6,602 research outputs found
Ignorance in Congressional Voting? Evidence from Policy Reversal on the Endangered Species Act
Objective: In 1978 Congress weakened several key provisions of the Endangered Species Act (ESA), which had been enacted only five years earlier. The objective is to compare alternative explanations for this policy reversal. Methods: Probit and multinomial logit models are used to explain empirically how senators voted in both 1973 and 1978, and to investigate why many senators switched their vote from supporting ESA to weakening it. Results: The findings here indicate that party affiliation and policymaker preferences were not important to the 1973 vote, but they were key variables in the 1978 votes and the vote-switching decision. Proxies for unexpected economic impacts of ESA on individual states have little explanatory power. Conclusions: Ignorance, as measured here, does not appear to explain this policy reversal. Rather, an influx of relatively conservative Democrats between 1973 and 1978 presents itself as the leading explanation.endangered species act, congressional voting
The Mass-Metallicity Relation for Giant Planets
Exoplanet discoveries of recent years have provided a great deal of new data
for studying the bulk compositions of giant planets. Here we identify 47
transiting giant planets () whose stellar
insolation is low enough (, or roughly ) that they are not affected
by the hot Jupiter radius inflation mechanism(s). We compute a set of new
thermal and structural evolution models and use these models in comparison with
properties of the 47 transiting planets (mass, radius, age) to determine their
heavy element masses. A clear correlation emerges between the planetary heavy
element mass and the total planet mass, approximately of the form . This finding is consistent with the core accretion model of
planet formation. We also study how stellar metallicity [Fe/H] affects
planetary metal-enrichment and find a weaker correlation than has been
previously reported from studies with smaller sample sizes. We confirm a strong
relationship between the planetary metal-enrichment relative to the parent star
and the planetary mass, but see no relation in
with planet orbital properties or stellar mass.
The large heavy element masses of many planets ( ) suggest
significant amounts of heavy elements in H/He envelopes, rather than cores,
such that metal-enriched giant planet atmospheres should be the rule. We also
discuss a model of core-accretion planet formation in a one-dimensional disk
and show that it agrees well with our derived relation between mass and .Comment: Accepted to The Astrophysical Journal. This revision adds a
substantial amount of discussion; the results are the sam
Unveiling E-bike potential for commuting trips from GPS traces
Common goals of sustainable mobility approaches are to reduce the need for travel, to facilitate modal shifts, to decrease trip distances and to improve energy efficiency in the transportation systems. Among these issues, modal shift plays an important role for the adoption of vehicles with fewer or zero emissions. Nowadays, the electric bike (e-bike) is becoming a valid alternative to cars in urban areas. However, to promote modal shift, a better understanding of the mobility behaviour of e-bike users is required. In this paper, we investigate the mobility habits of e-bikers using GPS data collected in Belgium from 2014 to 2015. By analysing more than 10,000 trips, we provide insights about e-bike trip features such as: distance, duration and speed. In addition, we offer a deep look into which routes are preferred by bike owners in terms of their physical characteristics and how weather influences e-bike usage. Results show that trips with higher travel distances are performed during working days and are correlated with higher average speeds. Usage patterns extracted from our data set also indicate that e-bikes are preferred for commuting (home-work) and business (work related) trips rather than for recreational trips
The Role of Stellar Feedback in the Dynamics of HII Regions
Stellar feedback is often cited as the biggest uncertainty in galaxy
formation models today. This uncertainty stems from a dearth of observational
constraints as well as the great dynamic range between the small scales (<1 pc)
where the feedback occurs and the large scales of galaxies (>1 kpc) that are
shaped by this feedback. To bridge this divide, in this paper we aim to assess
observationally the role of stellar feedback at the intermediate scales of HII
regions. In particular, we employ multiwavelength data to examine several
stellar feedback mechanisms in a sample of 32 HII regions in the Large and
Small Magellanic Clouds (LMC and SMC, respectively). Using optical, infrared,
radio, and X-ray images, we measure the pressures exerted on the shells from
the direct stellar radiation, the dust-processed radiation, the warm ionized
gas, and the hot X-ray emitting gas. We find that the warm ionized gas
dominates over the other terms in all of the sources, although two have
comparable dust-processed radiation pressures to their warm gas pressures. The
hot gas pressures are comparatively weak, while the direct radiation pressures
are 1-2 orders of magnitude below the other terms. We discuss the implications
of these results, particularly highlighting evidence for hot gas leakage from
the HII shells and regarding the momentum deposition from the dust-processed
radiation to the warm gas. Furthermore, we emphasize that similar observational
work should be done on very young HII regions to test whether direct radiation
pressure and hot gas can drive the dynamics at early times.Comment: 19 pages, 8 figures; accepted by Ap
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The binding site distance test score: a robust method for the assessment of predicted protein binding sites
We propose a novel method for scoring the accuracy of
protein binding site predictions – the Binding-site Distance Test
(BDT) score. Recently, the Matthews Correlation Coefficient (MCC)
has been used to evaluate binding site predictions, both by developers
of new methods and by the assessors for the community wide
prediction experiment – CASP8. Whilst being a rigorous scoring
method, the MCC does not take into account the actual 3D location
of the predicted residues from the observed binding site. Thus, an
incorrectly predicted site that is nevertheless close to the observed
binding site will obtain an identical score to the same number of nonbinding
residues predicted at random. The MCC is somewhat affected
by the subjectivity of determining observed binding residues
and the ambiguity of choosing distance cutoffs. By contrast the BDT
method produces continuous scores ranging between 0 and 1, relating
to the distance between the predicted and observed residues.
Residues predicted close to the binding site will score higher than
those more distant, providing a better reflection of the true accuracy
of predictions. The CASP8 function predictions were evaluated using
both the MCC and BDT methods and the scores were compared.
The BDT was found to strongly correlate with the MCC
scores whilst also being less susceptible to the subjectivity of defining
binding residues. We therefore suggest that this new simple
score is a potentially more robust method for future evaluations of
protein-ligand binding site predictions
Removal of Hot Saturns in Mass-Radius Plane by Runaway Mass Loss
The hot Saturn population exhibits a boundary in mass-radius space, such that
no planets are observed at a density less than 0.1 g cm. Yet,
planet interior structure models can readily construct such objects as the
natural result of radius inflation. Here, we investigate the role XUV-driven
mass-loss plays in sculpting the density boundary by constructing interior
structure models that include radius inflation, photoevaporative mass loss and
a simple prescription of Roche lobe overflow. We demonstrate that planets
puffier than 0.1 g cm experience a runaway mass loss caused by
adiabatic radius expansion as the gas layer is stripped away, providing a good
explanation of the observed edge in mass-radius space. The process is also
visible in the radius-period and mass-period spaces, though smaller,
high-bulk-metallicity planets can still survive at short periods, preserving a
partial record of the population distribution at formation.Comment: 10 pages, 5 figures, submitted to ApJ Letter
Sobrecargas en crecimiento de grietas por fatiga biaxial
El presente trabajo se centra en el estudio de grietas de fatiga bajo cargas biaxiales. Se presenta una nueva metodología
para evaluar el efecto de las sobrecargas basada en la evaluación experimental del factor de intensidad de tensiones
efectivo y de la apertura de la grieta (Crack Opening Displacement, COD). El estudio se ha realizado en probetas
cilíndricas de acero de bajo contenido en carbono sometidas a cargas de tracción y torsión. Los datos experimentales se
han obtenido mediante la técnica de correlación de imágenes digitales. Se ha comparado la evolución de la grieta con y
sin sobrecarga. Además, se ha utilizado un procedimiento de detección de carga de apertura. Dicho procedimiento se
había desarrollado previamente en fatiga uniaxial para el caso biaxial. Dicho procedimiento permite poner de manifiesto
el cambio originado por un ciclo de sobrecarga.Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tech
Heathlands, fire and grazing. A paleoenvironmental view of las Hurdes (Caceres, Spain) history during the last 1200 years
Objetivo del estudio: Se hace un estudio diacrónico del cambio de vegetación a través del análisis palinológico de depósitos sedimentarios. Ésta es una herramienta esencial tanto para diseñar estrategias de sonido en la gestión del paisaje como para comprender su carácter dinámico y antropogénico.
Área de estudio: La Meseguera (Ladrillar, Cáceres, España) está situada en la región de Hurdes, en la parte occidental de Sistema Ibérico y comenzó a desarrollarse a principios del período islámico (aproximadamente 770 d C), en una zona ampliamente
dominado por el breza.
Material y métodos: Polen, palinomorfos no polínicos y la tasa de acumulación de carbón (CHAR) combinada con los datos históricos son indicadores útiles para evaluar el papel creciente de la influencia humana sobre la vegetación.
Principales resultados: El uso del fuego y la ganadería representa los principales impulsores del cambio del paisaje en el curso de la historia. El establecimiento de planes de reforestación en bosques, a partir de mediados del siglo XX, cambió sustancialmente en las características regionales. La presencia esporádica de pólenes de haya es detectada hasta el siglo XVI, lo que implica su presencia más occidental en el Sistema Ibérico Central.
Aspectos destacados de la investigación: La integración del análisis del polen y los datos históricos es una herramienta esencial a los cambios en la vegetación del Holoceno. Estos cambios se han debido principalmente a perturbaciones antropogénicas, específicamente al fuego y a la ganadería.Aim of study: The diachronic study of vegetation change through palynological analysis of sedimentary deposits is an essential tool both to design sound strategies on landscape management and to understand its anthropogenic dynamics.
Area of study: La Meseguera mire (Ladrillar, Cáceres, Spain) is located in the Hurdes region in the western part of Iberian Central System and started to develop at the beginning of the Islamic period (ca. 770 cal AD), in an area widely dominated by heathland.
Material and methods: Pollen, non-pollen palynomorphs and charcoal accumulation rate (CHAR) combined with historical data are useful indicators to assess the increasing role of human influence on vegetation.
Main results: The use of fire and livestock husbandry represents the main drivers of landscape change in the course of the history. The establishment of forest afforestation plans, from the middle of 20th century, changed substantially the regional features. The sporadic presence of beech pollen is detected until 16th century, which implies the most
western location in the Iberian Central Mountain System.
Research highlights: The integration of pollen analysis and historical data is an essential tool when studying the changes in Holocene vegetation. These changes have been mainly driven by anthropogenic disturbances, more specifically by fire and livestock husbandry.peerReviewe
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