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Wu, Hua-Zhi, Man-Ni Cai, Yu An, Cheng Lan, Jia-Li Wei, and Xiao-Ning Sun. "Runx3 might participate in regulating dendriti cell function in patients with irritable bowel syndrome." Asian Pacific Journal of Tropical Medicine 7, no. 9 (2014): 754–56. http://dx.doi.org/10.1016/s1995-7645(14)60130-9.
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Fujishima, Kazuto, Junko Kurisu, Midori Yamada та Mineko Kengaku. "βIII spectrin controls the planarity of Purkinje cell dendrites by modulating perpendicular axon-dendrite interactions". Development 147, № 24 (2020): dev194530. http://dx.doi.org/10.1242/dev.194530.
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ABSTRACTThe mechanism underlying the geometrical patterning of axon and dendrite wiring remains elusive, despite its crucial importance in the formation of functional neural circuits. The cerebellar Purkinje cell (PC) arborizes a typical planar dendrite, which forms an orthogonal network with granule cell (GC) axons. By using electrospun nanofiber substrates, we reproduce the perpendicular contacts between PC dendrites and GC axons in culture. In the model system, PC dendrites show a preference to grow perpendicularly to aligned GC axons, which presumably contribute to the planar dendrite arborization in vivo. We show that βIII spectrin, a causal protein for spinocerebellar ataxia type 5, is required for the biased growth of dendrites. βIII spectrin deficiency causes actin mislocalization and excessive microtubule invasion in dendritic protrusions, resulting in abnormally oriented branch formation. Furthermore, disease-associated mutations affect the ability of βIII spectrin to control dendrite orientation. These data indicate that βIII spectrin organizes the mouse dendritic cytoskeleton and thereby regulates the oriented growth of dendrites with respect to the afferent axons.
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Larkum, M. E., M. G. Rioult, and H. R. Luscher. "Propagation of action potentials in the dendrites of neurons from rat spinal cord slice cultures." Journal of Neurophysiology 75, no. 1 (1996): 154–70. http://dx.doi.org/10.1152/jn.1996.75.1.154.
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1. We examined the propagation of action potentials in the dendrites of ventrally located presumed motoneurons of organotypic rat spinal cord cultures. Simultaneous patch electrode recordings were made from the dendrites and somata of individual cells. In other experiments we visualized the membrane voltage over all the proximal dendrites simultaneously using a voltage-sensitive dye and an array of photodiodes. Calcium imaging was used to measure the dendritic rise in Ca2+ accompanying the propagating action potentials. 2. Spontaneous and evoked action potentials were recorded using high-resistance patch electrodes with separations of 30-423 microm between the somatic and dendritic electrodes. 3. Action potentials recorded in the dendrites varied considerably in amplitude but were larger than would be expected if the dendrites were to behave as passive cables (sometimes little or no decrement was seen for distances of > 100 microm). Because the amplitude of the action potentials in different dendrites was not a simple function of distance from the soma, we suggest that the conductance responsible for the boosting of the action potential amplitude varied in density from dendrite to dendrite and possibly along each dendrite. 4. The dendritic action potentials were usually smaller and broader and arrived later at the dendritic electrode than at the somatic electrode irrespective of whether stimulation occurred at the dendrite or soma or as a result of spontaneous synaptic activity. This is clear evidence that the action potential is initiated at or near the soma and spreads out into the dendrites. The conduction velocity of the propagating action potential was estimated to be 0.5 m/s. 5. The voltage time courses of previously recorded action potentials were generated at the soma using voltage clamp before and after applying 1 microM tetrodotoxin (TTX) over the soma and dendrites. TTX reduced the amplitude of the action potential at the dendritic electrode to a value in the range expected for dendrites that behave as passive cables. This indicates that the conductance responsible for the actively propagating action potentials is a Na+ conductance. 6. The amplitude of the dendritic action potential could also be initially reduced more than the somatic action potential using 1-10 mM QX-314 (an intracellular sodium channel blocker) in the dendritic electrode as the drug diffused from the dendritic electrode toward the soma. Furthermore, in some cases the action potential elicited by current injection into the dendrite had two components. The first component was blocked by QX-314 in the first few seconds of the diffusion of the blocker. 7. In some cells, an afterdepolarizing potential (ADP) was more prominent in the dendrite than in the soma. This ADP could be reversibly blocked by 1 mM Ni2+ or by perfusion of a nominally Ca2+-free solution over the soma and dendrites. This suggests that the back-propagating action potential caused an influx of Ca2+ predominantly in the dendrites. 8. With the use of a voltage-sensitive dye (di-8-ANEPPS) and an array of photodiodes, the action potential was tracked along all the proximal dendrites simultaneously. The results confirmed that the action potential propagated actively, in contrast to similarly measured hyperpolarizing pulses that spread passively. There were also indications that the action potential was not uniformly propagated in all the dendrites, suggesting the possibility that the distribution of Na+ channels over the dendritic membrane is not uniform. 9. Calcium imaging with the Ca2+ fluorescent indicator Fluo-3 showed a larger percentage change in fluorescence in the dendrites than in the soma. Both bursts and single action potentials elicited sharp rises in fluorescence in the proximal dendrites, suggesting that the back-propagating action potential causes a concomitant rise in intracellular calcium concentration...
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Ligon, Cheryl, Eunju Seong, Ethan J. Schroeder та ін. "δ-Catenin engages the autophagy pathway to sculpt the developing dendritic arbor". Journal of Biological Chemistry 295, № 32 (2020): 10988–1001. http://dx.doi.org/10.1074/jbc.ra120.013058.
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The development of the dendritic arbor in pyramidal neurons is critical for neural circuit function. Here, we uncovered a pathway in which δ-catenin, a component of the cadherin–catenin cell adhesion complex, promotes coordination of growth among individual dendrites and engages the autophagy mechanism to sculpt the developing dendritic arbor. Using a rat primary neuron model, time-lapse imaging, immunohistochemistry, and confocal microscopy, we found that apical and basolateral dendrites are coordinately sculpted during development. Loss or knockdown of δ-catenin uncoupled this coordination, leading to retraction of the apical dendrite without altering basolateral dendrite dynamics. Autophagy is a key cellular pathway that allows degradation of cellular components. We observed that the impairment of the dendritic arbor resulting from δ-catenin knockdown could be reversed by knockdown of autophagy-related 7 (ATG7), a component of the autophagy machinery. We propose that δ-catenin regulates the dendritic arbor by coordinating the dynamics of individual dendrites and that the autophagy mechanism may be leveraged by δ-catenin and other effectors to sculpt the developing dendritic arbor. Our findings have implications for the management of neurological disorders, such as autism and intellectual disability, that are characterized by dendritic aberrations.
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Velte, Toby J., and Richard H. Masland. "Action Potentials in the Dendrites of Retinal Ganglion Cells." Journal of Neurophysiology 81, no. 3 (1999): 1412–17. http://dx.doi.org/10.1152/jn.1999.81.3.1412.
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Action potentials in the dendrites of retinal ganglion cells. The somas and dendrites of intact retinal ganglion cells were exposed by enzymatic removal of the overlying endfeet of the Müller glia. Simultaneous whole cell patch recordings were made from a ganglion cell’s dendrite and the cell’s soma. When a dendrite was stimulated with depolarizing current, impulses often propagated to the soma, where they appeared as a mixture of small depolarizations and action potentials. When the soma was stimulated, action potentials always propagated back through the dendrite. The site of initiation of action potentials, as judged by their timing, could be shifted between soma and dendrite by changing the site of stimulation. Applying QX-314 to the soma could eliminate somatic action potentials while leaving dendritic impulses intact. The absolute amplitudes of the dendritic action potentials varied somewhat at different distances from the soma, and it is not clear whether these variations are real or technical. Nonetheless, the qualitative experiments clearly suggest that the dendrites of retinal ganglion cells generate regenerative Na+ action potentials, at least in response to large direct depolarizations.
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Al-Gahtani, Masoud, and Rian Dippenaar. "Mechanical Properties of Dendritic and Inter-Dendritic Regions in As-Cast Medium-Carbon Steel." Advanced Materials Research 894 (February 2014): 104–9. http://dx.doi.org/10.4028/www.scientific.net/amr.894.104.
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During solidification of steel, dendrite nucleation and growth leads to the segregation of alloying elements in the inter-dendritic regions. The dendrite arms are low in carbon while alloying elements segregate to the inter-dendritic regions. During subsequent hot-rolling, this variation in alloying element content leads to the formation of regions of high and low solute content, which in turn, leads to the formation of microstructural banding during heat treatment. In the present study, the respective mechanical properties of these dendritic and inter-dendritic regions were studied in medium carbon steel in order to investigate the rotation of dendrites during hot rolling.
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Volfovsky, N., H. Parnas, M. Segal, and E. Korkotian. "Geometry of Dendritic Spines Affects Calcium Dynamics in Hippocampal Neurons: Theory and Experiments." Journal of Neurophysiology 82, no. 1 (1999): 450–62. http://dx.doi.org/10.1152/jn.1999.82.1.450.
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The role of dendritic spine morphology in the regulation of the spatiotemporal distribution of free intracellular calcium concentration ([Ca2+]i) was examined in a unique axial-symmetrical model that focuses on spine–dendrite interactions, and the simulations of the model were compared with the behavior of real dendritic spines in cultured hippocampal neurons. A set of nonlinear differential equations describes the behavior of a spherical dendritic spine head, linked to a dendrite via a cylindrical spine neck. Mechanisms for handling of calcium (including internal stores, buffers, and efflux pathways) are placed in both the dendrites and spines. In response to a calcium surge, the magnitude and time course of the response in both the spine and the parent dendrite vary as a function of the length of the spine neck such that a short neck increases the magnitude of the response in the dendrite and speeds up the recovery in the spine head. The generality of the model, originally constructed for a case of release of calcium from stores, was tested in simulations of fast calcium influx through membrane channels and verified the impact of spine neck on calcium dynamics. Spatiotemporal distributions of [Ca2+]i, measured in individual dendritic spines of cultured hippocampal neurons injected with Calcium Green-1, were monitored with a confocal laser scanning microscope. Line scans of spines and dendrites at a <1-ms time resolution reveal simultaneous transient rises in [Ca2+]i in spines and their parent dendrites after application of caffeine or during spontaneous calcium transients associated with synaptic or action potential discharges. The magnitude of responses in the individual compartments, spine–dendrite disparity, and the temporal distribution of [Ca2+]i were different for spines with short and long necks, with the latter being more independent of the dendrite, in agreement with prediction of the model.
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Christie, J. M., and G. L. Westbrook. "Regulation of Backpropagating Action Potentials in Mitral Cell Lateral Dendrites by A-Type Potassium Currents." Journal of Neurophysiology 89, no. 5 (2003): 2466–72. http://dx.doi.org/10.1152/jn.00997.2002.
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Dendrodendritic synapses, distributed along mitral cell lateral dendrites, provide powerful and extensive inhibition in the olfactory bulb. Activation of inhibition depends on effective penetration of action potentials into dendrites. Although action potentials backpropagate with remarkable fidelity in apical dendrites, this issue is controversial for lateral dendrites. We used paired somatic and dendritic recordings to measure action potentials in proximal dendritic segments (0–200 μm from soma) and action potential-generated calcium transients to monitor activity in distal dendritic segments (200–600 μm from soma). Somatically elicited action potentials were attenuated in proximal lateral dendrites. The attenuation was not due to impaired access resistance in dendrites or to basal synaptic activity. However, a single somatically elicited action potential was sufficient to evoke a calcium transient throughout the lateral dendrite, suggesting that action potentials reach distal dendritic compartments. Block of A-type potassium channels ( I A) with 4-aminopyridine (10 mM) prevented action potential attenuation in direct recordings and significantly increased dendritic calcium transients, particularly in distal dendritic compartments. Our results suggest that I A may regulate inhibition in the olfactory bulb by controlling action potential amplitudes in lateral dendrites.
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Zhao, Shanrong, Jin Tan, Jiyang Wang, Xiaohong Xu, and Hong Liu. "A Dendrite with "Sierpinski Gasket" Fractal Morphology in Matt Glaze of LiAlSiO4-SiO2 System." Fractals 11, no. 03 (2003): 271–76. http://dx.doi.org/10.1142/s0218348x03001525.
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In this paper, we introduce a dendritic crystal, formed in matt glaze of LiAlSiO 4- SiO 2, having "Sierpinski gasket" fractal morphology. The crystal structure of this "Sierpinski gasket" dendrite is β-quartz. β-quartz can grow two kinds of fractal patterns: snow-shaped dendrite and "Sierpinski gasket" dendrite, depending on different supercooling conditions. These two kinds of fractals can develop together in one dendritic crystal. The evolution of the boundary morphologies between these two kinds of fractal dendrites can be described by another fractal — Koch curve. The "Sierpinski gasket" dendrite is a rather new fractal growth pattern which can introduce new opportunities to fractal growth research of nonlinear sciences.
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Schiller, Yitzhak. "Inter-Ictal- and Ictal-Like Epileptic Discharges in the Dendritic Tree of Neocortical Pyramidal Neurons." Journal of Neurophysiology 88, no. 6 (2002): 2954–62. http://dx.doi.org/10.1152/jn.00525.2001.
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Dendritic mechanisms have been implied to play a key role in the formation of epileptic discharges. However, presently only a handful of direct dendritic recordings have been reported during epileptic discharges. In this study, I performed simultaneous voltage recordings from the soma and apical dendrite of the same neuron combined with calcium-imaging measurements to investigate inter-ictal- and ictal-like epileptic discharges in dendrites of layer 5 pyramidal neurons. Neocortical brain slices treated with bicuculline (BCC) produced both isolated “inter-ictal” paroxysymal depolarization shift (PDS) responses and electrographic seizures. Concomitant voltage recordings from the soma and apical dendrite revealed that PDS responses developed in both the apical dendrites and soma. However, the two responses differed from one another. In apical dendrites, the PDS was significantly higher in amplitude and shorter in duration compared with the somatic PDS. The PDS response in dendrites had a peak amplitude of 68.9 ± 2.2 (SD) mV, peak voltage value of 9.3 ± 2.7 mV, and half-width of 203.8 ± 38.4 ms. In contrast, the somatic PDS had a peak amplitude of 48.7 ± 2.7 mV, peak voltage value of −11.9 ± 3.1 mV, and half-width of 247.8 ± 57.3 ms ( P < 0.01, n = 18). In addition the apical dendritic PDS always preceded the somatic counterpart in all 18 neurons examined. Concomitant calcium-imaging measurements showed the PDS evoked large calcium influx into the entire dendritic tree including the apical tuft, basal, and oblique dendrites. The PDS evoked [Ca2+]i were not uniform along the dendritic tree, being highest in the oblique dendrites (71.3 ± 14.5 μM) and lowest at the distal tuft branches (9.3 ± 0.7 μM). The PDS responses persisted after blockade of voltage-gated sodium channels by intracellular QX-314 but became narrower (by 69.6 ± 9.7%) following intracellular administration of the voltage-gated calcium channel blocker D600. Electrographic seizures recorded in the soma and apical dendrites were composed of recurrent bursts. The initial bursts represented PDS responses. During the seizure the amplitude of bursts gradually attenuated and reached an average value of 26 ± 13% of the initial ictal PDS burst. Double recordings during electrographic seizures revealed the initial one to four ictal bursts appeared first at the apical dendrite while later ictal bursts were always observed first at the soma. In conclusion, the results of this study show “inter-ictal” PDS responses originated in the apical dendritic tree, were partially mediated by voltage-gated calcium channels and spread throughout the dendritic tree including the fine tuft, basal, and oblique dendrites. During electrographic seizures the origin of epileptic bursts shifted from the apical dendritic tree to the soma-basal region.
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Lüscher, Hans-R., and Matthew E. Larkum. "Modeling Action Potential Initiation and Back-Propagation in Dendrites of Cultured Rat Motoneurons." Journal of Neurophysiology 80, no. 2 (1998): 715–29. http://dx.doi.org/10.1152/jn.1998.80.2.715.
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Lüscher, Hans-R. and Matthew E. Larkum. Modeling action potential initiation and back-propagation in dendrites of cultured rat motoneurons. J. Neurophysiol. 80: 715–729, 1998. Regardless of the site of current injection, action potentials usually originate at or near the soma and propagate decrementally back into the dendrites. This phenomenon has been observed in neocortical pyramidal cells as well as in cultured motoneurons. Here we show that action potentials in motoneurons can be initiated in the dendrite as well, resulting in a biphasic dendritic action potential. We present a model of spinal motoneurons that is consistent with observed physiological properties of spike initiation in the initial segment/axon hillock region and action potential back-propagation into the dendritic tree. It accurately reproduces the results presented by Larkum et al. on motoneurons in organotypic rat spinal cord slice cultures. A high Na+-channel density of ḡ Na = 700 mS/cm2 at the axon hillock/initial segment region was required to secure antidromic invasion of the somato-dendritic membrane, whereas for the orthodromic direction, a Na+-channel density of ḡ Na = 1,200 mS/cm2 was required. A “weakly” excitable ( ḡ Na = 3 mS/cm2) dendritic membrane most accurately describes the experimentally observed attenuation of the back-propagated action potential. Careful analysis of the threshold conditions for action potential initiation at the initial segment or the dendrites revealed that, despite the lower voltage threshold for spike initiation in the initial segment, an action potential can be initiated in the dendrite before the initial segment fires a spike. Spike initiation in the dendrite depends on the passive cable properties of the dendritic membrane, its Na+-channel density, and local structural properties, mainly the diameter of the dendrites. Action potentials are initiated more easily in distal than in proximal dendrites. Whether or not such a dendritic action potential invades the soma with a subsequent initiation of a second action potential in the initial segment depends on the actual current source-load relation between the action potential approaching the soma and the electrical load of the soma together with the attached dendrites.
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Nithianandam, Vanitha, and Cheng-Ting Chien. "Actin blobs prefigure dendrite branching sites." Journal of Cell Biology 217, no. 10 (2018): 3731–46. http://dx.doi.org/10.1083/jcb.201711136.
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The actin cytoskeleton provides structural stability and adaptability to the cell. Neuronal dendrites frequently undergo morphological changes by emanating, elongating, and withdrawing branches. However, the knowledge about actin dynamics in dendrites during these processes is limited. By performing in vivo imaging of F-actin markers, we found that F-actin was highly dynamic and heterogeneously distributed in dendritic shafts with enrichment at terminal dendrites. A dynamic F-actin population that we named actin blobs propagated bidirectionally at an average velocity of 1 µm/min. Interestingly, these actin blobs stalled at sites where new dendrites would branch out in minutes. Overstabilization of F-actin by the G15S mutant abolished actin blobs and dendrite branching. We identified the F-actin–severing protein Tsr/cofilin as a regulator of dynamic actin blobs and branching activity. Hence, actin blob localization at future branching sites represents a dendrite-branching mechanism to account for highly diversified dendritic morphology.
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Grueber, Wesley B., Lily Y. Jan, and Yuh Nung Jan. "Tiling of the Drosophila epidermis by multidendritic sensory neurons." Development 129, no. 12 (2002): 2867–78. http://dx.doi.org/10.1242/dev.129.12.2867.
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Insect dendritic arborization (da) neurons provide an opportunity to examine how diverse dendrite morphologies and dendritic territories are established during development. We have examined the morphologies of Drosophila da neurons by using the MARCM (mosaic analysis with a repressible cell marker) system. We show that each of the 15 neurons per abdominal hemisegment spread dendrites to characteristic regions of the epidermis. We place these neurons into four distinct morphological classes distinguished primarily by their dendrite branching complexities. Some class assignments correlate with known proneural gene requirements as well as with central axonal projections. Our data indicate that cells within two morphological classes partition the body wall into distinct, non-overlapping territorial domains and thus are organized as separate tiled sensory systems. The dendritic domains of cells in different classes, by contrast, can overlap extensively. We have examined the cell-autonomous roles of starry night (stan) (also known as flamingo (fmi)) and sequoia (seq) in tiling. Neurons with these genes mutated generally terminate their dendritic fields at normal locations at the lateral margin and segment border, where they meet or approach the like dendrites of adjacent neurons. However, stan mutant neurons occasionally send sparsely branched processes beyond these territories that could potentially mix with adjacent like dendrites. Together, our data suggest that widespread tiling of the larval body wall involves interactions between growing dendritic processes and as yet unidentified signals that allow avoidance by like dendrites.
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Kilo, Lukas, Tomke Stürner, Gaia Tavosanis, and Anna B. Ziegler. "Drosophila Dendritic Arborisation Neurons: Fantastic Actin Dynamics and Where to Find Them." Cells 10, no. 10 (2021): 2777. http://dx.doi.org/10.3390/cells10102777.
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Neuronal dendrites receive, integrate, and process numerous inputs and therefore serve as the neuron’s “antennae”. Dendrites display extreme morphological diversity across different neuronal classes to match the neuron’s specific functional requirements. Understanding how this structural diversity is specified is therefore important for shedding light on information processing in the healthy and diseased nervous system. Popular models for in vivo studies of dendrite differentiation are the four classes of dendritic arborization (c1da–c4da) neurons of Drosophila larvae with their class-specific dendritic morphologies. Using da neurons, a combination of live-cell imaging and computational approaches have delivered information on the distinct phases and the time course of dendrite development from embryonic stages to the fully developed dendritic tree. With these data, we can start approaching the basic logic behind differential dendrite development. A major role in the definition of neuron-type specific morphologies is played by dynamic actin-rich processes and the regulation of their properties. This review presents the differences in the growth programs leading to morphologically different dendritic trees, with a focus on the key role of actin modulatory proteins. In addition, we summarize requirements and technological progress towards the visualization and manipulation of such actin regulators in vivo.
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Dong, Yan Bo, Ming Chen, and Xi Wang. "Numerical Simulation of Binary Alloy Crystal Growth Using Phase-Field Method." Advanced Materials Research 842 (November 2013): 57–60. http://dx.doi.org/10.4028/www.scientific.net/amr.842.57.
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The competitive growth of multiple dendrites and crystal growth of directional solidification in a Mg-Al binary alloy were simulated using phase-field model, and the effect of undercooling value on the microstructural dendritic growth pattern in directional solidification process was studied in the paper. The simulation results showed the impingement of the adjacent grains, which made the dendrite growth inhibited in the competitive growth of multiple dendrites, and in directional solidification process, quantitative comparison of different undercooling values that predicted the columnar dendrite evolution were carried out. With the increasing of the undercooling value, the dendrite tip radius and second dendrite arms became smaller, and the crystal structure is more uniform and dense.
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Cook, Erik P., and Daniel Johnston. "Voltage-Dependent Properties of Dendrites That Eliminate Location-Dependent Variability of Synaptic Input." Journal of Neurophysiology 81, no. 2 (1999): 535–43. http://dx.doi.org/10.1152/jn.1999.81.2.535.
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Voltage-dependent properties of dendrites that eliminate location-dependent variability of synaptic input. We examined the hypothesis that voltage-dependent properties of dendrites allow for the accurate transfer of synaptic information to the soma independent of synapse location. This hypothesis is motivated by experimental evidence that dendrites contain a complex array of voltage-gated channels. How these channels affect synaptic integration is unknown. One hypothesized role for dendritic voltage-gated channels is to counteract passive cable properties, rendering all synapses electrotonically equidistant from the soma. With dendrites modeled as passive cables, the effect a synapse exerts at the soma depends on dendritic location (referred to as location-dependent variability of the synaptic input). In this theoretical study we used a simplified three-compartment model of a neuron to determine the dendritic voltage-dependent properties required for accurate transfer of synaptic information to the soma independent of synapse location. A dendrite that eliminates location-dependent variability requires three components: 1) a steady-state, voltage-dependent inward current that together with the passive leak current provides a net outward current and a zero slope conductance at depolarized potentials, 2) a fast, transient, inward current that compensates for dendritic membrane capacitance, and 3) both αamino-3-hydroxy-5-methyl-4-isoxazolepropionic acid– and N-methyl-d-aspartate–like synaptic conductances that together permit synapses to behave as ideal current sources. These components are consistent with the known properties of dendrites. In addition, these results indicate that a dendrite designed to eliminate location-dependent variability also actively back-propagates somatic action potentials.
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Kalb, R. G. "Regulation of motor neuron dendrite growth by NMDA receptor activation." Development 120, no. 11 (1994): 3063–71. http://dx.doi.org/10.1242/dev.120.11.3063.
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Spinal motor neurons undergo great changes in morphology, electrophysiology and molecular composition during development. Some of this maturation occurs postnatally when limbs are employed for locomotion, suggesting that neuronal activity may influence motor neuron development. To identify features of motor neurons that might be regulated by activity we first examined the structural development of the rat motor neuron cell body and dendritic tree labeled with cholera toxin-conjugated horseradish peroxidase. The motor neuron cell body and dendrites in the radial and rostrocaudal axes grew progressively over the first month of life. In contrast, the growth of the dendritic arbor/cell and number of dendritic branches was biphasic with overabundant growth followed by regression until the adult pattern was achieved. We next examined the influence of neurotransmission on the development of these motor neuron features. We found that antagonism of the N-methyl-D-aspartate (NMDA) subtype of glutamate receptor inhibited cell body growth and dendritic branching in early postnatal life but had no effect on the maximal extent of dendrite growth in the radial and rostrocaudal axes. The effects of NMDA receptor antagonism on motor neurons and their dendrites was temporally restricted; all of our anatomic measures of dendrite structure were resistant to NMDA receptor antagonism in adults. These results suggest that the establishment of mature motor neuron dendritic architecture results in part from dendrite growth in response to afferent input during a sensitive period in early postnatal life.
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Chen, Wei R., Gongyu Y. Shen, Gordon M. Shepherd, Michael L. Hines, and Jens Midtgaard. "Multiple Modes of Action Potential Initiation and Propagation in Mitral Cell Primary Dendrite." Journal of Neurophysiology 88, no. 5 (2002): 2755–64. http://dx.doi.org/10.1152/jn.00057.2002.
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The mitral cell primary dendrite plays an important role in transmitting distal olfactory nerve input from olfactory glomerulus to the soma-axon initial segment. To understand how dendritic active properties are involved in this transmission, we have combined dual soma and dendritic patch recordings with computational modeling to analyze action-potential initiation and propagation in the primary dendrite. In response to depolarizing current injection or distal olfactory nerve input, fast Na+ action potentials were recorded along the entire length of the primary dendritic trunk. With weak-to-moderate olfactory nerve input, an action potential was initiated near the soma and then back-propagated into the primary dendrite. As olfactory nerve input increased, the initiation site suddenly shifted to the distal primary dendrite. Multi-compartmental modeling indicated that this abrupt shift of the spike-initiation site reflected an independent thresholding mechanism in the distal dendrite. When strong olfactory nerve excitation was paired with strong inhibition to the mitral cell basal secondary dendrites, a small fast prepotential was recorded at the soma, which indicated that an action potential was initiated in the distal primary dendrite but failed to propagate to the soma. As the inhibition became weaker, a “double-spike” was often observed at the dendritic recording site, corresponding to a single action potential at the soma. Simulation demonstrated that, in the course of forward propagation of the first dendritic spike, the action potential suddenly jumps from the middle of the dendrite to the axonal spike-initiation site, leaving the proximal part of primary dendrite unexcited by this initial dendritic spike. As Na+conductances in the proximal dendrite are not activated, they become available to support the back-propagation of the evoked somatic action potential to produce the second dendritic spike. In summary, the balance of spatially distributed excitatory and inhibitory inputs can dynamically switch the mitral cell firing among four different modes: axo-somatic initiation with back-propagation, dendritic initiation either with no forward propagation, forward propagation alone, or forward propagation followed by back-propagation.
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Galenko, Peter K., Dieter M. Herlach, G. Phanikumar, and O. Funke. "Phase-Field Modeling of Dendritic Solidification in Undercooled Droplets Processed by Electromagnetic Levitation." Materials Science Forum 508 (March 2006): 431–36. http://dx.doi.org/10.4028/www.scientific.net/msf.508.431.
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The results on modeling dendritic solidification from undercooled melts processed by the electromagnetic levitation technique are discussed. In order to model the details of formation of dendritic patterns we use a phase-field model of dendritic growth in a pure undercooled system with convection of the liquid phase. The predictions of the phase-field model are discussed referring to our latest high accuracy measurements of dendrite growth velocities in nickel samples. Special emphasis is given to the growth of dendrites at small and moderate undercoolings. At small undercoolings, the theoretical predictions deviate systematically from experimental data for solidification of nickel dendrites. It is shown that small amounts of impurities and forced convective flow can lead to an enhancement of the velocity of dendritic solidification at small undercoolings.
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Sharp, D. J., W. Yu, and P. W. Baas. "Transport of dendritic microtubules establishes their nonuniform polarity orientation." Journal of Cell Biology 130, no. 1 (1995): 93–103. http://dx.doi.org/10.1083/jcb.130.1.93.
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The immature processes that give rise to both axons and dendrites contain microtubules (MTs) that are uniformly oriented with their plus-ends distal to the cell body, and this pattern is preserved in the developing axon. In contrast, developing dendrites gradually acquire nonuniform MT polarity orientation due to the addition of a subpopulation of oppositely oriented MTs (Baas, P. W., M. M. Black, and G. A. Banker. 1989. J. Cell Biol. 109:3085-3094). In theory, these minus-end-distal MTs could be locally nucleated and assembled within the dendrite itself, or could be transported into the dendrite after their nucleation within the cell body. To distinguish between these possibilities, we exposed cultured hippocampal neurons to nanomolar levels of vinblastine after one of the immature processes had developed into the axon but before the others had become dendrites. At these levels, vinblastine acts as a kinetic stabilizer of MTs, inhibiting further assembly while not substantially depolymerizing existing MTs. This treatment did not abolish dendritic differentiation, which occurred in timely fashion over the next two to three days. The resulting dendrites were flatter and shorter than controls, but were identifiable by their ultrastructure, chemical composition, and thickened tapering morphology. The growth of these dendrites was accompanied by a diminution of MTs from the cell body, indicating a net transfer of MTs from one compartment into the other. During this time, minus-end-distal microtubules arose in the experimental dendrites, indicating that new MT assembly is not required for the acquisition of nonuniform MT polarity orientation in the dendrite. Minus-end-distal microtubules predominated in the more proximal region of experimental dendrites, indicating that most of the MTs at this stage of development are transported into the dendrite with their minus-ends leading. These observations indicate that transport of MTs from the cell body is an essential feature of dendritic development, and that this transport establishes the nonuniform polarity orientation of MTs in the dendrite.
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Oakley, J. C., P. C. Schwindt, and W. E. Crill. "Dendritic Calcium Spikes in Layer 5 Pyramidal Neurons Amplify and Limit Transmission of Ligand-Gated Dendritic Current to Soma." Journal of Neurophysiology 86, no. 1 (2001): 514–27. http://dx.doi.org/10.1152/jn.2001.86.1.514.
Full textAbstract:
Long-lasting, dendritic, Ca2+-dependent action potentials (plateaus) were investigated in layer 5 pyramidal neurons from rat neocortical slices visualized by infrared-differential interference contrast microscopy to understand the role of dendritic Ca2+ spikes in the integration of synaptic input. Focal glutamate iontophoresis on visualized dendrites caused soma firing rate to increase linearly with iontophoretic current until dendritic Ca2+ responses caused a jump in firing rate. Increases in iontophoretic current caused no further increase in somatic firing rate. This limitation of firing rate resulted from the inability of increased glutamate to change evoked plateau amplitude. Similar nonlinear patterns of soma firing were evoked by focal iontophoresis on the distal apical, oblique, and basal dendrites, whereas iontophoresis on the soma and proximal apical dendrite only evoked a linear increase in firing rate as a function of iontophoretic current without plateaus. Plateau amplitude recorded in the soma decreased as the site of iontophoresis was moved farther from the soma, consistent with decremental propagation of the plateau to the soma. Currents arriving at the soma summed if plateaus were evoked on separate dendrites or if subthreshold responses were evoked from sites on the same dendrite. If plateaus were evoked at two sites on the same dendrite, only the proximal plateau was seen at the soma. Just-subthreshold depolarizations at two sites on the same dendrite could sum to evoke a plateau at the proximal site. We conclude that the plateaus prevent current from ligand-gated channels distal to the plateau-generating region from reaching the soma and directly influencing firing rate. The implications of plateau properties for synaptic integration are discussed.
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Golding, Nace L., William L. Kath, and Nelson Spruston. "Dichotomy of Action-Potential Backpropagation in CA1 Pyramidal Neuron Dendrites." Journal of Neurophysiology 86, no. 6 (2001): 2998–3010. http://dx.doi.org/10.1152/jn.2001.86.6.2998.
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In hippocampal CA1 pyramidal neurons, action potentials are typically initiated in the axon and backpropagate into the dendrites, shaping the integration of synaptic activity and influencing the induction of synaptic plasticity. Despite previous reports describing action-potential propagation in the proximal apical dendrites, the extent to which action potentials invade the distal dendrites of CA1 pyramidal neurons remains controversial. Using paired somatic and dendritic whole cell recordings, we find that in the dendrites proximal to 280 μm from the soma, single backpropagating action potentials exhibit <50% attenuation from their amplitude in the soma. However, in dendritic recordings distal to 300 μm from the soma, action potentials in most cells backpropagated either strongly (26–42% attenuation; n = 9/20) or weakly (71–87% attenuation; n = 10/20) with only one cell exhibiting an intermediate value (45% attenuation). In experiments combining dual somatic and dendritic whole cell recordings with calcium imaging, the amount of calcium influx triggered by backpropagating action potentials was correlated with the extent of action-potential invasion of the distal dendrites. Quantitative morphometric analyses revealed that the dichotomy in action-potential backpropagation occurred in the presence of only subtle differences in either the diameter of the primary apical dendrite or branching pattern. In addition, action-potential backpropagation was not dependent on a number of electrophysiological parameters (input resistance, resting potential, voltage sensitivity of dendritic spike amplitude). There was, however, a striking correlation of the shape of the action potential at the soma with its amplitude in the dendrite; larger, faster-rising, and narrower somatic action potentials exhibited more attenuation in the distal dendrites (300–410 μm from the soma). Simple compartmental models of CA1 pyramidal neurons revealed that a dichotomy in action-potential backpropagation could be generated in response to subtle manipulations of the distribution of either sodium or potassium channels in the dendrites. Backpropagation efficacy could also be influenced by local alterations in dendritic side branches, but these effects were highly sensitive to model parameters. Based on these findings, we hypothesize that the observed dichotomy in dendritic action-potential amplitude is conferred primarily by differences in the distribution, density, or modulatory state of voltage-gated channels along the somatodendritic axis.
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Chen, Ming, Yu Jiang, Wen Long Sun, Xiao Dong Hu, and Chun Li Liu. "Numerical Simulation of Binary Alloy Crystal Growth of Multiple Dendrites and Direcitonal Solidification Using Phase-Field Method." Advanced Materials Research 774-776 (September 2013): 703–6. http://dx.doi.org/10.4028/www.scientific.net/amr.774-776.703.
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Phase field method (PFM) offers the prospect of carrying out realistic numerical calculation on dendrite growth in metallic systems. The dendritic growth process of multiple dendrites and direcitonal solidification during isothermal solidifications in a Fe-0.5mole%C binary alloy were simulated using phase field model. Competitive growth of multiple equiaxed dendrites were simulated, and the effect of anisotropy on the solute segregation and microstructural dedritic growth pattern in directional solidification process was studied in the paper. The simulation results showed the impingement of arbitrarily oriented grains, and the grains began to impinge and coalesce the adjacent grains with time going on, which made the dendrite growth inhibited obviously. In the directional solidification, the maximum concentration gradient showed in the dendrite tip, and highest solute concentration existed at the bottom of the dendrites. With the increasing of the anisotropy, dendrite tip radius became smaller, and the crystal structure is more uniform and dense.
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Göbel, Werner, and Fritjof Helmchen. "New Angles on Neuronal Dendrites In Vivo." Journal of Neurophysiology 98, no. 6 (2007): 3770–79. http://dx.doi.org/10.1152/jn.00850.2007.
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Imaging technologies are well suited to study neuronal dendrites, which are key elements for synaptic integration in the CNS. Dendrites are, however, frequently oriented perpendicular to tissue surfaces, impeding in vivo imaging approaches. Here we introduce novel laser-scanning modes for two-photon microscopy that enable in vivo imaging of spatiotemporal activity patterns in dendrites. First, we developed a method to image planes arbitrarily oriented in 3D, which proved particularly beneficial for calcium imaging of parallel fibers and Purkinje cell dendrites in rat cerebellar cortex. Second, we applied free linescans—either through multiple dendrites or along a single vertically oriented dendrite—to reveal fast dendritic calcium dynamics in neocortical pyramidal neurons. Finally, we invented a ribbon-type 3D scanning method for imaging user-defined convoluted planes enabling simultaneous measurements of calcium signals along multiple apical dendrites. These novel scanning modes will facilitate optical probing of dendritic function in vivo.
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Ybarra, Natividad, Peter J. Hemond, Michael P. O'Boyle, and Kelly J. Suter. "Spatially Selective, Testosterone-Independent Remodeling of Dendrites in Gonadotropin-Releasing Hormone (GnRH) Neurons Prepubertally in Male Rats." Endocrinology 152, no. 5 (2011): 2011–19. http://dx.doi.org/10.1210/en.2010-0871.
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Adult GnRH neurons exhibit a stereotypic morphology with a small soma, single axon, and single dendrite arising from the soma with little branching. The adult morphology of GnRH neurons in mice reflects an anatomical consolidation of dendrites over postnatal development. We examined this issue in rat GnRH neurons with biocytin filling in live hypothalamic slices from infant males, as adult littermates and in gonad-intact males, castrated males, and in males with one of three levels of testosterone (T) treatment. Somatic area and total dendritic length were significantly greater in infant males than in adults. Moreover, total numbers of dendrite branches were greater in infant males as compared with adults. The number of higher order branches and the lengths of higher order branches were also greater in infant males than in adults. Most interestingly, in adults a single dendrite arose from the somata, consistently at 180° from the axon. In contrast, prepubertal animals had an average of 2.2 ± 0.2 primary dendrites arising from somata (range, one to seven primary dendrites). Angles relative to the axon at which dendrites in prepubertal males emanated from GnRH somata were highly variable. Castration at 25 d of age and castration at 25 d of age with one of three levels of T treatment did not influence morphological parameters when GnRH neurons were examined between 40 d and 48 d of age. Thus, a spatially selective remodeling of primary dendrites and consolidation of distal GnRH dendritic arbors occurs during postnatal development and is largely independent of T.
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Segal, M. "Fast imaging of [Ca]i reveals presence of voltage-gated calcium channels in dendritic spines of cultured hippocampal neurons." Journal of Neurophysiology 74, no. 1 (1995): 484–88. http://dx.doi.org/10.1152/jn.1995.74.1.484.
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1. Cultured hippocampal neurons were recorded with a patch pipette containing 100 microM of the calcium indicator Fluo-3, and one of their dendrites, carrying dendritic spines, was visualized with a x100, 1.3-numerical aperture oil objective. Calcium spikes evoked by depolarizing the somata and changes in free dendrite and spine calcium concentrations ([Ca]d and [Ca]s, respectively) were monitored with a cooled charge-coupled device (CCD) camera, acquiring images at a rate of 17-20 ms per frame. In the majority of spine-dendrite pairs, [Ca]s rose faster and to a higher level than the adjacent [Ca]d. Likewise, topical application of glutamate evoked a faster and larger change in [Ca]s than in [Ca]d. The rise of intracellular calcium concentration in response to a depolarizing current pulse, but not in response to glutamate, was reduced in the presence of the calcium antagonist verapamil in both dendrites and spines. It is suggested that dendritic spines possess voltage-gated calcium channels.
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Feng, Chengye, Pankajam Thyagarajan, Matthew Shorey, et al. "Patronin-mediated minus end growth is required for dendritic microtubule polarity." Journal of Cell Biology 218, no. 7 (2019): 2309–28. http://dx.doi.org/10.1083/jcb.201810155.
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Microtubule minus ends are thought to be stable in cells. Surprisingly, in Drosophila and zebrafish neurons, we observed persistent minus end growth, with runs lasting over 10 min. In Drosophila, extended minus end growth depended on Patronin, and Patronin reduction disrupted dendritic minus-end-out polarity. In fly dendrites, microtubule nucleation sites localize at dendrite branch points. Therefore, we hypothesized minus end growth might be particularly important beyond branch points. Distal dendrites have mixed polarity, and reduction of Patronin lowered the number of minus-end-out microtubules. More strikingly, extra Patronin made terminal dendrites almost completely minus-end-out, indicating low Patronin normally limits minus-end-out microtubules. To determine whether minus end growth populated new dendrites with microtubules, we analyzed dendrite development and regeneration. Minus ends extended into growing dendrites in the presence of Patronin. In sum, our data suggest that Patronin facilitates sustained microtubule minus end growth, which is critical for populating dendrites with minus-end-out microtubules.
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Zhao, Long Zhi, Xin Yan Jiang, Ming Juan Zhao, and Jian Zhang. "Phase-Field Simulation of Dendrite Growth of Magnesium Alloy under Non-Isothermal Solidification." Advanced Materials Research 848 (November 2013): 231–35. http://dx.doi.org/10.4028/www.scientific.net/amr.848.231.
Full textAbstract:
The phase-field model was built by coupling with the concentration field and temperature field,The dendrite growth process of Magnesium alloy was simulated under the different anisotropic strength and different undercooling.The results show that with the enlarge of anisotropic strength, dendritic morphology change from seaweed-like to snow-like, trunk grows along the optimal direction,and the secondary dendrite arm grow along the most optimize direction as well; With undercooling increasing, the more coarse primary dendrite arm, the more developed secondary dendrite arm, dendrites around the thermal diffusion layer becomes thinner,and dendrite tip’s thermal diffusion layer is thinner than the dendrite roots,but segregation phenomenon decreases slowly. When Δ=1.0, the grain will directly generate cellular dendrite and it does’t appear segregation phenomenon
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Meunier, Claude, and Boris Lamotte d'Incamps. "Extending Cable Theory to Heterogeneous Dendrites." Neural Computation 20, no. 7 (2008): 1732–75. http://dx.doi.org/10.1162/neco.2008.12-06-425.
Full textAbstract:
Dendrites may exhibit many types of electrical and morphological heterogeneities at the scale of a few micrometers. Models of neurons, even so-called detailed models, rarely consider such heterogeneities. Small-scale fluctuations in the membrane conductances and the diameter of dendrites are generally disregarded and spines merely incorporated into the dendritic shaft. Using the two-scales method known as homogenization, we establish explicit expressions for the small-scale fluctuations of the membrane voltage, and we derive the cable equation satisfied by the voltage when these fluctuations are averaged out. This allows us to rigorously establish under what conditions a heterogeneous dendrite can be approximated by a homogeneous cable. We consider different distributions of synapses, orderly or random, on a passive dendrite, and we investigate when replacing excitatory and inhibitory synaptic conductances by their local averages leads to a small error in the voltage. This indicates in which regimes the approximations made in compartmental models are justified. We extend these results to active membranes endowed with voltage-dependent conductances or NMDA receptors. Then we examine under which conditions a spiny dendrite behaves as a smooth dendrite. We discover a new regime where this holds true, namely, when the conductance of the spine neck is small compared to the conductance of the synapses impinging on the spine head. Spines can then be taken into account by an effective excitatory current, the capacitance of the dendrite remaining unchanged. In this regime, the synaptic current transmitted from a spine to the dendritic shaft is strongly attenuated by the weak coupling conductance, but the total current they deliver can be quite substantial. These results suggest that pedunculated spines and stubby spines might play complementary roles in synaptic integration. Finally, we analyze how varicosities affect voltage diffusion in dendrites and discuss their impact on the spatiotemporal integration of synaptic input.
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Hundekar, Prateek, Swastik Basu, Xiulin Fan, et al. "In situ healing of dendrites in a potassium metal battery." Proceedings of the National Academy of Sciences 117, no. 11 (2020): 5588–94. http://dx.doi.org/10.1073/pnas.1915470117.
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The use of potassium (K) metal anodes could result in high-performance K-ion batteries that offer a sustainable and low-cost alternative to lithium (Li)-ion technology. However, formation of dendrites on such K-metal surfaces is inevitable, which prevents their utilization. Here, we report that K dendrites can be healed in situ in a K-metal battery. The healing is triggered by current-controlled, self-heating at the electrolyte/dendrite interface, which causes migration of surface atoms away from the dendrite tips, thereby smoothening the dendritic surface. We discover that this process is strikingly more efficient for K as compared to Li metal. We show that the reason for this is the far greater mobility of surface atoms in K relative to Li metal, which enables dendrite healing to take place at an order-of-magnitude lower current density. We demonstrate that the K-metal anode can be coupled with a potassium cobalt oxide cathode to achieve dendrite healing in a practical full-cell device.
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Cazé, Romain D. "Any neuron can perform linearly non-separable computations." F1000Research 10 (July 6, 2021): 539. http://dx.doi.org/10.12688/f1000research.53961.1.
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Multiple studies have shown how dendrites enable some neurons to perform linearly non-separable computations. These works focus on cells with an extended dendritic arbor where voltage can vary independently, turning dendritic branches into local non-linear subunits. However, these studies leave a large fraction of the nervous system unexplored. Many neurons, e.g. granule cells, have modest dendritic trees and are electrically compact. It is impossible to decompose them into multiple independent subunits. Here, we upgraded the integrate and fire neuron to account for saturating dendrites. This artificial neuron has a unique membrane voltage and can be seen as a single layer. We present a class of linearly non-separable computations and how our neuron can perform them. We thus demonstrate that even a single layer neuron with dendrites has more computational capacity than without. Because any neuron has one or more layer, and all dendrites do saturate, we show that any dendrited neuron can implement linearly non-separable computations.
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Cazé, Romain D. "Any neuron can perform linearly non-separable computations." F1000Research 10 (September 16, 2021): 539. http://dx.doi.org/10.12688/f1000research.53961.2.
Full textAbstract:
Multiple studies have shown how dendrites enable some neurons to perform linearly non-separable computations. These works focus on cells with an extended dendritic arbor where voltage can vary independently, turning dendritic branches into local non-linear subunits. However, these studies leave a large fraction of the nervous system unexplored. Many neurons, e.g. granule cells, have modest dendritic trees and are electrically compact. It is impossible to decompose them into multiple independent subunits. Here, we upgraded the integrate and fire neuron to account for saturating dendrites. This artificial neuron has a unique membrane voltage and can be seen as a single layer. We present a class of linearly non-separable computations and how our neuron can perform them. We thus demonstrate that even a single layer neuron with dendrites has more computational capacity than without. Because any neuron has one or more layer, and all dendrites do saturate, we show that any dendrited neuron can implement linearly non-separable computations.
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Hamze, Kassem, Sabine Autret, Krzysztof Hinc, et al. "Single-cell analysis in situ in a Bacillus subtilis swarming community identifies distinct spatially separated subpopulations differentially expressing hag (flagellin), including specialized swarmers." Microbiology 157, no. 9 (2011): 2456–69. http://dx.doi.org/10.1099/mic.0.047159-0.
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The non-domesticated Bacillus subtilis strain 3610 displays, over a wide range of humidity, hyper-branched, dendritic, swarming-like migration on a minimal agar medium. At high (70 %) humidity, the laboratory strain 168 sfp + (producing surfactin) behaves very similarly, although this strain carries a frameshift mutation in swrA, which another group has shown under their conditions (which include low humidity) is essential for swarming. We reconcile these different results by demonstrating that, while swrA is essential for dendritic migration at low humidity (30–40 %), it is dispensable at high humidity. Dendritic migration (flagella- and surfactin-dependent) of strains 168 sfp + swrA and 3610 involves elongation of dendrites for several hours as a monolayer of cells in a thin fluid film. This enabled us to determine in situ the spatiotemporal pattern of expression of some key players in migration as dendrites develop, using gfp transcriptional fusions for hag (encoding flagellin), comA (regulation of surfactin synthesis) as well as eps (exopolysaccharide synthesis). Quantitative (single-cell) analysis of hag expression in situ revealed three spatially separated subpopulations or cell types: (i) networks of chains arising early in the mother colony (MC), expressing eps but not hag; (ii) largely immobile cells in dendrite stems expressing intermediate levels of hag; and (iii) a subpopulation of cells with several distinctive features, including very low comA expression but hyper-expression of hag (and flagella). These specialized cells emerge from the MC to spearhead the terminal 1 mm of dendrite tips as swirling and streaming packs, a major characteristic of swarming migration. We discuss a model for this swarming process, emphasizing the importance of population density and of the complementary roles of packs of swarmers driving dendrite extension, while non-mobile cells in the stems extend dendrites by multiplication.
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Gramatikov, Dimitar, and Svetomir Hadzi Jordanov. "Extraordinary regularities of zinc dendrites’ growth under appropriate electrolysis conditions." Journal of the Serbian Chemical Society, no. 00 (2022): 29. http://dx.doi.org/10.2298/jsc220122029g.
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A case study is given of dendritic growth during zinc electrolysis in conditions that promote it. Subject of the main interest was how the electrolysis parameters affect the duration of dendrites life. The selected set of parameters did provide a surprisingly regular dendrite?s life, i.e. period from start of the electrolysis until dendrites detachment from the cathode. Dendrite?s growth did proceed with lowering of the zinc current efficiency, and the end of life was manifested by intensive hydrogen evolution due to corrosion of detached zinc deposit in the acid electrolyte. Current efficiency was successfully followed by the bubble counting technique, invented especially for kinetic studies of gas including reactions. The acquired results on dendrites? life duration were so exact that it was easy to unify all five mono-variable dependencies into one five-variable expression. The calculated values of life duration did differ from the measured ones by only ?3%! This is a proof that the developed expression accurately presents the real nature of dendritic growth under the applied conditions, i.e. 0.5 to 2 M zinc (II) ions, 0.41 to 3.06 M H2SO4, 10 to 2500 mg dm-3 copper (II) ions, 0.14 to 14 g dm-3 hexamethylenetetramine, and 4.25 to 103 mA dm-2 current density. The eventual broader region of Zn dendrites? strict regular growth is not excluded.
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Ferrer, I. "Dementia of Frontal Lobe Type and Amyotrophy." Behavioural Neurology 5, no. 2 (1992): 87–96. http://dx.doi.org/10.1155/1992/535897.
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Dementia of frontal lobe type may precede motor signs in a number of adult patients with amyotrophy. Neuropathological studies have shown neuron loss, spongiosis and gliosis mainly in layers II and III of the frontal and temporal lobes, together with myelin pallor of the subcortical white matter. Golgi studies revealed loss of dendritic spines on the apical dendrite of layer III pyramidal neurons, decreased numbers of dendrites, amputation and tortuosities of dendrites, and distal and proximal dendritic swellings and enlargements. Calbindin D-28K immunocytochemistry revealed a marked decrease in the number of cortical immunoreactive neurons and loss of immunoreactivity in dendrites of the remaining cells. These features indicate that pyramidal and non-pyramidal neurons in layers II and III are severely damaged, and suggest that cortical processing is seriously impaired in patients with frontal lobe type dementia.
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Hallensleben, Philipp, Felicitas Scholz, Pascal Thome, et al. "On Crystal Mosaicity in Single Crystal Ni-Based Superalloys." Crystals 9, no. 3 (2019): 149. http://dx.doi.org/10.3390/cryst9030149.
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In the present work, we investigate the evolution of mosaicity during seeded Bridgman processing of technical Ni-based single crystal superalloys (SXs). For this purpose, we combine solidification experiments performed at different withdrawal rates between 45 and 720 mm/h with advanced optical microscopy and quantitative image analysis. The results obtained in the present work suggest that crystal mosaicity represents an inherent feature of SXs, which is related to elementary stochastic processes which govern dendritic solidification. In SXs, mosaicity is related to two factors: inherited mosaicity of the seed crystal and dendrite deformation. Individual SXs have unique mosaicity fingerprints. Most crystals differ in this respect, even when they were produced using identical processing conditions. Small differences in the orientation spread of the seed crystals and small stochastic orientation deviations continuously accumulate during dendritic solidification. Direct evidence for dendrite bending in a seeded Bridgman growth process is provided. It was observed that continuous or sudden bending affects the growth directions of dendrites. We provide evidence which shows that some dendrites continuously bend by 1.7° over a solidification distance of 25 mm.
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Wang, Wenli, Wenqiang Liu, Xin Yang, Rongrong Xu, and Qiuyun Dai. "Multi-scale simulation of the dendrite growth during selective laser melting of rare earth magnesium alloy." Modelling and Simulation in Materials Science and Engineering 30, no. 1 (2021): 015005. http://dx.doi.org/10.1088/1361-651x/ac3ca3.
Full textAbstract:
Abstract The solidification microstructure of the alloy fabricated by the selective-laser-melting (SLM) process can significantly impact its mechanical properties. In this study, a multi-scale model which couples the macroscale model for thermal-fluid and microscale cellular automata (CA) was proposed to simulate the complex solidification evolution and the dendrite growth (from planar to cellular to dendritic growth) during the SLM process. The solid–liquid interface of CA was dispersed with the bilinear interpolation method. On that basis, the curvature was accurately determined, and the calculation result was well verified by employing the Kurz–Giovanola–Trivedi analytical solution. The dendrite morphology, solute distribution, and primary dendrite arm spacing during the solidification of the SLM molten pool were quantitatively analyzed with the proposed model, well consistent with the experiment. The distribution of the undercooling field and the concentration field at the tip of dendrites different orientations were analyzed, and the two competing growth mechanisms of converging and diverging growth were revealed. Moreover, the research also indicates that during the growth of dendrites, the result of dendrite competition is determined by the height of the dendrite tip position in the direction of the thermal gradient, while the distribution of the concentration field (symmetrical or asymmetric) at the tip of the dendrite critically impacted the competing growth form of dendrites.
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Kelliher, Michael T., Yang Yue, Ashley Ng, et al. "Autoinhibition of kinesin-1 is essential to the dendrite-specific localization of Golgi outposts." Journal of Cell Biology 217, no. 7 (2018): 2531–47. http://dx.doi.org/10.1083/jcb.201708096.
Full textAbstract:
Neuronal polarity relies on the selective localization of cargo to axons or dendrites. The molecular motor kinesin-1 moves cargo into axons but is also active in dendrites. This raises the question of how kinesin-1 activity is regulated to maintain the compartment-specific localization of cargo. Our in vivo structure–function analysis of endogenous Drosophila melanogaster kinesin-1 reveals a novel role for autoinhibition in enabling the dendrite-specific localization of Golgi outposts. Mutations that disrupt kinesin-1 autoinhibition result in the axonal mislocalization of Golgi outposts. Autoinhibition also regulates kinesin-1 localization. Uninhibited kinesin-1 accumulates in axons and is depleted from dendrites, correlating with the change in outpost distribution and dendrite growth defects. Genetic interaction tests show that a balance of kinesin-1 inhibition and dynein activity is necessary to localize Golgi outposts to dendrites and keep them from entering axons. Our data indicate that kinesin-1 activity is precisely regulated by autoinhibition to achieve the selective localization of dendritic cargo.
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Wan, Weihao, Dongling Li, Haizhou Wang, et al. "Automatic Identification and Quantitative Characterization of Primary Dendrite Microstructure Based on Machine Learning." Crystals 11, no. 9 (2021): 1060. http://dx.doi.org/10.3390/cryst11091060.
Full textAbstract:
Dendrites are important microstructures in single-crystal superalloys. The distribution of dendrites is closely related to the heat treatment process and mechanical properties of single-crystal superalloys. The primary dendrite arm spacing (PDAS) is an important length scale to describe the distribution of dendrites. In this work, the second-generation single crystal superalloy HT901 with a diameter of 15 mm was imaged under a metallurgical microscope. An automatic dendrite core identification and full-field quantitative statistical analysis method is proposed to automatically detect the dendrite core and calculate the local PDAS. The Faster R-CNN algorithm combined with test time augmentation (TTA) technology is used to automatically identify the dendrite cores. The local multi-directional algorithm combined with Voronoi tessellation is used to determine the local nearest neighbor dendrite and calculate the local PDAS and coordination number. The accuracy of using Faster R-CNN combined with TTA to detect the dendrite core of HT901 reaches 98.4%, which is 15.9% higher than using Faster R-CNN alone. The algorithm calculates the local PDAS of all dendrites in H901 and captures the Gaussian distribution of the local PDAS. The average PDAS determined by the Gaussian distribution is 415 μm, which is only a small difference from the average spacing λ¯ (420 μm) calculated by the traditional method. The technology analyzes the relationship between the local PDAS and the distance from the center of the sample. The local PDAS near the center of HT901 are larger than those near the edge. The results suggests that the method enables the rapid, accurate and quantitative dendritic distribution characterization.
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Alizzi, Rebecca A., Derek Xu, Conrad M. Tenenbaum, Wei Wang, and Elizabeth R. Gavis. "The ELAV/Hu protein Found in neurons regulates cytoskeletal and ECM adhesion inputs for space-filling dendrite growth." PLOS Genetics 16, no. 12 (2020): e1009235. http://dx.doi.org/10.1371/journal.pgen.1009235.
Full textAbstract:
Dendritic arbor morphology influences how neurons receive and integrate extracellular signals. We show that the ELAV/Hu family RNA-binding protein Found in neurons (Fne) is required for space-filling dendrite growth to generate highly branched arbors of Drosophila larval class IV dendritic arborization neurons. Dendrites of fne mutant neurons are shorter and more dynamic than in wild-type, leading to decreased arbor coverage. These defects result from both a decrease in stable microtubules and loss of dendrite-substrate interactions within the arbor. Identification of transcripts encoding cytoskeletal regulators and cell-cell and cell-ECM interacting proteins as Fne targets using TRIBE further supports these results. Analysis of one target, encoding the cell adhesion protein Basigin, indicates that the cytoskeletal defects contributing to branch instability in fne mutant neurons are due in part to decreased Basigin expression. The ability of Fne to coordinately regulate the cytoskeleton and dendrite-substrate interactions in neurons may shed light on the behavior of cancer cells ectopically expressing ELAV/Hu proteins.
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He, Liu, Lotte van Beem, Berend Snel, Casper C. Hoogenraad, and Martin Harterink. "PTRN-1 (CAMSAP) and NOCA-2 (NINEIN) are required for microtubule polarity in Caenorhabditis elegans dendrites." PLOS Biology 20, no. 11 (2022): e3001855. http://dx.doi.org/10.1371/journal.pbio.3001855.
Full textAbstract:
The neuronal microtubule cytoskeleton is key to establish axon-dendrite polarity. Dendrites are characterized by the presence of minus-end out microtubules. However, the mechanisms that organize these microtubules with the correct orientation are still poorly understood. Using Caenorhabditis elegans as a model system for microtubule organization, we characterized the role of 2 microtubule minus-end related proteins in this process, the microtubule minus-end stabilizing protein calmodulin-regulated spectrin-associated protein (CAMSAP/PTRN-1), and the NINEIN homologue, NOCA-2 (noncentrosomal microtubule array). We found that CAMSAP and NINEIN function in parallel to mediate microtubule organization in dendrites. During dendrite outgrowth, RAB-11-positive vesicles localized to the dendrite tip to nucleate microtubules and function as a microtubule organizing center (MTOC). In the absence of either CAMSAP or NINEIN, we observed a low penetrance MTOC vesicles mislocalization to the cell body, and a nearly fully penetrant phenotype in double mutant animals. This suggests that both proteins are important for localizing the MTOC vesicles to the growing dendrite tip to organize microtubules minus-end out. Whereas NINEIN localizes to the MTOC vesicles where it is important for the recruitment of the microtubule nucleator γ-tubulin, CAMSAP localizes around the MTOC vesicles and is cotranslocated forward with the MTOC vesicles upon dendritic growth. Together, these results indicate that microtubule nucleation from the MTOC vesicles and microtubule stabilization are both important to localize the MTOC vesicles distally to organize dendritic microtubules minus-end out.
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Lindsay, K. A., J. M. Ogden, and J. R. Rosenberg. "Dendritic Subunits Determined by Dendritic Morphology." Neural Computation 13, no. 11 (2001): 2465–76. http://dx.doi.org/10.1162/089976601753195978.
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A theoretical framework is presented in which arbitrarily branched dendritic structures with nonhomogeneous membrane properties and nonuniform geometry can be transformed into an equivalent unbranched structure (equivalent cable). Rall's equivalent cylinder is seen to be one part of the equivalent cable in the special case of dendrites satisfying the Rall criteria. The relation between the branched dendrite and its equivalent unbranched representation is uniquely defined by an invertible mapping that connects configurations of inputs on the branched structure with those on the unbranched structure, and conversely. This mapping provides a new definition of dendritic subunit and provides a mechanism for characterizing local and nonlocal signal processing within dendritic structures.
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Schutter, Erik De. "Dendritic Voltage and Calcium-Gated Channels Amplify the Variability of Postsynaptic Responses in a Purkinje Cell Model." Journal of Neurophysiology 80, no. 2 (1998): 504–19. http://dx.doi.org/10.1152/jn.1998.80.2.504.
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De Schutter, Erik. Dendritic voltage and calcium-gated channels amplify the variability of postsynaptic responses in a Purkinje cell model. J. Neurophysiol. 80: 504–519, 1998. The dendrites of most neurons express several types of voltage and Ca2+-gated channels. These ionic channels can be activated by subthreshold synaptic input, but the functional role of such activations in vivo is unclear. The interaction between dendritic channels and synaptic background input as it occurs in vivo was studied in a realistic computer model of a cerebellar Purkinje cell. It previously was shown using this model that dendritic Ca2+ channels amplify the somatic response to synchronous excitatory inputs. In this study, it is shown that dendritic ion channels also increased the somatic membrane potential fluctuations generated by the background input. This amplification caused a highly variable somatic excitatory postsynaptic potential (EPSP) in response to a synchronous excitatory input. The variability scaled with the size of the response in the model with excitable dendrite, resulting in an almost constant coefficient of variation, whereas in a passive model the membrane potential fluctuations simply added onto the EPSP. Although the EPSP amplitude in the active dendrite model was quite variable for different patterns of background input, it was insensitive to changes in the timing of the synchronous input by a few milliseconds. This effect was explained by slow changes in dendritic excitability. This excitability was determined by how the background input affected the dendritic membrane potentials in the preceding 10–20 ms, causing changes in activation of voltage and Ca2+-gated channels. The most important model variables determining the excitability at the time of a synchronous input were the Ca2+-activation of K+ channels and the inhibitory synaptic conductance, although many other model variables could be influential for particular background patterns. Experimental evidence for the amplification of postsynaptic variability by active dendrites is discussed. The amplification of the variability of EPSPs has important functional consequences in general and for cerebellar Purkinje cells specifically. Subthreshold, background input has a much larger effect on the responses to coherent input of neurons with active dendrites compared with passive dendrites because it can change the effective threshold for firing. This gives neurons with dendritic calcium channels an increased information processing capacity and provides the Purkinje cell with a gating function.
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Nosov Yu. G., Krymov V. M., Vasiliev M.G., . Chikiryaka A.V., and Nikolaev V..i. "Formation of a dendrite structure in crystals NiFeGaCo alloy in the process of growing by the Stepanov method." Physics of the Solid State 64, no. 14 (2022): 2430. http://dx.doi.org/10.21883/pss.2022.14.54345.167.
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The process of growing crystals of the NiFeGaCo alloy by the Stepanov method has been developed. It was found that the structural perfection is disturbed by the formation of dendrites, which are distributed inhomogeneously both along the length and in the cross sections of the crystals. The blocking effect of the dendrites on growth crystals of the martensite phase, which appears when the samples are cooled to the temperature of the transition of the crystal to the martensite state, is found. The elemental composition of dendritic formations was studied and it was shown that the iron content in the dendrite is approximately 30% higher, and the gallium content is 40% lower than in the matrix. Based on the modeling of heat transfer processes in the real growth zone, taking into account the experiments performed, recommendations were obtained for suppressing the formation of dendrites Keywords: Dendritic structure, shape memory alloys, Stepanov's method.
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Cornejo, Victor Hugo, Netanel Ofer, and Rafael Yuste. "Voltage compartmentalization in dendritic spines in vivo." Science 375, no. 6576 (2022): 82–86. http://dx.doi.org/10.1126/science.abg0501.
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Dendritic spines’ electrical function? Dendritic spines are small protrusions that cover the dendrites of most neurons in the brain. Their electrical properties are still controversially discussed. Cornejo et al . used an array of techniques to investigate the degree of voltage attenuation by dendritic spine necks in pyramidal neurons of the mouse neocortex. Spines not only synchronously depolarized in response to backpropagating action potentials, but local and transient depolarization also occurred. Isolated depolarization in individual spines reflected localized synaptic activation. A significant voltage gradient between dendritic spine and dendrite indicated that spines may constitute elementary electric compartments. The spine neck resistance is thus not negligible and may substantially contribute to the regulation of synaptic efficacy in the central nervous system. —PRS
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Liu, Qiang, Xiang Jie Yang, and Zhi Ling Liu. "Phase-Field Simulation of Double Dendritic Growth in Solidification of Binary Alloy with Forced Convection." Advanced Materials Research 189-193 (February 2011): 1421–25. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.1421.
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A phase-field approach which incorporates mass and momentum and solute conservation equations for simulation of Al-Cu binary alloy solidification is studied. The effect of force convection on the double dendrite growth and solute profile during the solidification of binary alloy were investigated. The results indicate that dendritic grows unsymmetrically under a forced flow, the growth velocity of the upstream tip is faster than the downstream tip. The downstream tip of the first dendrite and the upstream tip of the second dendrite are influenced each other, the upstream tip of the second dendrite will Coarsen, and the concentration at the boundary between them is the highest. Moreover, the interaction between the two dendrites is more and more obvious with the increasing of the flow speed.
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Lu, Y., Je Hyun Lee, Y. H. Jang, S. S. Kim, Myung Hoon Oh, and Dang Moon Wee. "Mechanical Properties of Directionally Arrayed Dendrites in the Ni3Al Matrix Alloy." Advanced Materials Research 29-30 (November 2007): 71–74. http://dx.doi.org/10.4028/www.scientific.net/amr.29-30.71.
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Ni3Al shows the unique feature of increasing strength with increasing temperature. However, it is too brittle to use as a structural material due to grain boundary weakness. Ductility could be enhanced by controlling grains using directional solidification. In order to increase the ductility or strength of Ni3Al alloys, a ductile γ (Ni-rich) phase of dendrite fibers or a strong β (NiAl) phase of dendrite fibers were arrayed in the γ´ (Ni3Al) matrix by directional solidification. The dendrite spacing could be controlled by varying the solidification rates, and the volume fraction of the γ or β phase could be changed by using alloy compositions, from 23 to 27 at. % Al-Ni alloy. With increasing solidification rates, the dendrite spacing decreased, which caused the tensile strength to be enhanced and the elongation to decrease, evidently due to the phase boundary augmentation. With increasing Al content, the γ dendritic microstructure changed to β dendrites in the γ´ matrix, which resulted in a decrease in elongation as a result of an increase in the volume fraction of the brittle β dendrites in the γ´ matrix.
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Gao, Zihao, Changsheng Zhu, Meiling Qi, Canglong Wang, Yinlong Wang, and Borui Zhao. "Multi-phase field model simulation based on MPI+OpenMP parallel: Evolution of seaweed and dendritic structure in directional solidification." AIP Advances 12, no. 3 (2022): 035018. http://dx.doi.org/10.1063/5.0084012.
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A multi-phase model was established to imitate the growth of algal and dendritic grains during directional solidification. We studied the effects of temperature on the growth of bi-crystals and quantitatively analyzed the influence of anisotropic strength, thermal gradient, and pulling velocity on the evolution of bi-crystals. The results show that both weaker anisotropy strength and smaller pulling velocity can maintain the formation of seaweed tissue. The increase in the pulling velocity can degenerate the seaweed grains into dendrites and improve the growth rate of the dendrites, which make grain B produce more spindles, thereby accelerating the elimination of grain A. The thermal gradient is inversely proportional to the average initial spacing of dendrites. When the thermal gradient is too small, dendritic dendrites produce developed secondary dendrite arms, which, in turn, develop into tertiary dendrite arms to occupy the grain boundary, accelerating the elimination of seaweed grains. In addition, the multi-phase field model is solved by using central processing unit serial computation, single MPI (message passing interface) parallel programming method calculation, and MPI+OpenMP hybrid parallel programming structure, and the relevant factors affecting the efficiency of program operation are analyzed and tested. By comparing the computational efficiency of the three methods, it can be seen that the MPI+OpenMP hybrid parallel programming technology can make full use of computing resources in the case of large computing scale, further optimize the MPI parallel model, and obtain a higher acceleration ratio.
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Zhang, Pei, Feng Shan Du, Zhi Qiang Xu, and Ling Ling Zhao. "Numerical Simulation on the Dendritic Spacing and Microporosity in A356 Alloy Ingot." Materials Science Forum 575-578 (April 2008): 115–20. http://dx.doi.org/10.4028/www.scientific.net/msf.575-578.115.
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A stochastic mathematic model contained the effects of dendrite morphology, solidification shrinkage and dissolved gases was formed to simulate microporosity formation and growth. Microporosities appear in the interspaces of primary dendrites as well as secondary dendrites from microscopic view of A356 aluminum alloy experimental ingot with a metal mold. In the past literatures it took the volumetric fraction of microporosities as a function of the local density. In the present work a single pore size and distribution were predicted concerning the combination of shrinkage and dissolved gases and dendritic spacing. The dendritic spacing is a main parameter to decide the pore pattern. For shrinkage and dissolved gases causes, the favorable one is determined by dendritic spacing, also the local cool rate and tip growth rate. The dense degree of the experimental ingots in different casting conditions was discussed. The variations of dens degree from the measured values in different casting conditions are similar to that of porosity volume fraction from the predicted results.
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Lin, Chin-Hsien, Hsun Li, Yi-Nan Lee, Ying-Ju Cheng, Ruey-Meei Wu, and Cheng-Ting Chien. "Lrrk regulates the dynamic profile of dendritic Golgi outposts through the golgin Lava lamp." Journal of Cell Biology 210, no. 3 (2015): 471–83. http://dx.doi.org/10.1083/jcb.201411033.
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Constructing the dendritic arbor of neurons requires dynamic movements of Golgi outposts (GOPs), the prominent component in the dendritic secretory pathway. GOPs move toward dendritic ends (anterograde) or cell bodies (retrograde), whereas most of them remain stationary. Here, we show that Leucine-rich repeat kinase (Lrrk), the Drosophila melanogaster homologue of Parkinson’s disease–associated Lrrk2, regulates GOP dynamics in dendrites. Lrrk localized at stationary GOPs in dendrites and suppressed GOP movement. In Lrrk loss-of-function mutants, anterograde movement of GOPs was enhanced, whereas Lrrk overexpression increased the pool size of stationary GOPs. Lrrk interacted with the golgin Lava lamp and inhibited the interaction between Lva and dynein heavy chain, thus disrupting the recruitment of dynein to Golgi membranes. Whereas overexpression of kinase-dead Lrrk caused dominant-negative effects on GOP dynamics, overexpression of the human LRRK2 mutant G2019S with augmented kinase activity promoted retrograde movement. Our study reveals a pathogenic pathway for LRRK2 mutations causing dendrite degeneration.