Streptavidin Modified Carbon Nanotube Based Graphite Electrode for Label‐Free Sequence Specific DNA Detection

Disposable graphite pencil electrodes (PGE) modified with multiwalled carbon nanotubes (MWCNTs)‐streptavidin (STR) conjugates were used for electrochemical monitoring of label‐free DNA hybridization. The surface morphology of PGE electrode before and after hybridization was characterized by scanning electron microscopy. Electrochemical impedance spectroscopy was used to monitor each step of the construction of the DNA biosensor. The biosensor was demonstrated to have excellent selectivity, being able to differentiate complementary sequences from a noncomplementary ones and in addition select the target sequence of DNA from a mixture of other DNA without loss in current sensitivity.     

Polynomial Basis Multiplication over GF(2 m )

In this paper, we describe, analyze and compare various multipliers. Particularly, we investigate the standard modular multiplication, the Montgomery multiplication, and the matrix–vector multiplication techniques.     

A computational study on the amine-oxidation mechanism of monoamine oxidase: insight into the polar nucleophilic mechanism

The proposed polar nucleophilic mechanism of MAO was investigated using quantum chemical calculations employing the semi-empirical PM3 method. In order to mimic the reaction at the enzyme's active site, the reactions between the flavin and the p-substituted benzylamine substrate analogs were modeled. Activation energies and rate constants of all the reactions were calculated and compared with the published experimental data. The results showed that electron-withdrawing groups at the para position of benzylamine increase the reaction rate. A good correlation between the log of the calculated rate constants and the electronic parameter (sigma) of the substituent was obtained. These results agree with the previous kinetic experiments on the effect of p-substituents on the reduction of MAO-A by benzylamine analogs. In addition, the calculated rate constants showed a correlation with the rate of reduction of the flavin in MAO-A. In order to verify the results obtained from the PM3 method single-point B3LYP/6-31G*//PM3 calculations were performed. These results demonstrated a strong reduction in the activation energy for the reaction of benzylamine derivatives having electron-withdrawing substituents, which is in agreement with the PM3 calculations and the previous experimental QSAR study. PM3 and B3LYP/6-31G* energy surfaces were obtained for the overall reaction of benzylamine with flavin. Results suggest that PM3 is a reasonable method for studying this kind of reaction. These theoretical findings support the proposed polar nucleophilic mechanism for MAO-A.     

Thermodynamics of Pb2+ and Ni2+ adsorption onto natural bentonite from aqueous solutions

Removal of Pb2+ and Ni2+ from aqueous solutions by sorption onto natural bentonite was investigated. Experiments were carried out as a function of particle size, the amount of bentonite, pH, concentration of metals, contact time, and temperature. The adsorption patterns of metal ions onto followed the Langmuir, Freundlich, and Dubinin-Radushkevich isotherms. This included adsorption isotherms of single-metal solutions at 303 K by batch experiments. The thermodynamic parameters (DeltaH,DeltaS,DeltaG) for Pb2+ and Ni2+ sorption onto bentonite were also determined from the temperature dependence. The adsorptions were endothermic reactions. The results suggested that natural bentonite is suitable as a sorbent material for recovery and adsorption of metal ions from aqueous solutions.     

On unsteady unidirectional flows of a second grade fluid

Some properties of unsteady unidirectional flows of a fluid of second grade are considered for flows produced by the sudden application of a constant pressure gradient or by the impulsive motion of one or two boundaries. Exact analytical solutions for these flows are obtained and the results are compared with those of a Newtonian fluid. It is found that the stress at the initial time on the stationary boundary for flows generated by the impulsive motion of a boundary is infinite for a Newtonian fluid and is finite for a second grade fluid. Furthermore, it is shown that initially the stress on the stationary boundary, for flows started from rest by sudden application of a constant pressure gradient is zero for a Newtonian fluid and is not zero for a fluid of second grade. The required time to attain the asymptotic value of a second grade fluid is longer than that for a Newtonian fluid. It should be mentioned that the expressions for the flow properties, such as velocity, obtained by the Laplace transform method are exactly the same as the ones obtained for the Couette and Poiseuille flows and those which are constructed by the Fourier method. The solution of the governing equation for flows such as the flow over a plane wall and the Couette flow is in a series form which is slowly convergent for small values of time. To overcome the difficulty in the calculation of the value of the velocity for small values of time, a practical method is given. The other property of unsteady flows of a second grade fluid is that the no-slip boundary condition is sufficient for unsteady flows, but it is not sufficient for steady flows so that an additional condition is needed. In order to discuss the properties of unsteady unidirectional flows of a second grade fluid, some illustrative examples are given.     

Adsorption of Acid Blue 193 from aqueous solutions onto Na-bentonite and DTMA-bentonite

Dodecyltrimethylammonium bromide-modified bentonite (DTMA-bentonite) was prepared and tested as an adsorbent for an acid dye (Acid Blue 193, AB193) removal from aqueous solution in comparison with Na-bentonite. The effect of various experimental parameters was investigated using a batch adsorption technique. In this manner, the adsorption isotherms, adsorption kinetics, and temperature and pH effects upon Acid Blue 193 adsorption on Na-bentonite and DTMA-bentonite were thoroughly examined. Results show that a pH value of 1.5 is favorable for the adsorption of Acid Blue 193. The isothermal data could be well described by the Freundlich equation. The dynamical data fit well with the pseudo-second-order kinetic model. The adsorption capacity of DTMA-bentonite (740.5 mg g(-1)) was found to be around 11 times higher than that of Na-bentonite (67.1 mg g(-1)) at 20 degrees C. Thermodynamic parameters such as activation energy (E(a)) and change in the free energy (DeltaG(0)), the enthalpy (DeltaH(0)), and the entropy (DeltaS(0)) were also evaluated. The overall adsorption process was exothermic but it is only spontaneous at 20 degrees C. The results indicate that Na-bentonite and DTMA-bentonite could be employed as low-cost alternatives to activated carbon in wastewater treatment for the removal of color which comes from textile dyes.     

Delay modes in thick single-crystal yttrium-iron-garnet ISCS

Experimental room-temperature delay and loss figures obtained at S band frequencies for magnetoelastic radial and axial propagation in axially magnetised, [100]-oriented, thick yttrium-iron-garnet discs are reported. Samples with aspect ratios of 0.1 and 0.4 were used in a dielectric-loaded TM010 re-entrant cavity.     

Some comments on domain structures in block copolymers

Although samples of amorphous polymers cast from solution are usually assumed to be isotropic, they may, in fact, have some anisotropy due to the Bénard effect, in which the convection currents produced by evaporation are organized into a regular arrangement of cells. A pattern of hexagonal convection cell is easily visible during casting of SBS triblock copolymers. The anisotropy is demonstrated by comparing the small-angle x-ray diffraction diagrams taken through the face and edge of the films. The domain structures in two SBS copolymers are characterized by diffraction measurements. The smallangle diagram of a triblock polymer containing 50% styrene indicated a lamellar structure, while that from a 28% styrene copolymer is interpreted as arising from a hexagonal array of polystyrene cylinders dispersed in a continuous polybutadiene phase. Published diffraction data for block copolymers and other amphiphiles are surveyed in an attempt to place some limitations on the composition ranges over which the various types of domain structure exist. The factors which determine the dimensions of the two domains in lamellar phases formed from diblock copolymers are examined theoretically, and the predicted dimensions are compared with experimental results.     

Compensation of superstrate effects on the resonant behavior of themicrostrip ring structure by using an air-gap control

In this paper, spectral-domain analysis is utilized to investigate the possibility of compensation of superstrate shielding effects on the resonant behavior of the microstrip ring structure by means of an adjustable air-gap inserted between the substrate and the ground plane. In order to provide the desired amount of tuning, the adjustment of the proper gap thickness is discussed for various structural parameter cases. It is shown that the resonant frequency shift due to superstrate shielding can be compensated, the resonant bandwidth and, hence, the electromagnetic interference can be directly controlled resulting of the proposed tuning scheme