Non-linear photochemical pathways in laser induced atmospheric aerosol formation

We measured the chemical composition and the size distribution of aerosols generated by femtosecond-Terawatt laser pulses in the atmosphere using an aerosol mass spectrometer (AMS). We show that nitric acid condenses in the form of ammonium nitrate, and that oxidized volatile organics also contribute to particle growth. These two components account for two thirds and one third, respectively, of the dry laser-condensed mass. They appear in two different modes centred at 380 nm and 150 nm. The number concentration of particles between 25 and 300 nm increases by a factor of 15. Pre-existing water droplets strongly increase the oxidative properties of the laser-activated atmosphere, substantially enhancing the condensation of organics under laser illumination.Comment: 19 pages, 5 figure

Survivor: An Approach for Adding Dependability to Legacy Workflow Systems

Although they often provide critical services, most workflow systems are not dependable. There has been much literature on dependable/survivable distributed systems; most is concerned with developing new architectures, not adapting pre-existing ones. Additionally, the literature is focused on hardening, security-based defense, as opposed to recovery. For deployed systems, it is often infeasible to completely replace existing infrastructures; what is more pragmatic are ways in which existing distributed systems can be adapted to offer better dependability. In this paper, we outline a general architecture that can easily be retrofitted to legacy workflow systems in order to improve dependability and fault tolerance. We do this by monitoring enactment and replicating partial workflow states as tools for detection, analysis and recovery. We discuss some policies that can guide these mechanisms. Finally, we describe and evaluate our implementation, Survivor, which modified an existing workflow system provided by the Naval Research Lab

Low temperature tunneling current enhancement in silicide/Si Schottky contacts with nanoscale barrier width

The low temperature electrical behavior of adjacent silicide/Si Schottky contacts with or without dopant segregation is investigated. The electrical characteristics are very well modeled by thermionic-field emission for non-segregated contacts separated by micrometer-sized gaps. Still, an excess of current occurs at low temperature for short contact separations or dopant-segregated contacts when the voltage applied to the device is sufficiently high. From two-dimensional self-consistent non-equilibrium Green's function simulations, the dependence of the Schottky barrier profile on the applied voltage, unaccounted for in usual thermionic-field emission models, is found to be the source of this deviation

Disparate effects of chronic and acute theophylline on cyclosporine A nephrotoxicity

Abstract : We previously developed a model of acute cyclosporine A (CsA)-induced vasomotor nephrotoxicity in rabbits. As exogenous adenosine infusion mimics the haemodynamic changes that characterize acute renal failure (ARF), we wanted to know whether adenosine was a mediator in this model and whether an adenosine receptor blocker could prevent the CsA-induced ARF. Group 1 were untreated controls. Group 2 received CsA (25 mg/kg per day) for 5 days. Renal function parameters were measured, showing ARF in all animals compared to controls. Theophylline (1 mg/kg i.v. bolus) was then administered and renal function was reassessed. Theophylline significantly reduced renal vascular resistance (-8%) and increased renal blood flow (RBF) (+20%), glomerular filtration rate (GFR) (+50%), filtration fraction (+24%) and diuresis (+73%), suggesting that adenosine was involved in the CsA-induced ARF. In group 3, theophylline (30 mg/kg per day) was given concomitantly with CsA for 5 days. GFR was normalized, but theophylline did not hinder the drop in RBF seen with CsA alone in group 2. Microscopy observation of the kidneys showed that chronic theophylline administration aggravated the morphological changes induced by CsA alone. We conclude that CsA administration for 5 days induced a vasomotor nephropathy with an adenosine-mediated afferent arteriolar constriction which cannot be prevented by concomitant theophylline administratio

L'ombre d'un doute ? Interactions perceptivo-motrices lors de tâches de close-shadowing auditive et audio-visuelles

International audienceOne classical argument in favor of a functional role of the motor system in speech perception comes from the close shadowing task in which a subject has to identify and to repeat as quickly as possible an auditory speech stimulus. The fact that close shadowing can occur very rapidly and much faster than manual identification of the speech target is taken to suggest that perceptually-induced speech representations are already shaped in a motor-compatible format. Another argument is provided by audiovisual interactions often interpreted as referring to a multisensory-motor framework. In this study, we attempted to combine these two paradigms by testing whether the visual modality could speed motor response in a close-shadowing task. To this aim, both oral and manual responses were evaluated during the perception of auditory and audio-visual speech stimuli, clear or embedded in white noise. Overall, oral responses were much faster than manual ones, but it also appeared that they were less accurate in noise, which suggests that motor representations evoked by the speech input could be rough at a first processing stage. In the presence of acoustic noise, the audiovisual modality led to both faster and more accurate responses than the auditory modality. No interaction was however observed between modality and response. Altogether, these results are interpreted within a two-stage sensory-motor framework, in which the auditory and visual streams are integrated together and with internally generated motor representations before a final decision may be available.Un argument classique en faveur des théories motrices de la perception de la parole provient du paradigme de " close-shadowing " (répétition rapide). Le fait que cette tâche de close-shadowing entraîne des réponses orales bien plus rapides qu'en réponses manuelles suggère en effet un codage des représentations perceptives dans un format moteur, compatible avec une réponse orale. Un autre argument est apporté par les interactions audio-visuelles lors de la perception de parole, souvent interprétées en référence à un couplage fonctionnel entre audition, vision et motricité. Dans cette étude, nous avons combiné ces deux paradigmes de manière à tester si la modalité visuelle pouvait induire des réponses motrices plus rapides lors d'une tâche de close-shadowing. Pour ce faire, différentes tâches de catégorisation orale et manuelle de stimuli de parole présentés auditivement ou audio-visuellement, en présence ou non d'un bruit blanc, ont été réalisées. De manière générale, les réponses orales ont été plus rapides que les réponses manuelles, mais aussi moins précises, notamment dans le bruit, ce qui suggère que la représentation motrice induite par la stimulation pourrait être peu précise dans un premier niveau de traitement. En présence d'un bruit acoustique, la modalité audiovisuelle s'est avérée à la fois plus rapide et plus précise que la modalité auditive. Aucune interaction entre le mode de réponse et la modalité de présentation des stimuli n'a cependant été observée. Nous interprétons l'ensemble de ces résultats dans un cadre théorique proposant l'existence de boucles perceptivo-motrices, dans lesquelles les entrées auditives et visuelles seraient intégrées et reliées à la génération interne de représentations motrices préalablement au processus final de décision

Central nesfatin-1-expressing neurons are sensitive to peripheral inflammatory stimulus

Recently, a novel factor with anorexigenic properties was identified and called nesfatin-1. This protein (82 aac) is not only expressed in peripheral organs but it is also found in neurons located in specific structures including the hypothalamus and the brainstem, two sites strongly involved in food intake regulation. Here, we studied whether some of the neurons that become activated following an injection of an anorectic dose of lipopolysaccharides (LPS) exhibit a nesfatin-1 phenotype. To this end, we used double immunohistochemistry to target the expression of the immediate-early gene c-fos and of nesfatin-1 on coronal frozen sections of the rat brain. The number of c-Fos+/nesfatin-1+ neurons was evaluated in the immunosensitive structures reported to contain nesfatin-1 neurons; i.e. paraventricular hypothalamic nucleus (PVN), supraoptic nucleus (SON), arcuate nucleus (ARC) and nucleus of the solitary tract (NTS). LPS strongly increased the number of c-Fos+/nesfatin-1+ neurons in the PVN, SON and NTS, and to a lesser extent in the ARC. Triple labeling showed that a portion of the nesfatin-1 neurons activated in response to LPS within the NTS are catecholaminergic since they co-express tyrosine hydroxylase (TH). Our data therefore indicate that a portion of nesfatin-1 neurons of both the hypothalamus and brainstem are sensitive to peripheral inflammatory signals, and provide the first clues suggesting that centrally released nesfatin-1 may contribute to the neural mechanisms leading to endotoxaemic anorexia

L'ombre d'un doute ? Interactions perceptivo-motrices lors de tâches de close-shadowing auditive et audio-visuelles

International audienceOne classical argument in favor of a functional role of the motor system in speech perception comes from the close shadowing task in which a subject has to identify and to repeat as quickly as possible an auditory speech stimulus. The fact that close shadowing can occur very rapidly and much faster than manual identification of the speech target is taken to suggest that perceptually-induced speech representations are already shaped in a motor-compatible format. Another argument is provided by audiovisual interactions often interpreted as referring to a multisensory-motor framework. In this study, we attempted to combine these two paradigms by testing whether the visual modality could speed motor response in a close-shadowing task. To this aim, both oral and manual responses were evaluated during the perception of auditory and audio-visual speech stimuli, clear or embedded in white noise. Overall, oral responses were much faster than manual ones, but it also appeared that they were less accurate in noise, which suggests that motor representations evoked by the speech input could be rough at a first processing stage. In the presence of acoustic noise, the audiovisual modality led to both faster and more accurate responses than the auditory modality. No interaction was however observed between modality and response. Altogether, these results are interpreted within a two-stage sensory-motor framework, in which the auditory and visual streams are integrated together and with internally generated motor representations before a final decision may be available.Un argument classique en faveur des théories motrices de la perception de la parole provient du paradigme de " close-shadowing " (répétition rapide). Le fait que cette tâche de close-shadowing entraîne des réponses orales bien plus rapides qu'en réponses manuelles suggère en effet un codage des représentations perceptives dans un format moteur, compatible avec une réponse orale. Un autre argument est apporté par les interactions audio-visuelles lors de la perception de parole, souvent interprétées en référence à un couplage fonctionnel entre audition, vision et motricité. Dans cette étude, nous avons combiné ces deux paradigmes de manière à tester si la modalité visuelle pouvait induire des réponses motrices plus rapides lors d'une tâche de close-shadowing. Pour ce faire, différentes tâches de catégorisation orale et manuelle de stimuli de parole présentés auditivement ou audio-visuellement, en présence ou non d'un bruit blanc, ont été réalisées. De manière générale, les réponses orales ont été plus rapides que les réponses manuelles, mais aussi moins précises, notamment dans le bruit, ce qui suggère que la représentation motrice induite par la stimulation pourrait être peu précise dans un premier niveau de traitement. En présence d'un bruit acoustique, la modalité audiovisuelle s'est avérée à la fois plus rapide et plus précise que la modalité auditive. Aucune interaction entre le mode de réponse et la modalité de présentation des stimuli n'a cependant été observée. Nous interprétons l'ensemble de ces résultats dans un cadre théorique proposant l'existence de boucles perceptivo-motrices, dans lesquelles les entrées auditives et visuelles seraient intégrées et reliées à la génération interne de représentations motrices préalablement au processus final de décision

DFT study of dihydrogen addition to molybdenum π-heteroaromatic complexes: a prerequisite step for the catalytic hydrodenitrogenation process

International audienceThe range of molybdenum hydride complexes that are sought to participate in the important catalytic hydrodenitrogenation process (HDN) of nitrogen containing polycyclic aromatic hydrocarbons were evaluated by DFT studies. The previously synthesized stable (η6-quinoline)Mo(PMe3)3 complex 1N, in which molybdenum is bonded to the heterocyclic ring, was chosen as a model. The hydrogenation of the quinone heterocycle, which was postulated as the initial step in the overall HDN reaction, is found to occur via three consecutive steps of the oxidative addition of dihydrogen to Mo in 1N. Successive transfer of hydrogen atoms from the metal to the heterocycle leads to the ultimate formation of the tetrahydrido molybdenum intermediate Mo(PMe3)4H413 and 2,2,3,3-tetrahydroquinoline C9H11N 14. All the involved intermediates and transition states have been fully characterized by DFT. This computational modeling of the hydrogenation of quinoline, as a part of extended HDN catalytic processes, provides a fundamental understanding of such mechanism