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Predictions of marine ice-sheet behaviour require models able to simulate grounding-line migration. We present results of an intercomparison experiment for plan-view marine ice-sheet models. Verification is effected by comparison with approximate analytical solutions for flux across the grounding line using simplified geometrical configurations (no lateral variations, no buttressing effects from lateral drag). Perturbation experiments specifying spatial variation in basal sliding parameters permitted the evolution of curved grounding lines, generating buttressing effects. The experiments showed regions of compression and extensional flow across the grounding line, thereby invalidating the boundary layer theory. Steady-state grounding-line positions were found to be dependent on the level of physical model approximation. Resolving grounding lines requires inclusion of membrane stresses, a sufficiently small grid size (<500 m), or subgrid interpolation of the grounding line. The latter still requires nominal grid sizes of <5 km. For larger grid spacings, appropriate parameterizations for ice flux may be imposed at the grounding line, but the short-time transient behaviour is then incorrect and different from models that do not incorporate grounding-line parameterizations. The numerical error associated with predicting grounding-line motion can be reduced significantly below the errors associated with parameter ignorance and uncertainties in future scenarios.
It is hypothesized that some young supernovae might have the correct properties to accelerate cosmic rays, which in turn might generate gamma-ray emission by-products. We search for gamma-ray excesses towards supernovae in nearby galaxies which were serendipitously within the field of view of the HESS telescopes within a year of the supernova event. HESS cherenkov air-shower data collected between December 2003 and March 2015 were considered and compared to recent catalogs. Nine candidate supernovae were identified and analysed. No significant emission from these supernovae has been found, and upper limits for their very high energy emission are reported.
The objective of the Apollon 10 PW project is the generation of 10 PW peak power pulses of 15 fs at
. In this paper a brief update on the current status of the Apollon project is presented, followed by a more detailed presentation of our experimental and theoretical investigations of the temporal characteristics of the laser. More specifically the design considerations as well as the technological and physical limitations to achieve the intended pulse duration and contrast are discussed.
Rates of CO2 exchange across the air-water interface in oceans and lakes measured to date by the L-DGO group are summarized. They range from 3 to 38 moles/m2/yr. The possible causes for this range include the differences in salinity, mean wind speed, and pH. Wind tunnel studies comparing fresh water and sea water are required before a satisfactory explanation can be found.
Based on radiocarbon and optically stimulated luminescence (OSL) results obtained in the last 5 yr, this paper discusses the absolute chronology of the formation of one of the largest sand dunes within NW Belgium, the Great Ridge of Maldegem-Stekene. Multiproxy analysis of 6 sedimentary sequences points to a complex formation history covering the entire Late Glacial. Dry phases, characterized by eolian deflation and sedimentation, alternated with wet phases in which numerous mostly shallow dune slacks were filled with freshwater. The latter reached their highest water level during the first half of the Allerød, attracting both animals (e.g. European elk) and humans (Federmesser hunter-gatherers). Near the end of the Allerød, all dune slacks finally disappeared as they were filled in with windblown sand ("coversand"), likely forcing prehistoric hunter-gatherers to leave the area.
In 1572, when the provinces of Holland and Zeeland were almost completely overrun by the ‘Geuzen’, Pope Gregory XIII (1572-1585) succeeded to the Holy See. In 1578 this Pope forbade the Roman Catholics in the rebellious provinces to give any civil or military service to the rebels’ authority—on penalty of excommunication—and identified Catholicism with being faithful to the Spanish cause. When this Pope died in 1585, there was reasonable hope held in Rome that the recapture of the Northern Netherlands—and hence the restoration of Catholicism—would soon be realized, as Parma’s campaign was succeeding in the South of the Netherlands and one town after another fell into his hands.
During the pontificates of Sixtus V (1585-1590) and Clement VIII (1592–1605) it gradually became clear to the Holy See that in the Northern Netherlands an independent state under Calvinist authority might be in the making. In these provinces the episcopal sees, set up in 1559, were either vacant or deserted since the bishops lived in exile. In spite of requests by Philip II the Holy See postponed the appointment of new bishops. However, in 1592 Clement VIII appointed an administrator, a ‘vicar apostolic’, who, in the name of the Pope, was to administer all the provinces where Calvinism had gained the upper hand, notably the area north of the great rivers in the present-day Netherlands. This vicar apostolic Sasbout Vosmeer (1592–1614) was consecrated in 1602 and given the title of archbishop of Philippi inpartibus infidelium.
We consider here the effects of inertia on the instability of a flat liquid film under the effects of capillary and intermolecular forces (van der Waals interaction). Firstly, we perform a linear stability analysis within the long-wave approximation, which shows that the inclusion of inertia does not produce new regions of instability other than the one previously known from the usual lubrication case. The wavelength,
, corresponding to the maximum growth,
and the critical (marginal) wavelength do not change. The most affected feature of the instability under an increase of the Laplace number is the noticeable decrease of the growth rates of the unstable modes. In order to put in evidence the effects of the bidimensional aspects of the flow (neglected in the long-wave approximation), we also calculate the dispersion relation of the instability from the linearized version of the complete Navier–Stokes (N–S) equations. Unlike the long-wave approximation, the bidimensional model shows that
can vary significantly with inertia when the aspect ratio of the film is not sufficiently small. We also perform numerical simulations of the nonlinear N–S equations and analyse to which extent the linear predictions can be applied depending on both the amount of inertia involved and the aspect ratio of the film.
The objective of the Apollon project is the generation of 10 PW peak power pulses of 15 fs at 1 shot/minute. In this paper the Apollon facility design, the technological challenges and the current progress of the project will be presented.
The growing number of spastic ataxia of Charlevoix-Saguenay (SACS) gene mutations reported worldwide has broadened the clinical phenotype of autosomal recessive spastic ataxia of Charlevoix-Saguenay (ARSACS). The identification of Quebec ARSACS cases without two known SACS mutation led to the development of a multi-modal genomic strategy to uncover mutations in this large gene and explore phenotype variability.
Search for SACS mutations by combining various methods on 20 cases with a classical French-Canadian ARSACS phenotype without two mutations and a group of 104 sporadic or recessive spastic ataxia cases of unknown cause. Western blot on lymphoblast protein from cases with different genotypes was probed to establish if they still expressed sacsin.
A total of 12 mutations, including 7 novels, were uncovered in Quebec ARSACS cases. The screening of 104 spastic ataxia cases of unknown cause for 98 SACS mutations did not uncover carriers of two mutations. Compounds heterozygotes for one missense SACS mutation were found to minimally express sacsin.
The large number of SACS mutations present even in Quebec suggests that the size of the gene alone may explain the great genotypic diversity. This study does not support an expanding ARSACS phenotype in the French-Canadian population. Most mutations lead to loss of function, though phenotypic variability in other populations may reflect partial loss of function with preservation of some sacsin expression. Our results also highlight the challenge of SACS mutation screening and the necessity to develop new generation sequencing methods to ensure low cost complete gene sequencing.
Despite electrification, over 90% of rural households in certain areas of South Africa continue to depend on fuelwood, and this affects woody vegetation structure, with associated cascading effects on biodiversity within adjacent lands. To promote sustainable use, the interactions between anthropogenic and environmental factors affecting vegetation structure in savannahs need to be understood. Airborne light detection and ranging (LiDAR) data collected over 4758 ha were used to examine woody vegetation structure in five communal rangelands around 12 settlements in Bushbuckridge, a municipality in the Kruger to Canyons Biosphere Reserve (South Africa). The importance of underlying abiotic factors was evaluated by measuring size class distributions across catenas and using canonical correspondence analysis. Landscape position was significant in determining structure, indicating the importance of underlying biophysical factors. Differences in structure were settlement-specific, related to mean annual precipitation at one site, and human population density and intensity of use at the other four sites. Size class distributions of woody vegetation revealed human disturbance gradients around settlements. Intensity of use affected the amplitude, not the shape, of the size class distribution, suggesting the same height classes were being harvested across settlements, but amount harvested varied between settlements. Highly used rangelands result in a disappearance of disturbance gradients, leading to homogeneous patches of low woody cover around settlements with limited rehabilitation options. Reductions in disturbance gradients can serve as early warning indicators of woodland degradation, a useful tool in planning for conservation and sustainable development.
Apexes of commercial pyramidal silicon scanning microscopy tips were magnetically functionalized by means of local focused electron beam induced deposition. High aspect ratio supertips and local tip coatings with varying apex diameters can be produced by varying exposure time, beam current, and scan mode. The carbonyl precursor Co2(CO)8 was used as source of magnetic metal. Tip performance was tested with magnetic force microscopy (tapping / lift-retrace mode) and magnetically actuated cantilever atomic force microscopy. The deposit contains 34±2 at.% Co, dispersed as 2-5 nm metal nanocrystals in a carbonaceous matrix. Specific surface reactions and Boudouard reactions are proposed to explain the resulting deposit composition measured by Auger spectroscopy. The electrical resistivity is 104 higher than bulk Co resistivity.
A new method for surface functionalization of inherently reactive polymers such as polyesters has been developed. It is based on the direct nucleophilic attack on the ester group in the polyethyleneterephtalate backbone by the acid moiety of polyacrylic acid (PAA) catalyzed by titaniumisopropoxide. The PAA grafted surfaces were characterized by X-ray photoelectron spectroscopy to demonstrated the presence of a thin grafted layer rendering the substrates hydrophilic. Subsequent acid group activation using N-ethyl-N'-(3-dimethylaminopropyl) carbodiimide hydrochloride allowed for in-situ collagen immobilization rendering the surfaces cell adhesive. Human smooth muscle and urothelial cells successfully seeded these surfaces, reaching confluence after 7 days.
We present first results of anisotropy and exchange coupling studies of a system with two different magnetic layers (Fe and Co) separated by a nonmagnetic Cr spacer. For the magnetic measurements we used the longitudinal magneto-optical Kerr effect and ferromagnetic resonance. The hysteresis data obtained from the trilayer were fit to a theoretical model which contains both bilinear and biquadratic coupling. The in-plane anisotropy was found to be four-fold with the same easy-axis orientation for both the Fe and the Co layers. An analysis of the easy-axishysteresis loops indicates long period oscillatory coupling and also suggests a short period coupling.
A technology platform is described for the integration of low-loss inductors, capacitors, and MEMS capacitors on a high-resistivity Si substrate. Using this platform the board space area taken up by e.g. a DCS PA output impedance matching circuit can be reduced by 50%. The losses of passive components that are induced by the semi-conducting Si substrate can effectively be suppressed using a combination of surface amorphisation and the use of poly crystalline Si substrates. A MEM switchable capacitor with a capacitance switching factor of 40 and an actuation voltage of 5V is demonstrated. A continuous tuneable dual-gap capacitor is demonstrated with a tuning ratio of 9 using actuation voltages below 15V.
A 1 μg High Burn Up Structure (HBS) fragment was extracted from a UO2 fuel pellet irradiated for 7 cycles in a EDF Pressurised Water Reactor (PWR). In situ examinations were performed with an Environmental Scanning Electron Microscope (ESEM) in order to characterize UO2 microstructure evolution during a temperature ramp up to 1,600K. The results are compared to previously published data on HBS annealing tests performed in a Knudsen cell where observed burst releases are explained as sample cracking during the experimental sequence.