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Application of a continuous kinetic model for the hydrocracking of vacuum gas oil
, Article Petroleum Science and Technology ; Vol. 32, Issue. 18 , 2014 , Pages 2245-2252 ; ISSN: 10916466 ; Khorasheh, F ; Farhadi, F ; Sharif University of Technology
Abstract
Hydrocracking is one of the most versatile petroleum refining processes for production of valuable products including gasoline, gas oil, and jet fuel. In this paper, a five-parameter continuous lumping model was used for kinetic modeling of hydrocracking of vacuum gas oil (VGO). The model parameters were estimated from industrial data obtained from a fixed bed reactor operating at an average temperature of 400°C and residence time of 0.3 h. Product distributions were obtained in terms of the weight fraction of various boiling point cuts. The model parameters were estimated using the Nelder-Mead optimization procedure and were correlated with temperature. Comparison of experimental and...
A new model based on multilayer kinetic adsorption mechanism for asphaltenes adsorption in porous media during dynamic condition
, Article Fluid Phase Equilibria ; Vol. 375, issue , 2014 , Pages 236-245 ; ISSN: 03783812 ; Ghotbi, C ; Taghikhani, V ; Shahrabadi, A ; Sharif University of Technology
Abstract
In this work, a new model based on multilayer kinetic adsorption mechanism has been proposed to account asphaltene adsorption in porous media under dynamic condition and the model was verified using experimental data obtained in this work and also with those reported in the literature. In the proposed model two steps are considered for asphaltene adsorption. The first step is taken as adsorption of asphaltenes on the surface of the porous media and the second step is taken as adsorption of asphaltenes on the asphaltenes already adsorbed on the porous media. The Crank-Nicholson method, central difference in space and trapezoidal rule in time, giving second order convergence in time was...
The modeling of kinetics and catalyst deactivation in propane dehydrogenation over Pt-Sn/γ-Al2O3 in presence of water as an oxygenated additive
, Article Petroleum Science and Technology ; Vol. 32, issue. 10 , Mar , 2014 , pp. 1139-1149 ; ISSN: 10916466 ; Fattahi, M ; Khorasheh, F ; Sharif University of Technology
Abstract
A reduction in catalyst's activity with time-on-stream and the formation of side products are two of the problems associated with catalytic propane dehydrogenation (PDH). Previous studies have indicated that the presence of small amounts of oxygenated additives such as water can reduce coke formation and enhance catalyst activity. The aim of the present work was to develop an appropriate kinetic model for PDH over a commercial Pt-Sn/γ-Al 2O3 catalyst in the presence of small amounts of water. Experimental data were obtained from a previous study where catalytic PDH was carried out in a bench scale reactor system at atmospheric pressure in the temperature range of 575-620°C in the presence of...
Effects of Ti-based catalysts on hydrogen desorption kinetics of nanostructured magnesium hydride
, Article International Journal of Hydrogen Energy ; Volume 39, Issue 36 , December , 2014 , Pages 21007–21014 ; ISSN: 03603199 ; Simchi, A ; Sadati, M ; Hosseini, H. M ; Targholizadeh, H ; Khakbiz, M ; Sharif University of Technology
Abstract
In the present work, the synergetic effect of Ti-based catalysts (TiH2 and TiO2 particles) on hydrogen desorption kinetics of nanostructured magnesium hydride was investigated. Nanostructured 84mol% MgH2-10%mol TiH2-6%mol TiO2 nanocomposite powder was prepared by high-energy ball milling and subjected to thermal analyses. Evaluation of the absorption/desorption properties revealed that the addition of the Ti-based catalysts significantly improved the hydrogen storage performance of MgH2. A decrease in the decomposition temperature (as high as 100°C) was attained after co-milling of MgH2 with the Ti-based catalysts. Meanwhile, solid-state chemical reactions between MgH2 and TiO2 nanoparticles...
Possible role for growth hormone in suppressing acylated ghrelin and hunger ratings during and after intermittent exercise of different intensities in obese individuals
, Article Acta Medica Iranica ; Vol. 52, Issue. 1 , 2014 , pp. 29-37 ; ISSN: 1735-9694 ; Kordi, M. R ; Taghikhani, M ; Ravasi, A. A ; Gaeini, A. A ; Tabrizi, A ; Sharif University of Technology
Abstract
Body weight is influenced by both food intake and energy expenditure. Acylated ghrelin enhances appetite, and its circulating level is suppressed by Growth Hormone. Data on the acylated ghrelin responses to exercise of different intensities in obese individuals are currently not available. This study examined the effects of an intermittent exercise protocol on acylated ghrelin levels and hunger ratings in obese people. Nine inactive male ran on the treadmill at 0900 with progressive intensities of 50, 60, 70, and 80% of VO2max for 10, 10, 5, and 2 min respectively. Blood samples were collected before the exercise at 0845 (-15 min as the resting values), after each workload (10, 23, 31, and...
Synthesizing and staining manganese oxide nanoparticles for cytotoxicity and cellular uptake investigation
, Article Biochimica et Biophysica Acta - General Subjects ; Vol. 1840, Issue. 1 , 2014 , pp. 428-433 ; ISSN: 03044165 ; Oghabian, M. A ; Ahmadi, R ; Shahbazi, N ; Hosseini, H. R. M ; Shanehsazzadeh, S ; Zangeneh, R. N ; Sharif University of Technology
Abstract
Background For decades, contrast agents have been used to reduce longitudinal (T1) or transverse (T2) relaxation times. High toxicity of gadolinium-based contrast agents leads researchers to new T1 contrast agents. Manganese oxide (MnO) nanoparticle (NP) with the lower peril and good enough signal change ability has been offered as a new possibility for magnetic resonance imaging (MRI). Methods The synthesized NPs were investigated for physicochemical and biological properties by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscope, dynamic light scattering (DLS), inductively coupled plasma, enzyme-linked immunosorbent assay, and 3 T magnetic resonance...
DNA and RNA extractions from eukaryotic and prokaryotic cells by graphene nanoplatelets
, Article RSC Advances ; Vol. 4, issue. 105 , 2014 , p. 60720-60728 ; Akhavan, O ; Shamsara, M ; Valimehr, S ; Rahighi, R ; Sharif University of Technology
Abstract
Graphene nanoplatelets with lateral dimensions of ∼50-200 nm and thicknesses <2 nm were utilized for the extraction of nucleic acids (NAs) from eukaryotic and prokaryotic cells. The graphene nanoplatelets (both chemically exfoliated graphene oxide nanoplatelets and hydrazine-reduced graphene oxide nanoplatelets) successfully extracted plasmid DNA (pDNA) from Escherichia coli bacteria, comparable to a conventional phenol-chloroform (PC) method. Furthermore, it was found that the yield of graphene nanoplatelets in genomic DNA (gDNA) and RNA extractions from embryonic stem cells (ESCs) was also comparable to the yield of the conventional methods. The effects of the graphene nanoplatelets on...
The effect of conventional immunosuppressive therapy on cytokine serum levels in pemphigus vulgaris patients
, Article Iranian Journal of Allergy, Asthma and Immunology ; Vol. 13, issue. 3 , June , 2014 , p. 174-183 ; 17351502 ; Esmaili, N ; Khezri, S ; Khamesipour, A ; Farahani, I. V ; Daneshpazhooh, M ; Rezaei N ; Sharif University of Technology
Abstract
Pemphigus vulgaris is an autoimmune disease, in which the role of Th17 cytokines needs to be further explored. This study was performed to assess serum levels of three interleukins (IL) required for Th17 differentiation (IL-β, IL-6 and IL-23) and two specific Th17 cytokines (IL- 17 and IL-22) in a group of patients with pemphigus vulgaris, at baseline, 3 weeks and 6 months after of treatment. Correlations between anti-desmogleins and cytokines with disease severity as well as the influence of therapy on the above factors were assessed. Forty-three first-admitted pemphigus vulgaris patients with the active disease entered the study, but only 31 completed the study. Forty-five healthy...
Modeling of coke formation and catalyst deactivation in propane dehydrogenation over a commercial Pt-Sn/γ-Al2O3 catalyst
, Article Petroleum Science and Technology ; Volume 31, Issue 23 , 2013 , Pages 2451-2462 ; 10916466 (ISSN) ; Soltani, M ; Farjoo, A ; Khorasheh, F ; Sharif University of Technology
2013
Abstract
Propane dehydrogenation was carried over a commercial Pt-Sn/γ-Al 2O3 catalyst at atmospheric pressure and reaction temperatures of 580, 600, and 620°C and WHSV of 11 h-1 in an experimental tubular quartz reactor. Propane conversions were measured for catalyst time on stream of up to nine days. The amounts of coke deposited on the catalyst were measured after one, three, six, and nine days on stream using a thermogravimetric differential thermal analyzer (TG-DTA) for each reaction temperature. The coke formation kinetics was successfully described by a coke formation model based on a monolayer-multilayer mechanism. In addition, catalyst deactivation was presented by a time-dependant...
Effects of temperature shifts and oscillations on recombinant protein production expressed in Escherichia coli
, Article Bioprocess and Biosystems Engineering ; Volume 36, Issue 11 , 2013 , Pages 1571-1577 ; 16157591 (ISSN) ; Herwig, C ; Sharif University of Technology
2013
Abstract
Escherichia coli is widely used host for the intracellular expression of many proteins. However, in some cases also secretion of protein from periplasm was observed. Improvement of both intracellular and extracellular production of recombinant protein in E. coli is an attractive goal in order to reduce production cost and increase process efficiency and economics. Since heat shock proteins in E. coli were reported to be helpful for protein refolding and hindering aggregation, in this work different types of single and periodic heat shocks were tested on lab scale to enhance intracellular and extracellular protein production. A single heat shock prior to induction and different oscillatory...
Evaluation of biodiesel production using lipase immobilized on magnetic silica nanocomposite particles of various structures
, Article Biochemical Engineering Journal ; Volume 79 , 2013 , Pages 267-273 ; 1369703X (ISSN) ; Kazemeini, M ; Arpanaei, A ; Sharif University of Technology
2013
Abstract
Nonporous and mesoporous silica-coated magnetite cluster nanocomposites particles were fabricated with various silica structures in order to develop a desired carrier for the lipase immobilization and subsequent biodiesel production. Lipase from Pseudomonas cepacia was covalently bound to the amino-functionalized particles using glutaraldehyde as a coupling agent. The hybrid systems that were obtained exhibited high stability and easy recovery regardless of the silica structure, following the application of an external magnetic field. The immobilized lipases were then used as the recoverable biocatalyst in a transesterification reaction to convert the soybean oil to biodiesel with methanol....
Tissue growth into three-dimensional composite scaffolds with controlled micro-features and nanotopographical surfaces
, Article Journal of Biomedical Materials Research - Part A ; Volume 101, Issue 10 , 2013 , Pages 2796-2807 ; 15493296 (ISSN) ; Simchi, A ; Dunlop, J. W. C ; Fratzl, P ; Bagheri, R ; Vossoughi, M ; Sharif University of Technology
2013
Abstract
Controlling topographic features at all length scales is of great importance for the interaction of cells with tissue regenerative materials. We utilized an indirect three-dimensional printing method to fabricate polymeric scaffolds with pre-defined and controlled external and internal architecture that had an interconnected structure with macro- (400-500 μm) and micro- (∼25 μm) porosity. Polycaprolactone (PCL) was used as model system to study the kinetics of tissue growth within porous scaffolds. The surface of the scaffolds was decorated with TiO2 and bioactive glass (BG) nanoparticles to the better match to nanoarchitecture of extracellular matrix (ECM). Micrometric BG particles were...
Screening and optimization of effective parameters in biological extraction of heavy metals from refinery spent catalysts using a thermophilic bacterium
, Article Separation and Purification Technology ; Volume 118 , October , 2013 , Pages 151-161 ; 13835866 (ISSN) ; Ghojavand, F ; Mousavi, S. M ; Yaghmaei, S ; Amiri, F ; Sharif University of Technology
2013
Abstract
This research aimed at finding the factors with more impact on the bioleaching of a spent hydrocracking catalyst by thermophilic acidophilic archaea called Acidianus brierleyi and determining the optimal condition in order to reach the maximum metals recovery. Initially, four more significant factors affecting the bioleaching efficiency including pH, pulp density, inoculation and elemental sulfur concentration, were screened and identified among ten key factors using Plackett-Burman factorial design. Next, a central composite design was applied to obtain the optimum conditions for achieving the maximum efficiency of the bioleaching process. pH 1.6, pulp density 0.6% (w/v), inoculation 4%...
Magnetic labelled horseradish peroxidase-polymer nanoparticles: A recyclable nanobiocatalyst
, Article Journal of the Serbian Chemical Society ; Volume 78, Issue 7 , 2013 , Pages 921-931 ; 03525139 (ISSN) ; Vossoughi, M ; Shahrokhian, S ; Alemzadeh, I ; Sharif University of Technology
2013
Abstract
In this study, the reusability and process stability of nano-reengineered horseradish peroxidase was investigated in a fluorescence-based sensing system for hydrogen peroxide determination as a model application. To this end, dendron macromolecules were attached to the enzyme surface through bio-conjugation techniques. The resulting enzyme-polymer nanoparticles, with an average size of 14(±2) nm, showed significant life time and thermal stability. For enzyme recovery and reusability purposes, the enzyme-polymer nanoparticles were labelled with magnetic nanoparticles with a labelling yield of 90 %. These labelled enzyme molecules showed significant process stability, i.e., up to 7 recycling...
Alkaline protease production by immobilized cells using B. licheniformis
, Article Scientia Iranica ; Volume 20, Issue 3 , 2013 , Pages 607-610 ; 10263098 (ISSN) ; Kazemi, A ; Nahid, P ; Yaghmaei, S ; Sabzevari, M. A ; Sharif University of Technology
2013
Abstract
In recent years there has been potential increase in the use of alkaline protease as industrial catalysts. Many major industrial and commercial applications, such as food and textile industries, and medical diagnoses, are highly dependent on the protease enzyme. In the cell immobilization technique, the free movement of microorganisms is restricted in the process, and a continuous system of fermentation can be used. In the present work, this technique has been used for alkaline protease production using different carriers, such as chitosan, corn cob and corn tassel. Enzyme activity before immobilization (72 h) was 78.3 U/ml. Corn cob, with 65% immobilization capacity and the highest enzyme...
Studies on glutaraldehyde crosslinked chitosan hydrogel properties for drug delivery systems
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 62, Issue 11 , 2013 , Pages 605-611 ; 00914037 (ISSN) ; Ramazani, S. A. A ; Shafiee, M ; Danaei, M ; Sharif University of Technology
2013
Abstract
Chitosan was crosslinked with different amount of glutaraldehyde to prepare appropriate hydrogels to be used as drug delivery system. The swelling behavior of freeze-dried hydrogels in aqueous media at different temperature and pHs has been examined. The swelling, porosity and biocompatibility behavior of samples were investigated to check effects of polymer/polymer and polymer/drug interactions on these system characteristics. Obtained experimental results illustrates that with increasing crosslinking agent from 0.068 to 0.30, swelling of the prepared samples degrees from 1200% to 600% and pore diameters change from 100 to 500 μm. To investigate systems biocompatibility in gastric...
Spectrophotometric determination of sulfide based on peroxidase inhibition by detection of purpurogallin formation
, Article Ecotoxicology and Environmental Safety ; Volume 91 , 2013 , Pages 117-121 ; 01476513 (ISSN) ; Kariminia, H. R ; Roosta Azad, R ; Sharif University of Technology
2013
Abstract
This paper presents a new method for spectrophotometirc detection of sulfide applying fungal peroxidase immobilized on sodium alginate. The sensing scheme was based on decrease of the absorbance of the orange compound, purpurogallin produced from pyrogallol and H2O2 as substrates, due to the inhibition of peroxidase by sulfide. Absorbance of purpurogallin was detected at 420nm by using a spectrophotometer. The proposed method could successfully detect the sulfide in the concentration range of 0.6-7.0μM with a detection limit of 0.4μM. The kinetic parameters of Michaelis-Menten with and without sulfide were also calculated. Possible inhibition mechanism of peroxidase by sulfide was deduced...
Kinetics and reaction mechanism of isothermal oxidation of Iranian ilmenite concentrate powder
, Article Journal of Thermal Analysis and Calorimetry ; Volume 112, Issue 2 , 2013 , Pages 781-789 ; 13886150 (ISSN) ; Sadrnezhaad, S. K ; Khoshnevisan, A ; Youzbashizadeh, H ; Sharif University of Technology
2013
Abstract
Thermal oxidation of commercial ilmenite concentrate from Kahnouj titanium mines, Iran, at 500-950 C was investigated for the first time. Fractional conversion was calculated from mass change of the samples during oxidation. Maximum FeO to Fe2O3 conversion of 98.63 % occurred at 900 C after 120 min. Curve fit trials together with SEM line scan results indicated constant-size shrinking core model as the closest kinetic mechanism of the oxidation process. Below 750 C, chemical reaction with activation energy of 80.65 kJ mol-1 and between 775 and 950 C, ash diffusion with activation energy of 53.50 kJ mol-1 were the prevailing mechanisms. X-ray diffraction patterns approved presence of...
Two nanostructured polymers: Polyaniline nanofibers and new linear-dendritic matrix of poly(citric acid)-block-poly(ethylene glycol) copolymers for environmental monitoring in novel biosensors
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 62, Issue 7 , Jul , 2013 , Pages 377-383 ; 00914037 (ISSN) ; Vossoughi, M ; Alemzadeh, I ; Naeini, A. T ; Darvish, M ; Sharif University of Technology
2013
Abstract
In this work two phenol biosensors, one based on polyaniline nanofibers (PNFs) and the other based on the newly created and introduced linear-dendritic matrix of poly(citric acid)-block-poly(ethylene glycol) copolymers (PCA-PEG-PCA), were chemically modified with horseradish peroxidase (HRP) enzyme. These phenol biosensors showed an oxidation peak at 0.55 V. The amperometric response for biosensors based on PNFs showed a linear response range from 2.5 × 10-6 to 2.5 × 10-5 mol/L, with a detection limit of 2.5 M phenol. Also, the amperometric response for a biosensor based on PCA-PEG-PCA showed a linear response range from 2.5 × 10-6 to 4 × 10-5 mol/L, with a detection limit of 1.5 M phenol
The comparision of Coprinus cinereus peroxidase enzyme and TiO 2 catalyst for phenol removal
, Article Journal of Environmental Science and Health - Part A Toxic/Hazardous Substances and Environmental Engineering ; Volume 48, Issue 3 , 2013 , Pages 300-307 ; 10934529 (ISSN) ; Tavakoli, O ; Sarrafzadeh, M. H ; Kariminia, H. R ; Sharif University of Technology
2013
Abstract
This article investigates phenol removal from an aqueous solution by using enzymatic and photocatalytic methods and the efficiency of these methods has been compared. In enzymatic and photocatalytic methods, Coprinus cinereus, peroxidase enzyme and commercial TiO2 powders (Degussa P-25) in aqueous suspension were used, respectively, in ambient temperature. The effects of different operating parameters such as duration of process, catalyst dosage or enzyme concentration, pH of the solution, initial phenol concentration and H2O2 concentration on both processes were examined. In enzymatic method, efficiency of degradation reached 100% within 5min, while in the photocatalytic method, the...