758 research outputs found
Identification of Biodiversity and Other Forest Attributes for Sustainable Forest Management: Siberian Forest Case Study
This paper attempts to identify characteristics of biodiversity and other (forest) ecosystem conditions that are considered essential for a description of ecosystem functioning and development of sustainable forest management practices in the Siberian forests. This is accomplished through an analysis of net primary production of phytomass (NPP) which acts as a proxy for ecosystem functioning. Rough Sets (RS) analysis is applied to study the Siberian ecoregions classified into compact and cohesive NPP performance classes. Through a heuristic procedure, a reduced set of attributes is generated for a NPP classification problem. In order to interpret relationships between various forest characteristics, so-called "interesting rules" are generated on a basis of reduced problem description. These "interesting rules" provide means to draw conclusions in the form of knowledge statements about functioning of the Siberian forests
Another short-burst host galaxy with an optically obscured high star formation rate: The case of GRB 071227
We report on radio continuum observations of the host galaxy of the short
gamma-ray burst 071227 (z=0.381) with the Australia Telescope Compact Array
(ATCA). We detect the galaxy in the 5.5 GHz band with an integrated flux
density of Fnu = 43 +/- 11 microJy, corresponding to an unobscured
star-formation rate (SFR) of about 24 Msun/yr, forty times higher than what was
found from optical emission lines. Among the ~30 well-identified and studied
host galaxies of short bursts this is the third case where the host is found to
undergo an episode of intense star formation. This suggests that a fraction of
all short-burst progenitors hosted in star-forming galaxies could be physically
related to recent star formation activity, implying a relatively short merger
time scale.Comment: 6 pages, ApJ, accepted for publicatio
Herschel observations of gamma-ray burst host galaxies: implications for the topology of the dusty interstellar medium
Long-duration gamma-ray bursts (GRBs) are indisputably related to star
formation, and their vast luminosity in gamma rays pin-points regions of star
formation independent of galaxy mass. As such, GRBs provide a unique tool for
studying star forming galaxies out to high-z independent of luminosity. Most of
our understanding of the properties of GRB hosts (GRBHs) comes from optical and
near-infrared (NIR) follow-up observations, and we therefore have relatively
little knowledge of the fraction of dust-enshrouded star formation that resides
within GRBHs. Currently ~20% of GRBs show evidence of significant amounts of
dust along the line of sight to the afterglow through the host galaxy, and
these GRBs tend to reside within redder and more massive galaxies than GRBs
with optically bright afterglows. In this paper we present Herschel
observations of five GRBHs with evidence of being dust-rich, targeted to
understand the dust attenuation properties within GRBs better. Despite the
sensitivity of our Herschel observations, only one galaxy in our sample was
detected (GRBH 070306), for which we measure a total star formation rate (SFR)
of ~100Mstar/yr, and which had a relatively high stellar mass
(log[Mstar]=10.34+0.09/-0.04). Nevertheless, when considering a larger sample
of GRBHs observed with Herschel, it is clear that stellar mass is not the only
factor contributing to a Herschel detection, and significant dust extinction
along the GRB sightline (A_{V,GRB}>1.5~mag) appears to be a considerably better
tracer of GRBHs with high dust mass. This suggests that the extinguishing dust
along the GRB line of sight lies predominantly within the host galaxy ISM, and
thus those GRBs with A_{V,GRB}>1~mag but with no host galaxy Herschel
detections are likely to have been predominantly extinguished by dust within an
intervening dense cloud.Comment: 14 pages, 7 figures. Accepted for publication in A&
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Learning the preferences of physicians for the organization of result lists of medical evidence articles
Objectives
Despite many clinical decision support systems (CDSSs) being rated as highly usable, CDSSs have not been widely adopted in clinical practice. We posit that there are factors aside from usability that impact adoption of CDSSs; in particular we are interested in the role played by MDs intrinsic motivation to use computer-based support. Our research aim is to investigate the relationship between usability and intrinsic motivation in order to learn about adoption of CDSS in clinical practice.
Methods
Following the evaluation of a CDSS, 19 MDs completed a 2 part questionnaire about their intrinsic motivation to use computer-based support in general and the usability of the evaluated CDSS.
Results
The analysis of MDs motivation to use computer-based support demonstrated that MDs are comfortable using computer-based support and in general find using it quite easy (a motivation rating of 0.66 on a (0, 1) scale was computed). However MDs also reported a perceived lack of competence associated with a lack of prior experience using technology in practice, which results in pressure and tension. The considered CDSS scored highly on all usability dimensions and a usability rating of 0.74 was recorded. The examination of the relationship between motivation and usability suggested that users who were motivated to use computer-based support experienced better usability than those who reported low levels of motivation.
Conclusions
Our small case study suggests that an important factor supplementing the usability of CDSSs is intrinsic motivation to use computer-based support in general. We posit that the lack of such a measure thus far in CDSS evaluation may to some extent explain seeming MD satisfaction with CDSSs on one hand, but their limited adoption on the other. We recommend that clinical managers responsible for deploying CDSS should invest in training MDs to use technology underlying computer-based support applications instead of focusing only on the features of the specific CDSS to be deployed
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Aligning Interdisciplinary Healthcare Team Behavior with Workflow Execution: An Example of a Radical Prostatectomy Workflow
Operationalizing care delivery through an interdisciplinary healthcare team (IHT) requires knowledge about the overall structure of an IHT and the behavioral rules that "control" the dynamics of this structure interpreted as team and clinical leadership maintenance and task allocation. While progress has been made in understanding IHT structure, there is less work on the behavioral aspects of an IHT associated with its dynamics. In this paper we fill this void by extending our Team and Workflow Management Framework (TWMF) with a set of rules to operationalize IHT behavior in terms of clinical leadership, coordination of workflow execution over multiple days as part of continuity of care, and management of tasks, including urgent ones that prevent planned workflow execution. We briefly describe a proof-of-concept implementation of extended TWMF in the form of a computer system for supporting cooperative execution of clinical workflows by an IHT. The system is built on top of an existing business workflow execution engine and employs behavioral rules to control the IHT behavior. We also illustrate the operations of TWMF in a case study where an IHT is executing a workflow for the management of post-operative inpatient recovery after radical prostatectomy
Sub-millimeter galaxies as progenitors of compact quiescent galaxies
Three billion years after the big bang (at redshift z=2), half of the most
massive galaxies were already old, quiescent systems with little to no residual
star formation and extremely compact with stellar mass densities at least an
order of magnitude larger than in low redshift ellipticals, their descendants.
Little is known about how they formed, but their evolved, dense stellar
populations suggest formation within intense, compact starbursts 1-2 Gyr
earlier (at 3<z<6). Simulations show that gas-rich major mergers can give rise
to such starbursts which produce dense remnants. Sub-millimeter selected
galaxies (SMGs) are prime examples of intense, gas-rich, starbursts. With a
new, representative spectroscopic sample of compact quiescent galaxies at z=2
and a statistically well-understood sample of SMGs, we show that z=3-6 SMGs are
consistent with being the progenitors of z=2 quiescent galaxies, matching their
formation redshifts and their distributions of sizes, stellar masses and
internal velocities. Assuming an evolutionary connection, their space densities
also match if the mean duty cycle of SMG starbursts is 42 (+40/-29) Myr
(consistent with independent estimates), which indicates that the bulk of stars
in these massive galaxies were formed in a major, early surge of
star-formation. These results suggests a coherent picture of the formation
history of the most massive galaxies in the universe, from their initial burst
of violent star-formation through their appearance as high stellar-density
galaxy cores and to their ultimate fate as giant ellipticals.Comment: ApJ (in press
A Giant Crater on 90 Antiope?
Mutual event observations between the two components of 90 Antiope were
carried out in 2007-2008. The pole position was refined to lambda0 =
199.5+/-0.5 eg and beta0 = 39.8+/-5 deg in J2000 ecliptic coordinates, leaving
intact the physical solution for the components, assimilated to two perfect
Roche ellipsoids, and derived after the 2005 mutual event season (Descamps et
al., 2007). Furthermore, a large-scale geological depression, located on one of
the components, was introduced to better match the observed lightcurves. This
vast geological feature of about 68 km in diameter, which could be postulated
as a bowl-shaped impact crater, is indeed responsible of the photometric
asymmetries seen on the "shoulders" of the lightcurves. The bulk density was
then recomputed to 1.28+/-0.04 gcm-3 to take into account this large-scale
non-convexity. This giant crater could be the aftermath of a tremendous
collision of a 100-km sized proto-Antiope with another Themis family member.
This statement is supported by the fact that Antiope is sufficiently porous
(~50%) to survive such an impact without being wholly destroyed. This violent
shock would have then imparted enough angular momentum for fissioning of
proto-Antiope into two equisized bodies. We calculated that the impactor must
have a diameter greater than ~17 km, for an impact velocity ranging between 1
and 4 km/s. With such a projectile, this event has a substantial 50%
probability to have occurred over the age of the Themis family.Comment: 30 pages, 3 Tables, 8 Figures. Accepted for publication in Icaru
Dust attenuation in 2<z<3 star-forming galaxies from deep ALMA observations of the Hubble Ultra Deep Field
17 pages, 7 figures, accepted version to be published in MNRASWe present the results of a new study of the relationship between infrared excess (IRX ≡ L IR/L UV), ultraviolet (UV) spectral slope (β) and stellar mass at redshifts 2 < z < 3, based on a deep Atacama Large Millimeter Array (ALMA) 1.3-mm continuum mosaic of the Hubble Ultra Deep Field. Excluding the most heavily obscured sources, we use a stacking analysis to show that z ≃ 2.5 star-forming galaxies in the mass range 9.25 ≤ log(M*/M ⊙) ≤ 10.75 are fully consistent with the IRX-β relation expected for a relatively grey attenuation curve, similar to the commonly adopted Calzetti law. Based on a large, mass-complete sample of 2 ≤ z ≤ 3 star-forming galaxies drawn frommultiple surveys, we proceed to derive a new empirical relationship between β and stellar mass, making it possible to predict UV attenuation (A1600) and IRX as a function of stellar mass, for any assumed attenuation law. Once again, we find that z ≃ 2.5 star-forming galaxies follow A1600-M* and IRX-M* relations consistent with a relatively grey attenuation law, and find no compelling evidence that star-forming galaxies at this epoch follow a reddening law as steep as the Small Magellanic Cloud (SMC) extinction curve. In fact, we use a simple simulation to demonstrate that previous determinations of the IRX-β relation may have been biased towards low values of IRX at red values of β, mimicking the signature expected for an SMC-like dust law. We show that this provides a plausible mechanism for reconciling apparently contradictory results in the literature and that, based on typical measurement uncertainties, stellar mass provides a cleaner prediction of UV attenuation than β. Although the situation at lower stellar masses remains uncertain, we conclude that for 2 < z < 3 star-forming galaxies with log(M*/M ⊙) ≥ 9.75, both the IRX-β and IRX-M* relations are well described by a Calzetti-like attenuation law.Peer reviewe
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