Diamagnetic Response of Normal-metal -- Superconductor Double Layers

The magnetic response of a proximity-coupled superconductor-normal metal sandwich is studied within the framework of the quasiclassical theory. The magnetization is evaluated for finite values of the applied magnetic field (linear and nonlinear response) at arbitrary temperatures and is used to fit recent experimental low-temperature data. The hysteretic behavior predicted from a Ginzburg-Landau approach and observed in experiments is obtained within the quasiclassical theory and shown to exist also outside the Ginzburg-Landau region.Comment: RevTex, 11 pages, 9 PostScript figures include

Local Density of States in a Dirty Normal Metal connected to a Superconductor

A superconductor in contact with a normal metal not only induces superconducting correlations, known as proximity effect, but also modifies the density of states at some distance from the interface. These modifications can be resolved experimentally in microstructured systems. We, therefore, study the local density of states $N(E,x)$ of a superconductor - normal metal heterostructure. We find a suppression of $N(E,x)$ at small energies, which persists to large distances. If the normal metal forms a thin layer of thickness $L_n$, a minigap in the density of states appears which is of the order of the Thouless energy $\sim \hbar D/L_n^2$. A magnetic field suppresses the features. We find good agreement with recent experiments of Gu\'eron {\it et al.}Comment: 5 pages, RevTeX, 7 Figures (included), Submitted to PRB. Revised version: One figure changed, missprints correcte

Charge transport through a SET with a mechanically oscillating island

We consider a single-electron transistor (SET) whose central island is a nanomechanical oscillator. The gate capacitance of the SET depends on the mechanical displacement, thus, the vibrations of the island vibrations may strongly influence the current-voltage characteristics, current noise, and higher cumulants of the current. Harmonic oscillations of the island and oscillations with random amplitude (e.g., due to the thermal activation) change the transport characteristics in a different way. The noise spectrum has a peak at the frequency of the island oscillations; when the island oscillates harmonically, the peak reduces to a $\delta$-peak. We show that knowledge of the SET transport properties helps to determine in what way the island oscillates, to estimate the amplitude, and the frequency of the oscillations

The connection between noise and quantum correlations in a double quantum dot

We investigate the current and noise characteristics of a double quantum dot system. The strong correlations induced by the Coulomb interaction create entangled two-electron states and lead to signatures in the transport properties. We show that the interaction parameter phi, which measures the admixture of the double-occupancy contribution to the singlet state and thus the degree of entanglement, can be directly accessed through the Fano factor of super-Poissonian shot noise.Comment: 5 pages, major revision, to be published in Phys. Rev.

Quantum transport signatures of chiral edge states in Sr2_2RuO4_4

We investigate transport properties of a double quantum dot based Cooper pair splitter, where the superconducting lead consists of Sr$_2$RuO$_4$. The proposed device can be used to explore the symmetry of the superconducting order parameter in Sr$_2$RuO$_4$ by testing the presence of gapless chiral edge states, which are predicted to exist if the bulk superconductor is described by a chiral $p$--wave state. The odd orbital symmetry of the bulk order parameter ensures that we can realize a regime where the electrons tunneling into the double dot system come from the chiral edge states and thereby leave their signature in the conductance. The proposed Cooper pair splitter has the potential to probe order parameters in unconventional superconductors.Comment: 5 page

Dynamic method to distinguish between left- and right-handed chiral molecules

We study quantum systems with broken symmetry that can be modelled as cyclic three-level atoms with coexisting one- and two-photon transitions. They can be selectively optically excited to any state. As an example, we show that left- and right-handed chiral molecules starting in the same initial states can evolve into different final states by a purely dynamic transfer process. That means, left- and right-handed molecules can be distinguished purely dynamically.Comment: 4 pages, submitted to Phys. Rev.

Spectral Features of the Proximity Effect

We calculate the local density of states (LDOS) of a superconductor-normal metal sandwich at arbitrary impurity concentration. The presence of the superconductor induces a gap in the normal metal spectrum that is proportional to the inverse of the elastic mean free path $l$ for rather clean systems. For a mean free path much shorter than the thickness of the normal metal, we find a gap size proportional to $l$ that approaches the behavior predicted by the Usadel equation (diffusive limit).Comment: LT22 proceeding

ZwanzigJahre diagnostisches Hirschsprung-Kompetenzzentrum in Basel

Zusammenfassung: Hintergrund: In vorliegendem Bericht werden die in 20 Jahren gesammelten Erfahrungen des Basler Hirschsprung-Kompetenzzentrums zusammengestellt. Methodik: Zwischen 1987 und 2006 wurden 19.365 Rektumschleimhautbiopsien untersucht. Die Biopsien stammten von 6615 Kindern mit chronischer Obstipation im Alter von einer Woche bis zu 4Jahren. Die Biopsien wurden in Lehrkrankenhäusern in ganz Deutschland gewonnen und auf Trockeneis per Intercity-Kurierdienst nach Basel transportiert. Das gefrorene Gewebe wurde im Kryostaten in Serienschnitten verarbeitet. An den Biopsien wurden enzymhistochemische Reaktionen durchgeführt. Ergebnis: Insgesamt wurden in 20Jahren 935 Morbus-Hirschsprung-Fälle (14%) diagnostiziert (769 klassische Hirschsprung-Erkrankungen, 68 totale Aganglionosen des Kolons, 98 ultrakurze Hirschsprung-Erkrankungen). Im Interesse einer Qualitätssicherung wurden alle Befunde durch einen zweiten unabhängigen Untersucher beurteilt. Es gab keine falsch-positiven oder falsch-negativen Diagnosen. Die Schnittpräparate waren innerhalb von 2h nach Erhalt auswertbar. Eine Acetylcholinesterase-Reaktion diente der Darstellung der Nervenfasern, die bei Vorliegen eines Hirschsprungs charakteristisch erhöht ist. Succinat- und Lactat-Dehydrogenase sowie Nitroxid-Synthetase ermöglichten eine elektive Nervenzellfärbung des Plexus submucosus und dienten als zweite Bestätigung einer Aganglionose. Schlussfolgerung: Von 100 chronisch obstipierten Kindern hatten im Mittel 12 eine Hirschsprung-Erkrankung. 2% der Kinder wiesen eine totale Kolonaganglionose oder einen ultrakurzen Hirschsprung auf. Die enzymhistochemische Hirschsprung-Diagnostik erwies sich als 100% zuverlässig und zeitsparen

Progress Towards the Development of a Long-Lived Venus Lander Duplex System

NASA has begun the development of a combined Stirling cycle power and cooling system (duplex) to enable the long-lived surface exploration of Venus and other harsh environments in the solar system. The duplex system will operate from the heat provided by decaying radioisotope plutonium-238 or its substitute. Since the surface of Venus has a thick, hot, and corrosive atmosphere, it is a challenging proposition to maintain sensitive lander electronics under survivable conditions. This development effort requires the integration of: a radioisotope or fission heat source; heat pipes; high-temperature, corrosion-resistant material; multistage cooling; a novel free-displacer Stirling convertor for the lander; and a minimal vibration thermoacoustic Stirling convertor for the seismometer. The first year effort includes conceptual system design and control studies, materials development, and prototype hardware testing. A summary of these findings and test results is presented in this report

Current concepts of enzyme histochemistry in modern pathology

Enzyme histochemistry serves as a link between biochemistry and morphology. It is based on metabolization of a substrate provided to a tissue enzyme in its orthotopic localization. Visualization is accomplished with an insoluble dye product. It is a sensitive dynamic technique that mirrors even early metabolic imbalance of a pathological tissue lesion, combined with the advantage of histotopographic enzyme localization. With the advent of immunohistochemistry and DNA-oriented molecular pathology techniques, the potential of enzyme histochemistry currently tends to be underrecognized. This review aims to draw attention to the broad range of applications of this simple, rapid and inexpensive method. Alkaline phosphatase represents tissue barrier functions in brain capillaries, duodenal enterocyte and proximal kidney tubule brush borders. Decrease in enzyme histochemical alkaline phosphatase activity indicates serious functional impairment. Enzyme histochemical increase in lysosomal acid phosphatase activity is an early marker of ischemic tissue lesions. Over the last four decades, acetylcholinesterase enzyme histochemistry has proven to be the gold standard for the diagnosis of Hirschsprung disease and is one of the most commonly applied enzyme histochemical methods today. Chloroacetate esterase and tartrate-resistant phosphatase are both resistant to formalin fixation, EDTA decalcification and paraffin embedding. Early enzyme histochemical insight into development of a pathologic tissue lesion and evaluation of function and vitality of tissue enhance our understanding of the pathophysiology of diseases. In this process, enzyme histochemistry constitutes a valuable complement to conventional histology, immunohistochemistry and molecular pathology for both diagnostic and experimental pathology