715 research outputs found
Evaluating uncertain CO2 abatement over the very long term
Climate change research with the economic methodology of cost–benefit analysis is challenging because of valuation and ethical issues associated with the long delays between CO2 emissions and much of their potential damages, typically of several centuries. The large uncertainties with which climate change impacts are known today and the possibly temporary nature of some envisaged CO2 abatement options exacerbate this challenge. For example, potential leakage of CO2 from geological reservoirs, after this greenhouse gas has been stored artificially underground for climate control reasons, requires an analysis in which the uncertain climatic consequences of leakage are valued over many centuries. We here present a discussion of some of the relevant questions in this context and provide calculations with the top–down energy-environment-economy model DEMETER. Given the long-term features of the climate change conundrum as well as of technologies that can contribute to its solution, we considered it necessary extending DEMETER to cover a period from today until the year 3000, a time span so far hardly investigated with integrated assessment models of climate change
Exploring the causes of adverse events in hospitals and potential prevention strategies
Objectives
To examine the causes of adverse events
(AEs) and potential prevention strategies to minimise the
occurrence of AEs in hospitalised patients.
Methods
For the 744 AEs identified in the patient record
review study in 21 Dutch hospitals, trained reviewers
were asked to select all causal factors that contributed
to the AE. The results were analysed together with data
on preventability and consequences of AEs. In addition,
the reviewers selected one or more prevention strategies
for each preventable AE. The recommended prevention
strategies were analysed together with four general
causal categories: technical, human, organisational and
patient-related factors.
Results
Human causes were predominantly involved in
the causation of AEs (in 61% of the AEs), 61% of those
being preventable and 13% leading to permanent
disability. In 39% of the AEs, patient-related factors were
involved, in 14% organisational factors and in 4%
technical factors. Organisational causes contributed
relatively often to preventable AEs (93%) and AEs
resulting in permanent disability (20%). Recommended
strategies to prevent AEs were quality assurance/peer
review, evaluation of safety behaviour, training and
procedures. For the AEs with human and patient-related
causes, reviewers predominantly recommended quality
assurance/peer review. AEs caused by organisational
factors were considered preventable by improving
procedures.
Discussion
Healthcare interventions directed at human
causes are recommended because these play a large
role in AE causation. In addition, it seems worthwhile to
direct interventions on organisational causes because the
AEs they cause are nearly always believed to be
preventable. Organisational factors are thus relatively
easy to tackle. Future research designs should allow
researchers to interview healthcare providers that were
involved in the event, as an additional source of
information on contributing factors.
A Structural and Dynamical Study of Late-Type, Edge-On Galaxies: I. Sample Selection and Imaging Data
We present optical (B & R) and infrared (K_s) images and photometry for a
sample of 49 extremely late-type, edge-on disk galaxies selected from the Flat
Galaxy Catalog of Karenchentsev et al. (1993). Our sample was selected to
include galaxies with particularly large axial ratios, increading the
likelihood that the galaxies in the sample are truly edge-on. We have also
concentrated the sample on galaxies with low apparent surface brightness, in
order to increase the representation of intrinisically low surface brightness
galaxies. Finally, the sample was chosen to have no apprarent bulges or optical
warps so that the galaxies represent undisturbed, ``pure disk'' systems. The
resulting sample forms the basis for a much larger spectroscopic study designed
to place constraints on the physical quantities and processes which shape disk
galaxies. The imaging data presented in this paper has been painstakingly
reduced and calibrated to allow accurate surface photometry of features as
faint as 30 mag/sqr-arcsec in B and 29 mag/sqr-arcsec in R on scales larger
than 10 arcsec. Due to limitations in sky subtraction and flat fielding, the
infrared data can reach only to 22.5 mag/sqr-arcsec in K_s on comparable
scales. As part of this work, we have developed a new method for quantifying
the reliability of surface photometry, which provides useful diagnostics for
the presence of scattered light, optical emission from infrared cirrus, and
other sources of non-uniform sky backgrounds.Comment: scheduled to appear in the Astronomical Journal, LaTeX, 36 pages
including 7 pages of figures (fig 1-2,4). A low resolution version of Figure
3 is included in JPEG format; contours are seriously degraded. A full
resolution Postscript version of Figure 3 (10.6Mb,gzipped) is available
through anonymous ftp at
ftp://ftp.astro.washington.edu/pub/users/jd/FGC/dalcanton.f3.ps.g
Hydrogen storage in depleted offshore gas fields in Brazil:Potential and implications for energy security
This article estimates the potential of using depleted offshore gas fields in Brazil for hydrogen storage and the effects this may have in terms of energy security. Brazil is starting to invest in producing green hydrogen associated with offshore wind energy generation. This initiative has stimulated the search for suitable locations to store hydrogen, including in depleted offshore gas reservoirs. The methodology used in this paper allows for identifying which of the 85 assessed depleted offshore gas fields are the most suitable for hydrogen storage and evaluating the storage capacity of the selected fields. In addition, a wind speed analysis is made to investigate possible locations for prospective wind energy generation projects that can accommodate green hydrogen production. As our main result, we find that the selected depleted offshore gas fields have the potential to store around 5483 TWh worth of hydrogen. This amount is equivalent to about 10 times the total annual electricity consumption in Brazil. Hence, Brazil can comfortably leverage its offshore wind potential in connection with hydrogen production to enhance the energy security of its electricity supply. Considering that to date primarily natural gas has been used as the main source of energy security in Brazil and that its share in the electricity sector has significantly increased over the last decade, the combination of hydrogen storage and renewable energy such as offshore wind power has the potential to provide a resilient and decarbonised electricity system in the country. Furthermore, hydrogen stored in offshore reservoirs in Brazil can become an important resource in the international energy market and constitute a possible key to energy security for countries to which Brazil may export hydrogen. We end our paper by providing comments on the challenges, opportunities, and prospects of offshore hydrogen storage in Brazil
Comparing Galaxies and Lyman Alpha Absorbers at Low Redshift
A scenario is explored in which Lyman alpha absorbers at low redshift arise
from lines of sight through extended galaxy disks, including those of dwarf and
low surface brightness galaxies. A population of galaxies is simulated based
upon observed distributions of galaxy properties, and the gas disks are modeled
using pressure and gravity confinement. Some parameter values are ruled out by
comparing simulation results with the observed galaxy luminosity function, and
constraints may be made on the absorbing cross sections of galaxies. Simulation
results indicate that it is difficult to match absorbers with particular
galaxies observationally since absorption typically occurs at high impact
parameters (>200 kpc) from luminous galaxies. Low impact parameter absorption
is dominated by low luminosity dwarfs. A large fraction of absorption lines is
found to originate from low surface brightness galaxies, so that the absorbing
galaxy is likely to be misidentified. Low redshift Lyman alpha absorber counts
can easily be explained by moderately extended galaxy disks when low surface
brightness galaxies are included, and it is easily possible to find a scenario
which is consistent with observed the galaxy luminosity function, with low
redshift Lyman limit absorber counts, and with standard nucleosynthesis
predictions of the baryon density, Omega_Baryon.Comment: 17 pages, 8 figures, accepted to the Astrophysical Journa
Pathways to Mexico’s climate change mitigation targets: a multi-model analysis
AbstractMexico’s climate policy sets ambitious national greenhouse gas (GHG) emission reduction targets—30% versus a business-as-usual baseline by 2020, 50% versus 2000 by 2050. However, these goals are at odds with recent energy and emission trends in the country. Both energy use and GHG emissions in Mexico have grown substantially over the last two decades. We investigate how Mexico might reverse current trends and reach its mitigation targets by exploring results from energy system and economic models involved in the CLIMACAP-LAMP project. To meet Mexico’s emission reduction targets, all modeling groups agree that decarbonization of electricity is needed, along with changes in the transport sector, either to more efficient vehicles or a combination of more efficient vehicles and lower carbon fuels. These measures reduce GHG emissions as well as emissions of other air pollutants. The models find different energy supply pathways, with some solutions based on renewable energy and others relying on biomass or fossil fuels with carbon capture and storage. The economy-wide costs of deep mitigation could range from 2% to 4% of GDP in 2030, and from 7% to 15% of GDP in 2050. Our results suggest that Mexico has some flexibility in designing deep mitigation strategies, and that technological options could allow Mexico to achieve its emission reduction targets, albeit at a cost to the country
A Nuclear Solution to Climate Change?
The U.N. Framework Convention on Climate Change calls for the stabilization of greenhouse gas concentrations at a level that would prevent dangerous changes in climate. An ambitious target would be stabilization at an equivalent doubling of the preindustrial CO2 concentration. To achieve this, fossil-fuel carbon emissions in 2050 should not exceed their current level, despite an expected doubling or tripling in world demand for energy.
Lacking a crystal ball that tells us the future, we simply select one possible scenario that achieves the emissions target. We assume that by 2050, world population and average per-capita energy consumption each rise by 50%, with annual world primary energy consumption reaching 900 EJ (exajoules, 1018 joules). A roughly equal contribution of 300 EJ each is assumed for conventional fossil fuels, for renewable and "decarbonized" fossil fuel sources, and for nuclear fission.
This is a challenging scenario, especially because restraining the increase in average per-capita energy consumption in the face of the economic aspirations of developing countries will require substantial improvements in energy efficiency
ENERGY SECURITY OF CHINA, INDIA, THE E.U. AND THE U.S. UNDER LONG-TERM SCENARIOS: RESULTS FROM SIX IAMs
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