Biosensors based on gold nanoelectrode ensembles and screen printed electrodes

Gold nanowires were synthesized within polycarbonate membranes according to an electroless deposition method, obtaining nanoelectrode ensembles (NEEs) with special electrochemical features. NEEs were coupled with home-produced carbon graphite screen printed electrodes and the electrochemical properties of the original nanoelectrode ensemble on screen printed substrate (NEE/SPS) assembly has been tested for sensors application. Glucose oxidase has been used as model enzyme in order to verify the feasibility of disposable gold NEE/SPS biosensors. Finally, different immobilisation and electrochemical deposition techniques based on either self assembled monolayers of cysteamine (CYS) or amino-propyl-triethoxysilane (APTES) and conductive polyaniline (PANI) molecular wires were used. Spatial patterning of the enzyme on the polycarbonate surface and of PANI wires on gold nanoelectrodes was obtained. Possible direct electron transfer between the enzyme and the PANI modified gold nanoelectrodes has been evaluated.     

Conformational characteristics of poly(vinylpyrrolidone). solvent-dependence of the chain dimensions

Conformational energies as function of rotational angles over two consecutive skeletal bonds for both meso and racemic diads of poly(Nvinyl-2-pyrrolidone) have been computed. The results of these calculations were used to formulate a statistical model that was then employed to calculate the unperturbed dimensions of this polymer. The conformational energies are sensitive to the Coulombic interactions, which are governed by the dielectric constant, of the solvent, and to the size of the solvent molecules. Consequently, the calculated values of the polymeric chain dimensions are strongly dependent on the nature of the solvent, as it was experimentally found before.     

Reversed-phase high-performance liquid chromatography method for the determination of prolactin in bacterial extracts and in its purified form

Reversed-phase high-performance liquid chromatography methodology for the determination of human prolactin (hPRL) in bacterial periplasmic space or in purified preparations has been developed. The technique, based on the high hydrophobicity of the hPRL molecule, allows its separation from the bulk of bacterial proteins. The precision for periplasmic shock fluid analysis was characterized by relative standard variations of 3-7% for intra-day and of 3-25% for inter-day determinations. Accuracy, evaluated by recovery tests, was of the order of 90%, a calibration curve being constructed with the use of a lyophilized osmotic shock fluid extract, which provided a stable, readily prepared internal reference. Sensitivity was of the order of 0.5 microg of hPRL. The methodology developed also provided a tool for comparing the hydrophobicity of glycosylated and non-glycosylated prolactin molecules obtained from several different species and of different preparations of native or biosynthetic human prolactin.     

Anomalous diffusion in living yeast cells

The viscoelastic properties of the cytoplasm of living yeast cells were investigated by studying the motion of lipid granules naturally occurring in the cytoplasm. A large frequency range of observation was obtained by a combination of video-based and laser-based tracking methods. At time scales from 10(-4) to 10(2) s, the granules typically perform subdiffusive motion with characteristics different from previous measurements in living cells. This subdiffusive behavior is thought to be due to the presence of polymer networks and membranous structures in the cytoplasm. Consistent with this hypothesis, we observe that the motion becomes less subdiffusive upon actin disruption.     

Harmonicity and gauge transformations in dimension 3

Let (M, ) be a contact manifold. Consider a particular class of gauge transformations for the contact form . In this note we study the harmonicity of the identity map of the manifold M, of dimension three, endowed with the Webster metric g and with another metric $\widetilde{g}$ obtained from g after a gauge transformation.     

Electron transport through high-κ dielectric barriers: A non-equilibrium Green’s function (NEGF) study

We present a simulation study of the coherent transport of electrons through high permittivity (high-κ) dielectric barriers using the non-equilibrium Green’s function (NEGF) formalism. Calculation and useful formula are established for a one-dimensional grid using a finite-difference scheme and an effective-mass depending on the position along the grid. A numerical simulation code is used to investigate the tunneling properties and the transmission coefficient of different metal–insulator–metal structures with stacked dielectrics and to compare single- or two-layer high-κ dielectric stacks in terms of tunneling transmission coefficient and local density-of-states. We particularly highlight the influence of wave-function reflections against barrier discontinuity on the transmission coefficient, especially in two-layer high-κ dielectric stacks.     

Isothermal catalytic combustion of <Emphasis Type="Italic">n</Emphasis>-pentane/air mixtures on platinum wire

The transient response of the input power necessary to maintain isothermal conditions after a step temperature perturbation applied to a platinum wire immersed in a gaseous fuel/air mixture allows for the measurement of the reaction heat flow rate, directly related to the rate of the catalytic combustion. The S-shaped variation of this rate in time is employed to evaluate the induction period of the catalytic ignition. The effect of mixture composition, total pressure, and catalyst temperature on the induction period for the catalytic ignition of lean to stoichiometric n-pentane/air mixtures on isothermally heated platinum wire is reported and discussed. The mixture composition was varied between 1.40 and 2.56% n-pentane in air, the total pressure between 20 and 101 kPa, and the wire temperature between 470 and 600 K. The reaction rates, turnover frequencies, overall and partial reaction orders, and activation energies were determined from the analysis of the obtained results and compared to other reported data.     

Synthesis and solution properties of comblike poly(mono-n-alkyl itaconates). I. Poly(monodecyl itaconate)

The monoester of itaconic acid with n-decyl alcohol was prepared and polymerized. The polymer was fractionated and characterized by viscometry, size-exclusion chromatography (SEC) and light scattering. Some of the common semiempirical relations for flexible and rigid polymers were used in order to obtain the unperturbed dimensions and the conformational parameters. Thermodynamic and dimensional parameters were determined and calculated. The results are compared with those reported previously for similar compounds.