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    Graphene oxide-starch-based micro-solid phase extraction of antibiotic residues from milk samples

    , Article Journal of Chromatography A ; Volume 1591 , 2019 , Pages 7-14 ; 00219673 (ISSN) Golzari Aqda, T ; Behkami, S ; Raoofi, M ; Bagheri, H ; Sharif University of Technology
    Elsevier B.V  2019
    In this study, a method was described for the extraction of three antibiotic residues from cow milk samples using a graphene oxide–starch–based nanocomposite. The prepared nanocomposites were employed as an extractive phase for micro-solid phase extraction of antibiotics from cow milk samples. The extracted antibiotics, i.e. amoxicillin, ampicillin and cloxacillin, were subsequently analyzed by high-performance liquid chromatography–ultraviolet detection (HPLC–UV). Important variables associated with the extraction and desorption efficiency were optimized. High extraction efficiencies for the selected antibiotics were conveniently achieved using the starch–based nanocomposite as the... 

    An ultrasensitive label free human papilloma virus DNA biosensor using gold nanotubes based on nanoporous polycarbonate in electrical alignment

    , Article Analytica Chimica Acta ; Volume 1048 , 2019 , Pages 31-41 ; 00032670 (ISSN) Shariati, M ; Ghorbani, M ; Sasanpour, P ; Karimizefreh, A ; Sharif University of Technology
    Elsevier B.V  2019
    An impedimetric human papilloma virus (HPV) DNA biosensor based on gold nanotubes (AuNTs) in label free detection was materialized. The AuNTs decorated nanoporous polycarbonate (AuNTs-PC) template as biosensor electrode was fabricated by electrodeposition method. The single strand DNA (ss-DNA) probe was covalently immobilized onto the AuNTs-PC electrode. The hybridization of target sequences with the ss-DNA probe was observed by the electrochemical impedance spectroscopy (EIS). The biosensor showed high selectivity and could differentiate between the complementary, mismatch and non-complementary DNA sequences. The EIS measurements were matched to Randle's equivalent circuit. The... 

    Liquid-liquid-liquid microextraction followed by HPLC with UV detection for quantitation of ephedrine in urine

    , Article Journal of Separation Science ; Volume 31, Issue 18 , 2008 , Pages 3212-3217 ; 16159306 (ISSN) Bagheri, H ; Khalilian, F ; Ahangar, L. E ; Sharif University of Technology
    Liquid-liquid-liquid microextraction (LLLME) in combination with HPLC and UV detection has been used as a sensitive method for the determination of ephedrine in urine samples. Extraction process was performed in a homemade total glass vial without using a Teflon ring, usually employed. Ephedrine was first extracted from 3.5 mL of urine sample (pH 12) into a microfilm of toluene/benzene (50:50). The analyte was subsequently back extracted into an acidic microdrop solution (pH 2) suspended in the organic phase. The extract was then injected into the HPLC system directly. An enrichment factor of 137 along with a good sample clean-up was obtained under the optimized conditions. The calibration... 

    Analysis of P300 classifiers in brain computer interface speller

    , Article 28th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, EMBS'06, New York, NY, 30 August 2006 through 3 September 2006 ; 2006 , Pages 6205-6208 ; 05891019 (ISSN); 1424400325 (ISBN); 9781424400324 (ISBN) Mirghasemi, H ; Fazel Rezai, R ; Shamsollahi, M. B ; Sharif University of Technology
    In this paper, the performance of five classifiers in P300 speller paradigm are compared. Theses classifiers are Linear Support Vector Machine (LSVM), Gaussian Support Vector Machine (RSVM), Neural Network (NN), Fisher Linear Discriminant (FLD), and Kernel Fisher Discriminant (KFD). In classification of P300 waves, there has been a trend to use SVM classifiers. Although they have shown a good performance, in this paper, it is shown that the FLD classifiers outperform the SVM classifiers. FLD classifier uses only ten channels of the recorded electroencephalogram (EEG) signals. This makes them a very good candidate for real-time applications. In addition, FLD approach does not need any... 

    Preparation of amine–modified lignin and its applicability toward online micro–solid phase extraction of valsartan and losartan in urine samples

    , Article Journal of Chromatography A ; Volume 1643 , 2021 ; 00219673 (ISSN) Taherzadeh Ghahfarrokhi, M ; Zeinali, S ; Bagheri, H ; Sharif University of Technology
    Elsevier B.V  2021
    In the present work, with the focus on an environmentally–friendly approach, some gels were prepared by synthesizing amine–modified lignin, extracted from sugarcane bagasse, and further esterification and subsequent freeze–drying. These lignin–based gels were implemented as extractive phases in an online micro–solid phase extraction (μSPE) setup in conjunction with high performance liquid chromatography (HPLC) with UV detector. The developed method was used for analytical determination of valsartan and losartan in urine samples. To study the effect of the functionalization process, the efficiency of the unmodified lignin and the functionalized lignin were compared both in the absence and the... 

    Vibration Analysis of FGM Beam Using RKPM Meshlesh Method

    , M.Sc. Thesis Sharif University of Technology Saljooghi, Reza (Author) ; Ahmadian, Mohammad Taghi (Supervisor)
    Due to special characteristics, nowadays functionally graded materials are of great interest of researchers. Continuous change of properties in these materials,decreases undesirable phenomena such as stresscon centration. On the other hand knowing vibration parameters of structures such as natural frequencies, to avoid damage, is important. So far, many researches have been devoted to vibration analysis of structures, such as beams.In this dissertation, free vibration analysis of FGM beams, are investigated, using RKPM, a meshlesh method. The system of equations of motion is derived using Lagrange’s method under the assumption of Euler-Bernoulli beam theory. Buckling analysis of FGM beams... 

    Numerical Modeling of a Smooth Notched Tensile Specimen Via Gradient Elasticity Based RKPM

    , M.Sc. Thesis Sharif University of Technology Alavi, Ali (Author) ; Mohammadi Shodja, Hosain (Supervisor)
    Recently, there has been a strong interest in the development of a new class of meshfree methods. As an alternative to the finite element method (FEM), mainly due to elimination of high cost mesh generation processes. In addition, the size effect is currently a subject of increasing interest since it is an important parameter in predicting, correctly, the mechanical behavior of materials with microstructure. It was well established that classical linear elastic continua which neglects the higher order terms is not able to describe size effects. In contrast, enhanced continuum theories such as nonlocal or gradient-dependent models do involve an internal length scale. Thorough this length... 

    Employing Enriched Meshfree MLSRK Method to Analyze 2D Linear Elastic Fracture Mechanics Problems

    , M.Sc. Thesis Sharif University of Technology Namakian, Reza (Author) ; Mohammadi Shoja, Hossein (Supervisor)
    The so-called moving least square reproducing kernel method (MLSRKM), which is a meshfree Galerkin method, has two special properties in comparison with its prior version, say moving least square method (MLSM): (i) stability in preserving completeness conditions to the desired order for a discrete reproducing formula due to implementation of shifted and scaled basis, (ii) use of more accurate quadrature weights in a discrete reproducing form, especially along boundaries. However, because of employing shifted basis in MLSRKM, some of enrichment techniques, specifically in the context of linear elastic fracture mechanics (LEFM) problems, cannot be applied to this method. Therefore, we are... 

    GRKPM: Theory and Applications in Laminated Composite Plates and Nonlinear Evolutionary Partial Differential Equations With Large Gradients

    , Ph.D. Dissertation Sharif University of Technology Hashemian, Alireza (Author) ; Mohammadi Shodja, Hossein (Supervisor)
    Reproducing kernel particle method (RKPM) is a meshfree method for solving various differential equations. RKPM is based on pure mathematics; therefore, it is in the center of attention of many scientists. One major problem in RKPM is satisfying the essential boundary conditions (EBCs) involving the derivative of the field function. This problem is considered herein and its solution is proposed. To this end, two actions should be undertaken. First, the concept of Hermitian interpolation is employed to add the derivative term to the reproducing equation of RKPM and a new meshless method called gradient RKPM (GRKPM) is introduced. Second, the corrected collocation method is modified so... 

    Numerical Analysis of a Plate Containing Multiple Circular Holes Via RKPM

    , M.Sc. Thesis Sharif University of Technology Soltani Mohammadi, Siavash (Author) ; Mohammdi Shodja, Hossein (Supervisor)
    In this thesis, some new models have been solved via RKPM method, which is one of the meshfree methods family. These models have never been solved via meshfree methods and their analytical solutions do not exist. At first, the RKPM shape functions and their first derivative formulation in 1D and 2D have been presented and then by using FORTRAN program, the shape functions and their first derivative have been obtained. To verifying the code some functions have been reproduced. In the next step by using the governing equations and penalty method whose formulation exists in chapter 2; some famous examples in linear elasticity have been solved via RKPM to verify the FORTRAN code. At last; some... 

    Vibration and buckling analysis of functionally graded beams using reproducing kernel particle method

    , Article Scientia Iranica ; Vol. 21, Issue 6 , 2014 , pp. 1896-1906 ; e-ISSN : 23453605 Saljooghi, R ; Ahmadian, M. T ; Farrahi, G. H ; Sharif University of Technology
    This paper presents vibration and buckling analysis of functionally graded beams with different boundary conditions, using reproducing kernel particle method (RKPM). Vibration of simple Euler-Bernoulli beam using RKPM is already developed and reported in the literature. Modeling of FGM beams using theoretical method or finite element technique is not evolved with accurate results for power law form of FGM with large power of "n" value so far. Accuracy of the RKPM results is very good and is not sensitive to n value. System of equations of motion is derived using Lagrange's method under the assumption of Euler-Bernoulli beam theory. Boundary conditions of the beam are taken into account using... 

    Automatic segmentation of brain MRI in high-dimensional local and non-local feature space based on sparse representation

    , Article Magnetic Resonance Imaging ; Volume 31, Issue 5 , 2013 , Pages 733-741 ; 0730725X (ISSN) Khalilzadeh, M. M ; Fatemizadeh, E ; Behnam, H ; Sharif University of Technology
    Automatic extraction of the varying regions of magnetic resonance images is required as a prior step in a diagnostic intelligent system. The sparsest representation and high-dimensional feature are provided based on learned dictionary. The classification is done by employing the technique that computes the reconstruction error locally and non-locally of each pixel. The acquired results from the real and simulated images are superior to the best MRI segmentation method with regard to the stability advantages. In addition, it is segmented exactly through a formula taken from the distance and sparse factors. Also, it is done automatically taking sparse factor in unsupervised clustering methods... 

    Response of reinforced concrete structures to macrocell corrosion of reinforcements. Part II: After propagation of microcracks via a numerical approach

    , Article Nuclear Engineering and Design ; Volume 242 , 2012 , Pages 7-18 ; 00295493 (ISSN) Kiani, K ; Shodja, H. M ; Sharif University of Technology
    Investigation of response of reinforced concrete (RC) structures due to axisymmetric macrocell corrosion of rebars is of concern after propagation of microcracks within the concrete medium. The geometry, boundary and interfaces conditions of the present problem are identical to those stated in part I. As seen in the companion paper, the exact solution to the boundary value problem corresponding to the uncracked steel-rust-concrete composite was possible. After appearance of the microcracks the concrete behavior becomes nonlinear anisotropic with post-cracking softening, and the associated problem is analytically intractable. Therefore, it is proposed to employ a novel meshless method, namely... 

    Free vibration analysis of FGM beams with different boundary conditions using RKPM meshless method

    , Article Proceedings of the ASME Design Engineering Technical Conference, 28 August 2011 through 31 August 2011 ; Volume 1, Issue PARTS A AND B , August , 2011 , Pages 1187-1191 ; 9780791854785 (ISBN) Saljooghi, R ; Ahmadian, M. T ; Sharif University of Technology
    This paper presents free vibration analysis of functionally graded material (FGM) beams with different boundary conditions, using RKPM (Reproducing Kernel Particle Method), which is a meshless method. System of equations of motion is derived by using Lagrange's method under the assumption of Euler-Bernoulli beam theory. Boundary conditions of beam are taken into account by using Lagrange multipliers. It is assumed that material properties of the beam vary continuously in the thickness direction according to the power-law form. RKPM is applied to obtain eigenvalue equation of vibration and natural frequencies are obtained. It should be noted that for special cases where the beam is uniform,... 

    Template-based electrodeposition of Pt/Ni nanowires and its catalytic activity towards glucose oxidation

    , Article Electrochimica Acta ; Volume 58, Issue 1 , 2011 , Pages 551-555 ; 00134686 (ISSN) Mahshid, S. S ; Mahshid, S ; Dolati, A ; Ghorbani, M ; Yang, L ; Luo, S ; Cai, Q ; Sharif University of Technology
    An electro-catalysis non-enzymatic electrode is proposed based on alloyed Pt/Ni nanowire arrays (NWAs) for the detection of glucose. The Pt/Ni NWAs were prepared by pulse electrodeposition of Pt and Ni within a nano-pore polycarbonate (PC) membrane followed by a chemical etching of the membrane. The electrode structure is characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The resulting Pt/Ni NWAs electrode shows high electrocatalytic activities towards the oxidation of glucose in alkaline solution. Consequently, a sensitive amperometric detection of glucose is achieved under 0.45 V vs. SCE with a low detection limit of 1.5 μM within a wide linear... 

    A well-dispersed Pt/Ni/TiO 2 nanotubes modified electrode as an amperometric non-enzymatic glucose biosensor

    , Article Sensor Letters ; Volume 9, Issue 5 , October , 2011 , Pages 1598-1605 ; 1546198X (ISSN) Mahshid, S. S ; Luo, S ; Yang, L ; Mahshid, S ; Dolati, A ; Ghorbani, M ; Cai, Q ; Sharif University of Technology
    In this study a novel Pt/Ni nanostructure consisting of nano-bushes and nanocubes was fabricated onto TiO 2 nanotubes. The scanning electron microscopy images showed that a large amount of well-dispersed nano-architectures had uniformly covered all over the surface which made an electrode with high surface area. It was obviously seen that the nanocube structures mainly consists of Ni had been grown on top of each other while the Pt colonies represented bush-like structures. As a non-enzymatic glucose biosensor, the Pt/Ni TiO 2 nanotubes modified electrode exhibited an excellent performance. The proposed biosensor had two linear ranges for detection of glucose from 0 to 0.12 mM (correlation... 

    Fibre position effects on the operation of opto-pair fibre displacement sensors

    , Article Optics and Laser Technology ; Volume 43, Issue 4 , 2011 , Pages 814-819 ; 00303992 (ISSN) Jafari, R ; Golnabi, H ; Sharif University of Technology
    In this article, two optical-fibre probes used in displacement measurements are reported. In one arrangement, two optical fibres with protective buffer jackets are placed together, while in the second arrangement, the protective buffer jackets are removed and the two fibres are placed with the claddings in contact, with a concomitant smaller centrecentre distance. As the core and cladding diameters are the same in both probes, the effect of the centrecentre distance on double-fibre designs can be investigated. The reflected output powers are recorded for the probes as a function of the axial distance from a reflective surface. A theoretical model is also implemented, which considers the... 

    Modal analysis of the dynamic response of Timoshenko beam under moving mass

    , Article Scientia Iranica ; Volume 22, Issue 2 , 2015 , Pages 331-344 ; 10263098 (ISSN) Roshandel, D ; Mofid, M ; Ghannadiasl, A ; Sharif University of Technology
    Sharif University of Technology  2015
    In this study, the dynamic response of a Timoshenko beam under moving mass is investigated. To this end, vectorial form orthogonality property of the Timoshenko beam free vibration modes is applied to the EEM (Eigenfunction Expansion Method). The implication of the vectorial form series and an appropriate inner product of mode shapes in combination are focused for a beam with arbitrary boundary conditions. Consequently, significant simplifications and efficacy in the utilization of the EEM in eliminating the spatial domain is achieved. In order to comprise validation, the present study is compared with the DET (Discrete Element Technique) and the RKPM (Reproducing Kernel Particle Method)  

    Optimisation of a microwave-assisted method for extracting withaferin A from Withania somnifera Dunal. using central composite design

    , Article Phytochemical Analysis ; Volume 21, Issue 6 , 2010 , Pages 544-549 ; 09580344 (ISSN) Mirzajani, F ; Ghassempour, A ; Jalali-Heravi, M ; Mirjalili, M. H ; Sharif University of Technology
    Introduction - Recently, there have been growing attention on the modification and optimisation of new extraction and quantification methods, caused by the lack of environmentally friendly methodologies for the extraction of phytochemicals from complex matrices. In the case of pharmaceutical compounds, not only the extraction procedure but also the analysis method should be efficient, precise, fast and easy.Objectives - The essential pharmaceutical characteristics and trace concentration of withanolides led us to modify and optimise the previously reported extraction and quantification procedure for withaferin A (WA) as a candidate for withanolides.Matrial and methods - The WA from the... 

    Selective voltammetric determination of d-penicillamine in the presence of tryptophan at a modified carbon paste electrode incorporating TiO2 nanoparticles and quinizarine

    , Article Journal of Electroanalytical Chemistry ; Volume 644, Issue 1 , Jan , 2010 , Pages 1-6 ; 15726657 (ISSN) Mazloum Ardakani, M ; Beitollahi, H ; Taleat, Z ; Naeimi, H ; Taghavinia, N ; Sharif University of Technology
    A carbon paste electrode (CPE) chemically modified with TiO2 nanoparticles and quinizarine (QZ) was used as a selective electrochemical sensor for the simultaneous determination of minor amounts of d-penicillamine (D-PA) and tryptophan (Trp). This modified electrode showed very efficient electrocatalytic activity for anodic oxidation of both d-PA and Trp. Substantial decreases of anodic overpotentials for both compounds made this analysis possible. Results of square wave voltammetry (SWV) using this modified electrode showed two well-resolved anodic waves for the oxidation of d-PA and Trp, which makes the simultaneous determination of both compounds possible. The peak potential for the...