Adjustment of the ratio of Ca/P in the ceramic coating on Mg alloy by plasma electrolytic oxidation

International Nuclear Information System (INIS)

Yao Zhongping; Li Liangliang; Jiang Zhaohua

2009-01-01

The ceramic coatings containing Ca and P were prepared on AZ91D Mg alloy by plasma electrolytic oxidation technique in NaOH system and Na 2 SiO 3 system, respectively. The phase composition, morphology and the element distribution of the coatings was studied by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. The corrosion resistance of the coatings was examined by polarizing curve methods in a 0.9% NaCl solution. In NaOH system, there were a large number of micro-holes distributing evenly on the surface of the coating, and the coating was mainly composed of Mg, Al, P and Ca. In Na 2 SiO 3 system, the micro-holes in the coatings were reduced greatly in number and the distribution of the micro-holes was uneven, and the coating was mainly composed of Mg, Al, Si, P and Ca. The ratio of Ca/P in the coating can be controlled by the adjustment of the technique parameters to a certain extent. The adjustment of the concentration of Ca 2+ in the electrolyte was an effective method to change the ratio of Ca/P in the coating in both systems; the reaction time and the working voltage for the adjustment of the ratio of Ca/P in the coating was more suitable for the NaSi 2 O 3 system than the NaOH system. The polarizing curve tests showed the coatings improved the corrosion resistance of the AZ91D Mg alloy in 0.9% NaCl solution by nearly two orders of magnitude.

Inositol phosphates influence the membrane bound Ca2+/Mg2+ stimulated ATPase from human erythrocyte membranes

International Nuclear Information System (INIS)

Kester, M.; Ekholm, J.; Kumar, R.; Hanahan, D.J.

1986-01-01

The modulation by exogenous inositol phosphates of the membrane Ca 2+ /Mg 2+ ATPase from saponin/EGTA lysed human erythrocytes was determined in a buffer (pH 7.6) containing histidine, 80 mM, MgCl 2 , 3.3 mM, NaCl, 74 mM, KCl, 30 mM, Na 2 ATP, 2.3 mM, ouabain, 0.83 mM, with variable amounts of CaCl 2 and EGTA. The ATPase assay was linear with time at 44 0 C. The inositol phosphates were commercially obtained and were also prepared from 32 P labeled rabbit platelet inositol phospholipids. Inositol triphosphate (IP 3 ) elevated the Ca 2+ /Mg 2+ ATPase activity over basal levels in a dose, time, and calcium dependent manner and were increased up to 85% of control values. Activities for the Na + /K + -ATPase and a Mg 2+ ATPase were not effected by IP 3 . Ca 2+ /Mg 2+ APTase activity with IP 2 or IP 3 could be synergistically elevated with calmodulin addition. The activation of the ATPase with IP 3 was calcium dependent in a range from .001 to .02 mM. The apparent Km and Vmax values were determined for IP 3 stimulated Ca 2+ /Mg 2+ ATPase

Break-up of Ca-montmorillonite particles by Na-montmorillonite

International Nuclear Information System (INIS)

Hedstroem, Magnus; Birgersson, Martin

2012-01-01

Document available in extended abstract form only. In the Swedish KBS-3 concept for a geological deep storage of spent nuclear fuel, bentonite of high montmorillonite content is proposed to serve as a buffer surrounding copper canisters containing the spent fuel. Montmorillonite has an exceptional affinity for water which results in the build-up of a swelling pressure when bentonite is placed in a confined volume. However, there is a concern that during and after a glaciation, meltwater of low ionic strength may cause the bentonite to swell extensively into fractures and turn into a sol that could be transported away by the seeping water. It is thus warranted to understand the behaviour of montmorillonite at aqueous condition of low ionic strength. Turbidity measurements were used to a large extent in previous work to follow the free swelling or settling process of montmorillonite in various aqueous solutions and thereby give information regarding sol formation. From theory we know that turbidity of a suspension is proportional to the particle concentration. However turbidity is also proportional to V p 2 where V p is the volume of the scattering particle. Thus the fact that turbidity of a Ca-montmorillonite suspension is higher than the turbidity of a Na- montmorillonite suspension of the same clay concentration indicates that Na-montmorillonite separate into smaller particles than Ca-montmorillonite. In this work we make use this size dependence to quantify the difference between Wyoming, Milos and Kutch montmorillonite in particular with respect to how mixed Ca/Na montmorillonite systems behave. Some Ca/Mg, Mg/Na and Na/K systems are also included for comparison. Figure 1 shows the final (stabilized) turbidity response of mixed Wy-Ca/Na montmorillonite as a function of the fraction of Ca 2+ in the clay. Starting material are suspensions of homo-ionic Wy-Ca and Wy-Na montmorillonite at a concentration of 1 g/l. The turbidity of the suspensions of the homo

Effect of calcium fluoride on sintering behaviour of SiO2-CaO-Na2O-MgO glass-ceramic system

Directory of Open Access Journals (Sweden)

Bahman Mirhadi

2012-09-01

Full Text Available The crystallization characteristics of glasses based on the SiO2-CaO-Na2O-MgO (SCNM system containing calcium fluoride (CaF2 have been investigated by differential thermal analysis (DTA, X-ray diffraction (XRD and scanning electron microscopy (SEM. The partial replacement of CaO by CaF2 in the studied glass-ceramics led to the development of different crystalline phase assemblages, including wollastonite and diopside using various heat-treatment processes. With the increase of CaF2 content, the crystallization temperature of the glass and the strength of the crystallization peak temperature decreases. Addition of CaF2 up to 6.0 mol%, as expected, improved the sinterability. This sample reached to maximum density by sintering at 950 °C.

Mg/Ca of Continental Ostracode Shells

Science.gov (United States)

Ito, E.; Forester, R. M.; Marco-Barba, J.; Mezquita, F.

2007-12-01

Marine ionic chemistry is thought to remain constant. This, together with the belief that marine calcifiers partition Mg/Ca in a systematic manner as functions of temperature (and Mg/Ca) of water forms the basis of the Mg/Ca thermometer. In continental settings both of these assumptions are usually not true. Continental waters contain a wide variety of solutes in absolute and relative ion concentrations. Hence, waters with identical Mg/Ca may have very different concentrations of Mg and Ca and very different anions. Here we use two examples to focus on the effects of ion chemistry on Mg/Ca partitioning in continental ostracode shells and we ignore the complexities of solute evolution, which can change Mg/Ca over timescales of minutes to millennia. Palacios-Fest and Dettman (2001) conducted a monthly study of ,Cypridopsis vidua at El Yeso Lake in Sonora, Mexico. They established a relation between temperature and average shell Mg/Ca using regression analyses on averaged data. When their Mg/Ca-temperature relation is applied to monthly ,C. vidua data from Page Pond near Cleveland, Ohio, water temperatures of -8 to -1°C are obtained. The observed Mg/Ca ranges for El Yeso Lake (0.31 to 0.46) and Page Pond (0.33 to 0.46) are similar, as are their specific conductivities (700 to 850μS for El Yeso Lake; 400 to 600μS for Page Pond). However, [Ca] is 140-260 mg/L for El Yeso, but only 70-90 mg/L for Page Pond. Page Pond data, in fact, shows a good temperature shell Mg/Ca relation for .C. vidua, but the relation is different from that at El Yeso. Hence, shell Mg/Ca is a multi-valued, family of curves function of temperature and Mg/Ca of water that depends on the [Mg] and [Ca] values in water and perhaps other factors. Our second example comes from sites near Valencia, Spain and involves shell data for ,Cyprideis torosa, an estuarine ostracode that is tolerant of a wide range of salinity and can live in continental waters as long as the carbonate alkalinity to Ca ratio is

In-situ thermal analysis and macroscopical characterization of Mg-xCa and Mg-0.5Ca-xZn alloy systems

Energy Technology Data Exchange (ETDEWEB)

Farahany, Saeed [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Bakhsheshi-Rad, Hamid Reza, E-mail: Rezabakhsheshi@gmail.com [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Idris, Mohd Hasbullah [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Abdul Kadir, Mohammed Rafiq [Medical Implants Technology Group, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Department of Biomechanics and Biomedical Materials, Faculty of Biomedical Engineering and Health Sciences, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Lotfabadi, Amir Fereidouni [Department of Manufacturing and Industrial Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia); Ourdjini, Ali [Department of Materials Engineering, Faculty of Mechanical Engineering, Universiti Teknologi Malaysia, 81310 Johor Bahru, Johor (Malaysia)

2012-01-10

Highlights: Black-Right-Pointing-Pointer The effect of Ca and Zn addition on Mg-Ca and Mg-Ca-Zn were investigated. Black-Right-Pointing-Pointer Ca and Zn addition decreased solid fraction at coherency point. Black-Right-Pointing-Pointer T{sub N}-T{sub DCP} increased by adding Ca and Zn in Mg-Ca and Mg-Ca-Zn, respectively. Black-Right-Pointing-Pointer Three reactions were detected when Zn/Ca atomic ratio less than 1.25 in Mg-Ca-Zn. Black-Right-Pointing-Pointer A new peak Mg{sub 51}Zn{sub 20} was identified in Mg-0.5Ca-9Zn in addition of other peaks. - Abstract: This research described the identification phases by thermal analysis and microscopy inspection of Mg-xCa and Mg-0.5%Ca-xZn alloys that were solidified at slow cooling rate. Analysis of cooling curve after Ca addition shows the evolution of the Mg{sub 2}Ca intermetallic phase at around 520 Degree-Sign C in addition to {alpha}-Mg phase. First derivative curves of alloys after the addition of Zn to Mg-0.5Ca alloy reveals three peaks related to {alpha}-Mg, Mg{sub 2}Ca and Ca{sub 2}Mg{sub 6}Zn{sub 3} for alloys that have Zn/Ca atomic ratio less than 1.23. The peak of Mg{sub 2}Ca reaction on the first derivative curves disappeared for alloys containing Zn/Ca ratio more than 1.23. A new peak was also observed at 330 Degree-Sign C for Mg-0.5Ca-9Zn which was identified as Mg{sub 51}Zn{sub 20}. Solid fraction at coherency point decreased with increasing Ca and Zn elements. However, coherency time and difference between the nucleation and coherency temperatures (T{sub N}-T{sub DCP}) increased by adding Ca and Zn in Mg-Ca and Mg-Ca-Zn systems.

Lithium-induced inhibition of Na-K ATPase and Ca ATPase activities in rat brain synaptosome.

Science.gov (United States)

Cho, Y. W.

1995-01-01

To explore the action mechanism of lithium in the brain, the author investigated the effects of lithium on Na-K ATPase and Ca ATPase in rat brain synaptosomes prepared from forebrains by the method of Booth and Clark. The activities of Na-K ATPase and Ca ATPase were assayed by the level of inorganic phosphate liberated from the hydrolysis of ATP. Lithium at the optimum therapeutic concentration of 1 mM decreased the activity of Na-K ATPase from the control value of 19.08 +/- 0.29 to 18.27 +/- 0.10 micromoles Pi/mg protein/h and also reduced the activity of Ca ATPase from 6.38 +/- 0.12 to 5.64 +/- 0.12 micromoles Pi/mg protein/h. The decreased activity of Na-K ATPase will decrease the rate of Ca2+ efflux, probably via an Na-Ca exchange mechanism and will increase the rate of Ca2+ entry by the depolarization of nerve terminals. The reduced activity of Ca ATPase will result in the decreased efflux of Ca2+. As a Conclusion, it can be speculated that lithium elevates the intrasynaptosomal Ca2+ concentration via inhibition of the activities of Na-K ATPase and Ca ATPase, and this increased [Ca2+]i will cause the release of neurotransmitters and neurological effects of lithium. PMID:7598829

Quantitative analysis of sodium di-uranate for Al, Ca, Fe, Mg, Mn, Na by flame-atomic absorption spectrometric method

International Nuclear Information System (INIS)

Jat, J.R.; Balaji Rao, Y.; Subba Rao, Y.

2015-01-01

Nuclear Fuel Complex (NFC) receives Sodium Di-Uranate (SDU) from Uranium Corporation of India Limited (UCIL) for producing sinterable UO 2 pellets for manufacturing fuel sub assemblies. Several impurities present in ore find their way into SDU during its conversion. Stringent specification have been laid down by the reactor designs for achieving the optimum performance of the fuel and several impurity element like Al, Ca, Fe, Mg, Mn, Na among others affects severely performance of UO 2 fuel. Most of the impurity including the above mentioned elements are generally analysed by ICP-OES method. However, determination of Al, Ca, Fe, Mg, Mn and Na by ICP-OES requires lot of dilution as they are present at high levels in SDU. Apart from introducing dilution error, dilution process is very tedious and time consuming work and not a preferred choice in an industrial lab like control lab where large analytical load exists and time bound analysis is a requirement. To avoid these difficulties a simple and reliable Flame Atomic absorption spectrometric technique has been developed for regular analysis. Present method involves dissolution of SDU sample in Conc. HNO 3 and after the complete dissolution the sample solution has been evaporated to near dryness on a hot plate. Subsequently sample solution has been brought into 4N HNO 3 medium

Determination of Ca, Cr, Cu, Fe, K, Mg, Na and Zn in Brazilian medicinal plants by neutron activation and atomic absorption; Determinacao de Ca, Cr, Cu, Fe, K, Mg, Na e Zn em plantas medicinais brasileiras por ativacao neutronica e absorcao atomica

Energy Technology Data Exchange (ETDEWEB)

Carvalho, Ricardo P. de; Sabino, Claudia de Vilhena S.; Franco, Milton B.; Amaral, Angela M.; Guedes, Joao B.; Assis, Adilson de C. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN), Belo Horizonte, MG (Brazil); Leite, Simone C.A.L.; Silva, Isabel R. [Pontificia Univ. Catolica de Minas Gerais, Belo Horizonte, MG (Brazil)

2002-07-01

Medicinal plants are available in the markets in Belo Horizonte, Minas Gerais. The objective of this work is to investigate the Ca, Cr, Cu, Fe, K, Mg, Na e Zn concentrations in two lots of usually known diuretics plants (azeitona do mato, cabelo de milho, cavalinha, cervejinha do campo, chapeu de couro, congonha de bugre, marmelinho do campo and quebra pedra) bought with an interval of time - six months - between the purchases. The elemental concentrations were determined applying k{sub 0} instrumental neutron activation analysis and atomic absorption spectrophotometry analysis. (author)

Thermodynamics of HEDPA protonation in different media and complex formation with Mg2+ and Ca2+

International Nuclear Information System (INIS)

Foti, Claudia; Giuffrè, Ottavia; Sammartano, Silvio

2013-01-01

Highlights: • Acid–base properties of etidronic acid in different ionic media and at different ionic strengths. • Complex formation of etidronate with Na + , K + , Ca 2+ and Mg 2+ . • Dependence on ionic strength analysed by a Debye–Hückel type equation and the SIT approach. • Suggested protonation constants calculated at I = 0.1 mol · L −1 and t = 25 °C, in different ionic media. -- Abstract: Acid–base properties of etidronic acid [(1-Hydroxyethane-1,1-diyil)bis(phosphonic acid), HEDPA] in different ionic media and at different ionic strengths (NaCl, KCl: I ⩽ 2 mol · L −1 ; (C 2 H 5 ) 4 NI: I ⩽ 1 mol · L −1 ) were studied at t = 25 °C, determining, by potentiometric and calorimetric techniques, protonation constants and enthalpy changes. The differences in the protonation constants in the different supporting electrolytes were also interpreted in terms of weak complex formation with M i L (with i = 1, 2), MLH j (with j = 1, 2, 3) and M 2 LH species (with L = HEDPA; M = Na + , K + ). The formation constants for the species of Ca 2+ and Mg 2+ , were determined by potentiometric titrations at different ionic strengths (0.1 ⩽ I/mol · L −1 ⩽ 1) in NaCl at t = 25 °C. The stability of these species is fairly high, as an example, at I = 0.1 mol · L −1 and t = 25 °C, for ML species, log β = 6.52 and 6.86, for Ca 2+ and Mg 2+ , respectively, obtained by considering simultaneously HEDPA–Na + interactions. The dependence on ionic strength was analysed by a Debye–Hückel type equation and the SIT (Specific ion Interaction Theory) approach for protonation thermodynamic parameters and by a Debye–Hückel type equation for Mg 2+ and Ca 2+ complex formation. The sequestering ability of HEDPA toward Ca 2+ and Mg 2+ was also analysed. A comparison with literature data is given

Mg and Ca isotope fractionation during CaCO3 biomineralisation

International Nuclear Information System (INIS)

Chang, Veronica T.-C.; Williams, R.J.P.; Makishima, Akio; Belshawl, Nick S.; O'Nions, R. Keith

2004-01-01

The natural variation of Mg and Ca stable isotopes of carbonates has been determined in carbonate skeletons of perforate foraminifera and reef coral together with Mg/Ca ratios to assess the influence of biomineralisation processes. The results for coral aragonite suggest its formation, in terms of stable isotope behaviour, approximates to inorganic precipitation from a seawater reservoir. In contrast, results for foraminifera calcite suggest a marked biological control on Mg isotope ratios presumably related to its low Mg content compared with seawater. The bearing of these observations on the use of Mg and Ca isotopes as proxies in paleoceanography is considered

Na, K, Ca, Mg, and U-series in fossil bone and the proposal of a radial diffusion–adsorption model of uranium uptake

International Nuclear Information System (INIS)

Cid, A.S.; Anjos, R.M.; Zamboni, C.B.; Cardoso, R.; Muniz, M.; Corona, A.; Valladares, D.L.

2014-01-01

Fossil bones are often the only materials available for chronological reconstruction of important archeological sites. However, since bone is an open system for uranium, it cannot be dated directly and therefore it is necessary to develop models for the U uptake. Hence, a radial diffusion–adsorption (RDA) model is described. Unlike the classic diffusion–adsorption (D–A) model, RDA uses a cylindrical geometry to describe the U uptake in fossil bones. The model was applied across a transverse section of a tibia of an extinct megamammal Macrauchenia patachonica from the La Paz Local Fauna, Montevideo State, Uruguay. Measurements of spatial distribution of Na, K, Ca, and Mg were also performed by neutron activation analysis (NAA). Gamma-ray spectrometric U-series dating was applied to determine the age of the bone sample. From U concentration profile, it was possible to observe the occurrence of a relatively slow and continuous uranium uptake under constant conditions that had not yet reached equilibrium, since the uranium distribution is a ∪-shaped closed-system. Predictions of the RDA model were obtained for a specific geochemical scenario, indicating that the effective diffusion coefficient D/R in this fossil bone is (2.4 ± 0.6)10 −12 cm 2 s −1 . Mean values of Na, K, Ca, and Mg contents along the radial line of the fossil tibia are consistent with the expected behavior for spatial distributions of these mineral elements across a modern bone section. This result indicates that the fossil tibia may have its mineral structure preserved. - Highlights: • The Radial diffusion–adsorption (RDA) model is described. • RDA uses a cylindrical geometry to describe the U uptake in fossil bones. • We show new data for an extinct Macrauchenia patachonica from Uruguay. • Spatial distributions of Na, K, Ca, Mg, and U across a fossil bone section. • Gamma-ray spectrometric U-series dating was applied to determine its age

In vitro degradation and electrochemical corrosion evaluations of microarc oxidized pure Mg, Mg-Ca and Mg-Ca-Zn alloys for biomedical applications.

Science.gov (United States)

Pan, Yaokun; He, Siyu; Wang, Diangang; Huang, Danlan; Zheng, Tingting; Wang, Siqi; Dong, Pan; Chen, Chuanzhong

2015-02-01

Calcium phosphate (CaP) ceramic coatings were fabricated on pure magnesium (Mg) and self-designed Mg-0.6Ca, Mg-0.55Ca-1.74Zn alloys by microarc oxidation (MAO). The coating formation, growth and biomineralization mechanisms were discussed. The coating degradability and bioactivity were evaluated by immersion tests in trishydroxymethyl-aminomethane hydrochloric acid (Tris-HCl) buffer and simulated body fluid (SBF) solutions, respectively. The coatings and corrosion products were characterized by scanning electron microscope (SEM), X-ray diffractometer (XRD), X-ray photoelectron spectrometer (XPS) and fourier transform infrared spectrometer (FT-IR). The electrochemical workstation was used to investigate the electrochemical corrosion behaviors of substrates and coatings. Results showed that Mg-0.55Ca-1.74Zn alloy exhibits the highest mechanical strength and electrochemical corrosion resistance among the three alloys. The MAO-coated Mg-0.55Ca-1.74Zn alloy has the potential to be served as a biodegradable implant. Copyright © 2014 Elsevier B.V. All rights reserved.

[Properties and localization of Mg- and Ca-ATpase activities in wheat embryo cell nuclei].

Science.gov (United States)

Vasil'eva, N A; Belkina, G G; Stepanenko, S Y; Atalykova, F I; Oparin, A I

1978-05-01

The isolated nuclei of wheat embryo possess the ATPase activity. The addition of Mg2+ and Ca2+ significantly increases the activities of nuclear ATPases, whereas Hg2+, Cu2+ and Mn2+ inhibit the activity. The activating effect of Mg2+ is enhanced by an addition of Na and K ions. The activity of wheat embryo nuclear Mg-ATPase is higher than its Ca-ATPase activity; both ATPases also differ in their pH optima. Separation of total nuclear protein according to the solubility of its individual protein components in wheat and strong salt solutions, using the detergents, as well as ammonium sulfate precipitation and dialysis do not result in separation of Mg-activated and Ca-activated ATPases, although their levels of activities and ratios change in the course of fractionation. The Mg- and Ca-ATPase activities of the wheat embryo nuclei were found in the nuclear fraction of albumin, in nonhistone proteins and nuclear membranes. In the albumin nuclear fraction and subfractions of non-histone proteins the higher level of activity is observed in Ca-ATPase, whereas in the nuclei and soluble fractions of residual proteins in Mg-ATPase.

Synthesis, bioactivity and preliminary biocompatibility studies of glasses in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2.

Science.gov (United States)

Tulyaganov, D U; Agathopoulos, S; Valerio, P; Balamurugan, A; Saranti, A; Karakassides, M A; Ferreira, J M F

2011-02-01

New compositions of bioactive glasses are proposed in the CaO-MgO-SiO(2)-Na(2)O-P(2)O(5)-CaF(2) system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO(4)) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts' cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C).

Instrumental neutron-activation analysis applications in the age dynamics assessment of Ca, Cl, K, Mg. Mn, Na, P, and Sr contents in the human cortical bone

International Nuclear Information System (INIS)

Zaichick, V.

2003-01-01

Full text: Senile osteoporosis and particularly osteoporosis among postmenopausal women represents an urgent problem of modern medicine. One of the main osteoporosis symptoms is a decrease in both bone mineral density and subsequent bone strength. The upper extremity of the femur in humans is a particularly vulnerable section of the skeleton, being subject to fracture and necrosis and to destruction of its cartilage. Iliac crest biopsies are commonly taken clinically on patients. It is known that the control of the mineral component providing bone strength is a good indicator to detect bone diseases like osteoporosis. Despite this, changes of chemical element contents occurring with age in the femoral head and the iliac crest of female and male separately have been little studied, but in iliac cortical bone have not been studied at all. The effect of age and sex on chemical element contents in intact cortical bone of femoral neck and iliac crest of 81 relatively healthy 15-55 years old women (n=36) and men (n=45) was investigated. All subjects had died suddenly and bone samples were obtained at necropsy from the right side of bodies within twenty-four hours after death. A tool made of titanium and plastic was used to clear samples from soft tissues and blood and to cut cortical part of bone. The IAEA and NIST reference materials (H-5 animal bone and SRM1486 bone meal) were used to estimate the precision and accuracy of results. Contents of Ca, Cl, K, Mg> Mn, Na, P, and Sr in intact bone samples were determined by instrumental neutron activation analysis using short-lived radionuclides. Our means data for each element of reference materials were within the certified 95 % confidence interval, and indicate an acceptable accuracy of the obtained results. No age- and sex-related differences in the cortical femoral neck composition were detected. Mean values (M±S.E.M.) of Ca, Cl, K, Mg, Mn, Na, P, and Sr mass fractions (on dry weight basis) for female and male all

Adsorption of acetanilide herbicides on soil and its components. II. Adsorption and catalytic hydrolysis of diethatyl-ethyl on saturated Na(+)-, K(+)-, Ca(2+)-, and Mg(2+)-montmorillonite.

Science.gov (United States)

Liu, W P; Fang, Z; Liu, H J; Yang, W C

2001-04-01

Adsorption and catalytic hydrolysis of the herbicide diethatyl-ethyl [N-chloroacetyl-N-(2,6-diethylphenyl)glycine ethyl ester] on homoionic Na(+)-, K(+)-, Ca(2+)-, and Mg(2+)-montmorillonite clays were investigated in water solution. The Freundlich adsorption coefficient, Ki, got from isotherms on clay followed the order of Na+ approximately K+ > Mg2+ approximately Ca2+. Analysis of FT-IR spectra of diethatyl-ethyl adsorbed on clay suggests probable bonding at the carboxyl and amide carbonyl groups of the herbicide. The rate of herbicide hydrolysis in homoionic clay suspensions followed the same order as that for adsorption, indicating that adsorption may have preceded and thus caused hydrolysis. Preliminary product identification showed that hydrolysis occurred via nucleophilic substitution at the carboxyl carbon, causing the cleavage of the ester bond and formation of diethatyl and its dechlorinated derivative, and at the amide carbon, yielding an ethyl ester derivative and its acid. These pathways also suggest that hydrolysis of diethatyl-ethyl was catalyzed by adsorption on the clay surface.

Formation of hydroxyapatite onto glasses of the CaO-MgO-SiO2 system with B2O3, Na2O, CaF2 and P2O5 additives.

Science.gov (United States)

Agathopoulos, S; Tulyaganov, D U; Ventura, J M G; Kannan, S; Karakassides, M A; Ferreira, J M F

2006-03-01

New bioactive glasses with compositions based on the CaO-MgO-SiO(2) system and additives of B(2)O(3), P(2)O(5), Na(2)O, and CaF(2) were prepared. The in vitro mineralization behaviour was tested by immersion of powders or bulk glasses in simulated body fluid (SBF). Monitoring of ionic concentrations in SBF and scanning electron microscopy (SEM) observations at the surface of the glasses were conducted over immersion time. Raman and infrared (IR) spectroscopy shed light on the structural evolution occurring at the surface of the glasses that leads to formation of hydroxyapatite.

The phase diagrams of KCaF3 and NaMgF3 by ab initio simulations

Science.gov (United States)

Jakymiw, Clément; Vočadlo, Lidunka; Dobson, David P.; Bailey, Edward; Thomson, Andrew R.; Brodholt, John P.; Wood, Ian G.; Lindsay-Scott, Alex

2018-04-01

ABF3 compounds have been found to make valuable low-pressure analogues for high-pressure silicate phases that are present in the Earth's deep interior and that may also occur in the interiors of exoplanets. The phase diagrams of two of these materials, KCaF3 and NaMgF3, have been investigated in detail by static ab initio computer simulations based on density functional theory. Six ABF3 polymorphs were considered, as follows: the orthorhombic perovskite structure (GdFeO3-type; space group Pbnm); the orthorhombic CaIrO3 structure ( Cmcm; commonly referred to as the "post-perovskite" structure); the orthorhombic Sb2S3 and La2S3 structures (both Pmcn); the hexagonal structure previously suggested in computer simulations of NaMgF3 ( P63/ mmc); the monoclinic structure found to be intermediate between the perovskite and CaIrO3 structures in CaRhO3 ( P21/ m). Volumetric and axial equations of state of all phases considered are presented. For KCaF3, as expected, the perovskite phase is shown to be the most thermodynamically stable at atmospheric pressure. With increasing pressure, the relative stability of the KCaF3 phases then follows the sequence: perovskite → La2S3 structure → Sb2S3 structure → P63/ mmc structure; the CaIrO3 structure is never the most stable form. Above about 2.6 GPa, however, none of the KCaF3 polymorphs are stable with respect to dissociation into KF and CaF2. The possibility that high-pressure KCaF3 polymorphs might exist metastably at 300 K, or might be stabilised by chemical substitution so as to occur within the standard operating range of a multi-anvil press, is briefly discussed. For NaMgF3, the transitions to the high-pressure phases occur at pressures outside the normal range of a multi-anvil press. Two different sequences of transitions had previously been suggested from computer simulations. With increasing pressure, we find that the relative stability of the NaMgF3 phases follows the sequence: perovskite → CaIrO3 structure → Sb2

Model study of ATP and ADP buffering, transport of Ca(2+) and Mg(2+), and regulation of ion pumps in ventricular myocyte

Science.gov (United States)

Michailova, A.; McCulloch, A.

2001-01-01

We extended the model of the ventricular myocyte by Winslow et al. (Circ. Res 1999, 84:571-586) by incorporating equations for Ca(2+) and Mg(2+) buffering and transport by ATP and ADP and equations for MgATP regulation of ion transporters (Na(+)-K(+) pump, sarcolemmal and sarcoplasmic Ca(2+) pumps). The results indicate that, under normal conditions, Ca(2+) binding by low-affinity ATP and diffusion of CaATP may affect the amplitude and time course of intracellular Ca(2+) signals. The model also suggests that a fall in ATP/ADP ratio significantly reduces sarcoplasmic Ca(2+) content, increases diastolic Ca(2+), lowers systolic Ca(2+), increases Ca(2+) influx through L-type channels, and decreases the efficiency of the Na(+)/Ca(2+) exchanger in extruding Ca(2+) during periodic voltage-clamp stimulation. The analysis suggests that the most important reason for these changes during metabolic inhibition is the down-regulation of the sarcoplasmic Ca(2+)-ATPase pump by reduced diastolic MgATP levels. High Ca(2+) concentrations developed near the membrane might have a greater influence on Mg(2+), ATP, and ADP concentrations than that of the lower Ca(2+) concentrations in the bulk myoplasm. The model predictions are in general agreement with experimental observations measured under normal and pathological conditions.

Effects of administration of potassium- and sodiumchlorides on faecal excretions and salivary and alimentary concentrations of, Na, K, 134Cs, Ca, Mg and P in reindeer fed a lichen diet

Directory of Open Access Journals (Sweden)

Hans Staaland

1998-02-01

Full Text Available A comparison of the effects of administration of 350 mmol d-1 of KC1 or NaCl on faecal excretions, salivary concentrations and concentrations and pools of Na, K, 134Cs, Ca, Mg, P, and water in the alimentary tract of reindeer was carried out using three groups of three 10 months old reindeer fed a lichen diet. One group was used as a control group with no mineral supplementation. The level of K supplementation mimicked K intakes from summer pastures. NaCl was given at a rate which would mimic intake from salt licks by domestic ruminants of similar body size. Treatment with KC1 increased the salivary and alimentary concentrations and the alimentary pool sizes of K and faecal excretion of K increased. A decrease in l34Cs concentrations in all parts of the gastrointestinal tract indicated greater absorption of 134Cs during the KC1 treatment than in NaCl treated and control animals. Increased intake of Na or K had no significant effect on the digestibility of the lichen diet, but urine production increased. Little effects on pools or concentrations of Ca, Mg and P were observed. NaCl treatment increased urinary and faecal excretion of Na, but did not affect the metabolism of any of the other studied minerals.

Na+/Ca2+ exchange and Na+/K+-ATPase in the heart

Science.gov (United States)

Shattock, Michael J; Ottolia, Michela; Bers, Donald M; Blaustein, Mordecai P; Boguslavskyi, Andrii; Bossuyt, Julie; Bridge, John H B; Chen-Izu, Ye; Clancy, Colleen E; Edwards, Andrew; Goldhaber, Joshua; Kaplan, Jack; Lingrel, Jerry B; Pavlovic, Davor; Philipson, Kenneth; Sipido, Karin R; Xie, Zi-Jian

2015-01-01

This paper is the third in a series of reviews published in this issue resulting from the University of California Davis Cardiovascular Symposium 2014: Systems approach to understanding cardiac excitation–contraction coupling and arrhythmias: Na+ channel and Na+ transport. The goal of the symposium was to bring together experts in the field to discuss points of consensus and controversy on the topic of sodium in the heart. The present review focuses on cardiac Na+/Ca2+ exchange (NCX) and Na+/K+-ATPase (NKA). While the relevance of Ca2+ homeostasis in cardiac function has been extensively investigated, the role of Na+ regulation in shaping heart function is often overlooked. Small changes in the cytoplasmic Na+ content have multiple effects on the heart by influencing intracellular Ca2+ and pH levels thereby modulating heart contractility. Therefore it is essential for heart cells to maintain Na+ homeostasis. Among the proteins that accomplish this task are the Na+/Ca2+ exchanger (NCX) and the Na+/K+ pump (NKA). By transporting three Na+ ions into the cytoplasm in exchange for one Ca2+ moved out, NCX is one of the main Na+ influx mechanisms in cardiomyocytes. Acting in the opposite direction, NKA moves Na+ ions from the cytoplasm to the extracellular space against their gradient by utilizing the energy released from ATP hydrolysis. A fine balance between these two processes controls the net amount of intracellular Na+ and aberrations in either of these two systems can have a large impact on cardiac contractility. Due to the relevant role of these two proteins in Na+ homeostasis, the emphasis of this review is on recent developments regarding the cardiac Na+/Ca2+ exchanger (NCX1) and Na+/K+ pump and the controversies that still persist in the field. PMID:25772291

A new aqueous activity model for geothermal brines in the system Na-K-Ca-Mg-H-Cl-SO4-H2O from 25 to 300 degrees C

DEFF Research Database (Denmark)

Hingerl, Ferdinand F.; Wagner, Thomas; Kulik, Dmitrii A.

2014-01-01

A revised formulation (named REUNIQUAC) of the Extended Universal QUAsiChemical (EUNIQUAC) activity model has been developed, which fits excess thermodynamic properties of binary and selected aqueous ternary electrolyte solutions in the system Na-K-Ca-Mg-H-Cl-SO4-H2O over temperatures from 298 to...

The examination of Na-Ca effect on some qualitative and ...

African Journals Online (AJOL)

The effect of salt stress (NaCl) on shoot height (cm), root length (cm), dry and fresh weight (g), chlorophyll a and b, total chlorophyll (mg-1) and carotenoid amount was investigated in this study. In addition, the positive effects of Ca+2 (20 mM) were also investigated. Triticum durum Desf. Mirzabey, Kunduru-1149, and DH-6 ...

Effects of Ca on microstructure, mechanical and corrosion properties and biocompatibility of Mg-Zn-Ca alloys.

Science.gov (United States)

Yin, Ping; Li, Nian Feng; Lei, Ting; Liu, Lin; Ouyang, Chun

2013-06-01

Zn and Ca were selected as alloying elements to develop an Mg-Zn-Ca alloy system for biomedical application due to their good biocompatibility. The effects of Ca on the microstructure, mechanical and corrosion properties as well as the biocompatibility of the as-cast Mg-Zn-Ca alloys were studied. Results indicate that the microstructure of Mg-Zn-Ca alloys typically consists of primary α-Mg matrix and Ca₂Mg₆Zn₃/Mg₂Ca intermetallic phase mainly distributed along grain boundary. The yield strength of Mg-Zn-Ca alloy increased slightly with the increase of Ca content, whilst its tensile strength increased at first and then decreased. Corrosion tests in the simulated body fluid revealed that the addition of Ca is detrimental to corrosion resistance due to the micro-galvanic corrosion acceleration. In vitro hemolysis and cytotoxicity assessment disclose that Mg-5Zn-1.0Ca alloy has suitable biocompatibility.

Impact of seawater [Ca2+] on the calcification and calcite Mg / Ca of Amphistegina lessonii

NARCIS (Netherlands)

Mewes, A.; Langer, G.; Thoms, S.; Nehrke, G.; Reichart, G. J.; de Nooijer, L. J.; Bijma, J.

2015-01-01

Mg / Ca ratios in foraminiferal tests are routinely used as paleotemperature proxies, but on long timescales, they also hold the potential to reconstruct past seawater Mg / Ca. The impact of both temperature and seawater Mg / Ca on Mg incorporation in Foraminifera has been quantified by a number of

The influence of some additives to the highly carbohydrate diet on the distribution of Al, Ca, Mg, Mn and Na in teeth enamel and bones of experimental animals

International Nuclear Information System (INIS)

Bakyrdzhiev, P.

1985-01-01

An instrument neutron activation analysis had been used for the investigation of diets with different salt and permanent basic composition. The diets with MgCl 2 and methylene blue additives were used. Three groups of animals Wistar, Hamster and S. Dawley with different genetic reactivity had been fed on adlibidum for 45 days. After killing the animals the teeth enamel, mandibula and tibia had been sampled and content of Al, Mg, Mn, Na and Cl 2 was determined by means of INAA. The samples were irradiated for 1 min in the rabbit system of the experimental reactor IRT-2000. Two measurements were carried out - after a cooling time of 1 min for the determination of Al, Ca, Cl 2 , Mg, and after 2 h cooling time - for Na and Mn. The precision of the analysis was between 4 and 12%

Speciation of Zn, Fe, Ca and Mg in wine with the Donnan Membrane Technique

NARCIS (Netherlands)

Lao, Mireia; Companys, Encarnació; Weng, Liping; Puy, Jaume; Galceran, Josep

2018-01-01

Free concentrations of Zn2+, Fe3+, Ca2+ and Mg2+ in a red wine (Raimat, Catalonia, Spain) have been determined, with the Donnan Membrane Technique (DMT) for the first time. The required equilibration time benefits from the acceptor solution including major cations. K+ and Na+, mainly unbound to any

Na, K, Ca, Mg, and U-series in fossil bone and the proposal of a radial diffusion-adsorption model of uranium uptake.

Science.gov (United States)

Cid, A S; Anjos, R M; Zamboni, C B; Cardoso, R; Muniz, M; Corona, A; Valladares, D L; Kovacs, L; Macario, K; Perea, D; Goso, C; Velasco, H

2014-10-01

Fossil bones are often the only materials available for chronological reconstruction of important archeological sites. However, since bone is an open system for uranium, it cannot be dated directly and therefore it is necessary to develop models for the U uptake. Hence, a radial diffusion-adsorption (RDA) model is described. Unlike the classic diffusion-adsorption (D-A) model, RDA uses a cylindrical geometry to describe the U uptake in fossil bones. The model was applied across a transverse section of a tibia of an extinct megamammal Macrauchenia patachonica from the La Paz Local Fauna, Montevideo State, Uruguay. Measurements of spatial distribution of Na, K, Ca, and Mg were also performed by neutron activation analysis (NAA). Gamma-ray spectrometric U-series dating was applied to determine the age of the bone sample. From U concentration profile, it was possible to observe the occurrence of a relatively slow and continuous uranium uptake under constant conditions that had not yet reached equilibrium, since the uranium distribution is a ∪-shaped closed-system. Predictions of the RDA model were obtained for a specific geochemical scenario, indicating that the effective diffusion coefficient D/R in this fossil bone is (2.4 ± 0.6)10(-12) cm(2)s(-1). Mean values of Na, K, Ca, and Mg contents along the radial line of the fossil tibia are consistent with the expected behavior for spatial distributions of these mineral elements across a modern bone section. This result indicates that the fossil tibia may have its mineral structure preserved. Copyright © 2014 Elsevier Ltd. All rights reserved.

Interaction between Na+/K+-pump and Na+/Ca2+-exchanger modulates intercellular communication.

Science.gov (United States)

Matchkov, Vladimir V; Gustafsson, Helena; Rahman, Awahan; Briggs Boedtkjer, Donna M; Gorintin, Sarah; Hansen, Anne Kirstine; Bouzinova, Elena V; Praetorius, Helle A; Aalkjaer, Christian; Nilsson, Holger

2007-04-13

Ouabain, a specific inhibitor of the Na(+)/K(+)-pump, has previously been shown to interfere with intercellular communication. Here we test the hypothesis that the communication between vascular smooth muscle cells is regulated through an interaction between the Na(+)/K(+)-pump and the Na(+)/Ca(2+)-exchanger leading to an increase in the intracellular calcium concentration ([Ca(2+)](i)) in discrete areas near the plasma membrane. [Ca(2+)](i) in smooth muscle cells was imaged in cultured rat aortic smooth muscle cell pairs (A7r5) and in rat mesenteric small artery segments simultaneously with force. In A7r5 coupling between cells was estimated by measuring membrane capacitance. Smooth muscle cells were uncoupled when the Na(+)/K(+)-pump was inhibited either by a low concentration of ouabain, which also caused a localized increase of [Ca(2+)](i) near the membrane, or by ATP depletion. Reduction of Na(+)/K(+)-pump activity by removal of extracellular potassium ([K(+)](o)) also uncoupled cells, but only after inhibition of K(ATP) channels. Inhibition of the Na(+)/Ca(2+)-exchange activity by SEA0400 or by a reduction of the equilibrium potential (making it more negative) also uncoupled the cells. Depletion of intracellular Na(+) and clamping of [Ca(2+)](i) at low concentrations prevented the uncoupling. The experiments suggest that the Na(+)/K(+)-pump may affect gap junction conductivity via localized changes in [Ca(2+)](i) through modulation of Na(+)/Ca(2+)-exchanger activity.

Influência da adição de íons Ca++ e Mg++ na dureza de géis de concentrado proteíco de soro de leite bovino Influence of the addition of Ca++ and Mg++ ions on the hardness of whey protein concentrate gels

Directory of Open Access Journals (Sweden)

Márcia de Mello Luvielmo

2002-08-01

Full Text Available Inúmeros estudos vêm sendo realizados com o objetivo de compreender o comportamento das proteínas do Concentrado Protéico de Soro (CPS. A capacidade destas proteínas em formar géis estáveis a temperaturas entre 70ºC e 90ºC, é uma propriedade funcional importante para a confecção de vários produtos alimentícios, tais como: produtos de padaria, cárneos, texturizados e lácteos. A concentração protéica, pH, composição iônica e temperatura podem ser controladas para obter um gel com as características desejadas. Neste trabalho foi investigado o efeito dos íons metálicos bivalentes Ca++ e Mg++, na propriedade de dureza de géis de CPS induzidos termicamente. Dispersões protéicas a 6; 7 e 8% de proteína do CPS a pH 6,3 com 0; 7,5; 15; 30 e 75mm de CaCl2 ou MgCl2 foram aquecidas a 75ºC por 45 min, resfriadas a 4ºC por 12 horas, e os géis avaliados em um texturômetro TA-XT2. Os géis formados com maiores concentrações do sal adicionado obtiveram maiores valores de dureza na faixa estudada. Nas concentrações de 15 a 75mM os valores de dureza dos géis com a adição de CaCl2 foram significativamente maiores (pSeveral studies have been carried out to understand the behaviour of whey protein concentrates (WPC. One of the most important properties of this functional ingredient is the capacity to form stable gels in the temperature range from 70 to 90ºC, which makes it a convenient component of many foods such as bakery, meat, texturized and milk products. Protein concentration, pH, ionic composition and temperature must be kept under control in order to form products with desirable characteristics. The aim of this work was to investigate the influence of metallic divalent ions, Ca++ and Mg++, on the hardness of thermally induced WPC gels. Dispersions of WPC at 6, 7 and 8% protein, at pH 6.3 containing 0, 7, 15, 30 and 75mM CaCl2 or MgCl2 were heated at 75ºC for 45 min, followed by cooling at 4ºC for 12 hours. The gels

The local structure of Ca-Na pyroxenes. 2-Xanes studies at the Mg and A1 K edges

International Nuclear Information System (INIS)

Mottana, A.; Cibin, G.; Paris, E.; Giuli, G.; Florence Univ., Florence

1999-01-01

X-ray absorption spectra at the Mg and A1 K edges have been recorded on synthetic endmember diopside (Di) and jadeite (Jd) and on a series of natural Fe-poor Ca-Na clinopyroxenes compositionally straddling the Jd-Di join. The spectra of C2/c members of the series (C-omphacites) are different from having P2/n symmetry (P-omphacites). Differences can be explained by theoretical spectra calculated via the multiple-scattering formalism on atomic clusters with at least 89 atoms, extending to a. 0.62 nm away from the Mg viz. A1 absorber: Xanes detects in these systems medium- rather than short-range order-disorder relationships. Near-edge features of C-omphacites reflect the single-type of octahedral arrangement of the back scattering nearest-neighbours (six O atoms) around the absorber (Mg resp. A1) at the centre of the cluster (site M1). Others arise again from medium-range order. P-omphacites show more complicated spectra than C-omphacites. Their additional features reflect the increased local disorder around the probed atom (Mg resp. A1) induced by the two alternative M1, M11 configurations of the six O atoms forming the first co-ordination spheres. Mg and A1 are confirmed to be preferentially partitioned in the M1 resp. M11 site of the P-omphacite crystal structure, however never exclusively, but in a ratio close to 85:15 (plus or minus 10%) that implies a certain degree of local disorder. Changes in the relative heights of some prominent features are more evident in the A1 than in the Mg K-edge spectra. They are diagnostic to qualitatively distinguish C-from P-omphacites

The local structure of Ca-Na pyroxenes. 2-Xanes studies at the Mg and A1 K edges

Energy Technology Data Exchange (ETDEWEB)

Mottana, A. [Rome Univ. Roma Tre, Rome (Italy). Dipt. di Scienze Geologiche; Murata, T. [Kyoto University of Education, Kyoto (Japan). Dept. of Physics; Marcelli, A. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Wu, Z.Y. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati]|[Laboratoire Piere Suee, Gif-sur Yvette Cedex, (France); Cibin, G. [Istituto Nazionale di Fisica Nucleare, Frascati, RM (Italy). Laboratori Nazionali di Frascati; Paris, E. [Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra; Giuli, G. [Camerino Univ., Camerino, MC (Italy). Dipt. di Scienze della Terra]|[Florence Univ., Florence (Italy). Dipt. di Scienze della Terra

1999-07-01

X-ray absorption spectra at the Mg and A1 K edges have been recorded on synthetic end member diopside (Di) and jadeite (Jd) and on a series of natural Fe-poor Ca-Na clinopyroxenes compositionally straddling the Jd-Di join. The spectra of C2/c members of the series (C-omphacites) are different from having P2/n symmetry (P-omphacites). Differences can be explained by theoretical spectra calculated via the multiple-scattering formalism on atomic clusters with at least 89 atoms, extending to a. 0.62 nm away from the Mg viz. A1 absorber: Xanes detects in these systems medium- rather than short-range order-disorder relationships. Near-edge features of C-omphacites reflect the single-type of octahedral arrangement of the back scattering nearest-neighbours (six O atoms) around the absorber (Mg resp. A1) at the centre of the cluster (site M1). Others arise again from medium-range order. P-omphacites show more complicated spectra than C-omphacites. Their additional features reflect the increased local disorder around the probed atom (Mg resp. A1) induced by the two alternative M1, M11 configurations of the six O atoms forming the first co-ordination spheres. Mg and A1 are confirmed to be preferentially partitioned in the M1 resp. M11 site of the P-omphacite crystal structure, however never exclusively, but in a ratio close to 85:15 (plus or minus 10%) that implies a certain degree of local disorder. Changes in the relative heights of some prominent features are more evident in the A1 than in the Mg K-edge spectra. They are diagnostic to qualitatively distinguish C-from P-omphacites.

Characterization of the Micro-Arc Coatings Containing β-Tricalcium Phosphate Particles on Mg-0.8Ca Alloy

Directory of Open Access Journals (Sweden)

Mariya B. Sedelnikova

2018-04-01

Full Text Available The characterization of the microstructure, morphology, topography, composition, and physical and chemical properties of the coatings containing β-tricalcium phosphate (β-TCP particles deposited by the micro-arc oxidation (MAO method on biodegradable Mg-0.8Ca alloy has been performed. The electrolyte for the MAO process included the following components: Na2HPO4·12H2O, NaOH, NaF, and β-Ca3(PO42 (β-TCP. The coating morphology, microstructure, and compositions have been studied using scanning electron microscopy (SEM, transmission electron microscopy (TEM, energy-dispersive X-ray spectroscopy (EDX, and X-ray diffraction (XRD. With increasing of the MAO voltage from 350 to 500 V, the coating thickness and surface average roughness of the coatings increased linearly from 6 to 150 µm and from 2 to 8 µm, respectively. The coating deposited at 350 V had more homogeneous porous morphology with numerous pores similar by sizes (2–3 µm than the coatings formed at 450–500 V. The β-TCP isometric particles were included in the coating surface. The XRD recognized the amorphous-crystalline structure in the coatings with incorporation of the following phases: β-TCP, α-TCP, MgO (periclase and hydroxyapatite (HA. The corrosion experiments showed that the biodegradation rate of the Mg-0.8Ca alloy coated by calcium phosphates is almost 10 times less than that of uncoated alloy.

The parietal cell gastric H, K-ATPase also functions as the Na, K-ATPase and Ca-ATPase in altered states.

Science.gov (United States)

Ray, Tushar

2013-01-01

This article offers an explanation for the apparent lack of Na, K-ATPase activity in parietal cells although ouabain has been known to inhibit gastric acid secretion since 1962. The gastric H, K-ATPase (proton-pump) seems to be acting in altered states, thus behaving like a Na, K-ATPase (Na-pump) and/or Ca-ATPase (Ca-pump) depending on cellular needs.  This conclusion is based on the following findings. First, parietal cell fractions do not exhibit Na, K-ATPase activity at pH 7.0 but do at pH 8.5. Second, the apical plasma membrane (APM) fraction exhibits a (Ca or Mg)-ATPase activity with negligible H, K-ATPase activity. However, when assayed with Mg alone in presence of the 80 k Da cytosolic proton-pump activator (HAF), the APM fraction reveals remarkably high H, K-ATPase activity, suggesting the observed low affinity of Ca (or Mg)-ATPase is an altered state of the latter. Third, calcium (between 1 and 4 µM) shows both stimulation and inhibition of the HAF-stimulated H, K-ATPase depending on its concentration, revealing a close interaction between the  proton-pump activator and local Ca concentration in gastric H, K-ATPase function. Such interactions suggest that Ca is acting as a terminal member of the intracellular signaling system for the HAF-regulated proton-pump. It appears that during resting state, the HAF-associated H, K-ATPase remains inhibited by Ca (>1 µM) and, prior to resumption of acid secretion the gastric H, K-ATPase acts temporarily as a Ca-pump for removing excess Ca from its immediate environment. This conclusion is consistent with the recent reports of immunochemical co-localization of the gastric H, K-ATPase and Ca-ATPase by superimposition in parietal cells, and a transitory efflux of Ca immediately preceding the onset of acid secretion. These new perspectives on proton-pump function would open new avenues for a fuller understanding of the intracellular regulation of the ubiquitous Na-pump.

Hydrogen absorption kinetics and structural properties of Mg85Ni10Ca5 and Mg90Ni10

International Nuclear Information System (INIS)

Aoki, Masakazu; Saito, Katsushi; Towata, Shin-ichi

2005-01-01

Mg 85 Ni 10 Ca 5 and Mg 90 Ni 10 were prepared by melting mixtures of the elements in mild steel crucibles and pouring them into copper molds. Hydrogen absorption kinetics and structural properties of the alloys were characterized by the volumetric method using a Sievert's apparatus, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The crystallite size of Mg in Mg 85 Ni 10 Ca 5 , which is evaluated by XRD peak broadening, is about 50% smaller than that in Mg 90 Ni 10 . In addition, the nanometer-scale structure composed of Mg, Mg 2 Ni, Mg 2 Ca was observed in Mg 85 Ni 10 Ca 5 . Mg 85 Ni 10 Ca 5 shows better hydrogen absorption kinetics than Mg 90 Ni 10 in the temperature range of room temperature to 573 K. The better absorption kinetics of Mg 85 Ni 10 Ca 5 is mainly attributed to the nanometer-scale structure

The existence and stability of the anions matching the MFk+2- formula (M = Li, Na, K, Be, Mg, Ca, B, Al, Ga)

Science.gov (United States)

Marchaj, Marzena; Freza, Sylwia; Skurski, Piotr

2013-02-01

The electronic stabilities of the MFk+2- anions (where M = Li, Na, K, Be, Mg, Ca, B, Al, Ga; and k is the maximal formal valence of atom M) were investigated at the OVGF/6-311 + G(3df) level. The vertical electron detachment energies (VDE) of the anions examined were found to be large (7.1-10.1 eV) albeit not significantly exceeding those for the corresponding MFk+1- superhalogen anions. Even though all the MFk+2- species studied were predicted to be both geometrically and electronically stable, some of them turned out to be thermodynamically unstable (i.e., susceptible to the F atom loss).

Carbonate mineral solubility at low temperatures in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system

Science.gov (United States)

Marion, Giles M.

2001-06-01

Carbonate minerals have played an important role in the geochemical evolution of Earth, and may have also played an important role in the geochemical evolution of Mars and Europa. Several models have been published in recent years that describe chloride and sulfate mineral solubilities in concentrated brines using the Pitzer equations. Few of these models are parameterized for subzero temperatures, and those that are do not include carbonate chemistry. The objectives of this work are to estimate Pitzer-equation bicarbonate-carbonate parameters and carbonate mineral solubility products and to incorporate them into the FREZCHEM model to predict carbonate mineral solubilities in the Na-K-Mg-Ca-H-Cl-SO 4-OH-HCO 3-CO 3-CO 2-H 2O system at low temperatures (≤25°C) with a special focus on subzero temperatures. Most of the Pitzer-equation parameters and equilibrium constants are taken from the literature and extrapolated into the subzero temperature range. Solubility products for 14 sodium, potassium, magnesium, and calcium bicarbonate and carbonate minerals are included in the model. Most of the experimental data are at temperatures ≥ -8°C; only for the NaHCO 3-NaCl-H 2O and Na 2CO 3-NaCl-H 2O systems are there bicarbonate and carbonate data to temperatures as low as -21.6°C. In general, the fit of the model to the experimental data is good. For example, calculated eutectic temperatures and compositions for NaHCO 3, Na 2CO 3, and their mixtures with NaCl and Na 2SO 4 salts are in good agreement with experimental data to temperatures as low as -21.6°C. Application of the model to eight saline, alkaline carbonate waters give predicted pHs ranging from 9.2 to 10.2, in comparison with measured pHs that range from 8.7 to 10.2. The model suggests that the CaCO 3 mineral that precipitates during seawater freezing is probably calcite and not ikaite. The model demonstrates that a proposed salt assemblage for the icy surface of Europa consisting of highly hydrated MgSO 4

Study and application of neutron activation analysis and related methods for determination of content of Na, K, Cu, Co, Mn, Ca, Mg, Fe, P and Zn in a lot of speciality fruits of Vietnam (banana, orange, longan, dragon and mango)

International Nuclear Information System (INIS)

Nguyen Van Minh; Le Thi Ngoc Trinh; Le Thai Dung; Ta Thi Tuyet Nhung; Nguyen Dang Khoa; Nguyen Tien Dat; Nguyen Thi Hong Tham; Cao Dong Vu

2007-01-01

To study the content of trace elements Na, K, Cu, Co, Mn, Ca, Mg, Fe, P and Zn in the speciality fruits is necessary and very important. We collected the studying samples in four Cities such as: Dalat, NhaTrang, HoChiMinh and BinhDuong. The studying samples are: Banana, Orange, Longan, Dragon and Mango. These samples were dried in the Deepfreezer at -40 o C. We analyzed Na, K, Cu, Co, Mn, Ca, Mg, Fe and Zn by neutron activation analysis (INAA, RNAA) and after irradiation measured total β for P. The studying results were shown in the tables. (author)

Study and application of neutron activation analysis and related methods for determination of content of Na, K, Cu, Co, Mn, Ca, Mg, Fe, P and Zn in a lot of speciality fruits of Vietnam (banana, orange, longan, dragon and mango)

Energy Technology Data Exchange (ETDEWEB)

Minh, Nguyen Van; Ngoc Trinh, Le Thi; Dung, Le Thai; Tuyet Nhung, Ta Thi; Khoa, Nguyen Dang; Dat, Nguyen Tien; Hong Tham, Nguyen Thi; Vu, Cao Dong [Center for Analytical Techniques, Nuclear Research Institute, Dalat (Viet Nam)

2007-12-15

To study the content of trace elements Na, K, Cu, Co, Mn, Ca, Mg, Fe, P and Zn in the speciality fruits is necessary and very important. We collected the studying samples in four Cities such as: Dalat, NhaTrang, HoChiMinh and BinhDuong. The studying samples are: Banana, Orange, Longan, Dragon and Mango. These samples were dried in the Deepfreezer at -40{sup o}C. We analyzed Na, K, Cu, Co, Mn, Ca, Mg, Fe and Zn by neutron activation analysis (INAA, RNAA) and after irradiation measured total {beta} for P. The studying results were shown in the tables. (author)

Effect of sterilization process on surface characteristics and biocompatibility of pure Mg and MgCa alloys

International Nuclear Information System (INIS)

Liu, X.L.; Zhou, W.R.; Wu, Y.H.; Cheng, Y.; Zheng, Y.F.

2013-01-01

The aim of this work was to investigate the effect of various sterilization methods on surface characteristics and biocompatibility of MgCa alloy, with pure Mg as a comparison, including steam autoclave sterilization (SA), ethylene oxide steam sterilization (EO), glutaraldehyde sterilization (GD), dry heat sterilization (DH) and Co60 γ ray radiation sterilization (R) technologies. The surface characterizations were performed by environmental scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, grazing incidence X-ray diffraction, water contact angle and surface free energy measurement, whereas the cytotoxicity and hemocompatibility were evaluated by cellular adhesive experiment, platelet adhesion and hemolysis test. The results showed that the five sterilization processes caused more changes on the surface of MgCa alloy than that on the surface of pure Mg. The GD sterilization caused the most obvious changes on the surface of the pure Mg, and the SA sterilization made the largest alteration on the MgCa alloy surface. The GD and DH sterilization processes could cause increases on surface free energy for both pure Mg and MgCa alloys, while the other three sterilization processes reduced the surface free energy. The DH and GD sterilization processes caused the least alteration on the cell adhesion on pure Mg surface, whereas the EO sterilization performed the greatest impact on the cell adhesion on the Mg–Ca alloy surface. The hemolysis percentage of pure Mg and MgCa alloys were reduced by SA sterilization, meanwhile the other four sterilization processes increased their hemolysis percentages significantly, especially for the EO sterilization. - Highlights: • The effect of sterilization on surface chemistry and biocompatibility was studied. • Sterilization caused more surface changes on MgCa alloy than pure Mg. • Co60 γ ray radiation is the most appropriate sterilization process

Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na) adsorbed to phyllosilicate clay minerals

Science.gov (United States)

Oerter, Erik; Finstad, Kari; Schaefer, Justin; Goldsmith, Gregory R.; Dawson, Todd; Amundson, Ronald

2014-07-01

In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit δ18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The δ18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured δ18O values up to 1.55‰ relative to pure water at 5% water content, declining to 0.49‰ depletion at 30% water content. K-montmorillonite enriched measured δ18O values up to 0.86‰ at 5% water content, declining to 0.11‰ enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the δ18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral

Synthesis of Al₂Ca Dispersoids by Powder Metallurgy Using a Mg-Al Alloy and CaO Particles.

Science.gov (United States)

Fujita, Junji; Umeda, Junko; Kondoh, Katsuyoshi

2017-06-28

The elemental mixture of Mg-6 wt %Al-1 wt %Zn-0.3 wt %Mn (AZ61B) alloy powder and CaO particles was consolidated by an equal-channel angular bulk mechanical alloying (ECABMA) process to form a composite precursor. Subsequently, the precursor was subjected to a heat treatment to synthesize fine Al₂Ca particles via a solid-state reaction between the Mg-Al matrix and CaO additives. Scanning electron microscopy-energy-dispersive spectroscopy (SEM-EDS) and electron probe micro-analysis on the precursor indicated that 4.7-at % Al atoms formed a supersaturated solid solution in the α-Mg matrix. Transmission electron microscopy-EDS and X-ray diffraction analyses on the AZ61B composite precursor with 10-vol % CaO particles obtained by heat treatment confirmed that CaO additives were thermally decomposed in the Mg-Al alloy, and the solid-soluted Ca atoms diffused along the α-Mg grain boundaries. Al atoms also diffused to the grain boundaries because of attraction to the Ca atoms resulting from a strong reactivity between Al and Ca. As a result, needle-like (Mg,Al)₂Ca intermetallics were formed as intermediate precipitates in the initial reaction stage during the heat treatment. Finally, the precipitates were transformed into spherical Al₂Ca particles by the substitution of Al atoms for Mg atoms in (Mg,Al)₂Ca after a long heat treatment.

Metallic elements (Ca, Hg, Fe, K, Mg, Mn, Na, Zn) in the fruiting bodies of Boletus badius.

Science.gov (United States)

Kojta, Anna K; Falandysz, Jerzy

2016-06-01

The aim of this study was to investigate and compare the levels of eight metallic elements in the fruiting bodies of Bay Bolete (Boletus badius; current name Imleria badia) collected from ten sites in Poland to understand better the value of this popular mushroom as an organic food. Bay Bolete fruiting bodies were collected from the forest area near the towns and villages of Kętrzyn, Poniatowa, Bydgoszcz, Pelplin, Włocławek, Żuromin, Chełmno, Ełk and Wilków communities, as well as in the Augustów Primeval Forest. Elements such as Ca, Fe, K, Mg, Mn, Na and Zn were analyzed by inductively coupled plasma atomic emission spectroscopy (ICP-OES), and mercury by cold vapor atomic absorption spectrometry (CV-AAS). This made it possible to assess the nutritional value of the mushroom, as well as possible toxicological risks associated with its consumption. The results were subjected to statistical analysis (Kruskal-Wallis test, cluster analysis, principal component analysis). Copyright © 2016 Elsevier Ltd. All rights reserved.

Near-UV and blue wavelength excitable Mg{sub 0.6}Ca{sub 2.16}Mo{sub 0.2}W{sub 0.8}O{sub 6}: Eu{sub 0.12}{sup 3+}/Na{sub 0.12}{sup +} high efficiency red phosphors

Energy Technology Data Exchange (ETDEWEB)

Khanna, A. [Smart Lighting Engineering Research Center, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Electrical Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Dutta, P.S., E-mail: duttap@rpi.edu [Smart Lighting Engineering Research Center, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States); Electrical Computer and Systems Engineering, Rensselaer Polytechnic Institute, Troy, NY 12180 (United States)

2015-05-15

Red phosphors with narrow emission around 615 nm (with FWHM~5–10 nm) having chemical compositions of A{sub 0.6}Ca{sub 2.16}Mo{sub 0.2}W{sub 0.8}O{sub 6}: Eu{sub 0.12}{sup 3+}/Na{sub 0.12}{sup +} (A=Mg, Sr) have been found to exhibit the highest luminescence amongst the molybdate–tungstate family when excited by sources in the 380–420 nm wavelength range. Thus they are most suitable for enhancing color rendering index and lowering color temperature in phosphor converted white LEDs (pc-WLEDs) with near-UV/blue LED excitation sources. The excitation band edge in the near UV/blue wavelength in the reported phosphor has been attributed to the coordination environment of the transition metal ion (Mo{sup 6+}, W{sup 6+}) and host crystal structure. Furthermore the quantum efficiency of the phosphors has been enhanced by adjusting activator concentration, suitable compositional alloying using substitutional alkaline earth metal cations and charge compensation mechanisms. - Graphical abstract: The charge transfer excitation of orthorhombic Mg{sub 0.6}Ca{sub 2.16}Mo{sub 0.2}W{sub 0.8}O{sub 6}: Eu{sub 0.12}{sup 3+}/Na{sub 0.12}{sup +} is significantly higher than tetragonal CaMoO{sub 4}: Eu{sup 3+} phosphors making Mg{sub 0.6}Ca{sub 2.16}Mo{sub 0.2}W{sub 0.8}O{sub 6}: Eu{sub 0.12}{sup 3+}/Na{sub 0.12}{sup +} prime candidates for fabrication of warm white phosphor-converted LEDs. - Highlights: • LED excitable Mg{sub 0.6}Ca{sub 2.16}Mo{sub 0.2}W{sub 0.8}O{sub 6}: Eu{sub 0.12}{sup 3+}/Na{sub 0.12}{sup +} phosphors were synthesized. • These phosphors are 10 times more intense than CaMoO{sub 4}: Eu{sup 3+} red phosphors. • Their intensity and efficiency were enhanced by materials optimization techniques. • Such techniques include compositional alloying, charge compensation, etc.

Biodegradable Orthopedic Magnesium-Calcium (MgCa Alloys, Processing, and Corrosion Performance

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Yuebin Guo

2012-01-01

Full Text Available Magnesium-Calcium (Mg-Ca alloy has received considerable attention as an emerging biodegradable implant material in orthopedic fixation applications. The biodegradable Mg-Ca alloys avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. They also provide sufficient mechanical strength in load carrying applications as opposed to biopolymers. However, the key issue facing a biodegradable Mg-Ca implant is the fast corrosion in the human body environment. The ability to adjust degradation rate of Mg-Ca alloys is critical for the successful development of biodegradable orthopedic implants. This paper focuses on the functions and requirements of bone implants and critical issues of current implant biomaterials. Microstructures and mechanical properties of Mg-Ca alloys, and the unique properties of novel magnesium-calcium implant materials have been reviewed. Various manufacturing techniques to process Mg-Ca based alloys have been analyzed regarding their impacts on implant performance. Corrosion performance of Mg-Ca alloys processed by different manufacturing techniques was compared. In addition, the societal and economical impacts of developing biodegradable orthopedic implants have been emphasized.

In vitro degradation and cytotoxicity of Mg/Ca composites produced by powder metallurgy.

Science.gov (United States)

Zheng, Y F; Gu, X N; Xi, Y L; Chai, D L

2010-05-01

Mg/Ca (1 wt.%, 5 wt.%, 10 wt.% Ca) composites were prepared from pure magnesium and calcium powders using the powder metallurgy method, aiming to enlarge the addition of Ca content without the formation of Mg(2)Ca. The microstructures, mechanical properties and cytotoxicities of Mg/Ca composite samples were investigated. The corrosion of Mg/Ca composites in Dulbecco's modified Eagle's medium (DMEM) for various immersion intervals was studied by electrochemical impedance spectroscopy measurements and environmental scanning electron microscope, with the concentrations of released Mg and Ca ions in DMEM for various immersion time intervals being measured. It was shown that the main constitutional phases were Mg and Ca, which were uniformly distributed in the Mg matrix. The ultimate tensile strength (UTS) and elongation of experimental composites decreased with increasing Ca content, and the UTS of Mg/1Ca composite was comparable with that of as-extruded Mg-1Ca alloy. The corrosion potential increased with increasing Ca content, whereas the current density and the impedance decreased. It was found that the protective surface film formed quickly at the initial immersion stage. With increasing immersion time, the surface film became compact, and the corrosion rate of Mg/Ca composites slowed down. The surface film consisted mainly of CaCO(3), MgCO(3)x3H(2)O, HA and Mg(OH)(2) after 72 h immersion in DMEM. Mg/1Ca and Mg/5Ca composite extracts had no significant toxicity (p>0.05) to L-929 cells, whereas Mg/10Ca composite extract induced approximately 40% reduced cell viability. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Decreasing extracellular Na+ concentration triggers inositol polyphosphate production and Ca2+ mobilization

International Nuclear Information System (INIS)

Smith, J.B.; Dwyer, S.D.; Smith, L.

1989-01-01

Removing extracellular Na+ (Na+o) evoked a large increase in cytosolic free Ca2+ concentration ([Ca2+]i in human skin fibroblasts. Decreasing [Na+]o from 120 to 14 mM caused the half-maximal peak increase in [Ca2+]i. Removing Na+o strongly stimulated 45 Ca2+ efflux and decreased total cell Ca2+ by about 40%. Bradykinin caused changes in [Ca2+]i, total Ca2+, and 45 Ca2+ fluxes similar to those evoked by removing Na+o. Prior stimulation of the cells with bradykinin prevented Na+o removal from increasing [Ca2+]i and vice versa. Na+o removal rapidly increased [ 3 H]inositol polyphosphate production. Loading the cells with Na+ had no effect on the increase in 45 Ca2+ efflux produced by Na+o removal. Therefore, decreasing [Na+]o probably stimulates a receptor(s) which is sensitive to extracellular, not intracellular, Na+. Removing Na+o also mobilized intracellular Ca2+ in smooth muscle and endothelial cells cultured from human umbilical and dog coronary arteries, respectively

Different thermostabilities of sarcoplasmic reticulum (Ca2+ + Mg2+)-ATPases from rabbit and trout muscles.

Science.gov (United States)

de Toledo, F G; Albuquerque, M C; Goulart, B H; Chini, E N

1995-05-01

Trout and rabbit (Ca2+ + Mg2+)-ATPases from sarcoplasmic reticulum were compared for differences in thermal inactivation and susceptibility to trypsin digestion. The trout ATPase is more heat-sensitive than the rabbit ATPase and is stabilized by Ca2+, Na+, K+ and nucleotides. Solubilization of both ATPases shows that the two ATPases have different protein-intrinsic inactivation kinetics. When digested by trypsin, the two ATPases display different cleavage patterns. The present results indicate that the trout and rabbit ATPases have dissimilarities in protein structure that may explain the differences in thermal inactivation kinetics.

Gastrointestinal transport of Ca2+ and Mg2+ during the digestion of a single meal in the freshwater rainbow trout.

Science.gov (United States)

Bucking, Carol; Wood, Chris M

2007-04-01

A diet containing an inert marker (ballotini beads, quantified by X-radiography) was used to quantify the transport of two essential minerals, Ca(2+) and Mg(2+) from the diet during the digestion and absorption of a single meal of commercial trout food (3% ration). Initially, net uptake of Ca(2+) was observed in the stomach followed by subsequent Ca(2+) fluxes along the intestine which were variable, but for the most part secretory. This indicated a net secretion of Ca(2+) along the intestinal tract resulting in a net assimilation of dietary Ca(2+) of 28%. Similar handling of Ca(2+) and Mg(2+) was observed along the gastrointestinal tract (GI), although net assimilation differed substantially between the cations, with Mg(2+) assimilation being close to 60%, mostly a result of greater uptake by the stomach. The stomach displayed the highest net uptake rates for both cations (1.5 and 1.3 mmol kg(-1) fish body mass for Ca(2+) and Mg(2+), respectively), occurring within 2 h following ingestion of the meal. Substantial secretions of both Ca(2+) and Mg(2+) were observed in the anterior intestine, which were attributed to bile and other intestinal secretions, while fluxes in the mid and posterior intestine were small and variable. The overall patterns of Ca(2+) and Mg(2+) handling in the GI tract were similar to those observed for Na(+) and K(+) (but not Cl(-)) in a previous study. Overall, these results emphasize the importance of dietary electrolytes in ionoregulatory homeostasis.

Characterization of Anthraquinone-DerivedRedox Switchable Ionophores and Their Complexes with Li+, Na+, K+, Ca+, and Mg+ Metal Ions

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Vaishali Vyas

2011-01-01

Full Text Available Anthraquinone derived redox switchable ionophores 1,5 bis (2-(2-(2-ethoxy ethoxy ethoxyanthracene-9,10-dione (V1 and 1,8-bis(2-(2-(2-ethoxyethoxyethoxy anthracene—9,10-dione (V2 have been used for isolation, extraction and liquid membrane transport studies of Li+, Na+, K+, Ca2+ and Mg2+ metal ions. These isolated complexes were characterized by melting point determination, CV and IR, 1H NMR spectral analysis. Ionophore V2 shows maximum shift in reduction potential (ΔE with Ca(Pic2. The observed sequence for the shifting in reduction potential (ΔE between V2 and their complexes is V2 calcium picrate (42 mV > V2 potassium picrate (33 mV > V2 lithium picrate (25 mV > V2 sodium picrate (18 mV > V2 magnesium picrate (15 mV. These findings are also supported by results of extraction, back extraction and transport studies. Ionophore V2 complexed with KPic and showed much higher extractability and selectivity towards K+ than V1. These synthetic ionophores show positive and negative cooperativity towards alkali and alkaline earth metal ions in reduced and oxidized state. Hence, this property can be used in selective separation and enrichment of metal ions using electrochemically driven ion transport.

Enhancement of the mechanoluminescence properties on Ca2MgSi2O7:Dy3+ phosphor by co-doping of charge compensator ions

Science.gov (United States)

Sahu, Ishwar Prasad

2016-08-01

In the present article, effect of charge compensator ions (R+ = Li+, Na+ and K+) on dysprosium-doped di-calcium magnesium di-silicate (Ca2MgSi2O7:Dy3+) phosphors were investigated. The Ca2MgSi2O7:Dy3+ and Ca2MgSi2O7:Dy3+, R+ phosphors, were prepared by solid-state reaction method. The crystal structures of sintered phosphors were an akermanite-type structure which belongs to the tetragonal crystallography. The peaks of mechanoluminescence (ML) intensity were increased linearly with increasing impact velocity of the moving piston. Thus, present investigation indicates that the piezoelectricity was responsible to produce ML in prepared phosphors. The time of the peak ML intensity and the decay rate did not change significantly with respect to increasing impact velocity. Addition of charge compensator ions enhances the luminescence intensity of prepared Ca2MgSi2O7:Dy3+ phosphors, because they neutralize the charge generated by Dy3+ substitution for Ca2+ ions. The role of Li+ ions among all charge compensator ions (Na+ or K+) used was found to be most effective for enhanced Dy3+ ion emission. These ML materials can be used in the devices such as stress sensor, fracture sensor, impact sensor, damage sensors, safety management monitoring system and fuse system for army warheads.

Mg,Ca-ATPase activity under irradiation

International Nuclear Information System (INIS)

Ladutin, V.V.; Orlova, V.V.; Lob, P.A.; Gerasiminko, I.V.; Mack, E.I.

2003-01-01

Full text: The influence of different doses irradiation at the Mg,Ca-ATPase activity at the rat brain has been investigated. The analyses were made at the apparatus of LKB and Carl-Ceis-Jena firm with help of reagents of Sigma and Boehringer firm. Rats decapitated after 1, 3, 6, 24 and 48 h after action of irradiation. Dose 0.206 C/kg. Erythrocytes. 1 and 3h after irradiation influence- decrease of Mg,Ca-ATPase activity to 86-87% relatively control level, 24 and 48 h - increase of activity to the control level. Dose 0.312 C/kg. Large hemispheres. 1h - decrease of ATPase activity to 90% relatively control, 3h - increase to control level, 24h - fall to 86%, after 48h small increase to 93% relatively control. Dose 9.287 C/kg. Large hemispheres. 1h - sharp fall of Mg, Ca-ATPase activity to 67 % relatively control, increase of activity to 96% after 3h and sharp fall of activity to 64% 6h after action of irradiation. Dose 9.287 C/kg. Cerebellum. 1h - sharp decrease of ATPase activity to 80%. After 3h -sharp increase to 160% relatively control level and sharp fall of ATPase activity to 47% relatively control after 6h. The mechanism of radiation pathology of active ion transport has been discussed

Teratological studies of DTPA-CaNa3, DTPA-ZnNa3 and quinamic acid in mice

International Nuclear Information System (INIS)

Luo Meichu; Ruan Tianming; Tong Shungao

1989-01-01

DTPA-CaNa 3 , DTPA-ZnNa 3 and quinamic acid are effective chelating agents for removing actinide elements from the body. In this experiment, different doses of DTPA-CaNa 3 , DTPA-ZnNa 3 and quinamic acid were given to mice on gestation days 6-10. Eight groups of mice received 0.8 and 2.0 mM/kg of DTPA-CaNa 3 , 3.8, 7.6, and 11.4 mM/kg of DTPA-ZnNa 3 and 0.42, 2.1, and 4.2 mM/kg of quinamic acid. Hypetonic saline and isotonic saline were given to two control groups. DTPA-CaNa 3 and quinamidic acid were found to be much more toxic to fetus of mice than DTPA-ZnNa 3 . When the doses of DTPA-CaMa 3 and quinamidic acid were 20 times higher than the human dose, the number of resorbed fetus was increased and the number and weight of live fetus were reduced. The result of injection with 7.6 mM/kg (200 times of human dose)DTPA-ZnNa 3 and that of injection with isotonic saline are the same. Therefore, we suggest that the DTPA-CaNa 3 and quinamidic acid should not be given to pregnant woman, if chelation therapy is needed, while the much safer DTPA-ZnNa 3 could be used

Phase formation in Mg-Sn-Si and Mg-Sn-Si-Ca alloys

Energy Technology Data Exchange (ETDEWEB)

Kozlov, A.; Groebner, J. [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Schmid-Fetzer, R., E-mail: schmid-fetzer@tu-clausthal.de [Institute of Metallurgy, Clausthal University of Technology, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)

2011-02-17

Research highlights: > The solidification paths of ternary and quaternary alloys are analyzed in detail, using the tool of thermodynamic calculations. > The precipitation sequence of phases and their amounts compare well with the microstructure of alloys. > The most efficient comparison to the experimental thermal analysis data is done by calculation of the enthalpy variation with temperature. > The viability of a procedure for the selection of multicomponent key samples is demonstrated for the development of the Mg-Ca-Si-Sn phase diagram. - Abstract: Experimental work is done and combined with the Calphad method to generate a consistent thermodynamic description of the Mg-Ca-Si-Sn quaternary system, validated for Mg-rich alloys. The viability of a procedure for the selection of multicomponent key samples is demonstrated for this multicomponent system. Dedicated thermal analysis with DTA/DSC on sealed samples is performed and the microstructure of slowly solidified alloys is analyzed using SEM/EDX. The thermodynamic description and phase diagram of the ternary Mg-Si-Sn system, developed in detail also in this work, deviates significantly from a previous literature proposal. The phase formation in ternary and quaternary alloys is analyzed using the tool of thermodynamic equilibrium and Scheil calculations for the solidification paths and compared with present experimental data. The significant ternary/quaternary solid solubilities of pertinent intermetallic phases are quantitatively introduced in the quaternary Mg-Ca-Si-Sn phase diagram and validated by experimental data.

Novel green-emitting Na2CaPO4F:Eu2+ phosphors for near-ultraviolet white light-emitting diodes

International Nuclear Information System (INIS)

Huang, Chien-Hao; Chen, Yen-Chi; Kuo, Te-Wen; Chen, Teng-Ming

2011-01-01

In this study, green-emitting Na 2 CaPO 4 F:Eu 2+ phosphors were synthesized by solid-state reactions. The excitation spectra of the phosphors showed a broad hump between 250 and 450 nm; the spectra match well with the near-ultraviolet (NUV) emission spectra of light-emitting diodes (LEDs). The emission spectrum showed an intense broad emission band centered at 506 nm. White LEDs were fabricated by integrating a 390 nm NUV chip comprising blue-emitting BaMgAl 10 O 17 :Eu 2+ , green-emitting Na 2 CaPO 4 F:0.02 Eu 2+ , and red-emitting CaAlSiN 3 :Eu 2+ phosphors into a single package; the white LEDs exhibited white light with a correlated color temperature of 5540 K, a color-rendering index of 90.75, and color coordinates (0.332, 0.365) close to those of ideal white light. - Highlights: → Novel green-emitting Na 2 CaPO 4 F:Eu 2+ phosphors were synthesized by solid-state reactions in this research. → White LEDs were fabricated by integrating a 390 nm NUV chip comprising blue-emitting BaMgAl 10 O 17 :Eu 2+ , green-emitting Na 2 CaPO 4 F:0.02Eu 2+ , and red-emitting CaAlSiN 3 :Eu 2+ phosphors into a single package. → The white LEDs exhibited white light with a correlated color temperature of 5540 K, a color-rendering index of 90.75, and color coordinates (0.332, 0.365) close to those of ideal white light.

Defect Study of MgO-CaO Material Doped with CeO2

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Han Zhang

2013-01-01

Full Text Available MgO-CaO refractories were prepared using analytical reagent chemicals of Ca(OH2 and Mg(OH2 as starting materials and CeO2 as dopant, then sintered at 1650°C for 3 h. The effect of CeO2 powders on the defect of MgO-CaO refractories was investigated. The sample characterizations were analyzed by the techniques of XRD and SEM. According to the results, with the addition of CeO2, the lattice constant of CaO increased, and the bulk density of the samples increased while apparent porosity decreased. The densification of MgO-CaO refractories was promoted obviously. In the sintering process, MgO grains grew faster than CaO, pores at the MgO-CaO grain boundaries decreased while pores in the MgO grains increased gradually, and no pores were observed in the CaO grains. The nature of the CeO2 promoting densification lies in the substitution and solution with CaO. Ce4+ approaches into CaO lattices, which enlarges the vacancy concentration of Ca2+ and accelerates the diffusion of Ca2+.

Corrosion behavior of die-cast Mg-4Al-2Sn-xCa alloy

Energy Technology Data Exchange (ETDEWEB)

Park, Kyung Chul; Kim, Byeong Ho; Kim, Kyung Ro [Defence Agency for Technology and Quality, Jinju (Korea, Republic of); Cho, Dae Hyun; Park, Ik Min [Pusan National University, Busan (Korea, Republic of)

2016-05-15

In the present work, the effect of Ca additions on microstructure and corrosion characteristics of high pressure die-cast Mg-4Al-2Sn alloy has been investigated. Mg-4Al-2Sn-xCa (x= 0, 0.3 and 0.7wt.%) alloy was prepared by using a high pressure die-casting method. Results indicated that the microstructure of Mg-4Al-2Sn alloy consisted of α-Mg, Mg{sub 17}Al{sub 12} and Mg{sub 2}Sn phase. With increase of Ca additions, CaMgSn phase was newly formed and grain size was sharply decreased. From the test results, the corrosion resistance of die-cast Mg-4Al-2Sn alloy was significantly improved by Ca addition. It is considered that stabilization of Mg(OH){sub 2} layer and refinements of microstructure with increase of Ca additions.

Crescimento , produção de matéria seca e acúmulo de N, P, K, Ca, Mg e S na parte aérea de mudas de andiroba (Carapa guianensis Aubl. cultivadas em solo de várzea, em função de diferentes doses de fósforo Growth, dry matter yield and N, P, K, Ca, Mg and S accumulation in andiroba seedling shoots (Carapa guianensis Aubl. cultivated in lowland soil, in function of phosphorus doses

Directory of Open Access Journals (Sweden)

Orlando Sílvio Caires Neves

2004-06-01

Full Text Available Com o objetivo de avaliar o efeito de diferentes doses de fósforo no crescimento e produção de matéria seca e acúmulo de N, P, K, Ca, Mg e S na parte aérea de mudas de andiroba, cultivadas em solo de várzea, foi conduzido um experimento em casa de vegetação, no Departamento de Ciências do Solo (DCS da Universidade Federal de Lavras (UFLA. O delineamento utilizado foi em blocos casualizados com cinco repetições e quatro doses de fósforo (0, 150, 300 e 450 mg dm-3 de P. Foram avaliados diâmetro do caule (mm, altura de plantas (cm, matéria seca de raiz, caule, folha e total (g planta-1. A partir dos teores dos elementos, determinou-se o acúmulo dos nutrientes com base na matéria seca. A máxima resposta física da planta de andiroba à adubação fosfatada foi obtida na faixa de 239 a 265 mg dm-3 de P. O máximo acúmulo de N, P, K, Ca, Mg e S foi atingido com as doses de 254; 287,5; 244,5; 254; 241; e 275 mg dm-3 de P, respectivamente. Os elementos em estudo que mais acumularam na parte aérea das mudas de andiroba seguem a seguinte ordem decrescente: N > Ca > K > Mg > S > P.To evaluate the effect of phosphorus application on growth, dry matter yield and N, P, K, Ca, Mg and S accumulation in "andiroba" seedling shoots, cultivated in lowland soil, an experiment was conducted under greenhouse conditions at the Soil Science Department (DCS of the Federal University of Lavras (UFLA. The experiment was conducted in a randomized block design, with five replications and four phosphorus doses (0, 150, 300 and 450 mg dm-3 of P. Stem diameter (mm, plant height (cm, root dry matter, stem, leafs and total (g plant-1 were evaluated and the accumulation of the nutrients based on dry matter was determined. The maximum physical response of andiroba to phosphorus was obtained between 239 to 265 mg dm-3 of P. The maximum accumulation of N, P, K, Ca, Mg and S was observed with the doses 254, 287,5, 244,5, 254, 241 and 275 mg dm-3 of P, respectively

Mg/Ca ratio in fertilization and agricultural soils, Mg percent of liming ...

African Journals Online (AJOL)

Strong increase of NPK (nitrogen, phosphorus and potassium) in mineral fertilization (fm) included relative delay in Mg supplementation and dilution in plant available silicon (Si) via recycled nutrients (rcl). (Silicon is not included in essential fertilizers in Finland.) Methods: We have assessed old data on Ca and Mg in ...

The synthesis and characterization of Mg-Zn-Ca alloy by powder metallurgy process

Energy Technology Data Exchange (ETDEWEB)

Annur, Dhyah; Franciska, P.L.; Erryani, Aprilia; Amal, M. Ikhlasul; Kartika, Ika, E-mail: pepeng2000@yahoo.com [Research center for Metallurgy and Material, Indonesian Institute of Science (Indonesia); Sitorus, Lyandra S. [Sultan Ageng Tirtayasa University (Indonesia)

2016-04-19

Known for its biodegradation and biocompatible properties, magnesium alloys have gained many interests to be researched as implant material. In this study, Mg-3Zn-1Ca, Mg-29Zn-1Ca, and Mg-53Zn-4.3Ca (in wt%) were synthesized by means of powder metallurgy method. The compression strength and corrosion resistance of magnesium alloy were thoroughly examined. The microstructures of the alloy were characterized using optical microscopy, Scanning Electron Microscope, and also X-ray diffraction analysis. The corrosion resistance were evaluated using electrochemical analysis. The result indicated that Mg- Zn- Ca alloy could be synthesized using powder metallurgy method. This study showed that Mg-29Zn-1Ca would make the highest mechanical strength up to 159.81 MPa. Strengthening mechanism can be explained by precipitation hardening and grain refinement mechanism. Phase analysis had shown the formation of α Mg, MgO, and intermetallic phases: Mg2Zn11 and also Ca2Mg6Zn3. However, when the composition of Zn reach 53% weight, the mechanical strength will be decreasing. In addition, all of Mg-Zn-Ca alloy studied here had better corrosion resistance (Ecorr around -1.4 VSCE) than previous study of Mg. This study indicated that Mg- 29Zn- 1Ca alloy can be further analyzed to be a biodegradable implant material.

Neutralization of Na2PO4: Reaction between Na3PO4 and CaCL2

International Nuclear Information System (INIS)

Xia Shenglan; Wang Luning

1990-01-01

The results of reaction Na 3 PO 4 with CaCl 2 in water at ambient and higher temperature are described. The reaction rate of Na 3 PO 4 with CaCl 2 is slow at ambient temperature and the reaction is complete at 260 deg C after 2 h. The products are Ca(OH) 2 and Ca 5 (PO 4 ) 3 (OH). The quantity of them is dependent upon the quanity of Na 3 PO 4 and CaCl 2 contained in water, all of them control pH of water

Corrosion study of resorbable Ca60Mg15Zn25 bulk metallic glasses in physiological fluids

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Rafał Babilas

2017-10-01

Full Text Available The corrosion activity of amorphous plates of Ca60Mg15Zn25 alloy was investigated. The biocompatible elements were selected for the alloy composition. The electrochemical corrosion and immersion tests were carried out in a multi-electrolyte fluid and Ringer's solution. Better corrosion behavior was observed for the samples tested in a multi-electrolyte fluid despite the active dissolution of Ca and Mg in Ringer's solution. The experimental results indicated that reducing concentration of NaCl from 8.6 g/dm3 for Ringer's solution to 5.75 g/dm3 caused the decrease of the corrosion rate. The volume of the hydrogen evolved after 480 min in Ringer's solution (40.1 ml/cm2 was higher in comparison with that obtained in a multi-electrolyte fluid (24.4 ml/cm2. The values of open-circuit potential (EOCP for the Ca60Mg15Zn25 glass after 1 h incubation in Ringer's solution and a multi-electrolyte fluid were determined to be −1553 and −1536 mV vs. a saturated calomel electrode (SCE. The electrochemical measurements indicated a shift of the corrosion current density (jcorr from 1062 μA/cm2 for the sample tested in Ringer's solution to 788 μA/cm2 for the specimen immersed in a multi-electrolyte fluid. The corrosion products analysis was conducted by using the X-ray photoelectron spectroscopy (XPS. The corrosion products were identified to be CaCO3, Mg(OH2, CaO, MgO and ZnO. The mechanism of corrosion process was proposed and described based on the microscopic observations. The X-ray diffraction and Fourier transform infrared spectroscopy (FTIR also indicated that Ca(OH2, CaCO3, Zn(OH2 and Ca(Zn(OH32·2H2O mainly formed on the surface of the studied alloy. Keywords: Ca-based metallic glasses, X-ray photoelectron spectroscopy, FTIR spectroscopy, X-ray diffraction, Corrosion resistance, Hydrogen evaluation

The ternary system K2SO4MgSO4CaSO4

Science.gov (United States)

Rowe, J.J.; Morey, G.W.; Silber, C.C.

1967-01-01

Melting and subsolidus relations in the system K2SO4MgSO4CaSO4 were studied using heating-cooling curves, differential thermal analysis, optics, X-ray diffraction at room and high temperatures and by quenching techniques. Previous investigators were unable to study the binary MgSO4CaSO4 system and the adjacent area in the ternary system because of the decomposition of MgSO4 and CaSO4 at high temperatures. This problem was partly overcome by a novel sealed-tube quenching method, by hydrothermal synthesis, and by long-time heating in the solidus. As a result of this study, we found: (1) a new compound, CaSO4??3MgSO4 (m.p. 1201??C) with a field extending into the ternary system; (2) a high temperature form of MgSO4 with a sluggishly reversible inversion. An X-ray diffraction pattern for this polymorphic form is given; (3) the inversion of ??-CaSO4 (anhydrite) to ??-CaSO4 at 1195??C, in agreement with grahmann; (1) (4) the melting point of MgSO4 is 1136??C and that of CaSO4 is 1462??C (using sealed tube methods to prevent decomposition of the sulphates); (5) calcium langbeinite (K2SO4??2CaSO4) is the only compound in the K2SO4CaSO4 binary system. This resolved discrepancies in the results of previous investigators; (6) a continuous solid solution series between congruently melting K2SOP4??2MgSO4 (langbeinite) and incongruently melting K2SO4??2CaSO4 (calcium langbeinite); (7) the liquidus in the ternary system consists of primary phase fields of K2SO4, MgSO4, CaSO4, langbeinite-calcium langbeinite solid solution, and CaSO4??3MgSO4. The CaSO4 field extends over a large portion of the system. Previously reported fields for the compounds (K2SO4??MgSO4??nCaSO4), K2SO4??3CaSO4 and K2SO4??CaSO4 were not found; (8) a minimum in the ternary system at: 740??C, 25% MgSO4, 6% CaSO4, 69% K2SO4; and ternary eutectics at 882??C, 49% MgSO4, 19% CaSO4, 32% K2SO4; and 880??, 67??5% MgSO4, 5% CaSO4, 27??5% K2SO4. ?? 1967.

Superhalogen properties of hetero-binuclear anions MM‧F4- and MM″F5- (M = Li, Na, M‧ = Be, Mg, Ca; M″ = B, Al, Ga)

Science.gov (United States)

Yang, Hui; Li, Ying; He, Hui-Min; Tong, Jing; Wu, Di; Li, Zhi-Ru

2017-09-01

Hetero-binuclear superhalogen anions, namely MM‧F4- and MM″F5- (M = Li, Na; M‧ = Be, Mg, Ca; M″ = B, Al, Ga), have been theoretically characterized at the MP2(FULL)/6-311+G(3df) level. It is found that two central atoms can be linked by at most three fluorine ligands. The large vertical electron detachment energies (VDEs, 7.449-8.978 eV) verify the superhalogen identity of these anions. The VDEs of both MM‧F4- and MM″F5- decrease when the atomic size of M increases whereas increase with the size of M‧ and M″. Besides, the extra electron distribution also has effect on the VDEs of such superhalogen anions.

Effect of Mg and Ca on the Stability of the MRI Contrast Agent Gd–DTPA in Seawater

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Johan Schijf

2018-04-01

Full Text Available Gadolinium diethylenetriaminepentaacetic acid (Gd–DTPA is widely applied as a contrast enhancer in medical MRI. As Gd–DTPA is only minimally captured in wastewater treatment plants (WTPs or degraded by UV light and other oxidative processes, concentrations in rivers have increased globally by orders of magnitude following its introduction in 1987. The complex also seems impervious to estuarine scavenging and is beginning to emerge in coastal waters, yet it is unknown how its stability is changed by competition for the DTPA ligand from major seawater cations. We performed potentiometric titrations at seawater ionic strength (0.7 M NaClO4 to determine dissociation constants of the five DTPA carboxylic acid groups, as well as stability constants of Mg, Ca, and Gd complexes with the fully deprotonated and single-protonated ligand. These are in general agreement with literature values at low ionic strength and confirm that complexes with Ca are more stable than with Mg. A new finding, that the DTPA complexes of Mg and Ca appear to be hydrolyzed at elevated pH, implies that their coordination in these chelates is less than hexadentate, enabling additional competition with Gd from dinuclear Mg and Ca species. Side-reaction coefficients for trace-metal-free seawater, calculated from our results, suggest that the higher abundance of Mg and Ca may significantly destabilize Gd–DTPA in coastal waters, causing dissociation and release of as much as 15% of the organically complexed Gd from the ligand. This effect could magnify the particle-reactivity and bioavailability of anthropogenic Gd in sensitive estuarine habitats, indicating an urgent need to further study the fate of this contaminant in marine environments.

Acúmulo e liberação de P, K, Ca e Mg em crotalária e milheto solteiros e consorciados

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Adriano Perin

2010-04-01

Full Text Available As características das leguminosas e gramíneas usadas como plantas de cobertura são bastante conhecidas, mas a velocidade com que os nutrientes associados à biomassa vegetal tornam-se disponíveis às culturas é ainda pouco estudada. O objetivo deste trabalho foi determinar o acúmulo e a taxa de liberação de nutrientes de crotalária e milheto solteiros ou consorciados. O delineamento experimental adotado foi blocos ao acaso, com quatro repetições. Os tratamentos foram crotalária, milheto, crotalária + milheto e vegetação espontânea. O acúmulo de P e Mg foi influenciado pela produção de massa, com valores elevados na crotalária, enquanto o acúmulo de Ca resultou tanto do maior teor quanto da maior produção de massa nos tratamentos com a leguminosa. A liberação de nutrientes dos resíduos apresentou dinâmica semelhante, com duas fases distintas: a primeira com taxas mais elevadas nos primeiros 15 dias e a segunda mais lenta a partir dessa fase. As taxas de liberação de K, Ca e Mg foram semelhantes, independentemente dos tratamentos. Os resíduos da crotalária apresentaram maior liberação de P do que as da vegetação espontânea, com meia vida de 11 dias e a vegetação espontânea de 17 dias. O Ca foi liberado mais lentamente do que os demais nutrientes, e o Mg mais rapidamente. As plantas espontâneas e o milheto apresentam importante potencial na reciclagem de K, e a crotalária se destacou na reciclagem de Ca e Mg.

Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

International Nuclear Information System (INIS)

Wang, S.F.; Li, Q.; Zu, X.T.; Xiang, X.; Liu, W.; Li, S.

2016-01-01

(Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M"2"+ ion active sites were coordinated by −OH of the water molecules except for EDTA anions. The MFe_2O_4 magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe_2O_4 of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly. - Graphical abstract: Schematic representation of the proposed model for MFe_2O_4 nanoparticle synthesis, starting from EDTA-chelated M"2"+ (M=Mg, Ca, or Ba) cations (left). High dispersion (Mg, Ca, Ba)-ferrite magnetic nanoparticles were prepared by a modified polyacrylamide gel route. Optimized utilization of polysaccharide, chelating agent, and sintering temperature allowed the formation of (Mg, Ca, Ba)-ferrite nanoparticles with a narrow diameter distribution. - Highlights: • We report a modified polyacrylamide gel route to synthesize (Mg, Ca, Ba)-ferrite magnetic nanoparticles. • Chelate mechanism of metal ions (Mg, Ca, Ba) and EDTA has been discussed. • Phase transformation process of (Mg, Ca, Ba)-ferrites has been discussed. • The preparation method increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles.

Probabilidade de resposta da cana-de-açúcar à adubação potássica em razão da relação K+ (Ca2++Mg2+ -0,5 do solo Probability of sugarcane response to potassium fertilizer as a function of soil K+ (Ca2++Mg2+ -0,5 ratio

Directory of Open Access Journals (Sweden)

Roberto dos Anjos Reis Junior

2001-09-01

Full Text Available O objetivo deste trabalho foi avaliar a probabilidade de resposta da produção de cana-de-açúcar à adubação potássica, em razão da relação K+ (Ca2++Mg2+ -0,5 no solo. Foram compilados dados de 106 experimentos de adubação potássica na cana-de-açúcar. Em cada experimento foi registrado o ciclo de cultivo (cana-planta ou cana-soca, os teores de K, Ca e Mg do solo antes da adubação potássica, a relação K+ (Ca2++Mg2+ -0,5, e se houve, ou não, resposta estatisticamente significativa da produção à adubação potássica. Foi utilizado o método estatístico de regressão logística, efetuado pelo procedimento CATMOD do Statistical Analysis System. A característica ciclo de cultivo foi eliminada do modelo, pois esta se apresentou como não-significativa no ajuste estatístico. A relação K+ (Ca2++Mg2+ -0,5 do solo influenciou a probabilidade de resposta da produção de cana-de-açúcar à adubação potássica. À medida que a relação K+ (Ca2++Mg2+ -0,5 aumentou, a probabilidade de resposta da produção de cana-de-açúcar à adubação potássica diminuiu. A relação K+ (Ca2++Mg2+ -0,5 no solo foi classificada em baixa (0,3349. A relação K+ (Ca2++Mg2+ -0,5 no solo deve ser usada como mais um critério para orientar a adubação potássica na cultura da cana-de-açúcar.This study was carried out to evaluate the effect of soil K+ (Ca2++Mg2+ -0.5 ratio on sugarcane yield response probability to potassium fertilizer. Results of 106 experiments of potassium fertilizer on sugarcane and their soil exchangeable K+, Ca2+ and Mg2+ were studied, evaluating the K+ (Ca2++Mg2+ -0.5 ratio in each experiment. The statistical method of logistic regression was used, carried out through CATMOD procedure of Statistical Analysis System. There was no difference of behavior of this ratio between plant cane and ratoons; therefore this characteristic was not significant during the adjustment of the statistical model. Soil K+ (Ca2++Mg2+ -0

Phase controlled synthesis of (Mg, Ca, Ba)-ferrite magnetic nanoparticles with high uniformity

Energy Technology Data Exchange (ETDEWEB)

Wang, S.F., E-mail: wangshifa2006@yeah.net [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Science and technology on vacuum technology and physics laboratory, Lanzhou Institute of Physics, Lanzhou 730000, Gansu (China); Li, Q. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Zu, X.T., E-mail: xtzu@uestc.edu.cn [Institute of Fundamental and Frontier Sciences, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Xiang, X.; Liu, W. [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, Sichuan (China); Li, S., E-mail: sean.li@unsw.edu.au [School of Material Science and Engineering, University of New South Wales, Sydney 2052 (Australia)

2016-12-01

(Mg, Ca, Ba)-ferrite magnetic nanoparticles were successfully synthesized through modifying the atomic ratio of polysaccharide and chelating agent at an optimal sintering temperature. In the process, the polysaccharide plays an important role in drastically shrinking the precursor during the gel drying process. In the metal-complex structure, M{sup 2+} ion active sites were coordinated by −OH of the water molecules except for EDTA anions. The MFe{sub 2}O{sub 4} magnetic nanoparticles exhibited enhanced magnetic properties when compared with nano-MFe{sub 2}O{sub 4} of similar particle size synthesized by other synthesis route reported in the literature. In particular, the sintering temperature improves the crystallinity and increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles significantly. - Graphical abstract: Schematic representation of the proposed model for MFe{sub 2}O{sub 4} nanoparticle synthesis, starting from EDTA-chelated M{sup 2+} (M=Mg, Ca, or Ba) cations (left). High dispersion (Mg, Ca, Ba)-ferrite magnetic nanoparticles were prepared by a modified polyacrylamide gel route. Optimized utilization of polysaccharide, chelating agent, and sintering temperature allowed the formation of (Mg, Ca, Ba)-ferrite nanoparticles with a narrow diameter distribution. - Highlights: • We report a modified polyacrylamide gel route to synthesize (Mg, Ca, Ba)-ferrite magnetic nanoparticles. • Chelate mechanism of metal ions (Mg, Ca, Ba) and EDTA has been discussed. • Phase transformation process of (Mg, Ca, Ba)-ferrites has been discussed. • The preparation method increases the hysteresis loop squareness ratio of (Mg, Ca, Ba)-ferrite nanoparticles.

Concentration effect on inter-mineral equilibrium isotope fractionation: insights from Mg and Ca isotopic systems

Science.gov (United States)

Huang, F.; Wang, W.; Zhou, C.; Kang, J.; Wu, Z.

2017-12-01

Many naturally occurring minerals, such as carbonate, garnet, pyroxene, and feldspar, are solid solutions with large variations in chemical compositions. Such variations may affect mineral structures and modify the chemical bonding environment around atoms, which further impacts the equilibrium isotope fractionation factors among minerals. Here we investigated the effects of Mg content on equilibrium Mg and Ca isotope fractionation among carbonates and Ca content on equilibrium Ca isotope fractionation between orthopyroxene (opx) and clinopyroxene (cpx) using first-principles calculations. Our results show that the average Mg-O bond length increases with decreasing Mg/(Mg+Ca) in calcite when it is greater than 1/48[1] and the average Ca-O bond length significantly decreases with decreasing Ca/(Ca+Mg+Fe) in opx when it ranges from 2/16 to 1/48[2]. Equilibrium isotope fractionation is mainly controlled by bond strengths, which could be measured by bond lengths. Thus, 103lnα26Mg/24Mg between dolomite and calcite dramatically increases with decreasing Mg/(Mg+Ca) in calcite [1] and it reaches a constant value when it is lower than 1/48. 103lnα44Ca/40Ca between opx and cpx significantly increases with decreasing Ca content in opx when Ca/(Ca+Mg+Fe) ranges from 2/16 to 1/48 [2]. If Ca/(Ca+Mg+Fe) is below 1/48, 103lnα44Ca/40Ca is not sensitive to Ca content. Based on our results, we conclude that the concentration effect on equilibrium isotope fractionation could be significant within a certain range of chemical composition of minerals, which should be a ubiquitous phenomenon in solid solution systems. [1] Wang, W., Qin, T., Zhou, C., Huang, S., Wu, Z., Huang, F., 2017. GCA 208, 185-197. [2] Feng, C., Qin, T., Huang, S., Wu, Z., Huang, F., 2014. GCA 143, 132-142.

Thermodynamic of hydration of a Wyoming montmorillonite saturated with Ca, Mg, Na and K

International Nuclear Information System (INIS)

Vieillard, P.; Blanc, P.; Gailhanou, H.; Gaboreau, S.; Giffaut, E.

2010-01-01

enthalpy of immersion, and isotherms of adsorption - desorption has been done for Wyoming montmorillonite saturated by Mg 2+ , Ca 2+ , Na + and K + . Smectite water-vapor pressure isotherms represent the total concentration of H 2 O taken up the sample which is distributed among the interlayers, the outer surfaces of particles and the open pore space in the sample. In order to retrieve standard state thermodynamic properties for smectite hydration and dehydration from such data, the amount of H 2 O in excess of that in the interlayer must be assessed and subtracted from the total amount taken up by the clay sample. Berend et al. (1995), Cases et al. (1992, 1997) provide careful measurements of recovering waters in both processes (hydration and dehydration) on Wyoming saturated by monovalent and divalent cations. Despite the fact that neither the hydration, nor the dehydration isotherm necessarily represents the equilibrium state of the system, the two isotherms together can be considered to bracket the equilibrium values of Xhs and the activity of H 2 O. Paired hydration and dehydration isotherm in the one hand and enthalpy of immersion in the other hand, which constitute the limits of these brackets can be regressed to assess standard state thermodynamic parameters (enthalpy and entropy) for the hydration- dehydration process. Experimental enthalpies of hydration are used in the determination of ΔH deg. hyd. W H1 and W H2 by the minimization technique. For the adsorption-desorption isotherms, the determination of parameters ΔS deg. hyd. W S1 and W S2 are obtained by minimizing the difference between measured sets of data (relative humidity and number of adsorbed interlayer water) and calculated ones. For each Wyoming saturated with one cation, six parameters are requested and characterize the standard state thermodynamic properties of hydration between smectite and interlayer H 2 O. Relations between hydration parameters ΔH deg. hyd. and ΔS deg. hyd. in the one hand

Close Association of Carbonic Anhydrase (CA2a and CA15a), Na+/H+ Exchanger (Nhe3b), and Ammonia Transporter Rhcg1 in Zebrafish Ionocytes Responsible for Na+ Uptake

Science.gov (United States)

Ito, Yusuke; Kobayashi, Sayako; Nakamura, Nobuhiro; Miyagi, Hisako; Esaki, Masahiro; Hoshijima, Kazuyuki; Hirose, Shigehisa

2013-01-01

Freshwater (FW) fishes actively absorb salt from their environment to tolerate low salinities. We previously reported that vacuolar-type H+-ATPase/mitochondrion-rich cells (H-MRCs) on the skin epithelium of zebrafish larvae (Danio rerio) are primary sites for Na+ uptake. In this study, in an attempt to clarify the mechanism for the Na+ uptake, we performed a systematic analysis of gene expression patterns of zebrafish carbonic anhydrase (CA) isoforms and found that, of 12 CA isoforms, CA2a and CA15a are highly expressed in H-MRCs at larval stages. The ca2a and ca15a mRNA expression were salinity-dependent; they were upregulated in 0.03 mM Na+ water whereas ca15a but not ca2a was down-regulated in 70 mM Na+ water. Immunohistochemistry demonstrated cytoplasmic distribution of CA2a and apical membrane localization of CA15a. Furthermore, cell surface immunofluorescence staining revealed external surface localization of CA15a. Depletion of either CA2a or CA15a expression by Morpholino antisense oligonucleotides resulted in a significant decrease in Na+ accumulation in H-MRCs. An in situ proximity ligation assay demonstrated a very close association of CA2a, CA15a, Na+/H+ exchanger 3b (Nhe3b), and Rhcg1 ammonia transporter in H-MRC. Our findings suggest that CA2a, CA15a, and Rhcg1 play a key role in Na+uptake under FW conditions by forming a transport metabolon with Nhe3b. PMID:23565095

Thermodynamic modeling of hydrogen storage capacity in Mg-Na alloys.

Science.gov (United States)

Abdessameud, S; Mezbahul-Islam, M; Medraj, M

2014-01-01

Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH3 hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems.

Evidence for a Na+/Ca2+ exchange mechanism in frog skin epithelium

DEFF Research Database (Denmark)

Madsen, K H; Brodin, Birger; Nielsen, R

1999-01-01

In the present study we investigated the possible existence of a Na+/Ca2+ exchange mechanism in the basolateral membrane of the frog skin epithelium and whether such a mechanism plays a role in the regulation of transepithelial Na+ transport. Cytosolic calcium ([Ca2+]i) was measured with the probe...... in serosal Na+ were followed by stepwise changes in [Ca2+]i. These observations indicate the existence of a Na+/Ca2+ exchange mechanism in the basolateral membrane of the frog skin epithelium. The transepithelial Na+ transport decreased from 13.2+/-1.8 to 9.2+/-1.5 microA cm-2 (n=8, P=0.049) when Na...

Sperm Na+, K+-ATPase α4 and plasma membrane Ca2+-ATPase (PMCA) 4 regulation in asthenozoospermia.

Science.gov (United States)

Lestari, Silvia W; Miati, Dessy Noor; Seoharso, P; Sugiyanto, R; Pujianto, Dwi A

2017-10-01

Asthenozoospermia, which is characterized by reduced motility, is one of the etiologies of male infertility. Its biochemical and functional consequences include altered ATPase activity. This study investigated the activities of Na + , K + -ATPase and Ca 2+ -ATPase and the expression of Na + , K + -ATPase α4 and PMCA4 isoforms in human sperm of asthenozoospermic infertile men. Nineteen samples from asthenozoospermic infertile couples were examined in this study. Computerized-assisted semen analysis (CASA) was performed, and the enzyme activity was measured based on the ability of ATPase to release organic phosphate from ATP as a substrate. The Na + , K + -ATPase α4 and PMCA4 isoform expression levels were measured by western immunoblotting, whereas the protein distribution was examined by immunocytochemistry. This showed that the Na + , K + -ATPase activity and the Na + , K + -ATPase α4 isoform expression were lower in the asthenozoospermia group than in the normozoospermia group (8.688±1.161 versus 13.851±1.884 µmol Pi/mg protein/h, respectively; p>0.05). In contrast, the Ca 2+ -ATPase activity was significantly higher in the asthenozoospermia group than in the normozoospermia group (11.154±1.186 versus 2.725±0.545 µmol Pi/mg protein/h, respectively; p0.05). The altered ATPase activity and isoform expression in asthenozoospermia may impair sperm structure and function.

MODELS FOR METAL-POOR STARS WITH ENHANCED ABUNDANCES OF C, N, O, Ne, Na, Mg, Si, S, Ca, AND Ti, IN TURN, AT CONSTANT HELIUM AND IRON ABUNDANCES

Energy Technology Data Exchange (ETDEWEB)

VandenBerg, Don A.; Dotter, Aaron [Department of Physics and Astronomy, University of Victoria, P.O. Box 3055, Victoria, B.C. V8W 3P6 (Canada); Bergbusch, Peter A. [Department of Physics, University of Regina, Regina, Saskatchewan S4S 0A2 (Canada); Ferguson, Jason W. [Department of Physics, Wichita State University, Wichita, KS 67260-0032 (United States); Michaud, Georges; Richer, Jacques [Departement de Physique, Universite de Montreal, Montreal, Quebec H3C 3J7 (Canada); Proffitt, Charles R., E-mail: vandenbe@uvic.ca, E-mail: Aaron.Dotter@gmail.com, E-mail: pbergbusch@accesscomm.ca, E-mail: proffitt@stsci.edu, E-mail: Jason.Ferguson@wichita.edu, E-mail: michaudg@astro.umontreal.ca, E-mail: jacques.richer@umontreal.ca [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

2012-08-10

Recent work has shown that most globular clusters have at least two chemically distinct components, as well as cluster-to-cluster differences in the mean [O/Fe], [Mg/Fe], and [Si/Fe] ratios at similar [Fe/H] values. In order to investigate the implications of variations in the abundances of these and other metals for H-R diagrams and predicted ages, grids of evolutionary sequences have been computed for scaled solar and enhanced {alpha}-element metal abundances, and for mixtures in which the assumed [m/Fe] value for each of the metals C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti has been increased, in turn, by 0.4 dex at constant [Fe/H]. These tracks, together with isochrones for ages from Almost-Equal-To 5 to 14 Gyr, have been computed for -3.0 {<=} [Fe/H] {<=}-0.6, with helium abundances Y = 0.25, 0.29, and 0.33 at each [Fe/H] value, using upgraded versions of the Victoria stellar structure program and the Regina interpolation code, respectively. Turnoff luminosity versus age relations from isochrones are found to depend almost entirely on the importance of the CNO cycle, and thereby mainly on the abundance of oxygen. Since C, N, and O, as well as Ne and S, do not contribute significantly to the opacities at low temperatures and densities, variations in their abundances do not impact the predicted T{sub eff} scale of red giants. The latter is a strong function of the abundances of only Mg and Si (and Fe, possibly to a lesser extent) because they are so abundant and because they are strong sources of opacity at low temperatures. For these reasons, Mg and Si also have important effects on the temperatures of main-sequence stars. Due to their low abundances, Na, Ca, and Ti are of little consequence for stellar models. The effects of varying the adopted solar metals mixture and the helium abundance at a fixed [Fe/H] are also briefly discussed.

Sintering and crystallization behavior of CaMgSi2O6-NaFeSi2O6 based glass-ceramics

International Nuclear Information System (INIS)

Goel, Ashutosh; Kansal, Ishu; Ferrari, Anna Maria; Pascual, Maria J.; Barbieri, Luisa; Bondioli, Federica; Lancellotti, Isabella; Ribeiro, Manuel J.; Ferreira, Jose M. F.

2009-01-01

We report on the synthesis, sintering, and crystallization behaviors of a glass with a composition corresponding to 90 mol % CaMgSi 2 O 6 -10 mol % NaFeSi 2 O 6 . The investigated glass composition crystallized superficially immediately after casting of the melt and needs a high cooling rate (rapid quenching) in order to produce an amorphous glass. Differential thermal analysis and hot-stage microscopy were employed to investigate the glass forming ability, sintering behavior, relative nucleation rate, and crystallization behavior of the glass composition. The crystalline phase assemblage in the glass-ceramics was studied under nonisothermal heating conditions in the temperature range of 850-950 deg. C in both air and N 2 atmosphere. X-ray diffraction studies adjoined with the Rietveld-reference intensity ratio method were employed to quantify the amount of crystalline phases, while electron microscopy was used to shed some light on the microstructure of the resultant glass-ceramics. Well sintered glass-ceramics with diopside as the primary crystalline phase were obtained where the amount of diopside varied with the heating conditions.

Thermodynamic Modeling of Hydrogen Storage Capacity in Mg-Na Alloys

Science.gov (United States)

Abdessameud, S.; Mezbahul-Islam, M.; Medraj, M.

2014-01-01

Thermodynamic modeling of the H-Mg-Na system is performed for the first time in this work in order to understand the phase relationships in this system. A new thermodynamic description of the stable NaMgH3 hydride is performed and the thermodynamic models for the H-Mg, Mg-Na, and H-Na systems are reassessed using the modified quasichemical model for the liquid phase. The thermodynamic properties of the ternary system are estimated from the models of the binary systems and the ternary compound using CALPHAD technique. The constructed database is successfully used to reproduce the pressure-composition isotherms for MgH2 + 10 wt.% NaH mixtures. Also, the pressure-temperature equilibrium diagram and reaction paths for the same composition are predicted at different temperatures and pressures. Even though it is proved that H-Mg-Na does not meet the DOE hydrogen storage requirements for onboard applications, the best working temperatures and pressures to benefit from its full catalytic role are given. Also, the present database can be used for thermodynamic assessments of higher order systems. PMID:25383361

Triphenyltin impairs a protein kinase A (PKA)-dependent increase of cytosolic Na+ and Ca2+ and PKA-independent increase of cytosolic Ca2+ associated with insulin secretion in hamster pancreatic β-cells

International Nuclear Information System (INIS)

Miura, Yoshikazu; Matsui, Hisao

2006-01-01

Oral administration of triphenyltin chloride (TPT) (60 mg/kg body weight) inhibits the insulin secretion by decreasing the cytoplasmic Ca 2+ concentration ([Ca 2+ ] i ) induced by glucose-dependent insulinotropic polypeptide (GIP) in pancreatic β-cells of the hamster. To test the possibility that the abnormal level of [Ca 2+ ] i induced by TPT administration could be due to a defect in the cAMP-dependent cytoplasmic Na + concentration ([Na + ] i ) in the β-cells, we investigated the effects of TPT administration on the changes of [Na + ] i induced by GIP, glucagon-like peptide-1 (GLP-1), or forskolin, an activator of adenylyl cyclase, and on the changes of [Na + ] i or [Ca 2+ ] i induced by 6-Bnz-cAMP, an activator of protein kinase A (PKA), and 8-pCPT-2'-O-Me-cAMP, an activator of Epac. The [Na + ] i and [Ca 2+ ] i were measured in islet cells loaded with sodium-binding benzofuran isophthalate (SBFI) and fura-2, respectively. In the presence of 135 mM Na + , TPT administration significantly reduced the rise in [Na + ] i by 10 nM GLP-1, 10 μM forskolin, and 50 μM 6-Bnz-cAMP, but had not effect in a Na + -free medium. In the presence of 135 mM Na + , TPT administration also reduced the rise in [Ca 2+ ] i by 8-pCPT-2'-O-Me-cAMP plus10 μM H-89, a inhibitor of PKA, and 6-Bnz-cAMP. Moreover, TPT administration significantly reduced the insulin secretion by 2 mM db-cAMP, GLP-1, GIP, and 8-pCPT-2'-O-Me-cAMP with and without H-89, and that by 6-Bnz-cAMP and forskolin. Our study suggested that TPT has inhibitory effects on the cellular Ca 2+ response due to a reduced Na + permeability through PKA-dependent mechanisms in hamster islet cells. Also TPT has the reduction of [Ca 2+ ] i related to Na + -dependent insulin secretion after an activation of Epac

DISSOLUTION BEHAVIOR OF BIOACTIVE GLASS CERAMICS WITH DIFFERENT CaO/MgO RATIOS

Directory of Open Access Journals (Sweden)

MUHAMMAD USMAN HASHMI

2010-03-01

Full Text Available In this work, powders of three different compositions, each having 34 SiO2-14.5 P2O5-1 CaF2-0.5 MgF (% wt and ratio of CaO/MgO varying from 11.5:1 to 1:11.5 were thoroughly mixed and melted under oxy-acetylene flame in a fire clay crucible that made the glass formation cheaper in time and cost. The melt of each composition was quenched in water to form three different glasses. Every glass was sintered at 950°C to form three glass ceramics named G1, G2 and G3 respectively. To study the dissolution behavior, each sample was immersed in a simulated body fluid (SBF for 2, 5, 10, 20 and 25 days at room temperature. Thin film XRD analysis revealed that the samples with larger CaO/MgO ratio exhibited better bioactivity. pH of SBF increased efficiently in case of G1 whereas in case of G2 and G3, this increase was slower due to greater amount of MgO. The concentrations of Ca, P, Mg and Si ions were measured by Atomic Absorption Spectroscopy. EDS analysis showed the increase in P and Ca ions and presence of C in G1 after 5 days immersion and after 10 days, in case of G2 indicating the higher formation rate of hydroxycarbonate Apatite layer in G1 as compared to G2 due to greater CaO/MgO ratio whereas in G3 Mg-hydroxycarbonate apatite (Ca(Mg5(CO3(PO43(OH (heneuite layer was recognized after 20 days showing the least bioactivity due to very large amount of Mg and the least CaO/MgO ratio.

Produção de matéria seca e eficiência nutricional para P, Ca e Mg em leguminosas herbáceas Dry matter production and nutritional efficiency for P, Ca and Mg in herbaceous legumes

Directory of Open Access Journals (Sweden)

Antonio Rodrigues Fernandes

2007-06-01

Full Text Available As leguminosas para adubação verde têm sido introduzidas nos sistemas agrícolas para a recuperação de solos desgastados pelo uso intensivo. O objetivo desse trabalho foi avaliar a resposta de leguminosas herbáceas à aplicação de calcário e fósforo sobre a produção de biomassa e eficiência nutricional para o P, Ca e Mg. O experimento foi desenvolvido em casa-de-vegetação do Departamento de Ciência do Solo da Universidade Federal Rural da Amazônia, utilizando-se um Latossolo Amarelo distrófico coletado na profundidade de 0 - 20 cm, em Belém, PA. O delineamento experimental usado foi o de blocos ao acaso, com arranjo de tratamentos em um fatorial 3³, onde foram comparadas três espécies de leguminosas: mucuna preta (Stizolobium atterrimum, mucuna cochinchinensis (Stilozobium cochinchinensis e feijão-de-porco (Canavalia ensiformes; três níveis de calagem: de calcário dolomítico (0, 4 e 8 t.ha-1 e de fósforo (0, 25 e 45 mg.dm-3, com quatro repetições cada um. Mucuna cochinchinensis e o feijão de porco produziram maiores quantidades de biomassa vegetal do que a mucuna preta, sendo que a primeira espécie acumulou maior quantidade de P e a segunda maior quantidade de Ca. Mucuna cochinchinensis apresentou maior eficiência de utilização de P, Ca e Mg na ausência da calagem. Nos solos intemperizados com baixa concentração de P, Ca e Mg, o feijão-de-porco e a mucuna cochinchinensis poderão ter melhor desempenho do que a mucuna preta, visto que apresentaram maior eficiência de translocação e de utilização desses nutrientes, respectivamente.The legumes used for green manure have been introduced in agricultural systems for recovering degraded soils by intensive use. The objective of this work was to evaluate the response of herbaceous legumes to liming and P application on dry matter and its nutritional efficiency. The experiment was developed in greenhouse at the Soil Science Department of the Federal University

Cytotoxicity assessment of adipose-derived mesenchymal stem cells on synthesized biodegradable Mg-Zn-Ca alloys

Energy Technology Data Exchange (ETDEWEB)

Fazel Anvari-Yazdi, Abbas [Department of Biomedical Engineering, Materials and Biomaterials Research Center (MBMRC), Tehran, IR (Iran, Islamic Republic of); Tahermanesh, Kobra, E-mail: tahermanesh.k@iums.ac.ir [Endometriosis and Gynecologic Disorders Research Center, Department of Ob. & Gyn., Rasoul-e Akram Hospital, Iran University of Medical Sciences (IUMS), Tehran, IR (Iran, Islamic Republic of); Hadavi, Seyed Mohammad Mehdi [Materials and Energy Research Center (MERC), Karaj, IR (Iran, Islamic Republic of); Talaei-Khozani, Tahereh [Tissue Engineering Lab, Anatomy Department, School of Medicine, Shiraz University of Medical Sciences (SUMS), Shiraz, IR (Iran, Islamic Republic of); Razmkhah, Mahboobeh [Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences (SUMS), Shiraz, IR (Iran, Islamic Republic of); Abed, Seyedeh Mehr [School of Medicine, Yasuj University of Medical Sciences (YUMS), Yasuj, IR (Iran, Islamic Republic of); Mohtasebi, Maryam Sadat [Shiraz Institute for Cancer Research, School of Medicine, Shiraz University of Medical Sciences (SUMS), Shiraz, IR (Iran, Islamic Republic of)

2016-12-01

Magnesium (Mg)-based alloys have been extensively considered as biodegradable implant materials for orthopedic surgery. Mg and its alloys are metallic biomaterials that can degrade in the body and promote new bone formation. In this study, the corrosion behavior and cytotoxicity of Mg-Zn-Ca alloys are evaluated with adipose-derived mesenchymal stem cells (ASCs). Mg-2Zn and Mg-2Zn-xCa (x = 1, 2 and 3 wt.%) alloys were designated. Mg alloys were analyzed with scanning electron microscopy and potentiodynamic polarization. To understand the in-vitro biocompatibility and cytotoxicity of Mg-2Zn and Mg-2Zn-xCa alloys, ASCs were cultured for 24 and 72 h in contact with 10%, 50% and 100% extraction of all alloys prepared in DMEM. Cell cytotoxicity and viability of ASCs were examined by MTT assay. Alloying elements including Zn and Ca improved the corrosion resistance of alloys were compared with pure Mg. The cytotoxicity results showed that all alloys had no significant adverse effects on cell viability in 24 h. After 72 h, cell viability and proliferation increased in the cells exposed to pure Mg and Mg-2Zn-1Ca extracts. The release of Mg, Zn and Ca ions in culture media had no toxic impacts on ASCs viability and proliferation. Mg-2Zn-1Ca alloy can be suggested as a good candidate to be used in biomedical applications. - Highlights: • Short and long term corrosion behavior of Mg-Zn-Ca alloys studied • Viability and toxicity of Adipose-derived Stem cells studied with Mg-Zn-Ca alloys • Understanding the morphology of cultured adipose stem cells on Mg alloys • Stem cells on Mg-Zn-Ca alloys could proliferate and expand.

Cytotoxicity assessment of adipose-derived mesenchymal stem cells on synthesized biodegradable Mg-Zn-Ca alloys

International Nuclear Information System (INIS)

Fazel Anvari-Yazdi, Abbas; Tahermanesh, Kobra; Hadavi, Seyed Mohammad Mehdi; Talaei-Khozani, Tahereh; Razmkhah, Mahboobeh; Abed, Seyedeh Mehr; Mohtasebi, Maryam Sadat

2016-01-01

Magnesium (Mg)-based alloys have been extensively considered as biodegradable implant materials for orthopedic surgery. Mg and its alloys are metallic biomaterials that can degrade in the body and promote new bone formation. In this study, the corrosion behavior and cytotoxicity of Mg-Zn-Ca alloys are evaluated with adipose-derived mesenchymal stem cells (ASCs). Mg-2Zn and Mg-2Zn-xCa (x = 1, 2 and 3 wt.%) alloys were designated. Mg alloys were analyzed with scanning electron microscopy and potentiodynamic polarization. To understand the in-vitro biocompatibility and cytotoxicity of Mg-2Zn and Mg-2Zn-xCa alloys, ASCs were cultured for 24 and 72 h in contact with 10%, 50% and 100% extraction of all alloys prepared in DMEM. Cell cytotoxicity and viability of ASCs were examined by MTT assay. Alloying elements including Zn and Ca improved the corrosion resistance of alloys were compared with pure Mg. The cytotoxicity results showed that all alloys had no significant adverse effects on cell viability in 24 h. After 72 h, cell viability and proliferation increased in the cells exposed to pure Mg and Mg-2Zn-1Ca extracts. The release of Mg, Zn and Ca ions in culture media had no toxic impacts on ASCs viability and proliferation. Mg-2Zn-1Ca alloy can be suggested as a good candidate to be used in biomedical applications. - Highlights: • Short and long term corrosion behavior of Mg-Zn-Ca alloys studied • Viability and toxicity of Adipose-derived Stem cells studied with Mg-Zn-Ca alloys • Understanding the morphology of cultured adipose stem cells on Mg alloys • Stem cells on Mg-Zn-Ca alloys could proliferate and expand

Post-Mesozoic Rapid Increase of Seawater Mg/Ca due to Enhanced Mantle-Seawater Interaction

Science.gov (United States)

Ligi, Marco; Bonatti, Enrico; Cuffaro, Marco; Brunelli, Daniele

2013-01-01

The seawater Mg/Ca ratio increased significantly from ~ 80 Ma to present, as suggested by studies of carbonate veins in oceanic basalts and of fluid inclusions in halite. We show here that reactions of mantle-derived peridotites with seawater along slow spreading mid-ocean ridges contributed to the post-Cretaceous Mg/Ca increase. These reactions can release to modern seawater up to 20% of the yearly Mg river input. However, no significant peridotite-seawater interaction and Mg-release to the ocean occur in fast spreading, East Pacific Rise-type ridges. The Mesozoic Pangean superocean implies a hot fast spreading ridge system. This prevented peridotite-seawater interaction and Mg release to the Mesozoic ocean, but favored hydrothermal Mg capture and Ca release by the basaltic crust, resulting in a low seawater Mg/Ca ratio. Continent dispersal and development of slow spreading ridges allowed Mg release to the ocean by peridotite-seawater reactions, contributing to the increase of the Mg/Ca ratio of post-Mesozoic seawater. PMID:24067442

Modulation of contraction by intracellular Na+ via Na(+)-Ca2+ exchange in single shark (Squalus acanthias) ventricular myocytes.

Science.gov (United States)

Näbauer, M; Morad, M

1992-01-01

1. The effect of direct alteration of intracellular Na+ concentration on contractile properties of whole-cell clamped shark ventricular myocytes was studied using an array of 256 photodiodes to monitor the length of the isolated myocytes. 2. In myocytes dialysed with Na(+)-free solution, the voltage dependence of Ca2+ current (ICa) and contraction were similar and bell shaped. Contractions activated at all voltages were completely suppressed by nifedipine (5 microM), and failed to show significant tonic components, suggesting dependence of the contraction on Ca2+ influx through the L-type Ca2+ channel. 3. In myocytes dialysed with 60 mM Na+, a ICa-dependent and a ICa-independent component of contraction could be identified. The Ca2+ current-dependent component was prominent in voltages between -30 to +10 mV. The ICa-independent contractions were maintained for the duration of depolarization, increased with increasing depolarization between +10 to +100 mV, and were insensitive to nifedipine. 4. In such myocytes, repolarization produced slowly decaying inward tail currents closely related to the time course of relaxation and the degree of shortening prior to repolarization. 5. With 60 mM Na+ in the pipette solution, positive clamp potentials activated decaying outward currents which correlated to the size of contraction. These outward currents appeared to be generated by the Na(+)-Ca(2+)-exchanger since they depended on the presence of intracellular Na+, and were neither suppressed by nifedipine nor by K+ channel blockers. 6. The results suggest that in shark (Squalus acanthias) ventricular myocytes, which lack functionally relevant Ca2+ release pools, both Ca2+ channel and the Na(+)-Ca2+ exchanger deliver sufficient Ca2+ to activate contraction, though the effectiveness of the latter mechanism was highly dependent on the [Na+]i. PMID:1338467

Determination of Mg/Ca ratio of stalagmite by laser multicollector inductively coupled plasma mass spectrometry

International Nuclear Information System (INIS)

He Xuexian; Zhu Xiangkun; Tang Suohan; Yang Chun; Cai Junjun; Li Shizhen; Li Zhihong

2005-01-01

A method for determining Mg/Ca of stalagmite by LA-MC-ICPMS is studied. 24 Mg/ 44 Ca (Mass 22, intensity of 44C a 2+ , collected by ion counting and mass 24, intensity of 24 Mg + , collected by Faraday cup) ratios were measured in replace of Mg/Ca ratios. Both diameter of laser sampling spot and laser moving increment were 2- μm. The curve of Mg/Ca vs. distance directly was obtained. The result indicates that relative Mg/Ca ratios changed from 0.5 to 2.0 this stalagmite and it is enough to reflect environmental factors act. (authors)

Superconducting tunnel junctions on MgB{sub 2} using MgO and CaF{sub 2} as a barrier

Energy Technology Data Exchange (ETDEWEB)

Sakoda, Masahito, E-mail: sakoda@cc.tuat.ac.jp [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16, Koganei, Tokyo 184-8588 (Japan); Aibara, Masato; Mede, Kazuya; Kikuchi, Motoyuki; Naito, Michio [Department of Applied Physics, Tokyo University of Agriculture and Technology, 2-24-16, Koganei, Tokyo 184-8588 (Japan)

2016-11-15

Highlights: • We have revised the manuscript according to reviewer's comments. The details are in “Response to Reviewers”. • Superconducting junctions with MgO and CaF{sub 2} barrier were fabricated in order to improve the quality of junctions. • In SIN junctions with MgO barrier, clear superconducting gap was observed. (). • In SIS junctions with CaF2 barrier, Josephson current was observed over 30 K. (). • The compatibility of each barrier material at the upper and lower interfaces was clarified. (). - Abstract: We report the fabrication of superconducting tunnel junctions, both of superconductor–insulator-normal metal (SIN) and superconductor–insulator-superconductor (SIS), on MgB{sub 2} using MgO and CaF{sub 2} as a barrier. The SIN junctions fabricated using an MgO barrier showed excellent quasi-particle characteristics, including a large superconducting gap (Δ) of 2.5–3 meV and a low zero-bias conductance. We have also fabricated SIS junctions with an MgO barrier, but the quasi-particle characteristics of the SIS junctions are not as good as those of the SIN junctions, namely a reduced superconducting gap and a high zero-bias conductance. It appears that top MgB{sub 2} electrodes do not grow well on an MgO barrier, which is also suggested from in-situ RHEED observation. The SIN junctions fabricated using a CaF{sub 2} barrier showed less sharp quasi-particle characteristics than using an MgO barrier. However, the SIS junctions using a CaF{sub 2} barrier showed a fairly large I{sub c}R{sub N} value at 4.2 K over 1 mV and also exhibited finite Josephson current up to almost the film's T{sub c} (∼30 K). The RHEED observation revealed that top MgB{sub 2} electrodes grow well on a CaF{sub 2} barrier.

Antibacterial characteristics of CaCO3-MgO composites

International Nuclear Information System (INIS)

Yamamoto, Osamu; Ohira, Toshiaki; Alvarez, Kelly; Fukuda, Masayuki

2010-01-01

Dentifrices, such as tooth-paste, are pastes containing insoluble abrasives that aid in the removal of plaque from the teeth and help to polish them. Composite powders contributing to oral hygiene application, i.e., nano-scale MgO crystallite dispersed in CaCO 3 grain, were fabricated by the thermal decomposition of dolomite. The composite obtained by heating at 800 deg. C consisted of CaCO 3 grains including 20 nm MgO fine crystallite, being the purpose powder in this study. The antibacterial activity of these powders related to gram-positive and gram-negative bacteria was evaluated in vitro. The thermal decomposition above 800 deg. C resulted in the mixture of CaO and MgO. Antibacterial activity of the composite enhanced with increasing powder concentration. Though antibacterial action toward Staphylococcus aureus was greater than towards Escherichia coli, the death rate constant was identical in both bacteria. It can be concluded that the obtained composite possesses two functions able to improve the oral hygiene: as a tooth abrasive and as an antibacterial agent.

Age-dependent changes in diastolic Ca2+ and Na+ concentrations in dystrophic cardiomyopathy: Role of Ca2+ entry and IP3

International Nuclear Information System (INIS)

Mijares, Alfredo; Altamirano, Francisco; Kolster, Juan; Adams, José A.; López, José R.

2014-01-01

Highlights: • Age-dependent increase in [Ca 2+ ] d and [Na + ] d in mdx cardiomyocytes. • Gadolinium significantly reduced both [Ca 2+ ] d and [Na + ] d at all ages. • IP 3 -pathway inhibition reduced cations concentrations in dystrophic cardiomyocytes. - Abstract: Duchenne muscular dystrophy (DMD) is a lethal X-inherited disease caused by dystrophin deficiency. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with a dilated cardiomyopathy that leads to progressive heart failure at the end of the second decade. The aim of the present study was to characterize the diastolic Ca 2+ concentration ([Ca 2+ ] d ) and diastolic Na + concentration ([Na + ] d ) abnormalities in cardiomyocytes isolated from 3-, 6-, 9-, and 12-month old mdx mice using ion-selective microelectrodes. In addition, the contributions of gadolinium (Gd 3+ )-sensitive Ca 2+ entry and inositol triphosphate (IP 3 ) signaling pathways in abnormal [Ca 2+ ] d and [Na + ] d were investigated. Our results showed an age-dependent increase in both [Ca 2+ ] d and [Na + ] d in dystrophic cardiomyocytes compared to those isolated from age-matched wt mice. Gd 3+ treatment significantly reduced both [Ca 2+ ] d and [Na + ] d at all ages. In addition, blockade of the IP 3 -pathway with either U-73122 or xestospongin C significantly reduced ion concentrations in dystrophic cardiomyocytes. Co-treatment with U-73122 and Gd 3+ normalized both [Ca 2+ ] d and [Na + ] d at all ages in dystrophic cardiomyocytes. These data showed that loss of dystrophin in mdx cardiomyocytes produced an age-dependent intracellular Ca 2+ and Na + overload mediated at least in part by enhanced Ca 2+ entry through Gd 3+ sensitive transient receptor potential channels (TRPC), and by IP 3 receptors

Phase Behavior of Aqueous NA-K-MG-CA-CI-NO3 Mixtures: Isopiestic Measurements and Thermodynamic Modeling

Energy Technology Data Exchange (ETDEWEB)

M.S. Gruszkiewiez; D.A. Palmer; R.D. Springer; P. Wang; A. Anderko

2006-09-14

A comprehensive model has been established for calculating thermodynamic properties of multicomponent aqueous systems containing the Na{sup +}, K{sup +}, Mg{sup 2+}, Ca{sup 2+}, Cl{sup -}, and NO{sub 3}{sup -} ions. The thermodynamic framework is based on a previously developed model for mixed-solvent electrolyte solutions. The framework has been designed to reproduce the properties of salt solutions at temperatures ranging from the freezing point to 300 C and concentrations ranging from infinite dilution to the fused salt limit. The model has been parameterized using a combination of an extensive literature database and new isopiestic measurements for thirteen salt mixtures at 140 C. The measurements have been performed using Oak Ridge National Laboratory's (ORNL) previously designed gravimetric isopiestic apparatus, which makes it possible to detect solid phase precipitation. Water activities are reported for mixtures with a fixed ratio of salts as a function of the total apparent salt mole fraction. The isopiestic measurements reported here simultaneously reflect two fundamental properties of the system, i.e., the activity of water as a function of solution concentration and the occurrence of solid-liquid transitions. The thermodynamic model accurately reproduces the new isopiestic data as well as literature data for binary, ternary and higher-order subsystems. Because of its high accuracy in calculating vapor-liquid and solid-liquid equilibria, the model is suitable for studying deliquescence behavior of multicomponent salt systems.

High-Strength Low-Alloy (HSLA) Mg-Zn-Ca Alloys with Excellent Biodegradation Performance

Science.gov (United States)

Hofstetter, J.; Becker, M.; Martinelli, E.; Weinberg, A. M.; Mingler, B.; Kilian, H.; Pogatscher, S.; Uggowitzer, P. J.; Löffler, J. F.

2014-04-01

This article deals with the development of fine-grained high-strength low-alloy (HSLA) magnesium alloys intended for use as biodegradable implant material. The alloys contain solely low amounts of Zn and Ca as alloying elements. We illustrate the development path starting from the high-Zn-containing ZX50 (MgZn5Ca0.25) alloy with conventional purity, to an ultrahigh-purity ZX50 modification, and further to the ultrahigh-purity Zn-lean alloy ZX10 (MgZn1Ca0.3). It is shown that alloys with high Zn-content are prone to biocorrosion in various environments, most probably because of the presence of the intermetallic phase Mg6Zn3Ca2. A reduction of the Zn content results in (Mg,Zn)2Ca phase formation. This phase is less noble than the Mg-matrix and therefore, in contrast to Mg6Zn3Ca2, does not act as cathodic site. A fine-grained microstructure is achieved by the controlled formation of fine and homogeneously distributed (Mg,Zn)2Ca precipitates, which influence dynamic recrystallization and grain growth during hot forming. Such design scheme is comparable to that of HSLA steels, where low amounts of alloying elements are intended to produce a very fine dispersion of particles to increase the material's strength by refining the grain size. Consequently our new, ultrapure ZX10 alloy exhibits high strength (yield strength R p = 240 MPa, ultimate tensile strength R m = 255 MPa) and simultaneously high ductility (elongation to fracture A = 27%), as well as low mechanical anisotropy. Because of the anodic nature of the (Mg,Zn)2Ca particles used in the HSLA concept, the in vivo degradation in a rat femur implantation study is very slow and homogeneous without clinically observable hydrogen evolution, making the ZX10 alloy a promising material for biodegradable implants.

Microstructure, mechanical properties and bio-corrosion properties of Mg-Zn-Mn-Ca alloy for biomedical application

International Nuclear Information System (INIS)

Zhang Erlin; Yang Lei

2008-01-01

Microstructure, mechanical properties and bio-corrosion properties of as-cast Mg-Zn-Mn-Ca alloys were investigated for biomedical application in detail by optical microscopy, scanning electronic microscopy (SEM), mechanical properties testing and electrochemical measurement. SEM and optical microscopy observation indicated that the grain size of the as-cast alloys significantly decreased with the increasing of Ca content up to 0.5 wt.%. Further increasing of Ca content did not refine the grain more. The phase constitute was mainly controlled by the atomic ratio of Zn to Ca. When the ratio was more than 1.0-1.2, the alloy was mainly composed of primary Mg and lamellar eutectic (α-Mg + Ca 2 Mg 6 Zn 3 ), while the alloy was composed of primary Mg and divorced eutectic (α-Mg + Mg 2 Ca + Ca 2 Mg 6 Zn 3 ) when the atomic ratio was less than 1.0-1.2. The yield strength of the as-cast alloy increased but the elongation and the tensile strength increased first and then decreased with the increasing of Ca content. It was thought that Mg 2 Ca phase deteriorated the tensile strength and ductility. Electrochemical measurements indicated that Mg 2 Ca phase improved the corrosion resistance of the as-cast alloy

Effect of calcium on the microstructure and corrosion behavior of microarc oxidized Mg-xCa alloys.

Science.gov (United States)

Pan, Yaokun; Chen, Chuanzhong; Feng, Rui; Cui, Hongwei; Gong, Benkui; Zheng, Tingting; Ji, Yarou

2018-01-16

Magnesium alloys are potential biodegradable implants for biomedical applications, and calcium (Ca) is one kind of ideal element being examined for magnesium alloys and biodegradable ceramic coatings owing to its biocompatibility and mechanical suitability. In this study, microarc oxidation (MAO) coatings were prepared on Mg-xCa alloys to study the effect of Ca on the microstructure and corrosion resistance of Mg-xCa alloys and their surface MAO coatings. The electrochemical corrosion behavior was investigated using an electrochemical workstation, and the degradability and bioactivity were evaluated by soaking tests in simulated body fluid (SBF) solutions. The corrosion products were characterized by scanning electron microscopy, x-ray diffractometry, and Fourier transform infrared spectrometry. The effects of Ca on the alloy phase composition, microstructure, MAO coating formation mechanism, and corrosion behavior were investigated. Results showed that the Mg-0.82Ca alloy and MAO-coated Mg-0.82Ca exhibited the highest corrosion resistance. The number and distribution of Mg 2 Ca phases can be controlled by adjusting the Ca content in the Mg-xCa alloys. The proper amount of Ca in magnesium alloy was about 0.5-0.8 wt. %. The pore size, surface roughness, and corrosion behavior of microarc oxidized Mg-xCa samples can be controlled by the number and distribution of the Mg 2 Ca phase. The corrosion behaviors of microarc oxidized Mg-Ca in SBF solutions were discussed.

Hereditary tubular transport disorders: implications for renal handling of Ca2+ and Mg2+.

NARCIS (Netherlands)

Dimke, H.; Hoenderop, J.G.J.; Bindels, R.J.M.

2010-01-01

The kidney plays an important role in maintaining the systemic Ca2+ and Mg2+ balance. Thus the renal reabsorptive capacity of these cations can be amended to adapt to disturbances in plasma Ca2+ and Mg2+ concentrations. The reabsorption of Ca2+ and Mg2+ is driven by transport of other electrolytes,

Beta decay of 31,32Na and 31Mg

International Nuclear Information System (INIS)

Klotz, G.; Baumann, P.; Bounajma, M.; Huck, A.; Knipper, A.; Walter, G.; Poves, A.; Retamosa, J.

1993-01-01

31,32 Na and 31 Mg beta decays were studied at the CERN on-line mass separator ISOLDE by gamma, gamma-gamma and neutron-gamma measurements. In the 31 Na decay, the assignment of previously reported γ transitions and the observation of a new level at 3760 keV lead to a revised decay scheme. In the 31 Mg → 31 Al decay, a new decay scheme involves ten β branches and three states are reported for the first time. New spectroscopic results have been obtained in the 32 Na β - decay. A previously non-interpreted 1436 keV γ ray is now assigned in the 32 Mg scheme. (author) 33 refs., 16 figs., 12 tabs

Phosphorylated intermediate of (Ca2+ + K+)-stimulated Mg2+-dependent transport ATPase in endoplasmic reticulum from rat pancreatic acinar cells

International Nuclear Information System (INIS)

Imamura, K.; Schulz, I.

1985-01-01

Formation and decomposition of the phosphorylated intermediate of endoplasmic reticulum (Ca 2+ + Mg 2+ )-ATPase from pancreatic acinar cells have been studied using lithium dodecyl sulfate- and tetradecyltrimethylammonium bromide-polyacrylamide gel electrophoresis. Incorporation of 32 P from [gamma- 32 P]ATP is Ca 2+ -dependent (approximate Km for free [Ca 2+ ] = 2-3 x 10(-8) mol/liter). Formation of the 100-kDa phosphoprotein is rapid, reaching maximal 32 P incorporation within 1 s at room temperature. At 4 degrees C, phosphorylation is slower and dephosphorylation is drastically decreased. For dephosphorylation, Mg 2+ and monovalent cations such as K + or Na + are necessary. Vanadate inhibits both 32 P incorporation and 32 P liberation dose dependently (Km = 3 x 10(-6) mol/liter), whereas mitochondrial inhibitors and ouabain have no effect. The phosphoprotein is stable at pH 2 and destabilizes with increasing pH being completely decomposed at pH 9. Reduction of 32 P incorporation in the presence of high concentrations of cold ATP and hydroxylamine suggests formation of acylphosphate present in the ATPase intermediate. The characteristics of Ca 2+ , cation, and pH dependencies of the ATPase activity are similar to those previously described for MgATP-dependent Ca 2+ transport into rough endoplasmic reticulum from pancreatic acinar cells. The data suggest that the 100-kDa phosphoprotein as described in this study is the intermediate of this Ca2+ transport ATPase

Relationships Between Temperature, pH, and Crusting on Mg/Ca Ratios in Laboratory-Grown Neogloboquadrina Foraminifera

Science.gov (United States)

Davis, Catherine V.; Fehrenbacher, Jennifer S.; Hill, Tessa M.; Russell, Ann D.; Spero, Howard J.

2017-11-01

Mg/Ca ratio paleothermometry in foraminifera is an important tool for the reconstruction and interpretation of past environments. However, existing Mg/Ca:temperature relationships for planktic species inhabiting middle- and high-latitude environments are limited by a lack of information about the development and impact of low-Mg/Ca ratio "crusts" and the influence of the carbonate system on Mg/Ca ratios in these groups. To address this, we cultured individual specimens of Neogloboquadrina incompta and Neogloboquadrina pachyderma in seawater across a range of temperature (6°-12°C) and pH (7.4-8.2). We found by laser ablation inductively couple mass spectrometry analyses of shells that culture-grown crust calcite in N. incompta had a lower Mg/Ca ratio than ontogenetic calcite formed at the same temperature, suggesting that temperature is not responsible for the low-Mg/Ca ratio of neogloboquadrinid crusts. The Mg/Ca:temperature relationship for ontogenetic calcite in N. incompta was consistent with the previously published culture-based relationship, and no significant relationship was found between Mg/Ca ratios and pH in this species. However, the Mg/Ca ratio in laboratory-cultured N. pachyderma was much higher than that reported in previous core top and sediment trap samples, due to lack of crust formation in culture. Application of our ontogenetic calcite-specific Mg/Ca:temperature relationships to fossil N. pachyderma and N. incompta from five intervals in cores from the Santa Barbara Basin and the Bering Sea shows that excluding crust calcite in fossil specimens may improve Mg/Ca-based temperature estimates.

Synthetic water soluble di-/tritopic molecular receptors exhibiting Ca2+/Mg2+ exchange.

Science.gov (United States)

Lavie-Cambot, Aurélie; Tron, Arnaud; Ducrot, Aurélien; Castet, Frédéric; Kauffmann, Brice; Beauté, Louis; Allouchi, Hassan; Pozzo, Jean-Luc; Bonnet, Célia S; McClenaghan, Nathan D

2017-05-23

Structural integration of two synthetic water soluble receptors for Ca 2+ and Mg 2+ , namely 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) and o-aminophenol-N,N,O-triacetic acid (APTRA), respectively, gave novel di- and tritopic ionophores (1 and 2). As Mg 2+ and Ca 2+ cannot be simultaneously complexed by the receptors, allosteric control of complexation results. Potentiometric measurements established stepwise protonation constants and showed high affinity for Ca 2+ (log K = 6.08 and 8.70 for 1 and 2, respectively) and an excellent selectivity over Mg 2+ (log K = 3.70 and 5.60 for 1 and 2, respectively), which is compatible with magnesium-calcium ion exchange. While ion-exchange of a single Mg 2+ for a single Ca 2+ is possible in both 1 and 2, the simultaneous binding of two Mg 2+ by 2 appears prohibitive for replacement of these two ions by a single Ca 2+ . Ion-binding and exchange was further rationalized by DFT calculations.

Structure-function relationships of Na+, K+, ATP, or Mg2+ binding and energy transduction in Na,K-ATPase

DEFF Research Database (Denmark)

Jorgensen, Peter L.; Pedersen, Per Amstrup

2000-01-01

Na,K-ATPase; Mutagenesis; Na+ binding; K+ binding; Tl+ binding; Mg2+ binding; ATP binding; Cation binding site; Energy transduction......Na,K-ATPase; Mutagenesis; Na+ binding; K+ binding; Tl+ binding; Mg2+ binding; ATP binding; Cation binding site; Energy transduction...

What is the Right Temperature Sensitivity for Foraminiferal Mg/ca Paleothermometry in Ancient Oceans?

Science.gov (United States)

Eggins, S.; Holland, K.; Hoenisch, B.; Spero, H. J.; Allen, K. A.

2013-12-01

Mg/Ca seawater thermometry has become a cornerstone of modern paleoceanography. Laboratory experiments, seafloor core-top samples, plankton trap and tow collected materials all indicate consistent temperature sensitivity (9-10% increase in Mg/Ca per °C) for a full range of modern planktic foraminifer species. While these results demonstrate the overall robustness of Mg/Ca paleothermometry for the modern ocean, it is an empirical tool for which there is limited understanding of its bio-physio-chemical basis and its applicability to ancient oceans. We have undertaken experimental cultures of Orbulina universa, Globigerinoides sacculifer and Globigerinoides ruber (pink) across a range of seawater compositions (temperature, carbonate chemistry and Mg/Casw) that encompass modern and ancient Paleogene and Cretaceous ocean compositions (Mg/Casw 0.25x to 2x modern and pCO2 = 200 to 1500 ppmv). Our results reveal that the sensitivity of the Mg/Ca-thermometer for planktic foraminifers reduces significantly with Mg/Casw, rather than remaining constant as has been widely assumed or, increasing at lower Mg/Casw as proposed recently by Evans and Müller (2012). These results indicate that the modern sensitivity of 9-10% increase in Mg/Ca per °C cannot yet be applied to obtain reliable relative temperature change estimates to ancient oceans. These results further suggest that variations in foraminiferal Mg/Ca compositions in ancient oceans with lower Mg/Casw may correspond to larger temperature variations than in the modern ocean. Evans D. and Müller W., Paleoceanography, vol. 27, PA4205, doi:10.1029/2012PA002315, 2012

The effect of changing seawater Ca and Mg concentrations upon the distribution coefficients of Mg and Sr in the skeletons of the scleractinian coral Pocillopora damicornis

Science.gov (United States)

Giri, Sharmila J.; Swart, Peter K.; Devlin, Quinn B.

2018-02-01

The skeletal composition of calcifying organisms, in particular Mg/Ca and Sr/Ca ratios, have been widely used to understand fluctuations in seawater chemistry throughout the Phanerozoic. While the success of applying these data to the geologic record depends on a knowledge of the distribution coefficients for these elements (DMg and DSr), there are scarcely any studies which have described how these values vary as a result of changing seawater Mg/Ca ratios. To address this, we have cultured the scleractinian coral, Pocillopora damicornis, in seawater with ranges of Mg and Ca concentrations. Here, we demonstrate that Mg/Ca and Sr/Ca ratios of coral skeletons correlate with total seawater Mg/Ca and Sr/Ca molar ratios, but that apparent DMg and DSr values do not remain constant across the range of experimental seawater treatments, with DMg values significantly increasing with seawater Mg/Ca ratios and DSr values significantly increasing with seawater Ca concentrations. These trends are not rate dependent and may be best explained by a Rayleigh distillation model, in which the calcifying space is semi-isolated from seawater during skeletogenesis (i.e. leaky). As there is a slight increase in DMg and decrease in DSr values between our "Jurassic" and "Modern" seawater treatments, the application of a constant distribution coefficient to estimate changes in ancient seawater chemistry may underestimate seawater Mg/Ca ratios and overestimate Sr/Ca throughout the Mesozoic and Cenozoic. We suggest that interpretations of seawater chemistry from fossil corals may be improved by using the relationships derived for skeletal and seawater Mg/Ca and Sr/Ca ratios established by our experiments, as they incorporate the effect of seawater Mg/Ca ratios on skeletal Mg/Ca and Sr/Ca ratios.

Investigation on microstructure characterization and property of rapidly solidified Mg-Zn-Ca-Ce-La alloys

Energy Technology Data Exchange (ETDEWEB)

Zhou Tao, E-mail: tzhou1118@163.com [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Chen Zhenhua, E-mail: chenzhenhua45@hotmail.com [College of Material Science and Engineering, Hunan University, Changsha 410082 (China); Yang Mingbo, E-mail: yangmingbo@cqit.edu.cn [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Hu Jianjun, E-mail: hujj@qq.com [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China); Xia Hua, E-mail: xiahua@cqut.edu.cn [College of Material Science and Engineering, Chongqing University of Technology, Chongqing 400054 (China)

2012-01-15

Rapidly solidified (RS) Mg-Zn-Ca-Ce-La (wt.%) alloys have been produced via atomizing the alloy melt and subsequent splat-quenching on the water-cooled copper twin-rollers in the form of flakes. Microstructure characterization, phase compositions and thermal stability of the alloys have been systematically investigated. The results showed that with addition of RE (Ce and La) to the Mg-6Zn-5Ca alloy, the stable intermetallic compounds i.e. the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (about 3 at.%), shortened as the T Prime phase, were formed at the expense of the binary Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases, which was possibly beneficial to the enhanced thermal stability of the alloy. In the Mg-6Zn-5Ca-3Ce-0.5La alloy, the composition of the T Prime phase in the grain interior was different from that at the grain boundaries, in which the segregation of the La elements was found, and the atomic percentage ratio of Zn to Ce in the T Prime phase within the grains was close to 2. Moreover, the stable Mg{sub 2}Ca phases were detected around the T Prime phases at the grain boundaries in the alloy. - Research Highlights: Black-Right-Pointing-Pointer The phase constitution of RS Mg-6Zn-5Ca alloy can be improved by RE additions. Black-Right-Pointing-Pointer In the Mg-Zn-Ca-Ce-La alloys, the Mg{sub x}Zn{sub y}RE{sub z} phase with a few Ca (T Prime phase) is formed. Black-Right-Pointing-Pointer The formation of the T Prime phase leads to the loss of the Mg-Zn and Ca{sub 2}Mg{sub 6}Zn{sub 3} phases. Black-Right-Pointing-Pointer The composition of the T Prime phase differs from the grain interior to the grain boundary.

Clinical value of single or combined IRMA of CEA, CA19-9, CA72-4 and MG-Ag in diagnosis of gastric cancer

International Nuclear Information System (INIS)

Li Jiangang; Chen Zhong; Liu Yun; Zhang Jun

2002-01-01

Four tumor markers CEA, CA19-9, CA72-4 and MG-Ag are chosen in diagnosis of gastric cancer and 228 cases are detected with single or combined methods in all. The results indicate that the positive rates of single detection are all above 70% and that of MG-Ag is the highest (90.4%). Combined detections of two tumor markers, as judged by double positivity, the positive rate of MG + CA72-4 is the highest (70.6%), next is MG + CA19-9 (64.6%). It is suggested that MG-Ag is the first choice in single detection, MG + CA72-4 group is the first choice in double combined detections and different tumor markers could be chosen according to historic type in follow-up patients

A DFT study of hydrogen adsorption on Be, Mg and Ca frameworks in erionite zeolite

Energy Technology Data Exchange (ETDEWEB)

Fellah, Mehmet Ferdi, E-mail: mferdi.fellah@btu.edu.tr

2017-02-01

Highlights: • Mg-ERI and Ca-ERI clusters have much lower chemical potential and hardness. • Adsorption enthalpies for Mg- and Ca-ERI are importantly greater than the liquefaction enthalpy of hydrogen. • Mg-ERI and Ca-ERI clusters have much HOMO-LUMO gap indicating higher reactivity. • Ca- and Mg-ERI are potential cryoadsorbent materials for hydrogen storage. - Abstract: The molecular hydrogen adsorption was investigated on additional frameworks with earth alkaline metal atoms (Be, Mg and Ca) in 24T ERI zeolite cluster model by means of Density Functional Theory study. HOMO and LUMO energy values, chemical potential, chemical hardness, electronegativity, adsorption energy and adsorption enthalpy values have been calculated in this study. Mg-ERI and Ca-ERI clusters have much lower chemical potentials with much lower adsorption energy values when compared to the value of Be-ERI cluster. Additionally, they are softer than Be-ERI cluster with respect to their lower chemical hardness values. Hydrogen adsorption enthalpy values were computed as −3.6 and −3.9 kJ/mol on Mg-ERI and Ca-ERI clusters, respectively. These adsorption enthalpy values are significantly larger than the enthalpy value of liquefaction for hydrogen molecule. This consequently specifies that Mg-ERI and Ca-ERI zeolite structures which have higher chemical reactivity appear to be a promising candidate cryoadsorbent for hydrogen storage.

Microstructures, mechanical properties and corrosion resistances of extruded Mg-Zn-Ca-xCe/La alloys.

Science.gov (United States)

Tong, L B; Zhang, Q X; Jiang, Z H; Zhang, J B; Meng, J; Cheng, L R; Zhang, H J

2016-09-01

Magnesium alloys are considered as good candidates for biomedical applications, the influence of Ce/La microalloying on the microstructure, mechanical property and corrosion performance of extruded Mg-5.3Zn-0.6Ca (wt%) alloy has been investigated in the current study. After Ce/La addition, the conventional Ca2Mg6Zn3 phases are gradually replaced by new Mg-Zn-Ce/La-(Ca) phases (T1'), which can effectively divide the Ca2Mg6Zn3 phase. The Ca2Mg6Zn3/T1' structure in Mg-Zn-Ca-0.5Ce/La alloy is favorably broken into small particles during the extrusion, resulting in an obvious refinement of secondary phase. The dynamic recrystallized grain size is dramatically decreased after 0.5Ce/La addition, and the tensile yield strength is improved, while further addition reverses the effect, due to the grain coarsening. However, the corrosion resistance of extruded Mg-Zn-Ca alloy deteriorates after Ce/La addition, because the diameter of secondary phase particle is remarkably decreased, which increases the amount of cathodic sites and accelerates the galvanic corrosion process. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effect of ionizing radiation on Ca2+-ATPase and Mg2+-ATPase: the role of ligands

International Nuclear Information System (INIS)

Dreval', V.I.

1994-01-01

The change of Ca 2+ -ATPase and Mg 2+ -ATPase activity in plasma membranes of thymocytes irradiated with doses of 10 2 , 10 3 and 10 4 Gy in the presence of Ca 2+ , Mg 2+ and ATP was studied. Stabilizing effect of Ca 2+ and Mg 2+ on Ca 2+ -ATPase and ATP on Mg 2+ -ATPase under irradiation was established

Comparison of the effectiveness of seven amiloride congeners as inhibitors of Na/H and Na/Ca antiport in cultured smooth muscle cells

International Nuclear Information System (INIS)

Smith, L.; Higgins, B.L.; Cragoe, E.J. Jr.; Smith, J.B.

1987-01-01

The authors cultured smooth muscle cells from rat aorta and assayed Na/Ca antiport by measuring the initial rate of 45 Ca influx in Na-loaded cells. Na/H antiport was assayed by measuring the initial rate of 22 Na influx in acid-loaded cells. The external medium was the same for both assays except Na was 10 mM for Na/H antiport and O for the Na/Ca antiport assay. The dose of each congener that caused 50% inhibition (I 50 ) was calculated using a log-log median effect plot. The linear regression coefficients ranged from 0.916 to 0.998. Of all the compounds tested only dimethylbenzamil is more potent as an inhibitor of Na/Ca compared to Na/H antiport

Exigências de minerais para cabras durante a gestação: Na, K, Mg, S, Fe e Zn Minerals requirements of goats during the pregnancy: Na, K, Mg, S, F and Zn

Directory of Open Access Journals (Sweden)

Roberto Germano Costa

2003-04-01

Full Text Available O trabalho foi realizado com o objetivo de estimar a retenção e a exigência líquida dos minerais Na, K, Mg, S, Fe e Zn durante a gestação de cabras com um ou dois fetos. A estimativa de retenção foi baseada na diferença entre o total de cada mineral depositado no feto, útero, membranas, fluídos fetais e glândula mamária dos animais nas diferentes etapas da gestação e o total de cada mineral armazenado nas cabras vazias, utilizando-se o modelo de predição ln=A+Bx+Cx2, em que x=tempo de gestação. Os conteúdos de Na, K, Mg, S, Fe e Zn, durante as gestações de um e dois fetos foram de: 13,2 e 21,4 mg; 13,3 e 21,3 g; 2,1 e 3,7 mg; 5,5 e 9,3 mg; 575,5 e 981,0 mg; 112,6 e 164,7 mg nas gestações, resultando em exigências líquidas diárias de 0,13 e 0,11 g; 0,21 e 0,31 g; 0,06 e 0,11g; 0,17 e 0,21 g; 22,94 e 40,51 mg; 2,63 e 2,78 mg, respectivamente.This work was carried out with the purpose of evaluating the retention and the requirement of Ca e P minerals during the pregnancy of goats with one or two foetus. The estimate of retention was based in the difference between the total of each mineral stored in the foetus, uterus, membranes, fetals fluids and mammary gland of animals in the differents phases of pregnancy and the total of each mineral stored in the empty goats, using the model of prediction ln=A+Bx+Cx2, where x=time of pregnancy. The comparison of the estimative with the real values obtained show that the suggested model explained with coherence and precision the biological behavior of minerals retention during all pregnancy. The contend of Na, K, Mg, S, Fe e Zn was: 13.2 and 21.4 mg; 13.3 and 21.3 g; 2.1 and 3.7 mg; 5.5 and 9.3 mg; 575.5 and 981.0 mg; 112.6 and 164.7 mg in the pregnancy of one and two foetus, respectively, that resulted in a diary liquid requirement of 0.13 and 0.11 g; 0.21 and 0.31 g 0.06 and 0.11g; 0.17 and 0.21 g; 22.94 and 40.51 mg; 2.63 and 2.78 mg, respectively.

The precipitation process in Mg-Ca-(Zn) alloys investigated by positron annihilation spectroscopy

International Nuclear Information System (INIS)

Ortega, Yanicet; Monge, Miguel Angel; Pareja, Ramiro

2008-01-01

Coincidence doppler broadening (CDB) spectroscopy has been applied to study the precipitation process induced by aging in Mg-1.0 wt.% Ca and Mg-1.0 wt.% Ca-1.0 wt.% Zn alloys. In addition positron lifetime experiments and microhardness measurements have been performed. A peak centered at ∼11.5 x 10 -3 m 0 c is found in the CDB ratio spectra of the alloys aged at 473 K. It is attributed to annihilations with the core electrons of Ca. The results indicate the formation of a particle dispersion that hardens the alloys. This dispersion is correlated with the appearance of the peak attributed to Ca atoms. Zn atoms in the Mg matrix inhibit the formation of quenched-in vacancies bound to Ca atoms in the aged ternary alloy producing the dispersion refinement

Stimulated emission (4F3/2 → 4I11/2 channel) with LD and Xe-flashlamp pumping of tetragonal, incommensurately modulated Ca2MgSi2O7:Nd3+(Na+) – a new disordered laser crystal

International Nuclear Information System (INIS)

Kaminskii, A A; Nakao, H; Ueda, K; Shirakawa, A; Bohatý, L; Becker, P; Liebertz, J; Kleinschrodt, R

2010-01-01

Non-centrosymmetric tetragonal crystal Ca 2 MgSi 2 O 7 :Nd 3+ (Na + ) with incommensurately modulated melilite-type structure is presented as a new laser crystal. By LD and Xe-flashlamp pumping its CW and free-running pulsed stimulated emission of the 4 F 3/2 → 4 I 11/2 generation channel of Nd 3+ lasant ions was excited

Mechanical properties and corrosion behavior of Mg-Gd-Ca-Zr alloys for medical applications.

Science.gov (United States)

Shi, Ling-Ling; Huang, Yuanding; Yang, Lei; Feyerabend, Frank; Mendis, Chamini; Willumeit, Regine; Ulrich Kainer, Karl; Hort, Norbert

2015-07-01

Magnesium alloys are promising candidates for biomedical applications. In this work, influences of composition and heat treatment on the microstructure, the mechanical properties and the corrosion behavior of Mg-Gd-Ca-Zr alloys as potential biomedical implant candidates were investigated. Mg5Gd phase was observed at the grain boundaries of Mg-10Gd-xCa-0.5Zr (x=0, 0.3, 1.2wt%) alloys. Increase in the Ca content led to the formation of additional Mg2Ca phase. The Ca additions increased both the compressive and the tensile yield strengths, but reduced the ductility and the corrosion resistance in cell culture medium. After solution heat treatment, the Mg5Gd particles dissolved in the Mg matrix. The compressive strength decreased, while the corrosion resistance improved in the solution treated alloys. After ageing at 200°C, metastable β' phase formed on prismatic planes and a new type of basal precipitates have been observed, which improved the compressive and tensile ultimate strength, but decreased the ductility. Copyright © 2015 Elsevier Ltd. All rights reserved.

The gastric H, K-ATPase system also functions as the Na, K-ATPase and Ca-ATPase in altered states [v1; ref status: indexed, http://f1000r.es/1eo

Directory of Open Access Journals (Sweden)

Tushar Ray

2013-07-01

Full Text Available This article offers an explanation for the apparent lack of Na, K-ATPase activity in parietal cells although ouabain has been known to inhibit gastric acid secretion since 1962. The gastric H, K-ATPase (proton-pump seems to be acting in altered states, thus behaving like a Na, K-ATPase (Na-pump and/or Ca-ATPase (Ca-pump depending on cellular needs.  This conclusion is based on the following findings. First, parietal cell fractions do not exhibit Na, K-ATPase activity at pH 7.0 but do at pH 8.5. Second, the apical plasma membrane (APM fraction exhibits a (Ca or Mg-ATPase activity with negligible H, K-ATPase activity. However, when assayed with Mg alone in presence of the 80 k Da cytosolic proton-pump activator (HAF, the APM fraction reveals remarkably high H, K-ATPase activity, suggesting the observed low affinity of Ca (or Mg-ATPase is an altered state of the latter. Third, calcium (between 1 and 4 µM shows both stimulation and inhibition of the HAF-stimulated H, K-ATPase depending on its concentration, revealing a close interaction between the  proton-pump activator and local Ca concentration in gastric H, K-ATPase function. Such interactions suggest that Ca is acting as a terminal member of the intracellular signaling system for the HAF-regulated proton-pump. It appears that during resting state, the HAF-associated H, K-ATPase remains inhibited by Ca (>1 µM and, prior to resumption of acid secretion the gastric H, K-ATPase acts temporarily as a Ca-pump for removing excess Ca from its immediate environment. This conclusion is consistent with the recent reports of immunochemical co-localization of the gastric H, K-ATPase and Ca-ATPase by superimposition in parietal cells, and a transitory efflux of Ca immediately preceding the onset of acid secretion. These new perspectives on proton-pump function would open new avenues for a fuller understanding of the intracellular regulation of the ubiquitous Na-pump.

Evidence for a Na+-Ca2+ exchanger in rat pancreatic ducts

DEFF Research Database (Denmark)

Hug, M; Pahl, C; Novak, I

1996-01-01

Only recently has it been recognized that intracellular Ca2+ is an important cellular mediator in pancreatic ducts. The aim of the present study was to characterize the Ca2+ efflux pathway in ducts freshly prepared from rat pancreas. Lowering of extracellular Na+ concentration resulted in a signi......Only recently has it been recognized that intracellular Ca2+ is an important cellular mediator in pancreatic ducts. The aim of the present study was to characterize the Ca2+ efflux pathway in ducts freshly prepared from rat pancreas. Lowering of extracellular Na+ concentration resulted...

Accumulation of 90Sr, Ca, Mg, K and Na in crane's-bill plants cultavated on soil and hydroponics

International Nuclear Information System (INIS)

Analyan, V.L.; Sarkisyan, G.A.

1981-01-01

Accumulation of 90 Sr in plants under the conditions of soil and hydroponic cultures from the viewpoint of the possibility of obtaining ''pure'' vegetable production has been studied. Predominant absorption of 90 Sr by soil plants as compared with calcium is shown. In the course of using the hydroponic cultivation method redominant radiostrontium absorption has been manifested to all investigated nuclides including potassium. The accumulation coefficients analysis has shown that among soil plants the fisarst place is occupied by potassium, while the 90 Sr coefficients are greater than Ca on hydroponics, where the true, not distorted by soil sorption processes absorptive plant capacity has been manifested, the first places in the series are occupied by 90 Sr and K, then come Ca and Mg

Sodium recognition by the Na+/Ca2+ exchanger in the outward-facing conformation.

Science.gov (United States)

Marinelli, Fabrizio; Almagor, Lior; Hiller, Reuben; Giladi, Moshe; Khananshvili, Daniel; Faraldo-Gómez, José D

2014-12-16

Na(+)/Ca(2+) exchangers (NCXs) are ubiquitous membrane transporters with a key role in Ca(2+) homeostasis and signaling. NCXs mediate the bidirectional translocation of either Na(+) or Ca(2+), and thus can catalyze uphill Ca(2+) transport driven by a Na(+) gradient, or vice versa. In a major breakthrough, a prokaryotic NCX homolog (NCX_Mj) was recently isolated and its crystal structure determined at atomic resolution. The structure revealed an intriguing architecture consisting of two inverted-topology repeats, each comprising five transmembrane helices. These repeats adopt asymmetric conformations, yielding an outward-facing occluded state. The crystal structure also revealed four putative ion-binding sites, but the occupancy and specificity thereof could not be conclusively established. Here, we use molecular-dynamics simulations and free-energy calculations to identify the ion configuration that best corresponds to the crystallographic data and that is also thermodynamically optimal. In this most probable configuration, three Na(+) ions occupy the so-called Sext, SCa, and Sint sites, whereas the Smid site is occupied by one water molecule and one H(+), which protonates an adjacent aspartate side chain (D240). Experimental measurements of Na(+)/Ca(2+) and Ca(2+)/Ca(2+) exchange by wild-type and mutagenized NCX_Mj confirm that transport of both Na(+) and Ca(2+) requires protonation of D240, and that this side chain does not coordinate either ion at Smid. These results imply that the ion exchange stoichiometry of NCX_Mj is 3:1 and that translocation of Na(+) across the membrane is electrogenic, whereas transport of Ca(2+) is not. Altogether, these findings provide the basis for further experimental and computational studies of the conformational mechanism of this exchanger.

Microstructure, biocorrosion and cytotoxicity evaluations of rapid solidified Mg-3Ca alloy ribbons as a biodegradable material

International Nuclear Information System (INIS)

Gu, X N; Zhou, W R; Zheng, Y F; Li, X L; Cheng, Y

2010-01-01

Rapidly solidified (RS) Mg-3Ca alloy ribbons were prepared by the melt-spinning technique at different wheel rotating speeds (15 m s -1 , 30 m s -1 and 45 m s -1 ) with the as-cast Mg-3Ca alloy ingot as a raw material. The RS45 Mg-3Ca alloy ribbon showed a much more fine grain size feature (approximately 200-500 nm) in comparison to the coarse grain size (50-100 μm) of the original as-cast Mg-3Ca alloy ingot. The corrosion electrochemical tests in simulated body fluid indicated that the corrosion rate of the as-cast Mg-3Ca alloy was strongly reduced by the RS procedure and tended to be further decreased with increasing wheel rotating speeds (1.43 mm yr -1 for RS15, 0.94 mm yr -1 for RS30 and 0.36 mm yr -1 for RS45). The RS Mg-3Ca alloy ribbons showed more uniform corrosion morphology compared with the as-cast Mg-3Ca alloy after polarization. The cytotoxicity evaluation revealed that the three experimental as-spun Mg-3Ca alloy ribbon extracts did not induce toxicity to the L-929 cells, whereas the as-cast Mg-3Ca alloy ingot extract did. The L-929 cells showed more improved adhesion on the surfaces of the three as-spun Mg-3Ca alloy ribbons than that of the as-cast Mg-3Ca alloy ingot.

Transplacental differences in Ca, Na, K, and electropotential in the guinea pig

International Nuclear Information System (INIS)

Kelman, B.J.; Twardock, A.R.

1983-07-01

The fetal side of hemochorial placentas from guinea pigs between 58 and 62 days gestation were perfused in situ. Concurrent measurements were made of the clearances of radiocalcium and tritiated water from maternal to fetal circulation of the placenta, transplacental potential difference (TPD), maternal plasma and perfusate Ca, Na, and K concentrations, maternal blood pressure, gross permeability of albumin in the placenta, and net water movements. Movement of Ca from dam to fetus appeared to occur against an electrochemical gradient and was not associated with the movements of Na and K across the placenta. A negative correlation between perfusate Na and K concentrations, not dependent on maternal plasma Na and K concentrations and abolished by high concentrations of Ca in the fetal circulation of the placenta, strongly supports the concept of a Na-K exchange mechanism in the placenta directed so that K is moved against a concentration gradient towards the dam. There was no evidence that the TPD existed at the site of maternal-fetal exchange for Ca, Na, or K

Study of sintering on Mg-Zn-Ca alloy system

Science.gov (United States)

Annur, Dhyah; Lestari, Franciska P.; Erryani, Aprilia; Kartika, Ika

2018-05-01

Magnesium and its alloy have gained a lot of interest to be used in biomedical application due to its biodegradable and biocompatible properties. In this study, sintering process in powder metallurgy was chosen to fabricatenonporous Mg-6Zn-1Ca (in wt%) alloy and porous Mg-6Zn-1Ca-10 Carbamide alloy. For creating porous alloy, carbamide (CO(NH2)2 was added to alloy system as the space holder to create porous structure material. Effect of the space holder addition and sintering temperature on porosity, phase formation, mechanical properties, and corrosion properties was observed. Sintering process was done in a tube furnace under Argon atmosphere in for 5 hours. The heat treatment was done in two steps; heated up at 250 °C for 4 hours to decompose spacer particle, followed by heated up at 580 °C or 630 °C for 5 hours. The porous structure of the resulted alloys was examined using Scanning Electron Microscope (SEM), while the phase formation was characterized by X-ray diffraction (XRD) analysis. Mechanical properties were examined using compression testing. From this study, increasing sintering temperature up to 630 °C reduced the mechanical properties of Mg-Zn-Ca alloy.

Antibacterial characteristics of CaCO{sub 3}-MgO composites

Energy Technology Data Exchange (ETDEWEB)

Yamamoto, Osamu, E-mail: yamamoto@cges.akita-u.ac.jp [Center for Geo-Environmental Science, Faculty of Engineering and Resource Science, Akita University, 1-1 Tegata Gakuen-machi, Akita 010-8502 (Japan); Ohira, Toshiaki; Alvarez, Kelly [Center for Geo-Environmental Science, Faculty of Engineering and Resource Science, Akita University, 1-1 Tegata Gakuen-machi, Akita 010-8502 (Japan); Fukuda, Masayuki [Division of Dentistry and Oral Surgery, Akita University Hospital, 1-1-1 Hondo, Akita 010-8543 (Japan)

2010-10-15

Dentifrices, such as tooth-paste, are pastes containing insoluble abrasives that aid in the removal of plaque from the teeth and help to polish them. Composite powders contributing to oral hygiene application, i.e., nano-scale MgO crystallite dispersed in CaCO{sub 3} grain, were fabricated by the thermal decomposition of dolomite. The composite obtained by heating at 800 deg. C consisted of CaCO{sub 3} grains including 20 nm MgO fine crystallite, being the purpose powder in this study. The antibacterial activity of these powders related to gram-positive and gram-negative bacteria was evaluated in vitro. The thermal decomposition above 800 deg. C resulted in the mixture of CaO and MgO. Antibacterial activity of the composite enhanced with increasing powder concentration. Though antibacterial action toward Staphylococcus aureus was greater than towards Escherichia coli, the death rate constant was identical in both bacteria. It can be concluded that the obtained composite possesses two functions able to improve the oral hygiene: as a tooth abrasive and as an antibacterial agent.

The precipitation process in Mg-Ca-(Zn) alloys investigated by positron annihilation spectroscopy

Energy Technology Data Exchange (ETDEWEB)

Ortega, Yanicet [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain); Departamento de Fisica de Materiales, Facultad de Ciencias Fisicas, Universidad Complutense de Madrid, 28040 Madrid (Spain)], E-mail: yanicet@fis.ucm.es; Monge, Miguel Angel; Pareja, Ramiro [Departamento de Fisica, Universidad Carlos III de Madrid, 28911 Leganes (Spain)

2008-09-08

Coincidence doppler broadening (CDB) spectroscopy has been applied to study the precipitation process induced by aging in Mg-1.0 wt.% Ca and Mg-1.0 wt.% Ca-1.0 wt.% Zn alloys. In addition positron lifetime experiments and microhardness measurements have been performed. A peak centered at {approx}11.5 x 10{sup -3}m{sub 0}c is found in the CDB ratio spectra of the alloys aged at 473 K. It is attributed to annihilations with the core electrons of Ca. The results indicate the formation of a particle dispersion that hardens the alloys. This dispersion is correlated with the appearance of the peak attributed to Ca atoms. Zn atoms in the Mg matrix inhibit the formation of quenched-in vacancies bound to Ca atoms in the aged ternary alloy producing the dispersion refinement.

Penurunan Kromium (Cr dalam Limbah Cair Proses Penyamakan Kulit Menggunakan Senyawa Alkali Ca(OH2, NaOH, dan NaHCO3 (Studi Kasus di Pt Trimulyo Kencana Mas Semarang

Directory of Open Access Journals (Sweden)

Tri Joko

2015-12-01

Full Text Available ABTRACT Background : One of the industrial type which use hazardous materials in its production process is leather tanning industry, by using chromium compound (Cr. Chromium is a heavy metal compound which recognized has a high poison energy. Result of analysis of sampel industrial liquid waste of leather tanning of PT Trimulyo Kencana Mas (TKM Semarang showed that total chromium concervation was 49,575 m/l. This total Chromium rate was still above the standard quality of which enabled maximal 2,0 mg/l, according to Kep51/MENLH/110/1995. Alkali compound of Ca(OH2, NaOH and NaHC03 is chemicals able to be used for the processing of industrial liquid waste of pregnant leather tanning of chromium, functioning to boost up condensation pH andprecipitated chromium so that obtained chrome in theform of hydroxide chromium (Cr(OH3. Methods : which used in this research is (quasi experimental, with experiment variable repeated or referred as one group pretest ‑ posttest design. Results : of this research showed that optimum pH for the compound of each alkali at condition of pH 8, with the efficiency dissociation of chromium was equal to 99,28 % by using alkali compound of Ca(OH2 and of NaOH, while usage of NaHC03 equal to 98,50 %. Conclusions: Alkali compound of Ca(OH2, NaOH and NaHCO3 can degrade chromium concentration (Cr in liquid waste with high efficiency, that is reaching under standard quality. The most effective Compound of Alkali, evaluated from the technical aspect for the degradation of chromium concentration in liquid waste is NaOH, because with only small dose can dissociate chromium in liquid waste with high efficiency (99,28 %, For economic reason and recommendation for application in the field is Ca(OH2. Keyword : Efficiency Ca(OH2,, hydroxide chromium, NaHCO3, NaOH, pH, Chromium Compound

Preparation and characterization of porous Mg-Zn-Ca alloy by space holder technique

Science.gov (United States)

Annur, D.; Lestari, Franciska P.; Erryani, A.; Sijabat, Fernando A.; G. P. Astawa, I. N.; Kartika, I.

2018-04-01

Magnesium had been recently researched as a future biodegradable implant material. In the recent study, porous Mg-Zn-Ca alloys were developed using space holder technique in powder metallurgy process. Carbamide (10-20%wt) was added into Mg-6Zn-1Ca (in wt%) alloy system as a space holder to create porous structure material. Sintering process was done in a tube furnace under Argon atmosphere in 610 °C for 5 hours. Porous structure of the resulted alloy was examined using Scanning Electron Microscope (SEM), while the phase formation was characterized by X-ray diffraction analysis (XRD). Further, mechanical properties of porous Mg-Zn-Ca alloy was examined through compression testing. Microstructure characterization showed higher content of Carbamide in the alloy would give different type of pores. However, compression test showed that mechanical properties of Mg-Zn-Ca alloy would decrease significantly when higher content of carbamide was added.

Microstructure, biocorrosion and cytotoxicity evaluations of rapid solidified Mg-3Ca alloy ribbons as a biodegradable material

Energy Technology Data Exchange (ETDEWEB)

Gu, X N; Zhou, W R; Zheng, Y F [State Key Laboratory for Turbulence and Complex System and Department of Advanced Materials and Nanotechnology, College of Engineering, Peking University, Beijing 100871 (China); Li, X L [Center for Biomedical Materials and Engineering, Harbin Engineering University, Harbin 150001 (China); Cheng, Y, E-mail: yfzheng@pku.edu.c [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China)

2010-06-01

Rapidly solidified (RS) Mg-3Ca alloy ribbons were prepared by the melt-spinning technique at different wheel rotating speeds (15 m s{sup -1}, 30 m s{sup -1} and 45 m s{sup -1}) with the as-cast Mg-3Ca alloy ingot as a raw material. The RS45 Mg-3Ca alloy ribbon showed a much more fine grain size feature (approximately 200-500 nm) in comparison to the coarse grain size (50-100 {mu}m) of the original as-cast Mg-3Ca alloy ingot. The corrosion electrochemical tests in simulated body fluid indicated that the corrosion rate of the as-cast Mg-3Ca alloy was strongly reduced by the RS procedure and tended to be further decreased with increasing wheel rotating speeds (1.43 mm yr{sup -1} for RS15, 0.94 mm yr{sup -1} for RS30 and 0.36 mm yr{sup -1} for RS45). The RS Mg-3Ca alloy ribbons showed more uniform corrosion morphology compared with the as-cast Mg-3Ca alloy after polarization. The cytotoxicity evaluation revealed that the three experimental as-spun Mg-3Ca alloy ribbon extracts did not induce toxicity to the L-929 cells, whereas the as-cast Mg-3Ca alloy ingot extract did. The L-929 cells showed more improved adhesion on the surfaces of the three as-spun Mg-3Ca alloy ribbons than that of the as-cast Mg-3Ca alloy ingot.

Grain refinement of Ca addition in a twin-roll-cast Mg-3Al-1Zn alloy

Energy Technology Data Exchange (ETDEWEB)

Jiang Bin, E-mail: jiangbinrong@cqu.edu.cn [National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400030 (China); College of Materials Science and Engineering, Chongqing University, Chongqing 400030 (China); Liu Wenjun [College of Materials Science and Engineering, Chongqing University, Chongqing 400030 (China); Qiu Dong; Zhang Mingxing [Division of Materials, School of Mechanical and Mining Engineering, University of Queensland, St Lucia, QLD 4072 (Australia); Pan Fusheng [National Engineering Research Center for Magnesium Alloys, Chongqing University, Chongqing 400030 (China)

2012-04-16

Highlights: Black-Right-Pointing-Pointer Grain refinement of Ca addition in a twin-roll-cast Mg-3Al-1Zn alloy was investigated. Black-Right-Pointing-Pointer Addition of 0.08 wt% Ca into Mg melts can significantly reduce the grain size to 30 {mu}m from 100 {mu}m. Black-Right-Pointing-Pointer Al{sub 2}Ca intermetallic particles have high potency to act as heterogeneous nucleation sites for {alpha}-Mg. - Abstract: Addition of 0.08 wt% Ca into AZ31 melts significantly reduces the average grain size of thin strips produced by twin-roll-cast to 30 {mu}m from 100 {mu}m. Like Zr, due to the high chemical activity, the Ca added into the melts reacts with Al and forms Al{sub 2}Ca intermetallic compound. X-ray diffraction result approves the existence of Al{sub 2}Ca in the thin strips, which formed in the melts. Crystallographic examination of relationship between Al{sub 2}Ca and Mg using the edge-to-edge matching model indicates that Al{sub 2}Ca particles are effective inoculants for heterogeneous nucleation of Mg. It is considered that Al{sub 2}Ca is a potential and effective grain refiner for Mg alloys and the grain refinement through addition of Ca in the AZ31 alloy is attributed to the inoculation effect of Al{sub 2}Ca particles formed in the melts.

The parietal cell gastric H, K-ATPase also functions as the Na, K-ATPase and Ca-ATPase in altered states [v2; ref status: indexed, http://f1000r.es/1tc

Directory of Open Access Journals (Sweden)

Tushar Ray

2013-09-01

Full Text Available This article offers an explanation for the apparent lack of Na, K-ATPase activity in parietal cells although ouabain has been known to inhibit gastric acid secretion since 1962. The gastric H, K-ATPase (proton-pump seems to be acting in altered states, thus behaving like a Na, K-ATPase (Na-pump and/or Ca-ATPase (Ca-pump depending on cellular needs.  This conclusion is based on the following findings. First, parietal cell fractions do not exhibit Na, K-ATPase activity at pH 7.0 but do at pH 8.5. Second, the apical plasma membrane (APM fraction exhibits a (Ca or Mg-ATPase activity with negligible H, K-ATPase activity. However, when assayed with Mg alone in presence of the 80 k Da cytosolic proton-pump activator (HAF, the APM fraction reveals remarkably high H, K-ATPase activity, suggesting the observed low affinity of Ca (or Mg-ATPase is an altered state of the latter. Third, calcium (between 1 and 4 µM shows both stimulation and inhibition of the HAF-stimulated H, K-ATPase depending on its concentration, revealing a close interaction between the  proton-pump activator and local Ca concentration in gastric H, K-ATPase function. Such interactions suggest that Ca is acting as a terminal member of the intracellular signaling system for the HAF-regulated proton-pump. It appears that during resting state, the HAF-associated H, K-ATPase remains inhibited by Ca (>1 µM and, prior to resumption of acid secretion the gastric H, K-ATPase acts temporarily as a Ca-pump for removing excess Ca from its immediate environment. This conclusion is consistent with the recent reports of immunochemical co-localization of the gastric H, K-ATPase and Ca-ATPase by superimposition in parietal cells, and a transitory efflux of Ca immediately preceding the onset of acid secretion. These new perspectives on proton-pump function would open new avenues for a fuller understanding of the intracellular regulation of the ubiquitous Na-pump.

THE THERMODYNAMIC PROPERTIES OF MELTS OF DOUBLE SYSTEM MgO – Al2O3, MgO – SiO2, MgO – CaF2, Al2O3 – SiO2, Al2O3 – CaF2, SiO2 – CaF2

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В. Судавцова

2012-04-01

Full Text Available Methodology of prognostication of thermodynamics properties of melts is presented from the coordinatesof liquidus of diagram of the state in area of equilibria a hard component is solution, on which energies ofmixing of Gibbs are expected in the double border systems of MgO – Al2O3, MgO – SiO2, MgO – CaF2,Al2O3 – SiO2, Al2O3 - CaF2, SiO2 - CaF2. For the areas of equilibrium there is quasibinary connection(MgAl2O4, Mg2SiO4, Al6Si2O13 – a grout at calculations was used equalization of Hauffe-Wagner. Theobtained data comport with literary

Reduction of CaO and MgO Slag Components by Al in Liquid Fe

Science.gov (United States)

Mu, Haoyuan; Zhang, Tongsheng; Fruehan, Richard J.; Webler, Bryan A.

2018-05-01

This study documents laboratory-scale observations of reactions between Fe-Al alloys (0.1 to 2 wt pct Al) with slags and refractories. Al in steels is known to reduce oxide components in slag and refractory. With continued development of Al-containing Advanced High-Strength Steel (AHSS) grade, the effects of higher Al must be examined because reduction of components such as CaO and MgO could lead to uncontrolled modification of non-metallic inclusions. This may lead to castability or in-service performance problems. In this work, Fe-Al alloys and CaO-MgO-Al2O3 slags were melted in an MgO crucible and samples were taken at various times up to 60 minutes. Inclusions from these samples were characterized using an automated scanning electron microscope equipped with energy dispersive x-ray analysis (SEM/EDS). Initially Al2O3 inclusions were modified to MgAl2O4, then MgO, then MgO + CaO-Al2O3-MgO liquid inclusions. Modification of the inclusions was faster at higher Al levels. Very little Ca modification was observed except at 2 wt pct Al level. The thermodynamic feasibility of inclusion modification and some of the mass transfer considerations that may have led to the differences in the Mg and Ca modification behavior were discussed.

Effect of organic matrices on the determination of the trace element chemistry (Mg, Sr, Mg/Ca, Sr/Ca) of aragonitic bivalve shells (Arctica islandica). Comparison of ICP-OES and LA-ICP-MS data

International Nuclear Information System (INIS)

Schoene, Bernd R.; Zhang, Zengjie; Jacob, Dorrit; Soldate, Analia; Gillikin, David P.; Tuetken, Thomas; Garbe-Shoenberg, Dieter; McConnaughey, Ted

2010-01-01

The element chemistry of biogenic carbonates can provide important data on past environments. However, the Sr/Ca and Mg/Ca ratios as well as the Mg and Sr concentrations of biological carbonates, especially aragonitic bivalves often depart from apparent thermodynamic equilibrium. When measured in situ by means of LA-ICP-MS, the Mg concentration is often substantially enriched (two- to threefold) near the organic-rich, annual growth lines. To test the hypothesis that some organic components exert a major influence on the skeletal metal content, the element chemistry of different shell components (insoluble organic matrix, IOM; dissolved CaCO 3 and soluble organics, SOM) of Arctica islandica was measured by means of ICP-OES and LA-ICP-MS. The ICP-OES data indicate that the IOM is strongly enriched in Mg (130 ppm) and depleted in Sr and Ca (10 ppm and 0.22 wt%, respectively) when compared to the whole biomineral (Mg: 68 to 99 ppm, Sr: 860 to 1,060 ppm, Ca: ∼35.72 wt%). Although the average relative abundance of the IOM barely exceeds 0.46 wt%, its chemical composition in combination with its heterogeneous distribution across the shell can significantly increase estimates of the Mg concentration if measured in situ by LA-ICP-MS. Depending on the distribution of the IOM, the Ca concentration may be significantly lower locally than the average Ca concentration of the whole shell (35.72 wt%). If this remains undetected, the Mg concentration of shell portions with higher than average IOM content is overestimated by LA-ICP-MS and, conversely, the Mg concentration is underestimated in shell portions with lower than average IOM content. Removal of the IOM prior to the chemical analysis by LA-ICP-MS or mathematical correction for the IOM-derived magnesium concentrations is therefore strongly advised. The different chemistry of the IOM may also exert a major control on the trace element to calcium ratios. Shell portions enriched in IOM will show up to 200 times higher Mg/Ca

Eocene greenhouse climate revealed by coupled clumped isotope-Mg/Ca thermometry.

Science.gov (United States)

Evans, David; Sagoo, Navjit; Renema, Willem; Cotton, Laura J; Müller, Wolfgang; Todd, Jonathan A; Saraswati, Pratul Kumar; Stassen, Peter; Ziegler, Martin; Pearson, Paul N; Valdes, Paul J; Affek, Hagit P

2018-02-06

Past greenhouse periods with elevated atmospheric CO 2 were characterized by globally warmer sea-surface temperatures (SST). However, the extent to which the high latitudes warmed to a greater degree than the tropics (polar amplification) remains poorly constrained, in particular because there are only a few temperature reconstructions from the tropics. Consequently, the relationship between increased CO 2 , the degree of tropical warming, and the resulting latitudinal SST gradient is not well known. Here, we present coupled clumped isotope (Δ 47 )-Mg/Ca measurements of foraminifera from a set of globally distributed sites in the tropics and midlatitudes. Δ 47 is insensitive to seawater chemistry and therefore provides a robust constraint on tropical SST. Crucially, coupling these data with Mg/Ca measurements allows the precise reconstruction of Mg/Ca sw throughout the Eocene, enabling the reinterpretation of all planktonic foraminifera Mg/Ca data. The combined dataset constrains the range in Eocene tropical SST to 30-36 °C (from sites in all basins). We compare these accurate tropical SST to deep-ocean temperatures, serving as a minimum constraint on high-latitude SST. This results in a robust conservative reconstruction of the early Eocene latitudinal gradient, which was reduced by at least 32 ± 10% compared with present day, demonstrating greater polar amplification than captured by most climate models.

Comparison of Ca2+ and Mg2+ enhancing aerobic granulation in SBR

International Nuclear Information System (INIS)

Liu Lin; Gao Dawen; Zhang Min; Fu Yuan

2010-01-01

Two sequencing batch reactors (SBRs) were operated to investigate the effect of Ca 2+ and Mg 2+ augmentation on aerobic granulation. Reactor R1 was augmented with Ca 2+ at 40 mg/L, while Mg 2+ was added to the reactor R2 with 40 mg/L. Results showed that the reactor R1 had a faster granulation process compared with R2, and the mature granules in R1 showed better physical characteristics. However, the mature granules in R2 had the higher production yield of polysaccharides and proteins, and aerobic granules in R2 experienced a faster substrate biodegradation. Microbial and genetic characteristics in mature granules were analyzed using polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) techniques. The results revealed that Mg 2+ addition led to higher microbial diversity in mature granules. In addition, an uncultured bacterium (AB447697) was major specie in R1, and β-proteobacterium was dominant in R2. It can be concluded that Ca 2+ had an important effect on physical properties of aerobic granules, while Mg 2+ played a key role on biological properties during the sludge granulation.

Sr/Ca and Mg/Ca in Glycymeris glycymeris (Bivalvia) shells from the Iberian upwelling system: Ontogeny and environmental control

Science.gov (United States)

Freitas, Pedro; Richardson, Christopher; Chenery, Simon; Monteiro, Carlos; Butler, Paul; Reynolds, David; Scourse, James; Gaspar, Miguel

2017-04-01

Bivalve shells have a great potential as high-resolution geochemical proxy archives of marine environmental conditions. In addition, sclerochronology of long-lived bivalve species (e.g. Arctica islandica) provides a timeline of absolutely dated shell material for geochemical analysis that can extend into the past beyond the lifetime of single individuals through the use of replicated crossmatched centennial to millennial chronologies. However, the interpretation of such records remains extremely challenging and complex, with multiple environmental and biological processes affecting element incorporation in the shell (e.g. crystal fabrics, organic matrix, biomineralization mechanisms and physiological processes). As a result, the effective use of bivalve shell elemental/Ca ratios as palaeoenvironmental proxies has been limited, often to species-specific applications or applications restricted to particular environmental settings. The dog-cockle, Glycymeris glycymeris, is a relatively long-lived bivalve (up to 200 years) that occurs in coarse-grained subtidal sediments of coastal shelf seas of Europe and North West Africa. Glycymeris glycymeris shells provide a valuable, albeit not fully explored, archive to reconstruct past environmental variability in an area lacking sclerochronological studies due to the rarity of long-lived bivalves and lack of coral reefs. In this study, we evaluate the potential of Sr/Ca and Mg/Ca ratios in G. glycymeris shells as geochemical proxies of upwelling conditions in the Iberian Upwelling System, the northern section of the Canary Current Eastern Boundary Upwelling System. Sr/Ca and Mg/Ca generally co-varied significantly and a clear ontogenetic, non-environmental related change in Sr/Ca and Ba/Ca variability was observed. High Sr/Ca and Mg/Ca ratios in older shells (> 10 years old) were found to be associated with the occurrence of growth lines deposited during the winter reduction in shell growth. Nevertheless, Sr/Ca and Mg/Ca

The effect of impurities on the electronic properties of MgO

Energy Technology Data Exchange (ETDEWEB)

Jalili, Seifollah [Department of Chemistry, K.N. Toosi University of Technology, P.O. Box 16315-1618, Tehran (Iran, Islamic Republic of); Computational Physical Sciences Research Laboratory, Department of Nano-Science, Institute for Studies in Theoretical Physics and Mathematics (IPM), P.O. Box 19395-5531, Tehran (Iran, Islamic Republic of)], E-mail: sjalili@nano.ipm.ac.ir; Majidi, Roya [Department of Physics, Shahid Beheshti University, Tehran (Iran, Islamic Republic of)

2008-10-01

The effect of impurities on the electronic properties of MgO is investigated using the full potential linearized augmented plane-wave plus local-orbitals method based on density functional theory. The electronic band structures and density of states of MgO in the presence of Ca, Li, and Na impurities were calculated. It is found that increasing the amount of Ca impurity decreases the energy band gap and increases the width of the upper part of the valence band. Some of the considered impurities (Li and Na) change the electronic properties of MgO extensively.

The effect of impurities on the electronic properties of MgO

International Nuclear Information System (INIS)

Jalili, Seifollah; Majidi, Roya

2008-01-01

The effect of impurities on the electronic properties of MgO is investigated using the full potential linearized augmented plane-wave plus local-orbitals method based on density functional theory. The electronic band structures and density of states of MgO in the presence of Ca, Li, and Na impurities were calculated. It is found that increasing the amount of Ca impurity decreases the energy band gap and increases the width of the upper part of the valence band. Some of the considered impurities (Li and Na) change the electronic properties of MgO extensively

Seasonal variations in Na, K, Mg and Ca charge balance in marine brown algae from Saurashtra Coast (NW coast of India)

Digital Repository Service at National Institute of Oceanography (India)

Rao, Ch.K.; Singbal, S.Y.S.

) strongly correlated with Cl content suggesting that these cations were balanced by chloride ions. Divalent cations (Ca + Mg) seem to be balanced by the anion sulphate. Ash content of the algae was accounted by these major cations and anions. Charge...

Na+-independent, nifedipine-resistant rat afferent arteriolar Ca2+ responses to noradrenaline

DEFF Research Database (Denmark)

Salomonsson, Max; Braunstein, Thomas Hartig; von Holstein-Rathlou, Niels-Henrik

2010-01-01

Abstract Aim: In rat afferent arterioles we investigated the role of Na(+) entry in noradrenaline (NA)-induced depolarization and voltage-dependent Ca(2+) entry together with the importance of the transient receptor potential channel (TRPC) subfamily for non-voltage-dependent Ca(2+) entry. Methods...

Effect of Alumina Incorporation on the Surface Mineralization and Degradation of a Bioactive Glass (CaO-MgO-SiO2-Na2O-P2O5-CaF2-Glycerol Paste

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Dilshat Tulyaganov

2017-11-01

Full Text Available This study investigates the dissolution behavior as well as the surface biomineralization in simulated body fluid (SBF of a paste composed of glycerol (gly and a bioactive glass in the system CaO-MgO-SiO2-Na2O-P2O5-CaF2 (BG. The synthesis of the bioactive glass in an alumina crucible has been shown to significantly affect its bioactivity due to the incorporation of aluminum (ca. 1.3–1.4 wt % into the glass network. Thus, the kinetics of the hydroxyapatite (HA mineralization on the glass prepared in the alumina crucible was found to be slower than that reported for the same glass composition prepared in a Pt crucible. It is considered that the synthesis conditions lead to the incorporation of small amount of aluminum into the BG network and thus delay the HA mineralization. Interestingly, the BG-gly paste was shown to have significantly higher bioactivity than that of the as-prepared BG. Structural analysis of the paste indicate that glycerol chemically interacts with the glass surface and strongly alter the glass network architecture, thus generating a more depolymerized network, as well as an increased amount of silanol groups at the surface of the glass. In particular, BG-gly paste features early intermediate calcite precipitation during immersion in SBF, followed by hydroxyapatite formation after ca. seven days of SBF exposure; whereas the HA mineralization seems to be suppressed in BG, probably a consequence of the incorporation of aluminum into the glass network. The results obtained within the present study reveal the positive effect of using pastes based on bioactive glasses and organic carriers (here alcohols which may be of interest not only due to their advantageous visco-elastic properties, but also due to the possibility of enhancing the glass bioactivity upon surface interactions with the organic carrier.

Analysis of Ca and Mg in blood of golden hamster using NAA technique

International Nuclear Information System (INIS)

Aguiar, Rodrigo O.; Zamboni, Cibele B.; Medeiros, Jose A.G.

2009-01-01

Neutron activation analysis (NAA) technique has been used to determine simultaneously Ca and Mg concentrations in whole blood of Golden Hamster. The reference values for Ca (0.17 - 0.29 gL -1 ) and Mg (0.042 - 0.074 gL -1 ) can be used to performed biochemistry investigation using whole blood. (author)

Quadruple-layered perovskite (CuCl)Ca2NaNb4O13

International Nuclear Information System (INIS)

Kitada, A.; Tsujimoto, Y.; Yamamoto, T.; Kobayashi, Y.; Narumi, Y.; Kindo, K.; Aczel, A.A.; Luke, G.M.; Uemura, Y.J.; Kiuchi, Y.; Ueda, Y.; Yoshimura, K.; Ajiro, Y.; Kageyama, H.

2012-01-01

We will present the synthesis, structure and magnetic properties of a new quadruple-layered perovskite (CuCl)Ca 2 NaNb 4 O 13 . Through a topotactic ion-exchange reaction with CuCl 2 , the precursor RbCa 2 NaNb 4 O 13 presumably having an incoherent octahederal tliting changes into (CuCl)Ca 2 NaNb 4 O 13 with a 2a p ×2a p ×2c p superstructure (tetragonal; a=7.73232(5) Å, c=39.2156(4) Å). The well-defined superstructure for the ion-exchanged product should be stabilized by the inserted CuCl 4 O 2 octahedral layers that firmly connect with neighboring perovskite layers. Magnetic studies show the absence of long-range magnetic ordering down to 2 K despite strong in-plane interactions. Aleksandrov′s group theory and Rietveld refinement of synchrotron X-ray diffraction data suggest the structure to be of I4/mmm space group with in-phase tilting along the a and b axes, a two-tilt system (++0). - Graphical Abstract: We present a quadruple-layered copper oxyhalide (CuCl)Ca 2 NaNb 4 O 13 synthesized through a topotactic ion-exchange reaction of RbCa 2 NaNb 4 O 13 with CuCl 2 . The compound has a well-defined superstructure. Magnetic studies suggest the absence of magnetic order even at 2 K. Highlights: ► (CuCl)Ca 2 NaNb 4 O 13 was prepared by ion-exchange reaction of RbCa 2 NaNb 4 O 13 with CuCl 2 . ► Compound has a 2a p ×2a p ×2c p superstructure (tetragonal; a=7.73 Å, c=39.21 Å). ► Such a well-defined superstructure was not observed in the precursor compound. ► Aleksandrov′s theory and Rietveld study suggest a (++0) octahedral tilting (I4/mmm). ► Magnetic studies revealed the absence of magnetic order down to 2 K.

Analysis of Ca and Mg in blood of golden hamster using NAA technique

Energy Technology Data Exchange (ETDEWEB)

Aguiar, Rodrigo O.; Zamboni, Cibele B.; Medeiros, Jose A.G. [Instituto de Pesquisas Energeticas e Nucleares (IPEN-CNEN/SP), Sao Paulo, SP (Brazil)], e-mail: rodrigoaguiar@usp.br, e-mail: czamboni@ipen.br, e-mail: jageiros@yahoo.com.br

2009-07-01

Neutron activation analysis (NAA) technique has been used to determine simultaneously Ca and Mg concentrations in whole blood of Golden Hamster. The reference values for Ca (0.17 - 0.29 gL{sup -1} ) and Mg (0.042 - 0.074 gL{sup -1} ) can be used to performed biochemistry investigation using whole blood. (author)

Cinética de absorção e eficiência nutricional de K+, Ca2+ e Mg2+ em plantas jovens de quatro clones de eucalipto Uptake kinetics and nutritional efficiency for K+, Ca2+ and Mg2+ in four eucalypt clones seedlings

Directory of Open Access Journals (Sweden)

Augusto Miguel Nascimento Lima

2005-12-01

Full Text Available Modelos mecanísticos baseados em princípios de transporte de solutos pode ser de grande utilidade para prever os impactos do cultivo de florestas plantadas, por exemplo, com eucalipto sobre o capital e fluxo de nutrientes no solo. Dentre as variáveis de entrada demandadas por tais modelos, tem-se os valores das constantes Vmax, Km e Cmin da cinética de absorção iônica. Assim, os objetivos do presente trabalho foram determinar os valores de Vmax, Km e Cmin para K, Ca e Mg, bem como avaliar as respectivas eficiências nutricionais de clones de eucalipto. O estudo consistiu de três ensaios em solução nutritiva (um para cada cátion, sendo utilizadas mudas propagadas vegetativamente de um híbrido de E. grandis x E. urophylla (clone 1213 e de três híbridos de E. grandis (clones 7074, 57 e 129. Com base nos teores de cada um desses nutrientes nas soluções de depleção, em cada tempo de amostragem, no volume inicial e final de solução nos vasos e no peso de matéria fresca de raízes, foram obtidos os valores das constantes cinéticas. Para K, o clone 7074 apresentou o menor valor de Vmax em relação aos demais clones, os quais não diferiram entre si, e em relação ao Km e Cmin, os clones não diferiram estatisticamente. Para Ca, os clones estudados diferiram quanto ao valor de Vmax e Km, não diferindo, entretanto, para o Cmin. Os menores valores de Km para Mg foram verificados para os clones 57 e 7074, ou seja, as proteínas transportadoras de Mg na membrana plasmática das células radiculares apresentaram maior afinidade para esse nutriente. Contudo, os valores de Vmax e Cmin não diferiram entre os clones estudados. Diferenças na eficiência nutricional dos clones estudados quanto a K e a Ca foram devidas às diferenças na eficiência de absorção, e para Mg às diferenças na eficiência de absorção e de utilização.The use of mechanistic models based on principles of solute transport may be of great utility to estimate

Microstructure, Tensile Properties, and Corrosion Behavior of Die-Cast Mg-7Al-1Ca- xSn Alloys

Science.gov (United States)

Wang, Feng; Dong, Haikuo; Sun, Shijie; Wang, Zhi; Mao, Pingli; Liu, Zheng

2018-02-01

The microstructure, tensile properties, and corrosion behavior of die-cast Mg-7Al-1Ca- xSn ( x = 0, 0.5, 1.0, and 2.0 wt.%) alloys were studied using OM, SEM/EDS, tensile test, weight loss test, and electrochemical test. The experimental results showed that Sn addition effectively refined grains and intermetallic phases and increased the amount of intermetallic phases. Meanwhile, Sn addition to the alloys suppressed the formation of the (Mg,Al)2Ca phase and resulted in the formation of the ternary CaMgSn phase and the binary Mg2Sn phase. The Mg-7Al-1Ca-0.5Sn alloy exhibited best tensile properties at room temperature, while Mg-7Al-1Ca-1.0Sn alloy exhibited best tensile properties at elevated temperature. The corrosion resistance of studied alloys was improved by the Sn addition, and the Mg-7Al-1Ca-0.5Sn alloy presented the best corrosion resistance.

Mg/Ca and Sr/Ca as novel geochemical proxies for understanding sediment transport processes within coral reefs

Science.gov (United States)

Gacutan, J.; Vila-Concejo, A.; Nothdurft, L. D.; Fellowes, T. E.; Cathey, H. E.; Opdyke, B. N.; Harris, D. L.; Hamylton, S.; Carvalho, R. C.; Byrne, M.; Webster, J. M.

2017-10-01

Sediment transport is a key driver of reef zonation and biodiversity, where an understanding of sediment dynamics gives insights into past reef processes and allows the prediction of geomorphic responses to changing environmental conditions. However, modal conditions within the back-reef seldom promote sediment transport, hence direct observation is inherently difficult. Large benthic foraminifera (LBF) have previously been employed as 'tracers' to infer sediment transport pathways on coral reefs, as their habitat is largely restricted to the algal flat and post-mortem, their calcium carbonate test is susceptible to sediment transport forces into the back-reef. Foraminiferal test abundance and post-depositional test alteration have been used as proxies for sediment transport, although the resolution of these measures becomes limited by low test abundance and the lack of variation within test alteration. Here we propose the novel use of elemental ratios as a proxy for sediment transport. Two species, Baculogypsina sphaerulata and Calcarina capricornia, were analysed using a taphonomic index within One Tree and Lady Musgrave reefs, Great Barrier Reef (Australia). Inductively coupled plasma-atomic emission spectrometry (ICP-AES) was used to determine Mg/Ca and Sr/Ca and these ratios were compared with taphonomic data. Decreases in test Mg/Ca accompany increases in Sr/Ca in specimens from algal-flat to lagoonal samples in both species, mirroring trends indicated by taphonomic values, therefore indicating a relationship with test alteration. To delineate mechanisms driving changes in elemental ratios, back-scattered electron (BSE) images, elemental mapping and in situ quantitative spot analyses by electron microprobe microanalysis (EPMA) using wavelength dispersive X-ray spectrometers (WDS) were performed on un-altered algal flat and heavily abraded tests for both species. EPMA analyses reveal heterogeneity in Mg/Ca between spines and the test wall, implying the loss of

Multi-proxy Reconstructions of the Eastern Equatorial Pacific: Measuring Sr/Ca, Ba/Ca, and Li/Mg in Modern Corals Using ICP-OES

Science.gov (United States)

Cheung, A. H.; Cole, J. E.; Vetter, L.; Jimenez, G.; Thompson, D. M.; Tudhope, A. W.

2017-12-01

Sea surface temperature (SST) in the Eastern Equatorial Pacific (EEP) exhibits large variability on multiple timescales. These variations are often related to modes of climate variability that exert significant influence on global climate, such as the El Niño Southern Oscillation. However, the short length and sparsity of instrumental data in the EEP limits our ability to discern changes in this region. Geochemical signals in corals can help extend instrumental data further back in time. While δ18O and Sr/Ca are the most commonly analyzed geochemical tracers of SST in corals, they often have site-specific complications. Several alternatives (e.g., Li/Mg) have been proposed to overcome these challenges, but have yet to be applied to long climate records, in part due to the cost and time required to measure these elements. Here, we develop a new method that uses Inductively Coupled Plasma-Optical Emission Spectrometry (ICP-OES) to analyze Li/Mg, Sr/Ca, and Ba/Ca ratios in coral aragonite. We apply this method to two Porites spp. corals collected from the northern Galapagos archipelago (Wolf and Darwin Islands). We specifically assess the fidelity of Li/Mg and Sr/Ca to reconstruct SST, and Ba/Ca to reconstruct upwelling conditions. Our results confirm that both Li/Mg and Sr/Ca track SST. We show that despite analytical noise, downcore reconstructions of Li/Mg have the potential to provide additional information about SST that is not present in reconstructions generated from Sr/Ca alone. Skeletal Ba/Ca shows little relationship with upwelling, perhaps because of the distance of our sites from the center of upwelling in the southern Galapagos. These results demonstrate the potential for analyzing Sr, Li, Ba, Mg simultaneously in corals with a cost- and time- efficient method, which may be applied to coral paleoclimate sites worldwide.

Adsorption of Na, Mg, and Al atoms on BN nanotubes

Energy Technology Data Exchange (ETDEWEB)

Beheshtian, Javad [Department of Chemistry, Shahid Rajaee Teacher Training University, P.O. Box: 16875-163, Tehran (Iran, Islamic Republic of); Peyghan, Ali Ahmadi, E-mail: ahmadi.iau@gmail.com [Young Researchers Club, Islamic Azad University, Islamshahr Branch, Tehran (Iran, Islamic Republic of); Bagheri, Zargham [Physics group, Science department, Islamic Azad University, Islamshahr Branch, P.O. Box: 33135-369, Islamshahr, Tehran (Iran, Islamic Republic of)

2012-12-30

Adsorption of three metals (Na, Mg, and Al) on the surface of BN nanotubes (BNNT) has been investigated by using density functional theory. Adsorption energies for Na and Al atoms have been calculated to be about - 0.22 to - 0.61 eV, respectively. Upon the metal adsorption, energy gap between highest occupied and lowest unoccupied orbitals of the tube is dramatically decreased, resulting in enhanced electrical conductivity. However, in the case of Mg atom, the low adsorption energy cannot change electronic property of the tube. The semi-conductive BNNT transform to n-type semiconductor after adsorption of Na atom. The metal adsorption modifies work function of the BNNT and consequently the field-emission current densities of metal-BNNT may be significantly enhanced. - Highlights: Black-Right-Pointing-Pointer Adsorption of Na, Mg, and Al atoms on the BN nanotubes (BNNT) was studied. Black-Right-Pointing-Pointer Adsorption energies for Na and Al atoms are about - 0.22 to - 0.61 eV, respectively. Black-Right-Pointing-Pointer Energy gap of the tube dramatically decreases upon the metals adsorption. Black-Right-Pointing-Pointer Semiconductor BNNT transform to n-type ones upon adsorption of Na and Al atoms. Black-Right-Pointing-Pointer The field-emission current densities of metal-BNNT may be significantly enhanced.

Study of solid state interactions in the systems ZnFe2O4 - CaO, ZnFe2O4 - MgO and zinc cake with CaO and MgO

Directory of Open Access Journals (Sweden)

Peltekov A.B.

2013-01-01

Full Text Available The solid state interactions of CaO and MgO with synthetic and industrial ZnFe2O4 (in zinc cake have been studied using chemical, XRD analysis and Mössbauer spectroscopy. The exchange reactions in the systems ZnFe2O4 - CaO and ZnFe2O4 - MgO have been investigated in the range of 850-1200ºC and duration up to 180 min. It has been established that Ca2+ and Mg2+ ions exchange Zn2+ in ferrite partially and the solubility of zinc in a 7% sulfuric acid solution increases. The possibilities for utilization of the obtained results in zinc hydrometallurgy have been discussed.

Formation process of micro arc oxidation coatings obtained in a sodium phytate containing solution with and without CaCO{sub 3} on binary Mg-1.0Ca alloy

Energy Technology Data Exchange (ETDEWEB)

Zhang, R.F. [School of Material and Electromechanics, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Zhang, Y.Q. [Zhejiang DunAn Light Alloy Technology CO,.LTD, Zhuji 311835 (China); Hunan University of Science and Technology, Xiangtan 411201 (China); Zhang, S.F.; Qu, B. [School of Material and Electromechanics, Jiangxi Science and Technology Normal University, Nanchang 330013 (China); Guo, S.B. [Hunan University of Science and Technology, Xiangtan 411201 (China); Xiang, J.H., E-mail: xiangjunhuai@163.com [School of Material and Electromechanics, Jiangxi Science and Technology Normal University, Nanchang 330013 (China)

2015-01-15

Highlights: • Compared to the Mg phase, the area of Mg{sub 2}Ca phase is much smaller. • The coatings are preferentially developed on the area adjacent to Mg{sub 2}Ca phase. • During MAO process, some sodium phytate molecules are hydrolyzed. • Anodic coatings are developed from uneven to uniform. - Abstract: Micro arc oxidation (MAO) is an effective method to improve the corrosion resistance of magnesium alloys. In order to reveal the influence of alloying element Ca and CaCO{sub 3} electrolyte on the formation process and chemical compositions of MAO coatings on binary Mg-1.0Ca alloy, anodic coatings after different anodizing times were prepared on binary Mg-1.0Ca alloy in a base solution containing 3 g/L sodium hydroxide and 15 g/L sodium phytate with and without addition of CaCO{sub 3}. The coating formation was studied by using scanning electron microscope (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The results show that Mg-1.0Ca alloy is composed of two phases, the Mg phase and Mg{sub 2}Ca phase. After treating for 5 s, the coating began to develop and was preferentially formed on the area nearby Mg{sub 2}Ca phase, which may be resulted from the intrinsic electronegative potential of the Mg phase than that of Mg{sub 2}Ca phase. Anodic coatings unevenly covered the total surface after 20 s. After 80 s, the coatings were uniformly developed on Mg-1.0Ca alloy with micro pores. During MAO process, some sodium phytate molecules are hydrolyzed into inorganic phosphate. CaCO{sub 3} has minor influence on the calcium content of the obtained MAO coatings.

Synthesis and thermoluminescence characterization of Na6Mg(SO4)4:RE (RE = Ce, Tb) phosphors

International Nuclear Information System (INIS)

Kore, Bhushan P.; Dhoble, N.S.; Dhoble, S.J.

2014-01-01

Thermoluminescence (TL) properties of sulfate-based phosphors activated by different rare earths have received tremendous attention to the field of radiation dosimetry. Those TL materials based on CaSO 4 have been widely applied for medical and environmental dosimetry. Taking this fact into account we have synthesized Na 6 Mg(SO 4 ) 4 doped with Ce and Tb by wet chemical method. The prepared phosphor was characterized by XRD, FTIR, photoluminescence (PL) and thermoluminescence. For TL study, the phosphor is irradiated with γ-rays from 60 Co source. For studying luminescence properties, the prepared phosphor was annealed at different temperatures and effects of these annealing temperatures on Na 6 Mg(SO 4 ) 4 samples are investigated and quantified. The changes in the glow curve and PL emission spectrum are also investigated as a function of annealing temperature and the annealing temperature was optimized. For calculation of trapping parameters various methods such as peak shape (PS) method, initial rise (IR) method, various heating rate (VHR) method, and computerized glow curve deconvolution (CGCD) are employed. - Highlights: • Na 6 Mg(SO 4 ) 4 phosphor was successfully prepared by wet chemical method. • Effect of annealing temperatures on PL and TL properties has been studied. • Different trap analysis methods were used for calculating the trapping parameters. • Effect of these methods on activation energies were investigated in detail

Regulation of the Na+/Ca2+ exchanger in rat pancreatic ducts

DEFF Research Database (Denmark)

Ankorina-Stark, I; Amstrup, J; Novak, I

2002-01-01

by hormones/agonists affecting pancreatic secretion. Whole pancreas, pure pancreatic acini and ducts were obtained from rats and used for RT-PCR and Western blot analysis, immunohistochemistry and intracellular Ca2+ measurements using Fura-2. RT-PCR analysis indicated Na+/Ca2+-exchanger isoforms NCX1.......3 and NCX1.7 in acini and pancreas. Western blot with NCX1 antibody identified bands of 70, 120 and 150 kDa in isolated ducts, acini and pancreas. Immunofluorescence experiments showed the Na+/Ca2+ exchanger on the basolateral membrane of acini and small intercalated/intralobular ducts, but in larger...

Evaluation of NaX and NaY packed beds for chromium uptake from multicomponent solution

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Maria Angélica Simões Dornellas de Barros

2014-04-01

Full Text Available In this paper the removal of chromium from Cr/Ca/Mg/K and Cr/Ca/Mg/K/Na solutions was investigated in NaX and NaY packed beds. The breakthrough curves presented some overshooting phenomena where chromium ions displaced the previous exchanged cations. Length of unused bed, overall mass transfer coefficient, operational ratio and dimensionless variance were obtained. According to such mass transfer parameters it was concluded that the chromium uptake is influenced by the competition and interaction of the entering ions. Such influences were verified through some differences in the dynamic selectivity obtained for each system. NaY seemed to have a higher affinity towards Cr3+ and its sites were more efficiently used in the ion exchange process.

Post-Mesozoic Rapid Increase of Seawater Mg/Ca due to Enhanced Mantle-Seawater Interaction

OpenAIRE

Marco Ligi; Enrico Bonatti; Marco Cuffaro; Daniele Brunelli

2013-01-01

The seawater Mg/Ca ratio increased significantly from ~ 80?Ma to present, as suggested by studies of carbonate veins in oceanic basalts and of fluid inclusions in halite. We show here that reactions of mantle-derived peridotites with seawater along slow spreading mid-ocean ridges contributed to the post-Cretaceous Mg/Ca increase. These reactions can release to modern seawater up to 20% of the yearly Mg river input. However, no significant peridotite-seawater interaction and Mg-release to the ...

Accumulation of /sup 90/Sr, Ca, Mg, K and Na in crane's-bill plants cultivated on soil and hydroponics

Energy Technology Data Exchange (ETDEWEB)

Analyan, V L; Sarkisyan, G A [AN Armyanskoj SSR, Erevan. Inst. Agrokhimicheskikh Problem i Gidroponiki

1981-01-01

Accumulation of /sup 90/Sr in plants under the conditions of soil and hydroponic cultures from the viewpoint of the possibility of obtaining ''pure'' vegetable production has been studied. Predominant absorption of /sup 90/Sr by soil plants as compared with calcium is shown. In the course of using the hydroponic cultivation method predominant radiostrontium absorption has been manifested to all investigated nuclides including potassium. The accumulation coefficients analysis has shown that among soil plants the first place is occupied by potassium, while the /sup 90/Sr coefficients are greater than Ca on hydroponics, where the true, not distorted by soil sorption processes absorptive plant capacity has been manifested, the first places in the series are occupied by /sup 90/Sr and K, then come Ca and Mg.

Microstructure, mechanical properties and bio-corrosion properties of Mg-Si(-Ca, Zn) alloy for biomedical application.

Science.gov (United States)

Zhang, Erlin; Yang, Lei; Xu, Jianwei; Chen, Haiyan

2010-05-01

Mg-Si alloy was investigated for biomedical application due to the biological function of Si in the human body. However, Mg-Si alloy showed a low ductility due to the presence of coarse Mg(2)Si. Ca and Zn elements were used to refine and modify the morphology of Mg(2)Si in order to improve the corrosion resistance and the mechanical properties. The cell toxicity of Mg, Zn and Ca metals was assessed by an MTT test. The test results indicated that increasing the concentrations of Mg, Zn and Ca ions did not cause cell toxicity, which showed that the release of these three elements would not lead to cell toxicity. Then, microstructure, mechanical properties and bio-corrosion properties of as-cast Mg-Si(-Ca, Zn) alloys were investigated by optical microscopy, scanning electronic microscopy, mechanical properties testing and electrochemical measurement. Ca element can slightly refine the grain size and the morphology Mg(2)Si phase in Mg-Si alloy. The bio-corrosion resistance of Mg-Si alloys was improved by the addition of Ca due to the reduction and refinement of Mg(2)Si phase; however, no improvement was observed in the strength and elongation. The addition of 1.6% Zn to Mg-0.6Si can modify obviously the morphology of Mg(2)Si phase from course eutectic structure to a small dot or short bar shape. As a result, tensile strength, elongation and bio-corrosion resistance were all improved significantly; especially, the elongation improved by 115.7%. It was concluded that Zn element was one of the best alloying elements of Mg-Si alloy for biomedical application. Copyright (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Dry etching of MgCaO gate dielectric and passivation layers on GaN

International Nuclear Information System (INIS)

Hlad, M.; Voss, L.; Gila, B.P.; Abernathy, C.R.; Pearton, S.J.; Ren, F.

2006-01-01

MgCaO films grown by rf plasma-assisted molecular beam epitaxy and capped with Sc 2 O 3 are promising candidates as surface passivation layers and gate dielectrics on GaN-based high electron mobility transistors (HEMTs) and metal-oxide semiconductor HEMTs (MOS-HEMTs), respectively. Two different plasma chemistries were examined for etching these thin films on GaN. Inductively coupled plasmas of CH 4 /H 2 /Ar produced etch rates only in the range 20-70 A/min, comparable to the Ar sputter rates under the same conditions. Similarly slow MgCaO etch rates (∼100 A/min) were obtained with Cl 2 /Ar discharges under the same conditions, but GaN showed rates almost an order of magnitude higher. The MgCaO removal rates are limited by the low volatilities of the respective etch products. The CH 4 /H 2 /Ar plasma chemistry produced a selectivity of around 2 for etching the MgCaO with respect to GaN

Raman microspectroscopic study of effects of Na(I) and Mg(II) ions on low pH induced DNA structural changes.

Science.gov (United States)

Muntean, C M; Segers-Nolten, G M J

2003-01-01

In this work a confocal Raman microspectrometer is used to investigate the influence of Na(+) and Mg(2+) ions on the DNA structural changes induced by low pH. Measurements are carried out on calf thymus DNA at neutral pH (7) and pH 3 in the presence of low and high concentrations of Na(+) and Mg(2+) ions, respectively. It is found that low concentrations of Na(+) ions do not protect DNA against binding of H(+). High concentrations of monovalent ions can prevent protonation of the DNA double helix. Our Raman spectra show that low concentrations of Mg(2+) ions partly protect DNA against protonation of cytosine (line at 1262 cm(-1)) but do not protect adenine and guanine N(7) against binding of H(+) (characteristic lines at 1304 and 1488 cm(-1), respectively). High concentrations of Mg(2+) can prevent protonation of cytosine and protonation of adenine (disruption of AT pairs). By analyzing the line at 1488 cm(-1), which obtains most of its intensity from a guanine vibration, high magnesium salt protect the N(7) of guanine against protonation. A high salt concentration can prevent protonation of guanine, cytosine, and adenine in DNA. Higher salt concentrations cause less DNA protonation than lower salt concentrations. Magnesium ions are found to be more effective in protecting DNA against binding of H(+) as compared with calcium ions presented in a previous study. Divalent metal cations (Mg(2+), Ca(2+)) are more effective in protecting DNA against protonation than monovalent ions (Na(+)). Copyright 2003 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 000-000, 2003

Cellular Response to Doping of High Porosity Foamed Alumina with Ca, P, Mg, and Si

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Edwin Soh

2015-03-01

Full Text Available Foamed alumina was previously synthesised by direct foaming of sulphate salt blends varying ammonium mole fraction (AMF, foaming heating rate and sintering temperature. The optimal product was produced with 0.33AMF, foaming at 100 °C/h and sintering at 1600 °C. This product attained high porosity of 94.39%, large average pore size of 300 µm and the highest compressive strength of 384 kPa. To improve bioactivity, doping of porous alumina by soaking in dilute or saturated solutions of Ca, P, Mg, CaP or CaP + Mg was done. Saturated solutions of Ca, P, Mg, CaP and CaP + Mg were made with excess salt in distilled water and decanted. Dilute solutions were made by diluting the 100% solution to 10% concentration. Doping with Si was done using the sol gel method at 100% concentration only. Cell culture was carried out with MG63 osteosarcoma cells. Cellular response to the Si and P doped samples was positive with high cell populations and cell layer formation. The impact of doping with phosphate produced a result not previously reported. The cellular response showed that both Si and P doping improved the biocompatibility of the foamed alumina.

Efeitos de relações CaSO4/CaCO3 na mobilidade de nutrientes no solo e no crescimento do algodoeiro

Directory of Open Access Journals (Sweden)

A. A. Silva

1998-09-01

Full Text Available O experimento, realizado em casa de vegetação no Departamento de Ciência do Solo da Universidade Federal de Lavras, teve por objetivo estudar o efeito de diferentes relações de CaSO4/CaCO3, que simulam o uso de gesso e calcário, na movimentação de nutrientes no solo e no crescimento do algodoeiro, cultivar IAC-20. As proporções de CaSO4/CaCO3 utilizadas foram: 0/100, 25/75, 50/50, 75/25 e 100/0, com base em peso equivalente, além de um tratamento-testemunha, sem aplicação de CaSO4 e CaCO3. Observou-se acentuada movimentação de cálcio e de sulfato em profundidade, como íons acompanhantes, com o aumento da relação CaSO4/CaCO3. Para o N-NO3- e Mg2+, ao contrário do N-NH4+ e K+, observou-se um acúmulo em profundidade, com a elevação da relação CaSO4/CaCO3. Neste estudo, o gesso teve pouco ou nenhum efeito sobre a acidez e Al trocável presentes nas camadas subsuperficiais. A produção de matéria seca do algodoeiro foi reduzida com o aumento da relação CaSO4/CaCO3, porém, quando comparada à do tratamento-testemunha, a aplicação de gesso aumentou-a significativamente, atestando o potencial de uso do gesso agrícola.

Age-dependent changes in diastolic Ca{sup 2+} and Na{sup +} concentrations in dystrophic cardiomyopathy: Role of Ca{sup 2+} entry and IP{sub 3}

Energy Technology Data Exchange (ETDEWEB)

Mijares, Alfredo [Instituto Venezolano de Investigaciones Científicas, Centro de Biofísica y Bioquímica, Caracas (Venezuela, Bolivarian Republic of); Altamirano, Francisco [Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616 (United States); Kolster, Juan [Centro de Investigaciones Biomédicas, México D.F. (Mexico); Adams, José A. [Division of Neonatology, Mount Sinai Medical Center, Miami, FL 33140 (United States); López, José R., E-mail: jrlopez@ucdavis.edu [Instituto Venezolano de Investigaciones Científicas, Centro de Biofísica y Bioquímica, Caracas (Venezuela, Bolivarian Republic of); Department of Molecular Biosciences, School of Veterinary Medicine, University of California, Davis, CA 95616 (United States)

2014-10-03

Highlights: • Age-dependent increase in [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} in mdx cardiomyocytes. • Gadolinium significantly reduced both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages. • IP{sub 3}-pathway inhibition reduced cations concentrations in dystrophic cardiomyocytes. - Abstract: Duchenne muscular dystrophy (DMD) is a lethal X-inherited disease caused by dystrophin deficiency. Besides the relatively well characterized skeletal muscle degenerative processes, DMD is also associated with a dilated cardiomyopathy that leads to progressive heart failure at the end of the second decade. The aim of the present study was to characterize the diastolic Ca{sup 2+} concentration ([Ca{sup 2+}]{sub d}) and diastolic Na{sup +} concentration ([Na{sup +}]{sub d}) abnormalities in cardiomyocytes isolated from 3-, 6-, 9-, and 12-month old mdx mice using ion-selective microelectrodes. In addition, the contributions of gadolinium (Gd{sup 3+})-sensitive Ca{sup 2+} entry and inositol triphosphate (IP{sub 3}) signaling pathways in abnormal [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} were investigated. Our results showed an age-dependent increase in both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} in dystrophic cardiomyocytes compared to those isolated from age-matched wt mice. Gd{sup 3+} treatment significantly reduced both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages. In addition, blockade of the IP{sub 3}-pathway with either U-73122 or xestospongin C significantly reduced ion concentrations in dystrophic cardiomyocytes. Co-treatment with U-73122 and Gd{sup 3+} normalized both [Ca{sup 2+}]{sub d} and [Na{sup +}]{sub d} at all ages in dystrophic cardiomyocytes. These data showed that loss of dystrophin in mdx cardiomyocytes produced an age-dependent intracellular Ca{sup 2+} and Na{sup +} overload mediated at least in part by enhanced Ca{sup 2+} entry through Gd{sup 3+} sensitive transient receptor potential channels (TRPC), and by IP{sub 3} receptors.

Improved CO_2 adsorption capacity and cyclic stability of CaO sorbents incorporated with MgO

International Nuclear Information System (INIS)

Farah Diana Mohd Daud; Kumaravel Vignesh; Srimala Sreekantan; Abdul Rahman Mohamed

2016-01-01

Calcium oxide (CaO) sorbents incorporated with magnesium oxide (MgO) were synthesized using a co-precipitation route. The sorbents were prepared with different MgO concentrations (from 5 wt% to 30 wt%). The as-prepared sorbents were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX) and BET surface area analysis techniques. The sintering effect of CaO sorbents was decreased after the incorporation of MgO. The sorbents with 5 wt% and 10 wt% of MgO retained their CO_2 adsorption capacity over multiple cycles. Most importantly, CaO with 10 wt% MgO showed constant CO_2 adsorption capacity over 30 carbonation cycles. The results revealed that CaO with 10 wt% MgO is sufficient to produce sorbents with high surface area, good structural stability and enhanced CO_2 adsorption capacity. (authors)

Japanese Papilio butterflies puddle using Na+ detected by contact chemosensilla in the proboscis.

Science.gov (United States)

Inoue, Takashi A; Hata, Tamako; Asaoka, Kiyoshi; Ito, Tetsuo; Niihara, Kinuko; Hagiya, Hiroshi; Yokohari, Fumio

2012-12-01

Many butterflies acquire nutrients from non-nectar sources such as puddles. To better understand how male Papilio butterflies identify suitable sites for puddling, we used behavioral and electrophysiological methods to examine the responses of Japanese Papilio butterflies to Na(+), K(+), Ca(2+), and Mg(2+). Based on behavioral analyses, these butterflies preferred a 10-mM Na(+) solution to K(+), Ca(2+), and Mg(2+) solutions of the same concentration and among a tested range of 1 mM to 1 M NaCl. We also measured the ion concentrations of solutions sampled from puddling sites in the field. Na(+) concentrations of the samples were up to 6 mM, slightly lower than that preferred by butterflies in the behavioral experiments. Butterflies that sipped the 10 mM Na(+) solution from the experimental trays did not continue to puddle on the ground. Additionally, butterflies puddled at sites where the concentrations of K(+), Ca(2+), and/or Mg(2+) were higher than that of Na(+). This suggests that K(+), Ca(2+), and Mg(2+) do not interfere with the detection of Na(+) by the Papilio butterfly. Using an electrophysiological method, tip recordings, receptor neurons in contact chemosensilla inside the proboscis evoked regularly firing impulses to 1, 10, and 100 mM NaCl solutions but not to CaCl(2) or MgCl(2). The dose-response patterns to the NaCl solutions were different among the neurons, which were classified into three types. These results showed that Japanese Papilio butterflies puddle using Na(+) detected by the contact chemosensilla in the proboscis, which measure its concentration.

Low temperature synthesis of CaZrO3 nanoceramics from CaCl2–NaCl molten eutectic salt

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Rahman Fazli

2015-06-01

Full Text Available CaZrO3 nanoceramics were successfully synthesized at 700 C using the molten salt method, and the effects of processing parameters, such as temperature, holding time, and amount of salt on the crystallization of CaZrO3 were investigated. CaCl2, Na2CO3, and nano-ZrO2 were used as starting materials. On heating, CaCl2–NaCl molten eutectic salt provided a liquid medium for the reaction of CaCO3 and ZrO2 to form CaZrO3. The results demonstrated that CaZrO3 started to form at about 600C and that, after the temperature was increased to 1,000C, the amounts of CaZrO3 in the resultant powders increased with a concomitant decrease in CaCO3and ZrO2 contents. After washing with hot distilled water, the samples heated for 3 h at 700C were single-phase CaZrO3 with 90–95 nm particle size. Furthermore, the synthesized CaZrO3 particles retained the size and morphology of the ZrO2 powders which indicated that a template mechanism dominated the formation of CaZrO3 by molten-salt method.

Creep characteristics of a hypoeutectic Mg-Ca binary alloy with a near-fully lamellar microstructure

International Nuclear Information System (INIS)

Terada, Yoshihiro; Tsukahara, Masashi; Shibayama, Atsushi; Murata, Yoshinori; Morinaga, Masahiko

2011-01-01

Highlights: → We develop a hypoeutectic Mg-Ca cast alloy with a near-fully lamellar microstructure. → Dislocations are introduced within the lamellar microstructure during casting. → The dislocation segments in the α-Mg plates are located on the basal planes. → Creep of the alloy is ascribed to the easy glide of the introduced dislocations. -- The creep behavior of a hypoeutectic Mg-14.8 mass% Ca cast alloy with an α-Mg/C14-Mg 2 Ca near-fully lamellar microstructure was investigated at 473 K. Transmission electron microscopy shows that dislocations are introduced within the lamellar microstructure of the alloy during casting; the dislocation segments in the α-Mg plates are located on basal planes. The stress exponent of the creep rate is unity in the early stage of transient creep. Creep deformation of the alloy is ascribed to the easy glide of the introduced dislocations.

ESTUDO DA CORRELAÇÃO DOS TEORES DE P, K, Al, Ca e Mg NO SOLO, COM A ALTURA DE BANANEIRAS DO CULTIVAR “MARMELO”, NA EMISSÃO DO CACHO P, K, Al, Ca, AND Mg SOIL CORRELATION STUDY WITH BANANA PLANT HEIGHT CULTIVAR "MARMELO" IN THE BUNCH EMISSION

Directory of Open Access Journals (Sweden)

Manoel Passos de Castro

2007-09-01

Full Text Available

A bananeira do cultivar “Marmelo” vem, a cada dia, sendo a melhor opção para os bananicultores, que fornecem frutas às fábricas de doces. Com o aumento dos plantios deste cultivar, necessitou-se de dados concretos, na indicação de glebas, para a formação de bananais, tomando como base a análise do solo. Para isto tomaram-se 40 amostras, constituídas cada uma de 12 sub-amostras, ao redor de 40 touceiras de bananas. Estas touceiras foram escolhidas ao acaso, em um bananal de 2,5 ha, plantado no espaçamento de 3m x 3m, com idade de três anos. Para cada amostra analisaram-se os teores de P, K, Ca + Mg e Al, sendo estes correlacionados com a altura da bananeira correspondente, na emissão da inflorescência. Com base nas análises estatísticas concluiu-se que: a. Em caso de não se indicar adubação, o plantio só deve ser efetuado em solos com mais de 50 ppm. de K; b. A indicação de adubos fosfatados deverá ser feita apenas quando o teor de P no solo for menor que 1 ppm; c. O teor de Ca + Mg do solo deverá ser elevado para 2 (dois mE/100 ml, utilizando-se calcário dolomítico; d. O alumínio tóxico do solo deve ser totalmente neutralizado.

For commercial banana production, flat fersain is preferable because farm implements and heavy machinery can move early in the fields, but in Goiás, flat land is generally of very low fertility. This study was undertaken to determine the growth of the “Marmelo” banana in this kind of poor soil, using correlations between analyses of soils and the heights of pseudo stems at flowering, and to suggest viable fertilization for its successful growth.

K-shell Photoionization of Na-like to Cl-like Ions of Mg, Si, S, Ar, and Ca

Science.gov (United States)

Witthoeft, M. C.; Garcia, J.; Kallman, T. R.; Bautista, M. A.; Mendoza, C.; Palmeri, P.; Quinet, P.

2010-01-01

We present R-matrix calculations of photoabsorption and photoionization cross sections across the K edge of Mg, Si, S, Ar, and Ca ions with more than 10 electrons. The calculations include the effects of radiative and Auger damping by means of an optical potential. The wave functions are constructed from single-electron. orbital bases obtained using a Thomas-Fermi-Dirac statistical model potential. Configuration interaction is considered among all states up to n = 3. The damping processes affect the resonances converging to the K-thresholds causing them to display symmetric profiles of constant width that smear the otherwise sharp edge at the photoionization threshold. These data are important for the modeling of features found in photoionized plasmas.

Origin of intergranular embrittlement of Al alloys induced by Na and Ca segregation: Grain boundary weakening

International Nuclear Information System (INIS)

Lu Guanghong; Zhang Ying; Deng Shenghua; Wang Tianmin; Kohyama, Masanori; Yamamoto, Ryoichi; Liu Feng; Horikawa, Keitaro; Kanno, Motohiro

2006-01-01

Using a first-principles computational tensile test, we show that the ideal tensile strength of an Al grain boundary (GB) is reduced with both Na and Ca GB segregation. We demonstrate that the fracture occurs in the GB interface, dominated by the break of the interfacial bonds. Experimentally, we further show that the presence of Na or Ca impurity, which causes intergranular fracture, reduces the ultimate tensile strength when embrittlement occurs. These results suggest that the Na/Ca-induced intergranular embrittlement of an Al alloy originates mainly from the GB weakening due to the Na/Ca segregation

Different modes of electrogenic Na+ absorption in the coprodeum of the chicken embryo: role of extracellular Ca2+.

Science.gov (United States)

Heinz, M; Krattenmacher, R; Hoffmann, B; Clauss, W

1991-01-01

Transepithelial electrogenic Na+ transport (INa) was investigated in the coprodeum of 20-days-old chicken embryos in Ussing chambers. Short circuit current (Isc) and transepithelial resistance (Rt) were 14.7 +/- 4.8 microA.cm-2 (n = 12) and 0.53 +/- 0.09 k omega.cm-2 (n = 12), respectively. INa was calculated from changes in Isc by substitution of mucosal Na+ by (N-methyl-D-glucamine) (NMDG). Isc inversed during Na+ removal, and INa was found to be 27.8 +/- 4.7 microA.cm-2 (n = 12). Amiloride (100 mumol.l-1) inhibited only about 60% of INa. Analysis of Isc fluctuations revealed a Lorentzian component in the power density spectrum with a corner frequency of about 57 Hz. This component was not correlated to INa, and its origin is still unclear. Removal of mucosal Ca2+ increased INa about 2.5-fold due to an increase of the amiloride-insensitive component of INa in additionally investigated adult tissues. The results clearly show that this is due to a non-selective cation channel with an "apparent" order of selectivity Cs+ greater than Na+ = K+ greater than Rb+ greater than Li+. The Ca2+ concentration required to block 50% of the Isc was about 18 mumol.l-1. The IscCa could also be suppressed by other divalent cations such as Mg2+ and Ba2+. Additionally, an INa-linked Lorentzian component occurred which dominated the control spectrum with a significantly higher corner frequency (about 88 Hz). The results indicate that Na+ absorption in the coprodeum of the chicken embryo is more complex than in adult hens.(ABSTRACT TRUNCATED AT 250 WORDS)

Biocompatibility and bioactivity of porous polymer-derived Ca-Mg silicate ceramics.

Science.gov (United States)

Fiocco, L; Li, S; Stevens, M M; Bernardo, E; Jones, J R

2017-03-01

Magnesium is a trace element in the human body, known to have important effects on cell differentiation and the mineralisation of calcified tissues. This study aimed to synthesise highly porous Ca-Mg silicate foamed scaffolds from preceramic polymers, with analysis of their biological response. Akermanite (Ak) and wollastonite-diopside (WD) ceramic foams were obtained from the pyrolysis of a liquid silicone mixed with reactive fillers. The porous structure was obtained by controlled water release from selected fillers (magnesium hydroxide and borax) at 350°C. The homogeneous distribution of open pores, with interconnects of modal diameters of 160-180μm was obtained and maintained after firing at 1100°C. Foams, with porosity exceeding 80%, exhibited compressive strength values of 1-2MPa. In vitro studies were conducted by immersion in SBF for 21days, showing suitable dissolution rates, pH and ionic concentrations. Cytotoxicity analysis performed in accordance with ISO10993-5 and ISO10993-12 standards confirmed excellent biocompatibility of both Ak and WD foams. In addition, MC3T3-E1 cells cultured on the Mg-containing scaffolds demonstrated enhanced osteogenic differentiation and the expression of osteogenic markers including Collagen Type I, Osteopontin and Osteocalcin, in comparison to Mg-free counterparts. The results suggest that the addition of magnesium can further enhance the bioactivity and the potential for bone regeneration applications of Ca-silicate materials. Here, we show that the incorporation of Mg in Ca-silicates plays a significant role in the enhancement of the osteogenic differentiation and matrix formation of MC3T3-E1 cells, cultured on polymer-derived highly porous scaffolds. Reduced degradation rates and improved mechanical properties are also observed, compared to Mg-free counterparts, suggesting the great potential of Ca-Mg silicates as bone tissue engineering materials. Excellent biocompatibility of the new materials, in accordance to

Surface modification of an Mg-1Ca alloy to slow down its biocorrosion by chitosan

International Nuclear Information System (INIS)

Gu, X N; Zheng, Y F; Lan, Q X; Cheng, Y; Xi, T F; Zhang, Z X; Zhang, D Y

2009-01-01

The surface morphologies before and after immersion corrosion test of various chitosan-coated Mg-1Ca alloy samples were studied to investigate the effect of chitosan dip coating on the slowdown of biocorrosion. It showed that the corrosion resistance of the Mg-Ca alloy increased after coating with chitosan, and depended on both the chitosan molecular weight and layer numbers of coating. The Mg-Ca alloy coated by chitosan with a molecular weight of 2.7 x 10 5 for six layers has smooth and intact surface morphology, and exhibits the highest corrosion resistance in a simulated body fluid.

Surface modification of an Mg-1Ca alloy to slow down its biocorrosion by chitosan

Energy Technology Data Exchange (ETDEWEB)

Gu, X N; Zheng, Y F; Lan, Q X [State Key Laboratory for Turbulence and Complex System and College of Engineering, Peking University, Beijing 100871 (China); Cheng, Y; Xi, T F [Center for Biomedical Materials and Tissue Engineering, Academy for Advanced Interdisciplinary Studies, Peking University, Beijing 100871 (China); Zhang, Z X [Biomedical Engineering Research Center, Research Institute of Peking University in Shenzhen, Shenzhen 518057 (China); Zhang, D Y, E-mail: gxn139888@pku.edu.c, E-mail: yfzheng@pku.edu.c, E-mail: 8lanqiuxiang@163.co, E-mail: chengyan@pku.edu.c, E-mail: top5460@163.co, E-mail: xitingfei@tom.co, E-mail: zhangdeyuan@lifetechmed.co [Lifetech Scientific (Shenzhen) Co. Ltd, Hi-Tech Park, Shenzhen 518000 (China)

2009-08-15

The surface morphologies before and after immersion corrosion test of various chitosan-coated Mg-1Ca alloy samples were studied to investigate the effect of chitosan dip coating on the slowdown of biocorrosion. It showed that the corrosion resistance of the Mg-Ca alloy increased after coating with chitosan, and depended on both the chitosan molecular weight and layer numbers of coating. The Mg-Ca alloy coated by chitosan with a molecular weight of 2.7 x 10{sup 5} for six layers has smooth and intact surface morphology, and exhibits the highest corrosion resistance in a simulated body fluid.

Surface modification of an Mg-1Ca alloy to slow down its biocorrosion by chitosan.

Science.gov (United States)

Gu, X N; Zheng, Y F; Lan, Q X; Cheng, Y; Zhang, Z X; Xi, T F; Zhang, D Y

2009-08-01

The surface morphologies before and after immersion corrosion test of various chitosan-coated Mg-1Ca alloy samples were studied to investigate the effect of chitosan dip coating on the slowdown of biocorrosion. It showed that the corrosion resistance of the Mg-Ca alloy increased after coating with chitosan, and depended on both the chitosan molecular weight and layer numbers of coating. The Mg-Ca alloy coated by chitosan with a molecular weight of 2.7 x 10(5) for six layers has smooth and intact surface morphology, and exhibits the highest corrosion resistance in a simulated body fluid.

A quantitative mechanistic description of Ni, Zn and Ca sorption on Na-montmorillonite. Part III: modelling

International Nuclear Information System (INIS)

Baeyens, B.; Bradbury, M.H.

1995-07-01

Titration and sorption measurements, carried out under a wide variety of conditions on Na-montmorillonite, were examined in terms of cation exchange and surface complexation mechanisms. A computer code called MINSORB was developed and used throughout this work. This code allowed the uptake of radionuclides by both mechanisms to be calculated simultaneously; also taking into account competitive reactions from other cations present. A stepwise iterative fitting/modelling procedure is described. For the case of Na-montmorillonite it is demonstrated that an electrostatic term in the surface complexation model is not required. A basic data set comprising of site capacities and protonation/deprotonation constants was defined, which was valid for all surface complexation sorption reactions. The main study was carried out with Ni, but impurity cations present in the system, particularly Zn, had to be examined in addition due to their competitive effects on Ni sorption. The surface complexation behaviour of Ni and Zn was investigated in detail to give intrinsic surface complexation constants on two of the =SOH type sites included in the model. The sorption of Mg, Ca and Mn is also considered, though in less detail, and estimated surface complexation constants for these nuclides are presented. Cation exchange was included in all of the calculations. Measured selectivity coefficients for Ni-Na, Zn-Na and Ca-Na exchange reactions are given. The model, with the derived parameters, allowed all the data from titration measurements through sorption edges to sorption isotherms to be calculated. (author) 31 figs., 9 tabs., refs

A quantitative mechanistic description of Ni, Zn and Ca sorption on Na-Montmorillonite. Part III: Modelling

International Nuclear Information System (INIS)

Baeyens, B.; Bradbury, M.H.

1995-07-01

Titration and sorption measurements, carried out under a wide variety of conditions on Na-montmorillonite, were examined in terms of cation exchange and surface complexation mechanisms. A computer code called MINSORB was developed and used throughout this work. This code allowed the uptake of radionuclides by both mechanisms to be calculated simultaneously; also taking into account competitive reactions from other cations present. A stepwise iterative fitting/modelling procedure is described. For the case of Na-montmorillonite it is demonstrated that an electrostatic term in the surface complexation model is not required. A basic data set comprising of site capacities and protonation/deprotonation constants was defined, which was valid for all surface complexation sorption reactions. The main study was carried out with Ni, but impurity cations present in the system, particularly Zn, had to be examined in addition due to their competitive effects on Ni sorption. The surface complexation behaviour of Ni and Zn was investigated in detail to give intrinsic surface complexation constants on two of the ≡SOH type sites included in the model. The sorption of Mg, Ca and Mn is also considered, though in less detail, and estimated surface complexation constants for these nuclides are presented. Cation exchange was included in all of the calculations. Measured selectivity coefficients for Ni-Na, Zn-Na and Ca-Na exchange reactions are given. The model, with the derived parameters, allowed all the data from titration measurements through sorption edges to sorption isotherms to be calculated. (author) 31 figs., 9 tabs., refs

Microstructure and bio-corrosion behaviour of Mg-5Zn-0.5Ca -xSr alloys as potential biodegradable implant materials

Science.gov (United States)

Yan, Li; Zhou, Jiaxing; Sun, Zhenzhou; Yang, Meng; Ma, Liqun

2018-04-01

Magnesium alloys are widely studied as biomedical implants owing to their biodegradability. In this work, novel Mg-5Zn-0.5Ca-xSr (x = 0, 0.14, 0.36, 0.50, 0.70 wt%) alloys were prepared as biomedical materials. The influence of strontium (Sr) addition on the microstructure, corrosion properties and corrosion morphology of the as-cast Mg-5Zn-0.5Ca-xSr alloys is investigated by a variety of techniques such as scanning electron microscopy, x-ray diffraction, and electrochemical measurements. The Sr-free alloy is composed of three phases, namely, α-Mg, CaMg2 and Ca2Mg6Zn3, while the alloys with the Sr addition consist of α-Mg, CaMg2 and Ca2Mg6Zn3 and Mg17Sr2. Corrosion experiments in Hank’s solution show that the addition of a small amount of Sr can improve the corrosion resistance of the Mg-5Zn-0.5Ca alloy. The corrosion products include Mg(OH)2, Zn(OH)2, Ca(OH)2, and HA (Ca5(PO4)3(OH)). Mg-5Zn-0.5Ca-0.36Sr alloy has the minimum weight loss rate (0.68 mm/a), minimal hydrogen evolution (0.08 ml/cm2/d) and minimum corrosion current density (7.4 μA/cm2), indicating that this alloy shows the best corrosion resistance.

Emission lines of Mg2 and Ca2 in planetary nebulae

International Nuclear Information System (INIS)

Gurzadyan, G.A.

1979-01-01

Conditions of exciting resonance lines in the emission of ionized magnesium (lambda lambda 2796+2803 Mg2) and calcium (lambda lambda 3934+3968 Ca2) in planetary nebulae have been analyzed. It is shown that the allowed lines are excited with the same mechanism, as the forbidden lines, i.e. inelastic electron collisions, but not with common fluorescence. The emission line lambda 2800 Mg2 of enough force can be observed only in the spectra of planetary nebulae with mean excitation (IC 2149) as well as in the spectra of diffuse nebulae. The line must not be observed in high-excited planetary nebulae (NGC 7026, 7662). The absence of emission lines H and K Ca2 in planetary nebulae spectra results from the fact, that their expected intensity is by 3-4 orders less than the intensity of the line lambda 2800 Mg2 or Hsub(β) hydrogen

Thermodynamic parameters for the protonation and the interaction of arsenate with Mg2+, Ca2+ and Sr2+: Application to natural waters.

Science.gov (United States)

Chillè, Donatella; Foti, Claudia; Giuffrè, Ottavia

2018-01-01

Thermodynamic parameters for the protonation of AsO 4 3- and for the interaction with Mg 2+ , Ca 2+ and Sr 2+ were reported, comprehensive also of their dependence on ionic strength, considering the 0.1 ≤ I ≤ 1 M range and using NaCl as background salt. The same speciation models were obtained for Mg 2+ , Ca 2+ and Sr 2+ systems, with the formation of three different species: ML, MLH and MLH 2 (L = AsO 4 3- ). Mono- and di-protonated species were very weak, with formation constant values (log K) ranging from 1.45 to 3.23. In order to have a complete picture of thermodynamic properties of the systems under study and to fill the shortage of thermodynamic data on arsenate complex systems, the ligand protonation and metal complex enthalpies were also determined by calorimetric titrations, at t = 25 °C and in NaCl at I = 0.7 M (for H + -AsO 4 3- species also at I = 0.1 M). On the light of the proposed speciation models, examples of As(V) distribution in some natural waters are reported. Copyright © 2017 Elsevier Ltd. All rights reserved.

Selective recovery of uranium from Ca-Mg uranates by chlorination

International Nuclear Information System (INIS)

Pomiro, Federico J.; Gaviría, Juan P.; Quinteros, Raúl D.

2017-01-01

A chlorination process is proposed for the uranium extraction and separation using Calcium−Magnesium uranates such as starting reactants which were obtained by precipitation from uranyl nitrate solutions with calcium hydroxide. The study is based on thermodynamic and reaction analysis using chlorine gas as chlorination agent. The results showed that the chlorination reaction of Ca uranate is more feasible to occur than the Mg uranate. The products obtained after chlorination reactions were washed with deionized water to remove the chlorides produced and analyzed. The XRD patterns of the washed products indicated that the chlorination between 400 and 500 °C result in a single phase of calcium uranate (CaUO 4 ) as reaction product. The formation of U 3 O 8 and MgU 3 O 10 was observed at temperatures between 600 °C and 700 °C for 8 hs. The optimal conditions to recover uranium were 3 l h −1 of chlorine and 10 hs of reaction at 700 °C being U 3 O 8 the single uranium product obtained. - Highlights: •The chlorination is an effective method for the recovery uranium from Ca-Mg uranates. •The optimal conditions were: 10 hs of reaction time at 700 °C using 3 l/h of Cl 2 (g). •U 3 O 8 is recovery by washing out the chlorination by-products.

Synthesis and Characterization Of CaMgO2 Nanoparticles Photocatalyst For the Decolorization Of Orange G Dye

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Atheel Alwash

2016-11-01

Full Text Available A series of heterogeneous basic catalysts of CaO, MgO and CaMgO2 at different calcination temperature were synthesized via solution combustion method. Different characterization techniques have been carried out to investigate the structure of the produced catalysts i.e. X-ray diffraction (XRD, particle size analyzer, morphology by atomic force microscope (AFM and reflection using UV-VIS diffuse reflectance spectra. The particles size analyzer revealed that the mixed oxide catalysts calcined at different calcination temperature possess smaller nano size particles compared to pure CaO. Moreover, the energy band gap was calculated based on the results of diffuse reflectance spectra. The energy band gap was reduced from 4.1 to 3.6 eV for the CaMgO2 catalyst calcined at 400 and 600 °C respectively compared to pure oxide catalysts. The higher decolorization efficiency was 100% after 60 min of photocatalytic reaction for CaMgO2 calcined at 600 °C compared to CaO and MgO with catalytic activity of 58% and 27% respectively.

Microstructure, mechanical property and corrosion behavior of interpenetrating (HA + β-TCP)/MgCa composite fabricated by suction casting

International Nuclear Information System (INIS)

Wang, X.; Dong, L.H.; Li, J.T.; Li, X.L.; Ma, X.L.; Zheng, Y.F.

2013-01-01

The novel interpenetrating (HA + β-TCP)/MgCa composites were fabricated by infiltrating MgCa alloy into porous HA + β-TCP using suction casting technique. The microstructure, mechanical properties and corrosion behaviors of the composites have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion tests. It was shown that the composites had compact structure and the interfacial bonding between MgCa alloy and HA + β-TCP scaffolds was very well. The ultimate compressive strength of the composites was about 500–1000 fold higher than that of the original porous scaffolds, and it still retained quarter-half of the strength of the bulk MgCa alloy. The electrochemical and immersion tests indicated that the corrosion resistance of the composites was better than that of the MgCa matrix alloy, and the corrosion products of the composite surface were mainly Mg(OH) 2 , HA and Ca 3 (PO 4 ) 2 . Meanwhile, the mechanical and corrosive properties of the (HA + β-TCP)/MgCa composites were adjustable by the choice of HA content. - Highlights: • The composites were fabricated by infiltrating MgCa alloy into porous HA + β-TCP. • The microstructure, mechanical and corrosion properties were investigated. • It showed composites had compact structures and good interfacial bonding. • The mechanical and corrosive properties can be adjustable by the HA content. • The corrosion mechanism of the composite has been explained

Reverse mode Na+/Ca2+ exchange mediated by STIM1 contributes to Ca2+ influx in airway smooth muscle following agonist stimulation

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Fox Jane

2010-12-01

Full Text Available Abstract Background Agonist stimulation of airway smooth muscle (ASM results in IP3 mediated Ca2+ release from the sarcoplasmic reticulum followed by the activation of store operated and receptor operated non-selective cation channels. Activation of these non-selective channels also results in a Na+ influx. This localised increase in Na+ levels can potentially switch the Na+/Ca2+ exchanger into reverse mode and so result in a further influx of Ca2+. The aim of this study was to characterise the expression and physiological function of the Na+/Ca2+ exchanger in cultured human bronchial smooth muscle cells and determine its contribution to agonist induced Ca2+ influx into these cells. Methods The expression profile of NCX (which encodes the Na+/Ca2+ exchanger homologues in cultured human bronchial smooth muscle cells was determined by reverse transcriptase PCR. The functional activity of reverse mode NCX was investigated using a combination of whole cell patch clamp, intracellular Ca2+ measurements and porcine airway contractile analyses. KB-R7943 (an antagonist for reverse mode NCX and target specific siRNA were utilised as tools to inhibit NCX function. Results NCX1 protein was detected in cultured human bronchial smooth muscle cells (HBSMC cells and NCX1.3 was the only mRNA transcript variant detected. A combination of intracellular Na+ loading and addition of extracellular Ca2+ induced an outwardly rectifying current which was augmented following stimulation with histamine. This outwardly rectifying current was inhibited by 10 μM KB-R7943 (an antagonist of reverse mode NCX1 and was reduced in cells incubated with siRNA against NCX1. Interestingly, this outwardly rectifying current was also inhibited following knockdown of STIM1, suggesting for the first time a link between store operated cation entry and NCX1 activation. In addition, 10 μM KB-R7943 inhibited agonist induced changes in cytosolic Ca2+ and induced relaxation of porcine

Composição corporal e exigências de macroelementos minerais (Ca, P, Mg, Na e K de bovinos não-castrados de quatro raças Zebuínas Body composition and macrominerals (Ca, P, Mg, Na and K requirements of bulls, from four Zebu breeds

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Mário Fonseca Paulino

1999-01-01

Full Text Available A composição corporal e as exigências de macroelementos minerais (Ca, P, Mg, Na e K para ganho de peso de bovinos de quatro raças zebuínas (Gir, Guzerá, Mocho-Tabapuã e Nelore foram estimadas com 63 animais não-castrados, com idade média de 24 meses e 366 kg de PVinicial. Dezesseis animais das raças Gir, Guzerá e Mocho-Tabapuã e 15 da raça Nelore foram usados. Quinze animais, quatro das raças Gir, Guzerá e Mocho-Tabapuã e três da Nelore, foram abatidos ao início do estudo e os demais, distribuídos em três grupos, com três animais de cada raça e alimentados individualmente, ad libitum, com ração contendo 50% de concentrado na matéria seca, até atingirem peso de abate de 405, 450 e 500 kg, respectivamente. Equações de regressão do logaritmo do conteúdo corporal de macroelementos minerais, em função do logaritmo do corpo vazio (PCV, foram ajustadas para estimar os composição corporal dos constituintes para qualquer PCV, dentro do intervalo incluído na pesquisa (250 a 450kg. Pela derivação destas equações, a composição do ganho de PCV foi obtida. Animais das quatro raças não diferiram quanto à composição corporal de macroelementos minerais e às exigências líquidas para ganho de peso. Houve decréscimo na concentração dos cinco macroelementos no PCV e no peso ganho, com a elevação do PCV. As exigências líquidas estimadas para ganho de PCV, para os cinco macrominerais, foram inferiores aos valores fixos sugeridos pelo ARC (1980. Os requerimentos líquidos estimados de Ca e P para ganho de peso de um bovino não-castrado de 400 kg PV foram 16 e 24% inferiores, respectivamente, aos propostos pelo AFRC (1991.The body composition and macrominerals requirements for weight gain of four Zebu breeds (Gyr, Guzera, Mocho-Tabapuã and Nellore were estimated using 63 bulls averaging 24 months of age and 366 kg initial LW. Sixteen animals from Gir, Guzera e Mocho-Tabapuã breeds and 15 from Nellore breed

Ion microprobe assessment of the heterogeneity of Mg/Ca, Sr/Ca and Mn/Ca ratios in Pecten maximus and Mytilus edulis (bivalvia shell calcite precipitated at constant temperature

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P. S. Freitas

2009-07-01

Full Text Available Small-scale heterogeneity of biogenic carbonate elemental composition can be a significant source of error in the accurate use of element/Ca ratios as geochemical proxies. In this study ion microprobe (SIMS profiles showed significant small-scale variability of Mg/Ca, Sr/Ca and Mn/Ca ratios in new shell calcite of the marine bivalves Pecten maximus and Mytilus edulis that was precipitated during a constant-temperature culturing experiment. Elevated Mg/Ca, Sr/Ca and Mn/Ca ratios were found to be associated with the deposition of elaborate shell features, i.e. a shell surface stria in P. maximus and surface shell disturbance marks in both species, the latter a common occurrence in bivalve shells. In both species the observed small-scale elemental heterogeneity most likely was not controlled by variable transport of ions to the extra-pallial fluid, but by factors such as the influence of shell organic content and/or crystal size and orientation, the latter reflecting conditions at the shell crystal-solution interface. In the mid and innermost regions of the P. maximus shell the lack of significant small-scale variation of Mg/Ca ratios, which is consistent with growth at constant temperature, suggest a potential application as a palaeotemperature proxy. Cross-growth band element/Ca ratio profiles in the interior of bivalve shells may provide more promising palaeo-environmental tools than sampling from the outer region of bivalve shells.

Effect of calcium content on the microstructure, hardness and in-vitro corrosion behavior of biodegradable Mg-Ca binary alloy

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Shervin Eslami Harandi

2013-02-01

Full Text Available Effect of calcium addition on microstructure, hardness value and corrosion behavior of five different Mg-xCa binary alloys (x = 0.7, 1, 2, 3, 4 wt. (% was investigated. Notable refinement in microstructure of the alloy occurred with increasing calcium content. In addition, more uniform distribution of Mg2Ca phase was observed in a-Mg matrix resulted in an increase in hardness value. The in-vitro corrosion examination using Kokubo simulated body fluid showed that the addition of calcium shifted the fluid pH value to a higher level similar to those found in pure commercial Mg. The high pH value amplified the formation and growth of bone-like apatite. Higher percentage of Ca resulted in needle-shaped growth of the apatite. Electrochemical measurements in the same solution revealed that increasing Ca content led to higher corrosion rates due to the formation of more cathodic Mg2Ca precipitate in the microstructure. The results therefore suggested that Mg-0.7Ca with the minimum amount of Mg2Ca is a good candidate for bio-implant applications.

Effect of calcium content on the microstructure, hardness and in-vitro corrosion behavior of biodegradable Mg-Ca binary alloy

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Shervin Eslami Harandi

2012-01-01

Full Text Available Effect of calcium addition on microstructure, hardness value and corrosion behavior of five different Mg-xCa binary alloys (x = 0.7, 1, 2, 3, 4 wt. (% was investigated. Notable refinement in microstructure of the alloy occurred with increasing calcium content. In addition, more uniform distribution of Mg2Ca phase was observed in a-Mg matrix resulted in an increase in hardness value. The in-vitro corrosion examination using Kokubo simulated body fluid showed that the addition of calcium shifted the fluid pH value to a higher level similar to those found in pure commercial Mg. The high pH value amplified the formation and growth of bone-like apatite. Higher percentage of Ca resulted in needle-shaped growth of the apatite. Electrochemical measurements in the same solution revealed that increasing Ca content led to higher corrosion rates due to the formation of more cathodic Mg2Ca precipitate in the microstructure. The results therefore suggested that Mg-0.7Ca with the minimum amount of Mg2Ca is a good candidate for bio-implant applications.

Exploring As-Cast PbCaSn-Mg Anodes for Improved Performance in Copper Electrowinning

Science.gov (United States)

Yuwono, Jodie A.; Clancy, Marie; Chen, Xiaobo; Birbilis, Nick

2018-06-01

Lead calcium tin (PbCaSn) alloys are the common anodes used in copper electrowinning (Cu EW). Given a large amount of energy consumed in Cu EW process, anodes with controlled oxygen evolution reaction (OER) kinetics and a lower OER overpotential are advantageous for reducing the energy consumption. To date, magnesium (Mg) has never been studied as an alloying element for EW anodes. As-cast PbCaSn anodes with the addition of Mg were examined herein, revealing an improved performance compared to that of the industrial standard PbCaSn anode. The alloy performances in the early stages of anode life and passivation were established from electrochemical studies which were designed to simulate industrial Cu EW process. The 24-hour polarization testing revealed that the Mg alloying depolarizes the anode potential up to 80 mV; thus, resulting in a higher Cu EW efficiency. In addition, scanning electron microscopy and X-ray photoelectron spectroscopy revealed that the alteration of the alloy microstructure and the corresponding interfacial reactions contribute to the changes of the anode electrochemical performances. The present study reveals for the first time the potency of Mg alloying in reducing the overpotential of PbCaSn anode.

Co-intercalation of Mg(2+) and Na(+) in Na(0.69)Fe2(CN)6 as a High-Voltage Cathode for Magnesium Batteries.

Science.gov (United States)

Kim, Dong-Min; Kim, Youngjin; Arumugam, Durairaj; Woo, Sang Won; Jo, Yong Nam; Park, Min-Sik; Kim, Young-Jun; Choi, Nam-Soon; Lee, Kyu Tae

2016-04-06

Thanks to the advantages of low cost and good safety, magnesium metal batteries get the limelight as substituent for lithium ion batteries. However, the energy density of state-of-the-art magnesium batteries is not high enough because of their low operating potential; thus, it is necessary to improve the energy density by developing new high-voltage cathode materials. In this study, nanosized Berlin green Fe2(CN)6 and Prussian blue Na(0.69)Fe2(CN)6 are compared as high-voltage cathode materials for magnesium batteries. Interestingly, while Mg(2+) ions cannot be intercalated in Fe2(CN)6, Na(0.69)Fe2(CN)6 shows reversible intercalation and deintercalation of Mg(2+) ions, although they have the same crystal structure except for the presence of Na(+) ions. This phenomenon is attributed to the fact that Mg(2+) ions are more stable in Na(+)-containing Na(0.69)Fe2(CN)6 than in Na(+)-free Fe2(CN)6, indicating Na(+) ions in Na(0.69)Fe2(CN)6 plays a crucial role in stabilizing Mg(2+) ions. Na(0.69)Fe2(CN)6 delivers reversible capacity of approximately 70 mA h g(-1) at 3.0 V vs Mg/Mg(2+) and shows stable cycle performance over 35 cycles. Therefore, Prussian blue analogues are promising structures for high-voltage cathode materials in Mg batteries. Furthermore, this co-intercalation effect suggests new avenues for the development of cathode materials in hybrid magnesium batteries that use both Mg(2+) and Na(+) ions as charge carriers.

Theoretical descriptions of novel triplet germylenes M1-Ge-M2-M3 (M1 = H, Li, Na, K; M2 = Be, Mg, Ca; M3 = H, F, Cl, Br).

Science.gov (United States)

Kassaee, Mohamad Zaman; Ashenagar, Samaneh

2018-02-06

In a quest to identify new ground-state triplet germylenes, the stabilities (singlet-triplet energy differences, ΔE S-T ) of 96 singlet (s) and triplet (t) M 1 -Ge-M 2 -M 3 species were compared and contrasted at the B3LYP/6-311++G**, QCISD(T)/6-311++G**, and CCSD(T)/6-311++G** levels of theory (M 1  = H, Li, Na, K; M 2  = Be, Mg, Ca; M 3  = H, F, Cl, Br). Interestingly, F-substituent triplet germylenes (M 3  = F) appear to be more stable and linear than the corresponding Cl- or Br-substituent triplet germylenes (M 3  = Cl or Br). Triplets with M 1  = K (i.e., the K-Ge-M 2 -M 3 series) seem to be more stable than the corresponding triplets with M 1  = H, Li, or Na. This can be attributed to the higher electropositivity of potassium. Triplet species with M 3  = Cl behave similarly to those with M 3  = Br. Conversely, triplets with M 3  = H show similar stabilities and linearities to those with M 3  = F. Singlet species of formulae K-Ge-Ca-Cl and K-Ge-Ca-Br form unexpected cyclic structures. Finally, the triplet germylenes M 1 -Ge-M 2 -M 3 become more stable as the electropositivities of the α-substituents (M 1 and M 2 ) and the electronegativity of the β-substituent (M 3 ) increase.

ß-Adrenergic Stimulation Increases RyR2 Activity via Intracellular Ca2+ and Mg2+ Regulation

Science.gov (United States)

Li, Jiao; Imtiaz, Mohammad S.; Beard, Nicole A.; Dulhunty, Angela F.; Thorne, Rick; vanHelden, Dirk F.; Laver, Derek R.

2013-01-01

Here we investigate how ß-adrenergic stimulation of the heart alters regulation of ryanodine receptors (RyRs) by intracellular Ca2+ and Mg2+ and the role of these changes in SR Ca2+ release. RyRs were isolated from rat hearts, perfused in a Langendorff apparatus for 5 min and subject to 1 min perfusion with 1 µM isoproterenol or without (control) and snap frozen in liquid N2 to capture their phosphorylation state. Western Blots show that RyR2 phosphorylation was increased by isoproterenol, confirming that RyR2 were subject to normal ß-adrenergic signaling. Under basal conditions, S2808 and S2814 had phosphorylation levels of 69% and 15%, respectively. These levels were increased to 83% and 60%, respectively, after 60 s of ß-adrenergic stimulation consistent with other reports that ß-adrenergic stimulation of the heart can phosphorylate RyRs at specific residues including S2808 and S2814 causing an increase in RyR activity. At cytoplasmic [Ca2+] adrenergic stimulation increased luminal Ca2+ activation of single RyR channels, decreased luminal Mg2+ inhibition and decreased inhibition of RyRs by mM cytoplasmic Mg2+. At cytoplasmic [Ca2+] >1 µM, ß-adrenergic stimulation only decreased cytoplasmic Mg2+ and Ca2+ inhibition of RyRs. The Ka and maximum levels of cytoplasmic Ca2+ activation site were not affected by ß-adrenergic stimulation. Our RyR2 gating model was fitted to the single channel data. It predicted that in diastole, ß-adrenergic stimulation is mediated by 1) increasing the activating potency of Ca2+ binding to the luminal Ca2+ site and decreasing its affinity for luminal Mg2+ and 2) decreasing affinity of the low-affinity Ca2+/Mg2+ cytoplasmic inhibition site. However in systole, ß-adrenergic stimulation is mediated mainly by the latter. PMID:23533585

Crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses; Li2O-SiO2, Na2O-SiO2, Na2O-CaO-SiO2 kei glass no kessho sekishutsu kyodo

Energy Technology Data Exchange (ETDEWEB)

Tsutsumi, K.; Otake, J.; Nagasaka, T.; Hino, M. [Tohoku University, Sendai (Japan)

1998-06-01

It has been known that crystallization of mold powder is effective on the disturbance of heat transfer between mold and solidified shell in production of middle carbon steel slabs in continuous casting process. But it has not yet been made clear which composition of mold powder is the most suitable for crystallization. The crystallization behavior of Li2O-SiO2, Na2O-SiO2 and Na2O-CaO-SiO2 glasses was observed by differential thermal analysis (DTA) and hot-thermocouple methods with DTA in the present work. As a result, addition of alkaline metal and alkaline earth metal oxides to SiO2 increased the critical cooling rate for glass formation in binary system of Li2O-SiO2 and Na2O-SiO2 and Li2O-SiO2 system crystallized easier than Na2O-SiO2 system. In ternary system of Na2O-CaO-SiO2, addition of Na2O hurried the critical cooling rate at CaO/SiO2=0.93 mass ratio, but the rate was almost constant in the composition range of more than 15 mass% Na2O. The slag of CaO/SiO2=0.93 made the rate faster than the slag of CaO/SiO2=0.47 at constant content of 10mass% Na2O. 17 refs., 10 figs., 3 tabs.

TheoSSA - Model WD Spectra on Demand: The Impact of Ne, Na, Mg, and Iron-group Elements on the Balmer Lines

Science.gov (United States)

Reindl, N.; Rauch, T.

2015-06-01

The registered German Astrophysical Virtual Observatory (GAVO) service TheoSSA provides easy access to synthetic stellar spectra. This GAVO database contains already ten thousands of these, which were calculated with different chemical compositions of the elements H to Ni. In addition to the database, it is possible to calculate individual spectra for hot, compact stars based on the Tübingen NLTE Model-Atmosphere Package (TMAP) via the TMAW service. The TMAW models were, in the pilot phase, restricted to the elements H, He, C, N, and O. Now, TMAW is extended to additionally consider opacities from Ne, Na, and Mg. Soon, TMAW will also be able to include the opacities from the so-called iron-group elements (Ca - Ni). We describe the improvements and show the impact of Ne, Na, Mg, and iron-group elements on the Balmer lines.

Eocene sea temperatures for the mid-latitude southwest Pacific from Mg/Ca ratios in planktonic and benthic foraminifera

Science.gov (United States)

Creech, John B.; Baker, Joel A.; Hollis, Christopher J.; Morgans, Hugh E. G.; Smith, Euan G. C.

2010-11-01

We have used laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) to measure elemental (Mg/Ca, Al/Ca, Mn/Ca, Zn/Ca, Sr/Ca, and Ba/Ca) ratios of 13 species of variably preserved early to middle Eocene planktonic and benthic foraminifera from New Zealand. The foraminifera were obtained from Ashley Mudstone, mid-Waipara River, South Island, which was deposited at bathyal depth ( ca. 1000 m) on the northern margin of the east-facing Canterbury Basin at a paleo-latitude of ca. 55°S. LA-ICP-MS data yield trace element depth profiles through foraminifera test walls that can be used to identify and exclude zones of surficial contamination and infilling material resulting from diagenetic coatings, mineralisation and detrital sediment. Screened Mg/Ca ratios from 5 species of foraminifera are used to calculate sea temperatures from late Early to early Middle Eocene ( ca. 51 to 46.5 Ma), a time interval that spans the termination of the Early Eocene Climatic Optimum (EECO). During this time, sea surface temperatures (SST) varied from 30 to 24 °C, and bottom water temperatures (BWT) from 21 to 14 °C. Comparison of Mg/Ca sea temperatures with published δ 18O and TEX 86 temperature data from the same samples (Hollis et al., 2009) shows close correspondence, indicating that LA-ICP-MS can provide reliable Mg/Ca sea temperatures even where foraminiferal test preservation is variable. Agreement between the three proxies also implies that Mg/Ca-temperature calibrations for modern planktonic and benthic foraminifera can generally be applied to Eocene species, although some species (e.g., V. marshalli) show significant calibration differences. The Mg/Ca ratio of the Eocene ocean is constrained by our data to be 35-50% lower than the modern ocean depending on which TEX 86 - temperature calibration (Kim et al., 2008; Liu et al., 2009) - is used to compare with the Mg/Ca sea temperatures. Sea temperatures derived from δ 18O analysis of foraminifera from Waipara show

The Effects of Temperature and Salinity on Mg Incorporation in Planktonic Foraminifera Globigerinoides ruber (white): Results from a Global Sediment Trap Mg/Ca Database

Science.gov (United States)

Gray, W. R.; Weldeab, S.; Lea, D. W.

2015-12-01

Mg/Ca in Globigerinoides ruber is arguably the most important proxy for sea surface temperature (SST) in tropical and sub tropical regions, and as such guides our understanding of past climatic change in these regions. However, the sensitivity of Mg/Ca to salinity is debated; while analysis of foraminifera grown in cultures generally indicates a sensitivity of 3 - 6% per salinity unit, core-top studies have suggested a much higher sensitivity of between 15 - 27% per salinity unit, bringing the utility of Mg/Ca as a SST proxy into dispute. Sediment traps circumvent the issues of dissolution and post-depositional calcite precipitation that hamper core-top calibration studies, whilst allowing the analysis of foraminifera that have calcified under natural conditions within a well constrained period of time. We collated previously published sediment trap/plankton tow G. ruber (white) Mg/Ca data, and generated new Mg/Ca data from a sediment trap located in the highly-saline tropical North Atlantic, close to West Africa. Calcification temperature and salinity were calculated for the time interval represented by each trap/tow sample using World Ocean Atlas 2013 data. The resulting dataset comprises >240 Mg/Ca measurements (in the size fraction 150 - 350 µm), that span a temperature range of 18 - 28 °C and 33.6 - 36.7 PSU. Multiple regression of the dataset reveals a temperature sensitivity of 7 ± 0.4% per °C (p < 2.2*10-16) and a salinity sensitivity of 4 ± 1% per salinity unit (p = 2*10-5). Application of this calibration has significant implications for both the magnitude and timing of glacial-interglacial temperature changes when variations in salinity are accounted for.

Effects of Na2CaEDTA on lead deposits in rabbit osseous tissue

International Nuclear Information System (INIS)

Doniec, J.; Trojanowska, B.; Trzcinka-Ochocka, M.; Garlicka, I.

1983-01-01

Radiochemical and autoradiographic methods were used for 210 Pb determination after Na 2 CaEDTA administration to rabbits. 210 Pb was determined in soft tissues, compact and trabecular bones and growing microareas on the endosteum of the long bone. After Na 2 CaEDTA injection lead was depleted from 'new' deposits mainly on the growing surface of both trabecular and compact bones. (Auth.)

Diagenesis of echinoderm skeletons: Constraints on paleoseawater Mg/Ca reconstructions

Science.gov (United States)

Gorzelak, Przemysław; Krzykawski, Tomasz; Stolarski, Jarosław

2016-09-01

One of the most profound environmental changes thought to be reflected in chemical composition of numerous geological archives is Mg/Ca ratio of the seawater, which has varied dramatically throughout the Phanerozoic. Echinoderms that today typically form high magnesium calcite skeletons are increasingly being utilized as a proxy for interpreting secular changes in seawater chemistry. However, accurate characterization of the diagenetic changes of their metastable high magnesium calcite skeletons is a prerequisite for assessing their original, major-element geochemical composition. Here we expand the existing models of diagenesis of echinoderm skeleton by integration of various analytical methods that up to now rarely have been used to assess the diagenetic changes of fossil echinoderms. We validated the preservation of a suite of differently preserved echinoderm ossicles, mostly crinoids, ranging in age from the Cambrian through Recent. In 13 of 99 fossil echinoderm ossicles we found well-preserved porous microstructure (stereom), non-luminescent behaviour or blotchy dark color in cathodoluminescence, and distinct nanostructural features (layered and nanocomposite structure). Moreover, in representatives of such preserved samples, distribution of sulphates associated with organic matter is identical to those in Recent echinoderms. Only such ossicles, despite of local micrometer-scale diagenetic changes, were herein considered well-preserved, retaining their original major-element skeletal composition. By contrast, majority of samples show transformation to the stable low magnesium calcite that leads to obliteration of the primary geochemical and micro/nanostructural features and is accompanied with increase in cathodoluminescence emission intensity. Using only well-preserved fossil echinoderm samples, we found purely random variation in Mg/Ca in echinoderm skeletons through the observed time series; any periodicities in echinoderm skeletal Mg/Ca ratio which might

Acid-base status determines the renal expression of Ca2+ and Mg2+ transport proteins.

NARCIS (Netherlands)

Nijenhuis, T.; Renkema, K.Y.; Hoenderop, J.G.J.; Bindels, R.J.M.

2006-01-01

Chronic metabolic acidosis results in renal Ca2+ and Mg2+ wasting, whereas chronic metabolic alkalosis is known to exert the reverse effects. It was hypothesized that these adaptations are mediated at least in part by the renal Ca2+ and Mg2+ transport proteins. The aim of this study, therefore, was

Complex transition metal hydrides incorporating ionic hydrogen: Synthesis and characterization of Na{sub 2}Mg{sub 2}FeH{sub 8} and Na{sub 2}Mg{sub 2}RuH{sub 8}

Energy Technology Data Exchange (ETDEWEB)

Humphries, Terry D., E-mail: terry_humphries81@hotmail.com [WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Takagi, Shigeyuki; Li, Guanqiao; Matsuo, Motoaki; Sato, Toyoto [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Sørby, Magnus H.; Deledda, Stefano; Hauback, Bjørn C. [Physics Department, Institute for Energy Technology, Kjeller NO-2027 (Norway); Orimo, Shin-ichi [WPI-Advanced Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

2015-10-05

Highlights: • Structures of Na{sub 2}Mg{sub 2}FeH{sub 8} and Na{sub 2}Mg{sub 2}RuH{sub 8} have been determined by XRD and PND. • Compounds incorporate independently coordinated ionic and covalent hydrogen. • [TH{sub 6}]{sup 4−} anion is surrounded by a cubic array of four Mg{sup 2+} and four Na{sup +} cations. • H{sup −} anions are octahedrally coordinated by four Na{sup +} and two Mg{sup 2+} cations. • Vibrational modes of the H{sup −} anions and complex hydride anion are observed. - Abstract: A new class of quaternary complex transition metal hydrides (Na{sub 2}Mg{sub 2}TH{sub 8} (T = Fe, Ru)) have been synthesized and their structures determined by combined synchrotron radiation X-ray and powder neutron diffraction. The compounds can be considered as a link between ionic and complex hydrides in terms of incorporating independently coordinated ionic and covalent hydrogen. These novel isostructural complex transition metal hydrides crystallize in the orthorhombic space group Pbam, where the octahedral complex hydride anion is surrounded by a cubic array of four Mg{sup 2+} and four Na{sup +} cations, forming distinct two-dimensional layers. An intriguing feature of these materials is the distorted octahedral coordination of the isolated H{sup −} anions by four Na{sup +} and two Mg{sup 2+} cations, which form layers between the transition metal containing layers. The vibrational modes of the H{sup −} anions and complex hydride anion are independently observed for the first time in a quaternary complex transition metal hydride system by Raman and IR spectroscopy.

Distinct interactions of Na+ and Ca2+ ions with the selectivity filter of the bacterial sodium channel NaVAb

International Nuclear Information System (INIS)

Ke, Song; Zangerl, Eva-Maria; Stary-Weinzinger, Anna

2013-01-01

Highlights: ► Ca 2+ translocates slowly in the filter, due to lack of “loose” knock-on mechanism. ► Identification of a high affinity binding site in Na V Ab selectivity filter. ► Changes of EEEE locus triggered by electrostatic interactions with Ca 2+ ions. -- Abstract: Rapid and selective ion transport is essential for the generation and regulation of electrical signaling pathways in living organisms. In this study, we use molecular dynamics simulations and free energy calculations to investigate how the bacterial sodium channel Na V Ab (Arcobacter butzleri) differentiates between Na + and Ca 2+ ions. Multiple nanosecond molecular dynamics simulations revealed distinct binding patterns for these two cations in the selectivity filter and suggested a high affinity calcium binding site formed by backbone atoms of residues Leu-176 and Thr-175 (S CEN ) in the sodium channel selectivity filter

Thermodynamic modeling of the Mg-Al-Ca system

Energy Technology Data Exchange (ETDEWEB)

Janz, A.; Groebner, J. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany); Cao, H.; Zhu, J.; Chang, Y.A. [Department of Materials Science and Engineering, University of Wisconsin, 1509 University Ave., Madison, WI 53706 (United States); Schmid-Fetzer, R. [Clausthal University of Technology, Institute of Metallurgy, Robert-Koch-Str. 42, D-38678 Clausthal-Zellerfeld (Germany)], E-mail: schmid-fetzer@tu-clausthal.de

2009-02-15

A thermodynamic model has been developed that provides a quantitative description for a wide area of the Mg-Al-Ca system. All available experimental data plus new key experiments using differential scanning calorimetry/differential thermal analysis have been considered to create a dataset which reproduces the primary crystallizing phases, the extensive ternary solubilities of binary phases and the ternary C36 Laves phase. This enables validated thermodynamic calculations in various areas of this ternary system.

Phase diagrams for systems Cu2S-AIIS (AII=Mg, Ca, Sr, Ba)

International Nuclear Information System (INIS)

Andreev, O.V.; Sikerina, N.V.; Solov'eva, A.V.

2005-01-01

By the methods of physicochemical analysis phase diagrams of Cu 2 S-A II S (A II =Mg, Ca, Sr, Ba) systems are studied. The system Cu 2 S-SrS is of eutectic type with eutectic coordinates 1095 K and 21.5 mol.% of SrS. Solubility of SrS in Cu 2 S is 2 mol.% at 1095 K. Regularities of phase diagram changes of Cu 2 S-A II S (A II =Mg, Ca, Sr, Ba) system are determined. Thermodynamic analysis is done [ru

Selective recovery of uranium from Ca-Mg uranates by chlorination

Energy Technology Data Exchange (ETDEWEB)

Pomiro, Federico J., E-mail: pomiro@cab.cnea.gov.ar [Departamento de Fisicoquímica y Control de Calidad, Complejo Tecnológico Pilcaniyeu, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. Bustillo 9500, 8400 S.C. de Bariloche, Río Negro (Argentina); Gaviría, Juan P. [Departamento de Fisicoquímica y Control de Calidad, Complejo Tecnológico Pilcaniyeu, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. Bustillo 9500, 8400 S.C. de Bariloche, Río Negro (Argentina); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET) (Argentina); Quinteros, Raúl D. [Departamento de Fisicoquímica y Control de Calidad, Complejo Tecnológico Pilcaniyeu, Centro Atómico Bariloche, Comisión Nacional de Energía Atómica, Av. Bustillo 9500, 8400 S.C. de Bariloche, Río Negro (Argentina); and others

2017-07-15

A chlorination process is proposed for the uranium extraction and separation using Calcium−Magnesium uranates such as starting reactants which were obtained by precipitation from uranyl nitrate solutions with calcium hydroxide. The study is based on thermodynamic and reaction analysis using chlorine gas as chlorination agent. The results showed that the chlorination reaction of Ca uranate is more feasible to occur than the Mg uranate. The products obtained after chlorination reactions were washed with deionized water to remove the chlorides produced and analyzed. The XRD patterns of the washed products indicated that the chlorination between 400 and 500 °C result in a single phase of calcium uranate (CaUO{sub 4}) as reaction product. The formation of U{sub 3}O{sub 8} and MgU{sub 3}O{sub 10} was observed at temperatures between 600 °C and 700 °C for 8 hs. The optimal conditions to recover uranium were 3 l h{sup −1} of chlorine and 10 hs of reaction at 700 °C being U{sub 3}O{sub 8} the single uranium product obtained. - Highlights: •The chlorination is an effective method for the recovery uranium from Ca-Mg uranates. •The optimal conditions were: 10 hs of reaction time at 700 °C using 3 l/h of Cl{sub 2}(g). •U{sub 3}O{sub 8} is recovery by washing out the chlorination by-products.

Effect of CaO on Hot Workability and Microstructure of Mg-9.5Zn-2Y Alloy

Science.gov (United States)

Kwak, Tae-yang; Kim, Daeguen; Yang, Jaehack; Yoon, Young-ok; Kim, Shae K.; Lim, Hyunkyu; Kim, Woo Jin

Mg-Zn-Y system alloys have been a great interest because Mg-Zn-Y alloys with I-phase exhibited high ductility at room and elevated temperatures. According to our preliminary experiments, the addition of CaO improved strength, but the process window became narrow. Therefore, the aim of current work was to find optimum extrusion conditions for CaO added Mg-Zn-Y alloys by processing maps. The 0.3 wt.% of CaO added Mg-9.5Zn-2Y (Mg95.6Zn3.8Y0.6) alloy was prepared by casting into steel mold and homogenizing. Hot compression test were performed in the Gleeble machine at temperature range of 250-400 °C with various strain rates. The alloys were extruded with a reduction ratio of 20:1. To analyze the microstructure and texture, optical micrograph, scanning electron microscope and electron backscattered diffraction were used. Moreover, we investigated the effects of metallic Ca addition in this alloy to compare with the addition of CaO.

Behaviour of CaO coating of gas atomized Mg powders using mechanical milling process

International Nuclear Information System (INIS)

Kim, Sun-Mi; Kim, Yong Hwan; Kim, Young Do; Kim, Taek-Soo

2011-01-01

Highlights: → This work is very new, since behaviour of CaO coating with milling time as desulfurizer is not frequently reported. → The manuscript reports the new manner of Mg powders desulfurizer development by the innovative process. - Abstract: In order to synthesize a thermally stable Mg powder as a desulfurizer of iron, pure Mg was gas atomized to powders and coated by CaO powders, to produce a thermally stable desulfurizer using a mechanical milling process. Since the effect of desulfurization is dependent on the degree of surface modification, coating behaviours such as the size, morphology and layer thickness were investigated as a function of milling condition. As the milling conducted from 10 min to 30 min, 1 h, 3 h, 6 h, 12 h, CaO particles began to stick on the surface of Mg powders. The layer of CaO formed from 1 h milling was about 17 μm thick and gradually thickened to be 28 μm, 32 μm and 37 μm with increasing the milling time to 3 h, 6 h and 12 h, respectively. The shape of coated powder became more spherical after 1 h milling, being mostly spherical after 6 h. Desulfurization rate and uniformity were evaluated for the various thickness of the coating layer.

Characterization of Bacillus subtilis YfkE (ChaA): a calcium-specific Ca2+/H+ antiporter of the CaCA family.

Science.gov (United States)

Fujisawa, Makoto; Wada, Yuko; Tsuchiya, Takahiro; Ito, Masahiro

2009-08-01

YfkE, a protein from Bacillus subtilis, exhibits homology to the Ca(2+):Cation Antiporter (CaCA) Family. In a fluorescence-based assay of everted membrane vesicles prepared from Na(+)(Ca(2+))/H(+) antiporter-defective mutant Escherichia coli KNabc, YfkE exhibited robust Ca(2+)/H(+) antiport activity, with a K (m) for Ca(2+) estimated at 12.5 muM at pH 8.5 and 113 muM at pH 7.5. Neither Na(+) nor K(+) served as a substrate. Mg(2+) also did not serve as a substrate, but inhibited the Ca(2+)/H(+) antiporter activity. The Ca(2+) transport capability of YfkE was also observed directly by transport assays in everted membrane vesicles using radiolabeled (45)Ca(2+). Transcriptional analysis from the putative yfkED operon using beta-garactosidase activity as a reporter revealed that both of the yfkE and yfkD genes are regulated by forespore-specific sigma factor, SigG, and the general stress response regulator, SigB. These results suggest that YfkE may be needed for Ca(2+) signaling in the sporulation or germination process in B. subtilis. ChaA is proposed as the designation for YfkE of B. subtilis.

Effect of vanadate and of removal of extracellular Ca2+ and Na+ on tension development and 45Ca efflux in rat and frog myocardium

DEFF Research Database (Denmark)

Gesser, H; Bonefeld-Jørgensen, Eva Cecilie

1983-01-01

Vanadate in the range 0-5 mM has positive inotropic effects on myocardial strips of frog and to a lesser extent on those of rat. Inhibiting the sarcolemmal Na+, Ca2+ exchange by a solution free of Ca2+ and Na+ caused a drop in 45Ca efflux and a transient increase in resting tension. These effects...... were more expressed for the frog than for the rat myocardium, which suggests that the Na+ for Ca2+ exchange across the cell membrane is more important in the frog than in the rat myocardium. A subsequent addition of vanadate at 2 or 5 mM had no effect on 45Ca efflux, while it increased the resting...... tension. This increase was higher for the frog than for the rat myocardium. These results suggest that the inotropic effects of vanadate may be due to an effect on membrane-bound Ca2+-ATPase....

Energetic prediction on the stability of A2Mg12Si7, A2Mg4Si3, and AMgSi in the A2Si–Mg2Si system (A = Ca, Sr and Ba) and their calculated electronic structures

International Nuclear Information System (INIS)

Imai, Yoji; Mori, Yoshihisa; Nakamura, Shigeyuki; Takarabe, Ken-ichi

2014-01-01

Highlights: • Formation energies of A 2 Mg 4 Si 3 , A 2 Mg 12 Si 7 , and AMgSi (A = Ca,Sr,Ba) were calculated. • All AMgSi are quite stable compared to mixture of A 2 Si and Mg 2 Si. • Ba 2 Mg 4 Si 3 and Sr 2 Mg 4 Si 3 are predicted to be stable, but Ca 2 Mg 4 Si 3 is not. • Ca 2 Mg 12 Si 7 and Sr 2 Mg 12 Si 7 are energetically unstable. • Stability of Ba 2 Mg 12 Si 7 is a tender subject. -- Abstract: In order to evaluate the relative stability of A 2 Mg 4 Si 3 , A 2 Mg 12 Si 7 , and AMgSi (A = Ca, Sr, and Ba) in the A 2 Si–Mg 2 Si system, electronic energy changes in the formation of these compounds were calculated using a density-functional theory with the Perdew–Wang generalized gradient approximations. It was found that (1) AMgSi’s are quite stable compared to equi-molar mixture of A 2 Si and Mg 2 Si, (2) Ba 2 Mg 4 Si 3 and Sr 2 Mg 4 Si 3 are also stable, (3) Ca 2 Mg 4 Si 3 and Ca 2 Mg 12 Si 7 are less stable than the mixture of CaMgSi and Mg 2 Si, and (4) Stability of Ba 2 Mg 12 Si 7 is a tender subject and Sr 2 Mg 12 Si 7 is energetically unstable compared to the mixture of Sr 2 Mg 4 Si 3 (or, SrMgSi) and Mg 2 Si. The presence of Sr 2 Mg 12 Si 7 may be due to the vibrational and/or configurational entropy, which are not treated in the present study. From the calculated electronic densities of state, complex compounds of SrMgSi and Mg 2 Si have both p-type and n-type character, depending on the ratio of SrMgSi and Mg 2 Si in that compound

Relationship between NaCl- and H2O2-induced cytosolic Ca2+ increases in response to stress in Arabidopsis.

Directory of Open Access Journals (Sweden)

Zhonghao Jiang

Full Text Available Salinity is among the environmental factors that affect plant growth and development and constrain agricultural productivity. Salinity stress triggers increases in cytosolic free Ca(2+ concentration ([Ca(2+]i via Ca(2+ influx across the plasma membrane. Salinity stress, as well as other stresses, induces the production of reactive oxygen species (ROS. It is well established that ROS also triggers increases in [Ca(2+]i. However, the relationship and interaction between salinity stress-induced [Ca(2+]i increases and ROS-induced [Ca(2+]i increases remain poorly understood. Using an aequorin-based Ca(2+ imaging assay we have analyzed [Ca(2+]i changes in response to NaCl and H2O2 treatments in Arabidopsis thaliana. We found that NaCl and H2O2 together induced larger increases in [Ca(2+]i in Arabidopsis seedlings than either NaCl or H2O2 alone, suggesting an additive effect on [Ca(2+]i increases. Following a pre-treatment with either NaCl or H2O2, the subsequent elevation of [Ca(2+]i in response to a second treatment with either NaCl or H2O2 was significantly reduced. Furthermore, the NaCl pre-treatment suppressed the elevation of [Ca(2+]i seen with a second NaCl treatment more than that seen with a second treatment of H2O2. A similar response was seen when the initial treatment was with H2O2; subsequent addition of H2O2 led to less of an increase in [Ca(2+]i than did addition of NaCl. These results imply that NaCl-gated Ca(2+ channels and H2O2-gated Ca(2+ channels may differ, and also suggest that NaCl- and H2O2-evoked [Ca(2+]i may reduce the potency of both NaCl and H2O2 in triggering [Ca(2+]i increases, highlighting a feedback mechanism. Alternatively, NaCl and H2O2 may activate the same Ca(2+ permeable channel, which is expressed in different types of cells and/or activated via different signaling pathways.

Unique antitumor property of the Mg-Ca-Sr alloys with addition of Zn

Science.gov (United States)

Wu, Yuanhao; He, Guanping; Zhang, Yu; Liu, Yang; Li, Mei; Wang, Xiaolan; Li, Nan; Li, Kang; Zheng, Guan; Zheng, Yufeng; Yin, Qingshui

2016-02-01

In clinical practice, tumor recurrence and metastasis after orthopedic prosthesis implantation is an intensely troublesome matter. Therefore, to develop implant materials with antitumor property is extremely necessary and meaningful. Magnesium (Mg) alloys possess superb biocompatibility, mechanical property and biodegradability in orthopedic applications. However, whether they possess antitumor property had seldom been reported. In recent years, it showed that zinc (Zn) not only promote the osteogenic activity but also exhibit good antitumor property. In our present study, Zn was selected as an alloying element for the Mg-1Ca-0.5Sr alloy to develop a multifunctional material with antitumor property. We investigated the influence of the Mg-1Ca-0.5Sr-xZn (x = 0, 2, 4, 6 wt%) alloys extracts on the proliferation rate, cell apoptosis, migration and invasion of the U2OS cell line. Our results show that Zn containing Mg alloys extracts inhibit the cell proliferation by alteration the cell cycle and inducing cell apoptosis via the activation of the mitochondria pathway. The cell migration and invasion property were also suppressed by the activation of MAPK (mitogen-activated protein kinase) pathway. Our work suggests that the Mg-1Ca-0.5Sr-6Zn alloy is expected to be a promising orthopedic implant in osteosarcoma limb-salvage surgery for avoiding tumor recurrence and metastasis.

Purinergic receptors stimulate Na+/Ca2+ exchange in pancreatic duct cells: possible role of proteins handling and transporting Ca2+

DEFF Research Database (Denmark)

Hansen, Mette R; Krabbe, Simon; Ankorina-Stark, Ieva

2009-01-01

). Since NCX can also be connected with epithelial Ca(2+) transport, we also investigated expression of some Ca(2+)-handling/transporting proteins. Expression analysis revealed that pancreatic ducts of rat and human duct cell line CFPAC-1 (also PANC-1 and Capan-1) express the Na(+)/Ca(2+) exchanger (splice...

(Solid + liquid) phase equilibria of (Ca(H2PO2)2 + CaCl2 + H2O) and (Ca(H2PO2)2 + NaH2PO2 + H2O) ternary systems at T = 323.15 K

International Nuclear Information System (INIS)

Cao, Hong-yu; Zhou, Huan; Bai, Xiao-qin; Ma, Ruo-xin; Tan, Li-na; Wang, Jun-min

2016-01-01

Graphical abstract: Solubility diagram of the (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) system at T = (323.15 and 298.15) K. - Highlights: • Phase diagrams of Ca 2+ -H 2 PO 2 − -Cl − -H 2 O, Ca 2+ -Na + -H 2 PO 2 − -H 2 O at 323.15 K were obtained. • Incompatible double salt of NaCa(H 2 PO 2 ) 3 in Ca 2+ -Na + -H 2 PO 2 − -H 2 O system was determined. • Density diagram of the corresponding liquid were simultaneously measured. - Abstract: Calcium hypophosphite has been widely used as an anti-corrosive agent, flame retardant, fertilizer, assistant for Ni electroless plating, and animal nutritional supplement. High purity calcium hypophosphite can be synthesized via the replacement reaction of sodium hypophosphite and calcium chloride. In this work, the (solid + liquid) phase equilibria of (Ca(H 2 PO 2 ) 2 + CaCl 2 + H 2 O) and (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) ternary systems at T = 323.15 K were studied experimentally via the classical isothermal solubility equilibrium method, and the phase diagrams for these two systems were obtained. It was found that two solid salts of CaCl 2 ·2H 2 O and Ca(H 2 PO 2 ) 2 exist in the (Ca(H 2 PO 2 ) 2 + CaCl 2 + H 2 O) system, and three salts of Ca(H 2 PO 2 ) 2 , NaH 2 PO 2 ·H 2 O and one incompatible double salt, NaCa(H 2 PO 2 ) 3 occur in the (Ca(H 2 PO 2 ) 2 + NaH 2 PO 2 + H 2 O) system.

Quantitative spectrographic analysis of Li, Na and Ca in uranium base materials, using the carrier distillation technique

International Nuclear Information System (INIS)

Gomes, R.P.; Brito, J. de.

1978-01-01

A spectrographic method for the quantitative determination of Ca, Li and Na in uranium base materials is described. The carrier destillation technique is used and a study is made for the selection of best carrier compounds. In U 3 O 8 matrix, the best results are obtained with 4% In 2 O 3 for the determination of Na and a 15% mixed carrier (3 NaCl + 1 Y 2 O 3 ) for the determination of Ca and Li. The minium determination limit for Ca and Li is 1 ppm while for Na it is 15 ppm. The precision of the method is calculated and the relative standard deviation is found to be 11, 16 and 6,5% for Ca, Li and Na respectively [pt

The influence of Ca-Mg-Al hydrotalcite synthesized from brine water on thermal and mechanical properties of HTlc-EVA composite

International Nuclear Information System (INIS)

Karina, Wiwiek; Heraldy, Eddy; Pramono, Edi; Heriyanto,; Astuti, Shanti

2016-01-01

Ca-Mg-Al hydrotalcite-like compound (Ca-Mg-Al HTlc) was prepared by co-precipitation method using brine water that is well known as the desalination process waste water. The structure of Ca-Mg-Al HTlc was determined by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis. Ca-Mg-Al HTlc was studied as a non-halogenated filler in ethylene vinyl acetate (EVA) matrix. Composites with different filler concentrations were prepared to evaluate the influence of Ca-Mg-Al HTlc on thermal and mechanical properties of EVA.The presence of Ca-Mg-Al HTlc in the composite has been confirmed by FTIR analysis. Thermal properties of composites show significant reduction of degradation temperature as well as the loading of HTlc in EVA. However, the total enthalpies combustion of composites with 1% and 5% HTlc loadings higher compared to neat EVA. Further, mechanical properties were determined by tensile test. The result shows that tensile strength and elongation at break of composites decrease relatively by Ca-Mg-Al HTlc addition

The influence of Ca-Mg-Al hydrotalcite synthesized from brine water on thermal and mechanical properties of HTlc-EVA composite

Energy Technology Data Exchange (ETDEWEB)

Karina, Wiwiek, E-mail: wiekarina@gmail.com; Heraldy, Eddy, E-mail: eheraldy@gmail.com; Pramono, Edi; Heriyanto,; Astuti, Shanti [Department of Chemistry, Faculty of Mathematics and Natural Sciences, Sebelas Maret University Jl. Ir. Sutami 36A, Kentingan, Surakarta 57126 (Indonesia)

2016-02-08

Ca-Mg-Al hydrotalcite-like compound (Ca-Mg-Al HTlc) was prepared by co-precipitation method using brine water that is well known as the desalination process waste water. The structure of Ca-Mg-Al HTlc was determined by X-Ray Diffraction (XRD) and Fourier Transform Infrared (FTIR) analysis. Ca-Mg-Al HTlc was studied as a non-halogenated filler in ethylene vinyl acetate (EVA) matrix. Composites with different filler concentrations were prepared to evaluate the influence of Ca-Mg-Al HTlc on thermal and mechanical properties of EVA.The presence of Ca-Mg-Al HTlc in the composite has been confirmed by FTIR analysis. Thermal properties of composites show significant reduction of degradation temperature as well as the loading of HTlc in EVA. However, the total enthalpies combustion of composites with 1% and 5% HTlc loadings higher compared to neat EVA. Further, mechanical properties were determined by tensile test. The result shows that tensile strength and elongation at break of composites decrease relatively by Ca-Mg-Al HTlc addition.

Investigation of structural and optical properties of CaTiO3 powders doped with Mg2+ and Eu3+ ions

International Nuclear Information System (INIS)

Oliveira, Larissa H.; Savioli, Julia; Moura, Ana P. de; Nogueira, Içamira C.; Li, Maximo S.; Longo, Elson; Varela, José A.; Rosa, Ieda L.V.

2015-01-01

In this work, CaTiO 3 powders doped with Mg 2+ ions and CaTiO 3 powders co-doped with Mg 2+ and Eu 3+ ions were prepared by the polymeric precursor method (PPM). These powders were characterized by different characterization techniques to study the influence of Mg 2+ doping as well as Mg 2+ and Eu 3+ co-doping in structural and optical properties of CaTiO 3 perovskite-type structure. The Rietveld refinement and Micro-Raman analyses suggested the substitution Mg 2+ and Eu 3+ ions in the A-site of CaTiO 3 perovskite. The influence of Mg 2+ doping can be detected by the displacement of calcium and oxygen atomic positions when compared to the non-doped CaTiO 3 powder. When Eu 3+ ions are added to the A-site of this perovskite the excess of positive charge can be compensated by the formation of calcium vacancies. Luminescence data showed that Ca 1-x Mg x TiO 3 and Ca 1x Mg x/2 Eu 2y/3 TiO 3 powders are potential materials for fabrication of lighting devices based on near-UV and blue LED using an excitation wavelength of 397 and/or 450 nm. - Highlights: • CaTiO 3 co-doped with Mg 2+ and Eu 3+ were obtained by the Polymeric Precursor Method. • Incorporation of Mg 2+ and Eu 3+ ions in the CaTiO 3 lattice. • Enhancement of the Eu 3+ photoluminescence

Controls of Ca/Mg/Fe activity ratios in pore water chemistry models of the Callovian-Oxfordian clay formation

International Nuclear Information System (INIS)

Lerouge, C.; Grangeon, S.; Wille, G.; Flehoc, C.; Gailhanou, H.; Gaucher, E.C.; Tournassat, C.; Vinsot, A.; Made, B.; Altmann, S.

2013-01-01

In the pore water chemistry model of the Callovian-Oxfordian clay formation, the divalent cations Ca, Mg, and Fe are controlled by equilibrium reactions with pure carbonates: calcite for Ca, dolomite for Mg, and siderite for Fe. Results of a petrological study and computing of the Ca/Mg and Ca/Fe activity ratios based on natural pore water chemistry provide evidence that equilibrium with pure calcite and pure dolomite is a reasonable assumption for undisturbed pore waters; on the other hand, siderite cannot be considered at equilibrium with pore waters at the formation scale. (authors)

Controls of Ca/Mg/Fe activity ratios in pore water chemistry models of the Callovian-Oxfordian clay formation

Energy Technology Data Exchange (ETDEWEB)

Lerouge, C.; Grangeon, S.; Wille, G.; Flehoc, C.; Gailhanou, H.; Gaucher, E.C.; Tournassat, C. [BRGM av. Claude Guillemin BP6009 45060 Orleans cedex 2 (France); Vinsot, A. [ANDRA Meuse/Haute-Marne Underground research Laboratory (URL), RD 960, 55290 Bure (France); Made, B.; Altmann, S. [ANDRA - Parc de la Croix Blanche, 1-7 rue Jean Monnet, 92298 Chatenay-Malabry Cedex (France)

2013-07-01

In the pore water chemistry model of the Callovian-Oxfordian clay formation, the divalent cations Ca, Mg, and Fe are controlled by equilibrium reactions with pure carbonates: calcite for Ca, dolomite for Mg, and siderite for Fe. Results of a petrological study and computing of the Ca/Mg and Ca/Fe activity ratios based on natural pore water chemistry provide evidence that equilibrium with pure calcite and pure dolomite is a reasonable assumption for undisturbed pore waters; on the other hand, siderite cannot be considered at equilibrium with pore waters at the formation scale. (authors)

Corrosion behaviour of Mg-Cu and Mg-Mo composites in 3.5% NaCl

International Nuclear Information System (INIS)

Budruk Abhijeet, S.; Balasubramaniam, R.; Gupta, M.

2008-01-01

The corrosion behaviour of pure magnesium, Mg-Cu (0.3, 0.6, and 1 vol.%) and Mg-Mo (0.1, 0.3, and 0.6 vol.%) composites has been studied in 3.5% NaCl solution by weight loss and polarisation methods. Corrosion rates determined by weight loss method were considerably higher than that determined by polarisation method. The corrosion rate increased with increasing volume fraction of reinforcement in Mg-Cu and Mg-Mo composites. At the same volume fraction of reinforcement, molybdenum reinforced composite corroded faster than copper reinforced composite. The galvanic current density between Mg-Cu and Mg-Mo couples has been experimentally measured using zero resistance ammeter technique. The experimentally observed galvanic current densities were in close agreement with those obtained using mixed potential theory analysis. SEM observation of corroded samples confirmed microgalvanic activity at the matrix/reinforcement interfaces. The poor corrosion resistance of composites has been attributed to microgalvanic effects between the matrix and reinforcements and inferior quality of surface films

Inorganic synthesis of Fe-Ca-Mg carbonates at low temperature

NARCIS (Netherlands)

Romanek, Christopher S.; Jiménez-López, Concepción; Navarro, Alejandro Rodriguez; Sánchez-Román, Monica; Sahai, Nita; Coleman, Max

2009-01-01

A set of free-drift experiments was undertaken to synthesize carbonates of mixed cation content (Fe, Ca, Mg) from solution at 25 and 70 °C to better understand the relationship between the mineralogy and composition of these phases and the solutions from which they precipitate. Metastable solid

Synthesis and structural characterization of the hexagonal anti-perovskite Na{sub 2}CaVO{sub 4}F

Energy Technology Data Exchange (ETDEWEB)

Green, Robert L., E-mail: rgreen@flpoly.org [Chemistry, Florida Polytechnic University, Lakeland, FL 33805 (United States); Avdeev, Maxim [Australian Science and Technology Organisation, Locked Bag 2001, Kirrawee DC, NSW 2232 (Australia); School of Chemistry, The University of Sydney, Sydney, NSW 2006 (Australia); Vogt, Thomas [NanoCenter and Department of Chemistry and Biochemistry, University of South Carolina, Columbia, SC 29208 (United States)

2017-06-15

The structural details of the ordered hexagonal oxyfluoride Na{sub 2}CaVO{sub 4}F prepared by solid-state synthesis using stoichiometric amounts of V{sub 2}O{sub 5}, CaCO{sub 3}, Na{sub 2}CO{sub 3} and NaF were characterized using high-resolution neutron powder diffraction. The structural changes between 25 °C and 750 °C revealed that the two structural subunits in this material behave different when heated: there is an expansion of the face-shared FNa{sub 4}Ca{sub 2} octahedra while the VO{sub 4} tetrahedra due to increased thermal disorder reveal marginal bond contractions. Bond valences and the global instability index point to significant structural disorder at 750 °C. - Graphical abstract: The structure of the novel oxyfluoride Na{sub 2}CaVO{sub 4}F is studied at room temperature and high-temperatures. The structure can be viewed as layers of compression and elongation of polyhedral subunits, which change as a function of temperature. - Highlights: • The novel oxyfluoride, Na{sub 2}CaVO{sub 4}F, is synthesized via solid-state method. • High-resolution neutron diffraction data is used to analyze the structure of Na{sub 2}CaVO{sub 4}F. • Structural subunits exhibit expansion and contraction with increasing temperature. • Higher temperatures increase instability within the structure of Na{sub 2}CaVO{sub 4}F.

Accumulation of /sup 90/Sr, Ca, Mg, K and Na in crane's-bill plants cultivated on soil and hydroponics

Energy Technology Data Exchange (ETDEWEB)

Analyan, V.L.; Sarkisyan, G.A. (AN Armyanskoj SSR, Erevan. Inst. Agrokhimicheskikh Problem i Gidroponiki)

1981-01-01

Accumulation of /sup 90/Sr in plants under the conditions of soil and hydroponic cultures from the viewpoint of the possibility of obtaining ''pure'' vegetable production has been studied. Predominant absorption of /sup 90/Sr by soil plants as compared with calcium is shown. In the course of using the hydroponic cultivation method predominant radiostrontium absorption has been manifested to all investigated nuclides including potassium. The accumulation coefficients analysis has shown that among soil plants the first place is occupied by potassium, while the /sup 90/Sr coefficients are greater than Ca on hydroponics, where the true, not distorted by soil sorption processes absorptive plant capacity has been manifested, the first places in the series are occupied by /sup 90/Sr and K, then come Ca and Mg.

Mössbauer and magnetic studies of surfactant mediated Ca-Mg doped ferrihydrite nanoparticles.

Science.gov (United States)

Layek, Samar; Mohapatra, M; Anand, S; Verma, H C

2013-03-01

Ultrafine (2-5 nm) particles of amorphous Ca-Mg co-doped ferrihydrite have been synthesized by surfactant mediated co-precipitation method. The evolution of the amorphous ferrihydrite by Ca-Mg co-doping is quite different from our earlier investigations on individual doping of Ca and Mg. Amorphous phase of ferrihydrite for the present study has been confirmed by X-ray diffraction (XRD) and Mössbauer spectroscopy at room temperature and low temperatures (40 K and 20 K). Hematite nanoparticles with crystallite size about 8, 38 and 70 nm were obtained after annealing the as-prepared samples at 400, 600 and 800 degrees C respectively in air atmosphere. Superparamagnetism has been found in 8 nm sized hematite nanoparticles which has been confirmed from the magnetic hysteresis loop with zero remanent magnetization and coercive field and also from the superparamagnetic doublet of its room temperature Mössbauer spectrum. The magnetic properties of the 38 and 70 nm sized particles have been studied by room temperature magnetic hysteresis loop measurements and Mössbauer spectroscopy. The coercive field in these hematite nanoparticles increases with increasing particle size. Small amount of spinel MgFe2O4 phase has been detected in the 800 degrees C annealed sample.

Luminescent properties of codoping Y{sub 2}O{sub 3}: Eu, Me (Me = Mg, Ca) nanorods

Energy Technology Data Exchange (ETDEWEB)

Liu Zhilong; Wang Qin; Yang Yuming; Tao Chunyan; Yang Hua, E-mail: huayang86@sina.co [Jilin University, College of Chemistry (China)

2010-08-15

Phosphors of nanorods Y{sub 2}O{sub 3}: Eu (Mg, Ca) have been prepared by the hydrothermal method. The effect of Mg, Ca co-dopants on the Y{sub 2}O{sub 3}: Eu phosphor photoluminescence (PL) property was investigated. Upon excitation with ultraviolet (UV) irradiation, it is shown that there is a strong emission at around 610 nm corresponding to the forced electric dipole {sup 5}D{sub 0}-{sup 7}F{sub 2} transition of Eu{sup 3+}. At a certain concentration, Mg, Ca ions' doping effectively enhanced the luminescent properties of Y{sub 2}O{sub 3}: Eu{sup 3+} nanorods and did not change the cubic phase of the host. The structure of Y{sub 2}O{sub 3}: Eu{sup 3+} (Mg, Ca) phosphors was characterized by X-Ray diffraction (XRD). From XRD patterns, it is indicated that the phosphor Y{sub 2}O{sub 3}:(Eu, Ca) forms without impurity phase. From SEM, TEM images, it is shown that the crystal size of the nanorods phosphors is about 1-2 {mu}m in length and 30-50 nm in diameter.

Microstructure and corrosion study of porous Mg-Zn-Ca alloy in simulated body fluid

Science.gov (United States)

Annur, Dhyah; Erryani, Aprilia; Lestari, Franciska P.; Nyoman Putrayasa, I.; Gede, P. A.; Kartika, Ika

2017-03-01

Magnesium alloys had been considered as promising biomedical devices due to their biocompatibility and biodegradability. In this present work, microstructure and corrosion properties of Mg-Zn-Ca-CaCO3 porous magnesium alloy were examined. Porous metals were fabricated through powder metallurgy process with CaCO3 addition as a foaming agent. CaCO3 content was varied (1, 5, and 10%wt) followed by sintering process in 650 °C in Argon atmosphere for 10 and 15 h. The microstructure of the resulted alloys was analyzed by scanning electron microscopy (SEM) equipped with energy dispersive spectrometry data (EDS). Further, to examine corrosion properties, electrochemical test were conducted using G750 Gamry Instrument in accordance with ASTM standard G5-94 in simulated body fluid (Hank’s solution). As it was predicted, increasing content of foaming agent was in line with the increasing of pore formation. The electrochemical testing indicated corrosion rate would increase along with the increasing of foaming agent. The porous Mg-Zn-Ca alloy which has more porosity and connecting area will corrode much faster because it can transport the solution containing chloride ion which accelerated the chemical reaction. Highest corrosion resistance was given by Mg-Zn-Ca-1CaCO3-10 h sintering with potential corrosion of  -1.59 VSCE and corrosion rate of 1.01 mmpy. From the microstructure after electrochemical testing, it was revealed that volcano shaped structure and crack would occur after exposure to Hank’s solution

Selenium Speciation in the Fountain Creek Watershed (Colorado, USA Correlates with Water Hardness, Ca and Mg Levels

Directory of Open Access Journals (Sweden)

James S. Carsella

2017-04-01

Full Text Available The environmental levels of selenium (Se are regulated and strictly enforced by the Environmental Protection Agency (EPA because of the toxicity that Se can exert at high levels. However, speciation plays an important role in the overall toxicity of Se, and only when speciation analysis has been conducted will a detailed understanding of the system be possible. In the following, we carried out the speciation analysis of the creek waters in three of the main tributaries—Upper Fountain Creek, Monument Creek and Lower Fountain Creek—located in the Fountain Creek Watershed (Colorado, USA. There are statistically significant differences between the Se, Ca and Mg, levels in each of the tributaries and seasonal swings in Se, Ca and Mg levels have been observed. There are also statistically significant differences between the Se levels when grouped by Pierre Shale type. These factors are considered when determining the forms of Se present and analyzing their chemistry using the reported thermodynamic relationships considering Ca2+, Mg2+, SeO42−, SeO32− and carbonates. This analysis demonstrated that the correlation between Se and water hardness can be explained in terms of formation of soluble CaSeO4. The speciation analysis demonstrated that for the Fountain Creek waters, the Ca2+ ion may be mainly responsible for the observed correlation with the Se level. Considering that the Mg2+ level is also correlating linearly with the Se levels it is important to recognize that without Mg2+ the Ca2+ would be significantly reduced. The major role of Mg2+ is thus to raise the Ca2+ levels despite the equilibria with carbonate and other anions that would otherwise decrease Ca2+ levels.

Mg/Ca partitioning between aqueous solution and aragonite mineral: a molecular dynamics study

NARCIS (Netherlands)

Ruiz-Hernandez, S.E.; Grau-Crespo, R.; Almora-Barrios, N.; Wolthers, M.; Ruiz-Salvador, A.R.; Fernandez, N.; Leeuw, N.H. de

2012-01-01

We have calculated the concentrations of Mg in the bulk and surfaces of aragonite CaCO3 in equilibrium with aqueous solution, based on molecular dynamics simulations and grand-canonical statistical mechanics. Mg is incorporated in the surfaces, in particular in the (001) terraces,

Effects of limestone, N, K and Mg fertilizers on Mg absorption by oats and barley

Energy Technology Data Exchange (ETDEWEB)

Alston, A M

1966-01-01

Oats grown in a pot experiment on two sandy loams were sampled at four stages of growth. Neither KCl nor MgSO/sub 4/. 7H/sub 2/O had any effect on yield but % Mg and total Mg uptake were consistently decreased by applying K and increased by applying Mg. Ca(NO/sub 3/)/sub 2/ increased % Mg more than did (NH/sub 4/)/sub 2/SO/sub 4/, but yield and total Mg uptake were higher where (NH/sub 4/)/sub 2/SO/sub 4/ was applied. The effects of fertilizers were similar on both soils. The effects of applying (NH/sub 4/)/sub 2/SO/sub 4/ and NaNO/sub 2/ to the soil on % Mg in barley were compared in a field experiment on an acid loam to which several rates of limestone had been applied. Treatments had no effect on the % Mg in grain or straw at maturity. At four earlier stages of growth (NH/sub 4/)/sub 2/SO)/sub 4/ increased % Mg in the plants more than did NaNO/sub 2/. Limestone slightly increased % Mg. Nitrification of NH/sub 4/ in the soil was rapid.

Phase Diagram of Al-Ca-Mg-Si System and Its Application for the Design of Aluminum Alloys with High Magnesium Content

Directory of Open Access Journals (Sweden)

Nikolay A. Belov

2017-10-01

Full Text Available The phase transformations in the Al-Ca-Mg-Si system have been studied using thermodynamic calculations and experimental methods. We show that at 10% Magnesium (Mg, depending on the concentrations of calcium (Ca and silicon (Si, the following phases crystallize first (apart from the aluminum (Al solid solution: Al4Ca, Mg2Si, and Al2CaSi2. We have found that the major part of the calculated concentration range is covered by the region of the primary crystallization of the Al2CaSi2 phase. Regardless of the Ca and Si content, the solidification of the aluminum-magnesium alloys ends with the following nonvariant eutectic reaction: L → (Al + Al4Ca + Mg2Si + Al3Mg2. With respect to the temperature and composition of the liquid phase, this reaction is close to the eutectic reaction in the Al-Mg binary system. The addition of Ca and Si to the Al-10% Mg base alloy increases its hardness, reduces its density, and has no negative influence on its corrosion resistance. We have also established that the near-eutectic alloy containing about 3% Ca and 1% Si has the optimum structure.

The Influence of Mg(II and Ca(II Ions on Rutin Autoxidation in Weakly Alkaline Aqueous Solutions

Directory of Open Access Journals (Sweden)

Živanović Slavoljub C.

2016-09-01

Full Text Available Rutin (quercetin-3-O-rutinoside is one of the most abundant bioflavonoids with various biological and pharmacological activities. Considering the ubiquitous presence of Mg(II and Ca(II ions in biological systems we decided to investigate their influence on the autoxidation of rutin in weakly alkaline aqueous solutions. Changes in UV-Vis spectra recorded during the rutin autoxidation in aqueous solution at pH 8.4 revealed that this process was very slow in the absence of metal ions. The presence of Mg(II and, especially Ca(II ion, increased the transformation rate of rutin. UV-Vis spectra recorded after prolonged autoxidation indicated the formation of humic acidlike products in the presence of Mg(II and Ca(II ions. Four new compounds formed during the initial stage of rutin autoxidation in the presence of Mg(II and Ca(II ions were detected by HPLCDAD. Based on the analysis of their DAD UV-Vis spectra and comparison of their retention times with the retention time value for rutin, we concluded that the initial rutin transformation products were formed by the water addition on double bond in ring C and hydroxylation of ring B. A very small decrease of the initial rutin concentration (4% was observed by HPLC-DAD in the absence of metal ions for the period of 90 minutes. However, rutin concentration decrease was much larger in the presence of Mg(II and Ca(II ions (14% and 24%, respectively. The more pronounced effect of Ca(II ion on the rutin autoxidation may be explained by the stronger binding of Mg(II ion to rutin and thus greater stabilizing effect on reaction intermediates caused by its higher ionic potential (charge/ionic radius ratio in comparison to Ca(II ion. The results of this study may contribute to the better understanding of interactions of Mg(II and Ca(II ions with natural phenolic antioxidants which are important for their various biological activities.

Ankyrin-B coordinates the Na/K ATPase, Na/Ca exchanger, and InsP3 receptor in a cardiac T-tubule/SR microdomain.

Directory of Open Access Journals (Sweden)

2005-12-01

Full Text Available We report identification of an ankyrin-B-based macromolecular complex of Na/K ATPase (alpha 1 and alpha 2 isoforms, Na/Ca exchanger 1, and InsP3 receptor that is localized in cardiomyocyte T-tubules in discrete microdomains distinct from classic dihydropyridine receptor/ryanodine receptor "dyads." E1425G mutation of ankyrin-B, which causes human cardiac arrhythmia, also blocks binding of ankyrin-B to all three components of the complex. The ankyrin-B complex is markedly reduced in adult ankyrin-B(+/- cardiomyocytes, which may explain elevated [Ca2+]i transients in these cells. Thus, loss of the ankyrin-B complex provides a molecular basis for cardiac arrhythmia in humans and mice. T-tubule-associated ankyrin-B, Na/Ca exchanger, and Na/K ATPase are not present in skeletal muscle, where ankyrin-B is expressed at 10-fold lower levels than in heart. Ankyrin-B also is not abundantly expressed in smooth muscle. We propose that the ankyrin-B-based complex is a specialized adaptation of cardiomyocytes with a role for cytosolic Ca2+ modulation.

A Ruddlesden-Popper-type layered perovskite, Na2Ca2Nb4O13

International Nuclear Information System (INIS)

Chiba, K.; Ishizawa, N.; Oishi, S.

1999-01-01

Single crystals of disodium dicalcium tetraniobium tridecaoxide, Na 2 Ca 2 Nb 4 O 13 , were grown by the flux method. The structure was determined in space group Bb2 1 m. Perovskite-type layers with the formula [(Ca 2 Na)Nb 4 O 13 ] - are concatenated by Na + cations near the interlayer, forming a Ruddlesden-Popper-type structure. The interlayer structure, composed of Na and O atoms, can be regarded as a rocksalt-type. NbO 6 octahedra are tilted about [010] and [001]. The off-centre displacement of Nb atoms suggests a ferroelectric nature along [010], with a calculated magnitude of polarization of 0.12 C m -2 . (orig.)

Rapid age determination of oysters using LA-ICP-MS line scans of shell Mg/Ca ratios

Science.gov (United States)

Gillikin, D. P.; Durham, S. R.; Goodwin, D. H.

2016-02-01

Magnesium to calcium (Mg/Ca) ratios exhibit a strong temperature dependence in foraminifera and corals, but not in bivalve mollusks. Various studies have reported Mg/Ca-temperature relationships with R2 values ranging from 0.3 to 0.8 and significantly different relationships for bivalves growing at different salinities. However, this poor temperature correlation does not render Mg/Ca data useless. A weak temperature dependence would allow time (seasons and years) to be determined along the growth axis of shells. This would provide information about age, growth rate and also allow other proxies to be aligned with time. Typically, oxygen isotopes (δ18O) are used to age shells without clear periodic growth lines, which is time consuming and expensive. Line scans using laser ablation systems can cover several centimeters of shell in a few minutes. We test this method on the resilifer of two oyster species (Crassostrea gigas and C. virginica) using a 193 nm Laser-Ablation-ICP-MS. Living oysters were collected from San Francisco Bay, North Carolina, South Carolina, and the Gulf of Mexico; fossil shells (Pleistocene) were also collected in South Carolina. Shells were sampled for δ18O values and Mg/Ca ratios. We use annual cycles in δ18O values to confidently determine age, then apply the Mg/Ca technique. Shells of both species exhibit annual cyclicity in Mg/Ca ratios using spot and line scan laser sampling, which matche the seasonal cyclicity determined using δ18O values. Results show a good correlation between ages determined using the different methods. We conclude that LA-ICP-MS line scans offer a rapid and inexpensive technique for determining age, growth rate, and timing of shell growth in oyster reslifers.

NiF2/NaF:CaF2/Ca Solid-State High-Temperature Battery Cells

Science.gov (United States)

West, William; Whitacre, Jay; DelCastillo, Linda

2009-01-01

Experiments and theoretical study have demonstrated the promise of all-solid-state, high-temperature electrochemical battery cells based on NiF2 as the active cathode material, CaF2 doped with NaF as the electrolyte material, and Ca as the active anode material. These and other all-solid-state cells have been investigated in a continuing effort to develop batteries for instruments that must operate in environments much hotter than can be withstood by ordinary commercially available batteries. Batteries of this type are needed for exploration of Venus (where the mean surface temperature is about 450 C), and could be used on Earth for such applications as measuring physical and chemical conditions in geothermal wells and oil wells. All-solid-state high-temperature power cells are sought as alternatives to other high-temperature power cells based, variously, on molten anodes and cathodes or molten eutectic salt electrolytes. Among the all-solid-state predecessors of the present NiF2/NaF:CaF2/Ca cells are those described in "Solid-State High-Temperature Power Cells" (NPO-44396), NASA Tech Briefs, Vol. 32, No. 5 (May 2008), page 40. In those cells, the active cathode material is FeS2, the electrolyte material is a crystalline solid solution of equimolar amounts of Li3PO4 and LiSiO4, and the active anode material is Li contained within an alloy that remains solid in the intended high operational temperature range.

Mg/Ca- Δ CO3porewater2- -temperature calibration for Globobulimina spp.: A sensitive paleothermometer for deep-sea temperature reconstruction

Science.gov (United States)

Weldeab, Syee; Arce, Adam; Kasten, Sabine

2016-03-01

Existing benthic foraminiferal Mg/Ca-temperature calibrations are surrounded by substantial uncertainties mainly due to low temperature sensitivity of Mg/Ca in most benthic foraminifers and the effect of carbonate ion concentration on benthic foraminiferal Mg/Ca. Here we present Mg/Ca analysis of Rose Bengal stained and exceptionally well-preserved tests of the infaunal benthic foraminifer Globobulimina spp. from 39 eastern equatorial Atlantic core top samples. Mg/Ca in Globobulimina spp. varies between 2.5 mmol/mol and 9.1 mmol/mol corresponding to bottom water temperatures (BWT) between 1.8 °C and 19.1 °C and Δ CO3pore water2- between 33.7 ± 4 and - 34.3 ± 4 μmol /kg in sediment depths between 1 and 10 cm. Mg/Ca and BWT are linearly correlated with a best fit of Mg/Ca [mmol/mol] = (0.36 ± 0.02) * BWT [°C] + 2.22 ± 0.19 (r2 = 0.92, p-value: 11 *10-20, and n = 39). Using total alkalinity and pH data of pore water samples from 64 Atlantic multi-corer sites, we obtained Δ CO3pore water2- data from the depth habitat range of Globobulimina spp. (≥1 cm ≤ 10 cm below sediment surface). We show that Δ CO3pore waterSUP>2- is significantly lower than and linearly co-varies with the ΔCO2-3 of the overlying bottom water: Δ CO3pore water2- = (0.67 ± 0.05) * Δ CO3bottom water2- - (39.84 ± 1.98); r2 = 0.75, p-value: 6 *10-20, n = 64. We found a Mg/Ca sensitivity of 0.009 ± 0.0044 mmol /mol per μmol/kg Δ CO3pore water2- and Mg/Ca temperature sensitivity of 0.32 ± 0.06 mmol /mol / °C after a correction for the Δ CO3pore water2- effect. This study provides a robust Mg/Ca-temperature calibration, highlights that Δ CO3pore water2- is spatially and most likely temporally variable, and contradicts the notion that infaunal foraminiferal Mg/Ca is relatively immune from ΔCO2-3 changes in the overlying bottom water. Furthermore, comparison of down core Mg/Ca data of Cibicides pachyderma and Globobulimina spp. demonstrates that the high temperature sensitivity of

Interaction in the NaIn(MoO4)2 - AMoO4 (A = Mg, Mn) systems

International Nuclear Information System (INIS)

Kotova, I.Yu.; Kozhevnikova, N.M.

2001-01-01

The results of investigation into NaIn(MoO 4 ) 2 - AMoO 4 (A = Mg, Mn) quasibinary cross-sections by means of X-ray diffraction and differential thermal analysis are presented. Conducted researches revealed that compounds NaMg 3 In(MoO 4 ) and NaMn 3 In(MoO 4 ) melting incongruently at 990 Deg C and 940 Deg C accordingly were formed in the NaIn(MoO 4 ) - AMoO 4 (A = Mg, Mn) systems. The data of initiation of X-ray diffraction pattern of NaMg 3 In(MoO 4 ) 5 are presented. The temperature dependences of conductivity, dielectric permeability and tangent of dielectric losses indicative on ionic-electronic nature conductivity are determined. Activation energy of conductivity in the Mg - Mn row changes moderately - from 9.91 till 5.71 eV [ru

Review: geological and experimental evidence for secular variation in seawater Mg/Ca (calcite-aragonite seas and its effects on marine biological calcification

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J. B. Ries

2010-09-01

Full Text Available Synchronized transitions in the polymorph mineralogy of the major reef-building and sediment-producing calcareous marine organisms and abiotic CaCO₃ precipitates (ooids, marine cements throughout Phanerozoic time are believed to have been caused by tectonically induced variations in the Mg/Ca ratio of seawater (molar Mg/Ca>2="aragonite seas", <2="calcite seas". Here, I assess the geological evidence in support of secular variation in seawater Mg/Ca and its effects on marine calcifiers, and review a series of recent experiments that investigate the effects of seawater Mg/Ca (1.0–5.2 on extant representatives of calcifying taxa that have experienced variations in this ionic ratio of seawater throughout the geologic past.

Secular variation in seawater Mg/Ca is supported by synchronized secular variations in (1 the ionic composition of fluid inclusions in primary marine halite, (2 the mineralogies of late stage marine evaporites, abiogenic carbonates, and reef- and sediment-forming marine calcifiers, (3 the Mg/Ca ratios of fossil echinoderms, molluscs, rugose corals, and abiogenic carbonates, (4 global rates of tectonism that drive the exchange of Mg²⁺ and Ca²⁺ along zones of ocean crust production, and (5 additional proxies of seawater Mg/Ca including Sr/Mg ratios of abiogenic carbonates, Sr/Ca ratios of biogenic carbonates, and Br concentrations in marine halite.

Laboratory experiments have revealed that aragonite-secreting bryopsidalean algae and scleractinian corals and calcite-secreting coccolithophores exhibit higher rates of calcification and growth in experimental seawaters formulated with seawater Mg/Ca ratios that favor their skeletal mineral. These results support the assertion that seawater Mg/Ca played an important role in determining which hypercalcifying marine organisms were the major reef-builders and sediment-producers throughout Earth history. The observation that primary

Investigating the influence of Na+ and Sr2+ on the structure and solubility of SiO2-TiO2-CaO-Na2O/SrO bioactive glass.

Science.gov (United States)

Li, Y; Placek, L M; Coughlan, A; Laffir, F R; Pradhan, D; Mellott, N P; Wren, A W

2015-02-01

This study was conducted to determine the influence that network modifiers, sodium (Na+) and strontium (Sr2+), have on the solubility of a SiO2-TiO2-CaO-Na2O/SrO bioactive glass. Glass characterization determined each composition had a similar structure, i.e. bridging to non-bridging oxygen ratio determined by X-ray photoelectron spectroscopy. Magic angle spinning nuclear magnetic resonance (MAS-NMR) confirmed structural similarities as each glass presented spectral shifts between -84 and -85 ppm. Differential thermal analysis and hardness testing revealed higher glass transition temperatures (Tg 591-760 °C) and hardness values (2.4-6.1 GPa) for the Sr2+ containing glasses. Additionally the Sr2+ (~250 mg/L) containing glasses displayed much lower ion release rates than the Na+ (~1,200 mg/L) containing glass analogues. With the reduction in ion release there was an associated reduction in solution pH. Cytotoxicity and cell adhesion studies were conducted using MC3T3 Osteoblasts. Each glass did not significantly reduce cell numbers and osteoblasts were found to adhere to each glass surface.

Ca/Na selectivity coefficients from the Poisson-Boltzmann theory

International Nuclear Information System (INIS)

Hedstroem, Magnus; Karnland, Ola

2010-01-01

Document available in extended abstract form only. A possible scenario in the post-glacial evolution of the bentonite buffer used in a KBS-3 repository for spent nuclear fuel is that parts of the buffer may erode due to sol formation caused by the extensive swelling of, in particular, Na-montmorillonite in water of low ionic strength. Presence of calcium in the interlayer has been shown to promote gel formation even in electrolytes with ionic strengths in the vicinity of those in glacial melt waters. In order to estimate the amount of calcium in the clay at the onset of glaciation one needs information of the selectivity coefficient for Ca/Na exchange. Hitherto, most experimental data for evaluating the Gaines-Thomas selectivity coefficient, K GT have been obtained in batch experiments, i.e. at high water-to-solid ratios. The conditions in highly compacted bentonite are, however, radically different in many respects, e.g. the interlayer space is on the nanometre scale and the concentration of counterions is in molar range. Therefore we would like to theoretically investigate the transferability of the selectivity coefficients, determined in batch experiments, to compacted conditions. We solve the Poisson-Boltzmann (PB) equation for two parallel charged surfaces in equilibrium with an external NaCl/CaCl 2 mixed solution. Integration of the ion concentration profiles obtained from the PB equation gives the occupancy of Na + and Ca 2+ in the clay. That information together with the composition of the external electrolyte is all that is needed for the calculation of K GT . With a surface layer-charge density of one charge per 145 A 2 , which is close to the value for Wyoming montmorillonite, we find a variation of the selectivity coefficient from about 4 M in batch to 8 M for compacted montmorillonite with dry density 1700 kg/m 3 . The significance as well as the physics behind these results will be presented in detail. The predictions, based on the PB theory, will

Microstructure and electric characteristics of AETiO3 (AE=Mg, Ca, Sr doped CaCu3Ti4O12 thin films prepared by the sol–gel method

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Dong Xu

2015-10-01

Full Text Available This paper focuses on the effects of alkline-earth metal titante AETiO3 (AE=Mg, Ca, Sr doping on the microstructure and electric characteristics of CaCu3Ti4O12 thin films prepared by the sol–gel method. The results showed that the grain size of CCTO thin films could be increased by MgTiO3 doping. The movement of the grain boundaries was impeded by the second phases of CaTiO3 and SrTiO3 concentrating at grain boundaries in CaTiO3 and SrTiO3 doped CCTO thin films. Rapid ascent of dielectric constant could be observed in 0.1Mg TiO3 doped CCTO thin films, which was almost as three times high as pure CCTO thin film and the descent of the dielectric loss at low frequency could also be observed. In addition, the nonlinear coefficient (α, threshold voltage (VT and leakage current (IL of AETiO3 doped CCTO thin films (AE=Mg, Ca, Sr showed different variation with the increasing content of the MgTiO3, CaTiO3 and SrTiO3.

Selective recovery of uranium from Ca-Mg uranates by chlorination

Science.gov (United States)

Pomiro, Federico J.; Gaviría, Juan P.; Quinteros, Raúl D.; Bohé, Ana E.

2017-07-01

A chlorination process is proposed for the uranium extraction and separation using Calciumsbnd Magnesium uranates such as starting reactants which were obtained by precipitation from uranyl nitrate solutions with calcium hydroxide. The study is based on thermodynamic and reaction analysis using chlorine gas as chlorination agent. The results showed that the chlorination reaction of Ca uranate is more feasible to occur than the Mg uranate. The products obtained after chlorination reactions were washed with deionized water to remove the chlorides produced and analyzed. The XRD patterns of the washed products indicated that the chlorination between 400 and 500 °C result in a single phase of calcium uranate (CaUO4) as reaction product. The formation of U3O8 and MgU3O10 was observed at temperatures between 600 °C and 700 °C for 8 hs. The optimal conditions to recover uranium were 3 l h-1 of chlorine and 10 hs of reaction at 700 °C being U3O8 the single uranium product obtained.

Signatures in magnetites formed by (Ca,Mg,Fe)CO3 thermal decomposition: Terrestrial and extraterrestrial implications

Science.gov (United States)

Jimenez-Lopez, Concepcion; Rodriguez-Navarro, Carlos; Rodriguez-Navarro, Alejandro; Perez-Gonzalez, Teresa; Bazylinski, Dennis A.; Lauer, Howard V.; Romanek, Christopher S.

2012-06-01

It has never been demonstrated whether magnetite synthesized through the heat-dependent decomposition of carbonate precursors retains the chemical and structural features of the carbonates. In this study, synthetic (Ca,Mg,Fe)CO3 was thermally decomposed by heating from 25 to 700 °C under 1 atm CO2, and by in situ exposure under vacuum to the electron beam of a transmission electron microscope. In both cases, the decomposition of the carbonate was topotactic and resulted in porous pseudomorphs composed of oriented aggregates of magnetite nanocrystals. Both calcium and magnesium were incorporated into nanophase magnetite, forming (Ca,Mg)-magnetites and (Ca,Mg)-ferrites when these elements were present in the parent material, thus preserving the chemical signature of the precursor. These results show that magnetites synthesized in this way acquire a chemical and structural inheritance from their carbonate precursor that indicates how they were produced. These results are not only important in the determination of the origin of chemically-impure, oriented nanophase magnetite crystals in general, but they also provide important insights into the origin of the large, euhedral, chemically-pure, [111]-elongated magnetites found within Ca-, Mg- and Fe-rich carbonates of the Martian meteorite ALH84001. Based on our experimental results, the chemically-pure magnetites within ALH84001 cannot be genetically related to the Ca-, Mg- and Fe-rich carbonate matrix within which they are embedded, and an alternative explanation for their occurrence is warranted.

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr

Science.gov (United States)

Li, H. F.; Xie, X. H.; Zheng, Y. F.; Cong, Y.; Zhou, F. Y.; Qiu, K. J.; Wang, X.; Chen, S. H.; Huang, L.; Tian, L.; Qin, L.

2015-01-01

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals. PMID:26023878

Development of biodegradable Zn-1X binary alloys with nutrient alloying elements Mg, Ca and Sr.

Science.gov (United States)

Li, H F; Xie, X H; Zheng, Y F; Cong, Y; Zhou, F Y; Qiu, K J; Wang, X; Chen, S H; Huang, L; Tian, L; Qin, L

2015-05-29

Biodegradable metals have attracted considerable attentions in recent years. Besides the early launched biodegradable Mg and Fe metals, Zn, an essential element with osteogenic potential of human body, is regarded and studied as a new kind of potential biodegradable metal quite recently. Unfortunately, pure Zn is soft, brittle and has low mechanical strength in the practice, which needs further improvement in order to meet the clinical requirements. On the other hand, the widely used industrial Zn-based alloys usually contain biotoxic elements (for instance, ZA series contain toxic Al elements up to 40 wt.%), which subsequently bring up biosafety concerns. In the present work, novel Zn-1X binary alloys, with the addition of nutrition elements Mg, Ca and Sr were designed (cast, rolled and extruded Zn-1Mg, Zn-1Ca and Zn-1Sr). Their microstructure and mechanical property, degradation and in vitro and in vivo biocompatibility were studied systematically. The results demonstrated that the Zn-1X (Mg, Ca and Sr) alloys have profoundly modified the mechanical properties and biocompatibility of pure Zn. Zn-1X (Mg, Ca and Sr) alloys showed great potential for use in a new generation of biodegradable implants, opening up a new avenue in the area of biodegradable metals.

Luminescent properties of Mg3Ca3(PO4)4: Eu2+ blue-emitting phosphor for white light emitting diodes

International Nuclear Information System (INIS)

Li Yinqun; Deng Degang; Wang Qian; Li Gaofeng; Hua Youjie; Jia Guohua; Huang Lihui; Zhao Shilong; Wang Huanping; Li Chenxia; Xu Shiqing

2012-01-01

A blue-emitting phosphor, Eu 2+ -activated Mg 3 Ca 3 (PO 4 ) 4 phosphor was synthesized by conventional solid-state reaction. X-ray powder diffraction (XRD) analysis confirmed the phase formation. Photoluminescence (PL) results showed that Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ could be efficiently excited by UV–visible light from 250 to 430 nm, which matched well with the emission wavelengths of near-UV and UV LED chips. The effects of the doped-Eu 2+ concentration in Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ on the PL were also investigated. The result reveals that Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ is a potential blue-emitting phosphor for white LEDs. - Graphical Abstract: The excitation spectra show a broad peak from 250 to 430 nm, which means Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor can be suitable for application in white LEDs excited by the near-UV and UV LEDs. The emission spectrum peaked at 456 nm with the full-width half-maximum (FWHM) of 102 nm is attributed to the 4f 6 5d 1 –4f 7 transition of the Eu 2+ ion. The asymmetric emission spectra show that Eu 2+ has more one emission center in Mg 3 Ca 3 (PO 4 ) 4 , which can be deconvoluted into at least four Gaussian components peaked at 423, 446, 483 and 510 nm. Highlights: ► Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor could be effectively excited by UV chips (360–430 nm). ► Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor is a potential blue-emitting phosphor for white LEDs. ► Mg 3 Ca 3 (PO 4 ) 4 : Eu 2+ phosphor shows a broadband emission.

MgO-templated carbon as a negative electrode material for Na-ion capacitors

Science.gov (United States)

Kado, Yuya; Soneda, Yasushi

2016-12-01

In this study, MgO-templated carbon with different pore structures was investigated as a negative electrode material for Na-ion capacitors. With increasing the Brunauer-Emmett-Teller surface area, the irreversible capacity increased, and the coulombic efficiency of the 1st cycle decreased because of the formation of solid electrolyte interface layers. MgO-templated carbon annealed at 1000 °C exhibited the highest capacity and best rate performance, suggesting that an appropriate balance between surface area and crystallinity is imperative for fast Na-ion storage, attributed to the storage mechanism: combination of non-faradaic electric double-layer capacitance and faradaic Na intercalation in the carbon layers. Finally, a Na-ion capacitor cell using MgO-templated carbon and activated carbon as the negative and positive electrodes, respectively, exhibited an energy density at high power density significantly greater than that exhibited by the cell using a commercial hard carbon negative electrode.

Effect of Si, Mn, Sn on Tensile and Corrosion Properties of Mg-4Zn-0.5Ca Alloys for Biodegradable Implant Materials

Energy Technology Data Exchange (ETDEWEB)

Cho, Dae Hyun; Nam, Ji Hoon; Lee, Byeong Woo; Park, Ji Yong; Shin, Hyun Jung; Park, Ik Min [Pusan National University, Busan (Korea, Republic of)

2015-03-15

Effect of elements Si, Mn, Sn on tensile and corrosion properties of Mg-4Zn-0.5Ca alloys were investigated. The results of tensile properties show that the yield strength, ultimate tensile strength and elongation of Mg-4Zn-0.5Ca alloy increased significantly with the addition of 0.6 wt% Mn. This is considered the grain refinement effect due to addition of Mn. However addition of 0.6 wt% Si decreased yield strength, ultimate tensile strength and elongation. The bio-corrosion behavior of Mg-4Zn-0.5Ca-X alloys were investigated using immersion tests and potentiodynamic polarization test in Hank's solution. Immersion test showed that corrosion rate of Mg-4Zn-0.5Ca-0.6Mn alloy was the lowest rate and addition of 1.0 wt% Sn accelerated corrosion rate due to micro-galvanic effect in α-Mg/CaMgSn phases interface. And corrosion potential (E{sub c}orr) of Mg-4Zn-0.5Ca-0.6Mn alloy was the most noble among Mg-4Zn-0.5Ca-X alloys.

ß-Adrenergic stimulation increases RyR2 activity via intracellular Ca2+ and Mg2+ regulation.

Directory of Open Access Journals (Sweden)

Jiao Li

Full Text Available Here we investigate how ß-adrenergic stimulation of the heart alters regulation of ryanodine receptors (RyRs by intracellular Ca(2+ and Mg(2+ and the role of these changes in SR Ca(2+ release. RyRs were isolated from rat hearts, perfused in a Langendorff apparatus for 5 min and subject to 1 min perfusion with 1 µM isoproterenol or without (control and snap frozen in liquid N2 to capture their phosphorylation state. Western Blots show that RyR2 phosphorylation was increased by isoproterenol, confirming that RyR2 were subject to normal ß-adrenergic signaling. Under basal conditions, S2808 and S2814 had phosphorylation levels of 69% and 15%, respectively. These levels were increased to 83% and 60%, respectively, after 60 s of ß-adrenergic stimulation consistent with other reports that ß-adrenergic stimulation of the heart can phosphorylate RyRs at specific residues including S2808 and S2814 causing an increase in RyR activity. At cytoplasmic [Ca(2+] 1 µM, ß-adrenergic stimulation only decreased cytoplasmic Mg(2+ and Ca(2+ inhibition of RyRs. The Ka and maximum levels of cytoplasmic Ca(2+ activation site were not affected by ß-adrenergic stimulation. Our RyR2 gating model was fitted to the single channel data. It predicted that in diastole, ß-adrenergic stimulation is mediated by 1 increasing the activating potency of Ca(2+ binding to the luminal Ca(2+ site and decreasing its affinity for luminal Mg(2+ and 2 decreasing affinity of the low-affinity Ca(2+/Mg(2+ cytoplasmic inhibition site. However in systole, ß-adrenergic stimulation is mediated mainly by the latter.

Study of chromites YbMIICr2O5,5 (MII - Mg, Ca, Sr, Ba by X-ray diffraction

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B. Kasenov

2012-03-01

Full Text Available Compounds of composition YbMeMnFeO5,5 (Me – Mg, Ca, Sr, Ba are synthesized from Yb2O3, , Cr2O3 and MgCO3, CaCO3, SrCO3, BaCO3 by solid phase method. X-ray powder diffraction showed that the compound YbMgCr2O5,5, YbCaCr2O5,5, YbSrCr2O5,5, YbBaCr2O5,5 crystallizes in the tetragonal crystal system.

Synthesis and luminescence properties of Eu -activated Ca4Mg5 ...

Indian Academy of Sciences (India)

Abstract. Ca4Mg5(PO4)6:Eu2+ blue-emitting phosphor was synthesized by the combustion-assisted synthesis method under reductive atmosphere. The products were characterized by powder X-ray diffraction (XRD), trans- mission electron microscopy (TEM) and photoluminescence (PL) spectrum. XRD analysis confirmed ...

Solid solubility of MgO in the calcium silicates of portland clinker. The effect of CaF2

Directory of Open Access Journals (Sweden)

Puertas, F.

1992-03-01

Full Text Available The solid solubility of MgO in the calcium silicates of portland clinker has been determined by XRD and XDS. The influence that the presence of CaF2 has on said solubility has also been verified. The solid solution limit of MgO in C3S at 1275 ºC lies at about 1.0% wt, where the triclinic form II stabilizes. The presence of CaF2 does not alter the maximum value of the MgO solubilized in that silicate, although there does take place the stabilization of the triclinic polymorph II at lower MgO contents (between 0.3 - 0.6% wt. The maximum amount of solubilized MgO in βC2 at 1.050 ºC lies around 0.5% wt. This value does not change by the presence of CaF2.Se ha determinado por DRX y EDX la solubilidad sólida del MgO en los silicatos cálcicos del clínker portland. Se ha comprobado, así mismo la influencia que sobre dicha solubilidad tiene la presencia de CaF2. El límite de disolución sólida del MgO en el C3S a 1.275º C se sitúa alrededor del 1,0% en peso, estabilizándose la forma triclínica II. La presencia de CaF2 no altera el valor máximo de MgO solubilizado en este silicato, aunque si se produce la estabilización del polimorfo triclínico II a contenidos menores de MgO (entre 0,3 – 0,6% en peso. La cantidad máxima de MgO solubilizado en e/ βC2S a 1.050 ºC se sitúa en torno al 0,5% en peso. Este valor no se ve modificado por la presencia de CaF2.

Stosowanie wenlafaksyny w dawkach większych niż 225 mg na dobę. Bilans ryzyka i korzyści

Directory of Open Access Journals (Sweden)

Łukasz Święcicki

2014-09-01

Full Text Available W pracy omówiono wyniki badań dotyczących stosowania wenlafaksyny w dawkach przewyższających 225 mg/dobę. Wydaje się, że stosowanie takich dawek może być celowe zwłaszcza u pacjentów z depresją lekooporną. W dawkach do 225 mg/dobę wenlafaksyna jest lekiem o działaniu głównie serotoninergicznym (hamującym wychwyt zwrotny serotoniny. W dawce przewyższającej 225 mg/dobę lek wywiera istotne działanie na hamowanie wychwytu zwrotnego noradrenaliny. Nie bez znaczenia jest również fakt, że w przypadku dawek w zakresie 225–300 mg/dobę zwiększa się hamowanie wychwytu zwrotnego serotoniny. Choć efekt ten jest stosunkowo niewielki (oceniany na około 5%, to zdaniem części autorów może być klinicznie znaczący. Cechy te sprawiają, że wenlafaksyna w dużych dawkach jest lekiem skuteczniejszym niż leki z grupy selektywnych inhibitorów wychwytu zwrotnego serotoniny (SSRI oceniane jako cała grupa, a także skuteczniejszym niż fluoksetyna. Pod względem skuteczności wenlafaksyna jest także lekiem najmniej porównywalnym z lekami z grupy trójpierścieniowych leków przeciwdepresyjnych. Tolerancja wenlafaksyny nawet w dużych dawkach jest zazwyczaj zadowalająca. Problem mogą stanowić przykre objawy występujące podczas odstawiania wenlafaksyny (zawroty głowy, nudności, wymioty, ogólne złe samopoczucie, nie ma jednak dostatecznych dowodów wskazujących na to, że częstość występowania oraz stopień nasilenia tych objawów mogłyby zależeć od stosowanej dawki leku – jest to raczej reakcja indywidualna.

Microwave energy-assisted formation of bioactive CaO–MgO–SiO2 ...

Indian Academy of Sciences (India)

Ogun State, South-west, Nigeria); MgO was obtained from. Mg(NO3)2·6H2O ... 2.3 Extraction of Ca from chicken eggshells. The chicken eggshells were washed with deionized water, oven-dried at .... There is no carbon peak observed .... present in critical concentrations could be biologically active. [28]. .... Solids 354 722.

Roles of transmembrane segment M1 of Na(+),K (+)-ATPase and Ca (2+)-ATPase, the gatekeeper and the pivot

DEFF Research Database (Denmark)

Einholm, Anja P.; Andersen, Jens Peter; Vilsen, Bente

2007-01-01

In this review we summarize mutagenesis work on the structure-function relationship of transmembrane segment M1 in the Na(+),K(+)-ATPase and the sarco(endo)plasmic reticulum Ca(2+)-ATPase. The original hypothesis that charged residues in the N-terminal part of M1 interact with the transported...... cations can be rejected. On the other hand hydrophobic residues in the middle part of M1 turned out to play crucial roles in Ca(2+) interaction/occlusion in Ca(2+)-ATPase and K(+) interaction/occlusion in Na(+),K(+)-ATPase. Leu(65) of the Ca(2+)-ATPase and Leu(99) of the Na(+),K(+)-ATPase, located...... of the extracytoplasmic gate in both the Ca(2+)-ATPase and the Na(+),K(+)-ATPase. Udgivelsesdato: 2007-Dec...

Surface characterization, in vitro and in vivo biocompatibility of Mg-0.3Sr-0.3Ca for temporary cardiovascular implant

Energy Technology Data Exchange (ETDEWEB)

Bornapour, M., E-mail: mandana.bornapour@mail.mcgill.ca [Light Metals and Advanced Magnesium Materials, Mining and Materials Engineering, McGill University, Montreal, Qc, H3A 0C5 (Canada); Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5 (Canada); Mahjoubi, H. [Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5 (Canada); Vali, H. [Department of Anatomy and Cell Biology, McGill University, Montreal, Qc, H3A 0C7 (Canada); Shum-Tim, D. [Department of Cardiac Surgery and Surgical Research, McGill University, Montreal, Qc H3G 1A1 (Canada); Cerruti, M. [Biointerface Lab, Mining and Materials Engineering, McGill University, Montreal, Qc H3A 0C5 (Canada); Pekguleryuz, M. [Light Metals and Advanced Magnesium Materials, Mining and Materials Engineering, McGill University, Montreal, Qc, H3A 0C5 (Canada)

2016-10-01

Magnesium-based alloys are attractive candidate materials for medical applications. Our earlier work showed that the ternary Mg-0.3Sr-0.3Ca alloy exhibits slower degradation rates than both binary Mg-Sr and Mg-Ca alloys. The ternary alloy immersed in simulated body fluid (SBF) forms a compact surface layer of corrosion products that we hypothesized to be a Sr-substituted hydroxyapatite (HA). The main objectives of the current work are to understand the bio-degradation mechanism of Mg-0.3Sr-0.3Ca, to identify the exact nature of its protective layer and to evaluate the in vitro and in vivo biocompatibility of the alloy for cardiovascular applications. To better simulate the physiological environment, the alloy was immersed in SBF which was daily refreshed. Raman spectroscopy and X-Ray photoelectron spectroscopy (XPS) confirmed the formation of a thin, Sr-substituted HA layer at the interface between the alloy and the corrosion products. In vitro biocompatibility evaluated via indirect cytotoxicity assays using HUVECs showed no toxicity effect and ions extracted from Mg-0.3Sr-0.3Ca in fact increased the viability of HUVECs after one week. In vivo tests were performed by implanting a tubular Mg-0.3Sr-0.3Ca stent along with a WE43 control stent into the right and left femoral artery of a dog. Post implantation and histological analyses showed no thrombosis in the artery with Mg-0.3Sr-0.3Ca stent after 5 weeks of implantation while the artery implanted with WE43 stent was extensively occluded and thrombosed. Microscopic observation of the Mg-0.3Sr-0.3Ca implant-tissue interface confirmed the in situ formation of Sr-substituted HA on the surface during in vivo test. These results show that the interfacial layer protects the surface of the Mg-0.3Sr-0.3Ca alloy both in vitro and in vivo, and is the key factor in the bio-corrosion resistance of the alloy. - Highlights: • The surface active elements of Sr and Ca alter the corrosion of Mg alloy in SBF • Sr

Surface characterization, in vitro and in vivo biocompatibility of Mg-0.3Sr-0.3Ca for temporary cardiovascular implant

International Nuclear Information System (INIS)

Bornapour, M.; Mahjoubi, H.; Vali, H.; Shum-Tim, D.; Cerruti, M.; Pekguleryuz, M.

2016-01-01

Magnesium-based alloys are attractive candidate materials for medical applications. Our earlier work showed that the ternary Mg-0.3Sr-0.3Ca alloy exhibits slower degradation rates than both binary Mg-Sr and Mg-Ca alloys. The ternary alloy immersed in simulated body fluid (SBF) forms a compact surface layer of corrosion products that we hypothesized to be a Sr-substituted hydroxyapatite (HA). The main objectives of the current work are to understand the bio-degradation mechanism of Mg-0.3Sr-0.3Ca, to identify the exact nature of its protective layer and to evaluate the in vitro and in vivo biocompatibility of the alloy for cardiovascular applications. To better simulate the physiological environment, the alloy was immersed in SBF which was daily refreshed. Raman spectroscopy and X-Ray photoelectron spectroscopy (XPS) confirmed the formation of a thin, Sr-substituted HA layer at the interface between the alloy and the corrosion products. In vitro biocompatibility evaluated via indirect cytotoxicity assays using HUVECs showed no toxicity effect and ions extracted from Mg-0.3Sr-0.3Ca in fact increased the viability of HUVECs after one week. In vivo tests were performed by implanting a tubular Mg-0.3Sr-0.3Ca stent along with a WE43 control stent into the right and left femoral artery of a dog. Post implantation and histological analyses showed no thrombosis in the artery with Mg-0.3Sr-0.3Ca stent after 5 weeks of implantation while the artery implanted with WE43 stent was extensively occluded and thrombosed. Microscopic observation of the Mg-0.3Sr-0.3Ca implant-tissue interface confirmed the in situ formation of Sr-substituted HA on the surface during in vivo test. These results show that the interfacial layer protects the surface of the Mg-0.3Sr-0.3Ca alloy both in vitro and in vivo, and is the key factor in the bio-corrosion resistance of the alloy. - Highlights: • The surface active elements of Sr and Ca alter the corrosion of Mg alloy in SBF • Sr

The Effect of Increasing Sn Content on High-Temperature Mechanical Deformation of an Mg-3%Cu-1%Ca Alloy

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Georgios S.E. Antipas

2013-11-01

Full Text Available Chill casting of magnesium alloy samples with secondary alloying elements of Cu, Ca and Sn at % w.t. concentrations in the range 1–5, 0.1–5 and 0.1–3 respectively, gave rise to appreciably enhanced resistance to high-temperature creep, while maintaining good heat conductivity. The latter was considered to be driven by Cu and Mg-Cu intermetallics while it was clear that Sn mediated the high-temperature performance, mainly via networks of Mg2Sn and MgCaSn precipitates along the Mg matrix grain boundaries. It was postulated that Sn formed intermetallics by preferential substitution of Ca atoms and, thus, did not degrade the heat conductivity by retaining Cu. The % w.t. stoichiometry with the optimum combination of heat conductivity and resistance to high-temperature creep was found to be Mg-3Cu-1Ca-0.1Sn.

Glass-ceramic coated Mg-Ca alloys for biomedical implant applications.

Science.gov (United States)

Rau, J V; Antoniac, I; Fosca, M; De Bonis, A; Blajan, A I; Cotrut, C; Graziani, V; Curcio, M; Cricenti, A; Niculescu, M; Ortenzi, M; Teghil, R

2016-07-01

Biodegradable metals and alloys are promising candidates for biomedical bone implant applications. However, due to the high rate of their biodegradation in human body environment, they should be coated with less reactive materials, such, for example, as bioactive glasses or glass-ceramics. Fort this scope, RKKP composition glass-ceramic coatings have been deposited on Mg-Ca(1.4wt%) alloy substrates by Pulsed Laser Deposition method, and their properties have been characterized by a number of techniques. The prepared coatings consist of hydroxyapatite and wollastonite phases, having composition close to that of the bulk target material used for depositions. The 100μm thick films are characterized by dense, compact and rough morphology. They are composed of a glassy matrix with various size (from micro- to nano-) granular inclusions. The average surface roughness is about 295±30nm due to the contribution of micrometric aggregates, while the roughness of the fine-texture particulates is approximately 47±4nm. The results of the electrochemical corrosion evaluation tests evidence that the RKKP coating improves the corrosion resistance of the Mg-Ca (1.4wt%) alloy in Simulated Body Fluid. Copyright © 2016 Elsevier B.V. All rights reserved.

Intracellular [Ca2+] and Vo2 after manipulation of the free-energy of the Na+/Ca(2+)-exchanger in isolated rat ventricular myocytes

NARCIS (Netherlands)

Fiolet, J. W.; Baartscheer, A.; Schumacher, C. A.

1995-01-01

We have investigated whether the Na+/Ca(2+)-exchanger has a functional regulatory role in the control of oxidative metabolism in suspensions of isolated rat ventricular myocytes. Therefore we simultaneously measured intracellular [Ca2+] ([Ca2+]i) with Indo-1 and respiratory rate (Vo2) after abrupt

Applications of /sup 43/Ca, /sup 25/Mg, and /sup 67/Zn NMR spectroscopies to biological systems

Energy Technology Data Exchange (ETDEWEB)

Shimizu, Tohru; Hatano, Masahiro [Tohoku Univ., Sendai (Japan). Chemical Research Inst. of Non-Aqueous Solutions

1983-12-01

/sup 43/Ca, /sup 25/Mg and /sup 67/Zn NMR spectroscopies applied to biologically important systems are summarized mainly on the basis of our findings. It was found from our studies that (1) /sup 25/Mg NMR can be utilized for studying the dynamic and/or static behavior of Mg/sup 2 +/ in the Mg/sup 2 +/ -ATP (ADP)-kinase ternary complexes and (2) /sup 67/Zn NMR bands of diluted Zn/sup 2 +/ are much narrower than predicted and thus can be applicable for studying the dynamic and/or static behavior of Zn/sup 2 +/ in Zn/sup 2 +/ -enzyme solutions. In addition, /sup 43/Ca NMR spectra were successfully applied to some Ca/sup 2 +/ -binding proteins. In concluding remarks, we discussed possibilities of applications of those metal NMR spectroscopies to medical purposes.

A fast Na+/Ca2+-based action potential in a marine diatom.

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Alison R Taylor

Full Text Available BACKGROUND: Electrical impulses in animals play essential roles in co-ordinating an array of physiological functions including movement, secretion, environmental sensing and development. Underpinning many of these electrical signals is a fast Na+-based action potential that has been fully characterised only in cells associated with the neuromuscular systems of multicellular animals. Such rapid action potentials are thought to have evolved with the first metazoans, with cnidarians being the earliest representatives. The present study demonstrates that a unicellular protist, the marine diatom Odontella sinensis, can also generate a fast Na+/Ca2+ based action potential that has remarkably similar biophysical and pharmacological properties to invertebrates and vertebrate cardiac and skeletal muscle cells. METHODOLOGY/PRINCIPAL FINDINGS: The kinetic, ionic and pharmacological properties of the rapid diatom action potential were examined using single electrode current and voltage clamp techniques. Overall, the characteristics of the fast diatom currents most closely resemble those of vertebrate and invertebrate muscle Na+/Ca2+ currents. CONCLUSIONS/SIGNIFICANCE: This is the first demonstration of voltage-activated Na+ channels and the capacity to generate fast Na+-based action potentials in a unicellular photosynthetic organism. The biophysical and pharmacological characteristics together with the presence of a voltage activated Na+/Ca2+ channel homologue in the recently sequenced genome of the diatom Thalassiosira pseudonana, provides direct evidence supporting the hypothesis that this rapid signalling mechanism arose in ancestral unicellular eukaryotes and has been retained in at least two phylogenetically distant lineages of eukaryotes; opisthokonts and the stramenopiles. The functional role of the fast animal-like action potential in diatoms remains to be elucidated but is likely involved in rapid environmental sensing of these widespread and

Low-Temperature Sintering Li3Mg1.8Ca0.2NbO6 Microwave Dielectric Ceramics with LMZBS Glass

Science.gov (United States)

Wang, Gang; Zhang, Huaiwu; Liu, Cheng; Su, Hua; Jia, Lijun; Li, Jie; Huang, Xin; Gan, Gongwen

2018-05-01

Li3Mg1.8Ca0.2NbO6 ceramics doped with Li2O-MgO-ZnO-B2O3-SiO2 glass (LMZBS) were prepared via a solid-state route. The LMZBS glass effectively reduced the sintering temperature of Li3Mg1.8Ca0.2NbO6 ceramics to 950°C. The effects of the LMZBS glass on the sintering behavior, microstructures and microwave dielectric properties of Li3Mg1.8Ca0.2NbO6 ceramics are discussed in detail. Among all the LMZBS doped Li3Mg1.8Ca0.2NbO6 ceramics, the sample with 1 wt.% of LMZBS glass sintered at 950°C for 4 h exhibited good dielectric properties: ɛ r = 16.7, Q × f = 31,000 GHz (9.92 GHz), τ f = - 1.3 ppm/°C. The Li3Mg1.8Ca0.2NbO6 ceramics possessed excellent chemical compatibility with Ag electrodes, and could be applied in low temperature co-fired ceramics (LTCC) applications.

Status Ca, Mg dan Zn pada Kambing Peranakan Etawah Muda yang Diberi Ransum Bentuk Mash dengan Pakan Sumber Serat Berbeda

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T. Toharmat

2007-08-01

Full Text Available Fibrous agricultural by-products are the component of most rations for ruminant raised intensively. Slow rate and low digestibility of the fibrous feed may limit mineral bioavailability. Present experiment aimed to clarify the influence of fibrous feed component in ration on the status of Ca, Mg and Zn in growing goats. Twenty of female Etawah-grade goats weighing of 13.5±2.14 kg were grouped and allocated into five treatments in a randomized block design. Rations composed of 50% fibrous feed and 50% concentrate. The fibrous feed component as treatments were: RG = napier grass, JP = rice straw, KC = cacao pod, JK = mixed rice straw and coffee husk, and CP = mixed rice straw, napier grass, coffee husk and cacao pod. Rations were offered at 3% of live weight. The result showed that fibrous feed influenced Ca, Mg, and Zn intake, Ca and Mg absorption, and Ca, Mg and Zn plasma of growing goats. Intake, absorption and plasma Ca, Mg, and Zn had positive correlation with dry mater intake. Absorption of Ca and Zn had positive correlations with crude fiber digestibility. Supplementation of Ca, Mg and Zn was necessary when the fibrous feed was included at the level of 50% in the ration of growing goats, but the supplement level varied according to the type of the fibrous feed.

Characterization of Na+ and Ca2+ channels in zebrafish dorsal root ganglion neurons.

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Yu-Jin Won

Full Text Available BACKGROUND: Dorsal root ganglia (DRG somata from rodents have provided an excellent model system to study ion channel properties and modulation using electrophysiological investigation. As in other vertebrates, zebrafish (Danio rerio DRG are organized segmentally and possess peripheral axons that bifurcate into each body segment. However, the electrical properties of zebrafish DRG sensory neurons, as compared with their mammalian counterparts, are relatively unexplored because a preparation suitable for electrophysiological studies has not been available. METHODOLOGY/PRINCIPAL FINDINGS: We show enzymatically dissociated DRG neurons from juvenile zebrafish expressing Isl2b-promoter driven EGFP were easily identified with fluorescence microscopy and amenable to conventional whole-cell patch-clamp studies. Two kinetically distinct TTX-sensitive Na(+ currents (rapidly- and slowly-inactivating were discovered. Rapidly-inactivating I(Na were preferentially expressed in relatively large neurons, while slowly-inactivating I(Na was more prevalent in smaller DRG neurons. RT-PCR analysis suggests zscn1aa/ab, zscn8aa/ab, zscn4ab and zscn5Laa are possible candidates for these I(Na components. Voltage-gated Ca(2+ currents (I(Ca were primarily (87% comprised of a high-voltage activated component arising from ω-conotoxin GVIA-sensitive Ca(V2.2 (N-type Ca(2+ channels. A few DRG neurons (8% displayed a miniscule low-voltage-activated component. I(Ca in zebrafish DRG neurons were modulated by neurotransmitters via either voltage-dependent or -independent G-protein signaling pathway with large cell-to-cell response variability. CONCLUSIONS/SIGNIFICANCE: Our present results indicate that, as in higher vertebrates, zebrafish DRG neurons are heterogeneous being composed of functionally distinct subpopulations that may correlate with different sensory modalities. These findings provide the first comparison of zebrafish and rodent DRG neuron electrical properties and

Potentiation of the isoproterenol-induced net /sup 45/Ca uptake into the ventricular myocardium of rats by means of 9. cap alpha. -fluorocortisoleacetate, dihydrotachysterole or NaH/sub 2/PO/sub 4/. Cancelling of the potentiation by organic Ca/sup 2 +/ antagonists or K/sup +/ and Mg/sup 2 +/ ions

Energy Technology Data Exchange (ETDEWEB)

Hein, R

1974-01-01

Myocardial necroses resembling infarctions as well as disseminated myocardial necroses can be induced in rats by high doses of isoprotenerol which effects a maximum stimulation of the decomposition of energy-rich phosphate. This leads to an isoprotenerol-induced increase of the transmembranous Ca/sup + +/ influx, flooding the myocardium with Ca/sup + +/ ions. It is these Ca/sup + +/ ions which then trigger the break-down of the ATP and creatine phosphate fractions by activating the myofibrit-ATPase and impairing the mitochondrial function. It seems that physiological Ca/sup + +/ antagonists such as K/sup +/- or Mg/sup + +/-salts counteract the loss of energy-rich phosphate, thus preventing necroses. A new group of organic Ca/sup + +/ antagonists (verapamil, substance D 600, prenylamine) appears to be even more effective in this respect. Given in appropriate doses, these substances may prevent the isoprotenerol-induced Ca/sup + +/ flooding of the myocardium to a large extent, so that a break-down of the ATP and creatine phosphate fractions is avoided. On the other hand, the isoprotenerol-induced increase of the Ca/sup + +/ influx may be further potentiated by a preliminary treatment of the animals with 9..cap alpha..-fluorocortisoleacetate, dihydrotachysterole or NaH/sub 2/PO/sub 4/. This results in an extreme loss of energy-rich phosphate from the myocardium with excessive enhancement of necrosis production. The findings suggest that - unrecognized so far - Ca/sup + +/ ions play a key role in the generation of myocardial necroses: the present assumption, according to which increased Ca/sup + +/ uptake into damaged myocardial fibres is only a result - or at the most an accompanying symptom - of necrosis can thus no longer be considered valid.

Effects of microstructure transformation on mechanical properties, corrosion behaviors of Mg-Zn-Mn-Ca alloys in simulated body fluid.

Science.gov (United States)

Zhang, Yuan; Li, Jianxing; Li, Jingyuan

2018-04-01

Magnesium and its alloys have unique advantages to act as resorbable bone fixation materials, due to their moderate mechanical properties and biocompatibility, which are similar to those of human tissue. However, early resorption and insufficient mechanical strength are the main problems that hinder their application. Herein, the effects of microstructure transformation on the mechanical properties and corrosion performance of Mg-Zn-Mn-Ca were investigated with electrochemical and immersion measurements at 37 °C in a simulated body fluid (SBF). The results showed that the number density of Ca 2 Mg 6 Zn 3 /Mg 2 Ca precipitates was remarkably reduced and grain sizes were gradually increased as the temperature increased. The alloy that received the 420 °C/24 h treatment demonstrated the best mechanical properties and lowest corrosion rate (5.94 mm/a) as well as presented a compact and denser film than the others. The improvement in mechanical properties could be explained by the eutectic compounds and phases (Mg 2 Ca/Ca 2 Mg 6 Zn 3 ) gradually dissolving into a matrix, which caused severely lattice distortion and facilitated structural re-arrangement of the increased Ca solute. Moreover, the difference in potential between the precipitates and the matrix is the main essence for micro-galvanic corrosion formation as well as accelerated the dissolution activity and current exchange density at the Mg/electrolyte interface. As a result, the best Mg alloys corrosion resistance must be matched with a moderate grain size and phase volume fractions. Copyright © 2018 Elsevier Ltd. All rights reserved.

Tricalcium phosphate based resorbable ceramics: Influence of NaF and CaO addition

Energy Technology Data Exchange (ETDEWEB)

Seeley, Zachary; Bandyopadhyay, Amit [W. M. Keck Biomedical Materials Research Lab, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 (United States); Bose, Susmita [W. M. Keck Biomedical Materials Research Lab, School of Mechanical and Materials Engineering, Washington State University, Pullman, WA 99164 (United States)], E-mail: sbose@wsu.edu

2008-01-10

Resorbable bioceramics have gained much attention due to their time-varying mechanical properties in-vivo. Implanted ceramics degrade allowing bone in-growth and eventual replacement of the artificial material with natural tissue. Calcium phosphate based materials have caught the most significant attention because of their excellent biocompatibility and compositional similarities to natural bone. Doping these ceramics with various metal ions has significantly influenced their properties. In this study, tricalcium phosphate (TCP) compacts were fabricated via uniaxial compression with five compositions: (i) pure TCP, (ii) TCP with 2.0 wt.% NaF, (iii) TCP with 3.0 wt.% CaO, (iv) TCP with a binary of 2.0 wt.% NaF and 0.5 wt.% Ag{sub 2}O, and (v) TCP with a quaternary of 1.0 wt.% TiO{sub 2}, 0.5 wt.% Ag{sub 2}O, 2.0 wt.% NaF, and 3.0 wt.% CaO. These compacts were sintered at 1250 deg. C for 4 h to obtain dense ceramic structures. Phase analyses were carried out using X-ray diffraction. The presence of NaF in TCP improved densification and increased compression strength from 70 ({+-} 25) to 130 ({+-} 40) MPa. Addition of CaO had no influence on density or strength. Human osteoblast cell growth behavior was studied using an osteoprecursor cell line (OPC 1) to assure that the biocompatibility of these ceramics was not altered due to the dopants. For long-term biodegradation studies, density, weight change, surface microstructure, and uniaxial compression strength were measured as a function of time in a simulated body fluid (SBF). Weight gain in SBF correlated strongly with precipitation viewed in the inter-connected pores of the samples. After 3 months in SBF, all samples displayed a reduction in strength. NaF, CaO and the quaternary compositions maintained the most steady strength loss under SBF.

Crystallization kinetics of bioactive glasses in the ZnO-Na2O-CaO-SiO2 system.

Science.gov (United States)

Malavasi, Gianluca; Lusvardi, Gigliola; Pedone, Alfonso; Menziani, Maria Cristina; Dappiaggi, Monica; Gualtieri, Alessandro; Menabue, Ledi

2007-08-30

The crystallization kinetics of Na(2)O.CaO.2SiO(2) (x = 0) and 0.68ZnO.Na(2)O.CaO.2SiO(2) (x = 0.68, where x is the ZnO stoichiometric coefficient in the glass formula) bioactive glasses have been studied using both nonisothermal and isothermal methods. The results obtained from isothermal XRPD analyses have showed that the first glass crystallizes into the isochemical Na(2)CaSi(2)O(6) phase, whereas the Na(2)ZnSiO(4) crystalline phase is obtained from the Zn-rich glass, in addition to Na(2)CaSi(2)O(6). The activation energy (Ea) for the crystallization of the Na(2)O.CaO.2SiO(2) glass is 193 +/- 10 and 203 +/- 5 kJ/mol from the isothermal in situ XRPD and nonisothermal DSC experiments, respectively. The Avrami exponent n determined from the isothermal method is 1 at low temperature (530 degrees C), and its value increases linearly with temperature increase up to 2 at 607 degrees C. For the crystallization of Na(2)CaSi(2)O(6) from the Zn-containing glass, higher values of both the crystallization temperature (667 and 661 degrees C) and Ea (223 +/- 10 and 211 +/- 5 kJ/mol) have been found from the isothermal and nonisothermal methods, respectively. The Na(2)ZnSiO(4) crystalline phase crystallizes at lower temperature with respect to Na(2)CaSi(2)O(6), and the Ea value is 266 +/- 20 and 245 +/- 15 kJ/mol from the isothermal and nonisothermal methods, respectively. The results of this work show that the addition of Zn favors the crystallization from the glass at lower temperature with respect to the Zn-free glass. In fact, it causes an increase of Ea for the Na diffusion process, determined using MD simulations, and consequently an overall increase of Ea for the crystallization process of Na(2)CaSi(2)O(6). Our results show good agreement between the Ea and n values obtained with the two different methods and confirm the reliability of the nonisothermal method applied to kinetic crystallization of glassy systems. This study allows the determination of the temperature

High-Resolution Mg/Ca Ratios in a Coralline Red Alga as a Proxy for Bering Sea Temperature Variations and Teleconnections

Science.gov (United States)

Halfar, J.; Steffen, H.; Kronz, A.; Steneck, R. S.; Adey, W.; Lebednik, P. A.

2009-05-01

We present the first continuous high-resolution record of Mg/Ca variations within an encrusting coralline red alga of the species Clathromorphum nereostratum from Amchitka Island, Aleutian Islands. Mg/Ca ratios of individual growth increments were analyzed by measuring a single point electron microprobe transect yielding a resolution of 15 samples/year on average, generating a continuous record from 1830 to 1967 of algal Mg/Ca variations. Results show that Mg/Ca ratios in the high-Mg calcite skeleton display pronounced annual cyclicity and archive late spring to late fall sea surface temperature (SST) corresponding to the main season of algal growth. Mg/Ca values correlate well to local SST (ERSSTJun-Nov, 1902-1967; r = 0.73 for 5-year mean), as well as to an air temperature record from the same region. Our data correlate well to a shorter Mg/Ca record from a second site, corroborating the ability of the alga to reliably record regional environmental signals. In addition, Mg/Ca ratios relate well to a 29-year stable oxygen isotope time series measured on the same sample, which provides additional support for the use of Mg as a paleotemperature proxy in coralline red algae, that is, unlike stable oxygen isotopes, not influenced by salinity fluctuations. High spatial correlation to large-scale SST variability in the North Pacific is observed, with patterns of strongest correlation following the direction of major oceanographic features (i.e., the signature of the Alaska Current and the Alaskan Stream), which play a key role in the exchange of water masses between the North Pacific and the Bering Sea through Aleutian Island passages. The time series further displays significant teleconnections with the signature of the Pacific Decadal Oscillation in the northeast Pacific and the Atlantic Multidecadal Oscillation.

High - Resolution SST Record Based on Mg/Ca Ratios of Late Holocene Planktonic Foraminifers From the Great Bahama Bank

Science.gov (United States)

Mueller, A.; Reijmer, J. J.; Roth, S.

2001-12-01

We analyzed five different planktic foraminifera species in the high resolution core MD 992201 off the Great Bahama Bank (79° 16.34 W; 25° 53.49 N) in 290 m water depth. This 38.05 m long core comprises a 7,000 year long Holocene record. The selected species were Orbulina universa, Globigerinoides ruber, Globigerinoides sacculifer, Globorotalia menardii and Globigerinella aequilateralis, which live in the upper 200 m of the water column. The Mg/Ca ratios of these different foraminifers show species-specific values, which represent a distinct habitat depth. With this species-specific Mg/Ca ratios we can reconstruct a temperature profile through the water column. The lowest Mg/Ca are shown by G. menardii (2.5 - 4 mmol/mol), followed by G. sacculifer (4.2 - 5.6 mmol/mol), G. ruber (5.1 - 7.2 mmol/mol) and G. aequilateralis (5.5 - 8.7 mmol/mol). Highest are shown by O. universa (6 - 14 mmol/mol). During the Little Ice Age, the Mg/Ca ratios of all species except for the deeper dwelling G. menardii, became more variable and showed lower ratios. The shallow dwelling species like G. ruber and G. sacculifer display an increase in the Mg/Ca ratios during the Medieval Warm Period. Our data show that transferring Mg/Ca ratios into SST based calibration curves known from literature needs re-evaluation. Species-specific calibration seems to be necessary to achieve reliable results.

A Novel MgO-CaO-SiO2 System for Fabricating Bone Scaffolds with Improved Overall Performance

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Hang Sun

2016-04-01

Full Text Available Although forsterite (Mg2SiO4 possesses good biocompatibility and suitable mechanical properties, the insufficient bioactivity and degradability hinders its further application. In this study, a novel MgO-CaO-SiO2 system was developed by adding wollastonite (CaSiO3 into Mg2SiO4 to fabricate bone scaffolds via selective laser sintering (SLS. The apatite-forming ability and degradability of the scaffolds were enhanced because the degradation of CaSiO3 could form silanol groups, which could offer nucleation sites for apatite. Meanwhile, the mechanical properties of the scaffolds grew with increasing CaSiO3 to 20 wt %. It was explained that the liquid phase of CaSiO3 promoted the densification during sintering due to its low melting point. With the further increase in CaSiO3, the mechanical properties decreased due to the formation of the continuous filling phase. Furthermore, the scaffolds possessed a well-interconnected porous structure and exhibited an ability to support cell adhesion and proliferation.

Description and crystal structure of albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O

Energy Technology Data Exchange (ETDEWEB)

Mereiter, K. [Vienna Univ. of Technology (Austria). Inst. of Chemical Technologies and Analytics

2013-04-15

Albrechtschraufite, MgCa{sub 4}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]{sub 2}.17-18H{sub 2}O, triclinic, space group P anti 1, a = 13.569(2), b = 13.419(2), c = 11.622(2) Aa, α = 115.82(1), β = 107.61(1), γ = 92.84(1) (structural unit cell, not reduced), V = 1774.6(5) Aa{sup 3}, Z = 2, Dc = 2.69 g/cm{sup 3} (for 17.5 H{sub 2}O), is a mineral that was found in small amounts with schroeckingerite, NaCa{sub 3}F[UO{sub 2}(CO{sub 3}){sub 3}](SO{sub 4}).10H{sub 2}O, on a museum specimen of uranium ore from Joachimsthal (Jachymov), Czech Republic. The mineral forms small grain-like subhedral crystals (= 0.2 mm) that resemble in appearance liebigite, Ca{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}]. ∝ 11H{sub 2}O. Colour pale yellow-green, luster vitreous, transparent, pale bluish green fluorescence under ultraviolet light. Optical data: Biaxial negative, nX = 1.511(2), nY = 1.550(2), nZ = 1.566(2), 2V = 65(1) (λ = 589 nm), r < v weak. After qualitative tests had shown the presence of Ca, U, Mg, CO{sub 2} and H{sub 2}O, the chemical formula was determined by a crystal structure analysis based on X-ray four-circle diffractometer data. The structure was later on refined with data from a CCD diffractometer to R1 = 0.0206 and wR2 = 0.0429 for 9,236 independent observed reflections. The crystal structure contains two independent [UO{sub 2}(CO{sub 3}){sub 3}]{sup 4-} anions of which one is bonded to two Mg and six Ca while the second is bonded to only one Mg and three Ca. Magnesium forms a MgF{sub 2}(O{sub carbonate}){sub 3}(H{sub 2}O) octahedron that is linked via the F atoms with three Ca atoms so as to provide each F atom with a flat pyramidal coordination by one Mg and two Ca. Calcium is 7- and 8-coordinate forming CaFO{sub 6}, CaF{sub 2}O{sub 2}(H{sub 2}O){sub 4}, CaFO{sub 3}(H{sub 2}O){sub 4} and CaO{sub 2}(H{sub 2}O){sub 6} coordination polyhedra. The crystal structure is built up from MgCa{sub 3}F{sub 2}[UO{sub 2}(CO{sub 3}){sub 3}].8H{sub 2}O layers parallel to (001) which

Surface characterization, in vitro and in vivo biocompatibility of Mg-0.3Sr-0.3Ca for temporary cardiovascular implant.

Science.gov (United States)

Bornapour, M; Mahjoubi, H; Vali, H; Shum-Tim, D; Cerruti, M; Pekguleryuz, M

2016-10-01

Magnesium-based alloys are attractive candidate materials for medical applications. Our earlier work showed that the ternary Mg-0.3Sr-0.3Ca alloy exhibits slower degradation rates than both binary Mg-Sr and Mg-Ca alloys. The ternary alloy immersed in simulated body fluid (SBF) forms a compact surface layer of corrosion products that we hypothesized to be a Sr-substituted hydroxyapatite (HA). The main objectives of the current work are to understand the bio-degradation mechanism of Mg-0.3Sr-0.3Ca, to identify the exact nature of its protective layer and to evaluate the in vitro and in vivo biocompatibility of the alloy for cardiovascular applications. To better simulate the physiological environment, the alloy was immersed in SBF which was daily refreshed. Raman spectroscopy and X-Ray photoelectron spectroscopy (XPS) confirmed the formation of a thin, Sr-substituted HA layer at the interface between the alloy and the corrosion products. In vitro biocompatibility evaluated via indirect cytotoxicity assays using HUVECs showed no toxicity effect and ions extracted from Mg-0.3Sr-0.3Ca in fact increased the viability of HUVECs after one week. In vivo tests were performed by implanting a tubular Mg-0.3Sr-0.3Ca stent along with a WE43 control stent into the right and left femoral artery of a dog. Post implantation and histological analyses showed no thrombosis in the artery with Mg-0.3Sr-0.3Ca stent after 5weeks of implantation while the artery implanted with WE43 stent was extensively occluded and thrombosed. Microscopic observation of the Mg-0.3Sr-0.3Ca implant-tissue interface confirmed the in situ formation of Sr-substituted HA on the surface during in vivo test. These results show that the interfacial layer protects the surface of the Mg-0.3Sr-0.3Ca alloy both in vitro and in vivo, and is the key factor in the bio-corrosion resistance of the alloy. Copyright © 2016 Elsevier B.V. All rights reserved.

Ketamine inhibits 45Ca influx and catecholamine secretion by inhibiting 22Na influx in cultured bovine adrenal medullary cells

International Nuclear Information System (INIS)

Takara, Hiroshi; Wada, Akihiko; Arita, Masahide; Izumi, Futoshi; Sumikawa, Koji

1986-01-01

The effects of ketamine, an intravenous anesthetic, on 22 Na influx, 45 Ca influx and catecholamine secretion were investigated in cultured bovine adrenal medullary cells. Ketamine inhibited carbachol-induced 45 Ca influx and catecholamine secretion in a concentration-dependent manner with a similar potency. Ketamine also reduced veratridine-induced 45 Ca influx and catecholamine secretion. The influx of 22 Na caused by carbachol or by veratridine was suppressed by ketamine with a concentration-inhibition curve similar to that of 45 Ca influx and catecholamine secretion. Inhibition by ketamine of the carbachol-induced influx of 22 Na, 45 Ca and secretion of catecholamines was not reversed by the increased concentrations of carbachol. These observations indicate that ketamine, at clinical concentrations, can inhibit nicotinic receptor-associated ionic channels and that the inhibition of Na influx via the receptor-associated ionic channels is responsible for the inhibition of carbachol-induced Ca influx and catecholamine secretion. (Auth.)

Luminescent properties of Na2CaSiO4:Eu2+ and its potential application in white light emitting diodes

International Nuclear Information System (INIS)

Wang, Zhijun; Li, Panlai; Li, Ting; Zhang, Xing; Li, Qingxuan; Yang, Zhiping; Guo, Qinglin

2013-01-01

Graphical abstract: Na 2 CaSiO 4 :Eu 2+ phosphor can be effectively excited by an ultraviolet and near-ultraviolet light, and produce a bright blue emission centered at 436 nm. The CIE chromaticity coordinations (x, y) of Na 2 CaSiO 4 :Eu 2+ (NSCE)/Li 2 SrSiO 4 :Eu 2+ (LSSE) vary with the molar ratio of the two constituents. When NSCE/LSSE is 1:3, the CIE chromaticity coordination is (0.332, 0.346), which is close to that of the natural sunlight (0.33, 0.33). The results indicate that Na 2 CaSiO 4 :Eu 2+ may be a promising blue phosphor for UV chip-based multi-phosphor converted white light emitting diodes. Highlights: ► Na 2 CaSiO 4 :Eu 2+ shows the blue emission with a peak at 436 nm and broad excitation band in the UV/n-UV range. ► White light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor with the Li 2 SrSiO 4 :Eu 2+ yellow phosphor. ► Na 2 CaSiO 4 :Eu 2+ would be a promising blue phosphor candidate for UV chip-based multi-phosphor converted white LEDs. - Abstract: A novel blue phosphor Na 2 CaSiO 4 :Eu 2+ is synthesized by a high temperature solid-state reaction, and its luminescent properties are systematically studied. Na 2 CaSiO 4 :Eu 2+ can be effectively excited by the 354 nm radiation, and create blue emission (436 nm). The emission intensity of Na 2 CaSiO 4 :Eu 2+ is influenced by the Eu 2+ doping content, and the optimal doping content is 1.5%, and the concentration quenching mechanism of Eu 2+ in Na 2 CaSiO 4 can be attributed to the multipolar interaction. The white light with CIE coordinates (0.332, 0.346) is generated by mixing the blue phosphor Na 2 CaSiO 4 :Eu 2+ with the yellow phosphor Li 2 SrSiO 4 :Eu 2+ . The results indicate that Na 2 CaSiO 4 :Eu 2+ may be a potential blue emitting phosphor for UV chip-based multi-phosphor converted white light emitting diodes

Mg/Ca Ratios in Coralline Red Algae as Temperature Proxies for Reconstructing Labrador Current Variability

Science.gov (United States)

Gamboa, G.; Hetzinger, S.; Halfar, J.; Zack, T.; Kunz, B.; Adey, W.

2009-05-01

Marine ecosystems and fishery productivity in the Northwestern Atlantic have been considerably affected by regional climate and oceanographic changes. Fluctuations of North Atlantic marine climate have been linked in part to a dominant pattern of atmospheric circulation known as the North Atlantic Oscillation, which has a strong influence on transport variability of the Labrador Current (LC). The cold LC originates in the Labrador Sea and flows southbound along the Eastern Canadian coastline causing an important cooling effect on marine waters off the Canadian Atlantic provinces. Although interdecadal and interannual variability of sea surface temperatures (SST) in the LC system have been documented, a long-term pattern has not been identified. In order to better understand the observed ecosystem changes and their relationship with climate variability in the Northwestern Atlantic, a century-scale reconstruction of spatial and temporal variations of the LC is needed. This, however, requires reliable long-term and high-resolution SST records, which are not available from short instrumental observations. Here we present the first century-scale SST reconstructions from the Northwest Atlantic using long-lived coralline red algae. Coralline red algae have a high-Mg calcite skeleton, live in shallow water worldwide and develop annual growth bands. It has previously been demonstrated that subannual resolution SSTs can be obtained from coralline red algal Mg/Ca ratios, a commonly used paleotemperature proxy. Specimens of the long-lived coralline red algae Clathromorphum compactum were collected alive in August 2008 along a latitudinal transect spanning the southern extent of LC flow in Nova Scotia and Newfoundland. This collection is supplemented with specimens from the same region collected in the 1960's. In order to reconstruct spatial and temporal patterns of the LC, selected samples of C. compactum were analyzed for Mg/Ca using Laser Ablation Inductively-Coupled Plasma

Na/Ca Intermixing around Silicate and Phosphate Groups in Bioactive Phosphosilicate Glasses Revealed by Heteronuclear Solid-State NMR and Molecular Dynamics Simulations.

Science.gov (United States)

Mathew, Renny; Stevensson, Baltzar; Edén, Mattias

2015-04-30

We characterize the intermixing of network-modifying Na(+)/Ca(2+) ions around the silicate (QSi(n)) and phosphate (QP(n)) tetrahedra in a series of 16 Na2O–CaO–SiO2–P2O5 glasses, whose P content and silicate network connectivity were varied independently. The set includes both bioactive and bioinactive compositions and also encompasses two soda-lime-silicate members devoid of P, as well as two CaO–SiO2 glasses and one Na2O–SiO2–P2O5 glass. The various Si/P↔Na/Ca contacts were probed by molecular dynamics (MD) simulations together with heteronuclear magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experimentation utilizing (23)Na{(31)P} and (23)Na{(29)Si} REDOR, as well as (31)P{ (23)Na} and (29)Si{(23)Na} REAPDOR. We introduce an approach for quantifying the extent of Na(+)/Ca(2+) ordering around a given QP(n) or QSi(n) group, encoded by the preference factor 0⩽ PM ⩽ 1 conveying the relative weights of a random cation intermixing (PM = 0) and complete preference/ordering (PM = 1) for one of the species M, which represents either Na(+) or Ca(2+). The MD-derived preference factors reveal phosphate and silicate species surrounded by Na(+)/Ca(2+) ions intermixed nearly randomly (PM ≲ 0.15), except for the QSi(4) and QSi(1) groups, which manifest more significant cation ordering with preference for Na+ and Ca2+, respectively. The overall weak preferences are essentially independent of the Si and P contents of the glass, whereas PM primarily correlates with the total amount of network modifiers: as the latter is increased, the Na/Ca distribution around the {QP(0), QSi(1), QSi(2)} groups with preference for Ca2(+ )tend to randomize (i.e., PCa decreases), while the PNa-values grow slightly for the {QP(1), QSi(3), QSi(4)} species already preferring coordination of Na. The set of experimental preference factors {PCa} for the orthophosphate (QP(0)) groups extracted from (31)P{(23)Na} REAPDOR NMR-derived M2(P–Na) dipolar second moments agrees

Control of temperature and aqueous Mg2+/Ca2+ ratio on the (trans-)formation of ikaite

Science.gov (United States)

Purgstaller, B.; Dietzel, M.; Baldermann, A.; Mavromatis, V.

2017-11-01

The calcium carbonate hexahydrate mineral ikaite (CaCO3 ṡ 6 H2O) has been documented in aquatic environments at near-freezing temperatures. An increase of the prevailing temperature in the depositional environment, results in the transformation of natural ikaite into less soluble calcium carbonate phases occasionally leaving calcite pseudomorphs in the sediments, which are considered as an indicator for primary cold water temperatures. Detailed understanding on the physicochemical parameters controlling ikaite (trans-)formation however, such as temperature and reactive solution chemical composition, are still under debate. In order to study the formation of ikaite, we conducted precipitation experiments under controlled physicochemical conditions (pH = 8.3 ± 0.1; T = 6, 12, and 18 ± 0.1 °C) at defined aqueous molar Mg/Ca ratios. The transformation of ikaite into anhydrous calcium carbonate polymorphs was investigated in solution and at air exposure. The obtained results reveal the formation of ikaite at temperatures up to 12 °C, whereas Mg-rich amorphous calcium carbonate precipitated at 18 °C. In contact with the reactive solution ikaite transformed into aragonite at aqueous molar Mg2+/Ca2+ ratios of ≥14. In contrast, ikaite separated from the Mg-rich solution and exposed to air transformed in all cases into calcite/vaterite. The herein obtained temperature limit of ≤12 for ikaite formation is significantly higher than formerly expected and most probably caused by (i) the high saturation degree of the solution with respect to ikaite and (ii) the slow dehydration of the aqueous Ca2+ ion at low temperatures. This result questions the suitability of calcite pseudomorphs (i.e. glendonites) as a proxy for near-freezing temperatures. Moreover, our findings show that the CaCO3 polymorph formed from ikaite is strongly controlled by the physicochemical conditions, such as aqueous molar Mg2+/Ca2+ ratio of the reactive fluid and H2O availability throughout the

Strong Dependence of Hydration State of F-Actin on the Bound Mg(2+)/Ca(2+) Ions.

Science.gov (United States)

Suzuki, Makoto; Imao, Asato; Mogami, George; Chishima, Ryotaro; Watanabe, Takahiro; Yamaguchi, Takaya; Morimoto, Nobuyuki; Wazawa, Tetsuichi

2016-07-21

Understanding of the hydration state is an important issue in the chemomechanical energetics of versatile biological functions of polymerized actin (F-actin). In this study, hydration-state differences of F-actin by the bound divalent cations are revealed through precision microwave dielectric relaxation (DR) spectroscopy. G- and F-actin in Ca- and Mg-containing buffer solutions exhibit dual hydration components comprising restrained water with DR frequency f2 (fw). The hydration state of F-actin is strongly dependent on the ionic composition. In every buffer tested, the HMW signal Dhyme (≡ (f1 - fw)δ1/(fwδw)) of F-actin is stronger than that of G-actin, where δw is DR-amplitude of bulk solvent and δ1 is that of HMW in a fixed-volume ellipsoid containing an F-actin and surrounding water in solution. Dhyme value of F-actin in Ca2.0-buffer (containing 2 mM Ca(2+)) is markedly higher than in Mg2.0-buffer (containing 2 mM Mg(2+)). Moreover, in the presence of 2 mM Mg(2+), the hydration state of F-actin is changed by adding a small fraction of Ca(2+) (∼0.1 mM) and becomes closer to that of the Ca-bound form in Ca2.0-buffer. This is consistent with the results of the partial specific volume and the Cotton effect around 290 nm in the CD spectra, indicating a change in the tertiary structure and less apparent change in the secondary structure of actin. The number of restrained water molecules per actin (N2) is estimated to be 1600-2100 for Ca2.0- and F-buffer and ∼2500 for Mg2.0-buffer at 10-15 °C. These numbers are comparable to those estimated from the available F-actin atomic structures as in the first water layer. The number of HMW molecules is roughly explained by the volume between the equipotential surface of -kT/2e and the first water layer of the actin surface by solving the Poisson-Boltzmann equation using UCSF Chimera.

Mechanisms of a human skeletal myotonia produced by mutation in the C-terminus of NaV1.4: is Ca2+ regulation defective?

Directory of Open Access Journals (Sweden)

Subrata Biswas

Full Text Available Mutations in the cytoplasmic tail (CT of voltage gated sodium channels cause a spectrum of inherited diseases of cellular excitability, yet to date only one mutation in the CT of the human skeletal muscle voltage gated sodium channel (hNaV1.4F1705I has been linked to cold aggravated myotonia. The functional effects of altered regulation of hNaV1.4F1705I are incompletely understood. The location of the hNaV1.4F1705I in the CT prompted us to examine the role of Ca(2+ and calmodulin (CaM regulation in the manifestations of myotonia. To study Na channel related mechanisms of myotonia we exploited the differences in rat and human NaV1.4 channel regulation by Ca(2+ and CaM. hNaV1.4F1705I inactivation gating is Ca(2+-sensitive compared to wild type hNaV1.4 which is Ca(2+ insensitive and the mutant channel exhibits a depolarizing shift of the V1/2 of inactivation with CaM over expression. In contrast the same mutation in the rNaV1.4 channel background (rNaV1.4F1698I eliminates Ca(2+ sensitivity of gating without affecting the CaM over expression induced hyperpolarizing shift in steady-state inactivation. The differences in the Ca(2+ sensitivity of gating between wild type and mutant human and rat NaV1.4 channels are in part mediated by a divergence in the amino acid sequence in the EF hand like (EFL region of the CT. Thus the composition of the EFL region contributes to the species differences in Ca(2+/CaM regulation of the mutant channels that produce myotonia. The myotonia mutation F1705I slows INa decay in a Ca(2+-sensitive fashion. The combination of the altered voltage dependence and kinetics of INa decay contribute to the myotonic phenotype and may involve the Ca(2+-sensing apparatus in the CT of NaV1.4.

Catalytic oxidation of methanol on Pt/X (X = CaTP, NaTP electrodes in sulfuric acid solution

Directory of Open Access Journals (Sweden)

Said Benmokhtar

2013-10-01

Full Text Available In this paper, we report the synthesis and characterization of electrodes based on NASICON type phosphates. The study of the electrochemical oxidation of methanol at ambient temperature on electrodes based on NASICON type Ca0,5Ti2(PO43 (CaTP and Na5Ti(PO43 (NaTP compared to that of the platinum electrode model has been conducted by cyclic voltammetry in acidic medium. The results showed a significant increase of current density on the electro oxidation of methanol on the material developed based NASICON structure CaTP, cons deactivation of the electro oxidation is observed the closed structure type NaTP.

Ultrasound-assisted extraction of Ca, K and Mg from in vitro citrus culture

Directory of Open Access Journals (Sweden)

Arruda Sandra C. C.

2003-01-01

Full Text Available An ultrasound extraction procedure for Ca, K and Mg from in vitro plant cultures is proposed, comparing cultures of different embryogenic levels of Citrus sinensis and Citrus limonia, employing ultrasound energy. Parameters related to metals extraction, such as plant material sampling, acid concentration and sonication time were investigated. For accuracy check, the proposed ultrasound extraction procedure was compared with a microwave-assisted digestion procedure and no differences in the results were verified at 95% of the confidence level. With this simple and accurate extraction procedure, it was possible to determine differences in Ca, K and Mg concentrations during Citrus embryo formation/development and between cultures (embryogenic and non-embryogenic. Finally, the ultrasound extraction method demonstrated to be an excellent alternative for handless sampling and operational costs.

Phase formation in Na2MoO4 - MgMoO4 - Cr2(MoO4)3 system

International Nuclear Information System (INIS)

Kotova, I.Yu.; Kozhevnikova, N.M.

1998-01-01

Interaction within Na 2 MoO 4 - MgMoO 4 - Cr 2 (MoO 4 ) 3 ternary system is studied by X ray phase and DTA methods. State diagram of NaCr(MoO 4 ) 2 - MgMoO 4 section is plotted. Production of ternary molybdates of Na 1-x Mg 1-x Cr 1+x (MoO 4 ) 3 , where 0 ≤ x ≤ 0.3, and NaMg 3 Cr(MoO 4 ) 5 composition is ascertained [ru

Influence of compositions on thermal stability and thermodynamic parameter in Ca-Mg-Cu bulk metallic glasses

Science.gov (United States)

Deshmukh, A. A.; Khond, A. A.; Palikundwar, U. A.

2018-05-01

In the present manuscript, influence of compositions on thermal stability (ΔTx) and thermodynamic parameter PHSS of Ca-Mg-Cu bulk metallic glasses (BMGs) is evaluated. The statistical approach of regression analysis is adopted to investigate the compositional variation with ΔTx and PHSS. It is found that calcium (Ca) and copper (Cu) content has goodlinear relationship with ΔTx and PHSS. It is observed that with increase in Ca content, ΔTx and PHSS decreases. On the other hand, increase in Cu content, both ΔTx and PHSS increases. Correlation fit of magnesium (Mg) content with both ΔTx and PHSS is very poor. A graph is also plotted to understand the relationship between ΔTx and PHSS. Result of the relationship between ΔTx and PHSS reveals that the alloy composition having more negative value of PHSS will have more stability. Therefore, compositions with more negative value of PHSS will lead to ease of BMGs formation in Ca-Mg-Cu alloy system and hence more stable it will be. It is expected that these results will be supportive in identifying the compositions having these elements for making BMGs.

Microstructure and mechanical properties of spray-deposited Mg-12.55Al-3.33Zn-0.58Ca-1Nd alloy

International Nuclear Information System (INIS)

Bai Pucun; Dong Taishang; Hou Xiaohu; Zhao Chunwang; Xing Yongming

2010-01-01

A Mg-Al-Zn-Ca-Nd magnesium alloy was prepared by spray forming technology, and the spray-deposited alloy was subsequently hot-extruded with a reduction rate of 16:1 at 623 K. The mechanical properties of the extruded alloy were investigated, and the result shows that the spray-formed Mg alloy offers superior tensile strength with poor ductility. The morphologies, fracture characteristic and chemical compositions of the extruded alloy were then explored by scanning electron microscopy with energy dispersive spectrometer. Furthermore, microstructure of the extruded alloy was examined by X-ray diffractometry and transmission electron microscopy. The results indicate that the microstructure of the spray-deposited magnesium alloy consists of α-Mg and Al 2 Ca phases, and the Al 2 Ca compound is distributed along the grain boundaries of the primary α-Mg. Moreover, twin substructure is found to exist in microstructure of the Al 2 Ca phase, rare earth Nd in the Al 2 Ca phase in the form of solid solution.

High pressure phase transitions in Mg{sub 1-x}Ca{sub x}O: Theory

Energy Technology Data Exchange (ETDEWEB)

Srivastava, Anurag; Chauhan, Mamta [Advanced Material Research Lab, Indian Institute of Information Technology and Management, Gwalior (India); Singh, R.K. [Department of Physics, ITM University, Gurgaon (India); Padegaonker, Rishikesh [Indian Embassy School, Sana (Yemen)

2011-08-15

We have analysed a B1 {yields} B2 structural phase transitions in Mg{sub 1-x}Ca{sub x}O solid solutions and their ground state properties by using first principle density functional theory and charge transfer interaction potential (CTIP) approach. The effects of exchange-correlation interactions are handled by the generalized gradient approximation with Perdew-Burke-Ernzerhof type parameterization. CTIP approach includes the long range modified Coulomb with charge transfer interactions and short range part of this model includes the van der Waals as well as Hafemeister Flygare type overlap repulsive interactions. The study observes a linear variation of calculated transition pressure, bulk modulus and lattice parameter of Mg{sub 1-x}Ca{sub x}O as a function of Ca composition. The observed results for the end point members are in agreement to their experimental counterparts and the deviations have been discussed. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Passivation kinetics of Mg-Nd-Gd-Zn-Zr (EV31A and Mg-Y-Nd-Gd-Zr (WE43C in NaOH solutions

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Jakraphan Ninlachart

2017-09-01

Full Text Available Passivation kinetics of two Mg-RE alloys, such as Mg-Nd-Gd-Zn-Zr (EV31A, and Mg-Y-Nd-Gd-Zr (WE43C were investigated in two different heat treated conditions (solution treated and overaged in 0.01 - 1.0 M NaOH solutions under potentiostatic conditions. Negative reaction order was observed in dilute NaOH which transitioned to positive values as the passivation time increased and in the 1 M NaOH as well. The passive layers showed platelet morphology and the size of the platelets decreased with increase in the NaOH concentration. The hydrogen evolution reaction (HER kinetics was not improved on the passive layer covered surface of the Mg-RE alloys in contrast to the improvements reported on the hydroxide covered pure magnesium. The electrochemical impedance increased with increase in the NaOH concentration in the solution treated condition of both Mg-RE alloys, whereas the overaged EV31A alloy showed a reverse trend. The passive layer of EV31A showed almost 100% higher charge carrier density than the film formed on the WE43C in the overaged condition. A better passivation behavior was observed in the solution treated condition than that in the overaged condition which could be attributed to the uniform distribution of the RE elements in the solution treated specimens. The WE43C alloy revealed better corrosion resistance in the alkaline solution than the EV31A alloy.

Development of Low Density CaMg-A1-Based Bulk Metallic Glasses (Preprint)

National Research Council Canada - National Science Library

Senkov, O. N; Scott, J. M; Miracle, D. B

2006-01-01

Low density Ca-Mg-Al-based bulk metallic glasses containing additionally Cu and Zn, were produced by a copper mold casting method as wedge-shaped samples with thicknesses varying from 0.5 mm to 10 rom...

Understanding corrosion behavior of Mg-Zn-Ca alloys from subcutaneous mouse model: effect of Zn element concentration and plasma electrolytic oxidation.

Science.gov (United States)

Jang, Yongseok; Tan, Zongqing; Jurey, Chris; Xu, Zhigang; Dong, Zhongyun; Collins, Boyce; Yun, Yeoheung; Sankar, Jagannathan

2015-03-01

Mg-Zn-Ca alloys are considered as suitable biodegradable metallic implants because of their biocompatibility and proper physical properties. In this study, we investigated the effect of Zn concentration of Mg-xZn-0.3Ca (x=1, 3 and 5wt.%) alloys and surface modification by plasma electrolytic oxidation (PEO) on corrosion behavior in in vivo environment in terms of microstructure, corrosion rate, types of corrosion, and corrosion product formation. Microstructure analysis of alloys and morphological characterization of corrosion products were conducted using x-ray computed tomography (micro-CT) and scanning electron microscopy (SEM). Elemental composition and crystal structure of corrosion products were determined using x-ray diffraction (XRD) and electron dispersive x-ray spectroscopy (EDX). The results show that 1) as-cast Mg-xZn-0.3Ca alloys are composed of Mg matrix and a secondary phase of Ca2Mg6Zn3 formed along grain boundaries, 2) the corrosion rate of Mg-xZn-0.3Ca alloys increases with increasing concentration of Zn in the alloy, 3) corrosion rates of alloys treated by PEO sample are decreased in in vivo environment, and 4) the corrosion products of these alloys after in vivo tests are identified as brucite (Mg(OH)2), hydroxyapatite (Ca10(PO4)6(OH)2), and magnesite (MgCO3·3H2O). Copyright © 2014 Elsevier B.V. All rights reserved.

Highly Resolved Mg/Ca Depth Profiles of Planktic Foraminifer test Walls Using Single shot Measurements of fs-LA-ICPMS

Science.gov (United States)

Jochum, K. P.; Schiebel, R.; Stoll, B.; Weis, U.; Haug, G. H.

2017-12-01

Foraminifers are sensitive archives of changes in climate and marine environment. It has been shown that the Mg/Ca signal is a suitable proxy of seawater temperature, because the incorporation of Mg depends on ambient water temperature. In contrast to most former studies, where this ratio is determined by solution-based bulk analysis of 20 - 30 specimens, we have investigated Mg/Ca in single specimens and single chambers at high resolution. A new fs-200 nm-LA-ICPMS technique was developed for the µm-sized layered calcite shells. To generate depth profiles with a resolution of about 50 nm/shot, we chose a low fluence of about 0.3 Jcm-2 and performed single shot measurements of the double charged 44Ca++ and the single charged 25Mg+ ions together. Precision (RSD) of the Mg/Ca data is about 5 %. Calibration was performed with the carbonate reference material MACS-3 from the USGS. Our results for different species from the Arabian Sea and Caribbean Sea demonstrate that Mg/Ca of different chambers vary and indicate that the foraminifer individuals built their chambers in different water depths and/or experienced seasonal changes in seawater temperature caused, for example, by upwelling (cold) versus stratified (warm) conditions. Typically, the Mg/Ca ratios of the final two chambers of the planktic foraminifer Globorotalia menardii from a sediment core of the Arabian Sea differ by about 5 mmol/mol from earlier chambers (2 mmol/mol) corresponding to seawater temperatures of 28 °C and 18 °C, respectively. In addition, mass fractions of other elements like Sr, Mn, Fe, Ba, and U have been determined with fs-LA-ICPMS using fast line scans, and thus provide further insights in the ecology of foraminifers.

The Influencing Mechanisms of Sodium Hexametaphosphate on Chalcopyrite Flotation in the Presence of MgCl2 and CaCl2

Directory of Open Access Journals (Sweden)

Wanqing Li

2018-04-01

Full Text Available Sea water has been used in flotation plants, showing a promising way to save fresh water usage. Previous studies indicated that divalent salts in sea water played negative roles in chalcopyrite flotation, but not much work have been conducted to understand the eliminating mechanisms. This study systematically investigated the effects of divalent cations of Ca2+ and Mg2+ on natural flotability of chalcopyrite in the absence of collectors and frothers. The reduced recovery was mainly due to the adsorption of Mg and Ca hydroxyl complexes and precipitation on chalcopyrite surfaces, giving rise to a less hydrophobic surface. The addition of sodium hexametaphosphate (SHMP, however, significantly improved chalcopyrite recovery. Species calculation, contact angle, zeta potential, FTIR and XPS analyses were conducted to understand the influencing mechanisms of divalent ions and the beneficial effects of SHMP on chalcopyrite recovery. The primary mechanism was that SHMP prevented the adsorption of positively charged Mg and Ca compounds or precipitation with hydrophilic properties such as Mg(OH2 on chalcopyrite surfaces, confirmed by the Derjguin-Landau-Verwey-Overbeek (DLVO theory. Secondly, SHMP reacted with Mg2+ and Ca2+ to form dissolvable complexes, thereby declining the formation of insoluble Mg2+ and Ca2+ compounds or precipitation.

New 3D gas density maps of NaI and CaII interstellar absorption within 300 pc

Science.gov (United States)

Welsh, B. Y.; Lallement, R.; Vergely, J.-L.; Raimond, S.

2010-02-01

Aims: We present new high resolution (R > 50 000) absorption measurements of the NaI doublet (5889-5895 Å) along 482 nearby sight-lines, in addition to 807 new measurements of the CaII K (3933 Å) absorption line. We have combined these new data with previously reported measurements to produce a catalog of absorptions towards a total of 1857 early-type stars located within 800 pc of the Sun. Using these data we have determined the approximate 3-dimensional spatial distribution of neutral and partly ionized interstellar gas density within a distance-cube of 300 pc from the Sun. Methods: All newly recorded spectra were analyzed by means of a multi-component line profile-fitting program, in most cases using simultaneous fits to the line doublets. Normalized absorption profiles were fitted by varying the velocity, doppler width and column density for all intervening interstellar clouds. The resulting total column densities were then used in conjunction with the Hipparcos distances of the target stars to construct inversion maps of the 3D spatial density distribution of the NaI and CaII bearing gas. Results: A plot of the equivalent width of NaI versus distance reveals a wall of neutral gas at ~80 pc that can be associated with the boundary wall to the central rarefied Local Cavity region. In contrast, a similar plot for the equivalent width of CaII shows no sharply increasing absorption at 80 pc, but instead we observe a slowly increasing value of CaII equivalent width with increasing sight-line distance sampled. Low values for the volume density of NaI (nNaI values in the range 10-8 >nNaI > 10-10 cm-3 are found for sight-lines with distance >300 pc. Both high and low values of the volume density of CaII (nCaII) are found for sight-lines 100 pc a value of nCaII ~ 10-9 cm-3 is typical for most sight-lines, indicating that the distribution of CaII bearing gas is fairly uniform throughout the general ISM. Our three maps of the 3D spatial distribution of local neutral Na

Study on the Microstructure, Mechanical Properties and Corrosion Behavior of Mg-Zn-Ca Alloy Wire for Biomaterial Application

Science.gov (United States)

Zheng, Maobo; Xu, Guangquan; Liu, Debao; Zhao, Yue; Ning, Baoqun; Chen, Minfang

2018-03-01

Due to their excellent biocompatibility and biodegradability, magnesium alloy wires have attracted much attention for biomaterial applications including orthopedic K-wires and sutures in wound closure. In this study, Mg-3Zn-0.2Ca alloy wires were prepared by cold drawing combined with proper intermediate annealing process. Microstructures, texture, mechanical properties and corrosion behavior of Mg-3Zn-0.2Ca alloy wire in a simulated body fluid were investigated. The results showed that the secondary phase and average grain size of the Mg-3Zn-0.2Ca alloy were refined in comparison with the as-extruded alloy and a strong (0002)//DD basal fiber texture system was formed after multi-pass cold drawing. After the annealing, most of the basal planes were tilted to the drawing direction (DD) by about 35°, presenting the characteristics of random texture, and the texture intensity decreased. The as-annealed wire shows good mechanical properties with the ultimate tensile strength (UTS), yield strength (YS) and elongation of 253 ± 8.5 MPa, 212 ± 11.3 MPa and 9.2 ± 0.9%, respectively. Electrochemical and hydrogen evolution measurements showed that the corrosion resistance of the Mg-3Zn-0.2Ca alloy wire was improved after the annealing. The immersion test indicated that the Mg-3Zn-0.2Ca wire exhibited uniform corrosion behavior during the initial period of immersion, but then exhibited local corrosion behavior.

Improved mechanical performance and delayed corrosion phenomena in biodegradable Mg-Zn-Ca alloys through Pd-alloying.

Science.gov (United States)

González, S; Pellicer, E; Fornell, J; Blanquer, A; Barrios, L; Ibáñez, E; Solsona, P; Suriñach, S; Baró, M D; Nogués, C; Sort, J

2012-02-01

The influence of partial substitution of Mg by Pd on the microstructure, mechanical properties and corrosion behaviour of Mg(72-x)Zn(23)Ca(5)Pd(x) (x=0, 2 and 6 at.%) alloys, synthesized by copper mould casting, is investigated. While the Mg(72)Zn(23)Ca(5) alloy is mainly amorphous, the addition of Pd decreases the glass-forming ability, thus favouring the formation of crystalline phases. From a mechanical viewpoint, the hardness increases with the addition of Pd, from 2.71 GPa for x=0 to 3.9 GPa for x=6, mainly due to the formation of high-strength phases. In turn, the wear resistance is maximized for an intermediate Pd content (i.e., Mg(70)Zn(23)Ca(5)Pd(2)). Corrosion tests in a simulated body fluid (Hank's solution) indicate that Pd causes a shift in the corrosion potential towards more positive values, thus delaying the biodegradability of this alloy. Moreover, since the cytotoxic studies with mouse preosteoblasts do not show dead cells after culturing for 27 h, these alloys are potential candidates to be used as biomaterials. Copyright © 2011 Elsevier Ltd. All rights reserved.

Calibrations for benthic foraminiferal Mg/Ca paleothermometry and the carbonate ion hypothesis

NARCIS (Netherlands)

Elderfield, H.; Yu, J.; Anand-Jha, P.; Kiefer, T.; Nyland, B.

2006-01-01

Benthic foraminiferal magnesium/calcium ratios were determined on one hundred and forty core-top samples from the Atlantic Ocean, the Norwegian Sea, the Indian Ocean, the Arabian Sea and the Pacific Ocean, mostly at sites with bottom water temperatures below 5 °C. Mg/Ca ratios are consistently

Improvement of the mechanical properties and corrosion resistance of biodegradable β-Ca3(PO4)2/Mg-Zn composites prepared by powder metallurgy: the adding β-Ca3(PO4)2, hot extrusion and aging treatment.

Science.gov (United States)

Yan, Yang; Kang, Yijun; Li, Ding; Yu, Kun; Xiao, Tao; Deng, Youwen; Dai, Han; Dai, Yilong; Xiong, Hanqing; Fang, Hongjie

2017-05-01

In this study, 10%β-Ca 3 (PO 4 ) 2 /Mg-6%Zn (wt.%) composites with Mg-6%Zn alloy as control were prepared by powder metallurgy. After hot extrusion, the as-extruded composites were aged for 72h at 150°C. The effects of the adding β-Ca 3 (PO 4 ) 2 , hot extrusion and aging treatment on their microstructure, mechanical properties and corrosion resistance were investigated. The XRD results identified α-Mg, MgZn phase and β-Ca 3 (PO 4 ) 2 phase in these composites. After hot extrusion, grains were significantly refined, and the larger-sized β-Ca 3 (PO 4 ) 2 particles and coarse MgZn phases were broken into linear-distributed β-Ca 3 (PO 4 ) 2 and MgZn phases along the extrusion direction. After aging treatment, the elements of Zn, Ca, P and O presented a more homogeneous distribution. The compressive strengths of the β-Ca 3 (PO 4 ) 2 /Mg-Zn composites were approximately double those of natural bone, and their densities and elastic moduli matched those of natural bone. The immersion tests and electrochemical tests revealed that the adding β-Ca 3 (PO 4 ) 2 , hot extrusion and aging treatment could promote the formation of protective corrosion product layer on the sample surface in Ringer's solution, which improved corrosion resistance of the β-Ca 3 (PO 4 ) 2 /Mg-Zn composites. The XRD results indicated that the corrosion product layer contained Mg(OH) 2 , β-Ca 3 (PO 4 ) 2 and hydroxyapatite (HA). The cytotoxicity assessments showed the as-extruded β-Ca 3 (PO 4 ) 2 /Mg-Zn composite aged for 72h was harmless to L-929 cells. These results suggested that the β-Ca 3 (PO 4 ) 2 /Mg-Zn composites prepared by powder metallurgy were promising to be used for bone tissue engineering. Copyright © 2017 Elsevier B.V. All rights reserved.

Interaction of peridotite with Ca-rich carbonatite melt at 3.1 and 6.5 GPa: Implication for merwinite formation in upper mantle, and for the metasomatic origin of sublithospheric diamonds with Ca-rich suite of inclusions

Science.gov (United States)

Sharygin, Igor S.; Shatskiy, Anton; Litasov, Konstantin D.; Golovin, Alexander V.; Ohtani, Eiji; Pokhilenko, Nikolay P.

2018-03-01

We performed an experimental study, designed to reproduce the formation of an unusual merwinite + olivine-bearing mantle assemblage recently described as a part of a Ca-rich suite of inclusions in sublithospheric diamonds, through the interaction of peridotite with an alkali-rich Ca-carbonatite melt, derived from deeply subducted oceanic crust. In the first set of experiments, we studied the reaction between powdered Mg-silicates, olivine and orthopyroxene, and a model Ca-carbonate melt (molar Na:K:Ca = 1:1:2), in a homogeneous mixture, at 3.1 and 6.5 GPa. In these equilibration experiments, we observed the formation of a merwinite + olivine-bearing assemblage at 3.1 GPa and 1200 °C and at 6.5 GPa and 1300-1400 °C. The melts coexisting with this assemblage have a low Si and high Ca content (Ca# = molar 100 × Ca/(Ca + Mg) > 0.57). In the second set of experiments, we investigated reaction rims produced by interaction of the same Ca-carbonate melt (molar Na:K:Ca = 1:1:2) with Mg-silicate, olivine and orthopyroxene, single crystals at 3.1 GPa and 1300 °C and at 6.5 GPa and 1400 °C. The interaction of the Ca-carbonate melt with olivine leads to merwinite formation through the expected reaction: 2Mg2SiO4 (olivine) + 6CaCO3 (liquid) = Ca3MgSi2O8 (merwinite) + 3CaMg(CO3)2 (liquid). Thus, our experiments confirm the idea that merwinite in the upper mantle may originate via interaction of peridotite with Ca-rich carbonatite melt, and that diamonds hosting merwinite may have a metasomatic origin. It is remarkable that the interaction of the Ca-carbonate melt with orthopyroxene crystals does not produce merwinite both at 3.1 and 6.5 GPa. This indicates that olivine grain boundaries are preferable for merwinite formation in the upper mantle.

Restrictions in Mg/Ca-Paleotemperature Estimations in High-Latitude Bottom Waters: Evidence from the Fram Strait and the Nordic Seas

Science.gov (United States)

Werner, K.; Marchitto, T. M., Jr.; Not, C.; Spielhagen, R. F.; Husum, K.

2014-12-01

Mg to Ca ratios of the benthic foraminifer species Cibicidoides wuellerstorfi provide a great potential for reconstructing bottom water temperatures, especially from the lower end of the temperature range between 0 and 6°C (Tisserand et al., 2013). A set of core top samples from the Fram Strait and the Norwegian margin have been studied for Mg/Ca ratios in C. wuellerstorfi in order to establish a calibration relationship to the environmental conditions. In this part of the northern North Atlantic the bottom water temperature range between -0.5 and -1°C. For the calibration to modern water mass conditions, modern oceanographic data from both existing conductivity-temperature-depth (CTD) casts and the World Ocean Data Base 2013 (Boyer et al., 2013) have been used. Benthic Mg/Ca ratios are relatively high suggesting a preference of C. wuellerstorfi to incorporate Mg below 0°C. Although no correlation has been found to existing temperature calibrations, the data are in line with earlier Mg/Ca data from C. wuellerstorfi in the area (Martin et al., 2002; Elderfield et al., 2006). The carbonate ion effect is most likely a main cause for the relatively high Mg/Ca ratios found in core top samples from the Fram Strait and the Nordic Seas, however, other factors may influence the values as well. Holocene records of benthic trace metal/Ca ratios from the eastern Fram Strait display trends similar to those found in other proxy indicators, despite the difficulties to constrain a temperature calibration for this low temperature range. In particular, the benthic B/Ca and Li/Ca records resemble trends in Holocene planktic foraminifer assemblages, suggesting to be influenced by environmental factors such as the carbonate ion effect consistent for the entire water column.

Electrochemical characteristics of bioresorbable binary MgCa alloys in Ringer's solution: Revealing the impact of local pH distributions during in-vitro dissolution.

Science.gov (United States)

Mareci, D; Bolat, G; Izquierdo, J; Crimu, C; Munteanu, C; Antoniac, I; Souto, R M

2016-03-01

Biodegradable magnesium-calcium (MgCa) alloy is a very attractive biomaterial. Two MgCa alloys below the solid solubility of Ca were considered, as to solely investigate the effect of Ca content on the behavior of magnesium and the pH changes associated to metal dissolution. X-ray diffraction analysis and optical microscopy showed that both Mg-0.63Ca and Mg-0.89Ca alloys were solely composed of α(Mg) phase. Degradation characteristics and electrochemical characterization of MgCa alloys were investigated during exposure to Ringer's solution at 37 °C by electrochemical impedance spectroscopy and scanning electrochemical microscopy. The impedance behavior showed both capacitive and inductive features that are related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds, and can be described in terms of an equivalent circuit. Scanning electron microscopy (SEM) was employed to view the surface morphology of the MgCa samples after 1 week immersion in Ringer's solution showing extensive precipitation of corrosion products, whereas the substrate shows evidence of a non-uniform corrosion process. Energy dispersive analysis showed that the precipitates contained oxygen, calcium, magnesium and chlorine, and the Mg:Ca ratios were smaller than in the alloys. Scanning electrochemical microscopy (SECM) was used to visualize local pH changes associated to these physicochemical processes with high spatial resolution. The occurrence of pH variations in excess of 3 units between anodic and cathodic half-cell reactions was monitored in situ. Copyright © 2015 Elsevier B.V. All rights reserved.

Combustion of Na2B4O7 + Mg + C to synthesis B4C powders

International Nuclear Information System (INIS)

Jiang Guojian; Xu Jiayue; Zhuang Hanrui; Li Wenlan

2009-01-01

Boron carbide powder was fabricated by combustion synthesis (CS) method directly from mixed powders of borax (Na 2 B 4 O 7 ), magnesium (Mg) and carbon. The adiabatic temperature of the combustion reaction of Na 2 B 4 O 7 + 6 Mg + C was calculated. The control of the reactions was achieved by selecting reactant composition, relative density of powder compact and gas pressure in CS reactor. The effects of these different influential factors on the composition and morphologies of combustion products were investigated. The results show that, it is advantageous for more Mg/Na 2 B 4 O 7 than stoichiometric ratio in Na 2 B 4 O 7 + Mg + C system and high atmosphere pressure in the CS reactor to increase the conversion degree of reactants to end product. The final product with the minimal impurities' content could be fabricated at appropriate relative density of powder compact. At last, boron carbide without impurities could be obtained after the acid enrichment and distilled water washing.

Bio-corrosion characterization of Mg-Zn-X (X = Ca, Mn, Si) alloys for biomedical applications.

Science.gov (United States)

Rosalbino, F; De Negri, S; Saccone, A; Angelini, E; Delfino, S

2010-04-01

The successful applications of magnesium-based alloys as biodegradable orthopedic implants are mainly inhibited due to their high degradation rates in physiological environment. This study examines the bio-corrosion behaviour of Mg-2Zn-0.2X (X = Ca, Mn, Si) alloys in Ringer's physiological solution that simulates bodily fluids, and compares it with that of AZ91 magnesium alloy. Potentiodynamic polarization and electrochemical impedance spectroscopy results showed a better corrosion behaviour of AZ91 alloy with respect to Mg-2Zn-0.2Ca and Mg-2Zn-0.2Si alloys. On the contrary, enhanced corrosion resistance was observed for Mg-2Zn-0.2Mn alloy compared to the AZ91 one: Mg-2Zn-0.2Mn alloy exhibited a four-fold increase in the polarization resistance than AZ91 alloy after 168 h exposure to the Ringer's physiological solution. The improved corrosion behaviour of the Mg-2Zn-0.2Mn alloy with respect to the AZ91 one can be ascribed to enhanced protective properties of the Mg(OH)(2) surface layer. The present study suggests the Mg-2Zn-0.2Mn alloy as a promising candidate for its applications in degradable orthopedic implants, and is worthwhile to further investigate the in vivo corrosion behaviour as well as assessed the mechanical properties of this alloy.

Effect of Mg, Ca, and Zn on stability of LiBH{sub 4} through computational thermodynamics

Energy Technology Data Exchange (ETDEWEB)

Lee, Sung Hoon; Manga, Venkateswara Rao; Liu, Zi-Kui [Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802 (United States)

2010-07-15

The effect of divalent metal-dopants, Mg, Ca, and Zn, on the stability of LiBH{sub 4} is studied by using the first-principles calculations and CALPHAD (CALculation of PHAse Diagram) modeling. The ground states of Mg{sub 1/2}BH{sub 4}, Ca{sub 1/2}BH{sub 4}, and Zn{sub 1/2}BH{sub 4} are shown to be I anti 4m2, F2dd, and I anti 4m2, respectively, through first-principles calculations. Positive enthalpy of mixing between Li and the alloying element is predicted, indicating unfavorable solubility of alloying elements in LiBH{sub 4} and thus offering possibility to decrease the stability of LiBH{sub 4}. The ionic sublattice model of (Li{sup +}, M{sup 2+}, Va){sub 1}(BH{sub 4}{sup -}){sub 1} is adopted for the metal substituted LiBH{sub 4} phase. It is observed that the addition of Mg or Zn has limited effect as the decomposition temperature is between those of LiBH{sub 4} and M{sub 1/2}BH{sub 4} for Mg and Zn substitutions. LiBH{sub 4} is destabilized with magnesium borides or LiZn{sub 4} formation but its decomposition temperature is higher than that of M{sub 1/2}BH{sub 4}. On the other hand, the addition of Ca significantly reduces the H{sub 2} releasing temperature due to the formation of highly stable CaB{sub 6}. (author)

Effect of forging process on microstructure, mechanical and corrosion properties of biodegradable Mg-1Ca alloy

International Nuclear Information System (INIS)

Harandi, Shervin Eslami; Hasbullah Idris, Mohd; Jafari, Hassan

2011-01-01

Research highlights: → Forging temperature demonstrates more pronounced effect compared to forging speed. → Precipitation of Mg 2 Ca phase at grain boundaries accelerates corrosion rate. → Forging process doesn't provide the corrosion resistance required for bone healing. -- Abstract: The performance of Mg-1Ca alloy, a biodegradable metallic material, may be improved by hot working in order that it may be of use in bone implant applications. In this study, Mg-1Ca cast alloy was preheated to different temperatures before undergoing forging process with various forging speeds. Macro- and microstructure of the samples were examined by stereo and scanning electron microscopes (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), respectively. To determine the mechanical properties of the alloy, hardness value and plastic deformation ability of the samples were measured. To investigate the corrosion behaviour of the alloy, immersion and electrochemical tests were performed on the samples in simulated body fluid and the corrosion products were characterized by SEM/EDS. The results showed that increasing forging temperature decreased grain size led to improved hardness value and plastic deformation ability of the alloy, whereas no significant effect was observed by changing forging speed. Moreover, forging at higher temperatures led to an increase in the amount of Mg 2 Ca phase at grain boundaries resulted in higher corrosion rates. It can be concluded that although forging process improved the mechanical properties of the alloy, it does not satisfy the corrosion resistance criteria required for bone healing.

Electrochemical characteristics of bioresorbable binary MgCa alloys in Ringer's solution: Revealing the impact of local pH distributions during in-vitro dissolution

Energy Technology Data Exchange (ETDEWEB)

Mareci, D., E-mail: danmareci@yahoo.com [Faculty of Chemical Engineering and Environmental Protection, The “Gheorghe Asachi” Technical University of Iasi, 700050, Iasi (Romania); Bolat, G. [Faculty of Chemical Engineering and Environmental Protection, The “Gheorghe Asachi” Technical University of Iasi, 700050, Iasi (Romania); Izquierdo, J. [Department of Chemistry, University of La Laguna, P.O. Box 456, E-38200 La Laguna (Tenerife) (Spain); Crimu, C.; Munteanu, C. [Faculty of Mechanical Engineering, The “Gheorghe Asachi” Technical University of Iasi, 700050, Iasi (Romania); Antoniac, I. [Faculty of Materials Science and Engineering, Politehnica of Bucharest, 060042 Bucharest (Romania); Souto, R.M., E-mail: rsouto@ull.es [Department of Chemistry, University of La Laguna, P.O. Box 456, E-38200 La Laguna (Tenerife) (Spain); Faculty of Materials Science and Engineering, Politehnica of Bucharest, 060042 Bucharest (Romania)

2016-03-01

Biodegradable magnesium–calcium (MgCa) alloy is a very attractive biomaterial. Two MgCa alloys below the solid solubility of Ca were considered, as to solely investigate the effect of Ca content on the behavior of magnesium and the pH changes associated to metal dissolution. X-ray diffraction analysis and optical microscopy showed that both Mg–0.63Ca and Mg–0.89Ca alloys were solely composed of α(Mg) phase. Degradation characteristics and electrochemical characterization of MgCa alloys were investigated during exposure to Ringer's solution at 37 °C by electrochemical impedance spectroscopy and scanning electrochemical microscopy. The impedance behavior showed both capacitive and inductive features that are related to the alloy charge transfer reaction and the relaxation of the absorbed corrosion compounds, and can be described in terms of an equivalent circuit. Scanning electron microscopy (SEM) was employed to view the surface morphology of the MgCa samples after 1 week immersion in Ringer's solution showing extensive precipitation of corrosion products, whereas the substrate shows evidence of a non-uniform corrosion process. Energy dispersive analysis showed that the precipitates contained oxygen, calcium, magnesium and chlorine, and the Mg:Ca ratios were smaller than in the alloys. Scanning electrochemical microscopy (SECM) was used to visualize local pH changes associated to these physicochemical processes with high spatial resolution. The occurrence of pH variations in excess of 3 units between anodic and cathodic half-cell reactions was monitored in situ. - Highlights: • Spontaneous degradation of MgCa alloys in Ringer's solution characterized at 37 °C • Reactivity differences between Mg0.63Ca and Mg0.89Ca are evidenced using multiscale electrochemical characterization. • Electrochemical activation occurs heterogeneously on the alloy surface. • Metal dissolution is accompanied by local pH changes. • Mg0.63Ca degrades faster

Electrical and microstructural properties of CaTiO3-doped K1/2Na1 ...

Indian Academy of Sciences (India)

KNN) and CaTiO3- modified K1/2Na1/2NbO3 (CTO-KNN) systems, were investigated. Discs doped with 0 to 0.55% mol of CaTiO3 (CTO) were sintered at 1125°C for 2 h. Although minority phases were found in doped samples, CaTiO3 was not ...

Surface reactivity and hydroxyapatite formation on Ca5MgSi3O12 ceramics in simulated body fluid

Science.gov (United States)

Xu, Jian; Wang, Yaorong; Huang, Yanlin; Cheng, Han; Seo, Hyo Jin

2017-11-01

In this work, the new calcium-magnesium-silicate Ca5MgSi3O12 ceramic was made via traditional solid-state reaction. The bioactivities were investigated by immerging the as-made ceramics in simulated body fluid (SBF) for different time at body temperature (37 °C). Then the samples were taken to measure X-ray powder diffraction (XRD), Scanning electron microscopy (SEM), X-ray energy-dispersive spectra (EDS), and Fourier transform infrared spectroscopy (FT-IR) measurements. The bone-like hydroxyapatite nanoparticles formation was observed on the ceramic surfaces after the immersion in SBF solutions. Ca5MgSi3O12 ceramics possess the Young's modulus and the bending strength and of 96.3 ± 1.2 GPa and 98.7 ± 2.3 MPa, respectively. The data suggest that Ca5MgSi3O12 ceramics can quickly induce HA new layers after soaking in SBF. Ca5MgSi3O12 ceramics are potential to be used as biomaterials for bone-tissue repair. The cell adherence and proliferation experiments are conducted confirming the reliability of the ceramics as a potential candidate.

Reversible hydrogen storage by NaAlH4 confined within a titanium-functionalized MOF-74(Mg) nanoreactor.

Science.gov (United States)

Stavila, Vitalie; Bhakta, Raghunandan K; Alam, Todd M; Majzoub, Eric H; Allendorf, Mark D

2012-11-27

We demonstrate that NaAlH(4) confined within the nanopores of a titanium-functionalized metal-organic framework (MOF) template MOF-74(Mg) can reversibly store hydrogen with minimal loss of capacity. Hydride-infiltrated samples were synthesized by melt infiltration, achieving loadings up to 21 wt %. MOF-74(Mg) possesses one-dimensional, 12 Å channels lined with Mg atoms having open coordination sites, which can serve as sites for Ti catalyst stabilization. MOF-74(Mg) is stable under repeated hydrogen desorption and hydride regeneration cycles, allowing it to serve as a "nanoreactor". Confining NaAlH(4) within these pores alters the decomposition pathway by eliminating the stable intermediate Na(3)AlH(6) phase observed during bulk decomposition and proceeding directly to NaH, Al, and H(2), in agreement with theory. The onset of hydrogen desorption for both Ti-doped and undoped nano-NaAlH(4)@MOF-74(Mg) is ∼50 °C, nearly 100 °C lower than bulk NaAlH(4). However, the presence of titanium is not necessary for this increase in desorption kinetics but enables rehydriding to be almost fully reversible. Isothermal kinetic studies indicate that the activation energy for H(2) desorption is reduced from 79.5 kJ mol(-1) in bulk Ti-doped NaAlH(4) to 57.4 kJ mol(-1) for nanoconfined NaAlH(4). The structural properties of nano-NaAlH(4)@MOF-74(Mg) were probed using (23)Na and (27)Al solid-state MAS NMR, which indicates that the hydride is not decomposed during infiltration and that Al is present as tetrahedral AlH(4)(-) anions prior to desorption and as Al metal after desorption. Because of the highly ordered MOF structure and monodisperse pore dimensions, our results allow key template features to be identified to ensure reversible, low-temperature hydrogen storage.

In vivo degradation behavior and biological activity of some new Mg-Ca alloys with concentration's gradient of Si for bone grafts

Science.gov (United States)

Trincă, Lucia Carmen; Fântânariu, Mircea; Solcan, Carmen; Trofin, Alina Elena; Burtan, Liviu; Acatrinei, Dumitru Mihai; Stanciu, Sergiu; Istrate, Bogdan; Munteanu, Corneliu

2015-10-01

Magnesium based alloys, especially Mg-Ca alloys, are biocompatible substrates with mechanical properties similar to those of bones. The biodegradable alloys of Mg-Ca provide sufficient mechanical strength in load carrying applications as opposed to biopolymers and also they avoid stress shielding and secondary surgery inherent with permanent metallic implant materials. The main issue facing a biodegradable Mg-Ca alloy is the fast degradation in the aggressive physiological environment of the body. The alloy's corrosion is proportional with the dissolution of the Mg in the body: the reaction with the water generates magnesium hydroxide and hydrogen. The accelerated corrosion will lead to early loss of the alloy's mechanical integrity. The degradation rate of an alloy can be improved mainly through tailoring the composition and by carrying out surface treatments. This research focuses on the ability to adjust degradation rate of Mg-Ca alloys by an original method and studies the biological activity of the resulted specimens. A new Mg-Ca alloy, with a Si gradient concentration from the surface to the interior of the material, was obtained. The surface morphology was investigated using scanning electron microscopy (VegaTescan LMH II, SE detector, 30 kV), X-ray diffraction (X'Pert equipment) and energy dispersive X-ray (Bruker EDS equipment). In vivo degradation behavior, biological compatibility and activity of Mg-Ca alloys with/without Si gradient concentration were studied with an implant model (subcutaneous and bony) in rats. The organism response to implants was characterized by using radiological (plain X-rays and computed tomography), biochemical and histological methods of investigation. The results sustained that Si gradient concentration can be used to control the rate of degradation of the Mg-Ca alloys for enhancing their biologic activity in order to facilitate bone tissue repair.

Effect of Homogenization on Microstructure Characteristics, Corrosion and Biocompatibility of Mg-Zn-Mn-xCa Alloys

Science.gov (United States)

Li, Jingyuan; Lai, Huiying; Xu, Yuzhao

2018-01-01

The corrosion behaviors of Mg-2Zn-0.2Mn-xCa (denoted as MZM-xCa alloys) in homogenization state have been investigated by immersion test and electrochemical techniques in a simulated physiological condition. The microstructure features were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA), and the corrosion mechanism was illustrated using atomic force microscope (AFM), X-ray photoelectron spectroscopy (XPS) and confocal laser scanning microscopy (CLSM). The electrochemical and immersion test verify the MZM-0.38% Ca owns the best corrosion performance with the corrosion rate of 6.27 mm/year. Furthermore, the film layer of MZM-0.38% Ca is more compact and denser than that of others. This improvement could be associated with the combined effects of the suitable content of Zn/Ca dissolving into the α-Mg matrix and the modification of Ca-containing compounds by heat-treatment. However, the morphologies were transformed from uniform corrosion to localized pitting corrosion with Ca further addition. It could be explained that the excessive Ca addition can strengthen the nucleation driving force for the second phase formation, and the large volumes fraction of micro-galvanic present interface sites accelerate the nucleation driving force for corrosion propagation. In addition, in vitro biocompatibility tests also show the MZM-0.38% Ca was safe to bone mesenchymal stem cells (BMSCs) and was promising to be utilized as implant materials. PMID:29389894

Effect of Homogenization on Microstructure Characteristics, Corrosion and Biocompatibility of Mg-Zn-Mn-xCa Alloys

Directory of Open Access Journals (Sweden)

Yuan Zhang

2018-02-01

Full Text Available The corrosion behaviors of Mg-2Zn-0.2Mn-xCa (denoted as MZM-xCa alloys in homogenization state have been investigated by immersion test and electrochemical techniques in a simulated physiological condition. The microstructure features were characterized using scanning electron microscopy (SEM, X-ray diffraction (XRD, transmission electron microscopy (TEM and electron probe microanalysis (EPMA, and the corrosion mechanism was illustrated using atomic force microscope (AFM, X-ray photoelectron spectroscopy (XPS and confocal laser scanning microscopy (CLSM. The electrochemical and immersion test verify the MZM-0.38% Ca owns the best corrosion performance with the corrosion rate of 6.27 mm/year. Furthermore, the film layer of MZM-0.38% Ca is more compact and denser than that of others. This improvement could be associated with the combined effects of the suitable content of Zn/Ca dissolving into the α-Mg matrix and the modification of Ca-containing compounds by heat-treatment. However, the morphologies were transformed from uniform corrosion to localized pitting corrosion with Ca further addition. It could be explained that the excessive Ca addition can strengthen the nucleation driving force for the second phase formation, and the large volumes fraction of micro-galvanic present interface sites accelerate the nucleation driving force for corrosion propagation. In addition, in vitro biocompatibility tests also show the MZM-0.38% Ca was safe to bone mesenchymal stem cells (BMSCs and was promising to be utilized as implant materials.

The role of Si and Ca on new wrought Mg-Zn-Mn based alloy

International Nuclear Information System (INIS)

Ben-Hamu, G.; Eliezer, D.; Shin, K.S.

2007-01-01

The development of new wrought magnesium alloys for automotive industry has increased in recent years due to their high potential as structural materials for low density and high strength/weight ratio demands. However, the poor mechanical properties of the magnesium alloys have led to search a new kind of magnesium alloys for better strength and ductility. Magnesium alloys show strong susceptibility to localized corrosion in chlorides solutions due to their inhomogeneous microstructure. The existence of intermetallics in the microstructure of magnesium alloys might represent initiation sites for localized corrosion. This is due to the formation of galvanic couples between the intermetallics and the surrounding matrix. The main objective of this research is to investigate the corrosion behavior of new magnesium alloys; Mg-Zn-Mn-Si-Ca (ZSMX) alloys. The ZSM6X1 + YCa alloys were prepared by using hot extrusion method. AC and DC polarization tests were carried out on the extruded rods, which contain different amounts of silicon or calcium. The potential difference in air between different phases and the matrix was examined using scanning Kelvin probe force microscopy (SKPFM). The phases present in the alloys have been identified by optical microscopy and scanning electron microscopy/energy dispersive X-ray spectroscopy. Four different phases were found, i.e. intermetallics containing Si-Mn, Mg-Si, Mg-Zn and Mg-Si-Ca phase. All phases exhibited higher potential differences relative to magnesium matrix indicating a cathodic behavior. The potential difference revealed significant dependence on the chemical composition of the phases. Based on the results obtained from the scanning Kelvin probe force microscopy, the cathodic phases are effective sites for the initiation of localized corrosion in Mg-Zn-Mn-Si-Ca alloys

Thidiazuron effects on shoot growth, return bloom, fruit set and nutrition of apples Efeito do thidiazuron no crescimento, no florescimento, na frutificação e na nutrição em macieiras

Directory of Open Access Journals (Sweden)

Cassandro Vidal Talamini do Amarante

2002-10-01

Full Text Available Apple (Malus domestica Borkh. trees, cultivars Gala and Fuji, were sprayed at full bloom with thidiazuron (TDZ at doses of 0, 5, 10, or 20 g ha-1 of a.i. in order to evaluate its effects on plant growth and development, return bloom, fruit set, nutrition, and fruit yield. Fruit set increased with TDZ dose in 'Gala' but not in 'Fuji'. TDZ did not affect fruit yield in any cultivar. In 'Gala', the return bloom was reduced in about 50% at TDZ doses of 10 or 20 g ha-1. TDZ increased shoot growth in both cultivars. In leaves, TDZ decreased the concentration of Ca and Mg in 'Gala' and of Mg in 'Fuji', but did not affect the chlorophyll content, leaf area, length, width, and dry mass per cm² regardless of cultivar. In fruits, the effect of TDZ varied according to the portion evaluated. Highest doses of TDZ decreased the concentration of Ca and K in 'Gala' and of K in 'Fuji' in the entire fruits (flesh + skin; in the skin, highest doses of TDZ reduced the levels of N, Ca, and Mg in both cultivars, in addition to the level of K in 'Fuji'.Macieiras (Malus domestica Borkh., cultivares Gala e Fuji, foram pulverizadas na plena floração com thidiazuron (TDZ nas doses de 0, 5, 10 e 20 g ha-1 de ingrediente ativo com o objetivo de serem avaliadas quanto ao crescimento, florescimento, nutrição, frutificação e rendimento de frutos. A frutificação efetiva aumentou com a dose de TDZ na cultivar Gala, mas não na cultivar Fuji. Os tratamentos não afetaram o rendimento de frutos em nenhuma cultivar. Na cultivar Gala o florescimento no ano posterior ao da aplicação de TDZ foi reduzido em cerca de 50% nas doses de 10 e 20 g ha-1. O TDZ promoveu aumento no crescimento dos ramos do ano em ambas as cultivares. Nas folhas, o aumento nas doses de TDZ reduziu os teores de Ca e Mg na cultivar Gala, e de Mg na cultivar Fuji mas não afetou o conteúdo de clorofila, área, comprimento, diâmetro e massa seca cm-2 da folha, em ambas as cultivares. Em frutos inteiros

Ion exchange reactions of major inorganic cations (H+, Na+, Ca2+, Mg2+ and K+) on beidellite: Experimental results and new thermodynamic database. Toward a better prediction of contaminant mobility in natural environments

International Nuclear Information System (INIS)

Robin, Valentin; Tertre, Emmanuel; Beaufort, Daniel; Regnault, Olivier; Sardini, Paul; Descostes, Michael

2015-01-01

Highlights: • Multi-site ion exchange model for beidellite for Na + , Ca 2+ , Mg 2+ , K + and H + . • Validity over the 1–7 pH range and total normality >5 × 10 −3 mol/L. • Application to equilibrium between smectite and acidic solution from mining sites. • Impact of crystal chemistry of smectites on their sorption properties. - Abstract: To our knowledge, no thermodynamic database is available in the literature concerning ion-exchange reactions occurring in low-charge smectite with tetrahedral charge (beidellite). The lack of this information makes it difficult to predict the mobility of contaminants in environments where beidellite and major cations, which act as competitors with contaminants for sorption on the clay phase, are present. The present study proposes a multi-site ion exchange model able to describe experimental data obtained for H + and the four major cations (Na + , Ca 2+ , Mg 2+ and K + ) found in natural waters interacting with a <0.3 μm size fraction of Na-beidellite. The nature of the sites involved in the sorption processes is assessed using qualitative structural data. Moreover, the effect of the charge location in the smectite on the selectivity coefficient values is discussed by comparison with the results reported in the literature for smectite characterized by octahedral charge (montmorillonite). The new thermodynamic database proposed in this study is based on the same total sorption site density and distribution of sites regardless of the cations investigated. This database is valid for a large range of physico-chemical conditions: a [1–7] pH range, a total normality higher than 5 × 10 −3 mol/L corresponding to a flocculated state for water/clay systems, and when sorption of ions pairs can be neglected. Note that this study provides evidence that a thermodynamic database describing ion exchange reactions between H + and the four major cations of natural water for smectite cannot be valid irrespective of the total

Removal of Ca(II) and Mg(II) from potassium chromate solution on Amberlite IRC 748 synthetic resin by ion exchange

International Nuclear Information System (INIS)

Yu Zhihui; Qi Tao; Qu Jingkui; Wang Lina; Chu Jinglong

2009-01-01

Experimental measurements have been made on the batch ion exchange of Ca(II) and Mg(II) from potassium chromate solution using cation exchanger of Amberlite IRC 748 as K + form. The ion exchange behavior of two alkaline-earth metals on the resin, depending on contact time, pH, temperature and resin dosage was studied. The adsorption isotherms were described by means of the Langmuir and Freundlich isotherms. For Ca(II) ion, the Langmuir model represented the adsorption process better than the Freundlich model. The maximum ion exchange capacity was found to be 47.21 mg g -1 for Ca(II) and 27.70 mg g -1 for Mg(II). The kinetic data were tested using Lagergren-first-order and pseudo-second-order kinetic models. Kinetic data correlated well with the pseudo-second-order kinetic model, indicating that the chemical adsorption was the rate-limiting step. Various thermodynamic parameters such as Gibbs free energy (ΔG o ), enthalpy (ΔH o ) and entropy (ΔS o ) were also calculated. These parameters showed that the ion exchange of Ca(II) and Mg(II) from potassium chromate solution was feasible, spontaneous and endothermic process in nature. The activation energy of ion-exchange (E a ) was determined as 12.34 kJ mol -1 for Ca(II) and 9.865 kJ mol -1 for Mg(II) according to the Arrhenius equation.

Characterization of Ti6Al7Nb alloy foams surface treated in aqueous NaOH and CaCl2 solutions.

Science.gov (United States)

Bütev, Ezgi; Esen, Ziya; Bor, Şakir

2016-07-01

Ti6Al7Nb alloy foams having 53-73% porosity were manufactured via evaporation of magnesium space holders. A bioactive 1µm thick sodium hydrogel titanate layer, NaxH2-xTiyO2y+1, formed after 5M NaOH treatment, was converted to crystalline sodium titanate, Na2TiyO2y+1, as a result of post-heat treatment. On the other hand, subsequent CaCl2 treatment of NaOH treated specimens induced calcium titanate formation. However, heat treatment of NaOH-CaCl2 treated specimens led to the loss of calcium and disappearance of the titanate phase. All of the aforementioned surface treatments reduced yield strengths due to the oxidation of the cell walls of the foams, while elastic moduli remained mostly unchanged. Accordingly, equiaxed dimples seen on the fracture surfaces of as-manufactured foams turned into relatively flat and featureless fracture surfaces after surface treatments. On the other hand, Ca- and Na-rich coating preserved their mechanical stabilities and did not spall during fracture. The relation between mechanical properties of foams and macro-porosity fraction were found to obey a power law. The foams with 63 and 73% porosity met the desired biocompatibility requirements with fully open pore structures and elastic moduli similar to that of bone. In vitro tests conducted in simulated body fluid (SBF) showed that NaOH-heat treated surfaces exhibit the highest bioactivity and allow the formation of Ca-P rich phases having Ca/P ratio of 1.3 to form within 5 days. Although Ca-P rich phases formed only after 15 days on NaOH-CaCl2 treated specimens, the Ca/P ratio was closer to that of apatite found in bone. Copyright © 2016 Elsevier Ltd. All rights reserved.

Effects of exchangeable Ca:Mg ratio on the dispersion of soils some ...

African Journals Online (AJOL)

The soils studied were acidic, low in nutrient level, showed high dispersion rate, high water- dispersible clay content and the textural class were loamy sand and sandy loam. The exchangeable Ca2+ and Mg2+ contents of the soils dominated the exchange complex. The cation exchange capacity (CEC) ranges between 4 ...

Experimental Study Of Precipitation Competition Of Ca(OH)2 And Mg(OH)2 On MSF Desalination Condition

International Nuclear Information System (INIS)

Sumijanto

2001-01-01

Competition study has been carried out by using sea water simulation containing of 142 on deposit ppm of bicarbonate ion, 400 ppm of calcium ion and 1272 ppm of magnesium ion. Experiment was performed by heating sample at temperature 50, 60, 70, 80, and 90 C for 30 minutes. Precipitation competition of Ca(OHh and Mg(OHh was analyzed by reduction of calcium and magnesium ion. Experiment data showed information that at the temperature bellow 800 o C CaCO 3 precipitation was more dominant, meanwhile above than 80 o C precipitation Mg(OH) 2 was more dominant. This competition occurred because at temperature more than 80 o C rate of hydroxyl ion formation and Mg(OH) 2 recipitation was greater than CaCO 3 precipitation and at temperature bellow 80 o C rate of hydrolysis carbonate ion was less than thermal decomposition bicarbonates ion

Thermoluminescent characteristics of LiF:Mg, Cu, P and CaSO_4:Dy for low dose measurement

International Nuclear Information System (INIS)

Del Sol Fernández, S.; García-Salcedo, R.; Mendoza, J. Guzmán; Sánchez-Guzmán, D.; Rodríguez, G. Ramírez; Gaona, E.; Montalvo, T. Rivera

2016-01-01

Thermoluminescence (TL) characteristics for LiF:Mg, Cu, P, and CaSO_4:Dy under the homogeneous field of X-ray beams of diagnostic irradiation and its verification using thermoluminescence dosimetry are presented. The irradiation were performed utilizing a conventional X-ray equipment installed at the Hospital Juárez Norte of México. Different thermoluminescence characteristics of two material were studied, such as batch homogeneity, glow curve, linearity, detection threshold, reproducibility, relative sensitivity and fading. Materials were calibrated in terms of absorbed dose to the standard calibration distance and they were positioned in a generic phantom. The dose analysis, verification and comparison with the measurements obtained by the TLD-100 were performed. Results indicate that the dosimetric peak appears at 202 °C and 277.5 °C for LiF:Mg, Cu, P and CaSO_4:Dy, respectively. TL response as a function of X-ray dose showed a linearity behavior in the very low dose range for all materials. However, the TLD-100 is not accurate for measurements below 4 mGy. CaSO_4:Dy is 80% more sensitive than TLD-100 and it show the lowest detection threshold, whereas LiF:Mg, Cu, P is 60% more sensitive than TLD-100. All materials showed very good repeatability. Fading for a period of one month at room temperature showed low fading LiF:Mg, Cu, P, medium and high for TLD-100 and CaSO_4:Dy. The results suggest that CaSO_4:Dy and LiF:Mg, Cu, P are suitable for measurements at low doses used in radiodiagnostic. - Highlights: • Several dosimetric characteristics were evaluated. • TL dose response to very low dose X-rays was studied. • The applications proposed for each material may be useful for diagnostic radiology dosimetry.

Synthesis, Crystal Structure, and Nonlinear Optical Properties of a New Alkali and Alkaline Earth Metal Carbonate RbNa5Ca5(CO38

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Qiaoling Chen

2016-12-01

Full Text Available A new nonlinear optical (NLO material, RbNa5Ca5(CO38, has been synthesized by the hydrothermal method. The crystal structure is established by single-crystal X-ray diffraction. RbNa5Ca5(CO38 crystallizes in the hexagonal crystal system with space group P63mc (No. 186. The structure of RbNa5Ca5(CO38 can be described as the adjacent infinite [CaCO3]∞ layers lying in the a-b plane bridged through standing-on-edge [CO3] groups by sharing O atoms (two-fold coordinated to build a framework with four types of tunnels running through the b-axis. The Rb, Na, and [Na0.67Ca0.33] atoms reside in these tunnels, respectively. The measurement of second harmonic generation (SHG indicated that RbNa5Ca5(CO38 is a phase-matchable material, which had SHG responses of approximately 1×KH2PO4 (KDP. Meanwhile, the results from the UV-VIS diffuse reflectance spectroscopy study of the powder samples indicated that the UV cut-off edges of RbNa5Ca5(CO38 is about 203 nm.

On the roles of the dopants in LiF: Mg,Cu,Na,Si thermoluminescent material

International Nuclear Information System (INIS)

Lee, J. I.; Kim, J. L.; Chang, S. Y.; Chung, K. S.; Choe, H. S.

2005-01-01

In this paper, some results of the study on the roles of the dopants in the LiF:Mg,Cu,Na,Si thermoluminescent (TL) material that was developed at the Korea Atomic Energy Research Inst. for radiation protection are presented. Although there have been many studies to investigate the roles of the dopants in LiF:Mg,Cu,P TL material in the TL process, there are some discrepancies in the understanding of the roles of Cu and P between various researchers. In case of LiF:Mg,Cu,Na,Si TL material, there are a few studies on the roles of the dopants. Three kinds of samples in each of which one dopant is excluded, and the optimised sample, were prepared for this study. The measurements and analysis of the three-dimensional TL spectra, based on the temperature, wavelength and intensity, and the glow curves for those samples are used in this study. The results show that Mg plays a role in the trapping of the charge carriers and Cu plays a role in the luminescence recombination process; however, the effect of Na and Si on the glow curve structure and the TL emission spectra is much less than that of Mg and Cu. It is considered that Na and Si each plays a role in the improvement of the luminescence efficiency. (authors)

Cross Section Measurements of the Reaction 23Na(p, γ)24Mg

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Boeltzig, Axel; Deboer, Richard James; Macon, Kevin; Wiescher, Michael; Best, Andreas; Imbriani, Gianluca; Gyürky, György; Strieder, Frank

2017-09-01

The reaction 23Na(p, γ)24Mg can provide a link from the NeNa to the MgAl cycle in stellar burning and is therefore of interest in nuclear astrophysics. To determine the reaction rates at stellar temperatures, new cross section measurements at low proton energies have been performed recently, and further experiments are underway. The current cross section data implies that the reaction rate up to temperatures of 1 GK is determined by a few narrow resonances and direct capture. Complementary to these experimental efforts at low proton energies, cross section measurements at higher energies can help to constrain the direct capture and broad resonance contributions to the cross section and reduce the uncertainty of the extrapolation towards stellar energies. In this paper we report an experiment to measure the 23Na(p, γ)24Mg cross section with a solid target setup at the St. ANA 5U accelerator at the University of Notre Dame. The experiment and the current status of data analysis will be described. This work benefited from support by the National Science Foundation under Grant No. PHY-1430152 (JINA-CEE), the Nuclear Science Laboratory (NSL), the Istituto Nazionale di Fisica Nucleare (INFN), and the Gran Sasso Science Institute (GSSI).

Assessment of CaSO{sub 4}:Dy and LiF:Mg,Ti thermoluminescent dosimeters performance in the dosimetry of clinical electron beams; Avaliacao do desempenho dos detectores termoluminesncetes de CaSO{sub 4}:Dy e LiF:Mg,Ti na dosimetria de feixes clinicos de eletrons

Energy Technology Data Exchange (ETDEWEB)

Nunes, Maira Goes

2008-07-01

The assessment of the performance of CaS0{sub 4}:Dy thermoluminescent detectors produced by IPEN in the dosimetry of clinical electron beams aims to propose an alternative to the LiF:Mg,Ti commercial dosimeters (TLD-100) largely applied in radiation therapy. The two types of thermoluminescent dosimeters were characterised with the use of PMMA, RMI-457 type solid water and water phantoms in radiation fields of 4, 6, 9, 12 and 16 MeV electrons of nominal energies in which the dose-response curves were obtained and the surface and depth doses were determined. The thermoluminescent response dependency with the electron nominal energies and the applied phantom were studied. The CaS0{sub 4}:Dy presented the same behaviour than the LiF:Mg,Ti in such a way that its application as an alternative to the TLD-100 pellets in the radiation therapy dosimetry of electron beams is viable and presents the significantly higher sensitivity to the electron radiation as its main advantage. (author)

Mg- and K-bearing borates and associated evaporites at Eagle Borax spring, Death Valley, California: A spectroscopic exploration

Science.gov (United States)

Crowley, J.K.

1996-01-01

Efflorescent crusts at the Eagle Borax spring in Death Valley, California, contain an array of rare Mg and K borate minerals, several of which are only known from one or two other localities. The Mg- and/or K-bearing borates include aristarainite, hydroboracite, kaliborite, mcallisterite, pinnoite, rivadavite, and santite. Ulexite and probertite also occur in the area, although their distribution is different from that of the Mg and K borates. Other evaporite minerals in the spring vicinity include halite, thenardite, eugsterite, gypsum-anhydrite, hexahydrite, and bloedite. Whereas the first five of these minerals are found throughout Death Valley, the last two Mg sulfates are more restricted in occurrence and are indicative of Mg-enriched ground water. Mineral associations observed at the Eagle Borax spring, and at many other borate deposits worldwide, can be explained by the chemical fractionation of borate-precipitating waters during the course of evaporative concentration. The Mg sulfate and Mg borate minerals in the Eagle Borax efflorescent crusts point to the fractionation of Ca by the operation of a chemical divide involving Ca carbonate and Na-Ca borate precipitation in the subsurface sediments. At many other borate mining localities, the occurrence of ulexite in both Na borate (borax-kernite) and Ca borate (ulexite-colemanite) deposits similarly reflects ulexite's coprecipitation with Ca carbonate at an early concentration stage. Such ulexite may perhaps be converted to colemanite by later reaction with the coexisting Ca carbonate - the latter providing the additional Ca2+ ions needed for the conversion. Mg and Ca-Mg borates are the expected late-stage concentration products of waters forming ulexite-colemanite deposits and are therefore most likely to occur in the marginal zones or nearby mud facies of ulexite-colemanite orebodies. Under some circumstances, Mg and Ca-Mg borates might provide a useful prospecting guide for ulexite-colemanite deposits

Ca and Mg determination from inhabitants of Brazil using neutron activation analysis

International Nuclear Information System (INIS)

Zamboni, C.B.; Oliveir, L.C.; Luciana Kovacs; Sabrina Metairon

2012-01-01

In this study the neutron activation analysis (NAA) technique was applied to determine Ca and Mg in whole blood from inhabitants of Brazil for the purpose of establishing concentration ranges indicative of sex and age. The initiative to perform these measurements is related to the increase in heart disease. According to recent statistics from WHO, the average is one death due to heart attack in Brazil, every five minutes. The measures were performed considering lifestyle factors (non-smokers, non-drinkers and no history of toxicological exposure) of Brazilian inhabitants. A healthy group constituted of male (n = 94) and female (n = 84) blood donors, ages between 18 and 70 years and above 50 kg, was selected from the blood banks and hematological laboratories of Brazil. The influence of sex was also investigated considering several age ranges (18-29, 30-40, 41-50, >50 years). The results show significant differences when a comparison is made by sex and age and may be useful to identify or prevent clinical diseases. These results emphasize the need to perform periodic evaluation of Ca and Mg in blood. (author)

Effect of phosphate additives on the microstructure, bioactivity, and degradability of microarc oxidation coatings on Mg-Zn-Ca-Mn alloy.

Science.gov (United States)

Dou, Jinhe; You, Qiongya; Gu, Guochao; Chen, Chuanzhong; Zhang, Xihua

2016-09-20

Calcium phosphate coatings were prepared on the surface of self-designed Mg-Zn-Ca-Mn alloy using microarc oxidization technology. To characterize the microstructures, cross-section morphologies, and compositions of the coatings, the authors used scanning electron microscopy equipped with an energy-disperse spectrometer, x-ray diffraction, and Fourier transform infrared spectroscopy. Potentiodynamic polarization in the simulated body fluid (SBF) was used to evaluate the corrosion behaviors of the samples. An SBF immersion test was used to evaluate the coating bioactivity and degradability. After the immersion tests, some bonelike apatite formed on the coating surfaces indicate that bioactivity of the coatings is excellent. The coating prepared in electrolyte containing (NaPO3)6 had slower degradation rate after immersion test for 21 days.

Mg-containing hydroxyapatite coatings on Ti-6Al-4V alloy for dental materials

Science.gov (United States)