Sample records for calcium carbonate crystallization

  1. Alginate hydrogel-mediated crystallization of calcium carbonate

    SciTech Connect

    Ma, Yufei [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China); Feng, Qingling, E-mail: biomater@mail.tsinghua.edu.c [State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Haidian District, Beijing 100084 (China)

    2011-05-15

    We documented a specific method for combining calcium ions and alginate molecules slowly and continuously in the mineralization system for the purpose of understanding the mediating function of alginate on the crystallization of calcium carbonate. The alginate was involved in the nucleation and the growth process of CaCO{sub 3}. The crystal size, morphology and roughness of crystal surface were significantly influenced by the type of the alginate, which could be accounted for by the length of the G blocks in alginate. A combination of Fourier transform infrared spectroscopy and thermogravimetric analysis showed that there were the chemical interactions between the alginate and the mineral phase. This strategic approach revealed the biologically controlled CaCO{sub 3} mineralization within calcium alginate hydrogels via the selective nucleation and the confined crystallization of CaCO{sub 3}. The results presented here could contribute to the understanding of the mineralization process in hydrogel systems. -- Graphical abstract: Schematic illustration of the growth of calcite aggregates with different morphologies obtained from (a) Low G alginate gels and (b) High G alginate gels. Display Omitted highlights: > We use a specific method for combining calcium ions and alginate molecules slowly and continuously in the mineralization system to understand the mediating function of alginate on the crystallization of CaCO{sub 3} crystals. > The crystal size, morphology and crystal surface roughness are influenced by the length of G blocks in alginate. There are chemical interactions between the alginate and the mineral phase. > We propose a potential mechanism of CaCO{sub 3} crystallization within High G and Low G calcium alginate hydrogel.

  2. The influence of xanthan on the crystallization of calcium carbonate

    NASA Astrophysics Data System (ADS)

    Yang, Xiaodeng; Xu, Guiying

    2011-01-01

    Calcium carbonate (CaCO 3) was crystallized in xanthan (XC) aqueous solutions. The CaCO 3 particles were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and thermogravimetry analysis (TGA) methods. The concentrations of XC, Ca 2+ and CO 32- ions and the ratios [Ca 2+]/[CO 32-] and [Mg 2+]/[Ca 2+] show evident influence on the aggregation and growth of CaCO 3 particles. The presence of Mg 2+ ions influences not only the morphology, but also the polymorph of CaCO 3.

  3. Calcium Carbonate

    MedlinePLUS

    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 ...

  4. Crystal structures of calcium hemicarboaluminate and carbonated calcium hemicarboaluminate from synchrotron powder diffraction data.

    PubMed

    Run?evski, Tom?e; Dinnebier, Robert E; Magdysyuk, Oxana V; Pöllmann, Herbert

    2012-10-01

    One of the main phases formed at the beginning of the carbonation reaction of cementitious building materials is the calcium hemicarboaluminate (abbreviated as Hc). This AFm (shorthand for hydrated calcium aluminate phases structurally related to hydrocalumite) phase was synthesized, crystallized and then studied by synchrotron X-ray powder diffraction and micro-Raman spectroscopy. At room temperature and standard experimental conditions two major cementitious phases were detected, the Hc phase (as a major phase) and carbonated calcium hemicarboaluminate (abbreviated as cHc). By increasing the temperature the Hc form transforms into cHc. The crystal structures of these important AFm phases were successfully solved and refined in the R3c space group of the trigonal crystal system. Hc has the unit-cell parameters a = 5.7757 (1) and c = 48.812 (2) Å, and cHc the unit-cell parameters a = 5.7534 (1) and c = 46.389 (1) Å. The two crystal structures are composed of positively charged main layers, [Ca(4)Al(2)(OH)(12)](2+), and negatively charged interlayers, [OH(2n)(CO(3))(1 - n)·4H(2)O](2-). The structure of the main layers is typical of the AFm family. Conversely, the interlayer region has a characteristic structure built up from water molecules and statistically distributed anions. In the interlayer, the Hc carbonate and hydroxyl anions are distributed in a 0.25:0.5 ratio, whereas the ratio of the anions in the cHc interlayers is 0.4:0.2. PMID:22992794

  5. Crystal growth of calcium carbonate in silk fibroin/sodium alginate hydrogel

    NASA Astrophysics Data System (ADS)

    Ming, Jinfa; Zuo, Baoqi

    2014-01-01

    As known, silk fibroin-like protein plays a pivotal role during the formation of calcium carbonate (CaCO3) crystals in the nacre sheets. Here, we have prepared silk fibroin/sodium alginate nanofiber hydrogels to serve as templates for calcium carbonate mineralization. In this experiment, we report an interesting finding of calcium carbonate crystal growth in the silk fibroin/sodium alginate nanofiber hydrogels by the vapor diffusion method. The experimental results indicate calcium carbonate crystals obtained from nanofiber hydrogels with different proportions of silk fibroin/sodium alginate are mixture of calcite and vaterite with unusual morphologies. Time-dependent growth study was carried out to investigate the crystallization process. It is believed that nanofiber hydrogels play an important role in the process of crystallization. This study would help in understanding the function of organic polymers in natural mineralization, and provide a novel pathway in the design and synthesis of new materials related unique morphology and structure.

  6. A Novel Growth Process of Calcium Carbonate Crystals in Silk Fibroin Hydrogel System

    E-print Network

    Paris-Sud XI, Université de

    to silk-fibroin-like protein in nacre in amino acid sequence and secondary structure [14] compared1 A Novel Growth Process of Calcium Carbonate Crystals in Silk Fibroin Hydrogel System Yufei Ma carbonate (CaCO3) crystal growth in the silk fibroin (SF) hydrogel with different concentrations by a simple

  7. Characterization of calcium carbonate crystals in pigeon yolk sacs with different incubation times.

    PubMed

    Song, Juan; Cheng, Haixia; Shen, Xinyu; Hu, Jingxiao; Tong, Hua

    2014-05-01

    Calcium carbonate crystals are known to form in the yolk sacs of fertile pigeon eggs at late stages of incubation. The composition and structure of these crystals were investigated, the crystallization environment was inspected, and the physical chemistry constants of the yolk fluid were determined through the incubation period. Polarized light microscopy was used to observe the generation and distribution of calcium carbonate crystals in the yolk sac. In addition, X-ray diffraction was employed to analyze the composition and crystal phase of the yolk sac. A decalcification and deproteination method was established to analyze the ultrastructure and composition of the crystals, as well as the internal relationship between inorganic and organic phases of the crystals. Additionally, scanning electron microscopy, transmission electron microscopy, X-ray energy dispersive spectroscopy, and Fourier transform infrared spectroscopy were used to evaluate the characteristics of the crystals. Our results demonstrated that the calcium carbonate crystals were mainly composed of vaterite and calcite, with vaterite being the major component. Vaterite, a type of biomaterial generated by an organic template control, presented as a concentric hierarchical spherical structure. The organic nature of the biomaterial prevented vaterite from transforming into calcite, which is more thermodynamically stable than vaterite. Additionally, the configuration, size, and aggregation of vaterite were also mediated by the organic template. This bio-vaterite was found during the incubation period and is valuable in calcium transport during embryonic development. PMID:24602270

  8. The effect of pigeon yolk sac fluid on the growth behavior of calcium carbonate crystals.

    PubMed

    Song, Juan; Cheng, Haixia; Shen, Xinyu; Tong, Hua

    2015-03-01

    Previous experiments have proved that thermodynamically unstable calcium carbonate vaterite can exist for long periods in the yolk sac of a pigeon embryo. The aim of this article was to demonstrate the effect of in vitro mineralization of yolk sac fluid on calcium carbonate by direct precipitation. Experiments were conducted using pigeon yolk sac fluid and using lecithin extracted from pigeon yolk sac fluid as a control to investigate the regulating effects of the organic components in the embryo on the formation of the calcium carbonate precipitate. Multiple characterization methods were employed to study the various morphological patterns, sizes, crystal growth, and crystal phase transformations of the calcium carbonate precipitates as regulated by the yolk sac fluid extracted at different stages of incubation. The experimental results demonstrate that as the incubation proceeds towards the later stages, the composition and environmental features of the yolk sac fluid become more favorable for the formation of relatively unstable calcium carbonate phases with high energies of the vaterite state. The experiments conducted with extracted lecithin as the template for crystal growth yielded similar results. A large amount of organic molecules with polar functional groups carried by the yolk sac fluid have strong effects and can both initially induce the crystallization and regulate the aggregation of calcium carbonate. Furthermore, this regulation process is found to be closely related to the lecithin contained in yolk sac fluid. These observations confirm the changes in yolk sac fluid composition during incubation have significant effects on the production of vaterite, which implicates the calcium transport during embryo growth. PMID:25681477

  9. Effect of silk sericin on morphology and structure of calcium carbonate crystal

    NASA Astrophysics Data System (ADS)

    Zhao, Rui-Bo; Han, Hua-Feng; Ding, Shao; Li, Ze-Hao; Kong, Xiang-Dong

    2013-06-01

    In this paper, silk sericin was employed to regulate the mineralization of calcium carbonate (CaCO3). CaCO3 composite particles were prepared by the precipitation reaction of sodium carbonate with calcium chloride solution in the presence of silk sericin. The as-prepared samples were collected at different reaction time to study the crystallization process of CaCO3 by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA) and X-ray diffraction (XRD). The results showed that silk sericin significantly affected the morphology and crystallographic polymorph of CaCO3. With increasing the reaction time, the crystal phase of CaCO3 transferred from calcite dominated to vaterite dominated mixtures, while the morphology of CaCO3 changed from disk-like calcite crystal to spherical vaterite crystal. These studies showed the potential of silk sericin used as a template molecule to control the growth of inorganic crystal.

  10. Results of the TTF-TCNQ and the calcium carbonate crystallization on the Long Duration Exposure Facility

    NASA Technical Reports Server (NTRS)

    Nielsen, Kjeld Flemming; Lind, M. David

    1992-01-01

    Experiment A0139A on the Long Duration Exposure Facility (LDEF) carried four large containers into orbit five years with crystal growth solutions for lead sulfide, calcium carbonate, and TTF-TCNQ. Although temperature data was lost, the experimental program had been working since the valves in all containers had been opened. All four experiments produced crystals of varying quality. The calcium carbonate crystals had the best appearance. The TTF-TCNQ crystals were packed together near the valve openings of the container. When taken apart, the single crystals showed some unusual morphological properties. X ray investigations as well as conductivity measurements on long duration space grown TTF-TCNQ crystals will be presented. Comparisons will be made with our previous space solution growth experiments. The TTF-TCNQ crystals are no longer of the highest interest, so this activity has been terminated in favor of calcium carbonate and calcium phosphate crystallizations.

  11. Dehydration and crystallization of amorphous calcium carbonate in solution and in air

    PubMed Central

    Ihli, Johannes; Wong, Wai Ching; Noel, Elizabeth H.; Kim, Yi-Yeoun; Kulak, Alexander N.; Christenson, Hugo K.; Duer, Melinda J.; Meldrum, Fiona C.

    2014-01-01

    The mechanisms by which amorphous intermediates transform into crystalline materials are poorly understood. Currently, attracting enormous interest is the crystallization of amorphous calcium carbonate, a key intermediary in synthetic, biological and environmental systems. Here we attempt to unify many contrasting and apparently contradictory studies by investigating this process in detail. We show that amorphous calcium carbonate can dehydrate before crystallizing, both in solution and in air, while thermal analyses and solid-state nuclear magnetic resonance measurements reveal that its water is present in distinct environments. Loss of the final water fraction—comprising less than 15% of the total—then triggers crystallization. The high activation energy of this step suggests that it occurs by partial dissolution/recrystallization, mediated by surface water, and the majority of the particle then crystallizes by a solid-state transformation. Such mechanisms are likely to be widespread in solid-state reactions and their characterization will facilitate greater control over these processes. PMID:24469266

  12. Effect of trace lanthanum ion on dissolution and crystal growth of calcium carbonate

    NASA Astrophysics Data System (ADS)

    Kamiya, Natsumi; Kagi, Hiroyuki; Tsunomori, Fumiaki; Tsuno, Hiroshi; Notsu, Kenji

    2004-07-01

    Impurity effects of trace lanthanum ion (La 3+) on the dissolution and growth of calcium carbonate were studied with in situ observation techniques. Dissolution kinetics of two polymorphs of calcium carbonate, calcite and vaterite, were investigated by monitoring the pH in the solution with laser-induced fluorescence spectroscopy using a pH-sensitive reagent, seminaphthorhodafluors. No effect on dissolution of vaterite was observed with the spectroscopic observations, whereas calcite dissolution was significantly inhibited by lanthanum ion with concentrations higher than 1 ?M. Crystal growth and dissolution processes of calcite under the lanthanum-doped condition were observed by means of atomic force microscopy. Step propagations during crystal growth and dissolution of calcite were inhibited by trace lanthanum ion (5 ?M). An insoluble thin layer of lanthanum carbonate deposited on the step site of the calcite surface could be a possible cause of the inhibitions observed both for dissolution and growth.

  13. A novel growth process of calcium carbonate crystals in silk fibroin hydrogel system.

    PubMed

    Ma, Yufei; Feng, Qingling; Bourrat, Xavier

    2013-05-01

    We report an interesting finding of calcium carbonate (CaCO3) crystal growth in the silk fibroin (SF) hydrogel with different concentrations by a simple ion diffusion method. The experimental results indicate that the CaCO3 crystals obtained from silk fibroin gels with low and high concentrations are all calcites with unusual morphologies. Time-dependent growth study was carried out to investigate the crystallization process. It is believed that silk fibroin hydrogel plays an important role in the process of crystallization. The possible formation mechanism of CaCO3 crystals is proposed. This study provides a better explanation of the influence of silk fibroin concentration and its structure on CaCO3 crystals growth. PMID:23498277

  14. Transformation of amorphous calcium carbonate to rod-like single crystal calcite via "copying" collagen template.

    PubMed

    Xue, Zhonghui; Hu, Binbin; Dai, Shuxi; Du, Zuliang

    2015-10-01

    Collagen Langmuir films were prepared by spreading the solution of collagen over deionized water, CaCl2 solution and Ca(HCO3)2 solution. Resultant collagen Langmuir monolayers were then compressed to a lateral pressure of 10mN/m and held there for different duration, allowing the crystallization of CaCO3. The effect of crystallization time on the phase composition and microstructure of CaCO3 was investigated. It was found that amorphous calcium carbonate (ACC) was obtained at a crystallization time of 6h. The amorphous CaCO3 was transformed to rod-like single crystal calcite crystals at an extended crystallization time of 12h and 24h, via "copying" the symmetry and dimensionalities of collagen fibers. Resultant calcite crystallites were well oriented along the longitudinal axis of collagen fibers. The ordered surface structure of collagen fibers and electrostatic interactions played key roles in tuning the oriented nucleation and growth of the calcite crystallites. The mineralized collagen possessing both desired mechanical properties of collagen fiber and good biocompatibility of calcium carbonate may be assembled into an ideal biomaterial for bone implants. PMID:26117783

  15. Calcium carbonate crystallization on xiphoid of the cuttlefish

    NASA Astrophysics Data System (ADS)

    Manoli, F.; Dalas, E.

    2000-08-01

    A mollusc shell, the xiphoid from cuttlefish was found to be a substrate favouring the deposition of aragonite crystals from stable supersaturated solutions at pH 8.50 and 25°C. The crystallization was studied at constant solution composition, thus making it possible for a relatively large amount of the overgrowths to be formed and to be identified exclusively as aragonite crystals. The apparent order found from kinetics data was n=4.1±0.4, thus suggesting a polynuclear mechanism. A surface energy of 24±3 mJ m -2 was calculated for the growing phase and a four-ion cluster forming the critical nucleus, according to the classical nucleation theory.

  16. Polyelectrolyte-directed nanoparticle aggregation: systematic morphogenesis of calcium carbonate by nonclassical crystallization.

    PubMed

    Song, Rui-Qi; Cölfen, Helmut; Xu, An-Wu; Hartmann, Jürgen; Antonietti, Markus

    2009-07-28

    Besides the classical atom/ion/molecule based mechanism, nonclassical crystallization provides a nanoparticle-based crystallization pathway toward single crystals. However, there is a lack of experimentally established strategies for engineering a range of crystalline microstructures from common nanoparticles by nonclassical crystallization. We demonstrate that a commercial random copolymer polyelectrolyte poly(4-styrene sulfonate)-co-(maleic acid) (PSS-co-MA) considerably guides crystallization of calcium carbonate (CC) with a high versatility. The bioinspired nonclassical crystallization protocol yielded a series of calcite microstructures. Calcite single crystals obtained at low supersaturation show a pseudo-dodecahedral shape with curved faces, whereas increasing supersaturation generated calcite mesocrystals with pseudo-octahedral shapes and scalloped surfaces. Further increase of supersaturation induced the formation of polycrystalline multilayered and hollow spheres. In the initial growth stage of all these microstructures, amorphous CC nanoparticles formed as the early product. Remarkably, microparticles with minimal primitive (P)-surface were captured as the prominent intermediate indicative of liquidlike behavior. Moreover, nanogranular structures exist broadly in the as-synthesized crystals. These results demonstrate that the polyelectrolyte can effectively stabilize the amorphous CC nanoparticle precursors, impart control over the evolution from amorphous precursors via a liquid aggregate through P-surface intermediates to the final crystals, and thus allow the morphogenesis. Simple variation of calcium and polyeletrolyte concentrations enables a systematic control over the size and morphology of particles among pseudo-dodecahedra, pseudo-octahedra, multilayered spheres, and hollow spheres, which are expressed in a morphology diagram. A unifying nanoparticle aggregation formation mechanism was suggested to explain the morphogenesis by the combination of nonclassical crystallization and surface area minimization principles. PMID:19572617

  17. Calcium carbonate crystallization in the presence of modified polysaccharides and linear polymeric additives

    NASA Astrophysics Data System (ADS)

    Matahwa, H.; Ramiah, V.; Sanderson, R. D.

    2008-10-01

    Crystallization of calcium carbonate was performed in the presence of grafted polysaccharides, polyacrylamide (PAM) and polyacrylic acid (PAA). The grafted polysaccharides gave crystal morphologies that were different from the unmodified polysaccharides but similar to the ones given by homopolymers of the grafted chains. PAM-grafted ?-cellulose gave rectangular platelets that aggregated to form 'spherical' crystals on the surface of the fiber, whereas PAA grafted ?-cellulose gave spherical crystals on the surface of the fiber. X-ray diffraction (XRD) spectroscopy showed that PAM-grafted ?-cellulose, PAM as well as the control (no polymeric additive) gave calcite crystals at both 25 and 80 °C. However, the PAA-grafted ?-cellulose and PAA homopolymer gave calcite and vaterite crystals at 25 °C with calcite and aragonite crystals along with traces of vaterite being formed at 80 °C. The fiber surface coverage by these crystals was more on the acrylic- and acrylamide-grafted cellulose than on the ungrafted ?-cellulose. The evolution of CaCO 3 polymorphs as well as crystal morphology in PAA-grafted starch was similar to that of PAA-grafted ?-cellulose at the two temperatures employed.

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

    SciTech Connect

    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)

    2010-09-21

    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 CO? sequestration.

  19. Interactions between acidic matrix macromolecules and calcium phosphate ester crystals: relevance to carbonate apatite formation in biomineralization.

    PubMed

    Moradian-Oldak, J; Frolow, F; Addadi, L; Weiner, S

    1992-01-22

    Control over crystal growth by acidic matrix macromolecules is an important process in the formation of many mineralized tissues. Earlier studies on the interactions between acidic macromolecules and carboxylate- and carbonate-containing crystals showed that the proteins recognize a specific stereochemical motif on the interacting plane. Here we show that a similar stereochemical motif is recognized by acidic mollusc shell macromolecules interacting with four different organic calcium phosphate-containing crystals. In addition, an acidic protein from vertebrate tooth dentin was also observed to recognize a similar structural motif in one of the crystals. The characteristic motif recognized is composed of rows of calcium ions and phosphates arranged in a plane defined by two free oxygens and a phosphorus atom emerging perpendicular to the affected face. These observations may have a direct bearing on the manner in which control over crystal growth is exerted on carbonate apatite crystals commonly found in vertebrate tissues. PMID:1348121

  20. Crystallization and assembling behavior of calcium carbonate controlled by Ca-organic fibers

    NASA Astrophysics Data System (ADS)

    Chen, Anliang; Ma, Peiyan; Fu, Zhengyi; Wu, Yan; Kong, Wei

    2013-08-01

    Calcium carbonate (CaCO3) crystals with different phases were obtained on the basis of one-dimensional Ca-deoxycholate fibers (Ca-DC fibers) under ambient conditions. Ca-DC fibers were prepared by the combination of Ca2+ ions and sodium deoxycholate (SDC) before the addition of sodium bicarbonate. Vaterite dominated mixtures could be easily obtained in the presence of Ca-DC fibers in the aqueous system at 10 °C. As the temperature was increased to 30 and 120 °C, pure vaterite and aragonite with novel morphologies were obtained, respectively. The framework formed by one-dimensional Ca-DC fibers was demonstrated to be the key role in mediating the crystallization and assembling behaviors of calcium carbonate. In this study, Ca-DC fibers, prepared as a novel insoluble organic polymorph controller, could even play an important role in the industrial production of CaCO3 with different polymorphs in future and other similar Ca-organic fibers are believed to have same functions as well.

  1. Perlinhibin, a cysteine-, histidine-, and arginine-rich miniprotein from abalone (Haliotis laevigata) nacre, inhibits in vitro calcium carbonate crystallization.

    PubMed

    Mann, Karlheinz; Siedler, Frank; Treccani, Laura; Heinemann, Fabian; Fritz, Monika

    2007-08-15

    We have isolated a 4.785 Da protein from the nacreous layer of the sea snail Haliotis laevigata (greenlip abalone) shell after demineralization with acetic acid. The sequence of 41 amino acids was determined by Edman degradation supported by mass spectrometry. The most abundant amino acids were cysteine (19.5%), histidine (17%), and arginine (14.6%). The positively charged amino acids were almost counterbalanced by negatively charged ones resulting in a calculated isoelectric point of 7.86. Atomic-force microscopy studies of the interaction of the protein with calcite surfaces in supersaturated calcium carbonate solution or calcium chloride solution showed that the protein bound specifically to calcite steps, inhibiting further crystal growth at these sites in carbonate solution and preventing crystal dissolution when carbonate was substituted with chloride. Therefore this protein was named perlinhibin. X-ray diffraction investigation of the crystal after atomic-force microscopy growth experiments showed that the formation of aragonite was induced on the calcite substrate around holes caused by perlinhibin crystal-growth inhibition. The strong interaction of the protein with calcium carbonate was also shown by vapor diffusion crystallization. In the presence of the protein, the crystal surfaces were covered with holes due to protein binding and local inhibition of crystal growth. In addition to perlinhibin, we isolated and sequenced a perlinhibin-related protein, indicating that perlinhibin may be a member of a family of closely related proteins. PMID:17496038

  2. Intrinsically disordered mollusk shell prismatic protein that modulates calcium carbonate crystal growth.

    PubMed

    Ndao, Moise; Keene, Ellen; Amos, Fairland F; Rewari, Gita; Ponce, Christopher B; Estroff, Lara; Evans, John Spencer

    2010-10-11

    The formation of calcite prism architecture in the prismatic layer of the mollusk shell involves the participation of a number of different proteins. One protein family, Asprich, has been identified as a participant in amorphous calcium carbonate stabilization and calcite architecture in the prismatic layer of the mollusk, Atrina rigida . However, the functional role(s) of this protein family are not fully understood due to the fact that insufficient quantities of these proteins are available for experimentation. To overcome this problem, we employed stepwise solid-phase synthesis to recreate one of the 10 members of the Asprich family, the 61 AA single chain protein, Asprich "3". We find that the Asprich "3" protein inhibits the formation of rhombohedral calcite crystals and induces the formation of round calcium carbonate deposits in vitro that contain calcite and amorphous calcium carbonate (ACC). This mineralization behavior does not occur under control conditions, and the formation of ACC and calcite is similar to that reported for the recombinant form of the Asprich "g" protein. Circular dichroism studies reveal that Asprich "3" is an intrinsically disordered protein, predominantly random coil (66%), with 20-30% ?-strand content, a small percentage of ?-turn, and little if any ?-helical content. This protein is not extrinsically stabilized by Ca(II) ions but can be stabilized by 2,2,2-trifluoroethanol to form a structure consisting of turn-like and random coil characteristics. This finding suggests that Asprich "3" may require other extrinsic interactions (i.e., with mineral or ionic clusters or other macromolecules) to achieve folding. In conclusion, Asprich "3" possesses in vitro functional and structural qualities that are similar to other reported for other Asprich protein sequences. PMID:20831150

  3. Formation of carbonate-apatite crystals after implantation of calcium phosphate ceramics

    Microsoft Academic Search

    G. Daculsi; R. Z. LeGeros; M. Heughebaert; I. Barbieux

    1990-01-01

    Summary  The aims of this study were (1) to determine at the crystal level, the nonspecific biological fate of different types of calcium\\u000a phosphate (Ca?P) ceramics after implantation in various sites (osseous and nonosseous) in animals and (2) to investigate the\\u000a crystallographic association of newly formed apatitic crystals with the Ca?P ceramics.\\u000a \\u000a Noncommercial Ca?P ceramics identified by X-ray diffraction as calcium

  4. Intrinsically Disordered and Pliable Starmaker-Like Protein from Medaka (Oryzias latipes) Controls the Formation of Calcium Carbonate Crystals

    PubMed Central

    Ró?ycka, Miros?awa; Wojtas, Magdalena; Jakób, Micha?; Stigloher, Christian; Grzeszkowiak, Miko?aj; Mazur, Maciej; O?yhar, Andrzej

    2014-01-01

    Fish otoliths, biominerals composed of calcium carbonate with a small amount of organic matrix, are involved in the functioning of the inner ear. Starmaker (Stm) from zebrafish (Danio rerio) was the first protein found to be capable of controlling the formation of otoliths. Recently, a gene was identified encoding the Starmaker-like (Stm-l) protein from medaka (Oryzias latipes), a putative homologue of Stm and human dentine sialophosphoprotein. Although there is no sequence similarity between Stm-l and Stm, Stm-l was suggested to be involved in the biomineralization of otoliths, as had been observed for Stm even before. The molecular properties and functioning of Stm-l as a putative regulatory protein in otolith formation have not been characterized yet. A comprehensive biochemical and biophysical analysis of recombinant Stm-l, along with in silico examinations, indicated that Stm-l exhibits properties of a coil-like intrinsically disordered protein. Stm-l possesses an elongated and pliable structure that is able to adopt a more ordered and rigid conformation under the influence of different factors. An in vitro assay of the biomineralization activity of Stm-l indicated that Stm-l affected the size, shape and number of calcium carbonate crystals. The functional significance of intrinsically disordered properties of Stm-l and the possible role of this protein in controlling the formation of calcium carbonate crystals is discussed. PMID:25490041

  5. Calcium crystal-associated diseases.

    PubMed

    Halverson, P B

    1996-05-01

    The significance of calcium-containing crystals is unknown. Circumstantial evidence suggests that crystals are associated with more severe arthritis. Addition of calcium pyrophosphate dihydrate crystals to a lapine meniscectomy model of osteoarthritis resulted in greater damage to cartilage compared with meniscectomy alone. Elimination of calcium pyrophosphate dihydrate crystals may occur extracellularly by enzymatic degradation. Spermine and spermidine both enhance the degradative activity of alkaline phosphatase on crystals. In familial calcium pyrophosphate dihydrate crystal deposition disease, genetic heterogeneity is likely because one family demonstrated a linkage to chromosome 8q, whereas another did not. Tumoral deposition of calcium pyrophosphate dihydrate crystals may occur in single locations without radiographic chondrocalcinosis in other joints. Hydroxyapatite crystals are found in the ligamenta flava from surgical specimens but not as tumoral depositions. Magnesium whitlockite crystals have been found not only in osteoarthritic articular cartilage but also in normal cartilage, suggesting that these crystals may be nonpathologic in at least some cases. PMID:8796988

  6. Optical planar waveguide in sodium-doped calcium barium niobate crystals by carbon ion implantation

    NASA Astrophysics Data System (ADS)

    Zhao, Jin-Hua; Qin, Xi-Feng; Wang, Feng-Xiang; Fu, Gang; Wang, Hui-Lin; Wang, Xue-Lin

    2013-07-01

    There is great interest in niobate crystals which belong to the tetragonal tungsten bronze (TTB) families owing to their intriguing properties. As one representative of such crystals, CBN (calcium barium niobate) has attracted rapidly growing attention. Because it has a higher Curie temperature than SBN (strontium barium niobate), possesses outstanding ferroelectric and it possesses optical properties. In addition, doped with sodium, CBN will show a higher Curie temperature than pure CBN. We report on the fabrication and characterization of optical planar waveguide in x-cut sodium-doped calcium barium niobate crystal by using C ion implantation. The guided-mode properties at the wavelength of 633 and 1539 nm are investigated through prism-coupling measurements, respectively. By applying direct end-face coupling arrangement, the near-field optical intensity distribution of waveguide modes is measured at 633 nm. For comparison, the modal profile of the same guided mode is also numerically calculated by the finite difference beam-propagation method via computer software BeamPROP. The transmission spectra of the waveguide before and after ion implantation treatments were investigated also. Our experiment results reveal that the waveguide could propagate light with transverse magnetic polarized direction only and it is assumed that the polarization selectivity of CBN crystal may responsible for this phenomenon.

  7. Photoinduced crystallization of calcium carbonate from a homogeneous precursor solution in the presence of partially hydrolyzed poly(vinyl alcohol)

    NASA Astrophysics Data System (ADS)

    Nishio, Takashi; Naka, Kensuke

    2015-04-01

    Photoinduced crystallization of calcium carbonate (CaCO3) was demonstrated by the photodecarboxylation of ketoprofen (KP, 2-(3-benzoylphenyl)propionic acid) under alkaline conditions (pH 10). 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 the precursor solution and was exposed to ultraviolet (UV) irradiation for different time periods. Thermogravimetric analysis of the obtained xerogels showed that increasing the UV irradiation time increased the amount of CaCO3 formed and the complete conversion of calcium ions to calcite was achieved after 50 min of UV irradiation. Furthermore, solid phase analyses suggested that nanometer-to-micron-sized calcite crystals were formed and dispersed in the obtained PVAPS matrix. Photoinduced crystallization of CaCO3 from homogenous solution was demonstrated. 2-(3-benzoylphenyl)propionic acid was used as a photoreactive CO2 generator. Partially hydrolyzed poly(vinyl alcohol) worked as a stabilizer in the solution. Complete conversion of Ca2+ to CaCO3 was achieved by UV irradiation for 50 min. Nanometer-to-micron-sized calcites dispersed in the poly(vinyl alcohol) matrix.

  8. Perlwapin, an abalone nacre protein with three four-disulfide core (whey acidic protein) domains, inhibits the growth of calcium carbonate crystals.

    PubMed

    Treccani, Laura; Mann, Karlheinz; Heinemann, Fabian; Fritz, Monika

    2006-10-01

    We have isolated a new protein from the nacreous layer of the shell of the sea snail Haliotis laevigata (abalone). Amino acid sequence analysis showed the protein to consist of 134 amino acids and to contain three sequence repeats of approximately 40 amino acids which were very similar to the well-known whey acidic protein domains of other proteins. The new protein was therefore named perlwapin. In addition to the major sequence, we identified several minor variants. Atomic force microscopy was used to explore the interaction of perlwapin with calcite crystals. Monomolecular layers of calcite crystals dissolve very slowly in deionized water and recrystallize in supersaturated calcium carbonate solution. When perlwapin was dissolved in the supersaturated calcium carbonate solution, growth of the crystal was inhibited immediately. Perlwapin molecules bound tightly to distinct step edges, preventing the crystal layers from growing. Using lower concentrations of perlwapin in a saturated calcium carbonate solution, we could distinguish native, active perlwapin molecules from denaturated ones. These observations showed that perlwapin can act as a growth inhibitor for calcium carbonate crystals in saturated calcium carbonate solution. The function of perlwapin in nacre growth may be to inhibit the growth of certain crystallographic planes in the mineral phase of the polymer/mineral composite nacre. PMID:16861275

  9. Calcium Carbonate Crystal Growth in Porous Media, in the presence of Water Miscible and Non-Miscible Organic Fluids

    NASA Astrophysics Data System (ADS)

    Jaho, Sofia; Sygouni, Varvara; Paraskeva, Christakis A.

    2015-04-01

    The deposition of sparingly soluble salts (scaling) within porous media is a major problem encountered in many industrial and environmental applications. In the oil industry scaling causes severe operational malfunctions and, therefore, increasing the total operating and maintenance cost [1]. The most common types of sparingly soluble salts located in oil fields include carbonate and sulfate salts of calcium, strondium and barium[1,2]. Multiple phase flow and tubing surface properties are some of the factors affecting scale formation [3]. The main purpose of the present work was the investigation of the precipitation mechanisms of calcium carbonate (CaCO3) through in situ mixing of two soluble salt solutions in a flow granular medium, in the presence of water miscible organic fluid (ethylene glycol) or non-miscible organic fluid (n-dodecane). All series of experiments were carried out in a two dimensional porous medium made of Plexiglas. For all solutions used in the experiments, the contact angles with the surface of the porous medium and the interfacial tensions were measured. During the experiments, the calcium carbonate crystal growth was continuously monitored and recorded through an optical microscope equipped with a digital programmed video camera. The snap-shots were taken within specific time intervals and their detailed procession gave information concerning the crystal growth rate and kinetics. The pH of the effluent was measured and fluids samples were collected for calcium analysis using Atomic Absorption Spectroscopy (AAS). In all experiments effluent calcium concentration decreased as a function of time, suggesting that CaCO3 precipitation took place inside the porous medium. Crystals of the precipitated salt were identified using Infrared Spectroscopy (IR) and the morphology of the crystals was examined using Scanning Electron Microscopy (SEM). The induction time for precipitation of CaCO3 crystals in the presence of n-dodecane was significantly reduced compared to the induction time where no oil phase was present. The interface of n-dodecane and supersaturated solutions seems to be very active and favored the formation of the CaCO3 crystalline enhancing the heterogeneous nucleation which generally demands a decreased energy barrier. Acknowledgments This research was partially funded by the European Union (European Social Fund-ESF) and Greek National Funds through the Operational Program "Education and Lifelong Learning" under the action Aristeia II (Code No4420). References 1. Merdhah A. B. and Yassin A. A., Scale formation in oil reservoir during water injection at high-salinity formation water, Journal of Applied Sciences, 7, 3198-3207 (2007). 2. Moghadasi J., Muller-Steinhagen H., Jamialahmadi M. and Sharif A., Model study on the kinetics of oil field formation damage due to salt precipitation from injection, Journal of Petroleum Science and Engineering, 43, 201-217 (2004). 3. Nancollas G. H. and Reddy M. M., The crystallization of calcium carbonate II. Calcite growth mechanism, Journal of Colloid and Interface Science, 37, 824-830 (1971).

  10. Calcium carbonate with magnesium overdose

    MedlinePLUS

    The combination of calcium carbonate and magnesium is commonly found in antacids, which are medicines that provide heartburn relief. Calcium carbonate with magnesium overdose occurs when someone accidentally or ...

  11. The structural consequences of calcium crystal deposition.

    PubMed

    Durcan, Laura; Bolster, Ferdia; Kavanagh, Eoin C; McCarthy, Geraldine M

    2014-05-01

    Calcium pyrophosphate dihydrate and basic calcium phosphate (BCP) crystals are the most common calcium-containing crystals associated with rheumatic disease. Clinical manifestations of calcium crystal deposition include acute or chronic inflammatory and degenerative arthritides and certain forms of periarthritis. The intra-articular presence of BCP crystals correlates with the degree of radiographic degeneration. Calcium crystal deposition contributes directly to joint degeneration. Vascular calcification is caused by the deposition of calcium hydroxyapatite crystals in the arterial intima. These deposits may contribute to local inflammation and promote further calcification, thus aggravating the atherosclerotic process. Calcium crystal deposition results in substantial structural consequence in humans. PMID:24703349

  12. Promotion and Inhibition of Calcium Carbonate Crystallization In Vitro by Matrix Protein From Blue Crab Exoskeleton

    Microsoft Academic Search

    M. E. GUNTHORPE; C. S. SIKES; A. P. WHEELER

    1990-01-01

    Soluble organic matrix isolated from dorsal carapaces of the blue crab, Callinectes sapidus, inhibited CaC03 crystallization when free in solution. Immobilized matrix complexes, prepared by crosslinking soluble matrix to decalcified crab carapace, promoted CaC03 formation in that crystallization in the presence of the immobilized soluble matrix complexes began sooner than in solution controls. In the experimental treatments, deposition of crystals

  13. Engineering calcium oxalate crystal formation in Arabidopsis

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many plants accumulate crystals of calcium oxalate. Just how these crystals form remains unknown. To gain insight into the mechanisms regulating calcium oxalate crystal formation, a crystal engineering approach was initiated utilizing the non-crystal accumulating plant, Arabidopsis. The success of t...

  14. Control of calcium carbonate crystallization by using anionic polymethylsiloxanes as templates

    SciTech Connect

    Neira-Carrillo, Andronico, E-mail: aneira@uchile.cl [Faculty of Veterinary and Animal Sciences, University of Chile, Santa Rosa 11735, PO Box 2-15, Santiago (Chile)] [Faculty of Veterinary and Animal Sciences, University of Chile, Santa Rosa 11735, PO Box 2-15, Santiago (Chile); Vasquez-Quitral, Patricio; Paz Diaz, Maria; Soledad Fernandez, Maria; Luis Arias, Jose [Faculty of Veterinary and Animal Sciences, University of Chile, Santa Rosa 11735, PO Box 2-15, Santiago (Chile)] [Faculty of Veterinary and Animal Sciences, University of Chile, Santa Rosa 11735, PO Box 2-15, Santiago (Chile); Yazdani-Pedram, Mehrdad [Faculty of Chemical and Pharmaceutical Science, University of Chile, S. Livingstone 1007, PO Box 233, Santiago (Chile)] [Faculty of Chemical and Pharmaceutical Science, University of Chile, S. Livingstone 1007, PO Box 233, Santiago (Chile)

    2012-10-15

    Sulfonated (SO{sub 3}H-PMS) and carboxylated (CO{sub 2}H-PMS) polymethylsiloxanes were synthesized and their effects as anionic template modifier on the CaCO{sub 3} crystal morphologies were evaluated. In vitro crystallization assays of CaCO{sub 3} were performed at room temperature by using gas diffusion method at different concentration, pH and time. SEM images of CaCO{sub 3} showed well-defined short calcite piles (ca. 5 {mu}m) and elongated calcite (ca. 20 {mu}m) when SO{sub 3}H-PMS was used. When CO{sub 2}H-PMS was used, the morphology of CaCO{sub 3} crystals was single-truncated at pH 7-9 and aggregated-modified calcite at pH 10-11. However, at pH 12 the least stable donut-shaped vaterite crystals were formed. EDS and XRD confirmed the presence of Si from anionic PMS templates on the CaCO{sub 3} surfaces and its polymorphism, respectively. Results showed that the selective morphologies of CaCO{sub 3} reflect the electrostatic interaction of anionic groups of functionalized PMS with Ca{sup 2+} adsorbed on CaCO{sub 3} crystals. Rounded and truncated-modified fluorescent CaCO{sub 3} was also produced by the inclusion of functionalized PMS into the lattice of CaCO{sub 3} matrix. We demonstrated that the anionic PMS offer a good modifier for polymer-controlled crystallization and a convenient approach for understanding the biomineralization field. - Graphical abstract: Optical photographs of rounded and truncated-modified fluorescent CaCO{sub 3} produced by the inclusion of sulfonated (SO{sub 3}H-PMS) polymethylsiloxanes into the lattice of CaCO{sub 3} matrix. Insert represents the simulation of modified and fluorescent CaCO{sub 3} crystals using Software JCrystal, (2008). Highlights: Black-Right-Pointing-Pointer We prepared two anionic polymethylsiloxanes (PMS) as templates. Black-Right-Pointing-Pointer Their modifier capacity on the CaCO{sub 3} crystal morphologies was demonstrated. Black-Right-Pointing-Pointer At pH 12, the least stable donut-shaped vaterite, was formed. Black-Right-Pointing-Pointer EDS confirmed the presence of Si from anionic PMS templates on the CaCO{sub 3} surfaces. Black-Right-Pointing-Pointer Fluorescent CaCO{sub 3} was produced by the inclusion of PMS into the CaCO{sub 3} matrix.

  15. Calcium carbonate crystallization in the ?-chitin matrix of the shell of pink shrimp, Pandalus borealis, during frozen storage

    Microsoft Academic Search

    A. Mikkelsen; S. B. Engelsen; H. C. B. Hansen; O. Larsen; L. H. Skibsted

    1997-01-01

    Calcium carbonate precipitates in the shell of pink shrimp, Pandalus borealis, during frozen storage (investigated for temperatures above ? 30°C), and as a result white spots appear in the shell. During continued frozen storage the white spots grow in size and eventually cover the entire, originally transparent, shell. Material isolated from shrimp shells was dried and subjected to infrared and

  16. CALCIUM CHANNELS INVOLVED IN CALCIUM OXALATE CRYSTAL FORMATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pistia stratiotes L. produces calcium (Ca) oxalate crystals in specialized cells called crystal idioblasts. Druse crystal idioblasts are produced in the adaxial mesophyll and raphide idioblasts are produced in the abaxial aerenchyma of this aquatic plant. Leaves formed on plants grown on 0 Ca medi...

  17. Calcium Oxalate Crystals in Eucalypt Ectomycorrhizae: Morphochemical Characterization

    PubMed Central

    Pylro, Victor Satler; de Freitas, André Luiz Moreira; Otoni, Wagner Campos; da Silva, Ivo Ribeiro; Borges, Arnaldo Chaer; Costa, Maurício Dutra

    2013-01-01

    Ectomycorrhizal fungi are ubiquitous in forest ecosystems, benefitting plants principally by increasing the uptake of water and nutrients such as calcium from the soil. Previous work has demonstrated accumulation of crystallites in eucalypt ectomycorrhizas, but detailed morphological and chemical characterization of these crystals has not been performed. In this work, cross sections of acetic acid-treated and cleared ectomycorrhizal fragments were visualized by polarized light microscopy to evaluate the location of crystals within cortical root cells. Ectomycorrhizal sections were also observed by scanning electron microscopy (SEM) coupled with energy dispersive x-ray (EDS) microprobe analysis. The predominant forms of crystals were crystal sand (granules) and concretions. Calcium, carbon and oxygen were detected by EDS as constituent elements and similar elemental profiles were observed between both crystal morphologies. All analyzed crystalline structures were characterized as calcium oxalate crystals. This is the first report of the stoichiometry and morphology of crystals occurring in eucalypt ectomycorrhizas in tropical soils. The data corroborates the role of ectomycorrhizae in the uptake and accumulation of calcium in the form of calcium oxalate crystals in hybrid eucalypt plants. PMID:23844062

  18. Crystallization of calcium oxalate from synthetic urine.

    PubMed

    Doremus, R H; Teich, S; Silvis, P X

    1978-05-01

    The precipitation of calcium oxalate from synthetic urine was followed from the disappearance of radioactive oxalate from solution. Rates of precipitation were also estimated from the time of appearance of crystals. Synthetic urine inhibited the rate of crystallization of calcium oxalate; this inhibition was a combined effect of ionic strength and specific inhibition by one or mroe components of the synthetic urine. Polyphosphate and polyacrylate ions strongly inhibited crystallization of calcium oxalate from synthetic urine; phosphonates, heparin, and polystyrene sulfonate showed much less inhibition. Inasmuch as citrate and pyrophosphate ions showed some inhibition, it seems that carboxylate and phosphate groups on a polymer chain are the most effective inhibitors. PMID:649296

  19. Calcium oxalate crystallization kinetics from calorimetric measurements

    Microsoft Academic Search

    O. Söhnel; M. Kroupa; G. Franková; V. Velich

    1997-01-01

    The kinetics of calcium oxalate monohydrate precipitation effected by mixing aqueous solutions of calcium chloride and sodium oxalate together in the stoichiometric ratio at 25 and 37°C, were studied using an isoperibolic reaction twin calorimeter. A method for inferring the crystal growth kinetic parameters from experimental progress curve giving the time development of the integral heat evolved during the precipitation

  20. Characterisation of calcium carbonate and its polymorphs from cockle shells ( Anadara granosa)

    Microsoft Academic Search

    Kh. Nurul Islam; Mustapha M. Noordin; Mohd Zobir Bin Hussein; Norshazlirah Shazlyn Bte Abd Rahman

    2011-01-01

    Calcium carbonate and its polymorphs from cockle shells (Anadara granosa) and commercial calcium carbonate were characterised using a variable pressure scanning electron microscopes (VPSEM), a transmission electron microscope (TEM), an energy dispersive X- ray analyser (EDX), X-ray diffraction (XRD) and Fourier transmission infrared spectroscopy (FT-IR). Cubic-like calcite crystals of commercial calcium carbonate and rod-like aragonite crystals of cockle shell powders

  1. Calcium phosphate scaffold from biogenic calcium carbonate by fast ambient condition reactions

    NASA Astrophysics Data System (ADS)

    Dutta, Abhishek; Fermani, Simona; Arjun Tekalur, Srinivasan; Vanderberg, Abigail; Falini, Giuseppe

    2011-12-01

    Calcium phosphate biogenic materials are biocompatible and promote bioactivity and osteoconductivity, which implies their natural affinity and tendency to bond directly to bones subsequently replacing the host bone after implantation owing to its biodegradability. Calcium hydrogen phosphate dihydrate, CaHPO 4·2H 2O, is known to be a nucleation precursor, in aqueous solutions, for apatitic calcium phosphates and, hence, a potential starting material for bone substitutes. Numerous approaches, via hydrothermal and ambient synthetic routes, have been used to produce calcium phosphate from biogenic calcium carbonate, taking advantage of the peculiar architecture and composition of the latter. In this article, the lamellar region of the cuttlefish bone ( Sepia officinalis) was used as a framework for the organized deposition of calcium phosphate crystals, at ambient conditions via a fast procedure involving an amorphous calcium carbonate intermediate, and ending with a conversion to calcium phosphate and a fixation procedure, thereby resulting in direct conversion of biogenic calcium carbonate into calcium phosphates at ambient conditions from the scale of months to hours.

  2. Polypropylene\\/calcium carbonate nanocomposites

    Microsoft Academic Search

    Chi-Ming Chan; Jingshen Wu; Jian-Xiong Li; Ying-Kit Cheung

    2002-01-01

    Polypropylene (PP) and calcium carbonate nanocomposites were prepared by melt mixing in a Haake mixer. The average primary particle size of the CaCO3 nanoparticles was measured to be about 44nm. The dispersion of the CaCO3 nanoparticles in PP was good for filler content below 9.2vol%. Differential scanning calorimetry (DSC) results indicated that the CaCO3 nanoparticles are a very effective nucleating

  3. Epidemiology of calcium pyrophosphate crystal arthritis and basic calcium phosphate crystal arthropathy.

    PubMed

    Abhishek, Abhishek; Doherty, Michael

    2014-05-01

    Calcium pyrophosphate crystal deposition (CPPD) is common and mainly associates with increasing age and osteoarthritis (OA). Recent studies suggest that CPPD occurs as the result of a generalized articular predisposition and may also associate with low cortical bone mineral density. The epidemiology of basic calcium phosphate (BCP) crystal deposition is poorly understood. Although periarticular BCP crystal deposits occurs at all ages and in both sexes, intra-articular BCP crystal deposition tends to associate with increasing age and OA. Calcium pyrophosphate and BCP crystals frequently coexist in joints with OA. PMID:24703342

  4. Formation of calcium pyrophosphate crystals in vitro: implications for calcium pyrophosphate crystal deposition disease (pseudogout)

    Microsoft Academic Search

    P. R. Hearn; R. G. G. Russell

    1980-01-01

    Little is known about how calcium pyrophosphate dihydrate (CaPPD) crystals form in vivo and give rise to chondrocalcinosis or pseudogout (pyrophosphate arthropathy or calcium pyrophosphate crystal deposition disease). In this study a simple method has been devised to define the conditions necessary for the deposition of crystals in vitro. Crystal formation is monitored by 45Ca in the presence of 1·5

  5. Spinning up the polymorphs of calcium carbonate

    PubMed Central

    Boulos, Ramiz A.; Zhang, Fei; Tjandra, Edwin S.; Martin, Adam D.; Spagnoli, Dino; Raston, Colin L.

    2014-01-01

    Controlling the growth of the polymorphs of calcium carbonate is important in understanding the changing environmental conditions in the oceans. Aragonite is the main polymorph in the inner shells of marine organisms, and can be readily converted to calcite, which is the most stable polymorph of calcium carbonate. Both of these polymorphs are significantly more stable than vaterite, which is the other naturally occurring polymorph of calcium carbonate, and this is reflected in its limited distribution in nature. We have investigated the effect of high shear forces on the phase behaviour of calcium carbonate using a vortex fluidic device (VFD), with experimental parameters varied to explore calcium carbonate mineralisation. Variation of tilt angle, rotation speed and temperature allow for control over the size, shape and phase of the resulting calcium carbonate. PMID:24448077

  6. Contribution of human uropontin to inhibition of calcium oxalate crystallization

    Microsoft Academic Search

    John R Asplin; Denise Arsenault; Joan H Parks; Fredric L Coe; John R Hoyer

    1998-01-01

    Contribution of human uropontin to inhibition of calcium oxalate crystallization. Uropontin (UP) is known to inhibit the growth and nucleation of calcium oxalate monohydrate (COM) crystals, and it also impedes attachment of calcium oxalate crystals to cultured renal epithelial cells. However, its role in normal defense against renal crystallization, and in pathogenesis of nephrolithiasis is unclear. In this study we

  7. Modulation of calcium oxalate monohydrate crystallization kinetics in vitro

    Microsoft Academic Search

    Dik J Kok; Socrates E Papafoulos; Leo J M J Blomen; Olav L M Bijvoet; S E Papapoulos

    1988-01-01

    Modulation of calcium oxalate monohydrate crystallization kinetics in vitro. The effects of several low and high molecular weight (mol wt) compounds on the kinetics of calcium oxalate crystallization were examined using a seeded crystal growth method in which the solubility, the growth and the agglomeration of calcium oxalate crystals were measured as three separate and system-independent parameters. Git-rate, magnesium, phosphate,

  8. Structural Characteristics of Synthetic Amorphous Calcium Carbonate

    SciTech Connect

    Michel, F. Marc; MacDonald, Jason; Feng, Jian; Phillips, Brian L.; Ehm, Lars; Tarabrella, Cathy; Parise, John B.; Reeder, Richard J. (SBU)

    2008-08-06

    Amorphous calcium carbonate (ACC) is an important phase involved in calcification by a wide variety of invertebrate organisms and is of technological interest in the development of functional materials. Despite widespread scientific interest in this phase a full characterization of structure is lacking. This is mainly due to its metastability and difficulties in evaluating structure using conventional structure determination methods. Here we present new findings from the application of two techniques, pair distribution function analysis and nuclear magnetic resonance spectroscopy, which provide new insight to structural aspects of synthetic ACC. Several important results have emerged from this study of ACC formed in vitro using two common preparation methods: (1) ACC exhibits no structural coherence over distances > 15 {angstrom} and is truly amorphous; (2) most of the hydrogen in ACC is present as structural H{sub 2}O, about half of which undergoes restricted motion on the millisecond time scale near room temperature; (3) the short- and intermediate-range structure of ACC shows no distinct match to any known structure in the calcium carbonate system; and (4) most of the carbonate in ACC is monodentate making it distinctly different from monohydrocalcite. Although the structure of synthetic ACC is still not fully understood, the results presented provide an important baseline for future experiments evaluating biogenic ACC and samples containing certain additives that may play a role in stabilization of ACC, crystallization kinetics, and final polymorph selection.

  9. Recovery of Lithium Hydroxide from Spent Lithium Carbonate using Crystallizations

    Microsoft Academic Search

    2008-01-01

    Recovery of LiOH from the spent Li2CO3 used as absorbent for carbon dioxide in breathing apparatus was successfully explored by precipitation and crystallization. A lithium hydroxide solution was prepared by precipitation of calcium carbonate using reaction of spent Li2CO3 and calcium hydroxide. The effects of the operating conditions on the reaction were investigated. Conversion of calcium carbonate was about 95%.

  10. Calcium Isotope Fractionation of Inorganic and Biogenic Calcium Carbonates

    Microsoft Academic Search

    F. Boehm; N. Gussone; J. Tang; M. Dietzel; B. Kisakurek; M. Amini; S. Reynaud; J. Reitner; W. Dullo; A. Eisenhauer

    2006-01-01

    Calcium isotope fractionation during precipitation of various experimental and biogenic calcium carbonates depends on mineralogy. Fractionation of 44Ca\\/40Ca increases from calcite to aragonite by about 0.7 permil. The temperature dependence of the fractionation is similar in calcites and aragonites (0.015 permil\\/K) and can be explained by the temperature-control on the carbonate ion concentration and consequently on precipitation rate. Following theoretical

  11. Calcium

    MedlinePLUS

    ... of calcium dietary supplements are carbonate and citrate. Calcium carbonate is inexpensive, but is absorbed best when taken ... antacid products, such as Tums® and Rolaids®, contain calcium carbonate. Each pill or chew provides 200–400 mg ...

  12. Recombinant perlucin nucleates the growth of calcium carbonate crystals: molecular cloning and characterization of perlucin from disk abalone, Haliotis discus discus.

    PubMed

    Wang, Ning; Lee, Youn-Ho; Lee, Jehee

    2008-02-01

    Perlucin is well known as an important functional protein regulating pearl formation and shell biomineralization. In this study, we cloned the perlucin gene from the abalone Haliotis discus discus cDNA library. The full-length cDNA of the abalone H. discus discus perlucin gene consisted of 1038 bp nucleotides, encoding a putative signal peptide of 22 amino acids and a mature protein of 129 amino acids, which shared 55% identity with the homologous protein in greenlip abalone. The mature protein coding sequence was inserted into pMal-c2X expression vector and it expressed the recombinant protein in E. coli (Rosetta-gammi DE3). The maltose binding protein (MBP) fusion perlucin successfully promoted calcium carbonate precipitation and directed calcite crystal morphological modification. The successful expression of active recombinant perlucin suggested that recombinant perlucin gene transfer has the capability by color modification to improve the pearl's value. In the view of molecular structure, perlucin was a typical C-type lectin, which contained one highly conserved carbohydrate recognition domain. Reverse transcription polymerase chain reaction (RT-PCR) results showed that perlucin gene was expressed not only in the mantle, but also in the gill and digestive tract. Further characterization of perlucin in abalone non-self recognition and disease resistance is promising and anticipated. PMID:18068384

  13. Calcium carbonate polymorph control using droplet-based microfluidics.

    PubMed

    Yashina, Alexandra; Meldrum, Fiona; Demello, Andrew

    2012-06-01

    Calcium carbonate (CaCO(3)) is one of the most abundant minerals and of high importance in many areas of science including global CO(2) exchange, industrial water treatment energy storage, and the formation of shells and skeletons. Industrially, calcium carbonate is also used in the production of cement, glasses, paints, plastics, rubbers, ceramics, and steel, as well as being a key material in oil refining and iron ore purification. CaCO(3) displays a complex polymorphic behaviour which, despite numerous experiments, remains poorly characterised. In this paper, we report the use of a segmented-flow microfluidic reactor for the controlled precipitation of calcium carbonate and compare the resulting crystal properties with those obtained using both continuous flow microfluidic reactors and conventional bulk methods. Through combination of equal volumes of equimolar aqueous solutions of calcium chloride and sodium carbonate on the picoliter scale, it was possible to achieve excellent definition of both crystal size and size distribution. Furthermore, highly reproducible control over crystal polymorph could be realised, such that pure calcite, pure vaterite, or a mixture of calcite and vaterite could be precipitated depending on the reaction conditions and droplet-volumes employed. In contrast, the crystals precipitated in the continuous flow and bulk systems comprised of a mixture of calcite and vaterite and exhibited a broad distribution of sizes for all reaction conditions investigated. PMID:22655005

  14. Calcium carbonate polymorph control using droplet-based microfluidics

    PubMed Central

    Yashina, Alexandra; Meldrum, Fiona; deMello, Andrew

    2012-01-01

    Calcium carbonate (CaCO3) is one of the most abundant minerals and of high importance in many areas of science including global CO2 exchange, industrial water treatment energy storage, and the formation of shells and skeletons. Industrially, calcium carbonate is also used in the production of cement, glasses, paints, plastics, rubbers, ceramics, and steel, as well as being a key material in oil refining and iron ore purification. CaCO3 displays a complex polymorphic behaviour which, despite numerous experiments, remains poorly characterised. In this paper, we report the use of a segmented-flow microfluidic reactor for the controlled precipitation of calcium carbonate and compare the resulting crystal properties with those obtained using both continuous flow microfluidic reactors and conventional bulk methods. Through combination of equal volumes of equimolar aqueous solutions of calcium chloride and sodium carbonate on the picoliter scale, it was possible to achieve excellent definition of both crystal size and size distribution. Furthermore, highly reproducible control over crystal polymorph could be realised, such that pure calcite, pure vaterite, or a mixture of calcite and vaterite could be precipitated depending on the reaction conditions and droplet-volumes employed. In contrast, the crystals precipitated in the continuous flow and bulk systems comprised of a mixture of calcite and vaterite and exhibited a broad distribution of sizes for all reaction conditions investigated. PMID:22655005

  15. Calcium carbonate scale formation and control

    Microsoft Academic Search

    Jitka MacAdam; Simon A. Parsons

    2004-01-01

    This paper focuses on the complex problem of calcium carbonate scale formation on heated surfaces and the possibilities of controlling or reducing this problem. The development of scale is a multistage process and is affected by a number of factors, these include supersaturation, pH, temperature and flow velocity. Calcium carbonate deposition can be ameliorated by chemical, physical or biological methods

  16. Growth and Characterization of Yttrium Calcium Oxy Borate (YCOB) Single Crystals for Nonlinear Optical Applications

    Microsoft Academic Search

    R. Arun Kumar; M. Senthilkumar; R. Dhanasekaran

    2008-01-01

    The growth of yttrium calcium oxy borate (YCOB) single crystals by the flux technique is reported. Polycrystalline YCOB sample was synthesized and confirmed. Differential thermal analysis was carried out with lithium carbonate flux. The growth of YCOB crystals by flux technique was attempted and several crystals with dimensions of 3×3×5 mm were obtained. Powder XRD analysis confirms the formation of YCOB

  17. Sr Incorporation and Calcium Isotopic Fractionation during Calcium Carbonate Precipitation

    Microsoft Academic Search

    A. Niedermayr; M. Dietzel; S. J. Köhler; F. Böhm; B. Kisakurek; A. Eisenhauer

    2009-01-01

    Element substitution and calcium isotopic fractionation can provide information about the mechanisms of CaCO3 precipitation, precipitation rates, temperatures and solution chemistry. In the present study precipitation experiments for the formation of the CaCO3 polymorphs: calcite, aragonite and vaterite were carried out. Calcium carbonates are formed at various Mg\\/Ca ratios or in presence of polyaspartic acid at temperatures between 5 and

  18. CALCIUM SULFITE CRYSTAL SIZING STUDIES

    EPA Science Inventory

    The report describes a reliable experimental method that can be used routinely to determine the crystal size distribution function, a measure that is required for a mathematical representation of the nucleation and growth processes involved in the settling, dewatering, and dispos...

  19. Molecular mechanisms of crystallization impacting calcium phosphate cements

    PubMed Central

    Giocondi, Jennifer L.; El-Dasher, Bassem S.; Nancollas, George H.; Orme, Christine A.

    2010-01-01

    The biomineral calcium hydrogen phosphate dihydrate (CaHPO4·2H2O), known as brushite, is a malleable material that both grows and dissolves faster than most other calcium minerals, including other calcium phosphate phases, calcium carbonates and calcium oxalates. Within the body, this ready formation and dissolution can play a role in certain diseases, such as kidney stone and plaque formation. However, these same properties, along with brushite’s excellent biocompatibility, can be used to great benefit in making resorbable biomedical cements. To optimize cements, additives are commonly used to control crystallization kinetics and phase transformation. This paper describes the use of in situ scanning probe microscopy to investigate the role of several solution parameters and additives in brushite atomic step motion. Surprisingly, this work demonstrates that the activation barrier for phosphate (rather than calcium) incorporation limits growth kinetics and that additives such as magnesium, citrate and bisphosphonates each influence step motion in distinctly different ways. Our findings provide details of how, and where, molecules inhibit or accelerate kinetics. These insights have the potential to aid in designing molecules to target specific steps and to guide synergistic combinations of additives. PMID:20308110

  20. Incorporation of Chromate into Calcium Carbonate Structure during Coprecipitation

    SciTech Connect

    Hua, Bin; Deng, Baolin; Thornton, Edward C.; Yang, J.; Amonette, James E.

    2006-09-08

    To assess treatment technologies and establish regulatory framework for chromate-contaminated site remediation, it is imperative to know the exact chromium speciation in soil matrices. In an earlier study, Thornton and Amonette (1999) reported that some chromate in the bulk particles was not accessible to gaseous reductants or solution-phase extractants, based on XANES studies. We hypothesized that part of this non-extractable chromate may reside in the structure of minerals such as calcium carbonate. To test this hypothesis, a number of calcium carbonate precipitates were prepared in the presence of various concentrations of chromate during the precipitation, which could coprecipitate chromate, or by adding chromate after the precipitation was completed. Hydrochloric acid was used to dissolve calcium carbonate and therefore extract the coprecipitated and surface attached chromate. The results showed that the coprecipitated chromate was non-extractable by hot alkaline solution or phosphate buffer, but could be solubilized by HCl in proportional to the amount of calcium carbonate dissolved. The X-ray diffraction experiments revealed that the coprecipitation of chromate with calcium carbonate had an influence on its crystal structure: the higher the chromate concentration, the greater the ratio of vaterite to calcite.

  1. Nacre-like calcium carbonate controlled by ionic liquid/graphene oxide composite template.

    PubMed

    Yao, Chengli; Xie, Anjian; Shen, Yuhua; Zhu, Jinmiao; Li, Hongying

    2015-06-01

    Nacre-like calcium carbonate nanostructures have been mediated by an ionic liquid (IL)-graphene oxide (GO) composite template. The resultant crystals were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy, and X-ray powder diffractometry (XRD). The results showed that either 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) or graphene oxide can act as a soft template for calcium carbonate formation with unusual morphologies. Based on the time-dependent morphology changes of calcium carbonate particles, it is concluded that nacre-like calcium carbonate nanostructures can be formed gradually utilizing [BMIM]BF4/GO composite template. During the process of calcium carbonate formation, [BMIM]BF4 acted not only as solvents but also as morphology templates for the fabrication of calcium carbonate materials with nacre-like morphology. Based on the observations, the possible mechanisms were also discussed. PMID:25842135

  2. Influence of calcium oxalate crystal accumulation on the calcium content of seeds from Medicago truncatula

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crystals of calcium oxalate often form in cells adjacent to the vascular bundles in the tissues along the xylem stream. This spatial crystal pattern suggests a role for calcium oxalate formation in regulating calcium transport and partitioning to edible organs such as seeds. To investigate this pote...

  3. Models for Amorphous Calcium Carbonate

    NASA Astrophysics Data System (ADS)

    Sinha, Sourabh

    Many species e.g. sea urchin form amorphous calcium carbonate (ACC) precursor phases that subsequently transform into crystalline CaCO3. It is certainly possible that the biogenic ACC might have more than 10 wt% Mg and ˜3 wt% of water. The structure of ACC and the mechanisms by which it transforms to crystalline phase are still poorly understood. In this dissertation our goal is to determine an atomic structure model that is consistent with diffraction and IR measurements of ACC. For this purpose a calcite supercell with 24 formula units, containing 120 atoms, was constructed. Various configurations with substitution of Ca by 6 Mg ions (6 wt.%) and insertion of 3-5 H 2O molecules (2.25-3.75 wt.%) in the interstitial positions of the supercell, were relaxed using a robust density function code VASP. The most noticeable effects were the tilts of CO3 groups and the distortion of Ca sub-lattice, especially in the hydrated case. The distributions of Ca-Ca nearest neighbor distance and CO3 tilts were extracted from various configurations. The same methods were also applied to aragonite. Sampling from the calculated distortion distributions, we built models for amorphous calcite/aragonite of size ˜ 1700 nm3 based on a multi-scale modeling scheme. We used these models to generate diffraction patterns and profiles with our diffraction code. We found that the induced distortions were not enough to generate a diffraction profile typical of an amorphous material. We then studied the diffraction profiles from several nano-crystallites as recent studies suggest that ACC might be a random array of nano-cryatallites. It was found that the generated diffraction profile from a nano-crystallite of size ˜ 2 nm3 is similar to that from the ACC.

  4. Modeling of Amorphous Calcium Carbonate

    NASA Astrophysics Data System (ADS)

    Sinha, Sourabh; Rez, Peter

    2011-10-01

    Many species (e.g. sea urchin) form amorphous calcium carbonate (ACC) precursor phases that subsequently transform into crystalline CaCO3. It is certainly possible that ACC might have up to 10 wt% Mg and ˜3 wt% of water. The structure of ACC and mechanisms by which it transforms to crystalline phase are still unknown. Our goal here is to determine an atomic structure model that is consistent with diffraction and IR measurements of ACC. For this purpose a calcite supercell with 24 formula units (120 atoms) was constructed. Various configurations with 6 Mg atoms substituting for Ca (6 wt%) and 3-5 H2O molecules (2.25- 3.75 wt%) inserted in the spaces between Ca atoms, were relaxed using VASP. Most noticeable effects were the tilts of CO3 groups and distortion of Ca sub-lattice, especially in the case of water. The distributions of nearest Ca-Ca distance and CO3 tilts were extracted from those configurations. We also performed the same analysis starting with aragonite. Sampling from above distributions we built models for amorphous calcite/aragonite of size ˜1700 nm^3. We found that the induced distortions were not enough to generate a diffraction pattern typical of an amorphous material. Next we studied diffraction pattern of several nano-crystallites as recent studies suggest that amorphous calcite might be composed of nano- crystallites. We could then generate a diffraction pattern that appeared similar to that from ACC, for a nano-crystallite of size ˜2 nm^3.

  5. Calcium stimulation of gastrin and gastric acid secretion: effect of small doses of calcium carbonate

    Microsoft Academic Search

    J Behar; M Hitchings; R D Smyth

    1977-01-01

    Oral calcium carbonate (0-5 g, pH 9-4) increased serum gastrin and gastric acid output with slight but insignificant change in serum calcium. A similar rise in serum calcium during an intravenous infusion of calcium gluconate failed to increase serum gastrin and gastric acid output. Both intragastric calcium actions were abolished by acidification of the calcium carbonate solution (pH 1-0). The

  6. Behavior of carbon isotopes during the hyperfiltration of calcium carbonate solutions through calcium bentonites 

    E-print Network

    Hinz, David William

    1987-01-01

    first by the heavy cement, tne lighter cement will precipitate upstream and adjacent to the early cement. Therefore, a carbon isotopic profile through a cement precipitated by hyperfi ltration will show heavy cement at the sandstone shale contact...BEHAVIOR OF CARBON ISOTOPES DURING THE HYPERFILTRATION OF CALCIUM CARBONATE SOLUTIONS THROUGH CALCIUM BENTONITES A Thesis DAVID WILLIAM HINZ Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirements...

  7. Br J Nutr . Author manuscript Calcium carbonate suppresses haem toxicity markers without calcium

    E-print Network

    Paris-Sud XI, Université de

    calcium phosphate side effects on colon carcinogenesis Ossama Allam , Diane Bahuaud , Sylviane Taché. Unexpectedly, high-calcium phosphate control diet-fed rats had more preneoplastic lesions in the colon than low-calcium, in contrast with previously tested calcium phosphate diet. The results suggest that calcium carbonate

  8. [Chondrocalcinosis. Clinical impact of intra-articular calcium phosphate crystals].

    PubMed

    Fuerst, M

    2014-06-01

    Calcium pyrophosphate dihydrate (CPPD) crystals are known to cause acute attacks of pseudogout in joints but crystal deposition has also been reported to be associated with osteoarthritis (OA). Aside from CPPD crystals, basic calcium phosphates (BCPs), consisting of carbonate-substituted hydroxyapatite (HA), tricalcium phosphate and octacalcium phosphate, have been found in synovial fluid, synovium and cartilage of patients with OA. Although CPPD crystals have been found to be associated with OA and are an important factor in joint disease, this has also recently been associated with a genetic defect. However, according to the most recent findings, the association of BCP crystals, such as apatite with OA is much stronger, as their presence significantly correlates with the severity of cartilage degeneration. Identification of BCP crystals in OA joints remains problematic due to a lack of simple and reliable methods of detection. The clinical and pathological relevance of cartilage mineralization in patients with OA is not completely understood. It is well established that mineralization of articular cartilage is often found close to hypertrophic chondrocytes. A significant correlation between the expression of type X collagen, a marker for chondrocyte hypertrophy and cartilage mineralization was observed. In the process of endochondral ossification, the link between hypertrophy and matrix mineralization is particularly well described. Hypertrophic chondrocytes in OA cartilage and at the growth line share certain features, not only hypertrophy but also a capability to mineralize the matrix. Recent data indicate that chondrocyte hypertrophy is a key factor in articular cartilage mineralization strongly linked to OA and does not characterize a specific subset of OA patients, which has important consequences for therapeutic strategies for OA. PMID:24924727

  9. Calcium Carbonate Precipitation by Ureolytic Subsurface Bacteria

    SciTech Connect

    Fujita, Y.; Colwell, Frederick Scott; Smith, Robert William; Ferris, F. G.; Lawson, R. L.

    2000-10-01

    Coprecipitation in carbonate minerals offers a means of slowing the transport of divalent radionuclides and contaminant metals (e.g.,90Sr2+, UO2+, Co2+) in the subsurface. It may be possible to accelerate this process by stimulating the native microbial community to generate chemical conditions favoring carbonate precipitation. In a preliminary evaluation of this approach, we investigated the ability of ureolytic subsurface bacteria to produce alkaline conditions conducive to calcium carbonate precipitation. Groundwater samples from the Eastern Snake River Plain (ESRP) aquifer in Idaho were screened for urea-hydrolyzing microorganisms; three isolates were selected for further evaluation. Analysis of 16S rRNA gene sequences indicated that two of the ESRP isolates were of the genus Pseudomonas , and the other was a Variovorax sp. The specific urease activities of the ESRP isolates appeared to be similar to each other but less than that of Bacillus pasteurii , a known urease-positive organism. However, calcium carbonate was rapidly precipitated in all cultures that were supplied with urea and calcium, and X-ray diffraction analyses indicated that calcite was always the predominant carbonate polymorph produced. The correspondence between measured calcium concentrations and equilibrium predictions suggested that the rate of calcite precipitation was directly linked to the rate of urea hydrolysis. These results are promising with respect to the potential utility of this approach for in situ remediation and indicate that further evaluation of this approach under conditions more closely simulating environmental conditions is warranted.

  10. Diagnosis and clinical manifestations of calcium pyrophosphate and basic calcium phosphate crystal deposition diseases.

    PubMed

    Ea, Hang-Korng; Lioté, Frédéric

    2014-05-01

    Basic calcium phosphate and pyrophosphate calcium crystals are the 2 main calcium-containing crystals that can deposit in all skeletal tissues. These calcium crystals give rise to numerous manifestations, including acute inflammatory attacks that can mimic alarming and threatening differential diagnoses, osteoarthritis-like lesions, destructive arthropathies, and calcific tendinitis. Awareness of uncommon localizations and manifestations such as intraspinal deposition (eg, crowned dens syndrome, tendinitis of longus colli muscle, massive cervical myelopathy compression) prevents inappropriate procedures and cares. Coupling plain radiography, ultrasonography, computed tomography, and synovial fluid analysis allow accurate diagnosis by directly or indirectly identifying the GRAAL of microcrystal-related symptoms. PMID:24703344

  11. Absence of rebound effect with calcium carbonate.

    PubMed

    Simoneau, G

    1996-01-01

    This was an open, randomised balance cross-over study in 12 healthy male volunteers. The antacid activity of calcium carbonate plus magnesium carbonate (Rennie and hydrotalcite (Talcid), given in the recommended dose of 2 tablets 4 times daily, were compared using 24 h intragastric measurement of pH. The volunteers received 2 tablets of calcium carbonate plus magnesium carbonate or hydrotalcite according to a randomised order 1 h after each meal and at bedtime. Results showed that both treatments have similar antacid efficacy and a similar duration of action of about one hour. There was no evidence of acid 'rebound' following either treatment during the second and third hours following the administration of antacid. PMID:9074901

  12. CALCIUM CARBONATE BUDGET OF THE SOUTHERN CALIFORNIA CONTINENTAL BORDERLAND

    E-print Network

    Luther, Douglas S.

    CALCIUM CARBONATE BUDGET OF THE SOUTHERN CALIFORNIA CONTINENTAL BORDERLAND A DISSERTATION SUBMITTED. I. Murphy K. J. Roy E.· D..·· Stroup A. H. Woodcock #12;iv ABSTRACT Calcium carbonate sedimentation is the change in amount of calcium carbonate in the Borderland with time. Transfer can be divided

  13. Influence of the surfactant nature on the calcium carbonate synthesis in water-in-oil emulsion

    NASA Astrophysics Data System (ADS)

    Szcze?, Aleksandra

    2009-02-01

    Calcium carbonate has been precipitated from water-in-oil emulsions consisting of n-hexane/nonionic surfactant (Brij 30) and its mixture with cationic (DTAB) or anionic surfactant (SDS) to which calcium chloride and sodium carbonate were added. It was found that the surfactant kind and its amount can regulate the size, form and morphology of the precipitated particles. In case of nonionic surfactant the water/surfactant ratio is the most important parameter that allows to obtain small and regular calcium carbonate crystals. Addition of the DTAB results in different morphology of particles having the same crystal form, whereas addition of SDS changes the kind of emulsion from water-in-oil to oil-in-water. Moreover, light transmittance and backscattering light measurements have been used as a method to study the kinetics of calcium carbonate precipitation in emulsion systems.

  14. Patterns of radiographic abnormalities associated with basic calcium phosphate and calcium pyrophosphate dihydrate crystal deposition in the knee

    Microsoft Academic Search

    P B Halverson; D J McCarty

    1986-01-01

    Radiographs and synovial fluids from 66 knees representing 59 patients with symptomatic osteoarthritis were evaluated to determine the pattern of radiographic abnormalities associated with basic calcium phosphate (BCP), calcium pyrophosphate dihydrate (CPPD), or both crystals together. Crystals were found in 71% of fluids. In general, CPPD crystals correlated with patient age, while BCP crystals correlated with joint degeneration. Synovial fluid

  15. Calcium carbonate mineralization mediated by in vitro cultured mantle cells from Pinctada fucata.

    PubMed

    Kong, Wei; Li, Shiguo; Xiang, Liang; Xie, Liping; Zhang, Rongqing

    2015-08-01

    Formation of the molluscan shell is believed to be an extracellular event mediated by matrix proteins. We report calcium carbonate mineralization mediated by Pinctada fucata mantle cells. Crystals only appeared when mantle cells were present in the crystallization solution. These crystals were piled up in highly ordered units and showed the typical characteristics of biomineralization products. A thin organic framework was observed after dissolving the crystals in EDTA. Some crystals had etched surfaces with a much smoother appearance than other parts. Mantle cells were observed to be attached to some of these smooth surfaces. These results suggest that mantle cells may be directly involved in the nucleation and remodeling process of calcium carbonate mineralization. Our result demonstrate the practicability of studying the mantle cell mechanism of biomineralization and contribute to the overall understanding of the shell formation process. PMID:26079887

  16. Modulation of calcium oxalate monohydrate crystallization kinetics in vitro.

    PubMed

    Kok, D J; Papapoulos, S E; Blomen, L J; Bijvoet, O L

    1988-09-01

    The effects of several low and high molecular weight (mol wt) compounds on the kinetics of calcium oxalate crystallization were examined using a seeded crystal growth method in which the solubility, the growth and the agglomeration of calcium oxalate crystals were measured as three separate and system-independent parameters. Citrate, magnesium, phosphate, pyrophosphate, chondroitinsulphate, pentosanpolysulphate and heparin were tested in a wide range of concentrations. The solubility of calcium oxalate crystals was increased only by citrate and magnesium. The crystal growth was inhibited by all compounds tested, but those with the high mol wt had the greatest effect at low concentrations. In contrast, inhibition of crystal agglomeration was achieved only by the low mol wt compounds; citrate was found to be the most potent inhibitor at concentrations likely to be present in normal urine. The high mol wt substances, despite their potent crystal growth inhibitory activity, had no effect on agglomeration. The results show that growth and agglomeration of calcium oxalate crystals are separate processes which are differently modulated by various compounds. They further provide a possible explanation for the pathogenetic role of citrate in hypocitraturic renal stone disease. PMID:2459439

  17. Alginate-controlled formation of nanoscale calcium carbonate and hydroxyapatite mineral phase within hydrogel networks.

    PubMed

    Xie, Minli; Olderøy, Magnus Ø; Andreassen, Jens-Petter; Selbach, Sverre Magnus; Strand, Berit L; Sikorski, Pawel

    2010-09-01

    A one-step method was used to make nanostructured composites from alginate and calcium carbonate or calcium phosphate. Nanometer-scale mineral phase was successfully formed within the gel network of alginate gel beads, and the composites were characterized. It was found that calcite was the dominating polymorph in the calcium carbonate mineralized beads, while stoichiometric hydroxyapatite was formed in the calcium phosphate mineralized beads. A combination of electron microscopy, Fourier-transform infrared spectroscopy, thermogravimetric analysis and powder X-ray diffraction showed that alginate played an active role in controlling mineral size, morphology and polymorphy. For the calcium phosphate mineralized beads, alginate was shown to modulate stoichiometric hydroxyapatite with low crystallinity at room temperature, which may have important applications in tissue engineering. The results presented in this work demonstrate important aspects of alginate-controlled crystallization, which contributes to the understanding of composite material design. PMID:20359556

  18. CHARACTERIZATION OF ARTICULAR CALCIUM-CONTAINING CRYSTALS BY SYNCHROTRON FTIR

    PubMed Central

    Rosenthal, Ann K.; Mattson, Eric; Gohr, Claudia M.; Hirschmugl, Carol J.

    2008-01-01

    Objective Sixty percent of synovial fluids from patients with severe osteoarthritis contain calcium pyrophosphate dihydrate (CPPD) or basic calcium phosphate (BCP) crystals. These bioactive crystals can be particularly difficult to accurately identify in complex biologic systems, such as in vitro models of crystal formation. We sought to determine if synchrotron FTIR (sFTIR) could be used to identify and characterize calcium-containing crystals in mineralization models. Methods CPPD and BCP crystals from porcine models of crystal formation were examined with an FTIR Microscope attached to a synchrotron light source. As a comparison, crystals from human synovial fluids were also examined. The sFTIR spectra generated were compared with known spectra of multiple forms of BCP and CPPD crystals, as well as spectra generated by synthetic CPPD and BCP crystals and cartilage proteoglycans, alone and in mixtures. Results sFTIR readily identified CPPD and BCP crystals in porcine models as well as in fresh synovial fluids. Brushite was also present in human and porcine samples, and whitlockite was seen in some porcine samples. Mixtures of minerals were commonly found in a single crystal aggregate in both human and porcine samples. In spectra from many CPPD crystals, the peak at the 1134 cm?1 found on the standard spectrum for CPPD was diminished. Addition of spectra from cartilage proteoglycans to those of synthetic CPPD crystals dampened the peak at this frequency region, much as this peak was diminished in biologically-derived CPPD crystals. Conclusion sFTIR analysis allows for accurate identification of CPPD and BCP crystals generated in vitro and will a useful research tool to study articular crystals. PMID:18472285

  19. Pyroelectric and dielectric properties of calcium barium niobate single crystals

    NASA Astrophysics Data System (ADS)

    Malyshkina, O. V.; Lisitsin, V. S.; Dec, J.; ?ukasiewicz, T.

    2014-09-01

    The effect of the calcium concentration on the pyroelectric and dielectric properties of Ca x Ba1 - x Nb2O6 (CBN) crystals has been studied over a wide temperature range. It has been shown that the calcium concentration only influences the Curie point of crystals of this class. It insignificantly changes the absolute values of the permittivity, the coercive field, and the remanent polarization and does not influence their temperature dependences and the shape of the dielectric hysteresis loop. The possibility of the existence of relaxor properties in CBN crystals has been discussed.

  20. Crystal structure of the calcium release-activated calcium channel Orai

    PubMed Central

    Hou, Xiaowei; Pedi, Leanne; Diver, Melinda M.; Long, Stephen B.

    2013-01-01

    The plasma membrane protein Orai forms the pore of the CRAC channel (calcium release-activated calcium channel) and generates sustained cytosolic calcium signals when triggered by depletion of calcium from the endoplasmic reticulum. The crystal structure of Orai from Drosophila melanogaster, determined at 3.35 angstrom resolution, reveals that the calcium channel is comprised of a hexameric assembly of Orai subunits arranged around a central ion pore. The pore traverses the membrane and extends 20 angstroms into the cytosol. A ring of glutamates on its extracellular side forms the selectivity filter. A basic region near the intracellular side can bind anions that may stabilize the closed state. The architecture of the channel differs markedly from other ion channels and gives insight into the principles of selective calcium permeation and gating. PMID:23180775

  1. Crystal agglomeration is a major element in calcium oxalate urinary stone formation

    Microsoft Academic Search

    Dik J Kok; Socrates E Papapoulos; Olav L M Bijvoet

    1990-01-01

    Crystal agglomeration is a major element in calcium oxalate urinary stone formation. The effects of urines from 36 healthy subjects and 86 calcium oxalate renal stone formers on calcium oxalate monohydrate crystallization kinetics were studied using a seeded crystal growth method in which the solubility, the growth and the agglomeration of the crystals are measured as three separate and system-independent

  2. 40 CFR 415.300 - Applicability; description of the calcium carbonate production subcategory.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...false Applicability; description of the calcium carbonate production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Carbonate Production Subcategory § 415.300 Applicability; description of the calcium carbonate production subcategory....

  3. 40 CFR 415.300 - Applicability; description of the calcium carbonate production subcategory.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...true Applicability; description of the calcium carbonate production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Carbonate Production Subcategory § 415.300 Applicability; description of the calcium carbonate production subcategory....

  4. 40 CFR 415.300 - Applicability; description of the calcium carbonate production subcategory.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...true Applicability; description of the calcium carbonate production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Carbonate Production Subcategory § 415.300 Applicability; description of the calcium carbonate production subcategory....

  5. 40 CFR 415.300 - Applicability; description of the calcium carbonate production subcategory.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...true Applicability; description of the calcium carbonate production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Carbonate Production Subcategory § 415.300 Applicability; description of the calcium carbonate production subcategory....

  6. 40 CFR 415.300 - Applicability; description of the calcium carbonate production subcategory.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...true Applicability; description of the calcium carbonate production subcategory. 415...CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Carbonate Production Subcategory § 415.300 Applicability; description of the calcium carbonate production subcategory....

  7. Introduction The formation of solid calcium carbonate (CaCO3) is

    E-print Network

    Hell, Stefan W.

    and of a particular amphiphilic acid have been used for epitaxial growth of 3-D crystals of silver propionate [8 crystallisation of silver propionate [8]. A new approach in the investigation of CaCO3 formation at interfaces In situ Brewster angle microscopy Æ Calcium carbonate formation Æ Kinetics Æ Critical cluster Colloid

  8. The formation and transformation mechanism of calcium carbonate in water

    NASA Astrophysics Data System (ADS)

    Ogino, Takeshi; Suzuki, Toshio; Sawada, Kiyoshi

    1987-10-01

    Highly supersaturated solutions of Ca 2+ and CO 2-3 ions rapidly precipitate amorphous calcium carbonate, ACC, the logarithmic thermodynamic solubility product of which is about -6.0 at 25°C. The ACC initially formed is transformed to a mixture of several crystalline calcium carbonate polymorphs within several minutes. The transformed polymorphs are vaterite and calcite at low temperature (14 to 30°C), and aragonite and calcite at high temperature (60 to 80°C). At intermediate temperatures (40 to 50°C) the formation of all three polymorphs was observed. Metastable polymorphs are gradually transformed to the stable form, calcite. It takes about 200 min at 25°C and 370 min at 30°C for the complete transformation of vaterite to calcite, and 1000-1300 min for that of aragonite to calcite at 60-80°C. At 50°C, vaterite is predominantly transformed at first to aragonite within 60 min, and then the aragonite is transformed to calcite in about 900 min. The results of the change in the ion activity product of the solution and the abundances of the polymorphs strongly suggest that the polymorphic transformation of vaterite and aragonite to calcite takes place through dissolution of the metastable phase and growth of the stable phase, calcite. The rate-determining step of the transformation is the growth of calcite. The relative abundance of vaterite becomes higher at 25°C with increasing concentrations of calcium and carbonate ions in the supersaturated solution. When the ion activity product of the initial supersaturated solution is lower than the solubility product of ACC at 25°C, only vaterite directly precipitates after some induction period. The vaterite crystals formed are free of calcite seeds and the vaterite saturated solutions are stable for several days.

  9. The formation and transformation mechanism of calcium carbonate in water

    Microsoft Academic Search

    Takeshi Ogino; Toshio Suzuki; Kiyoshi Sawada

    1987-01-01

    Highly supersaturated solutions of Ca 2+ and CO 2- 3 ions rapidly precipitate amorphous calcium carbonate, ACC, the logarithmic thermodynamic solubility product of which is about -6.0 at 25°C. The ACC initially formed is transformed to a mixture of several crystalline calcium carbonate polymorphs within several minutes. The transformed polymorphs are vaterite and calcite at low temperature (14 to 30°C),

  10. Aluminum Citrate Prevents Renal Injury from Calcium Oxalate Crystal Deposition

    PubMed Central

    Besenhofer, Lauren M.; Cain, Marie C.; Dunning, Cody

    2012-01-01

    Calcium oxalate monohydrate crystals are responsible for the kidney injury associated with exposure to ethylene glycol or severe hyperoxaluria. Current treatment strategies target the formation of calcium oxalate but not its interaction with kidney tissue. Because aluminum citrate blocks calcium oxalate binding and toxicity in human kidney cells, it may provide a different therapeutic approach to calcium oxalate-induced injury. Here, we tested the effects of aluminum citrate and sodium citrate in a Wistar rat model of acute high-dose ethylene glycol exposure. Aluminum citrate, but not sodium citrate, attenuated increases in urea nitrogen, creatinine, and the ratio of kidney to body weight in ethylene glycol–treated rats. Compared with ethylene glycol alone, the addition of aluminum citrate significantly increased the urinary excretion of both crystalline calcium and crystalline oxalate and decreased the deposition of crystals in renal tissue. In vitro, aluminum citrate interacted directly with oxalate crystals to inhibit their uptake by proximal tubule cells. These results suggest that treating with aluminum citrate attenuates renal injury in rats with severe ethylene glycol toxicity, apparently by inhibiting calcium oxalate’s interaction with, and retention by, the kidney epithelium. PMID:23138489

  11. Aluminum citrate prevents renal injury from calcium oxalate crystal deposition.

    PubMed

    Besenhofer, Lauren M; Cain, Marie C; Dunning, Cody; McMartin, Kenneth E

    2012-12-01

    Calcium oxalate monohydrate crystals are responsible for the kidney injury associated with exposure to ethylene glycol or severe hyperoxaluria. Current treatment strategies target the formation of calcium oxalate but not its interaction with kidney tissue. Because aluminum citrate blocks calcium oxalate binding and toxicity in human kidney cells, it may provide a different therapeutic approach to calcium oxalate-induced injury. Here, we tested the effects of aluminum citrate and sodium citrate in a Wistar rat model of acute high-dose ethylene glycol exposure. Aluminum citrate, but not sodium citrate, attenuated increases in urea nitrogen, creatinine, and the ratio of kidney to body weight in ethylene glycol-treated rats. Compared with ethylene glycol alone, the addition of aluminum citrate significantly increased the urinary excretion of both crystalline calcium and crystalline oxalate and decreased the deposition of crystals in renal tissue. In vitro, aluminum citrate interacted directly with oxalate crystals to inhibit their uptake by proximal tubule cells. These results suggest that treating with aluminum citrate attenuates renal injury in rats with severe ethylene glycol toxicity, apparently by inhibiting calcium oxalate's interaction with, and retention by, the kidney epithelium. PMID:23138489

  12. Increased calcium absorption from synthetic stable amorphous calcium carbonate: Double-blind randomized crossover clinical trial in post-menopausal women

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calcium supplementation is a widely recognized strategy for achieving adequate calcium intake. We designed this blinded, randomized, crossover interventional trial to compare the bioavailability of a new stable synthetic amorphous calcium carbonate (ACC) with that of crystalline calcium carbonate (C...

  13. Utilization of Calcium in Breads Highly Fortified with Calcium as Calcium Carbonate or as Dairy Calcium

    Microsoft Academic Search

    G. S. Ranhotra; J. A. Gelroth; S. D. Leinen

    2000-01-01

    Cereal Chem. 77(3):293-296 White pan breads were prepared with flour highly fortified with cal- cium (Ca), using Ca carbonate (Ca, 38.8%) or a high Ca whey powder (Ca, 5.6%) as the Ca source; bread was also prepared using Ca carbonate plus lactose. Ca was added to flour at 924 mg\\/100 g of flour, a level 4.4 times higher than specified

  14. Risk factors for calcium carbonate urolithiasis in goats.

    PubMed

    Nwaokorie, Eugene E; Osborne, Carl A; Lulich, Jody P; Fletcher, Thomas F; Ulrich, Lisa K; Koehler, Lori A; Buettner, Michelle T

    2015-08-01

    Objective-To identify demographic or signalment factors associated with calcium carbonate urolith formation in goats. Design-Retrospective case series and case-control study. Animals-354 goats with calcium carbonate uroliths (case animals) and 16,366 goats without urinary tract disease (control animals). Procedures-Medical records of the Minnesota Urolith Center were reviewed to identify case goats for which samples were submitted between January 1, 1984, and December 31, 2012. Control goats evaluated at US veterinary teaching hospitals in the same time period were identified by searching Veterinary Medical Database records. Age, breed, sex, reproductive status, geographic location, season, and anatomic location of collected uroliths were analyzed to identify risk or protective factors associated with calcium carbonate urolithiasis. Results-Nigerian dwarf goats had higher odds of developing calcium carbonate uroliths than did Pygmy goats (reference group). Several breeds had lower odds of this finding, compared with Pygmy goats; odds were lowest for mixed, Anglo-Nubian, and Toggenburg breeds. Breeds of African origin (Pygmy, Nigerian Dwarf, and Boer) comprised 146 of 275 (53%) case goats with data available. Goats of African descent had a higher risk of developing calcium carbonate uroliths than did goats of non-African descent (reference group). Males and neutered goats had higher odds of calcium carbonate urolithiasis, compared with females and sexually intact goats, respectively. Age category, geographic location, and season were associated with detection of calcium carbonate uroliths. Conclusions and Clinical Relevance-Goats with calcium carbonate uroliths were typically neutered males, > 1 year of age, and of African descent. This study identified factors associated with calcium carbonate urolithiasis in goats; however, these associations do not allow conclusions regarding cause-and-effect relationships. PMID:26176729

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

    PubMed

    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. PMID:22697480

  16. Evidence for calcium carbonate at the Mars Phoenix landing site.

    PubMed

    Boynton, W V; Ming, D W; Kounaves, S P; Young, S M M; Arvidson, R E; Hecht, M H; Hoffman, J; Niles, P B; Hamara, D K; Quinn, R C; Smith, P H; Sutter, B; Catling, D C; Morris, R V

    2009-07-01

    Carbonates are generally products of aqueous processes and may hold important clues about the history of liquid water on the surface of Mars. Calcium carbonate (approximately 3 to 5 weight percent) has been identified in the soils around the Phoenix landing site by scanning calorimetry showing an endothermic transition beginning around 725 degrees C accompanied by evolution of carbon dioxide and by the ability of the soil to buffer pH against acid addition. Based on empirical kinetics, the amount of calcium carbonate is most consistent with formation in the past by the interaction of atmospheric carbon dioxide with liquid water films on particle surfaces. PMID:19574384

  17. Calcium carbonate does not affect imatinib pharmacokinetics in healthy volunteers

    PubMed Central

    Tawbi, Hussein; Christner, Susan M.; Lin, Yan; Johnson, Matthew; Mowrey, Emily T.; Cherrin, Craig; Chu, Edward; Lee, James J.; Puhalla, Shannon; Stoller, Ronald; Appleman, Leonard R.; Miller, Brian M.; Beumer, Jan H.

    2013-01-01

    Purpose Imatinib mesylate (Gleevec®/Glivec®), has revolutionized the treatment of chronic myeloid leukemias (CML) and gastrointestinal stromal tumors (GIST), and there is evidence for an exposure response relationship. Calcium carbonate is increasingly used as a calcium supplement and in the setting of gastric upset associated with imatinib therapy. Calcium carbonate could conceivably elevate gastric pH and complex imatinib, thereby influencing imatinib absorption and exposure. We aimed to evaluate whether use of calcium carbonate has a significant effect on imatinib pharmacokinetics. Methods Eleven healthy subjects were enrolled in a 2-period, open-label, single-institution, randomized cross-over, fixed-schedule study. In one period, each subject received 400 mg of imatinib p.o.. In the other period, 4000 mg calcium carbonate (Tums Ultra®) was administered p.o. 15 min before 400 mg of imatinib. Plasma concentrations of imatinib and its active N-desmethyl metabolite CGP74588 were assayed by LC-MS; data were analyzed non-compartmentally, and compared after log transformation. Results Calcium carbonate administration did not significantly affect the imatinib area under the plasma concentration versus time curve (AUC) (41.2 ?g/mL•h alone versus 40.8 ?g/mL•h with calcium carbonate, P=0.99), maximum plasma concentration (Cmax) (2.35 ?g/mL alone versus 2.39 ?g/mL with calcium carbonate, P=0.89). Conclusions Our results indicate that the use of calcium carbonate does not significantly affect imatinib pharmacokinetics. PMID:24170263

  18. Accelerated carbonation of Friedel's salt in calcium aluminate cement paste

    Microsoft Academic Search

    S. Goñi; A. Guerrero

    2003-01-01

    The stability of Friedel's salt with respect to carbonation has been studied in calcium aluminate cement (CAC) pastes containing NaCl (3% of Cl? by weight of cement). Carbonation was carried out on a powdered sample in flowing 5% CO2 gas at 65% relative humidity to accelerate the process. At an intermediate carbonation step, a part of the sample was washed

  19. Evidence for Calcium Carbonate at the Mars Phoenix Landing Site

    Microsoft Academic Search

    W. V. Boynton; D. W. Ming; S. P. Kounaves; S. M. M. Young; R. E. Arvidson; M. H. Hecht; J. Hoffman; P. B. Niles; D. K. Hamara; R. C. Quinn; P. H. Smith; B. Sutter; D. C. Catling; R. V. Morris

    2009-01-01

    Carbonates are generally products of aqueous processes and may hold important clues about the history of liquid water on the surface of Mars. Calcium carbonate (approximately 3 to 5 weight percent) has been identified in the soils around the Phoenix landing site by scanning calorimetry showing an endothermic transition beginning around 725°C accompanied by evolution of carbon dioxide and by

  20. Crystal Morphology and 13Carbon/12Carbon Composition of Solid Oxalate in Cacti 1

    PubMed Central

    Rivera, E. R.; Smith, B. N.

    1979-01-01

    Morphology, crystal structure, and carbon isotopic composition of calcium oxalate from representative species from the family Cactaceae were determined using scanning electron microscopy, x-ray diffraction, and isotope ratio mass spectrometry. Crystals from one species in the Opuntieae tribe of the Cactaceae were druses with acute points composed of the monohydrate form of calcium oxalate (whewellite). Crystals from three species in the Cereeae tribe were the dihydrate form of calcium oxalate (weddellite) forming druses made up of tetragonal and isodiametric crystallites. The oxalate was relatively enriched in 13C isotope (-7.3 to - 8.7 ‰) compared with woody fibers (-13.3 to 14.1 ‰) from the same plants. Images PMID:16661115

  1. Thermal breakdown of calcium carbonate and constraints on its use as a biomarker

    NASA Astrophysics Data System (ADS)

    Thompson, Stephen P.; Parker, Julia E.; Tang, Chiu C.

    2014-02-01

    Observed differences in the thermal behaviour of calcium carbonates of biogenic and abiogenic origin (phase transformation and breakdown temperatures) are widely cited as potential biomarkers for whether life once existed on Mars. Although seemingly compelling, there has been no systematic investigation into the physical mechanism behind these apparent differences and therefore no direct proof that they are uniquely diagnostic of a biogenic versus abiogenic formation. In this paper we present a laboratory investigation into the thermal behaviour of two high purity calcium carbonates, one of which was produced in the presence of an amino acid as a biomimetic carbonate. In situ synchrotron X-ray powder diffraction measurements show the aragonite-to-calcite phase transition and calcite-to-oxide breakdown temperatures are significantly lower in the biomimetic carbonate. The observed thermal differences closely match reported differences between biogenic and geological abiogenic carbonates. The biomimetic carbonate exhibits a modified crystal morphology, with a highly strained internal crystal lattice, similar to biogenic carbonate structures. Since biogenic carbonates are formed in the presence of organic macromolecules such as amino acids, the induced microstrain appears to be the defining common factor as it adds an additional energy term to the carbonate lattice energy, which lowers the activation energy required for structural transformation or decomposition. Although produced via biomimetic means, the carbonate investigated here is nevertheless abiogenic in origin and we propose that given suitable localised conditions such as pooled water and a supply of organic molecules, naturally occurring biomimetic carbonates could have similarly formed on the martian surface and could therefore exhibit the same thermal characteristics as biogenic carbonate. Thus as a limiting case - without other supporting observations - the thermal behaviour of martian calcium carbonate might only be a marker for a pre-biotic organic chemistry having once been present rather than living organisms.

  2. Ris-R-1143(EN) Modelling Calcium Carbonate Deposition

    E-print Network

    Risø-R-1143(EN) CRACK2 - Modelling Calcium Carbonate Deposition from Bicarbonate Solution in Cracks of bicarbonate solution in a crack connecting the ends of a row of such columns. The cementitious material is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide dissolved in the pore

  3. Calcium carbonate does not affect nilotinib pharmacokinetics in healthy volunteers

    PubMed Central

    Tawbi, Hussein A.; Tran, An L.; Christner, Susan M.; Lin, Yan; Johnson, Matthew; Mowrey, Emily; Appleman, Leonard R.; Stoller, Ronald; Miller, Brian M.; Egorin, Merrill J.; Beumer, Jan H.

    2013-01-01

    Purpose Nilotinib is a second-generation oral tyrosine kinase inhibitor (TKI) with superior efficacy compared with imatinib mesylate in the treatment of chronic phase chronic myelogenous leukemia (CML). Calcium carbonate is commonly used as a source of calcium supplementation or as antacid to ameliorate the gastrointestinal side effects associated with nilotinib, which could have unknown effects on nilotinib absorption. The purpose of this study was to provide information on the effect of calcium carbonate on the PK of nilotinib in healthy volunteers. Methods Healthy subjects were enrolled in a 2-period, open-label, single-institution, randomized, cross-over, fixed-schedule study. In one period, each subject received 400 mg of nilotinib p.o. In the other period, 4000 mg calcium carbonate (4 X Tums Ultra 1000®) were administered p.o. 15 minutes prior to the nilonitib dose. Plasma samples were collected at specified timepoints, concentrations of nilotinib were quantitated by LC-MS, and data were analyzed non-compartmentally. Results Eleven subjects were evaluable. Calcium supplementation did not significantly affect nilotinib pharmacokinetic parameters including area under the plasma concentration versus time curve (AUC) (18.4 ?g/mL•h alone versus 16.9 ?g/mL•h with calcium carbonate, P=0.83; 80% power); maximum plasma concentration (Cmax) (0.670 ?g/mL alone versus 6.18 ?g/mL with calcium carbonate, P=0.97); or half-life (18.9 h alone versus 17.2 h with calcium carbonate, P=0.18). Conclusions Our results indicate that the use of calcium carbonate does not significantly affect nilotinib pharmacokinetics. PMID:24036846

  4. Behaviour of calcium carbonate in sea water

    USGS Publications Warehouse

    Cloud, P.E., Jr.

    1962-01-01

    Anomalies in the behaviour of calcium carbonate in natural solutions diminish when considered in context. Best values found by traditional oceanographie methods for the apparent solubility product constant K'CaCO3 in sea water at atmospheric pressure are consistent mineralogically-at 36 parts per thousand salinity and T-25??C, K'aragonlte is estimated as 1.12 ?? 10-6 and K'calcite as 0.61 ?? 10-6. At 30??C the corresponding values are 0.98 ?? 10-6 for aragonite and 0.53 ?? 10-6 for calcite. Because the K' computations do not compensate for ionic activity, however, they cannot give thermodynamically satisfactory results. It is of interest, therefore, that approximate methods and information now available permit the estimation from the same basic data of an activity product constant KCaCO3 close to that found in solutions to which Debye-Hu??ckel theory applies. Such methods indicate approximate Karagonite 7.8 ?? 10-9 for surface sea water at 29??C; Kcalcite would be proportionately lower. Field data and experimental results indicate that the mineralogy of precipitated CaCO3 depends primarily on degree of supersaturation, thus also on kinetic or biologic factors that facilitate or inhibit a high degree of supersaturation. The shallow, generally hypersaline bank waters west of Andros Island yield aragonitic sediments with O18 O16 ratios that imply precipitation mainly during the warmer months, when the combination of a high rate of evaporation, increasing salinity (and ionic strength), maximal temperatures and photosynthetic removal of CO2 result in high apparent supersaturation. The usual precipitate from solutions of low ionic strength is calcite, except where the aragonite level of supersaturation is reached as a result of diffusion phenomena (e.g. dripstones), gradual and marked evaporation, or biologic intervention. Published data also suggest the possibility of distinct chemical milieus for crystallographic variations in skeletal calcium carbonate. It appears that in nature aragonite precipitates from solutions that are supersaturated with respect to both calcite and aragonite and calcite between saturation levels for the two species. Such a relation is consistent with Ostwald's rule of successive reactions. Aragonitc of marine origin persists in contact with supersaturated interstitial solutions at ordinary temperature and pressure. Conversion to calcite follows transfer to solutions undersaturated with respect to aragonite or upon exposure to the moist atmosphere. ?? 1962.

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

    PubMed

    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. PMID:25934395

  6. Morphologies and elemental compositions of calcium crystals in phyllodes and branchlets of Acacia robeorum (Leguminosae: Mimosoideae)

    PubMed Central

    He, Honghua; Bleby, Timothy M.; Veneklaas, Erik J.; Lambers, Hans; Kuo, John

    2012-01-01

    Background and Aims Formation of calcium oxalate crystals is common in the plant kingdom, but biogenic formation of calcium sulfate crystals in plants is rare. We investigated the morphologies and elemental compositions of crystals found in phyllodes and branchlets of Acacia robeorum, a desert shrub of north-western Australia. Methods Morphologies of crystals in phyllodes and branchlets of A. robeorum were studied using scanning electron microscopy (SEM), and elemental compositions of the crystals were identified by energy-dispersive X-ray spectroscopy. Distributional patterns of the crystals were studied using optical microscopy together with SEM. Key Results According to the elemental compositions, the crystals were classified into three groups: (1) calcium oxalate; (2) calcium sulfate, which is a possible mixture of calcium sulfate and calcium oxalate with calcium sulfate being the major component; and (3) calcium sulfate · magnesium oxalate, presumably mixtures of calcium sulfate, calcium oxalate, magnesium oxalate and silica. The crystals were of various morphologies, including prisms, raphides, styloids, druses, crystal sand, spheres and clusters. Both calcium oxalate and calcium sulfate crystals were observed in almost all tissues, including mesophyll, parenchyma, sclerenchyma (fibre cells), pith, pith ray and cortex; calcium sulfate · magnesium oxalate crystals were only found in mesophyll and parenchyma cells in phyllodes. Conclusions The formation of most crystals was biologically induced, as confirmed by studying the crystals formed in the phyllodes from seedlings grown in a glasshouse. The crystals may have functions in removing excess calcium, magnesium and sulfur, protecting the plants against herbivory, and detoxifying aluminium and heavy metals. PMID:22294477

  7. Calcium carbonate scaling kinetics determined from radiotracer experiments with calcium-47

    SciTech Connect

    Turner, C.W.; Smith, D.W. [Atomic Energy of Canada Ltd., Chalk River, Ontario (Canada). Chalk River Labs.] [Atomic Energy of Canada Ltd., Chalk River, Ontario (Canada). Chalk River Labs.

    1998-02-01

    The deposition of calcium carbonate is one of the principal modes of fouling of the heat-transfer surface of a fresh-water-cooled heat exchanger. The deposition rate of calcium carbonate on a heat-transfer surface has been measured using a calcium-47 radiotracer and compared to the measured rate of thermal fouling. The crystalline phase of calcium carbonate that precipitates depends on the degree of supersaturation at the heat-transfer surface, with aragonite precipitating at higher supersaturations and calcite precipitating at lower supersaturations. Whereas the mass deposition rates were constant with time, the thermal fouling rates decreased throughout the course of each experiment as a result of densification of the deposit. It is proposed that the densification was driven by the temperature gradient across the deposit together with the retrograde solubility of calcium carbonate. The temperature dependence of the deposition rate yielded an activation energy of 79 {+-} 4 kJ/mol for the precipitation of calcium carbonate on a heat-transfer surface.

  8. Amorphous calcium carbonate precipitation by cellular biomineralization in mantle cell cultures of Pinctada fucata.

    PubMed

    Xiang, Liang; Kong, Wei; Su, Jing-Tan; Su, Jingtan; Liang, Jian; Zhang, Gui-You; Zhang, Guiyou; Xie, Li-Ping; Xie, Liping; Zhang, Rong-Qing; Zhang, Rongqing

    2014-01-01

    The growth of molluscan shell crystals is generally thought to be initiated from the extrapallial fluid by matrix proteins, however, the cellular mechanisms of shell formation pathway remain unknown. Here, we first report amorphous calcium carbonate (ACC) precipitation by cellular biomineralization in primary mantle cell cultures of Pinctada fucata. Through real-time PCR and western blot analyses, we demonstrate that mantle cells retain the ability to synthesize and secrete ACCBP, Pif80 and nacrein in vitro. In addition, the cells also maintained high levels of alkaline phosphatase and carbonic anhydrase activity, enzymes responsible for shell formation. On the basis of polarized light microscopy and scanning electron microscopy, we observed intracellular crystals production by mantle cells in vitro. Fourier transform infrared spectroscopy and X-ray diffraction analyses revealed the crystals to be ACC, and de novo biomineralization was confirmed by following the incorporation of Sr into calcium carbonate. Our results demonstrate the ability of mantle cells to perform fundamental biomineralization processes via amorphous calcium carbonate, and these cells may be directly involved in pearl oyster shell formation. PMID:25405357

  9. Nanoporous Structure and Medium-Range Order in Synthetic Amorphous Calcium Carbonate

    SciTech Connect

    Goodwin, Andrew L.; Michel, F. Marc; Phillips, Brian L.; Keen, David A.; Dove, Martin T.; Reeder, Richard J. (SBU); (Cambridge); (Oxford); (RAL)

    2010-12-03

    We adopt a reverse Monte Carlo refinement approach, using experimental X-ray total scattering data, to develop a structure model for synthetic, hydrated amorphous calcium carbonate (ACC). The ACC is revealed to consist of a porous calcium-rich framework that supports interconnected channels containing water and carbonate molecules. The existence of a previously unrecognized nanometer-scale channel network suggests mechanisms of how additives can be accommodated within the structure and provide temporary stabilization, as well as influence the crystallization process. Moreover, while lacking long-range order, the calcium-rich framework in the ACC contains similar Ca packing density to that present in calcite, aragonite, and vaterite, yielding clues of how the amorphous material converts into the different crystalline forms. Our results provide a new starting point for advancing our understanding of biomineralization as well as the development of biomimetic approaches to next-generation materials synthesis.

  10. Precipitation of calcium carbonate in aqueous solutions in presence of ethylene glycol and dodecane.

    NASA Astrophysics Data System (ADS)

    Natsi, Panagiota D.; Rokidi, Stamatia; Koutsoukos, Petros G.

    2015-04-01

    The formation of calcium carbonate (CaCO3) in aqueous supersaturated solutions has been intensively studied over the past decades, because of its significance for a number of processes of industrial and environmental interest. In the oil and gas production industry the deposition of calcium carbonate affects adversely the productivity of the wells. Calcium carbonate scale deposits formation causes serious problems in water desalination, CO2 sequestration in subsoil wells, in geothermal systems and in heat exchangers because of the low thermal coefficient of the salt. Amelioration of the operational conditions is possible only when the mechanisms underlying nucleation and crystal growth of calcium carbonate in the aqueous fluids is clarified. Given the fact that in oil production processes water miscible and immiscible hydrocarbons are present the changes of the dielectric constant of the fluid phase has serious impact in the kinetics of calcium carbonate precipitation, which remains largely unknown. The problem becomes even more complicated if polymorphism exhibited by calcium carbonate is also taken into consideration. In the present work, the stability of aqueous solutions supersaturated with respect to all calcium carbonate polymorphs and the subsequent kinetics of calcium carbonate precipitation were measured. The measurements included aqueous solutions and solutions in the presence of water miscible (ethylene glycol, MEG) and water immiscible organics (n-dodecane). All measurements were done at conditions of sustained supersaturation using the glass/ Ag/AgCl combination electrode as a probe of the precipitation and pH as the master variable for the addition of titrant solutions with appropriate concentration needed to maintenance the solution supersaturation. Initially, the metastable zone width was determined from measurements of the effect of the solution supersaturation on the induction time preceding the onset of precipitation at free-drift conditions. The rates of crystal growth were measured as a function of the solution supersaturation using the highly accurate and reproducible methodology of constant supersaturation. The dependence of the rates of crystal growth on supersaturation suggested surface diffusion controlled mechanism. At constant supersaturation it was possible to extend the time period for the growth of the initially forming polymorph, in a way that sufficient amount is precipitated for characterization with X-ray diffraction (XRD). Moreover, scanning electron microscopy (SEM) was used for the characterization of the morphology of the precipitated solid. In all cases and depending on the solution supersaturation vaterite formed first from solutions of high supersaturation while at low supersaturations calcite formed exclusively. The presence of dodecane reduced the stability of the supersaturated solutions with the crystals forming at the oil-water interface. The presence of ethylene glycol (concentrations between 10-80%) also affected the stability and the kinetics of calcium carbonate precipitation. The morphology of the formed crystals showed habit modifications: Spherical formations consisting of aggregated nanocrystals and calcite crystals with profound pits on the faces were the characteristic feature in the presence of dodecane. ACKNOWLEDGMENT This research was partially funded by the European Union (European Social Fund-ESF) and Greek National Funds through the Operational program Education and Lifelong Learning under the action Aristeia II( Code No 4420).

  11. Control of crystal habit and particle morphology of calcium sulfite hemihydrate crystals

    NASA Astrophysics Data System (ADS)

    Chen, Pao-Chi; Tai, Clifford Y.; Shih, Shin-Min

    1992-09-01

    Using a pH-stat apparatus, we produced crystals of calcium sulfite hemihydrate in a semibatch crystallizer by reacting Ca(OH) 2 with NaHSO 3 under various operational conditions. The habits of calcium sulfite hemihydrate obtained in this study were acicular, long-platelet, platelet and tabular. Each of them was prone to form agglomerates, depending on the pH value, solution composition and concentration of additives. At low pH and high concentration of sodium bisulfite the agglomerate of acicular crystal would form. In contrast, platelet and tabular crystals and their agglomerates were obtained at high pH and low levels of sodium bisulfite concentration. The particle morphology was not significantly altered by the addition of EDTA and DMA, but the crystal habit was tabular at low EDTA concentration and became platelet as the EDTA concentration increased.

  12. Biomineralization of calcium carbonates and their engineered applications: a review

    PubMed Central

    Dhami, Navdeep K.; Reddy, M. Sudhakara; Mukherjee, Abhijit

    2013-01-01

    Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process in which microbes produce inorganic materials as part of their basic metabolic activities. This technology has been widely explored and promising with potential in various technical applications. In the present review, the detailed mechanism of production of calcium carbonate biominerals by ureolytic bacteria has been discussed along with role of bacteria and the sectors where these biominerals are being used. The applications of bacterially produced carbonate biominerals for improving the durability of buildings, remediation of environment (water and soil), sequestration of atmospheric CO2 filler material in rubbers and plastics etc. are discussed. The study also sheds light on benefits of bacterial biominerals over traditional agents and also the issues that lie in the path of successful commercialization of the technology of microbially induced calcium carbonate precipitation from lab to field scale. PMID:24194735

  13. Influence of maleic acid copolymers on calcium orthophosphates crystallization at low temperature

    NASA Astrophysics Data System (ADS)

    Pelin, Irina M.; Popescu, Irina; Suflet, Dana M.; Aflori, Magdalena; Bulacovschi, Victor

    2013-08-01

    The goal of this study was to investigate the maleic acid copolymers role on calcium orthophosphates crystallization at low temperature. In this respect, two maleic acid copolymers with different structures [poly(sodium maleate-co-vinyl acetate) and poly(sodium maleate-co-methyl methacrylate)] were used. The syntheses of the calcium orthophosphates in the absence and in the presence of the copolymers were performed through the wet chemical method using calcium nitrate, ammonium dihydrogen phosphate and ammonium hydroxide as reactants. The syntheses were monitored in situ by potentiometric and conductometric measurements. To ensure the transformation of less thermodynamically stable calcium orthophosphates into more stable forms, the samples were aged 30 days in mother solutions, at room temperature. The presence of the copolymers in the final products was evidenced by FTIR spectroscopy and thermogravimetric analysis. Scanning and transmission electron microscopy and laser light scattering measurements gave information about the composites morphology and the size of the formed structures. X-ray diffraction evidenced that, as a function of comonomer structure and of copolymer concentration, the products could contain hydroxyapatite with low crystallinity, calcium-deficient or carbonated hydroxyapatite. At high concentration of poly(sodium maleate-co-methyl methacrylate) the transformation of brushite into apatitic structures was inhibited.

  14. A reactive force field for aqueous-calcium carbonate systems.

    PubMed

    Gale, Julian D; Raiteri, Paolo; van Duin, Adri C T

    2011-10-01

    A new reactive force field has been derived that allows the modelling of speciation in the aqueous-calcium carbonate system. Using the ReaxFF methodology, which has now been implemented in the program GULP, calcium has been simulated as a fixed charge di-cation species in both crystalline phases, such as calcite and aragonite, as well as in the solution phase. Excluding calcium from the charge equilibration process appears to have no adverse effects for the simulation of species relevant to the aqueous environment. Based on this model, the speciation of carbonic acid, bicarbonate and carbonate have been examined in microsolvated conditions, as well as bulk water. When immersed in a droplet of 98 water molecules and two hydronium ions, the carbonate ion is rapidly converted to bicarbonate, and ultimately carbonic acid, which is formed as the metastable cis-trans isomer under kinetic control. Both first principles and ReaxFF calculations exhibit the same behaviour, but the longer timescale accessible to the latter allows the diffusion of the carbonic acid to the surface of the water to be observed, where it is more stable at the interface. Calcium carbonate is also examined as ion pairs in solution for both CaCO(3)(0)((aq)) and CaHCO(3)(+)((aq)), in addition to the (1014) surface in contact with water. PMID:21850319

  15. Automatic photometric titrations of calcium and magnesium in carbonate rocks

    USGS Publications Warehouse

    Shapiro, L.; Brannock, W.W.

    1955-01-01

    Rapid nonsubjective methods have been developed for the determination of calcium and magnesium in carbonate rocks. From a single solution of the sample, calcium is titrated directly, and magnesium is titrated after a rapid removal of R2O3 and precipitation of calcium as the tungstate. A concentrated and a dilute solution of disodium ethylenediamine tetraacetate are used as titrants. The concentrated solution is added almost to the end point, then the weak solution is added in an automatic titrator to determine the end point precisely.

  16. Pathogenic Role of Basic Calcium Phosphate Crystals in Destructive Arthropathies

    PubMed Central

    Ea, Hang-Korng; Chobaz, Véronique; Nguyen, Christelle; Nasi, Sonia; van Lent, Peter; Daudon, Michel; Dessombz, Arnaud; Bazin, Dominique; McCarthy, Geraldine; Jolles-Haeberli, Brigitte; Ives, Annette; Van Linthoudt, Daniel; So, Alexander; Lioté, Frédéric; Busso, Nathalie

    2013-01-01

    Background basic calcium phosphate (BCP) crystals are commonly found in osteoarthritis (OA) and are associated with cartilage destruction. BCP crystals induce in vitro catabolic responses with the production of metalloproteases and inflammatory cytokines such as interleukin-1 (IL-1). In vivo, IL-1 production induced by BCP crystals is both dependant and independent of NLRP3 inflammasome. We aimed to clarify 1/ the role of BCP crystals in cartilage destruction and 2/ the role of IL-1 and NLRP3 inflammasome in cartilage degradation related to BCP crystals. Methodology/ Principal Findings synovial membranes isolated from OA knees were analysed by alizarin Red and FTIR. Pyrogen free BCP crystals were injected into right knees of WT, NLRP3 -/-, ASC -/-, IL-1? -/- and IL-1?-/- mice and PBS was injected into left knees. To assess the role of IL-1, WT mice were treated by intra-peritoneal injections of anakinra, the IL-1Ra recombinant protein, or PBS. Articular destruction was studied at d4, d17 and d30 assessing synovial inflammation, proteoglycan loss and chondrocyte apoptosis. BCP crystals were frequently found in OA synovial membranes including low grade OA. BCP crystals injected into murine knee joints provoked synovial inflammation characterized by synovial macrophage infiltration that persisted at day 30, cartilage degradation as evidenced by loss of proteoglycan staining by Safranin-O and concomitant expression of VDIPEN epitopes, and increased chondrocyte apoptosis. BCP crystal-induced synovitis was totally independent of IL-1? and IL-1? signalling and no alterations of inflammation were observed in mice deficient for components of the NLRP3-inflammasome, IL-1? or IL-1?. Similarly, treatment with anakinra did not prevent BCP crystal effects. In vitro, BCP crystals elicited enhanced transcription of matrix degrading and pro-inflammatory genes in macrophages. Conclusions/ Significance intra-articular BCP crystals can elicit synovial inflammation and cartilage degradation suggesting that BCP crystals have a direct pathogenic role in OA. The effects are independent of IL-1 and NLRP3 inflammasome. PMID:23468973

  17. Crystal growth of lanthanum calcium borate (LCB) single crystals from melt and its characterization

    NASA Astrophysics Data System (ADS)

    Senthi lkumar, M.; Kalidasan, M.; Sugan; Dhanasekaran, R.

    2013-01-01

    Non-linear optical lanthanum calcium borate (LCB) single crystals were grown by the melt growth method using the Czohralski technique. The polycrystalline LCB compound is synthesized using the solid state reaction method. The grown crystals were characterized by XRD, EDAX, DTA, HRXRD, specific heat, dielectric and NLO studies. The powder XRD pattern revealed the formation of LCB compound and the lattice parameters of the grown crystals were identified through single crystal XRD studies. The melting point of the LCB compound is analyzed by the DTA measurements. Good crystalline nature of the grown crystal is observed from HRXRD analysis. Specific heat measurements in the temperature range 50-550 °C are carried out for the as grown crystal samples. The results obtained by the dielectric and NLO studies are also presented.

  18. Alginate-controlled formation of nanoscale calcium carbonate and hydroxyapatite mineral phase within hydrogel networks

    Microsoft Academic Search

    Minli Xie; Magnus Ø. Olderøy; Jens-Petter Andreassen; Sverre Magnus Selbach; Berit L. Strand; Pawel Sikorski

    2010-01-01

    A one-step method was used to make nanostructured composites from alginate and calcium carbonate or calcium phosphate. Nanometer-scale mineral phase was successfully formed within the gel network of alginate gel beads, and the composites were characterized. It was found that calcite was the dominating polymorph in the calcium carbonate mineralized beads, while stoichiometric hydroxyapatite was formed in the calcium phosphate

  19. Crystal growth of calcium apatites from dilute solutions

    NASA Astrophysics Data System (ADS)

    Moreno, E. C.; Varughese, K.

    1981-05-01

    The dependence of the kinetics of crystal growth of hydroxyapatite, HA, on concentration of seeds and degree of solution supersaturation is examined. Empirical relations are obtained between the initial rates of precipitation and the two aforementioned variables. The results clearly indicate that the precipitating phase, under the selected experimental conditions, is HA. The driving force for precipitation is the supersaturation with respect to this calcium phosphate. The data obtained from kinetic studies are consistent with the BCF theory of crystal growth which relates the mean linear rate of growth to the degree of supersaturation. This observation is also valid for systems in which the precipitating phases are fluoridated hydroxyapatites, Ca 5F x?(OH) 1- x(PO 4) 3, FHA. In this case, supersaturation is calculated with respect to the specific FHA precipitated. The degree of fluoridation, x, appears to be determined by the activity of hydrofluoric acid in solution which remains fairly constant during precipitation but varies for each initial fluoride concentration used. Studies are reported on the kinetics of crystal growth of HA in the presence of biological inhibitors. Two proline-rich proteins and a peptide, statherin, of salivary origin are powerful inhibitors of HA crystal growth. It appears that their mode of action is related to their adsorption onto the surface of apatite seeds. The results suggest that the adsorption sites are the same as the sites where crystal growth takes place.

  20. Distribution of calcium carbonate in desert soils: A model

    SciTech Connect

    Mayer, L.; McFadden, L.D.; Harden, J.W.

    1988-04-01

    A model that describes the distribution of calcium carbonate in desert soils as a function of dust flux, time, climate, and other soil-forming factors shows which factors most strongly influence the accumulation of carbonate and can be used to evaluate carbonate-based soil age estimates or paleoclimatic reconstructions. Models for late Holocene soils have produced carbonate distributions that are very similar to those of well-dated soils in New Mexico and southern California. These results suggest that (1) present climate is a fair representation of late Holocene climate, (2) carbonate dust flux can be approximated by its Holocene rate, and (3) changes in climate and/or dust flux at the end of the Pleistocene effected profound and complex changes in soil carbonate distributions. Both higher carbonate dust flux and greater effective precipitation are required during the latest Pleistocene-early Holocene to explain carbonate distributions in latest Pleistocene soils. 21 refs., 4 figs., 1 tab.

  1. Structural changes in a protein fragment from abalone shell during the precipitation of calcium carbonate.

    PubMed

    Adamiano, Alessio; Bonacchi, Sara; Calonghi, Natalia; Fabbri, Daniele; Falini, Giuseppe; Fermani, Simona; Genovese, Damiano; Kralj, Damir; Montalti, Marco; Njegi? Džakula, Branka; Prodi, Luca; Sartor, Giorgio

    2012-11-01

    Mineralized tissues grow through biologically controlled processes in which specific macromolecules are involved. Some of these molecules, which are present in very low concentrations and are difficult to localize and characterize, become entrapped inside the mineralized tissue. Herein, a protein fragment, GP, which was obtained by the alkaline digestion of the green sheet of the abalone shell, is used as a probe to study the changes in molecular structure that occur during the precipitation of calcium carbonate. This important goal was achieved by exploiting a fluorescent tag in GP. The experimental results that were obtained by using spectroscopic-, chromatographic-, and microscopic techniques indicate that GP controls the precipitation kinetics and morphology of calcium carbonate crystals, and that it only undergoes structural reorganization when entrapped inside calcium carbonate crystals. To the best of our knowledge, this report represents one of the first studies on the conformational changes of a protein fragment that is involved in biomineralization processes on moving from the solution phase into the mineral phase. PMID:22996327

  2. Calcium supplements

    MedlinePLUS

    ... The two main forms of calcium pills are: Calcium carbonate: Over-the-counter antacid products, such as Tums and Rolaids contain calcium carbonate. These sources of calcium carbonate do not cost ...

  3. Calcium absorbability from milk products, an imitation milk, and calcium carbonate

    Microsoft Academic Search

    R. R. Recker; A. Bammi; M. J. Barger-Lux; R. P. Heaney

    1988-01-01

    Whole milk, chocolate milk, yogurt, imitation milk (prepared from dairy and nondairy products), cheese, and calcium carbonate were labeled with ⁴⁵Ca and administered as a series of test meals to 10 healthy postmenopausal women. Carrier Ca content of the test meals was held constant at 250 mg and subjects fasted before each meal. The absorbability of Ca from the six

  4. ATP-stabilized amorphous calcium carbonate nanospheres and their application in protein adsorption.

    PubMed

    Qi, Chao; Zhu, Ying-Jie; Lu, Bing-Qiang; Zhao, Xin-Yu; Zhao, Jing; Chen, Feng; Wu, Jin

    2014-05-28

    Calcium carbonate is a common substance found in rocks worldwide, and is the main biomineral formed in shells of marine organisms and snails, pearls and eggshells. Amorphous calcium carbonate (ACC) is the least stable polymorph of calcium carbonate, which is so unstable under normal conditions that it is difficult to be prepared in vitro because it rapidly crystallizes to form one of the more stable polymorphs in aqueous solution. Herein, we report the successful synthesis of highly stable ACC nanospheres in vitro using adenosine 5'-triphosphate disodium salt (ATP) as a stabilizer. The effect of ATP on the stability of ACC nanospheres is investigated. Our experiments show that ATP plays an unique role in the stabilization of ACC nanospheres in aqueous solution. Moreover, the as-prepared ACC nanospheres are highly stable in phosphate buffered saline for a relatively long period of time (12 days) even under relatively high concentrations of calcium and phosphate ions. The cytotoxicity tests show that the as-prepared highly stable ACC nanospheres have excellent biocompatibility. The highly stable ACC nanospheres have high protein adsorption capacity, implying that they are promising for applications in biomedical fields such as drug delivery and protein adsorption. PMID:24578276

  5. A critical analysis of calcium carbonate mesocrystals

    NASA Astrophysics Data System (ADS)

    Kim, Yi-Yeoun; Schenk, Anna S.; Ihli, Johannes; Kulak, Alex N.; Hetherington, Nicola B. J.; Tang, Chiu C.; Schmahl, Wolfgang W.; Griesshaber, Erika; Hyett, Geoffrey; Meldrum, Fiona C.

    2014-07-01

    The term mesocrystal has been widely used to describe crystals that form by oriented assembly, and that exhibit nanoparticle substructures. Using calcite crystals co-precipitated with polymers as a suitable test case, this article looks critically at the concept of mesocrystals. Here we demonstrate that the data commonly used to assign mesocrystal structure may be frequently misinterpreted, and that these calcite/polymer crystals do not have nanoparticle substructures. Although morphologies suggest the presence of nanoparticles, these are only present on the crystal surface. High surface areas are only recorded for crystals freshly removed from solution and are again attributed to a thin shell of nanoparticles on a solid calcite core. Line broadening in powder X-ray diffraction spectra is due to lattice strain only, precluding the existence of a nanoparticle sub-structure. Finally, study of the formation mechanism provides no evidence for crystalline precursor particles. A re-evaluation of existing literature on some mesocrystals may therefore be required.

  6. Deposition of calcium carbonate films by a polymer-induced liquid-precursor (PILP) process

    NASA Astrophysics Data System (ADS)

    Gower, Laurie B.; Odom, Damian J.

    2000-03-01

    A polypeptide additive has been used to transform the solution crystallization of calcium carbonate to a solidification process of a liquid-phase mineral precursor. In situ observations reveal that polyaspartate induces liquid-liquid phase separation of droplets of a mineral precursor. The droplets deposit on the substrate and coalesce to form a coating, which then solidifies into calcitic tablets and films. Transition bars form during the amorphous to crystalline transition, leading to sectorization of calcite tablets, and the defect textures and crystal morphologies are atypical of solution grown crystals. The formation of nonequilibrium crystal morphologies using an acidic polypeptide may have implications in the field of biomineralization, and the environmentally friendly aspects of this polymer-induced liquid-precursor (PILP) process may offer new techniques for aqueous-based processing of ceramic films, coatings, and particulates.

  7. CRYSTALLIZATION OF CALCIUM PHOSPHATE ORIENTED BY SELF-ASSEMBLING DIBLOCK COPOLYMERS,

    E-print Network

    Amrhein, Valentin

    CRYSTALLIZATION OF CALCIUM PHOSPHATE ORIENTED BY SELF-ASSEMBLING DIBLOCK COPOLYMERS, IN SOLUTION. MINERALIZATION OF CALCIUM PHOSPHATE IN PRESENCE OF DHBC 28 B. AMPHIPHILIC POLY(ETHYLENE OXIDE)-BLOCK-POLY(VALEROLACTONE) DIBLOCK COPOLYMERS AS TEMPLATE FOR CALCIUM PHOSPHATE MINERALIZATION 30 1. SELF-ASSEMBLY IN AQUEOUS

  8. Adsorption of Bovine Serum Albumin on Synthetic Carbonate Calcium Hydroxyapatite

    Microsoft Academic Search

    Kazuhiko Kandori; Miwa Saito; Taro Takebe; Akemi Yasukawa; Tatsuo Ishikawa

    1995-01-01

    Carbonate calcium hydroxyapatites (CAP) containing various amounts of carbonate ions from 0 to 10.1 wt.% were synthesized, and the adsorption behavior of bovine serum albumin (BSA) on these synthetic CAPs was investigated at pH 6.0 and 15°C. The size of the synthetic CAP particles decreased by uptaking CO2-3 ions. The FTIR spectra of CAPs revealed that the CO2-3 ions are

  9. Morphological development in calcium carbonate precipitation by the ethanolamine process

    Microsoft Academic Search

    M. Vu?ak; J. Peri?; M. N. Pons; S. Chanel

    1999-01-01

    Morphological development in calcium carbonate precipitation by the ethanolamine process at 30 and 60°C has been examined using different techniques (quantitative image analysis, laser diffraction, XRD, and FT-IR). The initially grown phase is of vaterite modification that at higher temperatures (60°C) transforms to a more stable aragonite phase within the reactor itself. A comparison of the form and structure of

  10. Porphyrin Amphiphiles as Templates for the Nucleation of Calcium Carbonate

    E-print Network

    Aksay, Ilhan A.

    Porphyrin Amphiphiles as Templates for the Nucleation of Calcium Carbonate Joydeep Lahiri amphiphiles.4-6 Model studies with small amphiphilic molecules at compressed Langmuir interfaces, pioneered associated with protein templates remain unknown at the molecular level. We have synthesized amphiphilic

  11. THE ROLE OF CALCIUM OXALATE CRYSTALS IN MEDICAGO TRUNCATULA DEFENSE AGAINST CHEWING INSECTS.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calcium oxalate crystals are the most common insoluble mineral found in plants and can appear in different sizes and shapes. Functions proposed for the crystals include roles in ion balance, tissue support, detoxification, and in light-gathering and -reflection. We use calcium oxalate defective (cod...

  12. CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTRACTORS

    EPA Science Inventory

    The rate of carbonate mineral dissolution from limestone was studied using a rotating disk apparatus and samples of limestone of varied composition. he purpose of this study was to determine the effect of limestone composition on the kinetics of carbonate mineral dissolution. he ...

  13. Sulfate in foraminiferal calcium carbonate : investigating a potential proxy for sea water carbonate ion concentration

    E-print Network

    Berry, Jeffrey Nicholas

    1988-01-01

    The sulfur content of planktonic and benthic foraminifera was measured in specimens recovered from deep-sea sediment cores and individuals grown in culture. A new method for measuring sulfur in foraminiferal calcium carbonate ...

  14. Crystal structure of the calcium pump of sarcoplasmic reticulum at 2.6 Aresolution

    Microsoft Academic Search

    Chikashi Toyoshima; Masayoshi Nakasako; Hiromi Nomura; Haruo Ogawa

    2000-01-01

    Calcium ATPase is a member of the P-type ATPases that transport ions across the membrane against a concentration gradient. Here we have solved the crystal structure of the calcium ATPase of skeletal muscle sarcoplasmic reticulum (SERCA1a) at 2.6 A ? resolution with two calcium ions bound in the transmembrane domain, which comprises ten a-helices. The two calcium ions are located

  15. A critical analysis of calcium carbonate mesocrystals

    PubMed Central

    Kim, Yi-Yeoun; Schenk, Anna S.; Ihli, Johannes; Kulak, Alex N.; Hetherington, Nicola B. J.; Tang, Chiu C.; Schmahl, Wolfgang W.; Griesshaber, Erika; Hyett, Geoffrey; Meldrum, Fiona C.

    2014-01-01

    The term mesocrystal has been widely used to describe crystals that form by oriented assembly, and that exhibit nanoparticle substructures. Using calcite crystals co-precipitated with polymers as a suitable test case, this article looks critically at the concept of mesocrystals. Here we demonstrate that the data commonly used to assign mesocrystal structure may be frequently misinterpreted, and that these calcite/polymer crystals do not have nanoparticle substructures. Although morphologies suggest the presence of nanoparticles, these are only present on the crystal surface. High surface areas are only recorded for crystals freshly removed from solution and are again attributed to a thin shell of nanoparticles on a solid calcite core. Line broadening in powder X-ray diffraction spectra is due to lattice strain only, precluding the existence of a nanoparticle sub-structure. Finally, study of the formation mechanism provides no evidence for crystalline precursor particles. A re-evaluation of existing literature on some mesocrystals may therefore be required. PMID:25014563

  16. A critical analysis of calcium carbonate mesocrystals.

    PubMed

    Kim, Yi-Yeoun; Schenk, Anna S; Ihli, Johannes; Kulak, Alex N; Hetherington, Nicola B J; Tang, Chiu C; Schmahl, Wolfgang W; Griesshaber, Erika; Hyett, Geoffrey; Meldrum, Fiona C

    2014-01-01

    The term mesocrystal has been widely used to describe crystals that form by oriented assembly, and that exhibit nanoparticle substructures. Using calcite crystals co-precipitated with polymers as a suitable test case, this article looks critically at the concept of mesocrystals. Here we demonstrate that the data commonly used to assign mesocrystal structure may be frequently misinterpreted, and that these calcite/polymer crystals do not have nanoparticle substructures. Although morphologies suggest the presence of nanoparticles, these are only present on the crystal surface. High surface areas are only recorded for crystals freshly removed from solution and are again attributed to a thin shell of nanoparticles on a solid calcite core. Line broadening in powder X-ray diffraction spectra is due to lattice strain only, precluding the existence of a nanoparticle sub-structure. Finally, study of the formation mechanism provides no evidence for crystalline precursor particles. A re-evaluation of existing literature on some mesocrystals may therefore be required. PMID:25014563

  17. Calcium carbonate as a possible dosimeter for high irradiation doses.

    PubMed

    Negron-Mendoza, Alicia; Uribe, Roberto M; Ramos-Bernal, Sergio; Camargo-Raya, Claudia; Gomez-Vidales, Virginia; Kobayashi, Kensei

    2015-06-01

    The aim of this work is to analyze the interactions of 5MeV electron beam radiation and a 290MeV/u Carbon beam with calcium carbonate (powder) at 298K and at different irradiation doses, for the potential use of calcium carbonate as a high-dose dosimeter. The irradiation doses with the electron beam were from 0.015 to 9MGy, and with Carbon beam from 1.5kGy to 8kGy. High-energy radiation induces the formation of free radicals in solid calcium carbonate that can be detected and measured by electron paramagnetic resonance (EPR). An increase of the EPR response for some of the free radicals produced in the sample was observed as a function of the irradiation dose. These measurements are reproducible; the preparation of the sample is simple and inexpensive; and the signal is stable for several months. The response curves show that the dosimeter tends to saturate at 10MGy. Based on these properties, we propose this chemical compound as a high-dose dosimeter, mainly for electron irradiation. PMID:25498239

  18. Accelerated carbonation of Friedel's salt in calcium aluminate cement paste

    SciTech Connect

    Goni, S.; Guerrero, A

    2003-01-01

    The stability of Friedel's salt with respect to carbonation has been studied in calcium aluminate cement (CAC) pastes containing NaCl (3% of Cl{sup -} by weight of cement). Carbonation was carried out on a powdered sample in flowing 5% CO{sub 2} gas at 65% relative humidity to accelerate the process. At an intermediate carbonation step, a part of the sample was washed and dried up to 10 cycles to simulate a dynamic leaching attack. The two processes were followed by means of X-ray diffraction (XRD), pH and Cl{sup -} analyses in the simulated pore solution.

  19. Impact of calcium on struvite crystal size, shape and purity

    NASA Astrophysics Data System (ADS)

    Le Corre, Kristell S.; Valsami-Jones, Eugenia; Hobbs, Phil; Parsons, Simon A.

    2005-10-01

    Struvite precipitation occurs spontaneously in wastewater treatment plants under conditions that are influenced by many factors including concentration of Mg 2+, NH 4+, and PO 43- ions, pH, temperature, and mixing energy. These parameters are often difficult to control and as a result struvite generates problems of scale deposits in areas such as pipes and recirculation pumps. At the same time, struvite is considered as a potentially marketable product as an alternative fertiliser. For those two reasons, it has become important to study the principles of struvite precipitation, and to assess the parameters controlling struvite crystallisation. In the present work, the influence of Ca 2+ ions on the precipitation of struvite was investigated in aqueous solutions containing Mg 2+, NH 4+, and PO 43- ions in a molar ratio 1:2:2 at room temperature and constant pH. Different laboratory experiments have been used to assess the effects of Ca 2+ ions on size, shape, and purity of the crystals formed. Tools used include particle size analysis, X-ray diffraction (XRD), and scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDS). The experimental results showed that the presence of calcium in the media can affect significantly struvite crystal growth and the characteristics of the crystal produced.

  20. Precipitates on granular iron in solutions containing calcium carbonate with trichloroethene and hexavalent chromium.

    PubMed

    Jeen, Sung-Wook; Jambor, John L; Blowes, David W; Gillham, Robert W

    2007-03-15

    Mineralogical examination, using scanning electron microscopy (SEM), X-ray diffractometry (XRD), and optical microscopy, was conducted on the Fe0-bearing reactive materials derived from long-term column experiments undertaken to assess the treatment capacity of Fe0 under different geochemical conditions. The columns received either deionized water or solutions of differing dissolved calcium carbonate concentrations, together either with trichloroethene (TCE) or hexavalent chromium (Cr(VI)). The major reaction product in the columns receiving deionized water was magnetite-maghemite, and for the columns receiving dissolved calcium carbonate, the main products were iron hydroxy carbonate and aragonite. Replacement of Fe0 by reaction products occurred mainly at the edges of the Fe0 particles, and penetrative replacement was focused along cracks and along and around graphitic inclusions. Fibrous or flake-shaped iron hydroxy carbonate mostly replaced the edges of the Fe0 particles. Aragonite had needle-shaped morphology, and some occurred as clusters of crystals. Aragonite was deposited on iron hydroxy carbonate, thus providing at least a partial armoring effect. The mineral was also observed to cement groups of Fe0 particles into compact aggregates. The Cr was present mostly as Cr(III) in Cr(III)-Fe(III) (oxy)hydroxides and in trace amounts in iron hydroxy carbonate. PMID:17410795

  1. Elemental bio-imaging of calcium phosphate crystal deposits in knee samples from arthritic patients

    PubMed Central

    Austin, Christine; Hare, Dominic; Rozelle, Andrew L.; Robinson, William H.; Grimm, Rudolf

    2012-01-01

    Laser ablation inductively coupled plasma mass spectrometry (LA ICP-MS) was employed to image deposits of calcium phosphate based crystals in knee cartilage and synovial fluid from arthritic patients. A reaction/collision cell containing hydrogen minimised plasma interferences on calcium and also improved the image quality without significant sensitivity reduction. Areas of high calcium and phosphorus intensities consistent with crystal deposits were observed for both the cartilage and synovial fluid samples. These areas were also characterised by high magnesium and strontium intensities. Distribution patterns of other elements such as copper and sulfur did not correlate with the crystal deposits. Filtered and non-filtered solutions of calcium phosphate crystals grown in synthetic synovial fluid were also imaged as further evidence of crystal deposits. The crystal deposits were detected in the unfiltered solution, and were absent from the filtered solutions. PMID:21305107

  2. Transformation mechanism of amorphous calcium carbonate into calcite in the sea urchin larval spicule

    PubMed Central

    Politi, Yael; Metzler, Rebecca A.; Abrecht, Mike; Gilbert, Benjamin; Wilt, Fred H.; Sagi, Irit; Addadi, Lia; Weiner, Steve; Gilbert, P. U. P. A.

    2008-01-01

    Sea urchin larval spicules transform amorphous calcium carbonate (ACC) into calcite single crystals. The mechanism of transformation is enigmatic: the transforming spicule displays both amorphous and crystalline properties, with no defined crystallization front. Here, we use X-ray photoelectron emission spectromicroscopy with probing size of 40–200 nm. We resolve 3 distinct mineral phases: An initial short-lived, presumably hydrated ACC phase, followed by an intermediate transient form of ACC, and finally the biogenic crystalline calcite phase. The amorphous and crystalline phases are juxtaposed, often appearing in adjacent sites at a scale of tens of nanometers. We propose that the amorphous-crystal transformation propagates in a tortuous path through preexisting 40- to 100-nm amorphous units, via a secondary nucleation mechanism. PMID:18987314

  3. CALCULATING THE PH OF CALCIUM CARBONATE SATURATION

    EPA Science Inventory

    Two new expressions for the pH of saturation (pH subs) were derived. One is a simplified equation developed from an aqueous carbonate equilibrium system in which correction for ionic strength was considered. The other is a more accurate quadratic formula that involves computerize...

  4. Electromechanically tunable carbon nanofiber photonic crystal.

    PubMed

    Rehammar, Robert; Ghavanini, Farzan Alavian; Magnusson, Roger; Kinaret, Jari M; Enoksson, Peter; Arwin, Hans; Campbell, Eleanor E B

    2013-02-13

    We demonstrate an electrically tunable 2D photonic crystal array constructed from vertically aligned carbon nanofibers. The nanofibers are actuated by applying a voltage between adjacent carbon nanofiber pairs grown directly on metal electrodes, thus dynamically changing the form factor of the photonic crystal lattice. The change in optical properties is characterized using optical diffraction and ellipsometry. The experimental results are shown to be in agreement with theoretical predictions and provide a proof-of-principle for rapidly switchable photonic crystals operating in the visible that can be fabricated using standard nanolithography techniques combined with plasma CVD growth of the nanofibers. PMID:23272804

  5. Effects of trace metals on the inhibition of calcium oxalate crystallization.

    PubMed

    Muñoz, J A; Valiente, M

    2005-08-01

    The aim of this study was to examine the possible effects of some trace metals on the inhibition of calcium oxalate crystallization. A test of urinary lithogenic risk was used to follow the crystallization of calcium oxalate from artificial urine in the presence of several metal ions assayed in their physiological concentrations. Interactions of these metal ions with known inhibitors of such crystallization (phytate, pyrophosphate, citrate and chondroitin sulphate) were also investigated. None of the metals affected the inhibition of calcium oxalate crystallization at concentrations approximating those found in normal urine, with the exception of the Fe3+ ions. Interactions of Fe3+ with some urinary components produced both synergic (phytate and pyrophosphate) and negative (citrate) effects on preventing crystallization. These effects are explained in terms of the affinity of the inhibitors for the calcium oxalate crystal surface and their ability to form stable complexes in urine. Because of the minimal concentrations, we conclude that physiological concentrations of trace elements in urine have no significant influence on calcium oxalate crystallization. In this sense, ferric ions, which exhibit an intrinsic high inhibitory capacity of calcium oxalate crystallization at physiological concentrations, even increased by the concomitant presence of phytate and pyrophosphate, are probably unable to act as powerful inhibitors in the presence of physiological urinary concentrations of citrate, due to the formation of highly stable complexes in solution without inhibitory activity. PMID:15937709

  6. Calcium carbonate scale control, effect of material and inhibitors.

    PubMed

    Macadam, J; Parsons, S A

    2004-01-01

    This paper focuses on developing a reproducible method for reducing calcium carbonate scale formation on heated surfaces where scaling can cause serious problems. It is known that calcium carbonate precipitation is sensitive to impurity ions, such as iron and zinc, even at trace concentration levels. In this paper two sets of experiments are reported. The first experiments were undertaken to investigate the effect of zinc, copper and iron dosing on CaCO3 nucleation and precipitation. Results from the experiments showed that the most effective inhibitor of CaCO3 precipitation was zinc and the effect was linked to dose levels and temperature. Copper and iron had little effect on precipitation in the dose range investigated. The second trial was undertaken to translate the precipitation data to scale formation. These tests were undertaken at 70 degrees C. 5 mg x L(-1) zinc dose reduced the scale formation by 35%. The effect of iron on calcium carbonate scaling rate was not significant. The physical nature of the material on which the scale is formed also influences the scaling. The scaling experiment was also used to investigate the effect of different surface material (stainless steel, copper and aluminium) on CaCO3 scale formation. Copper surface scaled the most. PMID:14982176

  7. Calcium oxalate crystals in Aster squamatus and Bellis perennis (Asteraceae: Astereae)

    Microsoft Academic Search

    Ciler Meric

    2009-01-01

    Calcium oxalate crystals in the tissues and organs of Aster squamatus and Bellis perennis (Asteraceae: Astereae) were investigated and their morphology and distribution were determined with a light microscope. Crystals in various sizes in the stem pith cells of A. squamatus were observed as styloids and bipyramids. No crystals were found in the epidermis and cortex cells of the stem.

  8. Divalent Europium Doped and Un-doped Calcium Iodide Scintillators: Scintillator Characterization and Single Crystal Growth

    SciTech Connect

    Boatner, Lynn A [ORNL; Ramey, Joanne Oxendine [ORNL; Kolopus, James A [ORNL; Neal, John S [ORNL

    2015-01-01

    The alkaline-earth scintillator, CaI2:Eu2+, was initially discovered around 1964 by Hofstadter, Odell, and Schmidt. Serious practical problems quickly arose, however, that were associated with the growth of large monolithic single crystals of this material due to its lamellar, mica-like structure. As a result of its theoretically higher light yield, CaI2:Eu2+ has the potential to exceed the excellent scintillation performance of SrI2:Eu2+. In fact, theoretical predictions for the light yield of CaI2:Eu2+ scintillators suggested that an energy resolution approaching 2% at 662 keV could be achievable. As in the case of the early SrI2:Eu2+ scintillator, the performance of CaI2:Eu2+ scintillators has traditionally suffered due, at least in part, to outdated materials synthesis, component stoichiometry/purity, and single-crystal-growth techniques. Based on our recent work on SrI2:Eu2+ scintillators in single-crystal form, we have developed new techniques that are applied here to CaI2:Eu2+ and pure CaI2 with the goal of growing large un-cracked crystals and, potentially, realizing the theoretically predicted performance of the CaI2:Eu2+ form of this material. Calcium iodide does not adhere to modern glassy carbon Bridgman crucibles - so there should be no differential thermal-contraction-induced crystal/crucible stresses on cooling that would result in crystal cracking of the lamellar structure of CaI2. Here we apply glassy carbon crucible Bridgman growth, high-purity growth-charge compounds, our molten salt processing/filtration technique, and extended vacuum-melt-pumping methods to the growth of both CaI2:Eu2+ and un-doped CaI2. Large scintillating single crystals were obtained, and detailed characterization studies of the scintillation properties of CaI2:Eu2+ and pure CaI2 single crystals are presented that include studies of the effects of plastic deformation of the crystals on the scintillator performance.

  9. Effect of carbonate and phosphate ratios on the transformation of calcium orthophosphates

    SciTech Connect

    Eliassi, Mohammad Daoud, E-mail: eliassi2007@gmail.com [Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China); Zhao, Wei [State Key Laboratory of Soil Erosion and Dryland Farming on Loess Plateau, Institute of Soil and Water Conservation, Chinese Academy of Sciences, Yangling 712100 (China); Tan, Wen Feng, E-mail: wenfeng.tan@hotmail.com [Key Laboratory of Arable Land Conservation (Middle and Lower Reaches of Yangtze River), Ministry of Agriculture, College of Resources and Environment, Huazhong Agricultural University, Wuhan 430070 (China)

    2014-07-01

    Graphical abstract: Complexes among phosphate, carbonate and calcium have been prepared via a facile hydrothermal route. The synthesized product at the low (0.15) and the high (1.8) molar ratio of PO{sub 4}{sup 3?}/CO{sub 3}{sup 2?} is calcium phosphate hydrate and hydroxylapatite (HAp), respectively. Molar ratios of PO{sub 4}{sup 3?}/CO{sub 3}{sup 2?} are effective on the reduction of carbonate activity during the crystallization of HAp. - Highlights: • Formation of different complexes from CO{sub 3}{sup 2?}, PO{sub 4}{sup 3?} and Ca{sup 2+} solutions at 60 °C. • Molar ratios of PO{sub 4}{sup 3?}/CO{sub 3}{sup 2} cause changes in phase and size of synthesized products. • Addition of PO{sub 4}{sup 3} inhibited the activity of CO{sub 3}{sup 2?} during bound with Ca{sup 2+}. • The phase transformation was completed, when CO{sub 3}{sup 2?} peaks disappeared in FTIR. • PO{sub 4}{sup 3?}, CO{sub 3}{sup 2?} and Ca{sup 2+} distributed heterogeneously on the surface of precipitation. - Abstract: Complexes among phosphate, carbonate and calcium have been synthesized by a designed hydrothermal method. Effects of carbonate and phosphate ratios on the transformation of calcium-orthophosphates were investigated. With X-ray diffraction measurement the synthesized product at the low (0.15) and the high (1.8) molar ratio of PO{sub 4}{sup 3?}/CO{sub 3}{sup 2?} is calcium phosphate hydrate at pH 9.0, and hydroxylapatite (HAp) at pH 8.0, respectively. Fourier transform infrared spectroscopy of product at the high ratio (1.8) of PO{sub 4}{sup 3?}/CO{sub 3}{sup 2?} shows that the CO{sub 3}{sup 2?} peaks disappear, and the strong peaks at 1412 and 1460 cm{sup ?1} are assigned to the vibrations of PO{sub 4}{sup 3?} in HAp. {sup 31}P nuclear magnetic resonance spectra of products at the low (0.15–0.6) to the high (1.2–1.8) ratios of PO{sub 4}{sup 3?}/CO{sub 3}{sup 2?} are obtained at 2.9 and 2.7 ppm, respectively. Molar ratios of PO{sub 4}{sup 3?}/CO{sub 3}{sup 2?} are effective on the reduction of carbonate activity during the formation and infiltration events of calcium-phosphate surface precipitates, and are subsequently enclosed during HAp formation.

  10. Comparison of the Absorption of Calcium Carbonate and Calcium Citrate after Roux-en-Y Gastric Bypass

    PubMed Central

    Tondapu, P.; Provost, D.; Adams-Huet, B.; Sims, T.; Chang, C.; Sakhaee, K.

    2015-01-01

    Introduction Roux-en-Y gastric bypass (RYGB) restricts food intake. Consequently, patients consume less calcium. In addition, food no longer passes through the duodenum, the main site of calcium absorption. Therefore, calcium absorption is significantly impaired. The goal of this study is to compare two common calcium supplements in gastric bypass patients. Method Nineteen patients were enrolled in a randomized, double-blinded, crossover study comparing the absorption of calcium from calcium carbonate and calcium citrate salts. Serum and urine calcium levels were assessed for peak values (Cmax) and cumulative calcium increment (area under the curve [AUC]). Serum PTH was assessed for minimum values (PTHmin) and cumulative PTH decrement (AUC). Statistical analysis was performed using a repeated analysis of variance model. Results Eighteen subjects completed the study. Calcium citrate resulted in a significantly higher serum Cmax (9.4+0.4 mg/dl vs. 9.2+0.3 mg/dl, p=0.02) and serum AUC (55+2 mg/dl vs. 54+2 mg/dl, p=0.02). Calcium citrate resulted in a significantly lower PTHmin (24+11 pg/ml vs. 30+13 pg/ml, p=0.01) and a higher AUC (?32+51 pg/ml vs. ?3+56 pg/ml, p=0.04). There was a non-significant trend for higher urinary AUC in the calcium citrate group (76.13+36.39 mg/6 h vs. 66.04+40.82, p=0.17). Conclusion Calcium citrate has superior bioavailability than calcium carbonate in RYGB patients. PMID:19437082

  11. Fractional absorption of active absorbable algal calcium (AAACa) and calcium carbonate measured by a dual stable-isotope method

    Technology Transfer Automated Retrieval System (TEKTRAN)

    With the use of stable isotopes, this study aimed to compare the bioavailability of active absorbable algal calcium (AAACa), obtained from oyster shell powder heated to a high temperature, with an additional heated seaweed component (Heated Algal Ingredient, HAI), with that of calcium carbonate. In ...

  12. The crystal structure of calcium-free human m-calpain suggests an electrostatic switch mechanism for activation by calcium

    PubMed Central

    Strobl, Stefan; Fernandez-Catalan, Carlos; Braun, Marianne; Huber, Robert; Masumoto, Hajime; Nakagawa, Kazuhiro; Irie, Akihiro; Sorimachi, Hiroyuki; Bourenkow, Gleb; Bartunik, Hans; Suzuki, Koichi; Bode, Wolfram

    2000-01-01

    Calpains (calcium-dependent cytoplasmic cysteine proteinases) are implicated in processes such as cytoskeleton remodeling and signal transduction. The 2.3-? crystal structure of full-length heterodimeric [80-kDa (dI-dIV) + 30-kDa (dV+dVI)] human m-calpain crystallized in the absence of calcium reveals an oval disc-like shape, with the papain-like catalytic domain dII and the two calmodulin-like domains dIV+dVI occupying opposite poles, and the tumor necrosis factor ?-like ?-sandwich domain dIII and the N-terminal segments dI+dV located between. Compared with papain, the two subdomains dIIa+dIIb of the catalytic unit are rotated against one another by 50°, disrupting the active site and the substrate binding site, explaining the inactivity of calpains in the absence of calcium. Calcium binding to an extremely negatively charged loop of domain dIII (an electrostatic switch) could release the adjacent barrel-like subdomain dIIb to move toward the helical subdomain dIIa, allowing formation of a functional catalytic center. This switch loop could also mediate membrane binding, thereby explaining calpains' strongly reduced calcium requirements in vivo. The activity status at the catalytic center might be further modulated by calcium binding to the calmodulin domains via the N-terminal linkers. PMID:10639123

  13. The co-effect of organic matrix from carp otolith and microenvironment on calcium carbonate mineralization.

    PubMed

    Ren, Dongni; Feng, Qingling; Bourrat, Xavier

    2013-08-01

    In vitro mineralization experiment is an effective way to study the effect of organic matrix on calcium carbonate crystallization, and to reveal the relationship between organic matrix and inorganic crystal in natural biominerals. In natural biominerals, organic matrix plays an important role in crystal formation and stability, together with microenvironment changes, they can affect crystal polymorph, morphology, density, size, orientation etc. In this work, we systematically studied the effects of different organic matrices in fish otoliths, the organic matrix concentration changes, as well as the co-effect of organic matrices with temperature, pH value and Mg ion changes in the in vitro CaCO3 mineralization experiments. The organic matrix and concentration change experiments prove that water soluble matrix (WSM) plays an important role in crystal form transition. It can induce CaCO3 crystals with same crystal polymorph as the otolith from which organic matrix was extracted. The temperature change experiment proves that CaCO3 has a tendency to form calcite, vaterite, and then aragonite in priority as temperature goes up. Under different temperature, WSM from lapillus/asteriscus still has the effect to mediate different CaCO3 crystals. The pH change experiment shows that, near the neutral environment, as pH value goes up, calcites have a tendency to form crystal aggregates with more faces exposed, the organic matrix still keeps crystal mediation effect. The Mg(2+) experiment shows that, Mg ion can promote aragonite formation, together with lapillus organic matrix, aragonites with different shapes are formed. PMID:23706232

  14. Application of pulsed spark discharge for calcium carbonate precipitation in hard water.

    PubMed

    Yang, Yong; Kim, Hyoungsup; Starikovskiy, Andrey; Fridman, Alexander; Cho, Young I

    2010-06-01

    The effect of underwater pulsed spark discharge on the precipitation of dissolved calcium ions was investigated in the present study. Water samples with different calcium hardness were prepared by continuous evaporation of tap water using a laboratory cooling tower. It was shown that the concentration of calcium ions dropped by 20-26% after 10-min plasma treatment, comparing with no drop for untreated cases. A laser particle counting method demonstrated that the total number of solid particles suspended in water increased by over 100% after the plasma treatment. The morphology and the crystal form of the particles were identified by both scanning electron microscopy and X-ray diffraction. Calcite with rhombohedron morphology was observed for plasma treated cases, comparing with the round structure observed for no-treatment cases. It was hypothesized that the main mechanisms for the plasma-assisted calcium carbonate precipitation might include electrolysis, local heating in the vicinity of plasma channel and a high electric field at the tip of plasma streamers, inducing structural changes in the electric double layer of hydrated ions. PMID:20494397

  15. Measurement of the spin diffusion rate of dipolar order in single crystal calcium fluoride

    E-print Network

    Boutis, Gregory Steven, 1975-

    2002-01-01

    This thesis reports on the first measurement of the spin diffusion rate of a two-spin correlated state, known as dipolar order, in a single crystal of calcium fluoride. The experimental results for the component of the ...

  16. Production and accumulation of calcium carbonate in the ocean: Budget of a nonsteady state

    SciTech Connect

    Milliman, J.D. (Woods Hole Oceanographic Institution, MA (United States))

    1993-12-01

    The calcium carbonate budget in the ocean has become of great interest to geochemists, sedimentologists and paleoceanographers. The carbonate system represents only a small part of the global carbon cycle, but it is intimately related to atmospheric carbon dioxide. This paper discusses calcium carbonate production and accumulations in the present-day marine environment and over the past 25,000 years. The new data faciliate a reevaluation of sea level control on the carbonate budget and allows redefinition of conceptual gaps. Oceans presently sediment more calcium as calcium carbonate than is brought in by terrestrial and hydrothermal sources; According to this model, oceans are seldom if ever in steady state in reguard to calcium carbonate. 197 refs., 13 figs., 3 tabs.

  17. ISOLATED MEDICAGO TRUNCATULA MUTANTS WITH INCREASED CALCIUM OXALATE CRYSTAL ACCUMULATION HAVE DECREASED ASCORBIC ACID LEVELS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The mechanisms controlling oxalate biosynthesis and calcium oxalate formation in plants remains largely unknown. As an initial step toward gaining insight into these regulatory mechanisms we initiated a mutant screen to identify plants that over-accumulate crystals of calcium oxalate. Four new mut...

  18. ADVANCES IN OUR UNDERSTANDING OF CALCIUM OXALATE CRYSTAL FORMATION AND FUNCTION IN PLANTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calcium oxalate crystal formation in plants appears to play a central role in a variety of important functions, including tissue calcium regulation, protection from herbivory, and metal detoxification. Evidence is mounting to support ascorbic acid as the primary precursor to oxalate biosynthesis. ...

  19. Nonstarter Lactic Acid Bacteria and Aging Temperature Affect Calcium Lactate Crystallization in Cheddar Cheese

    Microsoft Academic Search

    Y.-E. Chou; C. G. Edwards; L. O. Luedecke; M. P. Bates; S. Clark

    2003-01-01

    The occurrence of unappetizing calcium lactate crys- tals in Cheddar cheese is a challenge and expense to manufacturers, and this research was designed to un- derstand their origin. It was hypothesized that non- starter lactic acid bacteria (NSLAB) affect calcium lac- tate crystallization (CLC) by producing D(?)-lactate. This study was designed to understand the effect of NSLAB growth and aging

  20. Precipitation of calcium carbonate and calcium phosphate under diffusion controlled mixing

    SciTech Connect

    Tsigabu Gebrehiwet; James R. Henriksen; Luanjing Guo; Don T. Fox; Hai Huang; Lee Tu; Yoshiko Fujita; Robert W. Smith; George Redden

    2014-07-01

    Multi-component mineral precipitation in porous, subsurface environments is challenging to simulate or engineer when in situ reactant mixing is controlled by diffusion. In contrast to well-mixed systems, the conditions that favor mineral precipitation in porous media are distributed along chemical gradients, which evolve spatially due to concurrent mineral precipitation and modification of solute transport in the media. The resulting physical and chemical characteristics of a mixing/precipitation zone are a consequence of coupling between transport and chemical processes, and the distinctive properties of individual chemical systems. We examined the spatial distribution of precipitates formed in “double diffusion” columns for two chemical systems, calcium carbonate and calcium phosphate. Polyacrylamide hydrogel was used as a low permeability, high porosity medium to maximize diffusive mixing and minimize pressure- and density-driven flow between reactant solutions. In the calcium phosphate system, multiple, visually dense and narrow bands of precipitates were observed that were reminiscent of previously reported Liesegang patterns. In the calcium carbonate system, wider precipitation zones characterized by more sparse distributions of precipitates and a more open channel structure were observed. In both cases, formation of precipitates inhibited, but did not necessarily eliminate, continued transport and mixing of the reactants. A reactive transport model with fully implicit coupling between diffusion, chemical speciation and precipitation kinetics, but where explicit details of nucleation processes were neglected, was able to qualitatively simulate properties of the precipitation zones. The results help to illustrate how changes in the physical properties of a precipitation zone depend on coupling between diffusion-controlled reactant mixing and chemistry-specific details of precipitation kinetics.

  1. Carbonate-containing apatite (CAP) synthesis under moderate conditions starting from calcium carbonate and orthophosphoric acid.

    PubMed

    Pham Minh, Doan; Tran, Ngoc Dung; Nzihou, Ange; Sharrock, Patrick

    2013-07-01

    The synthesis of carbonate-containing apatite (CAP) from calcium carbonate and orthophosphoric acid under moderate conditions was investigated. In all cases, complete precipitation of orthophosphate species was observed. The reaction temperature influenced strongly the decomposition of calcium carbonate and therefore the composition of formed products. The reaction temperature of 80 °C was found to be effective for the complete decomposition of calcium carbonate particles after 48 h of reaction. Infra-red spectroscopy (IR), nuclear magnetic resonance (NMR), thermogravimetry/mass spectroscopy (TG-MS) coupling, and X-ray diffraction (XRD) characterizations allowed the identification of the composition of formed products. By increasing the reaction temperature from 20 °C to 80 °C, the content of A-type CAP increased and that of B-type CAP decreased, according to the favorable effect of temperature on the formation of A-type CAP. The total amount of carbonate content incorporated in CAP's structure, which was determined by TG-MS analysis, increased with the reaction temperature and reached up to 4.1% at 80 °C. At this temperature, the solid product was mainly composed of apatitic components and showed the typical flat-needle-like structure of CAP particles obtained in hydrothermal conditions. These results show an interesting one-step synthesis of CAP from calcium carbonate and orthophosphoric acid as low cost but high purity starting materials. PMID:23623121

  2. New kinetic model for the rapid step of calcium oxide carbonation by carbon dioxide Authors: Lydie Rouchon, Loc Favergeon, Michle Pijolat

    E-print Network

    Boyer, Edmond

    New kinetic model for the rapid step of calcium oxide carbonation by carbon dioxide Authors: Lydie oxide by gaseous carbon dioxide was monitored by thermogravimetry (TG). A kinetic model of Ca 94. Keywords: Carbonation, Calcium oxide, Kinetic modeling, TG Abstract Carbonation of solid calcium

  3. Characterization of bacteria isolated from palaeoproterozoic metasediments for sequestration of carbon dioxide and formation of calcium carbonate.

    PubMed

    Srivastava, Shaili; Bharti, Randhir K; Thakur, Indu Shekhar

    2015-01-01

    Bacterial community of palaeoproterozoic metasediments was enriched in the chemostat in the presence of different concentrations of NaHCO3. Six bacterial isolates were isolated from the chemostat on nutrient agar plates on the basis of distinct morphology. Denaturing gradient gel electrophoresis (DGGE) proved the presence of six operational taxonomic units (OTUs) at 50 and 100 mM NaHCO3. The OTU was reduced to three and one at enrichment concentration of 150 and 200 mM NaHCO3 respectively. These six isolates were tested for sequestration of carbon dioxide by (14)C metabolic labeling of NaH(14)CO3. Among the six isolates, one of the bacterium showed better potency to fix radiolabeled NaH(14)CO3. The isolate (ISTD04) was identified as Serratia sp. by 16S ribosomal RNA (16S rRNA) sequence analysis and was found to be same as the DGGE OTU sequence at 200-mM NaHCO3 concentration. The bacterium was tested for product formation in form of calcite crystals in presence of 5 % CO2. Scanning electron microscopy (SEM) of product formed by the bacterium revealed defined faceted rhombohedral structure which resembled calcite and vaterite phases of the crystal. Formation of calcium carbonate crystals was further confirmed by Fourier transform infrared (FTIR) spectroscopy as carbonate group showing strong vibration at 1,456 cm(-1). Major calcite phase diffraction peaks were determined by X-ray diffraction (XRD) analysis, and energy-dispersive X-ray (EDX) analysis showed the presence of CaO (72 %) and carbon (18 %). Bacterium use bicarbonate as carbon source for their growth as well as by-product formation in form of calcite shows carbon circulation and storage. PMID:25163561

  4. Nucleation of calcium oxalate crystals on an imprinted polymer surface from pure aqueous solution and urine

    Microsoft Academic Search

    Timothy J. Egan; AllenL Rodgers; Tewolde Siele

    2004-01-01

    Calcium oxalate (CaOx) is the most common component of human kidney stones. Heterogeneous nucleation is regarded as the key mechanism in this process. In this study, we have used an imprinted 6-methacrylamidohexanoic acid\\/divinylbenzene co-polymer as a biomimetic surface to nucleate CaOx crystal formation. The polymer was imprinted with either calcium oxalate monohydrate (COM) or dihydrate (COD) template crystals. These were

  5. Influence of polyvinylpyrrolidone on the precipitation of calcium carbonate and on the transformation of vaterite to calcite

    Microsoft Academic Search

    Hao Wei; Qiang Shen; Ying Zhao; Du-Jin Wang; Duan-Fu Xu

    2003-01-01

    The precipitation process of calcium carbonate (CaCO3) in the absence and presence of poly (N-vinyl-2-pyrrolidone) (PVP) was investigated using scanning electron microscopy, powder X-ray diffraction, and Fourier transform infrared spectroscopy methods at room temperature. The results indicate that PVP does not affect the polymorphy, but has influence on their morphology and size of CaCO3 crystals. With the addition of PVP,

  6. Calcium

    MedlinePLUS

    ... Consumer Datos en español Health Professional Other Resources Calcium Fact Sheet for Consumers What is calcium and what does it do? Calcium is a ... find out more about calcium? Disclaimer How much calcium do I need? The amount of calcium you ...

  7. Increased calcium absorption from synthetic stable amorphous calcium carbonate: double-blind randomized crossover clinical trial in postmenopausal women.

    PubMed

    Vaisman, Nachum; Shaltiel, Galit; Daniely, Michal; Meiron, Oren E; Shechter, Assaf; Abrams, Steven A; Niv, Eva; Shapira, Yami; Sagi, Amir

    2014-10-01

    Calcium supplementation is a widely recognized strategy for achieving adequate calcium intake. We designed this blinded, randomized, crossover interventional trial to compare the bioavailability of a new stable synthetic amorphous calcium carbonate (ACC) with that of crystalline calcium carbonate (CCC) using the dual stable isotope technique. The study was conducted in the Unit of Clinical Nutrition, Tel Aviv Sourasky Medical Center, Israel. The study population included 15 early postmenopausal women aged 54.9 ± 2.8 (mean ± SD) years with no history of major medical illness or metabolic bone disorder, excess calcium intake, or vitamin D deficiency. Standardized breakfast was followed by randomly provided CCC or ACC capsules containing 192 mg elemental calcium labeled with 44Ca at intervals of at least 3 weeks. After swallowing the capsules, intravenous CaCl2 labeled with 42Ca on was administered on each occasion. Fractional calcium absorption (FCA) of ACC and CCC was calculated from the 24-hour urine collection following calcium administration. The results indicated that FCA of ACC was doubled (± 0.96 SD) on average compared to that of CCC (p < 0.02). The higher absorption of the synthetic stable ACC may serve as a more efficacious way of calcium supplementation. PMID:24753014

  8. Plants defective in calcium oxalate crystal formation have more bioavailable calcium

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bioavailable calcium affects bone formation and calcification. Here we investigate how a single gene mutation altering calcium partitioning in the forage crop Medicago truncatula affects calcium bioavailability. Previously, the cod5 Medicago mutant was identified which contains wild-type amounts o...

  9. Multi-Functions of Carbonated Calcium Deficient Hydroxyapatite (CDHA)

    NASA Astrophysics Data System (ADS)

    Zhou, Huan

    Natural bone is a complex composite mainly constituted of inorganic minerals and organic collagen molecules. Calcium phosphate (CaP) based materials have been proposed as the predominant bone substitute for bone tissue engineering applications due to their chemical similarity to bone mineral. Amorphous carbonated calcium deficient hydroxyapatite (CDHA) is an important compound among CaP materials because of the amorphous crystallite structure. The presence of extra ions in its lattice structure not only influences cell attachment and proliferation of osteoblasts, but also helps in bone metabolism. Biomimetic coating approach is the most widely used approach to produce CDHA coatings to implant. It is a process using simulated body fluid (SBF) to deposit bone-like CDHA coating to various material surfaces. The CDHA formation mechanism, SBF compositions and reacting conditions of biomimetic coating have already been sufficiently studied and compared in the past 20 years. It is an attempt in this thesis to explore new applications of SBF in biomedical research, focusing on different biomaterial applications: 1) based on the low temperature reaction condition of SBF, bisphosphonate incorporated CDHA coatings were deposited onto Ti6Al4V surface for the treatment of osteoporosis; 2) amorphous calcium phosphate nanospheres with extra elements in the lattice structure were prepared by a novel microwave assisted approach, providing a new potential of CaP materials production; 3) CDHA particles formed in SBF can be used as great fillers with biopolymers for preparing biocomposites for biomedical applications; 4) based on the high activity of CDHA amorphous structure and the stabilization ability of ethanol, yttrium and europium doped calcium phosphates were prepared using CDHA as a sacrificing template. In the end, future work based on these observations in the thesis is addressed, including areas of drug delivery, biocomposite fabrication and preparation of functionalized calcium phosphate materials.

  10. Calcium isotope evidence for suppression of carbonate dissolution in carbonate-bearing organic-rich sediments

    NASA Astrophysics Data System (ADS)

    Turchyn, Alexandra V.; DePaolo, Donald J.

    2011-11-01

    Pore fluid calcium isotope, calcium concentration and strontium concentration data are used to measure the rates of diagenetic dissolution and precipitation of calcite in deep-sea sediments containing abundant clay and organic material. This type of study of deep-sea sediment diagenesis provides unique information about the ultra-slow chemical reactions that occur in natural marine sediments that affect global geochemical cycles and the preservation of paleo-environmental information in carbonate fossils. For this study, calcium isotope ratios (? 44/40Ca) of pore fluid calcium from Ocean Drilling Program (ODP) Sites 984 (North Atlantic) and 1082 (off the coast of West Africa) were measured to augment available pore fluid measurements of calcium and strontium concentration. Both study sites have high sedimentation rates and support quantitative sulfate reduction, methanogenesis and anaerobic methane oxidation. The pattern of change of ? 44/40Ca of pore fluid calcium versus depth at Sites 984 and 1082 differs markedly from that of previously studied deep-sea Sites like 590B and 807, which are composed of nearly pure carbonate sediment. In the 984 and 1082 pore fluids, ? 44/40Ca remains elevated near seawater values deep in the sediments, rather than shifting rapidly toward the ? 44/40Ca of carbonate solids. This observation indicates that the rate of calcite dissolution is far lower than at previously studied carbonate-rich sites. The data are fit using a numerical model, as well as more approximate analytical models, to estimate the rates of carbonate dissolution and precipitation and the relationship of these rates to the abundance of clay and organic material. Our models give mutually consistent results and indicate that calcite dissolution rates at Sites 984 and 1082 are roughly two orders of magnitude lower than at previously studied carbonate-rich sites, and the rate correlates with the abundance of clay. Our calculated rates are conservative for these sites (the actual rates could be significantly slower) because other processes that impact the calcium isotope composition of sedimentary pore fluid have not been included. The results provide direct geochemical evidence for the anecdotal observation that the best-preserved carbonate fossils are often found in clay or organic-rich sedimentary horizons. The results also suggest that the presence of clay minerals has a strong passivating effect on the surfaces of biogenic carbonate minerals, slowing dissolution dramatically even in relation to the already-slow rates typical of carbonate-rich sediments.

  11. Enhancement of carbon nanotube photoluminescence by photonic crystal nanocavities

    E-print Network

    Maruyama, Shigeo

    Enhancement of carbon nanotube photoluminescence by photonic crystal nanocavities R. Watahiki,1 T 153-8505, Japan Photonic crystal nanocavities are used to enhance photoluminescence from single the emission wavelengths of carbon nanotubes, demonstrating the ability to enhance photoluminescence from

  12. The progression of coronary artery calcification in predialysis patients on calcium carbonate or sevelamer

    Microsoft Academic Search

    D Russo; I Miranda; C Ruocco; Y Battaglia; E Buonanno; S Manzi; L Russo; A Scafarto; V E Andreucci

    2007-01-01

    Coronary artery calcification is more prevalent in dialysis patients than in patients without kidney disease and this is associated with high serum phosphorus. In this study, we evaluate the effect of calcium carbonate or sevelamer treatments on the progression of calcification in 90 predialysis patients. Inclusion criteria were stable serum calcium, phosphorus, parathyroid hormone, and a similar baseline total calcium

  13. Leaf calcium oxalate crystal structure and its role in defense against a chewing insect in Medicago truncatula

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crystals of calcium oxalate are common in plants and widely distributed among many plant families. These hard and largely insoluble crystals take on many shapes and sizes depending on the tissue and species. In Medicago truncatula, calcium oxalate crystals are abundant in leaves and accumulate in sh...

  14. Effects of chondroitin sulphate, human serum albumin and Tamm-Horsfall mucoprotein on calcium oxalate crystallization in undiluted human urine

    Microsoft Academic Search

    R. L. Ryall; R. M. Harnett; C. M. Hibberd; K. A. Edyvane; V. R. Marshall

    1991-01-01

    The effects of physiological concentrations of chondroitin sulphate, human serum albumin and Tamm-Horsfall mucoprotein on the crystallization of calcium oxalate in undiluted, ultrafiltered human urine were investigated using particle size analysis and scanning electron microscopy. Neither the amount of oxalate required to induce detectable calcium oxalate crystal nucleation nor crystal morphology was affected by the presence of any of these

  15. CALCIUM OXALATE CRYSTALS IN LEAVES OF GLYCINE SPECIES AND RELATED TAXA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calcium oxalate (CaOx) crystals occur in about three-fourths of all the flowering plants. The location and structure of the crystals have been used in some systematic studies. The Genus Glycine includes the cultivated soybean, the wild annual soybean, and about 22 wild perennial species. Our obje...

  16. Effect of calcium carbonate saturation of seawater on coral calcification

    USGS Publications Warehouse

    Gattuso, J.-P.; Frankignoulle, M.; Bourge, I.; Romaine, S.; Buddemeier, R.W.

    1998-01-01

    The carbonate chemistry of seawater is usually not considered to be an important factor influencing calcium-carbonate-precipitation by corals because surface seawater is supersaturated with respect to aragonite. Recent reports, however, suggest that it could play a major role in the evolution and biogeography of recent corals. We investigated the calcification rates of five colonies of the zooxanthellate coral Stylophora pistillata in synthetic seawater using the alkalinity anomaly technique. Changes in aragonite saturation from 98% to 585% were obtained by manipulating the calcium concentration. The results show a nonlinear increase in calcification rate as a function of aragonite saturation level. Calcification increases nearly 3-fold when aragonite saturation increases from 98% to 390%, i.e., close to the typical present saturation state of tropical seawater. There is no further increase of calcification at saturation values above this threshold. Preliminary data suggest that another coral species, Acropora sp., displays a similar behaviour. These experimental results suggest: (l) that the rate of calcification does not change significantly within the range of saturation levels corresponding to the last glacial-interglacial cycle, and (2) that it may decrease significantly in the future as a result of the decrease in the saturation level due to anthropogenic release of CO2 into the atmosphere. Experimental studies that control environmental conditions and seawater composition provide unique opportunities to unravel the response of corals to global environmental changes.

  17. Continuous precipitation of calcium carbonate using sonochemical reactor.

    PubMed

    Shirsath, S R; Sonawane, S H; Saini, D R; Pandit, A B

    2015-05-01

    The continuous production of calcium carbonate (CaCO3) by precipitation method at room temperature was carried out in a stirred reactor under ultrasonic environment and was compared with the conventional stirring method. The effect of various operating parameters such as Ca(OH)2 slurry concentration, CO2 flow rate and Ca(OH)2 slurry flow rate on the particle size of CaCO3 was investigated. The calcium carbonate particles were characterized by Fourier transform infrared (FTIR), wide angle X-ray diffraction (WXRD) and particle size. The morphology was studied by using scanning electron microscopic (SEM) images. The particle size obtained in the presence of ultrasonic environment was found to be smaller as compared to conventional stirring method. The particle size is found to be reduced with an increase in the concentrations of Ca(OH)2 and increased with increasing CO2 flow rate for both the methods. The slurry flow rate had a major effect on the particle size and the particle size decreased with increased slurry flow rate. Only calcite phase of CaCO3 was predominantly present as confirmed by the characterization techniques for both the preparation methods. In most of the cases rhombohedral calcite particles were observed. PMID:25534035

  18. Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate

    SciTech Connect

    Mesbah, Adel [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); Cau-dit-Coumes, Celine, E-mail: celine.cau-dit-coumes@cea.fr [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Renaudin, Guillaume [Clermont Universite, ENSCCF, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere (France); Frizon, Fabien [Commissariat a l'Energie Atomique et aux Energies Alternatives, CEA DEN/DTCD/SPDE, F-30207 Bagnols sur Ceze (France); Leroux, Fabrice [Clermont Universite, Universite Blaise Pascal, Laboratoire des Materiaux Inorganiques, BP 10448, F-63000 Clermont-Ferrand (France); CNRS, UMR 6002, F-63177 Aubiere (France)

    2012-08-15

    Decommissioning of old nuclear reactors may produce waste streams containing chlorides and carbonates, including radioactive {sup 36}Cl{sup -} and {sup 14}CO{sub 3}{sup 2-}. Their insolubilization by calcium monosulfoaluminate hydrate was investigated. Carbonates were readily depleted from the solution, giving at thermodynamic equilibrium monocarboaluminate, monocarboaluminate + calcite, or calcite only, depending on the initial ratio between the anion and calcium monosulfoaluminate hydrate. Chloride ions reacted more slowly and were precipitated as Kuzel's salt, Kuzel's and Friedel's salts, or Friedel's salt only. Rietveld refinement of X-Ray powder diffraction patterns was successfully used to quantify the phase distributions, which were compared to thermodynamic calculations. Moreover, analysing the lattice parameters of Kuzel's salt as a function of its chloride content showed the occurrence of a restricted solid solution towards the sulfate side with general formula 3CaO{center_dot}Al{sub 2}O{sub 3}{center_dot}xCaCl{sub 2}{center_dot}(1 - x)CaSO{sub 4}{center_dot}(12 - 2x){center_dot}H{sub 2}O (0.36 {<=} x {<=} 0.50).

  19. Tophaceous pseudogout (tumoral calcium pyrophosphate dihydrate crystal deposition disease)

    Microsoft Academic Search

    Tsuyoshi Ishida; Howard D Dorfman; Peter G Bullough

    1995-01-01

    Most cases of calcium deposition seen radiologically in soft tissues are caused by calcium hydroxyapatite and occur either as a complication of trauma with associated necrosis (eg, fat necrosis), generalized connective tissue diseases (eg, scleroderma), metabolic disturbances (eg, hyperparathyroidism, familial hyperphosphatemia), sarcoidosis, myeloma, or metastases. Hydroxyapatite deposits are seen at many soft tissue sites, including joint capsules, ligaments, blood vessels,

  20. Abstract No Hung0356 A P-XANES Study of Phosphate Sorption to Gibbsite and Calcium Carbonate

    E-print Network

    Sparks, Donald L.

    Abstract No Hung0356 A P-XANES Study of Phosphate Sorption to Gibbsite and Calcium Carbonate S to investigate phosphate sorption reactions to gibbsite (Al(OH)3) in the presence of calcium and to calcium solution and freeze-dried. Samples of phosphate sorbed to calcium carbonate were prepared in a similar

  1. Microbially Induced Calcium Carbonate Precipitation on Surface or in the Bulk of Soil

    Microsoft Academic Search

    Jian Chu; Viktor Stabnikov; Volodymyr Ivanov

    2012-01-01

    Microbial precipitation of calcium carbonate takes place in nature by different mechanisms. One of them is microbially induced carbonate precipitation (MICP), which is performed due to bacterial hydrolysis of urea in soil in the presence of calcium ions. The MICP process can be adopted to reduce the permeability and\\/or increase the shear strength of soil. In this paper, a study

  2. The performance of selected unsaturated coatings for calcium carbonate filler in polypropylene

    Microsoft Academic Search

    Arunee Tabtiang; Richard Venables

    2000-01-01

    The surface of ground calcium carbonate has been modified with several unsaturated acids and acid anhydrides of varying molecular weight. The modified calcium carbonates were then compounded with polypropylene, both in the presence and absence of dicumyl peroxide as an initiator, through twin screw extrusion to give compounds containing 75 phr of filler. Infrared analyses showed that reaction between each

  3. Effect of Strength Enhancement of Soil Treated with Environment-Friendly Calcium Carbonate Powder

    PubMed Central

    Park, Kyungho; Jun, Sangju; Kim, Daehyeon

    2014-01-01

    This study aims to investigate the effects of the strength improvement of soft ground (sand) by producing calcium carbonate powder through microbial reactions. To analyze the cementation effect of calcium carbonate produced through microbial reaction for different weight ratios, four different types of specimens (untreated, calcium carbonate, cement, and calcium carbonate + cement) with different weight ratios (2%, 4%, 6%, and 8%) were produced and cured for a period of 3 days, 7 days, 14 days, 21 days, and 28 days to test them. The uniaxial compression strength of specimens was measured, and the components in the specimen depending on the curing period were analyzed by means of XRD analysis. The result revealed that higher weight ratios and longer curing period contributed to increased strength of calcium carbonate, cement, and calcium carbonate + cement specimens. The calcium carbonate and the calcium carbonate + cement specimens in the same condition showed the tendency of decreased strength approximately 3 times and two times in comparison with the 8% cement specimens cured for 28 days, but the tendency of increased strength was approximately 4 times and 6 times in comparison with the untreated specimen. PMID:24688401

  4. Studies on the growth and characterization of tris (glycine) calcium(??) dichloride—a nonlinear optical crystal

    Microsoft Academic Search

    P. V. Dhanaraj; N. P. Rajesh

    2011-01-01

    A systematic characterization of a novel nonlinear optical material tris (glycine) calcium(??) dichloride (TGCC) is performed. The solubility and metastable zone width of TGCC were studied. TGCC single crystal of dimensions 34×23×5mm3 was grown by the slow evaporation technique. Single crystal X-ray diffraction studies reveal that the crystal belongs to orthorhombic system. Energy dispersive X-ray analysis confirms the presence of

  5. Growth and optical properties of a new nonlinear optical lanthanum calcium borate crystal

    Microsoft Academic Search

    X. W. Xu; T. C. Chong; G. Y. Zhang; S. D. Cheng; M. H. Li; C. C. Phua

    2002-01-01

    The monoclinic lanthanum calcium borate La2CaB10O19 (LCB) crystal was grown from its stoichiometric melt by the top-seeded pulling method. The unpolarized transmission spectrum of a 1-mm-thick (001)-cut LCB crystal was measured in the wavelength range of 190–3100nm. The crystal exhibited a high transmittance (>80%) and a short absorption edge (<190nm). The phase-matched second-harmonic generation (SHG) properties within the (010) plane

  6. In situ calcium carbonate dissolution in the Pacific Ocean

    SciTech Connect

    Feely, R. A. [NOAA Pacific Marine Environmental Laboratory; Sabine, Chris [NOAA, Seattle, WA; Lee, K. [Pohang University of Science and Technology (POSTECH), Pohang, Republic of Korea; Millero, F. J. [University of Miami; Lamb, M. F. [NOAA Pacific Marine Environmental Laboratory; Greeley, D. [NOAA Pacific Marine Environmental Laboratory; Bullister, J.L. [NOAA Pacific Marine Environmental Laboratory; Key, Robert [Princeton University; Peng, T.-H. [Atlantic Oceanographic & Meteorological Laboratory, NOAA; Kozyr, Alexander [ORNL; Ono, Tsueno [Frontier Research System for Global Change/Institute for Global Change Research, Japan; Wong, C. S. [Institute of Ocean Sciences, Climate Chemistry Laboratory, Sidney, BC Canada

    2002-01-01

    Over the past several years researchers have been working to synthesize the WOCE/ JGOFS global CO2 survey data to better understand carbon cycling processes in the oceans. The Pacific Ocean data set has over 35,000 sample locations with at least two carbon parameters, oxygen, nutrients, CFC tracers, and hydrographic parameters. In this paper we estimate the in situ CaCO3 dissolution rates in the Pacific Ocean water column. Calcium carbonate dissolution rates ranging from 0.01 1.1 mmol kg1 yr1 are observed in intermediate and deepwater beginning near the aragonite saturation horizon. In the North Pacific Intermediate Water between 400 and 800 m, CaCO3 dissolution rates are more than 7 times faster than observed in middle and deep water depths (average = 0.051 mmol kg1 yr1). The total amount of CaCO3 that is dissolved within the Pacific is determined by integrating excess alkalinity throughout the water column. The total inventory of CaCO3 added by particle dissolution in the Pacific Ocean, north of 40S, is 157 Pg C. This amounts to an average dissolution rate of approximately 0.31 Pg C yr1. This estimate is approximately 74% of the export production of CaCO3 estimated for the Pacific Ocean. These estimates should be considered to be upper limits for in situ carbonate dissolution in the Pacific Ocean, since a portion of the alkalinity increase results from inputs from sediments.

  7. Tuning calcium carbonate growth through physical confinement and templating with amyloid-like polypeptide aggregates

    NASA Astrophysics Data System (ADS)

    Colaco, Martin Francis

    The creation of useful composite materials requires precise control of the interface between the components in order to tune the overall shape and material properties. Despite the current research into nanotechnology, our ability to create materials with nanoscale precision is nascent. However, nature has a paradigm for the creation of finely structured composites under mild conditions called biomineralization. Through control of protein template assembly, solution conditions, and physical confinement, organisms are able to create useful optical and structural materials, such as bones, teeth, and mollusk shells. The objective of this thesis is to elucidate the importance of these various controls in synthetic systems to further our ability to create nanostructured materials. We begin by examining the formation of self-assembled monolayers (SAMs) of organosilanes on silica oxides. The formation of functionalized surfaces can help control the mineralization of amorphous or crystalline calcium carbonate. Long-chained organosilanes organize on surfaces to form dense, solid-like films, with the terminal groups determining the hydrophobicity and stereochemistry of the film. Our work has shown that uniform hydrophobic and hydrophilic films can be formed by using cleaned silica over glass or mica and through a vapor phase reaction over a liquid one. Additionally, we showed that mixed SAMs with phase-separated domains could be created through the selection of organosilanes and reaction conditions. We have built on these functionalized surfaces through the use of microfabrication and a gas permeable polymer to create three-dimensionally confined microcrystallizers. Other researchers have shown that one-dimensional confinement with a multi-functional surface (patterned with a small nucleating ordered region in a disordered SAM) can stabilize the creation of an amorphous calcium carbonate film before a single, large, micropatterned crystal is grown. Our work has determined that this methodology does not extend to three-dimensional confined systems, as the water has no method of escape. Through the addition of an insoluble hydroscopic polymer to our microreactors, amorphous calcium carbonate of controllable sizes can be grown. However, crystalline calcium carbonate cannot be grown without some type of templating. Studies of calcium carbonate templating have predominantly been performed on SAMs or in poorly characterized gels or protein films. The use of ordered protein or polypeptide aggregates for templating permits both geometry and charge surface density to be varied. We have studied the kinetics and final morphology of ordered aggregates of poly-L-glutamic acid and a copolymer of glutamic acid and alanine through experiments and simulations. Electrostatics, not structure, of the monomer appeared to be the dominating factor in the aggregation, as pH and salt concentration changes led to dramatic changes in the kinetics. Examining our experimental with existing models provided inconsistent results, so we developed a new model that yielded physically realistic rate constants, while generating better fits with longer lag phases and faster growths. However, despite the similarity of aggregation conditions, the two polypeptides yielded vastly different morphologies, with the PEA forming typical amyloid-like fibrils and PE forming larger, twisted lamellar aggregates. Templating with these aggregates also yielded dramatically different patterns. Polycrystalline rhombohedral calcite with smooth faces and edges grew on PEA fibrils, with minimal templating in evidence. However, on PE, numerous calcite crystals with triangular projections tracked the surface of the aggregate. The PE lamellae are characterized by extensive beta-sheet structure. In this conformation, the glutamic acid spacings on the surface of the aggregates can mimic the spacings of the carboxylates in the calcite lattice. In addition, the high negative charge density on the polypeptide surface led to a large number of nucleation sites. As the crystals grow, they impinge on

  8. Chemical controls on the magnesium content of amorphous calcium carbonate

    NASA Astrophysics Data System (ADS)

    Blue, C. R.; Dove, P. M.

    2015-01-01

    Amorphous calcium carbonate (ACC) is a metastable phase that forms in diverse biogeochemical settings. This material can incorporate significant amounts of magnesium and other elements, but the conditions that regulate composition are not established. Using a mixed flow reactor method, we synthesize Mg-free ACC (control) and amorphous magnesium calcium carbonate (ACMC) under controlled chemical conditions to determine the relationship between composition and inorganic solution chemistry. Input solutions contained a constant initial Mg/Ca ratio of 5/1 with variable total carbonate concentration, pH, and supersaturation. Within the reactor, input solution chemistry evolves in proportion to the extent of precipitation whereby the initial Mg/Ca ratio increases to values as high as 14 at steady state conditions. By this approach, we produce reproducible quantities of ACMC with 24 to >70 mol% Mg to give compositions of Mg(0.24-0.72)Ca(0.76-0.28)CO3·1.42-1.63H2O. The primary control on ACMC composition is the steady state solution composition that develops in the reactor during precipitation. Analysis of the data shows the Mg content of ACMC is regulated by the interplay of three factors at steady state conditions: (1) Mg/Ca ratio; (2) total carbonate concentration; and (3) solution pH. Using the Henderson-Kracek model to estimate the partition coefficients for the Mg content of ACMC, we find KD is approximately constant at 0.047 ± 0.003 when steady state pH is less than 9.5, but values of KD triple as steady state pH increases from 9.5 to 10.3. Our KD values are lower than previous estimates that are based upon initial solution composition. In contrast, our estimates of KD are determined from the solution chemistry at steady state conditions and for pH conditions that are less extreme than previous experimental studies. We suggest the approach of using steady state composition to estimate KD gives a more accurate representation of relationships between ACMC composition and local conditions. The findings demonstrate local pH and total carbonate concentration can be regulated at the time of formation to produce Mg amorphous carbonates of a designated composition.

  9. Study on the thermal decomposition kinetics of nano-sized calcium carbonate.

    PubMed

    Li, Dai-Xi; Shi, Hong-Yun; Jie, Deng; Xu, Yuan-Zhi

    2003-01-01

    This study of the thermal decomposition kinetics of various average diameter nano-particles of calcium carbonate by means of TG-DTA ( thermogravimetry and differential thermal analysis) showed that the thermal decomposition kinetic mechanisms of the same crystal type of calcium carbonate samples do not vary with decreasing of their average diameters; their pseudo-active energy (a); and that the top-temperature of decomposition T(p) decreases gently in the scope of micron-sized diameter, but decreases sharply when the average diameter decreases from micron region to nanometer region. The extraordinary properties of nano-particles were explored by comparing the varying regularity of the mechanisms and kinetic parameters of the solid-phase reactions as well as their structural characterization with the variation of average diameters of particles. These show that the aggregation, surface effect as well as internal aberrance and stress of the nano-particles are the main reason causing both E(a) and T(p) to decline sharply with the decrease of the average diameter of nano-particles. PMID:12765294

  10. Monodisperse Calcium Carbonate Microtablets Forming at 701C in Prerefrigerated CaCl2GelatinUrea Solutions

    E-print Network

    Tas, A. Cuneyt

    Monodisperse Calcium Carbonate Microtablets Forming at 701C in Prerefrigerated CaCl2­Gelatin Calcium carbonate particles with a unique tablet shape were produced by simply aging the prerefrigerated, and powder X-ray diffraction. Introduction Calcium carbonate (CaCO3) is an important ma- terial of marine

  11. Formate oxidation-driven calcium carbonate precipitation by Methylocystis parvus OBBP.

    PubMed

    Ganendra, Giovanni; De Muynck, Willem; Ho, Adrian; Arvaniti, Eleni Charalampous; Hosseinkhani, Baharak; Ramos, Jose Angel; Rahier, Hubert; Boon, Nico

    2014-08-01

    Microbially induced carbonate precipitation (MICP) applied in the construction industry poses several disadvantages such asammonia release to the air and nitric acid production. An alternative MICP from calcium formate by Methylocystis parvus OBBP is presented here to overcome these disadvantages. To induce calcium carbonate precipitation, M. parvus was incubated at different calcium formate concentrations and starting culture densities. Up to 91.4% ± 1.6% of the initial calcium was precipitated in the methane-amended cultures compared to 35.1% ± 11.9% when methane was not added. Because the bacteria could only utilize methane for growth, higher culture densities and subsequently calcium removals were exhibited in the cultures when methane was added. A higher calcium carbonate precipitate yield was obtained when higher culture densities were used but not necessarily when more calcium formate was added. This was mainly due to salt inhibition of the bacterial activity at a high calcium formate concentration. A maximum 0.67 ± 0.03 g of CaCO3 g of Ca(CHOOH)2(-1) calcium carbonate precipitate yield was obtained when a culture of 10(9) cells ml(-1) and 5 g of calcium formate liter(-)1 were used. Compared to the current strategy employing biogenic urea degradation as the basis for MICP, our approach presents significant improvements in the environmental sustainability of the application in the construction industry. PMID:24837386

  12. In situ study of ion-beam induced lattice damage in calcium fluoride crystals

    Microsoft Academic Search

    Ning Yu; Michael Nastasi; Kurt E. Sickafus; Kazuhiro Yasuda; Joseph R. Tesmer

    1997-01-01

    Lattice damage in calcium fluoride induced by 360 keV xenon ion irradiation was measured in situ using Rutherford backscattering and channeling (RBS\\/C) techniques. Calcium fluoride single crystals of (100) orientation were irradiated at ? 115 and 35°C by Xe ion beams along a random direction 15° off the (100) axis. A 2 MeV He ion-beam from a 3 MV tandem

  13. Growth and characterization of a novel nonlinear optical borate crystal--yttrium calcium borate (YCB).

    PubMed

    Arun Kumar, R; Arivanandhan, M; Dhanasekaran, R; Hayakawa, Y

    2013-06-01

    A new nonlinear optical single crystal yttrium calcium borate Y2CaB10O19 (YCB) was grown for the first time from its melt. The starting materials were prepared by the solid-state reaction method. The melting point of the synthesized material was identified to be 967 °C. YCB crystal exhibits monoclinic crystal structure with the space group C2. The crystalline perfection of the grown YCB crystal was found to be good. From the UV-VIS-NIR studies, the lower cutoff wavelength of the crystal occurs below 200 nm. The functional groups of the grown crystal were assigned using the FTIR data. The second harmonic generation (SHG) of the YCB crystal was observed using a Nd:YAG laser with a fundamental wavelength of 1064 nm. The laser damage threshold value of the YCB crystal was found to be very high - 10.5 GW/cm(2). PMID:23583874

  14. Growth and characterization of a novel nonlinear optical borate crystal - Yttrium calcium borate (YCB)

    NASA Astrophysics Data System (ADS)

    Arun Kumar, R.; Arivanandhan, M.; Dhanasekaran, R.; Hayakawa, Y.

    2013-06-01

    A new nonlinear optical single crystal yttrium calcium borate Y2CaB10O19 (YCB) was grown for the first time from its melt. The starting materials were prepared by the solid-state reaction method. The melting point of the synthesized material was identified to be 967 °C. YCB crystal exhibits monoclinic crystal structure with the space group C2. The crystalline perfection of the grown YCB crystal was found to be good. From the UV-VIS-NIR studies, the lower cutoff wavelength of the crystal occurs below 200 nm. The functional groups of the grown crystal were assigned using the FTIR data. The second harmonic generation (SHG) of the YCB crystal was observed using a Nd:YAG laser with a fundamental wavelength of 1064 nm. The laser damage threshold value of the YCB crystal was found to be very high - 10.5 GW/cm2.

  15. Methotrexate: should it still be considered for chronic calcium pyrophosphate crystal disease?

    PubMed

    Pascual, Eliseo; Andrés, Mariano; Sivera, Francisca

    2015-01-01

    Chronic calcium pyrophosphate crystal arthritis is a clinical consequence of the formation and deposition of these crystals in joints and can result in persistent arthritis. Curative treatment would require the removal of crystals from joints and tissues, but to date all agents tested have proven ineffective. Management of the inflammatory manifestations of chronic calcium pyrophosphate disease includes glucocorticoids, non-steroidal anti-inflammatory drugs, or colchicine, and responses are usually satisfactory. However, in some patients, the response to these agents is poor or they are contraindicated. Methotrexate had been reported as a promising option in small case series; however, in a recent issue of Arthritis Research & Therapy, a clinical trial failed to confirm the anticipated benefits. Here, we discuss some issues that might have influenced the results of the study, before deciding to abandon methotrexate as a therapeutic option for patients with chronic calcium pyrophosphate arthritis. PMID:25885915

  16. Optical properties of carbon nanofiber photonic crystals.

    PubMed

    Rehammar, R; Magnusson, R; Fernandez-Dominguez, A I; Arwin, H; Kinaret, J M; Maier, S A; Campbell, E E B

    2010-11-19

    Carbon nanofibers (CNFs) are used as components of planar photonic crystals. Square and rectangular lattices and random patterns of vertically aligned CNFs were fabricated and their properties studied using ellipsometry. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam. The refractive index of the individual nanofibers was found to be n(CNF) = 4.1. PMID:20972321

  17. Fabrication of calcium lanthanum sulfide ceramic by carbonate coprecipitating method

    SciTech Connect

    Tsai, M.S.; Hon, M.H. (National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Materials Science and Engineering)

    1995-03-01

    Translucent CLS (calcium lanthanum sulfide) pellets were formed by the carbonate coprecipitation method, CS[sub 2] sulfurization, and hot press sintering. For a La/Ca = 2.5 pellet with 1.3 mm in thickness, the transmittance at 13 [mu]m is about 25% after sintering at 1,150 C for 30 minutes and resulfurizing at 950 C for 1 hour. For a La/Ca = 15 pellet with 0.9 mm in thickness the IR transmittance is about 51% at 13 [mu]m after sintering at 1,050 C for 2 hours and resulfurizing at 950 C for 1 hour. Beta-La[sub 2]S[sub 3] is present as a second phase after sintering at 1,150 C for 30 minutes. After resulfurization, the second phase disappears for the La/Ca = 2.5 pellet, but still exists in the La/Ca = 15 pellet.

  18. In situ electron microscopy studies of calcium carbonate precipitation from aqueous solution with and without organic additives.

    PubMed

    Verch, Andreas; Morrison, Ian E G; Locht, Renee van de; Kröger, Roland

    2013-08-01

    For the understanding of mineral formation processes from solution it is important to obtain a deeper insight into the dynamics of crystal growth. In this study we applied for this purpose a novel atmospheric scanning electron microscope that allows the investigation of CaCO3 particle formation in solution under atmospheric conditions with a resolution of approximately 10nm. Furthermore it permits the in situ observation of the dynamics of crystal evolution. With this tool the precipitation of CaCO3 was studied in the absence and presence of additives, namely poly(acrylic acid) and poly(styrene sulfonate-co-maleic acid) which are known to influence the crystal growth rate and morphology. We determined particle growth rates and investigated the formation and dissolution dynamics of an observed transient phase, believed to be amorphous calcium carbonate. This technique also enabled us to study the depletion zones, areas of lower intensity due to reduced ion concentrations. Ion flux rates were obtained from the depletion zone width, which amounted to several ?m assuming the formation and dissolution dynamics of amorphous calcium carbonate being the rate determining process. This assumption was confirmed since the obtained fluxes were found to be in good agreement with fluxes derived from the experimentally observed crystal growth rates. PMID:23742840

  19. Inhibition of Calcium Oxalate Crystal Growth in vitro by Uropontin: Another Member of the Aspartic Acid-Rich Protein Superfamily

    Microsoft Academic Search

    H. Shiraga; W. Min; W. J. Vandusen; M. D. Clayman; D. Miner; C. H. Terrell; J. R. Sherbotie; J. W. Foreman; C. Przysiecki; E. G. Neilson; J. R. Hoyer

    1992-01-01

    The majority of human urinary stones are primarily composed of calcium salts. Although normal urine is frequently supersaturated with respect to calcium oxalate, most humans do not form stones. Inhibitors are among the multiple factors that may influence the complex process of urinary stone formation. We have isolated an inhibitor of calcium oxalate crystal growth from human urine by monoclonal

  20. Fasudil prevents calcium oxalate crystal deposit and renal fibrogenesis in glyoxylate-induced nephrolithic mice.

    PubMed

    Hu, Haiyan; Chen, Wei; Ding, Jiarong; Jia, Meng; Yin, Jingjing; Guo, Zhiyong

    2015-04-01

    Nephrolithiasis is a common kidney disease and one of the major causes of chronic renal insufficiency. We develop and utilize a glyoxylate induced mouse model of kidney calcium oxalate crystal deposition for studying the pharmacological effects of fasudil, a Rho associated protein kinase (ROCK) specific inhibitor, on the kidney injury and fibrosis caused by calcium oxalate crystallization and deposition. Glyoxylate was administrated intraperitoneally to C57BL/6J mice for five consecutive days to establish a mouse model of kidney calcium oxalate crystal formation and deposition. The results showed that the protein expression levels of E-cad and Pan-ck were lower, and the protein expression levels of ?-SMA and Vim were higher, in the kidney tissue of the glyoxylate induced model mice compared with the control mice. The changes in protein expression were weakened when the animals were pretreated with fasudil before glyoxylate administration. Expression of ROCK, PAI-1, and p-Smad proteins in the kidney tissue increased in response to glyoxylate treatment, and the increase was eased when the animals were pretreated with fasudil. Expression of Smad2 and Smad3 in the kidney tissue remained unchanged after glyoxylate administration. Cell apoptosis and proliferation in the kidney cortex and medulla were enhanced in response to the glyoxylate induced calcium oxalate crystal formation and deposition, and fasudil pre-treatment was able to attenuate the enhancement. The results suggest that Fasudil reduces the glyoxylate induced kidney calcium crystal formation and deposition and slows down the kidney fibrogenesis caused by calcium crystal deposition. The possible mechanism may be related the regulatory effects on Rho/ROCK signal transduction and epithelial-mesenchymal transition (EMT). PMID:25697583

  1. Tensile strength of sand, palygorskite and calcium carbonate mixtures and interpretation with the effective stress theory

    Microsoft Academic Search

    M. R. Mosaddeghi; M. A. Hajabbasi; H. Khademi

    2006-01-01

    Many soils in arid regions of the world including those of central Iran contain palygorskite and carbonates in their mineral fraction. There is, however, little information on the effects of these minerals on soil physical and mechanical behaviour. A laboratory experiment was carried out to evaluate tensile strength of artificial mixtures of sand–palygorskite–calcium carbonate (CaCO3). Palygorskite and calcium carbonate were

  2. Prevalence of sternoclavicular joint calcium pyrophosphate dihydrate crystal deposition on computed tomography.

    PubMed

    Shirazian, Hoda; Chang, Eric Y; Wolfson, Tanya; Gamst, Anthony C; Chung, Christine B; Resnick, Donald L

    2014-01-01

    We sought to determine the prevalence of sternoclavicular (SC) joint calcium pyrophosphate dihydrate (CPPD) crystal deposition and its association with age, osteoarthritis, and atlantoaxial CPPD crystal deposition. In 209 consecutive patients, computed tomographic examinations of the cervical spine were retrospectively reviewed. Overall prevalence of CPPD crystal deposition in the SC joint was 17.2% (36/209), which increased with age (P<.0001). There was also a significant association between SC CPPD and osteoarthritis (P=.024) as well as atlantoaxial joint CPPD crystal deposition (P=.006). PMID:24642252

  3. Effects of Mg/Ca ratio and temperature on the mineralogy of calcium carbonate precipitates and their paleooceanographic implications

    SciTech Connect

    Tsoi, M.Y.; Belli, S. [Vassar College, Poughkeepsie, NY (United States)

    1996-10-01

    Because of the importance of the global carbon cycle throughout the life of the Earth, scientists have tried to use components of it to find out past conditions of the Earth`s atmosphere, oceans, and climate. However, lack of knowledge about past conditions makes it difficult to paint a complete picture of the chemistry of ancient oceans and atmospheres. One approach is to use the mineralogy of ancient sedimentary carbonates to examine the problem from the standpoint that certain conditions dictate the formation of particular crystal structures. Thus, we need to more completely understand the conditions which influence the precipitation of carbonate minerals. We examine the effects of both seawater Mg/Ca ratio and temperature on the mineralogy of calcium carbonate precipitated from seawater. This will refine our knowledge of paleo-ocean chemistry.

  4. Coupled dissolution-precipitation as a mechanism for amorphous-to-crystalline calcium carbonate phase transition

    NASA Astrophysics Data System (ADS)

    Rodriguez-Navarro, Carlos Manuel; Kud?acz, Krzysztof; Ruiz-Agudo, Encarnacion

    2014-05-01

    Growing evidence shows that several calcium carbonate biominerals form via an amorphous precursor phase. Such a biomineralization strategy could also be applicable for the biomimetic synthesis of novel functional materials. A crucial step in this process is the transformation of amorphous calcium carbonate (ACC) into calcite. However, controversy exists as to what is the actual mechanism of this transformation: Is it a solid-solid (solid state) or a dissolution/precipitation mechanism? Determining the transition mechanism is critical for example in interpreting the formation of oriented crystalline structures in biominerals (e.g., echinoderm spicles). We studied calcium carbonate precipitation and phase transitions according to the overall reaction Ca(OH)2 + CO2 = CaCO3+ H2O. Mineral phase transformations during this reaction were studied using transmission electron microscopy (TEM). Our TEM analysis showed that two different types of ACC are sequentially formed during this reaction. Type I ACC shows no well-defined short-range order, while Type II ACC shows a short-range order corresponding to calcite. Following e-beam irradiation, Type I ACC particles transform into randomly oriented CaO nanocrystals, while irradiation of Type II ACC leads to the formation of pseudomorphs made up of perfectly oriented aggregates of calcite nanocrystals. Moreover, calcite crystals formed in solution or in air (85 % relative humidity) after Type II ACC are also pseudomorphs made up of porous aggregates of preferentially oriented calcite nanocrystals. Our results give experimental evidence showing that the ACC to calcite transformation under relevant biomineralization conditions (low T and P), also applicable in the biomimetic synthesis of calcite, is a pseudomorphic dissolution-precipitation process. This mechanism involves the tightly interface-coupled dissolution of the precursor amorphous phase (with the crystalline phase protostructure) and concomitant deposition of the crystalline product (calcite) on the remaining (not fully dissolved) precursor phase via epitaxial crystallization. The solubility and molar volume differences between parent and product phase explain the generation of porosity, which enables the progress of the reaction leading to a calcite pseudomorph.

  5. How calcium from calcium carbonate and milk benefit peptic ulcer patients

    Microsoft Academic Search

    X. Wang

    2000-01-01

    Calcium from calcium containing antacids and milk enhance the integrity of gastrointestinal mucosa and mucus, as it is the natural linker agent of these structures, which strengthens their defense function.

  6. Single Crystals of Single-Walled Carbon Nanotubes Formed by

    E-print Network

    Gimzewski, James

    -assembly of single crystals of single-walled carbon nano- tubes (SWCNTs) using thermolysis of nano of carbon nanotube fabrication is to form large uniform and ordered nano- and microstructuresSingle Crystals of Single-Walled Carbon Nanotubes Formed by Self-Assembly R. R. Schlittler,1 J. W

  7. Biomineralization of calcium carbonate polymorphs by the bacterial strains isolated from calcareous sites.

    PubMed

    Dhami, Navdeep Kaur; Reddy, M Sudhakara; Mukherjee, Abhijit

    2013-05-01

    Microbially induced calcium carbonate precipitation (MICCP) is a naturally occurring biological process that has various applications in remediation and restoration of a range of building materials. In the present investigation, five ureolytic bacterial isolates capable of inducing calcium carbonate precipitation were isolated from calcareous soils on the basis of production of urease, carbonic anhydrase, extrapolymeric substances, and biofilm. Bacterial isolates were identified as Bacillus megaterium, B. cereus, B. thuringiensis, B. subtilis, and Lysinibacillus fusiformis based on 16S rRNA analysis. The calcium carbonate polymorphs produced by various bacterial isolates were analyzed by scanning electron microscopy, confocal laser scanning microscopy, X ray diffraction, and Fourier transmission infra red spectroscopy. A strainspecific precipitation of calcium carbonate forms was observed from different bacterial isolates. Based on the type of polymorph precipitated, the technology of MICCP can be applied for remediation of various building materials. PMID:23648862

  8. Biomimetic growth of calcium oxalate crystals: synchrotron X-ray studies

    NASA Astrophysics Data System (ADS)

    Uysal, Ahmet; Stripe, Benjamin; Dutta, Pulak

    2010-03-01

    Oriented crystals of calcium oxalate monohydrate (COM) form one of the major constituents of kidney stones in humans, and these crystals are also found in many plants. It is widely accepted that an organic matrix of lipids and proteins is involved in the crystallization of COM, though their role is not well-understood [1]. Langmuir monolayers of lipids on supersaturated aqueous solutions can be used to mimic the lipid-crystal interface during mineralization. We have studied nucleation and growth of COM crystals under heneicosanoic acid monolayers at the air-water interface. We used synchrotron x-rays in the grazing incidence geometry to determine the structure of the organic monolayer and the orientation of COM crystals in-situ during crystallization. We see that the (-101) faces of COM crystals are parallel to the organic matrix. There is a commensurate relationship between the heneicosanoic acid monolayer and the (-101) crystal face that may be responsible from the oriented growth. Evolution of the monolayer structure with time will be described. [1]S. R. Khan, Calcium Oxalate in Biological Systems, CRC Press, Boca Raton, 1995

  9. Calcium Oxalate Crystals: An Integral Component of the Sclerotinia sclerotiorum/Brassica carinata Pathosystem

    PubMed Central

    Uloth, Margaret B.; Clode, Peta L.; You, Ming Pei; Barbetti, Martin J.

    2015-01-01

    Oxalic acid is an important virulence factor for disease caused by the fungal necrotrophic pathogen Sclerotinia sclerotiorum, yet calcium oxalate (CaOx) crystals have not been widely reported. B. carinata stems were infected with S. sclerotiorum and observed using light microscopy. Six hours post inoculation (hpi), CaOx crystals were evident on 46% of stem sections and by 72 hpi on 100%, demonstrating that the secretion of oxalic acid by S. sclerotiorum commences before hyphal penetration. This is the first time CaOx crystals have been reported on B. carinata infected with S. sclerotiorum. The shape of crystals varied as infection progressed. Long tetragonal rods were dominant 12 hpi (68% of crystal-containing samples), but by 72 hpi, 50% of stems displayed bipyramidal crystals, and only 23% had long rods. Scanning electron microscopy from 24 hpi revealed CaOx crystals in all samples, ranging from tiny irregular crystals (< 0.5 ?m) to large (up to 40 ?m) highly organized arrangements. Crystal morphology encompassed various forms, including tetragonal prisms, oval plates, crystal sand, and druses. Large conglomerates of CaOx crystals were observed in the hyphal mass 72 hpi and these are proposed as a strategy of the fungus to hold and detoxify Ca2+ions. The range of crystal morphologies suggests that S. sclerotiorum growth and infection controls the form taken by CaOx crystals. PMID:25816022

  10. Crystallization behaviour of hydroxide cobalt carbonates by aging: Environmental implications.

    NASA Astrophysics Data System (ADS)

    González-López, Jorge; Fernández-González, Angeles; Jimenez, Amalia

    2014-05-01

    Cobalt is a naturally occurring element widely distributed in water, sediments and air that is essential for living species, since it is a component of B12 vitamin and it is also a strategic and critical element used in a number of commercial, industrial and military applications. However, relatively high accumulations of cobalt in environment can be toxic for human and animal health. Cobalt usually occurs as Co2+ and Co3+ in aqueous solutions, where Co2+ is the most soluble and hence its mobility in water is higher. The study of the precipitation of cobalt carbonates is of great interest due to the abundance of carbonate minerals in contact with surface water and groundwater which can be polluted with Co2+. Previous works have demonstrated that the formation of Co-bearing calcium carbonates and Co-rich low crystallinity phases takes place at ambient conditions. With the aim of investigating the crystallization behavior of Co- bearing carbonates at ambient temperature, macroscopic batch-type experiments have been carried out by mixing aqueous solutions of CoCl2 (0.05M) and Na2CO3 (0.05M) during increasing reaction times (5 minutes and 1, 5, 24, 48, 96, 168, 720 and 1440 hours). The main goals of this work were (i) to analyse the physicochemical evolution of the system and (ii) to study the evolution of the crystallinity of the solid phases during aging. After a given reaction period, pH, alkalinity and dissolved Co2+ in the aqueous solutions were analysed. The evolution of the morphology and chemical composition of the solids with aging time was examined by SEM and TEM. The precipitates were also analyzed by X-ray powder diffraction (XRD) and the crystallinity degree was followed by the intensity and the full width at high medium (FWHM) of the main peaks. The results show that a low crystallinity phase was obtained at the very beginning of aging. This phase evolves progressively to form hydroxide carbonate cobalt (Co2CO3(OH)2) which crystallize with the spatial group P21/a (monoclinic system) after about 4 days. At the same time, the most important fall of cobalt content takes place, but pH and alkalinity values do not show significant changes. The evolution of the aqueous solutions is closely related to the increases of crystallinity degree. TEM study confirms the evolution of the shape of crystals, which exhibit platelet morphology at the end of aging time.

  11. Synthesis of calcium antimonate nano-crystals by the 18th dynasty Egyptian glassmakers

    Microsoft Academic Search

    S. Lahlil; I. Biron; M. Cotte; J. Susini; N. Menguy

    2010-01-01

    During the 18th Egyptian dynasty (1570–1292 B.C.), opaque white, blue and turquoise glasses were opacified by calcium antimonate\\u000a crystals dispersed in a vitreous matrix. The technological processes as well as the antimony sources used to manufacture these\\u000a crystals remain unknown. Our results shed a new light on glassmaking history: contrary to what was thought, we demonstrate\\u000a that Egyptian glassmakers did

  12. Growth and SAW properties of rare-earth calcium oxoborate crystals

    Microsoft Academic Search

    Hiroshi Nakao; Masahiro Nishida; Takashi Shikida; Hiroyuki Shimizu; Hiroaki Takeda; Tadashi Shiosaki

    2006-01-01

    Rare-earth calcium oxoborate RCa4O(BO3)3 (R, rare-earth elements; RCOB) (R=Pr, Nd, Sm, Eu, Dy, Ho, Er) bulk single crystals were grown by the Czochralski technique. Their melting temperature increased with a decrement of a rare-earth ion radius in RCOB. Surface acoustic wave (SAW) and pseudo-SAW (PSAW) properties of the RCOB crystal were investigated. The electro mechanical coupling factors k2 values of

  13. Calcium

    MedlinePLUS

    ... you eat. Foods rich in calcium include Dairy products such as milk, cheese, and yogurt Leafy, green vegetables Fish with soft bones that you eat, such as canned sardines and salmon Calcium-enriched foods such as breakfast ... tofu. Check the product labels. The exact amount of calcium you need ...

  14. Characterization of calcium crystals in Abelia using x-ray diffraction and electron microscopes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Localization, chemical composition, and morphology of calcium crystals in leaves and stems of Abelia mosanensis and A. ×grandiflora were analyzed with a variable pressure scanning electron microscope (VP-SEM) equipped with an X-ray diffraction system, low temperature SEM (LT-SEM) and a transmission ...

  15. Possible overestimation of shallow-depth calcium carbonate dissolution in the ocean

    E-print Network

    Follows, Mick

    of the global ocean carbon cycle. It implies a shorter timescale for the cycling of calcium carbonate within dissolution in the ocean, Global Biogeochem. Cycles, 20, GB4019, doi:10.1029/2006GB002727. 1. Introduction [2, and the marine carbon cycle. [3] A discussion of CaCO3 dissolution is aided by an examination of alkalinity

  16. The flame photometric determination of calcium in phosphate, carbonate, and silicate rocks

    USGS Publications Warehouse

    Kramer, H.

    1957-01-01

    A flame photometric method of determining calcium in phosphate, carbonate, and silicate locks has been developed Aluminum and phosphate interference was overcome by the addition of a large excess of magnesium. The method is rapid and suitable for routine analysis Results obtained are within ?? 2% of the calcium oxide content. ?? 1957.

  17. Sulfur dioxide inhibits calcium carbonate precipitation: Implications for early Mars and Earth

    E-print Network

    Halevy, Itay

    or H2SO3) whose conjugate base, sulfite (SO3 2À ), can form a mineral with calcium. This mineral, hannebachite (CaSO3 Â 1 2H2O), is $90 times more soluble than the least soluble calcium carbonate (calcite

  18. Effects of Calcium Carbonate on Ruminal Fermentation, Nutrient Digestibility, and Cow Performance1

    Microsoft Academic Search

    J. H. Clark; A. W. Plegge; C. L. Davis; G. C. McCoy

    1989-01-01

    Sixteen Holstein cows were used in a 4 x 4 Latin square design (four replicates) to investigate the effect of feeding calcium carbonate on feed intake, ruminal fermentation, apparent total tract nutrient digestibility, milk yield, and milk compo- sition. Supplementation of calcium car- bonate to diets that contained 60% concentrate and 40% corn silage (DM basis) decreased DM intake and

  19. Concentrations de carbonate de calcium sur les parois des hyphes mycliens

    E-print Network

    Boyer, Edmond

    Concentrations de carbonate de calcium sur les parois des hyphes mycéliens Gabriel CALLOT, Daniel, Place Viala, F 34060 Montpellier Cedex R�SUM� Après avoir rappelé la structure des hyphes mycéliens, les., 1980) ou d'oxalate de calcium identifié sur des hyphes de champignons ectomycorhiziens (CROIvtACK et al

  20. Growth Rate of Calcite Steps as a Function of Aqueous Calcium-to-Carbonate Ratio: Independent Attachment and Detachment of Calcium and Carbonate Ions

    SciTech Connect

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

    2010-01-01

    Growth rates of monolayer-height steps on the {1014} calcite surface have been measured as a function of the aqueous calcium-to-carbonate ratio. The maximum growth rates of the two common crystallographic orientations were found to deviate from the ideal stoichiometric ratio of 1:1, and dissolution features were observed under supersaturated solutions containing high calcium-to-carbonate ratios. To explain these phenomena, a theory is applied that treats the rates of attachment and detachment of aqueous calcium and carbonate ions separately. The resultant attachment rate constants are 1-3 orders of magnitude smaller than the water exchange rate of the constituent aqueous ions, suggesting that ligand-exchange processes may directly drive attachment. The broader implication is that the saturation state alone is not adequate to fully describe the rates of the multiple, independent reactions that occur on mineral surfaces under these conditions.

  1. Effects of calcium carbonate particulate releasing surgical anchors on bone and tendon healing

    E-print Network

    Medeiros, Jordan-Ryan J. I. K

    2007-01-01

    The Calaxo ® screw, developed by Smith and Nephew, is a novel biomedical composite composed of poly-DL-lactide-co-glycolide (PLLA:PGA) 85:15 and calcium carbonate particulates. Comparisons to an identical surgical anchor ...

  2. Organoaqueous calcium chloride electrolytes for capacitive charge storage in carbon nanotubes at sub-zero-temperatures.

    PubMed

    Gao, Yun; Qin, Zhanbin; Guan, Li; Wang, Xiaomian; Chen, George Z

    2015-06-23

    Solutions of calcium chloride in mixed water and formamide are excellent electrolytes for capacitive charge storage in partially oxidised carbon nanotubes at unprecedented sub-zero-temperatures (e.g. 67% capacitance retention at -60 °C). PMID:26060845

  3. Synthesis of calcium carbonate nanocrystals and their potential application as vessels for drug delivery

    NASA Astrophysics Data System (ADS)

    Vergaro, Viviana; Carata, Elisabetta; Panzarini, Elisa; Baldassare, Francesca; Dini, Luciana; Ciccarella, Giuseppe

    2015-06-01

    Pure and stable calcium carbonate (CaCO3) nanocrystals were synthesized by spray drying method. We exploited the opportunity to use them as vessels for drug delivery studying the biocompatibility and the internalization in HeLa cells.

  4. Aggregation patterns of bile salts: crystal structure of calcium cholate chloride heptahydrate.

    PubMed

    Hogan, A; Ealick, S E; Bugg, C E; Barnes, S

    1984-08-01

    Crystals of calcium cholate chloride heptahydrate, CaC24H39O7Cl . 7H2O, are monoclinic, space group P2(1), with a = 11.918(2), b = 8.636(1), c = 15.302(3) A, beta = 97.93(3) degrees, V = 1559.9(8) A3, and Z = 2. A trial structure was obtained by Patterson and Fourier techniques and was refined by full-matrix least-squares calculations using absorption corrected CuK-alpha diffractometer data. The final R index is 0.047. The crystal structure contains bilayer-type arrangements, with hydrophobic portions of cholate rings sandwiched between layers of polar groups that are interacting with calcium ions and water molecules. The calcium ion is coordinated to five water molecules and to the two carboxylate oxygen atoms of the cholate residue. Two additional water molecules are involved only in crystal packing through the formation of hydrogen bonds. Cholate-cholate hydrophobic interactions involve contacts between the hydrocarbon portions of the carboxylate sidechains and the A and B rings. This results in a staggered packing pattern that is nearly identical to that found in crystals of sodium cholate and rubidium deoxycholate. Similar bilayer aggregation patterns may also be involved in the formation of bile salt micelles in aqueous media. The characteristic bilayer packing arrangement can accommodate a variety of cation-binding patterns, as evidenced by the finding that calcium, sodium, and rubidium ions interact with the polar faces of the bilayers in different ways. The carboxylate sidechain displays two different conformations in the crystal structure of calcium cholate chloride heptahydrate. Variation in sidechain conformation may be of importance in the adjustment required to accommodate different cation coordination schemes. PMID:6491524

  5. Endocytosis precedes dissolution of basic calcium phosphate crystals by murine macrophages

    Microsoft Academic Search

    Jeanna L. Owens; Herman S. Cheung; Daniel J. McCarty

    1986-01-01

    Summary  Murine peritoneal macrophages were incubated with45Ca-labeled basic calcium phosphate (BCP) crystals in the presence or absence of cytochalasin B. Untreated macrophages solubilized\\u000a 30–50% of45Ca-BCP in 24 hours. Dissolution began within 3 hours and was linear thereafter. Twenty-three percent of BCP was cell-associated\\u000a by 3 hours. Endocytosis of crystal occurred continuously throughout the incubation. Endocytosis of crystal did not affect\\u000a the

  6. Phosphate and carbonate salts of calcium support robust bone building in osteoporosis123

    PubMed Central

    Recker, Robert R; Watson, Patrice; Lappe, Joan M

    2010-01-01

    Background: Calcium is an essential cotherapy in osteoporosis treatment. The relative effectiveness of various calcium salts for this purpose is uncertain. Many older women with osteoporosis have phosphorus intakes of <70% of the Recommended Dietary Allowance. Objective: Our objective was to test the hypothesis that calcium phosphate would better support anabolic bone building than would calcium carbonate. Design: This study was a 12-mo, randomized, positive-comparator, 2-arm, single-blind clinical trial in 211 patients treated with teriparatide who consumed <1000 mg phosphorus/d. Participants were randomly assigned to receive, in addition to teriparatide and 1000 IU cholecalciferol, 1800 mg calcium/d as either tricalcium phosphate or calcium carbonate. The primary endpoints were changes in lumbar spine and total hip bone mineral densities (BMDs); secondary endpoints were changes in bone resorption biomarkers and serum and urine calcium and phosphorus concentrations. Results: In the combined group, the lumbar spine BMD increased by 7.2%, and total hip BMD increased by 2.1% (P < 0.01 for both). However, there was no significant difference between calcium-treatment groups, and there were no significant between-group differences in serum calcium and phosphorus concentrations or in urine calcium concentrations. Bone resorption biomarkers increased in both groups, as expected with teriparatide, but the increases in the 2 calcium groups did not differ significantly. Conclusions: Tricalcium phosphate and calcium carbonate appear to be approximately equally effective in supporting bone building with a potent anabolic agent; phosphate salt may be preferable in patients with restricted phosphorus intakes. This trial was registered at clinicaltrials.gov as NCT00074711. PMID:20484446

  7. pH-dependent release from ethylcellulose microparticles containing alginate and calcium carbonate

    Microsoft Academic Search

    Mi Kyoung Kang; Jin-Chul Kim

    2010-01-01

    Ethylcellulose microparticles containing alginate and calcium carbonate nanoparticles were prepared by spray drying water-in-oil\\u000a emulsion. Alginate solution (3%) in distilled water was used as an aqueous phase, ethylcellulose solution (5%) in dichloromethane\\u000a as an oil phase, and sorbitan sesquioleate as an emulsifier. The nanoparticles of calcium carbonate were dispersed into the\\u000a emulsion. By spray-drying the emulsion, ethylcellulose microparticles containing alginate

  8. An unusual isotopic fractionation of boron in synthetic calcium carbonate precipitated from seawater and saline water

    Microsoft Academic Search

    Yingkai Xiao; Shizhen Li; Haizhen Wei; Aide Sun; Weijian Zhou; Weiguo Liu

    2006-01-01

    Inorganic calcium carbonate precipitation from natural seawater and saline water at various pH values was carried out experimentally.\\u000a The results show the clear positive relationships between boron concentration and ?11B of inorganic calcium carbonate with the pH of natural seawater and saline water. However, the variations of boron isotopic\\u000a fractionation between inorganic calcite and seawater\\/saline water with pH are inconsistent

  9. Calcium carbonate nucleation driven by ion binding in a biomimetic matrix revealed by in situ electron microscopy

    NASA Astrophysics Data System (ADS)

    Smeets, Paul J. M.; Cho, Kang Rae; Kempen, Ralph G. E.; Sommerdijk, Nico A. J. M.; de Yoreo, James J.

    2015-04-01

    The characteristic shapes, structures and properties of biominerals arise from their interplay with a macromolecular matrix. The developing mineral interacts with acidic macromolecules, which are either dissolved in the crystallization medium or associated with insoluble matrix polymers, that affect growth habits and phase selection or completely inhibit precipitation in solution. Yet little is known about the role of matrix-immobilized acidic macromolecules in directing mineralization. Here, by using in situ liquid-phase electron microscopy to visualize the nucleation and growth of CaCO3 in a matrix of polystyrene sulphonate (PSS), we show that the binding of calcium ions to form Ca–PSS globules is a key step in the formation of metastable amorphous calcium carbonate (ACC), an important precursor phase in many biomineralization systems. Our findings demonstrate that ion binding can play a significant role in directing nucleation, independently of any control over the free-energy barrier to nucleation.

  10. Calcium carbonate nucleation driven by ion binding in a biomimetic matrix revealed by in situ electron microscopy.

    PubMed

    Smeets, Paul J M; Cho, Kang Rae; Kempen, Ralph G E; Sommerdijk, Nico A J M; De Yoreo, James J

    2015-04-01

    The characteristic shapes, structures and properties of biominerals arise from their interplay with a macromolecular matrix. The developing mineral interacts with acidic macromolecules, which are either dissolved in the crystallization medium or associated with insoluble matrix polymers, that affect growth habits and phase selection or completely inhibit precipitation in solution. Yet little is known about the role of matrix-immobilized acidic macromolecules in directing mineralization. Here, by using in situ liquid-phase electron microscopy to visualize the nucleation and growth of CaCO3 in a matrix of polystyrene sulphonate (PSS), we show that the binding of calcium ions to form Ca-PSS globules is a key step in the formation of metastable amorphous calcium carbonate (ACC), an important precursor phase in many biomineralization systems. Our findings demonstrate that ion binding can play a significant role in directing nucleation, independently of any control over the free-energy barrier to nucleation. PMID:25622001

  11. Thermodynamic properties of synthetic calcium-free carbonate cancrinite

    NASA Astrophysics Data System (ADS)

    Kurdakova, S. V.; Grishchenko, R. O.; Druzhinina, A. I.; Ogorodova, L. P.

    2014-01-01

    Calcium-free carbonate cancrinite with formula unit Na8.28[Al5.93Si6.07O24](CO3)0.93(OH)0.49·3.64H2O (CAN) has been synthesized under hydrothermal conditions. The product has been characterized by the methods of scanning electronic microscopy and energy dispersive X-ray analysis, Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis with FTIR of evolved gases (TGA-FTIR), and X-ray powder diffraction. The heat capacity of CAN has been measured from 6 to 259 K via low-temperature adiabatic calorimetry. A linear combination of Einstein functions has been used to approximate the obtained data on the heat capacity. The thermal contributions to the entropy and enthalpy of CAN in the temperature range 0-300 K have been calculated from these data. The heat capacity and third-law absolute entropy of CAN at 298.15 K are 1,047 ± 30 and 1,057 ± 35 J mol-1 K-1, respectively. High-temperature oxide-melt solution calorimetry has been used to determine the enthalpy of formation from elements of CAN at 298.15 K; the value equals -14,684 ± 50 kJ mol-1. The Gibbs energy of formation from elements at 298.15 K has been calculated and totaled -13,690 ± 51 kJ mol-1.

  12. GFP facilitates native purification of recombinant perlucin derivatives and delays the precipitation of calcium carbonate.

    PubMed

    Weber, Eva; Guth, Christina; Weiss, Ingrid M

    2012-01-01

    Insolubility is one of the possible functions of proteins involved in biomineralization, which often limits their native purification. This becomes a major problem especially when recombinant expression systems are required to obtain larger amounts. For example, the mollusc shell provides a rich source of unconventional proteins, which can interfere in manifold ways with different mineral phases and interfaces. Therefore, the relevance of such proteins for biotechnological processes is still in its infancy. Here we report a simple and reproducible purification procedure for a GFP-tagged lectin involved in biomineralization, originally isolated from mother-of-pearl in abalone shells. An optimization of E. coli host cell culture conditions was the key to obtain reasonable yields and high degrees of purity by using simple one-step affinity chromatography. We identified a dual functional role for the GFP domain when it became part of a mineralizing system in vitro. First, the GFP domain improved the solubility of an otherwise insoluble protein, in this case recombinant perlucin derivatives. Second, GFP inhibited calcium carbonate precipitation in a concentration dependent manner. This was demonstrated here using a simple bulk assay over a time period of 400 seconds. At concentrations of 2 µg/ml and higher, the inhibitory effect was observed predominantly for HCO(3) (-) as the first ionic interaction partner, but not necessarily for Ca(2+). The interference of GFP-tagged perlucin derivatives with the precipitation of calcium carbonate generated different types of GFP-fluorescent composite calcite crystals. GFP-tagging offers therefore a genetically tunable tool to gently modify mechanical and optical properties of synthetic biocomposite minerals. PMID:23056388

  13. GFP Facilitates Native Purification of Recombinant Perlucin Derivatives and Delays the Precipitation of Calcium Carbonate

    PubMed Central

    Weber, Eva; Guth, Christina; Weiss, Ingrid M.

    2012-01-01

    Insolubility is one of the possible functions of proteins involved in biomineralization, which often limits their native purification. This becomes a major problem especially when recombinant expression systems are required to obtain larger amounts. For example, the mollusc shell provides a rich source of unconventional proteins, which can interfere in manifold ways with different mineral phases and interfaces. Therefore, the relevance of such proteins for biotechnological processes is still in its infancy. Here we report a simple and reproducible purification procedure for a GFP-tagged lectin involved in biomineralization, originally isolated from mother-of-pearl in abalone shells. An optimization of E. coli host cell culture conditions was the key to obtain reasonable yields and high degrees of purity by using simple one-step affinity chromatography. We identified a dual functional role for the GFP domain when it became part of a mineralizing system in vitro. First, the GFP domain improved the solubility of an otherwise insoluble protein, in this case recombinant perlucin derivatives. Second, GFP inhibited calcium carbonate precipitation in a concentration dependent manner. This was demonstrated here using a simple bulk assay over a time period of 400 seconds. At concentrations of 2 µg/ml and higher, the inhibitory effect was observed predominantly for HCO3? as the first ionic interaction partner, but not necessarily for Ca2+. The interference of GFP-tagged perlucin derivatives with the precipitation of calcium carbonate generated different types of GFP-fluorescent composite calcite crystals. GFP-tagging offers therefore a genetically tunable tool to gently modify mechanical and optical properties of synthetic biocomposite minerals. PMID:23056388

  14. Formate Oxidation-Driven Calcium Carbonate Precipitation by Methylocystis parvus OBBP

    Microsoft Academic Search

    Giovanni Ganendra; Willem De Muynck; Adrian Ho; Eleni Charalampous Arvaniti; Baharak Hosseinkhani; Jose Angel Ramos; Hubert Rahier; Nico Boon

    2014-01-01

    Microbially induced carbonate precipitation (MICP) applied in the\\u000a construction industry poses several disadvantages such as ammonia\\u000a release to the air and nitric acid production. An alternative MICP from\\u000a calcium formate by Methylocystis parvus OBBP is presented here to\\u000a overcome these disadvantages. To induce calcium carbonate precipitation,\\u000a M. parvus was incubated at different calcium formate concentrations and\\u000a starting culture densities. Up

  15. Calcium oxalate crystal matrix extract: the most potent macromolecular inhibitor of crystal growth and aggregation yet tested in undiluted human urine in vitro

    Microsoft Academic Search

    I. R. Doyle; V. R. Marshall; C. J. Dawson; R. L. Ryall

    1995-01-01

    Demineralization of calcium oxalate (CaOx) crystals precipitated from human urine in vitro yields an organic crystal matrix extract (CME) consisting predominantly of a single protein which we originally named crystal matrix protein but have subsequently shown to be a urinary form of prothrombin activation peptide fragment 1 (F1). The aim of this study was to determine whether CME is a

  16. Influence of eggshell matrix proteins on the precipitation of calcium carbonate (CaCO 3)

    NASA Astrophysics Data System (ADS)

    Hernández-Hernández, A.; Vidal, M. L.; Gómez-Morales, J.; Rodríguez-Navarro, A. B.; Labas, V.; Gautron, J.; Nys, Y.; García Ruiz, J. M.

    2008-04-01

    To understand the role of eggshell organic matrix on the biomineralization process, we have tested the influence of different purified fractions of the eggshell organic matrix on calcium carbonate (CaCO 3) precipitation. Purification was carried out after successive anion-exchange chromatography, hydrophobic interaction chromatography and gel filtration chromatography of two different prepurified eggshell extracts (A) and (B); the purified fractions (named g, h, n and r) and ( c', g', i', k') respectively were diluted to 50 ?g/ml before being tested in vitro and analysed by the sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) procedure and mass spectrometry. The precipitation experiments were carried out by the method of vapour diffusion on crystallization mushrooms. Each purified fraction showed a different effect on CaCO 3 precipitation. Some of them exhibited a strong inhibitory effect on nucleation, thus suppressing the precipitation of CaCO 3 almost totally while the others did not produce any notable effect. However, all fractions favoured the precipitation of calcite over the other CaCO 3 polymorphs. Additionally, all fractions modified in a different manner the size and morphology of the precipitated calcite crystals.

  17. Synthesis, crystal structure and properties of a new lead calcium diborate

    NASA Astrophysics Data System (ADS)

    Cao, Jian; Pan, Shilie; Gao, Junyu; Huang, Zhenjun; Dong, Xiaoyu; Zhang, Min

    2012-07-01

    Single crystals of a novel lead calcium borate, PbCaB2O5, have been successfully grown by spontaneous crystallization method for the first time. The single-crystal X-ray structural analysis showed that PbCaB2O5 crystallizes in the triclinic space group P1¯ with a = 3.6736(6) Å, b = 6.5363(11) Å, c = 9.7585(17) Å, ? = 100.504(2)°, ? = 90.752(2)°, ? = 91.627(2)°, and Z = 2. The crystal structure consists of isolated B2O5 units, PbO5 and Pb/CaO7 polyhedra. Spectrum properties of PbCaB2O5 were reported.

  18. Evolution of the calcium hydroxyapatite crystal structure under plasma deposition and subsequent reducing treatment

    NASA Astrophysics Data System (ADS)

    Shamrai, V. F.; Karpikhin, A. E.; Sirotinkin, V. P.; Kalita, V. I.; Komlev, D. I.

    2014-03-01

    The structure of hydroxyapatite plasma coatings on a titanium substrate has been investigated by the X-ray Rietveld method. The hydroxyapatite crystal structure in plasma-deposited samples is characterized by strong distortions of its main element (tetrahedral PO4 cluster) and coordination calcium polyhedra, as well as calcium deficit in the Ca2 site; however, these features do not change the main motif of the hydroxyapatite structure. The bond distortions in PO4 clusters are estimated by the Bauer method. It is shown that hydrothermal treatment leads to the almost complete recovery of the hydroxyapatite structure.

  19. SURVEY OF NUMBER AND ARRANGEMENT OF CALCIUM OXALATE CRYSTALS IN LEAVES OF ANNUAL AND PERENNIAL SOYBEAN AND ALLIED TAXA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean is only one of many flowering plants that contain calcium oxalate crystals in its plant organs, especially in the leaves. Even though the functional significance of the crystals is still not understood, the sometimes massive amount, location and structure of crystals have been used in syste...

  20. Comment on "Single Crystals of Single-Walled Carbon Nanotubes

    E-print Network

    Kono, Junichiro

    et al. (1) reported the production of single crystals of single-walled carbon nano- tubes (SWCNTsComment on "Single Crystals of Single-Walled Carbon Nanotubes Formed by Self-Assembly" Schlittler) by the thermolysis of nano- patterned structures of alternating layers of C60 and nickel. Electron diffraction, high

  1. Crystallization kinetics of calcium oxalate hydrates studied by scanning confocal interference microscopy

    NASA Astrophysics Data System (ADS)

    Grohe, Bernd; Rogers, Kem A.; Goldberg, Harvey A.; Hunter, Graeme K.

    2006-10-01

    Scanning confocal interference microscopy (SCIM) is an optical technique that allows the visualization of structures below the limits of classical optical microscopy (?250 nm). This study represents the first use of SCIM to analyze the formation of calcium oxalate crystals, the major constituent of kidney stones. Crystals were nucleated and grown on the glass bottom of Petri dishes in the presence and absence of the polyelectrolyte inhibitor poly- L-aspartic acid (poly-asp). In the absence of poly-asp, monoclinic calcium oxalate monohydrate (COM) nucleated from {1 0 0} or {0 1 0} faces. The first observed particles were 70-120 nm in diameter and grew by a step-like progression in the [0 0 1] and [0 1 0] directions. Addition of poly-asp had several effects on calcium oxalate formation. First, the number of particles was increased, but their sizes were decreased. Second, the rate of COM growth in the [0 0 1] direction was decreased to a greater extent than the rate along [0 1 0]. Third, the formation of tetragonal calcium oxalate dihydrate (COD) crystals was favored. Fourth, the rates of COD growth along <1 1 0> and allied directions were decreased, whereas that parallel to <0 0 1> is increased. Sequences of highly resolved growth fronts show step displacement for COM and moving crystal edges for COD. Analysis of image sequences suggested that growth is strongly affected by competing and alternating processes, in which diffusion processes are rate-limiting and induce nonlinear growth. This study shows that SCIM is a powerful technique for the quantitative analysis of crystallization processes and for determining the mode of action of inhibitors.

  2. Effect of calcium carbonate combined with calcitonin on hypercalcemia in hemodialysis patients.

    PubMed

    Wei, Yong; Kong, Xiang Lei; Li, Wen Bin; Wang, Zun Song

    2014-12-01

    This short-term study assessed the efficacy and safety of calcium carbonate combined with calcitonin in the treatment of hypercalcemia in hemodialysis patients. Patients (n=64) on hemodialysis for chronic kidney disease for more than 6 months were included based on total serum calcium more than 10.5 mg/dL. All patients were randomized (1:1) to receive calcium carbonate combined with calcitonin (Group I) or lanthanum carbonate (Group II) for 12 weeks. Blood levels of calcium, phosphorus and intact parathyroid hormone (iPTH) were measured every month, bone mass density (BMD) and coronary artery calcium scores (CACS) were measured at 3 months. During the study period, serum calcium decreased from 10.72 ± 0.39 to 10.09 ± 0.28 mg/dL (P < 0.05), serum phosphorus decreased from 6.79 ± 1.05 to 5.46 ± 1.18 mg/dL (P < 0.05), and serum iPTH levels in the Group I and Group II were not significantly different from the baseline. There were no significant differences in CACS in either group. There were no significant differences in the BMD values between Group I and baseline. In Group II, the BMD values at the lumbar spine and femoral neck were significantly lower than those before the trial and significantly lower than the corresponding values of Group I (P<0.05). Calcium carbonate combined with calcitonin and lanthanum carbonate were equally effective in the suppression of hypercalcemia in hemodialysis patients. There were no serious treatment-related adverse events in treatment with calcium carbonate combined with calcitonin. PMID:24674384

  3. Specific Adsorption of Osteopontin and Synthetic Polypeptides to Calcium Oxalate Monohydrate Crystals

    PubMed Central

    Taller, Adam; Grohe, Bernd; Rogers, Kem A.; Goldberg, Harvey A.; Hunter, Graeme K.

    2007-01-01

    Protein-crystal interactions are known to be important in biomineralization. To study the physicochemical basis of such interactions, we have developed a technique that combines confocal microscopy of crystals with fluorescence imaging of proteins. In this study, osteopontin (OPN), a protein abundant in urine, was labeled with the fluorescent dye AlexaFluor-488 and added to crystals of calcium oxalate monohydrate (COM), the major constituent of kidney stones. In five to seven optical sections along the z axis, scanning confocal microscopy was used to visualize COM crystals and fluorescence imaging to map OPN adsorbed to the crystals. To quantify the relative adsorption to different crystal faces, fluorescence intensity was measured around the perimeter of the crystal in several sections. Using this method, it was shown that OPN adsorbs with high specificity to the edges between {100} and {121} faces of COM and much less so to {100}, {121}, or {010} faces. By contrast, poly-L-aspartic acid adsorbs preferentially to {121} faces, whereas poly-L-glutamic acid adsorbs to all faces approximately equally. Growth of COM in the presence of rat bone OPN results in dumbbell-shaped crystals. We hypothesize that the edge-specific adsorption of OPN may be responsible for the dumbbell morphology of COM crystals found in human urine. PMID:17496021

  4. Bioinspired synthesis of fluorescent calcium carbonate/carbon dot hybrid composites.

    PubMed

    Guo, Shanshan; Yang, Miao; Chen, Min; Zhang, Juan; Liu, Kang; Ye, Ling; Gu, Wei

    2015-04-21

    Herein, we report a novel method to synthesise fluorescent calcium carbonate/carbon dots (CaCO3/CDs) by simply mixing CaCl2 and Na2CO3 solutions in the presence of CDs. There are two roles of CDs in this easy and cost-effective biomimetic strategy, that is as the template to direct the formation and assembly of calcite nanocrystals into hierarchical spheres with diameters in the range of 200-300 nm and simultaneously as the phosphor to enable the CaCO3 to emit blue fluorescence under UV (365 nm) irradiation with a quantum yield of 56.2%. The CaCO3/CD hybrid composites possessing unique fluorescence properties are potentially useful in various applications. PMID:25845422

  5. Isolation and metagenomic characterization of bacteria associated with calcium carbonate and struvite precipitation in a pure moving bed biofilm reactor-membrane bioreactor.

    PubMed

    Gonzalez-Martinez, A; Leyva-Díaz, J C; Rodriguez-Sanchez, A; Muñoz-Palazon, B; Rivadeneyra, A; Poyatos, J M; Rivadeneyra, M A; Martinez-Toledo, M V

    2015-04-01

    A bench-scale pure moving bed bioreactor-membrane bioreactor (MBBR-MBR) used for the treatment of urban wastewater was analyzed for the identification of bacterial strains with the potential capacity for calcium carbonate and struvite biomineral formation. Isolation of mineral-forming strains on calcium carbonate and struvite media revealed six major colonies with a carbonate or struvite precipitation capacity in the biofouling on the membrane surface and showed that heterotrophic bacteria with the ability to precipitate calcium carbonate and struvite constituted ~7.5% of the total platable bacteria. These belonged to the genera Lysinibacillus, Trichococcus, Comamomas and Bacillus. Pyrosequencing analysis of the microbial communities in the suspended cells and membrane biofouling showed a high degree of similarity in all the samples collected with respect to bacterial assemblage. The study of operational taxonomic units (OTUs) identified through pyrosequencing suggested that ~21% of the total bacterial community identified in the biofouling could potentially form calcium carbonate or struvite crystals in the pure MBBR-MBR system used for the treatment of urban wastewater. PMID:26000766

  6. Sulfur Cycling Mediates Calcium Carbonate Geochemistry in Modern Marine Stromatolites

    NASA Technical Reports Server (NTRS)

    Visscher, P. T.; Hoeft, S. E.; Bebout, B. M.; Reid, R. P.

    2004-01-01

    Modem marine stromatolites forming in Highborne Cay, Exumas (Bahamas), contain microbial mats dominated by Schizothrix. Although saturating concentrations of Ca2+ and CO32- exist, microbes mediate CaCO3 precipitation. Cyanobacterial photosynthesis in these stromatolites aids calcium carbonate precipitation by removal of HS+ through CO2 use. Photorespiration and exopolymer production predominantly by oxygenic phototrophs fuel heterotrophic activity: aerobic respiration (approximately 60 umol/sq cm.h) and sulfate reduction (SR; 1.2 umol SO42-/sq cm.h) are the dominant C- consuming processes. Aerobic microbial respiration and the combination of SR and H2S oxidation both facilitate CaCO3 dissolution through H+ production. Aerobic respiration consumes much more C on an hourly basis, but duel fluctuating O2 and H2 depth profiles indicate that overall, SR consumes only slightly less (0.2-0.5) of the primary production. Moreover, due to low O2 concentrations when SR rates are peaking, reoxidation of the H2S formed is incomplete: both thiosulfate and polythionates are formed. The process of complete H2S oxidation yields H+. However, due to a low O2 concentration late in the day and relatively high O2 concentrations early in the following morning, a two-stage oxidation takes place: first, polythionates are formed from H2S, creating alkalinity which coincides with CaCO3 precipitation; secondly, oxidation of polythionates to sulfate yields acidity, resulting in dissolution, etc. Vertical profiles confirmed that the pH peaked late in the afternoon (greater than 8.8) and had the lowest values (less than 7.4) early in the morning. Thus, the effect of this S-cycling through alkalinity production, followed by acidification during H2S oxidation, results in a six times stronger fluctuation in acidity than photosynthesis plus aerobic respiration accomplish. This implies that anaerobic processes play a pivotal role in stromatolite formation.

  7. Effects of switching from calcium carbonate to lanthanum carbonate on bone mineral metabolism in hemodialysis patients.

    PubMed

    Manabe, Rie; Fukami, Kei; Ando, Ryotaro; Sakai, Kazuko; Kusumoto, Takuo; Hazama, Takuma; Adachi, Takeki; Kaida, Yusuke; Nakayama, Yosuke; Ueda, Seiji; Kohno, Keisuke; Wada, Yoshifumi; Yamagishi, Sho-ichi; Okuda, Seiya

    2013-04-01

    Phosphate binders are useful for the treatment of hyperphosphatemia in hemodialysis (HD) patients. This study was performed to examine the effects of switching from calcium carbonate (CC) to lanthanum carbonate (LC) on bone mineral metabolism and inflammatory markers in HD patients. We conducted 29 stable HD patients receiving CC, which was replaced by LC and followed-up for 12 weeks. Patients underwent determinants of blood chemistries such as serum calcium (Ca), phosphorus, parathyroid hormone (PTH) and vitamin D status, and interleukin-6 (IL-6) mRNA levels in whole blood cells were evaluated by real-time PCR just before and after the treatment with LC. Corrected Ca [corrected] levels were significantly reduced, but serum phosphorus levels (P levels) were unchanged after LC treatment. Switching to LC increased whole-PTH, osteocalcin, 1,25(OH)(2) D(3) levels and 1,25(OH)(2) D(3)/25(OH)D(3) ratio. 1,25(OH)(2) D(3)/25(OH)D(3) ratio was negatively correlated with HD duration. Furthermore, whole blood cell IL-6 mRNA levels were significantly reduced by LC treatment. We provided that the switching from CC to LC improved Ca overload and ameliorated vitamin D and inflammatory status in HD patients. These observations suggest that LC may play a protective role for the progression of atherosclerosis and vascular calcification in these patients. PMID:23586511

  8. The influence of kinetics on the oxygen isotope composition of calcium carbonate

    E-print Network

    Watkins, Jim

    on equilibrium fractionation of oxygen isotopes between calcium carbonate and water. Equili- brium oxygen isotope isotopes equilibrium kinetic carbonic anhydrase paleothermometry a b s t r a c t Paleotemperature reconstructions rely on knowledge of the equilibrium separation of oxygen isotopes between aqueous solution

  9. Aggregation of calcium oxalate crystals: effect of urine and various inhibitors.

    PubMed

    Felix, R; Monod, A; Broge, L; Hansen, N M; Fleisch, H

    1977-01-01

    The influence of various factors on aggregation of calcium oxalate crystals in vitro was determined. Aggregation was assessed by filtering the crystal suspension and measuring the flow rate through a filter. 10% urine completely inhibited aggregation. Orthophosphate and magnesium at concentrations occuring in urine had no effect. Citrate had no effect at 10(-4) M ,but did inhibit at 10(-3) M. The latter effect is probably due to calcium binding. Pyrophosphate and disodium dichioromethylene diphosphonate (C12MDP) inhibited strongly at 10(-4) M, disodium ethane-1-hydroxy-1,1-diphosphonate (EHDP) at 10(-5) M, whereas pentanemonophosphonate had no effect. Uromucoid also did not show any inhibitory activity. Studies by means of heat inactivation, ultrafiltration and fractionation on DEAE-cellulose and gel-filtration indicated that the inhibitory activity was heterogenous and that the major part was larger than 10 000 daltons. PMID:16372

  10. Herbal extracts of Tribulus terrestris and Bergenia ligulata inhibit growth of calcium oxalate monohydrate crystals in vitro

    Microsoft Academic Search

    V. S. Joshi; B. B. Parekh; M. J. Joshi; A. B. Vaidya

    2005-01-01

    A large number of people in this world are suffering from urinary stone problem. Calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) containing stones (calculi) are commonly found. In the present study, COM crystals were grown by a double diffusion gel growth technique using U-tubes. The gel was prepared from hydrated sodium metasilicate solution. The gel framework acts like

  11. Effects of calcium carbonate and hydroxyapatite on zinc and iron retention in postmenopausal women

    SciTech Connect

    Dawson-Hughes, B.; Seligson, F.H.; Hughes, V.A.

    1986-07-01

    We measured the effect of calcium carbonate and hydroxyapatite on whole-body retention of zinc-65 in 11 and iron-59 in 13 healthy, postmenopausal women. In a single-blind, controlled, crossover study, each subject, on three occasions, ingested a standard test meal supplemented with iron-59 or zinc-65 and capsules containing placebo or 500 mg elemental calcium as calcium carbonate or hydroxyapatite. Whole-body countings were performed prior to, 30 min after, and 2 wk after each meal. Mean (SEM) zinc retention was 18.1 +/- 1.0% with placebo (control) and did not vary significantly with calcium carbonate (110.0 +/- 8.6% of control) or hydroxyapatite (106.0 +/- 7.9% of control). Iron retention, 6.3 +/- 2.0% with placebo, was significantly reduced with both calcium carbonate (43.3 +/- 8.8% of control, p = 0.002) and hydroxyapatite (45.9 +/- 10.0% of control, p = 0.003). Iron absorption may be significantly reduced when calcium supplements are taken with meals.

  12. A simple method for quantitating the propensity for calcium oxalate crystallization in urine

    NASA Technical Reports Server (NTRS)

    Wabner, C. L.; Pak, C. Y.

    1991-01-01

    To assess the propensity for spontaneous crystallization of calcium oxalate in urine, the permissible increment in oxalate is calculated. The previous method required visual observation of crystallization with the addition of oxalate, this warranted the need for a large volume of urine and a sacrifice in accuracy in defining differences between small incremental changes of added oxalate. Therefore, this method has been miniaturized and spontaneous crystallization is detected from the depletion of radioactive oxalate. The new "micro" method demonstrated a marked decrease (p < 0.001) in the permissible increment in oxalate in urine of stone formers versus normal subjects. Moreover, crystallization inhibitors added to urine, in vitro (heparin or diphosphonate) or in vivo (potassium citrate administration), substantially increased the permissible increment in oxalate. Thus, the "micro" method has proven reliable and accurate in discriminating stone forming from control urine and in distinguishing changes of inhibitory activity.

  13. Synthesis and crystal structure of a new calcium borate, CaB 6O 10

    Microsoft Academic Search

    Xuean Chen; Ming Li; Xinan Chang; Hegui Zang; Weiqiang Xiao

    2008-01-01

    A new calcium borate, CaB6O10, has been prepared by solid-state reactions at temperature below 750°C. The single-crystal X-ray structural analysis showed that CaB6O10 crystallizes in the monoclinic space group P21\\/c with a=9.799(1)Å, b=8.705(1)Å, c=9.067(1)Å, ?=116.65(1)°, Z=4. It represents a new structure type in which two [B3O7]5? triborate groups are bridged by one oxygen atom to form a [B6O13]8? group that

  14. Optical assessment on a new self-frequency doubling crystal: neodymium-doped lanthanum calcium borate

    Microsoft Academic Search

    Rui Guo; Yicheng Wu; Peizhen Fu; Fangli Jing

    2005-01-01

    A new, to our knowledge, neodymium-doped lanthanum calcium borate crystal (Nd3+:La2CaB10O19, Nd:LCB) has been grown by the flux method. The spectroscopic parameters for Nd:LCB crystal have also been calculated based on Judd-Ofelt theory. The intensity parameters Omegat are Omega2=4.96×10-20 cm2, Omega4=3.94× 10-20 cm2, and Omega6=3.71×10-20 cm2. The radiative lifetime taur is 349 mus. The absorption band at 800 nm has

  15. Diphosphonates Inhibit Formation of Calcium Phosphate Crystals in vitro and Pathological Calcification in vivo

    Microsoft Academic Search

    Marion D. Francis; R. Graham G. Russell; Herbert Fleisch

    1969-01-01

    Two diphosphonates containing the P-C-P bond, CH3C(OH)(PO3HNa)2 and H2C(PO3HNa)2, inhibit the crystallization of calcium phosphate in vitro and prevent aortic calcification of rats given large amounts of vitamin D3. The diphosphonates therefore have effects similar to those described for compounds containing the P-O-P bond but are active when administered orally.

  16. Electroacoustical constants and Rayleigh SAW propagation characteristics of rare-earth calcium oxoborate single crystals

    Microsoft Academic Search

    Hiroyuki SHIMIZU; Ayako KONDO; Masahiro NISHIDA; Hiroaki TAKEDA; Takashi NISHIDA; Tadashi SHIOSAKI

    2005-01-01

    Electro-acoustical constants (?ij T , sij E , dij) of the rare- earth calcium oxoborate RCa4O(BO3)3 (R = La, Gd, Y; RCOB) piezoelectric single crystals, which belong to the monoclinic structure with point group m, were evaluated. Their electro- acoustical constants were systematically compared to the ionic radius of the R-site ions. The piezoelectric constants d11, d12, d13, d31, d32

  17. Photoinduced non-linear optical effects in lanthanum calcium borate single crystals

    Microsoft Academic Search

    Ali H. Reshak; S. Auluck; I. V. Kityk; A. Majchrowski; D. Kasprowicz; M. Drozdowski; J. Kisielewski; T. Lukasiewicz; E. Michalski

    2006-01-01

    We have revealed that lanthanum calcium borate (La2CaB10O19) crystals show two-photon absorption (TPA) favored by UV laser field. UV-induced TPA measurements were performed under illumination\\u000a of a Xe-F laser (? = 217nm) as a photoinducing (pumping) beam. This pumping laser beam created a thin surface layer (about\\u000a 85 nm) that was a source of the observed photoinduced TPA. Use of

  18. Timing Resolution and Decay Time of LSO Crystals Co-Doped With Calcium

    Microsoft Academic Search

    Tomasz Szczesniak; Marek Moszynski; Agnieszka Synfeld-Kazuch; ?. S?widerski; Merry A. Spurrier Koschan; Chuck L. Melcher

    2010-01-01

    A comparative study of five 5 × 5 × 5 mm3 LSO:Ce samples with different co-dopings of calcium, from 0 to 0.4% is reported. All the results are compared to those obtained with selected 10 × 10 × 5 mm3 LSO crystal, tested in previous studies. The influence of Ca co-dopant on scintillator parameters was studied using a Photonis XP20D0

  19. Exotic behavior and crystal structures of calcium under pressure

    PubMed Central

    Oganov, Artem R.; Ma, Yanming; Xu, Ying; Errea, Ion; Bergara, Aitor; Lyakhov, Andriy O.

    2010-01-01

    Experimental studies established that calcium undergoes several counterintuitive transitions under pressure: fcc ? bcc ? simple cubic ? Ca-IV ? Ca-V, and becomes a good superconductor in the simple cubic and higher-pressure phases. Here, using ab initio evolutionary simulations, we explore the behavior of Ca under pressure and find a number of new phases. Our structural sequence differs from the traditional picture for Ca, but is similar to that for Sr. The ?-tin (I41/amd) structure, rather than simple cubic, is predicted to be the theoretical ground state at 0 K and 33–71 GPa. This structure can be represented as a large distortion of the simple cubic structure, just as the higher-pressure phases stable between 71 and 134 GPa. The structure of Ca-V, stable above 134 GPa, is a complex host-guest structure. According to our calculations, the predicted phases are superconductors with Tc increasing under pressure and reaching approximately 20 K at 120 GPa, in good agreement with experiment. PMID:20382865

  20. [Chondrocalcinosis due to calcium pyrophosphate deposition (CPPD). From incidental radiographic findings to CPPD crystal arthritis].

    PubMed

    Tausche, A-K; Aringer, M

    2014-05-01

    If acute arthritis occurs in the elderly in addition to typical degenerative, load-related joint complaints, this is often induced by crystal deposition. The crystals lead to activation of the immune system resulting in acute inflammation. In addition to gout, calcium pyrophosphate deposition (CPPD) disease in particular must also be taken into consideration. Diagnostically important are imaging techniques, e.g. early specific alterations of cartilage can be shown by joint sonography and later calcium pyrophosphate crystals can be detected as cartilage calcification (chondrocalcinosis) by radiography. Important for the diagnosis of crystal arthropathy is usually the microscopic detection of specific crystals in the synovial fluid and is supported by exclusion of septic arthritis by arthrocentesis. In contrast to gout, which can be well controlled by the pharmaceutical lowering of uric acid levels, there is no causal therapy for CPPD disease so far. As CPPD may occur as a secondary effect in metabolic disorders, such as hyperparathyroidism or hemochromatosis, it seems to be important to search for the underlying disease. The following article presents the current knowledge on clinically relevant aspects of the pathogenesis, diagnosis and therapy of CPPD disease. PMID:24811359

  1. Calcium

    MedlinePLUS

    ... prevent falls in women, but not in men. Metabolic syndrome. Some evidence suggests that getting more calcium from ... vitamin D, might lower the risk of developing metabolic syndrome. Cancer. Research shows that healthy older women who ...

  2. pH-dependent release property of alginate beads containing calcium carbonate particles.

    PubMed

    Han, M R; Kwon, M C; Lee, H Y; Kim, J C; Kim, J D; Yoo, S K; Sin, I S; Kim, S M

    2007-12-01

    Alginate bead containing calcium carbonate particle were prepared by dropping the suspension of alginate/calcium carbonate (4/1, w/w) into aqueous solution of CaCl(2) (0.1 M). The pH-dependent release property of the bead was observed for 12 h using blue dextran as a model drug. The release increased up to 4 h in a saturation manner. When no calcium carbonate was contained, the release exhibited no marked variation with pH and the values were 27-39%. On the other hand, in case calcium carbonate was included in the matrix of alginate beads, intensive release(40-50%) was achieved in acidic and neutral conditions and the degrees of release were suppressed in alkali conditions and the values were approximately 20%. The pH-sensitive release property is possibly because the particles of calcium carbonate embedded in the matrix of beads were leached out in acidic and neutral conditions, leaving cavities in the matrix. The cavities are likely to be main pathways for the release of blue dextran. PMID:17926170

  3. Effect of acid rain on calcium carbonate saturation in the Albemarle sound of North Carolina

    SciTech Connect

    Rudolph, K.A.; Burgess, S.K.; Willey, J.D.; Kieber, R.J. [Univ. of North Carolina, Wilmington, NC (United States)

    1996-10-01

    The effects of acidic rainwater additions on calcium carbonate solubility and alkalinity in the poorly buffered, biologically active and commercially important waters of the Albemarle Sound, NC are reported. Samples collected monthly at four sites were analyzed for salinity, pK total alkalinity, and calcium concentrations. Five percent and 10% dilutions of sulfuric acid at pH 4, mimicking acid rain additions, were added and total alkalinity and calcium concentrations again determined. The addition of acid decreased the alkalinity in the Albemarle samples by as much as 15%, although the magnitude of the impact depended both on site and season. The effects of acid additions on dissolved calcium concentrations were more variable,. and also displayed a site and season dependency. Calcium concentrations, alkalinity, and pH values were also determined during controlled laboratory experiments, where 25 mg/L Callinectes sapidus shells were added to Albemarle Sound water. All three analytes increased significantly upon acid additions relative to controls.

  4. Calcium-isotope fractionation in selected modern and ancient marine carbonates

    Microsoft Academic Search

    Thomas Steuber; Dieter Buhl

    2006-01-01

    The calcium-isotope composition (?44\\/42Ca) was analyzed in modern, Cretaceous and Carboniferous marine skeletal carbonates as well as in bioclasts, non-skeletal components, and diagenetic cements of Cretaceous and Carboniferous limestones. In order to gain insight in Ca2+aq–CaCO3-isotope fractionation mechanisms in marine carbonates, splits of samples were analyzed for Sr, Mg, Fe, and Mn concentrations and for their oxygen and carbon isotopic

  5. Effect of fluoride on crystal growth of calcium apatites in the presence of a salivary inhibitor.

    PubMed

    Margolis, H C; Varughese, K; Moreno, E C

    1982-01-01

    The effect of fluoride on the kinetics of crystal growth of calcium apatites was studied using seed crystals of hydroxyapatite coated with PRP-3, a proline-rich phosphoprotein salivary inhibitor of crystal growth. Initial precipitation rates in the presence of PRP-3, under conditions of partial inhibition, were enhanced by fluoride, effectively counteracting the inhibitory activity of the macromolecule. This rate enhancement is related to an increase in the precipitation driving force, i.e., the degree of supersaturation with respect to the precipitating phase; in this case a fluoridated hydroxyapatite. The growth of this phase takes place at the uncovered crystal growth sites which have been previously shown to be the same sites as the adsorption sites for the protein inhibitors. Explanations based on fluoride activation of secondary crystal growth sites and on the displacement of adsorbed inhibitor by fluoride are not substantiated by the present results. It has been demonstrated that under conditions of maximum coverage of available crystal growth sites by PRP-3, resulting in no apparent crystal growth, measurable crystal growth is observed upon the addition of fluoride (1 ppm). This phenomenon is best explained by the fact that at maximum PRP-3 coverage, a small number (16%) of crystal growth sites remain uncovered, which support an unmeasurable rate of crystal growth. Upon the addition of fluoride, this rate is significantly enhanced. It is suggested that the fraction of uncovered growth sites is related to steric interactions of the PRP-3 molecule in the adsorbed state. Overall, the results presented suggest that fluoride can accelerate crystal growth in an environment such as the enamel surface where the acquired pellicle is formed. PMID:6293672

  6. Original article Availability of calcium from skim milk, calcium sulfate

    E-print Network

    Paris-Sud XI, Université de

    Original article Availability of calcium from skim milk, calcium sulfate and calcium carbonate; accepted 19 November 1999) Abstract --Dairy products provide abundant, accessible calcium for humans, while some calcium sulfate-rich mineral waters could provide appreciable amounts of calcium

  7. Revisiting spatial distribution and biochemical composition of calcium-containing crystals in human osteoarthritic articular cartilage

    PubMed Central

    2013-01-01

    Introduction Calcium-containing (CaC) crystals, including basic calcium phosphate (BCP) and calcium pyrophosphate dihydrate (CPP), are associated with destructive forms of osteoarthritis (OA). We assessed their distribution and biochemical and morphologic features in human knee OA cartilage. Methods We prospectively included 20 patients who underwent total knee replacement (TKR) for primary OA. CaC crystal characterization and identification involved Fourier-transform infra-red spectrometry and scanning electron microscopy of 8 to 10 cartilage zones of each knee, including medial and lateral femoral condyles and tibial plateaux and the intercondyle zone. Differential expression of genes involved in the mineralization process between cartilage with and without calcification was assessed in samples from 8 different patients by RT-PCR. Immunohistochemistry and histology studies were performed in 6 different patients. Results Mean (SEM) age and body mass index of patients at the time of TKR was 74.6 (1.7) years and 28.1 (1.6) kg/m², respectively. Preoperative X-rays showed joint calcifications (chondrocalcinosis) in 4 cases only. The medial femoro-tibial compartment was the most severely affected in all cases, and mean (SEM) Kellgren-Lawrence score was 3.8 (0.1). All 20 OA cartilages showed CaC crystals. The mineral content represented 7.7% (8.1%) of the cartilage weight. All patients showed BCP crystals, which were associated with CPP crystals for 8 joints. CaC crystals were present in all knee joint compartments and in a mean of 4.6 (1.7) of the 8 studied areas. Crystal content was similar between superficial and deep layers and between medial and femoral compartments. BCP samples showed spherical structures, typical of biological apatite, and CPP samples showed rod-shaped or cubic structures. The expression of several genes involved in mineralization, including human homolog of progressive ankylosis, plasma-cell-membrane glycoprotein 1 and tissue-nonspecific alkaline phosphatase, was upregulated in OA chondrocytes isolated from CaC crystal-containing cartilages. Conclusions CaC crystal deposition is a widespread phenomenon in human OA articular cartilage involving the entire knee cartilage including macroscopically normal and less weight-bearing zones. Cartilage calcification is associated with altered expression of genes involved in the mineralisation process. PMID:24004678

  8. Crystal structure of complex natural aluminum magnesium calcium iron oxide

    NASA Astrophysics Data System (ADS)

    Rastsvetaeva, R. K.; Aksenov, S. M.; Verin, I. A.

    2010-07-01

    The structure of a new natural oxide found near the Tashelga River (Eastern Siberia) was studied by X-ray diffraction. The pseudo-orthorhombic unit cell parameters are a = 5.6973(1) Å, b = 17.1823(4) Å, c = 23.5718(5) Å, ? = 90°, sp. gr. Pc. The structure was refined to R = 0.0516 based on 4773 reflections with | F| > 7?( F) taking into account the twin plane perpendicular to the z axis (the twin components are 0.47 and 0.53). The crystal-chemical formula ( Z = 4) is Ca2Mg{2/IV}Fe{2/(2+)IV}[Al{14/VI}O31(OH)][Al{2/IV}O][AlIV]ALIV(OH)], where the Roman numerals designate the coordination of the atoms. The structure of the mineral is based on wide ribbons of edge-sharing Al octahedra (an integral part of the spinel layer). The ribbons run along the shortest x axis and are inclined to the y and z axes. The adjacent ribbons are shifted with respect to each other along the y axis, resulting in the formation of step-like layers in which the two-ribbon thickness alternates with the three-ribbon thickness. Additional Al octahedra and Mg and Fe2+ tetrahedra are located between the ribbons. The layers are linked together to form a three-dimensional framework by Al tetrahedra, Ca polyhedra, and hydrogen bonds with the participation of OH groups.

  9. Therapeutic effect of Xue Niao An on glyoxylate-induced calcium oxalate crystal deposition based on urinary metabonomics approach

    PubMed Central

    Peng, Zhongjiang; Chen, Wei; Gao, Songyan; Su, Li; Li, Na; Wang, Li; Lou, Ziyang; Dong, Xin; Guo, Zhiyong

    2014-01-01

    The anti-nephrolithiasis effect of Xue Niao An (XNA) capsules is explored by analyzing urine metabolic profiles in mouse models, with ultra-high performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF/MS). An animal model of calcium oxalate crystal renal deposition was established in mice by intra-abdominal injection of glyoxylate. Then, treatment with XNA by intra-gastric administration was performed. At the end of the study, calcium deposition in kidney was measured by Von Kossa staining under light microscopy, and the Von Kossa staining changes showed that XNA significantly alleviated the calcium oxalate crystal deposition. Meanwhile, urine samples for fifteen metabolites, including amino acids and fatty acids, with significant differences were detected in the calcium oxalate group, while XNA treatment attenuated metabolic imbalances. Our study indicated that the metabonomic strategy provided comprehensive insight on the metabolic response to XNA treatment of rodent renal calcium oxalate deposition. PMID:25411524

  10. Thermodynamics of calcium-isotope-exchange reactions. 1. Exchange between isotopic calcium carbonates and aqueous calcium ions

    Microsoft Academic Search

    Rongsen Zhang; Charles P. Nash; Peter A. Rock

    1988-01-01

    This paper reports the authors results for the direct experimental determination of the equilibrium constant for the calcium-isotope-exchange reaction ⁴°CaCOâ(s) + ⁴⁴CaClâ(aq) reversible ⁴⁴CaCOâ(s) + ⁴°CaClâ(aq). The reaction was studied in electrochemical double cells without liquid junction of the type shown in eq 2. The experimental value of the equilibrium constant at 295 +\\/- 2 K is K = 1.08

  11. Immobilization of Pseudomonas sp. DG17 onto sodium alginate–attapulgite–calcium carbonate

    PubMed Central

    Wang, Hong Qi; Hua, Fei; Zhao, Yi Cun; Li, Yi; Wang, Xuan

    2014-01-01

    A strain of Pseudomonas sp. DG17, capable of degrading crude oil, was immobilized in sodium alginate–attapulgite–calcium carbonate for biodegradation of crude oil contaminated soil. In this work, proportion of independent variables, the laboratory immobilization parameters, the micromorphology and internal structure of the immobilized granule, as well as the crude oil biodegradation by sodium alginate–attapulgite–calcium carbonate immobilized cells and sodium alginate–attapulgite immobilized cells were studied to build the optimal immobilization carrier and granule-forming method. The results showed that the optimal concentrations of sodium alginate–attapulgite–calcium carbonate and calcium chloride were 2.5%–3.5%, 0.5%–1%, 3%–7% and 2%–4%, respectively. Meanwhile, the optimal bath temperature, embedding cell amount, reaction time and multiplication time were 50–60 °C, 2%, 18 h and 48 h, respectively. Moreover, biodegradation was enhanced by immobilized cells with a total petroleum hydrocarbon removal ranging from 33.56% ± 3.84% to 56.82% ± 3.26% after 20 days. The SEM results indicated that adding calcium carbonate was helpful to form internal honeycomb-like pores in the immobilized granules. PMID:26019567

  12. Dissolution of calcium pyrophosphate crystals by polyphosphates: an in vitro and ex vivo study

    PubMed Central

    Cini, R; Chindamo, D; Catenaccio, M; Lorenzini, S; Selvi, E; Nerucci, F; Picchi, M; Berti, G; Marcolongo, R

    2001-01-01

    OBJECTIVE—To determine the dissolving ability (DA) of linear pentasodium tripolyphosphate (PSTP), cyclic trisodium metaphosphate (TSMP), polymeric sodium metaphosphate (SMP) on synthetic crystals of calcium pyrophosphate dihydrate (CPPD) and on crystalline aggregates of menisci from patients with chondrocalcinosis (CC).?METHODS—Synthetic CPPD crystals were mixed with phosphate buffered saline (PBS), which contained the different polyphosphates, for one hour at 37°C. The calcified menisci were obtained from the knees of four female patients with CPPD disease who underwent total arthroscopic meniscectomy for degenerative meniscal lesions. Meniscal cryosections and fragments were incubated in SMP (15 mg/ml PBS) at 37°C for one hour and 24 hours, respectively. Histological evaluation on meniscal samples after polyphosphate incubation was carried out by ordinary transmitted light microscopy and polarised light microscopy. The dissolution of CPPD crystals by polyphosphates was assessed by atomic absorption spectroscopy, which determined the amount of calcium liberated from synthetic crystals and meniscal fragments. Cytotoxicity of SMP was evaluated by tetrazolium salt assay and by an ultrastructural study on cultured chondrocytes.?RESULTS—SMP and PSTP showed higher DA on CPPD crystals than TSMP. Analysis of the DA values at increasing concentrations of SMP showed that a concentration of 15 mg/ml completely dissolved 2.0 mg CPPD crystals. The solution of meniscal CPPD crystals showed a significant increase of calcium concentration after three hours and 24 hours of SMP incubation (p=0.0001; Kruskal-Wallis analysis of variance) compared with fragments incubated in PBS control solution. Macroscopic and microscopic evaluation of meniscal specimens showed a notable reduction of CPPD deposits. A 50% inhibitory dose on cultured chondrocytes was reached at the maximum concentration of SMP used in this work (15 mg/ml); ultrastructural analysis did not show morphological alterations in the treated cells.?CONCLUSION—The results of this study indicate that linear polyphosphates are effective in dissolving both synthetic and ex vivo CPPD crystal aggregates. This suggests a potential therapeutic use for these molecules in the treatment of symptomatic CC.?? PMID:11557654

  13. Carbonate and magnesium interactive effect on calcium phosphate precipitation.

    PubMed

    Cao, Xinde; Harris, Willie

    2008-01-15

    Precipitation of Ca phosphates, an important process in controlling P stability and activity in P-fertilized soils and P-rich wastewater, is often affected by other components. The purpose of this study was to document interactive effects of CO3(2-) and Mg2+ on Ca phosphate precipitation under conditions simulating (i) dairy manure-amended soil leachate (system I; pH 7.1) and (ii) P recovery from flushed dairy manure wastewater (system II; pH 9.2). Hydroxyapatite (HAP) and more soluble amorphous Ca phosphate (ACP) were formed in the control solutions of system I and system II, respectively. Carbonate only slightly affected the crystallinity of the precipitate, but significantly reduced the precipitation rate via CO3(2-) competition for PO4(3-) (system I) or preemptive CaCO3 precipitation (system II). Magnesium severely inhibited both precipitate crystallinity and precipitation rate, allowing formation of ACP in both systems, presumably due to Mg2+ incorporation into the Ca phosphate structure to form Mg2+ -substituted structure that crystallized to whitlockite upon heating. Coexistence of CO32- and Mg2+ in system I showed a synergistic inhibitory effect, compared to their individual presence, probably because both CO3(2-) and Mg2+ were incorporated into the precipitate. However, in system II, the individual inhibitory effect of CO3(2-) or Mg2+ was eliminated when both were present. The likely mechanism involves formation of aqueous MgCO3 (aq) which reduces free CO3(2-) and Mg2+ activities, resulting in less preemptive CaCO3 formation and enhanced Ca phosphate precipitation. PMID:18284143

  14. Crystal structure of complex natural aluminum magnesium calcium iron oxide

    SciTech Connect

    Rastsvetaeva, R. K., E-mail: rast@ns.crys.ras.ru; Aksenov, S. M.; Verin, I. A. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2010-07-15

    The structure of a new natural oxide found near the Tashelga River (Eastern Siberia) was studied by X-ray diffraction. The pseudo-orthorhombic unit cell parameters are a = 5.6973(1) A, b = 17.1823(4) A, c = 23.5718(5) A, {beta} = 90{sup o}, sp. gr. Pc. The structure was refined to R = 0.0516 based on 4773 reflections with vertical bar F vertical bar > 7{sigma}(F) taking into account the twin plane perpendicular to the z axis (the twin components are 0.47 and 0.53). The crystal-chemical formula (Z = 4) is Ca{sub 2}Mg{sub 2}{sup IV}Fe{sub 2}{sup (2+)IV}[Al{sub 14}{sup VI}O{sub 31}(OH)][Al{sub 2}{sup IV}O][Al{sup IV}]AL{sup IV}(OH)], where the Roman numerals designate the coordination of the atoms. The structure of the mineral is based on wide ribbons of edge-sharing Al octahedra (an integral part of the spinel layer). The ribbons run along the shortest x axis and are inclined to the y and z axes. The adjacent ribbons are shifted with respect to each other along the y axis, resulting in the formation of step-like layers in which the two-ribbon thickness alternates with the three-ribbon thickness. Additional Al octahedra and Mg and Fe{sup 2+} tetrahedra are located between the ribbons. The layers are linked together to form a three-dimensional framework by Al tetrahedra, Ca polyhedra, and hydrogen bonds with the participation of OH groups.

  15. CALCIUM HYDROXIDE AND CALCIUM CARBONATE PARTICLE SIZE EFFECTS ON REACTIVITY WITH SULFUR DIOXIDE

    EPA Science Inventory

    The paper reports results of measurements of the effect of in situ calcium-based sorbent particle size upon reactivity with 3000 ppm SO2 in an 1100 c drop-tube furnace, using on-line collection of the reacted sorbent with a particle cascade impactor. Significant agglomeration occ...

  16. Basic calcium phosphate crystal-induced Egr-1 expression stimulates mitogenesis in human fibroblasts

    SciTech Connect

    Zeng, Xiao R. [Department of Biomedical Engineering, University of Miami, Coral Gablek, FL 33146 (United States); Sun Yubo [Division of Rheumatology and Immunology, Department of Medicine, University of Miami School of Medicine, Miami, FL 33101 (United States); Wenger, Leonor [Department of Biomedical Engineering, University of Miami, Coral Gablek, FL 33146 (United States); Cheung, Herman S. [Department of Biomedical Engineering, University of Miami, Coral Gablek, FL 33146 (United States) and Division of Rheumatology and Immunology, Department of Medicine, University of Miami School of Medicine, Miami, FL 33101 (United States) and Research Service and the Geriatric Research, Education, and Clinical Center, Veterans Affairs Medical Center, Miami, FL 33125 (United States)]. E-mail: hcheung@med.miami.edu

    2005-05-13

    Previously, we have reported that basic calcium phosphate (BCP) crystals stimulate mitogenesis and synthesis of matrix metalloproteinases in cultured human foreskin and synovial fibroblasts. However, the detailed mechanisms involved are still unclear. In the present study, using RT-PCR and Egr-1 promoter analysis we showed that BCP crystals could stimulate early growth response gene Egr-1 transcription through a PKC{alpha}-dependent p44/p42 MAPK pathway. Using a retrovirus gene expression system (Clontech) to overexpress Egr-1 in human fibroblast BJ-1 cells resulted in promotion of mitogenesis measured either by MTT cell proliferation analysis or by direct cell counting. The results demonstrate that Egr-1 may play a key role in mediating BCP crystal-induced synovial fibroblast mitogenesis.

  17. Evidence for a causal relationship between the structure, size, and load of calcium pyrophosphate dihydrate crystals, and attacks of pseudogout

    Microsoft Academic Search

    A Swan; B Heywood; B Chapman; H Seward; P Dieppe

    1995-01-01

    OBJECTIVE--To investigate any relationship between the nature, size, and numbers of synovial fluid (SF) calcium pyrophosphate dihydrate (CPPD) crystals, and attacks of pseudogout. METHODS--Knee SF was aspirated from nine selected patients, first during an attack of pseudogout (acute sample) and again later when the attack had subsided (interval sample). CPPD crystals were extracted, weighed, examined by high resolution transmission electron

  18. Madin-Darby canine kidney cells are injured by exposure to oxalate and to calcium oxalate crystals

    Microsoft Academic Search

    R. L. Hackett; P. N. Shevock; S. R. Khan

    1994-01-01

    The reaction of Madin-Darby canine kidney cells (MDCK) to potassium oxalate (KOx), calcium oxalate monohydrate (COM) crystals, or a combination of the two was studied. The most noticeable effect of exposure of the cells to either KOx or COM crystals was loss of cells from the monolayer ranging from 20% to 30%, depending upon the particular treatment. Cellular enzyme values

  19. Inhibition of the growth of urinary calcium hydrogen phosphate dihydrate crystals with aqueous extracts of Tribulus terrestris and Bergenia ligulata

    Microsoft Academic Search

    Vimal S. Joshi; Bharat B. Parekh; Mihir J. Joshi; Ashok D. B. Vaidya

    2005-01-01

    Urinary type calcium hydrogen phosphate dihydrate (CHPD) or Brushite crystals were grown by the single diffusion gel technique in silica hydro-gels. The gel framework acts as a three dimensional crucible in which the crystal nuclei are delicately held in the position of their formation and nutrients are supplied for their growth. This technique can be utilized as a simplified screening

  20. MEDICAGO TRUNCATULA MUTANTS DEMONSTRATE THE ROLE OF PLANT CALCIUM OXALATE CRYSTALS AS AN EFFECTIVE DEFENSE AGAINST CHEWING INSECTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Calcium oxalate is the most abundant insoluble mineral found in plants and its crystals have been reported in over 200 plant families. In the barrel medic, Medicago truncatula Gaertn., these crystals accumulate predominantly in a sheath surrounding secondary veins of leaves. Mutants of M. truncatul...

  1. Magnesium whitlockite, a calcium phosphate crystal of special interest in pathology.

    PubMed

    Lagier, R; Baud, C A

    2003-01-01

    Whitlockite (in fact magnesium whitlockite) is a calcium orthophosphate crystal in which, in biological conditions, magnesium is partly substituted for calcium. Identified in X-ray or electron diffraction patterns, it occurs in physiological or pathological conditions at extra or intratissular sites, mainly in tissues of non-epithelial origin. In a range of pathological calcifications investigated by X-ray diffraction, we noted that whitlockite appeared to be frequently associated with apatite, particularly in "dystrophic calcifications" of tuberculous origin. These personal observations could be correlated with documented data in oral pathology (dental calculus, salivary stones, and dental caries). Whitlockite deposits have also been reported in non-infectious conditions, such as in aortic media, cartilage, and bone tissue. Whereas the formation of both apatite and magnesium whitlockite appears to be caused by the binding of their constituting ions with proteolipids, magnesium inhibits apatite originating from amorphous calcium phosphate to the benefit of whitlockite formation. Possibly, the development of magnesium whitlockite may provide an interesting marker for magnesium metabolism. Further studies linking histology to crystallography might relate the crystal to issues, such as tuberculous calcifications or diseases of bone tissue, and might be useful for potential diagnostic orientation. PMID:12908523

  2. Carbon Nanotube-Reinforced Thermotropic Liquid Crystal Polymer Nanocomposites

    E-print Network

    Kim, Jun Young

    This paper focuses on the fabrication via simple melt blending of thermotropic liquid crystal polyester (TLCP) nanocomposites reinforced with a very small quantity of modified carbon nanotube (CNT) and the unique effects ...

  3. The Influence of Calcium Carbonate Grain Coatings on Contaminant Reactivity in Vadose Zone Sediments

    SciTech Connect

    Zachara, John M.; Chambers, Scott; Brown Jr., Gordon E.; Eggleston, Carrick M.

    2001-06-01

    Calcium carbonate (CaCO3) is widely distributed through the Hanford vadose zone as a minor phase. As a result of current and past geochemical processes, CaCO3 exists as grain coatings, intergrain fill, and distinct caliche layers in select locations. Calcium carbonate may also precipitate when high-level wastes react with naturally Ca- and Mg-saturated Hanford sediments. Calcium carbonate is a very reactive mineral phase. Sorption reactions on its surface may slow the migration of certain contaminants (Co, Sr), but its surface coatings on other mineral phases may diminish contaminant retardation (for example, Cr) by blocking surface reaction sites of the substrate. This project explores the behavior of calcium carbonate grain coatings, including how they form and dissolve, their reactivity toward key Hanford contaminants, their impact (as surface coatings) on the reactivity of other mineral substrates, and on their in-ground composition and minor element enrichment. The importance of CaCO3 as a contaminant sorbent will be defined in all of its different manifestations in Hanford sediments: dispersed minor lithic fragments, pedogenic carbonate coatings on gravel and stringers in silt, and nodules in clay and paleosols. Mass action models will be developed that allow understanding and prediction of the geochemical effects of CaCO3 on contaminant retardation in Hanford sediments.

  4. Calcium-oxalate crystals and crystal cells in determinate root nodules of legumes

    Microsoft Academic Search

    J. M. Sutherland; J. I. Sprent

    1984-01-01

    Early reports of the presence of calciumoxalate crystals in the cortices ofPhaseolus vulgaris root nodules have been confirmed. Crystals were found in all six genera examined (Cajanus, Desmodium, Glycine, Lespedeza, Phaseolus, Vigna) that have determinate nodules and export ureides. They were absent from six genera examined that have indeterminate nodules and export amides. The possible physiological significance of these structures

  5. Effects of phosphorus-containing calcium preparation (bone meal powder) and calcium carbonate on serum calcium and phosphorus in young and old healthy volunteers: a double-blinded crossover study

    Microsoft Academic Search

    Minoru Tsuboi; Masataka Shiraki; Michiyasu Hamada; Hideo Shimodaira

    2000-01-01

    To evaluate the effects of bone meal powder (BEC) on calcium and phosphorus metabolism, a calcium absorption test was conducted\\u000a using a preparation of calcium carbonate (CAC) as the control drug. A total of 12 healthy volunteers, consisting of 6 younger\\u000a (aged 20–29 years, 3 men and 3 women) and 6 older (aged 60–69 years, 3 men and 3 women)

  6. The determination of calcium in phosphate, carbonate, and silicate rocks by flame photometer

    USGS Publications Warehouse

    Kramer, Henry

    1956-01-01

    A method has been developed for the determination of calcium in phosphate, carbonate, and silicate rocks using the Beckman flame photometer, with photomultiplier attachement. The sample is dissolved in hydrofluoric, nitric, and perchloric acids, the hydrofluoric and nitric acids are expelled, a radiation buffer consisting of aluminum, magnesium, iron, sodium, potassium, phosphoric acid, and nitric acid is added, and the solution is atomized in an oxy-hydrogen flame with an instrument setting of 554 mµ. Measurements are made by comparison against calcium standards, prepared in the same manner, in the 0 to 50 ppm range. The suppression of calcium emission by aluminum and phosphate was overcome by the addition of a large excess of magnesium. This addition almost completely restores the standard curve obtained from a solution of calcium nitrate. Interference was noted when the iron concentration in the aspirated solution (including the iron from the buffer) exceeded 100 ppm iron. Other common rock-forming elements did not interfere. The results obtained by this procedure are within ± 2 percent of the calcium oxide values obtained by other methods in the range 1 to 95 percent calcium oxide. In the 0 to 1 percent calcium oxide range the method compares favorably with standard methods.

  7. An atlas of the distribution of calcium carbonate in sediments of the deep sea

    Microsoft Academic Search

    David E. Archer

    1996-01-01

    The goals of this study were to: (1) digest available sedimentary data into a format appropriate for validating models of oceanic calcium carbonate (CaCOâ) dynamics, (2) estimate the inventory of deep sea CaCOâ available for neutralization of fossil fuel carbon dioxide, and (3) determine the variability of CaCOâ preservation relative to local saturation conditions. CaCOâ concentrations in global deep sea

  8. Crystal structure and phase transformations of calcium yttrium orthophosphate, Ca 3Y(PO 4) 3

    NASA Astrophysics Data System (ADS)

    Fukuda, Koichiro; Iwata, Tomoyuki; Niwa, Takahiro

    2006-11-01

    Crystal structure and phase transformations of calcium yttrium orthophosphate Ca 3Y(PO 4) 3 were investigated by X-ray powder diffraction, selected-area electron diffraction, transmission electron microscopy and optical microscopy. The high-temperature phase is isostructural with eulytite, cubic (space group I4¯3d) with a=0.983320(5) nm, V=0.950790(8) nm 3, Z=4 and D x=3.45 Mg m -3. The crystal structure was refined with a split-atom model, in which the oxygen atoms are distributed over two partially occupied sites. Below the stable temperature range of eulytite, the crystal underwent a martensitic transformation, which is accompanied by the formation of platelike surface reliefs. The inverted crystal is triclinic (space group P1) with a=1.5726(1) nm, b=0.84267(9) nm, c=0.81244(8) nm, ?=109.739(4)°, ?=90.119(5)°, ?=89.908(7)°, V=1.0134(1) nm 3, Z=4 and D x=3.24 Mg m -3. The crystal grains were composed of pseudo-merohedral twins. The adjacent twin domains were related by the pseudo-symmetry mirror planes parallel to {101¯} with the composition surface {101¯}. When the eulytite was cooled relatively slowly from the stable temperature range, the decomposition reaction of Ca 3Y(PO 4) 3? ?-Ca 3(PO 4) 2+YPO 4 occurred.

  9. Growth and optical properties of a new nonlinear optical lanthanum calcium borate crystal

    NASA Astrophysics Data System (ADS)

    Xu, X. W.; Chong, T. C.; Zhang, G. Y.; Cheng, S. D.; Li, M. H.; Phua, C. C.

    2002-04-01

    The monoclinic lanthanum calcium borate La 2CaB 10O 19 (LCB) crystal was grown from its stoichiometric melt by the top-seeded pulling method. The unpolarized transmission spectrum of a 1-mm-thick (0 0 1)-cut LCB crystal was measured in the wavelength range of 190-3100 nm. The crystal exhibited a high transmittance (>80%) and a short absorption edge (<190 nm). The phase-matched second-harmonic generation (SHG) properties within the (0 1 0) plane of a 1.7-mm-thick (0 0 1)-cut LCB crystal were studied for the first time with a Spectra-Physics 3900S Ti:sapphire CW tunable laser. The room-temperature phase-matching (PM) wavelength was found to be 869 nm when the light propagation and polarization directions of the fundamental beam were parallel to the [0 0 1] and [0 1 0] axes, respectively. The full width at half maximum (FWHM) of the wavelength-tuning curve was found to be about 6 nm.The phase-matched SHG of the LCB crystal exhibited a small temperature coefficient of 0.05 nm/°C between 24°C and 150°C and was quite stable for generating visible light upon temperature changes.

  10. Crystal Structure of Calcium-depleted Bacillus licheniformis?-amylase at 2.2 Å Resolution

    Microsoft Academic Search

    M. Machius; G. Wiegand; R. Huber

    1995-01-01

    The three-dimensional structure of the calcium-free form ofBacillus licheniformis?-amylase (BLA) has been determined by multiple isomorphous replacement in a crystal of space groupP43212 (a=b=119.6 Å,c=85.4 Å). The structure was refined using restrained crystallographic refinement to anR-factor of 0.177 for 28,147 independent reflections with intensitiesFObs0 at 2.2 Å resolution, with root mean square deviations of 0.008 Å and 1.4° from ideal

  11. ANNUAL REPORT. THE INFLUENCE OF CALCIUM CARBONATE GRAIN COATINGS ON CONTAMINANT REACTIVITY IN VADOSE ZONE SEDIMENTS

    EPA Science Inventory

    The primary objective of this project is to investigate the role of calcium carbonate grain coatings on adsorption and heterogeneous reduction reactions of key chemical and radioactive contaminants in sediments on the Hanford Site. Research will ascertain whether these coatings p...

  12. PROGRESS REPORT. THE INFLUENCE OF CALCIUM CARBONATE GRAIN COATINGS ON CONTAMINANT REACTIVITY IN VADOSE ZONE SEDIMENTS

    EPA Science Inventory

    This project explores the behavior of calcium carbonate grain coatings, including how they form and dissolve, their reactivity toward key Hanford contaminants, their impact (as surface coatings) on the reactivity of other mineral substrates, and on their in-ground composition and...

  13. Shallow rocky bottom benthic assemblages as calcium carbonate producers in the Alboran Sea (southwestern Mediterranean)

    Microsoft Academic Search

    Emma CEBRIÁN; Enric BALLESTEROS; Miquel CANALS

    2000-01-01

    Zonation patterns and species composition of the different assemblages encountered along the bathymetric axis are considered in order to quantify the biomass and calcium carbonate content of communities thriving in rocky bottoms of La Herradura (southwestern Mediterranean) between 0 and 50 m depth. Algal biomass is lower but total biomass is slightly higher to values recorded in other Mediterranean areas

  14. Decomposition rate constant of fine calcium carbonate powder in a fluidized bed

    Microsoft Academic Search

    Kono

    1981-01-01

    Although many papers have been published on the decomposition rate of calcium carbonate (limestone) in the form of large particles, there are very few data available on the decomposition rate of fine limestone particles (smaller than 100..mu..) under a high heat transfer rate condition as in a fluidized bed. Information of this type would be useful for design of a

  15. A model for calcium carbonate neutralization in the presence of armoring

    E-print Network

    Primicerio, Mario

    A model for calcium carbonate neutralization in the presence of armoring L. Fusia , M. Primicerioa (armoring). We suppose that neutralization is governed by a first order reaction, with the reaction rate, Reaction Kinetics, Armoring, Partial Differential Equations, multi-scale modelling 1. Introduction

  16. EXPERIMENTAL DETERMINATION OF THE CALCIUM CARBONATE SATURATION STATES OF WATER SYSTEMS (TECHNICAL NOTE)

    EPA Science Inventory

    Emphasis is given to the fact that saturation indexes only indicate the tendency of a water to dissolve or precipitate calcium carbonate (CaCo3). The rate at which a given water attains equilibrium cannot be derived from the saturation index value....

  17. Calcium Channel Blockers Reduce Blood Pressure in Part by Inhibiting Vascular Smooth Muscle Carbonic Anhydrase I

    Microsoft Academic Search

    Ioan Puscas; Ludovic Gilau; Marcela Coltau; Radu Pasca; Gabriela Domuta; Michael Baican; Alex Hecht

    2000-01-01

    Calcium channel blockers are a group of drugs used for the treatment of hypertension. Carbonic anhydrase (CA) I detected in vascular smooth muscle and in other cells in the organism has a major role in the acid-base balance and in vascular processes. Our previous work has proven that verapamil inhibits CA activity by a direct mechanism of action. Starting from

  18. Biomimetic soy protein nanocomposites with calcium carbonate crystalline arrays for use as wood adhesive

    E-print Network

    and bonding strength of soy protein adhesives. Glue strength of soy protein hybrid adhesive was higher than 6 2010 Available online 21 March 2010 Keywords: Wood glue Calcium carbonate Gecko adhesion Soy protein the adhesion strength. The structure and morphology of the adhesive and its fracture bonding interface

  19. CO.sub.2 Pretreatment prevents calcium carbonate formation

    DOEpatents

    Neavel, Richard C. (Baytown, TX); Brunson, Roy J. (Buffalo Grove, IL); Chaback, Joseph J. (Worthington, OH)

    1980-01-01

    Scale formation during the liquefaction of lower ranking coals and similar carbonaceous materials is significantly reduced and/or prevented by pretreatment with carbon dioxide. The carbon dioxide pretreatment is believed to convert the scale-forming components to the corresponding carbonate prior to liquefaction. The pretreatment is accomplished at a total pressure within the range from about 14 to about 68 atmospheres and a carbon dioxide partial pressure within the range from about 14 to about 34 atmospheres. Temperature during pretreatment will generally be within the range from about 100.degree. to about 200.degree. C.

  20. Hot alkali carbonation of sodium metaphosphate modified fly ash/calcium aluminate blend hydrothermal cements

    SciTech Connect

    Sugama, T. [Brookhaven National Lab., Upton, NY (United States). Energy Efficiency and Conservation Div.] [Brookhaven National Lab., Upton, NY (United States). Energy Efficiency and Conservation Div.

    1996-11-01

    Sodium metaphosphate-modified fly ash/calcium aluminate blend (SFCB) cements were prepared by autoclaving for 1 day at 300 C and their resistance was evaluated in a highly concentrated Na{sub 2}CO{sub 3} solution at 300 C. The hydroxyapatite and analcime phases formed in the autoclaved SFCB cements played an essential role in conferring resistance to the degradation of cements caused by alkali carbonation. Although the carbonating reaction of the analcime phase led to the formation of cancrinite, this analcime cancrinite transformation did not show any influence on the changes in the mechanical and physical properties of the cements. Additionally, there was no formation of the water-soluble calcium bicarbonate in the cements exposed for 28 days. Contrarily, the conventional class G cement systems were very vulnerable to a hot alkali carbonation. The major reason for the damage caused by carbonation of the cements was the fact that the xonotlite phase formed in the 300{degree} autoclaved cements was converted into two carbonation products, calcite and pectolite. Furthermore, the reaction between calcite and carbonic acid derived from Na{sub 2}CO{sub 3} led to the formation of water-soluble calcium bicarbonate, thereby causing the alteration of dense structures into porous ones and the loss of strength of cements.

  1. Rapid hydrothermal flow synthesis and characterisation of carbonate- and silicate-substituted calcium phosphates

    PubMed Central

    Knowles, Jonathan C; Rehman, Ihtesham; Darr, Jawwad A

    2013-01-01

    A range of crystalline and nano-sized carbonate- and silicate-substituted hydroxyapatite has been successfully produced by using continuous hydrothermal flow synthesis technology. Ion-substituted calcium phosphates are better candidates for bone replacement applications (due to improved bioactivity) as compared to phase-pure hydroxyapatite. Urea was used as a carbonate source for synthesising phase pure carbonated hydroxyapatite (CO3-HA) with ?5?wt% substituted carbonate content (sample 7.5CO3-HA) and it was found that a further increase in urea concentration in solution resulted in biphasic mixtures of carbonate-substituted hydroxyapatite and calcium carbonate. Transmission electron microscopy images revealed that the particle size of hydroxyapatite decreased with increasing urea concentration. Energy-dispersive X-ray spectroscopy result revealed a calcium deficient apatite with Ca:P molar ratio of 1.45 (±0.04) in sample 7.5CO3-HA. For silicate-substituted hydroxyapatite (SiO4-HA) silicon acetate was used as a silicate ion source. It was observed that a substitution threshold of ?1.1?wt% exists for synthesis of SiO4-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy. PMID:22983020

  2. The effect of benzotriazoles on calcium carbonate scale formation

    NASA Astrophysics Data System (ADS)

    Zafiropoulou, A.; Dalas, E.

    2000-11-01

    Benzotriazoles have been used satisfactorily for the last 25 years as a corrosion inhibitor for copper pipelines. The effect of six benzotriazoles on the crystal growth of calcite was investigated at sustained supersaturation. The rates of crystal growth measured in the presence of benzotriazoles at concentrations of 7.5×10 -5 M were drastically increased. The apparent order of the reaction found from kinetic data was n=2±0.2, thus suggesting a surface diffusion controlled mechanism.

  3. Solute carbon and carbon segregation in magnesium oxide single crystals — a secondary ion mass spectrometry study

    Microsoft Academic Search

    Friedemann Freund

    1986-01-01

    If carbon is to be analyzed by secondary ion mass spectroscopy (SIMS) in an oxide such as MgO, one has to know how the carbon is incorporated in the oxide host structure, before a successful experiment can be planned. If the carbon impurities derive from dissolved CO2 component which form a solid solution while the crystal grew from a melt

  4. Refined crystal structure of Ca[B 8 O 11 (OH) 4 ]—A synthetic calcium analog of strontioborite

    Microsoft Academic Search

    N. A. Yamnova; Yu. K. Egorov-Tismenko; N. V. Zubkova; O. V. Dimitrova; A. P. Kantor

    2005-01-01

    A calcium analog of strontioborite, namely, Ca[B8O11(OH)4], is synthesized under hydrothermal conditions (T = 270C, P = 20 atm) within the framework of the study of the phase formation in the CaCl2 Rb2CO3 B2O3 system. The crystal structure of the synthetic calcium borate [a = 7.4480(5) ?, b = 8.2627(5) ?, c = 9.8102(6) ?, ? = 108.331(1), V =

  5. Evidence for Calcium Carbonate at the Phoenix Landing Site

    NASA Technical Reports Server (NTRS)

    Boynton, W. V.; Ming, D. W.; Sutter, B.; Arvidson, R. E.; Hoffman, J.; Niles, P. B.; Smith, P.

    2009-01-01

    The Phoenix mission has recently finished its study of the north polar environment of Mars with the aim to help understand both the current climate and to put constraints on past climate. An important part of understanding the past climate is the study of secondary minerals, those formed by reaction with volatile compounds such as H2O and CO2. This work describes observations made by the Thermal and Evolved-Gas Analyzer (TEGA) on the Phoenix Lander related to carbonate minerals. Carbonates are generally considered to be products of aqueous processes. A wet and warmer climate during the early history of Mars coupled with a much denser CO2 atmosphere are ideal conditions for the aqueous alteration of basaltic materials and the subsequent formation of carbonates. Carbonates (Mg- and Ca-rich) are predicted to be thermodynamically stable minerals in the present martian environment, however, there have been only a few indications of carbonates on the surface by a host of orbiting and landed missions to Mars. Carbonates (Mg-rich) have been suggested to be a component (2-5 wt %) of the martian global dust based upon orbital thermal emission spectroscopy. The identifications, based on the presence of a 1480 cm-1 absorption feature, are consistent with Mgcarbonates. A similar feature is observed in brighter, undisturbed soils by Mini-TES on the Gusev plains. Recently, Mg-rich carbonates have been identified in the Nili Fossae region by the CRISM instrument onboard the Mars Reconnaissance Orbiter. Carbonates have also been confirmed as aqueous alteration phases in martian meteorites so it is puzzling why there have not been more discoveries of carbonates by landers, rovers, and orbiters. Carbonates may hold important clues about the history of liquid water and aqueous processes on the surface of Mars.

  6. The Properties and Characteristics of Concretes Containing Calcium Carbonate (CaCO3) and Synthetic Lightweight Aggregate

    NASA Astrophysics Data System (ADS)

    Ramos, Matthew J.

    The purpose of this study was to investigate the efficacy of precipitated calcium carbonate as a means for enhancing the mechanical and environmental favorability of concretes containing synthetic lightweight aggregates (SLA), which are comprised of recycled mixed plastic and fly ash. Compressive strength tests show that 2% calcium carbonate additions are able to mitigate strength decreases induced by SLA as well as decrease concrete density when compared to NWA concretes. SLA concretes containing 5% calcium carbonate do not show the same trend. Instead, strength decreases and density increases are observed. Furthermore, increases in aluminum trisulphate (AFt) phase mineralization are observed through scanning electron microscopy. Results suggest that calcium carbonate additions increase early hydration and stabilize AFt minerals thaumasite and ettringite throughout hydration. It is proposed that increased AFt phase mineralization causes reductions in concrete density. However, a limit to this relationship was observed as additions of greater than 2% calcium carbonate exceed the potential for increased hydration, causing a threshold effect that resulted in calcium carbonate acting as filler, which increases density. Improved mechanical properties and the ability to stabilize waste plastics, fly ash, and CO2 emissions make the use of 2% calcium carbonate in conjunction with SLA a favorable alternative to ordinary concretes.

  7. Climatically driven loss of calcium in steppe soil as a sink for atmospheric carbon

    USGS Publications Warehouse

    Lapenis, A.G.; Lawrence, G.B.; Bailey, S.W.; Aparin, B.F.; Shiklomanov, A.I.; Speranskaya, N.A.; Torn, M.S.; Calef, M.

    2008-01-01

    During the last several thousand years the semi-arid, cold climate of the Russian steppe formed highly fertile soils rich in organic carbon and calcium (classified as Chernozems in the Russian system). Analysis of archived soil samples collected in Kemannaya Steppe Preserve in 1920, 1947, 1970, and fresh samples collected in 1998 indicated that the native steppe Chernozems, however, lost 17-28 kg m-2 of calcium in the form of carbonates in 1970-1998. Here we demonstrate that the loss of calcium was caused by fundamental shift in the steppe hydrologic balance. Previously unleached soils where precipitation was less than potential evapotranspiration are now being leached due to increased precipitation and, possibly, due to decreased actual evapotranspiration. Because this region receives low levels of acidic deposition, the dissolution of carbonates involves the consumption of atmospheric CO2. Our estimates indicate that this climatically driven terrestrial sink of atmospheric CO2 is ???2.1-7.4 g C m-2 a-1. In addition to the net sink of atmospheric carbon, leaching of pedogenic carbonates significantly amplified seasonal amplitude of CO2 exchange between atmosphere and steppe soil. Copyright 2008 by the American Geophysical Union.

  8. Nanoscale Confinement Controls the Crystallization of Calcium Phosphate: Relevance to Bone Formation

    PubMed Central

    Cantaert, Bram; Beniash, Elia; Meldrum, Fiona C.

    2015-01-01

    A key feature of biomineralization processes is that they take place within confined volumes, in which the local environment can have significant effects on mineral formation. Herein, we investigate the influence of confinement on the formation mechanism and structure of calcium phosphate (CaP). This is of particular relevance to the formation of dentine and bone, structures of which are based on highly mineralized collagen fibrils. CaP was precipitated within 25–300 nm diameter, cylindrical pores of track etched and anodised alumina membranes under physiological conditions, in which this system enables systematic study of the effects of the pore size in the absence of a structural match between the matrix and the growing crystals. Our results show that the main products were polycrystalline hydroxapatite (HAP) rods, together with some single crystal octacalcium phosphate (OCP) rods. Notably, we demonstrate that these were generated though an intermediate amorphous calcium phosphate (ACP) phase, and that ACP is significantly stabilised in confinement. This effect may have significance to the mineralization of bone, which can occur through a transient ACP phase. We also show that orientation of the HAP comparable, or even superior to that seen in bone can be achieved through confinement effects alone. Although this simple experimental system cannot be considered, a direct mimic of the in vivo formation of ultrathin HAP platelets within collagen fibrils, our results show that the effects of physical confinement should not be neglected when considering the mechanisms of formation of structures, such as bones and teeth. PMID:24115275

  9. Magnesium supplementation did not affect the increasing bone zinc concentration in rats given excess calcium as carbonate.

    PubMed

    Ohata, Aiko; Takasugi, Satoshi; Matsui, Tohru

    2008-11-01

    We investigated the effect of magnesium supplementation on zinc distribution in rats given excess calcium as carbonate. Rats were given a control diet (5 g/kg calcium and 0.5 g/kg magnesium), a high calcium diet (HC, 25 g/kg calcium and 0.5 g/kg magnesium) or the high calcium diet supplied with magnesium (HCM, 25 g/kg calcium and 2.5 g/kg magnesium) for 4 weeks. Calcium carbonate and magnesium oxide were used for increasing these mineral concentrations in diets. Although feed intake did not differ among the groups, the excess calcium suppressed feed efficiency, irrespective of dietary magnesium concentration. Femoral magnesium concentration was lower in the HC group than in the control and the HCM groups. Femoral zinc concentration was higher in the HC group and the HCM group than in the control group. The zinc concentration in the kidney was lower in the HC group and the HCM group than in the control group. The excess calcium did not affect zinc concentration in plasma and other tissues such as the liver, testis, and spleen, irrespective of dietary magnesium. These results suggest that the increasing bone zinc and the decreasing renal zinc do not result from magnesium insufficiency in rats given excess calcium as carbonate. PMID:18560770

  10. Crystallization of calcium oxalate monohydrate at dipalmitoylphosphatidylcholine monolayers in the presence of chondroitin sulfate A

    NASA Astrophysics Data System (ADS)

    Ouyang, Jian-Ming; Deng, Sui-Ping; Zhong, Jiu-Ping; Tieke, Bernd; Yu, Shu-Hong

    2004-10-01

    The growth and aggregation of calcium oxalate monohydrate (COM) crystals beneath dipalmitoylphosphatidylcholine (DPPC) monolayers in the presence of chondroitin sulfate A (C 4S) was systematically examined under different surface pressure. The results indicated that the addition of C 4S can inhibit the crystal growth and prevent the aggregation of COM crystals. Under a DPPC monolayer, well-defined three-dimensional hexagonal prisms and three-dimensional rhombus prisms with sharply angled tips were obtained. The DPPC monolayer at a surface pressure of 10 mN/m can match the Ca 2+ distance of the (1¯ 0 1) face of COM better than at 20 mN/m. The addition of C 4S could cooperatively modulate the interaction strength between the monolayer (or itself) with the specific morphology determining faces such as (1¯ 0 1) and (0 2 0), and thus results in remarkable stabilization of the (1¯ 0 1) faces. The dramatic changes in morphological details were due to the strong electrostatic interactions between the Ca 2+-rich (1¯ 0 1) crystal faces of COM and the polyanionic polysaccharide C 4S together with the negatively charged sites of the zwitterionic DPPC monolayers. The increase of the concentration of C 4S can further enhance the stabilization of the (1¯ 0 1) face.

  11. Optical assessment on a new self-frequency doubling crystal: neodymium-doped lanthanum calcium borate

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Wu, Yicheng; Fu, Peizhen; Jing, Fangli

    2005-04-01

    A new, to our knowledge, neodymium-doped lanthanum calcium borate crystal (Nd3+:La2CaB10O19, Nd:LCB) has been grown by the flux method. The spectroscopic parameters for Nd:LCB crystal have also been calculated based on Judd-Ofelt theory. The intensity parameters ?t are ?2=4.96×10-20 cm2, ?4=3.94× 10-20 cm2, and ?6=3.71×10-20 cm2. The radiative lifetime ?r is 349 ?s. The absorption band at 800 nm has a FWHM of 12 nm. The absorption cross section is ?a=2.40×10-20 cm2, and the emission cross sections at 1070 nm are ?X=3.02×10-19 cm2, ?Y=2.33×10-19 cm2, and ?Z=2.68×10-19 cm2. The measured fluorescence lifetime ?f is 64 ?s, and the quantum efficiency ? is 18.3%. In comparison with other Nd-doped laser crystals, the calculated parameters show that Nd:LCB crystal satisfies the fundamental spectral condition for laser emission.

  12. Effects of calcium nitride and calcium carbonate gasifying agents on the porosity of Ni 3 Ti–TiC composites produced by combustion synthesis

    Microsoft Academic Search

    Douglas E. Burkes; Jack Milwid; Guglielmo Gottoli; John J. Moore

    2006-01-01

    Combustion synthesis or Self-propagating High Temperature Synthesis (SHS) has been used to produce highly porous materials\\u000a intended for biomedical applications. Two novel gasifying agents, calcium nitride and calcium carbonate, were employed to\\u000a increase product porosity and pore size during the combustion synthesis reaction for two SHS chemical compositions. A greater\\u000a increase in apparent porosity of the products was gained using

  13. Synthesis of sodium caseinate-calcium carbonate microspheres and their mineralization to bone-like apatite

    NASA Astrophysics Data System (ADS)

    Xu, Zhewu; Liang, Guobin; Jin, Lin; Wang, Zhenling; Xing, Chao; Jiange, Qing; Zhang, Zhiguang

    2014-06-01

    Phosphoproteins can induce and stabilize calcium carbonate (CaCO3) vaterite, which has desirable features for high reactivity. The purpose of this study was to synthesize bioactive CaCO3 microspheres for bone regeneration. Sodium caseinate (NaCas)-containing CaCO3 microspheres, with the crystal phase of vaterite, were synthesized by fast precipitation in an aqueous solution of CaCl2, Na2CO3, and 2 mg/mL of NaCas. The uniform microspheres exhibited rougher surfaces and lower negative charges than CaCO3 particles without NaCas addition. Fourier-transform infrared spectroscopy (FT-IR) of the microspheres showed characteristic peaks or bands corresponding to phosphate and hydroxyl groups. Thermogravimetric analysis (TGA) curves exhibited approximately 5% weight loss below 600 °C due to the decomposition of NaCas. Scanning electron microscope (SEM) images showed lath-like hydroxyapatite (HAp) on the surface after soaking in simulated body fluid (SBF) at 37 °C for 5 and 10 days. Energy dispersive X-ray spectrometry (EDS) revealed that the agglomerates were composed of Ca, C, O, P, Na, and Mg elements, and the Ca/P ratios ranged from 1.53 to 1.56. X-ray diffraction (XRD) patterns exhibited peaks characteristic of hydroxyapatite. The results of this study demonstrated that the addition of NaCas induced the formation of vaterite microspheres which possesses an enhanced apatite formation after soaking in SBF at 37 °C for 5 and 10 days. These NaCas-CaCO3 microspheres may be a potential biomaterial for bone regeneration.

  14. Oxygen isotope fractionation during the dolomitization of calcium carbonate

    Microsoft Academic Search

    Alan Matthews; Amitai Katz

    1977-01-01

    The oxygen isotope fractionation accompanying the hydrothermal dolomitization of CaCO 3 between 252 and 295°C has been investigated. Dolomitization (which occurs via the crystallization of one or more intermediate magnesian calcite phases) is characterised by a progressive lowering in 8 O , which smoothly correlates with the change in the Mg\\/(Mg + Ca) and the Sr \\/( Mg + Ca

  15. Investigating the Role of Carbonate Ion Concentration on the Magnesium Content of Amorphous Calcium Carbonate

    NASA Astrophysics Data System (ADS)

    Blue, C.; Dove, P. M.; Han, N.

    2011-12-01

    The fields of biomineralization and carbonate geochemistry are undergoing a paradigm shift with the realization that the formation of calcite with diverse compositions and textures can be understood within the framework of multiple pathways to mineralization. Many organisms do not form their skeletons via the classical step-growth process, but instead mineralization occurs through a mesocrystal pathway that begins with the formation of amorphous calcium carbonate (ACC), which subsequently transforms to calcite. Little is known about factors that regulate this type of calcification because the last 50 years of research have focused almost entirely on step-growth processes. In particular, new findings indicate that the chemical signatures and properties of calcites that form via an amorphous pathway are significantly different. Variable temperature has been shown to influence the amount of magnesium that is incorporated into ACC, but the effect of alkalinity has not been constrained. Here, a flow-through method was developed to produce ACC within a geochemically relevant pH range and with a constant supersaturation, and to determine the effect of carbonate ion concentration on magnesium uptake. The experimental approach uses a high precision syringe pump to prepare ACC under specified and constant chemical conditions. This study used two syringes that contained: 1) 100 ml of MgCl2?6H2O and CaCl2?2H2O such that the Mg/Ca ratio is fixed at 5:1 (modern seawater), and 2) 100 ml of 60mM - 400mM NaHCO3. The initial sodium bicarbonate solutions were buffered to a pH of 9.75 using NaOH, and upon mixing with the 5:1 Mg/Ca solution the resulting pH range was 9.2 - 9.7. All experiments were performed at temperatures between 21.5 and 23 degrees Celsius. Solution and solids were collected on 0.20 micron filter paper with a vacuum pump running continuously. Experiments were typically conducted for an hour and a half and all samples were rinsed with distilled deionized water before collection. The final ACC samples were characterized using a combination of SEM, Raman Spectroscopy, and ICP-OES. Preliminary results indicate that the Mg content of ACC increases with the carbonate ion concentration of the input solution. This shift in composition corresponds with measurements of a smaller average particle size. Future work will determine if the ACC that forms at these different carbonate concentrations subsequently influences the composition and structure of the final crystalline products. Findings from this work may lead to better predictions of how biological calcification processes will respond to the shifts in carbonate chemistry that accompany ocean acidification.

  16. Carbonation as a binding mechanism for coal/calcium hydroxide pellets. [Quarterly] technical report, March 1, 1993--May 31, 1993

    SciTech Connect

    Lytle, J.; Hackley, K.; Dagamac, M. [Illinois State Geological Survey, Champaign, IL (United States); Berger, R. [Illinois Univ., Urbana, IL (United States); Schanche, G. [Army Construction Engineering Research Lab., Champaign, IL (United States)

    1993-09-01

    This research is an investigation of calcium hydroxide, a sulfur-capturing sorbent, as a binder for coal fines. The reaction of carbon dioxide with calcium hydroxide, referred to as carbonation, is being studied as a method of improving pellet quality. Carbonation forms a cementitious matrix of calcium carbonate. The effect of particle size and compaction pressure on pellet strength was studied using a laboratory hydraulic press. Particle distributions with mean sizes of 200, 90 and 40 microns were tested. The results indicate that pellet strength increased with decreasing particle size and increasing compaction pressure when calcium hydroxide was used as a binder. Pellets containing 10 wt% calcium hydroxide increased in strength by approximately 40% when air dried for one day. This increase in strength is attributed to carbonation of the calcium hydroxide via atmospheric carbon dioxide. Corn starch, an adhesive binder, was tested at the finest particle size. Pellet strength did not increase as a function of increasing compaction pressure. At the finest particle size and highest compaction pressure (18,750 psi), dried pellets formed with 2 wt% corn starch were equivalent in strength to pellets containing 5 wt% calcium hydroxide.

  17. Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation

    PubMed Central

    2011-01-01

    Ureolytically-driven calcium carbonate precipitation is the basis for a promising in-situ remediation method for sequestration of divalent radionuclide and trace metal ions. It has also been proposed for use in geotechnical engineering for soil strengthening applications. Monitoring the occurrence, spatial distribution, and temporal evolution of calcium carbonate precipitation in the subsurface is critical for evaluating the performance of this technology and for developing the predictive models needed for engineering application. In this study, we conducted laboratory column experiments using natural sediment and groundwater to evaluate the utility of geophysical (complex resistivity and seismic) sensing methods, dynamic synchrotron x-ray computed tomography (micro-CT), and reactive transport modeling for tracking ureolytically-driven calcium carbonate precipitation processes under site relevant conditions. Reactive transport modeling with TOUGHREACT successfully simulated the changes of the major chemical components during urea hydrolysis. Even at the relatively low level of urea hydrolysis observed in the experiments, the simulations predicted an enhanced calcium carbonate precipitation rate that was 3-4 times greater than the baseline level. Reactive transport modeling results, geophysical monitoring data and micro-CT imaging correlated well with reaction processes validated by geochemical data. In particular, increases in ionic strength of the pore fluid during urea hydrolysis predicted by geochemical modeling were successfully captured by electrical conductivity measurements and confirmed by geochemical data. The low level of urea hydrolysis and calcium carbonate precipitation suggested by the model and geochemical data was corroborated by minor changes in seismic P-wave velocity measurements and micro-CT imaging; the latter provided direct evidence of sparsely distributed calcium carbonate precipitation. Ion exchange processes promoted through NH4+ production during urea hydrolysis were incorporated in the model and captured critical changes in the major metal species. The electrical phase increases were potentially due to ion exchange processes that modified charge structure at mineral/water interfaces. Our study revealed the potential of geophysical monitoring for geochemical changes during urea hydrolysis and the advantages of combining multiple approaches to understand complex biogeochemical processes in the subsurface. PMID:21943229

  18. Geophysical monitoring and reactive transport modeling of ureolytically-driven calcium carbonate precipitation.

    PubMed

    Wu, Yuxin; Ajo-Franklin, Jonathan B; Spycher, Nicolas; Hubbard, Susan S; Zhang, Guoxiang; Williams, Kenneth H; Taylor, Joanna; Fujita, Yoshiko; Smith, Robert

    2011-01-01

    Ureolytically-driven calcium carbonate precipitation is the basis for a promising in-situ remediation method for sequestration of divalent radionuclide and trace metal ions. It has also been proposed for use in geotechnical engineering for soil strengthening applications. Monitoring the occurrence, spatial distribution, and temporal evolution of calcium carbonate precipitation in the subsurface is critical for evaluating the performance of this technology and for developing the predictive models needed for engineering application. In this study, we conducted laboratory column experiments using natural sediment and groundwater to evaluate the utility of geophysical (complex resistivity and seismic) sensing methods, dynamic synchrotron x-ray computed tomography (micro-CT), and reactive transport modeling for tracking ureolytically-driven calcium carbonate precipitation processes under site relevant conditions. Reactive transport modeling with TOUGHREACT successfully simulated the changes of the major chemical components during urea hydrolysis. Even at the relatively low level of urea hydrolysis observed in the experiments, the simulations predicted an enhanced calcium carbonate precipitation rate that was 3-4 times greater than the baseline level. Reactive transport modeling results, geophysical monitoring data and micro-CT imaging correlated well with reaction processes validated by geochemical data. In particular, increases in ionic strength of the pore fluid during urea hydrolysis predicted by geochemical modeling were successfully captured by electrical conductivity measurements and confirmed by geochemical data. The low level of urea hydrolysis and calcium carbonate precipitation suggested by the model and geochemical data was corroborated by minor changes in seismic P-wave velocity measurements and micro-CT imaging; the latter provided direct evidence of sparsely distributed calcium carbonate precipitation. Ion exchange processes promoted through NH4+ production during urea hydrolysis were incorporated in the model and captured critical changes in the major metal species. The electrical phase increases were potentially due to ion exchange processes that modified charge structure at mineral/water interfaces. Our study revealed the potential of geophysical monitoring for geochemical changes during urea hydrolysis and the advantages of combining multiple approaches to understand complex biogeochemical processes in the subsurface. PMID:21943229

  19. All three Ca[superscript 2+]-binding loops of photoproteins bind calcium ions: The crystal structures of calcium-loaded apo-aequorin and apo-obelin

    SciTech Connect

    Deng, Lu; Vysotski, Eugene S.; Markova, Svetlana V.; Liu, Zhi-Jie; Lee, John; Rose, John; Wang, Bi-Cheng (Georgia)

    2010-07-13

    The crystal structures of calcium-loaded apoaequorin and apo-obelin have been determined at resolutions 1.7 {angstrom} and 2.2 {angstrom}, respectively. A calcium ion is observed in each of the three EF-hand loops that have the canonical calcium-binding sequence, and each is coordinated in the characteristic pentagonal bipyramidal configuration. The calcium-loaded apo-proteins retain the same compact scaffold and overall fold as the unreacted photoproteins containing the bound substrate, 2-hydroperoxycoelenterazine, and also the same as the Ca{sup 2+}-discharged obelin bound with the product, coelenteramide. Nevertheless, there are easily discerned shifts in both helix and loop regions, and the shifts are not the same between the two proteins. It is suggested that these subtle shifts are the basis of the ability of these photoproteins to sense Ca{sup 2+} concentration transients and to produce their bioluminescence response on the millisecond timescale. A mechanism of intrastructural transmission of the calcium signal is proposed.

  20. Optical Study of Liquid Crystal Doped with Multiwalled Carbon Nanotube

    NASA Astrophysics Data System (ADS)

    Gharde, Rita A.; Thakare, Sangeeta Y.

    2014-11-01

    Liquid crystalline materials have been useful for display devices i.e watches, calculators, automobile dashboards, televisions, multi media projectors etc. as well as in electro tunable lasers, optical fibers and lenses. Carbon nanotube is chosen as the main experimental factor in this study as it has been observed that Carbon Nano Tube influence the existing properties of liquid crystal host and with the doping of CNT can enhance1 the properties of LC. The combination of carbon nanotube (CNT) and liquid crystal (LC) materials show considerable interest in the scientific community due to unique physical properties of CNT in liquid crystal. Dispersion of CNTs in LCs can provide us a cheap, simple, versatile and effective means of controlling nanotube orientation on macroscopic scale with no restrictions on nanotube type. LCs have the long range orientational order rendering them to be anisotropic phases. If CNTs can be well dispersed in LC matrix, they will align with their long axes along the LC director to minimize distortions of the LC director field and the free energy. In this paper, we doped liquid crystal (Cholesteryl Nonanoate) by a small amount of multiwall carbon nanotube 0.05% and 0.1% wt. We found that by adding carbon nanotube to liquid crystals the melting point of the mixture is decreased but TNI is increased. It has been also observed that with incereas in concentration of carbon nanotube into liquid crystal shows conciderable effect on LC. The prepared samples were characterized using various techniques to study structural, thermal and optical properties i.e PMS, FPSS, UV-Vis spectroscopy, FT-IR measurements, and DTA.

  1. Construction of two ureolytic model organisms for the study of microbially induced calcium carbonate precipitation.

    PubMed

    Connolly, James; Kaufman, Megan; Rothman, Adam; Gupta, Rashmi; Redden, George; Schuster, Martin; Colwell, Frederick; Gerlach, Robin

    2013-09-01

    Two bacterial strains, Pseudomonas aeruginosa MJK1 and Escherichia coli MJK2, were constructed that both express green fluorescent protein (GFP) and carry out ureolysis. These two novel model organisms are useful for studying bacterial carbonate mineral precipitation processes and specifically ureolysis-driven microbially induced calcium carbonate precipitation (MICP). The strains were constructed by adding plasmid-borne urease genes (ureABC, ureD and ureFG) to the strains P. aeruginosa AH298 and E. coli AF504gfp, both of which already carried unstable GFP derivatives. The ureolytic activities of the two new strains were compared to the common, non-GFP expressing, model organism Sporosarcina pasteurii in planktonic culture under standard laboratory growth conditions. It was found that the engineered strains exhibited a lower ureolysis rate per cell but were able to grow faster and to a higher population density under the conditions of this study. Both engineered strains were successfully grown as biofilms in capillary flow cell reactors and ureolysis-induced calcium carbonate mineral precipitation was observed microscopically. The undisturbed spatiotemporal distribution of biomass and calcium carbonate minerals were successfully resolved in 3D using confocal laser scanning microscopy. Observations of this nature were not possible previously because no obligate urease producer that expresses GFP had been available. Future observations using these organisms will allow researchers to further improve engineered application of MICP as well as study natural mineralization processes in model systems. PMID:23835134

  2. Calcium pyrophosphate crystal deposition: the effect of soluble iron in a kinetic study using a gelatin matrix model.

    PubMed

    Mandel, G S; Halverson, P B; Mandel, N S

    1988-06-01

    The kinetics of calcium pyrophosphate dihydrate (CPPD) crystal growth was studied by allowing calcium and pyrophosphate (PPi-4) ions to diffuse through a denatured collagen matrix (biological grade gelatin) in the presence of either ferric or ferrous ions. Ferric and, to some extent, ferrous ions blocked the migration of the PPi-4 diffusion gradient. This retardation in the [PPi-4] gradient led to numerous changes in the patterns of CPPD crystal formation. At the initial stages of crystal growth, the iron ions induced more crystal growth compared to control. At later incubation times, ferrous and ferric ions enhanced crystal growth at the expense of crystal nucleation. The presence of both ferrous and ferric ions resulted in the more rapid formation of the two crystals observed in vivo, triclinic CPPD and monoclinic CPPD. Further, both ferrous and ferric ions also reduced the solubility of the crystalline material in the broad diffuse band which formed when the Ca+2 and PPi-4 gradients first met. In this system, the presence of either ferrous or ferric ions increased the amount of hydroxyproline included in the crystalline precipitates. Iron was also incorporated into the crystals, particularly into the triclinic CPPD and monoclinic CPPD crystals. PMID:2840734

  3. Pathogenesis of calcium-containing gallstones. Canine ductular bile, but not gallbladder bile, is supersaturated with calcium carbonate.

    PubMed Central

    Rege, R V; Moore, E W

    1986-01-01

    Calcium precipitation in bile is a requisite event in the initiation and growth of all pigment gallstones. Calcium solubility in bile is thus of great importance. This is the first attempt to define the ion-product of CaCO3 in bile in any species. If the ion-product: [Ca++] X [CO = 3] exceeds solubility product (K'sp), the sample is supersaturated and CaCO3 precipitation is thermodynamically possible. We have recently determined K'sp of calcite to be 3.76 X 10(-8) mol/liter at 37 degrees C and total ionic strength = 0.16 M. Gallbladder (GB) bile was obtained from 15 anesthetized dogs after 12-24-h fasts. Duct bile was obtained from three dogs (n = 12) during variable taurocholate infusion. Samples were assayed for pH, partial pressure of carbon dioxide (PCO2), total bile salt concentration ([TBS]), total calcium concentration ([Ca]), and free calcium ion concentration ([Ca++]). With increasing [TBS] in both GB and duct bile, there was a linear decline in pH, a curvilinear decline in [HCO-3] and [CO = 3], and linear increase in [Ca++] and [Ca]. All ductular samples were supersaturated with CaCO3, with saturation indices (SI) as high as 17.5 and a mean of 8.36 +/- 1.43 (SE). In sharp contrast, none of the GB samples were supersaturated, due to the marked decline in [CO = 3] upon concentration and acidification of bile. In GB bile, the SI ranged from 0.006 to 0.126, with a mean of 0.039 +/- 0.011. The gallbladder thus produced a change in the SI from a value as high as 17.5 to a value as low as 0.006 in concentrated GB bile, which is a nearly 3,000-fold change. The average change in the SI was approximately 215-fold. Since all duct samples were supersaturated, and since the dog does not normally form gallstones, the data support our previous hypotheses that: (a) in canine bile, as in canine pancreatic juice, a nucleating factor is necessary for CaCO3 precipitation; (b) bile salts are important buffers for Ca++ in bile; and (c) normal GB mucosal function (concentration and acidification of bile) plays an important role in reducing CaCO3 lithogenicity in GB bile. PMID:3944252

  4. The role of calcium oxalate crystal deposition in cerebral vessels during ethylene glycol poisoning.

    PubMed

    Froberg, K; Dorion, R P; McMartin, K E

    2006-01-01

    Ethylene glycol (EG) poisoning can lead to serious morbidity or death, which occurs following conversion of ethylene glycol to toxic metabolites. These metabolites affect multiple organ/systems leading to metabolic acidosis, cardiopulmonary depression, acute renal failure and central nervous system deficits. Treatment consists of correcting metabolic acidosis with bicarbonate administration, dialysis to remove toxic metabolites and administration of fomepizole or ethanol to prevent conversion of EG to toxic intermediates. Occasionally in the literature, fatal cases of EG poisoning have been described in which calcium oxalate crystal deposition has occurred in the walls of CNS vessels, sometimes with associated neuropathy. We describe a case of fatal EG poisoning in which the development of rapid cerebral edema was documented by CT scan and was accompanied by definitive evidence of birefringent crystals within walls of CNS blood vessels, with associated inflammation and edema. This case and others in the literature suggest that cerebral edema, and perhaps injury to other organs, could result from oxalate crystal deposition in small blood vessels in the brain and other organs. PMID:16749551

  5. Calciphytoliths (calcium oxalate crystals) analysis for the identification of decayed tea plants (Camellia sinensis L.)

    PubMed Central

    Zhang, Jianping; Lu, Houyuan; Huang, Linpei

    2014-01-01

    The history of tea is poorly known, mainly due to the questionable identification of decayed tea plants in archaeological samples. This paper attempts to test the utility of calciphytoliths (calcium oxalate crystals) for the identification of tea in archaeological samples. It provides the first survey of the macropatterns of calciphytoliths in several species of Theaceae and common non-Theaceae plants. Crystals were extracted from 45 samples of tea, Theaceae and common non-Theaceae plants, and detected microscopically between crossed polarizers. In tea plants, druse and trichome base are the most distinctive crystals. Druses have the smallest diameter (11.65 ± 3.64??m), and trichome bases have four distinctive straight and regular cracks, similar to a regular extinction cross. The results provide morphological criteria for distinguishing tea from other plants, specifically the presence of identifiable druses together with calcified trichome bases. The implications are significant for understanding the history of tea and plant exploitation, especially for plants for which the preservation of macrofossils is poor. PMID:25342006

  6. UV-induced nonlinear absorption in lanthanum calcium borate single crystals.

    PubMed

    Kityk, I V; Majchrowski, A; Michalski, E; Kasprowicz, D; Drozdowski, M; Kisielewski, J; Lukasiewicz, T; Sahraoui, B

    2006-05-11

    It has been revealed that lanthanum calcium borate (La2CaB10O19) crystals show two-photon absorption (TPA) induced by a UV laser field. UV-induced TPA measurements were performed in the spectral range of 475-1130 nm using as fundamental beam the third harmonics of the 28 ps Nd-YAG pulsed laser as a pumping beam for LiB3O5 optical parametrized generator using Z-scan method. Investigations performed by the Z-scan method were done during illumination by a Xe-F laser (lambda = 217 nm) as a photoinducing (pumping) beam. The pumping laser beam created a thin surface layer (about 80-90 nm) that was the source of the observed photoinduced TPA. The highest values of the TPA beta coefficients were achieved for polarization of the pumping light directed along the second-order crystallographic axis of the investigated crystals. The obtained values of the TPA coefficients were higher than those for the BiB3O6 crystals investigated earlier by us. PMID:16671719

  7. Calciphytoliths (calcium oxalate crystals) analysis for the identification of decayed tea plants (Camellia sinensis L.).

    PubMed

    Zhang, Jianping; Lu, Houyuan; Huang, Linpei

    2014-01-01

    The history of tea is poorly known, mainly due to the questionable identification of decayed tea plants in archaeological samples. This paper attempts to test the utility of calciphytoliths (calcium oxalate crystals) for the identification of tea in archaeological samples. It provides the first survey of the macropatterns of calciphytoliths in several species of Theaceae and common non-Theaceae plants. Crystals were extracted from 45 samples of tea, Theaceae and common non-Theaceae plants, and detected microscopically between crossed polarizers. In tea plants, druse and trichome base are the most distinctive crystals. Druses have the smallest diameter (11.65 ± 3.64??m), and trichome bases have four distinctive straight and regular cracks, similar to a regular extinction cross. The results provide morphological criteria for distinguishing tea from other plants, specifically the presence of identifiable druses together with calcified trichome bases. The implications are significant for understanding the history of tea and plant exploitation, especially for plants for which the preservation of macrofossils is poor. PMID:25342006

  8. X-ray absorption spectroscopy identifies calcium-uranyl-carbonate complexes at environmental concentrations.

    SciTech Connect

    Kelly, S. D.; Kemner, K. M.; Brooks, S. C.; Biosciences Division; ORNL

    2007-01-01

    Current research on bioremediation of uranium-contaminated groundwater focuses on supplying indigenous metal-reducing bacteria with the appropriate metabolic requirements to induce microbiological reduction of soluble uranium(VI) to poorly soluble uranium(IV). Recent studies of uranium(VI) bioreduction in the presence of environmentally relevant levels of calcium revealed limited and slowed uranium(VI) reduction and the formation of a Ca-UO{sub 2}-CO{sub 3} complex. However, the stoichiometry of the complex is poorly defined and may be complicated by the presence of a Na-UO{sub 2}-CO{sub 3} complex. Such a complex might exist even at high calcium concentrations, as some UO{sub 2}-CO{sub 3} complexes will still be present. The number of calcium and/or sodium atoms coordinated to a uranyl carbonate complex will determine the net charge of the complex. Such a change in aqueous speciation of uranium(VI) in calcareous groundwater may affect the fate and transport properties of uranium. In this paper, we present the results from X-ray absorption fine structure (XAFS) measurements of a series of solutions containing 50 {micro}M uranium(VI) and 30 mM sodium bicarbonate, with various calcium concentrations of 0-5 mM. Use of the data series reduces the uncertainty in the number of calcium atoms bound to the UO{sub 2}-CO{sub 3} complex to approximately 0.6 and enables spectroscopic identification of the Na-UO{sub 2}-CO{sub 3} complex. At nearly neutral pH values, the numbers of sodium and calcium atoms bound to the uranyl triscarbonate species are found to depend on the calcium concentration, as predicted by speciation calculations.

  9. X-ray Absorption Spectroscopy Identifies Calcium-Uranyl-Carbonate Complexes at Environmental Concentrations

    SciTech Connect

    Kelly, Shelly D [Argonne National Laboratory (ANL); Kemner, Kenneth M [Argonne National Laboratory (ANL); Brooks, Scott C [ORNL

    2007-01-01

    Current research on bioremediation of uranium-contaminated groundwater focuses on supplying indigenous metal-reducing bacteria with the appropriate metabolic requirements to induce microbiological reduction of soluble uranium(VI) to poorly soluble uranium(IV). Recent studies of uranium(VI) bioreduction in the presence of environmentally relevant levels of calcium revealed limited and slowed uranium(VI) reduction and the formation of a Ca-UO2-CO3 complex. However, the stoichiometry of the complex is poorly defined and may be complicated by the presence of a Na-UO2-CO3 complex. Such a complex might exist even at high calcium concentrations, as some UO2-CO3 complexes will still be present. The number of calcium and/or sodium atoms coordinated to a uranyl carbonate complex will determine the net charge of the complex. Such a change in aqueous speciation of uranium(VI) in calcareous groundwater may affect the fate and transport properties of uranium. In this paper, we present the results from X-ray absorption fine structure (XAFS) measurements of a series of solutions containing 50 lM uranium(VI) and 30 mM sodium bicarbonate, with various calcium concentrations of 0-5 mM. Use of the data series reduces the uncertainty in the number of calcium atoms bound to the UO2-CO3 complex to approximately 0.6 and enables spectroscopic identification of the Na-UO2-CO3 complex. At nearly neutral pH values, the numbers of sodium and calcium atoms bound to the uranyl triscarbonate species are found to depend on the calcium concentration, as predicted by speciation calculations.

  10. Heats of adsorption of CO/sub 2/ and NH/sub 3/ on synthetic zeolites. communication 5. Adsorption of carbon dioxide on calcium zeolites

    SciTech Connect

    Zuerev, A.V.; Khvoshchev, S.S.

    1985-12-10

    The authors study the changes in adsorption heat of CO/sub 2/ upon the substitution of Na/sup +/ by Ca/sup 2 +/ in faujasite, chabazite, mordenite, erionite, and L zeolites. The substitution of sodium ions by calcuium ions in the crystal lattices of faujasites, chabazites, mordenites, and erionites leads to an increase in the heats of adsorption of carbon dioxide at relatively low occupancies. The extent of the occupancy ranges, for which enhanced heats of adsorption are found, correlate in general with the amounts of calcium cations which may directly interact with the adsorbed molecules.

  11. Density functional theory for carbon dioxide crystal

    SciTech Connect

    Chang, Yiwen; Mi, Jianguo, E-mail: mijg@mail.buct.edu.cn; Zhong, Chongli [State Key Laboratory of Organic-Inorganic Composites, Beijing University of Chemical Technology, Beijing 100029 (China)

    2014-05-28

    We present a density functional approach to describe the solid?liquid phase transition, interfacial and crystal structure, and properties of polyatomic CO{sub 2}. Unlike previous phase field crystal model or density functional theory, which are derived from the second order direct correlation function, the present density functional approach is based on the fundamental measure theory for hard-sphere repulsion in solid. More importantly, the contributions of enthalpic interactions due to the dispersive attractions and of entropic interactions arising from the molecular architecture are integrated in the density functional model. Using the theoretical model, the predicted liquid and solid densities of CO{sub 2} at equilibrium triple point are in good agreement with the experimental values. Based on the structure of crystal-liquid interfaces in different planes, the corresponding interfacial tensions are predicted. Their respective accuracies need to be tested.

  12. Matrix Gla Protein Expression in NRK-52E Cells Exposed to Oxalate and Calcium Oxalate Monohydrate Crystals

    Microsoft Academic Search

    Bing Gao; Takahiro Yasui; Xiuli Lu; Hongge Zhou; Jian Liu; Ping Liu; Atsushi Okada; Chunling Xiao; Kenjiro Kohri

    2010-01-01

    Purpose: Matrix Gla protein (MGP), a potent calcification inhibitor in extracellular matrix, is a molecular determinant regulating vascular calcification. Here, we characterized MGP expression in cultured renal tubular epithelial cells exposed to oxalate and calcium oxalate monohydrate (COM) crystals. Methods:NRK-52E cells were cultured and exposed to medium containing oxalate or COM for 1, 3, 6, 12 and 24 h. The

  13. Medicago truncatula-derived calcium oxalate crystals have a negative impact on chewing insect performance via their physical properties

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant structural traits often act as defenses against herbivorous insects, causing them to avoid feeding on a given plant or tissue. Mineral crystals of calcium oxalate in Medicago truncatula Gaertn. (Fabaceae) leaves have previously been shown to be effective deterrents of lepidopteran insect feedi...

  14. Growth of neodymium lanthanum calcium borate (NdLCB) single crystals by the Czochralski method and its characterisation

    NASA Astrophysics Data System (ADS)

    Senthilkumar, M.; Kalidasan, M.; Sugan, S.; Dhanasekaran, R.

    2013-01-01

    The synthesis of neodymium lanthanum calcium borate (NdLCB) was carried out using solid state reaction method. The NdLCB single crystals were grown by the Czochralski method using platinum wire as a seed. The single phase of NdLCB is confirmed by powder X-ray diffraction analysis. EDAX analysis is carried out to find the presence of constituent elements of NdLCB. Single crystal X-ray diffraction analysis was performed to find the lattice parameters and crystal system. Nd concentration in the crystal is determined using ICP-OES measurements. Optical studies such as UV-vis-NIR and photoluminescence were carried out for the NdLCB crystal and the results are analysed. SEM and etching analysis were carried out to analyse the surface morphology and the growth pattern of the as grown NdLCB crystals respectively.

  15. In situ synthesis and modification of calcium carbonate nanoparticles via a bobbling method

    Microsoft Academic Search

    LiNa Zhao; JingDong Feng; ZiChen Wang

    2009-01-01

    Modified calcium carbonate (CaCO3) nanoparticles with cubic- and spindle-like configuration were synthesized in situ by the typical bobbling (gas-liquid-solid) method. The modifiers, such as sodium stearate, octadecyl dihydrogen phosphate\\u000a (ODP) and oleic acid (OA), were used to obtain hydrophobic nanoparticles. The different modification effects of the modifiers\\u000a were investigated by measuring the active ratio, whiteness and the contact angle. Moreover,

  16. Pliocene calcium carbonate sedimentation patterns of the Ontong Java Plateau: ODP Sites 804 and 806

    Microsoft Academic Search

    Carin Andersson

    1998-01-01

    Two deep-sea cores from the northeastern slope of the Ontong Java Plateau, Ocean Drilling Program Site 806 (2520 mbsl) and Site 804 (3861 mbsl), has been studied with the purpose of investigating Pliocene (Site 806, 2.4–3.8 Ma; Site 804, 1.8–4.4 Ma) sub- and supralysoclinal changes in calcium carbonate accumulation, based on CaCO3, coarse-fraction and faunal data. At the shallower site,

  17. Factorial design analysis for adsorption of dye on activated carbon beads incorporated with calcium alginate

    Microsoft Academic Search

    Gurusamy Annadurai; Ruey-Shin Juang; Duu-Jong Lee

    2002-01-01

    Batch adsorption equilibrium of the dye Rhodamine 6G, using activated carbon beads incorporated with calcium alginate (ACCA beads), was studied. The effects of several factors governing the adsorption process, such as dye concentration (100–300 mg\\/l), pH (7–9), and temperature (30–60°C), on percent of adsorption were investigated at a fixed dosage of ACCA beads (1 g\\/l). High percentages of adsorption of

  18. Imaging calcium carbonate distribution in human sweat pore in vivo using nonlinear microscopy

    NASA Astrophysics Data System (ADS)

    Chen, Xueqin; Gasecka, Alicja; Formanek, Florian; Galey, Jean-Baptiste; Rigneault, Hervé

    2015-03-01

    Nonlinear microscopies, including two-photon excited autofluorescence (TPEF) and coherent anti-Stokes Raman scattering (CARS), were used to study individual human sweat pore morphology and topically applied antiperspirant salt penetration inside sweat pore, in vivo on human palms. Sweat pore inner morphology in vivo was imaged up to the depth of 100 ?m by TPEF microscopy. The 3D penetration and distribution of "in situ calcium carbonate" (isCC), an antiperspirant salt model, was investigated using CARS microscopy.

  19. Calcium isotopic composition of marine biogenic carbonates: influences of mineralogy and biology

    Microsoft Academic Search

    F. Böhm; N. Gussone; A. Eisenhauer; A. Heuser; A. Haase-Schramm; J. Vacelet; J. Reitner; W.-C. Dullo

    2003-01-01

    We measured the calcium isotopic composition (Ca-44\\/Ca-40 ratios, delta44Ca) of reef corals, coralline sponges, and benthic and planktonic gastropods. The resulting values are compared to published data of planktonic foraminifera and inorganic aragonite precipitates (Gussone et al., in press). All carbonates are depleted in Ca-44 with respect to seawater. The isotope data form three distinct clusters: (1) inorganic aragonite, aragonitic

  20. Enhanced hydrogen production from biomass with in situ carbon dioxide capture using calcium oxide sorbents

    Microsoft Academic Search

    Nicholas H. Florin; Andrew T. Harris

    2008-01-01

    The steam gasification of biomass, in the presence of a calcium oxide (CaO) sorbent for carbon dioxide (CO2) capture, is a promising pathway for the renewable and sustainable production of hydrogen (H2). In this work, we demonstrate the potential of using a CaO sorbent to enhance hydrogen output from biomass gasifiers. In addition, we show that CaO materials are the

  1. The effects of particle size and origin of calcium carbonate on performance and ossification characteristics in broiler chicks.

    PubMed

    Guinotte, F; Nys, Y; de Monredon, F

    1991-09-01

    The following physico-chemical characteristics of various calcium sources, differing in origin and particle size were determined: mineral composition, sieve and image analysis, apparent solubility (AS), surface area (SA), porous volume, specific gravity, and compressibility (C). The AS, SA, and C values were related more to the calcium particle size than to its origin and were higher in ground calcium sources. Calcium retention of seashells treated with phosphoric acid, oyster shells, and limestone using two particle sizes, ground or particulate, was assayed in 98 broiler chicks. Particulate marble was also tested in this experiment. Calcium retention expressed as a percentage of calcium ingestion was decreased when coarse particles of calcium were supplied in lieu of pulverized sources (40 versus 49%). An experiment with a 3 x 3 x 3 factorial arrangement of treatments were tested using 576 broiler chicks. Treatments included three calcium sources (phosphorus-treated shell, oyster shell, and marble), three particle sizes [ground (less than .15 mm), medium (.6 to 1.18 mm) and coarse (greater than 1.18 mm)] and three levels of calcium (.5,.7, and .9%) with ground limestone as a reference. Performance, tibial morphometry, breaking strength variables, and ash content were measured at 4 wk of age. Weight gain and feed conversion were ameliorated with ground particles of calcium. Cortical thickness, length of the tibia, stiffness, stress, and tibia ash were diminished when coarse particles of calcium were incorporated in the diets. Conversely, the origin of the calcium source hardly affected these criteria. Additionally, the incorporation of phosphorus-treated shells was assayed in 112 broiler chicks. Coarse particles decreased calcium retention. Consequently, ultimate stress, the modulus of elasticity, and stress were impaired. It is concluded that differences in utilization of calcium carbonate sources by the broiler chick is primarily a result of particle size rather than origin. Ground particles of calcium (pan to .15 mm) significantly improves performance and tibial ossification characteristics in broiler chicks. PMID:1780262

  2. Tribological and antioxidation synergistic effect study of sulfonate-modified nano calcium carbonate.

    PubMed

    Zhongyi, He; Liping, Xiong; Sheng, Han; Aixi, Chen; Jianwei, Qiu; Xisheng, Fu

    2013-01-01

    A middle base number sulphonate-modified nano calcium carbonate (SMC) with an average size of 35 nm was synthesized, and its tribological and antioxidation synergistic behaviors with ashless antioxidant N-phenyl-?-naphthylamine (T531) in hydrogenated oil (5Cst) were evaluated. The results demonstrate that adding this synthesized additive even at a low amount (<2.0 wt.%) can evidently improve its load-carrying capacity by 1.5 times and enhance its antiwear performance; in addition, the friction-reducing effect of additive in the high load was better than that in low load. The SMC have a good synergistic antioxidation effect with T531, which verifies the nano calcium carbonate compound was a kind of multifunctional and high-performance additive. The chemical composition of the rubbing surface which formed on the boundary film was analyzed by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicating that the excellent antiwear and load-carrying performance could be attributed to the forming of boundary lubrication film which composed of calcium carbonate, oxides, ferrites, sulphide and FeSO4, and so on. Its ability to increase oxidation free energy of base oil is the main reason for increasing its antioxidant collaboration property with ashless antioxidant T531. PMID:23658705

  3. Effects of high molecular weight urinary macromolecules on crystallization of calcium oxalate dihydrate.

    PubMed

    Drach, G W; Kraljevich, Z; Randolph, A D

    1982-04-01

    Timed urinary collections from 8 normal (Nl) persons of 11 stone forming (SF) patients were passed through ultrafiltration apparatus to remove macromolecules in the ranges 1000-30,000 d, 30,000-50,000 d, and over 50,000 d. No macromolecules could be recovered from either group in the 30,000-50,000 d range, and no low molecular weight macromolecules (LMWMM) (less than 30,000 d) were recovered from stone forming urines. Significant amounts of LMWMM (mean 105.8 +/- 17.63 mg./l.) were recovered from normal urine, but these extracts had no effects on calcium oxalate dihydrate (COD) nucleation (Bo) or linear growth (G) rates in a continuous crystallization (MSMPR) system. Urines from SF contained nearly twice the concentration of high molecular weight macromolecules (HMWMM) when compared to Nl urines. SF HMWMM differed from Nl in immunoelectrophoresis separation by absence of a dense band that was present in Nl extracts. This band reappeared in SF extract after boiling. Comparison of effects of addition of SF or Nl HMWMM to the COD-MSMPR crystallization system revealed no major quantitative differences in Bo or G, but SF HMWMM had a remarkable stabilizing effect on total mass (MT) of COD crystals produced. This effect was confirmed by analysis of oxalate residual supersaturation after crystallization. We conclude that SF excrete higher concentrations of HMWMM and almost no LMWMM when compared to normals. This higher concentration of HMWMM must contribute to increased Bo and decreased G noted in SF urine additive experiments previously reported. The mechanism of rapid removal of oxalate (i,e, stabilization) noted in experiments with SF HMWMM is not obvious at this time. PMID:7069862

  4. Crystal structure transformers in inorganic nitrites, nitrates, and carbonates

    Microsoft Academic Search

    C. N. R. Rao; B. Prakash; M. Natarajan

    1975-01-01

    A critical survey of the data describing crystal structure transformations in inorganic nitrites, nitrates and carbonates is compiled. Data on crystallographic, thermodynamic, spectroscopic, electrical, dielectric and other properties are given for each solid. Experimental techniques used to obtain the data are given and comments on the data are included in the tables. The literature is surveyed up to June 1973.

  5. Bacillus megaterium mediated mineralization of calcium carbonate as biogenic surface treatment of green building materials.

    PubMed

    Dhami, Navdeep Kaur; Reddy, M Sudhakara; Mukherjee, Abhijit

    2013-12-01

    Microbially induced calcium carbonate precipitation is a biomineralization process that has various applications in remediation and restoration of range of building materials. In the present study, calcifying bacteria, Bacillus megaterium SS3 isolated from calcareous soil was applied as biosealant to enhance the durability of low energy, green building materials (soil-cement blocks). This bacterial isolate produced high amounts of urease, carbonic anhydrase, extra polymeric substances and biofilm. The calcium carbonate polymorphs produced by B. megaterium SS3 were analyzed by scanning electron microscopy, confocal laser scanning microscopy, X-ray diffraction and Fourier transmission infra red spectroscopy. These results suggested that calcite is the most predominant carbonate formed by this bacteria followed by vaterite. Application of B. megaterium SS3 as biogenic surface treatment led to 40 % decrease in water absorption, 31 % decrease in porosity and 18 % increase in compressive strength of low energy building materials. From the present investigation, it is clear that surface treatment of building materials by B. megaterium SS3 is very effective and eco friendly way of biodeposition of coherent carbonates that enhances the durability of building materials. PMID:23793943

  6. Combined hydrogen production and storage with subsequent carbon crystallization.

    PubMed

    Lueking, Angela D; Gutierrez, Humberto R; Fonseca, Dania A; Narayanan, Deepa L; Van Essendelft, Dirk; Jain, Puja; Clifford, Caroline E B

    2006-06-21

    We provide evidence of low-temperature hydrogen evolution and possible hydrogen trapping in an anthracite coal derivative, formed via reactive ball milling with cyclohexene. No molecular hydrogen is added to the process. Raman-active molecular hydrogen vibrations are apparent in samples at atmospheric conditions (300 K, 1 bar) for samples prepared 1 year previously and stored in ambient air. Hydrogen evolves slowly at room temperature and is accelerated upon sample heating, with a first increase in hydrogen evolution occurring at approximately 60 degrees C. Subsequent chemical modification leads to the observation of crystalline carbons, including nanocrystalline diamond surrounded by graphene ribbons, other sp2-sp3 transition regions, purely graphitic regions, and a previously unidentified crystalline carbon form surrounded by amorphous carbon. The combined evidence for hydrogen trapping and carbon crystallization suggests hydrogen-induced crystallization of the amorphous carbon materials, as metastable hydrogenated carbons formed via the high-energy milling process rearrange into more thermodynamically stable carbon forms and molecular hydrogen. PMID:16771488

  7. Effect of six kinds of scale inhibitors on calcium carbonate precipitation in high salinity wastewater at high temperatures.

    PubMed

    Li, Xiaochen; Gao, Baoyu; Yue, Qinyan; Ma, Defang; Rong, Hongyan; Zhao, Pin; Teng, Pengyou

    2015-03-01

    Precipitation of calcium carbonate (CaCO3) scale on heat transfer surfaces is a serious and expensive problem widely occurring in numerous industrial processes. In this study, we compared the scale inhibition effect of six kinds of commercial scale inhibitors and screened out the best one (scale inhibitor SQ-1211) to investigate its scale inhibition performance in highly saline conditions at high temperature through static scale inhibition tests. The influences of scale inhibitor dosage, temperature, heating time and pH on the inhibition efficiency of the optimal scale inhibitor were investigated. The morphologies and crystal structures of the precipitates were characterized by Scanning Electron Microscopy and X-ray Diffraction analysis. Results showed that the scale inhibition efficiency of the optimal scale inhibitor decreased with the increase of the reaction temperature. When the concentration of Ca(2+) was 1600mg/L, the scale inhibition rate could reach 90.7% at 80°C at pH8. The optimal scale inhibitor could effectively retard scaling at high temperature. In the presence of the optimal scale inhibitor, the main crystal structure of CaCO3 changed from calcite to aragonite. PMID:25766020

  8. Effects of magnesium ions and water molecules on the structure of amorphous calcium carbonate: a molecular dynamics study.

    PubMed

    Tomono, Hidekazu; Nada, Hiroki; Zhu, Fangjie; Sakamoto, Takeshi; Nishimura, Tatsuya; Kato, Takashi

    2013-11-27

    Molecular dynamics simulations were conducted to elucidate the effects of Mg(2+) and H2O additives on the structure of amorphous calcium carbonate (ACC). New potential parameters for Mg(2+) ions were developed. The distribution function of the angle formed by three nearest-neighbor atoms was introduced to analyze the short-range local structure of ACC. The simulation indicated that ACC had a weakly ordered local structure resembling the local structure of a CaCO3 crystal. The local structure of pure ACC resembled that of vaterite. The formation of the vaterite-like local structure was hindered by Mg(2+) ions, whereas H2O molecules did not significantly influence the structure of ACC when the fraction of H2O molecules was low. However, when the fraction of H2O was high, the formation of a monohydrocalcite-like local structure was promoted. The effects of the additives on the structure of ACC were verified using the size of the additives and the interaction between the additives and CaCO3. The simulated structure of ACC was compared with the structure of CaCO3 crystals nucleated through the formation of ACC particles in real systems. PMID:24188003

  9. Tuning the dissolution kinetics of wollastonite via chelating agents for CO2 sequestration with integrated synthesis of precipitated calcium carbonates.

    PubMed

    Zhao, Huangjing; Park, Youngjune; Lee, Dong Hyun; Park, Ah-Hyung Alissa

    2013-09-28

    Carbon mineralization has recently received much attention as one of the most promising options for CO2 sequestration. The engineered weathering of silicate minerals as a means of permanent carbon storage has unique advantages such as the abundance of naturally occurring calcium and magnesium-bearing minerals and the formation of environmentally-benign and geologically stable solids via a thermodynamically favored carbonation reaction. However, several challenges need to be overcome to successfully deploy carbon mineralization on a large scale. In particular, the acceleration of the rate-limiting mineral dissolution step along with process optimization is essential to ensure the economic feasibility of the proposed carbon storage technology. In this study, the effect of various types of chelating agents on the dissolution rate of calcium-bearing silicate mineral, wollastonite, was explored to accelerate its weathering rate. It was found that chelating agents such as acetic acid and gluconic acid significantly improved the dissolution kinetics of wollastonite even at a much diluted concentration of 0.006 M by complexing with calcium in the mineral matrix. Calcium extracted from wollastonite was then reacted with a carbonate solution to form precipitated calcium carbonate (PCC), while tuning the particle size and the morphological structure of PCC to mimic commercially available PCC-based filler materials. PMID:23925694

  10. Purification and characterization of a rabbit salivary protein, a potent inhibitor of crystal growth of calcium phosphate salts.

    PubMed

    Spielman, A I; Bernstein, A; Hay, D I; Blum, M; Bennick, A

    1991-01-01

    Human saliva is supersaturated with respect to basic calcium phosphate salts but is stabilized by specific macromolecules that inhibit calcium phosphate precipitation. One of the families of inhibitory proteins in human and monkey saliva is the acidic proline-rich proteins. The purpose of this study was to isolate and characterize inhibitors of calcium phosphate precipitation from rabbit parotid saliva. Saliva was fractionated by immunoaffinity chromatography and anion exchange chromatography. Individual fractions were assayed for their ability to inhibit calcium phosphate crystal growth and the fraction associated with the inhibition was purified by repeated anion exchange chromatography, preparative gel electrophoresis and electroelution. A major (APRP) and two minor proteins (AM1, AM2) that were inhibitory were purified. APRP is an acidic proline-rich phospho-glycoprotein and a very potent inhibitor of secondary crystal growth of calcium phosphate as it was active at a concentration of 2 x 10(-8) M in a standard assay. The N-terminal sequence of one APRP was EYENLDGSLAATQNDDD?Q and a clostripain fragment of APRP had the following N-terminal sequence PQHRPPRPGGH-????SPPP?GN???PPP. Although the N-terminal segment of APRP does not resemble that of proline-rich proteins, alignment of the clostripain fragment with the repeat region of such proteins from rat, mouse, monkey and man revealed a high degree of similarity, indicating a structural relationship with the proline-rich protein family. PMID:2012527

  11. Climate warming shifts carbon allocation from stemwood to roots in calcium-depleted spruce forests

    NASA Astrophysics Data System (ADS)

    Lapenis, Andrei; Lawrence, Gregory; Buyantuev, Alexander

    2015-04-01

    Increased greening of northern forests, measured by the Normalized Difference Vegetation Index (NDVI), has been presented as evidence that a warmer climate has increased both net primary productivity (NPP) and the carbon sink in boreal forests. However, higher production and greener canopies may accompany changes in carbon allocation that favor foliage or fine roots over less decomposable woody biomass. Furthermore, tree core data throughout mid- and northern latitudes have revealed a divergence problem (DP), a weakening in tree ring responses to warming over the past half century that is receiving increasing attention, but remains poorly understood. Often, the same sites exhibit trend inconsistency phenomenon (TIP), namely positive, or no trends in growing season NDVI where negative trends in tree ring indexes are observed. Here we studied growth of two Norway spruce (Picea abies) stands in western Russia that exhibited both the DP and TIP but were subject to soil acidification and calcium depletion of differing timing and severity. Our results link the decline in radial growth starting in 1980 to a shift in carbon allocation from wood to roots driven by a combination of two factors: (a) soil acidification that depleted calcium and impaired root function and (b) earlier onset of the growing season that further taxed the root system. The latter change in phenology appears to act as a trigger at both sites to push trees into nutrient limitation as the demand for Ca increased with the longer growing season, thereby causing the shift in carbon allocation.

  12. Climate warming shifts carbon allocation from stemwood to roots in calcium-depleted spruce forests

    USGS Publications Warehouse

    Lapenis, Andrei Gennady; Lawrence, Gregory B.; Heim, Alexander; Zheng, Chengyang; Shortle, Walter

    2013-01-01

    Increased greening of northern forests, measured by the Normalized Difference Vegetation Index (NDVI), has been presented as evidence that a warmer climate has increased both net primary productivity (NPP) and the carbon sink in boreal forests. However, higher production and greener canopies may accompany changes in carbon allocation that favor foliage or fine roots over less decomposable woody biomass. Furthermore, tree core data throughout mid- and northern latitudes have revealed a divergence problem (DP), a weakening in tree ring responses to warming over the past half century that is receiving increasing attention, but remains poorly understood. Often, the same sites exhibit trend inconsistency phenomenon (TIP), namely positive, or no trends in growing season NDVI where negative trends in tree ring indexes are observed. Here we studied growth of two Norway spruce (Picea abies) stands in western Russia that exhibited both the DP and TIP but were subject to soil acidification and calcium depletion of differing timing and severity. Our results link the decline in radial growth starting in 1980 to a shift in carbon allocation from wood to roots driven by a combination of two factors: (a) soil acidification that depleted calcium and impaired root function and (b) earlier onset of the growing season that further taxed the root system. The latter change in phenology appears to act as a trigger at both sites to push trees into nutrient limitation as the demand for Ca increased with the longer growing season, thereby causing the shift in carbon allocation.

  13. Calcium Isotope Signature of Amorphous Calcium Carbonate: A Probe of Crystallization Pathway? (Invited)

    Microsoft Academic Search

    A. C. Gagnon; D. J. Depaolo; J. J. Deyoreo

    2010-01-01

    Stable isotope fractionation is sensitive to the energy landscape of nucleation and growth. Thus isotope ratios represent a promising tool to understand the chemical mechanisms controlling precipitation in geological systems. To realize this potential we must (1) determine the isotopic fractionation associated with different growth pathways, (2) use these isotopic constraints to test nucleation or growth mechanism, and (3) compare

  14. Alignment of carbon nanotubes in nematic liquid crystals.

    PubMed

    van der Schoot, Paul; Popa-Nita, V; Kralj, S

    2008-04-17

    The self-organizing properties of nematic liquid crystals can be used to align carbon nanotubes dispersed in them. Because the nanotubes are so much thinner than the elastic penetration length, the alignment is caused by the coupling of the unperturbed director field to the anisotropic interfacial tension of the nanotubes in the nematic host fluid. In order to relate the degree of alignment of the nanotubes to the properties of the nematic liquid crystal, we treat the two components on the same footing and combine Landau-de Gennes free energies for the thermotropic ordering of the liquid crystal and for the lyotropic nematic ordering of carbon nanotubes caused by their mutually excluded volumes. The phase ordering of the binary mixture is analyzed as a function of the volume fraction of the carbon nanotubes, the strength of the coupling and the temperature. We find that the degree of ordering of the nanorods is enslaved by the properties of the host liquid and that it can be tuned by raising or lowering the temperature or by increasing or decreasing their concentration. By comparing the theory to recent experiments, we find the anchoring energy of multiwalled carbon nanotubes to be in the range from 10(-10) to 10(-7) N m(-1). PMID:18366216

  15. Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Final technical report, 1 September, 1992--31 August, 1993

    SciTech Connect

    Rapp, D.; Lytle, J.; Hackley, K.; Dagamac, M. [Illinois State Geological Survey, Champaign, IL (United States); Berger, R. [Univ. of Illinois, Urbana, IL (United States); Schanche, G. [Army Construction Engineering Research Lab., Champaign, IL (United States)

    1993-12-31

    This research was an investigation of calcium hydroxide, a sulfur-capturing sorbent, as a binder for coal fines. The reaction of carbon dioxide with calcium hydroxide, referred to as carbonation, was studied as a method for improving pellet quality. Carbonation forms a cementitious matrix of calcium carbonate. Research has demonstrated that calcium hydroxide is a viable binder for coal fines and that a roller-and-die pellet mill is an effective method of pellet formation. From a minus 28 mesh preparation plant fine coal sample, a roller-and-die pellet mill produced strong pellets when 5 and 10% calcium hydroxide was used as a binder. The pellets containing 10% calcium hydroxide strengthened considerably when air cured. This increase in strength was attributed to carbonation via atmospheric carbon dioxide. Pellets containing 10 wt% calcium hydroxide were produced using an extruder but pellets formed in this manner were much weaker than pellets produced with the roller-and-die mill. In tests performed using a laboratory hydraulic press, the effect of particle size and compaction pressure on pellet strength was studied. Particle distributions with mean sizes of 200, 90 and 40 microns were tested. The results indicate that pellet strength increased with decreasing particle size and increasing compaction pressure when calcium hydroxide was used as a binder. Pellets containing 10 wt% calcium hydroxide increased in strength by approximately 40% when air dried for one day. As above, this increase in strength was attributed to carbonation of the calcium hydroxide via atmospheric carbon dioxide.

  16. Growth of aragonite calcium carbonate nanorods in the biomimetic anodic aluminum oxide template

    NASA Astrophysics Data System (ADS)

    Lee, Inho; Han, Haksoo; Lee, Sang-Yup

    2010-04-01

    In this study, a biomimetic template was prepared and applied for growing calcium carbonate (CaCO 3) nanorods whose shape and polymorphism were controlled. A biomimetic template was prepared by adsorbing catalytic dipeptides into the pores of an anodic aluminum oxide (AAO) membrane. Using this peptide-adsorbed template, mineralization and aggregation of CaCO 3 was carried out to form large nanorods in the pores. The nanorods were aragonite and had a structure similar to nanoneedle assembly. This aragonite nanorod formation was driven by both the AAO template and catalytic function of dipeptides. The AAO membrane pores promoted generation of aragonite polymorph and guided nanorod formation by guiding the nanorod growth. The catalytic dipeptides promoted the aggregation and further dehydration of calcium species to form large nanorods. Functions of the AAO template and catalytic dipeptides were verified through several control experiments. This biomimetic approach makes possible the production of functional inorganic materials with controlled shapes and crystalline structures.

  17. The crystallization of tough thermoplastic resins in the presence of carbon fibers

    NASA Technical Reports Server (NTRS)

    Theil, M. H.

    1986-01-01

    The crystallization kinetics of the thermoplastic resins poly(phenylene sulfide) (PPS) and poly(aryl-ether-ether-ketone) (PEEK) in the presence and in the abscence of carbon fibers was studied. How carbon fiber surfaces in composites affect the crystallization of tough thermoplastic polymers that may serve as matrix resins were determined. The crystallization kinetics of such substances can provide useful information about the crystallization mechanisms and, thus, indicate if the presence of carbon fibers cause any changes in such mechanisms.

  18. Crystal structures of carbonates up to Mbar pressures determined by single crystal synchrotron radiation diffraction

    NASA Astrophysics Data System (ADS)

    Merlini, M.

    2013-12-01

    The recent improvements at synchrotron beamlines, currently allow single crystal diffraction experiments at extreme pressures and temperatures [1,2] on very small single crystal domains. We successfully applied such technique to determine the crystal structure adopted by carbonates at mantle pressures. The knowledge of carbon-bearing phases is in fact fundamental for any quantitative modelling of global carbon cycle. The major technical difficulty arises after first order transitions or decomposition reactions, since original crystal (apx. 10x10x5 ?m3) is transformed in much smaller crystalline domains often with random orientation. The use of 3D reciprocal space visualization software and the improved resolution of new generation flat panel detectors, however, allow both identification and integration of each single crystal domain, with suitable accuracy for ab-initio structure solution, performed with direct and charge-flipping methods and successive structure refinements. The results obtained on carbonates, indicate two major crystal-chemistry trends established at high pressures. The CO32- units, planar and parallel in ambient pressure calcite and dolomite structures, becomes non parallel in calcite- and dolomite-II and III phases, allowing more flexibility in the structures with possibility to accommodate strain arising from different cation sizes (Ca and Mg in particular). Dolomite-III is therefore also observed to be thermodynamically stable at lower mantle pressures and temperatures, differently from dolomite, which undergoes decomposition into pure end-members in upper mantle. At higher pressure, towards Mbar (lowermost mantle and D'' region) in agreement with theoretical calculations [3,4] and other experimental results [5], carbon coordination transform into 4-fold CO4 units, with different polymerisation in the structure depending on carbonate composition. The second important crystal chemistry feature detected is related to Fe2+ in Fe-bearing magnesite, which spontaneously oxidises at HP/HT, forming Fe3+ carbonates, Fe3+ oxides and reduced carbon (diamonds). Single crystal diffraction approach allowed full structure determination of these phases, yielding to the discovery of few unpredicted structures, such as Mg2Fe2C4O13 and Fe13O19, which can be well reproduced in different experiments. Mg2Fe2C4O13 carbonate present truncated chain C4O13 groups, and Fe13O19 oxide, whose stoichiometry is intermediate between magnetite and hematite, is a one-layer structure, with features encountered in superconducting materials. The results fully support the ideas of unexpected complexities in the mineralogy of the lowermost mantle, and single crystal technique, once properly optimized in ad-hoc synchrotron beamlines, is fundamental for extracting accurate structural information, otherwise rarely accessible with other experimental techniques. References: [1] Merlini M., Hanfland M. (2013). Single crystal diffraction at Mbar conditions by synchrotron radiation. High Pressure Research, in press. [2] Dubrovinsky et al., (2010). High Pressure Research, 30, 620-633. [3] Arapan et al. (1997). Phys. Rev. Lett., 98, 268501. [4] Oganov et al. (2008) EPSL, 273, 38-47. [5] Boulard et al. (2011) PNAS, 108, 5184-5187.

  19. Ferromagnetic Ordering in Carbon Nanotubes, Incorporated in Diamond Single Crystals

    E-print Network

    Dmitri Yerchuck; Vyacheslav Stelmakh; Alla Dovlatova; Yauhen Yerchak; Andrey Alexandrov

    2013-06-02

    The physical origin of the mechanism of the formation of ferromagnetic ordering in carbon nanotubes (NTs), produced by high energy ion beam modification of diamond single crystals in $\\langle{110}\\rangle$ and $\\langle{111}\\rangle$ directions has been found. It is concluded from analysis of experimental results on ferromagnetic spin wave resonance observed, that the only $\\pi$-electronic subsystem of given NTs is responsible for the appearance of ferromagnetism. It is determined by asymmetry in spin density distribution in Su-Schrieffer-Heeger (SSH) topological soliton lattice. The formation of SSH topological soliton lattice is considered in the frames of generalized SSH-model of organic conductors, in which $\\pi$-electronic subsystem is represented being to be 1D quantum Fermi liquid. The phenomenon of formation of uncompensated antiferromagnetic ordering coexisting with superconductivity at room temperature in carbon nanotubes, produced by high energy ion beam modification of diamond single crystals in $\\langle{100}\\rangle$ direction is argued.

  20. Ion microprobe measurement of strontium isotopes in calcium carbonate with application to salmon otoliths

    USGS Publications Warehouse

    Weber, P.K.; Bacon, C.R.; Hutcheon, I.D.; Ingram, B.L.; Wooden, J.L.

    2005-01-01

    The ion microprobe has the capability to generate high resolution, high precision isotopic measurements, but analysis of the isotopic composition of strontium, as measured by the 87Sr/ 86Sr ratio, has been hindered by isobaric interferences. Here we report the first high precision measurements of 87Sr/ 86Sr by ion microprobe in calcium carbonate samples with moderate Sr concentrations. We use the high mass resolving power (7000 to 9000 M.R.P.) of the SHRIMP-RG ion microprobe in combination with its high transmission to reduce the number of interfering species while maintaining sufficiently high count rates for precise isotopic measurements. The isobaric interferences are characterized by peak modeling and repeated analyses of standards. We demonstrate that by sample-standard bracketing, 87Sr/86Sr ratios can be measured in inorganic and biogenic carbonates with Sr concentrations between 400 and 1500 ppm with ???2??? external precision (2??) for a single analysis, and subpermil external precision with repeated analyses. Explicit correction for isobaric interferences (peak-stripping) is found to be less accurate and precise than sample-standard bracketing. Spatial resolution is ???25 ??m laterally and 2 ??m deep for a single analysis, consuming on the order of 2 ng of material. The method is tested on otoliths from salmon to demonstrate its accuracy and utility. In these growth-banded aragonitic structures, one-week temporal resolution can be achieved. The analytical method should be applicable to other calcium carbonate samples with similar Sr concentrations. Copyright ?? 2005 Elsevier Ltd.

  1. Recovery of calcium carbonate from waste gypsum and utilization for remediation of acid mine drainage from coal mines.

    PubMed

    Mulopo, J; Radebe, V

    2012-01-01

    The recovery of calcium carbonate from waste gypsum (a waste product of the reverse osmosis (RO) desalination process) was tested using sodium carbonate. Batch recovery of calcium carbonate from waste gypsum slurries by reacting with sodium carbonate under ambient conditions was used to assess the technical feasibility of CaCO(3) recovery and its use for pre-treatment of acid mine drainage (AMD) from coal mines. The effect of key process parameters, such as the slurry concentration (%) and the molar ratio of sodium carbonate to gypsum were considered. It was observed that batch waste gypsum conversion significantly increased with decrease in the slurry concentration or increase in the molar ratio of sodium carbonate to gypsum. The CaCO(3) recovered from the bench-scale batch reactor demonstrated effective neutralization ability during AMD pre-treatment compared with commercial laboratory grade CaCO(3). PMID:22828309

  2. Crystallization of Carbon-Oxygen Mixtures in White Dwarf Stars

    Microsoft Academic Search

    C. J. Horowitz; A. S. Schneider; D. K. Berry

    2010-01-01

    We determine the phase diagram for dense carbon\\/ oxygen mixtures in White\\u000aDwarf (WD) star interiors using molecular dynamics simulations involving liquid\\u000aand solid phases. Our phase diagram agrees well with predictions from Ogata et\\u000aal. and Medin and Cumming and gives lower melting temperatures than Segretain\\u000aet al. Observations of WD crystallization in the globular cluster NGC 6397 by

  3. Formation of calcium carbonate films on chitosan substrates in the presence of polyacrylic acid

    SciTech Connect

    He, Linghao; Xue, Rui [Zhengzhou University of Light Industry Henan Provincial Key Laboratory of Surface and Interface Science, Henan, Zhengzhou 450002 (China); Song, Rui, E-mail: rsong@gucas.ac.c [Zhengzhou University of Light Industry Henan Provincial Key Laboratory of Surface and Interface Science, Henan, Zhengzhou 450002 (China); College of Chemistry and Chemical Engineering, Graduate University of Chinese Academy of Sciences, Beijing 100049 (China)

    2009-05-15

    In this investigation, chitosan membranes with different surface average degrees of deacetylation (DA) are prepared and then are employed as the support matrix to culture calcium carbonate (CaCO{sub 3}). In the presence of high concentration of polyacrylic acid (PAA), the CaCO{sub 3} films obtained on the surface of all chitosan films mainly consisted of vaterite, which suggests the presence of bulk PAA plays an overwhelming part in stabilizing the vaterite. As a comparison, the influences of active groups indicate that only in case of low concentration PAA the thin CaCO{sub 3} films grown on chitosan with 8% DA mainly consisted of vaterite owing to the strong nucleation ability of -NH{sub 2} group, whereas, for those grown on chitosan with 80% DA the CaCO{sub 3} films mainly consisted of aragonite. A more complex scenario revealed that in the case of intermediate concentration of PAA the formed polymorphs behave as mixtures of vaterite and aragonite. - Graphical abstract: Chitosan membranes with different degrees of deacetylation (DA) are employed as support to culture calcium carbonate (CaCO{sub 3}). In high concentration of polyacrylic acid (PAA), the CaCO{sub 3} films obtained consisted of vaterite. However, the CaCO{sub 3} film grown on chitosan with 8% DA mainly consisted of vaterite as opposed to aragonite for chitosan with 8% DA. The schematic presentation of the formation of calcium carbonate on chitosan films with different degrees of acetylation in the presence of PAA with low-, mid- and high concentrations.

  4. Development of glass-ceramics by sintering and crystallization of fine powders of calcium-magnesium-aluminosilicate glass

    Microsoft Academic Search

    D. U. Tulyaganov; M. J. Ribeiro; J. A. Labrincha

    2002-01-01

    Natural raw materials normally used in the ceramic and glass industry were studied for the production of calcium–magnesium–aluminosilicate glass or glass-ceramic materials. Sintering and crystallization processes of fine powders of parent glass with chemical composition (wt.%) 46.00 SiO2, 15.90 Al2O3, 1.20 Fe2O3, 0.42 TiO2, 23.50 CaO, 9.37 MgO, 0.04 Na2O, 0.98 K2O, 1.95 P2O5 and 0.35 CaF2 were studied. Crystallization

  5. Peptide interactions with steel surfaces: Inhibition of corrosion and calcium carbonate precipitation

    SciTech Connect

    Mueller, E.; Sikes, C.S. (Univ. of South Alabama, Mobile, AL (United States). Mineralization Center); Little, B.J. (Stennis Space Center, MS (United States). Naval Research Lab.)

    1993-10-01

    Polyaspartate, a polyanionic peptide analog of an oyster-shell protein fraction, inhibited corrosion of AISI 1018 mild steel (UNS G10180) in seawater in a dose-dependent manner. A maximal inhibition of [approximately] 60% was obtained at a concentration of 100[mu]g mL[sup [minus]1]. Related peptides containing hydrophobic and/or phosphorylated amino acids had corrosion inhibition activities similar to or lower than polyaspartate in fresh and brackish waters. Binding studies demonstrated polyaspartate bound to mild steel in a dose- and time-dependent manner. Evidence for stainless steel (SS) binding was based on inhibition of calcium carbonate precipitation of the SS surface.

  6. Peptoid nanosheets as soluble, two-dimensional templates for calcium carbonate mineralization.

    PubMed

    Jun, Joo Myung V; Altoe, M Virginia P; Aloni, Shaul; Zuckermann, Ronald N

    2015-06-25

    Nacre-mimetic materials are of great interest, but difficult to synthesize, because they require the ordering of organic and inorganic materials on several length scales. Here we introduce peptoid nanosheets as a versatile two-dimensional platform to develop nacre mimetic materials. Free-floating zwitterionic nanosheets were mineralized with thin films of amorphous calcium carbonate (of 2-20 nm thickness) on their surface to produce planar nacre synthons. These can serve as tunable building blocks to produce layered brick and mortar nanoarchitectures. PMID:26021742

  7. Characterisation of Calcium Phosphate Crystals on Calcified Human Aortic Vascular Smooth Muscle Cells and Potential Role of Magnesium

    PubMed Central

    Louvet, Loïc; Bazin, Dominique; Büchel, Janine; Steppan, Sonja; Passlick-Deetjen, Jutta; Massy, Ziad A.

    2015-01-01

    Background Cardiovascular disease including vascular calcification (VC) remains the leading cause of death in patients suffering from chronic kidney disease (CKD). The process of VC seems likely to be a tightly regulated process where vascular smooth muscle cells are playing a key role rather than just a mere passive precipitation of calcium phosphate. Characterisation of the chemical and crystalline structure of VC was mainly led in patients or animal models with CKD. Likewise, Mg2+ was found to be protective in living cells although a potential role for Mg2+ could not be excluded on crystal formation and precipitation. In this study, the crystal formation and the role of Mg2+ were investigated in an in vitro model of primary human aortic vascular smooth muscle cells (HAVSMC) with physical techniques. Methodology/Principal Findings In HAVSMC incubated with increased Ca x Pi medium, only calcium phosphate apatite crystals (CPA) were detected by Micro-Fourier Transform InfraRed spectroscopy (µFTIR) and Field Effect Scanning Electron Microscope (FE — SEM) and Energy Dispersive X-ray spectrometry (EDX) at the cell layer level. Supplementation with Mg2+ did not alter the crystal composition or structure. The crystal deposition was preferentially positioned near or directly on cells as pictured by FE — SEM observations and EDX measurements. Large µFTIR maps revealed spots of CPA crystals that were associated to the cellular layout. This qualitative analysis suggests a potential beneficial effect of Mg2+ at 5 mM in noticeably reducing the number and intensities of CPA µFTIR spots. Conclusions/Significance For the first time in a model of HAVSMC, induced calcification led to the formation of the sole CPA crystals. Our data seems to exclude a physicochemical role of Mg2+ in altering the CPA crystal growth, composition or structure. Furthermore, Mg2+ beneficial role in attenuating VC should be linked to an active cellular role. PMID:25607936

  8. Development of poly(aspartic acid-co-malic acid) composites for calcium carbonate and sulphate scale inhibition.

    PubMed

    Mithil Kumar, N; Gupta, Sanjay Kumar; Jagadeesh, Dani; Kanny, K; Bux, F

    2015-05-01

    Polyaspartic acid (PSI) is suitable for the inhibition of inorganic scale deposition. To enhance its scale inhibition efficiency, PSI was modified by reacting aspartic acid with malic acid (MA) using thermal polycondensation polymerization. This reaction resulted in poly(aspartic acid-co-malic acid) (PSI-co-MA) dual polymer. The structural, chemical and thermal properties of the dual polymers were analysed by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. The effectiveness of six different molar ratios of PSI-co-MA dual polymer for calcium carbonate and calcium sulphate scale inhibition at laboratory scale batch experiments was evaluated with synthetic brine solution at selected doses of polymer at 65-70°C by the static scale test method. The performance of PSI-co-MA dual polymer for the inhibition of calcium carbonate and calcium sulphate precipitation was compared with that of a PSI single polymer. The PSI-co-MA exhibited excellent ability to control inorganic minerals, with approximately 85.36% calcium carbonate inhibition and 100% calcium sulphate inhibition at a level of 10?mg/L PSI-co-MA, respectively. Therefore, it may be reasonably concluded that PSI-co-MA is a highly effective scale inhibitor for cooling water treatment applications. PMID:25371160

  9. Fabrication of carbonate apatite block based on internal dissolution-precipitation reaction of dicalcium phosphate and calcium carbonate.

    PubMed

    Daitou, Fumikazu; Maruta, Michito; Kawachi, Giichiro; Tsuru, Kanji; Matsuya, Shigeki; Terada, Yoshihiro; Ishikawa, Kunio

    2010-05-01

    In this study, we investigated a novel method for fabrication of carbonate apatite block without ionic movement between precursor and solution by using precursor that includes all constituent ions of carbonate apatite. A powder mixture prepared from dicalcium phosphate anhydrous and calcite at appropriate Ca/P ratios (1.5, 1.67, and 1.8) was used as starting material. For preparation of specimens, the slurry made from the powder mixture and distilled water was packed in a split stainless steel mold and heat - treated, ranging from 60 degrees C to 100 degrees C up to 48 hours at 100% humidity. It appeared that carbonate apatite could be obtained above 70 degrees C and monophasic carbonate apatite could be obtained from the powder mixture at Ca/P ratio of 1.67. Carbonate content of the specimen was about 5-7%. Diametral tensile strength of the carbonate apatite blocks slightly decreased with increasing treatment temperature. The decrease in diametral tensile strength is thought to be related to the crystal size of the carbonate apatite formed. PMID:20448406

  10. Lignin peroxidase and protease production by Streptomyces viridosporus T7A in the presence of calcium carbonate. Nutritional and regulatory carbon sources.

    PubMed

    Macedo, J M; Gottschalk, L M; Bon, E P

    1999-01-01

    Streptomyces are good producers of enzymes of industrial interest, such as lignin peroxidase (LiP) and proteases. To optimize production of these enzymes by Streptomyces viridosporus T7A, two parameters were evaluated: carbon sources and calcium carbonate. Shake-flask fermentations were performed using culture media, with and without CaCO3, contained yeast extract, mineral salts and either glucose, lactose, galactose, or corn oil. In the absence of calcium carbonate, the maximum values for LiP and protease activities occurred during the idiophase with LiP activity being favored by glucose, corn oil, and galactose, and protease activity being favored only by corn oil. Calcium carbonate affected the cell morphology by reducing the size of the pellets. Moreover, in the presence of the salt, LiP production was growth-associated in all media but the glucose medium. Higher enzyme levels were observed when galactose and glucose were used as carbon sources. Protease activity was repressed by both glucose and galactose, whereas corn oil was the best carbon source for the enzyme production. Calcium carbonate increased LiP production by up to 2.6-fold. Such improvement was not observed for protease production, suggesting a selective effect of CaCO3 on LiP activity. PMID:15304693

  11. Polymorph selection and nanocrystallite rearrangement of calcium carbonate in carboxymethyl chitosan aqueous solution: Thermodynamic and kinetic analysis

    SciTech Connect

    Zhao, Donghui [Key Lab For Special Functional Materials Ministry of Education, Henan University, Kaifeng 475004 (China) [Key Lab For Special Functional Materials Ministry of Education, Henan University, Kaifeng 475004 (China); Key Lab of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi, Changning, Shanghai 200050 (China); Zhu, Yingchun, E-mail: yzhu@mail.sic.ac.cn [Key Lab of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi, Changning, Shanghai 200050 (China)] [Key Lab of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi, Changning, Shanghai 200050 (China); Li, Fang; Ruan, Qichao [Key Lab of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi, Changning, Shanghai 200050 (China)] [Key Lab of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi, Changning, Shanghai 200050 (China); Zhang, Shengmao [Key Lab For Special Functional Materials Ministry of Education, Henan University, Kaifeng 475004 (China)] [Key Lab For Special Functional Materials Ministry of Education, Henan University, Kaifeng 475004 (China); Zhang, Linlin; Xu, Fangfang [Key Lab of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi, Changning, Shanghai 200050 (China)] [Key Lab of Inorganic Coating Materials, Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi, Changning, Shanghai 200050 (China)

    2010-01-15

    In this article, the polymorph selection of calcium carbonate has been successfully achieved in water-soluble carboxymethyl chitosan aqueous solution at different temperatures (25-95 {sup o}C). Vaterite is formed in carboxymethyl chitosan solution 25 {sup o}C accompanied with trace of calcite, whereas pure aragonite is obtained at 95 {sup o}C. Scanning electron microscopy and transmission electron microscopy analyses show that the products are formed from the recrystallization of nanometer crystallites. Thermodynamic and kinetic analyses reveal that the polymorph of calcium carbonate is controlled and selected by kinetics in various temperatures. As a heterogeneous nucleator and stabilizing agent, carboxymethyl chitosan changes the nucleation and growth of calcium carbonate from thermodynamic into kinetic control. Under kinetic limitation, the reaction rate of aragonite increases along with the elevating of temperature and surpasses the rate of vaterite above 327 K.

  12. Restoration of parathyroid function after change of phosphate binder from calcium carbonate to lanthanum carbonate in hemodialysis patients with suppressed serum parathyroid hormone.

    PubMed

    Inaba, Masaaki; Okuno, Senji; Nagayama, Harumi; Yamada, Shinsuke; Ishimura, Eiji; Imanishi, Yasuo; Shoji, Shigeichi

    2015-03-01

    Control of phosphate is the most critical in the treatment of chronic kidney disease with mineral and bone disorder (CKD-MBD). Because calcium-containing phosphate binder to CKD patients is known to induce adynamic bone disease with ectopic calcification by increasing calcium load, we examined the effect of lanthanum carbonate (LaC), a non-calcium containing phosphate binder, to restore bone turnover in 27 hemodialysis patients with suppressed parathyroid function (serum intact parathyroid hormone [iPTH] ? 150 pg/mL). At the initiation of LaC administration, the dose of calcium-containing phosphate binder calcium carbonate (CaC) was withdrawn or reduced based on serum phosphate. After initiation of LaC administration, serum calcium and phosphate decreased significantly by 4 weeks, whereas whole PTH and iPTH increased. A significant and positive correlation between decreases of serum calcium, but not phosphate, with increases of whole PTH and iPTH, suggested that the decline in serum calcium with reduction of calcium load by LaC might increase parathyroid function. Serum bone resorption markers, such as serum tartrate-resistant acid phosphatase 5b, and N-telopeptide of type I collagen increased significantly by 4 weeks after LaC administration, which was followed by increases of serum bone formation markers including serum bone alkaline phosphatase, intact procollagen N-propeptide, and osteocalcin. Therefore, it was suggested that LaC attenuated CaC-induced suppression of parathyroid function and bone turnover by decreasing calcium load. In conclusion, replacement of CaC with LaC, either partially or totally, could increase parathyroid function and resultant bone turnover in hemodialysis patients with serum iPTH ? 150 pg/mL. PMID:25556148

  13. Characteristics of Cholesteryl Cetyl Carbonate Liquid Crystals as Drug Delivery Systems

    Microsoft Academic Search

    R. Chuealee; P. Aramwit; T. Srichana

    2007-01-01

    A thermotropic liquid crystals of cholesteryl cetyl carbonate was investigated as a novel nanosystem for delivery of lipophilic drugs. The aims were to synthesize, characterize and develop a formulation for amphotericin B (AmB) in cholesteryl cetyl carbonate liquid crystals. Cholesteryl cetyl carbonate was synthesized and identified by thin layer chromatography (TLC), flash column chromatography, Fourier transformed infrared (FTIR) spectroscopy, mass

  14. Increase in the dosage amount of vitamin D3 preparations by switching from calcium carbonate to lanthanum carbonate.

    PubMed

    Hyodo, Toru; Kawakami, Junko; Mikami, Noriko; Wakai, Haruki; Ishii, Daisuke; Yoshida, Kazunari; Iwamura, Masatsugu; Hida, Miho; Kurata, Yasuhisa

    2014-06-01

    It is widely known that dialysis patients who are administered vitamin D preparations have a better prognosis than patients who are not. In this study, of 22 patients on maintenance dialysis who had been administered calcium (Ca) carbonate in our hospital, we investigated the dosage amount of vitamin D3 preparations after the phosphorus (P) binder was switched from Ca carbonate to the newly developed lanthanum carbonate (LC). After completely switching to LC, the dosage amount of oral vitamin D3 preparation (alfacalcidol equivalent) was significantly increased from 0.094 ?g/day to 0.375 ?g/day (P = 0.0090). No significant changes were observed in the values of serum corrected Ca, alkaline phosphatase, intact parathyroid hormone and P after switching. The administration of LC enabled complete cessation of the administration of Ca carbonate preparations, and increased the dosage amount of vitamin D3 preparations. Therefore, LC may be a useful P binder to improve patient prognosis. PMID:24953761

  15. In situ X-ray pair distribution function analysis of accelerated carbonation of a synthetic calcium-?silicate?-hydrate gel

    SciTech Connect

    Morandeau, Antoine E.; White, Claire E. (Princeton)

    2015-01-01

    Calcium–silicate–hydrate (C–S–H) gel is the main binder component in hydrated ordinary Portland cement (OPC) paste, and is known to play a crucial role in the carbonation of cementitious materials, especially for more sustainable alternatives containing supplementary cementitious materials. However, the exact atomic structural changes that occur during carbonation of C–S–H gel remain unknown. Here, we investigate the local atomic structural changes that occur during carbonation of a synthetic calcium–silicate–hydrate gel exposed to pure CO? vapour, using in situ X-ray total scattering measurements and subsequent pair distribution function (PDF) analysis. By analysing both the reciprocal and real-space scattering data as the C–S–H carbonation reaction progresses, all phases present during the reaction (crystalline and non-crystalline) have been identified and quantified, with the results revealing the emergence of several polymorphs of crystalline calcium carbonate (vaterite and calcite) in addition to the decalcified C–S–H gel. Furthermore, the results point toward residual calcium being present in the amorphous decalcified gel, potentially in the form of an amorphous calcium carbonate phase. As a result of the quantification process, the reaction kinetics for the evolution of the individual phases have been obtained, revealing new information on the rate of growth/dissolution for each phase associated with C–S–H gel carbonation. Moreover, the investigation reveals that the use of real space diffraction data in the form of PDFs enables more accurate determination of the phases that develop during complex reaction processes such as C–S–H gel carbonation in comparison to the conventional reciprocal space Rietveld analysis approach.

  16. Salt-enhanced chemical weathering of building materials and bacterial mineralization of calcium carbonate as a treatment

    NASA Astrophysics Data System (ADS)

    Schiro, M.; Ruiz-Agudo, E.; Jroundi, F.; Gonzalez-Muñoz, M. T.; Rodriguez-Navarro, C.

    2012-04-01

    Salt weathering is an important mechanism contributing to the degradation and loss of stone building materials. In addition to the physical weathering resulting from crystallization pressure, the presence of salts in solution greatly enhances the chemical weathering potential of pore waters. Flow through experiments quantify the dissolution rates of calcite and quartz grains (63-125 micrometer diameter) when subjected to 1.0 ionic strength solutions of MgSO4, MgCl, Na2SO4 or NaCl. Results indicate that the identity of the cation is the primary control over the dissolution rate of both calcite and quartz substrates, with salt-enhanced dissolution occurring most rapidly in Mg2+ bearing solutions. It has been observed that weathering rates of rocks in nature, as well as building stones, are slowed down by naturally occurring or artificially produced patinas. These tend to be bacterially produced, durable mineralized coatings that lend some degree of protection to the underlying stone surface [1]. Our research shows that bacterially produced carbonate coatings can be quite effective at reducing chemical weathering of stone by soluble salts. The calcite-producing-bacteria used in this study were isolated from stone monuments in Granada, Spain [2] and cultivated in an organic-rich culture medium on a variety of artificial and natural substrates (including limestone, marble, sandstone, quartz, calcite single crystals, glass cover-slips, and sintered porous glass). Scanning electron microscopy (FESEM) was used to image bacterial calcite growth and biofilm formation. In-situ atomic force microscopy (AFM) enabled calculation of dissolution rates of untreated and bacterially treated surfaces. 2D-XRD showed the mineralogy and crystallographic orientation of bacterial calcium carbonate. Results indicate that bacterially produced calcite crystals form a coherent, mechanically resistant surface layer in perfect crystallographic continuity with the calcite substrate (self-epitaxy). These calcite biominerals are more resistant to chemical weathering by salt-enhanced dissolution, apparently due to the incorporation of organics (bacterial exopolymeric substances, EPS). Conversely, on silicate substrates, non-oriented vaterite forms, leading to limited protection. These preliminary results indicate that bacterial treatments have a significant potential to protect the stone built cultural heritage. [1] De Muynck et al. (2010) Ecol. Eng. 36, 118-136. [2] Jimenez-Lopez et al. (2007) Chemosphere 68, 1929-1936.

  17. Analyses of calcium carbonate scale deposition on four RO membranes under a seawater desalination condition.

    PubMed

    Kang, Nam Wook; Lee, Seockheon; Kim, Dooil; Hong, Seungkwan; Kweon, Ji Hyang

    2011-01-01

    Inorganic fouling is one of the critical operational issues in reverse osmosis membrane. Few researches investigated effects of membrane surface characteristics on inorganic fouling and on anti-scaling techniques although the fouling occurs on the membrane surface. The objective of this paper was to examine whether different characteristics of deposition of calcium carbonate solids would occur on four membranes having distinctive surface properties. A lab-scale cell reactor with a crossflow velocity was installed and two coupons were used for one type of membranes. Two feed waters were examined: concentrated synthetic seawater simulating a 30% recovery and a concentrate from a seawater RO plant in operation at Changwon, Korea. The amounts of solid deposition on the attached membranes were increased in all four membranes but the degree of deposition on each membrane was different. Various types of calcium carbonate solids were clearly detected by both XRD and SEM analyses. In general, a membrane with greater roughness and negative surface charge appeared to form more scales. This implied that membrane surface characteristics such as roughness and surface charge affected inorganic fouling, presumably by providing favourable sites for precipitation and enhancing attraction of species to the membrane surface. PMID:22335098

  18. Soluble organic additive effects on stress development during drying of calcium carbonate suspensions.

    PubMed

    Wedin, Pär; Lewis, Jennifer A; Bergström, Lennart

    2005-10-01

    The effect of polymer, plasticizer, and surfactant additives on stress development during drying of calcium carbonate particulate coatings was studied using a controlled-environment apparatus that simultaneously monitors drying stress, weight loss, and relative humidity. We found that the calcium carbonate coatings display a drying stress evolution typical of granular films, which is characterized by a sharp capillary-induced stress rise followed by a rapid stress relaxation. The addition of a soluble polymer to the CaCO3 suspension resulted in a two-stage stress evolution process. The initial stress rise stems from capillary-pressure-induced stresses within the film, while the second, larger stress rise occurs due to solidification and shrinkage of the polymeric species. Measurements on the corresponding pure polymer solutions established a clear correlation between the magnitude of residual stress in both the polymer and CaCO3-polymer films to the physical properties of the polymer phase, i.e. its glass transition temperature, T(g), and Young's modulus. The addition of small organic molecules can reduce the residual stress observed in the CaCO3-polymer films; e.g., glycerol, which acts as a plasticizer, reduces the drying stress by lowering T(g), while surfactant additions reduce the surface tension of the liquid phase, and, hence, the magnitude of the capillary pressure within the film. PMID:16122547

  19. Biotic and abiotic effects on CO2 sequestration during microbially-induced calcium carbonate precipitation.

    PubMed

    Okyay, Tugba Onal; Rodrigues, Debora F

    2015-03-01

    In this study, CO2 sequestration was investigated through the microbially-induced calcium carbonate precipitation (MICP) process with isolates obtained from a cave called 'Cave Without A Name' (Boerne, TX, USA) and the Pamukkale travertines (Denizli, Turkey). The majority of the bacterial isolates obtained from these habitats belonged to the genera Sporosarcina, Brevundimonas, Sphingobacterium and Acinetobacter. The isolates were investigated for their capability to precipitate calcium carbonate and sequester CO2. Biotic and abiotic effects of CO2 sequestration during MICP were also investigated. In the biotic effect, we observed that the rate and concentration of CO2 sequestered was dependent on the species or strains. The main abiotic factors affecting CO2 sequestration during MICP were the pH and medium components. The increase in pH led to enhanced CO2 sequestration by the growth medium. The growth medium components, on the other hand, were shown to affect both the urease activity and CO2 sequestration. Through the Plackett-Burman experimental design, the most important growth medium component involved in CO2 sequestration was determined to be urea. The optimized medium composition by the Plackett-Burman design for each isolate led to a statistically significant increase, of up to 148.9%, in CO2 uptake through calcification mechanisms. PMID:25764465

  20. Extracellular matrix production and calcium carbonate precipitation by coral cells in vitro

    PubMed Central

    Helman, Yael; Natale, Frank; Sherrell, Robert M.; LaVigne, Michèle; Starovoytov, Valentin; Gorbunov, Maxim Y.; Falkowski, Paul G.

    2008-01-01

    The evolution of multicellularity in animals required the production of extracellular matrices that serve to spatially organize cells according to function. In corals, three matrices are involved in spatial organization: (i) an organic ECM, which facilitates cell–cell and cell–substrate adhesion; (ii) a skeletal organic matrix (SOM), which facilitates controlled deposition of a calcium carbonate skeleton; and (iii) the calcium carbonate skeleton itself, which provides the structural support for the 3D organization of coral colonies. In this report, we examine the production of these three matrices by using an in vitro culturing system for coral cells. In this system, which significantly facilitates studies of coral cell physiology, we demonstrate in vitro excretion of ECM by primary (nondividing) tissue cultures of both soft (Xenia elongata) and hard (Montipora digitata) corals. There are structural differences between the ECM produced by X. elongata cell cultures and that of M. digitata, and ascorbic acid, a critical cofactor for proline hydroxylation, significantly increased the production of collagen in the ECM of the latter species. We further demonstrate in vitro production of SOM and extracellular mineralized particles in cell cultures of M. digitata. Inductively coupled plasma mass spectrometry analysis of Sr/Ca ratios revealed the particles to be aragonite. De novo calcification was confirmed by following the incorporation of 45Ca into acid labile macromolecules. Our results demonstrate the ability of isolated, differentiated coral cells to undergo fundamental processes required for multicellular organization. PMID:18162537

  1. A pH-Sensitive, Biobased Calcium Carbonate Aragonite Nanocrystal as a Novel Anticancer Delivery System

    PubMed Central

    Ismail, Maznah; Tengku Ibrahim, Tengku Azmi; Zakaria, Zuki Abu Bakar

    2013-01-01

    The synthesised biobased calcium carbonate nanocrystals had demonstrated to be an effective carrier for delivery of anticancer drug doxorubicin (DOX). The use of these nanocrystals displayed high levels of selectivity and specificity in achieving effective cancer cell death without nonspecific toxicity. These results confirmed that DOX was intercalated into calcium carbonate nanocrystals at high loading and encapsulation efficiency (4.8 and 96%, resp.). The CaCO3/DOX nanocrystals are relatively stable at neutral pH (7.4), resulting in slow release, but the nanocrystals progressively dissociated in acidic pH (4.8) regimes, triggering faster release of DOX. The CaCO3/DOX nanocrystals exhibited high uptake by MDA MB231 breast cancer cells and a promising potential delivery of DOX to target cells. In vitro chemosensitivity using MTT, modified neutral red/trypan blue assay, and LDH on MDA MB231 breast cancer cells revealed that CaCO3/DOX nanocrystals are more sensitive and gave a greater reduction in cell growth than free DOX. Our findings suggest that CaCO3 nanocrystals hold tremendous promise in the areas of controlled drug delivery and targeted cancer therapy. PMID:24324966

  2. Biomediated Precipitation of Calcium Carbonate and Sulfur in a Faintly Acidic Hot Spring

    NASA Astrophysics Data System (ADS)

    Jiang, L.; Peng, X.; Qiao, H.

    2014-12-01

    A faintly acidic hot spring named "female Tower" (T=73.5 ?, pH=6.64 ) is located in the Jifei Geothermal Field?Yunnan province, Southwest China. The precipitates in the hot spring are composed of large amounts of calcite and sulfur, as reveals by XRD analysis. Scanning electron microscopy (SEM) analysis show the microbial mats are formed of various coccoid, rod and filamentous microbes. Transmission electron microscopy (TEM) analysis show that intracellular sulfur granules are commonly associated with these microbes. Energy dispersive X-ray spectrometer (EDS) analysis shows that the surface of microbes are mainly composed of Ca, C, O and S. A culture-independent molecular phylogenetic analysis demonstrates the majority of bacteria in the spring are sulfur-oxidizing bacteria. In the spring water, H2S concentration was up to 60 ppm, while SO42- concentration was only about 10 ppm. We suggest that H2S might be utilized by sulfur-oxidizing bacteria in this hot spring water, leading to the formation of sulfur granules intracellularly and extracellularly. In the meantime, this reaction increases the pH in ambient environments, which fosters the precipitation of calcium carbonate precipitation in the microbial mats. This study suggests that the sulfur-oxidizing bacteria could play an important role in calcium carbonate precipitation in faintly acidic hot spring environments.

  3. Synthesis of three-dimensional calcium carbonate nanofibrous structure from eggshell using femtosecond laser ablation

    PubMed Central

    2011-01-01

    Background Natural biomaterials from bone-like minerals derived from avian eggshells have been considered as promising bone substitutes owing to their biodegradability, abundance, and lower price in comparison with synthetic biomaterials. However, cell adhesion to bulk biomaterials is poor and surface modifications are required to improve biomaterial-cell interaction. Three-dimensional (3D) nanostructures are preferred to act as growth support platforms for bone and stem cells. Although there have been several studies on generating nanoparticles from eggshells, no research has been reported on synthesizing 3D nanofibrous structures. Results In this study, we propose a novel technique to synthesize 3D calcium carbonate interwoven nanofibrous platforms from eggshells using high repetition femtosecond laser irradiation. The eggshell waste is value engineered to calcium carbonate nanofibrous layer in a single step under ambient conditions. Our striking results demonstrate that by controlling the laser pulse repetition, nanostructures with different nanofiber density can be achieved. This approach presents an important step towards synthesizing 3D interwoven nanofibrous platforms from natural biomaterials. Conclusion The synthesized 3D nanofibrous structures can promote biomaterial interfacial properties to improve cell-platform surface interaction and develop new functional biomaterials for a variety of biomedical applications. PMID:21251288

  4. Synthesis and characterization of carbon nanoribbons and single crystal iron filled carbon nanotubes

    SciTech Connect

    Mahanandia, P. [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)], E-mail: pitam@physics.iisc.ernet.in; Nanda, K.K. [Materials Research Centre, Indian Institute of Science, Bangalore 560012 (India); Prasad, V.; Subramanyam, S.V. [Department of Physics, Indian Institute of Science, Bangalore 560012 (India)

    2008-12-01

    Carbon nanoribbons and single crystal iron filled multiwall carbon nanotubes (MWCNTs) have been synthesized by simple pyrolysis technique. SEM investigation shows that the material consist mainly carbon nanoribbons and carbon nanotubes (CNTs). X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), electron energy dispersive X-ray (EDX), transmission electron miscroscopy (TEM) and highresolution transmission electron miscroscopy (HRTEM) studies reveal carbon nanotubes are filled with {alpha}-Fe. Closer inspection of HRTEM images indicated that the bcc structure {alpha}-Fe nanowires are monocrystalline and Fe (1 1 0) plane is indeed perpendicular to the G (0 0 2) plane, whereas orientation of (0 0 2) lattice planes of carbon nanoribbon is perpendicular to the axis of growth. Magnetic properties studied by superconducting quantum interference device (SQUID) at 300 K and 10 K exhibited coercivity of 1037 Oe and 2023 Oe. The large coercitivity is strongly attributed to the small size monocrystalline single phase {alpha}-Fe, single domain nature of the encapsulated Fe crystal, magnetocrystalline shape anisotropy and ferromagnetic behaviour of localized states at the edges of the carbon nanoribbons.

  5. Preparation and characterization of nano-sized calcium carbonate as controlled release pesticide carrier for validamycin against Rhizoctonia solani

    Microsoft Academic Search

    Kun Qian; Tianyu Shi; Tao Tang; Shaoliang Zhang; Xili Liu; Yongsong Cao

    2011-01-01

    Nano-sized calcium carbonate (nano-CC) was studied in terms of acting as a carrier for a pesticide. Nano-CC was prepared by\\u000a reaction of calcium chloride and sodium carbonate by the reversed-phase microemulsion method and then loaded with the pesticide\\u000a validamycin. The resulting material was characterized by X-ray diffraction analysis and scanning electron microscopy. The\\u000a loading efficiency, sustained-release performance, germicidal efficacy, and

  6. Herbal extracts of Tribulus terrestris and Bergenia ligulata inhibit growth of calcium oxalate monohydrate crystals in vitro

    NASA Astrophysics Data System (ADS)

    Joshi, V. S.; Parekh, B. B.; Joshi, M. J.; Vaidya, A. B.

    2005-02-01

    A large number of people in this world are suffering from urinary stone problem. Calcium oxalate monohydrate (COM) and calcium oxalate dihydrate (COD) containing stones (calculi) are commonly found. In the present study, COM crystals were grown by a double diffusion gel growth technique using U-tubes. The gel was prepared from hydrated sodium metasilicate solution. The gel framework acts like a three-dimensional crucible in which the crystal nuclei are delicately held in the position of their formation, and nutrients are supplied for the growth. This technique can be utilized as a simplified screening static model to study the growth, inhibition and dissolution of urinary stones in vitro. The action of putative litholytic medicinal plants, Tribulus terrestris Linn. ( T.t) and Bergenia ligulata Linn. ( B.l.), has been studied in the growth of COM crystals. Tribulus terrestris and Bergenia ligulata are commonly used as herbal medicines for urinary calculi in India. To verify the inhibitive effect, aqueous extracts of Tribulus terrestris and Bergenia ligulata were added along with the supernatant solutions. The growth was measured and compared, with and without the aqueous extracts. Inhibition of COM crystal growth was observed in the herbal extracts. Maximum inhibition was observed in Bergenia ligulata followed by Tribulus terrestris. The results are discussed.

  7. Crystallization from Gels

    NASA Astrophysics Data System (ADS)

    Narayana Kalkura, S.; Natarajan, Subramanian

    Among the various crystallization techniques, crystallization in gels has found wide applications in the fields of biomineralization and macromolecular crystallization in addition to crystallizing materials having nonlinear optical, ferroelectric, ferromagnetic, and other properties. Furthermore, by using this method it is possible to grow single crystals with very high perfection that are difficult to grow by other techniques. The gel method of crystallization provides an ideal technique to study crystal deposition diseases, which could lead to better understanding of their etiology. This chapter focuses on crystallization in gels of compounds that are responsible for crystal deposition diseases. The introduction is followed by a description of the various gels used, the mechanism of gelling, and the fascinating phenomenon of Liesegang ring formation, along with various gel growth techniques. The importance and scope of study on crystal deposition diseases and the need for crystal growth experiments using gel media are stressed. The various crystal deposition diseases, viz. (1) urolithiasis, (2) gout or arthritis, (3) cholelithiasis and atherosclerosis, and (4) pancreatitis and details regarding the constituents of the crystal deposits responsible for the pathological mineralization are discussed. Brief accounts of the theories of the formation of urinary stones and gallstones and the role of trace elements in urinary stone formation are also given. The crystallization in gels of (1) the urinary stone constituents, viz. calcium oxalate, calcium phosphates, uric acid, cystine, etc., (2) the constituents of the gallstones, viz. cholesterol, calcium carbonate, etc., (3) the major constituent of the pancreatic calculi, viz., calcium carbonate, and (4) cholic acid, a steroidal hormone are presented. The effect of various organic and inorganic ions, trace elements, and extracts from cereals, herbs, and fruits on the crystallization of major urinary stone and gallstone constituents are described. In addition, tables of gel-grown organic and inorganic crystals are provided.

  8. Micro-remnants of carbon- and calcium-bearing impact breccias of buried crater broken at Takamatsu, Japan

    NASA Astrophysics Data System (ADS)

    Miura, Y.

    2011-12-01

    Introduction: Impact evidences are discussed by 30 extraterrestrial-rich elements and shocked minerals in microscopic sizes. Micro-remnants during impact reactions can be obtained by impact breccias. Impact evidences at buried and broken impact crater structure in Takamatsu, Shikoku, Japan have been reported mainly by gravity anomaly and shocked-related materials on the Cretaceous Ryoke granite [1-10]. Anomalous materials with carbon-bearing materials and impact-related materials which are not usually included in the Japanese granitic rocks are found at the drilled materials. Main purposes of the paper are to elucidate carbon- and calcium-bearing micro-particles at the drilled samples of Takamatsu, Shikoku, Japan [9-10]. Anomalous carbon and calcium-bearing micro-grains: The Ryoke granitic rock at Takamatsu, Japan has few carbon and calcium contents in bulk XRF analyses from surface to 1,500m in depth. However, drilled sample at 950 m in depth contains nano-grains with high carbon and CaSiCO3 (in 100nm size) in composition. Carbon-rich grains in Takamatsu show very weak nano-diamond-like peak in the Raman spectra which are formed at impact reaction on carbon-rich target rock. Formation of remained carbon-bearing grains: Main sources of carbon and calcium which cannot be found in the granitic rock are sedimentary rocks as follows: 1) Carbon sources mainly found near at crater bottom (ca. 950m in depth) are considered to be impact target rocks of sedimentary limestone (from sea-sediments) with carbon dioxides gas during impact reaction on sea-water impact. 2) Calcium sources to form nano-grains of CaSiCO3 in composition are also considered to be sedimentary limestone and silicate-bearing rocks stored in the shallow sea-bottom. Summary: The present study is summarized as follows: a) Carbon-rich frilled sample of 950m in depth at buried crater in Takamatsu, Japan are indicates the main sources from shallow sea-limestone during impact reaction on shallow sea-impact. b) Calcium-rich sources to form micro-grains of CaSiCO3 in composition are considered to be shallow sea- limestone during sea-impact reaction.

  9. Geochemical Signatures of Rapid Carbonate Crystallization in Well Scales

    NASA Astrophysics Data System (ADS)

    Giles, G. F.; Boles, J. R.

    2006-12-01

    Oxygen and carbon isotopes and trace element substitution are widely used for paleotemperature studies of the oceans and for interpreting carbonate veins in faults. What is not well understood is the effect of rapid (disequilibrium) crystallization on the geochemistry of carbonates. Carbonate precipitated as well scales form in a controlled environment, where fluid composition, temperature, and pressure changes are well known and crystallization rates, which are rapid, can be calculated. Calcite and aragonite well scales and their respective waters have been analyzed for geochemical and isotopic composition and compared to reservoir data (hydrostatic fluid levels, pressure, temperature, depth, perforation locations, etc.). Preliminary conclusions are that well scales show isotopic disequilibrium and highly variable magnesium content, apparently due to rapid crystallization. Several parameters indicate isotopic disequilibrium and rapid CO2 degassing for the well scales. The ?18O of scales is up to 7‰ more positive than expected for equilibrium. The magnitude of deviation from the expected oxygen fractionation factor related to temperature and pressure is linear, indicating that greater precipitation rates (i.e. larger pressure differentials) increase isotopic disequilibrium. Rapid CO2 degassing preferentially strips the lighter isotopes from the water, leaving precipitated calcite enriched in 13C. Most of the scale samples have positive ?13C values that range from +6.83 to +28.7 ‰, indicating rapid CO2 degassing. Assuming a constant input fluid composition, a positive correlation of carbon and oxygen isotopes is evidence of rapid crystallization. Vertical sample sets from different depths of the tubing and horizontal sample sets from transects of thick samples were analyzed for isotopic composition. All scales show positive (?13C/?18O) slopes (values typically +0.9 to +5.5), which is intermediate of Hendy's (1971) proposed rapid degassing range for ?13C/?18O co-variation of +0.6 to +8.3. Preliminary analyses of a few calcite scales, which formed around 50-70°C, show large variation of magnesium content from 4 to 16 mole percent. Past studies conclude that incorporation of Mg into calcite is independent of rate and rather, dependent on temperature and the saturation state of the starting solution. These samples come from waters with low [Mg2+]/Ca2+] ratios and wells with minimal temperature and fluid composition change, suggesting that precipitation rate instead is controlling the Mg content of the scales. The frequency of Mg variation in the scales positively correlates with the growth banding thickness in the scales.

  10. The chemistry of the calcium carbonate shells (i.e., tests) of certain foraminifera can be used to reconstruct records of past

    E-print Network

    Coull, Bruce C.

    160 The chemistry of the calcium carbonate shells (i.e., tests) of certain foraminifera can be used- cipitation (Emiliani 1955; Hester and Boyle 1982; Lea and Boyle 1989). For example, the stable carbon isotope; Zahn et al. 1986). The incorporation of the nutri- ent proxies barium and cadmium into the calcium

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

    NASA Astrophysics Data System (ADS)

    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 calcite from ACC on these SAMs remains unknown and is the objective of this research. Our preliminary observations of the transforming ACC film with in situ Raman spectroscopy have shown a strengthening of the symmetric mode of the carbonate ion suggesting ordering of the ACC. To fully determine the structural evolution of the mineral phase we will use both Raman and Extended X-Ray Absorption Fine Structure (EXAFS) measurements, coupled with morphological analysis using SEM.

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

    NASA Astrophysics Data System (ADS)

    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 ?44Ca signature of NFC and LCC crystals were used to determine possible differences of the precipitation rate during their formation. NFC and LCC have similar ?18O 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 shape of NFC could be ascribed to a growth related to fungal organic molecules or potentially inside fungal hyphae. Three microscopic morphologies of NFC, previously defined (Milliere et al., 2011a), have been also examined in order to trace the evolution of the NFC inside the soil porosity. The Ca isotope composition of the simple needles, which are supposed to be the original form of NFC are the less fractionated compared to the soil solution, whereas the Ca isotope composition of the two other microscopic morphologies, namely the simple needle with nanofibres and the simple needle with overgrowths, are more fractionated, like the LCC, indicating potentially the influence of biogenic processes in the formation of the simple needles. Milliere L, Hasinger O, Bindschedler S, Cailleau G, Spangenberg JE, Verrecchia EP. 2011a. Stable carbon and oxygen isotopic signatures of pedogenic needle fibre calcite. Geoderma 161, 74-87.

  13. Advances in synthesis of calcium phosphate crystals with controlled size and shape.

    PubMed

    Lin, Kaili; Wu, Chengtie; Chang, Jiang

    2014-10-01

    Calcium phosphate (CaP) materials have a wide range of applications, including biomaterials, adsorbents, chemical engineering materials, catalysts and catalyst supports and mechanical reinforcements. The size and shape of CaP crystals and aggregates play critical roles in their applications. The main inorganic building blocks of human bones and teeth are nanocrystalline CaPs; recently, much progress has been made in the application of CaP nanocrystals and their composites for clinical repair of damaged bone and tooth. For example, CaPs with special micro- and nanostructures can better imitate the biomimetic features of human bone and tooth, and this offers significantly enhanced biological performances. Therefore, the design of CaP nano-/microcrystals, and the shape and hierarchical structures of CaPs, have great potential to revolutionize the field of hard tissue engineering, starting from bone/tooth repair and augmentation to controlled drug delivery devices. Previously, a number of reviews have reported the synthesis and properties of CaP materials, especially for hydroxyapatite (HAp). However, most of them mainly focused on the characterizations and physicochemical and biological properties of HAp particles. There are few reviews about the control of particle size and size distribution of CaPs, and in particular the control of nano-/microstructures on bulk CaP ceramic surfaces, which is a big challenge technically and may have great potential in tissue engineering applications. This review summarizes the current state of the art for the synthesis of CaP crystals with controlled sizes from the nano- to the macroscale, and the diverse shapes including the zero-dimensional shapes of particles and spheres, the one-dimensional shapes of rods, fibers, wires and whiskers, the two-dimensional shapes of sheets, disks, plates, belts, ribbons and flakes and the three-dimensional (3-D) shapes of porous, hollow, and biomimetic structures similar to biological bone and tooth. In addition, this review will also summarize studies on the controlled formation of nano-/microstructures on the surface of bulk ceramics, and the preparation of macroscopical bone grafts with 3-D architecture nano-/microstructured surfaces. Moreover, the possible directions of future research and development in this field, such as the detailed mechanisms behind the size and shape control in various strategies, the importance of theoretical simulation, self-assembly, biomineralization and sacrificial precursor strategies in the fabrication of biomimetic bone-like and enamel-like CaP materials are proposed. PMID:24954909

  14. Preparation and structure of carbonated calcium hydroxyapatite substituted with heavy rare earth ions

    SciTech Connect

    Yasukawa, Akemi, E-mail: yasukawa@cc.hirosaki-u.ac.jp [School of Home Economics, Faculty of Education, Hirosaki University, 1-bunkyo, Hirosaki, Aomori 036-8560 (Japan)] [School of Home Economics, Faculty of Education, Hirosaki University, 1-bunkyo, Hirosaki, Aomori 036-8560 (Japan); Kandori, Kazuhiko [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan)] [School of Chemistry, Osaka University of Education, 4-698-1 Asahigaoka, Kashiwara, Osaka 582-8582 (Japan); Tanaka, Hidekazu [Department of Material Science, Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504 (Japan)] [Department of Material Science, Faculty of Science and Engineering, Shimane University, 1060 Nishikawatsu, Matsue, Shimane 690-8504 (Japan); Gotoh, Keiko [Faculty of Human Life and Environment, Nara Women's University, Kita-uoya-nishi, Nara 630-8506 (Japan)] [Faculty of Human Life and Environment, Nara Women's University, Kita-uoya-nishi, Nara 630-8506 (Japan)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer LnCaHap solid solution particles were prepared using five types of heavy rare earth ions by a precipitation method. Black-Right-Pointing-Pointer The length and the crystallinity of the LnCaHap particles first increased and then decreased with increasing Ln{sup 3+} contents. Black-Right-Pointing-Pointer A series of YCaHap solid solution particles formed with Y/(Y + Ca) = 0-0.10 were investigated using various methods in detail. -- Abstract: Calcium hydroxyapatite (CaHap) particles substituted five types of heavy rare earth ions (Ln: Y{sup 3+}, Gd{sup 3+}, Dy{sup 3+}, Er{sup 3+} and Yb{sup 3+}) were synthesized using a precipitation method and characterized using various means. These Ln ions strongly affected the crystal phases and the structures of the products. With increasing Ln/(Ln + Ca) in the starting solution ([X{sub Ln}]), the length and the crystallinity of the particles first increased and then decreased. The rare earth metal-calcium hydroxyapatite (LnCaHap) solid solution particles were obtained at [X{sub Y}] {<=} 0.10 for substituting Y system and at [X{sub Ln}] {<=} 0.01-0.03 for substituting the other Ln systems. LnPO{sub 4} was mixed with LnCaHap at higher [X{sub Ln}] for all Ln systems. A series of yttrium-calcium hydroxyapatite (YCaHap) solid solutions with [X{sub Y}] = 0-0.10 were investigated using XRD, TEM, ICP-AES, IR and TG-DTA in detail.

  15. The cytospin technique improves the detection of calcium pyrophosphate crystals in synovial fluid samples with a low leukocyte count.

    PubMed

    Robier, Christoph; Quehenberger, Franz; Neubauer, Manfred; Stettin, Mariana; Rainer, Franz

    2014-06-01

    In synovial fluids (SF) with low leukocyte or/and crystal counts, important features may be missed, if exclusively smears are examined by polarized microscopy. That may be overcome by cytocentrifuges, which use low-speed centrifugal force to concentrate cells onto a glass slide and thus enhance the number of cells per high power field (HPF). We compared the calcium pyrophosphate (CPP) crystal counts in cytospin preparations with those in common smears of SF. The number of CPP crystals was counted in 50 SF samples by polarized microscopy, and statistical comparisons of the mean values of the cytospin and smear preparations were performed using the Wilcoxon test. The reproducibility within the slides of the cytocentrifuge and smear samples was determined by Spearman's rank correlation. The crystal counts were significantly higher in the cytospin than in the smear preparations (median 96/10 HPF vs. 2.5/10 HPF, p < 0.0001). The correlation in the crystal count between the slides 1 and 2 was significantly higher within the cytocentrifuge than in the smear group (0.97 vs. 0.73, p = 0.0004). CPP-negative cytospin preparations in initially smear-positive slides were not observed. We confirmed that the cytospin technique significantly enhances the number of examinable crystals per HPF, compared to common smears. PMID:23388697

  16. Ellipsometric investigations of photonic crystals based on carbon nanofibers

    E-print Network

    Rehammar, R; Arwin, H; Kinaret, J M; Campbell, E E B

    2010-01-01

    Carbon nanofibers (CNF) are used as components of planar photonic crystals (PC). Square and rectangular lattices as well as random patterns of vertically aligned CNF were fabricated and their properties studied using ellipsometry. Conventional methods of ellipsometric analysis used in thin film ellipsometry are not applicable to these samples due to their nanostructured nature. We show that detailed information such as symmetry directions and the band structure of these novel materials can be extracted from considerations of the polarization state in the specular beam.

  17. Crystallization of carbon-oxygen mixtures in white dwarf stars.

    PubMed

    Horowitz, C J; Schneider, A S; Berry, D K

    2010-06-11

    We determine the phase diagram for dense carbon-oxygen mixtures in white dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and from Medin and Cumming and gives lower melting temperatures than Segretain et al. Observations of WD crystallization in the globular cluster NGC 6397 by Winget et al. suggest that the melting temperature of WD cores is close to that for pure carbon. If this is true, our phase diagram implies that the central oxygen abundance in these stars is less than about 60%. This constraint, along with assumptions about convection in stellar evolution models, limits the effective S factor for the 12C(?,?)16O reaction to S(300)?170??keV?b. PMID:20867223

  18. Crystallization of Carbon Oxygen Mixtures in White Dwarf Stars

    E-print Network

    C. J. Horowitz; A. S. Schneider; D. K. Berry

    2010-05-14

    We determine the phase diagram for dense carbon/ oxygen mixtures in White Dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and Medin and Cumming and gives lower melting temperatures than Segretain et al. Observations of WD crystallization in the globular cluster NGC 6397 by Winget et al. suggest that the melting temperature of WD cores is close to that for pure carbon. If this is true, our phase diagram implies that the central oxygen abundance in these stars is less than about 60%. This constraint, along with assumptions about convection in stellar evolution models, limits the effective S factor for the $^{12}$C($\\alpha,\\gamma$)$^{16}$O reaction to S_{300} <= 170 keV barns.

  19. Crystallization of Carbon Oxygen Mixtures in White Dwarf Stars

    E-print Network

    Horowitz, C J; Berry, D K

    2010-01-01

    We determine the phase diagram for dense carbon/ oxygen mixtures in White Dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and Medin and Cumming and gives lower melting temperatures than Segretain et al. Observations of WD crystallization in the globular cluster NGC 6397 by Winget et al. suggest that the melting temperature of WD cores is close to that for pure carbon. If this is true, our phase diagram implies that the central oxygen abundance in these stars is less than about 60%. This constraint, along with assumptions about convection in stellar evolution models, limits the effective S factor for the $^{12}$C($\\alpha,\\gamma$)$^{16}$O reaction to S_{300} <= 170 keV barns.

  20. Crystallization of Carbon-Oxygen Mixtures in White Dwarf Stars

    SciTech Connect

    Horowitz, C. J.; Schneider, A. S.; Berry, D. K. [Department of Physics and Nuclear Theory Center, Indiana University, Bloomington, Indiana 47405 (United States); University Information Technology Services, Indiana University, Bloomington, Indiana 47408 (United States)

    2010-06-11

    We determine the phase diagram for dense carbon-oxygen mixtures in white dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and from Medin and Cumming and gives lower melting temperatures than Segretain et al. Observations of WD crystallization in the globular cluster NGC 6397 by Winget et al. suggest that the melting temperature of WD cores is close to that for pure carbon. If this is true, our phase diagram implies that the central oxygen abundance in these stars is less than about 60%. This constraint, along with assumptions about convection in stellar evolution models, limits the effective S factor for the {sup 12}C({alpha},{gamma}){sup 16}O reaction to S{sub 300{<=}}170 keV b.

  1. The effect of seed crystals of hydroxyapatite and brushite on the crystallization of calcium oxalate in undiluted human urine in vitro: implications for urinary stone pathogenesis.

    PubMed Central

    Grover, Phulwinder K.; Kim, Dong-Sun; Ryall, Rosemary Lyons

    2002-01-01

    BACKGROUND: The aim of this study was to determine whether crystals of hydroxyapatite (HA) or brushite (BR) formed in urine promote the epitaxial deposition of calcium oxalate (CaOx) from undiluted human urine in vitro and thereby explain the occurrence of phosphate in the core of urinary stones consisting predominantly of CaOx. MATERIALS AND METHODS: Crystals of HA, BR, and CaOx were generated from human urine and their identity confirmed by X-ray analysis. Standard quantities of each crystal were then added to separate aliquots of pooled undiluted human urine and CaOx crystallization was induced by the addition of identical loads of sodium oxalate. Crystallization was monitored by Coulter Counter and (14) C-oxalate analysis and the precipitated crystals were examined by scanning electron microscopy. RESULTS: In comparison with the control to which no seeds were added, addition of CaOx crystals increased the deposition of (14) C-oxalate by 23%. On the other hand, seeds of HA and BR had no effect. These findings were supported by Coulter Counter analysis, which showed that the average modal sizes of crystal particles precipitated in the presence of HA and BR seeds were indistinguishable from those in the control, whereas those deposited in the presence of CaOx were significantly larger. Scanning electron microscopy confirmed these results, demonstrating that large aggregates of CaOx dihydrates were formed in the presence of CaOx seeds, whereas BR and to a lesser extent HA seeds were scattered free on the filtration membrane and attached like barnacles on the surface of the freshly precipitated CaOx crystals. CONCLUSION: Seed crystals of HA or BR do not promote CaOx deposition in urine in vitro and are therefore unlikely to influence CaOx crystal formation under physiologic conditions. However, binding of HA and BR crystals to, and their subsequent enclosure within, actively growing CaOx crystals might occur in vivo, thereby explaining the occurrence of mixed oxalate/phosphate stones. PMID:12149569

  2. A flow-system comparison of the reactivities of calcium superoxide and potassium superoxide with carbon dioxide and water vapor

    NASA Technical Reports Server (NTRS)

    Wood, P. C.; Ballou, E. V.; Spitze, L. A.; Wydeven, T.

    1982-01-01

    A single pass flow system was used to test the reactivity of calcium superoxide with respiratory gases and the performance was compared to that of potassium superoxide. The KO2 system is used by coal miners as a self-contained unit in rescue operations. Particular attention was given to the reactivity with carbon dioxide and water vapor at different temperatures and partial pressures of oxygen, carbon dioxide, and water vapor. The calcium superoxide beds were found to absorb CO2 and H2O vapor, releasing O2. The KO2 bed, however, released O2 at twice the rate of CO2 absorption at 37 C. It is concluded that the calcium superoxide material is not a suitable replacement for the KO2 bed, although Ca(O2)2 may be added to the KO2 bed to enhance the CO2 absorption.

  3. Sites of Calcium Uptake of Fish Otoliths correspond with macular Regions rich of Carbonic Anhydrase

    NASA Astrophysics Data System (ADS)

    Beier, M.; Anken, R.; Hilbig, R.

    Based on pharmacological data, it has been suggested that the enzyme carbonic anhydrase (CA) plays a prominent role in the mineralization of fish otoliths. In order to directly test this proposal, the topographical distribution of CA was histochemically analyzed in the utricular and saccular maculae of larval cichlid fish Oreochromis mossambicus. Further investigations were focussed on the sites of otolithic calcium uptake using the fluorescent calcium tracer alizarin-complexone (AC). Both in the utricle and the saccule, CA-rich areas were located on both sides of the sensory macula which reportedly contain ionocytes, specialized cells regulating the ionic composition of the endolymph. The reactivity of CA per ?m^2 was similar in all of these regions. In the saccule, the size of the dorsal and ventral CA-rich regions did not differ (and thus yielded the same total CA-reactivity), whereas, in the utricle, the medial CA-rich portion was considerably larger (and therefore had a higher total CA-reactivity) as compared to the laterally located area (the CA-rich regions are homologous in the both endorgans; however, anatomical references relative to the body axes of a fish differ, since the two maculae are located perpendicular to each other). AC-incubation resulted in a fluorescent band on the proximal surface of the otoliths (this surface lies next to the sensory epithelium). In saccular otoliths (sagittae), AC-fluorescence was distributed evenly within the band. However, in the utricular otoliths (lapilli), the medial portion of the AC-band was considerably broader as compared to its lateral aspect. These results strongly suggest that calcium uptake of otoliths takes place especially in those regions of their proximal face which are located adjacent to CA-rich areas of the macular epithelium. It is thus concluded that CA is directly involved in otolith calcification. Acknowledgement: This work was financially supported by the German Aerospace Center (DLR) (FKZ: 50 WB 9997).

  4. USE OF ACID LAKE REACIDIFICATION MODEL (ALaRM) TO ASSESS IMPACT OF BOTTOM SEDIMENTS ON CALCIUM CARBONATE TREATED LAKES

    Microsoft Academic Search

    Joseph V. DePinto; Richard D. Scheffe; Thomas C. Young; William G. Booty; James R. Rhea

    1987-01-01

    A mathematical model (ALaRM) for predicting the reacidification profile of calcium carbonate treated lakes has been calibrated and confirmed using data from two Lake Acidification Mitigation Project (LAMP) lakes. This manuscript focused on the use of ALaRM to evaluate the relative impact of bottom sediment processes on the reacidification rate of the LAMP lakes. Prior to liming the lakes exhibited

  5. Radiological hazards of TENORM in precipitated calcium carbonate generated as waste at nitrophosphate fertilizer plant in Pakistan

    Microsoft Academic Search

    Sabiha-Javied; Nasim-Akhtar; M. Tufail

    2011-01-01

    The NORM (naturally occurring radioactive material) in phosphate rock is transferred as TENORM (technologically enhanced naturally occurring radioactive material) to phosphatic fertilizers and to the waste generated by the chemical processes. The waste generated at the NP (nitrophosphate) fertilizer plant at Multan in Pakistan is PCC (precipitated calcium carbonate). Thirty samples of the PCC were collected from the heaps of

  6. Effects of Predrying and Vacuum Impregnation with Nano-Calcium Carbonate Solution on Strawberries, Carrots, Corn, and Blueberries

    Microsoft Academic Search

    Zhiqing Gong; Leyi Gao; Jianshen An; Min Zhang; A. S. Mujumdar; Jincai Sun

    2009-01-01

    Predrying followed by vacuum impregnation using a solution of nanosized calcium carbonate was carried out for several products such as strawberries, blueberries, carrots, and corn. This process improved impregnation mass of the functional substance in the products tested. Though products like butter candy taste sweet, due to their high content of sugar and fat they face high consumer resistance. The

  7. Comparison of the treatment effects of ossein-hydroxyapatite compound and calcium carbonate in osteoporotic females.

    PubMed

    Rüegsegger, P; Keller, A; Dambacher, M A

    1995-01-01

    The aim of the study was to evaluate whether ossein-hydroxyapatite (OHC) is more effective than calcium carbonate (CC) in preventing further bone loss in postmenopausal osteoporosis. Forty osteoporotic patients were monitored for 20 months. The patients were randomly assigned to one of two groups and treated in a double-masked manner with 1400 mg calcium per day, in the form of either OHC or CC. OHC consists of hydroxyapatite, collagens and non-collagenous proteins/peptides containing insulin-like growth factor I (IGF-I; 1341 ng), insulin-like growth factor II (IGF-II; 670 ng), transforming growth factor beta (TGF-beta; 166 ng) and osteocalcin (47 micrograms). The bone densities were evaluated at intervals of 4 months with high-precision peripheral quantitative computed tomography. After 20 months of treatment the loss of trabecular bone was 0.8 +/- 0.5% in the OHC group and 1.8 +/- 0.7% in the CC group. The difference between the OHC and CC groups was statistically significant. This study shows that OHC is more effective than CC in slowing peripheral trabecular bone loss in patients with manifest osteoporosis. PMID:7703621

  8. Size controlled hydroxyapatite and calcium carbonate particles: synthesis and their application as templates for SERS platform.

    PubMed

    Parakhonskiy, B V; Svenskaya, Yu I; Yashchenok, A ?; Fattah, H A; Inozemtseva, O A; Tessarolo, F; Antolini, R; Gorin, D A

    2014-06-01

    An elegant route for hydroxyapatite (HA) particle synthesis via ionic exchange reaction is reported. Calcium carbonate particles (CaCO3) were recrystallized into HA beads in water solution with phosphate ions. The size of initial CaCO3 particles was controlled upon the synthesis by varying the amount of ethylene glycol (EG) in aqueous solution. The average size of HA beads ranged from 0.6±0.1 to 4.3±1.1?m. Silver nanoparticles were deposited on the surface of HA and CaCO3 particles via silver mirror reaction. Surface enhanced Raman scattering of silver functionalized beads was demonstrated by detecting Rhodamine B. CaCO3 and HA particles have a great potential for design of carrier which can provide diagnostic and therapeutic functions. PMID:24802965

  9. Inhibition of calcium carbonate precipitation by aqueous extract of Paronychia argentea

    NASA Astrophysics Data System (ADS)

    Belarbi, Zineb; Gamby, Jean; Makhloufi, Laid; Sotta, Bruno; Tribollet, Bernard

    2014-01-01

    This paper focuses on the development of a new green inhibitor “aqueous extract of Paronychia argentea” for reducing calcium carbonate scale formation on metallic surfaces. The effects of temperature and biocides on the efficiency of the inhibitor were investigated. Their antiscaling properties have been evaluated by the chronoamperometry method and the calcareous layers were characterized by scanning electron microscopy observations. A complete scaling inhibition was obtained with a concentration of 70 ppm of green inhibitor for calcocarbonically pure water at 20 °C and 45 °C. However, its efficiency was decreased at 60 °C. Different commercially available biocides named B310, B320, B330 and B340 were also tested. The biocide B340 was the only found not compatible with green inhibitor.

  10. Apo And Calcium-Bound Crystal Structures of Alpha-11 Giardin, An Unusual Annexin From 'Giardia Lamblia'

    SciTech Connect

    Pathuri, P.; Nguyen, E.T.; Svard, S.G.; Luecke, H.; /UC, Irvine /Uppsala U. /Karolinska Inst.

    2007-07-12

    Alpha-11 giardin is a member of the multi-gene alpha-giardin family in the intestinal protozoan, Giardia lamblia. This gene family shares an ancestry with the annexin super family, whose common characteristic is calcium-dependent binding to membranes that contain acidic phospholipids. Several alpha giardins are highly expressed during parasite-induced diarrhea in humans. Despite being a member of a large family of proteins, little is known about the function and cellular localization of alpha-11 giardin, although giardins are often associated with the cytoskeleton. It has been shown that Giardia exhibits high levels of alpha-11 giardin mRNA transcript throughout its life cycle; however, constitutive over-expression of this protein is lethal to the parasite. Determining the three-dimensional structure of an alpha-giardin is essential to identifying functional domains shared in the alpha-giardin family. Here we report the crystal structures of the apo and Ca{sup 2+}-bound forms of alpha-11 giardin, the first alpha giardin to be characterized structurally. Crystals of apo and Ca{sup 2+}-bound alpha-11 giardin diffracted to 1.1 angstroms and 2.93 angstroms, respectively. The crystal structure of selenium-substituted apo alpha-11 giardin reveals a planar array of four tandem repeats of predominantly {alpha}-helical domains, reminiscent of previously determined annexin structures, making this the highest-resolution structure of an annexin to date. The apo alpha-11 giardin structure also reveals a hydrophobic core formed between repeats I/IV and II/III, a region typically hydrophilic in other annexins. Surprisingly, the Ca{sup 2+}-bound structure contains only a single calcium ion, located in the DE loop of repeat I and coordinated differently from the two types of calcium sites observed in previous annexin structures. The apo and Ca{sup 2+}-bound alpha-11 giardin structures assume overall similar conformations; however, Ca2+-bound alpha-11 giardin crystallized in a lower-symmetry space group with four molecules in the asymmetric unit. Vesicle-binding studies suggest that alpha-11 giardin, unlike most other annexins, does not bind to vesicles composed of acidic phospholipids in a calcium-dependent manner.

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

    SciTech Connect

    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.

  12. Sites of calcium uptake of fish otoliths correspond with macular regions rich of carbonic anhydrase

    NASA Astrophysics Data System (ADS)

    Beier, M.; Anken, R.; Hilbig, R.

    2006-01-01

    Based on pharmacological data, it has been suggested that the enzyme carbonic anhydrase (CAH) plays a prominent role in the mineralization of fish otoliths. To directly test this proposal, the topographical distribution of CAH was histochemically analyzed in the utricular and saccular maculae of larval cichlid fish Oreochromis mossambicus. Further investigations were focussed on the sites of otolithic calcium uptake using the fluorescent calcium tracer alizarin-complexone (AC). Both in the utricle and the saccule, CAH-reactivity was prominent in regions on both sides of the sensory macula (centrifugal (cf) and centripetal (cp) areas), which reportedly contain ionocytes, specialized cells regulating the ionic composition of the endolymph. (The terms centrifugal and centripetal were chosen instead of lateral and medial, because the saccule is positioned perpendicular to the utricle; “lateral” and “medial” thus do not allow an unambiguous allocation of the respective regions.) In the saccule, the size of cf and cp did not differ from each other, whereas, in the utricle, cp was considerably larger as compared to cf (CAH-reactivity per ?m2 was nearly identical in both areas of both endorgans). AC-incubation resulted in a fluorescent band on the proximal surface of the otoliths (this surface lies next to the sensory epithelium). In saccular otoliths (sagittae), the area of the band did not differ between centrifugal and centripetal otolith regions, whereas in the utricular otoliths (lapilli), the area of the centripetal AC-band was larger in size as compared to the centrifugal one (AC-fluorescence per ?m2 did not differ between the areas analyzed in both types of otoliths). These results strongly suggest that calcium/carbonate uptake of otoliths takes place especially in those regions of their proximal face which are located adjacent to CAH-rich areas of the macular epithelium. It is thus concluded that CAH is directly involved in otolith calcification. The differences in CAH-localization/AC-uptake in the two endorgans analyzed are discussed on the basis of their different functional properties (saccule, hearing; utricle, graviperception).

  13. The effect of antiscalant addition on calcium carbonate precipitation for a simplified synthetic brackish water reverse osmosis concentrate.

    PubMed

    Greenlee, Lauren F; Testa, Fabrice; Lawler, Desmond F; Freeman, Benny D; Moulin, Philippe

    2010-05-01

    The primary limitations to inland brackish water reverse osmosis (RO) desalination are the cost and technical feasibility of concentrate disposal. To decrease concentrate volume, a side-stream process can be used to precipitate problematic scaling salts and remove the precipitate with a solid/liquid separation step. The treated concentrate can then be purified through a secondary reverse osmosis stage to increase overall recovery and decrease the volume of waste requiring disposal. Antiscalants are used in an RO system to prevent salt precipitation but might affect side-stream concentrate treatment. Precipitation experiments were performed on a synthetic RO concentrate with and without antiscalant; of particular interest was the precipitation of calcium carbonate. Particle size distributions, calcium precipitation, microfiltration flux, and scanning electron microscopy were used to evaluate the effects of antiscalant type, antiscalant concentration, and precipitation pH on calcium carbonate precipitation and filtration. Results show that antiscalants can decrease precipitate particle size and change the shape of the particles; smaller particles can cause an increase in microfiltration flux decline during the solid/liquid separation step. The presence of antiscalant during precipitation can also decrease the mass of precipitated calcium carbonate. PMID:20350741

  14. Cholesteric liquid crystal-carbon nanotube hybrid architectures for gas detection

    NASA Astrophysics Data System (ADS)

    Chang, Chin-Kai; Chiu, Shih-Wen; Kuo, Hui-Lung; Tang, Kea-Tiong

    2012-01-01

    The ability of a hybrid material that is based on cholesteric liquid crystal and carbon nanotube to detect acetone vapor is investigated. We find that the phase transition in this cholesteric liquid crystal-carbon nanotube hybrid will enable carbon nanotube to form conducting networks under the higher vapor concentration. This cholesteric liquid crystal-carbon nanotube hybrid exhibits an obvious change in reflected color and electrical resistance in the early and later stages of gas diffusion, respectively. This hybrid architecture has potential application as a gas sensor with a high dynamic range.

  15. Hydroxypropyl-?-cyclodextrin functionalized calcium carbonate microparticles as a potential carrier for enhancing oral delivery of water-insoluble drugs

    PubMed Central

    Zhang, Lihua; Zhu, Wufu; Lin, Qisi; Han, Jin; Jiang, Liqun; Zhang, Yanzhuo

    2015-01-01

    The objective of the present study was to demonstrate that a novel hydroxypropyl-?-cyclodextrin functionalized calcium carbonate (HP-?-CD/CC) based amorphous solid dispersion (ASD) can be used to increase the solubility and oral bioavailability of water-insoluble drugs. Irbesartan (IRB) was selected as a model compound and loaded into the nanoporous HP-?-CD/CC matrix using an immersion method. The IRB-loaded HP-?-CD/CC formulation was characterized by various analytical techniques, such as specific surface area analysis, scanning electron microscopy (SEM), dynamic light scattering (DLS), powder X-ray diffraction (PXRD), and differential scanning calorimetry (DSC). Analyses with PXRD and DSC confirmed that IRB was fully converted into the amorphous form in the nanopores of HP-?-CD/CC. From the solubility and dissolution tests, it was observed that the aqueous solubility and dissolution rate of IRB-loaded HP-?-CD/CC were increased significantly compared with those of pure IRB and IRB-loaded mesoporous silica. Likewise, the IRB-loaded HP-?-CD/CC formulation exhibited better absorption compared with that of the commercially available IRB capsules in beagle dogs. The mean peak plasma concentration (Cmax) and the area under the mean plasma concentration–time curve (AUC[0?48]) of IRB-loaded HP-?-CD/CC were 1.56- and 1.52-fold higher than that of the commercial product, respectively. Furthermore, the IRB-loaded HP-?-CD/CC formulation exhibited excellent stability against re-crystallization. These results clearly demonstrate that HP-?-CD/CC based porous ASD is a promising formulation approach to improve the aqueous solubility and the in vivo absorption performance of a water-insoluble compound like IRB. PMID:25995635

  16. Hydroxypropyl-?-cyclodextrin functionalized calcium carbonate microparticles as a potential carrier for enhancing oral delivery of water-insoluble drugs.

    PubMed

    Zhang, Lihua; Zhu, Wufu; Lin, Qisi; Han, Jin; Jiang, Liqun; Zhang, Yanzhuo

    2015-01-01

    The objective of the present study was to demonstrate that a novel hydroxypropyl-?-cyclodextrin functionalized calcium carbonate (HP-?-CD/CC) based amorphous solid dispersion (ASD) can be used to increase the solubility and oral bioavailability of water-insoluble drugs. Irbesartan (IRB) was selected as a model compound and loaded into the nanoporous HP-?-CD/CC matrix using an immersion method. The IRB-loaded HP-?-CD/CC formulation was characterized by various analytical techniques, such as specific surface area analysis, scanning electron microscopy (SEM), dynamic light scattering (DLS), powder X-ray diffraction (PXRD), and differential scanning calorimetry (DSC). Analyses with PXRD and DSC confirmed that IRB was fully converted into the amorphous form in the nanopores of HP-?-CD/CC. From the solubility and dissolution tests, it was observed that the aqueous solubility and dissolution rate of IRB-loaded HP-?-CD/CC were increased significantly compared with those of pure IRB and IRB-loaded mesoporous silica. Likewise, the IRB-loaded HP-?-CD/CC formulation exhibited better absorption compared with that of the commercially available IRB capsules in beagle dogs. The mean peak plasma concentration (C max) and the area under the mean plasma concentration-time curve (AUC[0?48]) of IRB-loaded HP-?-CD/CC were 1.56- and 1.52-fold higher than that of the commercial product, respectively. Furthermore, the IRB-loaded HP-?-CD/CC formulation exhibited excellent stability against re-crystallization. These results clearly demonstrate that HP-?-CD/CC based porous ASD is a promising formulation approach to improve the aqueous solubility and the in vivo absorption performance of a water-insoluble compound like IRB. PMID:25995635

  17. Mass transfer of reactive crystallization in synthesizing calcite nanocrystal

    Microsoft Academic Search

    Rong-yi Lin; Jia-yun Zhang; Yuan-qiang Bai

    2006-01-01

    An experimental study on the mass transfer and reactive crystallization of calcite nanocrystal was carried out in a Na5P3O10–Ca(OH)2–CO2–H2O multiphase system. According to the two-film theory and the two-steps crystal growth model, the kinetic characteristics in the system were investigated by the rate-comparison of the calcium hydroxyl dissolution, carbon dioxide absorption and calcium carbonate precipitation. The result indicated that the

  18. Mineral-fluid partitioning and isotopic fractionation of boron in synthetic calcium carbonate

    SciTech Connect

    Hemming, N.G.; Reeder, R.J.; Hanson, G.N. [State Univ. of New York, Stony Brook, NY (United States)

    1995-01-01

    Aragonite, high-Mg calcite, and Mg-free calcite have been grown under monitored laboratory conditions to investigate mineral-fluid partitioning and isotopic fractionation of boron into carbonates. At pH {approx} 8, both polymorphs have boron isotopic compositions 16.5% lower than the boron isotopic composition of the experimental fluid ({theta}{sup 11}B = 0 {+-} 0.7%). The isotopic composition of the synthetic minerals is identical to the calculated boron isotopic composition of the B(OH){sub 4}{sup -} species in the parent solutions, consistent with only B(OH){sub 4}{sup -} interacting with the crystal surface. The fractionation factor calculated from this isotopic offset is within analytical error of that measured between seawater and modern marine carbonates. The boron concentrations of the experimentally grown aragonite are 13.4, 85.1, and 379 ppm for total fluid boron concentrations of 0.59, 5.1, and 37.0 ppm, respectively. High-Mg calcite (HMC) coprecipitating with the aragonite has bulk boron concentrations of 5.6, 56.2, 260, and 1771 ppm for fluid boron concentrations of 0.59, 5.1. 37, and 272 ppm, respectively. Calcite boron concentrations are 1.78, 14.0, 137.7, by aragonite is greater than boron uptake by calcite grown under nearly identical conditions, while boron uptake by HMC is intermediate. Synthetic calcite crystals grown in solutions with greater than 4 ppm boron exhibit habit modification with the appearance of a subordinate form {l_brace}1120{r_brace} in addition to the dominant {l_brace}1014{r_brace}, the perfect cleavage rhombohedron, found in low-boron calcites. This is evidence of strong interaction of the borate with the crystal surface.

  19. Single-crystal synthesis, structure analysis, and physical properties of the calcium ferrite-type Na x Ti 2O 4 with 0.558< x<1

    Microsoft Academic Search

    Yasuhiko Takahashi; Kunimitsu Kataoka; Ken-Ichi Ohshima; Norihito Kijima; Junji Awaka; Kenji Kawaguchi; Junji Akimoto

    2007-01-01

    Single crystals of calcium ferrite CaFe2O4-type NaTi2O4 having millimeter-sized needle shapes were synthesized by a reaction of Na metal and TiO2 in a sealed iron vessel at 1473K. Sodium-deficient NaxTi2O4 single crystals with 0.558crystals as parent materials. The crystal structures of NaxTi2O4 with x=0.970, 0.912, 0.799, 0.751, 0.717,

  20. Application of pulsed spark discharge for calcium carbonate precipitation in hard water

    Microsoft Academic Search

    Yong Yang; Hyoungsup Kim; Andrey Starikovskiy; Alexander Fridman; Young I. Cho

    2010-01-01

    The effect of underwater pulsed spark discharge on the precipitation of dissolved calcium ions was investigated in the present study. Water samples with different calcium hardness were prepared by continuous evaporation of tap water using a laboratory cooling tower. It was shown that the concentration of calcium ions dropped by 20–26% after 10-min plasma treatment, comparing with no drop for

  1. The effects of calcitriol with calcium carbonate supplementation on inflammatory biomarkers in chronic kidney disease patients’ with low vitamin D

    PubMed Central

    Mohd, Rozita; Miswan, Norazinizah Ahmad; Bain, Arba'ayah; Cader, Rizna; Gafor, Abdul Halim Abdul; Mohammad, Marlyn; Shah, Shamsul Azhar; Kamaruddin, Nor Azmi; Kong, Norella CT

    2014-01-01

    Introduction Chronic kidney disease (CKD) patients’ are at risk of low vitamin D and chronic inflammation. We studied the effect of 12 weeks calcitriol and calcium carbonate supplementation on inflammatory mediators serum; interleukin-6 (IL-6), interleukin-10 (IL-10) and highly sensitive C-reactive protein (hs-CRP). Material and methods A prospective randomized study in CKD stages 2-4 with serum 25-hydroxyvitamin D (25-OHD) levels < 30 ng/ml. Patients were randomized into the Vitamin D + Calcium (Vitamin D + C) or Calcium group. Serums were analyzed at baseline, week 6 and 12. Results Fifty patients, median age of 53 (13.5) years were recruited. Their median IL-10 was 13.35 (25.22) pg/ml. At week 12, serum IL-6 was reduced in both groups (p = 0.001), serum IL-10 was maintained in the Vitamin D + C group (p = 0.06) and was reduced in the Calcium group (p = 0.001). CKD-diabetic patients had reduced serum IL-6 in both study groups (p = 0.001) and a reduction was seen in the Vitamin D + C group of the non-diabetics counterparts (p = 0.005). Serum IL-10 was reduced in the Calcium group (p < 0.05) whereas serum 25-OHD rose in both groups, regardless of their diabetic status (p < 0.05). Conclusions Twelve weeks, calcitriol supplementation maintained IL-10, had no effects on hs- CRP and had no additional benefit compared to calcium carbonate in reducing serum IL-6 except in non-diabetics.

  2. Fabrication and application of an activated carbon-coated quartz crystal sensor

    Microsoft Academic Search

    Young Han Kim; Kwang Jae Choi

    2002-01-01

    An activated carbon-coated quartz crystal sensor is developed to utilize in the determination of organic substance contained in air. The sensor is made of readily available activated carbon and phenol resin as binder and is prepared from relatively simple process comparing with other carbon-coated sensors. The detection performance of the sensor is examined by applying it to a specially designed

  3. Flux growth of yttrium calcium oxy borate (YCOB) single crystals for nonlinear optical applications

    Microsoft Academic Search

    R. Arun Kumar; R. Dhanasekaran

    2009-01-01

    Nonlinear optical single crystals of YCa4O(BO3)3 (YCOB) with good optical quality were grown from boron-tri-oxide flux for the first time. Polycrystalline YCOB samples were synthesized from the solid-state reaction method. Optimum conditions for the growth of YCOB crystals from the flux were determined. Single crystals of YCOB with dimensions 10×5×5mm3 were obtained by the method of ‘slow cooling’. The grown

  4. Crystal growth and scintillation properties of Ce-doped sodium calcium lutetium complex fluoride

    Microsoft Academic Search

    Shingo Wakahara; Yuki Furuya; Takayuki Yanagida; Yuui Yokota; Jan Pejchal; Makoto Sugiyama; Noriaki Kawaguchi; Daisuke Totsuka; Akira Yoshikawa

    0.1%, 0.5%, 1% and 3% Ce doped scintillation crystals based on NaF-CaF2-LuF3 solid solutions were grown from the melt using Micro-Pulling-Down (?-PD) method. The grown crystals were transparent and their transmittance was approximately 80% for the wavelengths longer than 320 nm. Concerning the scintillation properties, radio-luminescence peaks of the crystals were detected at approximately 330 nm. The light yield of

  5. Biocompatibility of Ricinus communis polymer with addition of calcium carbonate compared to titanium. Experimental study in guinea pigs

    PubMed Central

    Graça, Yorgos Luiz Santos De Salles; Opolski, Ana Cristina; Barboza, Barbara Evelin Gonçalves; Erbano, Bruna Olandoski; Mazzaro, Caroline Cantalejo; Klostermann, Flávia Caroline; Sucharski, Enéas Eduardo; Kubrusly, Luiz Fernando

    2014-01-01

    Objective The aim of the present investigation was to determine whether the difference in inflammatory tissue reaction between the Riccinus communis (castor) polymer with calcium carbonate and the titanium implant is statistically significant. Methods Thirty-two Cavia porcellus were allocated into four groups of eight animals each. We implanted the two types of materials in the retroperitoneal space of all the animals. They were euthanized at 7, 20, 30 and 40 days after surgery, and an histological study of the samples was conducted. Results All implants showed characteristics of chronic inflammation regardless of the material and timepoint of evaluation. There was no statistically significant difference between Pm+CaCO3 and Ti with regard to the presence of granulation tissue, tissue congestion, histiocytes, lymphocytes, neutrophils, giant cells, and fibrosis (P> 0.05). Conclusion The castor oil polymer plus calcium carbonate implant was not statistically different from the titanium implant regarding inflammatory tissue reaction. PMID:25140479

  6. Competitive Absorption of Polar and Non-Polar Liquids into Latex Bound Porous Structures of Fine Ground Calcium Carbonate

    Microsoft Academic Search

    Cathy J. Ridgway; Joachim Schoelkopf; Patrick A. C. Gane

    2011-01-01

    Fine calcium carbonate is frequently used as coating pigment, e.g. in paints, paper and board. Emulsion polymer latex provides\\u000a a typical binder incorporated in such coatings. Exposure of the resulting porous structure to liquid, depending on latex concentration\\u000a level, results in ab- and adsorption as the liquid is drawn into the structure by capillarity and the nature of the relative

  7. Small angle neutron scattering studies on non-aqueous dispersions of calcium carbonate. Part III. Concentrated dispersions

    Microsoft Academic Search

    I. Markovi?; R. H. Ottewill

    1986-01-01

    Small angle neutron scattering has been used to examine calcium carbonate dispersions in toluene over the w\\/w concentration range 5 to 40 %. The particles were stabilised by a combination of a surface active agent and a linear polymeric molecule. Analysis of the experimental data gave results for the structure factorS(Q) and the pair correlation functiong(r).Theoretical computations of the structure

  8. Fabrication and antifrosting performance of super hydrophobic coating based on modified nano-sized calcium carbonate and ordinary polyacrylate

    Microsoft Academic Search

    Hao Wang; Liming Tang; Xiaomin Wu; Wantian Dai; Yipeng Qiu

    2007-01-01

    Nano-sized calcium carbonate (CaCO3) particles were modified by heptadecafluorodecyl trimethoxysilane under acidic water condition. An ordinary polyacrylate prepared via radical copolymerization of methyl methacrylate, butyl acrylate, acrylic acid and ?-hydroxyethyl methacrylate was used as the binder to form hydrophobic coatings with the modified CaCO3. Super hydrophobic coating with water contact angle of 155° was obtained from modified CaCO3 and the

  9. Scanning electron microscopy and energy-dispersive X-ray microanalysis studies of several human calculi containing calcium phosphate crystals.

    PubMed

    Kodaka, T; Debari, K; Sano, T; Yamada, M

    1994-01-01

    Human calcium phosphate calculi: two sialoliths, a urolith, a rhinolith, and a tonsillolith were investigated by scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDX). The sialoliths and urolith had appositional shells with thick cortices, respectively, around several nuclei composed of calcospherulites and a rubber-film fragment. The rhinolith had a thin cortex with appositional laminations around a glomerulus-like mass of calcified cotton-like strings. The tonsillolith had a rough cortex with appositional laminations. Its porous interior was composed of numerous calcified conglomerates with microorganisms and calcified masses with fine appositional laminations around the conglomerates. The major crystals were identified as biological apatites (AP) with a sand-grain rather than a needle-like shape, and plate-shaped octacalcium phosphate (OCP). The AP deposits of the rhinolith probably were associated with magnesium (Mg) phosphates or contained Mg. No OCP was found in the rhinolith. The AP deposits were mainly formed by extracellular calcification. Hexahedral crystals, identified as Mg-containing whitlockite (WH), were precipitated in the internal spaces of the AP and OCP deposits. The rhinolith nucleus consisted of WH crystal deposits only. PMID:7701299

  10. Pilot-scale demonstration of the OSCAR process for high-temperature multipollutant control of coal combustion flue gas, using carbonated fly ash and mesoporous calcium carbonate

    SciTech Connect

    Gupta, H.; Thomas, T.J.; Park, A.H.A.; Iyer, M.V.; Gupta, P.; Agnihotri, R.; Jadhav, R.A.; Walker, H.W.; Weavers, L.K.; Butalia, T.; Fan, L.S. [Ohio State University, Columbus, OH (United States)

    2007-07-15

    A pilot-scale study of the Ohio State Carbonation Ash Reactivation (OSCAR) process was performed to demonstrate the reactivity of two novel calcium-based sorbents toward sulfur and trace heavy metal (arsenic, selenium, and mercury) capture in the furnace sorbent injection (FSI) mode on a 0.365 m{sup 3}/s slipstream of a bituminous coal-fired stoker boiler. The sorbents were synthesized by bubbling CO{sub 2} to precipitate calcium carbonate (a) from the unreacted calcium present in the lime spray dryer ash and (b) from calcium hydroxide slurry that contained a negatively charged dispersant. The heterogeneous reaction between these sorbents and SO{sub 2} gas occurred under entrained flow conditions by injecting fine sorbent powders into the flue gas slipstream. The reacted sorbents were captured either in a hot cyclone (about 650{sup o}C) or in the relatively cooler downstream baghouse (about 230{sup o}C). The baghouse samples indicated about 90% toward sulfation and captured arsenic, selenium and mercury to 800 ppmw, 175 ppmw and 3.6 ppmw, respectively.

  11. Phosphate binders and metabolic acidosis in patients undergoing maintenance hemodialysis—sevelamer hydrochloride, calcium carbonate, and bixalomer.

    PubMed

    Sanai, Toru; Tada, Hideo; Ono, Takashi; Fukumitsu, Toma

    2015-01-01

    The serum bicarbonate (HCO3(-)) levels are decreased in chronic hemodialysis (HD) patients treated with sevelamer hydrochloride (SH). We assessed the effects of bixalomer on the chronic metabolic acidosis in these patients. We examined 12 of the 122 consecutive Japanese patients with end-stage renal disease on HD, who orally ingested a dose of SH (?2250?mg), and an arterial blood gas analysis and biochemical analysis were performed before HD. Patients whose serum HCO3(-) levels were under 18?mmol/L were changed from SH to the same dose of bixalomer. A total of 12 patients were treated with a large amount of SH. Metabolic acidosis (a serum HCO3(-) level under 18?mmol/L) was found in eight patients. These patients were also treated with or without small dose of calcium carbonate (1.2?±?1.1?g). The dose of SH was changed to that of bixalomer. After 1 month, the serum HCO3(-) levels increased from 16.3?±?1.4 to 19.6?±?1.7?mmol/L (P?calcium carbonate with SH. In the present study, the development of chronic metabolic acidosis was induced by HCl containing phosphate binders, such as SH, and partially ameliorated by calcium carbonate, then subsequently improved after changing the treatment to bixalomer. PMID:24980286

  12. In vitro degradation and cell response of calcium carbonate composite ceramic in comparison with other synthetic bone substitute materials.

    PubMed

    He, Fupo; Zhang, Jing; Yang, Fanwen; Zhu, Jixiang; Tian, Xiumei; Chen, Xiaoming

    2015-05-01

    The robust calcium carbonate composite ceramics (CC/PG) can be acquired by fast sintering calcium carbonate at a low temperature (650 °C) using a biocompatible, degradable phosphate-based glass (PG) as sintering agent. In the present study, the in vitro degradation and cell response of CC/PG were assessed and compared with 4 synthetic bone substitute materials, calcium carbonate ceramic (CC), PG, hydroxyapatite (HA) and ?-tricalcium phosphate (?-TCP) ceramics. The degradation rates in decreasing order were as follows: PG, CC, CC/PG, ?-TCP, and HA. The proliferation of rat bone mesenchymal stem cells (rMSCs) cultured on the CC/PG was comparable with that on CC and PG, but inferior to HA and ?-TCP. The alkaline phosphatase (ALP) activity of rMSCs on CC/PG was lower than PG, comparable with ?-TCP, but higher than HA. The rMSCs on CC/PG and PG had enhanced gene expression in specific osteogenic markers, respectively. Compared to HA and ?-TCP, the rMSCs on the CC/PG expressed relatively lower level of collagen I and runt-related transcription factor 2, but showed more considerable expression of osteopontin. Although CC, PG, HA, and ?-TCP possessed impressive performances in some specific aspects, they faced extant intrinsic drawbacks in either degradation rate or mechanical strength. Based on considerable compressive strength, moderate degradation rate, good cell response, and being free of obvious shortcoming, the CC/PG is promising as another choice for bone substitute materials. PMID:25746269

  13. Nano-SIMS analysis of Mg, Sr, Ba and U in natural calcium carbonate.

    PubMed

    Sano, Yuji; Shirai, Kotaro; Takahata, Naoto; Hirata, Takafumi; Sturchio, Neil C

    2005-09-01

    Concentrations of minor (Mg and Sr) and trace (Ba and U) elements in four natural calcium carbonate samples were first analyzed by inductively coupled plasma mass spectrometry (ICP-MS) after chemical dissolution and calibrated against a standard dolomite. Their homogeneities were checked by in situ laser ablation (LA) ICP-MS with 10-20 spots. The carbonate samples were measured by using a high lateral resolution secondary ion mass spectrometer (Nano-SIMS NS50). A approximately 4 nA O- primary beam was used to sputter a 5-6-microm diameter crater on the sample surface, and secondary positive ions were extracted for mass analysis using an accelerating voltage of 8 kV and a Mattauch-Herzog geometry. A multi-collector system was adjusted to detect 26Mg+, 43Ca+, 88Sr+, 138Ba+, 238U16O+ and 238U16O2+ ions at the same time. A resolving power of 2500-5000 at 10% peak height was attained by an entrance slit set at 40 microm, and each exit slit at 50 microm with adequate flat-topped peaks. The observed 26Mg/43Ca, 88Sr/43Ca, 138Ba/43Ca and 238U16O2/43Ca ratios agreed well with those measured by LA-ICP-MS. Foraminifera shells were analyzed at 5-6 microm scale by Nano-SIMS. There was a large variation of the Mg/Ca ratios, up to +/- 38%, even in a single fragment of the shell, suggesting that although the ratios provide a useful paleoceanographic proxy at bulk scale, they may reflect a more complex pattern at < 10 microm scale. PMID:16363479

  14. Experimental study on mercury sorption by activated carbons and calcium hydroxide

    SciTech Connect

    Ghorishi, B. [Acurex Environmental Corp., Durham, NC (United States); Gullett, B.K. [Environmental Protection Agency, Research Triangel Park, NC (United States)

    1997-12-01

    Title III of the 1990 Air Act Amendments (CAAA) requires the U.S. Environmental Protection Agency (EPA) to submit a study on 189 hazardous air pollutants (HAPs) from industrial sources. This study will include an emission and risk (to public health) assessment of the HAPs. Among the 189 HAPs, mercury has drawn special attention due to its increased levels in the environment and well-documented food chain transport and bioaccumulation. Mercury, present in hazardous/municipal wastes and in coal, is readily volatilized during combustion and incineration processes. Mercury is the most volatile among various trace metals, and major portions of it can pass through existing particulate control devices. A sorbent that can react with mercury can effectively shift this metal from the vapor phase to the particulate (sorbent) phase, facilitating its removal. Mercury control processes which use adsorption on dry sorbents do not pose the problem of treatment and stabilization of the waste liquid stream and, therefore, seem very attractive for coal combustors and hazardous/municipal waste incinerators. The need to develop mercury control technologies and the attractive features of adsorption processes on dry sorbents led researchers to focus their efforts on the evaluation of the adsorption kinetics and sorbent capacity of many different solid sorbents. Past research has identified two different classes of sorbents to be effective in mercury removal: activated carbons and calcium-based sorbents.

  15. Interfacial energies for heterogeneous nucleation of calcium carbonate on mica and quartz.

    PubMed

    Li, Qingyun; Fernandez-Martinez, Alejandro; Lee, Byeongdu; Waychunas, Glenn A; Jun, Young-Shin

    2014-05-20

    Interfacial free energies often control heterogeneous nucleation of calcium carbonate (CaCO3) on mineral surfaces. Here we report an in situ experimental study of CaCO3 nucleation on mica (muscovite) and quartz, which allows us to obtain the interfacial energies governing heterogeneous nucleation. In situ grazing incidence small-angle X-ray scattering (GISAXS) was used to measure nucleation rates at different supersaturations. The rates were incorporated into classical nucleation theory to calculate the effective interfacial energies (?'). Ex situ Raman spectroscopy identified both calcite and vaterite as CaCO3 polymorphs; however, vaterite is the most probable heterogeneous nuclei mineral phase. The ?' was 24 mJ/m(2) for the vaterite-mica system and 32 mJ/m(2) for the vaterite-quartz system. The smaller ?' of the CaCO3-mica system led to smaller particles and often higher particle densities on mica. A contributing factor affecting ?' in our system was the smaller structural mismatch between CaCO3 and mica compared to that between CaCO3 and quartz. The extent of hydrophilicity and the surface charge could not explain the observed CaCO3 nucleation trend on mica and quartz. The findings of this study provide new thermodynamic parameters for subsurface reactive transport modeling and contribute to our understanding of mechanisms where CaCO3 formation on surfaces is of concern. PMID:24730716

  16. British Journal of Nutrition, 2010, Allam et al., Calcium carbonate blocks haem without side effect. Authors' Version 1 Calcium Carbonate Suppresses Haem Toxicity Markers without

    E-print Network

    Paris-Sud XI, Université de

    Toulouse, France Abstract Red meat intake is associated with increased risk of colorectal cancer. We have previously shown that haemin, haemoglobin and red meat promote carcinogen-induced preneoplastic lesions, by testing several doses and types of calcium salts. One in vitro study and two short-term studies in rats

  17. Pilot-scale demonstration of the OSCAR process for high-temperature multipollutant control of coal combustion flue gas, using carbonated fly ash and mesoporous calcium carbonate

    Microsoft Academic Search

    Himanshu Gupta; Theodore J. Thomas; Ah-Hyung A. Park; Mahesh V. Iyer; Puneet Gupta; Rajeev Agnihotri; Raja A. Jadhav; Harold W. Walker; Linda K. Weavers; Tarunjit Butalia; Liang-Shih Fan

    2007-01-01

    A pilot-scale study of the Ohio State Carbonation Ash Reactivation (OSCAR) process was performed to demonstrate the reactivity of two novel calcium-based sorbents toward sulfur and trace heavy metal (arsenic, selenium, and mercury) capture in the furnace sorbent injection (FSI) mode on a 0.365 m³\\/s slipstream of a bituminous coal-fired stoker boiler. The sorbents were synthesized by bubbling COâ to

  18. Extraction and estimation of the quantity of calcium oxalate crystals in the foliage of conifer and hardwood trees.

    PubMed

    Minocha, Rakesh; Chamberlain, Bradley; Long, Stephanie; Turlapati, Swathi A; Quigley, Gloria

    2015-05-01

    The main goal of this study was to develop a method for the extraction and indirect estimation of the quantity of calcium oxalate (CaOx) in the foliage of trees. Foliar tissue was collected from a single tree of each species (five conifers and five hardwoods) for comparison of extractions in different solvents using 10 replicates per species from the same pool of tissue. For each species, calcium (Ca) and oxalate were extracted sequentially in double deionized water and 2N acetic acid, and finally, five replicate samples were extracted in 5% (0.83N) perchloric acid (PCA) and the other five in 2N hydrochloric acid (HCl); three cycles of freezing and thawing were used for each solvent. Total ions were extracted by microwave digestion. Calcium was quantified with an inductively coupled plasma emission spectrophotometer method and oxalate was eluted and quantified using a high performance liquid chromatography method. This experiment was repeated again with two conifer and two hardwood species using four trees per species, and two analytical replicates for each tree. We report here that, regardless of age of individual trees within a species, time of collection or species type, the third extraction in PCA or HCl resulted in near equimolar quantities of Ca and oxalate (r(2)???0.99). This method provides an easy estimate of the quantity of CaOx crystals using a small sample of foliar tissue. An additional benefit of PCA is that it precipitates the nucleic acids and proteins, allowing the quantification of several free/soluble metabolites such as amino acids, polyamines, organic acids and inorganic elements all from a single sample extract. PMID:25934989

  19. Growth and assessment of physical properties of a new nonlinear optical crystal: Lanthanum calcium borate

    Microsoft Academic Search

    Fangli Jing; Peizhen Fu; Yicheng Wu; Yanlei Zu; Xian Wang

    2008-01-01

    Single crystals of La2CaB10O19 (LCB) were grown by flux method. The main physical properties of using LCB as a frequency conversion device were evaluated. The crystal has a high transparency from ultraviolet (UV) to infrared range. The four nonvanished nonlinear optical coefficients measured by Maker fringes method are 0.433, 0.484, 0.437 and 0.640pm\\/V for d21, d22, d23 and d14, respectively.

  20. Growth and spectroscopic properties of ytterbium-doped lanthanum calcium borate (Yb 3+:La 2CaB 10O 19) crystal

    Microsoft Academic Search

    Rui Guo; Yicheng Wu; Peizhen Fu; Fangli Jing

    2005-01-01

    A new ytterbium-doped lanthanum calcium borate crystal (Yb3+:La2CaB10O19, Yb:LCB) has been grown by the flux method. The spectroscopic properties have been investigated and the fundamental spectral parameters for Yb:LCB crystal have been calculated. Yb:LCB crystal has the strongest absorption at 976 nm with a full-width at half-maximum of 14 nm. The absorption and emission cross-sections are 1.16×10?20 and 3.51×10?20 cm2,

  1. Orientational coupling enhancement in a carbon nanotube dispersed liquid crystal.

    PubMed

    Basu, Rajratan; Iannacchione, Germano S

    2010-05-01

    We present a detailed study of a dilute suspension of carbon nanotubes (CNTs) in a pentylcyanobiphenyl (5CB) liquid crystal (LC) by probing the dielectric properties as a function of applied ac voltage and frequency. In principle, to minimize the elastic distortion in the nematic matrix, the monodispersed CNTs follow the nematic director without disturbing the director field significantly. A strong anchoring energy due to ?-? electron stacking between LC-CNT molecules results in an increase in the dielectric anisotropy for the hybrid system, indicating a significant enhancement in the orientational order parameter. The frequency-dependent dielectric anisotropy for the composite system reveals the intrinsic frequency response of the LC-CNT anchoring mechanism. As a matter of consequence, the extracted value of splay elastic constant suggests that LC-CNT anchoring has an impact on the structural modification of the hybrid LC+CNT system. This strong anchoring energy stabilizes local pseudonematic domains, giving rise to a nonzero dielectric anisotropy in the isotropic phase that also shows an intrinsic frequency response. PMID:20866245

  2. Crystal Structure and Ferroelectric Properties of Poly(vinylidene fluoride)Carbon nano tube Nanocomposite Film

    Microsoft Academic Search

    Ji Seok Lee; Gwang Ho Kim; Woo Nyon Kim; Kyung Hwan Oh; Hyeong Tae Kim; Seung Sang Hwang; Soon Man Hong

    2008-01-01

    We investigated the effect of carbon nanotube on the crystal structure and mechanical\\/ferroelectric\\/piezoelectric properties based on poly(vinylidene fluoride) (PVDF) and carbon nano tube (CNT) composite film. The composite films were prepared by solution blending method, and the films were formed by hot-pressing. The contents of CNT were from 0.001 wt.% to 1 wt.%. For inducing piezoelectric beta-crystal structure, the hot-pressed nano composite

  3. Preparation of calcium alginate microgel beads in an electrodispersion reactor using an internal source of calcium carbonate nanoparticles.

    PubMed

    Zhao, Yinyan; Carvajal, M Teresa; Won, You-Yeon; Harris, Michael T

    2007-12-01

    An electrodispersion reactor has been used to prepare calcium alginate (Ca-alginate) microgel beads in this study. In the electrodispersion reactor, pulsed electric fields are utilized to atomize aqueous mixtures of sodium alginate and CaCO3 nanoparticles (dispersed phase) from a nozzle into an immiscible, insulating second liquid (continuous phase) containing a soluble organic acid. This technique combines the features of the electrohydrodynamic force driven emulsion processes and externally triggered gelations in microreactors (the droplets) ultimately to yield soft gel beads. The average particle size of the Ca-alginate gels generated by this method changed from 412 +/- 90 to 10 +/- 3 microm as the applied peak voltage was increased. A diagram depicting structural information for the Ca-alginate was constructed as a function of the concentrations of sodium alginate and CaCO3 nanoparticles. From this diagram, a critical concentration of sodium alginate required for sol-gel transformation was observed. The characteristic highly porous structure of Ca-alginate particles made by this technique appears suitable for microencapsulation applications. Finally, time scale analysis was performed for the electrodispersion processes that include reactions in the microreactor droplets to provide guidelines for the future employment of this technique. This electrodispersion reactor can be used potentially in the formation of many reaction-based microencapsulation systems. PMID:17990899

  4. Evaluation of ERTS data for certain oceanographic uses. [precipitation of calcium carbonate in Lake Michigan, Lake Erie, and Lake Ontario

    NASA Technical Reports Server (NTRS)

    Strong, A. E. (principal investigator)

    1974-01-01

    The author has identified the following significant results. According to Lake Michigan records, the pH levels have been steadily increasing as the lake becomes more eutrophic. Numerous upwellings during the summer of 1973, beginning with the late July event, appear to be triggering a chemical precipitation of calcium carbonate. The upwelling provides abundant carbon dioxide into the surface water and results in massive blooms of phytoplankton. As the CO2 is utilized by these microscopic plants the pH is increased (acidity decreases) and CaCO3 no longer is able to remain in solution. The precipitation takes place where the phytoplankton are living, near depths of 10 meters. Therefore, the whiting observed by ERTS-1 is only seen in the green band, as red cannot penetrate but a few meters. With these whitings, secci disc readings lower in July from 10-15 meters to 3-5 meters and green, milky water is observed by research vessels. It appears that whitings have been becoming more frequent since the middle 60's but until ERTS-1 the extent had never been realized. Calcium levels are too low, presently, for a similar precipitate in Lakes Huron or Superior. However, whitings have been seen by ERTS-1 in Lakes Erie and Ontario where the calcium ion and pH levels are more like those found in Lake Michigan.

  5. Dielectric and electromechanical properties of rare earth calcium oxyborate piezoelectric crystals at high temperatures.

    PubMed

    Yu, Fapeng; Zhang, Shujun; Zhao, Xian; Yuan, Duorong; Qin, Lifeng; Wang, Qing-Ming; Shrout, Thomas R

    2011-04-01

    The electrical resistivity, dielectric, and electromechanical properties of ReCa(4)O(BO(3))(3) (ReCOB; Re = Er, Y, Gd, Sm, Nd, Pr, and La) piezoelectric crystals were investigated as a function of temperature up to 1000 °C. Of the studied crystals, ErCOB and YCOB were found to possess extremely high resistivity (p): p > 3 × 10(7) ?.cm at 1000 °C. The property variation in ReCOB crystals is discussed with respect to their disordered structure. The highest electromechanical coupling factor ?(26) and piezoelectric coefficient d(26) at 1000°C, were achieved in PrCOB crystals, with values being on the order of 24.7% and 13.1 pC/N, respectively. The high thermal stability of the electromechanical properties, with variation less than 25%, together with the low dielectric loss (<46%) and high mechanical quality factor (>1500) at elevated temperatures of 1000 °C, make ErCOB, YCOB, and GdCOB crystals promising for ultrahigh temperature electromechanical applications. PMID:21507766

  6. Removal of phosphate, magnesium and calcium from swine wastewater through crystallization enhanced by aeration.

    PubMed

    Suzuki, Kazuyoshi; Tanaka, Yasuo; Osada, Takashi; Waki, Miyoko

    2002-07-01

    In order to confirm the possibility of removing P04-P, Mg and Ca from swine wastewater through artificial crystallization by aeration, laboratory and pilot scale experiments were carried out using actual swine wastewater. The pH of swine wastewater increased up to approximately 8.5 with continuous aeration, and a large part of the soluble PO4-P, Mg and Ca was crystallized. The ingredients of the crystals were estimated as MAP and HAP according to their mole ratio of NH4-N, PO4-P, Mg and Ca. The sedimentation speed of crystals in swine wastewater was about 3 m h(-1), and over 90% of them had settled after standing 1 h. A pilot scale reactor with the dual functions of crystallization by aeration and settling was operated continuously using actual swine wastewater, with aeration conditions of HRT 4.1 h and 26m3 airh(-1) m(-2) cross section (18m3 air h(-1) m(-3) volume). During 50 days of operation, pH at the aeration column held stable at 8.0, and 65% of PO4-P, 51% of Mg, and 34% of Ca were removed. PMID:12171396

  7. Crystallization of sodium chloride from a concentrated calcium chloride-potassium chloride-sodium chloride solution in a CMSMPR crystallizer: Observation of crystal size distribution and model validation

    Microsoft Academic Search

    Byung Sang Choi

    2005-01-01

    Compared to overwhelming technical data available in other advanced technologies, knowledge about particle technology, especially in particle synthesis from a solution, is still poor due to the lack of available equipment to study crystallization phenomena in a crystallizer. Recent technical advances in particle size measurement such as Coulter counter and laser light scattering have made in\\/ex situ study of some

  8. Comparison of the Spectral Characteristics of Chromium-Containing Crystals of the Calcium Gallogermanate Type with Their Structural Features

    SciTech Connect

    Veremeichik, T. F., E-mail: vtam@ns.crys.ras.ru; Simonov, V. I. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

    2010-11-15

    The molecular refractions and characteristics of the circular dichroism spectra of unactivated and chromium{sub a}ctivated La{sub 3}Ga{sub 5.5}Ta{sub 0.5}O{sub 14}, La{sub 3}Ga{sub 5.5}Nb{sub 0.5}O{sub 14}, La{sub 3}Ga{sub 5}GeO{sub 14}, La{sub 3}Ga{sub 5}SiO{sub 14}, Sr{sub 3}Ga{sub 2}Ge{sub 4}O{sub 14}, and Ca{sub 3}Ga{sub 2}Ge{sub 4}O{sub 14}crystals are compared with their structural parameters. Correlations between the molecular refractions and the structural distortions responsible for the optical activity of crystals and correlations between the characteristics of circular dichroism bands of defects and chromium ions and the interatomic distances in polyhedra and their distortions are found. The calcium gallogermanate structures exhibit a unique correspondence between the electronic configuration of host ions and the local symmetry.

  9. Growth and assessment of physical properties of a new nonlinear optical crystal: Lanthanum calcium borate

    NASA Astrophysics Data System (ADS)

    Jing, Fangli; Fu, Peizhen; Wu, Yicheng; Zu, Yanlei; Wang, Xian

    2008-08-01

    Single crystals of La 2CaB 10O 19 (LCB) were grown by flux method. The main physical properties of using LCB as a frequency conversion device were evaluated. The crystal has a high transparency from ultraviolet (UV) to infrared range. The four nonvanished nonlinear optical coefficients measured by Maker fringes method are 0.433, 0.484, 0.437 and 0.640 pm/V for d21, d22, d23 and d14, respectively. The damage threshold of (0 0 1) plane of LCB was measured to be 11.5 GW/cm 2. Besides the good optical properties, the crystal also has good thermal and mechanical properties and stable chemical properties for processing and application. All these properties provide LCB with a good application prospect as a frequency conversion device.

  10. Crystallization of sodium chloride from a concentrated calcium chloride-potassium chloride-sodium chloride solution in a CMSMPR crystallizer: Observation of crystal size distribution and model validation

    NASA Astrophysics Data System (ADS)

    Choi, Byung Sang

    Compared to overwhelming technical data available in other advanced technologies, knowledge about particle technology, especially in particle synthesis from a solution, is still poor due to the lack of available equipment to study crystallization phenomena in a crystallizer. Recent technical advances in particle size measurement such as Coulter counter and laser light scattering have made in/ex situ study of some of particle synthesis, i.e., growth, attrition, and aggregation, possible with simple systems. Even with these advancements in measurement technology, to grasp fully the crystallization phenomena requires further theoretical and technical advances in understanding such particle synthesis mechanisms. Therefore, it is the motive of this work to establish the general processing parameters and to produce rigorous experimental data with reliable performance and characterization that rigorously account for the crystallization phenomena of nucleation, growth, aggregation, and breakage including their variations with time and space in a controlled continuous mixed-suspension mixed-product removal (CMSMPR) crystallizer. This dissertation reports the results and achievements in the following areas: (1) experimental programs to support the development and validation of the phenomenological models and generation of laboratory data for the purpose of testing, refining, and validating the crystallization process, (2) development of laboratory well-mixed crystallizer system and experimental protocols to generate crystal size distribution (CSD) data, (3) the effects of feed solution concentration, crystallization temperature, feed flow rate, and mixing speed, as well as different types of mixers resulting in the evolution of CSDs with time from a concentrated brine solution, (4) with statistically designed experiments the effects of processing variables on the resultant particle structure and CSD at steady state were quantified and related to each of those operating conditions by studying the detailed crystallization processes, such as nucleation, growth, and breakage, as well as agglomeration. The purification of CaCl2 solution involving the crystallization of NaCl from the solution mixture of CaCl2, KCl, and NaCl as shipped from Dow Chemical, Ludington, in a CMSMPR crystallizer was studied as our model system because of its nucleation and crystal growth tendencies with less agglomeration. This project also generated a significant body of experimental data that are available at URL that is http://www.che.utah.edu/˜ring/CrystallizationWeb.

  11. Carbonate crystals precipitated by freshwater bacteria and their use as a limestone consolidant.

    PubMed

    Zamarreño, Dania V; Inkpen, Robert; May, Eric

    2009-09-01

    Bacterial carbonate precipitation is known to be a natural phenomenon associated with a wide range of bacterial species. Recently, the ability of bacteria to produce carbonates has been studied for its value in the conservation of limestone monuments and concrete. This paper describes investigations of carbonate crystals precipitated by freshwater bacteria by means of histological (Loeffler's methylene blue and alcian blue-periodic acid-Schiff stain) and fluorescence (CTC [5-cyano-2,3-ditolyl tetrazolium chloride]) stains, determination of cell viability inside carbonate crystals, and pore size reduction in limestone by image analysis. Carbonate crystals were found to be composed of bacteria embedded in a matrix of neutral and acid polysaccharides. Cell viability inside the carbonate crystals decreased with time. On stone, bacteria were found to form carbonate crystals, with only a few bacteria remaining as isolated cells or as cell aggregates. Pore size was reduced by about 50%, but no blockage was detected. Taken together, the results of this research provide some reassurance to conservators that biocalcification by bacteria could be a safe consolidation tool in a restoration strategy for building stone conservation. PMID:19617383

  12. Calcium isotopic evidence for rapid recrystallization of bulk marine carbonates and implications for geochemical proxies

    NASA Astrophysics Data System (ADS)

    Fantle, Matthew S.

    2015-01-01

    Strontium and calcium isotopic data for bulk carbonate solids and pore fluids from ODP Sites 1170 and 1171 are presented. The data suggest that bulk carbonate sediments actively exchange with coexisting pore fluids over tens of millions of year time scales. Recrystallization rates constrained by Sr isotopes and Sr elemental data are ?3% per Ma at 1170A and ?7% per Ma at 1171A. The pore fluid chemistries at both sites are affected by advection, which occurs in the downwards direction at 1170 (?-25 m/Ma) and upwards at 1171A (?250 m/Ma). Both the direction and the rate of advection are reflected by the width of the diffusive boundary layer for Sr at both 1170A (?300 m) and 1171A (?50 m), compared to ODP Site 807A (?150 m) where no chemically-detectable advection is occurring. Recrystallization is supported not only by interpretations of pore fluid data, but also by the alteration of the bulk solid. This is especially true at 1171A, where advection drives significant alteration of Sr/Ca, Mg/Ca, and 87Sr/86Sr. Numerical simulations of pore fluid geochemical and isotopic evolution over tens of millions of years, conducted with a depositional, time-dependent reactive transport model, suggest that recrystallization rates in the upper tens of meters of the sedimentary section at both sites are more rapid than suggested by the Sr geochemical data. When the Sr-constrained rates are applied to the pore fluid Ca isotope data, the model does not predict pore fluid ?44Ca within analytical uncertainty. The simulations indicate rates that are initially ?20% to 40% per Ma in young, <1 Ma sediments. The Ca isotope data cannot be explained by either inaccurate diffusion coefficients, inaccurate temporal evolution of pore fluid Ca concentrations, or upwards advection. Ultimately, such high rates in young sediments can impact paleoclimate and paleoenvironmental proxies used by geoscientists to study the past. Diagenetic effects due to rapid recrystallization, demonstrated for the oxygen isotope and Mg/Ca paleotemperature proxies, can alter paleotemperature reconstructions by as much as 4 °C. This suggests a means for affecting not only absolute temperature estimates but also systematic differences between the two paleotemperature tools.

  13. Growth and spectroscopic properties of ytterbium-doped lanthanum calcium borate (Yb 3+:La 2CaB 10O 19) crystal

    NASA Astrophysics Data System (ADS)

    Guo, Rui; Wu, Yicheng; Fu, Peizhen; Jing, Fangli

    2005-01-01

    A new ytterbium-doped lanthanum calcium borate crystal (Yb 3+:La 2CaB 10O 19, Yb:LCB) has been grown by the flux method. The spectroscopic properties have been investigated and the fundamental spectral parameters for Yb:LCB crystal have been calculated. Yb:LCB crystal has the strongest absorption at 976 nm with a full-width at half-maximum of 14 nm. The absorption and emission cross-sections are 1.16 × 10 -20 and 3.51 × 10 -20 cm 2, respectively. The fluorescence lifetime is 0.95 ms. The ground-state energy level splitting is calculated to be 640 cm -1. In comparison with other Yb-doped laser crystals, the calculated parameters show that Yb:LCB crystal satisfies the fundamental spectral condition for laser emission.

  14. Kinetics of aggregation and crystallization of polyaspartic Acid stabilized calcium phosphate particles at high concentrations.

    PubMed

    Krogstad, Daniel V; Wang, Dongbo; Lin-Gibson, Sheng

    2015-05-11

    Bone is an important material to study due to its exceptional mechanical properties and relevance with respect to hard tissue regeneration and repair. A significant effort has been directed toward understanding the bone formation process and the production of synthetic bone mimicking materials. Here, the formation and structural evolution of calcium phosphate (CaP) was investigated in the presence of relatively high concentrations of calcium, phosphate, and polyaspartic acid (pAsp) using dynamic light scattering (DLS) and cryo-transmission electron microscopy (cryo-TEM). The incipient CaP aggregates were comprised of spherical nanoparticles (diameter ? 3-4 nm); they became preferentially aligned over time and eventually transformed into nanorods. The nanorods remained stable in suspension with no signs of further aggregation for at least four months. Detailed cryo-TEM suggested that the CaP nanorods formed through an oriented attachment mechanism. These results show that the reaction concentration greatly influences the mechanism and final properties of CaP. Mechanistic insights gained from this study will facilitate better design and fabrication of bioinspired materials. PMID:25901665

  15. Multi-scale studies on diamond crystal and carbon microtubular growth

    Microsoft Academic Search

    Gopinath Bhimarasetti

    2005-01-01

    Diamond and one-dimensional carbon tubular structures are two of the most technologically important materials today. Electronic devices utilizing the extreme properties of diamond could not be fully realized due to the lack of processes for large single crystals. The traditional methods for producing carbon nanotubes (CNTs) lack the ability to tune the internal diameters and morphologies essential for nano\\/microfluidics. In

  16. The glass transition and crystallization of propylene carbonate investigated by mechanical spectroscopy

    NASA Astrophysics Data System (ADS)

    Ying, X. N.

    2013-08-01

    A composite reed flexural vibration method is used to investigate the dynamic mechanical responses of propylene carbonate below room temperature. The mechanical spectrum of propylene carbonate is subtracted from a composite system consisting of the substrate and of propylene carbonate deposited on it. The mechanical spectrum relating to the glass transition and crystallization is identified. It suggests that an interfacial effect occurs in the crystalline state rather than the glass transition. This work supports the reliability of the composite reed flexural vibration method in the investigation on the glass transition of propylene carbonate. Finally, the determination of the glass transition temperature of propylene carbonate by mechanical spectroscopy was discussed.

  17. Calcium Carbonate Phosphate Binding Ion Exchange Filtration and Accelerated Denitrification Improve Public Health Standards and Combat Eutrophication in Aquatic Ecosystems

    PubMed Central

    Yanamadala, Vijay

    2010-01-01

    Cultural eutrophication, the process by which a lake becomes rich in dissolved nutrients as a result of point and nonpoint pollutant sources, is a major cause of the loss of natural lake ecosystems throughout the world. The process occurs naturally in all lakes, but phosphate-rich nutrient runoff from sources such as storm drains and agricultural runoff is a major cause of excess phosphate-induced eutrophication. Especially in Madrona Marsh, one of the last remaining vernal marshes in the greater Los Angeles area, California, cultural eutrophication has become a major problem. In this study, calcium carbonate was found to be an excellent phosphate binder, reducing up to 70% of the phosphates in a given sample of water, and it posed relatively negligent ecological repercussions. This study involved the testing of this principle in both the laboratory and the real ecosystem. A calcium carbonate lacing procedure was first carried out to determine its efficacy in Madrona Marsh. Through this, ammonia was found to interfere with the solubility of calcium carbonate and therefore to be a hindrance to the reduction of phosphate. Therefore, various approaches for reduction of ammonia were tested, including aeration, use of fiber growth media, and plants, mainly Caulerpa verticellata, chosen for it hardiness, primarily in an attempt to increase population of Nitrobacter and Nitrosomonas. All were successful in moderately reducing ammonia levels. In addition, soil sampling, sediment analysis, microscopic plant analysis, microorganism and macroinvertebrate identification, and rate law formulations were conducted. The effect of phosphate and ammonia reduction on the populations of enterobacteria was also an important focus of this experiment. Varying concentrations of phosphate, ammonia, and calcium carbonate in conjunction with phosphate were tested in Madrona Marsh to determine their effects on the populations of enteropathogens on nonspecific blood agar, MacConkey agar, and Hektoen agar. Initial analyses suggest a strong correlation between phosphate concentrations and bacterial populations; a 66% decrease in phosphate resulted in a 35% reduction in bacterial populations and a 45% reduction in enteropathogenic populations. Likewise, a strong correlation was shown between calcium carbonate concentrations and bacterial reduction greater than that which can be attributed to the phosphate reduction alone. This was followed by the construction of various phosphate binding calcium carbonate filters, which used the ion exchange principle, including a spring loading filter, PVC pipe filter, and a galvanized filter. All were tested with the aid of Stoke's law formulation. The experiment was extremely successful in designing a working phosphate-binding and ammonia-reducing filter, and a large-scale agitator-clarifier filter system is currently being planned for construction in Madrona Marsh; this filter will reduce phosphate and ammonia levels substantially in the following years, bringing ecological, economical, and health-related improvements to the overall ecosystem and habitat. PMID:16381147

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

    USGS Publications Warehouse

    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.

  19. Crystal structures of a novel, thermostable phytase in partially and fully calcium-loaded states

    Microsoft Academic Search

    Nam-Chul Ha; Byung-Chul Oh; Sejeong Shin; Hyun-Ju Kim; Tae-Kwang Oh; Young-Ok Kim; Kwan Yong Choi; Byung-Ha Oh

    2000-01-01

    Phytases hydrolyze phytic acid to less phosphorylated myo-inositol derivatives and inorganic phosphate. A thermostable phytase is of great value in applications for improving phosphate and metal ion availability in animal feed, and thereby reducing phosphate pollution to the environment. Here, we report a new folding architecture of a six-bladed propeller for phosphatase activity revealed by the 2.1 Å crystal structures

  20. ABSORPTION OF CALCIUM FROM THE CARBONATED DAIRY SOFT DRINK IS GREATER THAN THAT FROM FAT-FREE MILK AND CALCIUM-FORTIFIED ORANGE JUICE IN WOMEN

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study reports the intestinal calcium absorption of a new product that combines calcium and other nutrients from milk and the consumer's desire for soft drinks. The overall objective was to compare calcium absorption of commercially available products, the dairy soft drink, fat-free milk, and ca...

  1. Thermal stability and UV-shielding properties of polymethyl methacrylate and polystyrene modified with calcium carbonate nanoparticles

    Microsoft Academic Search

    Manoj Kumar Pal; Beena Singh; Jaiswar Gautam

    The influences of nanosized CaCO3 on the thermal and optical properties embedded in poly(methyl methacrylate) (PMMA) and polystyrene (PS) were investigated.\\u000a Calcium carbonate nanoparticles were synthesized by in situ deposition technique, and its nano size (32–35 nm) was confirmed\\u000a by scanning electron microscope (SEM) and X-ray studies. Nanocomposites samples of PMMA\\/CaCO3 and PS\\/CaCO3 were prepared with different filler loading (0–4 wt%)

  2. Mesoporous carbons with self-assembled surfaces of defined crystal orientation

    PubMed Central

    Jian, Kengqing; Truong, Trung C.; Hoffman, Wesley P.; Hurt, Robert H.

    2008-01-01

    The design of carbon sorbents traditionally focuses on the control of pore structure and the number and type of surface functional groups. The present paper explores the potential of also controlling the carbon crystal structure, or graphene layer orientation, in the immediate vicinity of the internal surfaces. We hypothesize that this crystal structure influences the properties of the carbon surfaces and affects the number and type of active sites for functionalization. Here a series of mesoporous carbons are fabricated by capillary infiltration of mesophase pitch (naphthalene homopolymer) into a series of controlled pore glass templates of different characteristic pore size followed by carbonization and template etching. The liquid crystalline mesogens are known to adopt perpendicular alignment (anchoring) at liquid/silica interfaces, which after carbonization lead to a high concentration of graphene edge sites at the inner surfaces. These surfaces are shown to have elevated chemical reactivity, and the pore structures are shown to be consistent with predictions of a quantitative model based on the negative replica concept. Overall, the use of mesophase pitch for templated mesoporous carbons allows systematic and simultaneous control of both pore structure and interfacial crystal structure through the well-defined rules of liquid crystal surface anchoring. PMID:19190761

  3. Investigation of early growth of calcium hydroxide crystals in cement solution by soft x-ray transmission microscopy

    SciTech Connect

    Harutyunyan, V. S.; Kirchheim, A. P.; Monteiro, P. J. M.; Aivazyan, A. P.; Fischer, P.

    2009-02-02

    Research on cement hydration was performed at the full-field soft transmission X-ray microscope XM-1 located at beamline 6.1.2 at the Advanced Light Source (ALS) in Berkeley CA which is operated by the Center for X-ray Optics, Lawrence Berkeley National Laboratory, Berkeley, California. A series of works [1-3] has been conducted using this microscope for the in situ observation and qualitative analysis of through-solution hydration products and products of topochemical reactions, which form in cementitious aqueous solutions. This paper studies the precipitation of the calcium hydroxide (CH) crystals from the cement solution. The analysis of successive images of the hydration process provides critical quantitative information about the growth rate of calcium hydroxide (CH) crystals, the supersaturation ratio, and the kinetic and diffusion coefficients of the growth process. ASTM Type II portland cement and 6% C{sub 4}A{sub 3}{bar S} admixture were mixed in aqueous solution and saturated with respect to CH and gypsum. The C{sub 4}A{sub 3}{bar S} admixture was included in the experimental program because of the general research program on expansive cements, and adding C{sub 4}A{sub 3}{bar S} to portland cement is an efficient method of generating ettringite and significant early-age expansion. The solution/solid materials ratio was 10 cm{sup 3}/g, which is higher than the one existing in regular concrete and mortars; to compensate for this dilution, the solution was originally saturated with CH and gypsum. To allow sufficient transmission of the soft X-rays, a small droplet was taken from the supernatant solution and assembled in the sample holder, and then squeezed between two silicon nitride windows for the analysis. The X-ray optical setup of the microscope XM-1 is described elsewhere [2]. In this experiment, a wavelength of 2.4 nm (516.6 eV) was used. The radiation transmitting the sample was detected using an X-ray CCD camera, with a resolution of 35 nm provided by Fresnel zone plate X-ray optics and magnification factor of about 2000. The recorded images have a circular field of view of approximately 10 {micro}m in diameter. The illumination time per image was in the range of 1 to 14 seconds depending largely on the absorption of the sample. The experimental work was conducted at room temperature T = 298 K.

  4. Calcium orthophosphates

    PubMed Central

    Dorozhkin, Sergey V.

    2011-01-01

    The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. This type of materials is of special significance for human beings, because they represent the inorganic part of major normal (bones, teeth and antlers) and pathological (i.e., those appearing due to various diseases) calcified tissues of mammals. For example, atherosclerosis results in blood vessel blockage caused by a solid composite of cholesterol with calcium orthophosphates, while dental caries and osteoporosis mean a partial decalcification of teeth and bones, respectively, that results in replacement of a less soluble and harder biological apatite by more soluble and softer calcium hydrogenphosphates. Therefore, the processes of both normal and pathological calcifications are just an in vivo crystallization of calcium orthophosphates. Similarly, dental caries and osteoporosis might be considered an in vivo dissolution of calcium orthophosphates. Thus, calcium orthophosphates hold a great significance for humankind, and in this paper, an overview on the current knowledge on this subject is provided. PMID:23507744

  5. Fixation of CO 2 by carbonating calcium derived from blast furnace slag

    Microsoft Academic Search

    Sanni Eloneva; Sebastian Teir; Justin Salminen; Carl-Johan Fogelholm; Ron Zevenhoven

    2008-01-01

    Industrial waste materials, such as steelmaking slags, appear to be potential raw materials for reducing CO2 emissions by carbonation. The suitability of applying a carbonation route based on acetic acid leaching to produce carbonates from blast furnace slag is presented in this study. The effect of solution pH, temperature, and CO2 pressure on the precipitation of carbonates was experimentally studied.

  6. Influence of carbon on the thermoluminescence and optically stimulated luminescence of ?-Al2O3:C crystals

    NASA Astrophysics Data System (ADS)

    Yang, Xin-Bo; Li, Hong-Jun; Bi, Qun-Yu; Cheng, Yan; Tang, Qiang; Xu, Jun

    2008-12-01

    ?-Al2O3:C crystal shows excellent thermoluminescence (TL) and optically stimulated luminescence (OSL) properties but the real role carbon plays in this crystal is still not clearly understood so far. In this work, ?-Al2O3:C crystal doping with different amounts of carbon were grown by the temperature gradient technique, and TL and OSL properties of as-grown crystals were investigated. Additionally, a mechanism was proposed to explain the role of carbon in forming the TL and OSL properties of ?-Al2O3:C. TL and OSL intensities of as-grown crystals increase with the increasing amount of carbon doping in the crystal, but no shift is found in the glow peak location at 465 K. As the amount of carbon doping in the crystals decreases, OSL decay rate becomes faster. With the increase in heating rate, the integral TL response of as-grown crystals decreases and glow peak shifts to higher temperatures. TL response decrease rate increases with the increasing amount of carbon doping in the crystals. All the TL and OSL response curves of as-grown crystals show linear-sublinear-saturation characteristic, and OSL dose response exhibits higher sensitivity and wider linear dose range than that of TL. The crystal doping with 5000 ppm carbon shows the best dosimetric properties. Carbon plays the role of a dopant in ?-Al2O3:C crystal and four-valent carbon anions replace the two-valent anions of oxygen during the crystal growth process, and large amounts of oxygen vacancies were formed, which corresponds to the high absorption coefficient of F and F+ centers in the crystals.

  7. Uptake of Cu 2+ by the calcium carbonates vaterite and calcite as studied by continuous wave (cw) and pulse electron paramagnetic resonance

    NASA Astrophysics Data System (ADS)

    Schosseler, P. M.; Wehrli, B.; Schweiger, A.

    1999-07-01

    The investigation of the Cu 2+ uptake by the calcium carbonate minerals vaterite and calcite with continuous wave and pulse electron paramagnetic resonance (EPR) yields information on a molecular scale about the relevant complexation reactions at the mineral-water interface. The structural assignment is based on changes in the coordination geometry of the copper complexes. Magnetic interactions of the unpaired Cu 2+ electron with nuclei of 13C-labeled carbonate ligands and protons from water or hydroxyl ligands in the first and second coordination spheres of the cation are detected by pulse EPR techniques. Our results show that the Cu 2+ ions are rapidly dehydrated upon adsorption on the mineral surface. The strong surface binding is due to monodentate coordination to three or four carbonate surface ions, comparable to chelate complexation in solution. The formation of square-planar or square-pyramidal copper complexes at exposed surface sites like kinks and steps yields a convincing explanation for the inhibition of calcium carbonate growth and dissolution. Upon recrystallization the Cu 2+ ions are integrated into the calcite lattice where they exhibit a dynamic Jahn-Teller effect. The resulting local lattice distortions are expected to destabilize the Cu xCa (1- x) CO 3( s) solid solution. Our results support the concept of a dynamic calcium carbonate surface, covered by a thin, structured surface layer. The detailed structural information obtained for Cu 2+ provides a better understanding of the interaction of other metal ions with calcium carbonate minerals.

  8. Combined effect of constant high voltage electrostatic field and variable frequency pulsed electromagnetic field on the morphology of calcium carbonate scale in circulating cooling water systems.

    PubMed

    Zhao, Ju-Dong; Liu, Zhi-An; Zhao, Er-Jun

    2014-01-01

    Research on scale inhibition is of importance to improve the heat transfer efficiency of heat exchangers. The combined effect of high voltage electrostatic and variable frequency pulsed electromagnetic fields on calcium carbonate precipitation was investigated, both theoretically and experimentally. Using energy dispersive spectrum analysis, the predominant phase was found to be CaCO(3). The formed crystal phases mainly consist of calcite and aragonite, which is, in part, verified by theory. The results indicate that the setting of water flow velocity, and high voltage electrostatic and variable frequency pulsed electromagnetic fields is very important. Favorable values of these parameters can have a significant anti-scaling effect, with 68.95% of anti-scaling ratio for scale sample 13, while unfavorable values do not affect scale inhibition, but rather promoted fouling, such as scale sample 6. By using scanning electron microscopy analysis, when the anti-scaling ratio is positive, the particle size of scale was found to become smaller than that of untreated sample and the morphology became loose. The X-ray diffraction results verify that the good combined effect favors the appearance and growth of aragonite and restrains its transition to calcite. The mechanism for scale reduction is discussed. PMID:25259497

  9. Controlling single and few-layer graphene crystals growth in a solid carbon source based chemical vapor deposition

    SciTech Connect

    Papon, Remi; Sharma, Subash; Shinde, Sachin M.; Vishwakarma, Riteshkumar; Tanemura, Masaki [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Kalita, Golap, E-mail: kalita.golap@nitech.ac.jp [Department of Frontier Materials, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya 466-8555 (Japan); Center for Fostering Young and Innovative Researchers, Nagoya Institute of Technology, Gokiso-cho, Showa-ku, Nagoya, 466-8555 (Japan)

    2014-09-29

    Here, we reveal the growth process of single and few-layer graphene crystals in the solid carbon source based chemical vapor deposition (CVD) technique. Nucleation and growth of graphene crystals on a polycrystalline Cu foil are significantly affected by the injection of carbon atoms with pyrolysis rate of the carbon source. We observe micron length ribbons like growth front as well as saturated growth edges of graphene crystals depending on growth conditions. Controlling the pyrolysis rate of carbon source, monolayer and few-layer crystals and corresponding continuous films are obtained. In a controlled process, we observed growth of large monolayer graphene crystals, which interconnect and merge together to form a continuous film. On the other hand, adlayer growth is observed with an increased pyrolysis rate, resulting few-layer graphene crystal structure and merged continuous film. The understanding of monolayer and few-layer crystals growth in the developed CVD process can be significant to grow graphene with controlled layer numbers.

  10. Calcium carbonate precipitation rate as a function of ion ratio in the presence & absence of Sr2+

    NASA Astrophysics Data System (ADS)

    Gebrehiwet, T.; Beig, M. S.; Fujita, Y.; Redden, G. D.; Smith, R. W.

    2010-12-01

    Tsigabu Gebrehiwet 1*, Mikala Beig 2, Yoshiko Fujita 3, George Redden 3 and Robert W. Smith 1 1University of Idaho, 1776 Science Center Dr, Idaho Falls,ID, 83402 (*tgebrehiwet@uidaho.edu; smithbob@uidaho.edu ) 27963 Grasmere Dr.Boulder, CO 80301(mbeig@alumni.rice.edu) 3Idaho National Laboratory, MS 2208, Idaho Falls, ID 83415 (Yoshiko.Fujita@inl.gov; George.Redden@inl.gov) Engineered in situ precipitation of calcium carbonate is a proposed strategy for remediating toxic or radioactive metals (e.g., Sr2+)in subsurface environments as well as for modifying the physical properties (e.g., stiffness, permeability) of geomedia. Inducing the precipitation reaction will likely involve manipulating the geochemical conditions by adding calcium, (bi)carbonate, or both, and relying on mixing of the two reactants. Under these conditions, the ratio of Ca2+ to CO32- will vary with distance from the mixing interface, and for most or all of the porous medium, a 1:1 stoichiometry between calcium and carbonate is unlikely to be achieved. Indeed, in engineered systems where rapid treatment is an important objective, very steep ion concentration gradients may be generated, which would result in local reactant ratios varying from very small to very large over short distances, depending on the mixing geometry and particular chemical composition of the mixing fluids. This in turn has an impact on the rate of mineral precipitation. Typically, the rate of calcium carbonate precipitation is expressed with an affinity-based rate law of the type: Rate = k(?-1)n, where k is a rate constant, ? is the saturation state for the mineral (e.g., calcite), and n is an empirical reaction order. The saturation state ? is defined as the ratio of the ion activity product to the mineral solubility product. In this expression, the rate is simply dependent on the value of ?; the actual activities of the individual ions (Ca2+ and CO32-) do not appear in the expression. In support of the development of engineered calcite precipitation schemes for contaminant immobilization, we have conducted experiments on CaCO3 precipitation kinetics under constant composition conditions where the supersaturation state (?) with respect to calcite is held constant at 12.8, but the ion activity ratio (Ca2+:CO32-) is varied. The objective is to examine the effect of the ion ratio on the mineral precipitation rate and on the distribution coefficient for co-precipitated Sr (DexSr). Our results to date indicate that precipitation rates vary by up to a factor of two with the maximum rate occurring at r=0.23, where r is carbonate to calcium ions ratio. In addition, although the extent of variation in the DexSr values is similar to that for the calcite precipitation rate, we have observed low correlation between strontium distribution coefficients and precipitation rates.

  11. The role of amorphous precursors in the crystallization of La and Nd carbonates.

    PubMed

    Vallina, Beatriz; Rodriguez-Blanco, Juan Diego; Brown, Andrew P; Blanco, Jesus A; Benning, Liane G

    2015-07-28

    Crystalline La and Nd carbonates can be formed from poorly-ordered nanoparticulate precursors, termed amorphous lanthanum carbonate (ALC) and amorphous neodymium carbonate (ANC). When reacted in air or in aqueous solutions these precursors show highly variable lifetimes and crystallization pathways. We have characterized these precursors and the crystallization pathways and products with solid-state, spectroscopic and microscopic techniques to explain the differences in crystallization mechanisms between the La and Nd systems. ALC and ANC consist of highly hydrated, 10-20 nm spherical nanoparticles with a general formula of REE2(CO3)3·5H2O (REE = La, Nd). The stabilities differ by ?2 orders of magnitude, with ANC being far more stable than ALC. This difference is due to the Nd(3+) ion having a far higher hydration energy compared to the La(3+) ion. This, together with temperature and reaction times, leads to clear differences not only in the kinetics and mechanisms of crystallization of the amorphous precursor La- and Nd-carbonate phases but also in the resulting crystallite sizes and morphologies of the end products. All crystalline La and Nd carbonates developed spherulitic morphologies when crystallization occurred from hydrous phases in solution at temperatures above 60 °C (La system) and 95 °C (Nd system). We suggest that spherulitic growth occurs due to a rapid breakdown of the amorphous precursors and a concurrent rapid increase in supersaturation levels in the aqueous solution. The kinetic data show that the crystallization pathway for both La and Nd carbonate systems is dependent on the reaction temperature and the ionic potential of the REE(3+) ion. PMID:26132514

  12. Study of phase transformation and crystal structure for 1D carbon-modified titania ribbons

    SciTech Connect

    Zhou, Lihui, E-mail: lhzhou@ecust.edu.cn; Zhang, Fang; Li, Jinxia

    2014-02-15

    One-dimensional hydrogen titanate ribbons were successfully prepared with hydrothermal reaction in a highly basic solution. A series of one-dimensional carbon-modified TiO{sub 2} ribbons were prepared via calcination of the mixture of hydrogen titanate ribbons and sucrose solution under N{sub 2} flow at different temperatures. The phase transformation process of hydrogen titanate ribbons was investigated by in-situ X-ray diffraction at various temperatures. Besides, one-dimensional carbon-modified TiO{sub 2} ribbons calcined at different temperatures were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, nitrogen adsorption isotherms, diffuse reflectance ultraviolet–visible spectroscopy, and so on. Carbon-modified TiO{sub 2} ribbons showed one-dimensional ribbon crystal structure and various crystal phases of TiO{sub 2}. After being modified with carbon, a layer of uniform carbon film was coated on the surface of TiO{sub 2} ribbons, which improved their adsorption capacity for methyl orange as a model organic pollutant. One-dimensional carbon-modified TiO{sub 2} ribbons also exhibited enhanced visible-light absorbance with the increase of calcination temperatures. - Highlights: • The synthesis of 1D carbon-modified TiO{sub 2} ribbons. • The phase transformation of 1D carbon-modified TiO{sub 2} ribbons. • 1D carbon-modified TiO{sub 2} exhibites enhanced visible-light absorbance.

  13. Boron and calcium isotope composition in Neoproterozoic carbonate rocks from Namibia: evidence for extreme environmental change

    Microsoft Academic Search

    Simone A. Kasemann; Chris J. Hawkesworth; Anthony R. Prave; Anthony E. Fallick; Paul N. Pearson

    2005-01-01

    The level and evolution of atmospheric carbon dioxide throughout Earth's history are key issues for palaeoclimate reconstructions, especially during times of extreme climate change such as those that marked the Neoproterozoic. The carbon isotope ratios of marine carbonates are crucial in the correlation and identification of Neoproterozoic glacial deposits, and they are also used as a record for biogeochemical cycling

  14. Calcium Isotopic Variation in Marine Evaporites and Carbonates: Applications to Late Miocene Mediterranean Brine Chemistry and Late Cenozoic Calcium Cycling in the Oceans

    E-print Network

    Hensley, Tabitha Michele

    2006-01-01

    of the equilibrium fractionation controlled oxygen isotopeequilibrium fractionation effects for calcium isotopes, butisotope fractionation in synthetically precipitated calcite is controlled by an equilibrium

  15. Exposure Assessment and Inflammatory Response Among Workers Producing Calcium Carbonate Nanomaterials

    NASA Astrophysics Data System (ADS)

    Cui, Ling

    Problem: Nanotechnology is one of the most rapidly growing fields of science and engineering, and its applications have expanded to numerous research and industrial sectors, from consumer products to medicine to energy. Nano-materials and nanotechnology promise substantial benefits. However, there are many uncertainties and concerns regarding human health and the environment. Numerous toxicological studies on animals and cells in vitro have demonstrated that nanomaterials could cause various adverse health effects, including inflammation, oxidative stress, fibrosis and mutagenesis in the lungs, and cardiovascular and nervous system impairment. Objectives: The overall objective of this study was to characterize particulate exposures in a calcium carbonate nanoparticle manufacturing facility, investigate possible respiratory and cardiovascular effects, and explore the plausibility of an inflammatory mechanism. The associations between exposure level and various health outcomes were investigated. Methodology: Each job was characterized by mass, number and surface area concentration. Job classification was performed based on ranking of the exposure level and statistical models. Lung function tests, exhaled NO and blood pressure (BP) were measured before and after the workshift in the year of 2011. Inflammatory cytokines from induced sputum were measured cross-sectionally in the year of 2011. Data of lung function tests and blood pressure were collected cross-sectionally in the year of 2012. The associations between each exposure metric and health measures in 2012 were investigated. Only mass concentration was linked to both 2011 and 2012 health outcomes. Results: The sampling and analytic methodology used in the study presents the potential to characterize nanoparticle exposure for a variety of operational processes. We found the highest mass exposure occurred at bagging job whereas the highest number and surface area concentration was found at modification. Modification is thought to be the primary emission source. It is discovered nanoparticles in the size range of 20-300nm dominate in this workplace, which consists of 90-98% of particle counts in the respirable fraction. Based on the sampling results from 2012, there was a strong relationship between number concentration in 5-25um range and the respirable mass concentration (r= 0.908); however, no such correlation was found between number concentration in nanoscale and respirable mass (r= 0.018). The deposited surface area in TB (r=0.66) and alveolar region (r=0.46) was modestly correlated with number concentration of particles in the nanoscale. A reduced FEV1 and increased BP were consistently found among medium-mass exposure compared to low-mass exposure, however no statistical significance was found. When comparing the four exposure metrics, we found number concentration and surface area concentration in general produce effects in similar direction, however opposite to mass concentration. Such observation is consistent with the correlation among these exposure metrics. Airway inflammatory responses presented a dose-response relationship using mass as exposure metric. The concentrations of IL1beta (p =0.043) and IL8 (p=0.008) in sputum among high mass-exposure group were statistically greater than that in low-mass exposure group. It suggested the inflammatory responses were associated with mass concentration of inhaled nanoparticle particles, which are mainly made up by agglomerated form of nanoparticles. At current stage, with limited understanding of the toxicological perspective of nanoparticle, a complete exposure assessment in nanoparticle facility needs to be conducted in both bulk- and nano-form.

  16. Journal of Crystal Growth 306 (2007) 152158 Co-precipitation of silica and alkaline-earth carbonates using

    E-print Network

    Hyde, Stephen

    2007-01-01

    Journal of Crystal Growth 306 (2007) 152­158 Co-precipitation of silica and alkaline of alkaline-earth carbonate crystals, and polymerisation of silicate species into silica. The resulting]. They are built in part of rod- shaped nano-crystallites of the alkaline-earth carbonate, typically 200 nm

  17. Optimization of Bifidobacterium longum growth by use of calcium carbonate-alginate beads

    Microsoft Academic Search

    Su-Han Song; Teak-Bum Kim; Hoon-Il Oh; Deok-Kun Oh

    2003-01-01

    High concentrations of ammonium and sodium ions inhibited Bifidobacterium longum growth more than a high calcium ion concentration. The optimal pH for B. longum growth was determined to be 5.0 due to the lower accumulation of ammonium ion. To reduce the accumulation of ammonium ion and obtain an enhanced growth of B. longum, the pH of the culture containing immobilized

  18. Class and Home Problems: Carbon Dioxide Capture from Coal-Fired Power Plants Using Calcium Looping

    ERIC Educational Resources Information Center

    Deshpande, Niranjani; Phalak, Nihar; Fan, Liang-Shih; Sundaresan, Sankaran

    2015-01-01

    Calcium looping is based on the simple premise of the reversible reaction between CO[subscript 2] and CaO. This reaction can be used for separation of CO2 from a mixture of gases; most notably the technology finds applications in CO[subscript 2] removal from gas streams in fossil fuel-based energy systems. This article gives a brief overview of…

  19. Technical Note: Calcium and carbon stable isotope ratios as paleodietary indicators.

    PubMed

    Melin, Amanda D; Crowley, Brooke E; Brown, Shaun T; Wheatley, Patrick V; Moritz, Gillian L; Yit Yu, Fred Tuh; Bernard, Henry; DePaolo, Donald J; Jacobson, Andrew D; Dominy, Nathaniel J

    2014-08-01

    Calcium stable isotope ratios are hypothesized to vary as a function of trophic level. This premise raises the possibility of using calcium stable isotope ratios to study the dietary behaviors of fossil taxa and to test competing hypotheses on the adaptive origins of euprimates. To explore this concept, we measured the stable isotope composition of contemporary mammals in northern Borneo and northwestern Costa Rica, two communities with functional or phylogenetic relevance to primate origins. We found that bone collagen ?(13) C and ?(15) N values could differentiate trophic levels in each assemblage, a result that justifies the use of these systems to test the predicted inverse relationship between bioapatite ?(13) C and ?(44) Ca values. As expected, taxonomic carnivores (felids) showed a combination of high ?(13) C and low ?(44) Ca values; however, the ?(44) Ca values of other faunivores were indistinguishable from those of primary consumers. We suggest that the trophic insensitivity of most bioapatite ?(44) Ca values is attributable to the negligible calcium content of arthropod prey. Although the present results are inconclusive, the tandem analysis of ?(44) Ca and ?(13) C values in fossils continues to hold promise for informing paleodietary studies and we highlight this potential by drawing attention to the stable isotope composition of the Early Eocene primate Cantius. PMID:24839035

  20. Deposition of Thin Films of Biocompatible Calcium Carbonate via Template-Driven Mineralization

    E-print Network

    Ajikumar, Parayil Kumaran

    Natural bone is a composite of collagen based hydrogel and inorganic dahilite crystals. The unusual combination of a hard inorganic material and an underlying elastic hydrogel network endows native bone with unique mechanical ...

  1. Crystal field theory analysis of rovibrational spectra of carbon monoxide monomers isolated in solid parahydrogen

    Microsoft Academic Search

    Mario E. Fajardo; C. Michael Lindsay; Takamasa Momose

    2009-01-01

    We report the first rotationally resolved and completely assigned rovibrational spectrum for a nonhydride molecule rotating in the solid phase: carbon monoxide (CO) monomers isolated in cryogenic solid parahydrogen (p-H2). We employ a modified crystal field theory model, in which the CO molecular spectroscopic constants are taken as adjustable parameters, to make good spectroscopic assignments for all the observed features.

  2. Crystallization and mutational studies of carbon monoxide dehydrogenase from moorella thermoacetica

    E-print Network

    Kim, Eun Jin

    2004-09-30

    Carbon Monoxide Dehydrogenase (CODH), also known as Acetyl-CoA synthase (ACS), is one of seven known Ni containing enzymes. CODH/ACS is a bifunctional enzyme which oxidizes CO to CO2 reversibly and synthesizes acetyl-CoA. Recently, X-ray crystal...

  3. Single walled carbon nano-tube, ferroelectric liquid crystal composites: Excellent diffractive tool

    Microsoft Academic Search

    A. K. Srivastava; E. P. Pozhidaev; V. G. Chigrinov; R. Manohar

    2011-01-01

    We present a switchable grating based on chiral single walled carbon nano-tube (SWCNT) doped ferroelectric liquid crystals (FLCs). The presence of SWCNTs improves the diffraction profile of the pure FLC. The diffraction efficiency, i.e., the ratio of intensities of first order and zero order maxima is more than 100% for the higher concentration of SWCNTs in pure FLC. This phenomenon

  4. Organic Light Emitting Diodes with Opal Photonic Crystal Layer and Carbon Nanotube Anode

    Microsoft Academic Search

    Raquel Ovalle Robles; Maria Del Rocio Nava; Christopher Williams; Mei Zhang; Shaoli Fang; Sergey Lee; Ray Baughman; Anvar Zakhidov

    2007-01-01

    We report electroluminescence intensity and spectral changes in light emission from organic light emitting diode (OLEDs) structures, which have thin transparent films of opal photonic crystal (PC). The anode in such PC-OLED is laminated on opal layer from free standing optically transparent multiwall carbon nanotubes (T-CNT) sheets made by dry spinning from CVD grown forests. Silica and polystyrene opal films

  5. Preparation of poly(methyl methacrylate) microcapsules by in situ polymerization on the surface of calcium carbonate particles.

    PubMed

    Sato, Katsuhiko; Nakajima, Tatsuya; Anzai, Jun-ichi

    2012-12-01

    Poly(methyl methacrylate) (PMMA) microcapsules were prepared by the in situ polymerization of methyl methacrylate (MMA) and N,N'-methylenebisacrylamide on the surface of calcium carbonate (CaCO(3)) particles, followed by the dissolution of the CaCO(3) core in ethylenediaminetetraacetic acid solution. The microcapsules were characterized using fluorescence microscopy, atomic force microscopy, scanning electron microscopy, and Fourier transform infrared spectroscopy. The average sizes of the CaCO(3) particles and PMMA capsules were 3.8±0.6 and 4.0±0.6 ?m, respectively. A copolymer consisting of MMA and rhodamine B-bearing MMA was also used to prepare microcapsules for fluorescent microscopy observations. Fluorescein isothiocyanate-labeled bovine serum albumin was enclosed in the PMMA microcapsules and its release properties were studied. PMID:22967350

  6. The use of thermovision technique to estimate the properties of highly filled polyolefins composites with calcium carbonate

    NASA Astrophysics Data System (ADS)

    Jakubowska, Paulina; Klozinski, Arkadiusz

    2015-05-01

    The aim of this work was to determine the possibility of thermovision technique usage for estimating thermal properties of ternary highly filled composites (PE-MD/iPP/CaCO3) and polymer blends (PE-MD/iPP) during mechanical measurements. The ternary, polyolefin based composites that contained the following amounts of calcium carbonate: 48, 56, and 64 wt % were studied. All materials were applying under tensile cyclic loads (x1, x5, x10, x20, x50, x100, x500, x1000). Simultaneously, a fully radiometric recording, using a TESTO infrared camera, was created. After the fatigue process, all samples were subjected to static tensile test and the maximum temperature at break was also recorded. The temperature values were analyzed in a function of cyclic loads and the filler content. The changes in the Young's modulus values were also investigated.

  7. Single crystals of DPPH grown from diethyl ether and carbon disulfide solutions - Crystal structures, IR, EPR and magnetization studies

    E-print Network

    Zilic, Dijana; Juric, Marijana; Molcanov, Kresimir; Rakvin, Boris; Planinic, Pavica; Zadro, Kreso; 10.1016/j.jmr.2010.08.005

    2012-01-01

    Single crystals of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) obtained from diethyl ether (ether) and carbon disulfide (CS2) were characterized by the X-ray diffraction, IR, EPR and SQUID magnetization techniques. The X-ray structural analysis and IR spectra showed that the DPPH form crystallized from ether (DPPH1) is solvent free, whereas that one obtained from CS2 (DPPH2) is a solvate of the composition 4DPPH.CS2. Principal values of the g-tensor were estimated by the X-band EPR spectroscopy at room and low (10 K) temperatures. Magnetization studies revealed the presence of antiferromagnetically coupled dimers in both types of crystals. However, the way of dimerization as well as the strength of exchange couplings are different in the two DPPH samples, which is in accord with their crystal structures. The obtained results improved parameters accuracy and enabled better understanding of properties of DPPH as a standard sample in the EPR spectrometry.

  8. Single crystals of DPPH grown from diethyl ether and carbon disulfide solutions - Crystal structures, IR, EPR and magnetization studies

    NASA Astrophysics Data System (ADS)

    Žili?, Dijana; Paji?, Damir; Juri?, Marijana; Mol?anov, Krešimir; Rakvin, Boris; Planini?, Pavica; Zadro, Krešo

    2010-11-01

    Single crystals of the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) obtained from diethyl ether (ether) and carbon disulfide (CS2) were characterized by the X-ray diffraction, IR, EPR and SQUID magnetization techniques. The X-ray structural analysis and IR spectra showed that the DPPH form crystallized from ether (DPPH1) is solvent free, whereas that one obtained from CS2 (DPPH2) is a solvate of the composition 4DPPH·CS2. Principal values of the g-tensor were estimated by the X-band EPR spectroscopy at room and low (10 K) temperatures. Magnetization studies revealed the presence of antiferromagnetically coupled dimers in both types of crystals. However, the way of dimerization as well as the strength of exchange couplings are different in the two DPPH samples, which is in accord with their crystal structures. The obtained results improved parameters accuracy and enabled better understanding of properties of DPPH as a standard sample in the EPR spectrometry.

  9. Effects of brine chemistry and polymorphism on clumped isotopes revealed by laboratory precipitation of mono- and multiphase calcium carbonates

    NASA Astrophysics Data System (ADS)

    Kluge, Tobias; John, Cédric M.

    2015-07-01

    Carbonate clumped isotopes are applied to an increasing number of geological archives to address a wide range of Earth science questions. However, the effect of changes in salinity on the carbonate clumped isotope technique has not been investigated experimentally yet. In particular, evaporated sea water and diagenetic fluids differ substantially from solutions used to calibrate the clumped isotope thermometer as they exhibit high ionic concentrations of e.g., Na+, Ca2+, Mg2+, and Cl-. High ionic concentrations are known to have an impact on ?18O values, and could potentially impact the successful application of clumped isotopes to the reconstruction of diagenetic processes, including precipitation temperatures and the origin of the diagenetic fluid. In order to address the potential influence of salt ions on the clumped isotope ?47 value we precipitated CaCO3 minerals (calcite, aragonite and vaterite), hydromagnesite and mixtures of these minerals in the laboratory from solutions containing different salt ions (Na+, Ca2+, Mg2+, Cl-) at various concentrations and temperatures. The precipitation of some mineralogies was restricted to solutions with specific ionic concentrations, limiting direct comparability. NaCl-rich solutions mostly led to vaterite formation. In control experiments CaCO3 minerals (calcite and aragonite) were precipitated from a CaCO3 supersaturated solution without addition of any other ions. Our results show that calcium carbonates precipitated from high NaCl concentrations yield ?47 values identical to our NaCl-free control solution. Although addition of Mg led to the formation of hydromagnesite, it also follows the same ?47-T calibration as calcite. In contrast, ?47 values increase together with increased CaCl2 concentrations, and deviate by a few 0.01‰ from expected equilibrium values. Overall, clumped isotope values of CaCO3 minerals precipitated between 23 °C and 91 °C (with and without NaCl addition) follow a line with a slope close to results from statistical thermodynamics. We conclude for calcium carbonate and hydromagnesite that the combined effect of salt ion concentration, acid fractionation and polymorphism is negligible for Cl- and Na+ with respect to clumped isotope geochemistry, but that offsets are possible in brines containing high concentrations of CaCl2.

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

    NASA Astrophysics Data System (ADS)

    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 ?13C 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 pH 9.0, calcite is isotopically indistinguishable from, or perhaps slightly lighter than, DIC. We will present data from additional high-pH experiments and discuss the results in the context of recently developed ion-by-ion growth models for calcite.

  11. [Study on IR of interaction of three modified-starchs and crystallization of calcium carbonate].

    PubMed

    Ding, Wei-Jia; An, Ying-Ge; Yang, Lin; Liao, Zhao-Jiang; Zhang, Xiu-Ying; Jiang, Kai

    2005-05-01

    Three types of CaCO3 can be synthesized through biomimetic synthesis. In the present work, carboxymethyl-starch, etherified-starch, and phosphate-starch, used as organic matrices, were studied by FTIR. The result shows that the intensity of C-O peaks of the three modified-starchs changed. In addition, the intensity of C-O peaks was weakened or vanished obviously with the increase in time. The action mechanism of the modified-starchs and CaCO3 was briefly discussed. PMID:16128067

  12. The Effect Of The Position And Configuration Of Carbon–Carbon Double Bonds On The Mesomorphism Of Thermotropic, Non-Amphiphilic Liquid Crystals

    Microsoft Academic Search

    S. M. Kelly

    1996-01-01

    The influence on their mesomorphic behaviour of introducing a carbon-carbon double bond into the chain, central linkage and alicyclic rings in the core of nematic and smectic liquid crystals (LCs) is discussed. Mesogens incorporating a trans-carbon-carbon double bond conjugated with an aromatic ring exhibit high mesophase-isotropic transition temperatures (Tc). However, they are photo-sensitive and can convert to the non-linear, non-mesogenic

  13. Conversion of alkali metal sulfate to the carbonate

    DOEpatents

    Sheth, Atul C. (Woodridge, IL)

    1982-01-01

    A process for converting potassium sulfate to potassium carbonate in which a mixture of potassium sulfate and calcium oxide are reacted at a temperature in the range of between about 700.degree. C. and about 800.degree. C. with a gaseous mixture having a minor amount of hydrogen and/or carbon monoxide in a diluent with the calcium oxide being present in an amount not greater than about 20 percent by weight of the potassium sulfate to produce an aqueous mixture of potassium sulfide, potassium bisulfide, potassium hydroxide and calcium sulfide and a gaseous mixture of steam and hydrogen sulfide. The potassium and calcium salts are quenched to produce an aqueous slurry of soluble potassium salts and insoluble calcium salts and a gaseous mixture of steam and hydrogen sulfide. The insoluble calcium salts are then separated from the aqueous solution of soluble potassium salts. The calcium salts are dried to produce calcium sulfide, calcium bisulfide and steam, and then, the calcium sulfide and calcium bisulfide are converted to the oxide and recycled. The soluble potassium salts are carbonated to produce potassium carbonate which is concentrated and the precipitated crystals separated. The sulfur-containing compounds are further treated.

  14. Nanoamorphous carbon-based photonic crystal infrared emitters

    DOEpatents

    Norwood, Robert A. (Tucson, AZ); Skotheim, Terje (Tucson, AZ)

    2011-12-13

    Provided is a tunable radiation emitting structure comprising: a nanoamorphous carbon structure having a plurality of relief features provided in a periodic spatial configuration, wherein the relief features are separated from each other by adjacent recessed features, and wherein the nanoamorphous carbon comprises a total of from 0 to 60 atomic percent of one or more dopants of the dopant group consisting of: transition metals, lanthanoids, electro-conductive carbides, silicides and nitrides. In one embodiment, a dopant is selected from the group consisting of: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Tc, Ru, Rh, Pd, Ag, Cd, La and other lanthanides, Hf, Ta, W, Rh, Os, Ir, Pt, Au, and Hg. In one embodiment, a dopant is selected from the group consisting of: electro-conductive carbides (like Mo.sub.2C), silicides (like MoSi.sub.2) and nitrides (like TiN).

  15. Chitin-Silk Fibroin Interactions: Relevance to Calcium Carbonate Formation in Invertebrates

    Microsoft Academic Search

    G. Falini; S. Weiner; L. Addadi

    2003-01-01

    In mineralized tissues chitin is almost always associated with proteins, many of which are known to have chitin recognition consensus sequences. It has been observed in some mollusk shells that there is a well-defined spatial relation between the crystallographic axes of the crystals and the chitin fibrils. This implies that the chitin functions directly or indirectly as a template for

  16. The crystallization of tough thermoplastic resins in the presence of carbon fibers

    NASA Technical Reports Server (NTRS)

    Theil, Michael H.

    1988-01-01

    The presence of carbon fibers increased the crystallization rates of both PEEK and PPS thermoplastic polymers. The effect was most pronounced at higher crystallization temperatures. Isothermal crystallization rates were analyzed by applying classical phenomenological nucleation theory. Unusually high values of the so-called Avrami exponent were found for neat PEEK. Isothermal crystallization of PEEK and PPS polymers produced crystalline samples having a wide variety of melting temperatures. The melting as observed by differential scanning calorimetry occurred as dual endotherms which were called primary (higher temperature) and secondary melting peaks. Each primary peak accounted for most of the crystallinity present. The secondary peaks represented the melting of crystallites formed later than those attributable to the primary endotherms. The presence of carbon fibers increased the thermal stability of both PEEK and PPS crystallites as manifested by higher temperatures for the primary melting peaks. This may be attributable to increased crystallite size, greater crystallite perfection, and/or favorable modification of the crystallite interface. Over the range studied, crystallization temperature strongly influenced the positions of the secondary peaks but not the primary peaks.

  17. The effects of CeO{sub 2} addition on crystallization behavior and pore size in microporous calcium titanium phosphate glass ceramics

    SciTech Connect

    Soleimani, F., E-mail: F.Soleimani@yahoo.com [Department of Materials Engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of); Rezvani, M., E-mail: M_Rezvani@tabrizu.ac.ir [Department of Materials Engineering, Faculty of Mechanical Engineering, University of Tabriz, Tabriz (Iran, Islamic Republic of)

    2012-06-15

    Highlights: ? We prepare a phosphate glass ceramic in the system of CaO–TiO{sub 2}–P{sub 2}O{sub 5} and add 2 to 6 mol% CeO{sub 2} to it. We determine the optimum percentage of CeO{sub 2} addition. ? We study phase separation, suitable time and temperature for crystallization in the microporous Calcium Titanium Phosphate Glass Ceramics utilizing DTA, SEM and XRD. ? We investigate on pore size utilizing BET and SEM techniques before and after CeO{sub 2} addition. ? CeO{sub 2} increases the pore size in the Calcium Titanium Phosphate Glass Ceramics. -- Abstract: In this research the effect of the addition of CeO{sub 2} to microporous Calcium Titanium Phosphate glass ceramics was studied. Different molar percentages of CeO{sub 2} were added to three samples of a base glass whose composition was P{sub 2}O{sub 5} 30, CaO 45, TiO{sub 2} 25 (mol%). The first sample had 2 mol% CeO{sub 2}, the second sample had 4 mol% CeO{sub 2}, and the third sample had 6 mol% CeO{sub 2}. The fourth sample did not contain any CeO{sub 2}. The glass samples were melted and crystallized to bulk glass ceramics by a conventional method. Differential Thermal Analysis (DTA) was utilized to determine the appropriate nucleation and crystallization temperatures. Among the samples, the DTA curve of the sample which had 2 mol% CeO{sub 2} had the sharpest crystallization peak. Therefore, this sample was chosen to prepare the glass ceramics. Using X-ray Diffraction (XRD) it was found that in all samples ?-Ca{sub 3}(PO{sub 4}){sub 2} and CaTi{sub 4}(PO{sub 4}){sub 6} were the major phases. The ?-Ca{sub 3}(PO{sub 4}){sub 2} phase was dissolved away by soaking the glass ceramics in HCl, leaving a porous skeleton of CaTi{sub 4}(PO{sub 4}){sub 6}. CeO{sub 2} addition increased the glass transition temperature and decreased the crystallization time and temperature. It was shown that CeO{sub 2} addition resulted in an increase in the mean pore diameter while the specific surface area decreased. The median pore diameter and specific surface area were determined as 27 nm and 14 m{sup 2}/g, respectively, for the sample containing 2 mol% CeO{sub 2}.

  18. Probing Ionic Crystals by the Invariom Approach: An Electron Density Study of Guanidinium Chloride and Carbonate.

    PubMed

    Nelyubina, Yulia V; Lyssenko, Konstantin A

    2015-06-26

    A comparative study of two guanidinium salts, chloride and carbonate, is carried out to test the performance of the invariom approach for ionic crystals. Although treating them as formed by isolated ions with no charge transfer between them, the invariom approach provides features of interionic contacts that are amazingly similar to those obtained from conventional charge density analysis of high-resolution X-ray diffraction data, thus emerging as an easy way towards reliable description of chemical bonding peculiarities in ionic crystals. PMID:26015224

  19. Carbon nanotube doped liquid crystal OCB cells: physical and electro-optical properties.

    PubMed

    Lu, Shin-Ying; Chien, Liang-Chy

    2008-08-18

    We report single-wall carbon nanotube (CNT) doped liquid crystal materials which show significant improvement in the response time for optical controlled birefringence (OCB) cells. Four different types of liquid crystals (LCs) were chosen to mix with CNTs and they demonstrated similar results in improving the response time. Experimental results show that the anchoring energy at alignment layers has been changed by CNT doping. CNTs were attracted to the alignment layer and modified the property of the surface. The anchoring enhancement is due to the pi-pi electron stacking between the CNTs, LC molecules and alignment layers. PMID:18711517

  20. Recycling indium from waste liquid crystal display panel by vacuum carbon-reduction.

    PubMed

    He, Yunxia; Ma, En; Xu, Zhenming

    2014-03-15

    This study investigated the recovery of indium from waste liquid crystal display (LCD) panel using vacuum carbon-reduction. First of all, high purity In2O3 was investigated. The results indicated that indium can be reclaimed from In2O3 using vacuum carbon-reduction in thermodynamics and dynamics. The conditions of 1223K, 50wt% carbon addition, 30min, and 1Pa were confirmed as the optimal conditions for pure In2O3 and high purity indium could be selectively recovered on condensing zone. Based on this, the experiment of the recovery of indium from waste LCD power was performed. The best parameters were confirmed as 1223K and 1Pa with 30wt% carbon addition for 30min. The recovery rate of indium from LCD powder could reach to 90wt%. No hazardous materials produced in this process. Therefore, this technique provides the possibility of reutilization of LCD in an environmentally friendly way. PMID:24491442