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1

Study of growth of calcium carbonate crystals on chitosan film  

Microsoft Academic Search

Biomimetic heterogeneous nucleation and growth of calcium carbonate crystals on the chitosan film as the template took place in supersaturated calcium bicarbonate solution. The specimen were characterized by optical microscopy, scanning electron microscopy, X-ray diffraction, attenuated total reflectance infrared spectroscopy. The obtained crystals proved to be calcite in sheets composed of fine crystal particles. Lab results indicated that proper additives

Fengying Zhang; Jie Wang; Zhengchi Hou; Ming Yu; Leidong Xie

2006-01-01

2

Growth of calcium carbonate crystal imitating stalagmite growth in nature  

Microsoft Academic Search

Calcite crystals were prepared by dropping a saturated calcium carbonate aqueous solution on a substrate. The calcite crystals were grown with a growth rate of approximately 0.7?m\\/day under the condition of aqueous temperature of 2°C, aqueous concentration of 0.006mol\\/l, and substrate temperature of 40°C. When the calcite substrate was used, calcite crystals were grown epitaxially. Na2CO3 and CaCl2 aqueous solutions

H. Miyazaki; M. Mizutani; T. Yamashita; H. Aoyama; H. Seue; T. Ota

2006-01-01

3

Synthesis of Calcium Carbonate Crystals Using Cells of Plant Leaves  

Microsoft Academic Search

In this paper, calcium carbonate (CaCO3) crystals were synthesized by using the leaves of the plant Scindapsus aureum. The resultant CaCO3 crystals were characterized by scanning electron microscopy and electron diffraction. The biomolecules of Scindapsus aureum was confirmed by using UV-vis analysis. The results showed that the elongated rhombohedral calcite crystals were produced in the cells of Scindapsus aureum leaves.

Long Chen; Xiaoping Fang; Shineng Zhang; Xiayu Wu; Jingjing Wu; Qinqin Cui; Liqi Yu; Qingqing Wang

2010-01-01

4

Water-soluble terpolymer-mediated calcium carbonate crystal modification.  

PubMed

The structure of the polymeric substrate plays an important role in the nucleation of calcium carbonate crystals. In this study a synthetic water-soluble poly(acrylamide-co-2-acrylamido-2-methyl-1-propane sodium sufonate-co-n-vinyl pyrrolidone) was found to be a substrate favoring the nucleation of polymorphs of calcium carbonate crystals under specific experimental conditions. Morphological characterization of the polymorphs was done using atomic force microscopy, scanning electron microscopy, energy dispersive spectroscopy, FTIR analysis, and X-ray diffraction. If calcium carbonate is precipitated in the presence of terpolymer, a remarkable increase in nucleation density (number of crystals per unit area) was observed. Stacked crystals of rhombohedral morphology that formed may be due to the presence of sodium sulfonate groups on the terpolymer. However, in the presence of poly-L-aspartic acid, almost all crystals are hollow and have needlelike or plate like morphology was formed. This change in calcium carbonate morphology can be explained by the variation of the polymer conformation, if poly- L-aspartic acid is present. PMID:15875838

Pai, Ranjith Krishna; Hild, Sabine; Ziegler, Andreas; Marti, Othmar

2004-04-13

5

Formation of calcium carbonate crystals by moderately halophilic bacteria  

Microsoft Academic Search

Production of calcium carbonate by moderately halophilic bacteria was investigated. The crystalline structures were identified by x?ray diffraction analysis. The results showed that the CaCO3 formation was a general phenomenon for moderately halophilic bacteria and the different salt concentrations in the growth medium were an important factor in the characteristics of crystals formed.

A. del Moral; E. Roldan; J. Navarro

1987-01-01

6

Synthesis of calcium carbonate vaterite crystals and their effect on stabilization of suspension polymerization of MMA  

Microsoft Academic Search

Spherical calcium carbonate vaterite crystals were synthesized and the effect of them on stabilization of suspension polymerization of methyl methacrylate was investigated. Suspension polymerization of methyl methacrylate could be stabilized with calcium carbonate vaterite crystals and sodium dodecylbenzene sulfonate of the concentrations from 25 to 100ppm. Poly(methyl methacrylate) beads coated with spherical calcium carbonate vaterite crystals were prepared. With an

Kiyomi Fuchigami; Yoshinari Taguchi; Masato Tanaka

2009-01-01

7

Alginate hydrogel-mediated crystallization of calcium carbonate  

SciTech Connect

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.

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

8

Calcium carbonate crystals promote calcium oxalate crystallization by heterogeneous or epitaxial nucleation: Possible involvement in the control of urinary lithogenesis  

Microsoft Academic Search

A large proportion of urinary stones have calcium oxalate (CaOx) as the major mineral phase. In these stones, CaOx is generally\\u000a associated with minor amounts of other calcium salts. Several reports showing the presence of calcium carbonate (CaCO3) and calcium phosphate in renal stones suggested that crystals of those salts might be present in the early steps of stone\\u000a formation.

S. Geider; B. Dussol; S. Nitsche; S. Veesler; P. Berth’ezène; P. Dupuy; J. P. Astier; R. Boistelle; Y. Berland; J. C. Dagorn; J. M. Verdier

1996-01-01

9

Synthesis of calcium carbonate crystals by using bacteria  

Microsoft Academic Search

The synthesis of calcium carbonate (CaCO3) crystals in the presence of bacteria Escherichia coliform (E. coli) was investigated. The products were characterized by scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray powder diffractometry. The results showed that, calcite spherical superstructures constructed from small rhombohedral building units were formed with bacteria, and the particles are much larger than those formed

Long Chen; Hui Zhang; Zhaopeng Qi; Wu Yao; Jing-Jian Wan; Ming Shao; Cun-Chao Zhang

2012-01-01

10

Egg-white-mediated crystallization of calcium carbonate  

NASA Astrophysics Data System (ADS)

In this paper, shape-controlled crystallization and self-assembly of CaCO3 hierarchical architectures has been successfully synthesized via the gas diffusion method in egg white solution. Stepwise growth and assembly of CaCO3 nanoparticles has been observed from transition of an amorphous CaCO3 to the crystallization and stabilization of platelet-like nanoparticles and eventually, the wool sphere-like CaCO3 hierarchical architectures assembling of nanoparticles. The proteins binding on nanoparticle surfaces proved to regulate the growth of nanoparticles and subsequent assembly into hierarchical superstructures via electrostatic and dipole interactions. The samples were characterized by scanning electron microscopy (SEM), powder X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and nano mechanical Tester. The measured average elastic modulus and the hardness of calcium carbonate hybrid materials were 5.32 GPa and 0.1886 GPa by the nano-indenter test, respectively.

Zheng, Liang; Hu, Yanli; Ma, Yongjun; Zhou, Yong; Nie, Fude; Liu, Xun; Pei, Chonghua

2012-12-01

11

Crystal Structure of Calcium-Deficient Carbonated Hydroxyapatite. Thermal Decomposition  

Microsoft Academic Search

Full Rietveld refinement of the crystal structure of the synthetic calcium-deficient carbonated apatite Ca13.40[Ca25.90 (NH4)0.10][(PO4)4.95(CO3)1.05(H2O)0.30][(OH)1.65(H2O)0.45] (space group P63\\/m; a=9.437(1), c=6.888(1) Å; Z=1; Rwp=5.23%) was carried out using X-ray powder diffraction data. The use of the model with the split position of O3 atom made it possible to find two orientations of CO3 triangles sharing one of their edges. They occupy

T. I. Ivanova; O. V. Frank-Kamenetskaya; A. B. Kol'tsov; V. L. Ugolkov

2001-01-01

12

The inhibition of calcium carbonate crystal growth by the cysteine-rich Mdm2 peptide  

Microsoft Academic Search

The crystal growth of calcite, the most stable calcium carbonate polymorph, in the presence of the cysteine-rich Mdm2 peptide (containing 48 amino acids in the ring finger configuration), has been investigated by the constant composition technique. Crystallization took place exclusively on well-characterized calcite crystals in solutions supersaturated only with respect to this calcium carbonate salt. The kinetic results indicated a

E. Dalas; A. Chalias; D. Gatos; K. Barlos

2006-01-01

13

Morphological control of calcium carbonate crystals by polyvinylpyrrolidone and sodium dodecyl benzene sulfonate  

Microsoft Academic Search

The crystallization of calcium carbonate was conducted by the reaction of sodium carbonate with calcium chloride in the presence of polyvinylpyrrolidone (PVP), sodium dodecylbenzene sulfonate (SDBS), or the mixture of PVP and SDBS, respectively. The morphology and polymorphism of these CaCO3 crystals were characterized with scanning electron microscopy (SEM) and powder X-ray diffraction (XRD). The results showed that the organic

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

2004-01-01

14

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

Microsoft Academic Search

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,

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

2008-01-01

15

Influence of segmented copolymers on the crystallization and aggregation of calcium carbonate  

Microsoft Academic Search

The carboxyl group interacts strongly with calcium ions, indicating that the hydrophilic polymers with the functional groups of –COOH should exert a great impact on the crystal design of calcium carbonate (CaCO3). In this paper, three copolymers were synthesized and subsequently used as additives to control the crystallization and aggregation behaviors of CaCO3. The results show that: (1) the hard-segmented

Hao Wei; Qiang Shen; Haihua Wang; Yanyan Gao; Ying Zhao; Duanfu Xu; Dujin Wang

2007-01-01

16

Effect of Taylor vortices on calcium carbonate crystallization by gas–liquid reaction  

Microsoft Academic Search

The effects of Taylor vortices on the mean size, size distribution, and morphology of calcium carbonate crystallized by the reaction of gaseous carbon dioxide and aqueous calcium hydroxide were experimentally investigated in a Couette–Taylor reactor. Via the absorption of CO2 gas into pure water, the mass transfer coefficient of CO2 at the gas–liquid interface was measured relative to the rotating

Sung Hoon Kang; Sang Goo Lee; Wang Mo Jung; Min Chan Kim; Woo-Sik Kim; Chang Kyun Choi; Robert S Feigelson

2003-01-01

17

Single Crystal Growth of Calcium Carbonate (Synthetic Calcite). Phase 1, Final Report.  

National Technical Information Service (NTIS)

The feasibility of calcite single crystal growth from a Li2CO3 solvent using the Heat Exchanger Method (HEM) was demonstrated. It was observed that a CO2 atmosphere is necessary to prevent decomposition of calcium carbonate (CaCO3). Under flowing CO2 at 1...

F. Schmid

1987-01-01

18

The influence of polyaspartate additive on the growth and morphology of calcium carbonate crystals  

Microsoft Academic Search

The addition of low levels of polyaspartate to a supersaturated calcium carbonate (CaCOsb3) solution leads to unusual morphologies in the inorganic phase. Spherulitic vaterite aggregates with helical protrusions, and distorted calcite crystals that contain spiral pits, have been produced. The helical particles are coated with an inorganic membrane that appears to be responsible for the helical twist. The polymer also

Laurie Anne Gower

1997-01-01

19

Calcium carbonate crystallization controlled by functional groups: A mini-review  

NASA Astrophysics Data System (ADS)

Various functional groups have been suggested to play essential roles on biomineralization of calcium carbonate (CaCO3) in natural system. 2D and 3D models of regularly arranged functional groups have been established to investigate their effect on CaCO3 crystallization. This mini-review summarizes the recent progress and the future development is prospected.

Deng, Hua; Shen, Xing-Can; Wang, Xiu-Mei; Du, Chang

2013-03-01

20

Growth of calcium carbonate crystals on the European Retrievable Carrier flight  

Microsoft Academic Search

On the Solution Growth Facility (SGF) of the European Retrievable Carrier (EURECA), clear, colorless crystals of calcium carbonate up to 3 mm long have been grown from aqueous solution without the use of a gel. This is a much improved result compared with previous solution growth of CaCO3.

K. F. Nielsen; M. D. Lind; A. Lindegaard-Andersen; L. Gerward; L. Groth-Andersen

1995-01-01

21

Kinetic Inhibition of Calcium Carbonate Crystal Growth in the Presence of Natural and Synthetic Organic Inhibitors  

Microsoft Academic Search

Addition of carboxylate-containing polymeric materials to a metastable supersaturated calcium carbonate solution greatly reduced\\u000a calcite crystal growth rates at constant supersaturation and pH = 8.5. Calcite crystallization rates were decreased to half\\u000a their value in pure solutions by a tannic acid concentration of about 0.3 ppm (parts per million); a fulvic acid concentration\\u000a of about 0.2 ppm; and a poly(acrylic

Zahid Amjad; Jeff Pugh; Michael M. Reddy

22

Polymorph and morphology of calcium carbonate crystals induced by proteins extracted from mollusk shell  

Microsoft Academic Search

The function of biomacromolecules during biomineralization was studied by simulating the nucleation and growth of calcium carbonates in vitro. The synthetic crystals nucleated and grew on different organic (EDTA-insoluble proteins) and inorganic (silicon) matrices with EDTA-soluble proteins extracted from mollusk shells. The polymorph and morphology of the crystals were investigated using scanning electron microscope (SEM), X-ray diffraction (XRD) and transmission

Q. L Feng; G Pu; Y Pei; F. Z Cui; H. D Li; T. N Kim

2000-01-01

23

Stable Prenucleation Calcium Carbonate Clusters  

Microsoft Academic Search

Calcium carbonate forms scales, geological deposits, biominerals, and ocean sediments. Huge amounts of carbon dioxide are retained as carbonate ions, and calcium ions represent a major contribution to water hardness. Despite its relevance, little is known about the precipitation mechanism of calcium carbonate, and specified complex crystal structures challenge the classical view on nucleation considering the formation of metastable ion

Denis Gebauer; Antje Völkel; Helmut Cölfen

2008-01-01

24

Effect of Hydraulic Activity on Crystallization of Precipitated Calcium Carbonate (PCC) for Eco-Friendly Paper  

PubMed Central

Wt% of aragonite, a CaCO3 polymorph, increased with higher hydraulic activity (°C) of limestone in precipitated calcium carbonate (PCC) from the lime-soda process (Ca(OH)2-NaOH-Na2CO3). Only calcite, the most stable polymorph, was crystallized at hydraulic activity under 10 °C, whereas aragonite also started to crystallize over 10 °C. The crystallization of PCC is more dependent on the hydraulic activity of limestone than CaO content, a factor commonly used to classify limestone ores according to quality. The results could be effectively applied to the determination of polymorphs in synthetic PCC for eco-friendly paper manufacture.

Kim, Jung-Ah; Han, Gi-Chun; Lim, Mihee; You, Kwang-Suk; Ryu, Miyoung; Ahn, Ji-Whan; Fujita, Toyohisa; Kim, Hwan

2009-01-01

25

Results of the TTF-TCNA and the Calcium Carbonate Crystallization on the Long Duration Exposure Facility.  

National Technical Information Service (NTIS)

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 progr...

K. F. Nielsen M. D. Lind

1992-01-01

26

The preparation of calcium carbonate crystals regulated by mixed cationic\\/cationic surfactants  

Microsoft Academic Search

Cationic surfactants, didodecyldimethylammonium bromide (DDAB), 1-dodecyl-3-methylimidazolium bromide ([C12mim]Br) and DDAB\\/[C12mim]Br mixture were used to induce the formation of calcium carbonate (CaCO3) crystals at ambient temperature. The obtained CaCO3 particles were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD) and thermogravimetric analysis (TGA). The morphologies of CaCO3 crystals changed from laminated cube to sphericity and string

Yingyuan Zhao; Shuxia Li; Li Yu; Yonghui Liu; Xiaoqing Wang; Jingjing Jiao

2011-01-01

27

Reactions of sulfur dioxide on calcium carbonate single crystal and particle surfaces at the adsorbed water carbonate interface  

Microsoft Academic Search

Sulfur dioxide reactions with calcium carbonate interfaces at 296 K in the presence and absence of adsorbed water result in the formation of adsorbed sulfite and sulfate. The extent of reaction is significantly enhanced, approximately five- to ten-fold for particulate and single crystal CaCO3 (calcite), respectively, in the presence of adsorbed water between 30 and 85% RH. Atomic force microscopy

Jonas Baltrusaitis; Courtney R. Usher; Vicki H. Grassian

2007-01-01

28

Effect of hydraulic activity on crystallization of precipitated calcium carbonate (PCC) for eco-friendly paper.  

PubMed

Wt% of aragonite, a CaCO(3) polymorph, increased with higher hydraulic activity ( degrees C) of limestone in precipitated calcium carbonate (PCC) from the lime-soda process (Ca(OH)(2)-NaOH-Na(2)CO(3)). Only calcite, the most stable polymorph, was crystallized at hydraulic activity under 10 degrees C, whereas aragonite also started to crystallize over 10 degrees C. The crystallization of PCC is more dependent on the hydraulic activity of limestone than CaO content, a factor commonly used to classify limestone ores according to quality. The results could be effectively applied to the determination of polymorphs in synthetic PCC for eco-friendly paper manufacture. PMID:20087470

Kim, Jung-Ah; Han, Gi-Chun; Lim, Mihee; You, Kwang-Suk; Ryu, Miyoung; Ahn, Ji-Whan; Fujita, Toyohisa; Kim, Hwan

2009-11-11

29

Transformation and crystallization energetics of synthetic and biogenic amorphous calcium carbonate  

PubMed Central

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

Radha, A. V.; Forbes, Tori Z.; Killian, Christopher E.; Gilbert, P. U. P. A.; Navrotsky, Alexandra

2010-01-01

30

XAFS study on the trace amounts of ytterbium ions incorporated in calcium carbonate crystal  

Microsoft Academic Search

We measured XAFS spectra of trace amount of ytterbium (Yb) incorporated in calcite, a stable phase of calcium carbonate. Calcium carbonate was precipitated from a mixed solution of CaCl2 aq and NaHCO3 aq with a given amount of YbCl3. Concentrations of Yb were 5?mol kg?1 in the starting solutions and Yb\\/Ca molar ratio in the precipitated calcium carbonate was 1.2?10?3.

H. Tsuno; H. Kagi; Y. Takahashi; T. Akagi; M. Nomura

2005-01-01

31

Calcium carbonate overdose  

MedlinePLUS

Tums overdose; Calcium overdose ... Calcium ... Products containing calcium carbonate, including Certain antacids (Tums, Chooz) Certain mineral supplements Certain hand lotions Certain vitamin and mineral supplements Note: ...

32

The constant composition method for crystallization of calcium carbonate at constant supersaturation  

NASA Astrophysics Data System (ADS)

The exact control of supersaturation is of great importance when studying the formation of crystalline and amorphous matter. The constant composition method is suitable for the study of crystallization processes at constant supersaturation by controlled addition of titrants to a crystallizer to maintain constant pH. Not all aspects necessary for successful operation of this method are obvious from the existing literature, and the method is often used in an incorrect way. The focus of the present work is to highlight pitfalls associated with the constant composition method. The method is assessed and described in detail to show that even if the solution pH is kept constant, the supersaturation may change. First and foremost, it is illustrated how crucial it is to use a chemical composition of the titrant solutions which is in accordance with the initially prepared aqueous solution. General rules are presented for carbonates as to how the composition of the titrant solutions should be calculated based on total alkalinity in order to maintain constant supersaturation. This has - to the knowledge of the authors - not been shown before. Then, it is shown how exchange of carbon dioxide with the atmosphere corrupts the constancy of the supersaturation level during an experiment. Third, it is pointed out that the ionic strength should be kept constant throughout crystallization experiments since a change in ionic strength alters the activity of the ions in solution. Here, the determination of the thermodynamic driving force (supersaturation) is explained based on the relevant chemical equilibria, total alkalinity and calculation of the activity coefficients. The calculations are presented for the least stable polymorph of calcium carbonate, vaterite, but can easily be extended to the other polymorphs and other pH-dependent systems allowing for crystallization studies at low and maintained supersaturation levels typical of naturally occurring processes in geology and biomineralization, as well as formation of mineral scales in industry.

Beck, R.; Seiersten, M.; Andreassen, J.-P.

2013-10-01

33

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

PubMed

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

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

2010-10-11

34

Peptide induced crystallization of calcium carbonate on wrinkle patterned substrate: implications for chitin formation in molluscs.  

PubMed

We here present the nucleation and growth of calcium carbonate under the influence of synthetic peptides on topographically patterned poly(dimethylsiloxane) (PDMS) substrates, which have a controlled density of defects between the wrinkles. Experiments with two lysine-rich peptides derived from the extracellular conserved domain E22 of the mollusc chitin synthase Ar-CS1, AKKKKKAS (AS8) and EEKKKKKES (ES9) on these substrates showed their influence on the calcium carbonate morphology. A transition from polycrystalline composites to single crystalline phases was achieved with the peptide AS8 by changing the pH of the buffer solution. We analyzed three different pH values as previous experiments showed that E22 interacts with aragonite biominerals more strongly at pH 7.75 than at pH 9.0. At any given pH, crystals appeared in characteristic morphologies only on wrinkled substrates, and did not occur on the flat, wrinkle-free PDMS substrate. These results suggest that these wrinkled substrates could be useful for controlling the morphologies of other mineral/peptide and mineral/protein composites. In nature, these templates are formed enzymatically by glycosyltransferases containing pH-sensitive epitopes, similar to the peptides investigated here. Our in vitro test systems may be useful to gain understanding of the formation of distinct 3D morphologies in mollusc shells in response to local pH shifts during the mineralization of organic templates. PMID:23736692

Ghatak, Anindita Sengupta; Koch, Marcus; Guth, Christina; Weiss, Ingrid M

2013-06-04

35

Study in Calcium Carbonate Crystal Formation at the Air/Water Interface in the Presence of a Magnetic Field.  

National Technical Information Service (NTIS)

Calcium carbonate aggregates as calcite on the surface of a Ca(OH)2 solution exposed to air. We grew these crystals on solution of initial concentration 0.30 mg/L. Our studies show static magnetic field to have no effect on the fractal dimension of these ...

T. M. Paschke

2001-01-01

36

Incorporation of strontium into the calcium carbonate crystals of the endolymphatic sac in the tree frog (Hyla arborea japonica).  

PubMed

Tree frogs were loaded with strontium chloride (SrCl2). The incorporation of strontium metal into the calcium carbonate (CaCO3) crystals located both in the inner ear and in the endolymphatic sac was studied by x-ray microanalysis (XMA) and scanning electron microscopy (SEM). In the inner ear, strontium was not recognized except for traces in a few crystals. When observed by SEM, these crystals had a faceted body and two pointed ends with rather smooth surfaces. However, in the endolymphatic sac, which greatly expands into the spinal canal, strontium was clearly present at every surface of all crystals. Careful examinations by point and line XMA revealed that strontium x-ray counts were highest at the pointed ends and decreased sharply and then gradually toward the equator of the crystals. SEM observations revealed that the crystals in the endolymphatic sac always had rough and irregular surfaces regardless of their shapes and sizes. Calcium was always found in crystals of both organs. Except for calcium and strontium, other elements including sodium and heavier elements were negligible in XMA. These findings suggest that strontium is incorporated into the crystals only in the endolymphatic sac, and the rough-surfaced covering of these crystals reflects newly deposited strontium salt. It seems to indicate that these crystals grow predominantly by accretion. PMID:3619090

Kawamata, S

1987-06-01

37

Influence of initial pH on the precipitation and crystal morphology of calcium carbonate induced by microbial carbonic anhydrase.  

PubMed

The dynamics of calcium carbonate (CaCO(3)) precipitation induced by microbial intracellular or extracellular carbonic anhydrase (CA) at initial pH 6.0, 6.5, 7.0 and 8.0 were investigated through the gaseous diffusion method. The results indicated that both the intracellular and extracellular CA could promote CaCO(3) precipitation. The Ca(2+) ions in the enzymatic systems at initial pH 8.0 were completely deposited at 48 h, which were respectively 21 h, 15 h and 14 h earlier compared with that at initial pH 6.0, pH 6.5 and pH 7.0, indicating that higher pH favored CaCO(3) precipitation in the experimental pH range, and was beneficial to the catalytic action of microbial CA on CaCO(3) precipitation. In addition, XRD analysis indicated that the CaCO(3) precipitates were mainly calcite crystals in the presence of microbial CA. With increasing deposition time, the crystals gradually changed from prism shape to pyramid-like or irregular polyhedral shape based on FESEM analysis. PMID:23006567

Li, Wei; Chen, Wei-Shan; Zhou, Peng-Peng; Cao, Long; Yu, Long-Jiang

2012-09-03

38

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

Microsoft Academic Search

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

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

1990-01-01

39

Results of the TTF-TCNA- and the Calcium Carbonate-Crystallization on the Long Duration Exposure Facility (Abstract oNly).  

National Technical Information Service (NTIS)

Experiment AO139A on the Long Duration Exposure Facility (LDEF) carried four large containers into orbit for five years with crystal growth solutions for lead sulfide, calcium carbonate, and tetra thiafulvalene- tetra cyanoquino methane (TTF-TCNQ). The LD...

K. F. Nielsen M. D. Lind

1991-01-01

40

A novel approach to study the dynamic process of calcium carbonate crystal growth by microcalorimetric method  

Microsoft Academic Search

Through microcalorimetric analysis of the precipitation process of CaCO3 in solutions, it is revealed that amorphous calcium carbonate (ACC) forms at the initial stage as a transient phase and finally transforms into crystalline phase. Due to the lowest dissolvability of calcite compares with other polymorphs, the transformation from the metastable phase to calcite is an endothermic process in this research.

Peng Wan; Hua Tong; Zhihong Zhu; Xinyu Shen; Juan Yan; Jiming Hu

2007-01-01

41

Effects of calcium preloading on the growth of calcium carbonate crystals in the endolymphatic sac of the tree frog, Hyla arbores japonica  

Microsoft Academic Search

Tree frogs, either with or without calcium chloride preloading, were maintained in a 0.8% strontium chloride solution for 1 week, then studied by X-ray microanalysis and scanning electron microscopy to determine the distribution of incorporated strontium in the endolymphatic crystals. In the absence of calcium preloading, strontium was detected on every surface of all the crystals, but after calcium preloading

Seiichi Kawamata

1988-01-01

42

Effect of precipitation conditions on the morphology of calcium carbonate: quantification of crystal shapes using image analysis  

Microsoft Academic Search

Extra-pure calcium carbonate was obtained in the laboratory by carbonation of a solution of calcium nitrate and monoethanolamine with carbon(IV) oxide under various operating conditions. The particle size and shape of the samples obtained were characterized by image analysis. The results show that the method of quantitative morphological characterization using defined shape descriptors enables us to get a better insight

M. Vu?ak; M. N. Pons; J. Peri?; H. Vivier

1998-01-01

43

21 CFR 184.1191 - Calcium carbonate.  

Code of Federal Regulations, 2013 CFR

...As a byproduct in the âLime soda processâ; (2) By precipitation of calcium carbonate from calcium hydroxide in the âCarbonation processâ; or (3) By precipitation of calcium carbonate from calcium chloride in the âCalcium...

2013-04-01

44

Investigation of scale inhibition mechanisms based on the effect of scale inhibitor on calcium carbonate crystal forms  

Microsoft Academic Search

To probe the scale inhibition mechanisms, calcium carbonate scale occurring before and after the addition of scale inhibitors\\u000a was collected. The results from scale SEM confirm that, without scale inhibitor, calcium carbonate scale shows rhombohedron\\u000a and hexagon, which are the characteristic feathers of calcite. After addition of inhibitors, morphology of scale is changed,\\u000a and the more efficient the scale inhibitor

GuiCai Zhang; JiJiang Ge; MingQin Sun; BinLin Pan; Tao Mao; ZhaoZheng Song

2007-01-01

45

Crystallization and aggregation behaviors of calcium carbonate in the presence of poly(vinylpyrrolidone) and sodium dodecyl sulfate.  

PubMed

An anionic surfactant interacts strongly with a polymer molecule to form a self-assembled structure, due to the attractive force of the hydrophobic association and electrostatic repulsion. In this crystallization medium, the surfactant-stabilized inorganic particles adsorbed on the polymer chains, as well as the bridging effect of polymer molecules, controlled the aggregation behavior of colloidal particles. In this presentation, the spontaneous precipitation of calcium carbonate (CaCO3) was conducted from the aqueous systems containing a water-soluble polymer (poly(vinylpyrrolidone), PVP) and an anionic surfactant (sodium dodecyl sulfate, SDS). When the SDS concentrations were lower than the onset of interaction between PVP and SDS, the precipitated CaCO3 crystals were typically hexahedron-shaped calcite; the increasing SDS concentration caused the morphologies of CaCO3 aggregates to change from the flower-shaped calcite to hollow spherical calcite, then to solid spherical vaterite. These results indicate that the self-organized configurations of the polymer/surfactant supramolecules dominate the morphologies of CaCO3 aggregates, implying that this simple and versatile method expands the morphological investigation of the mineralization process. PMID:16853360

Shen, Qiang; Wei, Hao; Wang, Liancheng; Zhou, Yong; Zhao, Ying; Zhang, Zhiqing; Wang, Dujin; Xu, Guiying; Xu, Duanfu

2005-10-01

46

Crystal size distributions of induced calcium carbonate crystals in polyaspartic acid and Mytilus edulis acidic organic proteins aqueous solutions  

Microsoft Academic Search

Different concentrations of soluble matrix extracts from Mytilus edulis and polyaspartic acid were mixed with CaCl2 aqueous solutions to produce CaCO3 crystallizations under controlled conditions. The obtained crystals were observed at several intervals of time by optical microscopy and scanning electron microscopy (SEM). Image treatment of the SEM images allowed quantifying the crystal size distribution (CSD) in different crystallization conditions.

Josep Roqué; Judit Molera; Màrius Vendrell-Saz; Nativitat Salvadó

2004-01-01

47

Co-Subsistence of Liquid Crystal Droplets and Calcium Carbonate Vaterite Crystals Reveals a Molecular Mechanism of Calcium Preservation in Embryogenesis  

Microsoft Academic Search

The yolk sac equipped with vitelline fluid, plays a crucial role in supplying nourishment to the developing chicken embryo during embryonic and early postnatal development. The absorption and utilization of calcium in embryogenesis has been investigated for years. However, the preservation process of the calcium as it is transported through the chorioallantois membrane during embryogenesis remains largely unknown. In this

Xuehong Xu; MengMeng Xu; Guanliang Cao; Odell Jones; Chuo Zhao; Lianxin Cao; Guifang Yan; Haiping He; Chuyu Zhang

2009-01-01

48

Calcium carbonate biomineralization utilizing a multifunctional ?-sheet peptide template.  

PubMed

We designed a novel multifunctional ?-sheet peptide template for calcium carbonate mineralization. The template self-supplies the mineral source, a carbonate ion, by hydrolysis of urea, and regulates the crystal phase and morphology of the obtained calcium carbonate. PMID:24040653

Murai, Kazuki; Higuchi, Masahiro; Kinoshita, Takatoshi; Nagata, Kenji; Kato, Katsuya

2013-10-01

49

21 CFR 73.1070 - Calcium carbonate.  

Code of Federal Regulations, 2013 CFR

...Specifications. Calcium carbonate shall meet the specifications for precipitated calcium carbonate in the United States Pharmacopeia XX (1980). (c) Uses and restrictions. Calcium carbonate may be safely used in amounts...

2013-04-01

50

Calcium Pyrophosphate Dihydrate, Hydroxyapatite, and Miscellaneous Crystals  

Microsoft Academic Search

\\u000a Calcium pyrophosphate dihydrate (CPPD) and hydro-xyapatite crystals are the most common calcium-containing crystals associated\\u000a with joint and periarticular disorders. Deposition of these crystals is frequently asymptomatic or can be intermittently symptomatic.\\u000a However, common clinical manifestations of calcium crystal deposition include acute or chronic inflammatory and degenerative\\u000a arthritides, and certain forms of periarthritis. In addition to these, a number of other

Geraldine McCarthy

51

Investigation of calcium crystals in OA knees.  

PubMed

For studies on matrix mineralization in osteoarthritis (OA), a clear analytical approach is necessary to identify and to quantify mineralization in the articular cartilage. The aim of this study is to develop an effective algorithm to quantify and to identify cartilage mineralization in the experimental setting. Four patients with OA of the knee undergoing total knee replacement and four control patients were included. Cartilage calcification was studied by digital contact radiography (DCR), field emission scanning electron microscopy (FE-SEM) X-ray element analysis and Raman spectroscopy (RS). DCR revealed mineralization in all OA cartilage specimens. No mineralization was observed in the control cartilage. Patient I showed rhomboid shaped crystals with a mean Ca:P molar ratio of 1.04 indicated the presence of calcium pyrophosphate dihydrate (CPPD) crystals, while Patients II, III and IV presented carbonate-substituted hydroxyapatite (HA). RS also showed the presence of CPPD crystals in Patient I while Patients II, III and IV revealed spectra confirming the presence of HA crystals. In the corresponding chondrocyte cell culture analyzed with SEM, the presence of CPPD crystals in the culture of Patient I and HA crystals in the culture of Patient II, III and IV was confirmed. No mineralization was found in the cell culture of the controls. The differentiation between BCP and CPPD crystals plays an important role, and the techniques presented here provide an accurate differentiation of these two types of crystals. For quantification of articular cartilage mineralization, DCR is a simple and accurate method. PMID:19639325

Fuerst, Martin; Lammers, L; Schäfer, F; Niggemeyer, O; Steinhagen, J; Lohmann, C H; Rüther, W

2009-07-29

52

Significance of the Mucopolysaccharides in Calcium Carbonate Stone  

Microsoft Academic Search

The present report deals with the histochemical and biochemical studies on the nature of the mucopolysacchari des which were thought to be the high molecular-weight organic substances in the calcium carbonate stone. The acid mucopolysacchari des were found, histochemically by alucian blue staining, between crystals of calcium carbonate in net-work fashion diffusely scattered throughout the sectioned material. Similar distribution of

T. Maki; T. Sato; T. Matsushiro; N. Suzuki; S. Takasawa; M. Toyoda; N. Nakamura; M. Okada; Y. Kikuchi; T. Watanabe; T. Nemoto; T. Sanjo

1968-01-01

53

Phase transitions in biogenic amorphous calcium carbonate.  

PubMed

Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC · H(2)O) ? dehydrated amorphous calcium carbonate (ACC) ? calcite. Unexpectedly, we find ACC · H(2)O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC · H(2)O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC · H(2)O in vitro. PMID:22492931

Gong, Yutao U T; Killian, Christopher E; Olson, Ian C; Appathurai, Narayana P; Amasino, Audra L; Martin, Michael C; Holt, Liam J; Wilt, Fred H; Gilbert, P U P A

2012-04-04

54

Phase transitions in biogenic amorphous calcium carbonate  

PubMed Central

Crystalline biominerals do not resemble faceted crystals. Current explanations for this property involve formation via amorphous phases. Using X-ray absorption near-edge structure (XANES) spectroscopy and photoelectron emission microscopy (PEEM), here we examine forming spicules in embryos of Strongylocentrotus purpuratus sea urchins, and observe a sequence of three mineral phases: hydrated amorphous calcium carbonate (ACC·H2O) ? dehydrated amorphous calcium carbonate (ACC) ? calcite. Unexpectedly, we find ACC·H2O-rich nanoparticles that persist after the surrounding mineral has dehydrated and crystallized. Protein matrix components occluded within the mineral must inhibit ACC·H2O dehydration. We devised an in vitro, also using XANES-PEEM, assay to identify spicule proteins that may play a role in stabilizing various mineral phases, and found that the most abundant occluded matrix protein in the sea urchin spicules, SM50, stabilizes ACC·H2O in vitro.

Gong, Yutao U. T.; Killian, Christopher E.; Olson, Ian C.; Appathurai, Narayana P.; Amasino, Audra L.; Martin, Michael C.; Holt, Liam J.; Wilt, Fred H.; Gilbert, P. U. P. A.

2012-01-01

55

Calcium oxalate crystals in eucalypt ectomycorrhizae: morphochemical characterization.  

PubMed

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

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

2013-07-02

56

21 CFR 582.5191 - Calcium carbonate.  

Code of Federal Regulations, 2013 CFR

...AND HUMAN SERVICES (CONTINUED) ANIMAL DRUGS, FEEDS, AND RELATED PRODUCTS SUBSTANCES GENERALLY RECOGNIZED AS SAFE Nutrients and/or Dietary Supplements 1 § 582.5191 Calcium carbonate. (a) Product. Calcium carbonate. (b)...

2013-04-01

57

Reaction of Calcium Hydroxide with Carbon Dioxide.  

National Technical Information Service (NTIS)

Details for carrying out an experiment on the reaction of calcium hydroxide with carbon dioxide are given. The addition of water is necessary for a reaction between dry calcium hydroxide and carbon dioxide. (ERA citation 02:005491)

F. W. Dorst

1975-01-01

58

Calcium Carbonate Mineralization.  

National Technical Information Service (NTIS)

The objectives of the present study were to determine the mechanisms of ion transport across mineralizing epithelia of barnacles, in particular to quantify the effects of altered protein structure on crystal form and arrangement and the effects of the mol...

K. M. Wilbur A. LeFurgey

1995-01-01

59

Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.  

ERIC Educational Resources Information Center

The gravimetric determination of calcium as calcium carbonate is described. This experiment is suitable for undergraduate quantitative analysis laboratories. It is less expensive than determination of chloride as silver chloride. (BB)

Henrickson, Charles H.; Robinson, Paul R.

1979-01-01

60

Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.  

ERIC Educational Resources Information Center

|The gravimetric determination of calcium as calcium carbonate is described. This experiment is suitable for undergraduate quantitative analysis laboratories. It is less expensive than determination of chloride as silver chloride. (BB)|

Henrickson, Charles H.; Robinson, Paul R.

1979-01-01

61

The role of Mg 2+ and Mg 2+\\/amino acid in controlling polymorph and morphology of calcium carbonate crystal  

Microsoft Academic Search

Mg2+ and the mixture of Mg2+\\/dl-aspartic or l-tyrosine were used as effective crystal nucleation and growth modifiers to control the crystallization of CaCO3. The polymorph and morphology of crystals were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR) and X-ray diffraction (XRD). The results demonstrated that various morphologies such as rod-shaped particles, spinose sphere particles, cauliflower-like crystals,

An-jian Xie; Yu-hua Shen; Xiao-yan Li; Zong-wei Yuan; Ling-guang Qiu; Chun-yan Zhang; Yuan-feng Yang

2007-01-01

62

Calcium Carbonate Dissolution in Sinking Particulate Matter  

Microsoft Academic Search

Atmospheric carbon dioxide is sequestered into the deep ocean via sinking particles that are produced in the euphotic zone. These particles are composed of organic carbon, calcium carbonate and silica that remineralizes as the particles sink through the water column. Calcium carbonate is a key component in ballasting the particles; according to model calculations it has the potential to determine

T. Jokulsdottir; D. Archer

2007-01-01

63

Preparation of monodispersed aragonite microspheres via a carbonation crystallization pathway  

Microsoft Academic Search

Monodispersed calcium carbonate microspheres were prepared by carbonating a calcium acetate aqueous solution with CO2 gas at a high pressure of 40 bar and a high temperature of 80 °C after 60 minutes of reaction. The products were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM), respectively. The XRD pattern showed that the crystal polymorph of the

Weijun Bao; Huiquan Li; Yi Zhang

2009-01-01

64

Adsorption and modification of calcium salt crystal growth by anionic peptides and spermine  

Microsoft Academic Search

Synthetic polyanions, including peptide analogs of naturally occurring proteins, have been shown to inhibit the nucleation and growth of calcium salt crystals. The binding characteristics of polyaspartate and aspartate-serine copolymers to calcium carbonate (calcite) and hydroxyapatite (HAP) are presented here. The binding is related to dosedependent inhibition of crystal growth measured by constant composition assays. Peptide phosphorylation had little effect

Erich Mueller; C. Steven Sikes

1993-01-01

65

Polypropylene\\/calcium carbonate nanocomposites  

Microsoft Academic Search

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

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

2002-01-01

66

Modulation of calcium oxalate monohydrate crystallization kinetics in vitro  

Microsoft Academic Search

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,

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

1988-01-01

67

Contribution of human uropontin to inhibition of calcium oxalate crystallization  

Microsoft Academic Search

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

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

1998-01-01

68

Zeta potential measurement of calcium carbonate.  

PubMed

The problem of scaling, which one finds in industrial heat exchangers, particularly in atmospheric coolers in nuclear power stations, depends on calcium carbonate deposits from fresh water. To better understand this phenomenon, we have examined the eventual implication of superficial electric charge of precipitated crystal nuclei. After a bibliographical review showing a fundamental divergence from already published results, this paper describes an experimental plant to measure the zeta potential in controlled conditions of thermodynamic equilibrium, oversaturation, or undersaturation of a CaCO(3)-H(2)O-CO(2) system taking into account simultaneously the three phases: gas, liquid, and solid. The zeta potential is measured by a crystalline-plug method with calcite or aragonite crystals. The potential cancels at thermodynamic equilibrium and is always negative for other conditions, in particular for oversaturation where the possibility of scaling exists. The analysis of these results suggests that the potential determining ions of the system are Ca(2+) and HCO(-)(3). PMID:12725831

Moulin, P; Roques, H

2003-05-01

69

The forgotten crystal arthritis: calcium pyrophosphate deposition.  

PubMed

Calcium pyrophosphate crystals are related to a variety of articular manifestations known as calcium pyrophosphate deposition (CPPD) arthritis. Acute CPPD arthritis is commonly known as pseudogout, but there are many other presentations. Diverse endocrine and metabolic diseases may be related to CPPD arthritis. Septic arthritis is in the differential diagnosis of acute CPPD arthritis. The treatment options for CPPD arthritis include non-steroidal anti-inflammatories and steroids. PMID:22428450

Ivory, Dedri; Velázquez, Celso R

70

Herbivory and Calcium Concentrations Affect Calcium Oxalate Crystal Formation in Leaves of Sida (Malvaceae)  

Microsoft Academic Search

Calcium oxalate crystals have potential roles in plants as part of a defence mechanism against herbivores and\\/or in accumulating excess calcium. To date, these potential roles have been studied independently. In this experimental study the effects of calcium levels and herbivory on the production of calcium oxalate crystals (i.e. druse, spherical crystal aggregates) were examined in seedlings of Sida rhombifolia.

Brenda Molano-Flores

2001-01-01

71

Structural Characteristics of Synthetic Amorphous Calcium Carbonate  

SciTech Connect

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.

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

2008-08-06

72

Amorphous calcium carbonate in the shells of adult Unionoida.  

PubMed

Shells of adult individuals from two different bivalve families, Hyriopsis cumingii and Diplodon chilensis patagonicus, were studied by Micro-Raman spectroscopy and Focussed Ion Beam-assisted TEM. The shells contain amorphous calcium carbonate in a zone at the interface between the periostracum and the prismatic layer. In this area, the initial prism structures protrude from the inner periostracum layer and it is demonstrated that these structures systematically consist of highly disordered and amorphous calcium carbonate. Within this zone, ordered and disordered areas are intermingled discounting the existence of a crystallization front and favouring models of domainal crystallization processes via so-called mesocrystals. These observations are the first documentation of the use of amorphous calcium carbonate as a precursor phase by adult mollusc species and lend further support to hypotheses postulating widespread use of amorphous phases as building material of skeletal tissue in biology. PMID:20850546

Jacob, D E; Wirth, R; Soldati, A L; Wehrmeister, U; Schreiber, A

2010-09-17

73

Calcium carbonate polymorph control using droplet-based microfluidics  

PubMed Central

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.

Yashina, Alexandra; Meldrum, Fiona; deMello, Andrew

2012-01-01

74

Calcium carbonate polymorph control using droplet-based microfluidics.  

PubMed

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

Yashina, Alexandra; Meldrum, Fiona; Demello, Andrew

2012-04-06

75

Biomimetic nucleation of calcium carbonate layers at the air-water interface  

Microsoft Academic Search

The interaction between calcium carbonate crystals and chitosan at the air-water interface was investigated. Chitosan was selected as an organic, pseudo-structural component of calcium carbonate biominerals in the subphase in the presence of octadecyl sulfate Langmuir monolayers. Calcite crystallization was studied using X-ray diffraction and optical microscope techniques; in-situ grazing incidence x-ray diffraction was performed at synchrotron sources. Calcite crystallization

Kyungil Kim

2008-01-01

76

Crystallization of calcium sulfate on polymeric surfaces.  

PubMed

Surface crystallization of calcium sulfate dihydrate (gypsum) on a series of polymeric surfaces was studied using a quartz microbalance system. Polyelectrolyte multilayer films (positively and negatively charged surfaces) were formed on the quartz crystal microbalance (QCM) sensors utilizing a layer-by-layer spin-assembly method. The kinetics of gypsum surface crystallization was quantified in terms of the evolution of gypsum mineral scale on the different surfaces. For comparison mineral scaling was also evaluated on silica and polyamide surfaces. For surfaces of the same charge polarity (+/-), the mass density of gypsum scale was lower (PSScrystal growth kinetics. Although aerial scale coverage correlated with the crystal mass density, the crystal number density did not correlate with the extent of surface scaling. Surface crystal size, morphology and crystal number density varied significantly at similar roughness levels, suggesting that surface chemical functionality may also affect surface crystallization. The present results suggest that there is merit in exploring methods for mitigation of mineral scaling on polymeric surfaces via alteration of surface both surface topography and chemistry. In this regards, an expanded systematic study is needed in order to quantitatively clarify the interplay between the above two factors in controlling surface crystallization. PMID:21316694

Lin, Nancy H; Shih, Wen-Yi; Lyster, Eric; Cohen, Yoram

2011-01-15

77

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...

78

Molecular mechanisms of crystallization impacting calcium phosphate cements  

PubMed Central

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.

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

2010-01-01

79

[Features of calcium crystals and calcium components in 54 plant species in salinized habitats of Tianjin].  

PubMed

Plant calcium (Ca) is composed of dissociated Ca2+ and easily soluble, slightly soluble, and hard soluble combined Ca salts. The hard soluble Ca salts can often engender Ca crystals. To understand the Ca status in different growth form plants in salinized habitats, 54 plant species were sampled from the salinized habitats in Tianjin, with the Ca crystals examined by microscope and the Ca components determined by sequential fractionation procedure. More Ca crystals were found in 38 of the 54 plant species. In 37 of the 38 plant species, drusy and prismatic Ca oxalate crystals dominated, whereas the cystolith of Ca carbonate crystal only appeared in the leaves of Ficus carica of Moraceae. The statistics according to growth form suggested that deciduous arbors and shrubs had more Ca oxalate crystal, liana had lesser Ca oxalate crystal, and herbs and evergreen arbors had no Ca oxalate crystal. From arbor, shrub, liana to herb, the concentration of HCl-soluble Ca decreased gradually, while that of water soluble Ca was in adverse. The concentration of water soluble Ca in herbs was significantly higher than that in arbors and shrubs. This study showed that in salinized habitats, plant Ca crystals and Ca components differed with plant growth form, and the Ca oxalate in deciduous arbors and shrubs played an important role in withstanding salt stress. PMID:22919834

Xu, Jing-Jing; Ci, Hua-Cong; He, Xing-Dong; Xue, Ping-Ping; Zhao, Xue-Lai; Guo, Jian-Tan; Gao, Yu-Bao

2012-05-01

80

Calcium sulfite hemihydrate dissolution and crystallization  

SciTech Connect

Experiments were conducted to measure the dissolution and crystallization rate of calcium sulfite hemihydrate in aqueous solutions typical of flue gas desulfurization processes. A stagnant mass transfer model integrated with solution equilibrium was developed to predict CaSO/sub 3/.1/2H/sub 2/O dissolution rates as a function of pH, temperature, solution composition,and particle size. The crystal growth rate was found to be a strong function of relative supersaturation and strongly inhibited by dissolved sulfate. The growth rate per unit BET surface area, R' (mole/cm/sup 2/-min), is given by: 9.7 x 10/sup -4/ exp(-10250/RT) x (RS/sub CaSO/sub 3// - 1)/sup 2/ x RS/sub CaSO/sub 4// - 1, where RS/sub CaSO/sub 3// and RS/sub CaSO/sub 4// are the relative saturations with respect to calcium sulfate (CaSO/sub 3/.1/2H/sub 2/O) and gypsum (CaSO/sub 4/.2H/sub 2/O) respective. Scanning electron microscopy and infrared spectroscopy demonstrated that solids generated in the presence of dissolved sulfate contained solid solution sulfate and crystallized as agglomerates of very thin platelets. In the absence of solid or dissolved sulfate, the solids were agglomerates of well-formed columnar, hexagonal crystals.

Tseng, C.H.P.

1984-01-01

81

Calcium carbonate nucleation in an alkaline lake surface water, Pyramid Lake, Nevada, USA  

USGS Publications Warehouse

Calcium concentration and calcite supersaturation (?) needed for calcium carbonate nucleation and crystal growth in Pyramid Lake (PL) surface water were determined during August of 1997, 2000, and 2001. PL surface water has ? values of 10-16. Notwithstanding high ?, calcium carbonate growth did not occur on aragonite single crystals suspended PL surface water for several months. However, calcium solution addition to PL surface-water samples caused reproducible calcium carbonate mineral nucleation and crystal growth. Mean PL surface-water calcium concentration at nucleation was 2.33 mM (n = 10), a value about nine times higher than the ambient PL surface-water calcium concentration (0.26 mM); mean ? at nucleation (109 with a standard deviation of 8) is about eight times the PL surface-water ?. Calcium concentration and ? regulated the calcium carbonate formation in PL nucleation experiments and surface water. Unfiltered samples nucleated at lower ? than filtered samples. Calcium concentration and ? at nucleation for experiments in the presence of added particles were within one standard deviation of the mean for all samples. Calcium carbonate formation rates followed a simple rate expression of the form, rate (mM/min) = A (?) + B. The best fit rate equation "Rate (? mM/? min) = -0.0026 ? + 0.0175 (r = 0.904, n = 10)" was statistically significant at greater than the 0.01 confidence level and gives, after rearrangement, ? at zero rate of 6.7. Nucleation in PL surface water and morphology of calcium carbonate particles formed in PL nucleation experiments and in PL surface-water samples suggest crystal growth inhibition by multiple substances present in PL surface water mediates PL calcium carbonate formation, but there is insufficient information to determine the chemical nature of all inhibitors.

Reddy, Michael M.; Hoch, Anthony

2012-01-01

82

Nucleation and crystal growth of calcium sulfite hemihydrate  

Microsoft Academic Search

In slurry scrubbing processes for flue gas desulfurization the precipitation rate of calcium sulfite affects scrubber solution composition, SOâ absorption, sulfite oxidation, and limestone utilization. Sludge quality and disposal costs are also a function of precipitation kinetics. The nucleation and crystal growth rates of calcium sulfate hemihydrate were measured in a continuous flow crystallizer at conditions that produced agglomerate crystals,

C. L. Gleason; G. T. Rochelle

2009-01-01

83

A new method for the study of calcium carbonate growth on steel surfaces  

Microsoft Academic Search

The growth of calcium carbonate crystals on a steel surface, known as scaling, has been investigated. A heat exchanger cell was built for this purpose, and the crystals formed on the surface were examined in a scanning electron microscope. Two surface active polymers with a diphosphate end group, differing in hydrophobic\\/hydrophilic ratio, were synthesized. The effect on crystal formation of

Per Kjellin; Krister Holmberg; Magnus Nydén

2001-01-01

84

Nucleation of calcium carbonate on bacterial nanoglobules  

NASA Astrophysics Data System (ADS)

Nucleation of calcium carbonate on microbial cell material may have been the dominant mode of microbial carbonate formation during most of Earth's history. Current knowledge predicts that nucleation takes place on the cell surface or on extracellular polymeric substances. However, the initial nucleation steps have not been described in detail and the process remains elusive. Here we describe the bacterial nucleation of calcium carbonate at the nanometer scale. In our precipitation experiment with sulfate reducing bacteria (SRB), the bulk of calcium carbonate precipitates on hundreds of individual globules 60 200 nm in diameter. Globules originate from the SRB cell surface but calcify significantly only when released to the culture medium. Similar globules have been observed, albeit at a much larger scale, in other bacterial precipitation experiments and in many natural microbial carbonates, suggesting that the process we describe could be an important step in microbial calcification.

Aloisi, G.; Gloter, A.; Krüger, M.; Wallmann, K.; Guyot, F.; Zuddas, P.

2006-12-01

85

Calcium, carbonic anhydrase and gastric acid secretion.  

PubMed

Previous data concerning the action of calcium (Ca) on gastric acid secretion (GAS) indicated that calcium ions increase GAS elicited by gastrin released through a vagal mechanism, and also by a direct effect on parietal cells. Our research showed that the stimulating effect of calcium on gastric acid secretion can be antagonized by verapamil administration, which reduces gastric acid secretion . In the present study we followed the effect induced by administration of calcium and Ca-chelating agents (disodium EDTA) on gastric acid secretion and on carbonic anhydrase (CA) activity. We selected two groups of healthy volunteers: Group I (n=21) received a single i.v. dose of CaCl2 (15 mg/kg b.w.), whereas Group II (n=22) received a single i.v. dose of disodium EDTA (5 mg/kg b.w.). We determined blood calcium before and after treatment, gastric acid secretion at 2 hours. erythrocyte CA II activity, and CA IV activity in membrane parietal cells, which were isolated from gastric mucosa obtained by endoscopic biopsy. Assessment of carbonic anhydrase activity was achieved by the stopped-flow method. In Group I calcium administration increased blood calcium, HCl output, CA II and CA IV activity as compared to initial values. In Group II, disodium EDTA reduced blood calcium, HCl output, CA II and CA IV activity as compared to initial values. The results demonstrated that increased blood calcium and GAS values after calcium administration correlated with the increase of erythrocyte CA II and parietal cell CA IV activity, while disodium EDTA induced a reversed process. Our results also show that cytosolic CA II and membrane CA IV values are sensitive to calcium changes and they directly depend on these levels. Our data suggest that intra- and extracellular pH changes induced by carbonic anhydrase might account for the modulation of the physiological and pathological secretory processes in the organism. PMID:11551141

Puscas, I; Coltau, M; Baican, M; Domuta, G; Hecht, A

2001-01-01

86

Effects of DPPC/Cholesterol liposomes on the properties of freshly precipitated calcium carbonate.  

PubMed

DPPC/Cholesterol liposomes of average diameter below 100nm were used as a matrix for calcium carbonate precipitation. Adsorption of calcium ions on the vesicles was determined via zeta potential measurement. It was found that with increasing calcium ions concentration the electrokinetic potential of the vesicles varied toward more positive values. The changes became smaller with the cholesterol content increase. Accumulation of calcium ions close to the vesicles membranes lead to attraction of CO(3)(2-) ions and enhances nucleation and growth of small calcium carbonate crystals that aggregates within lipid vesicles forming porous balls aggregates. However, dipalmitoylphosphatidylcholine (DPPC) does not change the CaCO(3) crystal forms and calcite is the only form obtained during precipitation. Moreover, the influence of the phospholipid on the calcium carbonate precipitation is enhanced by the induction of cholesterol to the lipid membranes. PMID:22796770

Szcze?, A

2012-06-23

87

Calcium acetate versus calcium carbonate as oral phosphate binder in pediatric and adolescent hemodialysis patients  

Microsoft Academic Search

Calcium carbonate is widely used as an oral phosphorus binder to control hyperphosphatemia in children on maintenance hemodialysis.\\u000a Intestinal calcium absorption may induce hypercalcemia, particularly if calcitriol is given simultaneously. In adults, calcium\\u000a acetate binds phosphorus more effectively than calcium carbonate, while reducing the frequency of hypercalcemic events. We\\u000a therefore compared calcium acetate with calcium carbonate in nine pediatric patients

Michael Wallot; Klaus-Eugen Bonzel; Andreas Winter; Birgit Geiirger; Bernhard Lettgen; Martin Bald

1996-01-01

88

Influence of calcium ions on the crystallization of sodium bicarbonate  

Microsoft Academic Search

In industrial crystallization of sodium bicarbonate (sodium hydrogenocarbonate), the presence of calcium ions in solutions is unavoidable due to the production process. The understanding of the Ca2+ role in NaHCO3 crystallization would be helpful for improving the quality of the final products.The influence of calcium ions on NaHCO3 crystallization was investigated in a 5-l mixed suspension mixed product removal crystallizer

Y. Zhu; Paul Demilie; Perrine Davoine; Thierry Cartage; Marie-Paule Delplancke-Ogletree

2005-01-01

89

Calcium sulfite and calcium sulfate crystallization: Volume 1, Effect of crystallizer type on gypsum size distribution: Final report  

Microsoft Academic Search

The purpose of this study was to measure crystal growth and nucleation kinetics of calcium sulfite hemihydrate with or without trace quantities of potential crystal modifiers and using different scales of crystallizer operation. The Crystal-Size Distribution (CSD) and morphology of calcium sulfite was observed in 240 ml and 9-liter continuous precipitators using CaClâ and Ca(OH)â to precipitate NaHSOâ in solutions

A. D. Randolph; B. J. Kelly; B. Keough

1986-01-01

90

Growth of calcium carbonate in polyacrylamide hydrogel: Investigation of the influence of polymer content  

Microsoft Academic Search

The growth of calcium carbonate crystals has attracted growing attention as a model system for biomineralisation processes. Organic molecules and gelatinous matrices are known to play an essential role in the formation of hard tissues. For the investigation of the function of specific influence factors, a model experiment is necessary. Several hydrogels were previously tested as growth matrices for calcium

Uta Helbig

2008-01-01

91

Calcination of calcium carbonate and blend therefor  

DOEpatents

A method for calcination of a calcium carbonate material comprising heating the calcium carbonate material to a temperature and for a time sufficient to calcine the material to the degree desired while in the presence of a catalyst; said catalyst comprising at least one fused salt having the formula MCO.sub.3.CaCO.sub.3.CaO.H.sub.2 O.sub.x, wherein M is an alkali metal and x is 0 to 1 and formed by fusing MCO.sub.3 and CaCO.sub.3 in a molar ratio of about 1:2 to 2:1, and a blend adapted to be heated to CaO comprising a calcium carbonate material and at least one such fused salt.

Mallow, William A. (Helotes, TX); Dziuk, Jr., Jerome J. (San Antonio, TX)

1989-01-01

92

Evaluation of Calcium Carbonate and Calcium Hydroxide Treatments of Prairie Drinking Water Dugouts  

Microsoft Academic Search

In 1987, lime (250 mg\\/L calcium carbonate or 250 mg\\/L calcium hydroxide) was added to four hardwater dugouts in northwestern Alberta to precipitate the phosphorus and algae and improve water quality. Calcium carbonate reduced algal biomass to 39 percent of pretreatment concentrations between June and August of 1987, but dugouts recovered to pretreatment concentrations during the next summer. Calcium hydroxide

T. P. Murphy; E. E. Prepas; J. T. Lim; J. M. Crosby; D. T. Walty

1990-01-01

93

Co-utilisation of CO2 and Calcium Silicate-rich Slags for Precipitated Calcium Carbonate Production (Part II)  

Microsoft Academic Search

Production of commercial calcium carbonate from calcium silicate- rich slag is an attractive concept for reducing CO2 emissions. In order for this calcium carbonate to be marketable it has to be very pure, requiring separation of calcium from the slag prior to carbonation. In this study, a process concept that produces relatively pure calcium carbonate from slag is presented. It

Sanni Eloneva; Sebastian Teir; Jaakko Savolahti; Carl-Johan Fogelholm; Ron Zevenhoven

94

Factors affecting the solubility of calcium pyrophosphate dihydrate crystals.  

PubMed Central

The solubility of triclinic calcium pyrophosphate dihydrate (CPPD) crystals was measured under varying conditions using 45Ca-labeled crystals, expressing solubility as micromoles per liter of 45Ca in solution. In a 0.1-M Tris-HC1 buffer pH 7.4, the solubility of accurately sized CPPD crystals (37-20mum) was 60muM with maximal solubility being attained after about 8 h incubation at 37degreeC. Reduction in crystal size, decrease in pH, increase in ionic strength, Mg++, citrate, and albumin all increased solubility. The most marked effects on solubility occurred when changing the calcium concentration or by enzymatic hydrolysis of inoganic pyrophosphate to orthophosphate. It was found that decreasing the ionized calcium level below 5 mg/100 ml resulted in a progressive enhancement of solubility. The observed solubility-enhancing effects of albumin could be explained solely on its calcium-binding ability and thereby, altered ionized calcium level. Diffusible calcium in synovial fluid was only 40% of the total calcium concentration, which means most joint fluids are normally near the critical concentration of 5 mg/100 ml of ionized calcium, below which solubility is enhanced. During surgery, especially parathyroidectomy, calcium levels fall, favoring dissolution of CPPD crystals. We speculate that the slight decrease in crystal size during dissolution frees them from their cartilaginous mold, resulting in a dose-dependent inflammatory reaction as they are "shed" into the joint space. Crystal shedding may be reinforced by the modest fall in joint fluid pH accompanying the inflammatory response.

Bennett, R M; Lehr, J R; McCarty, D J

1975-01-01

95

Fortification of All-Purpose Wheat-Flour Tortillas with Calcium Lactate, Calcium Carbonate, or Calcium Citrate Is Acceptable  

Microsoft Academic Search

Fortification helps provide adequate nutrients for indi- viduals not meeting daily needs. Foods may be fortified with calcium to assist individuals with lactose intoler- ance and others preferring not to consume traditional forms of dairy. This study examined the quality of all- purpose wheat-flour tortillas fortified with calcium lac- tate, calcium carbonate, or calcium citrate. These tortillas were compared to

JOELLE E. ROMANCHIK-CERPOVICZ; REBECCA J. MCKEMIE

96

Fortification of All-Purpose Wheat-Flour Tortillas with Calcium Lactate, Calcium Carbonate, or Calcium Citrate Is Acceptable  

Microsoft Academic Search

Fortification helps provide adequate nutrients for individuals not meeting daily needs. Foods may be fortified with calcium to assist individuals with lactose intolerance and others preferring not to consume traditional forms of dairy. This study examined the quality of all-purpose wheat-flour tortillas fortified with calcium lactate, calcium carbonate, or calcium citrate. These tortillas were compared to similarly prepared nonfortified flour

Joelle E. Romanchik-Cerpovicz; Rebecca J. McKemie

2007-01-01

97

Calcium sulfite and calcium sulfate crystallization: Volume 1, Effect of crystallizer type on gypsum size distribution: Final report  

SciTech Connect

The purpose of this study was to measure crystal growth and nucleation kinetics of calcium sulfite hemihydrate with or without trace quantities of potential crystal modifiers and using different scales of crystallizer operation. The Crystal-Size Distribution (CSD) and morphology of calcium sulfite was observed in 240 ml and 9-liter continuous precipitators using CaCl/sub 2/ and Ca(OH)/sub 2/ to precipitate NaHSO/sub 3/ in solutions resembling FGD liquors. Estimates of crystal nucleation and growth rates were obtained from these CSD data and correlated in a useful kinetics form suitable for CSD predictions in a computer model which simulates complex crystallizer configurations. These population balance-based CSD studies indicated that significant improvements in calcium sulfite particle size might be achieved by using precipitators with a size-dependent particle removal configuration. 25 refs., 20 figs., 9 tabs.

Randolph, A.D.; Kelly, B.J.; Keough, B.

1986-11-01

98

[The effect of glycosaminoglycans on calcium oxalate crystal formation].  

PubMed

The effect of glycosaminoglycans on calcium oxalate crystal formation in the supersaturated solution was studied by examining the size and shape of calcium oxalate crystals generated under an optical microscope. It was found that heparan sulfate and heparin were more effective growth inhibitors than chondroitin sulfate and hyaluronic acid at concentrations within their respective urinary range. With increasing calcium and/or glycosaminoglycans concentration in the solution, the degree of growth inhibition caused by glycosaminoglycans was enhanced. Calcium oxalate crystal shapes generated with various glycosaminoglycans varied with glycosaminoglycan species. One of the causes of those differences in the shape and degree of growth inhibition might be the structural differences between them, that is, the number of sulfate residue and O- or N-form they contain. Calcium oxalate crystal shapes in the presence of heparin or heparan sulfate at higher concentrations were similar to those of calcium oxalate monohydrate crystals in the urinary sediments of hyperoxaluric patients. These facts might suggest the possibility that heparin and/or heparan sulfate were present in the crystal forming region. PMID:2214470

Shirane, Y; Hamao, T; Kagawa, S

1990-07-01

99

Control of Predialytic Hyperphosphatemia by Oral Calcium Acetate and Calcium Carbonate  

Microsoft Academic Search

Since Mai et al. found, with the intestinal lavage technique, that the same dose of elemental calcium given as acetate (Ca Ac) complexed in the gut of uremic patients twice as much phosphate as calcium carbonate (CaCO3) while inducing a rather low calcium absorption, we wanted to see if half the dose of elemental calcium given as Ca Ac could

Ph. Morinière; M. Djerad; B. Boudailliez; N. El Esper; F. Boitte; P. F. Westeel; M. Compagnon; M. Brazier; J. M. Achard; A. Fournier

1992-01-01

100

Preparation and microelectrophoresis characterisation of calcium carbonate particles in the presence of anionic polyelectrolyte  

Microsoft Academic Search

Calcium carbonate (CaCO3) crystal growth experiments in the presence of the polystyrene sulfonate were made at ambient temperature. This polyelectrolyte inhibits the crystal growth in all directions and modifies the crystal structure and morphology. Further, the unstable vaterite CaCO3 crystalline structure was stabilized in the precipitation medium in the presence of the polyelectrolyte. Thus, at moderate polyelectrolyte concentration, spherical CaCO3

A. Jada; A. Verraes

2003-01-01

101

Dynamic response of porous calcium carbonate minerals  

SciTech Connect

A theoretical study of the shock-loaded response of calcium carbonate materials is presented in which both dry and water-saturated samples with porosities up to 50 percent are considered. Data are presented for the unloading response from 15.0 and 18.5 GPa, and calculations from a mixture model using a Mie-Grueneisen equation of state with volume-dependent parameters are compared to both the Hugoniot and the isentropic unloading response.

Drumheller, D.S.; Grady, D.E.

1985-01-01

102

Amorphous iron (II) carbonate: Crystallization energetics and comparison to other carbonate minerals related to CO2 sequestration  

NASA Astrophysics Data System (ADS)

The synthesis, characterization and crystallization energetics of amorphous iron (II) carbonate (AFC) are reported. AFC may form as a precursor for siderite (FeCO3). The enthalpy of crystallization (?Hcrys) of AFC is similar to that of amorphous magnesium carbonate (AMC) and more exothermic than that of amorphous calcium carbonate (ACC). This suggests that enthalpy of crystallization in carbonate systems is ionic-size controlled, which may have significant implications in a wide variety of conditions, including geological sequestration of anthropogenic carbon dioxide.

Sel, Ozlem; Radha, A. V.; Dideriksen, Knud; Navrotsky, Alexandra

2012-06-01

103

Improved calcium absorption from a newly formulated beverage compared with a calcium carbonate tablet  

Microsoft Academic Search

This trial assessed calcium excretion, as an indicator of calcium absorption, in 50 healthy men and postmenopausal women (ages 45-75), from a beverage containing calcium, magnesium, vitamins C, D, K, zinc, phosphorous, soy isoflavones, and inulin, compared with a calcium carbonate (CaCO3) tablet. At the end of each 4-week treatment period, subjects consumed a standardized low calcium meal plus the

Kevin C Maki; Mary R Dicklin; MarySue Cyrowski; Denise M Umporowicz; Yasuo Nagata; Grace Moon; Sam Forusz; Michael H Davidson

2002-01-01

104

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

PubMed Central

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.

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

2012-01-01

105

Substrate effect on surface adhesion/crystallisation of calcium carbonate  

NASA Astrophysics Data System (ADS)

The work reported primarily focuses on understanding the mechanisms of calcium carbonate (CaCO3) scale deposition on nano- and micro-structured polymer surfaces and on stainless steel surfaces treated with commercially available industrial coatings, taking untreated stainless steel as a reference substrate. The effect that a substrate's surface has on the deposition and growth of CaCO3 crystals in terms of its physical and chemical parameters is explored. In addition, substrate effects on crystal morphology are examined as the nature of the substrate is clearly shown to influence the prominent polymorph in CaCO3 deposition. Also, the adhesion of CaCO3 to a surface is affected by the mechanism of deposition and this is assessed by whether crystals migrated from the bulk solution to settle on the surface or heterogeneously nucleate on the surface itself and subsequently grow there. The work provides evidence that the surfaces are acting as nucleation sites for crystals to heterogeneously initiate and grow and is also a demonstration of crystals growing in confinement.

Cheong, W. C.; Gaskell, P. H.; Neville, A.

2013-01-01

106

Crystallization kinetics of lithium calcium aluminosilicate glass  

Microsoft Academic Search

The activation energy for crystal growth and the reaction mechanisms in LCAS glass crystallization have been studied. Uniform crystallization of the glass was found to result from two stage heating process. The isothermal and non?isothermal kinetics of crystallization of |3?spodumene from the LCAS glass system was investigated using guantitative X?ray diffraction (XRD) analysis and differential thermal analysis (DTA). The temperature

1990-01-01

107

Crystal morphology and carbon/carbon composition of solid oxalate in cacti.  

PubMed

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 (13)C isotope (-7.3 to - 8.7 per thousand) compared with woody fibers (-13.3 to 14.1 per thousand) from the same plants. PMID:16661115

Rivera, E R; Smith, B N

1979-12-01

108

Morphological effects of glycosaminoglycans on calcium oxalate monohydrate crystals.  

PubMed

The effects of individual glycosaminoglycan (GAG) species on calcium oxalate monohydrate (COM) crystal growth were studied in vitro by the observation of crystal morphology grown in a supersaturated calcium oxalate solution in the presence of GAGs using optical and scanning electron microscopes. GAGs affected the morphology of COM crystals differently depending on the species. The growth rates of the crystals formed in the presence of chondroitin-6-sulfate (ChS-C) were higher in length and lower in width and thickness than those of control crystals. The incorporation of dermatan sulfate or heparin into the crystals formed in the presence of these GAGs was revealed by X-ray microanalysis, whereas ChS-C was not detected in the crystals grown with it. The experiment using dicarboxylates, as a simple model of GAG molecules, showed that a distance between the side groups was important for their morphological effects. These findings suggested that the different effects of GAGs on the crystal morphology resulted from the differences in their interaction modes with COM crystal faces, that is, the differences in their binding behavior, their inhibition modes of crystal growth, and other roles played after binding to the crystals. PMID:8819889

Shirane, Y; Kurokawa, Y; Sumiyoshi, Y; Kagawa, S

1995-01-01

109

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

Microsoft Academic Search

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

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

1990-01-01

110

Precipitation of calcium carbonate by ultrasonic irradiation  

Microsoft Academic Search

Supersaturated solution of calcium carbonate ([Ca2+]=1.2 mmol\\/L, [HCO3?]=3.2 mmol\\/L, pH=8.8, T=30±0.5 °C), a scale forming component, was irradiated by an ultrasonic homogenizer (24 kHz, 15–250 W\\/cm2) to study the factors that affect its precipitation rate. The factors of (1) depth of horn immersion, (2) ultrasonic intensity and horn tip size and (3) cavitation, which can affect the precipitation rate were

I Nishida

2004-01-01

111

Calcium sulphate hemihydrate hydration leading to gypsum crystallization  

Microsoft Academic Search

The hydration of calcium sulphate hemihydrate (CaSO4·0.5H2O) leading to the crystallization of gypsum (calcium sulphate dihydrate – CaSO4·2H2O) has been the subject of several investigations over a long period and a vast amount of data is widely distributed throughout in the literature. In this review article an overall picture of the subject is presented. The properties of the two hemihydrates (?-

N. B. Singh; B. Middendorf

2007-01-01

112

The Skeletal Organic Matrix from Mediterranean Coral Balanophyllia europaea Influences Calcium Carbonate Precipitation  

PubMed Central

Scleractinian coral skeletons are made mainly of calcium carbonate in the form of aragonite. The mineral deposition occurs in a biological confined environment, but it is still a theme of discussion to what extent the calcification occurs under biological or environmental control. Hence, the shape, size and organization of skeletal crystals from the cellular level through the colony architecture, were attributed to factors as diverse as mineral supersaturation levels and organic mediation of crystal growth. The skeleton contains an intra-skeletal organic matrix (OM) of which only the water soluble component was chemically and physically characterized. In this work that OM from the skeleton of the Balanophyllia europaea, a solitary scleractinian coral endemic to the Mediterranean Sea, is studied in vitro with the aim of understanding its role in the mineralization of calcium carbonate. Mineralization of calcium carbonate was conducted by overgrowth experiments on coral skeleton and in calcium chloride solutions containing different ratios of water soluble and/or insoluble OM and of magnesium ions. The precipitates were characterized by diffractometric, spectroscopic and microscopic techniques. The results showed that both soluble and insoluble OM components influence calcium carbonate precipitation and that the effect is enhanced by their co-presence. The role of magnesium ions is also affected by the presence of the OM components. Thus, in vitro, OM influences calcium carbonate crystal morphology, aggregation and polymorphism as a function of its composition and of the content of magnesium ions in the precipitation media. This research, although does not resolve the controversy between environmental or biological control on the deposition of calcium carbonate in corals, sheds a light on the role of OM, which appears mediated by the presence of magnesium ions.

Goffredo, Stefano; Vergni, Patrizia; Reggi, Michela; Caroselli, Erik; Sparla, Francesca; Levy, Oren; Dubinsky, Zvy; Falini, Giuseppe

2011-01-01

113

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

Microsoft Academic Search

The skeletons of adult echinoderms comprise large single crystals of calcite with smooth convoluted fenestrated morphologies, raising many questions about how they form. By using water etching, infrared spectroscopy, electron diffraction, and environmental scanning electron microscopy, we show that sea urchin spine regeneration proceeds via the initial deposition of amorphous calcium carbonate. Because most echinoderms produce the same type of

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

2004-01-01

114

Ethanol assisted synthesis of pure and stable amorphous calcium carbonate nanoparticles.  

PubMed

Stable monodispersed amorphous calcium carbonate (ACC) nanoparticles can be synthesized in ethanol media by a facile method, and crystallization of ACC is kinetically controlled, resulting in the formation of three polymorphs in a mixed solvent of ethanol-water at different pH values. PMID:24022058

Chen, Shao-Feng; Cölfen, Helmut; Antonietti, Markus; Yu, Shu-Hong

2013-09-24

115

In vitro synthesis and stabilization of amorphous calcium carbonate (ACC) nanoparticles within liposomes  

SciTech Connect

We show that amorphous calcium carbonate (ACC) can be synthesized in phospholipid bilayer vesicles (liposomes). Liposome-encapsulated ACC nanoparticles are stable against aggregation, do not crystallize for at least 20 h, and are ideally suited to investigate the influence of lipid chemistry, particle size, and soluble additives on ACC in situ.

Tester, Chantel C.; Brock, Ryan E.; Wu, Ching-Hsuan; Krejci, Minna R.; Weigand, Steven; Joester, Derk (NWU)

2012-02-07

116

Biochemical and ultrastructural evidence for the origin of whitings: A biologically induced calcium carbonate precipitation mechanism  

Microsoft Academic Search

We propose that Bahamian whitings, floating patches of lime mud, are in part the result of biological precipitation of calcium carbonate induced by picoplankton and cellular components. The cells may act as nucleation sites for crystallization from seawater supersaturated with CaCO3. Our model represents a new hypothesis concerning Bahamian whiting formation and is based on several lines of evidence. Biochemical

L. L. Robbins; P. L. Blackwelder

1992-01-01

117

Effect of calcium carbonate on hardening, physicochemical properties, and in vitro degradation of injectable calcium phosphate cements.  

PubMed

The main disadvantage of apatitic calcium phosphate cements (CPCs) is their slow degradation rate, which limits complete bone regeneration. Carbonate (CO?²?) is the common constituent of bone and it can be used to improve the degradability of the apatitic calcium phosphate ceramics. This study aimed to examine the effect of calcite (CaCO?) incorporation into CPCs. To this end, the CaCO? amount (0-4-8-12 wt %) and its particle size (12.0-?m-coarse or 2.5-?m-fine) were systematically investigated. In comparison to calcite-free CPC, the setting time of the bone substitute was delayed with increasing CaCO? incorporation. Reduction of the CaCO? particle size in the initial powder increased the injectability time of the paste. During hardening of the cements, the increase in calcium release was inversely proportional to the extent of CO?²? incorporation into apatites. The morphology of the carbonate-free product consisted of large needle-like crystals, whereas small plate-like crystals were observed for carbonated apatites. Compressive strength decreased with increasing CaCO? content. In vitro accelerated degradation tests demonstrated that calcium release and dissolution rate from the set cements increased with increasing the incorporation of CO?²?, whereas differences in CaCO? particle size did not affect the in vitro degradation rate under accelerated conditions. PMID:22213632

Sariibrahimoglu, Kemal; Leeuwenburgh, Sander C G; Wolke, Joop G C; Yubao, Li; Jansen, John A

2011-12-30

118

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

Code of Federal Regulations, 2012 CFR

...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....

2012-07-01

119

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

Code of Federal Regulations, 2010 CFR

...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....

2009-07-01

120

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

Code of Federal Regulations, 2010 CFR

...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....

2010-07-01

121

Scintillation Properties of Unactivated Calcium Fluoride Crystal  

NASA Astrophysics Data System (ADS)

This paper presents scintillation properties of unactivated calcium fluoride exposed to X-rays and ?-rays from 6 keV to 662 keV. The relative pulse heights and linearity response have been measured. The photoelectron yields have been obtained. A clear full energy photopeak for Cs137 (662 keV) ?-rays has been observed.

Zhu, Y. C.; Lu, J. G.; You, K.; Shao, Y. Y.; Sun, H. S.; Zheng, Z. P.; Ye, M. H.; Cui, F. Z.; Yu, C. J.; Jiang, G. J.

122

Crystal structure of a calcium sulfate-urea complex  

Microsoft Academic Search

The crystal structure of CaSO4 · 4(CH4N2) has been determined from 2695 x-ray intensities measured on a diffractometer, and refined anisotropically to anR-factor of 0.059. The pseudotetragonal crystals contain linear chains of CaSO4 which strongly resemble those in other CaSO4 phases. A common dodecahedral coordination of calcium ions in all these phases is demonstrated, and its implications in the conversion

J. P. R. De Villiers; J. C. A. Boeyens

1975-01-01

123

Calcium Acetate versus Calcium Carbonate for the Control of Serum Phosphorus in Hemodialysis Patients  

Microsoft Academic Search

Recent in vitro and in vivo studies have shown that calcium acetate (CaAC) is a more effective phosphorus binder than, among other calcium salts, calcium carbonate (CaCO3). More efficient binding allows serum phosphorus to be controlled with a lower dose; moreover, less calcium seems to be absorbed when CaAC is used. These properties could reduce the incidence of hypercalcemia; however,

Jaume Almirall; Lluis Veciana; Joan Llibre

1994-01-01

124

The inhibition of calcium hydroxyapatite crystal growth by polyphosphonates and polyphosphates  

Microsoft Academic Search

The formation of crystalline calcium hydroxyapatite from solutions of calcium and phosphate ions and the inhibition of calcium hydroxyapatite crystal growth by polyphosphonates and polyphosphates have been studied. The polyphosphonates, disodium ethane-1-hydroxy-1,1-diphosphonate and disodium dichloromethane diphosphonate, are effective inhibitors of calcium hydroxyapatite crystal growth. The polyphosphates are also effective inhibitors of calcium hydroxyapatite crystal growth as long as the required

Marion D. Francis

1969-01-01

125

Protein mapping of calcium carbonate biominerals by immunogold.  

PubMed

The construction of metazoan calcium carbonate skeletons is finely regulated by a proteinaceous extracellular matrix, which remains embedded within the exoskeleton. In spite of numerous biochemical studies, the precise localization of skeletal proteins has remained for a long time as an elusive goal. In this paper, we describe a technique for visualizing shell matrix proteins on the surface of calcium carbonate crystals or within the biominerals. The technique is as follows: freshly broken pieces of biominerals or NaOCl then EDTA-etched polished surfaces are incubated with an antibody elicited against one matrix protein, then with a secondary gold-coupled antibody. After silver enhancement, the samples are subsequently observed with scanning electron microscopy by using back-scattered electron mode. In the present case, the technique is applied to a particular example, the calcitic prisms that compose the outer shell layer of the mediterranean fan mussel Pinna nobilis. One major soluble protein, caspartin, which was identified recently, was partly de novo sequenced after enzymatic digestions. A polyclonal antibody raised against caspartin was used for its localization within and on the prisms. The immunogold localization indicated that caspartin surrounds the calcitic prisms, but is also dispersed within the biominerals. This example illustrates the deep impact of the technique on the definition of intracrystalline versus intercrystalline matrix proteins. Furthermore, it is an important tool for assigning a putative function to a matrix protein of interest. PMID:17306364

Marin, Frédéric; Pokroy, Boaz; Luquet, Gilles; Layrolle, Pierre; De Groot, Klaas

2007-02-02

126

Control of calcium oxalate crystal structure and cell adherence by urinary macromolecules  

Microsoft Academic Search

Control of calcium oxalate crystal structure and cell adherence by urinary macromolecules. Crystal polymorphism is exhibited by calcium oxalates in nephrolithiasis, and we have proposed that a shift in the preferred crystalline form of calcium oxalate (CaOx) from monohydrate (COM) to dihydrate (COD) induced by urinary macromolecules reduces crystal attachment to epithelial cell surfaces, thus potentially inhibiting a critical step

Jeffrey A. Wesson; Elaine M. Worcester; John H. Wiessner; Neil S. Mandel; Jack G. Kleinman

1998-01-01

127

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

PubMed Central

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 increase in serum gastrin and gastric acid output after intragastric calcium carbonate was not affected, however, by a simultaneous intraduodenal acid load. Equivalent neutralising doses of magnesium hydroxide (pH 9-4) did not increase serum gastrin and gastric acid output above basal levels, whereas antral acidification with 20 ml 0-1 N HCl resulted in a slight decrease in serum gastrin. Intraduodenal calcium carbonate (pH 3-0) also increased serum gastrin and gastric acid output, whereas an equivalent volume of intraduodenal saline (pH 3-0) had no effect. These findings indicate that calcium increases serum gastrin by local stimulation of antral and duodenal mucosa. They also suggest that the action of calcium on gastric secretion is partly mediated by gastrin.

Behar, J; Hitchings, M; Smyth, R D

1977-01-01

128

Crystallization rules of calcium oxalate crystals in lithogenic urine and in healthy urine in vitro  

Microsoft Academic Search

Crystallization of calcium oxalate (CaOxa) was comparatively studied in vitro in diluted lithogenic urine and in diluted healthy urine by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier transform infrared (FT-IR) spectroscopy. In healthy urine, the crystallization was a growth-controlled process in the early stage of crystallization and a nucleation-controlled process in the middle and late stage.

Sui-Ping Deng; Hui Zheng; Jian-Ming Ouyang

2006-01-01

129

Bio-deposition of a calcium carbonate layer on degraded limestone by Bacillus species.  

PubMed

To obtain a restoring and protective calcite layer on degraded limestone, five different strains of the Bacillus sphaericus group and one strain of Bacillus lentus were tested for their ureolytic driven calcium carbonate precipitation. Although all the Bacillus strains were capable of depositing calcium carbonate, differences occurred in the amount of precipitated calcium carbonate on agar plate colonies. Seven parameters involved in the process were examined: calcite deposition on limestone cubes, pH increase, urea degrading capacity, extracellular polymeric substances (EPS)-production, biofilm formation, zeta-potential and deposition of dense crystal layers. The strain selection for optimal deposition of a dense CaCO(3) layer on limestone, was based on decrease in water absorption rate by treated limestone. Not all of the bacterial strains were effective in the restoration of deteriorated Euville limestone. The best calcite precipitating strains were characterised by high ureolytic efficiency, homogeneous calcite deposition on limestone cubes and a very negative zeta-potential. PMID:16491305

Dick, Jan; De Windt, Wim; De Graef, Bernard; Saveyn, Hans; Van der Meeren, Paul; De Belie, Nele; Verstraete, Willy

2006-02-21

130

Biochemical and ultrastructural evidence for the origin of whitings: A biologically induced calcium carbonate precipitation mechanism  

SciTech Connect

The authors propose that Bahamian whitings, floating patches of lime mud, are in part the result of biological precipitation of calcium carbonate induced by picoplankton and cellular components. The cells may act as nucleation sites for crystallization from seawater supersaturated with CaCO{sub 3}. Their model represents a new hypothesis concerning Bahamian whiting formation and is based on several lines of evidence. Biochemical data suggest that the macromolecules from carbonate suspended in Bahama Banks whitings are distinct from those found in the lime mud sediment producer Penicillus and from bottom sediment. Direct ultrastructural evidence indicates that mineralization occurs on the surfaces of picoplankton cells and degrading organic cellular components. The organic constituents include, but are not restricted to, whole and fragmented algal cell and composite structures {approximately}20-30 {mu}m in diameter. The observed calcium carbonate crystals are distinct from skeletal debris. Because of the magnitude of the whiting phenomenon, calculations of carbonate sediment production budgets should include the potential contribution of calcium carbonate produced by epicellular precipitation. Knowledge of carbonate mud genesis is critical to interpretation of ancient occurrences of lime mud as well as to understanding ancient and global carbon cycles.

Robbins, L.L. (Univ. of South Florida, Tampa (United States)); Blackwelder, P.L. (Rosenstiel School of Marine and Atmospheric Science, Miami, FL (United States))

1992-05-01

131

Studies on the role of calcium phosphate in the process of calcium oxalate crystal formation  

Microsoft Academic Search

Crystals of calcium phosphate (CaP) added to solutions with a composition corresponding to that at different levels of the\\u000a collecting duct (CD) and with different pH were rapidly dissolved at pH 5.0, 5.25 and 5.5. Only minor or no dissolution was\\u000a observed at higher pH levels. Despite this effect, CaP crystals induced nucleation or heterogeneous crystallization of CaOx\\u000a up to

Hans-Göran Tiselius; Bengt Lindbäck; Anne-Marie Fornander; Mari-Anne Nilsson

2009-01-01

132

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

PubMed

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

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

2012-06-15

133

Crystallization of calcium sulfate dihydrate and calcium sulfite hemihydrate from synthetic flue gas desulfurization solutions: Final report  

SciTech Connect

The precipitation of calcium sulfate dihydrate (CaSO/sub 4/.2H/sub 2/O) and calcium sulfite hemihydrate (CaSO/sub 3/.1/2H/sub 2/O) from high, up to 240,000 mg/L, total dissolved solids (TDS) solutions was studied at 50/sup 0/C. The solutions were selected to cover a range of solution compositions of magnesium, calcium, sodium, chloride, and sulfate. Precipitation rates along with crystal habit and size changes were measured to determine the effects of these dissolved species as compared to dilute solution conditions. Calcium sulfate dihydrate (gypsum) precipitation rate was accelerated in the high TDS solutions, especially those containing chloride ion. Alternatively, calcium sulfite hemihydrate precipitation rate was found to be faster in high sulfate ion containing solutions. Sodium ion appears to produce gypsum crystals more columnar in habit while solutions containing high amounts of calcium produced very lamellar gypsum crystals. Solutions containing magnesium produced acicular gypsum crystals. Calcium sulfite hemihydrate solids precipitated from solutions containing high sulfate concentrations were rod shaped and globular as compared to the lamellar calcium sulfite hemihydrate crystals precipitated from high chloride and dilute solution liquors. Calcium sulfate-calcium sulfite solid solutions were characterized using infrared spectroscopy. Ion scavenging of Na, Mg, and Cl by gypsum and calcium sulfite solids precipitated from these high TDS solutions was also investigated. 10 refs., 21 figs., 13 tabs.

Trofe, T.W.; Fishman, V.A.; Meserole, F.B.

1986-10-01

134

Hydroxyapatite Synthesized from Nanosized Calcium Carbonate via Hydrothermal Method  

NASA Astrophysics Data System (ADS)

Hydroxyapatite (HAp) was synthesized using a hydrothermal treatment method. Nanosized calcium carbonate (CaCO3) was used as the calcium source, while (NH4)2HPO4 was used as the phosphorous source. Well-crystallized HAp and a small amount of ?-tricalcium phosphate (?-TCP) were obtained after the hydrothermal reaction. FT-IR spectra show that under conditions of pH 6 and 250°C, the functional groups of OH- and PO43- were stronger than those under pH 10. This exhibits that the powder synthesized at pH 6 has more HAp phase than that at pH 10. SEM and TEM images show that HAp exhibits a rod-like shape about 10?m long and about 0.7?m wide at pH 6 and 250°C. After hydrothermal reaction at pH 6 and 250°C, most products are rod-like HAp with a small amount of ?-TCP synthesized as a byproduct and some residual CaCO3.

Wu, Yu-Shiang; Chang, Wen-Ku; Jou, Min

2011-06-01

135

Behaviour of calcium carbonate in sea water  

USGS Publications Warehouse

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.

Cloud, Jr. , P. E.

1962-01-01

136

Calcium Carbonate Precipitation as Influenced by Stream Primary Production.  

National Technical Information Service (NTIS)

The water chemistry, hydrology, and benthic primary production of the Logan River, in the Bear River Mountains in northern Utah, were monitored for one year to study the potential influence of periphyton photosynthesis on calcium carbonate precipitation i...

G. L. Rupp V. D. Adams

1981-01-01

137

Hydrophobic Modification and Characterization of Calcium Carbonate Nanopowders  

Microsoft Academic Search

Calcium carbonate nanopowder is an important engineering material used for various painting and polymer-based composite additive and filler. The hydrophobic modification on surface of calcium carbonate nanopowder was performed by using three silane coupling agents: i.e. 3-Aminopropyl triethoxysilane (APTES), 3-mercapto-propyl triethoxysilane (MPTES) and 3-ATRP trimethoxysilane (KH570). The Fourier Transform Infrared Spectrometry (FT-IR) was used to confirm the surface chemical coupling

Li Jirui; Zhuzhou Hunan

2010-01-01

138

Study of relation between crystal structure and laser damage of calcium flouride  

Microsoft Academic Search

The artificially grown calcium fluoride is one of key materials for microlithography and used for excimer laser optics etc. Such calcium fluoride is required high laser durability and laser induced bulk damage threshold (LIDT). However, the artificially grown calcium fluoride is not a complete crystal, and there are a lot of sub-grain boundaries inside the crystal that have the possibility

Minako Azumi; Eiichiro Nakahata

2010-01-01

139

Fortification of all-purpose wheat-flour tortillas with calcium lactate, calcium carbonate, or calcium citrate is acceptable.  

PubMed

Fortification helps provide adequate nutrients for individuals not meeting daily needs. Foods may be fortified with calcium to assist individuals with lactose intolerance and others preferring not to consume traditional forms of dairy. This study examined the quality of all-purpose wheat-flour tortillas fortified with calcium lactate, calcium carbonate, or calcium citrate. These tortillas were compared to similarly prepared nonfortified flour tortillas (control) and commercial nonfortified flour tortillas. Calcium-fortified tortillas contained 114 mg elemental calcium per standard serving (48 g tortilla), an 8.6-fold increase compared to nonfortified tortillas. Moisture contents and rollabilities of all tortillas were similar. Consumers (N=87) evaluated each tortilla in duplicate using a hedonic scale and reported liking the appearance, texture, flavor, aftertaste, and overall acceptability of all tortillas. However, the appearance of control tortillas was preferred over commercial tortillas (P<0.01), whereas the aftertaste of commercial tortillas or those fortified with calcium carbonate was preferred over the control (P<0.05). Despite these differences, consumers were equally willing to purchase both fortified and nonfortified tortillas, suggesting that appearance and aftertaste may not influence willingness to purchase. Overall, this study shows that fortification of flour tortillas with various forms of calcium is a feasible alternative calcium source. PMID:17324671

Romanchik-Cerpovicz, Joelle E; McKemie, Rebecca J

2007-03-01

140

Carbon dioxide absorption mechanisms of sodium added to calcium oxide at high temperatures  

Microsoft Academic Search

To apply the CO2 absorber at about 1000°C for integrated coal gasification combined cycle (IGCC) furnace, the reactions of calcium oxide and CO2 at high temperatures was examined. Calcium carbonate reacts with sodium hydrogen carbonate below 200°C and forms sodium–calcium complex carbonate. The sodium–calcium complex carbonate melts at 813°C, and the carbon dioxide absorption and discharge reversible reactions of calcium-oxide

Shunkichi Ueno; D. Doni Jayaseelan; Jihong She; Naoki Kondo; Tatsuki Ohji; Shuzo Kanzaki

2004-01-01

141

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

SciTech Connect

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.

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

142

Formation and Growth Mechanism of Calcium Carbonate Nanoparticles via a Bubbling Method  

NASA Astrophysics Data System (ADS)

The mechanism of formation and growth of calcium carbonate (CaCO3) nanoparticles by bubbling carbon dioxide in aqueous suspensions of calcium hydroxide was investigated using time-resolved in situ synchrotron small-angle X-ray scattering (SAXS) and transmission electron microscopey (TEM). In situ SAXS showed a significant change in the particles size in the primary reaction. This suggests that the nucleus forms CaCO3 at in this period. After the nucleation, the crystal grow with the reaction time to yield 40 nm CaCO3 nanoparticles. TEM showed fibrous or chain-like intermediates formed by aggregation of fine particles of CaCO3 as calcite. We propose that CaCO3 crystal nuclei generated in the primary reaction grow to yield fibrous or chain-like CaCO3 which then separates into individual particles to form CaCO3 nanoparticles.

Eguchi, K.; Satake, T.; Tajika, M.; Kuwamoto, S.; Yokoyama, K.; Matsui, J.; Issiki, T.; Umesaki, N.

2011-10-01

143

Crystal growth and characterization of calcium metaborate scintillators  

NASA Astrophysics Data System (ADS)

Calcium metaborate CaB2O4 single crystals were grown by the Czochralski (CZ) method with the radio-frequency (RF) heating system. In these crystals, a plane cleavage was observed along the growth direction. The crystals had an 80% transparency, and no absorption bands were detected in the 190-900 nm wavelength range. The 241Am 5.5 MeV ?-ray-excited radioluminescence spectrum of CaB2O4 demonstrated a broad intrinsic luminescence peak at 300-400 nm, which originated from the lattice defects or an exciton-based emission. According to the pulse height spectrum, when irradiated by neutrons from a 252Cf source, the scintillation light yielded approximately 3200 photons per neutron (ph/n).

Fujimoto, Y.; Yanagida, T.; Kawaguchi, N.; Fukuda, K.; Totsuka, D.; Watanabe, K.; Yamazaki, A.; Chani, V.; Nikl, M.; Yoshikawa, A.

2013-03-01

144

Dissolution kinetics of calcium carbonate in equatorial Pacific sediments  

SciTech Connect

Calcium carbonate dissolution exerts a major influence on the carbonate chemistry of seawater and is an important factor in regulating atmospheric CO2 concentration. The authors use a numerical model, based on an estimate of k determined from benthic chamber flux measurements, the distribution of CO3 2-in the water column and percent of CaCO3 in the sediments, to derive the total alkalinity flux from Pacific Ocean sediments. The significance of this budget is discussed as are the following questions: what is the rate of calcium carbonate dissolution on the deep sea floor what controls carbonate dissolution, organic carbon rain rates, or bottom water carbonate ion concentration what is the equations that relates carbonate dissolution to degree of undersaturation and what is the associate rate constant 43 refs., 10 figs., 4 tabs.

Berelson, W.M.; Hammond, D.E.; McManus, J.; Kilgore, T.E. (Univ. of Southern California, Los Angeles, CA (United States))

1994-06-01

145

Calcium Oxalate Crystals in the Aragonite-Producing Green Alga Penicillus and Related Genera  

Microsoft Academic Search

Calcium oxalate crystals occur in the marine green algae Penicillus, Rhipocephalus, and Udotea, known as producers of sedimentary aragonite needles. In contrast to the externally deposited aragonite crystals which are generally < 15 micrometers long, the oxalate crystals are larger (up to 150 micrometers) and are located in the vacuolar system of the plant. No calcium oxalate was found in

E. Imre Friedmann; William C. Roth; James B. Turner; Ronald S. McEwen

1972-01-01

146

Synthesis of calcium carbonate polymorphs in the presence of polyacrylic acid  

Microsoft Academic Search

Calcium carbonate precipitates are prepared from a solution of CaCl2 and K2CO3 in the presence of polyacrilic acid. The effect of polyacrilic acid incorporation in the [25–80°C] temperature range on crystal morphologies and CaCO3 precipitated polymorph concentrations are investigated using scanning electron microscopy and X-ray diffraction quantitative microstructural and phase analysis. Large changes in morphology and phase proportions are observed

S. Ouhenia; D. Chateigner; M. A. Belkhir; E. Guilmeau; C. Krauss

2008-01-01

147

A simple method to control the polymorphs of calcium carbonate in CO2-diffusion precipitation  

NASA Astrophysics Data System (ADS)

Using glycine as an additive and choosing different solution heights in the vessel, we can control the precipitation of calcium carbonate crystals on glass-clips with their polymorphs to be calcite, vaterite or aragonite. Then we tried to establish the causalities between experiment conditions and polymorphs on the aspect of nucleation energies. Qualitative analysis showed approving interpretation of results of the experiments. Further discussion summarized three ways in which additives may control polymorphs in biomineralization.

Hou, Wentao; Feng, Qingling

2005-08-01

148

Effect of calcium carbonate saturation of seawater on coral calcification  

Microsoft Academic Search

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

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

1998-01-01

149

A reactive force field for aqueous-calcium carbonate systems.  

PubMed

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

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

2011-08-18

150

Correlation between calcium carbonate content and emission characteristics of incense.  

PubMed

In Taiwan and China, calcium carbonate is commonly added as a filler during incense production to lower the cost. This study has found an unexpected benefit for this practice: it reduces particulate emission. Nine types of the popular incense on the local market were chosen for this study. The calcium content in raw material incense was analyzed by inductively coupled plasma atomic emission spectrometry, followed by X-ray diffraction (XRD) spectroscopy. The correlation between the calcium content and emission characteristics of incense was investigated. The calcium content varied from 1.8 to 60 mg/g (incense burned) among those nine different types of incense. Very little calcium (< 1%) was found in natural wood or plants, which is mainly the raw material of incense. Instead, most calcium was artificially added in the form of CaCO3 during manufacturing. The combustion characteristics, including burning rate, emission factors of particulate, ash, and solid-phase polycyclic aromatic hydrocarbons (S-PAHs), varied significantly among the nine types of incense. Incense containing 2% calcium would emit 30% less S-PAHs, compared with those with little (< 0.2%) calcium. More importantly, increasing the calcium content from 0.5 to 5% by adding CaCO3 reduced the particulate emission from incense by approximately 50%. PMID:17195491

Yang, Chi-Ru; Lin, Ta-Chang; Chang, Feng-Hsiang

2006-12-01

151

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

PubMed

The influence of mineral substrate composition and structure on bacterial calcium carbonate productivity and polymorph selection was studied. Bacterial calcium carbonate precipitation occurred on calcitic (Iceland spar single crystals, marble, and porous limestone) and silicate (glass coverslips, porous sintered glass, and quartz sandstone) substrates following culturing in liquid medium (M-3P) inoculated with different types of bacteria (Myxococcus xanthus, Brevundimonas diminuta, and a carbonatogenic bacterial community isolated from porous calcarenite stone in a historical building) and direct application of sterile M-3P medium to limestone and sandstone with their own bacterial communities. Field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), powder X-ray diffraction (XRD), and 2-dimensional XRD (2D-XRD) analyses revealed that abundant highly oriented calcite crystals formed homoepitaxially on the calcitic substrates, irrespective of the bacterial type. Conversely, scattered spheroidal vaterite entombing bacterial cells formed on the silicate substrates. These results show that carbonate phase selection is not strain specific and that under equal culture conditions, the substrate type is the overruling factor for calcium carbonate polymorph selection. Furthermore, carbonate productivity is strongly dependent on the mineralogy of the substrate. Calcitic substrates offer a higher affinity for bacterial attachment than silicate substrates, thereby fostering bacterial growth and metabolic activity, resulting in higher production of calcium carbonate cement. Bacterial calcite grows coherently over the calcitic substrate and is therefore more chemically and mechanically stable than metastable vaterite, which formed incoherently on the silicate substrates. The implications of these results for technological applications of bacterial carbonatogenesis, including building stone conservation, are discussed. PMID:22447589

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

2012-03-23

152

Dissolution of steelmaking slags in acetic acid for precipitated calcium carbonate production  

Microsoft Academic Search

A promising option for long-term storage of CO2 is to fixate carbon dioxide as magnesium- and calcium carbonates. Slags from iron and steel works are potential raw materials for carbonation due to their high contents of calcium silicates. Precipitated calcium carbonate (PCC) is used as filler and coating materials in paper. If slag could be used instead of limestone for

Sebastian Teir; Sanni Eloneva; Carl-Johan Fogelholm; Ron Zevenhoven

2007-01-01

153

Formation of a calcium phosphate-rich layer on absorbable calcium carbonate bone graft substitutes  

Microsoft Academic Search

The use of natural coral as a bone graft substitute is common in Europe. However, the bone-coral bonding mechanism remains elusive. A rat subcutaneous model was used to demonstrate changes at the surface of resorbable calcium carbonate in the form of natural coral. Histological results indicated in vivo formation of a calcium phosphate (CaP)-rich layer on the surface of the

C. J. Damien; J. L. Ricci; P. Christel; H. Alexander; J.-L. Patat

1994-01-01

154

Crystal structure of calcium dodecin (Rv0379), from Mycobacterium tuberculosis with a unique calcium-binding site  

PubMed Central

In eukaryotes, calcium-binding proteins play a pivotal role in diverse cellular processes, and recent findings suggest similar roles for bacterial proteins at different stages in their life cycle. Here, we report the crystal structure of calcium dodecin, Rv0379, from Mycobacterium tuberculosis with a dodecameric oligomeric assembly and a unique calcium-binding motif. Structure and sequence analysis were used to identify orthologs of Rv0379 with different ligand-binding specificity.

Arockiasamy, Arulandu; Aggarwal, Anup; Savva, Christos G; Holzenburg, Andreas; Sacchettini, James C

2011-01-01

155

Crystallization of calcium sulfate dihydrate and calcium sulfite hemihydrate from synthetic flue gas desulfurization solutions: Final report  

Microsoft Academic Search

The precipitation of calcium sulfate dihydrate (CaSOâ.2HâO) and calcium sulfite hemihydrate (CaSOâ.1\\/2HâO) from high, up to 240,000 mg\\/L, total dissolved solids (TDS) solutions was studied at 50°C. The solutions were selected to cover a range of solution compositions of magnesium, calcium, sodium, chloride, and sulfate. Precipitation rates along with crystal habit and size changes were measured to determine the effects

T. W. Trofe; V. A. Fishman; F. B. Meserole

1986-01-01

156

Crystal structure of calcium dodecin (Rv0379), from Mycobacterium tuberculosis with a unique calcium-binding site  

SciTech Connect

In eukaryotes, calcium-binding proteins play a pivotal role in diverse cellular processes, and recent findings suggest similar roles for bacterial proteins at different stages in their life cycle. Here, we report the crystal structure of calcium dodecin, Rv0379, from Mycobacterium tuberculosis with a dodecameric oligomeric assembly and a unique calcium-binding motif. Structure and sequence analysis were used to identify orthologs of Rv0379 with different ligand-binding specificity

Arockiasamy, Arulandu; Aggarwal, Anup; Savva, Christos G.; Holzenburg, Andreas; Sacchettini, James C. (TAM)

2011-09-28

157

Single Crystal Metals Encapsulated in Carbon Nanoparticles  

Microsoft Academic Search

Single-domain microcrystals of LaC_2 encapsulated within nanoscale polyhedral carbon particles have been synthesized in a carbon arc. Typical particle sizes are on the order of 20 to 40 nanometers. The stoichiometry and phase of the La-containing crystals have been assigned from characteristic lattice spacings observed by high-resolution transmission electron microscopy and energy dispersive spectroscopy (EDS). EDS spectra show that La

Rodney S. Ruoff; Donald C. Lorents; Bryan Chan; Ripudaman Malhotra; Shekhar Subramoney

1993-01-01

158

Ion chromatography detection of fluoride in calcium carbonate.  

PubMed

Fluoride in aquatic systems is increasing due to anthropogenic pollution, but little is known about how this fluoride affects organisms that live in and around aquatic habitats. Fluoride can bioaccumulate in structures comprised of calcium carbonate, such as shells and skeletons of both freshwater and saltwater species as diverse as snails, corals, and coccolithophorid algae. In this article, ion chromatography (IC) techniques are developed to detect and quantify fluoride in a matrix of calcium carbonate. Solid samples are dissolved in hydrochloric acid, pretreated to remove the majority of the chloride ions, and then analyzed using IC. With these methods, the 3? limit of detection is 0.2 mg of fluoride/kg of calcium carbonate. PMID:21859530

Lefler, Jamie E; Ivey, Michelle M

2011-09-01

159

Influence of solution concentration on controlled crystallization of calcium phosphate  

NASA Astrophysics Data System (ADS)

To investigate the influence of solution concentration on controlled crystallization of calcium phosphate, controlled crystallization in the presence of stearic acid monolayer from solutions of hydroxyapatite with different [Ca2+] have been studied by SEM, TEM with ED, IR, XRD. When [Ca2+] is 0.4 mM, octacalcium phosphate (OCP) which is a thermodynamically undersaturated phase in this condition precipitates due to the 'concentration effect' of charged headgroup -COO- of stearic monolayer to Ca2+ in the solution; while solution is supersaturated in which [Ca2+] is 4 mM, the first precipitates phase is hydroxyapatite (HAP) with (0001) parallel to the surface of stearic monolayer. Subsequent growth results in oriented OCP crystals, and all the crystals show a white semi- globular characters; while [Ca2+] is up to 5 mM, the increasing of mineralization rate results to the rapid nucleation of HAP into some core-like structure and the later growth of platelet-like OCP as the 'shell.' Nucleation of DCPD between OCP showing a flower-like structure also found at LB film/solution interface. The mechanism of influence of concentration was discussed.

Ma, C. L.; Qian, F.; Lu, H. B.

1998-02-01

160

Crystal growth of calcite from calcium bicarbonate solutions at constant PCO2 and 25??C: a test of a calcite dissolution model  

USGS Publications Warehouse

A highly reproducible seeded growth technique was used to study calcite crystallization from calcium bicarbonate solutions at 25??C and fixed carbon dioxide partial pressures between 0.03 and 0.3 atm. The results are not consistent with empirical crystallization models that have successfully described calcite growth at low PCO2 (< 10-3 atm). Good agreement was found between observed crystallization rates and those calculated from the calcite dissolution rate law and mechanism proposed by Plummer et al. (1978). ?? 1981.

Reddy, M. M.; Plummer, L. N.; Busenberg, E.

1981-01-01

161

Distribution of calcium carbonate in desert soils: A model  

SciTech Connect

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.

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

1988-04-01

162

Effects of alginic acid from marine algae on calcium carbonate electrodeposited coating  

NASA Astrophysics Data System (ADS)

The effect of alginic acid, extracted from the Lessonia trabeculata calcareous marine algae, was studied in the electrocrystallization of calcium carbonate (CaCO3) on indium tin oxide (ITO) transparent electrodes. Scanning electron microscopy, X-ray diffraction-collected data and microscopic observations show that the presence of Mg at the electrolyte induces the magnesium calcite and aragonite phase formation along with the changes in morphology and crystal orientation. Addition of alginic acid strongly inhibits the effect of Mg on the crystallization, receiving in favor of the nucleation and growth of calcite phase of CaCO3. These results suggest that the alginic acid acts as an organic template in the electrocrystallization of CaCO3, controlling the crystallographic orientation of crystal growth, and as a consequence, the crystal morphology.

Pavez, Jorge; Silva, Juan F.; Melo, Francisco

2005-09-01

163

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

PubMed

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

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

2012-09-20

164

Habit modification of calcium carbonate in the presence of malic acid  

NASA Astrophysics Data System (ADS)

The ability of malic acid to control calcium carbonate morphology has been investigated by aging calcium chloride solution in the presence of urea in a 90 °C bath. Malic acid favors the formation of calcite. A transition from single block to aggregate with special morphology occurs upon increasing malic acid concentration. The morphological development of CaCO3 crystal obviously depends on the starting pH. CaCO3 crystal grows from spindle seed to dumbbell in the pH regime from 7 to 11; while it evolves from spindle seed, through peanut, to sphere at pH=11.5. Both dumbbell and sphere consist of rods that are elongated along c-axis and capped with three smooth, well-defined rhombic {1 0 4} faces. A tentative growth mechanism is proposed based on the fractal model suggested by R. Kniep and S. Busch [Angew. Chem. Int. Ed. Engl. 35 (1996) 2624].

Mao, Zhaofeng; Huang, Jianhua

2007-02-01

165

CALCIUM OXALATE CRYSTAL FORMATION IS NOT ESSENTIAL FOR GROWTH OF MEDICAGO TRUNCATULA  

Technology Transfer Automated Retrieval System (TEKTRAN)

Plants invest a considerable amount of resources and energy into the formation of calcium oxalate crystals. A number of roles for crystal formation in plant growth and development have been assigned based on the prevalence of crystals, their spatial distribution, and the variety of crystal shapes. ...

166

[Inhibitory factors of calcium oxalate crystal growth in urinary macromolecules].  

PubMed

We studied the inhibitory effect of urinary glycosaminoglycans (GAGs), in the natural form, on calcium oxalate crystals. Control urine was collected from five healthy subjects and filtered by 5 microns and 0.22 micron membranes. The urine was cut off by a membrane of 30,000 M.W. and the remaining urine was fractionated into three groups by anion-exchange chromatography on DEAE-cellulose: peak A contained only protein, peak B both protein and GAGs and peak C only GAGs. Peak A and peak B were fractionated again through a Sephacryl S-200 gel column. Each fractionated sample was examined for the inhibitory effect on calcium oxalate crystal growth using the 14C-oxalate seeded crystal growth assay in a metastable solution developed by Koide et al. GAGs were determined by two-dimensional electrophoresis on cellulose acetate membrane. SDS-polyacrylamide electrophoresis was used to determine the molecular weights of proteins. Peak A was found to have many kinds of proteins which had low inhibitory effects. Peak B had three kinds of proteins such as those with molecular weights of 130,000, 45,000 and 35,000 as well as uronic acid. These proteins and uronic acid had high inhibitory effect and the highest inhibitory effect was found in the fraction of around 50,000 M.W. where protein and uronic acid were contained. The molecular weight of this protein was 42,000 by SDS electrophoresis. Uronic acid was a keratan sulphate by a two-dimensional electrophoresis. In peak C there were mainly chondroitin sulphate and a small amount of heparan sulfate which had high inhibitory effect.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2402111

Matsumoto, A; Terado, T; Kin, M; Nishio, S; Iwata, H; Takeuchi, M

1990-06-01

167

The effect of ions at the surface of calcium oxalate monohydrate crystals on cell-crystal interactions.  

PubMed

Magnesium is an abundant ion in biologic systems, including renal tubular fluid; however, the precise role of magnesium during the interaction of calcium oxalate crystals with cells has not been previously defined. In addition, the respective roles of calcium and hydrogen ions during the cell-crystal bonding interaction remain poorly defined. Here we report an atomic level three-dimensional study of a single crystal of calcium oxalate monohydrate (COM; whewellite) which was bathed in a solution of magnesium hexahydrate for 1 year. Magnesium was not incorporated into the structure of whewellite to any significant degree. Instead, COM accepted magnesium primarily as an adsorbate in a binding configuration which, as a surface phenomenon, is controlled by localized charge effects. The effect of magnesium and calcium on the efficiency of calcium oxalate crystal binding to renal cells was also investigated. When present in supraphysiologic concentrations (greater than 0.1 M), magnesium progressively inhibited adhesion of pre-formed COM crystals to cultured renal cells. Therefore, even though magnesium does not incorporate into the crystal structure of calcium oxalate, magnesium can exert important surface effects and change the interaction of pre-formed COM with molecules anchored on the cell surface. Similarly, binding was nearly blocked when the exogenous calcium concentration was > or =0.1 M (supraphysiologic range), although in lower concentrations (within the physiologic range) exogenous calcium promoted crystal adhesion. Finally, the ambient hydrogen ion concentration also influenced calcium oxalate crystal interactions with renal cells, with maximal binding occurring at a pH of 4. Therefore, hypercalciuria and/or an acidic urine could each promote renal stone formation via increased crystal adhesion to renal cells, a previously under-appreciated potential mechanism. PMID:14663633

Lieske, John C; Farell, Gerard; Deganello, Sergio

2003-12-09

168

Method for the conversion of calcium sulfoxy compounds into calcium carbonate compounds in sulfur oxide treatment processes  

SciTech Connect

A method for converting calcium sulfoxy compounds selected from the group consisting of casox and ca(Hsox)2 and their hydrates wherein X is 3 or 4 into calcium carbonate, the method consisting essentially of; converting the ca(Hsox)2 compounds into casox compounds by reacting the ca(Hsox)2 compounds with calcium carbonate in the presence of water, thereafter reacting the casox compounds with ammonia and carbon dioxide in the presence of water to produce nh4(Hsox) wherein X is 3 or 4 and calcium carbonate, thereafter separating the nh4(Hsox) and calcium carbonate and reacting the nh4(Hsox) with carbon to produce ammonia, hydrogen sulfide and carbon oxides.

Clark, W.E.

1980-05-06

169

Photonic crystals with porous carbon and metals  

NASA Astrophysics Data System (ADS)

Creation of periodic nano-structures at the scale of 100-1000 nm attracts increasing interest, since such structures would be photonic crystals (PC) with potential photonic band gap (PBG) in visible/infrared spectral range, where a number of exciting phenomena is expected. We suggested recently the concept of tunable PBG, by having electrically tunable material (e.g. conducting polymer or liquid crystal) as one of PC components. In the present talk we describe self-assembly methods to create metallic tunable PCs, made of carbon, and metals or semimetals. We have created optical photonic crystals with cubic superlattice symmetry and lattice parameters at optical wavelengths by a synthetic method, which is based on multi-step templating processes that start with self-assembled opals. Novel carbon PC materials obtained include diamond inverse opals, a new form of carbon called "cubic graphite", and truncated and untruncated inverse and direct opals of various insulators, semiconductors, and metals. The cubic graphite phase (which contains about 0.3 billion atoms in the unit cell) is based on the tiling of a three-dimensionally periodic surface with graphite sheets, like in theoretically proposed schwarzite phases. This cubic graphite is an analog of giant multi-walled fullerenes covalently bonded into an fcc crystal lattice. We also have developed a new technology to create from metals the structures which are most desirable for optical metallic photonic crystals with metallicity photonic band gaps in IR region, which are not related to Bragg scattering, but are derived from plasmon bands. At the same time such metallic inverted opal PC may serve as a matrix for even more sophisticated photonic crystals and advanced thermoelectrics with strongly suppressed thermal conductivity and unusual temperature dependence of electrical conductivity. The new features of metallic photonic crystals based on inverted opals in visible and IR regions are presented and discussed.

Zakhidov, Anvar A.

2000-03-01

170

The diagnosis of calcium pyrophosphate dihydrate crystal deposition disease: the good, the bad and… ultrasonography!  

PubMed

The diagnosis of calcium pyrophosphate dihydrate crystal deposition disease (CPPD) until recent years has been mainly based on the finding of typical crystals of calcium pyrophosphate dihydrate (CPP) in the synovial fluid of affected patients and on the presence of typical calcifications on plain X-rays.... PMID:22842294

Filippou, G; Frediani, B

2012-07-19

171

Calcium-Containing Crystal-Associated Arthropathies in the Elderly Population  

Microsoft Academic Search

\\u000a Crystal arthropathies commonly affect the elderly people and have been associated with the development of osteoarthritis.\\u000a This chapter will detail the clinical features of and treatment for calcium pyrophosphate deposition disease and other forms\\u000a of calcium-containing crystal-associated arthropathies.

Elisabeth B. Matson; Anthony M. Reginato

172

Tamm-Horsfall mucoproteins promote calcium oxalate crystal formation in urine: quantitative studies  

Microsoft Academic Search

The technique of rapid evaporation of whole urine to standard osmolality has been studied further and quantitative measurements made of the calcium oxalate crystals resulting, firstly by a microscope method and secondly by isotope method using 14C-oxalate. It is confirmed that ultrafiltration of urine prior to evaporation leads to a large reduction in calcium oxalate crystal formation and that this

G. A. Rose; S. Sulaiman

1982-01-01

173

Calcium oxalate crystal formation in the kidneys of rats injected with 4-hydroxy-L-proline  

Microsoft Academic Search

Calcium oxalate crystal formation induced in rat kidneys by intraperitoneal injection of 4-hydroxy-L-proline were studied by chemical, microscopic and size analysis techniques. Crystal growth rates were determined at different intervals of time from the size distribution curves. Calcium oxalate dihydrate (weddelite), formed in the first 2 hour after injection, undergoes gradual phase transformation to the more stable monohydrate (whewellite). This

R. Tawashi; M. Cousineau; M. Sharkawi

1980-01-01

174

Biologically mediated dissolution of calcium carbonate above the chemical lysocline?  

Microsoft Academic Search

We find a diverse but increasing amount of evidence to suggest considerable dissolution of calcium carbonate, perhaps as much as 60–80%, in the upper 500–1000m of the ocean, well above the chemical lysocline. The same biological processes that promote the rapid settling of carbonate particles (i.e. ingestion, digestion and egestion by zooplankton) as well as biologically mediated processes within flocculates

J. D. Milliman; P. J. Troy; W. M. Balch; A. K. Adams; Y.-H. Li; F. T. Mackenzie

1999-01-01

175

CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTACTORS  

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. The purpose of this study was to determine the effect of limestone composition on the kinetics of carbonate mineral dissolution. Th...

176

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 ...

177

Calcium Carbonate Scale Dissolution in Water Stabilized by Carbon Dioxide Treatment.  

National Technical Information Service (NTIS)

Calcium carbonate scale in potable water systems (especially hot-water pipes and exchangers) can restrict pipe flow, causing severe head loss and reducing heat transfer capacity. Chemical and mechanical methods of cleaning the distribution systems are con...

J. Harwood P. M. Temkar R. J. Scholze

1990-01-01

178

Calcium carbonate scale inhibitor for direct contact binary geothermal service  

Microsoft Academic Search

A 500 kw direct contact binary cycle pilot geothermal power plant was constructed and successfully operated free of scale at the US DOE East Mesa Geothermal Test Facility. The pilot plant used an Elgin tower direct contact heat exchanger with isobutane as the working fluid. Initial tests with the untreated 170 degree C geothermal brine gave heavy calcium carbonate fouling

M. H. Auerbach; R. A. Reimer; R. G. Olander; P. M. Rapier

1982-01-01

179

Recovery of Calcium Carbonate and Sulfur from FGD Scrubber Waste.  

National Technical Information Service (NTIS)

The report gives results of a demonstration of key process steps in the proprietary Kel-S process for recovering calcium carbonate and sulfur from lime/limestone flue gas desulfurization (FGD) scrubber waste. The steps are: reduction of the waste to calci...

R. P. Arganbright P. Huang G. S. Benner B. G. Mandelik T. S. Roche

1982-01-01

180

Calcium Carbonate Production, Coral Reef Growth, and Sea Level Change  

Microsoft Academic Search

Shallow, seaward portions of modern coral reefs produce about 4 kilograms of calcium carbonate per square meter per year, and protected areas produce about 0.8 kilogram per square meter per year. The difference is probably largely a function of water motion. The more rapid rate, equivalent to a maximum vertical accretion of 3 to 5 millimeters per year, places an

S. V. Smith; D. W. Kinsey

1976-01-01

181

Coprecipitation of alkali metal ions with calcium carbonate  

Microsoft Academic Search

The coprecipitation of alkali metal ions (Li + , Na + , K + and Rb + ) with calcium carbonate has been studied experimentally and the following results have been obtained: 1. (1) Alkali metal ions are more easily coprecipitated with aragonite than with calcite. 2. (2) The relationship between the amounts of alkali metal ions coprecipitated with aragonite

Minoru Okumura; Yasushi Kitano

1986-01-01

182

High Pressure Solubility of Calcium Carbonate in Seawater.  

National Technical Information Service (NTIS)

The saturation concentration of calcium carbonate, equilibrated with aragonitic oolites, is about 2.7 times larger after exposure to 1000 atmospheres than it is when saturation is achieved at 1 atmosphere. This suggests that deep ocean waters may be under...

R. M. Pytkowicz D. N. Conners

1964-01-01

183

Influence of electronic antifouling on agglomeration of calcium carbonate  

Microsoft Academic Search

Scaling represents a serious problem to many industries. Scaling in pipes leads to an increased pressure drop and often to complete blockage. On heat exchangers, it reduces the heat transfer. It may also lead to unstable operation which could result in unscheduled shutdown and loss of revenue. One of the most common types of scaling is due to calcium carbonate.

W. N. Al Nasser; A. H. Al Ruwaie; M. J. Hounslow; A. D. Salman

2011-01-01

184

Synthesis of nanostructured carbonated calcium hydroxyapatite by ultrasonic spray pyrolysis  

Microsoft Academic Search

Synthesis of high purity submicrometeric spherical particles are of considerable interest for a wide variety of applications, ranging from electronics via ceramics, catalysts to bioceramic due to their unique properties that are primary determined by size, composition and structure. In this paper, the synthesis of carbonate calcium hydroxyapatite by a spray pyrolysis process in an ultrasonic periodical physical field is

V. Jokanovi; I. Nik; D. Uskokovi

185

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

Microsoft Academic Search

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

John D. Milliman

1993-01-01

186

Crystal structure of the calcium pump of sarcoplasmic reticulum at 2.6 ? resolution  

Microsoft Academic Search

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 ? resolution with two calcium ions bound in the transmembrane domain, which comprises ten ?-helices. The two calcium ions are located side

Masayoshi Nakasako; Hiromi Nomura; Haruo Ogawa; Chikashi Toyoshima

2000-01-01

187

Calcium Carbonate Dissolution Rate in Limestone Contactors.  

National Technical Information Service (NTIS)

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

R. D. Letterman

1995-01-01

188

Calcium oxalate crystals in the aragonite-producing green alga penicillus and related genera.  

PubMed

Calcium oxalate crystals occur in the marine green algae Penicillus, Rhipocephalus, and Udotea, known as producers of sedimentary aragonite needles. In contrast to the externally deposited aragonite crystals which are generally < 15 micrometers long, the oxalate crystals are larger (up to 150 micrometers) and are located in the vacuolar system of the plant. No calcium oxalate was found in the related but noncalcifying genera Avrainvillea and Cladocephalus. PMID:17780990

Friedmann, E I; Roth, W C; Turner, J B; McEwen, R S

1972-09-01

189

Is citrate an inhibitor of calcium oxalate crystal growth in high concentrations of urine?  

Microsoft Academic Search

The effect of citrate on calcium oxalate (CaOx) crystal growth was studied in a system in which series of samples containing [45Ca]calcium chloride were brought to different levels of supersaturation with various concentrations of oxalate. The crystallization was assessed by measuring the amount of isotope remaining in solution 30 min after the addition of CaOx seed crystals to samples containing

H. Bek-Jensen; A.-M. Fornander; M.-A. Nilsson; H.-G. Tiselius

1996-01-01

190

Catalysis of petroleum coke gasification by calcium hydroxide and carbonate  

SciTech Connect

Catalysis of petroleum coke gasification in pure CO{sub 2} by Ca(OH){sub 2} or CaCO{sub 3} has been investigated with a thermobalance. The reactivity of the original coke is very low. Ca(OH){sub 2} kneaded with the carbon in water enhances the reactivity drastically, and thus realizes complete gasification at 900{degrees}C within 25 min. CaCO{sub 3} shows almost the same catalytic activity as Ca(OH){sub 2} except for the initial stage of gasification. The X-ray diffraction measurements and X-ray photoelectron spectroscopy of partly gasified samples reveal that the calcium promotes remarkably the formation of non-crystalline carbon, in other words, surface oxygen complexes, during gasification. The temperature programmed desorption shows that there are strong interactions between calcium and carbon, which contributes to the creation of reactive sites.

Ohtsuka, Yasuo; Yamauchi, Atsuko; Zhuang, Qianlin [Tohoku Univ., Sendai (Japan)

1996-12-31

191

Crystal Structure of Dipotassium Carbonate Trihydrate  

Microsoft Academic Search

The crystal structure of 2K2CO3?3H2O was determined by a sign-correlation procedure using three-dimensional data and refined by anisotropic least squares. The space group is C2?c with unit cell dimensions a = 11.887,b = 13.827,c = 7.112 Å and ? = 120.56°. The structure consists of columns of hydrogen-bonded carbonate ions and water molecules within and between which lie the cations.

F. D. Hunter; G. A. Jeffrey

1967-01-01

192

Long-term effects of calcium carbonate and 2.5 mEq\\/liter calcium dialysate on mineral metabolism  

Microsoft Academic Search

Long-term effects of calcium carbonate and 2.5 mEq\\/liter calcium dialysate on mineral metabolism. Many investigators have shown that calcium carbonate (CaCO3) is an effective phosphate binder which also prevents the potential disabling effects of aluminum (Al) accumulation. However, hypercalcemia may develop in a substantial numbers of patients. Thus, to control serum phosphate (PO4) and prevent hypercalcemia, we performed studies in

Eduardo Slatopolsky; Carol Weerts; Kathryn Norwood; Karla Giles; Patricia Fryer; Jane Finch; David Windus; James Delmez

1989-01-01

193

Reverse engineering the kidney: modelling calcium oxalate monohydrate crystallization in the nephron  

Microsoft Academic Search

Crystallization of calcium oxalate monohydrate in a section of a single kidney nephron (distal convoluted tubule) is simulated\\u000a using a model adapted from industrial crystallization. The nephron fluid dynamics is represented as a crystallizer\\/separator\\u000a series with changing volume to allow for water removal along the tubule. The model integrates crystallization kinetics and\\u000a crystal size distribution and allows the prediction of

A. BorissovaG; G. E. Goltz; J. P. Kavanagh; T. A. Wilkins

2010-01-01

194

The inhibitory effects of carboxymethyl inulin on the seeded growth of calcium carbonate.  

PubMed

Kinetics of precipitation of calcite (CaCO(3)) from aqueous solution in the presence of carboxymethyl inulin (CMI) was investigated under strictly controlled temperature, pH, supersaturation ratio (S=4.8) and ionic strength (I=0.1M). The highly reproducible constant composition technique was used to study the influence of biopolymers of crystal growth of CaCO(3), on CaCO(3) seed crystals at pH 8.5 and 25°C. The crystal growth of calcium carbonate (CaCO(3)) was inhibited in the presence of CMI at low concentration (2.5×10(-9) to 25×10(-9)mol/L). The larger number of negatively charged functional groups exhibited a 95% growth rate inhibition at a concentration of 15×10(-9)mol/L. The higher inhibition efficiency is related to the maximum surface charge density due to adsorbed polymer. PMID:22079106

K?rboga, Semra; Oner, Mualla

2011-10-25

195

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

PubMed Central

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.

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

196

Amorphous Calcium Carbonate in Biomineralization: Stable and Precursor Phases  

NASA Astrophysics Data System (ADS)

The biological formation of the crystalline polymorphs of calcium carbonate, aragonite and calcite, is widespread. The less stable polymorphs, vaterite and monohydrocalcite are also formed by some organisms. Surprisingly, the highly unstable phase, amorphous calcium carbonate (ACC), is formed by a variety of organisms from different phyla. Most of these are stable at least within the lifetime of the organism. The stable forms all have a stoichiometry of CaCO3.H2O. Despite the fact that they do not diffract X-rays. Studies of their short range order by EXAFS, reveal species specific variations in the number and distances of atoms that surround the calcium ion. Proteins extracted from stable biogenic ACC are able to stabilize the phase in vitro. ACC has also been identified as a transient precursor phase during the formation of the calcitic larval spicule of the sea urchin and the formation of the larval shell of a bivalve. The transient form has little or no water associated with the CaCO3. Preliminary EXAFS data suggest that the short range order of the sea urchin spicule transient ACC resembles calcite. Proteins extracted from these spicules are able to stabilize ACC provided Mg is present in the solution. As the mollusks and the echinoderms are on two different branches of the animal phylogenetic tree, it is conceivable that the strategy of using ACC as a precursor phase at least for larval mineralization may be widespread. It has yet to be shown that it is used by adults of either phylum. The manner in which organisms precipitate, stabilize and destabilize if necessary, this highly metastable phase of calcium carbonate presents many fascinating and enigmatic questions, whose solutions could well contribute to a better understanding of basic processes in biomineralization. For more details and references, see Addadi, L., Raz, S. and Weiner, S. (2003). Taking advantage of disorder: Amorphous calcium carbonate and its roles in biomineralization. Adv. Mat.15, 959-970.

Weiner, S.

2003-12-01

197

Textural properties of synthetic nano-calcite produced by hydrothermal carbonation of calcium hydroxide  

NASA Astrophysics Data System (ADS)

The hydrothermal carbonation of calcium hydroxide (Ca(OH)2) at high pressure of CO2 (initial PCO2 1/4 55 bar) and moderate to high temperature (30 and 90 1C) was used to synthesize fine particles of calcite. This method allows a high carbonation efficiency (about 95% of Ca(OH)2-CaCO3 conversion), a significant production rate (48 kg/m3 h) and high purity of product (about 96%). However, the various initial physicochemical conditions have a strong influence on the crystal size and surface area of the synthesized calcite crystals. The present study is focused on the estimation of the textural properties of synthesized calcite (morphology, specific surface area, average particle size, particle size distribution and particle size evolution with reaction time), using Rietveld refinements of X-ray diffraction (XRD) spectra, Brunauer-Emmett-Teller (BET) measurements, and scanning electron microscope (SEM) and transmission electron microscope (TEM) observations. This study demonstrate that the pressure, the temperature and the dissolved quantity of CO2 have a significant effect on the average particle size, specific surface area, initial rate of precipitation, and on the morphology of calcium carbonate crystals. In contrast, these PTx conditions used herein have an insignificant effect on the carbonation efficiency of Ca(OH)2. Finally, the results presented here demonstrate that nano-calcite crystals with high specific surface area (SBET 1/4 6-10m2/g) can be produced, with a high potential for industrial applications such as adsorbents and/or filler in papermaking industry.

Montes-Hernandez, G.; Fernández-Martínez, A.; Charlet, L.; Tisserand, D.; Renard, F.

2008-05-01

198

The coprecipitation of uranium with calcium carbonate  

Microsoft Academic Search

This report is one of the studies on the factors controlling the trace element contents of marine calcareous skeletons. The values of the distribution coefficients of UO22+ between solutions and carbonate precipitates were measured in the laboratory at 20±1‡C. From the determination of the uranium contents of marine calcareous skeletons and sea water, the values of uranium between marine calcareous

Yasushi Kitano; Tamotsu Oomori

1971-01-01

199

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...

200

Luminescence of divalent europium-doped calcium carbonate and oxalate  

Microsoft Academic Search

Divalent europium-doped calcium carbonate and oxalate were synthesized by means of co-precipitation, solid state reactions, and thermal decomposition processes under strictly controlled experimental conditions. Preliminary studies of the synthesized phosphor materials showed that CaCO3:Eu2+ and CaC2O4:Eu2+ have similar spectra, e.g. they both have broad band excitations and emissions with peaks at 350 and 450 nm, respectively. Their luminescence properties are

W.-M Li; T Hänninen; M Leskelä; J Saari; A Hase

2001-01-01

201

Carbon dioxide removal method employing packed solid calcium hydroxide  

SciTech Connect

In order to remove carbon dioxide from an off-gas stream and immobilize it in solid stable form, the gas is passed through a packed bed of calcium hydroxide maintained at a temperature in the range 10/sup 0/ C.-50/sup 0/ C., the moisture content of the gas being controlled so as to correspond to a relative humidity from 40% to 100% at the bed temperature.

Cheh, Ch. H.; Glass, R. W.

1985-01-08

202

Catalytic oxidation of carbon\\/carbon composite materials in the presence of potassium and calcium acetates  

Microsoft Academic Search

The catalytic effects of potassium acetate (KAC) and calcium acetate (CaAC) on the oxidation of carbon\\/carbon composites (C\\/C composites) used in aircraft brake system have been characterized. Potassium exhibited a very strong catalytic effect on the oxidation of the selected carbon samples, including C\\/C composite blocks impregnated with aqueous KAC solution and graphite powder physically mixed with KAC powder. The

Xianxian Wu; Ljubisa R. Radovic

2005-01-01

203

Carbon Nanotube Growth on Calcium Carbonate Supported Molybdenum-Transition Bimetal Catalysts  

Microsoft Academic Search

A comparison of different catalyst systems (Fe–Mo, Co–Mo or Ni–Mo nanoparticles supported on calcium carbonate) has been performed\\u000a in order to optimize the carbon nanotube (CNT) growth. The influences of the reaction temperature, metal loading and carbon\\u000a source on the synthesis of CNTs were investigated. Dense CNT networks have been synthesized by thermal chemical vapor deposition\\u000a (CVD) of acetylene at

Zhongrui Li; Enkeleda Dervishi; Yang Xu; Viney Saini; Meena Mahmood; Olumide Dereck Oshin; Alexandru R. Biris; Alexandru S. Biris

2009-01-01

204

Calcium carbonate scale control, effect of material and inhibitors.  

PubMed

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

Macadam, J; Parsons, S A

2004-01-01

205

A study of carbon dioxide absorption into aqueous monoethanolamine solution containing calcium nitrate in the gas–liquid reactive precipitation of calcium carbonate  

Microsoft Academic Search

The influence of calcium nitrate on the process of carbon dioxide absorption in aqueous monoethanolamine (MEA) solution has been considered. The experimental data obtained under typical conditions used for the industrial precipitation of calcium carbonate has been used to determine the speciation in solution and the supersaturation profile in the bulk liquid by means of a specially developed algorithm as

M Vu?ak; J Peri?; A Žmiki?; M. N Pons

2002-01-01

206

Arthritis associated with calcium oxalate crystals in an anephric patient treated with peritoneal dialysis  

SciTech Connect

The authors report a case of calcium oxalate arthropathy in a woman undergoing intermittent peritoneal dialysis who was not receiving pharmacologic doses of ascorbic acid. She developed acute arthritis, with calcium oxalate crystals in Heberden's and Bouchard's nodes, a phenomenon previously described in gout. Intermittent peritoneal dialysis may be less efficient than hemodialysis in clearing oxalate, and physicians should now consider calcium oxalate-associated arthritis in patients undergoing peritoneal dialysis who are not receiving large doses of ascorbic acid.

Rosenthal, A.; Ryan, L.M.; McCarty, D.J.

1988-09-02

207

Carbon nanotube seeded silicon crystal growth  

NASA Astrophysics Data System (ADS)

Crystal growth of liquid silicon on the heterogeneous surfaces of carbon nanotubes (CNTs) is simulated. Silicon atoms are concentrated to form perfect coaxial cylindrical configurations around CNT cores. The heredity effect makes silicon imprint cylindrical shapes of CNTs during the solidification. The CNTs have a great influence on the stacking sequence of silicon atoms. Growth competition between CNT cores is clearly observed, which results in defects at the shared interface. The internal potential field around CNTs is responsible for growth competition and the heredity effect.

Li, Y. F.; Li, H.; Sun, F. W.; Zhang, X. Q.; Liew, K. M.

2011-07-01

208

Inhibition of calcium oxalate monohydrate crystal growth using Algerian medicinal plants  

Microsoft Academic Search

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 artificial urine is prepared by mixing and stirring two equal volumes of solutions A and B. A screening of plant extracts from

M. Beghalia; S. Ghalem; H. Allali; A. Belouatek; A. Marouf

209

Study of relation between crystal structure and laser damage of calcium flouride  

NASA Astrophysics Data System (ADS)

The artificially grown calcium fluoride is one of key materials for microlithography and used for excimer laser optics etc. Such calcium fluoride is required high laser durability and laser induced bulk damage threshold (LIDT). However, the artificially grown calcium fluoride is not a complete crystal, and there are a lot of sub-grain boundaries inside the crystal that have the possibility of causing degradation of laser durability and LIDT. Moreover, mechanical properties of calcium fluoride are different according to the crystal axis, therefore there is a possibility that mechanical properties influences LIDT. In this study, we examined the relation between crystal structure and LIDT. First, we examined the relation between the crystal axis and LITD of single crystal calcium fruoride. The relation between the crystallographic axis and LIDT that the laser enters was examined. The ArF excimer laser and the fifth high harmonic of the Nd:YAG laser at 213nm were used for the irradiation source of light. We prepared samples that optical axes were <111>, <110> and <001> from the same crystal. From the result of this examination, when the laser irradiated in <111> axis, LIDT was the highest. Next, we observed the damage with polarizing microscope and optical microscope. The result of this observation suggested that the laser damage of calcium fluoride was related to the crystal orientation. Finally, we investigated the damage mechanism of calcium fluoride. It is thought that the laser irradiation induced stress is relaxed most easily when the optical axis is <111>. Therefore, LIDT of calcium fluoride is supposed to be highest when the optical axis is <111>.

Azumi, Minako; Nakahata, Eiichiro

2010-10-01

210

Oxalate ions and calcium oxalate crystals stimulate MCP-1 expression by renal epithelial cells  

Microsoft Academic Search

Oxalate ions and calcium oxalate crystals stimulate MCP-1 expression by renal epithelial cells.BackgroundCrystals of calcium oxalate monohydrate (COM) and excess oxalate ions (OX) stimulate an array of responses inducing localized injury and inflammation in the kidneys. These inflammatory responses are key regulators of development of nephrolithiasis. We propose that monocyte chemoattractant protein-1 (MCP-1), a chemokine with potent chemotactic activity for

Tohru Umekawa; Nasser Chegini; Saeed R. Khan

2002-01-01

211

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

PubMed

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

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

2013-03-23

212

Carbon dioxide enhances fragility of ice crystals  

NASA Astrophysics Data System (ADS)

Ice caps and glaciers cover 7% of the Earth, greater than the land area of Europe and North America combined, and play an important role in global climate. The small-scale failure mechanisms of ice fracture, however, remain largely elusive. In particular, little understanding exists about how the presence and concentration of carbon dioxide molecules, a significant component in the atmosphere, affects the propensity of ice to fracture. Here we use atomic simulations with the first-principles based ReaxFF force field capable of describing the details of chemical reactions at the tip of a crack, applied to investigate the effects of the presence of carbon dioxide molecules on ice fracture. Our result shows that increasing concentrations of carbon dioxide molecules significantly decrease the fracture toughness of the ice crystal, making it more fragile. Using enhanced molecular sampling with metadynamics we reconstruct the free energy landscape in varied chemical microenvironments and find that carbon dioxide molecules affect the bonds between water molecules at the crack tip and decrease their strength by altering the dissociation energy of hydrogen bonds. In the context of glacier dynamics our findings may provide a novel viewpoint that could aid in understanding the breakdown and melting of glaciers, suggesting that the chemical composition of the atmosphere can be critical to mediate the large-scale motion of large volumes of ice.

Qin, Zhao; Buehler, Markus J.

2012-11-01

213

Carbon dioxide capture from combustion flue gases with a calcium oxide chemical loop. Experimental results and process development  

Microsoft Academic Search

Post-combustion carbonate looping processes are based on the capture of carbon dioxide from the flue gases of an existing power plant in a circulating fluidized bed reactor (CFB) of calcium oxide (the carbonator) particles. The calcination of calcium carbonate in a new oxy-fired CFBC power plant regenerates the sorbent (calcium oxide particles) and obtains high purity carbon dioxide. This communication

M. Alonso; N. Rodríguez; B. González; G. Grasa; R. Murillo; J. C. Abanades

2010-01-01

214

Calcium carbonate mineralization: X-ray microdiffraction probing of the interface of an evaporating drop on a superhydrophobic surface.  

PubMed

The liquid/air interface of calcium bicarbonate solution drops was probed by synchrotron radiation microbeam scattering. The drops were deposited on a nanopatterned superhydrophobic poly(methyl methacrylate) surface and raster-scanned during evaporation by small-angle and wide-angle X-ray scattering. The appearance of about 200-nm-size calcite crystallites at the interface could be spatially resolved at the onset of crystallization. Diffuse scattering from the interface is attributed to a dense nanoscale amorphous calcium carbonate phase. Calcite was found to be the major phase in the solid residue with vaterite as minor phase. PMID:21663321

Accardo, Angelo; Burghammer, Manfred; Di Cola, Emanuela; Reynolds, Michael; Di Fabrizio, Enzo; Riekel, Christian

2011-06-13

215

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

PubMed

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

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

2010-04-29

216

Synthesis of some calcium phosphate crystals using the useful biomass for immobilization of microorganisms  

NASA Astrophysics Data System (ADS)

Three sources of biomass generated by primary industry were used as the raw material for the synthesis of calcium phosphate crystals. Phosphoric acid was extracted from burned rice chaff using a 30% nitric acid solution, while scallop shells and gypsum of plasterboard were used as calcium sources. The calcium phosphate crystals were synthesized by a method involving homogeneous precipitation, and the relationship between the composition and shape of the crystals and the pH at the time of the precipitation was investigated. Monetite crystals in a petal form with a diameter ranging from 0.1 to 2 ?m were precipitated at pH 2.0, while granular apatite crystals with a mean diameter of 1 ?m were precipitated at pH 6.0. We also investigated the ability of the synthesized calcium phosphate crystals to immobilize lactic acid bacteria for practical use in industrial bioreactor. It was determined that monetite crystals with a diameter of 2 ?m had the highest ability to fix lactic acid bacteria. The population of lactic acid bacteria was estimated to exceed 1,300 bacteria per crystal surface of 50 ?m2 suggesting that these crystals may be of practical use in industrial fermenters.

Kohiruimaki, T.

2011-10-01

217

Long-Term (6 Months) Cross-Over Comparison of Calcium Acetate with Calcium Carbonate as Phosphate Binder  

Microsoft Academic Search

A previous short-term study of 10 weeks in 8 patients had shown us that with half the dose of elemental calcium, calcium acetate (CaAc) could control predialysis plasma phosphate (PPO4) as well as calcium carbonate (CaCO3) but that the incidence of hypercalcemia was not decreased. To better appreciate the value of CaAc in comparison to CaCO3, CaAc was given to

F. Ben Hamida; I. El Esper; M. Compagnon; Ph. Morinière; A. Fournier

1993-01-01

218

Use of biopolymers as oriented supports for the stabilization of different polymorphs of biomineralized calcium carbonate with complex shape  

Microsoft Academic Search

This work concerns the use of different biopolymers such as chitosan, alginate or ?-carrageenan as substrates to contribute to the study of the crystallization of calcium carbonate. The experimental biomimetic approach involves the preparation of mixtures of biopolymer solutions with a solution of CaCl2, which is processed by means of spin-coating and then exposed to CO2 by a slow diffusion

Mario Díaz-Dosque; Pilar Aranda; Margarita Darder; Jaime Retuert; Mehrdad Yazdani-Pedram; José Luis Arias; Eduardo Ruiz-Hitzky

2008-01-01

219

Geometrically structured implants for cranial reconstruction made of biodegradable polyesters and calcium phosphate/calcium carbonate.  

PubMed

The aim of this study was the development of a processing pathway for manufacturing of biodegradable skull implants with individual geometry. The implants on the basis of polylactide and calcium phosphate/calcium carbonate were prepared by a combination of hot pressing and gas foaming. On the inside, the implant consists of a macroporous and faster degradable material (poly(D,L-lactide)+CaCO3) to allow the ingrowth of bone cells. The pore size is in the range of 200-400 microm. On the outside, the implant consists of a compact and slower biodegradable material (poly(L-lactide) and calcium phosphate) to ensure mechanical stability and protection. To overcome problems like inflammatory reactions caused by acidic degradation products of polylactide, the polyester was combined with basic filling materials (calcium salts). The filler neutralises the lactic acid produced during polymer degradation and increases the bioactivity of the material. The stabilised pH was demonstrated by long-term in vitro pH studies. Over a time period of 250 d in demineralised water, the pH was in the physiological range. The in vitro biocompatibility was shown by cell cultures with human osteoblasts. A good proliferation of the cells was observed over the whole test period of 4 weeks. PMID:14643598

Schiller, Carsten; Rasche, Christian; Wehmöller, Michael; Beckmann, Felix; Eufinger, Harald; Epple, Matthias; Weihe, Stephan

220

[Modulation of polysaccharide extracted from Laminaria on phase compositions of urinary crystal calcium oxalate].  

PubMed

The influence of sulfate polysaccharide (SPS) isolated from marine algae Laminaria japonica aresch on the growth of urinary crystal calcium oxalate (CaO(xa)) was investigated by means of X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and atomic absorption spectroscopy. SPS can stabilize thermodynamic metastable calcium oxalate dihydrate (COD) crystals. As the concentration of SPS increases from 0 to 0.60 mg x mL(-1), the mass percentage of COD crystals increases from 0 to 100%, and the relative supersaturation of calcium oxalate increases from 1.0 to 19.6. The ability of SPS to stabilize the existence of COD in aqueous solution and to increase the concentration of soluble calcium ions is favorable to the inhibition of CaO(xa) stone. Indicating that SPS is a potential green drug for prevention and cure of CaO(xa) urinary stones. PMID:18260434

Deng, Sui-Ping; Ouyang, Jian-Ming

2007-11-01

221

Synthesis and characterization of carbonated hydroxyapatite and bioinspired polymer-calcium phosphate nanocomposites  

NASA Astrophysics Data System (ADS)

Taking the inspiration from natural bone, where collagen provides sites for the nucleation and growth of carbonated hydroxyapatite, we have developed self-assembling calcium phosphate-block copolymer nanocomposites by using a bottom-up approach. In this regard, self-assembling thermo-reversibly gelling block copolymers based on the nonionic, zwitterionic, anionic, block copolymers conjugated to hydroxyapatite-nucleating peptides, and polylysine-polyleucine diblock copoly-peptides were employed as templates for the precipitation of nano-sized calcium phosphates from aqueous solutions. Calcium phosphate nanocrystals were formed at the polymer-inorganic interface presumably nucleated by the ionic interactions. Solid-state NMR, XRD, TEM, TGA, FTIR and X-ray scattering techniques were used to characterize the nanocomposites. NMR and scattering measurements of polymer-inorganic gel composites proved nanocomposite formation and templating by the polymer micelles. The inorganic fraction of the nanocomposites was found to vary between 30-55 wt%. TEM studies showed that the morphology and the size of the hydroxyapatite crystals in the nanocomposites were similar to the apatite in the bone. The findings in our studies provide information for developing guidelines for design of novel HAp-polymer nanocomposites and for the understanding of the mechanism of biomineralization. Moreover, this study may also offer routes for bioinspired bottom-up approaches for the development of a number of nanostructured composites including injectable nanocomposite biomaterials for potential orthopedic applications. As a part of the present study, the carbonate incorporation into the hydroxyapatite lattice under various pH conditions was also investigated. Crystalline sodium and carbonate containing calcium hydroxyapatite (NaCO 3HAp) powders were prepared using an oxidative decomposition of calcium-EDTA chelates in the sodium phosphate solution with hydrogen peroxide. Depending on pH, spherical particles with approximately 3.5 mum in diameter or hexagonal prismatic particles measuring 3 to 9 mum long were obtained. The precipitated particles were a single-phase NaCO3HAp. The carbonate content and the lattice parameters of the hydroxyapatite were a function of solution pH. Maximum carbonate incorporated into the HAp lattice was at pH=10. Formation of HAp on PMMA polymer films was also studied by using the same chelate decomposition method. Evolution of HAp coating as a function of experimental variables including time was examined.

Yusufoglu, Yusuf

222

Interaction between Osteopontin on Madin Darby Canine Kidney Cell Membrane and Calcium Oxalate Crystal  

Microsoft Academic Search

We recently reported that the addition of the protein osteopontin (OPN) resulted in an increase in the deposition of calcium oxalate (CaOx) crystals on the surface of Madin Darby canine kidney (MDCK) cells. To determine the degree to which this increased deposition is caused by OPN, we investigated the extent to which the CaOx crystal deposition produced by the expression

T. Yamate; K. Kohri; T. Umekawa; E. Konya; Y. Ishikawa; M. Iguchi; T. Kurita; M. Ohmura; S. Baltaci; T. Shono; H. Kanetake; J. Köllermann; S. Ebisuno; T. Nishikawa; M. Nishihata; T. Inagaki; T. Watanabe; K. Tozawa; K. Ueda; K. Sarica; K. Bakir; O. Topcu; M. Froehner; M. Haase

1999-01-01

223

Multi-Functions of Carbonated Calcium Deficient Hydroxyapatite (CDHA)  

NASA Astrophysics Data System (ADS)

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.

Zhou, Huan

224

Calcium carbonate precipitation in cyanobacterial mats from sandy tidal flats of the North Sea.  

PubMed

Precipitated calcium carbonate was found in annual cyanobacterial mats developing on the beaches of the North Sea barrier island Schiermonnikoog (the Netherlands). A variety of different calcium carbonate morphs were found in the cyanobacterial mucous secretions and identified by light- and scanning electron microscopy and X-ray diffraction. Most of the calcium carbonate seemed to be associated with degrading extracellular polymer. It is conceived that supersaturation of calcium carbonate resulted from the periodic evaporation of the mats and from the release of calcium from the cyanobacterial mucous as a result of its degradation. The analysis of the carbon stable isotopic composition of the calcium carbonate showed only a slight depletion of (13)C, indicating that it did not in major part originated from the decomposition of organic matter. The delta(18)O values of the calcium carbonate confirmed the temperature differences between spring and summer but excluded the possibility that excessive evaporative events controlled precipitation. The precipitation of calcium carbonate could represent a potential factor enhancing the stabilization of intertidal siliciclastic sediments through cementing the sand. The discovery of massive calcium carbonate precipitation in these cyanobacterial mats was unexpected and hitherto unknown. PMID:18380885

Kremer, B; Kazmierczak, J; Stal, L J

2008-01-01

225

Carbonation as a binding mechanism for coal/calcium hydroxide pellets  

SciTech Connect

Current coal mining and processing procedures produce a significant quanity of fine coal that is difficult to handle and transport. The objective of this work is to determine if these fines can be economically pelletized with calcium hydroxide, a sulfur capturing sorbent, to produce a clean-burning fuel for fluidized-bed combustors or stoker boilers. To harden these pellets, carbonation, which is the reaction of calcium hydroxide with carbon dioxide to produce a cementitious matrix of calcium carbonate, is being investigated. Previous research indicated that carbonation significantly improved compressive strength, impact and attrition resistance and weatherproofed'' pellets formed with sufficient calcium hydroxide (5 to 10% for minus 28 mesh coal fines).

Rapp, D.M.

1991-01-01

226

Evaluation of urine composition and calcium salt crystallization properties in standardized volume-adjusted 12-h night urine from normal subjects and calcium oxalate stone formers  

Microsoft Academic Search

The volume of 12-h night urine from ten normal men (NM), ten normal women (NW) and 31 male calcium stone formers (SFM) was adjusted to 750 ml and analysed with respect to supersaturation with calcium oxalate (CaOx) and calcium phosphate (CaP), inhibition of CaOx crystal growth and aggregation, as well as the CaOx and CaP crystallization propensity. Concentrations of oxalate

Hanne Bek-Jensen; Hans-Göran Tiselius

1997-01-01

227

THE COMPARISON PROPERTIES OF RECYCLE RUBBER POWDER, CARBON BLACK, AND CALCIUM CARBONATE FILLED NATURAL RUBBER COMPOUNDS  

Microsoft Academic Search

The effects of filler loading on the curing characteristics, swelling behavior, and mechanical properties of natural rubber compounds were studied using a conventional vulcanization system. Recycle rubber powder (RRP), carbon black (CB) (N550), and calcium carbonate (CaCO3) were used as fillers and the loading range was from 0 to 50 phr. Results show that the scorch time, t2, and cure time,

Hanafi Ismail; R. Nordin

2002-01-01

228

A multicenter study on the effects of lanthanum carbonate (Fosrenol™) and calcium carbonate on renal bone disease in dialysis patients  

Microsoft Academic Search

A multicenter study on the affects of lanthanum carbonate (Fosrenol™) and calcium carbonate on renal bone disease in dialysis patients.BackgroundLanthanum carbonate (LC) (Fosrenol™) is a novel new treatment for hyperphosphatemia. In this phase III, open-label study, we compared the effects of LC and calcium carbonate (CC) on the evolution of renal osteodystrophy (ROD) in dialysis patients.MethodsNinety-eight patients were randomized to

Patrick C. D'Haese; Goce B. Spasovski; Aleksander Sikole; Alastair Hutchison; Tony J. Freemont; Sylvie Sulkova; Charles Swanepoel; Svetlana Pejanovic; Llubica Djukanovic; Alessandro Balducci; Giorgio Coen; Waldysaw Sulowicz; Anibal Ferreira; Armando Torres; Slobodan Curic; Milan Popovic; Nada Dimkovic; Marc E. De Broe

2003-01-01

229

Mode of activation of the metabolic burst in polymorphonuclear leukocytes by calcium oxalate crystals.  

PubMed

Microcrystals of calcium oxalate cause an activation of the metabolic burst in polymorphonuclear leukocytes, measured as NBT reduction. Crystal-induced NBT reduction, which was mainly due to superoxide release, was accompanied by enzyme release. Modulation of calcium oxalate-induced activation by several agents resembles the effect of these agents on activation by opsonized zymosan and by phorbol myristate acetate. Both the activation of the metabolic burst and concomitant enzyme release could be counteracted by certain anions, such as oxalate, pyruvate and citrate, indicating that positive charges on the crystals play an important role in crystal-cell interaction. Removal of the negatively charged sialic acid from the cell surface by neuraminidase did not affect the the action of the crystals. The mechanism, by which calcium oxalate activates polymorphonuclear leukocytes, is discussed. PMID:3445822

Elferink, J G

1987-12-01

230

Morphology and composition of nanograde calcium phosphate needle-like crystals formed by simple hydrothermal treatment  

Microsoft Academic Search

Nanograde calcium phosphate needle-like crystals are prepared from wet synthesized Ca-P precipitates by simple hydrothermal treatment at 140°C and 0.3 MPa for 2 h. The morphology of these crystals is observed by transmission electron microscopy (TEM). The phase composition is tested through X-ray diffractometer (XRD) and infrared spectroscopy (IR). It is found that the morphology of these crystals is related

Li Yubao; K. DE GROOT; J. Wijn; C. P. A. T. Klein; S. V. D. Meer

1994-01-01

231

[*calcium-oxalate lithogenesis: crystallization in the presence of urine from healthy subjects].  

PubMed

In the present study we aim at describing the influence of urine of non-lithiasic subjects on the different crystallization stages of calcium oxalates. The experimental method consists in comparing the turbidimetric curves obtained by crystallization in pure synthetic urine to the curves obtained after addition of natural urine to the solution. Natural urine plays an important role on nucleation, crystal growth and agglomeration even if only small amounts (4% v/v) are added to the mother solution. Nucleation is favoured (decrease of the induction period and increase of the crystal number) by the presence of solid particles, such as cellular fragments, which play the role of substrates for heterogeneous nucleation. On the other hand, both the growth rate of the crystals and their degree of agglomeration are reduced. Moreover, the physical nature of the crystals which precipitate is different from that of the crystals which nucleate in synthetic urine. Under our conditions of high super-saturation, natural urine favours the nucleation of calcium oxalate dihydrate at the expenses of calcium oxalate trihydrate which forms in pure synthetic urine. A hypothesis on the origin of the lithogenesis process is made and a correlation between the localization of the calcium oxalate stones in the urinary tracts and their main constituents is proposed. PMID:7630471

Beaufays, J P; Bouche, R; Boistelle, R

1995-01-01

232

Calcium sulfite and calcium sulfate crystallization: Volume 2, Kinetics of calcium sulfite crystallization and predictions of crystal-size distribution: Final report  

SciTech Connect

Manipulation of the Crystal-Size Distribution (CSD) of gypsum from simulated flue gas desulfurization (FGD) liquors was studied using a bench-scale classified crystallizer configuration of the Double Draw-Off (DDO) type. This configuration allows for removal of two streams; one completely mixed (underflow) and one classified (overflow) containing only particles less than ca. 30 ..mu..m. Operation of a crystallizer in the double draw-off mode allows a size-dependent separation of particle residence times with decreased removal rate of product particles vis-a-vis overflow fines thus producing a significantly larger-sized average product. Variables which were studied for their effect on CSD were overflow/underflow ratio (DDO ratio), agitator rpm, over-all liquid phase retention time, pH, citric acid (crystal modifier) concentration, rate of make based on precipitant feeds and crystallizer configuration, i.e., DDO or Mixed Suspension Mixed Product Removal (MSMPR) operational modes. Conditions were found using the DDO configuration with citric acid addition to consistently produce a larger-size gypsum product averaging 130 to 180 ..mu..m (underflow, mass average size) with a rounded aggregate-like habit having excellent filtration properties. Citrate concentration in the product crystals was found to be less than 50 ppM. Prediction a priori of CSD and residual supersaturation (proportional to fouling tendency) with the author's Mark V CSD simulator using the process conditions of this study and the nucleation-growth rate kinetics previously developed by Etherton (EPRI CS1885) was in agreement with experimental results. A large-scale FGD by-product gypsum crystallizer could be confidently designed using the technology demonstrated in this study. 5 refs., 26 figs., 9 tabs.

Randolph, A.D.; Vaden, D.E.

1986-11-01

233

Calcium oxalate crystal formation in patients with hyperparathyroidism and hyperthyroidism and related metabolic disturbances.  

PubMed

The crystallization of calcium oxalate in the urine of patients with hyperparathyroidism and hyperthyroidism was studied using a mixed suspension mixed product removal (MSMPR) system. In addition, calcium metabolism in hyperthyroidism and its relationship to urolithiasis was investigated. The urines from all the three groups (normal subjects, hyperparathyroid and hyperthyroid patients) showed reduced nucleation rates and increased growth rates in comparison with the control synthetic urine. The nucleation rate was not significantly different between the three human urine groups, while the growth rate was significantly higher in the hyperparathyroid group compared to the normal and hyperthyroid groups. Crystal volume (suspension density) in the hyperparathyroid group was approximately twice that in the other two groups. Serum and ionized calcium levels in hyperparathyroid patients were higher than in normal subjects, while hyperthyroid patients had levels only slightly higher than those in normal subjects. The hyperparathyroid and hyperthyroid groups differed significantly from the normal group in urinary calcium excretion. These two groups also showed significantly higher levels of serum alkaline phosphatase and urinary hydroxyproline than did the normal group. Although hyperthyroid patients have a calcium metabolism similar to hyperparathyroid patients, the incidence of urolithiasis is no different between hyperthyroid and normal subjects. The results of both crystallization and calcium metabolism in hyperparathyroid patients were not significantly different between those with and without urolithiasis. The result of crystallization was also not significantly different between hyperparathyroid patients with and without hypercalciuria. This study suggests that hypercalciuria alone does not produce urinary stones and that urine from hyperparathyroid patients may contain promotors of calcium oxalate crystallization and calcium stone formation. PMID:2306555

Kohri, K; Kodama, M; Umekawa, T; Ishikawa, Y; Katayama, Y; Takada, M; Katoh, Y; Kataoka, K; Iguchi, M; Kurita, T

1990-01-01

234

A new method for the study of trace element partitioning between calcium carbonate and aqueous solution: A test case for Sr and Ba incorporation into calcite  

Microsoft Academic Search

A new experimental method (evaporation method) for calcium carbonate precipitation in aqueous solution was at- tempted in order to develop a convenient and controllable experimental technique for obtaining precise trace element partition coefficients. Calcite crystals were formed by evaporation of H2O from the aqueous mother solution using a dehumidifier, and the consumed Ca ions were supplied from a refill solution

YASUTAKA TERAKADO; MAMI TANIGUCHI

2006-01-01

235

Oxalate reduces calcium availability in the pads of the prickly pear cactus through formation of calcium oxalate crystals.  

PubMed

The pads (nopales) of the prickly pear cactus are considered to be a good source of minerals and other nutrients on the basis of compositional analysis. In this study, this analysis is taken a step further by assessing the availability of selected minerals in nopales using an in vitro digestion and dialysis method. The results obtained suggest that although nopales are enriched in a number of minerals, their tissue calcium is not freely available. Microscopic analysis, energy-dispersive X-ray microanalysis, and oxalate measurements suggest that this reduction in available calcium is a result of its sequestration in the form of calcium oxalate crystals. The issue of mineral availability in plant foods is important when the dependence of many populations around the world on plant foods as their main source of minerals and other nutrients is considered. PMID:14995148

McConn, Michele M; Nakata, Paul A

2004-03-10

236

Effect of calcium carbonate saturation of seawater on coral calcification  

USGS Publications Warehouse

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.

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

1998-01-01

237

Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate  

SciTech Connect

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).

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

238

Effects of nano calcium carbonate and nano calcium citrate on toxicity in ICR mice and on bone mineral density in an ovariectomized mice model  

NASA Astrophysics Data System (ADS)

Taking calcium supplements can reduce the risk of developing osteoporosis, but they are not readily absorbed in the gastrointestinal tract. Nanotechnology is expected to resolve this problem. In the present study, we examined whether the bioavailability of calcium carbonate and calcium citrate can be improved by reducing the particle size. The morphology of nano calcium carbonate and nano calcium citrate was characterized by dynamic laser-light scattering (DLS), field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The measurements obtained from DLS, FE-SEM and TEM were comparable. Acute and sub-chronic toxicity tests were performed to establish the safety of these products after oral administration. The no-observed-adverse-effect levels of nano calcium carbonate and nano calcium citrate were 1.3 and 2.3 g kg-1 body weight, respectively. The results of our in vivo studies indicate that administering nano calcium carbonate and nano calcium citrate can enhance the serum calcium concentration and maintain the whole-body bone mineral density in ovariectomized mice. These data suggest that nano calcium carbonate and nano calcium citrate are more bioavailable than micro calcium carbonate and micro calcium citrate, respectively.

Huang, Sherry; Chen, Jin Ching; Hsu, Chin Wei; Chang, Walter H.

2009-09-01

239

Crystallization of Calcium Sulfate and Uptake of Impurities.  

National Technical Information Service (NTIS)

The main effort of the research has thus been devoted to the specific objectives: identification of the kinetic and thermodynamic parameters that determine the uptake of foreign ions in calcium sulfate modifications; determination of the (re)crystallizati...

G. J. Witkamp

1989-01-01

240

Gas-flushed packaging contributes to calcium lactate crystals in Cheddar cheese.  

PubMed

Gas-flushed packaging is commonly used for cheese shreds and cubes to prevent aggregation and loss of individual identity. Appearance of a white haze on cubed cheese is unappealing to consumers, who may refrain from buying, resulting in lost revenue to manufacturers. The objective of this study was to determine whether gas flushing of Cheddar cheese contributes to the occurrence of calcium lactate crystals (CLC). Cheddar cheese was manufactured using standard methods, with addition of starter culture, annatto, and chymosin. Two different cheese milk compositions were used: standard (lactose:protein = 1.47, protein:fat = 0.90, lactose = 4.8%) and ultrafiltered (UF; lactose:protein = 1.23, protein:fat = 0.84, lactose = 4.8%), with or without adjunct Lactobacillus curvatus. Curds were milled when whey reached 0.45% titratable acidity, and pressed for 16 h. After aging at 7.2 degrees C for 6 mo, cheeses were cubed (1 x 1 x 4 cm) and either vacuum-packaged or gas-flushed with carbon dioxide, nitrogen, or a 50:50 mixture of carbon dioxide and nitrogen, then aged for an additional 3 mo. Heavy crystals were observed on surfaces of all cubed cheeses that were gas-flushed, but not on cheeses that were vacuum-packaged. Cheeses without Lb. curvatus exhibited L(+)-CLC on surfaces, whereas cheeses with Lb. curvatus exhibited racemic mixtures of L(+)/D(-)-CLC throughout the cheese matrices. The results show that gas flushing (regardless of gas composition), milk composition, and presence of nonstarter lactic acid bacteria, can contribute to the development of CLC on cheese surfaces. These findings stress the importance of packaging to cheese quality. PMID:16230683

Agarwal, S; Costello, M; Clark, S

2005-11-01

241

In situ calcium carbonate dissolution in the Pacific Ocean  

SciTech Connect

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.

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

242

Influence of the type of phospholipid head and of the conformation of the polyelectrolyte on the growth of calcium carbonate thin films on LB/LbL matrices.  

PubMed

Calcium carbonate is one of the most important biominerals, and it is the main constituent of pearls, seashells, and teeth. The in vitro crystallization of calcium carbonate using different organic matrices as templates has been reported. In this work, the growth of calcium carbonate thin films on special organic matrices consisting of layer-by-layer (LbL) polyelectrolyte films deposited on a pre-formed phospholipid Langmuir-Blodgett (LB) film has been studied. Two types of randomly coiled polyelectrolytes have been used: lambda-carrageenan and poly(acrylic acid). A precoating comprised of LB films has been prepared by employing a negatively charged phospholipid, the sodium salt of dimyristoilphosphatidyl acid (DMPA), or a zwitterionic phospholipid, namely dimyristoilphosphatidylethanolamine (DMPE). This approach resulted in the formation of particulate calcium carbonate continuous films with different morphologies, particle sizes, and roughness, as revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The crystalline structure of the calcium carbonate particles was analyzed by Raman spectroscopy. The randomly coiled conformation of the polyelectrolytes seems to be the main reason for the formation of continuous films rather than CaCO(3) isolated crystals. PMID:22429782

Ramos, Ana P; Espimpolo, Daniela M; Zaniquelli, Maria Elisabete D

2012-03-06

243

Metal-catalyzed crystallization of amorphous carbon to graphene  

Microsoft Academic Search

Metal-catalyzed crystallization of amorphous carbon to graphene by thermal annealing is demonstrated. In this ``limited source'' process scheme, the thickness of the precipitated graphene is directly controlled by the thickness of the initial amorphous carbon layer. This is in contrast to chemical vapor deposition processes, where the carbon source is virtually unlimited and controlling the number of graphene layers depends

Maxwell Zheng; Kuniharu Takei; Benjamin Hsia; Hui Fang; Xiaobo Zhang; Nicola Ferralis; Hyunhyub Ko; Yu-Lun Chueh; Yuegang Zhang; Roya Maboudian; Ali Javey

2010-01-01

244

Calcium carbonate production response to future ocean warming and acidification  

NASA Astrophysics Data System (ADS)

Anthropogenic carbon dioxide (CO2) emissions are acidifying the ocean, affecting calcification rates in pelagic organisms and thereby modifying the oceanic alkalinity cycle. However, the responses of pelagic calcifying organisms to acidification vary widely between species, contributing uncertainty to predictions of atmospheric CO2 and the resulting climate change. Meanwhile, ocean warming caused by rising CO2 is expected to drive increased growth rates of all pelagic organisms, including calcifiers. It thus remains unclear whether anthropogenic CO2 will ultimately increase or decrease the globally-integrated pelagic calcification rate. Here, we assess the importance of this uncertainty by introducing a variable dependence of calcium carbonate (CaCO3) production on calcite saturation state (?CaCO3) in the University of Victoria Earth System Climate Model, an intermediate complexity coupled carbon-climate model. In a series of model simulations, we examine the impact of this parameterization on global ocean carbon cycling under two CO2 emissions scenarios, both integrated to the year 3500. The simulations show a significant sensitivity of the vertical and surface horizontal alkalinity gradients to the parameterization, as well as the removal of alkalinity from the ocean through CaCO3 burial. These sensitivities result in an additional oceanic uptake of carbon when calcification depends on ?CaCO3 (of up to 13 % of total carbon emissions), compared to the case where calcification is insensitive to acidification. In turn, this response causes a reduction of global surface air temperature of up to 0.4 °C in year 3500, a 13 % reduction in the amplitude of warming. Narrowing these uncertainties will require better understanding of both temperature and acidification effects on pelagic calcifiers. Preliminary examination suggests that alkalinity observations can be used to constrain the range of uncertainties and may exclude large sensitivities of CaCO3 production on ?CaCO3.

Pinsonneault, A. J.; Matthews, H. D.; Galbraith, E. D.; Schmittner, A.

2011-12-01

245

Extracellular matrix production and calcium carbonate precipitation by coral cells in vitro  

Microsoft Academic Search

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

Yael Helman; Frank Natale; Robert M. Sherrell; Michèle Lavigne; Valentin Starovoytov; Maxim Y. Gorbunov; Paul G. Falkowski

2008-01-01

246

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

National Technical Information Service (NTIS)

This project investigated the role of calcium carbonate grain coatings on the reactivity of several key Hanford contaminants such as 60Co2+, 90Sr2+, 99TcO4 (CrO4)2-. Calcium carbonate in the Hanford subsurface is thought to play an important role in the f...

G. E. Brown S. Chambers C. M. Eggleston J. M. Zachara T. Kendelewicz C. S. Doyle

2004-01-01

247

THE INFLUENCE OF CALCIUM CARBONATE GRAIN COATINGS ON CONTAMINANT REACTIVITY IN VADOSE ZONE SEDIMENTS  

EPA Science Inventory

Fundamental research is proposed to investigate the role of calcium carbonate grain coatings on the vadose zone chemical reactivity of key Hanford contaminants (i.e., 60Co2+, 90Sr2+, CrO42-, and 99TcO4-). Calcium carbonate is widely distributed through the Hanford vadose zone as...

248

Effect of carbon nanotubes on the crystallization and ordering behavior of liquid crystals  

NASA Astrophysics Data System (ADS)

We used carbon nanotubes (CNTs) to affect the crystallization behavior of smectic, cholesteric and nematic liquid crystals and of their blends at different compositions. Using polarized microscopy and microscopic transmission ellipsometry we observed significant change in the crystal structure and orientation. The carbon nanotubes served as nucleation centers for crystal growth. Differential Scanning Calorimetry results showed large shifts in the phase transition temperatures. This is due to the effect of the CNTs on the crystallization kinetics. Research supported by: Assumption College Faculty Development Grant, funding for students' stipends, instrumentation and supplies, the NSF Polymers Program of the DMR, grant (DMR-0602473) and NASA grant (NAG8-1167).

Georgiev, Georgi; Gombos, Erin; McIntyre, Michael; Judith, Robert; Cebe, Peggy

2010-03-01

249

The nature of calcium-phosphate crystal formations grown on dentine surface  

NASA Astrophysics Data System (ADS)

Laboratory experiments conducted in Saratov State University in the first half of 2012 revealed crystal formations on the surface of etched dentine after it had been exposed to 95% ethanol in solution for 30 days at room temperature. It was discovered that the structures observed were calcium-phosphate crystals. The nature of crystal formation on rough dentine surface was described based on substance diffusion in solution, which resulted in dentine becoming spatially inhomogeneous over time. The crystal formation was established to be determined by the limited ion redistribution in dentine material.

Bessudnova, Nadezda O.; Bilenko, David I.; Venig, Sergey B.; Atkin, Vsevolod S.; Galushka, Viktor V.; Zakharevich, Andrey M.

2013-02-01

250

Imaging of chondrocalcinosis: calcium pyrophosphate dihydrate (CPPD) crystal deposition disease -- imaging of common sites of involvement.  

PubMed

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease is characterised by the accumulation of pyrophosphate dihydrate crystals in articular and periarticular tissues and it can be classified as sporadic, hereditary or secondary. The diagnosis frequently rests on radiographic findings. Computed tomography scanning can detect well mineralised deposits in joints and also ultrasound may be useful in detecting CPPD crystal deposits. About MRI recent studies have demonstrated the utility of high field in depiction of CPPD crystal deposits. The aim of this review is to focus on the clinical-classificative and radiological aspects of CPPD, particularly the contribution of the different imaging techniques. PMID:22325558

Magarelli, N; Amelia, R; Melillo, N; Nasuto, M; Cantatore, F; Guglielmi, G

2012-03-07

251

Hydrothermal growth of carbonate-containing hydroxyapatite single crystals  

Microsoft Academic Search

Single crystals of carbonate-containing hydroxyapatite have been grown hydrothermally by gradually heating with a temperature gradient applied to the vessel, using CaHPO4, H2O and carbon dioxide as dry ice. The optimum conditions to obtain large single crystals are: CaHPO4, 10 g\\/l; final temperature gradient, 33.5°C\\/cm; heating rate, 0.005°C\\/min; and carbon dioxide, 55 g\\/l. The largest crystal obtained was 12 mm

Atsuo Ito; Satoshi Nakamura; Hideki Aoki; Masaru Akao; Kay Teraoka; Sadao Tsutsumi; Kazuo Onuma; Tetsuya Tateishi

1996-01-01

252

Molecular mechanism of crystallization impacting calcium phosphate cements  

SciTech Connect

In summary, SPM data has shown that (1) Mg inhibits growth on all steps but relatively high Mg/Ca ratios are needed. Extracting the mechanism of interaction requires more modeling of the kinetic data, but step morphology is consistent with incorporation. (2) Citrate has several effects depending on the citrate/Ca ratio. At the lowest concentrations, citrate increases the step free energy without altering the step kinetics; at higher concentrations, the polar step is slowed. (3) Oxalate also slows the polar step but additionally stabilizes a new facet, with a [100]{sub Cc} step. (4) Etidronate has the greatest kinetic impact of the molecules studied. At 7{micro}M concentrations, the polar step slows by 60% and a new polar step appears. However, at the same time the [10-1]{sub Cc} increases by 67%. It should be noted that all of these molecules complex calcium and can effect kinetics by altering the solution supersaturation or the Ca to HPO{sub 4}{sup 2-} ratio. For the SPM data shown, this effect was corrected for to distinguish the effect of the molecule at the crystal surface from the effect of the molecule on the solution speciation. The goal of this paper is to draw connections between fundamental studies of atomic step motion and potential strategies for materials processing. It is not our intent to promote the utility of SPM for investigating processes in cement dynamics. The conditions are spectacularly different in many ways. The data shown in this paper are fairly close to equilibrium (S=1.6) whereas the nucleation of cements is initiated at supersaturation ratios in the thousands to millions. Of course, after the initial nucleation phase, the growth will occur at more modest supersaturations and as the cement evolves towards equilibrium certainly some of the growth will occur in regimes such as shown here. In addition to the difference in supersaturation, cements tend to have lower additive to calcium ratios. As an example, the additive to Ca ratio is {approx}10{sup -3} to 10{sup -4} for a pyrophosphate based cement (Grover et al., 2006). Where the in situ SPM approach provides unique insights is in providing details of where and how molecules inhibit or accelerate kinetics. This has the potential to aid in designing molecules to target specific steps and to guide synergistic combinations of additives. For example, it is unlikely that bulk techniques could deduce the simultaneous acceleration and inhibition effects of etidronate; or that citrate reduced growth rate by altering step density rather than step speed. In addition, SPM data translates to tractable questions for modelers. The questions changes from 'How does etidronate inhibit brushite growth?' to 'Why does etidronate bind strongly to the [101]{sub Cc} step while it doesn't to the [10-1]{sub Cc} step?' This is still a challenging question but it is far better defined. Given that step chemistries are generally different, it seems reasonable to expect that the greatest inhibition will be achieved not with one, but with several synergistically chosen additives. For example, the most effective growth inhibitors for brushite would target the two fast steps, namely the non-polar, [10-1]{sub Cc} and the polar, [101]{sub Cc} steps. Several molecules have been shown to slow the polar step, with etidronate as the most dramatic example. By contrast, only Mg was observed to slow the [10-1]{sub Cc} step. Thus, a combination of high concentrations of Mg to target the [10-1]{sub Cc} step with low concentrations of etidronate to target the polar steps, should be a more effective combination than either alone. However Mg is not a particularly good inhibitor in the sense that high concentrations are needed, and it is not specific. More ideally, an inhibitor would be designed to interact specifically with the [10-1] step, which would allow the two steps to be independently modified. Again, this provides an opportunity for tighter coupling with theoretical modeling. The question changes from 'What types of molecules will inhibit brushite growth' to 'What type of molecule

Giocondi, J L; El-Dasher, B S; Nancollas, G H; Orme, C A

2009-05-31

253

FKBP-12 exhibits an inhibitory activity on calcium oxalate crystal growth in vitro.  

PubMed

Urolithiasis and calcium oxalate crystal deposition diseases are still significant medical problems. In the course of nephrocalcin cDNA cloning, we have identified FKBP-12 as an inhibitory molecule of calcium oxalate crystal growth. lambdagt 11 cDNA libraries were constructed from renal carcinoma tissues and screened for nephrocalcin cDNA clones using anti-nephrocalcin antibody as a probe. Clones expressing recombinant proteins, which appeared to be antigenically cross-reactive to nephrocalcin, were isolated and their DNA sequences and inhibitory activities on the calcium oxalate crystal growth were determined. One of the clone lambda gt 11 #31-1 had a partial fragment (80 bp) of FKBP-12 cDNA as an insert. Therefore, a full-length FKBP-12 cDNA was PCR-cloned from the lambda gt 11 renal carcinoma cDNA library and was subcloned into an expression vector. The resultant recombinant FKBP-12 exhibited an inhibitory activity on the calcium oxalate crystal growth (Kd=10(-7) M). Physiological effect of the extracellular FKBP-12 was investigated in terms of macrophage activation and proinflammatory cytokine gene induction. Extracellular FKBP-12 failed to activate macrophages even at high concentrations. FKBP-12 seems an anti-stone molecule for the oxalate crystal deposition disease and recurrent stone diseases. PMID:11850587

Han, In Sook; Nakagawa, Yasushi; Park, Jong Wook; Suh, Min Ho; Suh, Sung Il; Shin, Song Woo; Ahn, Su Yul; Choe, Byung Kil

2002-02-01

254

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

Microsoft Academic Search

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

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

255

Co-precipitation of dissolved organic matter by calcium carbonate in Pyramid Lake, Nevada  

USGS Publications Warehouse

Our previous research has demonstrated that dissolved organic matter (DOM) influences calcium carbonate mineral formation in surface and ground water. To better understand DOM mediation of carbonate precipitation and DOM co-precipitation and/or incorporation with carbonate minerals, we characterized the content and speciation of DOM in carbonate minerals and in the lake water of Pyramid Lake, Nevada, USA. A 400-gram block of precipitated calcium carbonate from the Pyramid Lake shore was dissolved in 8 liters of 10% acetic acid. Particulate matter not dissolved by acetic acid was removed by centrifugation. DOM from the carbonate rock was fractionated into nine portions using evaporation, dialysis, resin adsorption, and selective precipitations to remove acetic acid and inorganic constituents. The calcium carbonate rock contained 0.23% DOM by weight. This DOM was enriched in polycarboxylic proteinaceous acids and hydroxy-acids in comparison with the present lake water. DOM in lake water was composed of aliphatic, alicyclic polycarboxylic acids. These compound classes were found in previous studies to inhibit calcium carbonate precipitation. DOM fractions from the carbonate rock were 14C-age dated at about 3,100 to 3,500 years before present. The mechanism of DOM co-precipitation and/or physical incorporation in the calcium carbonate is believed to be due to formation of insoluble calcium complexes with polycarboxylic proteinaceous acids and hydroxy-acids that have moderately large stability constants at the alkaline pH of the lake. DOM co-precipitation with calcium carbonate and incorporation in precipitated carbonate minerals removes proteinaceous DOM, but nearly equivalent concentrations of neutral and acidic forms of organic nitrogen in DOM remain in solution. Calcium carbonate precipitation during lime softening pretreatment of drinking water may have practical applications for removal of proteinaceous disinfection by-product precursors.

Leenheer, Jerry A.; Reddy, Michael M.

2008-01-01

256

Calcium bioavailability of calcium carbonate fortified soymilk is equivalent to cow's milk in young women.  

PubMed

Calcium (Ca)-fortified soymilk has gained popularity in the United States. Tricalcium phosphate (TCP)-fortified soymilk was shown to have a lower Ca bioavailability than cow's milk in men. However, the most popular soymilk in the U.S. is fortified with Ca carbonate (CC) and has not been evaluated. Ca bioavailability from CC-fortified soymilk (CCSM) and TCP-fortified soymilk (TCPSM) was compared with cow's milk in young healthy women using the dual stable isotope technique. In a 3-way crossover design, 20 volunteers (23 +/- 2 y old) consumed 250 mg Ca in cow's milk, CCSM, or TCPSM along with 10 mg 44Ca after an overnight fast. Cow's milk was extrinsically labeled, whereas each fortified soymilk was intrinsically labeled with each chemical salt of 44Ca at the manufacturing facility. Another stable isotope, 43Ca, was injected i.v. 1 h after the complete consumption of cow's milk or soymilk. Fractional Ca absorption was determined from the ratios of 43Ca:42Ca and 44Ca:42Ca by inductively coupled plasma (ICP)-MS in the 24-h urine samples. A mixed linear model (SAS proc mixed) was used to compare the fractional Ca absorption among groups. Fractional Ca absorption in CCSM (0.211 +/- 0.057) did not differ from that of cow's milk (0.217 +/- 0.040), but both were higher (P < 0.05) than that of TCPSM (0.181 +/- 0.039). Our result suggests that calcium absorption is equivalent for CCSM and cow's milk at similar calcium loads. PMID:16177199

Zhao, Yongdong; Martin, Berdine R; Weaver, Connie M

2005-10-01

257

Rates of Calcium Carbonate Deposition by Deep-Sea Organisms, Molluscs and the Coral-Algae Association  

Microsoft Academic Search

WHILE completing reports on the marine geochemistry of strontium and on calcium carbonate sedimentation in the Atlantic Ocean, I found that sufficient information was available to make an estimate of the calcium carbonate accumulation rates in the sea by deep-sea and littoral processes. The major agents of calcium carbonate accumulation in the littoral areas are presumably molluscs and the coral-algae

K. K. Turekian

1963-01-01

258

Morphology and polymorphic phase changes of calcium carbonate micro/nanocrystals using fruit extracts.  

PubMed

This study reveals the morphology and polymorphic phase changes of calcium carbonate crystals into a mixture of calcite and aragonite micro/nanocrystals of interesting morphology at room temperature by a simple reaction with fruit extracts of Tamarindus indica and Emblica officinalis respectively by mixing CaCO3 solutions with their corresponding extracts. The control experiments were carried out to establish the plausible role of tartaric acid from Tamarindus indica and ascorbic acid from Emblica officinalis in this regard. The quantitative determination of CaCO3 phases was done based on the use of intensities obtained from corresponding XRD spectrum. The molar % of aragonite was found to be more in case of TA and AA rather than TI and EO respectively, however the calcite was observed to be the predominant phase in all four reactions. Interestingly, the TI changes the rhombohedral morphology of calcite to elongated rods, whereas EO induces a great polymorphic phase change. PMID:21780397

Ankamwar, Balaprasad

2011-05-01

259

CO2 bioconversion using carbonic anhydrase (CA): Effects of PEG rigidity on the structure of bio-mineralized crystal composites.  

PubMed

The combined effect of both carbonic anhydrase (CA) and the rigidity of polyethylene glycol (PEG) were found to assist the bio-mineralized crystallization behavior of CO2 differentially. In this study, different forms of magnetically responsive calcium carbonate (CaCO3) crystal composites were successfully formed from gaseous CO2 by using the different forms of polyethylene glycols (PEGs) in a constant CO2 pressure controlled chamber. Polygonal particles were produced with more rigid polymer chains (branched PEG), whereas less rigid polymer chains (PEG) induced the formation of ellipsoidal particles. However, no morphological changes occurred without the presence of CA. PMID:23845271

Hwang, Ee Taek; Gang, Haemin; Gu, Man Bock

2013-07-09

260

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

SciTech Connect

Whole milk, chocolate milk, yogurt, imitation milk (prepared from dairy and nondairy products), cheese, and calcium carbonate were labeled with /sup 45/Ca 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 sources was compared by measuring fractional absorption by the double isotope method. The mean absorption values for all six sources were tightly clustered between 21 and 26% and none was significantly different from the others using one-way analysis of variance. We conclude that none of the sources was significantly superior or inferior to the others.

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

1988-01-01

261

Two-dimensional metal nano-particles and layers in dielectric calcium fluoride crystals  

NASA Astrophysics Data System (ADS)

Highly aggregated color centers in wide-band-gap dielectric calcium fluoride crystal, heated in a reduction atmosphere of Ca vapors (an "additive coloration" of the crystal), have been studied using spectroscopic and atomic-force microscopic techniques. These centers are large aggregates of anion vacancies and electrons that transform into metal structures. Evolution of these structures with increasing the number of such components has been traced from individual two-dimensional particles to large metal film fragments.

Angervaks, A. E.; Shcheulin, A. S.; Ryskin, A. I.; Fedorov, P. P.; Gainutdinov, R. V.

2013-02-01

262

Crystallization process of cubic ZrO 2 in calcium acetate solution  

Microsoft Academic Search

Ultrafine powders of cubic ZrO2 were obtained at about 270° C by heating hydrated amorphous ZrO2 in greater than 0.2 molal calcium acetate solutions. Ca2+ ions played a role as nucleii for crystallization and were introduced into distinct sites of the crystalline phases, that is, substituted for Zr4+ ions. Mn2+ ions produced almost the same effects on the crystallization of

H. Imishizawa; T. Tani; K. Matsuoka

1984-01-01

263

Crystallization of calcium sulfate dihydrate in the presence of some metal ions  

Microsoft Academic Search

Crystallization of calcium sulfate dihydrate (CaSO4·2H2O gypsum) in sodium chloride solutions in the presence of some metal ions, and over a range of relative super-saturation has been studied. The addition of metal ions, even at relatively low concentration (10-6 mol l-1), markedly retard the rate of crystallization of gypsum. Retardation effect was enhanced with increase in the additives contents. Moreover,

Samia K. Hamdona; Umaima A. Al Hadad

2007-01-01

264

Crystallization of calcium sulfate dihydrate in the presence of some metal ions  

Microsoft Academic Search

Crystallization of calcium sulfate dihydrate (CaSO4·2H2O gypsum) in sodium chloride solutions in the presence of some metal ions, and over a range of relative super-saturation has been studied. The addition of metal ions, even at relatively low concentration (10?6moll?1), markedly retard the rate of crystallization of gypsum. Retardation effect was enhanced with increase in the additives contents. Moreover, the effect

Samia K. Hamdona; Umaima A. Al Hadad

2007-01-01

265

Synthesis and thermal behavior of well-crystallized calcium-deficient phosphate apatite  

Microsoft Academic Search

Large crystals (0.5 × 0.5 × 10 mum) of calcium-deficient hydroxyapatites (DAp's) have been synthesized by aqueous precipitation under controlled conditions of pH and temperature. The samples have been characterized using chemical analysis, temperature-programmed dehydration (TPR). X-ray diffraction, IR spectroscopy, and transmission electron microscopy. They show that very well-crystallized DAp's with Ca\\/P close to 1.50 can be obtained under well-selected

Anne Mortier; Jacques Lemaitre; Luc Rodrique; Paul G. Rouxhet

1989-01-01

266

Effects of phosphate pollutants on the growth of the oyster Crassostrea virginica in the Pamlico River estuary and on calcium carbonate crystallization in vitro. Part 2. Extension. Period of project: September 1, 1984February 28, 1985  

Microsoft Academic Search

Four phosphates at various concentrations were studied for effect on shell growth of the clam Rangia cuneata over 24 h and 36 h using ⁴⁵Ca. Four phosphates, present in polluted waters, have been examined for their effects at various concentrations on crystallization rate of CaCOâ in vitro. Growth of the clam in the Pamlico River, North Carolina, were followed during

Wilbur

1986-01-01

267

Growth and characterization of pyrene crystals on carbon nanofibers  

Microsoft Academic Search

Pyrene crystals were grown on carbon nanofibers (CNFs) by dispersing pyrene polycrystals and CNFs in water during ultrasonic irradiation, and they were characterized by scanning electron microscopy, X-ray diffractometry (XRD) and spectroscopy. The XRD measurements indicated that the orientation and size of the pyrene crystals on the CNF aggregates were different from that of the added pyrene polycrystals. Based on

Satoshi Kubota; Hiromasa Nishikiori; Nobuaki Tanaka; Morinobu Endo; Tsuneo Fujii

2009-01-01

268

Structural study and crystal chemistry of the first stage calcium graphite intercalation compound  

Microsoft Academic Search

A novel and efficient synthesis method concerning the preparation of the first stage calcium graphite intercalation compound is provided. It makes use of a reaction between liquid metallic alloy and pyrolytic graphite. From now on it is especially easy to obtain bulk CaC6 samples. Thanks to such samples, it was possible to study in detail the crystal structure of this

Nicolas Emery; Claire. Herold; Philippe Lagrange

2005-01-01

269

Dissolution kinetics of calcium carbonate in equatorial Pacific sediments  

NASA Astrophysics Data System (ADS)

Benthic chambers were deployed in the equatorial eastern Pacific Ocean on a transect along the equator between 103°W and 140°W and on a transect across the equator at 140°W in order to establish the rate of calcium carbonate dissolution on the seafloor. Dissolution was determined from the rate of alkalinity increase within an incubation chamber, measured over an 80-120 hour incubation period. Dissolution rates were lowest at eastern Pacific sites (0.2-0.4 mmol CaCO3/m2/d) and highest at the equatorial, 140°W sites (0.5-0.7 mmol/m2/d). Both oxygen consumption rates and the degree of bottom water saturation govern dissolution rates. Measured dissolution and oxygen consumption rates are used with a numerical model to constrain the value of the dissolution rate constant k, formulated according to the equation developed by Keir [1980]: dissolution rate = k?(1-?)n. The observed dissolution fluxes are predicted by the model when k = 5 to 100%/d and n = 4.5. This range of k values has important implications regarding the type of carbonate dissolving and its location within the sediment column. At low values of k, organic carbon rain rates to the seafloor become the dominant driving force of carbonate dissolution. At higher values of k, the degree of bottom water undersaturation becomes more important. Dissolution of carbonate within equatorial Pacific sediments can be adequately described with k = 20 ± 10%/d, a rate constant much lower than some previously used values. Dissolution rates do not vary significantly over chamber boundary layer thicknesses between 200 and 800 ?m, indicating that dissolution is not controlled by hydrodynamic conditions. Chambers acidified with HCl yield very large dissolution rates, but for a given degree of acidification the dissolution rate was constant for sites ranging from water depths of 3300-4400 m. This implies that there are not more and less easily dissolved forms of CaCO3 arriving on the seafloor between these depths. A budget for alkalinity in the deep Pacific, predicted by the dissolution model and based on the assumption that all carbonate dissolution takes place in the sediments, is within 85% of the input required by a published box model alkalinity budget based on the distribution of nutrients and the water mass transport rates.

Berelson, William M.; Hammond, Douglas E.; McManus, James; Kilgore, Tammy E.

1994-06-01

270

Extraction of radiostrontium coprecipitated with calcium carbonate in soil  

SciTech Connect

The fraction of soil ZSr coprecipitated with calcium carbonate (CaCO3) was determined by extraction into 0.1M hydrochloric acid (HCl)-0.5M potassium chloride (KCl) after an initial extraction with either 1M ammonium acetate (NH4OAc) or 1M KCl to remove soluble salts and exchangeable cations. This procedure was tested on soil samples supplemented with 85 g CaCO3/kg containing coprecipitated YVSr. A significant amount of both YVSr and Ca remained undissolved in this extractant but were subsequently removed by extraction with 8M HNO3. The extraction procedure was also applied to a group of 16 ZSr-contaminated soil and stream bed sediment samples. The amount of Cs + Mg extracted by 0.1M HCl-0.5M KCl, following KCl extraction, was well correlated with but slightly lower than the amounts expected for a complete dissolution of the CaCO3. Pre-extraction with NH4OAc, rather than KCl, dissolved significantly more CaCO3, resulting in a lower estimate of the soil CaCO3. Several soil samples, taken from a radioactive waste burial trench that had received sodium carbonate (Na2CO3) treatment injections, revealed that up to 98% of the total ZSr was observed in a CaCO3 phase. Untreated soils typically exhibited 80 to 95% of their ZSr in a cation exchangeable form, i.e., extractable by either NH4OAc or KCl.

Spalding, B.P.

1985-01-01

271

Tumoral calcium pyrophosphate dihydrate crystal deposition disease of the temporomandibular joint: identification on crystallography.  

PubMed

This paper reports a case of calcium pyrophosphate dihydrate (CPPD) crystal deposition in the temporomandibular joint (TMJ) of a 59-year-old man with the chief complaint of severe pain in the left TMJ. On CT a radiopaque area was seen around the condylar process of the left TMJ with irregular destructive bony changes. A provisional diagnosis of crystalline-induced arthritis was made on histopathology of a biopsy specimen. Electron probe microanalysis (EPMA), scanning electron microscopy (SEM) and X-ray diffraction showed both CPPD and hydroxyapatite (HA) in the crystalline materials. Identification of these two types of crystal in crystal deposition disease of TMJ, using crystallography, is discussed. PMID:18844939

Mikami, Toshinari; Takeda, Yasunori; Ohira, Akinori; Hoshi, Hideki; Sugiyama, Yoshiki; Yoshida, Yasuo; Ambo, Junichi

2008-11-01

272

[Roundish crystal formations in the retina and vitreous body (calcium oxalate and scintillatio nivea)].  

PubMed

Crystals of calcium oxalate in the outer layers of the retina are usually found in blind eyes with long-standing retinal detachment. The crystals are strongly birefringent, mostly radially arranged, and round. In asteroid hyalosis - the scintillatio nivea of the vitreous - the crystals are always closely related to vitreous fibrils or the limiting membrane. The birefringent bodies are apparently formed and initially often covered by vitreous cells (hyalocytes). The birefringence corresponds to that of brushite (Ca HPO4 X 2 H2O). PMID:3713095

Pau, H

1986-03-01

273

Face-specific incorporation of osteopontin into urinary and inorganic calcium oxalate monohydrate and dihydrate crystals  

Microsoft Academic Search

Our aim was to examine the attachment to, and incorporation of intact, highly phosphorylated osteopontin (OPN) into inorganic\\u000a (i) and urinary (u) calcium oxalate monohydrate (COM) and dihydrate (COD) crystals. uCOM and uCOD crystals were precipitated\\u000a from ultrafiltered (UF) urine containing human milk OPN (mOPN) labelled with Alexa Fluor 647 fluorescent dye at concentrations\\u000a of 0.1–5.0 mg\\/L. iCOM and iCOD crystals

Lauren A. Thurgood; Alison F. Cook; Esben S. Sørensen; Rosemary L. Ryall

2010-01-01

274

Green backlighting for TV liquid crystal display using carbon nanotubes  

Microsoft Academic Search

A methodology to evaluate the emission characteristics of carbon nanotube layers in the context of liquid crystal display backlighting has been elaborated. Carbon nanotube layers with emission characteristics compatible with backlighting have been demonstrated for growth temperature as low as 400 °C, thanks to the use of plasma pretreatment before growth. This very low growth temperature allows to use soda

Gabriel Delepierre; Rami Mahfouz; Francisco J. Cadete Santos Aires; Jean Dijon

2010-01-01

275

Crystallization of Carbon Nanotube and Nanofiber Polypropylene Composites  

Microsoft Academic Search

A variety of semicrystalline isotactic polypropylene composites containing carbon nanotubes and nanofibers were produced by melt and solution techniques. The effect of the nanofillers on the crystallization process was investigated by transmission electron microscopy, scanning electron microscopy, and differential scanning calorimetry. Under the processing conditions applied in this study, the surfaces of the carbon nanomaterials act as nucleation sites in

J. Sandler; G. Broza; M. Nolte; K. Schulte; Y.-M. Lam; M. S. P. Shaffer

2003-01-01

276

Investigation of the initial period of sulphate scale formation Part 2. Kinetics of calcium sulphate crystal growth at its crystallization on a heat-exchange surface  

Microsoft Academic Search

Experimental data on calcium sulphate crystal growth (gypsum) from electrolytic solutions on a heated metal surface were considered. It was shown that crystals grew along a heat transfer surface, in parallel to it. The growth kinetics in the direction [100] under investigated experimental conditions were described by a quadratic dependence to supersaturation. The crystal growth in the direction [001] under

Oleg D. Linnikov

2000-01-01

277

Crystal chemistry and structure refinement of five hydrated calcium borates  

USGS Publications Warehouse

The crystal structures of the five known members of the series Ca2B6O11??xH2O (x = 1, 5, 5, 7, 9, and 13) have been refined by full-matrix least-squares techniques, yielding bond distances and angles with standard errors of less than 0??01 A?? and 0??5??, respectively. The results illustrate the crystal chemical principles that govern the structures of hydrated borate compounds. The importance of hydrogen bonding in the ferroelectric transition of colemanite is confirmed by more accurate proton assignments. ?? 1964.

Clark, J. R.; Appleman, D. E.; Christ, C. L.

1964-01-01

278

Tumoral calcium pyrophosphate dihydrate crystal deposition disease: a rare diagnosis by fine-needle aspiration.  

PubMed

Calcium pyrophosphate dihydrate crystal deposition disease (CPPD) is a well-recognized inflammatory joint disorder characterized by presence of calcium pyrophosphate dihydrate crystals in intraarticular and periarticular tissue. We report here a case of a 48-year-old male who presented with painless right hand swelling. Clinical suspicion was that of malignant soft tissue tumor. Fine-needle aspiration (FNA) yielded chalky white gritty material. Microscopic examination showed large areas of basophilic calcified material, histiocytes, giant cells and characteristic rhomboid shaped crystals. At places, chondroid material was also identified, hence, diagnosis of CPPD was made. This was confirmed on histopathological examination. Tophaceous/ tumoral pseudogout is a rare form of CPPD and it is important to recognize that this form can be diagnosed in FNA cytology (FNAC) and misdiagnosis of benign or malignant cartilaginous lesions can be avoided. PMID:19688761

Kishore, B; Khare, P; Gupta, R Jain; Gupta, C; Khare, V

2010-01-01

279

Heparin sulfate in the stone matrix and its inhibitory effect on calcium oxalate crystallization.  

PubMed

The nature of the soluble stone matrix and its possible role in urinary stone formation was studied. For this purpose we performed two-dimensional cellulose acetate membrane electrophoresis of the glycosaminoglycans (GAGs) which were contained in the soluble stone matrix, substances adsorbed onto calcium oxalate crystals in vitro (crystal surface binding substances, CSBS) and urinary macromolecules (UMMs). The main GAG in the soluble stone matrix and CSBS was found to be heparan sulfate, whereas the UMMs contained various GAGs usually seen in urine. An inhibition assay showed the soluble stone matrix to have the strongest inhibitory activity among these macromolecular substances when inhibitory activity was expressed in terms of uronic acid concentration. It is suggested that the main GAG in the soluble stone matrix consists of heparan sulfate, which has a strong inhibitory activity on calcium oxalate crystal growth and aggregation and constitutes part of the CSBS. PMID:8342253

Yamaguchi, S; Yoshioka, T; Utsunomiya, M; Koide, T; Osafune, M; Okuyama, A; Sonoda, T

1993-05-01

280

Evaluation of a routine method for determination of calcium oxalate crystal growth inhibition in diluted urine samples.  

PubMed

We have evaluated a routine method for determination of the inhibition of calcium oxalate crystal growth in diluted urine samples. A crystallization inhibition index is calculated from the decrease in [14C]oxalate concentration in a metastable solution of calcium chloride and sodium oxalate after addition of seed crystals of calcium oxalate. The coefficient of variation between different determinations on the same sample is less than 1.5%, and there is good correspondence between indices obtained by this method and by a more laborious older method. We also studied the influence of different urinary constituents on the crystal growth rate in the system; whereas there was significant inhibition with citrate, chondritin sulfate, and pyrophosphate, no effects were observed with ordinary urinary concentrations of calcium, magnesium, and oxalate. The mean inhibition index was lower in a group of male patients with calcium oxalate stone disease than in a control group of normal men. PMID:7471423

Tiselius, H G; Fornander, A M

1981-04-01

281

Polyelectrolyte effects on the crystallization phenomena of the lithium carbonate  

NASA Astrophysics Data System (ADS)

Anionic polyelectrolyte effects on the lithium carbonate crystallization phenomena were investigated. Li2CO3 crystals were obtained by reactive crystallization with seed crystals. Polyelectrolytes were dissolved into the reactive field before the reaction. Obtained crystals were observed with scanning electron microscopy (SEM) and crystal size and agglomeration degree were measured by the SEM images. The results show that Li2CO3 crystallized different shape and size from absence of polyelectrolyte in those reactive fields. Especially polyacrylic acid (PAA) improved on the agglomeration of the crystals and shaped them high aspect needles. Thus other experimental conditions including PAA molecular weight and concentration, reaction time, supersaturation by Li concentration were investigated in addition. As a result, obtained crystals were not different in each PAA molecular weight reactive fields. Meanwhile PAA concentration has optimum range. Li2CO3 formed less agglomeration and higher aspect around 1g/l. In the concentration, Li2CO3 did not agglomerate regardless of aging time and Li concentration. Moreover crystals became rectangle shape in higher Li concentration.(020) face intensity of the rectangle shape crystals increased according to XRD pattern. PAA affected the facial growth. These results may provide a method of morphological change and clearly crystallization of Li2CO3.

Watamura, Hiroto; Marukawa, Hironobu; Hirasawa, Izumi

2013-06-01

282

Distribution of calcium carbonate in surface sediments of the Atlantic Ocean  

Microsoft Academic Search

The areal distribution of calcium carbonate in the surface sediments of the Atlantic Ocean and adjacent seas and oceans is mapped on the basis of over 1700 data points. The first-order relation of carbonate distribution to water depth is evident in both the areal distribution and the plots of carbonate versus depth for 11 areas of the Atlantic. Superimposed on

P. E. Biscaye; V. Kolla; K. K. Turekian

1976-01-01

283

[SEM, XRD and FTIR investigation on crystal growth of calcium oxalate modulated by sodium tartrate].  

PubMed

Crystallization of calcium oxalate (CaOxa) was investigated in the presence of sodium tartrate (Na2 tart) of different concentration in a gel system by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. It was found that in the presence of a low concentration of Na2tart (0.01 mol x L(-1)), calcium oxalate monohydrate (COM) is the dominant crystal phase. The percentage of calcium oxalate dihydrate (COD) is less than 5%. In the XRD pattern the main diffraction peaks are (101), (020), and (202) planes of COM crystals. In the FTIR spectrum, the main asymmetric carbonyl stretching band nu(as) (COO-) and the metal-carboxylate stretch nu(s) (COO-) of COM occur at 1 618 and 1 317 cm(-1), respectively. With the concentration of Na2 tart increasing to 0. 10 and 0. 50 mol x L(-1), the percentage of COD crystals increases to 10% and 50%, respectively, and the surface area of COM crystals decreases. The diffraction peaks that assigned to the (200), (211), (411), and (213) planes of COD crystals become stronger and stronger. The temperature can influence the modulation of Na2 tart in terms of the phase composition and morphology of CaOxa crystals. As the temperature decreases, the percentage of COD increases. At a higher temperature beyond 47 degrees C, COM is the dominant phase; but COM is dominant when the temperature is lower than 27 degrees C. The nu(as) (COO-) and nu(s), (COO-) of COD crystals occur at 1 647.6 and 1 327.7 cm(-1), respectively. PMID:16883858

Zheng, Hui; Chen, Cun-Yuan; Ouyang, Jian-Ming

2006-05-01

284

Effect of storage temperature on crystal formation rate and growth rate of calcium lactate crystals on smoked Cheddar cheeses.  

PubMed

Previous studies have shown that storage temperature influences the formation of calcium lactate crystals on vacuum-packaged Cheddar cheese surfaces. However, the mechanisms by which crystallization is modulated by storage temperature are not completely understood. The objectives of this study were to evaluate the effect of storage temperature on smoked Cheddar cheese surfaces for (1) the number of discrete visible crystals formed per unit of cheese surface area; (2) growth rate and shape of discrete crystals (as measured by area and circularity); (3) percentage of total cheese surface area occupied by crystals. Three vacuum-packaged, random weight (?300 g) retail samples of naturally smoked Cheddar cheese, produced from the same vat of cheese, were obtained from a retail source. The samples were cut parallel to the longitudinal axis at a depth of 10mm from the 2 surfaces to give six 10-mm-thick slabs, 4 of which were randomly assigned to 4 different storage temperature treatments: 1, 5, 10°C, and weekly cycling between 1 and 10°C. Samples were stored for 30 wk. Following the onset of visible surface crystals, digital photographs of surfaces were taken every other week and evaluated by image analysis for number of discrete crystal regions and total surface area occupied by crystals. Specific discrete crystals were chosen and evaluated biweekly for radius, area, and circularity. The entire experiment was conducted in triplicate. The effects of cheese surface, storage temperature, and storage time on crystal number and total crystal area were evaluated by ANOVA, according to a repeated-measures design. The number of discrete crystal regions increased significantly during storage but at different rates for different temperature treatments. Total crystal area also increased significantly during storage, at rates that varied with temperature treatment. Storage temperature did not appear to have a major effect on the growth rates and shapes of the individual crystals that were chosen for analysis. The data indicated that the effect of storage temperature was complex, likely involving solubility changes, the formation of d(-) and l(+) lactic acid, and the occurrence of syneresis, which in turn affected the number of crystal formation sites and total crystal area on the cheese surface. PMID:23548293

Rajbhandari, P; Patel, J; Valentine, E; Kindstedt, P S

2013-03-30

285

Short-term effects of calcium carbonate, lactate, and gluconate on the calcium-parathyroid axis in normal elderly men and women.  

PubMed

We evaluated the impact of three calcium salts on the calcium-parathyroid axis in healthy elderly volunteers. Fasting subjects were administered a standardized 1-g calcium load on three occasions, using calcium carbonate, lactate, and gluconate in random sequence with 8 oz milk or orange juice as carrier. Blood and urine were collected at baseline and for 6 h following the calcium load. Each salt rapidly increased the serum-calcium concentration and urinary-calcium excretion. Response duration was shorter with gluconate than with the other salts, but peak responses were similar for all preparations. Urinary-calcium excretion was slightly lower when orange juice replaced milk, but calcemic responses were not different. Changes in immunoreactive-parathyroid hormone and renal-phosphorus handling did not differ among calcium salts. Except for a shorter duration of effect with gluconate, all three calcium salts provided similar short-term suppression of the parathyroid axis. PMID:3020960

Goddard, M; Young, G; Marcus, R

1986-11-01

286

Biomimetic Calcium Phosphate Crystallization: Synchrotron X-ray Studies  

NASA Astrophysics Data System (ADS)

The nucleation and growth of calcium phosphate by organic templates attract great attention due to its relevance to bone biomineralization. In spite of the vast studies in the field, the role of the organic templates in the process is still not well understood. One reason for this drawback is the lack of experimental tools to probe the organic template structure during the process. We studied the nucleation and growth of calcium phosphate under floating Langmuir monolayers, at the air/water interface, using two complementary X-ray scattering methods. We show that Grazing Incidence X-ray Diffraction (GID) and Grazing Incidence X-ray off-Specular Scattering (GIXOS) can reveal the organic-inorganic interface properties in situ. By using GID and GIXOS together, we can simultaneously determine the lateral interface structure and the electron density profile normal to the interface. Combined with ex situ methods, these techniques can improve our understanding of the role of the organic template during biomineralization.

Uysal, Ahmet; Stripe, Benjamin; Dutta, Pulak; Lin, Binhua; Meron, Mati

2012-02-01

287

Preparation, crystal structure and photoluminescence of garnet-type calcium tin titanium aluminates  

SciTech Connect

Colorless and transparent single crystals of Ca{sub 3}Sn{sub 2.2}Ti{sub 0.8}Al{sub 2}O{sub 12}, which emit blue-white light under ultraviolet light, were prepared by heating a mixture of oxides and calcium carbonate with a calcium and aluminum-rich composition at 1500 {sup o}C. Single crystal X-ray diffraction revealed that the crystal structure is the garnet-type with a cubic cell parameter (a=12.5309(3) A) and the space group, Ia 3-bar d (R1=0.0277, wR2=0.0663, and S=1.367 for all data). The structural formula is presented as Ca{sub 3}[Sn{sub 0.96}Ti{sub 0.04}]{sub octa}[Al{sub 0.67}Ti{sub 0.24}Sn{sub 0.09}]{sub tetra}O{sub 12}. Polycrystalline solid solutions of Ca{sub 3}Sn{sub 3-x}Ti{sub x}Al{sub 2}O{sub 12} were prepared by solid state reaction in air at 1370 {sup o}C with nominal titanium contents from x=0.6 to 1.4. The refined unit cell parameter decreased with increasing x. A broad blue-white emission with a peak wavelength of 465 nm was observed for the solid solutions at room temperature. -- Graphical abstract: Garnet-type solid solutions of Ca{sub 3}Sn{sub 3-x}Ti{sub x}Al{sub 2}O{sub 12} (x=0.6-1.4) were prepared. Sn{sup 4+} and Ti{sup 4+} partially occupy both tetrahedral and octahedral sites. The solid solutions showed a broad emission band peaking at 465 nm under UV excitation. Display Omitted Research highlights: {yields} New garnet-type solid solutions were found in the CaO-Al{sub 2}O{sub 3}-TiO{sub 2}-SnO{sub 2} system. {yields} Single crystals of Ca{sub 3}Sn{sub 2.2}Ti{sub 0.8}Al{sub 2}O{sub 12} were obtained by the self-flux method. {yields} Solid solutions with nominal compositions Ca{sub 3}Sn{sub 3-x}Ti{sub x}Al{sub 2}O{sub 12} (x=0.6-1.4) were prepared by solid state reaction at 1370 {sup o}C. {yields} Sn{sup 4+} and Ti{sup 4+} partially occupy both tetrahedral and octahedral sites, respectively, in the garnet-type structure. {yields} Ca{sub 3}Sn{sub 3-x}Ti{sub x}Al{sub 2}O{sub 12} solid solutions emitted blue-white light with a peak wavelength at 465 nm under UV irradiation.

Yamane, Hisanori, E-mail: yamane@tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan); Kawano, Tetsuya [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai 980-8577 (Japan)

2011-05-15

288

Calcium  

MedlinePLUS

... Office of Dietary Supplements Dietary Supplement Fact Sheet: Calcium QuickFacts Datos en español Health Professional Other Resources Create PDF What is calcium and what does it do? Calcium is a ...

289

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

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.

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

2010-01-01

290

Basic Calcium Phosphate Crystals Activate c-fos Expression Through a Ras/ERK Dependent Signaling Mechanism  

PubMed Central

Diseases caused by calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals occur frequently in osteoarthritic joints. Both crystals induce mitogenesis, metalloproteinase synthesis and secretion by fibroblasts and chondrocytes, promoting degradation of articular tissue. We investigated the mechanism by which BCP activates the c-fos proto-oncogene, which has been shown to activate various matrix metalloproteinases (MMPs). We demonstrate that BCP crystals induce c-fos expression primarily through a Ras/ERK dependent signaling mechanism targeting two highly conserved regulatory binding sites, the serum response element (SRE) and the cAMP response element (CRE). These results establish a calcium crystal induced, calcium/Calmodulin independent, signaling pathway in which BCP crystals activate Ras/MAPK, which can directly target an SRF-containing transcription factor complex, to induce fibroblasts to secrete metalloproteinases.

Major, Michael L.; Cheung, Herman S.; Misra, Ravi P.

2007-01-01

291

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

USGS Publications Warehouse

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.

Kramer, H.

1957-01-01

292

Calcium carbonate corrosivity in an Alaskan inland sea  

NASA Astrophysics Data System (ADS)

Ocean acidification is the hydrogen ion increase caused by the oceanic uptake of anthropogenic CO2, and is a focal point in marine biogeochemistry, in part, because this chemical reaction reduces calcium carbonate (CaCO3) saturation states (?) to levels that are corrosive (i.e. ? ? 1) to shell-forming marine organisms. However, other processes can drive CaCO3 corrosivity; specifically, the addition of tidewater glacial melt. Carbonate system data collected in May and September from 2009 through 2012 in Prince William Sound (PWS), a semi-enclosed inland sea located on the south-central coast of Alaska that is ringed with fjords containing tidewater glaciers, reveal the unique impact of glacial melt on CaCO3 corrosivity. Initial limited sampling was expanded in September 2011 to span large portions of the western and central sound, and included two fjords proximal to tidewater glaciers: Icy Bay and Columbia Bay. The observed conditions in these fjords affected CaCO3 corrosivity in the upper water column (<50 m) in PWS in two ways: (1) as spring-time formation sites of mode water with near-corrosive ? levels seen below the mixed layer across the sound, and (2) as point sources for surface plumes of glacial melt with corrosive ? levels (? for aragonite and calcite down to 0.60 and 1.02, respectively) and carbon dioxide partial pressures (pCO2) well below atmospheric levels. CaCO3 corrosivity in glacial melt plumes is poorly reflected by pCO2 or pHT, indicating that either one of these carbonate parameters alone would fail to track ? in PWS. The unique ? and pCO2 conditions in the glacial melt plumes enhances atmospheric CO2 uptake, which, if not offset by mixing or primary productivity, would rapidly exacerbate CaCO3 corrosivity in a positive feedback. The cumulative effects of glacial melt and air-sea gas exchange are likely responsible for the seasonal widespread reduction of ? in PWS; making PWS highly sensitive to increasing atmospheric CO2 and amplified CaCO3 corrosivity.

Evans, W.; Mathis, J. T.; Cross, J. N.

2013-09-01

293

Association of Vacancies with Calcium Impurities in Potassium Chloride Crystals  

Microsoft Academic Search

Measurements are made on the dc conductivity and dielectric loss in quenched KCl crystals doped with small amount of CaCl2. The evidence for formation of higher complexes is obtained from the decay of the conductivity during annealing after quenching. It is also found that there exists a relation between the number of free vacancies, nv, and that of impurity-vacancy associated

Tosiyuki Ninomiya

1960-01-01

294

Calcium oxalate crystal-induced cytolysis in polymorphonuclear leukocytes and erythrocytes.  

PubMed

Calcium oxalate microcrystals induce cytolysis of rabbit polymorphonuclear leukocytes (PMN's) and hemolysis of human erythrocytes. The effects on erythrocytes can be distinguished from those on PMN's because cytolysis of the latter is suppressed by substances such as cytochalasin A and N-naphthyl maleimide, known phagocytosis inhibitors. Polyvinylpyridine-N-oxide, a powerful hydrogen acceptor, has no protective effect. Cell injury of PMN's and erythrocytes is potentiated in the presence of cations, whereas poly-D-glutamic acid and other negatively charged compounds have an opposite effect. The results suggest that positive charges on the crystals play an essential role in calcium oxalate-induced cytolysis of PMN's and erythrocytes. PMID:7211577

Elferink, J G; Riemersma, R C

1980-11-01

295

Induction of crystallization of calcium oxalate dihydrate in micellar solutions of anionic surfactants.  

PubMed

Calcium oxalate dihydrate (CaC2O4 center dot (2+x)H2O; COD; x < or = 0.5) does not readily crystallize from electrolytic solutions but appears as a component in crystalluria. In this paper, we review in vitro studies on the factors responsible for its nucleation and growth with special attention given to the role of surfactants. The following surfactants were tested: dodecyl ammonium chloride (cationic), octaethylene mono-hexadecylether (non-ionic), sodium dodecyl sulfate (SDS, anionic), dioctyl sulphosuccinate (AOT, anionic), and sodium cholate (NaC, anionic). The cationic and some of the anionic surfactants (SDS, AOT) induced different habit modifications of growing calcium oxalate crystals by preferential adsorption at different crystal faces. In addition, the anionic surfactants effectively induced crystallization of COD at the expense of COM, the proportion of COD in the precipitates abruptly increasing above a critical surfactant concentration, close to, but not necessarily identical with the respective CMC. A mechanism is proposed, whereby crystallization of COD in the presence of surfactants is a consequence of the inhibition of COM by preferential adsorption of surfactant hemimicelles (two-dimensional surface aggregates) at the surfaces of growing crystals. PMID:8819887

Furedi-Milhofer, H; Tunik, L; Filipovic-Vincekovic, N; Skrtic, D; Babic-Ivancic, V; Garti, N

1995-01-01

296

Dynamics of Calcium Carbonate Precipitation in Double Diffusion Mixing Zones  

NASA Astrophysics Data System (ADS)

Engineered or natural processes in the subsurface that generate mineral precipitates are often involve the formation and evolution of reactant mixing zones within which chemical gradients are established and molecular-scale reactant mixing is coupled to changes in local permeability. The mixing interface is characterized by 1) macroscopic (volume averaged) and microscopic (pore scale) concentration gradients, and 2) reactions that can change local chemical conditions, permeability and therefore the rate and distribution of precipitation reactions. Experimental and modeling investigations are underway using double diffusion cells with gel-packed porous medium to characterize calcium carbonate precipitation, local permeability changes, and associated partitioning of trace metals. Each boundary solution contains a mineral forming reactant (e.g., Ca2+ and CO32-). The concentrations of the reactants are high enough such that supersaturated conditions are established if mixed. Mixing occurs as a result of the reactants diffusion toward each other in the porous media. The objectives of this study are to investigate the effects of reduction in permeability on 1) narrowing (“focusing”) of the precipitation zone, and 2) migration of the precipitation zone due to asymmetry across the mixing zone with respect to precipitation rates and/or local chemical conditions. Focusing is expected as a consequence of permeability reduction. Migration toward the carbonate boundary is expected due to changes in local pH conditions. In experiments with granular media where advective transport is possible (unlike in a gel) local changes in density and density unstable conditions caused by precipitation can create more complex mixing zones. The nature of the mixing zones controls the extent, nature and distributions of precipitates. The volume-averaged manifestations of pore and local reactions are not well represented by predictions based on simulations using volume-averaged conditions. Such processes can affect partitioning of divalent metals (e.g. Sr2+), which is the next phase of study.

Redden, G. D.; Tu, L.; Gebrehiwet, T.; Payne, B.; Huang, H.; Guo, L.

2009-12-01

297

Influence of impurity ions and magnetic field on the properties of freshly precipitated calcium carbonate  

Microsoft Academic Search

Static magnetic field (MF) effects on the properties of freshly precipitated calcium carbonate have been investigated in the presence of impurity ion Mg2+, Fe2+, or SO42?. One or both solutions, CaCl2 and Na2CO3, were exposure to MF (0.5T) for 20min at 20°C. Then calcium carbonate was precipitated and zeta potential, pH and light absorbance (?=543.3nm) were measured. The same parameters

Lucyna Ho?ysz; Emil Chibowski; Aleksandra Szcze?

2003-01-01

298

Effect of administering calcium carbonate to treat secondary hyperparathyroidism in nondialyzed patients with chronic renal failure  

Microsoft Academic Search

We administered calcium carbonate orally to determine its safety and efficacy in treating nondialyzed patients with mild to moderate renal failure and secondary hyperparathyroidism. Twenty patients with chronic renal failure (creatinine clearance levels ranging from 7.9 to 42.7 mL\\/min) participated in this study. After a 6-month control period, 3 g calcium carbonate was administered daily for 6 months. We studied

Yusuke Tsukamoto; Rika Moriya; Yasusi Nagaba; Tetsuo Morishita; Ibuki Izumida; Michihito Okubo

1995-01-01

299

Calcium carbonate deposition in Ca 2+ polluted Onondaga Lake, New York, U.S.A  

Microsoft Academic Search

Seasonal and long-term trends in the rate of calcium carbonate (CaCO3) deposition are documented for Ca2+ polluted Onondaga Lake, New York. These observations are based on particulate inorganic carbon and particulate calcium analyses of sediment trap collections, made weekly over the May-September interval for 10 years. Continuous deposition of CaCO3 was evident for the monitoring period of all 10 years.

Robert N. Womble; Charles T. Driscoll; Steven W. Effler

1996-01-01

300

Intracrystalline urinary proteins facilitate degradation and dissolution of calcium oxalate crystals in cultured renal cells.  

PubMed

We have previously proposed that intracrystalline proteins would increase intracellular proteolytic disruption and dissolution of calcium oxalate (CaOx) crystals. Chauvet MC, Ryall RL. J Struct Biol 151: 12-17, 2005; Fleming DE, van Riessen A, Chauvet MC, Grover PK, Hunter B, van Bronswijk W, Ryall RL. J Bone Miner Res 18: 1282-1291, 2003; Ryall RL, Fleming DE, Doyle IR, Evans NA, Dean CJ, Marshall VR. J Struct Biol 134: 5-14, 2001. The aim of this investigation was to determine the effect of increasing concentrations of intracrystalline protein on the rate of CaOx crystal dissolution in Madin-Darby canine kidney (MDCKII) cells. Crystal matrix extract (CME) was isolated from urinary CaOx monohydrate (COM) crystals. Cold and [14C]oxalate-labeled COM crystals were precipitated from ultrafiltered urine containing 0-5 mg/l CME. Crystal surface area was estimated from scanning electron micrographs, and synchrotron X-ray diffraction was used to determine nonuniform strain and crystallite size. Radiolabeled crystals were added to MDCKII cells and crystal dissolution, expressed as radioactive label released into the medium, was measured. Increasing CME content did not significantly alter crystal surface area. However, nonuniform strain increased and crystallite size decreased in a dose-response manner, both reaching saturation at a CME concentration of 3 mg/ and demonstrating unequivocally the inclusion of increasing quantities of proteins in the crystals. This was confirmed by Western blotting. Crystal dissolution also followed saturation kinetics, increasing proportionally with final CME concentration and reaching a plateau at a concentration of approximately 2 mg/l. These findings were complemented by field emission scanning electron microscopy, which showed that crystal degradation also increased relative to CME concentration. Intracrystalline proteins enhance degradation and dissolution of CaOx crystals and thus may constitute a natural defense against urolithiasis. The findings have significant ramifications in biomineral metabolism and pathogenesis of renal stones. PMID:18077596

Grover, Phulwinder K; Thurgood, Lauren A; Fleming, David E; van Bronswijk, Wilhelm; Wang, Tingting; Ryall, Rosemary L

2007-12-12

301

Carbon monoxide effects on calcium levels in vascular smooth muscle  

SciTech Connect

Previously the authors showed that carbon monoxide (CO) relaxes vascular smooth muscle in the working heart and thoracic aorta preparation perfused with hemoglobin-free, Krebs-Henseleit (KH) solution. The CO-induced relaxation was not caused by hypoxia, nor was it mediated by adrenergic influences, adenosine, or prostaglandins. In these studies the effect of CO on calcium (Ca/sup + +/) concentrations in vascular smooth muscle was determined using /sup 45/Ca as a tracer. Isolated rat thoracic aorta segments were incubated with /sup 45/Ca and gassed with O/sub 2/, N/sub 2/, or CO for 60 min. Verapamil was used to verify the effectiveness of the test system. Ca/sup + +/ concentrations were 488 /+ -/ 35 and 515 /+ -/ 26 mM/g tissue (X /+ -/ SE) in aortic rings gassed with O/sub 2/ and N/sub 2/, respectively. CO reduced Ca/sup + +/ concentrations significantly (P<0.01) by 29% to 369 /+ -/ 18 mM/g tissue. Verapamil treatment reduced Ca/sup + +/ concentrations by 40% to 314 /+ -/ 23 mM/g tissue. These results suggest that CO relaxes vascular smooth muscle and dilates blood vessels by decreasing Ca/sup + +/ concentrations in vascular smooth muscle.

Lin, H.; McGrath, J.J.

1988-01-01

302

Thermodynamic properties of synthetic calcium-free carbonate cancrinite  

NASA Astrophysics Data System (ADS)

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.

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

2013-09-01

303

Dissolution of calcium bilirubinate and calcium carbonate debris remaining after methyl tert-butyl ether dissolution of cholesterol gallstones.  

PubMed

Methyl tert-butyl ether rapidly dissolves cholesterol gallstones, although insoluble debris may remain. Total gallstone dissolution could be achieved if safe solvents for these noncholesterol components can be developed. We evaluated the in vitro ability of ethylenediaminetetraacetic acid, citrate, dimethyl sulfoxide, and ionic or nonionic detergents to dissolve the predominantly calcium bilirubinate and calcium carbonate debris remaining after methyl tert-butyl ether gallstone dissolution. Ethylenediaminetetraacetic acid 1% or 2% at pH 9.5 was the most effective of the solvents studied for dissolving calcium and bile pigment. The addition of cholate (25-200 mM) or polysorbate (1%-10%) to ethylenediaminetetraacetic acid 1% at pH 9.5 enhanced pigment dissolution compared to ethylenediaminetetraacetic acid alone. Dissolution of pellets prepared from human gallstones and composed predominantly of either calcium bilirubinate or calcium carbonate was 80% and 85% at 4 h using ethylenediaminetetraacetic acid 1% plus polysorbate-20 1% at pH 9.5. We conclude that ethylenediaminetetraacetic acid, either alone or with a detergent, is an effective solvent for methyl tert-butyl ether-insoluble gallstone debris and deserves assessment in vivo. PMID:2323524

Nelson, P E; Moyer, T P; Thistle, J L

1990-05-01

304

Liquid crystals of carbon nanotubes and graphene.  

PubMed

Liquid crystal ordering is an opportunity to develop novel materials and applications with spontaneously aligned nanotubes or graphene particles. Nevertheless, achieving high orientational order parameter and large monodomains remains a challenge. In addition, our restricted knowledge of the structure of the currently available materials is a limitation for fundamental studies and future applications. This paper presents recent methodologies that have been developed to achieve large monodomains of nematic liquid crystals. These allow quantification and increase of their order parameters. Nematic ordering provides an efficient way to prepare conductive films that exhibit anisotropic properties. In particular, it is shown how the electrical conductivity anisotropy increases with the order parameter of the nematic liquid crystal. The order parameter can be tuned by controlling the length and entanglement of the nanotubes. In the second part of the paper, recent results on graphene liquid crystals are reported. The possibility to obtain water-based liquid crystals stabilized by surfactant molecules is demonstrated. Structural and thermodynamic characterizations provide indirect but statistical information on the dimensions of the graphene flakes. From a general point of view, this work presents experimental approaches to optimize the use of nanocarbons as liquid crystals and provides new methodologies for the still challenging characterization of such materials. PMID:23459968

Zakri, Cécile; Blanc, Christophe; Grelet, Eric; Zamora-Ledezma, Camilo; Puech, Nicolas; Anglaret, Eric; Poulin, Philippe

2013-03-04

305

Efficacy, Tolerability, and Safety of Lanthanum Carbonate in Hyperphosphatemia: A 6Month, Randomized, Comparative Trial versus Calcium Carbonate  

Microsoft Academic Search

Background\\/Aims: Hyperphosphatemia is an important clinical consequence of renal failure, and its multiple adverse systemic effects are associated with significantly increased risks of morbidity and mortality in dialysis patients. Existing oral phosphate binders have not permitted control of serum phosphate within currently accepted guidelines. This study compares lanthanum carbonate with calcium carbonate for control of serum phosphate in hemodialysis patients.

A. J. Hutchison; B. Maes; J. Vanwalleghem; G. Asmus; E. Mohamed; R. Schmieder; W. Backs; R. Jamar; A. Vosskühler

2005-01-01

306

Exotic behavior and crystal structures of calcium under pressure  

PubMed Central

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.

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

2010-01-01

307

Thermal properties of single-walled carbon nanotube crystal  

Microsoft Academic Search

In this work, the thermal properties of a single-walled carbon nanotube (SWCNT) crystal are studied. The thermal conductivity of the SWCNT crystal is found to have a linear dependence on temperature in the temperature range from 1.9 K to 100.0 K. In addition, a peak (658 W\\/mK) is found at a temperature of about 100.0 K. The thermal conductivity decreases

Li-Jun Hu; Ji Liu; Zheng Liu; Cai-Yu Qiu; Hai-Qing Zhou; Lian-Feng Sun

2011-01-01

308

Polymer crystallization enabled carbon nanotube functionalization  

NASA Astrophysics Data System (ADS)

CNTs were periodically decorated with polymer lamellar crystals using both controlled solution crystallization and physical vapor deposition methods, resulting in nano hybrid shish-kebab (NHSK) structures. The periodicity of the polymer lamellae varies from 20 - 100 nm. The kebabs are approximately 5 nm thick with a lateral size of 20 nm to micrometers, which can be readily controlled by varying the crystallization conditions. Both polyethylene and Nylon 6,6 have been successfully decorated on multi-walled as well as single-walled CNTs. The detailed formation mechanism was attributed to size dependent soft epitaxy. Since the polymer kebabs can be easily removed, these unique NHSKs can serve as templates to fabricate a variety of CNTs-containing hybrid materials with controlled pattering on the CNT surface. This method thus opens a gateway to periodical patterning on CNTs or similar 1D nanowires in an ordered and controlled manner.

Li, Christopher; Li, Lingyu; Li, Bing; Yavorsky, Cristin

2007-03-01

309

Radiation defect formation in strontium and calcium fluoride crystals doped by divalent cadmium and zinc ions  

NASA Astrophysics Data System (ADS)

Ionization radiation is shown to reduce impurity ions to the univalent state in strontium and calcium fluoride crystals doped by divalent cadmium and zinc ions. In this case, a univalent ion is surrounded by eight equivalent fluorine ions and exhibits cubic symmetry O h . At room temperature, the symmetry of the center is revealed to be sequentially lowered to C 3 v and then to C 2 v owing to the addition to the nearest environment of the impurity univalent ion of one or two anion vacancies, respectively, which are intrinsic defects not forming in undoped strontium and calcium fluoride crystals. Stable intrinsic defects are assumed to form through the separation of anion vacancy-interstitial fluorine ion pairs in the electric field induced by the reduced impurity ions. This electric field lowers the energy barrier to thermal separation of charged intrinsic defects.

Egranov, A. V.; Radzhabov, E. A.; Nepomnyashchikh, A. I.; Ivashechkin, V. F.; Vasil'Eva, I. E.

2008-09-01

310

Effect of a magnetic water treatment on homogeneous and heterogeneous precipitation of calcium carbonate.  

PubMed

In this paper are reported experimental results on the effect of a magnetic field on the precipitation process of calcium carbonate scale from a hard water. Carbonically pure water was circulated at a constant flow rate in a magnetic field. After this treatment, calcium carbonate precipitation was induced by degassing dissolved carbonic gas. The nucleation time was identified from the variations of the pH and the Ca(2+) concentration. The ratio between homogeneous and heterogeneous nucleation was determined from the measurement of the mass of precipitated calcium carbonate. It is shown that the magnetic treatment increases the total amount of precipitate. This effect depends on the solution pH, the flow rate and the duration of the treatment. In addition, the magnetic treatment modifies the ratio between homogeneous/heterogeneous nucleation. Homogeneous nucleation is promoted by an increasing the pH of water, the flow rate as well as the residence time. The magnetic treatment enhances these effects with a maximum for a 15 min treatment time. It is shown that the presence of calcium carbonate colloid particles is not necessary. It is advanced that the main magnetic effects concern the associations of ionic species which are present in the solution and which are involved in the nucleation process of calcium carbonate precipitation. PMID:16650455

Fathi, Alimi; Mohamed, Tlili; Claude, Gabrielli; Maurin, Georges; Mohamed, Ben Amor

2006-05-02

311

Luminescence properties of manganese-activated calcium gallate single-crystals  

SciTech Connect

The authors investigate the photoluminescence and the optical properties of monocrystals of calcium gallates activated by magnesium ions as candidate materials for solid state lasers. Excitation was carried out in the ultraviolet region by a xenon or deuterium lamp and by an iodide incandescent lamp in the visible region. A nitrogen laser was also used. Luminescence was determined by spectrophotometry. A range of parameters, including crystal lattice and defect behavior and manganese ion concentration, are investigated for their effect on the optimal emission properties of the crystals.

Londar', S.L.; Vasil'tsiv, V.I.; Zakharko, Ya.M.; Merinov, B.V.

1987-11-01

312

Selective crystallization of calcium salts by poly(acrylate)-grafted chitosan  

Microsoft Academic Search

The biopolymer chitosan was chemically modified by grafting polyacrylamide or polyacrylic acid in a homogeneous aqueous phase using potassium persulfate (KPS) as redox initiator system in the presence of N,N-methylene-bis-acrylamide as a crosslinking agent. The influence of the grafted chitosan on calcium salts crystallization in vitro was studied using the sitting-drop method. By using polyacrylamide grafted chitosan as substrate, rosette-like

Andrónico Neira-Carrillo; Mehrdad Yazdani-Pedram; Jaime Retuert; Mario Diaz-Dosque; Sebastien Gallois; José L. Arias

2005-01-01

313

Lumenal gating mechanism revealed in calcium pump crystal structures with phosphate analogues  

Microsoft Academic Search

P-type ion transporting ATPases are ATP-powered ion pumps that establish ion concentration gradients across biological membranes. Transfer of bound cations to the lumenal or extracellular side occurs while the ATPase is phosphorylated. Here we report at 2.3Å resolution the structure of the calcium-ATPase of skeletal muscle sarcoplasmic reticulum, a representative P-type ATPase that is crystallized in the absence of Ca2+

Chikashi Toyoshima; Hiromi Nomura; Takeo Tsuda

2004-01-01

314

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

Microsoft Academic Search

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.

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

1969-01-01

315

Characteristics of gypsum crystal growth over calcium-based slurry in desulfurization reactions  

Microsoft Academic Search

A wet absorption of sulfur dioxide in a batch-type reactor was carried out, using three calcium compounds, namely, CaCO3, CaO, and Ca(OH)2 as absorbents. Based on Fourier Transform Infrared, X-ray diffraction, and scanning electron microscopy analyses, the different absorbents resulted in the different reaction pathways and mechanisms of crystal formation at the early reaction stage. In particular, the CaSO3 ·

Kyung-jun Chu; Kyung-seun Yoo; Kyong-tae Kim

1997-01-01

316

Microstructural characterization of calcium flouride single crystals deformed in steady state  

Microsoft Academic Search

Calcium fluoride single crystals have been deformed in compression to conditions of steady-state deformation in the temperature range 590 to 907° C (0.53 to 0.72T\\/Tm). The deformation microstructures have been characterized using cold-stage transmission electron microscopy. The microstructure of deformed samples is seen to consist of dislocation tangles, networks and subgrain boundaries. Dislocation structures in the subgrain boundaries have been

William M. Sherry; John B. Vander Sande

1981-01-01

317

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

Microsoft Academic Search

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

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

2010-01-01

318

Pyrophosphate does not influence calcium oxalate or calcium phosphate crystal formation in concentrated whole human urine  

Microsoft Academic Search

1) Low pyrophosphate urine was generated by passage through a nylon coil bearing immobilised inorganic pyrophosphatase. High pyrophosphate urine was made by addition of inorganic pyrophosphate. 2) Urine samples of low, normal, and high pyrophosphate content were rapidly evaporated at 37°C to 1,050 or 1,250 mosmol\\/L and the crystals formed studied by microscope, isotope and chemical methods. 3) Urinary pyrophosphate

P. C. Hallson; G. A. Rose; S. Sulaiman

1983-01-01

319

Green backlighting for TV liquid crystal display using carbon nanotubes  

NASA Astrophysics Data System (ADS)

A methodology to evaluate the emission characteristics of carbon nanotube layers in the context of liquid crystal display backlighting has been elaborated. Carbon nanotube layers with emission characteristics compatible with backlighting have been demonstrated for growth temperature as low as 400 °C, thanks to the use of plasma pretreatment before growth. This very low growth temperature allows to use soda lime glass for the backlight unit and thus to expect very low cost and very low power consumption devices with this technology.

Delepierre, Gabriel; Mahfouz, Rami; Cadete Santos Aires, Francisco J.; Dijon, Jean

2010-08-01

320

Complexes Affecting the Solubility of Calcium Carbonate in Water.  

National Technical Information Service (NTIS)

Corrosion and scale formation in water distribution systems are generally controlled by pH adjustment. The proper pH depends on the calcium and alkalinity concentrations, but is also affected by formation of certain complexes. If a portion of the calcium ...

T. E. Larson F. W. Sollo F. F. McGurk

1973-01-01

321

Identification of proteins extracted from calcium oxalate and calcium phosphate crystals induced in the urine of healthy and stone forming subjects  

Microsoft Academic Search

The purpose of our study was to identify the proteins and investigate the differences, if any, between protein components\\u000a of the matrices of calcium oxalate (CaOx) and calcium phosphate (CaP) crystals induced in?vitro in whole human urine of healthy\\u000a individuals and kidney stone patients. In addition, preliminary studies were performed to understand the effect of centrifugation\\u000a and filtration of urine

Fouad Atmani; Patricia A. Glenton; Saeed R. Khan

1998-01-01

322

Crystal structure of complex natural aluminum magnesium calcium iron oxide  

NASA Astrophysics Data System (ADS)

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.

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

2010-07-01

323

Problems in polarized light microscopy observation of birefringence of calcium pyrophosphate dihydrate crystals.  

PubMed

To reconsider the problems arising from the use of the phase plate as a test plate inserted into a polarized light microscope system for the analysis of triclinic calcium pyrophosphate dihydrate (t-CPPD) crystals, or Ca(2)P(2)O(7) x 2H(2)O in the synovial fluid of arthritis patients, we made the polarized light microscopy observations using a phase plate with a retardation of 530 nm for the synthesized t-CPPD crystals well-characterized by X-ray powder pattern indexing and single crystal X-ray diffraction measurements. The microscopy observations were made of crystals of different sizes, thicknesses and shapes. The retardation was assessed using the interference color chart at four extinction and diagonal positions both with and without the test plate. The addition and subtraction states produced by superimposing the retardations of two anisotropic materials, that is, the t-CPPD crystal and the 530 nm phase plate, were deduced from the interference color change by inserting the test plate at four diagonal positions. When the color change of a crystal at a diagonal position resulting from 90-degree rotation exhibits no clear birefringence, the interference color chart was shown to be useless. We suggested the use of a compensator whose retardation can be changed to obtain an accurate value for the retardation of the crystal. PMID:20685127

Omura, Yoko; Okamoto, Renzo; Konno, Minoru; Shiro, Motoo

2010-07-16

324

Role of phosphate groups in inhibition of calcium oxalate crystal growth by osteopontin.  

PubMed

Osteopontin (OPN) inhibits the growth of calcium oxalate monohydrate (COM) and other crystal phases in a phosphorylation-dependent manner. In the present study, the role of OPN phosphate groups in adsorption to, incorporation into and inhibition of COM crystals was studied by comparing OPN isoforms differing in phosphorylation. OPN isoforms purified from rat bone (bOPN), which contains 10 phosphates, and cow milk (mOPN), which contains 25 phosphates, were compared with rat recombinant OPN (rOPN), which is not phosphorylated. Using fluorescence-labeled proteins and confocal microscopy, we show that mOPN and rOPN, like bOPN, adsorb preferentially to the edges between {100} and {121} faces of preformed COM crystals, and to a lesser extent to the {100} and {121} faces. Using scanning electron microscopy, we show that growth of COM in the presence of bOPN or mOPN results in a 'dumbbell' morphology, whereas crystals grown with rOPN are only slightly affected. COM crystals grown in the presence of low concentrations of fluorescence-labeled bOPN incorporate the protein into the crystal lattice. In crystals imaged in the {010} plane, incorporation of bOPN results in a cross-shaped pattern of fluorescence, consistent with preferential adsorption to {100}/{121} edges throughout the growth process. PMID:18703867

Hunter, Graeme K; Grohe, Bernd; Jeffrey, Sara; O'Young, Jason; Sørensen, Esben S; Goldberg, Harvey A

2008-08-15

325

The effect of procedural variables on TG, DTG and DTA curves of calcium carbonate  

Microsoft Academic Search

The effect of procedural variables, including sample mass, heating rate, particle size and partial pressure of carbon dioxide, on TG, DTG and DTA curves for the decomposition of A. R. calcium carbonate and limestone has been studied. Such variables have a marked effect, similar in magnitude for both DTG and DTA. The effect of sample mass, or depth of undiluted

F. W. Wilburn; J. H. Sharp; D. M. Tinsley; R. M. McIntosh

1991-01-01

326

Determination of Calcium Carbonate in Mixed Paint Pigments by a New, Specific, Titrimetric Technique.  

National Technical Information Service (NTIS)

There is no method of analysis that is specific for calcium carbonate in paint pigments and all quantitative methods are relatively tedious and time-consuming. A simple, volumetric technique is described in which the carbonate is titrated with normal acid...

M. H. Swann

1967-01-01

327

Calcium Carbonate Distribution in the Surface Sediments of the Indian Ocean  

Microsoft Academic Search

A comprehensive calcium carbonate map for the Indian Ocean surface sediments has been pre- pared from the analysis of about 1200 samples. The percent cbonaidistribution shows the well- known first-order correlation with depth and hence reflects the physiographic peculiarities of the Indian Ocean. Thus on topographic highs such as most of the mid-Indian ridge, Ninety East ridge, etc. the carbonate

Venkatarathnam Kolla; Allan W. H. Bé; Pierre E. Biscaye

1976-01-01

328

Investigation of the initial period of sulphate scale formation Part 3. Variations of calcium sulphate crystal growth rates at its crystallization on a heat-exchange surface  

Microsoft Academic Search

Histograms of average and instantaneous growth rate distributions for calcium sulphate crystals (gypsum) formed on a heat-exchange surface are considered. It was found that at small supersaturations the distribution curves of the crystal growth rates have positive skewness, with increase in supersaturation the symmetry of the curves grows (moment coefficient of skewness tends to zero), and the distribution law becomes

Oleg D. Linnikov

2000-01-01

329

Calcium Bioavailability of Calcium Carbonate Fortified Soymilk Is Equivalent to Cow's Milk in Young Women1,2  

Microsoft Academic Search

Calcium (Ca)-fortified soymilk has gained popularity in the United States. Tricalcium phosphate (TCP)-fortified soymilk was shown to have a lower Ca bioavailability than cow's milk in men. However, the most popular soymilk in the U.S. is fortified with Ca carbonate (CC) and has not been evaluated. Ca bioavailability from CC-fortified soymilk (CCSM) and TCP-fortified soymilk (TCPSM) was compared with cow's

Yongdong Zhao; Berdine R. Martin; Connie M. Weaver

330

Crystal structure of complex natural aluminum magnesium calcium iron oxide  

SciTech Connect

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.

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

331

Nucleation and morphology of barium carbonate crystals in a semi-batch crystallizer  

Microsoft Academic Search

A double-jet feed, semi-batch crystallization system was used to explore the nucleation kinetics, growth kinetics and morphology of barium carbonate crystals under a constant pH value. The nucleation rate and the growth rate can be determined successfully by the initial rate method. The results showed that heterogeneous nucleation is dominant in the primary nucleation mechanism, and the effect of specific

Pao-Chi Chen; G. Y Cheng; M. H Kou; P. Y Shia; P. O Chung

2001-01-01

332

Calcium  

MedlinePLUS

... strong bones and teeth. Why Do I Need Calcium? Bones grow rapidly during adolescence, and teens need ... and canned salmon with bones. Back Continue Working Calcium Into Your Diet Looking for ways to up ...

333

Crystallization process of amorphous silicon–carbon alloys  

Microsoft Academic Search

The crystallization behavior of amorphous silicon carbon alloys films was investigated using infrared spectroscopy and transmission electron microscopy. The films were prepared by plasma enhanced chemical vapor deposition and the thickness and composition were checked by Rutherford backscattering spectroscopy. Annealing processes were carried out in the temperature range of 750–1100 °C in a vacuum furnace. The changes in the infrared

L. Calcagno; P Musumeci; F Roccaforte; C Bongiorno; G Foti

2002-01-01

334

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

SciTech Connect

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.

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

1986-07-01

335

Multi proxy approach for the formation of calcium carbonates in alkaline man-made environments  

NASA Astrophysics Data System (ADS)

The formation of calcium carbonates, e.g. in drainage systems of tunnels, may be induced by degassing of CO2-rich groundwater which enters the building. However, the dissolution of portlandite (Ca(OH)2) from cements or the shotcrete of the tunnel wall bears an additional and immense potential for the formation of carbonates from alkaline solutions. Variations in trace element incorporation and distribution of the stable isotopes of carbon and oxygen in the precipitated calcium carbonates may represent powerful tools to identify individual mechanisms for carbonate formation. As portlandite dissolves, highly alkaline solutions are obtained. In this case, precipitation of calcium carbonate can be related to the absorption of CO2 from the atmosphere. Isotopic analyses of the calcite show that fixation of CO2 from the Earth's atmosphere leads to significantly lighter ^13Ccalcite values (down to -25 o/oo, VPDB) as expected for the fixation of groundwater carbonate (typical ^13Ccalcite values between -10 and -16o/oo, VPDB). The evolution of Sr/Ca ratios in the alkaline drainage solutions and in the corresponding calcium carbonate precipitation provides insight into the dissolution process at the concrete with respect to the amount of primarily dissolved portlandite from the cement. Moreover, an inverse relationship between Mg/Ca and Sr/Ca ratios is observed due to the liberation of aqueous strontium by the dissolution of portlandite and the formation of brucite (Mg(OH)2) at alkaline conditions. Less incorporation of magnesium in the calcite structure is a strong indicator for carbonate precipitation from highly alkaline environments. Applications of such multi proxy approaches are discussed with case studies. Main tasks are the reconstruction of the environmental conditions during primary CaCO3 formation and monitoring of ongoing precipitation of calcium carbonates and cement-water interaction in alkaline man-made environments.

Rinder, T.; Dietzel, M.; Leis, A.

2009-04-01

336

Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Technical report, September 1, 1991--November 30, 1991  

SciTech Connect

Current coal mining and processing procedures produce a significant quanity of fine coal that is difficult to handle and transport. The objective of this work is to determine if these fines can be economically pelletized with calcium hydroxide, a sulfur capturing sorbent, to produce a clean-burning fuel for fluidized-bed combustors or stoker boilers. To harden these pellets, carbonation, which is the reaction of calcium hydroxide with carbon dioxide to produce a cementitious matrix of calcium carbonate, is being investigated. Previous research indicated that carbonation significantly improved compressive strength, impact and attrition resistance and ``weatherproofed`` pellets formed with sufficient calcium hydroxide (5 to 10% for minus 28 mesh coal fines).

Rapp, D.M.

1991-12-31

337

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

SciTech Connect

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.

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

338

Calcium oxalate crystals in Opuntia ficusindica (L.) mill.: Development and relation to mucilage cells — A stereological analysis  

Microsoft Academic Search

Summary In the succulent tissue ofOpuntia ficusindica development of calcium oxalate crystals was followed from the shoot apex to its base, using stereological analysis. The stereological parameters relating to the crystal cells were compared with those of mucilage cells, of the same tissue. A fairly monotonic relation between the stereological parameters of the two populations was noted. The possible physiological

S. Trachtenberg; A. M. Mayer

1981-01-01

339

Crystallization of calcium sulfate dihydrate under simulated conditions of phosphoric acid production in the presence of aluminum and magnesium ions  

Microsoft Academic Search

The effect of Al3+ and Mg2+ ions, as additives, on the crystallization of gypsum was studied under simulated conditions of the phosphoric acid production. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80°C, and the turbidity of the reaction mixture was measured at different time periods to calculate the induction time of gypsum crystals formation.

M. M. Rashad; M. H. H. Mahmoud; I. A. Ibrahim; E. A. Abdel-Aal

2004-01-01

340

Synthesis of low density carbon crystal 'carbolite' by quenching of carbon gas  

NASA Astrophysics Data System (ADS)

A new carbon crystal named carbolite has been synthesized by quenching high temperature carbon gas on a room temperature substrate. The crystal has a density as small as 1.46 g/cm(sup 3) and is transparent for visible light. The crystal structure is hexagonal, and the dimensions of the unit cell are 1.193 nm in the a-direction and 1.062 nm in the c-direction. Along the c-axis, a parallel array of carbon chains is proposed. The array is made up of a triangular lattice in which the interchain distance is 0.344 nm and the mean interatomic distance within a carbon chain is 0.133 nm. The former value is close to the van der Waals distance between the honeycomb planes of graphite, and the latter value is close to the C-C bond length in the honeycomb plane. Intercalations of potassium, sodium, and iodine atoms are performed.

Tanuma, Sei-Ichi; Palnichenko, Andrei

1995-05-01

341

Amorphous calcium carbonate in form of spherical nanosized particles and its application as fillers for polymers  

Microsoft Academic Search

The synthesis of amorphous calcium carbonate (ACC) via a liquid precursor to give spherical particles with monodisperse distribution of diameters in the range of 0.4–1.2?m has been optimized to the level to obtain multigram yields per batch. The synthesis was achieved by precipitation of ACC from a strongly alkaline solution of calcium chloride (CaCl2) at ambient temperature using the hydrolysis

K. Gorna; M. Hund; M. Vu?ak; F. Gröhn; G. Wegner

2008-01-01

342

Oral calcium carbonate administration ameliorates the progression of renal failure in rats with hypertension  

Microsoft Academic Search

Oral calcium supplementation is reported to have phosphate-binding and antihypertensive effects. Since both phosphate binders and antihypertensive agents are reported to attenuate renal injury, we studied the effect of oral calcium carbonate (CaCO3) administration on the course of renal deterioration using doxorubicin-induced renal failure in rats treated with deoxycorticosterone acetate and salt for 10 weeks. Rats were divided into four

Makoto Nakamura; Hiromichi Suzuki; Yoichi Ohno; Akira Ohishi; Hiroshi Yamakawa; Hirokazu Okada; Takao Saruta

1995-01-01

343

Synthesis of novel amorphous calcium carbonate by sono atomization for reactive mixing.  

PubMed

Droplets of several micrometers in size can be formed in aqueous solution by atomization under ultrasonic irradiation at 2 MHz. This phenomenon, known as atomization, is capable of forming fine droplets for use as a reaction field. This synthetic method is called SARM (sono atomization for reactive mixing). This paper reports on the synthesis of a novel amorphous calcium carbonate formed by SARM. The amorphous calcium carbonate, obtained at a solution concentration of 0.8 mol/dm(3), had a specific surface area of 65 m(2)/g and a composition of CaCO(3)•0.5H(2)O as determined using thermogravimetric/differential thermal analysis (TG-DTA). Because the ACC had a lower hydrate composition than conventional amorphous calcium carbonate (ACC), the ACC synthesized in this paper was very stable at room temperature. PMID:21788149

Kojima, Yoshiyuki; Kanai, Makoto; Nishimiya, Nobuyuki

2011-05-08

344

Reactive oxygen species mediated calcium oxalate crystal-induced expression of MCP-1 in HK-2 cells  

Microsoft Academic Search

Under severe hyperoxaluric conditions calcium oxalate crystals often deposit in the renal interstitium and produce localized\\u000a inflammation. We have proposed that renal epithelial cells exposed to CaOx crystals produce chemoattractants such as monocyte\\u000a chemoattractant protein-1 (MCP-1). MCP-1 synthesis is mediated by reactive oxygen species (ROS). HK-2 cells of human renal\\u000a epithelial line were exposed to CaOx crystals for different lengths

Pouran Habibzadegah-Tari; Karen G. Byer; Saeed R. Khan

2006-01-01

345

Polymer crystallization-driven, periodical patterning on carbon nanotubes  

NASA Astrophysics Data System (ADS)

We report herein a unique means to periodically pattern polymers on carbon nanotubes (CNTs) using controlled polymer crystallization method. CNTs were periodically decorated with polymer lamellar crystals, resulting in nano hybrid shish-kebab (NHSK) structures. The periodicity of adjacent kebabs varies from 20 - 150 nm. The kebabs are approximately 5 nm thick (along CNT direction) with a lateral size of ˜ 20 nm to micrometers, which can be readily controlled by varying crystallization conditions. Both polyethylene and Nylon 66 were successfully decorated on single-walled carbon nanotubes (SWNT), multi-walled carbon nanotubes (MWNT), as well as vapor grown carbon nanofibers (CNF). The formation mechanism was attributed to ``size dependent soft epitaxy''. NHSK structure was discussed with an emphasis on the periodicity of adjacent kebabs. The influence of experimental parameters on the periodicity was investigated in details Since NHSK formation conditions depend upon CNT structures, it further provides a unique opportunity for CNT separation. The reported method opens a gateway to periodically patterning polymers and different functional groups on individual CNTs in an ordered and controlled manner, an attractive research field that is yet to be explored.

Li, Lingyu; Li, Christopher

2006-03-01

346

A novel calcium oxalate crystal growth inhibitory protein from the seeds of Dolichos biflorus (L.).  

PubMed

Recurrence and persistent side effects of present day treatment for urolithiasis restrict their use, so an alternate, using phytotherapy is being sought. Dolichos biflorus seeds, which are used as dietary food in India, possess antilithiatic properties. In the present study, a novel dimeric antilithiatic protein (98 kDa) from its seeds was purified based on its ability to inhibit calcium oxalate crystallization in vitro. Amino acid analysis of Dolichos biflorus antilithiatic protein showed abundant acidic amino acids. The mascot search engine presented sequence similarity with a calcium binding protein, calnexin of Pisum sativum from the m/z data obtained by MALDI TOF mass spectrometer. Above results demonstrate the anticalcifying/antilithiatic nature of a novel protein from the seeds of Dolichos biflorus and thus open new vistas for using plant proteins as therapeutic agents to treat urolithiasis. PMID:19488841

Bijarnia, Rakesh K; Kaur, Tanzeer; Singla, Surinder K; Tandon, Chanderdeep

2009-05-01

347

Effect of oral calcitriol pulse therapy on the lipid, calcium, and glucose homeostasis of hemodialysis-patients: Its safety in a combination with oral calcium carbonate  

Microsoft Academic Search

Objective: To more clearly elucidate the conflicting results that have been obtained after oral calcitriol pulse therapy on lipid, glucose, and calcium levels in hemodialysis (HD) patients, and to determine safety of oral calcitriol pulse therapy in a combination with calcium carbonate. Design: A randomized, crossover, placebo-controlled study. Setting: HD centers in 3 teaching university hospitals. Patients: Forty-eight chronic HD

Parviz Khajehdehi

2003-01-01

348

Selective crystallization of calcium salts by poly(acrylate)-grafted chitosan.  

PubMed

The biopolymer chitosan was chemically modified by grafting polyacrylamide or polyacrylic acid in a homogeneous aqueous phase using potassium persulfate (KPS) as redox initiator system in the presence of N,N-methylene-bis-acrylamide as a crosslinking agent. The influence of the grafted chitosan on calcium salts crystallization in vitro was studied using the sitting-drop method. By using polyacrylamide grafted chitosan as substrate, rosette-like CaSO4 crystals were observed. This was originated by the presence of sulfate coming from the initiator KPS. By comparing crystallization on pure chitosan and on grafted chitosan, a dramatic influence of the grafted polymer on the crystalline habit of both salts was observed. Substrates prepared by combining sulfate with chitosan or sulfate with polyacrylamide did not produce similar CaSO4 morphologies. Moreover, small spheres or donut-shaped CaCO3 crystals on polyacrylic acid grafted chitosan were generated. The particular morphology of CaCO3 crystals depends also on other synthetic parameters such as the molecular weight of the chitosan sample and the KPS concentration. PMID:15848410

Neira-Carrillo, Andrónico; Yazdani-Pedram, Mehrdad; Retuert, Jaime; Diaz-Dosque, Mario; Gallois, Sebastien; Arias, José L

2005-06-01

349

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

SciTech Connect

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 promote or discourage contaminant reaction with sediment mineral particles, and whether calcium carbonate phases resulting from waste-sediment reaction sequester contaminants through coprecipitation. The research will provide new conceptual models of contaminant reaction/retardation processes in Hanford sediments (for 90Sr2+ and Cr(VI)O4 2- primarily) and improved geochemical models to forecast the future behavior of in-ground contaminants.

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

2002-06-01

350

Carboxylated molecules regulate magnesium content of amorphous calcium carbonates during calcification  

PubMed Central

With the realization that many calcified skeletons form by processes involving a precursor phase of amorphous calcium carbonate (ACC), a new paradigm for mineralization is emerging. There is evidence the Mg content in biogenic ACC is regulated by carboxylated (acidic) proteins and other macromolecules, but the physical basis for such a process is unknown. We test the hypothesis that ACC compositions express a systematic relationship to the chemistry of carboxyl-rich biomolecules. A series of inorganic control experiments were conducted to establish the dependence of Mg/Ca ratios in ACC on solution composition. We then determined the influence of a suite of simple carboxylated organic acids on Mg content. Molecules with a strong affinity for binding Ca compared with Mg promote the formation of Mg-enriched ACC that is compositionally equivalent to high-magnesium calcites and dolomite. Measurements show Mg/Ca ratios are controlled by a predictable dependence upon the binding properties of the organic molecules. The trend appears rooted in the conformation and electrostatic potential topology of each molecule, but dynamic factors also may be involved. The dependence suggests a physical basis for reports that specific sequences of calcifying proteins are critical to modulating mineralization. Insights from this study may provide a plausible explanation for why some biogenic carbonates and carbonaceous cements often contain higher Mg signatures than those that are possible by classical crystal growth processes. The findings reiterate the controls of microenvironment on mineralization and suggest an origin of compositional offsets, or vital effects, long recognized by the paleoclimate community.

Wang, Dongbo; Wallace, Adam F.; De Yoreo, James J.; Dove, Patricia M.

2009-01-01

351

Carboxylated molecules regulate magnesium content of amorphous calcium carbonates during calcification.  

PubMed

With the realization that many calcified skeletons form by processes involving a precursor phase of amorphous calcium carbonate (ACC), a new paradigm for mineralization is emerging. There is evidence the Mg content in biogenic ACC is regulated by carboxylated (acidic) proteins and other macromolecules, but the physical basis for such a process is unknown. We test the hypothesis that ACC compositions express a systematic relationship to the chemistry of carboxyl-rich biomolecules. A series of inorganic control experiments were conducted to establish the dependence of Mg/Ca ratios in ACC on solution composition. We then determined the influence of a suite of simple carboxylated organic acids on Mg content. Molecules with a strong affinity for binding Ca compared with Mg promote the formation of Mg-enriched ACC that is compositionally equivalent to high-magnesium calcites and dolomite. Measurements show Mg/Ca ratios are controlled by a predictable dependence upon the binding properties of the organic molecules. The trend appears rooted in the conformation and electrostatic potential topology of each molecule, but dynamic factors also may be involved. The dependence suggests a physical basis for reports that specific sequences of calcifying proteins are critical to modulating mineralization. Insights from this study may provide a plausible explanation for why some biogenic carbonates and carbonaceous cements often contain higher Mg signatures than those that are possible by classical crystal growth processes. The findings reiterate the controls of microenvironment on mineralization and suggest an origin of compositional offsets, or vital effects, long recognized by the paleoclimate community. PMID:19955417

Wang, Dongbo; Wallace, Adam F; De Yoreo, James J; Dove, Patricia M

2009-12-02

352

Specific nephrotoxicity and cardiotoxicity of BT-CAL®, Sigma Anti-bonding Molecule Calcium Carbonate, in mice.  

PubMed

According to a high anti-osteoporotic efficacy of Sigma Anti-bonding Molecule Calcium Carbonate (SAC), repeated-dose toxicities of SAC were investigated to assess its feasibility as drug or functional food ingredient. Male ICR mice were given drinking water containing 0.006, 0.02 or 0.06% SAC for 4 weeks. SAC feeding decreased the body weights and feed and water consumptions of mice in a dose-dependent manner, especially, leading to severe emaciation and 70% death in 3 weeks in the high-dose (0.06%) group. Not only kidney and heart weights, but also the levels of blood urea nitrogen, creatinine, aspartate transaminase, and creatine phospokinase significantly increased after SAC administration, indicative of nephrotoxicity and cardiotoxicity. Such renal and cardiac toxicities were also confirmed by microscopic findings, exhibiting renal crystals and cardiac fibrosis, which may be due to the insoluble crystal formation and calcium overload, respectively. In conclusion, it is suggested that no observed adverse effect level of SAC is lower than 0.006% in mice, and that a long-term intake may cause serious adverse effects on renal and cardiac functions. PMID:23573102

Jang, Ja-Young; Cai, Jingmei; Kim, Jihyun; Kyung, Jangbeen; Kim, Dajeong; Choi, Ehn-Kyoung; Kim, Youngeun; Kim, Kwang-Sei; Park, Dongsun; Kang, Hyun-Gu; Kim, Yun-Bae

2013-03-25

353

Imaging joints for calcium pyrophosphate crystal deposition: a knock to the knees.  

PubMed

ABSTRACT: With advanced age, articular calcium pyrophosphate crystal deposition (CPPD) is common. Defining who has CPPD is of growing importance, given increases in longevity in many countries and the frequent association of chondrocalcinosis with osteoarthritis. Chondrocalcinosis detected by plain radiography serves as a major screening tool, but how many and which sites to screen have not been adequately defined in the past. The work of Abhishek and colleagues in the previous issue of Arthritis Research and Therapy sheds new light on the incomplete information from knee radiographs, and helps position us to learn more about the epidemiology, pathophysiology, diagnosis, and clinical impact of CPPD. PMID:23270654

Terkeltaub, Robert

2012-12-27

354

Synovial chondromatosis of the temporomandibular joint with calcium pyrophosphate dihydrate crystal deposition disease (pseudogout).  

PubMed

This report describes a very rare case of synovial chondromatosis with deposition of calcium pyrophosphate dihydrate (CPPD) crystals (pseudogout) in the temporomandibular joint (TMJ) of a 46-year-old male patient. Synovial chondromatosis is a non-neoplastic disease characterized by metaplasia of the connective tissue leading to chondrogenesis in the synovial membrane. Pseudogout is an inflammatory disease of the joints caused by the deposition of CPPD, producing similar symptoms to those observed in gout but not hyperuricaemia. Both diseases commonly affect the knee, hip and elbow joints, but rarely affect the TMJ. PMID:23166363

Matsumura, Y; Nomura, J; Nakanishi, K; Yanase, S; Kato, H; Tagawa, T

2012-12-01

355

Imaging joints for calcium pyrophosphate crystal deposition: a knock to the knees  

PubMed Central

With advanced age, articular calcium pyrophosphate crystal deposition (CPPD) is common. Defining who has CPPD is of growing importance, given increases in longevity in many countries and the frequent association of chondrocalcinosis with osteoarthritis. Chondrocalcinosis detected by plain radiography serves as a major screening tool, but how many and which sites to screen have not been adequately defined in the past. The work of Abhishek and colleagues in the previous issue of Arthritis Research and Therapy sheds new light on the incomplete information from knee radiographs, and helps position us to learn more about the epidemiology, pathophysiology, diagnosis, and clinical impact of CPPD.

2012-01-01

356

Estimating environmental conditions of carbonate crystal fan formation  

NASA Astrophysics Data System (ADS)

The sedimentary record reveals that the large-scale aspects of carbonate deposition have remained unchanged over > 3.4 Ga of Earth History. This reflects long term commonalities in the sources of DIC and alkalinity to seawater and the processes that generate and fill accommodation in sedimentary basins. Despite this stability, the record also reveals important first order changes in the nature of carbonate precipitation through time; this is documented in the decreasing abundance of sea floor carbonate precipitation. For example, carbonate crystal fans (large bladed crystals formed at the sediment-water interface, thought to be originally composed of aragonite) have a distinct distribution in time. They are common on Archean and Paleoproterozoic carbonate platforms and become rare by Neoproterozoic time, only reappearing during several unusual intervals (e.g. P-T mass extinction) in Phanerozoic basins. This has been interpreted as evidence for a decline in carbonate saturation through time. This pattern of distribution presents a fundamental problem. Despite being bathed in waters that are strongly supersaturated, direct precipitation of carbonate-bearing minerals on the sea floor is exceedingly rare in modern shallow tropical ocean basins. In order to examine this problem we examined processes controlling both the chemistry and physics of the sediment-water interface that could promote precipitation. Using a mathematical model to depict the influence of organic delivery and different microbial respiratory metabolisms on the carbonate chemistry within the shallow sediments, two non-unique chemical conditions emerge that indicate precipitation can be thermodynamically favorable on the seafloor from seawater with similar chemistry to today’s oceans. In agreement with modern porewater data, our results suggest that an important component inhibiting seafloor cementation is aerobic respiration in the shallow sediments. In addition to the chemical conditions of the interface, physical processes including high sedimentation rate, burrowing and seafloor agitation have the possibility of disrupting precipitation. We test hypotheses arising from our model results using geological observations of successions bearing crystal fans from the middle Ediacaran Rainstorm Member of the Johnnie Formation, Basin and Range, USA, and the Late Paleoproterozoic Rifle Formation, NW Territories Canada. By examining the accessory sediments associated with the cements from two specific examples from the record, quiescent periods with low background sedimentation rates emerge as important catalysts for growth. The accessory sediments associated with both examples are distinct from the surrounding sediments suggesting favorable conditions were not ever-present. Our analysis also shows that it is unlikely that all crystal fans result from a unique set of circumstances, rather there are several possible geobiological mechanisms that led to their deposition.

Bergmann, K. D.; Fischer, W. W.

2010-12-01

357

Studies on the Influence of Foreign Ions on the Calcium Carbonate Precipitation under Conditions of Water Heating. Final Report.  

National Technical Information Service (NTIS)

Measuring was necessary to determine the hitherto inadequately known solubility product of calcium carbonate in the temperature range between 10C and 80C in the presence of foreign ions; this was done to make exact predictions about the calcium carbonate ...

G. Hoelzel

1988-01-01

358

Evaluation of the attachment, proliferation, and differentiation of osteoblast on a calcium carbonate coating on titanium surface  

Microsoft Academic Search

Titanium has been reported to have some limitations in dental and orthopaedic clinical application. This study described a coating process using a simple chemical method to prepare calcium carbonate coatings on smooth titanium (STi) and sandblasted and acid-etched titanium (SATi), and evaluated the biological response of the materials in vitro. The surfaces of STi, SATi, calcium carbonate coated STi (CC-STi)

Yi Liu; Tao Jiang; Yi Zhou; Zhen Zhang; Zhejun Wang; Hua Tong; Xinyu Shen; Yining Wang

2011-01-01

359

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

National Technical Information Service (NTIS)

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. Ca...

J. Lytle K. Hackley M. Dagamac R. Berger G. Schanche

1993-01-01

360

How can calcium pyrophosphate crystals induce inflammation in hypophosphatasia or chronic inflammatory joint diseases?  

PubMed

Hypophosphatasia (HP) is a rare inborn error of bone and mineral metabolism characterized by a defect in the tissue non-specific alkaline phosphatase (TNSALP) gene. Calcium pyrophosphate dihydrate (CPPD) crystals are known to accumulate as substrates of TNSALP in tissues and joints of patients with HP. In CPPD-induced arthritis these crystals are known to induce an inflammatory response. HP patients do suffer from pain in their lower extremities. However, it is not clear whether CPPD crystals contribute to these musculoskeletal complaints in HP. As long as there is no curative treatment of HP, symptomatic treatment in order to improve clinical features, especially with regard to pain and physical activity, is of major interest to the patients. Knowledge of the mechanisms underlying crystal-induced cell activation, however, is limited. Here we describe recent advances in elucidating the signal transduction pathways activated by CPPD crystals as endogenous "danger signals". Recent investigations provided evidence that Toll/interleukin-1 receptor (TIR) domain containing receptors including Toll-like receptors (TLRs) and interleukin-1 receptor (IL-1R), as well as the triggering receptor expressed on myeloid cells 1 (TREM-1) and the NACHT-leucin rich repeat and pyrin-domain-containing protein (NALP3) containing inflammasome are essentially involved in acute CPPD crystal-induced inflammation. These receptors are considered in part as components of the innate immune system. Further studies are needed to improve our understanding of the pathophysiological mechanisms leading to inflammation and tissue destruction associated with deposition of microcrystals. They might support the development of new therapeutic strategies for crystal-induced inflammation. Eventually, patients with HP might as well profit from such strategies addressing these metabolic disorders secondary to the gene defect. PMID:18821074

Beck, C; Morbach, H; Richl, P; Stenzel, M; Girschick, H J

2008-09-28

361

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

SciTech Connect

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.

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

2001-06-01

362

Calcium Hydroxide and Calcium Carbonate Particle Size Effects on Reactivity with Sulfur Dioxide.  

National Technical Information Service (NTIS)

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. Sign...

B. K. Gullett J. A. Blom

1987-01-01

363

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...

364

Characteristics of gypsum crystal growth over calcium-based slurry in desulfurization reactions  

SciTech Connect

A wet absorption of sulfur dioxide in a batch-type reactor was carried out, using three calcium compounds, namely, CaCO{sub 3}, CaO, and Ca(OH){sub 2} as absorbents. Based on Fourier Transform Infrared, X-ray diffraction, and scanning electron microscopy analyses, the different absorbents resulted in the different reaction pathways and mechanisms of crystal formation at the early reaction stage. In particular, the CaSO{sub 3} {center_dot} {1/2}H{sub 2}O produced from CaO and Ca(OH){sub 2} showed spherical aggregates consisting of small subparticles, rather than plate or needle-like crystals, of CaSO{sub 4} {center_dot} 2H{sub 2}O from CaCO{sub 3}. This might be due to the different solubility of the absorbents in water.

Chu, K.J.; Yoo, K.S.; Kim, K.T. [Research Inst. of Industrial Science and Technology, Pohang (Korea, Republic of)

1997-02-01

365

Factors affecting ex-situ aqueous mineral carbonation using calcium and magnesium silicate minerals  

SciTech Connect

Carbonation of magnesium- and calcium-silicate minerals to form their respective carbonates is one method to sequester carbon dioxide. Process development studies have identified reactor design as a key component affecting both the capital and operating costs of ex-situ mineral sequestration. Results from mineral carbonation studies conducted in a batch autoclave were utilized to design and construct a unique continuous pipe reactor with 100% recycle (flow-loop reactor). Results from the flow-loop reactor are consistent with batch autoclave tests, and are being used to derive engineering data necessary to design a bench-scale continuous pipeline reactor.

Gerdemann, Stephen J.; Dahlin, David C.; O'Connor, William K.; Penner, Larry R.; Rush, G.E.

2004-01-01

366

Characterization of carbon nanotube thermotropic nematic liquid crystal composites  

NASA Astrophysics Data System (ADS)

Dispersions of carbon nanotubes (CNTs) in liquid crystals (LCs) have attracted attention due to their unique properties and possible applications in photonics and electronics. However, these are hard to stabilize, and the loading level in the equilibrium state in LC hosts is small. A practical way to monitor the quality and CNT incorporation in such equilibrium dispersions is required. Here, we compare different methods for characterising equilibrium CNT-LC composite materials.

Trushkevych, O.; Collings, N.; Hasan, T.; Scardaci, V.; Ferrari, A. C.; Wilkinson, T. D.; Crossland, W. A.; Milne, W. I.; Geng, J.; Johnson, B. F. G.; Macaulay, S.

2008-06-01

367

Influence of sodium dodecyl sulfate and static magnetic field on the properties of freshly precipitated calcium carbonate.  

PubMed

Properties of calcium carbonate precipitated from aqueous solutions of CaCl(2) and Na(2)CO(3) in the presence of sodium dodecyl sulfate (SDS) and S-S 0.1 T magnetic field (MF) were studied. The nucleation and precipitation processes of CaCO(3) were investigated by pH and zeta potential measurements at 20 +/- 1 degrees C up to 2 h after mixing the solutions. Also the amounts of calcium carbonate deposited on the glass surfaces and its structure were examined. It was found that SDS influences the kinetics of precipitation, crystallographic forms, and crystal size of CaCO(3). The SDS effects are more pronounced in MF presence. A small amount of SDS accelerates transformation of vaterite into calcite, whereas increasing surfactant concentration moderates such a transformation. On the other hand, in all the systems, MF in the presence of SDS causes a slower transformation of vaterite into calcite. These effects are reflected in pH and zeta potential changes, although there is no clear dependence between the SDS amount present during the precipitation and changes of the parameters investigated. It seems that MF effect is most significant at a defined optimal SDS concentration. The results, however, do not allow suggestion of any detailed mechanism of the field interaction. PMID:16114911

Chibowski, Emil; Szczes, Aleksandra; Holysz, Lucyna

2005-08-30

368

Effect of a new functional double-hydrophilic block copolymer PAAL on the morphology of calcium carbonate particles  

SciTech Connect

Calcium carbonate (CaCO{sub 3}) particles with various shapes were prepared by the reaction of sodium carbonate with calcium chloride in the presence of a new functional double-hydrophilic block copolymer poly (acrylic acid)-block-(acrylic hydroxy lactide) (PAAL) at room temperature. The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. The effects of pH, concentration of PAAL and CaCO{sub 3} on the crystal form and morphologies of the as-prepared CaCO{sub 3} were investigated. The results show that pH, concentration of PAAL and CaCO{sub 3} are important parameters for the control of morphologies of CaCO{sub 3}. Depending on the experimental conditions, various morphologies of CaCO{sub 3}, such as plate-like aggregates, poly-nucleated spheres, ellipsoids, monodispersed spheres, rhombohedras, etc., can be obtained. Especially, the optimal experimental conditions for the production of monodispersed spherical CaCO{sub 3} particles were determined.

Lei, M. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China)]. E-mail: leiming@aphy.iphy.ac.cn; Tang, W.H. [Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chinese Academy of Sciences, Beijing 100080 (China); Yu, J.G. [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

2005-04-20

369

Modulation of calcium oxalate monohydrate crystallization by citrate through selective binding to atomic steps  

SciTech Connect

The majority of human kidney stones are composed primarily of calcium oxalate monohydrate (COM) crystals. Thus, determining the molecular mechanisms by which urinary constituents modulate calcium oxalate crystallization is crucial for understanding and controlling urolithiassis in humans. A comprehensive molecular-scale view of COM shape modification by citrate, a common urinary constituent, obtained through a combination of in situ atomic force microscopy (AFM) and molecular modeling is now presented. We show that citrate strongly influences the growth morphology and kinetics on the (-101) face but has much lower effect on the (010) face. Moreover, binding energy calculations show that the strength of the citrate-COM interaction is much greater at steps than on terraces and is highly step-specific. The maximum binding energy, -166.5 kJ {center_dot} mol{sup -1}, occurs for the [101] step on the (-101) face. In contrast, the value is only -56.9 kJ {center_dot} mol-1 for the [012] step on the (010) face. The binding energies on the (-101) and (010) terraces are also much smaller, -65.4 and -48.9 kJ {center_dot} mol{sup -1} respectively. All other binding energies lie between these extremes. This high selectivity leads to preferential binding of citrate to the acute [101] atomic steps on the (-101) face. The strong citrate-step interactions on this face leads to pinning of all steps, but the anisotropy in interaction strength results in anisotropic reductions in step kinetics. These anisotropic changes in step kinetics are, in turn, responsible for changes in the shape of macroscopic COM crystals. Thus, the molecular scale growth morphology and the bulk crystal habit in the presence of citrate are similar, and the predictions of molecular simulations are fully consistent with the experimental observations.

Qiu, S R; Wierzbicki, A; Salter, E A; Zepeda, S; Orme, C A; Hoyer, J R; Nancollas, G H; Cody, A M; De Yoreo, J J

2004-10-19

370

Influence of surface modifiers on the structure of precipitated calcium carbonate  

SciTech Connect

A calcium carbonate (CaCO{sub 3}) sorbent synthesized in the presence of surface modifiers has recently been developed in this laboratory for the purpose of enhancing the reactivity toward SO{sub 2} at high temperatures (800--1150 C). The calcium carbonate particles are produced by precipitation from an aqueous suspension of calcium hydroxide by bubbling pure CO{sub 2}. The operating parameters such as suspension concentration, gas flow rate, and concentration of surface modifiers are varied to study their influence on the particle size, surface area, and pore volume. The synthesized CaCO{sub 3} particles exhibit dramatically high SO{sub 2} reactivity and sorbent utilization. The increased reactivity is primarily due to the development of an open initial pore structure of the sorbent brought about by the action of surface-active agents, compared to the conventional calcium-based sorbents. {zeta}-potential measurements indicate that addition and subsequent adsorption of anionic surfactants neutralize the high positive surface charge (30 mV) on the precipitated calcium carbonate and facilitate particle agglomeration and pore structure development. High surface area (>55 m{sup 2}/g) and pore volume (>0.175 cm{sup 3}/g) are obtained for particles with neutral or near-neutral surface changes.

Agnihotri, R.; Mahuli, S.K.; Chauk, S.S.; Fan, L.S. [Ohio State Univ., Columbus, OH (United States). Dept. of Chemical Engineering

1999-06-01

371

Kinetic peculiarities of diamond crystallization in K-Na-Mg-Ca-Carbonate-Carbon melt-solution  

NASA Astrophysics Data System (ADS)

The kinetic peculiarities of diamond crystallization in multicomponent K-Na-Mg-Ca-carbonate-carbon system have been studied in conditions of diamond stability at 1500-1800°C and 7.5-8.5 GPa. It has been established that the diamond phase nucleation density at a fixed temperature of 1600°C decreases from 1.3 × 105 nuclei/mm3 at 8.5 GPa to 3.7 × 103 nuclei/mm3 at 7.5 GPa. The fluorescence spectra of obtained diamond crystals contain peaks at 504 nm ( H3-defect), 575 nm (NV-center), and 638 nm (NV-defect), caused by the presence of nitrogen impurity. In the cathodoluminescence spectra, an A-band with the maximum at 470 nm is present. The obtained data make it possible to assign the synthesized diamonds in the carbonate-carbon system to the mixed Ia + Ib type.

Solopova, N. A.; Spivak, A. V.; Litvin, Yu. A.; Shiryaev, A. A.; Tsel'movich, V. A.; Nekrasov, A. N.

2013-02-01

372

Carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate  

Microsoft Academic Search

The carbothermic reduction of zinc sulfide in the presence of calcium oxide and lithium carbonate was studied using a thermogravimetric\\u000a analysis system (TGA), an X-ray diffractometer (XRD), an atomic absorption spectrometer (AAS), a carbon and sulfur determinator\\u000a (CSD), an elemental analyzer (EA), a scanning electron microscope (SEM) and a surface area analyzer (SAA). Experimental results\\u000a revealed that the reaction rate

Y. C. Peng; C. I. Lin; H. K. Chen

2007-01-01

373

Is CO 2 evolution in saline soils affected by an osmotic effect and calcium carbonate?  

Microsoft Academic Search

Salt-affected soils are widespread, particularly in arid climates, but information on nutrient dynamics and carbon dioxide\\u000a (CO2) efflux from salt-affected soils is scarce. Four laboratory incubation experiments were conducted with three soils. To determine\\u000a the influence of calcium carbonate (CaCO3) on respiration in saline and non-saline soils, a loamy sand (6.3% clay) was left unamended or amended with NaCl to

Raj Setia; Petra Marschner; Jeff Baldock; David Chittleborough

2010-01-01

374

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

Microsoft Academic Search

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

David E. Archer

1996-01-01

375

Textural properties of synthetic nano-calcite produced by hydrothermal carbonation of calcium hydroxide  

Microsoft Academic Search

The hydrothermal carbonation of calcium hydroxide (Ca(OH)2) at high pressure of CO2 (initial PCO2=55bar) and moderate to high temperature (30 and 90°C) was used to synthesize fine particles of calcite. This method allows a high carbonation efficiency (about 95% of Ca(OH)2–CaCO3 conversion), a significant production rate (48kg\\/m3h) and high purity of product (about 96%). However, the various initial physicochemical conditions

G. Montes-Hernandez; A. Fernández-Martínez; L. Charlet; Delphine Tisserand; F. Renard

2008-01-01

376

Crystal modification of calcium sulfate dihydrate in the presence of some surface-active agents.  

PubMed

The effect of surface-active agents (surfactants), as additives, on the crystallization of gypsum was studied under conditions of the simulated dihydrate process of phosphoric acid production. Calcium hydrogen phosphate and sulfuric acid were mixed with dilute phosphoric acid at 80 degrees C, and the turbidity of the reaction mixture was measured at different time periods to determine the induction time of gypsum crystal formation. Two types of surfactants, namely, cetyltrimethylammonium bromide (CTAB) as a cationic surfactant and sodium dodecyl sulfate (SDS) as an anionic surfactant were added to investigate their effects on the crystallization of gypsum. Addition of CTAB decreased the induction time and increased the growth efficiency, while addition of SDS increased the induction time and decreased the growth efficiency compared with the baseline (without additives). The surface energy increased with CTAB and decreased with SDS compared with the baseline. The percentage of fine crystals decreased in the presence of CTAB and increased in the presence of SDS compared with the baseline. Gypsum morphology changed from needle-like in the absence of additives to tabular in the presence of CTAB. PMID:14693140

Mahmoud, M H H; Rashad, M M; Ibrahim, I A; Abdel-Aal, E A

2004-02-01

377

Dielectric loss relaxation maxima of undoped and calcium doped NaCl crystals between 20 and 400°C  

Microsoft Academic Search

When studying the dielectric loss dependence of undoped (“pure”) and CaCl2 doped NaCl crystals on temperature and frequency, some further maxima were observed apart from the wellknown relaxation maxima of calcium complexes. The temperature of these maxima shifts with rising calcium content to lower temperatures (from 259 to 142°C), whereas the value of the maxima does not change with concentration

A. Kessler; E. Mariani

1964-01-01

378

Free-standing nanogold membranes as supports for the growth of calcium phosphate crystals.  

PubMed

Current strategies for bone tissue regeneration focus on the development of implantable matrices that mimic biological tissues. Inorganic composites are of special interest for bone substitute applications. It is necessary to create an artificial three-dimensional scaffold-like porous material with certain geometrical structure to induce bone growth. We report here the growth of calcium phosphate crystals on free-standing carboxylic acid functionalized gold nanoparticle membranes. The gold nanoparticle membrane is synthesized by the spontaneous reduction of aqueous chloroaurate ions by a diamine molecule at a liquid-liquid interface. This membrane is robust and malleable, and most importantly, the gold nanoparticles in the membrane may be functionalized with suitable ligands. In this study, the amino acids aspartic acid and cysteine together with an aromatic bifunctional molecule, anthranilic acid, were used to modify the surface of the gold nanoparticles in the membrane. The free carboxylic acid groups on the gold nanoparticles further to functionalization with these molecules were then used to bind Ca(2+) ions and reacted with phosphate ions to yield calcium phosphate. The nature of the nanogold surface modifier directed the formation of either crystalline hydroxyapatite or amorphous calcium phosphate. The nanogold membrane thus suggests potential biomedical application as biocompatible implants and grafts. PMID:16321063

Rautaray, Debabrata; Sastry, Murali

379

[Chemical structure of dicarboxylic acids and their capacity inhibiting of calcium oxalate crystal growth].  

PubMed

The effect of dicarboxylic acids with a three C-C bonds distance on the crystallization of calcium oxalate (CaOxa) was investigated in silica gel system by means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). These acids include succinic acid, maleic acid, fumaric acid, malic acid, L-aspartic acid and tartaric acid. All the dicarboxylic acids can inhibit the aggregation of calcium oxalate monohydrate (COM) and induce the formation of calcium oxalate dehydrate (COD). But their ability to inhibit the growth and aggregation of COM, to diminish the specific surface area of COM and to induce COD formation were strengthened as the number of the substituted hydroxyl or amino group increased. The molecular mechanisms were discussed in terms of chemical structures of dicarboxylic acids. Only the dicarboxylic acids with a HOOC-CH(R)-CH2-COOH (R=OH or NH2) group were found to have the best inhibitory effect on the CaOxa urinary stones. The results could provide some clue to looking for new drugs for urinary stones in clinic. PMID:18306777

Deng, Sui-ping; Hu, Peng; Ouyang, Jian-ming

2007-10-01

380

Urease-induced crystallizations of calcium phosphate and magnesium ammonium phosphate in synthetic urine and human urine.  

PubMed

An aggregometer technique was used to study urease-induced crystallizations in synthetic urine and human urine from healthy subjects and patients with chronic spinal cord injuries. The two different phases of crystallization, calcium phosphate and magnesium ammonium phosphate, were easily evaluated with a single assay using this technique. The crystallization of calcium phosphate and magnesium ammonium phosphate varied markedly among the different urine specimens after incubation with urease. The turbidity curves from human urine were divided into four patterns. We assumed that the variations in the patterns of the turbidity curves appeared to be mainly due to differences in the composition of the urine and in the original pH, and that the calcium and magnesium concentrations were very important in the urinary constituents. PMID:9286035

Ebisuno, S; Komura, T; Yamagiwa, K; Ohkawa, T

1997-01-01

381

Investigation of self-frequency doubling crystals, yttrium calcium oxyborate (YCOB), doped with neodymium or ytterbium  

NASA Astrophysics Data System (ADS)

There is a need for low cost red, green, and blue (RGB) lasers for a number of commercial applications such as high-resolution laser printing, full color laser display. While semiconductor lasers still have both availability (green and blue) and beam quality (red) problems, nonlinear frequency conversion of diode-pumped solid state lasers are good alternatives. Among them, self- frequency doubling is an attractive approach because of its simpler design and lower cost. Unfortunately, few known crystals possess self-frequency doubling property. A newly discovered yttrium calcium oxyborate (YCOB) can fill in the role because it has adequate lasing and nonlinear frequency conversion efficiency. More importantly, YCOB crystal melts congruently so that high quality, large size single crystals can be grown using conventional Czochralski melt pulling technique. The thermal mechanical properties, linear and nonlinear optical properties of YCOB, laser properties of Nd:YCOB and Yb:YCOB crystals were investigated. Based on the calculated second harmonic phase matching angles, Nd:YCOB laser rods were fabricated. Self-frequency doubled green emission with 62 mW output power and red emission with 16 mW output power were successfully demonstrated using diode-pumping. It is the first time to achieve the continuous wave (cw) red lasing in Nd doped rare-earth calcium oxyborates. Rare-earth ions doping in YCOB crystal can not only achieve lasing, but also affect the physical and chemical properties of the crystal. The stability field of YCOB is reduced in proportion to both the ionic size differences from yttrium and doping concentrations of the rare-earth ions. The doping also changes the linear and nonlinear optical properties of the material. For example, the second harmonic conversion efficiency of 20% Yb doped YCOB was enhanced by more than 15% compared to undoped YCOB. The absorption cutoff edge of 20% Yb:YCOB was red- shift by more than 60 nm. Similar effects were observed in Ce, or Pr, or Eu doped YCOB crystals. It is proposed that the rare-earth ions with variable oxidation states can serve as either donor or acceptor to the conjugated ?-orbits formed by the (BO3)3- planar groups in the YCOB structure to increase the delocalization of electron clouds, and thus increase the nonlinearity and result in the red-shift of the energy band-gap. In summary, the YCOB is the first nonhygroscopic nonlinear crystal with high damage threshold that can provide both large aperture and long nonlinear conversion length for high power laser applications. The Nd:YCOB shows promising features as a diode-pumped self-frequency doubling laser material to generate efficient, compact, low cost cw red and green emissions. Investigation of the whole rare-earth calcium oxyborate family compounds is just at the early stage. It is expected that these crystals would have a great impact on nonlinear optical device market in the very near future.

Ye, Qing

1999-09-01

382

Coprecipitation of phosphate with calcium carbonate in Lake Veluwe  

Microsoft Academic Search

Coprecipitation of dissolved phosphate with calcite (CaCO3) has been observed in many lakes. In 1979\\/1980 white flocks occurred in Lake Veluwe after the inlet of water with a high calcium content. A high oversaturation with respect to calcite occurred at that time, presently (1985–1987) the oversaturation is much smaller. The intense photosynthesis decreased and maximum summer pH values came down

Heleen J. Danen-Louwerse; Lambertus Lijklema; Monique Coenraats

1995-01-01

383

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

SciTech Connect

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.

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

1996-11-01

384

Isotactic polypropylene carbon nanotube composites -- crystallization and ordering behavior  

NASA Astrophysics Data System (ADS)

The field of Polymer Nanocomposites (PNCs) is growing steadily in recent years. We use carbon nanotubes (CNTs) to affect the crystallization behavior of the polymers. Isotactic Polypropylene (iPP) is very widely used and is a good model system to understand the physics of other similar polymers. iPP/CNT PNCs form ?, ?, and ? crystallographic phases under a variety of crystallization conditions: non-isothermal and isothermal melt crystallization, shear, stress, fiber extrusion, etc. The crystal growth is altered from spherulitic to ?-fibrillar upon the nucleation effect of CNTs. We are studying the effect of different temperature treatment schemes and different isothermal crystallization conditions. We found also that the smectic ordering in iPP is improved by the introduction of CNTs. We use Differential Scanning Calorimetry, Wide Angle X-ray scattering, Microscopic Transmission Ellipsometry and Avrami analysis. Research supported by: Assumption College Faculty Development Grant, funding for students' stipends, instrumentation and supplies, the NSF Polymers Program of the DMR, grant (DMR-0602473) and NASA grant (NAG8-1167).

Georgiev, Georgi; Judith, Robert; Gombos, Erin; McIntyre, Michael; Schoen, Scott; Cebe, Peggy; Mattera, Michael

2010-03-01

385

The inhibition of neuronal calcium ion channels by trace levels of yttrium released from carbon nanotubes  

Microsoft Academic Search

Carbon nanotubes (CNTs) are used with increasing frequency in neuroengineering applications. CNT scaffolds are used to transmit electrical stimulation to cultured neurons and to control outgrowth and branching patterns of neurites. CNTs have been reported to disrupt normal neuronal function including alterations in endocytotic capability and inhibition of ion channels. Calcium ion channels regulate numerous neuronal and cellular functions including

Lorin M. Jakubek; Spiro Marangoudakis; Jesica Raingo; Xinyuan Liu; Diane Lipscombe; Robert H. Hurt

2009-01-01

386

Calcium carbonate in cholesterol gallstones: Polymorphism, distribution, and hypotheses about pathogenesis  

Microsoft Academic Search

This study of sets of cholesterol gallstones collected consecutively from 222 patients in La Paz, Bolivia, and Mexico City, Mexico, has developed a reliable infrared (IR) spectroscopic method for the detection of calcium carbonate in cholesterol gallstones and provided the basis for simultaneous identification of each of its three polymorphs: calcite, vaterite, and aragonite. The peaks in the 854 to

Donald R. Taylor; Roger S. Crowther; John C. Cozart; Pamela Sharrock; Jinguang Wu; Roger D. Soloway

1995-01-01

387

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....

388

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...

389

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...

390

Carboxymethyl cellulose\\/alum modified precipitated calcium carbonate fillers: Preparation and their use in papermaking  

Microsoft Academic Search

Carboxymethyl cellulose and alum were used in the modification of precipitated calcium carbonate filler, and the use of modified fillers in papermaking was investigated. The alum dosage was found to be much critical to the effective precipitation and encapsulation of carboxymethyl cellulose on filler surfaces. When the dosages of carboxymethyl cellulose and alum were 4% and 12% (based on the

Jing Shen; Zhanqian Song; Xueren Qian; Fei Yang

2010-01-01

391

Effects of Sigma Anti-bonding Molecule Calcium Carbonate on bone turnover and calcium balance in ovariectomized rats  

PubMed Central

This study was conducted to evaluate the effect of Sigma Anti-bonding Molecule Calcium Carbonate (SAC) as therapy for ovariectomy-induced osteoporosis in rats. Three weeks after surgery, fifteen ovariectomized Sprague-Dawley rats were divided randomly into 3 groups: sham-operated group (sham), ovariectomized group (OVX) and SAC-treatment group (OVX+SAC). The OVX+SAC group was given drinking water containing 0.0012% SAC for 12 weeks. Bone breaking force and mineralization as well as blood parameters related to the bone metabolism were analyzed. In OVX animals, blood concentration of 17?-estradiol decreased significantly, while osteocalcin and type I collagen C-terminal telopeptides (CTx) increased. Breaking force, bone mineral density (BMD), calcium and phosphorus in femurs, as well as uterine and vaginal weights, decreased significantly following OVX. However, SAC treatment (0.0012% in drinking water) not only remarkably restored the decreased 17?-estradiol and increased osteocalcin and CTx concentrations, but also recovered decreased femoral breaking force, BMD, calcium and phosphorus, although it did not reversed reproductive organ weights. It is suggested that SAC effectively improve bone density by preventing bone turnover mediated osteocalcin, CTx and minerals, and that it could be a potential candidate for therapy or prevention of postmenopausal osteoporosis.

Choi, So-Young; Park, Dongsun; Yang, Goeun; Lee, Sun Hee; Bae, Dae Kwon; Hwang, Seock-Yeon; Lee, Paul K; Kim, Yun-Bae; Kim, Ill-Hwa

2011-01-01

392

Epigallocatechin-3-gallate reduces inflammation induced by calcium pyrophosphate crystals in vitro  

PubMed Central

Although osteoarthritis (OA) is defined as a cartilage disease, synovitis involving mononuclear cell infiltration and overexpression of proinflammatory mediators is common in early and late OA. Calcium crystals deposition is thought to be a factor that likely contributes to synovial inflammation. In recent years, significant interest has emerged in the beneficial health effects attributed to the green tea polyphenols and in particular to epigallocatechin-3-gallate (EGCG). It has been demonstrated that some of the actions of EGCG are linked to its ability to interfere with cell membranes. The objective of this study was to evaluate the influence of EGCG in some inflammatory aspects of OA and whether EGCG is able to interfere with membrane organization. We assessed the effect of EGCG on the production of proinflammatory cytokines and chemokines released by human fibroblast-like synoviocytes (FLS) and THP-1 cells stimulated with calcium pyrophosphate (CPP) crystals in presence of methyl-?-cyclodextrin (M?CD), a cholesterol-removing agent that disturbs lipid raft structures. The chemotactic effect of culture supernatants was also evaluated. EGCG inhibited interleukin (IL)-1?, transforming growth factor beta, IL-8, and chemokine (C–C motif) ligand 2 (CCL2) release by stimulated FLS and/or THP-1 cells in a dose-dependent manner. Supernatants of CPP-stimulated cells induced the migration of neutrophils and mononuclear cells which decreased in a dose-dependent manner in the presence of EGCG. EGCG increased cell viability when added to THP-1 cells treated with M?CD. Furthermore, M?CD enhanced the inflammatory response to CPP crystals increasing IL-8 and CCL2 secretion which was inhibited by EGCG in a dose-dependent manner. This study showed that EGCG is able to reduce the inflammatory response induced by CPP crystals in vitro. The identification of EGCG as dietary supplement capable of affording protection or modulating the inflammatory response to CPP crystals may have important implications in the prevention and treatment of OA and crystal-related arthropathies.

Oliviero, Francesca; Sfriso, Paolo; Scanu, Anna; Fiocco, Ugo; Spinella, Paolo; Punzi, Leonardo

2013-01-01

393

Epigallocatechin-3-gallate reduces inflammation induced by calcium pyrophosphate crystals in vitro.  

PubMed

Although osteoarthritis (OA) is defined as a cartilage disease, synovitis involving mononuclear cell infiltration and overexpression of proinflammatory mediators is common in early and late OA. Calcium crystals deposition is thought to be a factor that likely contributes to synovial inflammation. In recent years, significant interest has emerged in the beneficial health effects attributed to the green tea polyphenols and in particular to epigallocatechin-3-gallate (EGCG). It has been demonstrated that some of the actions of EGCG are linked to its ability to interfere with cell membranes. The objective of this study was to evaluate the influence of EGCG in some inflammatory aspects of OA and whether EGCG is able to interfere with membrane organization. We assessed the effect of EGCG on the production of proinflammatory cytokines and chemokines released by human fibroblast-like synoviocytes (FLS) and THP-1 cells stimulated with calcium pyrophosphate (CPP) crystals in presence of methyl-?-cyclodextrin (M?CD), a cholesterol-removing agent that disturbs lipid raft structures. The chemotactic effect of culture supernatants was also evaluated. EGCG inhibited interleukin (IL)-1?, transforming growth factor beta, IL-8, and chemokine (C-C motif) ligand 2 (CCL2) release by stimulated FLS and/or THP-1 cells in a dose-dependent manner. Supernatants of CPP-stimulated cells induced the migration of neutrophils and mononuclear cells which decreased in a dose-dependent manner in the presence of EGCG. EGCG increased cell viability when added to THP-1 cells treated with M?CD. Furthermore, M?CD enhanced the inflammatory response to CPP crystals increasing IL-8 and CCL2 secretion which was inhibited by EGCG in a dose-dependent manner. This study showed that EGCG is able to reduce the inflammatory response induced by CPP crystals in vitro. The identification of EGCG as dietary supplement capable of affording protection or modulating the inflammatory response to CPP crystals may have important implications in the prevention and treatment of OA and crystal-related arthropathies. PMID:23616769

Oliviero, Francesca; Sfriso, Paolo; Scanu, Anna; Fiocco, Ugo; Spinella, Paolo; Punzi, Leonardo

2013-04-17

394

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

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)

Minoru Tsuboi; Masataka Shiraki; Michiyasu Hamada; Hideo Shimodaira

2000-01-01

395

Calcium Carbonate Precipitation in Relation to Detergent Performance.  

National Technical Information Service (NTIS)

Sodium carbonate (soda) is potentially a good, cheap and from the environmental point of view safe alternative for the substitution of phosphates in laundry detergents. A major disadvantage of the application of soda in detergents is, however, that part o...

D. Verdoes

1991-01-01

396

In situ calcium carbonate dissolution in the Pacific Ocean  

Microsoft Academic Search

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

R. A. Feely; Chris Sabine; K. Lee; F. J. Millero; M. F. Lamb; D. Greeley; J. L. Bullister; Robert Key; T.-H. Peng; Alexander Kozyr; Tsueno Ono; C. S. Wong

2002-01-01

397

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

NASA Astrophysics Data System (ADS)

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.

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

2011-12-01

398

Synthesis and characterization of carbon nanoribbons and single crystal iron filled carbon nanotubes  

SciTech Connect

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.

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

399

Tamarind (Tamarindus indica) fruit shell carbon: A calcium-rich promising adsorbent for fluoride removal from groundwater.  

PubMed

Tamarindus indica fruit shells (TIFSs) are naturally calcium rich compounds. They were impregnated with ammonium carbonate and then carbonized, leading to ammonium carbonate activated ACA-TIFS carbon. The resulting materials and carbon arising from virgin fruit shells V-TIFS were characterized and assayed as adsorbent for the removal of fluoride anions from groundwater. The fluoride scavenging ability of TIFS carbons was due to naturally dispersed calcium compounds. X-ray diffraction (XRD) showed that TIFS carbon contained a mixture of calcium oxalate and calcium carbonate. Batch studies on the fluoride removal efficiency of TIFS carbons with respect to contact time, pH, initial fluoride concentration, and co-ion interference were conducted. Applicability of various kinetic models (viz., pseudo-first-order, pseudo-second-order, intra-particle diffusion and Elovich) and sorption isotherms were tested for batch techniques. The fluoride removal capacity of TIFS carbons was found to be 91% and 83% at a pH of 7.05 for V-TIFS and ACA-TIFS carbons, respectively. The practical applicability of TIFS carbons using groundwater samples was approved. The fluoride removal was greater in groundwater without hydrogen carbonate ions than those containing these ions. The characterizations of fluoride unloaded and loaded TIFS carbons were done by SEM and XRD studies. PMID:22626627

Sivasankar, V; Rajkumar, S; Murugesh, S; Darchen, A

2012-05-11

400

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

USGS Publications Warehouse

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.

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

401

Oxygen isotope fractionation during the dolomitization of calcium carbonate  

Microsoft Academic Search

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

Alan Matthews; Amitai Katz

1977-01-01

402

Nanoscale analysis of the morphology and surface stability of calcium carbonate polymorphs  

NASA Astrophysics Data System (ADS)

Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Results show that the dry forms are prone to ductility; while hydrous phases are found to be brittle. The (001) surface of monohydrocalcite appears to be the most stable (0.99 J/m2) whereas for the ikaite phase, the (001) surface is the most stable. The corresponding value is 0.2 J/m2, i.e. even lower than the surface energy of the Beautiful computed morphology pictures are obtained with Xiao's model and are very similar to the observed SEM images.

Sekkal, W.; Zaoui, A.

2013-04-01

403

Nanoscale analysis of the morphology and surface stability of calcium carbonate polymorphs  

PubMed Central

Under earth surface conditions, in ocean and natural water, calcium carbonate is ubiquitous, forming anhydrous and hydrous minerals. These hydrous phases are of considerable interest for their role as precursors to stable carbonate minerals. Atomistic simulation techniques have been employed here to perform a comprehensive and quantitative study of the structural and energetic stability of dry and hydrous surfaces of calcium carbonate polymorphs using two recently developed forcefields. Results show that the dry forms are prone to ductility; while hydrous phases are found to be brittle. The (001) surface of monohydrocalcite appears to be the most stable (0.99?J/m2) whereas for the ikaite phase, the (001) surface is the most stable. The corresponding value is 0.2?J/m2, i.e. even lower than the surface energy of the Beautiful computed morphology pictures are obtained with Xiao's model and are very similar to the observed SEM images.

Sekkal, W.; Zaoui, A.

2013-01-01

404

Investigation of high-reactivity calcium carbonate sorbent for enhanced SO{sub 2} capture  

SciTech Connect

Kinetics of ultrafast, high-temperature sulfation is investigated for two calcium carbonates from different sources, a commercial calcium hydroxide and a laboratory-made modified hydrated lime powder. Time-resolved kinetic data are obtained for a 0--600 ms time scale at a temperature of 1,080 C with in-situ particle size classification. A mean particle size of 3.9 {micro}m is considered for sorbent comparison studies. It is observed that the high-surface-area Forsby carbonate exhibits extraordinarily high reactivity (50% in 500 ms) compared to other carbonate and hydrate powders. The difference in reactivity is most prominent in the short time scale of under 50 ms. Thorough investigations of the internal pore structure and surface area evolution in the initial 50 ms are conducted for both calcination and sulfation. The results elucidate the influence of internal pore structure in determining the initial reactivity and the final sorbent utilization.

Ghosh-Dastidar, A.; Mahuli, S.K.; Agnihotri, R.; Fan, L.S. [Ohio State Univ., Columbus, OH (United States). Dept. of Chemical Engineering

1996-02-01

405

An idiopathic case of calcium pyrophosphate dihydrate crystal deposition disease with crowned dens syndrome in a young patient.  

PubMed

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease is rare in patients under the age of 40 in the absence of metabolic or familial predisposition. A high incidence of involvement of the transverse ligament of the atlas in CPPD deposition disease was reported. However, involvement of the craniocervical junction is rarely symptomatic. We report a rare case in a young male with severe idiopathic CPPD crystal deposition disease, including crowned dens syndrome in the cervical spine. PMID:19668044

Unlu, Zeliha; Tarhan, Serdar; Ozmen, Eylem Mete

2009-09-01

406

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

PubMed

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

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

2006-05-11

407

ACTIVE MEDIA: Interaction of Er3+ ions in Er-doped calcium — niobium — gallium garnet crystals  

NASA Astrophysics Data System (ADS)

The processes of nonradiative energy transfer in calcium — niobium — gallium garnet (CNGG) crystals doped with Er3+ ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations CEr=6% and 11% is transferred via the nonradiative co-operative processes 4I11/2? 4I15/2, 4I11/2? 4F7/2, 4I11/2? 4I15/2, 4I13/2? 4F9/2; and 4I13/2? 4I15/2, 4I13/2? 4I9/2, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes 4S3/2?4I9/2, 4I15/2?4I13/2, whose intensity depends on the concentration of Er3+ ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%.

Malov, A. V.; Ryabochkina, P. A.; Popov, A. V.; Bol'shakov, E. V.

2010-08-01

408

Interaction of Er{sup 3+} ions in Er-doped calcium - niobium - gallium garnet crystals  

SciTech Connect

The processes of nonradiative energy transfer in calcium - niobium - gallium garnet (CNGG) crystals doped with Er{sup 3+} ions are studied. It is found that the energy of erbium ions in the Er:CNGG crystal with the erbium atomic concentrations C{sub Er}=6% and 11% is transferred via the nonradiative co-operative processes {sup 4}I{sub 11/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 11/2{yields}} {sup 4}F{sub 7/2}, {sup 4}I{sub 11/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 13/2{yields}} {sup 4}F{sub 9/2}; and {sup 4}I{sub 13/2{yields}} {sup 4}I{sub 15/2}, {sup 4}I{sub 13/2{yields}} {sup 4}I{sub 9/2}, whose efficiency increases with increasing intensity of exciting radiation. It is shown that the cross-relaxation processes {sup 4}S{sub 3/2{yields}}{sup 4}I{sub 9/2}, {sup 4}I{sub 15/2{yields}}{sup 4}I{sub 13/2}, whose intensity depends on the concentration of Er{sup 3+} ions, are characteristic for Er:CNGG crystals with the Er atomic concentration above 1%. (active media)

Malov, A V [N.P. Ogarev Mordovian State University, Saransk (Russian Federation); Popov, A V [A M Prokhorov General Physics Institute, Russian Academy of Sciences, Moscow (Russian Federation); Ryabochkina, P A; Bol'shakov, E V

2010-08-03

409

A calcium oxide sorbent process for bulk separation of carbon dioxide  

SciTech Connect

This research effort is designed to investigate the technical feasibility of a high-temperature, high-pressure process for the bulk separation of CO{sub 2} from coal-derived gases. The two-year contract was awarded in September 1989. This report describes the research effort and results obtained during the first year of the effort. The overall project consists of 6 tasks, four of which were active during year 01. Tasks 1 and 2 were completed during the year while activity in Tasks 3 and 6 will carry over into year 02. Tasks 4 and 5 will be initiated during year 02. Three primary objectives were met in Task 1. A literature search on the calcination-carbonation reactions of CO{sub 2} with calcium-based sorbents was completed. A high temperature, high pressure (HTHP) electrobalance reactor suitable for studying the calcination and carbonation reactions was constructed. This reactor system is now fully operable and we are routinely collecting kinetics data at temperatures in the range of 550-900{degree}C and pressures of 1 to 15 atm. Samples of nine candidate calcium-based sorbents were acquired and tested. These samples were subjected to reaction screening tests as part of Task 2. As a result of these screening tests, chemically pure calcium carbonate, chemically pure calcium acetate, and the commercial dolomite were selected for more detailed kinetic testing. In Task 3, the HTHP electrobalance reactor is being used to study the calcination-carbonation behavior of the three base sorbents as a function of calcination temperature, carbonation temperature, carbonation pressure, and CO{sub 2} concentration.

Harrison, D.P.

1990-09-01

410

Complexation/encapsulation of green tea polyphenols in mixed calcium carbonate and phosphate micro-particles.  

PubMed

We used a double-jet mixer to encapsulate water-soluble polyphenols, green tea extract (GTE), with calcium-based inorganic materials. The device mixed calcium chloride solutions with a solution of carbonate and phosphate in the presence of a GTE solution, and formed micro-particles which capture the GTE molecules. The micro-particles were analysed by liquid chromatography coupled to tandem mass spectroscopy to determine the encapsulation yield and loading of the different GTE components. We established correlations between (1) the efficiency of the GTE encapsulation and the composition of the mixed anion solutions and (2) the protonation degree of the ions and the molar ratio of calcium cations and carbonate/phosphate anions. An optimal and reproducible GTE loading of about 40% with an encapsulation yield of 65% was observed for a carbonate/phosphate molar composition of 4?:?1. In addition, our experimental results showed that the process is selective and favours the encapsulation of gallated species which form stronger complexes with calcium cations. PMID:20945969

Elabbadi, Amal; Jeckelmann, Nicolas; Haefliger, Olivier P; Ouali, Lahoussine

2010-10-14

411

Crystallization and melting behavior of isotactic polypropylene and carbon nanotube nanocomposites  

Microsoft Academic Search

Polymer nanocomposites (PNCs) are the most recent development in the field of polymer science and technology. Geared toward creating novel polymer based materials, PNCs are the largest commercial application for nanotubes. Spherulitic polymer crystal growth was changed by inducing new fibrillar crystals on the surface of carbon nanotubes. Upon isothermal melt crystallization at 135^oC, CNTs lead to monoclinic crystal growth

Georgi Georgiev; Yaniel Cabrera; Lauren Wielgus; Zarnab Iftikhar; Michael Mattera; Peter Gati; Austin Potter; Peggy Cebe

2009-01-01

412

Nanocomposites of carbon nanotube fibers prepared by polymer crystallization.  

PubMed

Nanocomposites of carbon nanotube fibers have been prepared using controlled polymer crystallization confined in nanotube aerogel fibers. The polyethylene nanocomposites have been investigated by means of polarized optical microscopy (POM), scanning electron microscopy (SEM) and wide-angle X-ray diffraction (WAXD). The individual nanotubes are periodically decorated with polyethylene nanocrystals, forming aligned hybrid shish-kebab nanostructures. After melting and recrystallization, transcrystalline lamellae connecting the adjacent aligned nanotubes develop. Microstructural analysis shows that the nanotubes can nucleate the growth of both orthorhombic and monoclinic crystals of polyethylene in the quiescent state. The tensile strength, modulus, and axial electrical conductivity of these polyethylene/CNT composite fibers are as high as 600 MPa, 60 GPa, and 5000 S/m, respectively. PMID:20507070

Zhang, Shanju; Lin, Wei; Wong, Ching-Ping; Bucknall, David G; Kumar, Satish

2010-06-01

413

Study on crystallization of hydrogenated nanocrystalline silicon carbon films  

Microsoft Academic Search

Hydrogenated nanocrystalline silicon carbon (nc-SiCx:H) films were prepared by RF glow discharge of gas mixture of silane (SiH4) and ethene (C2H4) diluted heavily by hydrogen (H2). The effect of the gas volume ratio of (SiH4 + C2H4)\\/H2 (Xg) and C2H4\\/(SiH4 + C2H4) (Xc) on the crystallization and composition of films are described in the paper. When the Xg increases from

Weiqiang Han; Shoushan Fan; Binglin Gu

1996-01-01

414

Hierarchical assembly of carbon nanotubes-liquid crystal nanocomposite.  

PubMed

Fabrication of liquid crystalline (LC) nanomaterials in an aligned pattern along the multiwalled carbon nanotubes (CNT) has been reported here. The nanocomposite was prepared by sonicating esterified CNTs and the ferroelectric liquid crystal (FLC) in chloroform. The nanohybrid shish kebab (NHSK) like pattern was observed in SEM analysis. The nanocomposite materials were characterized by Fourier transform infrared spectroscopy (FTIR), polarizing optical microscopy and electron microscopy. The DC and AC electrical properties of the composite materials were investigated. The DC conductivity of the nanocomposite increased by 2 order from the FLC materials and AC relaxation has been observed, in the nanocomposite, which was totally absent in the FLC materials. PMID:18572572

Kundu, Sudarshan; Batabyal, Sudip K; Nayek, Prasenjit; Roy, Subir K

2008-04-01

415

Crystal structure analysis reveals Pseudomonas PilY1 as an essential calcium-dependent regulator of bacterial surface motility  

SciTech Connect

Several bacterial pathogens require the 'twitching' motility produced by filamentous type IV pili (T4P) to establish and maintain human infections. Two cytoplasmic ATPases function as an oscillatory motor that powers twitching motility via cycles of pilus extension and retraction. The regulation of this motor, however, has remained a mystery. We present the 2.1 {angstrom} resolution crystal structure of the Pseudomonas aeruginosa pilus-biogenesis factor PilY1, and identify a single site on this protein required for bacterial translocation. The structure reveals a modified {beta}-propeller fold and a distinct EF-hand-like calcium-binding site conserved in pathogens with retractile T4P. We show that preventing calcium binding by PilY1 using either an exogenous calcium chelator or mutation of a single residue disrupts Pseudomonas twitching motility by eliminating surface pili. In contrast, placing a lysine in this site to mimic the charge of a bound calcium interferes with motility in the opposite manner - by producing an abundance of nonfunctional surface pili. Our data indicate that calcium binding and release by the unique loop identified in the PilY1 crystal structure controls the opposing forces of pilus extension and retraction. Thus, PilY1 is an essential, calcium-dependent regulator of bacterial twitching motility.

Orans, Jillian; Johnson, Michael D.L.; Coggan, Kimberly A.; Sperlazza, Justin R.; Heiniger, Ryan W.; Wolfgang, Matthew C.; Redinbo, Matthew R. (UNC)

2010-09-21

416

Crystallization of Carbon-Oxygen Mixtures in White Dwarf Stars  

SciTech Connect

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.

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

417

Crystallization of Carbon-Oxygen Mixtures in White Dwarf Stars  

NASA Astrophysics Data System (ADS)

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 C12(?,?)O16 reaction to S300?170keVb.

Horowitz, C. J.; Schneider, A. S.; Berry, D. K.

2010-06-01

418

Biodegradation of inorganic components in paper documents: Formation of calcium oxalate crystals as a consequence of Aspergillus terreus Thom growth  

Microsoft Academic Search

A sample set of model graded papers containing known organic and inorganic components was used to culture an Aspergillus terreus strain able to produce acidic metabolites and cellulolytic enzymes. This study set out to document the biogenic formation of calcium oxalate crystals, as a consequence of fungal activity and growth, on a range of paper samples. Scanning electron microscopy and

Flavia Pinzari; Mirca Zotti; Antonella De Mico; Paolo Calvini

2010-01-01

419

Histopathological and ultrastructural studies of synovium in Milwaukee shoulder syndrome--a basic calcium phosphate crystal arthropathy  

Microsoft Academic Search

Light and electron microscopic study of synovial specimens from four patients with the Milwaukee shoulder syndrome disclosed vascular congestion, villous and focal synovial lining cell hyperplasia, occasional giant cells, and fibrin deposition both within and on the surface of the synovium. Although these changes are non-specific, the finding of basic calcium phosphate crystal aggregates in all four cases and the

P B Halverson; J C Garancis; D J McCarty

1984-01-01

420

CALCIUM OXALATE CRYSTAL MACROPATTERN IN LEAVES OF SPECIES FROM GROUPS GLYCINE AND SHUTERIA (GLYCININAE; PHASEOLEAE; PAPILIONOIDEAE; FABACEAE)  

Technology Transfer Automated Retrieval System (TEKTRAN)

Calcium oxalate crystals associated with leaf veins and mesophyll was determined for taxa in two groups Glycine and Shuteria of subtribe Glycininae. Trichomes and veins were identified as additional characters. The annual and wild perennial Glycine species have the most reduced characters by gener...

421

Crystal structure of the intermetallics produced by a calcium hydride method  

NASA Astrophysics Data System (ADS)

Practically important intermetallics TiNi, NiAl, Ni3Al, TiAl, and Zr3Al2 (St 101 alloy for gas absorbers) produced by the calcium hydride method are comprehensively studied. The total content of impurities in these intermetallic powders does not exceed 1 wt %, and the fraction of the main phase in compounds with a narrow homogeneity region is at least 93-96 vol %. The main phases in all powders under study have a defectless crystal lattice, and their lattice parameters point to a low content of dissolved impurities in all intermetallics except for Zr3Al2. A high degree of homogeneity of the phase compositions of the intermetallic powders is supported by a scanning electron microscopy investigation.

Kasimtsev, A. V.; Sviridova, T. A.

2012-05-01

422

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

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.

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

2010-07-13

423

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

PubMed Central

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.

2011-01-01

424

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

PubMed

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

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

2011-09-23

425

Geophysical Monitoring and Reactive Transport Modeling of Ureolytically-Driven Calcium Carbonate Precipitation  

SciTech Connect

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.

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

2011-09-01

426

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

SciTech Connect

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 NH{sub 4}{sup +} 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.

Wu, Y.; Ajo-Franklin, J.B.; Spycher, N.; Hubbard, S.S.; Zhang, G.; Williams, K.H.; Taylor, J.; Fujita, Y.; Smith, R.

2011-07-15

427

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

SciTech Connect

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.

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

428

High surface area calcium carbonate: Pore structural properties and sulfation characteristics  

SciTech Connect

Limestone or calcium carbonate (CaCO{sub 3}) used as a sorbent in the removal of acid gas precursors (SO{sub 2}) from combustion systems suffers from poor pore structural properties which causes low reactivity and incomplete utilization. The surface area and pore size distribution of CaCO{sub 3}, if tailored appropriately, can considerably enhance its reactivity for SO{sub 2}. This study focuses on the optimization of pore properties of CaCO{sub 3} particles and the enhancement of SO{sub 2} reactivity and ultimate utilization. The carbonate is produced by precipitation from an aqueous suspension of calcium hydroxide by injecting CO{sub 2}. The influence of operating parameters, suspension concentration, gas flow rate, and additives (surfactant) on the surface area and pore volume is investigated. The surface area of the carbonate powder can be controlled in the range of 10--70 m{sup 2}/g by varying the operating parameters. The SO{sub 2} reactivity and the ultimate utilization of the calcium carbonate indicate a dramatic improvement and can be correlated with the surface area and pore volume characteristics of the particles.

Wei, S.H.; Mahuli, S.K.; Agnihotri, R.; Fan, L.S. [Ohio State Univ., Columbus, OH (United States). Dept. of Chemical Engineering

1997-06-01

429

Calcium Carbonate Precipitation/Dissolution in Salt Water - Fresh Water Mixing Zones  

NASA Astrophysics Data System (ADS)

Mineral precipitation and dissolution in subsurface environments can have a dramatic effect on the permeability and porosity of formations and hence exert a feedback on the fluid flow. Many parameters influence mineral precipitation and dissolution, but the one addressed here concerns precipitation or dissolution that arises from mixing of saturated solutions with different salinities (or temperatures). This effect arises because the solubility of a mineral in solution depends non-linearly on salinity (or temperature). Examples include calcite precipitation and/or dissolution resulting from mixing of fresh and saline waters in coastal carbonate formations, or the precipitation of anhydrite (CaSO4) upon mixing of hydrothermal solutions with seawater. The present preliminary study focuses on flow, precipitation and dissolution along a salt water-fresh water interface in a porous medium. Emphasis is placed on the quantitative evolution of the flow field in both time and space, under different flow regimes and chemical compositions. Flow experiments were performed in a 2D flow cell packed with 1 mm diameter glass beads. Salt water and fresh water, both saturated with CaCO3, were injected simultaneously at equal flow rates at two inlets. The effluent acid from the outlets was collected and analyzed for Ca2+ concentration, in order to calculate precipitated/dissolved calcium carbonate (based on molar volume of the component) during the experiments. The equilibrium concentration of dissolved calcium carbonate in salt water was found to be higher than in fresh water. Calcium carbonate tended to precipitate in the mixing zone because the resulting mixture became supersaturated. The precipitation rate of calcium carbonate, and the forms of precipitation and subsequent dissolution, are highly dependent on the flow rate, the chemical composition of the injected fluids, and the salinity gradient.

Berkowitz, B.; Singurindy, O.; Lowell, R. P.

2001-12-01

430

Chemistry of calcium carbonate-rich shallow water sediments in the Bahamas  

SciTech Connect

The geochemistry of calcium carbonate-rich sediments from a variety of environments throughout the Bahamas was investigated with particular emphasis on the factors that control the pore water chemistry. Most sediments are supersaturated with respect to aragonite, the most abundant carbonate component. Experimental studies indicate that the observed in situ calcium carbonate ion activity products can often be produced as reversible metastable equilibria between the sediments and seawater. This is interpreted as being the result of interactions between the solutions and the minor high Mg-calcite component present in these sediments. Although the overlying waters are more supersaturated than the pore waters, carbonate dissolution, not precipitation, dominates in these sediments as a result of organic matter oxidation and the resulting increase in P/sub CO/sub 2//. The carbonate sediments of the Bahamas are remarkable for their purity, with the exception of special environments such as mangrove swamps and tidal flats with algal mats. Organic matter and heavy metal content is extremely low. Only minor sulfate reduction is occurring in most sediments. Phosphate is undetectable in all pore waters, probably as a result of adsorption on carbonate mineral surfaces. Other dissolved pore water components such as ammonia and DOC are much lower than typically found in shallow water fine-grained terrigeneous sediments.

Morse, J.W.; Zullig, J.J.; Bernstein, L.D.; Millero, F.J.; Milne, P.; Mucci, A.; Choppin, G.R.

1985-02-01

431

Preparation and structure evolution of bowknot-like calcium carbonate particles in the presence of poly(sodium 4-styrene sulfate).  

PubMed

Calcium carbonate particles with a novel bowknot-like superstructure were fabricated in the presence of poly(sodium 4-styrene sulfate) (PSS) and under the assistance of ultrasonication during the initial reaction stage. X-ray powder diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), selected area electron diffraction (SAED), and field-emission scanning electron microscopy (FE-SEM) equipped with energy-dispersive X-ray (EDX) were used to characterize the particles. Results demonstrated that the bowknot-like calcium carbonate particles were mainly composed of amorphous calcium carbonate (ACC) and some amounts of calcite and vaterite. Ultrasound irradiation associated with the presence of PSS affects the mesoscale crystallization, resulting in stepwise growth of the earlier bundles to the bowknot. Morphology evolution and dissolution of the bowknot particle were observed in different media, confirming that PSS and Ca(2+) ions in the solutions could accelerate and resist the transformation process, respectively. In the presence of PSS, ACC prefers to transform into vaterite. PMID:22867860

Xie, Lili; Song, Xiaoxue; Tong, Weijun; Gao, Changyou

2012-07-16

432

Relationship between the degeneration of the cruciate ligaments and calcium pyrophosphate dihydrate crystal deposition: anatomic, radiologic study with histologic correlation.  

PubMed

To investigate the association of calcium pyrophosphate dihydrate (CPPD) crystal deposition and cruciate ligament (CL) degeneration, 10 cadaveric knees were studied with 1.5-T magnetic resonance imaging and sectioned in three planes. The slices were evaluated with high-resolution Faxitron radiography. The images and specimens were evaluated by two radiologists. Histologic sections were obtained from eight that contained calcifications and from two without calcifications. Radiographs and histologic analysis demonstrated CPPD crystal deposition in 80% of specimens and 75% of CLs in these eight specimens. Degenerative changes were observed in 75% of them. Such analysis demonstrated no evidence of CPPD crystals or degeneration in the control specimens. PMID:23465989

Dirim, Berna; Resnick, Donald; Abreu, Marcelo; Wangwinyuvirat, Mani; Trudell, Debra J; Haghighi, Parviz

2012-06-08

433

Treatment of Secondary Hyperparathyroidism in Hemodialyzed Patients with High-Dose Calcium Carbonate without Vitamin D3 Supplements  

Microsoft Academic Search

Background: Vitamin D compounds are usually indicated for the treatment of secondary hyperparathyroidism in dialysis patients. The possibility to induce a reversal of hyperparathyroidism with calcium supplementation alone is controversial. The present study was conducted to assess if oral calcium carbonate may constitute a therapeutic option for the control of hyperparathyroidism in patients with high PTH concentrations at the beginning

José L. Teruel; María T. Tenorio; José R. Rodríguez; Roberto Marcén; Luis Orofino; Maite Rivera; Joaquín Ortuño

1999-01-01

434

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

NASA Astrophysics Data System (ADS)

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 ?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 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.

Kelly, Shelly D.; Kemner, Kenneth M.; Brooks, Scott C.

2007-02-01

435

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

SciTech Connect

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.

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

2007-01-01

436

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

SciTech Connect

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.

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

2007-01-01

437

Calcium channel blockers reduce blood pressure in part by inhibiting vascular smooth muscle carbonic anhydrase I.  

PubMed

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 our results in this article we studied in vitro and in vivo the effect of calcium channel blockers (verapamil and amlodipine) on erythrocyte CA I, on vascular smooth muscles CA I, and on arterial blood pressure values in human and in animals. Our in vitro and in vivo results have proved that verapamil and amlodipine are strong CA I inhibitors both in human erythrocytes and also in vascular smooth muscles in animals. In humans, calcium channel blockers studied here progressively reduce arterial blood pressure in hypertensive subjects, in parallel with progressive lowering of erythrocyte CA I activity in the normal range in normotensive subjects. From our point of view verapamil and amlodipine possess a dual mechanism of action: the first well-known action consists of their action on calcium channels. The second mechanism, suggested by us, directly acts on the vascular smooth muscle CA I isozyme, so that its inhibition should ensure an adequate pH for calcium ions transport through the channels, having as result vasodilation. This double mechanism could explain the hypotensive effect of verapamil and amlodipine, with a mechanism that partially dependent on CA I inhibition. PMID:11101200

Puscas, L; Gilau, L; Coltau, M; Pasca, R; Domuta, G; Baican, M; Hecht, A

2000-10-01