32,068 research outputs found
Impact of ICARDA Research on Australian Agriculture
Research and Development/Tech Change/Emerging Technologies,
Decoupling of morphological disparity and taxic diversity during the adaptive radiation of anomodont therapsids
Adaptive radiations are central to macroevolutionary theory. Whether triggered by acquisition of new traits or ecological opportunities arising from mass extinctions, it is debated whether adaptive radiations are marked by initial expansion of taxic diversity or of morphological disparity (the range of anatomical form). If a group rediversifies following a mass extinction, it is said to have passed through a macroevolutionary bottleneck, and the loss of taxic or phylogenetic diversity may limit the amount of morphological novelty that it can subsequently generate. Anomodont therapsids, a diverse clade of Permian and Triassic herbivorous tetrapods, passed through a bottleneck during the end-Permian mass extinction. Their taxic diversity increased during the Permian, declined significantly at the Permo–Triassic boundary and rebounded during the Middle Triassic before the clade's final extinction at the end of the Triassic. By sharp contrast, disparity declined steadily during most of anomodont history. Our results highlight three main aspects of adaptive radiations: (i) diversity and disparity are generally decoupled; (ii) models of radiations following mass extinctions may differ from those triggered by other causes (e.g. trait acquisition); and (iii) the bottleneck caused by a mass extinction means that a clade can emerge lacking its original potential for generating morphological variety
Diffuse Gamma Rays: Galactic and Extragalactic Diffuse Emission
"Diffuse" gamma rays consist of several components: truly diffuse emission
from the interstellar medium, the extragalactic background, whose origin is not
firmly established yet, and the contribution from unresolved and faint Galactic
point sources. One approach to unravel these components is to study the diffuse
emission from the interstellar medium, which traces the interactions of high
energy particles with interstellar gas and radiation fields. Because of its
origin such emission is potentially able to reveal much about the sources and
propagation of cosmic rays. The extragalactic background, if reliably
determined, can be used in cosmological and blazar studies. Studying the
derived "average" spectrum of faint Galactic sources may be able to give a clue
to the nature of the emitting objects.Comment: 32 pages, 28 figures, kapproc.cls. Chapter to the book "Cosmic
Gamma-Ray Sources," to be published by Kluwer ASSL Series, Edited by K. S.
Cheng and G. E. Romero. More details can be found at
http://www.gamma.mpe-garching.mpg.de/~aws/aws.htm
On the unification of dwarf and giant elliptical galaxies
The near orthogonal distributions of dwarf elliptical (dE) and giant
elliptical (E) galaxies in the mu_e-Mag and mu_e-log(R_e) diagrams have been
interpreted as evidence for two distinct galaxy formation processes. However,
continuous, linear relationships across the alleged dE/E boundary at M_B = -18
mag - such as those between central surface brightness (mu_0) and (i) galaxy
magnitude and (ii) light-profile shape (n) - suggest a similar, governing
formation mechanism. Here we explain how these latter two linear trends
necessitate a different behavior for dE and E galaxies, exactly as observed, in
diagrams involving mu_e (and also _e). A natural consequence is that the
distribution of dEs and Es in Fundamental Plane type analyses that use the
associated intensity I_e, or _e, are expected to appear different. Together
with other linear trends across the alleged dE/E boundary, such as those
between luminosity and color, metallicity, and velocity dispersion, it appears
that the dEs form a continuous extension to the E galaxies. The presence of
partially depleted cores in luminous (M_B < -20.5 mag) Es does however signify
the action of a different physical process at the centers (< ~300 pc) of these
galaxies.Comment: 5 pages from the proceedings of the 2004 conference "Penetrating bars
through masks of cosmic dust: the Hubble tuning fork strikes a new note".
Edited by D. L. Block, I. Puerari, K. C. Freeman, R. Groess, and E. K. Bloc
Optimization Under Uncertainty Using the Generalized Inverse Distribution Function
A framework for robust optimization under uncertainty based on the use of the
generalized inverse distribution function (GIDF), also called quantile
function, is here proposed. Compared to more classical approaches that rely on
the usage of statistical moments as deterministic attributes that define the
objectives of the optimization process, the inverse cumulative distribution
function allows for the use of all the possible information available in the
probabilistic domain. Furthermore, the use of a quantile based approach leads
naturally to a multi-objective methodology which allows an a-posteriori
selection of the candidate design based on risk/opportunity criteria defined by
the designer. Finally, the error on the estimation of the objectives due to the
resolution of the GIDF will be proven to be quantifiableComment: 20 pages, 25 figure
Interval Selection in the Streaming Model
A set of intervals is independent when the intervals are pairwise disjoint.
In the interval selection problem we are given a set of intervals
and we want to find an independent subset of intervals of largest cardinality.
Let denote the cardinality of an optimal solution. We
discuss the estimation of in the streaming model, where we
only have one-time, sequential access to the input intervals, the endpoints of
the intervals lie in , and the amount of the memory is
constrained.
For intervals of different sizes, we provide an algorithm in the data stream
model that computes an estimate of that, with
probability at least , satisfies . For same-length
intervals, we provide another algorithm in the data stream model that computes
an estimate of that, with probability at
least , satisfies . The space used by our algorithms is bounded
by a polynomial in and . We also show that no better
estimations can be achieved using bits of storage.
We also develop new, approximate solutions to the interval selection problem,
where we want to report a feasible solution, that use
space. Our algorithms for the interval selection problem match the optimal
results by Emek, Halld{\'o}rsson and Ros{\'e}n [Space-Constrained Interval
Selection, ICALP 2012], but are much simpler.Comment: Minor correction
Flexible non-parametric tests of sample exchangeability and feature independence
In scientific studies involving analyses of multivariate data, two questions
often arise for the researcher. First, is the sample exchangeable, meaning that
the joint distribution of the sample is invariant to the ordering of the units?
Second, are the features independent of one another, or can the features be
grouped so that the groups are mutually independent? We propose a
non-parametric approach that addresses these two questions. Our approach is
conceptually simple, yet fast and flexible. It controls the Type I error across
realistic scenarios, and handles data of arbitrary dimensions by leveraging
large-sample asymptotics. In the exchangeability detection setting, through
extensive simulations and a comparison against unsupervised tests of
stratification based on random matrix theory, we find that our approach
compares favorably in various scenarios of interest. We apply our method to
problems in population and statistical genetics, including stratification
detection and linkage disequilibrium splitting. We also consider other
application domains, applying our approach to post-clustering single-cell
chromatin accessibility data and World Values Survey data, where we show how
users can partition features into independent groups, which helps generate new
scientific hypotheses about the features.Comment: Main Text: 25 pages Supplementary Material: 39 page
Simultaneous determination of wave speed and arrival time of reflected waves using the pressure-velocity loop
This is the post print version of the article. The official published version can be found at the link below.In a previous paper we demonstrated that the linear portion of the pressure–velocity loop (PU-loop) corresponding to early systole could be used to calculate the local wave speed. In this paper we extend this work to show that determination of the time at which the PU-loop first deviates from linearity provides a convenient way to determine the arrival time of reflected waves (Tr). We also present a new technique using the PU-loop that allows for the determination of wave speed and Tr simultaneously. We measured pressure and flow in elastic tubes of different diameters, where a strong reflection site existed at known distances away form the measurement site. We also measured pressure and flow in the ascending aorta of 11 anaesthetised dogs where a strong reflection site was produced through total arterial occlusion at four different sites. Wave speed was determined from the initial slope of the PU-loop and Tr was determined using a new algorithm that detects the sampling point at which the initial linear part of the PU-loop deviates from linearity. The results of the new technique for detecting Tr were comparable to those determined using the foot-to-foot and wave intensity analysis methods. In elastic tubes Tr detected using the new algorithm was almost identical to that detected using wave intensity analysis and foot-to-foot methods with a maximum difference of 2%. Tr detected using the PU-loop in vivo highly correlated with that detected using wave intensity analysis (r 2 = 0.83, P < 0.001). We conclude that the new technique described in this paper offers a convenient and objective method for detecting Tr, and allows for the dynamic determination of wave speed and Tr, simultaneously
Towards a Robuster Interpretive Parsing
The input data to grammar learning algorithms often consist of overt forms that do not contain full structural descriptions. This lack of information may contribute to the failure of learning. Past work on Optimality Theory introduced Robust Interpretive Parsing (RIP) as a partial solution to this problem. We generalize RIP and suggest replacing the winner candidate with a weighted mean violation of the potential winner candidates. A Boltzmann distribution is introduced on the winner set, and the distribution’s parameter is gradually decreased. Finally, we show that GRIP, the Generalized Robust Interpretive Parsing Algorithm significantly improves the learning success rate in a model with standard constraints for metrical stress assignment
Does Microsoft Academic find early citations?
This is an accepted manuscript of an article published by Springer in Scientometrics on 27/10/2017, available online: https://doi.org/10.1007/s11192-017-2558-9
The accepted version of the publication may differ from the final published version.This article investigates whether Microsoft Academic can use its web search component to identify early citations to recently published articles to help solve the problem of delays in research evaluations caused by the need to wait for citation counts to accrue. The results for 44,398 articles in Nature, Science and seven library and information science journals 1996-2017 show that Microsoft Academic and Scopus citation counts are similar for all years, with no early citation advantage for either. In contrast, Mendeley reader counts are substantially higher for more recent articles. Thus, Microsoft Academic appears to be broadly like Scopus for citation count data, and is apparently not more able to take advantage of online preprints to find early citations
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