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    Efficient modulation technique for optical code division multiple access networks: Differential pulse position modulation

    , Article IET Optoelectronics ; Vol. 8, issue. 5 , 2014 , p. 181-190 Khazraei, S ; Shoaie, M. A ; Pakravan, M. R ; Sharif University of Technology
    In this study, the authors study a fibre-optic local area network deploying optical code division multiple access technique with differential M-ary pulse position modulation (DPPM). The authors present the performance analysis of DPPM signalling using a double optical hardlimiter receiver structure considering the impairment caused by interference of other users. The analysis assumes a set of bit asynchronous transmitters employing generalised optical orthogonal codes for their DPPM signalling (GOOC-DPPM). Using mathematical analysis and simulations, the authors have demonstrated that GOOCDPPM improves both frame error probability and the maximum achievable network throughput compared with... 

    Differential pulse voltammetric determination of propylthiouracil and methylthiouracil using their catalytic effects on the electrochemical oxidation of catechol

    , Article International Journal of Electrochemical Science ; Volume 2, Issue 2 , 2007 , Pages 158-168 ; 14523981 (ISSN) Shahrokhian, S ; Saberi, R. S ; Sharif University of Technology
    The electrochemical behavior of catechol in the presence of propylthiouracil (PTU) and methylthiouracil (MTU) at a glassy carbon electrode is thoroughly investigated. The cyclic voltammetric studies of the systems are performed in different pHs and sweep rates. The results of the voltammetric foundations show an electrocatalytic oxidation of catechol in the presence of PTU and MTU, leading to a remarkable increase in the anodic peak current of catechol together with the contemporaneous disappearance of the corresponding cathodic wave. The presented mechanism shows the nucleophilic addition/reduction of the electro-generated o-quinone by the PTU or MTU, which produced chemically reduced... 

    Enzymatic biosensing by covalent conjugation of enzymes to 3D-networks of graphene nanosheets on arrays of vertically aligned gold nanorods: application to voltammetric glucose sensing

    , Article Microchimica Acta ; Volume 185, Issue 3 , 2018 ; 00263672 (ISSN) Mazaheri, M ; Simchi, A ; Aashuri, H ; Sharif University of Technology
    Springer-Verlag Wien  2018
    The authors demonstrate efficient direct electron transfer from the enzyme glucose oxidase to vertically aligned gold nanorods with a diameter of ~160 nm and a length of ~2 μm that are covalently linkage to a 3-dimensional network of reduced graphene oxide nanosheets. The assembly can be prepared by a 2-step electrochemical procedure. This hybrid structure holds the enzyme in a favorable position while retaining its functionality that ultimately provides enhanced performance for enzymatic sensing of glucose without utilizing mediators. The nanorod assembly was applied to the voltammetric detection of glucose. Figures of merit include an electrochemical sensitivity of 12 μA·mM−1·cm−2... 

    Multi-walled carbon nanotube paste electrode for selective voltammetric detection of isoniazid

    , Article Microchimica Acta ; Volume 157, Issue 3-4 , 2007 , Pages 149-158 ; 00263672 (ISSN) Shahrokhian, S ; Amiri, M ; Sharif University of Technology
    A multi-walled carbon nanotube paste electrode (MWCPE) is prepared as an electrochemical sensor with high sensitivity and selectivity in responding to isoniazid. The electrochemical oxidation of isoniazid is investigated in buffered solution by cyclic and differential pulse voltammetry. The electrode is shown to be very effective for the detection of isoniazid in the presence of other biological reductant compounds. The electrochemical oxidation of cysteine, due to the high overvoltage, is completely stopped at the surface of MWCPE. The electrode exhibits a very good resolution between the voltammetric peak of isoniazid and the peaks of ascorbic acid (AA) and dopamine (DA). A resolution of... 

    Nucleophilic addition of thiaproline to electrochemically derived o-quinone, application to the sensitive voltammetric detection of thiaproline

    , Article Electroanalysis ; Volume 18, Issue 22 , 2006 , Pages 2225-2231 ; 10400397 (ISSN) Shahrokhian, S ; Amiri, M ; Sharif University of Technology
    The mechanism of electrochemical behavior of catechol in the presence of thiaproline is investigated by cyclic voltammetry, controlled-potential coulometry and spectrophotometric tracing of the reaction coordinate. The results indicate that thiaproline participate in with an ECEC mechanism in a nucleophilic (Michael) addition to o-quinone. Effect of pH of buffer solution on reaction pathway is studied and showed that addition of thiaproline to the o-quinone is performed only in solutions with pHs higher than 5. These results indicate that the addition of thiaproline is occurred first from amine functional group. In the second step, the addition of carboxylate group of thiaproline to C-5 of... 

    Voltammetric studies of propylthiouracil at a carbon-paste electrode modified with cobalt(II)-4-chlorosalophen: Application to voltammetric determination in pharmaceutical and clinical preparations

    , Article Microchimica Acta ; Volume 151, Issue 1-2 , 2005 , Pages 73-79 ; 00263672 (ISSN) Shahrokhian, S ; Jannat Rezvani, M. J ; Sharif University of Technology
    A carbon-paste electrode chemically modified with a Schiff-base complex of cobalt (cobalt(II)-4-chlorosalophen, CoClSal) is utilized to investigate the voltammetric response of propylthiouracil (PTU). The mechanism of electrocatalytic oxidation of the compound is investigated by means of cyclic voltammetric studies applying various pHs to the buffered solutions. The modified electrode exhibits effective catalytic properties that lower the anodic overpotential and enhance the rate of electron transfer for the electrochemical oxidation of PTU. The results of the cyclic voltammetric (CV) and differential pulse voltammetric (DPV) techniques showed that the modified electrode exhibits good... 

    Voltammetric monitoring of Cd (II) by nano-TiO2 modified carbon paste electrode sensitized using 1,2-bis-[o-aminophenyl thio] ethane as a new ion receptor

    , Article Sensors and Actuators, B: Chemical ; Vol. 192 , 2014 , pp. 648-657 ; ISSN: 09254005 Ramezani, S ; Ghobadi, M ; Bideh, B. N ; Sharif University of Technology
    The objective of the work ahead is presentation of a new carbon paste electrode (CPE) modified by TiO2 nanoparticles (TiO2NPs) and 1,2-bis-[o-aminophenyl thio] ethane (APTE) ligand as a selective cation receptor for determination of the Cd (II) ions using differential pulse anodic stripping voltammetry (DPASV). The electrode shows an excellent tendency to Cd (II) ions in presence of some interfering species. Under the optimum conditions, a linear calibration curve was obtained in the concentration range of 2.9 nM to 4.6 μM with a correlation coefficient of 0.9969 in the anodic potential of 0.54 (V vs. Ag/AgCl). The metal detection limit was 2.0 nM after 10 min preconcentration (S/N = 3). The... 

    Voltammetric determination of thiocytosine based on its electrocatalytic oxidation on the surface of carbon-paste electrode modified with cobalt schiff base complexes

    , Article Journal of Solid State Electrochemistry ; Volume 11, Issue 8 , 2007 , Pages 1133-1138 ; 14328488 (ISSN) Shahrokhian, S ; Amiri, M ; Sharif University of Technology
    The electrochemical oxidation of thiocytosine on the surface of carbon-paste electrode modified with Schiff base (salophen derivatives) complexes of cobalt is studied. The effect of the substituents in the structure of salophen on the catalytic property of the modified electrode is investigated by using cyclic and differential pulse voltammetry. Cobalt (II)-5-nitrosalophen, because of its electrophilic functional groups, leads to a considerable enhancement in the catalytic activity, sensitivity (peak current), and a marked increase in the anodic potential of the modified electrode. The differential pulse voltammetry is applied as a very sensitive method for the detection of thiocytosine. The... 

    The electrocatalytic examination of cephalosporins at carbon paste electrode modified with CoSalophen

    , Article Talanta ; Volume 71, Issue 4 , 2007 , Pages 1669-1674 ; 00399140 (ISSN) Jamasbi, E. S ; Rouhollahi, A ; Shahrokhian, S ; Haghgoo, S ; Aghajani, S ; Sharif University of Technology
    Elsevier  2007
    The electrocatalytic oxidation of cephalexin and cefazolin has been studied at a carbon paste electrode modified with cobalt salophen (CoSal) by cyclic voltammetry. The selectivity of the carbon paste modified with CoSal in detecting cephalexin and cefazolin was examined. To suggest the electrocatalytic mechanism for electro-oxidation of cefazolin, the electrochemical behavior of ceftriaxone was investigated which has a thiol group out of the beta lactam ring. The electrocatalytic oxidation of these antibiotics is shown to be irreversible at the CoSal modified electrode. Scan rate dependence of cefazolin, which is a sulfur-containing compound, has been examined. The results indicated that... 

    Voltammetric studies of a cobalt(II)-4-methylsalophen modified carbon-paste electrode and its application for the simultaneous determination of cysteine and ascorbic acid

    , Article Electrochimica Acta ; Volume 50, Issue 1 , 2004 , Pages 77-84 ; 00134686 (ISSN) Shahrokhian, S ; Karimi, M ; Sharif University of Technology
    A carbon-paste electrode (CPE) chemically modified with the cobalt(II)-4-methylsalophen (CoMSal) as a Schiff base complex was used as a highly sensitive and fairly selective electrochemical sensor for simultaneous, determination of minor mounts of ascorbic acid (AA) and cysteine. This modified electrode shows very efficient electrocatalytic activity for anodic oxidation of both AA and cysteine via substantially decreasing of anodic overpotentials for both compounds. The. mechanism of electrochemical oxidation of both AA and cysteine using CoMSal-modified electrode was thoroughly investigated by cyclic voltammetry and polarization studies. Results of cyclic voltammetry (CV) and differential... 

    Carbon paste electrode incorporating multi-walled carbon nanotube/cobalt salophen for sensitive voltammetric determination of tryptophan

    , Article Sensors and Actuators, B: Chemical ; Volume 123, Issue 2 , 2007 , Pages 942-949 ; 09254005 (ISSN) Shahrokhian, S ; Fotouhi, L ; Sharif University of Technology
    A modified carbon paste electrode is prepared by incorporating multi-walled carbon nanotube (MWCNT) and cobalt salophen (CoSal). A mixture of fine graphite powder with 10 wt% of MWCNT is applied for the preparation of carbon paste (by dispersing in Nujol) and finally modified with CoSal. The electrocatalytic oxidation of tryptophan (Trp) is investigated on the surface of the MWCNT/CoSal-modified electrode using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Using the modified electrode, the kinetics of the electro-oxidation of Trp is considerably enhanced, by lowering the anodic overpotential through a catalytic fashion. The mechanism of electrochemical behavior of Trp at... 

    Morphology-Dependent Electrocatalytic Activity of Silver Nanostructures and Differentia Pulse Voltammetry Determination of Atorvastatin at Silver Nanowires Modified Electrode

    , M.Sc. Thesis Sharif University of Technology Naseri, Amene (Author) ; Shahrokhian, Saeed (Supervisor) ; Hormozi Nezhad, Mohammad Reza (Supervisor)
    In this work two shapes of silver nanostructures including silver nanowires and silver nanocubeswere synthesized by polyol method. Silver nanostructures were characterized by SEM, XRD and UV-Vis spectroscopy. Afterwards the morphology-dependent electrocatalyticperformance of these nanocrystals on the differential pulse behavior of naltrexone (NAL) was investigated. To this aim the differential pulse voltammetric behavior of NAL on a glassy carbon electrode modified with electrochemical deposited gold nanoparticles conjugated with different shapes of silver nanostructures and nafion was investigated. It was proved that silver nanowires show more effective electrocatalytic activity toward... 

    Modification of well-aligned carbon nanotubes with dihexadecyl hydrogen phosphate: Application to highly sensitive nanomolar detection of simvastatin

    , Article Journal of Applied Electrochemistry ; Volume 44, Issue 2 , February , 2014 , Pages 263-277 ; ISSN: 0021891X Fayazfar, H ; Afshar, A ; Dolati, A ; Ghalkhani, M ; Sharif University of Technology
    The first usage of dihexadecyl hydrogen phosphate (DHP)-modified highly oriented multi-walled carbon nanotube (MWCNTs) forests in a sensor configuration was developed to investigate the electrochemical oxidation and determination of simvastatin (SV) in pharmaceutical dosage forms. Synthesis of well-aligned MWCNTs on a conductive Ta substrate by catalytic vapor deposition technique using a common chemical, ethylenediamine, and without being plasma-aided was reported. The electrochemical behavior and oxidation of SV at the aligned MWCNTs/DHP/Ta electrode were discussed in detail through cyclic voltammetry and differential pulse voltammetry. This modified electrode showed considerably higher... 

    Ultra-sensitive detection of leukemia by graphene

    , Article Nanoscale ; Vol. 6, issue. 24 , Dec , 2014 , p. 14810-14819 Akhavan, O ; Ghaderi, E ; Hashemi, E ; Rahighi, R ; Sharif Universit of Technology
    Graphene oxide nanoplatelets (GONPs) with extremely sharp edges (lateral dimensions ∼20-200 nm and thicknesses <2 nm) were applied in extraction of the overexpressed guanine synthesized in the cytoplasm of leukemia cells. The blood serums containing the extracted guanine were used in differential pulse voltammetry (DPV) with reduced graphene oxide nanowall (rGONW) electrodes to develop fast and ultra-sensitive electrochemical detection of leukemia cells at leukemia fractions (LFs) of ∼10-11 (as the lower detection limit). The stability of the DPV signals obtained by oxidation of the extracted guanine on the rGONWs was studied after 20 cycles. Without the guanine extraction, the DPV peaks... 

    Adsorptive stripping differential pulse voltammetric determination of mebendazole at a graphene nanosheets and carbon nanospheres/chitosan modified glassy carbon electrode

    , Article Sensors and Actuators, B: Chemical ; Volume 185 , 2013 , Pages 669-674 ; 09254005 (ISSN) Ghalkhani, M ; Shahrokhian, S ; Sharif University of Technology
    For the first time graphene nanosheets and carbon nanospheres/chitosan (GNS-CNS/CS) based nanocomposite film modified electrode was used for the electro-oxidation of mebendazole (MD). MD is a benzimidazole drug that is used to treat human infections caused by parasitic worms. MD causes slow immobilization and death of the worms by selectively and irreversibly blocking uptake of glucose. The electrochemical behavior of MD at GNS-CNS/CS modified glassy carbon electrode has been investigated using cyclic and differential pulse voltammetry in aqueous media at different pHs. The prepared electrode showed an excellent electrochemical activity toward the electro-oxidation of MD leading to a... 

    Efficient DPCM predictor for hardware implementation of lossless medical brain CT image compression

    , Article International Conference on Signals and Electronic Systems, ICSES'10 - Conference Proceeding, 7 September 2010 through 10 September 2010 ; September , 2010 , Pages 123-126 ; 9788390474342 (ISBN) Sepehrband, F ; Mortazavi, M ; Ghorshi, S ; Sharif University of Technology
    Computed Tomography (CT) medical images show a specific part of human body and present it in a digital form. Lossless image compression is one of the medical imaging applications. To implement such application on hardware we need a simple and fast algorithm. Differential pulse code modulation (DPCM) is a simple and efficient method for transforming image. In this paper best predictor for DPCM introduce in a manner in which has the best result in compression and also be efficient for hardware implementation. After transforming image by DPCM, Huffman encoding used to compress image. We introduce this method with application to brain CT images  

    Application of glassy carbon electrode modified with a carbon nanoparticle/melamine thin film for voltammetric determination of raloxifene

    , Article Journal of Electroanalytical Chemistry ; Volume 780 , 2016 , Pages 126-133 ; 15726657 (ISSN) Shahrokhian, S ; Ghalkhani, M ; Balotf, H ; Salimian, R ; Sharif University of Technology
    Elsevier B.V  2016
    As a selective estrogen receptor modulator, raloxifene (RXF) prevent of osteoporosis in postmenopausal women by estrogenic actions on bone and decreases the risk of invasive breast cancer by anti-estrogenic actions on the breast and uterus tissue. However, RXF may increase the risk of blood clots, including deep vein thrombosis and pulmonary embolism. For the first time glassy carbon electrode modified with a thin film of melamine/carbon nanoparticles (CNPs/Mela) was constructed and used for the sensitive voltammetric determination of RXF. In comparison with unmodified electrode, the presence of the CNPs/Mela film resulted in a remarkable increase in the peak currents and sharpness of the... 

    Development of a sensitive diagnostic device based on zeolitic imidazolate frameworks-8 using ferrocene-graphene oxide as electroactive indicator for pseudomonas aeruginosa detection

    , Article ACS Sustainable Chemistry and Engineering ; Volume 7, Issue 15 , 2019 , Pages 12760-12769 ; 21680485 (ISSN) Shahrokhian, S ; Ranjbar, S ; Sharif University of Technology
    American Chemical Society  2019
    Since Gram-negative bacteria have a predominant role in nosocomial infections, there are high demands to develop a fast and sensitive method for diagnosis of bacteria in clinical samples. To address this challenge, we designed a novel electrochemical biosensor based on aptamers immobilized in engineered zeolitic imidazolate Framework-8 (ZIFs-8) via EDC-NHS chemistry. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were conducted to monitor the electrochemical characterization. With respect to unique π-πinteractions between aptamer and graphene oxide (GO), the differential pulse voltammetry technique was applied with ferrocene-graphene oxide (Fc-GO) as an... 

    Carbon-paste electrode modified with cobalt-5-nitrolsalophen as a sensitive voltammetric sensor for detection of captopril

    , Article Sensors and Actuators, B: Chemical ; Volume 109, Issue 2 , 2005 , Pages 278-284 ; 09254005 (ISSN) Shahrokhian, S ; Karimi, M ; Khajehsharifi, H ; Sharif University of Technology
    The electrochemical behavior of captopril at the surface of a carbon-paste electrode (CPE) modified with cobalt-5-nitrolsalophen (CoNSal) is described. The prepared electrode shows an excellent electrocatalytic activity toward the oxidation of captopril, which is leading to marked lowering in the anodic overpotential and considerable improvement of sensitivity (anodic current). Whereas at the surface of unmodified electrode an electrochemical activity for captopril cannot be observed, a very sharp anodic wave with an anodic peak potential about 650 mV (versus Ag/AgCl) is obtained using the prepared modified electrode. This catalytic wave is assigned to mediating of Co(III)/Co(II) redox... 

    Anodic behavior of clioquinol at a glassy carbon electrode

    , Article Bioelectrochemistry ; Volume 80, Issue 2 , 2011 , Pages 175-181 ; 15675394 (ISSN) Ghalkhani, M ; Fernandes, I. P. G ; Oliveira, S. C. B ; Shahrokhian, S ; Oliveira-Brett, A. M ; Sharif University of Technology
    Clioquinol is an antifungal, antiprotozoal and an Alzheimer's disease drug with cytotoxic activity toward human cancer cells. The electrochemical behavior of clioquinol and its oxidation product was studied using cyclic, differential pulse and square-wave voltammetry over a wide pH range on a glassy carbon electrode. The results revealed that the oxidation of clioquinol is an irreversible pH-dependent process that proceeds with the transfer of one electron and one proton in an adsorption-controlled mechanism and results in the formation of a main oxidation product, which adsorbs very strongly on the glassy carbon surface. The charge transfer coefficient was calculated as 0.64. The adsorbed...