640 research outputs found
Transition of pupils from Key Stage 2 to 3 deemed gifted and talented in mathematics: an initial study
In this article Geoff Tennant and Dave Harries report on the early stages of a research project looking to examine the transition from Key Stage (KS) 2 to 3 of children deemed Gifted and Talented (G&T) in mathematics. An examination of relevant literature points towards variation in definition of key terms and underlying rationale for activities. Preliminary fieldwork points towards a lack of meaningful communication between schools, with primary school teachers in particular left to themselves to decide how to work with children deemed G&T. Some pointers for action are given, along with ideas for future research and a request for colleagues interested in working with us to get in touch
Techniques for monitoring human exposure to airborne trace metals
This thesis explores the techniques employed for monitoring human exposure to airborne trace elements in urban atmospheres using trace metal analysis of human hair
Discovery of a 3.6-hr Eclipsing Luminous X-Ray Binary in the Galaxy NGC 4214
We report the discovery of an eclipsing X-ray binary with a 3.62-hr period
within 24" of the center of the dwarf starburst galaxy NGC 4214. The orbital
period places interesting constraints on the nature of the binary, and allows
for a few very different interpretations. The most likely possibility is that
the source lies within NGC 4214 and has an X-ray luminosity of up to 7 e38
ergs/s. In this case the binary may well be comprised of a naked He-burning
donor star with a neutron-star accretor, though a stellar-mass black-hole
accretor cannot be completely excluded. There is no obvious evidence for a
strong stellar wind in the X-ray orbital light curve that would be expected
from a massive He star; thus, the mass of the He star should be <3-4 solar
masses. If correct, this would represent a new class of very luminous X-ray
binary -- perhaps related to Cyg X-3. Other less likely possibilities include a
conventional low-mass X-ray binary that somehow manages to produce such a high
X-ray luminosity and is apparently persistent over an interval of years; or a
foreground AM Her binary of much lower luminosity that fortuitously lies in the
direction of NGC 4214. Any model for this system must accommodate the lack of
an optical counterpart down to a limiting magnitude of 22.6 in the visible.Comment: 7 pages, ApJ accepted versio
Waterlogging limits growth on duplex soils
Duplex soils - soils with a sandy topsoil overlying a clayey subsoil -are ividespread in Western Australia\u27s agricultural areas (see map). These soils are potentially highly productive, but crop growth is variable and the soils can become waterlogged. Work on a duplex soil site near Beverley has shoivn that the soil ivaterlogs where the permeability of the clay is low, and that this permeability varies ividely over the site. Waterlogging accounts for an average of half of the variation in wheat yields on this site; surprisingly, lupins have so far appeared less sensitive to waterlogging- The Department of Agriculture and CSIRO dryland crops and soils group are studying the causes of reduced crop growth on duplex soils to devise management strategies to overcome the problems
Results of stubble research in Western Australia
Few farmers would question the desirability of retaining stubbles, both for control of erosion by wind and water, and to return organic matter to the soil. While the present debate is focused on the short term management of stubbles, longer term effects also need to be considered.
The Department of Agriculture has several long-running trials intended to measure long term effects
Field assessment of sediment trap efficiency under varying flow conditions
Knowledge of the collection efficiency of sediment traps, particularly under conditions of varying current speed, is presently more a matter of hope than confidence. We report here on a field experiment designed to determine, for a particular trap geometry, the effect of current speed and particle fall velocity on the collection efficiency of a moored trap relative to the presumably unbiased efficiency of an identical drifting trap. The experiment was performed in a deep estuarine tidal passage where a smoothly varying unidirectional flow and a spatially homogenous particle population mimicked laboratory flume conditions. A multiple-sample sediment trap integrated to a current meter partitioned the mass flux collected by the moored trap into one of four chambers according to the following speed intervals: \u3c12, 12–\u3c30, 30–\u3c50, and ≥50cm/s. The magnitude and particle characteristics of the flux collected at \u3c12 cm/s were indistinguishable from those simultaneously collected by drifting traps. At higher speeds, the relative efficiency of the moored trap ranged between 1% and 24% and the mean size and density of the trapped particles increased. These results support predictions based on laboratory studies that collection efficiency decreases with an increase in the trap Reynolds number or a decrease in particle fall velocity. The study demonstrates that consideration must be given to scaling both trap diameter and aspect ratio according to the expected flow conditions, and that knowledge of flow conditions at the trap mouth is necessary to properly interpret the flux data
Dynamics of nonequilibrium magnons in gapped Heisenberg antiferromagnets
Nonequilibrium dynamics in spin systems is a topic currently under intense
investigation as it provides fundamental insights into thermalization,
universality, and exotic transport phenomena. While most of the studies have
been focused on ideal closed quantum many-body systems such as ultracold atomic
quantum gases and one-dimensional spin chains, driven-dissipative Bose gases in
steady states away from equilibrium in classical systems also lead to
intriguing nonequilibrium physics. In this work, we theoretically investigate
out-of-equilibrium dynamics of magnons in a gapped Heisenberg quantum
antiferromagnet based on Boltzmann transport theory. We show that, by treating
scattering terms beyond the relaxation time approximation in the Boltzmann
transport equation, energy and particle number conservation mandate that
nonequilibrium magnons cannot relax to equilibrium, but decay to other
nonequilibrium stationary states, partially containing information about the
initial states. The only decay channel for these stationary states back to
equilibrium is through the non-conserving interactions such as boundary or
magnon-phonon scattering. At low temperatures, these non-conserving
interactions are much slower processes than intrinsic magnon-magnon interaction
in a gapped spin system. Using magnon-phonon interaction as a quintessential
type of non-conserving interaction, we then propose that nonequilibrium steady
states of magnons can be maintained and tailored using periodic driving at
frequencies faster than relaxation due to phonon interactions. These findings
reveal a class of classical material systems that are suitable platforms to
study nonequilibrium statistical physics and macroscopic phenomena such as
classical Bose-Einstein condensation of quasiparticles and magnon supercurrents
that are relevant for spintronic applications
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