252 research outputs found
Les espaces de l'halieutique
L'Ă©tang de Thau est un espace lagunaire semi fermĂ© dont les communications avec la mer sont limitĂ©es. L'exploitation de la palourde, ressource intrinsĂšquement peu mobile, est au coeur de l'activitĂ© de pĂȘche dans cet Ă©tang. Il semble donc, a priori, que les notions d'espace mis en oeuvre par l'exploitation de cette ressource prĂ©sentent un caractĂšre de proximitĂ© et une dimension localisĂ©e Ă l'Ă©cosystĂšme "Ă©tang de Thau". DĂšs lors, on pourrait penser que la connaissance Ă©cologique de ce milieu - oĂč d'importants programmes scientifiques ont Ă©tĂ© rĂ©alisĂ©es -, alliĂ©e Ă la faible mobilitĂ© de cette population de bivalves fouisseurs, constituent des conditions favorables Ă une gestion "efficace" de cet Ă©cosystĂšme. Ce sentiment est renforcĂ© par le contexte social dans lequel Ă©voluent les communautĂ©s de pĂȘcheurs qui ont derriĂšre elles une longue pratique de la gestion (prud'homies). Or, aprĂšs une pĂ©riode florissante achevĂ©e en 1992, cette pĂȘcherie traverse une crise aiguĂ«. Les professionnels constatent en effect une forte diminution des stocks qui se traduit par (i) une rĂ©gression des quantitĂ©s pĂȘchĂ©es par jours de travail (PUE) (ii) une diminution des prix (contre toute logique de marchĂ©) et (iii) une dĂ©croissance du nombre de pĂȘcheurs. ParallĂšlement on observe une transformation des mĂ©thodes de pĂȘche avec la gĂ©nĂ©ralisation de la pĂȘche en plongĂ©e aux dĂ©pens de "l'arseliĂšre" technique traditionnelle qui a quasiment disparu. Dans ce contexte, et Ă la demande de la profesison, un programme pluridisciplinaire (programme Palourde) a Ă©tĂ© mis en oeuvre afin d'identifier les limites du systĂšme actuel puis d'Ă©laborer un nouveau systĂšme de gestion. Ce travail a Ă©tĂ© menĂ© selon une dĂ©marche de concertation Ă©largie de l'ensemble des partenaires de l'exploitation (pĂȘcheurs, mareyeurs, gestionnaires) et de façon nĂ©gociĂ©e entre les acteurs... (RĂ©sumĂ© d'auteur
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.
An update on the Hirsch conjecture
The Hirsch conjecture was posed in 1957 in a letter from Warren M. Hirsch to
George Dantzig. It states that the graph of a d-dimensional polytope with n
facets cannot have diameter greater than n - d.
Despite being one of the most fundamental, basic and old problems in polytope
theory, what we know is quite scarce. Most notably, no polynomial upper bound
is known for the diameters that are conjectured to be linear. In contrast, very
few polytopes are known where the bound is attained. This paper collects
known results and remarks both on the positive and on the negative side of the
conjecture. Some proofs are included, but only those that we hope are
accessible to a general mathematical audience without introducing too many
technicalities.Comment: 28 pages, 6 figures. Many proofs have been taken out from version 2
and put into the appendix arXiv:0912.423
Artificial reefs: from ecological processes to fishing enhancement tools
info:eu-repo/semantics/publishedVersio
From error bounds to the complexity of first-order descent methods for convex functions
This paper shows that error bounds can be used as effective tools for
deriving complexity results for first-order descent methods in convex
minimization. In a first stage, this objective led us to revisit the interplay
between error bounds and the Kurdyka-\L ojasiewicz (KL) inequality. One can
show the equivalence between the two concepts for convex functions having a
moderately flat profile near the set of minimizers (as those of functions with
H\"olderian growth). A counterexample shows that the equivalence is no longer
true for extremely flat functions. This fact reveals the relevance of an
approach based on KL inequality. In a second stage, we show how KL inequalities
can in turn be employed to compute new complexity bounds for a wealth of
descent methods for convex problems. Our approach is completely original and
makes use of a one-dimensional worst-case proximal sequence in the spirit of
the famous majorant method of Kantorovich. Our result applies to a very simple
abstract scheme that covers a wide class of descent methods. As a byproduct of
our study, we also provide new results for the globalization of KL inequalities
in the convex framework.
Our main results inaugurate a simple methodology: derive an error bound,
compute the desingularizing function whenever possible, identify essential
constants in the descent method and finally compute the complexity using the
one-dimensional worst case proximal sequence. Our method is illustrated through
projection methods for feasibility problems, and through the famous iterative
shrinkage thresholding algorithm (ISTA), for which we show that the complexity
bound is of the form where the constituents of the bound only depend
on error bound constants obtained for an arbitrary least squares objective with
regularization
LRP-1 Promotes Cancer Cell Invasion by Supporting ERK and Inhibiting JNK Signaling Pathways
Background: The low-density lipoprotein receptor-related protein-1 (LRP-1) is an endocytic receptor mediating the clearance of various extracellular molecules involved in the dissemination of cancer cells. LRP-1 thus appeared as an attractive receptor for targeting the invasive behavior of malignant cells. However, recent results suggest that LRP-1 may facilitate the development and growth of cancer metastases in vivo, but the precise contribution of the receptor during cancer progression remains to be elucidated. The lack of mechanistic insights into the intracellular signaling networks downstream of LRP-1 has prevented the understanding of its contribution towards cancer.
Methodology/Principal Findings: Through a short-hairpin RNA-mediated silencing approach, we identified LRP-1 as a main regulator of ERK and JNK signaling in a tumor cell context. Co-immunoprecipitation experiments revealed that LRP-1 constitutes an intracellular docking site for MAPK containing complexes. By using pharmacological agents, constitutively active and dominant-negative kinases, we demonstrated that LRP-1 maintains malignant cells in an adhesive state that is favorable for invasion by activating ERK and inhibiting JNK. We further demonstrated that the LRP-1-dependent regulation of MAPK signaling organizes the cytoskeletal architecture and mediates adhesive complex turnover in cancer cells. Moreover, we found that LRP-1 is tethered to the actin network and to focal adhesion sites and controls ERK and JNK targeting to talin-rich structures.
Conclusions: We identified ERK and JNK as the main molecular relays by which LRP-1 regulates focal adhesion disassembly of malignant cells to support invasion
The Double Star Plasma Electron and Current Experiment
The Double Star Project is a collaboration between Chinese and European space agencies, in which two Chinese magnetospheric research spacecraft, carrying Chinese and European instruments, have been launched into equatorial (on 29 December 2003) and polar (on 25 July 2004) orbits designed to enable complementary studies with the Cluster spacecraft. The two Double Star spacecraft TC-1 and TC-2 each carry a Double Star Plasma Electron and Current Experiment (PEACE) instrument. These two instruments were based on Cluster Flight Spare equipment, but differ from Cluster instruments in two important respects. Firstly, a Double Star PEACE instrument has only a single sensor, which must be operated in a manner not originally envisaged in the Cluster context in order to sample the full range of energies. Secondly, the DPU hardware was modified and major changes of onboard software were implemented, most notably a completely different approach to data compression has been adopted for Double Star, which allows high resolution 3-dimensional distributions to be transmitted almost every spin, a significant improvement over Cluster. This paper describes these instruments, and includes examples of data collected in various magnetospheric regions encountered by the spacecraft which have been chosen to illustrate the power of combined Double Star and Cluster measurements
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Children's informed, signified and voluntary consent to heart surgery: Professionalsâ practical perspectives
Background: The law and literature about childrenâs consent generally assume that patients aged under-18 cannot consent until around 12 years, and cannot refuse recommended surgery. Children deemed pre-competent do not have automatic rights to information or to protection from unwanted interventions. However, the observed practitioners tend to inform young children s, respect their consent or refusal, and help them to âwantâ to have the surgery. Refusal of heart transplantation by 6-year-olds is accepted. Research question: What are possible reasons to explain the differences between theories and practices about the ages when children begin to be informed about elective heart surgery, and when their consent or refusal begins to be respected? Research design, participants and context: Research methods included reviews of related healthcare, law and ethics literature; observations and conversations with staff and families in two London hospitals; audio-recorded semi-structured interviews with a purposive sample of 45 healthcare professionals and related experts; interviews and a survey with parents and children aged 6- to 15-years having elective surgery (not reported in this paper); meetings with an interdisciplinary advisory group; thematic analysis of qualitative data and co-authorship of papers with participants. Ethical considerations: Approval was granted by four research ethics committees/authorities. All interviewees gave their informed written consent. Findings: Interviewees explained their views and experiences about childrenâs ages of competence to understand and consent or refuse, analysed by their differing emphases on informed, signified or voluntary consent. Discussion: Differing views about childrenâs competence to understand and consent are associated with emphases on consent as an intellectual, practical and/or emotional process. Conclusion: Greater respect for childrenâs practical signified, emotional voluntary and intellectual informed consent can increase respectful understanding of childrenâs consent. Nurses play a vital part in children's practitioner-patient relationships and physical care and therefore in all three elements of consent
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