Influence du nitrate d'hexyle et de la température de l'air admis sur les délais d'inflammation des huiles végétales dans un moteur diesel

Le but de ce travail est de vérifier l'influence, d'une part, d'u améliorant d'indice de cétane - le nitrate d'hexyle -, et d'autre part, de la température de l'air admis sur les délais d'inflammation des huiles végétales dans un moteur diesel à chambre de turbulence. Les résultats révèlent que dans un moteur sensible aux conditions rencontrées par le carburant au moment de l'injection : - 8 % environ de nitrate d'hexyle sont nécessaires aux huiles végétales courantes pour avoir les mêmes valeurs de délai d'inflammation que le gazole, - les huiles présentant les délais les plus longs, avec une température d'admission de 25 deg C. retrouvent les valeurs de délais du gazole lorsque l'air est admis à 105 ¼C (+80 deg C

Staphylococcus aureus pathogenicity in cystic fibrosis patients-results from an observational prospective multicenter study concerning virulence genes, phylogeny, and gene plasticity

Staphylococcus aureus and cystic fibrosis (CF) are closely interlinked. To date, however, the impact of S. aureus culture in CF airways on lung function and disease progression has only been elucidated to a limited degree. This analysis aims to identify bacterial factors associated to clinical deterioration. Data were collected during an observational prospective multi-center study following 195 patients from 17 centers. The average follow-up time was 80 weeks. S. aureus isolates (n = 3180) were scanned for the presence of 25 virulence genes and agr-types using single and multiplex PCR. The presence of specific virulence genes was not associated to clinical deterioration. For the agr-types 1 and 4, however, a link to the subjects' clinical status became evident. Furthermore, a significant longitudinal decrease in the virulence gene quantity was observed. Analyses of the plasticity of the virulence genes revealed significantly increased plasticity rates in the presence of environmental stress. The results suggest that the phylogenetic background defines S. aureus pathogenicity rather than specific virulence genes. The longitudinal loss of virulence genes most likely reflects the adaptation process directed towards a persistent and colonizing rather than infecting lifestyle

Five amino acids of the Xenopus laevis CRF (corticotropin- releasing factor) type 2 receptor mediate differential binding of CRF ligands in comparison with its human counterpart

The ligand selectivity of human (hCRF(2A)) and Xenopus laevis (xCRF(2)) forms of the corticotropin-releasing factor type 2 (CRF2) receptor differs. The purpose of this study was to identify amino acids in these two CRF2 receptors conferring these differences. An amino acid triplet in the third extracellular domain (Asp(262)Leu(263)Val(264) in hCRF(2A) or Lys(264)Tyr(265)IIe(266) in xCRF(2)) was found to diverge between both receptors. When binding and signaling characteristics of receptor mutants hR2KYI and xR2DLV were assessed, the tri-amino acid motif replacement produced receptors with binding properties resembling the xCRF(2) receptor. The converse mutation created a mutant receptor with a binding pharmacology identical to the profile of the hCRF(2A) receptor. This effect was most notable for xR2DLV, which possessed a binding affinity for astressin similar to15-fold greater for astressin than sauvagine. In contrast, the binding profiles of the hCRF(2A) receptor and hR2KYI did not differ. These data indicate that another domain of the xCRF(2) receptor mediated low-affinity binding of astressin. Two amino acids in the first extracellular domain differ in xCRF(2) (Asp(69)Ser(70)) and hCRF(2A) (Glu(66)Tyr(67)) receptors. The hCRF(2A) receptor mutant (hR2DS-KYI) bound astressin with a low affinity indistinguishable from the xCRF(2) receptor. Therefore, these data demonstrate that ligand selectivity differences between amphibian and human forms of the CRF2A receptor are governed by these two motifs of the extracellular domains of the xCRF(2) receptor

Rapid measurement of trunk MOE on standing trees using RIGIDIMETER

International audienc

Rapid measurement of trunk MOE on standing trees using RIGIDIMETER

Rigidimeter is a device developed in order to determine the modulus of elasticity (MOE) of standing trees. It was used on a hybrid Larch clonal test located at INRA, Orléans, France. Some of the examined trees were felled and remeasured. The goal of this study was to contribute to the validation of the Rigidimeter, as a fast non-destructive and reliable tool for rapid evaluation of MOE, an important mechanical property of wood. Two measurements in orthogonal directions improve the accuracy especially in the presence of reaction wood. We have showed that two measurements of diameter including bark with a precision of $\pm 1$ mm are sufficient to obtain a reliable second moment of area, which is an important parameter for the estimation of trunk MOE. Bark MOE is small compared to wood MOE, but bark thickness influences the measurement of tree diameter. A correction may be necessary to account for the presence of bark. We propose a method for estimating MOE of different trunk layers, such as bark and mature wood layer.Mesure rapide du module d'élasticité des arbres sur pied à l'aide du Rigidimètre. L'appareil que nous avons développé pour mesurer le module d'élasticité (MOE) des arbres sur pied, le Rigidimètre, est utilisé dans un test de mélèze hybride à l'INRA d'Orléans en France. L'objectif de l'étude est de contribuer à la validation de sa fiabilité pour la détermination rapide de cette propriété mécanique importante. Nous évaluons ici (1) la méthode de mesure du diamètre du tronc, (2) l'influence de l'écorce, (3) quelques détails de la procédure de mesure sur la précision de l'estimation du MOE du tronc. La méthode de mesure du diamètre proposé permet d'estimer correctement le moment quadratique de la section du tronc, un paramètre important de l'estimation du MOE. L'écorce influence l'estimation du MOE, non pas au travers de son MOE propre qui semble très faible, mais par l'intermédiaire de son épaisseur qui fait varier le diamètre sur écorce. Nous proposons une méthodologie de l'utilisation de l'appareil qui permet d'estimer le MOE des derniers cernes fabriqués, c'est-à-dire du bois adulte dans l'arbre sur pied