Seasonal and diurnal changes in photosynthetic limitation of young sweet orange trees

This study tests the hypothesis that potted sweet orange plants show a significant variation in photosynthesis over seasonal and diurnal cycles. even in well-hydrated conditions. This hypothesis was tested by measuring diurnal variations in leaf gas exchange, chlorophyll fluorescence, leaf water potential, and the responses of CO(2) assimilation to increasing air CO(2) concentrations in 1-year-old `Valencia` sweet orange scions grafted onto `Cleopatra` mandarin rootstocks during the winter and summer seasons in a subtropical climate. In addition, diurnal leaf gas exchange was evaluated under controlled conditions, with constant environmental conditions during both winter and summer. In relation to our hypothesis, a greater rate of photosynthesis is found during the summer compared to the winter. Reduced photosynthesis during winter was induced by cool night conditions, as the diurnal fluctuation of environmental conditions was not limiting. Low air and soil temperatures caused decreases in the stomatal conductance and in the rates of the biochemical reactions underlying photosynthesis (ribulose-1,5-bisphosphate (RuBP) carboxylation and RuBP regeneration) during the winter compared to the values obtained for those markers in the Summer. Citrus photosynthesis during the summer was riot impaired by biochemical or photochemical reactions. as CO(2) assimilation was only limited by stomatal conductance due to high leaf-to-air vapor pressure difference (VPD) during the afternoon. During the winter, the reduction in photosynthesis during the afternoon Was Caused by decreases in RuBP regeneration and stomatal conductance, which are both precipitated by low night temperature. (c) 2009 Elsevier B.V. All rights reserved.

Apports et limites de la scintigraphie pulmonaire dans le diagnostic de l'embolie pulmonaire [Value and limitation of pulmonary scintigraphy in the diagnosis of pulmonary embolism].

Perfusion lung scan, whether associated with a ventilation lung scan or not, is frequently used in the diagnosis of pulmonary emboli. The characteristics of perfusion lung scan are reviewed. The added diagnostic value of standard chest X-ray and of ventilation scan is discussed, as well as its use in the intensive care unit.

Interét et limites de l'evaluation du risque de récidive d'actes illégaux dans les expertises psychiatriques [Benefits and limitation of the assessment of second offense risk in psychiatric expertise].

The legislatives evolutions imply an important recourse to the psychiatric expertise in order to evaluate the potential dangerousness of a subject. However, in spite of the development of techniques and tools for this evaluation, the dangerousness assessment of a subject is in practice extremely complex and discussed in the scientific literature. The evolution of the concept of dangerousness to the risk assessment involved a technicisation of this evaluation which should not make forget the limits of these tools and the need for restoring the subject, the meaning and the clinic in this evaluation.

Initiation and limitation of Ly-49A NK cell receptor acquisition by T cell factor-1.

The establishment of clonally variable expression of MHC class I-specific receptors by NK cells is not well understood. The Ly-49A receptor is used by approximately 20% of NK cells, whereby most cells express either the maternal or paternal allele and few express simultaneously both alleles. We have previously shown that NK cells expressing Ly-49A were reduced or almost absent in mice harboring a single or no functional allele of the transcription factor T cell factor-1 (TCF-1), respectively. In this study, we show that enforced expression of TCF-1 in transgenic mice yields an expanded Ly-49A subset. Even though the frequencies of Ly-49A(+) NK cells varied as a function of the TCF-1 dosage, the relative abundance of mono- and biallelic Ly-49A cells was maintained. Mono- and biallelic Ly-49A NK cells were also observed in mice expressing exclusively a transgenic TCF-1, i.e., expressing a fixed amount of TCF-1 in all NK cells. These findings suggest that Ly-49A acquisition is a stochastic event due to limiting TCF-1 availability, rather than the consequence of clonally variable expression of the endogenous TCF-1 locus. Efficient Ly-49A acquisition depended on the expression of a TCF-1 isoform, which included a domain known to associate with the TCF-1 coactivator beta-catenin. Indeed, the proximal Ly-49A promoter was beta-catenin responsive in reporter gene assays. We thus propose that Ly-49A receptor expression is induced from a single allele in occasional NK cells due to a limitation in the amount of a transcription factor complex requiring TCF-1.

La limitation de responsabilité dans le transport multimodal

"Mémoire présenté à la Faculté des études supérieures en vue de l'obtention du grade de L.L.M. en droit des affaires"

Les causes de déchéance du droit à limitation de responsabilité du transporteur maritime international de marchandises sous connaissement

La présente étude examine les causes de déchéance du droit à limitation de responsabilité du transporteur maritime de marchandises. En règle générale, les plafonds d’indemnisation fixés par les conventions internationales écartent la réparation intégrale du préjudice causé par le transporteur maritime de marchandises. Cependant, il est également prévu un certain nombre de causes de déchéance de ce droit à limitation, pour lesquelles les conditions d’application diffèrent d’une convention internationale à l’autre (Règles de La Haye, Règles de La Haye-Visby, Règles de Hambourg et Règles de Rotterdam). Parallèlement, les tribunaux nationaux, par le recours à des notions propres de leurs systèmes juridiques, modifient l’étendue des causes de déchéance de ce droit. En somme, la déchéance du droit à limitation de responsabilité variera selon la convention internationale appliquée et selon la juridiction compétente. Ce qui, en définitive, porte atteinte à la structuration rationnelle du régime de responsabilité du transporteur maritime dans sa globalité et à l’objectif d’uniformisation poursuivi jusqu’ici.

Limitation of double folding potentials to simulate the polarization in reactions involving halo nuclei

In this work, we investigate the limitation of the use of strength coefficients on double folding potentials to study the presence of the threshold anomaly in the elastic scattering of halo nuclei at near barrier energies. For this purpose, elastic angular distributions and reaction cross sections for the He-6 on Bi-209 are studied. (c) 2008 Elsevier B.V. All rights reserved.