780 research outputs found
Capturing Preference Heterogeneity in Stated Choice Models: A Random Parameter Logit Model of the Demand for GM Food
Analyses of data from random utility models of choice data have typically used fixed parameter representations, with consumer heterogeneity introduced by including factors such as the age, gender etc of the respondent. However, there is a class of models that assume that the underlying parameters of the estimated model (and hence preferences) are different for each individual within the sample, and that choices can be explained by identifying the parameters of the distribution from which they are drawn. Such a random parameter model is applied to stated choice data from the UK, and the results compared with standard fixed parameter models. The results provide new evidence of preferences for various aspects of the UK food system, particularly in relation to GM food but other environmental and technical aspects also. Indications of how random parameter models might be developed further are discussed on the basis of these results.random parameter logit, choice modelling, GMOs, food safety, Food Consumption/Nutrition/Food Safety,
Metal-poor, Strongly Star-Forming Galaxies in the DEEP2 Survey: The Relationship between Stellar Mass, Temperature-based Metallicity, and Star Formation Rate
We report on the discovery of 28 metal-poor galaxies in DEEP2.
These galaxies were selected for their detection of the weak
[OIII]4363 emission line, which provides a "direct" measure of the
gas-phase metallicity. A primary goal for identifying these rare galaxies is to
examine whether the fundamental metallicity relation (FMR) between stellar
mass, gas metallicity, and star formation rate (SFR) holds for low stellar mass
and high SFR galaxies. The FMR suggests that higher SFR galaxies have lower
metallicity (at fixed stellar mass). To test this trend, we combine
spectroscopic measurements of metallicity and dust-corrected SFRs, with stellar
mass estimates from modeling the optical photometry. We find that these
galaxies are dex above the z~1 stellar mass-SFR relation, and
dex below the local mass-metallicity relation. Relative to the
FMR, the latter offset is reduced to 0.01 dex, but significant dispersion
remains (0.29 dex with 0.16 dex due to measurement uncertainties). This
dispersion suggests that gas accretion, star formation and chemical enrichment
have not reached equilibrium in these galaxies. This is evident by their short
stellar mass doubling timescale of Myr that suggests
stochastic star formation. Combining our sample with other z~1 metal-poor
galaxies, we find a weak positive SFR-metallicity dependence (at fixed stellar
mass) that is significant at 94.4% confidence. We interpret this positive
correlation as recent star formation that has enriched the gas, but has not had
time to drive the metal-enriched gas out with feedback mechanisms.Comment: Resubmitted to ApJ on March 6, 2015. Revised to discuss selection
biases and methodologies, and address the former by including more metal-rich
galaxies with robust non-detections of [OIII]4363. Primary results on FMR
analyses are unchanged. Additional figures are included to illustrate
selection biases; previous figures have been revised to improve presentatio
Precaution and Protectionism: GM Food and the WTO
The dispute between the US and EU over GM foods at the WTO is examined in terms of the issues it raises about protectionism and environmental protection and precaution. The issue of whether GM, GM Derived and Non-GM foods are equivalent to each other is examined using data from a national choice modelling study in the UK. These categories of food are critical since they underpin the EU's new food labelling regime which it hoped would defuse the WTO dispute. The results are analysed using a Bayesian mixed logit model which allows greater flexibility in the modelling of preference distributions. This is particularly crucial where, as in this case, bi-modal distributions are identified with some indifferent or mildly averse to GM foodtypes while others are strongly averse. A strong finding of the analysis is that people treat ingredients derived from GM crops (but free from altered DNA) as equivalent to GM ingredients. This supports a labelling regime based on process rather than simply product and suggests considerable consumer benefits from the EU's new GM labelling regime.GM food, mixed logit, WTP, Bayesian, WTO, International Relations/Trade, C11, C24, C25, D12, Q18,
Precaution and Protectionism: 'Likeness' and GM Food at the WTO
The dispute between the US and EU over GM foods at the WTO is examined in terms of the issues it raises about protectionism, environmental protection and precaution. The issue of whether GM, GM Derived and Non-GM foods are equivalent to each other is examined using data from a national choice modelling study in the UK. These categories of food are critical since they underpin the EU's new food labelling regime which it hoped would defuse the WTO dispute. The results are analysed using a Bayesian mixed logit model which allows greater flexibility in the modelling of preference distributions than that allowed through classical estimation. The Bayesian approach allows the use of censored normal and Johnson's SB distributions which can accommodate a bounded distribution with a probability mass point at zero (i.e. indifference). This is particularly important where, as in the case of GM food, we may expect some to be indifferent to the food whilst others dislike it, some strongly so. The results indicate bi-modal distributions regarding GM foodtypes, with some indifferent or mildly averse to GM foodtypes and others are strongly averse. A strong finding of the analysis is that most people treat ingredients derived from GM crops (but free from altered DNA) as equivalent to GM ingredients. This supports a labelling regime based on process rather than simply product and suggests considerable consumer benefits from the EU's new GM labelling regime.GM food, mixed logit, WTP, Bayesian, WTO, International Relations/Trade, Q51, Q55, Q56, Q58,
Recent faulting and active shortening of the Middle Atlas Mountains, Morocco, within the diffuse African-Eurasian plate boundary
The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file.Title from title screen of research.pdf file (viewed on July 8, 2009)Thesis (M.S.) University of Missouri-Columbia 2008.The intracontinental Atlas Mountains of northwest Africa are prominent tectonic elements in the broader, diffuse plate boundary zone between the converging African and Eurasian plates. This study focuses on constraining the recent shortening rate across the NE-SW striking Middle Atlas Mountains, which are obliquely oriented to the NNW-SSE direction of Late Cenozoic plate convergence. In the southwestern part of the Folded Middle Atlas, fault scarps of Quaternary alluvium, including a 4 meter composite scarp and a 1 meter single event scarp, attest to recent faulting along the mountain front. Detailed topographic mapping of the scarps provides a basis for geomorphic analysis and degradation modeling. To place these active tectonic observations in a larger context, the fault and fold geometry has been assessed by completing a 12.5 km balanced cross-section. Degradation modeling results suggest the Middle Atlas Mountains are shortening at a rate of 0.03 - 0.05 mm/yr, which is lower than the geodetic estimates. This implies that shortening at a regional scale is being accommodated by an alternative mechanism such as strike-slip motion.Includes bibliographical reference
A Magnified View of the Kinematics and Morphology of RCSGA 032727-132609: Zooming in on a Merger at z=1.7
We present a detailed analysis of multi-wavelength HST/WFC3 imaging and
Keck/OSIRIS near-IR AO-assisted integral field spectroscopy for a highly
magnified lensed galaxy at z=1.70. This young starburst is representative of
UV-selected star-forming galaxies (SFG) at z~2 and contains multiple individual
star-forming regions. Due to the lensing magnification, we can resolve spatial
scales down to 100pc in the source plane of the galaxy. The velocity field
shows disturbed kinematics suggestive of an ongoing interaction, and there is a
clear signature of a tidal tail. We constrain the age, reddening, SFR and
stellar mass of the star-forming clumps from SED modelling of the WFC3
photometry and measure their H-alpha luminosity, metallicity and outflow
properties from the OSIRIS data. With strong star formation driven outflows in
four clumps, RCSGA0327 is the first high redshift SFG at stellar mass <10^10
M_sun with spatially resolved stellar winds. We compare the H-alpha
luminosities, sizes and dispersions of the star-forming regions to other high-z
clumps as well as local giant HII regions and find no evidence for increased
clump star formation surface densities in interacting systems, unlike in the
local Universe. Spatially resolved SED modelling unveils an established stellar
population at the location of the largest clump and a second mass concentration
near the edge of the system which is not detected in H-alpha emission. This
suggests a picture of an equal-mass mixed major merger, which has not triggered
a new burst of star formation or caused a tidal tail in the gas-poor component.Comment: 22 pages, 16 figures, accepted to Ap
Probing Individual Star Forming Regions Within Strongly Lensed Galaxies at z > 1
Star formation occurs on physical scales corresponding to individual star
forming regions, typically of order ~100 parsecs in size, but current
observational facilities cannot resolve these scales within field galaxies
beyond the local universe. However, the magnification from strong gravitational
lensing allows us to measure the properties of these discrete star forming
regions within galaxies in the distant universe. New results from
multi-wavelength spectroscopic studies of a sample of extremely bright, highly
magnified lensed galaxies are revealing the complexity of star formation on
sub-galaxy scales during the era of peak star formation in the universe. We
find a wide range of properties in the rest-frame UV spectra of individual
galaxies, as well as in spectra that originate from different star forming
regions within the same galaxy. Large variations in the strengths and velocity
structure of Lyman-alpha and strong P Cygni lines such as C IV, and MgII
provide new insights into the astrophysical relationships between extremely
massive stars, the elemental abundances and physical properties of the nebular
gas those stars ionize, and the galactic-scale outflows they power.Comment: 4 pages, 3 figures. To be published in the Proceedings of IAU
Symposium 309. For more details and closely related work see also
arXiv:1310.6695 and arXiv:1406.335
Cattle breeding in Northern Australia: Revealing how consumers react to new technologies
In Australia, Bos taurus cattle breeds produce high quality meat, superior in taste and tenderness characteristics. Nevertheless, these breeds do not thrive in the Northern Australian environment. Stem cell transplant techniques could improve northern beef cattle breeding programs by facilitating crossbreeding via natural service. Focus groups were used in this study to explore consumer reaction to reproduction technologies and the implications for buying intentions. Findings suggested that consumers may react negatively to unconventional breeding technologies but the degree of this aversion is contingent upon how the technology is described. These findings are relevant for preparation of choice modeling surveys.Non-market valuation, consumers, focus groups, new technologies, beef,
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