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    Cost-effective, microstrip antenna driven ring resonator microwave biosensor for biospecific detection of glucose
    (Institute of Electrical and Electronics Engineers Inc., 2017) Camli, B.; Kusakci, E.; Lafci, B.; Salman, S.; Torun, H.; Yalcinkaya, A.D.
    We present a biosensor based on electromagnetic ring resonator for label-free detection of glucose. The sensing mechanism is based on the principle that the resonant frequencies of such structures depend on the structure geometry and the physical properties of the medium they are in, such as electrical permittivity. The sensor in this paper uses a split-ring resonator fabricated on a flame retardant four substrate via simple printed circuit board fabrication techniques. Glucose oxidase enzyme was incorporated in order to provide biospecificity for glucose. Conductive polymer poly(3,4-ethylenedioxythiophene)poly(styrenesulfonate), also known as PEDOT:PSS, was used for the immobilization of the enzyme on sensor surface. The redshift of the resonant frequency of the sensor in response to DI water, glucose, and NaCl solutions are shown to be in agreement with simulation results and theoretical expectations. In the presence of the enzyme, the sensor loaded with a glucose solution was observed to experience a resonant frequency shift of 17.5 MHz in 15 min, whereas other reagents such as fructose, sucrose, and NaCl did not respond significantly, confirming the biospecificity. The sensor was measured to have a sensitivity of 0.107 MHz/mgml-1. © 1995-2012 IEEE.
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    Solvent effects on free-radical copolymerization of styrene and 2-hydroxyethyl methacrylate: a DFT study
    (Royal Soc Chemistry, 2014) Ozaltin, T. Furuncuoglu; Dereli, B.; Karahan, O.; Salman, S.; Aviyente, V.
    The free-radical homopolymerization and copolymerization kinetics of styrene (ST) and 2-hydroxyethyl methacrylate (HEMA) in three different media (bulk, DMF, toluene) have been investigated by means of Density Functional Theory (DFT) calculations in combination with the Polarizable Continuum Model (PCM) and the Conductor-like Screening Model for Real Solvents (COSMO-RS). The conventional Transition State Theory (TST) is applied to calculate the rate parameters of polymerization. Calculated propagation rate constants are used to predict the monomer reactivity ratios, which are then used in the evaluation of the copolymer composition following the Mayo-Lewis equation. it is found that copolymerization reactions in bulk and toluene show similar transition geometries;, whereas, DMF has a tendency to form H-bonding interactions with the polar HEMA molecules, thus decreasing the reactivity of this monomer during homopolymerization and towards ST during copolymerization. Calculations of copolymer composition further show that the amount of HEMA monomer in the ST-HEMA copolymer system decreases in the polar DMF solution. The calculated spin densities of the radical species are in agreement with the rate parameters and confirm that the copolymerization propagation rate of the ST-HEMA system is in the order: k(p)(bulk) approximate to k(p)(toluene) > k(p)(DMF).