Electric control of collective atomic coherence in an Erbium doped solid

We demonstrate fast and accurate control of the evolution of collective atomic coherences in an Erbium doped solid using external electric fields. This is achieved by controlling the inhomogeneous broadening of Erbium ions emitting at 1536 nm using an electric field gradient and the linear Stark effect. The manipulation of atomic coherence is characterized with the collective spontaneous emission (optical free induction decay) emitted by the sample after an optical excitation, which does not require any previous preparation of the atoms. We show that controlled dephasing and rephasing of the atoms by the electric field result in collapses and revivals of the optical free induction decay. Our results show that the use of external electric fields does not introduce any substantial additional decoherence and enables the manipulation of collective atomic coherence with a very high degree of precision on the time scale of tens of ns. This provides an interesting resource for photonic quantum state storage and quantum state manipulation.Comment: 10 pages, 5 figure

General framework of the non-perturbative renormalization group for non-equilibrium steady states

This paper is devoted to presenting in detail the non-perturbative renormalization group (NPRG) formalism to investigate out-of-equilibrium systems and critical dynamics in statistical physics. The general NPRG framework for studying non-equilibrium steady states in stochastic models is expounded and fundamental technicalities are stressed, mainly regarding the role of causality and of Ito's discretization. We analyze the consequences of Ito's prescription in the NPRG framework and eventually provide an adequate regularization to encode them automatically. Besides, we show how to build a supersymmetric NPRG formalism with emphasis on time-reversal symmetric problems, whose supersymmetric structure allows for a particularly simple implementation of NPRG in which causality issues are transparent. We illustrate the two approaches on the example of Model A within the derivative expansion approximation at order two, and check that they yield identical results.Comment: 28 pages, 1 figure, minor corrections prior to publicatio

Spatio-Temporal Variability of Suspended Particulate Matter in a High-Arctic Estuary (Adventfjorden, Svalbard) Using Sentinel-2 Time-Series

Arctic coasts, which feature land-ocean transport of freshwater, sediments, and other terrestrial material, are impacted by climate change, including increased temperatures, melting glaciers, changes in precipitation and runoff. These trends are assumed to affect productivity in fjordic estuaries. However, the spatial extent and temporal variation of the freshwater-driven darkening of fjords remain unresolved. The present study illustrates the spatio-temporal variability of suspended particulate matter (SPM) in the Adventfjorden estuary, Svalbard, using in-situ field campaigns and ocean colour remote sensing (OCRS) via high-resolution Sentinel-2 imagery. To compute SPM concentration (CSPMsat), a semi-analytical algorithm was regionally calibrated using local in-situ data, which improved the accuracy of satellite-derived SPM concentration by ~20% (MRD). Analysis of SPM concentration for two consecutive years (2019, 2020) revealed strong seasonality of SPM in Adventfjorden. Highest estimated SPM concentrations and river plume extent (% of fjord with CSPMsat > 30 mg L−1) occurred during June, July, and August. Concurrently, we observed a strong relationship between river plume extent and average air temperature over the 24 h prior to the observation (R2 = 0.69). Considering predicted changes to environmental conditions in the Arctic region, this study highlights the importance of the rapidly changing environmental parameters and the significance of remote sensing in analysing fluxes in light attenuating particles, especially in the coastal Arctic Ocean.publishedVersio

Noise-induced macroscopic bifurcations in globally-coupled chaotic units

Large populations of globally-coupled identical maps subjected to independent additive noise are shown to undergo qualitative changes as the features of the stochastic process are varied. We show that for strong coupling, the collective dynamics can be described in terms of a few effective macroscopic degrees of freedom, whose deterministic equations of motion are systematically derived through an order parameter expansion.Comment: Phys. Rev. Lett., accepte

Vortex Glass and Vortex Liquid in Oscillatory Media

We study the disordered, multi-spiral solutions of two-dimensional homogeneous oscillatory media for parameter values at which the single spiral/vortex solution is fully stable. In the framework of the complex Ginzburg-Landau (CGLE) equation, we show that these states, heretofore believed to be static, actually evolve on ultra-slow timescales. This is achieved via a reduction of the CGLE to the evolution of the sole vortex position and phase coordinates. This true defect-mediated turbulence occurs in two distinct phases, a vortex liquid characterized by normal diffusion of individual spirals, and a slowly relaxing, intermittent, ``vortex glass''.Comment: 4 pages, 2 figures, submitted to Physical Review Letter

Coastal erosion and resulting impacts along the ice-rich permafrost coast of the Yukon Territory, Canada

Due to its fine grained and very ice-rich sediments, the coast of the Yukon Coastal Plain forms a very dynamic landscape. Changing climatic conditions add to this by lengthening open water periods and increasing permafrost temperature, which contributes to an increase of coastal erosion. Even though the Yukon Territory has no permanent settlements along its Beaufort coast, this region is of exceptional value as it serves as a calving area for the Porcupine Caribou Herd and it comprises numerous archaeological sites which are rare remains of the rich human history of this region. The importance of this area is underpinned by the fact that about two third of the coast of the Yukon Territory is protected as part of the Ivvavik National Park, which in turn is a candidate for the UNESCO world heritage site status. Additionally, recurring plans to develop oil and gas-related infrastructure would dramatically change the nature of the coastal environment. Yet, no up-to-date information is available on the erosion of this long coastal stretch, which is detrimental to both environmental and industrial planning in the area. Here, we present initial results of an assessment of shoreline dynamics and their influence on the coastal system in the Ivvavik National Park area. We first quantified shoreline changes of the approximately 150 km long coast by means of remote sensing data. We geocoded aerial photographs from the 1950s, the 1970s and the 1990s to a GeoEye scene from 2011 and digitized the respective shorelines. We then analyzed spatial and temporal shoreline dynamics by using the Esri ArcGIS extension DSAS (Digital Shoreline Analysis System). Then, we coupled these results with a large range of ecological and cultural datasets, including ecological units, freshwater habitat extents and archaeological site positions, in order to determine the vulnerability of the coastal environment of the Ivvavik National Park. Our initial results show that coastal erosion is prevailing along most parts of the coast and only very limited coastal stretches experience accumulation. The analyses allow us to draw initial conclusions about which habitats are most affected by arctic coastal changes and which archaeological sites are prone to get lost in the near future

ESROCOS: a robotic operating system for space and terrestrial applications

ESROCOS (http://www.h2020-esrocos.eu) is a European Project in the frame of the PERASPERA SRC, (http://www.h2020-peraspera.eu/), targeting the design of a Robot Control Operating Software (RCOS) for space robotics applications. The goal of the ESROCOS project is to provide an open-source framework to assist in the development of flight software for space robots, providing adequate features and performance with space-grade Reliability, Availability, Maintainability and Safety (RAMS) properties. This paper presents the ESROCOS project and summarizes the approach and the current status

Temporal and spatial variations in coastal dynamics along the Yukon coast, Canada

The Arctic is warming. This results in longer open-water periods during which waves can interact with the shore, and extends the duration in which the land and the sea are exposed to positive temperatures. Increasing active layer depths compound the effectiveness of wave action on the coast that is often composed of ice-bound and fine-grained sediments. As permafrost soils contain approximately twice as much carbon as is currently circulating in our atmosphere, the Arctic is one of the key areas requiring study to better understand global climate change processes. Due to the fact that Arctic permafrost coasts make up one third of the World’s coasts, their dynamics are of particular interest. We investigated spatio-temporal shoreline dynamics of the Yukon Coast, characterized by very ice-rich soils and a variety of coastal landforms. Over one hundred aerial photographs from the 1950’s, the 1970’s, and the 1990’s were georeferenced on the base of GeoEye and WorldView satellite imageries from 2011. By digitizing the shoreline for each time step and performing analyses using the Esri ArcGIS extension DSAS (Digital shoreline analysis system), we classified regions according to their rate and variability of coastal erosion. Some regions are very dynamic, showing phases of fast acceleration and deceleration of coastal retreat, others appear to be very stable with little change through time. Such regions may be directly adjacent. By coupling these spatial coastal dynamics data with LiDAR (Light Detection And Ranging) data from 2012 and 2013, we calculated the volumetric erosion along the Yukon coast. Additionally, we investigated infrared theodolite and real time kinematic GPS measurements from eight coastal monitoring sites maintained by the Geological Survey of Canada, covering the last 20 years. Together, these data allow us to measure coastal evolution over the last 60 years. The temporally better resolved ground survey data indicates that coastal erosion rates, in general, show a decelerating trend over the last 20 years. However, within the last three years rates of coastal erosion along some sites (e.g. the Yukon-Alaskan Border and Stokes Point West) are increasing at unprecedented rates up to 18 m/a. These first results will help to quantify the amount of carbon released by coastal erosion along the Yukon coast and identify the contribution of coastal processes operating along the Yukon coast to regional and global nutrient cycles

MHC class II-restricted antigen presentation by plasmacytoid dendritic cells drives proatherogenic T cell immunity

Background—Plasmacytoid dendritic cells (pDCs) bridge innate and adaptive immune responses and are important regulators of immuno-inflammatory diseases. However, their role in atherosclerosis remains elusive. Methods and Results—Here, we used genetic approaches to investigate the role of pDCs in atherosclerosis. Selective pDC deficiency in vivo was achieved using CD11c-Cre × Tcf4–/flox bone marrow transplanted into Ldlr–/– mice. Compared with control Ldlr–/– chimeric mice, CD11c-Cre × Tcf4–/flox mice had reduced atherosclerosis levels. To begin to understand the mechanisms by which pDCs regulate atherosclerosis, we studied chimeric Ldlr–/– mice with selective MHCII deficiency on pDCs. Significantly, these mice also developed reduced atherosclerosis compared with controls without reductions in pDC numbers or changes in conventional DCs. MHCII-deficient pDCs showed defective stimulation of apolipoprotein B100–specific CD4+ T cells in response to native low-density lipoprotein, whereas production of interferon-α was not affected. Finally, the atheroprotective effect of selective MHCII deficiency in pDCs was associated with significant reductions of proatherogenic T cell–derived interferon-γ and lesional T cell infiltration, and was abrogated in CD4+ T cell–depleted animals. Conclusions—This study supports a proatherogenic role for pDCs in murine atherosclerosis and identifies a critical role for MHCII-restricted antigen presentation by pDCs in driving proatherogenic T cell immunity