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Flexible bactericidal graphene oxide–chitosan layers for stem cell proliferation [electronic resource]
, Article Journal of Applied Surface Science ; 15 May 2014, Volume 301, Pages 456–462 ; Akhavan, O ; Simchi, A. (Abdolreza) ; Sharif University of Technology
Abstract
Graphene oxide (GO)–chitosan composite layers with stacked layer structures were synthesized using chemically exfoliated GO sheets (with lateral dimensions of ∼1 μm and thickness of ∼1 nm), and applied as antibacterial and flexible nanostructured templates for stem cell proliferation. By increasing the GO content from zero to 6 wt%, the strength and elastic modulus of the layers increased ∼80% and 45%, respectively. Similar to the chitosan layer, the GO–chitosan composite layers showed significant antibacterial activity (>77% inactivation after only 3 h) against Staphylococcus aureus bacteria. Surface density of the actin cytoskeleton fibers of human mesenchymal stem cells (hMSCs) cultured...
Nanodiamonds for surface engineering of orthopedic implants: Enhanced biocompatibility in human osteosarcoma cell culture [electronic resource]
, Article Diamond and Related Materials ; Volume 40, 2013, Pages 107-114 ; Shokrgozar, M. A ; Mehrjoo, M ; Tamjid, E ; Simchi, A ; Sharif University of Technology
Abstract
Recently, nanodiamonds have attracted interest in biomedical applications such as drug delivery, targeted cancer therapies, fabrication of tissue scaffolds, and biosensors. We incorporated diamond nanoparticles in alginate–bioactive glass films by electrophoretic process to prepare functional coatings for biomedical implants. Turbidity examination by time-resolved laser transmittance measurement revealed that a stable multi-component aqueous suspension of alginate, bioactive glass and diamond particles could be obtained at concentrations of 0.6, 1.3, and 0.65 g/l, respectively. Uniform films with ~ 5 μm thickness were deposited on 316 stainless steel foils by employing constant field...
Application of coupled lattice boltzmann and Phase-field methods for multiphase flow simulations
, Article ASME 2013 Heat Transfer Summer Conf. Collocated with the ASME 2013 7th Int. Conf. on Energy Sustainability and the ASME 2013 11th Int. Conf. on Fuel Cell Science, Engineering and Technology, HT 2013 ; 2013 ; ISBN: 9780791855492 ; Patil, D. V ; Banerjee, S ; Sharif University Of Technology
Abstract
Coupling of lattice Boltzmann (LB) and phase-field (PF) methods is discussed for simulation of a range of multiphase flow problems. The local relaxation and shifting operators make the LB method an attractive candidate for the simulation of the single-phase as well as multiphase flows. For simulating interface dynamics, LB methods require to be coupled with an appropriate scheme representing interfacial dynamics. To this end, we have used a model based on the order parameter, which could be either an index function or a phase-field variable, and coupled it with a LB solver for the simulation of various classes of complex multi-physics and multiphase flows. The LB method is used to compute...
Probabilistic optimal power flow in correlated hybrid wind-photovoltaic power systems
, Article IEEE Transactions on Smart Grid ; Vol. 5, issue. 1 , 2014 , p. 130-138 ; ISSN: 19493053 ; Fotuhi-Firuzabad, M ; Rashidinejad, M ; Sharif University of Technology
Abstract
As a matter of course, the unprecedented ascending penetration of distributed energy resources (DERs), mainly harvesting renewable energies (REs), is concomitant with environmentally friendly concerns. This type of energy resources are innately uncertain and bring about more uncertainties in the power system, consequently, necessitates probabilistic analyses of the system performance. Moreover, the uncertain parameters may have a considerable level of correlation to each other, in addition to their uncertainties. The two point estimation method (2PEM) is recognized as an appropriate probabilistic method in small scale or even medium scale problems. This paper develops a new methodology for...
Probabilistic power flow of correlated hybrid wind-photovoltaic power systems
, Article IET Renewable Power Generation ; Vol. 8, issue. 6 , 2014 , p. 649-658 ; ISSN: 17521416 ; Khajeh, M. G ; Rashidinejad, M ; Fotuhi-Firuzabad, M ; Sharif University of Technology
Abstract
As a matter of course, the unprecedented ascending penetration of distributed energy resources, mainly harvesting renewable energies such as wind and solar, is concomitant with environmentally friendly concerns. This type of energy resources are innately uncertain and bring about more uncertainties in the power system context, consequently, necessitates probabilistic analysis of the system performance. Moreover, the uncertain parameters may have a considerable level of correlation to each other, in addition to their uncertainties. The two point estimation method (2PEM) is recognised as an appropriate probabilistic method. This study proposes a new methodology for probabilistic power flow...
Optimizing size and operation of hybrid energy systems
, Article Proceedings of the 2013 IEEE 7th International Power Engineering and Optimization Conference, PEOCO 2013 ; 2013 , p. 489-494 ; ISBN: 9781470000000 ; Abbaspour-Tehrani-Fard, A ; Fotuhi-Firuzabad, M ; Othman, M. M ; Sharif University of Technology
Abstract
This paper presents a new method to simultaneously optimize components' size, set points of the control system and slope of PV panels of standalone hybrid energy systems (HESs) using the Passive Congregation PSO (PSOPC) approach. New control set points are defined for the HES, and a new operation strategy is presented based on the defined set points. The optimization algorithm determines the optimal values of the set points to efficiently optimize the HES operation. The effectiveness of the proposed control set points is finally verified through some numerical analyses. In this regard, the proposed optimization method is employed to optimize various HES configurations and compared with other...
Photocatalytic mechanism of action of apatite-coated Ag=AgBr=TiO 2 on phenol and Escherichia coli and Bacillus subtilis bacteria under various conditions
, Article Progress in Reaction Kinetics and Mechanism ; Vol. 1 , Vol.36 (1) , 2011 , pp.38-52 ; Gholami, M. R. (Mohammad Reza) ; Rahimnejad, S. (Sara) ; Pourbaba, R. (Reza) ; Haghighi, S.(Saeed) ; Sharif University Of Technology
Abstract
Multi-component photocatalysts based on apatite-coated Ag/AgBr/TiO(2) were prepared by the deposition method. The effects of various kinds of apatites, with hydroxyl and fluoro substituents, on photocatalytic activity were investigated. The antibacterial processes in the dark, and under visible light, on two types of bacteria indicate that the multi-composites can inhibit the growth of bacteria by two different mechanisms. TEM images and optical microscopic data demonstrate that by attaching the nanosize catalyst to the outer membrane of the cell, the bacteria could not derive nourishment from surrounding media, i.e. this component acts as bacteria-static. The mechanism for deactivation of...
Prolonging lifetime of PCM-based main memories through on-demand page pairing
, Article ACM Transactions on Design Automation of Electronic Systems ; Vol. 20, issue. 2 , 1 February , 2015 ; ISSN: 10844309 ; Arjomand, M ; Sarbazi-Azad, H ; Sharif University of Technology
Abstract
With current memory scalability challenges, Phase-Change Memory (PCM) is viewed as an attractive replacement to DRAM. The preliminary concern for PCM applicability is its limited write endurance that results in fast wear-out of memory cells. Worse, process variation in the deep-nanometer regime increases the variation in cell lifetime, resulting in an early and sudden reduction in main memory capacity due to the wear-out of a few cells. Recent studies have proposed redirection or correction schemes to alleviate this problem, but all suffer poor throughput or latency. In this article, we show that one of the inefficiency sources in current schemes, even when wear-leveling algorithms are used,...
A compression-based morphable PCM architecture for improving resistance drift tolerance
, Article Proceedings of the International Conference on Application-Specific Systems, Architectures and Processors ; 18-20 June , 2014 , pp. 232-239 ; ISSN: 10636862 ; ISBN: 9781479936090 ; Sarbazi-Azad, H
Abstract
Due to the growing demand for large memories, using emerging technologies such as Phase Change Memories (PCM) are inevitable. PCM with appropriate scalability, power consumption and multiple bits per cell storage capability is a probable candidate for substituting DRAM. Although storing multiple bits per cell seems to be a rational response to large memory demands, there is a significant problem to achieve this goal. Resistance drift problem is an important reliability concern that is coupled to a multi-level cell PCM (MLC PCM) memory system. In this paper, we propose a memory system architecture that, by exploiting the benefits of compression, converts resistance drift prone blocks to drift...
Reducing access latency of MLC PCMs through line striping
, Article Proceedings - International Symposium on Computer Architecture ; Article number 6853228 , 14-18 June , 2014 , p. 277-288 ; ISSN: 10636897 ; ISBN: 9781479943968 ; Arjomand, M ; Sarbazi-Azad, H ; Sharif University of Technology
Abstract
Although phase change memory with multi-bit storage capability (known as MLC PCM) offers a good combination of high bit-density and non-volatility, its performance is severely impacted by the increased read/write latency. Regarding read operation, access latency increases almost linearly with respect to cell density (the number of bits stored in a cell). Since reads are latency critical, they can seriously impact system performance. This paper alleviates the problem of slow reads in the MLC PCM by exploiting a fundamental property of MLC devices: the Most-Significant Bit (MSB) of MLC cells can be read as fast as SLC cells, while reading the Least-Significant Bits (LSBs) is slower. We propose...
Recent developments in dye-sensitized solar cells
, Article ChemPhysChem ; Vol. 15, issue. 18 , Dec , 2014 , p. 3902-3927 ; Tajabadi, F ; Taghavinia, N ; Sharif University of Technology
Abstract
The knowledge of dye-sensitized solar cells (DSCs) has expanded considerably in recent years. They are multiparameter and complex systems that work only if various parameters are tuned simultaneously. This makes it difficult to target to a single parameter to improve the efficiency. There is a wealth of knowledge concerning different DSC structures and characteristics. In this review, the present knowledge and recent achievements are surveyed with emphasis on the more promising cell materials and designs
Production of biodiesel from waste frying oil using whole cell biocatalysts: Optimization of effective factors
, Article Waste and Biomass Valorization ; Vol. 5, issue. 6 , 2014 , pp. 947-954 ; ISSN: 18772641 ; Kariminia, H. R ; Yaghmaei, S ; Sharif University of Technology
Abstract
Using whole cell as a catalyst of enzymatic transesterification is a method to produce biodiesel with fewer drawbacks and at a lower cost. In the present study, biodiesel was produced by the reaction of waste frying oil with methanol in the presence of Rhizopus oryzae PTCC 5174 in both immobilized and free forms. Effect of four influencing factors including temperature, methanol to oil molar ratio, amount of biomass, and shaking speed was investigated. Response surface methodology was used to find the optimum conditions of the transesterification reaction. Each factor was set at three levels and the yield of the biodiesel was considered as the response. A quadratic equation was well-fitted...
Application of sol-gel technique to synthesis of copper-cobalt spinel on the ferritic stainless steel used for solid oxide fuel cell interconnects
, Article Journal of Power Sources ; Vol. 266, issue , 2014 , pp. 79-87 ; ISSN: 03787753 ; Askari, M ; Ghorbanzadeh, M ; Sharif University of Technology
Abstract
The conductive CuCo2O4 spinel coating is applied on the surface of the AISI 430 ferritic stainless steel by the dip-coating sol-gel process and it is evaluated in terms of the microstructure, oxidation resistance and electrical conductivity. The results show that the CuCO2O 4 coating forms a double-layer scale consisting of a Cr, Fe-rich subscale and Cu-Co spinel top layer after 500 h in air at 800 °C. This scale is protective, acts as an effective barrier against Cr migration into the outer oxide layer and alleviates the cathode Cr-poisoning. The oxidation resistance is significantly enhanced by the protective coating with a parabolic rate constant of 5.8 × 10-13 gr2 cm-4 s -1, meanwhile...
The use of graphene in the self-organized differentiation of human neural stem cells into neurons under pulsed laser stimulation
, Article Journal of Materials Chemistry B ; Vol. 2, Issue. 34 , 2014 , Pages 5602-5611 ; ISSN: 20507518 ; Ghaderi, E ; Sharif University of Technology
Abstract
An effective and self-organized differentiation of human neural stem cells (hNSCs) into neurons was developed by the pulsed laser stimulation of the cells on graphene films (prepared by drop-casting a GO suspension onto quartz substrates). The effects of graphene oxide (GO) and hydrazine-reduced graphene oxide (rGO) sheets on the proliferation of hNSCs were examined. The higher proliferation of the cells on the GO was assigned to its better hydrophilicity. On the other hand, the rGO sheets, which have significantly better electrical conductivity than GO, exhibited more differentiation of the cells into neurons. The pulsed laser stimulation not only resulted in an accelerated differentiation...
Synthesis and characterization of gold nanotube/nanowire-polyurethane composite based on castor oil and polyethylene glycol
, Article Materials Science and Engineering C ; Vol. 42 , 2014 , pp. 341-349 ; ISSN: 09284931 ; Kasra,M ; Salahshour Kordestani, S ; Bagheri Hariri, M ; Sharif University of Technology
Abstract
Gold nanotubes/nanowires (GNT/NW) were synthesized by using the template-assisted electrodeposition technique and mixed with castor oil-polyethylene glycol based polyurethane (PU) to fabricate porous composite scaffolds for biomedical application. 100 and 50 ppm of GNT/NW were used to synthesize composites. The composite scaffolds were characterized by Fourier transform infrared spectroscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, and scanning electron microscopy. Cell attachment on polyurethane-GNT/NW composites was investigated using fat-derived mesenchymal stem cells. Addition of 50 or 100 ppm GNT/NW had significant effects on thermal, mechanical, and cell...
High-performance/low-temperature-processed dye solar cell counter electrodes based on chromium substrates with cube-like morphology
, Article Journal of Power Sources ; Vol. 260 , 2014 , Pages 299-306 ; ISSN: 03787753 ; Taghavinia, N ; Sharif University of Technology
Abstract
There is still an open question of how to prepare high-performance counter electrodes for dye solar cells (DSCs) at room temperature; a requirement for flexible DSCs. Here, we introduce Pt deposited cube-like chromium coating as a low-temperature highly-efficient counter electrode for DSCs. Cr is a chemically stable metal and can be easily electroplated on conductive substrates with high roughness (here ∼160 nm) and cube-like appearance. A cyclic electrochemical deposition method with optimized temperature and number of cycles is used to grow Pt nanoparticles on this surface and charge transfer resistance as low as 0.54 Ω cm2 and 0.27 Ω cm2 were obtained at 40 °C and 55 °C solution...
Cell-imprinted substrates act as an artificial niche for skin regeneration
, Article ACS Applied Materials and Interfaces ; Vol. 6, Issue. 15 , 2014 , Pages 13280-13292 ; ISSN: 19448244 ; Bonakdar, S ; Taghinejad, H ; Satarifard, V ; Heidari, M ; Majidi, M ; Sharifi, S ; Peirovi, A ; Saffar, S ; Taghinejad, M ; Abdolahad, M ; Mohajerzadeh, S ; Shokrgozar, M. A ; Rezayat, S. M ; Ejtehadi M. R ; Dalby, M. J ; Mahmoudi, M ; Sharif University of Technology
Abstract
Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed...
Antitumor effect of therapeutic HPV DNA vaccines with chitosan-based nanodelivery systems
, Article Journal of Biomedical Science ; Vol. 21, issue. 1 , July , 2014 ; ISSN: 10217770 ; Ghaemi, A ; Gorji, A ; Kalhor, H. R ; Sajadian, A ; Tabarraei, A ; Moradi, A ; Atyabi, F ; Kelishadi, M ; Sharif University of Technology
Abstract
Cervical cancer is the second-most-common cause of malignancies in women worldwide, and the oncogenic activity of the human papilloma virus types (HPV) E7 protein has a crucial role in anogenital tumors. In this study, we have designed a therapeutic vaccine based on chitosan nanodelivery systems to deliver HPV-16 E7 DNA vaccine, considered as a tumor specific antigen for immunotherapy of HPV-associated cervical cancer. We have developed a Nano-chitosan (NCS) as a carrier system for intramuscular administration using a recombinant DNA vaccine expressing HPV-16 E7 (NCS-DNA E7 vaccine). NCS were characterized in vitro for their gene transfection ability. Results: The transfection of CS-pEGFP...
Mesoporous TiO2 microbead electrodes for cobalt-mediator-based dye-sensitized solar cells
, Article Journal of Physical Chemistry C ; Vol. 118, issue. 30 , July , 2014 , p. 16472-16478 ; ISSN: 19327447 ; Taghavinia, N ; Hagfeldt, A ; Boschloo, G ; Sharif University of Technology
Abstract
Light scattering, porosity, surface area, and morphology of TiO2 working electrode can affect the power conversion efficiency of dye -sensitized solar cells dramatically. Here mesoporous TiO2 microbeads were tested as working electrode in dye-sensitized solar cells based on cobalt tris-bipyridine electrolyte. Power conversion efficiencies up to 6.4% were obtained with D35 dye adsorbed onto the light-scattering microbeads. Electron transport, studied using small light perturbation methods, was found to be significantly faster in the microbead films than in standard mesoporous TiO 2 films. This was attributed to the favorable assembly of nanocrystals in the microbeads, which can increase the...
Analyses of mass and heat transport interactions in a direct methanol fuel cell
, Article International Journal of Hydrogen Energy ; Vol. 39, issue. 21 , July , 2014 , p. 11224-11240 ; ISSN: 03603199 ; Baghalha, M ; Sharif University of Technology
Abstract
In this paper, a two-dimensional, two-phase, non-isothermal model is presented to predict the electrochemical, mass transfer and heat transfer behaviors in a direct methanol fuel cell (DMFC). Governing equations including the momentum, continuity, heat transfer, proton and electron transport, species transport for water, methanol, and all the gas species (carbon dioxide, methanol vapor, water vapor, oxygen, and nitrogen) and the auxiliary equations are coupled to studying the various phenomena in DMFC. The modeling results agree well with the four different experimental data in an extensive range of operation conditions. A parametric study is also performed to examine the effects of the cell...