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    The characteristics of serrated flow in superalloy IN738LC

    , Article Materials Science and Engineering A ; Volume 486, Issue 1-2 , 2008 , Pages 376-380 ; 09215093 (ISSN) Sharghi Moshtaghin, R ; Asgari, S ; Sharif University of Technology
    Serrated flow was investigated in superalloy IN738LC, a nickel-base γ′ age-hardened alloy. In this material serrated flow appeared between 350 and 450 °C and strain rate of (8.77 × 10-5 to 8.77 × 10-3) s-1. Activation energy for this process was calculated to be 0.69-0.86 eV which is in good agreement with the values reported for similar alloys. Results show that the diffusion rate of substitutional solute atoms at this temperature range is too low to cause this effect. This suggests that the interaction of solute atoms and moving dislocation is responsible for the observed serrated flow in this alloy. © 2007 Elsevier B.V. All rights reserved  

    A facile aerobic copper-catalyzed α-oxygenation of aryl thioacetamides: An efficient access to α-keto aryl thioamides

    , Article Synlett ; Issue 6 , 2008 , Pages 892-896 ; 09365214 (ISSN) Matloubi Moghaddam, F ; Mirjafary, Z ; Saeidian, H ; Jebeli Javan, M ; Sharif University of Technology
    Copper(II) efficiently catalyzes the aerobic oxidation of aryl thioacetamides into the corresponding α-keto aryl thioamides in moderate to high yields in the presence of K2CO3 under O 2 atmosphere. This protocol is simple, clean, and generates water as the only byproduct. A mechanism is proposed for the reaction course. © Georg Thieme Verlag Stuttgart  

    Effect of the attraction range of pair potential on the thermodynamic properties of fluids

    , Article Scientia Iranica ; Volume 14, Issue 2 , 2007 , Pages 118-125 ; 10263098 (ISSN) Parsafar, G. A ; Ahadzadeh, I ; Sharif University of Technology
    Sharif University of Technology  2007
    Recently, a new potential model has been proposed for the intermolecular interactions of model pure fluids and it was shown that the derived Equation Of State (EOS), based on this potential, can properly predict the thermodynamic properties of these.fluids. In addition to simplicity and, to some extent, the realistic form, this potential has a parameter (α) which controls the range of the attraction tail. In the first part of this study, the proposed potential and derived EOS are extended to binary mixtures of model fluids. In a similar manner to that of the pure fluids, the results obtained are consistent with the data available from simulation studies. In the second part, after... 

    Theoretical investigation of the enhanced solubility of perfluorobenzene in the supercritical carbon dioxide as a function of temperature and density by Monte Carlo simulation

    , Article Chemical Physics Letters ; Volume 444, Issue 1-3 , 2007 , Pages 48-55 ; 00092614 (ISSN) Tafazzoli, M ; Khanlarkhani, A ; Sharif University of Technology
    The absolute free energy of solvation of benzene and perfluorobenzene was measured in supercritical carbon dioxide using the expanded-ensemble method in the context of Monte Carlo (MC) Simulations. The MC calculations were carried out at 12 state points on the solvent phase diagram: (ρr = 0.5, 1.0, 1.5, 2.0; Tr = 1.01, 1.10, and 1.20). These conditions were chosen to address the accurance of specific molecular interactions between CO2 and fluorine. The greater stability of perfluorobenzene observed over all states investigated in this study attributed to the greater solvent accessible surface area and 25-30% increase in the strength of the interaction of this molecule with CO2 in the... 

    Organocatalytic synthesis of chiral benzopyrans

    , Article Tetrahedron Asymmetry ; Volume 17, Issue 12 , 2006 , Pages 1763-1767 ; 09574166 (ISSN) Govender, T ; Hojabri, L ; Matloubi Moghaddam, F ; Arvidsson, P. I ; Sharif University of Technology
    Benzopyrans, or chromenes, are widespread in nature and are considered to be a privileged scaffold in medicinal chemistry. Herein, we report the first organocatalyzed asymmetric synthesis of chiral benzopyrans. The benzopyran unit is constructed through a domino reaction involving an oxa-Michael attack of salicylic aldehyde derivatives onto α,β-unsaturated aldehydes, activated through iminium-ion formation with the organocatalyst, followed by an intramolecular aldol reaction and subsequent elimination of water. This overall reaction sequence provides benzopyrans with aromatic C-2 substituents in up to 60% yield and 60% enantioselectivity, while C-2 aliphatic analogues can be obtained in 90%... 

    Lattice relaxation in many-electron states of the diamond vacancy

    , Article Physical Review B - Condensed Matter and Materials Physics ; Volume 71, Issue 3 , 2005 ; 10980121 (ISSN) Heidari Saani, M ; Vesaghi, M. A ; Esfarjani, K ; Ghods Elahi, T ; Sayari, M ; Hashemi, H ; Gorjizadeh, N ; Sharif University of Technology
    Symmetric lattice relaxation around a vacancy in diamond and its effect on many electron states of the defect have been investigated. A molecular approach is used to evaluate accurately electron-electron (e-e) interaction via a semiempirical formalism which is based on a generalized Hubbard Hamiltonian. Coupling of the defect molecule to surrounding bulk is also considered using an improved Stillinger-Weber potential for diamond. Strong dependence of the electronic energy levels to the relaxation size of the nearest neighbor (NN) atoms indicates that in order to obtain quantitative results the effect of lattice relaxation should be considered. Except for the high spin state of the defect 5A... 

    Tip and sample flexibility effects on tapping mode (amplitude modulation) AFM measurements

    , Article Micro and Nano Letters ; Volume 6, Issue 12 , December , 2011 , Pages 1023-1028 ; 17500443 (ISSN) Pishkenari, H. N ; Meghdari, A ; Sharif University of Technology
    This Letter is devoted to the investigation of the tip, substrate and particle flexibility effects on the elastic deformation, the maximum repulsive force and the topography images in tapping mode (amplitude modulation) atomic force microscopy (TM-AFM). Several quantitative comparisons among the different models are presented and the effects of the elastic deformations on TM-AFM measurement are investigated  

    Emergence of molecular chirality due to chiral interactions in a biological environment

    , Article Journal of Biological Physics ; Vol. 40, issue. 4 , Jul , 2014 , p. 369-386 Tirandaz, A ; Ghahramani, F. T ; Shafiee, A ; Sharif University of Technology
    We explore the interplay between tunneling process and chiral interactions in the discrimination of chiral states for an ensemble of molecules in a biological environment. Each molecule is described by an asymmetric double-well potential and the environment is modeled as a bath of harmonic oscillators. We carefully analyze different time-scales appearing in the resulting master equation at both weak- and strong-coupling limits. The corresponding results are accompanied by a set of coupled differential equations characterizing optical activity of the molecules. We show that, at the weak-coupling limit, chiral interactions prohibit the coherent racemization induced by decoherence effects and... 

    Hybrid finite-element method-molecular dynamics approach for modelling of non-contact atomic force microscopy imaging

    , Article Micro and Nano Letters ; Volume 6, Issue 6 , June , 2011 , Pages 412-416 ; 17500443 (ISSN) Pishkenari, H. N ; Mahboobi, S. H ; Meghdari, A ; Sharif University of Technology
    Models capable of accurate simulation of the microcantilever dynamics coupled with complex tip-sample interactions are essential for interpretation of the imaging results in non-contact atomic force microscopy (AFM). In the present research, a combination of finite element and molecular dynamics methods are used for modelling the AFM system to overcome the drawbacks of conventional approaches that use a lumped system with van der Waals interaction. To illustrate the ability of the proposed scheme in providing images with atomic resolution, some simulations have been performed. In the conducted simulations, a diamond tip is interacting with nickel samples having different surface plane... 

    Mechanical differences between ATP and ADP actin states: A molecular dynamics study

    , Article Journal of Theoretical Biology ; Volume 448 , 2018 , Pages 94-103 ; 00225193 (ISSN) Mehrafrooz, B ; Shamloo, A ; Sharif University of Technology
    Academic Press  2018
    This paper aims to give a comprehensive atomistic modeling of the nanomechanical behavior of actin monomer. Actin is a ubiquitous and essential component of cytoskeleton which forms many different cellular structures. Despite for several years great effort has been devoted to the investigation of mechanical properties of the actin filament, studies on the nanomechanical behavior of actin monomer are still lacking. These scales are, however, important for a complete understanding of the role of actin as an important component in the cytoskeleton structure. Based on the accuracy of atomistic modeling methods such as molecular dynamics simulations, steered molecular dynamics method is performed... 

    Application of nano-structured materials in anaerobic digestion: Current status and perspectives

    , Article Chemosphere ; Volume 229 , 2019 , Pages 188-199 ; 00456535 (ISSN) Baniamerian, H ; Ghofrani Isfahani, P ; Tsapekos, P ; Alvarado Morales, M ; Shahrokhi, M ; Vossoughi, M ; Angelidaki, I ; Sharif University of Technology
    Elsevier Ltd  2019
    Nanotechnology is gaining more attention in biotechnological applications as a research area with a huge potential. Nanoparticles (NPs)can influence the rate of anaerobic digestion (AD)as the nano-sized structures, with specific physicochemical properties, interact with substrate and microorganisms. The present work has classified the various types of additives used to improve the AD processes. Nanomaterials as new additives in AD process are classified into four categories: Zero-valent metallic NPs, Metal oxide NPs, Carbon based nanomaterials, and Multi-compound NPs. In the following, application of nanomaterials in AD process is reviewed and negative and positive effects of these materials... 

    Qquantitative structure - retention relationship study of a variety of compounds in reversed-phase liquid chromatography: A PLS-MLR-STANN approach

    , Article QSAR and Combinatorial Science ; Volume 27, Issue 2 , 2008 , Pages 137-146 ; 1611020X (ISSN) Jalali Heravi, M ; Garkani Nejad, Z ; Kyani, A ; Sharif University of Technology
    A quantitative structure-retention relationships model has been developed to study the retention behavior of 87 aliphatic and aromatic compounds in Reversed-Phase Liquid Chromatography (RPLC) on five bonded-phase columns differing in silanol group acidity. Six numerical descriptors of Molecular Mass (M), partial charge of the most negative atom (NPCH), partial charge of the most positive hydrogen (PCHH), van der Waals volume (VOLUME), Dipole Moment (DIMO), and Highest Occupied Molecular Orbital (HOMO) have been calculated for each compound. A separate Multiple Linear Regression (MLR) model has been developed using the six descriptors for each column. Partial Least Square (PLS) combined with... 

    Photoluminescent carbon quantum dot/poly-L-Lysine core-shell nanoparticles: A novel candidate for gene delivery

    , Article Journal of Drug Delivery Science and Technology ; Volume 61 , 2021 ; 17732247 (ISSN) Hasanzadeh, A ; Mofazzal Jahromi, M. A ; Abdoli, A ; Mohammad Beigi, H ; Fatahi, Y ; Nourizadeh, H ; Zare, H ; Kiani, J ; Radmanesh, F ; Rabiee, N ; Jahani, M ; Mombeiny, R ; Karimi, M ; Sharif University of Technology
    Editions de Sante  2021
    Cationic polymers such as poly-L-lysine (PLL) are able to interact electrostatically with DNA to produce polymeric systems with nanometric diameters due to the neutralization and accumulation of DNA. This study integrates the outstanding properties of carbon quantum dots (CQDs) with PLL to develop a novel gene delivery vehicle with a core-shell hybrid nanostructure. The CQD/PLL core-shell nanoparticles (NPs) were, therefore, synthesized in such a way that they had narrow size distribution and an average diameter under 10 nm, both of which were confirmed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Fourier transform infrared (FTIR) spectroscopy exhibited that... 

    Evaluation of the effects of process parameters on granule mean size in a conical high shear granulator using response surface methodology

    , Article Powder Technology ; Volume 237 , 2013 , Pages 186-190 ; 00325910 (ISSN) Ranjbarian, S ; Farhadi, F ; Sharif University of Technology
    Response surface methodology was used to investigate the effects of operating parameters such as impeller speed, binder mass and granulation time on the average size of granules produced in a lab scale conical high shear granulator. Two quadratic models were proposed to express granule mean size as a function of impeller speed and binder mass as well as impeller speed and granulation time. It was found out that in the studied domain, the influence of each parameter on granule size differs from one another. While increasing binder mass at constant quantity of powder increased the average size linearly, increasing impeller speed changed the mean size in accordance with quadratic trend. The... 

    Influence of the tip mass on the tip-sample interactions in TM-AFM

    , Article Ultramicroscopy ; Volume 111, Issue 8 , Jul , 2011 , Pages 1423-1436 ; 03043991 (ISSN) Pishkenari, H. N ; Meghdari, A ; Sharif University of Technology
    This paper focuses on the influences of the tip mass ratio (the ratio of the tip mass to the cantilever mass), on the excitation of higher oscillation eigenmodes and also on the tip-sample interaction forces in tapping mode atomic force microscopy (TM-AFM). A precise model for the cantilever dynamics capable of accurate simulations is essential for the investigation of the tip mass effects on the interaction forces. In the present work, the finite element method (FEM) is used for modeling the AFM cantilever to consider the oscillations of higher eigenmodes oscillations. In addition, molecular dynamics (MD) is used to calculate precise data for the tip-sample force as a function of tip... 

    Chitosan-gelatin sheets as scaffolds for muscle tissue engineering

    , Article Artificial Cells, Nanomedicine and Biotechnology ; Volume 43, Issue 2 , Nov , 2015 , Pages 124-132 ; 21691401 (ISSN) Hajiabbas, M ; Mashayekhan, S ; Nazaripouya, A ; Naji, M ; Hunkeler, D ; Rajabi Zeleti, S ; Sharifiaghdas, F ; Sharif University of Technology
    Informa Healthcare  2015
    Hydrogels made of natural polymers [chitosan (CS) and gelatin (G)] have been prepared having mechanical properties similar to those of muscle tissues. In this study, the effect of polymer concentration and scaffold stiffness on the behavior of seeded muscle-derived cells (MDCs) on the CS-G hydrogel sheets has been evaluated. Both variables were found to be important in cell viability. Viability was assessed by observation of the cell morphology after 1 day as well as a 14-day MTT assay. The CS-G hydrogels were characterized using Fourier transform infrared (FTIR) analysis, which revealed evidences of strong intermolecular interactions between CS and G. Hydrogel samples with intermediate... 

    Characterization of carbon nanotube dispersion and filler network formation in melted polyol for nanocomposite materials

    , Article Powder Technology ; Volume 276 , 2015 , Pages 222-231 ; 00325910 (ISSN) Pircheraghi, G ; Foudazi, R ; Manas Zloczower, I ; Sharif University of Technology
    Elsevier  2015
    Different grades of carbon nanotubes (CNTs) were dispersed in poly(tetramethylene ether glycol) (PTMEG) without any solvent in the presence of a block copolymer dispersing agent by ultrasonication at a temperature well above the melting point of the PTMEG. The state of CNT dispersion at different length scales was evaluated by using optical microscopy, UV-Vis spectroscopy, rheological measurements, differential scanning calorimetry, thermogravimetric analysis and sedimentation tests. Optical microscopy can be used to characterize the state of dispersion and CNT network formation on a micrometer scale, whereas UV-Vis provides useful information about the dispersion of individual CNTs at... 

    CFD-DEM Model for Simulation of Non-spherical Particles in Hole Cleaning Process

    , Article Particulate Science and Technology ; Volume 33, Issue 5 , 2015 , Pages 472-481 ; 02726351 (ISSN) Akhshik, S ; Behzad, M ; Rajabi, M ; Sharif University of Technology
    Taylor and Francis Inc  2015
    During the well drilling process, particles are produced in different shapes. The shape of particles can influence the characteristics of particles transport process. The aim of this work is to analyze the effects of particle shape on the transportation mechanism. For this purpose, a three-dimensional model is prepared for simulation of particle transportation with spherical and non-spherical shapes, during deviated well drilling. The motion of particles and the non-Newtonian fluid flow are simulated via discrete element method and CFD, respectively. The two-way coupling scheme is used to incorporate the effects of fluid-particle interactions. Three different samples of non-spherical shapes... 

    Preparation and biological evaluation of radiolabeled-folate embedded superparamagnetic nanoparticles in wild-type rats

    , Article Journal of Radioanalytical and Nuclear Chemistry ; Volume 287, Issue 1 , January , 2011 , Pages 119-127 ; 02365731 (ISSN) Jalilian, A. R ; Hosseini Salekdeh, S. L ; Mahmoudi, M ; Yousefnia, H ; Majdabadi, A ; Pouladian, M ; Sharif University of Technology
    In this study, superparamagnetic iron oxide nanoparticles (SPION) embedded by folic acid (SPION-folate) were prepared by a modified co-precipitation method. The structure, size, morphology, magnetic property and relaxivity of the SPION-folate were characterized systematically by means of XRD, VSM, HRSEM and TEM and the interaction between folate and iron oxide (Fe3O 4) was characterized by FT-IR. The particle size was shown to be ≈5-10 nm. To ensure biocompatibility, the interaction of these SPION with mouse connective tissue cells (adhesive) was investigated using an MTT assay. Consequently, gallium-67 labeled nanoparticles ([67Ga]-SPION-folate) were prepared using 67Ga with a high labeling... 

    Mining the potential of label-free biosensors for in vitro antipsychotic drug screening

    , Article Biosensors ; Volume 8, Issue 1 , 2018 ; 20796374 (ISSN) Kilic, T ; Soler, M ; Fahimi Kashani, N ; Altug, H ; Carrara, S ; Sharif University of Technology
    MDPI AG  2018
    The pharmaceutical industry is facing enormous challenges due to high drug attribution rates. For the past decades, novel methods have been developed for safety and efficacy testing, as well as for improving early development stages. In vitro screening methods for drug-receptor binding are considered to be good alternatives for decreasing costs in the identification of drug candidates. However, these methods require lengthy and troublesome labeling steps. Biosensors hold great promise due to the fact that label-free detection schemes can be designed in an easy and low-cost manner. In this paper, for the first time in the literature, we aimed to compare the potential of label-free optical and...