Loading...
Search for:
concentration--parameter
0.006 seconds
Total 96 records
Synthesis and photocatalytic activity of WO3 nanoparticles prepared by the arc discharge method in deionized water
, Article Nanotechnology ; Volume 19, Issue 19 , 2008 ; 09574484 (ISSN) ; Iraji Zad, A ; Ahadian, M. M ; Mahdavi Ardakani, S. A ; Sharif University of Technology
2008
Abstract
In this paper, we discuss the synthesis and characterization of tungsten trioxide nanoparticles prepared by the arc discharge method in deionized (DI) water. The size and morphology of WO3 nanoparticles prepared using different arc currents (25, 35 and 45 A) were studied. Dynamic light scattering (DLS) and scanning electron microscopy (SEM) results indicate that at an arc current of 25 A, the size of the particles is about 30 nm, and this increases to 64 nm by increasing the arc current. This size increase caused a decrease of optical band gap from 2.9 to 2.6 eV. X-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) spectra demonstrate the formation of the WO3 phase....
Optimization of solid-phase microextraction of volatile phenols in water by a polyaniline-coated Pt-fiber using experimental design
, Article Analytica Chimica Acta ; Volume 581, Issue 1 , 2007 , Pages 71-77 ; 00032670 (ISSN) ; Noroozian, E ; Jalali Heravi, M ; Mollahosseini, A ; Sharif University of Technology
2007
Abstract
Solid-phase microextraction (SPME) coupled to gas chromatography (GC) was applied to the extraction of phenol and some of its volatile derivatives in water samples. The SPME fiber consisted of a thin layer of polyaniline, which was electrochemically coated on a fine Pt wire. The stability of the coating was such that it could be used at temperatures as high as 325 °C, without any deterioration. The effects of various parameters affecting the extraction efficiency were studied, simultaneously. From these, optimization of the extraction temperature, extraction time, coating thickness, sample pH, salt concentration and desorption time was carried out by means of a (26-2) fractional factorial...
Modeling of a cationic glucose-sensitive membrane with consideration of oxygen limitation
, Article Journal of Membrane Science ; Volume 254, Issue 1-2 , 2005 , Pages 119-127 ; 03767388 (ISSN) ; Wu, X. Y ; Sharif University of Technology
2005
Abstract
A theoretical model concerning simultaneous diffusion and reaction was developed to describe the steady state behavior of a cationic glucose-sensitive membrane with consideration of oxygen limitation and swelling-dependent diffusivities of involved species inside the membrane. Donnan equilibrium was used to find concentrations of buffer ions inside the membrane. The profiles of species concentrations, pH, polymer volume fraction and solute diffusivity inside the membrane were predicted by the model in response to step changes of glucose concentration in the external solution. The influence of various factors on the responsiveness of the membrane was analyzed using the model. The results...
Immersed solvent microextraction and gas chromatography-mass spectrometric detection of s-triazine herbicides in aquatic media
, Article Analytica Chimica Acta ; Volume 537, Issue 1-2 , 2005 , Pages 81-87 ; 00032670 (ISSN) ; Khalilian, F ; Sharif University of Technology
Elsevier
2005
Abstract
An immersed solvent microextraction (SME) method was successfully developed for the trace enrichment of s-triazine herbicides from aquatic media. A microdrop of butyl acetate was applied as the extraction solvent. After extraction, the microdrop was introduced directly into a gas chromatography-mass spectrometry (GC-MS) injection port. Some important extraction parameters such as type of solvent, extraction time, stirring rate, and temperature were investigated and optimized. The highest possible microdrop volume of 3 μl, a sampling temperature of 60°C, and use of butyl acetate are major parameters to obtain high enrichment factors. The enrichment factor and linearity was studied by...
Fungal bioleaching of e-waste utilizing molasses as the carbon source in a bubble column bioreactor
, Article Journal of Environmental Management ; Volume 307 , 2022 ; 03014797 (ISSN) ; Arshadi, M ; Yaghmaei, S ; Sharif University of Technology
Academic Press
2022
Abstract
Mobile phones are known as the most widely used electronic instruments, and an enormous number of discarded mobile phones are generated. The present work used a pure culture of Penicillium simplicissimum in a bubble column bioreactor to extract Cu and Ni from mobile phone printed circuit boards (MPPCBs) waste. Molasses was used as an efficient carbon source to enhance bioleaching efficiency and increase the cost benefits. The adaptation phase was done at Erlenmeyer flasks to reach 40 g/L of MPPCBs powder. The most significant parameters, including the mass of MPPCBs powder, aeration, molasses concentration, and their interaction, were optimized in order to leach the maximum possible Cu and...
Comparative study of commercial media to improve GMP manufacturing of recombinant human interferon β-1a by CHO cells in perfusion bioreactor
, Article Cytotechnology ; Volume 74, Issue 6 , 2022 , Pages 669-680 ; 09209069 (ISSN) ; Karimi Mostofi, R ; Sattarzadeh, A ; Shahbazi, M ; Aghazadeh, H ; Sharif University of Technology
Springer Science and Business Media B.V
2022
Abstract
Chinese hamster ovary cells are the main cellular factories for production of a wide range of recombinant proteins in biopharmaceutical industry. Recombinant human Interferon beta-1a (rh-IFN β-1a), as a cytokine is broadly used to treat multiple sclerosis. In this work, the cell line producing rh-IFN β-1a was studied to improve cell density along with the specific expression. For this reason different cell culture experiments were done using different commercial serum-free media to find the appropriate media providing higher cell density. It was shown DMEMF12, DMEM:ProCHO5, and CHO-S-SFM II led to higher cell density and shorter doubling time. Next, using these media, fed-batch, and...
Numerical modeling of surface reaction kinetics in electrokinetically actuated microfluidic devices
, Article Analytica Chimica Acta ; Vol. 838, issue , August , 2014 , pp. 64-75 ; ISSN: 00032670 ; Amini, Y ; Saidi, M. H ; Chakraborty, S ; Sharif University of Technology
Abstract
We outline a comprehensive numerical procedure for modeling of species transport and surface reaction kinetics in electrokinetically actuated microfluidic devices of rectangular cross section. Our results confirm the findings of previous simplified approaches that a concentration wave is created for sufficiently long microreactors. An analytical solution, developed for the wave propagation speed, shows that, when normalizing with the fluid mean velocity, it becomes a function of three parameters comprising the channel aspect ratio, the relative adsorption capacity, and the kinetic equilibrium constant. Our studies also reveal that the reactor geometry idealized as a slit, instead of a...
Comparison between Lagrangian and Eulerian approaches in predicting motion of micron-sized particles in laminar flows
, Article Atmospheric Environment ; Vol. 89, issue , 2014 , Pages 199-206 ; ISSN: 13522310 ; Rismanian, M ; Monjezi, M ; Zendehbad, M ; Fatehiboroujeni, S ; Sharif University of Technology
Abstract
Modeling the behavior of suspended particles in gaseous phase is important for diverse reasons; e.g. aerosol is usually the main subject of CFD simulations in clean rooms. Additionally, to determine the rate and sites of deposition of particles suspended in inhaled air, the motion of the particles should be predicted in lung airways. Meanwhile there are two basically different approaches to simulate the behavior of particles suspension, Lagrangian and Eulerian approaches. This study compares the results of these two approaches on simulating the same problem. An in-house particle tracking code was developed to simulate the motion of particles with Lagrangian approach. In order to simulate the...
Thorough tuning of the aspect ratio of gold nanorods using response surface methodology
, Article Analytica Chimica Acta ; Volume 779 , 2013 , Pages 14-21 ; 00032670 (ISSN) ; Robatjazi, H ; Jalali Heravi, M ; Sharif University of Technology
2013
Abstract
In the present work a central composite design based on response surface methodology (RSM) is employed for fine tuning of the aspect ratios of seed-mediated synthesized gold nanorods (GNRs). The relations between the affecting parameters, including ratio of l-ascorbic acid to Au3+ ions, concentrations of silver nitrate, CTAB, and CTAB-capped gold seeds, were explored using a RSM model. It is observed that the effect of each parameter on the aspect ratio of developing nanorods highly depends on the value of the other parameters. The concentrations of silver ions, ascorbic acid and seeds are found to have a high contribution in controlling the aspect ratios of NRs. The optimized parameters led...
Bioleaching kinetics of a spent refinery catalyst using Aspergillus niger at optimal conditions
, Article Biochemical Engineering Journal ; Volume 67 , 2012 , Pages 208-217 ; 1369703X (ISSN) ; Mousavi, S. M ; Yaghmaei, S ; Barati, M ; Sharif University of Technology
Elsevier
2012
Abstract
The kinetics of bioleaching of Mo, Ni, and Al from spent hydrocracking catalyst, using Aspergillus niger was studied. The four most effective bioleaching variables were selected in accordance with the Plackett-Burman design and were further optimized via central composite design (CCD). The optimal values of the variables for maximum multi-metal bioleaching were as follows: particle size 150-212. μm, sucrose 93.8. g/L, pulp density 3%. w/v, and pH 7. The maximum metal recoveries corresponding to these conditions were 99.5 ± 0.4% Mo, 45.8 ± 1.2% Ni, and 13.9 ± 0.1% Al. The relatively low Ni extraction was attributed to the precipitation of Ni in the presence of oxalic acid. Under the optimal...
Evaluating near highway air pollutant levels and estimating emission factors: Case study of Tehran, Iran
, Article Science of the Total Environment ; Volume 538 , December , 2015 , Pages 375-384 ; 00489697 (ISSN) ; Delavarrafiee, M ; Arhami, M ; Sharif University of Technology
Elsevier
2015
Abstract
A field sampling campaign was implemented to evaluate the variation in air pollutants levels near a highway in Tehran, Iran (Hemmat highway). The field measurements were used to estimate road link-based emission factors for average vehicle fleet. These factors were compared with results of an in tunnel measurement campaign (in Resalat tunnel). Roadside and in-tunnel measurements of carbon monoxide (CO) and size-fractionated particulate matter (PM) were conducted during the field campaign. The concentration gradient diagrams showed exponential decay, which represented a substantial decay, more than 50-80%, in air pollutants level in a distance between 100 and 150meters (m) of the highway. The...
Application of chitosan-citric acid nanoparticles for removal of chromium (VI)
, Article International Journal of Biological Macromolecules ; Volume 80 , September , 2015 , Pages 431-444 ; 01418130 (ISSN) ; Younesi, H ; Hajati, S ; Borghei, S. M ; Sharif University of Technology
Elsevier
2015
Abstract
In the present study, CS-CA nanoparticle was prepared for forming a new amide linkage, by grafting the amino groups of CS in the presence of carboxylic groups of CA that acts as cross-linking agent. The as-prepared CS-CA nanoparticle samples were characterized by use of dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier-transformed infrared spectroscopy (FTIR), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) techniques, which showed that the cross-linking agent preserved during the chemical modifications. The adsorption capacity of the CS-CA nanoparticles for the removal of Cr (VI) in aqueous solution was studied. The adsorption equilibrium data...
Investigating the effect of design parameters on the response time of a highly sensitive microbial hydrogen sulfide biosensor based on oxygen consumption
, Article Biosensors and Bioelectronics ; Volume 70 , 2015 , Pages 106-114 ; 09565663 (ISSN) ; Yazdian, F ; Amoabediny, G ; Hakim, M ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
A novel hydrogen sulfide microbial biosensor was developed based on investigating the influence of four design parameters: cell concentration, immobilization bed type, hydrogen sulfide concentration, and geometrical shape of the biosensor. Thiobacillus thioparus was used as the recognition element and it was immobilized on sodium alginate as well as agarose bed. The results were optimized by the application of statistical optimization software based on response time of the system. Oxygen reduction was considered as the detection sign. Sodium alginate solution with a concentration of 2.3% (w/v) and optical density of 10 at 605. nm was found as the optimum conditions for immobilization with...
Chitosan-gelatin sheets as scaffolds for muscle tissue engineering
, Article Artificial Cells, Nanomedicine and Biotechnology ; Volume 43, Issue 2 , Nov , 2015 , Pages 124-132 ; 21691401 (ISSN) ; Mashayekhan, S ; Nazaripouya, A ; Naji, M ; Hunkeler, D ; Rajabi Zeleti, S ; Sharifiaghdas, F ; Sharif University of Technology
Informa Healthcare
2015
Abstract
Hydrogels made of natural polymers [chitosan (CS) and gelatin (G)] have been prepared having mechanical properties similar to those of muscle tissues. In this study, the effect of polymer concentration and scaffold stiffness on the behavior of seeded muscle-derived cells (MDCs) on the CS-G hydrogel sheets has been evaluated. Both variables were found to be important in cell viability. Viability was assessed by observation of the cell morphology after 1 day as well as a 14-day MTT assay. The CS-G hydrogels were characterized using Fourier transform infrared (FTIR) analysis, which revealed evidences of strong intermolecular interactions between CS and G. Hydrogel samples with intermediate...
Polybutylene terephthalate-nickel oxide nanocomposite as a fiber coating
, Article Analytica Chimica Acta ; Volume 863, Issue 1 , 2015 , Pages 20-28 ; 00032670 (ISSN) ; Roostaie, A ; Sharif University of Technology
Elsevier
2015
Abstract
A highly efficient polybutylene terephthalate (PBT)-based nanocomposite containing nickel oxide nanoparticles was synthesized by electrospinning technique and used as a fiber coating for solid phase microextraction. The influential morphological parameters and capability of the prepared nanocomposite including the NiO content, the coating time, the PBT concentration and applied voltage were considered for optimization. The applicability of the synthesized fiber coating was examined by headspace solid phase micro extraction and gas chromatography mass spectrometry detection of some volatile organic compounds in aqueous samples. Among the synthesized nanocomposites and pristine PBT nanofibers,...
Simultaneous determination of epinephrine and acetaminophen concentrations using a novel carbon paste electrode prepared with 2,2′-[1,2 butanediylbis(nitriloethylidyne)]-bis-hydroquinone and TiO2 nanoparticles
, Article Colloids and Surfaces B: Biointerfaces ; Volume 76, Issue 1 , 2010 , Pages 82-87 ; 09277765 (ISSN) ; Beitollahi, H ; Sheikh Mohseni, M. A ; Benvidi, A ; Naeimi, H ; Nejati Barzoki, M ; Taghavinia, N ; Sharif University of Technology
2010
Abstract
A carbon paste electrode (CPE) modified with 2,2′-[1,2 butanediylbis(nitriloethylidyne)]-bis-hydroquinone (BBNBH) and TiO2 nanoparticles was used for the sensitive voltammetric determination of epinephrine (EP). The electrochemical response characteristics of the modified electrode toward EP and acetaminophen (AC) were investigated by cyclic and differential pulse voltammetry (CV and DPV). The results showed an efficient catalytic activity of the electrode for the electrooxidation of EP, which leads to a reduction in its overpotential by more than 270 mV. The effects of pH and potential sweep rate on the mechanism of the electrode process were investigated. The modified electrode exhibits an...
AFM spectral analysis of self-agglomerated metallic nanoparticles on silica thin films
, Article Current Nanoscience ; Volume 6, Issue 1 , 2010 , Pages 116-123 ; 15734137 (ISSN) ; Sharif University of Technology
2010
Abstract
Stochastic parameters of self-agglomerated metallic nanoparticles on a dielectric film surface were studied using atomic force microscopy (AFM) analysis. In this regard, the rough surfaces including the nanoparticles were analyzed and characterized using structure function, roughness exponent and power spectrum density of the AFM profiles and their gradients, for different metal concentrations and heat treatment temperatures. The diffusion parameters, such as activation energy, of the nanoparticles initially accumulated on the surface into a porous and aqueous silica thin film were obtained using the AFM spectral analysis of the profiles and their gradients. It was found that the tip...
Adsorption of proteins at the solution/air interface influenced by added non-ionic surfactants at very low concentrations for both components. 1. Dodecyl dimethyl phospine oxide
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 475, Issue 1 , June , 2015 , Pages 62-68 ; 09277757 (ISSN) ; Javadi, A ; Lylyk, S. V ; Bastani, D ; Fainerman, V. B ; Miller, R ; Sharif University of Technology
Abstract
The adsorption of proteins at liquid interfaces happens at rather low bulk concentrations due to their rather high surface activity. In contrast typical surfactants start to decrease the surface tension at bulk concentration in the range of mmol/l and reach a minimum value at about two or three orders of magnitude higher concentration. The two proteins studied here, β-lactoglobulin and β-casein, adsorb already remarkably at much lower concentrations, i.e. less than 1. μmol/l. When smallest amounts of a non-ionic surfactant are added to low concentrated protein solutions, changes in the surface tension are observed which cannot be explained by the existing theoretical models. An agreement...
Characterization of a microfluidic microbial fuel cell as a power generator based on a nickel electrode
, Article Biosensors and Bioelectronics ; Volume 79 , 2016 , Pages 327-333 ; 09565663 (ISSN) ; Yaghmaei, S ; Sharif University of Technology
Elsevier Ltd
2016
Abstract
This study reports the fabrication of a microfluidic microbial fuel cell (MFC) using nickel as a novel alternative for conventional electrodes and a non-phatogenic strain of Escherichia coli as the biocatalyst. The feasibility of a microfluidic MFC as an efficient power generator for production of bioelectricity from glucose and urea as organic substrates in human blood and urine for implantable medical devices (IMDs) was investigated. A maximum open circuit potential of 459mV was achieved for the batch-fed microfluidic MFC. During continuous mode operation, a maximum power density of 104Wm-3 was obtained with nutrient broth. For the glucose-fed microfluidic MFC, the maximum power density of...
The highest inhibition coefficient of phenol biodegradation using an acclimated mixed culture
, Article Water Science and Technology ; Volume 73, Issue 5 , 2016 , Pages 1033-1040 ; 02731223 (ISSN) ; Sharifi Abdar, P. S ; Borghei, S. M ; Sharif University of Technology
IWA Publishing
2016
Abstract
In this study a membrane biological reactor (MBR) was operated at 25±1 °C and pH = 7.5±0.5 to treat synthetic wastewater containing high phenol concentrations. Removal efficiencies of phenol and chemical oxygen demand (COD)were evaluated at four various hydraulic retention times (HRTs) of 24, 12, 8, and 4 hours. The removal rate of phenol (5.51 kg-Phenol kg-VSS-1 d-1), observed at HRT of 4 h,was the highest phenol degradation rate in the literature.According toCODtests, therewere no significant organic matter in the effluent, and phenol was degraded completely by mixed culture. Substrate inhibition was calculated from experimental growth parameters using the Haldane, Yano, and Edward...