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Preparation of biodegradable gelatin/PVA porous scaffolds for skin regeneration
, Article Artificial Cells, Nanomedicine and Biotechnology ; 2016 , Pages 1-8 ; 21691401 (ISSN) ; Dadbin, S ; Frounchi, M ; Rajabi, S ; Sharif University of Technology
Taylor and Francis Ltd
2016
Abstract
Porous scaffolds composed of gelatin/poly (vinyl alcohol), (Gel/PVA), were prepared using combination of freeze gelation and freeze drying methods. The effect of polymer concentration, gelatin/PVA ratio, and glutaraldehyde/gelatin ratio (GA/Gel) was investigated on morphology of pores, swelling ratio, biodegradation, and skin cell culture. At optimum preparation conditions the scaffolds had uniform pore size distributions showing high swelling ratio of 23.6. The scaffolds were of biodegradable nature and almost degraded in 28 days. Human dermal fibroblast cells (HDF) were cultured on the scaffolds and MTS assay was conducted to evaluate the influence of PVA on growth and proliferation of the...
Design of Pavement Subdrainage for Iran
, M.Sc. Thesis Sharif University of Technology ; Tabatabaei, Nader (Supervisor)
Abstract
It is widely recognized today that excess moisture in pavement layers, when combined with heavy truck traffic and moisture-susceptible materials, can reduce the service life. Temperatures below freezing can also contribute to durability problems of saturated materials. A major objective in pavement design is to keep the base, subbase, subgrade, and other susceptible paving materials from becoming saturated or even being exposed to constant high moisture levels over time. The use of subsurface drainage has gained popularity over the past two decades, and many pavement agencies now routinely specify drainable pavement structures to reduce moisture-related problems in avements. In this...
Fabrication of Nano Structure Tialite-fibroin Scaffold
, M.Sc. Thesis Sharif University of Technology ; Maddah Hosseini, Hamid Reza (Supervisor)
Abstract
The development of novel three dimensional degradable porous scaffolds is of great interest for tissue engineering.silk ibroin has recently received intensive attention as a material for use in fabrication of 3D porous scaffolds beacuse of its excellent biocompatibility, physical and mechanical properties, and easy processibility. However, silk alone has no osteoinductive property and considerebely lower mechanical properties than native bone. In order to overcome this limitation silk fibroin can be combined with other materials.the properties of scaffold can be significantly improved and new features can be endowed by the second ccomposition. The present study deals with fabrication of...
PLA microspheres-embedded pva hydrogels prepared by gamma-irradiation and freeze-thaw methods as drug release carriers
, Article International Journal of Polymeric Materials and Polymeric Biomaterials ; Volume 62, Issue 1 , 2013 , Pages 28-33 ; 00914037 (ISSN) ; Dadbin, S ; Frounchi, M ; Sharif University of Technology
2013
Abstract
A drug delivery system based on poly (vinyl alcohol) (PVA) hydrogels containing ibuprofen-loaded poly (lactic acid) (PLA) microspheres was developed to improve the release kinetics of this model drug. Gamma-irradiation and freeze-thawing were applied to prepare poly (vinyl alcohol) hydrogels. Properties and morphology of these composite hydrogels were investigated using FTIR, DSC, and SEM. In vitro release indicated that entrapment of the microspheres into the PVA hydrogels causes a reduction in both the release rate and the initial burst effect. PLA microspheres entrapped into the PVA hydrogels showed more suitable controlled release kinetics for drug delivery
Effects of saturation degrees, freezing-thawing, and curing on geotechnical properties of lime and lime-cement concretes
, Article Cold Regions Science and Technology ; Volume 160 , 2019 , Pages 242-251 ; 0165232X (ISSN) ; Saberian, M ; Tao, Z ; Mojtahedi, S.F ; Li, J ; Ghasemi, M ; Rezvani, S. S ; Li, W ; Sharif University of Technology
Elsevier B.V
2019
Abstract
There are very limited researches carried out to investigate the influence of saturation degrees, freezing-thawing, and curing times on geotechnical properties of lime concrete (LC) and lime-cement concrete (LCC) due to the capillary action and changes in groundwater table. Subsequently, the primary goal of this research is to investigate the influence of these parameters on mechanical properties of LC and LCC using unconfined compression tests, namely uniaxial compressive strength (UCS), stress-strain behavior, deformability index (I D ), secant modulus (E S ), failure strain, bulk modulus (K), resilient modulus (M R ), brittleness index (I B ), and shear modulus (G). At first, the...
Numerical investigation and optimization of indirect freeze desalination
, Article Desalination ; Volume 481 , 2020 ; Salakhi, M ; Afshin, H ; Hannani, S. K ; Sharif University of Technology
Elsevier B.V
2020
Abstract
Access to potable water with standard quality is an inevitable component of human's lives. Freeze desalination, by consuming lower energy compared to other techniques, relies on the exertion of a cold source which is then accompanied by simultaneous rejection of impurities from water. Regarding this, a numerical study on freeze desalination in a hollow cylinder is carried out to determine the effects of the design variables such as heat flux, hydraulic diameter, initial salt concentration, and freezing time on the ice mass, ice salinity, ice generation speed, and Nusselt number on the cold surface of the inner tube. Results show that increasing the value of heat flux from −250 [Formula...
Fabrication of a Multi-Layered Scaffold to Be Used in Dermal Wound Healing
, M.Sc. Thesis Sharif University of Technology ; Shamloo, Amir (Supervisor) ; Asghari, Mohsen (Co-Advisor)
Abstract
Wound healing by engineered scaffolds is a new step in bio-technology and medical studies in recent years. The goal of the current study is to propose a novel structure for a tissue-engineered scaffold to be used in wound healing. Influenced from the multi-layered structure of natural human skin, the fabricated scaffold consists of two layers to maximize similarity with natural skin. This product is comprised of an electrospun layer made of polycaprolactone and polyvinyl alcohol and a hydrogel layer made of chitosan and gelatin. In order to form a porous medium in the hydrogel layer, freeze-gelation was used instead of freeze drying. The evaluation of fabricated scaffolds was performed by...
Design and Operation of Proper Freeze Drying Process to Recover Active Biological Agent
, M.Sc. Thesis Sharif University of Technology ; Rosta Azad, Reza (Supervisor)
Abstract
One of the most important unit operations in the production of dry powder biological products involves a freeze dryer apparatus. In this process, Liqueur, which is containing the α-amylase enzyme, undergoes a frigidity condition in which loses its moisture during sublimation. Under these circumstances, applying an adequate supply of sublimation enthalpy without raising the temperature of the frigid material up to melting, plays an important role in the quality of the product and preventing degradation of the α-amylase enzyme. Freeze drying depends on two main factors; time and energy. Furthermore, it is necessary to obtain an optimal temperature and pressure for different steps and...
Modeling and comparison of different simulations for release of amoxicillin from chitosan hydrogels
, Article Polymer - Plastics Technology and Engineering ; Volume 52, Issue 11 , 2013 , Pages 1147-1153 ; 03602559 (ISSN) ; Ramazani S. A., A ; Shafiee, M ; Alemzadeh, I ; Ebrahimi, H ; Sharif University of Technology
2013
Abstract
In this research work, different devices made of glutaraldehyde cross-linked chitosan hydrogels loaded by amoxicillin, have been prepared using freeze-drying method. Effects of system parameters such as cross-linker concentration, pH, and gel structure on the morphology and release behavior of devices have been investigated using standard methods. Morphological studies were performed using SEM instrument and controlled releases are followed via spectrophotometeric method. Reaction of glutaraldehyde with chitosan has been studied using FTIR instrument. SEM micrographs have shown that with increasing cross-linker percentage in hydrogel, pore sizes increased where pore size distribution...
Preparation of biodegradable gelatin/PVA porous scaffolds for skin regeneration
, Article Artificial Cells, Nanomedicine and Biotechnology ; Volume 45, Issue 5 , 2017 , Pages 928-935 ; 21691401 (ISSN) ; Dadbin, S ; Frounchi, M ; Rajabi, S ; Sharif University of Technology
Taylor and Francis Ltd
2017
Abstract
Porous scaffolds composed of gelatin/poly (vinyl alcohol), (Gel/PVA), were prepared using combination of freeze gelation and freeze drying methods. The effect of polymer concentration, gelatin/PVA ratio, and glutaraldehyde/gelatin ratio (GA/Gel) was investigated on morphology of pores, swelling ratio, biodegradation, and skin cell culture. At optimum preparation conditions the scaffolds had uniform pore size distributions showing high swelling ratio of 23.6. The scaffolds were of biodegradable nature and almost degraded in 28 days. Human dermal fibroblast cells (HDF) were cultured on the scaffolds and MTS assay was conducted to evaluate the influence of PVA on growth and proliferation of the...
A novel approach for microparticle separation based on dielectrophoresis method
, Article Biomedical Physics and Engineering Express ; Volume 5, Issue 3 , 2019 ; 20571976 (ISSN) ; Sasanpour, P ; Fardindoost, S ; Irajizad, A ; Sharif University of Technology
Institute of Physics Publishing
2019
Abstract
A novel approach for particles size separation based on dielectrophoresis (DEP) method is introduced and analyzed both computationally and experimentally. The proposed technique has been utilized for the separation of polystyrene (PS) particles with 8, 6 and 2 μm diameters passing through microchannels with planar electrodes. The performance of the technique has been computationally analyzed using the finite element method (FEM). Considering the structure of the planar electrodes, we propose an approach based on applying an electric potential between one of the global electrodes, and a needle touched the top of the cell suspension. Results of both simulation and experiment show that by...
Engineering development of an instrument panel concept using a unified FE modeling approach
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Darijani, H ; Shamsaei, N ; Naghdabadi, R ; Sharif University of Technology
2006
Abstract
In today's global economy, the automotive design engineer's responsibilities are made more complex by the differences between regulatory requirements of the various global markets. This paper compares instrument panel head impact requirements of FMVSS 201 with its European counterparts, ECE 21. The behavior during a head impact test has been studied. Due to the gravity of the cockpit module, the sag has been analyzed to simulate shipping, loading, and assembly conditions. The interior parts of the vehicle cabin are exposed to temperature variations due to radiation effect of sun ray or freezing temperature in winter. Plastic parts appear to be more thermally susceptible than steel parts in...
Mathematical study of probe arrangement and nanoparticle injection effects on heat transfer during cryosurgery
, Article Computers in Biology and Medicine ; Volume 66 , Nov , 2015 , Pages 113-119 ; 00104825 (ISSN) ; Ramazani S. A. A ; Nazemidashtarjandi, S ; Sharif University of Technology
Elsevier Ltd
2015
Abstract
Blood vessels, especially large vessels have a greater thermal effect on freezing tissue during cryosurgery. Vascular networks act as heat sources in tissue, and cause failure in cryosurgery and reappearance of cancer. The aim of this study is to numerically simulate the effect of probe location and multiprobe on heat transfer distribution. Furthermore, the effect of nanoparticles injection is studied. It is shown that the small probes location near large blood vessels could help to reduce the necessary time for tissue freezing. Nanoparticles injection shows that the thermal effect of blood vessel in tissue is improved. Using Au, Ag and diamond nanoparticles have the most growth of ice ball...
Fabrication and characterization of a starch-based nanocomposite scaffold with highly porous and gradient structure for bone tissue engineering
, Article Biomedical Physics and Engineering Express ; Volume 4, Issue 5 , 2018 ; 20571976 (ISSN) ; Eslamian, M ; Bagheri, R ; Sharif University of Technology
Institute of Physics Publishing
2018
Abstract
Starch based scaffolds are considered as promising biomaterials for bone tissue engineering. In this study, a highly porous starch/polyvinyl alcohol (PVA) based nanocomposite scaffold with a gradient pore structure was made by incorporating different bio-additives, including citric acid, cellulose nanofibers, and hydroxyapatite (HA) nanoparticles. The scaffold was prepared by employing unidirectional and cryogenic freeze-casting and subsequently freeze-drying methods. Fourier transform infrared (FTIR) spectroscopy confirmed the cross-linking of starch and PVA molecules through multiple esterification phenomenon in the presence of citric acid as a cross-linking agent. Field emission scanning...
Experimental investigation on freeze-thaw durability of polymer concrete
, Article Frontiers of Structural and Civil Engineering ; Volume 15, Issue 4 , 2021 , Pages 1038-1046 ; 20952430 (ISSN) ; Heidarnezhad, F ; Moammer, O ; Jarrah, M ; Sharif University of Technology
Higher Education Press Limited Company
2021
Abstract
Assessing the durability of concrete is of prime importance to provide an adequate service life and reduce the repairing cost of structures. Freeze-thaw is one such test that indicates the ability of concrete to last a long time without a significant loss in its performance. In this study, the freeze-thaw resistance of polymer concrete containing different polymer contents was explored and compared to various conventional cement concretes. Concretes’ fresh and hardened properties were assessed for their workability, air content, and compressive strength. The mass loss, length change, dynamic modulus of elasticity, and residual compressive strength were determined for all types of concretes...
Fabrication and Chracatization of Novel Electrospun Chitosan Fibers Reinforced with Bacterial Cellulose and Nanodiamond for Wound Dressing Applications
, M.Sc. Thesis Sharif University of Technology ; Simchi, Abdolreza (Supervisor)
Abstract
Chronic wounds are among the serious injuries which have called the attention of scientists to invest in an effort to fabricate temporary skin grafts and wound dressing materials. One of the widely acceptable solutions to this obstacle is to design a bioactive scaffold capable of regenerating tissue as well as delivering active agents to the site specific area. To this end, natural biopolymers are considered as suitable candidates to be employed in regenerative medicine due to their excellent biocompatibility. In addition, nanoparticles possess special properties such as the ability in sequestering the drug release which make them promising candidates in the fabrication of the...
Fabrication and Characterization of Nanocomposite Bone Scaffold with Gradient Structure Based on Thermoplastic Starch
, M.Sc. Thesis Sharif University of Technology ; Bagheri, Reza (Supervisor)
Abstract
Tissue regeneration by bio-compatible/degradable scaffolds is one of the widely used approaches in the field of tissue engineering. In this study, a thermoplastic starch based nanocomposite scaffold with gradient structure was fabricated by unidirectional freeze drying method. To increase the stability of the scaffold in the aqueous media, PVA was added to starch solution. Then, the PVA and starch molecules were cross-linked by adding citric acid to the mixture. On the one hand, to improve the mechanical properties of the scaffold, and control its bio-degradability on the other, cellulose nano-fibers were employed. Also, the bioactivity of the scaffold was induced by using hydroxyapatite...
Preparation of Porous PVA Nanocomposite Hydrogels Via Gamma Irradiation
, M.Sc. Thesis Sharif University of Technology ; Frounchi, Masoud (Supervisor) ; Dadbin, Susan (Supervisor)
Abstract
In this research, porous polyvinyl¬ alcohol (PVA)/Montmorillonite nanoclay and polyvinyl alcohol/polyvinyl pyrrolidone (PVP)/Montmorillonite nanoclay nanocomposite sponges (foams) were fabricated by freeze-drying method. The foams were crosslinked using gamma irradiation. The pore size and interconnectivity of nanocomposites characterized by scanning electron microscopy (SEM), showed bimodal pore size distribution resulting from preparation method.
SEM micrographs displayed that addition of PVP ( wt% of total solid polymer) to the PVA sponges increased the pore size and interconnectivity, due to the optimal number of hydrogen bonds between functional groups of polymeric matrices....
SEM micrographs displayed that addition of PVP ( wt% of total solid polymer) to the PVA sponges increased the pore size and interconnectivity, due to the optimal number of hydrogen bonds between functional groups of polymeric matrices....
Performance Assessment of PEM Fuel Cell in Extreme Conditions (Sub- Freezing Temperatures)
, M.Sc. Thesis Sharif University of Technology ; Rajabi Qhahnuyeh, Abbas (Supervisor) ; Ahmadi, Pouria (Supervisor)
Abstract
Fossil fuels provide the most needs of the world's energy, however, continues to lead to two key problems. The first problem is their limitation, and the second problem is the creation of serious environmental issues. Therefore, the need for renewable energy sources is felt more than ever.As an energy source, hydrogen is the lightest, most efficient and cleanest fuel. One of its unique properties is efficiency, the production of electricity by fuel cells through the electrochemical process, has far greater efficiency than of mechanical energy production from fossil fuels in internal combustion engines or energy production in thermal power plants. A fuel cell is a device that converts...
Modeling Of The Climatic Parameters Effect Upon Pavement Performance In Different Regions Of Iran
, M.Sc. Thesis Sharif University of Technology ; Tabatabae, Nader (Supervisor)
Abstract
Environmental conditions have a significant effect on the performance of flexible pavements. External factors such as precipitation, temperature, freeze-thaw cycles, and depth to water table play a key role in defining the extent of the impact the environment effects on pavement performance. All types of pavement distress are either caused or aggravated by the environmental factors. Up until now, pavement design in Iran is done according to the AASHTO 1993, which is based on methods that have evolved from the AASHTO Road Test that was conducted at one specific geographic location. The newly released Mechanistic Empirical Pavement Design Guide (MEPDG) by the addition of climatic input makes...