The Beveridge curve depicts the empirical negative relationship between job vacancy rate and unemployment rate, and reflects the efficiency of the job matching process. Movements along a fixed ...downward sloping Beveridge curve are associated with cyclical shocks, while shifts of the curve arise from structural factors that alter the matching efficiency between job vacancies and unemployed workers. National and regional data on job vacancies and unemployment are combined to estimate the Beveridge curves of five European countries and their regions, focusing on the period 1975 to 2004. I also analyse whether shifts in European Beveridge curves are due to changes in the composition of the unemployed pool, labour market rigidities or cyclical and structural shocks. The empirical evidence suggests that changes in labour market rigidities, long term unemployment, as well as cyclical shocks are responsible for outward shifts in European Beveridge curves. I also find evidence of nonlinearities in the relation between unemployment and labour market institutions.
Cancer cells are able to reach distant tissues by migration and invasion processes. Enhanced ability to cope with physical stresses leading to cell membrane damages may offer to cancer cells high ...survival rate during metastasis. Consequently, down-regulation of the membrane repair machinery may lead to metastasis inhibition. We show that migration of MDA-MB-231 cells on collagen I fibrils induces disruptions of plasma membrane and pullout of membrane fragments in the wake of cells. These cells are able to reseal membrane damages thanks to annexins (Anx) that are highly expressed in invasive cancer cells. In vitro membrane repair assays reveal that MDA-MB-231 cells respond heterogeneously to membrane injury and some of them possess a very efficient repair machinery. Finally, we show that silencing of AnxA5 and AnxA6 leads to the death of migrating MDA-MB-231 cells due to major defect of the membrane repair machinery. Disturbance of the membrane repair process may therefore provide a new avenue for inhibiting cancer metastasis.
We present results from laboratory experiments of the downslope propagation of a finite volume released gravity current by means of combined PIV/PLIF measurements. The experimental data were used to ...estimate the global characteristics of the current, such as the propagation speed, the lateral surface and the buoyancy, revealing that thermal theory is a robust model that can predict such quantities properly, especially the models of Beghin et al. (1981), Maxworthy (2010) and the theoretical model of Dai (2013a). The collected data allowed also for the determination of the entrainment rates based on the turbulent fluxes instead using the variation of the volume flux, and the regions of entrainment/detrainment have been identified. The results support previous observations of the mechanism responsible for the buoyancy loss of the cloud and its consequent deceleration down the slope, as a large scale recirculation vortex at the back of the cloud. A very complex interior structure of the cloud is observed, with a large variety of turbulent processes taking place, such as the large-scale convectively unstable recirculation vortex at the scale of the current itself, the small-scale convectively unstable motions inside the head of the cloud and close to the bottom boundary and shear (Kelvin–Helmholtz) instabilities at the boundary between the current and the ambient water. The synoptic velocity and density measurements allowed also to test existent parametrizations of turbulent fluxes, that have been quantified in 2D fields with a high spatial resolution. Results confirm that parametrization laws based on the assumption of a constant turbulent diffusivity or mixing length do not apply for buoyancy clouds due to their high spatial heterogeneity. Hence, the parametrization of the turbulent diffusivities in such flows should be based on scalar quantities that avoid the problem of spatial heterogeneity and takes into account the different sources of turbulence production, e.g. using energetic considerations that compare the terms having a definite exchange of energy and acts as a source or a sink.
•Simultaneous velocity/density measurements of a downslope density cloud.•2D fields of turbulent fluxes with high spatial resolution.•Testing of existent parametrizations of turbulent diffusivities.
► We build a unique 10-year database of blowing snow events at an alpine site. ► Snow transport is observed at least 10.5% of the time in winter. ► Snow particles counters show potential improvements ...for the database. ► The Crocus snowpack model simulates satisfactorily the occurrence of blowing snow events. ► Wind effects on snow grains control the evolution of the modelled threshold wind speed.
Blowing snow events control the evolution of the snow pack in mountainous areas and cause inhomogeneous snow distribution. The goal of this study is to identify the main features of blowing snow events at an alpine site and assess the ability of the detailed snowpack model Crocus to reproduce the occurrence of these events in a 1D configuration. We created a database of blowing snow events observed over 10years at our experimental site. Occurrences of blowing snow events were divided into cases with and without concurrent falling snow. Overall, snow transport is observed during 10.5% of the time in winter and occurs with concurrent falling snow 37.3% of the time. Wind speed and snow age control the frequency of occurrence. Model results illustrate the necessity of taking the wind-dependence of falling snow grain characteristics into account to simulate periods of snow transport and mass fluxes satisfactorily during those periods. The high rate of false alarms produced by the model is investigated in detail for winter 2010/2011 using measurements from snow particle counters.
In alpine regions, wind-induced snow transport strongly influences the spatio-temporal evolution of the snow cover throughout the winter season. To gain understanding on the complex processes that ...drive the redistribution of snow, a new numerical model is developed. It directly couples the detailed snowpack model Crocus with the atmospheric model Meso-NH. Meso-NH/Crocus simulates snow transport in saltation and in turbulent suspension and includes the sublimation of suspended snow particles. The coupled model is evaluated against data collected around the experimental site of Col du Lac Blanc (2720 m a.s.l., French Alps). First, 1-D simulations show that a detailed representation of the first metres of the atmosphere is required to reproduce strong gradients of blowing snow concentration and compute mass exchange between the snowpack and the atmosphere. Secondly, 3-D simulations of a blowing snow event without concurrent snowfall have been carried out. Results show that the model captures the main structures of atmospheric flow in alpine terrain. However, at 50 m grid spacing, the model reproduces only the patterns of snow erosion and deposition at the ridge scale and misses smaller scale patterns observed by terrestrial laser scanning. When activated, the sublimation of suspended snow particles causes a reduction of deposited snow mass of 5.3% over the calculation domain. Total sublimation (surface + blowing snow) is three times higher than surface sublimation in a simulation neglecting blowing snow sublimation.
Cancer cells are exposed to major compressive and shearing forces during invasion and metastasis, leading to extensive plasma membrane damage. To survive this mechanical stress, they need to repair ...membrane injury efficiently. Targeting the membrane repair machinery is thus potentially a new way to prevent invasion and metastasis. We show here that annexin-A2 (ANXA2) is required for membrane repair in invasive breast and pancreatic cancer cells. Mechanistically, we show by fluorescence and electron microscopy that cells fail to reseal shear-stress damaged membrane when ANXA2 is silenced or the protein is inhibited with neutralizing antibody. Silencing of ANXA2 has no effect on proliferation in vitro, and may even accelerate migration in wound healing assays, but reduces tumor cell dissemination in both mice and zebrafish. We expect that inhibiting membrane repair will be particularly effective in aggressive, poor prognosis tumors because they rely on the membrane repair machinery to survive membrane damage during tumor invasion and metastasis. This could be achieved either with anti-ANXA2 antibodies, which have been shown to inhibit metastasis of breast and pancreatic cancer cells, or with small molecule drugs.
We report experiments on windblown sand that highlight a transition from saltation to collisional regime above a critical dimensionless mass flux or Shields number. The transition is first seen ...through the mass flow rate Q, which deviates from a linear trend with the Shields number and seems to follow a quadratic law. Other physical evidences confirm the change of the transport properties. In particular, the particle velocity and the height of the transport layer increases with increasing Shields number in the collisional regime while the latter are invariant with the wind strength in the saltation regime. Discrete numerical simulations support the experimental findings and ascertain that mid-air collisions are responsible for the change of transport regime.
Abstract Annexins are soluble proteins that bind to biological membranes containing negatively charged phospholipids, principally phosphatidylserine, in a Ca2+ -dependent manner. Annexin-A5 (AnxA5), ...the smallest member of the annexin family, presents unique properties of membrane binding and self-assembly into ordered two-dimensional (2D) arrays on membrane surfaces. We have previously reported that AnxA5 plays a central role in the machinery of membrane repair by enabling rapid resealing of plasma membrane disruption in murine perivascular cells. AnxA5 promotes membrane repair via the formation of a protective 2D bandage at membrane damaged site. Here, we review current knowledge on cell membrane repair and present recent findings on the role of AnxA5 in membrane resealing of human trophoblasts.
Using the original setup described in Gallée et al. (2013), the MAR regional climate model including a coupled snowpack/aeolian snow transport parameterization, was run at a fine spatial (5 km ...horizontal and 2 m vertical) resolution over 1 summer month in coastal Adélie Land. Different types of feedback were taken into account in MAR including drag partitioning caused by surface roughness elements. Model outputs are compared with observations made at two coastal locations, D17 and D47, situated respectively 10 and 100 km inland. Wind speed was correctly simulated with positive values of the Nash test (0.60 for D17 and 0.37 for D47) but wind velocities above 10 m s−1 were underestimated at both D17 and D47; at D47, the model consistently underestimated wind velocity by 2 m s−1. Aeolian snow transport events were correctly reproduced with the right timing and a good temporal resolution at both locations except when the maximum particle height was less than 1 m. The threshold friction velocity, evaluated only at D17 for a 7-day period without snowfall, was overestimated. The simulated aeolian snow mass fluxes between 0 and 2 m at D47 displayed the same variations but were underestimated compared to the second-generation FlowCaptTM values, as was the simulated relative humidity at 2 m above the surface. As a result, MAR underestimated the total aeolian horizontal snow transport for the first 2 m above the ground by a factor of 10 compared to estimations by the second-generation FlowCaptTM. The simulation was significantly improved at D47 if a 1-order decrease in the magnitude of z0 was accounted for, but agreement with observations was reduced at D17. Our results suggest that z0 may vary regionally depending on snowpack properties, which are involved in different types of feedback between aeolian transport of snow and z0.
A new framework for modeling sediment fining during transport is proposed. The model is based on a physical description of both abrasion and fragmentation processes. It attempts to describe and ...explain the changes in the grain‐size distribution of sediments during their transport in a water flow. Abrasion and fragmentation are modeled through the use of breakage frequency functions and daughter size distributions. These functions are determined experimentally for the specific case study which is presented. Comparison between the predictions from the model and experimental data from the case study show that (1) both abrasion and fragmentation are involved in the degradation, (2) fragmentation efficiency decreases during the experiment, and (3) the shape of the pebbles provides feedback between abrasion and fragmentation. This type of model is therefore appropriate for explaining degradation mechanisms, which is promising for a future application to rivers.
Key Points
Propose a new framework for modeling sediment fining during transport
Show that abrasion and fragmentation are both active in marly sediment fining
Show that fragmentation efficiency decreases during transport
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