Durée d’utilisation des équipements dans l’industrie manufacturière . Résultats de l’enquête 2007.

La Durée d’utilisation des équipements (DUE) productifs de l’industrie augmente en 2007; le travail posté progresse et la durée du travail s’allonge. Les entreprises éprouvent certaines difficultés pour ajuster leur DUE notamment à cause du manque de main d’oeuvre qualifiée.Production, capacité, productivité du capital, demande de travail.

Biofilms in porous media: development of macroscopic transport equations via volume averaging with closure for local mass equilibrium conditions

In this work, we upscale a pore-scale description of mass transport in a porous medium containing biofilm to develop the relevant Darcy-scale equations. We begin with the pore-scale descriptions of mass transport, interphase mass transfer, and biologically-mediated reactions; these processes are then upscaled using the method of volume averaging to obtain the macroscale mass balance equations. We focus on the case of local mass equilibrium conditions where the averaged concentrations in the fluid and biological phases can be assumed to be proportional and for which a one-equation macroscopic model may be developed. We predict the effective dispersion tensor by a closure scheme that is solved for the cases of both simple and complex unit cells. The domain of validity of the approach is clearly identified, both theoretically and numerically, and unitless groupings indicating the domain of validity are reported

Contribution of increasing plasma membrane to the energetic cost of early zebrafish embryogenesis

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Rodenfels, J., Sartori, P., Golfier, S., Nagendra, K., Neugebauer, K. M., & Howard, J. Contribution of increasing plasma membrane to the energetic cost of early zebrafish embryogenesis. Molecular Biology of the Cell, 31(7), (2020): 520-526, doi:10.1091/mbc.E19-09-0529.How do early embryos allocate the resources stored in the sperm and egg? Recently, we established isothermal calorimetry to measure heat dissipation by living zebra­fish embryos and to estimate the energetics of specific developmental events. During the reductive cleavage divisions, the rate of heat dissipation increases from ∼60 nJ · s−1 at the two-cell stage to ∼90 nJ · s−1 at the 1024-cell stage. Here we ask which cellular process(es) drive this increasing energetic cost. We present evidence that the cost is due to the increase in the total surface area of all the cells of the embryo. First, embryo volume stays constant during the cleavage stage, indicating that the increase is not due to growth. Second, the heat increase is blocked by nocodazole, which inhibits DNA replication, mitosis, and cell division; this suggests some aspect of cell proliferation contributes to these costs. Third, the heat increases in proportion to the total cell surface area rather than total cell number. Fourth, the heat increase falls within the range of the estimated costs of maintaining and assembling plasma membranes and associated proteins. Thus, the increase in total plasma membrane associated with cell proliferation is likely to contribute appreciably to the total energy budget of the embryo.The analysis of these data was initiated in the 2019 Physical Biology of the Cell course at the Marine Biological Laboratory in Woods Hole, MA. We acknowledge the support and feedback from the course directors and participants. This work was supported by funding from EMBO Long-Term Fellowship ALTF 754–2015 (to J.R.), the Eric and Wendy Schmidt Membership in Biology at the Institute for Advanced Study (to P.S.), National Institutes of Health (NIH) R21 HD094013 (to K.M.N.), and NIH R01 GM110386 (to J.H.). Its contents are solely the responsibility of the authors and do not necessarily represent the official views of the NIH

Pore-scale modelling of biofilm activity in the underground storage of hydrogen

The storage of hydrogen in the subsurface to compensate fluctuations in energy demand and supply is considered an important part of future energy strategies. It has been observed that, within the period of storage, there is a partial conversion of hydrogen in the presence of carbon dioxide to methane. This has been attributed to the activity of microorganisms (archaea and bacteria) indigenous to the storage site. The talk will look at pore-scale phenomena including the interplay of different microbes (methanogens, acetogens, and acetotrophs) within a biofilm at the gas—water interface, the growth and decay of the multi-species biofilm, and the diffusion, consumption, and production of the dissolved gases. A numerical model with interface tracking, based on a volume-of-fluid method, is proposed for investigating these effects. The aim of the study is the description and quantification of the dominant processes which determine the amount of biomass such a reservoir can support and the rate at which the microorganisms produce methane as a contribution to explaining the observed field-scale phenomenon

Instabilities in the dissolution of a porous matrix

A reactive fluid dissolving the surrounding rock matrix can trigger an instability in the dissolution front, leading to spontaneous formation of pronounced channels or wormholes. Theoretical investigations of this instability have typically focused on a steadily propagating dissolution front that separates regions of high and low porosity. In this paper we show that this is not the only possible dissolutional instability in porous rocks; there is another instability that operates instantaneously on any initial porosity field, including an entirely uniform one. The relative importance of the two mechanisms depends on the ratio of the porosity increase to the initial porosity. We show that the "inlet" instability is likely to be important in limestone formations where the initial porosity is small and there is the possibility of a large increase in permeability. In quartz-rich sandstones, where the proportion of easily soluble material (e.g. carbonate cements) is small, the instability in the steady-state equations is dominant.Comment: to be published in Geophysical Research Letter

Transcriptional regulation of secondary cell wall biosynthesis in Miscanthus sinensis

Cell wall recalcitrance is a major limitation hindering the exploitation of the enormous potential of lignocellulosic biomass as a renewable resource for energy and bio-based products. In the last decades, C4 grasses from the genus Miscanthus have emerged as a most promising energy crop for the production of lignocellulosic biomass in temperate climates. Secondary cell walls, which represent the largest proportion of lignocellulosic biomass are formed in specialised cells after cessation of growth. In higher plants, the formation of secondary cell walls is tightly regulated, both spatially and temporally, by a complex network of transcription factors. However, in Miscanthus only little is known about molecular players regulating secondary cell wall formation and lignin biosynthesis. In this study, application of the herbicide isoxaben was shown to trigger ectopic lignification in Miscanthus seedling roots. The chemical treatment may be exploited in the future to identify regulators and biosynthetic genes involved in lignification in Miscanthus. In addition, Miscanthus sinensis transcription factors related to SECONDARY WALLASSOCIATED NAC DOMAIN1 (SND1) and SECONDARY CELLWALL MYBs 1-4 (SCM1-4) were identified in the Miscanthus transcriptome, which act as regulators of secondary cell wall formation and lignin biosynthesis. During Miscanthus development, expression of MsSND1 and MsSCMs coincided with the onset of secondary cell wall formation and lignification of vascular tissue and sclerenchyma fibers. MsSND1 and MsVND7 were capable to fully restore growth in a SCW-deficient Arabidopsis thaliana mutant, suggesting they are the Miscanthus orthologues of the well characterised Arabidopsis determinants of SCW formation in fibers and vessels. Ectopic expression of MsSND1 and MsVND7 in tobacco leaves prompted the formation of patterned deposition of lignin, cellulose, and hemicellulose reminiscent of xylem elements. This observation was in sharp contrast to uniform lignification after transient expression of various MsSCMs. Expression of particular Miscanthus TFs led to specific cell wall compositions, providing attractive targets for biomass improvements. Transgenic Arabidopsis lines carrying an inducible system of MsSND1 revealed that MsSND1 regulates directly or indirectly the expression of a broad range of genes involved in secondary cell wall formation

A fully coupled HM –XFEM method with cohesive zone model: application to fluid-driven fracture network

International audienceA fully coupled HM –XFEM method with cohesive zone model: application to fluid-driven fracture networ

An Unusual 500,000 Bases Long Oscillation of Guanine and Cytosine Content in Human Chromosome 21

An oscillation with a period of around 500 kb in guanine and cytosine content (GC%) is observed in the DNA sequence of human chromosome 21. This oscillation is localized in the rightmost one-eighth region of the chromosome, from 43.5 Mb to 46.5 Mb. Five cycles of oscillation are observed in this region with six GC-rich peaks and five GC-poor valleys. The GC-poor valleys comprise regions with low density of CpG islands and, alternating between the two DNA strands, low gene density regions. Consequently, the long-range oscillation of GC% result in spacing patterns of both CpG island density, and to a lesser extent, gene densities.Comment: 15 pages (figures included), 5 figure