Identifying the Rules of Engagement Enabling Leukocyte Rolling, Activation, and Adhesion

The LFA-1 integrin plays a pivotal role in sustained leukocyte adhesion to the endothelial surface, which is a precondition for leukocyte recruitment into inflammation sites. Strong correlative evidence implicates LFA-1 clustering as being essential for sustained adhesion, and it may also facilitate rebinding events with its ligand ICAM-1. We cannot challenge those hypotheses directly because it is infeasible to measure either process during leukocyte adhesion following rolling. The alternative approach undertaken was to challenge the hypothesized mechanisms by experimenting on validated, working counterparts: simulations in which diffusible, LFA1 objects on the surfaces of quasi-autonomous leukocytes interact with simulated, diffusible, ICAM1 objects on endothelial surfaces during simulated adhesion following rolling. We used object-oriented, agent-based methods to build and execute multi-level, multi-attribute analogues of leukocytes and endothelial surfaces. Validation was achieved across different experimental conditions, in vitro, ex vivo, and in vivo, at both the individual cell and population levels. Because those mechanisms exhibit all of the characteristics of biological mechanisms, they can stand as a concrete, working theory about detailed events occurring at the leukocyte–surface interface during leukocyte rolling and adhesion experiments. We challenged mechanistic hypotheses by conducting experiments in which the consequences of multiple mechanistic events were tracked. We quantified rebinding events between individual components under different conditions, and the role of LFA1 clustering in sustaining leukocyte–surface adhesion and in improving adhesion efficiency. Early during simulations ICAM1 rebinding (to LFA1) but not LFA1 rebinding (to ICAM1) was enhanced by clustering. Later, clustering caused both types of rebinding events to increase. We discovered that clustering was not necessary to achieve adhesion as long as LFA1 and ICAM1 object densities were above a critical level. Importantly, at low densities LFA1 clustering enabled improved efficiency: adhesion exhibited measurable, cell level positive cooperativity

Une nouvelle approche de l'agriculture biologique

[fre] L'agriculture biologique est une pratique agricole. Elle doit être abordée comme telle, c'est-à-dire en jugeant de la cohérence des actions entreprises par rapport aux objectifs poursuivis ; l'analyse de cette pratique est conduite au niveau de cinq exploitations agricoles qui s'en réclament. [eng] Biological farming is a set of husbandry pratices. They must be judged as such i. e. by estimating whether decisions taken are consistent with stated objectives. This analysis is conducted for five farms which claim they engage in this "soft" type of farming.

Dinámicas campesinas y fitomejoramiento participativo : El caso de los sorgos blancos (Sorghum bicolor, L. Moench) en la región norte de Nicaragua = Farmers dynamics and participatory plant breeding: the case of white grain sorghums in the Northern region of Nicaragua

Dinámicas campesinas y fitomejoramiento participativo: el caso de los sorgos blancos (Sorghum bicolor, L. Moench) en la región norte de Nicaragua. En las regiones secas de Nicaragua, los sorgos blancos representan un grano básico cada vez más importante para las familias campesinas pobres. Desde 2002, el CIRAD y el CIAT manejan en colaboración con ONGs y grupos de productores experimentadores un proyecto de fitomejoramiento participativo de los sorgos dirigido a los pequeños productores. En esta publicación, los autores describen el arranque de este proyecto en el departamento de Madriz, norte de Nicaragua, e indican los resultados más originales de esta fase inicial. Ésta empezó con un diagnóstico intenso sobre los sistemas de cultivos, las variedades, los problemas de producción, los usos del sorgo y una predefinición de los objetivos de selección. Se identificaron los actores y las prácticas de la producción y los intercambios de semillas. Paralelamente, las variedades locales de sorgo tortillero y millón fueron caracterizadas morfo-agronómicamente. Como resultados, se resaltan los cambios recientes en las variedades y los sistemas de cultivo, la adopción rápida de los sorgos de ciclo corto tortillero mediante procesos informales de intercambios de semillas; las características notables de las variedades locales de sorgo tortillero y millón fueron cuantificadas. Estos datos sirvieron para implementar las actividades de selección participativa e identificar los progenitores y cruzamientos para los esquemas de fitomejoramiento participativo. Como perspectivas, los autores proponen insertar más este proceso de fitomejoramiento participativo en los proyectos endógenos fortaleciendo la agricultura familiar con un enfoque agroecológico y extenderlo a otros temas, cultivos y zonas en un marco interinstitucional de investigación-acción para pequeños agricultores en zonas marginales. = Farmers dynamics and participatory plant breeding: the case of white grain sorghums in the Northern region of Nicaragua. In the dry areas of Nicaragua, white grain sorghums are an important food crop for the poor farmers. Since 2002, CIRAD and CIAT manage in collaboration with NGOs and local experimenter farmers' groups a research project on sorghum participatory breeding addressed to the low-resources farmers. In this paper, the authors describe the start of the project in the Madriz department, North of Nicaragua, and indicate the most relevant results of this preliminary phase. This work started with an intensive participatory diagnostic about the cropping systems, the varieties, the production constraints, the sorghum utilizations and a pre-definition of the breeding objectives. The participants and practices of the seed production and exchanges were identified. At the same time, the local varieties of tortillero and millón sorghum were characterized for morphological and agronomic traits. Among the results emerge the recent changes concerning the varieties and the cropping systems, the rapid adoption of the short-cycle tortillero sorghum by the mean of informal processes of seed exchanges; the original traits of the millón varieties, like their extreme sensitivity to photoperiod, have been quantified. These data were used for implementing the activities of participatory variety selection and for choosing the parents and crosses for the participatory breeding schemes. As perspectives, the authors propose to integrate more this process of participatory breeding within the endogenous projects strengthening the family agriculture with an agro-ecological focus and extend it to other themes, crops and areas in an inter-institutional framework of research-action for small farmers in marginal areas

Banc de qualification pour une application de la méthode simplifiée d'analyse du risque de liquéfaction des sols à partir des essais in situ SPT et CPT

International audienceSoil liquefaction triggering during earthquakes is usually evaluated by the SPT or CPT based simplified method. This method, first proposed by Seed and Idriss in 1971, allows evaluating the factor of safety against liquefaction. Several states of the art have been published over the years, the later being at the NCEER' 1997 workshop (Youd et al., 2001). Practical utilisation of this state of the art provides results that are user-dependant. Whereas all the questions raised by the NCEER's practical utilisation are not exhaustively addressed in this paper, it has being found interesting to share the current practices. This paper provides the results of two benchmarks that put into practice the SPT and CPT based simplified method.Dans la pratique courante, la quantification du risque de liquéfaction des sols sous l'effet de séismes passe par l'utilisation de la méthode simplifiée appliquée aux essais in situ de type SPT ou CPT. Initialement proposée par Seed et Idriss en 1971, cette méthode permet d'estimer des coefficients de sécurité vis-à-vis de ce risque (F Sl). La méthode a fait l'objet d'états de l'art successifs dont le dernier a été établi par le NCEER lors d'un colloque en 1997 (Youd et al., 2001). Si la démarche empirique est largement acceptée, certains détails de sa mise en oeuvre pratique font débat, laissant à l'utilisateur l'initiative d'une interprétation. A défaut de résoudre toutes les indéterminations, il est apparu important de fiabiliser la progression des calculs des coefficients F sl à partir des données in-situ SPT et CTP. Dans ce but, un banc de qualification des options de calcul a été mis en partage entre utilisateurs pour aboutir à des recommandations de mise en oeuvre de la méthode simplifiée

VizieR Online Data Catalog: Classical Cepheids consistent radial velocities (Borgniet+, 2019)

VizieR On-line Data Catalog: J/A+A/631/A37. Originally published in: 2019A&A...631A..37BOur sample is made up of 64 Classical Galactic Cepheids with pulsation periods in the range 2 to 68 days. We provide the full details of our sample in Table A.1. We present both the six correlation templates built to derive tailored cross-correlation functions (CCFs), the CCFs themselves, and the derived radial velocity and line profile observable time series. All data are provided with the corresponding Cepheid name, the spectrograph used to observe the target, the Modified Julian Day (MJD) of the observation and the observation program identifier. The data are provided over three different wavelength ranges: "blue" from 390 to 498nm; "green" from 450 to 680nm; and "red" from 570 to 880nm, corresponding to the letters "b", "g", and "r" (first identifier within the file names). Depending on this range, the data are computed based on one (for the "blue" and "red" ranges) or four (for the "green" range) different correlation templates, corresponding to different sets of spectral lines selected based on their relative depth: weak, medium, deep and all lines. The corresponding identifiers are the letters "w", "m", "d", and "a" (second identifier within the file names). Finally, the radial velocities and other line profile observables are computed in three different ways for each star, each spectrograph, each wavelength range, and each template: first based on the CCF first moment or centroid, second based on a Gaussian fit of the CCF, and third based on a BiGaussian fit of the CCF. The corresponding identifiers are the letters "c", "g" and "b" (third identifier within the rv file names). (28 data files)

Selenide glass fibers for biochemical infrared sensing

International audienceThis chapter discusses the use of selenide glass fibers for biochemical sensing. Selenide glasses combine two unique properties: (1) high transparency in the mid-infrared, (2) excellent rheological properties for molding and drawing, which make them the most suitable candidate materials for infrared fiber technology. In particular, chalcogenide glasses exhibit high transparency over the spectral domain corresponding to molecular vibrations and are therefore of great interest for optical sensing applications. Here we review the basic principles of fiber-based spectroscopy and the properties of chalcogenide glasses such as selenides. We then review the state of the art in applications of fiber evanescent wave spectroscopy to chemical and biomedical sensing. © Springer International Publishing Switzerland 2017