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    Modeling catalyst deactivation in dehydrogenation of ethylbenzene to styrene

    , Article 11AIChE - 2011 AIChE Spring Meeting and 7th Global Congress on Process Safety, Conference Proceedings ; 2011 , Pages - ; 9780816910670 (ISBN) Babaei, J ; Baghalha, M ; Sharif University of Technology
    American Institute of Chemical Engineers  2011
    Abstract
    The long-term deactivation of a commercial K-promoted Fe2O3 catalyst used in the dehydrogenation of ethylbenzene to styrene monomer was investigated using 30 mo of operating data of three industrial SM radial fixed bed adiabatic reactors. The Langmuir-Hinshelwood, Hougen-Watson model was used for reaction kinetics modeling. The kinetics of coking from ethylbenzene and styrene and the short-term deactivation function due to the quick coke formation were considered in the model. The kinetics of long-term deactivation of the catalyst for ethylbenzene dehydrogenation to styrene at 550°-630°C were determined. Unknown parameters of the long-term activity function, related to the slow loss of... 

    Polypropylene foaming in a reactive process

    , Article Journal of Cellular Plastics ; Volume 43, Issue 6 , 2007 , Pages 445-458 ; 0021955X (ISSN) Frounchi, M ; Sharif Pakdaman, A ; Mousavi, S. A ; Dadbin, S ; Sharif University of Technology
    2007
    Abstract
    Long-chain branches are incorporated into the molecular backbone of a polypropylene (PP) in a foaming process. The branching of PP occurs by radical reactions of dicumyl peroxide and a tri-functional monomer, trimethylol propane trimethacrylate. Use of peroxide without tri-functional monomer results in scission of PP molecular chains and significant reduction in melt viscosity. The increase in melt viscosity in conjunction with the flow ability of the modified PP indicates that the polymer has a branched structure. Melting temperature of PP remains unchanged with branching reactions implying that reactions occur mainly in amorphous regions of PP. The improvement in melt strength and... 

    Irradiation mediated synthesis of a superabsorbent hydrogel network based on polyacrylamide grafted onto salep

    , Article Nuclear Instruments and Methods in Physics Research, Section B: Beam Interactions with Materials and Atoms ; Volume 266, Issue 18 , September , 2008 , Pages 3932-3938 ; 0168583X (ISSN) Rezanejade Bardajee, G ; Pourjavadi, A ; Soleyman, R ; Sheikh, N ; Sharif University of Technology
    2008
    Abstract
    The synthesis and swelling behavior of a new superabsorbent hydrogel based on natural salep grafted with polyacrylamide is described. The new biopolymer was synthesized via simultaneous crosslinking and graft copolymerization of acrylamide monomer onto a salep backbone using radiochemical methods. Various parameters such as relative contents of salep and acrylamide, as well as total dose of γ-rays were examined. The best synthesis condition is reported and a mechanism for superabsorbent hydrogel formation suggested. Factors affecting the swelling behavior of hydrogel were also studied. © 2008 Elsevier B.V. All rights reserved  

    Novel polyelectrolyte gels as absorbent polymers for nonpolar organic solvents based on polymerizable ionic liquids

    , Article Polymer (United Kingdom) ; Volume 53, Issue 25 , 2012 , Pages 5737-5742 ; 00323861 (ISSN) Pourjavadi, A ; Doulabi, M ; Hosseini, S. H ; Sharif University of Technology
    2012
    Abstract
    Novel class of polyelectrolyte gels based on the copolymer of vinylimidazolium-typed ionic liquid monomer and Dodecyl methacrylate was prepared by free radical polymerization. A small amount of 3-n-Dodecyl-1- vinylimidazolium tetrafluoroborate is incorporated into crosslinked polyacrylates to provide new lipophilic polyelectrolyte gels that evaluated for swelling in less-polar and nonpolar organic solvents. Their swelling degree becomes more than 50 times as much as their dried weights in some organic solvents. By varying the polarity of the neutral monomer in these polyelectrolyte gels, the design of gels that can absorb solvents of nearly any polarity is demonstrated. The present... 

    The role of mscl amphipathic n terminus indicates a blueprint for bilayer-mediated gating of mechanosensitive channels

    , Article Nature Communications ; Volume 7 , 2016 ; 20411723 (ISSN) Bavi, N ; Cortes, D. M ; Cox, C. D ; Rohde, P. R ; Liu, W ; Deitmer, J. W ; Bavi, O ; Strop, P ; Hill, A. P ; Rees, D ; Corry, B ; Perozo, E ; Martinac, B ; Sharif University of Technology
    Nature Publishing Group  2016
    Abstract
    The bacterial mechanosensitive channel MscL gates in response to membrane tension as a result of mechanical force transmitted directly to the channel from the lipid bilayer. MscL represents an excellent model system to study the basic biophysical principles of mechanosensory transduction. However, understanding of the essential structural components that transduce bilayer tension into channel gating remains incomplete. Here using multiple experimental and computational approaches, we demonstrate that the amphipathic N-terminal helix of MscL acts as a crucial structural element during tension-induced gating, both stabilizing the closed state and coupling the channel to the membrane. We... 

    Adhesion modification of polyethylenes for metallization using radiation-induced grafting of vinyl monomers

    , Article Surface and Coatings Technology ; Volume 201, Issue 16-17 , 2007 , Pages 7519-7529 ; 02578972 (ISSN) Shojaei, A ; Fathi, R ; Sheikh, N ; Sharif University of Technology
    2007
    Abstract
    The present paper demonstrates the performance of the radiation grafting technique as a chemically based surface pretreatment method to adhesion modification of polyethylene surfaces toward the metallic layer. Gamma irradiation over a dose range of 4-10 kGy is used for grafting of vinyl monomers including acrylamide (AAm) and 1-vinyl-2-pyrrolidone (NVP) onto the surface of three different polyethylenes including low density polyethylene (LDPE) and two kinds of high density polyethylenes, namely HDPE-1 and HDPE-2. The grafting yield is evaluated based on the weight increase of the samples. It is found that the grafting yield is dominated by the crystallinity of the polyethylene, so that lower... 

    Synthesis, characterization, and kinetic investigation of acrylic monomers derived from acetaminophen and ρ-cresol as model drug molecules

    , Article Journal of Applied Polymer Science ; Volume 100, Issue 6 , 2006 , Pages 4369-4374 ; 00218995 (ISSN) Vezvaie, M ; Taghizadeh, S. M ; Gholami, M. R ; Sharif University of Technology
    2006
    Abstract
    In this work, the synthesis, characterization, and kinetic investigation of the free-radical polymerization of 4-acetylaminobenzene propenoic ester (ABPE) and 4-methylbenzene propenoic ester (MBPE) were studied. The kinetic behaviors of ABPE and MBPE in the polymerization initiated by azobisisobutyronitrile in dimethylformamide solutions at temperatures between 50 and 120°C were investigated, and experimental and theoretical conversion-time curves were compared. Both monomers showed a polymerization ceiling temperature (T c ). Tc was calculated with experimental values of k pk1/2 with a constant concentration of 0.7 mol/L for monomers. Tc was about 141 and 131 °C for ABPE and MBPE,... 

    Geometry selects highly designable structures

    , Article Journal of Chemical Physics, Woodbury, NY, United States ; Volume 113, Issue 15 , 2000 , Pages 6437-6442 ; 00219606 (ISSN) Shahrezaei, V ; Ejtehadi, M. R ; Sharif University of Technology
    American Inst of Physics  2000
    Abstract
    The designability of structures in a two-dimensional hydrophobic-polar (HP) pair contact lattice model in a wide range of intermonomer interaction parameters was studied by considering HP constraints. The designability of all structures was clarified by enumerating all sequences of length 20. Results confirm that changing the intermolecular interactions affects the structure designability and also chooses the search space of the native state but the set of HDSs is invariant  

    Synthesis of Bone graft Substitute for Clinical Applications

    , M.Sc. Thesis Sharif University of Technology Khodabakhshi Tabar Ahangar, Zahra (Author) ; Abdekhodaie, Mohammad Jafar (Supervisor)
    Abstract
    The natural tissue of the bones consists of organic and inorganic parts. The bone mineral part contains calcium phosphate and its organic part is mainly of collagen fibers. The combination of these fibers and calcium phosphate makes the bone flexible and resistant to stresses. Many conditions, including osteoporosis and crashes, lead to fractures and cavities in bone. Bone cements are the most used materials used in orthopedic surgeries and spinal cord.The purpose of this study was to synthesis acrylic bone cement with properties determined by ASTM F 451 and Iso5833 for orthopedic applications, including joint replacement. Polymethyl methacrylate polymer was synthesized as the main component... 

    Multiwalled carbon nanotube-polyelectrolyte gels: Preparation and swelling behavior for organic solvents

    , Article Solid State Ionics ; Vol. 257 , 2014 , pp. 32-37 ; ISSN: 01672738 Pourjavadi, A ; Doulabi, M ; Sharif University of Technology
    Abstract
    In this article, we report the first multiwalled carbon nanotube-polyelectrolyte gel containing vinylimidazolium-typed ionic liquid monomer as an absorbent of less-polar or nonpolar organic solvents. To prepare such MWCNT-polyelectrolyte gel, the modified MWCNTs with polymerizable vinyl groups on their surfaces were prepared and then underwent copolymerizations with dodecyl methacrylate and vinylimidazolium in the presence of AIBN as initiator, yielding a cross-linked polyelectrolyte. In order to estimate the compatibility between the solvents and the polymers, a series of vinylimidazolium-typed ionic liquid monomers ([Cnvim][X]) with different alkyl tail length (C6, C10 and C12) and counter... 

    Sequence dependence of the binding energy in chaperone-driven polymer translocation through a nanopore

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 83, Issue 1 , January , 2011 ; 15393755 (ISSN) Abdolvahab, R. H ; Ejtehadi, M. R ; Metzler, R ; Sharif University of Technology
    2011
    Abstract
    We study the translocation of stiff polymers through a nanopore, driven by the chemical-potential gradient exerted by binding proteins (chaperones) on the trans side of the pore. Bound chaperones prevent backsliding through the pore and, therefore, partially rectify the polymer passage. We show that the sequence of chain monomers with different binding affinity for the chaperones significantly affects the translocation dynamics. In particular, we investigate the effect of the nearest-neighbor adjacency probability of the two monomer types. Depending on the magnitude of the involved binding energies, the translocation speed may either increase or decrease with the adjacency probability. We... 

    Simulation and control of monomer conversion in a continuous emulsion polymerization reactor

    , Article IFAC Proceedings Volumes (IFAC-PapersOnline), 7 June 2015 through 10 June 2015 ; Volume 48, Issue 8 , 2015 , Pages 315-320 ; 14746670 (ISSN) Barazandegan, M ; Shahrokhi, M ; Abedini, H ; Vafa, E ; Guay, M ; Gopaluni, B ; Huang, B ; Findeisen, R ; Sharif University of Technology
    IFAC Secretariat  2015
    Abstract
    A detailed pseudo-bulk model has been used for prediction of conversion and particle size distribution (PSD) of vinyl acetate in a continuous emulsion polymerization reactor. Finite volume (FV) and moment techniques are applied for solving population balance equation under continuous operation. It is found that both methods can predict sustained oscillations in the monomer conversion, however the FV method matches the experimental data better than the moment method. The monomer conversion and free surfactant concentration are controlled via two single control loops. In this work, a new control strategy for controlling monomer conversion has been proposed. It has been shown that monomer... 

    Modified carrageenan. 4. Synthesis and swelling behavior of crosslinked ΚC-g-AMPS superabsorbent hydrogel with antisalt and pH-responsiveness properties

    , Article Journal of Applied Polymer Science ; Volume 98, Issue 1 , 2005 , Pages 255-263 ; 00218995 (ISSN) Pourjavadi, A ; Hosseinzadeh, H ; Mazidi, R ; Sharif University of Technology
    2005
    Abstract
    To synthesize a novel biopolymer-based superabsorbent hydrogel, 2-acrylamido-2-methylpropanesulfonic acid (AMPS) was grafted onto kappa-carrageenan (ΚC) backbones. The graft copolymerization reaction was carried out in a homogeneous medium and in the presence of ammonium persulfate (APS) as an initiator, N,N,N′,N′-tetramethyl ethylenediamine (TMEDA) as an accelerator, and N,N′-methylene bisacrylamide (MBA) as a crosslinker. A proposed mechanism for ΚC-g-AMPS formation was suggested and the hydrogel structure was confirmed using FTIR spectroscopy. The affecting variables on swelling capacity, i.e., the initiator, the crosslinker, and the monomer concentration, as well as reaction temperature,... 

    Synthesis and Investigation of Properties of Intumescent Fireproofing Paint with Oxide Nanoparticles

    , M.Sc. Thesis Sharif University of Technology Hasannezhad, Asghar (Author) ; Dolati, Abolghasem (Supervisor)
    Abstract
    Intumescent paints are coatings designed for passive fire protection of steel and other materials. In this research, the performance of water-based intumescent coating with vinyl acetate resin for cellulose fire conditions and epoxy-based coatings for hydrocarbon fire conditions has been investigated. The fire resistance of coatings was evaluated according to the ASTM E119 standard for water-based coating and UL1709 standard for epoxy-based intumescent coating. For the water-based intumescent coating, the expansion of char was investigated in a furnace with a temperature of 800°C for 1 hour. Thermal decomposition was studied by thermogravimetric analysis (TGA). Also, flammability was... 

    Submicron nanoporous polyacrylamide beads with tunable size for verapamil imprinting

    , Article Journal of Applied Polymer Science ; Volume 125, Issue 1 , 2012 , Pages 189-199 ; 00218995 (ISSN) Nematollahzadeh, A ; Abdekhodaie, M. J ; Shojaei, A ; Sharif University of Technology
    2012
    Abstract
    Submicron sized polyacrylamide particles were prepared via modified precipitation polymerization method. Experimental design based on Taguchi approach was employed to study the influence of the polymerization composition including monomer (acrylamide), crosslinker (methylenebisacrylamide), initiator (azobisisobutyronitrile), and modifier (polyvinylpyrrolidone, K-30), on the size and morphology of the particles. Varying the polymerization composition, submicron-particles with sizes ranging between 100 and 600 nm were achieved. In all the cases, polydispersity index (PDI) of the particle size was found to be almost 1 indicating uniformity of the particle size. The concentration of crosslinker... 

    Inhibition mechanisms of a pyridazine-based amyloid inhibitor: as a β-sheet destabilizer and a helix bridge maker

    , Article Journal of Physical Chemistry B ; Volume 121, Issue 32 , 2017 , Pages 7633-7645 ; 15206106 (ISSN) Kalhor, H. R ; Jabbari, M. P ; Sharif University of Technology
    Abstract
    Conformational diseases have been investigated extensively in recent years; as a result, a number of drug candidates have been introduced as amyloid inhibitors; however, no effective therapies have been put forward. RS-0406 with pyridazine as its core chemical structure has so far shown promising results in inhibiting amyloid formation. In the present work, using molecular dynamics, we undertook the investigation of RS-0406 interactions with U-shaped Aβ1−42 and Aβ1−40 pentamers, Aβ1−42 monomers, and double-horseshoe-like Aβ1−42. To set better parameters for the small molecule, experimental and computational log P values were obtained. In addition, an analogue of RS-0406 was also simulated... 

    Optimization of synthesis conditions of a novel carrageenan-based superabsorbent hydrogel by taguchi method and investigation of its metal ions adsorption

    , Article Journal of Applied Polymer Science ; Volume 107, Issue 5 , 2008 , Pages 2970-2976 ; 00218995 (ISSN) Pourjavadi, A ; Amini Fazl, M. S ; Barzegar, Sh ; Sharif University of Technology
    2008
    Abstract
    The Taguchi method, a robust experimental design, was used for optimization of synthesis of a novel biopolymer-based superabsorbent hydrogel, kappa-carrageenan (K-C)-g-acrylic acid (AA)-co-2-acrylamido-2- methylpropanesulfonic acid (AMPS). The Taguchi method was applied for the experimental and standard 18 orthogonal arrays (OA) with seven factors and three levels for each factor. In the synthesis of the superabsorbent, N,N'-methylene bisacrylamide (MBA) as crosslinker, ammonium persulfate (APS) as initiator, monomer ratio (AA/AMPS), K-C concentration, Total Monomer, neutralization percent (NU), and reaction temperature were used as important factors. After analyzing with analysis of... 

    Optimized synthesis of carrageenan-graft-poly(sodium acrylate) superabsorbent hydrogel using the Taguchi method and investigation of its metal ion absorption

    , Article Polymer International ; Volume 56, Issue 2 , 2007 , Pages 283-289 ; 09598103 (ISSN) Pourjavadi, A ; Amini Fazl, M. S ; Sharif University of Technology
    2007
    Abstract
    The Taguchi method, a robust experimental design, was used for the optimization of the synthesis of a novel biopolymer-based superabsorbent hydrogel, carrageenan-graft-poly(sodium acrylate). The Taguchi method was applied for the experiment and standard 16 orthogonal arrays with five factors and four levels for each factor were used. In the synthesis of the superabsorbent hydrogel, N,N′-methylene bisacrylamide (MBA) was used as crosslinker, ammonium persulfate as initiator, and acrylic acid as monomer. Neutralization percent and reaction temperature were used as important factors. The analysis of variance results showed that the most important factor in this synthesis was MBA concentration.... 

    Synthesis, characterization and catalytic activity of novel monomeric and polymeric vanadyl Schiff base complexes

    , Article Journal of Molecular Catalysis A: Chemical ; Volume 245, Issue 1-2 , 2006 , Pages 12-16 ; 13811169 (ISSN) Boghaei, D. M ; Bezaatpour, A ; Behzad, M ; Sharif University of Technology
    2006
    Abstract
    This article describes the synthesis and characterization of two novel, as well as four previously reported, Schiff base complexes of oxovanadium(IV) and the study of their catalytic reactivity in the aerobic oxidation of olefins. The novel (5-Br-3-NO2salen) and (5-Br-3-NO2meso-stein) ligands were, respectively, synthesized from condensation of 5-bromo-3-nitro-2-hydroxybenzaldehyde with ethylenediamine or meso-1,2-diphenyl-1,2-ethylenediamine. The reaction of these ligands with VO(acac)2 readily resulted in the synthesis of their oxovanadium(IV) complexes [VO(5-Br-3-NO2salen)] and [VO(5-Br-3-NO2meso- stein)], respectively. The novel ligands and complexes were deliberately designed to... 

    Novel sulfobetaine-sulfonic acid-contained superswelling hydrogels

    , Article Polymers for Advanced Technologies ; Volume 16, Issue 9 , 2005 , Pages 659-666 ; 10427147 (ISSN) Kabiri, K ; Faraji Dana, S ; Zohuriaan Mehr, M. J ; Sharif University of Technology
    2005
    Abstract
    Novel hydrogels based on zwitterionic monomer [3-(methacrylamido)propyl] dimethyl (3-sulfopropyl) ammonium hydroxide (MPDSAH) and a strong acid monomer (2-acrylamido-2-methylpropane sulfonic acid, AMPS) were synthesized through solution polymerization under normal conditions to achieve nearly quantitative gel yield. The structure of the gels was confirmed using infrared spectroscopy. Thermal properties were simultaneously studied by differential scanning calorimetry and thermogravimetric analysis (DSC/TGA). The effects of the polymerization variables on the swelling capacity of the products were investigated. It was found that, in a certain range of the monomers mol ratio, increase of AMPS...