4,775 research outputs found
Essence and Cause: Making Something Be What It Is
Aristotle frequently describes essence as a “cause” or “explanation”, thus ascribing to essence some sort of causal or explanatory role. This explanatory role is often explicated by scholars in terms of essence “making the thing be what it is” or “making it the very thing that it is”. I argue that this is problematic, at least on the assumption that “making” expresses an explanatory relation, since it violates certain formal features of explanation. I then consider whether Aristotle is vulnerable to this problem by examining the explanatory role of essence in Posterior Analytics and Metaphysics Z 17
Vacuum Polarization for a Massless Spin-1/2 Field in the Global Monopole Spacetime at Nonzero Temperature
In this paper we present the effects produced by the temperature in the
renormalized vacuum expectation value of the zero-zero component of the
energy-momentum tensor associated with massless left-handed spinor field in the
pointlike global monopole spacetime. In order to develop this calculation we
had to obtain the Euclidean thermal Green function in this background. Because
the expression obtained for the thermal energy density cannot be expressed in a
closed form, its explicit dependence on the temperature is not completely
evident. So, in order to obtain concrete information about its thermal
behavior, we develop a numerical analysis of our result in the high-temperature
limit for specific values of the parameter which codify the presence
of the monopole.Comment: 22 pages, LaTex format, 5 figure
Star formation in low density HI gas around the Elliptical Galaxy NGC2865
Interacting galaxies surrounded by HI tidal debris are ideal sites for the
study of young clusters and tidal galaxy formation. The process that triggers
star formation in the low-density environments outside galaxies is still an
open question. New clusters and galaxies of tidal origin are expected to have
high metallicities for their luminosities. Spectroscopy of such objects is,
however, at the limit of what can be done with existing 8-10m class telescopes,
which has prevented statistical studies of these objects. NGC2865 is an
UV-bright merging elliptical galaxy with shells and extended HI tails. The
regions observed in this work were previously detected using multi-slit imaging
spectroscopy. We obtain new multislit spectroscopy of six young star-forming
regions around NGC2865, to determine their redshifts and metallicities. The six
emission-line regions are located 16-40 kpc from NGC2865 and they have similar
redshifts. They have ages of ~10Myears and an average metallicity of
12+log(O/H) ~ 8.6, suggesting a tidal origin for the regions. It is noted that
they coincide with an extended HI tail, which has projected density of N
< 10 cm, and displays a low surface brightness counterpart. These
regions may represent the youngest of the three populations of star clusters
already identified in NGC2865. The high, nearly-solar, oxygen abundances found
for the six regions in the vicinity of NGC2865 suggest that they were formed by
pre-enriched material from the parent galaxy, from gas removed during the last
major merger. Given the mass and the location of the HII regions, we can
speculate that these young star-forming regions are potential precursors of
globular clusters that will be part of the halo of NGC2865 in the future. Our
result supports the use of the multi-slit imaging spectroscopy as a useful tool
for finding nearly-formed stellar systems around galaxies.Comment: 7 pages, 2 figures accepted in A&
The effect of the availability of student credit on tuition: testing the Bennett hypothesis using evidence from a large-scale student loan program in Brazil
Exploring the expansion of FIES—a large student lending program in Brazil— we test whether eligibility for subsidized student lending causes tuition to rise, in accordance with the Bennett hypothesis. FIES rules created arguably exogenous variation in eligibility across different majors and higher education institutions, which we exploit in a difference-indifferences framework. Using unique information on tuition, we document that FIES eligibility caused tuition to rise. We then estimate a structural demand model to explore whether a reduction in the sensitivity of demand to price increases is one of the possible mechanisms behind this credit-driven tuition rise. Our results show that FIES expansion is associated with a reduction in the tuition elasticity of demand
A Multiwavelength Study on the Fate of Ionizing Radiation in Local Starbursts
The fate of ionizing radiation is vital for understanding cosmic ionization,
energy budgets in the interstellar and intergalactic medium, and star formation
rate indicators. The low observed escape fractions of ionizing radiation have
not been adequately explained, and there is evidence that some starbursts have
high escape fractions. We examine the spectral energy distributions of a sample
of local star-forming galaxies, containing thirteen local starburst galaxies
and ten of their ordinary star-forming counterparts, to determine if there
exist significant differences in the fate of ionizing radiation in these
galaxies. We find that the galaxy-to-galaxy variations in the SEDs is much
larger than any systematic differences between starbursts and non-starbursts.
For example, we find no significant differences in the total absorption of
ionizing radiation by dust, traced by the 24um, 70um, and 160um MIPS bands of
the Spitzer Space Telescope, although the dust in starburst galaxies appears to
be hotter than that of non-starburst galaxies. We also observe no excess
ultraviolet flux in the GALEX bands that could indicate a high escape fraction
of ionizing photons in starburst galaxies. The small H-alpha fractions of the
diffuse, warm ionized medium in starburst galaxies are apparently due to
temporarily boosted H-alpha luminosity within the star-forming regions
themselves, with an independent, constant WIM luminosity. This independence of
the WIM and starburst luminosities contrasts with WIM behavior in non-starburst
galaxies and underscores our poor understanding of radiation transfer in both
ordinary and starburst galaxies.Comment: 10 pages, 8 figures, accepted to ApJ 10/11/1
Herdabilidade dos escores da condição corporal de vacas ao parto e ao desmame em um rebanho da raça Canchim.
O objetivo desse trabalho foi estimar parâmetros genéticos e fenotípicos dos escores da condição corporal das vacas ao parto (ECCVP) e ao desmame (ECCVD) do bezerro em um rebanho da raça Canchim. Foram analisados os dados de 2.727 ECCVP e 1.328 ECCVD de 910 e 652 vacas, respectivamente, pertencentes à Embrapa Pecuária Sudeste. Os componentes de variância foram estimados por meio da Inferência Bayesiana, utilizando-se o Amostrador de Gibbs. Os ECCVP e ECCVD foram analisados por um modelo animal considerando os efeitos genético aditivo direto, de ambiente permanente do animal e residual como aleatórios, além dos efeitos fixos de grupo de contemporâneas (ano e mês de parto), sexo do bezerro e a idade da vaca (em anos) como covariável (efeitos linear e quadrático). As médias posteriores para a herdabilidade e para a proporção da variância de ambiente permanente para o ECCVP (0,19 e 0,04, respectivamente) e ECCVD (0,29 e 0,02, respectivamente) indicam que existe variância genética aditiva que pode justificar a inclusão dessas características como critérios de seleção e que o efeito de ambiente temporário (residual) é responsável pela maior parte da variância fenotípica
Preliminary evaluation of equine respiratory disease in a region of New Zealand
Inflammatory airway disease (IAD) is one of the most widespread conditions affecting horses
world-wide. Over-crowding, stabling conditions and exposure to irritants (such as bedding
dust) have been thought to contribute to the development of IAD. Since the majority of sport
horses in New Zealand are kept at pasture for prolonged periods, differing from intensive
stabling conditions seen in other countries, variations in the type and frequency of respiratory
pathologies might exist. In order to investigate this possibility, and determine the most
common respiratory conditions affecting horses requiring endoscopic examination, this
preliminary epidemiologic study was conducted. A retrospective analysis of 145 respiratory
endoscopies was conducted including examinations made at 2 veterinary clinics from June
2010 to October 2012. Respiratory endoscopies results were initially classified as normal or
abnormal. Abnormal results were further classified as: IAD, anatomical abnormalities,
intermittent airway obstruction, trauma, miscellaneous abnormalities. Presence of tracheal
secretions of any kind and quantity warranted classification as (IAD). Overall, 76.5% of the
animals requiring a respiratory endoscopy demonstrated abnormalities which justified the
examination: the majority of horses (42.7%) displayed some degree of IAD. Other common
findings included intermittent dorsal displacement of the soft palate (6.9%); bleeding in the
upper respiratory tract (3.45%), and laryngeal hemiplegia (15.2%). Inflammatory airway
disease (IAD) is one of the most widespread conditions affecting horses world-wide and it is
also prevalent in the population studied, despite different housing and managing practices
observed in New Zealand in comparison to other countries. Further studies are needed to
investigate subclinical abnormalities and the causes of the IAD in horses kept at pasture
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