium; i.e. proximity to equilibrium conditions is determined by the ratio of the net precipitation rate (R{sub p}) to the gross forward precipitation rate (R{sub f}), for conditions where ionic transport to the growing crystal surface is not rate-limiting. The value of R{sub p} has been experimentally measured under varying conditions, but the magnitude of R{sub f} is not generally known, and may depend on several factors. It is posited that, for systems with no trace constituents that alter the surface chemistry, R{sub f} can be estimated from the bulk far-from-equilibrium dissolution rate of calcite (R{sub b} or k{sub b}), since at equilibrium R{sub f} = R{sub b}, and R{sub p} = 0. Hence it can be inferred that R{sub f} {approx} R{sub p} + R{sub b}. The dissolution rate of pure calcite is measureable and is known to be a function of temperature and pH. At given temperature and pH, equilibrium precipitation is approached when R{sub p} (= R{sub f} - R{sub b}) << R{sub b}. For precipitation rates high enough that R{sub p} >> R{sub b}, both isotopic and trace element partitioning are controlled by the kinetics of ion attachment to the mineral surface, which tend to favor more rapid incorporation of the light isotopes of Ca and discriminate weakly between trace metals and Ca. With varying precipitation rate, a transition region between equilibrium and kinetic control occurs near R{sub p} {approx} R{sub b} for Ca isotopic fractionation. According to this model, Ca isotopic data can be used to estimate R{sub f} for calcite precipitation. Mechanistic models for calcite precipitation indicate that the molecular exchange rate is not constant at constant T and pH, but rather is dependent also on solution saturation state and hence R{sub p

  2. Removal of oxyanions from synthetic wastewater via carbonation process of calcium hydroxide: Applied and fundamental aspects

    Energy Technology Data Exchange (ETDEWEB)

    Montes-Hernandez, G., E-mail: German.MONTES-HERNANDEZ@obs.ujf-grenoble.fr [LGCA, University Joseph Fourier, Observatoire des Sciences de l' Univers de Grenoble and CNRS, BP 53 X, 38042 Grenoble Cedex 9 (France); LPG, University Joseph Fourier, Observatoire des Sciences de l' Univers de Grenoble and CNRS, BP 53 X, 38042 Grenoble Cedex 9 (France); Concha-Lozano, N. [LGCA, University Joseph Fourier, Observatoire des Sciences de l' Univers de Grenoble and CNRS, BP 53 X, 38042 Grenoble Cedex 9 (France); Renard, F. [LGCA, University Joseph Fourier, Observatoire des Sciences de l' Univers de Grenoble and CNRS, BP 53 X, 38042 Grenoble Cedex 9 (France); Physics of Geological Processes, University of Oslo (Norway); Quirico, E. [LPG, University Joseph Fourier, Observatoire des Sciences de l' Univers de Grenoble and CNRS, BP 53 X, 38042 Grenoble Cedex 9 (France)

    2009-07-30

    Removal of oxyanions (selenite, selenate, arsenate, phosphate and nitrate) during calcite formation was experimentally studied using aqueous carbonation of calcium hydroxide under moderate pressure (P{sub CO2} {approx_equal} 20 bar) and temperature (30 {sup o}C). The effects of Ca(OH){sub 2} dose (10 and 20 g), Ca(OH){sub 2} source (commercial pure material or alkaline paper mill waste) and oxyanion initial concentration (from 0 to 70 mg atom/L) were investigated for this anisobaric gas-liquid-solid system. The Ca(OH){sub 2} carbonation reaction allowed successfully the removal of selenite (>90%), arsenate (>78%) and phosphate ({approx_equal}100%) from synthetic solutions. Conversely, nitrate and selenate had not any physicochemical affinity/effect during calcite formation. The rate of CO{sub 2} transfer during calcite formation in presence of oxyanions was equal or slower than for an oxyanion-free system, allowing to define a retarding kinetic factor RF that can vary between 0 (no retarding effect) to 1 (total inhibition). For selenite and phosphate RF was quite high, close to 0.3. A small retarding effect was detected for arsenate (RF {approx} 0.05) and no retarding effect was detected for selenate and nitrate (RF {approx} 0). In general, RF depends on the oxyanion initial concentration, oxyanion nature and Ca(OH){sub 2} dose. The presence of oxyanions could also influence the crystal morphology and aggregation/agglomeration process. For example, a c-axis elongation of calcite crystals was clearly observed at the equilibrium, for calcite formation in presence of selenite and phosphate. The oxyanions removal process proposed herein was inspired on the common physicochemical treatment of wastewater using calcium hydroxide (Ca(OH){sub 2}). The particularity, for this novel method is the simultaneous calcium hydroxide carbonation with compressed carbon dioxide in order to stabilise the solid matter. This economical and ecological method could allow the removal of

  3. Acidosis and Urinary Calcium Excretion

    DEFF Research Database (Denmark)

    Alexander, R Todd; Cordat, Emmanuelle; Chambrey, Régine

    2016-01-01

    Metabolic acidosis is associated with increased urinary calcium excretion and related sequelae, including nephrocalcinosis and nephrolithiasis. The increased urinary calcium excretion induced by metabolic acidosis predominantly results from increased mobilization of calcium out of bone and inhibi...

  4. Enzyme-accelerated and structure-guided crystallization of calcium carbonate: role of the carbonic anhydrase in the homologous system.

    Science.gov (United States)

    Müller, Werner E G; Schlossmacher, Ute; Schröder, Heinz C; Lieberwirth, Ingo; Glasser, Gunnar; Korzhev, Michael; Neufurth, Meik; Wang, Xiaohong

    2014-01-01

    The calcareous spicules from sponges, e.g. from Sycon raphanus, are composed of almost pure calcium carbonate. In order to elucidate the formation of those structural skeletal elements, the function of the enzyme carbonic anhydrase (CA), isolated from this species, during the in vitro calcium carbonate-based spicule formation, was investigated. It is shown that the recombinant sponge CA substantially accelerates calcium carbonate formation in the in vitro diffusion assay. A stoichiometric calculation revealed that the turnover rate of the sponge CA during the calcification process amounts to 25 CO2s(-1) × molecule CA(-1). During this enzymatically driven process, initially pat-like particles are formed that are subsequently transformed to rhomboid/rhombohedroid crystals with a dimension of ~50 μm. The CA-catalyzed particles are smaller than those which are formed in the absence of the enzyme. The Martens hardness of the particles formed is ~4 GPa, a value which had been determined for other biogenic calcites. This conclusion is corroborated by energy-dispersive X-ray spectroscopy, which revealed that the particles synthesized are composed predominantly of the elements calcium, oxygen and carbon. Surprising was the finding, obtained by light and scanning electron microscopy, that the newly formed calcitic crystals associate with the calcareous spicules from S. raphanus in a highly ordered manner; the calcitic crystals almost perfectly arrange in an array orientation along the two opposing planes of the spicules, leaving the other two plane arrays uncovered. It is concluded that the CA is a key enzyme controlling the calcium carbonate biomineralization process, which directs the newly formed particles to existing calcareous spicular structures. It is expected that with the given tools new bioinspired materials can be fabricated. Copyright © 2013 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

  5. Calcium and bones

    Science.gov (United States)

    ... eat in their diet. Vitamin D is the hormone that helps the gut absorb more calcium. Many older adults have common risks that make bone health worse. Calcium intake in the diet (milk, cheese, yogurt) is low. Vitamin D levels are ...

  6. Calcium D-saccharate

    DEFF Research Database (Denmark)

    Garcia, André Castilho; Hedegaard, Martina Vavrusova; Skibsted, Leif Horsfelt

    2016-01-01

    Molar conductivity of saturated aqueous solutions of calcium d-saccharate, used as a stabilizer of beverages fortified with calcium d-gluconate, increases strongly upon dilution, indicating complex formation between calcium and d-saccharate ions, for which, at 25 °C, Kassoc = 1032 ± 80, ΔHassoc......° = -34 ± 6 kJ mol-1, and ΔSassoc° = -55 ± 9 J mol-1 K-1, were determined electrochemically. Calcium d-saccharate is sparingly soluble, with a solubility product, Ksp, of (6.17 ± 0.32) × 10-7 at 25 °C, only moderately increasing with the temperature: ΔHsol° = 48 ± 2 kJ mol-1, and ΔSassoc° = 42 ± 7 J mol-1...... K-1. Equilibria in supersaturated solutions of calcium d-saccharate seem only to adjust slowly, as seen from calcium activity measurements in calcium d-saccharate solutions made supersaturated by cooling. Solutions formed by isothermal dissolution of calcium d-gluconate in aqueous potassium d...

  7. Extracellular Calcium and Magnesium

    African Journals Online (AJOL)

    ABSTRACT. The cause of preeclampsia remains unknown and calcium and magnesium supplement are being suggested as means of prevention. The objective of this study was to assess magnesium and calcium in the plasma and cerebrospinal fluid of Nigerian women with preedamp sia and eclampsia. Setting was ...

  8. Calcite Dissolution Kinetics and Solubility in NaCl-CaCl2-MgCl2 Brines up to 1 bar pCO2 and 80\\deg C

    Science.gov (United States)

    Gledhill, D. K.; Morse, J. W.

    2004-12-01

    Sedimentary basins can contain close to 20% by volume pore fluids that are commonly classified as brines. These fluids can become undersaturated with respect to calcite as a result of migration, dispersive mixing or by anthropogenic injection of CO2. Both the solubility of calcite and its dissolution kinetics are currently poorly constrained in these concentrated solutions. This study measured calcite solubility and dissolution rates in geologically relevant NaCl-CaCl2-MgCl2 synthetic brines (50,000 to 200,000 mg L-1 TDS). The EQPITZER calculated calcium carbonate ion activity product at steady-state was in reasonable agreement (\\pm10%) with Kcal in low concentration brines but systematically exceeded Kcal with increasing brine concentration. The deviation was most strongly correlated with calcium activity and was independent of magnesium concentration. This has been interpreted as an uncertainty in the carbonate ion activity coefficient perhaps related to errors in the calcium interaction parameters with the carbonic acid system under these conditions. The dissolution rate dependency on brine concentration, pCO2 (0.1 to 1 bar) and temperature (25\\deg C to 80\\deg C) was modeled using the empirical rate equation R=k(1-\\Omega) n. Relative to an apparent kinetic solubility it was found that n could be assumed to be first order over the range of degree of disequilibrium investigated (\\Omega = 0.2 to 1.0). Rates increased with increasing pCO2 as did the sensitivity to brine concentration. At 0.1 bar rates were independent of concentration (k = 9.0\\pm1.0\\times10-3 moles m-2 hr-1). However, at higher partial pressures rates were linearly correlated to TDS. At 1 bar pCO2 and 25\\deg C the rate constant can be described by the linear regression k(moles m-2 hr-1) = 0.053 - 1.7\\times10-7(TDS), R2 = 0.996. The specific effects of Ca2+, Mg2+ and ionic strength were tested in addition to the inhibitory effect of the presence of 1000 mg L-1 SO42-. A roughly three fold

  9. Formation of hollow bone-like morphology of calcium carbonate on surfactant/polymer templates

    Science.gov (United States)

    Mantilaka, M. M. M. G. P. G.; Pitawala, H. M. T. G. A.; Rajapakse, R. M. G.; Karunaratne, D. G. G. P.; Upul Wijayantha, K. G.

    2014-04-01

    Novel hollow, bone-like structures of Precipitated Calcium Carbonate (PCC) are fabricated, for the first time, starting from naturally occurring dolomite. The hollow, bone-like structures are prepared by precipitating calcium carbonate on self-assembled poly(acrylic acid)/cetyltrimethylammonium chloride (PAA/CTAC) template. Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscopic (FE-SEM) studies reveal that the bone-like structure is composed of Amorphous Calcium Carbonate (ACC) nanoparticles in the center and calcite nanoparticles at the edges. Bone-like PCC particles are in particle length of 2-3 μm and particle width of 1 μm. The internal hollow structures of bone-like particles are observed from TEM images. As identified by FE-SEM images, the bone-like structure has been formed through the crystal growth of initially formed ACC nanoparticles. The ACC particles are stabilized in the center while the calcite crystals have been grown from the ACC toward the edges of the structure to form a bone-like morphology. We also propose a possible mechanism for the formation of hollow bone-like PCC in this study. The fabricated hollow, bone-like PCC has potential applications in the preparation of release systems such as drugs, cosmetics and pigments.

  10. Resetting of Mg isotopes between calcite and dolomite during burial metamorphism: Outlook of Mg isotopes as geothermometer and seawater proxy

    Science.gov (United States)

    Hu, Zhongya; Hu, Wenxuan; Wang, Xiaomin; Lu, Yizhou; Wang, Lichao; Liao, Zhiwei; Li, Weiqiang

    2017-07-01

    Magnesium isotopes are an emerging tool to study the geological processes recorded in carbonates. Calcite, due to its ubiquitous occurrence and the large Mg isotope fractionation associated with the mineral, has attracted great interests in applications of Mg isotope geochemistry. However, the fidelity of Mg isotopes in geological records of carbonate minerals (e.g., calcite and dolomite) against burial metamorphism remains poorly constrained. Here we report our investigation on the Mg isotope systematics of a dolomitized Middle Triassic Geshan carbonate section in eastern China. Magnesium isotope analysis was complemented by analyses of Sr-C-O isotopic compositions, major and trace element concentrations, and petrographic and mineralogical features. Multiple lines of evidence consistently indicated that post-depositional diagenesis of carbonate minerals occurred to the carbonate rocks. Magnesium isotope compositions of the carbonate rocks closely follow a mixing trend between a high δ26Mg dolomite end member and a low δ26Mg calcite end member, irrespective of sample positions in the section and calcite/dolomite ratio in the samples. By fitting the measured Mg isotope data using a two-end member mixing model, an inter-mineral Δ26Mgdolomite-calcite fractionation of 0.72‰ was obtained. Based on the experimentally derived Mg isotope fractionation factors for dolomite and calcite, a temperature of 150-190 °C was calculated to correspond to the 0.72‰ Δ26Mgdolomite-calcite fractionation. Such temperature range matches with the burial-thermal history of the local strata, making a successful case of Mg isotope geothermometry. Our results indicate that both calcite and dolomite had been re-equilibrated during burial metamorphism, and based on isotope mass balance of Mg, the system was buffered by dolomite in the section. Therefore, burial metamorphism may reset Mg isotope signature of calcite, and Mg isotope compositions in calcite should be dealt with caution in

  11. Calcium carbonate crystallisation at the microscopic level

    CERN Document Server

    Dobson, P S

    2001-01-01

    The primary concern of this thesis is the investigation of crystal nucleation and growth processes, and the effect of foreign substrates on the rate, extent and mechanism of crystallisation, with particular emphasis on the calcium carbonate system. A methodology, based on the in-line mixing of two stable solutions, which permits the continuous delivery of a solution with a constant, known supersaturation, has been developed and characterised. This has been used to induce CaCO sub 3 crystallisation in experimental systems involving the channel flow and wall jet techniques. The channel flow method has been adapted to facilitate the study of crystal growth at a single calcite crystal. Ca sup 2 sup + ion selective electrodes have been employed as a means of monitoring depletion of the supersaturated solution, downstream of the crystal substrate. The data obtained suggested a growth rate constant of 3x10 sup - sup 1 sup 2 mol cm sup - sup 2 s sup - sup 1 (and a reaction order of 1.52 on supersaturation). The ex-si...

  12. Biodiesel production through transesterification over natural calciums

    Energy Technology Data Exchange (ETDEWEB)

    Ngamcharussrivichai, Chawalit [Fuels Research Center, Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Phyathai Rd., Patumwan, Bangkok 10330 (Thailand); Center of Excellence for Petroleum, Petrochemicals and Advanced Materials, Chulalongkorn University, Phyathai Rd., Patumwan, Bangkok 10330 (Thailand); Nunthasanti, Pramwit; Tanachai, Sithikorn; Bunyakiat, Kunchana [Fuels Research Center, Department of Chemical Technology, Faculty of Science, Chulalongkorn University, Phyathai Rd., Patumwan, Bangkok 10330 (Thailand)

    2010-11-15

    Transesterification of palm kernel oil (PKO) with methanol over various natural calciums, including limestone calcite, cuttlebone, dolomite, hydroxyapatite, and dicalcium phosphate, has been investigated at 60 C and 1 atm. The study showed that dolomite, mainly consisting of CaCO{sub 3} and MgCO{sub 3}, is the most active catalyst. The calcination temperature largely affected the physicochemical properties, as evidenced by N{sub 2} adsorption-desorption measurement, TGA, SEM and XRD, and the transesterification performance of the resultant catalysts. It was found that the calcination of dolomite at 800 C resulted in a highly active mixed oxide. CaO was suggested to be the catalytically active site responsible for the methyl ester formation. Under the suitable reaction conditions, the amount of dolomite calcined at 800 C = 6 wt.% based on the weight of oil, the methanol/oil molar ratio = 30, and the reaction time = 3 h, the methyl ester content of 98.0% can be achieved. The calcined dolomite can be reused many times. The analyses of some important fuel properties indicated that the biodiesel produced had the properties that meet the standard of biodiesel and diesel fuel issued by the Department of Energy Business, Ministry of Energy, Thailand. (author)

  13. HYPERTHERMIA, INTRACELLULAR FREE CALCIUM AND CALCIUM IONOPHORES

    NARCIS (Netherlands)

    STEGE, GJJ; WIERENGA, PK; KAMPINGA, HH; KONINGS, AWT

    1993-01-01

    It is shown that heat-induced increase of intracellular calcium does not correlate with hyperthermic cell killing. Six different cell lines were investigated; in four (EAT, HeLa S3, L5178Y-R and L5178Y-S) heat treatments killing 90% of the cells did not affect the levels of intracellular free

  14. Calcite growth-rate inhibition by fulvic acids isolated from Big Soda Lake, Nevada, USA, The Suwannee River, Georgia, USA and by polycarboxylic acids

    Science.gov (United States)

    Reddy, Michael M.; Leenheer, Jerry

    2011-01-01

    Calcite crystallization rates are characterized using a constant solution composition at 25°C, pH=8.5, and calcite supersaturation (Ω) of 4.5 in the absence and presence of fulvic acids isolated from Big Soda Lake, Nevada (BSLFA), and a fulvic acid from the Suwannee River, Georgia (SRFA). Rates are also measured in the presence and absence of low-molar mass, aliphatic-alicyclic polycarboxylic acids (PCA). BSLFA inhibits calcite crystal-growth rates with increasing BSLFA concentration, suggesting that BSLFA adsorbs at growth sites on the calcite crystal surface. Calcite growth morphology in the presence of BSLFA differed from growth in its absence, supporting an adsorption mechanism of calcite-growth inhibition by BSLFA. Calcite growth-rate inhibition by BSLFA is consistent with a model indicating that polycarboxylic acid molecules present in BSLFA adsorb at growth sites on the calcite crystal surface. In contrast to published results for an unfractionated SRFA, there is dramatic calcite growth inhibition (at a concentration of 1 mg/L) by a SRFA fraction eluted by pH 5 solution from XAD-8 resin, indicating that calcite growth-rate inhibition is related to specific SRFA component fractions. A cyclic PCA, 1, 2, 3, 4, 5, 6-cyclohexane hexacarboxylic acid (CHXHCA) is a strong calcite growth-rate inhibitor at concentrations less than 0.1 mg/L. Two other cyclic PCAs, 1, 1 cyclopentanedicarboxylic acid (CPDCA) and 1, 1 cyclobutanedicarboxylic acid (CBDCA) with the carboxylic acid groups attached to the same ring carbon atom, have no effect on calcite growth rates up to concentrations of 10 mg/L. Organic matter ad-sorbed from the air onto the seed crystals has no effect on the measured calcite crystal-growth rates.

  15. General job performance of first-line supervisors: the role of conscientiousness in determining its effects on subordinate exhaustion.

    Science.gov (United States)

    Perry, Sara Jansen; Rubino, Cristina; Witt, L A

    2011-04-01

    In an integrated test of the job demands-resources model and trait activation theory, we predicted that the general job performance of employees who also hold supervisory roles may act as a demand to subordinates, depending on levels of subordinate conscientiousness. In a sample of 313 customer service call centre employees, we found that high-conscientiousness individuals were more likely to experience emotional exhaustion, and low-conscientiousness individuals were less likely as the general job performance of their supervisor improved. The results were curvilinear, such that high-conscientiousness individuals' exhaustion levelled off with very high supervisor performance (two standard deviations above the mean), and low-conscientiousness individuals' exhaustion levelled off as supervisor performance improved from moderate to high. These findings suggest high-conscientiousness employees may efficiently handle demands presented by a low-performing coworker who is their boss, but when performance expectations are high (i.e. high-performing boss), these achievement-oriented employees may direct their resources (i.e. energy and time) towards performance-related efforts at the expense of their well-being. Conversely, low-conscientiousness employees suffer when paired with a low-performing boss, but benefit from a supervisor who demonstrates at least moderate job performance.

  16. Patriarchal Hierarchies of Power and the Subordination of Women: Real Doll as a Replacement of Woman Figure

    Directory of Open Access Journals (Sweden)

    Natasha Shokri

    2015-08-01

    Full Text Available The social structure of the family has always been in the state of transformation. In the past centuries, the nuclear family was replaced with a Patriarchal Family which lasted for only two centuries from 16th to the beginning of 18th century. In this new structure of the family, men were privileged to play the role of the master and the women were marginalized and subordinated. Recent years, however, has witnessed a re-adjustment of this order towards a more equal distribution of power relations. These changes in family structure has ever since initiated new conflicts leading to establishment of the physical and psychological bonds between men and dolls. The present study aims to find out the major socio-psychological reasons behind this conflict. In a qualitative library based study, the researchers attempt to analyse the video interview of some of the doll-owners. In the survey conducted in this study, the video of “Guys and Dolls”, BBC Video Documentary, has been shown to 10 participants, five male and five female. Then, a questionnaire was distributed to ask for their opinion based on their gender. The findings of this analysis reveal that women can hardly accept the notion of using dolls as replacement to real partners in comparison with men. On the contrary, the male participants advocated the employment of dolls as sexual replacement for the real woman figure. Keywords: Patriarchy, Real Doll, Oedipus complex, Female Subordination, Family

  17. Are all types of expertise created equal? Car experts use different spatial frequency scales for subordinate categorization of cars and faces.

    Directory of Open Access Journals (Sweden)

    Assaf Harel

    Full Text Available A much-debated question in object recognition is whether expertise for faces and expertise for non-face objects utilize common perceptual information. We investigated this issue by assessing the diagnostic information required for different types of expertise. Specifically, we asked whether face categorization and expert car categorization at the subordinate level relies on the same spatial frequency (SF scales. Fifteen car experts and fifteen novices performed a category verification task with spatially filtered images of faces, cars, and airplanes. Images were categorized based on their basic (e.g. "car" and subordinate level (e.g. "Japanese car" identity. The effect of expertise was not evident when objects were categorized at the basic level. However, when the car experts categorized faces and cars at the subordinate level, the two types of expertise required different kinds of SF information. Subordinate categorization of faces relied on low SFs more than on high SFs, whereas subordinate expert car categorization relied on high SFs more than on low SFs. These findings suggest that expertise in the recognition of objects and faces do not utilize the same type of information. Rather, different types of expertise require different types of diagnostic visual information.

  18. Competitive adsorption of arsenate and phosphate onto calcite; experimental results and modeling with CCM and CD-MUSIC

    Science.gov (United States)

    Sø, Helle Ugilt; Postma, Dieke; Jakobsen, Rasmus; Larsen, Flemming

    2012-09-01

    The competitive adsorption of arsenate and phosphate onto calcite was studied in batch experiments using calcite-equilibrated solutions. The solutions had circum-neutral pH (7-8.3) and covered a wide span in the activity of Ca2+ and CO32-. The results show that the adsorption of arsenate onto calcite is strongly reduced by the presence of phosphate, whereas phosphate adsorption is only slightly reduced by arsenate addition. Simultaneous and sequential addition (3 h apart) yields the same reduction in adsorption, underlining the high reversibility of the system. The reduction in adsorption of both arsenate and phosphate is most likely due to competition for the same sorption sites at the calcite surface, considering the similarity in sorption edges, pKa's and geometry of the two anions. The strong reduction in arsenate adsorption by competition with phosphate suggests that adsorption of arsenate onto calcite is of minor importance in most groundwater aquifers, as phosphate is often present at concentration levels sufficient to significantly reduce arsenate adsorption. The CD-MUSIC model for calcite was used successfully to model adsorption of arsenate and phosphate separately. By combining the models for single sorbate systems the competitive adsorption of phosphate and arsenate onto calcite in the binary system could be predicted. This is in contrast to the constant capacitance model (CCM) which under-predicted the competition when combining the models for single sorbate systems. This study clearly shows the importance of performing competitive adsorption studies for validation of multi-component models and for estimating the mobility of an ion in the environment.

  19. An explanation for the 18O excess in Noelaerhabdaceae coccolith calcite

    Science.gov (United States)

    Hermoso, M.; Minoletti, F.; Aloisi, G.; Bonifacie, M.; McClelland, H. L. O.; Labourdette, N.; Renforth, P.; Chaduteau, C.; Rickaby, R. E. M.

    2016-09-01

    Coccoliths have dominated the sedimentary archive in the pelagic environment since the Jurassic. The biominerals produced by the coccolithophores are ideally placed to infer sea surface temperatures from their oxygen isotopic composition, as calcification in this photosynthetic algal group only occurs in the sunlit surface waters. In the present study, we dissect the isotopic mechanisms contributing to the ;vital effect;, which overprints the oceanic temperatures recorded in coccolith calcite. Applying the passive diffusion model of carbon acquisition by the marine phytoplankton widely used in biogeochemical and palaeoceanographic studies, our results suggest that the oxygen isotope offsets from inorganic calcite in fast dividing species Emiliania huxleyi and Gephyrocapsa oceanica originates from the legacy of assimilated 18O-rich CO2 that induces transient isotopic disequilibrium to the internal dissolved inorganic carbon (DIC) pool. The extent to which this intracellular isotopic disequilibrium is recorded in coccolith calcite (1.5 to +3‰ over a 10 to 25 °C temperature range) is set by the degree of isotopic re-equilibration between CO2 and water molecules before intracellular mineralisation. We show that the extent of re-equilibration is, in turn, set by temperature through both physiological (dynamics of the utilisation of the DIC pool) and thermodynamic (completeness of the re-equilibration of the relative 18O-rich CO2 influx) processes. At the highest temperature, less ambient aqueous CO2 is present for algal growth, and the consequence of carbon limitation is exacerbation of the oxygen isotope vital effect, obliterating the temperature signal. This culture dataset further demonstrates that the vital effect is variable for a given species/morphotype, and depends on the intricate relationship between the environment and the physiology of biomineralising algae.

  20. Testing Novel pH Proxies through Inorganic Calcite Precipitations and K/Pg Foraminifera

    Science.gov (United States)

    Super, J. R.; Pagani, M.; Wang, Z.

    2013-12-01

    Ocean pH proxies help constrain the carbon system in the paleocean and can be used to infer atmospheric CO2 when coupled with estimates of total alkalinity, aqueous pCO2 or dissolved inorganic carbon. This project investigates two novel pH proxies (cerium abundance and kinetically-controlled oxygen isotopes) through a series of precipitations of inorganic calcite, as well as the previously established boron isotope pH proxy. Precipitations are performed using varied pH and carbonate saturation states that span the range of typical ocean values as well as a 'free drift' that allows pH and saturation state to vary. The light rare earth element cerium speciates, depending on local oxidation-reduction conditions, between the soluble Ce3+ and highly insoluble Ce4+ ions, causing a relative depletion of cerium in ocean water. This project demonstrates how a suite rare earth elements, including cerium, partitions into inorganic calcite and how partitioning varies with changing pH and carbonate saturation state. Oxygen isotope fractionation is primarily controlled by temperature, but this project examines how pH and carbonate saturation state correlate with oxygen isotope values under kinetic conditions during the initial stage of precipitation. The effect of diagenesis on each proxy is simulated by dissolution of precipitated calcite in a pressure vessel. Results from the precipitations are used to inform a record of well-preserved benthic and planktonic foraminifera from DSDP Site 356 that range in age from the K/Pg boundary to the period when the δ13C gradient between the surface and deep ocean returned to pre-event levels. The pH record is used to infer the magnitude and length of the perturbation to the oceanic carbon system following the extinction event, particularly in terms of export productivity.

  1. Subglacial Calcites from Northern Victoria Land: archive of Antarctic volcanism in the Last Glacial Maximum

    Science.gov (United States)

    Frisia, Silvia; Weirich, Laura; Hellstrom, John; Borsato, Andrea; Golledge, Nicholas R.; Anesio, Alexandre M.; Bajo, Petra; Drysdale, Russell N.; Augustinus, Paul C.; Barbante, Carlo; Cooper, Alan

    2017-04-01

    Subglacial carbonates bear similarities to stalagmites in their fabrics and the potential to obtain precise chronologies using U-series methods. Their chemical properties also reflect those of their parent waters, which, in contrast to stalagmites, are those of subglacial meltwaters. In analogy to speleothems, stable Carbon isotope ratios and trace elements such as Uranium, Iron and Manganese provide the opportunity to investigate ancient extreme environments without the need to drill through thousands of metres of ice. Sedimentological, geochemical and microbial evidence preserved in LGM subglacial calcites from Northern Victoria Land, close to the East Antarctic Ice Sheet margin, allow us to infer that subglacial volcanism was active in the Trans Antarctic Mountain region and induced basal ice melting. We hypothesize that a meltwater reservoir was drained and injected into interconnected basal pore systems where microbial processes enhanced bedrock weathering and, thus, released micronutrients. Volcanic influence is supported by the presence of fluorine (F) and sulphur in sediment-laden calcite layers containing termophilic species. Notably, calcite δ13C points to dissolved inorganic carbon evolved from subglacial metabolic processes. Once transported to the sea, soluble iron likely contributed to fertilizing the Southern Ocean and CO2 drawdown. This is the first well-dated evidence for LGM volcanism in Antarctica, which complements the record of volcanic eruptions retrieved from Talos Dome ice core, and supports the hypothesis of large-scale volcanism as an important driver of climate change. We conclude that subglacial carbonates are equivalent to speleothems in their palaeoclimate potential and may become a most useful source of information of ecosystems and processes at peak glacials in high altitude/high latitude settings.

  2. Calcite/opal deposits at Yucca Mountain, Nevada: Pedogenic or hypogene?

    Energy Technology Data Exchange (ETDEWEB)

    Hill, C.A.; Schluter, C.M.; Harmon, R.S. [and others

    1994-01-01

    This study is part of the research program of the Yucca Mountain Project intended to provide the State of Nevada with a detailed assessment of the geology and geochemistry of Yucca Mountain and adjacent regions. The purpose of this paper is to consider all of the geological and geochemical data available for the calcite/opal deposits at Yucca Mountain and to ascertain whether this data favors a pedogenic or hyogene origin for these deposits. Far from being of esoteric concern, this subject is of paramount importance to the debate which rages around the suitability of Yucca Mountain as a high-level radioactive waste repository site. It is also the purpose of this paper to serve as a foundation for a lengthy feature article to be submitted for publication in 1994. In addition, a stand has been taken by the National Research Council of the National Academy of Sciences against the upwelling-water model (a vote of 17 to 0 against), and this same panel report has concluded that {open_quotes}there is no compelling evidence for the repetitive flooding of the environment by expulsion of groundwater{close_quotes} and that {open_quotes}instead, the evidence strongly supports the idea that the near-surface mineral deposits resulted from percolating rainwater, which carried soil minerals down into rock fractures{close_quotes}. Based on such information the Department of Energy has stated that it {open_quotes}finds no basis to continue to study the origin of these specific deposits{close_quotes}. This study, based upon many different independent lines of evidence, reaches the opposite conclusion and instead favors a hypogene spring-travertine origin for the controversial calcite/opal deposits at Yucca Mountain. This study recognizes a pedogenic carbonate component at Yucca Mountain, but argues that this component is distinct from, and sometimes intermixed with, the calcite/opal deposits.

  3. The evolution of Carbon isotopes in calcite in the presence of cyanobacteria

    Science.gov (United States)

    Grimm, Christian; Mavromatis, Vasileios; Pokrovsky, Oleg S.; Oelkers, Eric H.

    2016-04-01

    Stable isotopic compositions in carbonates are widely used as indicators of environmental conditions prevailing during mineral formation. This reconstruction is substantially based on the assumption that there is no change in the mineral composition over geological time. However, recent experimental studies have shown that carbon and magnesium isotopes in hydrous Mg-carbonates undergo continuous re-equilibration with the ambient solution even after mineral precipitation stopped ([1] and [2], respectively). To verify whether this holds true for anhydrous Ca-bearing carbonates which readily form at earth's surface environments, a series of batch system calcite precipitation experiments were performed in the presence of actively growing cyanobacteria Synechococcus sp. The bacteria were grown at ambient temperature in a BG11 culture medium (SIGMA C3061) and continuous stirring, air-bubbling and illumination. Calcite precipitation was initiated by the addition of 8.5mM CaCl2 and 0-50 mM NaHCO3 or NaHCO3-Na2CO3 mixtures. The presence of cyanobacteria is on one hand promoting CaCO3 formation due to increasing pH resulting from photosynthesis. On the other hand, actively growing cyanobacteria drastically change carbon isotope signature of the aqueous fluid phase by preferably incorporating the lighter 12C isotope into biomass [1]. This study explores the effect of continuously changing carbon isotope compositions in dissolved inorganic carbon (DIC) on precipitated calcite which is in chemical equilibrium with the ambient fluid phase. [1] Mavromatis et al. (2015). The continuous re-equilibration of carbon isotope compositions of hydrous Mg-carbonates in the presence of cyanobacteria. Chem. Geol. 404, 41-51 [2] Mavromatis et al. (2012). Magnesium isotope fractionation during hydrous magnesium carbonate precipitation with and without cyanobacteria. Geochim. Cosmochim. Acta 76, 161-174

  4. Calcium sensing in exocytosis

    DEFF Research Database (Denmark)

    Gustavsson, Natalia; Wu, Bingbing; Han, Weiping

    2012-01-01

    Neurotransmitters, neuropeptides and hormones are released through regulated exocytosis of synaptic vesicles and large dense core vesicles. This complex and highly regulated process is orchestrated by SNAREs and their associated proteins. The triggering signal for regulated exocytosis is usually...... an increase in intracellular calcium levels. Besides the triggering role, calcium signaling modulates the precise amount and kinetics of vesicle release. Thus, it is a central question to understand the molecular machineries responsible for calcium sensing in exocytosis. Here we provide an overview of our...

  5. Interaction of ethanol and water with the {1014} surface of calcite

    DEFF Research Database (Denmark)

    Cooke, David; Gray, R J; Sand, K K

    2010-01-01

    Molecular dynamics simulations have been used to model the interaction between ethanol, water, and the {1014} surface of calcite. Our results demonstrate that a single ethanol molecule is able to form two interactions with the mineral surface (both Ca-O and O-H), resulting in a highly ordered...... with water and for growth at the {1014} surface to occur. This observation, and its corresponding molecular explanation, may give some insight into the ability to control crystal form using mixtures of different organic solvents....

  6. Rapid high temperature field test method for evaluation of geothermal calcite scale inhibitors

    Energy Technology Data Exchange (ETDEWEB)

    Asperger, R.G.

    1982-08-01

    A test method is described which allows the rapid field testing of calcite scale inhibitors in high- temperature geothermal brines. Five commercial formulations, chosen on the basis of laboratory screening tests, were tested in brines with low total dissolved solids at ca 500 F. Four were found to be effective; of these, 2 were found to be capable of removing recently deposited scale. One chemical was tested in the full-flow brine line for 6 wks. It was shown to stop a severe surface scaling problem at the well's control valve, thus proving the viability of the rapid test method. (12 refs.)

  7. Scattering matrix measurements and light-scattering calculations of calcite particles

    Directory of Open Access Journals (Sweden)

    D. D. Dabrowska

    2011-09-01

    Full Text Available We present measurements of the complete scattering matrix as a function of the scattering angle of a sample of calcite particles collected near Lecce, Italy. The measurements are done at a wavelength of 647 nm in the scattering angle range 3°−177°. FESEM and SEM images show that the sample consists largely of flake-like particles. Ten different flake-like geometries are randomly generated and their scattering properties are simulated with DDA for sizes from 0.1 μm to 1 μm. Some preliminary comparisons of the simulations and the measurements are shown.

  8. Pulsed cathodoluminescence of diamond, calcite, spodumene, and fluorite under the action of subnanosecond electron beam

    Science.gov (United States)

    Baksht, E. Kh.; Burachenko, A. G.; Tarasenko, V. F.

    2010-11-01

    Amplitude and temporal characteristics of pulsed cathodoluminescence (PCL) of diamond (natural and synthetic), calcite, spodumene, and fluorite have been studied at a temporal resolution of ˜0.3 ns. The PCL was generated by electron beam pulses with a full width at half maximum (FWHM) of 0.1, 0.25, and 0.65 ns. The PCL spectra have been measured for the emission induced by 0.1- and 0.25-ns pulses at a beam current density of ˜90 A/cm2.

  9. Effects of initial supersaturation on spontaneous precipitation of calcium carbonate in the presence of charged poly-L-amino acids.

    Science.gov (United States)

    Njegić-Dzakula, Branka; Falini, Giuseppe; Brecević, Ljerka; Skoko, Zeljko; Kralj, Damir

    2010-03-15

    Spontaneous precipitation of calcium carbonate was investigated in two precipitation systems: (1) with initial supersaturation lower than that corresponding to the solubility of amorphous calcium carbonate (ACC), at which vaterite precipitated, and (2) with initial supersaturation higher than that of ACC solubility, at which a mixture of calcite and vaterite was formed. After the addition of an acidic polypeptide, poly-L-glutamic acid (pGlu) or poly-L-aspartic acid (pAsp), into (1) a significant inhibition of nucleation, expressed as an increase in induction time, and growth of vaterite, perceived as a dead zone, was observed. Extent of inhibition decreased in the order: Inh(pAps)>Inh(pGlu)>Inh(pLys). The addition of a polypeptide into (2) caused the inhibition of precipitation and changed the morphology and polymorphic composition of the precipitate; only vaterite appeared at approximately c(pAsp)=3 ppm, c(pGlu)=6 ppm, or c(pLys)=7 ppm. This finding is explained as a consequence of kinetic constraints through the inhibition of calcite nucleation and stronger binding of acidic polypeptide by the calcite surfaces than by the vaterite surfaces. Laboratory precipitation studies using conditions that resemble those in living organism should be run at an initial supersaturation corresponding to the solubility of ACC as a limiting condition. 2009 Elsevier Inc. All rights reserved.

  10. Effect of cationic and anionic surfactants on the application of calcium carbonate nanoparticles in paper coating.

    Science.gov (United States)

    Barhoum, Ahmed; Rahier, Hubert; Abou-Zaied, Ragab Esmail; Rehan, Mohamed; Dufour, Thierry; Hill, Gavin; Dufresne, Alain

    2014-02-26

    Modification of calcium carbonate particles with surfactant significantly improves the properties of the calcium carbonate coating on paper. In this study, unmodified and CTAB (hexadecyltetramethylammonium bromide)- and oleate-modified calcium carbonate nanoparticles were prepared using the wet carbonation technique for paper coating. CTAB (cationic surfactant) and sodium oleate (anionic surfactant) were used to modify the size, morphology, and surface properties of the precipitated nanoparticles. The obtained particles were characterized using X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, zeta potential measurements, thermal gravimetric analysis (TGA), and transmission electron microscopy (TEM). Coating colors were formulated from the prepared unmodified and modified calcium carbonates and examined by creating a thin coating layer on reference paper. The effect of calcium carbonate particle size and surface modification on paper properties, such as coating thickness, coating weight, surface roughness, air permeability, brightness, whiteness, opacity, and hydrophobicity, were investigated and compared with commercial ground (GCC) calcium carbonate-coated papers. The results show that the obtained calcium carbonate nanoparticles are in the calcite phase. The morphology of the prepared calcium carbonate nanoparticles is rhombohedral, and the average particle diameter is less than 100 nm. Compared to commercial GCC, the use of unmodified and CTAB- and oleate-modified calcium carbonate nanoparticles in paper coating improves the properties of paper. The highest measured paper properties were observed for paper coated with oleate-modifed nanoparticles, where an increase in smoothness (decrease in paper roughness) (+23%), brightness (+1.3%), whiteness (+2.8%), and opacity (+2.3%) and a decrease in air permeability (-26%) was obtained with 25% less coat weight. The water contact angle at a drop age time of 10 min was about 112° for the paper

  11. Bone repair in calcium-deficient rats: comparison of xylitol+calcium carbonate with calcium carbonate, calcium lactate and calcium citrate on the repletion of calcium.

    Science.gov (United States)

    Hämäläinen, M M

    1994-06-01

    The potential value of xylitol in calcium therapy was evaluated by comparing the effect of dietary xylitol (50 g/kg diet) + calcium carbonate with the effects of calcium carbonate, calcium lactate and calcium citrate on bone repair of young male rats after the rats consumed for 3 wk a calcium-deficient diet (0.2 g Ca/kg diet). After this calcium-depletion period, the rats were fed for 2 wk one of four diets, each containing 5 g Ca/kg diet as one of the four dietary calcium sources. The diet of the control animals was supplemented with CaCO3 (5 g Ca/kg diet) throughout the study. The Ca-deficient rats showed low bone mass, low serum calcium and high serum 1,25-dihydroxycholecalciferol, parathyroid hormone (1-34 fraction) and osteocalcin concentrations. They also excreted magnesium, phosphate and hydroxyproline in the urine in high concentrations, and had high bone alkaline phosphatase and tartrate-resistant acid phosphatase activities. Most of these changes were reversed by the administered of the calcium salts. The highest recoveries of femoral dry weight, calcium, magnesium and phosphate were observed in the groups receiving xylitol+CaCO3 and calcium lactate. Calcium lactate and calcium citrate caused low serum phosphate concentration compared with rats receiving CaCO3 and with the age-matched Ca-replete controls. Xylitol-treated rats excreted more calcium and magnesium in urine than did the other rats, probably due to increased absorption of these minerals from the gut. These results suggest that dietary xylitol improves the bioavailability of calcium salts.

  12. Calcium – how and why?

    Indian Academy of Sciences (India)

    Unknown

    Calcium is among the most commonly used ions, in a multitude of biological functions, so much so that it is impossible to imagine life without calcium. In this article I have attempted to address the question as to how calcium has achieved this status with a brief mention of the history of calcium research in biology. It appears ...

  13. Annual 18O/16O composition of authigenic calcite in varved lake sediments reflects regional air temperature

    Science.gov (United States)

    Wirth, Stefanie; Gilli, Adrian

    2015-04-01

    The oxygen isotopic composition (18O/16O) of authigenic calcite in lake sediments reflects the temperature and the isotopic composition of the lake water from which the calcite is precipitated and thus contains information about the climatic conditions at the time of calcite formation. Varved lake sediments containing laminae of authigenically precipitated calcite provide the possibility to analyze the 18O/16O composition at an annual resolution, thus yielding high-resolution climatic information. Yet, despite this high potential the number of studies having used this approach is relatively low. Reasons for this are probably sampling challenges, the scarceness of suitable varved sediments, missing instrumental records to compare with, as well as uncertainties regarding the factors influencing the calcite isotopic composition (water/air temperature, precipitation, lake-internal factors). Still, annually resolved data of the 18O/16O composition of calcite seems a promising climate proxy and we therefore investigated the 18O/16O pattern of the authigenic calcite in the varved sediments of Lake Zurich. Lake Zurich is a pre-alpine lake with a surface area of 88 km2, a maximal water depth of 137 m and a theoretical water residence time of 1.4 years. Sediments are varved since the late 19th century due to anthropogenic lake eutrophication. For this calibration study, we analyzed the 18O/16O composition of the authigenic calcite for the time period 1960-2010 at annual resolution. The δ18O values range from -10.8 to -13.4 o; and the pattern is dominated by a conspicuous shift to more enriched values between 1985 and 1987. The same shift has been observed for local to large-scale climatic parameters such as lake, river, and groundwater temperatures throughout Switzerland, the mean air temperature for Switzerland, and the NAO index. The consistency of the instrumental temperature data sets with the 18O/16O composition of the authigenic calcite emphasizes the high potential

  14. Calcium and Your Child

    Science.gov (United States)

    ... Milk Allergy Figuring Out Food Labels What's a Vegetarian? Osteoporosis Minerals Your Bones Mineral Chart Vitamin D ... Need to Drink Milk? Lactose Intolerance Becoming a Vegetarian Soy Foods and Health Calcium Bones, Muscles, and ...

  15. Stoichiometry of Calcium Medicines

    Science.gov (United States)

    Pinto, Gabriel

    2005-01-01

    The topic of calcium supplement and its effects on human lives is presented in the way of questions to the students. It enables the students to realize the relevance of chemistry outside the classroom surrounding.

  16. Magnesium, calcium and cancer

    National Research Council Canada - National Science Library

    Anghileri, Leopoldo J

    2009-01-01

    Magnesium ion (Mg(2+)) and calcium ion (Ca(2+)) control a diverse and important range of cellular processes, such as gene transcription, cell proliferation, neoplastic transformation, immune response and therapeutic treatment...

  17. Unraveling the Formation of Large Amounts of Calcite Scaling in Geothermal Wells in the Bavarian Molasse Basin: A Reactive Transport Modeling Approach

    OpenAIRE

    Wanner, Christoph; Eichinger, Florian; Jahrfeld, Thomas; Diamond, Larryn W.

    2017-01-01

    Results from reactive transport simulations performed for the geothermal plant in Kirchstockach, located in the Bavarian Molasse Basin in southern Germany, are presented to unravel the formation of calcite scaling. Simulation results successfully predict the calcite scaling profile observed along the production well if supersaturation with respect to calcite is specified for the model water leaving the pump at 800 m depth. This observation is in good agreement with a previous study suggesting...

  18. The adjectival subordinate clause in the production of meaning in the text: the prospect of Portuguese textbooks in high school

    Directory of Open Access Journals (Sweden)

    Aliana Lopes Câmara

    2016-12-01

    Full Text Available This paper studies how Portuguese textbooks of high school, approved by the Programa Nacional do Livro Didático-2015, approach the teaching of adjectival subordinate clause. Several researchers (Bagno, 2011; Neves, 2011; Travaglia, 2009, 2011 address the issue of grammar teaching, questioning the mechanistic and traditional teaching of identification and classification of linguistic units (morphological and syntactic. These authors argue the articulation of grammar with the teaching of reader and writer skills, so that linguistic resources are studied in mobilizing effects of meaning in the textual construction. The choice of textbooks corpus, therefore, was determined by the grammar teaching proposal explicitly stated in the manuals for the teacher (part attached to the textbook, under which linguistic resources are subsidiary to the reading and writing teaching. First we compare the proposal of manuals on the teaching of grammar and what was accomplished in the book of the student, more specifically on the proposals for the teaching of adjectival subordinate clause. Then, from the study on the functional description of the adjectival subordinate clause (Câmara, 2015, which is based on Functional Discourse Grammar (Hengeveld e Mackenzie, 2008, we studied how some descriptive aspects can be subsidiary for the teaching of the adjective clause, aiming at the development of reading and writing skills. The reason for the choice of this theoretical support is the fact that grammar is hierarchically structured in levels and layers of linguistic analysis, and the pragmatic units determine the semantic units, which in turn determine the morphosyntactic units which, in turn, determine the phonological units. The data show that remains, in the educational proposals of the relative clause in high school textbooks, a grammar teaching that focuses primarily in the nomenclature, metalanguage and in the normative grammar rules. There isn’t many

  19. Final Technical Report for DOE Award DE-FG02-07ER64403 [Modeling of Microbially Induced Calcite Precipitation for the Immobilization of Strontium-90 Using a Variable Velocity Streamtube Ensemble

    Energy Technology Data Exchange (ETDEWEB)

    Ginn, Timothy R. [University of California, Davis; Weathers, Tess [University of California, Davis

    2013-08-26

    Biogeochemical modeling using PHREEQC2 and a streamtube ensemble approach is utilized to understand a well-to-well subsurface treatment system at the Vadose Zone Research Park (VZRP) near Idaho Falls, Idaho. Treatment involves in situ microbially-mediated ureolysis to induce calcite precipitation for the immobilization of strontium-90. PHREEQC2 is utilized to model the kinetically-controlled ureolysis and consequent calcite precipitation. Reaction kinetics, equilibrium phases, and cation exchange are used within PHREEQC2 to track pH and levels of calcium, ammonium, urea, and calcite precipitation over time, within a series of one-dimensional advective-dispersive transport paths creating a streamtube ensemble representation of the well-to-well transport. An understanding of the impact of physical heterogeneities within this radial flowfield is critical for remediation design; we address this via the streamtube approach: instead of depicting spatial extents of solutes in the subsurface we focus on their arrival distribution at the control well(s). Traditionally, each streamtube maintains uniform velocity; however in radial flow in homogeneous media, the velocity within any given streamtube is spatially-variable in a common way, being highest at the input and output wells and approaching a minimum at the midpoint between the wells. This idealized velocity variability is of significance in the case of ureolytically driven calcite precipitation. Streamtube velocity patterns for any particular configuration of injection and withdrawal wells are available as explicit calculations from potential theory, and also from particle tracking programs. To approximate the actual spatial distribution of velocity along streamtubes, we assume idealized radial non-uniform velocity associated with homogeneous media. This is implemented in PHREEQC2 via a non-uniform spatial discretization within each streamtube that honors both the streamtube’s travel time and the idealized

  20. Linking crystal structure with temperature-sensitive vibrational modes in calcium carbonate minerals.

    Science.gov (United States)

    Xu, Ben; Poduska, Kristin M

    2014-09-07

    We demonstrate a correlation between how an IR-active vibrational mode responds to temperature changes and how it responds to crystallinity differences. Infrared (IR) spectroscopy was used to track changes in carbonate-related vibrational modes in three different CaCO3 polymorphs (calcite, aragonite, and vaterite) and CaMg(CO3)2 (dolomite) during heating. Of the three characteristic IR-active carbonate modes, the in-plane bending mode (ν4) shows the most pronounced changes with heating in polymorphs that have planar carbonate arrangements (calcite, aragonite, and dolomite). In contrast, this mode is virtually unchanged in vaterite, which has a canted arrangement of carbonate units. We correlate these trends with recent studies that identified the ν4 mode as most susceptible to changes related to crystallinity differences in calcite and amorphous calcium carbonate. Thus, our results suggest that studies of packing arrangements could provide a generalizable approach to identify the most diagnostic vibrational modes for tracking either temperature-dependent or crystallinity-related effects in IR-active solids.

  1. Retention of silica nanoparticles on calcium carbonate sands immersed in electrolyte solutions

    KAUST Repository

    Li, Yan Vivian

    2014-12-01

    © 2014 Elsevier Inc. Understanding nanoparticle-surface adhesion is necessary to develop inert tracers for subsurface applications. Here we show that nanoparticles with neutral surface charge may make the best subsurface tracers, and that it may be possible to used SiO2 nanoparticle retention to measure the fraction of solid surface that has positive charge. We show that silica nanoparticles dispersed in NaCl electrolyte solutions are increasingly retained in calcium carbonate (calcite) sand-packed columns as the solution ionic strength increases, but are not retained if they are injected in pure water or Na2SO4 electrolyte solutions. The particles retained in the NaCl experiments are released when the column is flushed with pure water or Na2SO4 solution. AFM measurements on calcite immersed in NaCl solutions show the initial repulsion of a silica colloidal probe as the surface is approached is reduced as the solution ionic strength increases, and that at high ionic strengths it disappears entirely and only attraction remains. These AFM measurements and their interpretation with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory shows the calcite surface charge is always negative for Na2SO4 solutions, but changes from negative to positive in a patchy fashion as the ionic strength of the NaCl solution increases. Since mixed-charge (patchy) surfaces may be common in the subsurface, nanoparticles with near-zero charge may make the best tracers.

  2. Adjustment errors of sunstones in the first step of sky-polarimetric Viking navigation: studies with dichroic cordierite/ tourmaline and birefringent calcite crystals

    National Research Council Canada - National Science Library

    Száz, Dénes; Farkas, Alexandra; Blahó, Miklós; Barta, András; Egri, Ádám; Kretzer, Balázs; Hegedüs, Tibor; Jäger, Zoltán; Horváth, Gábor

    2016-01-01

    According to an old but still unproven theory, Viking navigators analysed the skylight polarization with dichroic cordierite or tourmaline, or birefringent calcite sunstones in cloudy/foggy weather...

  3. Calcite Wettability in the Presence of Dissolved Mg2+ and SO42-

    DEFF Research Database (Denmark)

    Generosi, Johanna; Ceccato, Marcel; Andersson, Martin Peter

    2017-01-01

    with calcite even after rinsing with CaCO3-saturated deionized water, suggesting sorption on or in calcite. When the calcite-saturated solution of MgSO4 was replaced by calcite-saturated NaCl at the same ionic strength, adhesion force increased again, indicating that the effect is reversible and suggesting Mg...... replacement by Ca. Experiments with solutions of Na2SO4 and MgCl2 suggest that Mg2+ uptake is favored when SO42– is also present...

  4. Fluoride removal by calcite: evidence for fluorite precipitation and surface adsorption.

    Science.gov (United States)

    Turner, Brett D; Binning, Philip; Stipp, S L S

    2005-12-15

    Fluoride contamination of groundwater, both anthropogenic and natural, is a major problem worldwide. In this study, fluoride removal by crushed limestone (99% pure calcite) was investigated by batch studies and surface-sensitive techniques from solutions with fluoride concentrations from 150 micromol/L (3 mg/L) to 110 mM (approximately 2100 mg/L). Surface-sensitive techniques, including atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) as well as zeta potential measurements, confirm that, in addition to precipitation reactions, adsorption of fluoride also occurs. Results indicate that fluoride adsorption occurs immediately over the entire calcite surface with fluorite precipitating at step edges and kinks, where dissolved Ca2+ concentration is highest. The PHREEQ geochemical model was applied to the observed data and indicates that existing models, especially at low fluoride concentrations and high pH (>7.5) are not equipped to describe this complex system, largely because the PHREEQ model includes only precipitation reactions, whereas a combination of adsorption and precipitation parameters are required.

  5. Environmentally acceptable effect of hydrogen peroxide on cave "lamp-flora", calcite speleothems and limestones.

    Science.gov (United States)

    Faimon, Jirí; Stelcl, Jindrich; Kubesová, Svatava; Zimák, Jirí

    2003-01-01

    Mosses, algae, and cyanobacteria (lamp-flora) colonize illuminated areas in show caves. This biota is commonly removed by a sodium hypochlorite solution. Because chlorine and other deleterious compounds are released into a cave environment during lamp-flora cleansing, hydrogen peroxide was tested as an alternative agent. In a multidisciplinary study conducted in the Kateinská Cave (Moravian Karst, Czech Republic), 12 algae- and cyanobacteria taxons and 19 moss taxons were detected. The threshold hydrogen peroxide concentration for the destruction of this lamp-flora was found to be 15 vol.%. Based on laboratory experiments in stirred batch reactors, the dissolution rates of limestones and calcite speleothems in water were determined as 3.77 x 10-3 and 1.81 x 10-3 mol m-2 h-1, respectively. In the 15% peroxide solution, the limestone and speleothem dissolution rates were one order of magnitude higher, 2.00 x 10-2 and 2.21 x 10-2 mol m-2 h-1, respectively. So, the peroxide solution was recognised to attack carbonates somewhat more aggressively than karst water. In order to prevent the potential corrosion of limestone and speleothems, the reaching of preliminary peroxide saturation with respect to calcite is recommended, for example, by adding of few limestone fragments into the solution at least 10 h prior to its application.

  6. The effect of water on strain localization in calcite fault gouge sheared at seismic slip rates

    Science.gov (United States)

    Rempe, Marieke; Smith, Steven; Mitchell, Thomas; Hirose, Takehiro; Di Toro, Giulio

    2017-04-01

    Strain localization during coseismic slip in fault gouges is a critical mechanical process that has implications for understanding frictional heating, the earthquake energy budget and the evolution of fault rock microstructure. To assess the nature of strain localization during shearing of calcite fault gouges, high-velocity (vmax = 1m /s) rotary-shear experiments at normal stresses of 3-20 MPa were conducted under room-dry and wet conditions on synthetic calcite gouges containing dolomite gouge strain markers. When sheared at 1 m/s, the room-dry gouges showed a prolonged strengthening phase prior to dynamic weakening, whereas the wet gouges weakened nearly instantaneously. Microstructural analysis revealed that a thin (<600 μm) high-strain layer and through-going principal slip surface (PSS) developed after several centimeters of slip in both dry and wet gouges, and that strain localization at 1 m/s occurred progressively and rapidly. The strain accommodated in the bulk gouge layer did not change significantly with increasing displacement indicating that, once formed, the high-strain layer and PSS accommodated most of the displacement. Thus, a substantial strain gradient is present in the gouge layer. In water-dampened gouges, localization likely occurs during and after dynamic weakening. Our results suggest that natural fault zones in limestone are more prone to rapid dynamic weakening if water is present in the granular slipping zones.

  7. Remineralization of permeate water by calcite bed in the Daoura's plant (south of Morocco)

    Science.gov (United States)

    Biyoune, M. G.; Atbir, A.; Bari, H.; Hassnaoui, L.; Mongach, E.; Khadir, A.; Boukbir, L.; Bellajrou, R.; Elhadek, M.

    2017-04-01

    To face water shortage and to fight drought, the National office of Water and Electricity (ONEE) carried out a program aiming at constructing several desalination stations of seawater in the South of Morocco. However, the final product water after desalination (osmosis water) has turned out to be unbalanced and has an aggressive character. Therefore, a post-treatment of remineralization is necessary to recover the calco-carbonic equilibrium of water and to protect the distribution network from corrosion degradation. Thereby, our work aims to examine the performance of the remineralization used in Daoura plant by the calcite bed in the absence of carbon dioxide CO2 (without acidification), we have followed many parameters indicating the performance of this technique adopted such as pH, TAC (hydroxide, carbonate and bicarbonate content), Ca content, Langelier saturation index (LSI), Larson index (LR). The results obtained show that this technique adopted in Daoura plant brings to water back its entire calco-carbonic balance to measure up to the Moroccan standards of drinking water. Generally, the exploitation of the calcite bed technique for remineralization is simple, easy and it does not require any major efforts or precautions.

  8. Genesis and microstratigraphy of calcite coralloids analysed by high resolution imaging and petrography

    Science.gov (United States)

    Vanghi, V.; Frisia, S.; Borsato, A.

    2017-08-01

    The genesis of calcite coralloid speleothems from Lamalunga cave (Southern Italy) is here investigated from a purely petrographic perspective, which constitutes the basis for any subsequent chemical investigation. Lamalunga cave coralloids formed on bones and debris on the floor of the cave. They consist of elongated columnar crystals whose elongation progressively increases from the flanks to the tips of the coralloid, forming a succession of lens-shaped layers, which may be separated by micrite or impurity-rich layers. Organic molecules are preferentially concentrated toward the centre of convex lenses as highlighted by epifluorescence. Their occurrence on cave floor, lens-shaped morphology and concentration of impurities toward the apex of the convex lenses supports the hypothesis that their water supply was hydroaerosol, generated by the fragmentation of cave drips. Evaporation and degassing preferentially occurred on tips, enhancing the digitated morphology and trapping the organic molecules and impurities, carried by the hydroaerosol, between the growing crystals which became more elongated. Micrite layers, that cap some coralloid lenses, likely identify periods when decreasing in hydroaerosol resulted in stronger evaporation and higher supersaturation with respect to calcite of the parent film of fluid. This interpretation of coralloid formation implies that these speleothems can be used to extract hydroclimate information.

  9. TEM study of Pt-C replicas of calcite overgrowths precipitated from electrolyte solutions

    Science.gov (United States)

    Paquette, Jeanne; Vali, Hojatollah; Mucci, Alfonso

    1996-12-01

    The surface microtopography of synthetic magnesian calcite overgrowths on calcite powders was imaged on Pt-C replicas by transmission electron microscopy. The overgrowths were precipitated at room temperature under steady-state conditions from seawater-like solutions, in the presence and absence of Mg2+, SO42- and PO43- ions, and over a range of saturation states. Overgrowths produced from the Mg-free electrolyte show smooth coverage of the substrate with a few hillocks suggestive of spiral growth. Electrolytes containing Mg consistently produced patchy overgrowths on the {1014} faces of the seed crystals and differential inhibition of growth at their corners and edges. The patchy over-growths consist of flat-topped islands whose morphology is consistent with two-dimensional surface nucleation rather than spiral growth. The density of islands, their rounding, and their degree of coalescence increased with the saturation state of the precipitating solution. The effect of SO42- on the surface topography was imperceptible. Soluble reactive phosphate (SRP), on the other hand, clearly inhibited growth and dissolution along specific crystallographic directions. The development of irregular surfaces along specific edges and corners of the seed crystals shows that foreign ions promote the development of complex crystal morphology even at high saturation states.

  10. Effects of Citrate and Arginine on Sorption of Nickel to Yazd Sepiolite and Calcite

    Directory of Open Access Journals (Sweden)

    Ahmadreza Sheikhhosseini

    2017-03-01

    Full Text Available Introduction: Pollution of soil and water environment by release of heavy metals is of great concerns of the last decades. Sorption of heavy metals by low cost materials is considered as an inexpensive and efficient method used for removal of heavy metals from soil-water systems. The presence of different ligands with various complexing abilities can change the sorption properties of heavy metals and their fate in the environment as well. In order to assess the effect of citrate and arginine as natural organic ligands in soil environment, in a batch study we investigated the effects of these ligands on equilibrium sorption of nickel to sepiolite and calcite minerals and also kinetics of Ni sorption by these minerals. Materials and Methods: Minerals used in this study included sepiolite from Yazd (Iran and pure calcite (Analytical grade, Merck, Germany. Sepiolite was purified, saturated with Ca using 0.5 M CaCl2, powdered in a mortar and sieved by non-metal 230 mesh standard wire sieve. For equilibrium sorption study, in a 50-mL polyethylene centrifuge tube,0.3 g sample of each mineral was suspended in 30 mL of a 0.01 M CaCl2 solution containing 0, 5, 10, 20, 40, 60, 80 and 100 mg L-1 Ni (NiCl2 and containing zero (as control or 0.1mmol L-1 citrate or arginine ligands. The applied concentrationsfor each ligand can naturally occur in soils. Preparedtubes were shaken (180±2 rpm, 25±1oC for 24 h using an orbital shaker and centrifuged (4000×g for 10 min and the supernatants were analyzed for Ni concentration using an atomic absorption spectrophotometer (AAnalyst 200 Perkin-Elmer at a wavelength of 232 nm and a detection limit of 0.05 mg L-1. The quantity of Ni retained by each mineral at equilibrium was calculated using equation qe = (Ci - CeV/W where qe was the amount of nickel retained by mineral surface at equilibrium. Ci and Ce were the initial and the equilibrium concentrations (mg L-1 of Ni, respectively, V was the volume (L of the solution

  11. A comparison of amorphous calcium carbonate crystallization in aqueous solutions of MgCl2 and MgSO4: implications for paleo-ocean chemistry

    Science.gov (United States)

    Han, Mei; Zhao, Yanyang; Zhao, Hui; Han, Zuozhen; Yan, Huaxiao; Sun, Bin; Meng, Ruirui; Zhuang, Dingxiang; Li, Dan; Liu, Binwei

    2017-07-01

    Based on the terminology of "aragonite seas" and "calcite seas", whether different Mg sources could affect the mineralogy of carbonate sediments at the same Mg/Ca ratio was explored, which was expected to provide a qualitative assessment of the chemistry of the paleo-ocean. In this work, amorphous calcium carbonate (ACC) was prepared by direct precipitation in anhydrous ethanol and used as a precursor to study crystallization processes in MgSO4 and MgCl2 solutions having different concentrations at 60 °C (reaction times 240 and 2880 min). Based on the morphology of the aragonite crystals, as well as mineral saturation indices and kinetic analysis of geochemical processes, it was found that these crystals formed with a spherulitic texture in 4 steps. First, ACC crystallized into columnar Mg calcite by nearly oriented attachment. Second, the Mg calcite changed from columnar shapes into smooth dumbbell forms. Third, the Mg calcite transformed into rough dumbbell or cauliflower-shaped aragonite forms by local dissolution and precipitation. Finally, the aragonite transformed further into spherulitic radial and irregular aggregate forms. The increase in Ca2+ in the MgSO4 solutions compared with the MgCl2 solutions indicates the fast dissolution and slow precipitation of ACC in the former solutions. The phase transition was more complete in the 0.005 M MgCl2 solution, whereas Mg calcite crystallized from the 0.005 M MgSO4 solution, indicating that Mg calcite could be formed more easily in an MgSO4 solution. Based on these findings, aragonite and Mg calcite relative to ACC could be used to provide a qualitative assessment of the chemistry of the paleo-ocean. Therefore, calcite seas relative to high-Mg calcite could reflect a low concentration MgSO4 paleo-ocean, while aragonite seas could be related to an MgCl2 or high concentration of MgSO4 paleo-ocean.

  12. [Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

    NARCIS (Netherlands)

    Jonge, H.J. de; Gans, R.O.; Huls, G.A.

    2012-01-01

    Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate

  13. Constraints on the vital effect in coccolithophore and dinoflagellate calcite by oxygen isotopic modification of seawater

    Science.gov (United States)

    Hermoso, Michaël; Horner, Tristan J.; Minoletti, Fabrice; Rickaby, Rosalind E. M.

    2014-09-01

    In this study, we show that there are independent controls of 18O/16O and 13C/12C fractionation in coccolithophore and dinoflagellate calcite due to the contrasting kinetics of each isotope system. We demonstrate that the direction and magnitude of the oxygen isotope fractionation with respect to equilibrium is related to the balance between calcification rate and the replenishment of the internal pool of dissolved inorganic carbon (DIC). As such, in fast growing cells, such as those of Emiliania huxleyi and Gephyrocapsa oceanica (forming the so-called ;heavy group;), calcification of the internal carbon pool occurs faster than complete isotopic re-adjustment of the internal DIC pool with H2O molecules. Hence, coccoliths reflect the heavy oxygen isotope signature of the CO2 overprinting the whole DIC pool. Conversely, in large and slow growing cells, such as Coccolithus pelagicus ssp. braarudii, complete re-equilibration is achieved due to limited influx of CO2 leading to coccoliths that are precipitated in conditions close to isotopic equilibrium (;equilibrium group;). Species exhibiting the most negative oxygen isotope composition, such as Calcidiscus leptoporus (;light group;), precipitate coccolith under increased pH in the coccolith vesicle, as previously documented by the ;carbonate ion effect;. We suggest that, for the carbon isotope system, any observed deviation from isotopic equilibrium is only ;apparent;, as the carbon isotopic composition in coccolith calcite is controlled by a Rayleigh fractionation originating from preferential incorporation of 12C into organic matter. Therefore, species with low PIC/POC ratios as E. huxleyi and G. oceanica are shifted towards positive carbon isotope values as a result of predominant carbon fixation into the organic matter. By contrast, cells with higher PIC/POC as C. braarudii and C. leptoporus maintain, to some extent, the original negative isotopic composition of the CO2. The calcareous dinoflagellate

  14. Calcite Precipitation at an Arctic Geothermal Spring Leads to Endolith Colonization and Ecological Succession

    Science.gov (United States)

    Starke, V.; Fogel, M. L.; Steele, A.

    2012-12-01

    A critical question in microbial ecology concerns how environmental conditions affect community makeup. Troll Springs, a geothermal spring at 79°23'N, 13°26'E on Svalbard in the high Arctic, provides an opportunity to study microbial communities and succession along steep environmental gradients that impose strong selective pressures. At Troll, warm water is released into cold, dry climate conditions. Precipitation of calcite from the spring's waters has built terraces that host a range of microbial communities. Microorganisms exist in warm water as periphyton, in moist granular materials, and in cold, dry rock as endoliths. Troll therefore has two distinct ecosystems, aquatic and terrestrial, in close proximity, with different underlying environmental factors shaping their microbial communities. We use microscopic and phylogeny-based molecular methods to study microbial community makeup at Troll Springs. Periphyton are entrapped by precipitation of calcite, becoming precursors for endolithic communities. Much of the pore space originally occupied by periphyton becomes inhabited either by organisms that were already present in minor quantities in the periphyton, or by new organisms that colonized an environment for which they were well suited. This process differs from most endolith colonization, where rock predates the communities that colonize it. In the aquatic environments, the strongest dependence of community makeup is on pH and temperature, with gradual changes in community makeup along a pH/temperature gradient among the pools. Illumination (as limited by calcite precipitation) and thermal stability also appear to exert influence. In contrast, in the granular and endolithic terrestrial environments, where water is scarce and therefore exerts selective pressure, there is a strong relationship between community makeup and water content. The richness, evenness, and diversity of microbial taxa are all strongly correlated at Troll Springs. These parameters all

  15. A Model of Adding Relations in Multi-levels to a Formal Organization Structure with Two Subordinates

    Science.gov (United States)

    Sawada, Kiyoshi; Amano, Kazuyuki

    2009-10-01

    This paper proposes a model of adding relations in multi-levels to a formal organization structure with two subordinates such that the communication of information between every member in the organization becomes the most efficient. When edges between every pair of nodes with the same depth in L (L = 1, 2, …, H) levels are added to a complete binary tree of height H, an optimal set of depths {N1, N2, …, NL} (H⩾N1>N2> …>NL⩾1) is obtained by maximizing the total shortening path length which is the sum of shortening lengths of shortest paths between every pair of all nodes in the complete binary tree. It is shown that {N1, N2, …, NL}* = {H, H-1, …, H-L+1}.

  16. Aggressiveness and brain amine concentration in dominant and subordinate finishing pigs fed the beta-adrenoreceptor agonist ractopamine.

    Science.gov (United States)

    Poletto, R; Cheng, H W; Meisel, R L; Garner, J P; Richert, B T; Marchant-Forde, J N

    2010-09-01

    Under farm conditions, aggression related to the formation of social hierarchy and competition for resources can be a major problem because of associated injuries, social stress, and carcass losses. Any factor that may affect the regulation and amount of aggression within a farmed system, for instance, feeding the beta-adrenoreceptor agonist ractopamine (RAC), is therefore worthy of investigation. The objectives of this study were to assess the effects of the widely used swine feed additive RAC, considering also the effects of sex and social rank on aggressiveness and concentrations of brain amines, neurotransmitters essential for controlling aggression, in finishing pigs. Thirty-two barrows and 32 gilts (4 pigs/pen by sex) were fed either a control diet or a diet with RAC (Paylean, Elanco Animal Health, Greenfield, IN) added (5 mg/kg for 2 wk, followed by 10 mg/kg for 2 wk). The top dominant and bottom subordinate pigs (16 pigs/sex) in each pen were determined after mixing by a 36-h period of continuous behavioral observation. These pigs were then subjected to resident-intruder tests (maximum 300 s) during the feeding trial to measure aggressiveness. At the end of wk 4, the amygdala, frontal cortex, hypothalamus, and raphe nuclei were dissected and analyzed for concentrations of dopamine (DA); serotonin (5-HT); their metabolites 3,4-dihydroxyphenyl acetic acid (DOPAC) and homovanillic acid, and 5-hydroxyindoleacetic acid (5-HIAA), respectively; norepinephrine; and epinephrine using HPLC. Ractopamine-fed gilts performed more attacks during the first 30 s of testing than pigs in all other subgroups (P dominant control gilts and barrows, and both dominant and subordinate RAC-fed gilts performed the greatest percentage of attacks (P brain 5-HT synthesis) of dominant gilts (P brain monoamine profiling of a deficient serotonergic system in the raphe nuclei, amygdala, and frontal cortex, and enhanced DA metabolism in the amygdala, brain areas vital for aggression

  17. Contrasting patterns of comprehension for superordinate, basic-level, and subordinate names in semantic dementia and aphasic stroke patients.

    Science.gov (United States)

    Crutch, Sebastian J; Warrington, Elizabeth K

    2008-06-01

    It is well established that patients with semantic memory impairment show a relative sparing of general superordinate information as compared with more detailed item-specific information. The objective of the current study was to examine whether or not this superordinate superiority effect is also reliably observed in individuals with stroke. The participants were 3 patients with a diagnosis of semantic dementia (SD) and 4 left middle cerebral artery stroke patients. In the first experiment, participants were administered a series of spoken-word-picture matching tasks, in which picture identity was probed under two conditions: item name (e.g., goose, beetle, shark, hedgehog) and superordinate name (e.g., bird, insect, fish, mammal). The SD patients showed the predicted pattern of performance, identifying stimuli significantly more accurately by their superordinate term than by their specific name. By contrast, the stroke patients showed the reverse pattern of inferior performance in the superordinate condition in all versions of the experimental task. In a second experiment comparing comprehension ofbasic-level names (e.g., dog, bird, fish) and subordinate-level names (e.g., Dalmatian, sparrow, trout), stroke patients also showed a reversal of the normal basic-level effect, showing less accurate comprehension of basic-level names. The pattern of results documented among the stroke patients cannot be accommodated obviously or readily by existing models of conceptual knowledge. These contrasting abilities of SD patients, stroke patients, and normal healthy participants to process subordinate, basic-level, and superordinate names are considered in relation to disorders of executive processing and taxonomic categorization.

  18. Molecular dynamics simulations of the calcite/solution interface as a means to explore surface modifications induced by nitrate

    Energy Technology Data Exchange (ETDEWEB)

    Hofmann, Sascha; Schmidt, Moritz [Helmholtz-Zentrum Dresden-Rossendorf e.V., Dresden (Germany). Div. Surface Processes; Spijker, P. [Aalto Univ., Helsinki (Finland). Dept. of Applied Physics; Voitchovsky, K. [Durham Univ. (United Kingdom). Physics Dept.

    2016-07-01

    The reactivity of calcite, one of the most abundant minerals in the earth's crust, is determined by the molecular details of its interface with the contacting solution. Recently, it has been found that trace concentrations of NaNO{sub 3} severely affect calcite's (104) surface and its reactivity. Molecular dynamics (MD) simulations reveal density profiles of different ions near calcite's surface, with NO{sub 3}{sup -} able to reach closer to the surface than CO{sub 3}{sup 2-} and in higher concentrations. Additionally, incorporation of NO{sub 3}{sup -} into the surface significantly disturbs the water structure at the interface.

  19. Calcium in plant cells

    Directory of Open Access Journals (Sweden)

    V. V. Schwartau

    2014-04-01

    Full Text Available The paper gives the review on the role of calcium in many physiological processes of plant organisms, including growth and development, protection from pathogenic influences, response to changing environmental factors, and many other aspects of plant physiology. Initial intake of calcium ions is carried out by Ca2+-channels of plasma membrane and they are further transported by the xylem owing to auxins’ attractive ability. The level of intake and selectivity of calcium transport to ove-ground parts of the plant is controlled by a symplast. Ca2+enters to the cytoplasm of endoderm cells through calcium channels on the cortical side of Kaspary bands, and is redistributed inside the stele by the symplast, with the use of Ca2+-АТPases and Ca2+/Н+-antiports. Owing to regulated expression and activity of these calcium transporters, calclum can be selectively delivered to the xylem. Important role in supporting calcium homeostasis is given to the vacuole which is the largest depo of calcium. Regulated quantity of calcium movement through the tonoplast is provided by a number of potential-, ligand-gated active transporters and channels, like Ca2+-ATPase and Ca2+/H+ exchanger. They are actively involved in the inactivation of the calcium signal by pumping Ca2+ to the depo of cells. Calcium ATPases are high affinity pumps that efficiently transfer calcium ions against the concentration gradient in their presence in the solution in nanomolar concentrations. Calcium exchangers are low affinity, high capacity Ca2+ transporters that are effectively transporting calcium after raising its concentration in the cell cytosol through the use of protons gradients. Maintaining constant concentration and participation in the response to stimuli of different types also involves EPR, plastids, mitochondria, and cell wall. Calcium binding proteins contain several conserved sequences that provide sensitivity to changes in the concentration of Ca2+ and when you

  20. [Microbial geochemical calcium cycle].

    Science.gov (United States)

    Zavarzin, G A

    2002-01-01

    The participation of microorganisms in the geochemical calcium cycle is the most important factor maintaining neutral conditions on the Earth. This cycle has profound influence on the fate of inorganic carbon, and, thereby, on the removal of CO2 from the atmosphere. The major part of calcium deposits was formed in the Precambrian, when prokaryotic biosphere predominated. After that, calcium recycling based on biogenic deposition by skeletal organisms became the main process. Among prokaryotes, only a few representatives, e.g., cyanobacteria, exhibit a special calcium function. The geochemical calcium cycle is made possible by the universal features of bacteria involved in biologically mediated reactions and is determined by the activities of microbial communities. In the prokaryotic system, the calcium cycle begins with the leaching of igneous rock predominantly through the action of the community of organotrophic organisms. The release of carbon dioxide to the soil air by organotrophic aerobes leads to leaching with carbonic acid and soda salinization. Under anoxic conditions, of major importance is the organic acid production by primary anaerobes (fermentative microorganisms). Calcium carbonate is precipitated by secondary anaerobes (sulfate reducers) and to a smaller degree by methanogens. The role of the cyanobacterial community in carbonate deposition is exposed by stromatolites, which are the most common organo-sedimentary Precambrian structures. Deposition of carbonates in cyanobacterial mats as a consequence of photoassimilation of CO2 does not appear to be a significant process. It is argued that carbonates were deposited at the boundary between the "soda continent", which emerged as a result of subaerial leaching with carbonic acid, and the ocean containing Ca2+. Such ecotones provided favorable conditions for the development of the benthic cyanobacterial community, which was a precursor of stromatolites.