411 research outputs found
Relaxation Tribometry: A Generic Method to Identify the Nature of Contact Forces
Recent years have witnessed the development of so-called relaxation
tribometers, the free oscillation of which is altered by the presence of
frictional stresses within the contact. So far, analysis of such oscillations
has been restricted to the shape of their decaying envelope, to identify in
particular solid or viscous friction components. Here, we present a more
general expression of the forces possibly acting within the contact , and
retain six possible, physically relevant terms. Two of them, which had never
been proposed in the context of relaxation tribometry, only affect the
oscillation frequency, not the amplitude of the signal. We demonstrate that
each of those six terms has a unique signature in the time-evolution of the
oscillation, which allows efficient identification of their respective weights
in any experimental signal. We illustrate our methodology on a PDMS
sphere/glass plate torsional contact
Non-conservative evolution in Algols: where is the matter?
There is gathering indirect evidence suggesting non-conservative evolutions
in Algols. However, the systemic mass-loss rate is poorly constrained by
observations and generally set as a free parameter in binary-star evolution
simulations. Moreover, systemic mass loss may lead to observational signatures
that are still to be found. We investigate the impact of the outflowing gas and
the possible presence of dust grains on the spectral energy distribution (SED).
We used the 1D plasma code Cloudy and compared the results with the 3D
Monte-Carlo radiative transfer code Skirt for dusty simulations. The
circumbinary mass-distribution and binary parameters are computed with
state-of-the-art binary calculations done with the Binstar evolution code. The
outflowing material reduces the continuum flux-level of the stellar SED in the
optical and UV. Due to the time-dependence of this effect, it may help to
distinguish between different ejection mechanisms. Dust, if present, leads to
observable infrared excesses even with low dust-to-gas ratios and traces the
cold material at large distances from the star. By searching for such dust
emission in the WISE catalogue, we found a small number of Algols showing
infrared excesses, among which the two rather surprising objects SX Aur and CZ
Vel. We find that some binary B[e] stars show the same strong Balmer continuum
as we predict with our models. However, direct evidence of systemic mass loss
is probably not observable in genuine Algols, since these systems no longer
eject mass through the hotspot mechanism. Furthermore, owing to its high
velocity, the outflowing material dissipates in a few hundred years. If hot
enough, the hotspot may produce highly ionised species such as SiIV and
observable characteristics that are typical of W Ser systems.Comment: Accepted for piblications in A&A; 21 pages, 19 figure
Augmenter le nombre de plurilingues en Union européenne en créant des itinéraires différents pour y parvenir : l'expérience de la Belgique
La problématique du plurilinguisme est centrale en Union européenne. Pourtant les systèmes d'enseignement ont peu évolué pour s'adapter aux besoins. Apparaissent toutefois ici et là des dispositifs plus originaux pour répondre aux attentes plurilingues ET aux profils des apprenants. Cet article vise à en faire un état en Belgique en accordant une attention particulière à la filière immersive et en tentant de lister les avantages et inconvénients de chacun d'eux.The problematic of plurilingualism is central in the European Union. Yet education systems have evolved little to fit the needs. But here and there appear more original devices to meet plurilingual expectations AND learner profiles. This article aims to make a review of a state in Belgium, paying particular attention to the immersive sector and trying to list the advantages and disadvantages of each of them.La problemática del plurilingüismo es clave en la Unión Europea. Sin embargo, los sistemas de enseñanza han evolucionado poco para adaptarse a las necesidades. Con todo, aparecen aquí y allá dispositivos más originales para responder a las expectativas plurilingües Y a los perfiles de los discentes. Este artículo se propone presentar un estado de la cuestión de dichos dispositivos en Bélgica con especial atención al itinerario de inmersión e intentando dar cuenta de las ventajas e inconvenientes de cada uno de ellos
Enolases: Storage compounds in seeds? Evidence from a proteomic comparison of zygotic and somatic embryos of Cyclamen persicum Mill
Somatic embryogenesis is well established for the economic relevant ornamental crop Cyclamen and thus could supplement the elaborate propagation via seeds. However, the use of somatic embryogenesis for commercial large scale propagation is still limited due to physiological disorders and asynchronous development within emerged embryos. To overcome these problems, profound knowledge of the physiological processes in Cyclamen embryogenesis is essential. Thus, the proteomes of somatic and zygotic embryos were characterised in a comparative approach. Protein separation via two dimensional IEF-SDS PAGE led to a resolution of more than 1,000 protein spots/gel. Overall, 246 proteins were of differential abundance in the two tissues compared. Mass spectrometry analysis of the 300 most abundant protein spots resulted in the identification of 247 proteins, which represent 90 distinct protein species. Fifty-five percent of the 247 proteins belong to only three physiological categories: glycolysis, protein folding and stress response. The latter physiological process was especially predominant in the somatic embryos. Remarkably, the glycolytic enzyme enolase was the protein most frequently detected and thus is supposed to play an important role in Cyclamen embryogenesis. Data are presented that indicate involvement of "small enolases" as storage proteins in Cyclamen. A digital reference map was established via a novel software tool for the web-based presentation of proteome data linked to KEGG and ExPasy protein-databases and both were made publicly available online. © 2011 Springer Science+Business Media B.V
Regional differences of physical activity and sedentary behaviour in Swiss children are not explained by socio-demographics or the built environment
Objective We evaluated whether regional differences in
physical activity (PA) and sedentary behaviour (SB) existed along language boundaries within Switzerland and
whether potential differences would be explained by sociodemographics or environmental characteristics.
Methods We combined data of 611 children aged 4 to 7
years from four regional studies. PA and SB were assessed
by accelerometers. Information about the socio-demographic background was obtained by questionnaires.
Objective neighbourhood attributes could be linked to
home addresses. Multivariate regression models were used
to test associations between PA and SB and socio-demographic characteristics and neighbourhood attributes.
Results Children from the German compared to the
French-speaking region were more physically active and
less sedentary (by 10–15 %, p\0.01). Although Germanspeaking children lived in a more favourable environment
and a higher socioeconomic neighbourhood (differences
p\0.001), these characteristics did not explain the differences in PA behaviour between French and German
speaking.
Conclusions Factors related to the language region,
which might be culturally rooted were among the strongest
correlates of PA and SB among Swiss children, independent of individual, social and environmental factors
Multiscale Finite-Difference-Diffusion-Monte-Carlo Method for Simulating Dendritic Solidification
We present a novel hybrid computational method to simulate accurately
dendritic solidification in the low undercooling limit where the dendrite tip
radius is one or more orders of magnitude smaller than the characteristic
spatial scale of variation of the surrounding thermal or solutal diffusion
field. The first key feature of this method is an efficient multiscale
diffusion Monte-Carlo (DMC) algorithm which allows off-lattice random walkers
to take longer and concomitantly rarer steps with increasing distance away from
the solid-liquid interface. As a result, the computational cost of evolving the
large scale diffusion field becomes insignificant when compared to that of
calculating the interface evolution. The second key feature is that random
walks are only permitted outside of a thin liquid layer surrounding the
interface. Inside this layer and in the solid, the diffusion equation is solved
using a standard finite-difference algorithm that is interfaced with the DMC
algorithm using the local conservation law for the diffusing quantity. Here we
combine this algorithm with a previously developed phase-field formulation of
the interface dynamics and demonstrate that it can accurately simulate
three-dimensional dendritic growth in a previously unreachable range of low
undercoolings that is of direct experimental relevance.Comment: RevTeX, 16 pages, 10 eps figures, submitted to J. Comp. Phy
Early manganese-toxicity response in Vigna unguiculata L. - A proteomic and transcriptomic study
The apoplast is known to play a predominant role in the expression of manganese (Mn) toxicity in cowpea (Vigna unguiculata L.) leaves. To unravel early Mn-toxicity responses after 1-3 days Mn treatment also in the leaf symplast, we studied the symplastic reactions induced by Mn in two cultivars differing in Mn tolerance on a total cellular level. Comparative proteome analyses of plants exposed to low or high Mn allowed to identify proteins specifically affected by Mn, particularly in the Mn-sensitive cowpea cultivar. These proteins are involved in CO2 fixation, stabilization of the Mn cluster of the photosystem II, pathogenesis-response reactions and protein degradation. Chloroplastic proteins important for CO2 fixation and photosynthesis were of lower abundance upon Mn stress suggesting scavenging of metabolic energy for a specific stress response. Transcriptome analyses supported these findings, but additionally revealed an upregulation of genes involved in signal transduction only in the Mn-sensitive cultivar. In conclusion, a coordinated interplay of apoplastic and symplastic reactions seems to be important during the Mn-stress response in cowpea. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA
Multiscale Random-Walk Algorithm for Simulating Interfacial Pattern Formation
We present a novel computational method to simulate accurately a wide range
of interfacial patterns whose growth is limited by a large scale diffusion
field. To illustrate the computational power of this method, we demonstrate
that it can be used to simulate three-dimensional dendritic growth in a
previously unreachable range of low undercoolings that is of direct
experimental relevance.Comment: 4 pages RevTex, 6 eps figures; substantial changes in presentation,
but results and conclusions remain the sam
Wingless-related integration site (WNT) signaling is activated during the inflammatory response upon cardiac surgery: A translational study
ObjectiveCardiac surgery and the use of cardiopulmonary bypass initiate a systemic inflammatory response. Wingless-related integration site (WNT) signaling is part of the innate immunity and has been attributed a major role in the regulation of inflammation. In preclinical research, WNT-5a may sustain an inflammatory response and cause endothelial dysfunction. Our aim was to investigate WNT signaling after cardiac surgery and its association with postoperative inflammation (Clinicaltrials.gov, NCT04058496).MethodsIn this prospective, single-center, observational study, 64 consecutive patients for coronary artery bypass grafting (CABG) ± valve surgery were assigned into three groups: off-pump CABG (n = 28), on-pump CABG (n = 16) and combined valve-CABG surgery (n = 20). Blood samples were acquired before surgery, at intensive care unit (ICU) admission and 4, 8, and 48 h thereafter. Plasma concentrations of WNT-5a and its antagonists Secreted frizzled-related protein 1 (sFRP-1), Secreted frizzled-related protein 5 (sFRP-5), and WNT inhibitory factor 1 (WIF-1) were determined by enzyme-linked immunosorbent assay. In addition, plasma concentrations of six inflammatory cytokines were measured by multiplex immunoassay. Parameters were analyzed for evolution of plasma concentration over time, interactions, intergroup differences, and association with clinical outcome parameters.ResultsAt baseline, WNT-5a, sFRP-1, and WIF-1 were present in a minimal concentration, while sFRP-5 was elevated. A higher baseline value of WNT-5a, sFRP-5, and WIF-1 resulted in higher subsequent values of the respective parameter. At ICU admission, WNT-5a and sFRP-5 reached their maximum and minimum value, respectively. WIF-1 decreased over time and was lowest 8 h after surgery. sFRP-1 changed minimally over time. While WNT-5a returned to the baseline within 48 h, sFRP-5 and WIF-1 did not reach their baseline value at 48 h. Of the investigated WNT system components, only WIF-1 partially reflected the severity of surgery. WNT-5a and WIF-1 had an impact on postoperative fluid balance and noradrenaline requirement.ConclusionWNT-5a, sFRP-5, and WIF-1 are part of the systemic inflammatory response after cardiac surgery. WNT-5a peaks immediately after cardiac surgery and returns to baseline within 48 h, presumably modulated by its antagonist sFRP-5. Based on this translational study, WNT-5a antagonism may be further investigated to assess potentially beneficial effects in patients with a dysregulated inflammation after cardiac surgery
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