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Much of the latent promise of metal additive manufacturing (AM) rests in the potential for controlled creation of spatially tailored microstructures, designed to optimize key build-scale properties through systematic variation across a build. Component optimization possibilities and performance potential expand enormously when this becomes possible. However, the extreme conditions created by AM energy sources and the nature of alloy solidification under such conditions are not adequately understood. Modeling and simulation tools capable of quantitatively predicting AM microstructural outputs would enable a major leap forward. We demonstrate through experimental validation that a multiscale (nm/ns to mm/ms) simulation framework coupling CALPHAD thermodynamic models, microstructure scale phase field simulations, and laser track scale multiphysics simulations can quantitatively predict tailored microstructure formation in laser processed Ti-Nb. Extensive simulations and analysis of detailed microstructural predictions over a broad range of conditions reveal scaling laws for characteristic microstructural features that should generalize to a wide range of materials. Several of our findings highlight the central importance of the alloy freezing range ΔTf, which provides the basis of a generalized strategy for optimizing spatial control of microstructure during AM. This proposed strategy integrates alloy design with process design & control to identify optimal material and process condition combinations. We have also identified conditions and phenomena that appear to require a more complete treatment of far from equilibrium solidification kinetics, highlighting a fundamental need in the field. We anticipate that further development of such methodologies will contribute centrally to realizing the potential of materials with spatially tailored microstructure. keywords: Additive manufacturing, Laser powder bed fusion, Multiscale modeling, Phase field modeling, Solidification, Tailored microstructure ispartof: MATERIALS TODAY vol:51 pages:65-86 status: published

The effects of cold surface temperature, wet air state (temperature and humidity) and original drop size on frost dendrites growth of two neighboring separate frozen water drops of same size under natural convection conditions were investigated by quantitative measurement. It was determined that for different cold plate surface temperature conditions, i.e., the ordinary-low temperature and the cryogenic temperature range, the frost formation mechanism is different. Under the conditions that the air temperature is not too high and absolute humidity is not too excessive, the influence of frozen water drop size on the longest dendrite of frost crystals becomes more and more obvious with the decrease in cold plate temperature. The changes in air temperature and relative humidity both change air absolute humidity, so they have similar effects on the growth of dendrites. However, the effect of wet air state on the growth of frost dendrites is not monotonous, which needs to be considered comprehensively in combination with heat and mass transfer and the existence of heavy phase layer. The thickness of ‘the initial continuous frost layer’ was measured and it was disclosed that the initial frost layer thickness is 1.7–3.0 times that of the height of the frozen water drop diameter. This value may be possibly used as initial frost layer thickness in heat and mass transfer-based frost layer growth prediction models, at least for ordinary-low temperature conditions.

The epitaxial growth of dendrites, which often results in a strong texture, is the most common phenomenon during the laser additive manufacturing process. In this study, the epitaxial growth of dendrites and texture evolution in three directions were studied by changing the z-increment, pulse period, and track offset, respectively. The influence of the molten pool interface on the growth and competition of dendrites is analyzed. Both green grains ( // BD) with rotated cube texture in the molten pool overlapping zones and red grains ( // BD) with fiber texture in the molten pool center zones coexist for different z-increment samples, forming the typical sandwich texture feature. In a short pulse period, the dendrites can grow directly epitaxially and form the strong fiber texture due to gentle interface and short distance. With the decrease of the track offset, the molten pool morphology changes from flat to narrow and deep. When θ is close to 90°, dendrites grow along the secondary dendrite arms at the overlapping zone, forming V-shape grains. This work also provides a promising method for texture customization for laser additive manufacturing.

In the phase-field simulation of dendrite growth during the solidification of an alloy, the computational cost becomes extremely high when the diffusion length is significantly larger than the curvature radius of a dendrite tip. In such cases, the adaptive mesh refinement (AMR) method is effective for improving the computational performance. In this study, we perform a three-dimensional dendrite growth phase-field simulation in which AMR is implemented via parallel computing using multiple graphics processing units (GPUs), which provide high parallel computation performance. In the parallel GPU computation, we apply dynamic load balancing to parallel computing to equalize the computational cost per GPU. The accuracy of an AMR refinement condition is confirmed through the single-GPU computations of columnar dendrite growth during the directional solidification of a binary alloy. Next, we evaluate the efficiency of dynamic load balancing by performing multiple-GPU parallel computations for three different directional solidification simulations using a moving frame algorithm. Finally, weak scaling tests are performed to confirm the parallel efficiency of the developed code.

Lithium Li dendrite growth is a long standing challenge leading to short cycle life and safety issues in Li metal batteries. Li dendrite growth is kinetically controlled by ion transport, the concentration gradient, and the local electric field. In this study, an internal electric field is generated between the anode and Au modified separator to eliminate the concentration gradient of Li . The Li Au alloy is formed during the first cycle of Li plating stripping, which causes Li deposition on the Au modified side and lithium anode electrode, reversing the lithium dendrite growth direction. The electrically coupled Li metal electrode and Au modified film create a uniform electric potential and Li concentration distribution, resulting in reduced concentration polarization and stable Li deposition. As a result, the Au modified separator improves the lifespan of Li amp; 8214;Li batteries; the Li amp; 8214;LiFePO4 cells show excellent capacity retention gt;97.8 after 350 cycles , and Li amp; 8214;LiNi0.8Co0.1Mn0.1O2 cells deliver 75.1 capacity retention for more than 300 cycles at 1C rate. This strategy offers an efficient approach for commercial application in advanced metallic Li batteries

In this work we develop a combined experimental and inverse continuum modelling approach to the problem of determining properties of a lithium electrolyte from NMR measurements of ion concentration in a test cell. The experimental set-up consists of an enclosed, lithium-electrolyte-filled tube with lithium electrodes at either end. A constant current is passed between these electrodes and the resulting evolution of the spatial distribution of the lithium ions is monitored using NMR imaging techniques. Using the recently developed tools of inverse modelling, in combination with the concentration measurements acquired with NMR imaging, it is shown that the standard Planck-Nernst electrolyte model results in predictions of negative transference numbers. The observation of growing lithium dendrites on the cathode suggests the cause for these unphysical predictions and motivates the formulation of a generalized Planck-Nernst model that explicitly accounts for the presence of these growing lithium-metal dendrites. In this approach, lithium depletion in a dendritic region adjacent to the cathode is modelled by adding a suitably-chosen spatially distributed sink term. It is demonstrated that a model in which lithium is lost from the electrolyte uniformly throughout the dendritic region provides predictions of electrolyte data consistent with the literature and thereby remedies the shortcoming of the standard Planck-Nernst model. In addition, a state-of-the-art Bayesian technique is used to quantify the uncertainty of the inferred material properties.

Class I ventral posterior dendritic arborisation (c1vpda) proprioceptive sensory neurons respond to contractions in theDrosophilalarval body wall during crawling. Their dendritic branches run along the direction of contraction, possibly a functional requirement to maximise membrane curvature during crawling contractions. Although the molecular machinery of dendritic patterning in c1vpda has been extensively studied, the process leading to the precise elaboration of their comb-like shapes remains elusive. Here, to link dendrite shape with its proprioceptive role, we performed long-term, non-invasive,in vivotime-lapse imaging of c1vpda embryonic and larval morphogenesis to reveal a sequence of differentiation stages. We combined computer models and dendritic branch dynamics tracking to propose that distinct sequential phases of targeted growth and stochastic retraction achieve efficient dendritic trees both in terms of wire and function. Our study shows how dendrite growth balances structure–function requirements, shedding new light on general principles of self-organisation in functionally specialised dendrites.In briefAn optimal wire and function trade-off emerges from noisy growth and stochastic retraction duringDrosophilaclass I ventral posterior dendritic arborisation (c1vpda) dendrite development.HighlightsC1vpda dendrite outgrowth follows wire constraints.Stochastic retraction of functionally suboptimal branches in a subsequent growth phase.C1vpda growth rules favour branches running parallel to larval body wall contraction.Comprehensive growth model reproduces c1vpda developmentin silico.

This repository contains the code and data used to generate the figures and the analysis in Castro et al., "Achieving functional neuronal dendrite structure through sequential stochastic growth and retraction". Raw images are included for potential further analysis.

Thyroid hormone (TH) plays important roles in the developing brain. TH deficiency in early life leads to severe developmental impairment in the hippocampus. However, the mechanisms of TH action in the developing hippocampus are still largely unknown. In this study, we generated 3,5,3’-tri-iodo-l-thyronine (T3)-free neuronal supplement, based on the composition of neuronal supplement 21 (NS21), to examine the effect of TH in the developing hippocampus using primary cultured neurons. Effects of TH on neurons were compared between cultures in this T3-free culture medium (-T3 group) and a medium in which T3 was added (+T3 group). Morphometric analysis and RT-qPCR were performed on 7, 10, and 14 days in vitro (DIV). On 10 DIV, a decreased dendrite arborization in -T3 group was observed. Such difference was not observed on 7 and 14 DIV. Brain-derived neurotrophic factor (Bdnf) mRNA levels also decreased significantly in -T3 group on 10 DIV. We then confirmed protein levels of phosphorylated neurotrophic tyrosine kinase type 2 (NTRK2, TRKB), which is a receptor for BDNF, on 10 DIV by immunocytochemistry and Western blot analysis. Phosphorylated NTRK2 levels significantly decreased in -T3 group compared to +T3 group on 10 DIV. Considering the role of BDNF on neurodevelopment, we examined its involvement by adding BDNF on 8 and 9 DIV. Addition of 10 ng/ml BDNF recovered the suppressed dendrite arborization induced by T3 deficiency on 10 DIV. We show that the lack of TH induces a developmental delay in primary hippocampal neurons, likely caused through a decreased Bdnf expression. Thus, BDNF may play a role in TH-regulated dendritogenesis.

Condensation frosting is a type of icing encountered ubiquitously in our daily lives. Understanding the dynamics of condensation frosting is essential in developing effective technologies to suppress frost accretions that compromise heat transfer and system integrity. Here, we present an experimental study on ice dendrite growth atop a single frozen drop, an important step affecting the subsequent frosting process, and the properties of fully-developed frost layers. We evaluate the effect of natural convection by comparing the growth dynamics of ice dendrites on the surface of a frozen drop with three different orientations with respect to gravity. The results show that both the average deposition rate and its spatial variations are profoundly altered by surface orientations. Such behavior is confirmed by a numerical simulation, showing how gravity-assisted (hindered) vapor diffusion yields the deposition outcomes. These findings benefit the optimization of anti-/de- frosting technologies and the rational design of heat exchangers.

International audience; The European standards “Euro” limit the emission of several pollutants from thermal engine vehicles. The particle number (PN) and particulate mass (PM) emissions are specifically limited since 2011, hence modern Diesel engines are equipped with a Diesel particulate filter (DPF). On-board diagnostic (OBD) regulations impose to perform the self-diagnostic of the DPF. Nowadays, this diagnostic is done through a very simple backpressure monitoring, but the forthcoming steps will probably require a more sophisticated system, such as a resistive soot sensor. The aim of this study is to investigate the mechanisms leading to the formation of bridge-like soot deposits brought to light by scanning electron microscopy. A 2D model taking into account the aerodynamic transport and the electrostatic effects was used to improve our understanding of the soot deposition process. The model presented in this paper includes a force that has been neglected so far in previous works about resistive soot sensors: the dielectrophoresis. In this theoretical frame, this force affects particles motion in such a way that they tend to numerically build the bridge-like structures that are observed experimentally. Simulation shown that the dielectrophoresis mainly impact large particles – over 150 nm diameter.

Due to the extensive applications in the automotive and aerospace industries of Al–7Si–Mg casting alloys, an understanding of their dendrite microstructural formation in three dimensions is of great importance in order to control the desirable microstructure, so as to modify the performance of castings. For this reason, a three-dimensional cellular automaton model (3-D CA) allowing for the prediction of dendrite growth of ternary alloys is presented. The growth kinetics of the solid/liquid (S/L) interface is calculated based on the solutal equilibrium approach. This proposed model introduces a modified decentered octahedron algorithm for neighborhood tracking, in order to eliminate the effects of mesh dependency on dendrite growth. The thermodynamic and kinetic data needed in the simulations are obtained through coupling with the Pandat software package in combination with thermodynamic/kinetic/equilibrium phase diagram calculation databases. The solute interactions between alloying elements are considered in the model. The model was first used to simulate the Al–7Si dendrite, followed by a validation using theoretical predictions. The influence of Mg content on the dendrite growth dynamics and dendrite morphologies was investigated. Also, the model was applied to Al–7Si–0.5Mg dendrite simulation both with and without a consideration of solute interactions between the Si and Mg alloying elements and the effects on dendrite growth process was analyzed using the simulation results. This model was finally used in order to simulate the dendrite growth in different crystallographic orientations in an Al–7Si–0.36Mg ternary alloy during polycrystalline solidification, resulting in a predicted secondary dendrite arm spacing (SDAS) and dendrite volume fraction data that show a reasonable agreement with experimental results. The single dendrite and polycrystalline growth simulations effectively demonstrate the capability of this model in predicting the three-dimensional dendrite microstructure of ternary alloys.

Although electrical fires constitute the greatest percentage of the main causes of building fires, the critical evidence used by fire investigators to identify electrical fires is not always convincing to the general public. In this study, we scrutinized the microstructures of fire-causing copper wires and simulated the external environmental conditions required for the formation of fire-causing arc beads. Our metallographic investigation revealed that the primary thermal dendrites of copper at the fire-causing arc bead grew parallel to one another, but in the opposite direction to the heat flow. We determined the relationships of the undercooling (∆T0), the growth velocity (ν), and the primary spacing (λ) of the dendrites with respect to the electrical wire’s diameter. Accordingly, fire investigators can now identify fire-causing arc beads in terms of these metallographic characteristics, thereby providing clear scientific evidence for litigant judgments of electrical fires.

Summary Mutations in the Golgi SNARE (SNAP [soluble NSF attachment protein] receptor) protein Membrin (encoded by the GOSR2 gene) cause progressive myoclonus epilepsy (PME). Membrin is a ubiquitous and essential protein mediating ER-to-Golgi membrane fusion. Thus, it is unclear how mutations in Membrin result in a disorder restricted to the nervous system. Here, we use a multi-layered strategy to elucidate the consequences of Membrin mutations from protein to neuron. We show that the pathogenic mutations cause partial reductions in SNARE-mediated membrane fusion. Importantly, these alterations were sufficient to profoundly impair dendritic growth in Drosophila models of GOSR2-PME. Furthermore, we show that Membrin mutations cause fragmentation of the presynaptic cytoskeleton coupled with transsynaptic instability and hyperactive neurotransmission. Our study highlights how dendritic growth is vulnerable even to subtle secretory pathway deficits, uncovers a role for Membrin in synaptic function, and provides a comprehensive explanatory basis for genotype-phenotype relationships in GOSR2-PME., Graphical Abstract, Highlights • Epilepsy/ataxia-linked mutations in Membrin confer partial Golgi SNARE defects • Partial reductions in membrane trafficking strongly impair dendritic growth • Synaptic morphology and function tightly depend upon efficient secretory trafficking, In this study, Praschberger et al. utilize in vitro assays, patient-derived cells, and Drosophila models to unravel how mutations in the essential Golgi SNARE protein Membrin cause progressive myoclonus epilepsy and to demonstrate a selective vulnerability of developing neurons to partial impairment of ER-to-Golgi trafficking.

Die Untersuchungen im Rahmen dieses Promotionsprojektes zielen auf ein tieferes Verständnis der Grenzflächenveränderung während der kathodischen Abscheidung von metallischem Lithium ab. Die kathodische Lithiummetallabscheidung wurde mit dem verwendeten Probermodulaufbau hinsichtlich der unterschiedlichen Einflussparameter (Stromdichte, Temperatur, Präparation der Elektrolytoberfläche) auf unterschiedlichen Festelektrolyten erfolgreich untersucht. Die Morphologieunterschiede (Dendrite/Whisker) konnten durch die in situ Beobachtung im HREM visualisiert werden. Im Stromdichtebereich bis 50 mA/cm² konnte whiskerartiges Wachstum beobachtet werden, im Grenzbereich zwischen 100 mA/cm² - 300 mA/cm² sowohl laterales als auch vertikales Wachstum, und ab 300 mA/cm² konnte dendritisches Wachstum beobachtet werden. Der Einfluss der Oberflächenpräparation auf die laterale Ausdehnungsrichtung der Metallabscheidung konnte ebenso gezeigt werden, wie die Ausbildung einer oberflächlichen Abreaktionsschicht auf dem Elektrolyten. Untersuchungen zur Reversibilität haben gezeigt, dass die Kontaktfläche zwischen Metallabscheidung und Festelektrolyt entscheidend ist für die Reversibilität der Metallabscheidung. Durch Kontaktverluste während der Auflösung kommt es zu einem Verlust an Aktivmaterial. Mit den impedanzspektroskopischen Messungen während der kathodischen Metallabscheidung konnte eine Veränderung des Grenzflächenwiderstands gezeigt werden. Zudem konnten Informationen bezüglich der Leitfähigkeit des Festelektrolytmaterials erlangt werden., The investigations within this project focus on a deeper understanding of changes in the interface during the cathodic deposition of metallic lithium. The cathodic lithium metal deposition was successfully investigated with the used prober module setup with regard to the different influencing parameters (current density, temperature, preparation of electrolyte surface) on different solid electrolytes. The morphological differences (dendrites/whiskers) could be visualized by the in situ observation in the HRSEM.The whisker-like growth was observed in the current density range up to 50 mA/cm² and both the lateral and the vertical growth could be observed in the transition region between 100 mA/cm² - 300 mA/cm² and over 300 mA/cm² only dendritic growth was observed. The influence of the preparation of the solid electrolyte surface and the formation of a reaction layer on the surface of the electrolyte have also been shown.The contact area between metal deposit and solid electrolyte is the main factor determing reversibility. Contact loss during the metal dissolution leads to a loss of active material. With impedance spectroscopic measurements during the cathodic metal deposition, a change in the interfacial resistance could be observed. From the impedance spectra measured with microelectrodes the conductivity of the solid electrolyte material could also be obtained.

The solid–liquid interface of metallic systems of small entropy of fusion is characterized by a rough interface and dendritic morphology. In contrast, systems of high entropy of fusion like semimetals and semiconductors show smooth interfaces and facetted interfaces. The present work demonstrates that, in an undercooled melt of a metal–metalloid alloy Ni2B of intermediate entropy of fusion, a transition from a rough to a smooth interface is induced by forced convection of the melt. Electrostatic levitation is used to container-less undercool droplets in a quiescent state with no convection while electromagnetic levitation (EML) is used to undercool droplets with forced convection. The growth velocity of the solid phase is monitored as a function of undercooling by a high-speed video camera. The data are analysed within dendrite growth theory. In the case of EML, a transition from a rough to a smooth interface is indicated during dendrite growth in the undercooled melt. This is confirmed by facetted micros...

An important tool to study dendritic growth in metallic alloys is the in-situ polychromatic X-radiography. Since solutal interaction is a dominant factor influencing dendrite growth, the determination of liquid concentrations is crucial to interpret the image data. Laboratory experiments with polychromatic X-ray sources require reference measurements of samples of known composition and thickness to convert intensities into concentrations because of the wavelength dependency of the absorption coefficient. Calibration measurements and fitted intensity functions are used to determine solutal concentrations in an Al-Ge sample without using in-situ reference samples.

An undercooled melt possesses an enhanced free enthalpy that opens up the possibility to crystallize metastable crystalline solids in competition with their stable counterparts. Crystal nucleation selects the crystallographic phase whereas the growth dynamics controls microstructure evolution. We apply containerless processing techniques such as electromagnetic and electrostatic levitation to containerlesss undercool and solidify metallic melts. Owing to the complete avoidance of heterogeneous nucleation on container-walls a large undercooling range becomes accessible with the extra benefit that the freely suspended drop is direct accessible for in situ observation of crystallization far away from equilibrium. Results of investigations of maximum undercoolability on pure zirconium are presented showing the limit of maximum undercoolability set by the onset of homogeneous nucleation. Rapid dendrite growth is measured as a function of undercooling by a high-speed camera and analysed within extended theories of non-equilibrium solidification. In such both supersaturated solid solutions and disordered superlattice structure of intermetallics are formed at high growth velocities. A sharp interface theory of dendrite growth is capable to describe the non-equilibrium solidification phenomena during rapid crystallization of deeply undercooled melts. Eventually, anomalous growth behaviour of Al-rich Al–Ni alloys is presented, which may be caused by forced convection.

International audience; One mechanism for the formation of equiaxed grains is the detachment of dendrite fragments which is believed to be at the origin of the central equiaxed core region in casting processes. Unfortunately, the dynamics of the fragmentation phenomena cannot be revealed by classicalmethods. Investigation of a unrefined Al–7 wt-%Si alloy using in situ and real time synchrotron X-radiography and X-ray topography at the European Synchrotron Radiation Facility, has allowed verification of the existence of dendrite fragmentation and of cascade fragmentation duringdirectional solidification, and to study the evolution of the growth and sedimentation of the equiaxed grains formed from these fragments. An examination of the crystallographic misorientation of dendrites as fragmentation is ongoing. These results contribute to the understanding of the characteristics of the columnar to equiaxed transition and to knowledge of the origin of new equiaxed grains in unrefined alloys.

Under certain thermal conditions (G approximate to 1 x 10(4) K/m, v(s) approximate to 1 x 10(-3) m/s), < 1 1 0 > twinned dendrites appear in aluminum alloys and can overgrow regular columnar dendrites, provided that some convection is also present in the melt. In order to check the stability of such morphologies, directionally solidified twinned samples of Al-Zn were partially remelted in a Bridgman furnace and then resolidified under controlled conditions, with minimal convection. It was found that, although twin planes remain stable during partial remelting, non-twinned dendrites regrow during solidification. They have a crystallographic orientation given by those of the twinned and untwinned "seed" regions, and grow along preferred directions that tend to be those of normal specimens. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The effect of interfacial ordering kinetics on growth morphology is examined for undercooling solidification of intermetallics. The focus is on NiAl, which has been found to solidify into completely irregular seaweed-like morphologies at growth velocities of ∼2 m s−1. The transition from regular dendritic to seaweed growth in this material is simulated using a hybrid deterministic–probabilistic model of microstructure evolution, taking account of the interfacial kinetic effects. Modelling shows that seaweed formation in intermetallic forming systems can be attributed in part to transient entrapment of the chemical and orientational disorder at the solid/liquid interface. Both types of disorder trapping give rise to strongly preferential depression of the interfacial temperature, while orientational disorder trapping also reduces the definitiveness of crystal orientation at the interface. These effects counterbalance the role of crystallographic anisotropy in promoting growth into preferred directions, and hence lead to relatively easy breakdown of regular dendritic patterns in highly ordered materials.

Electromagnetic and electrostatic levitation are applied to containerless undercool and solidify metallic melts. A large undercooling range becomes accessible with the extra benefit that the freely suspended drop is accessible directly for in situ observation. The short-range order in undercooled melts is investigated by combining levitation with elastic neutron scattering and X-ray scattering using synchrotron radiation. Muon Spin Rotation (µSR) experiments show magnetic ordering in deeply undercooled Co80Pd20 alloys. The onset of magnetic ordering stimulates nucleation. Results on nucleation undercooling of zirconium are presented showing the limit of maximum undercoolability set by the onset of homogeneous nucleation. Metastable phase diagrams are determined by applying energy-dispersive X-ray diffraction of Ni-V alloys with varying concentration. Nucleation is followed by crystal growth. Rapid dendrite growth velocity is measured on levitation-processed samples as a function of undercooling ∆T by using high-speed video camera technique. Solute trapping in dilute solid solutions and disorder trapping in intermetallic compounds are experimentally verified. Measurements of glass-forming Cu-Zr alloy show a maximum in the V(∆T) relation that is indicative for diffusion-controlled growth. The influence of convection on dendrite growth of Al50Ni50 is shown by comparative measurements of dendrite growth velocity on Earth and in reduced gravity. Eventually, faceting of a rough interface by convection is presented as observed on Ni2B alloys.

A free dendrite growth under forced fluid flow is analyzed for solidification of a nonisothermal binary system. Using an approach to dendrite growth developed by Bouissou and Pelcé, the analysis is presented for the parabolic dendrite interface with small anisotropy of surface energy growing at arbitrary Péclet numbers. The stable growth mode is obtained from the solvability condition giving the stability criterion for the dendrite tip velocity V and dendrite tip radius ρ as a function of the growth Péclet number, flow Péclet number, and Reynolds number. In limiting cases, the obtained stability criterion presents known criteria for small and high growth Péclet numbers of the solidifying system with and without convective fluid flow. © 2013 American Physical Society.

Our previous work showed that loss of the KIAA2022 gene protein results in intellectual disability with language impairment and autistic behavior (KIDLIA, also referred to as XPN). However, the cellular and molecular alterations resulting from a loss of function of KIDLIA and its role in autism with severe intellectual disability remain unknown. Here, we show that KIDLIA plays a key role in neuron migration and morphogenesis. We found that KIDLIA is distributed exclusively in the nucleus. In the developing rat brain, it is expressed only in the cortical plate and subplate region but not in the intermediate or ventricular zone. Usingin uteroelectroporation, we found that short hairpin RNA (shRNA)-mediated knockdown of KIDLIA leads to altered neuron migration and a reduction in dendritic growth and disorganized apical dendrite projections in layer II/III mouse cortical neurons. Consistent with this, in cultured rat neurons, a loss of KIDLIA expression also leads to suppression of dendritic growth and branching. At the molecular level, we found that KIDLIA suppression leads to an increase in cell-surface N-cadherin and an elevated association of N-cadherin with δ-catenin, resulting in depletion of free δ-catenin in the cytosolic compartment. The reduced availability of cytosolic δ-catenin leads to elevated RhoA activity and reduced actin dynamics at the dendritic growth cone. Furthermore, in neurons with KIDLIA knockdown, overexpression of δ-catenin or inhibition of RhoA rescues actin dynamics, dendritic growth, and branching. These findings provide the first evidence on the role of the novel protein KIDLIA in neurodevelopment and autism with severe intellectual disability.

International audience; The impulse atomization process developed at the University of Alberta (Canada) enables metallic powders to be solidified with controlled process parameters and improved properties. In order to investigate the microstructure morphologies in droplets of Al- 4.5wt.%Cu alloys, three-dimensional reconstructions of several droplets are obtained by using synchrotron X-ray micro-tomography, allowing a visualization of the inner microstructure in three dimensions. The analysis of the reconstructed volumes reveals that a wide range of morphology, from highly branched to "finger-bundle", can be obtained for different droplets of similar diameter and produced in the same batch. Unexpectedly for this alloy, microstructural features also indicate that the development of the dendrite arms (primary and of higher orders) occurs in most droplets along crystallographic axes, instead of the usual directions observed in conventional casting technologies.

International audience; A segregation model for multiple phase transformations is coupled with thermodynamic equilibrium calculations, including dendritic, peritectic and eutectic reactions. Its predictions are compared with measurements deduced from an electro-magnetic levitation solidification experiment of an aluminum-nickel alloy. Quantitative agreement is found for the cooling curve and the fraction of microstructures, providing a validation of the kinetics of phase transformations. The effects of nucleation undercooling and coupling with thermodynamic equilibrium calculations are discussed.

If a liquid is undercooled below its equilibrium melting temperature an excess Gibbs free energy is created. This gives access to solidification of metastable solids under non-equilibrium conditions. In the present work, techniques of containerless processing are applied. Electromagnetic and electrostatic levitation enable to freely suspend a liquid drop of a few millimeters in diameter. Heterogeneous nucleation on container walls is completely avoided leading to large undercoolings. The freely suspended drop is accessible for direct observation of rapid solidification under conditions far away from equilibrium by applying proper diagnostic means. Nucleation of metastable crystalline phases is monitored by X-ray diffraction using synchrotron radiation during non-equilibrium solidification. While nucleation preselects the crystallographic phase, subsequent crystal growth controls the microstructure evolution. Metastable microstructures are obtained from deeply undercooled melts as supersaturated solid solutions, disordered superlattice structures of intermetallics. Nucleation and crystal growth take place by heat and mass transport. Comparative experiments in reduced gravity allow for investigations on how forced convection can be used to alter the transport processes and design materials by using undercooling and convection as process parameters.

Cultured neurons from bdnf-/- mice display reduced densities of synaptic terminals, although in vivo these deficits are small or absent. Here we aimed at clarifying the local responses to postsynaptic brain-derived neurotrophic factor (BDNF). To this end, solitary enhanced green fluorescent protein (EGFP)-labeled hippocampal neurons from bdnf-/- mice were compared with bdnf-/- neurons after transfection with BDNF, bdnf-/- neurons after transient exposure to exogenous BDNF, and bdnf+/+ neurons in wild-type cultures. Synapse development was evaluated on the basis of presynaptic immunofluorescence and whole-cell patch-clamp recording of miniature postsynaptic currents. It was found that neurons expressing BDNF::EGFP for at least 16 h attracted a larger number of synaptic terminals than BDNF-deficient control neurons. Transfected BDNF formed clusters in the vicinity of glutamatergic terminals and produced a stronger upregulation of synaptic terminal numbers than high levels of ambient BDNF. Glutamatergic and GABAergic synapses reacted differently to postsynaptic BDNF: glutamatergic input increased, whereas GABAergic input decreased. BDNF::EGFP-expressing neurons also differed from BDNF-deficient neurons in their dendrite morphology: they exhibited weaker dendrite elongation and stronger dendrite initiation. The upregulation of glutamatergic synaptic input and the BDNF-induced downregulation of GABAergic synaptic terminal numbers by postsynaptic BDNF depended on tyrosine receptor kinase B activity, as deduced from the blocking effects of K252a. The suppression of dendrite elongation was also prevented by block of tyrosine receptor kinase B but required, in addition, glutamate receptor activity. Dendritic length decreased with the number of glutamatergic contacts. These results illuminate the role of BDNF as a retrograde synaptic regulator of synapse development and the dependence of dendrite elongation on glutamatergic input.

Rapid solidification is a well established method for the preparation of metals and alloys in metastable states, giving access to a range of novel materials properties [1]. An important crystal-growth mechanism in these techniques is dendritic growth, which provides the most effective means of heat and solute rejection during solidification. Dendritic growth has attracted recent attention both from the theoretical [2 – 5] and the experimental side [6 – 9].

Drop tubes and electromagnetic levitation are described as techniques for containerless processing. The constraints of maximum undercoolability of metals are discussed with respect to thermodynamic considerations and the onset of homogeneous nucleation. Dendrite growth occurring in undercooled melts is described on the basis of experimental investigations and modern dendrite growth theories. The importance of the knowledge of thermophysical properties in the understanding of both nucleation and crystal growth in undercooled melts is pointed out. Experimental techniques are presented which allow the measurement of the dependence of such properties on temperature in particular by using electromagnetic positioning in future space missions.

Solidification needs an undercooling to drive the solidification front. If large undercoolings are achieved, metastable solid materials are solidified from the undercooled melt. Containerless processing provides the conditions to achieve large undercoolings since heterogeneous nucleation on container walls is completely avoided. In the present contribution both electromagnetic and electrostatic levitation are applied. The velocity of rapidly advancing dendrites is measured as a function of undercooling by a High-Speed-Camera. The dendrite growth dynamics is investigated in undercooled melts of intermetallic compounds. The Al50Ni50 alloy is studied with respect to disorder trapping that leads to a disordered superlattice structure if the melt is undercooled beyond a critical undercooling. Disorder trapping is evidenced by in situ energy dispersive diffraction using synchrotron radiation of high intensity to record full diffraction pattern on levitated samples within a short time interval. Experiments on Ni2B using different processing techniques of varying the level of convection reveal convection-induced faceting of rapidly growing dendrites. Eventually, the growth velocity is measured in an undercooled melt of glass forming Cu50Zr50 alloy. A maximum in the growth velocity–undercooling relation is proved. This is understood by the fact that the temperature dependent diffusion coefficient counteracts the thermodynamic driving force for rapid growth if the temperature of the undercooled melt is approaching the temperature regime above the glass transition temperature. The analysis of this result allows for determining the activation energy of atomic attachment kinetics at the solid–liquid interface that is comparable to the activation energy of atomic diffusion as determined by independent measurements of the atomic diffusion in undercooled Cu50Zr50 alloy melt.