Search for: cytology
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    Multi-objective dynamic cell formation problem: A stochastic programming approach

    , Article Computers and Industrial Engineering ; Volume 98 , 2016 , Pages 323-332 ; 03608352 (ISSN) Zohrevand, A. M ; Rafiei, H ; Zohrevand, A. H ; Sharif University of Technology
    Elsevier Ltd 
    This paper addresses dynamic cell formation problem (DCFP) which has been explored vastly for several years. Although a considerable body of literature in this filed, two remarkable aspects have been significantly ignored so far, as uncertainty and human-related issues. In order to compensate such a shortage, this paper develops a bi-objective stochastic model. The first objective function of the developed model seeks to minimize total cost of machine procurement, machine relocation, inter-cell moves, overtime utilization, worker hiring/laying-off, and worker moves between cells; while the second objective function maximizes labor utilization of the cellular manufacturing system. In the... 

    Mathematical modeling and analytical solution of two-phase flow transport in an immobilized-cell photo bioreactor using the homotopy perturbation method (HPM)

    , Article International Journal of Hydrogen Energy ; Volume 41, Issue 41 , 2016 , Pages 18405-18417 ; 03603199 (ISSN) Zeibi Shirejinia, S ; Fattahi, M ; Sharif University of Technology
    Elsevier Ltd 
    In the present study, a theoretical model of a reaction–diffusion within an entrapped-cell photobioreactor packed with gel-granules containing immobilized photosynthetic bacterial cells is presented. The model is based on a system of two coupled nonlinear reaction–diffusion equations under steady-state condition for biochemical reactions occurring in the photobioreactor that describes the substrate and product concentration within the gel-granule. Simple analytical expressions for the concentration of substrate and product have been derived for all values of reaction–diffusion parameters, demonstrating competition between the diffusion and reaction in the gel-granule, using the homotopy... 

    Simulation of the effects of oxygen carriers and scaffold geometry on oxygen distribution and cell growth in a channeled scaffold for engineering myocardium

    , Article Mathematical Biosciences ; Volume 294 , 2017 , Pages 160-171 ; 00255564 (ISSN) Zehi Mofrad, A ; Mashayekhan, S ; Bastani, D ; Sharif University of Technology
    This study proposes a mathematical model to evaluate the impact of oxygen carriers and scaffold geometry on oxygen distribution and cell growth in a 3D cardiac construct using computational fluid dynamics (CFD). Flow equations, oxygen balance equation and cell balance equation were solved using special initial and boundary conditions. The modeling results revealed that 55% increase in cardiac cell density occurred by using 6.4% perfluorocarbon oxygen carrier (PFC) compared to pure culture medium without PFC supplementation. Moreover, the effects of the scaffold geometry on cell density were examined by changing the channel numbers and the construct length. A 30% increase in the average cells... 

    Biomimetic proteoglycan nanoparticles for growth factor immobilization and delivery

    , Article Biomaterials Science ; Volume 8, Issue 4 , 2020 , Pages 1127-1136 Zandi, N ; Mostafavi, E ; Shokrgozar, M. A ; Tamjid, E ; Webster, T. J ; Annabi, N ; Simchi, A ; Sharif University of Technology
    Royal Society of Chemistry  2020
    The delivery of growth factors is often challenging due to their short half-life, low stability, and rapid deactivation. In native tissues, the sulfated residual of glycosaminoglycan (GAG) polymer chains of proteoglycans immobilizes growth factors through the proteoglycans'/proteins' complexation with nanoscale organization. These biological assemblies can influence growth factor-cell surface receptor interactions, cell differentiation, cell-cell signaling, and mechanical properties of the tissues. Here, we introduce a facile procedure to prepare novel biomimetic proteoglycan nanocarriers, based on naturally derived polymers, for the immobilization and controlled release of growth factors.... 

    Unified model of brain tissue microstructure dynamically binds diffusion and osmosis with extracellular space geometry

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 94, Issue 3 , 2016 ; 15393755 (ISSN) Yousefnezhad, M ; Fotouhi, M ; Vejdani, K ; Kamali Zare, P ; Sharif University of Technology
    American Physical Society  2016
    We present a universal model of brain tissue microstructure that dynamically links osmosis and diffusion with geometrical parameters of brain extracellular space (ECS). Our model robustly describes and predicts the nonlinear time dependency of tortuosity (λ=D/D∗) changes with very high precision in various media with uniform and nonuniform osmolarity distribution, as demonstrated by previously published experimental data (D = free diffusion coefficient, D∗ = effective diffusion coefficient). To construct this model, we first developed a multiscale technique for computationally effective modeling of osmolarity in the brain tissue. Osmolarity differences across cell membranes lead to changes... 

    Modeling self-assembly of the surfactants into biological bilayer membranes with special chemical structures using dissipative particle dynamics method

    , Article Scientia Iranica ; Volume 23, Issue 3 , 2016 , Pages 942-950 ; 10263098 (ISSN) Yaghoubi, S ; Pishevar, A. R ; Saidi, M. S ; Shirani, E ; Sharif University of Technology
    Sharif University of Technology  2016
    The aim of this study is to simulate the self-assembly of the surfactant molecules with special chemical structure and bending stiffiness into bilayer membranes using a mesoscopic Dissipative Particle Dynamics (DPD) method. The surfactants are modeled with special chemical structure and bending stiffiness. To confirm that the novel model is physical, we determine the interaction parameters based on matching the compressibility and solubility of the DPD system with real physics of the uid. To match the mutual solubility for binary uids, we use the relation between DPD parameters and x-parameters in Flory-Huggins-type models. Unsaturated bonds can change the stiffiness of a lipid membrane,... 

    An interface–particle interaction approach for evaluation of the co-encapsulation efficiency of cells in a flow-focusing droplet generator

    , Article Sensors (Switzerland) ; Volume 20, Issue 13 , 2020 , Pages 1-17 Yaghoobi, M ; Saidi, M. S ; Ghadami, S ; Kashaninejad, N ; Sharif University of Technology
    MDPI AG  2020
    Droplet-based microfluidics offers significant advantages, such as high throughput and scalability, making platforms based on this technology ideal candidates for point-of-care (POC) testing and clinical diagnosis. However, the efficiency of co-encapsulation in droplets is suboptimal, limiting the applicability of such platforms for the biosensing applications. The homogeneity of the bioanalytes in the droplets is an unsolved problem. While there is extensive literature on the experimental setups and active methods used to increase the efficiency of such platforms, passive techniques have received less attention, and their fundamentals have not been fully explored. Here, we develop a novel... 

    Dielectrophoretic cell sorting via sliding cells on 3D silicon microelectrodes

    , Article Proceedings of the IEEE International Conference on Micro Electro Mechanical Systems (MEMS), 22 January 2017 through 26 January 2017 ; 2017 , Pages 147-150 ; 10846999 (ISSN) ; 9781509050789 (ISBN) Xing, X ; Chan, M. L ; Roshan, K. A ; Yobas, L ; Sharif University of Technology
    This work presents an innovative design for a flow-through dielectrophoretic cell sorting based on silicon bulk microelectrodes featuring sidewall undercuts. The microelectrodes are configured into an interdigitated array with digits extending across the flow chamber at an oblique angle against the flow stream. Target cells under dielectrophoretic forces and hydrodynamic drag can slide along the digits to a dedicated outlet. The design has been showcased for continuous-flow sorting of viable and non-viable mammalian cells, achieving a throughput of 16,600 cells/min, an order of magnitude higher than those reported for existing continuous-flow cell sorting designs using thin-film or... 

    Investigation of the equivalent material properties and failure stress of the re-entrant composite lattice structures using an analytical model

    , Article Composite Structures ; 2020 Veisi, H ; Farrokhabadi, A ; Sharif University of Technology
    Elsevier Ltd  2020
    In the present study, a novel theoretical model is developed, based on classical laminate theory, to predict the equivalent mechanical properties of the re-entrant lattice structures, which composed of continuous fiber reinforced composite struts. Three main mechanism of stretching, flexing and hinging are considered and a general closed-form formulation is derived to estimate the auxetic honeycomb's elastic and shear modulus as well as Poisson's ratios. In spite of previous studies in which the response of honeycomb structures is modeled using beam theory, here, each strut of unit cell is expressed as a composite laminate with orthotropic mechanical properties and classical laminate theory... 

    Integrated system of multiple batches to evaluate the continuous performance of microbial cells in decolourization processes

    , Article Journal of Environmental Chemical Engineering ; Volume 6, Issue 1 , February , 2018 , Pages 728-735 ; 22133437 (ISSN) Vatandoostarani, S ; Bagheri Lotfabad, T ; Heidarinasab, A ; Ebadipour, N ; Yaghmaei, S ; Sharif University of Technology
    Elsevier Ltd  2018
    Azo dye degradation in wastewater treatment is a subject which has garnered the attention of many research studies. In this study, an innovative approach, namely, an integrated system of five batches (ISFB), was developed to investigate the capability of Saccharomyces cerevisiae ATCC 9763 for continuous degradation of methyl red as a representative azo dye. Toward this end, an expanded immobilized microbial bed (EIMB) reactor was established with a bed of encapsulated yeast cells in sodium alginate. EIMB reactor was run in two modes, single batch and ISFB. Moreover, durability of the microbial cells was evaluated by repeating the continuous decolourization eight sequential times in EIMB at... 

    Enzymatic outside-in cross-linking enables single-step microcapsule production for high-throughput three-dimensional cell microaggregate formation

    , Article Materials Today Bio ; Volume 6 , 2020 Van Loo, B ; Salehi, S. S ; Henke, S ; Shamloo, A ; Kamperman, T ; Karperien, M ; Leijten, J ; Sharif University of Technology
    Elsevier B.V  2020
    Cell-laden hydrogel microcapsules enable the high-throughput production of cell aggregates, which are relevant for three-dimensional tissue engineering and drug screening applications. However, current microcapsule production strategies are limited by their throughput, multistep protocols, and limited amount of compatible biomaterials. We here present a single-step process for the controlled microfluidic production of single-core microcapsules using enzymatic outside-in cross-linking of tyramine-conjugated polymers. It was hypothesized that a physically, instead of the conventionally explored biochemically, controlled enzymatic cross-linking process would improve the reproducibility,... 

    Structural stability and sustained release of protein from a multilayer nanofiber/nanoparticle composite

    , Article International Journal of Biological Macromolecules ; Volume 75 , April , 2015 , Pages 248-257 ; 01418130 (ISSN) Vakilian, S ; Mashayekhan, S ; Shabani, I ; Khorashadizadeh, M ; Fallah, A ; Soleimani, M ; Sharif University of Technology
    Elsevier  2015
    The cellular microenvironment can be engineered through the utilization of various nano-patterns and matrix-loaded bioactive molecules. In this study, a multilayer system of electrospun scaffold containing chitosan nanoparticles was introduced to overcome the common problems of instability and burst release of proteins from nanofibrous scaffolds. Bovine serum albumin (BSA)-loaded chitosan nanoparticles was fabricated based on ionic gelation interaction between chitosan and sodium tripolyphosphate. Suspension electrospinning was employed to fabricate poly-e{open}-caprolacton (PCL) containing protein-loaded chitosan nanoparticles with a core-shell structure. To obtain the desired scaffold... 

    Porous gelatin/poly(ethylene glycol) scaffolds for skin cells

    , Article Soft Materials ; Volume 15, Issue 1 , 2017 , Pages 95-102 ; 1539445X (ISSN) Vahidi, M ; Frounchi, M ; Dadbin, S ; Sharif University of Technology
    Biocompatible porous polymeric scaffolds provide a suitable environment for proliferation of stem cells in human body. In this research work, porous gelatin–poly(ethylene glycol), PEG, based scaffolds were prepared using combination of freeze-gelation and freeze-extraction methods. Effects of various parameters such as freezing temperature, cross-linking agent, concentrations of gelatin and PEG and their blending ratio on physical and mechanical properties, swelling ratio, porosity, pore size, and degradation rate of scaffolds were investigated. Also, proliferation of fibroblast skin cells on the scaffolds was examined by MTS assay to assess the suitability of the scaffolds in wound healing... 

    Self-organization of developing embryo using scale-invariant approach

    , Article Theoretical Biology and Medical Modelling ; Volume 8, Issue 1 , 2011 ; 17424682 (ISSN) Tiraihi, A ; Tiraihi, M ; Tiraihi, T ; Sharif University of Technology
    Background: Self-organization is a fundamental feature of living organisms at all hierarchical levels from molecule to organ. It has also been documented in developing embryos. Methods. In this study, a scale-invariant power law (SIPL) method has been used to study self-organization in developing embryos. The SIPL coefficient was calculated using a centro-axial skew symmetrical matrix (CSSM) generated by entering the components of the Cartesian coordinates; for each component, one CSSM was generated. A basic square matrix (BSM) was constructed and the determinant was calculated in order to estimate the SIPL coefficient. This was applied to developing C. elegans during early stages of... 

    Tissue growth into three-dimensional composite scaffolds with controlled micro-features and nanotopographical surfaces

    , Article Journal of Biomedical Materials Research - Part A ; Volume 101, Issue 10 , 2013 , Pages 2796-2807 ; 15493296 (ISSN) Tamjid, E ; Simchi, A ; Dunlop, J. W. C ; Fratzl, P ; Bagheri, R ; Vossoughi, M ; Sharif University of Technology
    Controlling topographic features at all length scales is of great importance for the interaction of cells with tissue regenerative materials. We utilized an indirect three-dimensional printing method to fabricate polymeric scaffolds with pre-defined and controlled external and internal architecture that had an interconnected structure with macro- (400-500 μm) and micro- (∼25 μm) porosity. Polycaprolactone (PCL) was used as model system to study the kinetics of tissue growth within porous scaffolds. The surface of the scaffolds was decorated with TiO2 and bioactive glass (BG) nanoparticles to the better match to nanoarchitecture of extracellular matrix (ECM). Micrometric BG particles were... 

    Fabrication of a highly ordered hierarchically designed porous nanocomposite via indirect 3D printing: Mechanical properties and in vitro cell responses

    , Article Materials and Design ; Volume 88 , 2015 , Pages 924-931 ; 02641275 (ISSN) Tamjid, E ; Simchi, A ; Sharif University of Technology
    Elsevier Ltd  2015
    Design and development of biodegradable scaffolds with highly uniform and controlled internal structure that stimulate tissue regeneration are the focus of many studies. The aim of this work is to apply a modified three-dimensional (3D) printing process to fabricate polymer-matrix composites with controlled internal architecture. Computationally-designed plaster molds with various pore sizes in the range of 300-800. μm were prepared by employing 3D printing of a water-based binder. The molds were converted to ε-polycaprolactone (PCL) and PCL/bioactive glass (BG) composite scaffolds by solvent casting and freeze drying methods. Optical and electron microscopy studies revealed that the pore... 

    Characterization of nanostructured biodegradable Zn-Mn alloy synthesized by mechanical alloying

    , Article Journal of Alloys and Compounds ; Volume 735 , 2018 , Pages 1319-1327 ; 09258388 (ISSN) Sotoudeh Bagha, P ; Khaleghpanah, S ; Sheibani, S ; Khakbiz, M ; Zakeri, A ; Sharif University of Technology
    Elsevier Ltd  2018
    In this study, nanostructured biodegradable pure Zn, Zn-4 wt. % Mn and Zn-24 wt % Mn alloys were produced by 20 h mechanical alloying and consequent cold pressing and sintering. Structural evolutions were investigated using the X-ray diffraction technique. Also, the microstructure was characterized by scanning electron microscopy. The effects of alloy composition on density, mechanical properties, corrosion behavior in Hank's solution, cell viability and cell attachment were investigated. Crystallite size of the synthesized alloys after 20 h of milling reached to less than 40 nm and remained less than 80 nm after consolidation and sintering for 1 h. Alloys contain MnZn13 as second phase... 

    Mid-defense: Mitigating protocol-level attacks in TOR using indistinguishability obfuscation

    , Article 2014 11th International ISC Conference on Information Security and Cryptology, ISCISC 2014 ; 3- 4 September , 2014 , pp. 214-219 ; ISBN: 9781479953837 Soltani, M ; Najafi, S ; Jalili, R ; Sharif University of Technology
    TOR is one of the most famous anonymity networks. TOR works correctly when at least one honest relay exists along an established circuit. However, many attacks reveal anonymity of TOR communications by watermarking traffics, changing timings, counting cells per packets, and recently, introducing errors in cells. This paper focuses on protocol-level attacks which can de-anonymize users by changing a cell, and provides a solution for this attack by changing the way integrities of cells are checked. The proposed design allows all relays, not just the exit node, to check the integrity of cells, independently. In addition, this paper proposes a novel method, based on the concept of... 

    Alumina feeding system changes in aluminum electrochemical cell with d18 technology for energy efficiency (Case study: Almahdi-hormozal aluminum smelter)

    , Article 147th Annual Meeting and Exhibition of the Minerals, Metals and Materials Society, TMS 2018, 11 March 2018 through 15 March 2018 ; Volume Part F12 , 2018 , Pages 721-728 ; 23671181 (ISSN); 9783319725253 (ISBN) Siahooei, M. A ; Samimi, A ; Baharvand, B ; Sharif University of Technology
    Springer International Publishing  2018
    Aluminum reduction cells have benefited from point feeding technology for a long time, but there are still smelters which are using the old technology of center break and center feed system. Due to several factors this system is no longer approved and there have been a few attempts worldwide to upgrade these cells so as to implement the newer technology by applying mechanical and automation changes. In this paper we will present an attempt which was made in order to retrofit a so-called center break cell to point feeder cell. The results show that this project has decreased the energy consumption and anode effect frequency. Furthermore, there has been a significant increase in current... 

    Liquid color recognition by using an optical reflection system

    , Article Journal of Applied Sciences ; Volume 12, Issue 18 , 2012 , Pages 1917-1924 ; 18125654 (ISSN) Siadat, M ; Golnabi, H ; Sharif University of Technology
    ANSInet  2012
    Operation of an optomechanical system for color reflection study is reported. The reported system consists of a double-fiber optical design and an electro-mechanical scanning system. In the double-fiber arrangement one fiber transmits the source light to the target surface and the second one sends the reflected light off the sample target to a photodetector. By scanning the double-fiber probe in one-direction reflection properties of different color liquid samples are investigated in this study. A cubic cell made of glass material is used as the liquid container and reflection signals are compared for different filled color liquids. The maximum reflection signals are: for the yellow color...