An Improved Observation Model for Super-Resolution under Affine Motion

Super-resolution (SR) techniques make use of subpixel shifts between frames in an image sequence to yield higher-resolution images. We propose an original observation model devoted to the case of non isometric inter-frame motion as required, for instance, in the context of airborne imaging sensors. First, we describe how the main observation models used in the SR literature deal with motion, and we explain why they are not suited for non isometric motion. Then, we propose an extension of the observation model by Elad and Feuer adapted to affine motion. This model is based on a decomposition of affine transforms into successive shear transforms, each one efficiently implemented by row-by-row or column-by-column 1-D affine transforms. We demonstrate on synthetic and real sequences that our observation model incorporated in a SR reconstruction technique leads to better results in the case of variable scale motions and it provides equivalent results in the case of isometric motions

On the relative importance of ecology and geographic isolation as drivers for differentiation of call types of red crossbillLoxia curvirostrain the Palearctic

Efforts to understand the process of speciation have been central to the research of biologists since the origin of evolutionary biology as a discipline. While it is well established that geographic isolation has played a key role in many speciation events, particularly in birds, there is ongoing debate about how frequent speciation is in the partial or complete absence of geographical isolation. In the red crossbill Loxia curvirostra, good arguments do exist for sympatric speciation processes. In this species, several classes of calls are clustered in distinct groups, so‐called ‘call types', which mate assortatively. Often, several call types can be found at a single site, breeding and feeding next to each other. It has been hypothesized that red crossbill call types evolved by specialising in extracting seeds from cones of different conifer species. Alternatively, call types might have evolved in temporal geographic isolation. Within Europe, little is known about the distribution of the various call types and preferences for distinct food resources. In this study, we analysed the temporal and spatial occurrence of red crossbill call types in the Palearctic, investigated potential reasons for call‐type composition at a site, and compared the occurrence of call types with the fructification of conifers. Call‐type composition changed with site and season but hardly with conifer species. With our data, we could localise range areas of twelve different call types, which cannot be explained by conifer species occurrence. Therefore, we suggest that call types evolved in parapatry in most of the northern Palearctic region, and, although contradictory results exist from Iberia, we argue that differentiation might be driven by the same drivers there as well. Additionally, we discuss the potential influence of anthropogenic changes of forest composition and distribution on call types, which offers a unique possibility for future studies

Conductance of Distorted Carbon Nanotubes

We have calculated the effects of structural distortions of armchair carbon nanotubes on their electrical transport properties. We found that the bending of the nanotubes decreases their transmission function in certain energy ranges and leads to an increased electrical resistance. Electronic structure calculations show that these energy ranges contain localized states with significant $\sigma$-$\pi$ hybridization resulting from the increased curvature produced by bending. Our calculations of the contact resistance show that the large contact resistances observed for SWNTs are likely due to the weak coupling of the NT to the metal in side bonded NT-metal configurations.Comment: 5 pages RevTeX including 4 figures, submitted to PR

Répercussions hémodynamiques rénales de la surcharge salée aiguë isotonique chez le chien

Intrarenal hemodynamic changes during acute isotonic saline loading in the dog. 85Kr autoradiograms, perfusions of silastic and injections of thioflavine S labelled red blood cells (R.B.C.) have been used to study the intrarenal hemodynamic changes induced in the dog by an acute isotonic expansion of the extracellular fluid volume. The silastic injected specimens showed a generalized vasodilatation, without however, any change of the diameter of the glomerular tufts. As the ratio of the number of labelled R.B.C. of the superficial glomeruli to the number of the R.B.C. of the juxtamedullary glomeruli has decreased, we can conclude that the relative juxtamedullary glomerular capillary volume has increased. The autoradiographs showed that the velocity of the blood flow increased in the superficial cortex and the vasa recta and decreases in the juxtamedullary cortical region. This slowing seems to be due to the marked dilatation of the capillary bed of the latter region. It is then concluded that the natriuresis could be linked mainly to changes of peritubular factors induced by the vasodilatation which is itself more marked in the juxtamedullary cortex.Répercussions hémodynamiques rénales de la surcharge salée aiguë isotonique chez le chien. Les changements hémodynamiques intrarénaux ont été étudiés chez des chiens soumis à une surcharge salée isotonique aiguë, à l'aide d'autoradiographies au Kr85, de perfusion de silastic et d'injections de globules rouges marqués à la Thioflavine S. La surcharge a entraîné une vasodilatation rénale généralisée (moules au silastic). Le décompte des globules rouges marqués par glomérule montra une diminution du leur nombre dans les glomérules superficiels par rapport aux glomérules juxtamédullaires. Ceci traduit une augmentation relative du volume capillaire glomérulaire juxtamédullaire. Par ailleurs, la vitesse du flux sanguin (autoradiographies) a augments dans le cortex superficiel, les vasa recta et diminué dans la région juxtamédullaire. Une dilatation excessive du lit capillaire de cette dernière semble expliquer le ralentissement de son flux sanguin. Le diamètre des floculi glomérulaires n'a pas changé sous l'effet de la surcharge. La natriurèse peut ainsi être reliée principalement à la baisse de réabsorption tubulaire secondaire aux changements des facteurs péritubulaires induits par la vasodilatation, elle-même maximale au niveau du cortex interne

Effects of invasion by birch on the growth of planted spruce at a post-extraction peatland

Planting forest on cutover peatlands may be regarded as a viable restoration technique in western Canada, where natural bogs are treed with a high density of Black Spruce, Picea mariana. Fertilizer is needed to promote P. mariana establishment on cutover peatlands; however, it also encourages spontaneous colonisation by non-peatland species such as Paper Birch, Betula papyrifera. This study aimed to assess the most appropriate fertilizer dose for P. mariana establishment and growth against the trade-off of birch invasion; consequently, we monitored the effect of B. papyrifera on P. mariana growth. Four levels of fertilizer dose were applied below-ground, but flooding of the site following planting allowed fertilizer to reach the surface and favoured the colonisation of B. papyrifera. Seven years after planting, fertilizer promoted P. mariana survival and the highest fertilizer dose improved both P. mariana and B. papyrifera growth, while the lowest fertilizer dose promoted spruce growth, to a lesser degree, without promoting birch growth as much as higher doses of fertilizer. Birch removal had a significant positive effect on the growth of P. mariana, possibly by allowing greater light penetration and higher near-surface soil moisture. Avoiding B. papyrifera colonisation on site is more effective than cutting due to the ability of birch to regenerate rapidly from stumps. In practice, if planting coniferous trees is the chosen restoration option, the risk of birch colonisation can be minimised by leaving a thicker remnant peat deposit, burying fertilizer near the planted seedlings, and planning planting to avoid flooding during the growing season post-planting whenever possible

Ecological restoration of rich fens in Europe and North America: from trial and error to an evidence-based approach

Fens represent a large array of ecosystem services, including the highest biodiversity found among wetlands, hydrological services, water purification and carbon sequestration. Land use change and strong drainage has severely damaged or annihilated these services in many parts of North America and Europe, which urges the need of restoration plans at the landscape level. We review the major constraints for the restoration of rich fens and fen water bodies in agricultural areas in Europe and disturbed landscapes in North America: 1) habitat quality problems: drought, eutrophication, acidification, and toxicity, 2) recolonization problems: species pools, ecosystem fragmentation and connectivity, genetic variability, invasive species, and provide possible solutions. We discuss both positive and negative consequences of restoration measures, and their causes. The restoration of wetland ecosystem functioning and services has, for a long time, been based on a trial and error approach. By presenting research and practice on the restoration of rich fen ecosystems within agricultural areas, we demonstrate the importance of biogeochemical and ecological knowledge at different spatial scales for the management and restoration of biodiversity, water quality, carbon sequestration and other ecosystem services, especially in a changing climate. We define target processes that enable scientists, nature managers, water managers and policy makers to choose between different measures and to predict restoration prospects for different types of deteriorated fens and their starting conditions

Resonant Andreev reflections in superconductor-carbon-nanotube devices

Resonant Andreev reflection through superconductor-carbon-nanotube devices was investigated theoretically with a focus on the superconducting proximity effect. Consistent with a recent experiment, we find that for high transparency devices on-resonance, the Andreev current is characterized by a large value and a resistance dip; low-transparency off-resonance devices give the opposite result. We also give evidence that the observed low-temperature transport anomaly may be a natural result of Andreev reflection process

Persistent currents in carbon nanotubes based rings

Persistent currents in rings constructed from carbon nanotubes are investigated theoretically. After studying the contribution of finite temperature or quenched disorder on covalent rings, the complexity due to the bundle packing is addressed. The case of interacting nanotori and self-interacting coiled nanotubes are analyzed in details in relation with experiments.Comment: 7 sections, 9 figure

Spatial mapping of flow-induced molecular alignment in a noncrystalline biopolymer fluid using double quantum filtered (DQF) 23Na MRI

Flow-induced molecular alignment was observed experimentally in a non-liquid- crystalline bioplymeric fluid during developed tubular flow. The fluid was comprised of rigid rods of the polysaccharide xanthan and exhibited shear-thinning behavior. Without a requirement for optical transparency or the need for an added tracer, 23Na magic angle (MA) double quantum filtered (DQF) magnetic resonance imaging (MRI) enabled the mapping of the anisotropic molecular arrangement under flow conditions. A regional net molecular alignment was found in areas of high shear values in the vicinity of the tube wall. Furthermore, the xanthan molecules resumed random orientations after the cessation of flow. The observed flow-induced molecular alignment was correlated with the rheological properties of the fluid. The work demonstrates the ability of 23Na MA DQF magnetic resonance to provide a valuable molecular-mechanical link

N/P addition is more likely than N addition alone to promote a transition from moss-dominated to graminoid-dominated tundra in the High-Arctic

Nutrient availability for tundra vegetation could change drastically due to increasing temperatures and frequency of nitrogen deposition in the Arctic. Few studies have simultaneously examined the response of plant communities to these two pressures over a long period. This study aims to assess which driver between increasing nitrogen (N) and phosphorus (P) availability through global warming and increasing N availability alone via N deposition is more likely to transform arctic wetland vegetation and whether there is a time lag in this response. An annual fertilization experiment simulating these nutrient inputs was conducted for 17 years in the Canadian High-Arctic to assess the impact on aboveground net primary productivity, floristic composition, and plant nutrient concentration. While the primary productivity of mosses remains unchanged by fertilization after 17 years, productivity of graminoids was increased slightly by N addition (36% increase at the highest dose). In contrast, the primary productivity of graminoids increased strongly with N/P addition (over 227% increase). We noted no difference in graminoid productivity between the 2nd and 5th year of the experiment, but we observed a 203% increase between the 5th and 17th year in the N/P addition treatments. We also noted a 49% decrease in the total moss cover and an 155% increase in the total graminoid cover between the 2nd and 17th year of N/P addition. These results indicate that the impact of warming through increased N/P availability was greater than those of N deposition alone (N addition) and promoted the transition from a moss-dominated tundra to a graminoid-dominated tundra. However, this transition was subject to a time lag of up to 17 years, suggesting that increased productivity of graminoids resulted from a release of nutrients via the decomposition of lower parts of the moss mat. © 2022 by the authors. Licensee MDPI, Basel, Switzerland