Convexity properties of the condition number II

In our previous paper [SIMAX 31 n.3 1491-1506(2010)], we studied the condition metric in the space of maximal rank matrices. Here, we show that this condition metric induces a Lipschitz-Riemann structure on that space. After investigating geodesics in such a nonsmooth structure, we show that the inverse of the smallest singular value of a matrix is a log-convex function along geodesics (Theorem 1). We also show that a similar result holds for the solution variety of linear systems (Theorem 31). Some of our intermediate results, such as Theorem 12, on the second covariant derivative or Hessian of a function with symmetries on a manifold, and Theorem 29 on piecewise self-convex functions, are of independent interest. Those results were motivated by our investigations on the com- plexity of path-following algorithms for solving polynomial systems.Comment: Revised versio

Floral stem cell termination involves the direct regulation of AGAMOUS by PERIANTHIA

In Arabidopsis, the population of stem cells present in young flower buds is lost after the production of a fixed number of floral organs. The precisely timed repression of the stem cell identity gene WUSCHEL (WUS) by the floral homeotic protein AGAMOUS (AG) is a key part of this process. In this study, we report on the identification of a novel input into the process of floral stem cell regulation. We use genetics and chromatin immunoprecipitation assays to demonstrate that the bZIP transcription factor PERIANTHIA (PAN) plays a role in regulating stem cell fate by directly controlling AG expression and suggest that this activity is spatially restricted to the centermost region of the AG expression domain. These results suggest that the termination of floral stem cell fate is a multiply redundant process involving loci with unrelated floral patterning functions

Remote Sensing of Snow in the Solar Spectrum: Experiments in the French Alps.

Two experiments were perfonned irliApril and December 1992 in the French Alps using simultaneous relnote sensing and ground truth data. Snow grain site and soot content of samples collected in thefield were measured. The Landsat thematic mapper (TM) sensor was used because it has a good spatial resolution, a middle infrared channel which is sensitive to grain size and a thermal infraredchannel. Firstj the reflectance data were compared with the theoretical results obtained from a bidirectional reflectance model. Then, some remote sehstng-derived snow parameters wbre comparediWith the outpllt ofa snow metamorphism model (CROCUS),viz., lower elevation of the snowcover, lhe surface grl1in size and the surface temperature. A digital elevation model was used to obtain thelocal incidenc:f angles and the elevation of each snow pixel. The pixels were then grouped according to CROCUS classification (range, elevation, slope, and orientation) and the mean snow chart;cheracteristicsfor each class were .compared with the tROCUS results. The lower limit of snow and the surface grain size derived from TM data were compared favourably with the model results. Larger differences werefound for the temperature, because it varies rapidly and is very sensitive to shadowing by the snrrounding mountains and also because its remote measurement is dependent on atmospheric conditions

Special issue: Innovations in farming systems approaches: Introduction

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Livestock and Local Development: Going to a New Humananimal Relationship

Along the past ten years, the French National Agency for Research (ANR) has financed projects regarding livestock. Results of five projects were gathered to understand the long-term livestock trends. At the end of the 19th century, animal breeding was oriented towards the production of goods to meet the local, regional, national and global demand, according to the zone. The market gradually became the key-factor to norm both production and consumption. It is now integrating environmental norms and is starting to invest in the social domain. However, this economical vision of animal production does not take into account the other functions of livestock, from “farm fork” to “table fork”. So, in parallel to the multi-functionality of livestock at the farm level, which is mentioned by several authors, livestock has a significant role at the local scale. Furthermore, in the past four decades, animal production sector has known several serious scandals with severe consequences in human health. At the same time, the FAO scoop in 2006 about the significant environmental impact of animal breeding has chocked a large part of the human society. Hence, in parallel to the discredit of animal production towards the consumers, these successive crises have led a part of the local and global society to question the human-animal relationship. In this way, a large part of the urban population with no contact with the rural world, would easily believe in animal welfare, and break the supply chain leading to the slaughterhouse. And to confirm this trend, research institutes are already seeking alternatives to meat and animal proteins. Consequently, maybe it is time now to think imagine other farming systems based on other human-animal relationships and other environment-society interactions; and perhaps to establish an adequate set of policies to strengthen this perspective

Ethanol application at veraison decreases acidity in Cabernet Sauvignon grapes

Research NoteSpraying ethanol (5 % v/v in water) onto grape clusters at mid-veraison led to a 30 % drop in the malic acid concentration at harvest. As a consequence, titratable acidity also dropped by 10 %. The concentration of tartaric acid did not change significantly. The mode of action of ethanol on malic acid metabolism is discussed.

Adjuvants and delivery systems in veterinary vaccinology: current state and future developments

Modern adjuvants should induce strong and balanced immune responses, and it is often desirable to induce specific types of immunity. As an example, efficient Th1-immunity-inducing adjuvants are highly in demand. Such adjuvants promote good cell-mediated immunity against subunit vaccines that have low immunogenicity themselves. The development of such adjuvants may take advantage of the increased knowledge of the molecular mechanisms and factors controlling these responses. However, knowledge of such molecular details of immune mechanisms is relatively scarce for species other than humans and laboratory rodents, and in addition, there are special considerations pertaining to the use of adjuvants in veterinary animals, such as production and companion animals. With a focus on veterinary animals, this review highlights a number of approaches being pursued, including cytokines, CpG oligonucleotides, microparticles and liposomes. (Résumé d'auteur