299 research outputs found
Past plant use in Jordan as revealed by archaeological and ethnoarchaeological phytolith signatures
Ninety-six phytolith samples were analysed from seven
archaeological sites ranging from the Pre-Pottery
Neolithic to the Classical period and from two
ethnoarchaeological sites in Jordan. The aims were to
test the possibility of detecting past irrigation with the
methodology outlined by Madella et al. (2009) and
Jenkins et al. (Chapter 21, this volume) and to study the
contextual and temporal variation of plant use in
Jordan. We utilised a water availability index using the
proportion of phytolith types and ordination statistical
methods to explore the similarities between the
phytolith assemblages. The result of applying the
irrigation methodology was promising, with contexts
from water channels showing the greatest indication of
water availability. Changes in plant use through time
were also apparent with regard to phytolith densities
and taxonomy. Date palm was identified in the Pottery
Neolithic, providing one of the earliest records for this
taxon in Jordan. This study shows the potential of both
the water availability index and the value of inter-site
comparison of phytolith assemblages
Professionalism, golf coaching and a master of science degree
A distinction can be made between 'professionalisation', which is concerned with occupational status and standing, and 'professionalism,' which refers to matters of quality and standards of practice (especially specialized knowledge, ethics and altruism). The purpose of this stimulus article is to present key features of contemporary medical professionalism as a basis for critically reflecting on discourse associated with Tiger Woods' current coach, Sean Foley. It is suggested that that provision of a Master of Science degree in golf teaching/coaching would facilitate the development of 'professionalism' in golf coaches
Dynamics and stress in gravity driven granular flow
We study, using simulations, the steady-state flow of dry sand driven by
gravity in two-dimensions. An investigation of the microscopic grain dynamics
reveals that grains remain separated but with a power-law distribution of
distances and times between collisions.
While there are large random grain velocities, many of these fluctuations are
correlated across the system and local rearrangements are very slow. Stresses
in the system are almost entirely transfered by collisions and the structure of
the stress tensor comes almost entirely from a bias in the directions in which
collisions occur.Comment: 4 pages, 3 eps figures, RevTe
Benchmark low-mass objects in Moving Groups
This is an Open Access article distributed under the terms of the Creative Commons Attribution License 2.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.In order to compile a sample of ultracool dwarfs that will serve as benchmarks for testing theoretical formation and evolutionary models, we selected low-mass cool (>M7) objects that are potentially members of five known young Moving Groups in the solar neighbourhood. We have studied the kinematics of the sample, finding that 49 targets belong to the young disk area, from which 36 are kinematic member of one of the five moving groups under study. Some of the identified low-mass members have been spectroscopically characterised (T-eff, log g) and confirmed as young members through a detailed study of age indicators
The research-teaching nexus: A case study of students' awareness, experiences and perceptions of research
This paper presents a case study of students' awareness, experiences and perceptions of research in a 'new' university in the UK. The findings are based on a questionnaire of almost 200 students and five small group interviews. Many of the students participating in this research perceived clear benefits to their learning from staff research, including being taught by enthusiastic staff, enhanced staff credibility, and the reflected glory of being taught by well-known researchers. However, they also perceived disadvantages, particularly with regard to staff availability, and did not believe that staff research should take priority over their needs as learners. They recognised that their awareness of the nature of research and the development of research skills increased most when they were actively involved in undertaking research projects. Several students also perceived benefits for future employment from their participation in research activities. The questionnaire has been used by several other universities around the world to benchmark their practices. © 2010 Taylor & Francis
Symmetry-breaking instability in a prototypical driven granular gas
Symmetry-breaking instability of a laterally uniform granular cluster (strip
state) in a prototypical driven granular gas is investigated. The system
consists of smooth hard disks in a two-dimensional box, colliding inelastically
with each other and driven, at zero gravity, by a "thermal" wall. The limit of
nearly elastic particle collisions is considered, and granular hydrodynamics
with the Jenkins-Richman constitutive relations is employed. The hydrodynamic
problem is completely described by two scaled parameters and the aspect ratio
of the box. Marginal stability analysis predicts a spontaneous symmetry
breaking instability of the strip state, similar to that predicted recently for
a different set of constitutive relations. If the system is big enough, the
marginal stability curve becomes independent of the details of the boundary
condition at the driving wall. In this regime, the density perturbation is
exponentially localized at the elastic wall opposite to the thermal wall. The
short- and long-wavelength asymptotics of the marginal stability curves are
obtained analytically in the dilute limit. The physics of the symmetry-breaking
instability is discussed.Comment: 11 pages, 14 figure
Velocity correlations in dense granular gases
We report the statistical properties of spherical steel particles rolling on
an inclined surface being driven by an oscillating wall. Strong dissipation
occurs due to collisions between the particles and rolling and can be tuned by
changing the number density. The velocities of the particles are observed to be
correlated over large distances comparable to the system size. The distribution
of velocities deviates strongly from a Gaussian. The degree of the deviation,
as measured by the kurtosis of the distribution, is observed to be as much as
four times the value corresponding to a Gaussian, signaling a significant
breakdown of the assumption of negligible velocity correlations in a granular
system.Comment: 4 pages, 4 Figure
Onset of thermal convection in a horizontal layer of granular gas
The Navier-Stokes granular hydrodynamics is employed for determining the
threshold of thermal convection in an infinite horizontal layer of granular
gas. The dependence of the convection threshold, in terms of the inelasticity
of particle collisions, on the Froude and Knudsen numbers is found. A simple
necessary condition for convection is formulated in terms of the
Schwarzschild's criterion, well-known in thermal convection of (compressible)
classical fluids. The morphology of convection cells at the onset is
determined. At large Froude numbers, the Froude number drops out of the
problem. As the Froude number goes to zero, the convection instability turns
into a recently discovered phase separation instability.Comment: 6 pages, 6 figures. An extended version. A simple and universal
necessary criterion for convection presente
A nonlinear hydrodynamical approach to granular materials
We propose a nonlinear hydrodynamical model of granular materials. We show
how this model describes the formation of a sand pile from a homogeneous
distribution of material under gravity, and then discuss a simulation of a
rotating sandpile which shows, in qualitative agreement with experiment, a
static and dynamic angle of repose.Comment: 17 pages, 14 figures, RevTeX4; minor changes to wording and some
additional discussion. Accepted by Phys. Rev.
Clustering transitions in vibro-fluidized magnetized granular materials
We study the effects of long range interactions on the phases observed in
cohesive granular materials. At high vibration amplitudes, a gas of magnetized
particles is observed with velocity distributions similar to non-magnetized
particles. Below a transition temperature compact clusters are observed to form
and coexist with single particles. The cluster growth rate is consistent with a
classical nucleation process. However, the temperature of the particles in the
clusters is significantly lower than the surrounding gas, indicating a
breakdown of equipartition. If the system is quenched to low temperatures, a
meta-stable network of connected chains self-assemble due to the anisotropic
nature of magnetic interactions between particles.Comment: 4 pages, 5 figure
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