Search for: flow-kinetics
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    Quantitative determination of optical trapping strength and viscoelastic moduli inside living cells

    , Article Physical Biology ; Volume 10, Issue 4 , 2013 ; 14783967 (ISSN) Mas, J ; Richardson, A. C ; Reihani, S. N. S ; Oddershede, L. B ; Berg Sorensen, K ; Sharif University of Technology
    With the success of in vitro single-molecule force measurements obtained in recent years, the next step is to perform quantitative force measurements inside a living cell. Optical traps have proven excellent tools for manipulation, also in vivo, where they can be essentially non-invasive under correct wavelength and exposure conditions. It is a pre-requisite for in vivo quantitative force measurements that a precise and reliable force calibration of the tweezers is performed. There are well-established calibration protocols in purely viscous environments; however, as the cellular cytoplasm is viscoelastic, it would be incorrect to use a calibration procedure relying on a viscous environment.... 

    Investigation of segregation of large particles in a pressurized fluidized bed with a high velocity gas: A discrete particle simulation

    , Article Powder Technology ; Volume 246 , September , 2013 , Pages 398-412 ; 00325910 (ISSN) Alavi Shoushtari, N ; Hosseini, S. A ; Soleimani, R ; Sharif University of Technology
    A numerical study on mixing/segregation phenomena in a pressurized fluidized bed with large particles of Geldart D type of binary density but same diameter with high velocity gas was performed by the use of discrete particle simulation. Particle mixtures are composed of spherical particles with 2mm diameter and 1g/cm3 flotsam density and different jetsam densities of 1.25, 2 and 2.5g/cm3 with jetsam volume fraction of 0.5. The particles are initially packed approaching perfect mixing state in a rectangular bed and then fluidized by gas uniformly injected at the bottom of the bed. Effect of increase of pressure and density ratio was investigated and mixing/segregation behavior is discussed in... 

    Breakup of microdroplets in asymmetric T junctions

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 5 , 2013 ; 15393755 (ISSN) Samie, M ; Salari, A ; Shafii, M. B ; Sharif University of Technology
    Symmetric T junctions have been used widely in microfluidics to generate equal-sized microdroplets, which are applicable in drug delivery systems. A newly proposed method for generating unequal-sized microdroplets at a T junction is investigated theoretically and experimentally. Asymmetric T junctions with branches of identical lengths and different cross sections are utilized for this aim. An equation for the critical breakup of droplets at asymmetric T junctions and one for determining the breakup point of droplets are developed. A good agreement was observed between the theories (present and previous) and the experiments  

    Thin liquid film flow over substrates with two topographical features

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 2 , 2013 ; 15393755 (ISSN) Mazloomi, A ; Moosavi, A ; Sharif University of Technology
    A multicomponent lattice Boltzmann scheme is used to investigate the surface coating of substrates with two topographical features by a gravity-driven thin liquid film. The considered topographies are U- and V-shaped grooves and mounds. For the case of substrates with two grooves, our results indicate that for each of the grooves there is a critical width such that if the groove width is larger than the critical width, the groove can be coated successfully. The critical width of each groove depends on the capillary number, the contact angle, the geometry, and the depth of that groove. The second groove critical width depends on, in addition, the geometry and the depth of the first groove;... 

    Plasma core at the center of a sonoluminescing bubble

    , Article Physical Review E - Statistical, Nonlinear, and Soft Matter Physics ; Volume 87, Issue 1 , 2013 ; 15393755 (ISSN) Bemani, F ; Sadighi Bonabi, R ; Sharif University of Technology
    Considering high temperature and pressure during single bubble sonoluminescence collapse, a hot plasma core is generated at the center of the bubble. In this paper a statistical mechanics approach is used to calculate the core pressure and temperature. A hydrochemical model alongside a plasma core is used to study the bubble dynamics in two host liquids of water and sulfuric acid 85 wt % containing Ar atoms. Calculation shows that the extreme pressure and temperature in the plasma core are mainly due to the interaction of the ionized Ar atoms and electrons, which is one step forward to sonofusion. The thermal bremsstrahlung mechanism of radiation is used to analyze the emitted optical energy... 

    Geometry effects in Eulerian/Granular simulation of a turbulent FCC riser with a (kg-g)-KTGF model

    , Article International Journal of Chemical Reactor Engineering ; Volume 8 , 2010 ; 15426580 (ISSN) Nazif, H. R ; Basirat Tabrizi, H ; Farhadpour, F. A ; Sharif University of Technology
    Three-dimensional, transient turbulent particulate flow in an FCC riser is modeled using an Eulerian/Granular approach. The turbulence in the gas phase is described by a modified realizable (kg-g) closure model and the kinetic theory of granular flow (KTGF) is employed for the particulate phase. Separate simulations are conducted for a rectangular and a cylindrical riser with similar dimensions. The model predictions are validated against experimental data of Sommerfeld et al (2002) and also compared with the previously reported LES-KTGF simulations of Hansen et al (2003) for the rectangular riser. The (kg-g)-KTGF model does not perform as well as the LES-KTGF model for the riser with a... 

    Adsorption of proteins at the solution/air interface influenced by added nonionic surfactants at very low concentrations for both components. 3. dilational surface rheology

    , Article Journal of Physical Chemistry B ; Volume 119, Issue 9 , January , 2015 , Pages 3768-3775 ; 15206106 (ISSN) Fainerman, V. B ; Aksenenko, E. V ; Lylyk, S. V ; Lotfi, M ; Miller, R ; Sharif University of Technology
    The influence of the addition of the nonionic surfactants C12DMPO, C14DMPO, C10OH, and C10EO5 at concentrations between 10-5 and 10-1 mmol/L to solutions of β-casein (BCS) and β-lactoglobulin (BLG) at a fixed concentration of 10-5 mmol/L on the dilational surface rheology is studied. A maximum in the viscoelasticity modulus |E| occurs at very low surfactant concentrations (10-4 to 10-3 mmol/L) for mixtures of BCS with C12DMPO and C14DMPO and for mixtures of BLG with C10EO5, while for mixture of BCS with C10EO5 the value of |E| only slightly increased. The |E| values... 

    Reduction of production rate in y-shaped microreactors in the presence of viscoelasticity

    , Article Analytica Chimica Acta ; Volume 990 , 2017 , Pages 121-134 ; 00032670 (ISSN) Helisaz, H ; Saidi, M. H ; Sadeghi, A ; Sharif University of Technology
    The viscoelasticity effects on the reaction-diffusion rates in a Y-shaped microreactor are studied utilizing the PTT rheological model. The flow is assumed to be fully developed and considered to be created under a combined action of electroosmotic and pressure forces. In general, finite-volume-based numerical simulations are conducted to handle the problem; however, analytical solutions based on the depthwise averaging approach are also obtained for the case for which there is no reaction between the inlet components. The analytical solutions are found to predict accurate results when the width to height ratio is at least 10 and acceptable results for lower aspect ratios. An investigation... 

    Chebyshev collocation spectral lattice boltzmann method in generalized curvilinear coordinates

    , Article Computers and Fluids ; Volume 146 , 2017 , Pages 154-173 ; 00457930 (ISSN) Hejranfar, K ; Hajihassanpour, M ; Sharif University of Technology
    In this work, the Chebyshev collocation spectral lattice Boltzmann method is implemented in the generalized curvilinear coordinates to provide an accurate and efficient low-speed LB-based flow solver to be capable of handling curved geometries with non-uniform grids. The low-speed form of the D2Q9 and D3Q19 lattice Boltzmann equations is transformed into the generalized curvilinear coordinates and then the spatial derivatives in the resulting equations are discretized by using the Chebyshev collocation spectral method and the temporal term is discretized with the fourth-order Runge–Kutta scheme to provide an accurate and efficient low-speed flow solver. All boundary conditions are... 

    High-order weighted essentially nonoscillatory finite-difference formulation of the lattice boltzmann method in generalized curvilinear coordinates

    , Article Physical Review E ; Volume 95, Issue 2 , 2017 ; 24700045 (ISSN) Hejranfar, K ; Saadat, M. H ; Taheri, S ; Sharif University of Technology
    In this work, a high-order weighted essentially nonoscillatory (WENO) finite-difference lattice Boltzmann method (WENOLBM) is developed and assessed for an accurate simulation of incompressible flows. To handle curved geometries with nonuniform grids, the incompressible form of the discrete Boltzmann equation with the Bhatnagar-Gross-Krook (BGK) approximation is transformed into the generalized curvilinear coordinates and the spatial derivatives of the resulting lattice Boltzmann equation in the computational plane are solved using the fifth-order WENO scheme. The first-order implicit-explicit Runge-Kutta scheme and also the fourth-order Runge-Kutta explicit time integrating scheme are... 

    Construction of scaffolds composed of acellular cardiac extracellular matrix for myocardial tissue engineering

    , Article Biologicals ; Volume 53 , 2018 , Pages 10-18 ; 10451056 (ISSN) Esmaeili Pourfarhangi, K ; Mashayekhan, S ; Ghanbari Asl, S ; Hajebrahimi, Z ; Sharif University of Technology
    Academic Press  2018
    High rates of mortality and morbidity stemming from cardiovascular diseases unveil extreme limitations in current therapies despite enormous advances in medical and pharmaceutical sciences. Following myocardial infarction (MI), parts of myocardium undergo irreversible remodeling and is substituted by a scar tissue which eventually leads to heart failure (HF). To address this issue, cardiac patches have been utilized to initiate myocardial regeneration. In this study, a porous cardiac patch is fabricated using a mixture of decellularized myocardium extracellular matrix (ECM) and chitosan (CS). Results of rheological measurements, SEM, biodegradation test, and MTT assay showed that the... 

    Interfacial instability of growing drop: experimental study and conceptual analysis

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 347, Issue 1-3 , 2009 , Pages 167-174 ; 09277757 (ISSN) Javadi, A ; Bastani, D ; Kragel, J ; Miller, R ; Sharif University of Technology
    Elsevier  2009
    Capillary pressure experiments were performed at the water/hexane interface including adsorption and mass exchange of hexanol under different conditions. The results from growing drop experiments show that instabilities due to Marangoni convection not only depend on the same parameters as have been reported for quasi-static interfaces, such as direction of mass transfer, distribution coefficient and ratio of diffusion coefficients, but also on the experimental conditions such as dispersed phase flow rate, capillary tip size, size of growing drop and its lifetime. Based on a new flow expansion model for mass transfer, a new approach is presented for data analysis, which includes the various... 

    Design and fabrication of a two-phase diamond nanoparticle aided fast PCR device

    , Article Analytica Chimica Acta ; Volume 1068 , 2019 , Pages 28-40 ; 00032670 (ISSN) Madadelahi, M ; Ghazimirsaeed, E ; Shamloo, A ; Sharif University of Technology
    Elsevier B.V  2019
    Polymerase Chain Reaction (PCR) is an important and prevalent technique in biotechnology because of its crucial role in cloning DNA fragments and diagnostic applications. In the present study, a high-throughput two-phase PCR device is designed and fabricated which utilizes a serpentine microchannel together with a spiral structure. The former is for the droplet-generation and mixing and the latter is for the thermal cycling process. Moreover, the effect of diamond nanoparticles (diamondNP) on the performance of PCR is also investigated while using commercial PCR devices and the fabricated PCR device designed in this study. Using numerical simulation, it is shown that within the simple and... 

    On the viscosity of composite suspensions of aluminum and ammonium perchlorate particles dispersed in hydroxyl terminated polybutadiene-New empirical model

    , Article Journal of Colloid and Interface Science ; Volume 299, Issue 2 , 2006 , Pages 962-971 ; 00219797 (ISSN) Arefinia, R ; Shojaei, A ; Sharif University of Technology
    The rheological properties of fuel suspensions with various solid loadings up to close their maximum packing fraction and suspending media having different viscosities are investigated using the rotational viscometer at relatively low shear rates in which suspensions behave as Newtonian fluids. Aluminum (Al) and ammonium perchlorate (AP) particles are major solid components of any solid fuel system which should be distributed uniformly inside a polymeric binder based on hydroxyl terminated polybutadiene (HTPB). The experimental data generated in this investigation indicates that the relative viscosity of the suspensions is independent of viscosity of polymer binder, but in addition to solid... 

    Modification of rock/fluid and fluid/fluid interfaces during MEOR processes, using two biosurfactant producing strains of Bacillus stearothermophilus SUCPM#14 and Enterobacter cloacae: A mechanistic study

    , Article Colloids and Surfaces B: Biointerfaces ; Vol. 117 , May , 2014 , pp. 457-465 ; ISSN: 09277765 Sarafzadeh, P ; Zeinolabedini Hezave, A ; Mohammadi, S ; Niazi, A ; Ayatollahi, S ; Sharif University of Technology
    During any microbial enhanced oil recovery process, both cells and the metabolic products of bacteria govern the tertiary oil recovery efficiency. However, very accurate examination is needed to find the functionality of these tiny creatures at different reservoir conditions. In this regard, the effect of cell structure on ultimate microbial recovery efficiency which is the most dominant mechanism based on the microorganism types (gram-negative or gram-positive) was systematically investigated. At the first stage, possible different active mechanisms using Bacillus stearothermophilus SUCPM#14 strain were tested using specially designed injection protocol, in situ and ex situ core flooding... 

    Rheology of interfacial layers

    , Article Current Opinion in Colloid and Interface Science ; Vol. 19, issue. 6 , 2014 , pp. 514-519 ; ISSN: 13590294 Karbaschi, M ; Lotfi, M ; Kragel, J ; Javadi, A ; Bastani, D ; Miller, R ; Sharif University of Technology
    Dilational and shear viscoelasticities are important properties of interfacial layers. These quantities are particularly relevant in all systems which contain a huge internal interfacial area such as foams and emulsions. Therefore, also the 3D rheological behavior of foams or emulsions studied by respective methods is superimposed by the 2D interfacial rheology.We report on recent developments in dilational and shear rheology from an experimental point of view as well as discuss the state of the art of the underlying theories. Examples of most relevant experiments are also presented and discussed. Although not yet extensively investigated, the links between bulk rheology of foams and... 

    Supramolecular polycaprolactone nanocomposite based on functionalized hydroxyapatite

    , Article Journal of Bioactive and Compatible Polymers ; Volume 27, Issue 5 , January , 2012 , Pages 467-480 ; 08839115 (ISSN) Mehmanchi, M ; Shokrollahi, P ; Atai, M ; Omidian, H ; Bagheri, R ; Sharif University of Technology
    SAGE  2012
    Arms bearing ureido-pyrimidinone functional groups with self-association capability (through quadruple hydrogen bonds) were successfully grafted onto hydroxyapatite nanoparticles. The supramolecularly modified nanoparticles (nHApUPy) exhibited enhanced colloidal stability compared to the original hydroxyapatite nanoparticles and were uniformly dispersed in supramolecular polycaprolactone in PCL(UPy)2/HApUPy nanocomposites at different filler loadings. The combined atomic force microscopy, mechanical, and rheological analyses confirmed a high degree of compatibility of HApUPy nanoparticles with the polymer matrix. The temperature dependence of the supramolecular structure in PCL(UPy)2/HApUPy... 

    Fast dynamic interfacial tension measurements and dilational rheology of interfacial layers by using the capillary pressure technique

    , Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 407 , August , 2012 , Pages 159-168 ; 09277757 (ISSN) Javadi, A ; Krägel, J ; Makievski, A. V ; Kovalchuk, V. I ; Kovalchuk, N. M ; Mucic, N ; Loglio, G ; Pandolfini, P ; Karbaschi, M ; Miller, R ; Sharif University of Technology
    Elsevier  2012
    The oscillating drop and bubble analyzer (ODBA) is an experimental set-up based on the measurement of capillary pressure under static and dynamic conditions. It allows studies of slow and fast dynamic surface and interfacial tensions, following different growing and oscillating drop or bubble protocols, as well as determination of the dilational interfacial visco-elasticity of liquid interfacial layers. For the visco-elasticity studies, drops or bubbles are subjected to harmonic oscillations of area or volume in a broad frequency range, and the resulting harmonic capillary pressure response is analyzed by Fourier analysis. Also, transient relaxations can be easily performed, which are of... 

    Fabrication and characterization of conductive chitosan/gelatin-based scaffolds for nerve tissue engineering

    , Article International Journal of Biological Macromolecules ; Volume 74 , 2015 , Pages 360-366 ; 01418130 (ISSN) Baniasadi, H ; Ramazani S. A., A ; Mashayekhan, S ; Sharif University of Technology
    This paper reports on the development of conductive porous scaffolds by incorporating conductive polyaniline/graphene (PAG) nanoparticles into a chitosan/gelatin matrix for its potential application in peripheral nerve regeneration. The effect of PAG content on the various properties of the scaffold is investigated and the results showed that the electrical conductivity and mechanical properties increased proportional to the increase in the PAG loading, while the porosity, swelling ratio and in vitro biodegradability decreased. In addition, the biocompatibility was evaluated by assessing the adhesion and proliferation of Schwann cells on the prepared scaffolds using SEM and MTT assay,... 

    Comparison of rheological behavior of branched polypropylene prepared by chemical modification and electron beam irradiation under air and N2

    , Article Radiation Physics and Chemistry ; Volume 79, Issue 10 , 2010 , Pages 1088-1094 ; 0969806X (ISSN) Mousavi, S. A ; Dadbin, S ; Frounchi, M ; Venerus, D. C ; Medina, T. G ; Sharif University of Technology
    Chemical and electron beam irradiation methods were used to introduce a branched structure into polypropylene and propylene-ethylene copolymer. The chemical method was carried out in an internal mixer using initiator and TMPTMA monomer. In irradiation method, the polymer was irradiated by electron beam under air and nitrogen atmosphere. The branched structure in the modified polymer was confirmed by rheological measurements. While degradation was significant in chemical method, branching occurred efficiently by irradiation under air. Small amount of ethylene in the propylene copolymer promoted branching over degradation