7,608 research outputs found
Modelling the impact of the recession on greenhouse gases from agriculture in Ireland
working paperThe effects of the recession of 2009 have been felt across the economy of
Ireland. The rapid contraction in economic activity has had its effect on greenhouse
gas (GHG) emissions as well. It is possible to model the recession’s effect on
agricultural GHG in the FAPRI-Ireland GHG model using the latest international
commodity price projections from Food and Agricultural Policy Research Institute
(FAPRI). The FAPRI-Ireland GHG model creates projections of future levels of Irish
agricultural activity and then uses a mix of national and default emissions factors to
convert this activity to estimates of annual GHG emissions from now to 2020. Our
model is shocked using post-downturn commodity price projections for a selection of
exogenous prices. The changes to these international commodity prices reflect the
international market response to the downturn, and as such they have an impact on the
level of GHG emitted by the agricultural sector in Ireland. This analysis finds that,
despite the depth and breadth of the recession, the impact on GHG emissions from
Irish agriculture has been muted. The impact of the shock is to reduce the projected
annual emissions from the sector by only 0.14 Mt by 2020. This compares to the 2.97
Mt reduction in annual emissions which the sector would have to achieve if, for
example, a reduction target of 20 percent on 2005 levels were to be imposed
Marine Debris Survey Manual
Over the last several years, concern has increased about
the amount of man-made materials lost or discarded at
sea and the potential impacts to the environment. The
scope of the problem depends on the amounts and types
of debris. One problem in making a regional comparison
of debris is the lack of a standard methodology. The
objective of this manual is to discuss designs and methodologies for assessment studies of marine debris.
This manual has been written for managers, researchers,
and others who are just entering this area of study
and who seek guidance in designing marine debris surveys.
Active researchers will be able to use this manual
along with applicable references herein as a source for
design improvement. To this end, the authors have synthesized their work and reviewed survey techniques that
have been used in the past for assessing marine debris,
such as sighting surveys, beach surveys, and trawl surveys,
and have considered new methods (e.g., aerial photography).
All techniques have been put into a general survey
planning framework to assist in developing different marine
debris surveys. (PDF file contains 100 pages.
Student understanding of the Boltzmann factor
We present results of our investigation into student understanding of the
physical significance and utility of the Boltzmann factor in several simple
models. We identify various justifications, both correct and incorrect, that
students use when answering written questions that require application of the
Boltzmann factor. Results from written data as well as teaching interviews
suggest that many students can neither recognize situations in which the
Boltzmann factor is applicable, nor articulate the physical significance of the
Boltzmann factor as an expression for multiplicity, a fundamental quantity of
statistical mechanics. The specific student difficulties seen in the written
data led us to develop a guided-inquiry tutorial activity, centered around the
derivation of the Boltzmann factor, for use in undergraduate statistical
mechanics courses. We report on the development process of our tutorial,
including data from teaching interviews and classroom observations on student
discussions about the Boltzmann factor and its derivation during the tutorial
development process. This additional information informed modifications that
improved students' abilities to complete the tutorial during the allowed class
time without sacrificing the effectiveness as we have measured it. These data
also show an increase in students' appreciation of the origin and significance
of the Boltzmann factor during the student discussions. Our findings provide
evidence that working in groups to better understand the physical origins of
the canonical probability distribution helps students gain a better
understanding of when the Boltzmann factor is applicable and how to use it
appropriately in answering relevant questions
The central elliptical galaxy in fossil groups and formation of BCGs
We study the dominant central giant elliptical galaxies in ``Fossil groups''
using deep optical (R-band) and near infrared (Ks-band) photometry. These
galaxies are as luminous as the brightest cluster galaxies (BCGs), raising
immediate interest in their link to the formation of BCGs and galaxy clusters.
However, despite apparent similarities, the dominant fossil galaxies show
non-boxy isophotes, in contrast to the most luminous BCGs. This study suggests
that the structure of the brightest group galaxies produced in fossil groups
are systematically different to the majority of BCGs. If the fossils do indeed
form from the merger of major galaxies including late-types within a group,
then their disky nature is consistent with the results of recent numerical
simulations of semi-analytical models which suggest that gas rich mergers
result in disky isophote ellipticals.
We show that fossils form a homogeneous population in which the velocity
dispersion of the fossil group is tightly correlated with the luminosity of the
dominant elliptical galaxy. This supports the scenario in which the giant
elliptical galaxies in fossils can grow to the size and luminosity of BCGs in a
group environment. However, the boxy structure of luminous BCGs indicate that
they are either not formed as fossils, or have undergone later gas-free mergers
within the cluster environment.Comment: 5 pages, 4 figures, Accepted for publication in MNRAS letter
Integrated Delivery Networks: In Search of Benefits and Market Effects
Integrated Delivery Networks (IDNs) have very different stated purposes than mere collections of hospitals: to coordinate care across the continuum of health services and to manage population health. IDN advocates claim that these complex enterprises yield both societal benefits and performance advantages over less integrated competitors. The purpose of this analysis is to evaluate the evidence to support these claims.For the study, researchers performed a review of the academic literature on IDN performance, as well as an analysis of publicly available quality and financial data from 15 of the biggest not-for-profit IDNs in the U.S., including Sutter Health in Northern California. The authors compared the publicly available performance information on the IDNs' flagship hospital in its principal regional market with that flagship's most significant in-market competitor. The study found that it is possible for integrated delivery networks to offer meaningful benefits, but there is little evidence they have reduced costs or improved the quality of care. Findings include:Hospital-physician integration has raised physician costs, hospital prices and per capita medical care spending;Hospital integration into health plan operations and capitated contracting was not associated either with clinical efficiency or financial efficiencyProviders are likely to see a decrease in operating margins and return on capital as they invest in IDN developmen
The Volatility Trend of Protosolar and Terrestrial Elemental Abundances
We present new estimates of protosolar elemental abundances based on an
improved combination of solar photospheric abundances and CI chondritic
abundances. These new estimates indicate CI chondrites and solar abundances are
consistent for 60 elements. We compare our new protosolar abundances with our
recent estimates of bulk Earth composition (normalized to aluminium), thereby
quantifying the devolatilization in going from the solar nebula to the
formation of the Earth. The quantification yields a linear trend , where is the Earth-to-Sun abundance ratio and
is the 50 condensation temperature of elements. The best fit
coefficients are: and . The
quantification of these parameters constrains models of devolatilization
processes. For example, the coefficients and determine a
critical devolatilization temperature for the Earth K. The terrestrial abundances of elements with are depleted compared with solar abundances,
whereas the terrestrial abundances of elements with are indistinguishable from solar abundances. The
terrestrial abundance of Hg ( = 252 K) appears anomalously high under the
assumption that solar and CI chondrite Hg abundances are identical. To resolve
this anomaly, we propose that CI chondrites have been depleted in Hg relative
to the Sun by a factor of . We use the best-fit volatility trend to
derive the fractional distribution of carbon and oxygen between volatile and
refractory components (, ). We find (, ) for carbon and (, ) for
oxygen.Comment: Accepted for publication in Icarus. 28 pages, 12 figures, 5 tables.
Compared to v1, the results and conclusion are the same, while discussion of
results and implications is expanded considerabl
Galaxies in Clusters: the Observational Characteristics of Bow-Shocks, Wakes and Tails
The dynamical signatures of the interaction between galaxies in clusters and
the intracluster medium (ICM) can potentially yield significant information
about the structure and dynamical history of clusters. To develop our
understanding of this phenomenon we present results from numerical modelling of
the galaxy/ICM interaction, as the galaxy moves through the cluster. The
simulations have been performed for a broad range, of ICM temperatures (kT =
1,4 and 8 keV), representative of poor clusters or groups through to rich
clusters. There are several dynamical features that can be identified in these
simulations; for supersonic galaxy motion, a leading bow-shock is present, and
also a weak gravitationally focussed wake or tail behind the galaxy (analogous
to Bondi-Hoyle accretion). For galaxies with higher mass-replenishment rates
and a denser interstellar medium (ISM), the dominant feature is a dense
ram-pressure stripped tail. In line with other simulations, we find that the
ICM/galaxy ISM interaction can result in complex time- dependent dynamics, with
ram-pressure stripping occurring in an episodic manner. In order to facilitate
this comparison between the observational consequences of dynamical studies and
X-ray observations we have calculated synthetic X-ray flux and hardness maps
from these simulations. These calculations predict that the ram-pressure
stripped tail will usually be the most visible feature, though in nearby
galaxies the bow-shock preceding the galaxy should also be apparent in deeper
X-ray observations. We briefly discuss these results and compare with X-ray
observations of galaxies where there is evidence of such interactions.Comment: 14 pages, 8 diagrams, MNRAS (in press
Mapping the Physical Properties of Cosmic Hot Gas with Hyper-spectral Imaging
A novel inversion technique is proposed to compute parametric maps showing
the temperature, density and chemical composition of cosmic hot gas from X-ray
hyper-spectral images. The parameters are recovered by constructing a unique
non-linear mapping derived by combining a physics-based modelling of the X-ray
spectrum with the selection of optimal bandpass filters. Preliminary results
and analysis are presented.Comment: 6 pages, 5 figures; accepted by the 5th IEEE Workshop on Application
of Computer Vision (WACV/MOTION 2005), Breckenridge, CO, USA, 2005; uses
ieee.cls (included). For a pdf version with full-resolution figures, try
http://www.cs.bham.ac.uk/~exc/Research/Papers/ieee_astro_05.pd
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