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Sample records for calcium 40 reactions

  1. Limestone reaction in calcium aluminate cement–calcium sulfate systems

    Energy Technology Data Exchange (ETDEWEB)

    Bizzozero, Julien, E-mail: julien.bizzozero@gmail.com; Scrivener, Karen L.

    2015-10-15

    This paper reports a study of ternary blends composed of calcium aluminate cement, calcium sulfate hemihydrate and limestone. Compressive strength tests and hydration kinetics were studied as a function of limestone and calcium sulfate content. The phase evolution and the total porosity were followed and compared to thermodynamic simulation to understand the reactions involved and the effect of limestone on these binders. The reaction of limestone leads to the formation of hemicarboaluminate and monocarboaluminate. Increasing the ratio between sulfate and aluminate decreases the extent of limestone reaction.

  2. Elements from chlorine to calcium nuclear reactions

    CERN Document Server

    Kunz, Wunibald

    1968-01-01

    Nuclear Tables: Part II Nuclear Reactions, Volume 3: The Elements from Chlorine to Calcium contains tabulations of the nuclear reaction values of elements chlorine, argon, potassium, and calcium. These tabulations provide the calculated Q-values of the elements and their isotopes. This book will be of value to general chemistry researchers.

  3. Urea hydrolysis and calcium carbonate reaction fronts

    Science.gov (United States)

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

    2010-12-01

    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

  4. Diffusion-reaction compromise the polymorphs of precipitated calcium carbonate

    Institute of Scientific and Technical Information of China (English)

    Han Wang; Wenlai Huang; Yongsheng Han

    2013-01-01

    Diffusion is seldom considered by chemists and materialists in the preparation of materials while it plays an important role in the field of chemical engineering.If we look at crystallization at the atomic level,crystal growth in a solution starts from the diffusion of ions to the growing surface followed by the incorporation of ions into its lattice.Diffusion can be a rate determining step for the growth of crystals.In this paper,we take the crystallization of calcium carbonate as an example to illustrate the microscopic processes of diffusion and reaction and their compromising influence on the morphology of the crystals produced.The diffusion effect is studied in a specially designed three-cell reactor.Experiments show that a decrease of diffusion leads to retardation of supersaturation and the formation of a continuous concentration gradient in the reaction cell,thus promoting the formation of cubic calcite particles.The reaction rate is regulated by temperature.Increase of reaction rate favors the formation of needle-like aragonite particles.When diffusion and reaction play joint roles in the reaction system,their compromise dominates the formation of products,leading to a mixture of cubic and needle-like particles with a controllable ratio.Since diffusion and reaction are universal factors in the preparation of materials,the finding of this paper could be helpful in the controlled synthesis of other materials.

  5. Effect of Reaction Pathway on the Extent and Mechanism of Uranium(VI) Immobilization with Calcium and Phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Mehta, Vrajesh S.; Maillot, Fabien; Wang, Zheming; Catalano, Jeffrey G.; Giammar, Daniel E.

    2016-03-15

    Phosphate addition to subsurface environments contaminated with uranium can be used as an in situ remediation approach. Batch experiments were conducted to evaluate the dependence of the extent and mechanism of uranium uptake on the pathway for reaction with calcium phosphates. At pH 4.0 and 6.0 uranium uptake occurred via autunite (Ca(UO2)(PO4)3) precipitation irrespective of the starting forms of calcium and phosphate. At pH 7.5, the uptake mechanism depended on the nature of the calcium and phosphate. When dissolved uranium, calcium, and phosphate were added simultaneously, uranium was structurally incorporated into a newly formed amorphous calcium phosphate solid. Adsorption was the dominant removal mechanism for uranium contacted with pre-formed amorphous calcium phosphate solids,. When U(VI) was added to a suspension containing amorphous calcium phosphate solids as well as dissolved calcium and phosphate, then removal occurred through precipitation (57±4 %) of autunite and adsorption (43±4 %) onto calcium phosphate. The solid phase speciation of the uranium was determined using X-ray absorption spectroscopy and laser induced fluorescence spectroscopy. Dissolved uranium, calcium, and phosphate concentrations with saturation index calculations helped identify removal mechanisms and determine thermodynamically favorable solid phases.

  6. Preparation of Phenolized Calcium Lignosulfonate andCharacterization of the Reaction by IR Spectroscopy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A kind of calcium lignosulfonate was phenolized by phenol with sulfuric acid as catalyst. The calcium lignosulfonate and its phenolized derivatives were characterized by infrared spectroscopy. It is proved that the extent and type of the phenolizing reaction can be deduced from the IR spectra of the calcium lignosulfonate and its phenolized derivatives.

  7. 40 CFR 424.40 - Applicability; description of the covered calcium carbide furnaces with wet air pollution control...

    Science.gov (United States)

    2010-07-01

    ... covered calcium carbide furnaces with wet air pollution control devices subcategory. 424.40 Section 424.40... FERROALLOY MANUFACTURING POINT SOURCE CATEGORY Covered Calcium Carbide Furnaces With Wet Air Pollution Control Devices Subcategory § 424.40 Applicability; description of the covered calcium carbide...

  8. Synthesis and reaction behavior of calcium silicate hydrate in basic system

    Institute of Scientific and Technical Information of China (English)

    刘桂华; 贺强; 李小斌; 彭志宏; 周秋生

    2004-01-01

    At the molar ratio of CaO to SiO2 of 1, with calcium hydroxide and sodium silicate, calcium silicate hydrate was synthesized at 50, 100, 170 ℃, respectively. The results show that temperature favors the formation of calcium silicate hydrate with perfect structure. When calcium silicate hydrate reacts with caustic solution, the decomposition rate of calcium silicate hydrate increases with the increasing caustic concentration and decreases with the raising synthesis temperature and the prolongation of reaction time. The decomposition rate is all less than 1.2 % in caustic solution, and XRD pattern of the residue after reaction with caustic solution is found as the same as that of original calcium silicate hydrate, which indicates the stable existence of calcium silicate hydrate in caustic solution.When reacted with soda solution, the decomposition rate increases with the increasing soda concentration and reaction time, while decreases with the synthesis temperature. The decomposition rate is more than 2% because CaO · SiO2 · H2O(CSH( Ⅰ )), except Ca5 (OH)2Si6O16 · 4H2O and Ca6Si6O17 (OH)2, is decomposed. So the synthesis temperature and soda concentration should be controlled in the process of transformation of sodium aluminosilicate hydrate into calcium silicate hydrate.

  9. Pressure induced reactions amongst calcium aluminate hydrate phases

    KAUST Repository

    Moon, Ju-hyuk

    2011-06-01

    The compressibilities of two AFm phases (strätlingite and calcium hemicarboaluminate hydrate) and hydrogarnet were obtained up to 5 GPa by using synchrotron high-pressure X-ray powder diffraction with a diamond anvil cell. The AFm phases show abrupt volume contraction regardless of the molecular size of the pressure-transmitting media. This volume discontinuity could be associated to a structural transition or to the movement of the weakly bound interlayer water molecules in the AFm structure. The experimental results seem to indicate that the pressure-induced dehydration is the dominant mechanism especially with hygroscopic pressure medium. The Birch-Murnaghan equation of state was used to compute the bulk modulus of the minerals. Due to the discontinuity in the pressure-volume diagram, a two stage bulk modulus of each AFm phase was calculated. The abnormal volume compressibility for the AFm phases caused a significant change to their bulk modulus. The reliability of this experiment is verified by comparing the bulk modulus of hydrogarnet with previous studies. © 2011 Elsevier Ltd. All rights reserved.

  10. 40 CFR 721.982 - Calcium, bis(2,4-pentanedionato-O,O′).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Calcium, bis(2,4-pentanedionato-O,Oâ²... Substances § 721.982 Calcium, bis(2,4-pentanedionato-O,O′). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance calcium, bis(2,4-pentanedionato-O,O′) (PMN P-93-214,...

  11. Reactions of calcium-based sorbents with sulfur in coal during gasification

    Energy Technology Data Exchange (ETDEWEB)

    Rehmat, A.; Abbasian, M.J.; Leppin, D.; Banerjee, D.D.

    1987-01-01

    This status report outlines the results obtained to date of the current research program supported jointly by the Gas Research Institute and the State of Illinois Center for Research on Sulfur in Coal. The overall objective is to obtain data related to the efficient utilization of high-sulfur Illinois coal in a One-Step Desulfurization Process by employing in-situ removal of sulfur using calcium-based sorbents. The project includes a study of fluidization behavior of coal char/sorbent mixtures and the reactions of calcium-based sorbents with sulfur present in the coal during gasification. The tests are conducted in bench-scale units; an 8-inch fluidization column is utilized for fluidization tests, and a thermobalance reactor is used for gas-solid reactions. The test parameters include the choice of sorbent, sorbent size, the effect of temperature on sulfation and sulfidation reactions, the effect of the steam-to-hydrogen sulfide ratio on the sulfidation reaction, the effect of the steam on the sulfation reaction, and the influence of exposure time on sulfation of the presulfided sorbent. The reaction conditions for these reactions have been chosen to be directly applicable to scale-up of the One-Step Desulfurization Process. 7 refs., 9 figs., 11 tabs.

  12. Synthesis of Calcium(II) Amidinate Precursors for Atomic Layer Deposition through a Redox Reaction between Calcium and Amidines.

    Science.gov (United States)

    Kim, Sang Bok; Yang, Chuanxi; Powers, Tamara; Davis, Luke M; Lou, Xiabing; Gordon, Roy G

    2016-08-22

    We have prepared two new Ca(II) amidinates, which comprise a new class of ALD precursors. The syntheses proceed by a direct reaction between Ca metal and the amidine ligands in the presence of ammonia. Bis(N,N'-diisopropylformamidinato)calcium(II) (1) and bis(N,N'-diisopropylacetamidinato)calcium(II) (2) adopt dimeric structures in solution and in the solid state. X-ray crystallography revealed asymmetry in one of the bridging ligands to afford the structure [(η(2) -L)Ca(μ-η(2) :η(2) -L)(μ-η(2) :η(1) -L)Ca(η(2) -L)]. These amidinate complexes showed unprecedentedly high volatility as compared to the widely employed and commercially available Ca(II) precursor, [Ca3 (tmhd)6 ]. In CaS ALD with 1 and H2 S, the ALD window was approximately two times wider and lower in temperature by about 150 °C than previously reported with [Ca3 (tmhd)6 ] and H2 S. Complexes 1 and 2, with their excellent volatility and thermal stability (up to at least 350 °C), are the first homoleptic Ca(II) amidinates suitable for use as ALD precursors.

  13. Kinetic study of the setting reaction of a calcium phosphate bone cement.

    Science.gov (United States)

    Fernández, E; Ginebra, M P; Boltong, M G; Driessens, F C; Ginebra, J; De Maeyer, E A; Verbeeck, R M; Planell, J A

    1996-11-01

    The setting reaction of a calcium phosphate bone cement consisting of a mixture of 63.2 wt % alpha-tertiary calcium phosphate (TCP)[alpha-Ca3(PO4)2], 27.7 wt % dicalcium phosphate (DCP) (CaHPO4), and 9.1 wt % of precipitated hydroxyapatite [(PHA) used as seed material] was investigated. The cement samples were prepared at a liquid-to-powder ratio of: L/P = 0.30 ml/g. Bi-distilled water was used as liquid solution. After mixing the powder and liquid, some samples were molded and aged in Ringer's solution at 37 degrees C. At fixed time intervals they were unmolded and then immediately frozen in liquid nitrogen at a temperature of TN = -196 degrees C, lyofilized, and examined by X-ray diffraction as powder samples. The compressive strength versus time was also measured in setting samples of this calcium phosphate bone cement. The crystal entanglement morphology was examined by scanning electron microscopy. The results showed that: 1) alpha-TCP reacted to a calcium-deficient hydroxyapatite (CDHA), Ca9(HPO4)(PO4)5O H, whereas DCP did not react significantly; 2) the reaction was nearly finished within 32 h, during which both the reaction percentage and the compressive strength increased versus time, with a strong correlation between them; and 3) the calcium phosphate bone cement showed in general a structure of groups of interconnected large plates distributed among agglomerations of small crystal plates arranged in very dense packings.

  14. Heterogeneous reactions of gaseous methanesulfonic acid with calcium carbonate and kaolinite particles

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Heterogeneous reactions of gaseous methanesulfonic acid (MSA) with calcium carbonate (CaCO3) and kaolinite particles at room temperature were investigated using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and ion chromatography (IC).Methanesulfonate (MS-) was identified as the product in the condensed phase,in accordance with the product of the reaction of gaseous MSA with NaCl and sea salt particles.When the concentration of gaseous MSA was 1.34 × 10-13 molecules cm-3,the uptake coefficient was (1.21 ± 0.06) × 10-8 (1) for the reaction of gaseous MSA with CaCO3 and (4.10 ± 0.65) × 10 10 (1) for the reaction with kaolinite.Both uptake coefficients were significantly smaller than those of the reactions of gaseous MSA with NaCl and sea salt particles.

  15. Tissue reaction and material biodegradation of a calcium sulfate/apatite biphasic bone substitute in rat muscle

    Directory of Open Access Journals (Sweden)

    Jian-Sheng Wang

    2016-07-01

    Conclusion: Calcium sulfate hydroxyapatite bone substitute can be used as a carrier for antibiotics or other drugs, without adverse reaction due to the fast resorption of the calcium sulfate. No bone formation was seen despite treating the bone substitute with autologous bone marrow.

  16. Connexin 40 and ATP-dependent intercellular calcium wave in renal glomerular endothelial cells.

    Science.gov (United States)

    Toma, Ildikó; Bansal, Eric; Meer, Elliott J; Kang, Jung Julie; Vargas, Sarah L; Peti-Peterdi, János

    2008-06-01

    Endothelial intracellular calcium ([Ca(2+)](i)) plays an important role in the function of the juxtaglomerular vasculature. The present studies aimed to identify the existence and molecular elements of an endothelial calcium wave in cultured glomerular endothelial cells (GENC). GENCs on glass coverslips were loaded with Fluo-4/Fura red, and ratiometric [Ca(2+)](i) imaging was performed using fluorescence confocal microscopy. Mechanical stimulation of a single GENC caused a nine-fold increase in [Ca(2+)](i), which propagated from cell to cell throughout the monolayer (7.9 +/- 0.3 microm/s) in a regenerative manner (without decrement of amplitude, kinetics, and speed) over distances >400 microm. Inhibition of voltage-dependent calcium channels with nifedipine had no effect on the above parameters, but the removal of extracellular calcium reduced Delta[Ca(2+)](i) by 50%. Importantly, the gap junction uncoupler alpha-glycyrrhetinic acid or knockdown of connexin 40 (Cx40) by transfecting GENCs with Cx40 short interfering RNA (siRNA) almost completely eliminated Delta[Ca(2+)](i) and the calcium wave. Breakdown of extracellular ATP using a scavenger cocktail (apyrase and hexokinase) or nonselective inhibition of purinergic P2 receptors with suramin, had similar blocking effects. Scraping cells off along a line eliminated physical contact between cells but did not effect calcium wave propagation. Using an ATP biosensor technique, we detected a significant elevation in extracellular ATP (Delta = 76 +/- 2 microM) during calcium wave propagation, which was abolished by Cx40 siRNA treatment (Delta = 6 +/- 1 microM). These studies suggest that connexin 40 hemichannels and extracellular ATP are key molecular elements of the glomerular endothelial calcium wave, which may serve important juxtaglomerular functions.

  17. A novel microwave synthesis of calcium hydroxyapatite. Optimisation and investigation of a microwave assisted reaction route

    CERN Document Server

    Zawahreh, Y

    2001-01-01

    Hydroxyapatite is a bioactive calcium phosphate used in non-load bearing applications, such as space-filling in maxillofacial reconstruction. As a coating, hydroxyapatite is used on load-bearing orthopaedic metal prostheses to improve fixation and/or biocompatibility. Conventional synthesis processes for the production of hydroxyapatite are time-consuming and labour-intensive. Microwave irradiation was investigated as a means to enhance the synthesis reaction using calcium hydroxide (Ca(OH) sub 2) and orthophosphoric acid (H sub 3 PO sub 4) as reactants. An initial set of reactions indicated the feasibility of the microwave synthesis route. Optimisation reactions were then performed followed by investigation sets of reactions. Parameters such as microwave power, irradiation time, and reactant concentrations were varied. Using 0.5M Ca(OH) sub 2 and 0.3M H sub 3 PO sub 4 , a phase-pure hydroxyapatite powder with a stoichiometric molar Ca/P ratio of 1.67 was produced in 60 seconds at 450W and 2.45GHz. The microw...

  18. A laboratory study of the heterogeneous reaction of nitric acid on calcium carbonate particles

    Science.gov (United States)

    Goodman, A. L.; Underwood, G. M.; Grassian, V. H.

    2000-12-01

    It has been postulated that the reaction of nitric acid with calcium carbonate, namely, CaCO3(s) + 2HNO3(g) → Ca(NO3)2(s) + CO2(g) + H2O(g), plays an important role in the atmosphere. In this study, transmission FTIR spectroscopy, diffuse reflectance UV-visible spectroscopy, transmission electron microscopy and a Knudsen cell reactor coupled to a quadrupole mass spectrometer have been used to investigate the heterogeneous reactivity of HNO3 on CaCO3 at 295 K as a function of relative humidity. Transmission FTIR spectroscopy was used to probe both gas-phase and adsorbed products and showed that the reaction of HNO3 and CaCO3 is limited to the surface of the CaCO3 particle in the absence of adsorbed water. However, in the presence of water vapor, the reaction is greatly enhanced and is not limited to the surface of the particle producing both solid calcium nitrate and gaseous carbon dioxide. The enhanced reactivity of the particles is attributed to the presence of a layer of adsorbed water on the particle surface. The amount of adsorbed water on the particle surface is strongly dependent on the extent of the reaction. This can be understood in terms of the increased hydrophilicity of calcium nitrate as compared to calcium carbonate. Data from experiments using a mass-calibrated Knudsen cell reactor showed the stoichiometry for the reaction determined from gas-phase species deviated from that expected from the balanced equation. Water adsorption on the particle surface and gases dissolved into the water layer appear to be the cause of this discrepancy. The measured uptake coefficient accounting for the BET area of the sample is determined to be 2.5±0.1×10-4 for HNO3 on CaCO3 under dry conditions and is found to increase in the presence of water vapor. Atmospheric implications of the results presented here are discussed.

  19. Hydrothermal and mechanochemical reactions of rice husk ash with calcium hydroxide

    Energy Technology Data Exchange (ETDEWEB)

    Sugita, S.; Isojima, Y. [Hachinohe Institute of Technology, Aomori (Japan); Yu, Q. [Wuhan University of Technology, (Taiwan, Province of China)

    1998-05-01

    It is well known that a calcium silicate hydrate, commonly referred to as C-S-H gel, is important for cement to exhibit strength. Silica is present in rice husk ash to around 90%. When sufficiently sintered and crushed, rice husk ash mostly comprises amorphous silica having a large surface area. It is reactive, and is considered to contribute to improvement of concrete strength and durability. In this study, rice husk ash is reacted with calcium hydroxide under hydrothermal conditions or mechanochemical conditions at normal temperature, to synthesize Ca(1.5)SiO(3.5){center_dot}xH2O as one of the calcium silicate hydrates. It has an average particle size of 10{mu}m or smaller, which varies depending on synthesis method and condition. The compound synthesized at 40degC is composed of flocs having a porous structure and large specific surface area, as is the case with a C-S-H gel present in Portland cement paste. It loses the above structure and moisture in the fine pores gradually, when heated, but remains amorphous at up to 750degC. It is transformed into wollastonite, when heated to 780degC. 7 refs., 8 figs., 3 tabs.

  20. Calcium-Magnesium-Aluminosilicate (CMAS) Reactions and Degradation Mechanisms of Advanced Environmental Barrier Coatings

    Science.gov (United States)

    Ahlborg, Nadia L.; Zhu, Dongming

    2013-01-01

    The thermochemical reactions between calcium-magnesium-aluminosilicate- (CMAS-) based road sand and several advanced turbine engine environmental barrier coating (EBC) materials were studied. The phase stability, reaction kinetics and degradation mechanisms of rare earth (RE)-silicates Yb2SiO5, Y2Si2O7, and RE-oxide doped HfO2 and ZrO2 under the CMAS infiltration condition at 1500 C were investigated, and the microstructure and phase characteristics of CMAS-EBC specimens were examined using Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). Experimental results showed that the CMAS dissolved RE-silicates to form crystalline, highly non-stoichiometric apatite phases, and in particular attacking the silicate grain boundaries. Cross-section images show that the CMAS reacted with specimens and deeply penetrated into the EBC grain boundaries and formed extensive low-melting eutectic phases, causing grain boundary recession with increasing testing time in the silicate materials. The preliminary results also showed that CMAS reactions also formed low melting grain boundary phases in the higher concentration RE-oxide doped HfO2 systems. The effect of the test temperature on CMAS reactions of the EBC materials will also be discussed. The faster diffusion exhibited by apatite and RE-doped oxide phases and the formation of extensive grain boundary low-melting phases may limit the CMAS resistance of some of the environmental barrier coatings at high temperatures.

  1. Calcium Hex aluminate reaction sintering by Spark Plasma Sintering; Sinterizacion reactiva de Hexaluminato de Calcio mediante Spark Plasma Sintering

    Energy Technology Data Exchange (ETDEWEB)

    Iglesia, P. G. de la; Garcia-Moreno, O.; Torrecillas, R.; Menendez, J. L.

    2012-11-01

    Calcium hex aluminate (CaAl{sub 1}2O{sub 1}9) is the most alumina-rich intermediate compound of the CaO-Al{sub 2}O{sub 3} system. The formation of this aluminate is produced by the reaction between calcium oxide and alumina with the consequent formation of intermediates compounds with lower alumina content with increasing temperature (CaAl{sub 2}O{sub 4}, CaAl4O{sub 7}). In this study we studied the variation of sintering parameters for obtaining dense and pure calcium hex aluminate by reaction sintering by Spark Plasma Sintering (SPS). A mixing of Al{sub 2}O{sub 3} and CaCO{sub 3} were used as reactive. Final densities close to the theoretical and phase transformation over 93% were achieved by this method. (Author) 22 refs.

  2. Chemical looping coal gasification with calcium ferrite and barium ferrite via solid--solid reactions

    Energy Technology Data Exchange (ETDEWEB)

    Siriwardane, Ranjani [U.S. Department of Energy/NETL; Riley, Jarrett [Oak Ridge Inst. for Science and Education (ORISE), Oak Ridge, TN (United States); Tian, Hanjing [West Virginia Univ., Morgantown, WV (United States); Richards, George [U.S. Department of Energy/NETL

    2016-01-01

    Coal gasification to produce synthesis gas by chemical looping was investigated with two oxygen carriers, barium ferrite (BaFe2O4) and calcium ferrite (CaFe2O4). Thermo-gravimetric analysis (TGA) and fixed-bed flow reactor data indicated that a solid–solid interaction occurred between oxygen carriers and coal to produce synthesis gas. Both thermodynamic analysis and experimental data indicated that BaFe2O4 and CaFe2O4 have high reactivity with coal but have a low reactivity with synthesis gas, which makes them very attractive for the coal gasification process. Adding steam increased the production of hydrogen (H2) and carbon monoxide (CO), but carbon dioxide (CO2) remained low because these oxygen carriers have minimal reactivity with H2 and CO. Therefore, the combined steam–oxygen carrier produced the highest quantity of synthesis gas. It appeared that neither the water–gas shift reaction nor the water splitting reaction promoted additional H2 formation with the oxygen carriers when steam was present. Wyodak coal, which is a sub-bituminous coal, had the best gasification yield with oxygen carrier–steam while Illinois #6 coal had the lowest. The rate of gasification and selectivity for synthesis gas production was significantly higher when these oxygen carriers were present during steam gasification of coal. The rates and synthesis gas yields during the temperature ramps of coal–steam with oxygen carriers were better than with gaseous oxygen.

  3. Reaction of calcium-based sorbents with sulfur componds during gasification. Annual report, October 1, 1986-September 30, 1987

    Energy Technology Data Exchange (ETDEWEB)

    Rehmat, A.; Abbasian, M.J.

    1988-01-01

    This report outlines the objectives and the data obtained under the project related to the efficient utilization of high-sulfur Illinois coal in a One-Step Coal Gasification/Desulfurization Process by employing in-situ removal of sulfur using calcium-based sorbents. The scope of the research included a study of fluidization behavior of coal char/sorbent mixtures and the reactions of calcium-based sorbents with sulfur present in the coal during gasification. Tests were conducted in bench-scale units; an 8-inch (0.2 meter) fluidization column was utilized for fluidization tests, and a thermobalance reactor was used for gas/solid sulfidation and sulfation reactions. The test parameters included the choice of sorbent, sorbent size, the effect of temperature on the sulfidation and sulfation reactions, the effect of the steam-to-hydrogen sulfide ratio on the sulfidation reaction, the effect of the steam on the sulfation reaction, and the influence of exposure time on sulfation of the presulfided sorbent. The reaction conditions for these reactions were chosen to be applicable to scale-up of an in-situ desulfurization-type coal gasification process such as the one proposed by the Institute of Gas Technology (IGT) and KRW Energy Systems, Inc., of the USA.

  4. Subcutaneous tissue reaction to castor oil bean and calcium hydroxide in rats

    Directory of Open Access Journals (Sweden)

    Samira Esteves Afonso Camargo

    2010-06-01

    Full Text Available Castor oil bean cement (COB is a new material that has been used as an endodontic sealer, and is a candidate material for direct pulp capping. OBJECTIVE: The purpose of this study was to evaluate the biocompatibility of a new formulation of COB compared to calcium hydroxide cement (CH and a control group without any material, in the subcutaneous tissue of rats. MATERIAL AND METHODS: The materials were prepared, packed into polyethylene tubes, and implanted in the rat dorsal subcutaneous tissue. Animals were sacrificed at the 7th and 50th days after implantation. A quantitative analysis of inflammatory cells was performed and data were subjected to ANOVA and Tukey's tests at 5% significance level. RESULTS: Comparing the mean number of inflammatory cells between the two experimental groups (COB and CH and the control group, statistically significant difference (p=0.0001 was observed at 7 and 50 days. There were no significant differences (p=0.111 between tissue reaction to CH (382 inflammatory cells and COB (330 inflammatory cells after 7 days. After 50 days, significantly more inflammatory cells (p=0.02 were observed in the CH group (404 inflammatory cells than in the COB group (177 inflammatory cells. CONCLUSIONS: These results demonstrate that the COB cement induces less inflammatory response within long periods.

  5. Reaction of calcium-based sorbents with sulfur compounds during gasification. Final report, 1 October 1986-30 June 1991

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Rehmat, A.

    1991-12-01

    The report outlines the objectives and the data obtained under the project related to the efficient utilization of high-sulfur Illinois coal in a One-Step Coal Gasification/Desulfurization Process by employing in-situ removal of sulfur using calcium-based sorbents. The research was supported jointly by the Gas Research Institute and the State of Illinois Center for Research on Sulfur in Coal. The scope of the research included a study of fluidization behavior of coal char/sorbent mixtures and the reactions of calcium-based sorbents with sulfur present in the coal during gasification as well as sulfation of the sulfided sorbents. The test parameters included the choice of sorbent, sorbent size, the effect of temperature and pressure, and the reactant gas composition on the sulfidation and sulfation reactions. The reaction conditions for these reactions were chosen to be applicable to scale-up of an in-situ desulfurization-type coal gasification process such as the one proposed by the Institute of Gas Technology (IGT) and KRW Energy Systems, Inc., of the U.S.A. A PC-based computer model was developed that is capable of describing a fluidized-bed gasifier with in-bed calcium-based sorbents.

  6. Calcium phosphate composite materials including inorganic powders, BSA or duplex DNA prepared by W/O/W interfacial reaction method

    Energy Technology Data Exchange (ETDEWEB)

    Fujiwara, Masahiro [National Institute of Advanced Industrial Science and Technology (AIST), Kansai Center, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan)], E-mail: m-fujiwara@aist.go.jp; Shiokawa, Kumi; Morigaki, Kenichi; Tatsu, Yoshiro; Nakahara, Yoshiko [National Institute of Advanced Industrial Science and Technology (AIST), Kansai Center, 1-8-31 Midorigaoka, Ikeda, Osaka 563-8577 (Japan)

    2008-03-10

    We reported before that inorganic reaction occurring at the interface of W/O/W emulsion is advantageous to produce hollow spheres (microcapsules) of inorganic matrices such as silica. This process enables us to include various materials into inorganic matrices directly. Calcium phosphates were also produced from NH{sub 4}H{sub 2}PO{sub 4} and Ca(OH){sub 2} by this interfacial reaction method. Various biomaterials are directly incorporated into crystalline calcium phosphate matrices, when the biomaterials are added to the inner water phase of the W/O/W emulsion. ZrO{sub 2} and Al{sub 2}O{sub 3} powders were effectively encapsulated in calcium phosphates such as hydroxyapatite (HAp). The images of backscattered electron of FE-SEM observations indicated that ZrO{sub 2} particles were included in HAp, while they adhered to the surface of HAp in the case of a simple precipitation method. Biomacromolecules such as BSA and duplex DNA were also included in HAp using the inner water phases dissolving them. Fluorescent microscopy observations revealed that biomacromolecules incorporated in HAp localized in some domains of the HAp matrices. Biomacromolecules thus included were scarcely liberated into deionized water, indicating their strong encapsulation in HAp. This general and simple methodology will provide various composite materials of calcium phosphates, which are applicable to regenerative medicine, DDS, GDS and more.

  7. Reaction of calcium-based sorbents with sulfur compounds during gasification. Second annual report, October 1987-September 1988

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Rehmat, A.

    1989-01-01

    This report outlines the objective and the data obtained under the project related to efficient utilization of high-sulfur Illinois coal in a One-Step Coal Gasification/Desulfurization Process by employing in-situ removal of sulfur using calcium-based sorbents. The research was supported jointly by the Gas Research Institute and the State of Illinois Center for Research on Sulfur in Coal. The scope of the research included a study of the reaction of calcium-based sorbent with sulfur present in the coal at gasification conditions. Low-pressure tests were conducted in an ambient-pressure quartz electrobalance and high-pressure tests were conducted in a high-pressure/high-temperature thermobalance reactor. The test parameters included temperature, pressure, H/sub 2/S concentration, and sorbent particle size. The sulfidation reaction tests at elevated pressure were conducted with both fully calcined and half-calcined sorbents.

  8. A role for calcium hydroxide and dolomite in water: acceleration of the reaction under ultraviolet light.

    Science.gov (United States)

    Nagase, Hiroyasu; Tsujino, Hidekazu; Kurihara, Daisuke; Saito, Hiroshi; Kawase, Masaya

    2014-04-01

    Organic environmental pollutants are now being detected with remarkably high frequency in the aquatic environment. Photodegradation by ultraviolet light is sometimes used as a method for removing organic chemicals from water; however, this method is relatively inefficient because of the low degradation rates involved, and more efficient methods are under development. Here we show that the removal of various organic pollutants can be assisted by calcined dolomite in aqueous solution under irradiation with ultraviolet light. It was possible to achieve substantial removal of bisphenol A, chlorophenols, alkylphenols, 1-naphthol and 17β-estradiol. The major component of dolomite responsible for the removal was calcium hydroxide. Our results demonstrate that the use of calcium hydroxide with ultraviolet light irradiation can be a very effective method of rapidly removing organic environmental pollutants from water. This is a new role for calcium hydroxide and dolomite in water treatment.

  9. Pore-scale network modeling of microbially induced calcium carbonate precipitation: Insight into scale dependence of biogeochemical reaction rates

    Science.gov (United States)

    Qin, Chao-Zhong; Hassanizadeh, S. Majid; Ebigbo, Anozie

    2016-11-01

    The engineering of microbially induced calcium carbonate precipitation (MICP) has attracted much attention in a number of applications, such as sealing of CO2 leakage pathways, soil stabilization, and subsurface remediation of radionuclides and toxic metals. The goal of this work is to gain insight into pore-scale processes of MICP and scale dependence of biogeochemical reaction rates. This will help us develop efficient field-scale MICP models. In this work, we have developed a comprehensive pore-network model for MICP, with geochemical speciation calculated by the open-source PHREEQC module. A numerical pseudo-3-D micromodel as the computational domain was generated by a novel pore-network generation method. We modeled a three-stage process in the engineering of MICP including the growth of biofilm, the injection of calcium-rich medium, and the precipitation of calcium carbonate. A number of test cases were conducted to illustrate how calcite precipitation was influenced by different operating conditions. In addition, we studied the possibility of reducing the computational effort by simplifying geochemical calculations. Finally, the effect of mass transfer limitation of possible carbonate ions in a pore element on calcite precipitation was explored.

  10. Low temperature synthesis of high quality carbon nanospheres through the chemical reactions between calcium carbide and oxalic acid

    Energy Technology Data Exchange (ETDEWEB)

    Xie Yonggui, E-mail: xieyg2004@163.com [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Huang Qizhong, E-mail: qzhuang@mail.csu.edu.cn [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Huang Baiyun [State Key Laboratory for Powder Metallurgy, Central South University, Changsha, Hunan 410083 (China); Xie Xiangmin [Applied Chemistry Department, College of Science, Hunan Agricultural University, Changsha, Hunan 410128 (China)

    2010-11-01

    Carbon nanospheres (CNSs) were synthesized through the chemical reactions of calcium carbide and oxalic acid without using catalysts. The chemical reactions were carried out in a sealed stainless steel pressure vessel with various molar ratios at temperatures of 65-250 deg. C. The synthesized CNSs have been characterized using scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) attached to the SEM, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Raman spectroscopy. The total yield of carbonaceous materials relative to the starting material is about 4% (w/w). SEM and TEM results reveal that the percentage of CNSs is high (>95%). The CNSs that have been synthesized are roe-like spheres of relatively uniform size with diameters of 60-120 nm. The attached EDS result shows that the carbon content of CNSs reaches up to 98%.

  11. Fischer-Tropsch diesel production over calcium-promoted Co/alumina catalyst: Effect of reaction conditions

    Energy Technology Data Exchange (ETDEWEB)

    A.R. de la Osa; A. De Lucas; A. Romero; J.L. Valverde; P. Sanchez [University of Castilla-La Mancha, Ciudad Real (Spain). Chemical Engineering Department

    2011-05-15

    The effects of reaction conditions on the Fischer-Tropsch activity and product distribution of an alkali-earth metal promoted cobalt based catalyst were studied. The influence of the promoter on the reducibility and cobalt particle size was studied by different techniques, including N{sub 2} adsorption, X-ray diffraction, temperature-programmed reduction, temperature-programmed desorption and acid-base titrations. Experiments were carried out on a bench-scale fixed bed reactor and catalysts were prepared by incipient wetness impregnation. It was observed that addition of a small amount of calcium oxide as a promoter (0.6 wt.%) improved the cobalt oxide reducibility and reduced the formation of cobalt-aluminate species. A positive correlation between basicity and particle size was observed. In terms of FTS results, CO conversion and C{sub 5}{sup +} selectivity were found to be enhanced by the addition of this promoter. It was important to note that the addition of calcium shifted the distribution to mainly C{sub 16}-C{sub 18} hydrocarbons fraction, which could be greatly considered for a diesel formulation. Furthermore, the variation of the reaction conditions seemed to influence product distribution in a lesser extent than unpromoted catalyst. Also, a displacement of hydrocarbon distribution to higher molecular weight with decreasing space velocity and temperature was observed. Moreover, the addition of calcium to the cobalt based catalyst was found to greatly maintain selectivity to C{sub 5}{sup +} for a wide range of H{sub 2}/CO molar ratios. 60 refs., 10 figs., 5 tabs.

  12. Low Density Lipoproteins Promote Unstable Calcium Handling Accompanied by Reduced SERCA2 and Connexin-40 Expression in Cardiomyocytes

    Science.gov (United States)

    Cabello, Nuria; Llach, Anna; Vallmitjana, Alexander; Benítez, Raúl; Badimon, Lina; Cinca, Juan; Llorente-Cortés, Vicenta; Hove-Madsen, Leif

    2013-01-01

    The damaging effects of high plasma levels of cholesterol in the cardiovascular system are widely known, but little attention has been paid to direct effects on cardiomyocyte function. We therefore aimed at testing the hypothesis that Low Density Lipoprotein (LDL) cholesterol affects calcium dynamics and signal propagation in cultured atrial myocytes. For this purpose, mRNA and protein expression levels were determined by real time PCR and western blot analysis, respectively, and intracellular calcium was visualized in fluo-4 loaded atrial HL-1 myocyte cultures subjected to field stimulation. At low stimulation frequencies all cultures had uniform calcium transients at all tested LDL concentrations. However, 500 µg LDL/mL maximally reduced the calcium transient amplitude by 43% from 0.30±0.04 to 0.17±0.02 (p<0.05). Moreover, LDL-cholesterol dose-dependently increased the fraction of alternating and irregular beat-to-beat responses observed when the stimulation interval was shortened. This effect was linked to a concurrent reduction in SERCA2, RyR2, IP3RI and IP3RII mRNA levels. SERCA2 protein levels were also reduced by 43% at 200 µg LDL/mL (p<0.05) and SR calcium loading was reduced by 38±6% (p<0.001). By contrast, HDL-cholesterol had no significant effect on SERCA expression or SR calcium loading. LDL-cholesterol also slowed the conduction velocity of the calcium signal from 3.2+0.2 mm/s without LDL to 1.7±0.1 mm/s with 500 µg LDL/mL (p<0.05). This coincided with a reduction in Cx40 expression (by 44±3%; p<0.05 for mRNA and by 79±2%; p<0.05 for Cx40 protein at 200 µg/ml LDL) whereas the Cx-43 expression did not significantly change. In conclusion, LDL-cholesterol destabilizes calcium handling in cultured atrial myocytes subjected to rapid pacing by reducing SERCA2 and Cx40 expression and by slowing the conduction velocity of the calcium signal. PMID:23516438

  13. 40 CFR 415.300 - Applicability; description of the calcium carbonate production subcategory.

    Science.gov (United States)

    2010-07-01

    ... resulting from the production of calcium carbonate by the milk of lime process and by the recovery process... calcium carbonate production subcategory. 415.300 Section 415.300 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Calcium Carbonate Production Subcategory § 415.300 Applicability; description of...

  14. 40 CFR 415.30 - Applicability; description of the calcium carbide production subcategory.

    Science.gov (United States)

    2010-07-01

    ... calcium carbide production subcategory. 415.30 Section 415.30 Protection of Environment ENVIRONMENTAL... SOURCE CATEGORY Calcium Carbide Production Subcategory § 415.30 Applicability; description of the calcium carbide production subcategory. The provisions of this subpart are applicable to discharges resulting...

  15. 40 CFR 424.50 - Applicability; description of the other calcium carbide furnaces subcategory.

    Science.gov (United States)

    2010-07-01

    ... calcium carbide furnaces subcategory. 424.50 Section 424.50 Protection of Environment ENVIRONMENTAL... CATEGORY Other Calcium Carbide Furnaces Subcategory § 424.50 Applicability; description of the other calcium carbide furnaces subcategory. The provisions of this subpart are applicable to...

  16. Expansion of powerhouse structures due to alkali-aggregate reaction and the use of low calcium fly ash to ameliorate the reaction in future construction

    Energy Technology Data Exchange (ETDEWEB)

    Langley, W.S. [W.S. Langley Concrete and Material Technology Inc., NS (Canada); Brown, E. [Nova Scotia Power Corp., Halifax, NS (Canada)

    2001-07-01

    A study was conducted to examine a reaction in concrete between the alkalies found in the pore fluid and certain siliceous aggregates. This reaction, called alkali-aggregate reactivity caused disruptive expansion in a concrete powerhouse structure in Nova Scotia in 1962. The structure was constructed with meta-sediments and biotite schists. This combination caused expansion and resulted in problems with the operation of the plant within 10 years after construction. Subsequent studies showed that the reactive aggregates were widespread and that the problem could be solved using 15 to 30 per cent fly ash replacement of the cement. Now, low calcium fly ash is used on a regular basis to lessen the potential for alkali-aggregate reaction. Nova Scotia fly ash was also being studied for its use as a cement replacement and enhancement of concrete durability. It was concluded that this particular fly ash is an excellent supplementary cement material to offset disruptive expansions. The fly ash has been used since the mid 1980s for solving expansion problems in powerhouses. 6 refs., 3 tabs., 12 figs.

  17. Reaction mechanism and influence factors analysis for calcium sulfide generation in the process of phosphogypsum decomposition

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Liping, E-mail: lpma2522@hotmail.com [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China); Niu, Xuekui; Hou, Juan; Zheng, Shaocong; Xu, Wenjuan [Faculty of Environmental Science and Engineering, Kunming University of Science and Technology, Kunming 650093 (China)

    2011-11-10

    Highlights: Black-Right-Pointing-Pointer Reusing phosphogypsum is to decompose and recycle Ca and sulfur. Black-Right-Pointing-Pointer FactSage6.1 software was used to simulate the decomposition reactions. Black-Right-Pointing-Pointer Experiments had been taken with high sulfur concentration coal as reducing agent. Black-Right-Pointing-Pointer The reaction mechanism of CaS generation had been analysis, 1100 Degree-Sign C could be the best temperature for PG decomposition. - Abstract: FactSage6.1 software simulation and experiments had been used to analysis the reaction mechanism and influence factors for CaS generation during the process of phosphogypsum decomposition. Thermodynamic calculation showed that the reaction for CaS generation was very complex and CaS was generated mainly through solid-solid reaction and gas-solid reaction. The proper CO and CO{sub 2} have benefit for improving the decomposition effects of phosphogypsum and reducing the generation of CaS at 1100 Degree-Sign C. Using high sulfur concentration coal as reducer, the proper reaction conditions to control the generation of CaS were: the coal particle size was between 60 mesh and 100 mesh, reaction temperature was above 1100 Degree-Sign C and the heating rate was 5 Degree-Sign C/min. Experimental and theoretical calculation indicated that the concentration of CaS was only ten percents in the solid product at 1100 Degree-Sign C, which is favorable for the further cement producing using solid production.

  18. 40 CFR 721.4461 - Hydrofluoric acid, reaction products with octane (generic).

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrofluoric acid, reaction products... New Uses for Specific Chemical Substances § 721.4461 Hydrofluoric acid, reaction products with octane... identified generically as a hydrofluoric acid, reaction products with octane (PMN P-99-0052) is subject...

  19. 40 CFR 721.4385 - Hydrofluoric acid, reaction products with heptane.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Hydrofluoric acid, reaction products... Specific Chemical Substances § 721.4385 Hydrofluoric acid, reaction products with heptane. (a) Chemical... hydrofluoric acid, reaction products with heptane (PMN P-98-1036; CAS No. 207409-71-0) is subject to...

  20. Mg-doped biphasic calcium phosphate by a solid state reaction route: Characterization and evaluation of cytotoxicity

    Energy Technology Data Exchange (ETDEWEB)

    Webler, Geovana D. [Instituto de Física, Universidade Federal de Alagoas, Maceió-AL 57072970 (Brazil); Correia, Ana C.C.; Barreto, Emiliano [Laboratório de Biologia Celular, Universidade Federal de Alagoas, Maceió-AL 57072970 (Brazil); Fonseca, Eduardo J.S., E-mail: eduardo@fis.ufal.br [Instituto de Física, Universidade Federal de Alagoas, Maceió-AL 57072970 (Brazil)

    2015-07-15

    Hydroxyapatite (HAP) and β-tricalcium phosphate (β-TCP) are widely used in tissue engineering because of their chemical similarity to the inorganic bone phase. In this work, we prepare biphasic calcium phosphate (BCP, a mixture of HAP and β-TCP) doped with different concentrations of magnesium to investigate the influence of magnesium on the BCP crystal structure. Magnesium is known to be an important element in the composition of bones and teeth. Recent research has shown that the doping of magnesium into BCP improves its bone metabolism and mechanical properties without affecting its biocompatibility. The samples were prepared by solid-state reaction from calcium carbonate, monobasic ammonium phosphate, and magnesium nitrate hexahydrate. Varying concentrations of magnesium were used and its modifications were examined by different characterization techniques. The phase composition and morphology of the ceramic powders were characterized by X-ray diffraction and scanning electron microscopy, respectively. The functional groups were analyzed using Fourier transform infrared spectroscopy and Raman spectroscopy. Cell viability experiments, using macrophage-like cell lines J774, showed that the synthesized Mg-doped BCP did not exhibit cytotoxicity regardless of the doses assayed or the different concentrations of magnesium used, suggesting it as a good material for potential biological applications. - Highlights: • Simple and fast method for the preparation of the Mg-BCP. • Study of the influence of the incorporation of Mg in the BCP. • Cell viability showed that the synthesized Mg-BCP did not exhibit cytotoxicity.

  1. Strength of the $E_{\\text{p}}$=1.842 MeV resonance in the $^{40}$Ca(p,$\\gamma$)$^{41}$Sc reaction revisited

    CERN Document Server

    Schmidt, Konrad; Anders, Michael; Bemmerer, Daniel; Caciolli, Antonio; Dietz, Mirco; Elekes, Zoltán; Junghans, Arnd R; Menzel, Marie-Luise; Schwengner, Ronald; Wagner, Andreas; Zuber, Kai

    2014-01-01

    The strength of the $E_{\\rm p} = 1.842$ MeV resonance in the $^{40}$Ca(p,$\\gamma$)$^{41}$Sc reaction is determined with two different methods: First, by an absolute strength measurement using calcium hydroxide targets, and second, relative to the well-determined strength of the resonance triplet at $E_\\alpha$ = 4.5 MeV in the $^{40}$Ca($\\alpha$,$\\gamma$)$^{44}$Ti reaction. The present new value of $\\omega\\gamma=(0.192\\pm0.017)$ eV is 37% (equivalent to $3.5\\sigma$) higher than the evaluated literature value. In addition, the ratio of the strengths of the 1.842 MeV $^{40}$Ca(p,$\\gamma$)$^{41}$Sc and 4.5 MeV $^{40}$Ca($\\alpha$,$\\gamma$)$^{44}$Ti resonances has been determined to be $0.0229\\pm0.0018$. The newly corrected strength of the 1.842-MeV resonance can be used in the future as a normalization point for experiments with calcium targets.

  2. 40 CFR 721.2625 - Reaction product of alkane-diol and epichlorohydrin.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Reaction product of alkane-diol and epichlorohydrin. 721.2625 Section 721.2625 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Specific Chemical Substances § 721.2625 Reaction product of alkane-diol and epichlorohydrin. (a)...

  3. 40 CFR 721.10125 - Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle and alkenoic acid alkyl ester (generic). 721.10125 Section... Substances § 721.10125 Alkenedioic acid, dialkyl ester, reaction products with polyaminocarbomonocycle...

  4. Coupled-channels description of the 40Ca+58,64Ni transfer and fusion reactions

    CERN Document Server

    Scamps, G; Hagino, K; Haas, F; Courtin, S

    2016-01-01

    Preliminary experimental data for nucleon transfer reactions of the 40Ca+58Ni and 40Ca+64Ni systems are analyzed with the coupled- channels approach. It is shown that a simple treatment for the transfer in the coupled-channels method cannot reproduce simultaneously the transfer probabilities and the sub-barrier enhancement of fusion cross sections.

  5. Investigation of inelastic 40Ca(p,p')X reaction at 1 GeV

    CERN Document Server

    Miklukho, O V; Andreev, V A; Fedorov, O Ya; Hatanaka, K; Ilyin, D; Izotov, A A; Kisselev, A Yu; Levchenko, M P; Noro, T; Prokofiev, A N; Revenko, R; Sakaguchi, H; Shvedchikov, A V; Tatarenko, A; Trush, S I; Zhdanov, A A

    2011-01-01

    The polarization of the secondary protons in the inelastic (p,p') reaction on the 40Ca nucleus and the relative cross sections of this reaction at 1 GeV of the initial proton energy were measured in a wide range of the scattered proton momenta (K) at lab angles \\theta=13.5 and \\theta=21.0 degrees. The final protons from the reaction were detected by means of a magnetic spectrometer equipped with multiwire proportional chamber polarimeter.

  6. Modified calcium oxide as stable solid base catalyst for Aldol condensation reaction

    Indian Academy of Sciences (India)

    Ying Tang; Jingfang Xu; Xuefan Gu

    2013-03-01

    A highly efficient and stable solid-base catalyst for Aldol condensation was prepared by modifying commercial CaO with benzyl bromide in a simple way. It was found that modified CaO can effectively catalyse the Aldol condensation of cyclohexanone and benzaldehyde, as well as various benzaldehydes, to produce 2-benzylidenecyclohexanone with a good selectivity and high yield. Higher yield of 95.8% was obtained over modified CaO after 3 h, which is short compared with the yield of 92.1% after 12 h over commercial CaO. The influence of several reaction parameters, such as temperature, catalyst loading, was investigated. The humidity test over modified CaO reveals that the basic centres of modified CaO are stable for CO2 and moisture. From the results of Fourier transform-infrared (FT-IR) and Thermogravity analysis (TG) characterization, the modifier was bonded on surface of CaO chemically and almost no Ca(OH)2 formed during the modification process. The type of aldehyde has great influence on the yield of aldol condensation.

  7. Revised analysis of $^{40}$Ca+$^{96}$Zr fusion reactions

    CERN Document Server

    Esbensen, H; Stefanini, A M

    2016-01-01

    Fusion data for $^{40}$Ca+$^{96}$Zr are analyzed by coupled-channels calculations that are based on a standard Woods-Saxon potential and include couplings to multiphonon excitations and transfer channels. The couplings to multiphonon excitations are the same as used in a previous work. The transfer couplings are calibrated to reproduce the measured neutron transfer data. This type of calculation gives a poor fit to the fusion data. However, by multiplying the transfer couplings with a $\\sqrt{2}$ one obtains an excellent fit. The scaling of the transfer strengths is supposed to simulate the combined effect of neutron and proton transfer, and the calculated one- and two-nucleon transfer cross sections are indeed in reasonable agreement with the measured cross sections.

  8. Morphometric immunohistochemical examination of the inflammatory tissue reaction after implantation of calcium phosphate-coated titanium plates in rats.

    Science.gov (United States)

    Walschus, Uwe; Hoene, Andreas; Neumann, Hans-Georg; Wilhelm, Lutz; Lucke, Silke; Lüthen, Frank; Rychly, Joachim; Schlosser, Michael

    2009-02-01

    Calcium phosphate (CaP) preparations are established coatings for titanium-based medical implants used for bone reconstruction. However, biodegradation of the coating can result in microparticles that subsequently cause inflammatory reactions. The present study was therefore aimed at investigating the inflammatory response to two series of CaP-coated titanium plates: Ti-brushite (Ti-B) and Ti-hydroxyapatite (Ti-H) implants. Fifteen male LEW.1A rats received one plate of each series and a pellet (5 x 2 mm) of sol-gel derived silica/CaP (SCP implants) implanted into the back musculature. After 7, 14 and 28 days, five rats were killed and the implants were removed with the surrounding tissue. Quantitative immunohistochemistry was performed on frozen sections. Total monocytes/macrophages, tissue macrophages, T-cells, MHC-class-II-positive cells and proliferating cells were counted. For the Ti-B implants, the number of monocytes/macrophages remained constant while the other cell populations increased. In contrast, for the Ti-H implants the number of monocytes/macrophages decreased while the other cell populations remained constant. The SCP implants demonstrated degradation and scattering into smaller particles with an increase for all cell populations except the proliferating cells. Human mesenchymal stem cells demonstrated adherence and a flat morphology on Ti-B and Ti-H implants and no remarkable difference between both implants. Taken together, the in vivo data demonstrate that the short-term inflammatory response against a hydroxyapatite coating is lower in comparison to a brushite coating, and that the morphology of cells growing in vitro is similar on both layers.

  9. Europium doped di-calcium magnesium di-silicate orange–red emitting phosphor by solid state reaction method

    Directory of Open Access Journals (Sweden)

    Ishwar Prasad Sahu

    2015-07-01

    Full Text Available A new orange–red europium doped di-calcium magnesium di-silicate (Ca2MgSi2O7:Eu3+ phosphor was prepared by the traditional high temperature solid state reaction method. The prepared Ca2MgSi2O7:Eu3+ phosphor was characterized by X-ray diffractometer (XRD, transmission electron microscopy (TEM, field emission scanning electron microscopy (FESEM with energy dispersive x-ray spectroscopy (EDX, fourier transform infrared spectra (FTIR, photoluminescence (PL and decay characteristics. The phase structure of sintered phosphor was akermanite type structure which belongs to the tetragonal crystallography with space group P4¯21m, this structure is a member of the melilite group and forms a layered compound. The chemical composition of the sintered Ca2MgSi2O7:Eu3+ phosphor was confirmed by EDX spectra. The PL spectra indicate that Ca2MgSi2O7:Eu3+ can be excited effectively by near ultraviolet (NUV light and exhibit bright orange–red emission with excellent color stability. The fluorescence lifetime of Ca2MgSi2O7:Eu3+ phosphor was found to be 28.47 ms. CIE color coordinates of Ca2MgSi2O7:Eu3+ phosphor is suitable as orange-red light emitting phosphor with a CIE value of (X = 0.5554, Y = 0.4397. Therefore, it is considered to be a new promising orange–red emitting phosphor for white light emitting diode (LED application.

  10. Microscopic study of $^{40}$Ca+$^{58,64}$Ni fusion reactions

    CERN Document Server

    Bourgin, D; Courtin, S; Haas, F

    2016-01-01

    Background: Heavy-ion fusion reactions at energies near the Coulomb barrier are influenced by couplings between the relative motion and nuclear intrinsic degrees of freedom of the colliding nuclei. The time-dependent Hartree-Fock (TDHF) theory, incorporating the couplings at the mean-field level, as well as the coupled-channels (CC) method are standard approaches to describe low energy nuclear reactions. Purpose: To investigate the effect of couplings to inelastic and transfer channels on the fusion cross sections for the reactions $^{40}$Ca+$^{58}$Ni and $^{40}$Ca+$^{64}$Ni. Methods: Fusion cross sections around and below the Coulomb barrier have been obtained from coupled-channels (CC) calculations, using the bare nucleus-nucleus potential calculated with the frozen Hartree-Fock method and coupling parameters taken from known nuclear structure data. The fusion thresholds and neutron transfer probabilities have been calculated with the TDHF method. Results: For $^{40}$Ca+$^{58}$Ni, the TDHF fusion threshold ...

  11. 40 CFR 721.10154 - Quaternary ammonium compounds, dicoco alkyldimethyl, chlorides, reaction products with silica.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Quaternary ammonium compounds, dicoco alkyldimethyl, chlorides, reaction products with silica. 721.10154 Section 721.10154 Protection of Environment... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10154 Quaternary ammonium...

  12. Precipitation of calcium phosphate at 40° C from neutral solution

    Science.gov (United States)

    Lundager Madsen, Hans E.; Christensson, Finn

    1991-12-01

    Calcium phosphate formation was studied in the pH range 5brushite (CaHPO 4·2H 2O) is the role product, and octacalcium phosphate predominates at low concentrations. ACP is subsequently transformed into brushite or apatite (Ca 5OH(PO 4) 3), the latter always crytocrystalline, but brushite crystals often redissolve and leave apatite as the end product. The formation and evolution of precipitates are chiefly governed by solubilities of the different crystalline phases; for apatite, the excess solubility of small crystals as determined by the Gibbs-Kelvin equation plays an important role.

  13. Adverse hepatic reactions associated with calcium carbimide and disulfiram therapy: Is there still a role for these drugs?

    Institute of Scientific and Technical Information of China (English)

    Carmen Verge; M Isabel Lucena; Enrique López-Torres; M José Puche-García; Enrique Fraga; Manuel Romero-Gomez; Raúl J Andrade

    2006-01-01

    Disulfiram and calcium carbimide are two alcohol deterrants widely used in alcoholism treatment, however,there exist great concerns over their safety. Reports on hepatotoxicity, mainly related to disulfiram therapy, have been published. The hepatotoxic potential of calcium carbimide is less well characterized. Here, we describe four cases of liver damage related to this therapeutic group that were submitted to a Registry of hepatotoxicity and point out the limitations that we face when prescribing these compounds. A reassessment of the role of these compounds in the management of alcohol dependence is clearly needed.

  14. 40 CFR 721.10188 - Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Fatty acids, tall-oil, reaction... Fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine (generic). (a... generically as fatty acids, tall-oil, reaction products with 4-methyl-2-pentanone and aliphatic polyamine...

  15. Development of the Neck in Fusion Reactions 40Ca+90,96Zr

    Institute of Scientific and Technical Information of China (English)

    王宁; 吴锡真; 李祝霞

    2003-01-01

    The neck dynamics and nucleon transfer through the neck in fusion reactions 40 Ca +90,96Zr are studied by applying the improved quantum molecular dynamics model. A special attention is paid to the dynamic behaviour of the neck development at touching point and to the contribution of excess neutrons in a neutron-rich target (or projectile) to neck formation and nucleon transfer.

  16. Haploinsufficiency of the 22q11.2-microdeletion gene Mrpl40 disrupts short-term synaptic plasticity and working memory through dysregulation of mitochondrial calcium

    Science.gov (United States)

    Devaraju, Prakash; Yu, Jing; Eddins, Donnie; Mellado-Lagarde, Marcia M.; Earls, Laurie R.; Westmoreland, Joby J.; Quarato, Giovanni; Green, Douglas R.; Zakharenko, Stanislav S.

    2016-01-01

    Hemizygous deletion of a 1.5- to 3-megabase region on chromosome 22 causes 22q11.2 deletion syndrome (22q11DS), which constitutes one of the strongest genetic risks for schizophrenia. Mouse models of 22q11DS have abnormal short-term synaptic plasticity (STP) that contributes to working memory deficiencies similar to those in schizophrenia. We screened mutant mice carrying hemizygous deletions of 22q11DS genes and identified haploinsufficiency of Mrpl40 (mitochondrial large ribosomal subunit protein 40) as a contributor to abnormal STP. Two-photon imaging of the genetically encoded fluorescent calcium indicator GCaMP6, expressed in presynaptic cytosol or mitochondria, showed that Mrpl40 haploinsufficiency deregulates STP via impaired calcium extrusion from the mitochondrial matrix through the mitochondrial permeability transition pore. This led to abnormally high cytosolic calcium transients in presynaptic terminals and deficient working memory but did not affect long-term spatial memory. Thus, we propose that mitochondrial calcium deregulation is a novel pathogenic mechanism of cognitive deficiencies in schizophrenia. PMID:27184122

  17. Kinetic behavior of the reaction between hydroxyl radical and the SV40 minichromosome

    Energy Technology Data Exchange (ETDEWEB)

    Ly, A. [Department of Radiology, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0610 (United States); Aguilera, J.A. [Department of Radiology, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0610 (United States); Milligan, J.R. [Department of Radiology, University of California at San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0610 (United States)]. E-mail: jmilligan@ucsd.edu

    2007-06-15

    Aqueous solutions containing the minichromosomal form of the virus SV40 and the radical scavenger DMSO were subjected to {gamma}-irradiation, and the resulting formation of single-strand breaks (SSB) was quantified. Under the irradiation conditions, most SSBs were produced as a consequence of hydroxyl radical ( {sup {center_dot}}OH) reactions. By controlling the competition between DMSO and the viral DNA substrate for {sup {center_dot}}OH, we are able to estimate the rate coefficient for the reaction of {sup {center_dot}}OH with the SV40 minichromosome. The results cannot be described adequately by homogeneous competition kinetics, but it is possible to describe the rate coefficient for the reaction as a function of the scavenging capacity of the solution. The experimentally determined rate coefficient lies in the range 1x10{sup 9}-2x10{sup 9} L mol{sup -1} s{sup -1} at 10{sup 7} s{sup -1}, and increases with increasing scavenging capacity.

  18. The pairing correlation study in the {sup 40}Ar+{sup 208}Pb reaction

    Energy Technology Data Exchange (ETDEWEB)

    Mijatović, T., E-mail: tea.mijatovic@irb.hr; Szilner, S.; Malenica, D. Jelavić; Prepolec, L.; Soić, N.; Tokić, V. [Ruđer Bošković Institute, Zagreb (Croatia); Corradi, L.; Fioretto, E.; Goasduff, A.; Stefanini, A. M.; Dobón, J. J. Valiente [INFN - Laboratori Nazionali di Legnaro, Legnaro (Italy); Montanari, D.; Courtin, S.; Haas, F. [IPHC, CNRS/IN2P3 and Université de Strasbourg, Strasbourg (France); Gadea, A. [IFIC, CSIC-Universidad de Valencia, Valencia (Spain); Montagnoli, G.; Scarlassara, F.; Ur, C. A. [INFN and Università di Padova, Padova (Italy); Pollarolo, G. [INFN and Università di Torino, Torino (Italy)

    2015-10-15

    The multinucleon transfer reaction {sup 40}Ar+{sup 208}Pb has been measured at E{sub lab} = 260 MeV with the large solid angle magnetic spectrometer PRISMA. Mass and charge yields, differential and total cross sections, total kinetic energy loss distributions of different channels were simultaneously studied. Angular distributions were measured in a wide angular range by matching three different angular settings of the spectrometer. Absolute cross sections were obtained after the response function of the spectrometer was evaluated. These cross sections for different transfer channels allow the discussion of the role played by nucleon-nucleon correlations.

  19. Experimental results for studies of the 40Ca(α,γ)44Ti reaction rates

    Science.gov (United States)

    Robertson, Daniel; Becker, Hans-Werner; Bowers, Matt; Collon, Philippe; Goerres, Joachim; Lu, Wenting; Schmitt, Chris; Wiescher, Michael

    2011-10-01

    Observational studies of galactic γ emitters such as 44Ti have highlighted their use in nucleosynthesis studies of massive stars in their late stage stellar evolution and final explosive demise in core collapse supernova events. Models used in the simulation of such γ emitters rely heavily upon reliable reaction rates for both the creation and annihilation of these isotopes over large temperature ranges. The production of 44Ti mainly through the 40Ca(α,γ)44Ti reaction is thought to take place primarily in the α-rich freeze out phase of a core collapse supernova. However, current supernova models predict lower 44Ti to 56Ni ratios than observed, creating a need for more information about its production mechanism. A number of previous studies include prompt γ-ray measurements, recoil mass separator experiments and the use of AMS, all giving greatly different reaction rates. Aiding in the refinement of these needed rates, the results of experiments at the DTL, Bochum and NSL, Notre Dame will be presented against the backdrop of these previous measurements. Work supported by grant # 0758100 and # 0822648.

  20. Some Properties of Over 40 Years Women with High School and Over Regarding Menopausal Period and Conception of Calcium Source Foods in Diyarbakır

    Directory of Open Access Journals (Sweden)

    Günay Saka

    2005-01-01

    Full Text Available The aim of this study was to determine the properties of women in pre or post menopausal period and their conception of calcium source foods. We interviewed randomly selected, aged over 40 years, 390 women with high school or higher education level in Diyarbakir. Body mass indexes (BMI of the women were also calculated by measuring height and weight. 28,72% of the study population were postmenopausal. Of the postmenopausal women, 18,75 % had experienced a surgical or medical intervention causing menopause. Average menopausal age was 45,63±4,60 for natural menopause. According to BMI 37,44% of the women was with over weight and 8,21% of them was with obesity. Prevalence of overweight was higher in post menopausal women than others (16,10% - 5,00% (p: 000. Only 24,62 % of the women attended to a physician for medical counseling. 14,61% of them were using calcium supplementary drugs and 6,41% of them were using estrogen regularly. Although most of the women (82,31% had information bout increasing calcium requirement during postmenopausal period but 35,13% of them were consuming calcium source foods sufficiently. This result showed that knowledge on good nutrition was not reflected to their nutritional habits, and health education programmes should be conducted on this manner.

  1. Preparation, characterization of Mo catalysts supported on Ni- containing calcium deficient hydroxyapatite and reactivity for the thiophene HDS reaction

    Directory of Open Access Journals (Sweden)

    Cherif A.

    2013-09-01

    Full Text Available Ni-containing Calcium Hydroxyapatite (NiCaHAp; 3.31 wt.% Ni was synthesized by coprecipitation and used as catalyst support. Molybdenum was supported on NiCaHAp by impregnation using ammonium heptamolybdate. The prepared catalysts Mo(x/NiCaHAp (x: 2 to 8 wt % in Mo were characterized by elemental analysis, XRD, FT-IR, N2 adsorption-desorption and TEM-EDX. The catalysts were sulfided in-situ at 673 K under flowing H2S/H2 (15 Vol.% H2S and tested in hydrodesulfurization (HDS of thiophene at 673 K. The main XRD peaks of hydroxyapatite CaHAp phase were observed in all samples and a peak due probably to crystalline MoO3 phase was also identified from the results. However, no crystalline phase of NiO was found for the catalysts, which showed its Ni species were highly dispersed. The sulfided catalysts Mo(x/NiCaHAp presented are active in HDS of thiophene, despite the presence of some large MoO3 crystallites and incomplete sulfidation. This activity may be due to interaction of NiO and MoO3 on CaHAp resulting in the formation of Ni-Mo-S phase under flowing H2S/H2. When the molybdenum content increased the HDS activity increasead slightly, which was caused by the agglomeration of MoO3. The Mo(8/NiCaHAp catalyst is about two times less active for thiophene HDS than the commercial NiMoP/Al2O3.

  2. Reactions Involving Calcium and Magnesium Sulfates as Potential Sources of Sulfur Dioxide During MSL SAM Evolved Gas Analyses

    Science.gov (United States)

    McAdam, A. C.; Knudson, C. A.; Sutter, B.; Franz, H. B.; Archer, P. D., Jr.; Eigenbrode, J. L.; Ming, D. W.; Morris, R. V.; Hurowitz, J. A.; Mahaffy, P. R.; Navarro-Gonzalez, R.

    2016-01-01

    The Sample Analysis at Mars (SAM) and Chemistry and Mineralogy (CheMin) instruments on the Mars Science Laboratory (MSL) have analyzed several subsamples of 860 C). Sulfides or Fe sulfates were detected by CheMin (e.g., CB, MJ, BK) and could contribute to the high temperature SO2 evolution, but in most cases they are not present in enough abundance to account for all of the SO2. This additional SO2 could be largely associated with x-ray amorphous material, which comprises a significant portion of all samples. It can also be attributed to trace S phases present below the CheMin detection limit, or to reactions which lower the temperatures of SO2 evolution from sulfates that are typically expected to thermally decompose at temperatures outside the SAM temperature range (e.g., Ca and Mg sulfates). Here we discuss the results of SAM-like laboratory analyses targeted at understanding this last possibility, focused on understanding if reactions of HCl or an HCl evolving phase (oxychlorine phases, chlorides, etc.) and Ca and Mg sulfates can result in SO2 evolution in the SAM temperature range.

  3. The effects of retrograde reactions and of diffusion on 39Ar-40Ar ages of micas

    DEFF Research Database (Denmark)

    Allaz, Julien; Engi, Martin; Berger, Alfons

    2011-01-01

    Effects of metamorphic reactions occurring during decompression were explored to understand their influence on 39Ar-40Ar ages of micas. Monometamorphic metasediments from the Lepontine Alps (Switzerland) were studied. Collected samples reached lower amphibolite facies during the Barrovian....../K and Cl/K ratios) did not change and the resulting ages can be interpreted unambiguously. In mineral separates containing two white micas, Ca/K and Cl/K ratios were variable, reflecting non-simultaneous laboratory degassing of the two heterochemical Ar-reservoirs. These ratios were used to identify each...... Ar reservoir and to unravel the age. In a chlorite-margarite-biotite-calcschist equilibrated near 560 °C and 0.65 GPa, biotite, margarite, and muscovite all yield ages around 18 Ma. At slightly higher grade (560-580 °C, 0.8-0.9 GPa), the assemblage muscovite-paragonite-plagioclase is at equilibrium...

  4. An Investigation of the 40Ar(n,p)40Cl Reaction Cross-Section below 50MeV at Crocker Nuclear Laboratory

    Science.gov (United States)

    Walsh, Nicholas Ian

    Large underground liquid argon detectors are poised to detect neutrinos from the next galactic supernova. Liquid argon detectors are uniquely sensitive to the electron neutrino, thus giving them the capability to detect neutronization neutrinos for the first time. One background that may mimic the signal of this low-energy neutrino interaction in argon is the beta-decay of Cl-40 which is produced in argon by a fast neutron reaction. Previous measurements of this 40Ar+n->40Cl+p reaction cross section exist only below 15 MeV and the measurements differ by a factor of two. Using the U.C. Davis Crocker Nuclear Laboratory neutron beam this cross-section is determined by fitting to a parametrized model for neutron energies up to 50 MeV. Neutrons at this facility are generated from mono-energetic protons impinging on a thick beryllium target. Then, the neutrons that pass through the collimator are measured by time-of-flight and a fast-neutron activation technique. Using the neutron fluxes generated from five different proton energies, including 50 MeV protons, the 40Ar(n,p)40Cl reaction cross section is measured by irradiating liquid argon in each beam and counting the subsequent gammas from the Cl-40 decay in a high-purity germanium detector.

  5. The opening of maitotoxin-sensitive calcium channels induces the acrosome reaction in human spermatozoa: differences from the zona pellucida

    Institute of Scientific and Technical Information of China (English)

    Julio C Chávez; Claudia L Trevi(n)o; Gerardo A de Blas; José L de la Vega-Beltrán; Takuya Nishigaki; Mayel Chirinos; María Elena González-González; Fernando Larrea; Alejandra Solís; Alberto Darszon

    2011-01-01

    The acrosome reaction(AR),an absolute requirement for spermatozoa and egg fusion,requires the influx of Ca2+into the spermatozoa through voltage-dependent Ca2+channels and store-operated channels.Maitotoxin(MTx),a Ca2+-mobilizing agent,has been shown to be a potent inducer of the mouse sperm AR,with a pharmacology similar to that of the zona pellucida(ZP),possibly suggesting a common pathway for both inducers.Using recombinant human ZP3(rhZP3),mouse ZP and two MTx channel blockers(U73122 and U73343),we investigated and compared the MTx-and ZP-induced ARs in human and mouse spermatozoa.Herein,we report that MTx induced AR and elevated intracellular Ca2+([Ca2+]1)in human spermatozoa,both of which were blocked by U73122 and U73343.These two compounds also inhibited the MTx-induced AR in mouse spermatozoa.In disagreement with our previous proposal,the AR triggered by rhZP3 or mouse ZP was not blocked by U73343,indicating that in human and mouse spermatozoa,the AR induction by the physiologicalligands or by MTx occurred through distinct pathways.U73122,but not U73343(inactive analogue),can block phospholipase C(PLC).Another PLC inhibitor,edelfosine,also blocked the rhZP3-and ZP-induced ARs.These findings confirmed the participation of a PLC-dependent signalling pathway in human and mouse zona protein-induced AR.Notably,edelfosine also inhibited the MTx-induced mouse sperm AR but not that of the human,suggesting that toxin-induced AR is PLC-dependent in mice and PLC-independent in humans.

  6. Effectof Material Ratio on Phase Transfer Rate of Calcium Ions During Reaction between Calcium Sulfate Dihydrate and Ammonium Carbonate%二水硫酸钙与碳酸铵反应过程中物料比对钙离子相转移速率的影响

    Institute of Scientific and Technical Information of China (English)

    陈昌国; 周加贝; 夏素兰; 王子宁; 宫源; 刘仕忠

    2015-01-01

    选择二水硫酸钙晶须为研究对象,在温度、搅拌速度、料浆浓度不变的条件下,探究了二水硫酸钙与碳酸铵反应过程中物料比 n(NH 4)2 CO 3:nCaSO 4∙2 H 2 O 对钙离子相转移速率的影响。结果表明,物料比在1.05∶1~1.4∶1之间时,生成的碳酸钙沉淀于溶液中,钙离子相转移是溶解-结晶过程,二水硫酸钙转化率和碳酸钙颗粒粒径均随物料比增大而增大,即相转移速率与物料比成正比。%Calcium sulfate dihydrate whiskers were applied under constant temperature,stirring speed and slurry concentration.The material ratio of n(NH 4 )2 CO 3 ∶nCaSO 4 ∙2 H 2 O was changed to study its effect on phase transfer of calcium ions during the reaction between calcium sulfate dihydrate and ammonium car-bonate.The result showed that calcium carbonate crystals were precipitate in solution as the material ratio between 1.05∶1 and 1.4∶1,so corresponding mechanism of calcium ions phase transfer was dissolution-precipitation.It could found that both the conversion rate of calcium sulfate dihydrate and the calcium car-bonate particles size were increased with the increasing value of materials ratio.It indicated that the phase transfer rate of calcium ions was proportional to the material ratio.

  7. Excitation functions for(d,x)reactions on $^{133}$Cs up to $E_d = 40$ MeV

    CERN Document Server

    Tárkányi, F; Takács, S; Hermanne, A; Baba, M; Ignatyuk, A V

    2016-01-01

    In the frame of a systematic study of excitation functions of deuteron induced reactions the excitation functions of the $^{133}$Cs(d,x)$^{133m,133mg,131mg}$Ba, ${134,132}$Cs and $^{129m}$Xe nuclear reactions were measured up to 40 MeV deuteron energies by using the stacked foil irradiation technique and $\\gamma$-ray spectroscopy of activated samples. The results were compared with calculations performed with the theoretical nuclear reaction codes ALICE-IPPE-D, EMPIRE II-D and TALYS calculation listed in the TENDL-2014 library. A moderate agreement was obtained. Based on the integral yields deduced from our measured cross sections, production of $^{131}$Cs via the $^{133}$Cs(d,4n)$^{131}$Ba $\\longrightarrow$ $^{131}$Cs reaction and $^{133}$Ba via $^{133}$Cs(d,2n) reactions is discussed in comparison with other charged particle production routes.

  8. 40 CFR 721.6477 - Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alkyl polycarboxylic acids, esters... Alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols, reaction products with maleic... identified generically as alkyl polycarboxylic acids, esters with ethoxylated fatty alcohols,...

  9. Isospin transport and reaction mechanism in nuclear reactions in the range 20–40 MeV/n

    Energy Technology Data Exchange (ETDEWEB)

    Barlini, S., E-mail: barlini@fi.infn.it; Piantelli, S.; Casini, G.; Olmi, A.; Bini, M.; Pasquali, G.; Poggi, G.; Stefanini, A. A.; Valdré, S.; Pastore, G. [Dipartimento di Fisica ed Astronomia dell’Università and INFN Sezione di Firenze, Firenze (Italy); Bougault, R.; Lopez, O.; Le Neindre, N.; Parlog, M.; Vient, E. [LPC, IN2P3-CNRS, ENSICAEN et Université de Caen, F-14050 Caen-Cedex (France); Bonnet, E.; Chibhi, A.; Frankland, J. D. [GANIL, CEA/DSM-CNRS/IN2P3, B.P.5027, F-14076 Caen cedex (France); Borderie, B.; Rivet, M. F. [Institut de Physique Nucléaire, CNRS/IN2P3, Université Paris-Sud 11, F-91406 Orsay cedex (France); and others

    2015-10-15

    In recent years, many efforts have been devoted to the investigation of the isospin degree of freedom in nuclear reactions. Comparing systems involving partners with different N/Z, it has been possible to investigate the isospin transport process and its influence on the final products population. This can be then related to the symmetry energy term of the nuclear EOS. From the experimental point of view, this task requires detectors able to measure both charge and mass of the emitted products, in the widest possible range of energy and size of the fragments. With this objective, the FAZIA and GARFIELD+RCo apparatus have been used with success in some recent experiments.

  10. Isospin transport and reaction mechanism in nuclear reactions in the range 20-40 MeV/n

    Science.gov (United States)

    Barlini, S.; Piantelli, S.; Casini, G.; Olmi, A.; Bini, M.; Pasquali, G.; Poggi, G.; Stefanini, A. A.; Bougault, R.; Bonnet, E.; Borderie, B.; Chibhi, A.; Frankland, J. D.; Gruyer, D.; Lopez, O.; Le Neindre, N.; Parlog, M.; Rivet, M. F.; Vient, E.; Rosato, E.; Vigilante, M.; Bruno, M.; Marchi, T.; Morelli, L.; Cinausero, M.; Degerlier, M.; Gramegna, F.; Kozik, T.; Twarog, T.; Fabris, D.; Valdré, S.; Pastore, G.

    2015-10-01

    In recent years, many efforts have been devoted to the investigation of the isospin degree of freedom in nuclear reactions. Comparing systems involving partners with different N/Z, it has been possible to investigate the isospin transport process and its influence on the final products population. This can be then related to the symmetry energy term of the nuclear EOS. From the experimental point of view, this task requires detectors able to measure both charge and mass of the emitted products, in the widest possible range of energy and size of the fragments. With this objective, the FAZIA and GARFIELD+RCo apparatus have been used with success in some recent experiments.

  11. Excitation functions of alpha particle induced reactions on natTi up to 40 MeV

    Science.gov (United States)

    Uddin, M. S.; Scholten, B.

    2016-08-01

    Excitation functions of the reactions natTi(α,x)48Cr, natTi(α,x)48V and natTi(α,x)46,48Sc were determined by the stacked-foil activation technique up to 40 MeV. The radioactivities produced in the natTi target were measured by γ-ray spectrometry using HPGe detector. The reaction natTi(α,x)51Cr was used to determine the beam parameters. New experimental values for the above reactions have been obtained. An intercomparison of our data with the available literature values has been done. The cross section results obtained in this work could be useful in defining new monitor reactions, radiation safety and isotope production.

  12. Calcium supplements

    Science.gov (United States)

    ... do not help. Always tell your provider and pharmacist if you are taking extra calcium. Calcium supplements ... 2012:chap 251. The National Osteoporosis Foundation (NOF). Clinician's Guide to prevention and treatment of osteoporosis . National ...

  13. Sequestration of Sr(II) by calcium oxalate—A batch uptake study and EXAFS analysis of model compounds and reaction products

    Science.gov (United States)

    Singer, David M.; Johnson, Stephen B.; Catalano, Jeffrey G.; Farges, François; Brown, Gordon E., Jr.

    2008-10-01

    Calcium oxalate monohydrate (CaC 2O 4·H 2O—abbreviated as CaOx) is produced by two-thirds of all plant families, comprising up to 80 wt.% of the plant tissue and found in many surface environments. It is unclear, however, how CaOx in plants and soils interacts with metal ions and possibly sequesters them. This study examines the speciation of Sr(II) aq following its reaction with CaOx. Batch uptake experiments were conducted over the pH range 4-10, with initial Sr solution concentrations, [Sr] aq, ranging from 1 × 10 -4 to 1 × 10 -3 M and ionic strengths ranging of 0.001-0.1 M, using NaCl as the background electrolyte. Experimental results indicate that Sr uptake is independent of pH and ionic strength over these ranges. After exposure of CaOx to Sr aq for two days, the solution Ca concentration, [Ca] aq, increased for all samples relative to the control CaOx suspension (with no Sr added). The amount of Sr aq removed from solution was nearly equal to the total [Ca] aq after exposure of CaOx to Sr. These results suggest that nearly 90% of the Sr is removed from solution to a solid phase as Ca is released into solution. We suggest that the other 10% is sequestered through surface adsorption on a solid phase, although we have no direct evidence for this. Extended X-ray absorption fine structure (EXAFS) spectroscopy was used to determine the molecular-level speciation of Sr in the reaction products. Deconvolutions of the Sr K-edge EXAFS spectra were performed to identify multi-electron excitation (MEE) features. MEE effects were found to give rise to low-frequency peaks in the Fourier transform before the first shell of oxygen atoms and do not affect EXAFS fitting results. Because of potential problems caused by asymmetric distributions of Sr-O distances when fitting Sr K-edge EXAFS data using the standard harmonic model, we also employed a cumulant expansion model and an asymmetric analytical model to account for anharmonic effects in the EXAFS data. For Sr

  14. CsxH3-xPW12O40 heteropoly salts catalyzed quinoline synthesis via Friedlander reaction

    Institute of Scientific and Technical Information of China (English)

    Ezzat Rafiee; Fereshte Khajooei Nejad; Mohammad Joshaghani

    2011-01-01

    Various type of cesium partially substituted phosphotungstate, CsxH3-xPW12O40 (x = 1.0, 2.0 and 2.5), were synthesized and their catalytic activities were investigated in the synthesis of quinoline. It was shown that catalytic activities of these catalysts correlated to surface acidity and total number of acidic sites. Finally, a series of quinoline derivatives were synthesized with Cs2.5H0.5PW12O40 via the Friedlander reaction in high to excellent yields and the plausible mechanism was proposed. Simple experiment, catalyst reusability, short reaction time and preclusion of toxic solvent are the advantages of this method.

  15. The reaction pp to p pi /sup -/ pi /sup +/p at 25 and 40 GeV/c

    CERN Document Server

    Antipov, Yu M; Baud, R; Busnello, R; Damgaard, G; Kienzle, W; Kienzle-Focacci, M N; Klanner, Robert; Landsberg, L G; Lebedev, A A; Lechanoine-Leluc, C; Lecomte, P; Martin, M; Roinishvili, V N; Sard, R D; Snyder, A; Yotch, F A

    1975-01-01

    The reaction pp to p pi /sup -/ pi /sup +/p has been studied at 25 and 40 GeV/c at the Serpukhov proton synchrotron using the CERN-IHEP spectrometer. The differential cross section has been determined as a function of four-momentum transfer to the proton (0.05-0.30 (GeV/c) /sup 2/) and p pi pi mass (up to 2.2 and 2.6 GeV/c/sup 2/). (18 refs).

  16. Improved sinterability and conductivity enhancement of 10-mol% calcium-doped ceria using different fuel-aided combustion reactions and its structural characterisation

    Energy Technology Data Exchange (ETDEWEB)

    Ong, P.S., E-mail: pohshing@gmail.com [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Tan, Y.P., E-mail: yptan@science.upm.edu.my [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Putra Laboratory for Catalysis Science and Technology, Department Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Taufiq-Yap, Y.H., E-mail: yap@science.upm.edu.my [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Putra Laboratory for Catalysis Science and Technology, Department Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Zainal, Z., E-mail: zulkar@science.upm.edu.my [Department of Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia); Putra Laboratory for Catalysis Science and Technology, Department Chemistry, Faculty of Science, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor (Malaysia)

    2014-07-01

    Highlights: • The analysis of the combustion parameters for different fuel-aided combustion syntheses of Ce{sub 0.9}Ca{sub 0.1}O{sub 1.9} is investigated. • The influence of fuel and its direct correlation with calculated thermochemistry is studied. • A complex reaction equation based on stoichiometric mole of fuels to propellant chemistry concept is created. • The influence of fuel utilised on the combustion process and on physiochemical properties is examined. • Ce{sub 0.9}Ca{sub 0.1}O{sub 1.9} ceramic from citric acid-aided combustion synthesis showed the highest conductivity (σ{sub 800°c} = 0.017 S cm{sup −1}). - Abstract: Cubic fluorite structure of ceria doped with 10-mol% calcium, Ce{sub 0.9}Ca{sub 0.1}O{sub 1.9}, was prepared using fuel-aided combustion techniques, utilising glycine, urea and citric acid as fuels along with metal nitrates as the oxidiser. The influence of fuel utilised on the combustion process and on physiochemical properties was thoroughly studied. The results of X-ray diffraction showed that all powders calcined at 400 °C were of single phase with cubic fluorite structure. Conductivity optimisation was achieved via ceramic sintering at various temperatures within 1000–1200 °C. The results showed that Ce{sub 0.9}Ca{sub 0.1}O{sub 1.9} ceramic prepared using citric acid-aided combustion synthesis had higher ionic conductivity, σ{sub 800°c} = 0.017 S cm{sup −1}, and lower activation energy, E{sub a} = 0.84 eV, compared to Ce{sub 0.9}Ca{sub 0.1}O{sub 1.9} ceramics prepared using glycine and urea. The scanning electron microscopy (SEM) results showed that pellets sintered at 1200 °C were dense, and the relative densities of these pellets were over 95%, determined using the Archimedes method.

  17. A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with [COW12O40]5-

    Institute of Scientific and Technical Information of China (English)

    Fatemeh F. Bamoharram; Mohammad M. Heravi; Touran Ardalan; Pouran Ardalan

    2009-01-01

    A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with potassium 12-tungsto cobalt (Ⅲ) ate ion, K5[CoW12O40], abbreviated as Co(Ⅲ)W, has been performed in different solvents. The studies were carried out in methanol, ethanol, acetonitrile and acetic acid/water. The rate constants, reaction rates and activation parameters were calculated. Our findings show that the rate of disappearance of the Co(Ⅲ) is pseudo-first order. The kinetic data is strongly affected by used solvents. The maximum and minimum rate constants were achieved in the ethanol and acetic acid/water (70/30) as a solvent, respectively. In all of the used solvents, negative value of activation entropies was observed, but negative activation enthalpies are observed in methanol, ethanol and acetonitrile. The reaction rate is increased with increase of Co(Ⅲ) concentration.

  18. Study of activation cross-sections of deuteron induced reactions on rhodium up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Ditroi, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Tarkanyi, F.; Takacs, S. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron Radioisotope Center (CYRIC) Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2011-09-15

    Highlights: {yields} Excitation function measurement of deuteron induced reactions on rhodium up to 40 MeV. {yields} Model code calculations with EMPIRE, ALICE and TALYS. {yields} Integral production yield calculation. {yields} Thin layer activation (TLA) with the produced isotopes. - Abstract: In the frame of a systematic study of the activation cross-sections of deuteron induced nuclear reactions, excitation functions of the {sup 103}Rh(d,x) {sup 100,101,103}Pd, {sup 100g,101m,101g,102m,102g}Rh and {sup 103g}Ru reactions were determined up to 40 MeV. Cross-sections were measured with the activation method using a stacked foil irradiation technique. Excitation functions of the contributing reactions were calculated using the ALICE-IPPE, EMPIRE-II and TALYS codes. From the measured cross-section data integral production yields were calculated and compared with experimental integral yield data reported in the literature. From the measured cross-sections and previous data, activation curves were deduced to support thin layer activation (TLA) on rhodium and Rh containing alloys.

  19. A Comparative Effectiveness Study of Bone Density Changes in Women Over 40 Following Three Bone Health Plans Containing Variations of the Same Novel Plant-sourced Calcium

    Directory of Open Access Journals (Sweden)

    Gilbert R. Kaats, Harry G. Preuss, Harry A. Croft, Samuel C. Keith, Patti L. Keith

    2011-01-01

    Full Text Available Background: The US Surgeon General's Report on Bone Health suggests America's bone-health is in jeopardy and issued a “call to action” to develop bone-health plans incorporating components of (1 improved nutrition, (2 increased health literacy, and (3 increased physical activity.Objective: To conduct a Comparative Effectiveness Research (CER study comparing changes in bone mineral density in healthy women over-40 with above-average compliance when following one of three bone health Plans incorporating the SG's three components.Methods: Using an open-label sequential design, 414 females over 40 years of age were tested, 176 of whom agreed to participate and follow one of three different bone-health programs. One Plan contained a bone-health supplement with 1,000 IUs of vitamin D3 and 750 mg of a plant-sourced form of calcium for one year. The other two Plans contained the same plant form of calcium, but with differing amounts of vitamin D3 and other added bone health ingredients along with components designed to increase physical activity and health literacy. Each group completed the same baseline and ending DXA bone density scans, 43-chemistry blood test panels, and 84-item Quality of Life Inventory (QOL. Changes for all subjects were annualized as percent change in BMD from baseline. Using self-reports of adherence, subjects were rank-ordered and dichotomized as “compliant” or “partially compliant” based on the median rating. Comparisons were also made between the treatment groups and two theoretical age-adjusted expected groups: a non-intervention group and a group derived from a review of previously published studies on non-plant sources of calcium.Results: There were no significant differences in baseline BMD between those who volunteered versus those who did not and between those who completed per protocol (PP and those who were lost to attrition. Among subjects completing per protocol, there were no significant differences

  20. Multifaceted Role of Calcium in Cancer.

    Science.gov (United States)

    Sarode, Gargi S; Sarode, Sachin C; Patil, Shankargouda

    2017-01-01

    Role of calcium in bone remodeling and tooth remineral-ization is well known. However, calcium also plays a very imperative role in many biochemical reactions, which are essential for normal functioning of cells. The calcium associated tissue homeostasis encompasses activities like proliferation, cell death, cell motility, oxygen, and nutrient supply.

  1. New Measurements of the Astrophysically Important ^44Ti Radionuclide Through the ^40Ca(α,γ)^44Ti Reaction

    Science.gov (United States)

    Robertson, Daniel; Becker, Hans-Werner; Collon, Philippe; Goerres, Joachim; Wiescher, Michael

    2010-11-01

    The relatively short-lived radionuclide ^44Ti (t1/2=58.9 ± 0.3 yrs), is of considerable importance in the study of nucleosynthesis in explosive stellar environments. It's production predominantly through the ^40Ca(α,γ)^44Ti reaction, takes place during α-rich freeze-out, in the inner most layers of a core-collapse supernova. A number of experimental studies have been previously performed to determine the stellar reaction rate. These studies included prompt γ-ray measurements from in-beam experiments, atom counting techniques utilizing accelerator mass spectrometry (AMS) and multi energy step measurements at the DRAGON recoil mass separator. The resulting calculated reaction rates show drastic disagreement. New results from experiments at the DTL, Bochum and NSL, Notre Dame, used both gamma spectroscopy and AMS techniques to measure the reaction, and investigate the discrepancies in both the experimental and predicted results. Final results of the experiments and their impact on the reaction rate will be discussed.

  2. Effects of pH value of reaction solution on structure and electrochemical performance of calcium-containing active material of secondary zinc electrodes

    Institute of Scientific and Technical Information of China (English)

    陈华; 王建明; 郑奕; 张鉴清; 曹楚南

    2004-01-01

    The calcium-containing active material of secondary alkaline zinc electrodes was prepared by a chemical coprecipitation method and characterized by scanning electron microscopy(SEM) and X-ray diffractometry(XRD).Their electrochemical performance was tested by the Galvanstatic charge-discharge method. The experimental results show that the sample synthesized at pH = 11.15 has a typical calcium zincate crystal. The zinc electrode using this sample as active material shows higher discharge capacity, more negative discharge plateau potential and longer cycle lifetime.

  3. [Calcium carbide of different crystal formation synthesized by calcium carbide residue].

    Science.gov (United States)

    Lu, Zhong-yuan; Kang, Ming; Jiang, Cai-rong; Tu, Ming-jing

    2006-04-01

    To recycle calcium carbide residue effectively, calcium carbide of different crystal form, including global aragonite, calcite and acicular calcium carbide was synthesized. Both the influence of pretreatment in the purity of calcium carbide, and the influence of temperatures of carbonization reaction, release velocity of carbon dioxide in the apparition of calcium carbide of different crystal form were studied with DTA-TG and SEM. The result shows that calcium carbide residue can take place chemistry reaction with ammonia chlorinate straight. Under the condition that pH was above 7, the purity of calcium carbide was above 97%, and the whiteness was above 98. Once provided the different temperatures of carbonization reaction and the proper release velocity of carbon dioxide, global aragonite, calcite and acicular calcium carbide were obtained.

  4. Calcium regulation in endosymbiotic organelles of plants

    OpenAIRE

    Bussemer, Johanna; Vothknecht, Ute C.; Chigri, Fatima

    2009-01-01

    In plant cells calcium-dependent signaling pathways are involved in a large array of biological processes in response to hormones, biotic/abiotic stress signals and a variety of developmental cues. This is generally achieved through binding of calcium to diverse calcium-sensing proteins, which subsequently control downstream events by activating or inhibiting biochemical reactions. Regulation by calcium is considered as a eukaryotic trait and has not been described for prokaryotes. Neverthele...

  5. Activation cross-sections of deuteron induced nuclear reactions on rhenium up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Ditrói, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Tárkányi, F.; Takács, S. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2013-02-01

    Highlights: ► Excitation function measurement of deuteron induced reactions on rhenium up to 40 MeV. ► Model code calculations with EMPIRE-D, ALICE-D and TALYS (TENDL-2011). ► Integral production yield calculation. ► Thin layer activation (TLA) curves; {sup 185}Os and {sup 186}Re. -- Abstract: As a part of a thorough work of excitation functions on deuteron induced reactions, experimental cross-sections of {sup 185,183m,183g,182}Os and {sup 188,186,184m,184g,183}Re activation products on {sup nat}Re were measured up to 40 MeV for the first time with the activation method using a stacked foil irradiation technique and high resolution γ-spectrometry. Comparison with the former results of other laboratories and with the predictions of the ALICE-IPPE and EMPIRE-3 model codes, modified for improved calculations for deuteron reactions, and with data in the TENDL-2011 library are also presented. Thick target yields were given deduced from our experimental cross-sections and compared with the few literature values. For practical applications (thin layer activation) also activity versus depth distributions were calculated for selected isotopes.

  6. Analysis of the normal optical, Michel and molecular potentials on the $^{40}$Ca($^6$Li, d)$^{44}$ Ti reaction

    Indian Academy of Sciences (India)

    MAZUMDER UTTAM K; SOMADDER ANOCK; HOQUE ENAMUL; HAQUE YASMEEN; DAS SUSANTA K; SEN GUPTA H M

    2016-06-01

    Full finite-range (FFR) distorted-wave Born approximation (DWBA) method has been applied to analyse the angular distributions of cross-sections of the $^{40}$Ca($^{6}$Li, d)$^{44}$Ti reaction at 28 MeV incident energy for the 22 transitions involving both the bound and unbound states of $^{44}$Ti byusing the normal optical, Michel and molecular potentials. The extracted spectroscopic factors for the three optical potentials are compared with those of some previous studies of zero-range (ZR) calculations of the$^{40}$Ca($^{6}$Li, d)$^{44}$Ti reaction using the normal optical potential. The $\\chi^{2}$ values of all the levels are obtained for the three optical potentials to estimate the quality of the fits. Molecular and Michel potentials have been used for the first time to analyse the four-nucleon transfer reaction and it seems that the molecular potential fits the experimental data more satisfactorily for some of the states than the normal optical and Michel potentials.

  7. 40 CFR 721.2076 - D-Glucuronic acid, polymer with 6-deoxy-L-mannose and D-glucose, acetate, calcium magnesium...

    Science.gov (United States)

    2010-07-01

    ...-deoxy-L-mannose and D-glucose, acetate, calcium magnesium potassium sodium salt. 721.2076 Section 721...-Glucuronic acid, polymer with 6-deoxy-L-mannose and D-glucose, acetate, calcium magnesium potassium sodium... identified as D-Glucuronic acid, polymer with 6-deoxy-L-mannose and D-glucose, acetate, calcium...

  8. Bone reaction adjacent to microplasma-sprayed calcium phosphate-coated oral implants subjected to an occlusal load, an experimental study in the dog

    NARCIS (Netherlands)

    Junker, R.; Manders, P.J.D.; Wolke, J.G.C.; Borisov, Y.; Braceras, I.; Jansen, J.A.

    2011-01-01

    BACKGROUND: A new microplasma spraying equipment (MSE) to deposit calcium phosphate (CaP) ceramic coatings onto titanium substrates has been developed. With this system, it is possible to spray fine particles and to apply textured hydroxylapatite coatings onto titanium surfaces. Moreover, due to the

  9. Activation cross-sections of deuteron induced nuclear reactions on gold up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tarkanyi, F. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Ditroi, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Takacs, S.; Kiraly, B. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron and Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2011-06-15

    Cross-sections of deuteron induced nuclear reactions on gold were measured up to 40 MeV by using the standard stacked foil irradiation technique and high resolution gamma-ray spectroscopy. Experimental cross-sections and derived integral yields are reported for the {sup 197}Au(d,xn){sup 197m,197g,195m,195g}Hg and {sup 197}Au(d,x){sup 198g,196m,196g,195,194}Au nuclear reactions. The experimental data are analyzed and compared to literature and predictions of the ALICE-IPPE, EMPIRE and TALYS theoretical model codes. The application of the new cross-sections for accelerator technology, medical radioisotope production, thin layer activation and dose calculation is discussed.

  10. Activation cross-sections of deuteron induced nuclear reactions on manganese up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Ditroi, F., E-mail: ditroi@atomki.hu [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Tarkanyi, F.; Takacs, S. [Institute of Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron and Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2011-09-01

    In the frame of a systematic study on activation cross-sections of deuteron induced reactions experimental excitation functions on {sup 55}Mn were measured with the activation method using the stacked foil irradiation technique up to 40 MeV. By using high resolution {gamma}-ray spectrometry, cross-section data for the production of {sup 56,54,52}Mn and {sup 51}Cr were determined. Comparison with the earlier published data and with the results predicted by the ALICE-IPPE and EMPIRE-II theoretical codes - improved for more reliable calculations for d-induced reactions - and with data in the TENDL 2010 libraries are also included. Thick target yields were calculated from a fit to our experimental excitation curves and implications for practical applications in industrial (Thin Layer Activation) accelerator technology are discussed.

  11. Diagnosis and assessment of skeletal related disease using calcium 41

    Science.gov (United States)

    Hillegonds, Darren J [Oakland, CA; Vogel, John S [San Jose, CA; Fitzgerald, Robert L [Encinitas, CA; Deftos, Leonard J [Del Mar, CA; Herold, David [Del Mar, CA; Burton, Douglas W [San Diego, CA

    2012-05-15

    A method of determining calcium metabolism in a patient comprises the steps of administering radioactive calcium isotope .sup.41Ca to the patient, allowing a period of time to elapse sufficient for dissemination and reaction of the radioactive calcium isotope .sup.41Ca by the patient, obtaining a sample of the radioactive calcium isotope .sup.41Ca from the patient, isolating the calcium content of the sample in a form suitable for precise measurement of isotopic calcium concentrations, and measuring the calcium content to determine parameters of calcium metabolism in the patient.

  12. [Microbial geochemical calcium cycle].

    Science.gov (United States)

    Zavarzin, G A

    2002-01-01

    The participation of microorganisms in the geochemical calcium cycle is the most important factor maintaining neutral conditions on the Earth. This cycle has profound influence on the fate of inorganic carbon, and, thereby, on the removal of CO2 from the atmosphere. The major part of calcium deposits was formed in the Precambrian, when prokaryotic biosphere predominated. After that, calcium recycling based on biogenic deposition by skeletal organisms became the main process. Among prokaryotes, only a few representatives, e.g., cyanobacteria, exhibit a special calcium function. The geochemical calcium cycle is made possible by the universal features of bacteria involved in biologically mediated reactions and is determined by the activities of microbial communities. In the prokaryotic system, the calcium cycle begins with the leaching of igneous rock predominantly through the action of the community of organotrophic organisms. The release of carbon dioxide to the soil air by organotrophic aerobes leads to leaching with carbonic acid and soda salinization. Under anoxic conditions, of major importance is the organic acid production by primary anaerobes (fermentative microorganisms). Calcium carbonate is precipitated by secondary anaerobes (sulfate reducers) and to a smaller degree by methanogens. The role of the cyanobacterial community in carbonate deposition is exposed by stromatolites, which are the most common organo-sedimentary Precambrian structures. Deposition of carbonates in cyanobacterial mats as a consequence of photoassimilation of CO2 does not appear to be a significant process. It is argued that carbonates were deposited at the boundary between the "soda continent", which emerged as a result of subaerial leaching with carbonic acid, and the ocean containing Ca2+. Such ecotones provided favorable conditions for the development of the benthic cyanobacterial community, which was a precursor of stromatolites.

  13. Calcium in diet

    Science.gov (United States)

    ... D is needed to help your body use calcium. Milk is fortified with vitamin D for this reason. ... of calcium dietary supplements include calcium citrate and calcium carbonate. Calcium citrate is the more expensive form of ...

  14. Numerical Simulation of Reaction-Diffusion during Carburization of HK40 Steel

    Institute of Scientific and Technical Information of China (English)

    Meili ZHU; Qiang XU; Junshan ZHANG

    2003-01-01

    Two types of carbides M23C6 and M7C3 precipitate orderly as carbon concentration in a high Cr-Ni austenitic steel increases during carburization process. The mathematical model that describes diffusion of carbon and the precipitation of M23C6 and M7C3 has been studied. A criterion to judge when the transformation of M23C6 to M7C3 is over and M7C3 precipitates directly has been given in simulated calculation. By applying the model, the carburization of HK40 steel has been calculated by means of finite difference computation techniques. The pack carburization tests for the HK40 steel have been carried out at 1273 K. The comparison between the experimental and the calculated results show acceptable agreement.

  15. Structural Evolution under Reaction Conditions of Supported (NH43HPMo11VO40 Catalysts for the Selective Oxidation of Isobutane

    Directory of Open Access Journals (Sweden)

    Fangli Jing

    2015-03-01

    Full Text Available When using heteropolycompounds in the selective oxidation of isobutane to methacrolein and methacrylic acid, both the keeping of the primary structure (Keggin units and the presence of acidic sites are necessary to obtain the desired products. The structural evolution of supported (NH43HPMo11VO40 (APMV catalysts under preliminary thermal oxidizing and reducing treatments was investigated. Various techniques, such as TGA/DTG (Thermo-Gravimetric Analysis/Derivative Thermo-Gravimetry, H2-TPR (Temperature Programed Reduction, in situ XRD (X-Ray Diffraction and XPS (X-ray Photoelectron Spectroscopy, were applied. It was clearly evidenced that the thermal stability and the reducibility of the Keggin units are improved by supporting 40% APMV active phase on Cs3PMo12O40 (CPM. The partial degradation of APMV takes place depending on temperature and reaction conditions. The decomposition of ammonium cations (releasing NH3 leads to the formation of vacancies favoring cationic exchanges between vanadium coming from the active phase and cesium coming from the support. In addition, the vanadium expelled from the Keggin structure is further reduced to V4+, species, which contributes (with Mo5+ to activate isobutane. The increase in reducibility of the supported catalyst is assumed to improve the catalytic performance in comparison with those of unsupported APMV.

  16. Synthesis of calcium superoxide

    Science.gov (United States)

    Rewick, R. T.; Blucher, W. G.; Estacio, P. L.

    1972-01-01

    Efforts to prepare Ca(O2) sub 2 from reactions of calcium compounds with 100% O3 and with O(D-1) atoms generated by photolysis of O3 at 2537 A are described. Samples of Ca(OH) sub 2, CaO, CaO2, Ca metal, and mixtures containing suspected impurities to promote reaction have been treated with excess O3 under static and flow conditions in the presence and absence of UV irradiation. Studies with KO2 suggest that the superoxide anion is stable to radiation at 2537 A but reacts with oxygen atoms generated by the photolysis of O3 to form KO3. Calcium superoxide is expected to behave in an analogous.

  17. Calcium Electroporation

    DEFF Research Database (Denmark)

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

    2015-01-01

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

  18. Calcium aluminate in alumina

    Science.gov (United States)

    Altay, Arzu

    The properties of ceramic materials are determined not only by the composition and structure of the phases present, but also by the distribution of impurities, intergranular films and second phases. The phase distribution and microstructure both depend on the fabrication techniques, the raw materials used, the phase-equilibrium relations, grain growth and sintering processes. In this dissertation research, various approaches have been employed to understand fundamental phenomena such as grain growth, impurity segregation, second-phase formation and crystallization. The materials system chosen was alumina intentionally doped with calcium. Atomic-scale structural analyses of grain boundaries in alumina were carried on the processed samples. It was found that above certain calcium concentrations, CA6 precipitated as a second phase at all sintering temperatures. The results also showed that abnormal grain growth can occur after precipitation and it is not only related to the calcium level, but it is also temperature dependent. In order to understand the formation mechanism of CA6 precipitates in calcium doped alumina samples, several studies have been carried out using either bulk materials or thin films The crystallization of CA2 and CA6 powders has been studied. Chemical processing techniques were used to synthesize the powders. It was observed that CA2 powders crystallized directly, however CA6 powders crystallized through gamma-Al 2O3 solid solution. The results of energy-loss near-edge spectrometry confirmed that gamma-Al2O3 can dissolve calcium. Calcium aluminate/alumina reaction couples have also been investigated. All reaction couples were heat treated following deposition. It was found that gamma-Al2O3 was formed at the interface as a result of the interfacial reaction between the film and the substrate. gamma-Al 2O3 at the interface was stable at much higher temperatures compared to the bulk gamma-Al2O3 formed prior to the CA6 crystallization. In order to

  19. 40 Ca+58Fe,58Ni反应中的径向膨胀流研究%Radial Expansion Flow in Reactions of 40 Ca+58Fe and 40 Ca+58Ni

    Institute of Scientific and Technical Information of China (English)

    明照宇; 张丰收; 陈列文; 朱志远

    2001-01-01

    By means of using an isospin-dependent Boltzmann-Langevin equation which includes isospin-dependent symmetry energy, Coulomb energy, isospin-dependent nucleon-nucleon cross sections, Pauli blocking, and initialization, the radial expansion flow of reaction systems 40 Ca+58Ni and 40 Ca+58Fe at 53, 100, 150, and 200 MeV/u in the central collisions were studied. It has shown that the more neutron-rich system exhibits smaller radial expansion flow. It was found that the neutron-rich system had smaller threshold energy which may provide a new method to determine the isospin dependent nuclear equation of state from calculated result and linear fitting result.%利用同位旋相关的Boltzmann-Langevin方程研究了40Ca+58Fe和40Ca+58 Ni两个反应系统在53,100,150和200MeV/u入射能量下对心碰撞的径向膨胀流. 发现对于丰中子系统40Ca+58Fe的径向膨胀流系统性地小于稳定系统40 Ca+58Ni的径向膨胀流. 在假定轰击能量与反应体系的压缩密度呈抛物线关系时,能够解释入射能量和径向膨胀流之间呈现的直线关系. 提取了出现径向膨胀流的轰击能量阈值,发现对丰中子系统40Ca+58Fe得到的能量阈值小于稳定系统40Ca+58Ni所得到的能量阈值.

  20. Effects of Symmetry Energy in the Reaction 40Ca+124Sn at 140 MeV/nucleon

    CERN Document Server

    Zhang, Fang; Yong, Gao-Chan; Zuo, Wei

    2012-01-01

    The density-dependent symmetry energy is a hot topic in nuclear physics. Many laboratories over the world are planning to perform related experiments to probe the symmetry energy. Based on the semiclassical Boltzmann-Uehling-Uhlenbeck (BUU) transport model, we study the effects of nuclear symmetry energy in the central reaction 40Ca+124Sn at 140MeV/nucleon in the laboratory system. It is found that the rapidity distribution of free nucleon's neutron-to-proton ratio is sensitive to the symmetry energy, especially at large rapidities. The free neutron-to-proton ratios at small or large rapidities may reflect high or low density behavior of nuclear symmetry energy. To probe the density dependence of nuclear symmetry energy, it is better to give the kinetic distribution and the rapidity distribution of emitted nucleons at the same time.

  1. Dry reforming reaction over nickel catalysts supported on nanocrystalline calcium aluminates with different CaO/Al2O3 ratios

    Institute of Scientific and Technical Information of China (English)

    Atiyeh Ranjbar; Mehran Rezaei

    2012-01-01

    Nanocrystalline calcium aluminates with different CaO/Al2O3 ratios were prepared by a facile co-precipitation method using Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) (PEG-PPG-PEG,MW:5800) as a surfactant.They were employed as catalyst support for nickel catalysts in methane reforming with carbon dioxide.The prepared samples were characterized by X-ray diffraction (XRD),N2 adsorption (BET),temperature-programmed reduction and oxidation (TPR-TPO),and scanning electron microscopy (SEM) techniques.Catalysts showed a relatively high catalytic activity and stability.TPR analysis revealed that the catalysts with higher CaO content are more difficult to be reduced.TPO analysis showed that the 5 wt%Ni/CA and 5 wt%Ni/C 12A7 catalysts with higher CaO amount were effective against coke deposition.

  2. Implications for (d ,p ) reaction theory from nonlocal dispersive optical model analysis of 40Ca(d ,p )41Ca

    Science.gov (United States)

    Waldecker, S. J.; Timofeyuk, N. K.

    2016-09-01

    The nonlocal dispersive optical model (NLDOM) nucleon potentials are used for the first time in the adiabatic analysis of a (d ,p ) reaction to generate distorted waves both in the entrance and exit channels. These potentials were designed and fitted by Mahzoon et al. [Phys. Rev. Lett. 112, 162503 (2014), 10.1103/PhysRevLett.112.162503] to constrain relevant single-particle physics in a consistent way by imposing the fundamental properties, such as nonlocality, energy-dependence and dispersive relations, that follow from the complex nature of nuclei. However, the NLDOM prediction for the 40Ca(d ,p )41Ca cross sections at low energy, typical for some modern radioactive beam ISOL (isotope separation online) facilities, is about 70% higher than the experimental data despite being reduced by the NLDOM spectroscopic factor of 0.73. This overestimation comes most likely either from insufficient absorption or due to constructive interference between ingoing and outgoing waves. This indicates strongly that additional physics arising from many-body effects is missing in the widely used current versions of (d ,p ) reaction theories.

  3. Carbon Dioxide Adsorption by Calcium Zirconate at Higher Temperature

    Directory of Open Access Journals (Sweden)

    K. B. Kale

    2012-12-01

    Full Text Available The CO2 adsorption by calcium zirconate was explored at pre- and post- combustion temperature condition. The several samples of the calcium zirconate were prepared by different methods such as sol-gel, solid-solid fusion, template and micro-emulsion. The samples of the calcium zirconate were characterized by measurement of surface area, alkalinity/acidity, and recording the XRD patterns and SEM images. The CO2 adsorptions by samples of the calcium zirconate were studied in the temperature range 100 to 850 oC and the CO2 adsorptions were observed in the ranges of 6.88 to 40.6 wt % at 600 0C and 8 to 16.82 wt% at in between the temperatures 200 to 300 oC. The effect of Ca/Zr mol ratio in the samples of the calcium zirconate on the CO2 adsorption and alkalinity were discussed. The adsorbed moisture by the samples of the calcium zirconate was found to be useful for the CO2 adsorption. The promoted the samples of the calcium zirconate by K+, Na+, Rb+, Cs+, Ag+ and La3+ showed the increased CO2 adsorption. The exposure time of CO2 on the samples of the calcium zirconate showed the increased CO2 adsorption. The samples of the calcium zirconate were found to be regenerable and reusable several times for the adsorption of CO2 for at the post- and pre-combustion temperature condition. Copyright © 2012 by BCREC Undip. All rights reservedReceived: 23rd June 2012, Revised: 28th August 2012, Accepted: 30th August 2012[How to Cite: K. B. Kale, R. Y. Raskar, V. H. Rane and A. G.  Gaikwad (2012. Carbon Dioxide Adsorption by Calcium Zirconate at Higher Temperature. Bulletin of Chemical Reaction Engineering & Catalysis, 7 (2: 124-136. doi:10.9767/bcrec.7.2.3686.124-136] [How to Link / DOI: http://dx.doi.org/10.9767/bcrec.7.2.3686.124-136 ] | View in 

  4. Effect of calcium on adsorptive removal of As(III) and As(V) by iron oxide-based adsorbents

    KAUST Repository

    Uwamariya, V.

    2014-06-25

    The effects of calcium on the equilibrium adsorption capacity of As(III) and As(V) onto iron oxide-coated sand (IOCS) and granular ferric hydroxide (GFH) were investigated through batch experiments, rapid small-scale column tests (RSSCT) and kinetics modelling. Batch experiments showed that at calcium concentrations≤20 mg/L, high As(III) and As(V) removal efficiencies by IOCS and GFH are achieved at pH 6. An increase of the calcium concentration to 40 and 80 mg/L reversed this trend, giving higher removal efficiencies at higher pH (8). The adsorption capacities of IOCS and GFH at an equilibrium arsenic concentration of 10 g/L were found to be between 2.0 and 3.1 mg/g for synthetic water without calcium and between 2.8 and 5.3 mg/g when 80 mg/L of calcium was present at the studied pH values. After 10 hours of filter run in RSSCT, approximately 1000 empty bed volumes, the ratios of C/Co for As(V) were 26% and 18% for calcium-free model water; and only 1% and 0.2% after addition of 80 mg/L of Ca for filter columns with IOCS and GFH, respectively. The adsorption of As(III) and As(V) onto GFH follows a second-order reaction, with and without addition of calcium. The adsorption of As(III) and As(V) onto IOCS follows a first-order reaction without calcium addition, and moves to the second-reaction-order kinetics when calcium is added. Based on the intraparticle diffusion model, the main controlling mechanism for As(III) adsorption is intraparticle diffusion, while surface diffusion contributes greatly to the adsorption of As(V).

  5. Experimental Probe to the Isospin-Dependent Properties of Hot Nuclei in Reactions 40Ar+112,124 Sn at 30 MeV/u

    Institute of Scientific and Technical Information of China (English)

    肖志刚; 靳根明; 吴和宇; 魏志勇; 王宏伟; 段利敏; 柳永英; 李祖玉; 张保国; 诸永泰; 王素芳; 卢朝晖; 朱海东; 胡荣江

    2001-01-01

    Protons are emitted in a greater quantity in a neutron-deficient system 40Ar+112Sn while triton emissions are greater in a neutron-rich system 40Ar+124Sn at an incident energy of 30 MeV/u. Similar to neutrons, proton emission provides a dominant contribution to neutralize the system N/Z in the decay process of the hot nuclei.The emission of hydrogen isotopes with high energies is much enhanced in the 112Sn system. The original temperature of the hot nuclei in the 40Ar+112Sn reaction is 5.8+0.3 MeV, about 0.7 MeV higher than 5.1+0.3MeV as in the 40Ar+124Sn reaction.

  6. Why does neutron transfer play different roles in sub-barrier fusion reactions $^{32}$S+$^{94,96}$Zr and $^{40}$Ca+$^{94,96}$Zr?

    CERN Document Server

    Sargsyan, V V; Antonenko, N V; Scheid, W; Zhang, H Q

    2014-01-01

    The sub-barrier capture (fusion) reactions $^{32}$S+$^{90,94,96}$Zr, $^{36}$S+$^{90,96}$Zr, $^{40}$Ca+$^{90,94,96}$Zr, and $^{48}$Ca+$^{90,96}$Zr with positive and negative $Q$-values for neutron transfer are studied within the quantum diffusion approach and the universal fusion function representation. For these systems, the s-wave capture probabilities are extracted from the experimental excitation functions and are also analyzed. Different effects of the positive $Q_{xn}$-value neutron transfer in the fusion enhancement are revealed in the relatively close reactions $^{32}$S+$^{94,96}$Zr and $^{40}$Ca+$^{94,96}$Zr.

  7. 窑法磷酸中磷酸钙对P2O5反吸过程%Reactions between P2O5 and calcium phosphate in kiln phosphoric acid

    Institute of Scientific and Technical Information of China (English)

    吕莉; 梁斌; 刘强; 刘维燥; 杨宏辉; 吴潘; 李春

    2016-01-01

    Side reactions of gaseous product P2O5 with phosphate ores (so-called P2O5 back absorption) in rotary kiln produce large quantities of low melting point solid products, which could form a kiln ring, block material flow and cause unstable operation of the kiln. The back absorption of gaseous P2O5 with calcium phosphate was studied at different temperatures and the products were characterized for P2O5 content, morphology, phase composition, structure and thermal stability by chemical analysis and other techniques of SEM, XRD, IR, Raman, TG and DSC. The experimental results show that temperature significantly affected the back absorption, which was occurred above 500℃. Calcium metaphosphate was formed at 500—900℃ with almost pure calcium metaphosphate at 900℃. Calcium metaphosphate decomposed into calcium pyrophosphate and P2O5at 1000—1300℃ with almost pure calcium pyrophosphate at 1300℃.%窑法磷酸生产中,气体产物 P2O5与磷矿发生副反应(俗称 P2O5反吸)生成大量低熔点物料,导致窑内结圈堵料,造成生产装置不能稳定运行。以磷酸钙与 P2O5的反应为研究对象,采用化学分析与 SEM、XRD、IR、Raman、TG及DSC等表征手段对不同温度下该反应产物的P2O5含量、形貌、物相组成、结构及热稳定性能等进行研究,探讨磷矿对P2O5的反吸行为。研究表明,反吸过程与反应温度密切相关,磷酸钙与P2O5在500℃以上发生反应,在500~900℃时,磷酸钙与P2O5反应生成偏磷酸钙,900℃反吸产物几乎为纯偏磷酸钙;在1000~1300℃时,反吸产物偏磷酸钙分解为稳定的焦磷酸钙,同时释放出P2O5气体,1300℃时反吸产物几乎为纯焦磷酸钙。

  8. Calcium regulation in endosymbiotic organelles of plants.

    Science.gov (United States)

    Bussemer, Johanna; Vothknecht, Ute C; Chigri, Fatima

    2009-09-01

    In plant cells calcium-dependent signaling pathways are involved in a large array of biological processes in response to hormones, biotic/abiotic stress signals and a variety of developmental cues. This is generally achieved through binding of calcium to diverse calcium-sensing proteins, which subsequently control downstream events by activating or inhibiting biochemical reactions. Regulation by calcium is considered as a eukaryotic trait and has not been described for prokaryotes. Nevertheless, there is increasing evidence indicating that organelles of prokaryotic origin, such as chloroplasts and mitochondria, are integrated into the calcium-signaling network of the cell. An important transducer of calcium in these organelles appears to be calmodulin. In this review we want to give an overview over present data showing that endosymbiotic organelles harbour calcium-dependent biological processes with a focus on calmodulin-regulation.

  9. Calcium and bones

    Science.gov (United States)

    Bone strength and calcium ... calcium (as well as phosphorus) to make healthy bones. Bones are the main storage site of calcium in ... your body does not absorb enough calcium, your bones can get weak or will not grow properly. ...

  10. Calcium Test

    Science.gov (United States)

    ... if a person has symptoms of a parathyroid disorder , malabsorption , or an overactive thyroid. A total calcium level is often measured as part of a routine health screening. It is included in the comprehensive metabolic panel (CMP) and the basic metabolic panel (BMP) , ...

  11. Calcium Carbonate

    Science.gov (United States)

    ... doctor if you have or have ever had kidney disease or stomach conditions.tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking calcium carbonate, call your doctor.

  12. The Role of Calcium in Osteoporosis

    Science.gov (United States)

    Arnaud, C. D.; Sanchez, S. D.

    1991-01-01

    Calcium requirements may vary throughout the lifespan. During the growth years and up to age 25 to 30, it is important to maximize dietary intake of calcium to maintain positive calcium balance and achieve peak bone mass, thereby possibly decreasing the risk of fracture when bone is subsequently lost. Calcium intake need not be greater than 800 mg/day during the relatively short period of time between the end of bone building and the onset of bone loss (30 to 40 years). Starting at age 40 to 50, both men and women lose bone slowly, but women lose bone more rapidly around the menopause and for about 10 years after. Intestinal calcium absorption and the ability to adapt to low calcium diets are impaired in many postmenopausal women and elderly persons owing to a suspected functional or absolute decrease in the ability of the kidney to produce 1,25(OH)2D2. The bones then become more and more a source of calcium to maintain critical extracellular fluid calcium levels. Excessive dietary intake of protein and fiber may induce significant negative calcium balance and thus increase dietary calcium requirements. Generally, the strongest risk factors for osteoporosis are uncontrollable (e.g., sex, age, and race) or less controllable (e.g., disease and medications). However, several factors such as diet, physical activity, cigarette smoking, and alcohol use are lifestyle related and can be modified to help reduce the risk of osteoporosis.

  13. The Thermal Decomposition of Calcium Carbonate

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The thermogravimetry(TG) and derivative thermogravimetry(DTG) curves of the thermal decomposition reaction of calcium carbonate have been measured at five different heating rates. The kinetic parameters and the reaction mechanism of the reaction were evaluated from analysis of the TG and DTG curves by using the Ozawa method, the combined integral and differential methods and the reduced equations derived by us.

  14. Bioceramics of calcium orthophosphates.

    Science.gov (United States)

    Dorozhkin, Sergey V

    2010-03-01

    A strong interest in use of ceramics for biomedical applications appeared in the late 1960's. Used initially as alternatives to metals in order to increase a biocompatibility of implants, bioceramics have become a diverse class of biomaterials, presently including three basic types: relatively bioinert ceramics, bioactive (or surface reactive) and bioresorbable ones. Furthermore, any type of bioceramics could be porous to provide tissue ingrowth. This review is devoted to bioceramics prepared from calcium orthophosphates, which belong to the categories of bioresorbable and bioactive compounds. During the past 30-40 years, there have been a number of major advances in this field. Namely, after the initial work on development of bioceramics that was tolerated in the physiological environment, emphasis was shifted towards the use of bioceramics that interacted with bones by forming a direct chemical bond. By the structural and compositional control, it became possible to choose whether the bioceramics of calcium orthophosphates was biologically stable once incorporated within the skeletal structure or whether it was resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics, which is able to regenerate bone tissues, has been developed. Current biomedical applications of calcium orthophosphate bioceramics include replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Potential future applications of calcium orthophosphate bioceramics will include drug-delivery systems, as well as they will become effective carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes.

  15. Reaction cross sections for protons on {sup 12}C, {sup 40}Ca, {sup 90}Zr and {sup 208}Pb at energies between 80 and 180 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Auce, A.; Ingemarsson, A.; Johansson, R. [and others

    2005-04-01

    Results of reaction cross section measurements on {sup 12}C, {sup 40}Ca, {sup 90}Zr and {sup 208}Pb at incident proton energies between 80 and 180 MeV and for {sup 58}Ni at 81 MeV are presented. The experimental procedure is described and the results are compared with earlier measurements and predictions using macroscopic and microscopic models.

  16. 40 CFR 721.9672 - Amides, tall-oil fatty, N-[2-[2-hydroxyethyl)amino]ethyl], reaction products with sulfur dioxide...

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Amides, tall-oil fatty, N- ethyl... Specific Chemical Substances § 721.9672 Amides, tall-oil fatty, N- ethyl], reaction products with sulfur... and significant new uses subject to reporting. (1) The chemical substance identified as amides,...

  17. Asymmetric Fission in the 78Kr+40Ca reactions at 5.5 MeV/nucleon

    Directory of Open Access Journals (Sweden)

    Roy R.

    2012-02-01

    Full Text Available The cross section, kinetic energy distribution and angular distribution of fragments with atomic number 3 ≤ Z ≤ 28 emitted in the reaction 78Kr + 40Ca at the bombarding energy of 5.5 MeV/nucleon and coincidence between light charged particles and fragments were measured by means of the 4π-INDRA array to study the decay mechanism of medium mass excited nucleus. Global features indicate a high degree of relaxation and are compatible with a binary fission from compound nucleus. The mean value of the kinetic energy distributions of fragments indicates dominance of Coulomb interaction, while the width of the distribution signals large fluctuations. Inclusive cross-section distributions of fragments with charge 3 ≤ Z ≤ 28 are bell-shaped and a strong even-odd-staggering (o-es is observed for 3 ≤ Z ≤ 12. Coincidence measurements suggest that the light partners in very asymmetric fission are emitted at excitation energies below the particle emission thresholds. Data were confronted to the predictions of statistical model describing the decay of compound nuclei by emission of light particles and fragments. Calculations assuming spherical fission fragments and finite-range liquid drop fission barriers are not able to explain the experimental features. Attempts have been made to improve the agreement with experimental data. The analysis indicates the strong influence of the shape parameterization of the potential energy surface in describing the fission process of intermediate mass compound nuclei.

  18. Gel time of calcium acrylate grouting material

    Institute of Scientific and Technical Information of China (English)

    韩同春

    2004-01-01

    Calcium acrylate is a polymerized grout, and can polymerize in an aqueous solution. The polymerization reaction utilizes ammonium persulfate as a catalyst and sodium thiosulfate as the activator. Based on the theory of reaction kinetics, this study on the relation between gel time and concentration of activator and catalyst showed that gel time of calcium acrylate is inversely proportional to activator and catalyst concentration. A formula of gel time is proposed, and an example is provided to verify the proposed formula.

  19. Calcium carbonate-calcium phosphate mixed cement compositions for bone reconstruction.

    Science.gov (United States)

    Combes, C; Bareille, R; Rey, C

    2006-11-01

    The feasibility of making calcium carbonate-calcium phosphate (CaCO(3)-CaP) mixed cements, comprising at least 40% (w/w) CaCO(3) in the dry powder ingredients, has been demonstrated. Several original cement compositions were obtained by mixing metastable crystalline CaCO(3) phases with metastable amorphous or crystalline CaP powders in aqueous medium. The cements set within at most 1 h at 37 degrees C in atmosphere saturated with water. The hardened cement is microporous and exhibits weak compressive strength. The setting reaction appeared to be essentially related to the formation of a highly carbonated nanocrystalline apatite phase by reaction of the metastable CaP phase with part or almost all of the metastable CaCO(3) phase. The recrystallization of metastable CaP varieties led to a final cement consisting of a highly carbonated poorly crystalline apatite analogous to bone mineral associated with various amounts of vaterite and/or aragonite. The presence of controlled amounts of CaCO(3) with a higher solubility than that of the apatite formed in the well-developed CaP cements might be of interest to increase resorption rates in biomedical cement and favors its replacement by bone tissue. Cytotoxicity testing revealed excellent cytocompatibility of CaCO(3)-CaP mixed cement compositions.

  20. Doc2b promotes GLUT4 exocytosis by activating the SNARE-mediated fusion reaction in a calcium- and membrane bending-dependent manner.

    Science.gov (United States)

    Yu, Haijia; Rathore, Shailendra S; Davis, Eric M; Ouyang, Yan; Shen, Jingshi

    2013-04-01

    The glucose transporter GLUT4 plays a central role in maintaining body glucose homeostasis. On insulin stimulation, GLUT4-containing vesicles fuse with the plasma membrane, relocating GLUT4 from intracellular reservoirs to the cell surface to uptake excess blood glucose. The GLUT4 vesicle fusion reaction requires soluble N-ethylmaleimide-sensitive factor attachment protein receptors (SNAREs) as the core fusion engine and a group of regulatory proteins. In particular, the soluble C2-domain factor Doc2b plays a key role in GLUT4 vesicle fusion, but its molecular mechanism has been unclear. Here we reconstituted the SNARE-dependent GLUT4 vesicle fusion in a defined proteoliposome fusion system. We observed that Doc2b binds to GLUT4 exocytic SNAREs and potently accelerates the fusion kinetics in the presence of Ca(2+). The stimulatory activity of Doc2b requires intact Ca(2+)-binding sites on both the C2A and C2B domains. Using electron microscopy, we observed that Doc2b strongly bends the membrane bilayer, and this membrane-bending activity is essential to the stimulatory function of Doc2b in fusion. These results demonstrate that Doc2b promotes GLUT4 exocytosis by accelerating the SNARE-dependent fusion reaction by a Ca(2+)- and membrane bending-dependent mechanism. Of importance, certain features of Doc2b function appear to be distinct from how synaptotagmin-1 promotes synaptic neurotransmitter release, suggesting that exocytic Ca(2+) sensors may possess divergent mechanisms in regulating vesicle fusion.

  1. 40 CFR 721.10145 - Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino...

    Science.gov (United States)

    2010-07-01

    ... alcohol, halogenated alkane, substituted epoxide, and amino compound (generic). 721.10145 Section 721... Modified reaction products of alkyl alcohol, halogenated alkane, substituted epoxide, and amino compound... identified generically as modified reaction products of alkyl alcohol, halogenated alkane,...

  2. 广东省63例钙拮抗药致心脏不良反应报告分析%Analysis of 63 Cases of Cardiac Adverse Reactions Induced by Calcium Antagonists in Guangdong Province

    Institute of Scientific and Technical Information of China (English)

    李洵; 刘秋琼; 陈文颖; 黄李琳; 林秋晓; 谭淑敏

    2013-01-01

    OBJECTIVE: To probe into the occurrence of calcium antagonists induced cardiac adverse reactions (ADR), and to explore the regularity of it in order to provide guidance for clinical rational drug use and ensure safe and effective drug use. METHODS : A total of 63 cases of calcium antagonists drug induced cardiac ADR reported by Guangdong province between Jan. 2002 and Jun. 2012 were analyzed statistically. RESULTS: The occurrence of cardiac ADR was not significantly associated with gender but closely related with age. ADR was mostly found in elderly patients aged 41 years old or above; the time of ADR occurred mostly within 1 day; dihydropyridine calcium antagonist caused cardiac ADR took up the highest proportion (60 cases, 95.24%); main clinical manifestations were heart palpitations, tachycardia, arrhythmias and so on, and palpitation occupied the highest percentage (76.19% ); high proportion of cardiac ADR were caused by conventional tablets (58.73% ), and the number of cardiac ADR induced by controlled or sustained-release formulations was reduced significantly. CONCLUSION: ADR monitoring, timely prevention, reporting and updating of ADR should be more emphasized in hypertensive patients receiving calcium antagonist to reduce the incidence of ADR and further enhance the effect of drug treatment.%目的:了解钙拮抗药致心脏不良反应(ADR)的发生特点及规律,以减少ADR的重复发生.方法:对广东省2002年1月-2012年6月上报的63例钙拮抗药致心脏ADR进行统计、分析.结果:心脏ADR的发生与性别关系不大,与年龄关系密切,以41岁以上的中、老年患者居多;ADR发生时间多集中在24h内;二氢吡啶类钙拮抗药引起的ADR比例最高(60例,95.24%);心脏ADR临床表现以心悸、心动过速、心律失常等为主,其中心悸构成比例最高(76.19%);心脏ADR报告药物剂型以普通片构成比例最高(58.73%),缓、控释制剂导致的ADR明显减少.结论:应加强高血压

  3. 40 CFR 721.5560 - Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz[c...

    Science.gov (United States)

    2010-07-01

    ... (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6-oxide. 721.5560 Section 721... Formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with 6H-dibenz oxaphosphorin-6... identified as formaldehyde, polymer with (chloromethyl) oxirane and phenol, reaction products with...

  4. 40 CFR 721.10190 - Formaldehyde, polymer with aliphatic diamine and phenol, reaction products with 4-methyl-2...

    Science.gov (United States)

    2010-07-01

    ... diamine and phenol, reaction products with 4-methyl-2-pentanone (generic). 721.10190 Section 721.10190... Formaldehyde, polymer with aliphatic diamine and phenol, reaction products with 4-methyl-2-pentanone (generic... identified generically as formaldehyde, polymer with aliphatic diamine and phenol, reaction products with...

  5. Synthesis of calcium hydroxyapatite from calcium carbonate and different orthophosphate sources: A comparative study

    Energy Technology Data Exchange (ETDEWEB)

    Pham Minh, Doan, E-mail: doan.phamminh@mines-albi.fr [Universite de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Lyczko, Nathalie; Sebei, Haroun; Nzihou, Ange [Universite de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Sharrock, Patrick [Universite de Toulouse, SIMAD, IUT Paul Sabatier, Avenue Georges Pompidou, 81104 Castres (France)

    2012-08-01

    Highlights: Black-Right-Pointing-Pointer Calcium hydroxyapatite was synthesized from CaCO{sub 3} and four orthophosphates. Black-Right-Pointing-Pointer Only H{sub 3}PO{sub 4} led to the complete precipitation of orthophosphate species. Black-Right-Pointing-Pointer H{sub 3}PO{sub 4} was also the most efficient for calcium dissolution. Black-Right-Pointing-Pointer Reaction pathway was dissolution-precipitation accompanied by agglomeration step. - Abstract: The synthesis of calcium hydroxyapatite (Ca-HA) starting from calcium carbonate and different orthophosphate sources, including orthophosphoric acid, potassium, sodium and ammonium dihydrogen orthophosphates, was investigated under ambient conditions. The reaction started with calcium carbonate dissolution in an acid medium, followed by rapid precipitation of calcium cations with orthophosphate species to form calcium phosphate based particles which were in the size range of 0.4-1 {mu}m. These particles then agglomerated into much larger ones, up to 350 {mu}m in diameter (aggregates). These aggregates possessed an unstable porous structure which was responsible for the porosity of the final products. The highest specific surface area and pore volume were obtained with potassium dihydrogen orthophosphate. On the other hand, orthophosphoric acid led to the highest dissolution of calcium carbonate and the complete precipitation of orthophosphate species. Under ambient conditions, calcium phosphate based solid products of low crystallinity were formed. Different intermediates were identified and a reaction pathway proposed.

  6. Dynamical Dipole mode in the 40,48 Ca +152,144Sm fusion reactions at 11 MeV/nucleon

    Science.gov (United States)

    Parascandolo, C.; Pierroutsakou, D.; Alba, R.; Del Zoppo, A.; Maiolino, C.; Santonocito, D.; Agodi, C.; Baran, V.; Boiano, A.; Colonna, M.; Coniglione, R.; De Filippo, E.; Di Toro, M.; Emanuele, U.; Farinon, F.; Guglielmetti, A.; La Commara, M.; Martin, B.; Mazzocchi, C.; Mazzocco, M.; Rizzo, C.; Romoli, M.; Signorini, C.; Silvestri, R.; Soramel, F.; Strano, E.; Torresi, D.; Trifirò, A.; Trimarchi, M.

    2016-05-01

    The excitation of the dynamical dipole mode along the fusion path was investigated in the formation of a heavy compound nucleus in the A=190 mass region. To form the compound nucleus, the 40Ca + 152Sm and 48Ca + 144Sm reactions were employed at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion-evaporation and fission events were studied simultaneously for the first time. Our results for evaporation and fission events (preliminary) show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.

  7. Dynamical Dipole mode in the 40,48 Ca +152,144Sm fusion reactions at 11 MeV/nucleon

    Directory of Open Access Journals (Sweden)

    Parascandolo C.

    2016-01-01

    Full Text Available The excitation of the dynamical dipole mode along the fusion path was investigated in the formation of a heavy compound nucleus in the A=190 mass region. To form the compound nucleus, the 40Ca + 152Sm and 48Ca + 144Sm reactions were employed at Elab=11 and 10.1 MeV/nucleon, respectively. Both fusion–evaporation and fission events were studied simultaneously for the first time. Our results for evaporation and fission events (preliminary show that the dynamical dipole mode survives in reactions involving heavier nuclei than those studied previously.

  8. Oyster shell calcium induced parotid swelling

    Directory of Open Access Journals (Sweden)

    Muthiah Palaniappan

    2014-01-01

    Full Text Available A 59 year old female consumer was started on therapy with oyster shell calcium in combination with vitamin D3 and she presented with swelling below the ear, after two doses. She stopped the drug by herself and the swelling disappeared in one day. She started the drug one day after recovery and again she developed the swelling. She was advised to stop the drug with a suggestion to take lemon to enhance parotid secretion and the swelling subsided. Calcium plays major role in salivary secretion and studies have shown reduced parotid secretion in rats, deficient of vitamin D. But in humans involvement of calcium and vitamin D3 in parotid secretion is unknown. However, the patient had no history of reaction though she had previously taken vitamin D3 with calcium carbonate which was not from oyster shell. Hence, we ruled out vitamin D3 in this reaction and suspecting oyster shell calcium as a culprit. This adverse drug reaction (ADR was assessed using World Health Organization (WHO causality assessment, Naranjo′s and Hartwig severity scales. As per WHO causality assessment scale, the ADR was classified as "certain". This reaction was analyzed as per Naranjo′s algorithm and was classified as probable. According to Hartwig′s severity scale the reaction was rated as mild. Our case is an example of a mild but rare adverse effect of oyster shell calcium carbonate which is widely used.

  9. Study of the N=28 shell closure by one neutron transfer reaction: astrophysical application and {beta}-{gamma} spectroscopy of neutron rich nuclei around N=32/34 and N=40; Etude de la fermeture de couche N=28 autour du noyau {sub 18}{sup 46}Ar{sub 28} par reaction de transfert d'un neutron: application a l'astrophysique et Spectroscopie {beta}-{gamma} de noyaux riches en neutrons de N=32/34 et N=40

    Energy Technology Data Exchange (ETDEWEB)

    Gaudefroy, L

    2005-09-15

    The study of the N=28 shell closure has been presented as well as its astrophysical implications. Moreover the structure of neutron rich nuclei around N=32/34 and 40 was studied. The N=28 shell closure has been studied trough the one neutron transfer reaction on {sup 44,46}Ar nuclei. Excitation energies of states in {sup 45,47}Ar nuclei have been obtained, as well as their angular momenta and spectroscopic factors. These results were used to show that N=28 is still a good magic number in the argon isotopic chain. We interpreted the evolution of the spin-orbit partner gaps in terms of the tensor monopolar proton-neutron interaction. Thanks to this latter, we showed it is not necessary to summon up a reduction of the intensity of the spin-orbit force in order to explain this evolution in N=29 isotopes from calcium to argon chains. The neutron capture rates on {sup 44,46}Ar have been determined thanks to the results of the transfer reaction. Their influence on the nucleosynthesis of {sup 46,48}Ca was studied. We proposed stellar conditions to account for the abnormal isotopic ratio observed in the Allende meteorite concerning {sup 46,48}Ca isotopes. The beta decay and gamma spectroscopy of neutron rich nuclei in the scandium to cobalt region has been studied. We showed that beta decay process is dominated by the {nu}f{sub 5/2} {yields} {pi}f{sub 7/2} Gamow-Teller transition. Moreover, we demonstrated that the {nu}g{sub 9/2} hinders this process in the studied nuclei, and influences their structure, by implying the existence of isomers. Our results show that N=34 is not a magic number in the titanium chain and the superior ones. (author)

  10. Contribution of intracellular calcium and pH in ischemic uncoupling of cardiac gap junction channels formed of connexins 43, 40, and 45: a critical function of C-terminal domain.

    Directory of Open Access Journals (Sweden)

    Giriraj Sahu

    Full Text Available Ischemia is known to inhibit gap junction (GJ mediated intercellular communication. However the detail mechanisms of this inhibition are largely unknown. In the present study, we determined the vulnerability of different cardiac GJ channels formed of connexins (Cxs 43, 40, and 45 to simulated ischemia, by creating oxygen glucose deprived (OGD condition. 5 minutes of OGD decreased the junctional conductance (Gj of Cx43, Cx40 and Cx45 by 53±3%, 64±1% and 85±2% respectively. Reduction of Gj was prevented completely by restricting the change of both intracellular calcium ([Ca(2+]i and pH (pHi with potassium phosphate buffer. Clamping of either [Ca(2+]i or pHi, through BAPTA (2 mM or HEPES (80 mM respectively, offered partial resistance to ischemic uncoupling. Anti-calmodulin antibody attenuated the uncoupling of Cx43 and Cx45 significantly but not of Cx40. Furthermore, OGD could reduce only 26±2% of Gj in C-terminus (CT truncated Cx43 (Cx43-Δ257. Tethering CT of Cx43 to the CT-truncated Cx40 (Cx40-Δ249, and Cx45 (Cx45-Δ272 helped to resist OGD mediated uncoupling. Moreover, CT domain played a significant role in determining the junction current density and plaque diameter. Our results suggest; OGD mediated uncoupling of GJ channels is primarily due to elevated [Ca(2+]i and acidic pHi, though the latter contributes more. Among Cx43, Cx40 and Cx45, Cx43 is the most resistant to OGD while Cx45 is the most sensitive one. CT of Cx43 has major necessary elements for OGD induced uncoupling and it can complement CT of Cx40 and Cx45.

  11. 葡萄糖酸钙口服液在预防机采血小板献血不良反应中的应用%Preventive Efficacy of Calcium Gluconate Oral Liquid against Apheresis Platelet Donation-induced Adverse Reaction

    Institute of Scientific and Technical Information of China (English)

    古贤清

    2015-01-01

    OBJECTIVE:To evaluate the preventive efficacy of calcium gluconate oral liquid against apheresis platelet donation-induced adverse reaction.METHODS:From July 2012 to June 2013 , a total of 248 cases of apheresis platelet donors in our blood center were assigned to control group giving none treatment during blood collection, with 1 treatment unit of blood collected once in 140 cases and 2 treatment units of blood collected once in 108 cases; from July 2013 to June 2014, another 288 cases of apheresis platelet donors in the observation group were administered with calcium gluconate oral liquid before blood collection, with 1 treatment unit of blood collected once in 152 cases and 2 treatment units of blood collected once in 136 cases.The incidence of adverse reactions was compared between the two groups.RESULTS:Adverse reactions were noted in 2.63% ( 4/152 ) of the one treatment unit apheresis platelet donors, 3.68%(5/136) of the two treatment units apheresis platelet donors and 3.13%(9/288) of the total patients in the observation group, which were significantly less than in the control group [ 22.14%(31/140), 35.19%(38/108) and 27.82% (69/248) respectively] (P<0.05).The incidence of citrate reaction in the observation group was significantly less than in the control group [55.56%(5/9) vs.81.16%(56/69);P<0.05].CONCLUSIONS:Citrate reaction is the predominant adverse reaction in apheresis platelet donors.Administration of calcium gluconate oral liquid before platelet collection can significantly prevent or reduce the incidence of apheresis platelet donation-induced adverse reaction, which thus is worthy of clinical recommendation.%目的:观察葡萄糖酸钙口服液预防机采血小板献血不良反应的效果。方法:选择惠州市中心血站2012年7月—2013年6月248例机采血小板献血者作为对照组,采血期间不做任何处理,其中140例1次采1个治疗单位,108例1次采2个治疗单位;选择2013年7月—2014年6月288例采

  12. Theoretical study of fusion reactions $^{32}$S + $^{94,96}$Zr and $^{40}$Ca + $^{94,96}$Zr and quadrupole deformation of $^{94}$Zr

    CERN Document Server

    Wang, Bing; Zhao, En-Guang; Zhou, Shan-Gui

    2015-01-01

    The dynamic coupling effects on fusion cross sections for reactions $^{32}$S + $^{94,96}$Zr and $^{40}$Ca + $^{94,96}$Zr are studied with the universal fusion function formalism and an empirical coupled channel (ECC) model. An examination of the reduced fusion functions shows that the total effect of couplings to inelastic excitations and neutron transfer channels on fusion in $^{32}$S + $^{94}$Zr ($^{40}$Ca + $^{94}$Zr) is almost the same as that in $^{32}$S + $^{96}$Zr ($^{40}$Ca + $^{96}$Zr). The enhancements of the fusion cross section at sub-barrier energies due to inelastic channel coupling and neutron transfer channel coupling are evaluated separately by using the ECC model. The results show that effect of couplings to inelastic excitations channels in the reactions with $^{94}$Zr as target should be similar as that in the reactions with $^{96}$Zr as target. This implies that the quadrupole deformation parameters $\\beta_2$ of $^{94}$Zr and $^{96}$Zr should be similar to each other. However, $\\beta_2$'s...

  13. Calcium and caffeine interaction in increased calcium balance in ovariectomized rats

    Directory of Open Access Journals (Sweden)

    Sandra Tavares da Silva

    2013-06-01

    Full Text Available OBJECTIVE: This study investigated the effects of caffeine intake associated with inadequate or adequate calcium intake in laparotomized or ovariectomized rats by means of the calcium balance. Forty adults Wistar rats were ovariectomized or laparotomized. METHODS: The animals (n=40 were randomly placed in eight groups receiving the AIN-93 diet with 100% or 50% of the recommended calcium intake with or without added caffeine (6mg/kg/day. The animals were kept in individuals metabolic cages at a temperature of 24°±2ºC, light/dark cycles of 12/12 hours, and deionized water available ad libitum. On the 8th week of the experiment, food consumption was measured and 24-hour urine and 4-day feces were collected to determine calcium balance [Balance=Ca intake-(Urinary Ca+Fecal Ca]. RESULTS: Animals with adequate calcium intake presented higher balances and rates of calcium absorption and retention (p<0.05 than those with inadequate calcium intake, regardless of caffeine intake (p<0.05. Caffeine intake did not affect urinary calcium excretion but increased balance (p<0.05 in the groups with adequate calcium intake. CONCLUSION: Adequate calcium intake attenuated the negative effects of estrogen deficiency and improved calcium balance even in the presence of caffeine.

  14. Calcium and Vitamin D

    Science.gov (United States)

    ... Cart Home › Patients › Treatment › Calcium/Vitamin D Calcium/Vitamin D Getting enough calcium and vitamin D is ... the-counter medications and calcium supplements. What is Vitamin D and What Does it Do? Vitamin D ...

  15. Research on the melting characteristics during the reaction process of phosphogypsum and calcium sulfide%磷石膏和硫化钙反应过程的熔融特性研究

    Institute of Scientific and Technical Information of China (English)

    万甜明; 张志业; 王辛龙; 杨秀山; 钟本和

    2011-01-01

    To explore the dominant factors that cause the problems such as coating formation, ring formation, bonding and blocking,etc. ,in rotary kiln used in the industrial production of sulfuric acid,the melting characteristics of decomposition process of phosphogypsum are investigated. With phosphogypsum and calcium sulfide as raw materials, ash melting point measuring instrument is used to study the effects of additives and reaction atmosphere on the melting softening temperature (ST) in the CaSO4 and CaS solid-solid reaction. The results show that, the effective additive of increasing the melting softening temperature during the decomposition of phosphogypsum are kaolin and mixed atmosphere containing SO2 ,CO2 and N2 ,respectively. The additives such as SiO2 ,A1PO4 ,FePO4 ·2H2O,Na2SiF6 ,and so on,play a role in fluxing action.%为探讨影响磷石膏分解制硫酸生产过程中回转窑内结皮、结罔和粘结堵塞等问题的主导因素,以磷石膏和硫化钙为原料,采用微机灰熔融性测定仪研究了不同添加剂和反应气氛对CaSO4和CaS固-固反应中熔融软化温度(ST)的影响.结果表明,提高磷石膏制硫酸反应中熔融软化温度的有效添加剂是高岭土和SO2、CO2、N2的混合气氛,而起助熔作用的添加剂是SiO2、AlPO4、FePO4·2H2O、Na2 SiF6等.

  16. A sequential injection system for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples.

    Science.gov (United States)

    Mesquita, Raquel B R; Rangel, António O S S

    2004-08-01

    A sequential injection methodology for the spectrophotometric determination of calcium, magnesium and alkalinity in water samples is proposed. A single manifold is used for the determination of the three analytes, and the same protocol sequence allows the sequential determination of calcium and magnesium (the sum corresponds to the water hardness). The determination of both metals is based on their reaction with cresolphtalein complexone; mutual interference is minimized by using 8-hydroxyquinoline for the determination of calcium and ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) for the determination of magnesium. Alkalinity determination is based on a reaction with acetic acid, and corresponding color change of Bromcresol Green. Working ranges of 0.5 - 5 mg dm(-3) for Ca, 0.5 - 10 mg dm(-3) for Mg, and 10 - 100 mg HCO3- dm(-3), for alkalinity have been achieved. The results for water samples were comparable to those of the reference methods and to a certified reference water sample. RSDs lower than 5% were obtained, a low reagent consumption and a reduced volume of effluent have been accomplished. The determination rate for calcium and magnesium is 80 h(-1), corresponding to 40 h(-1) per element, while 65 determinations of alkalinity per hour could be carried out.

  17. Porosity prediction of calcium phosphate cements based on chemical composition.

    Science.gov (United States)

    Öhman, Caroline; Unosson, Johanna; Carlsson, Elin; Ginebra, Maria Pau; Persson, Cecilia; Engqvist, Håkan

    2015-07-01

    The porosity of calcium phosphate cements has an impact on several important parameters, such as strength, resorbability and bioactivity. A model to predict the porosity for biomedical cements would hence be a useful tool. At the moment such a model only exists for Portland cements. The aim of this study was to develop and validate a first porosity prediction model for calcium phosphate cements. On the basis of chemical reaction, molar weight and density of components, a volume-based model was developed and validated using calcium phosphate cement as model material. 60 mol% β-tricalcium phosphate and 40 mol% monocalcium phosphate monohydrate were mixed with deionized water, at different liquid-to-powder ratios. Samples were set for 24 h at 37°C and 100% relative humidity. Thereafter, samples were dried either under vacuum at room temperature for 24 h or in air at 37 °C for 7 days. Porosity and phase composition were determined. It was found that the two drying protocols led to the formation of brushite and monetite, respectively. The model was found to predict well the experimental values and also data reported in the literature for apatite cements, as deduced from the small absolute average residual errors (brushite, monetite and apatite cements. The model gives a good estimate of the final porosity and has the potential to be used as a porosity prediction tool in the biomedical cement field.

  18. Imaging calcium in neurons.

    Science.gov (United States)

    Grienberger, Christine; Konnerth, Arthur

    2012-03-08

    Calcium ions generate versatile intracellular signals that control key functions in all types of neurons. Imaging calcium in neurons is particularly important because calcium signals exert their highly specific functions in well-defined cellular subcompartments. In this Primer, we briefly review the general mechanisms of neuronal calcium signaling. We then introduce the calcium imaging devices, including confocal and two-photon microscopy as well as miniaturized devices that are used in freely moving animals. We provide an overview of the classical chemical fluorescent calcium indicators and of the protein-based genetically encoded calcium indicators. Using application examples, we introduce new developments in the field, such as calcium imaging in awake, behaving animals and the use of calcium imaging for mapping single spine sensory inputs in cortical neurons in vivo. We conclude by providing an outlook on the prospects of calcium imaging for the analysis of neuronal signaling and plasticity in various animal models.

  19. 40 CFR 721.6181 - Fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl ether...

    Science.gov (United States)

    2010-07-01

    ... substituted oxirane, formaldehyde-phenol polymer glycidyl ether, substituted proplyamine and...-phenol polymer glycidyl ether, substituted proplyamine and polyethylenepolyamines (generic). (a) Chemical... as fatty acid, reaction product with substituted oxirane, formaldehyde-phenol polymer glycidyl...

  20. Process for the preparation of calcium superoxide

    Science.gov (United States)

    Ballou, E. V.; Wood, P. C.; Wydeven, T. J.; Spitze, L. A. (Inventor)

    1978-01-01

    Calcium superoxide is prepared in high yields by spreading a quantity of calcium peroxide diperoxyhydrate on the surface of a container, positioning said container in a vacuum chamber on a support structure through which a coolant fluid can be circulated, partially evacuating said vacuum chamber, allowing the temperature of the diperoxyhydrate to reach the range of about 0 to about 40 C; maintaining the temperature selected for a period of time sufficient to complete the disproproriation of the diperoxyhydrate to calcium superoxide, calcium hydroxide, oxygen, and water; constantly and systematically removing the water as it is formed by sweeping the reacting material with a current of dry inert gas and/or by condensation of said water on a cold surface; backfilling the chamber with a dry inert gas; and finally, recovering the calcium superoxide produced.

  1. Continuous Modeling of Calcium Transport Through Biological Membranes

    Science.gov (United States)

    Jasielec, J. J.; Filipek, R.; Szyszkiewicz, K.; Sokalski, T.; Lewenstam, A.

    2016-08-01

    In this work an approach to the modeling of the biological membranes where a membrane is treated as a continuous medium is presented. The Nernst-Planck-Poisson model including Poisson equation for electric potential is used to describe transport of ions in the mitochondrial membrane—the interface which joins mitochondrial matrix with cellular cytosis. The transport of calcium ions is considered. Concentration of calcium inside the mitochondrion is not known accurately because different analytical methods give dramatically different results. We explain mathematically these differences assuming the complexing reaction inside mitochondrion and the existence of the calcium set-point (concentration of calcium in cytosis below which calcium stops entering the mitochondrion).

  2. Activation cross-sections of longer lived products of deuteron induced nuclear reactions on ytterbium up to 40 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Tárkányi, F. [Institute for Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Ditrói, F., E-mail: ditroi@atomki.hu [Institute for Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Takács, S. [Institute for Nuclear Research of the Hungarian Academy of Sciences (ATOMKI), Debrecen (Hungary); Hermanne, A. [Cyclotron Laboratory, Vrije Universiteit Brussel (VUB), Brussels (Belgium); Yamazaki, H.; Baba, M.; Mohammadi, A. [Cyclotron Radioisotope Center (CYRIC), Tohoku University, Sendai (Japan); Ignatyuk, A.V. [Institute of Physics and Power Engineering (IPPE), Obninsk (Russian Federation)

    2013-06-01

    Highlights: •Experimental excitation function of deuteron induced reactions on natural ytterbium up to 40 MeV. •Model code calculations with EMPIRE-D, ALICE-D and TALYS (TENDL-2011 and 2012). •Physical yield calculation. •Tabulated experimental results. •Discussion of medical and industrial applications. -- Abstract: In the frame of a systematic study of the activation cross-sections of the deuteron induced nuclear reactions, excitation functions of the {sup nat}Yb(d,xn){sup 177,173,172mg,171mg,170,169}Lu, {sup nat}Yb(d,x){sup 175,169}Yb and {sup nat}Yb(d,x){sup 173,172,168,167,165}Tm reactions are studied up to 40 MeV, a few of them for the first time. Cross-sections were measured with the activation method using a stacked foil irradiation technique and high resolution γ-ray spectrometry. The experimental data are analyzed and compared to the results of the theoretical model codes ALICE-IPPE, EMPIRE-II and TALYS. From the measured cross-section data integral production yields were calculated. Applications of the new cross-sections are discussed.

  3. Neuronal apoptosis and inflammatory reaction in rat models of focal cerebral ischemia following 40-minute suspended moxibustion

    Institute of Scientific and Technical Information of China (English)

    Rixin Chen; Zhimai Lv; Mingren Chen; Xin An; Dingyi Xie; Jing Yi

    2011-01-01

    The treatment duration of heat-sensitive moxibustion (approximately 40 minutes on average) is longer than that of traditional suspended moxibustion.The present study investigated expression changes of three inflammatory and apoptosis-associated proteins (inducible nitric oxide synthase,cyclooxygenase-2 and caspase-3) in transient middle cerebral artery occlusion model rats following suspended moxibustion for 40 minutes,to explore the mechanisms underlying neuroprotective action of suspended moxibustion.The results indicated that suspended moxibustion at acupoint Dazhui (DU 14) for 40 minutes reduced the cortical expression of caspase-3,cyclooxygenase-2 and inducible nitric oxide synthase proteins of transient middle cerebral artery occlusion model rats,as well as decreasing infarct volume and ameliorating the neurological deficit score.Outcomes with 40 minutes of moxibustion were superior to the outcomes after suspended moxibustion for 15 minutes.

  4. Calcium signaling in physiology and pathophysiology

    Institute of Scientific and Technical Information of China (English)

    He-ping CHENG; Sheng WEI; Li-ping WEI; Alexei VERKHRATSKY

    2006-01-01

    Calcium ions are the most ubiquitous and pluripotent cellular signaling molecules that control a wide variety of cellular processes.The calcium signaling system is represented by a relatively limited number of highly conserved transporters and channels,which execute Ca2+ movements across biological membranes and by many thousands of Ca2+-sensitive effectors.Molecular cascades,responsible for the generation of calcium signals,are tightly controlled by Ca2+ ions themselves and by genetic factors,which tune the expression of different Ca2+-handling molecules according to adaptational requirements.Ca2+ ions determine normal physiological reactions and the development of many pathological processes.

  5. Calcium quarks.

    Science.gov (United States)

    Niggli, Ernst; Egger, Marcel

    2002-05-01

    Elementary subcellular Ca2+ signals arising from the opening of single ion channels may offer the possibility to examine the stochastic behavior and the microscopic chemical reaction rates of these channel proteins in their natural environment. Such an analysis can yield detailed information about the molecular function that cannot be derived from recordings obtained from an ensemble of channels. In this review, we summarize experimental evidence suggesting that Ca2+ sparks, elementary Ca2+ signaling events of cardiac and skeletal muscle excitation contraction coupling, may be comprised of a number of smaller Ca2+ signaling events, the Ca2+ quarks.

  6. A study of proton breakup from exotic nuclei through various reaction mechanisms in 40A - 80AMeV energy range

    Directory of Open Access Journals (Sweden)

    Kumar Ravinder

    2014-03-01

    Full Text Available We have studied the single proton breakup from weakly bound exotic nuclei due to several reaction mechanisms separately and their total and the interference effects, in order to clarify quantitatively which mechanism would dominate the measured observables. We have considered: (i the recoil effect of the core-target Coulomb potential which we distinguish from the direct proton-target Coulomb potential, and (ii nuclear breakup, which consists of stripping and diffraction. Thus, we have calculated the absolute values of breakup cross sections and parallel momentum distributions (LMD for 8B and 17F projectiles on a light and a heavy target in a range of intermediate incident energies (40A–80A MeV for each reaction mechanism. Furthermore the interference among the two Coulomb effects and nuclear diffraction has been studied in detail. The calculation of the direct and recoil Coulomb effects separately and of their interference is the new and most relevant aspect of this work.

  7. A study of proton breakup from exotic nuclei through various reaction mechanisms in 40A - 80AMeV energy range

    Science.gov (United States)

    Kumar, Ravinder; Bonaccorso, Angela

    2014-03-01

    We have studied the single proton breakup from weakly bound exotic nuclei due to several reaction mechanisms separately and their total and the interference effects, in order to clarify quantitatively which mechanism would dominate the measured observables. We have considered: (i) the recoil effect of the core-target Coulomb potential which we distinguish from the direct proton-target Coulomb potential, and (ii) nuclear breakup, which consists of stripping and diffraction. Thus, we have calculated the absolute values of breakup cross sections and parallel momentum distributions (LMD) for 8B and 17F projectiles on a light and a heavy target in a range of intermediate incident energies (40A-80A MeV) for each reaction mechanism. Furthermore the interference among the two Coulomb effects and nuclear diffraction has been studied in detail. The calculation of the direct and recoil Coulomb effects separately and of their interference is the new and most relevant aspect of this work.

  8. Kinetics of calcium sulfoaluminate formation from tricalcium aluminate, calcium sulfate and calcium oxide

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xuerun, E-mail: xuerunli@163.com; Zhang, Yu; Shen, Xiaodong, E-mail: xdshen@njut.edu.cn; Wang, Qianqian; Pan, Zhigang

    2014-01-15

    The formation kinetics of tricalcium aluminate (C{sub 3}A) and calcium sulfate yielding calcium sulfoaluminate (C{sub 4}A{sub 3}$) and the decomposition kinetics of calcium sulfoaluminate were investigated by sintering a mixture of synthetic C{sub 3}A and gypsum. The quantitative analysis of the phase composition was performed by X-ray powder diffraction analysis using the Rietveld method. The results showed that the formation reaction 3Ca{sub 3}Al{sub 2}O{sub 6} + CaSO{sub 4} → Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 6CaO was the primary reaction < 1350 °C with and activation energy of 231 ± 42 kJ/mol; while the decomposition reaction 2Ca{sub 4}Al{sub 6}O{sub 12}(SO{sub 4}) + 10CaO → 6Ca{sub 3}Al{sub 2}O{sub 6} + 2SO{sub 2} ↑ + O{sub 2} ↑ primarily occurred beyond 1350 °C with an activation energy of 792 ± 64 kJ/mol. The optimal formation region for C{sub 4}A{sub 3}$ was from 1150 °C to 1350 °C and from 6 h to 1 h, which could provide useful information on the formation of C{sub 4}A{sub 3}$ containing clinkers. The Jander diffusion model was feasible for the formation and decomposition of calcium sulfoaluminate. Ca{sup 2+} and SO{sub 4}{sup 2−} were the diffusive species in both the formation and decomposition reactions. -- Highlights: •Formation and decomposition of calcium sulphoaluminate were studied. •Decomposition of calcium sulphoaluminate combined CaO and yielded C{sub 3}A. •Activation energy for formation was 231 ± 42 kJ/mol. •Activation energy for decomposition was 792 ± 64 kJ/mol. •Both the formation and decomposition were controlled by diffusion.

  9. Decay of excited nuclei produced in (78,82)Kr+(40)Ca reactions at 5.5 MeV/nucleon

    Energy Technology Data Exchange (ETDEWEB)

    Gomez Del Campo, Jorge [ORNL; Ademard, G. [GANIL, CEA, Caen, France & CNRS, IN2P3, Caen, France; Wieleczko, J. P. [Grand Accelerateur National d' Ions Lourds (GANIL); Bonnet, E. [Grand Accelerateur National d' Ions Lourds (GANIL); Frankland, J. D. [GANIL, CEA, Caen, France & CNRS, IN2P3, Caen, France; Moisan, J. [GANIL, CEA, Caen, France & CNRS, IN2P3, Caen, France; Del Campo, J. G. [Oak Ridge National Laboratory (ORNL); La Commara, M. [Universita Federico II and INFN Napoli; Vigilante, M. [Universita Federico II and INFN Napoli; Rosato, E. [Universita Federico II and INFN Napoli; Spadaccini, A. [Universita` di Napoli “Federico II”; Pierroutsakou, D. [Universita` di Napoli “Federico II”; Romoli, M. [Universita` di Napoli “Federico II”; Kalandarov, Sh. A. [Uzbek Acad Sci, Uzbekistan; Adamian, G. G. [Uzbek Acad Sci, Uzbekistan; Beck, C. [IPHC, IN2P3-CNRS, Strasbourg Cedex2, France; Barlini, S. [1st Nazl Fis Nucl, Florence, Italy; Borderie, B. [IPNO, IN2P3-CNRS and Universit´e Paris-Sud 11, Orsay Cedex, France; Rivet, M. F. [IPNO, IN2P3-CNRS and Universit´e Paris-Sud 11, Orsay Cedex, France; Bougault, R. [LPC, IN2P3-CNRS, ENSICAEN and Universit´e, Caen Cedex, France; Le Neindre, N, [LPC, IN2P3-CNRS, ENSICAEN and Universit´e, Caen Cedex, France; Parlog, M. [LPC, IN2P3-CNRS, ENSICAEN and Universit´e, Caen Cedex, France; Dayras, R. [CEA, Cetre de Sacaly, Gif-sur-Yvette, France; De Angelis, G. [INFN, Laboratori Nazionali di Legnaro, Italy; Kravchuk, Leonid V [ORNL; De Sanctis, J. [Universita di Bologna; Lautesse, P. [IPNL, IN2P3-CNRS et Universit´e, Villeurbanne Cedex, France; Roy, R. [Universite de Laval, Quebec, Canada; D' Onofrio, A. [Universita di Napoli, Caserta, Italy

    2011-01-01

    Decay modes of excited nuclei are investigated in {sup 78,82}Kr+{sup 40}Ca reactions at 5.5 MeV/nucleon. Charged products were measured by means of the 4{pi} INDRA array. Kinetic-energy spectra and angular distributions of fragments with atomic number 3 {le} Z {le} 28 indicate a high degree of relaxation and are compatible with a fissionlike phenomenon. Persistence of structure effects is evidenced from elemental cross sections ({sigma}{sub Z}) as well as a strong odd-even staggering (o-e-s) of the light-fragment yields. The magnitude of the staggering does not significantly depend on the neutron content of the emitting system. Fragment-particle coincidences suggest that the light partners in very asymmetric fission are emitted either cold or at excitation energies below the particle emission thresholds. The evaporation residue cross section of the {sup 78}Kr+{sup 40}Ca reaction is slightly higher than the one measured in the {sup 82}Kr+{sup 40}Ca reaction. The fissionlike component is larger by {approx}25% for the reaction having the lowest neutron-to-proton ratio. These experimental features are confronted to the predictions of theoretical models. The Hauser-Feshbach approach including the emission of fragments up to Z = 14 in their ground states as well as excited states does not account for the main features of {sigma}{sub Z}. For both reactions, the transition-state formalism reasonably reproduces the Z distribution of the fragments with charge 12 {le} Z {le} 28. However, this model strongly overestimates the light-fragment cross sections and does not explain the o-e-s of the yields for 6 {le} Z {le} 10. The shape of the whole Z distribution and the o-e-s of the light-fragment yields are satisfactorily reproduced within the dinuclear system framework which treats the competition among evaporation, fusion-fission, and quasifission processes. The model suggests that heavy fragments come mainly from quasifission while light fragments are predominantly populated

  10. 40 CFR 721.3830 - Formaldehyde, reaction products with an alkylated phenol and an aliphatic amine (generic).

    Science.gov (United States)

    2010-07-01

    ... an alkylated phenol and an aliphatic amine (generic). 721.3830 Section 721.3830 Protection of... products with an alkylated phenol and an aliphatic amine (generic). (a) Chemical substance and significant..., reaction products with an alkylated phenol and an aliphatic amine (PMN P-99-0531) is subject to...

  11. Apatite Formation from Amorphous Calcium Phosphate and Mixed Amorphous Calcium Phosphate/Amorphous Calcium Carbonate.

    Science.gov (United States)

    Ibsen, Casper J S; Chernyshov, Dmitry; Birkedal, Henrik

    2016-08-22

    Crystallization from amorphous phases is an emerging pathway for making advanced materials. Biology has made use of amorphous precursor phases for eons and used them to produce structures with remarkable properties. Herein, we show how the design of the amorphous phase greatly influences the nanocrystals formed therefrom. We investigate the transformation of mixed amorphous calcium phosphate/amorphous calcium carbonate phases into bone-like nanocrystalline apatite using in situ synchrotron X-ray diffraction and IR spectroscopy. The speciation of phosphate was controlled by pH to favor HPO4 (2-) . In a carbonate free system, the reaction produces anisotropic apatite crystallites with large aspect ratios. The first formed crystallites are highly calcium deficient and hydrogen phosphate rich, consistent with thin octacalcium phosphate (OCP)-like needles. During growth, the crystallites become increasingly stoichiometric, which indicates that the crystallites grow through addition of near-stoichiometric apatite to the OCP-like initial crystals through a process that involves either crystallite fusion/aggregation or Ostwald ripening. The mixed amorphous phases were found to be more stable against phase transformations, hence, the crystallization was inhibited. The resulting crystallites were smaller and less anisotropic. This is rationalized by the idea that a local phosphate-depletion zone formed around the growing crystal until it was surrounded by amorphous calcium carbonate, which stopped the crystallization.

  12. Calcium and Mitosis

    Science.gov (United States)

    Hepler, P.

    1983-01-01

    Although the mechanism of calcium regulation is not understood, there is evidence that calcium plays a role in mitosis. Experiments conducted show that: (1) the spindle apparatus contains a highly developed membrane system that has many characteristics of sarcoplasmic reticulum of muscle; (2) this membrane system contains calcium; and (3) there are ionic fluxes occurring during mitosis which can be seen by a variety of fluorescence probes. Whether the process of mitosis can be modulated by experimentally modulating calcium is discussed.

  13. Calcium ferrite formation from the thermolysis of calcium tris (maleato) ferrate(III)

    Indian Academy of Sciences (India)

    B S Randhawa; Kamaljeet Sweety

    2000-08-01

    For preparing calcium ferrite, calcium tris (maleato) ferrate(III) precursor was prepared by mixing aqueous solutions of iron(III) maleate, calcium maleate and maleic acid. Various physico-chemical techniques i.e. TG, DTG, DTA, Mössbauer, XRD, IR etc have been used to study the decomposition behaviour from ambient to 900°C and ferrite formation. Three consecutive decomposition steps leading to the formation of -Fe2O3 and calcium carbonate have been observed at various stages of thermolysis. In the final stage the ferrite, Ca2Fe2O5, is obtained as a result of solid state reaction between -Fe2O3 and calcium carbonate at 788°C, a temperature much lower than for ceramic method. The results have been compared with those of the oxalate precursor.

  14. Calcium - Function and effects

    NARCIS (Netherlands)

    Liang, Jianfen; He, Yifan; Gao, Qian; Wang, Xuan; Nout, M.J.R.

    2016-01-01

    Rice is the primary food source for more than half of the world population. Levels of calcium contents and inhibitor - phytic acid are summarized in this chapter. Phytic acid has a very strong chelating ability and it is the main inhibit factor for calcium in rice products. Calcium contents in br

  15. Calcium Orthophosphate-Based Bioceramics

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2013-09-01

    Full Text Available Various types of grafts have been traditionally used to restore damaged bones. In the late 1960s, a strong interest was raised in studying ceramics as potential bone grafts due to their biomechanical properties. A bit later, such synthetic biomaterials were called bioceramics. In principle, bioceramics can be prepared from diverse materials but this review is limited to calcium orthophosphate-based formulations only, which possess the specific advantages due to the chemical similarity to mammalian bones and teeth. During the past 40 years, there have been a number of important achievements in this field. Namely, after the initial development of bioceramics that was just tolerated in the physiological environment, an emphasis was shifted towards the formulations able to form direct chemical bonds with the adjacent bones. Afterwards, by the structural and compositional controls, it became possible to choose whether the calcium orthophosphate-based implants remain biologically stable once incorporated into the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of regenerative bioceramics was developed and such formulations became an integrated part of the tissue engineering approach. Now calcium orthophosphate scaffolds are designed to induce bone formation and vascularization. These scaffolds are often porous and harbor different biomolecules and/or cells. Therefore, current biomedical applications of calcium orthophosphate bioceramics include bone augmentations, artificial bone grafts, maxillofacial reconstruction, spinal fusion, periodontal disease repairs and bone fillers after tumor surgery. Perspective future applications comprise drug delivery and tissue engineering purposes because calcium orthophosphates appear to be promising carriers of growth factors, bioactive peptides and various types of cells.

  16. Calcium signaling and epilepsy.

    Science.gov (United States)

    Steinlein, Ortrud K

    2014-08-01

    Calcium signaling is involved in a multitude of physiological and pathophysiological mechanisms. Over the last decade, it has been increasingly recognized as an important factor in epileptogenesis, and it is becoming obvious that the excess synchronization of neurons that is characteristic for seizures can be linked to various calcium signaling pathways. These include immediate effects on membrane excitability by calcium influx through ion channels as well as delayed mechanisms that act through G-protein coupled pathways. Calcium signaling is able to cause hyperexcitability either by direct modulation of neuronal activity or indirectly through calcium-dependent gliotransmission. Furthermore, feedback mechanisms between mitochondrial calcium signaling and reactive oxygen species are able to cause neuronal cell death and seizures. Unravelling the complexity of calcium signaling in epileptogenesis is a daunting task, but it includes the promise to uncover formerly unknown targets for the development of new antiepileptic drugs.

  17. Catalytic oxidation of calcium sulfite in solution/aqueous slurry

    Institute of Scientific and Technical Information of China (English)

    WU Xiao-qin; WU Zhong-biao; WANG Da-hui

    2004-01-01

    Forced oxidation of calcium sulfite aqueous slurry is a key step for the calcium-based flue gas desulfurization(FGD) residue. Experiments were conducted in a semi-batch system and a continuous flow system on lab scales. The main reactor in semi-batch system is a 1000 ml volume flask. It has five necks for continuous feeding of gas and a batch of calcium sulfite solution/aqueous slurry. In continuous flow system, the main part is a jacketed Pyrex glass reactor in which gas and solution/aqueous slurry are fed continuously. Calcium sulfite oxidation is a series of complex free-radical reactions. According to experimental results and literature data, the reactions are influenced significantly by manganese as catalyst. At low concentration of manganese and calcium sulfite, the reaction rate is dependent on 1.5 order of sulfite concentration, 0.5 order of manganese concentration, and zero order of oxygen concentration in which the oxidation is controlled by chemical kinetics. With concentrations of calcium sulfite and manganese increasing, the reactions are independent gradually on the constituents in solution but are impacted by oxygen concentration. Manganese can accelerate the free-radical reactions, and then enhances the mass transfer of oxygen from gas to liquid. The critical concentration of calcium sulfite is 0.007 mol/L, manganese is 10-4 mol/L, and oxygen is of 0.2-0.4 atm.

  18. Characterization of incomplete fusion in the reactions Ar + KCl at 32,40,52 and 74 MeV/u; Caracterisation de la fusion incomplete dans les reactions Ar + KCl a 32,40,52 et 74 Mev/u

    Energy Technology Data Exchange (ETDEWEB)

    Bisquer, E. [Lyon-1 Univ., 69 - Villeurbanne (France). Inst. de Physique Nucleaire]|[Universite Claude Bernard, 69 - Lyon (France)

    1996-12-20

    Heavy ion collisions at intermediate energies (10 to 100 A.MeV) have been investigated and gave evidence to the persistence of so-called low energy mechanisms such as incomplete fusion. This thesis aims at determining the energy threshold beyond which such a mechanism does not occur any more. First we investigated the so-called conventional incomplete fusion. This mechanism is well known from low energy studies: a thermalized compound nucleus is formed which further de-excites by evaporating particles. Residues will be therefore detected in coincidence with mainly light particles. Ar + KCl at incident energies of 32, 40, 52 and 74 A.MeV has been selected for this analysis. These experiments have been performed using the INDRA multidetector in GANIL (Caen). The detection performance of INDRA allowed to use new analysis methods via global variables. In a first step, global variables have been compared in order to find the one that is the most appropriate to our study. Then incomplete fusion events have been extracted from raw events recorded at incident energies of 32, 40 and 52 A.MeV. It turned out that the contribution of this mechanisms was very weak at 52. A.MeV. It turned out that the contribution of this mechanism was very weak at 52 A.MeV and even zero at 74 A.MeV. We then investigated events in which three fragments were detected which could possibly sign multifragmentation. We did not find instantaneous multifragmentation with any expansion contribution. We also performed BNV simulations in order to compare our experimental results to model predictions, solving in a semi-classical way the Vlasov transport equation. A good agreement has been obtained on the size of the compound nucleus formed. However the excitation energy has not been reproduced, as the code seems to overestimate the energy taken away by preequilibrium particles. Incomplete fusion decreases as a function of energy but is not replaced by instantaneous multifragmentation with any expansion

  19. Implications for (d,p) reaction theory from nonlocal dispersive optical model analysis of $^{40}$Ca(d,p)$^{41}$Ca

    CERN Document Server

    Waldecker, S J

    2016-01-01

    The nonlocal dispersive optical model (NLDOM) nucleon potentials are used for the first time in the adiabatic analysis of a (d,p) reaction to generate distorted waves both in the entrance and exit channels. These potentials were designed and fitted by Mahzoon $et \\text{ } al.$ [Phys. Rev. Lett. 112, 162502 (2014)] to constrain relevant single-particle physics in a consistent way by imposing the fundamental properties, such as nonlocality, energy-dependence and dispersive relations, that follow from the complex nature of nuclei. However, the NLDOM prediction for the $^{40}$Ca(d,p)$^{41}$Ca cross sections at low energy, typical for some modern radioactive beam ISOL facilities, is about 70$\\%$ higher than the experimental data despite being reduced by the NLDOM spectroscopic factor of 0.73. This overestimation comes most likely either from insufficient absorption or due to constructive interference between ingoing and outgoing waves. This indicates strongly that additional physics arising from many-body effects ...

  20. Decay of excited nuclei produced in the 78,82Kr+40Ca reactions at 5.5 MeV/nucleon

    Directory of Open Access Journals (Sweden)

    Le Neindre N.

    2011-10-01

    Full Text Available Decay modes of excited nuclei are studied in 78,82Kr + 40Ca reactions at 5.5 MeV/nucleon by means of light-charged particles measured in coincidence with intermediate mass fragments and fission-like fragments. Inclusive cross-section distributions of fragments with charge 3 ≤ Z ≤ 28 are bell-shaped and a strong oddeven-staggering (o-e-s is observed for 3 ≤ Z ≤ 12. Coincidence measurements suggest that the light partners in very asymmetric fission are emitted at excitation energies below the particle emission thresholds. Data were confronted to the predictions of statistical models describing the decay of compound nuclei by emission of light particles and fragments. Comparison with models suggests that the o-e-s of the light-fragment yields is mainly due to the successive steps of compound nucleus disintegration.

  1. Discussion on the mechanism of the calcium absorption in the human body

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The present article discusses a new mechanism of calcium absorption in the human body. The mechanism is revealed as follows. First, after food is digested in the stomach, calcium ions (Ca2+) are released. The small intestine secretes amino acid or short peptide chain with small molecniar weight automatically, which are called chelating agent; when the calcium ions from the stomach get to the small intestine, the reaction of the chelating agent with the calcium ions occurs, producing the neutral amino acid calcium chelate. Then, this kind of calcium chelate with small molecular weight is absorbed as a whole into the tissues of the small intestine. After being absorbed, in the cell the calcium chelate can break down its chelating bond automatically and decompose into the amino acid and calcium ion again. Finally, the calcium ion goes into blood through portal vein and is transferred to the organs and also deposits on the bone. The reason for the body's calcium insufficiency, which has no linear relation with the calcium intake amount, is the lack of the amino acid secreted by the small intestine. The main barrier that influences the calcium absorption is anion pollution. The calcium absorptivity of the body has nothing to do with the solubility of the calcium source out of the body.A new kind of calcium supplement agent--glycine calcium chelate--is synthesized, whose molecular weight is 206.06(containing a molecular water). If the glycine calcium chelate is used to make calcium supplement agent, about 20 mg calcium element (converted from the glycine calcium chelate,the same below, no longer indicated) per day for one person,50 mg at most, is enough to maintain the positive balance of calcium metabolism.``

  2. Self-Setting Calcium Orthophosphate Formulations

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2013-11-01

    Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are bioactive and biodegradable grafting bioceramics in the form of a powder and a liquid. After mixing, both phases form pastes, which set and harden forming either a non-stoichiometric calcium deficient hydroxyapatite or brushite. Since both of them are remarkably biocompartible, bioresorbable and osteoconductive, self-setting calcium orthophosphate formulations appear to be promising bioceramics for bone grafting. Furthermore, such formulations possess excellent molding capabilities, easy manipulation and nearly perfect adaptation to the complex shapes of bone defects, followed by gradual bioresorption and new bone formation. In addition, reinforced formulations have been introduced, which might be described as calcium orthophosphate concretes. The discovery of self-setting properties opened up a new era in the medical application of calcium orthophosphates and many commercial trademarks have been introduced as a result. Currently such formulations are widely used as synthetic bone grafts, with several advantages, such as pourability and injectability. Moreover, their low-temperature setting reactions and intrinsic porosity allow loading by drugs, biomolecules and even cells for tissue engineering purposes. In this review, an insight into the self-setting calcium orthophosphate formulations, as excellent bioceramics suitable for both dental and bone grafting applications, has been provided.

  3. Calcium is important forus.

    Institute of Scientific and Technical Information of China (English)

    高利平

    2005-01-01

    Calcium is important for our health.We must have it in our diet to stay well.A good place to get it is from dairy products like milk, cheese and ice cream.One pound of cheese has fifty times the calcium we should have every day.Other foods have less.For example,a pound of beans also has calcium.But it has only three times the amount we ought to have daily.

  4. Dysbalance of astrocyte calcium under hyperammonemic conditions.

    Directory of Open Access Journals (Sweden)

    Nicole Haack

    Full Text Available Increased brain ammonium (NH4(+/NH3 plays a central role in the manifestation of hepatic encephalopathy (HE, a complex syndrome associated with neurological and psychiatric alterations, which is primarily a disorder of astrocytes. Here, we analysed the influence of NH4(+/NH3 on the calcium concentration of astrocytes in situ and studied the underlying mechanisms of NH4(+/NH3-evoked calcium changes, employing fluorescence imaging with Fura-2 in acute tissue slices derived from different regions of the mouse brain. In the hippocampal stratum radiatum, perfusion with 5 mM NH4(+/NH3 for 30 minutes caused a transient calcium increase in about 40% of astrocytes lasting about 10 minutes. Furthermore, the vast majority of astrocytes (∼ 90% experienced a persistent calcium increase by ∼ 50 nM. This persistent increase was already evoked at concentrations of 1-2 mM NH4(+/NH3, developed within 10-20 minutes and was maintained as long as the NH4(+/NH3 was present. Qualitatively similar changes were observed in astrocytes of different neocortical regions as well as in cerebellar Bergmann glia. Inhibition of glutamine synthetase resulted in significantly larger calcium increases in response to NH4(+/NH3, indicating that glutamine accumulation was not a primary cause. Calcium increases were not mimicked by changes in intracellular pH. Pharmacological inhibition of voltage-gated sodium channels, sodium-potassium-chloride-cotransporters (NKCC, the reverse mode of sodium/calcium exchange (NCX, AMPA- or mGluR5-receptors did not dampen NH4(+/NH3-induced calcium increases. They were, however, significantly reduced by inhibition of NMDA receptors and depletion of intracellular calcium stores. Taken together, our measurements show that sustained exposure to NH4(+/NH3 causes a sustained increase in intracellular calcium in astrocytes in situ, which is partly dependent on NMDA receptor activation and on release of calcium from intracellular stores. Our study

  5. Protein kinase C interaction with calcium: a phospholipid-dependent process.

    LENUS (Irish Health Repository)

    Bazzi, M D

    1990-08-21

    The calcium-binding properties of calcium- and phospholipid-dependent protein kinase C (PKC) were investigated by equilibrium dialysis in the presence and the absence of phospholipids. Calcium binding to PKC displayed striking and unexpected behavior; the free proteins bound virtually no calcium at intracellular calcium concentrations and bound limited calcium (about 1 mol\\/mol of PKC) at 200 microM calcium. However, in the presence of membranes containing acidic phospholipids, PKC bound at least eight calcium ions per protein. The presence of 1 microM phorbol dibutyrate (PDBu) in the dialysis buffer had little effect on these calcium-binding properties. Analysis of PKC-calcium binding by gel filtration under equilibrium conditions gave similar results; only membrane-associated PKC bound significant amounts of calcium. Consequently, PKC is a member of what may be a large group of proteins that bind calcium in a phospholipid-dependent manner. The calcium concentrations needed to induce PKC-membrane binding were similar to those needed for calcium binding (about 40 microM calcium at the midpoint). However, the calcium concentration required for PKC-membrane binding was strongly influenced by the phosphatidylserine composition of the membranes. Membranes with higher percentages of phosphatidylserine required lower concentrations of calcium. These properties suggested that the calcium sites may be generated at the interface between PKC and the membrane. Calcium may function as a bridge between PKC and phospholipids. These studies also suggested that calcium-dependent PKC-membrane binding and PKC function could be regulated by a number of factors in addition to calcium levels and diacylglycerol content of the membrane.

  6. Characterization of calcium isotopes in natural and synthetic barite

    Science.gov (United States)

    Griffith, E.M.; Schauble, E.A.; Bullen, T.D.; Paytan, A.

    2008-01-01

    The mineral barite (BaSO4) accommodates calcium in its crystal lattice, providing an archive of Ca-isotopes in the highly stable sulfate mineral. Holocene marine (pelagic) barite samples from the major ocean basins are isotopically indistinguishable from each other (??44/40Ca = -2.01 ?? 0.15???) but are different from hydrothermal and cold seep barite samples (??44/40Ca = -4.13 to -2.72???). Laboratory precipitated (synthetic) barite samples are more depleted in the heavy Ca-isotopes than pelagic marine barite and span a range of Ca-isotope compositions, ??44/40Ca = -3.42 to -2.40???. Temperature, saturation state, a Ba2 + / a SO42 -, and aCa2+/aBa2+ each influence the fractionation of Ca-isotopes in synthetic barite; however, the fractionation in marine barite samples is not strongly related to any measured environmental parameter. First-principles lattice dynamical modeling predicts that at equilibrium Ca-substituted barite will have much lower 44Ca/40Ca than calcite, by -9??? at 0 ??C and -8??? at 25 ??C. Based on this model, none of the measured barite samples appear to be in isotopic equilibrium with their parent solutions, although as predicted they do record lower ??44/40Ca values than seawater and calcite. Kinetic fractionation processes therefore most likely control the extent of isotopic fractionation exhibited in barite. Potential fractionation mechanisms include factors influencing Ca2+ substitution for Ba2+ in barite (e.g. ionic strength and trace element concentration of the solution, competing complexation reactions, precipitation or growth rate, temperature, pressure, and saturation state) as well as nucleation and crystal growth rates. These factors should be considered when investigating controls on isotopic fractionation of Ca2+ and other elements in inorganic and biogenic minerals. ?? 2008 Elsevier Ltd.

  7. Proton scattering on unstable nuclei: study of {sup 40}S(p,p`) and {sup 43}Ar(p,p`) reactions, development of detection system MUST; Diffusion de protons par des noyaux instables: Etudes des reactions {sup 40}S(p,p`) et {sup 43}Ar(p,p`), developpement du systeme de detection MUST

    Energy Technology Data Exchange (ETDEWEB)

    Marechal, F

    1998-02-06

    We measured for the first time the elastic and inelastic proton scattering on the {sup 40}S unstable nucleus. The experiment was performed in inverse kinematics at the NSCL AT Michigan State University with a {sup 40}S secondary beam bombarding a CH{sub 2} target at 30 MeV/A. We obtained the elastic scattering angular distribution and two points of the inelastic distribution to the first 2{sup +} excited state found to be located at 860{+-}90 KeV. With a coupled channel analysis, the {beta}{sub 2} quadrupolar deformation parameter is found to be equal to 0.35{+-}0.05. This value can be compared to 0.28{+-}0.02 obtained by coulomb excitation. A macroscopic analysis allowed us to extract the neutron and proton transition matrix element ratio M{sub n}/M{sub p} which is equal to 1.88{+-}0.38. This value, greater than N/Z, could indicate an isovector effect in the first 2{sup +} state excitation which could be due to a difference between the neutron and proton vibrations. The microscopic analysis gives the possibility to test the densities and the transition densities to the first 2{sup +} state. The calculated densities for the {sup 40}S nucleus show a neutron skin. However the microscopic analysis yields a M{sub n}/M{sub p} ratio of 1.40{+-}0.20. A similar elastic and inelastic proton scattering experiment allowed us to get a deformation parameter of 0.25{+-}0.03 for the {sup 43}Ar nucleus. To develop the study of direct reactions induced by radioactive beams at GANIL, we have developed and built, in collaboration with the CEA-Saclay and the CEA-Bruyeres, the new detector MUST.It is based on the silicon strip technology, and is dedicated to the measurement of recoiling light particles emitted in these reactions. The results obtained with a {sup 40}Ar beam at 77 Me V/A, have shown the good performances of the detector for the particle identification as well as for the resolutions, and allow us to consider now a large experimental programme concerning these direct

  8. Injectable hydrogels derived from phosphorylated alginic acid calcium complexes

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Han-Sem; Song, Minsoo, E-mail: minsoosong00@gmail.com; Lee, Eun-Jung; Shin, Ueon Sang, E-mail: usshin12@dankook.ac.kr

    2015-06-01

    Phosphorylation of sodium alginate salt (NaAlg) was carried out using H{sub 3}PO{sub 4}/P{sub 2}O{sub 5}/Et{sub 3}PO{sub 4} followed by acid–base reaction with Ca(OAc){sub 2} to give phosphorylated alginic acid calcium complexes (CaPAlg), as a water dispersible alginic acid derivative. The modified alginate derivatives including phosphorylated alginic acid (PAlg) and CaPAlg were characterized by nuclear magnetic resonance spectroscopy for {sup 1}H, and {sup 31}P nuclei, high resolution inductively coupled plasma optical emission spectroscopy, Fourier transform infrared spectroscopy, and thermogravimetric analysis. CaPAlg hydrogels were prepared simply by mixing CaPAlg solution (2 w/v%) with NaAlg solution (2 w/v%) in various ratios (2:8, 4:6, 6:4, 8:2) of volume. No additional calcium salts such as CaSO{sub 4} or CaCl{sub 2} were added externally. The gelation was completed within about 3–40 min indicating a high potential of hydrogel delivery by injection in vivo. Their mechanical properties were tested to be ≤ 6.7 kPa for compressive strength at break and about 8.4 kPa/mm for elastic modulus. SEM analysis of the CaPAlg hydrogels showed highly porous morphology with interconnected pores of width in the range of 100–800 μm. Cell culture results showed that the injectable hydrogels exhibited comparable properties to the pure alginate hydrogel in terms of cytotoxicity and 3D encapsulation of cells for a short time period. The developed injectable hydrogels showed suitable physicochemical and mechanical properties for injection in vivo, and could therefore be beneficial for the field of soft tissue engineering. - Highlights: • Preparation of water-soluble alginic acid complexes with calcium phosphate • Self-assembly of the phosphorylated alginic acid calcium complexes with sodium alginate • Preparation of injectable hydrogels with diverse gelation times within about 3–40 min.

  9. Effect of inhibitors on macroscopical oxidation kinetics of calcium sulfite

    Institute of Scientific and Technical Information of China (English)

    ZHAO Yi; WANG Li-dong; WANG Xiao-ming; LI Qiang-wei; XU Pei-yao

    2005-01-01

    In the presence of inhibitors, the macroscopical oxidation kinetics of calcium sulfite, the main byproduct in wet limestone scrubbing, was studied for the first time by adding different inhibitors and varying pH, concentration of calcium sulfite, oxygen partial pressure, concentration of inhibitors and temperature. The mathematical model about the general oxidation reaction was established,which was controlled by three steps involving dissolution of calcium sulfite, mass transfer of oxygen and chemical reaction in the solution.It was concluded that the general reaction was controlled by mass transfer of oxygen under uncatalyzed conditions, while it was controlled by dissolution of calcium sulfite after adding three kinds of inhibitors. Thus, the theory was provided for investigating the mechanism and oxidation kinetics of sulfite. The beneficial references were also supplied for design of oxidation technics in the wet limestone scrubbing.

  10. Effects of calcium ion, calpains, and calcium channel blockers on retinitis pigmentosa.

    Science.gov (United States)

    Nakazawa, Mitsuru

    2011-01-01

    Recent advances in molecular genetic studies have revealed many of the causative genes of retinitis pigmentosa (RP). These achievements have provided clues to the mechanisms of photoreceptor degeneration in RP. Apoptosis is known to be a final common pathway in RP and, therefore, a possible therapeutic target for photoreceptor rescue. However, apoptosis is not a single molecular cascade, but consists of many different reactions such as caspase-dependent and caspase-independent pathways commonly leading to DNA fractionation and cell death. The intracellular concentration of calcium ions is also known to increase in apoptosis. These findings suggest that calpains, one of the calcium-dependent proteinases, play some roles in the process of photoreceptor apoptosis and that calcium channel antagonists may potentially inhibit photoreceptor apoptosis. Herein, the effects of calpains and calcium channel antagonists on photoreceptor degeneration are reviewed.

  11. Effects of Calcium Ion, Calpains, and Calcium Channel Blockers on Retinitis Pigmentosa

    Directory of Open Access Journals (Sweden)

    Mitsuru Nakazawa

    2011-01-01

    Full Text Available Recent advances in molecular genetic studies have revealed many of the causative genes of retinitis pigmentosa (RP. These achievements have provided clues to the mechanisms of photoreceptor degeneration in RP. Apoptosis is known to be a final common pathway in RP and, therefore, a possible therapeutic target for photoreceptor rescue. However, apoptosis is not a single molecular cascade, but consists of many different reactions such as caspase-dependent and caspase-independent pathways commonly leading to DNA fractionation and cell death. The intracellular concentration of calcium ions is also known to increase in apoptosis. These findings suggest that calpains, one of the calcium-dependent proteinases, play some roles in the process of photoreceptor apoptosis and that calcium channel antagonists may potentially inhibit photoreceptor apoptosis. Herein, the effects of calpains and calcium channel antagonists on photoreceptor degeneration are reviewed.

  12. The structure effects in polarization and cross section in inelastic A(p,p')X reaction with the 40Ca and 12C nuclei at 1 GeV

    CERN Document Server

    Miklukho, O V; Amalsky, G M; Andreev, V A; Gavrilov, G E; Izotov, A A; Kozlenko, N G; Kravchenko, P V; Levchenko, M P; Novinskiy, D V; Prokofiev, A N; Shvedchikov, A V; Trush, S I; Zhdanov, A A

    2016-01-01

    The polarization of the secondary protons in inelastic (p,p') reaction on the 40Ca and 12C nuclei at the initial proton energy 1 GeV was measured in the wide range of the scattered proton momenta at a laboratory angle 21 degree. The cross section of the reactions were measured as well. The outgoing protons from the reaction were detected using a magnetic spectrometer equipped with a multiwire-proportional chambers polarimeter. A structure in the polarization and cross section data, related probably to scattering of the nucleon correlation in the nuclei, was observed.

  13. Study of the reactions resulting in heavy fragment formation in the collisions {sup 40}Ar + Cu, Ag and Au at 8 to 115 MeV/u; Etude des reactions avec formation d`un fragment lourd dans les collisions {sup 40}Ar + Cu, Ag et Au de 8 a 115 MeV/u

    Energy Technology Data Exchange (ETDEWEB)

    Colin, Eric Yves [Universite Claude Bernard Lyon-1, 69 - Lyon (France)

    1998-11-06

    This work concerns the study of nuclear collisions showing a heavy fragment in {sup 40}Ar + Cu, Ag and Au from 8 A MeV to 115 A MeV. The reactions are classified by centrality or collision violence via the multiplicity of charged particles detected in a 4{pi} array. For the most peripheral reactions (low multiplicities) we always find a projectile-like fragment with velocity near to that of the beam and a heavy target-like fragment with very small velocity. For the more central collisions we find the well-known incomplete fusion reactions at 17 and 27 A MeV. Above 27 A MeV two groups of very dissipative reactions are observed, both with high charged particle multiplicities. The first reaction group forms several fragments with Z {<=} 10 and average longitudinal velocity near to that of c.m. These are very rare, and are found only for the highest 1% of multiplicities. They produce a heavy fragment and a forward spray ({theta}{<=}60 angle) of particles with charge going from 1 to {approx_equal}13. The momentum carried out by the spray is randomly spread over all the particles. In spite of the increase of momentum carried by this spray with increasing beam energy, a heavy emission source is formed with 1 - 2 GeV of excitation energy. After a phase of expansion, especially signaled by Z = 1 particles, this source then evaporates many particles. Finally we observed the remaining heavy residual nucleus. (author) 117 refs., 85 figs., 12 tabs.

  14. Calcium requirement of phytochrome-mediated fern-spore germination: no direct phytochrome-calcium interaction in the phytochrome-initiated transduction chain

    Science.gov (United States)

    Scheuerlein, R.; Wayne, R.; Roux, S. J.

    1989-01-01

    Phytochrome-mediated germination of fern spores of Dryopteris paleacea Sw. was initiated by a saturating red-light (R) irradiation after 20 h of imbibition. For its realization external Ca2+ was required, with a threshold at a submicromolar concentration, and an optimum was reached around 10(-4) M. At concentrations > or = 10(-1) M only a reduced response was obtained, based probably on an unspecific osmotic or ionic effect. The germination response was inhibited by La3+, an antagonist of Ca2+. From these results it is concluded that Ca2+ influx from the medium into the spores may be an important event in phytochrome-mediated germination. In the absence of Ca2+ the R-stimulated system remained capable of responding to Ca2+, added as late as 40 h after R. Moreover, Ca2+ was effective even if added after the active form of phytochrome, Pfr, had been abolished by far-red (FR) 24 h after R. Thus, the primary effect of Pfr, that initiates the transduction chain, does not require calcium. "Coupling" of Pfr to subsequent dark reactions has been investigated by R-FR irradiations with various dark intervals. The resulting "escape kinetics" were characterized by a lag phase (6 h) and half-maximal escape from FR reversibility (19 h). These kinetics were not significantly changed by the presence or absence of calcium. Thus, direct interaction of Pfr and calcium is not a step in the transduction chain initiated by the active form of phytochrome.

  15. Acidosis and Urinary Calcium Excretion

    DEFF Research Database (Denmark)

    Alexander, R Todd; Cordat, Emmanuelle; Chambrey, Régine

    2016-01-01

    Metabolic acidosis is associated with increased urinary calcium excretion and related sequelae, including nephrocalcinosis and nephrolithiasis. The increased urinary calcium excretion induced by metabolic acidosis predominantly results from increased mobilization of calcium out of bone and inhibi...

  16. Intervention effects of atorvastatin calcium tablets on soluble CD40 ligand and C-reactive protein in patients with cardiac angina%阿托伐他汀钙片对心绞痛患者血清可溶性CD40配体与C反应蛋白的干预研究

    Institute of Scientific and Technical Information of China (English)

    王庆玲; 杨永全

    2011-01-01

    Objective To investigate the intervention of level of atorvastatin calcium tablets (lipitor) on soluble CD40 (CD40L) and high sensitivity C-reactive protein (hs-CRP) in patients with angina.Methods 65 patients with coronary heart disease were divided into stable angina (SA group,n= 30) and unstable angina (UA group,n= 35).The vein blood was collected in the hospitalized morning,2,4,6 weeks after treatment and serum levels of hs-CRP and CD40L were measured and compared between the two groups.Results The levels of soluable CD40L [(20.52± 2.91)μg/L] and CRP [(7.96±1.69) mg/L] in UA group were higher than SA group [(7.96±-1.35) tg/L and ( 1.58 ± 0.91 ) mg/L] (t = 21.705、18.493,both P< 0.05) before treatment,and after treatment,their levels in the two groups were significantly lower than pre-treatment (P<0.01).Conclusions CD40L and hs-CRP may involved in the pathophysiology of unstable angina process and can be used as an indicator reflecting vulnerable plaque.Lipitor might enhance stability of atherosclerotic plaque and prevent acute coronary events by reducing levels of CD40L and hs-CRP.%目的 探讨阿托伐他汀钙片对心绞痛患者血清可溶性CD40配体(CD40L)与高敏C反应蛋白(hs-CRP)的干预作用.方法 65例冠心病患者,其中稳定型心绞痛患者30例(SA组),不稳定型心绞痛患者35例(UA组),所有患者于入院当天清晨、治疗后2、4、6周静脉血,测定血清hsCRP、血清可溶性CD40L水平,并对两组结果进行比较.结果 治疗前UA组血清可溶性CD40L、hs-CRP浓度分别为(20.52±2.91)μg/L、(7.96±1.69) mg/L,明显高于SA组(7.96±1.35)μg/L、(1.58±0.91) mg/L(t=21.705、18.493,均P<0.05),而两组治疗后血清可溶性CD40L、hs-CRP浓度均较治疗前明显降低(均P<0.01).结论 血清可溶性CD40L、hs-CRP参与了不稳定型心绞痛的病理生理过程,可以作为反映易损斑块的指标,阿托伐他汀钙片可通过降低血清可溶性CD40L、hs-CRP而加强粥样硬化斑块的稳定性.

  17. Calcium signaling in neurodegeneration

    Directory of Open Access Journals (Sweden)

    Dreses-Werringloer Ute

    2009-05-01

    Full Text Available Abstract Calcium is a key signaling ion involved in many different intracellular and extracellular processes ranging from synaptic activity to cell-cell communication and adhesion. The exact definition at the molecular level of the versatility of this ion has made overwhelming progress in the past several years and has been extensively reviewed. In the brain, calcium is fundamental in the control of synaptic activity and memory formation, a process that leads to the activation of specific calcium-dependent signal transduction pathways and implicates key protein effectors, such as CaMKs, MAPK/ERKs, and CREB. Properly controlled homeostasis of calcium signaling not only supports normal brain physiology but also maintains neuronal integrity and long-term cell survival. Emerging knowledge indicates that calcium homeostasis is not only critical for cell physiology and health, but also, when deregulated, can lead to neurodegeneration via complex and diverse mechanisms involved in selective neuronal impairments and death. The identification of several modulators of calcium homeostasis, such as presenilins and CALHM1, as potential factors involved in the pathogenesis of Alzheimer's disease, provides strong support for a role of calcium in neurodegeneration. These observations represent an important step towards understanding the molecular mechanisms of calcium signaling disturbances observed in different brain diseases such as Alzheimer's, Parkinson's, and Huntington's diseases.

  18. Experimental studies on the neutron emission spectrum and induced radioactivity of the sup 7 Li(d,n) reaction in the 20-40 MeV region

    CERN Document Server

    Baba, M; Hagiwara, M; Sugimoto, M; Miura, T; Kawata, N; Yamadera, A; Orihara, H

    2002-01-01

    To improve the data accuracy of the neutron emission spectrum of the sup 7 Li(d,n) reaction and the radioactivity ( sup 7 Be, sup 3 H, etc.) accumulated in the sup 7 Li target in IFMIF, we have measured the neutron emission spectrum and the radioactivity of sup 7 Be induced in the lithium target for 25 MeV deuterons at the Tohoku University AVF cyclotron (K=110) facility. Neutron spectra were measured with the time-of-flight (TOF) method at four laboratory angles by using a beam swinger system and a well collimated TOF channel. Induced radioactivity was measured by detecting the gamma-rays from sup 7 Be with a pure Ge detector. Experimental results are compared with other experimental data. The present result of neutron emission spectra are in qualitative agreement with other experimental data but that of sup 7 Be production was much larger than expected by the recent codes. Measurement will be extended to several incident energies up to 40 MeV.

  19. Experimental studies on the neutron emission spectrum and induced radioactivity of the {sup 7}Li(d,n) reaction in the 20-40 MeV region

    Energy Technology Data Exchange (ETDEWEB)

    Baba, M. E-mail: babam@cyric.tohoku.ac.jp; Aoki, T.; Hagiwara, M.; Sugimoto, M.; Miura, T.; Kawata, N.; Yamadera, A.; Orihara, H

    2002-12-01

    To improve the data accuracy of the neutron emission spectrum of the {sup 7}Li(d,n) reaction and the radioactivity ({sup 7}Be, {sup 3}H, etc.) accumulated in the {sup 7}Li target in IFMIF, we have measured the neutron emission spectrum and the radioactivity of {sup 7}Be induced in the lithium target for 25 MeV deuterons at the Tohoku University AVF cyclotron (K=110) facility. Neutron spectra were measured with the time-of-flight (TOF) method at four laboratory angles by using a beam swinger system and a well collimated TOF channel. Induced radioactivity was measured by detecting the gamma-rays from {sup 7}Be with a pure Ge detector. Experimental results are compared with other experimental data. The present result of neutron emission spectra are in qualitative agreement with other experimental data but that of {sup 7}Be production was much larger than expected by the recent codes. Measurement will be extended to several incident energies up to 40 MeV.

  20. Behavior of calcium silicate hydrate in aluminate solution

    Institute of Scientific and Technical Information of China (English)

    LI Xiao-bin; ZHAO Zhuo; LIU Gui-hua; ZHOU Qiu-sheng; PENG Zhi-hong

    2005-01-01

    Using calcium hydroxide and sodium silicate as starting materials, two kinds of calcium silicate hydrates, CaO · SiO2 · H2O and 2CaO · SiO2 · 1.17H2O, were hydro-thermally synthesized at 120 ℃. The reaction rule of calcium silicate hydrate in aluminate solution was investigated. The result shows that CaO · SiO2 · H2O is more stable than 2CaO · SiO2 · 1.17H2 O in aluminate solution and its stability increases with the increase of reaction temperature but decreases with the increase of caustic concentration. The reaction between calcium silicate hydrate and aluminate solution is mainly through two routes. In the first case, Al replaces partial Si in calcium silicate hydrate, meanwhile 3CaO · Al2 O3 · xSiO2 · (6-2x) H2 O (hydro-garnet) is formed and some SiO2 enters the solution. In the second case, calcium silicate hydrate can react directly with aluminate solution, forming hydro-garnet and Na2O · Al2O3 · 2SiO2 · nH2O (DSP). The desilication reaction of aluminate solution containing silicate could contribute partially to forming DSP.

  1. Syntheses and Structure Determinations of Calcium Thiolates.

    Science.gov (United States)

    Chadwick, Scott; Englich, Ulrich; Noll, Bruce; Ruhlandt-Senge, Karin

    1998-09-07

    The exploration of synthetic methodologies toward heavy alkaline-earth chalcogenolates resulted in the preparation and structural characterization of a family of calcium thiolates, including [Ca(SC(6)F(5))(2)(py)(4)], 1 (py = pyridine), the separated ion-triple [Ca(18-crown-6)(NH(3))(3))][SMes](2).2THF, 2 (Mes = 2,4,6-tBu(3)C(6)H(2)), and the contact triple [Ca(18-crown-6)(SMes)(2)].THF, 3. Compound 1 was prepared by treating [Ca(N(SiMe(3))(2))(2)](2) with 4 equiv of HSC(6)F(5) under addition of pyridine. The thiolates 2 and 3 were synthesized by treatment of calcium metal dissolved in dry, liquid NH(3) under addition of 2 equiv of HSMes and crown ether or, alternatively, by the reduction of MesSSMes with calcium metal in dry, liquid ammonia. We also report two reaction products isolated during attempted calcium thiolate syntheses: [CaBr(4)(THF)(2)(&mgr;(2)-Li)(2)(THF)(4)], 4, isolated as the product of a salt elimination reaction between CaBr(2) and 2 equiv of [Li(THF)(n)()S-2,4,6-(i)()Pr(3)C(6)H(2)](m)(). [(NH(4))(py)(SC(6)F(5))], 5, was obtained as the sole product in the reaction of metallic calcium with HSC(6)F(5) in liquid ammonia under addition of pyridine. All compounds were characterized by single-crystal X-ray crystallography in addition to IR and NMR spectroscopy.

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

    Science.gov (United States)

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

    2010-03-01

    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.

  3. 40 CFR 63.11524 - Am I subject to this subpart?

    Science.gov (United States)

    2010-07-01

    ... chrome, standard ferromanganese, silicomanganese, ferromanganese silicon, calcium carbide or other..., ferrosilicon, ferrotitanium using the aluminum reduction process, ferrovanadium, ferromolybdenum, calcium... a permit under 40 CFR part 70 or 40 CFR part 71, provided you are not otherwise required by law...

  4. Pyrochemical recovery of plutonium from calcium fluoride reduction slag

    Science.gov (United States)

    Christensen, D.C.

    A pyrochemical method of recovering finely dispersed plutonium metal from calcium fluoride reduction slag is claimed. The plutonium-bearing slag is crushed and melted in the presence of at least an equimolar amount of calcium chloride and a few percent metallic calcium. The calcium chloride reduces the melting point and thereby decreases the viscosity of the molten mixture. The calcium reduces any oxidized plutonium in the mixture and also causes the dispersed plutonium metal to coalesce and settle out as a separate metallic phase at the bottom of the reaction vessel. Upon cooling the mixture to room temperature, the solid plutonium can be cleanly separated from the overlying solid slag, with an average recovery yield on the order of 96 percent.

  5. Calcium regulation of oxidative phosphorylation in rat skeletal muscle mitochondria.

    Science.gov (United States)

    Kavanagh, N I; Ainscow, E K; Brand, M D

    2000-02-24

    Activation of oxidative phosphorylation by physiological levels of calcium in mitochondria from rat skeletal muscle was analysed using top-down elasticity and regulation analysis. Oxidative phosphorylation was conceptually divided into three subsystems (substrate oxidation, proton leak and phosphorylation) connected by the membrane potential or the protonmotive force. Calcium directly activated the phosphorylation subsystem and (with sub-saturating 2-oxoglutarate) the substrate oxidation subsystem but had no effect on the proton leak kinetics. The response of mitochondria respiring on 2-oxoglutarate at two physiological concentrations of free calcium was quantified using control and regulation analysis. The partial integrated response coefficients showed that direct stimulation of substrate oxidation contributed 86% of the effect of calcium on state 3 oxygen consumption, and direct activation of the phosphorylation reactions caused 37% of the increase in phosphorylation flux. Calcium directly activated phosphorylation more strongly than substrate oxidation (78% compared to 45%) to achieve homeostasis of mitochondrial membrane potential during large increases in flux.

  6. Calcium and Your Child

    Science.gov (United States)

    ... for dinner. Create mini-pizzas by topping whole-wheat English muffins or bagels with pizza sauce, low- ... Minerals Do I Need to Drink Milk? Lactose Intolerance Becoming a Vegetarian Soy Foods and Health Calcium ...

  7. Stoichiometry of Calcium Medicines

    Science.gov (United States)

    Pinto, Gabriel

    2005-01-01

    The topic of calcium supplement and its effects on human lives is presented in the way of questions to the students. It enables the students to realize the relevance of chemistry outside the classroom surrounding.

  8. 3-Bromopyruvate inhibits calcium uptake by sarcoplasmic reticulum vesicles but not SERCA ATP hydrolysis activity.

    Science.gov (United States)

    Jardim-Messeder, Douglas; Camacho-Pereira, Juliana; Galina, Antonio

    2012-05-01

    3-Bromopyruvate (3BrPA) is an antitumor agent that alkylates the thiol groups of enzymes and has been proposed as a treatment for neoplasias because of its specific reactivity with metabolic energy transducing enzymes in tumor cells. In this study, we show that the sarco/endoplasmic reticulum calcium (Ca(2+)) ATPase (SERCA) type 1 is one of the target enzymes of 3BrPA activity. Sarco/endoplasmic reticulum vesicles (SRV) were incubated in the presence of 1mM 3BrPA, which was unable to inhibit the ATPase activity of SERCA. However, Ca(2+)-uptake activity was significantly inhibited by 80% with 150 μM 3BrPA. These results indicate that 3BrPA has the ability to uncouple the ATP hydrolysis from the calcium transport activities. In addition, we observed that the inclusion of 2mM reduced glutathione (GSH) in the reaction medium with different 3BrPA concentrations promoted an increase in 40% in ATPase activity and protects the inhibition promoted by 3BrPA in calcium uptake activity. This derivatization is accompanied by a decrease of reduced cysteine (Cys), suggesting that GSH and 3BrPA increases SERCA activity and transport by pyruvylation and/or S-glutathiolation mediated by GSH at a critical Cys residues of the SERCA.

  9. Calcium and Calcium-Base Alloys

    Science.gov (United States)

    1949-01-01

    should be satisfactory, because the electrolytic process for •(!>: A. H. Everts and G. D. Baglev’, " Physical «nrt m<„.+„4 i «_ of Calcium«, Electrochem...Rev. Metalurgie , 3j2, (1), 129 (1935). 10 ^sm^mssss^ma^^ extension between two known loads, is preferable to the value of 3,700,000 p.B.i. obtained

  10. Conduction calorimetric studies of ternary binders based on Portland cement, calcium aluminate cement and calcium sulphate

    OpenAIRE

    Torrens Martín, David; Fernández Carrasco, Lucía; Blanco Varela, M.Teresa

    2013-01-01

    Different binders of Portland cement, calcium aluminate cement and calcium sulphate (PC/CAC/CS) have been investigated to determinate the in¿uence the CAC and CS amount in the reactions mechanism. Several mixtures were studied, ratios of 100, 85/15 and 75/25 of PC/CAC with 0, 3 and 5 % of CS. Conduction calorimetric technique was used to follow the hydration during 100 h. The XRD and FTIR techniques were used as support in the analysis of the hydration products. The results have shown tha...

  11. [Calcium suppletion for patients who use gastric acid inhibitors: calcium citrate or calcium carbonate?].

    NARCIS (Netherlands)

    Jonge, H.J. de; Gans, R.O.; Huls, G.A.

    2012-01-01

    Various calcium supplements are available for patients who have an indication for calcium suppletion. American guidelines and UpToDate recommend prescribing calcium citrate to patients who use antacids The rationale for this advice is that water-insoluble calcium carbonate needs acid for adequate ab

  12. Hydrothermal Formation of Calcium Copper Tetrasilicate.

    Science.gov (United States)

    Johnson-McDaniel, Darrah; Comer, Sara; Kolis, Joseph W; Salguero, Tina T

    2015-12-01

    We describe the first hydrothermal synthesis of CaCuSi4 O10 as micron-scale clusters of thin platelets, distinct from morphologies generated under salt-flux or solid-state conditions. The hydrothermal reaction conditions are surprisingly specific: too cold, and instead of CaCuSi4 O10 , a porous calcium copper silicate forms; too hot, and calcium silicate (CaSiO3 ) forms. The precursors also strongly impact the course of the reaction, with the most common side product being sodium copper silicate (Na2 CuSi4 O10 ). Optimized conditions for hydrothermal CaCuSi4 O10 formation from calcium chloride, copper(II) nitrate, sodium silicate, and ammonium hydroxide are 350 °C at 3000 psi for 72 h; at longer reaction times, competitive delamination and exfoliation causes crystal fragmentation. These results illustrate that CaCuSi4 O10 is an even more unique material than previously appreciated.

  13. Calcium in plant cells

    Directory of Open Access Journals (Sweden)

    V. V. Schwartau

    2014-04-01

    Full Text Available The paper gives the review on the role of calcium in many physiological processes of plant organisms, including growth and development, protection from pathogenic influences, response to changing environmental factors, and many other aspects of plant physiology. Initial intake of calcium ions is carried out by Ca2+-channels of plasma membrane and they are further transported by the xylem owing to auxins’ attractive ability. The level of intake and selectivity of calcium transport to ove-ground parts of the plant is controlled by a symplast. Ca2+enters to the cytoplasm of endoderm cells through calcium channels on the cortical side of Kaspary bands, and is redistributed inside the stele by the symplast, with the use of Ca2+-АТPases and Ca2+/Н+-antiports. Owing to regulated expression and activity of these calcium transporters, calclum can be selectively delivered to the xylem. Important role in supporting calcium homeostasis is given to the vacuole which is the largest depo of calcium. Regulated quantity of calcium movement through the tonoplast is provided by a number of potential-, ligand-gated active transporters and channels, like Ca2+-ATPase and Ca2+/H+ exchanger. They are actively involved in the inactivation of the calcium signal by pumping Ca2+ to the depo of cells. Calcium ATPases are high affinity pumps that efficiently transfer calcium ions against the concentration gradient in their presence in the solution in nanomolar concentrations. Calcium exchangers are low affinity, high capacity Ca2+ transporters that are effectively transporting calcium after raising its concentration in the cell cytosol through the use of protons gradients. Maintaining constant concentration and participation in the response to stimuli of different types also involves EPR, plastids, mitochondria, and cell wall. Calcium binding proteins contain several conserved sequences that provide sensitivity to changes in the concentration of Ca2+ and when you

  14. Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

    OpenAIRE

    Wilson, Rosamund J; Copley, J Brian

    2017-01-01

    Background Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. Scope A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent...

  15. 以石灰乳为中和剂的柠檬酸钙合成反应过程与机理研究%Research on Citric Acid Calcium Synthetic Reaction Process and Its Mechanism with Lime Milk as Neutralizer

    Institute of Scientific and Technical Information of China (English)

    颜鑫; 刘小忠; 李玉茶; 傅国新

    2012-01-01

    以石灰乳为中和剂合成柠檬酸钙工艺简单,成本低廉,便于大规模生产.将柠檬酸溶液加入石灰乳中的方案是一个快速、简单的反 应过程,其pH值操作曲线简单,终点突跃明显,易于操作控制,其产品为微弱酸性的缓冲体系,可生产高溶解性的柠檬酸钙.将石灰乳加入柠檬酸溶液的方案是一个慢速、复杂的反应过程,其pH值操作曲线有3个平台、3个突跃,突跃虽多但不很明显,反应时间长,生产中难以操作控制,其产品不再是缓冲体系,可能呈强碱性,易造成产品质量不合格.%The synthesis process of citric acid calcium is simple, low cost, and in favor of mass production process with citric acid and lime milk as raw material. The scheme is a rapid, simple reaction process using citric acid solution to join the lime milk, and its pH value operation curve is simple, the sudden jump is clear and easy to control, and its products will be weak acid buffer system which can produce the high solubility of citric acid calcium. Instead, the another scheme is a slow, complex reaction process using lime milk to join citric acid solution, and its pH value operation curve has three platforms, three sudden jumps, but the jumps being not obvious, and the reaction time is long, the production is hard to operate, and its products will no longer be buffer system, may show a strong alkali, easy to cause product quality problem.

  16. Inositol trisphosphate and calcium signalling

    Science.gov (United States)

    Berridge, Michael J.

    1993-01-01

    Inositol trisphosphate is a second messenger that controls many cellular processes by generating internal calcium signals. It operates through receptors whose molecular and physiological properties closely resemble the calcium-mobilizing ryanodine receptors of muscle. This family of intracellular calcium channels displays the regenerative process of calcium-induced calcium release responsible for the complex spatiotemporal patterns of calcium waves and oscillations. Such a dynamic signalling pathway controls many cellular processes, including fertilization, cell growth, transformation, secretion, smooth muscle contraction, sensory perception and neuronal signalling.

  17. Production of calcium-stearate by lipase using hydrogenated beef tallow.

    Science.gov (United States)

    Lee, Hyang-Bok; Kwon, Jin-Soo; Kim, Young-Bum; Kim, Eun-Ki

    2009-05-01

    Calcium-stearate has been traditionally produced by chemical methods, producing wastes and requiring high energy because of high temperature operation. To achieve enzymatic production of calcium-stearate at unfavorable conditions, i.e., pH 10 and 60 degrees C, suitable lipase was selected and reaction conditions were optimized using calcium hydroxide and hydrogenated beef tallow as substrates. Under optimum conditions, 95% of beef tallow, in 2.5 h, was converted into calcium-stearate by using commercial lipase SDL 451. Investigation of the time-course reaction revealed that fatty acid was initially produced by lipase, followed by conversion into calcium-stearate. The fatty acid production rate was faster than that of the conversion into calcium-stearate at the beginning of the reaction. Alkaline pH, originating from the addition of calcium hydroxide, increased the converting reaction. This is the first report demonstrating that chemical production of calcium-stearate can be replaced by enzymatic reaction, thereby creating a cleaner process.

  18. Kinetics of the Carbonate Leaching for Calcium Metavanadate

    Directory of Open Access Journals (Sweden)

    Peiyang Shi

    2016-10-01

    Full Text Available The sodium salt roasting process was widely used for extracting vanadium due to its high yield rate of vanadium. However, the serious pollution was a problem. The calcium roasting process was environmentally friendly, but the yield rate of vanadium was relatively lower. Focusing on the calcium metavanadate produced in the calcium roasting process of vanadium minerals, the mechanism of the carbonate leaching for calcium metavanadate and its leaching kinetics of calcium metavanadate were studied. With the increase of the leaching agent content, the decrease of the particle size, the increase of the temperature and the increase of the reaction time, the leaching rate of vanadium increased, and the constant of reaction rate increased. In the carbonate leaching process, the calcium carbonate was globular and attached to the surface of calcium metavanadate. In the solution containing bicarbonate radical, lots of cracks formed in the dissolution process. However, the cracks were relatively fewer in the solution containing carbonate. In the present study, the carbonate leaching for calcium metavanadate was controlled by diffusion, the activation energy reached maximum and minimum in the sodium bicarbonate and the sodium carbonate solution, respectively. The activation energy value in the ammonium bicarbonate solution was between those two solutions. The kinetic equations of the carbonate leaching for calcium metavanadate were as follows: 1 − 2/3η − (1 − η2/3 = 4.39[Na2CO3]0.75/r0 × exp(−2527.06/Tt; 1 − 2/3η − (1 − η2/3 = 7.89[NaHCO3]0.53/r0 × exp(−2530.67/Tt; 1 − 2/3η − (1 − η2/3 = 6.78[NH4HCO3]0.69/r0 × exp(−2459.71/Tt.

  19. Gravimetric Determination of Calcium as Calcium Carbonate Hydrate.

    Science.gov (United States)

    Henrickson, Charles H.; Robinson, Paul R.

    1979-01-01

    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)

  20. Calcium and Calcium Supplements: Achieving the Right Balance

    Science.gov (United States)

    ... bone mass, which is a risk factor for osteoporosis. Many Americans don't get enough calcium in their diets. Children and adolescent girls are at particular risk, but so are adults age 50 and older. How much calcium you ...

  1. Mechano-activated surface modification of calcium carbonate in wet stirred mill and its properties

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Surface modification of calcium carbonate particles using sodium stearate(SDS) as a modification agent incorporated with the simultaneous wet ultra-fine grinding in the laboratory stirred mill was investigated. The physical properties and application properties of modified calcium carbonate were measured and evaluated. The action mechanism between SDS and calcium carbonate in the modification was studied by infrared spectrometry(IR) and X-ray photoelectron energy spectroscopy(XPS). The results indicate that the crushing mechanic force intensity can obviously influence the modification effect of calcium carbonate because of mechano-chemical effect. The hydrophilic surface of calcium carbonate is turned into hydrophobic after modification. The properties of polyethylene(PE) filled by modified calcium carbonate powder is markedly improved. And the adsorption of SDS could occur by chemical reaction with calcium carbonate surface.

  2. Calcium, vitamin D and bone

    OpenAIRE

    Borg, Andrew A.

    2012-01-01

    Calcium, protein and vitamin D are the main nutrients relevant to bone health. This short article discusses the importance of vitamin D and its relation to calcium homeostasis. The various causes, clinical manifestations and treatment are outlined.

  3. Calcium ion channel and epilepsy

    Institute of Scientific and Technical Information of China (English)

    Yudan Lü; Weihong Lin; Dihui Ma

    2006-01-01

    OBJECTIVE: To review the relationship between calcium ion channel and epilepsy for well investigating the pathogenesis of epilepsy and probing into the new therapeutic pathway of epilepsy.DATA SOURCES: A computer-based online research Calcium ion channel and epilepsy related articles published between January 1994 and December 2006 in the CKNI and Wanfang database with the key words of "calcium influxion, epilepsy, calcium-channel blocker". The language was limited to Chinese. At the same time,related articles published between January 1993 and December 2006 in Pubmed were searched for on online with the key words of "calcium influxion, epilepsy" in English.STUDY SELECTION: The materials were selected firstly. Inclusive criteria: ① Studies related to calcium ion channel and the pat1hogenesis of epilepsy. ② Studies on the application of calcium ion channel blocker in the treatment of epilepsy. Exclusive criteria: repetitive or irrelated studies.DATA EXTRACTION: According to the criteria, 123 articles were retrieved and 93 were excluded due to repetitive or irrelated studies. Altogether 30 articles met the inclusive criteria, 11 of them were about the structure and characters of calcium ion channel, 10 about calcium ion channel and the pathogenesis of epilepsy and 9 about calcium blocker and the treatment of epilepsy.DATA SYNTHESIS: Calcium ion channels mainly consist of voltage dependent calcium channel and receptor operated calcium channel. Depolarization caused by voltage gating channel-induced influxion is the pathological basis of epileptic attack, and it is found in many studies that many anti-epileptic drugs have potential and direct effect to rivalizing voltage-dependent calcium ion channel.CONCLUSION: Calcium influxion plays an important role in the seizure of epilepsy. Some calcium antagonists seen commonly are being tried in the clinical therapy of epilepsy that is being explored, not applied in clinical practice. If there are enough evidences to

  4. Calcium carbonate overdose

    Science.gov (United States)

    Calcium carbonate is not very poisonous. Recovery is quite likely. But, long-term overuse is more serious than a single overdose, because it can cause kidney damage. Few people die from an antacid overdose. Keep all medicines in child-proof bottles and out ...

  5. High Blood Calcium (Hypercalcemia)

    Science.gov (United States)

    ... as well as kidney function and levels of calcium in your urine. Your provider may do other tests to further assess your condition, such as checking your blood levels of phosphorus (a mineral). Imaging studies also may be helpful, such as bone ...

  6. Solar Imagery - Chromosphere - Calcium

    Data.gov (United States)

    National Oceanic and Atmospheric Administration, Department of Commerce — This dataset consists of full-disk images of the sun in Calcium (Ca) II K wavelength (393.4 nm). Ca II K imagery reveal magnetic structures of the sun from about 500...

  7. Calcium addition in straw gasification

    DEFF Research Database (Denmark)

    Risnes, H.; Fjellerup, Jan Søren; Henriksen, Ulrik Birk

    2003-01-01

    The present work focuses on the influence of calcium addition in gasification. The inorganic¿organic element interaction as well as the detailed inorganic¿inorganic elements interaction has been studied. The effect of calcium addition as calcium sugar/molasses solutions to straw significantly...

  8. Calcium intake and prostate cancer among African Americans: effect modification by vitamin D receptor calcium absorption genotype.

    Science.gov (United States)

    Rowland, Glovioell W; Schwartz, Gary G; John, Esther M; Ingles, Sue Ann

    2012-01-01

    High dietary intake of calcium has been classified as a probable cause of prostate cancer, although the mechanism underlying the association between dietary calcium and prostate cancer risk is unclear. The vitamin D receptor (VDR) is a key regulator of calcium absorption. In the small intestine, VDR expression is regulated by the CDX-2 transcription factor, which binds a polymorphic site in the VDR gene promoter. We examined VDR Cdx2 genotype and calcium intake, assessed by a food frequency questionnaire, in 533 African-American prostate cancer cases (256 with advanced stage at diagnosis, 277 with localized stage) and 250 African-American controls who participated in the California Collaborative Prostate Cancer Study. We examined the effects of genotype, calcium intake, and diet-gene interactions by conditional logistic regression. Compared with men in the lowest quartile of calcium intake, men in the highest quartile had an approximately twofold increased risk of localized and advanced prostate cancer (odds ratio [OR] = 2.20, 95% confidence interval [CI] = 1.40, 3.46), with a significant dose-response. Poor absorbers of calcium (VDR Cdx2 GG genotype) had a significantly lower risk of advanced prostate cancer (OR = 0.41, 95% CI = 0.19, 0.90). The gene-calcium interaction was statistically significant (p = 0.03). Among men with calcium intake below the median (680 mg/day), carriers of the G allele had an approximately 50% decreased risk compared with men with the AA genotype. These findings suggest a link between prostate cancer risk and high intestinal absorption of calcium.

  9. Role of magnesium on the biomimetic deposition of calcium phosphate

    Science.gov (United States)

    Sarma, Bimal K.; Sarma, Bikash

    2016-10-01

    Biomimetic depositions of calcium phosphate (CaP) are carried out using simulated body fluid (SBF), calcifying solution and newly developed magnesium containing calcifying solution. Calcium phosphate has a rich phase diagram and is well known for its excellent biocompatibility and bioactivity. The most common phase is hydroxyapatite (HAp), an integral component of human bone and tooth, widely used in orthopedic and dental applications. In addition, calcium phosphate nanoparticles show promise for the targeted drug delivery. The doping of calcium phosphate by magnesium, zinc, strontium etc. can change the protein uptake by CaP nanocrystals. This work describes the role of magnesium on the nucleation and growth of CaP on Ti and its oxide substrates. X-ray diffraction studies confirm formation of HAp nanocrystals which closely resemble the structure of bone apatite when grown using SBF and calcifying solution. It has been observed that magnesium plays crucial role in the nucleation and growth of calcium phosphate. A low magnesium level enhances the crystallinity of HAp while higher magnesium content leads to the formation of amorphous calcium phosphate (ACP) phase. Interestingly, the deposition of ACP phase is rapid when magnesium ion concentration in the solution is 40% of calcium plus magnesium ions concentration. Moreover, high magnesium content alters the morphology of CaP films.

  10. Calcium Oxide Supported on Monoclinic Zirconia as a Highly Active Solid Base Catalyst

    NARCIS (Netherlands)

    Frey, A.M.; Haasterecht, van T.; Jong, de K.P.; Bitter, J.H.

    2013-01-01

    Calcium oxide supported on ZrO2 is a highly active catalyst for base-catalyzed reactions such as aldol-type reactions and transesterification reactions. The role of key parameters during preparation, that is, impregnation versus precipitation, heat treatment, and metal oxide loading on the basicity

  11. Physicochemical properties of calcium polycarbophil, a water-absorbing polymer.

    Science.gov (United States)

    Yamada, T; Kitayama, M; Yamazaki, M; Nagata, O; Tamaj, I; Tsuji, A

    1996-07-01

    The physicochemical properties of calcium polycarbophil were examined. Calcium polycarbophil was decalcified rapidly under acidic conditions, affording polycarbophil. Polycarbophil absorbed about 10 times its own weight of water under acidic conditions, but the swelling ratio markedly increased at above pH 4.0 and reached 70 times the initial weight under neutral conditions. The swelling of polycarbophil was not affected by non-ionic osmolarity, but was affected by ionic strength, showing a decrease with increase of ionic strength. Monovalent metal ions such as sodium and potassium ions in gastrointestinal fluid did not reduce the equilibrium swelling of polycarbophil, but divalent ions such as calcium and magnesium ions did. However, calcium ion only slightly reduced the equilibrium swelling under sodium-rich conditions. The viscosity (as an indicator of fluidity) of polycarbophil was larger than that of CMC-Na at every shear rate and polymer content examined.

  12. Calcium signaling in taste cells.

    Science.gov (United States)

    Medler, Kathryn F

    2015-09-01

    The sense of taste is a common ability shared by all organisms and is used to detect nutrients as well as potentially harmful compounds. Thus taste is critical to survival. Despite its importance, surprisingly little is known about the mechanisms generating and regulating responses to taste stimuli. All taste responses depend on calcium signals to generate appropriate responses which are relayed to the brain. Some taste cells have conventional synapses and rely on calcium influx through voltage-gated calcium channels. Other taste cells lack these synapses and depend on calcium release to formulate an output signal through a hemichannel. Beyond establishing these characteristics, few studies have focused on understanding how these calcium signals are formed. We identified multiple calcium clearance mechanisms that regulate calcium levels in taste cells as well as a calcium influx that contributes to maintaining appropriate calcium homeostasis in these cells. Multiple factors regulate the evoked taste signals with varying roles in different cell populations. Clearly, calcium signaling is a dynamic process in taste cells and is more complex than has previously been appreciated. This article is part of a Special Issue entitled: 13th European Symposium on Calcium.

  13. [Allergy of calcium phosphate cement material following skull reconstruction: a case report].

    Science.gov (United States)

    Mizowaki, Takashi; Miyake, Shigeru; Yoshimoto, Yuji; Matsuura, Yoshitaka; Akiyama, Sou

    2013-04-01

    The paste form of calcium phosphate cement is often used in skull reconstruction because of the biocompatibility and early handling of these cements. Although it had rarely been shown to produce a foreign body reaction, we encountered a patient who experienced an allergic reaction to calcium phosphate cements(Biopex®. A patch test was performed and a positive reaction to magnesium phosphate was obtained. Biopex® contains magnesium phosphate, so we diagnosed this case as allergic reaction. Pathological analysis revealed infiltration of plasmacytes in the bone flap around the calcium phosphate cement. The postoperative course was uneventful 3 years after surgery. Allergy to calcium phosphate cements is rare, but must be considered in differential diagnosis of its side effects.

  14. Calmodulin activation by calcium transients in the postsynaptic density of dendritic spines.

    Directory of Open Access Journals (Sweden)

    Daniel X Keller

    Full Text Available The entry of calcium into dendritic spines can trigger a sequence of biochemical reactions that begins with the activation of calmodulin (CaM and ends with long-term changes to synaptic strengths. The degree of activation of CaM can depend on highly local elevations in the concentration of calcium and the duration of transient increases in calcium concentration. Accurate measurement of these local changes in calcium is difficult because the spaces are so small and the numbers of molecules are so low. We have therefore developed a Monte Carlo model of intracellular calcium dynamics within the spine that included calcium binding proteins, calcium transporters and ion channels activated by voltage and glutamate binding. The model reproduced optical recordings using calcium indicator dyes and showed that without the dye the free intracellular calcium concentration transient was much higher than predicted from the fluorescent signal. Excitatory postsynaptic potentials induced large, long-lasting calcium gradients across the postsynaptic density, which activated CaM. When glutamate was released at the synapse 10 ms before an action potential occurred, simulating activity patterns that strengthen hippocampal synapses, the calcium gradient and activation of CaM in the postsynaptic density were much greater than when the order was reversed, a condition that decreases synaptic strengths, suggesting a possible mechanism underlying the induction of long-term changes in synaptic strength. The spatial and temporal mechanisms for selectivity in CaM activation demonstrated here could be used in other signaling pathways.

  15. Fruit Calcium: Transport and Physiology

    Directory of Open Access Journals (Sweden)

    Bradleigh eHocking

    2016-04-01

    Full Text Available Calcium has well-documented roles in plant signaling, water relations and cell wall interactions. Significant research into how calcium impacts these individual processes in various tissues has been carried out; however, the influence of calcium on fruit ripening has not been thoroughly explored. Here, we review the current state of knowledge on how calcium may impact fruit development, physical traits and disease susceptibility through facilitating developmental and stress response signaling, stabilizing membranes, influencing water relations and modifying cell wall properties through cross-linking of de-esterified pectins. We explore the involvement of calcium in hormone signaling integral to ripening and the physiological mechanisms behind common disorders that have been associated with fruit calcium deficiency (e.g. blossom end rot in tomatoes or bitter pit in apples. This review works towards an improved understanding of how the many roles of calcium interact to influence fruit ripening, and proposes future research directions to fill knowledge gaps. Specifically, we focus mostly on grapes and present a model that integrates existing knowledge around these various functions of calcium in fruit, which provides a basis for understanding the physiological impacts of sub-optimal calcium nutrition in grapes. Calcium accumulation and distribution in fruit is shown to be highly dependent on water delivery and cell wall interactions in the apoplasm. Localized calcium deficiencies observed in particular species or varieties can result from differences in xylem morphology, fruit water relations and pectin composition, and can cause leaky membranes, irregular cell wall softening, impaired hormonal signaling and aberrant fruit development. We propose that the role of apoplasmic calcium-pectin crosslinking, particularly in the xylem, is an understudied area that may have a key influence on fruit water relations. Furthermore, we believe that improved

  16. The Formation Process of Silico-Ferrite of Calcium (SFC) from Binary Calcium Ferrite

    Science.gov (United States)

    Ding, Xiang; Guo, Xing-Min

    2014-08-01

    Silico-ferrite of calcium (SFC) is a significant equilibrium crystalline phase in the Fe2O3-CaO-SiO2 (FCS) ternary system and a key bonding phase in the sintering process of fine iron ore. In this work, the formation process of SFC from binary calcium ferrite has been determined by X-ray diffraction and field-emission scanning electron microscopy. Experiments were carried out under air at 1473 K (1200 °C) by adding SiO2 and Fe2O3 into CaO·Fe2O3 (CF). It was found that the formation of SFC is dominated by solid-state reactions in the FCS ternary system, in which Fe2O3 reacts with CaO·Fe2O3 to form the binary calcium ferrite phase. The chemical composition of binary calcium ferrite is Ca2.5Fe15.5O25 and approximately Ca2Fe12O20 (CaO·3Fe2O3). Then Si4+ and Ca2+ ions take the place of Fe3+ ion in preference located on the octahedral layers which belongs to (0 0 18) plane of binary calcium ferrite. The crystal structure of binary calcium ferrite gradually transforms from orthorhombic to triclinic, and the grain is refined with the addition of silica due to the smaller radius of Si4+ ion. A solid solution SFC forms completely when the content of SiO2 reaches approximately 3.37 wt pct at 1473 K (1200 °C).

  17. Effect of Indole Butyric Acid on the Transportation of Stored Calcium in Malus hupehensis Rhed. Seedling

    Institute of Scientific and Technical Information of China (English)

    LI Jia; YANG Hong-qiang; YAN Tian-li; SHU Huai-rui

    2006-01-01

    Calcium (Ca) plays an important role in the metabolism of higher plants. Recently, research on Ca2+ in plants has been focused especially at the cellular and molecular levels. Uptake, transport, and distribution are also very important for Ca to accomplish its function at the whole-plant level. In this experiment, one-year-old apple seedlings (M. hupehensis Rehd.) were investigated to determine the distribution of stored Ca, the different forms of Ca, and Ca2+-ATPase activity after treatment with indole butyric acid (IBA). The results showed that the total Ca measured in mature leaves and Ca2+-ATPase activity in tender leaves were higher compared with those in the control (CK). Calcium nitrate and calcium chloride (ALe-Ca) and calcium phosphate and calcium carbonate (HAC-Ca) decreased in both mature leaves and shoots,whereas water-soluble calcium (H2O-Ca), calcium pectate (NaCl-Ca), and calcium oxalate (HCl-Ca) increased. The percentage of active calcium, calcium pectate, and water-soluble calcium increased, whereas the percentage of calcium phosphate and calcium carbonate decreased. When treated with IBA, calcium fractions and percentage of the different forms of Ca was enhanced in 40 part per million (ppm) IBA compared with 20 ppm IBA and water. The results indicated that IBA increased the percentage of both active calcium (NaCl-Ca and H2O-Ca) in tender shoots and boosted the transportation of stored Ca in plants. IBA promoted Ca2+-ATPase activity and Ca2+ uptake in tender shoots of M. hupehensis. It can improve the total Ca contents and the relative percentage of Ca.

  18. DISTILLATION OF CALCIUM

    Science.gov (United States)

    Barton, J.

    1954-07-27

    This invention relates to an improvement in the process for the purification of caicium or magnesium containing an alkali metal as impurity, which comprises distiiling a batch of the mixture in two stages, the first stage distillation being carried out in the presence of an inert gas at an absolute pressure substantially greater than the vapor pressure of calcium or maguesium at the temperature of distillation, but less than the vaper pressure at that temperature of the alkali metal impurity so that only the alkali metal is vaporized and condensed on a condensing surface. A second stage distilso that substantially only the calcium or magnesium distills under its own vapor pressure only and condenses in solid form on a lower condensing surface.

  19. C2-domain containing calcium sensors in neuroendocrine secretion.

    Science.gov (United States)

    Pinheiro, Paulo S; Houy, Sébastien; Sørensen, Jakob B

    2016-12-01

    The molecular mechanisms for calcium-triggered membrane fusion have long been sought for, and detailed models now exist that account for at least some of the functions of the many proteins involved in the process. Key players in the fusion reaction are a group of proteins that, upon binding to calcium, trigger the merger of cargo-filled vesicles with the plasma membrane. Low-affinity, fast-kinetics calcium sensors of the synaptotagmin family - especially synaptotagmin-1 and synaptotagmin-2 - are the main calcium sensors for fast exocytosis triggering in many cell types. Their functions extend beyond fusion triggering itself, having been implicated in the calcium-dependent vesicle recruitment during activity, docking of vesicles to the plasma membrane and priming, and even in post-fusion steps, such as fusion pore expansion and endocytosis. Furthermore, synaptotagmin diversity imparts distinct properties to the release process itself. Other calcium-sensing proteins such as Munc13s and protein kinase C play important, but more indirect roles in calcium-triggered exocytosis. Because of their higher affinity, but intrinsic slower kinetics, they operate on longer temporal and spatial scales to organize assembly of the release machinery. Finally, the high-affinity synaptotagmin-7 and Doc2 (Double C2-domain) proteins are able to trigger membrane fusion in vitro, but cellular measurements in different systems show that they may participate in either fusion or vesicle priming. Here, we summarize the properties and possible interplay of (some of) the major C2-domain containing calcium sensors in calcium-triggered exocytosis. This article is part of a mini review series: "Synaptic Function and Dysfunction in Brain Diseases".

  20. Association of serum calcium levels with infarct size in acute ischemic stroke: Observations from Northeast India

    Directory of Open Access Journals (Sweden)

    Meghna Borah

    2016-01-01

    Full Text Available Background: Calcium is known to be major mediator in ischemic neuronal cell death. Recent studies have shown that elevated serum calcium levels at admission in patients with stroke have been associated with less severe clinical deficits and with better outcomes. Aim: The aim of this to determine the correlation between serum calcium (total, corrected, and ionized and infarct size (IS in patients with acute ischemic stroke. Materials and Methods: Data were collected from 61 patients presenting with acute ischemic stroke from May 2015 to April 2016 at a tertiary care institute in Northeast India. Only patients aged ≥40 years and diagnosed as having acute ischemic cerebrovascular stroke with clinical examination and confirmed by a computed tomography scan were included in the study. Serum calcium levels (total, albumin corrected, and ionized were collapsed into quartiles, and these quartile versions were used for calculating correlation. Pearson's correlation coefficient was used for comparing calcium levels with IS. Results: Total calcium, albumin-corrected calcium, and ionized calcium had a statistically significant negative correlation with IS with r = −0.578, −0.5396, and −0.5335, respectively. Total and ionized calcium showed a significant negative correlation with IS across all four quartiles. Albumin-corrected calcium levels showed a significant negative correlation with IS only across the lowest and highest quartiles. Conclusion: The findings in our study suggest that serum calcium can be used as a prognostic indicator in ischemic stroke as its levels directly correlates with the IS.

  1. Models of calcium signalling

    CERN Document Server

    Dupont, Geneviève; Kirk, Vivien; Sneyd, James

    2016-01-01

    This book discusses the ways in which mathematical, computational, and modelling methods can be used to help understand the dynamics of intracellular calcium. The concentration of free intracellular calcium is vital for controlling a wide range of cellular processes, and is thus of great physiological importance. However, because of the complex ways in which the calcium concentration varies, it is also of great mathematical interest.This book presents the general modelling theory as well as a large number of specific case examples, to show how mathematical modelling can interact with experimental approaches, in an interdisciplinary and multifaceted approach to the study of an important physiological control mechanism. Geneviève Dupont is FNRS Research Director at the Unit of Theoretical Chronobiology of the Université Libre de Bruxelles;Martin Falcke is head of the Mathematical Cell Physiology group at the Max Delbrück Center for Molecular Medicine, Berlin;Vivien Kirk is an Associate Professor in the Depar...

  2. Calcium signaling mediates cold sensing in insect tissues.

    Science.gov (United States)

    Teets, Nicholas M; Yi, Shu-Xia; Lee, Richard E; Denlinger, David L

    2013-05-28

    The ability to rapidly respond to changes in temperature is a critical adaptation for insects and other ectotherms living in thermally variable environments. In a process called rapid cold hardening (RCH), insects significantly enhance cold tolerance following brief (i.e., minutes to hours) exposure to nonlethal chilling. Although the ecological relevance of RCH is well-established, the underlying physiological mechanisms that trigger RCH are poorly understood. RCH can be elicited in isolated tissues ex vivo, suggesting cold-sensing and downstream hardening pathways are governed by brain-independent signaling mechanisms. We previously provided preliminary evidence that calcium is involved in RCH, and here we firmly establish that calcium signaling mediates cold sensing in insect tissues. In tracheal cells of the freeze-tolerant goldenrod gall fly, Eurosta solidaginis, chilling to 0 °C evoked a 40% increase in intracellular calcium concentration as determined by live-cell confocal imaging. Downstream of calcium entry, RCH conditions significantly increased the activity of calcium/calmodulin-dependent protein kinase II (CaMKII) while reducing phosphorylation of the inhibitory Thr306 residue. Pharmacological inhibitors of calcium entry, calmodulin activation, and CaMKII activity all prevented ex vivo RCH in midgut and salivary gland tissues, indicating that calcium signaling is required for RCH to occur. Similar results were obtained for a freeze-intolerant species, adults of the flesh fly, Sarcophaga bullata, suggesting that calcium-mediated cold sensing is a general feature of insects. Our results imply that insect tissues use calcium signaling to instantly detect decreases in temperature and trigger downstream cold-hardening mechanisms.

  3. Measurement of Cross Sections for the 10B(n,α)'7Li Reaction at 4.0 and 5.0 MeV Using an Asymmetrical Twin Gridded Ionization Chamber

    Institute of Scientific and Technical Information of China (English)

    ZHANG Guo-Hui; LIU Xiang; LIU Jia-Ming; XUE Zhi-Hua; WU Hao; CHEN Jin-Xiang

    2011-01-01

    @@ Cross sections of the 10B(n, α) 7Li reaction (including the total, the "leaking" alpha, forward alpha and backward alpha parts) at En=4.0 and 5.OMcV were measured using an asymmetrical twin gridded ionization chamber and two back-to-back 10B samples.Measurements were performed at the 4.5MV Van de Graaff accelerator of Peking University.Monoenergetic neutrons were produced through the 2H(d, n)3 He reaction with a deuterium gas target.Absolute neutron flux was determined by a 238 U sample set inside the gridded ionization chamber and a BF3 long counter was employed as a neutron flux monitor and for normalization.The present results are compared with previous measurements and evaluations.

  4. Calcium signalling and calcium channels: evolution and general principles.

    Science.gov (United States)

    Verkhratsky, Alexei; Parpura, Vladimir

    2014-09-15

    Calcium as a divalent cation was selected early in evolution as a signaling molecule to be used by both prokaryotes and eukaryotes. Its low cytosolic concentration likely reflects the initial concentration of this ion in the primordial soup/ocean as unicellular organisms were formed. As the concentration of calcium in the ocean subsequently increased, so did the diversity of homeostatic molecules handling calcium. This includes the plasma membrane channels that allowed the calcium entry, as well as extrusion mechanisms, i.e., exchangers and pumps. Further diversification occurred with the evolution of intracellular organelles, in particular the endoplasmic reticulum and mitochondria, which also contain channels, exchanger(s) and pumps to handle the homeostasis of calcium ions. Calcium signalling system, based around coordinated interactions of the above molecular entities, can be activated by the opening of voltage-gated channels, neurotransmitters, second messengers and/or mechanical stimulation, and as such is all-pervading pathway in physiology and pathophysiology of organisms.

  5. Elemental calcium intake associated with calcium acetate/calcium carbonate in the treatment of hyperphosphatemia

    Science.gov (United States)

    Wilson, Rosamund J; Copley, J Brian

    2017-01-01

    Background Calcium-based and non-calcium-based phosphate binders have similar efficacy in the treatment of hyperphosphatemia; however, calcium-based binders may be associated with hypercalcemia, vascular calcification, and adynamic bone disease. Scope A post hoc analysis was carried out of data from a 16-week, Phase IV study of patients with end-stage renal disease (ESRD) who switched to lanthanum carbonate monotherapy from baseline calcium acetate/calcium carbonate monotherapy. Of the intent-to-treat population (N=2520), 752 patients with recorded dose data for calcium acetate (n=551)/calcium carbonate (n=201) at baseline and lanthanum carbonate at week 16 were studied. Elemental calcium intake, serum phosphate, corrected serum calcium, and serum intact parathyroid hormone levels were analyzed. Findings Of the 551 patients with calcium acetate dose data, 271 (49.2%) had an elemental calcium intake of at least 1.5 g/day at baseline, and 142 (25.8%) had an intake of at least 2.0 g/day. Mean (95% confidence interval [CI]) serum phosphate levels were 6.1 (5.89, 6.21) mg/dL at baseline and 6.2 (6.04, 6.38) mg/dL at 16 weeks; mean (95% CI) corrected serum calcium levels were 9.3 (9.16, 9.44) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Of the 201 patients with calcium carbonate dose data, 117 (58.2%) had an elemental calcium intake of at least 1.5 g/day, and 76 (37.8%) had an intake of at least 2.0 g/day. Mean (95% CI) serum phosphate levels were 5.8 (5.52, 6.06) mg/dL at baseline and 5.8 (5.53, 6.05) mg/dL at week 16; mean (95% CI) corrected serum calcium levels were 9.7 (9.15, 10.25) mg/dL and 9.2 (9.06, 9.34) mg/dL, respectively. Conclusion Calcium acetate/calcium carbonate phosphate binders, taken to control serum phosphate levels, may result in high levels of elemental calcium intake. This may lead to complications related to calcium balance. PMID:28182142

  6. Relation of urinary calcium and magnesium excretion to blood pressure

    DEFF Research Database (Denmark)

    Kesteloot, Hugo; Tzoulaki, Ioanna; Brown, Ian J

    2011-01-01

    of calcium and magnesium in 2 cross-sectional studies. The International Study of Macro- and Micro-Nutrients and Blood Pressure (INTERMAP) comprised 4,679 persons aged 40-59 years from 17 population samples in China, Japan, the United Kingdom, and the United States, and the International Cooperative Study...

  7. Coexistance of C40 and C54 TiSi2 during the solid state reaction of Ti/Mo/Si system

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effect of a 0.9 nm Mo interlayer at the interface of Ti film depositedon a Si substrate on phase formation of TiSi2 during annealing has been studiedby using transmission electron micro-diffraction technique. When Ti/Mo/Si was an-nealed at low temperature as 550℃ for 30 min in Ar ambient, a metastable phase, i.e.,hexagonal C40 TiSi2, and the equilibrium phase, i.e., orthorhombic C54 TiSi2, wereboth detected. The experimental patterns of the C40 and C54 compare well with thesimulated ones.

  8. Scattering lengths of calcium and barium isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Dammalapati, U.; Willmann, L.; Knoop, S. [Kernfysisch Versneller Instituut (KVI), University of Groningen, Zernikelaan 25, 9747 AA Groningen (Netherlands); LaserLaB Vrije Universiteit, De Boelelaan 1081, 1081 HV Amsterdam (Netherlands)

    2011-11-15

    We have calculated the s-wave scattering length of all the even isotopes of calcium (Ca) and barium (Ba) in order to investigate the prospect of Bose-Einstein condensation (BEC). For Ca we have used an accurate molecular potential based on detailed spectroscopic data. Our calculations show that Ca does not provide other isotopes alternative to the recently Bose condensed {sup 40}Ca that suffers strong losses because of a very large scattering length. For Ba we show by using a model potential that the even isotopes cover a broad range of scattering lengths, opening the possibility of BEC for at least one of the isotopes.

  9. Monitoring of Adverse Drug Reactions Associated with Antihypertensive Medicines at a University Teaching Hospital in New Delhi

    Directory of Open Access Journals (Sweden)

    Fowad Khurshid

    2012-09-01

    Full Text Available Aim To monitor the adverse drug reactions (ADRs caused by antihypertensive medicines prescribed in a university teaching hospital.Methods:he present work was an open, non-comparative, observational study conducted on hypertensive patients attending the Medicine OPD of Majeedia Hospital, Jamia Hamdard, New Delhi, India by conducting patient interviews and recording the data on ADR monitoring form as recommended by Central Drugs Standard Control Organization (CDSCO, Government of India.Results:A total of 21 adverse drug reactions were observed in 192 hypertensive patients. Incidence of adverse drug reactions was found to be higher in patients more than 40 years in age, and females experienced more ADRs (n = 14, 7.29 % than males, 7 (3.64 %. Combination therapy was associated with more number of adverse drug reactions (66.7 % as against monotherapy (33.3 %. Calcium channel blockers were found to be the most frequently associated drugs with adverse drug reactions (n = 7, followed by diuretics (n = 5, and beta- blockers (n = 4. Among individual drugs, amlodipine was found to be the commonest drug associated with adverse drug reactions (n = 7, followed by torasemide (n = 3. Adverse drug reactions associated with central nervous system were found to be the most frequent (42.8 % followed by musculo-skeletal complaints (23.8 % and gastro-intestinal disorders (14.3 %. Conclusions:The present pharmacovigilance study represents the adverse drug reaction profile of the antihypertensive medicines prescribed in our university teaching hospital. The above findings would be useful for physicians in rational prescribing. Calcium channel blockers were found to be the most frequently associated drugs with adverse drug reactions.

  10. Effect of substrate nature on the electrochemical deposition of calcium-deficient hydroxyapatites

    Science.gov (United States)

    Gualdrón-Reyes, A. F.; Domínguez-Vélez, V.; Morales-Morales, J. A.; Cabanzo, R.; Meléndez, A. M.

    2017-01-01

    Calcium phosphates were obtained by reducing nitrate ions to produce hydroxide ions on TiO2/stainless steel and TiO2/titanium electrodes. TiO2 coatings on metallic substrates were prepared by sol-gel dip-coating method. The morphology of deposits was observed by FESEM. Chemical nature of calcium phosphate deposits was identified by Raman micro-spectroscopy and FESEM/EDS microanalysis. Electrochemical behavior of nitrate and nitrite reduction on stainless steel and titanium electrodes was studied by linear sweep voltammetry. In addition, voltammetric study of the calcium phosphate electrodeposition on both electrodes was performed. From these measurements was selected the potential to form a calcium phosphate. A catalytic current associated to nitrate reduction reaction was obtained for stainless steel electrode, leading to significant deposition of calcium phosphate. Ca/P ratio for both substrates was less than 1.67. The formation of calcium deficient hydroxyapatite was confirmed by Raman spectroscopy.

  11. Effect of calcium source on structure and properties of sol-gel derived bioactive glasses.

    Science.gov (United States)

    Yu, Bobo; Turdean-Ionescu, Claudia A; Martin, Richard A; Newport, Robert J; Hanna, John V; Smith, Mark E; Jones, Julian R

    2012-12-18

    The aim was to determine the most effective calcium precursor for synthesis of sol-gel hybrids and for improving homogeneity of sol-gel bioactive glasses. Sol-gel derived bioactive calcium silicate glasses are one of the most promising materials for bone regeneration. Inorganic/organic hybrid materials, which are synthesized by incorporating a polymer into the sol-gel process, have also recently been produced to improve toughness. Calcium nitrate is conventionally used as the calcium source, but it has several disadvantages. Calcium nitrate causes inhomogeneity by forming calcium-rich regions, and it requires high temperature treatment (>400 °C) for calcium to be incorporated into the silicate network. Nitrates are also toxic and need to be burnt off. Calcium nitrate therefore cannot be used in the synthesis of hybrids as the highest temperature used in the process is typically 40-60 °C. Therefore, a different precursor is needed that can incorporate calcium into the silica network and enhance the homogeneity of the glasses at low (room) temperature. In this work, calcium methoxyethoxide (CME) was used to synthesize sol-gel bioactive glasses with a range of final processing temperatures from 60 to 800 °C. Comparison is made between the use of CME and calcium chloride and calcium nitrate. Using advanced probe techniques, the temperature at which Ca is incorporated into the network was identified for 70S30C (70 mol % SiO(2), 30 mol % CaO) for each of the calcium precursors. When CaCl(2) was used, the Ca did not seem to enter the network at any of the temperatures used. In contrast, Ca from CME entered the silica network at room temperature, as confirmed by X-ray diffraction, (29)Si magic angle spinning nuclear magnetic resonance spectroscopy, and dissolution studies. CME should be used in preference to calcium salts for hybrid synthesis and may improve homogeneity of sol-gel glasses.

  12. Chitosan Derivatives/Calcium Carbonate Composite Capsules Prepared by the Layer-by-Layer Deposition Method

    Directory of Open Access Journals (Sweden)

    Takashi Sasaki

    2008-01-01

    Full Text Available Core/shell capsules composed of calcium carbonate whisker core (rod-like shape and chitosan/chitosansulfate shell were prepared by the layer-by-layer deposition technique. Two chitosan samples of different molecular weights (Mw=9.7×104 and 1.09×106g·mol-1 were used as original materials. Hollow capsules were also obtained by dissolution of the core in hydrochloric acid. Electron microscopy revealed that the surface of the shell is rather ragged associated with some agglomerates. The shell thickness l obeys a linear relation with respect to the number of deposited layers m as l=md+a(a>0. The values of d (thickness per layer were 4.0 and 1.0 nm for the higher and lower Mw chitosan materials, respectively, both of which are greater than the thickness of the monolayer. The results suggest that the feature of the deposition does not obey an ideal homogeneous monolayer-by-monolayer deposition mechanism. Shell crosslinked capsules were also prepared via photodimerization reaction of cinnamoyl groups after a deposition of cinnamoyl chitosan to the calcium carbonate whisker core. The degree of crosslink was not enough to stabilize the shell structure, and hollow capsule was not obtained.

  13. Calcium – how and why?

    Indian Academy of Sciences (India)

    J K Jaiswal

    2001-09-01

    Calcium is among the most commonly used ions, in a multitude of biological functions, so much so that it is impossible to imagine life without calcium. In this article I have attempted to address the question as to how calcium has achieved this status with a brief mention of the history of calcium research in biology. It appears that during the origin and early evolution of life the Ca2+ ion was given a unique opportunity to be used in several biological processes because of its unusual physical and chemical properties.

  14. Calcium Phosphate Biomaterials: An Update

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Current calcium phosphate (CaP) biomaterials for bone repair, substitution, augmentation and regeneration include hydroxyapatite ( HA ) from synthetic or biologic origin, beta-tricalcium phosphate ( β-TCP ) , biphasic calcium phosphate (BCP), and are available as granules, porous blocks, components of composites (CaP/polymer) cements, and as coatings on orthopedic and dental implants. Experimental calcium phosphate biomaterials include CO3- and F-substituted apatites, Mg-and Zn-substituted β-TCP, calcium phosphate glasses. This paper is a brief review of the different types of CaP biomaterials and their properties such as bioactivity, osteoconductivity, osteoinductivity.

  15. Calcium measurement methods

    Directory of Open Access Journals (Sweden)

    CarloAlberto Redi

    2010-09-01

    Full Text Available Rightly stressed by prof. Wolfgang Walz in the Preface to the series Neuromethods series, the “careful application of methods is probably the most important step in the process of scientific inquiry”. Thus, I strongly suggest to all those interested in calcium signaling and especially to the new-comers in the hot topic of neuroscience (which has so much space even in science-society debate for its implications in legal issues and in the judge-decision process to take profit from this so well edited book. I am saying this since prof. Verkhratsky and prof. Petersen......

  16. Extracellular calcium sensing and extracellular calcium signaling

    Science.gov (United States)

    Brown, E. M.; MacLeod, R. J.; O'Malley, B. W. (Principal Investigator)

    2001-01-01

    , localized changes in Ca(o)(2+) within the ECF can originate from several mechanisms, including fluxes of calcium ions into or out of cellular or extracellular stores or across epithelium that absorb or secrete Ca(2+). In any event, the CaR and other receptors/sensors for Ca(o)(2+) and probably for other extracellular ions represent versatile regulators of numerous cellular functions and may serve as important therapeutic targets.

  17. Semi-Discrete Systems and Intracellular Calcium Dynamics

    Energy Technology Data Exchange (ETDEWEB)

    Pearson, J.; Dawson, S.P.; Mitkov, I.

    1998-10-24

    Intracellular calcium is sequestered in closed membranes such as the sarcoplasmic or endoplasmic reticula and released at discretely distributed protein/receptor channels. The release kinetics can result in the propagation of waves of elevated calcium concentration. The main physical processes are reactions at the release sites and diffusion between the sites. The theory of chemical wave propagation in reaction-diffusion systems is in large part devoted to the study of systems in which there are no extrinsic inhomogeneities. The discrete distribution of the release sites plays a key role in determining the nature of the propagating wave. The authors analyze some simple reaction-diffusion models in order to elucidate the role of discreteness for chemical wave propagation.

  18. Multilevel complexity of calcium signaling:Modeling angiogenesis

    Institute of Scientific and Technical Information of China (English)

    Luca; Munaron; Marco; Scianna

    2012-01-01

    Intracellular calcium signaling is a universal,evolutionary conserved and versatile regulator of cell biochemistry.The complexity of calcium signaling and related cell machinery can be investigated by the use of experimental strategies,as well as by computational approaches.Vascular endothelium is a fascinating model to study the specific properties and roles of calcium signals at multiple biological levels.During the past 20 years,live cell imaging,patch clamp and other techniques have allowed us to detect and interfere with calcium signaling in endothelial cells(ECs),providing a huge amount of information on the regulation of vascularization(angiogenesis) in normal and tumoral tissues.These data range from the spatiotemporal dynamics of calcium within different cell microcompartments to those in entire multicellular and organized EC networks.Beside experimental strategies,in silico endothelial models,specifically designed for simulating calcium signaling,are contributing to our knowledge of vascular physiol-ogy and pathology.They help to investigate and predict the quantitative features of proangiogenic events moving through subcellular,cellular and supracellular levels.This review focuses on some recent developments of computational approaches for proangiogenic endothelial calcium signaling.In particular,we discuss the creation of hybrid simulation environments,which combine and integrate discrete Cellular Potts Models.They are able to capture the phenomenological mechanisms of cell morphological reorganization,migration,and intercellular adhesion,with single-cell spatiotemporal models,based on reaction-diffusion equations that describe the agonist-induced intracellular calcium events.

  19. Optimization of calcium phosphate fine ceramic powders preparation

    Science.gov (United States)

    Sezanova, K.; Tepavitcharova, S.; Rabadjieva, D.; Gergulova, R.; Ilieva, R.

    2013-12-01

    The effect of biomimetic synthesis method, reaction medium and further precursor treatments on the chemical and phase composition, crystal size and morphology of calcium phosphates was examined. Nanosized calcium phosphate precursors were biomimetically precipitated by the method of continuous precipitation in three types of reaction media at pH 8: (i) SBF as an inorganic electrolyte system; (ii) organic (glycerine) modified SBF (volume ratio of 1:1); (iii) polymer (10 g/l xanthan gum or 10 g/l guar gum) modified SBF (volume ratio of 1:1). After maturation (24 h) the samples were lyophilized, calcinated at 300°C for 3 hours, and washed with water, followed by new gelation, lyophilization and step-wise (200, 400, 600, 800, and 1000°C, each for 3 hours) sintering. The reaction medium influenced the chemical composition and particle size but not the morphology of the calcium phosphate powders. In all studied cases bi-phase calcium phosphate fine powders with well-shaped spherical grains, consisting of β-tricalcium phosphate (β-TCP) and hydroxyapatite (HA) with a Ca/P ratio of 1.3 - 1.6 were obtained. The SBF modifiers decreased the particle size of the product in the sequence guar gum ˜ xanthan gum < glycerin < SBF medium.

  20. Desulfurization of fuels with calcium-based sorbents

    Energy Technology Data Exchange (ETDEWEB)

    Abbasian, J.; Rehmat, A.; Leppin, D.; Banerjee, D.D. (Institute of Gas Technology, Chicago, IL (USA))

    1990-04-01

    Calcium-based sorbents, such as limestone and dolomite, are viable candidates for sulphur-capturing agents in an in-situ coal gasification/desulfurization process. The effect of limestone addition on the hydrodynamics of a fluidized-bed gasifier, desulfurization of the product gas, and stabilization of the solid wastes have been studied. The hydrodynamic characteristics of coal char/limestone mixtures, such as mixing and fines retention, have been studied in a 0.2 m diameter fluidization column. Kinetic data pertaining to the reaction between calcium oxide (which is obtained by calcination of limestone and dolomite) and hydrogen sulfide have been obtained by a gravimetric technique in the temperature range of 650 to 1050{degree}C. Kinetic data relating to the reaction between calcium sulfide (which is obtained by sulfidation of calcium-based sorbents) and oxygen have been obtained in the temperature range of 800 to 1050{degree}C and in the pressure range of 2 to 3.1 MPa. The operating conditions for these reactions have been chosen to be within the application range of a commercial coal gasification process that is accompanied by in situ desulfurization. 14 refs., 8 figs., 7 tabs.

  1. Improved preparation and cooperative calcium contraction of glycerinated Vorticella.

    Science.gov (United States)

    Asai, H; Ochiai, T; Fukui, K; Watanabe, M; Kano, F

    1978-03-01

    An improved method for the preparation of glycerinated Vorticella convallaria was investigated. The pretreatment of living vorticellas with a medium containing 0.1% saponins and subsequent treatment with an extraction medium containing 35% glycerol at about 0 degrees C was satisfactory. The equilibrium average length of contractile stalks of glycerinated vorticellas was measured at various free calcium concentrations in the reaction medium. It was found that the contractile element in the spasmoneme of the stalk is contracted by a cooperative interaction involving at least two calcium ions.

  2. Synthesis, structure, and frequency-doubling effect of calcium cyanurate.

    Science.gov (United States)

    Kalmutzki, Markus; Ströbele, Markus; Wackenhut, Frank; Meixner, Alfred J; Meyer, H-Jürgen

    2014-12-15

    Calcium cyanurate is synthesized by reacting calcium chloride with potassium cyanate following a solid-state reaction. The formation of the new compound Ca3(O3C3N3)2 (CCY), which occurs by the cyclotrimerization of cyanate ions, was examined thermoanalytically and the crystal structure was determined by single-crystal structure analysis. The structure of CCY is closely related to the structure of the well-known oxoborate β-BaB2O4 (BBO). Second harmonic generation (SHG) measurements on crystal powders show a higher SHG efficiency for CCY than for BBO by about one order of magnitude.

  3. Phase composition, mechanical performance and in vitro biocompatibility of hydraulic setting calcium magnesium phosphate cement.

    Science.gov (United States)

    Klammert, Uwe; Reuther, Tobias; Blank, Melanie; Reske, Isabelle; Barralet, Jake E; Grover, Liam M; Kübler, Alexander C; Gbureck, Uwe

    2010-04-01

    Brushite (CaHPO(4) x 2H(2)O)-forming calcium phosphate cements are of great interest as bone replacement materials because they are resorbable in physiological conditions. However, their short setting times and low mechanical strengths limit broad clinical application. In this study, we showed that a significant improvement of these properties of brushite cement could be achieved by the use of magnesium-substituted beta-tricalcium phosphate with the general formula Mg(x)Ca((3-x))((PO(4))(2) with 0 cement reactants. The incorporation of magnesium ions increased the setting times of cements from 2 min for a magnesium-free matrix to 8-11 min for Mg(2.25)Ca(0.75)(PO(4))(2) as reactant. At the same time, the compressive strength of set cements was doubled from 19 MPa to more than 40 MPa after 24h wet storage. Magnesium ions were not only retarding the setting reaction to brushite but were also forming newberyite (MgHPO(4) x 3H(2)O) as a second setting product. The biocompatibility of the material was investigated in vitro using the osteoblast-like cell line MC3T3-E1. A considerable increase of cell proliferation and expression of alkaline phosphatase, indicating an osteoblastic differentiation, could be noticed. Scanning electron microscopy analysis revealed an obvious cell growth on the surface of the scaffolds. Analysis of the culture medium showed minor alterations of pH value within the physiological range. The concentrations of free calcium, magnesium and phosphate ions were altered markedly due to the chemical solubility of the scaffolds. We conclude that the calcium magnesium phosphate (newberyite) cements have a promising potential for their use as bone replacement material since they provide a suitable biocompatibility, an extended workability and improved mechanical performance compared with brushite cements.

  4. Vitamin D, Calcium, and Bone Health

    Science.gov (United States)

    ... in Balance › Vitamin D, Calcium, and Bone Health Vitamin D, Calcium, and Bone Health March 2012 Download ... also helps keep your bones strong. Why are vitamin D and calcium important to bone health? Vitamin ...

  5. Calcium, vitamin D, and your bones

    Science.gov (United States)

    ... page: //medlineplus.gov/ency/patientinstructions/000490.htm Calcium, vitamin D, and your bones To use the sharing ... and maintain strong bones. How Much Calcium and Vitamin D do I Need? Amounts of calcium are ...

  6. Calcium and magnesium concentrations in mature human milk: influence of calcium intake, age and socioeconomic level.

    Science.gov (United States)

    Vítolo, M R; Valente Soares, L M; Carvalho, E B; Cardoso, C B

    2004-03-01

    Concentrations of calcium and magnesium were measured in mature milk, collected between 30 and 90 days after childbirth, from a group of 90 mothers between 14 and 39 years of age, exclusively breastfeeding. The group was divided into three sub-groups: low socioeconomic-level adolescents (LSAd), low socioeconomic-level adults (LSA), and high socioeconomic-level adults (HSA). Each mother's nutritional status was determined using the body-mass index (BMI) and her eating habits, obtained on the basis of a 24-h dietary recall. Adolescent and adult mothers in the low socioeconomic-level group had lower average calcium intake (LSAd = 618.4 +/- 555.2 mg and LSA = 679.4 +/- 411.4 mg) than adult mothers in the higher socioeconomic-level group (853.6 +/- 415.5 mg). The average concentration of calcium in the adolescent mothers' milk (LSAd) was significantly lower (5.30 +/- 1.42 mmol Ca/L, P = 0.01) than that of the two adult groups (LSA = 5.82 +/- 1.55 mmol Ca/L and HSA = 6.40 mmol Ca/L). The average magnesium concentrations for all groups did not show significant differences (LSAd = 1.06 +/- 0.18, LSA = 1.16 +/- 0.23 and HSA = 1.11 +/- 0.23 mmol Mg/L, for P= 0.16). These results indicate that magnesium concentrations in mature human milk do not seem to depend on maternal nutritional status. The condition of adolescence, however, associated with lower calcium intake by the mother, resulted in lower calcium concentrations in the milk secreted when compared to that of adult mothers.

  7. Vitamin D and Intestinal Calcium Absorption

    OpenAIRE

    Christakos, Sylvia; Dhawan, Puneet; Porta, Angela; Mady, Leila J.; Seth, Tanya

    2011-01-01

    The principal function of vitamin D in calcium homeostasis is to increase calcium absorption from the intestine. Calcium is absorbed by both an active transcellular pathway, which is energy dependent, and by a passive paracellular pathway through tight junctions. 1,25Dihydroxyvitamin D3 (1,25(OH)2D3) the hormonally active form of vitamin D, through its genomic actions, is the major stimulator of active intestinal calcium absorption which involves calcium influx, translocation of calcium throu...

  8. Mammary-Specific Ablation of the Calcium-Sensing Receptor During Lactation Alters Maternal Calcium Metabolism, Milk Calcium Transport, and Neonatal Calcium Accrual

    OpenAIRE

    Mamillapalli, Ramanaiah; VanHouten, Joshua; Dann, Pamela; Bikle, Daniel; Chang, Wenhan; Brown, Edward; Wysolmerski, John

    2013-01-01

    To meet the demands for milk calcium, the lactating mother adjusts systemic calcium and bone metabolism by increasing dietary calcium intake, increasing bone resorption, and reducing renal calcium excretion. As part of this adaptation, the lactating mammary gland secretes PTHrP into the maternal circulation to increase bone turnover and mobilize skeletal calcium stores. Previous data have suggested that, during lactation, the breast relies on the calcium-sensing receptor (CaSR) to coordinate ...

  9. Reaction Graph

    Institute of Scientific and Technical Information of China (English)

    傅育熙

    1998-01-01

    The paper proposes reaction graphs as graphical representations of computational objects.A reaction graph is a directed graph with all its arrows and some of its nodes labeled.Computations are modled by graph rewriting of a simple nature.The basic rewriting rules embody the essence of both the communications among processes and cut-eliminations in proofs.Calculi of graphs are ideentified to give a formal and algebraic account of reaction graphs in the spirit of process algebra.With the help of the calculi,it is demonstrated that reaction graphs capture many interesting aspects of computations.

  10. Analytical models of calcium binding in a calcium channel

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jinn-Liang [Department of Applied Mathematics, National Hsinchu University of Education, Hsinchu 300, Taiwan (China); Eisenberg, Bob [Department of Molecular Biophysics and Physiology, Rush University, Chicago, Illinois 60612 (United States)

    2014-08-21

    The anomalous mole fraction effect of L-type calcium channels is analyzed using a Fermi like distribution with the experimental data of Almers and McCleskey [J. Physiol. 353, 585 (1984)] and the atomic resolution model of Lipkind and Fozzard [Biochemistry 40, 6786 (2001)] of the selectivity filter of the channel. Much of the analysis is algebraic, independent of differential equations. The Fermi distribution is derived from the configuration entropy of ions and water molecules with different sizes, different valences, and interstitial voids between particles. It allows us to calculate potentials and distances (between the binding ion and the oxygen ions of the glutamate side chains) directly from the experimental data using algebraic formulas. The spatial resolution of these results is comparable with those of molecular models, but of course the accuracy is no better than that implied by the experimental data. The glutamate side chains in our model are flexible enough to accommodate different types of binding ions in different bath conditions. The binding curves of Na{sup +} and Ca{sup 2+} for [CaCl{sub 2}] ranging from 10{sup −8} to 10{sup −2} M with a fixed 32 mM background [NaCl] are shown to agree with published Monte Carlo simulations. The Poisson-Fermi differential equation—that includes both steric and correlation effects—is then used to obtain the spatial profiles of energy, concentration, and dielectric coefficient from the solvent region to the filter. The energy profiles of ions are shown to depend sensitively on the steric energy that is not taken into account in the classical rate theory. We improve the rate theory by introducing a steric energy that lumps the effects of excluded volumes of all ions and water molecules and empty spaces between particles created by Lennard-Jones type and electrostatic forces. We show that the energy landscape varies significantly with bath concentrations. The energy landscape is not constant.

  11. 21 CFR 184.1191 - Calcium carbonate.

    Science.gov (United States)

    2010-04-01

    ... HUMAN CONSUMPTION (CONTINUED) DIRECT FOOD SUBSTANCES AFFIRMED AS GENERALLY RECOGNIZED AS SAFE Listing of... soda process”; (2) By precipitation of calcium carbonate from calcium hydroxide in the...

  12. The human acrosome reaction

    Institute of Scientific and Technical Information of China (English)

    H.W.G.Baker; D.Y.Liu; C.Garrett; M.Martic

    2000-01-01

    We developed tests of sperm-oocyte interaction: sperm-zona binding, zona-induced acrosome reaction, spermzona penetration and sperm-oolemma binding, using oocytes which failed to fertilise in clinical in vitro fertilization (IVF). Although oocyte defects contribute to failure of sperm oocyte interaction, rarely are all oocytes from one woman affected. Low or zero fertilization in standard IVFwas usually caused by sperm abnormalities. Poor sperm-zona pellucida binding was frequently associated with failure of standard IVF and obvious defects of sperm motility or morphology. The size and shape of the acrosome is particularly important for sperm binding to the oocyte. The proportion of acrosome intact sperm in the insemination medium was related to the IVF rate. Inducing the acrosome reaction with a calcium ionophore reduced sperm-zona binding. Blocking acrosome dispersal with an acrosin inhibitor prevented spermzona penetration. Sperm-zona penetration was even more highly related to IVF rates than was sperm-zona binding. Some patients had low or zero fertilization rates with standard IVF but normal sperm by conventional tests and normal sperm-zona binding. Few of their sperm underwent the acrosome reaction on the surface of the zona and none penetrated the zona. In contrast, fertilization and pregnancy rates were high with intracytoplasmic sperm injection. We call thiscondition defective zona pellucida induced acrosome reaction. Discovery of the nature of the abnormalities in the signal transduction and effector pathways of the human zona pellucida induced acrosome reaction should result in simpler tests and treatments for the patients and also provide new leads for contraceptive development.

  13. Methylene blue adsorption on graphene oxide/calcium alginate composites.

    Science.gov (United States)

    Li, Yanhui; Du, Qiuju; Liu, Tonghao; Sun, Jiankun; Wang, Yonghao; Wu, Shaoling; Wang, Zonghua; Xia, Yanzhi; Xia, Linhua

    2013-06-05

    Graphene oxide has been used as an adsorbent in wastewater treatment. However, the dispersibility in aqueous solution and the biotoxicity to human cells of graphene oxide limits its practical application in environmental protection. In this research, a novel environmental friendly adsorbent, calcium alginate immobilized graphene oxide composites was prepared. The effects of pH, contact time, temperature and dosage on the adsorption properties of methylene blue onto calcium alginate immobilized graphene oxide composites were investigated. The equilibrium adsorption data were described by the Langmuir and Freundlich isotherms. The maximum adsorption capacity obtained from Langmuir isotherm equation was 181.81 mg/g. The pseudo-first order, pseudo-second order, and intraparticle diffusion equation were used to evaluate the kinetic data. Thermodynamic analysis of equilibriums indicated that the adsorption reaction of methylene blue onto calcium alginate immobilized graphene oxide composites was exothermic and spontaneous in nature.

  14. Evolution of the Calcium Paradigm: The Relation between Vitamin D, Serum Calcium and Calcium Absorption

    Directory of Open Access Journals (Sweden)

    Borje E. Christopher Nordin

    2010-09-01

    Full Text Available Osteoporosis is the index disease for calcium deficiency, just as rickets/osteomalacia is the index disease for vitamin D deficiency, but there is considerable overlap between them. The common explanation for this overlap is that hypovitaminosis D causes malabsorption of calcium which then causes secondary hyperparathyroidism and is effectively the same thing as calcium deficiency. This paradigm is incorrect. Hypovitaminosis D causes secondary hyperparathyroidism at serum calcidiol levels lower than 60 nmol/L long before it causes malabsorption of calcium because serum calcitriol (which controls calcium absorption is maintained until serum calcidiol falls below 20 nmol/L. This secondary hyperparathyroidism, probably due to loss of a “calcaemic” action of vitamin D on bone first described in 1957, destroys bone and explains why vitamin D insufficiency is a risk factor for osteoporosis. Vitamin D thus plays a central role in the maintenance of the serum (ionised calcium, which is more important to the organism than the preservation of the skeleton. Bone is sacrificed when absorbed dietary calcium does not match excretion through the skin, kidneys and bowel which is why calcium deficiency causes osteoporosis in experimental animals and, by implication, in humans.

  15. Diffusive spatio-temporal noise in a first-passage time model for intracellular calcium release

    KAUST Repository

    Flegg, Mark B.

    2013-01-01

    The intracellular release of calcium from the endoplasmic reticulum is controlled by ion channels. The resulting calcium signals exhibit a rich spatio-temporal signature, which originates at least partly from microscopic fluctuations. While stochasticity in the gating transition of ion channels has been incorporated into many models, the distribution of calcium is usually described by deterministic reaction-diffusion equations. Here we test the validity of the latter modeling approach by using two different models to calculate the frequency of localized calcium signals (calcium puffs) from clustered IP3 receptor channels. The complexity of the full calcium system is here limited to the basic opening mechanism of the ion channels and, in the mathematical reduction simplifies to the calculation of a first passage time. Two models are then studied: (i) a hybrid model, where channel gating is treated stochastically, while calcium concentration is deterministic and (ii) a fully stochastic model with noisy channel gating and Brownian calcium ion motion. The second model utilises the recently developed two-regime method [M. B. Flegg, S. J. Chapman, and R. Erban, "The two-regime method for optimizing stochastic reaction-diffusion simulations," J. R. Soc., Interface 9, 859-868 (2012)] in order to simulate a large domain with precision required only near the Ca2+ absorbing channels. The expected time for a first channel opening that results in a calcium puff event is calculated. It is found that for a large diffusion constant, predictions of the interpuff time are significantly overestimated using the model (i) with a deterministic non-spatial calcium variable. It is thus demonstrated that the presence of diffusive noise in local concentrations of intracellular Ca2+ ions can substantially influence the occurrence of calcium signals. The presented approach and results may also be relevant for other cell-physiological first-passage time problems with small ligand concentration

  16. 40 CFR 424.51 - Specialized definitions.

    Science.gov (United States)

    2010-07-01

    ... STANDARDS FERROALLOY MANUFACTURING POINT SOURCE CATEGORY Other Calcium Carbide Furnaces Subcategory § 424.51... definitions, abbreviations and methods of analysis set forth in 40 CFR part 401 shall apply to this subpart....

  17. The determination of ultrafiltrable calcium and magnesium in serum.

    Science.gov (United States)

    Danielson, B G; Pallin, E; Sohtell, M

    1982-01-01

    Ultrafiltrate of human serum was investigated in order to evaluate the serum content of calcium and magnesium. The acid and base concentrations and pH of the serum was altered through titration with HCl- or NaOH-solutions. The Pco2 was varied in the titrated serum using different carbon dioxide tensions. This was performed when serum was filtered in a recycling system. It is shown that the analysis of calcium and magnesium have to be done under anaerobic conditions or at standardized pH and Pco2 situations, as the concentrations vary with both pH and Pco2. The concentration ratio between ultrafiltrate and serum for calcium and magnesium was found to be 0.56 and 0.74 respectively at pH=7.41 and Pco2=40 mmHg.

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

    Science.gov (United States)

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

    2014-11-01

    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. 99 mass% as CaCO3) or precipitated calcium carbonate (PCC).

  19. Hybrid calcium phosphate coatings for implants

    Science.gov (United States)

    Malchikhina, Alena I.; Shesterikov, Evgeny V.; Bolbasov, Evgeny N.; Ignatov, Viktor P.; Tverdokhlebov, Sergei I.

    2016-08-01

    Monophasic biomaterials cannot provide all the necessary functions of bones or other calcined tissues. It is necessary to create for cancer patients the multiphase materials with the structure and composition simulating the natural bone. Such materials are classified as hybrid, obtained by a combination of chemically different components. The paper presents the physical, chemical and biological studies of coatings produced by hybrid technologies (HT), which combine primer layer and calcium phosphate (CaP) coating. The first HT type combines the method of vacuum arc titanium primer layer deposition on a stainless steel substrate with the following micro-arc oxidation (MAO) in phosphoric acid solution with addition of calcium compounds to achieve high supersaturated state. MAO CaP coatings feature high porosity (2-8%, pore size 5-7 µm) and surface morphology with the thickness greater than 5 µm. The thickness of Ti primer layer is 5-40 µm. Amorphous MAO CaP coating micro-hardness was measured at maximum normal load Fmax = 300 mN. It was 3.1 ± 0.8 GPa, surface layer elasticity modulus E = 110 ± 20 GPa, roughness Ra = 0.9 ± 0.1 µm, Rz = 7.5 ± 0.2 µm, which is less than the titanium primer layer roughness. Hybrid MAO CaP coating is biocompatible, able to form calcium phosphates from supersaturated body fluid (SBF) solution and also stimulates osteoinduction processes. The second HT type includes the oxide layer formation by thermal oxidation and then CaP target radio frequency magnetron sputtering (RFMS). Oxide-RFMS CaP coating is a thin dense coating with good adhesion to the substrate material, which can be used for metal implants. The RFMS CaP coating has thickness 1.6 ± 0.1 µm and consists of main target elements calcium and phosphorus and Ca/P ratio 2.4. The second HT type can form calcium phosphates from SBF solution. In vivo study shows that hybrid RFMS CaP coating is biocompatible and produces fibrointegration processes.

  20. FORMATION OF PHOSPHATE-CONTAINING CALCIUM-FLUORIDE AT THE EXPENSE OF ENAMEL, HYDROXYAPATITE AND FLUORAPATITE

    NARCIS (Netherlands)

    CHRISTOFFERSEN, J; CHRISTOFFERSEN, MR; ARENDS, J; LEONARDSEN, ES

    1995-01-01

    During the caries process complex reactions involving calcium, phosphate, hydrogen and fluoride ions as main species take place. In this study the precipitation and dissolution reactions occurring in suspensions of enamel, hydroxyapatite (HAP) and fluorapatite (FAP) on addition of fluoride were inve

  1. Interpreting the Marine Calcium Isotope Record: Influence of Reef Builders

    Science.gov (United States)

    Boehm, F.; Eisenhauer, A.; Farkas, J.; Kiessling, W.; Veizer, J.; Wallmann, K.

    2008-12-01

    The calcium isotopic composition of seawater as recorded in brachiopod shells varied substantially during the Paleozoic (Farkas et al. 2007, Geochim. Cosmochim. Acta, 71, 5117-5134). The most prominent feature of the record is an excursion to higher 44Ca/40Ca values that started during the Early Carboniferous and lasted until the Permian. The shift occurred shortly after the transition from a calcite-sea to an aragonite-sea (Sandberg 1983, Nature 305, 19-22; Stanley and Hardie 1998, Pal3, 144, 3-19). It therefore has been interpreted to reflect a change in the average calcium isotope fractionation of carbonates produced in the oceans. Aragonite is depleted by about 0.6 permil in 44Ca/40Ca compared to calcite (Gussone et al. 2005, Geochim. Cosmochim. Acta, 69, 4485-4494). Consequently a transient shift from calcite dominated to an aragonite dominated calcium carbonate sedimentation could have caused the observed 0.5 permil isotope shift. We compare the marine calcium isotope record with a new compilation of the Phanerozoic trends in the skeletal mineralogy of marine invertebrates (Kiessling et al. 2008, Nature Geoscience, 1, 527-530). The compilation is based on data collected in the PaleoReef database and the Paleobiology Database, which include information on Phanerozoic reef complexes and taxonomic collection data of Phanerozoic biota, respectively. We find a strong positive correlation between the calcium isotope ratios and the abundance of aragonitic reef builders from the Silurian until the Permian at a sample resolution of about 10 million years. The two records, however, diverge in the Triassic, when reefs were dominated by aragonite but the calcium isotope values remained at a relatively low level. We also find a good correlation between calcium isotopes and the proportion of aragonite in the general record of Phanerozoic biota. However, in this case the records start to diverge already in the latest Carboniferous. The observations suggest that the

  2. Calcium binding protein-mediated regulation of voltage-gated calcium channels linked to human diseases

    Institute of Scientific and Technical Information of China (English)

    Nasrin NFJATBAKHSH; Zhong-ping FENG

    2011-01-01

    Calcium ion entry through voltage-gated calcium channels is essential for cellular signalling in a wide variety of cells and multiple physiological processes. Perturbations of voltage-gated calcium channel function can lead to pathophysiological consequences. Calcium binding proteins serve as calcium sensors and regulate the calcium channel properties via feedback mechanisms. This review highlights the current evidences of calcium binding protein-mediated channel regulation in human diseases.

  3. Zintl and intermetallic phases grown from calcium/lithium flux

    Science.gov (United States)

    Blankenship, Trevor

    Metal flux synthes is a useful alternative method to high temperature solid state synthesis; it allows easy diffusion of reactants at lower temperatures, and presents favorable conditions for crystal growth. A mixed flux of calcium and lithium in a 1:1 ratio was explored in this work; this mixture melts at 300°C and is an excellent solvent for main group elements and CaH 2. Reactions of p-block elements in a 1:1 Ca/Li flux have produced several new intermetallic and Zintl phases. Electronegative elements from groups 14 and 15 are reduced to anions in this flux, yielding charge-balanced products. More electropositive metals from group 13 are not fully reduced; the resulting products are complex intermetallics. The reactions of tin or lead and carbon in Ca/Li flux produced the analogous phases Ca11Tt3C8 (Tt = Sn, Pb) in the monoclinic C21/c space group (a = 13.2117(8) A, b =10.7029(7) A, c = 14.2493(9) A, beta = 105.650(1)° for the Sn analog). These compounds are carbide Zintl phases that includes the rare combination of C3 4- and C22- units as well as Sn4- or Pb4- anions. Ca/Li flux reactions of CaH2 and arsenic have produced the Zintl phases LiCa3As 2H in orthorhombic Pnma (a = 11.4064(7), b = 4.2702(3), c = 11.8762(8) A), and Ca 13As6C0.46N1.155H6.045in tetragonal P4/mbm (a = 15.7493(15), c = 9.1062(9) A). The complex stoichiometry of the latter phase was caused by incorporation of light element contaminants and was studied by neutron diffraction, showing mixing of anionic sites to achieve charge balance. Ca/Li flux reactions with group 13 metals have resulted in several new intermetallic phases. Reactions of indium and CaH2 in the Ca/Li flux (with or without boron) formed Ca53In13B4-x H23+x(2.4 < x < 4.0) in cubic space group Im-3 (a = 16.3608(6) A) which features metallic indium atoms and ionic hydride sites. The electronic properties of this "subhydride" were confirmed by 1H and 115In NMR spectroscopy. Attempts to replace boron with carbon yielded Ca12InC13-x

  4. Inclusion variations and calcium treatment optimization in pipeline steel production

    Science.gov (United States)

    Liu, Jian-Hua; Wu, Hua-Jie; Bao, Yan-Ping; Wang, Min

    2011-10-01

    SiCa line and SiCaBaFe alloy were injected into liquid pipeline steel at the end of LF refining as calcium treatment, and samples were taken from the ladles, mould, and slabs. Analysis of Ca content and inclusions shows that Ca content in steel decreases obviously in the following process after calcium treatment; the compositions, morphology, and sizes of inclusions also vary much in the production; primary inclusions in the ladles prior to calcium treatment are mainly Al2O3 inclusions, but they turn to fine irregular CaS-CaO-Al2O3 compound inclusions after the treatment, then become fine globular CaO-Al2O3 inclusions in the mould, and finally change to a few larger irregular CaS-CaO-Al2O3 complex inclusions in the slabs. Thermodynamic study reveals that inclusion variations are related with the preferential reactions among Ca, Al2O3, and S and the precipitation of S in CaO-Al2O3 inclusions with high sulfur capacity. New evaluation standards for calcium treatment in high-grade pipeline steel were put forward according to the inclusion variations and requirements of pipeline steel on inclusion controlling, and the calcium process was studied and optimized.

  5. Calcium signals in olfactory neurons.

    Science.gov (United States)

    Tareilus, E; Noé, J; Breer, H

    1995-11-09

    Laser scanning confocal microscopy in combination with the fluorescent calcium indicators Fluo-3 and Fura-Red was employed to estimate the intracellular concentration of free calcium ions in individual olfactory receptor neurons and to monitor temporal and spatial changes in the Ca(2+)-level upon stimulation. The chemosensory cells responded to odorants with a significant increase in the calcium concentration, preferentially in the dendritic knob. Applying various stimulation paradigma, it was found that in a population of isolated cells, subsets of receptor neurons display distinct patterns of responsiveness.

  6. Fabrications of zinc-releasing biocement combining zinc calcium phosphate to calcium phosphate cement.

    Science.gov (United States)

    Horiuchi, Shinya; Hiasa, Masahiro; Yasue, Akihiro; Sekine, Kazumitsu; Hamada, Kenichi; Asaoka, Kenzo; Tanaka, Eiji

    2014-01-01

    Recently, zinc-releasing bioceramics have been the focus of much attention owing to their bone-forming ability. Thus, some types of zinc-containing calcium phosphate (e.g., zinc-doped tricalcium phosphate and zinc-substituted hydroxyapatite) are examined and their osteoblastic cell responses determined. In this investigation, we studied the effects of zinc calcium phosphate (ZCP) derived from zinc phosphate incorporated into calcium phosphate cement (CPC) in terms of its setting reaction and MC3T3-E1 osteoblast-like cell responses. Compositional analysis by powder X-ray diffraction analysis revealed that HAP crystals were precipitated in the CPC containing 10 or 30wt% ZCP after successfully hardening. However, the crystal growth observed by scanning electron microscopy was delayed in the presence of additional ZCP. These findings indicate that the additional zinc inhibits crystal growth and the conversion of CPC to the HAP crystals. The proliferation of the cells and alkaline phosphatase (ALP) activity were enhanced when 10wt% ZCP was added to CPC. Taken together, ZCP added CPC at an appropriate fraction has a potent promotional effect on bone substitute biomaterials.

  7. Calcium orthophosphates as bioceramics: state of the art.

    Science.gov (United States)

    Dorozhkin, Sergey V

    2010-11-30

    In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30-40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics-which is able to promote regeneration of bones-was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes.

  8. Calcium Orthophosphates as Bioceramics: State of the Art

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2010-11-01

    Full Text Available In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30–40 years. Namely, by structural and compositional control, it became possible to choose whether calcium orthophosphate bioceramics were biologically stable once incorporated within the skeletal structure or whether they were resorbed over time. At the turn of the millennium, a new concept of calcium orthophosphate bioceramics—which is able to promote regeneration of bones—was developed. Presently, calcium orthophosphate bioceramics are available in the form of particulates, blocks, cements, coatings, customized designs for specific applications and as injectable composites in a polymer carrier. Current biomedical applications include artificial replacements for hips, knees, teeth, tendons and ligaments, as well as repair for periodontal disease, maxillofacial reconstruction, augmentation and stabilization of the jawbone, spinal fusion and bone fillers after tumor surgery. Exploratory studies demonstrate potential applications of calcium orthophosphate bioceramics as scaffolds, drug delivery systems, as well as carriers of growth factors, bioactive peptides and/or various types of cells for tissue engineering purposes.

  9. Ultrasound influence upon calcium carbonate precipitation on bacterial cellulose membranes.

    Science.gov (United States)

    Stoica-Guzun, Anicuta; Stroescu, Marta; Jinga, Sorin; Jipa, Iuliana; Dobre, Tanase; Dobre, Loredana

    2012-07-01

    The effect of ultrasonic irradiation (40 kHz) on the calcium carbonate deposition on bacterial cellulose membranes was investigated using calcium chloride (CaCl(2)) and sodium carbonate (Na(2)CO(3)) as starting reactants. The composite materials containing bacterial cellulose-calcium carbonate were characterized by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and color measurements. The polymorphs of calcium carbonate that were deposited on bacterial cellulose membranes in the presence or in the absence of ultrasonic irradiation were calcite and vaterite. The morphology of the obtained crystals was influenced by the concentration of starting solutions and by the presence of ultrasonic irradiation. In the presence of ultrasonic irradiation the obtained crystals were bigger and in a larger variety of shapes than in the absence of ultrasounds: from cubes of calcite to spherical and flower-like vaterite particles. Bacterial cellulose could be a good matrix for obtaining different types of calcium carbonate crystals.

  10. 21 CFR 184.1187 - Calcium alginate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium alginate. 184.1187 Section 184.1187 Food... Specific Substances Affirmed as GRAS § 184.1187 Calcium alginate. (a) Calcium alginate (CAS Reg. No. 9005.... Calcium alginate is prepared by the neutralization of purified alginic acid with appropriate pH...

  11. Topotactic exchange and intercalation of calcium phosphate

    Science.gov (United States)

    Lima, Cicero B. A.; Airoldi, Claudio

    2004-11-01

    The precursor (NH 4) 2Ca(H 2PO 4) 2ṡH 2O (CaAP) compound was obtained by combining a calcium chloride solution with dibasic ammonium phosphate. After submitting it to a thermal treatment, crystalline calcium phosphate, Ca(H 2PO 4) 2ṡH 2O (CaP) was isolated. X-ray diffraction patterns for this compound indicated good crystallinity, with a peak at 2θ=12.8°, to give an interlamellar distance of 697 pm, which changed to 1550 pm, when the reaction employed phenylphosphonic acid, and to 1514 pm when intercalated with methylamine. Phosphorus and calcium analysis from colorimetric and gravimetric methods gave for CaP 24.2 and 15.8%, respectively, to yield a P:Ca molar ratio equal to two. The phosphorus nuclear magnetic resonance presented a peak centered at -1.23 ppm, in agreement with the existence of phosphate groups in protonated form. CaAP showed a mass loss of 21.2% in the 466 to 541 K interval due to ammonia and water elimination to yield Ca(PO 3) 3, and CaP can be dehydrated at 440 K for 6 h. A topotactical exchange occurred when CaP is intercalated with methylamine or reacted with phenylphosphonic acid to yield the phosphonate compound and the infrared spectrum of the resulting compound clearly showed the presence of PO 4 and PO 3 groups. The topotactic exchange was also demonstrated by X-ray diffractometry in following the stages of decomposition from 527 to 973 K.

  12. Calcium isotope analysis by mass spectrometry.

    Science.gov (United States)

    Boulyga, Sergei F

    2010-01-01

    The variations in the isotopic composition of calcium caused by fractionation in heterogeneous systems and by nuclear reactions can provide insight into numerous biological, geological, and cosmic processes, and therefore isotopic analysis finds a wide spectrum of applications in cosmo- and geochemistry, paleoclimatic, nutritional, and biomedical studies. The measurement of calcium isotopic abundances in natural samples has challenged the analysts for more than three decades. Practically all Ca isotopes suffer from significant isobaric interferences, whereas low-abundant isotopes can be particularly affected by neighboring major isotopes. The extent of natural variations of stable isotopes appears to be relatively limited, and highly precise techniques are required to resolve isotopic effects. Isotope fractionation during sample preparation and measurements and instrumental mass bias can significantly exceed small isotope abundance variations in samples, which have to be investigated. Not surprisingly, a TIMS procedure developed by Russell et al. (Russell et al., 1978. Geochim Cosmochim Acta 42: 1075-1090) for Ca isotope measurements was considered as revolutionary for isotopic measurements in general, and that approach is used nowadays (with small modifications) for practically all isotopic systems and with different mass spectrometric techniques. Nevertheless, despite several decades of calcium research and corresponding development of mass spectrometers, the available precision and accuracy is still not always sufficient to achieve the challenging goals. The present article discusses figures of merits of presently used analytical methods and instrumentation, and attempts to critically assess their limitations. In Sections 2 and 3, mass spectrometric methods applied to precise stable isotope analysis and to the determination of (41)Ca are described. Section 4 contains a short summary of selected applications, and includes tracer experiments and the potential use

  13. Biodiesel Production from Castor Oil by Using Calcium Oxide Derived from Mud Clam Shell

    Directory of Open Access Journals (Sweden)

    S. Ismail

    2016-01-01

    Full Text Available The catalytic potential of calcium oxide synthesized from mud clam shell as a heterogeneous catalyst for biodiesel production was studied. The mud clam shell calcium oxide was characterized using particle size analyzer, Fourier transform infrared spectroscopy, scanning electron microscopy, and BET gas sorption analyzer. The catalyst performance of mud clam shell calcium oxide was studied in the transesterification of castor oil as biodiesel. Catalyst characterization and transesterification study results of synthesized catalyst proved the efficiency of the natural derived catalyst for biodiesel production. A highest biodiesel yield of 96.7% was obtained at optimal parameters such as 1 : 14 oil-to-methanol molar ratio, 3% w/w catalyst concentration, 60°C reaction temperature, and 2-hour reaction time. Catalyst reusability test shows that the synthesized calcium oxide from mud clam shell is reusable up to 5 times.

  14. Analysis of Adverse Reactions to Detoxicating Tablets(Pills)of Cow-bezoar in 40 Cases%牛黄解毒片(丸)40例不良反应分析

    Institute of Scientific and Technical Information of China (English)

    邹明畅; 倪鸿昌

    2007-01-01

    目的 分析牛黄解毒片(丸)所致的不良反应的一般规律及其特点,为临床合理用药提供参考.方法 对1994年1月-2006年6月国内公开发表的药学杂志刊登的有关牛黄解毒片(丸)所致40例不良反应进行分类统计与分析.结果 牛黄解毒片(丸)可致免疫系统、消化系统、泌尿系统等不良反应,最常见为过敏反应.结论 牛黄解毒片(丸)可引起一定的不良反应,临床需注意其合理使用.

  15. 头孢菌素致双硫仑样反应40例临床分析%Clinical Analysis to 40 Disulfiram-like Reactions Caused by Cephalosporin

    Institute of Scientific and Technical Information of China (English)

    温宇英; 丁乾; 韩继媛

    2004-01-01

    目的:引起临床医师对头孢菌素导致双硫仑样反应的重视.方法:对协和医院2003年1~6月期间由于使用头孢菌素导致的双硫仑样反应40例进行回顾性分析.结果:①双硫仑样反应可出现于各性别、年龄及原发病的患者.②导致双硫仑样反应的药物见于头孢唑啉、头孢哌酮、头孢哌酮加舒巴坦、拉氧头孢等.③症状有颜面潮红、胸闷、头痛、心悸、恶心呕吐、气促、烦躁、低血压、心绞痛、呼吸困难等.④接触含乙醇制品的途径除饮用各种酒类外还见于反复乙醇皮肤消毒及服用藿香正气水等含乙醇制剂.⑤双硫仑样反应出现于使用头孢菌素的过程中及疗程结束后72 h内.⑥双硫仑样反应出现于饮酒后10~40 min.⑦一般于30 min~12 h内缓解.结论:医护人员应对双硫仑样反应给与足够的重视,尤其是老年人和心血管疾病患者.

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

    Science.gov (United States)

    Rodriguez-Blanco, Juan Diego; Shaw, Samuel; Benning, Liane G

    2011-01-01

    The kinetics and mechanisms of nanoparticulate amorphous calcium carbonate (ACC) crystallization to calcite, via vaterite, were studied at a range of environmentally relevant temperatures (7.5-25 °C) using synchrotron-based in situ time-resolved Energy Dispersive X-ray Diffraction (ED-XRD) in conjunction with high-resolution electron microscopy, ex situ X-ray diffraction and infrared spectroscopy. The crystallization process occurs in two stages; firstly, the particles of ACC rapidly dehydrate and crystallize to form individual particles of vaterite; secondly, the vaterite transforms to calcite via a dissolution and reprecipitation mechanism with the reaction rate controlled by the surface area of calcite. The second stage of the reaction is approximately 10 times slower than the first. Activation energies of calcite nucleation and crystallization are 73±10 and 66±2 kJ mol(-1), respectively. A model to calculate the degree of calcite crystallization from ACC at environmentally relevant temperatures (7.5-40 °C) is also presented.

  17. Calcium-Amidoborane-Ammine Complexes : Thermal Decomposition of Model Systems

    NARCIS (Netherlands)

    Harder, Sjoerd; Spielmann, Jan; Tobey, Briac

    2012-01-01

    Hydrocarbon-soluble model systems for the calcium-amidoborane-ammine complex Ca(NH2BH3)2.(NH3)2 were prepared and structurally characterized. The following complexes were obtained by the reaction of RNH2BH3 (R=H, Me, iPr, DIPP; DIPP=2,6-diisopropylphenyl) with Ca(DIPP-nacnac)(NH2).(NH3)2 (DIPP-nacna

  18. Calcium Orthophosphate Cements and Concretes

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2009-03-01

    Full Text Available In early 1980s, researchers discovered self-setting calcium orthophosphate cements, which are a bioactive and biodegradable grafting material in the form of a powder and a liquid. Both phases form after mixing a viscous paste that after being implanted, sets and hardens within the body as either a non-stoichiometric calcium deficient hydroxyapatite (CDHA or brushite, sometimes blended with unreacted particles and other phases. As both CDHA and brushite are remarkably biocompartible and bioresorbable (therefore, in vivo they can be replaced with newly forming bone, calcium orthophosphate cements represent a good correction technique for non-weight-bearing bone fractures or defects and appear to be very promising materials for bone grafting applications. Besides, these cements possess an excellent osteoconductivity, molding capabilities and easy manipulation. Furthermore, reinforced cement formulations are available, which in a certain sense might be described as calcium orthophosphate concretes. The concepts established by calcium orthophosphate cement pioneers in the early 1980s were used as a platform to initiate a new generation of bone substitute materials for commercialization. Since then, advances have been made in the composition, performance and manufacturing; several beneficial formulations have already been introduced as a result. Many other compositions are in experimental stages. In this review, an insight into calcium orthophosphate cements and concretes, as excellent biomaterials suitable for both dental and bone grafting application, has been provided.

  19. Frozen delivery of brushite calcium phosphate cements.

    Science.gov (United States)

    Grover, Liam M; Hofmann, Michael P; Gbureck, Uwe; Kumarasami, Balamurgan; Barralet, Jake E

    2008-11-01

    Calcium phosphate cements typically harden following the combination of a calcium phosphate powder component with an aqueous solution to form a matrix consisting of hydroxyapatite or brushite. The mixing process can be very important to the mechanical properties exhibited by cement materials and consequently when used clinically, since they are usually hand-mixed their mechanical properties are prone to operator-induced variability. It is possible to reduce this variability by pre-mixing the cement, e.g. by replacing the aqueous liquid component with non-reactive glycerol. Here, for the first time, we report the formation of three different pre-mixed brushite cement formulations formed by freezing the cement pastes following combination of the powder and liquid components. When frozen and stored at -80 degrees C or less, significant degradation in compression strength did not occur for the duration of the study (28 days). Interestingly, in the case of the brushite cement formed from the combination of beta-tricalcium phosphate with 2 M orthophosphoric acid solution, freezing the cement paste had the effect of increasing mean compressive strength fivefold (from 4 to 20 MPa). The increase in compression strength was accompanied by a reduction in the setting rate of the cement. As no differences in porosity or degree of reaction were observed, strength improvement was attributed to a modification of crystal morphology and a reduction in damage caused to the cement matrix during manipulation.

  20. Factors affecting calcium balance in Chinese adolescents.

    Science.gov (United States)

    Yin, Jing; Zhang, Qian; Liu, Ailing; Du, Weijing; Wang, Xiaoyan; Hu, Xiaoqi; Ma, Guansheng

    2010-01-01

    Chinese dietary reference intakes (DRIs) for calcium were developed mainly from studies conducted amongst Caucasians, yet a recent review showed that reference calcium intakes for Asians are likely to be different from those of Caucasians (Lee and Jiang, 2008). In order to develop calcium DRIs for Chinese adolescents, it is necessary to explore the characteristics and potential influencing factors of calcium metabolic balance in Chinese adolescents. A total of 80 students (15.1+/-0.8 years) were recruited stratified by gender from a 1-year calcium supplementation study. Subjects were randomly designed to four groups and supplemented with calcium carbonate tablets providing elemental calcium at 63, 354, 660, and 966 mg/day, respectively. Subjects consumed food from a 3-day cycle menu prepared by staff for 10 days. Elemental calcium in samples of foods, feces, and urine was determined in duplicates by inductively coupled plasma atomic emission spectrometry. The total calcium intake ranged from 352 to 1323 mg/day. The calcium apparent absorption efficiency and retention in boys were significantly higher than that in girls (68.7% vs. 46.4%, 480 mg/day vs. 204 mg/day, PCalcium retention increased with calcium intakes, but did not reach a plateau. Calcium absorption efficiency in boys increased with calcium intake up to 665 mg/day, and decreased after that. In girls, calcium absorption efficiency decreased with calcium intake. Calcium absorption efficiency increased within 1 year after first spermatorrhea in boys, but decreased with pubertal development in girls. Sex, calcium intake, age, and pubertal development were the most important determinants of calcium absorption (R(2)=0.508, Pcalcium intake, age, and pubertal development are important factors for calcium retention and absorption during growth, which should be considered for the development of calcium DRIs for Chinese adolescents.

  1. Magnesium supplementation through seaweed calcium extract rather than synthetic magnesium oxide improves femur bone mineral density and strength in ovariectomized rats.

    Science.gov (United States)

    Bae, Yun Jung; Bu, So Young; Kim, Jae Young; Yeon, Jee-Young; Sohn, Eun-Wha; Jang, Ki-Hyo; Lee, Jae-Cheol; Kim, Mi-Hyun

    2011-12-01

    Commercially available seaweed calcium extract can supply high amounts of calcium as well as significant amounts of magnesium and other microminerals. The purpose of this study was to investigate the degree to which the high levels of magnesium in seaweed calcium extract affects the calcium balance and the bone status in ovariectomized rats in comparison to rats supplemented with calcium carbonate and magnesium oxide. A total of 40 Sprague-Dawley female rats (7 weeks) were divided into four groups and bred for 12 weeks: sham-operated group (Sham), ovariectomized group (OVX), ovariectomized with inorganic calcium and magnesium supplementation group (OVX-Mg), and ovariectomized with seaweed calcium and magnesium supplementation group (OVX-SCa). All experimental diets contained 0.5% calcium. The magnesium content in the experimental diet was 0.05% of the diet in the Sham and OVX groups and 0.1% of the diet in the OVX-Mg and OVX-SCa groups. In the calcium balance study, the OVX-Mg and OVX-SCa groups were not significantly different in calcium absorption compared to the OVX group. However, the femoral bone mineral density and strength of the OVX-SCa group were higher than those of the OVX-Mg and OVX groups. Seaweed calcium with magnesium supplementation or magnesium supplementation alone did not affect the serum ALP and CTx levels in ovariectomized rats. In summary, consumption of seaweed calcium extract or inorganic calcium carbonate with magnesium oxide demonstrated the same degree of intestinal calcium absorption, but only the consumption of seaweed calcium extract resulted in increased femoral bone mineral density and strength in ovariectomized rats. Our results suggest that seaweed calcium extract is an effective calcium and magnesium source for improving bone health compared to synthetic calcium and magnesium supplementation.

  2. 40 CFR 415.36 - Pretreatment standards for new sources (PSNS).

    Science.gov (United States)

    2010-07-01

    ...) EFFLUENT GUIDELINES AND STANDARDS INORGANIC CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Carbide... works must comply with 40 CFR part 403 and achieve the following pretreatment standards for new...

  3. Calcium Orthophosphates as Bioceramics: State of the Art

    OpenAIRE

    Dorozhkin, Sergey V

    2010-01-01

    In the late 1960s, much interest was raised in regard to biomedical applications of various ceramic materials. A little bit later, such materials were named bioceramics. This review is limited to bioceramics prepared from calcium orthophosphates only, which belong to the categories of bioactive and bioresorbable compounds. There have been a number of important advances in this field during the past 30–40 years. Namely, by structural and compositional control, it became possible to choose whet...

  4. Mitochondrial calcium uptake.

    Science.gov (United States)

    Williams, George S B; Boyman, Liron; Chikando, Aristide C; Khairallah, Ramzi J; Lederer, W J

    2013-06-25

    Calcium (Ca(2+)) uptake into the mitochondrial matrix is critically important to cellular function. As a regulator of matrix Ca(2+) levels, this flux influences energy production and can initiate cell death. If large, this flux could potentially alter intracellular Ca(2+) ([Ca(2+)]i) signals. Despite years of study, fundamental disagreements on the extent and speed of mitochondrial Ca(2+) uptake still exist. Here, we review and quantitatively analyze mitochondrial Ca(2+) uptake fluxes from different tissues and interpret the results with respect to the recently proposed mitochondrial Ca(2+) uniporter (MCU) candidate. This quantitative analysis yields four clear results: (i) under physiological conditions, Ca(2+) influx into the mitochondria via the MCU is small relative to other cytosolic Ca(2+) extrusion pathways; (ii) single MCU conductance is ∼6-7 pS (105 mM [Ca(2+)]), and MCU flux appears to be modulated by [Ca(2+)]i, suggesting Ca(2+) regulation of MCU open probability (P(O)); (iii) in the heart, two features are clear: the number of MCU channels per mitochondrion can be calculated, and MCU probability is low under normal conditions; and (iv) in skeletal muscle and liver cells, uptake per mitochondrion varies in magnitude but total uptake per cell still appears to be modest. Based on our analysis of available quantitative data, we conclude that although Ca(2+) critically regulates mitochondrial function, the mitochondria do not act as a significant dynamic buffer of cytosolic Ca(2+) under physiological conditions. Nevertheless, with prolonged (superphysiological) elevations of [Ca(2+)]i, mitochondrial Ca(2+) uptake can increase 10- to 1,000-fold and begin to shape [Ca(2+)]i dynamics.

  5. The preparation of calcium superoxide for air breathing and scrubbing applications

    Science.gov (United States)

    Ballou, E. V.; Wood, P. C.; Spitze, L. A.; Wydeven, T.

    1976-01-01

    There is interest in the preparation of high-purity calcium superoxide as an oxygen source for breathing apparatus because both the available oxygen and the capacity for carbon dioxide removal, per unit weight of superoxide, are higher than that of a number of other chemical oxygen sources. A review of earlier findings shows that the general method used by Vol'nov and coworkers for the decomposition of calcium peroxide diperoxyhydrate can yield preparations containing more than 58.4% calcium superoxide maximum predicted for an equimolar disproportionation reaction. The decomposition of solid calcium peroxide diperoxyhydrate is studied using an apparatus that allows good control of the critical reaction parameters. The removal of water from decomposing calcium peroxide diperoxyhydrate, before the same water has an opportunity to back react with the calcium superoxide formed in the reaction, constitutes the rationale of the experiments. Even with allowance for the anomalies observed in the analytical results, the yields appear to be in the 65+ percent range, and optimization of the experimental variables is still being pursued.

  6. Calcium isotopes in wine

    Science.gov (United States)

    Holmden, C. E.

    2011-12-01

    The δ 44/40Ca values of bottled wine vary between -0.76% to -1.55% on the seawater scale and correlate weakly with inverse Ca concentration and Mg/Ca ratio, such that the lowest δ 44/40Ca values have the highest Ca concentrations and lowest Mg/Ca ratios. The correlation is notable in the sense that the measured wines include both whites and reds sampled from different wine growing regions of the world, and cover a wide range of quality. Trends among the data yield clues regarding the cause of the observed isotopic fractionation. White wines, and wines generally perceived to be of lower quality, have lower δ 44/40Ca values compared to red wines and wines of generally perceived higher quality. Quality was assessed qualitatively through sensory evaluation, price, and scores assigned by critics. The relationship between δ 44/40Ca and wine quality was most apparent when comparing wines of one varietal from one producer from the same growing region. In the vineyard, wine quality is related to factors such as the tonnage of the crop and the ripeness of the grapes at the time of harvesting, the thickness of the skins for reds, the age of the vines, as well as the place where the grapes were grown (terroir). Quality is also influenced by winemaking practices such as fermentation temperature, duration of skin contact, and barrel ageing. Accordingly, the relationship between δ 44/40Ca and wine quality may originate during grape ripening in the vineyard or during winemaking in the cellar. We tested the grape ripening hypothesis using Merlot grapes sampled from a vineyard in the Okanagan, British Columbia, using sugar content (degrees Brix) as an indicator of ripeness. The grapes were separated into pulp, skin, and pip fractions and were analyzed separately. Thus far, there is no clear evidence for a systematic change in δ 44/40Ca values associated with progressive ripening of grapes in the vineyard. On the day of harvesting, the δ 44/40Ca value of juice squeezed from

  7. Dopaminergic regulation of dendritic calcium: fast multisite calcium imaging.

    Science.gov (United States)

    Zhou, Wen-Liang; Oikonomou, Katerina D; Short, Shaina M; Antic, Srdjan D

    2013-01-01

    Optimal dopamine tone is required for the normal cortical function; however it is still unclear how cortical-dopamine-release affects information processing in individual cortical neurons. Thousands of glutamatergic inputs impinge onto elaborate dendritic trees of neocortical pyramidal neurons. In the process of ensuing synaptic integration (information processing), a variety of calcium transients are generated in remote dendritic compartments. In order to understand the cellular mechanisms of dopaminergic modulation it is important to know whether and how dopaminergic signals affect dendritic calcium transients. In this chapter, we describe a relatively inexpensive method for monitoring dendritic calcium fluctuations at multiple loci across the pyramidal dendritic tree, at the same moment of time (simultaneously). The experiments have been designed to measure the amplitude, time course and spatial extent of action potential-associated dendritic calcium transients before and after application of dopaminergic drugs. In the examples provided here the dendritic calcium transients were evoked by triggering the somatic action potentials (backpropagation-evoked), and puffs of exogenous dopamine were applied locally onto selected dendritic branches.

  8. Formation of calcium complexes by borogluconate in vitro and during calcium borogluconate infusion in sheep.

    Science.gov (United States)

    Farningham, D A

    1985-07-01

    The effect of borogluconate on plasma calcium fractions was studied in vitro and in vivo in sheep. In vitro calcium chloride was more effective in raising ionised plasma calcium than calcium borogluconate. Sodium borate or gluconate added to blood caused only small decreases in blood ionised calcium. However, together, a synergistic reduction in ionised calcium was observed. Following calcium borogluconate infusions into sheep, total plasma calcium rose primarily because of an increase in the unionised ultrafiltrable fraction. Other changes observed following the infusion were hypercalciuria, decreased glomerular filtration rate and acidosis. Sodium borogluconate administered subcutaneously lowered total plasma calcium. This probably resulted from enhanced calcium excretion. It is suggested that since the anionic component of calcium solutions alters the availability and retention of calcium, it is likely to affect clinical efficacy significantly.

  9. Solid state NMR study calcium phosphate ceramics

    Energy Technology Data Exchange (ETDEWEB)

    Miquel, J.L.; Facchini, L.; Legrand, A.P. (Laboratoire de Physique Quantique, Paris (France). CNRS, URA421, ESPCI); Rey, C. (CNRS, Toulouse (France). ENSC. Laboratoire de Physico-chimie des Solides); Lemaitre, J. (EPF Lausanne (France). Laboratoire de Technologie des Poudres)

    1990-04-01

    High-resolution {sup 31}P and {sup 1}H NMR spectra at 40 and 121 MHz {sup 31}P and 300 MHz {sup 1}H of synthetic and biological samples of calcium phosphates have been obtained by magic angle spinning (MAS) at spinning speeds up to 6.5 kHz, and high power proton decoupling. The samples include crystalline hydroxyapatite, a deficient hydroxyapatite characterized by a Ca/P atomic ratio of 1.5, a poorly crystallized hydroxyapatite, monetite, brushite, octacalcium phosphate, {beta}-tricalcium phosphate and rabbit femoral bone. The interactions between nuclei in unlike structures and the mobility of acid protons are discussed. (author). 11 refs.; 2 figs.; 1 tab.

  10. [Calcium metabolism characteristics in microgravity].

    Science.gov (United States)

    Grigor'ev, A I; Larina, I M; Morukov, B V

    1999-06-01

    The results of research of calcium exchange parameters at cosmonauts taken part in long space flights (SF) onboard of orbital stations "SALUT" and "MIR" within 1978-1998 were generalized. The analysis of data received during observation of 44 cosmonauts (18 of them have taken part in long SF twice) was done. The observation was carried out before and after SF by duration 30-438 days. The content of a total calcium in blood serum was increased basically by the increase of its ionized fraction after flights of moderate (3-6 months) and large duration (6-14 months) along with the significant increase of PTH and decrease of calcitonin levels. The content of osteocalcin after SF was increased. Three cosmonauts participated in research of calcium kinetics using stable isotopes before, in time and after a 115-day SF. Reduction of intestinal absorption, excretion through a gastrointestinal tract, and increase of calcium excretion with urine were marked in time of SF. In early postflight period a level of intestinal absorption, on the average, was much lower than in SF, and the calcium removal through intestine was increased. Both renal and intestinal excretion of calcium were not normalized in 3.5-4.5 months after end of SF. Increase of resorbtive processes in bone tissues which induced negative bone balance during flight was observed in all test subjects, proceeding from estimations of speed of the basic calcium flows made on the basis of mathematical modeling. The conclusion about decrease in speed of bone tissue remodeling and strengthening of its resorption proves to be true by data of research of biochemical and endocrine markers.

  11. Calcium wave of tubuloglomerular feedback.

    Science.gov (United States)

    Peti-Peterdi, János

    2006-08-01

    ATP release from macula densa (MD) cells into the interstitium of the juxtaglomerular (JG) apparatus (JGA) is an integral component of the tubuloglomerular feedback (TGF) mechanism that controls the glomerular filtration rate. Because the cells of the JGA express a number of calcium-coupled purinergic receptors, these studies tested the hypothesis that TGF activation triggers a calcium wave that spreads from the MD toward distant cells of the JGA and glomerulus. Ratiometric calcium imaging of in vitro microperfused isolated JGA-glomerulus complex dissected from rabbits was performed with fluo-4/fura red and confocal fluorescence microscopy. Activation of TGF by increasing tubular flow rate at the MD rapidly produced a significant elevation in intracellular Ca(2+) concentration ([Ca(2+)](i)) in extraglomerular mesangial cells (by 187.6 +/- 45.1 nM) and JG renin granular cells (by 281.4 +/- 66.6 nM). Subsequently, cell-to-cell propagation of the calcium signal at a rate of 12.6 +/- 1.1 microm/s was observed upstream toward proximal segments of the afferent arteriole and adjacent glomeruli, as well as toward intraglomerular elements including the most distant podocytes (5.9 +/- 0.4 microm/s). The same calcium wave was observed in nonperfusing glomeruli, causing vasoconstriction and contractions of the glomerular tuft. Gap junction uncoupling, an ATP scavenger enzyme cocktail, and pharmacological inhibition of P(2) purinergic receptors, but not adenosine A(1) receptor blockade, abolished the changes in [Ca(2+)](i) and propagation of the calcium wave. These studies provided evidence that both gap junctional communication and extracellular ATP are integral components of the TGF calcium wave.

  12. Ammonium deficiency caused by heterogeneous reactions during a super Asian dust episode

    Science.gov (United States)

    Hsu, Shih-Chieh; Lee, Celine Siu Lan; Huh, Chih-An; Shaheen, Robina; Lin, Fei-Jan; Liu, Shaw Chen; Liang, Mao-Chang; Tao, Jun

    2014-06-01

    Mineral dust particles exert profound impacts on air quality, visibility, and ocean biogeochemistry. Interactions between dust particles and other anthropogenic pollutants modify not only the size spectrum and morphology but also physicochemical properties of dust particles, thereby affecting their radiative properties and ability to act as cloud condensation nuclei and in turn their impact on climate. Here we report field observations on the surface chemical transformations in a super Asian dust plume captured in coastal areas of China and the adjacent marginal seas. The dust plume showed enhanced concentrations of sulfate, nitrate, and calcium along with a decrease in ammonium. The percentages of total Ca in water-soluble form increased from an intrinsic value of ~5% to 25-40% at four stations along the path of the dust plume. From these increases, we estimated the extent to which carbonate was modified by heterogeneous reactions and calculated that the enhanced sulfate and nitrate could account for 40-60% of the observed concentrations. Our observation suggests that the formation of ammonium sulfate via the H2SO4-NH3-H2O ternary system was impeded by heterogeneous reactions in the marine boundary layer when dust loads exceeded a certain threshold. A conceptual model is proposed to elucidate the heterogeneous reactions during the super Asian dust event and their impacts on atmospheric chemistry.

  13. Extracellular calcium sensing receptor in human pancreatic cells

    Science.gov (United States)

    Rácz, G Z; Kittel, Á; Riccardi, D; Case, R M; Elliott, A C; Varga, G

    2002-01-01

    Background and aims: The extracellular calcium sensing receptor (CaR) plays a key role in the calcium homeostatic system and is therefore widely expressed in tissues involved in calcium metabolism. However, the CaR has also been identified in other tissues where its role is less clear. We have investigated the presence of the CaR in the human pancreas. Methods: Messenger RNA for the CaR was detected by reverse transcription-polymerase chain reaction and the protein was localised by immunostaining. CaR function was assayed in Capan-1 cells by measuring intracellular calcium and [3H] thymidine incorporation. Results: The receptor was highly expressed in human pancreatic ducts. It was also expressed in exocrine acinar cells, in islets of Langerhans, and in intrapancreatic nerves and blood vessels. The CaR was expressed in both normal and neoplastic human tissue samples but was detected in only one of five ductal adenocarcinoma cells lines examined. Experiments on the CaR expressing adenocarcinoma cell line Capan-1 showed that the CaR was functional and was linked to mobilisation of intracellular calcium. Stimulation of the CaR reduced Capan-1 cell proliferation. Conclusions: We propose that the CaR may play multiple functional roles in the human pancreas. In particular, the CaR on the duct luminal membrane may monitor and regulate the Ca2+ concentration in pancreatic juice by triggering ductal electrolyte and fluid secretion. This could help to prevent precipitation of calcium salts in the duct lumen. The CaR may also help to regulate the proliferation of pancreatic ductal cells. PMID:12377811

  14. Effect of solute concentration on fibroin regulated biomineralization of calcium phosphate

    Energy Technology Data Exchange (ETDEWEB)

    Kong Xiangdong [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Institute of Biochemistry, Zhejiang Sci-Tech University, Hangzhou 310018 (China); Sun Xiaodan [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China); Cui Fuzhai [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)]. E-mail: cuifz@mail.tsinghua.edu.cn; Ma Chen [Biomaterials Laboratory, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084 (China)

    2006-05-15

    In this paper we used UV/Visible method to study the effect of solute concentration on fibroin regulated biomineralization of calcium phosphate. During the reaction process, ultraviolet-visible spectrophotometer was used to track the extinction in the reaction solution. It is found that kinetics of the biomineralization can be strongly affected by the presence of fibroin. Fibroin with higher concentration has more positive effect on the biomineralization process. Under the appropriate reaction conditions, wave crest and wave trough appear in the kinetic curves of fibroin biomineralization. The wave crest and wave trough phenomenon is mainly related with the process of phase separation. X-ray Diffraction (XRD) result shows the calcium phosphate before the wave trough is mainly amorphous calcium phosphate, while after the wave trough crystal of hydroxyapatite (HA) and brushite (DCPD) are the mainly ingredients.

  15. The effect of compressive loading magnitude on in situ chondrocyte calcium signaling.

    Science.gov (United States)

    Madden, Ryan M J; Han, Sang-Kuy; Herzog, Walter

    2015-01-01

    Chondrocyte metabolism is stimulated by deformation and is associated with structural changes in the cartilage extracellular matrix (ECM), suggesting that these cells are involved in maintaining tissue health and integrity. Calcium signaling is an initial step in chondrocyte mechanotransduction that has been linked to many cellular processes. Previous studies using isolated chondrocytes proposed loading magnitude as an important factor regulating this response. However, calcium signaling in the intact cartilage differs compared to isolated cells. The purpose of this study was to investigate the effect of loading magnitude on chondrocyte calcium signaling in intact cartilage. We hypothesized that the percentage of cells exhibiting at least one calcium signal increases with increasing load. Fully intact rabbit femoral condyle and patellar bone/cartilage samples were incubated in calcium-sensitive dyes and imaged continuously under compressive loads of 10-40 % strain. Calcium signaling was primarily associated with the dynamic loading phase and greatly increased beyond a threshold deformation of about 10 % nominal tissue strain. There was a trend toward more cells exhibiting calcium signaling as loading magnitude increased (p = 0.133). These results provide novel information toward identifying mechanisms underlying calcium-dependent signaling pathways related to cartilage homeostasis and possibly the onset and progression of osteoarthritis.

  16. Calcium supplement: humanity's double-edged sword.

    Science.gov (United States)

    Bunyaratavej, Narong; Buranasinsup, Shutipen

    2011-10-01

    The principle aim of the present study is to investigate the dark side of calcium, pollutions in calcium preparation especially lead (Pb), mercury (Hg) and cadmium (Cd). The collected samples were the different calcium salts in the market and 18 preparations which were classified into 3 groups: Calcium carbonate salts, Chelated calcium and natural-raw calcium. All samples were analyzed for lead, cadmium and mercury by inductively Coupled Plasma Mass Spectrometry (ICP-MS) technique, in house method based on AOAC (2005) 999.10 by ICP-MS. The calcium carbonate and the natural-raw calcium in every sample contained lead at 0.023-0.407 mg/kg of calcium powder. Meanwhile, the natural-raw calcium such as oyster, coral and animal bone showed amount of lead at 0.106-0.384 mg/kg with small amounts of mercury and cadmium. The chelated calcium such as calcium gluconate, calcium lactate and calcium citrate are free of lead.

  17. Measurement of calcium content of gallstones by computed tomography and the relationship between gallbladder function and calcification of gallstones

    Energy Technology Data Exchange (ETDEWEB)

    Yoneda, Masashi; Tamasawa, Naoki; Takebe, Kazuo (Hirosaki Univ. (Japan). School of Medicine); Makino, Isao; Sakuraba, Kiyoshi; Tamura, Toyokazu

    1990-08-01

    To evaluate the relationship between gallbladder function and calcification of gallstones, we studied gallbladder contractility by oral cholecystography, the computed tomography (CT) number of stones for 30 gallstone patients, calcium content of 13 stones operatively extirpated, and the degree of inflammatory change in 13 surgical gallbladder specimens. There was significant correlation between the calcium content and CT numbers of stones, and 1% of the calcium content of gallstone was approximately equal to 40 Hounsfield Units (HU) of the CT number. The calcium content of stones in patients with normal gallbladder contractility was extrapolated to be below 1.5%, while that with poor contractility ranged from 0% to 21%. Additionally there is a possibility that calcium content increases, related to the inflammatory change of gallbladder. Hence our results suggested that measurement of the CT number of stones is useful to evaluate the calcium content of gallstones, and that the gallbladder contractility could be one of the factors to influence calcification of stones. (author).

  18. Capture reactions

    NARCIS (Netherlands)

    Endt, P.M.

    1956-01-01

    Capture reactions will be considered here from the viewpoint of the nuclear spectroscopist. Especially important to him are the capture of neutrons, protons, and alpha particles, which may proceed through narrow resonances, offering a well defined initial state for the subsequent deexcitation proces

  19. Calcium isotope constraints on the end-Permian mass extinction.

    Science.gov (United States)

    Payne, Jonathan L; Turchyn, Alexandra V; Paytan, Adina; Depaolo, Donald J; Lehrmann, Daniel J; Yu, Meiyi; Wei, Jiayong

    2010-05-11

    The end-Permian mass extinction horizon is marked by an abrupt shift in style of carbonate sedimentation and a negative excursion in the carbon isotope (delta(13)C) composition of carbonate minerals. Several extinction scenarios consistent with these observations have been put forward. Secular variation in the calcium isotope (delta(44/40)Ca) composition of marine sediments provides a tool for distinguishing among these possibilities and thereby constraining the causes of mass extinction. Here we report delta(44/40)Ca across the Permian-Triassic boundary from marine limestone in south China. The delta(44/40)Ca exhibits a transient negative excursion of approximately 0.3 per thousand over a few hundred thousand years or less, which we interpret to reflect a change in the global delta(44/40)Ca composition of seawater. CO(2)-driven ocean acidification best explains the coincidence of the delta(44/40)Ca excursion with negative excursions in the delta(13)C of carbonates and organic matter and the preferential extinction of heavily calcified marine animals. Calcium isotope constraints on carbon cycle calculations suggest that the average delta(13)C of CO(2) released was heavier than -28 per thousand and more likely near -15 per thousand; these values indicate a source containing substantial amounts of mantle- or carbonate-derived carbon. Collectively, the results point toward Siberian Trap volcanism as the trigger of mass extinction.

  20. Response to an oral calcium load in nephrolithiasis patients with fluctuating parathyroid hormone and ionized calcium levels

    Directory of Open Access Journals (Sweden)

    Gomes S.A.

    2004-01-01

    Full Text Available the response to an oral calcium load test was assessed in 17 hypercalciuric nephrolithiasis patients who presented elevated parathyroid hormone (PTH irrespective of the ionized calcium (sCa2+ levels. Blood samples were collected at baseline (0 min and at 60 and 180 min after 1 g calcium load for serum PTH, total calcium, sCa2+, and 1.25(OH2D3 determinations. According to the sCa2+ level at baseline, patients were classified as normocalcemic (N = 9 or hypercalcemic (N = 8. Six healthy subjects were also evaluated as controls. Bone mineral density was reduced in 14/17 patients. In the normocalcemic group, mean PTH levels at 0, 60 and 180 min (95 ± 76, 56 ± 40, 57 ± 45 pg/ml, respectively did not differ from the hypercalcemic group (130 ± 75, 68 ± 35, 80 ± 33 pg/ml but were significantly higher compared to healthy subjects despite a similar elevation in sCa2+ after 60 and 180 min vs baseline in all 3 groups. Mean total calcium and 1.25(OH2D3 were similar in the 3 groups. Additionally, we observed that 5 of 9 normocalcemic patients presented a significantly higher concentration-time curve for serum PTH (AUC0',60',180' than the other 4 patients and the healthy subjects, suggesting a primary parathyroid dysfunction. These data suggest that the individual response to an oral calcium load test may be a valuable dynamic tool to disclose a subtle primary hyperparathyroidism in patients with high PTH and fluctuating sCa2+ levels, avoiding repeated measurements of both parameters.

  1. Response to an oral calcium load in nephrolithiasis patients with fluctuating parathyroid hormone and ionized calcium levels

    Directory of Open Access Journals (Sweden)

    S.A. Gomes

    2004-09-01

    Full Text Available the response to an oral calcium load test was assessed in 17 hypercalciuric nephrolithiasis patients who presented elevated parathyroid hormone (PTH irrespective of the ionized calcium (sCa2+ levels. Blood samples were collected at baseline (0 min and at 60 and 180 min after 1 g calcium load for serum PTH, total calcium, sCa2+, and 1.25(OH2D3 determinations. According to the sCa2+ level at baseline, patients were classified as normocalcemic (N = 9 or hypercalcemic (N = 8. Six healthy subjects were also evaluated as controls. Bone mineral density was reduced in 14/17 patients. In the normocalcemic group, mean PTH levels at 0, 60 and 180 min (95 ± 76, 56 ± 40, 57 ± 45 pg/ml, respectively did not differ from the hypercalcemic group (130 ± 75, 68 ± 35, 80 ± 33 pg/ml but were significantly higher compared to healthy subjects despite a similar elevation in sCa2+ after 60 and 180 min vs baseline in all 3 groups. Mean total calcium and 1.25(OH2D3 were similar in the 3 groups. Additionally, we observed that 5 of 9 normocalcemic patients presented a significantly higher concentration-time curve for serum PTH (AUC0',60',180' than the other 4 patients and the healthy subjects, suggesting a primary parathyroid dysfunction. These data suggest that the individual response to an oral calcium load test may be a valuable dynamic tool to disclose a subtle primary hyperparathyroidism in patients with high PTH and fluctuating sCa2+ levels, avoiding repeated measurements of both parameters.

  2. The effect of variable calcium and very low calcium diets on human calcium metabolism. Ph.D. Thesis. Final Report

    Science.gov (United States)

    Chu, J.

    1971-01-01

    The effects of a very low calcium diet, with variable high and low protein intake, on the dynamics of calcium metabolism and the mechanism of calciuretics, are examined. The experiment, using male subjects, was designed to study the role of intestinal calcium absorption on urinary calcium excretion, and the rate of production of endogeneously secreted calcium in the gastrointestinal tract. The study showed an average of 70% fractional absorption rate during very low calcium intake, and that a decrease in renal tubular reabsorption of calcium is responsible for calciuretic effects of high protein intake. The study also indicates that there is a tendency to develop osteoporosis after long periods of low calcium intake, especially with a concurrent high protein intake.

  3. Synthesis and Formation Mechanisms of Calcium Ferrite Compounds

    Institute of Scientific and Technical Information of China (English)

    Hesham I. Saleh

    2004-01-01

    Calcium ferrite compounds were prepared using calcium nitrate and iron nitrate with different molar ratios, 1:1, 0.5:1, and 1:0.5,respectively. The reactions of formation were investigated at different temperatures following the differential thermal analysis (DTA) results. Calcium ferrite compounds are CaFeO3, Ca2FeO3.5, Ca2Fe2O5, CaFe2O4, CaFe4O7, Ca7.2Fe0.8Fe30O53,Ca3Fe15O25, Ca4Fe14O25, and Ca4Fe9O17. Other reactive species of calcium nitrate are still present after firing at 450℃.Compounds were characterized using X-ray diffraction (XRD), DTA, TG, magnetic susceptibility, infrared spectra and scanning electron microscope (SEM). It is concluded that the formation mechanism of Ca-ferrite compounds depends mainly on the valency of iron cations which in role depends on its molar ratio and the existing atmosphere.

  4. Changes in intracellular calcium in brain cells of aged rats

    Institute of Scientific and Technical Information of China (English)

    Yu Li; Yunpeng Cao

    2008-01-01

    BACKGROUND: Studies have shown that voltage-dependent calcium influx, and enhancement of certain calcium-dependent processes in neurons, is related to aging. OBJECTIVE: To observe changes in intracellular calcium ([Ca2+]i) in neurons of aged rats, and to compare with young rats. DESIGN, TIME AND SETTING: A randomized control experiment of neurophysiology was performed at the Central Laboratory of School of Pharmaceutical Science, China Medical University from June to August 2004. MATERIALS: Ten male, healthy, Wistar rats, 19 months old, were selected for the aged group. Ten male, 3-month-old, Wistar rats were selected for the young control group. Fura-2/AM was provided by the Institute of Pharmaceutical Research of Chinese Academy of Medical Sciences, and the F-2000 fluorospectrophotometer was a product of Hitachi, Japan. METHODS: Fluorescence Fura-2 spectrophotometer was used to measure [Ca2+]i in acutely dissociated brain cells of aged and young rats. The concentration of extracellular potassium was controlled by adding different volumes of chloridated potassium solution of high concentration. MAIN OUTCOME MEASURES: [Ca2+]i in neurons of young and aged rats in the presence of 1 mmol/L extracellular calcium concentration and 0 mmol/L (resting state), 5, 10, 20, and 40 mmol/L extracellular potassium. Absolute increase of [Ca2+]i in neurons of young and aged rats when extraceUular potassium was 5,10,20, 40 mmol/L. RESULTS: In the presence of 1 mmol/L extracellular Ca2+ and 0 mmol/L (resting state), 5, 10, 20, and 40 mmol/L extracellular potassium, [Ca2+]i in the neurons of aged rats was significantly less than that in young rats (P 0.05). CONCLUSION: The overload of [Ca2+]i in neurons of aged rats is greater than that of young rats under the same circumstances.

  5. Vitamin D and intestinal calcium absorption.

    Science.gov (United States)

    Christakos, Sylvia; Dhawan, Puneet; Porta, Angela; Mady, Leila J; Seth, Tanya

    2011-12-05

    The principal function of vitamin D in calcium homeostasis is to increase calcium absorption from the intestine. Calcium is absorbed by both an active transcellular pathway, which is energy dependent, and by a passive paracellular pathway through tight junctions. 1,25Dihydroxyvitamin D(3) (1,25(OH)(2)D(3)) the hormonally active form of vitamin D, through its genomic actions, is the major stimulator of active intestinal calcium absorption which involves calcium influx, translocation of calcium through the interior of the enterocyte and basolateral extrusion of calcium by the intestinal plasma membrane pump. This article reviews recent studies that have challenged the traditional model of vitamin D mediated transcellular calcium absorption and the crucial role of specific calcium transport proteins in intestinal calcium absorption. There is also increasing evidence that 1,25(OH)(2)D(3) can enhance paracellular calcium diffusion. The influence of estrogen, prolactin, glucocorticoids and aging on intestinal calcium absorption and the role of the distal intestine in vitamin D mediated intestinal calcium absorption are also discussed.

  6. Synthesis of phenylbutazone calcium and its condition optimization%保泰松钙的合成及条件优化

    Institute of Scientific and Technical Information of China (English)

    严宾; 吴玉祥

    2015-01-01

    目的:研究保泰松钙的合成方法,确定合成工艺中关键参数。方法以保泰松为原料,经碱液溶解及成钙盐两步合成保泰松钙,并分别从氢氧化钠加入量、活性炭脱色温度、乙酸钙加入量及滴加温度和甲基叔丁基醚洗涤温度这5个条件对保泰松钙的合成产率及纯度进行研究。结果优化条件:氢氧化钠加入量为30.0 g、脱色温度为50.0℃、乙酸钙加入量为134.4 g、乙酸钙滴加温度为50.0℃及甲基叔丁基醚洗涤温度为40.0℃,经过优化使得保泰松钙的合成回收率提升至98.6%,纯度达99.7%。结论该优化方法操作简单,反应条件温和且合成得到的保泰松钙结构经质谱和核磁共振证实。%Objective To study the synthetic method of phenylbutazone calcium and to determine the key parameters of synthetic technology. Methods With phenylbutazone as the raw material,phenylbutazone calcium was synthesized by dissolution with alkaline solution and calcium salt forming. The yield rate and purity of phenylbutazone calcium synthesis were researched from the 5 conditions of the adding amount of sodium hydroxide,active carbon decolorization temperature,adding amount of calcium ac-etate and dropwise adding temperature and washing temperature of methyl tertiary butyl ether. Results The optimized conditions were the sodium hydroxide mass of 30.0 g,the decolorization temperature of 50.0℃,the calcium acetate amount of 134.4 g,and the dropwise add temperature of calcium acetate was 50.0℃and the wash temperature of 40.0℃. The recovery rate of phenylbutazone calcium synthesis by optimization was increased to 98.6%and the purity was reached to 99.7%. Conclusion This method is easy to operate and its reaction condition is gentle,moreover the structure of synthesized phenylbutazone calcium is verified by the mass spectrum and nuclear magnetic resonance(NMR).

  7. Calcium electroporation in three cell lines; a comparison of bleomycin and calcium, calcium compounds, and pulsing conditions

    DEFF Research Database (Denmark)

    Frandsen, Stine Krog; Gissel, Hanne; Hojman, Pernille;

    2013-01-01

    electroporation and electrochemotherapy. METHODS: The effects of calcium electroporation and bleomycin electroporation (alone or in combination) were compared in three different cell lines (DC-3F, transformed Chinese hamster lung fibroblast; K-562, human leukemia; and murine Lewis Lung Carcinoma). Furthermore...... survival at similar applied voltage parameters. The effect of calcium electroporation is independent of calcium compound. GENERAL SIGNIFICANCE: This study strongly supports the use of calcium electroporation as a potential cancer therapy and the results may aid in future clinical trials....

  8. Association between calcium ionophore A23187 induced acrosome reaction rate, total acrosin activity and semen analysis, the outcome of in vitro fertilization%钙离子载体A23187诱发的精子顶体反应率、顶体酶总活性与精液参数及体外受精结局的关系研究

    Institute of Scientific and Technical Information of China (English)

    郭小桥; 余波澜; 周华; 司沙沙; 曹定娅; 刘见桥; 孙筱放

    2013-01-01

    Objective To investigate the association between the calcium ionophore A23187 induced sperm acrosome reaction rate, total acrosin activity and semen parameters and the IVF outcome, and to compare the predictive value for the male fertility and the outcome of IVF between calcium ionophore A23187 induced sperm acrosome reaction rate and sperm total acrosoin activity. Methods Sperm acrosome reaction was induced by calcium ionophore A23187,while sperm acrosin activity was determined by the modified Kennedy method. In this study, 150 cycles of IVF-ET were included, which were divided into Normal semen Group (85 cycles), Teratospermia Group (44 cycles), Asthenozoospermia Group (6 cycles). Compare the association between the calcium ionophore A23187 induced sperm acrosome reaction rate, total acrosin activity and normal morphology sperm percentage, concentration, activity in the 150 cycles and subgroups. Analyze the difference of the sperm acrosome reaction rate and total acrosin activity in Pregnancy Group and Non-pregnancy Group. Use the Receiver Operating Characteristic curve to make out the threshold of the sperm acrosome reaction rate and total acrosin activity for predicting the IVF pregnancy outcomes. Results In this 150 samples, there are no statistically significant differences between sperm acrosome reaction rate and sperm concentration, progressive velocity rate, the percentage of normal sperm morphology, fertility rate, and their related coefficient are respectively as follow:0.120, 0.018, 0.084, 0.054(P>0.05). But the negative correlation is statistically significant different between sperm acrosome reaction rate and teratozoospermia index(r=-0.183, P=0.025). There are significant correlations between sperm acrosin activity and sperm concentration(r=0.172, P0.05) and fertility rate(r=0.039, P>0.05). There are no statistically significant differences between sperm acrosome rate and fertility rate in Normal semen Group(r=-0.039, P>0.05), Teratospermia Group

  9. Effects of Silicate, Phosphate, and Calcium on the Stability of Aldopentoses.

    Science.gov (United States)

    Nitta, Sakiko; Furukawa, Yoshihiro; Kakegawa, Takeshi

    2016-06-01

    Ribose is an important constituent of RNA: ribose connects RNA bases and forms a strand of sugar phosphates. Accumulation of ribose on prebiotic Earth was difficult because of its low stability. Improvement in the yield of ribose by the introduction of borate or silicate in a formose-like reaction has been proposed. The effects of borates have been further analyzed and confirmed in subsequent studies. Nonetheless, the effects of silicates and phosphates remain unclear. In the present study, we incubated aldopentoses in a highly alkaline aqueous solution at a moderate temperature to determine the effects of silicate or phosphate on the degradation rates of ribose and its isomeric aldopentoses. The formation of a complex of silicate (or phosphate) with ribose was also analyzed in experiments with (29)Si and (31)P nuclear magnetic resonance (NMR). We found that silicate or phosphate complexes of ribose were not detectable under our experimental conditions. The stability of ribose and lyxose improved after addition of 40-fold molar excess (relative to a pentose) of sodium silicate or sodium phosphate to the alkaline solution. The stability was not improved further when an 80-fold molar excess of sodium silicate or sodium phosphate was added. Calcium was removed from these solutions by precipitation of calcium salts. The drop in Ca(2+) concentration might have improved the stability of ribose and lyxose, which are susceptible to aldol addition. The improvement of ribose stability by the removal of Ca(2+) and by addition of silicate or phosphate was far smaller than the improvement by borate. Furthermore, all aldopentoses showed similar stability in silicate- and phosphate-containing solutions. These results clearly show that selective stabilization of ribose by borate cannot be replaced by the effects of silicate or phosphate; this finding points to the importance of borate in prebiotic RNA formation.

  10. The effect of calcium gluconate and other calcium supplements as a dietary calcium source on magnesium absorption in rats.

    Science.gov (United States)

    Chonan, O; Takahashi, R; Yasui, H; Watanuki, M

    1997-01-01

    The effects of commercially available calcium supplements (calcium carbonate, calcium gluconate, oyster shell preparation and bovine bone preparation) and gluconic acid on the absorption of calcium and magnesium were evaluated for 30 days in male Wistar rats. There were no differences in the apparent absorption ratio of calcium among rats fed each calcium supplement; however, the rats fed the calcium gluconate diet had a higher apparent absorption ratio of magnesium than the rats fed the other calcium supplements. Dietary gluconic acid also more markedly stimulated magnesium absorption than the calcium carbonate diet, and the bone (femur and tibia) magnesium contents of rats fed the gluconic acid diet were significantly higher than those of the rats fed the calcium carbonate diet. Furthermore, the weight of cecal tissue and the concentrations of acetic acid and butyric acid in cecal digesta of rats fed the calcium gluconate diet or the gluconic acid diet were significantly increased. We speculate that the stimulation of magnesium absorption in rats fed the calcium gluconate diet is a result of the gluconic acid component and the effect of gluconic acid on magnesium absorption probably results from cecal hypertrophy, magnesium solubility in the large intestine and the effects of volatile fatty acids on magnesium absorption.

  11. Estimation of presynaptic calcium currents and endogenous calcium buffers at the frog neuromuscular junction with two different calcium fluorescent dyes

    Directory of Open Access Journals (Sweden)

    Dmitry eSamigullin

    2015-01-01

    Full Text Available At the frog neuromuscular junction, under physiological conditions, the direct measurement of calcium currents and of the concentration of intracellular calcium buffers—which determine the kinetics of calcium concentration and neurotransmitter release from the nerve terminal—has hitherto been technically impossible. With the aim of quantifying both Ca2+ currents and the intracellular calcium buffers, we measured fluorescence signals from nerve terminals loaded with the low-affinity calcium dye Magnesium Green or the high-affinity dye Oregon Green BAPTA-1, simultaneously with microelectrode recordings of nerve-action potentials and end-plate currents. The action-potential-induced fluorescence signals in the nerve terminals developed much more slowly than the postsynaptic response. To clarify the reasons for this observation and to define a spatiotemporal profile of intracellular calcium and of the concentration of mobile and fixed calcium buffers, mathematical modeling was employed. The best approximations of the experimental calcium transients for both calcium dyes were obtained when the calcium current had an amplitude of 1.6 ± 0.08 рА and a half-decay time of 1.2 ± 0.06 ms, and when the concentrations of mobile and fixed calcium buffers were 250 ± 13 µM and 8 ± 0.4 mM, respectively. High concentrations of endogenous buffers define the time course of calcium transients after an action potential in the axoplasm, and may modify synaptic plasticity.

  12. Mechanism of store-operated calcium entry

    Indian Academy of Sciences (India)

    Devkanya Dutta

    2000-12-01

    Activation of receptors coupled to the phospholipase C/IP3 signalling pathway results in a rapid release of calcium from its intracellular stores, eventually leading to depletion of these stores. Calcium store depletion triggers an influx of extracellular calcium across the plasma membrane, a mechanism known as the store-operated calcium entry or capacitative calcium entry. Capacitative calcium current plays a key role in replenishing calcium stores and activating various physiological processes. Despite considerable efforts, very little is known about the molecular nature of the capacitative channel and the signalling pathway that activates it. This review summarizes our current knowledge about store operated calcium entry and suggests possible hypotheses for its mode of activation.

  13. The ins and outs of mitochondrial calcium.

    Science.gov (United States)

    Finkel, Toren; Menazza, Sara; Holmström, Kira M; Parks, Randi J; Liu, Julia; Sun, Junhui; Liu, Jie; Pan, Xin; Murphy, Elizabeth

    2015-05-22

    Calcium is thought to play an important role in regulating mitochondrial function. Evidence suggests that an increase in mitochondrial calcium can augment ATP production by altering the activity of calcium-sensitive mitochondrial matrix enzymes. In contrast, the entry of large amounts of mitochondrial calcium in the setting of ischemia-reperfusion injury is thought to be a critical event in triggering cellular necrosis. For many decades, the details of how calcium entered the mitochondria remained a biological mystery. In the past few years, significant progress has been made in identifying the molecular components of the mitochondrial calcium uniporter complex. Here, we review how calcium enters and leaves the mitochondria, the growing insight into the topology, stoichiometry and function of the uniporter complex, and the early lessons learned from some initial mouse models that genetically perturb mitochondrial calcium homeostasis.

  14. Familial hypocalciuric hypercalcemia and calcium sensing receptor

    DEFF Research Database (Denmark)

    Mrgan, Monija; Nielsen, Sanne; Brixen, Kim

    2014-01-01

    Familial hypocalciuric hypercalcemia (FHH) is a lifelong, benign autosomal dominant disease characterized by hypercalcemia, normal to increased parathyroid hormone level, and a relatively low renal calcium excretion. Inactivation of the calcium-sensing receptor in heterozygous patients results in...

  15. Decalcification of calcium polycarbophil in rats.

    Science.gov (United States)

    Yamada, T; Saito, T; Takahara, E; Nagata, O; Tamai, I; Tsuji, A

    1997-03-01

    The in vivo decalcification of calcium polycarbophil was examined. The decalcification ratio of [45Ca]calcium polycarbophil in the stomach after oral dosing to rats was more than 70% at each designated time and quite closely followed in the in vitro decalcification curve, indicating that the greater part of the calcium ion is released from calcium polycarbophil under normal gastric acidic conditions. The residual radioactivity in rat gastrointestine was nearly equal to that after oral administration of either [45Ca]calcium chloride + polycarbophil. The serum level of radioactivity was nearly equal to that after oral dosing of [45Ca]calcium lactate. These results indicate that the greater part of orally administered calcium polycarbophil released calcium ions to produce polycarbophil in vivo.

  16. Mineral/solution reaction rates in a mixed flow reactor: Wollastonite hydrolysis

    Science.gov (United States)

    Rimstidt, J. Donald; Dove, Patricia M.

    1986-11-01

    A newly developed mixed flow reactor was used to measure the rate of hydrolysis of wollastonite over the pH range of 3 to 8. This design avoids abrasion of the solid sample by confining it within a nylon mesh while the reacting solution is circulated over it by a stirrer. The rate of reaction was determined from the difference of the compositions of the input and output solutions following the methods used by chemical engineers for the analysis of mixed flow reactors, also called continuously stirred tank reactors (CSTR). This apparatus, constructed from easily obtainable parts, avoids many of the problems inherent in studying mineral/solution reaction kinetics in batch reactors. The hydrolysis of wollastonite CaSiO3 + 2 H+ + H2O = Ca2+ + H4SiO4 can be fit to a rate law of the form: dnH+/ dt = kadKH+mH+/(1.0 + KH+mH+) where kad = 9.80 × 10 -8molm-2sec-1 and KH+ = 2.08 × 10 5. Over the pH range of 4 to 7, the data also may fit a simple linear form: dnH+/ dt = - Ak+( aH+) 0.40 where k+ = 3.80 × 10 -6 sec -1 at 25°C. The presence of calcium ion in the solution at concentrations up to 1.0 mol kg -1 produces only a minor reduction of the reaction rate. The activation energy for this reaction is 79.2 kJ mol -1. Examination of the surfaces of the reacted grains showed no evidence of incongruent reaction leading to a product layer but did show the extensive development of etch pits leading to a rapid increase in the specific surface area. At large extents of reaction at low pH, diffusion of ions into or from these deep etch pits may limit the reaction rate.

  17. The oxygen evolution reaction on cobalt Part I. Reaction order experiments and impedance measurements

    NARCIS (Netherlands)

    Kobussen, A.G.C.; Willems, H.; Wit, J.H.W. de; Broers, G.H.J.

    1984-01-01

    It was found that the oxygen evolution reaction on cobalt in concentrated KOH solutions can be described differently for low and high overpotentials. In the overpotential range from 150 to 280 mV, the reaction has a Tafel slope of approximately 40 mV and a reaction order with respect to the KOH acti

  18. Effect of airborne particle on SO 2-calcite reaction

    Science.gov (United States)

    Böke, Hasan; Göktürk, E. Hale; Caner-Saltık, Emine N.; Demirci, Şahinde

    1999-02-01

    In modern urban atmosphere, sulphur dioxide (SO 2) attacks calcite (CaCO 3) in calcareous stone-producing gypsum (CaSO 4·2H 2O) which forms crust at rain sheltered surfaces and accelerates erosion at areas exposed to rain. The airborne particles collected on stone surfaces have always been considered to enhance the gypsum crust formation and thus it is believed that they should be removed from the surface to decrease the effects of SO 2. In this study, our aim was to investigate this event by carrying out a series of experiments in laboratory using pure calcium carbonate powder to represent calcareous stone. Sodium montmorillonite, activated carbon, ferric oxide, vanadium pentoxide and cupric chloride were mixed in the pure calcium carbonate powder as substitutes of the airborne particles in the polluted atmosphere. The samples have been exposed at nearly 10 ppmv SO 2 concentrations at 90% relative humidity conditions in a reaction chamber for several days. The mineralogical composition of the exposed samples were determined by X-ray diffraction (XRD) analysis and infrared spectrometer (IR). Sulphation reaction products, calcium sulphite hemihydrate, gypsum and unreacted calcite, were determined quantitatively using IR. Exposed samples have also been investigated morphologically using a scanning electron microscope (SEM). Experimental results reveal that calcium sulphite hemihydrate is the main reaction product of the SO 2-calcite reaction. It turns out that airborne particles play an important catalytic role in the oxidation of calcium sulphite hemihydrate into gypsum, although their presence does not very significantly affect the extent of sulphation reaction. This behaviour of airborne particles is explained by the presence of liquid film on the calcium carbonate surface where a series of reactions in the gas-liquid-solid interfaces takes place.

  19. Calcium channel blockers and Alzheimer's disease

    Institute of Scientific and Technical Information of China (English)

    Yi Tan; Yulin Deng; Hong Qing

    2012-01-01

    Alzheimer's disease is characterized by two pathological hallmarks: amyloid plaques and neurofi-brillary tangles. In addition, calcium homeostasis is disrupted in the course of human aging. Recent research shows that dense plaques can cause functional alteration of calcium signals in mice with Alzheimer's disease. Calcium channel blockers are effective therapeutics for treating Alzheimer's disease. This review provides an overview of the current research of calcium channel blockers in-volved in Alzheimer's disease therapy.

  20. Variable efficacy of calcium carbonate tablets.

    Science.gov (United States)

    Kobrin, S M; Goldstein, S J; Shangraw, R F; Raja, R M

    1989-12-01

    Orally administered calcium carbonate tablets are commonly prescribed as a calcium supplement and for their phosphate-binding effects in renal failure patients. Two cases are reported in which a commercially available brand of calcium carbonate tablets appeared to be ineffective. Formal investigation of the bioavailability of this product revealed it to have impaired disintegration and dissolution and a lack of clinical efficacy. Recommendations that will enable physicians to avoid prescribing and pharmacists to avoid dispensing ineffective calcium carbonate tablets are proposed.

  1. Teaching Calcium-Induced Calcium Release in Cardiomyocytes Using a Classic Paper by Fabiato

    Science.gov (United States)

    Liang, Willmann

    2008-01-01

    This teaching paper utilizes the materials presented by Dr. Fabiato in his review article entitled "Calcium-induced release of calcium from the cardiac sarcoplasmic reticulum." In the review, supporting evidence of calcium-induced calcium release (CICR) is presented. Data concerning potential objections to the CICR theory are discussed as well. In…

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

    Science.gov (United States)

    Runčevski, Tomče; Dinnebier, Robert E; Magdysyuk, Oxana V; Pöllmann, Herbert

    2012-10-01

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

  3. Bone Substitute Fabrication Based on Dissolution-Precipitation Reactions

    Directory of Open Access Journals (Sweden)

    Kunio Ishikawa

    2010-02-01

    Full Text Available Although block- or granular-type sintered hydroxyapatite are known to show excellent tissue responses and good osteoconductivity, apatite powder elicits inflammatory response. For the fabrication of hydroxyapatite block or granules, sintering is commonly employed. However, the inorganic component of bone and tooth is not high crystalline hydroxyapatite but low crystalline B-type carbonate apatite. Unfortunately, carbonate apatite powder cannot be sintered due to its instability at high temperature. Another method to fabricate apatite block and/or granule is through phase transformation based on dissolution-precipitation reactions using a precursor phase. This reaction basically is the same as a setting and hardening reaction of calcium sulfate or plaster. In this paper, apatite block fabrication methods by phase transformation based on dissolution-precipitation reactions will be discussed, with a focus on the similarity of the setting and hardening reaction of calcium sulfate.

  4. 由低品位菱镁矿制备碳酸钙和氧化镁%Preparation of Calcium Carbonate and Magnesia from Low-grade Magnesite

    Institute of Scientific and Technical Information of China (English)

    朱世玲; 张悦; 薛向欣

    2013-01-01

      低品位菱镁矿经煅烧、消化、碳化反应及镁的沉淀反应可制备碳酸钙和氧化镁,沉淀反应产生的氯化钙母液可循环使用,并实现低品位菱镁矿中钙和镁的完全分离。结果表明,低品位菱镁矿950℃煅烧2 h时,其失重率接近理论失重率;煅烧粉末中主要含有MgO和CaO。消化、碳化反应的最佳条件为:反应温度20℃,反应时间1 h,CaCl2过量系数0,CO2流量400 mL/h,相应镁溶出率为95.0%。氧化镁产物中MgO含量为95.6%;碳酸钙产物中MgO和CaO的含量分别为1.24%和53.40%。%The low-grade magnesite was calcined, hydrated and then reacted with CO2 and calcium chloride solution to obtain calcium carbonate and the solution of MgCl2. The precipitation reaction of magnesium was processed to produce MgO, and filtrate of CaCl2 solution can be used circularly. In addition, calcium and magnesium contained in low-grade magnesite was separated. The results showed that the mass loss of the low-grade magnesite calcined at 950℃for 2 h was close to the theoretical mass loss, and the calcined low-grade magnesite mainly contained CaO and MgO. The best conditions of hydrated and carbonized reaction was:20℃for 1 h, the excess coefficient of CaCl2 was 0, and CO2 gas flow of 400 mL/h, under which the dissolved ratio of magnesium was 95.0%. The content of MgO in magnesia was 95.6%, the content of MgO and CaO in calcium carbonate was 1.24%and 53.40%, respectively.

  5. 21 CFR 582.5217 - Calcium phosphate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium phosphate. 582.5217 Section 582.5217 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Supplements 1 § 582.5217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....

  6. 21 CFR 582.1217 - Calcium phosphate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium phosphate. 582.1217 Section 582.1217 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Additives § 582.1217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....

  7. 21 CFR 182.1217 - Calcium phosphate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium phosphate. 182.1217 Section 182.1217 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Substances § 182.1217 Calcium phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic)....

  8. Abnormalities of serum calcium and magnesium

    Science.gov (United States)

    Neonatal hypocalcemia is defined as a total serum calcium concentration of <7 mg/dL or an ionized calcium concentration of <4 mg/dL (1mmol/L). In very low birth weight (VLBW) infants, ionized calcium values of 0.8 to 1 mmol/L are common and not usually associated with clinical symptoms. In larger in...

  9. Acute calcium homeostasis in MHS swine.

    Science.gov (United States)

    Harrison, G G; Morrell, D F; Brain, V; Jaros, G G

    1987-07-01

    To elucidate a pathogenesis for the reduction in bone calcium content observed in MHS individuals, we studied the acute calcium homeostasis of MHS swine. This was achieved by the serial measurement, with a calcium selective electrode, of calcium transients in Landrace MHS (five) and control Landrace/large white cross MH negative (five) swine following IV bolus injection of calcium gluconate 0.1 mmol X kg-1--a dose which induced an acute 45 per cent increase in plasma ionised calcium. Experimental animals were anaesthetised with ketamine 10 mg X kg-1 IM, thiopentone (intermittent divided doses) 15-25 mg X kg-1 (total) IV and N2O/O2 (FIO2 0.3) by IPPV to maintain a normal blood gas, acid/base state. The plasma ionised calcium decay curve observed in MHS swine did not differ from that of control normal swine. Further it was noted that the induced acute rise in plasma ionised calcium failed to trigger the MH syndrome in any MHS swine. It is concluded that the mechanisms of acute calcium homeostasis in MHS swine are normal. An explanation for the reduction in bone calcium content observed in MHS individuals must be sought, therefore, through study of the slow long-term component of the calcium regulatory process. In addition, the conventional strictures placed on the use, in MHS patients, of calcium gluconate are called in question.

  10. 21 CFR 582.6219 - Calcium phytate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium phytate. 582.6219 Section 582.6219 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium phytate. (a) Product. Calcium phytate. (b) Conditions of use. This substance is...

  11. 21 CFR 582.3189 - Calcium ascorbate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium ascorbate. 582.3189 Section 582.3189 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL....3189 Calcium ascorbate. (a) Product. Calcium ascorbate. (b) Conditions of use. This substance...

  12. 21 CFR 182.3189 - Calcium ascorbate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium ascorbate. 182.3189 Section 182.3189 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... Calcium ascorbate. (a) Product. Calcium ascorbate. (b) Conditions of use. This substance is...

  13. 21 CFR 582.7187 - Calcium alginate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Calcium alginate. 582.7187 Section 582.7187 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) ANIMAL... Calcium alginate. (a) Product. Calcium alginate. (b) Conditions of use. This substance is...

  14. Calcium Carbonate versus Sevelamer Hydrochloride as Phosphate Binders after Long-Term Disease Progression in 5/6 Nephrectomized Rats

    Directory of Open Access Journals (Sweden)

    Suvi Törmänen

    2014-01-01

    Full Text Available Our aim was to compare the effects of calcium carbonate and sevelamer-HCl treatments on calcium-phosphate metabolism and renal function in 5/6 nephrectomized (NX rats so that long-term disease progression preceded the treatment. After 15-week progression, calcium carbonate (3.0%, sevelamer-HCl (3.0%, or control diets (0.3% calcium were given for 9 weeks. Subtotal nephrectomy reduced creatinine clearance (−40%, plasma calcidiol (−25%, and calcitriol (−70% and increased phosphate (+37%, parathyroid hormone (PTH (11-fold, and fibroblast growth factor-23 (FGF-23 (4-fold. In NX rats, calcium carbonate diet increased plasma (+20% and urinary calcium (6-fold, reduced plasma phosphate (−50% and calcidiol (−30%, decreased creatinine clearance (−35% and FGF 23 (−85%, and suppressed PTH without influencing blood pH. In NX rats, sevelamer-HCl increased urinary calcium (4-fold and decreased creatinine clearance (−45%, PTH (−75%, blood pH (by 0.20 units, plasma calcidiol (−40%, and calcitriol (−65%. Plasma phosphate and FGF-23 were unchanged. In conclusion, when initiated after long-term progression of experimental renal insufficiency, calcium carbonate diet reduced plasma phosphate and FGF-23 while sevelamer-HCl did not. The former induced hypercalcemia, the latter induced acidosis, while both treatments reduced vitamin D metabolites and deteriorated renal function. Thus, delayed initiation influences the effects of these phosphate binders in remnant kidney rats.

  15. Calcium pyrophosphate deposition disease: clinical manifestations

    Directory of Open Access Journals (Sweden)

    M.A. Cimmino

    2012-01-01

    Full Text Available Calcium pyrophosphate deposition (CPPD disease is an arthropathy caused by calcium pyrophosphate dihydrate (CPP crystal deposits in articular tissues, most commonly fibrocartilage and hyaline cartilage. According to EULAR, four different clinical presentations can be observed: 1 asymptomatic CPPD; 2 osteoarthritis (OA with CPPD; 3 acute CPP crystal arthritis; 4 chronic CPP inflammatory crystal arthritis. Acute CPP crystal arthritis is characterized by sudden onset of pain, swelling and tenderness with overlying erythema, usually in a large joint, most often the knee, wrist, shoulder, and hip. Occasionally, ligaments, tendons, bursae, bone and the spine can be involved. CPPD of the atlanto-occipital joint (crowned dens syndrome can cause periodic acute cervico-occipital pain with fever, neck stiffness and laboratory inflammatory syndrome. Chronic inflammatory arthritis is characterized by joint swelling, morning stiffness, pain, and high ESR and CRP. The relationship between OA and CPPD is still unclear. The main problem is whether such crystals are directly involved in the pathogenesis of OA or if they are the result of joint degeneration. Diagnosis is based on evaluation of history and clinical features, conventional radiology, and synovial fluid examination. Non-polarized light microscopy should be used initially to screen for CPPD crystals based upon their characteristic morphology, and compensated polarized light microscopy, showing the crystals to be weakly positive birefringent, is recommended for definitive identification, although this last pattern only occurs in about 20% of samples. The main goals of CPPD therapy are control of the acute or chronic inflammatory reaction and prevention of further episodes.

  16. Oxalate co-precipitation synthesis of calcium zirconate and calcium titanate powders.

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez-Sanchez, Bernadette A.; Tuttle, Bruce Andrew

    2009-06-01

    Fine powders of calcium zirconate (CaZrO{sub 3}, CZ) and calcium titanate (CaTiO{sub 3}, CT) were synthesized using a nonaqueous oxalate co-precipitation route from Ca(NO{sub 3}){sub 2}{center_dot}4 H{sub 2}O and group(IV) n-butoxides (Ti(OBu{sup n}){sub 4} or Zr(OBu{sup n}){sub 4}). Several reaction conditions and batch sizes (2-35 g) were explored to determine their influence on final particle size, morphology, and phase. Characterization of the as-prepared oxalate precursors, oven dried oxalate precursors (60-90 C), and calcined powders (635-900 C) were analyzed with TGA/DTA, XRD, TEM, and SEM. Densification and sintering studies on pressed CZ pellets at 1375 and 1400 C were also performed. Through the developed oxalate co-precipitation route, densification temperatures for CZ were lowered by 125 C from the 1500 C firing temperature required for conventional mixed oxide powders. Low field electrical tests of the CZ pellets indicated excellent dielectric properties with dielectric constants of {approx}30 and a dissipation factor of 0.0004 were measured at 1 kHz.

  17. Experimental research on combustion fluorine retention using calcium-based sorbets during coal combustion (Ⅰ)

    Institute of Scientific and Technical Information of China (English)

    QI Qing-jie; LIN Zhi-yan; LIU Jian-zhong; WU Xian; ZHOU Jun-hu; CEN Ke-fa

    2008-01-01

    In order to provide experimental guide to commercial use of fluorine pollution control during coal combustion, with fluorine pollution control during coal combustion in mind, this paper proposed the theory of combustion fluorine retention technology. Feasibility of fluorine retention reaction with calcium-based fluorine retention agent was analyzed through thermo-dynamic calculation during coal combustion. By simulating the restraining and retention effects and influential factors of calcium-based sorbets on vaporized fluoride during experimental combustion using fixed bed tube furnace, the paper systematically explored the influential law of such factors as combustion temperature, retention time, and added quantities of calcium-based sorbets on effects of fluorine retention. The research result shows that adding calcium-based fluorine retention agent in coal combustion has double effects of fluorine retention and sulfur retention, it lays an experimental foundation for commercial test of combustion fluorine retention.

  18. Evaluation of the Chemical and Mechanical Properties of Hardening High-Calcium Fly Ash Blended Concrete

    Directory of Open Access Journals (Sweden)

    Wei-Jie Fan

    2015-09-01

    Full Text Available High-calcium fly ash (FH is the combustion residue from electric power plants burning lignite or sub-bituminous coal. As a mineral admixture, FH can be used to produce high-strength concrete and high-performance concrete. The development of chemical and mechanical properties is a crucial factor for appropriately using FH in the concrete industry. To achieve sustainable development in the concrete industry, this paper presents a theoretical model to systematically evaluate the property developments of FH blended concrete. The proposed model analyzes the cement hydration, the reaction of free CaO in FH, and the reaction of phases in FH other than free CaO. The mutual interactions among cement hydration, the reaction of free CaO in FH, and the reaction of other phases in FH are also considered through the calcium hydroxide contents and the capillary water contents. Using the hydration degree of cement, the reaction degree of free CaO in FH, and the reaction degree of other phases in FH, the proposed model evaluates the calcium hydroxide contents, the reaction degree of FH, chemically bound water, porosity, and the compressive strength of hardening concrete with different water to binder ratios and FH replacement ratios. The evaluated results are compared to experimental results, and good consistencies are found.

  19. Calcium oxalate monohydrate precipitation investigation by thermometric method

    Science.gov (United States)

    Söhnel, O.; Costa-Bauzá, A.; Velich, V.

    1993-01-01

    Calcium oxalate monohydrate (COM) precipitation from diluted solutions of 100 mol m -3 ionic strength at 25°C was studied by an isoperibolic reaction twin calorimeter. The molar reaction enthalpy was determined as - 17.5 kJ mol -1. Results achieved with a pure system were highly reproducible. Citrate, pyrophosphate and phytate retard COM precipitation that is manifested mainly by an induction period appearance and a decrease of the initial precipitation rate. Effect of the studied impurities on individual precipitation experiments carried out under identical conditions was to some extent "random", i.e. the reaction extent reached at arbitrary time considerably differed for individual experiments. Impurity effectiveness in retarding spontaneous precipitation increases in succession citrate phytate.

  20. Do proton pump inhibitors decrease calcium absorption?

    Science.gov (United States)

    Hansen, Karen E; Jones, Andrea N; Lindstrom, Mary J; Davis, Lisa A; Ziegler, Toni E; Penniston, Kristina L; Alvig, Amy L; Shafer, Martin M

    2010-12-01

    Proton pump inhibitors (PPIs) increase osteoporotic fracture risk presumably via hypochlorhydria and consequent reduced fractional calcium absorption (FCA). Existing studies provide conflicting information regarding the direct effects of PPIs on FCA. We evaluated the effect of PPI therapy on FCA. We recruited women at least 5 years past menopause who were not taking acid suppressants. Participants underwent three 24-hour inpatient FCA studies using the dual stable isotope method. Two FCA studies were performed 1 month apart to establish baseline calcium absorption. The third study occurred after taking omeprazole (40 mg/day) for 30 days. Each participant consumed the same foods during all FCA studies; study meals replicated subjects' dietary habits based on 7-day diet diaries. Twenty-one postmenopausal women ages 58 ± 7 years (mean ± SD) completed all study visits. Seventeen women were white, and 2 each were black and Hispanic. FCA (mean ± SD) was 20% ± 10% at visit 1, 18% ± 10% at visit 2, and 23% ± 10% following 30 ± 3 days of daily omeprazole (p = .07, ANOVA). Multiple linear regression revealed that age, gastric pH, serum omeprazole levels, adherence to omeprazole, and 25-hydroxyvitamin D levels were unrelated to changes in FCA between study visits 2 and 3. The 1,25-dihydroxyvitamin D(3) level at visit 2 was the only variable (p = .049) associated with the change in FCA between visits 2 and 3. PPI-associated hypochlorhydria does not decrease FCA following 30 days of continuous use. Future studies should focus on identifying mechanisms by which PPIs increase the risk of osteoporotic fracture.

  1. Nicotine alpha 4 beta 2 receptor-mediated free calcium in an animal model of facial nucleus injury

    Institute of Scientific and Technical Information of China (English)

    Dawei Sun; Wenhai Sun; Yanqing Wang; Fugao Zhu; Rui Zhou; Yanjun Wang; Banghua Liu; Xiuming Wan; Huamin Liu

    2010-01-01

    Previous studies have demonstrated that the cholinergic system,via nicotinic receptors,regulates intracellular free calcium levels in the facial nucleus under normal physiological conditions.However,the regulation of nicotinic receptors on free calcium levels following facial nerve injury remains unclear.In the present study,an animal model of facial nerve injury was established,and changes in nicotinic receptor expression following facial nerve injury in rats were detected using reverse transcription polymerase chain reaction.Nicotinic receptor-mediated changes of free calcium levels following facial nucleus injury were determined by laser confocal microscopy.Results showed no significant difference in nicotinic receptor expression between the normal group and the affected facial nerve nucleus.The nicotinic receptor α4β2 subtype increased free calcium levels following facial nerve injury by promoting calcium transmembrane influx,and L-type voltage-gated calcium channel-mediated influx of calcium ions played an important role in promoting calcium transmembrane influx.The nicotinic receptor-mediated increase of free calcium levels following facial nerve injury provides an important mechanism for the repair of facial nerve injury.

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

    Science.gov (United States)

    Zhou, Huan

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

  3. Heterogeneous uptake and reactivity of formic acid on calcium carbonate particles: a Knudsen cell reactor, FTIR and SEM study.

    Science.gov (United States)

    Al-Hosney, Hashim A; Carlos-Cuellar, Sofia; Baltrusaitis, Jonas; Grassian, Vicki H

    2005-10-21

    The heterogeneous uptake and reactivity of formic acid (HCOOH), a common gas-phase organic acid found in the environment, on calcium carbonate (CaCO(3)) particles have been investigated using a Knudsen cell reactor, Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). FTIR measurements show that the adsorption of formic acid on the surface of calcium carbonate results in the formation of calcium formate. Besides calcium formate, carbonic acid is also a reaction product under dry conditions (dry conditions and at low pressures, the initial uptake coefficient of formic acid on CaCO(3) particles is measured to be 3 +/- 1 x 10(-3) and decreases as the surface saturates with adsorbed products. The maximum surface coverage of formic acid under dry conditions is determined to be (3 +/- 1)x 10(14) molecules cm(-2). Under humidified conditions (RH >10%), adsorbed water on the surface of the carbonate particles participates in the surface reactivity of these particles, which results in the enhanced uptake kinetics and extent of reaction of this organic acid on CaCO(3) as well as opens up several new reaction pathways. These reaction pathways include: (i) the water-assisted dissociation of carbonic acid to CO(2) and H(2)O and (ii) the formation of calcium formate islands and crystallites, as evident by SEM images. The results presented here show that adsorbed water plays a potentially important role in the surface chemistry of gas-phase organic acids on calcium carbonate particles.

  4. Calcium biofortification and bioaccessibility in soilless "baby leaf" vegetable production.

    Science.gov (United States)

    D'Imperio, Massimiliano; Renna, Massimiliano; Cardinali, Angela; Buttaro, Donato; Serio, Francesco; Santamaria, Pietro

    2016-12-15

    Calcium is an essential nutrient for human health, because it is a structural component and takes part in a variety of biological processes. The aim of this study was to increase Ca content of baby leaf vegetables (BLV: basil, mizuna, tatsoi and endive), as fresh-cut products. For the production of biofortified BLV, a floating system with two level of Ca (100 and 200mgL(-1)) in the nutrient solution was used. In addition, the assessment of bioaccessibility of Ca, by in vitro digestion process, was performed. In all vegetables, the Ca biofortification (200mgL(-1)) caused a significant Ca enrichment (9.5% on average) without affecting vegetables growth, oxalate contents and marketable quality. Calcium bioaccessibility ranged from 25% (basil) to 40% (endive) but the biofortified vegetables showed more bioaccessible Ca. These results underline the possibility to obtain Ca biofortified BLV by using agronomic approaches.

  5. Exploration of As(III)/As(V) Uptake from Aqueous Solution by Synthesized Calcium Sulfate Whisker☆

    Institute of Scientific and Technical Information of China (English)

    Xiaojuan Chen; Liuchun Yang; Junfeng Zhang; Yan Huang

    2014-01-01

    Although common calcium-containing minerals such as calcite and gypsum may fix arsenic, the interaction be-tween modified calcic minerals and arsenic has seldom been reported. The uptake behavior of As(III)/As(V) from aqueous solutions by calcium sulfate whisker (CSW, dihydrate or anhydrite) synthesized through a cooling recrystal ization method was explored. A series of batch experiments were conducted to examine the effect of pH, reaction time, whisker dosage, and initial As concentration. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the samples prepared. The results showed that pH of the aqueous solution was an important parameter for As(III)/As(V) uptake, and an excellent removal efficiency could be achieved under strongly alkaline condition. The data from batch experiments for reaction of As(V) with calcium sulfate dihydrate whisker (CSDW) and calcium sulfate anhydrous whisker (CSAW) were well described with extended Langmuir EXT1 model, from which theoretic maximum adsorption capacity of 46.57 mg As(V)·(g CSDW)−1 and 39.18 mg As(V)·(g CSAW)−1 were obtained. Some calcium arsenate solids products, such as CaAsO3(OH) (weilite, syn), Ca3(AsO4)2 (calcium arsenate), CaO–As2O5, Ca–As–O, Ca5(AsO4)3OH·xH2O (calcium arsenate hydroxide hydrate), and CaH(AsO4)·2H2O (hydrogen calcium arsenic oxide hydrate), were detected at pH = 12.5 through XRD analysis. This indicates that the interaction mechanism between As(V) and CSW is a complex adsorption process combined with surface dissolution and chemical precipitation.

  6. Dihydropyridine type calcium channel blocker-induced turbid dialysate in patients undergoing peritoneal dialysis.

    Science.gov (United States)

    Yoshimoto, K; Saima, S; Nakamura, Y; Nakayama, M; Kubo, H; Kawaguchi, Y; Nishitani, H; Nakamura, Y; Yasui, A; Yokoyama, K; Kuriyama, S; Shirai, D; Kugiyama, A; Hayano, K; Fukui, H; Horigome, I; Amagasaki, Y; Tsubakihara, Y; Kamekawa, T; Ando, R; Tomura, S; Okamoto, R; Miwa, S; Koyama, T; Echizen, H

    1998-08-01

    We previously reported that manidipine, a new dihydropyridine type calcium channel blocker, produced chylous peritoneal dialysate being visually indistinguishable from infective peritonitis in 5 patients undergoing continuous ambulatory peritoneal dialysis (CAPD) [Yoshimoto et al. 1993]. To study whether such an adverse drug reaction would also be elicited by other commonly prescribed calcium channel blockers in CAPD patients, we have conducted postal inquiry to 15 collaborating hospitals and an institutional survey in International Medical Center of Japan as to the possible occurrence of calcium channel blocker-associated non-infective, turbid peritoneal dialysate in CAPD patients. Our diagnostic criteria for drug-induced turbidity of dialysate as a) it developed within 48 h after the administration of a newly introduced calcium channel blocker to the therapeutic regimen, b) absence of clinical symptoms of peritoneal inflammation (i.e., pyrexia, abdominal pain, nausea or vomiting), c) the fluid containing normal leukocyte counts and being negative for bacterial and fungal culture of the fluid, and d) it disappeared shortly after the withdrawal of the assumed causative agent. Results showed that 19 out of 251 CAPD patients given one of the calcium channel blockers developed non-infective turbid peritoneal dialysis that fulfilled all the above criteria. Four calcium channel blockers were suspected to be associated with the events: benidipine [2 out of 2 (100%) patients given the drug], manidipine [15 out of 36 (42%) patients], nisoldipine [1 out of 11 (9%) patients] and nifedipine [1 out of 159 (0.6%)] in descending order of frequency. None of the patients who received nicardipine, nilvadipine, nitrendipine, barnidipine and diltiazem (25, 7, 2, 1 and 8 patients, respectively) exhibited turbid dialysate. In conclusion, we consider that certain dihydropyridine type calcium channel blockers would cause turbid peritoneal dialysate being similar to that observed in

  7. Calcium signaling mediates antifungal activity of triazole drugs in the Aspergilli.

    Science.gov (United States)

    Liu, Fei-fei; Pu, Li; Zheng, Qing-qing; Zhang, Yuan-wei; Gao, Rong-sui; Xu, Xu-shi; Zhang, Shi-zhu; Lu, Ling

    2015-08-01

    Azoles are widely applied and largely effective as antifungals; however, the increasing prevalence of clinically resistant isolates has yet to be matched by approaches to improve the efficacy of antimicrobial therapy. In this study, using the model fungus Aspergillus nidulans and one of the most common human pathogen Aspergillus fumigatus as research materials, we present the evidence that calcium signaling is involved in the azole-antifungals-induced stress-response reactions. In normal media, antifungal-itraconazole (ITZ) is able to induce the [Ca(2+)]c increased sharply but the addition of calcium chelator-EGTA or BAPTA almost blocks the calcium influx responses, resulted in the dramatically decreasing of [Ca(2+)]c transient. Real-time PCR analysis verified that six-tested Ca(2+)-inducible genes-two calcium channels (cchA/midA), a calmodulin-dependent phosphatase-calcineurin (cnaA), a transcription factor-crzA, and two calcium transporters (pmrA/pmcA)-could be transiently up-regulated by adding ITZ, indicating these components are involved in the azole stress-response reaction. Defect of cnaA or crzA caused more susceptibility to azole antifungals than did single mutants or double deletions of midA and cchA. Notably, EGTA may influence Rh123 accumulation as an azole-mimicking substrate through the process of the drug absorption. In vivo studies of a Galleria mellonella model identified that the calcium chelator works as an adjunct antifungal agent with azoles for invasive aspergillosis. Most importantly, combination of ITZ and EGTA or ITZ with calcium signaling inhibitor-FK506 greatly enhances the ITZ efficacy. Thus, our study provides potential clues that specific inhibitors of calcium signaling could be clinically useful adjuncts to conventional azole antifungals in the Aspergilli.

  8. Effect of soluble calcium on the renneting properties of casein micelles as measured by rheology and diffusing wave spectroscopy.

    Science.gov (United States)

    Sandra, S; Ho, M; Alexander, M; Corredig, M

    2012-01-01

    Addition of calcium chloride to milk has positive effects on cheese-making because it decreases coagulation time, creates firmer gels, and increases curd yield. Although addition of calcium chloride is a widely used industrial practice, the effect of soluble calcium on the preliminary stages of gelation is not fully understood. In addition, it is not known whether the manner of addition and equilibration of the soluble calcium would affect the rennetability of the casein micelles. Therefore, the aim of this paper was to study the details of the coagulation behavior of casein micelles in the presence of additional calcium, and to elucidate whether the manner in which this cation is added (directly as calcium chloride or by gradual exchange through dialysis) affects the functionality of the micelles. Calcium was added as CaCl(2) (1 mM final added concentration) directly to skim milk or indirectly using dialysis against 50 volumes of milk. Additional soluble calcium did not affect the primary phase of the renneting reaction, as demonstrated by the analysis of the casein macropeptide (CMP) released in solution; however, it shortened the coagulation time of the micelles and increased the firmness of the gel. The turbidity parameter of samples with or without calcium showed that similar amounts of CMP were needed for particle interactions to commence. However, the amount of CMP released at the point of gelation, as indicated by rheology, was lesser for samples with added calcium, which can be attributed to a greater extent of calcium bridging on the surface or between micelles. The results also showed that the manner in which calcium was presented to the micelles did not influence the mechanism of gelation.

  9. Presynaptic calcium signalling in cerebellar mossy fibres

    DEFF Research Database (Denmark)

    Thomsen, Louiza Bohn; Jörntell, Henrik; Midtgaard, Jens

    2010-01-01

    Whole-cell recordings were obtained from mossy fibre terminals in adult turtles in order to characterize the basic membrane properties. Calcium imaging of presynaptic calcium signals was carried out in order to analyse calcium dynamics and presynaptic GABA B inhibition. A tetrodotoxin (TTX....... Calcium imaging using Calcium-Green dextran revealed a stimulus-evoked all-or-none TTX-sensitive calcium signal in simple and complex rosettes. All compartments of a complex rosette were activated during electrical activation of the mossy fibre, while individual simple and complex rosettes along an axon......)-sensitive fast Na(+) spike faithfully followed repetitive depolarizing pulses with little change in spike duration or amplitude, while a strong outward rectification dominated responses to long-lasting depolarizations. High-threshold calcium spikes were uncovered following addition of potassium channel blockers...

  10. Store-operated calcium signaling in neutrophils.

    Science.gov (United States)

    Clemens, Regina A; Lowell, Clifford A

    2015-10-01

    Calcium signals in neutrophils are initiated by a variety of cell-surface receptors, including formyl peptide and other GPCRs, FcRs, and integrins. The predominant pathway by which calcium enters immune cells is termed SOCE, whereby plasma membrane CRAC channels allow influx of extracellular calcium into the cytoplasm when intracellular ER stores are depleted. The identification of 2 key families of SOCE regulators, STIM calcium "sensors" and ORAI calcium channels, has allowed for genetic manipulation of SOCE pathways and provided valuable insight into the molecular mechanism of calcium signaling in immune cells, including neutrophils. This review focuses on our current knowledge of the molecules involved in neutrophil SOCE and how study of these molecules has further informed our understanding of the role of calcium signaling in neutrophil activation.

  11. Drosophila mushroom body Kenyon cells generate spontaneous calcium transients mediated by PLTX-sensitive calcium channels.

    Science.gov (United States)

    Jiang, Shaojuan Amy; Campusano, Jorge M; Su, Hailing; O'Dowd, Diane K

    2005-07-01

    Spontaneous calcium oscillations in mushroom bodies of late stage pupal and adult Drosophila brains have been implicated in memory consolidation during olfactory associative learning. This study explores the cellular mechanisms regulating calcium dynamics in Kenyon cells, principal neurons in mushroom bodies. Fura-2 imaging shows that Kenyon cells cultured from late stage Drosophila pupae generate spontaneous calcium transients in a cell autonomous fashion, at a frequency similar to calcium oscillations in vivo (10-20/h). The expression of calcium transients is up regulated during pupal development. Although the ability to generate transients is a property intrinsic to Kenyon cells, transients can be modulated by bath application of nicotine and GABA. Calcium transients are blocked, and baseline calcium levels reduced, by removal of external calcium, addition of cobalt, or addition of Plectreurys toxin (PLTX), an insect-specific calcium channel antagonist. Transients do not require calcium release from intracellular stores. Whole cell recordings reveal that the majority of voltage-gated calcium channels in Kenyon cells are PLTX-sensitive. Together these data show that influx of calcium through PLTX-sensitive voltage-gated calcium channels mediates spontaneous calcium transients and regulates basal calcium levels in cultured Kenyon cells. The data also suggest that these calcium transients represent cellular events underlying calcium oscillations in the intact mushroom bodies. However, spontaneous calcium transients are not unique to Kenyon cells as they are present in approximately 60% of all cultured central brain neurons. This suggests the calcium transients play a more general role in maturation or function of adult brain neurons.

  12. Mechanism of calcium phosphates precipitation in liquid crystals; Mecanisme de precipitation de phosphates de calcium dans des cristaux liquides

    Energy Technology Data Exchange (ETDEWEB)

    Prelot, B.; Zemb, T

    2004-04-01

    The possibility of using as a precursor an easily wet meso-porous powder would be a breakthrough in the preparation of nuclear waste storage ceramics. A concentrated solution containing ions to be stored would wet a dry powder and then, subjected to mild compression, lead to a micro-crystalline matrix of calcium phosphate at acceptable temperatures. Since no porous calcium phosphate different from calcined bone (patented) is described as porous precursor, we have compared the different synthesis routes towards meso-porous ceramics. First, we considered homogeneous precipitation of slats in water: using initially off-stoichiometry in reaction, micron-sized hydroxyapatite particles are produced with a specific surface up to 100 m{sup 2}/g. Then, we consider the classical route of precipitation of an hybrid material in the miscibility gap of a phase diagram, when an hexagonal liquid crystal is used a matrix for precipitation. The surfactant family consists in single chain surfactants containing phosphates as head-group to poison the growing surface of calcium phosphate nano-domains. Since the reaction is still too brutal, we considered using a cat-anionic precursor material of controllable surface charge. For certain concentrations and molar ratios, a new structure not yet described in surfactant precipitation literature is observed: since the periodicity is lower than twice the chain length, a disordered constant curvature monolayer (instead of the classical cylinder of twice chain length diameter) of surfactant is implied. Finally, we have investigated synthesis routes implying slow dissolution of pre-formed calcium phosphate in an already existing hexagonal matrix. For all these routes of synthesis, micro-structural determinations using SAXS, WARS and BET are performed, with a special attention to comparison of the precipitation material, the matrix obtained with all elements present, and also the material obtained after calcinations. (authors)

  13. Assessing HER2 amplification by IHC, FISH, and real-time polymerase chain reaction analysis (real-time PCR) following LCM in formalin-fixed paraffin embedded tissue from 40 women with ovarian cancer.

    Science.gov (United States)

    Hillig, Thore; Thode, Jørgen; Breinholt, Marie F; Franzmann, Maria-Benedicte; Pedersen, Carsten; Lund, Flemming; Mygind, Henrik; Sölétormos, György; Rudnicki, Martin

    2012-12-01

    We compare HER2 receptor amplification analysis by immunohistochemistry (IHC), fluorescence in situ hybridization (FISH), and real-time polymerase chain reaction (real-time PCR) DNA copy-number assay following laser capture microdissection (LCM) in formalin-fixed paraffin embedded tissue from 40 women with verified ovarian cancer. We speculate that LCM should result in a more accurate assessment of HER2 amplification in our real-time PCR assay compared with IHC and FISH. HER2 overexpression measured by IHC, FISH, or real-time PCR was found in 5.0%, 5.0%, and 22.5%, respectively. HER2 negative results measured by IHC, FISH, or real-time PCR were found in 95%, 92.5%, and 60.0%, respectively. Analysis failed for IHC, FISH, or real-time PCR in 0%, 2.5%, or 17.5% of cases. Concordance between IHC and FISH, IHC and real-time PCR, or FISH and real-time PCR were 89.7%, 72.7%, or 78.1%, respectively. Only few ovarian cancer patients were HER2 overexpressed measured by IHC or FISH and thus could be eligible for antibody-based therapy with trastuzumab (Herceptin). Interestingly, we find an increased number of HER2 positive patients by real-time PCR analysis on microdissected cancer cells, suggesting a number of HER2 positive patients not detected by current methods. Thus, the concept of quantitative measurement of HER2 on microdissected cancer cells should be explored further.

  14. Isothermal calorimetry of enzymatic biodiesel reaction

    DEFF Research Database (Denmark)

    Fjerbæk Søtoft, Lene; Westh, Peter; Christensen, Knud Villy

    2010-01-01

    reaction mixture kinetics using ITC. It is possible to determine thermodynamic properties like reaction enthalpy and reaction rate, and the difficulty in actually measuring the true non-mass transfer limited reaction kinetics is exposed by the high time resolution of ITC. Based on the measured enthalpy...... and composition change in the system, the heat of reaction at 40°C for the two systems has been determined to -9.8 ± 0.9 kJ/mole biodiesel formed from rapeseed oil and methanol, and - 9.3 ± 0.7 kJ/mole when rapeseed oil and ethanol is used....

  15. Evaluation of therapeutic effect of salmon calcitonin, alfacalcidol, calcium carbonate in the treatment of 40 cases of osteoporotic intertrochanteric fractures%鲑降钙素、阿法骨化醇、碳酸钙联合应用治疗骨质疏松性股骨粗隆间骨折40例疗效分析

    Institute of Scientific and Technical Information of China (English)

    王思成; 刘祥飞; 吴献民; 何金国; 张友忠; 杨国庆

    2013-01-01

      目的:比较鲑降钙素、阿法骨化醇、碳酸钙联合应用与单用鲑降钙素治疗骨质疏松性股骨粗隆间骨折的临床疗效。方法:将80例行闭合复位PFNA内固定术治疗的骨质疏松性股骨粗隆间骨折患者,随机分为实验组及对照组。分别给予肌注鲑降钙素+口服阿法骨化醇和碳酸钙和单纯肌注鲑降钙素。治疗6个月及1年后测定骨密度值及观察骨折愈合时间并进行比较。结果:实验组治疗6个月和1年后腰椎和股骨颈,Ward三角及大转子4个部位BMD较对照组均显著上升(P<0.05)。实验组与对照组比较,骨折愈合时间有显著性差异。结论:闭合复位PFNA内固定术治疗骨质疏松性股骨粗隆间骨折后,给予肌注鲑降钙素+口服阿法骨化醇和钙剂可显著提高患者的骨密度,缩短骨折的愈合时间,明显优于单纯给予肌注鲑降钙素的疗效。%ABSTRACT Objective:To study the clinical efficacy of a monotherapy of salmon calcitonin or a combination therapy of salmon calcitonin with alfacalcidol and calcium carbonate on osteoporotic intertrochanteric fracture. Methods:Eighty patients with osteoporotic intertrochanteric fractures who received a reduction and internal fixation with PFNA were randomly divided into either experimental group or control one. Patients in experimental group were administrated with intramuscular salmon calcitonin plus oral alfacalcidol and calcium carbonate while only intramuscular salmon calcitonin was given in control group. BMD was measured again after 6 months or 1 year treatment, and fracture healing time was observed. The obtained data were statistically analyzed. Results:BMD of lumbar spine, neck of femur, trochiter and Ward’s triangular area were more significantly increased in experimental group than in control group (P<0.05). The comparisons of fracture healing time between two groups showed significant differences. Conclusion:After closed reduction

  16. Mechanisms of calcium transport in small intestine. Overall review of the contract, September 1, 1972--March 1, 1976

    Energy Technology Data Exchange (ETDEWEB)

    DeLuca, H.F.

    1976-01-01

    Progress is reported in the following areas of research: role of high molecular weight protein in calcium transport in vitamin D deficient chicks; subcellular localization of 1,25-(OH)/sub 2/D/sub 3/; receptor proteins for 1,25-(OH)/sub 2/D/sub 3/; effects of high calcium diet, strontium diet, EHDP, and parathyroidectomy on intestinal calcium transport in chicks; effects of analogs of 1,25-(OH)/sub 2/D/sub 3/ on intestinal calcium transport; discrimination by chicks against vitamin D/sub 2/ compounds by metabolism; effects of extract of Solanum malacoxylan on intestinal calcium absorption in nephrectomized rats; and role of vitamin D in phosphate transport reactions in the intestine. (HLW)

  17. Real-time study of the modification of the peptide bond by atomic calcium.

    Science.gov (United States)

    Kummer, Kurt; Vyalikh, Denis V; Blüher, Anja; Sivkov, Victor; Maslyuk, Volodymyr V; Bredow, Thomas; Mertig, Ingrid; Mertig, Michael; Molodtsov, Serguei L

    2011-03-17

    Strong chemical interaction between bacterial surface protein layers and calcium atoms deposited in situ on top was revealed by means of photoemission spectroscopy. The interaction appears to mainly happen at the oxygen site of the peptide bonds and involves a large charge transfer from Ca 4s states into the peptide backbone. Chemical kinetics of this reaction was characterized using time-dependent valence band photoemission, and the reaction rate constant was determined.

  18. Class and Home Problems: Carbon Dioxide Capture from Coal-Fired Power Plants Using Calcium Looping

    Science.gov (United States)

    Deshpande, Niranjani; Phalak, Nihar; Fan, Liang-Shih; Sundaresan, Sankaran

    2015-01-01

    Calcium looping is based on the simple premise of the reversible reaction between CO[subscript 2] and CaO. This reaction can be used for separation of CO2 from a mixture of gases; most notably the technology finds applications in CO[subscript 2] removal from gas streams in fossil fuel-based energy systems. This article gives a brief overview of…

  19. Calcium channel antagonists in hypertension.

    Science.gov (United States)

    Ambrosioni, E; Borghi, C

    1989-02-01

    The clinical usefulness of calcium entry-blockers for the treatment of high blood pressure is related to their capacity to act upon the primary hemodynamic derangement in hypertension: the increased peripheral vascular resistance. They can be used alone or in combination with other antihypertensive agents for the treatment of various forms of hypertensive disease. The calcium entry-blockers appear to be the most useful agents for the treatment of hypertension in the elderly and for the treatment of hypertension associated with ischemic heart disease, pulmonary obstructive disease, peripheral vascular disease, and supraventricular arrhythmias. They are effective in reducing blood pressure in pregnancy-associated hypertension and must be considered as first-line therapy for the treatment of hypertensive crisis.

  20. Calcium isotopic compositions of mid-ocean ridge basalts

    Science.gov (United States)

    Zhu, H.; Zhang, Z.; Sun, W.; Wang, G. Q.

    2015-12-01

    Previous studies have demonstrated that Earth's mantle has heterogeneous calcium isotopic compositions. But the reason why mantle has its heterogeneity remains uncertain. In general, δ44/40Ca values of mantle xenolith samples have a variation of >0.45‰. While ultramafic rocks, especially dunites, have higher δ44/40Ca values than volcanic rocks, and there is a positive correlation between δ44/40Ca and Ca/Mg. These phenomena imply that the heterogeneity of Ca isotopic compositions of mantle xenolith samples might result from different degrees of melt extraction, as indicated by large Ca isotopic fractionation between co-existing clinopyroxene and orthopyroxene. However, because ancient marine carbonate has its own unique calcium isotopic characteristics, recycling of even a small amount of ancient marine carbonates into the mantle could also cause the heterogeneity of Ca isotopes in Earth's mantle. This could be the reason why oceanic island basalts (OIB) have lighter Ca isotopic compositions than the mantle xenolith. Thus, the lighter Ca isotopic compositions in the mantle source cannot only be ascribed to magmatic processes. Therefore, it is more important to know calcium isotopic characteristics during partial melting and oceanic crust contamination.Mid-ocean ridge basalts (MORB) are formed from the partial melts of the upper mantle and are rarely affected by crustal contamination. Different types of MORB, including D-MORB, N-MORB and E-MORB, have experienced different degrees of partial melting and contamination of enriched end-members. Here we report calcium isotopic characteristic of different types of MORB, we believe it will be very helpful to understand the behaviors of Ca isotopes during partial melting and it is possible to provide further information to discover the reason why calcium isotopic compositions is heterogeneous in Earth's mantle. This work was supported by Natural Science Foundation of China (No. 41373007, No. 41490632 and No. 91328204

  1. The calcium-alkali syndrome

    OpenAIRE

    Arroyo, Mariangeli; Fenves, Andrew Z.; Emmett, Michael

    2013-01-01

    The milk-alkali syndrome was a common cause of hypercalcemia, metabolic alkalosis, and renal failure in the early 20th century. It was caused by the ingestion of large quantities of milk and absorbable alkali to treat peptic ulcer disease. The syndrome virtually vanished after introduction of histamine-2 blockers and proton pump inhibitors. More recently, a similar condition called the calcium-alkali syndrome has emerged as a common cause of hypercalcemia and alkalosis. It is usually caused b...

  2. Calcium phosphate polymer hybrid materials

    OpenAIRE

    2011-01-01

    Calcium phosphate (CaP) is of strong interest to the medical field because of its potential for bone repair, gene transfection, etc.1-3 Nowadays, the majority of the commercially available materials are fabricated via “classical” materials science approaches, i.e. via high temperature or high pressure approaches, from rather poorly defined slurries, or from organic solvents.3,4 Precipitation of inorganics with (polymeric) additives from aqueous solution on the other hand enables the synthesis...

  3. The use of calcium carbide in one-pot synthesis of symmetric diaryl ethynes.

    Science.gov (United States)

    Zhang, Weiwei; Wu, Huayue; Liu, Zhiqing; Zhong, Ping; Zhang, Lin; Huang, Xiaobo; Cheng, Jiang

    2006-12-14

    An efficient Pd-catalyzed copper and amine free coupling reaction of acetylene and aryl bromides was achieved with calcium carbide as an acetylene source, using inorganic base and easily prepared, air-stable aminophosphine ligand in common organic solvents, providing symmetric diaryl ethynes in one-pot with yields ranged from moderate to excellent.

  4. CCN3 and calcium signaling

    Directory of Open Access Journals (Sweden)

    Li Chang Long

    2003-08-01

    Full Text Available Abstract The CCN family of genes consists presently of six members in human (CCN1-6 also known as Cyr61 (Cystein rich 61, CTGF (Connective Tissue Growth Factor, NOV (Nephroblastoma Overexpressed gene, WISP-1, 2 and 3 (Wnt-1 Induced Secreted Proteins. Results obtained over the past decade have indicated that CCN proteins are matricellular proteins, which are involved in the regulation of various cellular functions, such as proliferation, differentiation, survival, adhesion and migration. The CCN proteins have recently emerged as regulatory factors involved in both internal and external cell signaling. CCN3 was reported to physically interact with fibulin-1C, integrins, Notch and S100A4. Considering that, the conformation and biological activity of these proteins are dependent upon calcium binding, we hypothesized that CCN3 might be involved in signaling pathways mediated by calcium ions. In this article, we review the data showing that CCN3 regulates the levels of intracellular calcium and discuss potential models that may account for the biological effects of CCN3.

  5. Store-Operated Calcium Channels.

    Science.gov (United States)

    Prakriya, Murali; Lewis, Richard S

    2015-10-01

    Store-operated calcium channels (SOCs) are a major pathway for calcium signaling in virtually all metozoan cells and serve a wide variety of functions ranging from gene expression, motility, and secretion to tissue and organ development and the immune response. SOCs are activated by the depletion of Ca(2+) from the endoplasmic reticulum (ER), triggered physiologically through stimulation of a diverse set of surface receptors. Over 15 years after the first characterization of SOCs through electrophysiology, the identification of the STIM proteins as ER Ca(2+) sensors and the Orai proteins as store-operated channels has enabled rapid progress in understanding the unique mechanism of store-operate calcium entry (SOCE). Depletion of Ca(2+) from the ER causes STIM to accumulate at ER-plasma membrane (PM) junctions where it traps and activates Orai channels diffusing in the closely apposed PM. Mutagenesis studies combined with recent structural insights about STIM and Orai proteins are now beginning to reveal the molecular underpinnings of these choreographic events. This review describes the major experimental advances underlying our current understanding of how ER Ca(2+) depletion is coupled to the activation of SOCs. Particular emphasis is placed on the molecular mechanisms of STIM and Orai activation, Orai channel properties, modulation of STIM and Orai function, pharmacological inhibitors of SOCE, and the functions of STIM and Orai in physiology and disease.

  6. Effective radii of deuteron induced reactions

    CERN Document Server

    Hashimoto, Shintaro; Ogata, Kazuyuki; Minomo, Kosho; Chiba, Satoshi

    2011-01-01

    The continuum-discretized coupled-channels method (CDCC) for exclusive reactions and the eikonal reaction theory (ERT) as an extension of CDCC to inclusive reactions are applied to deuteron induced reactions. The CDCC result reproduces experimental data on the reaction cross section for $d+^{58}$Ni scattering at 200 MeV/nucleon and ERT does data on the neutron-stripping cross section for inclusive $^7$Li$(d,n)$ reaction at 40 MeV. For deuteron induced reactions at 200 MeV/nucleon, target-dependence of the reaction, elastic-breakup, nucleon-stripping, nucleon-removal, complete- and incomplete-fusion cross sections is clearly explained by simple formulae. Accuracy of the Glauber model is also investigated.

  7. —Part I. Interaction of Calcium and Copper-Calcium Alloy with Electrolyte

    Science.gov (United States)

    Zaikov, Yurii P.; Batukhtin, Victor P.; Shurov, Nikolay I.; Ivanovskii, Leonid E.; Suzdaltsev, Andrey V.

    2014-06-01

    This paper describes the interaction between calcium and molten CaCl2 and the solubility of calcium in this melt, depending on the calcium content in the copper-calcium alloy that comes in contact with the molten CaCl2. The negative influence of the dissolved calcium on the current efficiency was verified. The negative effects of moisture and CaO impurities on the calcium current efficiency were demonstrated. The dependence of the current efficiency and the purity of the metal obtained by the electrolysis conditions were studied in a laboratory electrolyzer (20 to 80 A).

  8. Autogenous vein graft thrombosis following exposure to calcium-free solutions (calcium paradox).

    Science.gov (United States)

    Nozick, J H; Farnsworth, P; Montefusco, C M; Parsonnet, V; Ruigrok, T J; Zimmerman, A N

    1981-01-01

    The morphological and functional effects of calcium-free and calcium-containing solutions on canine jugular vein intima were examined under conditions which closely resemble those techniques currently employed in peripheral vascular and aortocoronary bypass surgery. Veins that had been exposed only to calcium-containing solutions remained patent for the duration of the experimental period. Vein perfusion with a calcium-free solution, however, resulted in disruption of the jugular vein intima once calcium ions were reintroduced. Autogenous as a femoral arterial graft became thrombosed within 60 minutes. It is therefore suggested that vein grafts of autogenous origin be irrigated with calcium-containing solutions to prevent intimal damage and thrombosis.

  9. Vitamin D-enhanced duodenal calcium transport.

    Science.gov (United States)

    Wongdee, Kannikar; Charoenphandhu, Narattaphol

    2015-01-01

    For humans and rodents, duodenum is a very important site of calcium absorption since it is exposed to ionized calcium released from dietary complexes by gastric acid. Calcium traverses the duodenal epithelium via both transcellular and paracellular pathways in a vitamin D-dependent manner. After binding to the nuclear vitamin D receptor, 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] upregulates the expression of several calcium transporter genes, e.g., TRPV5/6, calbindin-D9k, plasma membrane Ca(2+)-ATPase1b, and NCX1, thereby enhancing the transcellular calcium transport. This action has been reported to be under the regulation of parathyroid-kidney-intestinal and bone-kidney-intestinal axes, in which the plasma calcium and fibroblast growth factor-23 act as negative feedback regulators, respectively. 1,25(OH)2D3 also modulates the expression of tight junction-related genes and convective water flow, presumably to increase the paracellular calcium permeability and solvent drag-induced calcium transport. However, vitamin D-independent calcium absorption does exist and plays an important role in calcium homeostasis under certain conditions, particularly in neonatal period, pregnancy, and lactation as well as in naturally vitamin D-impoverished subterranean mammals.

  10. Calcium channel as a potential anticancer agent.

    Science.gov (United States)

    Kriazhev, L

    2009-11-01

    Anticancer treatment in modern clinical practices includes chemotherapy and radiation therapy with or without surgical interventions. Efficiency of both methods varies greatly depending on cancer types and stages. Besides, chemo- and radiotherapy are toxic and damaging that causes serious side effects. This fact prompts the search for alternative methods of antitumor therapy. It is well known that prolonged or high increase of intracellular calcium concentration inevitably leads to the cell death via apoptosis or necrosis. However, stimulation of cell calcium level by chemical agents is hardly achievable because cells have very sophisticated machinery for maintaining intracellular calcium in physiological ranges. This obstacle can be overridden, nevertheless. It was found that calcium channels in so called calcium cells in land snails are directly regulated by extracellular calcium concentration. The higher the concentration the higher the calcium intake is through the channels. Bearing in mind that extracellular/intracellular calcium concentration ratio in human beings is 10,000-12,000 fold the insertion of the channel into cancer cells would lead to fast and uncontrollable by the cells calcium intake and cell death. Proteins composing the channel may be extracted from plasma membrane of calcium cells and sequenced by mass-spectrometry or N-terminal sequencing. Either proteins or corresponding genes could be used for targeted delivery into cancer cells.

  11. Variations in onset of action potential broadening: effects on calcium current studied in chick ciliary ganglion neurones.

    Science.gov (United States)

    Pattillo, J M; Artim, D E; Simples, J E; Meriney, S D

    1999-02-01

    1. The voltage dependence and kinetic properties of stage 40 ciliary ganglion calcium currents were determined using short (10 ms) voltage steps. These properties aided the interpretation of the action potential-evoked calcium current described below, and the comparison of our data with those observed in other preparations. 2. Three different natural action potential waveforms were modelled by a series of ramps to generate voltage clamp commands. Calcium currents evoked by these model action potentials were compared before and after alterations in the repolarization phase of each action potential. 3. Abrupt step repolarizations from various time points were used to estimate the time course of calcium current activation during each action potential. Calcium current evoked by fast action potentials (duration at half-amplitude, 0.5 or 1.0 ms) did not reach maximal activation until the action potential had repolarized by 40-50 %. In contrast, calcium current evoked by a slow action potential (duration at half-amplitude, 2.2 ms) was maximally activated near the peak of the action potential. 4. Slowing the rate of repolarization of the action potential (broadening) from different times was used to examine effects on peak and total calcium influx. With all three waveforms tested, broadening consistently increased total calcium influx (integral). However, peak calcium current was either increased or decreased depending on the duration of the control action potential tested and the specific timing of the initiation of broadening the repolarization phase. 5. The opposite effects on peak calcium current observed with action potential broadening beginning at different time points in repolarization may provide a mechanism for the variable effects of potassium channel blockers on transmitter release magnitude.

  12. Clogging and Cementation Caused by Calcium or Iron Biogrouts

    Science.gov (United States)

    Ivanov, V.; Chu, J.; Naeimi, M.

    2012-12-01

    Chemical grouts are often used to reduce the hydraulic conductivity of soil for seepage control purposes. However, chemical grouts can be expensive and environmentally unfriendly. Therefore, two new biogrouts were tested for their bioclogging and biocementation properties. The first was calcium-based biogrout, which contained urease-producing bacteria, calcium chloride and urea for the crystallization of calcite due to enzymatic hydrolysis of urea. The second was iron-based biogrout, which consisted of urease-producing bacteria, ferric chelate, and urea for the precipitation of ferric hydroxide and carbonate due to enzymatic hydrolysis of urea. The permeability of sand (P, 10^-5 m/s), treated with calcium-based biogrout, linearly decreased as a function of the content of precipitated calcium (C, % w/w) according to the following equation: P = 5.1 - 4.0 C. Meanwhile, the permeability of sand treated with iron-based biogrout dropped to 2.7x10^-6 m/s at content of precipitated iron (F, % w/w) about 0.35 % w/w , by the equation: P = 5.1 - 14.6 F , and then slowly decreased to 1.4x10^-7 m/s at content of precipitated iron 1.8% w/w by the following equation: P = 0.36 - 0.23F. Both biogrouts have approximately same efficiency in the reduction of permeability of sand to low values. However, the mechanisms of bioclogging are probably different because the reduction of permeability by calcium-based biogrout was described by linear function of precipitated calcium but the reduction of permeability by iron-based biogrout showed two steps of the clogging. Different functions and mechanisms were related probably to the different type of precipitates. The images of biogrouted sand samples show that calcium-based biogrout produced white amorphous or crystallised calcium carbonate, while iron-based biogrout produced gel-like brown precipitate without visible crystals. The unconfined compressive strengths of the sand treated with different biogrouts (Y, kPa) increased by power

  13. Calcium carbonate crystallisation at the microscopic level

    CERN Document Server

    Dobson, P S

    2001-01-01

    The primary concern of this thesis is the investigation of crystal nucleation and growth processes, and the effect of foreign substrates on the rate, extent and mechanism of crystallisation, with particular emphasis on the calcium carbonate system. A methodology, based on the in-line mixing of two stable solutions, which permits the continuous delivery of a solution with a constant, known supersaturation, has been developed and characterised. This has been used to induce CaCO sub 3 crystallisation in experimental systems involving the channel flow and wall jet techniques. The channel flow method has been adapted to facilitate the study of crystal growth at a single calcite crystal. Ca sup 2 sup + ion selective electrodes have been employed as a means of monitoring depletion of the supersaturated solution, downstream of the crystal substrate. The data obtained suggested a growth rate constant of 3x10 sup - sup 1 sup 2 mol cm sup - sup 2 s sup - sup 1 (and a reaction order of 1.52 on supersaturation). The ex-si...

  14. Thermodynamics and Kinetics of Calcium Sulphoaluminate

    Institute of Scientific and Technical Information of China (English)

    GUO Huiling; XIE Junlin

    2011-01-01

    The formation process of calcium suphoaluminate(C4A3S)was investigated by the X-ray diffraction technique and then the thermodynamics was analyzed,finally the kinetics of which was studied by SC-132.XRD results show that the formation of C4A3S is accomplished in three different kinds of ways:one is by solid reaction of Ca(OH)2/CaO,Al2O3 and CaSO4,other two ways are through such interstitial products as ℃ and increases as temperature rising;the quantity of reaches the highest at 1300 ℃-1350 ℃ and then falls at >1350℃.Kinetics study shows that the formation rate of C4A3S can be described as first-order kinetics at high temperature,and it belongs to the random nucleation growth mechanism.The apparent activation energy is 456.37 kJ·mol-1 and pre-exponential factor is 1.545×1012.

  15. Calcium signals can freely cross the nuclear envelope in hippocampal neurons: somatic calcium increases generate nuclear calcium transients

    Directory of Open Access Journals (Sweden)

    Bading Hilmar

    2007-07-01

    Full Text Available Abstract Background In hippocampal neurons, nuclear calcium signaling is important for learning- and neuronal survival-associated gene expression. However, it is unknown whether calcium signals generated by neuronal activity at the cell membrane and propagated to the soma can unrestrictedly cross the nuclear envelope to invade the nucleus. The nuclear envelope, which allows ion transit via the nuclear pore complex, may represent a barrier for calcium and has been suggested to insulate the nucleus from activity-induced cytoplasmic calcium transients in some cell types. Results Using laser-assisted uncaging of caged calcium compounds in defined sub-cellular domains, we show here that the nuclear compartment border does not represent a barrier for calcium signals in hippocampal neurons. Although passive diffusion of molecules between the cytosol and the nucleoplasm may be modulated through changes in conformational state of the nuclear pore complex, we found no evidence for a gating mechanism for calcium movement across the nuclear border. Conclusion Thus, the nuclear envelope does not spatially restrict calcium transients to the somatic cytosol but allows calcium signals to freely enter the cell nucleus to trigger genomic events.

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

    Science.gov (United States)

    Romanchik-Cerpovicz, Joelle E; McKemie, Rebecca J

    2007-03-01

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

  17. Effectiveness of nano-calcium phosphate paste on sensitivity during and after bleaching: a randomized clinical trial

    OpenAIRE

    LOGUERCIO, Alessandro Dourado; Lidia Yileng TAY; HERRERA,Daniel Rodrigo; Bauer,Jose; Reis, Alessandra

    2015-01-01

    The study aimed to evaluate the effectiveness of in-office bleaching and associated tooth sensitivity on application of nano-calcium phosphate paste as desensitizing agent. Bleaching was performed with 35% hydrogen peroxide gel in 40 patients who were randomly divided into placebo and nano-calcium phosphate paste groups. Bleaching efficacy (BE) was evaluated using a value-oriented Vita shade guide. Tooth sensitivity was recorded using a numeric rating scale (0–4) during bleaching and up...

  18. Calcium Carbide: A Unique Reagent for Organic Synthesis and Nanotechnology.

    Science.gov (United States)

    Rodygin, Konstantin S; Werner, Georg; Kucherov, Fedor A; Ananikov, Valentine P

    2016-04-01

    Acetylene, HC≡CH, is one of the primary building blocks in synthetic organic and industrial chemistry. Several highly valuable processes have been developed based on this simplest alkyne and the development of acetylene chemistry has had a paramount impact on chemical science over the last few decades. However, in spite of numerous useful possible reactions, the application of gaseous acetylene in everyday research practice is rather limited. Moreover, the practical implementation of high-pressure acetylene chemistry can be very challenging, owing to the risk of explosion and the requirement for complex equipment; special safety precautions need to be taken to store and handle acetylene under high pressure, which limit its routine use in a standard laboratory setup. Amazingly, recent studies have revealed that calcium carbide, CaC2 , can be used as an easy-to-handle and efficient source of acetylene for in situ chemical transformations. Thus, calcium carbide is a stable and inexpensive acetylene precursor that is available on the ton scale and it can be handled with standard laboratory equipment. The application of calcium carbide in organic synthesis will bring a new dimension to the powerful acetylene chemistry.

  19. A honeycomb composite of mollusca shell matrix and calcium alginate.

    Science.gov (United States)

    You, Hua-jian; Li, Jin; Zhou, Chan; Liu, Bin; Zhang, Yao-guang

    2016-03-01

    A honeycomb composite is useful to carry cells for application in bone, cartilage, skin, and soft tissue regenerative therapies. To fabricate a composite, and expand the application of mollusca shells as well as improve preparing methods of calcium alginate in tissue engineering research, Anodonta woodiana shell powder was mixed with sodium alginate at varying mass ratios to obtain a gel mixture. The mixture was frozen and treated with dilute hydrochloric acid to generate a shell matrix/calcium alginate composite. Calcium carbonate served as the control. The composite was transplanted subcutaneously into rats. At 7, 14, 42, and 70 days after transplantation, frozen sections were stained with hematoxylin and eosin, followed by DAPI, β-actin, and collagen type-I immunofluorescence staining, and observed using laser confocal microscopy. The composite featured a honeycomb structure. The control and composite samples displayed significantly different mechanical properties. The water absorption rate of the composite and control group were respectively 205-496% and 417-586%. The composite (mass ratio of 5:5) showed good biological safety over a 70-day period; the subcutaneous structure of the samples was maintained and the degradation rate was lower than that of the control samples. Freezing the gel mixture afforded control over chemical reaction rates. Given these results, the composite is a promising honeycomb scaffold for tissue engineering.

  20. Calcium Impact on Milk Gels Formation

    DEFF Research Database (Denmark)

    Koutina, Glykeria

    and dense gel structure and with little seperation of whey due to participation of calcium to the final gel structure. On the other hand, the combination of heat treatment and calcium addition to milk with pH values lower than 5.6 will still produce gel structures which are dominated by the decrease of p......Calcium is one of the several elements that can be found in milk distributed between the micellar and the serum milk phase. Calcium is important from a nutritional point of view, but its contribution to the functional and structural properties of dairy products has only recently been...... acknowledgement. The presence of calcium in a dynamic equilibrium between the serum and the micellar milk phase make the distribution susceptible to certain physicochemical conditions and to technological treatments of milk resulting in fluctuations in pH and temperature and also sensitive to addition of calcium...

  1. Altered calcium signaling in cancer cells.

    Science.gov (United States)

    Stewart, Teneale A; Yapa, Kunsala T D S; Monteith, Gregory R

    2015-10-01

    It is the nature of the calcium signal, as determined by the coordinated activity of a suite of calcium channels, pumps, exchangers and binding proteins that ultimately guides a cell's fate. Deregulation of the calcium signal is often deleterious and has been linked to each of the 'cancer hallmarks'. Despite this, we do not yet have a full understanding of the remodeling of the calcium signal associated with cancer. Such an understanding could aid in guiding the development of therapies specifically targeting altered calcium signaling in cancer cells during tumorigenic progression. Findings from some of the studies that have assessed the remodeling of the calcium signal associated with tumorigenesis and/or processes important in invasion and metastasis are presented in this review. The potential of new methodologies is also discussed. This article is part of a Special Issue entitled: Membrane channels and transporters in cancers.

  2. Morphology and Physical Properties of Calcium Zincate%锌负极材料锌酸钙的晶体形貌和物化性质研究

    Institute of Scientific and Technical Information of China (English)

    金达莱; 岳林海; 徐铸德

    2005-01-01

    Polymorphic calcium zincate has been successfully synthesized in alkaline solution at various concentrations as well as at different temperatures. SEM images indicated that the concentration of the alkaline solution affected significantly the morphology of the calcium zincate crystal. Calcium zincate crystalline changed from regular parallelogram to unregular small crashed grains at a higher alkali concentration. And hexagonal calcium zincare crystal was obtained at higher reaction temperature. The stoichiometric composition for calcium zincate was Ca(OH)2·2Zn(OH)2·(2n-2)H2O as analyzed by TG, where n decreased with the increase of the alkaline concentration. XRD analysis showed that the temperature affected differently the growth of each face of the crystal, which led to the hexagonal shape of calcium zincate crystal.

  3. Influence of Calcium on the Initial Stages of the Sol-Gel Synthesis of Bioactive Glasses.

    Science.gov (United States)

    Côté, Alexander S; Cormack, Alastair N; Tilocca, Antonio

    2016-11-17

    Understanding how calcium interacts with silica sources and influences their polycondensation in aqueous solutions is of central importance for the development of more effective biomaterials by sol-gel approaches. For this purpose, the atomic-scale evolutions of a calcium-containing precursor solution corresponding to a typical sol-gel bioactive glass and of a corresponding Ca-free solution were compared using reactive molecular dynamics simulations. The simulations highlight a significantly faster rate of condensation when calcium is present in the initial solution, resulting in the formation of large and ramified silica clusters within 5 ns, which are absent in the Ca-free system. This different behavior has been analyzed and interpreted in terms of the Ca-induced nanosegregation in calcium-rich and silica-rich regions, which promotes the condensation reactions within the latter. By identifying a possible mechanism behind the limited incorporation of calcium in the silica nanoclusters formed in the early stages of the sol-gel process, these results could guide further studies aimed at identifying favorable experimental conditions to enhance initial calcium incorporation and thus produce sol-gel biomaterials with improved properties.

  4. T-type calcium channel expression in cultured human neuroblastoma cells

    Institute of Scientific and Technical Information of China (English)

    Xianjie Wen; Shiyuan Xu; Lingling Wang; Hua Liang; Chengxiang Yang; Hanbing Wang; Hongzhen Liu

    2011-01-01

    Human neuroblastoma cells (SH-SY5Y) have similar structures and functions as neural cells and have been frequently used for cell culture studies of neural cell functions. Previous studies have revealed Land N-type calcium channels in SH-SY5Y cells. However, the distribution of the low -voltage activated calcium channel (namely called T-type calcium channel, including Cav3.1, Cav3.2, and Cav3.3) in SH-SY5Y cells remains poorly understood. The present study detected mRNA and protein expression of the T-type calcium channel (Cav3.1, Cav3.2, and Cav3.3) in cultured SH-SY5Y cells using real-time polymerase chain reaction (PCR) and western blot analysis. Results revealed mRNA and protein expression from all three T-type calcium channel subtypes in SH-SY5Y cells. Moreover,Cav3.1 was the predominant T-type calcium channel subtype in SH-SY5Y cells.

  5. Unexpectedly large charge radii of neutron-rich calcium isotopes

    Science.gov (United States)

    Garcia Ruiz, R. F.; Bissell, M. L.; Blaum, K.; Ekström, A.; Frömmgen, N.; Hagen, G.; Hammen, M.; Hebeler, K.; Holt, J. D.; Jansen, G. R.; Kowalska, M.; Kreim, K.; Nazarewicz, W.; Neugart, R.; Neyens, G.; Nörtershäuser, W.; Papenbrock, T.; Papuga, J.; Schwenk, A.; Simonis, J.; Wendt, K. A.; Yordanov, D. T.

    2016-06-01

    Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain `magic’ numbers of protons and neutrons. The calcium chain in particular is both unique and puzzling: evidence of doubly magic features are known in 40,48Ca, and recently suggested in two radioactive isotopes, 52,54Ca. Although many properties of experimentally known calcium isotopes have been successfully described by nuclear theory, it is still a challenge to predict the evolution of their charge radii. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. The experimental results are complemented by state-of-the-art theoretical calculations. The large and unexpected increase of the size of the neutron-rich calcium isotopes beyond N = 28 challenges the doubly magic nature of 52Ca and opens new intriguing questions on the evolution of nuclear sizes away from stability, which are of importance for our understanding of neutron-rich atomic nuclei.

  6. Unexpectedly large charge radii of neutron-rich calcium isotopes

    CERN Document Server

    Garcia Ruiz, R F; Blaum, K; Ekström, A; Frömmgen, N; Hagen, G; Hammen, M; Hebeler, K; Holt, J D; Jansen, G R; Kowalska, M; Kreim, K; Nazarewicz, W; Neugart, R; Neyens, G; Nörtershäuser, W; Papenbrock, T; Papuga, J; Schwenk, A; Simonis, J; Wendt, K A; Yordanov, D T

    2016-01-01

    Despite being a complex many-body system, the atomic nucleus exhibits simple structures for certain ‘magic’ numbers of protons and neutrons. The calcium chain in particular is both unique and puzzling: evidence of doubly magic features are known in 40,48Ca, and recently suggested in two radioactive isotopes, 52,54Ca. Although many properties of experimentally known calcium isotopes have been successfully described by nuclear theory, it is still a challenge to predict the evolution of their charge radii. Here we present the first measurements of the charge radii of 49,51,52Ca, obtained from laser spectroscopy experiments at ISOLDE, CERN. The experimental results are complemented by state-of-the-art theoretical calculations. The large and unexpected increase of the size of the neutron-rich calcium isotopes beyond N = 28 challenges the doubly magic nature of 52Ca and opens new intriguing questions on the evolution of nuclear sizes away from stability, which are of importance for our understanding of neutron-...

  7. Overbased Calcium sulfonate Detergent Technology Overview

    Institute of Scientific and Technical Information of China (English)

    MA Qing-gao; MUIR Ronald J.

    2009-01-01

    Overbased calcium sulfonate is used widely as detergent in automotive and marine lubricants, as well as various industrial oil applications. In this paper, the process to produce overbased calcium sulfonate is overviewed. The sulfonate structure and molecular weight and its molecular weight distribution, the enclosed calcium carbonate nanoparticle size and crystalline structure, properties of the carrier oil, all influence its properties, such as stability, viscosity, and detergency of the system.

  8. Calcium phosphates and glass composite coatings on zirconia for enhanced biocompatibility.

    Science.gov (United States)

    Kim, Hae-Won; Georgiou, George; Knowles, Jonathan C; Koh, Young-Hag; Kim, Hyoun-Ee

    2004-08-01

    Calcium phosphates (CaP) and phosphate-based glass (P-glass, xCaO-(0.55-x) Na(2)O-0.45P(2)O(5) composition) composite coatings were obtained on a strong ZrO(2) to improve biocompatibility, the mechanical strength and biological activity. Hydroxyapatite (HA) and P-glass mixed powder slurries were coated on the ZrO(2) substrate, and subsequently heat-treated to obtain CaP- and P-glass composite coatings. The effects of glass composition (x=0.3, 0.4, 0.5 mol), mixing ratio of glass to HA (30%, 40%, 50% wt/wt), and heat treatment temperature (800 degrees C, 900 degrees C, 1000 degrees C) on the coating properties were investigated. After heat treatment, additional calcium phosphates, i.e., dicalcium phosphate (DCP) and tricalcium phosphate (TCP), were crystallized, resulting in the formation of triphasic calcium phosphates (HA-TCP-DCP) surrounded by a glass phase. The relative amounts of the crystalline phases varied with coating variables. The higher heat treatment temperature and glass amount, and the lower CaO content in the glass composition rendered the composite coatings to retain the higher amounts of TCP and DCP while the initial HA decreased. These appearance of additional crystalline phases and reduction of HA amount were attributed to the combined effects, i.e., the melting-crystallization of P-glass and the reaction between glass liquid phase and HA powder during thermal treatment. As a result of the glass phase in the composite coatings, their microstructures became much denser when compared to the pure HA coating. In particular, a completely dense structure was obtained at coating conditions with large amount of glass addition (50 wt%) at the glass composition of lower CaO content (0.3 mol CaO), and the following heat treatment above 800 degrees C for 2h. As a result, the adhesion strengths of the composite coating layers were significantly improved when compared to the pure HA coating. The highest strength of the composite coating was approximately 40

  9. Osteoblasts detect pericellular calcium concentration increase via neomycin-sensitive voltage gated calcium channels.

    Science.gov (United States)

    Sun, Xuanhao; Kishore, Vipuil; Fites, Kateri; Akkus, Ozan

    2012-11-01

    The mechanisms underlying the detection of critically loaded or micro-damaged regions of bone by bone cells are still a matter of debate. Our previous studies showed that calcium efflux originates from pre-failure regions of bone matrix and MC3T3-E1 osteoblasts respond to such efflux by an increase in the intracellular calcium concentration. The mechanisms by which the intracellular calcium concentration increases in response to an increase in the pericellular calcium concentration are unknown. Elevation of the intracellular calcium may occur via release from the internal calcium stores of the cell and/or via the membrane bound channels. The current study applied a wide range of pharmaceutical inhibitors to identify the calcium entry pathways involved in the process: internal calcium release from endoplasmic reticulum (ER, inhibited by thapsigargin and TMB-8), calcium receptor (CaSR, inhibited by calhex), stretch-activated calcium channel (SACC, inhibited by gadolinium), voltage-gated calcium channels (VGCC, inhibited by nifedipine, verapamil, neomycin, and ω-conotoxin), and calcium-induced-calcium-release channel (CICRC, inhibited by ryanodine and dantrolene). These inhibitors were screened for their effectiveness to block intracellular calcium increase by using a concentration gradient induced calcium efflux model which mimics calcium diffusion from the basal aspect of cells. The inhibitor(s) which reduced the intracellular calcium response was further tested on osteoblasts seeded on mechanically loaded notched cortical bone wafers undergoing damage. The results showed that only neomycin reduced the intracellular calcium response in osteoblasts, by 27%, upon extracellular calcium stimulus induced by concentration gradient. The inhibitory effect of neomycin was more pronounced (75% reduction in maximum fluorescence) for osteoblasts seeded on notched cortical bone wafers loaded mechanically to damaging load levels. These results imply that the increase in

  10. Bone mass and breast milk calcium concentration are associated with vitamin D receptor gene polymorphisms in adolescent mothers.

    Science.gov (United States)

    Bezerra, Flávia F; Cabello, Giselda M K; Mendonça, Laura M C; Donangelo, Carmen M

    2008-02-01

    Lactation-associated bone loss has been reported in adolescent mothers. Polymorphisms in the vitamin D receptor (VDR) gene may contribute to differences in the physiologic skeletal response to lactation in these mothers. We evaluated the influence of VDR gene polymorphisms ApaI, BsmI, and TaqI on bone mass, bone and calcium-related hormones, and breast milk calcium of lactating adolescents with habitually low calcium intake. Total body bone mineral content (TBMC), total body bone mineral density (TBMD), lumbar spine BMD (LSBMD), serum hormones [intact parathyroid hormone (iPTH), 25-hydroxyvitamin D, insulin-like growth factor-I (IGF1), prolactin, and estradiol), and breast milk calcium were measured in 40 lactating Brazilian adolescents (15-18 y), and compared by VDR genotype subgroups after adjustment for calcium intake and postmenarcheal and lactational periods. TBMD and LSBMD Z scores were -0.55 +/- 1.01 and -1.15 +/- 1.48, respectively. LSBMD was higher (21%; P milk calcium and serum iPTH were higher (24 and 80%, respectively; P milk calcium are significantly associated with VDR genotypes in lactating Brazilian adolescents. Those with aa and tt genotypes had a better bone status and those with bb genotype had greater breast milk calcium.

  11. Calcium binding proteins and calcium signaling in prokaryotes.

    Science.gov (United States)

    Domínguez, Delfina C; Guragain, Manita; Patrauchan, Marianna

    2015-03-01

    With the continued increase of genomic information and computational analyses during the recent years, the number of newly discovered calcium binding proteins (CaBPs) in prokaryotic organisms has increased dramatically. These proteins contain sequences that closely resemble a variety of eukaryotic calcium (Ca(2+)) binding motifs including the canonical and pseudo EF-hand motifs, Ca(2+)-binding β-roll, Greek key motif and a novel putative Ca(2+)-binding domain, called the Big domain. Prokaryotic CaBPs have been implicated in diverse cellular activities such as division, development, motility, homeostasis, stress response, secretion, transport, signaling and host-pathogen interactions. However, the majority of these proteins are hypothetical, and only few of them have been studied functionally. The finding of many diverse CaBPs in prokaryotic genomes opens an exciting area of research to explore and define the role of Ca(2+) in organisms other than eukaryotes. This review presents the most recent developments in the field of CaBPs and novel advancements in the role of Ca(2+) in prokaryotes.

  12. Disease causing mutations of calcium channels.

    Science.gov (United States)

    Lorenzon, Nancy M; Beam, Kurt G

    2008-01-01

    Calcium ions play an important role in the electrical excitability of nerve and muscle, as well as serving as a critical second messenger for diverse cellular functions. As a result, mutations of genes encoding calcium channels may have subtle affects on channel function yet strongly perturb cellular behavior. This review discusses the effects of calcium channel mutations on channel function, the pathological consequences for cellular physiology, and possible links between altered channel function and disease. Many cellular functions are directly or indirectly regulated by the free cytosolic calcium concentration. Thus, calcium levels must be very tightly regulated in time and space. Intracellular calcium ions are essential second messengers and play a role in many functions including, action potential generation, neurotransmitter and hormone release, muscle contraction, neurite outgrowth, synaptogenesis, calcium-dependent gene expression, synaptic plasticity and cell death. Calcium ions that control cell activity can be supplied to the cell cytosol from two major sources: the extracellular space or intracellular stores. Voltage-gated and ligand-gated channels are the primary way in which Ca(2+) ions enter from the extracellular space. The sarcoplasm reticulum (SR) in muscle and the endoplasmic reticulum in non-muscle cells are the main intracellular Ca(2+) stores: the ryanodine receptor (RyR) and inositol-triphosphate receptor channels are the major contributors of calcium release from internal stores.

  13. Regulation of cardiomyocyte autophagy by calcium.

    Science.gov (United States)

    Shaikh, Soni; Troncoso, Rodrigo; Criollo, Alfredo; Bravo-Sagua, Roberto; García, Lorena; Morselli, Eugenia; Cifuentes, Mariana; Quest, Andrew F G; Hill, Joseph A; Lavandero, Sergio

    2016-04-15

    Calcium signaling plays a crucial role in a multitude of events within the cardiomyocyte, including cell cycle control, growth, apoptosis, and autophagy. With respect to calcium-dependent regulation of autophagy, ion channels and exchangers, receptors, and intracellular mediators play fundamental roles. In this review, we discuss calcium-dependent regulation of cardiomyocyte autophagy, a lysosomal mechanism that is often cytoprotective, serving to defend against disease-related stress and nutrient insufficiency. We also highlight the importance of the subcellular distribution of calcium and related proteins, interorganelle communication, and other key signaling events that govern cardiomyocyte autophagy.

  14. Altered calcium signaling following traumatic brain injury

    Directory of Open Access Journals (Sweden)

    John Thomas Weber

    2012-04-01

    Full Text Available Cell death and dysfunction after traumatic brain injury (TBI is caused by a primary phase, related to direct mechanical disruption of the brain, and a secondary phase which consists of delayed events initiated at the time of the physical insult. Arguably, the calcium ion contributes greatly to the delayed cell damage and death after TBI. A large, sustained influx of calcium into cells can initiate cell death signaling cascades, through activation of several degradative enzymes, such as proteases and endonucleases. However, a sustained level of intracellular free calcium is not necessarily lethal, but the specific route of calcium entry may couple calcium directly to cell death pathways. Other sources of calcium, such as intracellular calcium stores, can also contribute to cell damage. In addition, calcium-mediated signal transduction pathways in neurons may be perturbed following injury. These latter types of alterations may contribute to abnormal physiology in neurons that do not necessarily die after a traumatic episode. This review provides an overview of experimental evidence that has led to our current understanding of the role of calcium signaling in death and dysfunction following TBI.

  15. Sintering of calcium phosphate bioceramics.

    Science.gov (United States)

    Champion, E

    2013-04-01

    Calcium phosphate ceramics have become of prime importance for biological applications in the field of bone tissue engineering. This paper reviews the sintering behaviour of these bioceramics. Conventional pressureless sintering of hydroxyapatite, Ca10(PO4)6(OH)2, a reference compound, has been extensively studied. Its physico-chemistry is detailed. It can be seen as a competition between two thermally activated phenomena that proceed by solid-state diffusion of matter: densification and grain growth. Usually, the objective is to promote the first and prevent the second. Literature data are analysed from sintering maps (i.e. grain growth vs. densification). Sintering trajectories of hydroxyapatite produced by conventional pressureless sintering and non-conventional techniques, including two-step sintering, liquid phase sintering, hot pressing, hot isostatic pressing, ultrahigh pressure, microwave and spark plasma sintering, are presented. Whatever the sintering technique may be, grain growth occurs mainly during the last step of sintering, when the relative bulk density reaches 95% of the maximum value. Though often considered very advantageous, most assisted sintering techniques do not appear very superior to conventional pressureless sintering. Sintering of tricalcium phosphate or biphasic calcium phosphates is also discussed. The chemical composition of calcium phosphate influences the behaviour. Similarly, ionic substitutions in hydroxyapatite or in tricalcium phosphate create lattice defects that modify the sintering rate. Depending on their nature, they can either accelerate or slow down the sintering rate. The thermal stability of compounds at the sintering temperature must also be taken into account. Controlled atmospheres may be required to prevent thermal decomposition, and flash sintering techniques, which allow consolidation at low temperature, can be helpful.

  16. Heart failure drug digitoxin induces calcium uptake into cells by forming transmembrane calcium channels

    OpenAIRE

    2008-01-01

    Digitoxin and other cardiac glycosides are important, centuries-old drugs for treating congestive heart failure. However, the mechanism of action of these compounds is still being elucidated. Calcium is known to potentiate the toxicity of these drugs, and we have hypothesized that digitoxin might mediate calcium entry into cells. We report here that digitoxin molecules mediate calcium entry into intact cells. Multimers of digitoxin molecules also are able to form calcium channels in pure plan...

  17. The Role of Calcium in Prevention and Treatment of Osteoporosis.

    Science.gov (United States)

    Heaney, Robert P.

    1987-01-01

    Osteoporosis results from several factors. Calcium deficiency is only one, and high calcium intake will prevent only those cases in which calcium is the limiting factor. Calcium cannot reverse, but only arrest, bone loss. A high calcium intake for every member of the population is advocated. (Author/MT)

  18. Calcium imaging perspectives in plants.

    Science.gov (United States)

    Kanchiswamy, Chidananda Nagamangala; Malnoy, Mickael; Occhipinti, Andrea; Maffei, Massimo E

    2014-03-04

    The calcium ion (Ca2+) is a versatile intracellular messenger. It provides dynamic regulation of a vast array of gene transcriptions, protein kinases, transcription factors and other complex downstream signaling cascades. For the past six decades, intracellular Ca2+ concentration has been significantly studied and still many studies are under way. Our understanding of Ca2+ signaling and the corresponding physiological phenomenon is growing exponentially. Here we focus on the improvements made in the development of probes used for Ca2+ imaging and expanding the application of Ca2+ imaging in plant science research.

  19. The Electronic Structure of Calcium

    DEFF Research Database (Denmark)

    Jan, J.-P.; Skriver, Hans Lomholt

    1981-01-01

    The electronic structure of calcium under pressure is re-examined by means of self-consistent energy band calculations based on the local density approximation and using the linear muffin-tin orbitals (LMTO) method with corrections to the atomic sphere approximation included. At zero pressure.......149 Ryd, respectively, relative to the s band, give the best possible agreement. Under increasing pressure the s and p electrons are found to transfer into the d band, and Ca undergoes metal-semimetal-metal electronic transitions. Calculations of the bandstructure and the electronic pressure, including...

  20. Calcium Solubility and Cation Exchange Properties in Zeoponic Soil

    Science.gov (United States)

    Beiersdorfer, Raymond E.

    1999-01-01

    An important aspect of a regenerative life support system at a Lunar or Martian outpost is the ability to produce food. Essential plant nutrients, as well as a solid support substrate, can be provided by: (1) treated Lunar or Martian regolith; (2) a synthetic soil or (3) some combination of both. A synthetic soil composed of ammonium- and potassium-saturated chinoptlolite (a zeolite mineral) and apatite, can provide slow-release fertilization of plants via dissolution and ion-exchange reactions. Previous equilibrium studies (Beiersdorfer, 1997) on mixtures of synthetic hydroxyapatite and saturated-clinoptilolite indicate that the concentrations of macro-nutrients such as ammonium, phosphorous, potassium, magnesium, and calcium are a function of the ratio of chinoptilolite to apatite in the sample and to the ratio of potassium to ammonium on the exchange sites in the clinoptilolite. Potassium, ammonium, phosphorous, and magnesium are available to plants at sufficient levels. However, calcium is deficient, due to the high degree of calcium adsorption by the clinoptilolite. Based on a series of batch-equilibration experiments, this calcium deficiency can be reduced by (1) treating the clinoptilolite with CaNO3 or (2) adding a second Ca-bearing mineral (calcite, dolomite or wollastonite) to the soil. Treating the Cp with CaNO3 results in increased Ca in solution, decreased P in solution and decreased NH4 in solution. Concentrations of K were not effected by the CaNO3 treatment. Additions of Cal, Dol and Wol changed the concentrations of Ca and P in solution in a systematic fashion. Cal has the greatest effect, Dol the least and Wol is intermediate. The changes are consistent with changes expected for a common ion effect with Ca. Higher concentrations of Ca in solution with added Cal, Dol or Wol do not result in changes in K or NH4 concentrations.

  1. Calcium

    Science.gov (United States)

    ... don't have enough of the intestinal enzyme lactase that helps digest the sugar (lactose) in dairy ... free dairy products are readily available, as are lactase drops that can be added to dairy products ...

  2. Calcium

    Science.gov (United States)

    ... tingling in the fingers, convulsions, and abnormal heart rhythms that can lead to death if not corrected. ... that includes weight-bearing physical activity (such as walking and running). Osteoporosis is a disease of the ...

  3. Calcium

    Science.gov (United States)

    ... for dinner. Create mini-pizzas by topping whole-wheat English muffins or bagels with pizza sauce and ... Fitness Center Vitamin D Smart Supermarket Shopping Lactose Intolerance Vitamins and Minerals Vitamin Chart Mineral Chart Food ...

  4. Calcium oxide based catalysts for ethanolysis of soybean oil

    Directory of Open Access Journals (Sweden)

    Kornkanok Watcharathamrongkul

    2010-12-01

    Full Text Available Transesterification of soybean oil and ethanol catalyzed by calcium oxides prepared from the calcinations of CaO,Ca(OH2, limestone, and Ca(OH2/CaO as solid base catalysts was investigated. It was found that the catalytic activitiessignificantly depended upon their base site strengths and their structures. Increases in catalytic performance of CaO could beachieved by loading Ca(OH2 on CaO and calcinations at a high temperature. The catalytic reaction using a 9:1 molar ratio ofethanol to oil at 70 °C, using CaO loaded with 3.7 wt% Ca(OH2 exhibited the optimal results, where the conversion of soybeanoil reached 96.3% after 10 hrs of the reaction.

  5. CHEMICAL MODIFICATION OF THE SURFACE OF CALCIUM ALGINATE GEL BEADS

    Institute of Scientific and Technical Information of China (English)

    Cong-ming Xiao; Li-chun Zhou

    2004-01-01

    The chemical modification of the surface of calcium alginate gel beads (CAGB) via grafting copolymerization with vinyl acetate (VAc) was studied. The optimum reaction conditions with activation and graft copolymerization two steps were explored. First, 5 grams CAGB with 2.5 mm initial diameter was initiated with 0.0493 mol/L K2S2O8 at 51 ℃ for 30 min in 15 mL 1% PVA/H2O. Then 4.34 mol/L VAc was added dropwise and the reaction was allowed to proce at 48 ℃ for 3 h. The grafting efficiency could come up to 30%. It was found the stability of modified CAGB in the air and in electrolyte solutions was greatly improved.

  6. Testosterone increases urinary calcium excretion and inhibits expression of renal calcium transport proteins.

    NARCIS (Netherlands)

    Hsu, Y.J.; Dimke, H.; Schoeber, J.P.H.; Hsu, S.C.; Lin, S.H.; Chu, P.; Hoenderop, J.G.J.; Bindels, R.J.M.

    2010-01-01

    Although gender differences in the renal handling of calcium have been reported, the overall contribution of androgens to these differences remains uncertain. We determined here whether testosterone affects active renal calcium reabsorption by regulating calcium transport proteins. Male mice had hig

  7. 76 FR 51991 - Determination That PENTETATE CALCIUM TRISODIUM (Trisodium Calcium Diethylenetriaminepentaacetate...

    Science.gov (United States)

    2011-08-19

    ... new drug applications (ANDAs) for PENTETATE CALCIUM TRISODIUM (Ca-DTPA) solution for intravenous or... ANDA that does not refer to a listed drug. PENTETATE CALCIUM TRISODIUM (Ca-DTPA) solution for... HUMAN SERVICES Food and Drug Administration Determination That PENTETATE CALCIUM TRISODIUM...

  8. Effect of lowering dietary calcium intake on fractional whole body calcium retention

    Energy Technology Data Exchange (ETDEWEB)

    Dawson-Hughes, B.; Stern, D.T.; Shipp, C.C.; Rasmussen, H.M.

    1988-07-01

    Although fractional calcium absorption is known to vary inversely with calcium intake, the extent and timing of individual hormonal and calcium absorption responses to altered calcium intake have not been defined. We measured fractional whole body retention of orally ingested /sup 47/Ca, an index of calcium absorption, in nine normal women after they had eaten a 2000-mg calcium diet for 8 weeks and a 300-mg calcium diet for 1, 2, 4, and 8 weeks. After the diet change, serum intact PTH (32.2% increase; P = 0.005), serum 1,25-dihydroxyvitamin D (1,25-(OH)2D; 43.8% increase; P = 0.003), and fractional whole body calcium retention (42.8% increase; P = 0.004) increased within 1 week. Although the PTH and calcium retention responses remained fairly constant throughout the low calcium intake period, serum 1,25-(OH)2D concentrations declined toward baseline after week 1. Thus, the late increase in calcium retention may have resulted from calcium absorption that was independent of 1,25-(OH)2D stimulation.

  9. Protein intake and calcium absorption – Potential role of the calcium sensor receptor

    Science.gov (United States)

    Dietary protein induces calcium excretion but the source of this calcium is unclear. Evidence from short-term studies indicates that protein promotes bone resorption, but many epidemiologic studies do not corroborate this. Evidence is also mixed on weather protein promotes calcium absorption. Stud...

  10. Behaviour of calcium carbonate in sea water

    Science.gov (United States)

    Cloud, P.E.

    1962-01-01

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

  11. Bioactivity evaluation of commercial calcium phosphate-based bioceramics for bone regeneration

    Energy Technology Data Exchange (ETDEWEB)

    Borrós, S.; Mas, A.

    2016-11-01

    Calcium phosphate-based bioceramics constitute a great promise for bone tissue engineering as they chemically resemble to mammalian bone and teeth. Their use is a viable alternative for bone regeneration as it avoids the use of autografts and allografts, which usually involves immunogenic reactions and patient’s discomfort. This work evolves around the study of the bioactivity potential of different commercially available bone substitutes based in calcium phosphate through the characterization of their ionic exchangeability when immersed in simulated body fluid (SBF). (Author)

  12. The preparation of calcium superoxide at subambient temperatures and pressures. [oxygen source for breathing apparatus

    Science.gov (United States)

    Ballou, E. V.; Wood, P. C.; Spitze, L. A.; Wydeven, T.; Stein, R.

    1977-01-01

    The effects of disproportionations at lower temperatures and also of a range of reaction chamber pressures on the preparation of calcium superoxide, Ca(O2)2, from calcium peroxide diperoxyhydrate were studied. About 60% purity of product was obtained by a disproportionation procedure. The significance of features of this procedure for a prospective scale-up of the mass prepared in a single experiment is considered. The optimum pressure for product purity was determined, and the use of a molecular sieve desiccant is described.

  13. Aging Reduces L-type Calcium Channel Current and the Vasodilatory Response of Small Mesenteric Arteries to Calcium Channel Blockers

    Directory of Open Access Journals (Sweden)

    Sulayma A Albarwani

    2016-05-01

    Full Text Available Calcium channel blockers are widely used to treat cardiovascular disease (CVD including hypertension. As aging is an independent risk factor for CVD, the use of calcium channel blockers increases with increasing age. Hence, this study was designed to evaluate the effect of aging on the sensitivity of small mesenteric arteries to L-type voltage-gated calcium channel (LTCC blockers and also to investigate whether there was a concomitant change in calcium current density. Third order mesenteric arteries from male F344 rats, aged 2.5 - 3 months (young and 22 - 26 months (old were mounted on wire myograph to measure the tension during isometric contraction. Arteries were contracted with 100 mM KCl and were then relaxed in a cumulative concentration-response dependent manner with nifedipine (0.1nM - 10 µM, verapamil (0.1nM-10 µM or diltiazem (0.1nM - 10µM. Relaxation-concentration response curves produced by cumulative concentrations of three different calcium channel blockers (CCBs in arteries of old rats were shifted to the right with statistically significant IC50s. pEC50 ± s.e.m: (8.37 ± 0.06 vs 8.04 ± 0.05 , 7.40 ± 0.07 vs 6.81 ± 0.04 and 6.58 ± 0.07 vs 6.34 ± 0.06 in young vs old. It was observed that the maximal contractions induced by 100 mM KCl, phenylephrine and reversed by sodium nitroprusside were not different between young and old groups. However, Bay K 8644 increased resting tension by 23±4.8% in young arteries and 4.7±1.6% in old arteries. LTCC current density were also significantly lower in old arteries (-2.77 ± 0.45 pA/pF compared to young arteries (-4.5 ± 0.40 pA/pF; with similar steady-state activation and inactivation curves. Parallel to this reduction, the expression of Cav1.2 protein was reduced by 57 ± 5% in arteries from old rats compared to those from young rats. In conclusion, our results suggest that aging reduces the response of small mesenteric arteries to the vasodilatory effect of the CCBs and this may

  14. Alcohol dispersions of calcium hydroxide nanoparticles for stone conservation.

    Science.gov (United States)

    Rodriguez-Navarro, Carlos; Suzuki, Amelia; Ruiz-Agudo, Encarnacion

    2013-09-10

    Alcohol dispersions of Ca(OH)2 nanoparticles, the so-called nanolimes, are emerging as an effective conservation material for the consolidation of stone, mortars, and plasters present in old masonry and/or mural paintings. To better understand how this treatment operates, to optimize its performance and broaden its applications, here we study the nano and microstructural characteristics, carbonation behavior, and consolidation efficacy of colloidal alcohol dispersions of Ca(OH)2 nanoparticles produced by both homogeneous (commercial nanolime) and heterogeneous phase synthesis (aged slaked lime and carbide lime putties). We observe that the alcohol not only provides a high colloidal stability to Ca(OH)2 particles, but also affects the kinetics of carbonation and CaCO3 polymorph selection. This is due to the pseudomorphic replacement of Ca(OH)2 particles by calcium alkoxides upon reaction with ethanol or 2-propanol. The extent of this replacement reaction depends on Ca(OH)2 size and time. Hydrolysis of alkoxides speeds up the carbonation process and increases the CaCO3 yield. The higher degree of transformation into calcium alkoxide of both the commercial nanolime and the carbide lime fosters metastable vaterite formation, while calcite precipitation is promoted upon carbonation of the aged slaked lime due its lower reactivity, which limits calcium alkoxide formation. A higher consolidation efficacy in terms of strength gain of treated porous stone is achieved in the latter case, despite the fact that the carbonation is much faster and reaches a higher yield in the former ones. Formation of alkoxides, which has been neglected in previous studies, needs to be considered when applying nanolime treatments. These results show that the use Ca(OH)2 nanoparticle dispersions prepared with either aged slaked lime or carbide lime putties is an economical and effective conservation alternative to commercial nanolimes produced by homogeneous phase synthesis. Ultimately, this

  15. Calcium signaling in pluripotent stem cells.

    Science.gov (United States)

    Apáti, Ágota; Pászty, Katalin; Erdei, Zsuzsa; Szebényi, Kornélia; Homolya, László; Sarkadi, Balázs

    2012-04-28

    Pluripotent stem cells represent a new source of biological material allowing the exploration of signaling phenomena during normal cell development and differentiation. Still, the calcium signaling pathways and intracellular calcium responses to various ligands or stress conditions have not been sufficiently explored as yet in embryonic or induced pluripotent stem cells and in their differentiated offspring. This is partly due to the special culturing conditions of these cell types, the rapid morphological and functional changes in heterogeneous cell populations during early differentiation, and methodological problems in cellular calcium measurements. In this paper, we review the currently available data in the literature on calcium signaling in pluripotent stem cells and discuss the potential shortcomings of these studies. Various assay methods are surveyed for obtaining reliable data both in undifferentiated embryonic stem cells and in specific, stem cell-derived human tissues. In this paper, we present the modulation of calcium signaling in human embryonic stem cells (hESC) and in their derivates; mesenchymal stem cell like (MSCl) cells and cardiac tissues using the fluorescent calcium indicator Fluo-4 and confocal microscopy. LPA, trypsin and angiotensin II were effective in inducing calcium signals both in HUES9 and MSCl cells. Histamine and thrombin induced calcium signal exclusively in the MSCl cells, while ATP was effective only in HUES9 cells. There was no calcium signal evoked by GABA, even at relatively high concentrations. In stem cell-derived cardiomyocytes a rapid increase in the beating rate and an increase of the calcium signal peaks could be observed after the addition of adrenaline, while verapamil led to a strong decrease in cellular calcium and stopped spontaneous contractions in a relaxed state.

  16. Comparison of Calcium Phosphate and Zinc Oxide Nanoparticles as Dermal Penetration Enhancers for Albumin.

    Science.gov (United States)

    Shokri, Narges; Javar, H A

    2015-01-01

    Dermal drug delivery is highly preferred by patients due to its several advantages. Protein therapeutics have attracted huge attention recently. Since dermal delivery of proteins encounter problems, in this investigation, zinc oxide nanoparticles and calcium phosphate nanoparticles were compared as enhancers for dermal permeation of albumin. Albumin was applied simultaneously with zinc oxide nanoparticles or calcium phosphate nanoparticles on pieces of mouse skin. Skin permeation of albumin over time was determined using a diffusion cell. Skin distribution of the nanoparticles and albumin over time was determined by optical and fluorescence microscopy. Zinc oxide nanoparticles and calcium phosphate nanoparticles acted as enhancers for skin permeation of albumin. Cumulative permeated albumin in presence of zinc oxide nanoparticles after 0, 0.5, 1, 1.5 and 2 h, were 0±0, 11.7±3.3, 21.1±3.5, 40.2±3.6 and 40.2±3.6 mg, respectively and in presence of calcium phosphate nanoparticles were 0±0, 20.9±7.4, 33.8±5.5, 33.8±3.7 and 33.8±3.7 mg, respectively. After 0.5 h, little amount of albumin was permeated in presence of every kind of the nanoparticles. After 0.5 or 1 h, the permeated albumin in presence of calcium phosphate nanoparticles was more than that in presence of zinc oxide nanoparticles and after 1.5 h the permeated albumin in presence of zinc oxide nanoparticles was more than that in presence of calcium phosphate nanoparticles. Images of skin distribution of the two nanoparticles over time, were somewhat different and distribution of albumin correlated with the distribution of the nanoparticles alone. The profiles of albumin permeation (in presence of each of the nanoparticles) versus time was delayed and linear for both nanoparticles while the slope for calcium phosphate nanoparticles was higher than zinc oxide nanoparticles. The enhancer effect of zinc oxide nanoparticles was stronger while the enhancer effect of calcium phosphate nanoparticles was

  17. Impacts of calcium addition and different oil types and levels on in vitro rumen fermentation and digestibility.

    Science.gov (United States)

    Gülşen, Nurettin; Umucalilar, Huzur Derya; Inal, Fatma; Hayirli, Armagan

    2006-12-01

    This in vitro study was designed to investigate the effects of calcium addition to substrates differing in source and level of oil on fermentation, gas production, and digestibility parameters. Substrates were made from basal mixtures containing three levels of calcium salt (0, 1, and 2% CaCl2) to contain three levels (3, 6, and 9%) of two types (sunflower and soy) of oil. After collecting from two Holstein bulls and mixing with buffer, rumen fluid was used to incubate the resulting 18 mixtures in duplicate. Ionizable calcium, pH and NH3-N concentration were measured during incubation. Gas production was measured at 6, 12, 24, and 48 h after incubation. Kinetics parameters of gas production and in vitro dry matter digestibility (IVDMD) were calculated from regression coefficients of an exponential equation and a linear equation, respectively. Data were analysed using 3-way ANOVA with repeated measure option in which the parameter time was a subplot. Oil type did not affect pH and ionizable calcium concentration. There were linear increases and decreases in pH and ionizable calcium concentration in response to increasing oil and calcium levels, respectively. However, with increasing oil levels there were no interactions between calcium addition and oil level on pH and ionizable calcium concentration. None of the treatments affected NH3-N concentration. The amount of gas produced from substrates containing sunflower oil was greater than soy oil (41.7 vs. 40.5 ml). Cumulative gas production and amount of gas production from insoluble but slowly fermentable portion of the supplemental mixtures linearly decreased and linearly increased as oil and calcium levels increased in the substrates, respectively. However, interactions of calcium addition and oil level on gas production and kinetics of gas production were lacking. Oil type did not affect IVDMD. Despite lacking main effects, interaction of calcium addition and oil level indicated that increasing calcium level

  18. THE INFLUENCE OF TEMPERATURE AND ADMIX- TURES ON ACTIVATION OF LOW CALCIUM FLY ASH

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    According to composition and structure properties of low calcium fly ash, the activation and reaction degree of fly ash-lime and fly ash-lime-gypsum system were studied in different alkali surroundings and temperatures by thermal-gravity analysis.The degree of reaction and pore structure analysis test results show that composite alkali play an important role in the activation and degree of reaction of fly ash at room temperature. But when increasing curing temperature, gypsum would play an important role in activation and hydration of fly ash.

  19. Calcium homeostasis and cone signaling are regulated by interactions between calcium stores and plasma membrane ion channels.

    Directory of Open Access Journals (Sweden)

    Tamas Szikra

    Full Text Available Calcium is a messenger ion that controls all aspects of cone photoreceptor function, including synaptic release. The dynamic range of the cone output extends beyond the activation threshold for voltage-operated calcium entry, suggesting another calcium influx mechanism operates in cones hyperpolarized by light. We have used optical imaging and whole-cell voltage clamp to measure the contribution of store-operated Ca(2+ entry (SOCE to Ca(2+ homeostasis and its role in regulation of neurotransmission at cone synapses. Mn(2+ quenching of Fura-2 revealed sustained divalent cation entry in hyperpolarized cones. Ca(2+ influx into cone inner segments was potentiated by hyperpolarization, facilitated by depletion of intracellular Ca(2+ stores, unaffected by pharmacological manipulation of voltage-operated or cyclic nucleotide-gated Ca(2+ channels and suppressed by lanthanides, 2-APB, MRS 1845 and SKF 96365. However, cation influx through store-operated channels crossed the threshold for activation of voltage-operated Ca(2+ entry in a subset of cones, indicating that the operating range of inner segment signals is set by interactions between store- and voltage-operated Ca(2+ channels. Exposure to MRS 1845 resulted in approximately 40% reduction of light-evoked postsynaptic currents in photopic horizontal cells without affecting the light responses or voltage-operated Ca(2+ currents in simultaneously recorded cones. The spatial pattern of store-operated calcium entry in cones matched immunolocalization of the store-operated sensor STIM1. These findings show that store-operated channels regulate spatial and temporal properties of Ca(2+ homeostasis in vertebrate cones and demonstrate their role in generation of sustained excitatory signals across the first retinal synapse.

  20. An Intracellular Calcium Oscillations Model Including Mitochondrial Calcium Cycling

    Institute of Scientific and Technical Information of China (English)

    SHI Xiao-Min; LIU Zeng-Rong

    2005-01-01

    @@ Calcium is a ubiquitous second messenger. Mitochondria contributes significantly to intracellular Ca2+ dynamics.The experiment of Kaftan et al. [J. Biol. Chem. 275(2000) 25465] demonstrated that inhibiting mitochondrial Ca2+ uptake can reduce the frequency of cytosolic Ca2+ concentration oscillations of gonadotropes. By considering the mitochondrial Ca2+ cycling we develop a three-variable model of intracellular Ca2+ oscillations based on the models of Atri et al. [Biophys. J. 65 (1993) 1727] and Falcke et al. [Biophys. J. 77 (1999) 37]. The model reproduces the fact that mitochondrial Ca2+ cycling increases the frequency of cytosolic Ca2+ oscillations, which accords with Kaftan's results. Moreover the model predicts that when the mitochondria overload with Ca2+, the cytosolic Ca2+ oscillations vanish, which may trigger apoptosis.

  1. Effect of the calcium to phosphate ratio of tetracalcium phosphate on the properties of calcium phosphate bone cement.

    Science.gov (United States)

    Burguera, Elena F; Guitian, Francisco; Chow, Laurence C

    2008-06-01

    Six different tetracalcium phosphate (TTCP) products were synthesized by solid state reaction at high temperature by varying the overall calcium to phosphate ratio of the synthesis mixture. The objective was to evaluate the effect of the calcium to phosphate ratio on a TTCP-dicalcium phosphate dihydrate (DCPD) cement. The resulting six TTCP-DCPD cement mixtures were characterized using X-ray diffraction analysis, scanning electron microscopy, and pH measurements. Setting times and compressive strength (CS) were also measured. Using the TTCP product with a Ca/P ratio of 2.0 resulted in low strength values (25.61 MPa) when distilled water was used as the setting liquid, even though conversion to hydroxyapatite was not prevented, as confirmed by X-ray diffraction. The suspected CaO presence in this TTCP may have affected the cohesiveness of the cement mixture but not the cement setting reaction, however no direct evidence of CaO presence was found. Lower Ca/P ratio products yielded cements with CS values ranging from 46.7 MPa for Ca/P ratio of 1.90 to 38.32 MPa for Ca/P ratio of 1.85. When a dilute sodium phosphate solution was used as the setting liquid, CS values were 15.3% lower than those obtained with water as the setting liquid. Setting times ranged from 18 to 22 min when water was the cement liquid and from 7 to 8 min when sodium phosphate solution was used, and the calcium to phosphate ratio did not have a marked effect on this property.

  2. 21 CFR 182.8217 - Calcium phosphate.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 3 2010-04-01 2009-04-01 true Calcium phosphate. 182.8217 Section 182.8217 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) FOOD FOR... phosphate. (a) Product. Calcium phosphate (mono-, di-, and tribasic). (b) Conditions of use. This...

  3. Bespuiten met calcium kan neusrot voorkomen

    NARCIS (Netherlands)

    Zandstra, G.B.; Marcelis, L.F.M.

    2000-01-01

    Oorzaak van neusrot bij paprika is een calciumtekort in de vrucht. Een bespuiting met calcium vlak na de bloei heeft een zeer gunstig effect. In bijgaande tabel gegevens over het effect van spuiten met calcium op het optreden van neusrot bij paprika

  4. Stochastic models of intracellular calcium signals

    Energy Technology Data Exchange (ETDEWEB)

    Rüdiger, Sten, E-mail: sten.ruediger@physik.hu-berlin.de

    2014-01-10

    Cellular signaling operates in a noisy environment shaped by low molecular concentrations and cellular heterogeneity. For calcium release through intracellular channels–one of the most important cellular signaling mechanisms–feedback by liberated calcium endows fluctuations with critical functions in signal generation and formation. In this review it is first described, under which general conditions the environment makes stochasticity relevant, and which conditions allow approximating or deterministic equations. This analysis provides a framework, in which one can deduce an efficient hybrid description combining stochastic and deterministic evolution laws. Within the hybrid approach, Markov chains model gating of channels, while the concentrations of calcium and calcium binding molecules (buffers) are described by reaction–diffusion equations. The article further focuses on the spatial representation of subcellular calcium domains related to intracellular calcium channels. It presents analysis for single channels and clusters of channels and reviews the effects of buffers on the calcium release. For clustered channels, we discuss the application and validity of coarse-graining as well as approaches based on continuous gating variables (Fokker–Planck and chemical Langevin equations). Comparison with recent experiments substantiates the stochastic and spatial approach, identifies minimal requirements for a realistic modeling, and facilitates an understanding of collective channel behavior. At the end of the review, implications of stochastic and local modeling for the generation and properties of cell-wide release and the integration of calcium dynamics into cellular signaling models are discussed.

  5. Oligofructose stimulates calcium absorption in adolescents

    NARCIS (Netherlands)

    Heuvel, E.G.H.M. van den; Muys, T.; Dokkum, W. van; Schaafsma, G.

    1999-01-01

    Background: In rats, nondigestible oligosaccharides stimulate calcium absorption. Recently, this effect was also found in human subjects. Objective: The objective of the study was to investigate whether consumption of 15 g oligofructose/d stimulates calcium absorption in male adolescents. Design: Tw

  6. ALG-2, a multifunctional calcium binding protein?

    DEFF Research Database (Denmark)

    Tarabykina, Svetlana; Mollerup, Jens; Winding Gojkovic, P.;

    2004-01-01

    ALG-2 was originally discovered as a pro-apoptotic protein in a genetic screen. Due to its ability to bind calcium with high affinity it was postulated to provide a link between the known effect of calcium in programmed cell death and the molecular death execution machinery. This review article...

  7. Simulating complex calcium-calcineurin signaling network

    NARCIS (Netherlands)

    Cui, J.; Kaandorp, J.A.

    2008-01-01

    Understanding of processes in which calcium signaling is involved is of fundamental importance in systems biology and has many applications in medicine. In this paper we have studied the particular case of the complex calcium-calcineurin-MCIP-NFAT signaling network in cardiac myocytes, the understan

  8. Adding calcium improves lithium ferrite core

    Science.gov (United States)

    Lessoff, H.

    1969-01-01

    Adding calcium increases uniformity of grain growth over a wide range of sintering temperatures and reduces porosity within the grain. Ferrite cores containing calcium have square hysteresis loops and high curie temperatures, making them useful in coincident current memories of digital electronic computers.

  9. Calcium, snails, and birds: a case study

    Directory of Open Access Journals (Sweden)

    R. Mänd

    2000-10-01

    Full Text Available Recent studies have shown that wild birds breeding in acidified areas have difficulties with obtaining sufficient calcium for their eggshells, and that the cause of it is the shortage of land snails. Many birds have to search for Ca-rich snail shells on a daily basis during egg production. Molluscs depend on litter calcium, which has decreased due to acidification of the environment. Calcium limitation may be a widespread phenomenon also in non-acidified, naturally Ca-poor areas. The problem is that while in the latter areas the time for development of specific adaptations may have been sufficient, then in acidified areas, on the contrary, calcium shortage is a recent phenomenon. Therefore, since the extent of calcium limitation in non-acidified areas is hard to derive from observational data, experimental approach is needed. We provide experimental evidence that specific calcium deficit does affect reproductive traits also in the birds breeding in naturally base-poor habitats. Our study was conducted in a heterogeneous woodland area in Estonia containing deciduous forest patches as well as base-poor pine forest with low snail abundance. Ca supplementation, using snail shell and chicken eggshell fragments, was carried out for pied flycatchers and great tits. Extra calcium affected positively several reproductive traits like egg volume and eggshell thickness, start of breeding, and fledglings’ parameters. The negative relationship between calcium availability and lay-date suggests that birds adjust their breeding tactics to conditions of Ca deficiency, for example, by postponing laying.

  10. Calcium Orthophosphates in Nature, Biology and Medicine

    Directory of Open Access Journals (Sweden)

    Sergey V. Dorozhkin

    2009-04-01

    Full Text Available The present overview is intended to point the readers’ attention to the important subject of calcium orthophosphates. These materials are of the special significance because they represent the inorganic part of major normal (bones, teeth and dear antlers and pathological (i.e. those appearing due to various diseases calcified tissues of mammals. Due to a great chemical similarity with the biological calcified tissues, many calcium orthophosphates possess remarkable biocompatibility and bioactivity. Materials scientists use this property extensively to construct artificial bone grafts that are either entirely made of or only surface-coated with the biologically relevant calcium orthophosphates. For example, self-setting hydraulic cements made of calcium orthophosphates are helpful in bone repair, while titanium substitutes covered by a surface layer of calcium orthophosphates are used for hip joint endoprostheses and as tooth substitutes. Porous scaffolds made of calcium orthophosphates are very promising tools for tissue engineering applications. In addition, technical grade calcium orthophosphates are very popular mineral fertilizers. Thus ere calcium orthophosphates are of great significance for humankind and, in this paper, an overview on the current knowledge on this subject is provided.

  11. Calcium Forms,Subcelluar Distribution and Ultrastructure of Pulp Cells as Influenced by Calcium Deficiency in Apple (Malus pumila) Fruits

    Institute of Scientific and Technical Information of China (English)

    CHEN Jian-hui; ZHOU Wei

    2004-01-01

    Calcium in Red Fuji and Starkrimson apples during storage were fractionated by sequent extracting. Localization and distribution of calcium and influence of calcium nutrition on cell ultrastructure were observed by transmission electron microscopy combined with in situ precipitation of calcium with an improved method of potassium pyroantimonate technique. Results indicated that spraying calcium solution on surface of young fruits increased contents of calcium in all forms. During storage, contents of soluble calcium and pectic calcium declined and thosein calcium phosphate, calcium oxalate and calcium silicate increased. Calcium contents of Red Fuji in all forms were higher than those of Starkrimson, indicating that calcium accumulating capability of Red Fuji fruits preceded that of Starkrimson. Under transmission electron microscopy, calcium antimonite precipitates (CaAP) was mainly distributed in cell wall, tonoplast, nuclear membrane and nucleoplasm,much more CaAP deposited in vacuole. Calcium deficiency during storage leads to decrease of CaAP in locations mentioned above, disappearance of compartmentation, and entrance of CaAP to cytoplasm. Transformation from soluble calcium and pectic calcium to calcium phosphate,oxalate and damages of biomembranes structuraly and functionally resulted from calcium deficiency during storage were the crucial causation of physiological disorder.

  12. Calcium-sensing receptor: a key target for extracellular calcium signaling in neurons

    Directory of Open Access Journals (Sweden)

    Brian L Jones

    2016-03-01

    Full Text Available Though both clinicians and scientists have long recognized the influence of extracellular calcium on the function of muscle and nervous tissue, recent insights reveal that the mechanisms allowing changes in extracellular calcium to alter cellular excitability have been incompletely understood. For many years the effects of calcium on neuronal signaling were explained only in terms of calcium entry through voltage-gated calcium channels and biophysical charge screening. More recently however, it has been recognized that the calcium-sensing receptor is prevalent in the nervous system and regulates synaptic transmission and neuronal activity via multiple signaling pathways. Here we review the multiplicity of mechanisms by which changes in extracellular calcium alter neuronal signaling and propose that multiple mechanisms are required to describe the full range of experimental observations.

  13. [Calcium and vitamin D in osteology].

    Science.gov (United States)

    Amling, M; Barvencik, F

    2015-06-01

    Calcium homeostasis is of paramount physiological and pathophysiological importance in health and disease. This article focuses on the skeletal relevance of calcium and vitamin D in daily clinical practice. Against the background of an endemic vitamin D deficiency in Germany and the increasing number of patients with drug-induced (proton pump inhibitor) enteral calcium uptake problems, it is of critical importance to understand that a vitamin D level of > 30 µg/l (> 75 nmol/l) is required for intact skeletal mineralization and that furthermore, a physiological gastric acid production is essential for a normal enteral uptake of calcium from foodstuffs. Therefore, a guideline-conform handling of vitamin D and calcium substitution is required not only for patients with rheumatoid diseases but also for any osteological therapy.

  14. Calcium ion currents mediating oocyte maturation events

    Directory of Open Access Journals (Sweden)

    Tosti Elisabetta

    2006-05-01

    Full Text Available Abstract During maturation, the last phase of oogenesis, the oocyte undergoes several changes which prepare it to be ovulated and fertilized. Immature oocytes are arrested in the first meiotic process prophase, that is morphologically identified by a germinal vesicle. The removal of the first meiotic block marks the initiation of maturation. Although a large number of molecules are involved in complex sequences of events, there is evidence that a calcium increase plays a pivotal role in meiosis re-initiation. It is well established that, during this process, calcium is released from the intracellular stores, whereas less is known on the role of external calcium entering the cell through the plasma membrane ion channels. This review is focused on the functional role of calcium currents during oocyte maturation in all the species, from invertebrates to mammals. The emerging role of specific L-type calcium channels will be discussed.

  15. Application of Calcium Phosphate Materials in Dentistry

    Directory of Open Access Journals (Sweden)

    Jabr S. Al-Sanabani

    2013-01-01

    Full Text Available Calcium phosphate materials are similar to bone in composition and in having bioactive and osteoconductive properties. Calcium phosphate materials in different forms, as cements, composites, and coatings, are used in many medical and dental applications. This paper reviews the applications of these materials in dentistry. It presents a brief history, dental applications, and methods for improving their mechanical properties. Notable research is highlighted regarding (1 application of calcium phosphate into various fields in dentistry; (2 improving mechanical properties of calcium phosphate; (3 biomimetic process and functionally graded materials. This paper deals with most common types of the calcium phosphate materials such as hydroxyapatite and tricalcium phosphate which are currently used in dental and medical fields.

  16. Formation, characterization and properties of hydroxyapatite-calcium polycarboxylate and calcium polyvinylphosphonate composites for biomedical applications

    Science.gov (United States)

    Greish, Yaser Elhanafy

    A hot pressing technique was used to prepare composites anticipated to be biocompatible. Composites were formed by reactions between tetracalcium phosphate (Ca4(PO4)2O, TetCP) and a biomedical polymer. Polymers used in this study were poly(acrylic-co-itaconic), and poly(vinyl phosphonic acid) (PVPA). The processing technique is commonly used in metallurgy where powder mixtures are hot pressed at elevated pressures, and temperatures. Powder mixtures of TetCP with both polymers were compacted at temperatures up to 300°C, pressures up to 690 MPa for up to 60 minutes. The effects of varying these conditions as well as the TetCP:polymer weight ratios on the reaction kinetics were studied using X-ray diffraction (XRD), Fourier-transform-infrared (FT-IR), 13C, and 31P nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), scanning electron microscope (SEM) and transmission electron microscope (TEM). Results showed that TetCP was converted to hydroxyapatite (Ca10 (PO4)6(OH)2, HAp) with the formation of a Ca salt of the polymer. The reaction kinetics were found to increase with increasing compaction time, temperature and pressure. Formation of anhydrous calcium phosphate (CaHPO4, DCPA) was also observed when PVPA was used. The reaction appears to start with the softening of the polymer when it was heated at temperatures equal to or greater than its glass transition temperature (Tg). The molten polymer flows and surrounds the TetCP grains, permitting a direct reaction to take place on the interface between them. The Ca polysalt appear to form first followed by formation of HAp in case of the copolymer and DCPA then HAp in case of PVPA. Tensile strengths and elastic moduli of the composites increased when the compaction time and temperature were increased. However, when the applied pressure was increased, these properties increased then reduced at higher pressures. The improvement in mechanical properties was related to the increase in densification of

  17. Design of in situ dispersible and calcium cross-linked alginate pellets as intestinal-specific drug carrier by melt pelletization technique.

    Science.gov (United States)

    Nurulaini, Harjoh; Wong, Tin Wui

    2011-06-01

    Conventional alginate pellets underwent rapid drug dissolution and loss of multiparticulate characteristics such as aggregation in acidic medium, thereby promoting oral dose dumping. This study aimed to design sustained-release dispersible alginate pellets through rapid in situ matrix dispersion and cross-linking by calcium salts during dissolution. Pellets made of alginate and calcium salts were prepared using a solvent-free melt pelletization technique that prevented reaction between processing materials during agglomeration and allowed such a reaction to occur only in dissolution phase. Drug release was remarkably retarded in acidic medium when pellets were formulated with water-soluble calcium acetate instead of acid-soluble calcium carbonate. Different from calcium salt-free and calcium carbonate-loaded matrices that aggregated or underwent gradual erosion, rapid in situ solvation of calcium acetate in pellets during dissolution resulted in burst of gas bubbles, fast pellet breakup, and dispersion. The dispersed fragments, though exhibiting a larger specific surface area for drug dissolution than intact matrix, were rapidly cross-linked by Ca(2+) from calcium acetate and had drug release retarded till a change in medium pH from 1.2 to 6.8. Being dispersible and pH-dependent in drug dissolution, these pellets are useful as multiparticulate intestinal-specific drug carrier without exhibiting dose dumping tendency of a "single-unit-like" system via pellet aggregation.

  18. Calcium-imaging with Fura-2 in isolated cerebral microvessels

    DEFF Research Database (Denmark)

    Hess, Jörg; Jensen, Claus V.; Diemer, Nils Henrik

    1991-01-01

    Neuropathology, cytoplasmic free calcium, Fura-2 fluorescence, image analysis, blood-brain barrier......Neuropathology, cytoplasmic free calcium, Fura-2 fluorescence, image analysis, blood-brain barrier...

  19. Modelling biological and chemically induced precipitation of calcium phosphate in enhanced biological phosphorus removal systems.

    Science.gov (United States)

    Barat, R; Montoya, T; Seco, A; Ferrer, J

    2011-06-01

    The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Reactor (SBR) operated for EBPR and finally validated with two experiments. The precipitation model proposed was able to reproduce the dynamics of amorphous calcium phosphate (ACP) formation and later crystallization to hydroxyapatite (HAP) under different scenarios. The model successfully characterised the EBPR performance of the SBR, including the biological, physical and chemical processes.

  20. Calcium channel antagonists increase morphine-induced analgesia and antagonize morphine tolerance.

    Science.gov (United States)

    Contreras, E; Tamayo, L; Amigo, M

    1988-04-13

    The influence of calcium channel blockers on morphine-induced analgesia and on tolerance to the chronic administration of the opiate was investigated in mice. The effects of a test dose of morphine were significantly increased by the administration of diltiazem, flunarizine, nicardipine and verapamil. In contrast, nifedipine induced an antagonistic effect. The calcium channel antagonists did not change the reaction time to thermal stimulation in mice (hot plate test). The administration of nifedipine, flunarizine and verapamil reduced the intensity of the tolerance induced by a single dose of morphine administered in a slow release preparation. Diltiazem induced a non-significant decrease of the process. The present results are in accordance with the known interaction of acute and chronic morphine administration with the intracellular calcium concentration in neurones of the central nervous system.

  1. Effect of galactooligosaccharides on calcium absorption and preventing bone loss in ovariectomized rats.

    Science.gov (United States)

    Chonan, O; Matsumoto, K; Watanuki, M

    1995-02-01

    The effects of galactooligosaccharides (GOS), a mixture of galactosyl oligosaccharides formed from lactose by the transgalactosyl reaction of beta-D-galactosidase derived from Bacillus circulans, on calcium absorption and prevention of bone loss were examined in ovariectomized (OVX) Wistar rats. Rats fed on a diet containing GOS absorbed calcium more efficiently than those on the control diet after 8-10 days and 18-20 days, and the bone (femur and tibia) ash weight and tibia calcium content of OVX rats fed on the GOS diet were significantly higher than those of the control animals. Although the serum total cholesterol of the ovariectomized rats was significantly elevated, GOS produced a significant hypocholesterolemic effect in the OVX rats. GOS, which is fermented by bacteria in the lower part of the intestine, enhanced volatile fatty acid production, and thus prevented bone loss and lower serum total cholesterol concentration in the ovariectomized rats.

  2. Decreased renal vitamin K-dependent γ-glutamyl carboxylase activity in calcium oxalate calculi patients

    Institute of Scientific and Technical Information of China (English)

    陈俊汇; 刘继红; 章咏裳; 叶章群; 王少刚

    2003-01-01

    Objective To study the activity of vitamin K-dependent γ-glutamyl carboxylase in patients with calcium oxalate (CaOx) urolithiasis compared with healthy individuals and to assess its relationship to the renal calcium oxalate urolithiasis. Methods Renal parenchymas were harvested from urolithic patients and renal tumor patients undergoing nephrectomy. The renal carboxylase activity was evaluated as the radioactivity of [14C] labeled sodium bicarbonate in carboxylic reactions in vitro using β-liquid scintillation counting. Results Significantly reduced activity of renal vitamin K-dependent γ-glutamyl carboxylase was observed in the urolithic group as compared with normal controls (P<0.01). Conclusion It suggests that the reduced carboxylase activity observed in the urolithic patients may play an important role in the course of renal calcium oxalate urolithiasis.

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

    Science.gov (United States)

    Kojima, Yoshiyuki; Kanai, Makoto; Nishimiya, Nobuyuki

    2012-03-01

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

  4. Effect of Calcium Leaching on the Properties of Cement-based Composites

    Institute of Scientific and Technical Information of China (English)

    LLIN Weiting; CHENG An; HUANG Ran; CHEN Chuntao; ZHOU Xingang

    2011-01-01

    Leaching is one of the major factors that alter the mechanical properties of cementbased composites.This study is aimed to investigate the effect of leaching on the properties of cementbased composites.Specimens with two water/cementitious ratios and two mineral admixtures were tested.An electrical potential was applied to accelerate the leaching process.Compressive strength test,scanning electronic microscopy,thermogravimetric analysis and X-ray diffraction analysis were conducted.Test results demonstrated that the calcium leaching reduced compressive strengths of concrete specimens,and such effect was prominent on the specimens without mineral admixtures.The leaching resistance increased with a decrease in water/cementitious ratio and an increase in amount of mineral admixtures.The mineral admixtures would reduce the amount of calcium hydroxide and refine the pore structure through pozzolanic reactions.A fair relationship was found between the calcium leaching and the compressive strength.

  5. Identification of the hydrate gel phases present in phosphate-modified calcium aluminate binders

    Energy Technology Data Exchange (ETDEWEB)

    Chavda, Mehul A.; Bernal, Susan A. [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Apperley, David C. [Solid-State NMR Group, Department of Chemistry, Durham University, Durham DH1 3LE (United Kingdom); Kinoshita, Hajime [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom); Provis, John L., E-mail: j.provis@sheffield.ac.uk [Department of Materials Science and Engineering, The University of Sheffield, Sheffield S1 3JD (United Kingdom)

    2015-04-15

    The conversion of hexagonal calcium aluminate hydrates to cubic phases in hydrated calcium aluminate cements (CAC) can involve undesirable porosity changes and loss of strength. Modification of CAC by phosphate addition avoids conversion, by altering the nature of the reaction products, yielding a stable amorphous gel instead of the usual crystalline hydrate products. Here, details of the environments of aluminium and phosphorus in this gel were elucidated using solid-state NMR and complementary techniques. Aluminium is identified in both octahedral and tetrahedral coordination states, and phosphorus is present in hydrous environments with varying, but mostly low, degrees of crosslinking. A {sup 31}P/{sup 27}Al rotational echo adiabatic passage double resonance (REAPDOR) experiment showed the existence of aluminium–phosphorus interactions, confirming the formation of a hydrated calcium aluminophosphate gel as a key component of the binding phase. This resolves previous disagreements in the literature regarding the nature of the disordered products forming in this system.

  6. Calcium-sensitive immunoaffinity chromatography

    DEFF Research Database (Denmark)

    Henriksen, Maiken L; Lindhardt Madsen, Kirstine; Skjoedt, Karsten

    2014-01-01

    Immunoaffinity chromatography is a powerful fractionation technique that has become indispensable for protein purification and characterization. However, it is difficult to retrieve bound proteins without using harsh or denaturing elution conditions, and the purification of scarce antigens...... to homogeneity may be impossible due to contamination with abundant antigens. In this study, we purified the scarce, complement-associated plasma protein complex, collectin LK (CL-LK, complex of collectin liver 1 and kidney 1), by immunoaffinity chromatography using a calcium-sensitive anti-collectin-kidney-1 m...... chromatography was superior to the traditional immunoaffinity chromatographies and resulted in a nine-fold improvement of the purification factor. The technique is applicable for the purification of proteins in complex mixtures by single-step fractionation without the denaturation of eluted antigens...

  7. Catalysis of Photochemical Reactions.

    Science.gov (United States)

    Albini, A.

    1986-01-01

    Offers a classification system of catalytic effects in photochemical reactions, contrasting characteristic properties of photochemical and thermal reactions. Discusses catalysis and sensitization, examples of catalyzed reactions of excepted states, complexing ground state substrates, and catalysis of primary photoproducts. (JM)

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

    Energy Technology Data Exchange (ETDEWEB)

    Pham Minh, Doan, E-mail: doan.phamminh@mines-albi.fr [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Tran, Ngoc Dung; Nzihou, Ange [Université de Toulouse, Mines Albi, CNRS, Centre RAPSODEE, Campus Jarlard, F-81013 Albi cedex 09 (France); Sharrock, Patrick [Université de Toulouse, SIMAD, IUT Paul Sabatier, Avenue Georges Pompidou, 81104 Castres (France)

    2013-07-01

    The synthesis of carbonate-containing apatite (CAP) from calcium carbonate and orthophosphoric acid under moderate conditions was investigated. In all cases, complete precipitation of orthophosphate species was observed. The reaction temperature influenced strongly the decomposition of calcium carbonate and therefore the composition of formed products. The reaction temperature of 80 °C was found to be effective for the complete decomposition of calcium carbonate particles after 48 h of reaction. Infra-red spectroscopy (IR), nuclear magnetic resonance (NMR), thermogravimetry/mass spectroscopy (TG–MS) coupling, and X-ray diffraction (XRD) characterizations allowed the identification of the composition of formed products. By increasing the reaction temperature from 20 °C to 80 °C, the content of A-type CAP increased and that of B-type CAP decreased, according to the favorable effect of temperature on the formation of A-type CAP. The total amount of carbonate content incorporated in CAP's structure, which was determined by TG–MS analysis, increased with the reaction temperature and reached up to 4.1% at 80 °C. At this temperature, the solid product was mainly composed of apatitic components and showed the typical flat-needle-like structure of CAP particles obtained in hydrothermal conditions. These results show an interesting one-step synthesis of CAP from calcium carbonate and orthophosphoric acid as low cost but high purity starting materials. Highlights: • The synthesis of carbonate-containing apatites from CaCO{sub 3} and H{sub 3}PO{sub 4} was studied. • The decomposition of CaCO{sub 3} particles was complete at 80 °C, 13.2 bar for 48 h. • The transformation of CaCO{sub 3} and H{sub 3}PO{sub 4} into apatitic products was also complete. • Pure carbonate-containing apatite was directly obtained without water-rising step.

  9. The influence of calcium on technological properties and micropurity of steel castings

    Directory of Open Access Journals (Sweden)

    J. Hampl

    2016-07-01

    Full Text Available The paper analyzes the technological parameters, micro-purity and mechanical properties of castings of steel alloyed with calcium. The effect of calcium on the steel was analyzed on samples taken in the process of casting heavy castings and ingots of the weight of ranging from 40 000 to 60 000 kg. Samples for the determination of the liquidus temperature and the solidus temperature of cast steels were analysed using differential thermal analysis (DTA. The production of low alloyed steel grades was performed on the EAF - ASEA-SKF facilities and the production of highalloyed steels on the EAF - ASEA-SKF - SS-VOD facilities. The purity calcium was added into the steel by the injection of a stuffed profile.

  10. Preparation of tricalcium phosphate/calcium pyrophosphate structures via rapid prototyping.

    Science.gov (United States)

    Gbureck, Uwe; Hölzel, Tanja; Biermann, Isabell; Barralet, Jake E; Grover, Liam M

    2008-04-01

    Custom made tricalcium phosphate/calcium pyrophosphate bone substitutes with a well-defined architecture were fabricated in this study using 3D powder printing with tricalcium phosphate (TCP) powder and a liquid phase of phosphoric acid. The primary formed matrix of dicalcium phosphate dihydrate (DCPD, brushite) was converted in a second step to calcium pyrophosphate (CPP) by heat treatment in the temperature range 1,100-1,300 degrees C. The structures exhibited compressive strengths between 0.8 MPa and 4 MPa after sintering at 1,100-1,250 degrees C, higher strengths were obtained by increasing the amount of pyrophosphate formed in the matrix due to a post-hardening regime prior sintering as well as by the formation of a glass phase from TCP and calcium pyrophosphate above 1,280 degrees C, which resulted in a strong densification of the samples and compressive strength of >40 MPa.

  11. Simultaneous spectrophotometric determination of atorvastatin calcium and amlodipine besylate in tablets

    Directory of Open Access Journals (Sweden)

    Khan M

    2006-01-01

    Full Text Available Two simple, accurate and precise methods for simultaneous estimation of atorvastatin calcium and amlodipine besylate in combined dosage form have been described. First method employs formation and solving of simultaneous equations using 245 nm and 363 nm as two analytical wavelengths. Second is dual wavelength method, which uses the difference of absorbance value at 259.9 nm and 354 nm for estimation of atorvastatin calcium and absorbance at 363 nm for amlodipine besylate. Fifty percent methanol was used as solvent, in which atorvastatin calcium and amlodipine besylate shows linearity in the range of 0-40 µg/ml and 0-20 µg/ml, respectively. Standard deviation was < 1.5 in the assay of tablets. Methods were validated as per ICH norms and accuracy, precision, repeatability and robustness was found to be with in the acceptable limit.

  12. A review: Different methods producing different particles size and distribution in synthesis of calcium carbonate nano particles

    Science.gov (United States)

    Sulimai, N. H.; Rusop, M.; Alrokayan, Salman A. H.; Khan, Haseeb A.

    2016-07-01

    Carbonates exist as 73 percent of world crust carbon. Abundance and bioavailability of Calcium Carbonates offer reliable resources, costs saving and environmental friendly potentials in its applications. Studies proven nano-sized Calcium Cabonate (nCC) employs a more significant characteristics compared to larger sizes. Properties of nCC is affected by the dispersion of the particles in which agglomeration occurs. It is important to gain more understanding of the conditions contributing or stunting the agglomeration to gain more control of the particles morphology and dynamic. A few recent studies with different methods to prepare calcium carbonate nanoparticles were listed in Table 1 .Particle size and dispersity of calcium carbonate are affected by different conditions of its preparation. Other factors such as mechanical aggression, concentration of solution, temperature of precipitation, pH of reaction are all contributing factors towards particle sizes and distribution.

  13. Effect of Temperature on Precipitation Rate of Calcium Carbonate Produced through Microbial Metabolic Process of Bio Materials

    Directory of Open Access Journals (Sweden)

    Prima Yane Putri

    2016-09-01

    Full Text Available Concrete is the most widely used construction material in civil engineering. But plain concrete is a brittle material and has little resistance to cracking. The cracking in concrete promotes deterioration such as the corrosion of reinforcing rebar, therefore, repair in filling the crack is often carried out. Recently, repair methods using bio-based materials associated with microbial metabolic processes leading to precipitation of calcium carbonate have been intensively studied. In this study, influencing factors on the precipitation rate depending on the constituents of bio-based material comprising yeast, glucose and calcium acetate mixed in tris buffer solution was examined for improving the rate of initial reactions. In addition, effect of temperature change on the amount of calcium carbonate precipitation was also investigated. The precipitates were identified by X-ray diffraction. It was shown that the increase of temperature lead to a change on calcium carbonate precipitation and caused the pH decrease under 7.0.

  14. Fast kinetics of calcium signaling and sensor design.

    Science.gov (United States)

    Tang, Shen; Reddish, Florence; Zhuo, You; Yang, Jenny J

    2015-08-01

    Fast calcium signaling is regulated by numerous calcium channels exhibiting high spatiotemporal profiles which are currently measured by fluorescent calcium sensors. There is still a strong need to improve the kinetics of genetically encoded calcium indicators (sensors) to capture calcium dynamics in the millisecond time frame. In this review, we summarize several major fast calcium signaling pathways and discuss the recent developments and application of genetically encoded calcium indicators to detect these pathways. A new class of genetically encoded calcium indicators designed with site-directed mutagenesis on the surface of beta-barrel fluorescent proteins to form a pentagonal bipyramidal-like calcium binding domain dramatically accelerates calcium binding kinetics. Furthermore, novel genetically encoded calcium indicators with significantly increased fluorescent lifetime change are advantageous in deep-field imaging with high light-scattering and notable morphology change.

  15. 40 CFR 415.34 - [Reserved

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 28 2010-07-01 2010-07-01 true 415.34 Section 415.34 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) EFFLUENT GUIDELINES AND STANDARDS INORGANIC CHEMICALS MANUFACTURING POINT SOURCE CATEGORY Calcium Carbide Production Subcategory § 415.34...

  16. Relationship of calcium absorption with 25(OH)D and calcium intake in children with rickets.

    Science.gov (United States)

    Thacher, Tom D; Abrams, Steven A

    2010-11-01

    Nutritional rickets has long been considered a disease caused by vitamin D deficiency, but recent data indicate that inadequate dietary calcium intake is an important cause of rickets, particularly in tropical countries. Children with rickets due to calcium deficiency do not have very low 25(OH)D concentrations, and serum 1,25(OH)(2) D values are markedly elevated. Studies of Nigerian children with rickets demonstrated they have high fractional calcium absorption. A high-phytate diet was demonstrated to increase calcium absorption compared with the fasting state, and enzymatic dephytinization did not significantly improve calcium absorption. When given vitamin D, children with rickets have a marked increase in 1,25(OH)(2) D concentrations without any change in fractional calcium absorption. No positive relationship was found between fractional calcium absorption and serum 25(OH)D concentrations in children on low-calcium diets. More research is needed to understand the interaction between calcium and vitamin D and the role of vitamin D in calcium absorption.

  17. [Allergic reactions to transfusion].

    Science.gov (United States)

    Hergon, E; Paitre, M L; Coeffic, B; Piard, N; Bidet, J M

    1987-04-01

    Frequent allergic reactions following transfusion are observed. Usually, they are benign but sometimes we observe severe allergic reactions. Adverse reactions may be brought about by least two mechanisms. First, immediate-type hypersensibility reactions due to IgE. Secondly, anaphylactic-type reactions due to interaction between transfused IgA and class specific anti IgA in the recipient's plasma. They are characterized by their severest form (anaphylactic shock). The frequency of severe reactions following the transfusion blood plasma is very low. These transfusion reactions are complement-mediated and kinins-mediated. Prevention of allergic reactions is necessary among blood donors and recipients.

  18. Elasticity of calcium and calcium-sodium amphiboles

    Science.gov (United States)

    Brown, J. Michael; Abramson, Evan H.

    2016-12-01

    Measurements of single-crystal elastic moduli under ambient conditions are reported for nine calcium to calcium-sodium amphiboles that lie in the composition range of common crustal constituents. Velocities of body and surface acoustic waves measured by Impulsive Stimulated Light Scattering (ISLS) were inverted to determine the 13 moduli characterizing these monoclinic samples. Moduli show a consistent pattern: C33 > C22 > C11 and C23 > C12 > C13 and C44 > C55 ∼ C66 and for the uniquely monoclinic moduli, |C35| ≫ C46 ∼ |C25| > |C15| ∼ 0. Most of the compositionally-induced variance of moduli is associated with aluminum and iron content. Seven moduli (C11C12C13C22C44C55C66) increase with increasing aluminum while all diagonal moduli decrease with increasing iron. Three moduli (C11, C13 and C44) increase with increasing sodium and potassium occupancy in A-sites. The uniquely monoclinic moduli (C15C25 and C35) have no significant compositional dependence. Moduli associated with the a∗ direction (C11C12C13C55 and C66) are substantially smaller than values associated with structurally and chemically related clinopyroxenes. Other moduli are more similar for both inosilicates. The isotropically averaged adiabatic bulk modulus does not vary with iron content but increases with aluminum content from 85 GPa for tremolite to 99 GPa for pargasite. Increasing iron reduces while increasing aluminum increases the isotropic shear modulus which ranges from 47 GPa for ferro-actinolite to 64 GPa for pargasite. These results exhibit far greater anisotropy and higher velocities than apparent in earlier work. Quasi-longitudinal velocities are as fast as ∼9 km/s and (intermediate between the a∗- and c-axes) are as slow as ∼6 km/s. Voigt-Reuss-Hill averaging based on prior single crystal moduli resulted in calculated rock velocities lower than laboratory measurements, leading to adoption of the (higher velocity) Voigt bound. Thus, former uses of the upper Voigt bound can

  19. Calcium intake and calcium deficiency in toddlers in a slum population of Bhubaneswar

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    Sonali Kar

    2014-12-01

    Full Text Available Introduction: When considering their children's nutrition, parents often think more about fat grams, carbs, and calories, and forget about calcium, a mineral that is important to help build strong and healthy bones and collagen structures like teeth. The RDI recommendation for 1-3 years is minimum 400mg/day. Calcium is selectively present in milk and milk products besides vegetables like spinach and fruits like orange. The current study was undertaken in the urban field practice area of KIMS that caters to a slum population of nearly 20,000. Aims & Objectives: To assess the knowledge of mothers regarding calcium rich foods and its deficiency and their sociodemographic conditions; to assess the average intake of Calcium using the 7 day recall method; to find the prevalence of possible calcium deficiency in the study population ie 1-3 years of age. Methods: All the mothers with children in the age group 1-3 years were recruited in the study after due informed consent, the final sample being nearly 284. The male female child ratio was 56:44. Mostly women i.e. 83% had some formal education and out of the total nearly 65% had heard never heard of calcium and of those who had heard only 30% could say that milk was the best source of calcium. Result: Average daily Calcium intake was poor i.e. 288mg/d which was worse for the female child 233mg/d. Teeth eruption defects or infections and bone deformities were taken as a proxy for calcium deficiency and were detected in 69.2% and 32% respectively. Diarrhea and skin infections were more in those whose calcium intake was less than 220mg/d which was mildly significant. Conclusion: The study suggests more emphasis on dietary calcium intake and probably recommend calcium supplements for the socioeconomically compromised class who probably cannot afford dietary sources of calcium

  20. Effect of calcium intake on urinary oxalate excretion in calcium stone-forming patients

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    Nishiura J.L.

    2002-01-01

    Full Text Available Dietary calcium lowers the risk of nephrolithiasis due to a decreased absorption of dietary oxalate that is bound by intestinal calcium. The aim of the present study was to evaluate oxaluria in normocalciuric and hypercalciuric lithiasic patients under different calcium intake. Fifty patients (26 females and 24 males, 41 ± 10 years old, whose 4-day dietary records revealed a regular low calcium intake (<=500 mg/day, received an oral calcium load (1 g/day for 7 days. A 24-h urine was obtained before and after load and according to the calciuria under both diets, patients were considered as normocalciuric (NC, N = 15, diet-dependent hypercalciuric (DDHC, N = 9 or diet-independent hypercalciuric (DIHC, N = 26. On regular diet, mean oxaluria was 30 ± 14 mg/24 h for all patients. The 7-day calcium load induced a significant decrease in mean oxaluria compared to the regular diet in NC and DIHC (20 ± 12 vs 26 ± 7 and 27 ± 18 vs 32 ± 15 mg/24 h, respectively, P<0.05 but not in DDHC patients (22 ± 10 vs 23 ± 5 mg/24 h. The lack of an oxalate decrease among DDHC patients after the calcium load might have been due to higher calcium absorption under higher calcium supply, with a consequent lower amount of calcium left in the intestine to bind with oxalate. These data suggest that a long-lasting regular calcium consumption <500 mg was not associated with high oxaluria and that a subpopulation of hypercalciuric patients who presented a higher intestinal calcium absorption (DDHC tended to hyperabsorb oxalate as well, so that oxaluria did not change under different calcium intake.

  1. Vitamin D, calcium homeostasis and aging

    Science.gov (United States)

    Veldurthy, Vaishali; Wei, Ran; Oz, Leyla; Dhawan, Puneet; Jeon, Yong Heui; Christakos, Sylvia

    2016-01-01

    Osteoporosis is characterized by low bone mass and microarchitecture deterioration of bone tissue, leading to enhanced bone fragility and consequent increase in fracture risk. Evidence is accumulating for an important role of calcium deficiency as the process of aging is associated with disturbed calcium balance. Vitamin D is the principal factor that maintains calcium homeostasis. Increasing evidence indicates that the reason for disturbed calcium balance with age is inadequate vitamin D levels in the elderly. In this article, an overview of our current understanding of vitamin D, its metabolism, and mechanisms involved in vitamin D-mediated maintenance of calcium homeostasis is presented. In addition, mechanisms involved in age-related dysregulation of 1,25(OH)2D3 action, recommended daily doses of vitamin D and calcium, and the use of vitamin D analogs for the treatment of osteoporosis (which remains controversial) are reviewed. Elucidation of the molecular pathways of vitamin D action and modifications that occur with aging will be an active area of future research that has the potential to reveal new therapeutic strategies to maintain calcium balance. PMID:27790378

  2. Lead removal in rats using calcium alginate.

    Science.gov (United States)

    Savchenko, Olga V; Sgrebneva, Marina N; Kiselev, Vladimir I; Khotimchenko, Yuri S

    2015-01-01

    Lead (Pb) exposure, even at low levels, causes a variety of health problems. The aims of this study were to investigate the tissue distribution of lead in the bodies of rats, to evaluate lead removal from the internal organs and bones using calcium alginate in doses of 500, 200 and 100 mg/kg per day for 28 days and to assess the impact of calcium alginate on the level of essential elements. Lead (Pb), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu) and zinc (Zn) levels in the blood, hearts, kidneys, livers and femurs of the experimental animals were measured using mass spectrometry with inductively coupled plasma. The results revealed that lead acetate exposure increased the levels of Pb in the blood and organs of the animals and significantly reduced contents of Ca, Mn, Fe, Cu and Zn. Treatment with calcium alginate in dose 500 mg/kg contributed to significant decreases in the amount of lead in the kidney, heart and bones of animals and a slight increase in the content of essential elements in the liver, kidneys and heart, although these changes were not significant. Decreasing of lead was not significant in the internal organs, bones and blood of animals treated with calcium alginate 200 and 100 mg/kg. Consequently, calcium alginate dose of 500 mg/kg more efficiently removes lead accumulated in the body. Calcium alginate does not have negative effect on level of essential elements quite the contrary; reducing the levels of lead, calcium alginate helps normalize imbalances of Ca, Mn, Fe, Cu and Zn. The results of this study suggest that calcium alginate may potentially be useful for the treatment and prevention of heavy metal intoxications.

  3. Biocompatibility of a new nanomaterial based on calcium silicate implanted in subcutaneous connective tissue of rats

    Directory of Open Access Journals (Sweden)

    Petrović Violeta

    2012-01-01

    Full Text Available The aim of the study was to investigate rat connective tissue response to a new calcium silicate system 7, 15, 30 and 60 days after implantation. Twenty Wistar albino male rats received two tubes half-filled with a new calcium silicate system (NCSS or MTA in subcutaneous tissue. The empty half of the tubes served as controls. Five animals were sacrificed after 7, 15, 30 and 60 days and samples of the subcutaneous tissue around implanted material were submitted to histological analysis. The intensity of inflammation was evaluated based on the number of inflammatory cells present. Statistical analysis was performed using one way ANOVA and Holm Sidak's multiple comparison tests. Mild to moderate inflammatory reaction was observed after 7, 15 and 30 days around a NCSS while mild inflammatory reaction was detected after 60 days of implantation. In the MTA group, mild to moderate inflammatory reaction was found after 7 and 15 days while mild inflammatory reaction was present after 30 and 60 days. There was no statistically significant difference in the intensity of inflammatory reactions between the tested materials and control groups in any experimental period (ANOVA p>0.05. Regarding the intensity of inflammatory reactions at different experimental periods, a statistically significant difference was observed between 7 and 30 days, 7 and 60 days and 15 to 60 days for both materials. For the controls, a statistically significant difference was found between 7 and 60 days and 15 and 60 days of the experiment (Holm Sidak < p 0.001. Subcutaneous tissue of rats showed good tolerance to a new calcium silicate system. Inflammatory reaction was similar to that caused by MTA. [Projekat Ministarstva nauke Republike Srbije, br. 172026

  4. The effect of GlycoPEGylation on the physical stability of human rFVIIa with increasing calcium chloride concentration

    DEFF Research Database (Denmark)

    Plesner, Bitten; Westh, Peter; Hvidt, Søren

    2011-01-01

    The effects of calcium chloride on the structural, kinetic and thermal stability of recombinant human factor VIIa (rFVIIa) were investigated using rFVIIa and two GlycoPEGylated recombinant human FVIIa derivatives, a linear 10 kDa PEG and a branched 40 kDa PEG, respectively. Three different CaCl(2...... scanning calorimetry (DSC) and circular dichroism (CD), and aggregation behaviour, measured by light scattering (LS), were affected by the increasing calcium concentration. Increasing the CaCl(2) concentration from 10mM to 35 mM resulted in a decrease in the apparent unfolding temperature, T(m), of r......FVIIa compounds was practically independent of the CaCl(2) concentration. From the obtained results, it is concluded that GlycoPEGylation postpones the calcium induced thermal destabilisation of rFVIIa, and a much higher calcium concentration also postpones the thermally induced aggregation of r...

  5. Effectiveness of a theory-driven nutritional education program in improving calcium intake among older Mauritian adults.

    Science.gov (United States)

    Bhurosy, Trishnee; Jeewon, Rajesh

    2013-01-01

    Background. Low calcium intake, a risk factor of osteoporosis and subsequent fractures, has been previously reported among post-menopausal women in Mauritius. Objective. To assess the effectiveness of a theory-based educational intervention in improving the calcium intake, self-efficacy, and knowledge of older Mauritians. Methodology. The study was conducted as a pre- and post-test design which was evaluated through a baseline, immediate postintervention, and 2-month follow-up assessments. Participants were adults (n = 189) aged ≥40 years old from 2 urban community-based centres. The intervention group (IG) (n = 98) participated in 6 weekly interactive lessons based on the health belief model (HBM). The main outcome measures were calcium intake, HB scale scores, knowledge scores, and physical activity level (PAL). Anthropometric measurements were also assessed. Results. The IG significantly increased its baseline calcium intake, knowledge and self-efficacy (P adults when compared to the CG (P older community-based Mauritian adults.

  6. Brushite-based calcium phosphate cement with multichannel hydroxyapatite granule loading for improved bone regeneration.

    Science.gov (United States)

    Sarkar, Swapan Kumar; Lee, Byung Yeol; Padalhin, Andrew Reyas; Sarker, Avik; Carpena, Nathaniel; Kim, Boram; Paul, Kallyanshish; Choi, Hwan Jun; Bae, Sang-Ho; Lee, Byong Taek

    2016-01-01

    In this work, we report brushite-based calcium phosphate cement (CPC) system to enhance the in vivo biodegradation and tissue in-growth by incorporation of micro-channeled hydroxyapatite (HAp) granule and silicon and sodium addition in calcium phosphate precursor powder. Sodium- and silicon-rich calcium phosphate powder with predominantly tri calcium phosphate (TCP) phase was synthesized by an inexpensive wet chemical route to react with mono calcium phosphate monohydrate (MCPM) for making the CPC. TCP nanopowder also served as a packing filler and moderator of the reaction kinetics of the setting mechanism. Strong sintered cylindrical HAp granules were prepared by fibrous monolithic (FM) process, which is 800 µm in diameter and have seven micro-channels. Acid sodium pyrophosphate and sodium citrate solution was used as the liquid component which acted as a homogenizer and setting time retarder. The granules accelerated the degradation of the brushite cement matrix as well as improved the bone tissue in-growth by permitting an easy access to the interior of the CPC through the micro-channels. The addition of micro-channeled granule in the CPC introduced porosity without sacrificing much of its compressive strength. In vivo investigation by creating a critical size defect in the femur head of a rabbit model for 1 and 2 months showed excellent bone in-growth through the micro-channels. The granules enhanced the implant degradation behavior and bone regeneration in the implanted area was significantly improved after two months of implantation.

  7. Synthesis, QSAR and calcium channel modulator activity of new hexahydroquinoline derivatives containing nitroimidazole.

    Science.gov (United States)

    Miri, Ramin; Javidnia, Katayoun; Mirkhani, Hossein; Hemmateenejad, Bahram; Sepeher, Zahra; Zalpour, Masomeh; Behzad, Taherh; Khoshneviszadeh, Mehdi; Edraki, Najmeh; Mehdipour, Ahmad R

    2007-10-01

    The discovery that 1,4-dihydropyridine class of calcium channel antagonists inhibit Ca2+ influx represented a major therapeutic advance in the treatment of cardiovascular disease. In contrast to the effects of known calcium channel blockers of the Nifedipine-type, the so-called calcium channel agonists, such as Bay K8644 and CGP 28392, increase calcium influx by binding at the same receptor regions. Our goal was to discover a dual cardioselective Ca2+-channel agonist/vascular selective smooth muscle Ca2+ channel antagonist third-generation 1,4-dihydropyridine drug which would have a suitable therapeutic profile for treating congestive heart failure (CHF) patients. A series of unsymmetrical alkyl, cycloalkyl and aryl ester analogues of 2-methyl-4-(1-methyl)-5-nitro-2-imidazolyl-5-oxo-1,4,5,6,7, 8-hexahydroquinolin-3-arboxylate were synthesized using modified Hantzsch reaction. All compounds show calcium antagonist activity on guinea-pig ileum longitudinal smooth muscle and some of them show agonist effect activity on guinea-pig auricle. Effect of structural parameters on the Ca2+ channel agonist/antagonist was evaluated by quantitative structure-activity relationship analysis. These compounds could be considered as a synthon for developing a suitable drug for treating CHF patients.

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

    Science.gov (United States)

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

    2012-01-01

    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).

  9. Molecular imaging of in vivo calcium ion expression in area postrema of total sleep deprived rats: Implications for cardiovascular regulation by TOF-SIMS analysis

    Science.gov (United States)

    Mai, Fu-Der; Chen, Li-You; Ling, Yong-Chien; Chen, Bo-Jung; Wu, Un-In; Chang, Hung-Ming

    2010-05-01

    Excessive calcium influx in chemosensitive neurons of area postrema (AP) is detrimental for sympathetic activation and participates in the disruption of cardiovascular activities. Since total sleep deprivation (TSD) is a stressful condition known to harm the cardiovascular function, the present study is aimed to determine whether the in vivo calcium expression in AP would significantly alter following TSD by the use of time-of-flight secondary ion mass spectrometry (TOF-SIMS) and calretinin (a specific calcium sensor protein in AP neurons) immunohistochemistry. The results indicated that in normal rats, the calcium intensity was estimated to be 0.5 × 10 5 at m/ z 40.08. However, following TSD, the intensity for calcium ions was greatly increased to 1.2 × 10 5. Molecular imaging revealed that after TSD, various strongly expressed calcium signals were distributed throughout AP with clear identified profiles instead of randomly scattered within this region in normal rats. Immunohistochemical staining corresponded well with ionic image in which a majority of calcium-enriched gathering co-localized with calretinin positive neurons. The functional significance of TSD-induced calcium augmentation was demonstrated by increased heart rate and mean arterial pressure, clinical markers for cardiovascular dysfunction. Considering AP-mediated sympathetic activation is important for cardiovascular regulation, exaggerated calcium influx in AP would render this neurocircuitry more vulnerable to over-excitation, which might serve as the underlying mechanism for the development of TSD-relevant cardiovascular deficiency.

  10. Local calcium elevation and cell elongation initiate guided motility in electrically stimulated osteoblast-like cells.

    Directory of Open Access Journals (Sweden)

    Nurdan Ozkucur

    rearrangements underlying EF-guided migration of osteoblast-like cell types and reveal a requirement for calcium in these reactions. We show for the first time here that dcEFs trigger different patterns of intracellular calcium elevation and positional shifting in osteogenic cell types that migrate in opposite directions.

  11. Calcium Signaling Is Required for Erythroid Enucleation.

    Science.gov (United States)

    Wölwer, Christina B; Pase, Luke B; Russell, Sarah M; Humbert, Patrick O

    2016-01-01

    Although erythroid enucleation, the property of erythroblasts to expel their nucleus, has been known for 7ore than a century, surprisingly little is known regarding the molecular mechanisms governing this unique developmental process. Here we show that similar to cytokinesis, nuclear extrusion requires intracellular calcium signaling and signal transduction through the calmodulin (CaM) pathway. However, in contrast to cytokinesis we found that orthochromatic erythroblasts require uptake of extracellular calcium to enucleate. Together these functional studies highlight a critical role for calcium signaling in the regulation of erythroid enucleation.

  12. Calcium Signaling Is Required for Erythroid Enucleation.

    Directory of Open Access Journals (Sweden)

    Christina B Wölwer

    Full Text Available Although erythroid enucleation, the property of erythroblasts to expel their nucleus, has been known for 7ore than a century, surprisingly little is known regarding the molecular mechanisms governing this unique developmental process. Here we show that similar to cytokinesis, nuclear extrusion requires intracellular calcium signaling and signal transduction through the calmodulin (CaM pathway. However, in contrast to cytokinesis we found that orthochromatic erythroblasts require uptake of extracellular calcium to enucleate. Together these functional studies highlight a critical role for calcium signaling in the regulation of erythroid enucleation.

  13. The Influence of Calcium Chloride Salt Solution on the Transport Properties of Cementitious Materials

    Directory of Open Access Journals (Sweden)

    Yaghoob Farnam

    2015-01-01

    Full Text Available The chemical interaction between calcium chloride (CaCl2 and cementitious binder may alter the transport properties of concrete which are important in predicting the service life of infrastructure elements. This paper presents a series of fluid and gas transport measurements made on cementitious mortars before and after exposure to various solutions with concentrations ranging from 0% to 29.8% CaCl2 by mass. Fluid absorption, oxygen diffusivity, and oxygen permeability were measured on mortar samples prepared using Type I and Type V cements. Three primary factors influence the transport properties of mortar exposed to CaCl2: (1 changes in the degree of saturation, (2 calcium hydroxide leaching, and (3 formation of chemical reaction products (i.e., Friedel’s salt, Kuzel’s salt, and calcium oxychloride. It is shown that an increase in the degree of saturation decreases oxygen permeability. At lower concentrations (~12%, the formation of chemical reaction products (mainly calcium oxychloride is a dominant factor decreasing the fluid and gas transport in concrete.

  14. [Study on the influence of mineralizer on the structures and spectral properties of calcium aluminates].

    Science.gov (United States)

    Zheng, Huai-Li; Liu, Jun-Yu; Li, Lin-Tao; Li, Fang

    2009-11-01

    The present paper investigated the effect of mineralizer on the structure and properties of calcium aluminates formation. Calcium aluminates powder was synthesized under high temperature calcination by mixing bauxite, limestone and a certain amount of mineralizer. The product structure, compositional information and spectral properties were carefully characterized by XRD, IR and DTA-TG, and the mineralization mechanism of mineralizer was studied during the process of calcium aluminates preparation. The results showed that calcium aluminates powder could be obtained under lower temperature calcination after adding mineralizer to the raw materials. The main products of the reaction were CaAl10 O18 and CaAl2 Si2 O8 without mineralizer, however, the main products of the reaction were CaAl3 BO7 and Ca3 Al10 O18 with mineralizer, in which Al2 O3s could be extracted easily, while CaAl2 Si2 O8 was reduced greatly in which Al2 O3 could not be extracted easily. At the same time, it is easy for calcspar to decompose after adding mineralizer. It is favorable to Al-Si bond break and Al stripping from bauxite. These facts could improve the extraction rate of Al2 O3 from raw materials. Also, in the case of adding mineralizer to the raw mixes, the crystal structure and composition are changed, which is beneficial to reducing calcination temperature.

  15. Thermochemistry of calcium oxide and calcium hydroxide in fluoride slags

    Science.gov (United States)

    Chattopadhyay, S.; Mitchell, A.

    1990-08-01

    Calcium oxide activity in binary CaF2-CaO and ternary CaF2-CaO-Al2O3 and CaF2-CaO-SiO2 slags has been determined by CO2-slag equilibrium experiments at 1400 °C. The carbonate ca-pacity of these slags has also been computed and compared with sulfide capacity data available in the literature. The similarity in trends suggests the possibility of characterizing carbonate capacity as an alternative basicity index for fluoride-base slags. Slag-D2O equilibrium experi-ments are performed at 1400°C with different fluoride-base slags to determine water solubility at two different partial pressures of D2O, employing a new slag sampling technique. A novel isotope tracer detection technique is employed to analyze water in the slags. The water solubility data found show higher values than the previous literature data by an order of magnitude but show a linear relationship with the square root of water vapor partial pressure. The activity of hydroxide computed from the data is shown to be helpful in estimating water solubility in in-dustrial electroslag remelting (ESR) slags.

  16. Effect of calcium chloride addition on ice cream structure and quality.

    Science.gov (United States)

    Costa, F F; Resende, J V; Abreu, L R; Goff, H D

    2008-06-01

    The influence of calcium fortification by the addition of calcium chloride on quality parameters of ice cream based on physical properties was investigated, as was the effect of kappa-carrageenan at modifying the effects of this calcium fortification. Four ice cream mixes of conventional composition, with added kappa-carrageenan (0 or 0.025%) and added calcium chloride (0 or 4.4 g L(-1) = 40 mM of added Ca(2+)), were prepared. Modulated temperature-differential scanning calorimetry was used to investigate the effect of calcium chloride on the nucleation temperature, enthalpy of melting, and freezing point depression. The protein composition of 15.4% (wt/wt) reconstituted skim milk powder solutions with or without 4.4 g L(-1) added CaCl(2) and in the supernatant after ultracentrifugation was determined. Fat particle size distributions in ice cream were characterized by light scattering. Ice crystal sizes before and after temperature cycling were determined by cold-stage light microscopy. The results demonstrated that the addition of calcium chloride led to a substantial increase in ice crystal sizes and in fat partial coalescence, which were exacerbated by the addition of kappa-carrageenan. These results can be explained by the interaction between Ca(2+) ions and casein micelles, rather than any effects on freezing point depression. The calcium ions led to a more compact micelle, less serum beta-casein, and high fat destabilization, all of which would be expected to reduce macromolecular structure and volume occupancy in the unfrozen phase, which led to increased rates of ice recrystallization.

  17. Inactivation kinetics and pharmacology distinguish two calcium currents in mouse pancreatic B-cells

    Energy Technology Data Exchange (ETDEWEB)

    Hopkins, W.F.; Satin, L.S.; Cook, D.L. (Univ. of Washington School of Medicine, Seattle (USA))

    1991-02-01

    Voltage-dependent calcium currents were studied in cultured adult mouse pancreatic B-cells using the whole-cell voltage-clamp technique. When calcium currents were elicited with 10-sec depolarizing command pulses, the time course of inactivation was well fit by the sum of two exponentials. The more rapidly-inactivating component had a time constant of 75 +/- 5 msec at 0 mV and displayed both calcium influx- and voltage-dependent inactivation, while the more slowly-inactivating component had a time constant of 2750 +/- 280 msec at 0 mV and inactivated primarily via voltage. The fast component was subject to greater steady-state inactivation at holding potentials between -100 and -40 mV and activated at a lower voltage threshold. This component was also significantly reduced by nimodipine (0.5 microM) when a holding potential of -100 mV was used, whereas the slow component was unaffected. In contrast, the slow component was greatly increased by replacing external calcium with barium, while the fast component was unchanged. Cadmium (1-10 microM) displayed a voltage-dependent block of calcium currents consistent with a greater effect on the high-threshold, more-slowly inactivating component. Taken together, the data suggest that cultured mouse B-cells, as with other insulin-secreting cells we have studied, possess at least two distinct calcium currents. The physiological significance of two calcium currents having distinct kinetic and steady-state inactivation characteristics for B-cell burst firing and insulin secretion is discussed.

  18. H{sub 3}PW{sub 12}O{sub 40} (HPA), an efficient and reusable catalyst for biodiesel production related reactions. Esterification of oleic acid and etherification of glycerol

    Energy Technology Data Exchange (ETDEWEB)

    Sepulveda, Jorge H.; Vera, Carlos R.; Yori, Juan C.; Badano, Juan M., E-mail: jsepulve@fiq.unl.edu.a [Instituto de Investigaciones en Catalisis y Petroquimica, Santiago del Estero Santa Fe (Argentina); Santarosa, Daniel; Mandelli, Dalmo [Pontificia Universidade Catolica de Campinas, SP (Brazil). Faculdade Quimica

    2011-07-01

    In esterification of oleic acid with methanol at 25 deg C HPA displayed the highest activity. Moreover the HPA could be reused after being transformed into its cesium salt. In the reaction of etherification of glycerol HPA and Amberlyst 35W showed similar initial activity levels. The results of acid properties demonstrate that HPA is a strong protonic acid and that both surface and bulk protons contribute to the acidity. Because of its strong affinity for polar compounds, HPA is also seemingly dissolved in both oleic acid and methanol. The reaction in this case proceeds with the catalyst in the homogenous phase. (author)

  19. Synthesis of spherical calcium phosphate particles for dental and orthopedic applications.

    Science.gov (United States)

    Bohner, Marc; Tadier, Solène; van Garderen, Noémie; de Gasparo, Alex; Döbelin, Nicola; Baroud, Gamal

    2013-01-01

    Calcium phosphate materials have been used increasingly in the past 40 years as bone graft substitutes in the dental and orthopedic fields. Accordingly, numerous fabrication methods have been proposed and used. However, the controlled production of spherical calcium phosphate particles remains a challenge. Since such particles are essential for the synthesis of pastes and cements delivered into the host bone by minimally-invasive approaches, the aim of the present document is to review their synthesis and applications. For that purpose, production methods were classified according to the used reagents (solutions, slurries, pastes, powders), dispersion media (gas, liquid, solid), dispersion tools (nozzle, propeller, sieve, mold), particle diameters of the end product (from 10 nm to 10 mm), and calcium phosphate phases. Low-temperature calcium phosphates such as monetite, brushite or octacalcium phosphate, as well as high-temperature calcium phosphates, such as hydroxyapatite, β-tricalcium phosphate or tetracalcium phosphate, were considered. More than a dozen production methods and over hundred scientific publications were discussed.

  20. Synthesis of spherical calcium phosphate particles for dental and orthopedic applications

    Science.gov (United States)

    Bohner, Marc; Tadier, Solène; van Garderen, Noémie; de Gasparo, Alex; Döbelin, Nicola; Baroud, Gamal

    2013-01-01

    Calcium phosphate materials have been used increasingly in the past 40 years as bone graft substitutes in the dental and orthopedic fields. Accordingly, numerous fabrication methods have been proposed and used. However, the controlled production of spherical calcium phosphate particles remains a challenge. Since such particles are essential for the synthesis of pastes and cements delivered into the host bone by minimally-invasive approaches, the aim of the present document is to review their synthesis and applications. For that purpose, production methods were classified according to the used reagents (solutions, slurries, pastes, powders), dispersion media (gas, liquid, solid), dispersion tools (nozzle, propeller, sieve, mold), particle diameters of the end product (from 10 nm to 10 mm), and calcium phosphate phases. Low-temperature calcium phosphates such as monetite, brushite or octacalcium phosphate, as well as high-temperature calcium phosphates, such as hydroxyapatite, β-tricalcium phosphate or tetracalcium phosphate, were considered. More than a dozen production methods and over hundred scientific publications were discussed. PMID:23719177

  1. Relationship between sealing ability of Activ GP and Gutta Flow and methods of calcium hydroxide removal

    Directory of Open Access Journals (Sweden)

    Vineeta Nikhil

    2012-01-01

    Full Text Available Aim: To evaluate the effect of method of calcium hydroxide intracanal dressing removal, on sealing ability of Gutta Flow and Activ GP. Materials and Methods: Seventy extracted mandibular premolars were sectioned at CEJ and canals were prepared with profile 4% rotary file till #40. Canals were filled with calcium hydroxide, coronally sealed with Cavit G and stored at 37°C. After 7 days, samples were divided on the basis of calcium hydroxide removal method (Master apical file, Navi Tip FX, and F File and obturating material (Activ GP and Gutta Flow. Three coats of nail polish were applied except 2 mm around apical foramen and samples were immersed in India ink dye, sectioned, and observed under stereomicroscope for microleakage. Results: The results were statistically analyzed with one way ANOVA-F with Tukey HSD test with the null hypothesis set as 5%. Conclusions: The seal of the canal system was adversely impacted by residual calcium hydroxide when Activ GP and Gutta Flow were used as obturating material and the sealing ability of Activ GP and Gutta Flow was better when MAF was used for removal of calcium hydroxide than F file or Navi tip FX.

  2. Hydrolytic conversion of amorphous calcium phosphate into apatite accompanied by sustained calcium and orthophosphate ions release.

    Science.gov (United States)

    Niu, Xufeng; Chen, Siqian; Tian, Feng; Wang, Lizhen; Feng, Qingling; Fan, Yubo

    2017-01-01

    The aim of this study is to investigate the calcium and orthophosphate ions release during the transformation of amorphous calcium phosphate (ACP) to hydroxyapatite (HA) in aqueous solution. The ACP is prepared by a wet chemical method and further immersed in the distilled water for various time points till 14d. The release of calcium and orthophosphate ions is measured with calcium and phosphate colorimetric assay kits, respectively. The transition of ACP towards HA is detected by x-ray diffraction (XRD), transmission electron microscopy (TEM), and fourier transform infrared spectroscopy (FTIR). The results indicate that the morphological conversion of ACP to HA occurs within the first 9h, whereas the calcium and orthophosphate ions releases last for over 7d. Such sustained calcium and orthophosphate ions release is very useful for ACP as a candidate material for hard tissue regeneration.

  3. Calcium acetate versus calcium carbonate as phosphorus binders in patients on chronic haemodialysis: a controlled study.

    Science.gov (United States)

    Ring, T; Nielsen, C; Andersen, S P; Behrens, J K; Sodemann, B; Kornerup, H J

    1993-01-01

    The first reported double-blind cross-over comparison between the phosphorus binders calcium carbonate and calcium acetate was undertaken in 15 stable patients on chronic maintenance haemodialysis. Detailed registration of diet and analysis of the protein catabolic rate suggested an unchanged phosphorus intake during the study. It was found that predialytic serum phosphate concentration was significantly decreased by 0.11 mmol/l (0.34 mg/dl) (P = 0.021, 95% confidence limits 0.02-0.21 mmol/l; 0.06-0.65 mg/dl) during calcium acetate treatment. The calcium phosphate product was insignificantly decreased during treatment with calcium acetate whereas we could not exclude the possibility that calcium concentration had increased.

  4. Structures of apicomplexan calcium-dependent protein kinases reveal mechanism of activation by calcium

    Energy Technology Data Exchange (ETDEWEB)

    Wernimont, Amy K; Artz, Jennifer D.; Jr, Patrick Finerty; Lin, Yu-Hui; Amani, Mehrnaz; Allali-Hassani, Abdellah; Senisterra, Guillermo; Vedadi, Masoud; Tempel, Wolfram; Mackenzie, Farrell; Chau, Irene; Lourido, Sebastian; Sibley, L. David; Hui, Raymond (Toronto); (WU-MED)

    2010-09-21

    Calcium-dependent protein kinases (CDPKs) have pivotal roles in the calcium-signaling pathway in plants, ciliates and apicomplexan parasites and comprise a calmodulin-dependent kinase (CaMK)-like kinase domain regulated by a calcium-binding domain in the C terminus. To understand this intramolecular mechanism of activation, we solved the structures of the autoinhibited (apo) and activated (calcium-bound) conformations of CDPKs from the apicomplexan parasites Toxoplasma gondii and Cryptosporidium parvum. In the apo form, the C-terminal CDPK activation domain (CAD) resembles a calmodulin protein with an unexpected long helix in the N terminus that inhibits the kinase domain in the same manner as CaMKII. Calcium binding triggers the reorganization of the CAD into a highly intricate fold, leading to its relocation around the base of the kinase domain to a site remote from the substrate binding site. This large conformational change constitutes a distinct mechanism in calcium signal-transduction pathways.

  5. Calcium isotopic compositions as tracers of vegetation activity in boreal permafrost ecosystems (Kulingdakan watershed, Central Siberia)

    Science.gov (United States)

    Bagard, M.; Schmitt, A.; Chabaux, F. J.; Viers, J.; Pokrovsky, O. S.; Prokushkin, A. S.; Stille, P.; Dupré, B.

    2010-12-01

    In this work, we propose to investigate the geochemical potential of calcium isotopic fractionations in a forested boreal watershed to trace the impact of vegetation activity. This is the first study carried out in a geographical area characterized by deep and continuous permafrost. For this survey, we measured Ca and Sr isotopic compositions in the different compartments (stream waters, soil solutions, precipitations, rock, soils and soil leachates, vegetation) of a 4,100 ha Siberian watershed, the Kulingdakan watershed (Putorana Plateau, Central Siberia). Our results show that the activity of the vegetation is the only process that fractionates significantly calcium isotopes within the watershed. Indeed, Ca uptake by plants and its subsequent storage in larch tree organs favours 40Ca relatively to 44Ca. Vegetation decomposition releases light δ44/40Ca that affects calcium isotopic compositions of soil solution and soil exchangeable fractions. However, this biological impact is significant only for the South-facing slope of the watershed. Indeed, soil pools from the North-facing slope present no imprint of organic matter degradation in their δ44/40Ca signatures. Furthermore, the major difference between South- and North- facing slopes lies in the importance of the vegetation and its decomposition rate. Thus, we propose that in boreal permafrost areas with limited runoff, the available stock of biomass is critical to induce or not a significant vegetation impact on the calcium isotopic compositions in the soil-water system. As a consequence, the study of preserved calcium isotopic compositions in paleosoil exchangeable phases might bring relevant information on the evolution of biological activity at the watershed scale.

  6. Influence of calcium on the inotropic actions of hyperosmotic agents, norepinephrine, paired electrical stimulation, and treppe.

    Science.gov (United States)

    Willerson, J T; Crie, J S; Adcock, R C; Templeton, G H; Wildenthal, K

    1974-10-01

    To analyze the interaction of calcium ion concentration with hypertonic agents and with other inotropic interventions, isolated right ventricular cat papillary muscles were studied under isometric conditions in Krebs-Ringer bicarbonate solution. Extracellular calcium concentrations were varied between 2.5 and 11.0 mM. Maximal inotropic effects occurred between 5 and 8.0 mM calcium and further elevation to 11.0 mM was without additional influence. The effect of hyperosmotic sucrose and mannitol on papillary muscle performance was compared with that of 10(-6) M norepinephrine at calcium concentrations of 2.5 and 10.0 mM and with paired electrical stimulation in 10.0 mM calcium. Both norepinephrine and the hyperosmotic agents produced significant increases in developed tension and in the maximal rate of tension rise (dT/dt) in Krebs-Ringer in 2.5 and 4.0 mM calcium. In 10 mM calcium norepinephrine increased developed tension and dT/dt, but sucrose and mannitol caused no change or small reductions in both. Paired electrical stimulation, like hyperosmolality, caused no increase in dT/dt in 10 mM calcium. The presence of a potent pharmacological inhibitor of systolic calcium transfer across the cell membrane (D600, 10(-6) M) reduced developed tension and dT/dt by 76+/-2.7 and 74+/-2.0%, respectively, and prevented and in fact reversed the expected increase in dT/dt associated with an increase in rate of stimulation (treppe). However, hypertonic mannitol and paired pacing persisted in causing marked increases in developed tension and dT/dt even in the presence of D600, suggesting that their inotropic effects are not dependent on increased intracellular transfer of calcium during systole through cell membrane channels in which D600 acts as a competitive inhibitor. The results of these studies suggest that apparent functional saturation of intracellular calcium receptor sites eliminates any additional inotropic effect of hyperosmolality or paired pacing. The data are

  7. Neutron interaction with doubly-magic {sup 40}Ca

    Energy Technology Data Exchange (ETDEWEB)

    Smith, A.B. [Argonne National Lab., IL (United States)]|[Univ. of Arizona, Tucson, AZ (United States)

    1993-11-01

    Differential neutron elastic and inelastic-scattering cross sections of elemental calcium (96.94% doubly-magic {sup 40}Ca) are measured from {approx} 1.5 to 10 MeV with sufficient detail to determine their energy-averaged behavior in the highly fluctuating environment. These results, combined with values previously reported in the literature, are assessed in the contexts of optical-statistical, dispersive optical, and coupled-channels models, applicable to the energy domain 0 {yields} 30+ MeV, with particular emphasis on the lower energies where the interpretations are sensitive to the dispersion relationship and the effective mass. The interpretations define the energy dependencies of the potential parameters (resolving prior ambiguities), suggest that previous estimates of the prominent low-energy (n,p) and (n,a) reactions are too large, reasonably describe observables to at least 30 MeV, and provide a vehicle for extrapolation into the bound-state regime that gives a good description of hole- and particle-state binding energies. The resulting real-potential parameters (in contrast to many {sup 40}Ca parameters reported in the literature) are shown consistent with global trends.

  8. A Selected Reaction Monitoring (SRM)-Based Method for Absolute Quantification of Aβ38, Aβ40, and Aβ42 in Cerebrospinal Fluid of Alzheimer's Disease Patients and Healthy Controls

    DEFF Research Database (Denmark)

    Pannee, Josef; Portelius, Erik; Oppermann, Madalina

    2013-01-01

    ). Samples were prepared by solid-phase extraction and quantification was performed using stable-isotope labeled Aβ peptides as internal standards. The diagnostic performance of the method was evaluated on two independent clinical materials with research volunteers who were cognitively normal and AD patients...... to that obtained by ELISA and even better separation was obtained using the Aβ42/Aβ40 ratio. The developed assay is sensitive and is not influenced by matrix effects, enabling absolute quantification of Aβ42, Aβ40, and Aβ38 in CSF, while it retains the ability to distinguish AD patients from controls. We suggest...

  9. Effect of the smear layer in the removal of calcium hydroxide from root canal walls

    Directory of Open Access Journals (Sweden)

    Hakan Arslan

    2012-01-01

    Full Text Available Background: The aim of this study was to investigate whether the smear layer influences the removal of calcium hydroxide from the root canal with manual or rotary instruments. Materials and Methods: The root canals of 48 freshly extracted single-rooted maxillary incisors were prepared to apical size 40 (n=40 and finally irrigated with sodium hypochlorite (group A, or ethylene diamine tetra acetic acid (EDTA followed by sodium hypo chlorite (group B. 20 teeth were assigned to each group, while the remaining eight teeth served as positive and negative controls. Each group was divided into two subgroups of 10 teeth (subgroup I - calcium hydroxide was removed with master apical file; subgroup II - with profile file; and, in all removal procedures, citric acid was used for irrigation. The percentage of calcium hydroxide-[Ca(OH [Ca(OH 2 ] coated surface area was calculated by image processing analysis. Results: Considering the root canal as a whole, the removal of Ca(OH 2 from the dentinal walls in group B showed significantly better results (P<0.05 as compared to group A. Conclusions: Under the conditions of this study, it can be concluded that the smear layer is important in the removal of calcium hydroxide.

  10. Experimental Research on Glauberite Dissolution in Calcium Liquid with Different Ion Concentration%不同离子浓度钙液环境中钙芒硝溶解试验研究

    Institute of Scientific and Technical Information of China (English)

    徐军; 梁卫国; 张继龙; 徐素国; 张传达

    2013-01-01

    为了提高岩盐伴生性钙芒硝矿进行资源化利用效率,对取自盐化制碱厂的淡钙液与钙芒硝矿进行了溶解反应试验,以测试钙芒硝与淡钙液的反应速率,并提出一定条件下钙芒硝与淡钙液的理想反应量.通过恒温40℃条件下,钙芒硝与去离子水、硝性近饱和卤水、钙性卤水进行一系列溶解对比试验,发现当钙性卤水中主要离子浓度比Na+∶Cl-∶Ca2+为1∶3.37∶1.03时,为最佳溶解组分配比,其最大溶解速率为54.689 g/(m2·h),溶解速率与Na2SO4浓度关系曲线拟合方程y=-8.482Ln(x) +57.362,相关系数R2=0.895.试验结果为探讨研究在岩盐伴生条件下钙芒硝溶解转化利用的最佳开采方案提供依据.%In order to improve the utilization of glauberite within salt rock,dissolving reaction experiment is introduced on low concentration calcium liquid derived from the saline alkali factory and glauberite,aiming at testing their reaction rate and proposing that at which concentration of calcium liquid it can react the best with glauberite on certain conditions.At reaction temperature 40 ℃,glauberite reacts with deionized water,nearly saturated brine containing sodium salt or calcium salt respectively,discovering that the best proportion of Na + ∶ Cl-∶ Ca2 + is 1 ∶ 3.37 ∶1.03,with the highest dissolution rate 54.689g/(m2 · h) whose curve fitting equation with the concentration of Na2SO4 is y =-8.482Ln(x) + 57.362,with its correlation coefficient R2 =0.895.The experiment results provide evidence for investigating the best mining scheme of glauberite within salt rock.

  11. Calcium contributes to photoprotection and repair of photosystem II in peanut leaves during heat and high irradiance

    Institute of Scientific and Technical Information of China (English)

    Sha Yang; Fang Wang; Feng Guo; Jing-Jing Meng; Xin-Guo Li; Shu-Bo Wan

    2015-01-01

    In this study, we investigated the effects of exogenous calcium nitrate on photoinhibition and thylakoid protein level in peanut plants under heat (40 °C) and high irradiance (HI) (1,200 mmol/m2 per s) stress. Compared with control seedlings (cultivated in 0 mmol/L Ca(NO3)2 medium), the maximal photochemical efficiency of photosystem II (PSII) in Ca2þ‐treated plants showed a slight decrease after 5 h stress, accompanied by lower degree of PSII closure (1‐qP), higher non‐photochemical quenching, and lower level of membrane damage. Ca2þ inhibitors were used to analyze the varieties of antioxidant enzymes activity and PSII proteins. These results indicated that Ca2þ could protect the subunits of PSII reaction centers from photoinhibition by reducing the generation of reactive oxygen species. In the presence of both ethyleneglycol‐bis(2‐aminoethylether)‐tetraacetic acid and ascorbic acid (AsA), the net degradation of the damaged D1 protein was faster than that only treated with AsA. Our previous study showed that either the transcriptional or the translational level of calmodulin was obviously higher in Ca2þ‐treated plants. These results suggested that, under heat and HI stress, the Ca2þ signal transduction pathway can al eviate the photoinhibition through regulating the protein repair process besides an enhanced capacity for scavenging reactive oxygen species.

  12. Si-TCP synthesized from "Mg-free" reagents employed as calcium phosphate cement

    Directory of Open Access Journals (Sweden)

    Mariana Motisuke

    2012-08-01

    Full Text Available The influence of silicon doping on calcium phosphate cement were explored in this work. α-TCP and Si-α-TCP were prepared by solid state reaction employing "Mg-free" CaHPO4, CaCO3 and CaSiO3 as precursors. It was possible to obtain TCP powders with low contents of β phase as contaminant. Cement liquid phase was an aqueous solution containing 2.5 wt. (% of Na2HPO4 and 1.5 wt. (% of citric acid. The liquid-to-powder ratio was 0.6 mL.g-1. Chemical, physical and mechanical properties of the cement samples were determined by means of XRD, FTIR, XRF, compressive strength and SEM. The calcium phosphate cements obtained achieved satisfactory properties; however, Si-α-TCP presented a decrease on the rate of setting reaction.

  13. DECOMPOSITION STUDY OF CALCIUM CARBONATE IN COCKLE SHELL

    Directory of Open Access Journals (Sweden)

    MUSTAKIMAH MOHAMED

    2012-02-01

    Full Text Available Calcium oxide (CaO is recognized as an efficient carbon dioxide (CO2 adsorbent and separation of CO2 from gas stream using CaO based adsorbent is widely applied in gas purification process especially at high temperature reaction. CaO is normally been produced via thermal decomposition of calcium carbonate (CaCO3 sources such as limestone which is obtained through mining and quarrying limestone hill. Yet, this study able to exploit the vast availability of waste resources in Malaysia which is cockle shell, as the potential biomass resources for CaCO3 and CaO. In addition, effect of particle size towards decomposition process is put under study using four particle sizes which are 0.125-0.25 mm, 0.25-0.5 mm, 1-2 mm, and 2-4 mm. Decomposition reactivity is conducted using Thermal Gravimetric Analyzer (TGA at heating rate of 20°C/minutes in inert (Nitrogen atmosphere. Chemical property analysis using x-ray fluorescence (XRF, shows cockle shell is made up of 97% Calcium (Ca element and CaO is produced after decomposition is conducted, as been analyzed by x-ray diffusivity (XRD analyzer. Besides, smallest particle size exhibits the highest decomposition rate and the process was observed to follow first order kinetics. Activation energy, E, of the process was found to vary from 179.38 to 232.67 kJ/mol. From Arrhenius plot, E increased when the particle size is larger. To conclude, cockle shell is a promising source for CaO and based on four different particles sizes used, sample at 0.125-0.25 mm offers the highest decomposition rate.

  14. Astrocyte calcium signaling: the third wave.

    Science.gov (United States)

    Bazargani, Narges; Attwell, David

    2016-02-01

    The discovery that transient elevations of calcium concentration occur in astrocytes, and release 'gliotransmitters' which act on neurons and vascular smooth muscle, led to the idea that astrocytes are powerful regulators of neuronal spiking, synaptic plasticity and brain blood flow. These findings were challenged by a second wave of reports that astrocyte calcium transients did not mediate functions attributed to gliotransmitters and were too slow to generate blood flow increases. Remarkably, the tide has now turned again: the most important calcium transients occur in fine astrocyte processes not resolved in earlier studies, and new mechanisms have been discovered by which astrocyte [Ca(2+)]i is raised and exerts its effects. Here we review how this third wave of discoveries has changed our understanding of astrocyte calcium signaling and its consequences for neuronal function.

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

    Directory of Open Access Journals (Sweden)

    Huaigang Cheng

    2014-01-01

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

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

    Science.gov (United States)

    Ea, Hang-Korng; Lioté, Frédéric

    2014-05-01

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

  17. 40 CFR 63.7143 - What definitions apply to this subpart?

    Science.gov (United States)

    2010-07-01

    ... lime or calcium hydroxide via the chemical reaction of the lime product with water. Lime cooler means... kiln calcination process including, calcitic lime, dolomitic lime, and dead-burned dolomite....

  18. Transport of calcium in seedlings and cuttings of mung bean

    Energy Technology Data Exchange (ETDEWEB)

    Broadbent, W.

    1984-01-01

    At germination, a very small proportion of stored calcium is mobilized to the axis in the absence of exogenous supplies of calcium. There is no evidence for transport in phloem since exported calcium does not enter the seedling root. /sup 45/Calcium is not redistributed when applied to cotyledons at germination of leaves of seedlings. A subsequent large addition of unlabelled calcium promotes a small redistribution from leaves. Triiodobenzoic acid (TIBA), applied to leaves, leads to a small reduction in calcium accumulation but does not effect redistribution. Auxin is without effect and auxin plus TIBA promotes accumulation. These results are discussed in relation to possible extracellular binding sites for calcium.

  19. ERp57 modulates mitochondrial calcium uptake through the MCU.

    Science.gov (United States)

    He, Jingquan; Shi, Weikang; Guo, Yu; Chai, Zhen

    2014-06-01

    ERp57 participates in the regulation of calcium homeostasis. Although ERp57 modulates calcium flux across the plasma membrane and the endoplasmic reticulum membrane, its functions on mitochondria are largely unknown. Here, we found that ERp57 can regulate the expression of the mitochondrial calcium uniporter (MCU) and modulate mitochondrial calcium uptake. In ERp57-silenced HeLa cells, MCU was downregulated, and the mitochondrial calcium uptake was inhibited, consistent with the effect of MCU knockdown. When MCU was re-expressed in the ERp57 knockdown cells, mitochondrial calcium uptake was restored. Thus, ERp57 is a potent regulator of mitochondrial calcium homeostasis.

  20. Calcium signaling in neocortical development.

    Science.gov (United States)

    Uhlén, Per; Fritz, Nicolas; Smedler, Erik; Malmersjö, Seth; Kanatani, Shigeaki

    2015-04-01

    The calcium ion (Ca(2+) ) is an essential second messenger that plays a pivotal role in neurogenesis. In the ventricular zone (VZ) of the neocortex, neural stem cells linger to produce progenitor cells and subsequently neurons and glial cells, which together build up the entire adult brain. The radial glial cells, with their characteristic radial fibers that stretch from the inner ventricular wall to the outer cortex, are known to be the neural stem cells of the neocortex. Migrating neurons use these radial fibers to climb from the proliferative VZ in the inner part of the brain to the outer layers of the cortex, where differentiation processes continue. To establish the complex structures that constitute the adult cerebral cortex, proliferation, migration, and differentiation must be tightly controlled by various signaling events, including cytosolic Ca(2+) signaling. During development, cells regularly exhibit spontaneous Ca(2+) activity that stimulates downstream effectors, which can elicit these fundamental cell processes. Spontaneous Ca(2+) activity during early neocortical development depends heavily on gap junctions and voltage dependent Ca(2+) channels, whereas later in development neurotransmitters and synapses exert an influence. Here, we provide an overview of the literature on Ca(2+) signaling and its impact on cell proliferation, migration, and differentiation in the neocortex. We point out important historical studies and review recent progress in determining the role of Ca(2+) signaling in neocortical development.