1,097 research outputs found
Metastable Solid Solutions in the Gallium Antimonide-Germanium Pseudobinary System
Abstract unavailable
Prediction of explosive yield and other characteristics of liquid propellant rocket explosions Final report
Explosive hazards and yield predictions for liquid rocket propellant
Effects of publication bias on conservation planning
Conservation planning needs reliable information on spatial patterns of
biodiversity. However, existing data sets are skewed: some habitats, taxa, and
locations are under-represented. Here, we map geographic publication density at
the sub-national scale of individual 'provinces'. We query the Web of Science
catalogues SCI and SSCI for biodiversity-related publications including country
and province names (for the period 1993-2016). We combine these data with other
provincial-scale factors hypothesised to affect research (i.e. economic
development, human presence, infrastructure and remoteness). We show that sites
that appear to be understudied, compared with the biodiversity expected from
their bioclimatic conditions, are likely to have been inaccessible to
researchers for a diversity of reasons amongst which current or recent armed
conflicts are notable. Finally, we create a priority list of provinces where
geographic publication bias is of most concern, and discuss how our
provincial-scale model can assist in adjusting for publication biases in
conservation planning.Comment: 10 pages; 3 figures; 1 table;R code on
https://github.com/raffael-hickisch; data at
https://zenodo.org/record/998889; interactive at
http://bit.ly/publication_density_ma
Distorted Copulas: Constructions and Tail Dependence
Given a copula C, we examine under which conditions on an order isomorphism ψ of [0, 1] the distortion C ψ: [0, 1]2 → [0, 1], C ψ(x, y) = ψ{C[ψ−1(x), ψ−1(y)]} is again a copula. In particular, when the copula C is totally positive of order 2, we give a sufficient condition on ψ that ensures that any distortion of C by means of ψ is again a copula. The presented results allow us to introduce in a more flexible way families of copulas exhibiting different behavior in the tails
Population Changes and Location-Specific Differences for Otolith-Derived Age and Growth of Recreationally Harvested Spotted Seatrout (Cynoscion nebulosus) From Alabama in 2007
Spotted seatrout (Cynoscion nebulosus), is a nonmigratory game fish common in the Gulf of Mexico that is important in estuarine ecosystems. Population dynamics of spotted seatrout were examined using otolith-based age-and-growth models derived from observed and back-calculated length-at-age values. These data were used to identify sex-based differences and annular variation. Recent growth was quantified, using marginal increment analysis for comparisons between sexes and the two major bays in Alabama (Mobile Bay and Mississippi Sound). Sex ratios were also compared for these locations. Our results show that females were larger than males and that fish collected in Mobile Bay were larger than those from Mississippi Sound. Combined data from both bays resulted in a sex ratio that approached 1 : 1; however, examination of each bay individually showed that the Mississippi Sound had a female-biased population and that Mobile Bay had a male-biased population. Differences in observed length-at-age measurements became evident between males and females by age 2 with females typically larger than males, whereas the maximum age for males was greater. The oldest females were age 5 and the oldest males were age 8. Compared to previous estimates of trout growth in Alabama, results showed an increase in the modal length of fish and increased growth rates. Results suggest faster growth of the fish in the current population and decreased harvest of larger fish compared to historic estimates. This may be indicative of ecosystem-wide changes in spotted seatrout populations and highlights the need to closely monitor this population
Selective Analysis of Redox Processes at the Electrode Interface with Time-Resolved Raman Spectroscopy
Electrochemistry and electrochemical reactions are increasingly important in the transition to a sustainable chemical industry. The electron transfer that drives such reactions takes place within nanometers of the electrode surface, and follow-up chemical reactions take place within the diffusion layer. Hence, understanding electrochemical reactions requires time-, potential-, and spatially resolved analysis. The confocal nature of Raman spectroscopy provides high spatial resolution, in addition to detailed information on molecular structure. The intrinsic weakness of nonresonant Raman scattering, however, is not sensitive enough for relatively minor changes to the solution resulting from reactions at the electrode interface. Indeed, the limit of detection is typically well above the concentrations used in electrochemical studies. Here, we show that surface-enhanced Raman scattering (SERS) and resonance Raman (rR) spectroscopy allow for spatially and time-resolved analysis of solution composition at (<1-2 nm) and near (within 5 μm) the electrode surface, respectively, in a selective manner for species present at low (<1 mM) concentrations. We show changes in concentration of species at the electrode surface, without the need for labels, specific adsorption, or resonance enhancement, using a SERS-active gold electrode prepared readily by electrochemical surface roughening. A combination of smooth and roughened gold electrodes is used to distinguish between surface and resonance enhancement using the well-known redox couples ferrocene and 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS). We discuss the impact of specific adsorption on the spectral analysis with the ruthenium(II) polypyridyl complex, [Ru(bpy)3]2+. The dual function of the electrode (surface enhancement and electron transfer) in the analysis of solution processes is demonstrated with the reversible oxidation of TMA (4,N,N-trimethylaniline), where transient soluble species are identified in real time, with rapid spectral acquisition, making use of localized enhancement. We anticipate that this approach will find use in elucidating electro(catalytic) reactions at electrode interfaces.</p
Strain localization and percolation of stable structure in amorphous solids
Spontaneous strain localization occurs during mechanical tests of a model
amorphous solid simulated using molecular dynamics. The degree of localization
depends upon the extent of structural relaxation prior to mechanical testing.
In the most rapidly quenched samples higher strain rates lead to increased
localization, while the more gradually quenched samples exhibit the opposite
strain rate dependence. This transition coincides with the k-core percolation
of atoms with quasi-crystal-like short range order. The authors infer the
existence of a related microstructural length scale.Comment: 4 pages, 4 figure
Identifying stellar streams in the 1st RAVE public data release
We searched for and detected stellar streams or moving groups in the solar
neighbourhood, using the data provided by the 1st RAVE public data release.
This analysis is based on distances to RAVE stars estimated from a
color-magnitude relation that was calibrated on Hipparcos stars. Our final
sample consists of 7015 stars selected to be within 500 pc of the Sun and to
have distance errors better than 25%. Together with radial velocities from RAVE
and proper motions from various data bases, there are estimates for all 6
phase-space coordinates of the stars in the sample. We characterize the orbits
of these stars through suitable proxies for their angular momentum and
eccentricity, and compare the observed distribution to the expectations from a
smooth distribution. On this basis we identify at least four "phase space
overdensities" of stars on very similar orbits in the Solar neighbourhood. We
estimate the statistical significance of these overdensities by Monte Carlo
simulations. Three of them have been identified previously: the Sirius and
Hercules moving group and a stream found independently in 2006 by Arifyanto and
Fuchs and Helmi et al. In addition, we have found a new stream candidate on a
quite radial orbit, suggesting an origin external to the Milky Way's disk.
Also, there is evidence for the Arcturus stream and the Hyades-Pleiades moving
group in the sample. This analysis, using only a minute fraction of the final
RAVE data set, shows the power of this experiment to probe the phase-space
substructure of stars around the Sun.Comment: accepted for publication in Ap
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