The maximum modulus of a trigonometric trinomial

Let Lambda be a set of three integers and let C_Lambda be the space of 2pi-periodic functions with spectrum in Lambda endowed with the maximum modulus norm. We isolate the maximum modulus points x of trigonometric trinomials T in C_Lambda and prove that x is unique unless |T| has an axis of symmetry. This permits to compute the exposed and the extreme points of the unit ball of C_Lambda, to describe how the maximum modulus of T varies with respect to the arguments of its Fourier coefficients and to compute the norm of unimodular relative Fourier multipliers on C_Lambda. We obtain in particular the Sidon constant of Lambda

Une strate herbacée monopoliste : quelle concurrence vis-à-vis de l'eau pour le peuplement adulte ?

L'adaptation des forêts aux changements climatiques est un enjeu crucial pour l'avenir. Sachant que, dans bien des cas, il faudra faire face à un problème de disponibilité en eau, une des stratégies consisterait à diminuer la densité des peuplements forestiers pour limiter le stress hydrique. Mais si, profitant de la réduction du couvert arboré, la strate herbacée explosait et exacerbait la concurrence ? Où placer le curseur ? Deux expérimentations d'Irstea donnent quelques indications pour les espèces du sous-bois dites monopolistes

LC–ESI–FT–MSn metabolite profiling of symphytum officinale l. Roots leads to isolation of comfreyn a, an unusual arylnaphthalene lignan

Preparations of comfrey (Symphytum officinale L.) roots are used topically to reduce inflammation. Comfrey anti-inflammatory and analgesic properties have been proven in clinical studies. However, the bioactive compounds associated with these therapeutic activities are yet to be identified. An LC–ESI–Orbitrap–MSn metabolite profile of a hydroalcoholic extract of comfrey root guided the identification of 20 compounds, including a new arylnaphthalene lignan bearing a rare δ-lactone ring, named comfreyn A. Its structure was determined using extensive 2D NMR and ESI–MS experiments. Additionally, the occurrence of malaxinic acid, caffeic acid ethyl ester, along with the lignans ternifoliuslignan D, 3-carboxy-6,7-dihydroxy-1-(3′,4′-dihydroxyphenyl)-naphthalene, globoidnan A and B, and rabdosiin was reported in S. officinale for the first time. These results helped to redefine the metabolite profile of this medicinal plant. Finally, caffeic acid ethyl ester and comfreyn A were found to significantly inhibit E-selectin expression in IL-1β stimulated human umbilical vein endothelial cells (HUVEC), with EC values of 64 and 50 µM, respectively

A symphytum officinale root extract exerts anti-inflammatory properties by affecting two distinct steps of NF-κB signaling

Symphytum officinale, commonly known as comfrey, constitutes a traditional medicinal plant with a long-standing therapeutic history, and preparations thereof have been widely used for the treatment of painful muscle and joint complaints, wound and bone healing, and inflammation. Today, its topical use is based on its analgesic and anti-inflammatory effects, which have been substantiated by modern clinical trials. However, the molecular basis of its action remained elusive. Here, we show that a hydroalcoholic extract of comfrey root impairs the development of a pro-inflammatory scenario in primary human endothelial cells in a dose-dependent manner. The extract, and especially its mucilagedepleted fraction, impair the interleukin-1 (IL-1) induced expression of pro-inflammatory markers including E-selectin, VCAM1, ICAM1, and COX-2. Both preparations inhibit the activation of NF-kappa B, a transcription factor of central importance for the expression of these and other pro-inflammatory genes. Furthermore, our biochemical studies provide evidence that comfrey inhibits NF-kappa B signaling at two stages: it dampens not only the activation of IKK1/2 and the subsequent I kappa B alpha degradation, but also interferes with NF-kappa B p65 nucleo-cytoplasmatic shuttling and transactivation. These results provide a first mechanistic insight into the mode of action of a century-old popular herbal medicine

Observatoire régional du fonctionnement des forêts mélangées dans le contexte des changements globaux : Dispositif expérimental OPTMix. Rapport final de la convention Région Centre-Val de Loire - Irstea

The report include a detailled desciprtion of the site, the instruments and measurements running. First results are also presented.OPTMix est un dispositif de suivi à long terme lourdement instrumenté pour l'acquisition de données robustes. Il permet d’étudier l’effet de différents facteurs - climat, gestion sylvicole, présence des grands herbivores- et de leurs interactions sur le fonctionnement des forêts de plaine. OPTMix présente deux originalités : l’étude combinée des effets de densité et de mélange, en présence ou pas d’ongulés sauvages. Les résultats issus de ce dispositif seront une aide aux gestionnaires forestiers pour définir leurs recommandations pour une gestion durable des ressources naturelles face aux contraintes actuelles et futures et notamment celles liées au changement climatique. Ce dispositif unique a pour ambition d’attirer d’autres chercheurs et équipes de recherche pour compléter les travaux d’Irstea sur la thématique du fonctionnement des forêts mélangées en zone tempérée dans le contexte des changements de climat et de pratiques