Evaluation of far-field tsunami hazard in French Polynesia based on historical data and numerical simulations

International audienceThe first tsunami hazard map of French Polynesia is presented here on the basis of historical data, and numerical simulations. French Polynesia, because of its central position in the most tsunami prone ocean, the Pacific, is strongly exposed to far-field tsunamis. As no previous study on the area had been conducted, we compiled catalogues of all the historical observations (14 events), and tide gauges records (69 marigrams). The catalogues emphasise the higher hazard associated to the Marquesas archipelago, but also the deficiency of robust data in most other parts of French Polynesia. The recourse to numerical simulations allowed us to complement the existing records, and to test tsunami scenarii over different bathymetry and topography configurations, representative of the diversity of islands in French Polynesia. The tsunami hazard map assigns a high exposure level to the Marquesas and the island of Rurutu. Other islands of the Austral, and the Gambier archipelago have a elevated level of exposure, as well as three islands of Society: Tahiti, Moorea, and Huahine. All other islands of French Polynesia are considered as moderately exposed

Lower bumblebee colony reproductive success in agricultural compared with urban environments

Urbanization represents a rapidly growing driver of land-use change. While it is clear that urbanization impacts species abundance and diversity, direct effects of urban land use on animal reproductive success are rarely documented. Here, we show that urban land use is linked to long-term colony reproductive output in a key pollinator. We reared colonies from wild-caught bumblebee (Bombus terrestris) queens, placed them at sites characterized by varying degrees of urbanization from inner city to rural farmland and monitored the production of sexual offspring across the entire colony cycle. Our land-use cluster analysis identified three site categories, and this categorization was a strong predictor of colony performance. Crucially, colonies in the two clusters characterized by urban development produced more sexual offspring than those in the cluster dominated by agricultural land. These colonies also reached higher peak size, had more food stores, encountered fewer parasite invasions and survived for longer. Our results show a link between urbanization and bumblebee colony reproductive success, supporting the theory that urban areas provide a refuge for pollinator populations in an otherwise barren agricultural landscape

Modelling Tundra Ponds as Initiators of Peat Plateau Thaw, Northern Hudson Bay Lowland, Manitoba

Frozen peat in permafrost regions poses a potential source of increased greenhouse gas production should these deposits thaw. Ponds on frozen peat plateaus in northern Manitoba are numerically modelled as heat sources to determine their potential to promote thaw. Modelling indicates that anticipated climate warming of approximately 2 °C between 2020 and 2050 will produce taliks up to few metres thick beneath ponds a few tens of metres across. However, active-layer thickness in the subaerial parts of peat plateaus will not increase beyond the peat thickness. These findings assume 1) a climate warming rate under a moderately effective intervention in greenhouse gas production, 2) pond freezing regimes that represent both rapid ice formation and ice formation delayed by rapid snow accumulation and 3) snow thermal conductivities that anticipate snow conductivity increase during the freeze interval. These conditions and properties may turn out to be less conducive to talik expansion than the values that will actually occur. Despite these uncertainties, peat plateau pond sizes and plateau margin positions can be monitored to ascertain the onset of accelerated thawing

Permafrost and Peatland Evolution in the Northern Hudson Bay Lowland, Manitoba

The northern Hudson Bay lowland includes the largest area of frozen peat plateau bog in Canada. Polar bear denning habitat, caribou forage, carbon storage, and wetland drainage control provided by peat plateaus will be affected if post-Little Ice Age warming continues. Mapping and thermal modeling of frozen peat plateau stability indicate that permafrost peatlands are stable at a mean annual air temperature as warm as -3.5˚C. In the peat plateaus of the northern lowland, permafrost can be absent at the peat plateau margins where peat plateaus border fens or lakes. Here, insulating snow accumulations permit thawed conditions at mean annual air temperatures colder than -3.5˚C. Continued warming will result in expansion of thawed zones, subsidence at plateau margins, and even collapse of plateau surfaces, resulting in conversion to fen. This process has already occurred across north-central Manitoba, Saskatchewan, and Alberta since the end of the Little Ice Age, and there are signs that it is extending into the northern Hudson Bay lowland. Wave erosion of subsiding plateau borders at lake shorelines is also resulting in loss of peat plateau bog.Les basses-terres du nord de la baie d’Hudson comprennent la plus grande zone composée de tourbière oligotrophe de plateaux tourbeux du Canada. Advenant que le réchauffement du post-Petit Âge glaciaire se poursuive, l’habitat de tanières de l’ours polaire, les zones de fourrage du caribou, le stockage de carbone et la régulation du drainage des zones humides découlant de la présence de plateaux palsiques en subiront des conséquences. Le mappage et la modélisation thermique de la stabilité du plateau palsique gelé indiquent que les tourbières de pergélisol sont stables lorsque la température moyenne annuelle de l’air est aussi chaude que -3,5 ˚C. Dans les plateaux palsiques des basses-terres du Nord, le pergélisol peut être absent en marge des plateaux palsiques lorsque les plateaux palsiques bordent des tourbières basses ou des lacs. Ici, les accumulations de neige isolante donnent lieu à des conditions de décongélation moyennant des températures moyennes annuelles de l’air plus froides que -3,5 ˚C. Le réchauffement continu se traduira par l’agrandissement des zones de décongélation, l’affaissement à la hauteur des marges des plateaux et même l’effondrement des surfaces de plateaux, ce qui transformera ces zones en tourbières basses. Ce processus a déjà commencé à se produire dans le centre-nord du Manitoba, de la Saskatchewan et de l’Alberta depuis la fin du Petit Âge glaciaire, sans compter qu’il y a des signes indiquant que cela s’étend dans le nord des basses-terres de la baie d’Hudson. L’érosion par les vagues des bordures de plateaux subsidantes à la hauteur des littoraux de lacs se traduit également par la perte de tourbières oligotrophes de plateaux tourbeux.  Mots clés : tourbière basse, basses-terres de la baie d’Hudson, lac, plateau palsique, tourbière, pergélisol, ours polaire, décongélation, parc national Wapus

Dynamic liquefaction of shear zones in intact loess during simulated earthquake loading

The 2010-2011 Canterbury earthquake sequence in New Zealand exposed loess-mantled slopes in the area to very high levels of seismic excitation (locally measured as >2 g). Few loess slopes showed permanent local downslope deformation, and most of these showed only limited accumulated displacement. A series of innovative dynamic back pressured shear-box tests were undertaken on intact and remoulded loess samples collected from one of the recently active slopes replicating field conditions under different simplified horizontal seismic excitations. During each test, the strength reduction and excess pore water pressures generated were measured as the sample failed. Test results suggest that although dynamic liquefaction could have occurred, a key factor was likely to have been that the loess was largely unsaturated at the times of the large earthquake events. The failure of intact loess samples in the tests was complex and variable due to the highly variable geotechnical characteristics of the material. Some loess samples failed rapidly as a result of dynamic liquefaction as seismic excitation generated an increase in pore-water pressure, triggering rapid loss of strength and thus of shear resistance. Following initial failure, pore pressure dissipated with continued seismic excitation and the sample consolidated, resulting in partial shear-strength recovery. Once excess pore-water pressures had dissipated, deformation continued in a critical effective stress state with no further change in volume. Remoulded and weaker samples, however, did not liquefy, and instead immediately reduced in volume with an accompanying slower and more sustained increase in pore pressure as the sample consolidated. Thereafter excess pressures dissipated and deformation continued at a critical state. The complex behaviour explained why, despite exceptionally strong ground shaking, there was only limited displacement and lack of run-out: dynamic liquefaction was unlikely to occur in the freely draining slopes. Dynamic liquefaction however remained a plausible mechanism to explain loess failure in some of the low-angle toe slopes, where a permanent water table was present in the loess

A visual processing advantage for young-adolescent deaf observers: Evidence from face and object matching tasks

It is unresolved whether the permanent auditory deprivation that deaf people experience leads to the enhanced visual processing of faces. The current study explored this question with a matching task in which observers searched for a target face among a concurrent lineup of ten faces. This was compared with a control task in which the same stimuli were presented upside down, to disrupt typical face processing, and an object matching task. A sample of young-adolescent deaf observers performed with higher accuracy than hearing controls across all of these tasks. These results clarify previous findings and provide evidence for a general visual processing advantage in deaf observers rather than a face-specific effect

CTF3 Design Report: Preliminary Phase

The design of CLIC is based on a two-beam scheme, where the short pulses of high power 30 GHz RF are extracted from a drive beam running parallel to the main beam. The 3rd generation CLIC Test Facility (CTF3) will demonstrate the generation of the drive beam with the appropriate time structure, the extraction of 30 GHz RF power from this beam, as well as acceleration of a probe beam with 30 GHz RF cavities. The project makes maximum use of existing equipment and infrastructure of the LPI complex, which became available after the closure of LEP. In the first stage of the project, the "Preliminary Phase", the existing LIL linac and the EPA ring, both modified to suit the new requirements, are used to investigate the technique of frequency multiplication by means of interleaving bunches from subsequent trains. This report describes the design of this phase

Modelling autosomal dominant optic atrophy associated with OPA1 variants in iPSC-derived retinal ganglion cells

Autosomal dominant optic atrophy (DOA) is the most common inherited optic neuropathy, characterised by the preferential loss of retinal ganglion cells (RGCs), resulting in optic nerve degeneration and progressive bilateral central vision loss. Over 60% of genetically confirmed DOA patients carry variants in the nuclear OPA1 gene, which encodes for a ubiquitously expressed, mitochondrial GTPase protein. OPA1 has diverse functions within the mitochondrial network, facilitating inner membrane fusion and cristae modelling, regulating mitochondrial DNA maintenance and coordinating mitochondrial bioenergetics. There are currently no licensed disease-modifying therapies for DOA and the disease mechanisms driving RGC degeneration are poorly understood. Here, we describe the generation of isogenic, heterozygous OPA1 null iPSC (OPA1+/-) through CRISPR/Cas9 gene editing of a control cell line, in conjunction with the generation of DOA patient-derived iPSC carrying OPA1 variants, namely, the c.2708_2711delTTAG variant (DOA iPSC), and previously reported missense variant iPSC line (c.1334G>A, DOA+ iPSC) and CRISPR/Cas9 corrected controls. A two-dimensional (2D) differentiation protocol was used to study the effect of OPA1 variants on iPSC-RGC differentiation and mitochondrial function. OPA1+/-, DOA and DOA+ iPSC showed no differentiation deficit compared to control iPSC lines, exhibiting comparable expression of all relevant markers at each stage of differentiation. OPA1+/- and OPA1 variant iPSC-RGCs exhibited impaired mitochondrial homeostasis, with reduced bioenergetic output and compromised mitochondrial DNA maintenance. These data highlight mitochondrial deficits associated with OPA1 dysfunction in human iPSC-RGCs, and establish a platform to study disease mechanisms that contribute to RGC loss in DOA, as well as potential therapeutic interventions

The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package

The Astropy project supports and fosters the development of open-source and openly-developed Python packages that provide commonly-needed functionality to the astronomical community. A key element of the Astropy project is the core package Astropy, which serves as the foundation for more specialized projects and packages. In this article, we provide an overview of the organization of the Astropy project and summarize key features in the core package as of the recent major release, version 2.0. We then describe the project infrastructure designed to facilitate and support development for a broader ecosystem of inter-operable packages. We conclude with a future outlook of planned new features and directions for the broader Astropy project

Postoperative peri-axillary seroma following axillary artery cannulation for surgical treatment of acute type A aortic dissection

The arterial cannulation site for optimal tissue perfusion and cerebral protection during cardiopulmonary bypass (CPB) for surgical treatment of acute type A aortic dissection remains controversial. Right axillary artery cannulation confers significant advantages, because it provides antegrade arterial perfusion during cardiopulmonary bypass, and allows continuous antegrade cerebral perfusion during hypothermic circulatory arrest, thereby minimizing global cerebral ischemia. However, right axillary artery cannulation has been associated with serious complications, including problems with systemic perfusion during cardiopulmonary bypass, problems with postoperative patency of the artery due to stenosis, thrombosis or dissection, and brachial plexus injury. We herein present the case of a 36-year-old Caucasian man with known Marfan syndrome and acute type A aortic dissection, who had direct right axillary artery cannulation for surgery of the ascending aorta. Postoperatively, the patient developed an axillary perigraft seroma. As this complication has, not, to our knowledge, been reported before in cardiothoracic surgery, we describe this unusual complication and discuss conservative and surgical treatment options