Electrical conductivity and thermal behavior of solid electrolytes based on alkali carbonates and sulfates

Both thermal stability and electrical conductivity of alkali ion conducting Na2CO3 and Na2SO4, were improved by adding alkaline earth carbonates and sulfates, respectively, as well as insulating materials like ¿-Al2O3. The admixing of divalent compounds causes two effects. First a more or less extended solution can exist depending on the radius of the alkaline earth ion and is accompanied by an increase in electrical conductivity. Secondly, a phase mixture with an excess of dopant was observed that shows an enhancement in conductivity and mechanical stability. This phenomenon known as composite effect was observed in the following systems: Na2CO3-BaCO3, Na2CO3-SrCO3, Na2SO4-BaSO4, Na2SO4-¿-Al2O3

Scenario of inflationary cosmology from the phenomenological Λ\Lambda models

Choosing the three phenomenological models of the dynamical cosmological term $\Lambda$, viz., $\Lambda \sim (\dot a/a)^2$, $\Lambda \sim {\ddot a/a}$ and $\Lambda \sim \rho$ where $a$ is the cosmic scale factor, it has been shown by the method of numerical analysis that the three models are equivalent for the flat Universe $k=0$. The evolution plots for dynamical cosmological term $\Lambda$ vs. time $t$ and also the cosmic scale factor $a$ vs. $t$ are drawn here for $k=0, +1$. A qualitative analysis has been made from the plots which supports the idea of inflation and hence expanding Universe.Comment: 12 latex pages with 12 figures; Replaced with the revised version; Accepeted for `J. Non-lin. Frac. Phen. Sci. Engg.

A limit on the detectability of the energy scale of inflation

We show that the polarization of the cosmic microwave background can be used to detect gravity waves from inflation if the energy scale of inflation is above 3.2 times 10^15 GeV. These gravity waves generate polarization patterns with a curl, whereas (to first order in perturbation theory) density perturbations do not. The limiting ``noise'' arises from the second--order generation of curl from density perturbations, or rather residuals from its subtraction. We calculate optimal sky coverage and detectability limits as a function of detector sensitivity and observing time.Comment: 4 pages, 3 figures, submitted to PR

On matching conditions for cosmological perturbations

We derive the matching conditions for cosmological perturbations in a Friedmann Universe where the equation of state undergoes a sharp jump, for instance as a result of a phase transition. The physics of the transition which is needed to follow the fate of the perturbations is clarified. We dissipate misleading statements made recently in the literature concerning the predictions of the primordial fluctuations from inflation and confirm standard results. Applications to string cosmology are considered.Comment: 20 pages, latex (revtex), no figure

Biosensorisches On-Line-Monitoring der Qualität von Zuckerrübenrohsaft

Zuckerrüben, die im Herbst gerodet wurden, werden bis zu ihrer Verarbeitung, die sich bis zum Ende eines Jahres erstrecken kann, unter Freiluftbedingungen gelagert. Während der Lagerungsperiode kommt es zu einem anaeroben Abbau von Saccharose in der Zuckerrübe zu Glucose und Fructose, wodurch die Ausbeute an Weißzucker sinkt. Zur Optimierung des Rodungs- und Lagerungszeitregimes sind die Zuckerproduzenten an einer kontinuierlichen Bestimmung von Glucose im Rohsaft interessiert. Darüberhinaus ermöglicht die kontinuierliche Erfassung der Lactatkonzentration im Rohsaft, die Aufschluß über den mikrobiellen Zustand der verarbeiteten Rüben gibt, den Zuckerproduzenten ein rechtzeitiges Eingreifen in den Produktionsprozeß im Sinne einer Desinfektion. Mit Hilfe enzymatisch-amperometrischer Biosensoren kann man sowohl Glucose als auch Lactat im Zuckerrübenrohsaft on line bestimmen, wenn die Sensorpräparation an die besonderen Bedingungen dieses Mediums angepaßt wird. Die Ergebnisse belegen die grundsätzliche Eignung von Biosensoren für die Bestimmung von Glucose im strömenden Zuckerrübenrohsaft zur Prozeß- und Qualitätskontrolle. Voraussetzungen für den Einsatz sind jedoch eine Anpassung der Sensorpräparation an die besonderen Bedingungen im Rohsaft und die strömungstechnische Optimierung der Meßanordnung in der Produktionsanlage. Während für die Enzymimmobilisierung bekannte Lösungen als geeignete Verfahren übernommen und weiterentwickelt wurden, sind die Fixierung des Mediators und die Gestaltung der diffusionslimitierenden Membran weiter anwendungsspezifisch zu optimieren. Analoge Schwerpunkte bestehen bei der Entwicklung von Lactatsensoren für diesen Anwendungsfall

The Coulomb law in the pure gauge U(1) theory on a lattice

We study the heavy charge potential in the Coulomb phase of pure gauge compact U(1) theory on the lattice. We calculate the static potential $V_W(T,{\vec R})$ from Wilson loops on a $16^3 \times 32$ lattice and compare with the predictions of lattice perturbation theory. We investigate finite size effects and, in particular, the importance of non-Coulomb contributions to the potential. We also comment on the existence of a maximal coupling in the Coulomb phase of pure gauge U(1) theory.Comment: 14 pages. LaTeX file and 3 postscript figure

A new approach to spherically symmetric junction surfaces and the matching of FLRW regions

We investigate timelike junctions (with surface layer) between spherically symmetric solutions of the Einstein-field equation. In contrast to previous investigations this is done in a coordinate system in which the junction surface motion is absorbed in the metric, while all coordinates are continuous at the junction surface. The evolution equations for all relevant quantities are derived. We discuss the no-surface layer case (boundary surface) and study the behaviour for small surface energies. It is shown that one should expect cases in which the speed of light is reached within a finite proper time. We carefully discuss necessary and sufficient conditions for a possible matching of spherically symmetric sections. For timelike junctions between spherically symmetric space-time sections we show explicitly that the time component of the Lanczos equation always reduces to an identity (independently of the surface equation of state). The results are applied to the matching of FLRW models. We discuss `vacuum bubbles' and closed-open junctions in detail. As illustrations several numerical integration results are presented, some of them indicate that the junction surface can reach the speed of light within a finite time.Comment: new version - corrected boundary surface discussion, improved presentation, and corrected reference 22 pages, many figure

Electrochemical investigations on multi-metallic electrodes for amperometric NO gas sensors

Abstract The activities of Pt/YSZ, PtAu/YSZ and RhPtAu/YSZ thick film electrodes in O 2 , N 2 and NO, N 2 gas mixtures at high temperatures were investigated by electrochemical impedance spectroscopy (EIS) and linear sweep voltammetry (LSV). As compared with the Pt/YSZ electrode the cathodic O 2 reduction at both multi-metallic electrodes is strongly inhibited, which is confirmed by charge transfer resistance for cathodic O 2 reduction as follows: R ct (Pt/YSZ) < R ct (PtAu/YSZ) < R ct (RhPtAu/YSZ). In contrast to that the cathodic NO reduction is accelerated only by the RhPtAu/YSZ electrode, indicating that the RhPtAu mixture is a suitable working electrode material for amperometric NO sensors based on the solid electrolyte (YSZ). A new amperometric NO sensor with only one working electrode made of RhPtAu mixture was tested in simulated gas mixtures containing NO, O 2 , N 2 , resulting in a linear response to the NO concentration, which is nearly independent of the O 2 concentration