2,488 research outputs found
Reviving botany in the curriculum: The botanical journey of two Western Australian early childhood teachers
Environmental education across the early years has become increasingly important in Australia since the implementation of the Early Years Learning Framework and the Australian Curriculum. These documents promote a connection to nature for young children as well as environmental responsibility. In Western Australia, large areas of natural environments are bush spaces, accessible by young children, families and schools. There is no existing research investigating early childhood teacher’s knowledge of plants in these bush spaces and the utilisation of these spaces in teaching botany as part of their teaching practice. The discussion in this article examines part of a larger year-long multi-site case study of the changes in the botanical understanding of two early childhood teachers of children aged 5–8 years, in Western Australian schools both before and after the Mosaic Approach, botanical practices and Indigenous knowledges were incorporated into their teaching practice. This article focuses on the changes of botanical literacies of the early childhood teachers specifically. The findings suggest that using inquiry-based and place-based methods and including First Nations Peoples’ perspectives about plants whilst teaching in the bush can significantly increase the plant knowledge and understanding of teachers, as well their own scientific and botanical literacies
A Barren Landscape?
We consider the generation of a non-perturbative superpotential in F-theory
compactifications with flux. We derive a necessary condition for the generation
of such a superpotential in F-theory. For models with a single volume modulus,
we show that the volume modulus is never stabilized by either abelian
instantons or gaugino condensation. We then comment on how our analysis extends
to a larger class of compactifications. From our results, it appears that among
large volume string compactifications, metastable de Sitter vacua (should any
exist) are non-generic.Comment: 14 pages, comments adde
Quantum Invariants, Modular Forms, and Lattice Points II
We study the SU(2) Witten--Reshetikhin--Turaev invariant for the Seifert
fibered homology spheres with M-exceptional fibers. We show that the WRT
invariant can be written in terms of (differential of) the Eichler integrals of
modular forms with weight 1/2 and 3/2. By use of nearly modular property of the
Eichler integrals we shall obtain asymptotic expansions of the WRT invariant in
the large-N limit. We further reveal that the number of the gauge equivalent
classes of flat connections, which dominate the asymptotics of the WRT
invariant in N ->\infinity, is related to the number of integral lattice points
inside the M-dimensional tetrahedron
Characterizing Operations Preserving Separability Measures via Linear Preserver Problems
We use classical results from the theory of linear preserver problems to
characterize operators that send the set of pure states with Schmidt rank no
greater than k back into itself, extending known results characterizing
operators that send separable pure states to separable pure states. We also
provide a new proof of an analogous statement in the multipartite setting. We
use these results to develop a bipartite version of a classical result about
the structure of maps that preserve rank-1 operators and then characterize the
isometries for two families of norms that have recently been studied in quantum
information theory. We see in particular that for k at least 2 the operator
norms induced by states with Schmidt rank k are invariant only under local
unitaries, the swap operator and the transpose map. However, in the k = 1 case
there is an additional isometry: the partial transpose map.Comment: 16 pages, typos corrected, references added, proof of Theorem 4.3
simplified and clarifie
Type IIB Flux Vacua from M-theory via F-theory
We study in detail some aspects of duality between type IIB and M-theory. We
focus on the duality between type IIB string theory on K3 x T^2/Z_2 orientifold
and M-theory on K3 x K3, in the F-theory limit. We give the explicit map
between the fields and in particular between the moduli of compactification,
studying their behavior under the F-theory limit. Turning on fluxes generates a
potential for the moduli both in type IIB and in M-theory. We verify that the
type IIB analysis gives the same results of the F-theory analysis. In
particular, we check that the two potentials match.Comment: 24 pages; reference correcte
A 2dF spectroscopic study of globular clusters in NGC 5128: Probing the formation history of the nearest giant Elliptical
We have performed a spectroscopic study of globular clusters (GCs) in the
giant elliptical NGC 5128 using the 2dF facility at the Anglo-Australian
telescope. We obtained integrated optical spectra for a total of 254 GCs, 79 of
which are newly confirmed on the basis of their radial velocities and spectra.
In addition, we obtained an integrated spectrum of the galaxy starlight along
the southern major axis. We derive an empirical metallicity distribution
function (MDF) for 207 GCs (~14 of the estimated total GC system) based upon
Milky Way GCs. This MDF is multimodal at high statistical significance with
peaks at [Z/H]~-1.3 and -0.5. A comparison between the GC MDF and that of the
stellar halo at 20 kpc (~4 Reff) reveals close coincidence at the metal-rich
ends of the distributions. However, an inner 8 kpc stellar MDF shows a clear
excess of metal-rich stars when compared to the GCs. We compare a higher S/N
subsample (147 GCs) with two stellar population models which include non-solar
abundance ratio corrections. The vast majority of our sample (~90%) appears
old, with ages similar to the Milky Way GC system. There is evidence for a
population of intermediate-age (~4-8 Gy) GCs (<15% of the sample) which are on
average more metal-rich than the old GCs. We also identify at least one younger
cluster (~1-2 Gy) in the central regions of the galaxy. Our observations are
consistent with a picture where NGC 5128 has undergone at least two mergers
and/or interactions involving star formation and limited GC formation since
z=1, however the effect of non-canonical hot stellar populations on the
integrated spectra of GCs remains an outstanding uncertainty in our GC age
estimates.Comment: 17 figures, some long table
The Sensitivity of Harassment to Orbit: Mass Loss from Early-Type Dwarfs in Galaxy Clusters
We conduct a comprehensive numerical study of the orbital dependence of
harassment on early-type dwarfs consisting of 168 different orbits within a
realistic, Virgo-like cluster, varying in eccentricity and pericentre distance.
We find harassment is only effective at stripping stars or truncating their
stellar disks for orbits that enter deep into the cluster core. Comparing to
the orbital distribution in cosmological simulations, we find that the majority
of the orbits (more than three quarters) result in no stellar mass loss. We
also study the effects on the radial profiles of the globular cluster systems
of early-type dwarfs. We find these are significantly altered only if
harassment is very strong. This suggests that perhaps most early-type dwarfs in
clusters such as Virgo have not suffered any tidal stripping of stars or
globular clusters due to harassment, as these components are safely embedded
deep within their dark matter halo. We demonstrate that this result is actually
consistent with an earlier study of harassment of dwarf galaxies, despite the
apparent contradiction. Those few dwarf models that do suffer stellar stripping
are found out to the virial radius of the cluster at redshift=0, which mixes
them in with less strongly harassed galaxies. However when placed on
phase-space diagrams, strongly harassed galaxies are found offset to lower
velocities compared to weakly harassed galaxies. This remains true in a
cosmological simulation, even when halos have a wide range of masses and
concentrations. Thus phase-space diagrams may be a useful tool for determining
the relative likelihood that galaxies have been strongly or weakly harassed.Comment: 17 pages, 13 figures, Accepted to MNRAS 8th September 201
The Kinematics and Dynamics of the Globular Clusters and the Planetary Nebulae of NGC 5128
A new kinematic and dynamic study of the halo of the giant elliptical galaxy,
NGC 5128, is presented. From a spectroscopically confirmed sample of 340
globular clusters and 780 planetary nebulae, the rotation amplitude, rotation
axis, velocity dispersion, and the total dynamical mass are determined for the
halo of NGC 5128. The globular cluster kinematics were searched for both radial
dependence and metallicity dependence by subdividing the globular cluster
sample into 158 metal-rich ([Fe/H] > -1.0) and 178 metal-poor ([Fe/H] < -1.0)
globular clusters. Our results show the kinematics of the metal-rich and
metal-poor subpopulations are quite similar. The kinematics are compared to the
planetary nebula population where differences are apparent in the outer regions
of the halo. The total mass of NGC 5128 is found using the Tracer Mass
estimator (Evans et al. 2003), to determine the mass supported by internal
random motions, and the spherical component of the Jeans equation to determine
the mass supported by rotation. We find a total mass of (1.0+/-0.2) x 10^(12)
Msun from the planetary nebulae data out to a projected radius of 90 kpc and
(1.3+/-0.5) x 10^(12) Msun from the globular clusters out to a projected radius
of 50 kpc. Lastly, we present a new and homogeneous catalog of known globular
clusters in NGC 5128. This catalog combines all previous definitive cluster
identifications from radial velocity studies and HST imaging studies, as well
as 80 new globular clusters from a study of M.A. Beasley et al. (2007, in
preparation).Comment: Accepted in the Astronomical Journal,52 pages, 13 figures, 6 tables -
Changes made to Table 1 from originally submitted 0704.118
Liberating microfossils from indurated carbonates: comparison of three disaggregation methods
This is the final version. Available on open access from Copernicus Publications via the DOI in this recordThree disaggregation methods (Calgon, acetic acid, and electric pulse fragmentation [EPF]) have
been applied to a range of heavily lithified, carbonate-rich sedimentary rock samples of Paleogene age. Samples
are predominantly from the carbonate-rich, shallow water domain (<250 m palaeo-water depth) of Tanzania,
Malta and the United Arab Emirates (Paleogene Tethys Ocean). The effectiveness and efficiency of each
method has been compared, as well as the preservation of the resultant liberated microfossil material (primarily
larger foraminifera; LF). Of the three methods, the most efficient and effective was EPF, which liberated the
largest number of LF in a very short processing time and resulted in the best preservation. Samples with calcitic,
silicic, and clay matrices and cements were successfully disaggregated using EPF. In this study, recovered
microfossils were largely >500 µm suggesting this technique may be more appropriate for liberating larger
microfossils (e.g., LFs), however, we discuss nuances to the method which would allow for more effective
recovery of smaller microfossil specimens. The more traditional acetic acid method was also able to
disaggregate a number of the samples, however, preservation of the LF was compromised. We suggest a best
practice methodology for implementing EPF in micropalaeontological studies.Natural Environment Research Council (NERC
The sensitivity of harassment to orbit: Mass loss from early-type dwarfs in galaxy clusters
We conduct a comprehensive numerical study of the orbital dependence of harassment on early-type dwarfs consisting of 168 different orbits within a realistic, Virgo-like cluster, varying in eccentricity and pericentre distance. We find harassment is only effective at stripping stars or truncating their stellar discs for orbits that enter deep into the cluster core. Comparing to the orbital distribution in cosmological simulations, we find that the majority of the orbits (more than three quarters) result in no stellar mass loss. We also study the effects on the radial profiles of the globular cluster systems of early-type dwarfs. We find these are significantly altered only if harassment is very strong. This suggests that perhaps most early-type dwarfs in clusters such as Virgo have not suffered any tidal stripping of stars or globular clusters due to harassment, as these components are safely embedded deep within their dark matter halo. We demonstrate that this result is actually consistent with an earlier study of harassment of dwarf galaxies, despite the apparent contradiction. Those few dwarf models that do suffer stellar stripping are found out to the virial radius of the cluster at redshift = 0, which mixes them in with less strongly harassed galaxies. However when placed on phase-space diagrams, strongly harassed galaxies are found offset to lower velocities compared to weakly harassed galaxies. This remains true in a cosmological simulation, even when haloes have a wide range of masses and concentrations. Thus phase-space diagrams may be a useful tool for determining the relative likelihood that galaxies have been strongly or weakly harassed
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