2,157 research outputs found
Development of real-time PCR and hybridization methods for detection and identification of thermophilic Campylobacter spp. in pig faecal samples
Aims: To develop a real-time (rt) PCR for species differentiation of thermophilic Campylobacter and to develop a method for assessing co-colonization of pigs by Campylobacter spp.
Methods and results: The specificity of a developed 5’nuclease rt-PCR for species-specific identification of C. jejuni, C. coli, C. lari, C. upsaliensis and of a hipO gene nucleotide probe for detection of C. jejuni by colony-blot hybridization were determined by testing a total of 75 reference strains of Campylobacter spp. and related organisms. The rt-PCR method allowed species-specific detection of Campylobacter spp. in naturally infected pig faecal samples after an enrichment step, whereas the hybridization approach enhanced the specific isolation of C. jejuni (present in minority to C. coli) from pigs.
Conclusions: The rt-PCR was specific for Campylobacter jejuni, C. coli, C. lari, and C. upsaliensis and the colony-blot hybridization approach provided an effective tool for isolation of C. jejuni from pig faecal samples typically dominated by C. coli.
Significance and impact of study: Species differentiation between thermophilic Campylobacter is difficult by phenotypic methods and the developed rt-PCR provides an easy and fast method for such differentiation. Detection of C. jejuni by colony hybridization may increase the isolation rate of this species from pig feces
Patchy Reconnection in a Y-Type Current Sheet
We study the evolution of the magnetic field in a Y-type current sheet
subject to a brief, localized magnetic reconnection event. The reconnection
produces up- and down-flowing reconnected flux tubes which rapidly decelerate
when they hit the Y-lines and underlying magnetic arcade loops at the ends of
the current sheet. This localized reconnection outflow followed by a rapid
deceleration reproduces the observed behavior of post-CME downflowing coronal
voids. These simulations support the hypothesis that these observed coronal
downflows are the retraction of magnetic fields reconnected in localized
patches in the high corona.Comment: 4 pages, 3 figure
Paper Session I-A - Modeling Current and Future Launch Vehicle Processing Using Object-Oriented Simulation Techniques
STARSIM, an acronym for Space Transportation Activities and Resources Simulation, is an objectoriented, menu-driven, user-friendly, decision support system for simulating National Space Transportation System (NSTS) processing, as well as Personnel Launch System (PLS)-National Launch System (NLS), PLS-Proton, PLS-Titan IV, Hermes-Ariane 5 and Cargo Transfer Return Vehicle (CTRV) processing. For each launch system modeled, output is displayed numerically (for global statistical information), in pie chart form (to visualize percentages of subcategories associated with a main category) and in Gantt chart form (for visualizing when and where each launch vehicle experiences waiting, processing, blocking and maintenance periods, and the reasons for blocking). Users may input a comprehensive set of system parameters (e.g., number of launch vehicles, processing times at each facility, number of bays at a particular facility) using a window-based environment, or by supplying an existing input data file. Data for existing launch systems and representative data for proposed systems are used to illustrate output for the models mentioned above. The object-oriented methodology employed in the initial model (i.e., NSTS processing) permitted additional models to be implemented in a minimum amount of time and effort
A Model for Patchy Reconnection in Three Dimensions
We show, theoretically and via MHD simulations, how a short burst of
reconnection localized in three dimensions on a one-dimensional current sheet
creates a pair of reconnected flux tubes. We focus on the post-reconnection
evolution of these flux tubes, studying their velocities and shapes. We find
that slow-mode shocks propagate along these reconnected flux tubes, releasing
magnetic energy as in steady-state Petschek reconnection. The geometry of these
three-dimensional shocks, however, differs dramatically from the classical
two-dimensional geometry. They propagate along the flux tube legs in four
isolated fronts, whereas in the two-dimensional Petschek model, they form a
continuous, stationary pair of V-shaped fronts.
We find that the cross sections of these reconnected flux tubes appear as
teardrop shaped bundles of flux propagating away from the reconnection site.
Based on this, we argue that the descending coronal voids seen by Yohkoh SXT,
LASCO, and TRACE are reconnected flux tubes descending from a flare site in the
high corona, for example after a coronal mass ejection. In this model, these
flux tubes would then settle into equilibrium in the low corona, forming an
arcade of post-flare coronal loops.Comment: 27 pages plus 16 figure
American Institute of Aeronautics and Astronautics 1 RADIATION-DRIVEN FLAME SPREAD OVER THERMALLY-THICK FUELS IN QUIESCENT MICROGRAVITY ENVIRONMENTS
Abstract Microgravity experiments on flame spread over thermally thick fuels were conducted using foam fuels to obtain low density and thermal conductivity, and thus large spread rate (S f ) compared to dense fuels such as PMMA. This scheme enabled meaningful results to be obtained even in 2.2 second drop tower experiments. It was found that, in contrast conventional understanding; steady spread can occur over thick fuels in quiescent microgravity environments, especially when a radiatively active diluent gas such as CO 2 is employed. This is proposed to be due to radiative transfer from the flame to the fuel surface. Additionally, the transition from thermally thick to thermally thin behavior with decreasing bed thickness is demonstrated
Economic performance or electoral necessity? Evaluating the system of voluntary income to political parties
Whilst the public funding of political parties is the norm in western democracies, its comprehensive introduction has been resisted in Britain. Political and electoral arrangements in Britain require parties to function and campaign on a regular basis, whilst their income follows cycles largely related to general elections. This article shows that the best predictor of party income is the necessity of a well-funded general election campaign rather than party performance. As a result, income can only be controlled by parties to a limited degree, which jeopardises their ability to determine their own financial position and fulfil their functions as political parties
A Plasma {\beta} Transition Within a Propagating Flux Rope
We present a 2.5D MHD simulation of a magnetic flux rope (FR) propagating in
the heliosphere and investigate the cause of the observed sharp plasma beta
transition. Specifically, we consider a strong internal magnetic field and an
explosive fast start, such that the plasma beta is significantly lower in the
FR than the sheath region that is formed ahead. This leads to an unusual FR
morphology in the first stage of propagation, while the more traditional view
(e.g. from space weather simulations like Enlil) of a `pancake' shaped FR is
observed as it approaches 1 AU. We investigate how an equipartition line,
defined by a magnetic Weber number, surrounding a core region of a propagating
FR can demarcate a boundary layer where there is a sharp transition in the
plasma beta. The substructure affects the distribution of toroidal flux, with
the majority of the flux remaining in a small core region which maintains a
quasi-cylindrical structure. Quantitatively, we investigate a locus of points
where the kinetic energy density of the relative inflow field is equal to the
energy density of the transverse magnetic field (i.e. effective tension force).
The simulation provides compelling evidence that at all heliocentric distances
the distribution of toroidal magnetic flux away from the FR axis is not linear;
with 80% of the toroidal flux occurring within 40% of the distance from the FR
axis. Thus our simulation displays evidence that the competing ideas of a
pancaking structure observed remotely can coexist with a quasi-cylindrical
magnetic structure seen in situ.Comment: 11 pages of text + 6 figures. Accepted to ApJ on 16 Oct 201
Structural basis for the modulation of MRP2 activity by phosphorylation and drugs.
Multidrug resistance-associated protein 2 (MRP2/ABCC2) is a polyspecific efflux transporter of organic anions expressed in hepatocyte canalicular membranes. MRP2 dysfunction, in Dubin-Johnson syndrome or by off-target inhibition, for example by the uricosuric drug probenecid, elevates circulating bilirubin glucuronide and is a cause of jaundice. Here, we determine the cryo-EM structure of rat Mrp2 (rMrp2) in an autoinhibited state and in complex with probenecid. The autoinhibited state exhibits an unusual conformation for this class of transporter in which the regulatory domain is folded within the transmembrane domain cavity. In vitro phosphorylation, mass spectrometry and transport assays show that phosphorylation of the regulatory domain relieves this autoinhibition and enhances rMrp2 transport activity. The in vitro data is confirmed in human hepatocyte-like cells, in which inhibition of endogenous kinases also reduces human MRP2 transport activity. The drug-bound state reveals two probenecid binding sites that suggest a dynamic interplay with autoinhibition. Mapping of the Dubin-Johnson mutations onto the rodent structure indicates that many may interfere with the transition between conformational states
Collections Education: The Extended Specimen and Data Acumen
Biodiversity scientists must be fluent across disciplines; they must possess the quantitative, computational, and data skills necessary for working with large, complex data sets, and they must have foundational skills and content knowledge from ecology, evolution, taxonomy, and systematics. To effectively train the emerging workforce, we must teach science as we conduct science and embrace emerging concepts of data acumen alongside the knowledge, tools, and techniques foundational to organismal biology. We present an open education resource that updates the traditional plant collection exercise to incorporate best practices in twenty-first century collecting and to contextualize the activities that build data acumen. Students exposed to this resource gained skills and content knowledge in plant taxonomy and systematics, as well as a nuanced understanding of collections-based data resources. We discuss the importance of the extended specimen in fostering scientific discovery and reinforcing foundational concepts in biodiversity science, taxonomy, and systematics
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