4,443 research outputs found
Willingness to pay for environmental attributes of non-food agricultural products: a real choice experiment
This paper investigates consumers’ willingness to pay (WTP) a price premium for two environmental attributes of a non-food agricultural product. We study individual preferences for roses associated with an eco-label and a carbon footprint using an economic experiment combining discrete choice questions and real economic incentives involving real purchases of roses against cash. The data are analyzed with a mixed logit model and reveal significant premiums for both environmental attributes of the product.WILLINGNESS TO PAY;ENVIRONMENTAL ATTRIBUTES;NON-FOOD PRODUCT;REAL CHOICE EXPERIMENT;MIXED LOGIT
Early fall and late winter diets of migratory caribou in northwest Alaska
Lichens are the primary winter forage for large herds of migratory caribou (Rangifer tarandus). Caribou select for lichens more than they are available across the landscape and they generally avoid, during winter, habitat that has been burned by wildfires for decades while lichen abundance recovers. However, the relative importance of lichens in the diet is subject to debate. From 2010-2013, we conducted one of the largest microhistological studies of the early fall (58 samples from 1 site) and late winter (338 samples from 58 sites) diets of barren-ground caribou. Lichens conÂstituted ~ 71% of the late winter diets of caribou in northwest Alaska, whereas moss (11%) and shrubs (9%) were the next most common forage items. Early fall diets were very similar to late winter, perhaps because deciduous vegetation is senescent during both periods. Diets of males, non-pregnant females and pregnant females were not significantly different. Pregnancy was not associated with the abundance of any forage type during winter but was associated with higher physiological stress. This result was expected as fall body condition dictates conception, caribou are ‘capital’ breeders, and gestation can be energetically demanding. Caribou that migrated south (i.e., wintered south of 67.1°N) had lower levels of nutritional stress, higher levels of lichen in the diet, and lower levels of moss and shrubs compared to caribou that did not migrate south. Future investigations into the potential connection between lichen abundance in the winter diet and survivorship, as well as linking the late summer diets of individuals to their reproductive success, should be undertaken
Multi-Locus Estimates of Population Structure and Migration in a Fence Lizard Hybrid Zone
A hybrid zone between two species of lizards in the genus Sceloporus (S. cowlesi and S. tristichus) on the Mogollon Rim in Arizona provides a unique opportunity to study the processes of lineage divergence and merging. This hybrid zone involves complex interactions between 2 morphologically and ecologically divergent subspecies, 3 chromosomal groups, and 4 mitochondrial DNA (mtDNA) clades. The spatial patterns of divergence between morphology, chromosomes and mtDNA are discordant, and determining which of these character types (if any) reflects the underlying population-level lineages that are of interest has remained impeded by character conflict. The focus of this study is to estimate the number of populations interacting in the hybrid zone using multi-locus nuclear data, and to then estimate the migration rates and divergence time between the inferred populations. Multi-locus estimates of population structure and gene flow were obtained from 12 anonymous nuclear loci sequenced for 93 specimens of Sceloporus. Population structure estimates support two populations, and this result is robust to changes to the prior probability distribution used in the Bayesian analysis and the use of spatially-explicit or non-spatial models. A coalescent analysis of population divergence suggests that gene flow is high between the two populations, and that the timing of divergence is restricted to the Pleistocene. The hybrid zone is more accurately described as involving two populations belonging to S. tristichus, and the presence of S. cowlesi mtDNA haplotypes in the hybrid zone is an anomaly resulting from mitochondrial introgression
Communication: Truncated non-bonded potentials can yield unphysical behavior in molecular dynamics simulations of interfaces
Non-bonded potentials are included in most force fields and therefore widely
used in classical molecular dynamics simulations of materials and interfacial
phenomena. It is commonplace to truncate these potentials for computational
efficiency based on the assumption that errors are negligible for reasonable
cutoffs or compensated for by adjusting other interaction parameters. Arising
from a metadynamics study of the wetting transition of water on a solid
substrate, we find that the influence of the cutoff is unexpectedly strong and
can change the character of the wetting transition from continuous to first
order by creating artificial metastable wetting states. Common cutoff
corrections such as the use of a force switching function, a shifted potential,
or a shifted force do not avoid this. Such a qualitative difference urges
caution and suggests that using truncated non-bonded potentials can induce
unphysical behavior that cannot be fully accounted for by adjusting other
interaction parameters
Sequence of a putative Vitis vinifera PR-1
Research Note
Blow-Up of Test Fields Near Cauchy Horizons
The behaviour of test fields near a compact Cauchy horizon is investigated.
It is shown that solutions of nonlinear wave equations on Taub spacetime with
generic initial data cannot be continued smoothly to both extensions of the
spacetime through the Cauchy horizon. This is proved using an energy method.
Similar results are obtained for the spacetimes of Moncrief containing a
compact Cauchy horizon and for more general matter models.Comment: 10 pages, Plain TeX, MPA-AR-92-
Effective temperatures of a heated Brownian particle
We investigate various possible definitions of an effective temperature for a
particularly simple nonequilibrium stationary system, namely a heated Brownian
particle suspended in a fluid. The effective temperature based on the
fluctuation dissipation ratio depends on the time scale under consideration, so
that a simple Langevin description of the heated particle is impossible. The
short and long time limits of this effective temperature are shown to be
consistent with the temperatures estimated from the kinetic energy and Einstein
relation, respectively. The fluctuation theorem provides still another
definition of the temperature, which is shown to coincide with the short time
value of the fluctuation dissipation ratio
Variation of sperm length and heteromorphism in drosophilid species
International audienc
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