740 research outputs found
Functional Sequential Treatment Allocation
Consider a setting in which a policy maker assigns subjects to treatments,
observing each outcome before the next subject arrives. Initially, it is
unknown which treatment is best, but the sequential nature of the problem
permits learning about the effectiveness of the treatments. While the
multi-armed-bandit literature has shed much light on the situation when the
policy maker compares the effectiveness of the treatments through their mean,
much less is known about other targets. This is restrictive, because a cautious
decision maker may prefer to target a robust location measure such as a
quantile or a trimmed mean. Furthermore, socio-economic decision making often
requires targeting purpose specific characteristics of the outcome
distribution, such as its inherent degree of inequality, welfare or poverty. In
the present paper we introduce and study sequential learning algorithms when
the distributional characteristic of interest is a general functional of the
outcome distribution. Minimax expected regret optimality results are obtained
within the subclass of explore-then-commit policies, and for the unrestricted
class of all policies
Feeding regimens in finishing phase of beef cattle on corporal development and meat quality.
Despite to be a traditional activity in southern Brazil, beef cattle production based exclusively in natural grasslands normally presents low animal productivity, reflecting a misunderstanding of basic management practices like control of forage allowance and or lack of utilization of others possibilities of foraging
A Multiwavelength View of a Mass Outflow from the Galactic Center
The Galactic center (GC) lobe is a degree-tall shell of gas that spans the
central degree of our Galaxy. It has been cited as evidence for a mass outflow
from our GC region, which has inspired diverse models for its origin. However,
most work has focused on the morphology of the GC lobe, which has made it
difficult to draw strong conclusions about its nature. Here, I present a
coherent, multiwavelength analysis of new and archival observations of the GC
lobe. Radio continuum emission shows that the GC lobe has a magnetized layer
with a diameter of 110 pc and an equipartition field strength ranging from 40
to 100 G. Recombination line emission traces an ionized shell nested
within the radio continuum with diameter of 80 pc and height 165 pc.
Mid-infrared maps at 8 and 15 m show that the GC lobe has a third layer of
warm dust and PAH-emission that surrounds the radio continuum shell with a
diameter of 130 pc. Assuming adiabatic expansion of the gas in the GC lobe, its
formation required an energy input of about ergs. I compare
the physical conditions of the GC lobe to several models and find best
agreement with the canonical starburst outflow model. The formation of the GC
lobe is consistent with the currently observed pressure and star formation rate
in the central tens of parsecs of our Galaxy. Outflows of this scale are more
typical of dwarf galaxies and would not be easily detected in nearby spiral
galaxies. Thus, the existence of such an outflow in our own Galaxy may indicate
that it is relatively common phenomenon in the nuclei of spiral galaxies.
(Abridged)Comment: Accepted to ApJ. 15 pages, 8 (compressed) figure
A Region of Violent Star Formation in the Irr Galaxy IC 10: Structure and Kinematics of Ionized and Neutral Gas
We have used observations of the galaxy IC 10 at the 6-m telescope of the
Special Astrophysical Observatory with the SCORPIO focal reducer in the
Fabry-Perot interferometer mode and with the MPFS spectrograph to study the
structure and kinematics of ionized gas in the central region of current
intense star formation. Archive VLA 21-cm observations are used to analyze the
structure and kinematics of neutral gas in this region. High-velocity wings of
the H-alpha and [SII] emission lines were revealed in the inner cavity of the
nebula HL 111 and in other parts of the complex of violent star formation. We
have discovered local expanding neutral-gas shells around the nebulae HL 111
and HL 106.Comment: 22 pages, 10 figures; accepted in Astronomy Report
Impact of age norms and stereotypes on managers' hiring decisions of retirees
Purpose -Our study investigates the role of managers in the re-employment of early retirees and asks what the effect is of managers’ age norms and stereotypes on managers’ employment decisions.
Design/methodology/approach- A combination of a factorial study and a survey was conducted. First, information on the age norms and stereotypes was collected. Secondly, profiles of hypothetical retired job applicants were presented to the employers, who were asked to make a specific hiring decision. The information collected during both studies was combined in the analysis and multilevel models were estimated.
Findings -The results indicate that higher age norms result in a higher propensity to hire an early retiree. Stereotypes, by contrast, do not influence managers’ decisions. Early retirees’ chances for re-employment are also related to their own circumstances (physical appearance and relevant experience) and organisational forces, as they are hired when organisations face labour force shortages.
Research limitation / implications – with the use of vignettes study we deal with hypothetical hiring situation.
Originality value- Although the effect of age norms and age stereotypes has been often suggested, not much empirical evidence was presented to support this notion. Our study estimates the effect of age norms and stereotypes on hiring decision.
key words: bridge employment; early retirees; age norms; age stereotypes; multilevel models.
Gas Emission Spectrum in the Irr Galaxy IC 10
Spectroscopic long-slit observations of the dwarf Irr galaxy IC 10 were
conducted at the 6-m Special Astrophysical Observatory telescope with the
SCORPIO focal reducer. The ionized-gas emission spectra in the regions of
intense current star formation were obtained for a large number of regions in
IC 10. The relative abundances of oxygen, N+, and S+ in about twenty HII
regions and in the synchrotron superbubble were estimated. We found that the
galaxy-averaged oxygen abundance is 12 + log(O/H) = 8.17 +- 0.35 and the
metallicity is Z = 0.18 +- 0.14 Z_sun. Our abundances estimated from the strong
emission lines are found to be more reliable than those obtained by comparing
diagnostic diagrams with photoionization models.Comment: Abridged; accepted in Astronomy Letter
Dialectics and difference: against Harvey's dialectical post-Marxism
David Harvey`s recent book, Justice, nature and the geography of difference (JNGD), engages with a central philosophical debate that continues to dominate human geography: the tension between the radical Marxist project of recent decades and the apparently disempowering relativism and `play of difference' of postmodern thought. In this book, Harvey continues to argue for a revised `post-Marxist' approach in human geography which remains based on Hegelian-Marxian principles of dialectical thought. This article develops a critique of that stance, drawing on the work of Jacques Derrida, Gilles Deleuze and Felix Guattari. I argue that dialectical thinking, as well as Harvey's version of `post-Marxism', has been undermined by the wide-ranging `post-' critique. I suggest that Harvey has failed to appreciate the full force of this critique and the implications it has for `post-Marxist' ontology and epistemology. I argue that `post-Marxism', along with much contemporary human geography, is constrained by an inflexible ontology which excessively prioritizes space in the theory produced, and which implements inflexible concepts. Instead, using the insights of several `post-' writers, I contend there is a need to develop an ontology of `context' leading to the production of `contextual theories'. Such theories utilize flexible concepts in a multilayered understanding of ontology and epistemology. I compare how an approach which produces a `contextual theory' might lead to more politically empowering theory than `post-Marxism' with reference to one of Harvey's case studies in JNGD
Usability Guidelines for Desktop Search Engines
In this article we describe a usability evaluation of eight desktop search engines (DSEs). We used the heuristic walkthrough method to gather usability problems as well as individual strengths and weaknesses of the tested search engines. The results of the evaluation are integrated into a set of 30 design guidelines for user-friendly DSEs
Polycyclic aromatic hydrocarbons in the dwarf galaxy IC 10
Infrared observations from the Spitzer Space Telescope archive are used to
study the dust component of the interstellar medium in the IC~10 irregular
galaxy. Dust distribution in the galaxy is compared to the distributions of
H and [SII] emission, neutral hydrogen and CO clouds, and ionizing
radiation sources. The distribution of polycyclic aromatic hydrocarbons (PAH)
in the galaxy is shown to be highly non-uniform with the mass fraction of these
particles in the total dust mass reaching 4%. PAHs tend to avoid bright HII
regions and correlate well with atomic and molecular gas. This pattern suggests
that PAHs form in the dense interstellar gas. We propose that the significant
decrease of the PAH abundance at low metallicity is observed not only globally
(at the level of entire galaxies), but also locally (at least, at the level of
individual HII regions). We compare the distribution of the PAH mass fraction
to the distribution of high-velocity features, that we have detected earlier in
wings of H and SII lines, over the entire available galaxy area. No
conclusive evidence for shock destruction of PAHs in the IC~10 galaxy could be
found.Comment: Accepted for publication in Astronomy Report
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