8,504 research outputs found

    Stationary problems for equation of the KdV type and dynamical rr-matrices.

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    We study a quite general family of dynamical rr-matrices for an auxiliary loop algebra L(su(2)){\cal L}({su(2)}) related to restricted flows for equations of the KdV type. This underlying rr-matrix structure allows to reconstruct Lax representations and to find variables of separation for a wide set of the integrable natural Hamiltonian systems. As an example, we discuss the Henon-Heiles system and a quartic system of two degrees of freedom in detail.Comment: 25pp, LaTe

    Development of a nucleic acid lateral flow immunoassay for simultaneous detection of Listeria spp. and Listeriamonocytogenes in food

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    We present a new nucleic acid lateral flow immunoassay (NALFIA) for the assessment of listeria contamination. The detection procedure starts with enrichment of sample in Half Fraser broth (24 h). Following isolation of DNA, a duplex PCR is performed with two labelled primer sets, one generic and directed to a specific sequence of the gene encoding 16S rRNA from Listeria spp. and the other specific and directed to a part of the prfA gene encoding the central virulence gene regulator from the food pathogen Listeria monocytogenes (3.5 h). The PCR solution is directly added to the one-step assay device and the appearance of a grey/black line is indicative of the presence of specific amplicons (max 15 min). In all tests performed, the method correctly identified L. monocytogenes and strains of Listeria spp. PCR material of over 20 food samples was tested by NALFIA. The method proved to be useful for the detection of L. monocytogenes in different kinds of food sample

    High-precision Atomic Physics Laboratories in Space: White Dwarfs and Subdwarfs

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    The 21st European Workshop on White Dwarfs was held in Austin, TX from July 23rd to 27th of 2018Stellar atmospheres are prime laboratories to determine atomic properties of highly ionized species. Reliable opacities are crucial ingredients for the calculation of stellar atmospheres of white dwarfs and subdwarfs. A detailed investigation on the precision of many iron-group oscillator strengths is still outstanding. To make progress, we used the Hubble Space Telescope Imaging Spectrograph to measure high-resolution spectra of three hot subdwarfs that exhibit extremely high iron-group abundances. The predicted relative strengths of the identified lines are compared with the observations to judge the quality of Kurucz’s line data and to determine correction factors for abundance determinations of the respective elements.Astronom

    Temperature and Kinematics of CIV Absorption Systems

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    We use Keck HIRES spectra of three intermediate redshift QSOs to study the physical state and kinematics of the individual components of CIV selected heavy element absorption systems. Fewer than 8 % of all CIV lines with column densities greater than 10^{12.5} cm^{-2} have Doppler parameters b < 6 km/s. A formal decomposition into thermal and non-thermal motion using the simultaneous presence of SiIV gives a mean thermal Doppler parameter b_{therm}(CIV) = 7.2 km/s, corresponding to a temperature of 38,000 K although temperatures possibly in excess of 300,000 K occur occasionally. We also find tentative evidence for a mild increase of temperature with HI column density. Non-thermal motions within components are typically small (< 10 km/s) for most systems, indicative of a quiescent environment. The two-point correlation function (TPCF) of CIV systems on scales up to 500 km/s suggests that there is more than one source of velocity dispersion. The shape of the TPCF can be understood if the CIV systems are caused by ensembles of objects with the kinematics of dwarf galaxies on a small scale, while following the Hubble flow on a larger scale. Individual high redshift CIV components may be the building blocks of future normal galaxies in a hierarchical structure formation scenario.Comment: submitted to the ApJ Letters, March 16, 1996 (in press); (13 Latex pages, 4 Postscript figures, and psfig.sty included

    Quantal interferometry with dissipative internal motion

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    In presence of dissipation, quantal states may acquire complex-valued phase effects. We suggest a notion of dissipative interferometry that accommodates this complex-valued structure and that may serve as a tool for analyzing the effect of certain kinds of external influences on quantal interference. The concept of mixed-state phase and concomitant gauge invariance is extended to dissipative internal motion. The resulting complex-valued mixed-state interference effects lead to well-known results in the unitary limit and in the case of dissipative motion of pure quantal states. Dissipative interferometry is applied to fault-tolerant geometric quantum computation.Comment: Slight revision, journal reference adde

    Fractal geometry of critical Potts clusters

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    Numerical simulations on the total mass, the numbers of bonds on the hull, external perimeter, singly connected bonds and gates into large fjords of the Fortuin-Kasteleyn clusters for two-dimensional q-state Potts models at criticality are presented. The data are found consistent with the recently derived corrections-to-scaling theory. However, the approach to the asymptotic region is slow, and the present range of the data does not allow a unique identification of the exact correction exponentsComment: 7 pages, 8 figures, Late

    Nucleic Acid Lateral Flow Immunoassay for the Detection of Pathogenic Bacteria from Food

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    Nucleic acid lateral flow immunoassay (NALFIA) is a method combining molecular biological principle of detection with immunochemical principle of visualisation. Following isolation of DNA from the sample, a duplex PCR with two primer sets, of which one was labelled with biotin and the other with digoxigenin or fluorescein, respectively, was performed. The PCR solution and carbon particles conjugated with avidin are directly added to the nitrocellulose membrane with two test lines of immobilised antibodies specific for digoxigenin and fluorescein. The appearance of a black line indicates the presence of specific amplicon. We would like to present the NALFIA for the simultaneous detection of L. monocytogenes in particular and the genus Listeria in general, in food. Bacteria from the genus Listeria frequently contaminate a large variety of foods. Occurrence of Listeria strains in food may indicate errors in good hygienic and manufacturing practice, only L. monocytogenes is a significant human and animal pathogen responsible for the serious illness listeriosis. Conventional microbiological methods for L. monocytogenes detection are laborious and take several days to achieve a confirmed identification

    The Distribution of Metallicity in the IGM at z~2.5: OVI and CIV Absorption in the Spectra of 7 QSOs

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    We present a direct measurement of the metallicity distribution function for the high redshift intergalactic medium. We determine the shape of this function using survival statistics, which account for both detections and non-detections of OVI and CIV associated with HI absorption in quasar spectra. Our OVI sample probes the metal content of ~50% of all baryons at z~2.5. We find a median intergalactic abundance of [O,C/H]=-2.82; the differential abundance distribution is approximately lognormal with mean ~-2.85 and \sigma=0.75 dex. Some 60-70% the Lya forest lines are enriched to observable levels ([O,C/H]>-3.5) while the remaining ~30% of the lines have even lower abundances. Thus we have not detected a universal metallicity floor as has been suggested for some Population III enrichment scenaria. In fact, we argue that the bulk of the intergalactic metals formed later than the first stars that are thought to have triggered reionization. We do not observe a significant trend of decreasing metallicity toward the lower density IGM, at least within regions that would be characterized as filaments in numerical simulations. However, an [O/H] enhancement may be present at somewhat high densities. We estimate that roughly half of all baryons at these redshifts have been enriched to [O/H]>=-3.5. We develop a simple model for the metallicity evolution of the IGM, to estimate the chemical yield of galaxies formed prior to z~2.5. We find that the typical galaxy recycled 0.1-0.4% of its mass back into the IGM as heavy elements in the first 3 Gyr after the Big Bang.Comment: 23 pages in emulateapj, 19 figures. Accepted to ApJ, pending review of new changes. Revised comparison between our results and Schaye et al (2003

    Quantum Mechanics in Non-Inertial Frames with a Multi-Temporal Quantization Scheme: II) Non-Relativistic Particles

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    The non-relativistic version of the multi-temporal quantization scheme of relativistic particles in a family of non-inertial frames (see hep-th/0502194) is defined. At the classical level the description of a family of non-rigid non-inertial frames, containing the standard rigidly linear accelereted and rotating ones, is given in the framework of parametrized Galilei theories. Then the multi-temporal quantization, in which the gauge variables, describing the non-inertial effects, are not quantized but considered as c-number generalized times, is applied to non relativistic particles. It is shown that with a suitable ordering there is unitary evolution in all times and that, after the separation of center of mass, it is still possible to identify the inertial bound states. The few existing results of quantization in rigid non-inertial frames are recovered as special cases
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