Are pinholes the cause of excess current in superconducting tunnel junctions? A study of Andreev current in highly resistive junctions

In highly resistive superconducting tunnel junctions, excess subgap current is usually observed and is often attributed to microscopic "pinholes" in the tunnel barrier. We have studied the subgap current in superconductor-insulator-superconductor (SIS) and superconductor-insulator-normal-metal (SIN) junctions. In Al/AlOx/Al junctions, we observed a decrease of 2 orders of magnitude in the current upon the transition from the SIS to the SIN regime, where it then matched theory. In Al/AlOx/Cu junctions, we also observed generic features of coherent diffusive Andreev transport in a junction with a homogenous barrier. We use the quasiclassical Keldysh-Green function theory to quantify single- and two-particle tunneling and find good agreement over 2 orders of magnitude in transparency. We argue that our observations rule out pinholes as the origin of the excess current.Comment: 4 pages, 4 figure

Uheldsmodeller for signalregulerede vejkryds

Projektets emne er "Uheldsmodeller for signalregulerede vejkryds" og hovedformålet har været at bruge Generaliserede Lineære Modeller (GLM) til beskrivelse af det forventede antal uheld i vejkryds. Det har endvidere være tanken at finde effekten af, at inddrage bløde trafikanter samt trafikkens svingbevægelser som forklarende variable i uheldsmodeller. Desuden er der afprøvet en mikromodel for 410-uheld. &nbsp

New methods for quantification of amoxicillin and clindamycin in human plasma using HPLC with UV detection

OBJECTIVES: We aimed to develop simple and rapid HPLC methods for determination of amoxicillin and clindamycin in human plasma. METHODS: Plasma samples were pretreated by direct deproteinization with acetonitrile and the analytical separation took place on a reverse phase Poroshell 120 EC-C18 column (2.7 μm, 2.1 × 100 mm) with a gradient of acetonitrile. UV detection at 229 nm for amoxicillin and 204 nm for clindamycin was used for determination of the antibiotics in plasma. RESULTS: The calibration curves were linear over the concentration ranges of 1–100 mg/L for amoxicillin and 1–15 mg/L for clindamycin with a correlation coefficient of ≥0.98. Intra-assay precisions were all ≤15% and the accuracies were within ±15%. The limit of quantification (LOQ) was found to be 0.5 mg/L for amoxicillin and 1 mg/L for clindamycin with inter-assay imprecision coefficient of variances (CVs) of 18.7% and 15.6%, respectively. The present HPLC methods were successfully applied on spike-in samples and on plasma samples collected 4–6 and 3.5–5.5 h after oral antibiotic administration of 500 mg of amoxicillin and 600 mg of clindamycin, respectively. CONCLUSIONS: We have developed HPLC methods with UV detection for quantification of amoxicillin and clindamycin in human plasma. The methods are fast, simple and suitable for use in routine settings and clinical studies

Hastighed og uheldsrisiko i kryds.

Undersøgelsen omhandler uheldsrisikoen i kryds beliggende på strækninger med forskellige hastighedsgrænser. Kun 4-benede signalregulerede kryds er medtaget. Alle krydsene (ca. 500 stk) er opdelt i 7 grupper, afhængig af om krydset er beliggende i by- eller landområde, og af den tilladte hastighed i krydsets hovedretning. Derefter er uheldsrisikoen beregnet for hver af disse 7 krydsgrupper. Uheldsrisikoen er beregnet både som uheldsfrekvenser og vha. regressionanalyser. Resultaterne viser, at risikoen er stigende for større tilladt hastighed. Især er antallet af dræbte og tilskadekomne stigende. 80 km/t kryds er signifikant mere uheldsbelastede end andre kryds

Nanoscale interaction layer at the interface between Al films and SiO2 substrates of Al/AlOx/Al Josephson tunnel junctions

An interaction layer is found at the Al/SiO2 interface in Al/AlOx/Al tunnel junctions grown on SiO2 substrates. The amorphous intermixing layer has an average thickness of about 5 nm. We present the detailed structure of this interfacial layer as determined by transmission electron microscopy. The layer contains alumina with aluminum being octahedrally coordinated according to electron energy loss spectroscopy analysis rather than tetrahedrally coordinated, where the latter coordination is the most common type in amorphous alumina. Depth profiles of the Al-O and Si-O bonding characteristics were also investigated using energy loss near edge structure