Bekki-Nozaki Amplitude Holes in Hydrothermal Nonlinear Waves

We present and analyze experimental results on the dynamics of hydrothermal waves occuring in a laterally-heated fluid layer. We argue that the large-scale modulations of the waves are governed by a one-dimensional complex Ginzburg-Landau equation (CGLE). We determine quantitatively all the coefficients of this amplitude equation using the localized amplitude holes observed in the experiment, which we show to be well described as Bekki-Nozaki hole solutions of the CGLE.Comment: 4 pages, uses RevTeX, 9 EPS figure

KNR4, a suppressor of Saccharomyces cerevisiae cwh mutants, is involved in the transcriptional control of chitin synthase genes

The KNR4 gene, originally isolated by complementation of a K9 killer-toxinresistant mutant displaying reduced levels of both 1,3-b-glucan and 1,3-bglucan synthase activity, was recloned from a YCp50 genomic library as a suppressor of Saccharomyces cerevisiae calcofluor-white-hypersensitive (cwh) mutants. In these mutants, which were characterized by increased chitin levels, the suppressor effect of KNR4 resulted, for some of them, in a lowering of polymer content to close to wild-type level, with no effect on the contents of b-glucan and mannan. In all cases, this effect was accompanied by a strong reduction in mRNA levels corresponding to CHS1, CHS2 and CHS3, encoding chitin synthases, without affecting expression of FKS1 and RHO1, two genes encoding the catalytic subunit and a regulatory component of 1,3-b-glucan synthase, respectively. Overexpression of KNR4 also inhibited expression of CHS genes in wild-type strains and in two other cwh mutants, whose sensitivity to calcofluor white was not suppressed by this gene. The physiological relevance of the KNR4 transcriptional effect was addressed in two different ways. In a wild-type strain exposed to a-factor, overexpression of this gene inhibited CHS1 induction and delayed shmoo formation, two events which are triggered in response to the pheromone, whereas it did not affect bud formation and cell growth in a chs1 chs2 double mutant. A chimeric protein made by fusing green fluorescent protein to the C terminus of Knr4p which fully complemented a knr4D mutation was found to localize in patches at presumptive bud sites in unbudded cells and at the incipient bud site during bud emergence. Taken together, these results demonstrate that KNR4 has a regulatory role in chitin deposition and in cell wall assembly. A mechanism by which this gene affects expression of CHS genes is proposed

New regime of droplet generation in a T-shape microfluidic junction

International audienceWe present an experimental study of a new regime of monodisperse micro-droplet generation that we named the balloon regime. A dispersion of oil in water in a T-junction microfluidic system was studied. Several microfluidic devices having different cross-sections of the continuous and the dispersed phases micro-channels were tested. This new regime appears only for low- dispersed phase velocity. The micro-droplet size is mainly related to the geometry of the T-junction micro-channels especially its width and depth, and independent of the continuous and dispersed phases velocities. In our experiments, the velocities of the continuous and the dispersed phases vc and vd respectively, have been varied in a wide range: vc from 0.5 to 500 mm/s, and vd from 0.01 to 30 mm/s. We show that the continuous phase only controls the micro-droplet density, while the dispersed phase linearly changes the frequency of the micro-droplet generation. Another particularity of the present regime, which differentiates it from all other known regimes, is that the micro-droplet retains its circular shape throughout its formation at the T junction, and undergoes no deformation due to the drag forces. We propose a mechanism to explain the formation of microdroplets in this new regime

Innovateurs ordinaires : Une enquête sociologique sur des startups françaises

texte provisoire d'un ouvrageCe document est la version de travail d’un projet d’ouvrage sur les startups françaises. Il s’agit d’une synthèse des résultats d’une enquête sociologique sur les entreprises considérées comme innovantes commencée en 2005 et qui a donné lieu à plusieurs publications académiques. Les chapitres de cet ouvrage explorent successivement les différents aspects de la création de ces entreprises considérées comme innovantes. Nous commençons par les fondateurs, leurs parcours personnel et professionnel, les logiques selon lesquelles ils s’engagent dans ces projets. Ils ne ressemblent guère à la figure de l’entrepreneur visionnaire et quasiment héroïque souvent véhiculée par les médias ou par une partie de la littérature économique. Il s’agit plutôt d’ingénieurs ou de cadres, souvent passionnés par la technique, mais pas toujours, en majorité confrontés à des formes d’incertitude professionnelle (licenciement, risque de perte d’emploi, difficultés dans leur entreprise), parfois de chercheurs du secteur public souhaitant créer des activités à partir de leurs travaux sans pour autant quitter leur emploi. Nous présentons ensuite leurs « innovations » et les projets des entreprises qu’ils fondent. Nous en proposons une typologie. Puis, nous nous intéresserons au processus de création en suivant ses différentes étapes, des débuts tendus vers la définition et la mise en œuvre de leur « projet » jusqu’aux phases de stabilisation relative, de crise, de réorientation. Une partie des entreprises que nous avons étudiées ont cessé leur activité. Cela nous permet d’analyser la façon dont les histoires s’achèvent. Nous explorons aussi les contextes aussi bien historiques que géographiques dans lesquels ces tentatives prennent place. Les startups que nous avons étudiées sont en partie l’expression d’un « monde économique » particulier, celui des activités d’innovation technique, dont l’histoire peut être retracée en remontant au moins à la deuxième partie du XIXe siècle. Ce monde a généré progressivement des institutions (universités à orientation technologique, parcs industriels, pépinières, capital-risque, etc.) et un vocabulaire qui lui sont spécifiques. Situé dans le temps, ce monde l’est également dans l’espace avec des systèmes économiques locaux organisés autour des activités d’innovation qui sont particulièrement développés dans certaines agglomérations (Grenoble, Toulouse), ce qui contribue à spécifier le contexte dans lequel se créent les entreprises « innovantes »

Les chaînes relationnelles dans un suivi longitudinal d'entreprises de création récente

International audienceEn 2009 nous avons entrepris un suivi d'entreprises dont nous avions étudié la création lors d'une enquête conduite en 2005 et 2006 (Grossetti et Barthe, 2008). Dans la première phase d'enquête, nous avions utilisé une méthode consistant à rédiger des narrations à partir de sources croisées (au moins deux entretiens dans la plupart des cas, plus des sources documentaires), narrations soumises aux enquêtés pour correction éventuelle. Ces narrations faisaient ensuite l'objet d'un codage à plusieurs niveaux : les parcours des fondateurs ; les séquences d'accès aux ressources (permettant de mettre au jour des chaînes relationnelles) ; les réseaux multi-centrés (les fondateurs et la nouvelle entreprises elle-même) et multi-niveaux (individus, organisations) caractérisant le processus de création à certains moments types (avant le dépôt des statuts, durant la première année après celui-ci, après deux ans d'existence). Dans le suivi, nous reprenons cette méthode pour 25 des 53 entreprises enquêtées dans la première phase. Nous sommes confrontés à divers problèmes que nous exposerons dans cette communication : codage de séquences lorsque les ressources se multiplient (montée en masse) ou qu'elles disparaissent ; caractérisation des phases de développement de l'entreprise ; codage d'événements ; distinction entre accès par relations et accès par d'autres moyens

Chemically modified polysulfones for molecular imprinting. Synthesis and complexation with a fluorescent model template

Polysulfone (PSU) was chemically modified to prepare new molecular imprinted membranes (MIMs). Several amounts of amine and sulfonyl groups were introduced into the PSU chemical structure in order to create interactions with acid or base templates, such as biomolecules or biomacromolecules. A fluorescent dye, Acridine Orange base (AO), was used as a model template and its complexation with the prepared PSUs was monitored by spectroscopic techniques. This study showed an absence of complexation with the native PSU and a strong complexation with the aminated and the sulfonated PSUs. Partially allylated PSU bearing amine or sulfonyl groups were also synthesized. These compounds are expected to be used as precursors for designing new crosslinked molecular imprinting membranes (MIMs), exhibiting high stability of the template memory

Chemically modified polysulfones for molecular imprinting. Synthesis and complexation with a fluorescent model template

Polysulfone (PSU) was chemically modified to prepare new molecular imprinted membranes (MIMs). Several amounts of amine and sulfonyl groups were introduced into the PSU chemical structure in order to create interactions with acid or base templates, such as biomolecules or biomacromolecules. A fluorescent dye, Acridine Orange base (AO), was used as a model template and its complexation with the prepared PSUs was monitored by spectroscopic techniques. This study showed an absence of complexation with the native PSU and a strong complexation with the aminated and the sulfonated PSUs. Partially allylated PSU bearing amine or sulfonyl groups were also synthesized. These compounds are expected to be used as precursors for designing new crosslinked molecular imprinting membranes (MIMs), exhibiting high stability of the template memory

Role for T-type Ca2+Ca 2+ channels in sleep waves

International audienceSince their discovery more than 30 years ago, low-threshold T-type $Ca 2+$ channels (T channels) have been suggested to play a key role in many EEG waves of non-REM sleep, which has remained exclusively linked to the ability of these channels to generate low-threshold $Ca 2+$ potentials and associated high-frequency bursts of action potentials. Our present understanding of the biophysics and physiology of T channels, however, highlights a much more diverse and complex picture of the pivotal contributions that they make to different sleep rhythms. In particular, recent experimental evidence has conclusively demonstrated the essential contribution of thalamic T channels to the expression of slow waves of natural sleep and the key role played by $Ca 2+$ entry through these channels in the activation or modulation of other voltage-dependent channels that are important for the generation of both slow waves and sleep spindles. However, the precise contribution to sleep rhythms of T channels in cortical neurons and other sleep-controlling neuronal networks remains unknown, and a full understanding of the cellular and network mechanisms of sleep delta waves is still lacking

The Economic Impacts of Port Activity in Antwerp: A Disaggregated Analysis

The importance of ports is usually measured by indicators such as added value, employment and investment on a much aggregated level. This paper tries to define the importance of the port of Antwerp for the regional and national economy on a disaggregated level. It attempts to identify, quantify and locate the mutual relationships between the different players in the port and between these players and other industries. Finally, it proposes a method to calculate the effects of changes in port activity at a detailed level. A sector analysis is done by means of a reduced regional input-output table, through a bottom-up approach. The most important customers and suppliers of the port's key players or stakeholders are identified. A geographical analysis is feasible by using data on a disaggregated level. Each customer or supplier can be located by means of their postcode. In this way, the extent of the economic impact of the port of Antwerp is quantified.