63 research outputs found

    Rapid and Sensitive Detection of Yersinia pestis Using Amplification of Plague Diagnostic Bacteriophages Monitored by Real-Time PCR

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    BACKGROUND: Yersinia pestis, the agent of plague, has caused many millions of human deaths and still poses a serious threat to global public health. Timely and reliable detection of such a dangerous pathogen is of critical importance. Lysis by specific bacteriophages remains an essential method of Y. pestis detection and plague diagnostics. METHODOLOGY/PRINCIPAL FINDINGS: The objective of this work was to develop an alternative to conventional phage lysis tests--a rapid and highly sensitive method of indirect detection of live Y. pestis cells based on quantitative real-time PCR (qPCR) monitoring of amplification of reporter Y. pestis-specific bacteriophages. Plague diagnostic phages phiA1122 and L-413C were shown to be highly effective diagnostic tools for the detection and identification of Y. pestis by using qPCR with primers specific for phage DNA. The template DNA extraction step that usually precedes qPCR was omitted. phiA1122-specific qPCR enabled the detection of an initial bacterial concentration of 10(3) CFU/ml (equivalent to as few as one Y. pestis cell per 1-microl sample) in four hours. L-413C-mediated detection of Y. pestis was less sensitive (up to 100 bacteria per sample) but more specific, and thus we propose parallel qPCR for the two phages as a rapid and reliable method of Y. pestis identification. Importantly, phiA1122 propagated in simulated clinical blood specimens containing EDTA and its titer rise was detected by both a standard plating test and qPCR. CONCLUSIONS/SIGNIFICANCE: Thus, we developed a novel assay for detection and identification of Y. pestis using amplification of specific phages monitored by qPCR. The method is simple, rapid, highly sensitive, and specific and allows the detection of only live bacteria

    The Space Physics Environment Data Analysis System (SPEDAS)

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    With the advent of the Heliophysics/Geospace System Observatory (H/GSO), a complement of multi-spacecraft missions and ground-based observatories to study the space environment, data retrieval, analysis, and visualization of space physics data can be daunting. The Space Physics Environment Data Analysis System (SPEDAS), a grass-roots software development platform (www.spedas.org), is now officially supported by NASA Heliophysics as part of its data environment infrastructure. It serves more than a dozen space missions and ground observatories and can integrate the full complement of past and upcoming space physics missions with minimal resources, following clear, simple, and well-proven guidelines. Free, modular and configurable to the needs of individual missions, it works in both command-line (ideal for experienced users) and Graphical User Interface (GUI) mode (reducing the learning curve for first-time users). Both options have “crib-sheets,” user-command sequences in ASCII format that can facilitate record-and-repeat actions, especially for complex operations and plotting. Crib-sheets enhance scientific interactions, as users can move rapidly and accurately from exchanges of technical information on data processing to efficient discussions regarding data interpretation and science. SPEDAS can readily query and ingest all International Solar Terrestrial Physics (ISTP)-compatible products from the Space Physics Data Facility (SPDF), enabling access to a vast collection of historic and current mission data. The planned incorporation of Heliophysics Application Programmer’s Interface (HAPI) standards will facilitate data ingestion from distributed datasets that adhere to these standards. Although SPEDAS is currently Interactive Data Language (IDL)-based (and interfaces to Java-based tools such as Autoplot), efforts are under-way to expand it further to work with python (first as an interface tool and potentially even receiving an under-the-hood replacement). We review the SPEDAS development history, goals, and current implementation. We explain its “modes of use” with examples geared for users and outline its technical implementation and requirements with software developers in mind. We also describe SPEDAS personnel and software management, interfaces with other organizations, resources and support structure available to the community, and future development plans

    Spatio-temporal dynamics of single-cycle optical pulses and nonlinear frequency conversion

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    We model propagation of initially single-cycle wave packet exhibiting paraxial spatial diffraction in a homogeneous isotropic dielectric medium with normal group velocity dispersion and instantaneous cubic nonlinearity. We show that for higher input intensity, the number of field oscillations is increased and the temporal spectrum shifts to shorter wavelengths in the axial beam part and to longer wavelengths at the periphery of the beam, and this is accompanied by the formation of closed surfaces of equal phase. We find that at tripled frequencies a minimum of spectral density forms at low spatial frequencies, which is characteristic for single-cycle pulses. At higher spatial frequencies, the maximum of the spectral density shifts to quadruple temporal frequencies

    Influence of thermal ageing process on the crack propagation of rubber used for tire application

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    The present work studies the influence of thermal aging behaviour of rubber compounds based on natural rubber (NR), styrene butadiene rubber (SBR) and their blend NR/SBR 60/40 on dynamic-mechanical and fatigue crack growth properties. The thermal ageing at the temperatures 70 and 110 degrees C has been applied, which closely simulates the real service conditions of tires. Dynamic mechanical analysis (DMA) and fatigue crack growth (FCG) properties were characterised for the aged samples. The loss compliance J" has been determined as a parameter, which effectively is detecting the embrittlement or softening/hardening behaviour of the aged rubber. Finally, the FCG studies revealed that increase in aging temperature has deleterious effect on crack growth resistance as was reflected in all the aged materials
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