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calcium
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Microwave assisted selective oxidation of benzylic alcohols with calcium hypochlorite under solvent-free conditions
, Article Monatshefte fur Chemie ; Volume 132, Issue 5 , 2001 , Pages 655-658 ; 00269247 (ISSN) ; Saidi, M. R ; Bolourtchian, M ; Shirzi, J. S ; Sharif University of Technology
2001
Abstract
A remarkably fast microwave assisted selective oxidation of benzylic alcohols with calcium hypochlorite under solvent-free conditions is described
The conduction mechanism in Gd1-x-zCexCazBa2Cu3O7-δ
, Article Superconductor Science and Technology ; Volume 21, Issue 9 , 4 July , 2008 ; 09532048 (ISSN) ; Mofakham, S ; Akhavan, M ; Sharif University of Technology
2008
Abstract
We have investigated the substitution of Ce and divalent Ca with a radius similar to Gd in Gd1-x-zCexCazBa 2Cu3O7-δ. We have prepared Gd 1-x-zCexCazBa2Cu3O 7-δ compounds with different concentrations of Ce and Ca by the standard solid-state reaction technique. X-ray diffraction (XRD) experiments are performed and the results are refined by the Rietveld method. XRD analysis shows a predominantly single-phase perovskite structure with orthorhombic Pmmm symmetry. In Gd1-x-zCexCazBa2Cu 3O7-δ compounds, induced suppression of T c due to Ce doping is compensated by hole doping with increasing Ca substitution for Gd. With the increase of Ca content, Tc increases up to an optimum value; thereafter...
Study of scratch resistance in homo- and co-polypropylene filled with nanometric calcium carbonate
, Article Materials Science and Engineering A ; Volume 445-446 , 2007 , Pages 526-536 ; 09215093 (ISSN) ; Lesan Khosh M., R ; Bagheri, R ; Sharif University of Technology
2007
Abstract
In this study, homo- and co-polypropylene were modified by nanometric calcium carbonate and the effect of additive on scratch resistance was evaluated. Results of this study show that the length of scratch curvature can be considered as an acceptable criterion to evaluate the scratch resistance of polymers. Also, it was found that addition of calcium carbonate to homo-polypropylene increases scratch resistance of this polymer, but its effect on co-polypropylene is insignificant. Based on the results of this work, one may claim that incorporation of nanometric particles with good adhesion to the matrix and well dispersion might be effective in enhancement of scratch resistance. Formation of...
Aluminothermic-carbothermal reduction synthesis of nano crystalline Al2O3-Ti(C,N) composite with different bed types
, Article Iranian Journal of Materials Science and Engineering ; Volume 12, Issue 1 , 2015 , Pages 66-75 ; 17350808 (ISSN) ; Naghizadeh, R ; Samadi, H ; Nemati, A ; Sharif University of Technology
Iran University of Science and Technology
2015
Abstract
Ceramic-matrix composites containing TiC-TiN have been used in a variety of application because of their superior properties such as high hardness, good wear resistance and high chemical stability. In this research, effect of coke and coke/calcium beds in synthesis of Al2O3-Ti(C, N) composites using alumino-carbothermic reduction ofTiO2 has been investigated. Al, TiO2 and active carbon with additives of extra carbon and NaCl and without additives, in separate procedures, have been mixed. Afterwards, mixtures were pressed and synthesized in 1200°C for 4hrs, in coke and coke/calcium beds, separately. Al2O3-Ti(C,N) composite was synthesized in ternary system of Al-TiO2-C with excess carbon and...
Molecular dynamics simulations of orai reveal how the third transmembrane segment contributes to hydration and ca2+ selectivity in calcium release-activated calcium channels
, Article Journal of Physical Chemistry B ; Volume 122, Issue 16 , 2018 , Pages 4407-4417 ; 15206106 (ISSN) ; Berti, C ; Ejtehadi, M. R ; Furini, S ; Sharif University of Technology
American Chemical Society
2018
Abstract
Calcium release-activated calcium (CRAC) channels open upon depletion of Ca2+ from the endoplasmic reticulum, and when open, they are permeable to a selective flux of calcium ions. The atomic structure of Orai, the pore domain of CRAC channels, from Drosophila melanogaster has revealed many details about conduction and selectivity in this family of ion channels. However, it is still unclear how residues on the third transmembrane helix can affect the conduction properties of the channel. Here, molecular dynamics and Brownian dynamics simulations were employed to analyze how a conserved glutamate residue on the third transmembrane helix (E262) contributes to selectivity. The comparison...
Ion-pair extraction-reaction of calcium using Y-shaped microfluidic junctions: An optimized separation approach
, Article Chemical Engineering Journal ; Volume 334 , 2018 , Pages 2603-2615 ; 13858947 (ISSN) ; Karimi Sabet, J ; Amini, Y ; Sharif University of Technology
Elsevier B.V
2018
Abstract
In this research, a continuous microsolvent extraction-reaction was developed for the efficient separation of calcium ion. This study gives a preliminary possible practical application of microfluidic devices in chemical exchange reaction for enrichment of 48Ca stable isotope. For this purpose, in the first stage, the hydrodynamic behavior of two immiscible liquids in a simple Y-shaped microfluidic junction is experimentally investigated, and then ion-pair extraction-reaction of Ca2+ using picric acid as a counter-ion and dicyclohexano-18-crown-6 (DC18C6) as a lipophilic ionophore is studied in this microfluidic and conventional batch method. The impact of main process parameters, including...
MAO-derived hydroxyapatite/TiO 2 nanostructured multi-layer coatings on titanium substrate
, Article Applied Surface Science ; Volume 261 , 2012 , Pages 37-42 ; 01694332 (ISSN) ; Golestani Fard, F ; Rezaie, H. R ; Mirhosseini, S. M. M ; Sharif University of Technology
2012
Abstract
In this study, titanium substrates which previously oxidized through Micro arc oxidation method, was coated by Hydroxyapatite (HAp) coating once more by means of the same method. Morphology, topography and chemical properties as well as phase composition and thickness of layers were studied to reveal the effect of the electrolyte concentration on coating features. According to results, the obtained coatings are consisted of HAp and titania as the major phases along with minor amounts of calcium titanate and α-tri calcium phosphate. Ca and P are present on surface of obtained layers as well as predictable Ti and O based on the XPS results. Thickness profile of coatings figured out that by...
Using commercial calcium ionophores to make lanthanide sensors
, Article Journal of Radioanalytical and Nuclear Chemistry ; Volume 331, Issue 4 , 2022 , Pages 1751-1758 ; 02365731 (ISSN) ; Saveliev, M ; Legin, A ; Yaghmaei, S ; Babain, V ; Kirsanov, D ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
Developing chemical sensors with pronounced sensitivity towards lanthanides is a very important task related to the analytical control of industrial processes in nuclear industry. Various diamides of organic acids were shown to be very effective for such sensing applications when employed as ligands in plasticized polymeric membranes of potentiometric sensors. The chemical structures of some of these ligands (diamides of diglycolic acid) are very similar to those suggested in 80’s as Ca(II) ionophores that were later commercialized. We have hypothesized that commercial ionophores ETH 129 (N,N,N′,N′-tetra[cyclohexyl] diglycolic acid diamide) and ETH 5234...
Simulation of Cement Hydrate by the Use of Molecular Dynamics and Developing a Reactive Forcefield for Calcium-carbonate Systems
, M.Sc. Thesis Sharif University of Technology ; Khoei, Amir Reza (Supervisor) ; Abdolhosseini Qomi, Mohammad Javad (Co-Advisor)
Abstract
Concrete is the most used man-made material on earth, albeit is responsible for the ten percent of the carbon dioxide gas emitted by human to atmosphere. Also the most important constituent of concrete, hydrated cement, has a sophisticated structure yet its precipitation, composition, mechanical properties and morphology has been the subject of dispute among cement researchers. On the other hand, according to the increasing focus on sustainable development, design of optimum materials has become important. Several models have been proposed for the structure of cement hydrate while every model has its own advantages and disadvantages. Recently, a combinatorial model at atomic scale has been...
Reactive Crystallization in an Impinging Jets Reactor
, M.Sc. Thesis Sharif University of Technology ; Molaei Dehkordi, Asghar (Supervisor)
Abstract
Reactive crystallization or precipitation is an important industrial process. Many chemicals and biochemicals such as catalysts and pigments are produced by precipitation. Because of the advantages of impinging jets in chemical engineering processes, the main aim of this research was to investigate the application of this method in precipitation and to study the effects of different operating and design parameters on the product’s quality and properties. Two chemical models of barium sulfate and copper oxalate were used as main products. Each of these chemicals was produced by a liquid-liquid reaction of two aqueous solutions, which were fed to an impinging-jets reactor. Effects of...
Experimental Investigation of Henna powder as an Additive to Drilling Fluid
, M.Sc. Thesis Sharif University of Technology ; Masihi, Mohsen (Supervisor) ; Shadizadeh, Reza (Supervisor)
Abstract
A critical property in designing drilling fluids is the concerns for environmental damages and cost efficiency of mud additives used to complete a well safely and economically. Designing drilling fluids for harsh environments such as high temperature, high salinity formation water, lime and cement contamination demands proper selection of deflocculant (thinner) materials to achieve a successful drilling operation. This study presents a novel thinner material that satisfies the goal of an environmentally and economically acceptable mud in drilling lime contamination areas where drilling carbonate formations with high concentration of calcium ions tends to flocculate clay particles in...
Rigorous modeling of gypsum solubility in Na-Ca-Mg-Fe-Al-H-Cl-H2O system at elevated temperatures
, Article Neural Computing and Applications ; Volume 25, Issue 3 , September , 2014 , pp 955-965 ; ISSN: 09410643 ; Gharagheizi, F ; Lemraski, A. S ; Jamialahmadi, M ; Mohammadi, A. H ; Ebrahimi, M ; Sharif University of Technology
Abstract
Precipitation and scaling of calcium sulfate have been known as major problems facing process industries and oilfield operations. Most scale prediction models are based on aqueous thermodynamics and solubility behavior of salts in aqueous electrolyte solutions. There is yet a huge interest in developing reliable, simple, and accurate solubility prediction models. In this study, a comprehensive model based on least-squares support vector machine (LS-SVM) is presented, which is mainly devoted to calcium sulfate dihydrate (or gypsum) solubility in aqueous solutions of mixed electrolytes covering wide temperature ranges. In this respect, an aggregate of 880 experimental data were gathered from...
Crystallization of hydroxyapatite during hydrothermal treatment on amorphous calcium phosphate layer coated by PEO technique
, Article Ceramics International ; Volume 39, Issue 2 , 2013 , Pages 1793-1798 ; 02728842 (ISSN) ; Arbabi, A ; Mehdinezhad Roshan, A ; Sharif University of Technology
2013
Abstract
Surface modification of titanium implants is recently considered by several researchers. In this study, PEO was performed over commercially Ti-6Al-4V alloy pellets in an aqueous electrolyte containing calcium acetate (C.A.) and calcium glycerphosphate (Ca-GP) with a Ca/P molar ratio of 6.8, and applying current density of 0.212 A/cm2, frequency of 100 Hz and duty ratio of 60% for 4 min. In the next step, hydrothermal treatments were carried out for various durations and at different temperatures inside an autoclave chamber containing a NaOH solution with pH of 11.5. XRD and SEM results confirmed formation of needle-shaped HAp after all hydrothermal conditions. Maximum intensity of HAp peaks...
MAO-derived hydroxyapatite-TiO 2 nanostructured bio-ceramic films on titanium
, Article Materials Research Bulletin ; Volume 47, Issue 11 , 2012 , Pages 3407-3412 ; 00255408 (ISSN) ; Golestani Fard, F ; Rezaie, H. R ; Mirhosseini, S. M. M ; Ziaee, A ; Sharif University of Technology
2012
Abstract
Micro Arc Oxidation (MAO) process was utilized to fabricate nano bioceramic TiO 2-hydroxyapatite coatings on titanium substrates. Samples were produced in electrolytes contained 1 g/l β-glycerophosphate and 5, 10 and 15 g/l calcium acetate for 3, 6 and 10 min at 350 V. The techniques including XRD, XPS, SEM, FESEM and EDX were employed to study the effect of processing parameters. Hydroxyapatite, anatase, α-tri calcium phosphate and calcium titanate phases as well as 30-60 nm-size crystals were detected in the coating layer. It was also observed that the pore volume would increase by increasing the electrolyte concentration. The growth time was also found to influence the total pore volume....
Dimensionless correlation for the prediction of permeability reduction rate due to calcium sulphate scale deposition in carbonate grain packed column
, Article Journal of the Taiwan Institute of Chemical Engineers ; Volume 41, Issue 3 , 2010 , Pages 268-278 ; 18761070 (ISSN) ; Kharrat, R ; Soltanieh, M ; Sharif University of Technology
Abstract
In this work, an experimental and theoretical study has been conducted to investigate the permeability reduction due to CaSO4 scale deposition in packed column porous media. Permeability reduction by calcium sulphate deposition follows a systematic trend considering various important parameters that are affected in this complex process. Hence, a novel dimensionless model has been proposed for the prediction of permeability reduction rate with high accuracy. The developed model is based on the data obtained from glass bead and carbonate grain packed column at low pressure. The proposed model was validated with Berea sandstone cores data at high pressure (100-20,678 kPa), various flow rates...
Optimization of l-asparaginase immobilization onto calcium alginate beads
, Article Chemical Engineering Communications ; Volume 204, Issue 2 , 2017 , Pages 216-220 ; 00986445 (ISSN) ; Alemzadeh, I ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
In this study, anti-leukemic enzyme L-asparaginase (E.C.3.5.1.1) from Escherichia coli ATCC 11303 was modified by the microencapsulation technique onto calcium alginate beads. Using response surface methodology (RSM), a three-level full factorial design, the values of concentration of sodium alginate, concentration of calcium chloride, and enzyme loading were investigated to obtain the highest residual L-asparaginase (L-ASNase) activity % (immobilized enzyme activity/free enzyme activity). The effects of the studied factors on immobilization were evaluated The predicted values by the model were close to the experimental values, indicating suitability of the model. The results presented that...
Fabrication and properties of polycaprolactone composites containing calcium phosphate-based ceramics and bioactive glasses in bone tissue engineering: a review
, Article Polymer Reviews ; Volume 58, Issue 1 , 2018 , Pages 164-207 ; 15583724 (ISSN) ; Tajbakhsh, S ; Shojaei, A ; Sharif University of Technology
Taylor and Francis Inc
2018
Abstract
Polycaprolactone (PCL) is a bioresorbable and biocompatible polymer that has been widely used in long-term implants and controlled drug release applications. However, when it comes to tissue engineering, PCL suffers from some shortcomings such as slow degradation rate, poor mechanical properties, and low cell adhesion. The incorporation of calcium phosphate-based ceramics and bioactive glasses into PCL has yielded a class of hybrid biomaterials with remarkably improved mechanical properties, controllable degradation rates, and enhanced bioactivity that are suitable for bone tissue engineering. This review presents a comprehensive study on recent advances in the fabrication and properties of...
In vitro dissolution of plasma-sprayed hydroxyapatite coatings with different characteristics: Experimental study and modeling
, Article Biomedical Materials ; Volume 3, Issue 1 , 2008 ; 17486041 (ISSN) ; Ziaei Moayyed, A. A ; Sheikh Mehdi Mesgar, A ; Sharif University of Technology
2008
Abstract
The dissolution of plasma-sprayed hydroxyapatite (PHA) coatings with different characteristics, produced by various spraying conditions, in a Tris-buffered solution at pH 7.4 was experimentally studied through the measurement of the release of calcium ions. The phase composition of the coatings at surface and interface, and the porosity were evaluated. The analytical modeling revealed that the calcium dissolution process was composed of two stages. The first stage was found to be both surface and diffusion controlled. The second stage was an exactly diffusion-controlled dissolution. In the first stage, the rate of dissolution and the solubility of the coatings with minimum contents of...
Investigation of salts behavior at liquid–liquid interfaces
, Article Springer Proceedings in Mathematics and Statistics, 26 August 2013 through 30 August 2013 ; Volume 117 , July , 2015 , Pages 265-270 ; 21941009 (ISSN) ; 9783319123066 (ISBN); 9783319123066 (ISBN) ; Bahramian, A ; Soltani, M ; Pourafshary, P ; Sarikhani, K ; Chen, P ; Ejtehadi, M. R ; Makarov R. N ; Melnik R. V. N ; Kotsireas I. S ; Shodiev H ; Cojocaru M. G ; Cojocaru M. G ; Makarov R. N ; Melnik R. V. N ; Kotsireas I. S ; Shodiev H ; Sharif University of Technology
Springer New York LLC
2015
Abstract
We have used molecular dynamics simulation to investigate hydrophilic– hydrophobic interfaces between calcium chloride (CaCl2) aqueous solutions and normal hexane. The results demonstrate the increasing impact of salt concentration on the liquid–liquid interfacial tension, hence, negative adsorption of CaCl2 according to Gibbs adsorption isotherm. Moreover, we calculated the density profiles of hexane, water, and the counter ions. The results reveal an electrical double layer near the interface and the less affinity of calcium cations toward the interface than that of chloride anions. Orientation of water molecules at the studied concentrations may result in developing a positively charged...
Production of extracellular protease and determination of optimal condition by bacillus licheniformis BBRC 100053
, Article International Journal of Engineering, Transactions B: Applications ; Volume 22, Issue 3 , 2009 , Pages 221-228 ; 1728-144X (ISSN) ; Yaghmaei, S ; Haji Hosseini, R ; Sharif University of Technology
Materials and Energy Research Center
2009
Abstract
The production of protease by Bacillus licheniformis BBRC 100053 was studied. The most appropriate medium for the growth and protease production is composed of: lactose 1%, yeast extract 0.5%, peptone 0.5%, KH2 PO 4 0.1%, MgSO4 .7H2 O 0.02%. Enzyme production corresponded with growth and reached a maximums level (589 U/ml) during the stationary phase at 35°C, pH equivalent to 10 and with 150 rpm after 73 hours. Protease activity was highest at pH 8 and 45°C. The best carbon sources are respectively lactose and maltose and the best nitrogen source is peptone. The protease was highly active and stable from pH 7.0 to 11.0 with an optimum at pH 7-8....