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Surface pattern formation of Smart Cut™ silicon-on-insulator (SOI) substrates is investigated using a new process derived from this technology. The local control of SOI surface roughness is achieved by using hetero-temperature surface activated bonding to introduce locally bespoke shear stresses into bonded silicon wafers. The finite element method is used to back up experimental measurements of these large deformations to determine the amount of shear stresses introduced into the structure, and to determine its impact on the fracture mechanism. [ABSTRACT FROM AUTHOR]

Much of the Antarctic coast is covered by seasonal landfast sea ice (fast ice), which serves as an important habitat for ice algae. Fast‐ice algae provide a key early season food source for pelagic and benthic food webs, and contribute to biogeochemical cycling in Antarctic coastal ecosystems. Summertime fast ice is undergoing a decline, leading to more seasonal fast ice with unknown impacts on interconnected Earth system processes. Our understanding of the spatiotemporal variability of Antarctic fast ice, and its impact on polar ecosystems is currently limited. Evaluating the overall productivity of fast‐ice algae has historically been hampered by limitations in observations and models. By linking new fast‐ice extent maps with a one‐dimensional sea‐ice biogeochemical model, we provide the first estimate of the spatio‐seasonal variability of Antarctic fast‐ice algal gross primary production (GPP) and its annual primary production on a circum‐Antarctic scale. Experiments conducted for the 2005–2006 season provide a mean fast ice‐algal production estimate of 2.8 Tg C/y. This estimate represents about 12% of overall Southern Ocean sea‐ice algae production (estimated in a previous study), with the mean fast‐ice algal production per area being 3.3 times higher than that of pack ice. Our Antarctic fast‐ice GPP estimates are probably underestimated in the Ross Sea and Weddell Sea sectors because the sub‐ice platelet layer habitats and their high biomass are not considered. Plain Language Summary: Antarctic landfast sea ice (fast ice) is sea ice fastened to the coastline of Antarctica and provides a prolific habitat for microalgae. These ice algae are ecologically important because their production takes place early in the season when water column primary production is low. By combining a new satellite data set and a biogeochemical sea‐ice algal growth model, this study provides the first estimate of circum‐Antarctic fast‐ice algal production: 2.8 million tonnes of carbon per year, which is about 12% of the total Antarctic sea‐ice algal production. The mean algal primary production per area in fast ice is 3.3 times higher than that of pack ice. Key Points: First estimate of circum‐Antarctic landfast sea‐ice annual gross primary production, with a focus on the 2005–2006 seasonMean landfast sea‐ice algal primary production is 2.8 TgC/y, representing 12% (range 5%–19%) of total Southern Ocean ice algal productivityMean modeled landfast sea‐ice algal production per area is 3.3 times higher than that of pack ice [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) stacking using hybrid bonding is the most scalable method for 3D integration. As the hybrid bonding pad width is reduced to adopt a higher number of interconnections, the ability to extract the contact resistivity at the bonding interface with high accuracy is critical. Using specific electrical test structures and a dedicated methodology, we extract the contact resistivity for hybrid bonding pad widths down to 400 nm for a Cu/SiO2 hybrid bonding integration. Very low values around 10−11 Ω cm2 were obtained for our reference process, close to the those of Cu grain boundaries. A comprehensive analysis of the experimental contact resistivity is performed to understand its increase with the Cu recess within the bonding pads. Based on thermomechanical simulations and experimental results, the influence of both the pad thickness and initial dishing on the interface closure is discussed, for bonding pad width down to 100 nm. These analyses enable us to propose process conditions to reach low contact resistivity with low sensitivity to wafer-to-wafer overlay for hybrid bonding stacking using bonding pad widths down to 100 nm. [ABSTRACT FROM AUTHOR]

A new technique is assessed in order to measure, at the wafer scale, direct bonding energies. It is derived from the standard Double Cantilever Beam (DCB) method and uses interferometry in confocal IR laser source microscopy to measure crack openings. Such a bonding energy measurement protocol has better accuracy compared to other techniques. This is due to a better confocal microscopy resolution and the high intensity of the laser source. The elastic energy stored in bent wafers is obtained by measuring the beam curvature. DCB deformation models are discussed from the short-range crack opening theory to long distance beam-bending theories. Comparison is made between models, experimental results, and FEM simulations. Finally, the bonding energy error during standard measurements is estimated. [ABSTRACT FROM AUTHOR]

Wall-pressure and velocity statistics in the turbulent boundary layer (TBL) on a cambered controlled-diffusion aerofoil at $8^{\circ }$ incidence, a Mach number of 0.25 and a chord-based Reynolds number ${Re}_c=1.5\times 10^{5}$ are analysed at four locations on the suction side with zero and adverse pressure gradients (ZPG and APG), characterised by increasing Reynolds numbers based on momentum thickness, ${Re}_{\theta }=319$ , 390, 877 and $1036$. The strong APG yields a highly non-equilibrium TBL at the trailing edge that significantly affects the turbulent flow statistics. Different normalisations of the full wall-pressure statistics involved in trailing-edge noise are analysed for the first time in such strong APG with convex curvature, and compared with available experimental and numerical data. Good overall agreement is found in the ZPG region, and most results obtained in previous APG TBL can be extended to the present highly non-equilibrium case. The presence of strong APG augments the intensity of wall-pressure fluctuations noticeably at low frequencies, shortens the streamwise and broadens the spanwise coherence of wall-pressure fluctuations in both time and space, and significantly reduces the convection velocity. The wall-pressure power spectral density are found to scale with the displacement thickness, the Zaragola–Smits velocity and the root-mean-squared pressure, the latter possibly being replaced by the local maximum Reynolds shear stress. The other two key parameters to trailing-edge noise modelling, the spanwise coherence length and the convection velocity, rather scale with displacement thickness and friction velocity, respectively. [ABSTRACT FROM AUTHOR]

Sea ice forms a barrier to the exchange of energy, gases, moisture and particles between the ocean and atmosphere around Antarctica. Ice temperature, salinity and the composition of ice crystals determine whether a particular slab of sea ice is habitable for microorganisms and permeable to exchanges between the ocean and atmosphere, allowing, for example, carbon dioxide (CO2) from the atmosphere to be absorbed or outgassed by the ocean. Spring sea ice can have high concentrations of algae and absorb atmospheric CO2. In the summer of 2016–2017 off East Antarctica, we found decayed and porous granular ice layers in the interior of the ice column, which showed high algal pigment concentrations. The maximum chlorophyll a observed in the interior of the ice column was 67.7 μg/L in a 24% porous granular ice layer between 0.8 and 0.9 m depth in 1.7 m thick ice, compared to an overall mean sea‐ice chlorophyll a (± one standard deviation) of 13.5 ± 21.8 μg/L. We also found extensive surface melting, with instances of snow meltwater apparently percolating through the ice, as well as impermeable superimposed ice layers that had refrozen along with melt ponds on top of the ice. With future warming, the structures we describe here could occur earlier and/or become more persistent, meaning that sea ice would be more often characterized by patchy permeability and interior ice algal accumulations. Plain Language Summary: The growth and melt of Antarctic sea ice is one of the largest seasonal events on Earth. The rapid changes visible at its surface correspond to changes hidden inside the sea ice. East Antarctic sea‐ice samples were collected in 2016–2017 from the icebreaker RSV Aurora Australis to investigate the internal structure of sea ice in summer. Capping the sea ice, impermeable layers inhibited vertical transfer of material through the ice, but ponds had also melted through these layers to allow exchange between the ocean and atmosphere. We also found high concentrations of ice algae deep inside the sea ice, which might be inaccessible to grazers but important for absorbing atmospheric carbon dioxide. With warming temperatures, the observed ice characteristics may become more common or persist longer in each summer with potential consequences for ecosystem processes. Key Points: East Antarctic summer sea ice can be rotten, with melt ponds, but otherwise sealed by superimposed ice and mostly stratified brineDeep layers of decayed granular crystals allow infiltration of relatively nutrient‐rich seawater and sustain algal assemblagesEvidence for incorporation of old pack ice floes into landfast sea ice [ABSTRACT FROM AUTHOR]

The distortion of homogeneous isotropic turbulence interacting with a porous cylinder is calculated by means of the rapid distortion theory (RDT). The porous treatment, characterised by a constant static permeability, is modelled as an impedance boundary condition accounting for the Darcy's flow within the body. The RDT algorithm is first validated through comparisons with published velocity measurements in the stagnation region of an impermeable cylinder placed downstream of a turbulence grid. Subsequently, the impact of porosity on the velocity field is investigated through the analysis of the one-dimensional spectra at different locations near the body and the velocity variance along the stagnation streamline. The porous surface affects the incoming turbulence distortion near the cylinder by reducing the blocking effect of the body and by altering the vorticity deformation caused by the mean flow. The former leads to an attenuation of the one-dimensional velocity spectrum in the low-frequency range, whereas the latter results in an amplification of the high-frequency components. This trend is found to be strongly dependent on the turbulence scale and influences the evolution of the velocity fluctuations in the stagnation region. The porous RDT is finally adapted to model the turbulence distortion in the vicinity of the leading edge of a NACA-0024 profile fitted with melamine foam. The good agreement between the calculations and the experimental results demonstrates that the present methodology can improve the understanding of the physical mechanisms involved in the aerofoil-turbulence interaction noise reduction through porosity and be instrumental in designing such passive noise-mitigation treatments. [ABSTRACT FROM AUTHOR]

Antarctic sea ice can incorporate high levels of iron (Fe) during its formation and has been suggested as an important source of this essential micronutrient to Southern Ocean surface waters during the melt season. Over the last decade, a limited number of studies have quantified the Fe pool in Antarctic sea ice, with a focus on late winter and spring. Here we study the distribution of operationally defined dissolved and particulate Fe from nine sites sampled between Wilkes Land and King George V Land during austral summer 2016/2017. Results point toward a net heterotrophic sea‐ice community, consistent with the observed nitrate limitation (<1 μM). We postulate that the recycling of the high particulate Fe pool in summer sea ice supplies sufficient (∼3 nM) levels of dissolved Fe to sustain ice algal growth. The remineralization of particulate Fe is likely favored by high concentrations of exopolysaccharides (113–16,290 μg xeq L−1) which can serve as a hotspot for bacterial activity. Finally, results indicate a potential relationship between glacial meltwater discharged from the Moscow University Ice Shelf and the occurrence of Fe‐rich (∼4.3 μM) platelet ice in its vicinity. As climate change is expected to result in enhanced Fe‐rich glacial discharge and changes in summer sea‐ice extent and quality, the processes influencing Fe distribution in sea ice that persists into summer need to be better constrained. Plain Language Summary: Iron (Fe) plays a crucial role in microalgal physiology and can control their growth in the Southern Ocean, where Fe concentrations are naturally low. Antarctic sea ice can incorporate high levels of Fe during its formation triggering phytoplankton blooms at the sea‐ice edge during the melt season. No studies to date have assessed sea‐ice Fe distributions in East Antarctica during mid‐ to late summer. Here we discuss Fe distribution in parallel with key sea‐ice physical and biological parameters measured during an expedition to East Antarctica in summer 2016/2017 to answer our central question: is Fe limiting sea‐ice primary productivity during summer? Results suggest nitrate, rather than Fe is the key nutrient controlling sea‐ice algal growth at this time of the year. We also found Fe‐rich platelet ice incorporated underneath pack ice sampled near the Moscow University Ice Shelf which suggests the potential accretion of Fe‐rich ice shelf waters under the sea ice. As climate change is expected to accelerate Antarctic ice shelve melting, a better understanding of how increased rates of glacial meltwater discharge will impact the distribution of Fe within the sea ice during summer is needed. Key Points: Primary production in East Antarctic fast and pack sea ice is not Fe‐limited during summerLow nitrate and high exopolysaccharide concentrations suggest heterotrophic dominance in Antarctic summer sea iceFe‐rich platelet sea ice near the Moscow University Ice Shelf indicates an influence of glacial meltwater in the coastal distribution of Fe [ABSTRACT FROM AUTHOR]

Winter to summer CO2 dynamics within landfast sea ice in McMurdo Sound (Antarctica) were investigated using bulk ice pCO2 measurements, air-snow-ice CO2 fluxes, dissolved inorganic carbon (DIC), total alkalinity (TA), and ikaite saturation state. Our results suggest depth-dependent biotic and abiotic controls that led us to discriminate the ice column in three layers. At the surface, winter pCO2 supersaturation drove CO2 release to the atmosphere while spring-summer pCO2 undersaturation led to CO2 uptake most of the time. CO2 fluxes showed a diel pattern superimposed upon this seasonal pattern which was potentially assigned to either ice skin freeze-thaw cycles or diel changes in net community production. In the ice interior, the pCO2 decrease across the season was driven by physical processes, mainly independent of the autotrophic and heterotrophic phases. Bottom sea ice was characterized by a massive biomass build-up counterintuitively associated with transient heterotrophic activity and nitrate plus nitrite accumulation. This inconsistency is likely related to the formation of a biofilm. This biofilm hosts both autotrophic and heterotrophic activities at the bottom of the ice during spring and may promote calcium carbonate precipitation. [ABSTRACT FROM AUTHOR]

Studies the operating conditions of the use of the flowing afterglow of a microwave discharge to inactivate bacterial spores. Operating conditions of Montreal and Grenoble apparatuses; Biological indicators; Reduced pressure operation without plasma; Influence of the gas composition, flow rate and pressure.

We use field observations from late spring and a one‐dimensional sea‐ice model to explore a high nutrient, high chlorophyll system in Antarctic land‐fast ice. Lack of variability in chlorophyll a concentration and organic carbon content over the 17‐day sampling period suggests a balance between macronutrient sources and biological uptake. Nitrate, nitrite, phosphate, and ammonium were measured at concentrations well above salinity‐predicted levels, indicating nutrient accumulation fueled by remineralization processes. However, silicic acid (DSi) was depleted relative to seawater and was potentially limiting. One‐dimensional physical‐biogeochemical sea‐ice model simulations at the observation site achieve extremely high algal growth and DSi uptake with a DSi half‐saturation constant used for pelagic diatoms (KSi = 3.9 μM) and are not sufficiently improved by tuning the DSi:carbon ratio or DSi remineralization rate. In contrast, diatom biomass in the bottom ice, which makes up 70% of the observed chlorophyll, is simulated using KSi an order of magnitude higher (50 μM), a value similar to that measured in a few Antarctic diatom cultures. Some sea‐ice diatoms may therefore experience limitation at relatively high ambient DSi concentrations compared to pelagic diatoms. Our study highlights the urgent need for observational data on sea‐ice algal affinity for DSi to further support this hypothesis. A lower algal growth rate increases model predictions of DSi in the upper sea ice to more accurate concentrations. The model currently does not account for the non‐diatom communities that dominate those layers, and thus, modeling diatom communities overpredicts DSi uptake in the upper ice. Plain Language Summary: Microscopic, single‐celled algae growing inside Antarctic sea ice play a small, but important, role in the carbon cycle of polar oceans. These algae use photosynthesis to convert carbon dioxide to organic carbon and are an important food source for larger organisms. The growth of sea‐ice algae is partly controlled by their uptake of essential nutrients under favorable light conditions. Therefore, a better understanding of nutrients in sea ice can improve ecosystem models. We studied two weeks of measurements of coastal sea‐ice characteristics in late spring at a site in East Antarctica. There were high amounts of both algae and nutrients, indicating recycling processes that return nutrients to the sea ice, even as algae consume nutrients. Sticky biofilms may also prevent nutrients from being removed by seawater. We then tested a sea‐ice model to see if it matched our field measurements. We had to adjust how readily algal cells in the model take up silicon—a nutrient used to build diatoms' (the dominant algal group) walls—from their environment to obtain a close match. Previously used values were taken from experiments with non‐ice associated marine algae, so better estimates specific to sea‐ice algae are needed to accurately include sea‐ice processes in large‐scale models. Key Points: We observed high chlorophyll a and macronutrient concentrations co‐occurring at the bottom of Antarctic land‐fast sea ice in late springRemineralization processes and adsorption within sea ice best explain the required sources of nitrate and nitrite, phosphate, and ammoniumBiogeochemical modeling suggests that sea‐ice diatoms have a lower affinity for silicic acid than pelagic diatoms [ABSTRACT FROM AUTHOR]

The noise from the flow around a circular cylinder in the critical regime is investigated by combining a compressible wall-resolved large eddy simulation and a Ffowcs Williams and Hawkings analogy on solid and porous surfaces. This simulation is validated by comparing several flow parameters with previous experimental and numerical data in the same flow regime. Significantly reduced drag and increased vortex shedding Strouhal number (0.33) are observed. Two slightly asymmetric laminar separation bubbles (LSBs) on the cylinder surface at about 100° are shown to trigger turbulence through Kelvin-Helmholtz (KH) shear-layer instability. The latter contributes to a narrowband hump in the wall-pressure fluctuations with a tone at a Strouhal number of 27, which can be as intense as the dominant vortex shedding tone. The ratio of the corresponding Strouhal numbers is consistent with the proposed variation with the Reynolds number by Prasad and Williamson [(1997). J. Fluid Mech. 333, 375–402]. The dominant far-field noise source is still the vortex shedding dipolar tone radiating mostly at 90°. Yet, two additional broadband noise sources are evidenced in the wake, one at low frequencies caused by the wake oscillation and another one at high frequencies caused by the KH instability mostly directly toward the LSB locations. [ABSTRACT FROM AUTHOR]

In the Southern Ocean, polynyas exhibit enhanced rates of primary productivity and represent large seasonal sinks for atmospheric CO2. Three contrasting east Antarctic polynyas were visited in late December to early January 2017: the Dalton, Mertz, and Ninnis polynyas. In the Mertz and Ninnis polynyas, phytoplankton biomass (average of 322 and 354 mg chlorophyll a (Chl a)/m2, respectively) and net community production (5.3 and 4.6 mol C/m2, respectively) were approximately 3 times those measured in the Dalton polynya (average of 122 mg Chl a/m2 and 1.8 mol C/m2). Phytoplankton communities also differed between the polynyas. Diatoms were thriving in the Mertz and Ninnis polynyas but not in the Dalton polynya, where Phaeocystis antarctica dominated. These strong regional differences were explored using physiological, biological, and physical parameters. The most likely drivers of the observed higher productivity in the Mertz and Ninnis were the relatively shallow inflow of iron‐rich modified Circumpolar Deep Water onto the shelf as well as a very large sea ice meltwater contribution. The productivity contrast between the three polynyas could not be explained by (1) the input of glacial meltwater, (2) the presence of Ice Shelf Water, or (3) stratification of the mixed layer. Our results show that physical drivers regulate the productivity of polynyas, suggesting that the response of biological productivity and carbon export to future change will vary among polynyas. Key Points: In summer 2016–2017, phytoplankton biomass and NCP in the Mertz and Ninnis polynyas were 3 times those measured in the Dalton polynyaIron‐rich Circumpolar Deep Water and sea ice meltwater best explained this productivity contrast.The productivity contrast between the three polynyas could not be explained by the meteoric water, the Ice Shelf Water, or stratification [ABSTRACT FROM AUTHOR]

Broadband shock-associated noise (BBSAN) is a particular high-frequency noise that is generated in imperfectly expanded jets. BBSAN results from the interaction of turbulent structures and the series of expansion and compression waves which appears downstream of the convergent nozzle exit of moderately under-expanded jets. This paper focuses on the impact of the pressure waves generated by BBSAN from a large eddy simulation of a non-screeching supersonic round jet in the near-field. The flow is under-expanded and is characterized by a high Reynolds number Rej=1.25×106 and a transonic Mach number Mj=1.15. It is shown that BBSAN propagates upstream outside the jet and enters the supersonic region leaving a characteristic pattern in the physical plane. This pattern, also called signature, travels upstream through the shock-cell system with a group velocity between the acoustic speed Uc-a∞ and the sound speed a∞ in the frequency-wavenumber domain (Uc is the convective jet velocity). To investigate these characteristic patterns, the pressure signals in the jet and the near-field are decomposed into waves traveling downstream (p+) and waves traveling upstream (p-). A novel study based on a wavelet technique is finally applied on such signals in order to extract the BBSAN signatures generated by the most energetic events of the supersonic jet. [ABSTRACT FROM AUTHOR]

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Die-to-wafer interconnections such as copper pillars play a vital role in order to enable 3-D integration. This interconnection type allows increasing the density of interconnects but the occurrence of defects, especially intermetallic compounds (IMC) and Kirkendall voids, may reduce the lifetime at elevated operating conditions. This paper investigates the physical degradation mechanisms in copper pillars and micro-bumps, caused by IMC and void formation during stress tests such as electromigration (EM) and high temperature storage. The resistance evolution of the tested interconnections motivated the derivation of a novel analytical model to separate the resistance increases caused by IMC growth and void formation. This allows the real time monitoring of changes in the kinetics, which gives a better understanding of the underlying physics and of the failure mechanisms. In order to validate the model, an additional test series on copper pillars under EM stress with varying conditions is conducted and the model is applied on the monitored resistance evolution. The different stress conditions allowed the extraction of the IMC formation activation energy, which is compared against parameter extraction using classical mean time to failure analysis as well as material parameters of IMC growth that are already reported in the literature. [ABSTRACT FROM AUTHOR]

Abstract: The vertical transport of surface water and carbon into ocean's interior, known as subduction, is one of the main mechanisms through which the ocean influences Earth's climate. New instrumental approaches have shown the occurrence of localized and intermittent subduction episodes associated with small‐scale ocean circulation features. These studies also revealed the importance of such events for the export of organic matter, the so‐called eddy‐pump. However, the transient and localized nature of episodic subduction hindered its large‐scale evaluation to date. In this work, we present an approach to detect subduction events at the scale of the Southern Ocean using measurements collected by biogeochemical autonomous floats (BGCArgo). We show how subduction events can be automatically identified as anomalies of spiciness and Apparent Oxygen Utilization (AOU) below the mixed layer. Using this methodology over more than 4,000 profiles, we detected 40 subduction events unevenly distributed across the Sothern Ocean. Events were more likely found in hot spots of eddy kinetic energy (EKE), downstream major bathymetric features. Moreover, the bio‐optical measurements provided by BGCArgo allowed measuring the amount of Particulate Organic Carbon (POC) being subducted and assessing the contribution of these events to the total downward carbon flux at 100 m (EP100). We estimated that the eddy‐pump represents less than 19% to the EP100 in the Southern Ocean, although we observed particularly strong events able to locally duplicate the EP100. This approach provides a novel perspective on where episodic subduction occurs that will be naturally improved as BGCArgo observations continue to increase. [ABSTRACT FROM AUTHOR]

Background: In France, advance directives are favourably perceived by most of the population, although the drafting rate is low. This ambivalence is challenging because advance directives are meant to promote the autonomy and freedom of choice of patients. The purpose of this study was to analyse the content of advance directives written by patients suffering from malignant haemopathies to better understand how patients put them into practice. These could be relevant as early as the initial diagnosis of haematological malignancies because of the uncertain course of the disease. Methods: This was a multicentre, qualitative, descriptive study. The advance directives written by patients with malignant haemopathies treated in one of the six French hospital departments were included in the study from 01/06/2008 to 15/04/2016. A thematic analysis of the advance directives was performed by two researchers: a senior haematologist and a research assistant. Results: The median age of the patients was 69. Most were women (sex ratio: 0.59), living as a couple (57%), with lymphoid pathologies (66%), who were still alive two years after the instructions were written (63%) and had nominated a health care proxy (88.6%). Free texts (62.9%) were richer in content than pre-defined forms. The advance directives were used in three ways: for a purely legal purpose, to focus on medical treatments or actions, or to communicate a message to the family. Three main themes emerged: (1) refusal of medical treatment (100%), in which patients express refusal of life-sustaining care (97.1%). The actual treatments or the moment when they should be limited or stopped were not always mentioned in detail. (2) A desire for effective pain relief to avoid suffering (57.1%) and (3) messages for their family (34.3%), such as funeral arrangements (17.1%) and messages of love or trust (14.3%). Conclusions: Patients who write advance directives are not necessarily at the end of their lives. Their content mainly conveys treatment wishes, although patients also use them to pass on personal messages to their close family. This emerging role of advance directives to communicate messages within the family should be valued, even if it is not their original purpose. [ABSTRACT FROM AUTHOR]

Abstract: Sea ice is a dynamic biogeochemical reactor and a double interface actively interacting with both the atmosphere and the ocean. However, proper understanding of its annual impact on exchanges, and therefore potentially on the climate, notably suffer from the paucity of autumnal and winter data sets. Here we present the results of physical and biogeochemical investigations on winter Antarctic pack ice in the Weddell Sea (R. V. Polarstern AWECS cruise, June–August 2013) which are compared with those from two similar studies conducted in the area in 1986 and 1992. The winter 2013 was characterized by a warm sea ice cover due to the combined effects of deep snow and frequent warm cyclones events penetrating southward from the open Southern Ocean. These conditions were favorable to high ice permeability and cyclic events of brine movements within the sea ice cover (brine tubes), favoring relatively high chlorophyll‐a (Chl‐a) concentrations. We discuss the timing of this algal activity showing that arguments can be presented in favor of continued activity during the winter due to the specific physical conditions. Large‐scale sea ice model simulations also suggest a context of increasingly deep snow, warm ice, and large brine fractions across the three observational years, despite the fact that the model is forced with a snowfall climatology. This lends support to the claim that more severe Antarctic sea ice conditions, characterized by a longer ice season, thicker, and more concentrated ice are sufficient to increase the snow depth and, somehow counterintuitively, to warm the ice. [ABSTRACT FROM AUTHOR]

Since its introduction in the late 19th century, symmetry breaking has been found to play a crucial role in physics. In particular, it appears as one key phenomenon controlling hydrodynamic and acoustic instabilities in problems with rotational symmetries. A previous paper investigated its desired potential application to the control of circumferential thermoacoustic modes in one annular cavity coupled with multiple flames (Bauerheim et al., J. Fluid Mech., vol. 760, 2014, pp. 431-465). The present paper focuses on a similar problem when symmetry breaking appears unintentionally, for example when uncertainties due to tolerances are taken into account. It yields a large uncertainty quantification (UQ) problem containing numerous uncertain parameters. To tackle this well-known 'curse of dimensionality', a novel UQ methodology is used. It relies on the active subspace approach to construct a reduced set of input variables. This strategy is applied on two annular cavities coupled by 19 flames to determine its modal risk factor, i.e. the probability of an azimuthal acoustic mode being unstable. Since each flame is modelled by two uncertain parameters, it leads to a large UQ problem involving 38 parameters. An acoustic network model is then derived, which yields a nonlinear dispersion relation for azimuthal modes. This nonlinear problem, subject to bifurcations, is solved quasi-analytically. Results show that the dimension of the probabilistic problem can be drastically reduced, from 38 uncertain parameters to only 3. Moreover, it is found that the three active variables are related to physical quantities, which unveils underlying phenomena controlling the stability of the two coupled cavities. The first active variable is associated with a coupling strength controlling the bifurcation of the system, while the two others correspond to a symmetry-breaking effect induced by the uncertainties. Thus, an additional destabilization effect appear caused by the non-uniform pattern of the uncertainty distribution, which breaks the initial rotating symmetry of the annular cavities. Finally, the active subspace is exploited by fitting the response surface with polynomials (linear, quadratic and cubic). By comparing accuracy and cost, results prove that 5% error can be achieved with only 30 simulations on the reduced space, whereas 2000 are required on the complete initial space. It exemplifies that this novel UQ technique can accurately predict the risk factor of an annular configuration at low cost as well as unveil key parameters controlling the stability. [ABSTRACT FROM AUTHOR]

Intracerebral administration of recombinant adeno-associated vector (AAV) has been performed in several clinical trials. However, delivery into the brain requires multiple injections and is not efficient to target the spinal cord, thus limiting its applications. To assess widespread and less invasive strategies, we tested intravenous (IV) or intrathecal (that is, in the cerebrospinal fluid (CSF)) delivery of a rAAVrh10-egfp vector in adult and neonate rats and studied the effect of the age at injection on neurotropism. IV delivery is more efficient in neonates and targets predominantly Purkinje cells of the cerebellum and sensory neurons of the spinal cord and dorsal root ganglia. A single intra-CSF administration of AAVrh10, single strand or oversized self-complementary, is efficient for the targeting of neurons in the cerebral hemispheres, cerebellum, brainstem and spinal cord. Green fluorescent protein (GFP) expression is more widespread in neonates when compared with adults. More than 50% of motor neurons express GFP in the three segments of the spinal cord in neonates and in the cervical and thoracic regions in adults. Neurons are almost exclusively transduced in neonates, whereas neurons, astrocytes and rare oligodendrocytes are targeted in adults. These results expand the possible routes of delivery of AAVrh10, a serotype that has shown efficacy and safety in clinical trials concerning neurodegenerative diseases. [ABSTRACT FROM AUTHOR]