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1

Composite phospholipid-calcium carbonate microparticles: influence of anionic phospholipids on the crystallization of calcium carbonate.  

PubMed

The synthesis and characterization of calcium carbonate microparticles by reaction of calcium chloride and ammonium bicarbonate in the presence of negatively charged phospholipid mixtures of negative and zwitterionic phospholipids has been reported. Negatively charged phospholipids influence the crystal morphology of calcium carbonate and induce the formation of thermodynamically less stable veterite polymorph as opposed to calcite polymorph. The phospholipids are entrapped in the calcium carbonate microparticles during the crystallization process, with a uniform distribution of phospholipids in the interior of the microparticles. This phenomenon was exploited to encapsulate a model hydrophobic fluorophore, the tris(4,7-diphenyl-1,10-phenanthroline)ruthenium(II) dichloride complex, to simulate encapsulation of hydrophobic drug molecules. Thermogravimetric analysis reveals that, in these microparticles, the calcium carbonate and the phospholipid exhibit strong interactions. PMID:16471842

Gopal, Krishna; Lu, Zonghuan; de Villiers, Melgardt M; Lvov, Yuri

2006-02-16

2

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

3

Polymorph-selective crystallization of calcium carbonate inspired by biomineralization  

NASA Astrophysics Data System (ADS)

This dissertation primarily examines bioinspired mineralization, focusing on the polymorph-selective crystallization of calcium carbonate. (1) The effect of epitaxy on the polymorphic control of calcium carbonate was studied with aragonite-type inorganic substrates. The critical epitaxial mismatch for aragonite growth, when conditions disfavor aragonite, seems to be less than 7.1%. Larger epitaxial strain appeared to prohibit aragonite formation even though the substrates had the same crystal structure. The epitaxy required for aragonite nucleation seems to be more precise than that often suggested for biological systems. (2) Polymers of different aqueous-solution properties were tested to observe the effect on the crystallization of calcium carbonate. Near exclusive formation of aragonite was attained through the inhibition of more stable calcite with poly(vinyl alcohol). The contributing characteristics of poly(vinyl alcohol) seemed to be its ability to hydrogen bond and its tendency to adsorb non-specifically onto solid surfaces. Similar inhibition activity is suggested for various biomacromolecules involved in biogenic aragonite formation of mollusks, with the biomacromolecules acting in the same way as poly(vinyl alcohol). (3) Polymer surfaces imprinted by aragonite-type crystals (strontium carbonate) were studied as substrates for the crystallization of calcium carbonate. Only calcite formed under vaterite-, aragonite-, and calcite-favorable conditions. This result seemed to arise from the nature of functional groups, rather than from the molecular structure of the imprint. Interaction between the functional groups and calcium carbonate is suggested to have enhanced the crystallization rate, resulting in the rapid formation of the thermodynamically stable calcite irrespective of the bulk crystallization conditions. (4) A catechol-based monomer was synthesized in the course of developing a dental adhesive, which mimics the functionalities of mussel adhesive proteins. The coupling behavior of the monomer to hydroxyapatite, a mineral component of dentin, was studied. (5) Multiple denaturation of fibrillar collagen was reexamined with a highly sensitive differential scanning calorimeter. Multiple states of collagen were recognized by the appearance of several denaturation peaks: oxidized tropocollagen, intact tropocollagen, immature fibrils, and mature fibrils. The immature fibrils were identified as an intermediate state of collagen assembly, since it disappeared with time at constant temperature.

Kim, Il Won

4

The influence of xanthan on the crystallization of calcium carbonate  

NASA Astrophysics Data System (ADS)

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

Yang, Xiaodeng; Xu, Guiying

2011-01-01

5

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

6

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

PubMed

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

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

2012-10-01

7

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

NASA Astrophysics Data System (ADS)

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

Ming, Jinfa; Zuo, Baoqi

2014-01-01

8

Capillarity creates single-crystal calcite nanowires from amorphous calcium carbonate.  

PubMed

Single-crystal calcite nanowires are formed by crystallization of morphologically equivalent amorphous calcium carbonate (ACC) particles within the pores of track etch membranes. The polyaspartic acid stabilized ACC is drawn into the membrane pores by capillary action, and the single-crystal nature of the nanowires is attributed to the limited contact of the intramembrane ACC particle with the bulk solution. The reaction environment then supports transformation to a single-crystal product. PMID:22069168

Kim, Yi-Yeoun; Hetherington, Nicola B J; Noel, Elizabeth H; Kröger, Roland; Charnock, John M; Christenson, Hugo K; Meldrum, Fiona C

2011-12-23

9

Crystallization and Transformation Mechanism of Calcium Carbonate Polymorphs and the Effect of Magnesium Ion  

Microsoft Academic Search

The crystallization of calcium carbonate was carried out by mixing CaCl2 and Na2CO3 solutions. The morphology of precursor formed prior to the nucleation of the polymorphous crystals (calcite and vaterite) varies depending on the feed concentration. The faster nucleation rate of polymorphous crystals in 0.2 mol\\/L than in 0.05 mol\\/L solution results in the prompt disappearance of the precursor at

Mitsutaka Kitamura

2001-01-01

10

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

NASA Astrophysics Data System (ADS)

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

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

2013-06-01

11

The crystal polymorphism of calcium carbonate is determined by the matrix structure in quail eggs.  

PubMed

Two calcified structures, the eggshell and sperm-associated body (SB), are present in the eggs of the Japanese quail, Coturnix japonica. X-ray diffractometry showed that calcium carbonates take the form of calcite in the eggshell and aragonite in the SB. The aim of the present study was to identify the factors that determine the morphology of calcium carbonate crystals. The matrix of EDTA-treated eggshell was a meshwork of vesicles, 200 to 500 nm in diameter, connected by fine fibers or fibrous sheets. The matrix of SB cortex was a radiation of rod-shaped projections approximately 130 nm in width. In vitro crystal formation was achieved by adding dissociated matrix substances to test solutions. When eggshell matrix material was added, formation of calcite crystals, which had many vesicular holes on their surface, was observed. When SB matrix material dissociated by sonication was added, rhombohedral calcite crystals formed at protein concentrations of 100 microg/mL or lower, and elongated and bundled crystals formed at concentrations of 150 microg/mL or higher. When SB matrix material dissociated by pipetting was added, aragonite crystals formed. These observations indicate that the matrix structure is the principal factor in determining the crystal polymorphism of calcium carbonate. PMID:19903967

Iwasawa, A; Uzawa, M; Rahman, M A; Ohya, Y; Yoshizaki, N

2009-12-01

12

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

PubMed Central

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

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

2014-01-01

13

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

PubMed

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

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

2014-01-01

14

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

NASA Technical Reports Server (NTRS)

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

Nielsen, Kjeld Flemming; Lind, M. David

1992-01-01

15

Free energy and structure of calcium carbonate nanoparticles during early stages of crystallization  

NASA Astrophysics Data System (ADS)

We introduce a metadynamics based scheme for computing the free energy of nanoparticles as a function of their crystalline order. The method is applied to small nanoparticles of the biomineral calcium carbonate to determine the preferred structure during early stages of crystal growth. For particles 2 nm in diameter, we establish a large energetic preference for amorphous particle morphologies. Particles with partial crystalline order consistent with vaterite are also observed with substantially lower probability. The absence of the stable calcite phase and stability of the amorphous state support recent conjectures that calcite formation starts via the deposition of amorphous calcium carbonate.

Quigley, D.; Rodger, P. M.

2008-06-01

16

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

PubMed

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

Ma, Yufei; Feng, Qingling; Bourrat, Xavier

2013-05-01

17

Effect of polyacrylic acid and polyethylene glycol on the crystallization of calcium carbonates in the presence of magnesium ions  

Microsoft Academic Search

The effect of polyacrylic acid and polyethylene glycol on the crystallization of calcium carbonates in the presence of magnesium\\u000a ions was studied. It was found that the presence of magnesium ions in solution and the treatment temperature (80°C) influence\\u000a the formation of the final products of calcium carbonate crystallization. In binary mixtures, low-molecular-weight polyacrylic\\u000a acid and polyethylene glycol affect synergistically,

I. V. Shestak; P. D. Vorob’ev; D. V. Cherednichenko; E. V. Vorob’eva; G. V. Bondareva; N. Strnadova

2011-01-01

18

Enzyme-accelerated and structure-guided crystallization of calcium carbonate: role of the carbonic anhydrase in the homologous system.  

PubMed

The calcareous spicules from sponges, e.g. from Sycon raphanus, are composed of almost pure calcium carbonate. In order to elucidate the formation of those structural skeletal elements, the function of the enzyme carbonic anhydrase (CA), isolated from this species, during the in vitro calcium carbonate-based spicule formation, was investigated. It is shown that the recombinant sponge CA substantially accelerates calcium carbonate formation in the in vitro diffusion assay. A stoichiometric calculation revealed that the turnover rate of the sponge CA during the calcification process amounts to 25 CO2s(-1) × molecule CA(-1). During this enzymatically driven process, initially pat-like particles are formed that are subsequently transformed to rhomboid/rhombohedroid crystals with a dimension of ~50 ?m. The CA-catalyzed particles are smaller than those which are formed in the absence of the enzyme. The Martens hardness of the particles formed is ~4 GPa, a value which had been determined for other biogenic calcites. This conclusion is corroborated by energy-dispersive X-ray spectroscopy, which revealed that the particles synthesized are composed predominantly of the elements calcium, oxygen and carbon. Surprising was the finding, obtained by light and scanning electron microscopy, that the newly formed calcitic crystals associate with the calcareous spicules from S. raphanus in a highly ordered manner; the calcitic crystals almost perfectly arrange in an array orientation along the two opposing planes of the spicules, leaving the other two plane arrays uncovered. It is concluded that the CA is a key enzyme controlling the calcium carbonate biomineralization process, which directs the newly formed particles to existing calcareous spicular structures. It is expected that with the given tools new bioinspired materials can be fabricated. PMID:23978410

Müller, Werner E G; Schlossmacher, Ute; Schröder, Heinz C; Lieberwirth, Ingo; Glasser, Gunnar; Korzhev, Michael; Neufurth, Meik; Wang, Xiaohong

2014-01-01

19

Effect of dendrimers on the crystallization of calcium carbonate in aqueous solution.  

PubMed

Construction of organic-inorganic hybrid materials with controlled mineralization analogous to those produced by nature is now a current interest for both organic and inorganic chemists to understand the mechanism of natural biomineralization processes as well as to seek industrial and technological applications. Model systems, in which low-molecular-weight, linear polymeric organic materials have been used to study the effect of molecular properties such as charge and functionality on inorganic crystallization, are providing insights into the possible mechanisms operating in biology. Due to unique and well-defined secondary structures of the dendrimers, the starburst dendrimers should be a good candidate for studying inorganic crystallization. This review provides a general survey of recent research on crystal nucleation and growth of calcium carbonate by a carboxylic acid derivative of hyperbranched polyphenylene polymer, poly(amidoamine) (PAMAM) dendrimers with carboxylate groups at the external surface, and poly(propyleneimine) dendrimers modified with long aliphatic chains. PMID:21132483

Naka, Kensuke

2003-01-01

20

Effect of Dendrimers on the Crystallization of Calcium Carbonate in Aqueous Solution  

NASA Astrophysics Data System (ADS)

Construction of organic-inorganic hybrid materials with controlled mineralization analogous to those produced by nature is now a current interest for both organic and inorganic chemists to understand the mechanism of natural biomineralization processes as well as to seek industrial and technological applications. Model systems, in which low-molecular-weight, linear polymeric organic materials have been used to study the effect of molecular properties such as charge and functionality on inorganic crystallization, are providing insights into the possible mechanisms operating in biology. Due to unique and well-defined secondary structures of the dendrimers, the starburst dendrimers should be a good candidate for studying inorganic crystallization. This review provides a general survey of recent research on crystal nucleation and growth of calcium carbonate by a carboxylic acid derivative of hyperbranched polyphenylene polymer, poly(amidoamine) (PAMAM) dendrimers with carboxylate groups at the external surface, and poly(propyleneimine) dendrimers modified with long aliphatic chains.

Naka, Kensuke

21

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

22

Peptide Induced Crystallization of Calcium Carbonate on Wrinkle Patterned Substrate: Implications for Chitin Formation in Molluscs  

PubMed Central

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.

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

2013-01-01

23

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

24

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

NASA Technical Reports Server (NTRS)

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 LDEF was in excellent condition after the long orbital stay, and although the temperature data was lost, the experiment program had been working since the valves in all containers were opened. All four experiments produced crystals; however, they were of varying quality. The calcium carbonate crystals had the best appearance. The TTF-TCNQ crystals were packed together near the valve openings of the container. When taken apart, the single crystals showed some unusual morphological properties. X-ray investigations as well as conductivity measurements on the long duration space grown TTF-TCNQ crystals are presented, and pictures of the calcium carbonate are shown. Comparisons are made with previous space solution growth experiments on the European Spacelab Mission and the Apollo-Soyuz Test Project.

Nielsen, Kjeld Flemming; Lind, M. David

1991-01-01

25

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

NASA Astrophysics Data System (ADS)

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

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

2013-07-01

26

Linking crystal structure with temperature-sensitive vibrational modes in calcium carbonate minerals.  

PubMed

We demonstrate a correlation between how an IR-active vibrational mode responds to temperature changes and how it responds to crystallinity differences. Infrared (IR) spectroscopy was used to track changes in carbonate-related vibrational modes in three different CaCO3 polymorphs (calcite, aragonite, and vaterite) and CaMg(CO3)2 (dolomite) during heating. Of the three characteristic IR-active carbonate modes, the in-plane bending mode (?4) shows the most pronounced changes with heating in polymorphs that have planar carbonate arrangements (calcite, aragonite, and dolomite). In contrast, this mode is virtually unchanged in vaterite, which has a canted arrangement of carbonate units. We correlate these trends with recent studies that identified the ?4 mode as most susceptible to changes related to crystallinity differences in calcite and amorphous calcium carbonate. Thus, our results suggest that studies of packing arrangements could provide a generalizable approach to identify the most diagnostic vibrational modes for tracking either temperature-dependent or crystallinity-related effects in IR-active solids. PMID:25027312

Xu, Ben; Poduska, Kristin M

2014-07-30

27

COPRECIPITATION AND ADSORPTION FOR REMOVAL OF CADMIUM, LEAD, AND ZINC BY THE LIME - SODA ASH WATER SOFTENING PROCESS (CRYSTALLIZATION, HEAVY METAL, CALCIUM-CARBONATE)  

Microsoft Academic Search

The crystallization kinetics for the precipitation of calcium carbonate and magnesium hydroxide in the presence of cadmium, lead, and zinc were studied. The kinetics for the precipitation have been studied in a continuous reactor operated under MSMPR (mixed suspension mixed product removal) conditions. Reactor residence times, effluent alkalinity conditions, and initial heavy metal concentrations (acting as impurity) were varied to

TSUN-KUO CHANG

1985-01-01

28

Calcium oxalate crystals in plants  

Microsoft Academic Search

Calcium (Ca) oxalate crystals occur in many plant species and in most organs and tissues. They generally form within cells\\u000a although extracellular crystals have been reported. The crystal cells or idioblasts display ultrastructural modifications\\u000a which are related to crystal precipitation. Crystal formation is usually associated with membranes, chambers, or inclusions\\u000a found within the cell vacuole(s). Tubules, modified plastids and enlarged

Vincent R. Franceschi; Harry T. Horner

1980-01-01

29

Calcium carbonate with magnesium overdose  

MedlinePLUS

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

30

Development of artificial seed crystal for crystallization of calcium phosphate.  

PubMed

An artifical seed crystal material consisting of calcium silicate hydrate (5CaO x 6SiO2 x 5H2O : tobermorite crystals) applicable for phosphorus removal by crystallization was developed. Card-house shaped tobermorite crystals were developed on the seed material where orthophosphate crystallized as a calcium phosphate. The seed material can be manufactured by mixing siliceous and calcareous raw materials, pelletizing and subsequent autoclaving. Laboratory experiments were conducted to apply the new developed seed crystal material in the phosphorus recovery from sludge sidestreams of a wastewater treatment plant. In this crystallization process, the performance the carbon dioxide degassingprocess usually carried out when applying crystallization was not necessary, the hydroxyapatite was able to crystallize at a pH of 8.0 to 8.5 without precipitation of calcium carbonates. In the treatment of a sidestream with orthophosphate concentrations of 50 mgl(-1) and COD concentrations between 200 to 400 mgl(-1), phosphorus removal efficiencies ranging from 75 to 85% were observed. The seed crystal material was collected after the laboratory experiments and the chemical estimation and the germination test for agricultural reuse were performed. As a result, it was shown that the hydroxyapatite precipitated on the seed material had a 100% fusibility to soil and had characteristics to be a good nutrient source as a fertilizer for plants. PMID:11804345

Moriyama, K; Kojima, T; Minawa, Y; Matsumoto, S; Nakamachi, K

2001-11-01

31

Crystal growth of calcium carbonate on the cellulose acetate/pyrrolidon blend films in the presence of L-aspartic acid  

NASA Astrophysics Data System (ADS)

The morphogenesis and growth process of calcium carbonate on the cellulose acetate/polyvinyl pyrrolidone (CA/PVP) blend films in the presence of L-aspartic acid was carefully investigated. The results showed that the concentration of L-aspartic acid, the initial pH value of reaction solution and temperature turned out to be important factors for the control of morphologies and polymorphs of calcium carbonate. Complex morphologies of CaCO3 particles, such as cubes, rose-like spheres, twinborn-spheres, cone-like, bouquet-like, etc. could be obtained under the different experimental conditions. The dynamic process of formation of rose-like sphere crystals was analyzed by monitoring the continuous morphological and structural evolution and components of crystals in different crystal stages. This research may provide a promising method to prepare other inorganic materials with complex morphologies.

Zhang, Xiuzhen; Xie, Anjian; Huang, Fangzhi; Shen, Yuhua

2014-03-01

32

The structural consequences of calcium crystal deposition.  

PubMed

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

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

2014-05-01

33

Calcium carbonate crystallizations on hypogean mural paintings: a pilot study of monitoring and diagnostics in Roman catacombs  

NASA Astrophysics Data System (ADS)

One of the deterioration processes affecting mural paintings and rock surfaces within manmade hypogea consists in the formation of calcium carbonate crystallizations, which can create thick coverage and incrustations, even in some cases speleothems. These chemical reactions necessarily require the availability of calcium sources, which can be also of anthropogenic origin (e.g., lime-based mortars). Microclimate parameters also represent environmental forcing factors, on which the morphology and the degree of crystallinity of the precipitated carbonates depend. Understanding past/recent dynamics of carbonate precipitation implies a deep knowledge of the relationships between the exposed surfaces and the microclimate conditions, the impacts of external factors (e.g., groundwater infiltration and percolation from the overlying soil) and how they change over time. This is particularly fundamental for the preservation of hypogean sites which have not comparison with other typologies of environment due to their uniqueness, such as the ancient catacombs carved underneath the suburbs of Rome (Italy), since the 2nd century AD. In this paper we present the multidisciplinary methodological approach designed for the instrumental monitoring of the microphysical environment of the Catacombs of Saints Mark, Marcellian and Damasus, in the framework of the co-operation between the Institute for the Conservation and Valorization of Cultural Heritage and Pontifical Commission for Sacred Archaeology, Vatican, on the project HYPOGEA. Temperature inside the catacomb and on the surfaces, air relative humidity and CO2 concentration are the main of the parameters continuously measured by means of data loggers installed within the cubicles. Contemporarily, standardized methods of photographic documentation and digital micro-photogrammetry are used for change detection analysis of the painted surfaces and ancient plasters, as well as of the test areas purposely realized by applying fresh lime mortars simulating the former surfaces. Parallel laboratory investigations (e.g., diamond anvil cell FT-IR spectroscopy, X-ray diffraction, thin section observations under polarized light microscope, conventional microbiological investigations) are complementarily employed to characterize the calcite crystallizations, in terms of compositional, textural and mineralogical properties. Hence, it is expected to find a correlation between the microclimate conditions and the degree of crystallinity and morphology of the incrustations developed on the surfaces of the fresh samples. A specific study of the stratigraphic sequence of the calcite crystallizations already formed on the ancient surfaces is also included, to perform a back-analysis of the microclimate variations inside the cubicles through centuries of use and abandonment. In this regard, the precise knowledge of the conservation history of the monitored cubicles is adopted as a temporal guide to hypothesize the time frames, to which the observed strata are presumably to be referred. The main outcome of this pilot study is the establishment of a methodological approach suitable for the monitoring of crystallization phenomena inside catacombs, to be potentially exported to similar contexts. The findings of the research will also constitute the scientific base for the design of the most appropriate measures of environmental conditioning, also in the perspective to open the catacombs to visitors.

Tapete, D.; Fratini, F.; Mazzei, B.; Camaiti, M.; Cantisani, E.; Riminesi, C.; Manganelli Del Fà, R.; Cuzman, O.; Tiano, P.

2012-04-01

34

Transformation of amorphous calcium carbonate into aragonite  

NASA Astrophysics Data System (ADS)

Amorphous calcium carbonate (ACC) is one of the important precursors of calcium carbonate crystal phases and its transformation plays key roles in biomineralization. In this paper, the transformation of ACC is studied in the presence of magnesium ion, which often appears in the crystallization of calcium carbonate. We use powder X-ray diffraction, Fourier transformed infrared (FTIR) spectroscopy and scanning electron microscopy to monitor this transformation process and find that in high Mg2+ environment, there appears a transformation process with multiple-step self-assembly from ACC into aragonite. To the best of our knowledge, it is the first time the growth of aragonite via the nano-crystal particles assembly and transformation has been discovered, which may have a great significance in understanding the mystery of aragonite formation in an ocean.

Zhang, Zhuona; Xie, Yidong; Xu, Xurong; Pan, Haihua; Tang, Ruikang

2012-03-01

35

DISSOLUTION AND CRYSTALLIZATION OF CALCIUM SULFITE PLATELETS  

EPA Science Inventory

The paper discusses the dissolution and crystallization of calcium sulfite platelets. The rates of calcium sulfite dissolution and crystallization are important in slurry scrubbing processes for flue gas desulfurization. The rates affect the scrubber solution composition, SO2 abs...

36

Zeta potential measurement of calcium carbonate  

Microsoft Academic Search

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

P. Moulin; H. Roques

2003-01-01

37

Phase transitions in biogenic amorphous calcium carbonate  

NASA Astrophysics Data System (ADS)

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

Gong, Yutao

38

Far infrared (THz) absorption spectra for the quantitative differentiation of calcium carbonate crystal structures: Exemplified in mixtures and in paper coatings  

NASA Astrophysics Data System (ADS)

In this paper, far-infrared (FIR) spectroscopic techniques have been employed to detect different calcium carbonate crystal concentrations in powder mixtures. We have compared absorption spectral features of both pure and mixtures of natural ground calcium carbonate (GCC) and synthetic precipitated calcium carbonate (PCC). It is evident that the absorbance data differentiate clearly and unequivocally between calcite and aragonite in the spectral range of 2-18 THz. Also, from the absorbance measurement of two sets of mixtures, we have revealed a linear relationship between the ratio of some selected absorbance peaks of the mixtures and concentration of a particular pigment within the mixture. This innovative technique could be a novel, practicable technique for quality control or for analyzing coating and/or filler pigments and extenders in the paper making and printing industries. Finally, we have proven in the case of paper that, surface roughness and print color play no role as far as the locations and magnitudes of the absorbance spectral features are concerned.

Bawuah, Prince; Kiss, Márton Zsolt; Silfsten, Pertti; Tåg, Carl-Mikael; Gane, Patrick A. C.; Peiponen, Kai-Erik

2014-05-01

39

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

40

Immunolocalization of an acid phosphatase from pearl oyster (Pinctada fucata) and its in vitro effects on calcium carbonate crystal formation.  

PubMed

Distribution of an acid phosphatase, AcPase I, from pearl oyster (Pinctada fucata) in different tissues was investigated via enzyme activity determination and immunohistochemistry. Positive reactions were observed in sections of digestive gland, base of gill filaments, and epithelia of the outer side of the middle fold and the inner side of the outer fold, which indicated AcPase I might participate in processes besides immune defense, such as calcium metabolism or shell formation. Its effects on CaCO(3) crystal formation were studied in vitro. Results revealed that AcPase I inhibited CaCO(3) precipitation in a dose-dependent manner and had no affinity for calcium. CaCO(3) crystals induced by AcPase I exhibited a cluster needle-like morphology, which proved to be aragonite. The morphology and size of the aragonites varied with different concentrations of AcPase I. Our observations described here may provide important clues to further understanding of the correlations between mineralization and immune defense in the oyster. PMID:17619219

Jing, Gu; Yan, Zhenguang; Li, Yu; Xie, Liping; Zhang, Rongqing

2007-01-01

41

Induction of carbonic anhydrase in SaOS-2 cells, exposed to bicarbonate and consequences for calcium phosphate crystal formation.  

PubMed

Ca-phosphate/hydroxyapatite crystals constitute the mineralic matrix of vertebrate bones, while Ca-carbonate dominates the inorganic matrix of otoliths. In addition, Ca-carbonate has been identified in lower percentage in apatite crystals. By using the human osteogenic SaOS-2 cells it could be shown that after exposure of the cells to Ca-bicarbonate in vitro, at concentrations between 1 and 10 mm, a significant increase of Ca-deposit formation results. The crystallite nodules formed on the surfaces of SaOS-2 cells become denser and larger in the presence of bicarbonate if simultaneously added together with the mineralization activation cocktail (?-glycerophosphate/ascorbic acid/dexamethasone). In parallel, with the increase of Ca-deposit formation, the expression of the carbonic anhydrase-II (CA-II) gene becomes upregulated. This effect, measured on transcriptional level is also substantiated by immunohistological studies. The stimulatory effect of bicarbonate on Ca-deposit formation is prevented if the carbonic anhydrase inhibitor acetazolamide is added to the cultures. Mapping the surface of the Ca-deposit producing SaOS-2 cells by scanning electron microscopy coupled with energy-dispersive X-ray analysis revealed an accumulation of the signals for the element carbon and, as expected, also for phosphorus. Finally, it is shown that ortho-phosphate and hydrolysis products of polyphosphate inhibit CA-II activity, suggesting a feedback regulatory system between the CA-driven Ca-carbonate deposition and a subsequent inactivation of this process by ortho-phosphate. Based on the presented data we suggest that Ca-carbonate deposits act as bioseeds for a downstream Ca-phosphate deposition process. We propose that activators for CA, especially for CA-II, might be beneficial for the treatment of bone deficiency diseases. PMID:23953824

Müller, Werner E G; Schröder, Heinz C; Schlossmacher, Ute; Grebenjuk, Vlad A; Ushijima, Hiroshi; Wang, Xiaohong

2013-11-01

42

Calcium Oxalate Crystals in Eucalypt Ectomycorrhizae: Morphochemical Characterization  

PubMed Central

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.

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

2013-01-01

43

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

2013-01-01

44

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

45

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

PubMed

Stimulation of microbially induced calcium carbonate precipitation (MICCP) is likely to be influenced by calcium sources. In order to study such influences, we performed MICCP using Bacillus sp. CR2 in nutrient broth containing urea, supplemented with different calcium sources (calcium chloride, calcium oxide, calcium acetate and calcium nitrate). The experiment lasted 7 days, during which bacterial growth, urease activity, calcite production and pH were measured. Our results showed that calcium chloride is the better calcium source for MICCP process, since it provides higher urease activity and more calcite production. The influences of calcium sources on MICCP were further studied using Fourier transform-infrared (FTIR) spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. These analyses confirmed that the precipitate formed was CaCO3 and composed of predominantly calcite crystals with a little amount of aragonite and vaterite crystals. The maximum yield of calcite precipitation was achievable with calcium chloride followed by calcium nitrate as a calcium source. The results of present study may be applicable to media preparation during efficient MICCP process. PMID:24643454

Achal, Varenyam; Pan, Xiangliang

2014-05-01

46

Influence of calcium ions on the crystallization of sodium bicarbonate  

NASA Astrophysics Data System (ADS)

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 Ca 2+ role in NaHCO 3 crystallization would be helpful for improving the quality of the final products. The influence of calcium ions on NaHCO 3 crystallization was investigated in a 5-l mixed suspension mixed product removal crystallizer under controlled conditions. A density meter was used for continuous supersaturation monitoring. After a steady state had been reached, different CaCl 2 amounts were added at a constant flow rate. It was found that limited calcium ion levels in the system reduce drastically the nucleation frequency of NaHCO 3 and has a limited influence on crystal growth rate. The supersaturation measurements and other methods confirmed this phenomenon. The relationship between the Ca 2+ influence on NaHCO 3 crystallization, the calcium carbonate solubility and its metastable zone in concentrated NaHCO 3 solution was established. In fact, Ca 2+ has a maximum effect on NaHCO 3 crystallization kinetics when the saturation of calcium carbonate in NaHCO 3 solution has been reached, and the effect is constant in the metastable zone. The excess of Ca 2+ precipitates in NaHCO 3 solution as CaCO 3, as observed by energy dispersive X-ray and X-ray diffraction. This explained why an increasing Ca 2+ concentration in the solution has a limited influence on NaHCO 3 crystal size distribution and habit, but decreases the crystal purity. It is also confirmed that an impurity as Ca 2+ has no influence on the equilibrium NaHCO 3-Na 2CO 3.

Zhu, Yi; Demilie, Paul; Davoine, Perrine; Cartage, Thierry; Delplancke-Ogletree, Marie-Paule

2005-02-01

47

Nucleation and crystallization in calcium aluminate glasses  

Microsoft Academic Search

The crystallization and nucleation mechanisms of a eutectic composition (46.5 wt% CaO, 53.5 wt% Al2O3) calcium aluminate glass were investigated by DTA, XRD and SEM. The crystallization temperature was found to vary from 940°C to 1040°C, and two phases appeared in the crystallized samples: Ca12Al14O33 (major phase) and CaAl2O4 (minor phase). Two kinds of crystal structures, dendritic and spherulitic, were

Wenyan Li; Brian S. Mitchell

1999-01-01

48

Calcium Carbonate and Its Hydrates  

Microsoft Academic Search

This paper is concerned with observations on the preparation of phases which may exist in the system CaCO3-H2O in the presence of 'additives', with a qualitative explanation of the appearance of unstable phases under such conditions. It has been found that the tendency for metastable phases of calcium carbonate to be precipitated from aqueous solutions is increased not only by

R. Brooks; L. M. Clark; E. F. Thurston

1950-01-01

49

Physicochemical characterization of calcium strontium tartrate crystals  

Microsoft Academic Search

Mixed single crystals of calcium strontium tartrate (CST) of high optical quality and morphological perfection have been grown from light irradiated sodium meta silicate gel medium at ambient temperature. The results obtained on characterization of CST crystals using EDX, chemical analysis, X-ray diffraction and infra-red spectral techniques are reported. A thermogravimetric study is carried out in order to study the

K. Suryanarayana; S. M. Dharmaprakash

1997-01-01

50

Spinning up the polymorphs of calcium carbonate  

NASA Astrophysics Data System (ADS)

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

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

2014-01-01

51

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

52

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

53

Control the polymorphism and morphology of calcium carbonate precipitation from a calcium acetate and urea solution  

Microsoft Academic Search

Two metastable calcium carbonate polymorphs, rod-like aragonite and spherical vaterite are selectively formed in this study. Aragonite rods were synthesized from a calcium acetate (Ca(AC)2) and urea (CO(NH2)2) solution under a given condition. In contrast, the addition of polyacrylamide (PAM) and oleic acid results in the formation of spherical vaterite. The morphology, size and crystal structure were characterized by means

Chengyu Wang

2008-01-01

54

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

55

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

56

Absence of rebound effect with calcium carbonate  

Microsoft Academic Search

Summary  This was an open, randomised, balance cross-over study in 12 healthy male volunteers. The antacid activity of calcium carbonate\\u000a plus magnesium carbonate (Rennie®) and hydrotalcite (Talcid®), given in the recommended dose of 2 tablets 4 times daily, were\\u000a compared using 24 h intragastric measurement of pH. The volunteers received 2 tablets of calcium carbonate plus magnesium\\u000a carbonate or hydrotalcite according

G. Simoneau

1996-01-01

57

The crystallization of calcium carbonate on porcine and human cardiac valves and the antimineralization effect of sodium alginate  

NASA Astrophysics Data System (ADS)

The use of biprosthetic valves remains limited, due to poor long-term durability, primarily as a result of tissue calcification. Porcine and human cardiac valve leaflets were found to be a substrate favoring the deposition of vaterite crystals from stable supersaturated solution at pH 8.5 at 25°C. The apparent order for vaterite crystallization reaction was found to be n=1, suggesting a surface diffusion controlled mechanism. The crystallization was studied by the constant composition technique, thus making it possible for relatively large amounts of the overgrowth phase to be formed and identified exclusively as vaterite. Analysis of the initial rates of the reaction as a function of the solution supersaturation, according to the classical nucleation theory, yielded a value of 23.4 mJ m -2 for the surface energy of the growing phase and a three-ion cluster forming the critical nucleus. A novel "in vitro" anticalcification process based on the treatment of porcine and human heart valves with sodium alginate has been developed. This anticalcification procedure reduced mineralization of porcine and human valves up to 53% and 45%, respectively. Kinetic analysis according to a Langmuir type adsorption isotherm lead to the calculation of an affinity constant K aff=19.3×104 mol -1 dm 3 for the adsorption of sodium alginate to the substrate.

Kanakis, J.; Malkaj, P.; Petroheilos, J.; Dalas, E.

2001-03-01

58

Gasification of carbon using calcium oxide  

SciTech Connect

In order to understand the carbon-calcium oxide system in more detail, this study was undertaken to prepare dispersed calcium oxide on Spherocarb supports and to measure the change in crystallinity of the catalyst as well as the amount of carbon gasified at 760/sup 0/C as functions of time. Hence, any changes in catalytic activity of calcium oxide might be correlated with the observed changes in its crystallinity.

zur Loye, H.C.; Kershaw, R.; Dwight, K.; Wold, A.; Pabst, J.K.; Lang, R.J.

1984-01-01

59

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

60

Biosynthesis of L-Ascorbic Acid and Conversion of Carbons 1 and 2 of L-Ascorbic Acid to Oxalic Acid Occurs within Individual Calcium Oxalate Crystal Idioblasts  

Microsoft Academic Search

the pattern OxA . AsA (erythorbic acid) . l-galactose . d-mannose. Our results demonstrate that P. stratiotes crystal idioblasts synthesize the OxA used for crystal formation, the OxA is derived from the number 1 and 2 carbons of AsA, and the proposed pathway of ascorbic acid synthesis via d-mannose and l-galactose is operational in individual P. stratiotes crystal idioblasts. These

Todd A. Kostman; Nathan M. Tarlyn; Frank A. Loewus; Vincent R. Franceschi

2001-01-01

61

Calcium Sulfite Crystal Sizing Studies.  

National Technical Information Service (NTIS)

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 settlin...

L. O. Edwards

1979-01-01

62

Effects of additives and templates on calcium carbonate mineralization in vitro.  

PubMed

The review focuses on the effects of several important additives and templates controlling the calcium carbonate crystals formation and the complexity of the crystal morphologies in vitro. Additives include soluble matrices extracted from shells and pearls, amino-acids, magnesium ions and collagen among others. Templates include modified single crystal silicon, natural biominerals among others. Mechanisms proposed to explain the phenomena are not systematic, further studies are necessary to explain how organic matrices mediate calcium carbonate mineralization. PMID:20951597

Ren, Dongni; Feng, Qingling; Bourrat, Xavier

2011-04-01

63

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

64

On the growth of calcium tartrate tetrahydrate single crystals  

Microsoft Academic Search

Calcium tartrate single crystals were grown using silica gel as the growth medium. Calcium formate mixed with formic acid\\u000a was taken as the supernatant solution. It was observed that the nucleation density was reduced and the size of the crystals\\u000a was improved to a large extent compared to the conventional way of growing calcium tartrate crystals with calcium chloride.\\u000a The

X. Sahaya Shajan; C. Mahadevan

2004-01-01

65

Calcium oxalate crystal growth in human urinary stones  

Microsoft Academic Search

Calcium oxalate stones are very common and increasing. Crystal growth is no less important than the crystal nucleation in the pathogenesis of stone formation. The crystal growth was studied in human calcium oxalate stones by a combined electron microscopy and x-ray diffraction. The main mode of weddellite growth was interpenetration twinning of tetrahedral bipyramids. Bipyramids may form as initial crystal

K. M. Kim; F. B. Johnson

1981-01-01

66

Synthesis of needle-like aragonite from calcium chloride and sparingly soluble magnesium carbonate  

Microsoft Academic Search

Needle-like or branch-like aragonite was prepared from sparingly soluble magnesium carbonate and calcium chloride aqueous solution. The morphology, particle size, and aspect ratio (ratio of length to diameter of the particle) of the aragonite particles were characterized with SEM. The polymorphs and crystal size were characterized with XRD. Comparing with the reactants calcium sulfate and sodium carbonate, which were used

Zeshan Hu; Yulin Deng

2004-01-01

67

Nutrient Requirements and Interactions Bone Repair in Calcium-Deficient Rats: Comparison of Xylitol + Calcium Carbonate with Calcium Carbonate, Calcium Lactate and Calcium Citrate on the Repletion of Calcium1'2'3 i  

Microsoft Academic Search

The potential value of xylitol in calcium therapy was evaluated by comparing the effect of dietary xylitol (50 g\\/kg diet) + calcium carbonate with the ef fects of calcium carbonate, calcium lactate and calcium citrate on bone repair of young male rats after the rats consumed for 3 wk a calcium-deficient diet (0.2 g Ça\\/kg diet). After this calcium-depletion period,

MAURI M. HÃ

68

Hydroxyapatite crystal growth on calcium hydroxyapatite ceramics  

Microsoft Academic Search

Calcium hydroxyapatite (Ca-HAP) ceramics containing tricalcium phosphate (TCP) were soaked in three solutions: phosphate buffer, tris buffer, and simulated body fluid (SBF). Petal-like crystals of Ca-HAP were deposited on the Ca-HAP ceramics when (i) Ca-HAP ceramics contained a-TCP, (ii) the soaking solution contained phosphate ion and (iii) the pH of soaking solution was higher than 7.3. These conditions facilitate the

Masayuki Asada; Yoshinari Miura; Akiyoshi Osaka; Katsutoshi Oukami; Seishiro Nakamura

1988-01-01

69

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

70

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

71

Membrane-associated crystallization of calcium oxalate in vitro  

Microsoft Academic Search

Summary  Incubation of proximal tubular brush border membrane in a metastable calcium oxalate solution of low supersaturation resulted\\u000a in the equimolar depletion of calcium and oxalate and the formation of monoclinic calcium oxalate crystals. We propose that\\u000a membrane fragments from sloughed epithelial cells of the nephron can similarly induce crystallization in urine that is metastable\\u000a for calcium oxalate.

Saeed R. Khan; Paula N. Shevock; Raymond L. Hackett

1990-01-01

72

Precipitation of calcium carbonate from a calcium acetate and ammonium carbamate batch system  

NASA Astrophysics Data System (ADS)

In this paper, we report a novel approach for preparing precipitated calcium carbonate using solutions of ammonium carbamate and calcium acetate as the sources of calcium and carbon dioxide, respectively. Two different concentrations of the starting solutions at three different temperatures (15, 25 and 50 °C) were used for the reaction. The influence of temperature and concentration on the polymorphism and the resulting morphology of calcium carbonate are discussed. The most important parameter for controlling a particular crystal structure and precipitate morphology were the concentrations of the initial solutions. When initial solutions with lower concentrations were used, the crystal form of the precipitate changed with time. Regardless the different polymorphism at different temperatures, after one day only the calcite form was detected in all samples, regardless of at which temperature the samples were prepared. At higher concentrations, pure vaterite or a mixture of vaterite and calcite were present at the beginning of the experiment. After one day, pure vaterite was found in the samples that were prepared at 15 and 25 °C. If calcium carbonate precipitated at 50 °C, the XRD results showed a mixture of calcite and vaterite regardless of the time at which the sample was taken. The morphology of calcium carbonate particles prepared at various conditions changed from calcite cubes to spherical particles of vaterite and aragonite needles. When a low starting concentration was used, the morphology at the initial stage was strongly affected by the temperature at which the experiments were conducted. However, after one day only, cubes were present in all cases at low initial concentrations. In contrast, at high concentrations spherical particles precipitated at all three temperatures at the beginning of the reaction. Spherical particles were made up from smaller particles. Over time, the size of the particles was diminishing due to their disintegration into primary particles; after one day, particles of 30-50 nm were obtained. The lower the temperature was during the experiment, the faster the larger particles fell apart. To our knowledge, this behavior has thus far not yet been reported. Moreover, for the first time ammonium carbamate and calcium acetate are used together to prepare calcium carbonate.

Prah, J.; Ma?ek, J.; Draži?, G.

2011-06-01

73

Crystallization in Carbon Nanostructures  

NASA Astrophysics Data System (ADS)

We investigate ground state configurations for atomic potentials including both two- and three-body nearest-neighbor interaction terms. The aim is to prove that such potentials may describe crystallization in carbon nanostructures such as graphene, nanotubes, and fullerenes. We give conditions in order to prove that planar energy minimizers are necessarily honeycomb, namely graphene patches. Moreover, we provide an explicit formula for the ground state energy which exactly quantifies the lower-order surface energy contribution. This allows us to give some description of the geometry of ground states. By recasting the minimization problem in three-space dimensions, we prove that ground states are necessarily nonplanar and, in particular, rolled-up structures like nanotubes are energetically favorable. Eventually, we check that the C20 and C60 fullerenes are strict local minimizers, hence stable.

Mainini, Edoardo; Stefanelli, Ulisse

2014-06-01

74

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) [Helotes, TX; Dziuk, Jr., Jerome J. (San Antonio, TX)

1989-01-01

75

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

Microsoft Academic Search

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

J Behar; M Hitchings; R D Smyth

1977-01-01

76

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

PubMed

The preparation and application of overbased nanodetergents with excess alkaline calcium carbonate is a good example of nanotechnology in practice. The phase transformation of calcium carbonate is of extensive concern since CaCO(3) serves both as an important industrial filling material and as the most abundant biomineral in nature. Industrially valuable overbased nanodetergents have been prepared based on calcium salts of heavy alkylbenzene sulfonate by a one-step process under ambient pressure, the carbonation reaction has been monitored by the instantaneous temperature changes and total base number (TBN). A number of analytical techniques such as TGA, DLS, SLS, TEM, FTIR, and XRD have been utilized to explore the carbonation reaction process and phase transformation mechanism of calcium carbonate. An enhanced understanding on the phase transformation of calcium carbonate involved in calcium sulfonate nanodetergents has been achieved and it has been unambiguously demonstrated that amorphous calcium carbonate (ACC) transforms into the vaterite polymorph rather than calcite, which would be of crucial importance for the preparation and quality control of lubricant additives and greases. Our results also show that a certain amount of residual Ca(OH)(2) prevents the phase transformation from ACC to crystalline polymorphs. Moreover, a vaterite nanodetergent has been prepared for the first time with low viscosity, high base number, and uniform particle size, nevertheless a notable improvement on its thermal stability is required for potential applications. PMID:21507412

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

2011-07-01

77

Mucins and calcium phosphate precipitates additively stimulate cholesterol crystallization  

Microsoft Academic Search

Human biliary mucin and calcium binding pro- tein (CBP) influence formation of both calcium salt precipi- tates and cholesterol crystals and colocalize in the center of cholesterol gallstones. We investigated how physiological concentrations of these proteins regulate cholesterol crys- tallization in model biles, supersaturated with cholesterol and calcium salts, mimicking pathological human bile. Us- ing polarizing light microscopy and nephelometry

A. A. van den Berg; Buul van J. D; G. N. J. Tytgat; A. K. Groen; J. D. Ostrow

1998-01-01

78

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

PubMed

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

Fuerst, M

2014-06-01

79

Association of calcium oxalate monohydrate crystals with MDCK cells  

Microsoft Academic Search

Association of calcium oxalate monohydrate crystals with MDCK cells. Many factors are presently known which determine the risk of calcium oxalate (CaOx) stone formation in the kidney, although the early events in the pathogenesis of this disease are still to be elucidated. One of these early events is the interaction of intraluminal crystals with the epithelial cells lining the renal

Carl F Verkoelen; Johannes C Romijn; Willem C de Bruijn; Egbert R Boevé; Lu-Cheng Cao; Fritz H Schröder

1995-01-01

80

Strain-Specific Ureolytic Microbial Calcium Carbonate Precipitation  

PubMed Central

During a study of ureolytic microbial calcium carbonate (CaCO3) precipitation by bacterial isolates collected from different environmental samples, morphological differences were observed in the large CaCO3 crystal aggregates precipitated within bacterial colonies grown on agar. Based on these differences, 12 isolates were selected for further study. We hypothesized that the striking differences in crystal morphology were the result of different microbial species or, alternatively, differences in the functional attributes of the isolates selected. Sequencing of 16S rRNA genes showed that all of the isolates were phylogenetically closely related to the Bacillus sphaericus group. Urease gene diversity among the isolates was examined by using a novel application of PCR-denaturing gradient gel electrophoresis (DGGE). This approach revealed significant differences between the isolates. Moreover, for several isolates, multiple bands appeared on the DGGE gels, suggesting the apparent presence of different urease genes in these isolates. The substrate affinities (Km) and maximum hydrolysis rates (Vmax) of crude enzyme extracts differed considerably for the different strains. For certain isolates, the urease activity increased up to 10-fold in the presence of 30 mM calcium, and apparently this contributed to the characteristic crystal formation by these isolates. We show that strain-specific calcification occurred during ureolytic microbial carbonate precipitation. The specificity was mainly due to differences in urease expression and the response to calcium.

Hammes, Frederik; Boon, Nico; de Villiers, Johan; Verstraete, Willy; Siciliano, Steven Douglas

2003-01-01

81

Effect of diphosphonate on crystallization of calcium oxalate in vitro  

Microsoft Academic Search

The effect of diphosphonate on crystallization of calcium oxalate in vitro. Reliable techniques for the calculation of activity product (state of saturation), formation product (limit of metastability) and crystal growth of calcium oxalate were devised. The activity product at saturation was 2.53 × 10–?9M2, and was independent of duration of incubation, solid-to-solution ratio, pH, calcium concentration or ionic strength. These

Charles Y C Pak; Masahiro Ohata; Karen Holt

1975-01-01

82

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

PubMed

Calcium carbonate is widely used as an oral phosphorus binder to control hyperphosphatemia in children on maintenance hemodialysis. Intestinal calcium absorption may induce hypercalcemia, particularly if calcitriol is given simultaneously. In adults, calcium acetate binds phosphorus more effectively than calcium carbonate, while reducing the frequency of hypercalcemic events. We therefore compared calcium acetate with calcium carbonate in nine pediatric patients on long-term maintenance hemodialysis. Following a 1-week withdrawal of phosphorus binders, calcium carbonate was administered for 7 weeks; after a second withdrawal, calcium acetate was given for another 7 weeks. All patients received calcitriol regularly. Both agents lowered the serum phosphorus concentration significantly (calcium carbonate 5.7 +/- 1.4 vs. 7.7 +/- 2.1 mg/ dl, P < 0.005; calcium acetate 5.8 +/- 1.4 vs. 7.8 +/- 2.0 mg/dl, P < 0.005). Significantly less elementary calcium was ingested with calcium acetate than with calcium carbonate: 750 (375-1,500) vs. 1,200 (0-3,000) mg calcium/day, P < 0.0001. Wit calcium carbonate serum calcium increased significantly. The number of episodes of hyperphosphatemia or hypercalcemia did not differ between treatments. Intact plasma parathyroid hormone (PTH) decreased significantly with both phosphate binders, and serum 25-hydroxyvitamin D3 increased. There was a close relationship between serum phosphorus and PTH in prepubertal but not in pubertal patients. We conclude that hyperphosphatemia can be controlled effectively by both calcium acetate and calcium carbonate in pediatric hemodialysis patients. The oral load of elementary calcium is reduced significantly by binding phosphorus with calcium acetate instead of calcium carbonate; nevertheless, hypercalcemic episodes remain equally frequent with both phosphate binders. PMID:8897570

Wallot, M; Bonzel, K E; Winter, A; Geörger, B; Lettgen, B; Bald, M

1996-10-01

83

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

PubMed

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

Ea, Hang-Korng; Lioté, Frédéric

2014-05-01

84

Protein induced morphosynthesis of calcium carbonate  

Microsoft Academic Search

A widespread phenomenon in the biological world is biomineralization, a process by which organisms precipitate inorganic minerals. Over 60 biominerals are known, the most abundant of which are calcium carbonates, silica and iron oxides. These biominerals are organized hierarchically and are ordered at many length scales that reflect remarkable physical characteristics. The theme of the above organic-inorganic interactions, and concepts

S. Nayar; A. Sinha

2003-01-01

85

Effects of functional groups and soluble matrices in fish otolith on calcium carbonate mineralization.  

PubMed

Calcium carbonate mineralization is significantly influenced by organic matrices in vivo. The effect mainly relies on functional groups in proteins. In order to study the influence of functional groups on calcium carbonate mineralization, -OH, -NH2 and -COOH groups were grafted onto single crystal silicon chips, and such modified chips were used as substrates in in vitro mineralization experiments. An x-ray photoelectron spectroscopy (XPS) test was conducted to examine the grafting efficiency, and the three groups were successfully grafted. Calcium carbonate mineralization on a modified silicon substrate was examined by a scanning electron microscope (SEM) and x-ray diffraction (XRD), and the results showed that the effects of -OH, -NH2 and -COOH groups were quite different. Furthermore, a water-soluble protein matrix (WSM) and an acid-soluble protein matrix (ASM) extracted from fish otolith were adsorbed onto the -COOH-modified silicon substrate, and the effects of the protein matrices on calcium carbonate mineralization were studied. The results showed that both WSM and ASM of lapillus could mediate aragonite crystallization, but the size and morphology of the formed crystals were different. The WSM and ASM of asteriscus adsorbed on the silicon substrate had little effect on calcium carbonate mineralization; almost all the crystals were calcite, while both asteriscus WSM and ASM in solution could mediate vaterite crystals, and the morphologies of vaterite crystal aggregates were different. PMID:20844320

Ren, Dongni; Li, Zhuo; Gao, Yonghua; Feng, Qingling

2010-10-01

86

Calcium tartrate crystals in the midgut of the grape leafhopper.  

PubMed

Calcium tartrate crystals were observed in the midgut of grape leafhoppers. This unique compound was found for the first time in insects. The size of the crystals varied strongly between and within individuals with a mean length of 153 +/- 87 microm and a mean width of 71 +/- 46 microm. In addition, the number of crystals per individual showed a broad variation and ranged from 1 to 150 crystals/individual. The occurrence of calcium tartrate crystals as well as the number of crystals per individual followed the same seasonal pattern as seasonal vine leaf concentrations of tartaric acid found in a previous study, indicating that calcium tartrate is formed to neutralize the tartaric acid in the gut system. It further implies that the grape leafhopper, rather than being a pure phloem sucker, employs a mixed feeding strategy to satisfy its demands for calcium uptake. PMID:16365709

Böll, S; Schmitt, T; Burschka, C; Schreier, P; Schwappach, P; Herrmann, J V

2005-12-01

87

Calcium-containing crystals and osteoarthritis: Implications for the clinician  

Microsoft Academic Search

The clinical implication of articular deposits of calciumcontaining crystals (specifically of calcium pyrophosphate dihydrate\\u000a and hydroxyapatite) in osteoarthritis is unknown. Recent longitudinal studies have suggested that in some instances calcium\\u000a crystals are direct participants in cartilage damage, while in other situations they are merely markers of joint damage. Better\\u000a understanding of the mechanisms of crystal formation, especially in relation to

Christopher W. Wu; Robert Terkeltaub; Kenneth C. Kalunian

2005-01-01

88

Aragonite nanorods in calcium carbonate/polymer hybrids formed through self-organization processes from amorphous calcium carbonate solution.  

PubMed

Nanostructured inorganic/polymer hybrid thin films comprising aragonite nanorods derived from aqueous suspensions of amorphous calcium carbonate (ACC) are prepared. For the formation of calcium carbonate (CaCO?)/polymer hybrids, spincoated and annealed films of poly(vinyl alcohol) (PVA) that function as polymer matrices are soaked in aqueous colloidal solutions dispersing ACC stabilized by poly(acrylic acid) (PAA). In the initial stage, calcite thin films form on the surface. Subsequently, aragonite crystals start to form inside the PVA matrix that contains PVA crystallites which induce aragonite nucleation. Nanostructured hybrids composed of calcite thin films consisting of nanoparticles and assembled aragonite nanorods are formed in the matrices of PVA. PMID:24425526

Kajiyama, Satoshi; Nishimura, Tatsuya; Sakamoto, Takeshi; Kato, Takashi

2014-04-24

89

Preparation and Characterization of Calcium Carbonate Nanoparticles  

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 this study, we prepared and characterized calcium carbonate nanoparticle to improve the solubility by using bottom-up method. The experiment was done by titrating calcium chloride with sodium carbonate with the addition of polyvinylpyrrolidone (PVP) as stabilizer, using ultra-turrax. Various concentrations of calcium chloride and sodium carbonate as well as various speed of stirring were used to prepare the calcium carbonate nanoparticles. Evaluations studied were including particle size, polydispersity index (PI) and zeta potential with particle analyzer, surface morphology with scanning electron microscope, and saturated solubility. In addition, to test the ability of PVP to prevent particles growth, short stability study was performed by storing nano CaCO3 suspension at room temperature for 2 weeks. Results show that using 8000 rpm speed of stirring, the particle size tends to be bigger with the range of 500-600 nm (PI between 0.2-0.4) whereas with stirring speed of 4000 rpm, the particle size tends to be smaller with 300-400 nm (PI between 0.2-0.4). Stirring speed of 6000 rpm produced particle size within the range of 400-500 nm (PI between 0.2-0.4). SEM photograph shows that particles are monodisperse confirming that particles were physically stable without any agglomeration within 2 weeks storage. Taken together, nano CaCO3 is successfully prepared by bottom-up method and PVP is a good stabilizer to prevent the particle growth.

Hassim, Aqilah; Rachmawati, Heni

2010-10-01

90

Raising Urinary Citrate Lowers Calcium Oxalate and Calcium Phosphate Crystal Formation in Whole Urine  

Microsoft Academic Search

Crystal formation in whole urine was studied by the technique of rapid evaporation to 1,250 mosmol\\/l with and without raising citrate concentration by 40–50%. The added citrate reduced calcium oxalate crystal formation at pH 5.3 by about 25 % and reduced calcium phosphate crystal formation at pH 6.8 by some 42%. These results support the view that citrate is important

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

1983-01-01

91

Carbon Nanotube Nucleated Polymer Crystallization  

Microsoft Academic Search

Crystallinity studies were performed on carbon nanotube?doped Poly(m?phenylenevinylene?co?2,5?dioctyloxy?p?phenylenevinylene) (PmPV) and Poly (vinyl alcohol) (PVOH). Differential Scanning Calorimetry (DSC) of the composites verified that carbon nanotubes nucleate polymer crystallization.

K. P. Ryan; M. Cadek; A. Drury; M. Ruether; W. J. Blau; J. N. Coleman

2005-01-01

92

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

93

Studies on calcium oxalate monohydrate crystallization: influence of inhibitors.  

PubMed

A simple model to study calcium oxalate monohydrate (COM) crystallization on different substrates is presented and the action of different potential inhibitors is evaluated and discussed. COM heterogeneous nucleation was assayed on solid surfaces as calcium phosphate, mixtures of mucin with calcium phosphate, and wax. In the presence of a non-protected non-renewed solid surface in contact with normal urine, COM crystal formation could be detected at short intervals (3 h). The most active heterogeneous nucleation capacity corresponded to calcium phosphate. In the presence of 10% mucin, owing to the renewal of the surface layer no COM crystal were detected on the pellet's surface. The study of citrate and pentosan polysulphate (a semisynthetic polysaccharide) on COM heterogeneous nucleation demonstrated some important inhibitory effects when concentration increased and time decreased. Maximum effects were selectively manifested on calcium phosphate surfaces. Only phytic acid at adequate concentration exhibited a total inhibitory capacity of COM formation, even during longer intervals (15 h). PMID:7521089

Grases, F; Kroupa, M; Costa-Bauzá, A

1994-01-01

94

Precipitation of calcium carbonate from a calcium acetate and ammonium carbamate batch system  

Microsoft Academic Search

In this paper, we report a novel approach for preparing precipitated calcium carbonate using solutions of ammonium carbamate and calcium acetate as the sources of calcium and carbon dioxide, respectively. Two different concentrations of the starting solutions at three different temperatures (15, 25 and 50°C) were used for the reaction. The influence of temperature and concentration on the polymorphism and

J. Prah; J. Macek; G. Drazic

2011-01-01

95

Taylor vortex effect on flocculation of hairy crystals of calcium lactate in anti-solvent crystallization  

NASA Astrophysics Data System (ADS)

A Taylor vortex flow was applied to inhibit the crystal flocculation of calcium lactate in anti-solvent crystallization. When using a conventional MSMPR crystallizer, hairy crystals of calcium lactate were formed and flocculated in the crystallizer. The whole suspension in the crystallizer then gelated and the solution trapped in the flocculated crystals was hardly removable from the gelated suspension. Thus, no purification of calcium lactate was achievable when using anti-solvent crystallization in the MSMPR crystallizer, regardless of a batch or continuous operating mode. In contrast, when using a Couette-Taylor (CT) crystallizer, short needle crystals (about 40 ?m) were produced and their flocculation/entanglement was completely prevented. Due to the effective mixing of the Taylor vortex, a high supersaturation was induced in the inlet region of the CT crystallizer, thereby nucleating a high number of needle crystals. This then restricted any one-dimensional overgrowth of crystals, preventing the formation of hairy crystals. According to this mechanism, the mean crystal size was reduced when increasing the rotation speed of the CT crystallizer, the feed concentration, and flow rate. Moreover, the recovery ratio of calcium lactate crystals in the CT crystallizer was always greater than 83% and depended most significantly on the feed flow rate.

Lee, Sooyun; Lee, Choul-Ho; Kim, Woo-Sik

2013-06-01

96

The roles of water and polyelectrolytes in the phase transformation of amorphous calcium carbonate  

NASA Astrophysics Data System (ADS)

Amorphous calcium carbonate (ACC) is a metastable phase of calcium carbonates and it is a precursor during the biomineralization of calcium carbonate in nature. Different ACC in the absence and presence of the additives of poly(sodium 4-styrene sulfonate) and poly(acrylic acid) were prepared and their transformation processes under controls of water were investigated. It was found that ACC powders generally contained about 15% water. Two different transformations via thermal and solution pathways were studied in the present work. We found that water was released from the ACC samples when the temperature was above 100 °C and the calcium carbonate began to crystallize at around 270-400 °C, which resulted the calcite crystals. The involvement of the polymer additives could inhibit this crystallization process and the crystallization temperature shifted to the higher values. During the solution transformation, the evolution steps of the ACC in different water-ethanol solution were monitored by FT-IR. In this case, water could accelerate the transformation and crystallization of ACC. An increasing of the water amount in the mixed solvents always led to the promotion of the transformation kinetics. Interestingly, the other metastable crystal phases of calcium carbonates, vaterite and aragonite, were readily to be induced during the solution transformation of ACC when the low water amounts were applied. However, water could still make them turned into the stable calcite phase with the experimental time prolonged. Since the additives influenced the transformation of ACC and inhibited the transformation of metastable crystal phase, they could be used to stabilize different phases of calcium carbonates in the solutions. The current experimental results confirmed that the controls of water amount and additives played important roles in the transformation of ACC.

Xu, Xu-Rong; Cai, An-Hua; Liu, Rui; Pan, Hai-Hua; Tang, Rui-Kang; Cho, Kilwon

2008-08-01

97

Calcium carbonate precipitation by marine bacteria  

Microsoft Academic Search

Calcium carbonate precipitation by bacterial activity was noted in seawater collected from offshore Bermuda as well as from Halifax Harbor, provided that a minimum of 70 mg\\/liter of organic matter was added in addition to trimethylamine?N?oxide (TMAO) or sodium nitrate (final minimum concentrations, 1.33 and 0.17 g\\/liter, respectively). Observations made during these investigations indicated that the pH was the most

James A. Novitsky

1981-01-01

98

Calcium oxalate crystal growth in human urinary stones  

SciTech Connect

Calcium oxalate stones are very common and increasing. Crystal growth is no less important than the crystal nucleation in the pathogenesis of stone formation. The crystal growth was studied in human calcium oxalate stones by a combined electron microscopy and x-ray diffraction. The main mode of weddellite growth was interpenetration twinning of tetrahedral bipyramids. Bipyramids may form as initial crystal seeds, develop from anhedral crystals (crystals which lack flat symmetric faces) of spherular or mulberry shape, develop on the surface of preformed bipyramids by spiral dislocation mechanisms, or develop on whewellite crystal by heterogeneous nucleation and epitaxy. Heterogeneous nucleations of whewellite on weddellite, and calcium apatite on whewellite were also observed. Whewellite grew mainly by parallel twinning. Interpenetration twinning was exceptional. Transformation of anhedral to euhedral (completely bounded by flat faces that are set ar fixed angles to one another) whewellite occurred by parallel fissurations followed by brick wall like stacking of the crystals, while euhedral transformation of weddellite occurred by protrusion of bipyramids frm anhedral crystal surface. Occasionally, an evidence of crystal dissolution was noted. Although an aggregation of crystals is believed to play a pivotal role in stone nidus formation, growth in size of the formed crystals, and twinning and epitactic crystal intergrowth apparently play a significant role in the obstructive urinary stone formation.

Kim, K.M.; Johnson, F.B.

1981-01-01

99

Structural and spectroscopic studies on calcium succinate single crystals  

NASA Astrophysics Data System (ADS)

Calcium succinate crystals have been grown by gel aided solution growth technique. The structure of the crystal is solved by single crystal XRD analysis. The Crystal structure of the title compound is triclinic having space group P(1) Powder XRD studies confirmed the good crystalline nature of the sample. The different functional groups and their assigned vibrations are discussed by FT-IR and FT Raman spectroscopic studies.

Binitha, M. P.; Pradyumnan, P. P.

2014-04-01

100

Substitution of dietary calcium chloride for calcium carbonate reduces urinary ph and urinary phosphorus excretion in adult cats  

Microsoft Academic Search

In a 4×4?vvk cross?over study, eight adult cats were given four moist diets containing identical amounts of calcium (13.9 mmol\\/MJ) but with different ratios of calcium carbonate to calcium chloride, the calcium salts providing half of the total dietary calcium. Increasing amounts of calcium chloride were substituted for equimolar amounts of calcium carbonate. Higher intakes of calcium chloride caused significantly

F. J. H. Pastoor; R. Opitz; A. Th. Van ‘t Klooster; A. C. Beynen

1994-01-01

101

Differentiation of Calcium Carbonate Polymorphs by Surface Analysis Techniques - An XPS and TOF-SIMS study  

PubMed Central

Calcium carbonate has evoked interest owing to its use as a biomaterial, and for its potential in biomineralization. Three polymorphs of calcium carbonate, i.e. calcite, aragonite, and vaterite were synthesized. Three conventional bulk analysis techniques, Fourier transform infrared (FTIR), X-ray diffraction (XRD), and SEM, were used to confirm the crystal phase of each polymorphic calcium carbonate. Two surface analysis techniques, X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectroscopy (TOF-SIMS), were used to differentiate the surfaces of these three polymorphs of calcium carbonate. XPS results clearly demonstrate that the surfaces of these three polymorphs are different as seen in the Ca(2p) and O(1s) core-level spectra. The different atomic arrangement in the crystal lattice, which provides for a different chemical environment, can explain this surface difference. Principal component analysis (PCA) was used to analyze the TOF-SIMS data. Three polymorphs of calcium carbonate cluster into three different groups by PCA scores. This suggests that surface analysis techniques are as powerful as conventional bulk analysis to discriminate calcium carbonate polymorphs.

Ni, Ming; Ratner, Buddy D.

2013-01-01

102

DETERMINATION OF CALCIUM AND MAGNESIUM CARBONATES IN SOIL  

Microsoft Academic Search

For determining the alkaline earth carbonate conteni of calcareous soils ; by the present methods, calcium and magnesium carbonates are measured together ; and results are expressed as calcium carbonate equivalent. A new method has been ; devised for the determination of each compound separately. It involves the use ; of Ca⁴⁵ and a cation exchange resin. The method is

Amer

1959-01-01

103

Calcium Tartrate Crystals in the Midgut of the Grape Leafhopper  

Microsoft Academic Search

Calcium tartrate crystals were observed in the midgut of grape leafhoppers. This unique compound was found for the first time\\u000a in insects. The size of the crystals varied strongly between and within individuals with a mean length of 153 ± 87 ?m and\\u000a a mean width of 71 ± 46 ?m. In addition, the number of crystals per individual showed a broad

S. Böll; T. Schmitt; C. Burschka; P. Schreier; P. Schwappach; J. V. Herrmann

2005-01-01

104

Bridgman growth of large-aperture yttrium calcium oxyborate crystal  

SciTech Connect

Highlights: ? YCOB is a novel non-linear optical crystal possessing good thermal, mechanical and nonlinear optical properties. ? Large size crystal growth is key technology question for YCOB crystal. ? YCOB crystals 3 in. in diameter were grown with modified vertical Bridgman method. ? It is a more effective growth method to obtain large size and high quality YCOB crystal. -- Abstract: Large-aperture yttrium calcium oxyborate YCa{sub 4}O(BO{sub 3}){sub 3} (YCOB) crystals with 3 in. in diameter were grown with modified vertical Bridgman method, and the large crystal plate (63 mm × 68 mm × 20 mm) was harvested for high-average power frequency conversion system. The crack, facet growth and spiral growth can be effectively controlled in the as-grown crystal, and Bridgman method displays more effective in obtain large size and high quality YCOB crystal plate than Czochralski technique.

Wu, Anhua, E-mail: wuanhua@mail.sic.ac.cn [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China); Jiang, Linwen; Qian, Guoxing; Zheng, Yanqing; Xu, Jun; Shi, Erwei [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)] [Shanghai Institute of Ceramics, Chinese Academy of Sciences, 1295 Dingxi Road, Shanghai 200050 (China)

2012-09-15

105

Preparation of porosity-controlled calcium carbonate by thermal decomposition of volume content-variable calcium carboxylate derivatives.  

PubMed

We demonstrate a novel approach for synthesizing porosity-controlled calcium carbonate by one-step thermal decomposition of various calcium carboxylate derivatives as well as their mixtures with different molar ratios. By varying the volume content of calcium in the calcium compounds or mixtures, the resulting porous calcium carbonate exhibits distinct porosity and structures that are very promising for various applications. PMID:22935875

Yu, Hai-Dong; Tee, Si Yin; Han, Ming-Yong

2013-05-14

106

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

107

Calcium Acetate versus Calcium Carbonate as Phosphate Binders in Hemodialysis Patients  

Microsoft Academic Search

We conducted a randomized unblinded parallel clinical trial to compare the effectiveness, side effects and tolerance between calcium acetate (CA) and calcium carbonate (CC) in 80 stable chronic hemodialysis patients selected on the basis of their acceptable control of serum phosphorus (P) levels with aluminum hydroxide (AH). All patients were dialyzed against the same calcium dialyzate (1.62 mmol\\/l). The serum

F. Caravaca; I. Santos; J. J. Cubero; J. F. Esparrago; M. Arrobas; J. L. Pizarro; R. Robles; E. Sanchez-Casado

1992-01-01

108

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

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

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

111

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

112

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

113

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

Code of Federal Regulations, 2013 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....

2013-07-01

114

Bivalves build their shells from amorphous calcium carbonate  

NASA Astrophysics Data System (ADS)

One of the most common shell structures in the bivalve class is the prism and nacre structure. It is widely distributed amongst both freshwater and marine species and gives cultured pearls their sought-after lustre. In freshwater bivalves, both shell structures (prism and nacre) consist of aragonite. Formation of the shell form an amorphous precursor phase is a wide-spread strategy in biomineralization and presents a number of advantages for the organisms in the handling of the CaCO3 material. While there is already evidence that larval shells of some mollusk species use amorphous calcium carbonate (ACC) as a transient precursor phase for aragonite, the use of this strategy by adult animals was only speculated upon. We present results from in-situ geochemistry, Raman spectroscopy and focused-ion beam assisted TEM on three species from two different bivalve families that show that remnants of ACC can be found in shells from adult species. We show that the amorphous phase is not randomly distributed, but is systematically found in a narrow zone at the interface between periostracum and prism layer. This zone is the area where spherulitic CaCO3- structures protrude from the inner periostracum to form the initial prisms. These observations are in accordance with our earlier results on equivalent structures in freshwater cultured pearls (Jacob et al., 2008) and show that the original building material for the prisms is amorphous calcium carbonate, secreted in vesicles at the inner periostracum layer. Quantitative temperature calibrations for paleoclimate applications using bivalve shells are based on the Mg-Ca exchange between inorganic aragonite (or calcite) and water. These calibrations, thus, do not take into account the biomineral crystallization path via an amorphous calcium carbonate precursor and are therefore likely to introduce a bias (a so-called vital effect) which currently is not accounted for. Jacob et al. (2008) Geochim. Cosmochim. Acta 72, 5401-5415

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

2012-04-01

115

The influence of magnetic fields on calcium carbonate precipitation  

Microsoft Academic Search

Laboratory experiments were undertaken to assess the effects of magnetic treatment on calcium carbonate precipitate. Static test solutions of calcium chloride, calcium sulphate and sodium carbonate were placed in a magnetic field. After magnetic treatment the solutions CaCl2\\/Na2CO3 and CaSO4\\/Na2CO3 were mixed and changes in precipitation recorded and compared with non-magnetised solutions. The results of this study support earlier work

Rebecca A Barrett; Simon A Parsons

1998-01-01

116

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

117

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

118

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

PubMed

Mollusks shell formation is mediated by matrix proteins and many of these proteins have been identified and characterized. However, the mechanisms of protein control remain unknown. Here, we report the ubiquitylation of matrix proteins in the prismatic layer of the pearl oyster, Pinctada fucata. The presence of ubiquitylated proteins in the prismatic layer of the shell was detected with a combination of western blot and immunogold assays. The coupled ubiquitins were separated and identified by Edman degradation and liquid chromatography/mass spectrometry (LC/MS). Antibody injection in vivo resulted in large amounts of calcium carbonate randomly accumulating on the surface of the nacreous layer. These ubiquitylated proteins could bind to specific faces of calcite and aragonite, which are the two main mineral components of the shell. In the in vitro calcium carbonate crystallization assay, they could reduce the rate of calcium carbonate precipitation and induce the calcite formation. Furthermore, when the attached ubiquitins were removed, the functions of the EDTA-soluble matrix of the prismatic layer were changed. Their potency to inhibit precipitation of calcium carbonate was decreased and their influence on the morphology of calcium carbonate crystals was changed. Taken together, ubiquitylation is involved in shell formation. Although the ubiquitylation is supposed to be involved in every aspect of biophysical processes, our work connected the biomineralization-related proteins and the ubiquitylation mechanism in the extracellular matrix for the first time. This would promote our understanding of the shell biomineralization and the ubiquitylation processes. PMID:22558208

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

2012-01-01

119

Ubiquitylation Functions in the Calcium Carbonate Biomineralization in the Extracellular Matrix  

PubMed Central

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

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

2012-01-01

120

The effect of carboxymethyl chitosan on the precipitation of calcium carbonate  

Microsoft Academic Search

It is believed that chitosan plays an important role on the formation of specific inorganic–organic hybrid structure of shells. In this paper, insoluble chitoan was modified to a water-soluble macromolecule—carboxymethyl chitosan (CMCS), and further used as an additive in the crystallization process of calcium carbonate (CaCO3). The combination investigation of XRD, Micro FT-IR and SEM on the precipitated crystals shows

P. Liang; Ying Zhao; Qiang Shen; Dujin Wang; Duanfu Xu

2004-01-01

121

Physicochemical characteristics of Ba 2+ mixed calcium tartrate crystals  

Microsoft Academic Search

Non-linear optical single crystals of barium mixed calcium tartrate tetrahydrate with molecular formula Ca0.8Ba0.2C4H4O6·4H2O (CBT) have been grown in gels using a chemical reaction method at ambient temperature. The physical and chemical characteristics of gel grown CBT crystals have been investigated by employing Vickers micro hardness, etching, and thermal techniques. The single crystalline habit of CBT is deviated from that

K Suryanarayana; S. M Dharmaprakash

2002-01-01

122

Stability of calcium carbonate and magnesium carbonate in rainwater and nitric acid solutions  

Microsoft Academic Search

Carbonation of magnesium and calcium silicates has emerged as an interesting option for long term storage of captured CO2. However, carbonated minerals are not stable in acidic environments. This study was conducted to determine if synthetically carbonated minerals dissolve in acidic rain and release CO2. Synthetic magnesium and calcium carbonates were leached in nitric acid solutions of various acidities, as

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

2006-01-01

123

Calcium Oxide Matrices and Carbon Dioxide Sensors  

PubMed Central

Homogeneous matrices of calcium oxide (CaO) were prepared by mixing this material with polyethylene glycol (PEG) acting as malleable inert support in order to obtain processable composites. Preliminary tests were carried out to assess the best concentration of CaO in the composite, individuated in the CaO/PEG weight ratio of 1/4. Experimental data highlighted that the composite was able to selectively detect carbon dioxide (CO2) via a nanogravimetric method by performing the experiments inside an atmosphere-controlled chamber filled with CO2. Furthermore, the composite material showed a linear absorption of CO2 as a function of the gas concentration inside the atmosphere-controlled chamber, thus paving the way for the possible use of these matrices for applications in the field of sensor devices for long-term evaluation of accumulated environmental CO2.

Terencio, Tercio Bezerra Correia; Bavastrello, Valter; Nicolini, Claudio

2012-01-01

124

Calcium oxide matrices and carbon dioxide sensors.  

PubMed

Homogeneous matrices of calcium oxide (CaO) were prepared by mixing this material with polyethylene glycol (PEG) acting as malleable inert support in order to obtain processable composites. Preliminary tests were carried out to assess the best concentration of CaO in the composite, individuated in the CaO/PEG weight ratio of 1/4. Experimental data highlighted that the composite was able to selectively detect carbon dioxide (CO(2)) via a nanogravimetric method by performing the experiments inside an atmosphere-controlled chamber filled with CO(2). Furthermore, the composite material showed a linear absorption of CO(2) as a function of the gas concentration inside the atmosphere-controlled chamber, thus paving the way for the possible use of these matrices for applications in the field of sensor devices for long-term evaluation of accumulated environmental CO(2). PMID:22778620

Terencio, Tercio Bezerra Correia; Bavastrello, Valter; Nicolini, Claudio

2012-01-01

125

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

PubMed Central

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

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

1979-01-01

126

Hydration number of calcium palmitate LB film deposited on a piezoelectric quartz crystal plate  

Microsoft Academic Search

The calcium palmitate monolayer formed from palmitic acid on calcium-containing substrate can be examined regarding the study of hydration by applying the quartz crystal microbalance (QCM) technique. Monolayers of calcium palmitate were deposited on piezoelectric crystal plate by the Langmuir-Blodgett (LB) technique. Analysis of complete conversion to calcium palmitate was performed by identification of its infrared spectra. The estimation of

B. I. Seo; H. Lee; J. J. Chung; S. H. Cha; K. H. Lee; W. J. Seo; Y. Cho; H. B. Park; W. S. Kim

1998-01-01

127

Structural characterization of amorphous calcium carbonate-binding protein: an insight into the mechanism of amorphous calcium carbonate formation.  

PubMed

ACC (amorphous calcium carbonate) plays an important role in biomineralization process for its function as a precursor for calcium carbonate biominerals. However, it is unclear how biomacromolecules regulate the formation of ACC precursor in vivo. In the present study, we used biochemical experiments coupled with bioinformatics approaches to explore the mechanisms of ACC formation controlled by ACCBP (ACC-binding protein). Size-exclusion chromatography, chemical cross-linking experiments and negative staining electron microscopy reveal that ACCBP is a decamer composed of two adjacent pentamers. Sequence analyses and fluorescence quenching results indicate that ACCBP contains two Ca²?-binding sites. The results of in vitro crystallization experiments suggest that one Ca²?-binding site is critical for ACC formation and the other site affects the ACC induction efficiency. Homology modelling demonstrates that the Ca²?-binding sites of pentameric ACCBP are arranged in a 5-fold symmetry, which is the structural basis for ACC formation. To the best of our knowledge, this is the first report on the structural basis for protein-induced ACC formation and it will significantly improve our understanding of the amorphous precursor pathway. PMID:23646881

Su, Jingtan; Liang, Xiao; Zhou, Qiang; Zhang, Guiyou; Wang, Hongzhong; Xie, Liping; Zhang, Rongqing

2013-07-15

128

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

129

Calcium oxalate monohydrate crystals stimulate gene expression in renal epithelial cells  

Microsoft Academic Search

Calcium oxalate monohydrate crystals stimulate gene expression in renal epithelial cells. Primary or secondary hyperoxaluria is associated with calcium oxalate nephrolithiasis, interstitial fibrosis and progressive renal insufficiency. Monolayer cultures of nontransformed monkey kidney epithelial cells (BSC-1 line) and calcium oxalate monohydrate (COM) crystals were used as a model system to study cell responses to crystal interactions that might occur in

Mary S Hammes; John C Lieske; Shashi Pawar; Benjamin H Spargo; F Gary Toback

1995-01-01

130

Crystallization of calcium oxalate in the presence of dodecylammonium chloride  

NASA Astrophysics Data System (ADS)

The influence of cationic surfactant, dodecylammonium chloride (DDACI), on spontaneous crystallization of calcium oxalate has been investigated. A combination of thermogravimetric analysis, X-ray diffraction and optical microscopy was used for crystal phase identification. Properties of the surfactant/electrolyte systems (critical micelle concentration (CMC) and apparent dissociation degree) were determined on the basis of conductivity, surface tension and EMF data. Presence of DDACl did not affect nucleation; calcium oxalate monohydrate (COM) was the only hydrate formed. At the concentration below the CMC, DDACl showed no influence on the volume of the precipitate formed, but at DDACl concentrations equal to or higher than the CMC the overall crystallization was strongly inhibited. The inhibitory effect of DDACl on the crystal growth could be explained by its adsorption on the growing crystal faces, thus reducing the available surface area for further crystal development. The prevention of crystal aggregation observed at all investigated DDACl concentrations could be explained by the formation of a surfactant layer with the ionic headgroups oriented toward liquid phase, what produces electrostatic repulsions between COM particles.

S?krti?, D.; Filipovi?-Vincekovi?, N.; Füredi-Milhofer, H.

1991-10-01

131

Evidence for calcium carbonate at the Mars Phoenix landing site.  

PubMed

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

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

2009-07-01

132

Effect of indigenous plant extracts on calcium oxalate crystallization having a role in urolithiasis  

Microsoft Academic Search

Crystallization process has a major role in urolithiasis. In the present study, effect of two indigenous plants extracts namely\\u000a Boerhavia diffusa and Bryophyllum pinnatum extract was determined on the crystallization of calcium oxalate crystals. Effect on the number, size and type of calcium\\u000a oxalate crystals was observed. Results showed significant activity of both extracts against calcium oxalate crystallization\\u000a at different

Fauzia Yasir; Muhammad A. Waqar

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

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

Microsoft Academic Search

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

S. Goñi; A. Guerrero

2003-01-01

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

Urea hydrolysis and calcium carbonate reaction fronts  

NASA Astrophysics Data System (ADS)

The mobility of toxic or radioactive metal contaminants in subsurface environments can be reduced by the formation of mineral precipitates that form co-precipitates with the contaminants or that isolate them from the mobile fluid phase. An engineering challenge is to control the spatial distribution of precipitation reactions with respect to: 1) the location of a contaminant, and 2) where reactants are introduced into the subsurface. One strategy being explored for immobilizing contaminants, such as Sr-90, involves stimulating mineral precipitation by forming carbonate ions and hydroxide via the in situ, microbially mediated hydrolysis of urea. A series of column experiments have been conducted to explore how the construction or design of such an in situ reactant production strategy can affect the temporal and spatial distribution of calcium carbonate precipitation, and how the distribution is coupled to changes in permeability. The columns were constructed with silica gel as the porous media. An interval midway through the column contained an adsorbed urease enzyme in order to simulate a biologically active zone. A series of influent solutions were injected to characterize hydraulic properties of the column (e.g., bromide tracer), profiles of chemical conditions and reaction products as the enzyme catalyzes urea hydrolysis (e.g., pH, ammonia, urea), and changes that occur due to CaCO3 precipitation with the introduction of a calcium+urea solutions. In one experiment, hydraulic conductivity was reduced as precipitate accumulated in a layer within the column that had a higher fraction of fine grained silica gel. Subsequent reduction of permeability and flow (for a constant head condition) resulted in displacement of the hydrolysis and precipitation reaction profiles upstream. In another experiment, which lacked the physical heterogeneity (fine grained layer), the precipitation reaction did not result in loss of permeability or flow velocity and the reaction profile, characterized by the pH profile and hydrolysis reaction species, was extended downstream of the enzyme zone. Downstream extension of the reaction profile was due partially to the partial mobility of the enzyme in the column. The experiments are helping to illustrate the complexity of transient reaction fronts as well as the needs and challenges for advanced modeling approaches. A modeling platform developed at the Idaho National Laboratory, which is capable of simulating tightly coupled physical-chemical processes (the Reactive Transport simulator), is being applied to pre-experimental simulations and post-experimental interpretation of results.

Fox, D. T.; Redden, G. D.; Henriksen, J.; Fujita, Y.; Guo, L.; Huang, H.

2010-12-01

137

RECOVERY OF CALCIUM CARBONATE AND SULFUR FROM FGD SCRUBBER WASTE  

EPA Science Inventory

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 calcium sulfide (using coal as...

138

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

139

Pathogenic Role of Basic Calcium Phosphate Crystals in Destructive Arthropathies  

PubMed Central

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

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

2013-01-01

140

[Basic calcium phosphate crystal deposition disease].  

PubMed

Hydroxyapatite crystals are a common cause of periarticular disease. Virtually, any joint can be involved, but the shoulder is by far most commonly involved. These calcifications, often asymptomatic, can lead to an acute microcrystalline tendinitis or bursitis, which may simulate infection. The diagnosis of periarticular calcifications relies on imaging techniques using X-rays or ultrasounds. Treatment of acute tendinitis or bursitis includes icing, rest, analgesics or non steroidal anti-inflammatory drug and oral steroids or local steroids injection. Removal of the deposit can be considered in patients with chronic pain, particularly at the shoulder. PMID:21737231

Bardin, Thomas; Richette, Pascal

2011-09-01

141

Calcium Carbonate Formation by Genetically Engineered Inorganic Binding Peptides  

NASA Astrophysics Data System (ADS)

Understanding how organisms are capable of forming (synthesize, crystallize, and organize) solid minerals into complex architectures has been a fundamental question of biomimetic materials chemistry and biomineralization for decades. This study utilizes short peptides selected using a cell surface display library for the specific polymorphs of calcium carbonate, i.e., aragonite and calcite, to identify two sets of sequences which can then be used to examine their effects in the formation, crystal structure, morphology of the CaCO3 minerals. A procedure of counter selection, along with fluorescence microscopy (FM) characterization, was adapted to insure that the sequences on the cells were specific to their respective substrate, i.e., aragonite or calcite. From the resulting two sets of sequences selected, five distinct strong binders were identified with a variety of biochemical characteristics and synthesized for further study. Protein derived peptides, using the known sequences of the proteins that are associated with calcite or aragonite, were also designed using a bioinformatics-based similarity analysis of the two sets of binders. In particular, an aragonite binding protein segment, AP7, a protein found in nacre, was chosen for this design and the resulting effects of the designed peptides and the AP7 were examined. Specifically, the binding affinities of the selected and the protein derived peptides off the cells were then tested using FM; these studies resulted in different binding characteristics of the synthesized and cellular bound peptides. Two of the peptides that displayed strong binding on the cells bound to neither of the CaCO 3 substrates and both the high and low similarity protein-derived peptides bound to both polymorphs. However, two of the peptides were found to only bind to their respective polymorph showing; these results are significant in that with this study it is demonstrated that the designed peptides based on experimental library-based selection and sequence identification, can be designed to have recognition capability to a given crystal structure, specifically, in this case, of calcium carbonate. Calcite mineralization with the peptides produced vaterite when several of the peptides were used in the synthesis process, many having unique morphologies studied using scanning electron microscopy (SEM). The amount of vaterite crystal percentage in these biomineralized mixtures was calculated and it was found to be closely related to peptide concentration for the aragonite-binding peptides. In the aragonite mineralization experiments, a separate solid phase, namely, calcium nitrate hydrate, was produced for one of the peptides along with the other polymorphs of calcite carbonate (ie., aragonite, calcite and vaterite) in the solution in the form of a flat film. These biomineralization results are examined in the light of the effects of peptide sequences and their related solid-binding characteristics

Gresswell, Carolyn Gayle

142

Dielectric spectrum of rare-earth-doped calcium fluoride crystals  

Microsoft Academic Search

Calcium fluoride crystals doped with ErF3 and YbF3 have been grown using the vertical Bridgman method. The real and imaginary parts of the complex dielectric constant, ?? and ??, have been measured at five audio-frequencies (1–100kHz) over the temperature range 150–300K. From the observed relaxation processes the activation energy for dipole reorientation and the relaxation time constant,?0, have been determined.

I. Nicoara; M. Munteanu; N. Pecingina-Girjioaba; Marius Stef; L. Lighezan

2006-01-01

143

Chronic calcium pyrophosphate crystal deposition disease arthropathy associated with hypomagnesemia.  

PubMed

We describe a case of a young woman with a magnesium renal wasting syndrome leading to severe hypomagnesemia and a chronic pseudo-osteoaritis calcium pyrophosphate crystal deposition disease (CPDD) arthropathy. A chronic CPDD arthropathy secondary to hypomagnesemia has not been previously reported. The identification of CPDD, particularly in the young, can be a clue to the presence of a potentially treatable underlying metabolic disorder, such as hypomagnesemia. PMID:19078120

Erickson, A R; Yeun, J Y; Enzenauer, R J

1997-02-01

144

The determining role of calcium carbonate on surface deformation during scratching of calcium carbonate-reinforced polyethylene composites  

Microsoft Academic Search

The scratch-induced surface damage of neat and calcium carbonate-reinforced high density polyethylene is described in terms of characteristics of scratch morphology and scratch deformation parameters. Under identical test conditions, calcium carbonate-reinforced high density polyethylene composites exhibit significantly reduced susceptibility to scratch deformation and stress whitening compared to neat high density polyethylene. The resistance to scratch deformation is discussed in terms

M. Tanniru; R. D. K. Misra; K. Berbrand; D. Murphy

2005-01-01

145

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

146

Advances in our understanding of calcium oxalate crystal formation and function in plants  

Microsoft Academic Search

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

Paul A. Nakata

2003-01-01

147

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

148

Isolation and partial characterization of crystal matrix protein as a potent inhibitor of calcium oxalate crystal aggregation: evidence of activation peptide of human prothrombin  

Microsoft Academic Search

In order to clarify the characteristics of crystal matrix protein (CMP), which exhibits a remarkable affinity for calcium oxalate crystals and may be important in stone pathogenesis, we have isolated CMP from macromolecular matrix substances of newly-formed calcium oxalate crystals. Purification of CMP consisted of calcium oxalate crystal formation, dissolution of crystals, electrodialysis, anion exchange chromatography and high-performance liquid chromatography.

K. Suzuki; M. Moriyama; C. Nakajima; K. Kawamura; K. Miyazawa; R. Tsugawa; N. Kikuchi; K. Nagata

1994-01-01

149

Observation of the phase transition in the growth of a biomineralized calcium carbonate.  

PubMed

Transmission electron microscope studies of the cellular nucleation sites of a biomineralized calcium carbonate(aragonite) in the lamellar nacreous layer of the bivalvia Cristaria plicata (Leach) shell showed that the low density calcium particles were confined within some large vesicles of the bivalve mantle cells on which the crystalline aragonite phases were deposited. These vesicles served as the nucleation sites for the growth of the crystals. The crystalline phases at the first few lamellae were mostly imperfect while the whole nacreous layer acquitted itself into a highly oriented biomineralized aragonite. The structure of the vesicles is addressed in detail. PMID:2025279

Huang, L J; Li, H D

1991-04-30

150

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

151

Calcium phosphate crystal growth under controlled atmosphere in electrochemical deposition  

Microsoft Academic Search

Cathodic deposition of calcium phosphate (Ca–P) on titanium was studied under controlled atmospheres. Electrochemical deposition was conducted in a sealed electrochemical cell with a controlled flow of nitrogen, carbon dioxide or compressed air. The Ca–P phases of the depositions on titanium were examined by X-ray diffraction, Fourier transform–infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. Experimental results showed that

Xiong Lu; Zhanfeng Zhao; Yang Leng

2005-01-01

152

Calcium acetate versus calcium carbonate as phosphate-binding agents in chronic haemodialysis.  

PubMed

Hyperphosphataemia plays a key role in the pathogenesis of renal osteodystrophy, and phosphate-binding agents are required in many chronic dialysis patients. Aluminium hydroxide and calcium carbonate are well-established phosphate binders, but their use is associated with toxicity or poor efficacy. Calcium acetate is known to be a potent phosphate binder, and has recently been used successfully in chronic dialysis patients. In this randomized cross-over trial in 31 chronic haemodialysis patients, equimolar doses of calcium acetate and calcium carbonate were administered for 6 weeks each. Compliance was estimated from tablet counts, and biochemical parameters were measured at the end of each treatment period. Of the 31 patients 23 completed both treatment arms; of the remainder, three withdrew due to adverse symptoms, hypercalcaemia necessitated treatment withdrawal in two, and three died. Non-compliance was significantly higher with acetate (18.3% tablets not taken) than with carbonate (8.7%). Serum phosphate was significantly lower after treatment with acetate (1.51 mmol/l) than with carbonate (1.80), as was the Ca x PO4 product (3.59 vs 4.18 respectively) and PTH (17.8 vs 25.4 pmol/l respectively). Serum calcium was significantly higher after acetate therapy (2.40 vs 2.32 mmol/l). No significant difference was found for sodium, potassium, bicarbonate, urea, creatinine, and haemoglobin. This study confirms that the treatment of hyperphosphataemia is more effective with calcium acetate than with calcium carbonate. For the first time an associated beneficial effect on secondary hyperparathyroidism has also been demonstrated. Patient tolerability of calcium acetate was considerably poorer, probably due in part to tablet formulation and bulkiness, as well as possible direct gastrointestinal effects of the acetate salt. PMID:7800211

Pflanz, S; Henderson, I S; McElduff, N; Jones, M C

1994-01-01

153

Waste oil shale ash as a novel source of calcium for precipitated calcium carbonate: carbonation mechanism, modeling, and product characterization.  

PubMed

In this paper, a method for converting lime-containing oil shale waste ash into precipitated calcium carbonate (PCC), a valuable commodity is elucidated. The mechanism of ash leachates carbonation was experimentally investigated in a stirred semi-batch barboter-type reactor by varying the CO(2) partial pressure, gas flow rate, and agitation intensity. A consistent set of model equations and physical-chemical parameters is proposed to describe the CaCO(3) precipitation process from oil shale ash leachates of complex composition. The model enables the simulation of reactive species (Ca(2+), CaCO(3), SO(4)(2-), CaSO(4), OH(-), CO(2), HCO(3)(-), H(+), CO(3)(2-)) concentration profiles in the liquid, gas, and solid phases as well as prediction of the PCC formation rate. The presence of CaSO(4) in the product may also be evaluated and used to assess the purity of the PCC product. A detailed characterization of the PCC precipitates crystallized from oil shale ash leachates is also provided. High brightness PCC (containing up to ? 96% CaCO(3)) with mean particle sizes ranging from 4 to 10 ?m and controllable morphology (such as rhombohedral calcite or coexisting calcite and spherical vaterite phases) was obtained under the conditions studied. PMID:21872990

Velts, O; Uibu, M; Kallas, J; Kuusik, R

2011-11-15

154

Biomineralization of calcium carbonates and their engineered applications: a review  

PubMed Central

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

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

2013-01-01

155

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

156

Adhesion, internalization and metabolism of calcium oxalate monohydrate crystals by renal epithelial cells  

Microsoft Academic Search

Adhesion, internalization and metabolism of calcium oxalate monohydrate crystals by renal epithelial cells. The interaction between crystals that nucleate in the nephron lumen and tubular cells could be an important determinant of renal calcification. Kidney epithelial cells in monolayer culture (BSC-1 line), used to model the tubule, rapidly bound and internalized crystals of calcium oxalate monohydrate (COM), the most common

John C Lieske; Rebbecca Norris; Hewson Swift; F Gary Toback

1997-01-01

157

Drug loading into porous calcium carbonate microparticles by solvent evaporation.  

PubMed

Drug loading into porous carriers may improve drug release of poorly water-soluble drugs. However, the widely used impregnation method based on adsorption lacks reproducibility and efficiency for certain compounds. The aim of this study was to evaluate a drug-loading method based on solvent evaporation and crystallization, and to investigate the underlying drug-loading mechanisms. Functionalized calcium carbonate (FCC) microparticles and four drugs with different solubility and permeability properties were selected as model substances to investigate drug loading. Ibuprofen, nifedipine, losartan potassium, and metronidazole benzoate were dissolved in acetone or methanol. After dispersion of FCC, the solvent was removed under reduced pressure. For each model drug, a series of drug loads were produced ranging from 25% to 50% (w/w) in steps of 5% (w/w). Loading efficiency was qualitatively analyzed by scanning electron microscopy (SEM) using the presence of agglomerates and drug crystals as indicators of poor loading efficiency. The particles were further characterized by mercury porosimetry, specific surface area measurements, differential scanning calorimetry, and USP2 dissolution. Drug concentration was determined by HPLC. FCC-drug mixtures containing equivalent drug fractions but without specific loading strategy served as reference samples. SEM analysis revealed high efficiency of pore filling up to a drug load of 40% (w/w). Above this, agglomerates and separate crystals were significantly increased, indicating that the maximum capacity of drug loading was reached. Intraparticle porosity and specific surface area were decreased after drug loading because of pore filling and crystallization on the pore surface. HPLC quantification of drugs taken up by FCC showed only minor drug loss. Dissolution rate of FCC loaded with metronidazole benzoate and nifedipine was faster than the corresponding FCC-drug mixtures, mainly due to surface enlargement, because only small fractions of amorphous drug (12.5%, w/w, and 8.9%, w/w, respectively) were found by thermal analysis. Combination of qualitative SEM analysis and HPLC quantification was sufficient to proof the feasibility of the solvent-evaporation method for the loading of various drugs into FCC. Mechanistic investigation revealed that a high specific surface area of the carrier is required to facilitate heterogeneous nucleation, and large pore sizes (up to 1?m) are beneficial to reduce crystallization pressures and allow drug deposition within the pores. The solvent-evaporation method allows precise drug loading and appears to be suitable for scale-up. PMID:24568926

Preisig, Daniel; Haid, David; Varum, Felipe J O; Bravo, Roberto; Alles, Rainer; Huwyler, Jörg; Puchkov, Maxim

2014-08-01

158

Automatic photometric titrations of calcium and magnesium in carbonate rocks  

USGS Publications Warehouse

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

Shapiro, L.; Brannock, W. W.

1955-01-01

159

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

160

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

Microsoft Academic Search

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

John C. Lieske; Gerard Farell; Sergio Deganello

2004-01-01

161

Influence of Substrate Mineralogy on Bacterial Mineralization of Calcium Carbonate: Implications for Stone Conservation  

PubMed Central

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.

Jroundi, Fadwa; Schiro, Mara; Ruiz-Agudo, Encarnacion; Gonzalez-Munoz, Maria Teresa

2012-01-01

162

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

2012-06-01

163

Prevention of calcium carbonate precipitation from calcium chloride kill fluid in CO/sub 2/-laden formations  

SciTech Connect

Water containing high concentrations of calcium chloride can now be efficiently used as a kill fluid in production wells having heavily laden carbon dioxide formations. This investigation has determined that the amount of calcium carbonate scale normally produced under these conditions can be reduced by increasing the carbon dioxide partial pressure and increasing the tubing pressure leading from the casing annulus.

Kapelke, M.S.; Caballero, E.P.

1984-04-01

164

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

165

Onset of Orientational Order in Amorphous Calcium Carbonate (ACC) upon Dehydration  

NASA Astrophysics Data System (ADS)

Crystallization of amorphous calcium carbonate (ACC) into one of the anhydrous crystalline polymorphs (vaterite, calcite, and aragonite) is a topic of extensive current research in biomineralization. We performed molecular dynamics simulations of ACC to characterize the dehydration-induced variation in the distance-dependent orientational order of Ca cations around CO32- anions and to examine how such changes in the local structure facilitates nucleation in ACC. Our observations provide molecular scale basis for the formation of vaterite by internal reorganization of ACC nano-particles, which is in-line with the previous experimental demonstration that vaterite is the precursor for the crystallization of calcite or aragonite.

Saharay, Moumita; James Kirkpatrick, R.

2014-01-01

166

Mass Transport and Physical Properties of Large Crystals of Calcium Apatites: Studies of Ca(OH)2 Crystals for Use in Electrolytic Conversion of Calcium Fluorapatite Crystals to Calcium Hydroxyapatite.  

National Technical Information Service (NTIS)

In order to convert single crystals of calcium fluorapatite to calcium hydroxyapatite, an electrolytic cell technique will be explored. To use such a technique, the cathode compartment must consist of a source of hydroxyl ions and a barrier to the flow of...

A. D. Franklin K. F. Young

1973-01-01

167

Mass Transport and Physical Properties of Large Crystals of Calcium Apatites: Studies of Ca(OH)2 Crystals for Use in Electrolytic Conversion of Calcium Fluorapatite Crystals to Calcium Hydroxyapatite.  

National Technical Information Service (NTIS)

In order to convert single crystals of calcium fluorapatite to calcium hydroxyapatite, an electrolytic cell technique will be explored. To utilize such a technique, the cathode compartment must consist of a source of hydroxyl ions and a barrier to the flo...

A. D. Franklin K. F. Young

1975-01-01

168

The influence of aliphatic amines, diamines, and amino acids on the polymorph of calcium carbonate precipitated by the introduction of carbon dioxide gas into calcium hydroxide aqueous suspensions  

NASA Astrophysics Data System (ADS)

The influence of aliphatic organic additives including amines, diamines and amino acids, on the polymorph of calcium carbonate (CaCO3) precipitated from a calcium hydroxide (Ca(OH)2) suspensions and carbon dioxide gas (CO2) was studied by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). The amorphous calcium carbonate, vaterite, aragonite and calcite were observed for the precipitated samples with organic additives. While the precipitation without organic additive, only the stable phase; calcite was obtained. The observed crystal phases were related with the alkyl chain length in the aliphatic part of additives. These results suggested that hydrophobic interactions due to the van der Waals force between organic additives and surface of inorganic precipitates could not be ignored. We concluded that covering or adsorbing of these organic additives on the precipitates surfaces retarded the successive dissolution/recrystallisation process in the aqueous systems. The results revealed that not only the polar interaction from the hydrophilic functional groups, as the former reports proposed, but also the van der Waals interactions from the hydrophobic alkyl groups played the important role in the phase transformation of CaCO3.

Chuajiw, Wittaya; Takatori, Kazumasa; Igarashi, Teruki; Hara, Hiroki; Fukushima, Yoshiaki

2014-01-01

169

A critical analysis of calcium carbonate mesocrystals  

PubMed Central

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

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

2014-01-01

170

Electromechanically tunable carbon nanofiber photonic crystal.  

PubMed

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

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

2013-02-13

171

Growth and thermal behavior of mixed crystals of calcium cadmium tartrate in silica gels  

Microsoft Academic Search

In this study, calcium cadmium tartrate single crystals were grown in silica gel at ambient temperature. Effects of various\\u000a parameters like gel pH, gel aging, gel density, and concentration of reactants on the growth of these crystals were studied.\\u000a Crystals having different morphologies and habits were obtained. Transparent, diamond-like pyramidal-shaped crystals of calcium\\u000a cadmium tartrate were obtained. Some of the

D. K. Sawant; H. M. Patil; D. S. Bhavsar; J. H. Patil; K. D. Girase

172

Formation of hollow bone-like morphology of calcium carbonate on surfactant/polymer templates  

NASA Astrophysics Data System (ADS)

Novel hollow, bone-like structures of Precipitated Calcium Carbonate (PCC) are fabricated, for the first time, starting from naturally occurring dolomite. The hollow, bone-like structures are prepared by precipitating calcium carbonate on self-assembled poly(acrylic acid)/cetyltrimethylammonium chloride (PAA/CTAC) template. Fourier Transform Infrared Spectroscopy (FT-IR), X-ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Field Emission Scanning Electron Microscopic (FE-SEM) studies reveal that the bone-like structure is composed of Amorphous Calcium Carbonate (ACC) nanoparticles in the center and calcite nanoparticles at the edges. Bone-like PCC particles are in particle length of 2-3 ?m and particle width of 1 ?m. The internal hollow structures of bone-like particles are observed from TEM images. As identified by FE-SEM images, the bone-like structure has been formed through the crystal growth of initially formed ACC nanoparticles. The ACC particles are stabilized in the center while the calcite crystals have been grown from the ACC toward the edges of the structure to form a bone-like morphology. We also propose a possible mechanism for the formation of hollow bone-like PCC in this study. The fabricated hollow, bone-like PCC has potential applications in the preparation of release systems such as drugs, cosmetics and pigments.

Mantilaka, M. M. M. G. P. G.; Pitawala, H. M. T. G. A.; Rajapakse, R. M. G.; Karunaratne, D. G. G. P.; Upul Wijayantha, K. G.

2014-04-01

173

Influence of some polysaccharides on the production of calcium carbonate filler particles  

NASA Astrophysics Data System (ADS)

The influence of different water-soluble polysaccharides, dextrans (cationic, anionic and non-ionic) and soluble starch, on the precipitation of calcium carbonate, has been investigated in the model system in which calcium hydroxide and carbonic acid were reactants. In the absence of additives, the formation of metastable phases, vaterite and amorphous calcium carbonate is observed at the early stage of the process, and as a consequence of the solution-mediated transformation process calcite appears in the system as the only solid phase in equilibrium. In the presence of starch, vaterite is found in the final precipitate, with the content increasing with the increase of starch concentration, probably as a consequence of calcite nucleation and crystal growth inhibition. Non-ionic dextran causes the inhibition of vaterite nucleation, which results in the formation of calcite as a predominant solid phase throughout the precipitation process. The crystal size of the so-formed calcite reduces by increasing the relative molecular mass ( Mr) of neutral dextran. The presence of charged dextrans, either cationic or anionic, causes inhibition of the overall precipitation process: in the case of anionic dextran the inhibition seems to be the consequence of its reaction with Ca 2+ ions (supersaturation decrease), while cationic dextran most probably adsorbs electrostatically onto the negatively charged surfaces of calcite and vaterite.

Kontrec, Jasminka; Kralj, Damir; Bre?evi?, Ljerka; Falini, Giuseppe

2008-10-01

174

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

PubMed

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

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

2014-05-28

175

Randomized crossover study comparing the phosphate-binding efficacy of calcium ketoglutarate versus calcium carbonate in patients on chronic hemodialysis  

Microsoft Academic Search

The objective of the study was to evaluate the phosphate-binding efficacy, side effects, and cost of therapy of calcium ketoglutarate granulate as compared with calcium carbonate tablets in patients on chronic hemodialysis. The study design used was a randomized, crossover open trial, and the main outcome measurements were plasma ionized calcium levels, plasma phosphate levels, plasma intact parathyroid hormone (PTH)

S Bro; RA Rasmussen; J Handberg; K Olgaard; B Feldt-Rasmussen

1998-01-01

176

The effect of carboxymethyl chitosan on the precipitation of calcium carbonate  

NASA Astrophysics Data System (ADS)

It is believed that chitosan plays an important role on the formation of specific inorganic-organic hybrid structure of shells. In this paper, insoluble chitoan was modified to a water-soluble macromolecule—carboxymethyl chitosan (CMCS), and further used as an additive in the crystallization process of calcium carbonate (CaCO 3). The combination investigation of XRD, Micro FT-IR and SEM on the precipitated crystals shows that the addition of CMCS obviously changed the crystal morphology, but did not induce the transformation of the crystal form, i.e., CaCO 3 keeps calcite form in all the cases no matter whether CMCS exists or not in the precipitation systems. The morphological variation of CaCO 3 strongly depends on the CMCS concentration in the aqueous solutions.

Liang, Po; Zhao, Ying; Shen, Qiang; Wang, Dujin; Xu, Duanfu

2004-02-01

177

Calcium-Decorated Carbon Nanotubes for Hydrogen Storage  

Microsoft Academic Search

Using the first-principles pseudopotential density-functional method, we carry out a systematic search for high-capacity hydrogen storage media based on individually dispersed calcium atoms on carbon nanotubes (CNTs). We find that Ca clustering is suppressed on boron-doped and defective carbon nanotubes and that up to six H2 molecules can bind to a Ca atom with a binding energy of ˜0.2 eV\\/H2.

Hoonkyung Lee; Jisoon Ihm; Marvin L. Cohen; Steven G. Louie

2009-01-01

178

Calcium acetate versus calcium carbonate for the control of serum phosphorus in hemodialysis patients.  

PubMed

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, in clinical practice few reports have compared these two calcium salts, and results disagree. We evaluated in a 24-week prospective cross-over study the clinical efficiency of CaCO3 and CaAC in 10 selected chronic hemodialysis patients. Only 7 patients completed the study period. The patients were randomly assigned to start treatment with one of the two calcium salts; after 12 weeks they shifted to the other treatment. Serum analytical tests included weekly control of calcium, phosphorus, and alkaline phosphatase. PTH values (intact molecule) were obtained initially and at the end of every study period. The same good control of the phosphorus level (4.79 +/- 0.6 vs. 4.94 +/- 0.8 mg/dl) was obtained with CaAC (mean doses 4.1 +/- 0.3 g/day) as with CaCO3 (mean doses 4.01 +/- 0.8 g/day). The mean serum calcium levels were similar (10.36 +/- 0.5 vs. 10.20 +/- 0.5 mg/dl). The dose of elemental calcium administered was significantly less with CaAC (957 +/- 83 mg/day) than with CaCO3 (1,590 +/- 317 mg/day). However, the incidence of hypercalcemia (Ca > 11 mg/dl) was similar during the two treatment periods (13% with CaAC vs. 14% with CaCO3). Also the incidence of Ca x P products 765 was comparable (9.5 vs. 11.9%).(ABSTRACT TRUNCATED AT 250 WORDS) PMID:7977479

Almirall, J; Veciana, L; Llibre, J

1994-01-01

179

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

180

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

181

Efficiency of Calcium Silicate and Carbonate in Soybean Disease Control  

Microsoft Academic Search

Silicon (Si) affects the susceptibility of plants to fungal attack. In plants with low Si accumulation, disease-control mechanisms involve the accumulation of phenolic compounds and Si. This study compared the effects of calcium silicate and carbonate doses on the control of soybean (Glycine max) diseases. A sandy soil was collected from Santa Vitória, Minas Gerais state, Brazil, of which 200

Antonio Nolla; Gaspar Henrique Korndörfer; Lísias Coelho

2006-01-01

182

Facile preparation of calcium carbonate particles with unusual morphologies by precipitation reaction  

NASA Astrophysics Data System (ADS)

Calcium carbonate particles with different morphologies were prepared by the reaction of sodium carbonate with calcium chloride in the presence of different organic additives at 25°C and 80°C. The as-prepared products were characterized with scanning electron microscopy and X-ray diffraction. The results showed that both organic additives and temperature turned out to be important parameters for the control of morphologies of CaCO 3. Various crystal morphologies of CaCO 3, such as, plate, rhombohedra, ellipsoids, whisker, dendrite, etc. can be obtained depending on the experimental conditions. In particular, monodispersed rhombohedral calcite particles, whiskers of aragonite and exquisite dendrite-shaped CaCO 3 aggregates were obtained with polyacrylic acid, cetyltrimethylammonium bromide and polyvinyl alcohol as additives at 80°C, respectively.

Yu, Jiaguo; Lei, Ming; Cheng, Bei; Zhao, Xiujian

2004-02-01

183

Osteopontin Is a Critical Inhibitor of Calcium Oxalate Crystal Formation and Retention in Renal Tubules  

Microsoft Academic Search

Calcium nephrolithiasis is the most common form of renal stone disease, with calcium oxalate (CaOx) being the predominant constituent of renal stones. Current in vitro evi- dence implicates osteopontin (OPN) as one of several macro- molecular inhibitors of urinary crystallization with potentially important actions at several stages of CaOx crystal formation and retention. To determine the importance of OPN in

JEFFREY A. WESSON; RICHARD J. JOHNSON; MARRILDA MAZZALI; ANNE M. BESHENSKY; SUSAN STIETZ; CECI GIACHELLI; LUCY LIAW; CHARLES E. ALPERS; WILLIAM G. COUSER; JACK G. KLEINMAN; JEREMY HUGHES

2003-01-01

184

Renal cell osteopontin production is stimulated by calcium oxalate monohydrate crystals  

Microsoft Academic Search

Renal cell osteopontin production is stimulated by calcium oxalate monohydrate crystals. Specific anions in tubular fluid, including uropontin (UP), the urinary form of human osteopontin (OPN), block adhesion to renal tubular cells of the most common crystal in kidney stones, calcium oxalate monohydrate (COM). In this study, monkey renal epithelial cells (BSC-1 line) in monolayer culture constitutively secreted UP into

John C Lieske; Mary S Hammes; John R Hoyer; F Gary Toback

1997-01-01

185

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

186

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

187

Calcium oxalate crystal interaction with renal tubular epithelium, mechanism of crystal adhesion and its impact on stone development  

Microsoft Academic Search

The interaction between renal epithelial cells and calcium oxalate (CaOx) crystals and\\/or oxalate ions plays a critical role in the formation of urinary stones. Epithelial cells respond to hyperoxaluria and the presence of CaOx crystals in the kidneys by increased enzymuria and internalization of the crystals. Crystal cell interaction results in movement of crystals from the luminal to the basolateral

S. R. Khan

1995-01-01

188

Calcium carbonate binding mechanisms in the setting of calcium and calcium–magnesium putty-limes  

Microsoft Academic Search

Calcium and calcium magnesium putty-limes (C-L and C-M-L) were characterized, through SEM, Porosimeter and Chemical Analysis, to obtain information on the microstructure of their solid-phases. Irregular agglomerates of portlandite grains and large acicular crystallites of brucite are differently interconnected to form a cellular solid matrix dispersed into the saturated aqueous solution of the hydroxides. The setting of these putty-limes was

Dario T. Beruto; Fabrizio Barberis; Rodolfo Botter

2005-01-01

189

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

2004-05-01

190

Calcium oxalate crystals in tomato and tobacco plants: morphology and in vitro interactions of crystal-associated macromolecules.  

PubMed

Plants form calcium oxalate crystals with unique morphologies under well-controlled conditions. We studied the morphology of single calcium oxalate monohydrate (whewellite) crystals extracted from tomato and tobacco leaves. These crystals have a pseudotetrahedral shape. We identified the (101), (101) or (102), (110), and (hk0) faces as stable faces. The morphology is chiral with unique handedness. We also show that calcium oxalate monohydrate crystals isolated from tomato, tobacco, and bougainvillea leaves contain macromolecules rich in Gly, Glx, and Ser. Crystal-associated macromolecules extracted from tomato and tobacco influence the morphology of calcium oxalate monohydrate crystals grown in vitro, promoting preferential development of the [120] faces. Furthermore, crystal-associated macromolecules from tobacco promote nucleation of calcium oxalate monohydrate crystals, whereas model polypeptides do not have any significant effect on nucleation. These results imply an active role of the crystal-associated macromolecules in the formation of pseudotetrahedral shapes in vitro, and these properties may in part be responsible for the unique chiral morphology of the natural pyramidal-shaped crystals. PMID:11405466

Bouropoulos, N; Weiner, S; Addadi, L

2001-05-01

191

Impact of calcium on struvite crystal size, shape and purity  

NASA Astrophysics Data System (ADS)

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

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

2005-10-01

192

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

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

Chikashi Toyoshima; Masayoshi Nakasako; Hiromi Nomura; Haruo Ogawa

2000-01-01

193

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

194

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

SciTech Connect

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

Goni, S.; Guerrero, A

2003-01-01

195

Effect of indigenous plant extracts on calcium oxalate crystallization having a role in urolithiasis.  

PubMed

Crystallization process has a major role in urolithiasis. In the present study, effect of two indigenous plants extracts namely Boerhavia diffusa and Bryophyllum pinnatum extract was determined on the crystallization of calcium oxalate crystals. Effect on the number, size and type of calcium oxalate crystals was observed. Results showed significant activity of both extracts against calcium oxalate crystallization at different concentrations (P < 0.05). Size of the crystals gradually reduced with the increasing concentration of both extracts. The number of calcium oxalate monohydrate crystals which are injurious to epithelial cells gradually reduced and at the highest concentration of extracts (100 mg/ml) completely disappeared (P < 0.05). These results confirm that B. diffusa and B. pinnatum extracts have antiurolithic activity and have the ability to reduce crystal size as well as to promote the formation of calcium oxalate dihydrate (COD) crystals rather than monohydrate (COM) crystals. Control of crystal size and formation of COD rather than COM crystals, in combination with the diuretic action of extracts is an important way to control urolithiasis. PMID:21643743

Yasir, Fauzia; Waqar, Muhammad A

2011-10-01

196

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...

197

Experimental calcium-oxalate crystal production and dissolution by selected wood-rot fungi  

Microsoft Academic Search

Twenty-six species of white-rotting Agaricomycotina fungi (Basidiomycota) were screened for their ability to produce calcium-oxalate (CaOx) crystals in vitro. Most were able to produce CaOx crystals in malt agar medium in the absence of additional calcium. In the same medium enriched with Ca2+, all the species produced CaOx crystals (weddellite or whewellite). Hyphae of four species (Ganoderma lucidum, Polyporus ciliatus, Pycnoporus

Matteo Guggiari; Raphael Bloque; Michel Aragno; Eric Verrecchia; Daniel Job; Pilar Junier

2011-01-01

198

Birefringence simulation of annealed ingot of calcium fluoride single crystal  

NASA Astrophysics Data System (ADS)

We developed a method for simulating birefringence of an annealed ingot of calcium fluoride single crystal caused by the residual stress after annealing process. The method comprises the heat conduction analysis that provides the temperature distribution during the ingot annealing, the elastic thermal stress analysis using the assumption of the stress-free temperature that provides the residual stress after annealing, and the birefringence analysis of an annealed ingot induced by the residual stress. The finite element method was applied to the heat conduction analysis and the elastic thermal stress analysis. In these analyses, the temperature dependence of material properties and the crystal anisotropy were taken into account. In the birefringence analysis, the photoelastic effect gives the change of refractive indices, from which the optical path difference in the annealed ingot is calculated by the Jones calculus. The relation between the Jones calculus and the approximate method using the stress components averaged along the optical path is discussed theoretically. It is found that the result of the approximate method agrees very well with that of the Jones calculus in birefringence analysis. The distribution pattern of the optical path difference in the annealed ingot obtained from the present birefringence calculation methods agrees reasonably well with that of the experiment. The calculated values also agree reasonably well with those of the experiment, when a stress-free temperature is adequately selected.

Ogino, H.; Miyazaki, N.; Mabuchi, T.; Nawata, T.

2008-01-01

199

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

200

Precipitation of calcium carbonate from seawater  

NASA Astrophysics Data System (ADS)

Slight perturbations of the oceanic DOC by addition of oxalic acid, tryptophan, and sodium humate did not affect the magnesium content of spontaneously precipitated Mg-calcites. However, the copresence of spontaneously precipitated aragonite and of Mg-calcite as a function of the initial degree of supersaturation was changed by the dissolved organic matter. Times of nucleation for carbonates was affected by organic matter at low organic concentrations because of coating and at high concentrations due to complexation.

Jiliang, Li; Pytkowicz, R. M.

1988-12-01

201

Bacterial Calcium Carbonate Precipitation in Cave Environments: A Function of Calcium Homeostasis  

Microsoft Academic Search

To determine if microbial species play an active role in the development of calcium carbonate (CaCO3) deposits (speleothems) in cave environments, we isolated 51 culturable bacteria from a coralloid speleothem and tested their ability to dissolve and precipitate CaCO3. The majority of these isolates could precipitate CaCO3 minerals; scanning electron microscopy and X-ray diffractrometry demonstrated that aragonite, calcite and vaterite

Eric D. Banks; Nicholas M. Taylor; Jason Gulley; Brad R. Lubbers; Juan G. Giarrizzo; Heather A. Bullen; Tori M. Hoehler; Hazel A. Barton

2010-01-01

202

Calcium carbonate deposit formation during the liquefaction of low rank coals  

Microsoft Academic Search

The major findings in the liquefaction work with low rank coals were that oolite formation and wall scale growth were primarily related to coal rank. Both forms of calcium carbonate deposits were detected with every low rank coal tested. As long as the calcium in the coal was present in the humate form, calcium carbonate deposition occurred. The physical withdrawal

J. B. Stone; K. L. Trachte; S. K. Poddar

1979-01-01

203

Precipitation of calcium and magnesium carbonates from homogeneous supersaturated solutions  

Microsoft Academic Search

Homogeneous (unseeded) precipitation of calcium and magnesium carbonates in the CaO–MgO–CO2–H2O system in supersaturated solutions was investigated. The induction period (?) of spontaneous nucleation and the composition of precipitated solid phases were determined. The influence of saturation degree (chemical affinity) and Mg2+\\/Ca2+ activity ratio in solution on the kinetics of CaCO3 nucleation was studied. The order of CaCO3 homogeneous nucleation

O. S. Pokrovsky

1998-01-01

204

Effect of urinary macromolecules and chondroitin sulphate on calcium oxalate crystallization in urine.  

PubMed

After filtration and ultrafiltration (10 kD) of 24 hour urine specimens from 12 healthy male subjects, calcium oxalate crystallization was induced in the filtered (FILTD) and ultrafiltered (UF) fractions by administration of a sodium oxalate load. In addition crystallization was also induced in UF fractions to which physiological quantities of chondroitin sulphate (CHON) had been added (UF+CHON). The rate of calcium oxalate crystallization was determined by measuring the rate at which turbidity increased. Crystal numbers and sizes were measured with a Malvern particle size analyzer and by scanning electron microscopy. Crystallization rates, crystal numbers and crystal sizes were generally lower in UF fractions than in FILTD fractions suggesting that urinary macromolecules are promoters of calcium oxalate crystallization. No increase in crystallization rate, crystal numbers or sizes occurred when chondroitin sulphate was added to UF fractions, indicating that the promoter activity of urinary macromolecules is not due to this particular glycosaminoglycan. On the contrary, crystallization rates were qualitatively lower in UF+CHON fractions than in UF fractions alone, suggesting a possible inhibitory role for chondroitin sulphate in real urine. Scanning electron microscopy revealed that while aggregates were present in UF and FILTD fractions, they were absent in UF+CHON fractions. This observation indicates that chondroitin sulphate might be an inhibitor of calcium oxalate crystal aggregation in real urine. PMID:7973501

Rodgers, A L; Ball, D; Harper, W

1994-03-01

205

Crystallization of Polyetheretherketone (PEEK) in Carbon Fiber Composites.  

National Technical Information Service (NTIS)

The tendency of carbon fiber to nucleate the crystallization of PEEK has been evaluated by DSC and other techniques. As the carbon fiber content was increased, the supercooling necessary for PEEK crystallization decreased. The repeated melting (at 396 C) ...

Y. C. Lee R. S. Porter

1985-01-01

206

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

207

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

208

Absorption of inorganic halides produced from Freon 12 by calcium carbonate containing iron(III) oxide  

SciTech Connect

Inorganic halides produced by the catalytic decomposition of Freon 12 were fixed by calcium carbonate, which is the main component of limestone. Iron(III) oxide, which is present as a contaminant in limestone, promoted the absorption of the halides by calcium carbonate at low temperatures. The supposed action of iron(III) oxide was to first react with inorganic halides, forming iron halides, and, then, transfer them to calcium carbonate to replace carbonate ion in a catalytic way. Thus, calcium carbonate containing iron oxides (limestone) can be used as an effective absorbent for the inorganic halogens produced during the decomposition of Freons.

Imamura, Seiichiro; Matsuba, Yoichi; Yamada, Etsu; Takai, Kenji; Utani, Kazunori [Kyoto Inst. of Tech. (Japan). Dept. of Chemistry] [Kyoto Inst. of Tech. (Japan). Dept. of Chemistry

1997-09-01

209

Effect of wastewater composition on the calcium carbonate precipitation in upflow anaerobic sludge blanket reactors  

Microsoft Academic Search

Calcium carbonate often precipitates in anaerobic reactors treating wastewater with high calcium content. The aim of this\\u000a paper is to study the effect of wastewater composition on calcium carbonate precipitation in upflow anaerobic sludge blanket\\u000a (UASB) reactors. Two laboratory-scale UASB reactors were operated with calcium-containing influents using acetate and carbohydrate\\u000a as substrate, respectively. There was an obvious accumulation of inorganic

Shucheng Yang; Yanling He; Yonghong Liu; Charles Chou; Pengxiang Zhang; Dongqi Wang

2010-01-01

210

Calcium pyrophosphate dihydrate and hydroxyapatite crystal deposition in the joint: New developments relevant to the clinician  

Microsoft Academic Search

The major types of crystals containing calcium, which causes arthropathy and periarticular disease, are calcium pyrophosphate\\u000a dihydrate and basic calcium phosphates, including hydroxyapatite. Exciting advances include the identification of mutations\\u000a in the gene ANKH associated with disordered inorganic pyrophosphate (PPi) transport in some kindred with familial chondrocalcinosis linked\\u000a to chromosome 5p. In addition, central basic mechanisms governing cartilage calcification and

Salih Pay; Robert Terkeltaub

2003-01-01

211

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

212

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

2010-06-01

213

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

214

Triamterene and renal stone formation: The influence of triamterene and triamterene stones on calcium oxalate crystallization  

Microsoft Academic Search

Summary  A constant composition method has been used to compare the effects of triamterene renal stone material, synthetic triamterene\\u000a precipitates, and soluble triamterene on the nucleation and crystallization kinetics of calcium oxalate in aqueous solutionin vitro. Crystallization studies have been carried out with the concentrations of calcium and oxalate ions maintained constant by\\u000a the potentiometrically controlled addition of concentrated reagent solutions

Donald J. White; George H. Nancollas

1987-01-01

215

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

SciTech Connect

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 is largely restored by addition of human urinary Tamm-Horsfall protein (uromucoid). Albumin does not have this effect.

Rose, G.A.; Sulaiman, S.

1982-01-01

216

Isolation and purification of a new glycoprotein from human urine inhibiting calcium oxalate crystallization  

Microsoft Academic Search

A calcium oxalate crystal growth inhibitor was isolated from human urine using DEAE-Sephacel gel followed by Sephacryl S-300 chromatography and FPLC column. The isolated inhibitor was a uronic-acid-rich protein (UAP). It was found to be a glycoprotein with a molecular weight of 35 000 Da as determined by SDS-polyacrylamide gel electrophoresis. Inhibitory activity was demonstrated using a calcium oxalate crystallization

Fouad Atmani; Bernard Lacour; Tilman Drüeke; Michel Daudon

1993-01-01

217

Morphological conversion of calcium oxalate crystals into stones is regulated by osteopontin in mouse kidney.  

PubMed

An important process in kidney stone formation is the conversion of retentive crystals in renal tubules to concrete stones. Osteopontin (OPN) is the major component of the kidney calcium-containing stone matrix. In this study, we estimated OPN function in early morphological changes of calcium oxalate crystals using OPN knockout mice: 100 mg/kg glyoxylate was intra-abdominally injected into wildtype mice (WT) and OPN knockout mice (KO) for a week, and 24-h urine oxalate excretion showed no significant difference between WT and KO. Kidney crystal depositions were clearly detected by Pizzolato staining but not by von Kossa staining in both genotypes, and the number of crystals in KO was significantly fewer than in WT. Morphological observation by polarized light optical microphotography and scanning electron microphotography (SEM) showed large flower-shaped crystals growing in renal tubules in WT and small and uniform crystals in KO. X-ray diffraction detected the crystal components as calcium oxalate monohydrate in both genotypes. Immunohistochemical staining of OPN showed that the WT crystals contained OPN protein but not KO crystals. We concluded that OPN plays a crucial role in the morphological conversion of calcium oxalate crystals to stones in mouse kidneys. PMID:18505365

Okada, Atsushi; Nomura, Shintaro; Saeki, Yukihiko; Higashibata, Yuji; Hamamoto, Shuzo; Hirose, Masahito; Itoh, Yasunori; Yasui, Takahiro; Tozawa, Keiichi; Kohri, Kenjiro

2008-10-01

218

Transglutaminase-induced crosslinking of gelatin-calcium carbonate composite films.  

PubMed

The effects of transglutaminase (TGase) on the rheological profiles and interactions of gelatin-calcium carbonate solutions were studied. In addition, mechanical properties, water vapour permeability and microstructures of gelatin-calcium carbonate films were also investigated and compared. Fluorescence data suggested that the interaction of TGase and gelation-calcium carbonate belonged to a static quenching mechanism, and merely one binding site between TGase and gelatin-calcium carbonate was identified. Moreover, differential scanning calorimetry (DSC), the mechanical properties and the water vapour permeability studies revealed that TGase favoured the strong intramolecular polymerisation of the peptides in gelatin. The microstructures of the surfaces and cross sections in gelatin-calcium carbonate films were shown by scanning electron microscope (SEM) micrographs. The results of the fourier transform infrared spectroscopy (FTIR) indicated that TGase caused conformational changes in the proteins films. Therefore, TGase successfully facilitated the formation of gelatin-calcium carbonate composite films. PMID:25053075

Wang, Yuemeng; Liu, Anjun; Ye, Ran; Wang, Wenhang; Li, Xin

2015-01-01

219

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

220

The roles of water and polyelectrolytes in the phase transformation of amorphous calcium carbonate  

Microsoft Academic Search

Amorphous calcium carbonate (ACC) is a metastable phase of calcium carbonates and it is a precursor during the biomineralization of calcium carbonate in nature. Different ACC in the absence and presence of the additives of poly(sodium 4-styrene sulfonate) and poly(acrylic acid) were prepared and their transformation processes under controls of water were investigated. It was found that ACC powders generally

Xu-Rong Xu; An-Hua Cai; Rui Liu; Hai-Hua Pan; Rui-Kang Tang; Kilwon Cho

2008-01-01

221

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

Microsoft Academic Search

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

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

2003-01-01

222

Rhesus monkeys (Macaca mulatta) as a model for calcium pyrophosphate dihydrate crystal deposition disease.  

PubMed

Calcium pyrophosphate dihydrate crystal deposition disease (CPDD) was recognized in 4 of 30 free-ranging rhesus macaques. By means of tissue radiography, focal radiodensities were noted in lumbar intervertebral discs, menisci, and articular cartilage. Crystal deposits were identified as calcium pyrophosphate dihydrate (Ca2P2O7 X 2H2O) by means of X-ray diffraction. The pathogenesis of calcium pyrophosphate dihydrate arthropathy in man remains elusive. However, with the recognition of this arthritis in a well defined population of aged nonhuman primates, a model now exists to facilitate the study of this disease. PMID:3009819

Renlund, R C; Pritzker, K P; Cheng, P T; Kessler, M J

1986-01-01

223

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

224

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

225

Crystallization process and some properties of calcium mica–apatite glass-ceramics  

Microsoft Academic Search

A feature of calcium–mica is the great glass stability of the melt. However, the calcium–mica glass-ceramic disintegrates naturally in air. If the disintegration is hindered by the separation of other materials, glass-ceramics containing calcium–mica become usable. In this study, mica–apatite glass-ceramics with the different ratio of fluoroapatite (Ca10(PO4)6F2) to calcium–mica (Ca0.5Mg3(AlSi3O10)F2), were prepared and the crystallization process, microstructure development and

Seiichi Taruta; Kazuya Mukoyama; Sofia Saori Suzuki; Kunio Kitajima; Nobuo Takusagawa

2001-01-01

226

Fracture of ultrafine calcium carbonate/polypropylene composites  

SciTech Connect

The strength and fracture properties of a polypropylene filled with ultrafine calcium carbonate (0.07 micron) have been studied in the composition range of 0 to 40 percent by volume. Untreated and surface treated (with stearic acid and a titanate coupling agent) grades have been considered. The untreated filler caused a decrease of toughness, whereas a maximum, at about 10 percent, was observed for the treated filler. The fracture energy was analyzed in terms of the crack-pinning model. Due to the very small size of particles, the pinning contribution proved to be negligible. 30 references.

Levita, G.; Marchetti, A.; Lazzeri, A.

1989-02-01

227

CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION  

SciTech Connect

Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids single-celled, marine algae that are the major global producers of calcium carbonate to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

V.J. Fabry

2001-07-01

228

CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION  

SciTech Connect

Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

V.J. Fabry, Ph.D.

2002-04-05

229

CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION  

SciTech Connect

Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

V.J. Fabry, Ph.D.

2001-09-10

230

CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION  

SciTech Connect

Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

V.J. Fabry, Ph.D.

2003-04-15

231

CALCIUM CARBONATE PRODUCTION BY COCCOLITHOPHORID ALGAE IN LONG TERM, CARBON DIOXIDE SEQUESTRATION  

SciTech Connect

Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

V.J. Fabry, Ph.D.

2002-09-30

232

Calcium Carbonate Produced by Coccolithophorid Algae in Long Term, Carbon Dioxide Sequestration  

SciTech Connect

Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO2 through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids - single-celled, marine algae that are the major global producers of calcium carbonate - to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

V.J. Fabry

2007-06-30

233

Calcium Carbonate Production by Coccolithophorid Algae in Long Term, Carbon Dioxide Sequestration  

SciTech Connect

Predictions of increasing levels of anthropogenic carbon dioxide (CO{sub 2}) and the specter of global warming have intensified research efforts to identify ways to sequester carbon. A number of novel avenues of research are being considered, including bioprocessing methods to promote and accelerate biosequestration of CO{sub 2} from the environment through the growth of organisms such as coccolithophorids, which are capable of sequestering CO{sub 2} relatively permanently. Calcium and magnesium carbonates are currently the only proven, long-term storage reservoirs for carbon. Whereas organic carbon is readily oxidized and releases CO{sub 2} through microbial decomposition on land and in the sea, carbonates can sequester carbon over geologic time scales. This proposal investigates the use of coccolithophorids--single-celled, marine algae that are the major global producers of calcium carbonate--to sequester CO{sub 2} emissions from power plants. Cultivation of coccolithophorids for calcium carbonate (CaCO{sub 3}) precipitation is environmentally benign and results in a stable product with potential commercial value. Because this method of carbon sequestration does not impact natural ecosystem dynamics, it avoids controversial issues of public acceptability and legality associated with other options such as direct injection of CO{sub 2} into the sea and ocean fertilization. Consequently, cultivation of coccolithophorids could be carried out immediately and the amount of carbon sequestered as CaCO{sub 3} could be readily quantified. The significant advantages of this approach warrant its serious investigation. The major goals of the proposed research are to identify the growth conditions that will result in the maximum amount of CO{sub 2} sequestration through coccolithophorid calcite production and to evaluate the costs/benefits of using coccolithophorid cultivation ponds to abate CO{sub 2} emissions from power plants.

V. J. Fabry

2006-06-30

234

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

NASA Astrophysics Data System (ADS)

Paleotemperature reconstructions rely on knowledge of the equilibrium separation of oxygen isotopes between aqueous solution and calcium carbonate. Although oxygen isotope separation is expected on theoretical grounds, the temperature-dependence remains uncertain because other factors, such as slow exchange of isotopes between dissolved CO2-species and water, can obscure the temperature signal. This is problematic for crystal growth experiments on laboratory timescales and for interpreting the oxygen isotope composition of crystals formed in natural settings. We present results from experiments in which inorganic calcite is precipitated in the presence of 0.25?M dissolved bovine carbonic anhydrase (CA). The presence of dissolved CA accelerates oxygen isotope equilibration between the dissolved carbon species CO2, H2CO3, HCO3-, CO32- and water, thereby eliminating this source of isotopic disequilibrium during calcite growth. The experimental results allow us to isolate, for the first time, kinetic oxygen isotope effects occurring at the calcite-water interface. We present a framework of ion-by-ion growth of calcite that reconciles our new measurements with measurements of natural cave calcites that are the best candidate for having precipitated under near-equilibrium conditions. Our findings suggest that isotopic equilibrium between calcite and water is unlikely to have been established in laboratory experiments or in many natural settings. The use of CA in carbonate precipitation experiments offers new opportunities to refine oxygen isotope-based geothermometers and to interrogate environmental variables other than temperature that influence calcite growth rates.

Watkins, James M.; Nielsen, Laura C.; Ryerson, Frederick J.; DePaolo, Donald J.

2013-08-01

235

Electrochemically assisted co-deposition of calcium phosphate\\/collagen coatings on carbon\\/carbon composites  

Microsoft Academic Search

Calcium phosphate (CaP)\\/collagen coatings were prepared on the surface of carbon\\/carbon (C\\/C) composites by electrochemically assisted co-deposition technique. The effects of collagen concentration in the electrolyte on morphology, structure and composition of the coatings were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adhesive strength of the

Xueni Zhao; Tao Hu; Hejun Li; Mengdi Chen; Sheng Cao; Leilei Zhang; Xianghui Hou

2011-01-01

236

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

237

An apparent kinetic model for the carbonation of calcium oxide by carbon dioxide  

Microsoft Academic Search

For the apparent kinetics of the carbonation reaction of calcium oxide by carbon dioxide, as a kind of noncatalytic gas–solid reaction, a model equation has been proposed as follows: X=kbt\\/(b+t), where X is the conversion of CaO; k, a kinetic rate constant (time?1); b, a constant (time) equivalent to the time taken to attain half the ultimate conversion of CaO,

Deuk Ki Lee

2004-01-01

238

The Effect of Calcium and Magnesium on Carbonate Mineral Precipitation during Reactive Transport in a Model Subsurface Pore Structure  

NASA Astrophysics Data System (ADS)

Carbonate mineral precipitation in the subsurface at the interface of two advecting fluids can result in physical and chemical changes in the pore network. This can affect various applications including carbon sequestration. In this work, we evaluate the precipitation kinetics of carbonates in a microfluidic pore network when carbonate in water is mixed transverse to flow with a synthetic brine containing an equimolar concentration of calcium (Ca, 10 mM) and concentrations of magnesium (Mg) ranging from 2 to 40 mM. Mineral precipitation was monitored using reflected brightfield microscopy and mineral polymorphs were determined using Raman spectroscopy. Although Mg was present, only calcium carbonate (CaCO3) polymorphs were observed. The presence of Mg affected both the rate of precipitation and the prevalence of different CaCO3 morphologies. The rate of precipitation with 40mM Mg was about half of the rate as when no Mg was present. The calcium carbonate polymorph aragonite increased from <5% of the precipitated crystal area to >20% as the Mg concentration increased from 0 mM to 40 mM. Energy dispersive spectroscopy (EDS) results showed Mg2+ incorporated into the crystal lattice of the CaCO3 polymorph calcite at 8 to 14 mole% when Mg concentration in solution was highest. The incorporation of Mg2+ into the crystals was likely responsible for the reduction in precipitation rate at high solution concentrations of Mg. Significant pore blockage occurred along the mixing zone, indicating that carbonate precipitation may be of concern along the CO2 plume margins and affect the efficiency of CO2 injection.

Boyd, V.; Werth, C. J.; Valocchi, A. J.; Fouke, B. W.

2012-12-01

239

Quartz crystal microbalance for comparison of calcium phosphate precipitation on planar and rough phospholipid bilayers.  

PubMed

The planar and rough phospholipid bilayers at the surfaces of quartz crystal and titania-modified quartz crystal were fabricated via the surface modification, respectively, and characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM), cyclic voltammetry (CV) and piezoelectric measurement. The formation of calcium phosphate on planar and rough phospholipid bilayers was investigated in detail using in situ quartz crystal microbalance (QCM) and X-ray diffraction (XRD) techniques. The obtained results showed that the calcium phosphate precipitation was closely related to the roughness and surface potential of phospholipid bilayers. Compared with planar phospholipid bilayers, the rough phospholipid bilayers exhibited a higher deposition rate of calcium phosphate. The presence of anionic phosphatidylserine (PS) in phosphatidylcholine (PC)/PS phospholipid induced PC/PS surface with negative charge, thus showing significantly enhanced calcium phosphate precipitation. PMID:24495457

Yang, Zhengpeng; Zhang, Chunjing; Huang, Lina

2014-04-01

240

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

241

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

Microsoft Academic Search

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

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

1991-01-01

242

From The Cover: Adhesion at calcium oxalate crystal surfaces and the effect of urinary constituents  

Microsoft Academic Search

Kidney stones, aggregates of microcrystals, most commonly contain calcium oxalate monohydrate (COM) as the primary constituent. The aggregation of COM microcrystals and their attachment to epithelial cells are thought to involve adhesion at COM crystal surfaces, mediated by anionic molecules or urinary macromolecules. Identification of the most important functional group-crystal face adhesive combinations is crucial to understanding the stability of

Xiaoxia Sheng; Taesung Jung; Jeffrey A. Wesson; Michael D. Ward

2005-01-01

243

Calcium oxalate nephrolithiasis: Effect of renal crystal deposition on the cellular composition of the renal interstitium  

Microsoft Academic Search

Urinary calcium oxalate (CaOx) crystals and crystal agglomerates are normally harmlessly excreted, but in nephrolithiasis they are retained by tubular epithelial cells and shifted into the renal interstitium. This crystalline material induces an inflammatory response consisting of an increase in the number of interstitial cells and an expansion of the extracellular matrix. The newly arrived cells either derive from the

Ruud de Water; Cindy Noordermeer; Theo H. van der Kwast; Horst Nizze; Egbert R. Boevé; Dik J. Kok; Fritz H. Schröder

1999-01-01

244

An unidentified macromolecular inhibitory constituent of calcium oxalate crystal growth in human urine  

Microsoft Academic Search

We have detected and isolated a macromolecular constituent in normal human urine possessing calcium crystal growth inhibitory activity. The purification procedure consisted of two anion exchange chromatographies and one affinity chromatography. The crystal growth inhibitor was found to be heterogeneous in net charge as well as in size. It has not been identified. It is not an uronic acid-containing glycosaminoglycan,

S. Sørensen; K. Hansen; S. Bak; S. J. Justesen

1990-01-01

245

Calcium Oxalate Crystals in Monocotyledons: A Review of their Structure and Systematics  

Microsoft Academic Search

Three main types of calcium oxalate crystal occur in monocotyledons: raphides, styloids and druses, although intermediates are sometimes recorded. The presence or absence of the different crystal types may represent ‘useful’ taxonomic characters. For instance, styloids are characteristic of some families of Asparagales, notably Iridaceae, where raphides are entirely absent. The presence of styloids is therefore a synapomorphy for some

CHRISTINA J. PRYCHID; PAULA J. RUDALL

1999-01-01

246

Twin crystals of calcium oxalate in the seed coat of the kidney bean  

Microsoft Academic Search

Summary Examination of the seed coat of the kidney beanPhaseolus vulgaris L. (var. Kentucky Wonder) in the mature dry condition revealed a layer of cells in which almost every component cell contains a calcium oxalate crystal. These crystals were isolated and studied by light and scanning electron microscopy, and we determined with powder X-ray diffraction that the crystalline substance is

H. J. Arnott; M. A. Webb

1983-01-01

247

Tophaceous pseudogout (tumoral calcium pyrophosphate dihydrate crystal deposition disease)  

Microsoft Academic Search

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

Tsuyoshi Ishida; Howard D Dorfman; Peter G Bullough

1995-01-01

248

Calcium  

MedlinePLUS

... calcium. Veggies. You'll also find calcium in broccoli and dark green, leafy vegetables (especially collard and ... of calcium such as dark green, leafy vegetables, broccoli, chickpeas, and calcium-fortified products, including orange juice, ...

249

Modification of nanostructured calcium carbonate for efficient gene delivery.  

PubMed

In this study, a facile method to modify nanostructured calcium carbonate (CaCO3) gene delivery systems by adding calcium phosphate (CaP) component was developed. CaCO3/CaP/DNA nanoparticles were prepared by the co-precipitation of Ca(2+) ions with plasmid DNA in the presence of carbonate and phosphate ions. For comparison, CaCO3/DNA nanoparticles and CaP/DNA co-precipitates were also prepared. The effects of carbonate ion/phosphate ion (CO3(2-)/PO4(3-)) ratio on the particle size and gene delivery efficiency were investigated. With an appropriate CO3(2-)/PO4(3-) ratio, the co-existence of carbonate and phosphate ions could control the size of co-precipitates effectively, and CaCO3/CaP/DNA nanoparticles with a decreased size and improved stability could be obtained. The in vitro gene transfections mediated by different nanoparticles in 293T cells and HeLa cells were carried out, using pGL3-Luc as a reporter plasmid. The gene transfection efficiency of CaCO3/CaP/DNA nanoparticles could be significantly improved as compared with CaCO3/DNA nanoparticles and CaP/DNA co-precipitates. The confocal microscopy study indicated that the cellular uptake and nuclear localization of CaCO3/CaP/DNA nanoparticles were significantly enhanced as compared with unmodified CaCO3/DNA nanoparticles. PMID:24732398

Zhao, Dong; Wang, Chao-Qun; Zhuo, Ren-Xi; Cheng, Si-Xue

2014-06-01

250

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

251

Inhibition of calcium oxalate crystallization by glutamic acid: Different effects at low and high concentrations  

NASA Astrophysics Data System (ADS)

The effects of L-aspartic acid, alanine and L-glutamic acid on the crystallization of calcium oxalate were followed by two methods: measurements of the changes in calcium ion concentrations and determination of crystal size distribution in the calcium oxalate precipitate. The changes in calcium ion concentration were detected by a specific calcium electrode and are expressed as Discriminating Index (DI) values. Median size and number of crystals per milliliter were determined by Particle Data Counter. Glutamic acid in the range of 0-200 ppm was added to solutions of CaCl 2 which were subsequently mixed with solutions of Na 2C 2O 4 to yield CaC 2O 4 precipitation. At relatively high concentrations of glutamic acid, namely 20-200 ppm, the precipitation of calcium oxalate is retarded. However, at low concentrations, 2.5-20 ppm oxalate precipitation is enhanced. The two independent methods yield well-correlated results. Both L-aspartic acid and alanine did not affect the precipitation of calcium oxalate at similar experimental conditions.

Azoury, Reuven; Randolph, Alan D.; Drach, George W.; Perlberg, Saul; Garti, Nissim; Sarig, Sara

1983-11-01

252

Tamm-Horsfall glycoprotein-inhibitor or promoter of calcium oxalate monohydrate crystallization processes?  

Microsoft Academic Search

The processes of calcium oxalate monohydrate (COM) crystal nucleation, growth and aggregation (agglomeration) generally have been studied using a wide variety of assay systems\\/conditions. This paper reviews the apparently conflicting data on the effects of Tamm-Horsfall glycoprotein (THP) on COM crystallization processes in vitro, with the main emphasis on crystal aggregation. According to its well-known physico-chemical properties. THP has a

B. Hess; Gerhardt A; Brit J Nutr; Paul O. Schwille

1992-01-01

253

Two year comparison of sevelamer and calcium carbonate effects on cardiovascular calcification and bone density  

Microsoft Academic Search

Background. Calcium-based phosphate binders may induce tissue calcification, and little is known about their effects on bone density. We compared the effects of a calcium with a non-calcium phosphate binder on both arterial calcification and bone density measured by computed tomography. Methods. Seventy-two adult haemodialysis patients were randomized to treatment with calcium carbonate (CC) or sevelamer (SEV) for 2 years.

Hans-Gernot Asmus; Johan Braun; Rolfdieter Krause; Reinhard Brunkhorst; Herwig Holzer; Walter Schulz; Hans-Hellmut Neumayer; Paolo Raggi; Jurgen Bommer

2005-01-01

254

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

255

Studies on growth, thermal and dielectric behavior of calcium succinate trihydrate single crystals  

NASA Astrophysics Data System (ADS)

Calcium succinate trihydrate crystals have been grown by gel aided solution growth technique and the effect of different growth parameters on the growth of the crystal is investigated. The compound is characterized by X-ray single crystal structure determinations and powder X-ray diffraction (XRD) technique. The thermogravimetric (TG), differential thermal analysis (DTA) and differential scanning calorimetric (DSC) studies were carried out to investigate the thermal stability of the crystal. The dielectric behavior of the title compound crystal was investigated by measuring the dielectric constant and a c conductivity as a function of frequency at temperatures ranging from 30 °C to 110 °C.

Binitha, M. P.; Pradyumnan, P. P.

2014-06-01

256

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

257

Effect of AC Electromagnetic Field on Zeta Potential of Calcium Carbonate  

Microsoft Academic Search

The influence of an AC electromagnetic field on the interface potentials (zeta potential) of calcium carbonate in an aqueous solution was investigated. By using a suspension of calcium carbonate microparticles in an electrolytic solution, we investigated the changes in the zeta potential of the particles by treating them to a weak AC electromagnetic field at different frequencies; the frequencies ranged

S. Umeki; H. Shimabukuro; T. Watanabe; T. Kato; S. Taniguchi; K. Tohji

2008-01-01

258

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

PubMed Central

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

Park, Kyungho; Jun, Sangju; Kim, Daehyeon

2014-01-01

259

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...

260

The role of magnesium in stabilising amorphous calcium carbonate and controlling calcite morphologies  

Microsoft Academic Search

Calcium carbonate has been precipitated from aqueous solutions containing magnesium under conditions of high supersaturation. The precipitates were analysed over time using X-ray diffraction (XRD) and Infrared Spectroscopy (IR), and it was demonstrated that in all cases amorphous calcium carbonate (ACC) was the first phase formed. The magnesium content of the ACC was defined by the Mg:Ca ratio in the

Eva Loste; Rory M. Wilson; Ram Seshadri; Fiona C. Meldrum

2003-01-01

261

Amorphous and crystalline calcium carbonate distribution in the tergite cuticle of moulting Porcellio scaber (Isopoda, Crustacea)  

Microsoft Academic Search

The main mineral components of the isopod cuticle consists of crystalline magnesium calcite and amorphous calcium carbonate. During moulting isopods moult first the posterior and then the anterior half of the body. In terrestrial species calcium carbonate is subject to resorption, storage and recycling in order to retain significant fractions of the mineral during the moulting cycle. We used synchrotron

Frank Neues; Sabine Hild; Matthias Epple; Othmar Marti; Andreas Ziegler

2011-01-01

262

Why Does Calcium Carbonate Precipitate in the Ocean Crust?  

NASA Astrophysics Data System (ADS)

Calcium carbonate (CaCO3) precipitation in extant ocean crust may provide lessons for industrial carbon dioxide (CO2) sequestration to mitigate against future climate change. The formation and alteration of the ocean crust during mid-ocean ridge spreading plays an integral role in the geological carbon (C) cycle. Magma-degassing during mid-ocean ridge volcanism releases large volumes of CO2 to the oceans and atmosphere, whereas the precipitation of CaCO3 minerals in rocks and veins during hydrothermal alteration of the ocean crust is a major mechanism of natural CO2 sequestration. However, the physical and chemical conditions that control the nature, extent and rate of calcium carbonate precipitation in the ocean crust are not well known, and the magnitudes of the carbon fluxes associated with the formation and alteration of the ocean crust remain poorly quantified. Mesozoic ocean crust contains significantly more hydrothermal CaCO3 than young ocean crust, but the past ocean conditions responsible for this enhanced C-uptake by the ocean crust are yet to be determined. The thermal, hydrogeologic, and chemical characteristics of active, low temperature seawater-basalt interaction have been investigated by a series of integrated studies in young ocean crust (<3.6 Ma) on the eastern flank of the Juan de Fuca ridge (JdFR). This has included sampling by scientific ocean drilling of CaCO3 veins, their parent fluids, and the basalts that host the veins. This area provides a unique opportunity to investigate the conditions of in situ hydrothermal CaCO3 precipitation on short geologic timescales. Fluid and vein analyses provide boundary conditions for geochemical modeling using 'Phreeqc' to determine why basement fluids are saturated with respect to CaCO3. We evaluate the controlling effects of key parameters including fluid dissolved inorganic carbon (DIC), Mg and Ca concentrations, alkalinity, temperature, and pH on CaCO3 precipitation. Our results provide insights into how differing past conditions (e.g. ocean temperature and pCO2) affected the ocean crustal C-reservoir, and enable better quantification of the magnitude of this reservoir and how it has varied over geological time. This information is directly applicable to the development of industrial scale CO2 sequestration using methods that mimic but accelerate natural CO2-drawdown processes.

Coggon, R. M.; Teagle, D. A.; Harris, M.; John, C. M.; Smith-Duque, C. E.; Alt, J.

2012-12-01

263

Composition and properties of silver-containing calcium carbonate-calcium phosphate bone cement.  

PubMed

The introduction of silver, either in the liquid phase (as silver nitrate solution: Ag(L)) or in the solid phase (as silver phosphate salt: Ag(S)) of calcium carbonate-calcium phosphate (CaCO3-CaP) bone cement, its influence on the composition of the set cement (C-Ag(L) and C-Ag(S) cements with a Ca/Ag atomic ratio equal to 10.3) and its biological properties were investigated. The fine characterisation of the chemical setting of silver-doped and reference cements was performed using FTIR spectroscopy. We showed that the formation of apatite was enhanced from the first hours of maturation of C-Ag(L) cement in comparison with the reference cement, whereas a longer period of maturation (about 10 h) was required to observe this increase for C-Ag(S) cement, although in both cases, silver was present in the set cements mainly as silver phosphate. The role of silver nitrate on the setting chemical reaction is discussed and a chemical scheme is proposed. Antibacterial activity tests (S. aureus and S. epidermidis) and in vitro cytotoxicity tests (human bone marrow stromal cells (HBMSC)) showed that silver-loaded CaCO3-CaP cements had antibacterial properties (anti-adhesion and anti-biofilm formation) without a toxic effect on HBMSC cells, making C-Ag(S) cement a promising candidate for the prevention of bone implant-associated infections. PMID:23892487

Jacquart, Sylvaine; Siadous, Robin; Henocq-Pigasse, Christel; Bareille, Reine; Roques, Christine; Rey, Christian; Combes, Christèle

2013-12-01

264

Efficient calcium lactate production by fermentation coupled with crystallization-based in situ product removal.  

PubMed

Lactic acid is a platform chemical with various industrial applications, and its derivative, calcium lactate, is an important food additive. Fermentation coupled with in situ product removal (ISPR) can provide more outputs with high productivity. The method used in this study was based on calcium lactate crystallization. Three cycles of crystallization were performed during the fermentation course using a Bacillus coagulans strain H-1. As compared to fed-batch fermentation, this method showed 1.7 times higher average productivity considering seed culture, with 74.4% more l-lactic acid produced in the fermentation with ISPR. Thus, fermentation coupled with crystallization-based ISPR may be a biotechnological alternative that provides an efficient system for production of calcium lactate or lactic acid. PMID:24780270

Xu, Ke; Xu, Ping

2014-07-01

265

Interleukin 1? blockade improves signs and symptoms of chronic calcium pyrophosphate crystal arthritis resistant to treatment.  

PubMed

A 54-year-old woman with recurrent episodes of bilateral knee arthritis was admitted several times to the Department of Rheumatology. She was diagnosed to have chronic calcium pyrophosphate crystal arthritis. Interleukin 1? (IL-1?) plays a central role in the pathogenesis of inflammation induced by calcium pyrophosphate crystals, and IL-1? blockade may be an effective treatment in patients with severe chronic calcium pyrophosphate crystal arthritis. Because of the short effect of treatment with corticosteroids and the frequent attacks of arthritis, the patient was treated with the IL-1 receptor antagonist anakinra. She responded well after 1 week with normalization of inflammation. Eight months after the initiation of treatment, the patient has had no relapses, although we were unable to withdraw the anakinra. PMID:22832289

Diamantopoulos, Andreas P; Brodin, Christer; Hetland, Helene; Haugeberg, Glenn

2012-09-01

266

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

267

Relations for the determination of the polymorphic composition of calcium carbonate precipitated in saturated sodium chloride solutions  

Microsoft Academic Search

The purification of concentrated sodium chloride solutions from calcium and magnesium ions is realized by precipitating them in the form of calcium carbonate and magnesium hydroxide using a reagent solution composed of sodium carbonate and sodium hydroxide. The functioning of the industrial process depends on the polymorphic composition of the precipitated calcium carbonate. The classical experimental design method is used

C. Berger; A. Dandeu; C. Carteret; B. Humbert; H. Muhr; E. Plasari; J. M. Bossoutrot

268

The Influence of pH on the Oxygen Isotope Composition of Calcium Carbonate  

NASA Astrophysics Data System (ADS)

Oxygen isotope fractionation between calcium carbonate and water is temperature-dependent and can therefore be used as a paleothermometer. Although oxygen isotope fractionation is expected from principles of equilibrium isotopic partitioning, the temperature-dependence remains uncertain because other factors, such as slow exchange between dissolved inorganic carbon (DIC) species and water, can obscure the temperature signal. Oxygen isotopic equilibrium between aqueous solution and calcium carbonate includes two distinct equilibria: equilibrium of the DIC species in solution (i.e., CO2(aq), H2CO3, HCO3-, and CO32-) with water, and equilibrium between the dissolved inorganic carbon with the precipitated carbonate. To isolate kinetic isotope effects that arise at the mineral-solution interface, isotopic equilibrium among DIC species must be maintained. This can be accomplished by dissolving the enzyme carbonic anhydrase (CA) into the solution, thereby reducing the time required for isotopic equilibration between DIC species by approximately two orders of magnitude between pH 7.7 and 9.3. We conduct calcite growth experiments aimed specifically at measuring the pH-dependence of kinetic oxygen isotope effects during precipitation of calcite. We precipitated calcite from aqueous solution at a constant pH and controlled supersaturation over the pH range 7.7-9.3. For each experiment, a gas mixture of N2 and CO2 is constantly bubbled through a beaker containing ~1300 mL of solution (30 mM CaCl2 + 5 mM NH4Cl + 0.1 mM SrCl2). As CO2 from the gas dissolves into solution, calcite crystals grow on the beaker walls. The pH of the solution is maintained by use of an autotitrator with NaOH as the titrant. We control the temperature, pH, the pCO2 of the gas inflow, and the gas inflow rate, and monitor the total alkalinity, the pCO2 of the gas outflow, and the amount of NaOH added. A constant crystal growth rate of ~1.6 mmol/m2/hr is maintained over all experiments. We will present results from this set of experiments and discuss kinetic oxygen isotope effects in the context of a recently-developed ion-by-ion growth model of calcite.

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

2013-12-01

269

Urinary glycosaminoglycans are selectively included into calcium oxalate crystals precipitated from whole human urine.  

PubMed

Urinary glycosaminoglycans are selectively included into calcium oxalate (CaOx) crystals precipitated from whole human urine: The presence of glycosaminoglycans (GAGs) in the organic matrix of urinary stones, and their known effects on CaOx crystallization have prompted speculation regarding their role in CaOx urolithiasis. The aim of this study was to examine the involvement of GAGs in the early stages of CaOx crystallization in human urine. Urine samples were collected from healthy men and CaOx crystallization was induced by the addition of a sodium oxalate load. The crystals were harvested and demineralized, and the GAG content of the resulting extract analysed by cellulose acetate electrophoresis. Only one GAG, heparan sulphate (HS) was detected in the organic matrix of the crystals; chondroitin sulphate (ChS), the most abundant urinary GAG, was conspicuously absent. Further experiments, in which varying amounts of HS and ChS were added to ultrafiltered (10,000 Da) urine prior to induction of calcium oxalate crystallization, showed that ChS was included into the crystals only when HS was absent from the urine. It was concluded that the selective inclusion of GAGs into crystals and stones is a function related more to relative binding affinity than to ambient GAG concentration and that HS and ChS compete for specific binding sites on the crystal surface. PMID:7747154

Suzuki, K; Mayne, K; Doyle, I R; Ryall, R L

1994-01-01

270

Electron paramagnetic resonance study of vanadyl ion doped in ?-calcium formate single crystal  

NASA Astrophysics Data System (ADS)

Results of an EPR study of vanadyl ion (VO 2+) doped in single crystals of ?-calcium formate are reported. Impurity sites in the unit cell and the molecular structure of the vanadyl complexes in the crystal are discussed. The spin-Hamiltonian parameters are determined from single-crystal EPR data at room temperature and from powder EPR data at room temperature and at liquid nitrogen temperature. The g and A tensors are found to be axially symmetric. From the optical and EPR data, the MO bonding coefficients and crystal field parameters are calculated and discussed. Two distinct vanadyl complexes at substitutional sites (Ca 2+) and one interstitial vanadyl complex have been identified.

Umar, M.; Singh, R. J.; Chand, Prem; Upreti, G. C.

271

Chemical, microstructural and strength development of calcium and magnesium carbonate binders  

Microsoft Academic Search

The influence of magnesium on the chemistry of calcium carbonate formation has been studied. It was found that the type of carbonate formed by subjecting compacts of Ca(OH)2 and Mg(OH)2 to carbon dioxide (up to 20 atm CO2 pressure) for variable periods of time is largely controlled by the molar proportion of calcium to magnesium in the initial mixture. Increasing magnesium

P. De Silva; L. Bucea; V. Sirivivatnanon

2009-01-01

272

Carbothermic reduction of zinc sulfide in the presence of calcium carbonate  

Microsoft Academic Search

Carbothermic reduction of zinc sulfide in the presence of calcium carbonate was investigated by employing an X-ray diffractometer\\u000a (XRD), a carbon and sulfur determinator, a scanning electron microscope (SEM), an energy-dispersive X-ray analysis (EDX),\\u000a and a surface area analyzer. Experimental results revealed that calcium carbonate was completely decomposed to CaO in the\\u000a initial stage and CaO was then involved in

Che-Ming Wu; Chun-I Lin; Hsi-Kuei Chen

2006-01-01

273

Calcium phosphate crystallization under terrestrial and microgravity conditions  

Microsoft Academic Search

Calcium phosphate crystalline powders grown under terrestrial and space (EURECA 1992–1993 flight) conditions in the Solution Growth Facility are analyzed and compared by optical and electron microscopy (scanning and transmission), electron and X-ray microdiffraction and microanalyses. On earth, only small, micrometer size scale, spherolites of hydroxyapatite (HAP) grow. In space, the HAP spherolites reach hundreds of micrometer. Also, octacalcium phosphate

H. E. Lundager Madsen; F. Christensson; L. E. Polyak; E. I. Suvorova; M. O. Kliya; A. A. Chernov

1995-01-01

274

Influence of calcium carbonate on U(VI) sorption to soils.  

PubMed

The high stability of calcium uranyl carbonate complexes in the circumneutral pH range has a strong impact on U(VI) sorption in calcareous soils. To quantify this influence, sorption of U(VI) to soils in the presence of naturally occurring calcium carbonate was investigated by conducting batch experiments in which either U(VI) concentration or solution pH was varied. Two soils containing different calcium carbonate concentrations were selected, one from Oak Ridge, TN, and another from Altamont Pass, CA. The results show that the presence of calcium carbonate in soils strongly affects U(VI) sorption. Higher concentrations of soil calcium carbonate lead to a pronounced suppression of the pH-dependent sorption curve in the neutral pH range because of the formation of a very stable neutral complex of calcium uranyl carbonate in solution. A surface complexation model considering both strong and weak sites for ferrihydrite and ionizable hydroxyl sites for clay minerals was compared with experimental results, and U(VI) binding parameters were reasonably estimated. Fair agreement was found between the model predictions and sorption data, which span a wide range of U(VI) concentrations and pH. The results also show that appropriate solution-to-solid ratios need to be used when measuring distribution coefficients in calcareous soils to avoid complete CaCO3 dissolution and consequent dilution of calcium uranyl carbonate complexes. PMID:14717170

Zheng, Zuoping; Tokunaga, Tetsu K; Wan, Jiamin

2003-12-15

275

Peptides of Matrix Gla Protein Inhibit Nucleation and Growth of Hydroxyapatite and Calcium Oxalate Monohydrate Crystals  

PubMed Central

Matrix Gla protein (MGP) is a phosphorylated and ?-carboxylated protein that has been shown to prevent the deposition of hydroxyapatite crystals in the walls of blood vessels. MGP is also expressed in kidney and may inhibit the formation of kidney stones, which mainly consist of another crystalline phase, calcium oxalate monohydrate. To determine the mechanism by which MGP prevents soft-tissue calcification, we have synthesized peptides corresponding to the phosphorylated and ?-carboxylated sequences of human MGP in both post-translationally modified and non-modified forms. The effects of these peptides on hydroxyapatite formation and calcium oxalate crystallization were quantified using dynamic light scattering and scanning electron microscopy, respectively. Peptides YGlapS (MGP1-14: Y?EpSHEpSMEpSYELNP), YEpS (YEpSHEpSMEpSYELNP), YGlaS (Y?ESHESMESYELNP) and SK-Gla (MGP43-56: SKPVH?ELNR?EACDD) inhibited formation of hydroxyapatite in order of potency YGlapS > YEpS > YGlaS > SK-Gla. The effects of YGlapS, YEpS and YGlaS on hydroxyapatite formation were on both crystal nucleation and growth; the effect of SK-Gla was on nucleation. YGlapS and YEpS significantly inhibited the growth of calcium oxalate monohydrate crystals, while simultaneously promoting the formation of calcium oxalate dihydrate. The effects of these phosphopeptides on calcium oxalate monohydrate formation were on growth of crystals rather than nucleation. We have shown that the use of dynamic light scattering allows inhibitors of hydroxyapatite nucleation and growth to be distinguished. We have also demonstrated for the first time that MGP peptides inhibit the formation of calcium oxalate monohydrate. Based on the latter finding, we propose that MGP function not only to prevent blood-vessel calcification but also to inhibit stone formation in kidney.

Goiko, Maria; Dierolf, Joshua; Gleberzon, Jared S.; Liao, Yinyin; Grohe, Bernd; Goldberg, Harvey A.; de Bruyn, John R.; Hunter, Graeme K.

2013-01-01

276

Peptides of Matrix Gla protein inhibit nucleation and growth of hydroxyapatite and calcium oxalate monohydrate crystals.  

PubMed

Matrix Gla protein (MGP) is a phosphorylated and ?-carboxylated protein that has been shown to prevent the deposition of hydroxyapatite crystals in the walls of blood vessels. MGP is also expressed in kidney and may inhibit the formation of kidney stones, which mainly consist of another crystalline phase, calcium oxalate monohydrate. To determine the mechanism by which MGP prevents soft-tissue calcification, we have synthesized peptides corresponding to the phosphorylated and ?-carboxylated sequences of human MGP in both post-translationally modified and non-modified forms. The effects of these peptides on hydroxyapatite formation and calcium oxalate crystallization were quantified using dynamic light scattering and scanning electron microscopy, respectively. Peptides YGlapS (MGP1-14: Y?EpSHEpSMEpSYELNP), YEpS (YEpSHEpSMEpSYELNP), YGlaS (Y?ESHESMESYELNP) and SK-Gla (MGP43-56: SKPVH?ELNR?EACDD) inhibited formation of hydroxyapatite in order of potency YGlapS > YEpS > YGlaS > SK-Gla. The effects of YGlapS, YEpS and YGlaS on hydroxyapatite formation were on both crystal nucleation and growth; the effect of SK-Gla was on nucleation. YGlapS and YEpS significantly inhibited the growth of calcium oxalate monohydrate crystals, while simultaneously promoting the formation of calcium oxalate dihydrate. The effects of these phosphopeptides on calcium oxalate monohydrate formation were on growth of crystals rather than nucleation. We have shown that the use of dynamic light scattering allows inhibitors of hydroxyapatite nucleation and growth to be distinguished. We have also demonstrated for the first time that MGP peptides inhibit the formation of calcium oxalate monohydrate. Based on the latter finding, we propose that MGP function not only to prevent blood-vessel calcification but also to inhibit stone formation in kidney. PMID:24265810

Goiko, Maria; Dierolf, Joshua; Gleberzon, Jared S; Liao, Yinyin; Grohe, Bernd; Goldberg, Harvey A; de Bruyn, John R; Hunter, Graeme K

2013-01-01

277

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

NASA Astrophysics Data System (ADS)

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

Uysal, Ahmet; Stripe, Benjamin; Dutta, Pulak

2010-03-01

278

Effects of Monocarboxylic Acid Addition on Crystallization of Calcium Phosphate in a Hydrogel Matrix  

NASA Astrophysics Data System (ADS)

In biomineralization, it is thought that water-soluble organic substances control crystal growth of minerals in hard tissues. The roles of organic substances are not well understood, because the biomineralization process is established by complicated parameters. Crystal growth in hydrogel matrixes can be regarded as simplified model system of biomineralization. In the present study, we investigated the effects of propionic acid (Pro) on crystalline phases and crystal morphologies of calcium phosphate formed in polymeric hydrogel matrixes as the model system of biomineralization. Crystalline phase of the precipitates was octacalcium phosphate (OCP) with spherical shape regardless of Pro concentrations. The fibrous crystals formed under the condition without addition of Pro. The crystal morphologies composing spherical crystals were changed from fibrous to plate-like shape with increasing Pro concentrations. Generally, OCP crystal has plate-like shape exposing (100) face, which calcium ions exist on. Therefore, crystal growth rate of [100] direction of OCP was decreased by Pro adsorbed on (100) face. As a result, crystal morphology composing spherulite became plate-like shape with increasing Pro concentrations.

Yokoi, T.; Kawashita, M.; Ohtsuki, C.

2011-10-01

279

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

280

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

281

A new approach to calculate the risk of calcium oxalate crystallization from unprepared native urine  

Microsoft Academic Search

This work focuses on the in vitro calcium-oxalate (CaOx) crystallization behaviour of native and synthetic urine samples\\u000a in order to establish a CaOx crystallization risk index for unprepared native urine. Native 24-h urine samples from healthy\\u000a persons and from stone-formers were examined. Within a [Ca2+] versus added oxalate (Ox2?) diagram, we observed fields which allow the discrimination of each urine

Norbert Laube; Anke Schneider; Albrecht Hesse

2000-01-01

282

Structure, Chemistry and Crystallization Conditions of Calcium Oxalates — The Main Components of Kidney Stones  

Microsoft Academic Search

The present work contains the results of studies of crystal chemistry and crystallization of calcium oxalates from human renal\\u000a stones (whewellite and weddellite). These minerals are the most frequently occurring components of these pathogenic stones.\\u000a The whewellite-dominant stones usually occur as polynuclear spherulite aggregates with characteristic radial microstructure\\u000a (Fig. 1a). On the surface of whewellite stones, bipyramidic structures of weddellite

Alina R. Izatulina; Vladislav Yu. Yelnikov

283

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

284

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

PubMed

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

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

2013-05-01

285

FT-Raman spectroscopic study of calcium-rich and magnesium-rich carbonate minerals.  

PubMed

Calcium and magnesium carbonates are important minerals found in sedimentary environments. Although sandstones are the most common rock colonized by endolith organisms, the production of calcium and magnesium carbonates is important in survival strategies of organisms and as a source for the removal of oxalate ions. Extremophile organisms in some situations may convert or destroy carbonates of calcium and magnesium, which gives important information about the conditions under which these organisms can survive. The identification on the surface of Mars of 'White Rock' formations, in Juventae Chasma or Sabaea Terra, as possibly carbonate rocks makes the study of these minerals a prerequisite of remote Martian exploration. Here, we show the protocol for the identification by Raman spectroscopy of different calcium and magnesium carbonates and we present a database of relevance in the search for life, extinct or extant, on Mars; this will be useful for the assessment of data obtained from remote, miniaturized Raman spectrometers now proposed for Mars exploration. PMID:16029849

Edwards, Howell G M; Villar, Susana E Jorge; Jehlicka, Jan; Munshi, Tasnim

2005-08-01

286

Stable calcium adsorbates on carbon nanostructures: Applications for high-capacity hydrogen storage  

NASA Astrophysics Data System (ADS)

We have investigated the stability of calcium adsorbates on carbon nanotubes and defective graphene using first-principles calculations. For ultranarrow carbon nanotubes, we find that the effect of chirality is more important to the adsorption as compared to the diameter (D) . The binding energy for a calcium atom absorbed on the (5,0) tube is about 1.4 eV higher than that on the (3,3) tube. We also find that calcium atoms on the octagon defect of graphene are also stable. The binding energies of calcium adsorbates on narrow tubes (3.2Åcalcium monolayer should be stable without clustering. The results show that every calcium atom can uptake four to five H2 and the hydrogen storage can reach 9wt% .

Yang, Xiaobao; Zhang, R. Q.; Ni, Jun

2009-02-01

287

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

Microsoft Academic Search

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

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

2008-01-01

288

Calcium pyrophosphate dihydrate crystal deposition disease mimicking malignant soft tissue tumor  

Microsoft Academic Search

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease has multiple clinical features with variable courses creating several pitfalls in clinical diagnosis. There are number of reported cases mimicking malignant skeletal tumors such as chondrosarcoma. However, no case of CPPD disease with radiographic noncalcified soft tissue mass has been reported in the literature. Here we report a case of CPPD disease clinically

Hasan Havitçioglu; Hasan Tatari; Önder Baran; Metin Manisali; Sermin Özkal; Mustafa Seçil; Dinç Özaksoy; Kutsal Yörükoglu

2003-01-01

289

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 glacier melt. To highlight this process, we present carbonate system data collected in May (spring) and September (autumn) starting 2009 through 2012 from 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. Initial sampling in PWS covered limited stations in the western sound, and ? levels corrosive to aragonite, a form of CaCO3, were observed in association with glacial melt during autumn. Beginning in September 2011, expanded sampling spanned 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 depth 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. The cumulative effect of glacial melt is likely responsible for the seasonal widespread reduction of ? in PWS; however, glacial melt-driven CaCO3 corrosivity is poorly reflected by pCO2 or pHT, indicating that any one of those carbonate parameters alone would inadequately track corrosive conditions in PWS. The unique conditions of the carbonate system in the surface glacial melt plumes enhances atmospheric CO2 uptake, which, if not offset by mixing or primary productivity, would exacerbate CaCO3 corrosivity in a positive feedback via ocean acidification. These effects from glacial melt make PWS highly sensitive to climate change and susceptible to amplified CaCO3 corrosivity.

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

2013-12-01

290

Liquid crystal polyester-carbon fiber composites  

NASA Technical Reports Server (NTRS)

Liquid crystal polymers (LCP) have been developed as a thermoplastic matrix for high performance composites. A successful melt impregnation method has been developed which results in the production of continuous carbon fiber (CF) reinforced LCP prepreg tape. Subsequent layup and molding of prepreg into laminates has yielded composites of good quality. Tensile and flexural properties of LCP/CF composites are comparable to those of epoxy/CF composites. The LCP/CF composites have better impact resistance than the latter, although epoxy/CF composites possess superior compression and shear strength. The LCP/CF composites have good property retention until 200 F (67 % of room temperature value). Above 200 F, mechanical properties decrease significantly. Experimental results indicate that the poor compression and shear strength may be due to the poor interfacial adhesion between the matrix and carbon fiber as adequate toughness of the LCP matrix. Low mechanical property retention at high temperatures may be attributable to the low beta-transition temperature (around 80 C) of the LCP matrix material.

Chung, T. S.

1984-01-01

291

Recovery of calcium carbonate and hydrogen sulfide from waste calcium sulfide  

SciTech Connect

The removal of H{sub 2}S from hot coal gas using a limestone-based sorbent generates a large quantity of calcium sulfide waste (e.g., 67 tons/day from the gasification of 1,000 tons/day of 3% S coal) that cannot be landfilled because of potential H{sub 2}S evolution and sulfide leaching. In the process proposed here, the CaS is dissolved by reaction with H{sub 2}S complexed with aqueous MDEA or other alkanolamines. In the second step, the highly soluble Ca(HS){sub 2} reacts readily with CO{sub 2}, also complexed with aqueous MDEA, to precipitate pure CaCO{sub 3} of uniform crystal size and to form MDEA-complexed H{sub 2}S in solution. The solution from step 2 is split--half is recycled to step 1 and half is sent to a stripper to recover H{sub 2}S and from there to the column where the needed CO{sub 2} is absorbed from a combustion gas.

Brooks, M.W.; Lynn, S. [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering] [Univ. of California, Berkeley, CA (United States). Dept. of Chemical Engineering; [Lawrence Berkeley National Lab., CA (United States)

1997-10-01

292

The mechanism of calcium oxalate crystal-induced haemolysis of human erythrocytes.  

PubMed Central

Calcium oxalate (CaOx) crystals cause membrane damage in human erythrocytes, evident from K+ leakage and haemoglobin release. Whereas the hydrogen acceptor polyvinylpyridine-N-oxide is without effect on CaOx crystal-induced haemolysis, polyanions and negative proteins are strongly inhibitory. This indicates that positive charges are of importance for induction of haemolysis. These positive charges are located on the CaOx crystals. Removal of the negatively charged sialic acid from the cell surface does not affect CaOx crystal-induced haemolysis. CaOx crystals are able to release glucose from negatively charged liposomes, but not from positively charged liposomes. The results are compatible with the view that positive charges on the crystals are of predominant importance in CaOx-induced haemolysis, and that their interactions with negative charges or polarizable structures in the lipid part of the membrane leads to membrane disruption.

Elferink, J. G.

1987-01-01

293

Effect of replacing calcium oxide with calcium halide on crystallization and some physical properties of calcium vanadium phosphate glass ceramics  

NASA Astrophysics Data System (ADS)

The effect of halide ions on density, electrical, magnetic and crystallization kinetics for (20X-50P 2O 5-30V 2O 5) mole% has been investigated, where X=CaO, CaF 2, CaCl 2 and CaBr 2. Halide ions reduce the glass transition temperature, crystallization temperature and activation energy of crystallization. Density, electrical conductivity and magnetic susceptibility increase while molar volume, glass thermal stability and interatomic distance between transition metal ions decrease as the halide ions replace the oxygen ions in these glasses.

Assem, E. E.

2011-02-01

294

Increasing Soil Calcium Availability Alters Forest Soil Carbon Stocks  

NASA Astrophysics Data System (ADS)

Acid deposition in the Northeastern U.S. has been linked to a loss of soil base cations, especially calcium (Ca). While much research has addressed the effects of Ca depletion on soil and stream acidification, few studies have investigated its effects on ecosystem carbon (C) balance. We studied the long-term effects of increased Ca availability on C cycling in a northern hardwood forest in the Adirondack Park, NY. In 1989, calcium carbonate (lime) was added to ~ 100 ha of the Woods Lake Watershed to ameliorate the effects of soil Ca depletion. An additional 100 ha were maintained as controls. We hypothesized that the lime addition would improve forest health and that this improvement would be evident in increased tree biomass, leaf litter, and fine root production. Within the forest floor, we anticipated that the increased pH associated with liming would stimulate microbial activity resulting in increased decomposition and basal soil respiration, and reduced C stocks. Additionally, we hypothesized that increased Ca availability could enhance Ca-OM complexation in the upper mineral soils, leading to increased C stocks in these horizons. Eighteen years after liming, soil pH and exchangeable Ca pools remained elevated in the forest floor and upper mineral soil of the limed plots. Forest floor C stocks were significantly larger in limed plots (68 vs. 31 t C ha-1), and were driven primarily by greater C accumulation in the forest floor Oa horizon. Mineral soil C stocks did not differ between limed and control soils. Liming did not affect tree growth, however a net decline in biomass was observed across the entire watershed. There was a trend for larger fine root and foliar litter inputs in limed plots relative to controls, but the observed forest floor accumulation appears to be driven primarily by a suppression of decomposition. Liming reduced basal soil respiration rates by 17 and 43 % in the Oe and Oa horizons, respectively. This research suggests that Ca may stabilize soil organic matter and that long-term Ca depletion caused by acid deposition could have large, unexpected effects on ecosystem C dynamics.

Melvin, A.; Goodale, C. L.

2011-12-01

295

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

296

Solubility, inhibition of crystallization and microscopic analysis of calcium oxalate crystals in the presence of fractions from Humulus lupulus L.  

NASA Astrophysics Data System (ADS)

Procedures for obtaining noncytotoxic and nonmutagenic extracts from Humulus lupulus L. of high potency for inhibition and dissolving of model (calcium oxalate crystals) and real kidney stones, obtained from patients after surgery, are presented. Multistep extraction procedures were performed in order to obtain the preparations with the highest calcium complexing properties. The composition of obtained active fractions was analyzed by GC/MS and NMR methods. The influence of preparations on inhibition of formation and dissolution of model and real kidney stones were evaluated based on conductrometric titration, flame photometry and microscopic analysis. The "fraction soluble in methanol" obtained from water-alkaline extracts contains sugar alcohols and organic acids, and is effective in dissolving the kidney stones. The "fraction insoluble in methanol" contains only sugar derivatives and it changes the morphology of the crystals, making them "jelly-like". Both fractions are potentially effective in kidney stone therapy.

Fr?ckowiak, Anna; Ko?lecki, Tomasz; Skibi?ski, Przemys?aw; Gawe?, Wies?aw; Zaczy?ska, Ewa; Czarny, Anna; Piekarska, Katarzyna; Gancarz, Roman

2010-11-01

297

Freeze-drying yields stable and pure amorphous calcium carbonate (ACC).  

PubMed

A simple synthetic method is presented for the precipitation of high purity, dry amorphous calcium carbonate (ACC) based on freeze-drying saturated, counter ion free CaCO3 solutions, where the ACC produced shows an extended atmospheric stability. Translation of the methodology to amorphous calcium phosphate demonstrates the generality of the approach. PMID:23478859

Ihli, Johannes; Kulak, Alexander N; Meldrum, Fiona C

2013-04-18

298

Influence of lysozyme on the precipitation of calcium carbonate: a kinetic and morphologic study  

NASA Astrophysics Data System (ADS)

Several mechanisms have been proposed to explain the interactions between proteins and mineral surfaces, among them a combination of electrostatic, stereochemical interactions and molecular recognition between the protein and the crystal surface. To identify the mechanisms of interaction in the lysozyme-calcium carbonate model system, the effect of this protein on the precipitation kinetics and morphology of calcite crystals was examined. The solution chemistry and morphology of the solid were monitored over time in a set of time-series free-drift experiments in which CaCO 3 was precipitated from solution in a closed system at 25°C and 1 atm total pressure, in the presence and absence of lysozyme. The precipitation of calcite was preceded by the precipitation of a metastable phase that later dissolved and gave rise to calcite as the sole phase. With increasing lysozyme concentration, the nucleation of both the metastable phase and calcite occurred at lower ? calcite, indicating that lysozyme favored the nucleation of both phases. Calcite growth rate was not affected by the presence of lysozyme, at least at protein concentrations ranging from 0 mg/mL to 10 mg/mL. Lysozyme modified the habit of calcite crystals. The degree of habit modification changed with protein concentration. At lower concentrations of lysozyme, the typical rhombohedral habit of calcite crystals was modified by the expression of {110} faces, which resulted from the preferential adsorption of protein on these faces. With increasing lysozyme concentration, the growth of {110}, {100}, and finally {001} faces was sequentially inhibited. This adsorption sequence may be explained by an electrostatic interaction between lysozyme and calcite, in which the inhibition of the growth of {110}, {100}, and {001} faces could be explained by a combined effect of the density of carbonate groups in the calcite face and the specific orientation (perpendicular) of these carbonate groups with respect to the calcite surface. Overgrowth of calcite in the presence of lysozyme demonstrated that the protein favored and controlled the nucleation on the calcite substrate. Overgrowth crystals nucleated epitaxially in lines which run diagonal to rhombohedral {104} faces.

Jimenez-Lopez, Concepcion; Rodriguez-Navarro, Alejandro; Dominguez-Vera, Jose M.; Garcia-Ruiz, Juan M.

2003-05-01

299

Growth, crystal structure and thermal properties of calcium bis(malate) dihydrate  

Microsoft Academic Search

A new coordination compound crystal of calcium with malic acid is prepared by gel aided solution growth. Single crystal X-ray diffraction studies revealed that the structural formula of the compound is Ca(C4H4O5)2·2H2O. It crystallizes in the monoclinic system with space group C2\\/c, Z=4, with unit cell parameters a=15.916(9)Å, b=5.886(3)Å, c=13.046(6)Å and ?=90.678(4)°. Data were collected by oscillation method and full-matrix

T. Jini; K. V. Saban; G. Varghese; S. Naveen; M. A. Sridhar; J. S. Prasad

2007-01-01

300

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

301

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

302

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 semienclosed inland sea located on the south-central coast of Alaska and 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 over a portion of 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 reduction of ? in PWS, making PWS highly sensitive to increasing atmospheric CO2 and amplified CaCO3 corrosivity.

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

2014-01-01

303

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

304

Calcium oxalate monohydrate crystallization: citrate inhibition of nucleation and growth steps  

NASA Astrophysics Data System (ADS)

The inhibitory action of citrate on calcium oxalate monohydrate (COM) crystallization has been examined in terms of nucleation and crystal growth kinetic properties. Lag-time data for the appearance of crystals and [ 14C] oxalate incorporation under crystal growth conditions allowed us to investigate the influence of citrate at physiological levels (3.5mM). Moreover, through the use of the EQUIL software, we formulated our solutions based on calculations of solute composition such that free calcium concentrations were the same in the absence and presence of this tricarboxylic acid. The presence of citrate had little effect on the apparent interfacial free energy as determined by nucleation kinetic studies, but total particle production was greater in the absence of citrate; this was evident from electron microscopy and was also indicated by corresponding values of pre-exponential terms of the Gibbs-Thomson equation. Crystal growth rates were lowered in the presence of citrate to 30% of the uninhibited value, and distinctive morphological habit modifications were also observed by scanning electron microscopy. Together, these findings suggest that citrate may influence COM crystallization at several stages, and we present a model for face-specific growth inhibition by citrate acting on the (010) COM crystal face.

Antinozzi, Peter A.; Brown, Charles M.; Purich, Daniel L.

1992-11-01

305

Reduction of Carbon During High-Temperature Vaporization in the Calcium-Carbonate-Silicate System  

NASA Astrophysics Data System (ADS)

Last year we reported the formation of a wide range of calcium silicates during vaporization of CaCO3-CaSO4/CaSO4 x 2H2O-SiO2 mixtures by a laser pulse, with application to the Chicxulub impact. It was shown that complex redox processes occur in the vapor cloud under dry conditions yielding part of the Si in metallic form and half the carbon as graphite. Here we investigated experimentally the Ca, Si and C high temperature chemistry using calcium carbonate-silicate targets. We used natural spurrite (Ca2SiO4 x CaCO3)and a compressed mixture of powders of CaCO3 and SiO2 with the same atomic Ca/Si ratio as in spurrite. The Ca-Si chemistry was found to be the same as in the previous research and independent of the initial state of Ca and Si in the target. Reduction of Si was found to be higher than in Gerasimov et al., amounting up to 9% of total Si. Different forms of reduced C were identified: C as graphite, silicon carbide, and complex carbon agglomerates of fullerene type.

Gerasimov, M. V.; Dikov, Yu. P.; Yakovlev, O. I.; Wlotzka, F.

1996-03-01

306

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.

2014-01-01

307

Adsorption of sodium polyacrylate in high solids loading calcium carbonate slurries  

Microsoft Academic Search

The adsorption of sodium polyacrylate (NaPAA) in slurries with up to 75wt.% calcium carbonate was investigated with the use of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and adsorption of probe molecules. Analysis of the IR spectra demonstrated that the carboxylate groups of NaPAA adsorbed onto ground calcium carbonate (GCC) in three different modes. These modes were shown to be

Joshua J. Taylor; Wolfgang M. Sigmund

2010-01-01

308

Synthesis and characterization of cellulose acetate–calcium carbonate hybrid nanocomposite  

Microsoft Academic Search

A hybrid nanocomposite composed of calcium carbonate (CaCO3) and cellulose acetate (CA) was fabricated by bubbling CO2 gas into the mixture of CA and Ca(OH)2 solution. Cellulose acetate–calcium carbonate (CA–CC) nanocomposite was characterized by spectral, thermal and optical methods. FTIR and XRD analysis confirmed the formation of the hybrid nanocomposite and XRD confirmed the formation of CaCO3 with calcite polymorph.

Amalraj John; Yi Chen; Jaehwan Kim

309

Mixtures composed of liquid crystals and carbon nanotubes  

NASA Astrophysics Data System (ADS)

The phenomenological model to describe the liquid crystal-carbon nanotubes mixture presented in a previous paper [P. van der Schoot, V. Popa-Nita, and S. Kralj, J. Phys. Chem. B 112, 4512 (2008)] has been extended to include the isotropic carbon nanotubes-nematic thermotropic liquid crystal interaction. It is assumed that the carbon nanotubes in the isotropic phase act as an external random field on liquid crystal component. The influence of the randomly orientational disorder on the phase diagram of the mixture and orientational order parameters profiles of both components is theoretically analyzed for different values of temperature, volume fraction of carbon nanotubes, nematic carbon nanotubes-nematic liquid crystal coupling strength and the random field strength.

Popa-Nita, V.

2014-04-01

310

Mixtures composed of liquid crystals and carbon nanotubes.  

PubMed

The phenomenological model to describe the liquid crystal-carbon nanotubes mixture presented in a previous paper [P. van der Schoot, V. Popa-Nita, and S. Kralj, J. Phys. Chem. B 112, 4512 (2008)] has been extended to include the isotropic carbon nanotubes-nematic thermotropic liquid crystal interaction. It is assumed that the carbon nanotubes in the isotropic phase act as an external random field on liquid crystal component. The influence of the randomly orientational disorder on the phase diagram of the mixture and orientational order parameters profiles of both components is theoretically analyzed for different values of temperature, volume fraction of carbon nanotubes, nematic carbon nanotubes-nematic liquid crystal coupling strength and the random field strength. PMID:24784308

Popa-Nita, V

2014-04-28

311

CALCIUM OXALATE CRYSTAL ATTACHMENT TO CULTURED KIDNEY EPITHELIAL CELL LINES  

Microsoft Academic Search

PurposeCultured kidney epithelial cell lines have frequently been used in urolithiasis research, and in particular in studies related to the interactions between stone crystals and cell membranes. There is evidence that when epithelial cell lines are transformed or serially passed to immortalize them, they experience changes in both cell physiology and morphology. Stone research utilizing cell cultures is frequently necessary

MICHAEL W. BIGELOW; JOHN H. WIESSNER; JACK G. KLEINMAN; NEIL S. MANDEL

1998-01-01

312

Calcium pyrophosphate dihydrate and basic calcium phosphate crystalinduced arthropathies: Update on pathogenesis, clinical features, and Therapy  

Microsoft Academic Search

Calcium-containing crystals are the most common class for the osteoarthritic joint. They are responsible for acute periarthritis\\u000a and destructive arthropathies, and for tissue deposits mimicking tumor-like masses. These crystals encompassed mainly calcium\\u000a pyrophosphate dihydrate and basic calcium phosphate crystals, with the latter being related to hydroxyapatite, carbonate-substituted\\u000a apatite, and octacalcium phosphate. Calcification deposit mechanisms will be reviewed with respect to

Hang-Korng Ea; Frédéric Lioté

2004-01-01

313

Pore fluid chemistry and spectral induced polarization signatures of calcium carbonate  

NASA Astrophysics Data System (ADS)

Calcium carbonate (CaCO3) minerals are a key family of compounds that frequently precipitate during natural and engineered subsurface processes. They play important roles in elemental cycling within geosystems and can be utilized in the context of environmental remediation (such as metal sequestration through co-precipitation) and in geotechnical engineering (such as improving soil strength or decreasing rock permeability). Characterizing the spatial extent and temporal dynamics of carbonate mineral precipitation is critical for these studies. Our previous research has indicated the potential of geophysical methods, particularly spectral induced polarization (SIP) for tracking the onset and evolution of mineral precipitates, including calcite. Here, we experimentally document the significant role of pore fluid chemistry and surface charge structure on the SIP signature of calcium carbonates. Our column studies revealed that the SIP signature of calcium carbonate is dictated by surface charge structure that relies heavily on surface complexation properties, such as charge density and speciation. For calcium carbonate, the primary potential determining ions (PDIs) are calcium and carbonate ions and the SIP signatures of calcium carbonate are primarily controlled by the concentrations of these species. Our data show that calcium carbonates in thermodynamic equilibrium with pore fluid produce a negligible SIP response due to very small (if any) surface charges. In contrast, systems that are over saturated with respect to calcium carbonate (i.e., far from equilibrium) produce significant SIP responses, which is consistent with high surface charge densities shown by high zeta potential values in previous studies. Our studies reveal that a closed system that transitions from over-saturation to equilibrium conditions is accompanied by significant decrease of SIP signals (and vice-versa). The studies also show that the effect of pH on SIP signature of calcium carbonate is manifested through its impact on calcite solubility and carbonate speciation and that the effects of other indifferent ions (such as Na and Cl) are minor. Our study illustrates the critical role of surface charge structure on SIP signatures of calcium carbonate minerals, which provides a fundamental basis for understanding the physiochemical mechanisms of SIP responses associated with natural and engineered processes.

Wu, Y.; Hubbard, S. S.; Ajo Franklin, J. B.; Williams, K. H.

2010-12-01

314

Large-scale synthesis of carbon spheres by reduction of supercritical CO 2 with metallic calcium  

NASA Astrophysics Data System (ADS)

Carbon spheres with approximate uniform diameters of about 1-2 ?m were synthesized by chemical reduction of supercritical CO 2 with metallic calcium at 550 °C. The products were characterized by techniques including XRD, scanning electron microscope, Raman, and transmission electron microscopy. The formation mechanism was thought to be as follows: the thermal movement of carbon nano-granules on the surface of metallic calcium leads to the formation of carbon spheres, which was confirmed by reference experiments at different temperatures. What is more, the formation mechanism of carbon sphere in supercritical CO 2 system was discussed.

Lou, Zhengsong; Chen, Changle; Zhao, Dejian; Luo, Shengli; Li, Zhongchun

2006-04-01

315

Macropinocytosis is the major mechanism for endocytosis of calcium oxalate crystals into renal tubular cells.  

PubMed

During an initial phase of kidney stone formation, the internalization of calcium oxalate (CaOx) crystals by renal tubular cells has been thought to occur via endocytosis. However, the precise mechanism of CaOx crystal endocytosis remained unclear. In the present study, MDCK renal tubular cells were pretreated with inhibitors specific to individual endocytic pathways, including nystatin (lipid raft/caveolae-mediated), cytochalasin D (actin-dependent or macropinocytosis), and chlorpromazine (CPZ; clathrin-mediated) before exposure to plain (non-labeled), or fluorescence-labeled CaOx monohydrate (COM) crystals. Quantitative analysis by flow cytometry revealed that pretreatment with nystatin and CPZ slightly decreased the crystal internalization, whereas the cytochalasin D pretreatment caused a marked decrease in crystal uptake. Immunofluorescence study and laser-scanning confocal microscopic examination confirmed that the cytochalasin D-pretreated cells had dramatic decrease of the internalized crystals, whereas the total number of crystals interacted with the cells was unchanged (crystals could adhere but were not internalized). These data have demonstrated for the first time that renal tubular cells endocytose COM crystals mainly via macropinocytosis. These novel findings will be useful for further tracking the endocytosed crystals inside the cells during the course of kidney stone formation. PMID:23695784

Kanlaya, Rattiyaporn; Sintiprungrat, Kitisak; Chaiyarit, Sakdithep; Thongboonkerd, Visith

2013-12-01

316

High Calcium (~80mol%) Late Stage Carbonate in ALH84001  

NASA Astrophysics Data System (ADS)

Brief petrological, chemical and textural description of previously undescribed high Ca late stage carbonate in Martian meteorite ALH84001. This carbonate surrounds Mg rich carbonates and rosette fragments.

Gildea, K. J.; Holland, G.; Lyon, I. C.; Chatzitheodoridis, E.; Burgess, R.

2006-03-01

317

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

NASA Astrophysics Data System (ADS)

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

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

2014-03-01

318

Efficient in vivo gene transfer by intraperitoneal injection of plasmid DNA and calcium carbonate microflowers in mice.  

PubMed

Gene transfer to intraperitoneal organs is thought to be a promising approach to treat such conditions as peritoneal fibrosis and peritoneal dissemination of cancers. We previously discovered that simple instillation of naked plasmid DNA (pDNA) onto intraperitoneal organs such as the liver and stomach could effectively transfer foreign genes in mice. In this study, we developed a novel nonviral method to enhance transfection efficiency of naked pDNA to intraperitoneal organs using a calcium carbonate suspension containing pDNA. Using commercially available calcium carbonate, we successfully transfected pDNA to the stomach. Handling of commercially available calcium carbonate, however, was troublesome owing to rapid precipitation and caking. To obtain slowly settling particles of calcium carbonate, we tried to synthesize novel versions of such particles and succeeded in creating flower-shaped particles, named calcium carbonate microflowers. Sedimentation of calcium carbonate microflowers was sufficiently slow for in vivo experiments. Moreover, the transfection efficiency of the suspension of calcium carbonate microflowers to the stomach was more effective than that of commercially available calcium carbonate, especially at low concentrations. Intraperitoneal injection of the suspension of calcium carbonate microflowers containing pDNA greatly enhanced naked pDNA transfer to whole intraperitoneal organs in mice. Furthermore, lactate dehydrogenase activities in intraperitoneal fluid and plasma were not raised by the suspension of calcium carbonate microflowers. PMID:22670625

Fumoto, Shintaro; Nakajima, Sayuri; Mine, Toyoharu; Yoshikawa, Naoki; Kitahara, Takashi; Sasaki, Hitoshi; Miyamoto, Hirotaka; Nishida, Koyo

2012-07-01

319

Comparison of Nanoscale Calcium Oxide Versus Commercial Calcium Oxide with Respect to Decomposition of Carbon Tetrachloride.  

National Technical Information Service (NTIS)

The increasing amount of chlorocarbons in our environment causes a need to find an easy, effective and inexpensive way for their destruction. Calcium oxide seems to be a good choice as the adsorbing and decomposing agent. Three different types of calcium ...

O. Koper K. J. Klabunde

1994-01-01

320

Pore-size-dependent calcium carbonate precipitation controlled by surface chemistry.  

PubMed

Induced mineral precipitation is potentially important for the remediation of contaminants, such as during mineral trapping during carbon or toxic metal sequestration. The prediction of precipitation reactions is complicated by the porous nature of rocks and soils and their interaction with the precipitate, introducing transport and confinement effects. Here X-ray scattering measurements, modeling, and electron microscopies were used to measure the kinetics of calcium carbonate precipitation in a porous amorphous silica (CPG) that contained two discrete distributions of pore sizes: nanopores and macropores. To examine the role of the favorability of interaction between the substrate and precipitate, some of the CPG was functionalized with a self-assembled monolayer (SAM) similar to those known to enhance nucleation densities on planar substrates. Precipitation was found to occur exclusively in macropores in the native CPG, while simultaneous precipitation in nanopores and macropores was observed in the functionalized CPG. The rate of precipitation in the nanopores estimated from the model of the X-ray scattering matched that measured on calcite single crystals. These results suggest that the pore-size distribution in which a precipitation reaction preferentially occurs depends on the favorability of interaction between substrate and precipitate, something not considered in most studies of precipitation in porous media. PMID:24815551

Stack, Andrew G; Fernandez-Martinez, Alejandro; Allard, Lawrence F; Bañuelos, José L; Rother, Gernot; Anovitz, Lawrence M; Cole, David R; Waychunas, Glenn A

2014-06-01

321

The effect of alginates, fucans and phenolic substances from the brown seaweed Padina gymnospora in calcium carbonate mineralization in vitro  

NASA Astrophysics Data System (ADS)

The mineralization of calcium carbonate (CaCO 3) in the brown seaweed Padina gymnospora is a biologically induced process and is restricted to the cell wall surface. It has been suggested that the CaCO 3 crystallization that occurs over the thallus cell wall surface is induced by changes in the surface pH caused by a local efflux of OH -, Ca ++ and HCO3- ions. However, no studies on the roles of the P. gymnospora cell wall components in this mineralization process had been performed. Therefore, we evaluated the influence of a subset of P. gymnospora cell wall molecules on CaCO 3 crystallization in vitro. The molecules tested were the anionic polysaccharides alginates and fucans (with potential nucleation activity) and phenolic substances (secondary metabolites with amphipathic property). The crystallization assays were performed using polystyrene microbridges as the crystallization apparatus. Crystals formed in the microbridges were analyzed using scanning electron microscopy. Interestingly, the results confirmed that the phenolic substances have the specific capability of changing the morphology of calcite crystals grown in vitro by inducing an elongated morphology in the direction of the c-axis. This morphology is similar to that induced by molecules that attach to { h k 0}-crystal planes. It was also shown that the alginates and the fucans do not specifically modulate the morphology of the growing crystals. In fact, these crystals exhibited a rounded shape due to the slower growth rates of several new crystal planes that appeared in the place of the original corners and edges.

Salgado, L. T.; Amado Filho, G. M.; Fernandez, M. S.; Arias, J. L.; Farina, M.

2011-04-01

322

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

323

Intracrystalline Proteins Promote Dissolution of Urinary Calcium Oxalate Crystals in Cultured Renal Epithelial Cells  

NASA Astrophysics Data System (ADS)

We have proposed that internalized calcium oxalate (CaOx) crystals containing intracrystalline proteins would be vulnerable to intracellular dissolution. The aims of this study were (1) to measure non-uniform strain and crystallite size in CaOx monohydrate (COM) crystals containing increasing amounts of intracrystalline crystal matrix extract (CME) and (2) to compare the rates of crystal dissolution in Madin-Darby canine kidney (MDCKII) cells. CME was isolated by demineralization of COM crystals generated from human urine. Cold and 14C-oxalate-labelled COM crystals were precipitated from ultrafiltered urine containing CME at final concentrations of 0-5mg/L. Non-uniform strain and crystallite size were determined using synchrotron X-ray diffraction with Rietveld whole-pattern peak fitting and profile analysis, and the protein content of the crystals was analyzed using SDS-PAGE and Western blotting for prothrombin fragment 1. Radiolabeled crystals were added to MDCKII cells and dissolution was expressed as radioactive label released into the medium relative to that in the crystals at zero time. Non-uniform strain increased and crystallite size decreased proportionally with rising CME concentration, reaching saturation between approximately 1 and 5 mg/L, and demonstrating unequivocally the inclusion of increasing quantities of proteins in the crystals. This was confirmed by SDS-PAGE and Western blotting. Crystal dissolution also followed saturation kinetics. These findings were confirmed by field emission scanning electron microscopy (FESEM), which showed that the degree of crystal degradation increased relative to CME concentration. We conclude that intracrystalline proteins enhance intracellular dissolution of CaOx crystals and thus may provide a natural defense against stone pathogenesis.

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

2007-04-01

324

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

325

Sulfur Cycling Mediates Calcium Carbonate Geochemistry in Modern Marine Stromatolites  

NASA Technical Reports Server (NTRS)

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

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

2004-01-01

326

Oxygen Spectroscopy and Polarization-Dependent Imaging Contrast (PIC)-Mapping of Calcium Carbonate Minerals and Biominerals.  

PubMed

X-ray absorption near-edge structure (XANES) spectroscopy and spectromicroscopy have been extensively used to characterize biominerals. Using either Ca or C spectra, unique information has been obtained regarding amorphous biominerals and nanocrystal orientations. Building on these results, we demonstrate that recording XANES spectra of calcium carbonate at the oxygen K-edge enables polarization-dependent imaging contrast (PIC) mapping with unprecedented contrast, signal-to-noise ratio, and magnification. O and Ca spectra are presented for six calcium carbonate minerals: aragonite, calcite, vaterite, monohydrocalcite, and both hydrated and anhydrous amorphous calcium carbonate. The crystalline minerals reveal excellent agreement of the extent and direction of polarization dependences in simulated and experimental XANES spectra due to X-ray linear dichroism. This effect is particularly strong for aragonite, calcite, and vaterite. In natural biominerals, oxygen PIC-mapping generated high-magnification maps of unprecedented clarity from nacre and prismatic structures and their interface in Mytilus californianus shells. These maps revealed blocky aragonite crystals at the nacre-prismatic boundary and the narrowest calcite needle-prisms. In the tunic spicules of Herdmania momus, O PIC-mapping revealed the size and arrangement of some of the largest vaterite single crystals known. O spectroscopy therefore enables the simultaneous measurement of chemical and orientational information in CaCO3 biominerals and is thus a powerful means for analyzing these and other complex materials. As described here, PIC-mapping and spectroscopy at the O K-edge are methods for gathering valuable data that can be carried out using spectromicroscopy beamlines at most synchrotrons without the expense of additional equipment. PMID:24821199

DeVol, Ross T; Metzler, Rebecca A; Kabalah-Amitai, Lee; Pokroy, Boaz; Politi, Yael; Gal, Assaf; Addadi, Lia; Weiner, Steve; Fernandez-Martinez, Alejandro; Demichelis, Raffaella; Gale, Julian D; Ihli, Johannes; Meldrum, Fiona C; Blonsky, Adam Z; Killian, Christopher E; Salling, C B; Young, Anthony T; Marcus, Matthew A; Scholl, Andreas; Doran, Andrew; Jenkins, Catherine; Bechtel, Hans A; Gilbert, Pupa U P A

2014-07-17

327

A case of calcium pyrophosphate dihydrate crystal deposition disease presenting as an acute polyarthritis.  

PubMed Central

We report a case of calcium pyrophosphate dihydrate crystal deposition disease (CPDD) presenting as an acute polyarthritis. A 66-yr-old woman was admitted with a 5-day history of fever and multiple joint pain including wrists, elbows, shoulders, knees, and ankles developed 5 days before admission. Her plain radiographs of wrists, elbows, shoulders, knees, and ankles showed chondrocalcinosis. The pubic symphysis, lumbar intervertebral discs, and both hip joints, which were asymptomatic, also had calcium deposits. The compensated polarized microscopic examination of the joint fluid, aspirated from the right knee revealed intracellular and extracellular weakly positive birefringent crystals, confirming the CPDD. This case showed that CPDD may manifest as an acute polyarthritis mimicking acute onset rheumatoid arthritis.

Song, Jung Soo; Lee, Yong Hwan; Kim, Sung Soo; Park, Won

2002-01-01

328

A case of calcium pyrophosphate dihydrate crystal deposition disease presenting as an acute polyarthritis.  

PubMed

We report a case of calcium pyrophosphate dihydrate crystal deposition disease (CPDD) presenting as an acute polyarthritis. A 66-yr-old woman was admitted with a 5-day history of fever and multiple joint pain including wrists, elbows, shoulders, knees, and ankles developed 5 days before admission. Her plain radiographs of wrists, elbows, shoulders, knees, and ankles showed chondrocalcinosis. The pubic symphysis, lumbar intervertebral discs, and both hip joints, which were asymptomatic, also had calcium deposits. The compensated polarized microscopic examination of the joint fluid, aspirated from the right knee revealed intracellular and extracellular weakly positive birefringent crystals, confirming the CPDD. This case showed that CPDD may manifest as an acute polyarthritis mimicking acute onset rheumatoid arthritis. PMID:12068153

Song, Jung Soo; Lee, Yong Hwan; Kim, Sung Soo; Park, Won

2002-06-01

329

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

NASA Technical Reports Server (NTRS)

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

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

1991-01-01

330

Inhibition of calcium oxalate monohydrate crystallization by the combination of citrate and osteopontin  

NASA Astrophysics Data System (ADS)

The design of effective crystallization inhibitors of calcium oxalate monohydrate (COM), the primary constituent of kidney stones, is a significant goal. Inhibitory molecules identified in urine include a small organic anion, citrate, and osteopontin (OPN), an aspartic acid-rich protein. The results of molecular-scale analyses combining force microscopy with molecular modeling raised the possibility that inhibition of COM crystallization might be increased by the additive effects of citrate and OPN because they act on different crystal faces. Constant composition (CC) kinetics studies of COM crystal growth now confirm that additive effects are, indeed, achieved in vitro when both citrate and OPN are present. These results suggest that a strategy employing combinations of inhibitors may provide a useful therapeutic approach to urinary stone disease.

Wang, Lijun; Zhang, Wei; Qiu, S. Roger; Zachowicz, William J.; Guan, Xiangying; Tang, Ruikang; Hoyer, John R.; De Yoreo, James J.; Nancollas, George H.

2006-05-01

331

Crystallization of brushite from EDTA-chelated calcium in agar gels  

NASA Astrophysics Data System (ADS)

Brushite (dicalcium phosphate dihydrate, CaHPO 4·2H 2O, DCPD) has been crystallized from ethylenediaminetetraacetic acid (EDTA)-chelated calcium in agar gels at initial pH 4.5-6.4 and Ca/P molar ratio above about 0.8. White, spherular crystalline DCPD aggregates up to 1 mm in diameter grew in 8-10 weeks. Liesegang ring were occassionally observed at initial gel pH 5 and Ca/P molar ratio near 1. Crystals were characterized by X-ray diffraction analysis, scanning electron microscopy, and infrared absorption spectroscopy. Brushite crystals were also grown in agar gels with either unchelated Ca initially present in the gels and EDTA in overlying solutions, or EDTA initially present in the gels and unchelated Ca in overlying solutions. These crystals grew as 2-3 mm aggregates mainly within 1-3 cm of the gel-solution interface.

Plovnick, Ross H.

1991-10-01

332

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

NASA Astrophysics Data System (ADS)

Crystallization of calcium sulfate dihydrate (CaSO 4·2H 2O 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, the effect was enhanced as the relative super-saturation decreases. Influence of mixed additives on the rate of crystallization (Cd 2++Arg, Cd 2++H 3PO 4 and Cd 2++PAA) has also been studied. Direct adsorption experiments of these metal ions on the surface of gypsum crystals have been made for comparison.

Hamdona, Samia K.; Al Hadad, Umaima A.

2007-02-01

333

Conoscopic interferometry for probing electro-optic coefficients of strontium calcium barium niobate crystal  

NASA Astrophysics Data System (ADS)

The relation between the linear electro-optic effect and conoscopic interference has been investigated in a biased electro-optic crystal strontium calcium barium niobate (CSBN). Based on the change of interference patterns with applied field, an interferometric method for probing electro-optic coefficients of electro-optic crystals has been proposed. In our case, the linear electro-optic coefficients of CSBN:50 was first probed at ?33=(141.0±0.5)×10 -12 m/V and ?13=(85.0±0.5)×10 -12 m/V.

Wang, Ankai; Gao, CH. Y.; Xu, J. Q.; Zhang, H. J.; Sun, Sh. Q.

2011-07-01

334

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

335

ESR studies of X-irradiated strontium mixed calcium tartrate crystals  

Microsoft Academic Search

The electron spin resonance spectra of X-ray irradiated single crystals of strontium doped calcium tartrate tetrahydrate (CST) with molecular formula Ca0.88Sr0.12C4H4O6·4H2O grown in gels has been investigated. Only one species of free radical but with two magnetically unequivalent sites was observed at room temperature. The free radical was found to be the result of the splitting of a C–H bond

K. Suryanarayana; S. M Dharmaprakash; A. Ananda

2000-01-01

336

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

337

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

Microsoft Academic Search

Ionization radiation is shown to reduce impurity ions to the univalent state in strontium and calcium fluoride crystals doped\\u000a by divalent cadmium and zinc ions. In this case, a univalent ion is surrounded by eight equivalent fluorine ions and exhibits\\u000a cubic symmetry O\\u000a \\u000a h\\u000a . At room temperature, the symmetry of the center is revealed to be sequentially lowered to

A. V. Egranov; E. A. Radzhabov; A. I. Nepomnyashchikh; V. F. Ivashechkin; I. E. Vasil’eva

2008-01-01

338

Calcium pyrophosphate dihydrate crystal deposition disease mimicking malignant soft tissue tumor.  

PubMed

Calcium pyrophosphate dihydrate (CPPD) crystal deposition disease has multiple clinical features with variable courses creating several pitfalls in clinical diagnosis. There are number of reported cases mimicking malignant skeletal tumors such as chondrosarcoma. However, no case of CPPD disease with radiographic noncalcified soft tissue mass has been reported in the literature. Here we report a case of CPPD disease clinically mimicking soft tissue tumor with its magnetic resonance imaging appearance and histopathology. PMID:12897986

Havitçio?lu, Hasan; Tatari, Hasan; Baran, Onder; Manisali, Metin; Ozkal, Sermin; Seçil, Mustafa; Ozaksoy, Dinç; Yörüko?lu, Kutsal

2003-07-01

339

Electronic structure and bonding in calcium apatite crystals: Hydroxyapatite, fluorapatite, chlorapatite, and bromapatite  

Microsoft Academic Search

We present a detailed analysis of the electronic structure, bonding, charge transfer, and optical properties of selected perfect-crystal calcium apatites [ Ca10(PO4)6X2 with X=(OH)-,F-,Cl- , or Br- ]. The ab initio orthogonalized linear combinations of atomic orbitals-density-functional-theory-based computational method is used to obtain the band structure, total and partial density of states, bond order, Mulliken effective charge, dielectric constant, and

Paul Rulis; Lizhi Ouyang; W. Y. Ching

2004-01-01

340

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

PubMed

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

Tausche, A-K; Aringer, M

2014-05-01

341

Biomimetic calcium phosphate crystal mineralization on electrospun cellulose-based scaffolds.  

PubMed

Novel cellulose based-scaffolds were studied for their ability to nucleate bioactive calcium phosphate crystals for future bone healing applications. Cellulose-based scaffolds were produced by electrospinning cellulose acetate (CA) dissolved in a mixture of acetone/dimethylacetamide (DMAc). The resulting nonwoven CA mats containing fibrils with diameters in the range of 200 nm to 1.5 ?m were saponified by NaOH/ethanol for varying times to produce regenerated cellulose scaffolds. Biomimetic crystal growth nucleated from the fiber surface was studied as a function of surface chemistry. Regenerated cellulose scaffolds of varying treatments were soaked in simulated body fluid (SBF) solution. Scaffolds that were treated with CaCl(2), a mixture of carboxymethyl cellulose (CMC) and CaCl(2), and NaOH and CaCl(2), were analyzed using X-ray photoelectron spectroscopy, X-ray powder diffraction, and scanning electron microscopy to understand the growth of bioactive calcium phosphate (Ca-P) crystals as a function of surface treatment. The crystal structure of the nucleated Ca-P crystals had a diffraction pattern similar to that of hydroxyapatite, the mineralized component of bone. The study shows that the scaffold surface chemistry can be manipulated, providing numerous routes to engineer cellulosic substrates for the requirements of scaffolding. PMID:21355545

Rodríguez, Katia; Renneckar, Scott; Gatenholm, Paul

2011-03-01

342

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

343

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

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 a double diffusion gel growth technique using U-tubes. The gel was prepared from hydrated sodium metasilicate solution. The gel framework acts like

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

2005-01-01

344

Formation and Structure of Coherent, Ultra-thin Calcium Carbonate Films below Monolayers of Stearic Acid at the Oil\\/Water Interface  

Microsoft Academic Search

Detailed investigations of interfacial crystallization procedures are important to understand the\\u000a basic principles of biomineralization processes. These interfacial phenomena can also be used to form new\\u000a types of biomimetic composite materials. In a series of experiments we studied the influence of Langmuir-monolayers\\u000a on the formation of ultra-thin calcium carbonate films. We systematically compared experiments performed\\u000a at the water surface with results

M. Maas; H. Rehage; H. Nebel; M. Epple

345

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

346

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

347

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

PubMed Central

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

2013-01-01

348

Recovery of calcium carbonate from steelmaking slag and utilization for acid mine drainage pre-treatment.  

PubMed

The conversion of steelmaking slag (a waste product of the steelmaking process) to calcium carbonate (CaCO(3)) was tested using hydrochloric acid, ammonium hydroxide and carbon dioxide via a pH-swing process. Batch reactors were used to assess the technical feasibility of calcium carbonate recovery and its use for pre-treatment of acid mine drainage (AMD) from coal mines. The effects of key process parameters, such as the amount of acid (HCl/calcium molar ratio), the pH and the CO(2) flow rate were considered. It was observed that calcium extraction from steelmaking slag significantly increased with an increase in the amount of hydrochloric acid. The CO(2) flow rate also had a positive effect on the carbonation reaction rate but did not affect the morphology of the calcium carbonate produced for values less than 2 L/min. The CaCO(3) recovered from the bench scale batch reactor demonstrated effective neutralization ability during AMD pre-treatment compared with the commercial laboratory grade CaCO(3). PMID:22643421

Mulopo, J; Mashego, M; Zvimba, J N

2012-01-01

349

Alkali carbonation of calcium aluminate cements: influence of set-retarding admixtures under hydrothermal conditions  

Microsoft Academic Search

The preferential uptake of aluminium ions by lactone and carboxylic acid groups in glucuronic-6,3-lactone and gluconic acid suggested that these organic admixtures have a high potential as set-retarding admixtures of high-temperature calcium aluminate cement slurry. However, the liberation of abundant free calcium ions caused by the adsorption of aluminium ions by the admixtures, increased the carbonation rate of hydrated cement

T. Sugama; N. R. Carciello; G. Gray

1992-01-01

350

Inhibitive effect of calcium gluconate and sodium molybdate on carbon steel  

Microsoft Academic Search

There is an increasing demand for eco-friendly inhibitors for use in cooling water systems. Both calcium gluconates and molybdate are eco-friendly, non-toxic chemicals. The corrosion inhibition of calcium gluconate and sodium molybdate on carbon steel in neutral aqueous media was evaluated by means of weight loss, electrochemical polarisation and impedance techniques. A synergistic effect was observed when these two eco-friendly

S. M. A. Shibli; V. Anitha Kumary

2004-01-01

351

A calcium oxide sorbent process for bulk separation of carbon dioxide  

SciTech Connect

In this experimental investigation, a laboratory-scale fixed-bed reactor containing a calcium-based sorbent is being used to study the feasibility of combining CO{sub 2} removal with the water gas shift reaction. The sorptive properties of the calcium oxide sorbent were studied as a function of carbonation temperature and pressure, synthesis gas composition, reactor space velocity, and sorbent composition and properties.

Harrison, D.P.; Han, C.

1994-10-01

352

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

353

Effects of an aqueous extract from Phyllantus niruri on calcium oxalate crystallization in vitro.  

PubMed

Phyllanthus niruri is a plant used in Brazilian folk medicine for the treatment of urolithiasis. It was previously observed that P. niruri shows no toxicity, potentially increases calculus voiding by stone forming patients and inhibits the endocytosis of calcium oxalate (CaOx) crystals by MDCK cells. In addition, in a rat model of urolithiasis it reduced calculus growth. In the present study, we evaluated the effect of an aqueous extract of P. niruri on CaOx crystallization in vitro. CaOx precipitation was induced by the addition of 0.1 M sodium oxalate to unfiltered urine samples from Wistar rats (n=14) and normal humans (n=18) in the presence or absence of P. niruri extract (0.25 mg/ml of urine). The presence of CaOx crystals was evaluated immediately and 24 h later. In vitro crystallization of human urine produced typical mono- and dihydrated CaOx crystals, but only a few typical CaOx crystals were found in rat urine. The presence of P. niruri extract did not inhibit CaOx precipitation and even more crystals were obtained, although they were significantly smaller than those in the control urine. Crystal aggregation observed 24 h after crystallization was also inhibited by P. niruri extract. The results showed an inhibitory effect of P. niruri extract on CaOx crystal growth and aggregation in human urine, suggesting that it may interfere with the early stages of stone formation and may represent an alternative form of treatment and/or prevention of urolithiasis PMID:12599017

Barros, M E; Schor, N; Boim, M A

2003-02-01

354

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

Microsoft Academic Search

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

J. M. Sutherland; J. I. Sprent

1984-01-01

355

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

356

Summary of ENDF/B-V evaluations for carbon, calcium, iron, copper, and lead and ENDF/B-V Revision 2 for calcium and iron  

SciTech Connect

This report, together with documents already published, describes the ENDF/B-V evaluations of the neutron and gamma-ray-production cross sections for carbon, calcium, iron, copper, and lead and the ENDF/B-V Revision 2 evaluations for calcium and iron.

Fu, C Y

1982-09-01

357

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

358

Ab initio simulation on the crystal structure and elastic properties of carbonated apatite.  

PubMed

Ab initio quantum mechanical (QM) calculations were employed to study the crystal structure and elastic properties of carbonated apatite (CAp). Two locations for the carbonate ion in the apatite lattice were considered: carbonate substituting for OH(-) ion (type-A), and for PO4(3-) ion (type-B) with possible charge compensation mechanisms. A combined type-AB substitution (two carbonate ions replacing one phosphate group and one hydroxyl group, respectively) was also investigated. The results show that the most energetically stable substitution is type-AB, followed by type-A and then type-B. The most stable configuration of type-A has its carbonate triangular plane almost parallel to c-axis at z=0.46. The lowest energy configuration of type-B is that with a sodium ion substituting for a calcium ion for charge balance and the carbonate lying on the b/c-plane of apatite. Lattice parameter changes after carbonate substitution in hydroxyapatite (HA) agree with reported experimental results qualitatively: for type-A, lattice parameter a increases but c decreases; and for type-B, lattice parameter a decreases but c increases. Using the calculated CAp stable structures, we also calculated the elastic properties of CAp and compared them with those of HA and biological apatites. PMID:23811277

Ren, Fuzeng; Lu, Xiong; Leng, Yang

2013-10-01

359

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

2012-03-01

360

Active electrochemical dissolution of molybdenum and application for room-temperature synthesis of crystallized luminescent calcium molybdate film  

SciTech Connect

Calcium molybdate (CaMoO{sub 4}) with a scheelite-type structure has been of practical interest for a long time because of its attractive luminescence property. It provides green emission as an available solid-state laser material. Crystallized luminescent calcium molybdate (CaMoO{sub 4}) film has been prepared on a molybdenum substrate in an alkaline solution containing calcium ions by active electrochemical dissolution of molybdenum at room temperature (25 C). The dissolution rate became faster with an increase of pH value. A high concentration of calcium (0.02M) and a high pH value (13) favored the reaction of film formation. The film showed only a single green emission at 536 nm with the excitation of 285 nm at liquid-nitrogen temperature ({minus}196 C), strongly suggesting that it consisted of well-crystallized defect-free crystals.

Cho, W.S.; Yashima, Masatomo; Kakihana, Masato; Kudo, Akihiko; Sakata, Tadayoshi; Yoshimura, Masahiro [Tokyo Inst. of Tech., Yokohama (Japan)

1997-03-01

361

Phase stabilities and mechanical properties of two new carbon crystals  

NASA Astrophysics Data System (ADS)

Density functional calculations are used to systematically evaluate phase stabilities and mechanical properties of two recently proposed carbon crystals (K4 and M-carbon), along with graphite, cubic diamond and hexagonal diamond. It is found that the K4 carbon, which can be referred to as a twin of the cubic diamond crystal, is mechanically unstable, implying that it cannot be formed. Remarkably, our calculations not only substantiate the M-carbon phase is a highly incompressible and potentially superhard material but also show that it exhibits mechanical stability. Moreover, a surprisingly small activation barrier (about 0.018 eV/atom) for the transformation of M-carbon to graphite explains some paradoxical experimental observations.

Liang, Y.; Zhang, W.; Chen, L.

2009-09-01

362

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

Microsoft Academic Search

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

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

1994-01-01

363

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

Microsoft Academic Search

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

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

2005-01-01

364

Crystal-matrix relationships in experimentally induced urinary calcium oxalate monohydrate crystals, an ultrastructural study  

Microsoft Academic Search

Summary  Calcium oxalate monohydrate crystalluria was experimentally induced in male rats by administration of ethylene glycol. The\\u000a crystalluria particles were separated by filtration and studied by scanning and transmission electron microscopy. They were\\u000a associated with cellular degradation products. Organic material was present both on the surfaces of crystalluria particles\\u000a as well as within them and was organized in radial striations and

Saeed R. Khan; Raymond L. Hackett

1987-01-01

365

Adsorption of sodium polyacrylate in high solids loading calcium carbonate slurries.  

PubMed

The adsorption of sodium polyacrylate (NaPAA) in slurries with up to 75 wt.% calcium carbonate was investigated with the use of attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and adsorption of probe molecules. Analysis of the IR spectra demonstrated that the carboxylate groups of NaPAA adsorbed onto ground calcium carbonate (GCC) in three different modes. These modes were shown to be dependent on the solids loading and age of the slurry. Further investigation lead to the determination of the chelating ability of NaPAA at high solids loading. PMID:19875128

Taylor, Joshua J; Sigmund, Wolfgang M

2010-01-15

366

The mechanical and NIR studies on ultrafine calcium carbonate treated by four surface modifiers  

NASA Astrophysics Data System (ADS)

Calcium carbonate was surface treated by acrylic acid monomer, its polymerization with varied mean molecular weight and PS/PAA copolymer. Coating efficiencies for these four series of surface-treated calcium carbonate were investigated. They differ from each other in many aspects. We hypothesize that the treating molecules bond to and align on the particle surface in different ways before and after monolayer coverage was reached. NIR spectra of surface-treated samples studied not only reflected the amount of bonded treating agents by means of the value of absorbance, but also gave rich structural information of surface layer. This gave us a powerful means to investigate the interface of particle surface.

Shui, Miao; Yue, Linhai; Xu, Zhude

2004-01-01

367

Determination of citric acid based on inhibition of the crystal growth of calcium fluoride.  

PubMed

Inhibition of the growth of calcium fluoride crystals in the presence of citrate was followed using a kinetic-potentiometric technique and a calcium ion-selective electrode, and as a consequence, a method for the determination of citrate in the range 0.5-2.4 micrograms ml-1 has been developed. The method was successfully applied to the determination of citrate contained in pharmaceutical products and urine. Urine analysis requires prior separation of phosphate, sulphate and magnesium(II). Elimination of these interferences was studied and accomplished using precipitation processes. Magnesium and phosphate were jointly eliminated in basic media by the addition of ammonium ions. Phosphate and sulphate were eliminated with barium(II). Phosphate was also eliminated as a lithium salt. PMID:2008941

Grases, F; Costa-Bauzá, A; March, J G

1991-01-01

368

Reinforcement of calcium phosphate cement with multi-walled carbon nanotubes and bovine serum albumin for injectable bone substitute applications.  

PubMed

This paper presents the development of novel alternative injectable calcium phosphate cement (CPC) composites for orthopaedic applications. The new CPC composites comprise ?-tri-calcium phosphate (?-TCP) and di-calcium phosphate anhydrous (DCPA) mixed with bovine serum albumin (BSA) and incorporated with multi-walled carbon nanotubes (MWCNTs) or functionalized MWCNTs (MWCNTs-OH and MWCNTs-COOH). Scanning electron microscopy (SEM), compressive strength tests, injectability tests, Fourier transform infrared spectroscopy and X-ray diffraction were used to evaluate the properties of the final products. Compressive strength tests and SEM observations demonstrated particularly that the concomitant admixture of BSA and MWCNT improved the mechanical properties, resulting in stronger CPC composites. The presence of MWCNTs and BSA influenced the morphology of the hydroxyapatite (HA) crystals in the CPC matrix. BSA was found to act as a promoter of HA growth when bounded to the surface of CPC grains. MWCNT-OH-containing composites exhibited the highest compressive strengths (16.3 MPa), being in the range of values for trabecular bone (2-12 MPa). PMID:21316621

Chew, Kean-Khoon; Low, Kah-Ling; Sharif Zein, Sharif Hussein; McPhail, David S; Gerhardt, Lutz-Christian; Roether, Judith A; Boccaccini, Aldo R

2011-04-01

369

Effect of pH on Quality of Calcium Carbonate Film Deposited From Moderately Hard and Hard Water  

Microsoft Academic Search

Calcium carbonate deposits are a problem in cast-iron water-distribution systems. These deposits can be reduced by adjusting the pH of the water during treatment. The softness or hardness of the water is also significant regarding the amount and permeability of the calcium carbonate deposited.

Mark A. McClanahan; Kalil H. Mancy

1974-01-01

370

Kinetic Aspects and Heats of Reaction between Components in Thermal Decomposition of Ammonium Nitrate-Calcium (Magnesium) Carbonate Mixtures  

Microsoft Academic Search

The kinetics of heat absorption in thermal decomposition of commercial ammonium nitrate-calcium (magnesium) carbonate mixture\\u000a and a model mixture of ammonium nitrate and calcium carbonate was studied. Rate equations of the processes and temperature\\u000a dependences of constants in these equations were determined. The heats of these reactions were calculated.

Yu. I. Rubtsov; A. I. Kazakov; M. K. Rustambekov; M. S. Starshinov

2005-01-01

371

Aspects on the Interaction between Sodium Carboxymethylcellulose and Calcium Carbonate and the Relationship to Specific Site Adsorption  

Microsoft Academic Search

The mechanisms of adsorption and association for sodium carboxymethylcellulose (NaCMC) in calcium carbonate suspensions have been determined from isothermal calorimetry and adsorption measurements. The equilibrium adsorption isotherms were determined by two different methods of separation; a depletion method and a serum exchange method. The enthalpy of dilution for NaCMC was determined on supernatants obtained from the calcium carbonate suspensions in

Kaj Backfolk; Serge Lagerge; Jarl B. Rosenholm; Dan Eklund

2002-01-01

372

Successful Control of Hyperparathyroidism in Patients on Continuous Ambulatory Peritoneal Dialysis Using Magnesium Carbonate and Calcium Carbonate as Phosphate Binders  

Microsoft Academic Search

To avoid the use of aluminium as a phosphate binder, patients on CAPD who were stable were dialysed against a peritoneal dialysis fluid which was magnesium free. A mixture of calcium and magnesium carbonate was used as a phosphate binder over a period in excess of 1 year. Vitamin D analogues were used in the majority. Results show satisfactory control

Victor Parsons; Dianne Baldwin; Caje Moniz; Joanne Marsden; Elizabeth Ball; Ian Rifkin

1993-01-01

373

Chemical analysis and molecular models for calcium-oxygen-carbon interactions in black carbon found in fertile amazonian anthrosoils.  

PubMed

Carbon particles containing mineral matter promote soil fertility, helping it to overcome the rather unfavorable climate conditions of the humid tropics. Intriguing examples are the Amazonian Dark Earths, anthropogenic soils also known as "Terra Preta de Índio'' (TPI), in which chemical recalcitrance and stable carbon with millenary mean residence times have been observed. Recently, the presence of calcium and oxygen within TPI-carbon nanoparticles at the nano- and mesoscale ranges has been demonstrated. In this work, we combine density functional theory calculations, scanning transmission electron microscopy, energy dispersive X-ray spectroscopy, Fourier transformed infrared spectroscopy, and high resolution X-ray photoelectron spectroscopy of TPI-carbons to elucidate the chemical arrangements of calcium-oxygen-carbon groups at the molecular level in TPI. The molecular models are based on graphene oxide nanostructures in which calcium cations are strongly adsorbed at the oxide sites. The application of material science techniques to the field of soil science facilitates a new level of understanding, providing insights into the structure and functionality of recalcitrant carbon in soil and its implications for food production and climate change. PMID:24892495

Archanjo, Braulio S; Araujo, Joyce R; Silva, Alexander M; Capaz, Rodrigo B; Falcão, Newton P S; Jorio, Ado; Achete, Carlos A

2014-07-01

374

Density functional theory for carbon dioxide crystal  

NASA Astrophysics Data System (ADS)

We present a density functional approach to describe the solid-liquid phase transition, interfacial and crystal structure, and properties of polyatomic CO2. Unlike previous phase field crystal model or density functional theory, which are derived from the second order direct correlation function, the present density functional approach is based on the fundamental measure theory for hard-sphere repulsion in solid. More importantly, the contributions of enthalpic interactions due to the dispersive attractions and of entropic interactions arising from the molecular architecture are integrated in the density functional model. Using the theoretical model, the predicted liquid and solid densities of CO2 at equilibrium triple point are in good agreement with the experimental values. Based on the structure of crystal-liquid interfaces in different planes, the corresponding interfacial tensions are predicted. Their respective accuracies need to be tested.

Chang, Yiwen; Mi, Jianguo; Zhong, Chongli

2014-05-01

375

Density functional theory for carbon dioxide crystal.  

PubMed

We present a density functional approach to describe the solid-liquid phase transition, interfacial and crystal structure, and properties of polyatomic CO2. Unlike previous phase field crystal model or density functional theory, which are derived from the second order direct correlation function, the present density functional approach is based on the fundamental measure theory for hard-sphere repulsion in solid. More importantly, the contributions of enthalpic interactions due to the dispersive attractions and of entropic interactions arising from the molecular architecture are integrated in the density functional model. Using the theoretical model, the predicted liquid and solid densities of CO2 at equilibrium triple point are in good agreement with the experimental values. Based on the structure of crystal-liquid interfaces in different planes, the corresponding interfacial tensions are predicted. Their respective accuracies need to be tested. PMID:24880310

Chang, Yiwen; Mi, Jianguo; Zhong, Chongli

2014-05-28

376

Medicago truncatula mutants demonstrate the role of plant calcium oxalate crystals as an effective defense against chewing insects.  

PubMed

Calcium oxalate is the most abundant insoluble mineral found in plants and its crystals have been reported in more than 200 plant families. In the barrel medic Medicago truncatula Gaertn., these crystals accumulate predominantly in a sheath surrounding secondary veins of leaves. Mutants of M. truncatula with decreased levels of calcium oxalate crystals were used to assess the defensive role of this mineral against insects. Caterpillar larvae of the beet armyworm Spodoptera exigua Hübner show a clear feeding preference for tissue from calcium oxalate-defective (cod) mutant lines cod5 and cod6 in choice test comparisons with wild-type M. truncatula. Compared to their performance on mutant lines, larvae feeding on wild-type plants with abundant calcium oxalate crystals suffer significantly reduced growth and increased mortality. Induction of wound-responsive genes appears to be normal in cod5 and cod6, indicating that these lines are not deficient in induced insect defenses. Electron micrographs of insect mouthparts indicate that the prismatic crystals in M. truncatula leaves act as physical abrasives during feeding. Food utilization measurements show that, after consumption, calcium oxalate also interferes with the conversion of plant material into insect biomass during digestion. In contrast to their detrimental effects on a chewing insect, calcium oxalate crystals do not negatively affect the performance of the pea aphid Acyrthosiphon pisum Harris, a sap-feeding insect with piercing-sucking mouthparts. The results confirm a long-held hypothesis for the defensive function of these crystals and point to the potential value of genes controlling crystal formation and localization in crop plants. PMID:16514014

Korth, Kenneth L; Doege, Sarah J; Park, Sang-Hyuck; Goggin, Fiona L; Wang, Qin; Gomez, S Karen; Liu, Guangjie; Jia, Lingling; Nakata, Paul A

2006-05-01

377

Biomimetic Precipitation of Uniaxially Grown Calcium Phosphate Crystals from Full-Length Human Amelogenin Sols  

PubMed Central

Human dental enamel forms over a period of 2 – 4 years by substituting the enamel matrix, a protein gel mostly composed of a single protein, amelogenin with fibrous apatite nanocrystals. Self-assembly of a dense amelogenin matrix is presumed to direct the growth of apatite fibers and their organization into bundles that eventually comprise the mature enamel, the hardest tissue in the mammalian body. This work aims to establish the physicochemical and biochemical conditions for the synthesis of fibrous apatite crystals under the control of a recombinant full-length human amelogenin matrix in combination with a programmable titration system. The growth of apatite substrates was initiated from supersaturated calcium phosphate solutions in the presence of dispersed amelogenin assemblies. It was shown earlier and confirmed in this study that binding of amelogenin onto apatite surfaces presents the first step that leads to substrate-specific crystal growth. In this work, we report enhanced nucleation and growth under conditions at which amelogenin and apatite carry opposite charges and adsorption of the protein onto the apatite seeds is even more favored. Experiments at pH below the isoelectric point of amelogenin showed increased protein binding to apatite and at low Ca/P molar ratios resulted in a change in crystal morphology from plate-like to fibrous and rod-shaped. Concentrations of calcium and phosphate ions in the supernatant did not show drastic decreases throughout the titration period, indicating controlled precipitation from the protein suspension metastable with respect to calcium phosphate. It is argued that ameloblasts in the developing enamel may vary the density of the protein matrix at the nano scale by varying local pH, and thus control the interaction between the mineral and protein phases. The biomimetic experimental setting applied in this study has thus proven as convenient for gaining insight into the fundamental nature of the process of amelogenesis.

Uskokovic, Vuk; Li, Wu; Habelitz, Stefan

2011-01-01

378

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

379

Recovery of calcium carbonate and hydrogen sulfide from waste calcium sulfide  

Microsoft Academic Search

The removal of HâS from hot coal gas using a limestone-based sorbent generates a large quantity of calcium sulfide waste (e.g., 67 tons\\/day from the gasification of 1,000 tons\\/day of 3% S coal) that cannot be landfilled because of potential HâS evolution and sulfide leaching. In the process proposed here, the CaS is dissolved by reaction with HâS complexed with

Mark W. Brooks; Scott Lynn

1997-01-01

380

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

381

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

382

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

PubMed Central

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.

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

2012-01-01

383

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

384

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

385

In vitro elution of daptomycin by a synthetic crystallic semihydrate form of calcium sulfate, stimulan.  

PubMed

A synthetic crystallic semihydrate form of calcium sulfate, Stimulan, was evaluated as a biodegradable carrier for the daily in vitro elution of daptomycin. Daptomycin and Stimulan were admixed at a ratio of 95:5. Elution lasted for 28 days. Eluted concentrations peaked on days 1 and 11, when the mean values were 1,320.1 and 949.2 microg/ml, respectively. The lowest eluted concentration was detected on day 28. These results support the application of the system described in experimental models of osteomyelitis. PMID:19398646

Kanellakopoulou, Kyriaki; Panagopoulos, Periklis; Giannitsioti, Efthymia; Tsaganos, Thomas; Carrer, Dionyssia-Pinelopi; Efstathopoulos, Nicolas; Giamarellos-Bourboulis, Evangelos J

2009-07-01

386

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

USGS Publications Warehouse

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

Kramer, Henry

1956-01-01

387

Carbon deposition from propylene on polycrystalline and single crystal iron  

Microsoft Academic Search

In a study of Fischer-Tropsch catalyst poisoning, experiments showed that the rate of carbon deposition from propylene on polycrystalline iron foil or single crystal iron surfaces went through a maximum at approx. 600°C. Carbon formation from propylene occurred only in the presence of hydrogen, increased with increasing hydrogen partial pressure, and was independent of propylene partial pressure. No gasification of

B. J. Cooper; D. L. Trimm

1980-01-01

388

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

Microsoft Academic Search

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

T. Rinder; M. Dietzel; A. Leis

2009-01-01

389

Mineralogy and Morphology of Calcium Carbonate as a Function of Magnesium Concentration in Artificial Seawater  

Microsoft Academic Search

Magnesium ions in solution affected the mineralogy and the morphology of calcium carbonate from which they precipitated. Low mag- nesium calcite was precipitated from a solution of low ionic products with respect to carbonate and Mg:Ca concentration ratio of less than 3:1. Arago- nite was formed in a solution of Mg:Ca concentration ratio of more than 4: 1. However, the

AHMED I. RVSHDI

1992-01-01

390

Fractionated-combustion analysis of carbonate-containing phases in composite materials of the hydroxyapatite-calcium carbonate system  

NASA Astrophysics Data System (ADS)

Materials in the hydroxyapatite (HA)-calcium carbonate (CC) system were synthesized by a precipitation method from aqueous solutions. According to the data of X-ray phase analysis and IR spectroscopy, the powders consisted of CC and AB-type carbonate-substituted HA (CHA). In order to determine the content of carbonate-containing phases in materials, the temperature-temporal mode of fractionated-combustion analysis of carbon was developed. The quantitative phase ratios and the degree of substitution of carbonate groups in CHA were determined. It was shown that the degree of substitution of carbonate groups in CHA increased from 2.47 to 5.31 wt % as the CC content increased from 13.50 to 88.33 wt %.

Goldberg, M. A.; Shibaeva, T. V.; Smirnov, V. V.; Kutsev, S. V.; Barinov, S. M.; Grigorovich, K. V.

2012-12-01

391

In situ measurements of calcium carbonate dissolution rates in deep-sea sediments  

SciTech Connect

Benthic fluxes of alkalinity, carbon dioxide, and oxygen have been measured using an in situ incubation chamber at three sites (MANOP Sites C and S and PACFLUX Site SC) in the central equatorial north Pacific. At two carbonate-rich sites (C and SC), a budget for oxygen, alkalinity, and TCO{sub 2} fluxes indicate a net CaCO{sub 3} dissolution rate of approximately 0.4 mmol m{sup {minus}2} day{sup {minus}1}. This rate is only 20% of previous estimates but is consistent with a dissolution rate constant predicted from laboratory experiments with deep-sea sediments and derived from in situ flux measurements in sediments of the southern California borderland. Organic matter oxidation in the sediment column provides the acid for 60-100% of the calcium carbonate dissolution occurring at these sites with the remainder derived from undersaturated bottom water. At a low-carbonate site (S), no carbonate dissolution in the sediment or on the sea floor is apparent, although sediment traps indicate a rain of CaCO{sub 3} through 3,400 m. The rates of remineralization relative to resuspension or erosion at this site must differ for organic carbon and calcium carbonate, so that carbonate grains reaching the sea floor are physically removed by erosion or resuspension before they dissolve, while organic carbon is largely oxidized before it can be physically removed.

Berelson, W.M.; Hammond, D.E. (Univ. of Southern California, Los Angeles (USA)); Cutter, G.A. (Old Dominion Univ., Norfolk, VA (USA))

1990-11-01

392

Phase diagram for controlled crystallization of calcium phosphate under acidic organic monolayers  

NASA Astrophysics Data System (ADS)

The effect of ionic concentration and pH on matrix-regulated crystallization may be important in biomineralization processes and biomimetic synthesis of materials. This effect in the system of calcium phosphate solution under stearic acid monolayers was investigated. In experiments, the solution conditions ranged in concentration of Ca ion of 0.1-20mM and in pH of 5.3-7.0. It was found that at the initial stage of the controlled crystallization, the (0001)-oriented hydroxyapatite (HAp) precipitations under the acidic monolayers always occur. At solution conditions near the solubility isotherms of octacalcium phosphate (OCP) and dicalcium phosphate dihydrate (DCPD) in the solubility phase diagram, precipitations of OCP and DCPD phases can form together with HAp precipitation, respectively. Orientations of DCPD or OCP phase precipitations were irregular.

Cui, F. Z.; Zhou, L. F.; Cui, H.; Ma, C. L.; Lu, H. B.; Li, H. D.

1996-12-01

393

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...

394

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....

395

The Effect of Calcium Carbonate on the Stability of Acid Treated Papers.  

National Technical Information Service (NTIS)

Exposure of kraft wood pulps to an acidic medium results in a destabilization of wood pulp. The degree of destabilization appears to depend on the concentration of acid the pulp is exposed to. The addition of calcium carbonate to acid destabilized pulp do...

E. L. Graminski E. J. Parks

1980-01-01

396

Coexistence of three calcium carbonate polymorphs in the shell of the Antarctic clam Laternula elliptica  

NASA Astrophysics Data System (ADS)

We analyzed shell cuts of five individuals of the Antarctic bivalve Laternula elliptica from three locations along the Antarctic Peninsula by means of Confocal Raman Microscopy (CRM) as well as Electron Microprobe (EMP). The shell of L. elliptica has been previously described as being composed of aragonite exclusively. Now, CRM mapping reveals that three polymorphs of calcium carbonate - aragonite, calcite, and vaterite - are present in the chondrophore region of the examined individuals. Annual shell growth layers continue through aragonite and vaterite, suggesting simultaneous mineralization of both polymorphs. Spatially congruent EMP scans showed that the calcium carbonate polymorph affects the distribution of magnesium and strontium within the chondrophore. This is, to our knowledge, the first report of the coexistence of these three calcium carbonate polymorphs within the mineralized structures of a marine calcifying organism. Particularly the presence of vaterite is unexpected, but shows striking similarities to some fish otoliths. The strong effect of the calcium carbonate polymorph on trace element incorporation restrict the suitability of magnesium and strontium based proxies for the chondrophore area of L. elliptica.

Nehrke, Gernot; Poigner, Harald; Wilhelms-Dick, Dorothee; Brey, Thomas; Abele, Doris

2012-05-01

397

Carbon nanotubes-titanium electrode for detecting calcium deposition by osteoblasts  

Microsoft Academic Search

The objective of this in vitro present study was to develop an electrode which can detect calcium deposition by osteoblasts. The primary biomaterial for this electrode is anodized Ti, developed by chemical etching and passivation treatments. Carbon nanotubes (CNTs), because of their enhancement in electron transfer reaction, are essential to consider when designing the electrodes. For this, parallel multiwall CNTs

S. Sirivisoot; Chang Yao; Xingcheng Xiao; B. W. Sheldon; T. J. Webster

2007-01-01

398

Influence of excessive filler coating on the tensile properties of LDPE–calcium carbonate composites  

Microsoft Academic Search

Calcium carbonate fillers are usually coated with stearic acid to reduce their surface energy and improve their dispersion in polymers. Commercial products are often over-coated and contain an excess of surfactant. It was found that stearic acid linearly increases the modulus and yield stress of LDPE but reduces its tensile strength, yield strain, and ultimate elongation. The influence of surfactant

Maged A. Osman; Ayman Atallah; Ulrich W. Suter

2004-01-01

399

Quaternary Climate Change as Revealed by Calcium Carbonate Fluctuations in Western Equatorial Atlantic Sediments.  

National Technical Information Service (NTIS)

Fluctuations of total calcium carbonate content in eight western Equatorial Atlantic cores are used to evaluate Quaternary climate change. Both pelagic Mid-Atlantic Ridge and terrigenousrich continental-rise cores that span the last 130,000 years show ide...

J. E. Damuth

1974-01-01

400

Increased Reflux Symptoms After Calcium Carbonate Supplementation and Successful Anti-Helicobacter pylori Treatment  

Microsoft Academic Search

We used data from a randomized placebo-controlled clinical trial to examine the relationship between Helicobacter pylori and reflux symptoms in nonulcer dyspepsia patients randomly assigned anti-Helicobacter pylori triple therapy alone, calcium carbonate alone, or in combination with triple therapy, tetracycline, or placebo. We compared risk differences for posttreatment Helicobacter pylori status and increased reflux symptoms from crude, multivariable and stratified

Lori A. Fischbach; Pelayo Correa; Mark Feldman; Elizabeth Fontham; Elisa Priest; Karen J. Goodman; Rajeev Jain

2003-01-01

401

Magnesium and Strontium Incorporation into Calcium Carbonate Polymorphs and ACC - Experimental Study  

Microsoft Academic Search

Incorporation of magnesium and strontium into aragonite and calcite is well known and has been extensively used for temperature reconstruction. Moreover, knowledge on element incorporation behaviour provides fundamental insight into calcium carbonate growth mechanisms. Element and isotope distributions are also used for monitoring aspects to evaluate ongoing sinter formation and inhibition effects in man made environments. However, the precipitation rate

A. Niedermayr; M. Dietzel; S. J. Köhler; S. Petautschnig

2010-01-01

402

Effect of calcium carbonate saturation state on the calcification rate of an experimental coral reef  

Microsoft Academic Search

The concentration of CO2 in the atmosphere is projected to reach twice the preindustrial level by the middle of the 21st century. This increase will reduce the concentration of CO32- of the surface ocean by 30% relative to the preindustrial level and will reduce the calcium carbonate saturation state of the surface ocean by an equal percentage. Using the large

Chris Langdon; Taro Takahashi; Colm Sweeney; Dave Chipman; John Goddard; Francesca Marubini; Heather Aceves; Heidi Barnett; Marlin J. Atkinson

2000-01-01

403

Modified calcium carbonate coatings with rapid absorption and extensive liquid uptake capacity  

Microsoft Academic Search

Special rapidly absorbing coatings with high absorption capacity are demonstrated based on new modified calcium carbonates which have been designed based on the absorption behaviour predicted by a combination of previous modelling using discrete pore and throat size distributions [Colloids Surf. A: Physicochem. Eng. Aspects 206 (2002) 217]. Firstly, the absorption driving force is determined by the proportion of fine

Cathy J Ridgway; Patrick A. C Gane; Joachim Schoelkopf

2004-01-01

404

Study on the Functionality of Nano-Precipitated Calcium Carbonate as Filler in Thermoplastics  

Microsoft Academic Search

This research aims to investigate the functionality of nano-precipitated calcium carbonate (NPCC) as filler in thermoplastic resins based on property enhancement. Three types of thermoplastics were used: polyethylene (PE), polypropylene (PP) and polyvinyl chloride (PVC). The resins were evaluated by determining the effect of different NPCC loading on the chemical structure, thermal and mechanical properties of thermoplastics. Results showed that

Blessie A. Basilia; Marian Elaine G. Panganiban; Archilles Allen V. C. Collado; Michael Oliver D. Pesigan; Persia Ada de Yro

2007-01-01

405

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

406

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

PubMed Central

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

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

2013-01-01

407

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

1996-11-01

408

Evidence for Calcium Carbonate at the Phoenix Landing Site  

NASA Technical Reports Server (NTRS)

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

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

2009-01-01

409

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

410

Catechin prevents the calcium oxalate monohydrate induced renal calcium crystallization in NRK-52E cells and the ethylene glycol induced renal stone formation in rat  

PubMed Central

Background Reactive oxygen species play important roles in renal calcium crystallization. In this study, we examined the effects of catechin, which have been shown to have antioxidant properties on the renal calcium crystallization. Methods In the vitro experiment, the changes of the mitochondrial membrane potential, expression of superoxide dismutase (SOD), 4-hydroxynonenal (4-HNE), cytochrome c, and cleaved caspase 3 were measured to show the effects of catechin treatment on the NRK-52E cells induced by calcium oxalate monohydrate (COM). In the vivo study, Sprague–Dawley rats were administered 1% ethylene glycol (EG) to generate a rat kidney stone model and then treated with catechin (2.5 and 10 mg/kg/day) for 14 days. The urine and serum variables were dected on 7 and 14 days after EG administration. The expression of cytochrome c, cleaved caspase 3, SOD, osteopontin (OPN), malondialdehyde (MDA), 8-hydroxy-2?-deoxyguanosine (8-OHdG) in kidney were measured. Furthermore, the mitochondrial microstructure in the kidney was also examined by transmission electron microscopy. Results Catechin treatment could prevent the changes in mitochondrial membrane potential and expression of SOD, 4-HNE, cytochrome c, and cleaved caspase 3 in NRK-52E cells induced by the COM. For the in vivo experiments, the EG administration induced renal calcium crystallization was also prevented by the catechin. The expression of SOD, OPN, MDA, OPN and 8-OHdG, were increased after EG administration and this increase was diminished by catechin. Moreover, catechin also prevented EG induced mitochondrial collapse in rat. Conclusions Catechin has preventive effects on renal calcium crystallization both in vivo and in vitro, and provide a potential therapeutic treatment for this disease.

2013-01-01

411

Characterization of carbon nanotube thermotropic nematic liquid crystal composites  

Microsoft Academic Search

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,

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

2008-01-01

412

Electrochemically assisted co-deposition of calcium phosphate/collagen coatings on carbon/carbon composites  

NASA Astrophysics Data System (ADS)

Calcium phosphate (CaP)/collagen coatings were prepared on the surface of carbon/carbon (C/C) composites by electrochemically assisted co-deposition technique. The effects of collagen concentration in the electrolyte on morphology, structure and composition of the coatings were systematically investigated using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transformed infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). The adhesive strength of the coatings was also evaluated by scratch tests and tensile bond tests. It was demonstrated that the coatings of three-dimensional collagen network structure was formed on the C/C composites from the electrolyte containing collagen. The surface of the collagen network was covered by uniform CaP aggregates. The coatings were actually composites of CaP and collagen. Hydroxyapatite (HA) was a favorable composition in the coatings with the increase of the collagen concentration in the electrolyte. The formed collagen network increased the cohesive and adhesive strength of the coatings. The adhesive strength between the coatings and substrates increased as the collagen concentration in the electrolyte increased. The coatings prepared at the collagen concentration of 500 mg/L in the electrolyte were not scraped off until the applied load reached 32.0 ± 2.2 N and the average tensile adhesive strength of the coatings was 4.83 ± 0.71 MPa. After C/C coated with composite coatings (500 mg/L) being immersed in a 10 -3 M Ca (OH) 2 solution at 30-33 °C for 96 h, nano-structured HA/collagen coatings similar to the natural human bone were obtained on the C/C.

Zhao, Xueni; Hu, Tao; Li, Hejun; Chen, Mengdi; Cao, Sheng; Zhang, Leilei; Hou, Xianghui

2011-02-01

413

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

414

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

2012-07-30

415

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

416

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

417

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

PubMed

The effects of physiological concentrations of chondroitin sulphate, human serum albumin and Tamm-Horsfall mucoprotein on the crystallization of calcium oxalate in undiluted, ultrafiltered human urine were investigated using particle size analysis and scanning electron microscopy. Neither the amount of oxalate required to induce detectable calcium oxalate crystal nucleation nor crystal morphology was affected by the presence of any of these macromolecules. Chondroitin sulphate had no effect on the amount of crystalline material deposited or on the size of the particles precipitated in response to a standard oxalate load. Human serum albumin slightly reduced the size of the crystal aggregates and caused a small increase in the amount of crystal matter precipitated. By contrast, Tamm-Horsfall mucoprotein significantly inhibited crystal aggregation and markedly increased the volume of matter deposited, although this could not be attributed to a promotion of solute precipitation. It was concluded that chondroitin sulphate, human serum albumin and Tamm-Horsfall mucoprotein cannot account for the inhibitory effects of macromolecules with a relative mass greater than 10 kDa in spun and filtered urine. Nonetheless, Tamm-Horsfall mucoprotein is likely to inhibit crystal aggregation in whole urine in vivo and may therefore be instrumental in preventing calcium oxalate stone formation. PMID:1909472

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

1991-01-01

418

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

NASA Astrophysics Data System (ADS)

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

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

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