3,816 research outputs found
Wick's theorem for q-deformed boson operators
In this paper combinatorial aspects of normal ordering arbitrary words in the
creation and annihilation operators of the q-deformed boson are discussed. In
particular, it is shown how by introducing appropriate q-weights for the
associated ``Feynman diagrams'' the normally ordered form of a general
expression in the creation and annihilation operators can be written as a sum
over all q-weighted Feynman diagrams, representing Wick's theorem in the
present context.Comment: 9 page
Draft Genome Sequence of Frankia sp. Strain CcI6, a Salt-Tolerant Nitrogen-Fixing Actinobacterium Isolated from the Root Nodule of Casuarina cunninghamiana
Members of the actinomycete genus Frankia form a nitrogen-fixing symbiosis with 8 different families of actinorhizal plants. We report a 5.57-Mbp draft genome sequence for Frankia sp. strain CcI6, a salt-tolerant nitrogen-fixing actinobacterium isolated from root nodules of Casurina cunninghamiana grown in Egyptian soils
Some recursive formulas for Selberg-type integrals
A set of recursive relations satisfied by Selberg-type integrals involving
monomial symmetric polynomials are derived, generalizing previously known
results. These formulas provide a well-defined algorithm for computing
Selberg-Schur integrals whenever the Kostka numbers relating Schur functions
and the corresponding monomial polynomials are explicitly known. We illustrate
the usefulness of our results discussing some interesting examples.Comment: 11 pages. To appear in Jour. Phys.
Prevalence of plasmid-mediated quinolone resistance determinants in Enterobacteriaceae from Tunisia
AbstractThe spread of plasmid-mediated quinolone resistance determinants (qnr-like determinants, aac(6âČ)-Ib-cr and qepA genes) was evaluated in a collection of 281 nalidixic acid-resistant enterobacterial isolates recovered between September 2005 and December 2007 at the Sahloul Hospital, Sousse, Tunisia. Sixteen percent of those isolates carried qnr genes encoding the QnrB1, QnrB2, QnrA6 or QnrS1 determinants. Most qnr-positive isolates were extended-spectrum Ă-lactamase (ESBL) producers, being predominantly of the CTX-M-15 type, but also of the SHV-28 and SHV-12 types. The qnr genes were located on plasmids with a size in the range 55â150 kb. The qnrB2 gene was associated with sul1-type integron structures and the qnrB1 gene was associated with orf1005, whereas the genetic environment of qnrA6 was unknown. In two isolates, the qnrS1 gene was located downstream of an ISEcl2 element on plasmids that often carried the narrow-spectrum Ă-lactamase gene blaLAP-2; qepA and aac(6âČ)-Ib-cr were not detected. The present study highlights the wide spread of Qnr-like determinants in Tunisia, with an association with the ESBL CTX-M-15 in human clinical isolates
An experimental setup combining a highly sensitive detector forreaction products with a mass-selected cluster source andalow-temperature STM for advanced nanocatalysis measurements
We report on a home-built detector for catalytic reaction measurements offering good gas isolation from the surrounding ultrahigh vacuum components, high sensitivity for reaction products and a fast response time of 10ms enabling dynamic studies correlated to reactant gas pulses. The device is mounted in ultrahigh vacuum and combined with a low-temperature scanning tunneling microscope and a source for the deposition of mass-selected clusters. This combination allows for a direct correlation between surface morphology and catalytic properties of model catalysts. The performances of the new detector are illustrated by measurements on two model systems. Thermal desorption spectroscopy of CO carried out on morphologically well characterized Pt on TiO2(110)-(1Ă1) reveals several desorption features, which can be attributed to different surface sites. Catalytic CO oxidation performed by alternatingly pulsing isotopic CO and O2 on a Pt film on yttria stabilized zirconia reveals the CO or O rich temperature regimes. The CO2 production rate correlated with either one of the reactants can perfectly be reproduced by a kinetic reaction model giving access to the respective adsorption energie
Permanent Draft Genome sequence for Frankia sp. strain CcI49, a Nitrogen-Fixing Bacterium Isolated from Casuarina cunninghamiana that Infects Elaeagnaceae
Frankia sp. strain CcI49 was isolated from Casuarina cunninghamiana nodules. However the strain was unable to re-infect Casuarina, but was able to infect other actinorhizal plants including Elaeagnaceae. Here, we report the 9.8-Mbp draft genome sequence of Frankia sp. strain CcI49 with a G+C content of 70.5 % and 7,441 candidate protein-encoding genes. Analysis of the genome revealed the presence of a bph operon involved in the degradation of biphenyls and polychlorinated biphenyls
Draft Genome Sequence of Frankia sp. Strain Thr, a Nitrogen-Fixing Actinobacterium Isolated from the Root Nodules of Casuarina cunninghamiana Grown in Egypt
Nitrogen-fixing actinobacteria of the genus Frankia are symbionts of woody dicotyledonous plants termed actinorhizal plants. We report here a 5.3-Mbp draft genome sequence for Frankia sp. stain Thr, a nitrogen-fixing actinobacterium isolated from root nodules of Casuarina cunninghamiana collected in Egypt
Scaling and energy transfer in rotating turbulence
The inertial-range properties of quasi-stationary hydrodynamic turbulence
under solid-body rotation are studied via high-resolution direct numerical
simulations. For strong rotation the nonlinear energy cascade exhibits
depletion and a pronounced anisotropy with the energy flux proceeding mainly
perpendicularly to the rotation axis. This corresponds to a transition towards
a quasi-two-dimensional flow similar to a linear Taylor-Proudman state. In
contrast to the energy spectrum along the rotation axis which does not scale
self-similarly, the perpendicular spectrum displays an inertial range with
-behavior. A new phenomenology gives a rationale for the
observations. The scaling exponents of structure functions up to
order measured perpendicular to the rotation axis indicate reduced
intermittency with increasing rotation rate. The proposed phenomenology is
consistent with the inferred asymptotic non-intermittent behavior
.Comment: to be published in Europhysics Letters (www.epletters.net), minor
changes to match version in prin
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