54,223 research outputs found
Spectral evolution of the microquasar XTE J1550-564 over its entire 2000 outburst
We report on RXTE observations of the microquasar XTE J1550-564 during a ~70
day outburst in April-June 2000. We study the evolution of the PCA+HEXTE
spectra over the outburst. The source transited from an initial Low Hard State
(LS), to an Intermediate State (IS), and then back to the LS. The source shows
an hysteresis effect similar to what is observed in other sources, favoring a
common origin for the state transitions in soft X-ray transients. The first
transition occurs at a ~ constant 2-200 keV flux, which probably indicates a
change in the relative importance of the emitting media. The second transition
is more likely driven by a drop in the mass accretion rate.
In both LS, the spectra are characterized by the presence of a strong
power-law tail (Compton corona) with a variable high energy cut-off. During the
IS, the spectra show the presence of a ~0.8 keV thermal component (accretion
disk). We discuss the apparently independent evolution of the two media, and
show that right after the X-ray maximum on MJD 51662, the decrease of the
source luminosity is due to a decrease of the power-law luminosity, at a
constant disk luminosity. This, together with the detection of radio emission
(with a spectrum typical of optically thin synchrotron emission), may suggest
that the corona is ejected and further detected as a discrete radio ejection.Comment: Accepted for publication in ApJ. 9 pages, 4 figures, abstract
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Climate change impacts on water for irrigated horticulture in the Vale of Evesham. Final Report
This project has undertaken a scoping review and assessment of the impacts of climate change on
irrigated horticulture in the Vale of Evesham, an area of intense irrigated production located within the
Environment Agency’s Warwickshire Avon CAMS Catchment. The research was based on a
combination of methodologies including desk-based review of published and grey literature, computer
agroclimatic and water balance modelling, GIS mapping, meetings with key informants and a
stakeholder workshop.
Future climate datasets were derived from the latest UK Climate Impacts Programme (UKICIP02)
climatology, using selected emission scenarios for the 2020s, 2050s and 2080s. These scenarios were
then used to model and map the future agroclimatic conditions under which agriculture might operate
and the consequent impacts on irrigation need (depths of water applied) and volumetric demand. This
was complimented by a postal survey to abstractors and a stakeholder workshop, to identify, review
and assess farmer adaptation options and responses. The key findings arising from the research,
implications for water resource management and recommendations for further work are summarised
below.
Using a geographical information system (GIS), a series of agroclimate maps have been produced, for
the baseline and selected UKCIP02 scenario. The maps show major changes in agroclimate within the
catchment over the next 50 years. The driest agroclimate zones are currently located around
Worcester, Evesham, Tewkesbury and Gloucester, corresponding to areas where horticultural
production and irrigation demand are most concentrated. By the 2020s, all agroclimate zones are
predicted to increase in aridity. By the 2050s the entire catchment is predicted to have a drier
agroclimate than is currently experienced anywhere in the driest parts of the catchment. This will have
major impacts on the pattern of land use and irrigation water demand. Cont/d
The 10 Tesla muSR instrument: detector solutions
Solutions to the detector system of the High-Field muSR instrument at the
Paul Scherrer Institut (PSI) in Switzerland are presented. The strict technical
requirements are fulfilled through the application of Geiger-mode Avalanche
Photodiodes.Comment: 6 pages, 4 figure
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Vectorial targeting of an endogenous apical membrane sialoglycoprotein and uvomorulin in MDCK cells.
We studied the cell-surface delivery pathways of newly synthesized membrane glycoproteins in MDCK cells and for this purpose we characterized an endogenous apical integral membrane glycoprotein. By combining a pulse-chase protocol with domain-selective cell-surface biotinylation, immune precipitation, and streptavidin-agarose precipitation (Le Bivic et al. 1989. Proc. Natl. Acad. Sci USA. 86:9313-9317), we followed the appearance at the cell surface of a major apical sialoglycoprotein, gp114, a basolateral protein, uvomorulin, and a transcytosing protein, the polyimmunoglobulin receptor (pIg-R). We determined that both gp114 and uvomorulin appeared to be delivered directly to their respective surface, with mistargeting levels of 8 and 2%, respectively. Using the same technique, the pIg-R was first detected on the basolateral domain and then on the apical domain, to be finally released into the apical medium, as described (Mostov, K. E., and D. L. Deitcher. 1986. Cell. 46:613-621). To directly determine whether the gp114 pool present on the basolateral surface was a precursor of the apical gp114, we compared it with the equivalent pIg-R pool, by labeling with sulfo-NHS-SS-biotin, a cleavable, tight junction-impermeable probe, and by following the fraction of this probe that became resistant to basal glutathione and accessible to apical glutathione during incubation at 37 degrees C. We found that, contrary to pIg-R, basolateral gp114 was poorly endocytosed and was not transcytosed to the apical side. These results demonstrate that an endogenous apical integral membrane glycoprotein of Madin-Darby canine kidney cells is sorted intracellularly and is vectorially targeted to the apical surface
Nesting Induced Peierls-type Instability for Compressed Li-CI16
Alkalies are considered to be simple metals at ambient conditions. However,
recently reported theoretical and experimental results have shown an unexpected
and intriguing correlation between complex structures and an enhanced
superconducting transition temperature in lithium under pressure. In this
article we analyze the pressure induced Fermi surface deformation in bcc
lithium, and its relation to the observed cI16 structure. According to our
calculations, the Fermi surface becomes increasingly anisotropic with pressure
and develops an extended nesting along the bcc [121] direction. This nesting
induces a phonon instability of both transverse modes at N, so that a
Peierls-type mechanism is proposed to explain the stability of Li-cI16.Comment: Proceedings of Fukuoka 2006 Conference on Novel Pressure-induced
Phenomena in Condensed Matter Systems. To be published in J. Phys. Soc. Jpn.
2 pages and 3 figure
Fractional diffusion models of cardiac electrical propagation: role of structural heterogeneity in dispersion of repolarization
Structural heterogeneity constitutes one of the main substrates influencing impulse propagation in living tissues. In cardiac muscle, improved understanding on its role is key to advancing our interpretation of cell-to-cell coupling, and how tissue structure modulates electrical propagation and arrhythmogenesis in the intact and diseased heart. We propose fractional diffusion models as a novel mathematical description of structurally heterogeneous excitable media, as a mean of representing the modulation of the total electric field by the secondary electrical sources associated with tissue inhomogeneities. Our results, validated against in-vivo human recordings and experimental data of different animal species, indicate that structural heterogeneity underlies many relevant characteristics of cardiac propagation, including the shortening of action potential duration along the activation pathway, and the progressive modulation by premature beats of spatial patterns of dispersion of repolarization. The proposed approach may also have important implications in other research fields involving excitable complex media
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