Reactions of [NH3+·, H2O] with carbonyl compounds: a McLafferty rearrangement within a complex?

AbstractThe reactions of the water solvated ammonia radical cation [NH3·+, H2O] with a variety of aldehydes and ketones were investigated. The reactions observed differ from those of low energy aldehydes and ketones radical cations, although electron transfer from the keto compound to ionized ammonia is thermodynamically allowed within the terbody complexes initially formed. The main process yields an ammonia solvated enol with loss of water and an alkene. This process corresponds formally to a McLafferty fragmentation within a complex. With aldehydes, another reaction can take place, namely the transfer of the hydrogen from the CHO group to ammonia, leading to the proton bound dimer of ammonia and water, and to the NH4+ cation. Comparison between the available experimental results leads to the conclusion that the McLafferty fragmentation occurs within the terbody complex initially formed, with no prior ligand exchange, the water molecule acting as a spectator partner

Dimer and trimer procyanidins in Carignan and Mourvèdre grapes and red wines

Dimer procyanidins, galloylated or not, and trimers were analysed in the red grapes Carignan and Mourvedre. Procyanidins were extracted from the various parts of the grape bunch and then quantified by HPLC. In Carignan and Mourvedre grapes, procyanidin B2 was the major component in seeds, whereas procyanidin B1 was the major component in stems and skins. Trimeric procyanidins were also present in grapes in larger amounts. Various red wines were produced from Carignan and Mourvedre grapes, using different winemaking procedures: entire crushed harvest, destemmed harvest, carbonic maceration and heating of the harvest. Entire crushed harvest gave red wines with the highest levels of procyanidins. An important release of procyanidins, especially procyanidin B1 from skins and stems, when present, occurred.Procyanidines dimères et trimères des raisins et vins rouges de Carignan et MourvèdreDes procyanidines dimères galloylées et non-galloylées, et trimères sont dosées dans deux cépages rouges: Carignan et Mourvèdre. Les procyanidines sont extraites des différentes parties de la grappe puis quantifiées par CLHP en phase inverse. Dans le raisin de Carignan et de Mourvedre, la procyanidine B2 est la plus abondante dans les pepins, tandis que la procyanidine B1 est la plus abondante dans les rafles et pellicules. Les procyanidines trimères sont aussi présentes en quantités importantes. Différents vins rouges ont été élabores à partir des cépages Carignan et Mourvèdre, en utilisant plusieurs téchniques de vinification: vendange foulée; vendange éraflée, macération carbonique et le chauffage de la vendange. Les quantités les plus abondantes de procyanidines sont obtenues dans des vins issus d'une vendange entière et foulée

Nuevas evidencias acerca de la presencia de Stegomastodon platensis Ameghino, 1888, Proboscidea: Gomphotheriidae, en el Pleistoceno tardío de Chile central

This paper contextualizes, describes and taxonomically assigned cranial and dental Gomphotheriidae materials from the El Trebal 1, late Pleistocene form central Chile. Starting from metric and morphological variables fossils are included in Stegomastodon platensisStegomastodon platensis. Taxonomic implications of this finding as well as some regional paleoenvironmental history are discussed.El presente trabajo contextualiza, describe, y asigna taxonómicamente los materiales craneales y dentales de Gomphotheriidae provenientes del sitio El Trebal 1, Pleistoceno tardío de Chile central. A partir de variables métricas y morfológicas los fósiles son incluidos en Stegomastodon platensisStegomastodon platensis. Se discuten las implicancias taxonómicas de este hallazgo así como algunos antecedentes paleoambientales regionales

Modelled subglacial floods and tunnel valleys control the life cycle of transitory ice streams

Ice streams are corridors of fast-flowing ice that control mass transfers from continental ice sheets to oceans. Their flow speeds are known to accelerate and decelerate, their activity can switch on and off, and even their locations can shift entirely. Our analogue physical experiments reveal that a life cycle incorporating evolving subglacial meltwater routing and bed erosion can govern this complex transitory behaviour. The modelled ice streams switch on and accelerate when subglacial water pockets drain as marginal outburst floods (basal decoupling). Then they decelerate when the lubricating water drainage system spontaneously organizes itself into channels that create tunnel valleys (partial basal recoupling). The ice streams surge or jump in location when these water drainage systems maintain low discharge but they ultimately switch off when tunnel valleys have expanded to develop efficient drainage systems. Beyond reconciling previously disconnected observations of modern and ancient ice streams into a single life cycle, the modelling suggests that tunnel valley development may be crucial in stabilizing portions of ice sheets during periods of climate change

Prognostic factors to succeed in surgical treatment of chronic acromioclavicular dislocations

AbstractIntroductionTreatment of chronic acromioclavicular joint dislocation (ACJD) remains a poorly known and controversial subject. Given the many surgical options, it is not always easy to determine which steps are indispensable.MethodsThis article reports a multicenter prospective study. The clinical and radiological follow-up involved a comparative analysis of the preoperative and postoperative data at 1 year, including pain (visual analogue scale), subjective functional incapacity (QuickDASH), and the objective Constant score, as well as a comparative analysis of vertical and horizontal movements measured on simple x-rays.ResultsBased on a series of 140 operated ACJDs, we included 24 chronic ACJDs. The mean time to surgery was 46 weeks (range, 1 month to 4 years). The patients’ mean age was 41 years, with a majority of males (75%), 72% of whom participated in recreational sports. Professionally, 40% of the subjects had jobs involving manual labor. We noted 40% grade III, 24% grade IV, and 36% grade V injury according to the Rockwood classification. In 92% of cases, coracoclavicular stabilization was provided by a double button implant, reinforced with a biological graft in 88% of the cases. In 29%, millimeters to centimeters of the distal clavicle were resected and acromioclavicular stabilization was associated in 54%. We observed complications in 33% of the cases. At 1 year postoperative, 21 patients underwent clinical and radiological follow-up (87.5%). Only 35% of the patients were satisfied or very satisfied, whereas 100% of them would recommend the operation. Full-time work was resumed in 91% of the cases and all sports could be resumed in 86%. The pre- and postoperative values at 1 year changed as follows: the mean Constant score improved from 61 to 87 (p=0.00002); the subjective QuickDASH score decreased from 41 to 9 (p=0.00002); and radiologically significant reduction of the initial displacement was observed in the vertical plane (p<10−3) and the horizontal plane (p=0.022).ConclusionIn this study, the favorable prognostic factors found were: time to surgery less than 3 months (p=0.02), associated acromioclavicular stabilization, and postoperative immobilization with a sling extended to 6 weeks. However, resection of the distal clavicle did not influence the final result.Level of proofLevel II prospective non-randomized comparative study

Anomalous J/ψJ/\psi suppression in Pb-Pb interactions at 158 GeV per nucleon

The Drell-Yan and J/psi cross-sections measured in Pb-Pb collisions are compared with the values extrapolated from the results obtained in proton and light ion induced reactions. While the Drell-Yan production exhibits the normal expected behaviour, the yield of J/psi in Pb-Pb interactions is abnormally low, as it lies 9 standard deviations below the expected value. Moreover, the departure from the expected behaviour increases significantly from peripheral to central collisions. (C) 1997 Elsevier Science B.V