736 research outputs found
OPEN ACCESS AND MISSING MARKETS IN ARTISANAL FISHING
This paper combines a model of open access fisheries exploitation with a distance-based approach to missing labor and product markets. The model generates predictions about the circumstances under which exploitation increases or decreases with distance. An econometric model is estimated with survey data from artisanal fishing households in Minahasa, Indonesia. The results can be used to assess the impacts of improved transportation infrastructure on fishery exploitation.Marketing,
Empirical ugri-UBVRc Transformations for Galaxies
We present empirical color transformations between Sloan Digital Sky Survey
ugri and Johnson-Cousins UBVRc photometry for nearby galaxies (D < 11 Mpc). We
use the Local Volume Legacy (LVL) galaxy sample where there are 90 galaxies
with overlapping observational coverage for these two filter sets. The LVL
galaxy sample consists of normal, non-starbursting galaxies. We also examine
how well the LVL galaxy colors are described by previous transformations
derived from standard calibration stars and model-based galaxy templates. We
find significant galaxy color scatter around most of the previous
transformation relationships. In addition, the previous transformations show
systematic offsets between transformed and observed galaxy colors which are
visible in observed color-color trends. The LVL-based transformations
show no systematic color offsets and reproduce the observed color-color galaxy
trends.Comment: Accepted for publication in MNRAS (9 pages, 6 figures, 4 tables
Spitzer Local Volume Legacy (LVL) SEDs and Physical Properties
We present the panchromatic spectral energy distributions (SEDs) of the Local
Volume Legacy (LVL) survey which consists of 258 nearby galaxies (11 Mpc).
The wavelength coverage spans the ultraviolet to the infrared (1500
to 24 m) which is utilized to derive global physical
properties (i.e., star formation rate, stellar mass, internal extinction due to
dust.). With these data, we find color-color relationships and correlated
trends between observed and physical properties (i.e., optical magnitudes and
dust properties, optical color and specific star formation rate, and
ultraviolet-infrared color and metallicity). The SEDs are binned by different
galaxy properties to reveal how each property affects the observed shape of
these SEDs. In addition, due to the volume-limited nature of LVL, we utilize
the dwarf-dominated galaxy sample to test star formation relationships
established with higher-mass galaxy samples. We find good agreement with the
star-forming "main-sequence" relationship, but find a systematic deviation in
the infrared "main-sequence" at low luminosities. This deviation is attributed
to suppressed polycyclic aromatic hydrocarbon (PAH) formation in low
metallicity environments and/or the destruction of PAHs in more intense
radiation fields occurring near a suggested threshold in sSFR at a value of
log() 10.2.Comment: Accepted for publication in MNRAS (15 pages, 14 figures, 1 table
The Spitzer Local Volume Legacy (LVL) Global Optical Photometry
We present the global optical photometry of 246 galaxies in the Local Volume
Legacy (LVL) survey. The full volume-limited sample consists of 258 nearby (D <
11 Mpc) galaxies whose absolute B-band magnitude span a range of -9.6 < M_B <
-20.7 mag. A composite optical (UBVR) data set is constructed from observed
UBVR and SDSS ugriz imaging, where the ugriz magnitudes are transformed into
UBVR. We present photometry within three galaxy apertures defined at UV,
optical, and IR wavelengths. Flux comparisons between these apertures reveal
that the traditional optical R25 galaxy apertures do not fully encompass
extended sources. Using the larger IR apertures we find color-color
relationships where later-type spiral and irregular galaxies tend to be bluer
than earlier-type galaxies. These data provide the missing optical emission
from which future LVL studies can construct the full panchromatic
(UV-optical-IR) spectral energy distributions.Comment: Accepted for publication in MNRAS (9 pages, 5 figures, 5 tables
Validation of 3 Food Outlet Databases: Completeness and Geospatial Accuracy in Rural and Urban Food Environments
Despite interest in the built food environment, little is known about the validity of commonly used secondary data. The authors conducted a comprehensive field census identifying the locations of all food outlets using a handheld global positioning system in 8 counties in South Carolina (2008â2009). Secondary data were obtained from 2 commercial companies, Dun & Bradstreet, Inc. (D&B) (Short Hills, New Jersey) and InfoUSA, Inc. (Omaha, Nebraska), and the South Carolina Department of Health and Environmental Control (DHEC). Sensitivity, positive predictive value, and geospatial accuracy were compared. The field census identified 2,208 food outlets, significantly more than the DHEC (n = 1,694), InfoUSA (n = 1,657), or D&B (n = 1,573). Sensitivities were moderate for DHEC (68%) and InfoUSA (65%) and fair for D&B (55%). Combining InfoUSA and D&B data would have increased sensitivity to 78%. Positive predictive values were very good for DHEC (89%) and InfoUSA (86%) and good for D&B (78%). Geospatial accuracy varied, depending on the scale: More than 80% of outlets were geocoded to the correct US Census tract, but only 29%â39% were correctly allocated within 100 m. This study suggests that the validity of common data sources used to characterize the food environment is limited. The marked undercount of food outlets and the geospatial inaccuracies observed have the potential to introduce bias into studies evaluating the impact of the built food environment
The Evolutionary Status of Isolated Dwarf Irregular Galaxies II. Star Formation Histories and Gas Depletion
The results of UBV and H alpha imaging of a large sample of isolated dwarf
irregular galaxies are interpreted in the context of composite stellar
population models. The observed optical colors are best fit by composite
stellar populations which have had approximately constant star formation rates
for at least 10 Gyr. The galaxies span a range of central surface brightness,
from 20.5 to 25.0 mag arcsec^{-2}; there is no correlation between surface
brightness and star formation history. Although the current star formation
rates are low, it is possible to reproduce the observed luminosities without a
major starburst episode. The derived gas depletion timescales are long,
typically ~20 Gyr. These results indicate that dwarf irregular galaxies will be
able to continue with their slow, but constant, star formation activity for at
least another Hubble time.
The sample of isolated dIs is compared to a sample of star bursting dwarf
galaxies taken from the literature. The star bursting dwarf galaxies have many
similar properties; the main difference between these two types of gas-rich
dwarf galaxies is that the current star formation is concentrated in the center
of the star bursting systems while it is much more distributed in the quiescent
dIs. This results in pronounced color gradients for the starbursting dwarf
galaxies, while the majority of the quiescent dwarf irregular galaxies have
minor or non-existent color gradients. Thus, the combination of low current
star formation rates, blue colors, and the lack of significant color gradients
indicates that star formation percolates slowly across the disk of normal dwarf
galaxies in a quasi-continuous manner.Comment: 16 pages, uses emulateapj, to appear in The Astronomical Journal
(April 2001
Does the availability of snack foods in supermarkets vary internationally?
BackgroundCross-country differences in dietary behaviours and obesity rates have been previously reported. Consumption of energy-dense snack foods and soft drinks are implicated as contributing to weight gain, however little is known about how the availability of these items within supermarkets varies internationally. This study assessed variations in the display of snack foods and soft drinks within a sample of supermarkets across eight countries.MethodsWithin-store audits were used to evaluate and compare the availability of potato chips (crisps), chocolate, confectionery and soft drinks. Displays measured included shelf length and the proportion of checkouts and end-of-aisle displays containing these products. Audits were conducted in a convenience sample of 170 supermarkets across eight developed nations (Australia, Canada, Denmark, Netherlands, New Zealand, Sweden, United Kingdom (UK), and United States of America (US)).ResultsThe mean total aisle length of snack foods (adjusted for store size) was greatest in supermarkets from the UK (56.4 m) and lowest in New Zealand (21.7 m). When assessed by individual item, the greatest aisle length devoted to chips, chocolate and confectionery was found in UK supermarkets while the greatest aisle length dedicated to soft drinks was in Australian supermarkets. Only stores from the Netherlands (41%) had less than 70% of checkouts featuring displays of snack foods or soft drinks.ConclusionWhilst between-country variations were observed, overall results indicate high levels of snack food and soft drinks displays within supermarkets across the eight countries. Exposure to snack foods is largely unavoidable within supermarkets, increasing the likelihood of purchases and particularly those made impulsively.<br /
Oxygen and Nitrogen in Leo A and GR 8
We present elemental abundances for multiple HII regions in Leo A and GR 8
obtained from long slit optical spectroscopy of these two nearby low luminosity
dwarf irregular galaxies. As expected from their luminosities, and in agreement
with previous observations, the derived oxygen abundances are extremely low in
both galaxies. High signal-to-noise ratio observations of a planetary nebula in
Leo A yield 12 + log(O/H) = 7.30 +/- 0.05; "semi-empirical" calculations of the
oxygen abundance in four HII regions in Leo A indicate 12 + log(O/H) = 7.38 +/-
0.10. These results confirm that Leo A has one of the lowest ISM metal
abundances of known nearby galaxies. Based on results from two HII regions with
high signal-to-noise measurements of the weak [O III] 4363 line, the mean
oxygen abundance of GR 8 is 12 + log(O/H) = 7.65 +/- 0.06; using "empirical"
and "semi-empirical" methods, similar abundances are derived for 6 other GR 8
HII regions. Similar to previous results in other low metallicity galaxies, the
mean log(N/O) = -1.53 +/- 0.09 for Leo A and -1.51 +/- 0.07 for GR 8. There is
no evidence of significant variations in either O/H or N/O in the HII regions.
The metallicity-luminosity relation for nearby (D < 5 Mpc) dwarf irregular
galaxies with measured oxygen abundances has a mean correlation of 12 +
log(O/H) = 5.67 - 0.151 M_B with a dispersion in oxygen about the relationship
of 0.21. These observations confirm that gas-rich low luminosity galaxies have
extremely low elemental abundances in the ionized gas-phase of their
interstellar media. Although Leo A has one of the lowest metal abundances of
known nearby galaxies, detection of tracers of an older stellar population
indicate that it is not a newly formed galaxy as has been proposed for some
other similarly low metallicity star forming galaxies.Comment: 36 pages, 7 figures. Accepted to Ap
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