369 research outputs found
Operationalising factors that explain the emergence of infectious diseases : A case study of the human campylobacteriosis epidemic
Peer reviewedPublisher PD
Mining whole genome sequence data to efficiently attribute individuals to source populations
Acknowledgements: The Campylobacter work in this project was supported by Food Standards Scotland project FSS00017 and the Scottish Government (Rural and Environment Science and Analytical Services Division) project A13559368.Peer reviewedPublisher PD
The Use of Interdisciplinary Approaches to Understand the Biology of Campylobacter jejuni
Funding Information: This work was supported by a scholarship grant from the University of Aberdeen and Curtin University.Peer reviewedPublisher PD
Detection of Gravitational Redshift on the Solar Disk by Using Iodine-Cell Technique
With an aim to examine whether the predicted solar gravitational redshift can
be observationally confirmed under the influence of the convective Doppler
shift due to granular motions, we attempted measuring the absolute spectral
line-shifts on a large number of points over the solar disk based on an
extensive set of 5188-5212A region spectra taken through an iodine-cell with
the Solar Domeless Telescope at Hida Observatory. The resulting heliocentric
line shifts at the meridian line (where no rotational shift exists), which were
derived by finding the best-fit parameterized model spectrum with the observed
spectrum and corrected for the earth's motion, turned out to be weakly
position-dependent as ~ +400 m/s near the disk center and increasing toward the
limb up to ~ +600 m/s (both with a standard deviation of sigma ~ 100 m/s).
Interestingly, this trend tends to disappear when the convectiveshift due to
granular motions (~-300 m/s at the disk center and increasing toward the limb;
simulated based on the two-component model along with the empirical
center-to-limb variation) is subtracted, finally resulting in the averaged
shift of 698 m/s (sigma = 113 m/s). Considering the ambiguities involved in the
absolute wavelength calibration or in the correction due to convective Doppler
shifts (at least several tens m/s, or more likely up to <~100 m/s), we may
regard that this value is well consistent with the expected gravitational
redshift of 633 m/s.Comment: 28 pages, 12 figures, electronic materials as ancillary data (table3,
table 4, ReadMe); accepted for publication in Solar Physic
A SLUGGS and Gemini/GMOS combined study of the elliptical galaxy M60: wide-field photometry and kinematics of the globular cluster system
We present new wide-field photometry and spectroscopy of the globular clusters (GCs) around NGC 4649 (M60), the third brightest galaxy in the Virgo cluster. Imaging of NGC 4649 was assembled from a recently obtained Hubble Space Telescope/Advanced Camera for Surveys mosaic, and new Subaru/Suprime-Cam and archival CanadaâFranceâHawaii Telescope/MegaCam data. About 1200 sources were followed up spectroscopically using combined observations from three multi-object spectrographs: Keck/Deep Imaging Multi-Object Spectrograph, Gemini/Gemini Multi-Object Spectrograph and Multiple Mirror Telescope/Hectospec. We confirm 431 unique GCs belonging to NGC 4649, a factor of 3.5 larger than previous data sets and with a factor of 3 improvement in velocity precision. We confirm significant GC colour bimodality and find that the red GCs are more centrally concentrated, while the blue GCs are more spatially extended. We infer negative GC colour gradients in the innermost 20 kpc and flat gradients out to large radii. Rotation is detected along the galaxy major axis for all tracers: blue GCs, red GCs, galaxy stars and planetary nebulae. We compare the observed properties of NGC 4649 with galaxy formation models. We find that formation via a major merger between two gas-poor galaxies, followed by satellite accretion, can consistently reproduce the observations of NGC 4649 at different radii. We find no strong evidence to support an interaction between NGC 4649 and the neighbouring spiral galaxy NGC 4647. We identify interesting GC kinematic features in our data, such as counter-rotating subgroups and bumpy kinematic profiles, which encode more clues about the formation history of NGC 4649
Recent Advances in Understanding Particle Acceleration Processes in Solar Flares
We review basic theoretical concepts in particle acceleration, with
particular emphasis on processes likely to occur in regions of magnetic
reconnection. Several new developments are discussed, including detailed
studies of reconnection in three-dimensional magnetic field configurations
(e.g., current sheets, collapsing traps, separatrix regions) and stochastic
acceleration in a turbulent environment. Fluid, test-particle, and
particle-in-cell approaches are used and results compared. While these studies
show considerable promise in accounting for the various observational
manifestations of solar flares, they are limited by a number of factors, mostly
relating to available computational power. Not the least of these issues is the
need to explicitly incorporate the electrodynamic feedback of the accelerated
particles themselves on the environment in which they are accelerated. A brief
prognosis for future advancement is offered.Comment: This is a chapter in a monograph on the physics of solar flares,
inspired by RHESSI observations. The individual articles are to appear in
Space Science Reviews (2011
Phylogeographic analysis reveals multiple international transmission events have driven the global emergence of Escherichia coli O157:H7
This work was supported by: Scotland by Food Standards Scotland [Grant Number FS102029] and University of Aberdeen; New Zealand, Institute of Environmental Science and Research; Canada, the Public Health Agency of Canada; United States, United States Department of AgriculturePeer reviewedPostprin
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