High—Speed Analyzing PCR Products of M.tuberculosis Genome Stained by Ethidium Bromide on Microchip Gel Electrophoresis

The technique of microchip gel electrophoresis(MCGE) was used to analyze the polymerase chain reaction (PCR) products of M.tuberculosis Genome stained by ethidium bromide,The electrophoretic Process was completed within 3-4 min and the results show that the technique of microchip electrophoresis is a high-speed and high-sensitivity analyzing method.     

Effect of grain boundaries on paraconductivity of YBa2Cu3Ox

To investigate the effect of grain boundaries on paraconductivity of YBa₂Cu₃O_x, melt-textured and c-axis oriented thin films with controlled grain boundaries (superconducting transition width, ΔT, varying between 0.54 and 2.85 K) were prepared, and dc-conductivity has been measured as a function of temperature. In the logarithmic plots of excess-conductivity (Δσ) and reduced temperature (?), starting from low values of ?, we have observed three different regions namely critical region, mean field region and short wave fluctuation region. A correlation is observed between the range of critical region and ΔT, which is found to increase with ΔT. While for ΔT values smaller than 2.5 K only static critical region is observed, for higher ΔTs both static and dynamic critical regions are observed. In the mean field region a crossover from 3D to 2D was observed for all the samples. At ? values larger than 0.24, the excess-conductivity decreased sharply as ?⁻³, which suggested the existence of the short wave fluctuations.     

Equivalence between polymer nanocomposites and thin polymer films: Effect of processing conditions and molecular origins of observed behavior

Recently we established a quantitative equivalence in thermomechanical properties between polystyrene-silica nanocomposites and planar freestanding polystyrene thin films. This equivalence was quantified by drawing a direct analogy between film thickness and an appropriate experimental particle spacing. Using these findings, here we unequivocally show that the glass transition process in confined geometries is controlled by the mean volume fraction of polymer that is affected by the presence of surfaces. Since separate signatures of the bulk and the surface layers are never found, we can clearly rule out any simple “two layer” model which postulates the existence of surfaces which are dynamically decoupled from the bulk. Rather, we argue that the modification of properties at the surfaces propagates into the bulk through a spatial gradient: macroscopic experimental techniques average over these gradients and yield a broadened signature relative to the bulk polymer. In a second aspect of this paper we focus on the role of processing conditions on the results obtained. We have developed a new method of processing the nanocomposites which results in a better dispersion of the nanoparticles in the matrix. However, these samples did not show the unique glass transition behavior seen in the first set of nanocomposites discussed above. This indicates that processing conditions can profoundly affect the nature of the particle-polymer interface which controls the macroscopic behavior of these important systems.     

Coherent control in a single semiconductor quantum dot exhibiting excitonic and biexcitonic features

We have developed a simplified theoretical model to analyze the phenomenon of coherent control in a single semiconductor quantum dot excited by a pair of optical pulses. The first pulse populates a biexciton state by two-photon absorption while the second pulse generates population in the exciton state via deexcitation from the biexciton state. We have used density-matrix analysis for a 3-level system to calculate the time dependent biexciton and exciton state populations. The usual 9×9 matrix has been reduced to a 6×6 matrix. The time variation of the population in each state and it’s dependence on the pulse delay manifest coherent control. Numerical estimates made for In_0.5Ga_0.5As/GaAs single quantum dots qualitatively agree with the recent experimental results. PACS 78.67.Hc; 42.50.Md; 78.55.Cr     

Numerical evidence of Luttinger liquid to Fermi liquid transformation in lithium doped trans-polyacetylene chain

We report on the first direct numerical evidence of doping-induced transformation of Tomonaga-Luttinger liquid to Fermi liquid in quasi-one-dimensional lithium doped trans-polyacetylene chain. Using density functional theoretical calculation, an analysis of density of states near the Fermi energy reveals a power-law scaling factor of Tomonaga-Luttinger liquid at low dopant concentration in the metallic regime. As soon as the doping level reaches 0.0763e/C, normal power-law scaling factor of Fermi liquid has been realized as a special case of Luttinger liquid in one dimension. The variation of density-density correlation is consistent with the present theoretical prediction.     

Synthesis and study of fluorescence properties of Cu nanoparticles

ZnO nanoparticles, of average size of 10–15 nm, homogeneously dispersed in a silica matrix were prepared by a two stage citric acid/sol–gel process and thermal treatments up to 700 °C. The precursors formed at the early stages of the synthesis and their thermal evolution were investigated by FTIR, ²⁹Si NMR MAS and CPMAS, ¹³C CPMAS and T_1ρ(¹H). A unidentate complex was revealed in the gel, together with other complexes in which citrate carboxylate groups are bound to one Zn²⁺ ion or act as a bridge between two Zn²⁺ ions. A comparison of the results from nanocomposite and silica samples prepared by the same method showed that chemical interactions between amorphous silica and zinc ions are not present either in the precursors or in the final materials. As a consequence, ZnO particles do not react with silica matrix when they are heated up to 700 °C. This result is ascribed to a nanophase segregation of zinc citrate complexes from the host matrix.     

Novel antifoam for fermentation processes: fluorocarbon-hydrocarbon hybrid unsymmetrical bolaform surfactant

As foaming appears as a problem in chemical and fermentation processes that inhibits reactor performance, the eminence of a novel fluorocarbon-hydrocarbon unsymmetrical bolaform (FHUB: OH(CH2)11N+(C2H4)2(CH2)2(CF2)5CF3 I-) surfactant as an antifoaming agent as well as a foam-reducing agent was investigated and compared with other surfactants and a commercial antifoaming agent. The surface elasticity of FHUB was determined as 4 mN/m, indicating its high potential on thinning of the foam film. The interactions between FHUB and the microoganism were investigated in a model fermentation process related with an enzyme production by recombinant Escherichia coli, in V = 3.0 dm3 bioreactor systems with V(R) = 1.65 dm3 working volume at air inlet rate of Q(o)/V(R) = 0.5 dm3 dm(-3) min(-1) and agitation rate of N = 500 min(-1) oxygen transfer conditions, at T = 37 degrees C, pH(o) = 7.2, and C(FHUB) = 0 and 0.1 mM, in a glucose-based defined medium. As FHUB did not influence the metabolism, specific enzyme activity values obtained with and without FHUB were close to each other; however, because of the slight decrease in oxygen transfer coefficient, slightly lower volumetric enzyme activity and cell concentrations were obtained. However, when FHUB is compared with widely used silicon oil based Antifoam A, with the use of the FHUB, higher physical oxygen transfer coefficient (K(L)a) values are obtained. Moreover, as the amount required for the foam control is very low, minute changes in the working volume of the bioreactor were obtained indicating the high potential of the use of FHUB as an antifoaming agent as well as a foam-reducing agent.     

Note on a direct method of solving problems of elastic plates with circular boundaries having prescribed displacement

Zusammenfassung Zweck dieser Mitteilung ist die Herleitung einer direkten Methode für die Lösung des zweiten Randwertproblems in einer elastischen Scheibe mit kreisförmiger Begrenzung. Zur Veranschaulichung der Methode wird das Problem der unendlichen Scheibe mit einer thermoelastischen Verzerrungsquelle in endlichem Abstand von einem kreisförmigen Loch mit fixiertem Rand gelöst.