84 research outputs found
High-resolution spatial mapping of a superconducting NbN wire using single-electron detection
Superconducting NbN wires have recently received attention as detectors for
visible and infrared photons. We present experiments in which we use a NbN wire
for high-efficiency (40 %) detection of single electrons with keV energy. We
use the beam of a scanning electron microscope as a focussed, stable, and
calibrated electron source. Scanning the beam over the surface of the wire
provides a map of the detection efficiency. This map shows features as small as
150 nm, revealing wire inhomogeneities. The intrinsic resolution of this
mapping method, superior to optical methods, provides the basis of a
characterization tool relevant for photon detectors.Comment: 2009 IEEE Toronto International Conference, Science and Technology
for Humanity (TIC-STH
Improved efficacy response attributed to diagnostic selection – Interim results of the phase 1 experience from ALKA-372-001
n/
Normal-superconducting transition induced by high current densities in YBa2Cu3O7-d melt-textured samples and thin films: Similarities and differences
Current-voltage characteristics of top seeded melt-textured YBa2Cu3O7-d are
presented. The samples were cut out of centimetric monoliths. Films
characteristics were also measured on microbridges patterned on thin films
grown by dc sputtering. For both types of samples, a quasi-discontinuity or
quenching was observed for a current density J* several times the critical
current density Jc. Though films and bulks much differ in their magnitude of
both Jc and J*, a proposal is made as to a common intrinsic origin of the
quenching phenomenon. The unique temperature dependence observed for the ratio
J*/Jc, as well as the explanation of the pre-quenching regime in terms of a
single dissipation model lend support to our proposal.Comment: 10 pages, 10 figures, submitted to Physical Review
A two-species model of a two-dimensional sandpile surface: a case of asymptotic roughening
We present and analyze a model of an evolving sandpile surface in (2 + 1)
dimensions where the dynamics of mobile grains ({\rho}(x, t)) and immobile
clusters (h(x, t)) are coupled. Our coupling models the situation where the
sandpile is flat on average, so that there is no bias due to gravity. We find
anomalous scaling: the expected logarithmic smoothing at short length and time
scales gives way to roughening in the asymptotic limit, where novel and
non-trivial exponents are found.Comment: 7 Pages, 6 Figures; Granular Matter, 2012 (Online
The T7-Related Pseudomonas putida Phage ϕ15 Displays Virion-Associated Biofilm Degradation Properties
Formation of a protected biofilm environment is recognized as one of the major causes of the increasing antibiotic resistance development and emphasizes the need to develop alternative antibacterial strategies, like phage therapy. This study investigates the in vitro degradation of single-species Pseudomonas putida biofilms, PpG1 and RD5PR2, by the novel phage ϕ15, a ‘T7-like virus’ with a virion-associated exopolysaccharide (EPS) depolymerase. Phage ϕ15 forms plaques surrounded by growing opaque halo zones, indicative for EPS degradation, on seven out of 53 P. putida strains. The absence of haloes on infection resistant strains suggests that the EPS probably act as a primary bacterial receptor for phage infection. Independent of bacterial strain or biofilm age, a time and dose dependent response of ϕ15-mediated biofilm degradation was observed with generally a maximum biofilm degradation 8 h after addition of the higher phage doses (104 and 106 pfu) and resistance development after 24 h. Biofilm age, an in vivo very variable parameter, reduced markedly phage-mediated degradation of PpG1 biofilms, while degradation of RD5PR2 biofilms and ϕ15 amplification were unaffected. Killing of the planktonic culture occurred in parallel with but was always more pronounced than biofilm degradation, accentuating the need for evaluating phages for therapeutic purposes in biofilm conditions. EPS degrading activity of recombinantly expressed viral tail spike was confirmed by capsule staining. These data suggests that the addition of high initial titers of specifically selected phages with a proper EPS depolymerase are crucial criteria in the development of phage therapy
Demonstration of age-dependent capsular material on Pasteurella haemolytica serotype 1
Extracellular capsular material was demonstrated on early log-phase cells of Pasteurella haemolytica serotype 1 by the fluorescent-antibody and several capsular staining techniques. The presence of this material was shown to be age dependent. Wide capsules were demonstrable on cells from 2- to 12-h cultures, whereas cells from 16- to 22-h cultures had very little cell-associated capsular material. The Maneval technique most clearly demonstrated the presence of capsules on cells from young (6-h) cultures when compared with other capsule staining techniques.Not peer reviewedVeterinary Parasitology, Microbiology and Public HealthPatholog
The Major Surface-Associated Saccharides of Klebsiella pneumoniae Contribute to Host Cell Association
Analysing the pathogenic mechanisms of a bacterium requires an understanding of the composition of the bacterial cell surface. The bacterial surface provides the first barrier against innate immune mechanisms as well as mediating attachment to cells/surfaces to resist clearance. We utilised a series of Klebsiella pneumoniae mutants in which the two major polysaccharide layers, capsule and lipopolysaccharide (LPS), were absent or truncated, to investigate the ability of these layers to protect against innate immune mechanisms and to associate with eukaryotic cells. The capsule alone was found to be essential for resistance to complement mediated killing while both capsule and LPS were involved in cell-association, albeit through different mechanisms. The capsule impeded cell-association while the LPS saccharides increased cell-association in a non-specific manner. The electrohydrodynamic characteristics of the strains suggested the differing interaction of each bacterial strain with eukaryotic cells could be partly explained by the charge density displayed by the outermost polysaccharide layer. This highlights the importance of considering not only specific adhesin:ligand interactions commonly studied in adherence assays but also the initial non-specific interactions governed largely by the electrostatic interaction forces
OBSERVATION DE LA DISPERSION DES ONDES ACOUSTIQUES DANS LES SOLIDES
Dans une expérience d'impulsion de chaleur dans InSb et Ge, nous avons observé la dispersion des phonons de haute fréquence en utilisant le seuil à 2 Ɗ des jonctions tunnel supraconductrices. La spectrométrie des phonons par mesure du temps de vol a également été appliquée au problème de l'absorption dans le germanium dopé Sb, sous pression.In a heat pulse experiment in InSb and Ge, we have observed the dispersion of high frequency phonons by using the threshold at 2 Ɗ of superconducting tunnel junctions. The phonon spectrometry by measurement of the time of flight has also been applied to the problem of absorption in Sb doped germanium under pressure
Effect of pinning on the response of superconducting strips to an external pulsed current
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