481 research outputs found
Smoothing tautologies, hidden dynamics, and sigmoid asymptotics for piecewise smooth systems
Switches in real systems take many forms, such as impacts, electronic relays,
mitosis, and the implementation of decisions or control strategies. To
understand what is lost, and what can be retained, when we model a switch as an
instantaneous event, requires a consideration of so-called hidden terms. These
are asymptotically vanishing outside the switch, but can be encoded in the form
of nonlinear switching terms. A general expression for the switch can be
developed in the form of a series of sigmoid functions. We review the key steps
in extending the Filippov's method of sliding modes to such systems. We show
how even slight nonlinear effects can hugely alter the behaviour of an
electronic control circuit, and lead to `hidden' attractors inside the
switching surface.Comment: 12 page
Doping dependence of superconducting gap in YBa_2Cu_3O_y from universal heat transport
Thermal transport in the T -> 0 limit was measured as a function of doping in
high-quality single crystals of the cuprate superconductor YBa_2Cu_3O_y. The
residual linear term kappa_0/T is found to decrease as one moves from the
overdoped regime towards the Mott insulator region of the phase diagram. The
doping dependence of the low-energy quasiparticle gap extracted from kappa_0/T
is seen to scale closely with that of the pseudogap, arguing against a
non-superconducting origin for the pseudogap. The presence of a linear term for
all dopings is evidence against the existence of a quantum phase transition to
an order parameter with a complex (ix) component.Comment: 2 pages, 2 figures, submitted to M2S-Rio 2003 Proceeding
Stellar Chemical Signatures And Hierarchical Galaxy Formation
ABRIDGED: To compare the chemistries of stars in the Milky Way dSph galaxies
with stars in the Galaxy, we have compiled a large sample of Galactic stellar
abundances from the literature. As found in previous studies, the [alpha/Fe]
ratios of most stars in the dSph galaxies are generally lower than similar
metallicity Galactic stars in this extended sample. Our kinematically selected
stars confirm that this is true for all major stellar components of the Galaxy,
including the halo, thin disk, and thick disk. There is marginal overlap in the
low [alpha/Fe] ratios between dSph stars and Galactic halo stars on extreme
retrograde orbits, but this is not supported by other element ratios, like
[Ba/Y]. Thus, the full chemical signature of most of the dSph stars are
distinct from the main components of the Galaxy. This result rules out
continuous merging of low mass galaxies similar to these dSph satellites during
the formation of the Galaxy, which is discuss further. The new environments
offered by the dSph galaxies also allow us to examine fundamental assumptions
related to nucleosynthesis. The metal-poor stars ([Fe/H] < -1.8) in the dSph
galaxies have [alpha/Fe] ratio that are consistent with predictions from the
alpha-process (alpha-rich freeze out). This may also explain the very low Y
abundances, and could suggest a separate r-process site for this light (first
peak r-process) element. In stars with higher metallicities ([Fe/H] > -1.8),
contributions from the s-process are expected; [Ba/Y] is still much higher in
the dSph stars than similar metallicity Galactic stars though, consistent with
s-process contributions from only the low metallicity AGB stars in dSph
galaxies. Finally, the Na-Ni trend in Galactic halo stars is confirmed, but
discuss this in terms of nucleosynthesis, and not the accretion of dSphs.Comment: Accepted for Sept 2004 Astronomical Journal; 26 pages, 9 figures, 3
table
A Comparison of Elemental Abundance Ratios in Globular Clusters, Field Stars, and Dwarf Spheroidal Galaxies
We have compiled a sample of globular clusters with high quality stellar
abundances from the literature to compare to the chemistries of stars in the
Galaxy and those in dwarf spheroidal galaxies. Of the 45 globular clusters
examined, 29 also have kinematic information. Most of the globular clusters
belong to the Galactic halo, however a signficant number have disk kinematics
or belong to the bulge. Focusing on the [alpha/Fe] and light r-process element
ratios, we find that most globular cluster stars mimic those of the field stars
of similar metallicities, and neither clearly resembles the presently available
stellar abundances in the dwarf galaxies (including the globular clusters in
the Large Magellanic Cloud). The exceptions to these general elemental ratio
comparisons are already known in the literature, e.g., omega Centauri, Palomar
12, and Terzan 7 associated with the Sagittarius remnant, and Ruprecht 106
which has a high radial velocity and low [alpha/Fe] ratio. A few other globular
clusters show more marginal peculiarities. The most notable one being the halo
cluster M68 which has a high Galactocentric rotational velocity, a slightly
younger age, and a unique [Si/Ti] ratio. The [Si/Ti] ratios decrease with
increasing [Fe/H] at intermediate metallicities, which is consistent with very
massive stars playing a larger role in the early chemical evolution of the
Galaxy. The chemical similarities between globular clusters and field stars
with [Fe/H]<-1.0 suggests a shared chemical history in a well mixed early
Galaxy. The differences to the published chemistries of stars in the dwarf
spheroidal galaxies suggests that neither the globular clusters, halo stars,
nor thick disk stars had their origins in small isolated systems like the
present-day Milky Way dwarf satellites.Comment: 24 pages, including 10 figures (8 are in color) and 4 tables;
Accepted for publication in the Astronomical Journa
Thermal Conductivity across the Phase Diagram of Cuprates: Low-Energy Quasiparticles and Doping Dependence of the Superconducting Gap
Heat transport in the cuprate superconductors YBaCuO and
LaSrCuO was measured at low temperatures as a function of
doping. A residual linear term kappa_{0}/T is observed throughout the
superconducting region and it decreases steadily as the Mott insulator is
approached from the overdoped regime. The low-energy quasiparticle gap
extracted from kappa_{0}/T is seen to scale closely with the pseudogap. The
ubiquitous presence of nodes and the tracking of the pseudogap shows that the
overall gap remains of the pure d-wave form throughout the phase diagram, which
excludes the possibility of a complex component (ix) appearing at a putative
quantum phase transition and argues against a non-superconducting origin to the
pseudogap. A comparison with superfluid density measurements reveals that the
quasiparticle effective charge is weakly dependent on doping and close to
unity.Comment: 12 pages, 9 figure
Sheep Updates 2006 - part 3
This session covers six papers from different authors:
GRAZING
1. Making better use of clover, Karen Venning and Andrew Thompson, Department of Primary Industries, Victoria
2. Grazing systems demonstration to optimise pasture utilisation and stocking rate, Mike Hyder, Sue-Ellen Shaw, Kelly Hill and Ron McTaggart, Department of Agriculture and Food Western Australia.
3. Know your audience to increase their rate of practice change - Lifetime Wool as an example, Gus Rose, Department of Agriculture and Food Western Australia, Carolyn Kabore, Kazresearch
REPRODUCTION
4. Lifetime Wool - Ewe Management Guidlines, Mandy Curnow, Department of Agriculture and Food Western Australia
5. Achieving the best reproductive performance from your hoggets, Kenyon PR, Morris ST, West DM, Perkins NR, Pinchbeck GL., Institute of Veterinary, Animal and Biomedical Sciences, Massey University, New Zealand.
6. Lifetime Wool: Twin futures, Dr Ralph Behrendt, Department of Primary Industries, Victori
Field-Induced Thermal Metal-to-Insulator Transition in Underdoped LSCO
The transport of heat and charge in cuprates was measured in single crystals
of La_{2-x}Sr_xCuO_{4+\delta} (LSCO) across the doping phase diagram at low
temperatures. In underdoped LSCO, the thermal conductivity is found to decrease
with increasing magnetic field in the T goes to 0 limit, in striking contrast
to the increase observed in all superconductors, including cuprates at higher
doping. In heavily underdoped LSCO, where superconductivity can be entirely
suppressed with an applied field, we show that a novel thermal
metal-to-insulator transition takes place upon going from the superconducting
state to the field-induced normal state.Comment: 4 pages, 3 figures, minor changes, replaced with published versio
Developing and enhancing biodiversity monitoring programmes: a collaborative assessment of priorities
1.Biodiversity is changing at unprecedented rates, and it is increasingly important that these changes are quantified through monitoring programmes. Previous recommendations for developing or enhancing these programmes focus either on the end goals, that is the intended use of the data, or on how these goals are achieved, for example through volunteer involvement in citizen science, but not both. These recommendations are rarely prioritized.
2.We used a collaborative approach, involving 52 experts in biodiversity monitoring in the UK, to develop a list of attributes of relevance to any biodiversity monitoring programme and to order these attributes by their priority. We also ranked the attributes according to their importance in monitoring biodiversity in the UK. Experts involved included data users, funders, programme organizers and participants in data collection. They covered expertise in a wide range of taxa.
3.We developed a final list of 25 attributes of biodiversity monitoring schemes, ordered from the most elemental (those essential for monitoring schemes; e.g. articulate the objectives and gain sufficient participants) to the most aspirational (e.g. electronic data capture in the field, reporting change annually). This ordered list is a practical framework which can be used to support the development of monitoring programmes.
4.People's ranking of attributes revealed a difference between those who considered attributes with benefits to end users to be most important (e.g. people from governmental organizations) and those who considered attributes with greatest benefit to participants to be most important (e.g. people involved with volunteer biological recording schemes). This reveals a distinction between focussing on aims and the pragmatism in achieving those aims.
5.Synthesis and applications. The ordered list of attributes developed in this study will assist in prioritizing resources to develop biodiversity monitoring programmes (including citizen science). The potential conflict between end users of data and participants in data collection that we discovered should be addressed by involving the diversity of stakeholders at all stages of programme development. This will maximize the chance of successfully achieving the goals of biodiversity monitoring programmes
Classification of accelerometer wear and non-wear events in seconds for monitoring free-living physical activity
_____________________________________________________________ This article is brought to you by Swansea University. Any person downloading material is agreeing to abide by the terms of the repository licence. Authors are personally responsible for adhering to publisher restrictions or conditions. When uploading content they are required to comply with their publisher agreement and the SHERPA RoMEO database to judge whether or not it is copyright safe to add this version of the paper to this repository. Design: A bi-moving-window-based approach was used to combine acceleration and skin temperature data to identify wear and non-wear time events in triaxial accelerometer data that monitor physical activity. Setting: Local residents in Swansea, Wales, UK. Participants: 50 participants aged under 16 years (n=23) and over 17 years (n=27) were recruited in two phases: phase 1: design of the wear/non-wear algorithm (n=20) and phase 2: validation of the algorithm (n=30). Methods: Participants wore a triaxial accelerometer (GeneActiv) against the skin surface on the wrist (adults) or ankle (children). Participants kept a diary to record the timings of wear and non-wear and were asked to ensure that events of wear/non-wear last for a minimum of 15 min. Results: The overall sensitivity of the proposed method was 0.94 (95% CI 0.90 to 0.98) and specificity 0.91 (95% CI 0.88 to 0.94). It performed equally well for children compared with adults, and females compared with males. Using surface skin temperature data in combination with acceleration data significantly improved the classification of wear/non-wear time when compared with methods that used acceleration data only ( p<0.01). Conclusions: Using either accelerometer seismic information or temperature information alone is prone to considerable error. Combining both sources of data can give accurate estimates of non-wear periods thus giving better classification of sedentary behaviour. This method can be used in population studies of physical activity in free-living environments
The Neoliberalisation of Higher Education in England: An Alternatives is Possible
In this article, we provide a critical explanation and critique of neoliberal policy. We attempt an innovative focus ranging from the wider contemporary political and ideological shifts, to specific higher education influences and consequences, of neoliberalism. We do this in three parts that follows a narrative logic where we explore the bigger picture, which we then locate concentrating on specific and particular examples with a long view of class struggle. In the first part, we lay out neoliberalism and explicate its basic principles in abstraction. This is necessary for part two, where we contextualise neoliberalism specifically within the English higher education system with specific reference to the policy agenda of the Government. In the third and final part of the article we suggest an alternative higher education model that simultaneously exists and flourishes with and against the neoliberal hegemony.
We conclude by suggesting the possibility of class formation and struggle in this moment of history when neoliberalism is expanding and deepening
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