6,749 research outputs found
Actual and potential distribution of an invasive canola pest, Meligethes viridescens (Coleoptera: Nitidulidae), in Canada
Meligethes viridescens (Fabricius), bronzed or rape blossom beetle, is a widespread and common pest of oilseed rape [Brassica napus L. and Brassica rapa L. (Brassicaceae)] in the western Palaearctic subregion. The establishment of M. viridescens in eastern North America has raised concern that its presence is a potential risk to the Canadian canola industry, especially to the prairie ecozone of western Canada where up to 4 million ha of summer canola (B. napus and B. rapa) are grown annually. Study of museum specimens indicated that M. viridescens was first recorded in Nova Scotia in 1947. Field surveys indicated that, as of 2001, M. viridescens was established as far west as Saint-Hyacinthe, Quebec. A CLIMEXTM model for M. viridescens in Europe was developed and validated with actual distribution records. In Canada the model predicted that once introduced, M. viridescens would readily survive in the canola-growing areas. The actual distribution of M. viridescens in eastern Canada matched the predicted distribution well. The westward dispersal to and establishment of M. viridescens in canola-growing areas of Ontario and western Canada, particularly southern Manitoba, appear to be inevitable. Establishment in these areas presents the risk of substantial production losses to canola producer
First experimental evidence of one-dimensional plasma modes in superconducting thin wires
We have studied niobium superconducting thin wires deposited onto a
SrTiO substrate. By measuring the reflection coefficient of the wires,
resonances are observed in the superconducting state in the 130 MHz to 4 GHz
range. They are interpreted as standing wave resonances of one-dimensional
plasma modes propagating along the superconducting wire. The experimental
dispersion law, versus , presents a linear dependence over the
entire wave vector range. The modes are softened as the temperature increases
close the superconducting transition temperature. Very good agreement are
observed between our data and the dispersion relation predicted by Kulik and
Mooij and Sch\"on.Comment: Submitted to Physical review Letter
Uniform in bandwidth exact rates for a class of kernel estimators
Given an i.i.d sample , taking values in \RRR^{d'}\times \RRR^d,
we consider a collection Nadarya-Watson kernel estimators of the conditional
expectations \EEE(+d_g(z)\mid Z=z), where belongs to a
compact set H\subset \RRR^d, a Borel function on \RRR^{d'} and
are continuous functions on \RRR^d. Given two
bandwidth sequences h_n<\wth_n fulfilling mild conditions, we obtain an exact
and explicit almost sure limit bounds for the deviations of these estimators
around their expectations, uniformly in g\in\GG,\;z\in H and h_n\le h\le
\wth_n under mild conditions on the density , the class \GG, the kernel
and the functions . We apply this result to prove
that smoothed empirical likelihood can be used to build confidence intervals
for conditional probabilities \PPP(Y\in C\mid Z=z), that hold uniformly in
z\in H,\; C\in \CC,\; h\in [h_n,\wth_n]. Here \CC is a Vapnik-Chervonenkis
class of sets.Comment: Published in the Annals of the Institute of Statistical Mathematics
Volume 63, p. 1077-1102 (2011
Barite encrustation of benthic sulfur-oxidizing bacteria at a marine cold seep
Crusts and chimneys composed of authigenic barite are found at methane seeps and hydrothermal vents that expel fluids rich in barium. Microbial processes have not previously been associated with barite precipitation in marine cold seep settings. Here, we report on the precipitation of barite on filaments of sulfide-oxidizing bacteria at a brine seep in the Gulf of Mexico. Barite-mineralized bacterial filaments in the interiors of authigenic barite crusts resemble filamentous sulfide-oxidizing bacteria of the genus Beggiatoa. Clone library and iTag amplicon sequencing of the 16S rRNA gene show that the barite crusts that host these filaments also preserve DNA of Candidatus Maribeggiatoa, as well as sulfate-reducing bacteria. Isotopic analyses show that the sulfur and oxygen isotope compositions of barite have lower δ34S and δ18O values than many other marine barite crusts, which is consistent with barite precipitation in an environment in which sulfide oxidation was occurring. Laboratory experiments employing isolates of sulfide-oxidizing bacteria from Gulf of Mexico seep sediments showed that under low sulfate conditions, such as those encountered in brine fluids, sulfate generated by sulfide-oxidizing bacteria fosters rapid barite precipitation localized on cell biomass, leading to the encrustation of bacteria in a manner reminiscent of our observations of barite-mineralized Beggiatoa in the Gulf of Mexico. The precipitation of barite directly on filaments of sulfide-oxidizing bacteria, and not on other benthic substrates, suggests that sulfide oxidation plays a role in barite formation at certain marine brine seeps where sulfide is oxidized to sulfate in contact with barium-rich fluids, either prior to, or during, the mixing of those fluids with sulfate-containing seawater in the vicinity of the sediment/water interface. As with many other geochemical interfaces that foster mineral precipitation, both biological and abiological processes likely contribute to the precipitation of barite at marine brine seeps such as the one studied here
Itinerancy and Hidden Order in
We argue that key characteristics of the enigmatic transition at in indicate that the hidden order is a density wave formed within
a band of composite quasiparticles, whose detailed structure is determined by
local physics. We expand on our proposal (with J.A. Mydosh) of the hidden order
as incommnesurate orbital antiferromagnetism and present experimental
predictions to test our ideas. We then turn towards a microscopic description
of orbital antiferromagnetism, exploring possible particle-hole pairings within
the context of a simple one-band model. We end with a discussion of recent
high-field and thermal transport experiment, and discuss their implications for
the nature of the hidden order.Comment: 18 pages, 7 figures. v2 contains added referenc
Resonant X-Ray Scattering from URu_{2}Si_{2}
Based on a localized crystal electric field model for the U^{4+} in the
(5f)^2-configuration, we analyze the resonant x-ray scattering spectra around U
M_{IV} and M_{V} edges in URu_{2}Si_{2}, taking full Coulomb and spin-orbit
interactions into account. We consider two level schemes, a singlet model of
Santini and Amoretti and a doublet model of Ohkawa and Shimizu, and assume the
antiferroquadrupolar order and the antiferromagnetic order as candidates for
the ambient pressure phase and the high pressure phase. It is found that the
spectral shapes as a function of photon energy are independent of the assumed
level scheme, but are quite different between the antiferroquadrupole and
antiferromagnetic phases, This may be useful to determine the character of the
ordered phase.Comment: 8 pages, 5 figures, submitted to JPS
Neural processing of criticism and positive comments from relatives in individuals with schizotypal personality traits
Objectives. High negative expressed emotion by family members towards schizophrenia patients increases the risk of subsequent relapse. The study aimed to determine whether individuals with high schizotypy (HS) and low schizotypy (LS) would differ in activation of brain areas involved in cognitive control when listening to relative criticism
Fluctuation Conductivity in Insulator-Superconductor Transitions with Dissipation
We analyze here the fluctuation conductivity in the vicinity of the critical
point in a 2D Josephson junction array shunted by an Ohmic resistor.We find
that at the Gaussian level, the conductivity acquires a logarithmic dependence
on when the dissipation is sufficiently small. In the renormalized
classical regime, this logarithmic dependence gives rise to a leveling-off of
the resistivity at low to intermediate temperatures when fluctuations are
included. We show, however, that this trend does not persist to T=0 at which
point the resistivity vanishes. The possible relationship of the leveling of
the resistivity to the low temperature transport in granlar superconductors is
discussed.Comment: 4 page
Transients Among Binaries with Evolved Low-Mass Companions
We show that stable disk accretion should be very rare among low-mass X-ray
binaries and cataclysmic variables whose evolution is driven by the nuclear
expansion of the secondary star on the first giant branch. Stable accretion is
confined to neutron-star systems where the secondary is still relatively
massive, and some supersoft white dwarf accretors. All other systems, including
all black-hole systems, appear as soft X-ray transients or dwarf novae. All
long-period neutron-star systems become transient well before most of the
envelope mass is transferred, and remain transient until envelope exhaustion.
This complicates attempts to compare the numbers of millisecond pulsars in the
Galactic disk with their LMXB progenitors, and also means that the pulsar spin
rates are fixed in systems which are transient rather than steady, contrary to
common assumption. The long-period persistent sources Sco X-2, LMC X-2, Cyg X-2
and V395 Car must have minimum companion masses > 0.75 Msun if they contain
neutron stars, and still larger masses if they contain black holes. The
companion in the neutron-star transient GRO J1744-2844 must have a mass <0.87
Msun. The existence of any steady sources at all at long periods supports the
ideas that (a) the accretion disks in many, if not all, LMXBs are strongly
irradiated by the central source, and (b) mass transfer is thermally unstable
in long-period supersoft X-ray sources.Comment: 10 pages, Latex, 1 ps figure, Ap.J., accepted Feb. 15, 199
The Calar Alto lunar occultation program: update and new results
We present an update of the lunar occultation program which is routinely
carried out in the near-IR at the Calar Alto Observatory. A total of 350 events
were recorded since our last report (Fors et al. 2004). In the course of eight
runs we have observed, among others, late-type giants, T-Tauri stars, and
infrared sources. Noteworthy was a passage of the Moon close to the galactic
center, which produced a large number of events during just a few hours in July
2004. Results include the determinations of the angular diameter of RZ Ari, and
the projected separations and brightness ratios for one triple and 13 binary
stars, almost all of which representing first time detections. Projected
separations range from 0.09arcsec to 0.007arcsec. We provide a quantitative
analysis of the performance achieved in our observations in terms of angular
resolution and sensitivity, which reach about 0.003arcsec and K~8.5mag,
respectively. We also present a statistical discussion of our sample, and in
particular of the frequency of detection of binaries among field stars.Comment: 8 pages, 2 figures. Accepted for publication in A&
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