396 research outputs found
The complex interplay between tidal inertial waves and zonal flows in differentially rotating stellar and planetary convective regions:I. Free waves
Quantifying tidal interactions in close-in two-body systems is of prime
interest since they have a crucial impact on the architecture and on the
rotational history of the bodies. Various studies have shown that the
dissipation of tides in either body is very sensitive to its structure and to
its dynamics, like differential rotation which exists in the outer convective
enveloppe of solar-like stars and giant gaseous planets. In particular, tidal
waves may strongly interact with zonal flows at the so-called corotation
resonances, where the wave's Doppler-shifted frequency cancels out. We aim to
provide a deep physical understanding of the dynamics of tidal inertial waves
at corotation resonances, in the presence of differential rotation profiles
typical of low-mass stars and giant planets. By developping an inclined
shearing box, we investigate the propagation and the transmission of free
inertial waves at corotation, and more generally at critical levels, which are
singularities in the governing wave differential equation. Through the
construction of an invariant called the wave action flux, we identify different
regimes of wave transmission at critical levels, which are confirmed with a
one-dimensional three-layer numerical model. We find that inertial waves can be
either fully transmitted, strongly damped, or even amplified after crossing a
critical level. The occurrence of these regimes depends on the assumed profile
of differential rotation, on the nature as well as the latitude of the critical
level, and on wave parameters such as the inertial frequency and the
longitudinal and vertical wavenumbers. Waves can thus either deposit their
action flux to the fluid when damped at critical levels, or they can extract
action flux to the fluid when amplified at critical levels. Both situations
could lead to significant angular momentum exchange between the tidally
interacting bodies.Comment: 25 pages, 12 figures, 4 tables, accepted for publication in Astronomy
& Astrophysic
Complex dynamics for the study of neural activity in the human brain
CongrĂšs sous lâĂ©gide de la SociĂ©tĂ© Française de GĂ©nie Biologique et MĂ©dical (SFGBM).National audienceNeural mass modeling is a part of computational neuroscience that was developed to study the general behavior of interacting neuronal populations. This type of mesoscopic model is able to generate output signals that are comparable with experimental data such as electroencephalograms. Classically, neural mass models consider two interconnected populations. One interaction have been modeled in two differents ways. In this work we propose and analyze a neural mass model embedding both approaches and compare the generated time series to real data
Robust Bregman Clustering
International audienceUsing a trimming approach, we investigate a k-means type method based on Bregman divergences for clustering data possibly corrupted with clutter noise. The main interest of Bregman divergences is that the standard Lloyd algorithm adapts to these distortion measures, and they are well-suited for clustering data sampled according to mixture models from exponential families. We prove that there exists an optimal codebook, and that an empirically optimal codebook converges a.s. to an optimal codebook in the distortion sense. Moreover, we obtain the sub-Gaussian rate of convergence for k-means 1 â n under mild tail assumptions. Also, we derive a Lloyd-type algorithm with a trimming parameter that can be selected from data according to some heuristic, and present some experimental results
Optimism and the psychological recovery process among informal caregivers of inpatients suffering from depressive disorder ::a descriptive exploratory study
Narrow band selected high redshift galaxy candidates contaminated by lower redshift O[III] ultrastrong emitter line galaxies
Context. Lyman Break Galaxies (LBG) and Narrow Band (NB) surveys have been
successful at detecting large samples of high-redshift galaxies. Both methods
are subject to contamination from low-redshift interlopers. Aims. In this
paper, our aim is to investigate the nature of low-redshift interlopers in NB
Lyman- emitters (LAE) searches. Methods. From previous HAWK-I NB
imaging at z 7.7 we identify three objects that would have been selected
as high-redshift LAEs had our optical data been one magnitude shallower (but
still one to two magnitudes fainter than the near infrared data). We follow-up
these objects in spectroscopy with XSHOOTER at the VLT. Results. Despite low
quality data due to bad weather conditions, for each of the three objects we
identify one, and only one emission line, in the spectra of the objects, that
we identify as the O[III]5007A line. This result combined to spectral energy
density fitting and tests based on line ratios of several populations of
galaxies we infer that the 3 objects are ultrastrong line emitters at redshifts
1.1. Conclusions. From this work and the literature we remark that the
O[III] line appears to be a common source of contamination in high-redshift LBG
and LAE samples and we suggest that efforts be put to characterize with high
accuracy the O[III] luminosity function out to redshift 3 or higher.Comment: 7 pages, 4 figures, accepted by A&
Grxcr1 promotes hair bundle development by destabilizing the physical interaction between Harmonin and Sans usher syndrome proteins
© The Author(s), 2018. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Cell Reports 25 (2018): 1281â1291, doi:10.1016/j.celrep.2018.10.005.Morphogenesis and mechanoelectrical transduction
of the hair cell mechanoreceptor depend on the correct
assembly of Usher syndrome (USH) proteins
into highly organized macromolecular complexes.
Defects in these proteins lead to deafness and
vestibular areflexia in USH patients. Mutations in a
non-USH protein, glutaredoxin domain-containing
cysteine-rich 1 (GRXCR1), cause non-syndromic
sensorineural deafness. To understand the deglutathionylating
enzyme function of GRXCR1 in deafness,
we generated two grxcr1 zebrafish mutant
alleles. We found that hair bundles are thinner in
homozygous grxcr1 mutants, similar to the USH1
mutants ush1c (Harmonin) and ush1ga (Sans).
In vitro assays showed that glutathionylation promotes
the interaction between Ush1c and Ush1ga
and that Grxcr1 regulates mechanoreceptor development
by preventing physical interaction between
these proteins without affecting the assembly
of another USH1 protein complex, the Ush1c-
Cadherin23-Myosin7aa tripartite complex. By elucidating
the molecular mechanism through which
Grxcr1 functions, we also identify a mechanism that
dynamically regulates the formation of Usher protein
complexes.This work was supported by grants from the NIH (DC004186, OD011195, and HD22486)
Une <i>culina</i> de type « pompĂ©ien » en territoire lyonnais : lâespace culinaire de la <i>villa</i> de Goiffieux Ă Saint-Laurent-dâAgny (RhĂŽne)
International audienceThe excavations conducted on the site of Goiffieux at Saint-Laurent-dâAgny, between 2008 and 2011, brought to light a vast villa belonging to the colony of Lugdunum and occupied as soon as its foundation in the years 30-40 BC. Mainly devoted to viticulture, this establishment is equipped at the beginning of our era with private baths, associated to a small well-preserved kitchen. In this article functional equipment (hob, bench) are analysed, as well as food waste found in this area (fauna, plant remains and pottery assemblages). The kitchen is linked to water devices that we can identify to a water mill and latrines. Its masonry hob equipped with vault reserves of fuel, and fed by the adjacent praefurnium, is a characteristic of urban culinae known in Campania and there is no equivalent in the Tres Galliae rural space. It attests to a strong influence of Italic architectural patterns, which goes together with the adoption of new culinary practices.Les fouilles menĂ©es de 2008 Ă 2011 sur le site de Goiffieux, Ă Saint-Laurent-dâAgny, y ont mis au jour une vaste villa rattachĂ©e Ă la colonie de Lugdunum et occupĂ©e dĂšs sa phase de fondation, dans les annĂ©es 30-40 av. J.-C. Principalement dĂ©diĂ© Ă la viticulture, ce domaine de rendement se dote au dĂ©but de notre Ăšre de bains privĂ©s, associĂ©s Ă une petite cuisine aux vestiges bien conservĂ©s. Cet article sâintĂ©resse Ă ses amĂ©nagements fonctionnels (table Ă feu, paillasse) aussi bien quâaux reliefs alimentaires retrouvĂ©s dans cet espace (faune, carporestes et assemblages cĂ©ramiques). La cuisine est associĂ©e Ă des Ă©quipements hydrauliques, que lâon propose dâidentifier Ă un petit moulin hydraulique et Ă un espace de latrine. Sa table Ă feu maçonnĂ©e, dotĂ©e de rĂ©serves Ă combustible voĂ»tĂ©es et alimentĂ©e par le praefurnium adjacent, est caractĂ©ristique des culinae urbaines reconnues en Campanie et ne possĂšde aucun Ă©quivalent dans les campagnes des Trois Gaules. Elle tĂ©moigne dâune forte influence des modĂšles architecturaux italiques, qui va de pair avec lâadoption de nouveaux modes de prĂ©paration alimentaire
Degradation mechanism of Ti-6Al-2Sn-4Zr-2Mo-Si alloy exposed to solid NaCl deposit at high temperature
This study focuses on the corrosion behaviour of Ti-6Al-2Sn-4Zr-2Mo-Si alloy in presence of NaCl deposit in air at 560 °C. The active oxidation mechanism at the origin of the corrosion phenomenon enhancement in presence of solid NaCl is thought to be connected to the formation of both external and internal thick oxidation areas. Thermodynamic calculations allowed showing the role played by the diïŹerent alloying elements in the forma-tion of the external oxide and detailed TEM characterisations brought new insights regarding the nature and origin of the internal oxidation area
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