Phloem sap exudates as a criterion for sink strength appreciation in Vitis vinifera cv. Pinot noir grapevines

The temporal evolution of the main compounds present in the phloem sap feeding the cluster of Vitis vinifera Pinot noir has been determined from the beginning of flowering until fruit set, after improvement of the facilitated exudation technique. The retained composition for the dipping solution was: HEPES (10 mM, pH 7.5), EDTA (10 mM). The first ramification of the cluster, maintained in situ, was sectionned then immersed in the dipping solution in order to favour the phloem exudation. The major organic components of the phloem sap were carbohydrates, amino acids and organic acids (i.e. sucrose, glutamine and tartrate, respectively). For each metabolic group, the mean exuded quantities correspond to 300 nmol per cluster in 4 h. The sharp increase in both organic compounds and potassium released over the flowering time-course reflects the rise of the mass flow supplying the cluster and underline the increasing sink strength of this organ. Moreover, the increasing contents of glutamine and hexoses in the exudate suggest a regulation in the allocation of assimilates to the reproductive organs.Les exsudats de sève phloémique comme critère d'appreciation de la force de puits de la grappe chez Vitis vinifera cv. Pinot noirL'évolution temporelle des principaux constituants de la sève libérienne alimentant la grappe de Vitis vinifera Pinot noir a été étudiée au cours de la floraison, après adaptation d'une technique de prélèvement par exsudation facilitée. La composition de la solution d'exsudation retenue est la suivante: HEPES (10 mM, pH 7,5), EDTA (10 mM). Sur la grappe maintenue in situ, l'extrémité de la première ramification est sectionnée puis immergée dans le milieu précédemment défini pour permettre la récupération des assimilats. Les composés organiques prédominants dans la sève libérienne sont les glucides solubles, les acides aminés et les acides organiques (saccharose, glutamine et tartrate respectivement). Pour chacun de ces groupes métaboliques, les quantités moyennes exsudées sont voisines de 300 nmol par grappe en 4 heures. Les quantités croissantes de glucides, d'acides aminés et de potassium collectées entre Je début de l'anthèse et la nouaison reflètent l'augmentation de flux de masse parvenant à la grappe et soulignent l'évolution de la force d'appel de ce puits. De plus, la part croissante de la glutamine et des hexoses dans les exsudats suggère une régulation dans la distribution des assimilats aux organes reproducteurs

Transient backbending behavior in the Ising model with fixed magnetization

The physical origin of the backbendings in the equations of state of finite but not necessarily small systems is studied in the Ising model with fixed magnetization (IMFM) by means of the topological properties of the observable distributions and the analysis of the largest cluster with increasing lattice size. Looking at the convexity anomalies of the IMFM thermodynamic potential, it is shown that the order of the transition at the thermodynamic limit can be recognized in finite systems independently of the lattice size. General statistical mechanics arguments and analytical calculations suggest that the backbending in the caloric curve is a transient behaviour which should not converge to a plateau in the thermodynamic limit, while the first order transition is signalled by a discontinuity in other observables.Comment: 24 pages, 11 figure

Constraints on the χ_(c1) versus χ_(c2) polarizations in proton-proton collisions at √s = 8 TeV

The polarizations of promptly produced χ_(c1) and χ_(c2) mesons are studied using data collected by the CMS experiment at the LHC, in proton-proton collisions at √s=8  TeV. The χ_c states are reconstructed via their radiative decays χ_c → J/ψγ, with the photons being measured through conversions to e⁺e⁻, which allows the two states to be well resolved. The polarizations are measured in the helicity frame, through the analysis of the χ_(c2) to χ_(c1) yield ratio as a function of the polar or azimuthal angle of the positive muon emitted in the J/ψ → μ⁺μ⁻ decay, in three bins of J/ψ transverse momentum. While no differences are seen between the two states in terms of azimuthal decay angle distributions, they are observed to have significantly different polar anisotropies. The measurement favors a scenario where at least one of the two states is strongly polarized along the helicity quantization axis, in agreement with nonrelativistic quantum chromodynamics predictions. This is the first measurement of significantly polarized quarkonia produced at high transverse momentum