1,501 research outputs found
Functional data analysis of multi-species abundance and occupancy data sets
Multi-species indicators are widely used to condense large, complex amounts of information on multiple separate species by forming a single index to inform research, policy and management. Much detail is typically lost when such indices are constructed. Here we investigate the potential of Functional Data Analysis, focussing upon Functional Principal ComponentAnalysis (FPCA), which can be easily carried out using standard R programs, as a tool for displaying features of the underlying information. Illustrations are provided using data from the UK Butterflies for the New Millennium and UK Butterfly Monitoring Scheme databases. The FPCAs conducted result in a huge simplification in terms of dimensional reduction, allowing species occupancy and abundance to be reduced to two and three dimensions, respectively. We show that a functional principal component arises for both occupancy and abundance analyses that distinguishes between species that increase or decrease over time, and that it differs from percentage trend, which is a simplification of complex temporal changes. We find differences in species patterns of occupancy and abundance, providing a warning against routinely combining both types of index within multi-species indicators, for example when using occupancy as a proxy for abundance when sufficient abundance data are not available. By identifying the differences between species, figures displaying functional principal component scores are much more informative than the simple bar plots of percentages of significant trends that often accompany multi-species indicators. Informed by the outcomes of the FPCA, we make recommendations for accompanying visualisations for multi-species indicators, and discuss how these are likely to be context and audience specific. We show that, in the absence of FPCA, using mean species occupancy and total abundance can provide additional, accessible information to complement species-level trends. At the simplest level, we suggest using jitter plots to display variation in species-level trends. We recommend the routine augmentation of multi-species indicators in the future with additional statistical procedures and figures, to serve as an aid to improve communication and understanding of biodiversity metrics, as well as reveal potentially hidden patterns of behaviourand guide additional directions for investigation
Utilizing Ionic Liquids to Enable the Future of Closed-Loop Life Support Technology
Current oxygen recovery technology onboard the International Space Station only recovers approximately 50% of the oxygen from metabolic carbon dioxide, thus requiring resupply mass in order to sustain life onboard. Future long duration manned missions will require maximum oxygen recovery in order to reduce resupply mass. Complete recovery of oxygen can be achieved through Bosch technology. The challenge with this technology is that the solid carbon produced during the process results in undesired catalyst resupply mass. Although there have been several approaches to solve this challenge, in order to totally eliminate the need for resupply only one potential process has been identified. This process is a fully-regenerable Ionic Liquid (IL)-based Bosch system that employs in situ resources. In 2016, efforts were made that proved the feasibility of an IL-based Bosch system. ILs were used to electroplate iron onto a copper substrate and to regenerate the iron by extracting the iron from the copper substrate and product carbon. In 2017, efforts were initiated to scale the proposed technology. Here we report the results of those efforts as well as an IL-based Bosch system concept and basic reactor design
Discovery of the Millisecond X-Ray Pulsar HETE J1900.1-2455
We report the discovery of millisecond pulsations from the low-mass X-ray
binary HETE J1900.1-2455 which was discovered by the detection of a type I
X-ray burst by the High Energy Transient Explorer 2 (HETE-2). The neutron star
emits coherent pulsations at 377.3 Hz and is in an 83.3 minute circular orbit
with a companion with a mass greater than 0.016 solar masses and likely less
than 0.07 solar masses. The companion star's Roche lobe could be filled by a
brown dwarf with no need for heating or non-standard evolution. During one
interval with an unusually high X-ray flux, the source produced quasiperiodic
oscillations with a single peak at 883 Hz and on subsequent days, the
pulsations were suppressed. We consider the distribution of spin versus orbital
period in neutron star low-mass X-ray binaries.Comment: 8 pages, to appear in Ap
Trends and indicators for quantifying moth abundance and occupancy in Scotland
Moths form an important part of Scotlandâs biodiversity and an up-to-date assessment of their status is needed given their value as a diverse and species-rich taxon, with various ecosystem roles, and the known decline of moths within Britain. We use long-term citizen-science data to produce species-level trends and multi-species indicators for moths in Scotland, to assess population (abundance) and distribution (occupancy) changes.
Abundance trends for moths in Scotland are produced using Rothamsted Insect Survey count data, and, for the first time, occupancy models are used to estimate occupancy trends for moths in Scotland, using opportunistic records from the National Moth Recording Scheme. Species-level trends are combined to produce abundance and occupancy indicators. The associated uncertainty is estimated using a parametric bootstrap approach, and comparisons are made with alternative published approaches.
Overall moth abundance (based on 176 species) in Scotland decreased by 20% for 1975-2014 and by 46% for 1990-2014. The occupancy indicator, based on 230 species, showed a 16% increase for 1990-2014. Alternative methods produced similar indicators and conclusions, suggesting robustness of the results, although rare species may be under-represented in our analyses. Species abundance and occupancy trends were not clearly correlated; in particular species with negative population trends showed varied occupancy responses. Further research into the drivers of moth population changes is required, but increasing occupancy is likely to be driven by a warming summer climate facilitating range expansion, whereas population declines may be driven by reductions in habitat quality, changes in land management practices and warmer, wetter winters
Developmental origin underlies evolutionary rate variation across the placental skull
The placental skull has evolved into myriad forms, from longirostrine whales to globular primates, and with a diverse array of appendages from antlers to tusks. This disparity has recently been studied from the perspective of the whole skull, but the skull is composed of numerous elements that have distinct developmental origins and varied functions. Here, we assess the evolution of the skull's major skeletal elements, decomposed into 17 individual regions. Using a high-dimensional morphometric approach for a dataset of 322 living and extinct eutherians (placental mammals and their stem relatives), we quantify patterns of variation and estimate phylogenetic, allometric and ecological signal across the skull. We further compare rates of evolution across ecological categories and ordinal-level clades and reconstruct rates of evolution along lineages and through time to assess whether developmental origin or function discriminate the evolutionary trajectories of individual cranial elements. Our results demonstrate distinct macroevolutionary patterns across cranial elements that reflect the ecological adaptations of major clades. Elements derived from neural crest show the fastest rates of evolution, but ecological signal is equally pronounced in bones derived from neural crest and paraxial mesoderm, suggesting that developmental origin may influence evolutionary tempo, but not capacity for specialisation. This article is part of the theme issue 'The mammalian skull: development, structure and function'
Developmental origin underlies evolutionary rate variation across the placental skull
The placental skull has evolved into myriad forms, from longirostrine whales to globular primates, and with a diverse array of appendages from antlers to tusks. This disparity has recently been studied from the perspective of the whole skull, but the skull is composed of numerous elements that have distinct developmental origins and varied functions. Here, we assess the evolution of the skull's major skeletal elements, decomposed into 17 individual regions. Using a high-dimensional morphometric approach for a dataset of 322 living and extinct eutherians (placental mammals and their stem relatives), we quantify patterns of variation and estimate phylogenetic, allometric and ecological signal across the skull. We further compare rates of evolution across ecological categories and ordinal-level clades and reconstruct rates of evolution along lineages and through time to assess whether developmental origin or function discriminate the evolutionary trajectories of individual cranial elements. Our results demonstrate distinct macroevolutionary patterns across cranial elements that reflect the ecological adaptations of major clades. Elements derived from neural crest show the fastest rates of evolution, but ecological signal is equally pronounced in bones derived from neural crest and paraxial mesoderm, suggesting that developmental origin may influence evolutionary tempo, but not capacity for specialisation. This article is part of the theme issue 'The mammalian skull: development, structure and function'
Investigating High-Energy Proton-Induced Reactions on Spherical Nuclei: Implications for the Pre-Equilibrium Exciton Model
A number of accelerator-based isotope production facilities utilize 100- to
200-MeV proton beams due to the high production rates enabled by high-intensity
beam capabilities and the greater diversity of isotope production brought on by
the long range of high-energy protons. However, nuclear reaction modeling at
these energies can be challenging because of the interplay between different
reaction modes and a lack of existing guiding cross section data. A Tri-lab
collaboration has been formed among the Lawrence Berkeley, Los Alamos, and
Brookhaven National Laboratories to address these complexities by
characterizing charged-particle nuclear reactions relevant to the production of
established and novel radioisotopes. In the inaugural collaboration
experiments, stacked-targets of niobium foils were irradiated at the Brookhaven
Linac Isotope Producer (E=200 MeV) and the Los Alamos Isotope Production
Facility (E=100 MeV) to measure Nb(p,x) cross sections between 50
and 200 MeV. The measured cross-section results were compared with literature
data as well as the default calculations of the nuclear model codes TALYS, CoH,
EMPIRE, and ALICE. We developed a standardized procedure that determines the
reaction model parameters that best reproduce the most prominent reaction
channels in a physically justifiable manner. The primary focus of the procedure
was to determine the best parametrization for the pre-equilibrium two-component
exciton model. This modeling study revealed a trend toward a relative decrease
for internal transition rates at intermediate proton energies (E=20-60 MeV)
in the current exciton model as compared to the default values. The results of
this work are instrumental for the planning, execution, and analysis essential
to isotope production.Comment: 37 pages, 62 figures. Revised version, published in Physical Review
Transgressing the moral economy: Wheelerism and management of the nationalised coal industry in Scotland
This article illuminates the links between managerial style and political economy in post-1945 Britain, and explores the origins of the 1984â1985 miners' strike, by examining in longer historical context the abrasive attitudes and policies of Albert Wheeler, Scottish Area Director of the National Coal Board (NCB). Wheeler built on an earlier emphasis on production and economic criteria, and his micro-management reflected pre-existing centralising tendencies in the industries. But he was innovative in one crucial aspect, transgressing the moral economy of the Scottish coalfield, which emphasised the value of economic security and changes by joint industrial agreement
Search for Millisecond Periodicities in Type I X-ray Bursts of the Rapid Burster
We have searched the rising portion of type I X-ray bursts observed from the
Rapid Burster with the Rossi X-ray Timing Explorer for the presence of
periodicities. The 95 per cent confidence upper limit on the average
root-mean-square variation of near coherent pulsations with a width of <1 Hz
(in 60--2048 Hz) during the first second of the bursts is <8.8 per cent. We
find a possible detection (>98 per cent significance) at 306.5 Hz.Comment: Submitted to MNRAS. 7 pages, 2 figures; uses mn.sty and psfi
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