The energetic convenience of electrolytic water splitting is limited by thermodynamics. Consequently, significant levels of hydrogen production can only be obtained with an electrical energy ...consumption exceeding 45 kWh kg(-1)H2. Electrochemical reforming allows the overcoming of such thermodynamic limitations by replacing oxygen evolution with the oxidation of biomass-derived alcohols. Here we show that the use of an original anode material consisting of palladium nanoparticles deposited on to a three-dimensional architecture of titania nanotubes allows electrical energy savings up to 26.5 kWh kg(-1)H2 as compared with proton electrolyte membrane water electrolysis. A net energy analysis shows that for bio-ethanol with energy return of the invested energy larger than 5.1 (for example, cellulose), the electrochemical reforming energy balance is advantageous over proton electrolyte membrane water electrolysis.
The functional organization of the parieto-frontal system is crucial for understanding cognitive-motor behavior and provides the basis for interpreting the consequences of parietal lesions in humans ...from a neurobiological perspective. The parieto-frontal connectivity defines some main information streams that, rather than being devoted to restricted functions, underlie a rich behavioral repertoire. Surprisingly, from macaque to humans, evolution has added only a few, new functional streams, increasing however their complexity and encoding power. In fact, the characterization of the conduction times of parietal and frontal areas to different target structures has recently opened a new window on cortical dynamics, suggesting that evolution has amplified the probability of dynamic interactions between the nodes of the network, thanks to communication patterns based on temporally-dispersed conduction delays. This might allow the representation of sensory-motor signals within multiple neural assemblies and reference frames, as to optimize sensory-motor remapping within an action space characterized by different and more complex demands across evolution.
•Propose a method for quantitative evaluation of tractography algorithm performances.•Investigate the effect of the tractography method on connectivity estimation.•Study white matter bottleneck ...configurations in an ex-vivo macaque brain.•Provide a 59-areas tracer-based connectivity matrix and parcellation for the macaque.
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Diffusion-weighted magnetic resonance imaging (DW-MRI) tractography is a non-invasive tool to probe neural connections and the structure of the white matter. It has been applied successfully in studies of neurological disorders and normal connectivity. Recent work has revealed that tractography produces a high incidence of false-positive connections, often from “bottleneck” white matter configurations. The rich literature in histological connectivity analysis studies in the macaque monkey enables quantitative evaluation of the performance of tractography algorithms. In this study, we use the intricate connections of frontal, cingulate, and parietal areas, well established by the anatomical literature, to derive a symmetrical histological connectivity matrix composed of 59 cortical areas. We evaluate the performance of fifteen diffusion tractography algorithms, including global, deterministic, and probabilistic state-of-the-art methods for the connectivity predictions of 1711 distinct pairs of areas, among which 680 are reported connected by the literature. The diffusion connectivity analysis was performed on a different ex-vivo macaque brain, acquired using multi-shell DW-MRI protocol, at high spatial and angular resolutions. Across all tested algorithms, the true-positive and true-negative connections were dominant over false-positive and false-negative connections, respectively. Moreover, three-quarters of streamlines had endpoints location in agreement with histological data, on average. Furthermore, probabilistic streamline tractography algorithms show the best performances in predicting which areas are connected. Altogether, we propose a method for quantitative evaluation of tractography algorithms, which aims at improving the sensitivity and the specificity of diffusion-based connectivity analysis. Overall, those results confirm the usefulness of tractography in predicting connectivity, although errors are produced. Many of the errors result from bottleneck white matter configurations near the cortical grey matter and should be the target of future implementation of methods.
The cerebral cortex is the largest and most intricately connected part of the mammalian brain. Its size and complexity has increased during the course of evolution, allowing improvements in old ...functions and causing the emergence of new ones, such as language. This has expanded the behavioural and cognitive repertoire of different species and has determined their competitive success. To allow the relatively rapid emergence of large evolutionary changes in a structure of such importance and complexity, the mechanisms by which cortical circuitry develops must be flexible and yet robust against changes that could disrupt the normal functions of the networks.
ABSTRACT
In addition to neuronal death and elimination of synapses, the production of transient, exuberant axons, and axonal branches is a general phenomenon in development across species and ...systems. To understand what drives the decision of which axons are maintained and which are eliminated, it is important to monitor the interaction of juvenile axons at their target. As old and more recent work show, unlike what is claimed by Ribeiro Gomez et al. (2019), in the cerebral cortex, both classes of axons branch in the white matter near the target; axons destined to be maintained massively invade the gray matter where they develop terminal arbors and synapses. Axons destined to elimination remain in the white matter although a few transient, exploratory branches can enter the cortex. Axonal behavior and fate seem dictated by positional information probably conveyed by thalamic afferents and activity. Unlike what is suggested by Ribeiro Gomez et al. (2019), axonal selection should not be confused with synaptic reduction, which is a later event with minor or no impact on the topography of the connection.
A
ll brain operations are implemented by networks of neurons. Unfortunately, the networks underlying even the most elementary brain operations remain elusive. This is due to the complexity of the ...networks, their heterogeneity, and to the multiple computations performed by the axons. Poffenberger’s paradigm is one example of a simple task aimed at characterizing the temporal properties of an interhemispheric network which has remained elusive to this day.
In the development of anti/de-icing systems for aeronautics, wind turbines or telecommunication antennas to date, less attention is paid to coating strategies. The majority of studies dealing with ...coatings have focused mainly on reducing ice adhesion forces, to easily remove ice, once it has formed. In this study we focused on an alternative strategy that consists of promoting the shedding of liquid water as a way to reduce the total amount of water present on the surface that can freeze. Shedding of liquid from the surface can be enhanced by modification of surface wettability, by means of the application of superhydrophobic coatings, i.e. water repellent coatings, characterized by low water adhesion forces.
To study the effect of superhydrophobic coatings on surfaces exposed to icing conditions, tests were performed in an open loop icing wind tunnel (IWT) on a standard NACA0021 airfoil in two different icing conditions. Three samples were used during the tests, each one is characterized by different wettability properties. To simulate the presence on anti/de-icing system, the wing was also equipped with an electrical heater, mounted at the inner side of the wing leading edge.
Results from IWT tests demonstrated that surface wettability is an important controlling factor not only for reducing ice accretion on the wing, but also for reducing by up to 80% the energy required to avoid ice accretion on the wing. The findings from IWT tests as described, together with results from a previous work on drop shedding, reinforced the hypothesis that shedding of drops is the key controlling mechanism for an efficient icing mitigation strategy.
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► Application of a superhydrophobic coating (SHC) has many benefits to avoid icing. ► (1) A reduction of heating power to keep the leading edge of the airfoil ice free. ► (2) A reduction or an absence of runback ice was seen using SHC. ► Low adhesion causes liquid water to shed due to drop rebound or aerodynamic drag. ► Claims to date in the literature as to icephobic benefits of SHC are in doubt.
Extracting microanatomical information beyond the image resolution of MRI would provide valuable tools for diagnostics and neuroscientific research. A number of mathematical models already suggest ...microstructural interpretations of diffusion MRI (dMRI) data. Examples of such microstructural features could be cell bodies and neurites, e.g. the axon's diameter or their orientational distribution for global connectivity analysis using tractography, and have previously only been possible to access through conventional histology of post mortem tissue or invasive biopsies. The prospect of gaining the same knowledge non-invasively from the whole living human brain could push the frontiers for the diagnosis of neurological and psychiatric diseases. It could also provide a general understanding of the development and natural variability in the healthy brain across a population. However, due to a limited image resolution, most of the dMRI measures are indirect estimations and may depend on the whole chain from experimental parameter settings to model assumptions and implementation.
Here, we review current literature in this field and highlight the integrative work across anatomical length scales that is needed to validate and trust a new dMRI method. We encourage interdisciplinary collaborations and data sharing in regards to applying and developing new validation techniques to improve the specificity of future dMRI methods.
•Validation methods should challenge the interpretation of dMRI.•dMRI contain information beyond the specificity of single validation techniques.•Sharing data, methods and software are key for dMRI development.
Magnetic reconnection is a process that converts magnetic energy into kinetic energy, both bulk and thermal. We study the energy partition in magnetotail reconnection in the presence of cold ion ...populations of ionospheric origin using kinetic simulations. We compare two simulations with one or two ion populations, but same ion moments. The ion distribution in the simulation with cold ions therefore corresponds to a non‐Maxwellian distribution with a large tail. The global energy budget does not change in the two cases, but when focusing on sub‐populations, the hot ion population (i.e., the tail of the velocity distribution function) gains more energy than the cold ion population (i.e., the core of the distribution). Hot and cold ions also gain different percentages of bulk and thermal energy.
Plain Language Summary
Magnetic reconnection is a process that converts magnetic energy into acceleration (bulk kinetic energy) and heating (thermal kinetic energy). In the magnetosphere, we often see a cold plasma population of ionospheric origin, on top of the hot magnetospheric plasma. We study the energy partition in magnetotail reconnection in the presence of those cold ions using simulations. We compare two simulations with and without cold ions, but same global parameters. We observe that the total energy partition is not significantly different between the simulations. But when focusing on the cold ion simulation, we see that hot ions gains more energy than cold ions and also have a larger bulk over thermal energy gain.
Key Points
The energy budget in magnetic reconnection is not significantly affected by cold ion beams for constant inflow plasma global parameters
The hotter ion population gains more energy during magnetic reconnection than the colder one
Most of the energy gain of hot ions is in the form of internal energy, while the energy transferred to the cold ions is more balanced
In primates, different cortical areas send axons of different diameters into comparable tracts, notably the corpus callosum (Tomasi S, Caminiti R, Innocenti GM. 2012. Areal differences in diameter ...and length of corticofugal projections. Cereb Cortex. 22:1463-1472). We now explored if an area also sends axons of different diameters to different targets. We find that the parietal area PEc sends thicker axons to area 4 and 6, and thinner ones to the cingulate region (area 24). Areas 4 and 9, each sends axons of different diameters to the nucleus caudatus, to different levels of the internal capsule, and to the thalamus. The internal capsule receives the thickest axon, followed by thalamus and nucleus caudatus. The 2 areas (4 and 9) differ in the diameter and length of axons to corresponding targets. We calculated how diameter determines conduction velocity of the axons and together with pathway length determines transmission delays between different brain sites. We propose that projections from and within the cerebral cortex consist of a complex system of lines of communication with different geometrical and time computing properties.
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