2,270 research outputs found
Rangeland Rehydration: Collaboration between Land Managers, Government and Private Experts
In the rangelands of New South Wales, Australia, many successful soil erosion control techniques have been developed. These techniques have been implemented by the Western Local Land Services (WLLS), rehabilitating 23,000 ha since 2004. However the focus was on degraded land with little regard to catchment dynamics and the threatening processes that were causing the degradation.
With the introduction of Ecosystem Management Understanding (EMU)âą in 2016, the focus was broadened to address grazing properties in a drainage ecosystem context. There is a focus on understanding landscape function and designing projects that address threatening processes.
With the integration of the WLLS and EMU approaches, effort is now put into saving threatened landscapes and resurrecting degraded landscapes. Both approaches have been integrated to restore soil moisture, reduce grazing impacts, restore calm water and save productive landscapes. In this process, landscape objectives and outcomes are identified and priority projects developed. A major benefit is the increased capacity of land managers to understand landscape processes and then to design and implement projects on their properties. This knowledge is allowing land managers to focus on being rain ready during droughts. The level of ownership has provided a forward looking focus for land managers, building resilience during drought.
Each grazing property will approach the same issue differently, depending on resources and preferences. Some approaches use earthworks while other approaches use soft filters to improve rainfall management. Earthwork techniques include champagne banks, waterponding, waterspreading, contour furrows and erosion control structures across roads. Soft filters are placed in flow lines to slow water and can be constructed from mesh, branches or rocks.
We tell this story through examples of projects and demonstrate the success of a collaborative approach to landscape rehydration
The Chromospheric Activity and Ages of M Dwarf Stars in Wide Binary Systems
We investigate the relationship between age and chromospheric activity for
139 M dwarf stars in wide binary systems with white dwarf companions. The age
of each system is determined from the cooling age of its white dwarf component.
The current limit for activity-age relations found for M dwarfs in open
clusters is 4 Gyr. Our unique approach to finding ages for M stars allows for
the exploration of this relationship at ages older than 4 Gyr. The general
trend of stars remaining active for a longer time at later spectral type is
confirmed. However, our larger sample and greater age range reveals additional
complexity in assigning age based on activity alone. We find that M dwarfs in
wide binaries older than 4 Gyr depart from the log-linear relation for clusters
and are found to have activity at magnitudes, colors and masses which are
brighter, bluer and more massive than predicted by the cluster relation. In
addition to our activity-age results, we present the measured radial velocities
and complete space motions for 161 white dwarf stars in wide binaries.Comment: 22 pages including 9 figures and 5 tables. Accepted for publication
in The Astronomical Journa
A Hubble Space Telescope Survey of Extended [OIII]5007A Emission in a Far-Infrared Selected Sample of Seyfert Galaxies: Results
We present the results of a Hubble Space Telescope (HST) survey of extended
[OIII] emission in a sample of 60 nearby Seyfert galaxies (22 Seyfert 1's and
38 Seyfert 2's), selected by mostly isotropic properties. The comparison
between the semi major axis size of their [OIII] emitting regions (R_Maj) shows
that Seyfert 1's and Seyfert 2's have similar distributions, which seems to
contradict Unified Model predictions. We discuss possible ways to explain this
result, which could be due either to observational limitations or the models
used for the comparison with our data. We show that Seyfert 1 Narrow Line
Regions (NLR's) are more circular and concentrated than Seyfert 2's, which can
be attributed to foreshortening in the former. We find a good correlation
between the NLR size and luminosity, following the relation R_Maj propto
L([OIII])^0.33, which is flatter than a previous one found for QSO's and
Seyfert 2's. We discuss possible reasons for the different results, and their
implications to photoionization models. We confirm previous results which show
that the [OIII] and radio emission are well aligned, and also find no
correlation between the orientation of the extended [OIII] emission and the
host galaxy major axis. This agrees with results showing that the torus axis
and radio jet are not aligned with the host galaxy rotation axis, indicating
that the orientation of the gas in the torus, and not the spin of the black
hole, determine the orientation of the accretion disk, and consequently the
orientation of the radio jet.Comment: 17 pages including 12 figures, to appear in Ap
Thermal Properties of Two-Dimensional Advection Dominated Accretion Flow
We study the thermal structure of the widely adopted two-dimensional
advection dominated accretion flow (ADAF) of Narayan & Yi (1995a). The critical
radius for a given mass accretion rate, outside of which the optically thin hot
solutions do not exist in the equatorial plane, agrees with one-dimensional
study. However, we find that, even within the critical radius, there always
exists a conical region of the flow, around the pole, which cannot maintain the
assumed high electron temperature, regardless of the mass accretion rate, in
the absence of radiative heating. This could lead to torus-like advection
inflow shape since, in general, the ions too will cool down. We also find that
Compton preheating is generally important and, if the radiative efficiency,
defined as the luminosity output divided by the mass accretion rate times the
velocity of light squared, is above sim 4x10^-3, the polar region of the flow
is preheated above the virial temperature by Compton heating and it may result
in time-dependent behaviour or outflow while accretion continues in the
equatorial plane. Thus, under most relevant circumstances, ADAF solutions may
be expected to be accompanied by polar outflow winds. While preheating
instabilities exist in ADAF, as for spherical flows, the former are to some
extent protected by their characteristically higher densities and higher
cooling rates, which reduce their susceptibility to Compton driven overheating.Comment: 18 pages including 4 figures. AASTEX. Submitted to Ap
The impact of mining and mining exploration on range resources and pastoral pursuits in the Pilbara, Gascoyne, Murchison and Goldfields regions of Western Australia
Mining activity occurs very widely over relatively small areas of the rangelands. However, it is an intense landuse which can create significant offsite effects. Mining activity is most common around metamorphic \u27greenstone\u27 belts and broad drainages. Pastoralists reported both benefits and adverse affects as a consequence of mining activity. The main grievances related to unnecessary and excessive disturbance of pastoral land and the failure of operators to inform the pastoralist of their intentions
Asymptotic Normalization Coefficients for 13C+p->14N
The proton exchange reaction has been measured
at an incident energy of 162 MeV. Angular distributions were obtained for
proton transfer to the ground and low lying excited states in . Elastic
scattering of on also was measured out to the rainbow angle
region in order to find reliable optical model potentials. Asymptotic
normalization coefficients for the system have been
found for the ground state and the excited states at 2.313, 3.948, 5.106 and
5.834 MeV in . These asymptotic normalization coefficients will be used
in a determination of the S-factor for at solar
energies from a measurement of the proton transfer reaction
.Comment: 5 pages, 6 figure
A deep Chandra observation of the Perseus cluster: shocks and ripples
We present preliminary results from a deep observation lasting almost 200 ks,
of the centre of the Perseus cluster of galaxies around NGC 1275. The X-ray
surface brightness of the intracluster gas beyond the inner 20 kpc, which
contains the inner radio bubbles, is very smooth apart from some low amplitude
quasi-periodic ripples. A clear density jump at a radius of 24 kpc to the NE,
about 10 kpc out from the bubble rim, appears to be due to a weak shock driven
by the northern radio bubble. A similar front may exist round both inner
bubbles but is masked elsewhere by rim emission from bright cooler gas. The
continuous blowing of bubbles by the central radio source, leading to the
propagation of weak shocks and viscously-dissipating sound waves seen as the
observed fronts and ripples, gives a rate of working which balances the
radiative cooling within the inner 50 kpc of the cluster core.Comment: Accepted for publication in MNRAS (minor changes) Higher picture
quality available from http://www-xray.ast.cam.ac.uk/papers/per_200ks.pd
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