868 research outputs found
New South Wales Vegetation Classification and Assessment : part 1, plant communities of the NSW Western Plains
For the Western Plains of New South Wales, 213 plant communities are classified and described and their protected area and threat status assessed. The communities are listed on the NSW Vegetation Classification and Assessment database (NSWVCA). The full description of the communities is placed on an accompanying CD together with a read-only version of the NSWVCA database.
The NSW Western Plains is 45.5 million hectares in size and covers 57% of NSW. The vegetation descriptions are based on over 250 published and unpublished vegetation surveys and maps produced over the last 50 years (listed in a bibliography), rapid field checks and the expert knowledge on the vegetation. The 213 communities occur over eight Australian bioregions and eight NSW Catchment Management Authority areas. As of December 2005, 3.7% of the Western Plains was protected in 83 protected areas comprising 62 public conservation reserves and 21 secure property agreements. Only one of the eight bioregions has greater than 10% of its area represented in protected areas. 31 or 15% of the communities are not recorded from protected areas. 136 or 64% have less than 5% of their pre-European extent in protected areas. Only 52 or 24% of the communities have greater than 10% of their original extent protected, thus meeting international guidelines for representation in protected areas. 71 or 33% of the plant communities are threatened, that is, judged as being âcritically endangeredâ, âendangeredâ or âvulnerableâ.
While 80 communities are recorded as being of âleast concernâ most of these are degraded by lack of regeneration of key species due to grazing pressure and loss of top soil and some may be reassessed as being threatened in the future. Threatening processes include vegetation clearing on higher nutrient soils in wetter regions, altered hydrological regimes due to draw-off of water from river systems and aquifers, high continuous grazing pressure by domestic stock, feral goats and rabbits, and in some places native herbivores â preventing regeneration of key plant species, exotic weed invasion along rivers and in fragmented vegetation, increased salinity, and over the long term, climate change.
To address these threats, more public reserves and secure property agreements are required, vegetation clearing should cease, re-vegetation is required to increase habitat corridors and improve the condition of native vegetation, environmental flows to regulated river systems are required to protect inland wetlands, over-grazing by domestic stock should be avoided and goat and rabbit numbers should be controlled and reduced. Conservation action should concentrate on protecting plant communities that are threatened or are poorly represented in protected areas
RELATIONSHIP ANALYSIS OF IMAGE DESCRIPTIONS: AN ONTOLOGICAL, CONTENT ANALYTIC APPROACH
The relationships humans express when describing images have powerful, but poorly understood, effects on how visual information is represented, structured, and processed in information systems. This study evaluates the benefits and difficulties of using content analysis and ontological analysis as predictors of relationship instances and types occurring in image descriptions. A random sample of 36 documented reference transactions from the administrative files of the Pittsburgh Photographic Library is analyzed in light of three describing contexts: image searcher, curator, and cataloger. Through the qualitative and quantitative assessment of image descriptions, the research leads to several key findings and contributions. The most important findings vindicate the claim that recognition, capture, and classification of relationship instances can be empirically grounded utilizing content analysis and ontological tools and methods. Evidence comes in successfully ascertaining and capturing in a Corpus the existence of 1,655 relationship instances. Further, the analysis finds evidence of relationship types and subtypes of relationships whose members share certain recognizable properties in common. The study also brings useful, new insights to the capture of background information surrounding events using situation-templates, introduces methods for formulating case relations and image attributes as binary predicates, and it offers a new, finer-grained definition of relationship. Contributions of this study include a corpus of relationship instances, an ontology of relationship types, and a methodological framework that provides significantly better results than earlier studies in the prediction of relationships (the architecture of which is depicted in Figure 22 on page 102). There are a number of ways this research could be extended and corroborated. First, event analysis ought to be tied to a system of semantic frame analysis. Second, test the content analysis form against other texts, which will result in elaboration of the core ontology of relationship types. Third, expand image description analysis beyond the current domain to include image description in visual ethnography, art history and criticism, and photography practices. Fourth, test how inference engines reason over relationships in knowledge-based environments. Finally, to aid in the analysis of the meanings of relationships, more work is needed in formalizing the ontological concepts used in image descriptions
Ionized nebulae surrounding brightest cluster galaxies
We present IFU observations of six emission-line nebulae that surround the
central galaxy of cool core clusters. Qualitatively similar nebulae are
observed in cool core clusters even when the dynamics and possibly formation
and excitation source are different. Evidence for a nearby secondary galaxy
disturbing a nebula, as well as AGN and starburst driven outflows are presented
as possible formation mechanisms. One nebula has a rotation velocity of the
same amplitude as the underlying molecular reservoir, which implies that the
excitation or formation of a nebula does not require any disturbance of the
molecular reservoir within the central galaxy. Bulk flows and velocity shears
of a few hundred km/s are seen across all nebulae. The majority lack any
ordered rotation, their configurations are not stable so the nebulae must be
constantly reshaping, dispersing and reforming. The dimmer nebulae are
co-spatial with dust features whilst the more luminous are not. Significant
variation in the ionization state of the gas is seen in all nebulae through the
non-uniform [NII]/H_alpha ratio. There is no correlation between the line ratio
and H_alpha surface brightness, but regions with excess blue or UV light have
lower line ratios. This implies that UV from massive, young stars act in
combination with an underlying heating source that produces the observed
low-ionization spectra.Comment: 12 pages, accepted for publication in MNRA
Seeing the way: visual sociology and the distance runner's perspective
Employing visual and autoethnographic data from a twoâyear research project on distance runners, this article seeks to examine the activity of seeing in relation to the activity of distance running. One of its methodological aims is to develop the linkage between visual and autoethnographic data in combining an observationâbased narrative and sociological analysis with photographs. This combination aims to convey to the reader not only some of the specific subcultural knowledge and particular ways of seeing, but also something of the runner's embodied feelings and experience of momentum en route. Via the combination of narrative and photographs we seek a more effective way of communicating just how distance runners see and experience their training terrain. The importance of subjecting mundane everyday practices to detailed sociological analysis has been highlighted by many sociologists, including those of an ethnomethodological perspective. Indeed, without the competence of social actors in accomplishing these mundane, routine understandings and practices, it is argued, there would in fact be no social order
Mass transport by buoyant bubbles in galaxy clusters
We investigate the effect of three important processes by which AGN-blown
bubbles transport material: drift, wake transport and entrainment. The first of
these, drift, occurs because a buoyant bubble pushes aside the adjacent
material, giving rise to a net upward displacement of the fluid behind the
bubble. For a spherical bubble, the mass of upwardly displaced material is
roughly equal to half the mass displaced by the bubble, and should be ~
10^{7-9} solar masses depending on the local ICM and bubble parameters. We show
that in classical cool core clusters, the upward displacement by drift may be a
key process in explaining the presence of filaments behind bubbles. A bubble
also carries a parcel of material in a region at its rear, known as the wake.
The mass of the wake is comparable to the drift mass and increases the average
density of the bubble, trapping it closer to the cluster centre and reducing
the amount of heating it can do during its ascent. Moreover, material dropping
out of the wake will also contribute to the trailing filaments. Mass transport
by the bubble wake can effectively prevent the build-up of cool material in the
central galaxy, even if AGN heating does not balance ICM cooling. Finally, we
consider entrainment, the process by which ambient material is incorporated
into the bubble. AbridgedComment: Accepted for publication in MNRAS. 17 pages, 4 figures, 2 tables.
Formatted for letter paper and adjusted author affiliations
Star-Forming Brightest Cluster Galaxies at 0.25 < z < 1.25: A Transitioning Fuel Supply
We present a multi-wavelength study of 90 brightest cluster galaxies (BCGs)
in a sample of galaxy clusters selected via the Sunyaev Zel'dovich effect by
the South Pole Telescope, utilizing data from various ground- and space-based
facilities. We infer the star formation rate (SFR) for the BCG in each cluster,
based on the UV and IR continuum luminosity, as well as the [O II] emission
line luminosity in cases where spectroscopy is available, finding 7 systems
with SFR > 100 Msun/yr. We find that the BCG SFR exceeds 10 Msun/yr in 31 of 90
(34%) cases at 0.25 < z < 1.25, compared to ~1-5% at z ~ 0 from the literature.
At z > 1, this fraction increases to 92(+6)(-31)%, implying a steady decrease
in the BCG SFR over the past ~9 Gyr. At low-z, we find that the specific star
formation rate in BCGs is declining more slowly with time than for field or
cluster galaxies, most likely due to the replenishing fuel from the cooling ICM
in relaxed, cool core clusters. At z > 0.6, the correlation between cluster
central entropy and BCG star formation - which is well established at z ~ 0 -
is not present. Instead, we find that the most star-forming BCGs at high-z are
found in the cores of dynamically unrelaxed clusters. We investigate the
rest-frame near-UV morphology of a subsample of the most star-forming BCGs
using data from the Hubble Space Telescope, finding complex, highly asymmetric
UV morphologies on scales as large as ~50-60 kpc. The high fraction of
star-forming BCGs hosted in unrelaxed, non-cool core clusters at early times
suggests that the dominant mode of fueling star formation in BCGs may have
recently transitioned from galaxy-galaxy interactions to ICM cooling.Comment: 20 pages, 10 figures. Submitted for publication in ApJ. Comments
welcom
Regime shifts and panarchies in regional scale social-ecological water systems
In this article we summarize histories of nonlinear, complex interactions among societal, legal, and ecosystem dynamics in six North American water basins, as they respond to changing climate. These case studies were chosen to explore the conditions for emergence of adaptive governance in heavily regulated and developed social-ecological systems nested within a hierarchical governmental system. We summarize resilience assessments conducted in each system to provide a synthesis and reference by the other articles in this special feature. We also present a general framework used to evaluate the interactions between society and ecosystem regimes and the governance regimes chosen to mediate those interactions. The case studies show different ways that adaptive governance may be triggered, facilitated, or constrained by ecological and/or legal processes. The resilience assessments indicate that complex interactions among the governance and ecosystem components of these systems can produce different trajectories, which include patterns of (a) development and stabilization, (b) cycles of crisis and recovery, which includes lurches in adaptation and learning, and (3) periods of innovation, novelty, and transformation. Exploration of cross scale (Panarchy) interactions among levels and sectors of government and society illustrate that they may constrain development trajectories, but may also provide stability during crisis or innovation at smaller scales; create crises, but may also facilitate recovery; and constrain system transformation, but may also provide windows of opportunity in which transformation, and the resources to accomplish it, may occur. The framework is the starting point for our exploration of how law might play a role in enhancing the capacity of social-ecological systems to adapt to climate change
Cosmological Galaxy Formation Simulations Using SPH
We present the McMaster Unbiased Galaxy Simulations (MUGS), the first 9
galaxies of an unbiased selection ranging in total mass from 5
M to 2 M simulated using n-body smoothed
particle hydrodynamics (SPH) at high resolution. The simulations include a
treatment of low temperature metal cooling, UV background radiation, star
formation, and physically motivated stellar feedback. Mock images of the
simulations show that the simulations lie within the observed range of
relations such as that between color and magnitude and that between brightness
and circular velocity (Tully-Fisher). The greatest discrepancy between the
simulated galaxies and observed galaxies is the high concentration of material
at the center of the galaxies as represented by the centrally peaked rotation
curves and the high bulge-to-total ratios of the simulations determined both
kinematically and photometrically. This central concentration represents the
excess of low angular momentum material that long has plagued morphological
studies of simulated galaxies and suggests that higher resolutions and a more
accurate description of feedback will be required to simulate more realistic
galaxies. Even with the excess central mass concentrations, the simulations
suggest the important role merger history and halo spin play in the formation
of disks.Comment: 16 pages, 16 figures, submitted to MNRAS, movies available at
http://mugs.mcmaster.ca . Comments welcome
Astrophysically Motivated Bulge-Disk Decompositions of SDSS Galaxies
We present a set of bulge-disk decompositions for a sample of 71,825 SDSS
main-sample galaxies in the redshift range 0.003<z<0.05. We have fit each
galaxy with either a de Vaucouleurs ('classical') or an exponential ('pseudo-')
bulge and an exponential disk. Two dimensional Sersic fits are performed when
the 2-component fits are not statistically significant or when the fits are
poor, even in the presence of high signal-to-noise. We study the robustness of
our 2-component fits by studying a bright subsample of galaxies and we study
the systematics of these fits with decreasing resolution and S/N. Only 30% of
our sample have been fit with two-component fits in which both components are
non-zero. The g-r and g-i colours of each component for the two-component
models are determined using linear templates derived from the r-band model. We
attempt a physical classification of types of fits into disk galaxies,
pseudo-bulges, classical bulges, and ellipticals. Our classification of
galaxies agrees well with previous large B+D decomposed samples. Using our
galaxy classifications, we find that Petrosian concentration is a good
indicator of B/T, while overall Sersic index is not. Additionally, we find that
the majority of green valley galaxies are bulge+disk galaxies. Furthermore, in
the transition from green to red B+D galaxies, the total galaxy colour is most
strongly correlated with the disk colour.Comment: 28 pages, 34 figures, MNRAS accepte
- âŠ