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Sample records for calcium 48 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. Isospin dependence of reactions $^{48}$Ca+$^{243-251}$Bk

    CERN Document Server

    Shen, Caiwan; Boilley, Davoid; Kosenko, Grigory; Zhao, Enguang

    2008-01-01

    The fusion process of $^{48}$Ca induced reactions is studied with the two-step model. In this model, the fusion process is devided into two stages: first, the sticking stage where projectile and target come to the touching point over the Coulomb barrier from infinite distance, and second, the formation stage where the di-nucleus formed with projectile and target evolve to form the spherical compound nucleus from the touching point. By the use of the statistical evaporation model, the residue cross sections for different neutron evaporation channels are analyzed. From the results, optimum reactions are given to synthesize $Z$ = 117 element with $^{48}$Ca induced reactions.

  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. Spin distribution in preequilibrium reactions for 48Ti + n.

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D

    2005-04-06

    Cross section measurements were made of prompt {gamma}-ray production as a function of incident neutron energy on a {sup 48}Ti sample. Partial {gamma}-ray cross sections for transitions in {sup 45-48}Ti, {sup 44-48}Sc, and {sup 42-45}Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction {gamma} rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The {gamma}-ray excitation functions were converted to partial {gamma}-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). The data are presented for neutron energies E{sub n} between 1 to 200 MeV. These results are compared with model calculations which include compound nuclear and pre-equilibrium emission. The model calculations are performed using the STAPRE reaction code for E{sub n} up to 20 MeV and the GNASH reaction code for E{sub n} up to 120 MeV. Using the GNASH reaction code the effect of the spin distribution in preequilibrium reactions has been investigated. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK). The multistep direct (MSD) part of the FKK theory was calculated for a one-step process. The contribution from higher steps is estimated to be small. The spin distribution of the multistep compound (MSC) part of FKK theory is assumed to be the same as in the compound nucleus. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the {gamma}-ray production cross sections were calculated and compared with experimental data. The difference in the partial {gamma}-ray cross sections using spin distributions with and without

  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. 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.

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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...

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Spin distribution in preequilibrium reactions for 48Ti + n.

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, Dugersuren [North Carolina State Univ., Raleigh, NC (United States)

    2005-04-12

    Cross section measurements were made of prompt γ-ray production as a function of incident neutron energy on a 48Ti sample. Partial γ-ray cross sections for transitions in 45-48Ti, 44-48Sc, and 42-45Ca have been determined. Energetic neutrons were delivered by the Los Alamos National Laboratory spallation neutron source located at the LANSCE/WNR facility. The prompt-reaction γ rays were detected with the large-scale Compton-suppressed germanium array for neutron induced excitations (GEANIE). Neutron energies were determined by the time-of-flight technique. The γ-ray excitation functions were converted to partial γ-ray cross sections taking into account the dead-time correction, target thickness, detector efficiency and neutron flux (monitored with an in-line fission chamber). The data are presented for neutron energies En between 1 to 200 MeV. These results are compared with model calculations which include compound nuclear and pre-equilibrium emission. The model calculations are performed using the STAPRE reaction code for En up to 20 MeV and the GNASH reaction code for En up to 120 MeV. Using the GNASH reaction code the effect of the spin distribution in preequilibrium reactions has been investigated. The preequilibrium reaction spin distribution was calculated using the quantum mechanical theory of Feshbach, Kerman, and Koonin (FKK). The multistep direct (MSD) part of the FKK theory was calculated for a one-step process. The contribution from higher steps is estimated to be small. The spin distribution of the multistep compound (MSC) part of FKK theory is assumed to be the same as in the compound nucleus. The FKK preequilibrium spin distribution was incorporated into the GNASH calculations and the γ-ray production cross sections were calculated and compared with experimental data. The difference in the partial γ-ray cross sections using spin distributions with and without

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. New Results for Elements 115, 117, and 118 Produced in the Reactions 243Am+48Ca and 249BK/249Cf+48Ca

    Science.gov (United States)

    Utyonkov, V. K.; Oganessian, Yu. Ts.; Abdullin, F. Sh.; Alexander, C.; Binder, J.; Boll, R. A.; Dmitriev, S. N.; Ezold, J.; Felker, K.; Gostic, J. M.; Grzywacz, R. K.; Hamilton, J. H.; Henderson, R. A.; Itkis, M. G.; Miernik, K.; Miller, D.; Moody, K. J.; Polyakov, A. N.; Ramayya, A. V.; Roberto, J. B.; Ryabinin, M. A.; Rykaczewski, K. P.; Sagaidak, R. N.; Shaughnessy, D. A.; Shirokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Stoyer, N. J.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu. S.; Voinov, A. A.; Vostokin, G. K.

    2014-09-01

    The reactions of 243Am and 249Bk with 48Ca have been reinvestigated to provide new evidence for the discovery of elements 113, 115, and 117. Three isotopes 287-289115 were synthesized in the 243Am+48Ca reactions at five projectile energies, providing excitation functions and α-decay spectra of the produced isotopes. Decay properties of 287,288115 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time. The new 289115 events demonstrate the same decay properties as those observed for 289115 populated by a decay of 293117 produced in the 249Bk+48Ca reaction to provide cross-bombardment evidence. Results of recent experiments at the Dubna gas-filled recoil separator aimed at studying production crosssections, excitation functions, and nuclear decay properties for isotopes 293,294117 synthesized in the 249Bk+48Ca reaction at five projectile energies are presented. In addition, a single decay of 294118 was observed from the reaction with 249Cf - a result of the in-growth of 249Cf in the 249Bk target.

  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. Projectile influence on production cross section for ^48Ca-, ^50Ti-, and ^54Cr- induced fusion-evaporation reactions

    Science.gov (United States)

    Mayorov, D. A.; Werke, T. A.; Alfonso, M. C.; Bennett, M. E.; Folden, C. M., III

    2013-04-01

    Evaporation residue excitation functions for ^48Ca, ^50Ti + ^159Tb and ^48Ca, ^54Cr + ^162 Dy were measured at Texas A&M University using the vacuum spectrometer MARS. The produced residues are weakly deformed nuclei near the N = 126 shell closure. However, the production cross sections are insensitive to the associated shell stabilization to the fission barrier, an observation previously reported in literature. The ratio of maximum production cross sections between the ^48Ca/^50Ti and ^48Ca/^54Cr reactions is 47 and 7100, respectively. These substantial differences can be reproduced in theoretical calculations by inclusion of collective enhancements during de-excitation of the compound nucleus. The competition between quasifission and complete fusion further contributes to the observed separation in the excitation functions. Model-dependent estimates of the compound nucleus formation probability, PCN, yield ratios of PCN(^48Ca + ^159 Tb) / PCN(^50Ti + ^159 Tb) 2.5 and PCN(^48Ca + ^162Dy) / PCN(^54Cr + ^162Dy) 5. Heavy-ion fusion reactions with ^48Ca, ^50Ti, and ^54Cr projectiles are of interest due to modern-day efforts to synthesize superheavy elements 119 and 120 in warm fusion reactions with projectiles having Z 20.

  9. Study of neutron-deficient isotopes of Fl in the 239Pu, 240Pu + 48Ca reactions

    Science.gov (United States)

    Voinov, A. A.; Utyonkov, V. K.; Brewer, N. T.; Oganessian, Yu Ts; Rykaczewski, K. P.; Abdullin, F. Sh; Dmitriev, S. N.; Grzywacz, R. K.; Itkis, M. G.; Miernik, K.; Polyakov, A. N.; Roberto, J. B.; Sagaidak, R. N.; Shirokovsky, I. V.; Shumeiko, M. V.; Tsyganov, Yu S.; Subbotin, V. G.; Sukhov, A. M.; Sabelnikov, A. V.; Vostokin, G. K.; Hamilton, J. H.; Stoyer, M. A.; Strauss, S. Y.

    2016-07-01

    The results of the experiments aimed at the synthesis of Fl isotopes in the 239Pu + 48Ca and 240Pu + 48Ca reactions are presented. The experiment was performed using the Dubna gas-filled recoil separator at the U400 cyclotron. In the 239Pu+48Ca experiment one decay of spontaneously fissioning 284Fl was detected at 245-MeV beam energy. In the 240Pu+48Ca experiment three decay chains of 285Fl were detected at 245 MeV and four decays were assigned to 284Fl at the higher 48Ca beam energy of 250 MeV. The α-decay energy of 285Fl was measured for the first time and decay properties of its descendants 281Cn, 277Ds, 273Hs, 269Sg, and 265Rf were determined more precisely. The cross section of the 239Pu(48Ca,3n)284Fl reaction was observed to be about 20 times lower than those predicted by theoretical models and 50 times less than the value measured in the 244Pu+48Ca reaction. The cross sections of the 240Pu(48Ca,4-3n)284,285Fl at both 48Ca energies are similar and exceed that observed in the reaction with lighter isotope 239Pu by a factor of 10. The decay properties of the synthesized nuclei and their production cross sections indicate rapid decrease of stability of superheavy nuclei with departing from the neutron number N=184 predicted to be the next magic number.

  10. Clustering effects in 48Cr composite nuclei produced via 24Mg + 24Mg reaction

    Directory of Open Access Journals (Sweden)

    Cinausero M.

    2012-02-01

    Full Text Available In the framework of studying clustering effects in N=Z light nuclei, an experiment was carried out to get information on the properties of the 48Cr composite nuclei produced via the 24Mg +24Mg reaction. In particular, the study regards the 48Cr at 60 MeV of excitation energy where a resonance with a narrow width (170 KeV has been found by measuring the elastic and anelastic channels. To determine the deformation of this state, evaporative Light Charged Particles (LCP are measured and compared to the Statistical Model (SM predictions, which are very sensitive to nuclear deformation. The experiment was performed at LNL using the 8ĒLP apparatus to select LCPs and a Parallel Plate Avalanche Counter (PPAC system to detect the Evaporation Residues (ER. Preliminary results on the measurements of ER – LCP and LCP – LCP angular correlations are presented which indicate the presence of a very large deformation.The analysis will proceed with the extraction of the LCP energy spectra and with the angular correlations for high multiplicity channels to determine the deformation.

  11. Role of the breakup process in the {sup 48}Ca({sup 20}Ne,{sup 19}Ne n) reaction at 48 A.MeV

    Energy Technology Data Exchange (ETDEWEB)

    Laurent, H.; Scarpaci, J.A.; Beaumel, D.; Blumenfeld, Y.; Fortier, S.; Frascaria, N.; Gales, S.; Garron, J.P.; Guillot, J.; Lhenry, I. [Paris-11 Univ., 91 - Orsay (France). Inst. de Physique Nucleaire; Gillibert, A. [CEA Centre d`Etudes de Saclay, 91 - Gif-sur-Yvette (France). Dept. d`Astrophysique, de la Physique des Particules, de la Physique Nucleaire et de l`Instrumentation Associee; Roussel-Chomaz, P. [Grand Accelerateur National d`Ions Lourds (GANIL), 14 - Caen (France)] [and others

    1995-07-01

    A study of the reaction {sup 48}Ca({sup 20}Ne,{sup 19}Ne n) at 48 A.MeV has been performed at the GANIL facility. Calculations performed in the framework of the Bonaccorso-Brink model predict that the absorption process dominates over the elastic breakup process. Comparison of the neutron multiplicity calculated in a statistical model with the measured one confirms a significant contribution of the direct processes. Comparisons with calculated neutron angular distributions show the effect of the final state interaction. (author). 12 refs.

  12. 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.

  13. 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.

  14. Fusion and quasifission dynamics in the reactions $^{48}$Ca+$^{249}$Bk and $^{50}$Ti+$^{249}$Bk using TDHF

    CERN Document Server

    Umar, A S; Simenel, C

    2016-01-01

    Background: Synthesis of superheavy elements (SHE) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHE have been recently produced with doubly-magic $^{48}$Ca beams. However, SHE synthesis experiments with single-magic $^{50}$Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for $Z=117,119$ superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in $^{48}$Ca,$^{50}$Ti+$^{249}$Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleu...

  15. 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%.

  16. 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.

  17. 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.

  18. Study of the properties of the superheavy nuclei Z = 117 produced in the 249Bk + 48Ca reaction

    Science.gov (United States)

    Oganessian, Yu. Ts.; Abdullin, F. Sh.; Alexander, C.; Binder, J.; Boll, R. A.; Dmitriev, S. N.; Ezold, J.; Felker, K.; Gostic, J. M.; Grzywacz, R. K.; Hamilton, J. H.; Henderson, R. A.; Itkis, M. G.; Miernik, K.; Miller, D.; Moody, K. J.; Polyakov, A. N.; Ramayya, A. V.; Roberto, J. B.; Ryabinin, M. A.; Rykaczewski, K. P.; Sagaidak, R. N.; Shaughnessy, D. A.; Shirokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Stoyer, N. J.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu. S.; Utyonkov, V. K.; Voinov, A. A.; Vostokin, G. K.

    2014-03-01

    The reaction of 249Bk with 48Ca have been reinvestigated to provide new evidence for the discovery of element 117 on a larger number of events. The experiments were performed at five projectile energies and with a total beam dose of 48Ca of about 4.6×1019. Two isotopes 293,294117 were synthesized in the 249Bk+48Ca reaction, providing excitation functions and α-decay spectra of the produced isotopes that establishes these nuclei to be the products of the 4n- and 3n-evaporation channels, respectively. Decay properties of 293,294117 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time in 2010. The new 289115 events, populated by α decay of 293117, demonstrate the same decay properties as those observed for 289115 produced in the 243Am(48Ca,2n) reaction thus providing crossbombardment evidence. In addition, a single decay of 294118 was observed from the reaction with 249Cf - a result of the in-growth of 249Cf in the 249Bk target.

  19. Study of the properties of the superheavy nuclei Z = 117 produced in the 249Bk + 48Ca reaction

    Directory of Open Access Journals (Sweden)

    Oganessian Yu. Ts.

    2014-03-01

    Full Text Available The reaction of 249Bk with 48Ca have been reinvestigated to provide new evidence for the discovery of element 117 on a larger number of events. The experiments were performed at five projectile energies and with a total beam dose of 48Ca of about 4.6×1019. Two isotopes 293,294117 were synthesized in the 249Bk+48Ca reaction, providing excitation functions and α-decay spectra of the produced isotopes that establishes these nuclei to be the products of the 4n- and 3n-evaporation channels, respectively. Decay properties of 293,294117 and of all the daughter products agree with the data of the experiment in which these nuclei were synthesized for the first time in 2010. The new 289115 events, populated by α decay of 293117, demonstrate the same decay properties as those observed for 289115 produced in the 243Am(48Ca,2n reaction thus providing crossbombardment evidence. In addition, a single decay of 294118 was observed from the reaction with 249Cf – a result of the in-growth of 249Cf in the 249Bk target.

  20. P48—Triggered transmembrane signaling transduction of human monocytes:modilization of calcium ion and activation of protein kinase C(PKC)

    Institute of Scientific and Technical Information of China (English)

    CHANGZL; REHALL

    1995-01-01

    P48 is a cytokine which induces monocyte differentiation and the induction of cytotoxic activity.In this study,the signal transduction events involved in the stimulation of monocytes with the membrane form of P48 (mP48) were investigated.Monocyte stimulation with mP48 was found to involve the mobilization of intracellular calcium(Ca2+) and the activation and translocation of PKC from the cytosol to the membrane.Membane P48 induced a rapid rise of intracellular Ca2+ in a dose dependent maner.Similarly,the stimulation of monocytes with P48 was found to involve the activation and translocation of PKC.The translocation of PKC was rapid(within 0-5min) yet transient with PKC activity returning to control levels by 8 min.The functional role of protein kineses in P48 induced TNF secretion was studied using various kinese inhibitors.The PKC inhibitors,H-7 and sphingosine,were found to inhibit P48 induced TNF secretion with 50% inhibition at 5μM.HA1004,which inhibts cyclic nucleotide-dependent kinase(PKA,Ki 1.2μM),did not inhibit TNF secretion.H-8(PKA inhibitor) was found to be an effective inhibitor of TNF secretion only at high concentrations(30μM).The Calmodulin-dependent kinase inhibitor,W7(Ki 12μM) was found to be effective at concentration above 5μM.These findings suggest that P48-triggered TNF secretion involves transmembrane Ca2+ signaling and the subsequent activation of at least two protein kineses,PKC and CaMK.

  1. 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.

  2. Synthesis of the isotopes of elements 118 and 116 in the 249Cf and 245Cm+48Ca fusion reactions

    Energy Technology Data Exchange (ETDEWEB)

    Oganessian, Y T; Utyonkov, V K; Lobanov, Y V; Abdullin, F S; Polyakov, A N; Sagaidak, R N; Shirokovsky, I V; Tsyganov, Y S; Voinov, A A; Gulbekian, G G; Bogomolov, S L; Gikal, B N; Mezentsev, A N; Iliev, S; Subbotin, V G; Sukhov, A M; Subotic, K; Zagrebaev, V I; Vostokin, G K; Itkis, M G; Moody, K J; . Patin, J B; Shaughnessy, D A; Stoyer, M A; Stoyer, N J; Wilk, P A; Kenneally, J M; Landrum, J H; Wild, J F; Lougheed, R W

    2006-01-31

    The decay properties of {sup 290}116 and {sup 291}116, and the dependence of their production cross sections on the excitation energies of the compound nucleus, {sup 293}116, have been measured in the {sup 245}Cm({sup 48}Ca,xn){sup 293-x}116 reaction. These isotopes of element 116 are the decay daughters of element 118 isotopes, which are produced via the {sup 249}Cf+{sup 48}Ca reaction. They performed the element 118 experiment at two projectile energies, corresponding to {sup 297}118 compound nucleus excitation energies of E* = 29.2 {+-} 2.5 and 34.4 {+-} 2.3 MeV. During an irradiation with a total beam dose of 4.1 x 10{sup 19} {sup 48}Ca projectiles, three similar decay chains consisting of two or three consecutive {alpha} decays and terminated by a spontaneous fission (SF) with high total kinetic energy of about 230 MeV were observed. The three decay chains originated from the even-even isotope {sup 294}118 (E{sub {alpha}} = 11.65 {+-} 0.06 MeV, T{sub {alpha}} = 0.89{sub -0.31}{sup +1.07} ms) produced in the 3n-evaporation channel of the {sup 249}Cf+{sup 48}Ca reaction with a maximum cross section of 0.5{sub -0.3}{sup +1.6} pb.

  3. 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.

  4. Production and decay of the heaviest odd-Z nuclei in the 249Bk + 48Ca reaction

    Science.gov (United States)

    Oganessian, Yu Ts; Abdullin, F. Sh; Alexander, C.; Binder, J.; Boll, R. A.; Dmitriev, S. N.; Ezold, J.; Felker, K.; Gostic, J. M.; Grzywacz, R. K.; Hamilton, J. H.; Henderson, R. A.; Itkis, M. G.; Miernik, K.; Miller, D.; Moody, K. J.; Polyakov, A. N.; Ramayya, A. V.; Roberto, J. B.; Ryabinin, M. A.; Rykaczewski, K. P.; Sagaidak, R. N.; Shaughnessy, D. A.; Shirokovsky, I. V.; Shumeiko, M. V.; Stoyer, M. A.; Stoyer, N. J.; Subbotin, V. G.; Sukhov, A. M.; Tsyganov, Yu S.; Utyonkov, V. K.; Voinov, A. A.; Vostokin, G. K.

    2015-02-01

    The reaction of 249Bk with 48Ca has been investigated with an aim of synthesizing and studying the decay properties of isotopes of the new element 117. The experiments were performed at five projectile energies (in two runs, in 2009-2010 and 2012) and with a total beam dose of 48Ca ions of about 9x1019 The experiments yielded data on a-decay characteristics and excitation functions of the produced nuclei that establish these to be 293117 and 294117 - the products of the 4n- and 3n-evaporation channels, respectively. In total, we have observed 20 decay chains of Z=117 nuclides. The cross sections were measured to be 1.1 pb for the 3n and 2.4 pb for the 4n-reaction channel. The new 289115 events, populated by α decay of 117, demonstrate the same decay properties as those observed for 115 produced in the 243Am(48Ca,2n) reaction thus providing cross-bombardment evidence. In addition, a single decay of 294118 was observed from the reaction with 249Cf - a result of the in-growth of 249Cf in the 249Bk target. The observed decay chain of 294118 is in good agreement with decay properties obtained in 2002-2005 in the experiments with the reaction 249Cf(48Ca,3n)294118. The energies and half-lives of the odd-Z isotopes observed in the 117 decay chains together with the results obtained for lower-Z superheavy nuclei demonstrate enhancement of nuclear stability with increasing neutron number towards the predicted new magic number N=184.

  5. 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.

  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. Exploring reaction mechanisms and their competition in 58Ni+48Ca collisions at E = 25 AMeV

    Science.gov (United States)

    Francalanza, L.; Abbondanno, U.; Amorini, F.; Barlini, S.; Bini, M.; Bougault, R.; Bruno, M.; Cardella, G.; Casini, G.; Colonna, M.; D'Agostino, M.; De Filippo, E.; De Sanctis, J.; Geraci, E.; Giussani, A.; Gramegna, F.; Guiot, B.; Kravchuk, V.; La Guidara, E.; Lanzalone, G.; Le Neindre, N.; Maiolino, C.; Marini, P.; Morelli, L.; Olmi, A.; Pagano, A.; Papa, M.; Piantelli, S.; Pirrone, S.; Politi, G.; Poggi, G.; Porto, F.; Russotto, P.; Rizzo, F.; Vannini, G.; Vannucci, L.

    2014-03-01

    Latest results concerning the study of central collisions in 58Ni+48Ca reactions at Elab(Ni)=25 AMeV are presented. The experimental data, collected with the CHIMERA 4π device, have been analyzed in order to investigate the competition among different reaction mechanisms for central collisions in the Fermi energy domain. The method adopted to perform the centrality selection refers to the global variable "flow angle", that is related to the event shape in momentum space, as it is determined by the eigenvectors of the experimental kinetic-energy tensor. The main features of the reaction products were explored by using different constraints on some of the relevant observables, such as mass and velocity distributions and their correlations. Much emphasis was devoted to the competition between fusion-evaporation processes with subsequent identification of a heavy residue and a prompt multifragmentation mechanism. The reaction mechanism was simulated in the framework of transport theories (dynamical stochastic BNV calculations, followed by sequential SIMON code) and further comparison with dynamical calculations from transport model (QMD, CoMD) are in progress. Moreover, an extension of this study taking into account for the light particles has been envisaged.

  8. Exploring reaction mechanisms and their competition in 58Ni+48Ca collisions at E = 25 AMeV

    Directory of Open Access Journals (Sweden)

    Francalanza L.

    2014-03-01

    Full Text Available Latest results concerning the study of central collisions in 58Ni+48Ca reactions at Elab(Ni=25 AMeV are presented. The experimental data, collected with the CHIMERA 4π device, have been analyzed in order to investigate the competition among different reaction mechanisms for central collisions in the Fermi energy domain. The method adopted to perform the centrality selection refers to the global variable “flow angle”, that is related to the event shape in momentum space, as it is determined by the eigenvectors of the experimental kinetic-energy tensor. The main features of the reaction products were explored by using different constraints on some of the relevant observables, such as mass and velocity distributions and their correlations. Much emphasis was devoted to the competition between fusion-evaporation processes with subsequent identification of a heavy residue and a prompt multifragmentation mechanism. The reaction mechanism was simulated in the framework of transport theories (dynamical stochastic BNV calculations, followed by sequential SIMON code and further comparison with dynamical calculations from transport model (QMD, CoMD are in progress. Moreover, an extension of this study taking into account for the light particles has been envisaged.

  9. Chemical Identification of Dubnium as a Decay Product of Element 115 Produced in the Reaction $\\rm {^{48}Ca}+{^{243}Am}$

    CERN Document Server

    Dmitriev, S N; Utyonkov, V K; Shishkin, S V; Eremin, A V; Lobanov, Yu V; Chepigin, V I; Sokol, E A; Tsyganov, Yu S; Vostokin, G K; Aksenov, N V; Hussonnois, M; Itkis, M G; Aggeler, H W; Schumann, D; Bruchertseifer, H; Eichler, R; Shaughnessy, D A; Wilk, P A; Kenneally, J M; Stoyer, M A; Wild, J F

    2004-01-01

    The results of an experiment designed to identify $^{268}$Db as the terminal isotope in the $\\alpha $-decay chain of element 115 produced via the ${\\rm {^{243}Am}}({\\rm {^{48}Ca}},3n){\\rm {^{288}115}}$ reaction are presented. The $^{243}$Am target was bombarded with a beam dose of $3.4\\cdot 10^{18}$ $^{48}$Ca projectiles at an energy of 247 MeV at the center of the target. The reaction products were collected in the surface layer of a copper catcher block, which was removed with a lathe and then dissolved in concentrated HNO$_{3}$. The group-5 elements were separated by sorption onto Dowex $50{\\times} 8$ cation-exchange resin with subsequent desorption using 1 M HF, which forms anionic fluoride complexes of group-5 elements. The eluent was evaporated onto a 0.4 $\\mu$m thick polyethylene foil that was placed between a pair of semiconductor detectors surrounded by $^{3}$He neutron counters for measurement of $\\alpha$ particles, fission fragments, and neutrons. In the course of the experiment, we observed 15 spo...

  10. 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.

  11. 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.

  12. {sup 48}Ti(n,xnpa{gamma}) reaction cross sections using spallation neutrons for E{sub n} = 1 to 20 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Dashdorj, D; Mitchell, G E; Garrett, P E; Agvaanluvsan, U; Becker, J A; Bernstein, L A; Cooper, J R; Hoffman, R D; Younes, W; Devlin, N; Fotiades, N; Nelson, R O

    2005-01-06

    {gamma}-ray excitation functions have been measured for the interaction of fast neutrons with {sup 48}Ti (neutron energy from 1 MeV to 250 MeV). The Los Alamos National Laboratory spallation neutron source, at the LANSCE/WNR facility, provided a ''white'' neutron beam which is produced by bombarding a natural W target with a pulsed proton beam. The prompt-reaction {gamma} rays were measured with the large-scale Compton-suppressed Ge spectrometer, GEANIE. Neutron energies were determined by the time-of-flight technique. Excitation functions were converted to partial {gamma}-ray cross sections, taking into account the dead-time correction, the target thickness, the detector efficiency, and neutron flux (monitored with an in-line fission chamber). The data analysis is presented here for neutron energies between 1 to 20 MeV. Partial {gamma}-ray cross sections for transitions in {sup 47,48}Ti, {sup 48}Sc, and {sup 45}Ca have been determined. These results are compared to Hauser-Feshbach predictions calculated using the STAPRE code, which includes compound nuclear and pre-equilibrium emission. The partial cross sections for {gamma} rays, whose discrete {gamma}-ray cascade path leads to the ground state in {sup 48}Ti, {sup 47}Ti, {sup 48}Sc, and {sup 45}Ca have been summed to obtain estimates of the lower limits for reaction cross sections. Partial cross sections for unobserved {gamma}-rays are predicted from the STAPRE code. These lower limits are combined with Hauser-Feshbach calculations to deduce {sup 48}Ti(n,n'){sup 48}Ti, {sup 48}Ti(n,2n){sup 47}Ti, {sup 48}Ti(n,p){sup 48}Sc, and {sup 48}Ti(n,{alpha}){sup 45}Ca reaction channel cross sections.

  13. Recoil-alpha-fission and recoil-alpha-alpha-fission events observed in the reaction Ca-48 + Am-243

    CERN Document Server

    Forsberg, U; Andersson, L -L; Di Nitto, A; Düllmann, Ch E; Gates, J M; Golubev, P; Gregorich, K E; Gross, C J; Herzberg, R -D; Hessberger, F P; Khuyagbaatar, J; Kratz, J V; Rykaczewski, K; Sarmiento, L G; Schädel, M; Yakushev, A; Åberg, S; Ackermann, D; Block, M; Brand, H; Carlsson, B G; Cox, D; Derkx, X; Dobaczewski, J; Eberhardt, K; Even, J; Fahlander, C; Gerl, J; Jäger, E; Kindler, B; Krier, J; Kojouharov, I; Kurz, N; Lommel, B; Mistry, A; Mokry, C; Nazarewicz, W; Nitsche, H; Omtvedt, J P; Papadakis, P; Ragnarsson, I; Runke, J; Schaffner, H; Schausten, B; Shi, Y; Thörle-Pospiech, P; Torres, T; Traut, T; Trautmann, N; Türler, A; Ward, A; Ward, D E; Wiehl, N

    2015-01-01

    Products of the fusion-evaporation reaction Ca-48 + Am-243 were studied with the TASISpec set-up at the gas-filled separator TASCA at the GSI Helmholtzzentrum f\\"ur Schwerionenforschung. Amongst the detected thirty correlated alpha-decay chains associated with the production of element Z=115, two recoil-alpha-fission and five recoil-alpha-alpha-fission events were observed. The latter are similar to four such events reported from experiments performed at the Dubna gas-filled separator. Contrary to their interpretation, we propose an alternative view, namely to assign eight of these eleven decay chains of recoil-alpha(-alpha)-fission type to start from the 3n-evaporation channel 115-288. The other three decay chains remain viable candidates for the 2n-evaporation channel 115-289.

  14. 10. 23 MeV M1 transition in the /sup 48/Ca(p,p ') /sup 48/Ca/sup / reaction at 319 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Nanda, S.K.; Glashausser, C.; Jones, K.W.; McGill, J.A.; Carey, T.A.; McClelland, J.B.; Moss, J.M.; Seestrom-Morris, S.J.; Comfort, J.R.; Levenson, S.

    1984-02-01

    The cross section, analyzing power, and spin-flip probability have been measured for the M1 transition at 10.23 MeV excitation energy in the /sup 48/Ca(p,p') /sup 48/Ca /sup 48/Ca(p,p') /sup 48/Ca agreement with distorted-wave impulse approximation calculations; about 28% of the pure single particle (..nu..f/sub 7/2/ /sup -1/,f/sub 5/2/)M1 strength is observed. The results serve as a good calibration of results expected in heavy nuclei.

  15. Superoxide reductase from Desulfoarculus baarsii: reaction mechanism and role of glutamate 47 and lysine 48 in catalysis

    CERN Document Server

    Lombard, M; Touati, D; Fontecave, M; Nivière, V

    2015-01-01

    Superoxide reductase (SOR) is a small metalloenzyme that catalyzes reduction of O(2)(*)(-) to H(2)O(2) and thus provides an antioxidant mechanism against superoxide radicals. Its active site contains an unusual mononuclear ferrous center, which is very efficient during electron transfer to O(2)(*)(-) [Lombard, M., Fontecave, M., Touati, D., and Nivi{\\`e}re, V. (2000) J. Biol. Chem. 275, 115-121]. The reaction of the enzyme from Desulfoarculus baarsii with superoxide was studied by pulse radiolysis methods. The first step is an extremely fast bimolecular reaction of superoxide reductase with superoxide, with a rate constant of (1.1 +/- 0.3) x 10(9) M(-1) s(-1). A first intermediate is formed which is converted to a second one at a much slower rate constant of 500 +/- 50 s(-1). Decay of the second intermediate occurs with a rate constant of 25 +/- 5 s(-1). These intermediates are suggested to be iron-superoxide and iron-peroxide species. Furthermore, the role of glutamate 47 and lysine 48, which are the closest...

  16. 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.

  17. The utilization of adenosine triphosphate in rat mast cells during histamine release induced by anaphylactic reaction and compound 48/80

    DEFF Research Database (Denmark)

    Johansen, Torben; Chakravarty, N

    1975-01-01

    The ATP content of rat peritoneal mast cells has been studied in relation to histamine release induced by compound 48/80 and antigen-antibody (anaphylactic) reaction in vitro. When the ATP content of actively sensitized mast cells was reduced to different levels by oligomycin, a good correlation...... was obtained between the ATP levels and the amounts of histamine released by the anaphylactic reaction. A similar linear relation has previously been demonstrated between the ATP levels of mast cells and histamine release induced by compound 48/80. The ATP content of mast cells was also studied at different...... intervals after the exposure of the cells to antigen or compound 48/80. No significant change in the ATP content was observed in untreated mast cells during the short period when histamine release occurs. If, however, the mast cells were preincubated with oligomycin or 2-deoxyglucose to reduce the rate...

  18. 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.

  19. 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.

  20. Fusion and quasifission dynamics in the reactions 48Ca+249Bk and 50Ti+249Bk using a time-dependent Hartree-Fock approach

    Science.gov (United States)

    Umar, A. S.; Oberacker, V. E.; Simenel, C.

    2016-08-01

    Background: Synthesis of superheavy elements (SHEs) with fusion-evaporation reactions is strongly hindered by the quasifission (QF) mechanism which prevents the formation of an equilibrated compound nucleus and which depends on the structure of the reactants. New SHEs have been recently produced with doubly-magic 48Ca beams. However, SHE synthesis experiments with single-magic 50Ti beams have so far been unsuccessful. Purpose: In connection with experimental searches for Z =117 ,119 superheavy elements, we perform a theoretical study of fusion and quasifission mechanisms in 48Ca,50Ti+249Bk reactions in order to investigate possible differences in reaction mechanisms induced by these two projectiles. Methods: The collision dynamics and the outcome of the reactions are studied using unrestricted time-dependent Hartree-Fock (TDHF) calculations as well as the density-constrained TDHF method to extract the nucleus-nucleus potentials and the excitation energy in each fragment. Results: Nucleus-nucleus potentials, nuclear contact times, masses and charges of the fragments, as well as their kinetic and excitation energies strongly depend on the orientation of the prolate 249Bk nucleus. Long contact times associated with fusion are observed in collisions of both projectiles with the side of the 249Bk nucleus, but not on collisions with its tip. The energy and impact parameter dependencies of the fragment properties, as well as their mass-angle and mass-total kinetic energy correlations are investigated. Conclusions: Entrance channel reaction dynamics are similar with both 48Ca and 50Ti projectiles. Both are expected to lead to the formation of a compound nucleus by fusion if they have enough energy to get in contact with the side of the 249Bk target.

  1. Competition between fusion-evaporation and multifragmentation in central collisions in 58Ni + 48Ca reaction at 25 AMeV

    Science.gov (United States)

    Francalanza, L.; Abbondanno, U.; Amorini, F.; Barlini, S.; Bini, M.; Bougault, R.; Bruno, M.; Cardella, G.; Casini, G.; D'Agostino, M.; De Filippo, E.; De Sanctis, J.; Geraci, E.; Giussani, A.; Gramegna, F.; Guiot, B.; Kravchuk, V.; La Guidara, E.; Lanzalone, G.; Le Neindre, N.; Maiolino, C.; Marini, P.; Morelli, L.; Olmi, A.; Pagano, A.; Papa, M.; Piantelli, S.; Pirrone, S.; Politi, G.; Poggi, G.; Porto, F.; Russotto, P.; Rizzo, F.; Vannini, G.; Vannucci, L.

    2013-03-01

    The experimental data concerning the 58Ni+48Ca reaction at Elab(Ni)=25A MeV, collected by the CHIMERA 4π device, have been analyzed in order to investigate the competition among different reaction mechanisms for central collisions in the Fermi energy domain. The method adopted to select such central collisions, by means of construction of the kinetic energy tensor and, consequently, the evaluation of the "flow angle" event by event is presented. Some global variables, able to characterize the pattern of central collisions, have been constructed, and the main features of the reaction products are analyzed in terms of some observable, like mass and velocity distributions, as well as their correlations. Much emphasis was devoted to the competition between fusion-evaporation processes with consequent identification of a heavy residue and multifragmentation of a well defined (if any) transient nuclear system formed in central collisions.

  2. 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.

  3. Production of radon and thorium isotopes near N=126 shell closure in 48Ca and 54Cr induced fusion reactions on 162Dy

    Science.gov (United States)

    Mayorov, Dmitriy; Werke, Tyler; Alfonso, Marisa; Folden, Charles

    2012-03-01

    Production of spherical evaporation residues (EVRs) near N=126 shell in 48Ca and 54Cr induced reactions on a 162Dy target was investigated at the Texas A&M University Cyclotron Institute using the vacuum separator MARS. For the 54Cr+162Dy reaction, only upper limits for the 4n exit-channel cross section were measured; this can be attributed to a sizably increased fissility of the 216Th compound nucleus relative to 210Rn formed in the 48Ca bombardment. A factor of > 7300 separates the production cross sections of the 4n EVRs from each reaction. A semi-empirical estimate of the lower limit on the fusion probability, PCN, ratio between the two heavy ion projectiles is PCN(48Ca+162Dy)/PCN(54Cr+162Dy) > 1.2. Investigation of spherical nuclei produced by heavy ion fusion reactions is of current interest due to efforts to synthesize superheavy nuclei near Z=120, N=184 nucleon shells. EVRs produced near the N=126 shell closure have previously revealed surprisingly low survival probabilities despite stabilization from shell effects. Similarly, enhancement of the fission channel in the de-excitation cascade of 210Rn and 216Th is observed in this work and this result can be well modeled by the inclusion of collective effects into the statistical decay of excited nuclei calculations. These results suggest that cross sections for production of superheavy nuclei near predicted Z=120, N=184 closed shells may be small regardless of the anticipated strong shell effects.

  4. 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.

  5. Detection of OXA-48-type carbapenemase-producing Enterobacteriaceae in diagnostic laboratories can be enhanced by addition of bicarbonates to cultivation media or reaction buffers.

    Science.gov (United States)

    Studentova, Vendula; Papagiannitsis, Costas C; Izdebski, Radoslaw; Pfeifer, Yvonne; Chudackova, Eva; Bergerova, Tamara; Gniadkowski, Marek; Hrabak, Jaroslav

    2015-03-01

    Carbapenemase-mediated resistance to carbapenems in Enterobacteriaceae has become the main challenge in the treatment and prevention of infections recently. The partially unnoticed spread of OXA-48-type carbapenemase producers is usually assigned to low minimum inhibitory concentrations (MICs) of carbapenems that OXA-48-producing isolates often display. Therefore, there is an urgent need of specific and sensitive methods for isolation and detection of OXA-48 producers in clinical microbiology diagnostics. The influence of bicarbonates on carbapenem MICs against carbapenemase-producing Enterobacteriaceae was tested. We also checked whether the addition of bicarbonates to liquid media supplemented with meropenem may facilitate the selective enrichment of various carbapenemase producers in cultures. Furthermore, the sensitivity of carbapenemase confirmation by matrix-assisted laser desorption/ionization mass spectrometry (MALDI-TOF MS) and spectrophotometric hydrolysis assays upon the addition of NH4HCO3 was examined. The addition of NaHCO3 significantly increased MICs of ertapenem and meropenem for OXA-48 producers. Furthermore, liquid media supplemented with NaHCO3 and meropenem were reliable for the selective enrichment of carbapenemase producers. The presence of NH4HCO3 in buffers used in the spectrophotometric and MALDI-TOF MS carbapenemase detection increased the sensitivity of that assay. Our results demonstrate that bicarbonates in media or reaction buffers can enhance the sensitivity of screening methods and diagnostic tests for carbapenemase producers.

  6. Eleven new heaviest isotopes of elements Z = 105 to Z = 117 identified among the products of 249Bk+48Ca reactions

    Energy Technology Data Exchange (ETDEWEB)

    Oganessian, Yuri Ts. [FLNR-JINR, Russia; Abdullin, F. Sh. [Joint Institute for Nuclear Research, Dubna, Russia; Bailey, P. D. [Oak Ridge National Laboratory (ORNL); Benker, D. E. [Oak Ridge National Laboratory (ORNL); Bennett, M. E. [University of Nevada, Las Vegas; Dmitriev, S. [FLNR-JINR, Russia; Ezold, Julie G. [Oak Ridge National Laboratory (ORNL); Hamilton, J. H. [Vanderbilt University; Henderson, R. [Lawrence Livermore National Laboratory (LLNL); Itkis, M. G. [FLNR-JINR, Russia; Lobanov, Yu. V. [Joint Institute for Nuclear Research, Dubna, Russia; Mezentsev, A. N. [Joint Institute for Nuclear Research, Dubna, Russia; Moody, K. [Lawrence Livermore National Laboratory (LLNL); Nelson, S. L. [Lawrence Livermore National Laboratory (LLNL); Polyakov, A. N. [Joint Institute for Nuclear Research, Dubna, Russia; Porter, C. E. [Oak Ridge National Laboratory (ORNL); Ramayya, A. V. [Vanderbilt University; Riley, F. D. [Oak Ridge National Laboratory (ORNL); Roberto, James B [ORNL; Ryabinin, M. A. [Research Institute of Atomic Reactors, Dimitrovgrad, Russia; Rykaczewski, Krzysztof Piotr [ORNL; Taylor, R [Oak Ridge National Laboratory (ORNL); Tsyganov, Yu. S. [Joint Institute for Nuclear Research, Dubna, Russia; Utyonkov, V. [FLNR-JINR, Russia; Voinov, A. A. [Joint Institute for Nuclear Research, Dubna, Russia; Vostokin, G. K. [Joint Institute for Nuclear Research, Dubna, Russia; Wilk, P. A. [Lawrence Livermore National Laboratory (LLNL)

    2011-01-01

    The heaviest isotopes of elements Z = 117 to Z = 105, 294117, 293117, 290115, 289115, 286113, 285113, 282Rg, 281Rg, 278Mt, 274Bh, and 270Db, were identified by means of the Dubna gas-filled recoil separator among the products of the 249Bk + 48Ca reaction. The details of the observed six decay chains, indicating the production and decay of isotopes 293117 and 294117, are presented and discussed. The decay energies and resulting half-lives of these new nuclei show a strong rise of stability with increasing neutron number, validating the concept of the island of enhanced stability for superheavy nuclei.

  7. 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.

  8. 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.

  9. New insights into the 243Am + 48Ca reaction products previously observed in the experiments on elements 113, 115, and 117.

    Science.gov (United States)

    Oganessian, Yu Ts; Abdullin, F Sh; Dmitriev, S N; Gostic, J M; Hamilton, J H; Henderson, R A; Itkis, M G; Moody, K J; Polyakov, A N; Ramayya, A V; Roberto, J B; Rykaczewski, K P; Sagaidak, R N; Shaughnessy, D A; Shirokovsky, I V; Stoyer, M A; Subbotin, V G; Sukhov, A M; Tsyganov, Yu S; Utyonkov, V K; Voinov, A A; Vostokin, G K

    2012-01-13

    Results of a new series of experiments on the study of production cross sections and decay properties of the isotopes of element 115 in the reaction (243)Am+(48)Ca are presented. Twenty-one new decay chains originating from (288)115 were established as the product of the 3n-evaporation channel by measuring the excitation function at three excitation energies of the compound nucleus (291)115. The decay properties of all newly observed nuclei are in full agreement with those we measured in 2003. At the lowest excitation energy E*=33 MeV, for the first time we registered the product of the 2n-evaporation channel, (289)115, which was also observed previously in the reaction (249)Bk+(48)Ca as the daughter nucleus of the decay of (293)117. The maximum cross section for the production of (288)115 is found to be 8.5 pb at E*≈36 MeV.

  10. Reaction natYb+48Ca->217Th+3n: auto calibration process for DSSSD detector application (particular case)

    CERN Document Server

    Tsyganov, Yu

    2015-01-01

    The Dubna Gas-Filled Recoil Separator (DGFRS) is the mostly effective setup in use for the field of synthesis of superheavy elements. Application of DSSSD detector provides more precise energy and position detection for both implanted recoils and their alpha decays. To minimize contribution of background products the method of fctive correlation is applied at the DGFRS. To apply this method a precise calibration for 48 front strips is strongly required. Method of three peaks auto calibration is proposed with a first approximation step with 9.26 MeV 217Th peaks. Examples of alpha-decay original spectra and spectra after filtration procedures are presented.

  11. Analysis of in vitro reaction layers formed on 48S4 glass for applications in biomaterial field

    Science.gov (United States)

    Mami, M.; Oudadesse, H.; Dorbez-Sridi, R.; Dietrich, E.; Rocherullé, J.

    2007-11-01

    The purpose of this work is to study the formation of hydroxyapatite (Ca{10} (PO{4})6(OH){2}) on the surface of glass 48S4 with chemical composition: SiO{2}: 48%, CaO: 30%, Na{2}O: 18% and P{2}O{5}: 4% in weight ratio. This selected composition presents phosphorus contributions lower than that in BioglasscircledR [Hench et al. J. Biomed. Mater. 36, 117 (1971)] developed by L. Hench. Comparison of the kinetic formation of hydroxyapatite on the glass surfaces of these two biomaterials was made. The Material was prepared by melting and rapid quenching. It shows a bioactive character. This phenomenon is confirmed by the “in vitro” formation of hydroxycarbonate apatite (HCA) layer on the surface of glass after immersion in the Simulated Body Fluid (SBF). Before immersion in SBF, The proposed composition of glass was analyzed using several physicochemical methods like XRD, FTIR, SEM, and EDS confirming the composition and its amorphous state well. The pellets were soaked in SBF for 2 h, 1, 3, 7 and 15 days at 37 °C. The analyses of SBF after each immersion time were carried out using ICP-OES method. Results show important exchanges of ions between the surface of glass and the SBF. They revealed the formation of an amorphous CaO-P{2}O{5}- rich layer on the surface of the specimens after 1 day in the solution and a crystalline HCA{ }layer after 3 days immersion time as will be shown by XRD, EDS and FTIR analysis. The cristallinity increases with immersion time. After 15 days immersion in SBF liquid, the specimens are still fully covered by hydroxycarbonate apatite (HCA) layer.

  12. 心房颤动24 h和48 h对犬心房肌有效不应期及L型钙电流的影响%Effects of 24 h and 48 h atrial fibrillation on L-type calcium currents in canine atrial myocytes

    Institute of Scientific and Technical Information of China (English)

    张玲; 孙娟; 张广伟; 王欢; 侯月梅

    2013-01-01

    Objective To evaluate the effects of 24 h and 48 h atrial fibrillation(AF) on L-type calcium current (ICa-L)in atrial myocytes,and to investigate its possible mechanism and concordance.Methods Eighteen healthy adult mongrel canines were randomly divided into three groups:control group,24 h AF group and 48 h AF group,6 in each group.AF model was established by right atrial pacing with 600 bpm.The effective refractory period(ERP) of right atrial was measured by program stimulation.The atrial myocytes isolated from 24 h and 48 h AF canine,L-type calcium channel currents in atrial myocytes were recorded by patch clamp technique in the whole cell mode.The expressions of L-type voltage-dependent Ca2+ channel(LVDCC) α1c protein in atrium were measured by immunohistochemistry in three groups,semi-quantitative analysis of α1c protein expression was performed with pathological image analytic system.Results In 24 h AF group and 48 h AF group,AF can be induced in all the experiment animal.The pattern of ERP with an rapid drop in 6 h followed by a more gradual decline during hours 6 through 48 as the result of rapid pacing.The mean ERP was decreased by (12.13 ± 2.24) ms after 6 hours of pacing (from 141.00 ± 15.23 to 129.50 ± 8.64) ms (P < 0.01).Similarly,after 24 h pacing the mean ERP was decreased by (19.23 ± 2.14) ms (P< 0.01),and by (28.15 ±4.26) ms after 48 h pacing(P<0.01).Compared with control group(-6.69±0.08)pA/pF,the peak density of ICa-L was significantly reduced in 24 h AF group(-4.83±0.30)pA/pF,and it was reduced more in 48 h AF group(-3.70±0.50)pA/pF.Compared with control group,the protein expression of LVDCC α1c decreased significantly in group of 48 h and 24 h AF(P<0.05),but in the group of 48 h AF it decreased more (P<0.01).Conclusion The decrease of ICa-L may contribute to ionic basis of acute electrical remodeling of atrial cardiomyocytes caused by 24 h and 48 h AF in canine,which suggested that calcium channels blocker might prevent AF

  13. 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 ...

  14. Mass asymmetry dependence of scission times in the reactions of 18. 5[ital A] MeV [sup 136]Xe+[sup 48]Ti

    Energy Technology Data Exchange (ETDEWEB)

    Gui, M.; Hagel, K.; Wada, R.; Lou, Y.; Utley, D.; Xiao, B.; Li, J.; Natowitz, J.B. (Cyclotron Institute, Texas A M University, College Station, Texas 77843 (United States)); Enders, G.; Kuehn, W.; Metag, V.; Novotny, R.; Schwalb, O. (II Physikalisches Instituet, Universtaet Giessen, D-6300 Giessen (Germany)); Charity, R.J.; Freifelder, R.; Gobbi, A.; Henning, W.; Hildenbrand, K.D.; Mayer, R.; Simon, R.S.; Wessels, J.P. (Gesellschaft fuer Schwerionenfurschung, Planck Strasse 1, D-6100 Darmstadt (Germany)); Casini, G.; Olmi, A.; Stefanini, A.A. (Universita di Firenze and Istituto Nazionale di Fisica Nucleare, Florence (Italy))

    1993-10-01

    The multiplicities of [ital p] and [alpha] particles detected in coincidence with fragments emitted in fully relaxed collisions in the reactions of 18.5[ital A] MeV [sup 136]Xe+[sup 48]Ti have been measured for different exit channel mass asymmetries. A kinematic source analysis of the spectra and angular distributions of the light particles has been used to separate the total multiplicities into prescission and postscission contributions. From these results, the excitation energies at scission are determined using an empirical technique based upon previous measurements of light charged particle multiplicities observed in coincidence with evaporation residues. These excitation energies are found to decrease from [similar to]400 MeV to 110 MeV as the fragment mass asymmetry, [ital A][sub [ital H

  15. Mass asymmetry dependence of scission times in the reactions of 18.5A MeV 136Xe+48Ti

    Science.gov (United States)

    Gui, M.; Hagel, K.; Wada, R.; Lou, Y.; Utley, D.; Xiao, B.; Li, J.; Natowitz, J. B.; Enders, G.; Kühn, W.; Metag, V.; Novotny, R.; Schwalb, O.; Charity, R. J.; Freifelder, R.; Gobbi, A.; Henning, W.; Hildenbrand, K. D.; Mayer, R.; Simon, R. S.; Wessels, J. P.; Casini, G.; Olmi, A.; Stefanini, A. A.

    1993-10-01

    The multiplicities of p and α particles detected in coincidence with fragments emitted in fully relaxed collisions in the reactions of 18.5A MeV 136Xe+48Ti have been measured for different exit channel mass asymmetries. A kinematic source analysis of the spectra and angular distributions of the light particles has been used to separate the total multiplicities into prescission and postscission contributions. From these results, the excitation energies at scission are determined using an empirical technique based upon previous measurements of light charged particle multiplicities observed in coincidence with evaporation residues. These excitation energies are found to decrease from ~400 MeV to 110 MeV as the fragment mass asymmetry, AH/AL, varies from 4.8 to 1.0. A corresponding increase of the mean lifetime of the scissioning nucleus from ~5×10-22 s to ~1×10-20 s is derived using calculated statistical model decay widths. The extent to which this variation of lifetime with mass asymmetry may be attributed to completely damped deep inelastic collisions or to dynamic delays in the decay of a compound nucleus is discussed as is the need for inclusion of dynamics in the deexcitation calculations for hot nuclei. Observed three fragment events are also discussed.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. [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.

  1. 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...

  2. 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

  3. Study of the break reaction of Be{sup 11} on Ti{sup 48} target; the towing mode: a spectroscopic tool for the study of nuclei; Etude de la reaction de cassure du {sup 11}Be sur cible de {sup 48}Ti; le towing mode, un outil spectroscopique pour l'etude des noyaux

    Energy Technology Data Exchange (ETDEWEB)

    Lima, V

    2004-10-01

    In a towing mode reaction the projectile picks up a nucleon from the target and then breaks up by emitting one nucleon. The velocity of the emitted nucleon is boosted by the projectile velocity, leading to the emission of the nucleon in a narrow cone around the direction of the scattered projectile. This work is dedicated to the towing mode in halo nuclei such as Be{sup 11}. The experiment was performed at Ganil facility by bombarding a Ti{sup 48} target with a 41 MeV per nucleon Be{sup 11} beam, the reaction studied is: Ti{sup 48}(Be{sup 11}, Be{sup 10} + n + {gamma}). The first chapter reviews the various nuclear processes that take place when 2 nuclei collide with a particular attention for the towing mode. The second chapter is dedicated to solving the time dependant Schroedinger equation (TDSE) in order to assess the impact of various parameters such as incident energy, target charge or the linking energy of the nucleon, on the towing mode reaction. The third chapter deals with the experimental equipment and set-up including detectors and the data acquisition system. Computerized simulations have been performed in order to assess the efficiency of the detecting system, they are presented in the fourth chapter. A comparison between experimental data and the results from TDSE solving, concerning the energy spectra of the emitted particles, has enabled the author to deduce the spectroscopic factors for the different contributions of the fundamental state of Be{sup 11}, they are presented in the last chapter. The cross-sections of the towing mode are of the magnitude of several tens of milli-barns in the case of weakly bound nuclei like Be{sup 11} which make it an efficient tool to study intern structure of nuclei. (A.C.)

  4. Ca48+Bk249 Fusion Reaction Leading to Element Z =117: Long-Lived α-Decaying Db270 and Discovery of Lr266

    Science.gov (United States)

    Khuyagbaatar, J.; Yakushev, A.; Düllmann, Ch. E.; Ackermann, D.; Andersson, L.-L.; Asai, M.; Block, M.; Boll, R. A.; Brand, H.; Cox, D. M.; Dasgupta, M.; Derkx, X.; Di Nitto, A.; Eberhardt, K.; Even, J.; Evers, M.; Fahlander, C.; Forsberg, U.; Gates, J. M.; Gharibyan, N.; Golubev, P.; Gregorich, K. E.; Hamilton, J. H.; Hartmann, W.; Herzberg, R.-D.; Heßberger, F. P.; Hinde, D. J.; Hoffmann, J.; Hollinger, R.; Hübner, A.; Jäger, E.; Kindler, B.; Kratz, J. V.; Krier, J.; Kurz, N.; Laatiaoui, M.; Lahiri, S.; Lang, R.; Lommel, B.; Maiti, M.; Miernik, K.; Minami, S.; Mistry, A.; Mokry, C.; Nitsche, H.; Omtvedt, J. P.; Pang, G. K.; Papadakis, P.; Renisch, D.; Roberto, J.; Rudolph, D.; Runke, J.; Rykaczewski, K. P.; Sarmiento, L. G.; Schädel, M.; Schausten, B.; Semchenkov, A.; Shaughnessy, D. A.; Steinegger, P.; Steiner, J.; Tereshatov, E. E.; Thörle-Pospiech, P.; Tinschert, K.; Torres De Heidenreich, T.; Trautmann, N.; Türler, A.; Uusitalo, J.; Ward, D. E.; Wegrzecki, M.; Wiehl, N.; Van Cleve, S. M.; Yakusheva, V.

    2014-05-01

    The superheavy element with atomic number Z =117 was produced as an evaporation residue in the Ca48+Bk249 fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope 117294 and its decay products. A hitherto unknown α-decay branch in Db270 (Z =105) was observed, which populated the new isotope Lr266 (Z =103). The identification of the long-lived (T1/2=1.0-0.4+1.9 h) α-emitter Db270 marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an "island of stability."

  5. 48Ca+249Bk fusion reaction leading to element Z = 117: long-lived α-decaying 270Db and discovery of 266Lr.

    Science.gov (United States)

    Khuyagbaatar, J; Yakushev, A; Düllmann, Ch E; Ackermann, D; Andersson, L-L; Asai, M; Block, M; Boll, R A; Brand, H; Cox, D M; Dasgupta, M; Derkx, X; Di Nitto, A; Eberhardt, K; Even, J; Evers, M; Fahlander, C; Forsberg, U; Gates, J M; Gharibyan, N; Golubev, P; Gregorich, K E; Hamilton, J H; Hartmann, W; Herzberg, R-D; Heßberger, F P; Hinde, D J; Hoffmann, J; Hollinger, R; Hübner, A; Jäger, E; Kindler, B; Kratz, J V; Krier, J; Kurz, N; Laatiaoui, M; Lahiri, S; Lang, R; Lommel, B; Maiti, M; Miernik, K; Minami, S; Mistry, A; Mokry, C; Nitsche, H; Omtvedt, J P; Pang, G K; Papadakis, P; Renisch, D; Roberto, J; Rudolph, D; Runke, J; Rykaczewski, K P; Sarmiento, L G; Schädel, M; Schausten, B; Semchenkov, A; Shaughnessy, D A; Steinegger, P; Steiner, J; Tereshatov, E E; Thörle-Pospiech, P; Tinschert, K; Torres De Heidenreich, T; Trautmann, N; Türler, A; Uusitalo, J; Ward, D E; Wegrzecki, M; Wiehl, N; Van Cleve, S M; Yakusheva, V

    2014-05-02

    The superheavy element with atomic number Z=117 was produced as an evaporation residue in the (48)Ca+(249)Bk fusion reaction at the gas-filled recoil separator TASCA at GSI Darmstadt, Germany. The radioactive decay of evaporation residues and their α-decay products was studied using a detection setup that allowed measuring decays of single atomic nuclei with half-lives between sub-μs and a few days. Two decay chains comprising seven α decays and a spontaneous fission each were identified and are assigned to the isotope (294)117 and its decay products. A hitherto unknown α-decay branch in (270)Db (Z = 105) was observed, which populated the new isotope (266)Lr (Z = 103). The identification of the long-lived (T(1/2) = 1.0(-0.4)(+1.9) h) α-emitter (270)Db marks an important step towards the observation of even more long-lived nuclei of superheavy elements located on an "island of stability."

  6. 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.

  7. [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.

  8. 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 ...

  9. Nuclear molecules and their deexcitation channels, case of Cr{sup 48} generated by the Mg{sup 24} + Mg{sup 24} resonant reaction; Molecules nucleaires et leurs modes de desexcitation: le cas du {sup 48}Cr et de la reaction resonante {sup 24}Mg + {sup 24}Mg

    Energy Technology Data Exchange (ETDEWEB)

    Salsac, M.D

    2006-12-15

    This work is dedicated to the study of the resonance (E = 45,7 MeV, J{sup {pi}} = 36{sup +}, {gamma} = 170 keV) of the Mg{sup 24} + Mg{sup 24} composite nucleus. The PRISMA fragment spectrometer combined with the CLARA gamma detector have been used to study the deexcitation through inelastic channels of the composite system. It is showed that the resonant flux is mainly observed in the inelastic channels involving the contributions 0{sup +}, 2{sup +} and 4{sup +} of the band based on the fundamental state of Mg{sup 24}. This is in good agreement with the theoretical predictions of the molecular model of Uegaki and Abe. Only 30% of the resonant flux has been observed in the inelastic channels and in the transfer channels. The missing flux has been investigated in the fusion/evaporation deexcitation channels with the GASP gamma multi-detector. A weak resonant effect has been highlighted in some residual nuclei such as Ti{sup 45}, Ca{sup 42} and K{sup 39}. A link between the prolate di-nucleus Ca{sup 48} generated in Mg{sup 24} + Mg{sup 24} reaction and a Cr{sup 48} nucleus that has just undergone a Jacobi transition from oblate to prolate, has been discovered. To explain a part of the missing flux it is suggested that the dipolar giant resonance might feed very deformed nuclei through particle emission.

  10. 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.

  11. 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

  12. 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

  13. 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

  14. 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.

  15. 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.

  16. 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。

  17. 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.

  18. 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. ...

  19. 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.

  20. 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) , ...

  1. 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.

  2. 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.

  3. Clinical observation on Integrated Therapy of Tangshenkang Decoction,Calcium Dobesilate Combined with Astragalus Shuxuetong Treating 48 Cases of Phase IV Diabetic Nephropathy%糖肾康煎剂与羟苯磺酸钙联合黄芪疏血通治疗糖尿病肾病 IV 期48例的临床观察

    Institute of Scientific and Technical Information of China (English)

    唐光钰; 唐今尧

    2014-01-01

    Objective:To observe the clinical effect of Tangshenkang decoction combined with calcium dobesilate dispersible tablets and Astragalus and Shuxuetong injection in treatment of phase IV diabetic nephropathy.Methods:Ninety six patients with phase IV diabetic renal disease were randomly divided into control group (n =48)and treatment group (n =48).Patients in both groups were given insu-lin to control blood sugar,telmisartan and nifedipine tablets to control blood pressure,as well as astragalus injection and Shuxuetong in-jection.Besides,patients in the treatment group were given dispersible tablets and Tangshenkang decoction with calcium dobesilate.The treatment course was 14 days.The changes of clinical symptoms,24 h urinary albumin excretion,blood lipid and renal function were ob-served before and after treatment.Results:All indexes and clinical symptom score of patients in both groups after treatment were de-creased.The total effective rate of treatment group was 93.75%,while that of the control group was 68.8%,and the difference between the two groups was significant (P 0.05),while the treatment group showed significant improvement (P 0.05),so there was significant difference between the two groups (P <0.05).Conclusion:Tangshenkang decoction combined with calcium dobesilate dis-persed tablets and Astragalus shows definite clinical efficacy in the treatment of phase IV diabetic nephropathy.The therapy can improve clinical symptoms,reduce urinary protein excretion,improve renal microcirculation,promote the recovery of renal function,promote re-nal blood flow,so as to effectively block or reverse the disease progression,open up a new way for the optimization and combination ther-apy of diabetic nephropathy.%目的:观察糖肾康煎剂与羟苯磺酸钙分散片联合黄芪及疏血通注射液治疗糖尿病肾脏疾病 IV 期的临床疗效。方法:选取确诊的糖尿病肾脏疾病 IV 期患者96例,随机分为对照组和治疗组各48例。2组均

  4. 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.

  5. 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.

  6. 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.

  7. 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

  8. 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.

  9. 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.

  10. Supplementation with 1000 IU vitamin D/d leads to parathyroid hormone suppression, but not increased fractional calcium absorption, in 4-8-y-old children: A double-blind randomized controlled trial

    Science.gov (United States)

    The effects of vitamin D supplementation in healthy prepubertal children on physiologic outcomes have not been investigated. The objective was to evaluate the effects of supplementation with 1000 IU vitamin D(3)/d on calcium absorption. In a double-blind, placebo-controlled trial, we randomly assign...

  11. 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.

  12. 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 ...

  13. 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.

  14. Cross section ratio and angular distributions of the reaction p + d → 3He + η at 48.8 MeV and 59.8 MeV excess energy

    Science.gov (United States)

    Adlarson, P.; Augustyniak, W.; Bardan, W.; Bashkanov, M.; Bergmann, F. S.; Berłowski, M.; Bhatt, H.; Büscher, M.; Calén, H.; Ciepał, I.; Clement, H.; Coderre, D.; Czerwiński, E.; Demmich, K.; Doroshkevich, E.; Engels, R.; Erven, A.; Erven, W.; Eyrich, W.; Fedorets, P.; Föhl, K.; Fransson, K.; Goldenbaum, F.; Goslawski, P.; Goswami, A.; Grigoryev, K.; Gullström, C.-O.; Hauenstein, F.; Heijkenskjöld, L.; Hejny, V.; Hodana, M.; Höistad, B.; Hüsken, N.; Jany, A.; Jany, B. R.; Jarczyk, L.; Johansson, T.; Kamys, B.; Kemmerling, G.; Khan, F. A.; Khoukaz, A.; Kirillov, D. A.; Kistryn, S.; Kłos, B.; Kleines, H.; Krapp, M.; Krzemień, W.; Kulessa, P.; Kupść, A.; Lalwani, K.; Lersch, D.; Lorentz, B.; Magiera, A.; Maier, R.; Marciniewski, P.; Mariański, B.; Mikirtychiants, M.; Morsch, H.-P.; Moskal, P.; Ohm, H.; Ozerianska, I.; Passfeld, A.; Perez del Rio, E.; Piskunov, N. M.; Podkopał, P.; Prasuhn, D.; Pricking, A.; Pszczel, D.; Pysz, K.; Pyszniak, A.; Redmer, C. F.; Ritman, J.; Roy, A.; Rudy, Z.; Sawant, S.; Schadmand, S.; Sefzick, T.; Serdyuk, V.; Siudak, R.; Skorodko, T.; Skurzok, M.; Smyrski, J.; Sopov, V.; Stassen, R.; Stepaniak, J.; Stephan, E.; Sterzenbach, G.; Stockhorst, H.; Ströher, H.; Szczurek, A.; Täschner, A.; Trzciński, A.; Varma, R.; Wagner, G. J.; Węglorz, W.; Wolke, M.; Wrońska, A.; Wüstner, P.; Wurm, P.; Yamamoto, A.; Yurev, L.; Zabierowski, J.; Zieliński, M. J.; Zink, A.; Złomańczuk, J.; Żuprański, P.; Żurek, M.

    2014-06-01

    We present new data for angular distributions and on the cross section ratio of the p+d → 3He + η reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum Jülich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.

  15. Cross section ratio and angular distributions of the reaction p + d → {sup 3}He + η at 48.8 MeV and 59.8 MeV excess energy

    Energy Technology Data Exchange (ETDEWEB)

    Adlarson, P.; Calen, H.; Fransson, K.; Gullstroem, C.O.; Heijkenskjoeld, L.; Hoeistad, B.; Johansson, T.; Marciniewski, P.; Redmer, C.F.; Wolke, M.; Zlomanczuk, J. [Uppsala University, Division of Nuclear Physics, Department of Physics and Astronomy, Box 516, Uppsala (Sweden); Augustyniak, W.; Marianski, B.; Morsch, H.P.; Trzcinski, A.; Zupranski, P. [National Centre for Nuclear Research, Department of Nuclear Physics, Warsaw (Poland); Bardan, W.; Ciepal, I.; Czerwinski, E.; Hodana, M.; Jany, A.; Jany, B.R.; Jarczyk, L.; Kamys, B.; Kistryn, S.; Krzemien, W.; Magiera, A.; Moskal, P.; Ozerianska, I.; Podkopal, P.; Rudy, Z.; Skurzok, M.; Smyrski, J.; Wronska, A.; Zielinski, M.J. [Jagiellonian University, Institute of Physics, Krakow (Poland); Bashkanov, M.; Clement, H.; Doroshkevich, E.; Perez del Rio, E.; Pricking, A.; Skorodko, T.; Wagner, G.J. [Eberhard-Karls-Universitaet Tuebingen, Physikalisches Institut, Tuebingen (Germany); Physikalisches Institut der Universitaet Tuebingen, Kepler Center fuer Astro- und Teilchenphysik, Tuebingen (Germany); Bergmann, F.S.; Demmich, K.; Goslawski, P.; Huesken, N.; Khoukaz, A.; Passfeld, A.; Taeschner, A. [Westfaelische Wilhelms-Universitaet Muenster, Institut fuer Kernphysik, Muenster (Germany); Berlowski, M.; Stepaniak, J. [National Centre for Nuclear Research, High Energy Physics Department, Warsaw (Poland); Bhatt, H.; Lalwani, K.; Varma, R. [Indian Institute of Technology Bombay, Department of Physics, Mumbai, Maharashtra (India); Buescher, M.; Engels, R.; Goldenbaum, F.; Hejny, V.; Khan, F.A.; Lersch, D.; Lorentz, B.; Maier, R.; Ohm, H.; Prasuhn, D.; Schadmand, S.; Sefzick, T.; Stassen, R.; Sterzenbach, G.; Stockhorst, H.; Stroeher, H.; Wurm, P.; Zurek, M. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Coderre, D.; Ritman, J. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Ruhr-Universitaet Bochum, Institut fuer Experimentalphysik I, Bochum (Germany); Erven, A.; Erven, W.; Kemmerling, G.; Kleines, H.; Wuestner, P. [Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Forschungszentrum Juelich, Zentralinstitut fuer Engineering, Elektronik und Analytik, Juelich (Germany); Eyrich, W.; Hauenstein, F.; Krapp, M.; Zink, A. [Friedrich-Alexander-Universitaet Erlangen-Nuernberg, Physikalisches Institut, Erlangen (Germany); Fedorets, P. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); State Scientific Center of the Russian Federation, Institute for Theoretical and Experimental Physics, Moscow (Russian Federation); Foehl, K. [Justus-Liebig-Universitaet Giessen, II. Physikalisches Institut, Giessen (Germany); Goswami, A. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); Indian Institute of Technology Indore, Department of Physics, Indore, Madhya Pradesh (India); Grigoryev, K. [Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (Germany); RWTH Aachen, III. Physikalisches Institut B, Physikzentrum, Aachen (Germany); Petersburg Nuclear Physics Institute, High Energy Physics Division, Leningrad district (Russian Federation); Kirillov, D.A.; Piskunov, N.M. [Joint Institute for Nuclear Physics, Veksler and Baldin Laboratory of High Energiy Physics, Moscow region (Russian Federation); Klos, B.; Stephan, E.; Weglorz, W. [University of Silesia, August Chelkowski Institute of Physics, Katowice (Poland); Kulessa, P.; Pysz, K.; Siudak, R.; Szczurek, A. [Polish Academy of Sciences, The Henryk Niewodniczanski Institute of Nuclear Physics, Krakow (Poland); Kupsc, A.; Pszczel, D. [Uppsala University, Division of Nuclear Physics, Department of Physics and Astronomy, Box 516, Uppsala (Sweden); National Centre for Nuclear Research, High Energy Physics Department, Warsaw (Poland); Mikirtychiants, M. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (Germany); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (DE); Ruhr-Universitaet Bochum, Institut fuer Experimentalphysik I, Bochum (DE); Petersburg Nuclear Physics Institute, High Energy Physics Division, Leningrad district (RU); Pyszniak, A. [Uppsala University, Division of Nuclear Physics, Department of Physics and Astronomy, Box 516, Uppsala (SE); Jagiellonian University, Institute of Physics, Krakow (PL); Roy, A. [Indian Institute of Technology Indore, Department of Physics, Indore, Madhya Pradesh (IN); Sawant, S. [Indian Institute of Technology Bombay, Department of Physics, Mumbai, Maharashtra (IN); Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (DE); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (DE); Serdyuk, V. [Forschungszentrum Juelich, Institut fuer Kernphysik, Juelich (DE); Forschungszentrum Juelich, Juelich Center for Hadron Physics, Juelich (DE); Joint Institute for Nuclear Physics, Dzhelepov Laboratory of Nuclear Problems, Moscow region (RU); Sopov, V. [State Scientific Center of the Russian Federation, Institute for Theoretical and Experimental Physics, Moscow (RU); Yamamoto, A. [High Energy Accelerator Research Organization KEK, Tsukuba, Ibaraki (JP); Yurev, L. [Joint Institute for Nuclear Physics, Dzhelepov Laboratory of Nuclear Problems, Moscow region (RU); Zabierowski, J. [National Centre for Nuclear Research, Department of Cosmic Ray Physics, Lodz (PL); Collaboration: WASA-at-COSY Collaboration

    2014-06-15

    We present new data for angular distributions and on the cross section ratio of the p+d → {sup 3}He + η reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum Juelich) using a proton beam and a deuterium pellet target. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval. (orig.)

  16. Total and differential cross sections of the reaction p + d -> 3He + eta at 48.8 MeV and 59.8MeV excess energy

    CERN Document Server

    Adlarson, P; Bardan, W; Bashkanov, M; Bergmann, F S; Berłowski, M; Bhatt, H; Büscher, M; Calén, H; Ciepał, I; Clement, H; Coderre, D; Czerwiński, E; Demmich, K; Doroshkevich, E; Engels, R; Erven, A; Erven, W; Eyrich, W; Fedorets, P; Föhl, K; Fransson, K; Goldenbaum, F; Goslawski, P; Goswami, A; Grigoryev, K; Gullström, C --O; Hauenstein, F; Heijkenskjöld, L; Hejny, V; Hodana, M; Höistad, B; Hüsken, N; Jany, A; Jany, B R; Jarczyk, L; Johansson, T; Kamys, B; Kemmerling, G; Khan, F A; Khoukaz, A; Kirillov, D A; Kistryn, S; Kłos, B; Kleines, H; Krapp, M; Krzemień, W; Kulessa, P; Kupść, A; Lalwani, K; Lersch, D; Lorentz, B; Magiera, A; Maier, R; Marciniewski, P; Mariański, B; Mikirtychiants, M; Morsch, H --P; Moskal, P; Ohm, H; Ozerianska, I; Passfeld, A; del Rio, E Perez; Piskunov, N M; Podkopał, P; Prasuhn, D; Pricking, A; Pszczel, D; Pysz, K; Pyszniak, A; Redmer, C F; Ritman, J; Roy, A; Rudy, Z; Sawant, S; Schadmand, S; Sefzick, T; Serdyuk, V; Siudak, R; Skorodko, T; Skurzok, M; Smyrski, J; Sopov, V; Stassen, R; Stepaniak, J; Stephan, E; Sterzenbach, G; Stockhorst, H; Ströher, H; Szczurek, A; Täschner, A; Trzciński, A; Varma, R; Wagner, G J; Węglorz, W; Wolke, M; Wrońska, A; Wüstner, P; Wurm, P; Yamamoto, A; Yurev, L; Zabierowski, J; Zieliński, M J; Zink, A; Złomańczuk, J; Żuprański, P; Żurek, M

    2014-01-01

    We present new data for the cross section ratio of the p + d -> 3He + eta reaction at excess energies of Q = 48.8 MeV and Q = 59.8 MeV. The data have been obtained at the WASA-at-COSY experiment (Forschungszentrum J\\"ulich) using a proton beam and a deuterium pellet target. By using an ANKE data point at 59.4 MeV excess energy, an absolute normalization was performed and total and differential cross sections have been determined. While the shape of obtained angular distributions show only a slow variation with the energy, the new results indicate a distinct and unexpected total cross section fluctuation between Q = 20 MeV and Q = 60 MeV, which might indicate the variation of the production mechanism within this energy interval.

  17. 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.

  18. 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).

  19. 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.

  20. Experimental cross-sections of deuteron-induced reaction on {sup 89}Y up to 20 MeV; comparison of {sup nat}Ti(d,x){sup 48}V and {sup 27}Al(d,x){sup 24}Na monitor reactions

    Energy Technology Data Exchange (ETDEWEB)

    Lebeda, Ondřej, E-mail: lebeda@ujf.cas.cz; Štursa, Jan; Ráliš, Jan

    2015-10-01

    We measured cross-sections of the deuteron-induced reactions on {sup 89}Y in the energy range of 3.9–19.5 MeV. Excitation functions for formation of {sup 88}Zr, {sup 89m}Zr, {sup 89}Zr, {sup 88}Y, {sup 90m}Y and {sup 87m}Sr were determined and compared with previously published data and prediction of the TALYS code. Thick target yields for production of {sup 88}Zr, {sup 89}Zr{sup cum}, {sup 88}Y, {sup 90m}Y and {sup 87m}Sr were calculated from the measured cross-sections. Achievable activity versus radionuclidic purity of medically relevant {sup 89}Zr is discussed and compared with the production via the {sup 89}Y(p,n) reaction. Parallel use of titanium and aluminium beam monitors revealed systematic difference between the recommended cross-sections of both monitoring reactions and provided new cross-section data for formation of {sup 24}Na, {sup 27}Mg, {sup 43}Sc, {sup 44m}Sc, {sup 44}Sc, {sup 46}Sc, {sup 47}Sc and {sup 48}Sc. The cross-sections for the {sup nat}Ti(d,x){sup 46}Sc reactions agree very well with recently proposed recommended values.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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

  7. Alendronate affects calcium dynamics in cardiomyocytes in vitro.

    Science.gov (United States)

    Kemeny-Suss, Naomi; Kasneci, Amanda; Rivas, Daniel; Afilalo, Jonathan; Komarova, Svetlana V; Chalifour, Lorraine E; Duque, Gustavo

    2009-01-01

    Therapy with bisphosphonates, including alendronate (ALN), is considered a safe and effective treatment for osteoporosis. However, recent studies have reported an unexpected increase in serious atrial fibrillation (AF) in patients treated with bisphosphonates. The mechanism that explains this side effect remains unknown. Since AF is associated with an altered sarcoendoplasmic reticulum calcium load, we studied how ALN affects cardiomyocyte calcium homeostasis and protein isoprenylation in vitro. Acute and long-term (48h) treatment of atrial and ventricular cardiomyocytes with ALN (10(-8)-10(-6)M) was performed. Changes in calcium dynamics were determined by both fluorescence measurement of cytosolic free Ca(2+) concentration and western blot analysis of calcium-regulating proteins. Finally, effect of ALN on protein farnesylation was also identified. In both atrial and ventricular cardiomyocytes, ALN treatment delayed and diminished calcium responses to caffeine. Only in atrial cells, long-term exposure to ALN-induced transitory calcium oscillations and led to the development of oscillatory component in calcium responses to caffeine. Changes in calcium dynamics were accompanied by changes in expression of proteins controlling sarcoendoplasmic reticulum calcium. In contrast, ALN minimally affected protein isoprenylation in these cells. In summary, treatment of atrial cardiomyocytes with ALN-induced abnormalities in calcium dynamics consistent with induction of a self-stimulatory, pacemaker-like behavior, which may contribute to the development of cardiac side effects associated with these drugs.

  8. 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.

  9. 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.

  10. Single step preparation of nanosilver loaded calcium phosphate by low temperature co-conversion process.

    Science.gov (United States)

    Suwanprateeb, J; Thammarakcharoen, F; Wasoontararat, K; Chokevivat, W; Phanphiriya, P

    2012-09-01

    The preparation and characterization of nanosilver loaded calcium phosphate aiming to enhance the bactericidal performance by a single step co-conversion technique using low temperature ion exchange phosphorization in combination with Tollen's reaction were performed. Silver nitrate was used as a silver ion supply source (0.001-0.1 M) and glucose was employed as a reducing agent. After conversion, surface and shell zones of all samples comprised hydroxyapatite and metallic silver as the main phases regardless of silver nitrate concentration. However, hydroxyapatite, residual calcium sulfate and monetite were found in the core zone when using silver nitrate concentration lower than 0.1 M. The microstructure of all samples comprised the distribution of spherical-shaped silver nanoparticles within the cluster of calcium phosphate nanocrystals. Total silver content (range, 0.09-6.5 %) in the converted samples was found to linearly increase with increasing silver nitrate content. Flexural modulus and strength of converted samples generally decreased with increasing silver content. Effective antibacterial activity of two selected samples (0.001 and 0.005 M AgNO(3)) against two bacterial strains (Pseudomonas aeruginosa and Staphylococcus aureus) was observed. Cytotoxic potentials by MTT assay of both samples were observed at 24 and 48 h extraction respectively.

  11. 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.``

  12. 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.

  13. 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.

  14. Inhibitory effects of atractylone on mast cell-mediated allergic reactions.

    Science.gov (United States)

    Han, Na-Ra; Moon, Phil-Dong; Nam, Sun-Young; Ryu, Ka-Jung; Yoou, Myoung-Schook; Choi, Jung-Hye; Hwang, Sung-Yeoun; Kim, Hyung-Min; Jeong, Hyun-Ja

    2016-10-25

    This study investigated a salutary effect of atractylone (Atr) which is an active constituent of Pyeongwee-San (KMP6) on mast cell-mediated allergic reactions. Our previous report indicated that KMP6 regulated allergic reactions. Thus, this study sought to determine the potential of Atr in vitro models, compound 48/80-stimulated rat peritoneal mast cells (RPMCs), phorbol 12-myristate 13-acetate (PMA) plus A23187-stimulated human mast cell line (HMC-1) cells, and stem cell factor (SCF)-stimulated RPMCs as well as in vivo models, IgE-mediated passive cutaneous anaphylaxis (PCA), compound 48/80-induced systemic anaphylaxis, and compound 48/80-induced ear swelling. The results showed that Atr inhibited compound 48/80-induced RPMCs degranulation, intracellular calcium level, tryptase release, and histamine release. Atr inhibited the up-regulation of p56(lck) tyrosine kinase activity by compound 48/80. And Atr reduced tryptase and histamine releases from PMA plus A23187-stimulated HMC-1 cells. In addition, Atr decreased histidine decarboxylase activity and expression in the activated HMC-1 cells. Atr inhibited SCF-induced morphological alteration and filamentous actin formation in RPMCs. Atr improved IgE-induced PCA reaction by decreasing the levels of histamine, IgE, interleukin (IL)-4, IL-5, IL-6, vascular endothelial growth factor, and IL-13 in the serum of PCA-induced mice. Furthermore, Atr mitigated compound 48/80-induced systemic anaphylaxis and ear swelling. Taken together, these results of this study indicate that Atr regulates the degranulation of mast cell, proving its potential in the treatment of mast cell-mediated allergic reactions.

  15. 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.

  16. Inhibition of anaphylaxis-like reaction and mast cell activation by water extract from the fruiting body of Phellinus linteus.

    Science.gov (United States)

    Choi, Yun Ho; Yan, Guang Hai; Chai, Ok Hee; Lim, Jung Min; Sung, So Young; Zhang, Xin; Kim, Ji-Hyun; Choi, Su Hwan; Lee, Moo Sam; Han, Eui-Hyeog; Kim, Hyoung Tae; Song, Chang Ho

    2006-07-01

    Mast cell-mediated anaphylactic reaction is involved in many allergic diseases such as asthma and allergic rhinitis. Phellinus linteus has been used as a traditional herb medicine in oriental countries and is known to have anti-tumor, immunomodulatory, anti-inflammatory, and anti-allergic activities. However, roles of Phellinus linteus in the mast cell-mediated anaphylactic reactions have not fully been examined. In the present study, we have investigated the effects of water extract from the fruiting body of Phellinus linteus (WEPL) on mast cell-mediated anaphylaxis-like reactions. Oral administration of WEPL inhibited the compound 48/80-induced systemic anaphylaxis-like reaction and ear swelling response. WEPL also inhibited the anti-dinitrophenyl (DNP) IgE-mediated passive systemic and cutaneous anaphylaxis. WEPL had no cytotoxicity on rat peritoneal mast cells (RPMC). WEPL dose-dependently reduced histamine release from RPMC activated by compound 48/80 or anti-DNP IgE. Moreover, WEPL decreased the compound 48/80-induced calcium uptake into RPMC. Furthermore, WEPL increased the level of intracellular cAMP and significantly inhibited the compound 48/80-induced cAMP reduction in RPMC. These results suggest that WEPL may serve as an effective therapeutic agent for allergic diseases.

  17. 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.

  18. 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.

  19. 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...

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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 ...

  6. 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.

  7. 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

  8. 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...

  9. [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

  10. Injectable bioactive calcium-magnesium phosphate cement for bone regeneration.

    Science.gov (United States)

    Wu, Fan; Su, Jiacan; Wei, Jie; Guo, Han; Liu, Changsheng

    2008-12-01

    Novel injectable and degradable calcium-magnesium phosphate cement (CMPC) with rapid-setting characteristic was developed by the introduction of magnesium phosphate cement (MPC) into calcium phosphate cement (CPC). The calcium-magnesium phosphate cement prepared under the optimum P/L ratio exhibited good injectability and desired workability. It could set within 10 min at 37 degrees C in 100% relative humidity and the compressive strength could reach 47 MPa after setting for 48 h, indicating that the prepared cement has relatively high initial mechanical strength. The results of in vitro degradation experiments demonstrated the good degradability of the injectable CMPC, and its degradation rate occurred significantly faster than that of pure CPC in simulated body fluid (SBF) solution. It can be concluded that the novel injectable calcium-magnesium phosphate cement is highly promising for a wide variety of clinical applications, especially for the development of minimally invasive techniques.

  11. 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.

  12. 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

  13. 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...

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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)

  19. 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 ...

  20. Serum calcium concentration and prostate cancer risk: a multicenter study.

    Science.gov (United States)

    Salem, Sepehr; Hosseini, Mostafa; Allameh, Farzad; Babakoohi, Shahab; Mehrsai, Abdolrasoul; Pourmand, Gholamreza

    2013-01-01

    This study sought to further evaluate the possible effects of serum calcium level on prostate cancer (PC) risk, with considering the age, body mass index (BMI), and sex steroid hormones. Using data from a prospective multicenter study, serum calcium concentration, as well as thorough demographic and medical characteristics, were determined in 194 cases with newly diagnosed, clinicopathologically confirmed PC and 317 controls, without any malignant disease, admitted to the same network of hospitals. Serum total and ionized calcium levels were categorized into tertiles. Multivariate logistic regression model was used to estimate odds ratios (OR) and corresponding 95% confidence intervals (CI) after adjustment for major potential confounders, including age, BMI, smoking, alcohol, education, occupation, marital status, family history of PC, and sex hormones level. The mean serum calcium level (±SD) in case and control groups was 9.22 (±0.46) mg/dl and 9.48 (±0.51) mg/dl, respectively (P < 0.001). After adjustment for mentioned confounders, a significant trend of decreasing risk was found for serum total calcium concentration (OR = 0.27, 95% CI = 0.12-0.59, comparing the highest with the lowest tertile) and ionized calcium (OR = 0.25, 95% CI = 0.10-0.58). An increase of 1 mg/dl in serum calcium level was associated with a significant decrease in PC risk (OR = 0.52; 95% CI = 0.34-0.76). Our findings reveal the inverse association between serum total and ionized concentrations and PC risk, which supports the hypothesis that calcium may protect against PC. Furthermore, no evidence was found regarding age, BMI, and sex steroid hormones to modify the association between serum calcium and PC risk.

  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. Synthesis and Calcium Channel Blocking Activity of 1, 4-Dihydropyridine Derivatives Containing Ester Substitute and Phenyl Carbamoyl Group

    Directory of Open Access Journals (Sweden)

    Bassem Sadek

    2011-01-01

    Full Text Available Problem statement: Several studies on the synthesis of new nifedipine analogs have been carried out, but the literature reveled that no study on the synthesis and calcium channel blocking activity of the substituted ester with an amide (5-phenylcarbamoyl moiety has been reported. Approach: Six new derivatives of m-nifedipine have been successfully synthesized by substituting an ester moiety with an amide (5-phenylcarbamoyl moiety, using a modified Hantzsch reactions and tested for their pharmacological activities. The nifedipine analogs 1-6 were characterized and confirmed using elemental analysis, Infrared spectroscopy (IR, Nuclear Magnetic Resonance (1H NMR and Mass spectroscopy. The purity of the compounds was ascertained by melting point and TLC. The in vitro calcium channel blocking activities were evaluated using the high K+ concentration of Porcine Coronary Artery Smooth Muscles (PCASM assay. Results: The compounds (1-2 failed to exhibit any blocking activity (IC50 = 10−7 to 10−5 M range, while the compounds 3-6 relaxed precontracted porcine coronary artery smooth muscles with pEC50 values ranging between 4.37±0.10 (compound 3 and 6.46±0.07 (compound 5, indicating that compounds 3-6 exhibit comparable potencies in blocking calcium channels to reference drug varapamil (6.97±0.15 and m-nifedipine (6.48±0.05. Conclusion: The results of this study showed that some of the developed new compounds possess maximal calcium channel blocking effects comparable to m-nifedipine. The developed compounds in the present study will predicatively show an increased metabolic stability and consequently longer duration of actions compared to m-nifedipine and could be, therefore, suitable candidates for further optimization to be evaluated as a new class of antihypertensive drugs.

  9. 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.

  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. 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. Decay of the excited compound system {sup 48}Cr{sup *} formed through {sup 24}Mg + {sup 24}Mg, {sup 36}Ar + {sup 12}C and {sup 20}Ne + {sup 28}Si reactions

    Energy Technology Data Exchange (ETDEWEB)

    Santhosh, K.P.; Subha, P.V.; Priyanka, B. [Kannur University, School of Pure and Applied Physics, Payyanur, Kerala (India)

    2016-05-15

    The total cross section, the intermediate mass fragment (IMF) production cross section, and the cross section for the formation of light particle (LP) for the decay of {sup 48}Cr{sup *} formed through the entrance channel {sup 24}Mg+{sup 24}Mg, have been evaluated using the barrier penetration model, taking the scattering potential as the sum of the Coulomb and nuclear proximity potential, for various E{sub CM} values. The computed results have been compared with the available experimental data of the total cross section corresponding to E{sub CM}=44.4 MeV for the entrance channel {sup 24}Mg+{sup 24}Mg, and were found to be in good agreement. The experimental values for the LP production cross section for the channel {sup 24}Mg+{sup 24}Mg were also seen to be agreeing with our calculations. Hence we have extended our studies and have thus computed the total cross section, IMF cross section and LP cross section for the decay of {sup 48}Cr{sup *} formed through the other two entrance channels {sup 36}Ar+{sup 12}C, and {sup 20}Ne+{sup 28}Si with different E{sub CM} values. It was found that the computed total cross sections for the entrance channel {sup 36}Ar+{sup 12}C with E{sub CM}=47 MeV agree well with the corresponding experimental values. Hence, we hope that our predictions on the evaluations of the IMF cross sections and the light charged particle cross sections for the decay of {sup 48}Cr{sup *}, formed through the two entrance channels {sup 36}Ar+{sup 12}C, and {sup 20}Ne+{sup 28}Si, can be used for further experimental studies. (orig.)

  13. 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.

  14. [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.

  15. 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.

  16. 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

  17. 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).

  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. 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...

  1. 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.

  2. 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

  3. Octupole strength in the neutron-rich calcium isotopes

    CERN Document Server

    Riley, L A; Agiorgousis, M L; Baugher, T R; Bazin, D; Bowry, M; Cottle, P D; DeVone, F G; Gade, A; Glowacki, M T; Gregory, S D; Haldeman, E B; Kemper, K W; Lunderberg, E; Noji, S; Recchia, F; Sadler, B V; Scott, M; Weisshaar, D; Zegers, R G T

    2016-01-01

    Low-lying excited states of the neutron-rich calcium isotopes $^{48-52}$Ca have been studied via $\\gamma$-ray spectroscopy following inverse-kinematics proton scattering on a liquid hydrogen target using the GRETINA $\\gamma$-ray tracking array. The energies and strengths of the octupole states in these isotopes are remarkably constant, indicating that these states are dominated by proton excitations.

  4. CALCIUM REQUIREMENT AFTER PARATHYROIDECTOMY (PTX IN SECONDARY HYPERPARATHYROIDISM (2° HPT

    Directory of Open Access Journals (Sweden)

    YJ Kwon

    2012-06-01

    Full Text Available After PTX in 2°HPT, appropriate calcium and calcitriol was supplied to prevent hungry bone syndrome. Duration of admission was variable according to multiple causes. We hypothesized the admission duration was mainly affected by calcium requirement. The aims of this study were to evaluate PTX in 2°HPT in single center and to make equation for calcium requirement. We evaluated 91 patients with 94 PTX from Nov. 2003 to Dec.2011 in Korea Univ. Guro Hospital. We retrieved demographic details including sex, age, body weight, DM, hypertension, mode of renal replacement therapy, duration of dialysis, duration of admission, mode of PTX, method of anesthetics, number of glands removed, the largest gland length, the heaviest gland, and histologic profile of removed gland. We also gathered preoperative and postoperative (12 hrs and 48 hrs after PTX, discharge, 3 mo, 6 mo, 1 yr after PTX laboratory data such as calcium, phosphorus, iPTH, ALP, albumin, and Hb. We summated oral and intravenous calcium supplement during hospitalization after PTX. We prescribed oral calcitriol 2.0 μg/day after PTX. Statistical analysis was performed with SPSS ver. 12.0.1. We could find log(calcium total supplement during admission is correlated with preoperative ALP (p=0.000, preoperative iPTH (p+0.037, and Δ phosphorus 48 hrs after PTX (p=0.000 by multiple linear regression. Log (calcium total supplement during admission = 2.576 + 0.001 X preoperative ALP + 3.575 X 10-5 X preoperative iPTH + 0.06 X Δphosphorus 48 hrs after PTX. We believe this equation would be helpful to estimate calcium requirements after 48 hrs PTX and to give a clue about length of hospitalization. We also would evaluate whether this equation is predictable in our patients in the future.

  5. 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.

  6. Compound 48/80-induced serotonin release from brain mast cells

    Energy Technology Data Exchange (ETDEWEB)

    Lambracht-Hall, M.; Marathias, K.P.; Theoharides, T.C.

    1986-03-01

    Mast cells secrete a variety of potent mediators and are mostly known to participate in allergic reactions. Here the authors report that perfused brain mast cells can take up and release serotonin (5-HT) in response to compound 48/80. Thalamic or hypothalamic slices were loaded with /sup 3/H-5-HT (5 x 10/sup -7/M, for 12 min at 37/sup 0/C), washed and placed in individual 2 ml-perfusion wells. A Krebs-Ringer bicarbonate buffer with 1 x 10/sup -6/M imipramine (KRB + IMI) saturated with 5% CO/sub 2//95% O/sub 2/ at 37/sup 0/C and pH 7.4, was used throughout at a perfusion rate of 1 ml/min. After a 60 min wash in KRB + IMI, with or without Ca/sup +2/ + 0.1 M EDTA, the slices were perfused for 45 min with 100 ..mu..g/ml compound 48/80 with or without Ca/sup +2/. The tissue was washed for 30 min as before and then perfused with high K/sup +/ KRB (40mM KCl) for 45 min to induce neuronal depolarization. Finally, calcium was restored to Ca/sup +2/-depleted tissues and all samples were again perfused for 45 min with high K/sup +/ KRB. The first 5-HT peak due to 48/80-induced mast cell release was independent of extracellular Ca/sup +2/, while the second 5-HT peak due to high K/sup +/ was not. These studies indicate that the 48/80-induced 5-HT release was not of neuronal origin and that brain mast cells can utilize intracellular Ca/sup +2/, much like their peritoneal counterparts. The authors are now studying brain mast cells secretion in response to neuropeptides.

  7. Dual effect of magnesium on compound 48/80-induced histamine secretion from rat peritoneal mast cells

    DEFF Research Database (Denmark)

    Bertelsen, Niels Haldor; Johansen, Torben

    1991-01-01

    The effect of magnesium on the secretory response to compound 48/80 from rat peritoneal mast cells was studied. The decrease in secretion caused by calcium deprivation was enlarged by magnesium. Glucose partially counteracted the decrease caused by calcium deprivation but not the one caused by ma...

  8. 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.

  9. 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.

  10. 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......

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. Evaluation of pH, calcium ion release and antimicrobial activity of a new calcium aluminate cement

    Directory of Open Access Journals (Sweden)

    Fernanda de Carvalho Panzeri Pires-de-Souza

    2013-07-01

    Full Text Available This study evaluated the pH, calcium ion release and antimicrobial activity of EndoBinder (EB, containing different radiopacifiers: bismuth oxide (Bi2O3, zinc oxide (ZnO or zirconium oxide (ZrO2, in comparison to MTA. For pH and calcium ion release tests, 5 specimens per group (n = 5 were immersed into 10 mL of distilled and deionized water at 37°C. After 2, 4, 12, 24, 48 h; 7, 14 and 28 days, the pH was measured and calcium ion release quantified in an atomic absorption spectrophotometer. For antimicrobial activity, the cements were tested against S. aureus, E. coli, E. faecalis and C. albicans, in triplicate. MTA presented higher values for pH and calcium ion release than the other groups, however, with no statistically significant difference after 28 days (p > 0.05; and the largest inhibition halos for all strains, with no significant difference (E. coli and E. faecalis for pure EB and EB + Bi2O3 (p > 0.05. EB presented similar performance to that of MTA as regards pH and calcium ion release; however, when ZnO and ZrO2 were used, EB did not present antimicrobial activity against some strains.

  19. Isospin effects in {sup 40,48}Ca+{sup 40,48}Ca collisions

    Energy Technology Data Exchange (ETDEWEB)

    Henzl, V., E-mail: henzl@mit.ed [MSU-NSCL, 1 Cyclotron, East Lansing MI, 48824 (United States); Henzlova, D.; Kilburn, M. [MSU-NSCL, 1 Cyclotron, East Lansing MI, 48824 (United States); Verde, G. [INFN, Sezione di Catania. 64 Via S. Sofia, I-95123, Catania (Italy); Brown, D. [MSU-NSCL, 1 Cyclotron, East Lansing MI, 48824 (United States); Chbihi, A. [GANIL, CEA et IN2P3-CNRS, B.P. 5027, F-14076 Caen Cedex (France); Coupland, D. [MSU-NSCL, 1 Cyclotron, East Lansing MI, 48824 (United States); Elson, J. [Departments of Chemistry and Physics, Washington University, St. Louis, MO 63130 (United States); Famiano, M. [Western Michigan University, 2229 Everett Tower, Kalamazoo, MI 49008-5252 (United States); Herlitzius, C. [MSU-NSCL, 1 Cyclotron, East Lansing MI, 48824 (United States); Hudan, S. [Indiana Univ. Cyclotron Facility, 2401 Milo B. Sampson Lane, Bloomington, IN 47405-4001 (United States); Lee, J.; Lukyanov, S.; Lynch, W.; Rogers, A.; Sanetullaev, A. [MSU-NSCL, 1 Cyclotron, East Lansing MI, 48824 (United States); Sobotka, L. [Departments of Chemistry and Physics, Washington University, St. Louis, MO 63130 (United States); Souza, R.T. de [Indiana Univ. Cyclotron Facility, 2401 Milo B. Sampson Lane, Bloomington, IN 47405-4001 (United States); Sun, Z.Y.; Tsang, B. [MSU-NSCL, 1 Cyclotron, East Lansing MI, 48824 (United States)

    2010-03-01

    The isospin dependence of two proton correlations is studied in {sup 40}Ca+{sup 40}Ca and {sup 48}Ca+{sup 48}Ca collisions at E/A=80MeV. Measurements were performed with the HiRA detector array complemented by the 4pi Ball at NSCL. We observe a strong isospin dependence of the pp-correlation functions; however the emitting source radius extracted using the imaging technique yields no sensitivity to the isospin of the reaction system. We interpret this result as a consequence of smaller fraction of fast proton emission in the neutron rich {sup 48}Ca system.

  20. 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 ...

  1. 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 ...

  2. 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...

  3. 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 ...

  4. 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.

  5. 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...

  6. Enhanced expression of a calcium-dependent protein kinase from the moss Funaria hygrometrica under nutritional starvation

    Indian Academy of Sciences (India)

    Doyel Mitra; Man Mohan Johri

    2000-12-01

    Among the downstream targets of calcium in plants, calcium-dependent protein kinases (CDPKs) form an interesting class of kinases which are activated by calcium binding. They have been implicated in a diverse array of responses to hormonal and environmental stimuli. In order to dissect the role of CDPKs in the moss Funaria hygrometrica, a polymerase chain reaction (PCR)-based approach was adopted to clone the gene. Using degenerate PCR primers against conserved regions of CDPKs, a 900 bp amplicon was obtained from the genomic DNA of Funaria. Southern hybridization under low stringency conditions indicated the presence of several CDPK related sequences in the Funaria genome. This observation is consistent with reports of multigene families of CDPKs in other plants. The 900 bp fragment was subsequently used to isolate a 2.2 kb partial genomic clone of the CDPK gene from Funaria. The genomic clone encodes an open reading frame (ORF) of 518 amino acids. Interestingly, unlike other CDPK genes from plants, the entire 1.5 kb ORF is not interrupted by introns. The deduced amino acid sequence of the Funaria gene shows extensive homology with CDPKs from higher plants, 73% identity with the Fragaria CDPK and 71% identity with CDPK isoform 7 of Arabidopsis. Phylogenetic analysis revealed that the Funaria CDPK is closer to the CDPKs from higher plants like strawberry and Arabidopsis as compared to those from lower plants such as the liverwort Marchantia, the green alga Chlamydomonas or another moss Tortula. Northern analysis shows enhanced expression of the CDPK transcript within 24–48 h of starvation for nitrogen, phosphorus or sulphur. So far the only other kinase which is known to be induced by nutrient starvation in plants is the wpk 4 which is a snf-1 related kinase (SnRKs). To our knowledge this is the first report that implicates a CDPK in the starvation response.

  7. 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.

  8. 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.

  9. 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.

  10. 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

  11. 48 CFR 48.102 - Policies.

    Science.gov (United States)

    2010-10-01

    ... 48.102 Federal Acquisition Regulations System FEDERAL ACQUISITION REGULATION CONTRACT MANAGEMENT... of Federal Procurement Policy Act (41 U.S.C. 401, et seq.), agencies shall establish and maintain...: (1) Extent of the change. (2) Complexity of the change. (3) Development risk (e.g.,...

  12. 48 CFR 48.001 - Definitions.

    Science.gov (United States)

    2010-10-01

    ... VALUE ENGINEERING 48.001 Definitions. As used in this subpart— Acquisition savings means savings resulting from the application of a value engineering change proposal (VECP) to contracts awarded by the... implementation costs; (2) Concurrent contract savings, that are net reductions in the prices of other...

  13. Late reaction, persistent reaction and doubtful allergic reaction: The problems of interpretation

    Directory of Open Access Journals (Sweden)

    Sarma Nilendu

    2009-01-01

    Full Text Available The standard method of patch test reading is to read the test site for any positive allergy at 48hr and then again at 72/96 hr. A late reading on the seventh day is also advised to exclude the irritant reaction (IR and to notice some delayed development of allergic reaction. However, multiple visits are often difficult for the patient; therefore, this late reading is sometimes omitted. Here a case of plantar hyperkeratosis, due to allergic contact dermatitis, is reported with some insight into interpretation of the patch test. The patient showed delayed patch test reaction to formaldehyde and colophony, which has never been reported before.

  14. 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).

  15. 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

  16. Ion reactivity of calcium-deficient hydroxyapatite in standard cell culture media.

    Science.gov (United States)

    Gustavsson, J; Ginebra, M P; Engel, E; Planell, J

    2011-12-01

    Solution-mediated surface reactions occur for most calcium phosphate-based biomaterials and may influence cellular response. A reasonable extrapolation of such processes observed in vitro to in vivo performance requires a deep understanding of the underlying mechanisms. We therefore systematically investigated the nature of ion reactivity of calcium-deficient hydroxyapatite (CDHA) by exposing it for different periods of time to standard cell culture media of different chemical composition (DMEM and McCoy medium, with and without osteogenic supplements and serum proteins). Kinetic ion interaction studies of principal extracellular ions revealed non-linear sorption of Ca²⁺ (∼50% sorption) and K⁺ (∼8%) as well as acidification of all media during initial contact with CDHA (48h). Interestingly, inorganic phosphorus (P(i)) was sorbed from McCoy medium (∼50%) or when using osteogenic media containing β-glycerophosphate, but not from DMEM medium. Non-linear sorption data could be perfectly described by pseudo-first-order and pseudo-second-order sorption models. At longer contact time (21 days), and with frequent renewal of culture medium, sorption of Ca²⁺ remained constant throughout the experiment, while sorption of P(i) gradually decreased in McCoy medium. In great contrast, CDHA began to release P(i) slowly with time when using DMEM medium. Infrared spectra showed that CDHA exposed to culture media had a carbonated surface chemistry, suggesting that carbonate plays a key role in the ion reactivity of CDHA. Our data show that different compositions of the aqueous environment may provoke opposite ion reactivity of CDHA, and this must be carefully considered when evaluating the osteoinductive potential of the material.

  17. 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.

  18. Extracellular magnesium decreases the secretory response of rat peritoneal mast cells to compound 48/80 in vitro

    DEFF Research Database (Denmark)

    Bertelsen, Niels Haldor; Johansen, Torben

    1991-01-01

    Exposure of rat peritoneal mast cells to magnesium in the absence of extracellular calcium resulted in a time- and dose-dependent decrease in the secretory response induced by compound 48/80. The decrease was prevented by a low extracellular concentration of calcium. Furthermore, the decreased...... and the secretory stimulus. A dose-dependent decrease in antigen induced histamine secretion that was reversed by calcium was also observed. Exposure of the mast cells to magnesium for 15 min resulted in a parallel decrease in histamine secretion and in the cellular content of 45Ca2+. These observations suggest...... secretory responsiveness was dose-dependently restored by the addition of calcium to the cells simultaneously with compound 48/80. Preincubation with magnesium also inhibited antigen-induced histamine secretion in a dose-dependent manner. This was reversed by the simultaneous addition of calcium...

  19. 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.

  20. 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 

  1. 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.

  2. 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.

  3. Calcium Mass Balance during Citrate Hemodialysis: A Randomized Controlled Trial Comparing Normal and Low Ionized Calcium Target Ranges

    Science.gov (United States)

    Orsag, Alesa; Ponikvar, Rafael; Buturovic-Ponikvar, Jadranka

    2016-01-01

    Background Regional citrate anticoagulation (RCA) during hemodialysis interferes with calcium homeostasis. Optimal ionized calcium (iCa) target range during RCA and consequent calcium balance are unknown. Methods In a randomized controlled trial (ACTRN12613001029785) 30 chronic hemodialysis patients were assigned to normal (1.1–1.2 mmol/) or low (0.95–1.05 mmol/l) iCa target range during a single hemodialysis with RCA. The primary outcome was calcium mass balance during the procedure, using a partial spent dialysate collection method; magnesium mass balance was also measured. Intact parathormone (iPTH), total calcium (tCa) and magnesium were measured before and after procedures. Results Mean iCa during procedures was significantly different in the two groups (1.12±0.06 in normal and 1.06±0.07 mmol/l in low iCa group, p <0.001), resulting in different tCa (2.18±0.22 vs. 1.95±0.17, p = 0.003) after the procedure. Mean delivered calcium during the procedure was 58.3±4.8 mmol in the normal and 51.5±8.2 mmol in the low iCa group (p = 0.010), which resulted in a significantly higher mean positive calcium mass balance of 14.6±8.3 mmol (584±333 mg) per procedure in normal as compared to 7.2±8.5 mmol (290±341 mg) in low iCa group (p = 0.024). Linear mixed effects model showed a significant interaction effect of time and iCa target range group on iPTH, i.e. a significant increase in iPTH in the low as compared to normal iCa target group (p = 0.008). Magnesium mass balance was mildly negative and comparable in both groups. Conclusions Low iCa target range resulted in a significantly less positive calcium mass balance, but in a significant increase in iPTH. To achieve a more neutral calcium balance, we recommend allowing a mild hypocalcemia during hemodialysis with RCA, especially when it is used for prolonged periods. PMID:28030601

  4. 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...

  5. 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.

  6. 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

  7. 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.

  8. 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

  9. 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.

  10. 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.

  11. 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.

  12. Polygalacturonase production by calcium alginate immobilized Enterobacter aerogenes NBO2 cells.

    Science.gov (United States)

    Darah, I; Nisha, M; Lim, Sheh-Hong

    2015-03-01

    Bacterial cells of Enterobacter aerogenes NBO2 were entrapped in calcium alginate beads in order to enhance polygalacturonase production compared to free cells. The optimized condition of 5 % (w/v) sodium alginate concentration, agitation speed of 250 rpm, and 15 beads of calcium alginate with inoculum size of 4 % (v/v; 5.4 × 10(7) cells/ml) produced 23.48 U/mL of polygalacturonase compared to free cells of 18.54 U/ml. There was about 26.6 % increment in polygalaturonase production. However, in this study, there was 296.6 % of increment in polygalacturonase production after improvement parameters compared to before improvement parameters of calcium alginate bead immobilization cells (5.92 U/ml). This research has indicated that optimized physical parameters of calcium alginate bead immobilization cells have significantly enhanced the production of polygalacturonase.

  13. 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.

  14. Effect of amorphous phases during the hydraulic conversion of α-TCP into calcium-deficient hydroxyapatite.

    Science.gov (United States)

    Hurle, Katrin; Neubauer, Juergen; Bohner, Marc; Doebelin, Nicola; Goetz-Neunhoeffer, Friedlinde

    2014-09-01

    Powders of α-tricalcium phosphate (α-TCP), which readily react with water to form calcium-deficient hydroxyapatite (CDHA), are frequently used in bone cements. As, for clinical applications, it is important to adjust the setting reaction of the cements to a reasonable reaction time, exact knowledge of the hydration mechanism is essential. It is known that prolonged milling results in partial amorphization of α-TCP powders and that dissolution of the amorphous phase significantly accelerates the hydration, but it is not clear yet when the amorphous phase reacts in comparison to the crystalline α-TCP. Therefore the aim of this study was to investigate the development of quantitative phase content of α-TCP samples during hydration. For this purpose, three α-TCP powders, containing 0, 16 and 71wt.% of amorphous phase (ATCP), were mixed with either deionized water or a 0.1M Na2HPO4 aqueous solution. The crystalline evolution of the paste was assessed quantitatively during the first 48h of hydration at 23°C by G-factor quantification. The present investigations demonstrate that ATCP reacted earlier than crystalline α-TCP. The results also suggest the formation of an X-ray amorphous phase during the hydraulic conversion formation of α-TCP into CDHA.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Evaluation of antibacterial effects of different calcium hydroxide compositions on planktonic Enterococcus faecalis

    Directory of Open Access Journals (Sweden)

    Mahdi Tabrizizadeh

    2012-01-01

    Full Text Available Background and Aims: Calcium hydroxide has a pronounced antimicrobial activity against most of the bacterial species found in infected root canals and endodontic infections. It is one of the most frequently used intracanal medications in endodontic therapy. The objective of this study was to determine the antimicrobial efficacy of six calcium hydroxide formulations (mixed with saline, lidocaine 2%, chlorhexidine 2%, chlorhexidine 0.2%, Iodine Potassium iodide (IKI 2%, and glycerin on Enterococcus faecalis using agar diffusion test.Materials and Methods: Twelve culture plates were incubated with Enterococcus faecalis. Five cavities were made in each plate with 5 mm diameter and 4 mm depth. Two plates were randomly considered for each calcium hydroxide formulation and filled completely with creamy mixture of tested materials. The plates were incubated at 37ºC for 48 hours. The diameter of inhibition zone around each well was recorded in millimetres and data were submitted to ANOVA and Tukey tests.Results: The results of this study showed that all tested calcium hydroxide pastes had good antimicrobial activity. The antimicrobial activity of calcium hydroxide mixed with lidocaine, chlorhexidine 2% and IKI 2% were significantly greater than that of calcium hydroxide mixed with saline (P0.01.Conclusion: Considering the results of this study, lidocaine 2%, chlorhexidine 2% and IKI 2% are suggested to be used for preparation of calcium hydroxide paste. Further studies with different methods are needed for confirming these results.

  20. [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.

  1. 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.

  2. 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

  3. 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.

  4. 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.

  5. 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

  6. 48Ca Production in Matter Expanding from High Temperature and Density

    Science.gov (United States)

    Meyer, Bradley S.; Krishnan, Tracy D.; Clayton, Donald D.

    1996-05-01

    We calculate with a large nuclear reaction network the nuclear dynamics associated with the expansions and cooling of initially hot and dense matter. We study matter with neutron excess near that of 48Ca, because one objective is to clarify the nucleosynthesis of that abundant neutron-rich nucleus, whose origin has been enigmatic. Expecting that supernovae provide the site of its origin, we take initial temperatures near T9 = 10 but survey a wide range of initial densities, corresponding to a wide range in initial entropies. The highest entropies are probably associated with winds from newborn neutron stars in Type II collapse events, whereas the smallest entropies are probably associated with very high density Type Ia cores. Our survey objective is the analysis of the dynamics of the nuclear assembly as it cools, and how the correct description of it depends on the specific entropy. We show that resultant abundances of neutron-rich nuclei are very poorly represented by nuclear statistical equilibrium (NSE). The deviations from NSE are governed by the number of heavy nuclei assembled during the expansion, which differs significantly from the number demanded by NSE at both high and low entropy. High-entropy expansions are shown to contain too few nuclei, with the result that 48Ca cannot survive the expansion even though it would be expected to be abundant using NSE guidelines. Low-entropy expansions contain too many nuclei with respect to that guideline, with the result that 48Ca is more abundant than expected. In this case it is especially significant that the ratio of 48Ca to other major neutron-rich nuclei (e.g., 66Zn, 82Se) is substantially greater than NSE guidelines, which ameliorates overproduction limits from the latter. We show, furthermore, that the 48Ca nucleus itself plays a key role in the nuclear dynamics. In the low-entropy expansion, which is the one to which we must look for 48Ca origin, abundant 48Ca is a refractory post, a local abundance maximum

  7. 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.

  8. 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.

  9. 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.

  10. 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....

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. 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.

  16. 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...

  17. 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.

  18. The NA48 experiment

    CERN Multimedia

    1995-01-01

    The NA48 experiment is designed to study the Charge-Parity (CP) violation. CP violation is observed in certain very rare decays. Its study is important in understanding Nature's preference of matter over antimatter, which resulted in asymmetry soon after the Big Bang, creating a matter-dominated Universe.

  19. 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.

  20. 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.

  1. 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.

  2. Comparison of Skin Reaction between MTA (Produced in Iran) and CEM in Rabbit.

    Science.gov (United States)

    Shokravi, Marziyeh; Tabarsi, Bahareh; Moghaddamnia, Aliakbar; Sohanfaraji, Alieh; Pourghasem, Mohsen

    2012-01-01

    Pathological changes in pulp and periapical tissues are addressed by endodontic treatment. The material used in this treatment must be biocompatible. The aim of this study is to compare the skin reaction of Calcium Enriched Mixture (CEM) and Mineral Trioxide Aggregate (MTA) produced in Iran on rabbit. Sixteen male newzeland albino rabbits weighting 2 kg were used. The animals back hair was shaved, 24 hours before application of each material. The material was applied on two sites (2 × 2 cm) while the third site was used as control. All sites were covered by gauze and bandaged for 4 hours. Then the material's remnants were washed off the sites of application. Observations were performed in 1, 24, 48 and 72 hours after removing the materials. Erythematous surface areas were measured by the morphometric method. After sacrificing animals the skins were dissected and the specimens were prepared for histological evaluation. There were significant differences between CEM and MTA in erythematous surface areas at 1, 24 and 48 hours after removing the materials (pMTA and control sample (p=0.0001) and between MTA and CEM (p=0.035). There was no significant difference between control and CEM (p>0.05). The average erythematous surface areas were wider in MTA sites than CEM sites. As a conclusion it seems that biocompatibility of CEM could be more than MTA.

  3. 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…

  4. Chemical, modulus and cell attachment studies of reactive calcium phosphate filler-containing fast photo-curing, surface-degrading, polymeric bone adhesives.

    Science.gov (United States)

    Abou Neel, E A; Palmer, G; Knowles, J C; Salih, V; Young, A M

    2010-07-01

    The initial structure, setting and degradation processes of a poly(lactide-co-propylene glycol-co-lactide) dimethacrylate adhesive filled with 50, 60 or 70 wt.% reactive calcium phosphates (monocalcium phosphate monohydrate (MCPM)/beta-tricalcium phosphate (beta-TCP)) have been assessed using nuclear magnetic resonance, Fourier transform infrared spectroscopy, Raman, X-ray powder diffraction and gravimetric studies. Filler incorporation reduced the rapid light-activated monomer polymerization rates slightly, but not the final levels. Upon immersion in water for 24h, the set composite mass and volume increased due to water sorption. This promoted initial soluble MCPM loss from the composite surfaces, but also its reaction and monetite precipitation within the specimen bulk. After 48 h, composite gravimetric and chemical studies were consistent with surface erosion of polymer with reacted/remaining filler. The filled formulations exhibited more rapid early water sorption and subsequent surface erosion than the unfilled polymer. Calcium and phosphate release profiles and solution pH measurements confirmed early loss of surface MCPM with protons from polymer degradation products. At later times, the slower release of monetite/beta-TCP buffered composite storage solutions at approximately 5 instead of 3.2 for the unfilled polymer. Incorporation of filler increased both the early and later time material modulus. At intermediate times this effect was lost, presumably as a result of enhanced water sorption. The early modulus values obtained fell within the range reported for cancellous bone. Despite surface degradation, initial human mesenchymal cell attachment to both composites and polymer could be comparable with a non-degrading positive Thermanox control. These studies indicate that the filled formulations may be good candidates for bone repair. Release of calcium and phosphate ions provides components essential for such repair.

  5. 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.

  6. 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)....

  7. 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)....

  8. 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)....

  9. 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...

  10. 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.

  11. 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...

  12. 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...

  13. 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...

  14. 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...

  15. 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.

  16. 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-...

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. Regulation of Intestinal Epithelial Calcium Transport Proteins by Stanniocalcin-1 in Caco2 Cells

    Directory of Open Access Journals (Sweden)

    Jinmei Xiang

    2016-07-01

    Full Text Available Stanniocalcin-1 (STC1 is a calcium and phosphate regulatory hormone. However, the exact molecular mechanisms underlying how STC1 affects Ca2+ uptake remain unclear. Here, the expression levels of the calcium transport proteins involved in transcellular transport in Caco2 cells were examined following over-expression or inhibition of STC1. These proteins include the transient receptor potential vanilloid members (TRPV 5 and 6, the plasma membrane calcium ATPase 1b (PMCA1b, the sodium/calcium exchanger (NCX1, and the vitamin D receptor (VDR. Both gene and protein expressions of TRPV5 and TRPV6 were attenuated in response to over-expression of STC1, and the opposite trend was observed in cells treated with siRNASTC1. To further investigate the ability of STC1 to influence TRPV6 expression, cells were treated with 100 ng/mL of recombinant human STC1 (rhSTC1 for 4 h following pre-transfection with siRNASTC1 for 48 h. Intriguingly, the increase in the expression of TRPV6 resulting from siRNASTC1 was reversed by rhSTC1. No significant effect of STC1 on the expression of PMCA1b, NCX1 or VDR was observed in this study. In conclusion, the effect of STC1 on calcium transport in intestinal epithelia is due to, at least in part, its negative regulation of the epithelial channels TRPV5/6 that mediate calcium influx.

  2. Origins of dipole resonance strength fragmentation in calcium and titanium isotopes

    Directory of Open Access Journals (Sweden)

    Skorodumina Iu. A.

    2012-12-01

    Full Text Available Theoretical description of dipole resonances in 46Ti, 48Ti, 50Ti, 48Ca, 40Ca was performed. The distribution of the “hole” among the states of final nuclei was taken into account using information on pick-up reactions. The obtained results are in reasonable agreement with experimental data.

  3. 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.

  4. 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.

  5. Photonuclear reactions on titanium isotopes

    Energy Technology Data Exchange (ETDEWEB)

    Belyshev, S. S. [Moscow State University (Russian Federation); Dzhilavyan, L. Z. [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation); Ishkhanov, B. S.; Kapitonov, I. M. [Moscow State University (Russian Federation); Kuznetsov, A. A., E-mail: kuznets@depni.sinp.msu.ru; Orlin, V. N.; Stopani, K. A. [Moscow State University, Skobeltsyn Institute of Nuclear Physics (Russian Federation)

    2015-03-15

    The photodisintegration of titanium isotopes in the giant-dipole-resonance energy region is studied by the photon-activation method. Bremsstrahlung photons whose spectrum has the endpoint energy of 55 MeV is used. The yields and integrated cross sections are determined for photoproton reactions on the titanium isotopes {sup 47,48,49,50}Ti. The respective experimental results are compared with their counterparts calculated on the basis of the TALYS code and a combined photonucleon-reaction model. The TALYS code disregards the isospin structure of the giant dipole resonance and is therefore unable to describe the yield of photoproton reactions on the heavy titanium isotopes {sup 49,50}Ti.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. Effects of Astragalus membranaceus with supplemental calcium on bone mineral density and bone metabolism in calcium-deficient ovariectomized rats.

    Science.gov (United States)

    Kang, Se-Chan; Kim, Hee Jung; Kim, Mi-Hyun

    2013-01-01

    It has been reported that Astragalus membranaceus, an Asian traditional herb, has an estrogenic effect in vitro. To examine the possible role of A. membranaceus extract with supplemental calcium (Ca) on bone status in calcium-deficient (LCa) ovariectomized (OVX) rats, a total of 48 female rats were divided into six groups: (1) normal control, (2) sham operation with LCa (sham-LCa), (3) OVX with LCa (OVX-LCa), (4) A. membranaceus supplementation with OVX-LCa (OVX-MLCa), (5) Ca supplementation with OVX (OVX-Ca), and (6) A. membranaceus and Ca supplementation with OVX (OVX-MCa). A. membranaceus ethanol extract (500 mg/kg BW) and/or Ca (800 mg/kg BW) were administered orally for 8 weeks along with a Ca-deficient diet. Results revealed that Ca supplementation with or without A. membranaceus extract significantly improved bone mineral density, biomechanical strength, and ash weight of the femur and tibia in OVX rats. High Ca with A. membranaceus combination supplementation significantly increased the ash weight of the femur and tibia and decreased urinary Ca excretion compared with supplementation of Ca alone. Uterine weight was not changed by A. membranaceus administration in OVX rats. These results suggest that A. membranaceus extract combined with supplemental Ca may be more protective against the Ca loss of bone than A. membranaceus or supplementation of Ca alone in calcium-insufficient postmenopausal women.

  11. 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.

  12. 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.

  13. 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.

  14. 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...

  15. 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.

  16. 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.

  17. 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)

  18. 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)

  19. 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.

  20. 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…

  1. 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.

  2. 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...

  3. 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...

  4. 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.

  5. Disulfiram-like reaction with ornidazole

    Directory of Open Access Journals (Sweden)

    Sharma V

    2009-01-01

    Full Text Available Many drugs are implicated in causation of disulfiram-like reaction. The disulfiram-like reaction can vary in severity and can occasionally be fatal. The reaction is believed to result from inhibition of metabolism of acetaldehyde to acetate by inhibition of aldehyde dehydrogenase. The increase in serum acetaldehyde results in unpleasant clinical manifestations. Metronidazole is known to cause disulfiram-like reaction. Although no previous report has implicated ornidazole in causation of disulfiram-like reaction, caution has been advised with the use of all imidazoles. We report the case of a 48-year-old male, who was taking ornidazole and developed features of disulfiram-like reaction after taking alcohol. The patient was managed with supportive measures and improved. The report highlights the need for clinicians to advise patients to restrict intake of alcohol if they are being prescribed imidazole derivatives.

  6. 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.

  7. 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.

  8. 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

  9. 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).

  10. —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).

  11. 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.

  12. 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.

  13. 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.

  14. 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.

  15. On-chip preparation of calcium alginate particles based on droplet templates formed by using a centrifugal microfluidic technique.

    Science.gov (United States)

    Liu, Mei; Sun, Xiao-Ting; Yang, Chun-Guang; Xu, Zhang-Run

    2016-03-15

    A novel chip-based approach for the fabrication of oblate spheriodal calcium alginate particles was developed by combining the droplet template method and the centrifugal microfluidic strategy. Circular chips with multiple radial channels were designed. Sodium alginate solutions in radial channels were flung into CaCl2 solutions in the form of droplets under centrifugal force, and the droplets transformed into particles through cross-linking reaction. The size and morphology of particles could be controlled by regulating the centrifugal force, the channel geometry and the distance between the channel outlet and the CaCl2 solution. The throughput of particle production was evidently enhanced by increasing the number of radial channels to 48 and 64. The coefficients of variation of particle sizes were in the range of 5.2-5.6%, which indicated the monodisperse particles could be prepared by using the present method. With the chip configuration readily modified, the same platform could be used to produce Janus particles. The Janus particles showed clear interfaces owing to the high flight speed and the rapid gelling process of the droplets. This method would be capable of generating particles with complicated morphology and multifunction from diverse polymeric materials.

  16. Cost containment using cysteine HCl acidification to increase calcium/phosphate solubility in hyperalimentation solutions.

    Science.gov (United States)

    Schmidt, G L; Baumgartner, T G; Fischlschweiger, W; Sitren, H S; Thakker, K M; Cerda, J J

    1986-01-01

    The purpose of this study was to determine if (1) the calcium/phosphate insoluble product was inversely related to pH [when cysteine HC1 (CH) was added as neonatal supplementation at 0.5 mM/kg/day to hyperalimentation (HAL) solutions] and (2) the potential cost savings to the hospital. The pH of the HAL solutions was adjusted by adding various amounts of CH to the HAL solution. HAL solutions containing 27 mEq of calcium/liter and 30 mEq (15 mM) of phosphate/liter were compounded. Ten-milliliter aliquots were analyzed at 0, 12, 24, and 48 hr. All samples (n = 56) were filtered (0.22 mu), viewed with 7-10,000 X magnification scanning electron microscopy, and qualitatively analyzed with a Philips Energy Dispersive X-Ray Analysis System equipped with a SW9100 Microprocessor. Calcium/phosphate insoluble product was present in the 0-, 12-, 24-, and 48-hr samples from the CH-free solutions. The solutions containing 759 mg (4.17 mM)/liter of CH however, remained free of precipitant. This investigation demonstrated that addition of CH to HAL can foster significant cost containment (projected $82,000/yr tangible hospital savings) by the elimination of current calcium/phosphate separation procedures for neonates on parenteral nutrition.

  17. Effects of Dietary Calcium on Body Weight, Carcass Fat Content and Adipocyte Size in Male Rats

    Directory of Open Access Journals (Sweden)

    J Malekzadeh

    2006-07-01

    Full Text Available Introduction & Objective: Calcium is a micronutrient and now receiving much attention for its doubtful effects on weight and body fatness. A few mechanisms has been suggested for calcium effects on body fatness and the most emphasized one is the reducing of lipolysis and increasing lipogenesis via reducing parathyroid hormone levels. The present study is designed to evaluate the effects of nondairy dietary calcium on adipogenesis and adipocyte size in male Sprague dawley rats. Materials & Methods: This experimental study was done from November to September of 2005 at Tehran school of health, nutrition department. 48 male Spragu-Dawley rats from Damgostar Company were used in three randomly selected groups. The rats were fed low (0.2% W/W, usual (0.5% W/W and high (1.2% W/W dietary calcium based on AIN-93M purified diet. Rats were housed in 12 hours light-dark cycle, 22-25°C room temperature with free access to their respective diets. At the end of the experiment, rats were decapitated and carcass fat content, carcass ash content and mean adipocyte size in testis, peritoneal and subcutaneous fat pads were compared in three groups. The SPSS 11.5 was used as statistical software, running analysis of variance for comparing the effects. Results: weight gain, carcass fat content and adipocyte size, in groups were not significantly different, while serum parathyroid hormone concentrations in high calcium group was significantly lower than low calcium group (p<0.05 and insignificantly lower than usual calcium group [12.36, 23.57 and 42.2 pg/dl respectively]. Serum concentrations of 25-hydroxy cholecalciferol were also insignificantly lower in high calcium group. Conclusion: Our findings suggested that physiological concentration of dietary calcium is not effective on weight gain, body fatness and adipocyte size. Relatively equal fat content beside significant difference in serum parathyroid hormone levels is against the parathyroid theory of calcium

  18. 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...

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. Anticoagulant and calcium-binding properties of high molecular weight derivatives of human fibrinogen, produced by plasmin (fragments X).

    Science.gov (United States)

    Nieuwenhuizen, W; Gravesen, M

    1981-03-27

    Early plasmin degradation products (X fragments) of human fibrinogen were prepared in the presence of calcium-ions or EGTA, and purified on Sepharose 6B-CL. X fragments were characterized with respect to amino-terminal amino acids, polypeptide-chain composition, anticlotting properties and calcium-binding. Amino-terminal amino acids were alanine and tyrosine. The molecular weights of the chains were about 26 000, 58 000 and 48 000 for A alpha-, B beta- and gamma-chains, respectively. X fragments were about 6-times as potent in anticlotting behaviour as D fragments prepared in the presence of calcium ions. Calcium-binding properties were essentially identical to those of fibrinogen. No differences were observed between X fragments prepared in the presence of calcium ions and those prepared in the presence of EGTA. This indicates that the carboxy-terminal parts of the A alpha-chains of fibrinogen are not involved in calcium-binding and that differences in chain-remnants as observed in late plasmic degradation products (which depend on the presence of calcium ions or EGTA [23] in the incubation medium) are introduced beyond the stage of fragment X formation.

  5. 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...

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. Determinants of Calcium Infusion Rate During Continuous Veno-venous Hemofiltration with Regional Citrate Anticoagulation in Critically Ⅲ Patients with Acute Kidney Injury

    Institute of Scientific and Technical Information of China (English)

    De-Lin Liu; Li-Feng Huang; Wen-Liang Ma; Qi Ding; Yue Han; Yue Zheng; Wen-Xiong Li

    2016-01-01

    Background:It is unclear that how to decide the calcium infusion rate during continuous veno-venous hemofiltration (CVVH) with regional citrate anticoagulation (RCA).This study aimed to assess the determinants of calcium infusion rate during CVVH with RCA in critically ill patients with acute kidney injury (AKI).Methods:A total of 18 patients with AKI requiring CVVH were prospectively analyzed.Postdilution CVVH was performed with a fixed blood flow rate of 150 ml/min and a replacement fluid flow rate of 2000 ml/h for each new circuit.The infusion of 4% trisodium citrate was started at a rate of 29.9 mmol/h prefilter and adjusted according to postfilter ionized calcium.The infusion of 10% calcium gluconate was initiated at a rate of 5.5 mmol/h and adjusted according to systemic ionized calcium.The infusion rate oftrisodium citrate and calcium gluconate as well as ultrafiltrate flow rate were recorded at 1,2,4,6,12,and 24 h after starting CVVH,respectively.The calcium loss rate by CVVH was also calculated.Results:Fifty-seven sessions of CVVH were performed in 18 AKI patients.The citrate infusion rate,calcium loss rate by CVVH,and calcium infusion rate were 31.30 (interquartile range:2.70),4.60 ± 0.48,and 5.50 ± 0.35 mmol/h,respectively.The calcium infusion rate was significantly higher than that of calcium loss rate by CVVH (P < 0.01).The correlation coefficient between the calcium and citrate infusion rates,and calcium infusion and calcium loss rates by CVVH was-0.031 (P > 0.05) and 0.932 (P < 0.01),respectively.In addition,calcium infusion rate (mmol/h) =1.77 + 0.8 × (calcium loss rate by CVVH,mmol/h).Conclusions:The calcium infusion rate correlates significantly with the calcium loss rate by CVVH but not with the citrate infusion rate in a fixed blood flow rate during CVVH with RCA.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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...

  19. 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)

  20. 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.

  1. 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...

  2. 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.

  3. Preparation, characterization and catalytic properties of MCM-48 supported tungstophosphoric acid mesoporous materials for green synthesis of benzoic acid

    Science.gov (United States)

    Wu, Hai-Yan; Zhang, Xiao-Li; Chen, Xi; Chen, Ya; Zheng, Xiu-Cheng

    2014-03-01

    MCM-48 and tungstophosphoric acid (HPW) were prepared and applied for the synthesis of HPW/MCM-48 mesoporous materials. The characterization results showed that HPW/MCM-48 obtained retained the typical mesopore structure of MCM-48, and the textural parameters decreased with the increase loading of HPW. The catalytic oxidation results of benzyl alcohol and benzaldehyde with 30% H2O2 indicated that HPW/MCM-48 was an efficient catalyst for the green synthesis of benzoic acid. Furthermore, 35 wt% HPW/MCM-48 sample showed the highest activity under the reaction conditions.

  4. NA48 prototype calorimeter

    CERN Document Server

    1990-01-01

    This is a calorimeter, a detector which measures the energy of particles. When in use, it is filled with liquid krypton at -152°C. Electrons and photons passing through interact with the krypton, creating a shower of charged particles which are collected on the copper ribbons. The ribbons are aligned to an accuracy of a tenth of a millimetre. The folding at each end allows them to be kept absolutely flat. Each shower of particles also creates a signal in scintillating material embedded in the support disks. These flashes of light are transmitted to electronics by the optical fibres along the side of the detector. They give the time at which the interaction occurred. The photo shows the calorimeter at NA48, a CERN experiment which is trying to understand the lack of anti-matter in the Universe today.

  5. 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 ...

  6. 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 ...

  7. 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 ...

  8. ATP enhances spontaneous calcium activity in cultured suburothelial myofibroblasts of the human bladder.

    Directory of Open Access Journals (Sweden)

    Sheng Cheng

    Full Text Available BACKGROUND: Suburothelial myofibroblasts (sMF are located underneath the urothelium in close proximity to afferent nerves. They express purinergic receptors and show calcium transients in response to ATP. Therefore they are supposed to be involved in afferent signaling of the bladder fullness. Since ATP concentration is likely to be very low during the initial filling phase, we hypothesized that sMF Ca(2+ activity is affected even at very low ATP concentrations. We investigated ATP induced modulation of spontaneous activity, intracellular calcium response and purinergic signaling in cultured sMF. METHODOLOGY/PRINCIPAL FINDINGS: Myofibroblast cultures, established from cystectomies, were challenged by exogenous ATP in presence or absence of purinergic antagonist. Fura-2 calcium imaging was used to monitor ATP (10(-16 to 10(-4 mol/l induced alterations of calcium activity. Purinergic receptors (P2X1, P2X2, P2X3 were analysed by confocal immunofluorescence. We found spontaneous calcium activity in 55.18% ± 1.65 of the sMF (N = 48 experiments. ATP significantly increased calcium activity even at 10(-16 mol/l. The calcium transients were partially attenuated by subtype selective antagonist (TNP-ATP, 1 µM; A-317491, 1 µM, and were mimicked by the P2X1, P2X3 selective agonist α,β-methylene ATP. The expression of purinergic receptor subtypes in sMF was confirmed by immunofluorescence. CONCLUSIONS/SIGNIFICANCE: Our experiments demonstrate for the first time that ATP can modulate spontaneous activity and induce intracellular Ca(2+ response in cultured sMF at very low concentrations, most likely involving P2X receptors. These findings support the notion that sMF are able to register bladder fullness very sensitively, which predestines them for the modulation of the afferent bladder signaling in normal and pathological conditions.

  9. 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.

  10. 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

  11. 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...

  12. 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.

  13. 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...

  14. 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

  15. 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)

  16. 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.

  17. K You 48-2

    Institute of Scientific and Technical Information of China (English)

    1994-01-01

    K You 48-2 is a new combination of early hybrid rice with good grain quality and high yield, developed by combining male sterile line K-Qing A having japonica cytoplasm and indica genome aodrestorer line Ce 48-2. In the regional trial of Hubei Province in 1991, its yield was 4.4% higher than that of the CK Weiyou 48-2,

  18. 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

  19. 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

  20. 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.

  1. 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.

  2. Selective laser sintering of calcium phosphate materials for orthopedic implants

    Science.gov (United States)

    Lee, Goonhee

    Two technologies, Solid Freeform Fabrication (SFF) and bioceramics are combined in this work to prepare bone replacement implants with complex geometry. SFF has emerged as a crucial technique for rapid prototyping in the last decade. Selective Laser Sintering (SLS) is one of the established SFF manufacturing processes that can build three-dimensional objects directly from computer models without part-specific tooling or human intervention. Meanwhile, there have been great efforts to develop implantable materials that can assist in regeneration of bone defects and injuries. However, little attention has been focused in shaping bones from these materials. The main thrust of this research was to develop a process that can combine those two separate efforts. The specific objective of this research is to develop a process that can construct bone replacement material of complex geometry from synthetic calcium phosphate materials by using the SLS process. The achievement of this goal can have a significant impact on the quality of health care in the sense that complete custom-fit bone and tooth structures suitable for implantation can be prepared within 24--48 hours of receipt of geometric information obtained either from patient Computed Tomographic (CT) data, from Computer Aided Design (CAD) software or from other imaging systems such as Magnetic Resonance Imaging (MRI) and Holographic Laser Range Imaging (HLRI). In this research, two different processes have been developed. First is the SLS fabrication of porous bone implants. In this effort, systematic procedures have been established and calcium phosphate implants were successfully fabricated from various sources of geometric information. These efforts include material selection and preparation, SLS process parameter optimization, and development of post-processing techniques within the 48-hour time frame. Post-processing allows accurate control of geometry and of the chemistry of calcium phosphate, as well as

  3. 48 CFR 48.103 - Processing value engineering change proposals.

    Science.gov (United States)

    2010-10-01

    ... REGULATION CONTRACT MANAGEMENT VALUE ENGINEERING Policies and Procedures 48.103 Processing value engineering... Government are included in paragraphs (c) and (d) of the value engineering clauses prescribed in subpart 48.2..., Value Engineering, is used. (4) The contracting officer's determination of the duration of the...

  4. 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.

  5. 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.

  6. 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...

  7. 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

  8. 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.

  9. 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

  10. 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...

  11. 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

  12. 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.

  13. 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.

  14. 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.

  15. Preparation, characterization and catalytic properties of MCM-48 supported tungstophosphoric acid mesoporous materials for green synthesis of benzoic acid

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Hai-Yan; Zhang, Xiao-Li; Chen, Xi; Chen, Ya; Zheng, Xiu-Cheng, E-mail: zhxch@zzu.edu.cn

    2014-03-15

    MCM-48 and tungstophosphoric acid (HPW) were prepared and applied for the synthesis of HPW/MCM-48 mesoporous materials. The characterization results showed that HPW/MCM-48 obtained retained the typical mesopore structure of MCM-48, and the textural parameters decreased with the increase loading of HPW. The catalytic oxidation results of benzyl alcohol and benzaldehyde with 30% H{sub 2}O{sub 2} indicated that HPW/MCM-48 was an efficient catalyst for the green synthesis of benzoic acid. Furthermore, 35 wt% HPW/MCM-48 sample showed the highest activity under the reaction conditions. Highlights: • 5–45 wt% HPW/MCM-48 mesoporous catalysts were prepared and characterized. • Their catalytic activities for the green synthesis of benzoic acid were investigated. • HPW/MCM-48 was approved to be an efficient catalyst. • 5 wt% HPW/MCM-48 exhibited the highest catalytic activity.

  16. 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.

  17. 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.

  18. 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.

  19. [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.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. 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.

  5. 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...

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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...

  14. 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)

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. [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.

  20. 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

  1. Calcium intake and calcium deficiency in toddlers in a slum population of Bhubaneswar

    Directory of Open Access Journals (Sweden)

    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

  2. Effect of calcium intake on urinary oxalate excretion in calcium stone-forming patients

    Directory of Open Access Journals (Sweden)

    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.

  3. 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

  4. 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.

  5. Circulating vitamin D, calcium and risk of cerebrovascular disease: a systematic review and meta-analysis.

    Science.gov (United States)

    Chowdhury, Rajiv; Stevens, Sarah; Ward, Heather; Chowdhury, Susmita; Sajjad, Ayesha; Franco, Oscar H

    2012-08-01

    Available literature suggests that both vitamin D and calcium may be associated with a wide range of non-skeletal outcomes. However, epidemiological evidence supporting their individual associations with incident cerebrovascular disease is scarce. We conducted a systematic review and meta-analysis of prospective cohort studies, published before February 2012 and sought from MEDLINE, EMBASE, BIOSIS and the Science Citation Index databases, and reported cerebrovascular disease (defined as any fatal or non-fatal ischemic stroke, hemorrhagic stroke, cerebrovascular accident or transient ischemic attack) by circulating vitamin D (25-hydroxy vitamin D [25(OH)D] as active metabolite) and calcium levels. Two independent investigators abstracted information on 25(OH)D and calcium, cerebrovascular outcomes and other characteristics from selected studies. Relative risks (RRs) were pooled by both random and fixed effects meta-analyses and were further examined under different study-level characteristics. Publication bias was assessed with funnel plots and Egger's asymmetry test. From 5,778 initial references, nine unique prospective cohort studies met our inclusion criteria. Seven studies (involving 47,809 participants and 926 cerebrovascular events) focused on circulating 25(OH)D and 3 reported on circulating calcium (22,577 participants and 727 events). For 25(OH)D, in a comparison of individuals in the top third versus those in the bottom third at baseline, the combined RR for cerebrovascular disease, adjusted for several conventional risk factors, was 0.60 (95 % CI 0.48, 0.72). The corresponding RR in the prospective studies that reported on baseline circulating calcium levels for cerebrovascular disease was 1.40 (95 % CI 1.19, 1.64). There was no apparent evidence of heterogeneity or publication bias among included studies. Available data indicate that higher circulating level of vitamin D is associated with a decreased risk of cerebrovascular disease. Conversely

  6. 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

  7. 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.

  8. 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.

  9. 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).

  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. Phototoxic and contact toxic reactions of the exocarp of sweet oranges: a common cause of cheilitis?

    Science.gov (United States)

    Volden, G; Krokan, H; Kavli, G; Midelfart, K

    1983-05-01

    Irritant skin reactions were produced within 1 h after application of the exocarp of sweet oranges or alcoholic extracts therefrom. Such reactions faded within 48 h. The exocarp, or extracts thereof, induced phototoxic reactions which were strongest at 72 h after exposure. The phototoxic reactions were only induced in natural blondes and only with some oranges. The in vivo phototoxic reactions were confirmed in vitro, causing a slight but clear photo-inhibition of Candida albicans. Only some oranges inhibited growth.

  12. 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

  13. 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.

  14. 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.

  15. 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.

  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. [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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Isopropylation of Naphthalene over AlMCM-48 Mesoporous Molecular Sieves%AlMCM-48介孔分子筛对萘异丙基化反应的活性

    Institute of Scientific and Technical Information of China (English)

    王树国; 李英; 巩雁军; 吴东; 孙予罕; 钟炳

    2001-01-01

    The isopropylation of naphthalene with isopropanol over AlMCM-48 mesoporous molecular sieves was studied. AlMCM-48 showed high activity and shape selectivity to the isopropylation of naphthalene. Grafting aluminum on MCM-48 improved its acidity. It was found that with the increasing of Al content, the performance of AlMCM-48 catalysts for naphthalene conversion was enhanced. High naphthalene conversion of 89.5 % was achieved over AlMCM-48 with Si/Al=5.3 under the reaction conditions:n(isopropanol) /n(naphthalene)=2, temperature T=250 ℃ , time t=4 h.

  3. Role of calcium in the regulation of acetylcholine receptor synthese in cultured muscle cells*.

    Science.gov (United States)

    Birnbaum, M; Reis, M A; Shainberg, A

    1980-05-01

    Embroyonic muscles differentiated in vitro were used to study the effects of intracellular Ca2+ ([Ca2+1]i) variations on the amount of acetylcholine receptors ([AChR]) in the cell membrane. 2. Increased Ca2+ concentration in the growth medium ([Ca2+]o) caused a marked elevation of AChR levels, apparently through de novo synthesis. 3. Agents known to increase [Ca2+]i and its accumulation in the sarcoplasmic reticulum (SR), such as ionophore A23187, sodium dantrolene (DaNa), or high [Mg2+]o all enhanced alpha-bungarotoxin (alpha-BGT) binding after 48 h of treatment. 4. Electrical stimulation or caffeine, both affectors of SR calcium release, brought about a decrease in [AChR] probably by suppressing its synthesis. 5. The effects of simultaneous treatment with two AChR-inducing agents, namely, high [Ca2+]o in the presence of tetrodotoxin (TTX) or high [Mg2+]o were not additive, thus suggesting action via a common saturable mediator. 6. Intermediate AChR levels obtained following simultaneous treatments with opposing effects, e.g., electrical stimulation in the presence of high [Ca2+]o or DaNa, suggest contradictory actions on a common mediator. 7. All these observations indicate a strong correlation between SR calcium levels and [AChR] on myotubes; while calcium accumulation in the Sr was followed by increased AChR synthesis, calcium release was accompanied by suppression of receptor synthesis.

  4. Increase of a Calcium Independent Transglutaminase Activity in the Erythrocyte during the Infection with Plasmodium falciparum

    Directory of Open Access Journals (Sweden)

    Wasserman Moisés

    1999-01-01

    Full Text Available We have studied the activity of a calcium dependent transglutaminase (EC 2.3.2.13 during the growth of the parasite Plasmodium falciparum inside the infected human erythrocyte. There is only one detectable transglutaminase in the two-cell-system, and its origin is erythrocytic. No activity was detected in preparations of the parasite devoid of erythrocyte cytoplasm. The Michaelis Menten constants (Km of the enzyme for the substrates N'N'dimethylcaseine and putrescine were undistinguishable whether the cell extracts used in their determination were obtained from normal or from infected red cells. The total activity of transglutaminase in stringently synchronized cultures, measured at 0.5mM Ca2+, decreased with the maturation of the parasite. However, a fraction which became irreversibly activated and independent of calcium concentration was detected. The proportion of this fraction grew with maturation; it represented only 20% of the activity in 20 hr-old-trophozoites while in 48-hr-schizonts it was more than 85% of the total activity. The activation of this fraction of transglutaminase did not depend on an increase in the erythrocyte cytoplasmic calcium, since most of the calcium was shown to be located in the parasite.

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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.

  14. Rickets induced by calcium or phosphate depletion.

    OpenAIRE

    Abugassa, S.; Svensson, O.

    1990-01-01

    We studied the effects of calciopenia and phosphopenia on longitudinal growth, skeletal mineralization, and development of rickets in young Sprague-Dawley rats. At an age of 21 days, two experimental groups were given diets containing 0.02% calcium or 0.02% phosphorus; otherwise the diets were nutritionally adequate. After 7, 14, and 21 days, five animals from each group were randomly chosen. The animals were anaesthetized and blood samples were drawn for analysis of calcium, phosphorus, and ...

  15. Fractal aspects of calcium binding protein structures

    Energy Technology Data Exchange (ETDEWEB)

    Isvoran, Adriana [West University of Timisoara, Department of Chemistry, Pestalozzi 16, 300115 Timisoara (Romania)], E-mail: aisvoran@cbg.uvt.ro; Pitulice, Laura [West University of Timisoara, Department of Chemistry, Pestalozzi 16, 300115 Timisoara (Romania); Craescu, Constantin T. [INSERM U759/Institute Curie-Recherche, Centre Universitaire Paris-Sud, Batiment 112, 91405 Orsay (France); Chiriac, Adrian [West University of Timisoara, Department of Chemistry, Pestalozzi 16, 300115 Timisoara (Romania)

    2008-03-15

    The structures of EF-hand calcium binding proteins may be classified into two distinct groups: extended and compact structures. In this paper we studied 20 different structures of calcium binding proteins using the fractal analysis. Nine structures show extended shapes, one is semi-compact and the other 10 have compact shapes. Our study reveals different fractal characteristics for protein backbones belonging to different structural classes and these observations may be correlated to the physicochemical forces governing the protein folding.

  16. Physical Properties of Acidic Calcium Phosphate Cements

    OpenAIRE

    2014-01-01

    The gold standard for bone replacement today, autologous bone, suffers from several disadvantages, such as the increased risk of infection due to the need for two surgeries. Degradable synthetic materials with properties similar to bone, such as calcium phosphate cements, are a promising alternative. Calcium phosphate cements are suited for a limited amount of applications and improving their physical properties could extend their use into areas previously not considered possible. For example...

  17. Evaluation of quick disintegrating calcium carbonate tablets

    OpenAIRE

    Fausett, Hector; Gayser, Charles; Dash, Alekha K.

    2000-01-01

    The purpose of this investigation was to develop a rapidly disintegrating calcium carbonate (CC) tablet by direct compression and compare it with commercially available calcium tablets. CC tablets were formulated on a Carver press using 3 different forms of CC direct compressed granules (Cal-Carb 4450®, Cal-Carb 4457®, and Cal-Carb 4462®). The breaking strength was measured using a Stokes-Monsanto hardness tester. The disintegration and dissolution properties of the tablets were studied using...

  18. Calcium Imaging of Sonoporation of Mammalian Cells

    Science.gov (United States)

    Sabens, David; Aehle, Matthew; Steyer, Grant; Kourennyi, Dmitri; Deng, Cheri X.

    2006-05-01

    Ultrasound mediated delivery of compounds is a relatively recent development in drug delivery and gene transfection techniques. Due to the lack of methods for real-time monitoring of sonoporation at the cellular level, the efficiency of drug/gene delivery and sonoporation associated side effects, such as the loss of cell viability and enhanced apoptosis, have been studied only through post US exposure analyses, requiring days for cell incubation. Furthermore, because microporation appears to be transient in nature, it was not possible to correlate transfection with microporation on an individual cellular basis. By studying the role of calcium in the cell and using fluorescent calcium imaging to study sonoporation it is possible to quantify both cell porosity and sonoporation side effects. Since both post sonoporation cell survival and delivery efficiency are related to the dynamic process of the cell membrane poration, calcium imaging of sonoporation will provide important knowledge to obtain improved understanding of sonoporation mechanism. Our experimental results demonstrated the feasibility of calcium imaging of sonoporation in Chinese Hamster Ovary (CHO) cells. We have measured the changes in the intracellular calcium concentration using Fura-2, a fluorescent probe, which indicate influx or flow of Calcium across the cell membrane. Analysis of data identified key aspects in the dynamic sonoporation process including the formation of pores in the cell membrane, and the relative temporal duration of the pores and their resealing. These observations are obtained through the analysis of the rate the calcium concentration changes within the cells, making it possible to visualize membrane opening and repair in real-time through such changes in the intracellular calcium concentration.

  19. Is Excess Calcium Harmful to Health?

    OpenAIRE

    Daly, Robin M.; Ebeling, Peter R.

    2010-01-01

    Most current guidelines recommend that older adults and the elderly strive for a total calcium intake (diet and supplements) of 1,000 to 1,300 mg/day to prevent osteoporosis and fractures. Traditionally, calcium supplements have been considered safe, effective and well tolerated, but their safety has recently been questioned due to potential adverse effects on vascular disease which may increase mortality. For example, the findings from a meta-analysis of randomized controlled trials (current...

  20. Understanding calcium dynamics experiments and theory

    CERN Document Server

    Malchow, Dieter

    2003-01-01

    Intracellular Calcium is an important messenger in living cells. Calcium dynamics display complex temporal and spatial structures created by the concentration patterns which are characteristic for a nonlinear system operating far from thermodynamic equilibrium. Written as a set of tutorial reviews on both experimental facts and theoretical modelling, this volume is intended as an introduction and modern reference in the field for graduate students and researchers in biophysics, biochemistry and applied mathematics.

  1. Calcium-Phosphate-Osteopontin Particles Reduce Biofilm Formation and pH Drops in in situ-Grown Dental Biofilms

    DEFF Research Database (Denmark)

    Schlafer, Sebastian; Ibsen, Casper Jon Steenberg; Birkedal, Henrik;

    2016-01-01

    This two-period crossover study investigated the effect of calcium-phosphate-osteopontin particles on biofilm formation and pH in 48-h biofilms grown in situ. Bovine milk osteopontin is a highly phosphorylated glycoprotein that has been shown to interfere with bacterial adhesion to salivary......-coated surfaces. Calcium-phosphate-osteopontin particles have been shown to reduce biofilm formation and pH drops in a 5-species laboratory model of dental biofilm without affecting bacterial viability. Here, smooth surface biofilms from 10 individuals were treated ex vivo 6 times/day for 30 min with either...... calcium-phosphate-osteopontin particles or sterile saline. After growth, the amount of biofilm formed was determined by confocal microscopy, and pH drops upon exposure to glucose were monitored using confocal-microscopy-based pH ratiometry. A total of 160 biofilms were analysed. No adverse effects...

  2. Effect of angiotensin converting enzyme inhibitor on the calcium transients and calcium handling proteins in ventricular myocytes from rats with heart failure

    Institute of Scientific and Technical Information of China (English)

    WANG Li-chun; ZENG Wu-tao; LIU Jun; DONG Yu-gang; TANG An-li; FENG Chong; MA Hong; HE Jian-gui; LIAO Xin-xue; CHEN Wen-fang; LENG Xiu-yu; MA Li; MAI Wei-yi; TAO Jun

    2005-01-01

    Background Chronic heart failure (CHF) is associated with calcium transients and calcium handling proteins. Angiotensin converting enzyme (ACE) inhibitor has been demonstrated to have beneficial effect on CHF. Yet studies addressed to the relationship between ACE inhibitor and calcium transients in CHF are rare. The aim of this study was to investigate the influence of ACE inhibitor (perindopril) on the contractility and calcium transients and calcium handling proteins in ventricular myocytes from rats with experimental heart failure.Results The fraction of cell shortening (FS%) and [Ca2+]imax (nmol/L) were significantly reduced in group CHF-C compared with group PS (FS%: 7.51±1.15 vs 13.21±1.49;[Ca2+]imax:330.85±50.05 vs 498.16±14.07; both P<0.01), and restored at least partially in CHF-T group. In CHF-C group, the left ventricular mRNA of NCX1 and PLB were significantly upregulated in comparing with PS group (RNCX1/β-Actin: 0.51±0.12 vs 0.19±0.06, P<0.01; RPLB/β-Actin: 0.26±0.12 vs 0.20±0.08, P<0.05), while SERCA2 mRNA was downregulated (0.48±0.10 vs 0.80±0.11, P<0.01). The mRNA levels of NCX1 and SERCA2 in CHF-T group were between the CHF-C and PS group, and the differences of the latter two groups were significant (all P<0.05). In CHF-C and CHF-T groups, the protein expression of NCX1 were 1.141±0.047 and 1.074±0.081 times of that in PS group respectively (both P<0.05), and SERCA2 protein levels were 0.803±0.100 and 0.893±0.084 times of that in PS group respectively (both P<0.05). The protein expression of NCX1 and SERCA2 in the CHF-C and CHF-T groups is significantly different (both P<0.05).Conclusion ACE inhibitor could improve cardiac function of failing heart through directly enhancing the contractility of single cardiomyocyte, and these effects are probably mediated by its roles in preventing the deleterious changes of calcium transients and calcium handling proteins in CHF.

  3. [Bone and Nutrition. Vitamin D independent calcium absorption].

    Science.gov (United States)

    Masuyama, Ritsuko

    2015-07-01

    Vitamin D endocrine system is required for normal calcium and bone homeostasis. Trans-epithelial calcium absorption is initiated with calcium entry into the intestinal epithelial cells from luminal fluid through calcium permeable channels, and those expressions are strongly supported by vitamin D action. On the other hands, dietary treatment, mineral supplementation or restriction, successfully improves intestinal calcium absorption in global vitamin D receptor knock-out (VDR KO) mice, though vitamin D dependent active transport pathway is lacking. Dietary rescue of intestinal calcium absorption provided a positive calcium balance in this mouse model, and suggested that the major role of vitamin D function on calcium homeostasis was considered to be intestinal active absorption. To elucidate the entire process of intestinal calcium absorption, vitamin D independent calcium transport system was characterized into either trans-cellular or para-cellular process.

  4. 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.

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

    Science.gov (United States)

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

    2011-12-23

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

  6. Is Excess Calcium Harmful to Health?

    Directory of Open Access Journals (Sweden)

    Robin M. Daly

    2010-05-01

    Full Text Available Most current guidelines recommend that older adults and the elderly strive for a total calcium intake (diet and supplements of 1,000 to 1,300 mg/day to prevent osteoporosis and fractures. Traditionally, calcium supplements have been considered safe, effective and well tolerated, but their safety has recently been questioned due to potential adverse effects on vascular disease which may increase mortality. For example, the findings from a meta-analysis of randomized controlled trials (currently published in abstract form only revealed that the use of calcium supplements was associated with an ~30% increased risk of myocardial infarction. If high levels of calcium are harmful to health, this may alter current public health recommendations with regard to the use of calcium supplements for preventing osteoporosis. In this review, we provide an overview of the latest information from human observational and prospective studies, randomized controlled trials and meta-analyses related to the effects of calcium supplementation on vascular disease and related risk factors, including blood pressure, lipid and lipoprotein levels and vascular calcification.

  7. Apatite bone cement reinforced with calcium silicate fibers.

    Science.gov (United States)

    Motisuke, Mariana; Santos, Verônica R; Bazanini, Naiana C; Bertran, Celso A

    2014-10-01

    Several research efforts have been made in the attempt to reinforce calcium phosphate cements (CPCs) with polymeric and carbon fibers. Due to their low compatibility with the cement matrix, results were not satisfactory. In this context, calcium silicate fibers (CaSiO3) may be an alternative material to overcome the main drawback of reinforced CPCs since, despite of their good mechanical properties, they may interact chemically with the CPC matrix. In this work CaSiO3 fibers, with aspect ratio of 9.6, were synthesized by a reactive molten salt synthesis and used as reinforcement in apatite cement. 5 wt.% of reinforcement addition has increased the compressive strength of the CPC by 250% (from 14.5 to 50.4 MPa) without preventing the cement to set. Ca and Si release in samples containing fibers could be explained by CaSiO3 partial hydrolysis which leads to a quick increase in Ca concentration and in silica gel precipitation. The latter may be responsible for apatite precipitation in needle like form during cement setting reaction. The material developed presents potential properties to be employed in bone repair treatment.

  8. The Kinetics of Calcination of High Calcium Limestone

    Directory of Open Access Journals (Sweden)

    P. C. Okonkwo

    2012-02-01

    Full Text Available The kinetics of calcination of a high calcium type of limestone was studied. Ukpilla limestone found in the central region of Nigeria was studied. The limestone composition shows that the limestone has 51.29% calcium oxide and 41.53% loss on ignition and magnesium oxide content of 2.23%. The following parameters were determined; diffusion coefficient of lime layer, and mass transfer coefficient, conductivity of lime layer and beat transfer coefficient, convective parameter and diffusive parameter for temperatures 9000C, 10000C, 10600C and 10800C. The reaction was found to be limited by mass and heat transfers across the tune layer of the calcining article, theoptimal temperature of calcination was found to be 10600C. Diffusivity and mass transfer coefficient decreases with increase in calcination temperature. The thermal conductivity increases with increase in temperature. The diffusive and convective parameter decreases with increase in temperature. The reactivity of lime calcined at different temperatures were determined. The reactivity of the lime increases with decrease in calcination temperature.

  9. Usability of calcium carbide gas pressure method in hydrological sciences

    Science.gov (United States)

    Arsoy, S.; Ozgur, M.; Keskin, E.; Yilmaz, C.

    2013-10-01

    Soil moisture is a key engineering variable with major influence on ecological and hydrological processes as well as in climate, weather, agricultural, civil and geotechnical applications. Methods for quantification of the soil moisture are classified into three main groups: (i) measurement with remote sensing, (ii) estimation via (soil water balance) simulation models, and (iii) measurement in the field (ground based). Remote sensing and simulation modeling require rapid ground truthing with one of the ground based methods. Calcium carbide gas pressure (CCGP) method is a rapid measurement procedure for obtaining soil moisture and relies on the chemical reaction of the calcium carbide reagent with the water in soil pores. However, the method is overlooked in hydrological science applications. Therefore, the purpose of this study is to evaluate the usability of the CCGP method in comparison with standard oven-drying and dielectric methods in terms of accuracy, time efficiency, operational ease, cost effectiveness and safety for quantification of the soil moisture over a wide range of soil types. The research involved over 250 tests that were carried out on 15 different soil types. It was found that the accuracy of the method is mostly within ±1% of soil moisture deviation range in comparison to oven-drying, and that CCGP method has significant advantages over dielectric methods in terms of accuracy, cost, operational ease and time efficiency for the purpose of ground truthing.

  10. Oral calcium carbonate affects calcium but not phosphorus balance in stage 3-4 chronic kidney disease.

    Science.gov (United States)

    Hill, Kathleen M; Martin, Berdine R; Wastney, Meryl E; McCabe, George P; Moe, Sharon M; Weaver, Connie M; Peacock, Munro

    2013-05-01

    Patients with chronic kidney disease (CKD) are given calcium carbonate to bind dietary phosphorus, reduce phosphorus retention, and prevent negative calcium balance; however, data are limited on calcium and phosphorus balance during CKD to support this. Here, we studied eight patients with stage 3 or 4 CKD (mean estimated glomerular filtration rate 36 ml/min) who received a controlled diet with or without a calcium carbonate supplement (1500 mg/day calcium) during two 3-week balance periods in a randomized placebo-controlled cross-over design. All feces and urine were collected during weeks 2 and 3 of each balance period and fasting blood, and urine was collected at baseline and at the end of each week. Calcium kinetics were determined using oral and intravenous (45)calcium. Patients were found to be in neutral calcium and phosphorus balance while on the placebo. Calcium carbonate supplementation produced positive calcium balance, did not affect phosphorus balance, and produced only a modest reduction in urine phosphorus excretion compared with placebo. Calcium kinetics demonstrated positive net bone balance but less than overall calcium balance, suggesting soft-tissue deposition. Fasting blood and urine biochemistries of calcium and phosphate homeostasis were unaffected by calcium carbonate. Thus, the positive calcium balance produced by calcium carbonate treatment within 3 weeks cautions against its use as a phosphate binder in patients with stage 3 or 4 CKD, if these findings can be extrapolated to long-term therapy.

  11. The use of size-defined DNA-functionalized calcium phosphate nanoparticles to minimise intracellular calcium disturbance during transfection.

    Science.gov (United States)

    Neumann, Sebastian; Kovtun, Anna; Dietzel, Irmgard D; Epple, Matthias; Heumann, Rolf

    2009-12-01

    Calcium phosphate-based transfection methods are frequently used to transfer DNA into living cells. However, it has so far not been studied in detail to what extend the different transfection methods lead to a net calcium uptake. Upon subsequent resolution of the calcium phosphate, intracellular free ionic calcium-surges could result, inducing as side effect various physiological responses that may finally result in cell death. Here we investigated the overall calcium uptake by the human bladder carcinoma cell line T24 during the standard calcium phosphate transfection method and also during transfection with custom-made calcium phosphate/DNA nanoparticles by isotope labelling with (45)calcium. (45)Calcium uptake was strongly increased after 7h of standard calcium phosphate transfection but not if the transfection was performed with calcium phosphate nanoparticles. Time lapse imaging microscopy using the calcium-sensitive dye Fura-2 revealed large transient increases of the intracellular free calcium level during the standard calcium phosphate transfection but not if calcium phosphate nanoparticles were used. Consistently, the viability of cells transfected by calcium phosphate/DNA nanoparticles was not changed, in remarkable contrast to the standard method where considerable cell death occurred.

  12. Kinetics and Mechanism of Calcium Hydroxide Conversion into Calcium Alkoxides: Implications in Heritage Conservation Using Nanolimes.

    Science.gov (United States)

    Rodriguez-Navarro, Carlos; Vettori, Irene; Ruiz-Agudo, Encarnacion

    2016-05-24

    Nanolimes are alcohol dispersions of Ca(OH)2 nanoparticles used in the conservation of cultural heritage. Although it was believed that Ca(OH)2 particles were inert when dispersed in short-chain alcohols, it has been recently shown that they can undergo transformation into calcium alkoxides. Little is known, however, about the mechanism and kinetics of such a phase transformation as well as its effect on the performance of nanolimes. Here we show that Ca(OH)2 particles formed after lime slaking react with ethanol and isopropanol and partially transform (fractional conversion, α up to 0.08) into calcium ethoxide and isopropoxide, respectively. The transformation shows Arrhenius behavior, with apparent activation energy Ea of 29 ± 4 and 37 ± 6 kJ mol(-1) for Ca-ethoxide and Ca-isopropoxide conversion, respectively. High resolution transmission electron microscopy analyses of reactant and product phases show that the alkoxides replace the crystalline structure of Ca(OH)2 along specific [hkl] directions, preserving the external hexagonal (platelike) morphology of the parent phase. Textural and kinetic results reveal that this pseudomorphic replacement involves a 3D diffusion-controlled deceleratory advancement of the reaction front. The results are consistent with an interface-coupled dissolution-precipitation replacement mechanism. Analysis of the carbonation of Ca(OH)2 particles with different degree of conversion into Ca-ethoxide (α up to 0.08) and Ca-isopropoxide (α up to 0.04) exposed to air (20 °C, 80% relative humidity) reveals that Ca-alkoxides significantly reduce the rate of transformation into cementing CaCO3 and induce the formation of metastable vaterite, as opposed to stable calcite which forms in untransformed Ca(OH)2 samples. Similar effects are obtained when a commercial nanolime partially transformed into Ca-ethoxide is subjected to carbonation. Such effects may hamper/delay the strengthening or consolidation effects of nanolimes, thus having

  13. Molecular mechanisms of crystallization impacting calcium phosphate cements

    OpenAIRE

    2010-01-01

    The biomineral calcium hydrogen phosphate dihydrate (CaHPO4·2H2O), known as brushite, is a malleable material that both grows and dissolves faster than most other calcium minerals, including other calcium phosphate phases, calcium carbonates and calcium oxalates. Within the body, this ready formation and dissolution can play a role in certain diseases, such as kidney stone and plaque formation. However, these same properties, along with brushite’s excellent biocompatibility, can be used to gr...

  14. Factors to consider in the selection of a calcium supplement.

    OpenAIRE

    Shangraw, R F

    1989-01-01

    Calcium supplements are widely used, yet many questions remain as to the absorption of various calcium salts. Because the solubility of many calcium salts is dependent upon pH, the type of salt used, the condition of the patient, and the time of administration should be considered. Studies show that many calcium supplements on the market today do not meet standards of quality established in the "U.S. Pharmacopeia" (USP). Consumers must be discerning about the products they purchase. Calcium s...

  15. In Vitro Cytotoxicity of Calcium Silicate-Based Endodontic Cement as Root-End Filling Materials

    Directory of Open Access Journals (Sweden)

    Selen Küçükkaya

    2016-01-01

    Full Text Available The aim of this study was to evaluate the cytotoxicity of three types of calcium silicate-based endodontic cement after different incubation periods with human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were cultured from extracted third molars and seeded in 96-well plates. MTA, calcium enriched mixture (CEM cement, and Biodentine were prepared and added to culture insert plates which were immediately placed into 96-well plates containing cultured cells. After incubation periods of 24, 48, and 72 hours, cell viability was determined with WST-1 assay. Data were analysed statistically by ANOVA with repeated measures and Bonferroni tests. There was no significant difference in cell viability amongst the test materials after each incubation period (P>0.05. MTA and CEM presented more than 90% cell viability after 24 and 48 hours of incubation and showed statistically significant decrease in cell viability after 72 hours of incubation (P<0.05. Biodentine showed significantly less cell viability (73% after 24 hours of incubation, whereas more than 90% cell viability was seen after 48 and 72 hours of incubation (P<0.05. Despite the significant changes in cell viability over time, materials presented similar cytotoxicity profile. Biodentine and CEM can be considered as alternative materials for root-end surgery procedures.

  16. In Vitro Cytotoxicity of Calcium Silicate-Based Endodontic Cement as Root-End Filling Materials.

    Science.gov (United States)

    Küçükkaya, Selen; Görduysus, Mehmet Ömer; Zeybek, Naciye Dilara; Müftüoğlu, Sevda Fatma

    2016-01-01

    The aim of this study was to evaluate the cytotoxicity of three types of calcium silicate-based endodontic cement after different incubation periods with human periodontal ligament fibroblasts. Human periodontal ligament fibroblasts were cultured from extracted third molars and seeded in 96-well plates. MTA, calcium enriched mixture (CEM) cement, and Biodentine were prepared and added to culture insert plates which were immediately placed into 96-well plates containing cultured cells. After incubation periods of 24, 48, and 72 hours, cell viability was determined with WST-1 assay. Data were analysed statistically by ANOVA with repeated measures and Bonferroni tests. There was no significant difference in cell viability amongst the test materials after each incubation period (P > 0.05). MTA and CEM presented more than 90% cell viability after 24 and 48 hours of incubation and showed statistically significant decrease in cell viability after 72 hours of incubation (P Biodentine showed significantly less cell viability (73%) after 24 hours of incubation, whereas more than 90% cell viability was seen after 48 and 72 hours of incubation (P Biodentine and CEM can be considered as alternative materials for root-end surgery procedures.

  17. [Raynaud's phenomenon and calcium blocking agents. A preliminary open study with flunarizine].

    Science.gov (United States)

    Centonze, V; Campanale, G; Vino, M; Caporaletti, P; Magrone, D; Russo, P; Di Bari, M; Loragno, V; Albano, O

    1991-04-30

    Raynaud's phenomenon (Raynaud's disease), an accessual vascular acrosyndrome characterised by an important constriction of distal arterioles, has still no specific pharmacological therapy. In the last years, the use of calcium-entry-blockers (nifedipine, diltiazem, verapamil, nicardipine), drugs able to control the contractility of the vessels, showed some positive results. Considering this data, we appraised the efficacy of flunarizine, another calcium-entry-blocker, in a preliminary study of 28 patients (23 females, 5 males, aged between 15 and 48 years) suffering from Raynaud's disease. Apart from a statistically insignificant improvement of subjective symptoms (i.e. acroparesthesias, cold extremities) flunarizine (10 mg/day for 1 month) did not have positive results. Finally, this drug caused some side-effects: drowsiness, increase of weight and appetite, but without a real necessity for withdrawal of therapy.

  18. Calcium sulfoaluminate (Ye'elimite) hydration in the presence of gypsum, calcite, and vaterite

    Energy Technology Data Exchange (ETDEWEB)

    Hargis, Craig W. [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States); Telesca, Antonio [School of Engineering, University of Basilicata, Potenza (Italy); Monteiro, Paulo J.M., E-mail: monteiro@ce.berkeley.edu [Department of Civil and Environmental Engineering, University of California, Berkeley, CA (United States)

    2014-11-15

    Six calcium sulfoaluminate-based cementitious systems composed of calcium sulfoaluminate, calcite, vaterite, and gypsum were cured as pastes and mortars for 1, 7, 28 and 84 days. Pastes were analyzed with X-ray diffraction, thermogravimetric and differential thermal analyses. Mortars were tested for compressive strength, dimensional stability and setting time. Furthermore, pastes with a water/cementitious material mass ratio of 0.80 were tested for heat evolution during the first 48 h by means of isothermal conduction calorimetry. It has been found that: (1) both calcite and vaterite reacted with monosulfoaluminate to give monocarboaluminate and ettringite, with vaterite being more reactive; (2) gypsum lowered the reactivity of both carbonates; (3) expansion was reduced by calcite and vaterite, irrespective of the presence of gypsum; and (4) both carbonates increased compressive strength in the absence of gypsum and decreased compressive strength less in the presence of gypsum, with vaterite's action more effective than that of calcite.

  19. Preparation of calcium silicate absorbent from iron blast furnace slag.

    Science.gov (United States)

    Brodnax, L F; Rochelle, G T

    2000-09-01

    Calcium silicate hydrate (CSH) solids were prepared from hydrated lime and iron blast furnace slag in an aqueous agitated slurry at 92 degrees C. While it was hoped a minimal lime/slag ratio could be used to create near-amorphous CSH, the surface area of the product improved by increasing the lime/slag weight ratio to 2. The addition of gypsum to the lime/slag system dramatically improved the formation of surface area, creating solids with 139 m2/g after 30 hr of reaction when only a minimal amount of lime was present. The SO2 reactivity of solids prepared with gypsum greatly exceeded that of hydrated lime, achieving greater than 70-80% conversion of the alkalinity after 1 hr of reaction with SO2. The use of CaCl2 as an additive to the lime/slag system, in lieu of gypsum, also produced high-surface-area solids, 115 m2/g after 21 hr of reaction. However, the SO2 reactivity of these sorbents was relatively low given the high surface area. This emphasized that the correlation between surface area and SO2 reactivity was highly dependent on the solid phase, which was subsequently dependent on slurry composition.

  20. Simulation of Enzyme Catalysis in Calcium Alginate Beads

    Directory of Open Access Journals (Sweden)

    Ameel M. R. Al-Mayah

    2012-01-01

    Full Text Available A general mathematical model for a fixed bed immobilized enzyme reactor was developed to simulate the process of diffusion and reaction inside the biocatalyst particle. The modeling and simulation of starch hydrolysis using immobilized α-amylase were used as a model for this study. Corn starch hydrolysis was carried out at a constant pH of 5.5 and temperature of . The substrate flow rate was ranging from 0.2 to 5.0 mL/min, substrate initial concentrations 1 to 100 g/L. α-amylase was immobilized on to calcium alginate hydrogel beads of 2 mm average diameter. In this work Michaelis-Menten kinetics have been considered. The effect of substrate flow rate (i.e., residence time and initial concentration on intraparticle diffusion have been taken into consideration. The performance of the system is found to be affected by the substrate flow rate and initial concentrations. The reaction is controlled by the reaction rate. The model equation was a nonlinear second order differential equation simulated based on the experimental data for steady state condition. The simulation was achieved numerically using FINITE ELEMENTS in MATLAB software package. The simulated results give satisfactory results for substrate and product concentration profiles within the biocatalyst bead.

  1. Expanding the neuron's calcium signaling repertoire: intracellular calcium release via voltage-induced PLC and IP3R activation.

    Directory of Open Access Journals (Sweden)

    Stefanie Ryglewski

    2007-04-01

    Full Text Available Neuronal calcium acts as a charge carrier during information processing and as a ubiquitous intracellular messenger. Calcium signals are fundamental to numerous aspects of neuronal development and plasticity. Specific and independent regulation of these vital cellular processes is achieved by a rich bouquet of different calcium signaling mechanisms within the neuron, which either can operate independently or may act in concert. This study demonstrates the existence of a novel calcium signaling mechanism by simultaneous patch clamping and calcium imaging from acutely isolated central neurons. These neurons possess a membrane voltage sensor that, independent of calcium influx, causes G-protein activation, which subsequently leads to calcium release from intracellular stores via phospholipase C and inositol 1,4,5-trisphosphate receptor activation. This allows neurons to monitor activity by intracellular calcium release without relying on calcium as the input signal and opens up new insights into intracellular signaling, developmental regulation, and information processing in neuronal compartments lacking calcium channels.

  2. Effect of combining different calcium concentration dialysate on calcium balance in peritoneal dialysis patients

    Institute of Scientific and Technical Information of China (English)

    ZHAO Hui-ping; WU Bei; LU Li-xia; QIAO Jie; WU Xiang-lan; WANG Mei

    2012-01-01

    Background Calcium and phosphorus metabolic disturbance are common in dialysis patients and associated with increased morbidity and mortality.Therefore,maintaining the balance of calcium and phosphate metabolism and suitable intact parathyroid hormone(iPTH)level has become the focus of attention.We investigated the effects of different peritoneal dialysate calcium concentrations on calcium phosphate metabolism and iPTH in continuous ambulatory peritoneal dialysis(CAPD)patients.Methods Forty stable CAPD patients with normal serum calcium were followed for six months of treatment with 1.25 mmol/L calcium dialysate(DCa1.25,PD4,22 patients)or a combination of 1.75 mmol/L calcium dialysate(DCa1.75,PD2)and PD4(18 patients)twice a day respectively.Total serum calcium(after albumin correction),serum phosphorus,iPTH,alkaline phosphatase(ALP)and blood pressure were recorded before and 1,3 and 6 months after treatment commenced.Results No significant difference was found in baseline serum calcium,phosphorus between the two patient groups,but the levels of iPTH were significantly different.No significant changes were found in the dosage of calcium carbonate and active vitamin D during 6 months.In the PD4 group,serum calcium level at the 1st,3rd,6th months were significantly lower than the baseline(P<0.05).There was no significant difference in serum phosphorus after 6 months treatment.iPTH was significantly higher(P<0.001)at the 1st,3rd,and 6th months compared with the baseline.No differences were seen in ALP and blood pressure.In the PD4+PD2 group,no significant changes in serum calcium,phosphorus,iPTH,ALP and BP during the 6-month follow-up period.Conclusions Treatment with 1.25 mmol/L calcium dialysate for six months can decrease serum calcium,increase iPTH,without change in serum phosphorus,ALP,and BP.The combining of PD4 and PD2 can stabilize the serum calcium and avoid fluctuations in iPTH levels.

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

    Science.gov (United States)

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

  4. Influence of calcium ion on photosystem Ⅱ oxygen evolution

    Institute of Scientific and Technical Information of China (English)

    杜林方; 孙逊; 潘用华; 林宏辉; 梁厚果

    1995-01-01

    Treatment of photosystem Ⅱ particles with NaCl-washings,low-pH washings or detergentOG-solubilizings inhibited oxygen evolution and the inhibition was reversed by addition of exogenous Ca2+.Dynamic analysis with Ca2+reconstitution revealed two Ca2+binding sites with different affinities in theNaCl-washed PS Ⅱ particles or in the low-pH-treated ones.Oxygen-evolving PS Ⅱ core complex also con-tained the high and low affinity Ca2+binding sites.Ca2+enhanced the intensity of fluorescence emission of PSⅡ core complex.These results suggest that calcium play two roles in PS Ⅱ,the low affinity Ca2+is associ-ated with energy transfer while the high affinity Ca2+is concerned with water splitting reaction.

  5. Analysis of barium hydroxide and calcium hydroxide slurry carbonation reactors

    Energy Technology Data Exchange (ETDEWEB)

    Patch, K.D.; Hart, R.P.; Schumacher, W.A.

    1980-05-01

    The removal of CO/sub 2/ from air was investigated by using a continuous-agitated-slurry carbonation reactor containing either barium hydroxide (Ba(OH)/sub 2/) or calcium hydroxide (Ca(OH)/sub 2/). Such a process would be applied to scrub /sup 14/CO/sub 2/ from stack gases at nuclear-fuel reprocessing plants. Decontamination factors were characterized for reactor conditions which could alter hydrodynamic behavior. An attempt was made to characterize reactor performance with models assuming both plug flow and various degrees of backmixing in the gas phase. The Ba(OH)/sub 2/ slurry enabled increased conversion, but apparently the process was controlled under some conditions by phenomena differing from those observed for carbonation by Ca(OH)/sub 2/. Overall reaction mechanisms are postulated.

  6. Use of calcium oxide in palm oil methyl ester production

    Directory of Open Access Journals (Sweden)

    Kulchanat Prasertsit

    2014-04-01

    Full Text Available Introducing an untreated calcium oxide (CaO as a solid heterogeneous catalyst for biodiesel production from palm oil by transesterification was studied in this work. The four studied parameters were methanol to oil molar ratio, CaO catalyst concentration, reaction time, and water content. The results for palm oil show that when the water content is higher than 3%wt and the amount of CaO greater than 7%wt soap formation from saponification occurs. A higher methanol to oil molar ratio requires a higher amount of CaO catalyst to provide the higher product purity. The appropriate methanol to CaO catalyst ratio is about 1.56. Commercial grade CaO gives almost the same results as AR grade CaO. In addition, reusing commercial grade CaO for about 5 to 10 repetitions without catalyst regeneration drops the percentage of methyl ester purity approximately 5 to 10%, respectively.

  7. Calcium, Strontium and Barium Homogeneous Catalysts for Fine Chemicals Synthesis.

    Science.gov (United States)

    Sarazin, Yann; Carpentier, Jean-François

    2016-12-01

    The large alkaline earths (Ae), calcium, strontium and barium, have in the past 15 years yielded a brand new generation of heteroleptic molecular catalysts for the production of fine chemicals. However, the integrity of these complexes is often plagued by ligand redistribution equilibria in solution. This personal account retraces the paths followed in our research group towards the design of stable heteroleptic alkalino-earth complexes, including the use of intramolecular noncovalent Ae···H-Si and Ae···F-C interactions. Their implementation as homogenous precatalysts for reactions such as the intramolecular and intermolecular hydroamination and hydrophosphination of activated alkenes, the hydrophosphonylation of ketones, and the dehydrogenative coupling of amines and hydrosilanes that enable the efficient and controlled formations of CP, CN, or SiN σ-bonds, is presented in a synthetic perspective that highlights their overall outstanding catalytic performance.

  8. Calcium sensing receptors and calcium oscillations: calcium as a first messenger.

    Science.gov (United States)

    Breitwieser, Gerda E

    2006-01-01

    Calcium sensing receptors (CaR) are unique among G-protein-coupled receptors (GPCRs) since both the first (extracellular) and second (intracellular) messengers are Ca(2+). CaR serves to translate small fluctuations in extracellular Ca(2+) into intracellular Ca(2+) oscillations. In many cells and tissues, CaR also acts as a coincidence detector, sensing both changes in extracellular Ca(2+) plus the presence of various allosteric activators including amino acids, polyamines, and/or peptides. CaR oscillations are uniquely shaped by the activating agonist, that is, Ca(2+) triggers sinusoidal oscillations while Ca(2+) plus phenylalanine trigger transient oscillations of lower frequency. The distinct oscillation patterns generated by Ca(2+)versus Ca(2+) plus phenylalanine are the results of activation of distinct signal transduction pathways. CaR is a member of Family C GPCRs, having a large extracellular agonist binding domain, and functioning as a disulfide-linked dimer. The CaR dimer likely can be driven to distinct active conformations by various Ca(2+) plus modulator combinations, which can drive preferential coupling to divergent signaling pathways. Such plasticity with respect to both agonist and signaling outcomes allows CaR to uniquely contribute to the physiology of organs and tissues where it is expressed. This chapter will examine the structural features of CaR, which contribute to its unique properties, the nature of CaR-induced intracellular Ca(2+) signals and the potential role(s) for CaR in development and differentiation.

  9. Cerium incorporated MCM-48 (Ce-MCM-48) as a catalyst to inhibit bromate formation during ozonation of bromide-containing water: Efficacy and mechanism.

    Science.gov (United States)

    Li, Weiwei; Lu, Xiaowei; Xu, Ke; Qu, Jiuhui; Qiang, Zhimin

    2015-12-01

    The composite mesoporous sieve Ce-MCM-48 (cerium incorporated MCM-48) with different Si/Ce molar ratios were synthesized hydrothermally and characterized with X-ray diffraction, X-ray photoelectron spectroscopy, BET surface area, and pHpzc. Results indicate that Ce-MCM-48, especially with a Si/Ce molar ratio of 66 (i.e., Ce66-MCM-48), could significantly inhibit bromate (BrO3(-)) formation during ozonation of Br(-)-containing water, achieving 91% of inhibition efficiency at pH 7.6 and 25 °C. An acidic or alkaline pH decreased the inhibition efficiency of Ce66-MCM-48 to some extent, but reaction temperature ranging from 15 to 30 °C had no significant impact. By comparing the bromine mass balance, aqueous O3 decomposition, and newly formed H2O2 between O3 and O3/Ce66-MCM-48 processes, the inhibition mechanism was proposed: Ce66-MCM-48 promoted aqueous O3 decomposition to generate hydroxyl radicals (OH) that could merge into H2O2, so the oxidative transformation of Br(-) and HOBr/OBr(-) by O3 and OH was primarily suppressed. The catalytic ability of Ce66-MCM-48 was continuously regenerated through the circulating reactions between Ce(III) and Ce(IV) occurring on the catalyst surface. Besides its inhibition on BrO3(-) formation, Ce66-MCM-48 could also enhance the degradation of refractory organic micropollutants. Because of these distinct merits, Ce66-MCM-48 has potential applications to water treatment by ozone.

  10. Calcium homeostasis in barley aleurone

    Energy Technology Data Exchange (ETDEWEB)

    Jones, R.L.

    1990-02-21

    Under the auspices of the Department of Energy we investigated calcium homeostasis in aleurone cells of barley. This investigation was initiated to explore the role played by extracellular Ca{sup 2+} in gibberellic acid (GA)-induced synthesis and secretion of hydrolases in the aleurone layer. We have focused our attention on four topics that relate to the role of Ca{sup 2+} in regulating the synthesis of {alpha}-amylase. First, we determined the stoichiometry of Ca{sup 2+} binding to the two principal classes of barley {alpha}-amylase and examined some of the biochemical and physical properties of the native and Ca{sup 2+}-depleted forms of the enzyme. Second, since {alpha}-amylase is a Ca{sup 2+} containing metalloenzyme that binds one atom of Ca{sup 2+} per molecule, we developed methods to determine the concentration of Ca{sup 2+} in the cytosol of the aleurone cell. We developed a technique for introducing Ca{sup 2+}-sensitive dyes into aleurone protoplasts that allows the measurement of Ca{sup 2+} in both cytosol and endoplasmic reticulum (ER). Third, because the results of our Ca{sup 2+} measurements showed higher levels of Ca{sup 2+} in the ER than in the cytosol, we examined Ca{sup 2+} transport into the ER of control and GA-treated aleurone tissue. And fourth, we applied the technique of patch-clamping to the barley aleurone protoplast to examine ion transport at the plasma membrane. Our results with the patch-clamp technique established the presence of K{sup +} channels in the plasma membrane of the aleurone protoplast, and they showed that this cell is ideally suited for the application of this methodology for studying ion transport. 34 refs.

  11. The calcium-sensing receptor regulates mammary gland parathyroid hormone–related protein production and calcium transport

    OpenAIRE

    VanHouten, Joshua; Dann, Pamela; McGeoch, Grace; Brown, Edward M.; Krapcho, Karen; Neville, Margaret; Wysolmerski, John J

    2004-01-01

    The transfer of calcium from mother to milk during lactation is poorly understood. In this report, we demonstrate that parathyroid hormone–related protein (PTHrP) production and calcium transport in mammary epithelial cells are regulated by extracellular calcium acting through the calcium-sensing receptor (CaR). The CaR becomes expressed on mammary epithelial cells at the transition from pregnancy to lactation. Increasing concentrations of calcium, neomycin, and a calcimimetic compound suppre...

  12. 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.

  13. Preparation And Characterization Of Modified Calcium Oxide From Natural Sources And Their Application In The Transesterification Of Palm Oil

    Directory of Open Access Journals (Sweden)

    Aqliliriana

    2015-08-01

    Full Text Available Abstract Calcium oxide catalysts were prepared from natural calcium sources such as limestone and mud creeper shell and the catalytic activities were evaluated in the transesterification of palm oil. The raw material which mainly composed of calcium carbonate can be easily converted to calcium oxide CaO after calcination above 1000 K for few hours. Abundant cheap sources benign high conversion and nontoxic become main advantages of these catalysts. The catalysts were characterized by XRF TGA XRD CO2-TPD SEM and BET methods. Thermal decomposition of CaCO3 will produced CaO which later will be converted into calcium hydroxide CaOH2 via simple hydration technique. Under optimum reaction condition methanol to oil ratio 151 catalyst loading 3 wt. reaction temperature 338 K for 5 hours the highest conversion of palm oil to methyl ester recorded were 98 and 94 when using modified limestone and mud creeper shell respectively. The results observed an increment up to 80 by using modified catalysts with characterization results showed high in basicity and surface area. Hence promising materials via simple and cheap method can be achieved.

  14. Effect of divalent ions in acrosome reaction induced by glycosamineglycans in porcine spermatozoa.

    Science.gov (United States)

    Delgado, N M; Carranco, A; Merchant, H; Reyes, R

    1985-01-01

    Magnesium, calcium, and zinc at the concentration of 10 microM are capable of inducing a "true" acrosome reaction in the pig spermatozoa judged by the criteria of the fusion of the acrosome and the plasmatic membrane at the anterior region or the sperm nucleus. The optimal percent of acrosome reaction reached by any of the ions tested as a whole was 50%. When glycosamineglycan sulfate (GAGs) plus 10 microM of Mg++, Ca++, or Zn++ was added, they reach to 70-80% of acrosome reaction. At the electrom microscope, thin sections taken from pig spermatozoa treated with ions, GAGs, or ion + GAGs under optimal experimental conditions revealed the same pattern of acrosomal reaction. Results suggest the important role that divalent cations play in general in the induction of the acrosome reaction and question the so-called essential role of calcium ions.

  15. Synthesis and Structural Studies of Calcium and Magnesium Phosphinate and Phosphonate Compounds

    Science.gov (United States)

    Bampoh, Victoria Naa Kwale

    The work presented herein describes synthetic methodologies leading to the design of a wide array of magnesium and calcium based phosphinate and phosphonates with possible applications as bone scaffolding materials or additives to bone cements. The challenge to the chemistry of the alkaline earth phosphonate target compounds includes poor solubility of compounds, and poorly understood details on the control of the metal's coordination environment. Hence, less is known on phosphonate based alkaline earth metal organic frameworks as compared to transition metal phosphonates. Factors governing the challenges in obtaining crystalline, well-defined magnesium and calcium solids lie in the large metal diameters, the absence of energetically available d-orbitals to direct metal geometry, as well as the overall weakness of the metal-ligand bonds. A significant part of this project was concerned with the development of suitable reaction conditions to obtain X-ray quality crystals of the reaction products to allow for structural elucidation of the novel compounds. Various methodologies to aid in crystal growth including hydrothermal methods and gel crystallization were employed. We have used phosphinate and phosphonate ligands with different number of phosphorus oxygen atoms as well as diphosphonates with different linker lengths to determine their effects on the overall structural features. An interesting correlation is observed between the dimensionality of products and the increasing number of donor oxygen atoms in the ligands as we progress from phosphinic acid to the phosphorous acids. As an example, monophosphinate ligand only yielded one-dimensional compounds, whereas the phosphonates crystallize as one and two-dimensional compounds, and the di- and triphosphonate based compounds display two or three-dimensional geometries. This thesis provides a selection of calcium and magnesium compounds with one-dimensional geometry, as represented in a calcium phosphinate to novel

  16. Morphological and mechanical characterization of chitosan-calcium phosphate composites for potential application as bone-graft substitutes

    Directory of Open Access Journals (Sweden)

    Guilherme Maia Mulder van de Graaf

    Full Text Available Introduction: Bone diseases, aging and traumas can cause bone loss and lead to bone defects. Treatment of bone defects is challenging, requiring chirurgical procedures. Bone grafts are widely used for bone replacement, but they are limited and expensive. Due to bone graft limitations, natural, semi-synthetic, synthetic and composite materials have been studied as potential bone-graft substitutes. Desirable characteristics of bone-graft substitutes are high osteoinductive and angiogenic potentials, biological safety, biodegradability, bone-like mechanical properties, and reasonable cost. Herein, we prepared and characterized potential bone-graft substitutes composed of calcium phosphate (CP - a component of natural bone, and chitosan (CS - a biocompatible biopolymer. Methods CP-CS composites were synthetized, molded, dried and characterized. The effect of drying temperatures (38 and 60 °C on the morphology, porosity and chemical composition of the composites was evaluated. As well, the effects of drying temperature and period of drying (3, 24, 48 and 72 hours on the mechanical properties - compressive strength, modulus of elasticity and relative deformation-of the demolded samples were investigated. Results Scanning electron microscopy and gas adsorption-desorption analyses of the CS-CP composites showed interconnected pores, indicating that the drying temperature played an important role on pores size and distribution. In addition, drying temperature have altered the color (brownish at 60 °C due to Maillard reaction and the chemical composition of the samples, confirmed by FTIR. Conclusion Particularly, prolonged period of drying have improved mechanical properties of the CS-CP composites dried at 38 °C, which can be designed according to the mechanical needs of the replaceable bone.

  17. Development of poly(aspartic acid-co-malic acid) composites for calcium carbonate and sulphate scale inhibition.

    Science.gov (United States)

    Mithil Kumar, N; Gupta, Sanjay Kumar; Jagadeesh, Dani; Kanny, K; Bux, F

    2015-01-01

    Polyaspartic acid (PSI) is suitable for the inhibition of inorganic scale deposition. To enhance its scale inhibition efficiency, PSI was modified by reacting aspartic acid with malic acid (MA) using thermal polycondensation polymerization. This reaction resulted in poly(aspartic acid-co-malic acid) (PSI-co-MA) dual polymer. The structural, chemical and thermal properties of the dual polymers were analysed by using scanning electron microscopy, Fourier transform infrared spectroscopy, X-ray diffraction, differential scanning calorimetry and gel permeation chromatography. The effectiveness of six different molar ratios of PSI-co-MA dual polymer for calcium carbonate and calcium sulphate scale inhibition at laboratory scale batch experiments was evaluated with synthetic brine solution at selected doses of polymer at 65-70°C by the static scale test method. The performance of PSI-co-MA dual polymer for the inhibition of calcium carbonate and calcium sulphate precipitation was compared with that of a PSI single polymer. The PSI-co-MA exhibited excellent ability to control inorganic minerals, with approximately 85.36% calcium carbonate inhibition and 100% calcium sulphate inhibition at a level of 10 mg/L PSI-co-MA, respectively. Therefore, it may be reasonably concluded that PSI-co-MA is a highly effective scale inhibitor for cooling water treatment applications.

  18. The physiological role of mitochondrial calcium revealed by mice lacking the mitochondrial calcium uniporter.

    Science.gov (United States)

    Pan, Xin; Liu, Jie; Nguyen, Tiffany; Liu, Chengyu; Sun, Junhui; Teng, Yanjie; Fergusson, Maria M; Rovira, Ilsa I; Allen, Michele; Springer, Danielle A; Aponte, Angel M; Gucek, Marjan; Balaban, Robert S; Murphy, Elizabeth; Finkel, Toren

    2013-12-01

    Mitochondrial calcium has been postulated to regulate a wide range of processes from bioenergetics to cell death. Here, we characterize a mouse model that lacks expression of the recently discovered mitochondrial calcium uniporter (MCU). Mitochondria derived from MCU(-/-) mice have no apparent capacity to rapidly uptake calcium. Whereas basal metabolism seems unaffected, the skeletal muscle of MCU(-/-) mice exhibited alterations in the phosphorylation and activity of pyruvate dehydrogenase. In addition, MCU(-/-) mice exhibited marked impairment in their ability to perform strenuous work. We further show that mitochondria from MCU(-/-) mice lacked evidence for calcium-induced permeability transition pore (PTP) opening. The lack of PTP opening does not seem to protect MCU(-/-) cells and tissues from cell death, although MCU(-/-) hearts fail to respond to the PTP inhibitor cyclosporin A. Taken together, these results clarify how acute alterations in mitochondrial matrix calcium can regulate mammalian physiology.

  19. SECONDARY HYPERPARATHYROIDISM AFTER BARIATRIC SURGERY: TREATMENT IS WITH CALCIUM CARBONATE OR CALCIUM CITRATE?

    Science.gov (United States)

    BARETTA, Giorgio Alfredo Pedroso; CAMBI, Maria Paula Carlini; RODRIGUES, Arieli Luz; MENDES, Silvana Aparecida

    2015-01-01

    Background : Bariatric surgery, especially Roux-en-Y gastric bypass, can cause serious nutritional complications arising from poor absorption of essential nutrients. Secondary hyperparathyroidism is one such complications that leads to increased parathyroid hormone levels due to a decrease in calcium and vitamin D, which may compromise bone health. Aim : To compare calcium carbonate and calcium citrate in the treatment of secondary hyperparathyroidism. Method : Patients were selected on the basis of their abnormal biochemical test and treatment was randomly done with citrate or calcium carbonate. Results : After 60 days of supplementation, biochemical tests were repeated, showing improvement in both groups. Conclusion : Supplementation with calcium (citrate or carbonate) and vitamin D is recommended after surgery for prevention of secondary hyperparathyroidism. PMID:26537273

  20. Regulation of calcium phosphate formation by native amelogenins in vitro.

    Science.gov (United States)

    Kwak, Seo-Young; Kim, Sonia; Yamakoshi, Yasuo; Simmer, James P; Beniash, Elia; Margolis, Henry C

    2014-08-01

    Our previous in vitro studies have shown that recombinant full-length porcine amelogenin rP172 can transiently stabilize amorphous calcium phosphate (ACP) and uniquely guide the formation of well-aligned bundles of hydroxyapatite (HA) crystals, as seen in the secretory stage of amelogenesis. This functional capacity is dependent on the hydrophilic C-terminal domain of full-length amelogenin. However, we have also found that native phosphorylated (single S-16 site) forms of full-length (P173) and C-terminal cleaved (P148) amelogenins can stabilize ACP for > 2 d and prevent HA formation. The present study was carried out to test the hypothesis that, at reduced concentrations, native full-length P173 also has the capacity to guide ordered HA formation. The effect of P148 and P173 concentrations (0.2-2.0 mg/ml) on the rate of spontaneous calcium phosphate precipitation was monitored via changes in solution pH, while mineral phases formed were assessed using TEM. At higher P173 concentrations (1.0-2.0 mg/ml), limited mineral formation occurred and only ACP nanoparticles were observed during a 48 h period. However, at 0.4 mg/ml P173, a predominance of organized bundles of linear, needle-like HA crystals were observed. At 0.2 mg/ml of P173, limited quantities of less organized HA crystals were found. Although P148 similarly stabilized ACP, it did not guide ordered HA formation, like P173. Hence, the establishment of the hierarchical enamel structure during secretory stage amelogenesis may be regulated by the partial removal of full-length amelogenin via MMP20 proteolysis, while predominant amelogenin degradation products, like P148, serve to prevent uncontrolled mineral formation.

  1. Europium-doped calcium titanate: Optical and structural evaluations

    Energy Technology Data Exchange (ETDEWEB)

    Mazzo, Tatiana Martelli; Pinatti, Ivo Mateus [INCTMN, LIEC, Departamento de Química, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, SP (Brazil); Macario, Leilane Roberta [INCTMN, LIEC, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, 14800-900 Araraquara, SP (Brazil); Avansi, Waldir [Centro de Ciências Exatas e de Tecnologia, Departamento de Física, Universidade Federal de São Carlos, Jardim Guanabara, 13565-905 São Carlos, SP (Brazil); Moreira, Mario Lucio [Instituto de Física e Matemática, Universidade Federal de Pelotas, P.O. Box 354, Campus do Capão do Leão, 96001-970 Pelotas, RS (Brazil); Rosa, Ieda Lucia Viana, E-mail: ilvrosa@ufscar.br [INCTMN, LIEC, Departamento de Química, Universidade Federal de São Carlos, P.O. Box 676, 13565-905 São Carlos, SP (Brazil); Mastelaro, Valmor Roberto [Instituto de Física de São Carlos, Departamento de Física e Ciência dos Materiais, Universidade de São Paulo, P.O. Box 369, Av Trabalhador São Carlense 400, 13560-970 São Carlos, SP (Brazil); Varela, José Arana; Longo, Elson [INCTMN, LIEC, Instituto de Química, Universidade Estadual Paulista, P.O. Box 355, 14800-900 Araraquara, SP (Brazil)

    2014-02-05

    Highlights: • CaTiO{sub 3}:Eu{sup 3+} were obtained using low temperatures and very short reactional times. • The Eu{sup 3+} changes the local order–disorder of the [TiO{sub 6}] and [CaO{sub 12}] clusters. • Lifetime decay curves reveal two sites of symmetry of the Eu{sup 3+} in the CT matrix. • CaTiO{sub 3}:Eu{sup 3+} exhibit the strongest luminescent intensity and pure red color. -- Abstract: Pure Calcium Titanate (CT-pure) and Europium doped Calcium Titanate Ca{sub 1−x}Eu{sub x}TiO{sub 3} (x = 0.5%, 1.0% and 2.0% molar ratio of Eu{sup 3+} ions) powders were synthesized by hydrothermal microwave method (HTMW) at 140 °C for 8 min. The HTMW method appears to be an efficient method to prepare the luminescence materials using low temperatures and very short reactional times. In addition it is possible to determine specific correlations imposed by TiCl{sub 4} replacement by titanium isopropoxide [Ti(OC{sub 3}H{sub 7}){sub 4}] changing the reaction character and resulting in two different options of europium doping CT syntesis. To evaluate the influence of the structural order–disorder among the reactions and different properties of these materials, the following techniques were used for characterization. XANES spectroscopy that revealed that the introduction of Eu{sup 3+} ions into the CT lattice induces to significant changes in the local order–disorder around both, [TiO{sub 6}] and [CaO{sub 12}], complex clusters. PL spectra show Eu{sup 3+} emission lines ascribed to the Eu{sup 3+} transitions from {sup 5}D{sub 0} excited states to {sup 7}F{sub J} (J = 0, 1–4) fundamental states in CT:Eu{sup 3+} powders excited at 350 and 394 nm.

  2. Reaction cross-section predictions for nucleon induced reactions

    CERN Document Server

    Nobre, G P A; Escher, J E; Dietrich, F S

    2010-01-01

    A microscopic calculation of the optical potential for nucleon-nucleus scattering has been performed by explicitly coupling the elastic channel to all the particle-hole (p-h) excitation states in the target and to all relevant pickup channels. These p-h states may be regarded as doorway states through which the flux flows to more complicated configurations, and to long-lived compound nucleus resonances. We calculated the reaction cross sections for the nucleon induced reactions on the targets $^{40,48}$Ca, $^{58}$Ni, $^{90}$Zr and $^{144}$Sm using the QRPA description of target excitations, coupling to all inelastic open channels, and coupling to all transfer channels corresponding to the formation of a deuteron. The results of such calculations were compared to predictions of a well-established optical potential and with experimental data, reaching very good agreement. The inclusion of couplings to pickup channels were an important contribution to the absorption. For the first time, calculations of excitatio...

  3. STUDY OF REACTION SEQUENCES FOR FORMATION OF SOLID SOLUTION: 0,48 PbZrO3-0,47 PbTiO3-0,05 Pb (Cr1/5, Zn1/5, Sb 3/5 O3

    Directory of Open Access Journals (Sweden)

    N. Abdessalem

    2015-07-01

    Full Text Available To study the reaction sequences of formation of solid solution zirconate-lead titanate (PZT in this work, we took into account the effect of adding oxide dopants on the progress of the reaction, so we added oxides ZnO, Cr2O3, Sb2O3 to our material composition in small quantities so that the solid solution must verify the conditions of the perovskite structure. The results of the X-ray diffraction and thermal analysis allowed us to suggest a reaction mechanism. It is important to note that the substitution of a low concentration of ions forming the perovskite structure PZT (Pb2+, Zr4+ et Ti4+ by other ions (Zn2+, Cr3+ et Sb+5 in our study alters the reaction sequences training of the solid solution PZT and especially the formation of intermediate phase.

  4. Mechanism for defoaming by oils and calcium soap in aqueous systems.

    Science.gov (United States)

    Zhang, Hui; Miller, Clarence A; Garrett, Peter R; Raney, Kirk H

    2003-07-15

    The effect of oils, hardness, and calcium soap on foam stability of aqueous solutions of commercial surfactants was investigated. For conditions where negligible calcium soap was formed, stability of foams made with 0.1 wt% solutions of a seven-EO alcohol ethoxylate containing dispersed drops of n-hexadecane, triolein, or mixtures of these oils with small amounts of oleic acid could be understood in terms of entry, spreading, and bridging coefficients, i.e., ESB analysis. However, foams made from solutions containing 0.01 wt% of three-EO alcohol ethoxysulfate sodium salt and the same dispersed oils were frequently more stable than expected based on ESB analysis, reflecting that repulsion due to overlap of electrical double layers in the asymmetric oil-water-air film made oil entry into the air-water interface more difficult than the theory predicts. When calcium soap was formed in situ by the reaction of fatty acids in the oil with calcium, solid soap particles were observed at the surfaces of the oil drops. The combination of oil and calcium soap produced a synergistic effect facilitating the well-known bridging instability of foam films or Plateau borders and producing a substantial defoaming effect. A possible mechanism of instability involving increases in disjoining pressure at locations where small soap particles approach the air-water interface is discussed. For both surfactants with the triolein-oleic acid mixtures, calculated entry and bridging coefficients for conditions when calcium soap formed were positive shortly after foam generation but negative at equilibrium. These results are consistent with the experimental observation that most defoaming action occurred shortly after foam generation rather than at later times.

  5. 26 CFR 48.0-1 - Introduction.

    Science.gov (United States)

    2010-04-01

    ... 26 Internal Revenue 16 2010-04-01 2010-04-01 true Introduction. 48.0-1 Section 48.0-1 Internal Revenue INTERNAL REVENUE SERVICE, DEPARTMENT OF THE TREASURY (CONTINUED) MISCELLANEOUS EXCISE TAXES MANUFACTURERS AND RETAILERS EXCISE TAXES Introduction § 48.0-1 Introduction. The regulations in this part 48...

  6. Nanostructured ion-selective MCM-48 membranes

    NARCIS (Netherlands)

    Schmuhl, Riaan; Roy Chowdhury, Sankhanilay; Elshof, ten Johan E.; Berg, van den Albert; Blank, Dave H.A.

    2004-01-01

    Templated MCM-48 silica was prepared using CTAB as surfactant. The MCM-48 powders and thin films were characterized by different techniques. MCM-48 layers were deposited on macroporous α-alumina supports and silicon nitride microsieves. The water permeability of MCM-48 was compared with the permeabi

  7. Role of mitochondria and network connectivity in intercellular calcium oscillations

    CERN Document Server

    Dokukina, I V; Grachev, E A; Gunton, J D; Dokukina, Irina V.; Gracheva, Maria E.; Grachev, Eugene A.; Gunton, James D.

    2005-01-01

    Mitochondria are large-scale regulators of cytosolic calcium under normal cellular conditions. In this paper we model the complex behavior of mitochondrial calcium during the action of inositol 1,4,5-trisphosphate on a single cell and find results that are in good agreement with recent experimental studies. We also study the influence of the cellular network connectivity on intercellular signalling via gap junction diffusion. We include in our model the dependence of the junctional conductivity on the cytosolic calcium concentrations in adjacent cells. We consider three different mechanisms of calcium wave propagation through gap junctions: via calcium diffusion, inositol 1,4,5-trisphosphate diffusion, and both calcium and inositol 1,4,5-trisphosphate diffusion. We show that inositol 1,4,5-trisphosphate diffusion is the mechanism of calcium wave propagation and that calcium diffusion is the mechanism of synchronization of cytosolic calcium oscillations in adjacent cells. We also study the role of different to...

  8. THERMAL DEGRADATION AND FLAME RETARDANCY OF CALCIUM ALGINATE FIBERS

    Institute of Scientific and Technical Information of China (English)

    Qing-shan Kong; Bing-bing Wang; Quan Ji; Yan-zhi Xia; Zhao-xia Guo; Jian Yu

    2009-01-01

    Calcium alginate fibers were prepared by wet spinning of sodium alginate into a coagulating bath containing calcium chloride. The thermal degradation and flame retardancy of calcium alginate fibers were investigated with thermal gravimetry (TG), X-ray diffraction (XRD), limiting oxygen index (LOI) and cone calorimeter (CONE). The results show that calcium alginate fibers are inherently flame retardant with a LOI value of 34, and the heat release rate (HRR), total heat release (THR), CO and CO_2 concentrations during combustion are much lower compared with those of viscose fibers. Calcium carbonate and calcium oxide were formed during thermal degradation of calcium alginate fibers at different temperatures. The shape of calcium alginate fibers is well kept after LOI test. The rigid combustion residue char acts as an effective barrier to the outward diffusion of flame and heat. The combustion process and flame retardant mechanism of calcium alginate fibers are also discussed.

  9. Role of calcium in gravity perception of plant roots

    Science.gov (United States)

    Evans, Michael L.

    1986-01-01

    Calcium ions may play a key role in linking graviperception by the root cap to the asymmetric growth which occurs in the elongation zone of gravistimulated roots. Application of calcium-chelating agents to the root cap inhibits gravitropic curvature without affecting growth. Asymmetric application of calcium to one side of the root cap induces curvature toward the calcium source, and gravistimulation induces polar movement of applied (Ca-45)(2+) across the root cap toward the lower side. The action of calcium may be linked to auxin movement in roots since: (1) auxin transport inhibitors interfere both with gravitropic curvature and graviinduced polar calcium movement and (2) asymmetric application of calcium enhances auxin movement across the elongation zone of gravistimulated roots. Indirect evidence indicates that the calcium-modulated regulator protein, calmodulin, may be involved in either the transport or action of calcium in the gravitropic response mechanism of roots.

  10. Double Pion Production Reactions

    CERN Document Server

    Oset, E; Cano, F; Hernández, E; Kamalov, S S; Nacher, J C; Tejedor, J A G

    1999-01-01

    We report on reactions producing two pions induced by real and virtual photons or nucleons. The role of different resonances in these reactions is emphasized. Novel results on coherent two pion photoproduction in nuclei are also reported.

  11. Microfluidic chemical reaction circuits

    Science.gov (United States)

    Lee, Chung-cheng; Sui, Guodong; Elizarov, Arkadij; Kolb, Hartmuth C.; Huang, Jiang; Heath, James R.; Phelps, Michael E.; Quake, Stephen R.; Tseng, Hsian-rong; Wyatt, Paul; Daridon, Antoine

    2012-06-26

    New microfluidic devices, useful for carrying out chemical reactions, are provided. The devices are adapted for on-chip solvent exchange, chemical processes requiring multiple chemical reactions, and rapid concentration of reagents.

  12. Microscale Thermite Reactions.

    Science.gov (United States)

    Arnaiz, Francisco J.; Aguado, Rafael; Arnaiz, Susana

    1998-01-01

    Describes the adaptation of thermite (aluminum with metal oxides) reactions from whole-class demonstrations to student-run micro-reactions. Lists detailed directions and possible variations of the experiment. (WRM)

  13. Effects of calcium gluconate on the utilization of magnesium and the nephrocalcinosis in rats fed excess dietary phosphorus and calcium.

    Science.gov (United States)

    Chonan, O; Takahashi, R; Kado, S; Nagata, Y; Kimura, H; Uchida, K; Watanuki, M

    1996-08-01

    The effects of calcium gluconate on the utilization of magnesium and nephrocalcinosis in male Wistar rats made magnesium-deficient by adding excess dietary phosphorus (1.195 g of phosphorus/100 g of diet) and calcium (1.04 g of calcium/100 g of diet) were compared with the effects of calcium carbonate. The effects of dietary magnesium concentration on the magnesium status and nephrocalcinosis were also examined. Adding excess dietary phosphorus and calcium decreased the apparent magnesium absorption ratios and the concentrations of magnesium in the serum and femur and increased the deposition of calcium in the kidney, and the low magnesium condition (0.024 g of magnesium/100 g of diet) aggravated the deposition of calcium and the low magnesium status. The apparent magnesium absorption ratios and femur magnesium concentration in the rats fed a calcium gluconate diet (an equimolar mixture of calcium gluconate and calcium carbonate was used as a source of calcium) were significantly higher than in the rats fed a calcium carbonate diet (only calcium carbonate was used as a source of calcium), irrespective of dietary magnesium concentration. Dietary calcium gluconate lessened the accumulation of calcium in the kidney and increased the serum magnesium concentration compared with dietary calcium carbonate, when the rats were fed the normal magnesium diet (0.049 g of magnesium/100 g of diet) but not the low magnesium diet. We speculate that the increased utilization of magnesium by feeding the calcium gluconate diet to a limited extent prevented the low magnesium status and the severity of nephrocalcinosis caused by adding excess dietary phosphorus and calcium.

  14. High-Dose Vitamin D and Calcium Attenuates Bone Loss with Antiretroviral Therapy Initiation

    Science.gov (United States)

    Overton, Edgar Turner; Chan, Ellen S.; Brown, Todd T.; Tebas, Pablo; McComsey, Grace A.; Melbourne, Kathleen M.; Napoli, Andrew; Hardin, William Royce; Ribaudo, Heather J.; Yin, Michael T.

    2015-01-01

    Background Antiretroviral therapy (ART) initiation for HIV-1 infection is associated with 2-6% loss in bone mineral density (BMD). Objective To evaluate vitamin D3 (4000 IU daily) plus calcium (1000 mg calcium carbonate daily) supplementation on bone loss associated with ART initiation. Design 48-week prospective, randomized, double-blind, placebo-controlled study. Setting Thirty nine AIDS Clinical Trials Network research units. Participants ART-naïve HIV-infected adults. Measurements BMD by dual-energy X-ray absorptiometry (DXA); 25-hydroxy vitamin D (25(OH)D) levels, parathyroid hormone (PTH), phosphate metabolism, markers of bone turnover and systemic inflammation. Results 165 eligible subjects were randomized (79 Vitamin D/calcium (VitD/Cal); 86 placebo); 142 subjects with evaluable DXA data were included in the primary analysis. The study arms were well-balanced at baseline: median age 33 years; 90% male; 33% non-Hispanic black; median CD4 count 341 cells/mm3; and median 25(OH)D 23 ng/mL (57 nmol/L). At 48 weeks, subjects receiving placebo had greater decline in total hip BMD than VitD/Cal: −3.19% median change (1st-3rd quartile (Q1, Q3) −5.12%, −1.02%) vs. (−1.46% −3.16%,−0.40%). respectively (p=0.001). Lumbar spine BMD loss for the two groups was similar: −2.91% (−4.84%, −1.06%) vs. −1.41% (−3.78%, 0.00%), (p=0.085). At week 48, 90% of participants achieved HIV-1 RNA <50 copies/mL. Levels of 25(OH)D3 increased in the VitD/Cal but not the placebo group: median change of 24.5 (14.6, 37.8) vs. 0.7 (−5.3, 4.3) ng/mL, respectively (p<0.001). Additionally, increases in markers of bone turnover were blunted in the VitD/Cal group. Limitations No international sites were included; only 48 weeks of follow up Conclusion Vitamin D/calcium supplementation mitigates the loss of BMD seen with initiation of efavirenz/emtricitabine/tenofovir, particularly at the total hip, which is the site of greatest concern for fragility fracture. Primary Funding

  15. CNTF-ACM promotes mitochondrial respiration and oxidative stress in cortical neurons through upregulating L-type calcium channel activity.

    Science.gov (United States)

    Sun, Meiqun; Liu, Hongli; Xu, Huanbai; Wang, Hongtao; Wang, Xiaojing

    2016-09-01

    A specialized culture medium termed ciliary neurotrophic factor-treated astrocyte-conditioned medium (CNTF-ACM) allows investigators to assess the peripheral effects of CNTF-induced activated astrocytes upon cultured neurons. CNTF-ACM has been shown to upregulate neuronal L-type calcium channel current activity, which has been previously linked to changes in mitochondrial respiration and oxidative stress. Therefore, the aim of this study was to evaluate CNTF-ACM's effects upon mitochondrial respiration and oxidative stress in rat cortical neurons. Cortical neurons, CNTF-ACM, and untreated control astrocyte-conditioned medium (UC-ACM) were prepared from neonatal Sprague-Dawley rat cortical tissue. Neurons were cultured in either CNTF-ACM or UC-ACM for a 48-h period. Changes in the following parameters before and after treatment with the L-type calcium channel blocker isradipine were assessed: (i) intracellular calcium levels, (ii) mitochondrial membrane potential (ΔΨm), (iii) oxygen consumption rate (OCR) and adenosine triphosphate (ATP) formation, (iv) intracellular nitric oxide (NO) levels, (v) mitochondrial reactive oxygen species (ROS) production, and (vi) susceptibility to the mitochondrial complex I toxin rotenone. CNTF-ACM neurons displayed the following significant changes relative to UC-ACM neurons: (i) increased intracellular calcium levels (p ACM (p ACM promotes mitochondrial respiration and oxidative stress in cortical neurons through elevating L-type calcium channel activity.

  16. Assessment of salivary calcium, phosphate, magnesium, pH, and flow rate in healthy subjects, periodontitis, and dental caries

    Directory of Open Access Journals (Sweden)

    K S Rajesh

    2015-01-01

    Full Text Available Aim: This study was conducted to estimate and compare inorganic salivary calcium, phosphate, magnesium, salivary flow rate, and pH of unstimulated saliva and oral hygiene status of healthy subjects, subjects with periodontitis and dental caries, and to correlate salivary calcium level with number of intact teeth. Materials and Methods: The study population consisted of 48 systemically healthy subjects in the age group of 18-55 years, which was further divided into three groups: healthy, periodontitis, and dental caries. Oral hygiene index-simplified, probing pocket depth, clinical attachment level, the number of intact teeth, and active carious lesions were recorded. Estimation of inorganic salivary calcium, phosphate, and magnesium was performed spectrophotometrically using Vitros 5.1 FS. Statistical analysis was performed using the one-way analysis of variance test at 5% significance level. Results: There was a statistically significant increase in inorganic salivary calcium, phosphate, pH, flow rate, and poor oral hygiene status in periodontitis group compared to dental caries and healthy group. Conclusion: Subjects with increased inorganic salivary calcium, phosphate, pH, flow rate, and poor oral hygiene are at a higher risk of developing periodontitis. Since there is increased remineralization potential, these subjects have more number of intact teeth compared to the dental caries group.

  17. Meta-analysis of genome-wide association studies identifies six new Loci for serum calcium concentrations.

    Directory of Open Access Journals (Sweden)

    Conall M O'Seaghdha

    Full Text Available Calcium is vital to the normal functioning of multiple organ systems and its serum concentration is tightly regulated. Apart from CASR, the genes associated with serum calcium are largely unknown. We conducted a genome-wide association meta-analysis of 39,400 individuals from 17 population-based cohorts and investigated the 14 most strongly associated loci in ≤ 21,679 additional individuals. Seven loci (six new regions in association with serum calcium were identified and replicated. Rs1570669 near CYP24A1 (P = 9.1E-12, rs10491003 upstream of GATA3 (P = 4.8E-09 and rs7481584 in CARS (P = 1.2E-10 implicate regions involved in Mendelian calcemic disorders: Rs1550532 in DGKD (P = 8.2E-11, also associated with bone density, and rs7336933 near DGKH/KIAA0564 (P = 9.1E-10 are near genes that encode distinct isoforms of diacylglycerol kinase. Rs780094 is in GCKR. We characterized the expression of these genes in gut, kidney, and bone, and demonstrate modulation of gene expression in bone in response to dietary calcium in mice. Our results shed new light on the genetics of calcium homeostasis.

  18. Chemical transport reactions

    CERN Document Server

    Schäfer, Harald

    2013-01-01

    Chemical Transport Reactions focuses on the processes and reactions involved in the transport of solid or liquid substances to form vapor phase reaction products. The publication first offers information on experimental and theoretical principles and the transport of solid substances and its special applications. Discussions focus on calculation of the transport effect of heterogeneous equilibria for a gas motion between equilibrium spaces; transport effect and the thermodynamic quantities of the transport reaction; separation and purification of substances by means of material transport; and

  19. Procedure for the study of acidic calcium phosphate precursor phases in enamel mineral formation.

    Science.gov (United States)

    Siew, C; Gruninger, S E; Chow, L C; Brown, W E

    1992-02-01

    Considerable evidence suggests that an acidic calcium phosphate, such as octacalcium phosphate (OCP) or brushite, is involved as a precursor in enamel and other hard tissue formation. Additionally, there is in vitro evidence suggesting that fluoride accelerates and magnesium inhibits the hydrolysis of OCP to hydroxyapatite (OHAp). As the amount of OCP or brushite in enamel cannot be measured directly in the presence of an excess of hydroxyapatite, a procedure was developed that allows for their indirect in vivo quantification as pyrophosphate. This permits study of the effects of fluoride and magnesium ions on enamel mineral synthesis. Rat incisor calcium phosphate was labeled by intraperitoneal injection of NaH2(32)PO4. The rats were then subjected to various fluoride and magnesium treatments with subcutaneous implanted osmotic pumps. They were then killed at predetermined intervals; the nascent sections of the incisors were collected, cleaned, and pyrolyzed at 500 degrees C for 48 hours to convert acidic calcium phosphates to calcium pyrophosphate; the pyrophosphate was separated from orthophosphate by anion-exchange chromatography; and the resulting fractions were counted by liquid scintillation spectrometry. The activities of the pyro- and orthophosphate fractions were used to calculate the amount of acidic calcium phosphate present in the nascent mineral. The results demonstrated that the percentage of radioactive pyrophosphate in nascent incisors decreased with time, with increasing serum F- concentration, and with decreasing serum magnesium content. The technique described here should prove to be a powerful new tool for studying the effects of various agents on biological mineral formation.

  20. Aspirin plus calcium supplementation to prevent superimposed preeclampsia: a randomized trial.

    Science.gov (United States)

    Souza, E V; Torloni, M R; Atallah, A N; Santos, G M S dos; Kulay, L; Sass, N

    2014-05-01

    Preeclampsia is an important cause of maternal and perinatal morbidity and mortality. Previous studies have tested calcium supplementation and aspirin separately to reduce the incidence of preeclampsia but not the effects of combined supplementation. The objective of this study was to investigate the effectiveness of aspirin combined with calcium supplementation to prevent preeclampsia in women with chronic hypertension. A double-blind, placebo-controlled randomized clinical trial was carried out at the antenatal clinic of a large university hospital in São Paulo, SP, Brazil. A total of 49 women with chronic hypertension and abnormal uterine artery Doppler at 20-27 weeks gestation were randomly assigned to receive placebo (N = 26) or 100 mg aspirin plus 2 g calcium (N = 23) daily until delivery. The main outcome of this pilot study was development of superimposed preeclampsia. Secondary outcomes were fetal growth restriction and preterm birth. The rate of superimposed preeclampsia was 28.6% lower among women receiving aspirin plus calcium than in the placebo group (52.2 vs 73.1%, respectively, P=0.112). The rate of fetal growth restriction was reduced by 80.8% in the supplemented group (25 vs 4.8% in the placebo vs supplemented groups, respectively; P=0.073). The rate of preterm birth was 33.3% in both groups. The combined supplementation of aspirin and calcium starting at 20-27 weeks of gestation produced a nonsignificant decrease in the incidence of superimposed preeclampsia and fetal growth restriction in hypertensive women with abnormal uterine artery Doppler.