1,228 research outputs found
Inelastic deformation during sill and laccolith emplacement: Insights from an analytic elastoplastic model
Numerous geological observations evidence that inelastic deformation occurs
during sills and laccoliths emplacement. However, most models of sill and
laccolith emplacement neglect inelastic processes by assuming purely elastic
deformation of the host rock. This assumption has never been tested, so that
the role of inelastic deformation on the growth dynamics of magma intrusions
remains poorly understood. In this paper, we introduce the first analytical
model of shallow sill and laccolith emplacement that accounts for
elasto-plastic deformation of the host rock. It considers the intrusion's
overburden as a thin elastic bending plate attached to an
elastic-perfectly-plastic foundation. We find that, for geologically realistic
values of the model parameters, the horizontal extent of the plastic zone lp is
much smaller than the radius of the intrusion a. By modeling the quasi-static
growth of a sill, we find that the ratio lp/a decreases during propagation, as
1/ \sqrt a 4 P , with P the magma overpressure. The model
also shows that the extent of the plastic zone decreases with the intrusion's
depth, while it increases if the host rock is weaker. Comparison between our
elasto-plastic model and existing purely elastic models shows that plasticity
can have a significant effect on intrusion propagation dynamics, with e.g. up
to a doubling of the overpressure necessary for the sill to grow. Our results
suggest that plasticity effects might be small for large sills, but conversely
that they might be substantial for early sill propagation.
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Fluctuating thermal environments of shallow-water rocky reefs in the Gulf of California, Mexico.
As part of a broad-scale study of the biogeography of rocky reefs in the Gulf of California, Mexico (GOC), we collected a continuous 1-yr temperature time series at ~5 m water depth at 16 sites spanning 5° of latitude and ~700 km along the western boundary of the basin. Throughout the region, thermal conditions were most variable in summer with fluctuations concentrated at diurnal and semi-diurnal frequencies, likely associated with solar and wind forcing and vertical water column oscillations forced by internal waves. Temperatures in winter were less variable than in summer, and minimum temperatures also differed among sites. Thermal variability integrated across the diurnal and semi-diurnal frequency bands was greatest near the Midriff Islands in the northern GOC and decreased toward the southern sites. Diurnal variability was greater than semi-diurnal variability at 13 of the 16 sites. A statistic-of-extremes analysis indicated shortest return times for cooling events in summer, and reef organisms at many of the sites may experience anomalous 2 to 5 °C cooling events multiple times per month. The significant extent of local temperature variability may play important roles in limiting species occurrences among sites across this biogeographic region
Molecular cavity optomechanics: a theory of plasmon-enhanced Raman scattering
The conventional explanation of plasmon-enhanced Raman scattering attributes
the enhancement to the antenna effect focusing the electromagnetic field into
sub-wavelength volumes. Here we introduce a new model that additionally
accounts for the dynamical and coherent nature of the plasmon-molecule
interaction and thereby reveals an enhancement mechanism not contemplated
before: dynamical backaction amplification of molecular vibrations. We first
map the problem onto the canonical model of cavity optomechanics, in which the
molecular vibration and the plasmon are \textit{parametrically coupled}. The
optomechanical coupling rate, from which we derive the Raman cross section, is
computed from the molecules Raman activities and the plasmonic field
distribution. When the plasmon decay rate is comparable or smaller than the
vibrational frequency and the excitation laser is blue-detuned from the plasmon
onto the vibrational sideband, the resulting delayed feedback force can lead to
efficient parametric amplification of molecular vibrations. The optomechanical
theory provides a quantitative framework for the calculation of enhanced
cross-sections, recovers known results, and enables the design of novel systems
that leverage dynamical backaction to achieve additional, mode-selective
enhancement. It yields a new understanding of plasmon-enhanced Raman scattering
and opens a route to molecular quantum optomechanics.Comment: Extensively revised and improved version thanks to the hard work and
constructive comments of a careful Referee. Includes Supplemental Materia
Heralded single phonon preparation, storage and readout in cavity optomechanics
We analyze theoretically how to use the radiation pressure coupling between a
mechanical oscillator and an optical cavity field to generate in a heralded way
a single quantum of mechanical motion (a Fock state), and release on-demand the
stored excitation as a single photon. Starting with the oscillator close to its
ground state, a laser pumping the upper motional sideband leads to dynamical
backaction amplification and to the creation of correlated photon-phonon pairs.
The detection of one Stokes photon thus projects the macroscopic oscillator
into a single-phonon Fock state. The non-classical nature of this mechanical
state can be demonstrated by applying a readout laser on the lower sideband
(i.e. optical cooling) to map the phononic state to a photonic mode, and by
performing an autocorrelation measurement on the anti-Stokes photons. We
discuss the relevance of our proposal for the future of cavity optomechanics as
an enabling quantum technology.Comment: Accepted for publication in Physical Review Letters. Added References
42,4
Extrasolar planets and brown dwarfs around A-F type stars. II. A planet found with ELODIE around the F6V star HD 33564
We present here the detection of a planet orbiting around the F6V star HD
33564. The radial velocity measurements, obtained with the ELODIE echelle
spectrograph at the Haute-Provence Observatory, show a variation with a period
of 388 days. Assuming a primary mass of 1.25 Mo, the best Keplerian fit to the
data leads to a minimum mass of 9.1 MJup for the companion.Comment: 5 pages. Final version, accepted for publication (A&A). Some Spitzer
results on HD33564 (taken this year; not yet published), finally show that
the detection of IR excess around this star (by IRAS) is spuriou
PlotXpress, a webtool for normalization and visualization of reporter expression data [version 1; peer review: 3 approved]
In molecular cell biology, reporter assays are frequently used to investigate gene expression levels. Reporter assays employ a gene that encodes a light-emitting protein, of which the luminescence is quantified as a proxy of gene expression. Commercial parties provide reporter assay kits that include protocols and specialized detection machinery. However, downstream analysis of the output data and their presentation are not standardized. We have developed plotXpress to fill this gap, providing a free, open-source platform for the semi-automated analysis and standardized visualisation of experimental gene reporter data. Users can upload raw luminescence data acquired from a reporter gene assay with an internal control. In plotXpress, the data is corrected for sample variation with the internal control and the average for each condition is calculated. When a reference condition is selected the fold change is calculated for all other conditions, based on the selected reference. The results are shown as dot plots with a statistical summary, which can be adjusted to create publication-grade plots without requiring coding skills. Altogether, plotXpress is an open-source, low-threshold, web-based tool, that promotes a standardized and reproducible analysis while providing an appealing visualization of reporter data. The webtool can be accessed at: https://huygens.science.uva.nl/PlotXpress
Extrasolar planets and brown dwarfs around A-F type stars. IV. A candidate brown dwarf around the A9V pulsating star HD180777
We present here the detection of a brown dwarf orbiting the A9V star
HD180777. The radial velocity measurements, obtained with the ELODIE echelle
spectrograph at the Haute-Provence Observatory, show a main variation with a
period of 28.4 days. Assuming a primary mass of 1.7 Mo, the best Keplerian fit
to the data leads to a minimum mass of 25 MJup for the companion (the true mass
could be significantly higher). We also show that, after substraction of the
Keplerian solution from the radial velocity measurements, the residual radial
velocities are related to phenomena intrinsic to the star, namely pulsations
with typical periods of Gamma Dor stars. These results show that in some cases,
it is possible to disentangle radial velocity variations due to a low mass
companion from variations intrinsic to the observed star.Comment: 7 pages, final version, accepted for publication (A&A
Incidence of digital papillomatosis ("hairy warts") in a dairy herd. Response to surgery and autogenous vaccination
Digital papillomatosis (hairy warts) was
diagnosed in a dairy herd with a high level
of lameness (20%). Warts ranged from
mild to moderate to severe, with severity
increasing with length of lactations. All
milking cows (100%) had at least mild
lesions. Cows with severe lesions were
more likely to be lame. Severity of lesions
had no influence on 305-day ME milk production,
days open, or somatic cell counts.
Cows in milk more than 150 days and lame
produced 3 kg less milk per day than cows
that were not lame. Almost all warts were
in the interdigital cleft near the heel of the
rear feet. A few cows had lesions in the
front of the interdigital cleft or on the front
feet. No viral particles were observed or
isolated. A new, Gram-negative, motile,
facultatively anaerobic, spiral-shaped bacteria
was isolated from one lesion. The
cellular fatty acid profile of this bacterium
had no match to any other known bacteria
in any of three computer databases examined.
Cows with severe lesions were assigned
randomly to one of four groups: Group 1:
surgical removal and autogenous vaccination;
Group 2: surgical removal only;
Group 3: autogenous vaccination only, and
Group 4: control. Neither surgical removal
nor autogenous vaccination had a significant
effect on wart severity, lameness, or
milk production when cows were
inspected 10 wk later. Contemporary
evaluation of 249 herdmates revealed a
substantial number of severely affected
cows naturally improved. Of 25 severely
affected herd contemporaries, only 8 were
severely affected 10 wk later. Evidently,
natural improvement of lesions is a common
phenomenon with “hairy warts.
Les nouvelles dispositions du Code rural sur les introductions d'espèces issues de la loi du 2 février 1995 relative au renforcement de la protection de l'environnement
Prospective evaluation of quality of life after conventional abdominal aortic aneurysm surgery
Objectives:To evaluate the changes in quality of life following conventional abdominal aortic aneurysm repair.Design:Prospective study.Materials and methods:Fifty-nine consecutive patients (50 men; nine women) in two surgical centres were investigated preoperatively, and at 6 weeks, 3 months and 6 months postoperatively. Quality of life was measured using the Short Form 36 (SF 36) questionnaire and the York Quality of Life questionnaire, from which the Rosser index was calculated.Results:Rosser index assessment showed restoration of quality of life to preoperative levels by 3 months, and significant improvement at 6 months. Changes in the SF 36 revealed significant improvement in mental health, and physical role limitation at all times postoperatively. Social function worsened at 6 weeks but improved to preoperative levels by 3 and 6 months after surgery.Conclusions:Quality of life was improved after open aortic aneurysm repair. The time course of recovery shows a predominant improvement between 6 weeks and 3 months postoperatively
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