46,642 research outputs found
The Eurovision St Andrews collection of photographs
This report describes the Eurovision image collection compiled for the ImageCLEF (Cross Language Evaluation Forum) evaluation exercise. The image collection consists of around 30,000 photographs from the collection provided by the University of St Andrews Library. The construction and composition of this unique image collection are described, together with the necessary information to obtain and use the image collection
Cannabis and the lung
The use of cannabis is embedded within many societies, mostly used by the young and widely perceived to be safe. Increasing concern regarding the potential for cannabis to cause mental health effects has dominated cannabis research and the potential adverse respiratory effects have received relatively little attention. Studies on cannabis are challenging and subject to confounding by concomitant use of tobacco and other social factors, and while many of the studies referred to in this review are beset by the difficulties inherent in undertaking epidemiological research of the effects of cannabis, there is an emerging concern among many chest physicians who would suggest that habitual smoking of cannabis may contribute to the development of chronic obstructive pulmonary disease, pneumothorax and respiratory infections, including tuberculosis. Special attention should be given to the risk of lung cancer, particularly as biological plausibility may precede epidemiology
Imaging Spectroscopy of Type U and J Solar Radio Bursts with LOFAR
Radio U-bursts and J-bursts are signatures of electron beams propagating
along magnetic loops confined to the corona. The more commonly observed type
III radio bursts are signatures of electron beams propagating along magnetic
loops that extend into interplanetary space. Given the prevalence of solar
magnetic flux to be closed in the corona, it is an outstanding question why
type III bursts are more frequently observed than U-bursts or J-bursts. We use
LOFAR imaging spectroscopy between 30-80 MHz of low-frequency U-bursts and
J-bursts, for the first time, to understand why electron beams travelling along
coronal loops produce radio emission less often. The different radio source
positions were used to model the spatial structure of the guiding magnetic flux
tube and then deduce the energy range of the exciting electron beams without
the assumption of a standard density model. The radio sources infer a magnetic
loop 1 solar radius in altitude, with the highest frequency sources starting
around 0.6 solar radii. Electron velocities were found between 0.13 c and 0.24
c, with the front of the electron beam travelling faster than the back of the
electron beam. The velocities correspond to energy ranges within the beam from
0.7-11 keV to 0.7-43 keV. The density along the loop is higher than typical
coronal density models and the density gradient is smaller. We found that a
more restrictive range of accelerated beam and background plasma parameters can
result in U-bursts or J-bursts, causing type III bursts to be more frequently
observed. The large instability distances required before Langmuir waves are
produced by some electron beams, and the small magnitude of the background
density gradients make closed loops less facilitating for radio emission than
loops that extend into interplanetary space.Comment: 9 pages, 7 figure
Stopping Frequency of Type III Solar Radio Bursts in Expanding Magnetic Flux Tubes
Understanding the properties of type III radio bursts in the solar corona and
interplanetary space is one of the best ways to remotely deduce the
characteristics of solar accelerated electron beams and the solar wind plasma.
One feature of all type III bursts is the lowest frequency they reach (or
stopping frequency). This feature reflects the distance from the Sun that an
electron beam can drive the observable plasma emission mechanism. The stopping
frequency has never been systematically studied before from a theoretical
perspective. Using numerical kinetic simulations, we explore the different
parameters that dictate how far an electron beam can travel before it stops
inducing a significant level of Langmuir waves, responsible for plasma radio
emission. We use the quasilinear approach to model self-consistently the
resonant interaction between electrons and Langmuir waves in inhomogeneous
plasma, and take into consideration the expansion of the guiding magnetic flux
tube and the turbulent density of the interplanetary medium. We find that the
rate of radial expansion has a significant effect on the distance an electron
beam travels before enhanced leves of Langmuir waves, and hence radio waves,
cease. Radial expansion of the guiding magnetic flux tube rarefies the electron
stream to the extent that the density of non-thermal electrons is too low to
drive Langmuir wave production. The initial conditions of the electron beam
have a significant effect, where decreasing the beam density or increasing the
spectral index of injected electrons would cause higher type III stopping
frequencies. We also demonstrate how the intensity of large-scale density
fluctuations increases the highest frequency that Langmuir waves can be driven
by the beam and how the magnetic field geometry can be the cause of type III
bursts only observed at high coronal frequencies.Comment: 11 pages, 8 figures, accepted in Astronomy and Astrophysic
Shaping the future for primary care education and training project. Integrated health and social care: the perspectives of people using services: a mixed methods analysis
The aim of this study was to explore service users' perspectives concerning integrated health & social care, and
to identify the perceived strengths and weaknesses associated with the current workforce and services provided. The findings will be used to inform the education and training of
the health and social care workforce in the North West of Englan
Measuring, understanding and adapting to nexus trade-offs in the Sekong, Sesan and Srepok transboundary river basins
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