Search for: calcium-ion
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    Experimental Investigation of Henna powder as an Additive to Drilling Fluid

    , M.Sc. Thesis Sharif University of Technology Mahmoodi, Masoud (Author) ; Masihi, Mohsen (Supervisor) ; Shadizadeh, Reza (Supervisor)
    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... 

    Simulation of NO Production Process from Endothelial Cells and its Effect on Coronary Artery Flow Field

    , M.Sc. Thesis Sharif University of Technology Shahriari, Amir Hossein (Author) ; Firoozabadi, Bahar (Supervisor)
    Endothelial derived nitric oxide (NO) and its role in regulating the physiological conditions of blood vessels is one of the favorite topics among researchers. The majority of previous studies have focused on nitric oxide transport in blood vessels, less attention has been paid to its vasodilative effects in blood vessels. The main aim of this study is to propose an integrated model to study the effects of endothelial-derived nitric oxide on hemodynamic conditions of blood vessels. Nitric oxide is produced by endothelial cells upon exposure to mechanical forces such as hemodynamic shear stress. The synthesized nitric oxide then diffuses into the neighboring vascular smooth cells, where it... 

    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) Foroozan Jahromi, P ; Karimi Sabet, J ; Amini, Y ; Sharif University of Technology
    Elsevier B.V  2018
    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... 

    Investigation of Excitation-contraction behavior in Skeletal Muscle by Means of Chemomechanical Modeling

    , Ph.D. Dissertation Sharif University of Technology Karami, Mina (Author) ; Zohoor, Hassan (Supervisor) ; Firoozbakhsh, Keikhosrow (Supervisor)
    Numerous studies have shown a direct relationship between skeletal muscle active force and intracellular calcium ion concentrations; In fact, no matter how the muscle is stimulated (neurological, electrical, chemical, and mechanical stimuli), the main cause of muscle activation and consequently force generation is calcium ions.According to this scientific finding, the purpose of this study is to present a new chemo-mechanical multiscale model of skeletal muscle based on the fundamental principles of continuum thermodynamics. In this model, unlike other similar studies, muscle active force is not considered as the conventional multiplication of isometric force in a set of corrective... 

    Expression of functional recombinant human tissue transglutaminase (TG2) using the bac-to-bac baculovirus expression system

    , Article Advanced Pharmaceutical Bulletin ; Volume 6, Issue 1 , 2016 , Pages 49-56 ; 22285881 (ISSN) Yazdani, Y ; Azari, S ; Kalhor, H. R ; Sharif University of Technology
    Tabriz University of Medical Sciences 
    Tissue transglutaminase (TG2) is a unique multifunctional enzyme. The enzyme possesses enzymatic activities such as transamidation/crosslinking and non-enzymatic functions such as cell migration and signal transduction. TG2 has been shown to be involved in molecular mechanisms of cancers and several neurodegenerative diseases such as Alzheimer's disease. The present study aimed at cloning and expression of full length human TG2 in Bac-to-Bac baculovirus expression system and evaluation of its activity. Methods: pFastBac HTA donor vector containing coding sequence of human TG2 was constructed. The construct was transformed to DH10Bac for generating recombinant bacmid. The verified bacmid was... 

    Theoretical aspects of the enhancement of metal binding affinity by intramolecular hydrogen bonding and modulating p: K a values

    , Article New Journal of Chemistry ; Volume 41, Issue 24 , 2017 , Pages 15110-15119 ; 11440546 (ISSN) Motahari, A ; Fattahi, A ; Sharif University of Technology
    Royal Society of Chemistry  2017
    Polyols were used as model ligands for Mg2+, Ca2+, and Zn2+ complexes to study the role of the hydrogen bond network on the metal binding affinity and modulation of successive pKa values using density functional theory. The results confirm that the acidity of polyols dramatically increases upon metal complexation in the order Zn2+ > Mg2+ > Ca2+. For example, the three H-site positions in the hydroxyl groups of the heptaol, bound to Zn2+, are 11.2, 29.9, and 30.9 pKa units (in methanol) more acidic than those of pure heptaol. This acidity enhancement leads to making polyols as good ligands toward complexation. For instance, the formation constants of the heptaol in the presence of Zn2+, Mg2+,... 

    Smart water flooding performance in carbonate reservoirs: an experimental approach for tertiary oil recovery

    , Article Journal of Petroleum Exploration and Production Technology ; Volume 9, Issue 4 , 2019 , Pages 2643-2657 ; 21900558 (ISSN) Darvish Sarvestani, A ; Ayatollahi, S ; Bahari Moghaddam, M ; Sharif University of Technology
    Springer  2019
    Smart water flooding as a developing technique utilizes modified water chemistry in terms of salinity and composition to prepare the best-suited brine composition for a specific brine/oil/rock system to obtain higher oil recovery efficiency. Huge amount of unrecovered oil is expected to be remained in carbonate reservoirs; however, few research works on incremental oil recovery during smart water injection in carbonate cores at reservoir condition are reported. Several core flooding tests using one of the Iranian carbonate reservoir rock are conducted to check the effectiveness of smart water injection for more oil recovery efficiency. The results reaffirm the positive effect of sulfate ions... 

    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) Mohammadi, Z ; Ziaei Moayyed, A. A ; Sheikh Mehdi Mesgar, A ; Sharif University of Technology
    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... 

    Magnetic/pH-sensitive κ-carrageenan/sodium alginate hydrogel nanocomposite beads: Preparation, swelling behavior, and drug delivery

    , Article Journal of Biomaterials Science, Polymer Edition ; Vol. 25, issue. 17 , 2014 , p. 1891-1906 Mahdavinia, G. R ; Rahmani, Z ; Karami, S ; Pourjavadi, A ; Sharif University of Technology
    This work describes the preparation of magnetic and pH-sensitive beads based on κ-carrageenan and sodium alginate for use as drug-targeting carriers. Physical cross-linking using K+/Ca2+ ions was applied to obtain ionic cross-linked magnetic hydrogel beads. The produced magnetite beads were thoroughly characterized by TEM, SEM/EDS, XRD, FTIR, and VSM techniques. While the water absorbency (WA) of magnetic beads was enhanced by increasing the weight ratio of κ-carrageenan, introducing magnetic nanoparticles caused a decrease in WA capacity from 15.4 to 6.3 g/g. Investigation on the swelling of the hydrogel beads in NaCl, KCl, and CaCl2 solutions revealed the disintegration of beads depending... 

    Synthesis and characterization of a bentonite-alginate microspherical adsorbent for removal of uranyl ions from aqueous Solutions

    , Article Separation Science and Technology ; Volume 45, Issue 2 , 2010 , Pages 288-298 ; 01496395 (ISSN) Tayyebi, A ; Khanchi, A ; Ghofrani, M.B ; Outokesh, M ; Sharif University of Technogy
    A novel microspherical adsorbent for the removal of uranium from aqueous solutions was developed by immobilizing of natural bentonite in the polymeric matrix of calcium alginate. Different uptake properties of the prepared microspheres were examined using batch, stirred and column methods. The adsorbent showed high affinity toward uranium ions, especially at pHs above 3. Major uptake mechanisms included ion exchange, chelating of the (UO2)2+ ions to the -OH groups of alginate, and surface complexation with bentonite. Surprisingly, the capacity of microspheres was higher than both its constituents, revealing that a synergetic effect occurs. Adsorption kinetics was controlled by slow chemical... 

    DFT study of the interaction of thymine with Cu+ and Zn 2+

    , Article Scientia Iranica ; Volume 16, Issue 2 C , 2009 , Pages 75-80 ; 10263098 (ISSN) Shakorian Fard Jahromi, M ; Fattahi, A ; Sharif University of Technology
    Interaction of the DNA thymine base with Cu+ and Zn3+ was studied to explore: a) The metal binding energy (MIA) of thymine with Cu+ and Zn2+ and b) The possible correlation between charge transfer and MIAs. The gas-phase Cu+ and Zn2+ affinities of thymine, as well as the Mulliken charges, on the complexed metal cations were both determined at the same computational level, including the density functional level and employing the hybrid B3LYP exchange correlation potential in connection with the 6-311++G (d,p) basis set. All the molecular complexes were obtained by interaction between the most stable tautomer of thymine and two transition mono and divalent (Cu+, Zn2+) metal ions. To probe all... 

    Impact of ionic composition on modulating wetting preference of calcite surface: Implication for chemically tuned water flooding

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 568 , 2019 , Pages 470-480 ; 09277757 (ISSN) Saeedi Dehaghani, A. H ; Badizad, M. H ; Sharif University of Technology
    Elsevier B.V  2019
    Despite previous researches on ion-engineered waterflooding (IEWF), its underlying mechanisms are not fully understood, particularly in presence of additives, like surfactants. This paper concerned with the contribution of Ca 2+ , Mg 2+ , SO 4 2- and Na + into altering wettability of oil-wet carbonate minerals towards water preferred state. As a mechanistic study, an experiment workflow was conducted to probe the impact of ions' concentrations in SW, either with or without sodium dodecylbenzene sulfonate (SDBS) which is an anionic surfactant. At first, contact angle (CA) measurement was carried out to evaluate the degree of wettability reversal upon treating the oil-aged calcite slabs with... 

    Assessing the role of Ca2+ in skeletal muscle fatigue using a multi-scale continuum model

    , Article Journal of Theoretical Biology ; Volume 461 , 2019 , Pages 76-83 ; 00225193 (ISSN) Karami, M ; Calvo, B ; Zohoor, H ; Firoozbakhsh, K ; Grasa, J ; Sharif University of Technology
    Academic Press  2019
    The Calcium ion Ca2+ plays a critical role as an initiator and preserving agent of the cross-bridge cycle in the force generation of skeletal muscle. A new multi-scale chemo-mechanical model is presented in order to analyze the role of Ca2+ in muscle fatigue and to predict fatigue behavior. To this end, a cross-bridge kinematic model was incorporated in a continuum based mechanical model, considering a thermodynamic compatible framework. The contractile velocity and the generated active force were directly related to the force-bearing states that were considered for the cross-bridge cycle. In order to determine the values of the model parameters, the output results of an isometric simulation... 

    Characterization of ionic composition of TSP and PM10 during the Middle Eastern Dust (MED) storms in Ahvaz, Iran

    , Article Environmental Monitoring and Assessment ; Volume 184, Issue 11 , November , 2012 , Pages 6683-6692 ; 01676369 (ISSN) Shahsavani, A ; Naddafi, K ; Jaafarzadeh Haghighifard, N ; Mesdaghinia, A ; Yunesian, M ; Nabizadeh, R ; Arhami, M ; Yarahmadi, M ; Sowlat, M. H ; Ghani, M ; Jonidi Jafari, A ; Alimohamadi, M ; Motevalian, S. A ; Soleimani, Z ; Sharif University of Technology
    Because of the recent frequent observations of major dust storms in southwestern cities in Iran such as Ahvaz, and the importance of the ionic composition of particulate matters regarding their health effects, source apportionment, etc., the present work was conducted aiming at characterizing the ionic composition of total suspended particles (TSP) and particles on the order of ∼10 μm or less (PM10) during dust storms in Ahvaz in April-September 2010. TSP and PM10 samples were collected and their ionic compositions were determined using an ion chromatography. Mean concentrations of TSP and PM10 were 1,481.5 and 1,072.9 μg/m 3, respectively. Particle concentrations during the Middle Eastern... 

    Mechanistic study of wettability alteration of oil-wet calcite: The effect of magnesium ions in the presence and absence of cationic surfactant

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 482 , October , 2015 , Pages 403-415 ; 09277757 (ISSN) Karimi, M ; Al Maamari, R. S ; Ayatollahi, S ; Mehranbod, N ; Sharif University of Technology
    Elsevier  2015
    Over 60% of the world's discovered oil reserves are held in carbonate reservoirs, which are mostly naturally fractured. Conventional water flooding results in low oil recovery efficiency in these reservoirs as most of them are oil-wet. On account of negative capillary forces, injected brine cannot penetrate simply into an oil-wet matrix of fractured formations to force the oil out. Wettability alteration of the rock surface to preferentially more water-wet state has been extensively studied using both smart water and surfactants separately. This study aims to study the effects of Mg2+ as one of the most important wettability influencing ions on the wetting properties of oil-wet carbonate...