Loading...
Search for:
ions
0.009 seconds
Total 748 records
Modeling of a glucose sensitive composite membrane for closed-loop insulin delivery
, Article Journal of Membrane Science ; Volume 335, Issue 1-2 , 2009 , Pages 21-31 ; 03767388 (ISSN) ; Wu, X. Y ; Sharif University of Technology
2009
Abstract
A theoretical model was developed to describe a dynamic process involving an enzymatic reaction and diffusion of reactants and product inside glucose sensitive composite membrane. The composite membrane consisted of nanoparticles of a weakly acidic polymer, glucose oxidase and catalase embedded in a hydrophobic polymer. Time- and position-dependent diffusivity of involved species was considered in the model. Donnan equilibrium was used to find concentrations of buffer ions inside the membrane. The profiles of pH, species concentrations, volume fraction of swollen gel, polymer and water-filled space, as well as solute diffusivity inside the membrane were predicted by the model as a function...
Hydrolysis kinetics of lead silicate glass in acid solution
, Article Journal of Nuclear Materials ; Volume 389, Issue 3 , 2009 , Pages 427-431 ; 00223115 (ISSN) ; Sadrnezhaad, Kh ; Raisali, G ; Hamidi, A ; Sharif University of Technology
2009
Abstract
Hydrolysis kinetics of the lead silicate glass (LSG) with 40 mol% PbO in 0.5 N HNO3 aqueous acid solution was investigated. The surface morphology and the gel layer thickness were studied by scanning electron microscopy (SEM) micrographs. Energy dispersive X-ray spectroscopy (EDS) and inductively coupled plasma spectroscopy (ICP) were used to determine the composition of the gel layer and the aqueous solution, respectively. The silicon content of the dissolution products was determined by using weight-loss data and compositions of the gel layer and the solution. The kinetic parameters were determined using the shrinking-core-model (SCM) for rate controlling step. The activation energy...
Evaluations of structural, magnetic and various dielectric parameters of Ni-substituted Zn2W-type hexagonal ferrites for high frequency (1–6 GHz) applications
, Article Ceramics International ; Volume 45, Issue 18 , 2019 , Pages 24202-24211 ; 02728842 (ISSN) ; Shaukat, F ; Niaz Akhtar, M ; Ahmad, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
The structural, electrical, magnetic and high frequency properties of Ni-substituted Zn2W-type hexagonal ferrites were investigated for microwave applications. Ferrite powders with chemical compositions Ba0 · 5Sr0.5NixZn2-xFe16O27 (where Ni-substitution was varied from 0.0 to 1.5 with a step size of 0.5) were prepared using sol-gel auto-combustion at 1300 °C. X-ray diffraction (XRD) analysis confirmed the single-phase hexagonal ferrite structure. The lengths of both the axis i.e. minor and major (a, c) obtained from hkl values of XRD peaks were decreased with Ni-substitution due to the difference in ionic radius of the substituted metal ions. DC electrical resistivity obtained by two-point...
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) ; Calvo, B ; Zohoor, H ; Firoozbakhsh, K ; Grasa, J ; Sharif University of Technology
Academic Press
2019
Abstract
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...
Promotional effect of macrocyclization in O2Nx naphtha-aza-crown macrocyclic ligands on fluorescence chemosensing of Al(III)
, Article Journal of Luminescence ; Volume 205 , 2019 , Pages 219-227 ; 00222313 (ISSN) ; Zarepour jevinani, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Two new macrocyclic ligands Ln (L and L′) bearing two fluorophore naphthalene moieties were synthesized and characterized by employing 1H and 13C NMR, IR, microanalysis as well as mass spectrometry. Comparative studies on the effect of assorted metal cations as Cr(III), Cu(II), Zn(II), Cd(II), Pb(II), Na(I), Ni(II), Co(II), Ba(II), Fe(II), Al(III), Mg(II), Cs(I), Ca(II), Hg(II), K(I), Mn(II), Ag(I), Fe(III) on fluorescence and UV–vis spectra of Ln in ethanol illustrated that both of the macrocycles were sensitive and selective fluorescence chemosensors for Al(III). Remarkable binding constant values as 1.36 × 105 M−1 and 1.15 × 105 M−1 alongside 1:1 stoichiometry for Al(III)/L and Al(III)/L′...
Electrochemical sensors based on functionalized carbon nanotubes modified with platinum nanoparticles for the detection of sulfide ions in aqueous media
, Article Journal of Chemical Sciences ; Volume 131, Issue 3 , 2019 ; 09743626 (ISSN) ; Dolati, A ; Salmani Rezaie , S ; Sharif University of Technology
Springer
2019
Abstract
Abstract : Vertically aligned carbon nanotube (CNT) arrays were synthesized by thermal chemical vapor deposition (CVD) on stainless steel substrates coated by cobalt nanoparticles as catalyst. Morphological and elemental analyses conducted by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX) revealed that bamboo-like CNTs were blocked by Co nanoparticles at the tips. The fabricated nanotubes underwent functionalization by electrochemical oxidation in sulfuric acid, and the subsequent structural studies, as well as Fourier transform infrared (FTIR) spectroscopy confirmed that the tips of functionalized CNTs were opened while oxygenated functional groups were...
Promotional effect of macrocyclization in O2Nx naphtha-aza-crown macrocyclic ligands on fluorescence chemosensing of Al(III)
, Article Journal of Luminescence ; Volume 205 , 2019 , Pages 219-227 ; 00222313 (ISSN) ; Zarepour jevinani, M ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Two new macrocyclic ligands Ln (L and L′) bearing two fluorophore naphthalene moieties were synthesized and characterized by employing 1H and 13C NMR, IR, microanalysis as well as mass spectrometry. Comparative studies on the effect of assorted metal cations as Cr(III), Cu(II), Zn(II), Cd(II), Pb(II), Na(I), Ni(II), Co(II), Ba(II), Fe(II), Al(III), Mg(II), Cs(I), Ca(II), Hg(II), K(I), Mn(II), Ag(I), Fe(III) on fluorescence and UV–vis spectra of Ln in ethanol illustrated that both of the macrocycles were sensitive and selective fluorescence chemosensors for Al(III). Remarkable binding constant values as 1.36 × 105 M−1 and 1.15 × 105 M−1 alongside 1:1 stoichiometry for Al(III)/L and Al(III)/L′...
Optimized bioleaching of copper by indigenous cyanogenic bacteria isolated from the landfill of e-waste
, Article Journal of Environmental Management ; Volume 261 , 2020 ; Hassanpour, F ; Arshadi, M ; Yaghmaei, S ; Hamedi, J ; Sharif University of Technology
Academic Press
2020
Abstract
In this study, indigenous cyanogenic bacterial strains were isolated on nutrient, minimal salt, and soil extract media at various culture conditions from two distinct landfills of e-waste, Iran. Based on their cyanide formation profiles, five most potent isolates were selected for optimization and to this end, the influence of the most effective factors on cyanide production including pH, glycine concentration and temperature were assessed using one-factor at a time method (OFAT). Initial pH of 7, glycine concentration of 2 g/L and temperature of 30°C were obtained as optimal conditions for most of the isolates. Additionally, two bioleaching processes were applied for each bacteria to detect...
Comprehensive simulation of the effects of process conditions on plasma enhanced chemical vapor deposition of silicon nitride
, Article Semiconductor Science and Technology ; Volume 23, Issue 9 , 22 August , 2008 ; 02681242 (ISSN) ; Ilati, H ; Rashidian, B ; Sharif University of Technology
2008
Abstract
A numerical model for the deposition of silicon nitride using silane and ammonia mixture in a radio frequency plasma reactor has been developed. Plasma enhanced chemical vapor deposition process is simulated by combined analysis for the glow discharge, fluid flow and chemical reactions. The main goal is to investigate the effect of variations of the process parameters on the deposition rate, and uniformity of the resulting layer. The approach used is based on the theoretical partial differential equation models, without any empirical approximation of the critical data being used. Owing to the fact that the relevant equations are highly nonlinear, the discretization method is of great...
Mild steel carbon dioxide corrosion modelling in aqueous solutions
, Article Corrosion Engineering Science and Technology ; Volume 43, Issue 4 , 2008 , Pages 290-296 ; 1478422X (ISSN) ; Afshar, A ; Ghorbani, M ; Rahmaniyan, M ; Sharif University of Technology
2008
Abstract
A model for prediction of corrosion of mild steel in aqueous solutions containing carbon dioxide is proposed. In this model, formation of protective corrosion product is not yet considered, species concentration at the surface was calculated by using molecular diffusion phenomena and the diffusion equations were solved using the finite difference method. Calculated electrochemical currents at the steel surface may be used to determine the corrosion rate. The model was verified experimentally under atmospheric pressure and the effect of parameters, such as liquid velocity and pH, was investigated. The model can predict the electrochemical reaction rates when they were controlled by diffusion...
Electrocatalytic oxidation and nanomolar determination of guanine at the surface of a molybdenum (VI) complex-TiO2 nanoparticle modified carbon paste electrode
, Article Journal of Electroanalytical Chemistry ; Volume 624, Issue 1-2 , 2008 , Pages 73-78 ; 15726657 (ISSN) ; Taleat, Z ; Beitollahi, H ; Salavati Niasari, M ; Mirjalili, B. B. F ; Taghavinia, N ; Sharif University of Technology
Elsevier
2008
Abstract
A modified carbon paste electrode was prepared by incorporating TiO2 nanoparticles with bis[bis(salicylidene-1,4-phenylenediamine)molybdenum(VI)]. A mixture of fine graphite powder with 4 wt% of TiO2 nanoparticles was applied for the preparation of the carbon paste (by dispersing in paraffin) and finally modified with a molybdenum (VI) complex. The electrocatalytic oxidation of guanine (G) was investigated on the surface of the molybdenum (VI) complex-TiO2 nanoparticle modified carbon paste electrode (MCTNMCPE) using cyclic voltammetry (CV), differential pulse voltammetry (DPV), chronoamperometry (CHA) and chronocoloumetry (CHC). Using the modified electrode, the kinetics of G...
Synthesis of magnetic ions-doped QDs Synthesized Via a facial aqueous solution method for Optical/MR dual-modality imaging applications
, Article Journal of Fluorescence ; Volume 31, Issue 3 , 2021 , Pages 897-906 ; 10530509 (ISSN) ; Zare, H ; Shahedi, Z ; Fazaeli, Y ; Rahighi, R ; Sharif University of Technology
Springer
2021
Abstract
This research reports the preparation and examination of Cadmium Telluride (CdTe) Quantum Dots and doping CdTe QDs with Europium (Eu), Gadolinium (Gd), and Manganese (Mn) prepared in aqueous solution using TGA as a capping agent. Magnetic QDs (MQDs) are important agents for fluorescence (FL) /magnetic resonance (MR) dual-modal imaging due to their excellent optical and magnetic properties. Herein, the chemical bonds, structural, fluorescence, and magnetized properties of CdTe QDs and effect of Mn, Eu, and Gd ions doping on their properties were examined by X-ray powder diffraction (XRD), high-resolution transmission electron microscopy (HRTM), Energy-dispersive X-ray spectroscopy (EDX),...
Providing Multicolor Plasmonic Patterns with Au@Ag Core-Shell Nanostructures for Visual Discrimination of Biogenic Amines
, Article ACS Applied Materials and Interfaces ; Volume 13, Issue 17 , 2021 , Pages 20865-20874 ; 19448244 (ISSN) ; Ghasemi, F ; Bigdeli, A ; Hormozi Nezhad, M. R ; Sharif University of Technology
American Chemical Society
2021
Abstract
Biogenic amines (BAs) are known as substantial indicators of the quality and safety of food. Developing rapid and visual detection methods capable of simultaneously monitoring BAs is highly desired due to their harmful effects on human health. In the present study, we have designed a multicolor sensor array consisting of two types of gold nanostructures (i.e., gold nanorods (AuNRs) and gold nanospheres (AuNSs)) for the discrimination and determination of critical BAs (i.e., spermine (SM), tryptamine (TT), ethylenediamine (EA), tyramine (TR), spermidine (SD), and histamine (HT)). The design principle of the probe was based on the metallization of silver ions on the surface of AuNRs and AuNSs...
Mechanism of surfactant in trichloroethene degradation in aqueous solution by sodium persulfate activated with chelated-Fe(II)
, Article Journal of Hazardous Materials ; Volume 407 , 2021 ; 03043894 (ISSN) ; Li, M ; Gu, X ; Danish, M ; Shan, A ; Ali, M ; Qiu, Z ; Sui, Q ; Lyu, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
The mechanism of surfactants in surfactant-in situ chemical oxidation (S-ISCO) coupled process for trichloroethene (TCE) degradation was firstly reported. The performance of TCE solubilization and inhibition of TCE degradation in three nonionic surfactants (TW-80, Brij-35, TX-100) in PS/Fe(II)/citric acid (CA) system was compared and TW-80 was evaluated to be the optimal surfactant in S-ISCO coupled process due to the best TCE solubilizing ability and minimal inhibition for TCE degradation (only 31.8% TCE inhibition in the presence of 1 g L−1 TW-80 surfactant). The inhibition mechanism in TCE degradation was also demonstrated by comparing the strength of ROSs and PS utilization. In the...
Sol-gel-based solid-phase microextraction and gas chromatography-mass spectrometry determination of dextromethorphan and dextrorphan in human plasma
, Article Journal of Chromatography B: Analytical Technologies in the Biomedical and Life Sciences ; Volume 818, Issue 2 , 2005 , Pages 147-157 ; 15700232 (ISSN) ; Eshaghi, A ; Rouini, M. R ; Sharif University of Technology
2005
Abstract
A novel solid-phase microextraction (SPME) method was developed for isolation of dextromethorphan (DM) and its main metabolite dextrorphan (DP) from human plasma followed by GC-MS determination. Three different polymers, poly(dimethylsiloxane) (PDMS), poly(ethylenepropyleneglycol) monobutyl ether (Ucon) and polyethylene glycol (PEG) were synthesized as coated fibers using sol-gel methodologies. DP was converted to its acetyl-derivative prior to extraction and subsequent determination. The porosity of coated fibers was examined by SEM technique. Effects of different parameters such as fiber coating type, extraction mode, agitation method, sample volume, extraction time, and desorption...
Reinforced polydiphenylamine nanocomposite for microextraction in packed syringe of various pesticides
, Article Journal of Chromatography A ; Volume 1222 , January , 2012 , Pages 13-21 ; 00219673 (ISSN) ; Ayazi, Z ; Es'haghi, A ; Aghakhani, A ; Sharif University of Technology
2012
Abstract
Reinforced polydiphenylamine (PDPA) nanocomposite was synthesized by oxidation of diphenylamine in 4molL-1 sulfuric acid solution containing a fixed amount of carbon nanotubes (CNTs) in the presence of cetyltrimethylammonium bromide (CTAB). The surface characteristic of PDPA and PDPA/CNT nanocomposites was investigated using scanning electron microscopy (SEM). The prepared PDPA/CNT nanocomposite was used as an extraction medium for microextraction in packed syringe (MEPS) of selected pesticides from aquatic environment. The effect of CNT doping level and the presence of surfactant on the extraction capability of nanocomposite was investigated and it was revealed that when 4% (w/w) of CNT in...
Multiresidue determination of pesticides from aquatic media using polyaniline nanowires network as highly efficient sorbent for microextraction in packed syringe
, Article Analytica Chimica Acta ; Volume 740 , 2012 , Pages 43-49 ; 00032670 (ISSN) ; Alipour, N ; Ayazi, Z ; Sharif University of Technology
Abstract
A simple, rapid and sensitive method based on microextraction in packed syringe (MEPS), in combination with gas chromatography-mass spectrometry (GC-MS) was developed. Polyaniline (PANI) nanowires network was synthesized and used as sorbent of MEPS for the multiresidue determination of selected analytes from triazine, organochlrorine and organophosphorous pesticides in aqueous samples. The PANI nanowires network was prepared using soft template technique and its characterization was studied by scanning electron microscopy (SEM). The presence of micelles in this methodology showed to be an important parameter in shaping the growing polymer. Hexadecyltrimethylammonium bromide (HTAB) was used...
Amperometric sulfide detection using Coprinus cinereus peroxidase immobilized on screen printed electrode in an enzyme inhibition based biosensor
, Article Biosensors and Bioelectronics ; Volume 35, Issue 1 , 2012 , Pages 297-301 ; 09565663 (ISSN) ; Kariminia, H. R ; Ghadiri, M ; Roosta Azad, R ; Sharif University of Technology
2012
Abstract
In the present work, an amperometric inhibition biosensor for the determination of sulfide has been fabricated by immobilizing Coprinus cinereus peroxidase (CIP) on the surface of screen printed electrode (SPE). Chitosan/acrylamide was applied for immobilization of peroxidase on the working electrode. The amperometric measurement was performed at an applied potential of -150. mV versus Ag/AgCl with a scan rate of 100. mV in the presence of hydroquinone as electron mediator and 0.1. M phosphate buffer solution of pH 6.5. The variables influencing the performance of sensor including the amount of substrate, mediator concentration and electrolyte pH were optimized. The determination of sulfide...
Simulation of an innovative flow-field design based on a bio inspired pattern for PEM fuel cells
, Article Renewable Energy ; Volume 41 , 2012 , Pages 86-95 ; 09601481 (ISSN) ; Arbabi, F ; Moghaddam, G. K ; Sharif University of Technology
2012
Abstract
Proton exchange membrane (PEM) fuel cell performance is directly related to the bipolar plate design and their channels pattern. Power enhancements can be achieved by optimal design of the type, size, or patterns of the channels. It has been realized that the bipolar plate design has significant role on reactant transport as well as water management in a PEM Fuel cell. Present work concentrates on improvements in the fuel cell performance by optimization of flow-field design and channels configurations. A three-dimensional, multi-component numerical model of flow distribution based on Navier-Stokes equations using individual computer code is presented. The simulation results showed excellent...
Polypyrrole/polyamide electrospun-based sorbent for microextraction in packed syringe of organophosphorous pesticides from aquatic samples
, Article Journal of Separation Science ; Volume 35, Issue 1 , December , 2012 , Pages 114-120 ; 16159306 (ISSN) ; Ayazi, Z ; Aghakhani, A ; Alipour, N ; Sharif University of Technology
Abstract
A novel method based on microextraction in packed syringe (MEPS) as sample preparation technique coupled off-line with gas chromatography-mass spectrometry was developed using electrospun nanofibers as sorbent. For electrospinning of polypyrrole/polyamide-based nanofiber, a homogeneous solution containing nylon 6, ferric chloride and pyrrole monomer was prepared and then was drawn into a 2.5-mL syringe. By applying a voltage of 13akV between the needle of the syringe and an aluminum-foil collector, the nanofibers could be formed on the surface of the collector. The prepared sheet was used as the sorbent for MEPS to analyze some selected organophosphorous pesticides. Important parameters...