572 research outputs found
Scalar conservation laws with nonconstant coefficients with application to particle size segregation in granular flow
Granular materials will segregate by particle size when subjected to shear,
as occurs, for example, in avalanches. The evolution of a bidisperse mixture of
particles can be modeled by a nonlinear first order partial differential
equation, provided the shear (or velocity) is a known function of position.
While avalanche-driven shear is approximately uniform in depth, boundary-driven
shear typically creates a shear band with a nonlinear velocity profile. In this
paper, we measure a velocity profile from experimental data and solve initial
value problems that mimic the segregation observed in the experiment, thereby
verifying the value of the continuum model. To simplify the analysis, we
consider only one-dimensional configurations, in which a layer of small
particles is placed above a layer of large particles within an annular shear
cell and is sheared for arbitrarily long times. We fit the measured velocity
profile to both an exponential function of depth and a piecewise linear
function which separates the shear band from the rest of the material. Each
solution of the initial value problem is non-standard, involving curved
characteristics in the exponential case, and a material interface with a jump
in characteristic speed in the piecewise linear case
Defining âcomplementary and alternative medicineâ
The topic of complementary and alternative medicine (CAM) is controversial. CAM is a confusing term used to encapsulate a broad range of health-related practices. In this article we explore several CAM practices including homeopathy and manipulation therapies such as osteopathy and chiropractic. We examine the difficulty in understanding the meaning of the term CAM and argue that the term is unhelpful and should be avoided in the education of healthcare professionals. Medical educators should be careful to highlight the heterogeneity of health-related practices in teaching and treat each health-related practice as an individual entity without the need for the umbrella term CAM
The impact of the Tracey judgment on the rates and outcomes of in-hospital cardiac arrests in UK hospitals participating in the National Cardiac Arrest Audit.
AIMS: The aim was to determine if the 17 June 2014 Tracey judgment regarding 'do not attempt cardiopulmonary resuscitation' decisions led to increases in the rate of in-hospital cardiac arrests resulting in a resuscitation attempt (IHCA) and/or proportion of resuscitation attempts deemed futile. METHOD: Using UK National Cardiac Arrest Audit data, the IHCA rate and proportion of resuscitation attempts deemed futile were compared for two periods (pre-judgment (01 July 2012 - 16 June 2014, inclusive) and post-judgment (01 July 2014 - 30 June 2016, inclusive)) using interrupted time series analyses. RESULTS: A total of 43,109 IHCAs (115 hospitals) were analysed. There were fewer IHCAs post- than pre-judgment (21,324 vs 21,785, respectively). The IHCA rate was declining over time before the judgment but there was an abrupt and statistically significant increase in the period immediately following the judgment (p<0.001). This was not sustained post-judgment. The proportion of resuscitation attempts deemed futile was smaller post-judgment than pre-judgment (8.2% vs 14.9%, respectively). The rate of attempts deemed futile decreased post-judgment (p<0.001). CONCLUSION: The IHCA rate increased immediately after the Tracey judgment while the proportion of resuscitation attempts deemed futile decreased. The precise mechanisms for these changes are unclear
Probing the extremes of Seyfert activity: BeppoSAX observations of Narrow-Line Seyfert 1 galaxies
Results are presented for the first year of observations of a selected sample
of Narrow-Line Seyfert 1 galaxies (Ton S 180, RE J1034+396, Ark 564) obtained
with the imaging instruments onboard BeppoSAX. These are the first simultaneous
broad band (0.1--10 keV) spectra so far obtained for this class of objects.Comment: Contributed Talk, to appear in : The Active X-ray Sky: Results from
BeppoSAX and Rossi-XTE, Nuclear Physics B Proceedings Supplements, L. Scarsi,
H. Bradt, P. Giommi and F. Fiore (eds.), Elsevier Science B.V. 6 pages LateX
and 8 ps figures, using espcrc2 and epsfi
A general assessment of environmental and biological features of Windermere and their susceptibility to change
Bassenthwaite (Lake) is one of the larger Cumbrian lakes, certainly one of the most distinctive, and of considerable conservation and amenity value. Although its shores lack sizeable settlements, its main inflow receives sewage effluent from a major tourist centre (Keswick) and is subject to episodic floods. These influences, the growing development of leisure activities at the lake (e.g. sailing, time-share units), and recent road-construction, have led to past appraisals of ecological impacts and lake management. The lake has not been the subject of intense and long-term ecological study, but much scattered information exists that is relevant to future management decisions. In the present Report, commissioned by North West Water, such information - published and unpublished - is surveyed. Especial attention is given to evidence bearing on susceptibility to change, affecting the lake environment and its biota or species of conservation interest. Extensive use has been made of the results of a recent (1986-7) seasonal survey by the FBA
The 3D Structure of N132D in the LMC: A Late-Stage Young Supernova Remnant
We have used the Wide Field Spectrograph (WiFeS) on the 2.3m telescope at
Siding Spring Observatory to map the [O III] 5007{\AA} dynamics of the young
oxygen-rich supernova remnant N132D in the Large Magellanic Cloud. From the
resultant data cube, we have been able to reconstruct the full 3D structure of
the system of [O III] filaments. The majority of the ejecta form a ring of
~12pc in diameter inclined at an angle of 25 degrees to the line of sight. We
conclude that SNR N132D is approaching the end of the reverse shock phase
before entering the fully thermalized Sedov phase of evolution. We speculate
that the ring of oxygen-rich material comes from ejecta in the equatorial plane
of a bipolar explosion, and that the overall shape of the SNR is strongly
influenced by the pre-supernova mass loss from the progenitor star. We find
tantalizing evidence of a polar jet associated with a very fast oxygen-rich
knot, and clear evidence that the central star has interacted with one or more
dense clouds in the surrounding ISM.Comment: Accepted for Publication in Astrophysics & Space Science, 18pp, 8
figure
Application of the Analytic Hierarchy Process to Riparian Revegetation Policy Options
While riparian vegetation can play a major role in protecting land, water and natural habitat in catchments, there are high costs associated with tree planting and establishment and in diverting land from cropping. The distribution of costs and benefits of riparian revegetation creates conflicts in the objectives of various stakeholder groups, and elicitation of importance weights of objectives and determination of rankings of a number of policy options by these stakeholder groups becomes critical in decision-making. The analytic hierarchy process (AHP) is a multicriteria analysis technique that provides an appropriate tool to accommodate the conflicting views of various stakeholder groups. The AHP allows the users to assess the relative importance of multiple criteria (or multiple alternatives against a given criterion) in an intuitive manner. This paper presents an application of AHP to obtain preference weights of environmental, social and economic objectives which have been used in ranking riparian revegetation policy options in a small catchment (watershed) in north Queensland, Australia. The preference weights towards environmental, economic and social objectives have been obtained for the various stakeholder groups (landholders, representatives of local sugar mill staff, environmentalists, recreational fishers and the local community). The AHP technique has proved useful in eliciting objectives and ranking policy options as well as in checking for consistency of the statements of stakeholder groups. Implementation of this approach requires a complex data elicitation process
Magnetic fields in cosmic particle acceleration sources
We review here some magnetic phenomena in astrophysical particle accelerators
associated with collisionless shocks in supernova remnants, radio galaxies and
clusters of galaxies. A specific feature is that the accelerated particles can
play an important role in magnetic field evolution in the objects. We discuss a
number of CR-driven, magnetic field amplification processes that are likely to
operate when diffusive shock acceleration (DSA) becomes efficient and
nonlinear. The turbulent magnetic fields produced by these processes determine
the maximum energies of accelerated particles and result in specific features
in the observed photon radiation of the sources. Equally important, magnetic
field amplification by the CR currents and pressure anisotropies may affect the
shocked gas temperatures and compression, both in the shock precursor and in
the downstream flow, if the shock is an efficient CR accelerator. Strong
fluctuations of the magnetic field on scales above the radiation formation
length in the shock vicinity result in intermittent structures observable in
synchrotron emission images. Resonant and non-resonant CR streaming
instabilities in the shock precursor can generate mesoscale magnetic fields
with scale-sizes comparable to supernova remnants and even superbubbles. This
opens the possibility that magnetic fields in the earliest galaxies were
produced by the first generation Population III supernova remnants and by
clustered supernovae in star forming regions.Comment: 30 pages, Space Science Review
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Effect of a whey protein and rapeseed oil gel feed supplement on milk fatty acid composition of Holstein cows
Isoenergetic replacement of dietary saturated fatty acids (SFA) with cis-monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) can reduce cardiovascular disease (CVD) risk. Supplementing dairy cow diets with plant oils lowers milk fat SFA concentrations. However, this feeding strategy can also increase milk fat trans FA (TFA), and negatively impact rumen fermentation. Protection of oil supplements from the rumen environment is therefore needed. In the present study a whey protein gel (WPG) of rapeseed oil (RO) was produced for feeding to dairy cows, in two experiments. In Experiment 1 four multiparous Holstein-Friesian cows in mid-lactation were used in a change-over experiment, with 8-d treatment periods separated by a 5-day washout period. Total mixed ration diets containing 420 g RO or WPG providing 420 g of RO were fed and the effects on milk production, composition and FA concentration were measured. Experiment 2 involved four multiparous mid-lactation Holstein-Friesian cows in a 4 x 4 Latin square design experiment, with 28-d periods, to investigate the effect of incremental dietary inclusion (0, 271, 617 and 814 g/d supplemental oil) of WPG on milk production, composition and FA concentration in the last week of each period. There were minimal effects of WPG on milk FA profile in experiment 1, but trans-18:1 and total trans-MUFA were higher after 8 days of supplementation with RO than with WPG. Incremental diet inclusion of WPG in experiment 2 resulted in linear increases in milk yield, cis- and trans-MUFA and PUFA, and linear decreases in SFA (from 73 to 58 g/100 g FA), and milk fat concentration. The WPG supplement was effective at decreasing milk SFA concentration by replacement with MUFA and PUFA in experiment 2, but the increase in TFA suggested that protection was incomplete
Short-lived Nuclei in the Early Solar System: Possible AGB Sources
(Abridged) We review abundances of short-lived nuclides in the early solar
system (ESS) and the methods used to determine them. We compare them to the
inventory for a uniform galactic production model. Within a factor of two,
observed abundances of several isotopes are compatible with this model. I-129
is an exception, with an ESS inventory much lower than expected. The isotopes
Pd-107, Fe-60, Ca-41, Cl-36, Al-26, and Be-10 require late addition to the
solar nebula. Be-10 is the product of particle irradiation of the solar system
as probably is Cl-36. Late injection by a supernova (SN) cannot be responsible
for most short-lived nuclei without excessively producing Mn-53; it can be the
source of Mn-53 and maybe Fe-60. If a late SN is responsible for these two
nuclei, it still cannot make Pd-107 and other isotopes. We emphasize an AGB
star as a source of nuclei, including Fe-60 and explore this possibility with
new stellar models. A dilution factor of about 4e-3 gives reasonable amounts of
many nuclei. We discuss the role of irradiation for Al-26, Cl-36 and Ca-41.
Conflict between scenarios is emphasized as well as the absence of a global
interpretation for the existing data. Abundances of actinides indicate a
quiescent interval of about 1e8 years for actinide group production in order to
explain the data on Pu-244 and new bounds on Cm-247. This interval is not
compatible with Hf-182 data, so a separate type of r-process is needed for at
least the actinides, distinct from the two types previously identified. The
apparent coincidence of the I-129 and trans-actinide time scales suggests that
the last actinide contribution was from an r-process that produced actinides
without fission recycling so that the yields at Ba and below were governed by
fission.Comment: 92 pages, 14 figure files, in press at Nuclear Physics
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