337 research outputs found
Market Games In Finance Education
An electronic share market trading game was introduced to a large first year undergraduate finance course to allow students to experience share market trading. The response from students was positive. We surveyed a sample of 51 of the students in this class who undertook a further one-hour trading session as part of a separate research experiment. These students rate the game as a valuable learning experience. They suggest that their use of the game increased their understanding of share market and the way that prices are set. While the study results cannot be generalised to all students in the course, the results suggest that there are benefits to be gained from including an electronic share market trading game as part of the course
The Medical Library Association Data Services Competency: A Framework for Data Science and Open Science Skills Development
Increasingly, users of health and biomedical libraries need assistance with challenges they face in working with their own and others' data. Librarians have a unique opportunity to provide valuable support and assistance in data science and open science but may need to add to their expertise and skill set to have the most impact. This article describes the rationale for and development of the Medical Library Association Data Services Competency, which outlines a set of five key skills for data services and provides a course of study for gaining these skills
A Study on Marketing Behaviour of Rural Youth Entrepreneurs among Seven Different Ventures
The study was conducted among 210 rural youth entrepreneurs of seven different ventures in Krishnagiri district to assess their marketing behaviour. The entrepreneurial ventures selected for the study were Sericulture, Mushroom Production, Hi-tech nurseries (Polyhouse), Fruit and flower nursery, Fisheries, Poultry farming and Value addition (Tamarind processing and Millet based cookies).
Evolutionary Signatures in the Formation of Low-Mass Protostars. II. Towards Reconciling Models and Observations
A long-standing problem in low-mass star formation is the "luminosity
problem," whereby protostars are underluminous compared to the accretion
luminosity expected both from theoretical collapse calculations and arguments
based on the minimum accretion rate necessary to form a star within the
embedded phase duration. Motivated by this luminosity problem, we present a set
of evolutionary models describing the collapse of low-mass, dense cores into
protostars, using the Young & Evans (2005) model as our starting point. We
calculate the radiative transfer of the collapsing cores throughout the full
duration of the collapse in two dimensions. From the resulting spectral energy
distributions, we calculate standard observational signatures to directly
compare to observations. We incorporate several modifications and additions to
the original Young & Evans model in an effort to better match observations with
model predictions. We find that scattering, 2-D geometry, mass-loss, and
outflow cavities all affect the model predictions, as expected, but none
resolve the luminosity problem. A cycle of episodic mass accretion, however,
can resolve this problem and bring the model predictions into better agreement
with observations. Standard assumptions about the interplay between mass
accretion and mass loss in our model give star formation efficiencies
consistent with recent observations that compare the core mass function (CMF)
and stellar initial mass function (IMF). The combination of outflow cavities
and episodic mass accretion reduce the connection between observational Class
and physical Stage to the point where neither of the two common observational
signatures (bolometric temperature and ratio of bolometric to submillimeter
luminosity) can be considered reliable indicators of physical Stage.Comment: 27 pages. Accepted for publication in Ap
Externally Fed Accretion onto Protostars
The asymmetric molecular emission lines from dense cores reveal slow, inward
motion in the clouds' outer regions. This motion is present both before and
after the formation of a central star. Motivated by these observations, we
revisit the classic problem of steady, spherical accretion of gas onto a
gravitating point mass, but now include self-gravity of the gas and impose a
finite, subsonic velocity as the outer boundary condition. We find that the
accretion rate onto the protostar is lower than values obtained for isolated,
collapsing clouds, by a factor that is the Mach number of the outer flow.
Moreover, the region of infall surrounding the protostar spreads out more
slowly, at a speed close to the subsonic, incoming velocity. Our calculation,
while highly idealized, provides insight into two longstanding problems -- the
surprisingly low accretion luminosities of even the most deeply embedded
stellar sources, and the failure so far to detect spatially extended,
supersonic infall within their parent dense cores. Indeed, the observed
subsonic contraction in the outer regions of dense cores following star
formation appears to rule out a purely hydrodynamic origin for these clouds.Comment: accepted by MNRA
The Dust Emissivity Spectral Index in the Starless Core TMC-1C
In this paper we present a dust emission map of the starless core TMC-1C
taken at 2100 microns. Along with maps at 160, 450, 850 and 1200 microns, we
study the dust emissivity spectral index from the (sub)millimeter spectral
energy distribution, and find that it is close to the typically assumed value
of beta = 2. We also map the dust temperature and column density in TMC-1C, and
find that at the position of the dust peak (A_V ~ 50), the
line-of-sight-averaged temperature is ~7 K. Employing simple Monte Carlo
modeling, we show that the data are consistent with a constant value for the
emissivity spectral index over the whole map of TMC-1C.Comment: 11 pages, including 5 pages of figures. Accepted to Ap
The Millimeter Astronomy Legacy Team 90 GHz (MALT90) Pilot Survey
We describe a pilot survey conducted with the Mopra 22-m radio telescope in
preparation for the Millimeter Astronomy Legacy Team Survey at 90 GHz (MALT90).
We identified 182 candidate dense molecular clumps using six different
selection criteria and mapped each source simultaneously in 16 different lines
near 90 GHz. We present a summary of the data and describe how the results of
the pilot survey shaped the design of the larger MALT90 survey. We motivate our
selection of target sources for the main survey based on the pilot detection
rates and demonstrate the value of mapping in multiple lines simultaneously at
high spectral resolution.Comment: Accepted to ApJS. 23 pages and 16 figures. Full resolution version
with an appendix showing all the data (12.1 MB) is available at
http://malt90.bu.edu/publications/Foster_2011_Malt90Pilot.pd
Physical structure and CO abundance of low-mass protostellar envelopes
We present 1D radiative transfer modelling of the envelopes of a sample of 18
low-mass protostars and pre-stellar cores with the aim of setting up realistic
physical models, for use in a chemical description of the sources. The density
and temperature profiles of the envelopes are constrained from their radial
profiles obtained from SCUBA maps at 450 and 850 micron and from measurements
of the source fluxes ranging from 60 micron to 1.3 mm. The densities of the
envelopes within ~10000 AU can be described by single power-laws r^{-p} for the
class 0 and I sources with p ranging from 1.3 to 1.9, with typical
uncertainties of +/- 0.2. Four sources have flatter profiles, either due to
asymmetries or to the presence of an outer constant density region. No
significant difference is found between class 0 and I sources. The power-law
fits fail for the pre-stellar cores, supporting recent results that such cores
do not have a central source of heating. The derived physical models are used
as input for Monte Carlo modelling of submillimeter C18O and C17O emission. It
is found that class I objects typically show CO abundances close to those found
in local molecular clouds, but that class 0 sources and pre-stellar cores show
lower abundances by almost an order of magnitude implying that significant
depletion occurs for the early phases of star formation. While the 2-1 and 3-2
isotopic lines can be fitted using a constant fractional CO abundance
throughout the envelope, the 1-0 lines are significantly underestimated,
possibly due to contribution of ambient molecular cloud material to the
observed emission. The difference between the class 0 and I objects may be
related to the properties of the CO ices.Comment: 21 pages, 12 figures, accepted by A&
The First Provenance Challenge
The first Provenance Challenge was set up in order to provide a forum for the community to help understand the capabilities of different provenance systems and the expressiveness of their provenance representations. To this end, a Functional Magnetic Resonance Imaging workflow was defined, which participants had to either simulate or run in order to produce some provenance representation, from which a set of identified queries had to be implemented and executed. Sixteen teams responded to the challenge, and submitted their inputs. In this paper, we present the challenge workflow and queries, and summarise the participants contributions
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