2,588 research outputs found
Matching methods to produce maps for pest risk analysis to resources
Decision support systems (DSSs) for pest risk mapping are invaluable for guiding pest risk analysts seeking to add maps to pest risk analyses (PRAs). Maps can help identify the area of potential establishment, the area at highest risk and the endangered area for alien plant pests. However, the production of detailed pest risk maps may require considerable time and resources and it is important to match the methods employed to the priority, time and detail required. In this paper, we apply PRATIQUE DSSs to Phytophthora austrocedrae, a pathogen of the Cupressaceae, Thaumetopoea pityocampa, the pine processionary moth, Drosophila suzukii, spotted wing Drosophila, and Thaumatotibia leucotreta, the false codling moth. We demonstrate that complex pest risk maps are not always a high priority and suggest that simple methods may be used to determine the geographic variation in relative risks posed by invasive alien species within an area of concern
Invasive alien species in the food chain : advancing risk assessment models to address climate change, economics and uncertainty
Economic globalization depends on the movement of people and goods between countries. As these exchanges increase, so does the potential for translocation of harmful pests, weeds, and pathogens capable of impacting our crops, livestock and natural resources (Hulme 2009), with concomitant impacts on global food security (Cook et al. 2011)
Commensurate lattice distortion in the layered titanium oxypnictides NaTiO ( As, Sb) determined by X-ray diffraction
We report single crystal X-ray diffraction measurements on
NaTiO ( = As, Sb) which reveal a charge superstructure that
appears below the density wave transitions previously observed in bulk data.
From symmetry-constrained structure refinements we establish that the
associated distortion mode can be described by two propagation vectors, and , with (Sb) or (As), and primarily involves in-plane displacements of the Ti atoms
perpendicular to the Ti--O bonds. The results provide direct evidence for
phonon-assisted charge density wave order in NaTiO and identify
a proximate ordered phase that could compete with superconductivity in doped
BaTiSbO
Nonexistence of conformally flat slices of the Kerr spacetime
Initial data for black hole collisions are commonly generated using the
Bowen-York approach based on conformally flat 3-geometries. The standard
(constant Boyer-Lindquist time) spatial slices of the Kerr spacetime are not
conformally flat, so that use of the Bowen-York approach is limited in dealing
with rotating holes. We investigate here whether there exist foliations of the
Kerr spacetime that are conformally flat. We limit our considerations to
foliations that are axisymmetric and that smoothly reduce in the Schwarzschild
limit to slices of constant Schwarzschild time. With these restrictions, we
show that no conformally flat slices can exist.Comment: 5 LaTeX pages; no figures; to be submitted to Phys. Rev.
Effect of high flow oxygen on mortality in chronic obstructive pulmonary disease patients in prehospital setting: randomised controlled trial
Objectives To compare standard high flow oxygen treatment with titrated oxygen treatment for patients with an acute exacerbation of chronic obstructive pulmonary disease in the prehospital setting
Understanding initial data for black hole collisions
Numerical relativity, applied to collisions of black holes, starts with
initial data for black holes already in each other's strong field. The initial
hypersurface data typically used for computation is based on mathematical
simplifying prescriptions, such as conformal flatness of the 3-geometry and
longitudinality of the extrinsic curvature. In the case of head on collisions
of equal mass holes, there is evidence that such prescriptions work reasonably
well, but it is not clear why, or whether this success is more generally valid.
Here we study these questions by considering the ``particle limit'' for head on
collisions of nonspinning holes. Einstein's equations are linearized in the
mass of the small hole, and described by a single gauge invariant spacetime
function psi, for each multipole. The resulting equations have been solved by
numerical evolution for collisions starting from various initial separations,
and the evolution is studied on a sequence of hypersurfaces. In particular, we
extract hypersurface data, that is psi and its time derivative, on surfaces of
constant background Schwarzschild time. These evolved data can then be compared
with ``prescribed'' data, evolved data can be replaced by prescribed data on
any hypersurface, and evolved further forward in time, a gauge invariant
measure of deviation from conformal flatness can be evaluated, etc. The main
findings of this study are: (i) For holes of unequal mass the use of prescribed
data on late hypersurfaces is not successful. (ii) The failure is likely due to
the inability of the prescribed data to represent the near field of the smaller
hole. (iii) The discrepancy in the extrinsic curvature is more important than
in the 3-geometry. (iv) The use of the more general conformally flat
longitudinal data does not notably improve this picture.Comment: 20 pages, REVTEX, 26 PS figures include
The close limit from a null point of view: the advanced solution
We present a characteristic algorithm for computing the perturbation of a
Schwarzschild spacetime by means of solving the Teukolsky equation. We
implement the algorithm as a characteristic evolution code and apply it to
compute the advanced solution to a black hole collision in the close
approximation. The code successfully tracks the initial burst and quasinormal
decay of a black hole perturbation through 10 orders of magnitude and tracks
the final power law decay through an additional 6 orders of magnitude.
Determination of the advanced solution, in which ingoing radiation is absorbed
by the black hole but no outgoing radiation is emitted, is the first stage of a
two stage approach to determining the retarded solution, which provides the
close approximation waveform with the physically appropriate boundary condition
of no ingoing radiation.Comment: Revised version, published in Phys. Rev. D, 34 pages, 13 figures,
RevTe
Spermatogenesis drives rapid gene creation and masculinization of the X chromosome in stalk-eyed flies (Diopsidae)
Throughout their evolutionary history, genomes acquire new genetic material that facilitates phenotypic innovation and diversification. Developmental processes associated with reproduction are particularly likely to involve novel genes. Abundant gene creation impacts the evolution of chromosomal gene content and general regulatory mechanisms such as dosage compensation. Numerous studies in model organisms have found complex and, at times contradictory, relationships among these genomic attributes highlighting the need to examine these patterns in other systems characterized by abundant sexual selection. Therefore, we examined the association among novel gene creation, tissue-specific gene expression, and chromosomal gene content within stalk-eyed flies. Flies in this family are characterized by strong sexual selection and the presence of a newly evolved X chromosome. We generated RNA-seq transcriptome data from the testes for three species within the family and from seven additional tissues in the highly dimorphic species, Teleopsis dalmanni. Analysis of dipteran gene orthology reveals dramatic testes-specific gene creation in stalk-eyed flies, involving numerous gene families that are highly conserved in other insect groups. Identification of X-linked genes for the three species indicates that the X chromosome arose prior to the diversification of the family. The most striking feature of this X chromosome is that it is highly masculinized, containing nearly twice as many testes-specific genes as expected based on its size. All the major processes that may drive differential sex chromosome gene content—creation of genes with male-specific expression, development of male-specific expression from pre-existing genes, and movement of genes with male-specific expression—are elevated on the X chromosome of T. dalmanni. This masculinization occurs despite evidence that testes expressed genes do not achieve the same levels of gene expression on the X chromosome as they do on the autosomes. © The Author 2016
Head-on collision of unequal mass black holes: close-limit predictions
The close-limit method has given approximations in excellent agreement with
those of numerical relativity for collisions of equal mass black holes. We
consider here colliding holes with unequal mass, for which numerical relativity
results are not available. We try to ask two questions: (i) Can we get
approximate answers to astrophysical questions (ideal mass ratio for energy
production, maximum recoil velocity, etc.), and (ii) can we better understand
the limitations of approximation methods. There is some success in answering
the first type of question, but more with the second, especially in connection
with the issue of measures of the intrinsic mass of the colliding holes, and of
the range of validity of the method.Comment: 19 pages, RevTeX + 9 postscript figure
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