903 research outputs found
Internal parasites and association with diarrhoea in sheep at an abattoir in Western Australia
Diarrhoea (scouring) is an important issue for the sheep meat industry. Scouring is a major risk factor for fleece soiling and consequential carcase contamination with microbes that cause meat spoilage and potential dangers for humans (2). There is little information on the causes of scouring in sheep at slaughter. Strongyle worm infections are commonly implicated in scouring and reduced production, yet there is no published data quantifying strongyle infections in scouring and normal sheep at abattoirs. In addition, Giardia and Cryptosporidium have been associated with scouring in ruminants, but little is known about the prevalence, genotypes present or the effect on production in sheep populations. This study carried out at an abattoir in Western Australia (WA), aimed to investigate the extent of strongyle, Giardia and Cryptosporidium infections and any association with scouring in sheep
The Effect of Anxiety Disorders on Smoking Cessation in Cancer Patients
https://openworks.mdanderson.org/sumexp23/1125/thumbnail.jp
The Stationary Phase Method for a Wave Packet in a Semiconductor Layered System. The applicability of the method
Using the formal analysis made by Bohm in his book, {\em "Quantum theory"},
Dover Publications Inc. New York (1979), to calculate approximately the phase
time for a transmitted and the reflected wave packets through a potential
barrier, we calculate the phase time for a semiconductor system formed by
different mesoscopic layers. The transmitted and the reflected wave packets are
analyzed and the applicability of this procedure, based on the stationary phase
of a wave packet, is considered in different conditions. For the applicability
of the stationary phase method an expression is obtained in the case of the
transmitted wave depending only on the derivatives of the phase, up to third
order. This condition indicates whether the parameters of the system allow to
define the wave packet by its leading term. The case of a multiple barrier
systems is shown as an illustration of the results. This formalism includes the
use of the Transfer Matrix to describe the central stratum, whether it is
formed by one layer (the single barrier case), or two barriers and an inner
well (the DBRT system), but one can assume that this stratum can be comprise of
any number or any kind of semiconductor layers.Comment: 15 pages, 4 figures although figure 4 has 5 graph
PADAMOT : project overview report
Background and relevance to radioactive waste management
International consensus confirms that placing radioactive wastes and spent nuclear fuel deep
underground in a geological repository is the generally preferred option for their long-term
management and disposal. This strategy provides a number of advantages compared to leaving it
on or near the Earthâs surface. These advantages come about because, for a well chosen site, the
geosphere can provide:
âą a physical barrier that can negate or buffer against the effects of surface dominated natural
disruptive processes such as deep weathering, glaciation, river and marine erosion or
flooding, asteroid/comet impact and earthquake shaking etc.
âą long and slow groundwater return pathways from the facility to the biosphere along which
retardation, dilution and dispersion processes may operate to reduce radionuclide
concentration in the groundwater.
âą a stable, and benign geochemical environment to maximise the longevity of the engineered
barriers such as the waste containers and backfill in the facility.
âą a natural radiation shield around the wastes.
âą a mechanically stable environment in which the facility can be constructed and will
afterwards be protected.
âą an environment which reduces the likelihood of the repository being disturbed by inadvertent
human intrusion such as land use changes, construction projects, drilling, quarrying and
mining etc.
âą protection against the effects of deliberate human activities such as vandalism, terrorism and
war etc.
However, safety considerations for storing and disposing of long-lived radioactive wastes must
take into account various scenarios that might affect the ability of the geosphere to provide the
functionality listed above. Therefore, in order to provide confidence in the ability of a repository
to perform within the deep geological setting at a particular site, a demonstration of geosphere
âstabilityâ needs to be made. Stability is defined here to be the capacity of a geological and
hydrogeological system to minimise the impact of external influences on the repository
environment, or at least to account for them in a manner that would allow their impacts to be
evaluated and accounted for in any safety assessments.
A repository should be sited where the deep geosphere is a stable host in which the engineered
containment can continue to perform according to design and in which the surrounding
hydrogeological, geomechanical and geochemical environment will continue to operate as a
natural barrier to radionuclide movement towards the biosphere. However, over the long periods
of time during which long-lived radioactive wastes will pose a hazard, environmental change at
the surface has the potential to disrupt the stability of the geosphere and therefore the causes of
environmental change and their potential consequences need to be evaluated.
As noted above, environmental change can include processes such as deep weathering,
glaciation, river and marine erosion. It can also lead to changes in groundwater boundary
conditions through alternating recharge/discharge relationships. One of the key drivers for
environmental change is climate variability. The question then arises, how can geosphere stability be assessed with respect to changes in climate? Key issues raised in connection with
this are:
âą What evidence is there that 'going underground' eliminates the extreme conditions that
storage on the surface would be subjected to in the long term?
âą How can the additional stability and safety of the deep geosphere be demonstrated with
evidence from the natural system?
As a corollary to this, the capacity of repository sites deep underground in stable rock masses to
mitigate potential impacts of future climate change on groundwater conditions therefore needs to
be tested and demonstrated. To date, generic scenarios for groundwater evolution relating to
climate change are currently weakly constrained by data and process understanding. Hence, the
possibility of site-specific changes of groundwater conditions in the future can only be assessed
and demonstrated by studying groundwater evolution in the past. Stability of groundwater
conditions in the past is an indication of future stability, though both the climatic and geological
contexts must be taken into account in making such an assertion
Disk Diffusion Propagation Model for the Outburst of XTE J1118+480
We present a linear diffusion model for the evolution of the double-peaked
outburst in the transient source XTEJ1118+480. The model treats the two
outbursts as episodic mass deposition at the outer radius of the disk followed
by evolution of disk structure according to a diffusion process. We demonstrate
that light curves with fast-rise, exponential decay profile are a general
consequence of the diffusion process. Deconvolution of the light curve proves
to be feasible and gives an input function specifying mass deposition at the
outer disk edge as well as the total mass of the disk, both as functions of
time. The derived evolution of total disk mass can be correlated with the
observed evolution of the ~0.1 Hz QPO in the source reported in Wood et al.
(2000).Comment: 26 pages, 6 figures, accepted for publication in Ap
Design of hidden thermodynamic driving for non-equilibrium systems via mismatch elimination during DNA strand displacement
Recent years have seen great advances in the development of synthetic self-assembling molecular systems. Designing out-of-equilibrium architectures, however, requires a more subtle control over the thermodynamics and kinetics of reactions. We propose a mechanism for enhancing the thermodynamic drive of DNA strand-displacement reactions whilst barely perturbing forward reaction rates: the introduction of mismatches within the initial duplex. Through a combination of experiment and simulation, we demonstrate that displacement rates are strongly sensitive to mismatch location and can be tuned by rational design. By placing mismatches away from duplex ends, the thermodynamic drive for a strand-displacement reaction can be varied without significantly affecting the forward reaction rate. This hidden thermodynamic driving motif is ideal for the engineering of non-equilibrium systems that rely on catalytic control and must be robust to leak reactions
General-relativistic constraints on the equation of state of dense matter implied by kilohertz quasi-periodic oscillations in neutron-star X-ray binaries
If the observed millisecond variability in the X-ray flux of several
neutron-star low-mass X-ray binaries (LMXBs) is interpreted within a
general-relativistic framework (Kluzniak, Michelson \& Wagoner 1990) extant at
the time of discovery, severe constraints can be placed on the equation of
state (e.o.s.) of matter at supranuclear densities. The reported maximum
frequency (1.14 +- 0.01 kHz) of quasiperiodic oscillations observed in sources
as diverse as Sco X-1 and 4U 1728-34 would imply that the neutron star masses
in these LMXBs are M > 1.9 M_solar, and hence many equations of state would be
excluded. Among the very few still viable equations of state are the e.o.s. of
Phandaripande and Smith (1975), and e.o.s. AV14 + UVII of Wiringa, Fiks \&
Fabrocini (1988).Comment: The figures can be found in the references cited in the captions. A
longer version of this paper was submitted to a refereed journal on January
6, 1997 (345 days ago
The viscosity parameter alpha and the properties of accretion disc outbursts in close binaries
The physical mechanisms driving angular momentum transport in accretion discs
are still unknown. Although it is generally accepted that, in hot discs, the
turbulence triggered by the magneto-rotational instability is at the origin of
the accretion process in Keplerian discs, it has been found that the values of
the stress-to-pressure ratio (the alpha "viscosity" parameter) deduced from
observations of outbursting discs are an order of magnitude higher than those
obtained in numerical simulations. We test the conclusion about the
observation-deduced value of alpha using a new set of data and comparing the
results with model outbursts. We analyse a set of observations of dwarf-nova
and AM CVn star outbursts and from the measured decay times determine the
hot-disc viscosity parameter alpha_h. We determine if and how this method is
model dependent. From the dwarf-nova disc instability model we determine an
amplitude vs recurrence-time relation and compare it to the empirical
Kukarkin-Parenago relation between the same, but observed, quantities. We found
that all methods we tried, including the one based on the amplitude vs
recurrence-time relation, imply alpha_h ~ 0.1 - 0.2 and exclude values an order
of magnitude lower. The serious discrepancy between the observed and the
MRI-calculated values of the accretion disc viscosity parameter alpha is
therefore real since there can be no doubt about the validity of the values
deduced from observations of disc outbursts.Comment: Astronomy and Astrophysics, in press. (In Fig. 3b the upper sequence
of numbers and symbols is an artefact of the compilation on astro-ph) and
should be ignored.
When does the action start and finish? Making the case for an ethnographic action research in educational research
This paper explores how ethnographic and action research methodologies can be justifiably combined to create a new methodological approach in educational research. It draws on existing examples in both educational research and
development studies that have discussed the use of ethnography and action research in specific projects. Interpretations of ethnography and action research
are developed that aim to minimise the epistemological differences between them.
The paper also contextualises an âethnographic action researchâ approach with reference to an example of the authorâs research into participation in three âreceptionâ (first year of schooling) classes in the United Kingdom. It is argued that research into the theme of participation in early years education, using participative methods, was particularly suitable for this new methodological
approach
The Insulin Resistance Intervention after Stroke trial: a perspective on future practice and research
The prevention of recurrent events after ischaemic stroke and transient ischaemic attack is well established and based on lifestyle changes, antithrombotics, statins, antihypertensives and carotid surgery. The international IRIS trial assessed whether pioglitazone, a glucose-lowering insulin-sensitizing drug, would reduce recurrent vascular events in patients with ischaemic stroke or transient ischaemic attack. After 4.8 years, pioglitazone therapy was associated with reduced vascular events and new diabetes, and an increase in weight, oedema and bone fractures. Pioglitazone may add to the strategies for preventing further events in patients with stroke or transient ischaemic attack
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