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High-dimensional encoding schemes have emerged as a novel way to perform quantum information tasks. For high dimensionality, temporal and transverse spatial modes of photons are the two paradigmatic degrees of freedom commonly used in such experiments. Nevertheless, general devices for multi-outcome measurements are still needed to take full advantage of the high-dimensional nature of encoding schemes. We propose a general full-field mode sorting scheme consisting of only up to two optimized phase elements based on evolutionary algorithms that allows for joint sorting of azimuthal and radial modes. We further study the performance of our scheme through simulations in the context of high-dimensional quantum cryptography, where sorting in different mutually unbiased bases and high-fidelity measurement schemes are crucial.

High-dimensional encoding schemes have emerged as a novel way to perform quantum information tasks. For high dimensionality, temporal and transverse spatial modes of photons are the two paradigmatic degrees of freedom commonly used in such experiments. Nevertheless, general devices for multi-outcome measurements are still needed to take full advantage of the high-dimensional nature of encoding schemes. We propose a general full-field mode sorting scheme consisting of only up to two optimized phase elements based on evolutionary algorithms that allows for joint sorting of azimuthal and radial modes. We further study the performance of our scheme through simulations in the context of high-dimensional quantum cryptography, where sorting in different mutually unbiased bases and high-fidelity measurement schemes are crucial.

In recent years, neural networks have been used to solve phase retrieval problems in imaging with superior accuracy and speed than traditional techniques, especially in the presence of noise. However, in the context of interferometric imaging, phase noise has been largely unaddressed by existing neural network architectures. Such noise arises naturally in an interferometer due to mechanical instabilities or atmospheric turbulence, limiting measurement acquisition times and posing a challenge in scenarios with limited light intensity, such as remote sensing. Here, we introduce a 3D-2D Phase Retrieval U-Net (PRUNe) that takes noisy and randomly phase-shifted interferograms as inputs, and outputs a single 2D phase image. A 3D downsampling convolutional encoder captures correlations within and between frames to produce a 2D latent space, which is upsampled by a 2D decoder into a phase image. We test our model against a state-of-the-art singular value decomposition algorithm and find PRUNe reconstructions consistently show more accurate and smooth reconstructions, with a x2.5 - 4 lower mean squared error at multiple signal-to-noise ratios for interferograms with low (< 1 photon/pixel) and high (~100 photons/pixel) signal intensity. Our model presents a faster and more accurate approach to perform phase retrieval in extremely low light intensity interferometry in presence of phase noise, and will find application in other multi-frame noisy imaging techniques.

While the sentinel nature of freshwater systems is now well recognized, widespread integration of freshwater processes and patterns into our understanding of broader climate-driven Arctic terrestrial ecosystem change has been slow. We review the current understanding across Arctic freshwater systems of key sentinel responses to climate, which are attributes of these systems with demonstrated and sensitive responses to climate forcing. These include ice regimes, temperature and thermal structure, river baseflow, lake area and water level, permafrost-derived dissolved ions and nutrients, carbon mobilization (dissolved organic carbon, greenhouse gases, and radiocarbon), dissolved oxygen concentrations, lake trophic state, various aquatic organisms and their traits, and invasive species. For each sentinel, our objectives are to clarify linkages to climate, describe key insights already gained, and provide suggestions for future research based on current knowledge gaps. We suggest that tracking key responses in Arctic freshwater systems will expand understanding of the breadth and depth of climate-driven Arctic ecosystem changes, provide early indicators of looming, broader changes across the landscape, and improve protection of freshwater biodiversity and resources.

Les Caraïbes insulaires sont sensibles aux changements climatiques, aux variations du niveau de la mer, ainsi qu’aux ouragans et à une saisonnalité plus forte. C'est le cas d'Haïti, un pays situé sur l'île d'Hispaniola, qui a également été touché par la déforestation et l'agriculture étendue, augmentant ainsi sa vulnérabilité à l'érosion et aux inondations. Malgré cela, il n'existe pas suffisamment de données environnementales à long terme pour Haïti pour mieux évaluer les risques environnementaux actuels et futurs. Pour répondre à ce problème, une carotte de sédiments prélevée dans la Baie des Baradères, une baie peu profonde du sud-ouest d'Haïti, a été analysée pour reconstruire les changements de la végétation, déduire les principaux changements climatiques et du niveau de la mer dans la région, ainsi que les perturbations naturelles et humaines au cours des dernières 8500 années. Pour ce faire, une étude de pollen fossile a été effectuée. De plus, le balayage de carottes XRF haute résolution a également été utilisé pour documenter le contexte sédimentaire de la carotte et identifier les épisodes d'apport prononcé de sédiments terrestres dans la baie. La chronologie de la séquence a été établie avec 24 datations radiocarbone (14C) AMS. Les échantillons de pollen analysés couvrent les 7000 dernières années et forment six zones polliniques. Dans l'ensemble, les résultats montrent des évidences d'une élévation du niveau de la mer de 7000 à ~ 3000 ans cal AP (avant le présent), sur la base de pourcentages élevés de Rhizophora mangle et d'autres plantes côtières à la base de la carotte, qui diminuent progressivement en abondance vers le sommet. Les changements dans les taxons arboricoles reflètent une prédominance d'arbres adaptés à l'humidité à partir d'environ 4000 ans cal AP, ce qui correspond aux conditions humides générales pour l'Holocène moyen dans la région. Après ~ 2850 ans cal AP, les enregistrements polliniques mettent en évidence le début d'une tendance à, The Insular Caribbean region is susceptible to climate and sea-level changes, including periodic hurricanes and stronger seasonality. Such is the case for Haiti, a country located in Hispaniola Island, that has also been affected by deforestation and extensive farming, thus increasing its vulnerability to erosion and floods. Despite this, there is not enough long-term environmental data for Haiti to better asses modern-day and future environmental risk. To address this, a sediment core collected from Baie des Baradères, a shallow bay in southwestern Haiti, was analyzed to reconstruct vegetation changes and so infer the main climatic and sea-level changes in the area, as well as natural and human disturbances during the last 8500 years, using primarily fossil pollen. We also used high-resolution XRF core scanning to document the sedimentary context of the core and identify episodes of pronounced terrestrial sediment input into the bay. The chronology of the sequence was established with 24 AMS radiocarbon dates. The analyzed pollen samples span the last ~ 7000 years and form six pollen zones. Overall, the results show evidence of sea-level rise from 7000 to ~ 3000 cal yr BP (before present), based on high percentages of Rhizophora mangle and other coastal plants at the base of the core, which progressively decrease in abundance towards the top. Changes in the arboreal taxa reflect a predominance of moist-adapted trees starting at ~ 4000 cal yr BP, consistent with overall moister conditions for the middle Holocene in the region. After ~ 2850 cal yr BP, the pollen record evidence the onset of a drying trend that is maintained during most part of the late Holocene, with increases in shrubs and dry-adapted trees such as Pinus, Spondias, and Sapotaceae. Starting at ~ 1600 cal yr BP prominent peaks in Ti/Ca occur in at least five sections of the core. Despite most of these peaks probably represent the in-wash of terrestrially-derived sediments into the Baie des

While the sentinel nature of freshwater systems is now well-recognized, widespread integration of freshwater processes and patterns into our understanding of broader climate-driven Arctic terrestrial ecosystem change has been slow. We review the current understanding across Arctic freshwater systems of key sentinel responses to climate, which are attributes of these systems with demonstrated and sensitive responses to climate forcing. These include ice regimes, temperature and thermal structure, river baseflow, lake area and water level, permafrost-derived dissolved ions and nutrients, carbon mobilization (dissolved organic carbon, greenhouse gases, and radiocarbon), dissolved oxygen concentrations, lake trophic state, various aquatic organisms and their traits, and invasive species. For each sentinel, our objectives are to clarify linkages to climate, describe key insights already gained, and provide suggestions for future research based on current knowledge gaps. We suggest that tracking key responses in Arctic freshwater systems will expand understanding of the breadth and depth of climate-driven Arctic ecosystem changes, provide early indicators of looming, broader changes across the landscape, and improve protection of freshwater biodiversity and resources.

Permafrost is a fascinating but hidden world of ice, frozen soil, bacteria and gases. The transdisciplinary outreach project Frozen-Ground Cartoons (FGC) makes permafrost science accessible and fun for children, their parents and teachers around the globe.

Climate change and its consequences stand before us as the greatest challenge of our generation. The Arctic is warming at unprecedented rate and permafrost thaw is leading to irreversible changes with a global influence on climate. Permafrost carbon reservoir is twice as large as what is stored in the atmosphere. Upon thawing, permafrost organic carbon is vulnerable to be degraded by microorganisms resulting in additional greenhouse gas emissions. How fast and how much carbon will be released to the atmosphere with permafrost thaw remains highly uncertain. Mineral surfaces and cations can stabilize organic carbon in soils and sediments and mitigate its degradation as greenhouse gases. Yet, the interactions between minerals and organic carbon in permafrost and the consequences of changing soil conditions upon thawing are still poorly understood. This Ph.D. thesis tackles the influence of permafrost thaw on mineral organic carbon interactions and investigates how changing soil conditions may promote or mitigate organic carbon stabilization mechanisms. We found that up to 59% of total organic carbon is potentially mineral-protected. We observed that abrupt thaw increases the supply of stabilizing surfaces and cations. Upon gradual thaw, we highlighted that redox interface greatly influences the location of hotspots for mineral organic carbon interactions. These findings highlight that mineral organic carbon interactions can protect organic carbon despite permafrost thaw. We argue that mineral organic carbon interactions should be investigated together with other factors and included in the next generation of Earth System models to better predict climate trajectories., (AGRO - Sciences agronomiques et ingénierie biologique) -- UCL, 2022

Permafrost is a fascinating but hidden world of ice, frozen soil, bacteria and gases. The transdisciplinary outreach project Frozen-Ground Cartoons (FGC) makes permafrost science accessible and fun for children, their parents and teachers around the globe.

"Plus de 20 millions de km2 : c’est l’étendue occupée par le pergélisol (sol gelé) dans l’hémisphère nord. Il représente le socle des écosystèmes et des infrastructures du Nord. Il concerne la moitié des territoires de la Russie et du Canada, la presque totalité de celui de l’Alaska et une superficie substantielle dans plusieurs autres régions. Environ cinq millions de personnes vivent en zone de pergélisol. [...]"

While the sentinel nature of freshwater systems is now well-recognized, widespread integration of freshwater processes and patterns into our understanding of broader climate-driven Arctic terrestrial ecosystem change has been slow. We review the current understanding across Arctic freshwater systems of key sentinel responses to climate, which are attributes of these systems with demonstrated and sensitive responses to climate forcing. These include ice regimes, temperature and thermal structure, river baseflow, lake area and water level, permafrost-derived dissolved ions and nutrients, carbon mobilization (dissolved organic carbon, greenhouse gases, and radiocarbon), dissolved oxygen concentrations, lake trophic state, various aquatic organisms and their traits, and invasive species. For each sentinel, our objectives are to clarify linkages to climate, describe key insights already gained, and provide suggestions for future research based on current knowledge gaps. We suggest that tracking key responses in Arctic freshwater systems will expand understanding of the breadth and depth of climate-driven Arctic ecosystem changes, provide early indicators of looming, broader changes across the landscape, and improve protection of freshwater biodiversity and resources.

A multi-proxy paleolimnological analysis of a sediment core sequence from Lake Malaya Chabyda in Central Yakutia (Eastern Siberia, Russia) was conducted to investigate changes in lake processes, including lake development, sediment and organic carbon accumulation, and changes in primary productivity, within the context of Late Pleistocene and Holocene climate change. Age-depth modeling with 14C indicates that the maximum age of the sediment core is ∼14 cal kBP. Three distinct sedimentary units were identified within the sediment core. Sedimentological and biogeochemical properties in the deepest section of the core (663–584 cm; 14.1–12.3 cal kBP) suggests a lake environment mostly influenced by terrestrial vegetation, where organic carbon accumulation might have been relatively low (average ∼100 g OC m−2 a−1), although much higher than the global modern average. The middle section of the core (584–376 cm; 12.3–9.0 cal kBP) is characterized by higher primary productivity in the lake, much higher sedimentation, and a remarkable increase in OC delivery (average ∼300 g OC m−2 a−1). Conditions in the upper section of the core (<376 cm; < 9.0 cal kBP) suggest high primary productivity in the lake and high OC accumulation rates (average ∼200 g OC m−2 a−1), with stable environmental conditions. The transition from organic-poor and mostly terrestrial vegetation inputs (TOC/TNatomic ratios ∼20) to conditions dominated by aquatic primary productivity (TOC/TNatomic ratios <15) occurs at around 12.3 cal kBP. This resulted in an increase in the sedimentation rate of OC within the lake, illustrated by higher sedimentation rates and very high total OC concentrations (>30%) measured in the upper section of the core. Compact lake morphology and high sedimentation rates likely resulted in this lake acting as a significant OC sink since the Pleistocene-Holocene transition. Sediment accumulation rates declined after ∼8 cal k BP, however total OC concentrations were still notably high. T

The Action Group called ‘Standardized methods across Permafrost Landscapes: from Arctic Soils to Hydrosystems’ (SPLASH), funded by the International Permafrost Association, is a communitydriven effort aiming to provide a suite of standardized field strategies for sampling mineral and organic components in soils, sediments, surface water bodies and coastal environments across permafrost landscapes. This unified approach will allow data to be shared and compared, thus improving our understanding of the processes occurring during lateral transport in circumpolar Arctic watersheds. This is an international and transdisciplinary effort aiming to provide a fieldwork “tool box” of the most relevant sampling schemes and sample conservation procedures for mineral and organic permafrost pools. With climate change, permafrost soils are undergoing drastic transformations. Both localized abrupt thaw (thermokarst) and gradual ecosystem shifts (e.g., active layer thickening, vegetation changes) drive changes in hydrology and biogeochemical cycles (carbon, nutrients, and contaminants). Mineral and organic components interact along the “lateral continuum” (i.e., from soils to aquatic systems) changing their composition and reactivity across the different interfaces. The circumpolar Arctic region is characterized by high spatial heterogeneity (e.g., geology, topography, vegetation, and ground-ice content) and large inter-annual and seasonal variations in local climate and biophysical processes. Common sampling strategies, applied in different seasons and locations, could help to tackle the spatial and temporal complexity inextricably linked to biogeochemical processes. This unified approach developed in permafrost landscapes will allow us to overcome the following challenges: (1) identifying interfaces where detectable changes in mineral and organic components occur; (2) allowing spatial comparison of these detectable changes; and (3) capturing temporal (inter-/intra-annual) variatio

The Action Group called ‘Standardized methods across Permafrost Landscapes: from Arctic Soils to Hydrosystems’ (SPLASH), funded by the International Permafrost Association, is a community-driven effort aiming to provide a suite of standardized field strategies for sampling mineral and organic components in soils, sediments, surface water bodies and coastal environments across permafrost landscapes. This unified approach will allow data to be shared and compared, thus improving our understanding of the processes occurring during lateral transport in circumpolar Arctic watersheds. This is an international and transdisciplinary effort aiming to provide a fieldwork “tool box” of the most relevant sampling schemes and sample conservation procedures for mineral and organic permafrost pools. With climate change, permafrost soils are undergoing drastic transformations. Both localized abrupt thaw (thermokarst) and gradual ecosystem shifts (e.g., active layer thickening, vegetation changes) drive changes in hydrology and biogeochemical cycles (carbon, nutrients, and contaminants). Mineral and organic components interact along the “lateral continuum” (i.e., from soils to aquatic systems) changing their composition and reactivity across the different interfaces. The circumpolar Arctic region is characterized by high spatial heterogeneity (e.g., geology, topography, vegetation, and ground-ice content) and large inter-annual and seasonal variations in local climate and biophysical processes. Common sampling strategies, applied in different seasons and locations, could help to tackle the spatial and temporal complexity inextricably linked to biogeochemical processes. This unified approach developed in permafrost landscapes will allow us to overcome the following challenges: (1) identifying interfaces where detectable changes in mineral and organic components occur; (2) allowing spatial comparison of these detectable changes; and (3) capturing temporal (inter-/intra-annual) variati

The speed of light in vacuum, c, is a fundamental constant of nature. Photons belonging to a structured beam of finite transverse size have been observed to travel with a group velocity vg, smaller than c, also when propagating in vacuum. The paradox of slow photons in vacuum could, in a first approach, be explained as a simple projection effect that occurs when one measures the speed of light in a diverging vortex beam along the direction of the beam propagation. This effect, instead, reveals fundamental properties of structured light beams: they form a class of quasiparticle states characterized by the geometric properties of the beams such as the beam divergence, spin angular momentum, orbital angular momentum (OAM), and the group velocity. These anomalous propagation modes with group velocities different than that of c represent a class of Majorana quasiparticles with bosonic spectrum for integer OAM modes, cast in an infinite tower of quasiparticle states similar to those expected with photons propagating in a turbulent plasma.

An increased interest in Arctic environments, mainly due to climate change, has changed the conditions for permafrost research in recent years. This change has been accompanied by a global increase in scientific publications, as well as a trend towards open access publications. We have analyzed abstracts, titles and keywords for publications on permafrost from 1998 to 2017 to identify developments (topics, impact and collaboration) in the field of permafrost research in light of these changes. Furthermore, to understand how scientists build on and are inspired by each other's work, we have (a) developed citation networks from scientific publications on permafrost and (b) conducted an online survey on inspiration in permafrost science. Our results show an almost 400% increase in publications containing the word permafrost in the title, keywords or abstract over the study period, and a strong increase in climate‐change‐related research in terms of publications and citations. Survey respondents (n = 122) find inspiration not only in scientific journal publications, but to a large extent in books and public outreach materials. We argue that this increase in global‐scope issues (i.e., climate change) complementing core permafrost research has provided new incentives for international collaborations and wider communication efforts.

An increased interest in Arctic environments, mainly due to climate change, has changed the conditions for permafrost research in recent years. This change has been accompanied by a global increase in scientific publications, as well as a trend towards open access publications. We have analyzed abstracts, titles and keywords for publications on permafrost from 1998 to 2017 to identify developments (topics, impact and collaboration) in the field of permafrost research in light of these changes. Furthermore, to understand how scientists build on and are inspired by each other's work, we have (a) developed citation networks from scientific publications on permafrost and (b) conducted an online survey on inspiration in permafrost science. Our results show an almost 400% increase in publications containing the word permafrost in the title, keywords or abstract over the study period, and a strong increase in climate‐change‐related research in terms of publications and citations. Survey respondents (n = 122) find inspiration not only in scientific journal publications, but to a large extent in books and public outreach materials. We argue that this increase in global‐scope issues (i.e., climate change) complementing core permafrost research has provided new incentives for international collaborations and wider communication efforts.

© 2019 Optical Society of America. European Union’s Horizon 2020 Research and Innovation Programme (766970); Canada Research Chairs; Ontario’s Early Researcher Award; BK21 Plus Program (21A20131111123); National Research Foundation of Korea (2010-0018295); Korea Institute of Science and Technology Institutional Program (2E27800-18-P043); Ministerio de Economía y Competitividad (FIS2015-67963-P); Grant Agency of the Czech Republic (18-04291S); Internal Grant Agency of the Faculty of Sciences of Palacký University (PrF 2018-003), The ability to completely characterize the state of a system is an essential element for the emerging quantum technologies. Here, we present a compressed-sensing-inspired method to ascertain any rank-deficient qudit state, which we experimentally encode in photonic orbital angular momentum. We efficiently reconstruct these qudit states from a few scans with an intensified CCD camera. Since it only requires a small number of intensity measurements, our technique provides an easy and accurate way to identify quantum sources, channels, and systems. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement., Union Europea. H2020, Ministerio de Economia y Competitividad (MINECO), Grant Agency of the Czech Republic, Palacky University, Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

Permafrost occupies 20 million square kilometres of Earth's high-latitude and high-altitude landscapes. These regions are sensitive to climate change and human activities; hence, permafrost research is of considerable scientific and societal importance. However, the results of this research are generally not known by the general public. Communicating scientific concepts is an increasingly important task in the research world. Different ways to engage learners and incorporate narratives in teaching materials exist, yet they are generally underused. Here we report on an international scientific outreach project called Frozen-Ground Cartoons, which aims at making permafrost science accessible and fun for students, teachers, and parents through the creation of comic strips. We present the context in which the project was initiated, as well as recent education and outreach activities. The future phases of the project primarily involve a series of augmented reality materials, such as maps, photos, videos, and 3D drawings. With this project we aim to foster understanding of permafrost research among broader audiences, inspire future permafrost researchers, and raise public and science community awareness of polar science, education, outreach, and engagement.

Electromagnetic plane waves, solutions to Maxwell's equations, are said to be 'transverse' in vacuum. Namely, the waves' oscillatory electric and magnetic fields are confined within a plane transverse to the waves' propagation direction. Under tight-focusing conditions however, the field can exhibit longitudinal electric or magnetic components, transverse spin angular momentum, or non-trivial topologies such as Möbius strips. Here, we show that when a suitably spatially structured beam is tightly focused, a three-dimensional polarization topology in the form of a ribbon with two full twists appears in the focal volume. We study experimentally the stability and dynamics of the observed polarization ribbon by exploring its topological structure for various radii upon focusing and for different propagation planes., QN/Kuipers Lab

Electromagnetic plane waves, solutions to Maxwell's equations, are said to be 'transverse' in vacuum. Namely, the waves' oscillatory electric and magnetic fields are confined within a plane transverse to the waves' propagation direction. Under tight-focusing conditions however, the field can exhibit longitudinal electric or magnetic components, transverse spin angular momentum, or non-trivial topologies such as Möbius strips. Here, we show that when a suitably spatially structured beam is tightly focused, a three-dimensional polarization topology in the form of a ribbon with two full twists appears in the focal volume. We study experimentally the stability and dynamics of the observed polarization ribbon by exploring its topological structure for various radii upon focusing and for different propagation planes., QN/Kuipers Lab

We explore the complex design space of behaviour planning for autonomous driving. Design choices that successfully address one aspect of behaviour planning can critically constrain others. To aid the design process, in this work we decompose the design space with respect to important choices arising from the current state of the art approaches, and describe the resulting trade-offs. In doing this, we also identify interesting directions of future work., Comment: 8 pages, 6 figures

Permafrost occupies 20 million square kilometres of Earth's high-latitude and high-altitude landscapes. These regions are sensitive to climate change and human activities; hence, permafrost research is of considerable scientific and societal importance. However, the results of this research are generally not known by the general public. Communicating scientific concepts is an increasingly important task in the research world. Different ways to engage learners and incorporate narratives in teaching materials exist, yet they are generally underused. Here we report on an international scientific outreach project called Frozen-Ground Cartoons, which aims at making permafrost science accessible and fun for students, teachers, and parents through the creation of comic strips. We present the context in which the project was initiated, as well as recent education and outreach activities. The future phases of the project primarily involve a series of augmented reality materials, such as maps, photos, videos, and 3D drawings. With this project we aim to foster understanding of permafrost research among broader audiences, inspire future permafrost researchers, and raise public and science community awareness of polar science, education, outreach, and engagement.

Permafrost occupies 20 million square kilometres of Earth's high-latitude and high-altitude landscapes. These regions are sensitive to climate change and human activities; hence, permafrost research is of considerable scientific and societal importance. However, the results of this research are generally not known by the general public. Communicating scientific concepts is an increasingly important task in the research world. Different ways to engage learners and incorporate narratives in teaching materials exist, yet they are generally underused. Here we report on an international scientific outreach project called Frozen-Ground Cartoons, which aims at making permafrost science accessible and fun for students, teachers, and parents through the creation of comic strips. We present the context in which the project was initiated, as well as recent education and outreach activities. The future phases of the project primarily involve a series of augmented reality materials, such as maps, photos, videos, and 3D drawings. With this project we aim to foster understanding of permafrost research among broader audiences, inspire future permafrost researchers, and raise public and science community awareness of polar science, education, outreach, and engagement.

© Verein zur Förderung des Open Access Publizierens in den Quantenwissenschaften. All authors would like to thank Gerd Leuchs, Markus Grassl and Imran Khan for helpful discussions. F.B. acknowledges the financial support of the Vanier graduate scholarship of the NSERC. R.F. acknowledges the financial support of the Banting postdoctoral fellowship of the NSERC. This work was supported by Canada Research Chairs; Canada Foundation for Innovation (CFI); Canada Excellence Research Chairs, Government of Canada (CERC); Canada First Research Excellence Fund (CFREF); Natural Sciences and Engineering Research Council of Canada (NSERC); Singapore Ministry of Education (partly through the Academic Research Fund Tier 3 MOE2012-T3-1-009)and the National Research Foundation of Singapore; and Spanish Ministerio de Economia y Competitividad (MINECO)., Quantum key distribution is on the verge of real world applications, where perfectly secure information can be distributed among multiple parties. Several quantum cryptographic protocols have been theoretically proposed and independently realized in different experimental conditions. Here, we develop an experimental platform based on high-dimensional orbital angular momentum states of single photons that enables implementation of multiple quantum key distribution protocols with a single experimental apparatus. Our versatile approach allows us to experimentally survey different classes of quantum key distribution techniques, such as the 1984 Bennett & Brassard (BB84), tomographic protocols including the six-state and the Singapore protocol, and to investigate, for the first time, a recently introduced differential phase shift (Chau15) protocol using twisted photons. This enables us to experimentally compare the performance of these techniques and discuss their benefits and deficiencies in terms of noise tolerance in different dimensions., Ministerio de Economía y Competitividad (MINECO), Depto. de Óptica, Fac. de Ciencias Físicas, TRUE, pub

Ponds and lakes are abundant in Arctic permafrost lowlands. They play an important role in Arctic wetland ecosystems by regulating carbon, water, and energy fluxes and providing freshwater habitats. However, ponds, i. e., waterbodies with surface areas smaller than 1.0 x 10(4) m(2), have not been inventoried on global and regional scales. The Permafrost Region Pond and Lake (PeRL) database presents the results of a circum-Arctic effort to map ponds and lakes from modern (2002-2013) high-resolution aerial and satellite imagery with a resolution of 5m or better. The database also includes historical imagery from 1948 to 1965 with a resolution of 6m or better. PeRL includes 69 maps covering a wide range of environmental conditions from tundra to boreal regions and from continuous to discontinuous permafrost zones. Waterbody maps are linked to regional permafrost landscape maps which provide information on permafrost extent, ground ice volume, geology, and lithology. This paper describes waterbody classification and accuracy, and presents statistics of waterbody distribution for each site. Maps of permafrost landscapes in Alaska, Canada, and Russia are used to extrapolate waterbody statistics from the site level to regional landscape units. PeRL presents pond and lake estimates for a total area of 1.4 x 10(6) km(2) across the Arctic, about 17% of the Arctic lowland (<300ma. s.l.) land surface area. PeRL waterbodies with sizes of 1.0 x 10(6) m(2) down to 1.0 x 10(2) m(2) contributed up to 21% to the total water fraction. Waterbody density ranged from 1.0 x 10 to 9.4 x 10(1) km(-2). Ponds are the dominant waterbody type by number in all landscapes representing 45-99% of the total waterbody number. The implementation of PeRL size distributions in land surface models will greatly improve the investigation and projection of surface inundation and carbon fluxes in permafrost lowlands. Waterbody maps, study area boundaries, and maps of regional permafrost landscapes includi

Ponds and lakes are abundant in Arctic permafrost lowlands. They play an important role in Arctic wetland ecosystems by regulating carbon, water, and energy fluxes and providing freshwater habitats. However, ponds, i.e., waterbodies with surface areas smaller than 1. 0 × 104ĝ€m2, have not been inventoried on global and regional scales. The Permafrost Region Pond and Lake (PeRL) database presents the results of a circum-Arctic effort to map ponds and lakes from modern (2002-2013) high-resolution aerial and satellite imagery with a resolution of 5ĝ€m or better. The database also includes historical imagery from 1948 to 1965 with a resolution of 6ĝ€m or better. PeRL includes 69 maps covering a wide range of environmental conditions from tundra to boreal regions and from continuous to discontinuous permafrost zones. Waterbody maps are linked to regional permafrost landscape maps which provide information on permafrost extent, ground ice volume, geology, and lithology. This paper describes waterbody classification and accuracy, and presents statistics of waterbody distribution for each site. Maps of permafrost landscapes in Alaska, Canada, and Russia are used to extrapolate waterbody statistics from the site level to regional landscape units. PeRL presents pond and lake estimates for a total area of 1. 4 × 106ĝ€km2 across the Arctic, about 17ĝ€% of the Arctic lowland ( < ĝ€300ĝ€mĝ€a.s.l.) land surface area. PeRL waterbodies with sizes of 1. 0 × 106ĝ€m2 down to 1. 0 × 102ĝ€m2 contributed up to 21ĝ€% to the total water fraction. Waterbody density ranged from 1. 0 × 10 to 9. 4 × 101ĝ€kmĝ'2. Ponds are the dominant waterbody type by number in all landscapes representing 45-99ĝ€% of the total waterbody number. The implementation of PeRL size distributions in land surface models will greatly improve the investigation and projection of surface inundation and carbon fluxes in permafrost lowlands. Waterbody maps, study area boundaries, and maps of regional permafrost lan

Ponds and lakes are abundant in Arctic permafrost lowlands. They play an important role in Arctic wetland ecosystems by regulating carbon, water, and energy fluxes and providing freshwater habitats. However, ponds, i.e., waterbodies with surface areas smaller than 1. 0 × 104ĝ€m2, have not been inventoried on global and regional scales. The Permafrost Region Pond and Lake (PeRL) database presents the results of a circum-Arctic effort to map ponds and lakes from modern (2002-2013) high-resolution aerial and satellite imagery with a resolution of 5ĝ€m or better. The database also includes historical imagery from 1948 to 1965 with a resolution of 6ĝ€m or better. PeRL includes 69 maps covering a wide range of environmental conditions from tundra to boreal regions and from continuous to discontinuous permafrost zones. Waterbody maps are linked to regional permafrost landscape maps which provide information on permafrost extent, ground ice volume, geology, and lithology. This paper describes waterbody classification and accuracy, and presents statistics of waterbody distribution for each site. Maps of permafrost landscapes in Alaska, Canada, and Russia are used to extrapolate waterbody statistics from the site level to regional landscape units. PeRL presents pond and lake estimates for a total area of 1. 4 × 106ĝ€km2 across the Arctic, about 17ĝ€% of the Arctic lowland ( < ĝ€300ĝ€mĝ€a.s.l.) land surface area. PeRL waterbodies with sizes of 1. 0 × 106ĝ€m2 down to 1. 0 × 102ĝ€m2 contributed up to 21ĝ€% to the total water fraction. Waterbody density ranged from 1. 0 × 10 to 9. 4 × 101ĝ€kmĝ'2. Ponds are the dominant waterbody type by number in all landscapes representing 45-99ĝ€% of the total waterbody number. The implementation of PeRL size distributions in land surface models will greatly improve the investigation and projection of surface inundation and carbon fluxes in permafrost lowlands. Waterbody maps, study area boundaries, and maps of regional permafrost lan

Le terme « infrastructure » évoque spontanément les équipements routiers, ferroviaires, maritimes, le système d’électricité ou le réseau hydraulique. En science, les infrastructures de recherche réfèrent aux grands équipements scientiiques (observatoires astronomiques, synchrotrons, réseaux de surveillance de l’environnement), aux collections (musées d’histoire naturelle) ou encore aux infrastructures informationnelles (Internet et grandes bases de données). Sur le plan théorique, la notion d’« infrastructure sociotechnique » a été proposée au milieu des années 1990 par Star et Ruhleder pour étudier l’infrastructure d’un point de vue sociologique, c’est-à-dire du point de vue des pratiques associées à leur développement, cherchant ainsi à dépasser les visions purement techniques (voir Objet technique). Les études d’infrastructure (infrastructure studies) se sont développées autour de cette notion.

Un objet-frontière est une entité qui sert d’interface entre des mondes sociaux et des acteurs ayant des perspectives diférentes. Introduit par Star et Griesemer dans une étude de cas sur l’édiication d’un musée zoologique à Berkeley, ce concept s’inscrit dans le cadre de l’approche dite « écologique » des STS. Cette tradition de recherche, ancrée dans la sociologie interactionniste dont elle retient notamment le concept de « monde social », reprend certains éléments du cadre conceptuel de la sociologie de la traduction ou « théorie de l’acteur-réseau », mais elle ofre, selon Clarke et Star, « des afordances bien diférentes et poursuit des inalités analytiques distinctes » (2008, p. 122). Le modèle écologique des STS s’eforce de rendre compte des multiples traductions opérées simultanément par tous les acteurs d’un projet, plutôt que de suivre le point de vue unique des « entrepreneurs », c’est-à-dire des individus les plus activement engagés à l’égard du projet et qui mobilisent les autres autour d’eux (voir héorie de l’acteur-réseau et Construction sociale des technologies).

Plusieurs chercheurs s’interrogent sur le rôle des non-humains dans le développement de la science et de la technologie (voir héorie de l’acteur-réseau). Ces travaux, toutefois, ne confrontent pas la question des rapports entre humains et non-humains avec d’autres perspectives qui cherchent aussi à articuler les liens entre la technique et le social, comme le déterminisme technologique et les postures épistémologiques alternatives. En efet, pendant plusieurs années, la sociologie des techniques et la sociologie du travail se sont interrogées sur le statut des outils et des objets dans l’analyse du développement des technologies, et sur leur impact dans la vie sociale. À cet égard, diférentes postures ont été proposées.

Un objet-frontière est une entité qui sert d’interface entre des mondes sociaux et des acteurs ayant des perspectives diférentes. Introduit par Star et Griesemer dans une étude de cas sur l’édiication d’un musée zoologique à Berkeley, ce concept s’inscrit dans le cadre de l’approche dite « écologique » des STS. Cette tradition de recherche, ancrée dans la sociologie interactionniste dont elle retient notamment le concept de « monde social », reprend certains éléments du cadre conceptuel de la sociologie de la traduction ou « théorie de l’acteur-réseau », mais elle ofre, selon Clarke et Star, « des afordances bien diférentes et poursuit des inalités analytiques distinctes » (2008, p. 122). Le modèle écologique des STS s’eforce de rendre compte des multiples traductions opérées simultanément par tous les acteurs d’un projet, plutôt que de suivre le point de vue unique des « entrepreneurs », c’est-à-dire des individus les plus activement engagés à l’égard du projet et qui mobilisent les autres autour d’eux (voir héorie de l’acteur-réseau et Construction sociale des technologies).

Le terme « infrastructure » évoque spontanément les équipements routiers, ferroviaires, maritimes, le système d’électricité ou le réseau hydraulique. En science, les infrastructures de recherche réfèrent aux grands équipements scientiiques (observatoires astronomiques, synchrotrons, réseaux de surveillance de l’environnement), aux collections (musées d’histoire naturelle) ou encore aux infrastructures informationnelles (Internet et grandes bases de données). Sur le plan théorique, la notion d’« infrastructure sociotechnique » a été proposée au milieu des années 1990 par Star et Ruhleder pour étudier l’infrastructure d’un point de vue sociologique, c’est-à-dire du point de vue des pratiques associées à leur développement, cherchant ainsi à dépasser les visions purement techniques (voir Objet technique). Les études d’infrastructure (infrastructure studies) se sont développées autour de cette notion.

Plusieurs chercheurs s’interrogent sur le rôle des non-humains dans le développement de la science et de la technologie (voir héorie de l’acteur-réseau). Ces travaux, toutefois, ne confrontent pas la question des rapports entre humains et non-humains avec d’autres perspectives qui cherchent aussi à articuler les liens entre la technique et le social, comme le déterminisme technologique et les postures épistémologiques alternatives. En efet, pendant plusieurs années, la sociologie des techniques et la sociologie du travail se sont interrogées sur le statut des outils et des objets dans l’analyse du développement des technologies, et sur leur impact dans la vie sociale. À cet égard, diférentes postures ont été proposées.

Cette thèse a pour objet l'étude de l'évolution et de la dynamique sédimentaire de mares de thermokarst au Québec subarctique. Le site d'étude, situé près de Kuujjuarapik-Whapmagoostui en zone de pergélisol discontinu, renferme plusieurs mares de thermokarst ayant des propriétés limnologiques contrastées (exprimées notamment par la couleur). La recherche comporte trois axes méthodologiques: 1) lithostratigraphie et chronologie de sédiments de mares de thermokarst à l'aide d'analyses sédimentologiques, géochimiques et radiochronologiques; 2) biostratigraphie et reconstructions paléolimnologiques à l'aide de l'analyse des diatomées fossiles et des propriétés spectrales des sédiments; 3) dynamique géomorphologique et sédimentaire récente des mares par télédétection et piégeage des sédiments. Les analyses lithostratigraphiques et biostratigraphiques, jumelées aux résultats des datations, ont révélé la présence de trois faciès sédimentaires distincts, généralement les mêmes d'une mare à l'autre: 1) un faciès inférieur (LF, "Iower facies") d'origine marine postglaciaire (~ 7900 cal. a BP), subséquemment affecté par le développement du pergélisol; 2) une zone de transition organique/tourbeuse (TZ, "transition zone"), représentant les vestiges d'anciens sommets tourbeux des buttes de pergélisol; 3) un faciès supérieur lacustre (UF, "upper facies"), déposé depuis la fonte de ces buttes « 200 cal. a BP) et l'affaissement de la surface du sol qui en a résulté. L'analyse des diatomées a montré l'influence majeure de la présence de couches de tourbe (TZ) lors du développement initial des mares sur, d'une part les premiers assemblages d'espèces de diatomées (majoritairement benthiques et bryophiles), et d'autre part la source interne (in situ) de carbone organique dissous (COD), qui a progressivement diminué lors du développement des mares suite à son adsorption par les silts et argiles en suspension dans la colonne d'eau. Par ailleurs, il est démontré que la quasi-disparition

All evolutionary biologists are familiar with evolutionary units that evolve by vertical descent in a tree-like fashion in single lineages. However, many other kinds of processes contribute to evolutionary diversity. In vertical descent, the genetic material of a particular evolutionary unit is propagated by replication inside its own lineage. In what we call introgressive descent, the genetic material of a particular evolutionary unit propagates into different host structures and is replicated within these host structures. Thus, introgressive descent generates a variety of evolutionary units and leaves recognizable patterns in resemblance networks. We characterize six kinds of evolutionary units, of which five involve mosaic lineages generated by introgressive descent. To facilitate detection of these units in resemblance networks, we introduce terminology based on two notions, P3s (subgraphs of three nodes: A, B, and C) and mosaic P3s, and suggest an apparatus for systematic detection of introgressive descent. Mosaic P3s correspond to a distinct type of evolutionary bond that is orthogonal to the bonds of kinship and genealogy usually examined by evolutionary biologists. We argue that recognition of these evolutionary bonds stimulates radical rethinking of key questions in evolutionary biology (e.g., the relations among evolutionary players in very early phases of evolutionary history, the origin and emergence of novelties, and the production of new lineages). This line of research will expand the study of biological complexity beyond the usual genealogical bonds, revealing additional sources of biodiversity. It provides an important step to a more realistic pluralist treatment of evolutionary complexity.

All evolutionary biologists are familiar with evolutionary units that evolve by vertical descent in a tree-like fashion in single lineages. However, many other kinds of processes contribute to evolutionary diversity. In vertical descent, the genetic material of a particular evolutionary unit is propagated by replication inside its own lineage. In what we call introgressive descent, the genetic material of a particular evolutionary unit propagates into different host structures and is replicated within these host structures. Thus, introgressive descent generates a variety of evolutionary units and leaves recognizable patterns in resemblance networks. We characterize six kinds of evolutionary units, of which five involve mosaic lineages generated by introgressive descent. To facilitate detection of these units in resemblance networks, we introduce terminology based on two notions, P3s (subgraphs of three nodes: A, B, and C) and mosaic P3s, and suggest an apparatus for systematic detection of introgressive descent. Mosaic P3s correspond to a distinct type of evolutionary bond that is orthogonal to the bonds of kinship and genealogy usually examined by evolutionary biologists. We argue that recognition of these evolutionary bonds stimulates radical rethinking of key questions in evolutionary biology (e.g., the relations among evolutionary players in very early phases of evolutionary history, the origin and emergence of novelties, and the production of new lineages). This line of research will expand the study of biological complexity beyond the usual genealogical bonds, revealing additional sources of biodiversity. It provides an important step to a more realistic pluralist treatment of evolutionary complexity.

Le lymphome non hodgkinien représente le 5ième type de cancer le plus fréquemment rencontré chez les Canadiens. Le principal obstacle au diagnostic et au traitement du lymphome non hodgkinien est relié à la dissémination des cellules cancéreuses vers les organes périphériques et à la formation de métastases. La métastasie est un processus séquentiel se déroulant en plusieurs étapes où les interactions cellulaires entre les cellules tumorales et stromales jouent un rôle important. Ces interactions influencent la modulation de l'expression de certains gènes pouvant être impliqués dans la migration, la prolifération cellulaire, les interactions cellule-cellule ou cellule-matrice extracellulaire, l'angiogénèse ou encore dans les mécanismes d'évasion permettant d'échapper au système immunitaire. Afin d'identifier les gènes ainsi modulés, notre laboratoire a utilisé une approche génomique pour déterminer des gènes induits lors des contacts lympho-stromaux entre les cellules de lymphome et les cellules endothéliales. Cette approche a permis de démontrer que l'expression du gène Egr-1 (Early growth response-1) est induite dans les cellules endothéliales en contact avec les cellules de lymphome. EGR-1 est un facteur de transcription connu pour contrôler l'expression d'un éventail de gènes. Bien que la modulation de l'expression d'EGR-1 était plus importante lors d'un contact direct, la sécrétion de molécules solubles par les cellules de lymphome pouvait être suffisante pour amener cette modulation. À partir de ces résultats, le but premier de notre étude était de déterminer les signaux responsables de l'induction d'EGR-llors des contacts lympho-stromaux dans la croissance du lymphome de même que les conséquences sur le processus tumoral. Ces travaux ont permis d'établir que le facteur de croissance épidermique (EGF), exprimé de façon constitutive par les cellules de lymphome, représente un des facteurs pour l'induction de l'expression d'EGR-1 lors des contacts intercellulair

Les maladies cardiovasculaires sont une des premières causes de mortalité dans les pays industrialisés. L'infarctus du myocarde provoque la mort d'un grand nombre de cellules cardiaques, diminuant la qualité de vie des gens qui survivent à une telle attaque. La transplantation d'un organe entier présente des limites telles que la faible quantité de donneurs et la possibilité de rejet par l'organisme du receveur. Le cœur possède une capacité de se régénérer mais le nombre de cellules souches résidentes pouvant accomplir cette tâche apparaît être insuffisant. Afin d'aider à la régénération, des approches thérapeutiques tentent l'implantation de cellules fonctionnelles dans la zone infarcie. Les cellules implantées sont, entre autres, des myoblastes squelettiques, des cellules souches embryonnaires ou adultes (cellules souches mésenchymateuses) indifférenciées, des cardiomyocytes fœtaux. Les résultats positifs parfois obtenus ont vite fait passer ces études des animaux à l'humain. La mise au point de thérapies cellulaires efficaces pour le cœur nécessite la compréhension des mécanismes moléculaires gouvernant la différenciation et la morphogénèse cardiaques, et l'habileté à manipuler ces mécanismes. Les cellules de carcinome embryonnaire P19, un modèle de cellules souches embryonnaires (ES), peuvent se différencier en cardiomyocytes lorsqu'elles sont traitées avec l'acide rétinoïque (AR) ou l'ocytocine (OT). Des cellules de muscle squelettique sont aussi générées. D'autre part, l'AR permet la différenciation de cellules ES en adipocytes et l'OT inhibe la maturation finale de pré-adipocytes. Nous avons émis l'hypothèse que l'AR et l'OT peuvent induire les cellules P19 à générer, de façon concomitante mais dans des rapports différents, des adipocytes, cardiomyocytes et cellules de muscle squelettique. De plus, des analogues de l'AR capables d'activer préférentiellement les récepteurs de l'acide rétinoïque (RAR) ou les récepteurs de rétinoïdes-X (RXR) pourraient influence