Imaging of viroids in nuclei from tomato leaf tissue by in situ hybridization and confocal laser scanning microscopy.

The intracellular localization of viroids has been investigated by viroid-specific in situ hybridization and analysis by digital microscopy of the distribution of the fluorescent hybridization signals. Isolated nuclei from green leaf tissue of tomato plants infected with potato spindle tuber viroid (PSTVd) were bound to microscope slides, fixed with formaldehyde and hybridized with biotinylated transcripts of cloned PSTVd cDNA. The bound probe was detected with lissamine--rhodamine conjugated streptavidin. Nucleoli were identified by immunofluorescence using the monoclonal antibody Bv96 and a secondary FITC-conjugated antibody. In plants infected with either a lethal or an intermediate PSTVd strain, the highest intensity of fluorescence that arose from hybridization with the probe specific for the viroid (+)strand was found in the nucleoli, confirming results of previous fractionation studies. A similar distribution was found for (-)strand replication intermediates of PSTVd using specific (+)strand transcripts as hybridization probes. In order to determine if viroids are located at the surface or in the interior of the nucleoli, the distribution of the fluorescence hybridization signals was studied with a confocal laser scanning microscope (CLSM). It was shown by three-dimensional reconstruction that viroids are neither restricted to the surface of the nucleoli nor to a peripheral zone, but are instead homogeneously distributed throughout the nucleolus. The functional implications of the intranucleolar location of viroids and their replication intermediates are discussed with respect to proposed mechanisms of viroid replication and pathogenesis

Homogénéisation des signaux isotopiques, 18O et 3H, dans un système hydrologique de haute montagne : la Vallée d'Aoste (Italie)

L'analyse de l'origine et de la dynamique des écoulements souterrains dans l'aquifère du milieu alluvial de la plaine d'Aoste (Italie) a été menée en étudiant les teneurs isotopiques (18O et 3H) des eaux sur l'ensemble du système hydrologique. La démarche a consisté en un suivi isotopique des précipitations pluvio-neigeuses, des sources de versants, du réseau de surface et de l'aquifère alluvial, complété par des analyses ponctuelles concernant l'horizon superficiel des glaciers et les sous-écoulements glaciaires. Le signal d'entrée en 18O porté par les précipitations présente une grande variabilité liée au contexte orographique (effet d'écran) et climatique (pluie ou neige). Celle-ci est mise en évidence par les changements saisonniers du gradient 18O/altitude. En moyenne annuelle (1994), ce gradient établi en Vallée d'Aoste à partir de mesures sur les précipitations récoltées entre 300 et 3500 m d'altitude (sur huit stations) est de - 0.18 ± 0.02 ‰ pour 100 m, avec un écart-type (s) des valeurs de ± 4,8 ‰. L'ensemble des résultats en 18O montre au cours du cycle hydrologique, un amortissement à la fois important et progressif du signal d'entrée fourni par les précipitations. Cet amortissement, de l'ordre de 30 fois dans l'aquifère alluvial (sigma=± 0.15 ‰), est particulièrement sensible au niveau de la glace et des sous-écoulements glaciaires. En ce qui concerne les résultats en 3H, les teneurs mesurées dans les précipitations se révèlent être étroitement liées avec l'origine et la trajectoire des masses d'air humide. Par ailleurs, on note une bonne concordance entre les temps de séjour des eaux dans l'aquifère alluvial calculés à partir des valeurs en 18O et ceux fournis par le 3H.The hydrogeological study of the alluvial aquifer of the Aosta plain (Italy) is chosen as one of the most appropriate examples representative of the Italian-French-Swiss Alps. This study has been carried out using two environmental isotopes (18O and 3H) for groundwater samples taken from this aquifer in order to shed light on the origin of water and the hydrodynamic characteristics of the aquifer.The surface area of this aquifer is 70 km_ and mean elevation ranges between 400 and 700 m (asl). This surface area constitutes a part of the watershed area that amounts 2400 km_ with a mean elevation of 2200 m (asl). The watershed possesses several mountain peaks, Mt. Blanc, Mt. Cervin, Mt. Grand Paradis, the elevation of which rise to over 4000 m.The input signal, quantitative and qualitative as well, provided by the precipitation shows a wide variability linked to both orographic (screen effect) and climatic (rain or snow) influences. This variability is marked by differences in the 18O/altitude gradient, which is seasonally dependent. A unique and linear relation is observed during spring and summer ; in autumn and winter results show an important gradient up to 2000 m but a less important one for higher altitudes.The mean annual (1994) gradient of - 0.18 ± 0.02 ‰ for 100 m is determined in Aosta valley for altitudes between 300 and 3500 m, and the standard deviation (sigma) of the mean volume-weighted value for precipitation is ± 4.8 ‰. Furthermore, the 18O values measured in the alluvial aquifer have shown a very low dispersion (sigma=± 0.15 ‰), which corresponds to a buffering effect of a factor 30. These results evidenced, thus, an homogenization process within the different water bodies.To analyze this homogenization process, the different components of the hydrologic system have been studied, i.e. the monitoring of the springs and runoff waters, with complementary local measurements of the upper part of ice cores and the glacier underflows. Using standard deviations (sigma) as criteria for the homogenization process, one can see a large and progressive decrease along the hydrological cycle, with a special amplitude in ice cores and glacier underflows : precipitation (± 4.8 ‰), ice core (± 0.8 ‰), glacier underflow (± 0.10 ‰), spring (± 0.15 ‰), surface runoff network (± 0.3 ‰), alluvial aquifer (± 0.15 ‰).In ice cores, the different process : freezing and thawing, compression, and vapor / liquid / solid exchanges have caused the 18O homogenization. Dealing with the springs on the slopes of the valley, the preferential flow paths linked to the fracturation lead to a mixing of waters and hence to a very buffered outflow signal. The combined effect of all these explains the stability and the uniformity of the data found in the alluvial water body.As far as the 3H concentrations are concerned, the values measured are tightly linked with the origin and the transport of humid air masses. For closely spaced stations, a significant difference in the input signal has been correlated to various climatic influences. Using 3H data from the Thonon-les-Bains station (included in the WMO-IAEA observation network) as input, the calculated transit times of 2.5 to 7.5 years are very close to those calculated with 18O, i.e. 4 to 7 years

Crashworthiness of foam-filled and reinforced honeycomb crash absorbers in transverse direction

Honeycomb crash absorbers have been widely studied as energy absorption devices for use in automotive industries. However, none of these investigations have studied the side impact of empty and foam-filled honeycomb absorbers and adding stiffeners between the different layers of the corrugated sheets which are composing the honeycomb structure to analyse the structure under transverse (L-direction) impacts. In this paper, the foam-filled and reinforced honeycomb crash absorbers are investigated under axial (T) and transverse (L) loading directions. Experimental results for both empty and foam-filled specimens under quasi-static and impact loads were implemented to validate the developed finite element model. Finite element analysis (FEA) was performed to find out the crashworthiness behaviour of the structure under axial and transverse impacts according to road conditions. Finally, a new design of stiffened honeycomb crash absorber was developed and investigated to reduce the level of acceleration experienced by the passengers during the crash event. In this regard, it is concluded that all the requirements related to the energy absorption capabilities and generated deceleration under impact loading can be met by introducing an advanced method to reinforce honeycomb absorbers using stiffeners. It is also proven that the thickness of these stiffeners will not significantly influence the force levels. Due to increase of wall thickness from 1 to 3 mm, the mean crushing force increased from 129 kN to 148 kN. This growth is not sufficient as the goal is to obtain a mean crushing force of 300 kN. Thickening the stiffeners would lead to a loss of efficiency of the structure, as the small increase in mean force would not make up for the gain in mass. Thus, increasing the corrugated sheet’ thickness becomes necessary.Thailand Metal and Materials Technology Center (MTEC); Bangkok Expressway; Metro Public Company Ltd; Royal Academy of Engineering (RAE) through the Engineering X Transforming Systems through Partnership programm

Intracranial aneurismal pulsatility as a new individual criterion for rupture risk evaluation: Biomechanical and numerical approach (IRRAs project).

International audienceThis study was designed to highlight by means of numerical simulations, the correlation between aneurism sac pulsatility and the risk of rupture through the mechanical properties of the wall. In accordance to previous work suggesting a correlation between the risk of rupture and the material properties of cerebral aneurysms, twelve fluid-structure interaction (FSI) computations were performed on 12 "patient-specific" cases, corresponding to typical shapes and locations of cerebral aneurysms. The variations of the aneurismal volume during the cardiac cycle (3V) are compared using wall material characteristics of either degraded and non-degraded tissues. Aneurysms were located on 7 different arteries: Middle Cerebral Artery (4), Anterior Cerebral Artery (3), Internal Carotid Artery (1), Vertebral Artery (1), Ophthalmic Artery (1) and Basilar Artery (1). Aneurysms presented different shapes (uniform or multi-lobulated) and diastolic volumes (from 18 to 392 mm3). The pulsatility (3V/V) was significantly larger for a soft aneurismal material (average of 26 %) than for a stiff material (average of 4 %). The difference between 3V, for each condition, was statistically significant: p = 0.005. The difference in aneurismal pulsatility as highlighted in this work might be a relevant patientspecific predictor of aneurysm risk of rupture

LES-based Study of the Roughness Effects on the Wake of a Circular Cylinder from Subcritical to Transcritical Reynolds Numbers

This paper investigates the effects of surface roughness on the flow past a circular cylinder at subcritical to transcritical Reynolds numbers. Large eddy simulations of the flow for sand grain roughness of size k/D = 0.02 are performed (D is the cylinder diameter). Results show that surface roughness triggers the transition to turbulence in the boundary layer at all Reynolds numbers, thus leading to an early separation caused by the increased momentum deficit, especially at transcritical Reynolds numbers. Even at subcritical Reynolds numbers, boundary layer instabilities are triggered in the roughness sublayer and eventually lead to the transition to turbulence. The early separation at transcritical Reynolds numbers leads to a wake topology similar to that of the subcritical regime, resulting in an increased drag coefficient and lower Strouhal number. Turbulent statistics in the wake are also affected by roughness; the Reynolds stresses are larger due to the increased turbulent kinetic energy production in the boundary layer and separated shear layers close to the cylinder shoulders.We acknowledge “Red Española de Surpercomputación” (RES) for awarding us access to the MareNostrum III machine based in Barcelona, Spain (Ref. FI-2015-2-0026 and FI-2015-3-0011). We also acknowledge PRACE for awarding us access to Fermi and Marconi Supercomputers at Cineca, Italy (Ref. 2015133120). Oriol Lehmkuhl acknowledges a PDJ 2014 Grant by AGAUR (Generalitat de Catalunya). Ugo Piomelli acknowledges the support of the Natural Sciences and Engineering Research Council (NSERC) of Canada under the Discovery Grant Programme (Grant No. RGPIN-2016-04391). Ricard Borrell acknowledges a Juan de la Cierva postdoctoral grant (IJCI-2014-21034). Ivette Rodriguez, Oriol Lehmkuhl, Ricard Borrell and Assensi Oliva acknowledge Ministerio de Economía y Competitividad, Secretaría de Estado de Investigación, Desarrollo e Innovación, Spain (ref. ENE2014-60577-R).Peer ReviewedPostprint (author's final draft

Using LES to Study Reacting Flows and Instabilities in Annular Combustion Chambers

Great prominence is put on the design of aeronautical gas turbines due to increasingly stringent regulations and the need to tackle rising fuel prices. This drive towards innovation has resulted sometimes in new concepts being prone to combustion instabilities. In the particular field of annular combustion chambers, these instabilities often take the form of azimuthal modes. To predict these modes, one must compute the full combustion chamber, which remained out of reach until very recently and the development of massively parallel computers. Since one of the most limiting factors in performing Large Eddy Simulation (LES) of real combustors is estimating the adequate grid, the effects of mesh resolution are investigated by computing full annular LES of a realistic helicopter combustion chamber on three grids, respectively made of 38, 93 and 336 million elements. Results are compared in terms of mean and fluctuating fields. LES captures self-established azimuthal modes. The presence and structure of the modes is discussed. This study therefore highlights the potential of LES for studying combustion instabilities in annular gas turbine combustors