261 research outputs found
Melting and Dimensionality of the Vortex Lattice in Underdoped YBa2Cu3O6.60
Muon spin rotation measurements of the magnetic field distribution in the
vortex state of the oxygen deficient high-Tc superconductor YBa{2}Cu{3}O{6.60}
reveal a vortex-lattice melting transition at much lower temperature than that
in the fully oxygenated material. The transition is best described by a model
in which adjacent layers of ``pancake'' vortices decouple in the liquid phase.
Evidence is also found for a pinning-induced crossover from a solid 3D to
quasi-2D vortex lattice, similar to that observed in the highly anisotropic
superconductor Bi{2+x}Sr{2-x}CaCu{2}O{8+y}.Comment: 8 pages, 4 figures, 5 postscript file
The response of nematodes to deep-sea CO2 sequestration : a quantile regression approach
Author Posting. © The Author(s), 2010. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Deep Sea Research Part I: Oceanographic Research Papers 57 (2010): 696-707, doi:10.1016/j.dsr.2010.03.003.One proposed approach to ameliorate the effects of global warming is sequestration of
the greenhouse gas CO2 in the deep sea. To evaluate the environmental impact of this
approach, we exposed the sediment-dwelling fauna at the mouth of the Monterey
Submarine Canyon (3262 m) and a site on the nearby continental rise (3607 m) to CO2-
rich water. We measured meiobenthic nematode population and community metrics
after ~30-day exposures along a distance gradient from the CO2 source and with
sediment depth to infer the patterns of mortality. We also compared the nematode
response with that of harpacticoid copepods. Nematode abundance, average sediment
depth, tail-group composition, and length: width ratio did not vary with distance from
the CO2 source. However, quantile regression showed that nematode length and
diameter increased in close proximity to the CO2 source in both experiments. Further,
the effects of CO2 exposure and sediment depth (nematodes became more slender at
one site, but larger at the other, with increasing depth in the sediment) varied with body
size. For example, the response of the longest nematodes differed from those of
average length. We propose that nematode body length and diameter increases were
induced by lethal exposure to CO2-rich water and that nematodes experienced a high
rate of mortality in both experiments. In contrast, copepods experienced high mortality
rates in only one experiment suggesting that CO2 sequestration effects are taxon
specific.The Department of Energy
Office of Biological and Environmental Research supported this research under award
numbers DEâFG02â05ER64070 and DEâFG03â01ER63065 and the U.S. Department of
Energy, Fossil Energy Group (award DEâFC26â00NT40929). We also appreciate
significant support provided by the Monterey Bay Aquarium Research Institute (project
200002)
BICCO-Net II. Final report to the Biological Impacts of Climate Change Observation Network (BICCO-Net) Steering Group
âą BICCO-Net Phase II presents the most comprehensive single assessment of climate change impacts on UK biodiversity to date.
âą The results provide a valuable resource for the CCRA 2018, future LWEC report cards, the National Adaptation Programme and other policy-relevant initiatives linked to climate change impacts on biodiversity
Impacts of climate change on national biodiversity population trends
Climate change has had well-documented impacts on the distribution and phenology of species across many taxa, but impacts on speciesâ abundance, which relates closely to extinction risk and ecosystem function, have not been assessed across taxa. In the most comprehensive multi-taxa comparison to date, we modelled variation in national population indices of 501 mammal, bird, aphid, butterfly and moth species as a function of annual variation in weather variables, which through time allowed us to identify a component of speciesâ population growth that can be associated with post-1970s climate trends. We found evidence that these climate trends have significantly affected population trends of 15.8% of species, including eight with extreme (> 30% decline per decade) negative trends consistent with detrimental impacts of climate change. The modelled effect of climate change could explain 48% of the significant across-species population decline in moths and 63% of the population increase in winged aphids. The other taxa did not have significant across-species population trends or consistent climate change responses. Population declines in species of conservation concern were linked to both climatic and non-climatic factors respectively accounting for 42 and 58% of the decline. Evident differential impacts of climate change between trophic levels may signal the potential for future ecosystem disruption. Climate change has therefore already driven large-scale population changes of some species, had significant impacts on the overall abundance of some key invertebrate groups and may already have altered biological communities and ecosystems in Great Britain
A new approach to modelling the relationship between annual population abundance indices and weather data
Weather has often been associated with fluctuations in population sizes of species; however, it can be difficult to estimate the effects satisfactorily because population size is naturally measured by annual abundance indices whilst weather varies on much shorter timescales. We describe a novel method for estimating the effects of a temporal sequence of a weather variable (such as mean temperatures from successive months) on annual species abundance indices. The model we use has a separate regression coefficient for each covariate in the temporal sequence, and over-fitting is avoided by constraining the regression coefficients to lie on a curve defined by a small number of parameters. The constrained curve is the product of a periodic function, reflecting assumptions that associations with weather will vary smoothly throughout the year and tend to be repetitive across years, and an exponentially decaying term, reflecting an assumption that the weather from the most recent year will tend to have the greatest effect on the current population and that the effect of weather in previous years tends to diminish as the time lag increases. We have used this approach to model 501 species abundance indices from Great Britain and present detailed results for two contrasting species alongside an overall impression of the results across all species. We believe this approach provides an important advance to the challenge of robustly modelling relationships between weather and species population size
Cosmological distance indicators
We review three distance measurement techniques beyond the local universe:
(1) gravitational lens time delays, (2) baryon acoustic oscillation (BAO), and
(3) HI intensity mapping. We describe the principles and theory behind each
method, the ingredients needed for measuring such distances, the current
observational results, and future prospects. Time delays from strongly lensed
quasars currently provide constraints on with < 4% uncertainty, and with
1% within reach from ongoing surveys and efforts. Recent exciting discoveries
of strongly lensed supernovae hold great promise for time-delay cosmography.
BAO features have been detected in redshift surveys up to z <~ 0.8 with
galaxies and z ~ 2 with Ly- forest, providing precise distance
measurements and with < 2% uncertainty in flat CDM. Future BAO
surveys will probe the distance scale with percent-level precision. HI
intensity mapping has great potential to map BAO distances at z ~ 0.8 and
beyond with precisions of a few percent. The next years ahead will be exciting
as various cosmological probes reach 1% uncertainty in determining , to
assess the current tension in measurements that could indicate new
physics.Comment: Review article accepted for publication in Space Science Reviews
(Springer), 45 pages, 10 figures. Chapter of a special collection resulting
from the May 2016 ISSI-BJ workshop on Astronomical Distance Determination in
the Space Ag
Impacto da adubação orgĂąnica sobre a incidĂȘncia de tripes em cebola.
Analisou-se a relação entre adubação orgĂąnica e a incidĂȘncia de Thrips tabaci Lind. em cebola (Allium cepa L), na EE de Ituporanga,entre agosto e dezembro de 1998. Os tratamentos foram determinados de acordo com a necessidade de N para a cultura pela anĂĄlise de solo. Empregou-se como fonte orgĂąnica diversos adubos fornecendo 75 Kg/ha de N (esterco suĂno; adubo Barriga Verde proveniente de esterco de aves; composto orgĂąnico; esterco de peru; hĂșmus); 37,5 Kg/ha de N (metade da dose normal com esterco de suĂno); as testemunhas foram adubação mineral fornecendo 30-120-60 kg/ha de N-P2O5-K2O e o dobro da dose (60-240-120 kg/ha de N-P2O5-K2O); e testemunha sem adubação. Nenhum tratamento apresentou incidĂȘncia de T. tabaci superior Ă testemunha sem adubo. A adubação mineral em relação Ă orgĂąnica nĂŁo favoreceu significativamente a incidĂȘncia de T. tabaci . O processo de conversĂŁo do manejo do solo da ĂĄrea experimental de convencional para orgĂąnico pode ter
favorecido a infestação similar do inseto entre tratamentos. No perĂodo de maior incidĂȘncia de T. tabaci, a relação com nutrientes foi descrita por um modelo envolvendo K/Zn, B e N de maneira positiva. A correlação entre nutrientes e T. tabaci nĂŁo foi linear na maioria
das avaliaçÔes. A adubação orgĂąnica pode substituir a adubação mineral na cultura da cebola, pois foi possĂvel atingir nĂveis de produtividade similares para ambos tratamentos
Supervisors' Perceptions of the Performance of Cooperative Education Employees Working in Federal Agencies
Through cooperative education programs, many public agencies employ college students part time or intermittently and groom them for future full-time employment The combination of winnowing and nurturing that occurs in these programs is believed to produce higher performing employees This study tests this hypothesis by comparing Federal supervisors' perceptions of the performance of co-op employees with those recruited from other sources Data come from the 1992 Merit Principles Survey, US Merit Systems Protection Board The results indicate that co-op employees perform at high levels, but they do not outperform other employees as a whole Next, we compare the performance ratings of Federal workers from seven other recruitment sources to see if any source is superior Some interesting findings emerge Of course, performance ratings are an incomplete indicator of an employee's value to the organization These ratings merely reflect supervisors' perceptions, and while high performance is important, agencies may wish to promote other goals in their recruitment and retention efforts such as workforce diversityYeshttps://us.sagepub.com/en-us/nam/manuscript-submission-guideline
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How do i know who you think you are? A review of research methods on organizational identity
The notion of organizational identity was introduced in management studies in 1985. In the following 25 years, a vibrant debate about how to conceptualize organizational identities and related themes (multiple identities, identity change, interrelations between identity, image and culture) does not seem to have corresponded to explicit reflections about specific methodological issues. In this paper, the authors inductively review research methods adopted by studies of organizational identity published in top-level journals, with the purpose of deriving insights about the current status of research practices, uncovering their often tacit ontological and epistemological assumptions, and stimulating discussion about their possible evolution
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