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Mechanical Properties of Actin Assemblies
, M.Sc. Thesis Sharif University of Technology ; Kazemi, Mohammad Taghi (Supervisor)
Abstract
Actin filaments are the most abundant component of the cellular cytoskeleton and provide shape for the most eukaryotic cells. Actin constitutes 1-10% of the total protein in most cells and is present at even higher concentrations in muscle cells. The functions of actin are directly connected to its mechanical properties, therefore both experimental and computational understanding of the mechanical properties of actin filaments are essential to elucidate their functions in cells and muscles. Actin exists in two forms, actin monomers (G-actin) and actin filaments (F-actin), which have continuous polymerization and depolymerization processes. In the polymerization process, different...
Synthesis and Investigation of Properties of Intumescent Fireproofing Paint with Oxide Nanoparticles
, M.Sc. Thesis Sharif University of Technology ; 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...
Synthesis of Bone graft Substitute for Clinical Applications
, M.Sc. Thesis Sharif University of Technology ; 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...
Simulation and Control of Particle Size Distribution in a Continuous Emulsion Polymerization Reactor
, M.Sc. Thesis Sharif University of Technology ; Shahrokhi, Mohammad (Supervisor)
Abstract
In this work, a comprehensive dynamic model has been used for vinyl acetate emulsion polymerization in a continuous reactor to predict the evolution of product particle size distribution under isothermal condition. Method of finite-volume has been applied for solving the population balance equations and the results are compared with the results obtained from moment method. Finite-volume method has been selected as a precise technique to predict sustained oscillations, which occurs in continuous emulsion polymerization. After performing sensitivity analysis and verification of system’s controllability, feed rate of surfactant and initiator have been selected as proper manipulated variables to...
Multiwalled carbon nanotube-polyelectrolyte gels: Preparation and swelling behavior for organic solvents
, Article Solid State Ionics ; Vol. 257 , 2014 , pp. 32-37 ; ISSN: 01672738 ; 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...
Preparation and characterization of UHMWPE/graphene nanocomposites using bi-supported ziegler-natta polymerization
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Vol. 63, issue. 16 , 2014 , p. 815-819 ; Ramazani, S. A ; Sharif University of Technology
Abstract
Ultrahigh-molecular-weight polyethylene (UHMWPE)/graphene nanocomposites with molecular weights as high as 3 × 106 g/mol were prepared via in situ polymerization using a bi-supported Ziegler-Natta catalytic system. Effects of [Al]/[Ti] molar ratio, temperature, monomer pressure, and polymerization time on productivity of the catalyst have been investigated. Increasing [Al]/[Ti] molar ratio from 128 to 320, increased productivity from 1667 g PE/mmol Ti.h to maximum value which was 2420 g PE/mmol Ti.h. Further [Al]/[Ti] ratio decreased the productivity. Reaction temperature effect investigation reveals that the optimal activity was obtained at 60°C. the polymerization productivity increases...
Protein fibrillation and nanoparticle interactions: Opportunities and challenges
, Article Nanoscale ; Volume 5, Issue 7 , Jan , 2013 , Pages 2570-2588 ; 20403364 (ISSN) ; Kalhor, H. R ; Laurent, S ; Lynch, I ; Sharif University of Technology
2013
Abstract
Due to their ultra-small size, nanoparticles (NPs) have distinct properties compared with the bulk form of the same materials. These properties are rapidly revolutionizing many areas of medicine and technology. NPs are recognized as promising and powerful tools to fight against the human brain diseases such as multiple sclerosis or Alzheimer's disease. In this review, after an introductory part on the nature of protein fibrillation and the existing approaches for its investigations, the effects of NPs on the fibrillation process have been considered. More specifically, the role of biophysicochemical properties of NPs, which define their affinity for protein monomers, unfolded monomers,...
Cross-linked basic nanogel; robust heterogeneous organocalayst
, Article Chemical Engineering Journal ; Volume 232 , 2013 , Pages 453-457 ; 13858947 (ISSN) ; Hosseini, S. H ; Emami, Z. S ; Sharif University of Technology
2013
Abstract
A novel basic poly(ionic liquid) (PIL) was synthesized by miniemulsion polymerization of ionic liquid monomer 1-ethyl-3-vinylimidazolium bromide [EVim][Br] which was cross-linked by ionic liquid cross-linker 1,4-butanediyl-3,3'-bis-l-vinylimidazolium dibromide (BVD). Exchange of bromide anions in PIL nanogel with hydroxide, produced a supported basic ionic liquid catalyst. The catalytic performances of PIL nanogel with a size of about 200. nm was evaluated in the synthesis of 4. H-benzo[. b]pyrans by multi-component reaction in water. The present protocol represents a simple, ecologically safe and cost-effective route to synthesize 4. H-benzo[. b]pyrans with high products yield
Hydrophobic nanocarriers embedded in a novel dual-responsive poly(N-isopropylacrylamide)/chitosan/(cyclodextrin) nanohydrogel
, Article Journal of Polymer Research ; Volume 20, Issue 10 , 2013 ; 1572-8935 (Online ISSN) ; Hemmatinejad, N ; Pourjavadi, A ; Sharif University of Technology
2013
Abstract
The incorporation of modified β-cyclodextrin (β-CD) into a poly(N-isopropylacrylamide) (PNIPAAm)/chitosan (PNCS) nanohydrogel was studied. β-CD was functionalized with acrylic groups, with different numbers of vinyl bonds added per β-CD molecule. The surfactant-free dispersion polymerization (SFDP) semi-batch method was used to synthesize the nanohydrogel. Increasing the number of vinyl groups per β-CDAC (β-CD acrylate) molecule induced the formation of smaller nanogels with diameters ranging from 142 to 68 nm. The cyclodextrin-modified dual-responsive nanogels obtained presented an LCST (lower critical solution temperature) in aqueous medium at around 31 C. The incorporation of β-CDAC into...
Improvement in oil absorbency by using modified carbon nanotubes in preparation of oil sorbents
, Article Advances in Polymer Technology ; Volume 32, Issue 1 , 2013 ; 07306679 (ISSN) ; Doulabi, M ; Sharif University of Technology
2013
Abstract
This article reports the first oil-absorbent cross-linked copolymer consisting of modified multiwalled carbon nanotube (MWCNT) and showing high oil absorbency. Also, to investigate and evaluate the effective parameters on oil absorbency, cross-linked dodecyl methacrylate (DDMA)-diphenylacrylamide (DPAA) and DDMA-butyl acrylate (BA) copolymers were synthesized. DDMA was copolymerized with different mol% of DPAA or BA and cross-linked using azobisisobutyronitrile as the initiator and various weight percentages of 1,4-butandiol dimethacrylate, methylene bisacrylamide, or vinyl group-modified MWCNT cross-linkers. The effects of monomer feed composition, cross-linker concentration, and the...
Novel carbon-nanotube-based organogels as candidates for oil recovery
, Article Polymer International ; Volume 62, Issue 2 , JUN , 2013 , Pages 179-183 ; 09598103 (ISSN) ; Doulabi, M ; Soleyman, R ; Sharif University of Technology
2013
Abstract
A simple method for synthesis of novel organogels based on multiwalled carbon nanotubes (MWCNTs) is reported. Three classes of organogels were synthesized by crosslinking polymerization of dodecyl methacrylate with various weight percentages of 1,4-butanediol dimethacrylate, vinyl-group-modified MWCNTs or pristine MWCNTs in the presence of 2,2-azoisobutyronitrile as initiator. In this reaction, the carbon nanotubes (CNTs) served simultaneously as an adsorbent, a comonomer and a crosslinking agent. The oil-absorbent containing CNTs showed much higher swelling capacity in oil and organic solvents compared with that without CNTs. Therefore, CNT-based organogels can be introduced as a promising...
Design of pH-responsive nanoparticles of terpolymer of poly(methacrylic acid), polysorbate 80 and starch for delivery of doxorubicin
, Article Colloids and Surfaces B: Biointerfaces ; Volume 101 , January , 2013 , Pages 405-413 ; 09277765 (ISSN) ; Chan, H. K ; Raval, G ; Abdekhodaie, M. J ; Liu, Q ; Heerklotz, H ; Wu, X. Y ; Sharif University of Technology
2013
Abstract
This work focused on the design of new pH-responsive nanoparticles for controlled delivery of anticancer drug doxorubicin (Dox). Nanoparticles of poly(methacrylic acid)-polysorbate 80-grafted starch (PMAA-PS 80-g-St) were synthesized by using a one-pot method that enabled simultaneous grafting of PMAA and PS 80 onto starch and nanoparticle formation in an aqueous medium. The particles were characterized by FTIR, 1H NMR, TEM, DLS, and potentiometric titration. Dox loading and in vitro release from the nanoparticles were investigated. The FTIR and 1H NMR confirmed the chemical composition of the graft terpolymer. The nanoparticles were relatively spherical with narrow size distribution and...
Graphene oxide strongly inhibits amyloid beta fibrillation
, Article Nanoscale ; Volume 4, Issue 23 , 2012 , Pages 7322-7325 ; 20403364 (ISSN) ; Akhavan, O ; Ghavami, M ; Rezaee, F ; Ghiasi, S. M. A ; Sharif University of Technology
2012
Abstract
Since amyloid beta fibrillation (AβF) plays an important role in the development of neurodegenerative diseases, we investigated the effect of graphene oxide (GO) and their protein-coated surfaces on the kinetics of Aβ fibrillation in the aqueous solution. We showed that GO and their protein-covered surfaces delay the AβF process via adsorption of amyloid monomers. Also, the large available surface of GO sheets can delay the AβF process by adsorption of amyloid monomers. The inhibitory effect of the GO sheet was increased when we increase the concentration from 10% (in vitro; stimulated media) to 100% (in vivo; stimulated media). Conclusion: our results revealed that GO and their surface...
Crosslinked poly(ionic liquid) as high loaded dual acidic organocatalyst
, Article Journal of Molecular Catalysis A: Chemical ; Volume 365 , 2012 , Pages 55-59 ; 13811169 (ISSN) ; Hosseini, S. H ; Soleyman, R ; Sharif University of Technology
Abstract
A dual acidic heterogeneous organocatalyst was synthesized by copolymerization of acidic ionic liquid monomer (vinyl-3-(3-sulfopropyl) imidazolium hydrogen sulfate [VSim][HSO 4]) and ionic liquid crosslinker (1,4-butanediyl-3,3′-bis-l-vinyl imidazolium dihydrogen sulfate). The resulting ionic heterogeneous catalyst is shown to be an efficient dual acidic organocatalyst for synthesis of dihydropyrimidines using the Biginelli synthetic route under mild reaction conditions in high yields. Since monomers make the catalyst bed, crosslinked poly(ionic liquid) will have high loading level of acidic groups comparing to other heterogeneous acid catalysts. Despite of conventional heterogeneous ionic...
A superabsorbent hydrogel network based on poly ((2-dimethylaminoethyl) methacrylate) and sodium alginate obtained by γ-radiation: Synthesis and characterization
, Article Iranian Polymer Journal (English Edition) ; Volume 21, Issue 12 , 2012 , Pages 829-836 ; 10261265 (ISSN) ; Hooshyar, Z ; Zehtabi, F ; Pourjavadi, A ; Sharif University of Technology
2012
Abstract
In this study, the synthesis and characterization of a novel nano-porous superabsorbent hydrogel with high water swelling capacity is described. A nano-porous hydrogel was prepared by employing (2-dimethylaminoethyl) methacrylate (PDMAEMA) as a pH sensitive monomer and sodium alginate (SA) as a water soluble polysaccharide under γ-ray irradiation. The polymerization reaction was performed at room temperature in the absence of chemically toxic crosslinking agent and initiators. The interactive parameters including biopolymer backbone concentration, monomer concentration and γ-irradiation dose were selected as major factors in the synthesis of superabsorbent and three levels for each factor...
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) ; 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...
Synthesis and characterization of a novel (salep phosphate)-based hydrogel as a carrier matrix for fertilizer release
, Article Reactive and Functional Polymers ; Volume 72, Issue 10 , 2012 , Pages 667-672 ; 13815148 (ISSN) ; Doulabi, M ; Soleyman, R ; Sharif, S ; Eghtesadi, S. A ; Sharif University of Technology
Elsevier
2012
Abstract
Salep phosphate modified biopolymers with different phosphate contents were prepared via reacting salep (a multi-component polysaccharide obtained from dried tubers of certain natural terrestrial orchids) with a solution of primary and secondary sodium phosphates under basic conditions in a semidry process. Structural characterization of salep phosphates were carried out by 31P NMR, FT-IR spectra and TGA curves. Determination of the phosphate content in samples was done by a standard spectrophotometric method. Then, novel (salep phosphate)-based hydrogels were synthesized by graft copolymerization of acrylic acid (AA) monomer onto salep phosphate backbones. Effect of the phosphate contents...
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) ; 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...
Modeling and sensitivity analysis of styrene monomer production process and investigation of catalyst behavior
, Article Computers and Chemical Engineering ; Volume 40 , 2012 , Pages 1-11 ; 00981354 (ISSN) ; Ebrahimi, A. N ; Ramazani S.A., A ; Abdollahzadeh, H ; Sharif University of Technology
2012
Abstract
In this work, a fundamental kinetic model based upon the Hougen-Watson non-porosity formalism was derived and used to simulate dehydrogenation and oxidation axial flow reactors. In addition, partial pressure profiles of components during styrene production process inside porous catalyst were obtained using Dusty-Gas model. The preservation equations are adopted to calculate temperature and flow profiles in the reactors filled with iron-potassium promoted catalyst pellets. The presented mathematical model for ethylbenzene dehydrogenation consists of nonlinear simultaneous differential equations with multiple dependent variables. Simulation results such as selectivity and operating temperature...
The preparation and rheological investigation of polymer and hydrogel modified drilling mud
, Article Petroleum Science and Technology ; Volume 30, Issue 10 , 2012 , Pages 1059-1068 ; 10916466 (ISSN) ; Ramazani, S. A. A ; Khosravi, N ; Sharif University of Technology
2012
Abstract
The authors carried out the study to prepare chitosan N-isopropylacrylamide hydrogel via heating and radiation processes. Properties investigation of prepared samples revealed that radiation prepared samples show higher yield and swelling ratios in comparison with the heating prepared ones. Effects of hydrogel addition to drilling mud on its important rheological properties such as apparent viscosity, plastic viscosity, and stress-strain behavior are measured. The rheological properties of hydrogel were compared with cellulosemethylcarboxyl and resins that are widely used in drilling fluid. The results demonstrate that whereas linear polymer effects on mud properties are more significant in...