5,906 research outputs found
Nesting Common Eider (Somateria mollissima) Population Quintuples in Northwest Greenland
Common eider (Somateria mollissima) populations in Greenland severely declined throughout the 20th century. As a result, in 2001, harvest regulations were changed and the length of the hunting season was reduced. Recent data suggest that these changes have been successful, and population regrowth is occurring. In the Avanersuaq District, northwest Greenland, only one systematic survey quantifying the number of nesting eiders had previously been conducted, in 1997 and 1998. Although this district had historically been identified as having the largest number of breeding eiders in Greenland, the 1997â98 survey results showed a relatively small estimated population of 5000 pairs. However, it is not known to what extent changes in hunting regulations have affected nesting abundance in this area. Therefore, the Avanersuaq District was systematically resurveyed during the 2009 breeding season, approximately 11 years after the previous survey. These results showed that the population had increased to 5.4 times its 1997â98 size, with an annual compounded growth rate of 15.3%. On a single island, nearly 4500 active nests were observed. Five islands had more than 2600 nests each and comprised 75% of the total nests counted. Along with historical information to account for additional nesting habitat not surveyed, the observed population growth rate from this study suggests that the overall Avanersuaq common eider breeding population size ranges from 25 000 to 30 000 pairs, or roughly half of the total estimated West Greenland breeding population. Despite the significance of the Avanersuaq District as a breeding area for common eiders, we have only limited information about this population. The effects of recent extensions of the hunting season on this population are also unknown, and the only wintering location information is based on a few individuals banded in the 1920s and 1940s. Additional research on migratory movements is suggested before any further changes are made to hunting regulations.Au cours du XXe siĂšcle, les populations dâeiders Ă duvet (Somateria mollissima) ont connu un dĂ©clin considĂ©rable au Groenland. Câest pourquoi en 2001, le rĂšglement relatif Ă la chasse a Ă©tĂ© modifiĂ© et la saison de chasse a Ă©tĂ© raccourcie. Selon des donnĂ©es rĂ©centes, ces changements ont portĂ© fruits en ce sens que la population sâest accrue. Dans le district dâAvanersuaq, dans le nord-ouest du Groenland, seulement un relevĂ© systĂ©matique ayant pour but de quantifier le nombre dâeiders nicheurs a Ă©tĂ© fait, et câĂ©tait en 1997-1998. Bien quâau fil des ans, ce district a comptĂ© le plus grand nombre dâeiders reproducteurs du Groenland, le relevĂ© de 1997-1998 avait Ă©tabli que la population Ă©tait relativement petite, avec une estimation de 5 000 paires. On ne sait toutefois pas dans quelle mesure la modification du rĂšglement sur la chasse a eu des effets sur lâabondance dâeiders nichant dans la rĂ©gion. Par consĂ©quent, le district dâAvarsuaq a systĂ©matiquement fait lâobjet dâun autre relevĂ© pendant la saison de reproduction de 2009, soit environ 11 ans aprĂšs le relevĂ© dâorigine. Les rĂ©sultats ont permis de constater que la population sâĂ©tait accrue dans une mesure de 5,4 fois par rapport Ă sa taille de 1997-1998, ce qui correspondait Ă un taux dâaccroissement annuel composĂ© de 15,3 %. Sur une seule Ăźle, prĂšs de 4 500 nids actifs ont Ă©tĂ© observĂ©s. Cinq Ăźles comptaient plus de 2 600 nids par Ăźle, ce qui reprĂ©sentait 75 % du nombre total de nids rĂ©pertoriĂ©s. JumelĂ© aux donnĂ©es historiques tenant compte de lâhabitat de nidification supplĂ©mentaire et non relevĂ©, le taux dâaccroissement de la population observĂ© Ă partir de cette Ă©tude suggĂšre que la taille de la population globale dâeiders Ă duvet nicheurs dâAvanersuaq varie de 25 000 Ă 30 000 paires, ce qui correspond Ă environ la moitiĂ© du total estimĂ© de la population nicheuse de lâouest du Groenland. MalgrĂ© lâimportance que revĂȘt le district dâAvanersuaq comme aire de reproduction de lâeider Ă duvet, nous ne possĂ©dons que des renseignements restreints au sujet de cette population. Les effets quâaura le prolongement rĂ©cent de la saison de chasse sur cette population sont Ă©galement inconnus, et la seule information concernant la localisation de lâaire dâhivernage dont nous disposons a trait Ă quelques individus qui avaient Ă©tĂ© baguĂ©s dans les annĂ©es 1920 et 1940. Par consĂ©quent, il est suggĂ©rĂ© de pousser les recherches relatives aux mouvements migratoires plus loin avant dâapporter dâautres changements au rĂšglement de chasse
Ecological Effects of Fear: How Spatiotemporal Heterogeneity in Predation Risk Influences Mule Deer Access to Forage in a SkyâIsland System
Forage availability and predation risk interact to affect habitat use of ungulates across many biomes. Within skyâisland habitats of the Mojave Desert, increased availability of diverse forage and cover may provide ungulates with unique opportunities to extend nutrient uptake and/or to mitigate predation risk. We addressed whether habitat use and foraging patterns of female mule deer (Odocoileus hemionus) responded to normalized difference vegetation index (NDVI), NDVI rate of change (greenâup), or the occurrence of cougars (Puma concolor). Female mule deer used available greenâup primarily in spring, although growing vegetation was available during other seasons. Mule deer and cougar shared similar habitat all year, and our models indicated cougars had a consistent, negative effect on mule deer access to growing vegetation, particularly in summer when cougar occurrence became concentrated at higher elevations. A seemingly late parturition date coincided with diminishing NDVI during the lactation period. Skyâisland populations, rarely studied, provide the opportunity to determine how mule deer respond to growing foliage along steep elevation and vegetation gradients when trapped with their predators and seasonally limited by aridity. Our findings indicate that fear of predation may restrict access to the forage resources found in sky islands
Topical decolonization does not eradicate the skin microbiota of community-dwelling or hospitalized adults
Topical antimicrobials are often employed for decolonization and infection prevention and may alter the endogenous microbiota of the skin. The objective of this study was to compare the microbial communities and levels of richness and diversity in community-dwelling subjects and intensive care unit (ICU) patients before and after the use of topical decolonization protocols. We enrolled 15 adults at risk for Staphylococcus aureus infection. Community subjects (n = 8) underwent a 5-day decolonization protocol (twice daily intranasal mupirocin and daily dilute bleach-water baths), and ICU patients (n = 7) received daily chlorhexidine baths. Swab samples were collected from 5 anatomic sites immediately before and again after decolonization. A variety of culture media and incubation environments were used to recover bacteria and fungi; isolates were identified using matrix-assisted laser desorption ionizationâtime of flight mass spectrometry. Overall, 174 unique organisms were recovered. Unique communities of organisms were recovered from the community-dwelling and hospitalized cohorts. In the community-dwelling cohort, microbial richness and diversity did not differ significantly between collections across time points, although the number of body sites colonized with S. aureus decreased significantly over time (P = 0.004). Within the hospitalized cohort, richness and diversity decreased over time compared to those for the enrollment sampling (from enrollment to final sampling, P = 0.01 for both richness and diversity). Topical antimicrobials reduced the burden of S. aureus while preserving other components of the skin and nasal microbiota
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A Comparison of Isoconversional and Model-Fitting Approaches to Kinetic Parameter Estimation and Application Predictions
Chemical kinetic modeling has been used for many years in process optimization, estimating real-time material performance, and lifetime prediction. Chemists have tended towards developing detailed mechanistic models, while engineers have tended towards global or lumped models. Many, if not most, applications use global models by necessity, since it is impractical or impossible to develop a rigorous mechanistic model. Model fitting acquired a bad name in the thermal analysis community after that community realized a decade after other disciplines that deriving kinetic parameters for an assumed model from a single heating rate produced unreliable and sometimes nonsensical results. In its place, advanced isoconversional methods (1), which have their roots in the Friedman (2) and Ozawa-Flynn-Wall (3) methods of the 1960s, have become increasingly popular. In fact, as pointed out by the ICTAC kinetics project in 2000 (4), valid kinetic parameters can be derived by both isoconversional and model fitting methods as long as a diverse set of thermal histories are used to derive the kinetic parameters. The current paper extends the understanding from that project to give a better appreciation of the strengths and weaknesses of isoconversional and model-fitting approaches. Examples are given from a variety of sources, including the former and current ICTAC round-robin exercises, data sets for materials of interest, and simulated data sets
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Analysis of Samples for the ICTAC Lifetime-Prediction Round-Robin Exercise
Derivation of chemical kinetic models for prediction of material and component lifetimes is of broad interest and value. This work analyzes data that was distributed to me, among others, by the International Confederation for Thermal Analysis and Calorimetry (ICTAC) as part of a blind study of kinetic analysis. The results from this report will be combined with results from other parties to create a broader comparison of kinetic analysis methods. In addition to the eight ICTAC data sets, which appear to contain one set of simulated data, presumably for ground truth comparison, I created an additional simulated data set to compare the reliability of isoconversional and model-fitting approaches. It is usually possible to fit the data well with both isoconversional and model fitting approaches, although the isoconversional method is usually faster and provides better fits to the data, particularly for complex reaction profiles. The two methods often, but not always, give similar predictions. Predictions of the isoconversional model will fail to the extent that the reaction contains competitive or crossing-concurrent reaction characteristics. Model fitting will either do better or worse depending on how well the derived model includes the appropriate characteristics, and the probability of deriving a good model depends both on the sophistication of the modeling software and the skill of the analyst
Continental-scale patterns of pathogen prevalence: a case study on the corncrake
Pathogen infections can represent a substantial threat to wild populations, especially those already limited in size. To determine how much variation in the pathogens observed among fragmented populations is caused by ecological factors, one needs to examine systems where host genetic diversity is consistent among the populations, thus controlling for any potentially confounding genetic effects. Here, we report geographic variation in haemosporidian infection among European populations of corncrake. This species now occurs in fragmented populations, but there is little genetic structure and equally high levels of genetic diversity among these populations. We observed a longitudinal gradient of prevalence from western to Eastern Europe negatively correlated with national agricultural yield, but positively correlated with corncrake census population sizes when only the most widespread lineage is considered. This likely reveals a possible impact of local agriculture intensity, which reduced host population densities in Western Europe and, potentially, insect vector abundance, thus reducing the transmission of pathogens. We conclude that in the corncrake system, where metapopulation dynamics resulted in variations in local census population sizes, but not in the genetic impoverishment of these populations, anthropogenic activity has led to a reduction in host populations and pathogen prevalence
Characterizing Entanglement Sources
We discuss how to characterize entanglement sources with finite sets of
measurements. The measurements do not have to be tomographically complete, and
may consist of POVMs rather than von Neumann measurements. Our method yields a
probability that the source generates an entangled state as well as estimates
of any desired calculable entanglement measures, including their error bars. We
apply two criteria, namely Akaike's information criterion and the Bayesian
information criterion, to compare and assess different models (with different
numbers of parameters) describing entanglement-generating devices. We discuss
differences between standard entanglement-verificaton methods and our present
method of characterizing an entanglement source.Comment: This submission, together with the next one, supersedes
arXiv:0806.416
Comparison of the acceptability of various oil shale processes
Abstract While oil shale has the potential to provide a substantial fraction of our nation's liquid fuels for many decades, cost and environmental acceptability are significant issues to be addressed. Lawrence Livermore National Laboratory (LLNL) examined a variety of oil shale processes between the mid 1960s and the mid 1990s, starting with retorting of rubble chimneys created from nuclear explosion
Probability Models for Degree Distributions of Protein Interaction Networks
The degree distribution of many biological and technological networks has
been described as a power-law distribution. While the degree distribution does
not capture all aspects of a network, it has often been suggested that its
functional form contains important clues as to underlying evolutionary
processes that have shaped the network. Generally, the functional form for the
degree distribution has been determined in an ad-hoc fashion, with clear
power-law like behaviour often only extending over a limited range of
connectivities. Here we apply formal model selection techniques to decide which
probability distribution best describes the degree distributions of protein
interaction networks. Contrary to previous studies this well defined approach
suggests that the degree distribution of many molecular networks is often
better described by distributions other than the popular power-law
distribution. This, in turn, suggests that simple, if elegant, models may not
necessarily help in the quantitative understanding of complex biological
processes.
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