These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite.  

E-print Network

The kinetics and mechanisms of amorphous calcium carbonate (ACC) crystallization to calcite, via calcium carbonate (ACC) crystallization to calcite, via vaterite, were studied at a range formation of calcium carbonate minerals (e.g. calcite) occurs in a wide range of natural envi- ronments (e

Benning, Liane G.

2

Control of calcium carbonate crystallization utilizing amphiphilic block copolypeptides  

NASA Astrophysics Data System (ADS)

Control over the morphology of calcium carbonate (CaCO 3) crystals has been achieved through the use of anionic, amphiphilic block copolypeptides during crystallization. Microspheres of CaCO 3 can be synthesized by the introduction of preformed organic, amphiphilic block copolypeptide templates, poly( L-aspartate sodium salt) 100- block-[poly( L-phenylalanine) 25- random-( L-leucine) 25] ( 1) and poly( L-glutamate sodium salt) 100- block-[poly( L-phenylalanine) 25- random-( L-leucine) 25] ( 2). When cationic amphiphiles are used in lieu of the anionic amphiphiles, only CaCO 3 rhombohedra are produced. The self-assembling amphiphile controls the precipitation of the microspheres by acting as a template to form giant CaCO 3 microspheres. These microspheres are composed of nanocrystals ranging in size from 10 to 60 nm using 1 and 20 to 100 nm using 2.

Euliss, Larken E.; Bartl, Michael H.; Stucky, Galen D.

2006-01-01

3

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

4

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

E-print Network

1 A Novel Growth Process of Calcium Carbonate Crystals in Silk Fibroin Hydrogel System Yufei Ma fibroin hydrogel; Biomineralization 1. Introduction Calcium carbonate is an important mineral due to its) 2413-2420" DOI : 10.1016/j.msec.2013.02.006 #12;2 ABSTRACT We report an interesting finding of calcium

Paris-Sud XI, Université de

5

Crystal Structure of Calcium-Deficient Carbonated Hydroxyapatite. Thermal Decomposition  

Microsoft Academic Search

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

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

2001-01-01

6

Calcium Carbonate  

MedlinePLUS

... heart. Calcium carbonate also is used as an antacid to relieve heartburn, acid indigestion, and upset stomach. ... use.Do not take calcium carbonate as an antacid for more than 2 weeks unless your doctor ...

7

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

Microsoft Academic Search

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

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

2003-01-01

8

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

PubMed

The crystal growth of calcite, the most stable calcium carbonate polymorph, in the presence of the cysteine-rich Mdm2 peptide (containing 48 amino acids in the ring finger configuration), has been investigated by the constant composition technique. Crystallization took place exclusively on well-characterized calcite crystals in solutions supersaturated only with respect to this calcium carbonate salt. The kinetic results indicated a surface diffusion spiral growth mechanism. The presence of the Mdm2 peptide inhibited the crystal growth of calcite by 22-58% in the concentration range tested, through adsorption onto the active growth sites of the calcite crystal surface. The kinetic results favored a Langmuir-type adsorption model, and the value of the calculated affinity constant was k(aff)=147x10(4) dm(3)mol(-1), a(ads)=0.29. PMID:16678843

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

2006-08-15

9

Calcium carbonate crystal growth beneath Langmuir monolayers of acidic ?-hairpin peptides.  

PubMed

Four amphiphilic peptides with designed hairpin structure were synthesized and their monolayers were employed as model systems to study biologically inspired calcium carbonate crystallization. Langmuir monolayers of hairpin peptides were investigated by surface pressure area isotherms, surface potential isotherms, Brewster angle microscopy (BAM), atomic force microscopy (AFM) and Fourier transform infrared (FTIR) spectroscopy. A ?-hairpin conformation was found for all peptides at the air-water interface although their packing arrangements seem to be different. Crystallization of calcium carbonate under these peptide monolayers was investigated at different surface pressures and growth times both by in situ optical microscopy, BAM and ex situ investigations such as scanning electron microscopy (SEM) and transmission electron microscopy (TEM). An amorphous calcium carbonate precursor was found at the initial crystallization stage. The crystallization process occurred in three stages. It starts from the nucleation of amorphous particles being a kinetically controlled process. Crystal nuclei subsequently aggregate to large particles and vaterite crystals start to form inside the amorphous layer, with the monolayer fluidity exerting an important role. The third process includes the re-crystallization of vaterite to calcite, which is thermodynamically controlled by monolayer structural factors including the monolayer flexibility and packing arrangement of the polar headgroups. Thus, the kinetic factors, monolayer fluidity and flexibility as well as structure factors govern the crystal morphology and polymorph distribution simultaneously and synergistically. PMID:25292256

Gong, Haofei; Yang, Yi; Pluntke, Manuela; Marti, Othmar; Majer, Zsuzsa; Sewald, Norbert; Volkmer, Dirk

2014-10-22

10

Elucidating the Effect of Biomolecule Structure on Calcium Carbonate Crystal Formation  

NASA Astrophysics Data System (ADS)

Anthropogenic emissions of carbon dioxide have lead to a steady increase in atmospheric concentration. This greenhouse gas has been identified as a key driver of climate change and also has lead to increased acidification of marine and terrestrial waters. Calcium carbonate precipitation at the Earth's surface is an integral linkage in the global carbon cycle, especially in regards to regulating atmospheric carbon dioxide. As concern for the effect of increasing atmospheric CO2 levels grows, the need to understand calcium carbonate systems escalates concurrently. Calcium carbonate phases are the most abundant group of biominerals; therefore, elucidating the mechanism of biomineralization is critical to understanding CaCO3 precipitation and may aid in the development of novel carbon sequestration strategies. The ubiquity of microorganisms leads to an extensive number of biomolecules present in the Earth's systems, and thus an extensive range of possible effects on CaCO3 formation. Carboxylic acids are very common biomolecules and have a relatively simple structure, thus making them an ideal family of model compounds. This study examines the kinetics, thermodynamics, phase, and morphology of calcium carbonate crystals precipitated in the presence of carboxylate-containing biomolecules, including citric acid, succinic acid, and aspartic acid. The experiments utilize a unique (NH4)2CO3 gas-diffusion reactor, which allows in-situ measurements of chemical conditions during the precipitation and growth of crystals. Continuous monitoring of the in-situ conditions of pCO2, pH, [Ca2+], and optical absorbance provides data on the supersaturation at which nucleation occurs and the kinetics of mineral growth. The use of scanning electron microscopy and X-ray diffraction provides information on the morphology and mineralogy of precipitates. The combination of these data sets will provide an in-depth view of the ideal concentration of calcium ions required for solution saturation, as well as the effect of biomolecule structure on calcium carbonate crystals. Preliminary XRD and SEM analyses have shown vaterite, calcite, and amorphous CaCO3 to be the primary morphologies present. This analysis indicates a lack of stability for crystals grown quickly at elevated CO2 concentrations. The rate of precipitation of calcium carbonate solids and the subsequent decrease in free calcium concentration has been shown to be largely a function of pH.

Kulbok, K. E.; Duckworth, O.

2011-12-01

11

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. 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

12

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

NASA Astrophysics Data System (ADS)

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

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

14

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

NASA Astrophysics Data System (ADS)

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

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

2004-07-01

15

Calcium Carbonate Storage in Amorphous Form and Its Template-Induced Crystallization  

SciTech Connect

Calcium carbonate crystallization in organisms often occurs through the transformation from the amorphous precursor. It is believed that the amorphous phase could be temporarily stabilized and stored, until its templated transition to the crystalline form is induced. Here we develop a bio-inspired crystallization strategy that is based on the above mechanism. Amorphous calcium carbonate (ACC) spherulitic particles are formed and stabilized on a self-assembled monolayer (SAM) of hydroxy-terminated alkanethiols on Au surface. The ACC is stored as a reservoir for ions and is induced to crystallize on command by introducing a secondary surface that is functionalized with carboxylic acid-terminated SAM. This secondary surface acts as a template for oriented and patterned nucleation. Various oriented crystalline arrays and micropatterned films are formed. We also show that the ACC phase can be doped with foreign ions (e.g. Mg) and organic molecules (e.g. dyes) and that these dopants later function as growth modifiers of calcite crystals and become incorporated into the crystals during the transformation process of ACC to calcite. We believe that our strategy opens the way of using a stabilized amorphous phase as a versatile reservoir system that can be converted in a highly controlled fashion to a crystalline form upon contacting the nucleating template.

Han, T Y; Aizenberg, J

2007-08-31

16

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

NASA Astrophysics Data System (ADS)

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

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

2008-10-01

17

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

PubMed

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

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

2013-01-01

18

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

19

Calcium carbonate overdose  

MedlinePLUS

... is an ingredient that is commonly found in antacids (for heartburn) and some dietary supplements. Calcium carbonate ... Products containing calcium carbonate, including Certain antacids ... mineral supplements Note: This list may not be all-inclusive.

20

Effects of Additives and Templates on Calcium Carbonate Mineralization in vitro  

E-print Network

Accepted M anuscript Effects of Additives and Templates on Calcium Carbonate Mineralization controlling the calcium carbonate crystals formation and the complexity of the crystal morphologies in vitro organic matrices mediate calcium carbonate mineralization. Keywords: additive; template; in vitro

Paris-Sud XI, Université de

21

Relative bioavailability of calcium from calcium formate, calcium citrate, and calcium carbonate  

E-print Network

of calcium from calcium formate, a new experimental dietary calcium supplement, to that of calcium citrate and calcium carbonate. In a four-way crossover study, either a placebo or 1200 mg of calcium as calcium carbonate, calcium citrate, or calcium formate...

Hanzlik, Robert P.; Fowler, S. C.; Fisher, D. H.

2005-06-01

22

ORIGINAL PAPER Calcium Carbonate Nucleation in an Alkaline Lake  

E-print Network

ORIGINAL PAPER Calcium Carbonate Nucleation in an Alkaline Lake Surface Water, Pyramid Lake, Nevada (X) needed for calcium carbonate nucleation and crystal growth in Pyramid Lake (PL) surface water­16. Notwithstanding high X, calcium carbonate growth did not occur on aragonite single crystals suspended PL surface

23

Porphyrin Amphiphiles as Templates for the Nucleation of Calcium Carbonate  

E-print Network

Porphyrin Amphiphiles as Templates for the Nucleation of Calcium Carbonate Joydeep Lahiri of calcium carbonate observed with native biological templates: (1) highly oriented crystals have been was estimated by EDTA titrimetric analysis to be 9 mmol dm-3. Calcium carbonate crystals were obtained

Aksay, Ilhan A.

24

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

2014-09-01

25

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

26

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 ...

27

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

28

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

29

21 CFR 184.1191 - Calcium carbonate.  

...1) As a byproduct in the “Lime soda process”; (2) By precipitation of calcium carbonate from calcium hydroxide in the “Carbonation process”; or (3) By precipitation of calcium carbonate from calcium...

2014-04-01

30

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

31

Production of Calcite (Calcium Carbonate) Crystals by Soil Bacteria is a General Phenomenon  

Microsoft Academic Search

CERTAIN bacteria form crystals from the solutes in their aqueous environment, and some authors have associated this activity with the extensive deposits of CaCO3 in such places as the Grand Bahama, in spite of the belief that physicochemical effects, such as rapid changes in pH, salinity and temperature, are responsible1-4. Drew5 isolated a denitrifying bacterium able to form CaCO3 crystals

E. Boquet; A. Boronat; A. Ramos-Cormenzana

1973-01-01

32

Control of calcium carbonate crystallization by using anionic polymethylsiloxanes as templates  

SciTech Connect

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

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

2012-10-15

33

Rapid onset of calcium carbonate crystallization under the influence of a magnetic field  

Microsoft Academic Search

Although the mechanisms are not fully understood, magnetic treatment of water systems has been in existence for over a century. One of the major applications is to suppress water-scale deposition on the inner surface of boilers, heat exchangers and pipelines. Three dynamic rates play important roles in the crystallization process: these are association, dissociation and nucleation rates. In this paper

Y. Wang; J. Babchin; L. T. Chernyi; R. S. Chow; R. P. Sawatzky

1997-01-01

34

Calcium Carbonate Polyamorphism and Its Role in Biomineralization: How Many Amorphous Calcium Carbonates Are There?  

E-print Network

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

Cartwright, Julyan H E; Gale, Julian D; Gebauer, Denis; Sainz-Díaz, C Ignacio; 10.1002/anie.201203125

2012-01-01

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

CALCIUM CARBONATE DEPOSITION IN GEOTHERMAL WELLBORES  

E-print Network

CALCIUM CARBONATE DEPOSITION IN GEOTHERMAL WELLBORES MIRAVALLES GEOTHERMAL FIELD COSTA RICA CALCIUM CARBONATE DEPOSITION IN GEOTHERMAL WELLBORES MIRAVALLES GEOTHERMAL FIELD COSTA RICA BY Eduardo University. #12;ABSTRACT Calcium carbonate deposition takes place in the wells of the Miravalles geothermal

Stanford University

37

INTRODUCTION Pedogenic (secondary) calcium carbonate is,  

E-print Network

INTRODUCTION Pedogenic (secondary) calcium carbonate is, by definition, a product of soil processes of calcium for pe- dogenic calcium carbonate (Gile et al., 1979). In regard to the source of the carbonate; Cerling et al., 1989; Quade et al., 1989). Because pedogenic calcium carbonate is read- ily soluble, its

Ahmad, Sajjad

38

Calcium is incorporated into the calcium carbonate matrix of otoliths  

E-print Network

118 Calcium is incorporated into the calcium carbonate matrix of otoliths and into the calcium). In addition to calcium, trace elements, such as strontium, are also incorporated into the calcified components valence) allow strontium ions to act as replace- ments for calcium during the pro- cess of calcification

39

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

40

Production of precipitated calcium carbonate from calcium silicates and carbon dioxide  

Microsoft Academic Search

The possibilities for reducing carbon dioxide emissions from the pulp and paper industry by calcium carbonation are presented. The current precipitated calcium carbonate (PCC) production uses mined, crushed calcium carbonate as raw materials. If calcium silicates were used instead, carbon dioxide emissions from the calcination of carbonates would be eliminated. In Finland, there could, thus, be a potential for eliminating

Sebastian Teir; Sanni Eloneva; Ron Zevenhoven

2005-01-01

41

Clonorcis sinensis eggs are associated with calcium carbonate gallbladder stones.  

PubMed

Calcium carbonate gallbladder stones were easily neglected because they were previously reported as a rare stone type in adults. The aim of this study was to investigate the relationship between calcium carbonate stones and Clonorchis sinensis infection. A total of 598 gallbladder stones were studied. The stone types were identified by FTIR spectroscopy. The C. sinensis eggs and DNA were detected by microscopic examination and real-time fluorescent PCR respectively. And then, some egg-positive stones were randomly selected for further SEM examination. Corresponding clinical characteristics of patients with different types of stones were also statistically analyzed. The detection rate of C. sinensis eggs in calcium carbonate stone, pigment stone, mixed stone and cholesterol stone types, as well as other stone types was 60%, 44%, 36%, 6% and 30%, respectively, which was highest in calcium carbonate stone yet lowest in cholesterol stone. A total of 182 stones were egg-positive, 67 (37%) of which were calcium carbonate stones. The C. sinensis eggs were found adherent to calcium carbonate crystals by both light microscopy and scanning electron microscopy. Patients with calcium carbonate stones were mainly male between the ages of 30 and 60, the CO2 combining power of patients with calcium carbonate stones were higher than those with cholesterol stones. Calcium carbonate gallbladder stones are not rare, the formation of which may be associated with C. sinensis infection. PMID:24945791

Qiao, Tie; Ma, Rui-hong; Luo, Zhen-liang; Yang, Liu-qing; Luo, Xiao-bing; Zheng, Pei-ming

2014-10-01

42

Polymorphs calcium carbonate on temperature reaction  

NASA Astrophysics Data System (ADS)

Calcium carbonate (CaCO3) has three different crystal polymorphs, which are calcite, aragonite and vaterite. In this study, effect of reaction temperature on polymorphs and crystallite structure of CaCO3 was investigated. X-ray powder diffraction (XRD), fourier transform infrared (FTIR), and variable pressure scanning electron microscope (VPSEM) were used to characterize the obtained CaCO3 particles. The obtained results showed that CaCO3 with different crystal and particle structures can be formed by controlling the temperature during the synthesis process.

Chong, Kai-Yin; Chia, Chin-Hua; Zakaria, Sarani

2014-09-01

43

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. PMID:23844062

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

2013-01-01

44

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

45

Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.  

ERIC Educational Resources Information Center

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

Henrickson, Charles H.; Robinson, Paul R.

1979-01-01

46

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

47

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

PubMed

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

Abhishek, Abhishek; Doherty, Michael

2014-05-01

48

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

Microsoft Academic Search

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

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

1980-01-01

49

Polypropylene\\/calcium carbonate nanocomposites  

Microsoft Academic Search

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

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

2002-01-01

50

Calcium  

MedlinePLUS

... lead levels. Calcium carbonate is used as an antacid for “heartburn.” Calcium carbonate and calcium acetate are ... when given intravenously (by IV). Use as an antacid as calcium carbonate. Reducing phosphate levels in people ...

51

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 Idioblasts1  

PubMed Central

l-Ascorbic acid (AsA) and its metabolic precursors give rise to oxalic acid (OxA) found in calcium oxalate crystals in specialized crystal idioblast cells in plants; however, it is not known if AsA and OxA are synthesized within the crystal idioblast cell or transported in from surrounding mesophyll cells. Isolated developing crystal idioblasts from Pistia stratiotes were used to study the pathway of OxA biosynthesis and to determine if idioblasts contain the entire path and are essentially independent in OxA synthesis. Idioblasts were supplied with various 14C-labeled compounds and examined by micro-autoradiography for incorporation of 14C into calcium oxalate crystals. [14C]OxA gave heavy labeling of crystals, indicating the isolated idioblasts are functional in crystal formation. Incubation with [1-14C]AsA also gave heavy labeling of crystals, whereas [6-14C]AsA gave no labeling. Labeled precursors of AsA (l-[1-14C]galactose; d-[1-14C]mannose) also resulted in crystal labeling, as did the ascorbic acid analog, d-[1-14C]erythorbic acid. Intensity of labeling of isolated idioblasts followed 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 results are discussed with respect to fine control of calcium oxalate precipitation and the concept of crystal idioblasts as independent physiological compartments. PMID:11161021

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

2001-01-01

52

tice sites of calcium carbonate and affect Mars' soil geochemistry, and calcium carbonate can  

E-print Network

tice sites of calcium carbonate and affect Mars' soil geochemistry, and calcium carbonate can sample. 18. Estimation of the concentration of calcium carbonate in the sample is uncertain because qualification model (17). Other carbonates have decomposition temperatures that are lower than that of calcite

Kounaves, Samuel P.

53

Calcium carbonate and calcium sulfate in Martian meteorite EETA79001  

NASA Technical Reports Server (NTRS)

Chips of glassy Lithology C of EETA79001 were studied by scanning electron microscopy and energy dispersive X-ray spectroscopy to determine the mineralogy and petrogenesis of the glass that was shown by others to contain trapped Mars-like gases. Calcium carbonite was identified as massive to acicular crystals for which Ca, C, and O were the major elements. Calcium sulfate was identified as prismatic-acicular crystals with Ca and S as the major elements.

Gooding, J. L.; Wentworth, S. J.

1987-01-01

54

Spinning up the polymorphs of calcium carbonate  

PubMed Central

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

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

2014-01-01

55

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

56

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

57

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

E-print Network

BEHAVIOR OF CARBON ISOTOPES DURING THE HYPERFILTRATION OF CALCIUM CARBONATE SOLUTIONS THROUGH CALCIUM BENTONITES A Thesis DAVID WILLIAM HINZ Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirements... for the degree of MASTER OF SCIENCE May 1987 Major Subject: Geology BEHAVIOR OF CARBON ISOTOPES DURING THE HYPERFILTRATION OF CALCIUM CARBONATE SOLUTIONS THROUGH CALCIUM BENTONITES A Thesis by DAVID WILLIAM HINZ Approved as to style and content by...

Hinz, David William

2012-06-07

58

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

59

Effect of Langmuir monolayer of bovine serum albumin protein on the morphology of calcium carbonate  

E-print Network

Bovine serum albumin (BSA) Langmuir monolayer, as a model of biomineralization-associated proteins, was used to study its effect on regulated biomineralization of calcium carbonate. The effects of the BSA Langmuir monolayer and the concentration of the subphase solution on the nucleation and growth processes and morphology of the calcium carbonate crystal were investigated. The morphology and polymorphic phase of the resulting calcium carbonate crystals were characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Moreover, the interaction mechanisms of the subphase solution with the BSA Langmuir monolayer were discussed. It was found that BSA Langmuir monolayer could be used as a template to successfully manipulate the polymorphic phase and crystal morphology of calcium carbonate and had obvious influence on the oriented crystallization and growth. The final morphology or aggregation mode of the calcite crystal was closely dependent on the concentration of calcium bicarbonate...

Xue, Zhong-Hui; Hu, Bin-Bin; Du, Zu-Liang; 10.1016/j.msec.2009.03.016

2011-01-01

60

Arthropathies associated with calcium-containing crystals.  

PubMed

Monosodium urate crystals are clearly related to acute attacks of gout and to the hard tissue destruction of chronic tophaceous gout. Fortunately, the acute attacks are readily treated with anti-inflammatory drugs, and destructive changes due to tophi may be prevented or reversed, at least in part, by the intelligent control of serum urate levels. Control of gout is one of the premier success stories of modern medicine. In contrast, the number of patients who have arthritis associated with crystals that contain calcium appears to be rising--perhaps a function of better recognition, perhaps related to the aging of the population. CPPD and BCP crystals can be associated with acute or subacute inflammation, but as in acute gout, it is easily controlled with anti-inflammatory drugs or by local injections of corticosteroids. A direct relationship of BCP and CPPD crystals to the associated destructive arthropathies has been hypothesized and is supported by clinical observations, animal studies, and in vivo experiments. Unlike gout, which is usually associated with a systemic metabolic abnormality (i.e., hyperuricemia), calcium crystals deposition seem to be a localized phenomenon, although numerous local sites in several joints are often involved in a given patient. Tissue degeneration in gout clearly follows (tophaceous) crystal deposition. Calcium crystal deposition may follow, rather than precede, destructive joint changes. Alternatively, both destructive changes and crystal deposition may derive independently from a common, still obscure, biochemical abnormality of joint tissues. P. A. Dieppe and colleagues believe that calcium crystal deposition follows either primary or secondary tissue degeneration but that the crystals exert a positive feedback effect (amplification loop) that accelerates degeneration. Each of those formulations of a pathogenetic role for crystals may be true in a given case, analogous to the etiology of primary and secondary forms of hyperuricemia and to sodium urate crystal deposition coexistent with osteoarthritis (tophus formation in Heberden's nodes). Conclusive proof of a significant role for BCP or CPPD crystals in the pathogenesis of human joint tissue damage depends on interrupting the postulated disease mechanism and showing that this prevents joint deterioration and leads to significant repair of existing damage. Our current position is somewhat analogous to that of our colleagues who had to contend with management of gouty arthritis before the advent of effective drugs for control of hyperuricemia. PMID:3020071

McCarty, D J

1986-10-15

61

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

62

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. ?? 2011 U.S. Government.

Reddy, M.M.; Hoch, A.

2012-01-01

63

Calcium Carbonate Budgets the Basic Framework -*  

E-print Network

Calcium Carbonate Budgets � the Basic Framework -* *title provided by Jim Hendee #12 aragonite #12;#12;Carbonate Chemistry CO2aq (CO2 + H2O) H2CO3 CO2 HCO3 � + H+ CO3 2� + H+ bicarbonate carbonate CaCO3 Carbonic acid Mg2+ Ca2+ Na+ K+ Alkalinity Proportions of HCO3 � and CO3 2� adjust to balance

Kleypas, Joanie

64

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

E-print Network

Br J Nutr . Author manuscript Page /1 9 Calcium carbonate suppresses haem toxicity markers without-term studies in rats identified calcium carbonate as the most effective calcium salt to bind haem in vitro demonstrated that a diet containing 100 mol/g calcium carbonate did not promote aberrant crypt foci

Paris-Sud XI, Université de

65

Effect of Langmuir monolayer of bovine serum albumin protein on the morphology of calcium carbonate  

E-print Network

Bovine serum albumin (BSA) Langmuir monolayer, as a model of biomineralization-associated proteins, was used to study its effect on regulated biomineralization of calcium carbonate. The effects of the BSA Langmuir monolayer and the concentration of the subphase solution on the nucleation and growth processes and morphology of the calcium carbonate crystal were investigated. The morphology and polymorphic phase of the resulting calcium carbonate crystals were characterized by scanning electron microscopy (SEM) and X-ray diffraction analysis (XRD). Moreover, the interaction mechanisms of the subphase solution with the BSA Langmuir monolayer were discussed. It was found that BSA Langmuir monolayer could be used as a template to successfully manipulate the polymorphic phase and crystal morphology of calcium carbonate and had obvious influence on the oriented crystallization and growth. The final morphology or aggregation mode of the calcite crystal was closely dependent on the concentration of calcium bicarbonate solution. It is expected that this research would help to better understand the mechanism of biomineralization by revealing the interactions between protein matrices and crystallization of calcium carbonate crystal.

Zhong-Hui Xue; Shu-Xi Dai; Bin-Bin Hu; Zu-Liang Du

2011-06-14

66

Natural promoters of calcium oxalate monohydrate crystallization.  

PubMed

Crystallization is often facilitated by modifiers that interact with specific crystal surfaces and mediate the anisotropic rate of growth. Natural and synthetic modifiers tend to function as growth inhibitors that hinder solute attachment and impede the advancement of layers on crystal surfaces. There are fewer examples of modifiers that operate as growth promoters, whereby modifier-crystal interactions accelerate the kinetic rate of crystallization. Here, we examine two proteins, lysozyme and lactoferrin, which are observed in the organic matrix of three types of pathological stones: renal, prostatic, and pancreatic stones. This work focuses on the role of these proteins in the crystallization of calcium oxalate monohydrate (COM), the most prominent constituent of human kidney stones. Using a combination of experimental techniques, we show that these proteins, which are rich in l-arginine and l-lysine amino acids, promote COM growth. The synthesis and testing of peptides derived from contiguous segments of lysozyme's primary amino acid sequence revealed subdomains within the protein that operate either as an inhibitor or promoter of COM growth, with the latter exhibiting efficacies that nearly match that of the protein. We observed that cationic proteins promote COM growth over a wide range of modifier concentration, which differs from calcification promoters in the literature that exhibit dual roles as promoters and inhibitors at low and high concentration, respectively. This seems to suggest a unique mechanism of action for lysozyme and lactoferrin. Possible explanations for their effects on COM growth and crystal habit are proposed on the basis of classical colloidal theories and the physicochemical properties of peptide subdomains, including the number and spatial location of charged or hydrogen-bonding moieties. PMID:25119124

Farmanesh, Sahar; Chung, Jihae; Sosa, Ricardo D; Kwak, Jun Ha; Karande, Pankaj; Rimer, Jeffrey D

2014-09-10

67

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

PubMed Central

Little is known about how calcium pyrophosphate dihydrate (CaPPD) crystals form in vivo and give rise to chondrocalcinosis or pseudogout (pyrophosphate arthropathy or calcium pyrophosphate crystal deposition disease). In this study a simple method has been devised to define the conditions necessary for the deposition of crystals in vitro. Crystal formation is monitored by 45Ca in the presence of 1·5 mmol/l Ca and increasing concentrations of inorganic pyrophosphate (PPi) under simulated physiological conditions of pH and ionic strength. Concentrations of PPi required to initiate crystal formation were about 40 mmol/l in the absence and 175 mmol/l in the presence of 0·5 mmol/l Mg2+ at pH 7·4. Less PPi was required at higher pH values. The naturally occurring monoclinic and triclinic forms of CaPPD were produced after prolonged incubation in vitro, but the initial deposits were amorphous or orthorhombic. The physiological significance of these observations is discussed. Since much higher concentrations of PPi are required to form crystals in vitro than are found to occur naturally in synovial fluids from patients with pyrophosphate arthropathy, it is suggested that crystals are more likely to deposit initially within cartilage and that nucleating mechanisms may be important in vivo. Since other workers have observed a slow interconversion of other calcium pyrophosphate crystal forms into monoclinic and triclinic allomorphs under laboratory conditions, the reason why only these 2 forms occur under clinical conditions may reflect the long time available in vivo for the formation of crystals. PMID:6251756

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

1980-01-01

68

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

Code of Federal Regulations, 2010 CFR

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

2010-07-01

69

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

Code of Federal Regulations, 2013 CFR

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

2013-07-01

70

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

Code of Federal Regulations, 2012 CFR

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

2012-07-01

71

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

Code of Federal Regulations, 2011 CFR

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

2011-07-01

72

Calcination of calcium carbonate and blend therefor  

DOEpatents

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

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

1989-01-01

73

[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

74

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

75

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

76

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

77

CALCIUM CARBONATE BUDGET OF THE SOUTHERN CALIFORNIA CONTINENTAL BORDERLAND  

E-print Network

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

Luther, Douglas S.

78

Chemical Preparation of Carbonated Calcium Hydroxyapatite Powders at 37  

E-print Network

Chemical Preparation of Carbonated Calcium Hydroxyapatite Powders at 37 C in Urea-phase ceramic powder. Carbonated HA powders were formed from calcium nitrate tetrahydrate and di- ammonium properties. They were usually observed1 to be carbonate-substituted and calcium-de®cient. Synthetic body

Tas, A. Cuneyt

79

The expanded amelogenin polyproline region preferentially binds to apatite versus carbonate and promotes apatite crystal elongation  

PubMed Central

The transition from invertebrate calcium carbonate-based calcite and aragonite exo- and endoskeletons to the calcium phosphate-based vertebrate backbones and jaws composed of microscopic hydroxyapatite crystals is one of the great revolutions in the evolution of terrestrial organisms. To identify potential factors that might have played a role in such a transition, three key domains of the vertebrate tooth enamel protein amelogenin were probed for calcium mineral/protein interactions and their ability to promote calcium phosphate and calcium carbonate crystal growth. Under calcium phosphate crystal growth conditions, only the carboxy-terminus augmented polyproline repeat peptide, but not the N-terminal peptide nor the polyproline repeat peptide alone, promoted the formation of thin and parallel crystallites resembling those of bone and initial enamel. In contrast, under calcium carbonate crystal growth conditions, all three amelogenin-derived polypeptides caused calcium carbonate to form fused crystalline conglomerates. When examined for long-term crystal growth, polyproline repeat peptides of increasing length promoted the growth of shorter calcium carbonate crystals with broader basis, contrary to the positive correlation between polyproline repeat element length and apatite mineralization published earlier. To determine whether the positive correlation between polyproline repeat element length and apatite crystal growth versus the inverse correlation between polyproline repeat length and calcium carbonate crystal growth were related to the binding affinity of the polyproline domain to either apatite or carbonate, a parallel series of calcium carbonate and calcium phosphate/apatite protein binding studies was conducted. These studies demonstrated a remarkable binding affinity between the augmented amelogenin polyproline repeat region and calcium phosphates, and almost no binding to calcium carbonates. In contrast, the amelogenin N-terminus bound to both carbonate and apatite, but preferentially to calcium carbonate. Together, these studies highlight the specific binding affinity of the augmented amelogenin polyproline repeat region to calcium phosphates versus calcium carbonate, and its unique role in the growth of thin apatite crystals as they occur in vertebrate biominerals. Our data suggest that the rise of apatite-based biominerals in vertebrates might have been facilitated by a rapid evolution of specialized polyproline repeat proteins flanked by a charged domain, resulting in apatite crystals with reduced width, increased length, and tailored biomechanical properties.

Gopinathan, Gokul; Jin, Tianquan; Liu, Min; Li, Steve; Atsawasuwan, Phimon; Galang, Maria-Therese; Allen, Michael; Luan, Xianghong; Diekwisch, Thomas G. H.

2014-01-01

80

Calcium pyrophosphate dihydrate and basic calcium phosphate crystal-induced arthropathies: update on pathogenesis, clinical features, and therapy.  

PubMed

Calcium-containing crystals are the most common class for the osteoarthritic joint. They are responsible for acute periarthritis and destructive arthropathies, and for tissue deposits mimicking tumor-like masses. These crystals encompassed mainly calcium pyrophosphate dihydrate and basic calcium phosphate crystals, with the latter being related to hydroxyapatite, carbonate-substituted apatite, and octacalcium phosphate. Calcification deposit mechanisms will be reviewed with respect to extracellular inorganic pyrophosphate dysregulation mainly caused by modulation of specific membrane channel disorders. Genetic defects have been extensively studied and identified mutation of specific genes such as ANKH and COL. Pathogenesis of crystal-induced inflammation is related to synovial tissue and direct cartilage activation. Besides classical knee or wrist pseudogout attacks or Milwaukee shoulder arthropathies, clinicians should be aware of other specific common presentations, such as erosive calcifications, spinal cord compression by intraspinal masses, ligamentum flavum calcification, or atypical calcified tophus. Promising clinical results for preventing calcium crystal deposits and cartilage degradation are lacking. Practical imaging tools are needed to monitor reduction of calcification of fibrocartilage and articular cartilage as markers of drug efficacy. PMID:15134602

Ea, Hang-Korng; Lioté, Frédéric

2004-06-01

81

Epitaxial relationships between calcium carbonate and inorganic substrates.  

PubMed

The polymorph-selective crystallization of calcium carbonate has been studied in terms of epitaxial relationship between the inorganic substrates and the aragonite/calcite polymorphs with implication in bioinspired mineralization. EpiCalc software was employed to assess the previously published experimental results on two different groups of inorganic substrates: aragonitic carbonate crystals (SrCO3, PbCO3, and BaCO3) and a hexagonal crystal family (?-Al2O3, ?-SiO2, and LiNbO3). The maximum size of the overlayer (aragonite or calcite) was calculated for each substrate based on a threshold value of the dimensionless potential to estimate the relative nucleation preference of the polymorphs of calcium carbonate. The results were in good agreement with previous experimental observations, although stereochemical effects between the overlayer and substrate should be separately considered when existed. In assessing the polymorph-selective nucleation, the current method appeared to provide a better tool than the oversimplified mismatch parameters without invoking time-consuming molecular simulation. PMID:25226539

Yang, Taewook; Jho, Jae Young; Kim, Il Won

2014-01-01

82

Epitaxial Relationships between Calcium Carbonate and Inorganic Substrates  

PubMed Central

The polymorph-selective crystallization of calcium carbonate has been studied in terms of epitaxial relationship between the inorganic substrates and the aragonite/calcite polymorphs with implication in bioinspired mineralization. EpiCalc software was employed to assess the previously published experimental results on two different groups of inorganic substrates: aragonitic carbonate crystals (SrCO3, PbCO3, and BaCO3) and a hexagonal crystal family (?-Al2O3, ?-SiO2, and LiNbO3). The maximum size of the overlayer (aragonite or calcite) was calculated for each substrate based on a threshold value of the dimensionless potential to estimate the relative nucleation preference of the polymorphs of calcium carbonate. The results were in good agreement with previous experimental observations, although stereochemical effects between the overlayer and substrate should be separately considered when existed. In assessing the polymorph-selective nucleation, the current method appeared to provide a better tool than the oversimplified mismatch parameters without invoking time-consuming molecular simulation\\. PMID:25226539

Yang, Taewook; Jho, Jae Young; Kim, Il Won

2014-01-01

83

Calcium-containing crystals and osteoarthritis: implications for the clinician.  

PubMed

The clinical implication of articular deposits of calcium-containing crystals (specifically of calcium pyrophosphate dihydrate and hydroxyapatite) in osteoarthritis is unknown. Recent longitudinal studies have suggested that in some instances calcium crystals are direct participants in cartilage damage, while in other situations they are merely markers of joint damage. Better understanding of the mechanisms of crystal formation, especially in relation to inorganic pyrophosphate regulation, has lead to potential avenues for therapeutic intervention. The current treatment of osteoarthritis associated with calcium-containing crystals should involve nonsteroidal anti-inflammatory drugs, intra-articular steroids, and in resistant cases, joint irrigation can be considered. While preliminary studies suggest the possibility of favorable benefits from colchicine and hydroxycholorquine in this osteoarthritis disease subset, more rigorous studies need to be conducted to establish their roles. PMID:15918998

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

2005-06-01

84

Factors affecting the solubility of calcium pyrophosphate dihydrate crystals.  

PubMed Central

The solubility of triclinic calcium pyrophosphate dihydrate (CPPD) crystals was measured under varying conditions using 45Ca-labeled crystals, expressing solubility as micromoles per liter of 45Ca in solution. In a 0.1-M Tris-HC1 buffer pH 7.4, the solubility of accurately sized CPPD crystals (37-20mum) was 60muM with maximal solubility being attained after about 8 h incubation at 37degreeC. Reduction in crystal size, decrease in pH, increase in ionic strength, Mg++, citrate, and albumin all increased solubility. The most marked effects on solubility occurred when changing the calcium concentration or by enzymatic hydrolysis of inoganic pyrophosphate to orthophosphate. It was found that decreasing the ionized calcium level below 5 mg/100 ml resulted in a progressive enhancement of solubility. The observed solubility-enhancing effects of albumin could be explained solely on its calcium-binding ability and thereby, altered ionized calcium level. Diffusible calcium in synovial fluid was only 40% of the total calcium concentration, which means most joint fluids are normally near the critical concentration of 5 mg/100 ml of ionized calcium, below which solubility is enhanced. During surgery, especially parathyroidectomy, calcium levels fall, favoring dissolution of CPPD crystals. We speculate that the slight decrease in crystal size during dissolution frees them from their cartilaginous mold, resulting in a dose-dependent inflammatory reaction as they are "shed" into the joint space. Crystal shedding may be reinforced by the modest fall in joint fluid pH accompanying the inflammatory response. PMID:423

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

1975-01-01

85

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

E-print Network

Risø-R-1143(EN) CRACK2 - Modelling Calcium Carbonate Deposition from Bicarbonate Solution in Cracks: The numerical CRACK2 model simulates precipitation of calcite from calcium bi- carbo-nate solution (e is simulated as calcium hydroxide mixed with inert material but with sodium hydroxide dissolved in the pore

86

Pyroelectric and dielectric properties of calcium barium niobate single crystals  

NASA Astrophysics Data System (ADS)

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

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

2014-09-01

87

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

88

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

89

British Journal of Nutrition, 2010, Allam et al., Calcium carbonate blocks haem without side effect. Authors' Version 1 Calcium Carbonate Suppresses Haem Toxicity Markers without  

E-print Network

British Journal of Nutrition, 2010, Allam et al., Calcium carbonate blocks haem without side effect. Authors' Version 1 Calcium Carbonate Suppresses Haem Toxicity Markers without Calcium Phosphate Side identified calcium carbonate as the most effective calcium salt to bind haem in vitro and to decrease faecal

Paris-Sud XI, Université de

90

Nephrocalcin isoforms coat crystal surfaces and differentially affect calcium oxalate monohydrate crystal morphology, growth, and aggregation  

NASA Astrophysics Data System (ADS)

Calcium oxalate crystals were grown in the presence of each of the four isoforms of nephrocalcin (NC), a urinary protein proposed to inhibit kidney stone growth. Crystal size, morphology, and surface topography were assessed using optical microscopy, Coulter counter measurements, scanning electron microscopy (SEM), and atomic force microscopy (AFM). All crystals grown in the presence of NC isoforms were calcium oxalate monohydrates (COMs). Crystals formed in the presence of NC-A were smaller than control crystals, which were grown without NC, according to optical and SEM results, suggesting that NC-A restricts crystal growth. In contrast, samples grown with NC-C and NC-D exhibit more large crystals and several crystal aggregates, suggesting that NC-C and -D promote crystal growth and aggregation. Crystals grown with NC-B are not significantly larger or smaller than controls. AFM images of the crystals reveal significantly different surface textures on the control crystals relative to those grown with NC isoforms, indicating that NC acts by coating nascent calcium oxalate crystals. These are the first reported AFM images that show topography of NC-coated crystals. These findings suggest that NC isoforms have distinct interactions with different COM crystal faces, which may be responsible for their different effects on crystal growth and morphology.

Kurutz, Josh W.; Carvalho, Mauricio; Nakagawa, Yasushi

2003-08-01

91

Crystallization of calcium oxalate in minimally diluted urine  

NASA Astrophysics Data System (ADS)

Crystallization of calcium oxalate was studied in minimally diluted (92%) urine using a mixed suspension mixed product crystallizer in series with a Malvern particle sizer. The crystallization was initiated by constant flow of aqueous sodium oxalate and urine into the reaction vessel via two independent feed lines. Because the Malvern cell was in series with the reaction vessel, noninvasive measurement of particle sizes could be effected. In addition, aliquots of the mixed suspension were withdrawn and transferred to a Coulter counter for crystal counting and sizing. Steady-state particle size distributions were used to determine nucleation and growth kinetics while scanning electron microscopy was used to examine deposited crystals. Two sets of experiments were performed. In the first, the effect of the concentration of the exogenous sodium oxalate was investigated while in the second, the effect of temperature was studied. Calcium oxalate nucleation and growth rates were found to be dependent on supersaturation levels inside the crystallizer. However, while growth rate increased with increasing temperature, nucleation rates decreased. The favored phases were the trihydrate at 18°C, the dihydrate at 38° and the monohydrate at 58°C. The results of both experiments are in agreement with those obtained in other studies that have been conducted in synthetic and in maximally diluted urine and which have employed invasive crystal counting and sizing techniques. As such, the present study lends confidence to the models of urinary calcium oxalate crystallization processes which currently prevail in the literature.

Bretherton, T.; Rodgers, A.

1998-09-01

92

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

93

Aluminum Citrate Prevents Renal Injury from Calcium Oxalate Crystal Deposition  

PubMed Central

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

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

2012-01-01

94

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

95

Influence of active sites organisation on calcium carbonate formation at model biomolecular interfaces  

E-print Network

Influence of active sites organisation on calcium carbonate formation at model biomolecular in the matrix. Formation of solid calcium carbonate with two- component monolayers on subphases containing.V. All rights reserved. Keywords: Mixed model monolayers; Calcium carbonate formation; Phospholipids

Hell, Stefan W.

96

QUANTIFYING GROWTH AND CALCIUM CARBONATE DEPOSITION OF CALLIARTHRON CHEILOSPORIOIDES (CORALLINALES, RHODOPHYTA)  

E-print Network

NOTE QUANTIFYING GROWTH AND CALCIUM CARBONATE DEPOSITION OF CALLIARTHRON CHEILOSPORIOIDES Station of Stanford University, Pacific Grove, California 93950, USA Growth and calcium carbonate measurement of growth and calcium carbonate deposition at each meristem. In Calliarthron, meristematic

Martone, Patrick T.

97

Temperature-Dependent Heterogeneous Efflorescence of Mixed Ammonium Sulfate/Calcium Carbonate Particles  

E-print Network

Temperature-Dependent Heterogeneous Efflorescence of Mixed Ammonium Sulfate/Calcium Carbonate sulfate/calcium carbonate microparticles. Deliquescence and efflorescence relative humidities and calcium carbonate and (b) supersaturated with respect to ammonium sulfate and saturated with respect

98

Bacillus subtilis Gene Cluster Involved in Calcium Carbonate Biomineralization  

Microsoft Academic Search

Calcium carbonate precipitation, a widespread phenomenon among bacteria, has been investigated due to its wide range of scientific and technological implications. Nevertheless, little is known of the molecular mechanisms by which bacteria foster calcium carbonate mineralization. In our laboratory, we are studying calcite formation by Bacillus subtilis, in order to identify genes involved in the biomineralization process. A previous screening

Chiara Barabesi; Alessandro Galizzi; Giorgio Mastromei; Mila Rossi; Elena Tamburini; Brunella Perito

2007-01-01

99

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

100

Amorphous Calcium Carbonate Transforms into Calcite during Sea Urchin Larval Spicule Growth  

Microsoft Academic Search

Sea urchin larvae form an endoskeleton composed of a pair of spicules. For more than a century it has been stated that each spicule comprises a single crystal of the CaCO3 mineral, calcite. We show that an additional mineral phase, amorphous calcium carbonate, is present in the sea urchin larval spicule, and that this inherently unstable mineral transforms into calcite

Elia Beniash; Joanna Aizenberg; Lia Addadi; Stephen Weiner

1997-01-01

101

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

102

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

103

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

Microsoft Academic Search

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

L. L. Robbins; P. L. Blackwelder

1992-01-01

104

The inhibition of calcium hydroxyapatite crystal growth by polyphosphonates and polyphosphates  

Microsoft Academic Search

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

Marion D. Francis

1969-01-01

105

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. PMID:22778620

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

2012-01-01

106

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

107

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 PMID:16661115

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

1979-01-01

108

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

PubMed

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

Rivera, E R; Smith, B N

1979-12-01

109

Crucibleless crystal growth and Radioluminescence study of calcium tungstate single crystal fiber  

NASA Astrophysics Data System (ADS)

In this article, single phase and high optical quality scheelite calcium tungstate single crystal fibers were grown by using the crucibleless laser heated pedestal growth technique. The as-synthesized calcium tungstate powders used for shaping seed and feed rods were investigated by X-ray diffraction technique. As-grown crystals were studied by Raman spectroscopy and Radioluminescence measurements. The results indicate that in both two cases, calcined powder and single crystal fiber, only the expected scheelite CaWO4 phase was observed. It was verified large homogeneity in the crystal composition, without the presence of secondary phases. The Radioluminescence spectra of the as-grown single crystal fibers are in agreement with that present in Literature for bulk single crystals, presented a single emission band centered at 420 nm when irradiated with ?-rays.

Silva, M. S.; Jesus, L. M.; Barbosa, L. B.; Ardila, D. R.; Andreeta, J. P.; Silva, R. S.

2014-11-01

110

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

111

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, P.E., Jr.

1962-01-01

112

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

113

Crystal structure and morphology control of calcium oxalate using biopolymeric additives in crystallization  

NASA Astrophysics Data System (ADS)

Using the acid-rich polymeric additives, poly- L-aspartate (polyD), poly- L-glutamate (polyE), and polyacrylate (polyAA), the structure and morphology of calcium oxalate crystals were controlled during crystallization. In crystallization without the polymeric additives, twinned calcium oxalate monohydrate (COM) crystals were preferentially produced. However, the structural shift of calcium oxalate from a monohydrate (COM) to a dihydrate (COD) form occurred gradually when increasing the polymeric additive concentration, then COD crystals were exclusively crystallized beyond certain critical concentrations of the additives. These critical concentrations actually depended on the molecular configurations of the additives that determined the capability to control the crystallization. When increasing the additive concentration far beyond the critical level, shape modifications without structural changes occurred from a normal octahedral shape (bi-pyramid) to a rod shape (elongated octahedral shape), followed by a dumbbell shape, and finally a sphere shape. Due to its high binding affinity to the crystal surface, polyAA exhibited the most effective elongation in the [0 0 1] direction and clearest development of {1 0 0} faces, while polyE had the least effect on the crystals.

Jung, Taesung; Kim, Woo-Sik; Kyun Choi, Chang

2005-05-01

114

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...

115

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

E-print Network

Extracellular matrix production and calcium carbonate precipitation by coral cells in vitro Yael), which facilitates controlled deposition of a calcium carbonate skeleton; and (iii) the calcium carbonate to nematocysts, mucous glands, and sensory or nerve cells (2, 3). Many corals also precipitate calcium carbonate

116

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. PMID:22294477

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

2012-01-01

117

Influence of magnetic field on calcium carbonate precipitation  

Microsoft Academic Search

Effect of permanent magnetic field with north and south faces facing each other (0.16 T) on calcium carbonate precipitation type (homogeneous and heterogeneous) and solubility were investigated in different conditions of calcium carbonate water concentration, treatment-pH and water flow rate in the magnetic field. Treated water was exposed to a scaling test by degasifying dissolved CO2 in water. It was

Fathi Alimi; Mohamed Tlili; Mohamed Ben Amor; Claude Gabrielli; George Maurin

2007-01-01

118

Hydrophobic Modification and Characterization of Calcium Carbonate Nanopowders  

Microsoft Academic Search

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

Li Jirui; Zhuzhou Hunan

2010-01-01

119

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

NASA Astrophysics Data System (ADS)

During the 18th Egyptian dynasty (1570-1292 B.C.), opaque white, blue and turquoise glasses were opacified by calcium antimonate crystals dispersed in a vitreous matrix. The technological processes as well as the antimony sources used to manufacture these crystals remain unknown. Our results shed a new light on glassmaking history: contrary to what was thought, we demonstrate that Egyptian glassmakers did not use in situ crystallization but first synthesized calcium antimonate opacifiers, which do not exist in nature, and then added them to a glass. Furthermore, using transmission electron microscopy (TEM) for the first time in the study of Egyptian opaque glasses, we show that these opacifiers were nano-crystals. Prior to this research, such a process for glassmaking has not been suggested for any kind of ancient opaque glass production. Studying various preparation methods for calcium antimonate, we propose that Egyptian craftsmen could have produced Ca2Sb2O7 by using mixtures of Sb2O3 or Sb2O5 with calcium carbonates (atomic ratio Sb/Ca=1) heat treated between 1000 and 1100°C. We developed an original strategy focused on the investigation of the crystals and the vitreous matrices using an appropriate suite of high-sensitivity and high-resolution micro- and nano-analytical techniques (scanning electron microscopy (SEM), X-ray diffraction (XRD), TEM). Synchrotron-based micro X-ray absorption near edge spectroscopy (?-XANES) proved to be very well suited to the selective measure of the antimony oxidation state in the vitreous matrix. This work is the starting point for a complete reassessment not only of ancient Egyptian glass studies but more generally of high-temperature technologies used throughout antiquity.

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

2010-01-01

120

Amorphous Calcium Carbonate Precipitation by Cellular Biomineralization in Mantle Cell Cultures of Pinctada fucata  

PubMed Central

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

Xiang, Liang; Kong, Wei; Su, Jingtan; Liang, Jian; Zhang, Guiyou; Xie, Liping; Zhang, Rongqing

2014-01-01

121

Inhibition of calcium oxalate monohydrate crystal growth using polyelectrolytes  

NASA Astrophysics Data System (ADS)

The effects of polyacrylic acid and poly(ethylene glycol-block-acrylic acid) copolymer on the growth of calcium oxalate monohydrate (COM), a common renal stone constituent, have been investigated in aqueous solutions at 37 °C. A constant composition method has been utilized to investigate the crystallization kinetics of COM. The results of the experiment show that the retardation in mass transport in growth process is controlled by the nature of the polymer and its concentration. Monoclinic COM crystals were shown to be major components in the absence of polymers. In the presence of polymers monoclinic COM crystals were smaller and some of the crystals were less elongated, and small number of crystals grew in the shape of three-dimensional hexagonal prisms. The data on the growth kinetics of crystals in the presence of polyelectrolytes were examined from the standpoint of adsorption models. Polyelectrolyte effects were interpreted in terms of the adsorption of inhibitors onto the active growth sites on the crystal surface.

Akyol, Emel; Öner, Mualla

2007-09-01

122

Isolation of Medicago truncatula Mutants Defective in Calcium Oxalate Crystal Formation1  

PubMed Central

Plants accumulate crystals of calcium oxalate in a variety of shapes, sizes, amounts, and spatial locations. How and why many plants form crystals of calcium oxalate remain largely unknown. To gain insight into the regulatory mechanisms of crystal formation and function, we have initiated a mutant screen to identify the genetic determinants. Leaves from a chemically mutagenized Medicago truncatula population were visually screened for alterations in calcium oxalate crystal formation. Seven different classes of calcium oxalate defective mutants were identified that exhibited alterations in crystal nucleation, morphology, distribution and/or amount. Genetic analysis suggested that crystal formation is a complex process involving more than seven loci. Phenotypic analysis of a mutant that lacks crystals, cod 5, did not reveal any difference in plant growth and development compared with controls. This finding brings into question the hypothesized roles of calcium oxalate formation in supporting tissue structure and in regulating excess tissue calcium. PMID:11080287

Nakata, Paul A.; McConn, Michele M.

2000-01-01

123

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

124

Calcium Channels are Involved in Calcium Oxalate Crystal Formation in Specialized Cells of Pistia stratiotes L.  

PubMed Central

• Background and Aims Pistia stratiotes produces large amounts of calcium (Ca) oxalate crystals in specialized cells called crystal idioblasts. The potential involvement of Ca2+ channels in Ca oxalate crystal formation by crystal idioblasts was investigated. • Methods Anatomical, ultrastructural and physiological analyses were used on plants, fresh or fixed tissues, or protoplasts. Ca2+ uptake by protoplasts was measured with 45Ca2+, and the effect of Ca2+ channel blockers studied in intact plants. Labelled Ca2+ channel blockers and a channel protein antibody were used to determine if Ca2+ channels were associated with crystal idioblasts. • Key Results 45Ca2+ uptake was more than two orders of magnitude greater for crystal idioblast protoplasts than mesophyll protoplasts, and idioblast number increased when medium Ca was increased. Plants grown on media containing 1–50 µm of the Ca2+ channel blockers, isradipine, nifedipine or fluspirilene, showed almost complete inhibition of crystal formation. When fresh tissue sections were treated with the fluorescent dihydropyridine?type Ca2+ channel blocker, DM?Bodipy?DHP, crystal idioblasts were intensely labelled compared with surrounding mesophyll, and the label appeared to be associated with the plasma membrane and the endoplasmic reticulum, which is shown to be abundant in idioblasts. An antibody to a mammalian Ca2+ channel ?1 subunit recognized a single band in a microsomal protein fraction but not soluble protein fraction on western blots, and it selectively and heavily labelled developing crystal idioblasts in tissue sections. • Conclusions The results demonstrate that Ca oxalate crystal idioblasts are enriched, relative to mesophyll cells, in dihydropyridine?type Ca2+ channels and that the activity of these channels is important to transport and accumulation of Ca2+ required for crystal formation. PMID:15087302

VOLK, GAYLE M.; GOSS, LENORA J.; FRANCESCHI, VINCENT R.

2004-01-01

125

Protein adsorption at calcium oxalate monohydrate crystal surfaces.  

NASA Astrophysics Data System (ADS)

Calcium oxalate monohydrate (COM) crystals are the dominant inorganic phase in most kidney stones, and kidney stones form as aggregates of COM crystals and organic material, principally proteins, but little is known about the molecular level events at COM surfaces that regulate COM aggregation. We have examined the influence of polyelectrolytes on the force of adhesion between chemically modified atomic force microscopy (AFM) tips and selected COM crystal faces in saturated solution. In general, we found that polyanions bind to COM surfaces and block adhesion of a carboxylate functionalized AFM tip, while polycations had no measureable effect on adhesion force under the same conditions. We did observe a unique absence of interaction between poly(glutamic acid) and the COM (100) face compared to other synthetic polyanions, and some native urinary protein structures also exhibited unique face selective interactions, suggesting that simple electrostatic models will not completely explain the data.

Wesson, J.; Sheng, X.; Rimer, J.; Jung, T.; Ward, M.

2008-03-01

126

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

127

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

128

Effect of calcium carbonate saturation of seawater on coral calcification  

Microsoft Academic Search

The carbonate chemistry of seawater is usually not considered to be an important factor influencing calcium-carbonate-precipitation by corals because surface seawater is supersaturated with respect to aragonite. Recent reports, however, suggest that it could play a major role in the evolution and biogeography of recent corals. We investigated the calcification rates of five colonies of the zooxanthellate coral Stylophora pistillata

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

1998-01-01

129

21 CFR 184.1191 - Calcium carbonate.  

Code of Federal Regulations, 2010 CFR

...chloride in the “Calcium chloride process”. (b) The ingredient meets the specifications of the Food Chemicals Codex, 3d Ed. (1981), p. 46, which is incorporated by reference. Copies are available from the National Academy Press,...

2010-04-01

130

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

Microsoft Academic Search

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

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

1994-01-01

131

A reactive force field for aqueous-calcium carbonate systems.  

PubMed

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

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

2011-10-01

132

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

133

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

134

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

135

Bacteria can promote calcium oxalate crystal growth and aggregation.  

PubMed

Our previous report showed that uropathogenic bacteria, e.g., Escherichia coli, are commonly found inside the nidus of calcium oxalate (CaOx) kidney stones and may play pivotal roles in stone genesis. The present study aimed to prove this new hypothesis by direct examining CaOx lithogenic activities of both Gram-negative and Gram-positive bacteria. CaOx was crystallized in the absence (blank control) or presence of 10(5) CFU/ml E. coli, Klebsiella pneumoniae, Staphylococcus aureus, or Streptococcus pneumoniae. Fragmented red blood cell membranes and intact red blood cells were used as positive and negative controls, respectively. The crystal area and the number of aggregates were measured to initially screen for effects of bacteria on CaOx crystal growth and aggregation. The data revealed that all the bacteria tested dramatically increased the crystal area and number of crystal aggregates. Validation assays (spectrophotometric oxalate-depletion assay and an aggregation-sedimentation study) confirmed their promoting effects on both growth (20.17 ± 3.42, 17.55 ± 2.27, 16.37 ± 1.38, and 21.87 ± 0.85 % increase, respectively) and aggregation (57.45 ± 2.08, 51.06 ± 5.51, 55.32 ± 2.08, and 46.81 ± 3.61 % increase, respectively) of CaOx crystals. Also, these bacteria significantly enlarged CaOx aggregates, with the diameter greater than the luminal size of distal tubules, implying that tubular occlusion might occur. Moreover, these bacterial effects were dose-dependent and specific to intact viable bacteria, not intact dead or fragmented bacteria. In summary, intact viable E. coli, K. pneumoniae, S. aureus, and S. pneumoniae had significant promoting effects on CaOx crystal growth and aggregation. This functional evidence supported the hypothesis that various types of bacteria can induce or aggravate metabolic stone disease, particularly the CaOx type. PMID:23334195

Chutipongtanate, Somchai; Sutthimethakorn, Suchitra; Chiangjong, Wararat; Thongboonkerd, Visith

2013-03-01

136

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

137

Electrochemical treatments for selective growth of different calcium carbonate allotropic forms on carbon steel  

Microsoft Academic Search

Different allotropic forms of calcium carbonate scales (calcite and aragonite) were electrochemically deposited on carbon steel surfaces, using different electrochemical techniques: cyclic voltammetry or potentiostatic pulses. To simulate conditions of Mexican refinery cooling systems, this study was performed in the presence of known concentrations of other salts at pH 7.8 and 40°C with low and high calcium carbonate concentrations. Reduction

J. Mar??n-Cruz; E. Garc??a-Figueroa; M. Miranda-Hernández; I. González

2004-01-01

138

A critical analysis of calcium carbonate mesocrystals  

NASA Astrophysics Data System (ADS)

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.

2014-07-01

139

Were kinetics of Archean calcium carbonate precipitation related to oxygen concentration?  

NASA Technical Reports Server (NTRS)

Archean carbonates commonly contain decimetre- to metre-thick beds consisting entirely of fibrous calcite and neomorphosed fibrous aragonite that precipitated in situ on the sea floor. The fact that such thick accumulations of precipitated carbonate are rare in younger marine carbonates suggests an important change in the modes of calcium carbonate precipitation through time. Kinetics of carbonate precipitation depend on the concentration of inhibitors to precipitation that reduce crystallization rates and crystal nuclei formation, leading to kinetic maintenance of supersaturated solutions. Inhibitors also affect carbonate textures by limiting micrite precipitation and promoting growth of older carbonate crystals on the sea floor. Fe2+, a strong calcite-precipitation inhibitor, is thought to have been present at relatively high concentrations in Archean seawater because oxygen concentrations were low. The rise in oxygen concentration at 2.2-1.9 Ga led to the removal of Fe2+ from seawater and resulted in a shift from Archean facies, which commonly include precipitated beds, to Proterozoic facies, which contain more micritic sediment and only rare precipitated beds.

Sumner, D. Y.; Grotzinger, J. P.

1996-01-01

140

Modulation of Calcium Oxalate Dihydrate Growth by Selective Crystal-face Binding of Phosphorylated  

E-print Network

Modulation of Calcium Oxalate Dihydrate Growth by Selective Crystal-face Binding of Phosphorylated Biology, Faculty of Medicine, McGill University, Montreal, Quebec H3A 2B2, Canada Calcium oxalate growth with subsequent intracrystalline incorpo- ration (occlusion). Calcium oxalate is the major mineral

Gray, Jeffrey J.

141

Habit modification of calcium carbonate in the presence of malic acid  

NASA Astrophysics Data System (ADS)

The ability of malic acid to control calcium carbonate morphology has been investigated by aging calcium chloride solution in the presence of urea in a 90 °C bath. Malic acid favors the formation of calcite. A transition from single block to aggregate with special morphology occurs upon increasing malic acid concentration. The morphological development of CaCO 3 crystal obviously depends on the starting pH. CaCO 3 crystal grows from spindle seed to dumbbell in the pH regime from 7 to 11; while it evolves from spindle seed, through peanut, to sphere at pH=11.5. Both dumbbell and sphere consist of rods that are elongated along c-axis and capped with three smooth, well-defined rhombic {1 0 4} faces. A tentative growth mechanism is proposed based on the fractal model suggested by R. Kniep and S. Busch [Angew. Chem. Int. Ed. Engl. 35 (1996) 2624].

Mao, Zhaofeng; Huang, Jianhua

2007-02-01

142

Role of intermediary cells in Peltodon radicans (Lamiaceae) in the transfer of calcium and formation of calcium oxalate crystals  

Microsoft Academic Search

With the objective of studying the connection between calcium oxalate crystals formation and the phloem, fragments of l eaves of Peltodon radicans Pohl (Lamiaceae) were fixed a nd p rocessed, for light and electron-transmission microscopes. It was observed that the crystals occurred in the cells of the bundle sheath, juxtaposed in relation to the phloem. Intermediary cells established a connection

Elder Antônio Sousa Paiva; Silvia Rodrigues Machado

2005-01-01

143

CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTACTORS  

EPA Science Inventory

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

144

CALCIUM CARBONATE DISSOLUTION RATE IN LIMESTONE CONTRACTORS  

EPA Science Inventory

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

145

Biologically mediated dissolution of calcium carbonate above the chemical lysocline?  

Microsoft Academic Search

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

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

1999-01-01

146

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

Microsoft Academic Search

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

S. V. Smith; D. W. Kinsey

1976-01-01

147

Modification of calcium carbonate surface properties: macroscopic and microscopic investigations  

Microsoft Academic Search

Understanding the wettability of mineral powders and its modification by the addition of various surface active agents is crucial for many industrial applications. In many cases, wettability is investigated by macroscopic characterization techniques. In this framework, we decided to study non-porous calcium carbonate powders coated by known amounts of water-repellent molecules. A detailed characterization of the interface, focusing on the

M. Chamerois; M. François; F. Villiéras; J. Yvon

1999-01-01

148

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. PMID:25014563

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

149

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

150

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

151

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

152

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

E-print Network

Possible overestimation of shallow-depth calcium carbonate dissolution in the ocean K. Friis,1,2 R calcium carbonate (TA*) above the saturation horizon cannot be unambiguously interpreted in terms of local and biogeochemistry with explicit representation of the formation and dissolution of calcium carbonate. In particular

Follows, Mick

153

Are environmental conditions recorded by the organic matrices associated with precipitated calcium carbonate in cyanobacterial microbialites?  

E-print Network

calcium carbonate in cyanobacterial microbialites? P. GAUTRET 1 , R. DE WIT 2 , G. CAMOIN 3 AND S. GOLUBIC acid composition of organic matrices associated with calcium carbonate precipitates in microbialites Caledonia (Nouméa lagoon) and French Polynesia (Tikehau atoll). Calcium carbonate precipitation

Paris-Sud XI, Université de

154

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

E-print Network

The influence of kinetics on the oxygen isotope composition of calcium carbonate James M. Watkins a and calcium carbonate. Although oxygen isotope separation is expected on theoretical grounds, the temperature on equilibrium fractionation of oxygen isotopes between calcium carbonate and water. Equili- brium oxygen isotope

Watkins, Jim

155

Concentrations de carbonate de calcium sur les parois des hyphes mycliens  

E-print Network

Concentrations de carbonate de calcium sur les parois des hyphes mycéliens Gabriel CALLOT, Daniel possibilité de formation de carbonate de calcium sur les parois des filaments mycéliens. Parallèlement à ces, minéralogenèse. SUMMARY Concentration of calcium carbonate on the walls of fungal hyphae. The structure

Boyer, Edmond

156

A model for calcium carbonate neutralization in the presence of armoring  

E-print Network

A model for calcium carbonate neutralization in the presence of armoring L. Fusia , M. Primicerioa for the reaction between calcium carbonate (CaCO3) and a solution containing sulfuric acid (H2SO4). We assume system and where the neutralizing agent is calcium carbonate (see [3], [4], [5]). These mod- els have

Primicerio, Mario

157

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

E-print Network

Biomimetic soy protein nanocomposites with calcium carbonate crystalline arrays for use as wood 2010 Available online 21 March 2010 Keywords: Wood glue Calcium carbonate Gecko adhesion Soy protein crosslinking of calcium, carbonate, hydroxyl ions in the adhesive greatly improving the water- resistance

158

Introduction The formation of solid calcium carbonate (CaCO3) is  

E-print Network

Introduction The formation of solid calcium carbonate (CaCO3) is an important process in biological calcium carbonate (CaCO3) with two-component monolayers on sub- phases containing aqueous CaCO3 In situ Brewster angle microscopy Ã? Calcium carbonate formation Ã? Kinetics Ã? Critical cluster Colloid

Hell, Stefan W.

159

Dissolution Kinetics of Calcium Carbonate Minerals A.V. Subhas1  

E-print Network

Dissolution Kinetics of Calcium Carbonate Minerals A.V. Subhas1 *, N.E. Rollins2 , W. Berelson2 , J@gps.caltech.edu We present a novel measurement of the dissolution kinetics of calcium carbonate minerals in seawater. These experiments significantly impact our understanding of calcium carbonate response to ocean acidification, water

Simon, Emmanuel

160

Production of precipitated calcium carbonate from industrial by-product slags (Slag2PCC)  

E-print Network

Production of precipitated calcium carbonate from industrial by-product slags (Slag2PCC) Saostetun for mineral carbonation. Owing to their high calcium con- tent, steelmaking slags could be very suitable for this method, which could safely store carbon di- oxide for a very long time. If calcium could be ex- tracted

Zevenhoven, Ron

161

Biomimetic Synthesis of Macroscopic-Scale Calcium Carbonate Thin Films. Evidence for a Multistep Assembly Process  

E-print Network

Biomimetic Synthesis of Macroscopic-Scale Calcium Carbonate Thin Films. Evidence for a Multistep growth modification and cessation, and so on. Highly ordered calcium carbonate lamellae formed have synthesized macroscopic and continuous calcium carbonate thin films with thickness ranging from 0

Aksay, Ilhan A.

162

Osteoblast response to nanocrystalline calcium hydroxyapatite depends on carbonate content.  

PubMed

Normal bone mineral is a carbonated-apatite, but there are limited data on the effect of mineral containing carbonate on cell response. We characterized surface chemical compositions of three experimental carbonated hydroxyapatite (CO3(2-) HA) substrates and investigated their effect on osteoblast differentiation. Carbonate was incorporated into the hydroxyapatite powders while phosphate and hydroxyl groups were shown to be reduced by analyzing the chemical composition of the substrate surfaces. CO3(2-) HA powders with increasing carbonate concentrations designated as C1 (3.88%), C2 (4.85%), and C3 (5.82%) were molded, pressed, and fired into 14 mm discs. We observed that calcium phosphate ratios increased monotonically with increasing carbonate content, whereas differentiation of MG63 cells decreased. CO3(2-) HA surfaces also affected factor production. Addition of carbonate caused a 70% reduction in osteoprotegerin (OPG) compared to cultures on pure HA, but the effect of carbonate was not dose-dependent. Low carbonate content reduced VEGF-A by 80%, but higher levels of carbonate reversed this effect in a concentration dependent manner, with the C3 VEFG-A levels approximately twice that of C1 levels. These observations collectively indicate that bone cells are sensitive to carbonate content in bone mineral and the effects of carbonate substitution vary with the outcome being measured. Overall, this study provides a preliminary understanding of how carbonate substitution within hydroxyapatite modulates cellular behavior. PMID:24167147

Adams, Brandy R; Mostafa, Amany; Schwartz, Zvi; Boyan, Barbara D

2014-09-01

163

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

E-print Network

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

Berry, Jeffrey Nicholas

1988-01-01

164

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

165

Direct Observation of Completely Processed Calcium Carbonate Dust Particles  

SciTech Connect

This study presents, for the first time, field evidence of complete, irreversible processing of solid calcium carbonate (calcite)-containing particles and quantitative formation of liquid calcium nitrate particles apparently as a result of heterogeneous reaction of calcium carbonate-containing mineral dust particles with gaseous nitric acid. Formation of nitrates from individual calcite and sea salt particles was followed as a function of time in aerosol samples collected at Shoresh, Israel. Morphology and compositional changes of individual particles were observed using conventional scanning electron microscopy with energy dispersive analysis of X-rays (SEM/EDX) and computer controlled SEM/EDX. Environmental scanning electron microscopy (ESEM) was utilized to determine and demonstrate the hygroscopic behavior of calcium nitrate particles found in some of the samples. Calcium nitrate particles are exceptionally hygroscopic and deliquesce even at very low relative humidity (RH) of 9 -11% which is lower than typical atmospheric environments. Transformation of non-hygroscopic dry mineral dust particles into hygroscopic wet aerosol may have substantial impacts on light scattering properties, the ability to modify clouds and heterogeneous chemistry.

Laskin, Alexander; Iedema, Martin J.; Ichkovich, Aviad; Graber, Ellen R.; Taraniuk, Ilya; Rudich, Yinon

2005-05-27

166

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

Microsoft Academic Search

The calcium carbonate budget in the ocean has become of great interest to geochemists, sedimentologists and paleoceanographers. The carbonate system represents only a small part of the global carbon cycle, but it is intimately related to atmospheric carbon dioxide. This paper discusses calcium carbonate production and accumulations in the present-day marine environment and over the past 25,000 years. The new

John D. Milliman

1993-01-01

167

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

168

Calcium supplements  

MedlinePLUS

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

169

Does aridity influence the morphology, distribution and accumulation of calcium oxalate crystals in Acacia (Leguminosae: Mimosoideae)?  

PubMed

Calcium oxalate (CaOx) crystals are a common natural feature of many plant families, including the Leguminosae. The functional role of crystals and the mechanisms that underlie their deposition remain largely unresolved. In several species, the seasonal deposition of crystals has been observed. To gain insight into the effects of rainfall on crystal formation, the morphology, distribution and accumulation of calcium oxalate crystals in phyllodes of the leguminous Acacia sect. Juliflorae (Benth.) C. Moore & Betche from four climate zones along an aridity gradient, was investigated. The shapes of crystals, which include rare Rosanoffian morphologies, were constant between species from different climate zones, implying that morphology was not affected by rainfall. The distribution and accumulation of CaOx crystals, however, did appear to be climate-related. Distribution was primarily governed by vein density, an architectural trait which has evolved in higher plants in response to increasing aridity. Furthermore, crystals were more abundant in acacias from low rainfall areas, and in phyllodes containing high concentrations of calcium, suggesting that both aridity and soil calcium levels play important roles in the precipitation of CaOx. As crystal formation appears to be calcium-induced, we propose that CaOx crystals in Acacia most likely function in bulk calcium regulation. PMID:24157700

Brown, Sharon L; Warwick, Nigel W M; Prychid, Christina J

2013-12-01

170

Biologically mediated dissolution of calcium carbonate above the chemical lysocline?  

NASA Astrophysics Data System (ADS)

We find a diverse but increasing amount of evidence to suggest considerable dissolution of calcium carbonate, perhaps as much as 60-80%, in the upper 500-1000 m of the ocean, well above the chemical lysocline. The same biological processes that promote the rapid settling of carbonate particles (i.e. ingestion, digestion and egestion by zooplankton) as well as biologically mediated processes within flocculates and aggregates may be responsible - directly or indirectly - for much of this dissolution. The significance of shallow-water dissolution of carbonate particles necessitates further research into both its validity and, if true, specific causal mechanisms.

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

1999-10-01

171

Dissolution kinetics of calcium carbonate in sea water: VI. The near-equilibrium dissolution kinetics of calcium carbonate-rich deep sea sediments  

Microsoft Academic Search

The dissolution kinetics of calcium carbonate from calcium carbonate-rich deep-sea sediments collected in the Indian, Pacific, and Atlantic Oceans were studied using a pH-stat technique in natural ocean and pore water. Sediments from different localities have different reaction orders and rate constants. The rate of dissolution per gram of calcium carbonate changes with the extent of dissolution, and different size

1978-01-01

172

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...

173

Induction of calcium phosphate on IBED-TiO x -coated carbon–carbon composite  

Microsoft Academic Search

Carbon–carbon composite has mechanical properties similar to human bone, as well as good biocompatibility, but without bioactivity. TiOx film was deposited onto carbon–carbon composite by ion beam-enhanced deposition (IBED) technique, and a porous network was formed on the TiOx film after alkali treatment. The network induced the deposition of calcium phosphate layers with different morphologies and compositions from simulated body

Tao Fu; Yong Han; Ke-Wei Xu; Jin-Yong Li; Zhong-Xiao Song

2002-01-01

174

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

175

Compaction of functionalized calcium carbonate, a porous and crystalline microparticulate material with a lamellar surface.  

PubMed

In the present study, we aimed to characterize the compressibility and compactibility of the novel pharmaceutical excipient, functionalized calcium carbonate (FCC). We studied three FCC modifications and compared the values for compressibility and compactibility with mannitol, microcrystalline cellulose (MCC), and ground calcium carbonate (CC 330) as well as mixtures of paracetamol and MCC or FCC at drug loads of 0%, 25%, 50%, 75%, and 100% (w/w). We used Heckel analysis, modified Heckel analysis, and Leuenberger analysis to characterize the compaction and compression behavior of the mixtures. Compaction analysis of FCC showed this material to markedly differ from ground calcium carbonate, exhibiting properties, i.e. plastic deformability, similar to those of MCC. This effect was attributed to the highly lamellar structure of FCC particles whose thickness is of the order of a single crystal unit cell. According to Leuenberger parameters, we concluded that FCC-based tablet formulations had mechanical properties equal or superior to those formulated with MCC. FCC tablets with high tensile strength were obtained already at low compressive pressures. Owing to these favorable properties (i.e. marked tensile strength and porosity), FCC promises to be suitable for the preparation of solid dosage forms. PMID:24631309

Stirnimann, Tanja; Atria, Susanna; Schoelkopf, Joachim; Gane, Patrick A C; Alles, Rainer; Huwyler, Jörg; Puchkov, Maxim

2014-05-15

176

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

Microsoft Academic Search

In this paper are reported experimental results on the effect of a magnetic field on the precipitation process of calcium carbonate scale from a hard water. Carbonically pure water was circulated at a constant flow rate in a magnetic field. After this treatment, calcium carbonate precipitation was induced by degassing dissolved carbonic gas. The nucleation time was identified from the

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

2006-01-01

177

Hydration of a Portland cement blended with calcium carbonate  

Microsoft Academic Search

The hydration of a commercial Portland cement blended with calcium carbonate was studied by thermal analysis. TG, DTA and DTG analyses were performed on pastes prepared with a water to cement weight ratio of 0.5, after different setting times during the first 28 days of hydration. The analyses were run from 28°C to 1000°C with a 10°C\\/min heating rate and

Jo Dweck; Pedro Mauricio Buchler; Antonio Carlos Vieira Coelho; Frank K Cartledge

2000-01-01

178

Study of Shear and Compression Waves in Shocked Calcium Carbonate  

Microsoft Academic Search

In-material transverse and longitudinal particle velocity histories were measured in Carrara marble (polycrystalline calcium carbonate) under combined compression-shear, plate impact loading to peak levels between 0.5 GPa and 5 GPa (0.8% to 11% density compression). To accurately time -correlate the shear and compression waves, a method was implemented to simultaneously measure individual particle velocity components in a single experiment. The

John Bahram Aidun

1989-01-01

179

Calcium carbonate concretions: cyclic occurrence in the hamster vagina.  

PubMed

Three crystalline forms of calcium carbonate were identified in washings of the hamster vagina. Spherical concretions of vaterite and hexagonal concretions of calcite predominate on days 3 and 4 of the 4-day estrous cycle. Dumbbell-like concretions of aragonite predominate during pregnancy and pseudopregnancy. Each polymorph is associated with an acid-insoluble matrix. Concretions disappear after ovariectomy and reappear during daily injections of estrogen and progesterone. PMID:5114824

Alleva, J J; Alleva, F R; Fry, B E; Eanes, E D

1971-11-01

180

Characterization of different allotropic forms of calcium carbonate scales on carbon steel by electrochemical impedance spectroscopy  

Microsoft Academic Search

Calcium carbonate scales with allotropic forms of aragonite, calcite and a mixture of both, were selectively induced onto carbon steel substrates in a synthetic cooling water. Electrochemical impedance spectroscopy (EIS) was successfully applied to characterize these scales. The resistance and capacitance of the high frequency loop of impedance diagrams for the aragonite and aragonite—calcite scales were related to the morphology

J. Marín-Cruz; R. Cabrera-Sierra; M. A. Pech-Canul; I. González

2004-01-01

181

Mcanismes de prcipitation de carbonate de calcium dans les biofilms photosynthtiques  

E-print Network

M�canismes de pr�cipitation de carbonate de calcium dans les biofilms photosynth�tiques Pascale carbonate de calcium dans les syst�mes benthiques est souvent associ�e aux biofilms photosynth�tiques, et, les stromatolithes et les microbialithes. Cette biocalcification modifie les flux de CO2, de calcium

Paris-Sud XI, Université de

182

Self-generated diffusioosmotic flows from calcium carbonate micropumps.  

PubMed

Calcium carbonate particles, ubiquitous in nature and found extensively in geological formations, behave as micropumps in an unsaturated aqueous solution. The mechanism causing this pumping is diffusioosmosis, which drives flows along charged surfaces. Our calcium carbonate microparticles, roughly ?10 ?m in size, self-generate ionic gradients as they dissolve in water to produce Ca(2+), HCO(3)(-), and OH(-) ions that migrate into the bulk. Because of the different diffusion coefficients of these ions, spontaneous electric fields of roughly 1-10 V/cm arise in order to maintain electroneutrality in the solution. This electric field drives the diffusiophoresis of charged tracers (both positive and negative) as well as diffusioosmotic flows along charged substrates. Here we show experimentally how the directionality and speed of the tracers can be engineered by manipulating the tracer zeta potential, the salt gradients, and the substrate zeta potential. Furthermore, because the salt gradients are self-generated, here by the dissolution of solid calcium carbonate microparticles another manipulated variable is the placement of these particles. Importantly, we find that the zeta potentials on surfaces vary with both time and location because of the adsorption or desorption of Ca(2+) ions; this change affects the flows significantly. PMID:23072458

McDermott, Joseph J; Kar, Abhishek; Daher, Majd; Klara, Steve; Wang, Gary; Sen, Ayusman; Velegol, Darrell

2012-11-01

183

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

PubMed

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

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

2004-01-01

184

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

E-print Network

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

Boutis, Gregory Steven, 1975-

2002-01-01

185

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

PubMed

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

Ren, Dongni; Feng, Qingling; Bourrat, Xavier

2013-08-01

186

Magnesium and calcium in carbonate bedrock and groundwaters, Peninsular Malaysia  

NASA Astrophysics Data System (ADS)

Groundwaters draining Kuala Lumpur Limestone, Kinta Limestone and limestones of the Setul Formation were monitored over a 1 yr period. The closeness of the mean Mg:Ca + Mg ratios of the groundwaters (12.8%) and bedrock (13.3%) indicates calcium and magnesium dissolution to be broadly congruent. Ratios < 2.5and> 35% are much less common in groundwaters than in bedrock because of: (i) heterogeneity in bedrock mineralogy within groundwater catchments; (ii) differential solubilities of calcium and magnesium in calcites, high magnesium calcites and dolomites; and (iii) preferential precipitation of calcium in secondary carbonate deposits. In groundwaters with variable discharges, Mg:Ca + Mg correlates negatively with discharge, as calcium deposition per unit volume of water diminishes at higher flows. Use of groundwater survey data to locate areas of dolomitization and make specific inferences about the mineralogy of limestone formations is discussed, and estimates of net chemical denudation rates (range, 56.6-70.9m 3/km 2/yr) are presented.

Crowther, J.

187

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

2010-11-01

188

Single particle composition measurements of artificial Calcium Carbonate aerosols  

NASA Astrophysics Data System (ADS)

Mineral dust, with an estimated total source from natural and anthropogenic emissions of up to 2800 Tg/yr, is one of the two largest contributors to total aerosol mass, with only Sea salt having a similar source strength (up to 2600 Tg/yr). The composition of dust particles varies strongly depending on the production process and, most importantly, the source location. Therefore, the composition of single dust particles can be used both to trace source regions of air masses as well as to identify chemical aging processes. Here we present results of laboratory studies on generating artificial calcium carbonate (CaCO3) particles, a model compound for carbonaceous mineral dust particles. Particles were generated by atomizing an aqueous hydrogen carbonate solution. Water was removed using a silica diffusion dryer., then the particles were processed in an oven at temperatures up to 900°C, converting the hydrogen carbonate to its anhydrous form. The resulting aerosol was analyzed using an on-line single particle laser ablation aerosol particle time-of-flight mass spectrometer (LAAPTOF). The results confirm the conversion to calcium carbonate, and validate that the produced particles indeed can be used as a model compound for carbonaceous dust aerosols.

Zorn, S. R.; Mentel, T. F.; Schwinger, T.; Croteau, P. L.; Jayne, J.; Worsnop, D. R.; Trimborn, A.

2012-12-01

189

Proteomic analysis of a rare urinary stone composed of calcium carbonate and calcium oxalate dihydrate: a case report.  

PubMed

The objective of the present study was to investigate the matrix protein of a rare urinary stone that contained calcium carbonate. A urinary stone was extracted from a 34-year-old male patient with metabolic alkalosis. After X-ray diffractometry and infrared analysis of the stone, proteomic analysis was carried out. The resulting mass spectra were evaluated with protein search software, and matrix proteins were identified. X-ray diffraction and infrared analysis confirmed that the stone contained calcium carbonate and calcium oxalate dihydrate. Of the identified 53 proteins, 24 have not been previously reported from calcium oxalate- or calcium phosphate-containing stones. The protease inhibitors and several proteins related to cell adhesion or the cytoskeleton were identified for the first time. We analyzed in detail a rare urinary stone composed of calcium carbonate and calcium oxalate dihydrate. Considering the formation of a calcium carbonate stone, the new identified proteins should play an important role on the urolithiasis process in alkaline condition. PMID:24118610

Kaneko, Kiyoko; Matsuta, Yosuke; Moriyama, Manabu; Yasuda, Makoto; Chishima, Noriharu; Yamaoka, Noriko; Fukuuchi, Tomoko; Miyazawa, Katsuhito; Suzuki, Koji

2014-03-01

190

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

NASA Astrophysics Data System (ADS)

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

Kohiruimaki, T.

2011-10-01

191

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

192

Evaluation of cellular influences caused by calcium carbonate nanoparticles.  

PubMed

The cellular effects of calcium carbonate (CaCO?) nanoparticles were evaluated. Three kinds of CaCO? nanoparticles were employed in our examinations. One of the types of CaCO? nanoparticles was highly soluble. And solubility of another type of CaCO? nanoparticle was lower. A stable CaCO? nanoparticle medium dispersion was prepared and applied to human lung carcinoma A549 cells and human keratinocyte HaCaT cells. Then, mitochondrial activity, cell membrane damage, colony formation ability, DNA injury, induction of oxidative stress, and apoptosis were evaluated. Although the influences of CaCO? nanoparticles on mitochondrial activity and cell membrane damage were small, "soluble" CaCO? nanoparticles exerted some cellular influences. Soluble CaCO? nanoparticles also induced a cell morphological change. Colony formation was inhibited by CaCO? nanoparticle exposure. In particular, soluble CaCO? nanoparticles completely inhibited colony formation. The influence on intracellular the reactive oxygen species (ROS) level was small. Soluble CaCO? nanoparticles caused an increase in C/EBP-homologous protein (CHOP) expression and the activation of caspase-3. Moreover, CaCO? exposure increased intracellular the Ca²? level and activated calpain. These results suggest that cellular the influences of CaCO? nanoparticles are mainly caused by intracellular calcium release and subsequently disrupt the effect of calcium signaling. In conclusion, there is possibility that soluble CaCO? nanoparticles induce cellular influences such as a cell morphological change. Cellular influence of CaCO? nanoparticles is caused by intracellular calcium release. If inhaled CaCO? nanoparticles have the potential to influence cellular events. However, the effect might be not severe because calcium is omnipresent element in cell. PMID:24412303

Horie, Masanori; Nishio, Keiko; Kato, Haruhisa; Endoh, Shigehisa; Fujita, Katsuhide; Nakamura, Ayako; Kinugasa, Shinichi; Hagihara, Yoshihisa; Yoshida, Yasukazu; Iwahashi, Hitoshi

2014-03-01

193

Calcium  

MedlinePLUS

... when taken with food. Some over-the-counter antacid products, such as Tums® and Rolaids®, contain calcium ... calcium excretion and thereby lower blood calcium levels. Antacids containing aluminum or magnesium increase calcium loss in ...

194

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

E-print Network

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

Boyer, Edmond

195

Crystal structure of bovine annexin VI in a calcium-bound state.  

PubMed

The crystal structure of a calcium-bound form of bovine annexin VI has been determined with X-ray diffraction data to 2.9 A by molecular replacement. Six Ca2+ ions were found, five in AB loops, one in a DE loop. Two loops (II-AB, which binds calcium, and V-AB, which does not) have conformations that differ significantly from those in calcium-free, human recombinant annexin VI. There are only small differences between the calci- and the apo-annexin VI in the rest of the molecule. Calcium by itself does not promote a major conformational change. PMID:9748523

Avila-Sakar, A J; Creutz, C E; Kretsinger, R H

1998-09-01

196

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

PubMed

Calcium supplementation is a widely recognized strategy for achieving adequate calcium intake. We designed this blinded, randomized, crossover interventional trial to compare the bioavailability of a new stable synthetic amorphous calcium carbonate (ACC) with that of crystalline calcium carbonate (CCC) using the dual stable isotope technique. The study was conducted in the Unit of Clinical Nutrition, Tel Aviv Sourasky Medical Center, Israel. The study population included 15 early postmenopausal women aged 54.9?±?2.8 (mean?±?SD) years with no history of major medical illness or metabolic bone disorder, excess calcium intake, or vitamin D deficiency. Standardized breakfast was followed by randomly provided CCC or ACC capsules containing 192?mg elemental calcium labeled with (44) Ca at intervals of at least 3 weeks. After swallowing the capsules, intravenous CaCl2 labeled with (42) Ca on was administered on each occasion. Fractional calcium absorption (FCA) of ACC and CCC was calculated from the 24-hour urine collection following calcium administration. The results indicated that FCA of ACC was doubled (±?0.96 SD) on average compared to that of CCC (p?calcium supplementation. © 2014 American Society for Bone and Mineral Research. PMID:24753014

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

2014-10-01

197

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

198

Spectral features of biogenic calcium carbonates and implications for astrobiology  

NASA Astrophysics Data System (ADS)

The ability to discriminate biogenic from abiogenic calcium carbonate (CaCO3) would be useful in the search for extant or extinct life, since CaCO3 can be produced by both biotic and abiotic processes on Earth. Bioprecipitated CaCO3 material was produced during the growth of heterotrophic microbial isolates on medium enriched with calcium acetate or calcium citrate. These biologically produced CaCO3, along with natural and synthetic non-biologically produced CaCO3 samples, were analysed by reflectance spectroscopy (0.35-2.5 ?m), Raman spectroscopy (532 and 785 nm), and laser-induced fluorescence spectroscopy (365 and 405 nm excitation). Optimal instruments for the discrimination of biogenic from abiogenic CaCO3 were determined to be reflectance spectroscopy, and laser-induced fluorescence spectroscopy. Multiple absorption features in the visible light region occurred in reflectance spectra for most biogenic CaCO3 samples, which are likely due to organic pigments. Multiple fluorescence peaks occurred in emission spectra (405 nm excitation) of biogenic CaCO3 samples, which also are best attributed to the presence of organic compounds; however, further analyses must be performed in order to better determine the cause of these features to establish criteria for confirming the origin of a given CaCO3 sample. Raman spectroscopy was not useful for discrimination since any potential Raman peaks in spectra of biogenic carbonates collected by both the 532 and 785 nm lasers were overwhelmed by fluorescence. However, this also suggests that biogenic carbonates may be identified by the presence of this organic-associated fluorescence. No reliable spectroscopic differences in terms of parameters such as positions or widths of carbonate-associated absorption bands were found between the biogenic and abiogenic carbonate samples. These results indicate that the presence or absence of organic matter intimately associated with carbonate minerals is the only potentially useful spectral discriminator for the techniques that were examined, and that multiple spectroscopic techniques are capable of detecting the presence of associated organic materials. However, the presence or absence of intimately associated organic matter is not, in itself, an indicator of biogenicity.

Berg, B. L.; Ronholm, J.; Applin, D. M.; Mann, P.; Izawa, M.; Cloutis, E. A.; Whyte, L. G.

2014-09-01

199

Kinetic fractionation of carbon-13 during calcium carbonate precipitation  

Microsoft Academic Search

Kinetic isotope fractionation of 13 C during precipitation of CaCO 3 under open system conditions has been investigated. The isotope enrichment factor HCO 3 - - CaCO 3 varies between -0.35 ± 0.23 and -3.37 ± 0.36%. at 25°C depending on the rate of precipitation and mineralogy, the enrichment of 13 C in the solid carbonate phase decreasing with increasing

Jeffrey V. Turner

1982-01-01

200

Morphological and phase changes in calcium oxalate crystals grown in the presence of sodium diisooctyl sulfosuccinate  

Microsoft Academic Search

Calcium oxalate was crystallized in the presence of the anionic surfactant dioctyl sulphosuccinate, AOT, and the phase composition of the precipitates (by X-ray diffraction powder patterns and thermal analysis) and their crystal growth morphology (by scanning electron microscopy and electron diffraction) were determined. In the control systems and in the presence of low concentrations of AOT (below the critical micellar

L. Tunik; L. Addadi; N. Garti; H. Füredi-Milhofer

1996-01-01

201

Non-aqueous formation of the calcium carbonate polymorph vaterite: astrophysical implications  

E-print Network

We study the formation of calcium carbonate, through the solid-gas interaction of amorphous Ca-silicate with gaseous CO2, at elevated pressures, and link this to the possible presence of calcium carbonate in a number of circumstellar and planetary environments. We use in-situ synchrotron X-Ray powder diffraction to obtain detailed structural data pertaining to the formation of the crystalline calcium carbonate phase vaterite and its evolution with temperature. We found that the metastable calcium carbonate phase vaterite was formed alongside calcite, at elevated CO2 pressure, at room temperature and subsequently remained stable over a large range of temperature and pressure. We report the formation of the calcium carbonate mineral vaterite whilst attempting to simulate carbonate dust grain formation in astrophysical environments. This suggests that vaterite could be a mineral component of carbonate dust and also presents a possible method of formation for vaterite and its polymorphs on planetary surfaces.

Day, Sarah J; Parker, Julia E; Evans, Aneurin

2013-01-01

202

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

203

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

204

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

205

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.

2002-07-09

206

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

207

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.

2001-12-15

208

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.

2002-12-15

209

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

2005-01-24

210

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

211

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

212

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

213

Carbon nanopipettes characterize calcium release pathways in breast cancer cells  

NASA Astrophysics Data System (ADS)

Carbon-based nanoprobes are attractive for minimally invasive cell interrogation but their application in cell physiology has thus far been limited. We have developed carbon nanopipettes (CNPs) with nanoscopic tips and used them to inject calcium-mobilizing messengers into cells without compromising cell viability. We identify pathways sensitive to cyclic adenosine diphosphate ribose (cADPr) and nicotinic acid adenine dinucleotide phosphate (NAADP) in breast carcinoma cells. Our findings demonstrate the superior utility of CNPs for intracellular delivery of impermeant molecules and, more generally, for cell physiology studies. The CNPs do not appear to cause any lasting damage to cells. Their advantages over commonly used glass pipettes include smaller size, breakage and clogging resistance, and potential for multifunctionality such as in concurrent injection and electrical measurements.

Schrlau, Michael G.; Brailoiu, Eugen; Patel, Sandip; Gogotsi, Yury; Dun, Nae J.; Bau, Haim H.

2008-08-01

214

Optical properties of carbon nanofiber photonic crystals  

NASA Astrophysics Data System (ADS)

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

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

2010-11-01

215

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

216

Experimental investigation of factors controlling the calcium carbonate ion activity product of shallow water carbonate-rich sediments  

E-print Network

EXPERIMENTAL INVESTIGATION OF FACTORS CONTROLLING THE CALCIUM CARBONATE ION ACTIVITY PRODUCT OF SHALLOW WATER CARBONATE-RICH SEDIMENTS A Thesis by LAWRENCE DOUGLAS BERNSTEIN Submitted to the Graduate College of Texas A&M University... in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1983 Major Subject: Oceanography EXPERIMENTAL INVESTIGATION OF FACTORS CONTROLLING THE CALCIUM CARBONATE ION ACTIVITY PRODUCT OF SHALLOW WATER CARBONATE...

Bernstein, Lawrence Douglas

2012-06-07

217

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

218

A mineralogical characterization of biogenic calcium carbonates precipitated by heterotrophic bacteria isolated from cryophilic polar regions.  

PubMed

Precipitation of calcium carbonate (CaCO3(s) ) can be driven by microbial activity. Here, a systematic approach is used to identify the morphological and mineralogical characteristics of CaCO3(s) precipitated during the heterotrophic growth of micro-organisms isolated from polar environments. Focus was placed on establishing mineralogical features that are common in bioliths formed during heterotrophic activity, while in parallel identifying features that are specific to bioliths precipitated by certain microbial phylotypes. Twenty microbial isolates that precipitated macroscopic CaCO3(s) when grown on B4 media supplemented with calcium acetate or calcium citrate were identified. A multimethod approach, including scanning electron microscopy, high-resolution transmission electron microscopy, and micro-X-ray diffraction (?-XRD), was used to characterize CaCO3(s) precipitates. Scanning and transmission electron microscopy showed that complete CaCO3(s) crystal encrustation of Arthrobacter sp. cells was common, while encrustation of Rhodococcus sp. cells did not occur. Several euhedral and anhedral mineral formations including disphenoid-like epitaxial plates, rhomboid-like aggregates with epitaxial rhombs, and spherulite aggregates were observed. While phylotype could not be linked to specific mineral formations, isolates tended to precipitate either euhedral or anhedral minerals, but not both. Three anhydrous CaCO3(s) polymorphs (calcite, aragonite, and vaterite) were identified by ?-XRD, and calcite and aragonite were also identified based on TEM lattice-fringe d value measurements. The presence of certain polymorphs was not indicative of biogenic origin, although several mineralogical features such as crystal-encrusted bacterial cells, or casts of bacterial cells embedded in mesocrystals are an indication of biogenic origin. In addition, some features such as the formation of vaterite and bacterial entombment appear to be linked to certain phylotypes. Identifying phylotypes consistent with certain mineralogical features is the first step toward discovering a link between these crystal features and the precise underlying molecular biology of the organism precipitating them. PMID:25256888

Ronholm, J; Schumann, D; Sapers, H M; Izawa, M; Applin, D; Berg, B; Mann, P; Vali, H; Flemming, R L; Cloutis, E A; Whyte, L G

2014-11-01

219

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

Microsoft Academic Search

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

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

1994-01-01

220

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

221

Uptake of chloride and carbonate ions by calcium monosulfoaluminate hydrate  

SciTech Connect

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

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

2012-08-15

222

Growth of the calcium carbonate polymorph vaterite in mixtures of water and ethylene glycol at conditions of gas processing  

NASA Astrophysics Data System (ADS)

Long subsea tie-ins for transportation of moist gas and condensate require corrosion and hydrate control. The combination of alkalinity for corrosion mitigation and monoethylene glycol (MEG) for hydrate inhibition strongly affects the tolerance for produced formation water. The elevated alkalinity downstream of the injection point increases the risk of carbonate formation. Calcium carbonate is the most common precipitate at such conditions. Our previous findings (Flaten et al., 2009) [1] show that MEG governs calcium carbonate precipitation and promotes formation of the metastable polymorph vaterite. This paper describes crystal growth of vaterite in mixed MEG water solvent with 0-70 wt% MEG at temperatures of 40 and 70 °C in solutions with high calcium to carbonate ratios representative of the production conditions. Results of some experiments in solutions with stoichiometric amounts of the reactants are included for comparison. The growth rate of vaterite can be described by second-order kinetics in most of the investigated supersaturation range. The growth order is lower at high MEG contents and high calcium concentrations when the carbonate activity is reduced in order to maintain comparable supersaturation values. It is then probable that the low carbonate activity makes the reaction diffusion limited. MEG reduces the growth rate constant of vaterite when the reaction is second order. Increasing the MEG concentration from 0 to 50 wt%, decreases the growth rate constant kr from 1.9 to 0.7 nm/s at 40 °C and from 2.6 to 1.2 nm/s at 70 °C. The growth reduction can be explained by a change of either de-hydration or diffusion rate along the surface when the ions are incorporated into the crystal lattice. Further investigations into which of the two mechanisms that is rate determining is outside the scope of this work.

Flaten, Ellen Marie; Seiersten, Marion; Andreassen, Jens-Petter

2010-03-01

223

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

PubMed

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 dual role in modifying crystal aggregation: at high pH and low ionic strength (IS). THP is a powerful crystal aggregation inhibitor. Upon lowering pH and raising IS, THP viscosity increases, leading to reduced crystal aggregation inhibition. In the presence of additional calcium ions, some THPs even become strong promoters of crystal aggregation. This phenomenon seems to be more pronounced in THPs isolated from recurrent calcium stone formers whose proteins exhibit an abnormally high tendency of polymerization. Recent studies suggest an inherited molecular abnormality of THP among some severe recurrent calcium stone formers. PMID:1736492

Hess, B

1992-01-01

224

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

PubMed

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 in the genesis of kidney stones. We have tested the validity of this hypothesis by studying both the binding of monohydrate and dihydrate crystals to renal tubule cells and the effect of macromolecular urinary solutes on crystal structure. Renal tubule cells grown in culture bound 50% more CaOx monohydrate than dihydrate crystals of comparable size. The effects of macromolecules on the spontaneous nucleation of CaOx were examined in HEPES-buffered saline solutions containing Ca2+ and C2O4(2-) at physiologic concentrations and supersaturation. Many naturally occurring macromolecules known to be inhibitors of crystallization, specifically osteopontin, nephrocalcin and urinary prothrombin fragment 1, were found to favor the formation of calcium oxalate dihydrate in this in vitro system, while other polymers did not affect CaOx crystal structure. Thus, the natural defense against nephrolithiasis may include impeding crystal attachment by an effect of macromolecular inhibitors on the preferred CaOx crystal structure that forms in urine. PMID:9551403

Wesson, J A; Worcester, E M; Wiessner, J H; Mandel, N S; Kleinman, J G

1998-04-01

225

Characterization of a biodegradable coralline hydroxyapatite/calcium carbonate composite and its clinical implementation.  

PubMed

A partially converted, biodegradable coralline hydroxyapatite/calcium carbonate (CHACC) composite comprising a coral calcium carbonate scaffold enveloped by a thin layer of hydroxyapatite was used in the present study. The CHACC was characterized using powder x-ray diffraction, scanning electron microscopy and energy dispersive x-ray spectroscopy. The ability of the CHACC to promote conductive osteogenesis was assessed in vitro using human mesenchymal stem cells (hMSCs) and in vivo using an immunodeficient mouse model. The clinical performance of CHACC as a bone substitute to fill voids caused by excision of bone tumours was also observed in 16 patients. The CHACC was found to consist of two overlapping layers both morphologically and chemically. Hydroxyapatite formed a thin layer of nanocrystals on the surface and a thick rough crystal layer of around 30 µm in thickness enveloping the rock-like core calcium carbonate exoskeletal architecture. hMSCs cultured on CHACC in osteogenic medium demonstrated significant osteogenic differentiation. After subcutaneous implantation of CHACC incorporating osteogenically differentiated hMSCs and an anti-resorptive agent, risedronate, into an immunodeficient mouse model, bone formation was observed on the surface of the implants. Clinical application of CHACC alone in 16 patients for bone augmentation after tumour removal showed that after implantation, visible callus formation was observed at one month and clinical bone healing achieved at four months. The majority of the implanted CHACC was degraded in 18-24 months. In conclusion, CHACC appears to be an excellent biodegradable bone graft material. It biointegrates with the host, is osteoconductive, biodegradable and can be an attractive alternative to autogenous grafts. PMID:24288015

Fu, Kun; Xu, Qingguo; Czernuszka, Jan; Triffitt, James T; Xia, Zhidao

2013-12-01

226

Image-based Modeling of Biofilm-induced Calcium Carbonate Precipitation  

NASA Astrophysics Data System (ADS)

Pore scale biological processes in the subsurface environment are important to understand in relation to many engineering applications including environmental contaminant remediation, geologic carbon sequestration, and petroleum production. Specifically, biofilm induced calcium carbonate precipitation has been identified as an attractive option to reduce permeability in a lasting way in the subsurface. This technology may be able to replace typical cement-based grouting in some circumstances; however, pore-scale processes must be better understood for it to be applied in a controlled manor. The work presented will focus on efforts to observe biofilm growth and ureolysis-induced mineral precipitation in micro-fabricated flow cells combined with finite element modelling as a tool to predict local chemical gradients of interest (see figure). We have been able to observe this phenomenon over time using a novel model organism that is able to hydrolyse urea and express a fluorescent protein allowing for non-invasive observation over time with confocal microscopy. The results of this study show the likely existence of a wide range of local saturation indices even in a small (1 cm length scale) experimental system. Interestingly, the locations of high predicted index do not correspond to the locations of higher precipitation density, highlighting the need for further understanding. Figure 1 - A micro-fabricated flow cell containing biofilm-induced calcium carbonate precipitation. (A) Experimental results: Active biofilm is in green and dark circles are calcium carbonate crystals. Note the channeling behavior in the top of the image, leaving a large hydraulically inactive area in the biofilm mass. (B) Finite element model: The prediction of relative saturation of calcium carbonate (as calcite). Fluid enters the system at a low saturation state (blue) but areas of high supersaturation (red) are predicted within the hydraulically inactive area in the biofilm. If only effluent saturation was measured, precipitation may not even be predicted but we see local, pore-scale behavior dictating system behavior in this case. The flow cell is 1 cm in length and the porous media elements are 100 ?m.

Connolly, J. M.; Rothman, A.; Jackson, B.; Klapper, I.; Cunningham, A. B.; Gerlach, R.

2013-12-01

227

Calcium carbonate production response to future ocean warming and acidification  

NASA Astrophysics Data System (ADS)

Anthropogenic carbon dioxide (CO2) emissions are acidifying the ocean, affecting calcification rates in pelagic organisms, and thereby modifying the oceanic carbon and alkalinity cycles. However, the responses of pelagic calcifying organisms to acidification vary widely between species, contributing uncertainty to predictions of atmospheric CO2 and the resulting climate change. At the same time, ocean warming caused by rising CO2 is expected to drive increased growth rates of all pelagic organisms, including calcifiers. It thus remains unclear whether anthropogenic CO2 emissions will ultimately increase or decrease pelagic calcification rates. Here, we assess the importance of this uncertainty by introducing a dependence of calcium carbonate (CaCO3) production on calcite saturation state (?CaCO3) in an intermediate complexity coupled carbon-climate model. In a series of model simulations, we examine the impact of several variants of this dependence on global ocean carbon cycling between 1800 and 3500 under two different CO2 emissions scenarios. Introducing a calcification-saturation state dependence has a significant effect on the vertical and surface horizontal alkalinity gradients, as well as on the removal of alkalinity from the ocean through CaCO3 burial. These changes result in an additional oceanic uptake of carbon when calcification depends on ?CaCO3 (of up to 270 Pg C), compared to the case where calcification does not depend on acidification. In turn, this response causes a reduction of global surface air temperature of up to 0.4 °C in year 3500. Different versions of the model produced varying results, and narrowing this range of uncertainty will require better understanding of both temperature and acidification effects on pelagic calcifiers. Nevertheless, our results suggest that alkalinity observations can be used to constrain model results, and may not be consistent with the model versions that simulated stronger responses of CaCO3 production to changing saturation state.

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

2012-06-01

228

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. PMID:24688401

Park, Kyungho; Jun, Sangju; Kim, Daehyeon

2014-01-01

229

Magnetic treatment of calcium carbonate scale—effect of pH control  

Microsoft Academic Search

Results from a preliminary study into the effects of magnetic treatment on calcium carbonate formation are presented. A test rig was constructed to investigate the effect of orthogonally applied magnetic fields on solutions of calcium carbonate, with specific reference to changes in scale deposits formed. Results are compared with those of a reference system, identical in every way other than

Simon A. Parsons; Bao-Lung Wang; Simon J. Judd; Tom Stephenson

1997-01-01

230

Soluble organic additive effects on stress development during drying of calcium carbonate suspensions  

Microsoft Academic Search

The effect of polymer, plasticizer, and surfactant additives on stress development during drying of calcium carbonate particulate coatings was studied using a controlled-environment apparatus that simultaneously monitors drying stress, weight loss, and relative humidity. We found that the calcium carbonate coatings display a drying stress evolution typical of granular films, which is characterized by a sharp capillary-induced stress rise followed

Pär Wedin; Jennifer A. Lewis; Lennart Bergström

2005-01-01

231

Habit modification of calcium carbonate in the presence of malic acid  

SciTech Connect

The ability of malic acid to control calcium carbonate morphology has been investigated by aging calcium chloride solution in the presence of urea in a 90 deg. C bath. Malic acid favors the formation of calcite. A transition from single block to aggregate with special morphology occurs upon increasing malic acid concentration. The morphological development of CaCO{sub 3} crystal obviously depends on the starting pH. CaCO{sub 3} crystal grows from spindle seed to dumbbell in the pH regime from 7 to 11; while it evolves from spindle seed, through peanut, to sphere at pH=11.5. Both dumbbell and sphere consist of rods that are elongated along c-axis and capped with three smooth, well-defined rhombic {l_brace}1 0 4{r_brace} faces. A tentative growth mechanism is proposed based on the fractal model suggested by R. Kniep and S. Busch [Angew. Chem. Int. Ed. Engl. 35 (1996) 2624]. - Graphical abstract: Dumbbell-like CaCO{sub 3} particles obtained in the presence of malic acid.

Mao Zhaofeng [Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Huang Jianhua [Department of Chemistry, Zhejiang Sci-Tech University, Hangzhou 310018 (China)], E-mail: jhhuang@zstu.edu.cn

2007-02-15

232

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

SciTech Connect

Whole milk, chocolate milk, yogurt, imitation milk (prepared from dairy and nondairy products), cheese, and calcium carbonate were labeled with /sup 45/Ca and administered as a series of test meals to 10 healthy postmenopausal women. Carrier Ca content of the test meals was held constant at 250 mg and subjects fasted before each meal. The absorbability of Ca from the six sources was compared by measuring fractional absorption by the double isotope method. The mean absorption values for all six sources were tightly clustered between 21 and 26% and none was significantly different from the others using one-way analysis of variance. We conclude that none of the sources was significantly superior or inferior to the others.

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

1988-01-01

233

Crystallochemical characterization of calcium oxalate crystals isolated from seed coats of Phaseolus vulgaris and leaves of Vitis vinifera.  

PubMed

Calcium oxalate crystals are a major biomineralization product in higher plants. Their biological function and use are not well understood. In this work, we focus on the isolation and crystallochemical characterization of calcium oxalate crystals from seed coats of Phaseolus vulgaris (prisms) and leaves of Vitis vinifera (raphides and druses) using ultrastructural methods. A proposal based on crystal growth theory was used for explaining the existence of different morphologies shown by these crystals grown inside specialized cells in plants. PMID:12749080

Jáuregui-Zúñiga, David; Reyes-Grajeda, Juan Pablo; Sepúlveda-Sánchez, José David; Whitaker, John R; Moreno, Abel

2003-03-01

234

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

235

Influence of magnetic water treatment on the calcium carbonate phase formation and the electrochemical corrosion behavior of carbon steel  

Microsoft Academic Search

A study of the influence of magnetic water treatment on the calcium carbonate phase formation and the electrochemical corrosion behavior of carbon steel was carried out. The water was exposed to a magnetic field of 1T with a speed of flow through the magnet of 0.77m\\/s (1.56ml\\/s). The observations demonstrated that the calcite is the main form of calcium carbonate,

M. E Botello-Zubiate; A Alvarez; A Mart??nez-Villafañe; F Almeraya-Calderon; J. A Matutes-Aquino

2004-01-01

236

Fabrication of calcium lanthanum sulfide ceramic by carbonate coprecipitating method  

SciTech Connect

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

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

1995-03-01

237

Calcium carbonate obstructive urolithiasis in a red kangaroo (Macropus rufus).  

PubMed

A 6-yr-old male red kangaroo (Macropus rufus) presented for a history of inappetance, abnormal behavior, and unconfirmed elimination for 6 hr prior to presentation. Based on abdominal ultrasound, abdominocentesis, and cystocentesis, a presumptive diagnosis of urinary tract obstruction with uroabdomen and hydronephrosis was reached. Abdominal radiographs did not assist in reaching an antemortem diagnosis. Postmortem examination confirmed a urinary bladder rupture secondary to urethral obstruction by a single urethrolith. Bilateral hydronephrosis and hydroureter were identified and determined to be a result of bilateral ureteroliths. Urolith analysis revealed a composition of 100% calcium carbonate. A dietary analysis was performed, implicating an increased Ca:P ratio from a food preparation miscommunication as a contributing factor. Appropriate husbandry changes were made, and mob surveillance procedures were performed, which resolved the urolithiasis risk for the remaining five animals. PMID:23505728

Lindemann, Dana M; Gamble, Kathryn C; Corner, Sarah

2013-03-01

238

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

Microsoft Academic Search

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

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

1992-01-01

239

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

PubMed

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

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

2014-08-01

240

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

241

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

PubMed

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

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

2002-02-01

242

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

243

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

E-print Network

Abstract No Hung0356 A P-XANES Study of Phosphate Sorption to Gibbsite and Calcium Carbonate S solution and freeze-dried. Samples of phosphate sorbed to calcium carbonate were prepared in a similar sorbed to calcium carbonate at pH 8 (Fig. 1) show 2.14 2.16 2.18 2.20 normalizedabsorbance

Sparks, Donald L.

244

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

E-print Network

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

Tas, A. Cuneyt

245

Effect of mineralogy, salinity, and temperature on Li/Ca and Li isotope composition of calcium carbonate  

E-print Network

during growth of calcium carbonate. This study improves such understanding with two sets of new). This suggests little biological control during Li incorporation into biogenic calcium carbonates. The difference­15 www.elsevier.com/locate/chemgeo #12;1. Introduction Natural calcium carbonate may provide an archive

Henderson, Gideon

246

Design of a continuous process setup for precipitated calcium carbonate production from steel converter slag.  

PubMed

A mineral carbonation process "slag2PCC" for carbon capture, utilization, and storage is discussed. Ca is extracted from steel slag by an ammonium salt solvent and carbonated with gaseous CO2 after the separation of the residual slag. The solvent is reused after regeneration. The effects of slag properties such as the content of free lime, fractions of Ca, Si, Fe, and V, particle size, and slag storage on the Ca extraction efficiency are studied. Small particles with a high free-lime content and minor fractions of Si and V are the most suitable. To limit the amount of impurities in the process, the slag-to-liquid ratio should remain below a certain value, which depends on the slag composition. Also, the design of a continuous test setup (total volume ?75?L) is described, which enables quick process variations needed to adapt the system to the varying slag quality. Different precipitated calcium carbonate crystals (calcite and vaterite) are generated in different parts of the setup. PMID:24578147

Mattila, Hannu-Petteri; Zevenhoven, Ron

2014-03-01

247

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

PubMed

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

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

2013-08-01

248

Carbon dioxide enhances fragility of ice crystals  

NASA Astrophysics Data System (ADS)

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

Qin, Zhao; Buehler, Markus J.

2012-11-01

249

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

250

Controlled synthesis of crystalline calcium carbonate aggregates with unusual morphologies involving the phase transformation from amorphous calcium carbonate  

SciTech Connect

Peanut-shaped CaCO{sub 3} aggregates, featured of two dandelion-like heads built up from rod-like subunits, have been synthesized via a facile precipitation reaction between Na{sub 2}CO{sub 3} and CaCl{sub 2} at ambient temperature in the presence of magnesium ions and ethanol solvent. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and inductively coupled plasma atomic emission spectrometry (ICP-AES). The results show that a high magnesium concentration and ethanol solvent are necessary for the formation of the unusual peanut-like aggregates. In addition, a multistep phase transformation process from amorphous calcium carbonate (ACC) to a mixture of ACC and calcite and ultimately to calcite and aragonite was observed in the formation process of the unusual structures. A possible mechanism for the formation of the unusual peanut-shape aggregates has been proposed and discussed.

Tang Hua [State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Wuhan 430070 (China); Yu Jiaguo [State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Wuhan 430070 (China)], E-mail: jiaguoyu@yahoo.com; Zhao Xiufeng [State Key Laboratory of Advanced Technology for Material Synthesis and Processing, Wuhan University of Technology, Luoshi Road 122, Wuhan 430070 (China)

2009-04-02

251

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

252

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

Microsoft Academic Search

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

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

2010-01-01

253

Conversion of calcium sulphide to calcium carbonate during the process of recovery of elemental sulphur from gypsum waste.  

PubMed

The production of elemental sulphur and calcium carbonate (CaCO3) from gypsum waste can be achieved by thermally reducing the waste into calcium sulphide (CaS), which is then subjected to a direct aqueous carbonation step for the generation of hydrogen sulphide (H2S) and CaCO3. H2S can subsequently be converted to elemental sulphur via the commercially available chemical catalytic Claus process. This study investigated the carbonation of CaS by examining both the solution chemistry of the process and the properties of the formed carbonated product. CaS was successfully converted into CaCO3; however, the reaction yielded low-grade carbonate products (i.e. <90mass% as CaCO3) which comprised a mixture of two CaCO3 polymorphs (calcite and vaterite), as well as trace minerals originating from the starting material. These products could replace the Sappi Enstra CaCO3 (69mass% CaCO3), a by-product from the paper industry which is used in many full-scale AMD neutralisation plants but is becoming insufficient. The insight gained is now also being used to develop and optimize an indirect aqueous CaS carbonation process for the production of high-grade CaCO3 (i.e. >99mass% as CaCO3) or precipitated calcium carbonate (PCC). PMID:25128917

de Beer, M; Maree, J P; Liebenberg, L; Doucet, F J

2014-11-01

254

How calcium from calcium carbonate and milk benefit peptic ulcer patients  

Microsoft Academic Search

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

X. Wang

2000-01-01

255

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

E-print Network

The hydrothermal carbonation of calcium hydroxide (Ca(OH)2) at high pressure of CO2 (initial PCO2 1/4 55 bar) and moderate to high temperature (30 and 90 1C) was used to synthesize fine particles of calcite. This method allows a high carbonation efficiency (about 95% of Ca(OH)2-CaCO3 conversion), a significant production rate (48 kg/m3 h) and high purity of product (about 96%). However, the various initial physicochemical conditions have a strong influence on the crystal size and surface area of the synthesized calcite crystals. The present study is focused on the estimation of the textural properties of synthesized calcite (morphology, specific surface area, average particle size, particle size distribution and particle size evolution with reaction time), using Rietveld refinements of X-ray diffraction (XRD) spectra, Brunauer-Emmett-Teller (BET) measurements, and scanning electron microscope (SEM) and transmission electron microscope (TEM) observations. This study demonstrate that the pressure, the temperatu...

Montes-Hernandez, German; Charlet, L; Tisserand, Delphine; Renard, F

2008-01-01

256

The role of Tamm-Horsfall glycoprotein and Nephrocalcin in calcium oxalate monohydrate crystallization processes.  

PubMed

Theoretical considerations as well as clinical observations suggest that the aggregation of nucleated crystals is the most dangerous step in the formation of calcium oxalate (CaOx) renal stones. The effects of 2 major urinary glycoproteins, Tamm-Horsfall glycoprotein (THP) and Nephrocalcin (NC), on calcium oxalate monohydrate (COM) crystal aggregation in vitro are studied. At low ionic strength (IS) and high pH (within urinary limits), THP is a powerful crystal aggregation inhibitor (90% inhibition at 40 mg/l). Decreasing pH to 5.7 and raising IS to 0.21 increases TRP viscosity, thereby lowering THP crystal aggregation inhibition. Upon addition of calcium (5 mmol/l), some THPs are no more soluble and promote crystal aggregation (up to 70%). In the presence of citrate (5 mmol/l), which is only slightly inhibitory (14%), the promoting effect of THP is reversed into aggregation inhibition (up to 55%). There is evidence for a molecular abnormality in THPs from severe recurrent CaOx stone formers, since they exhibit increased polymerization and reduced solubility. The 14 kD (kilodalton), Gla-containing glycoprotein NC also strongly inhibits crystal aggregation. However, NC isolated from urines of recurrent CaOx stone formers and from CaOx renal stones are 10 times less inhibitory. Both are structurally abnormal in that they lack Gla and are less amphophilic. PMID:1808706

Hess, B

1991-09-01

257

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

SciTech Connect

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

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

1996-10-01

258

Calcium pyrophosphate dihydrate crystal deposition of multiple lumbar facet joints: a case report.  

PubMed

Pseudogout of the lumbar facet joints is rare. We report on a 69-year-old woman with 2-level symptomatic synovial cysts of the facet joints caused by calcium pyrophosphate dihydrate crystal deposition. She underwent surgical decompression for sciatica and low back pain. At one-year follow-up, she had recovered completely. PMID:22933691

Namazie, Mohamed Ridzwan bin Mohamed; Fosbender, Murray R

2012-08-01

259

New and unusual forms of calcium oxalate raphide crystals in the plant kingdom.  

PubMed

Calcium oxalate crystals in higher plants occur in five major forms namely raphides, styloids, prisms, druses and crystal sand. The form, shape and occurrence of calcium oxalate crystals in plants are species- and tissue-specific, hence the presence or absence of a particular type of crystal can be used as a taxonomic character. So far, four different types of needle-like raphide crystals have been reported in plants. The present work describes two new and unusual forms of raphide crystals from the tubers of Dioscorea polystachya-six-sided needles with pointed ends (Type V) and four-sided needles with beveled ends (Type VI). Both of these new types of needles are distinct from the other four types by each having a surrounding membrane that envelopes a bundle of 10-20 closely packed thin crystalline sheets. The previously known four types of needles have solid or homogenous crystalline material, surrounded by a membrane or lamellate sheath called a crystal chamber. Only the Type VI crystals have beveled ends and the needles of the other five types have pointed ends. PMID:25139563

Raman, Vijayasankar; Horner, Harry T; Khan, Ikhlas A

2014-11-01

260

Beam Foil Studies of Calcium II and Carbon I  

NASA Astrophysics Data System (ADS)

Because once ionized calcium and neutral and few times ionized carbon are of fundamental astrophysical interest, these systems have been studied using beam-foil methods. The beam-foil technique consists of a fast ion beam passing through a very thin foil and becoming electronically excited. As the excited ions de-excite they emit light that is analyzed by a spectrometer. Lifetimes in C I-C IV, and Ca II were measured using this method. In neutral carbon, lifetimes for the 1s^22s2p^2 3s ^5P_{1,2,3 }<=vels have been measured for the first time, and the lifetimes indicate differential mixing of these three levels with auto-ionizing triplets. In neutral carbon, the first beam-foil lifetime measurements are reported for five levels and the obtained values indicate significantly shorter lifetimes than did the previous arc emission measurements. In C II the first ANDC cascade corrected analysis for the lifetime of the 2s2p^2 ^2D levels are reported. The lifetimes reported here supercede the previous arc measurements for the 4f and the 6s in Ca II and are in fair agreement with theory. By analysing the cascade contribution to the decay curves of the 5s, 4d, and 4p levels an improved lifetime of the 5p was obtained. Six spectral lines have been identified as possible transitions in the Ca II doubly excited system. A number of problems including line broadening and subsequent blending, and cascade repopulations of levels were managed to make the measurements reported. These problems and some of the solutions to these problems are discussed in detail.

Haar, Roger Richard

261

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

262

Poly (vinylsulfonic acid) assisted synthesis of aqueous solution stable vaterite calcium carbonate nanoparticles.  

PubMed

Calcium carbonate nanoparticles of the vaterite polymorph were synthesized by combining CaCl2 and Na2CO3 in the presence of poly (vinylsulfonic acid) (PVSA). By studying the important experimental parameters we found that controlling PVSA concentration, reaction temperature, and order of reagent addition the particle size, monodispersity, and surface charge can be controlled. By increasing PVSA concentration or by decreasing temperature CCNPs with an average size from ?150 to 500 nm could be produced. We believe the incorporation of PVSA into the reaction plays a dual role to (1) slow down the nucleation rate by sequestering calcium and to (2) stabilize the resulting CCNPs as the vaterite polymorph, preventing surface calcification or aggregation into microparticles. The obtained vaterite nanoparticles were found to maintain their crystal structure and surface charge after storage in aqueous buffer for at least 5 months. The aqueous stable vaterite nanoparticles could be a useful platform for the encapsulation of a large variety of biomolecules for drug delivery or as a sacrificial template toward capsule formation for biosensor applications. PMID:24461857

Nagaraja, Ashvin T; Pradhan, Sulolit; McShane, Michael J

2014-03-15

263

Distribution of calcium carbonate in surface sediments of the Atlantic Ocean  

Microsoft Academic Search

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

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

1976-01-01

264

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

265

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

USGS Publications Warehouse

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

Kramer, H.

1957-01-01

266

A Systematic Examination of the Morphogenesis of Calcium Carbonate in the Presence of a Double-Hydrophilic Block Copolymer  

E-print Network

A Systematic Examination of the Morphogenesis of Calcium Carbonate in the Presence of a Double ´ block co- polymers ´ calcium ´ calcium carbo- nate ´ colloids ´ morphogenesis Introduction The synthesis synthesis of inorganic materials with complex form.[1] One of the most intensely examined systems is calcium

Qi, Limin

267

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

E-print Network

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

Medeiros, Jordan-Ryan J. I. K

2007-01-01

268

Removal of carbon dioxide by reactive crystallization in a scrubber—kinetics of barium carbonate crystals  

Microsoft Academic Search

A bubble column scrubber was utilized to remove simulated CO2 waste gas under a constant pH value. Using barium chloride solution as an absorbent reacting with CO2-gas in the scrubber under an alkaline solution condition, precipitates of barium carbonate were formed during the operation. Measured crystal size distributions at a given time were used to calculate the growth rate of

Pao-Chi Chen; K. L. Kou; H. K. Tai; S. L. Jin; C. L. Lye; C. Y. Lin

2002-01-01

269

Diversity and distribution of idioblasts producing calcium oxalate crystals in Dieffenbachia seguine (Araceae).  

PubMed

Although cells that synthesize crystals are known throughout the plant kingdom, their functional significance is still unknown. Mechanical support, mineral balance, waste sequestration, and protection against herbivores have all been proposed as crystal functions. To seek clues to their role(s), I systematically examined all organs except fruit of Dieffenbachia seguine (Araceae) for crystals. Crystals were found in nearly every organ. Raphides (long, slim, pointed crystals) were most common, but druses (crystal aggregates) and prisms were also found. Raphides varied in size by a factor of 10 and also in organization from tightly bundled to loosely organized. Biforines, a type of cell capable of expelling raphides, or biforine-like cells, were found in nearly all organs, but especially in leaves, spathes, and anthers. Different organs had different crystal complements, and characteristic crystals were found at specific locations, such as among pollen, along the undersides of leaf veins, and at root branch points. All crystals appeared to be composed of calcium oxalate, based on acid solubility. Possible roles of the crystals are discussed in light of these findings. PMID:21628273

Coté, Gary G

2009-07-01

270

Powder XRD and dielectric studies of gel grown calcium pyrophosphate crystals  

NASA Astrophysics Data System (ADS)

Formation of calcium pyrophosphate dihydrate (CPPD) crystals in soft tissues such as cartilage, meniscus and synovial tissue leads to CPPD deposition diseases. The appearance of these crystals in the synovial fluid can give rise to an acute arthritic attack with pain and inflammation of the joints, a condition called pseudo-gout. The growth of CPP crystals has been carried out, in the present study, using the single diffusion gel growth technique, which can broadly mimic in vitro the condition in soft tissues. The crystals were characterized by different techniques. The FTIR study revealed the presence of various functional groups. Powder XRD study was also carried out to verify the crystal structure. The dielectric study was carried out at room temperature by applying field of different frequency from 500 Hz to 1 MHz. The dielectric constant, dielectric loss and a.c. resistivity decreased as frequency increased, whereas the a.c. conductivity increased as frequency increased.

Parekh, Bharat; Parikh, Ketan; Joshi, Mihir

2013-06-01

271

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

SciTech Connect

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

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

2011-05-15

272

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

PubMed Central

Diseases caused by calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals occur frequently in osteoarthritic joints. Both crystals induce mitogenesis, metalloproteinase synthesis and secretion by fibroblasts and chondrocytes, promoting degradation of articular tissue. We investigated the mechanism by which BCP activates the c-fos proto-oncogene, which has been shown to activate various matrix metalloproteinases (MMPs). We demonstrate that BCP crystals induce c-fos expression primarily through a Ras/ERK dependent signaling mechanism targeting two highly conserved regulatory binding sites, the serum response element (SRE) and the cAMP response element (CRE). These results establish a calcium crystal induced, calcium/Calmodulin independent, signaling pathway in which BCP crystals activate Ras/MAPK, which can directly target an SRF-containing transcription factor complex, to induce fibroblasts to secrete metalloproteinases. PMID:17307136

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

2007-01-01

273

Thermodynamic analysis and crystal-chemical modeling of the defect structure of calcium iron garnets  

Microsoft Academic Search

This paper presents detailed analysis of the phase equilibria and thermodynamic stability of CaO, Fe2O3, Gd2O3, Nd2O3, Pr2O3, ZrO2, NiO, and ThO2, and detect formation during high-temperature synthesis of gadolinium (yttrium) calcium and zirconium calcium iron garnets\\u000a doped with praseodymium, neodymium, nickel, cerium, thorium, and other oxides. The origin of point defects in each garnet\\u000a is discussed. Crystal-chemical modeling indicates

Yu. P. Vorobiov

2006-01-01

274

INDUCTION OF CRYSTALLIZATION OF SPECIFIC CALCIUM OXALATE HYDRATES IN MICELLAR SOLUTIONS OF SURFACTANTS  

Microsoft Academic Search

The influence of octaethylene glycol mono-n-hexadecyl ether (C16EO8) and sodium dodecyl sulphate (SDS) on the crystallization of calcium oxalate from 0.3 mol dm sodium chloride solutions has been investigated. The critical micellar concentration (CMC) of C16EO8 in water and 0.3 mol dm NaCl was determined by surface tension measurements (CMCH2O=CMCNaCl = 7.2.10 mol dm). The kinetics of precipitation of calcium oxalate was followed

H. Füredi-Milhofer; R. Bloch; D. Skrtic; N. Filipovic-Vincekovic; N. Garti

1993-01-01

275

Determination of tensile, flexural properties and microstructural characterization of calcium carbonate filler reinforced polypropylene matrix composites  

Microsoft Academic Search

Calcium carbonate is one of the commonly used inorganic filler reinforcements in polypropylene matrix. In this research work,\\u000a granules of chicken egg shell containing natural organic calcium carbonate resource has been introduced to reinforce in the\\u000a polypropylene base material. The aim of this experimental study is to determine the tensile, flexural properties and to characterize\\u000a the microstructures of granular chicken

Sivarao; T. R. Vijayaram

2009-01-01

276

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

PubMed

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

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

2013-06-01

277

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

PubMed

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

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

1995-01-01

278

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

NASA Astrophysics Data System (ADS)

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

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

2006-10-01

279

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

PubMed Central

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

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

2012-01-01

280

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

NASA Astrophysics Data System (ADS)

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

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

2008-04-01

281

75 FR 39025 - Determination That ACTONEL (Risendronate Sodium) Tablets, 75 Milligrams, and ACTONEL WITH CALCIUM...  

Federal Register 2010, 2011, 2012, 2013

...CALCIUM (Risendronate Sodium and Calcium Carbonate (Copackaged)) Tablets, 35...CALCIUM (risendronate sodium and calcium carbonate (copackaged)) Tablets, 35...CALCIUM (risendronate sodium and calcium carbonate (copackaged)) Tablets,...

2010-07-07

282

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. PMID:20382865

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

2010-01-01

283

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

284

Decomposition of calcium carbonate and organic carbon in the deep oceans.  

PubMed

Simple mass-balance calculations indicate that in seawater the calcium variation (DeltaCa) correlates with the variation in the titration alkalinity (DeltaTA) and the variation in the total carbon dioxide (DeltasigmaCO(2)) or nitrate (DeltaNO(3)) according to the equations DeltaCa = 0.46288 DeltaTA + 0.074236 DeltasigmaCO(2) and DeltaCa = 0.5 DeltaTA + 0.53125 DeltaNO(3). The estimated values for DeltaCa from these equations, which agree with the values obtained from direct measurements, have been used to estimate the ratio of the in situ inorganic to organic carbon fluxes in the oceans. The precise vertical distribution of this ratio is shown for the first time. PMID:17750232

Chen, C T

1978-08-25

285

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

Microsoft Academic Search

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

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

2005-01-01

286

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

287

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

288

The role of prenucleation clusters in surface-induced calcium phosphate crystallization  

NASA Astrophysics Data System (ADS)

Unravelling the processes of calcium phosphate formation is important in our understanding of both bone and tooth formation, and also of pathological mineralization, for example in cardiovascular disease. Serum is a metastable solution from which calcium phosphate precipitates in the presence of calcifiable templates such as collagen, elastin and cell debris. A pathological deficiency of inhibitors leads to the uncontrolled deposition of calcium phosphate. In bone and teeth the formation of apatite crystals is preceded by an amorphous calcium phosphate (ACP) precursor phase. ACP formation is thought to proceed through prenucleation clusters-stable clusters that are present in solution already before nucleation-as was recently demonstrated for CaCO3 (refs 15,16). However, the role of such nanometre-sized clusters as building blocks for ACP has been debated for many years. Here we demonstrate that the surface-induced formation of apatite from simulated body fluid starts with the aggregation of prenucleation clusters leading to the nucleation of ACP before the development of oriented apatite crystals.

Dey, Archan; Bomans, Paul H. H.; Müller, Frank A.; Will, Julia; Frederik, Peter M.; de With, Gijsbertus; Sommerdijk, Nico A. J. M.

2010-12-01

289

Synthesis, crystal structure and properties of calcium and barium hydroxyapatites containing copper ions in hexagonal channels  

Microsoft Academic Search

Coloured ceramic calcium and barium phosphate apatites containing copper ions were prepared by solid state reactions at 1100°C. Single crystals were grown by melting the ceramics in Bi?M?Cu?O (M=Ca, Ba) fluxes at 1300°C, and subsequent controlled cooling. The powders were characterised by X-ray diffraction, IR and UV–vis diffuse reflectance spectroscopy and SQUID magnetometry. The single crystals have empirical formulas Ca5(PO4)3Cu0.27O0.86Hy

Andrey S. Karpov; Jürgen Nuss; Martin Jansen; Pavel E. Kazin; Yury D. Tretyakov

2003-01-01

290

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

PubMed

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

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

2013-04-01

291

Inhibition and dissolution of calcium oxalate crystals by Berberis Vulgaris-Q and other metabolites  

NASA Astrophysics Data System (ADS)

Inhibition and dissolution of calcium oxalate crystals in solutions containing a homoeopathic medicine Berberis Vulgaris-Q, amino acids such as aspartic acid, glutamic acid, ?-keto glutaric acid, a naturally occurring inhibitor and juices of some fruits of citrus group such as lemon, orange and mausammi have been studied. Considerable solubility was observed and found that in each case solubility changes with time or concentration periodically. Chelation may be one of the reasons for inhibition.

Das, Ishwar; Gupta, S. K.; Pandey, V. N.; Ansari, Shoeb A.

2004-07-01

292

Agglomeration kinetics of calcium sulphate hemihydrate crystals in sulpho-phosphoric solutions  

Microsoft Academic Search

In the present study we aim at describing the agglomeration kinetics of calcium sulphate hemihydrate crystals, growing in concentrated sulpho-phosphoric solutions simulating an industrial process of phosphoric acid production. The experiments were carried out at 90°C, with 40 wt% P2O5 and different excesses in H2SO4. Population densities and supersaturation were determined by periodically removing suspension samples. Agglomeration kinetics were deduced

M. El Moussaouiti; R. Boistelle; A. Bouhaouss; J. P. Klein

1996-01-01

293

Concave urinary crystallines: direct evidence of calcium oxalate crystals dissolution by citrate in vivo.  

PubMed

The changes in urinary crystal properties in patients with calcium oxalate (CaOx) calculi after oral administration of potassium citrate (K3cit) were investigated via atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), and zeta potential analyzer. The AFM and SEM results showed that the surface of urinary crystals became concave, the edges and corners of crystals became blunt, the average size of urinary crystallines decreased significantly, and aggregation of urinary crystals was reduced. These changes were attributed to the significant increase in concentration of excreted citrate to 492 ± 118?mg/L after K3cit intake from 289 ± 83?mg/L before K3cit intake. After the amount of urinary citrate was increased, it complexed with Ca(2+) ions on urinary crystals, which dissolved these crystals. Thus, the appearance of concave urinary crystals was a direct evidence of CaOx dissolution by citrate in vivo. The XRD results showed that the quantities and species of urinary crystals decreased after K3cit intake. The mechanism of inhibition of formation of CaOx stones by K3cit was possibly due to the complexation of Ca(2+) with citrate, increase in urine pH, concentration of urinary inhibitor glycosaminoglycans (GAGs), and the absolute value of zeta potential after K3cit intake. PMID:24363634

Shang, Yun-Feng; Xu, Meng; Zhang, Guang-Na; Ouyang, Jian-Ming

2013-01-01

294

Concave Urinary Crystallines: Direct Evidence of Calcium Oxalate Crystals Dissolution by Citrate In Vivo  

PubMed Central

The changes in urinary crystal properties in patients with calcium oxalate (CaOx) calculi after oral administration of potassium citrate (K3cit) were investigated via atomic force microscopy (AFM), scanning electron microscopy (SEM), X-ray powder diffractometry (XRD), and zeta potential analyzer. The AFM and SEM results showed that the surface of urinary crystals became concave, the edges and corners of crystals became blunt, the average size of urinary crystallines decreased significantly, and aggregation of urinary crystals was reduced. These changes were attributed to the significant increase in concentration of excreted citrate to 492 ± 118?mg/L after K3cit intake from 289 ± 83?mg/L before K3cit intake. After the amount of urinary citrate was increased, it complexed with Ca2+ ions on urinary crystals, which dissolved these crystals. Thus, the appearance of concave urinary crystals was a direct evidence of CaOx dissolution by citrate in vivo. The XRD results showed that the quantities and species of urinary crystals decreased after K3cit intake. The mechanism of inhibition of formation of CaOx stones by K3cit was possibly due to the complexation of Ca2+ with citrate, increase in urine pH, concentration of urinary inhibitor glycosaminoglycans (GAGs), and the absolute value of zeta potential after K3cit intake. PMID:24363634

Shang, Yun-Feng; Xu, Meng; Zhang, Guang-Na; Ouyang, Jian-Ming

2013-01-01

295

Calcium Carbonate Distribution in the Surface Sediments of the Indian Ocean  

Microsoft Academic Search

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

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

1976-01-01

296

On the fracture characteristics of impact tested high density polyethylene–calcium carbonate nanocomposites  

Microsoft Academic Search

The mechanical response of calcium carbonate-reinforced high density polyethylene nanocomposite is investigated and the behavior compared with the unreinforced polyethylene processed under similar conditions. The reinforcement of high density polyethylene with nanocalcium carbonate retains adequately high strength in the temperature range of ?40 to +20°C. The positive influence of reinforcement on the impact strength is reflected in the fracture characteristics

C. Deshmane; Q. Yuan; R. D. K. Misra

2007-01-01

297

Tunable fabrication of two-dimensional arrays of polymer nanobowls for biomimic growth of amorphous calcium carbonate.  

PubMed

Two-dimensional arrays of polymer nanobowls can be fabricated by an oxygen plasma etching technique. The 2D colloidal crystals made of SiO(2) @PMMA particles are fabricated by a convective self-assembly method. The oxygen plasma treatment is applied to the colloidal crystals to selectively etch the PMMA shells. Because the oxygen plasma etching proceeds in a layer-by-layer manner from top to bottom, the top parts of the PMMA shells are etched first, and the silica cores are exposed to the atmosphere, which can be removed with HF, leaving the bowl-shaped PMMA shells to form 2D arrays of polymer nanobowls. The size and packing density of the nanobowl arrays can be tuned with tightly controlled etching time. The polymer nanobowl arrays can also serve as a template to direct the growth of calcium carbonate within the interstice of the nanobowls. PMID:22753380

Ding, Tao; Song, Kai; Yang, Guoqiang; Tung, Chen-Ho

2012-09-26

298

Carbon Nanotube-Reinforced Thermotropic Liquid Crystal Polymer Nanocomposites  

E-print Network

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

Kim, Jun Young

299

Effet de l'apport de phosphore, de carbonate de calcium et d'oligo-lments (Cu, Mn, Zn, B)  

E-print Network

Agronomie Effet de l'apport de phosphore, de carbonate de calcium et d'oligo-éléments (Cu, Mn, Zn apports de phosphore, de carbonate de calcium et d'oligo-éléments (Mn, Cu, Zn, B), en vue de mieux celles de B lorsqu'on élève le pH par apport de carbonate de calcium; - l'accumulation préférentielle de

Paris-Sud XI, Université de

300

Calcium  

MedlinePLUS

... it from: Dairy products. Low-fat milk, yogurt, cheese, and cottage cheese are good sources of calcium. Veggies. You'll ... burritos or wraps. Fill them with eggs and cheese for breakfast; turkey, cheese, lettuce, tomato, and light ...

301

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

302

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

PubMed Central

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

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

2001-01-01

303

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

304

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

PubMed Central

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

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

2014-01-01

305

Theoretical study of the dimerization of calcium carbonate in aqueous solution under natural water conditions  

NASA Astrophysics Data System (ADS)

First principles calculations have been used to investigate the condensation reactions of hydrated calcium bicarbonate monomers in a simulated aqueous environment. The reaction pathway for the calcium bicarbonate dimerization process has been computed at the density functional theory-PBE level with the COSMO dielectric continuum model to simulate the hydrated environment. The results indicate that calcium bicarbonate dimers form via an associative mechanism: the first step involves a sevenfold calcium bicarbonate intermediate followed by the loss of one water molecule from the first coordination shell of calcium. Both steps are characterised by a low energy barrier of approximately 2 kcal mol -1, suggesting that the dimerization process is not kinetically hindered in aqueous solution. However, the Gibbs free energies for the condensation reactions to form the calcium bicarbonate dimers and the species Ca(HCO 3) 2(H 2O) 4, Ca(HCO 3) 3(H 2O) 3- and Ca 2(HCO 3)(H 2O) 103+, computed using the PBE and mPW1B95 density functional theory levels for the gas-phase component and the UAHF-CPCM solvation model for the hydration contribution, are all positive, which indicates that the formation of these early calcium bicarbonate clusters is thermodynamically unfavourable in aqueous solutions. Our calculations therefore suggest that the oligomerization of calcium carbonate is not spontaneous in water, at the conditions considered in our simulations, i.e. T = 298 K and neutral pH, which indicates that the nucleation of calcium carbonate cannot occur through a homogeneous process when calcium-bicarbonate ion pairs are the major source of CaCO 3 in the aqueous environment.

Di Tommaso, Devis; de Leeuw, Nora H.

2009-09-01

306

Calcium Carbonate Formation by Synechococcus sp. Strain PCC 8806 and Synechococcus sp. Strain PCC 8807  

SciTech Connect

Precipitation of CaCO3 catalyzed by the growth and physiology of cyanobacteria in the Genus Synechococcus represents a potential mechanism for sequestration of CO2 produced during the burning of coal for power generation. Microcosm experiments were performed in which Synechococcus sp. strain PCC 8806 and Synechococcus sp. strain PCC 8807 were tested for their ability to calcify when exposed to a fixed calcium concentration of 3.4 mM and bicarbonate concentrations of 0.5, 1.25 and 2.5 mM. Disappearance of soluble calcium was used as an indicator of CaCO3 formation; results from metabolically active microcosms were compared to controls with no cells or no carbonate added. Synechococcus sp. strain PCC 8806 removed calcium continuously over the duration of the experiment with approximately 18.6 mg of calcium in the solid phase. Calcium removal occurred over a two-day time period when Synechococcus sp. strain PCC 8807 was tested and only 8.9 mg of calcium was removed in the solid phase. The ability of the cyanobacteria to create an alkaline growth environment appeared to be the primary factor responsible for CaCO3 precipitation in these experiments. Removal of inorganic carbon by fixation into biomass was insignificant compared to the mass of inorganic carbon removed by incorporation into the growing CaCO3 solid.

Lee, Brady D.; William A. Apel; Michelle R. Walton

2006-12-01

307

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

308

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

EPA Science Inventory

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

309

Development and Application of Image Analysis to Quantify Calcium Lactate Crystals on the Surface of Smoked Cheddar Cheese  

Microsoft Academic Search

Calcium lactate crystals that form white specks or haze on the surface of cheese constitute a significant quality problem for producers of Cheddar cheese. Sub- jective methods to evaluate crystal coverage of cheese surfaces have been reported previously, but objective methods are currently lacking. The objectives of this work were to develop and evaluate an objective method tomeasuretheareaoccupiedbycalciumlactatecrystals on surfaces

P. Rajbhandari; P. S. Kindstedt

2005-01-01

310

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

311

A novel approach to the evaluation of calcium carbonate scale inhibitors  

SciTech Connect

Problems in cooling water systems are typically confined to three main areas: the deposition of mineral scale, the corrosion of metallic parts, and the growth of microbiological organisms. Chemical treatment of the recirculating water has proven the simplest and most cost effective way of maintaining control over these phenomena. The use of recently developed experimental methods, as well as traditional techniques, in the discovery of new calcium carbonate scale inhibitors are discussed. Atomic force microscopy and computer aided molecular design are presented as emerging technologies which can provide important contributions to the understanding of the mechanism of calcium carbonate inhibition and the investigation of new inhibitor chemistries. Calcium carbonate solubility stress experiments, constant composition techniques and process simulation, traditional scale inhibitor development methods, are also discussed. Results of representative experiments are also presented and discussed.

Kamrath, M.A.; Davis, R.V.; Johnson, D.A. [Nalco Chemical Co., Naperville, IL (United States)

1994-12-31

312

Polyelectrolyte effects on the crystallization phenomena of the lithium carbonate  

NASA Astrophysics Data System (ADS)

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

Watamura, Hiroto; Marukawa, Hironobu; Hirasawa, Izumi

2013-06-01

313

Agglomeration kinetics of calcium sulphate hemihydrate crystals in sulpho-phosphoric solutions  

NASA Astrophysics Data System (ADS)

In the present study we aim at describing the agglomeration kinetics of calcium sulphate hemihydrate crystals, growing in concentrated sulpho-phosphoric solutions simulating an industrial process of phosphoric acid production. The experiments were carried out at 90°C, with 40 wt% P 2O 5 and different excesses in H 2SO 4. Population densities and supersaturation were determined by periodically removing suspension samples. Agglomeration kinetics were deduced from the volume growth rates and agglomeration kernel calculated from the population density moments of order 0, 1 and 2. Agglomeration rates are linear functions of supersaturation if the excess in H 2SO 4 is less than 2%. At 2% and 4%, agglomeration is maximum for relative supersaturations of 10% and 25%, respectively. Beyond an excess of 4% in H 2SO 4, agglomeration is low. At very high supersaturations, the aggregates are brittle due to crystal habit elongation. At last, it is shown that P 2O 5 loss is due rather to agglomeration than to incorporation of phosphate in the calcium sulphate hemihydrate crystal lattice.

El Moussaouiti, M.; Boistelle, R.; Bouhaouss, A.; Klein, J. P.

1996-11-01

314

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

SciTech Connect

The primary objective of this project is to investigate the role of calcium carbonate grain coatings on adsorption and heterogeneous reduction reactions of key chemical and radioactive contaminants in sediments on the Hanford Site. Research will ascertain whether these coatings promote or discourage contaminant reaction with sediment mineral particles, and whether calcium carbonate phases resulting from waste-sediment reaction sequester contaminants through coprecipitation. The research will provide new conceptual models of contaminant reaction/retardation processes in Hanford sediments (for 90Sr2+ and Cr(VI)O4 2- primarily) and improved geochemical models to forecast the future behavior of in-ground contaminants.

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

2002-06-01

315

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

316

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

SciTech Connect

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

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

2001-06-01

317

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

Microsoft Academic Search

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

M. Machius; G. Wiegand; R. Huber

1995-01-01

318

10 / JOURNAL OF MATERIALS IN CIVIL ENGINEERING / JANUARY/FEBRUARY 2001 INHIBITING ACTION OF CALCIUM NITRITE ON CARBON STEEL REBARS  

E-print Network

by which calcium nitrite aids in the reduction of corrosion rate in a fresh carbon steel surface10 / JOURNAL OF MATERIALS IN CIVIL ENGINEERING / JANUARY/FEBRUARY 2001 INHIBITING ACTION OF CALCIUM NITRITE ON CARBON STEEL REBARS By M. Ramasubramanian,1 B. S. Haran,2 S. Popova,3 B. N. Popov,4 M. F

319

Analysis of mass transfer in the precipitation process of calcium carbonate using a gas\\/liquid reaction  

Microsoft Academic Search

Nowadays a typical method to produce calcium carbonate is based on the gas–liquid reaction between carbon dioxide and aqueous solutions of calcium hydroxide. Several chemical engineering processes are involved in this operation, such as mass transfer, chemical kinetics, etc. The aim of this research work is to study the global reaction process that involves absorption, reaction and precipitation processes. The

Diego Gómez-Díaz; José M. Navaza; Begoña Sanjurjo

2006-01-01

320

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

321

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

322

Microwave hydrothermal transformation of amorphous calcium carbonate nanospheres and application in protein adsorption.  

PubMed

Calcium carbonate and calcium phosphate are the main components of biominerals. Among all of the forms of biominerals, amorphous calcium carbonate (ACC) and amorphous calcium phosphate (ACP) are the most important forms because they play a pivotal role in the process of biomineralization and are the precursors to the crystalline polymorphs. In this work, we first synthesized ACC in vitro using adenosine 5'-triphosphate disodium salt (ATP) as the stabilizer and investigated the transformation of the ACC under microwave hydrothermal conditions, and ACC/ACP composite nanospheres and carbonated hydroxyapatite (CHA) nanospheres were successfully prepared. In this novel strategy, ATP has two main functions: it serves as the stabilizer for ACC and the phosphorus source for ACP and CHA. Most importantly, the morphology and the size of the ACC precursor can be well-preserved after microwave heating, so it provides a new method for the preparation of calcium phosphate nanostructured materials using phosphorus-containing biomolecule-stabilized ACC as the precursor. Furthermore, the as-prepared ACC/ACP composite nanospheres have excellent biocompatibility and high protein adsorption capacity, indicating that they are promising for applications in biomedical fields such as drug delivery and protein adsorption. PMID:24568728

Qi, Chao; Zhu, Ying-Jie; Chen, Feng

2014-03-26

323

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

324

CO.sub.2 Pretreatment prevents calcium carbonate formation  

DOEpatents

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

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

1980-01-01

325

The effect of benzotriazoles on calcium carbonate scale formation  

NASA Astrophysics Data System (ADS)

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

Zafiropoulou, A.; Dalas, E.

2000-11-01

326

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

327

Identification of human urinary trefoil factor 1 as a novel calcium oxalate crystal growth inhibitor  

PubMed Central

Previous research on proteins that inhibit kidney stone formation has identified a relatively small number of well-characterized inhibitors. Identification of additional stone inhibitors would increase understanding of the pathogenesis and pathophysiology of nephrolithiasis. We have combined conventional biochemical methods with recent advances in mass spectrometry (MS) to identify a novel calcium oxalate (CaOx) crystal growth inhibitor in normal human urine. Anionic proteins were isolated by DEAE adsorption and separated by HiLoad 16/60 Superdex 75 gel filtration. A fraction with potent inhibitory activity against CaOx crystal growth was isolated and purified by anion exchange chromatography. The protein in 2 subfractions that retained inhibitory activity was identified by matrix-assisted laser desorption/ionization–time-of-flight MS and electrospray ionization–quadrupole–time-of-flight tandem MS as human trefoil factor 1 (TFF1). Western blot analysis confirmed the mass spectrometric protein identification. Functional studies of urinary TFF1 demonstrated that its inhibitory potency was similar to that of nephrocalcin. The inhibitory activity of urinary TFF1 was dose dependent and was inhibited by TFF1 antisera. Anti–C-terminal antibody was particularly effective, consistent with our proposed model in which the 4 C-terminal glutamic residues of TFF1 interact with calcium ions to prevent CaOx crystal growth. Concentrations and relative amounts of TFF1 in the urine of patients with idiopathic CaOx kidney stone were significantly less (2.5-fold for the concentrations and 5- to 22-fold for the relative amounts) than those found in controls. These data indicate that TFF1 is a novel potent CaOx crystal growth inhibitor with a potential pathophysiological role in nephrolithiasis. PMID:16308573

Chutipongtanate, Somchai; Nakagawa, Yasushi; Sritippayawan, Suchai; Pittayamateekul, Jeeraporn; Parichatikanond, Paisal; Westley, Bruce R.; May, Felicity E.B.; Malasit, Prida; Thongboonkerd, Visith

2005-01-01

328

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. PMID:24044655

2013-01-01

329

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

Microsoft Academic Search

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

David E. Archer

1996-01-01

330

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

331

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...

332

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....

333

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

EPA Science Inventory

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

334

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

335

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

PubMed

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 X-ray powder diffraction, elemental analysis and Raman spectroscopy to quantify the ACC/calcite ratio, the mineral phase distribution and the composition within the anterior and posterior tergite cuticle during eight different stages of the moulting cycle of Porcellio scaber. The results show that most of the amorphous calcium carbonate (ACC) is resorbed from the cuticle, whereas calcite remains in the old cuticle and is shed during moulting. During premoult resorption of ACC from the posterior cuticle is accompanied by an increase within the anterior tergites, and mineralization of the new posterior cuticle by resorption of mineral from the anterior cuticle. This suggests that one reason for using ACC in cuticle mineralization is to facilitate resorption and recycling of cuticular calcium carbonate. Furthermore we show that ACC precedes the formation of calcite in distal layers of the tergite cuticle. PMID:21458575

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

2011-07-01

336

Measurement of calcium carbonate deposition in molluscs by controlled etching of radioactively labeled shells  

Microsoft Academic Search

Rates of calcium carbonate removal from shell pieces of Argopecten irradians (Say) and Mercenaria mercenaria (L.) were dependent on the type of etching fluid used and not shell origin. Etching was uniform over the entire shell surface, but surface morphology differed with etching fluids. Peak radioactivity was in early eluant fractions of shells etched immediately after radioactive labeling, and in

R. M. Dillaman; S. E. Ford

1982-01-01

337

Activity coefficients of bicarbonate, carbonate and calcium ions in sea water  

Microsoft Academic Search

Measurements of pH of sea water samples equilibrated with known partial pressures of CO 2 and with calcite and aragonite have enabled the determination of molal activity coefficient for bicarbonate, carbonate, and calcium ions in two sea water samples at 25°C and 1 atm total pressure. Results are: For standard artificial sea water (chlorinity = 19.0 , titration alkalinity =

Robert A. Berner

1965-01-01

338

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

PubMed

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 (CO?-HA) with ?5?wt% substituted carbonate content (sample 7.5CO?-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 7.5CO?-HA. For silicate-substituted hydroxyapatite (SiO?-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 SiO?-HA in the continuous hydrothermal flow synthesis system, which could be due to the decreasing yields with progressive increase in silicon acetate concentration. All the as-precipitated powders (without any additional heat treatments) were analysed using techniques including Transmission electron microscopy, X-ray powder diffraction, Differential scanning calorimetry, Thermogravimetric analysis, Raman spectroscopy and Fourier transform infrared spectroscopy. PMID:22983020

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

2013-09-01

339

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

340

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

341

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

NASA Astrophysics Data System (ADS)

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

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

2004-10-01

342

Calcium oxalate crystals induce renal inflammation by NLRP3-mediated IL-1? secretion.  

PubMed

Nephrocalcinosis, acute calcium oxalate (CaOx) nephropathy, and renal stone disease can lead to inflammation and subsequent renal failure, but the underlying pathological mechanisms remain elusive. Other crystallopathies, such as gout, atherosclerosis, and asbestosis, trigger inflammation and tissue remodeling by inducing IL-1? secretion, leading us to hypothesize that CaOx crystals may induce inflammation in a similar manner. In mice, intrarenal CaOx deposition induced tubular damage, cytokine expression, neutrophil recruitment, and renal failure. We found that CaOx crystals activated murine renal DCs to secrete IL-1? through a pathway that included NLRP3, ASC, and caspase-1. Despite a similar amount of crystal deposits, intrarenal inflammation, tubular damage, and renal dysfunction were abrogated in mice deficient in MyD88; NLRP3, ASC, and caspase-1; IL-1R; or IL-18. Nephropathy was attenuated by DC depletion, ATP depletion, or therapeutic IL-1 antagonism. These data demonstrated that CaOx crystals trigger IL-1?-dependent innate immunity via the NLRP3/ASC/caspase-1 axis in intrarenal mononuclear phagocytes and directly damage tubular cells, leading to the release of the NLRP3 agonist ATP. Furthermore, these results suggest that IL-1? blockade may prevent renal damage in nephrocalcinosis. PMID:23221343

Mulay, Shrikant R; Kulkarni, Onkar P; Rupanagudi, Khader V; Migliorini, Adriana; Darisipudi, Murthy N; Vilaysane, Akosua; Muruve, Daniel; Shi, Yan; Munro, Fay; Liapis, Helen; Anders, Hans-Joachim

2013-01-01

343

Calcium hydroxide and calcium carbonate particle-size effects on reactivity with sulfur dioxide  

SciTech Connect

This paper reports results of measurements of the effect of in-situ calcium-based sorbent particle size upon reactivity with 3000 ppm SO/sub 2/ in an 1100-C drop-tube furnace, using on-line collection of the reacted sorbent with a particle cascade impactor. Significant agglomeration occurred for Ca(OH)/sub 2/, while little was apparent for CaCO/sub 3/. Reactivity of all sorbent particles increases as the measured particle diameter decreases, such that conversion is inversely related to diameter to the 0.22 to 0.32 power. For these sorbents, Ca(OH)/sub 2/ particles had greater reactivity than the similarly sized CaCO/sub 3/ sorbent.

Gullett, B.K.; Blom, J.A.

1987-01-01

344

Oxygen isotope fractionation during the dolomitization of calcium carbonate  

Microsoft Academic Search

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

Alan Matthews; Amitai Katz

1977-01-01

345

Selective inclusion of proteins into urinary calcium oxalate crystals: comparison between stone-prone and stone-free population groups  

NASA Astrophysics Data System (ADS)

This study investigated whether incorporation of proteins into calcium oxalate urinary crystals is different in the black and white populations in South Africa and whether such differences could provide insight into the former group's remarkably low stone incidence. CaOx monohydrate (COM) and dihydrate (COD) crystals were precipitated from each group's urine after adjustment of the calcium concentrations to 0.5 and 12 mmol/l, respectively. Crystals were characterised by X-ray powder diffraction and scanning electron microscopy. Intracrystalline proteins were analysed by SDS-PAGE and immunodetected for urinary prothrombin fragment 1 (UPTF1) and osteopontin. Crystals precipitated from the black and white groups' control urines comprised mainly COM and COD, respectively. In both race groups UPTF1 was the major protein included in pure COM crystals while in pure COD it was osteopontin, but in the black group osteopontin was also included in COM. The black group's urine crystals incorporated significantly more intracrystalline protein. Selective inclusion of UPTF1 and osteopontin may be due to the unique crystal structure of COM and COD and the proteins' conformation at the different calcium concentrations at which these hydrates precipitate. The greater amount of intracrystalline inhibitory protein in the black group may be a factor in their low stone incidence.

Webber, D.; Rodgers, A. L.; Sturrock, E. D.

2003-11-01

346

Antioxidant Properties of Polysaccharide from the Brown Seaweed Sargassum graminifolium (Turn.), and Its Effects on Calcium Oxalate Crystallization  

PubMed Central

We investigated the effects of polysaccharides from the brown seaweed Sargassum graminifolium (Turn.) (SGP) on calcium oxalate crystallization, and determined its antioxidant activities. To examine the effects of SGP on calcium oxalate crystallization, we monitored nucleation and aggregation of calcium oxalate monohydrate crystals, using trisodium citrate as a positive control. We assessed antioxidant activities of SGP by determining its reducing power, its ability to scavenge superoxide radicals, and its activity in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. The nucleation inhibition ratio of trisodium citrate and SGP was 58.5 and 69.2%, respectively, and crystal aggregation was inhibited by 71.4 and 76.8%, respectively. Increasing concentrations of SGP resulted in increased scavenging of superoxide anions and DPPH radicals (IC50 = 1.9 and 0.6 mg/mL, respectively). These results suggest that SGP could be a candidate for treating urinary stones because of its ability to inhibit calcium oxalate crystallization and its antioxidant properties. PMID:22363225

Zhang, Chao-Yan; Wu, Wen-Hui; Wang, Jue; Lan, Min-Bo

2012-01-01

347

Complexation/encapsulation of green tea polyphenols in mixed calcium carbonate and phosphate micro-particles.  

PubMed

We used a double-jet mixer to encapsulate water-soluble polyphenols, green tea extract (GTE), with calcium-based inorganic materials. The device mixed calcium chloride solutions with a solution of carbonate and phosphate in the presence of a GTE solution, and formed micro-particles which capture the GTE molecules. The micro-particles were analysed by liquid chromatography coupled to tandem mass spectroscopy to determine the encapsulation yield and loading of the different GTE components. We established correlations between (1) the efficiency of the GTE encapsulation and the composition of the mixed anion solutions and (2) the protonation degree of the ions and the molar ratio of calcium cations and carbonate/phosphate anions. An optimal and reproducible GTE loading of about 40% with an encapsulation yield of 65% was observed for a carbonate/phosphate molar composition of 4?:?1. In addition, our experimental results showed that the process is selective and favours the encapsulation of gallated species which form stronger complexes with calcium cations. PMID:20945969

Elabbadi, Amal; Jeckelmann, Nicolas; Haefliger, Olivier P; Ouali, Lahoussine

2011-01-01

348

Multiple-Quantum NMR Coherence Growth in Single-Crystal and Powdered Calcium Fluoride  

NASA Astrophysics Data System (ADS)

Powdered and oriented single-crystal calcium fluoride (CaF 2) samples were used to determine the orientational dependence of 19F multiple-quantum (MQ) NMR coherence development in the absence of variations in lattice spacing and molecular motion on the experimental time scale. The normalized n-quantum coherence intensities and resultant effective spin-cluster size [ N(?)] of the powdered sample were found to be reproducible and insensitive to the cycle time chosen for the underlying eight-pulse MQ excitation sequence. Oscillations in the time-dependent 0Q and 2Q coherence intensities are seen in the oriented single-crystal samples. However, these oscillations are absent in the powdered CaF 2 sample, indicating damping by its orientational-based dipolar-coupling distribution. However, monotonic growth of the effective number of correlated nuclei, N(?), is still observed. In addition, the applicability of an average product-operator model of coherence growth based on the dimensionality of spin distribution, and previously only applied to powders, is tested for oriented single-crystal CaF 2 samples. The powdered and (100)-oriented single crystal show good agreement with the model, while the growth from the (111) orientation is slightly faster than predicted. This difference most likely arises from the unusual dipole structure of the (111)-oriented crystal, where nearest-neighbor couplings become zero. In addition, the refocused MQ signal intensity ( fMQ) is adversely effected by increasing the number of pulses applied in a fixed MQ preparation time. An empirical prediction of fMQ for samples with a static dipolar field is developed and serves as a basis for predicting the effects of motion on this MQ refocusing fraction. This relationship may also provide some insight into the possibility of extending the MQ technique to study correlations over larger length scales as the relatively rapid decay of fMQ typical limits the present experiment to ˜ 10 Å length scales.

Lathrop, D. A.; Handy, E. S.; Gleason, K. K.

349

The mineral phase in the cuticles of two species of Crustacea consists of magnesium calcite, amorphous calcium carbonate, and amorphous calcium phosphate.  

PubMed

The cuticules (shells) of the woodlice Porcellio scaber and Armadillidium vulgare were analysed with respect to their content of inorganic material. It was found that the cuticles consist of crystalline magnesium calcite, amorphous calcium carbonate (ACC), and amorphous calcium phosphate (ACP), besides small amounts of water and an organic matrix. It is concluded that the cuticle, which constitutes a mineralized protective organ, is chemically adapted to the biological requirements by this combination of different materials. PMID:15877152

Becker, Alexander; Ziegler, Andreas; Epple, Matthias

2005-05-21

350

Calcium oxalate crystallization index (COCI): an alternative method for distinguishing nephrolithiasis patients from healthy individuals.  

PubMed

Urinary supersaturation triggers lithogenic crystal formation. We developed an alternative test, designated calcium oxalate crystallization index (COCI), to distinguish nephrolithiasis patients from healthy individuals based on their urinary crystallization capability. The effect of urine volume, oxalate, phosphate, citrate, potassium, and sodium on COCI values was investigated. COCI values were determined in 24-hr urine obtained from nephrolithiasis patients (n=72) and matched healthy controls (n=71). Increases in urine oxalate and phosphate and decreases in urine volume and citrate resulted in significantly increased COCI values. The urinary COCI in nephrolithiasis patients was significantly higher than that in healthy individuals. Two healthy subjects who had elevated COCI values were found to have asymptomatic kidney calculi. The receiver operating characteristic analysis showed an area under the curve of the urinary COCI test of 0.9499 (95%CI: 0.9131-0.9868) for distinguishing between nephrolithiasis and healthy subjects. At the cutoff of 165 mg oxalate equivalence/day, the urinary COCI test provided sensitivity, specificity, and accuracy amounts of 83.33%, 97.18%, and 90.21%, respectively. Urinary COCI values were primarily dependent on urine volume, oxalate, and phosphate. The test provided high sensitivity and specificity for clinically discriminating nephrolithiasis patients from healthy controls. It might be used to detect individuals with asymptomatic kidney calculi. PMID:25117095

Yang, Bowei; Dissayabutra, Thasinas; Ungjaroenwathana, Wattanachai; Tosukhowong, Piyaratana; Srisa-Art, Monpichar; Supaprom, Thavorn; Insin, Numpon; Boonla, Chanchai

2014-01-01

351

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

PubMed

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

Zhang, Jianping; Lu, Houyuan; Huang, Linpei

2014-01-01

352

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

PubMed Central

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

Zhang, Jianping; Lu, Houyuan; Huang, Linpei

2014-01-01

353

EFFECTS OF SODIUM AND CALCIUM IN LIGNITE ON THE PERFORMANCE OF ACTIVATED CARBON PRODUCTS  

SciTech Connect

Powdered activated carbon (PAC) has traditionally been used by the water treatment industry for the removal of compounds contributing to taste and odor problems. PAC also has the potential to remove naturally occurring organic matter (NOM) from raw waters prior to disinfection, thus controlling the formation of regulated disinfection by-products (DBPs). Many small water systems are currently using PAC for taste and odor control and have the potential to use PAC for controlling DBPs. The Energy & Environmental Research Center has been working on the development of a PAC product to remove NOM from surface water supplies to prevent the formation of carcinogenic DBPs during chlorination. During previous studies, the sodium and calcium content of the lignites showed a significant effect on the sorption capacity of the activated carbon product. As much as a 130% increase in the humic acid sorption capacity of a PAC produced from a high-sodium-content lignite was observed. During this study, activated carbons were prepared from three coals representing high-sodium, low-sodium--low-calcium, and high-calcium compositions in two steps, an initial char formation followed by mild activation with steam to avoid excessive burnout. This set of carbons was characterized with respect to physical and chemical properties. The BET (Brunauer-Emmett-Teller) nitrogen adsorption isotherms gave relatively low surface areas (ranging from 245 to 370 m{sup 2}/g). The lowest-BET area was obtained for the high-sodium carbon, which can be attributed to enlargement of micropores as a result of sodium-catalyzed gasification reaction of the carbon structure. This hypothesis is consistent with the scanning electron microscopy microprobe analyses, which show that in both the coal and the activated carbon from this coal, the sodium is distributed over both the carbon structure and the mineral particles. Thus it is initially associated with carboxylate groups on the coal and then as sodium oxide or other active form in close proximity to the carbon and is, therefore, readily available for catalysis of gasification. Humate adsorption isotherms for the high-sodium carbon gave superior results as defined by very high intercepts in modified Freundlich plots. Thus the high-sodium carbon will be considerably more effective in reducing the humate concentration for a given carbon dosage. Analysis of adsorption isotherms indicated the results were consistent with the hypothesis that only the larger pores are effective for binding the large humate molecules, and that the larger pores developed during activation of the high-sodium char give the appropriate macropore structure for humate binding. Toluene adsorption isotherms indicated that the high-calcium carbon and the low-calcium, low-sodium carbon were superior to the high-sodium carbon for small molecules in aqueous solution, but not as effective as a Calgon F-400 commercial activated carbon. This is consistent with the low-BET surface areas observed for the lignite-derived carbons, and thus there are a lower number of sites for binding the smaller toluene molecule in these carbons.

Edwin S. Olson; Kurt E. Eylands; Daniel J. Stepan

2001-12-01

354

A geospatial assessment of the relationship between reef flat community calcium carbonate production and wave energy  

NASA Astrophysics Data System (ADS)

The ability of benthic communities inhabiting coral reefs to produce calcium carbonate underpins the development of reef platforms and associated sedimentary landforms, as well as the fixation of inorganic carbon and buffering of diurnal pH fluctuations in ocean surface waters. Quantification of the relationship between reef flat community calcium carbonate production and wave energy provides an empirical basis for understanding and managing this functionally important process. This study employs geospatial techniques across the reef platform at Lizard Island, Great Barrier Reef, to (1) map the distribution and estimate the total magnitude of reef community carbonate production and (2) empirically ascertain the influence of wave energy on community carbonate production. A World-View-2 satellite image and a field data set of 364 ground referencing points are employed, along with data on physical reef characteristics (e.g. bathymetry, rugosity) to map and validate the spatial distribution of the four major community carbonate producers (live coral, carbonate sand, green calcareous macroalgae and encrusting calcified algae) across the reef platform. Carbonate production is estimated for the complete reef platform from the composition of these community components. A synoptic model of wave energy is developed using the Simulating WAves Nearshore (SWAN) two-dimensional model for the entire reef platform. The relationship between locally derived measures of carbonate production and wave energy is evaluated at both the global scale and local scale along spatial gradients of wave energy traversing the reef platform. A wave energy threshold is identified, below which carbonate production levels appear to increase with wave energy and above which mechanical forcing reduces community production. This implies an optimal set of hydrodynamic conditions characterized by wave energy levels of approximately 300 J m-2, providing an empirical basis for management of potential changes in community carbonate production associated with climate change-driven increases in wave energy.

Hamylton, S. M.; Pescud, A.; Leon, J. X.; Callaghan, D. P.

2013-12-01

355

Geophysical Monitoring and Reactive Transport Modeling of Ureolytically-Driven Calcium Carbonate Precipitation  

SciTech Connect

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

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

2011-09-01

356

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

PubMed Central

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

2011-01-01

357

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

PubMed

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

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

2013-09-01

358

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

SciTech Connect

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

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

1993-09-01

359

Crystal structure of the intermetallics produced by a calcium hydride method  

NASA Astrophysics Data System (ADS)

Practically important intermetallics TiNi, NiAl, Ni3Al, TiAl, and Zr3Al2 (St 101 alloy for gas absorbers) produced by the calcium hydride method are comprehensively studied. The total content of impurities in these intermetallic powders does not exceed 1 wt %, and the fraction of the main phase in compounds with a narrow homogeneity region is at least 93-96 vol %. The main phases in all powders under study have a defectless crystal lattice, and their lattice parameters point to a low content of dissolved impurities in all intermetallics except for Zr3Al2. A high degree of homogeneity of the phase compositions of the intermetallic powders is supported by a scanning electron microscopy investigation.

Kasimtsev, A. V.; Sviridova, T. A.

2012-05-01

360

Atomic force microscopy of growth and dissolution of calcium oxalate monohydrate (COM) crystals  

NASA Astrophysics Data System (ADS)

The growth and dissolution of calcium oxalate monohydrate (COM) crystals up to 30 ?m in length were investigated in situ by atomic force microscopy. The fast-growing faces grew by the dislocation mechanism, the slow-growing ones (in most cases), by forming 2D-nuclei. The velocity of moving steps at different supersaturations, the normal rates of growth and dissolution of these faces were measured. The dissolution rate was found to be 3 times higher in the specially prepared Aqua RX water than in distilled water. Adding a small amount of Al and Fe ions to the water resulted in 5-fold increase of the dissolution rate. Intensive dissolution was observed even when these ions were added to a supersaturated solution.

Gvozdev, N. V.; Petrova, E. V.; Chernevich, T. G.; Shustin, O. A.; Rashkovich, L. N.

2004-02-01

361

RENAL HISTOPATHOLOGY AND CRYSTAL DEPOSITS IN PATIENTS WITH SMALL BOWEL RESECTION AND CALCIUM OXALATE STONE DISEASE  

PubMed Central

To date, the surgical anatomy and histopathology of kidneys from patients with stones and small bowel resection have not been studied. We present here materials from 11 cases, 10 Crohn’s disease and one with resection in infancy for unknown cause. Stones are predominantly calcium oxalate (CaOx). Urine stone risks included hyperoxaluria (urine oxalate excretion > 45 mg/day) in half of the cases, and reduced urine volume and pH. As in ileostomy and obesity bypass, inner medullary collecting ducts (IMCD) contain crystal deposits with associated cell injury, interstitial inflammation and papillary deformity. Cortical changes include modest glomerular sclerosis, tubular atrophy, and interstitial fibrosis. Interstitial papillary apatite (Randall’s) plaque is abundant, and CaOx stones grow over deposits as in ileostomy, idiopathic CaOx stone formers, and primary hyperparathyroidism. Abundant plaque is compatible with the low urine volume and pH. IMCD deposits all contain apatite; in 3 cases CaOx is also present. This is similar to findings in obesity bypass but not ileostomy. Mechanisms for CaOx in IMCD appear to include elevated urine, and presumably tubule fluid CaOx SS with a low calcium to oxalate ratio; mechanisms for the universal presence of IMCD apatite are unknown. PMID:20428098

Evan, Andrew P.; Lingeman, James E.; Worcester, Elaine M.; Bledsoe, Sharon B.; Sommer, Andre J.; Williams, James C.; Krambeck, Amy E.; Philips, Carrie L.; Coe, Fredric L

2013-01-01

362

Calcium sulfate crystallization along citrus root channels in a Florida soil exhibiting acid sulfate properties  

SciTech Connect

The authors observed euhedral crystals in Manatee soil in a citrus grove in St. Lucie County, Florida. The material was identified as gypsum (CaSO/sub 4/ /times/ 2H/sub 2/O) using x-ray diffraction and infrared spectra. Photomicrography and scanning electron microscopy revealed that gypsum accumulated both in old root channels and within citrus root tissue of the Btg horizon. The subsurface horizons had elevated sulfate levels, a low initial pH, a drop (0.5 unit) in pH upon air-drying. Electrical conductivity paralleled the concentration of water-soluble sulfate. High levels of calcium and sulfate occurred for horizons above the water table. This accumulation is attributed to groundwater bearing these ions and subsequently discharging them to the overlying soil. Dead citrus roots appear to act as wicks to aid water transfer from lower to higher horizons. The roots and their empty channels provide spaces in which the gypsum can precipitate if the concentrations of calcium and sulfate in the evaporating groundwater exceed the solubility product of gypsum.

Syslo, S.K.; Myhre, D.L.; Harris, W.G.

1988-02-01

363

Development of antimicrobial water filtration hybrid material from bio source calcium carbonate and silver nanoparticles  

NASA Astrophysics Data System (ADS)

Biobased calcium carbonate and silver hybrid nanoparticles were synthesized using a simple mechanochemical milling technique. The XRD spectrum showed that the hybrid materials is composed of crystalline calcite and silver nanoparticles. The TEM results indicated that the silver nanoparticles are discrete, uncapped and well stabilized in the surface of the eggshell derived calcium carbonate particles. The silver nanoparticles are spherical in shape and 5-20 nm in size. The SEM studies indicated that the eggshells are in micron size with the silver nanoparticle embedded in their surface. The hybrid eggshell/silver nanocomposite exhibited superior inhibition of E. coli growth using the Kirby-Bauer discs diffusion assay and comparing the zone of inhibition around the filter paper disc impregnated with the hybrid particles against pristine silver nanoparticles.

Apalangya, Vitus; Rangari, Vijaya; Tiimob, Boniface; Jeelani, Shaik; Samuel, Temesgen

2014-03-01

364

Relationship between the degeneration of the cruciate ligaments and calcium pyrophosphate dihydrate crystal deposition: anatomic, radiologic study with histologic correlation.  

PubMed

To investigate the association of calcium pyrophosphate dihydrate (CPPD) crystal deposition and cruciate ligament (CL) degeneration, 10 cadaveric knees were studied with 1.5-T magnetic resonance imaging and sectioned in three planes. The slices were evaluated with high-resolution Faxitron radiography. The images and specimens were evaluated by two radiologists. Histologic sections were obtained from eight that contained calcifications and from two without calcifications. Radiographs and histologic analysis demonstrated CPPD crystal deposition in 80% of specimens and 75% of CLs in these eight specimens. Degenerative changes were observed in 75% of them. Such analysis demonstrated no evidence of CPPD crystals or degeneration in the control specimens. PMID:23465989

Dirim, Berna; Resnick, Donald; Abreu, Marcelo; Wangwinyuvirat, Mani; Trudell, Debra J; Haghighi, Parviz

2013-01-01

365

Macromolecule loading into spherical, elliptical, star-like and cubic calcium carbonate carriers.  

PubMed

We fabricated calcium carbonate particles with spherical, elliptical, star-like and cubical morphologies by varying relative salt concentrations and adding ethylene glycol as a solvent to slow down the rate of particle formation. The loading capacity of particles of different isotropic (spherical and cubical) and anisotropic (elliptical and star-like) geometries is investigated, and the surface area of such carriers is analysed. Potential applications of such drug delivery carriers are highlighted. PMID:25044943

Parakhonskiy, Bogdan V; Yashchenok, Alexey M; Donatan, Senem; Volodkin, Dmitry V; Tessarolo, Francesco; Antolini, Renzo; Möhwald, Helmuth; Skirtach, Andre G

2014-09-15

366

Fabrication of hollow porous shells of calcium carbonate from self-organizing media  

Microsoft Academic Search

A RICH variety of elaborate microscopic skeletal structures composed of inorganic materials are produced in nature1. Such complex, three-dimensional structures, if produced synthetically, could find important applications as light-weight ceramics, catalyst supports, biomedical implants and robust membranes for high-temperature separation technology. Here we describe a method for synthesizing hollow porous shells of crystalline calcium carbonate (aragonite) that resemble the coccospheres

Dominic Walsh; Stephen Mann

1995-01-01

367

A biomineralization model for the incorporation of trace elements into foraminiferal calcium carbonate  

Microsoft Academic Search

Measurements of SrCa of benthic foraminifera show a linear decrease with water depth which is superimposed upon significant variability identified by analyses of individual foraminifera. New data for CdCa support previous work in defining a contrast between waters shallower and deeper than ? 2500 m.Measured element partition coefficients in foraminiferal calcium carbonate relative to sea water (D) have been described

H. Elderfield; C. J. Bertram; J. Erez

1996-01-01

368

Effect of magnetic water treatment on calcium carbonate precipitation: Influence of the pipe material  

Microsoft Academic Search

The main purpose of this work was to investigate the influence of the material of the pipe, through which scalant water (4mM of CaCO3) was magnetically treated, on the calcium carbonate precipitation process. Tested solutions were exposed to a magnetic field (MF) of 0.16T for 15min with different flow rates (0.54–0.94Lmin?1) and pH (6–7.5). Magnetic water treatment and pipe material

F. Alimi; M. M. Tlili; M. Ben Amor; G. Maurin; C. Gabrielli

2009-01-01

369

Facile surface modification of nanoprecipitated calcium carbonate by adsorption of sodium stearate in aqueous solution  

Microsoft Academic Search

A simple and solvent free two-step process for nanosized and surface-modified precipitated calcium carbonate (ns-PCC) synthesis has been proposed. Synthesized ns-PCC was thoroughly characterized by infra-red (IR), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Langmuir adsorption study. Dynamic laser scattering (DLS) results on particle size showed a good correlation with those obtained by the proposed empirical model. Two aspects

Hoang Vinh Tran; Lam Dai Tran; Hoang Dinh Vu; Hoang Thai

2010-01-01

370

Shadowing in inelastic scattering of muons on carbon, calcium and lead at low x Bj  

Microsoft Academic Search

Nuclear shadowing is observed in the per-nucleon cross sections of positive muons on carbon, calcium and lead as compared to deuterium. The data were taken by Fermilab experiment E665 using inelastically scattered muons of mean incident momentum 470 GeV\\/c. Cross-section ratios are presented in the kinematic region 0.0001< x Bj <0.56 and 0.1< Q 2<80 GeV2. The data are consistent

M. R. Adams; S. Aïd; P. L. Anthony; D. A. Averill; M. D. Baker; B. R. Baller; A. Banerjee; A. A. Bhatti; U. Bratzler; H. M. Braun; H. Breidung; W. Busza; T. J. Carroll; H. L. Clark; J. M. Conrad; R. Davisson; I. Derado; S. K. Dhawan; F. S. Dietrich; W. Dougherty; T. Dreyer; V. Eckardt; U. Ecker; M. Erdmann; G. Y. Fang; J. Figiel; R. W. Finlay; H. J. Gebauer; D. F. Geesaman; K. A. Griffioen; R. S. Guo; J. Haas; C. Halliwell; D. Hantke; K. H. Hicks; V. W. Hughes; H. E. Jackson; D. E. Jaffe; G. Jancso; D. M. Jansen; Z. Jin; S. Kaufman; R. D. Kennedy; E. R. Kinney; T. Kirk; H. G. E. Kobrak; A. V. Kotwal; S. Kunori; J. J. Lord; H. J. Lubatti; D. McLeod; P. Madden; S. Magill; A. Manz; H. Melanson; D. G. Michael; H. E. Montgomery; J. G. Morfin; R. B. Nickerson; J. Novak; S. O'Day; K. Olkiewicz; L. Osborne; R. Otten; V. Papavassiliou; B. Pawlik; F. M. Pipkin; D. H. Potterveld; E. J. Ramberg; A. Röser; J. J. Ryan; C. W. Salgado; A. Salvarani; H. Schellman; M. Schmitt; N. Schmitz; K. P. Schüler; G. Siegert; A. Skuja; G. A. Snow; S. Söldner-Rembold; P. Spentzouris; H. E. Stier; P. Stopa; R. A. Swanson; H. Venkataramania; M. Wilhelm; Richard Wilson; W. Wittek; S. A. Wolbers; A. Zghiche; T. Zhao

1995-01-01

371

Shadowing in inelastic scattering of muons on carbon, calcium and lead at low x Bj  

Microsoft Academic Search

Nuclear shadowing is observed in the per-nucleon cross sections of positive muons on carbon, calcium and lead as compared to deuterium. The data were taken by Fermilab experiment E665 using inelastically scattered muons of mean incident momentum 470 GeV\\/c. Cross-section ratios are presented in the kinematic region 0.0001xBjQ22. The data are consistent with no significant ? orQ2 dependence at fixedxBj.

M. R. Adams; S. Aïd; P. L. Anthony; D. A. Averill; M. D. Baker; B. R. Baller; A. Banerjee; A. A. Bhatti; U. Bratzler; H. M. Braun; H. Breidung; W. Busza; T. J. Carroll; H. L. Clark; J. M. Conrad; R. Davisson; I. Derado; S. K. Dhawan; F. S. Dietrich; W. Dougherty; T. Dreyer; V. Eckardt; U. Ecker; M. Erdmann; G. Y. Fang; J. Figiel; R. W. Finlay; H. J. Gebauer; D. F. Geesaman; K. A. Griffioen; R. S. Guo; J. Haas; C. Halliwell; D. Hantke; K. H. Hicks; V. W. Hughes; H. E. Jackson; D. E. Jaffe; G. Jancso; D. M. Jansen; Z. Jin; S. Kaufman; R. D. Kennedy; E. R. Kinney; T. Kirk; H. G. E. Kobrak; A. V. Kotwal; S. Kunori; J. J. Lord; H. J. Lubatti; D. McLeod; P. Madden; S. Magill; A. Manz; H. Melanson; D. G. Michael; H. E. Montgomery; J. G. Morfin; R. B. Nickerson; J. Novak; S. O'Day; K. Olkiewicz; L. Osborne; R. Otten; V. Papavassiliou; B. Pawlik; F. M. Pipkin; D. H. Potterveld; E. J. Ramberg; A. Röser; J. J. Ryan; C. W. Salgado; A. Salvarani; H. Schellman; M. Schmitt; N. Schmitz; K. P. Schüler; G. Siegert; A. Skuja; G. A. Snow; S. Söldner-Rembold; P. Spentzouris; H. E. Stier; P. Stopa; R. A. Swanson; H. Venkataramania; M. Wilhelm; Richard Wilson; W. Wittek; S. A. Wolbers; A. Zghiche; T. Zhao

1995-01-01

372

Calcium carbonate precipitation induced by a bacterium strain isolated from an oligotrophic cave in Central China  

Microsoft Academic Search

A heterotrophic Bacillus sp. strain (5C-1) was isolated from Heshang cave, an oligotrophic karst cave in the middle reaches of Yangtze River, and\\u000a identified by BIOLOG and 16S rDNA sequencing. Bacterially induced formation of calcium carbonate by 5C-1 was investigated\\u000a in several comparative experimental sets with or without the cell and extracellular enzymes. The temporal variations of both\\u000a the amount

Hongmei Wang; Cuiping Zeng; Qianying Liu; Deng Liu; Xuan Qiu; Linfeng Gong

2010-01-01

373

Stress development during drying of calcium carbonate suspensions containing carboxymethylcellulose and latex particles  

Microsoft Academic Search

Stress development during drying of coatings produced from aqueous dispersions of calcium carbonate particles in the presence and absence of organic binders was studied using a controlled-environment stress apparatus that simultaneously monitored drying stress, weight loss, and relative humidity. Specifically, the influence of two organic binders on drying stress evolution was investigated: (1) carboxymethylcellulose, a water-soluble viscosifying aid, and (2) a styrene–butadiene

Pär Wedin; Carlos J Martinez; Jennifer A Lewis; John Daicic; Lennart Bergström

2004-01-01

374

Involvement of VKORC1 in the inhibition of calcium oxalate crystal formation in HK-2 cells.  

PubMed

The vitamin K epoxide reductase complex subunit 1 (VKORC1), the rate-limiting enzyme for vitamin K recycling, is significantly down-regulated in the kidneys of urolithiasis patients. This study searched for direct evidence to define the inhibitory activity of VKORC1 against calcium oxalate (CaOx) crystal formation. In the experiment of VKORC1 overexpression, HK-2 cells were transfected with the pFLAG-CMV-7.1-VKORC1 plasmid as a pFLAG-CMV-7.1-VKORC1 transfection group or the pFLAG-CMV-7.1 plasmid as a pFLAG-CMV-7.1 control group. In the experiment of VKORC1 knockdown, HK-2 cells were transfected with the PGPU6/GFP/Neo-VKORC1shRNA-2 as a PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group or the PGPU6/GFP/Neo-shRNA-NC plasmid as a PGPU6/GFP/Neo-shRNA-NC control group. The expression of VKORC1 in HK-2 cells was detected by real-time quantitative PCR and Western blotting. The CaOx crystal formation was observed under the laser-scanning confocal microscope. It was found that the expression levels of VKORC1 mRNA and protein were significantly higher in the pFLAG-CMV-7.1-VKORC1 transfection group than in the pFLAG-CMV-7.1 control group (P<0.01). The number of CaOx crystals in HK-2 cells incubated in fluorescently labeled CaOx monohydrate (COM) crystal medium for 48 h was 14±4 per field (100×) in the pFLAG-CMV-7.1-VKORC1 transfection group and 26±5 per field (100×) in the pFLAG-CMV-7.1 control group respectively under the laser-scanning confocal microscope. The amount of CaOx crystal aggregation and formation in the pFLAG-CMV-7.1-VKORC1 transfection group was significantly reduced as compared with the pFLAG-CMV-7.1 control group (P<0.05). The expression levels of VKORC1 mRNA and protein were significantly lower in the PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group than in the PGPU6/GFP/Neo-shRNA-NC control group (P<0.05). The number of CaOx crystals in HK-2 cells incubated in fluorescently labeled COM crystal medium was 65±11 per field (100×) in the PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group and 24±6 per field (100×) in the PGPU6/GFP/Neo-shRNA-NC control group respectively under the laser-scanning confocal microscope. The amount of CaOx crystal aggregation and formation in the PGPU6/GFP/Neo-VKORC1shRNA-2 transfection group was significantly increased as compared with the PGPU6/GFP/Neo-shRNA-NC control group (P<0.05). These findings suggested that the VKORC1 protein could inhibit CaOx salt crystallization, adhesion and aggregation. This research would help us to understand the mechanisms involving the interaction between crystallization and epithelial cells and the formation of CaOx. PMID:24939302

Hu, Bo; Wu, Hao-ran; Ma, Zhi-yong; Wu, Zhuan-chang; Lu, Ying-mei; Shi, Guo-wei

2014-06-01

375

Tribological and Antioxidation Synergistic Effect Study of Sulfonate-Modified Nano Calcium Carbonate  

PubMed Central

A middle base number sulphonate-modified nano calcium carbonate (SMC) with an average size of 35 nm was synthesized, and its tribological and antioxidation synergistic behaviors with ashless antioxidant N-phenyl-?-naphthylamine (T531) in hydrogenated oil (5Cst) were evaluated. The results demonstrate that adding this synethesized additive even at a low amount (<2.0 wt.%) can evidently improve its load-carrying capacity by 1.5 times and enhance its antiwear performance; in addition, the friction-reducing effect of additive in the high load was better than that in low load. The SMC have a good synergistic antioxidation effect with T531, which verifies the nano calcium carbonate compound was a kind of multifunctional and high-performance additive. The chemical composition of the rubbing surface which formed on the boundary film was analyzed by using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The results indicating that the excellent antiwear and load-carrying performance could be attributed to the forming of boundary lubrication film which composed of calcium carbonate, oxides, ferrites, sulphide and FeSO4, and so on. Its ability to increase oxidation free energy of base oil is the main reason for increasing its antioxidant collaboration property with ashless antioxidant T531. PMID:23658705

Zhongyi, He; Liping, Xiong; Sheng, Han; Aixi, Chen; Jianwei, Qiu; Xisheng, Fu

2013-01-01

376

Preparation and characterization of ultra-hydrophobic calcium carbonate nanoparticles  

NASA Astrophysics Data System (ADS)

Anionic surfactants based on fatty acids are usually used to modify the particle surface properties of CaCO3 with the aim to enhance its dispersion and compatibility with polymer matrices. In this study sodium oleate was used for the preparation of ultrahydrophobic CaCO3 nanoparticles using a wet carbonation route. The effect of sodium oleate on the characteristics, particle size, morphology, surface potential, thermal decomposition and hydrophobicity of CaCO3, was investigated using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), Zeta potential, thermogravimetric analysis (TGA) and water contact angle measurement (WCA). The results showed that the addition of 2 wt% sodium oleate helps in reducing the particle size from 2 ?m length scalenohedral particles to 45 nm rhombohedral particles and modifying of the hydrophobic property of CaCO3.

Barhoum, A.; El-Sheikh, S. M.; Morsy, F.; El-Sherbiny, S.; Reniers, F.; Dufour, T.; Delplancke, M. P.; Van Assche, G.; Rahier, H.

2014-08-01

377

The relationship between blood carbon dioxide, acid-base balance and calcium metabolism in the hyperthermic laying hen  

E-print Network

THE RELATIONSHIP BETWEEN BLOOD CARBON DIOXIDE, ACID-BASE BALANCE AND CALCIUM METABOLISM IN THE HYPERTHERMIC LAYING HEN A Thesis by YOSHITAKA ONO Subrnittcd to thc Office of Graduate Studies of Texas AA, M University in partial I...'ulfillmcnt of thc requirements for thc dcgrcc of MASTER OF SCIENCE Dcccmbcr 1988 Major Sulajccu Poultry Scicncc THE RELATIONSHIP BETWEEN BLOOD CARBON DIOXIDE, ACID-BASE BALANCE AND CALCIUM METABOLISM IN THE HYPERTHERMIC LAYING HEN A Thesis by YOSHITAKA ONO...

Ono, Yoshitaka

2012-06-07

378

Crystal Structure of Metastasis-Associated Protein S100A4 in the Active, Calcium-Bound Form  

SciTech Connect

S100A4 (metastasin) is a member of the S100 family of calcium-binding proteins that is directly involved in tumorigenesis. Until recently, the only structural information available was the solution NMR structure of the inactive calcium-free form of the protein. Here we report the crystal structure of human S100A4 in the active calcium-bound state at 2.03 {angstrom} resolution that was solved by molecular replacement in the space group P6{sub 5} with two molecules in the asymmetric unit from perfectly merohedrally twinned crystals. The Ca{sup 2+}-bound S100A4 structure reveals a large conformational change in the three-dimensional structure of the dimeric S100A4 protein upon calcium binding. This calcium-dependent conformational change opens up a hydrophobic binding pocket that is capable of binding to target proteins such as annexin A2, the tumor-suppressor protein p53 and myosin IIA. The structure of the active form of S100A4 provides insight into its interactions with its binding partners and a better understanding of its role in metastasis.

Pathuri, P.; Vogeley, L.; Luecke, H.

2009-05-21

379

Dissolved Calcium and Magnesium Carbonates Promote Arsenate Release From Ferrihydrite in Flow Systems  

NASA Astrophysics Data System (ADS)

Field data from water systems around the world have shown that arsenic can reach toxic concentrations in dynamic groundwater systems. This is generally in contrast to analogous static systems at circumneutral pH, where arsenic is strongly retained by sorption to iron (hydr)oxides. Our research examines the effect of calcium and magnesium carbonates on As(V) mobility. In both dynamic flow and static experiments, arsenate was pre- sorbed to poorly crystalline iron hydroxides (1-10% sorption capacity), with varying aqueous compositions including calcium, magnesium, carbonate, sulfate, lactate, and other common groundwater species (pH 7.5-8). Thus we investigated how the dissolution of common carbonate minerals, specifically CaCO3 and MgCO3, affect arsenic behavior in the context of groundwater solutions. Under static (batch) conditions, no measurable arsenic (<10 ?g/L) is released into solutions containing alkaline earth metals (AEMs) and carbonates. When elevated concentrations of AEMs and carbonate are introduced by dynamic flow, however, arsenic is mobilized at up to 500 ?g/L, releasing significant proportions the total arsenic present. This is only the case when both of these species are present; with other common ion pairs, little to no arsenic is released. These results indicate that arsenate adsorption is kinetically controlled under flow conditions, resulting in very different mobility relative to otherwise equivalent static systems. Furthermore, the combination of alkaline earth metals and carbonates promotes As(V) mobility in column-based systems. We propose that these phenomena indicate a combination of physical and chemical effects by which diffusion limitation becomes dominant in limiting arsenic sorption in flow systems. Many carbonate-buffered aquifers, as well as those undergoing rapid mineralization of organic matter, could be affected by these processes of AEM-carbonate-limited sorption and increased arsenic mobility.

Saalfield, S. L.; Bostick, B. C.

2007-12-01

380

Polycrystalline apatite synthesized by hydrothermal replacement of calcium carbonates  

NASA Astrophysics Data System (ADS)

Aragonite and calcite single crystals can be readily transformed into polycrystalline hydroxyapatite pseudomorphs by hydrothermal treatment in a (NH 4) 2HPO 4 solution. Scanning electron microscopy of the reaction products showed that the transformation of aragonite to apatite is characterised by the formation of a sharp interface between the two phases and by the development of intracrystalline porosity in the hydroxyapatite phase. In addition, electron backscattered diffraction (EBSD) imaging showed that the c-axis of apatite is predominantly oriented perpendicular to the reaction front with no crystallographic relationship to the aragonite lattice. However, the Ca isotopic composition of the parent aragonite, measured by thermal ionization mass spectrometry was inherited by the apatite product. Hydrothermal experiments conducted with use of phosphate solutions prepared with water enriched in 18O (97%) further revealed that the 18O from the solution is incorporated in the product apatite, as measured by micro-Raman spectroscopy. Monitoring the distribution of 18O with Raman spectroscopy was possible because the incorporation of 18O in the PO 4 group of apatite generates four new Raman bands at 945.8, 932, 919.7 and 908.8 cm -1, in addition to the ?1(PO 4) symmetric stretching band of apatite located at 962 cm -1, which can be assigned to four 18O-bearing PO 4 species. The relative intensities of these bands reflect the 18O content in the PO 4 group of the apatite product. By using equilibrated and non-equilibrated solutions, with respect to the 18O distribution between aqueous phosphate and water, we could show that the concentration of 18O in the apatite product is linked to the degree of 18O equilibration in the solution. The textural and chemical observations are indicative of a coupled mechanism of aragonite dissolution and apatite precipitation taking place at a moving reaction interface.

Kasioptas, Argyrios; Geisler, Thorsten; Perdikouri, Christina; Trepmann, Claudia; Gussone, Nikolaus; Putnis, Andrew

2011-06-01

381

The crystallization of tough thermoplastic resins in the presence of carbon fibers  

NASA Technical Reports Server (NTRS)

The crystallization kinetics of the thermoplastic resins poly(phenylene sulfide) (PPS) and poly(aryl-ether-ether-ketone) (PEEK) in the presence and in the abscence of carbon fibers was studied. How carbon fiber surfaces in composites affect the crystallization of tough thermoplastic polymers that may serve as matrix resins were determined. The crystallization kinetics of such substances can provide useful information about the crystallization mechanisms and, thus, indicate if the presence of carbon fibers cause any changes in such mechanisms.

Theil, M. H.

1986-01-01

382

Carbonation as a binding mechanism for coal/calcium hydroxide pellets. Technical report, December 1, 1992--February 28, 1993  

SciTech Connect

Pelletization of fine coal with calcium hydroxide, a sulfur capturing sorbent, represents a method to produce a fuel which will burn in compliance with the recently passed Clean Air Act Amendments (CAAA`s). To harden the pellets, the reaction of carbon dioxide with calcium hydroxide, referred to as carbonation, is being studied. Carbonation forms a bonding matrix of calcium carbonate. This is a two-year research program. This report covers the second quarter of the second year. Research is indicating that 5 to 10 wt% calcium hydroxide pellets can be produced via a roller-and-die pellet mill and air cured to achieve sufficient quality for handling and transportation. This quarter, 1/2 inch-diameter pellets containing 10% calcium hydroxide were demonstrated to gradually react with atmospheric carbon dioxide (3 days) while air drying to achieve compressive strengths equivalent to those attained for fully dried pellets which had been carbonated for one-hour with 100% commercial grade carbon dioxide. It was also demonstrated that an organic, adhesive binder, corn starch, can be very effective at producing strong pellets but drying is required before appreciable pellet strength is attained. For pellets containing 2 wt% corn starch, it was determined that less than 50% of the ultimate strength was achieved as the pellets were dried from 20 wt% to 5 wt% moisture. Strength improved considerably as the pellet moisture content was reduced below 5 wt%.

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

1993-05-01

383

Tuning the dissolution kinetics of wollastonite via chelating agents for CO2 sequestration with integrated synthesis of precipitated calcium carbonates.  

PubMed

Carbon mineralization has recently received much attention as one of the most promising options for CO2 sequestration. The engineered weathering of silicate minerals as a means of permanent carbon storage has unique advantages such as the abundance of naturally occurring calcium and magnesium-bearing minerals and the formation of environmentally-benign and geologically stable solids via a thermodynamically favored carbonation reaction. However, several challenges need to be overcome to successfully deploy carbon mineralization on a large scale. In particular, the acceleration of the rate-limiting mineral dissolution step along with process optimization is essential to ensure the economic feasibility of the proposed carbon storage technology. In this study, the effect of various types of chelating agents on the dissolution rate of calcium-bearing silicate mineral, wollastonite, was explored to accelerate its weathering rate. It was found that chelating agents such as acetic acid and gluconic acid significantly improved the dissolution kinetics of wollastonite even at a much diluted concentration of 0.006 M by complexing with calcium in the mineral matrix. Calcium extracted from wollastonite was then reacted with a carbonate solution to form precipitated calcium carbonate (PCC), while tuning the particle size and the morphological structure of PCC to mimic commercially available PCC-based filler materials. PMID:23925694

Zhao, Huangjing; Park, Youngjune; Lee, Dong Hyun; Park, Ah-Hyung Alissa

2013-09-28

384

Incorporation of lead into calcium carbonate granules secreted by earthworms living in lead contaminated soils  

NASA Astrophysics Data System (ADS)

The influence of soil organisms on metal mobility and bioavailability in soils is not currently fully understood. We conducted experiments to determine whether calcium carbonate granules secreted by the earthworm Lumbricus terrestris could incorporate and immobilise lead in lead- and calcium-amended artificial soils. Soil lead concentrations were up to 2000 mg kg -1 and lead:calcium ratios by mass were 0.5-8. Average granule production rates of 0.39 ± 0.04 mg calcite earthworm -1 day -1 did not vary with soil lead concentration. The lead:calcium ratio in granules increased significantly with that of the soil ( r2 = 0.81, p = 0.015) with lead concentrations in granules reaching 1577 mg kg -1. X-ray diffraction detected calcite and aragonite in the granules with indications that lead was incorporated into the calcite at the surface of the granules. In addition to the presence of calcite and aragonite X-ray absorption spectroscopy indicated that lead was present in the granules mainly as complexes sorbed to the surface but with traces of lead-bearing calcite and cerussite. The impact that lead-incorporation into earthworm calcite granules has on lead mobility at lead-contaminated sites will depend on the fraction of total soil lead that would be otherwise mobile.

Fraser, A.; Lambkin, D. C.; Lee, M. R.; Schofield, P. F.; Mosselmans, J. F. W.; Hodson, M. E.

2011-05-01

385

Climate warming shifts carbon allocation from stemwood to roots in calcium-depleted spruce forests  

USGS Publications Warehouse

Increased greening of northern forests, measured by the Normalized Difference Vegetation Index (NDVI), has been presented as evidence that a warmer climate has increased both net primary productivity (NPP) and the carbon sink in boreal forests. However, higher production and greener canopies may accompany changes in carbon allocation that favor foliage or fine roots over less decomposable woody biomass. Furthermore, tree core data throughout mid- and northern latitudes have revealed a divergence problem (DP), a weakening in tree ring responses to warming over the past half century that is receiving increasing attention, but remains poorly understood. Often, the same sites exhibit trend inconsistency phenomenon (TIP), namely positive, or no trends in growing season NDVI where negative trends in tree ring indexes are observed. Here we studied growth of two Norway spruce (Picea abies) stands in western Russia that exhibited both the DP and TIP but were subject to soil acidification and calcium depletion of differing timing and severity. Our results link the decline in radial growth starting in 1980 to a shift in carbon allocation from wood to roots driven by a combination of two factors: (a) soil acidification that depleted calcium and impaired root function and (b) earlier onset of the growing season that further taxed the root system. The latter change in phenology appears to act as a trigger at both sites to push trees into nutrient limitation as the demand for Ca increased with the longer growing season, thereby causing the shift in carbon allocation.

Lapenis, Andrei Gennady; Lawrence, Gregory B.; Heim, Alexander; Zheng, Chengyang; Shortle, Walter

2013-01-01

386

Isotactic polypropylene carbon nanotube composites -- crystallization and ordering behavior  

NASA Astrophysics Data System (ADS)

The field of Polymer Nanocomposites (PNCs) is growing steadily in recent years. We use carbon nanotubes (CNTs) to affect the crystallization behavior of the polymers. Isotactic Polypropylene (iPP) is very widely used and is a good model system to understand the physics of other similar polymers. iPP/CNT PNCs form ?, ?, and ? crystallographic phases under a variety of crystallization conditions: non-isothermal and isothermal melt crystallization, shear, stress, fiber extrusion, etc. The crystal growth is altered from spherulitic to ?-fibrillar upon the nucleation effect of CNTs. We are studying the effect of different temperature treatment schemes and different isothermal crystallization conditions. We found also that the smectic ordering in iPP is improved by the introduction of CNTs. We use Differential Scanning Calorimetry, Wide Angle X-ray scattering, Microscopic Transmission Ellipsometry and Avrami analysis. Research supported by: Assumption College Faculty Development Grant, funding for students' stipends, instrumentation and supplies, the NSF Polymers Program of the DMR, grant (DMR-0602473) and NASA grant (NAG8-1167).

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

2010-03-01

387

Mechanochemical dissociation of calcium carbonate: laboratory data and relation to natural emissions of CO 2  

NASA Astrophysics Data System (ADS)

This paper investigates the possible role of mechanochemical CO 2 production due to stimulation from the action of friction on calcite. This experimentation has two objectives: firstly, to obtain information on the effect of the mechanical disassociation of carbon dioxide from the carbonates and, secondly, to simulate the conditions that may arise during a tectonic action. The action of disassociation has been observed on pure calcium carbonate from analyses ground at different times in a ring-roller mill. The ring-roller mill is a grinding system that mainly works through friction and, to a lesser extent, by non-hydrostatic compression. It has been observed that the grinding action determines an abundant release of carbon dioxide, with a non-linear trend that emulates the trend in the decrease in crystallinity. This indicates a close connection between crystallinity and the dissociation of carbonate. The Authors hypothesize a carbon dioxide release mechanism linked to the factures induced by the friction and the increase in the structural disorder induced in the lattice by the plastic sliding. This mechanism could play an important role in the natural release of CO 2, along with the other carbon dioxide sources that are already known of.

Martinelli, Giovanni; Plescia, Paolo

2004-05-01

388

Microscopic Evidence for a dense liquid phase of calcium carbonate (Invited)  

NASA Astrophysics Data System (ADS)

In the classical sense, minerals are presumed to nucleate directly from solution by overcoming a size-dependent free energy barrier that scales as the ratio of the macroscopic mineral-water interfacial tension cubed to the square of the thermodynamic supersaturation. However, experimental observations of the early stages of calcium carbonate mineralization demonstrate that under certain conditions formation of the crystalline polymorphs is preceded by the apparently spontaneous appearance of nanoscopic clusters that aggregate to produce metastable amorphous phases. This aggregation-based pathway is seemingly at odds with classical expectations. This research (Wallace et al., in press, Science) uses computational approaches to characterize the thermodynamic and dynamic properties of hydrated calcium carbonate cluster species, which are thus far only loosely constrained by experimental investigations. Replica exchange molecular dynamics simulations are employed to probe the initial formation of the clusters and lattice gas simulations are used to explore the general behavior of clusters at the onset of mineralization. The results suggest the growth of carbonate clusters may indeed proceed in the absence of any significant thermodynamic barrier. Moreover, the dynamical properties of the clusters are consistent with those of a dense liquid phase. Coalescence and dehydration of the nanoscale droplets result in the formation of a phase whose structure is consistent with that of amorphous calcium carbonate. These findings indicate that a spontaneous liquid-liquid phase separation may occur within the range of supersaturations spanned by natural waters. The coexistence of the dense and dilute liquid phases is described by a liquid-liquid binodal that may express a lower critical point near ambient temperature. Though liquid-liquid separation in simulations of the CaCO3-H2O system is an unexpected result, it suggests a means of generating nano- and mesoscopic phases consistent with established phase separation mechanisms and experimental observations.

Wallace, A. F.; Hedges, L.; Fernandez-Martinez, A.; Raiteri, P.; Gale, J. D.; Waychunas, G.; Whitelam, S.; Banfield, J. F.; De Yoreo, J. J.

2013-12-01

389

Interaction of organic compounds with calcium carbonate-II. Organo-carbonate association in Recent sediments  

Microsoft Academic Search

Surface area measurements as well as organic carbon, nitrogen and phosphorus analyses on various grain size fractions of carbonate mud samples confirm that in natural environments of carbonate deposition, surface sorption processes take place which are similar to those described earlier for dissolved organics and artificially suspended calcite particles in both seawater and synthetic solutions. The specific surface area of

Erwin Suess

1973-01-01

390

Constraining the cause of the end-Guadalupian extinction with coupled records of carbon and calcium isotopes  

NASA Astrophysics Data System (ADS)

A negative ?C13 excursion in carbonate sediments near the Guadalupian/Lopingian (Middle/Late Permian) boundary has been interpreted to have resulted from a large carbon cycle disturbance during the end-Guadalupian extinction event (ca. 260 Ma). However, the carbon isotope data alone are insufficient to uniquely determine the type and magnitude of perturbation to the global carbon cycle. Calcium isotopes can be used to further constrain the cause of a carbon isotope excursion because the carbon and calcium cycles are coupled via CaCO3 burial. In this study, we present coupled carbon and calcium isotope records from three Guadalupian-Lopingian (G/L) sections in China (Penglaitan and Chaotian) and Turkey (Köserelik Tepe). The ?C13 and ?Ca44/40 records differ among our studied sections and do not co-vary in the same manner. No section shows ?C13 and ?Ca44/40 changes consistent with massive, rapid volcanic CO2 emissions or methane clathrate destabilization. Additionally, many sections with large (>3‰) changes in ?C13 exhibit ?O18 evidence for diagenetic alteration. Only one section exhibits a large excursion in the ?Ca44/40 of limestone but the absence of a similar excursion in the ?Ca44/40 of conodont apatite suggests that the limestone excursion reflects a mineralogical control rather than a perturbation to the global calcium cycle. Hence, we interpret the large isotopic changes observed in some sections to have resulted from local burial conditions or diagenetic effects, rather than from a large carbon and calcium cycle disturbance. Perturbations to the global carbon and calcium cycles across the G/L transition were much less intense than the disturbances that occurred across the subsequent Permian-Triassic boundary. This finding is consistent with the much smaller magnitude of the end-Guadalupian extinction relative to the end-Permian.

Jost, Adam B.; Mundil, Roland; He, Bin; Brown, Shaun T.; Altiner, Demir; Sun, Yadong; DePaolo, Donald J.; Payne, Jonathan L.

2014-06-01

391

Crystal Structures of the GCaMP Calcium Sensor Reveal the Mechanism of Fluorescence Signal Change and Aid Rational Design  

SciTech Connect

The genetically encoded calcium indicator GCaMP2 shows promise for neural network activity imaging, but is currently limited by low signal-to-noise ratio. We describe x-ray crystal structures as well as solution biophysical and spectroscopic characterization of GCaMP2 in the calcium-free dark state, and in two calcium-bound bright states: a monomeric form that dominates at intracellular concentrations observed during imaging experiments and an unexpected domain-swapped dimer with decreased fluorescence. This series of structures provides insight into the mechanism of Ca{sup 2+}-induced fluorescence change. Upon calcium binding, the calmodulin (CaM) domain wraps around the M13 peptide, creating a new domain interface between CaM and the circularly permuted enhanced green fluorescent protein domain. Residues from CaM alter the chemical environment of the circularly permuted enhanced green fluorescent protein chromophore and, together with flexible inter-domain linkers, block solvent access to the chromophore. Guided by the crystal structures, we engineered a series of GCaMP2 point mutants to probe the mechanism of GCaMP2 function and characterized one mutant with significantly improved signal-to-noise. The mutation is located at a domain interface and its effect on sensor function could not have been predicted in the absence of structural data.

Akerboom, Jasper; Velez Rivera, Jonathan D.; Rodriguez Guilbe, María M.; Alfaro Malavé, Elisa C.; Hernandez, Hector H.; Tian, Lin; Hires, S. Andrew; Marvin, Jonathan S.; Looger, Loren L.; Schreiter, Eric R.; (MIT); (Puerto Rico); (HHMI)

2009-03-16

392

Isolation of a Crystal Matrix Protein Associated with Calcium Oxalate Precipitation in Vacuoles of Specialized Cells1  

PubMed Central

The formation of calcium (Ca) oxalate crystals is considered to be a high-capacity mechanism for regulating Ca in many plants. Ca oxalate precipitation is not a stochastic process, suggesting the involvement of specific biochemical and cellular mechanisms. Microautoradiography of water lettuce (Pistia stratiotes) tissue exposed to 3H-glutamate showed incorporation into developing crystals, indicating potential acidic proteins associated with the crystals. Dissolution of crystals leaves behind a crystal-shaped matrix “ghost” that is capable of precipitation of Ca oxalate in the original crystal morphology. To assess whether this matrix has a protein component, purified crystals were isolated and analyzed for internal protein. Polyacrylamide gel electrophoresis revealed the presence of one major polypeptide of about 55 kD and two minor species of 60 and 63 kD. Amino acid analysis indicates the matrix protein is relatively high in acidic amino acids, a feature consistent with its solubility in formic acid but not at neutral pH. 45Ca-binding assays demonstrated the matrix protein has a strong affinity for Ca. Immunocytochemical localization using antibody raised to the isolated protein showed that the matrix protein is specific to crystal-forming cells. Within the vacuole, the surface and internal structures of two morphologically distinct Ca oxalate crystals, raphide and druse, were labeled by the antimatrix protein serum, as were the surfaces of isolated crystals. These results demonstrate that a specific Ca-binding protein exists as an integral component of Ca oxalate crystals, which holds important implications with respect to regulation of crystal formation. PMID:14555781

Li, Xingxiang; Zhang, Dianzhong; Lynch-Holm, Valerie J.; Okita, Thomas W.; Franceschi, Vincent R.

2003-01-01

393

Self-diffusion parameters in carbon-subgroup crystals  

SciTech Connect

Self-diffusion parameters have been calculated for crystals of the carbon subgroup C (diamond), Si, Ge, {alpha}-Sn, Pb. It is shown that consideration of quantum effects in the delocalization of atoms leads to the following effect: at low temperatures (below the Debye temperature), the self-diffusion parameters depend strongly on temperature and the self-diffusion entropy is negative: s{sub d} < 0. With an increase in temperature, the function s{sub d} takes positive values. All thermodynamic parameters of self-diffusion in semiconductor crystals of carbon subgroup were calculated without any fitting parameters. The temperature dependences of self-diffusion parameters were studied for IVa-subgroup crystals upon isobaric heating from T = 0 K to the melting point. A good agreement with both experimental data and theoretical estimates obtained by other researchers is obtained. The correlation between the entropy and enthalpy of self-diffusion, as well as the correlation between the volume and entropy of self-diffusion for the entire temperature range under consideration, are discussed.

Magomedov, M. N., E-mail: mahmag@iwt.ru [Russian Academy of Sciences, Institute for Geothermal Research, Dagestan Scientific Center (Russian Federation)

2010-03-15

394

Genetics and mechanisms of crystal deposition in calcium pyrophosphate deposition disease.  

PubMed

Calcium pyrophosphate deposition (CPPD) disease (common in older adults) can be asymptomatic, associated with osteoarthritis, or can present as acute/chronic inflammatory arthritis. Due to the phenotypic complexity of CPPD, the European League Against Rheumatism (EULAR) recently made recommendations on terminology, diagnosis, and management based on available research evidence and expert consensus. There are no disease-modifying treatments for CPPD disease, and therapy remains nonspecific with the use of anti-inflammatory and analgesic drugs. For years, it has been known that inorganic phosphate and pyrophosphate regulate the formation of CPP or hydroxyapatite crystals. The discovery of ANKH (human homologue of progressive ankylosis) mutations in familial CPPD disease confirmed the importance of phosphate/pyrophosphate homeostasis in CPPD, with ANKH being a regulator of inorganic pyrophosphate transport. Despite progress in our understanding of the function of ANKH, much remains to be investigated. This review summarizes the genetic basis of this disease and focuses on the challenges of research in this area. PMID:22198832

Tsui, Florence W L

2012-04-01

395

Osteopontin knockdown in the kidneys of hyperoxaluric rats leads to reduction in renal calcium oxalate crystal deposition.  

PubMed

Osteopontin (OPN) expression is increased in kidneys of rats with ethylene glycol (EG) induced hyperoxaluria and calcium oxalate (CaOx) nephrolithiasis. The aim of this study is to clarify the effect of OPN knockdown by in vivo transfection of OPN siRNA on deposition of CaOx crystals in the kidneys. Hyperoxaluria was induced in 6-week-old male Sprague-Dawley rats by administering 1.5% EG in drinking water for 2 weeks. Four groups of six rats each were studied: Group A, untreated animals (tap water); Group B, administering 1.5% EG; Group C, 1.5% EG with in vivo transfection of OPN siRNA; Group D, 1.5% EG with in vivo transfection of negative control siRNA. OPN siRNA transfections were performed on day 1 and 8 by renal sub-capsular injection. Rats were killed at day 15 and kidneys were removed. Extent of crystal deposition was determined by measuring renal calcium concentrations and counting renal crystal deposits. OPN siRNA transfection resulted in significant reduction in expression of OPN mRNA as well as protein in group C compared to group B. Reduction in OPN expression was associated with significant decrease in crystal deposition in group C compared to group B. Specific suppression of OPN mRNA expression in kidneys of hyperoxaluric rats leads to a decrease in OPN production and simultaneously inhibits renal crystal deposition. PMID:24619192

Tsuji, Hidenori; Shimizu, Nobutaka; Nozawa, Masahiro; Umekawa, Tohru; Yoshimura, Kazuhiro; De Velasco, Marco A; Uemura, Hirotsugu; Khan, Saeed R

2014-06-01

396

Ion microprobe measurement of strontium isotopes in calcium carbonate with application to salmon otoliths  

USGS Publications Warehouse

The ion microprobe has the capability to generate high resolution, high precision isotopic measurements, but analysis of the isotopic composition of strontium, as measured by the 87Sr/ 86Sr ratio, has been hindered by isobaric interferences. Here we report the first high precision measurements of 87Sr/ 86Sr by ion microprobe in calcium carbonate samples with moderate Sr concentrations. We use the high mass resolving power (7000 to 9000 M.R.P.) of the SHRIMP-RG ion microprobe in combination with its high transmission to reduce the number of interfering species while maintaining sufficiently high count rates for precise isotopic measurements. The isobaric interferences are characterized by peak modeling and repeated analyses of standards. We demonstrate that by sample-standard bracketing, 87Sr/86Sr ratios can be measured in inorganic and biogenic carbonates with Sr concentrations between 400 and 1500 ppm with ???2??? external precision (2??) for a single analysis, and subpermil external precision with repeated analyses. Explicit correction for isobaric interferences (peak-stripping) is found to be less accurate and precise than sample-standard bracketing. Spatial resolution is ???25 ??m laterally and 2 ??m deep for a single analysis, consuming on the order of 2 ng of material. The method is tested on otoliths from salmon to demonstrate its accuracy and utility. In these growth-banded aragonitic structures, one-week temporal resolution can be achieved. The analytical method should be applicable to other calcium carbonate samples with similar Sr concentrations. Copyright ?? 2005 Elsevier Ltd.

Weber, P.K.; Bacon, C.R.; Hutcheon, I.D.; Ingram, B.L.; Wooden, J.L.

2005-01-01

397

Formation of calcium carbonate films on chitosan substrates in the presence of polyacrylic acid  

SciTech Connect

In this investigation, chitosan membranes with different surface average degrees of deacetylation (DA) are prepared and then are employed as the support matrix to culture calcium carbonate (CaCO{sub 3}). In the presence of high concentration of polyacrylic acid (PAA), the CaCO{sub 3} films obtained on the surface of all chitosan films mainly consisted of vaterite, which suggests the presence of bulk PAA plays an overwhelming part in stabilizing the vaterite. As a comparison, the influences of active groups indicate that only in case of low concentration PAA the thin CaCO{sub 3} films grown on chitosan with 8% DA mainly consisted of vaterite owing to the strong nucleation ability of -NH{sub 2} group, whereas, for those grown on chitosan with 80% DA the CaCO{sub 3} films mainly consisted of aragonite. A more complex scenario revealed that in the case of intermediate concentration of PAA the formed polymorphs behave as mixtures of vaterite and aragonite. - Graphical abstract: Chitosan membranes with different degrees of deacetylation (DA) are employed as support to culture calcium carbonate (CaCO{sub 3}). In high concentration of polyacrylic acid (PAA), the CaCO{sub 3} films obtained consisted of vaterite. However, the CaCO{sub 3} film grown on chitosan with 8% DA mainly consisted of vaterite as opposed to aragonite for chitosan with 8% DA. The schematic presentation of the formation of calcium carbonate on chitosan films with different degrees of acetylation in the presence of PAA with low-, mid- and high concentrations.

He, Linghao; Xue, Rui [Zhengzhou University of Light Industry Henan Provincial Key Laboratory of Surface and Interface Science, Henan, Zhengzhou 450002 (China); Song, Rui, E-mail: rsong@gucas.ac.c [Zhengzhou University of Light Industry Henan Provincial Key Laboratory of Surface and Interface Science, Henan, Zhengzhou 450002 (China); College of Chemistry and Chemical Engineering, Graduate University of Chinese Academy of Sciences, Beijing 100049 (China)

2009-05-15

398

Crystal structure and microstructure of cholesteryl oleyl carbonate.  

PubMed

The crystal structure as well as the microstructure, i.e., size and strain, of crystallites of cholesteryl oleyl carbonate was determined from X-ray powder diffraction data. The X-ray line broadening was analyzed through the refinement of TCH-pseudo-Voigt function parameters (isotropic effects) and the refinement of multipolar functions, i.e., symmetrized cubic harmonics (anisotropic effects). The crystal structure turns out to be primitive monoclinic, space group Pc, type I monolayer having two molecules per unit cell with parameters: a=18.921±0.006?, b=12.952±0.003?, c=9.276±0.002? and ?=91.32±0.03°. The average size of a well ground specimen of crystallites was 60nm. The average micro-strain, e.g., 45×10(-4) has been tentatively attributed to fatty chain conformational disorder. The unit cell parameters, including the lamellar thickness, of COC crystal is very closely similar to those of another, structurally similar cholesterol ester, e.g., cholesteryl oleate (CO) crystal, space group P2(1), type II monolayer. Type I monolayer structure has been established for COC on the basis of the intensity calculations of the XRD profiles of both CO and COC. The dipolar and structural disorder in a 4:1 molar, binary mixture of CO and COC can be accommodated in an induced smectic phase with a lamellar thickness, which is nearly equal to that of pure CO or pure COC. PMID:20951687

Das, Pradip; De, Joyes

2011-01-01

399

Study of the effect of magnesium concentration on the deposit of allotropic forms of calcium carbonate and related carbon steel interface behavior  

Microsoft Academic Search

Different allotropic forms of calcium carbonate scales were electrochemically deposited on a carbon steel surface in artificial underground Tunisian water at ?0.95VSCE and various Mg2+ concentrations. Because of the importance of the diffusion process, the rotating disk electrode was used. The deposition kinetics were analyzed by chronoamperometry measurements and the calcareous layers were characterized by electrochemical impedance spectroscopy (EIS) and

Y. Ben Amor; L. Bousselmi; B. Tribollet; E. Triki

2010-01-01

400

Optical Properties of Small Ice Crystals with Black Carbon Inclusions  

NASA Astrophysics Data System (ADS)

The optical properties of ice crystals play a fundamental role in modeling atmospheric radiation and hydrological cycle, which are critical in monitoring climate change. While Black Carbon (BC) is recognized as the dominant absorber with positive radiative forcing (warming) (Ramanathan & Carmichael, 2008), in-situ observations (Cappa, et al, 2012) indicate that the characterization of the mixing state of BC with ice crystals and other non-BC particles in global climate models (Ghan & Schwartz, 2007) needs further investigation. The limitation in the available mixing models is due to the drastically different absorbing properties of BC compared to other aerosols. We explore the scattering properties of ice crystals (in shapes commonly found in cirrus clouds and contrails - Yang, et al. 2012) with the inclusion of BC particles. The Discrete Dipole Approximation (DDA) (Yurkin & Hoekstra, 2011) is utilized to directly calculate the optical properties of the crystals with multiple BC inclusions, modeled as a distribution of spheres. The results are then compared with the most popular models of internal and external mixing (Liou, et al. 2011). The DDA calculations are carried out over a broad range of BC particle sizes and volume fractions within the crystal at the 532 nm wavelength and for ice crystals smaller than 50 ?m. The computationally intensive database generated in this study is critical for understanding the effect of different types of BC inclusions on the atmosphere radiative forcing. Examples will be discussed to illustrate the modification of BC optical properties by encapsulation in ice crystals and how the parameterization of the BC mixing state in global climate models can be improved. Acknowledgements Support by Sandia National Laboratories' LDRD (Laboratory Directed Research and Development) is gratefully acknowledged. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U. S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. Cappa, C.D., Onasch, T.B., Massoli, et al. (2012). Radiative absorption enhancements due to the mixing state of atmospheric black carbon. Science, 337(6098), 1078-1081. Ghan, S.J., & Schwartz, S.E. (2007). Aerosol properties and processes: A path from field and laboratory measurements to global climate models. Bulletin of the American Meteorological Society, 88(7), 1059-1083. Liou, K.N., Takano, Y., & Yang, P. (2011). Light absorption and scattering by aggregates: Application to black carbon and snow grains. Journal of Quantitative Spectroscopy and Radiative Transfer, 112(10), 1581-1594. Ramanathan, V., & Carmichael, G. (2008). Global and regional climate changes due to black carbon. Nature Geoscience, 1(4), 221-227. Yang, P., Bi, L., Baum, B.A., et al. (2013). Spectrally Consistent Scattering, Absorption, and Polarization Properties of Atmospheric Ice Crystals at Wavelengths from 0.2 to 100 ? m. Journal of the Atmospheric Sciences, 70(1), 330-347. Yurkin, M.A., & Hoekstra, A.G. (2011). The discrete-dipole-approximation code ADDA: capabilities and known limitations. Journal of Quantitative Spectroscopy and Radiative Transfer, 112(13), 2234-2247.

Yang, X.; Geier, M.; Arienti, M.

2013-12-01

401

Shadowing in inelastic scattering of muons on carbon, calcium and lead at low x$_{Bj}$  

E-print Network

Nuclear shadowing is observed in the per-nucleon cross-sections of positive muons on carbon, calcium and lead as compared to deuterium. The data were taken by Fermilab experiment E665 using inelastically scattered muons of mean incident momentum 470 GeV/c. Cross-section ratios are presented in the kinematic region 0.0001 < XBj <0.56 and 0.1 < Q**2 < 80 GeVc. The data are consistent with no significant nu or Q**2 dependence at fixed XBj. As XBj decreases, the size of the shadowing effect, as well as its A dependence, are found to approach the corresponding measurements in photoproduction.

Adams, M R; Anthony, P L; Averill, D A; Baker, M D; Baller, B R; Banerjee, A; Bhatti, A A; Bratzler, U; Braun, H M; Breidung, H; Busza, W; Carroll, T J; Clark, H L; Conrad, J M; Davisson, R; Derado, I; Dhawan, S K; Dietrich, F S; Dougherty, W; Dreyer, T; Eckardt, V; Ecker, U; Erdmann, M; Fang, G Y; Figiel, J; Finlay, R W; Gebauer, H J; Geesaman, D F; Griffioen, K A; Guo, R S; Haas, J; Halliwell, C; Hantke, D; Hicks, K H; Hughes, V W; Jackson, H E; Jaffe, D E; Jancso, G; Jansen, D M; Jin, Z; Kaufman, S; Kennedy, R D; Kinney, E R; Kirk, T; Kobrak, H G E; Kotwal, A V; Kunori, S; Lord, J J; Lubatti, H J; McLeod, D; Madden, P; Magill, S; Manz, A; Melanson, H; Michael, D G; Montgomery, H E; Morfín, J G; Nickerson, R B; Novák, J; O'Day, S; Olkiewicz, K; Osborne, L; Otten, R; Papavassiliou, V; Pawlik, B; Pipkin, F M; Potterveld, D H; Ramberg, E J; Röser, A; Ryan, J J; Salgado, C W; Salvarani, A; Schellman, H; Schmitt, M; Schmitz, N; Schüler, K P; Siegert, G; Skuja, A; Snow, G A; Soldner, S; Rembold, U; Spentzouris, P; Stier, H E; Stopa, P; Swanson, R A; Venkataramania, H; Wilhelm, M; Wilson, R; Wittek, W; Wolbers, S A; Zghiche, A; Zhao, T

1995-01-01

402

Shadowing in Inelastic Scattering of Muons on Carbon, Calcium and Lead at Low XBj  

E-print Network

Nuclear shadowing is observed in the per-nucleon cross-sections of positive muons on carbon, calcium and lead as compared to deuterium. The data were taken by Fermilab experiment E665 using inelastically scattered muons of mean incident momentum 470 GeV/c. Cross-section ratios are presented in the kinematic region 0.0001 < XBj <0.56 and 0.1 < Q**2 < 80 GeVc. The data are consistent with no significant nu or Q**2 dependence at fixed XBj. As XBj decreases, the size of the shadowing effect, as well as its A dependence, are found to approach the corresponding measurements in photoproduction.

Fermilab E665 Collaboration

1995-05-10

403

Peptide interactions with steel surfaces: Inhibition of corrosion and calcium carbonate precipitation  

SciTech Connect

Polyaspartate, a polyanionic peptide analog of an oyster-shell protein fraction, inhibited corrosion of AISI 1018 mild steel (UNS G10180) in seawater in a dose-dependent manner. A maximal inhibition of [approximately] 60% was obtained at a concentration of 100[mu]g mL[sup [minus]1]. Related peptides containing hydrophobic and/or phosphorylated amino acids had corrosion inhibition activities similar to or lower than polyaspartate in fresh and brackish waters. Binding studies demonstrated polyaspartate bound to mild steel in a dose- and time-dependent manner. Evidence for stainless steel (SS) binding was based on inhibition of calcium carbonate precipitation of the SS surface.

Mueller, E.; Sikes, C.S. (Univ. of South Alabama, Mobile, AL (United States). Mineralization Center); Little, B.J. (Stennis Space Center, MS (United States). Naval Research Lab.)

1993-10-01

404

Guided bone regeneration membrane made of polycaprolactone\\/calcium carbonate composite nano-fibers  

Microsoft Academic Search

In this study, new type of guided bone regeneration (GBR) membranes were fabricated by polycaprolactone (PCL)\\/CaCO3 composite nano-fibers with two different PCL to calcium carbonate (CaCO3) ratios (PCL:CaCO3=75:25wt% and 25:75wt%). The composite nano-fibers were successfully fabricated by electrospinning method and CaCO3 nano-particles on the surface of nano-fibers were confirmed by energy disperse X-ray (EDX) analysis. In order to achieve mechanical

K. Fujihara; M. Kotaki; S. Ramakrishna

2005-01-01

405

Sonoelectrochemical deposition of calcium phosphates on carbon materials: effect of current density  

Microsoft Academic Search

Calcium phosphate (CaP) coatings on carbon fabric substrate were produced by sonoelectrodeposition at different current densities\\u000a (5, 8, 13, 20 and 34 mA\\/cm2). The surface morphology and chemical composition of the coatings were characterized by SEM, Raman and FTIR spectra. The\\u000a results showed that at 5 mA\\/cm2 current density, the coating exhibits plate-like morphology, indicating an octacalcium phosphate (OCP) phase was pre-formed

H. M. Han; G. J. Phillips; S. V. Mikhalovsky; S. FitzGerald; A. W. Lloyd

2008-01-01

406

Recovery of calcium carbonate from waste gypsum and utilization for remediation of acid mine drainage from coal mines.  

PubMed

The recovery of calcium carbonate from waste gypsum (a waste product of the reverse osmosis (RO) desalination process) was tested using sodium carbonate. Batch recovery of calcium carbonate from waste gypsum slurries by reacting with sodium carbonate under ambient conditions was used to assess the technical feasibility of CaCO(3) recovery and its use for pre-treatment of acid mine drainage (AMD) from coal mines. The effect of key process parameters, such as the slurry concentration (%) and the molar ratio of sodium carbonate to gypsum were considered. It was observed that batch waste gypsum conversion significantly increased with decrease in the slurry concentration or increase in the molar ratio of sodium carbonate to gypsum. The CaCO(3) recovered from the bench-scale batch reactor demonstrated effective neutralization ability during AMD pre-treatment compared with commercial laboratory grade CaCO(3). PMID:22828309

Mulopo, J; Radebe, V

2012-01-01

407

Hierarchical assembly of carbon nanotubes-liquid crystal nanocomposite.  

PubMed

Fabrication of liquid crystalline (LC) nanomaterials in an aligned pattern along the multiwalled carbon nanotubes (CNT) has been reported here. The nanocomposite was prepared by sonicating esterified CNTs and the ferroelectric liquid crystal (FLC) in chloroform. The nanohybrid shish kebab (NHSK) like pattern was observed in SEM analysis. The nanocomposite materials were characterized by Fourier transform infrared spectroscopy (FTIR), polarizing optical microscopy and electron microscopy. The DC and AC electrical properties of the composite materials were investigated. The DC conductivity of the nanocomposite increased by 2 order from the FLC materials and AC relaxation has been observed, in the nanocomposite, which was totally absent in the FLC materials. PMID:18572572

Kundu, Sudarshan; Batabyal, Sudip K; Nayek, Prasenjit; Roy, Subir K

2008-04-01

408

Crystallization of Carbon-Oxygen Mixtures in White Dwarf Stars  

SciTech Connect

We determine the phase diagram for dense carbon-oxygen mixtures in white dwarf (WD) star interiors using molecular dynamics simulations involving liquid and solid phases. Our phase diagram agrees well with predictions from Ogata et al. and from Medin and Cumming and gives lower melting temperatures than Segretain et al. Observations of WD crystallization in the globular cluster NGC 6397 by Winget et al. suggest that the melting temperature of WD cores is close to that for pure carbon. If this is true, our phase diagram implies that the central oxygen abundance in these stars is less than about 60%. This constraint, along with assumptions about convection in stellar evolution models, limits the effective S factor for the {sup 12}C({alpha},{gamma}){sup 16}O reaction to S{sub 300{<=}}170 keV b.

Horowitz, C. J.; Schneider, A. S.; Berry, D. K. [Department of Physics and Nuclear Theory Center, Indiana University, Bloomington, Indiana 47405 (United States); University Information Technology Services, Indiana University, Bloomington, Indiana 47408 (United States)

2010-06-11

409

Increase in the dosage amount of vitamin D3 preparations by switching from calcium carbonate to lanthanum carbonate.  

PubMed

It is widely known that dialysis patients who are administered vitamin D preparations have a better prognosis than patients who are not. In this study, of 22 patients on maintenance dialysis who had been administered calcium (Ca) carbonate in our hospital, we investigated the dosage amount of vitamin D3 preparations after the phosphorus (P) binder was switched from Ca carbonate to the newly developed lanthanum carbonate (LC). After completely switching to LC, the dosage amount of oral vitamin D3 preparation (alfacalcidol equivalent) was significantly increased from 0.094 ?g/day to 0.375 ?g/day (P = 0.0090). No significant changes were observed in the values of serum corr