Finding optimal stimuli ensemble of a cortical network

We explore the determination of the optimal stimuli ensemble of a cortical network on the basis of numerical simulations of a local recurrent network. The optimal stimulus ensemble is determined with the Blahut-Arimoto algorithm using indices of population activity (multiunit activity and local field potentials). We show that the optimal stimulus ensemble is characterized by a distribution where the stimulus which induces a change in the dynamics of the network is highly represented. These results suggests that bifurcation points in the networks dynamic are highly informative and were in accordance with preliminary observation of electrophysiological recordings

Mémoire sociale et perspectives temporelles futures de salariés à la suite d’une catastrophe industrielle

Dans le contexte d’une catastrophe industrielle qui a entraîné la fermeture d’une usine chimique, les auteurs analysent le rôle que jouent la mémoire sociale et l’expérience antérieure au sein de l’organisation dans la construction de perspectives temporelles ouvertes sur des projets de reconversion, de mobilité ou de retraite anticipée. Les résultats obtenus par une analyse lexicale informatisée (ALCESTE) des entretiens semi directifs menés auprès de 15 salariés de l’usine permettent d’identifier quatre principales catégories de discours : 1) transition vers la préretraite, 2) Plan Social et possibilités de reconversion, 3) professionnalisation du métier, 4) spécificités du secteur d’activités. Pour chacune d’elles sont examinées les relations entre les modalités d’inscription des sujets dans la mémoire sociale et la définition de leurs perspectives temporelles futures. Cette étude permet d’appréhender les processus de construction de nouveaux rapports à l’organisation de travail à l’oeuvre dans une situation de transition spécifique, marquée par son caractère traumatique et son incertitude.This article examines the role played by social memory and previous work experience in the construction of relations with the company and prospects for the future as seen by employees who, as a result of an industrial disaster, were faced with the sudden closure of the chemical plant which employed them in the suburbs of Toulouse (September 2001). Faced with the sudden and unexpected loss of their jobs, employees in this plant must now choose between the different occupational reclassification choices that are being offered to them under a “Social Plan.” We presume that the development of career shift plans for these employees and, more broadly, their view of future prospects linked to the various spheres of their lives involve the activation or inhibition of memories which are shared within the work groups and which constitute a «social memory» of the company. A brief literature review of Maurice Halbwachs’s concept of social memory shows that the latter corresponds to a psychosocial construction which translates and expresses, through narratives and accounts, the events and experiences of a past history. As a support of the social identity of a given group of individuals, it is linked to a reflexive activity through which the subjects seek to redefine their perceptions of their past, present and future life trajectories inside and outside the organization.Data were collected through semi-structured interviews conducted with a sample of 15 former plant employees. The themes addressed were: the individual’s life plan, previous work experience, memories linked to company history and the subject’s relations with the various spheres of his or her life. The interview data were analyzed using ALCESTE software to separate the corpus into categories of statements based on which the subjects’ representations could be captured and analyzed. These categories were characterized by the text segments they contained and by the occurrences of words within these textual units.The results derived from the ALCESTE analysis highlight four forms of discourse (lexical and morphosyntactic) which reveal both differentiated relations with one’s personal and collective history in the company and specific outlooks on the future. The first form of discourse is characterized by an exploration of the future linked to the traumatic nature of the disaster. Suddenly faced with the prospect of withdrawal from working life, these subjects have difficulty constructing a new life plan because of the diverse nature of the opportunities offered by this early departure from the world of work. This exploration of the past, highly centred on the disaster, is oriented towards seeking to clarify the causes of an event which, to them, has remained largely unexplained. Therefore, it is reasonable to think that, for these subjects, the transition to retirement (which is contingent on the current choice of early retirement) will really only be achieved if they can make sense of the sudden end to their careers. The statements in the second category refer to discourses centred on the near past and the subjects’ current situation. The reported memories refer mainly to the painful event of the industrial disaster. Among employees undergoing retraining, this event gives rise to the perception of a radical break in their career path, and this perception is accompanied by a tendency to distance themselves from the company. Relatively disoriented by the traumatism experienced, these subjects are essentially preoccupied with their occupational reclassification and have great difficulty envisaging their future beyond the implementation of the Social Plan in which they are now actively involved. The third category of statements is characterized by discourses which evoke an occupational past, essentially perceived by the subjects as a continuous progression marked by a succession of work experiences and training actions. In formulating their retraining plan, these subjects wish above all to make the most of the knowledge acquired from their previous work experiences. For them, the proposed occupational reclassification is seen as an opportunity to make use of the transferable skills they developed while working in the plant. The statements in the last category mainly refer to the company’s industrial activities and the technical components of the trade. This form of discourse appears to reflect the importance of an identity related to the trade and memories relating to the subjects’ collective life in the company. Correlatively, these subjects have a hard time projecting themselves into the future and view occupational retraining as a trial to be overcome and a source of great uncertainty.To sum up, through discourse analysis, two main forms of association can be differentiated, that is, on the one hand, the ways the subjects incorporate social memory and, on the other hand, their outlooks on the future. The first form, made up of the first two categories, brings together the lexical contents essentially focused on the industrial disaster and the following transition phase. They express a feeling of disorientation among the subjects as well as the difficulty they experience developing new plans for the future. The second form, represented by the last two categories, is characterized by recollections of the trade practised and a valuing of the technical components of company activities. Perceptions of a future reclassification, seen in a more or less favourable light, are based on recollections of one’s experiences in the company. On the whole, the results of our study show that the development of plans for the future among these employees faced with the sudden loss of their jobs cannot be reduced to rational choices solely in response to the “objective” conditions defined by the reclassification mechanism. The development of such plans can be better understood through an analysis of the memory processes of recalling, valuing and forgetting a history which is both individual and collective, involved in this career transition.En el contexto de una catástrofe industrial que engendró el cierre de una fábrica química, los autores analizan el rol desempeñado por la memoria social y la experiencia anterior en el seno de la organización en la construcción de perspectivas temporales abiertas a proyectos de reconversión, movilidad o jubilación anticipada. Los resultados obtenidos mediante un análisis lexical informatizado (ALCESTE) de entrevistas semidirectivas efectuadas con 15 asalariados de la fabrica permiten identificar cuatro categorías principales de discurso : 1) transición a la jubilación, 2) Plan social y posibilidades de reconversión, 3) profesionalización del oficio, 4) especificidades del sector de actividades. Por cada una de ellas, se examinan las relaciones entre modalidades de inscripción de los sujetos en la memoria social y la definición de sus perspectivas temporales futuras. Este estudio permite de aprehender los procesos de construcción de nuevos vínculos con la organización del trabajo en vigor en una situación de transición especifica, marcada por su carácter traumático y su incertidumbre

Diels-Alder cycloaddition of o-quinonedimethides and alkylidene-5H-furan-2-ones: new and rapid access to lambertellol cores and arthrinone derivatives

International audienceAn efficient synthesis of deoxy-lambertellols was reported through a highly chemo- and diastereoselective intermolecular Diels-Alder cycloaddition between trans-1,2-disiloxybenzocyclobutenes and 2-methylproto- anemonine. Such transformation with d-substituted c- alkylidenebutenolides, to prepare new analogues of these tricyclic spirolactones, which would be very difficult to prepare by other ways, was also studied

Phytoseiid mite diversity (Acari: Mesostigmata) and assessment of their spatial distribution in French apple orchards

The present study reports the results of surveys carried out over two years in 173 apple orchards in France. Eleven species of Phytoseiidae were observed, among them three were dominant: Amblyseius andersoni, Kampimodromus aberrans and Typhlodromus (Typhlodromus) pyri. Cydnodromus californicus was also found but only in some orchards and nearly always in association with one of three dominant species. This observation confirms the faunal modification initiated more than ten years ago. Amblyseius andersoni was recorded in high densities in nearly all the regions considered. Typhlodromus (T.) pyri was also widespread, even if particularly frequent and abundant in the Rh¶ne-Alpes region. Kampimodromus aberrans was localised in some regions; it was especially frequent and abundant in the Mediterranean region. An identification key containing the eleven reported species is provided. TaylorÆs law was applied in order to characterize the Phytoseiidae distribution in apple orchards. The distribution is clearly aggregative, whatever the region and the Phytoseiidae species considered. Relationships between the occupation rate and the mean number of Phytoseiidae per leaf was established and an abacus was constructed to facilitate surveys and the counting during practical assessments of Phytoseiidae fauna in apple orchards

Trans-1,2-disiloxybenzocyclobutene, an adequate partner for the auto-oxisation: EPR/spin trapping and theoretical studies

International audienceThe auto-oxidation of trans-1,2-disiloxybenzocyclobutene was found to be very efficient, giving endoperoxide in quantitative yield. Each step of the mechanism of spin-forbidden addition of triplet oxygen O2 was studied by both EPR/spin trapping and theoretical studies

Assessment of cracks detection in pavement by a distributed fiber optic sensing technology

International audienceThis paper presents the feasibility of damage detection in asphalt pavements by embedded fiber optics as a new non-destructive inspection technique. The distributed fiber optic sensing technology based on the Rayleigh scattering was used in this study. The main advantage of this technique is that it allows to measure strains over a long length of fiber optic with a high spatial resolution, less than 1 cm. By comparing strain profiles measured at different times, an attempt was made to link strain changes with the appearance of damage (cracking) in the pavement. This non-destructive method was evaluated on accelerated pavement testing facility, in a bituminous pavement. In our experimentation, the optical fibers were placed near the bottom of the asphalt layer. The application of 728 000 heavy vehicle loads (65 kN dual wheel loads) was simulated in the experiment. Optical fiber measurements were made at regular intervals and surface cracking of the pavement was surveyed. After some traffic, a significant increase of strains was detected by the optical fibers at different points in the pavement structure, before any damage was visible. Later, cracking developed in the zones where the strain profiles were modified, X. Chapeleau et al. thus indicating a clear relationship between the increased strains and crack initiation. These first tests demonstrate that distributed fiber optic sensors based on Rayleigh scattering can be used to detect crack initiation and propagation in pavements, by monitoring strain profiles in the bituminous layers

Pharmacological analysis of transmission activation of two aphid-vectored plant viruses, turnip mosaic virus and cauliflower mosaic virus

Turnip mosaic virus (TuMV, family Potyviridae) and cauliflower mosaic virus (CaMV, family Caulimoviridae) are transmitted by aphid vectors. They are the only viruses shown so far to undergo transmission activation (TA) immediately preceding plant-to-plant propagation. TA is a recently described phenomenon where viruses respond to the presence of vectors on the host by rapidly and transiently forming transmissible complexes that are efficiently acquired and transmitted. Very little is known about the mechanisms of TA and on whether such mechanisms are alike or distinct in different viral species. We use here a pharmacological approach to initiate the comparison of TA of TuMV and CaMV. Our results show that both viruses rely on calcium signaling and reactive oxygen species (ROS) for TA. However, whereas application of the thiol-reactive compound N-ethylmaleimide (NEM) inhibited, as previously shown, TuMV transmission it did not alter CaMV transmission. On the other hand, sodium azide, which boosts CaMV transmission, strongly inhibited TuMV transmission. Finally, wounding stress inhibited CaMV transmission and increased TuMV transmission. Taken together, the results suggest that transmission activation of TuMV and CaMV depends on initial calcium and ROS signaling that are generated during the plant's immediate responses to aphid manifestation. Interestingly, downstream events in TA of each virus appear to diverge, as shown by the differential effects of NEM, azide and wounding on TuMV and CaMV transmission, suggesting that these two viruses have evolved analogous TA mechanisms