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Modified Chitosan. 2. H-chitoPAN, a novel pH-responsive superabsorbent hydrogel [electronic resource]
, Article Journal of Applied Polymer Science ; Volume 90, Issue 11, pages 3115–3121, 9 December 2003 ; Mahdavinia, G. R ; Zohuriaan-Mehr, M. J
Abstract
Chitosan was modified with polyacrylonitrile (PAN) through ceric-initiated graft copolymerization. The chitosan-g-PAN product was saponified using sodium hydroxide aqueous solution to prepare a novel superabsorbent hydrogel, H-chitoPAN. Duration of completing the saponification reaction as well as the water absorbency capacity of the hydrogel was decreased with increasing the alkaline concentration. Either chitosan-g-PAN or H-chitoPAN was characterized by FTIR spectroscopy and DSC, TGA, and DTG thermal methods. According to FTIR, all the nitrile groups were converted to carboxylate and carboxamide groups. Both modified chitosans exhibited enhanced thermal stability over chitosan. The...
An efficient routing algorithm for irregular mesh NoCs
, Article ISCAS 2010 - 2010 IEEE International Symposium on Circuits and Systems: Nano-Bio Circuit Fabrics and Systems, 30 May 2010 through 2 June 2010, Paris ; 2010 , Pages 3228-3231 ; 9781424453085 (ISBN) ; Sarbazi Azad, H ; Sharif University of Technology
2010
Abstract
Many researchers favor the mesh topology as the underlying topology of the communication infrastructure of modern SoCs because of its regularity and layout efficiency. However, variability in size and shape of modules used in systems-on-chip has resulted in the use of irregular meshes for practical NoCs. In this paper, we propose a deadlock free routing algorithm for irregular mesh NoCs. Experimental results confirm that the proposed algorithm exhibits a better performance in terms of message latency and power consumption compared to other known routing algorithms for irregular mesh NoCs
Modified Chitosan. 3. Superabsorbency, Salt- and pH-Sensivity of Smart Ampholitic hydrogels from Chitosan-g-PAN [electronic resource]
, Article Polymers for Advanced Technologies ; Volume 15, Issue 4, pages 173–180, April 2004 ; Zohuriaan-Mehr, M. J ; Pourjavadi, M. J
Abstract
Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric-initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan-g-PAN product was then hydrolyzed to yield a novel smart hydrogel (H-chitoPAN) with superabsorbing properties. The influence of add-on values as well as temperature and time of hydrolysis of the initial chitosan-g-PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH-sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a...
Modified carrageenan. 1. H-carragPAM, a novel biopolymer-based superabsorbent hydrogel [electronic resource]
, Article Journal of Bioactive and Compatible Polymers ; September 2005 Vol. 20 no. 5 475-490 ; Pourjavadi, A ; Mahdavinia, G. R ; Zohuriaan-Mehr, , M. J
Abstract
A novel kappa-carrageenan (C)-based superabsorbing hydrogel was synthesized through graft copolymerization of acrylamide (AAm) onto a C substrate in the presence of a crosslinking agent. The crosslinked C-poly(AAm) polymer graft was partially hydrolyzed in alkaline medium to yield a superabsorbent resin, H-carragPAM. The resin structure was confirmed using FTIR spectroscopy. The variables of graft copolymerization (monomer, initiator, polysaccharide and crosslinker concentration, reaction temperature and time as well as stirrer speed) that affected on the ultimate water-swelling capacity were optimized. The time-temperature variation of the copolymerization was investigated in terms of the...
Performance Evaluation of Deadlock Avoidance Based Routing Algorithms in Irregular Mesh NoCs
, M.Sc. Thesis Sharif University of Technology ; Sarbazi Azad, Hamid (Supervisor)
Abstract
It is now possible to integrate hundreds of modules (e.g. processors, memories) in a single silicon die. Handling the communication requirements between such modules by interconnecting them using shared buses is not possible from the performance point of view. One of the solutions is to use a network-on-chip (NoC) based communication infrastructure. NoCs were shown to be effective for solving the global interconnection problem among modules. These architectures emphasize the separation between computing and communication, and guarantee a good degree of design reuse and scalability. Mesh topology is favored by many researchers as the topology of NoCs because of its layout efficiency....
MBA-crosslinked Na-Alg/CMC as a smart full-polysaccharide superabsorbent hydrogels
, Article Carbohydrate Polymers ; Volume 66, Issue 3 , 2006 , Pages 386-395 ; 01448617 (ISSN) ; Barzegar, Sh ; Mahdavinia, G. R ; Sharif University of Technology
2006
Abstract
A novel superabsorbent hydrogel composed of carboxymethylcellulose (CMC) and sodium alginate (Na-Alg) was prepared by using methylenebisacrylamide (MBA) as a crosslinking agent. Ammonium persulfate (APS) was used as an initiator. For investigation of the effect of reaction variables on water absorbency of the hydrogels, the synthetic conditions were systematically optimized through studying the influential factors, including temperature, Na-Alg/CMC weight ratio and concentration of MBA and APS. Increase in MBA and APS concentration results in the decrease in water absorbency of the hydrogels. The water absorbency of the hydrogels increased with increasing of reaction temperature and...
Modified chitosan, 7 graft copolymerization of methacrylonitrile onto chitosan using ammonium persulfate initiator
, Article E-Polymers ; 2004 ; 16187229 (ISSN) ; Barzegar, S ; Mahdavinia, G. R ; Sharif University of Technology
European Polymer Federation
2004
Abstract
Graft copolymerization of methacrylonitrile (MAN) onto chitosan using ammonium persulfate (APS) as an initiator was studied. The reactions were carried out under argon atmosphere in a homogenous aqueous phase containing a small portion of acetic acid (AcOH). Evidence of graft copolymerization was obtained by FTIR spectroscopy, e.g., the appearance of nitrile in the spectrum of chitosan-graft-polymethacrylonitrile. The synthetic conditions were systematically optimized through studying the influential factors including temperature, as well as concentrations of initiator, MAN, AcOH, sodium dodecyl sulfate surfactant (SDS) and chitosan. The effects of individual factors were investigated by...
Experimental Study of Drying and Calcination of Simulated High-Level Waste (HLW)
, M.Sc. Thesis Sharif University of Technology ; Samadfam, Mohammad (Supervisor) ; Zahakifar, Fazel (Supervisor) ; Zaheri, Parisa (Co-Supervisor)
Abstract
One of the novel methods of stabilization of nuclear waste is the use of vitrification technology. In order to stabilize high level wastes (HLLW) in glass, it is required that the elements are in their oxide form. Therefore, it is necessary to evaporate the waste and turn it into a solid form so that the elements can be converted into oxide form in the calcination furnace. Hence, one of the challenges of stabilization is the optimization of evaporation and calcination conditions. In this research, the parameters affecting evaporation were first investigated. Using laboratory measurements of application: temperature (110 to 180 °C), presence of nitric acid (0.5 to 4 mol/L), ratio of zirconium...
Magnetic/pH-sensitive κ-carrageenan/sodium alginate hydrogel nanocomposite beads: Preparation, swelling behavior, and drug delivery
, Article Journal of Biomaterials Science, Polymer Edition ; Vol. 25, issue. 17 , 2014 , p. 1891-1906 ; Rahmani, Z ; Karami, S ; Pourjavadi, A ; Sharif University of Technology
2014
Abstract
This work describes the preparation of magnetic and pH-sensitive beads based on κ-carrageenan and sodium alginate for use as drug-targeting carriers. Physical cross-linking using K+/Ca2+ ions was applied to obtain ionic cross-linked magnetic hydrogel beads. The produced magnetite beads were thoroughly characterized by TEM, SEM/EDS, XRD, FTIR, and VSM techniques. While the water absorbency (WA) of magnetic beads was enhanced by increasing the weight ratio of κ-carrageenan, introducing magnetic nanoparticles caused a decrease in WA capacity from 15.4 to 6.3 g/g. Investigation on the swelling of the hydrogel beads in NaCl, KCl, and CaCl2 solutions revealed the disintegration of beads depending...
Synthesis and properties of highly swelling PAAm/chitosan semi-IPN hydrogels
, Article Macromolecular Symposia ; Volume 274, Issue 1 , 2008 , Pages 171-176 ; 10221360 (ISSN) ; Pourjavadi, A ; Zohuriaan Mehr, M. J ; Sharif University of Technology
2008
Abstract
A semi-interpenetrating polymer network (semi-IPN) hydrogel composed of crosslinked chitosan and Polyacrylamide (PAAm) was prepared in the presence of formaldehyde as a crosslinker. The swelling capacity of hydrogel was shown to be affected by the crosslinker and the PAAm/chitosan ratio. The PAAm/chitosan semiIPN hydrogels are swelled at low pHs that attributed to both osmotic pressure and repulsion of -NH3+ groups on chitosan backbones. The swelling of hydrogel in acidic pHs showed that with increasing of chitosan content in the hydrogel, the swelling capacity was increased. But the swelling capacity of hydrogel in neutral pH is reversed, i.e. the higher the PAAm/chitosan ratio, the higher...
A convenient one-step preparation of chitosan-poly(sodium acrylate-co-acrylamide) hydrogel hybrids with super-swelling properties
, Article Journal of Applied Polymer Science ; Volume 99, Issue 4 , 2006 , Pages 1615-1619 ; 00218995 (ISSN) ; Pourjavadi, A ; Zohuriaan Mehr, M. J ; Sharif University of Technology
2006
Abstract
Hydrogel hybrids were conveniently prepared from alkaline hydrolysis of chitosan-poly(acrylonitrile) mixture under highly practical conditions. The reaction of chitosan alkoxide anions with nitrile groups of poly(acrylonitrile) (PAN) forms crosslinking points and results in a three-dimensional network with superswelling ability in aqueous media. The hydrogel hybrid was identified using FTIR spectroscopy. The PAN content of the hydrolyzing feed affects proportionally the swelling capacity of the hydrogel hybrid. The swelling properties (capacity and rate) of the ampholytic hydrogel were investigated preliminarily. © 2005 Wiley Periodicals, Inc
Synthesis and super-swelling behavior of a novel protein-based superabsorbent hydrogel
, Article Polymer Bulletin ; Volume 57, Issue 6 , 2006 , Pages 813-824 ; 01700839 (ISSN) ; Kurdtabar, M ; Mahdavinia, G. R ; Hosseinzadeh, H ; Sharif University of Technology
2006
Abstract
In this work, we synthesize a novel protein-based superabsorbent hydrogel and study its swelling behavior. The crosslinking graft copolymerization of acrylic acid (AA) onto the hydrolyzed collagen as a protein backbone was carried out in a homogeneous medium. Potassium persulfate (KPS) as an initiator and N,N′-methylene bisacrylamide (MBA) as a crosslinker were used. The product's structure was established using FTIR spectroscopy. We were systematically optimized the certain variables of the graft copolymerization (i.e. the monomer, the initiator, and the crosslinker concentration) to achieve a hydrogel with maximum swelling capacity. Under this condition, maximum capacity of swelling in...
Modified chitosan III, superabsorbency, salt- and pH-sensitivity of smart ampholytic hydrogels from chitosan-g-PAN
, Article Polymers for Advanced Technologies ; Volume 15, Issue 4 , 2004 , Pages 173-180 ; 10427147 (ISSN) ; Zohuriaan Mehr, M. J ; Pourjavadi, A ; Sharif University of Technology
John Wiley and Sons Ltd
2004
Abstract
Polyacrylonitrile (PAN) grafted chitosan was prepared by ceric-initiated graft polymerization of acrylonitrile onto chitosan in a homogenous medium. The copolymer chitosan-g-PAN product was then hydrolyzed to yield a novel smart hydrogel (H-chitoPAN) with superabsorbing properties. The influence of add-on values as well as temperature and time of hydrolysis of the initial chitosan-g-PAN on swelling behavior of the hydrogel was evaluated in water and various salt solutions. The swelling kinetics of the superabsorbing hydrogel was studied as well. The hydrogels exhibited ampholytic and pH-sensitivity characteristics. Several sharp swelling changes were observed in lieu of pH variations in a...
Fabrication Patient-Specific Drill Guide Templates for Cervical Pedicle Screw Placement
, M.Sc. Thesis Sharif University of Technology ; Arjmand, Navid (Supervisor) ; Parnianpour, Mohammad (Supervisor) ; Azimi, Parisa (Co-Supervisor)
Abstract
One of the most common spinal surgeries involves spinal fusion or vertebral fixation, which is used to treat various conditions such as intervertebral disc disease, scoliosis (lateral deviation of the spinal column), fractures, infections, or the presence of tumors in the spinal column. In this surgical procedure, the use of pedicle screws and titanium rods prevents motion and friction between two vertebrae. Screws may enter the vertebrae in the wrong position and angle, causing bone weakening, rupture of nerve roots or blood vessels, weakness or lack of sensation in some parts of the body, spinal cord injury, and in severe cases, paralysis of the patient. For this reason, fusion surgery is...
Semi-IPN carrageenan-based nanocomposite hydrogels: Synthesis and swelling behavior
, Article Journal of Applied Polymer Science ; Volume 118, Issue 5 , 2010 , Pages 2989-2997 ; 00218995 (ISSN) ; Marandi, G. B ; Pourjavadi, A ; Kiani, G ; Sharif University of Technology
2010
Abstract
Inclusion of nano-clays into hydrogels is an efficient approach to produce nanocomposite hydrogels. The introduction of nano-clay into hydrogels causes an increase in water absorbency. In the present work, Nanocomposite hydro-gels based on kappa-carrageenan were synthesized using sodium montmorillonite as nano-clay. Acrylamide and meth-ylenebisacrylamide were used as monomer and crosslinker, respectively. The structure of nanocomposite hydrogels was investigated by XRD and SEM techniques. Swelling behavior of nanocomposite hydrogels was studied by varying clay and carrageenan contents as well as methylenebisacrylamide concentration. An optimum swelling capacity was achieved at 12% of sodium...
Modified chitosan 4. Superabsorbent hydrogels from poly(acrylic acid-co-acrylamide) grafted chitosan with salt- and pH-responsiveness properties
, Article European Polymer Journal ; Volume 40, Issue 7 , 2004 , Pages 1399-1407 ; 00143057 (ISSN) ; Pourjavadi, A ; Hosseinzadeh, H ; Zohuriaan, M. J ; Sharif University of Technology
2004
Abstract
Graft copolymerization of mixtures of acrylic acid (AA) and acrylamide (AAm) onto chitosan was carried out by using potassium persulfate (KPS) as a free radical initiator in the presence of methylenebisacrylamide (MBA) as a crosslinker. The effect of reaction variables, such as MBA concentration and AA/AAm ratio on the water absorbency capacity have been investigated. The polymer structures were confirmed by FTIR spectroscopy. Water absorbencies were compared for the hydrogels before and after alkaline hydrolysis. In the non-hydrolyzed hydrogel, enhanced water absorbency was obtained with increasing AA in monomer feed. However, after saponification, the sample with high AAm ratio exhibited...
Carrageenan-g-poly(sodium acrylate)/kaolin superabsorbent hydrogel composites: Synthesis, characterisation and swelling behaviour
, Article Polymers and Polymer Composites ; Volume 15, Issue 1 , 2007 , Pages 43-51 ; 09673911 (ISSN) ; Hosseinzadeh, H ; Mahdavinia, G. R ; Zohuriaan Mehr, M. J ; Sharif University of Technology
Rapra Technology Ltd
2007
Abstract
A novel superabsorbent hydrogel composite based on kappa-carrageenan (κC) was prepared by graft copolymerisation of acrylic acid (AA) in the presence of kaolin using methylenebisacrylamide (MBA) as a crosslinking agent and ammonium persulfate (APS) as an initiator. The synthetic variables (i.e. AA, MBA and APS concentration, and the amount of kaolin) affecting the water absorbency of the resulting superabsorbent composite were studied. Evidence of grafting and kaolin interaction was obtained by comparing the FTIR spectra of the initial substrates and of the superabsorbent composite. A new absorption band at 1722 cm-1 in the composite spectrum confirmed the kaolin-organic polymer linkage....
Modified carrageenan. 1. H-CarragPAM, a novel biopolymer-based superabsorbent hydrogel
, Article Journal of Bioactive and Compatible Polymers ; Volume 20, Issue 5 , 2005 , Pages 475-490 ; 08839115 (ISSN) ; Pourjavadi, A ; Mahdavinia, G. R ; Zohuriaan Mehr, M. J ; Sharif University of Technology
2005
Abstract
A novel kappa-carrageenan (κC)-based superabsorbing hydrogel was synthesized through graft copolymerization of acrylamide (AAm) onto a κC substrate in the presence of a crosslinking agent. The crosslinked κC-poly(AAm) polymer graft was partially hydrolyzed in alkaline medium to yield a superabsorbent resin, H-carragPAM. The resin structure was confirmed using FTIR spectroscopy. The variables of graft copolymerization (monomer, initiator, polysaccharide and crosslinker concentration, reaction temperature and time as well as stirrer speed) that affected on the ultimate water-swelling capacity were optimized. The time-temperature variation of the copolymerization was investigated in terms of...