Sharif Digital Repository

The electrochemical behavior of lamotrigine (LMT) at the pyrolytic graphite electrode (PGE) is investigated in detail by the means of cyclic voltammetry. During the electrochemical reduction of LMT, an irreversible cathodic peak appeared. Cyclic voltammetric studies indicated that the reduction process has an irreversible and adsorption-like behavior. The observed reduction peak is attributed to a two-electron process referring to the reduction of azo group. The electrode showed an excellent electrochemical activity toward the electro-reduction of LMT, leading to a significant improvement in sensitivity as compared to the glassy carbon electrode. The results of electrochemical impedance... 

Active Constellation Extension (ACE) is one of the techniques introduced for Peak to Average Power Ratio (PAPR) reduction of OFDM systems. In this technique, the constellation points are extended such that the PAPR is minimized but the minimum distance of the constellation points does not decrease. In this paper, an iterative ACE method is proposed for the PAPR reduction of OFDM systems with spatial diversity of Space Frequency Block Coding (SFBC). The proposed method is such that the PAPR is reduced simultaneously at all antennas, while the spatial encoding relationship still holds. In this method, at each iteration, the antenna with maximum PAPR is selected and the ACE algorithm is... 

Selected mapping (SLM) is a well-known technique for peak-to-average-power ratio (PAPR) reduction of orthogonal frequency-division multiplexing (OFDM) systems. In this technique, different representations of OFDM symbols are generated by rotation of the original OFDM frame by different phase sequences, and the signal with minimum PAPR is selected and transmitted. To compensate for the effect of the phase rotation at the receiver, it is necessary to transmit the index of the selected phase sequence as side information (SI). In this paper, an SLM technique is introduced for the PAPR reduction of space-frequency-block-coded OFDM systems with Alamouti coding scheme. Additionally, a suboptimum... 

In this paper, a metric based symbol predistortion method is introduced for Peak to Average Power Ratio (PAPR) reduction of the Space Frequency Block Coded (SFBC) Orthogonal Frequency Division Multiplexing (OFDM) systems with two transmitter antennas. In the proposed method, a metric is defined which shows the contribution of each frequency domain symbol to the time domain samples with high amplitude at both antennas. Then, the symbols with the highest metric values are chosen and predistorted such that the peak powers are reduced while the SFBC relationship between two antennas holds constant. Three variants of this method will be introduced. Then, this technique is extended to the general... 

Differential pulse polarography (DPP) was applied for the determination of the herbicide Tribenuron-methyl (TBM). This is a first study for various parameters affecting the reduction peak current were simultaneously optimized using experimental design and these results are different from other reports. The effect of factors such as voltage step, voltage step time, pulse amplitude, pulse time, sample pH, concentration of the supporting electrolyte and the mercury drop size were assessed by means of a (27-2) fractional factorial design. It was found that the effects and interactions of four out of seven factors were significant. Consequently, a central composite design (CCD) with four factors,... 

Electro-reduction behavior of testosterone at reduced graphene oxide/glassy carbon electrode (rGO/GCE) was studied. Cationic surfactant cetyltrimethylammonium bromide (CTAB) enhanced the reduction peak of testosterone. In borate buffer (pH 5.4) CTAB-testosterone showed a reduction peak at - 1.1 V (versus, Ag/AgCl). The increment of peak current obtained by deducting the reduction peak current of the CTAB-testosterone was rectilinear with testosterone concentration in the range of 2.0 to 210.0 nM, with a detection limit of 0.1 nM. The sensor was used for quantification of testosterone in biological fluids and drug  

Thin carbon nanoparticle/Nafion film (CNP/N), as a novel electrode material, is formed on the surface of the glassy carbon electrode in a simple solvent evaporation process. The electrochemical behavior of Azathioprine (Aza) at the CNP/N-modified electrode is investigated in detail by the means of cyclic voltammetry. During the electrochemical reduction of Aza, an irreversible cathodic peak is appeared. Cyclic voltammetric studies indicated that the reduction process has an irreversible and adsorption-like behavior. The observed reduction peak is attributed to a four-electron process referring to the reduction of nitro group to the corresponding hydroxylamine. The prepared electrode showed...