Search results for "Calcium"
showing 10 items of 1740 documents
Donnan equilibrium of ionic drugs in pH-dependent fixed charge membranes: theoretical modeling.
2002
Abstract We have studied theoretically the partition equilibrium of a cationic drug between an electrolyte solution and a membrane with pH-dependent fixed charges using an extended Donnan formalism. The aqueous solution within the fixed charge membrane is assumed to be in equilibrium with an external aqueous solution containing six ionic species: the cationic drug (DH + ), the salt cations (Na + and Ca 2+ ), the salt anion (Cl − ), and the hydrogen and hydroxide ions. In addition to these mobile species, the membrane solution may also contain four fixed species attached to the membrane chains: strongly acid sulfonic groups (SO 3 − ), weakly acid carboxylic groups in dissociated (COO − ) a…
Evaluation of changes in ion release and biological properties of NeoMTA‐Plus and Endocem‐MTA exposed to an acidic environment
2018
AIM To analyse in vitro changes in ion release and biological properties of Endocem-MTA (Maruchi, Wonju, Korea) and NeoMTA-Plus (Avalon Biomed Inc, Bradenton, FL, USA) exposed to acidic or neutral environment on human dental periodontal ligament stem cells (hPDLSCs). METHODOLOGY Cell viability and wound healing assays were performed using eluates of each material. Cell death and changes in phenotype induced by the set endodontic sealer eluates were evaluated through flow cytometry. To evaluate cell attachment to the different materials, hPDLSCs were directly seeded onto the material surfaces and analysed by scanning electron microscopy. The chemical composition of the materials was determin…
Fortification of milk with calcium: effect on calcium bioavailability and interactions with iron and zinc.
2006
Calcium solubility, dialysability, and transport and uptake (retention + transport) by Caco-2 cells as indicators of calcium bioavailability have been estimated in the in vitro gastrointestinal digests of milk and calcium fortified milk. A significant linear correlation (p < 0.05) was obtained between calcium uptake and the amount of soluble calcium added to the cells, and also between percentage calcium uptake and the calcium measured in the analyzed samples. The solubility, dialysis, transport, and uptake values are higher (p < 0.05) for calcium fortified milks than for nonfortified milks; that is, calcium fortification increases not only calcium content but also its bioavailability. An i…
Serum metal levels in a population of Spanish pregnant women
2022
Objective: To describe serum levels of calcium, copper, selenium, magnesium, iron and zinc and evaluate their relationship with maternal socio-demographic characteristics and dietary variables in women in the first trimester of pregnancy. Method: Cross-sectional study with 1279 participants from the INMA cohorts. Results: The concentrations of the elements analyzed were within the normal range. Associations with higher levels of these metals were found for calcium with white meat intake (p = 0.026), for cop-per with excess body weight (p 71 g/day) (p = 0.014) and having been born in Spain (p = 0.001). Further, lower iron levels were associated with being overweight (p = 0.021) or obese (p <…
Calcium, magnesium, sodium, potassium and iron content of infant formulas and estimated daily intakes
1996
The calcium, magnesium, sodium, potassium and iron content of a total of 22 different infant formulas marketed in Spain were measured by atomic spectrometry, and the mineral intake of infants fed exclusively with these formulas was estimated. The contents (mg/100kJ) are in the following ranges: Ca, 14-24; Mg, 1.1-2.8; Na, 5.6-9.8; K, 19-35; Fe, 0.02-0.50. These values coincide with those recommended by the Codex and European Society for Paediatric Gastroenterology and Nutrition (ESPGAN), and do not exceed the limits established by the European Union (EU). The mean values and ranges of estimated intakes for each formula type and period of infancy (0-1, 1-2, 2-3, 3-4 and 4-5 months) expressed…
Efficacy of the NaviTip FX irrigation needle in removing calcium hydroxide from root canal
2012
Objective: To evaluate the effectiveness of the NaviTip FX, brush-covered irrigation needle, in removing calcium hydroxide from the root canal. Study Design: Thirty single-rooted teeth were randomly divided into three groups: A - irrigation with a hypodermic needle inserted as far as possible without binding and activation with #30 K-type file; B - Irrigation with a hypodermic needle without activation; C - irrigation with NaviTip FX needle. Sodium hypoclorite 1% was used in irrigation. The root canals were examined trough scanning electron microscopy. Calcium hydroxide removal was recorded at 1, 5, and 10mm from the working length (WL) and the data were analysed using one-way ANOVA test (p…
Mechanisms and parameters controlling the tricalcium aluminate reactivity in the presence of gypsum.
2007
International audience; To understand the mechanisms and the parameters controlling the reactivity of tricalcium aluminate in the presence of gypsum at an early age, a study of the hydration of the “C3A–sulphate” system by isothermal microcalorimetry, conductimetry and a monitoring of the ionic concentrations of diluted system suspensions have been carried out with various gypsum quantities. The role of C3A source and its fineness were also studied. This work shows the fast initial formation of AFm phase followed by ettringite formation during the period when the sulphate is consumed. It has been highlighted that the time necessary to consume all the gypsum varies with the type of C3A and i…
Early C3A hydration in the presence of different kinds of calcium sulfate.
2009
International audience; Hydration reactions of C3A with various amounts of calcium sulfate hemihydrate, gypsum or a mixture of two, were investigated by isothermal microcalorimetry, and a monitoring of the ionic concentrations of diluted suspensions. This study shows that sulfate type used modifies the early C3A-CaSO4 hydration products and the rate of this hydration. The fast initial AFm formation observed before ettringite precipitation in the C3A-gypsum system is avoided as soon as hemihydrate is present in the suspension. This was attributed to.higher super saturation degrees and then higher nucleation frequency with regard to the ettringite obtained in the presence of hemihydrate. More…
Isotope shifts and hyperfine structure in the transitions of stable calcium isotopes and calcium-41
1998
Isotope shifts and hyperfine structure in the 4s2 1S0 → 4s4p 1P1 and 4s2 1S0 → 4s4d 1D2 transitions of calcium have been measured with high-precision laser spectroscopy. Calcium atoms in an atomic beam were excited with single-frequency cw dye and titanium sapphire lasers and then photoionized with the 363.8 nm or 514.5 nm line of an argon ion laser. The resulting ions were analyzed and detected with a quadrupole mass spectrometer. Isotope shifts for all stable calcium isotopes and the radionuclide 41Ca have been measured in both transitions. The corresponding field shift and specific mass shift coefficients as well as hyperfine structure constants for the isotopes 41, 43Ca have been derive…
Ultratrace analysis of calcium with high isotopic selectivity by diodelaser resonance ionisation mass spectrometry
1997
A resonance ionisation mass spectrometer for the ultratrace determination of calcium isotopes is presented. It achieves high overall efficiency, ultra-high isotopic abundance sensitivity of more than 1010 and complete suppression of isobars. The system can be used for isotope ratio studies on stable and long-lived trace isotopes with the final goal of radiodating via 41Ca-determination. For the different applications optical one-, two- or three-step resonance excitation and subsequent ionisation is applied using simple and inexpensive diodelasers. Additional mass analysis is accomplished in a commercial quadrupole mass spectrometer. The experimental set-up and first results on synthetical a…