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Littérature scientifique sur le sujet « Dendrites »

Auteur : Grafiati

Publié le 4 juin 2021

Mis à jour le 27 juillet 2024

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Articles de revues sur le sujet "Dendrites"

Larkum, M. E., M. G. Rioult et H. R. Luscher. « Propagation of action potentials in the dendrites of neurons from rat spinal cord slice cultures ». Journal of Neurophysiology 75, n^o 1 (1 janvier 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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Fujishima, Kazuto, Junko Kurisu, Midori Yamada et Mineko Kengaku. « βIII spectrin controls the planarity of Purkinje cell dendrites by modulating perpendicular axon-dendrite interactions ». Development 147, n^o 24 (24 novembre 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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Mitchell, Josephine W., Ipek Midillioglu, Ethan Schauer, Bei Wang, Chun Han et Jill Wildonger. « Coordination of Pickpocket ion channel delivery and dendrite growth in Drosophila sensory neurons ». PLOS Genetics 19, n^o 11 (9 novembre 2023) : e1011025. http://dx.doi.org/10.1371/journal.pgen.1011025.

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Sensory neurons enable an organism to perceive external stimuli, which is essential for survival. The sensory capacity of a neuron depends on the elaboration of its dendritic arbor and the localization of sensory ion channels to the dendritic membrane. However, it is not well understood when and how ion channels localize to growing sensory dendrites and whether their delivery is coordinated with growth of the dendritic arbor. We investigated the localization of the DEG/ENaC/ASIC ion channel Pickpocket (Ppk) in the peripheral sensory neurons of developing fruit flies. We used CRISPR-Cas9 genome engineering approaches to tag endogenous Ppk1 and visualize it live, including monitoring Ppk1 membrane localization via a novel secreted split-GFP approach. Fluorescently tagged endogenous Ppk1 localizes to dendrites, as previously reported, and, unexpectedly, to axons and axon terminals. In dendrites, Ppk1 is present throughout actively growing dendrite branches and is stably integrated into the neuronal cell membrane during the expansive growth of the arbor. Although Ppk channels are dispensable for dendrite growth, we found that an over-active channel mutant severely reduces dendrite growth, likely by acting at an internal membrane and not the dendritic membrane. Our data reveal that the molecular motor dynein and recycling endosome GTPase Rab11 are needed for the proper trafficking of Ppk1 to dendrites. Based on our data, we propose that Ppk channel transport is coordinated with dendrite morphogenesis, which ensures proper ion channel density and distribution in sensory dendrites.

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Christie, J. M., et G. L. Westbrook. « Regulation of Backpropagating Action Potentials in Mitral Cell Lateral Dendrites by A-Type Potassium Currents ». Journal of Neurophysiology 89, n^o 5 (1 mai 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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Göbel, Werner, et Fritjof Helmchen. « New Angles on Neuronal Dendrites In Vivo ». Journal of Neurophysiology 98, n^o 6 (décembre 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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Feng, Chengye, Pankajam Thyagarajan, Matthew Shorey, Dylan Y. Seebold, Alexis T. Weiner, Richard M. Albertson, Kavitha S. Rao, Alvaro Sagasti, Daniel J. Goetschius et Melissa M. Rolls. « Patronin-mediated minus end growth is required for dendritic microtubule polarity ». Journal of Cell Biology 218, n^o 7 (10 mai 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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Nithianandam, Vanitha, et Cheng-Ting Chien. « Actin blobs prefigure dendrite branching sites ». Journal of Cell Biology 217, n^o 10 (24 juillet 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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Schiller, Yitzhak. « Inter-Ictal- and Ictal-Like Epileptic Discharges in the Dendritic Tree of Neocortical Pyramidal Neurons ». Journal of Neurophysiology 88, n^o 6 (1 décembre 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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Sharp, D. J., W. Yu et P. W. Baas. « Transport of dendritic microtubules establishes their nonuniform polarity orientation. » Journal of Cell Biology 130, n^o 1 (1 juillet 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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Velte, Toby J., et Richard H. Masland. « Action Potentials in the Dendrites of Retinal Ganglion Cells ». Journal of Neurophysiology 81, n^o 3 (1 mars 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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Thèses sur le sujet "Dendrites"

Croydon, David Alexander. « Random fractal dendrites ». Thesis, University of Oxford, 2006. http://ora.ox.ac.uk/objects/uuid:4e17aebc-456d-4891-8527-692331ebff05.

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Dendrites are tree-like topological spaces, and in this thesis, the physical characteristics of various random fractal versions of this type of set are investigated. This work will contribute to the development of analysis on fractals, an area which has grown considerably over the last twenty years. First, a collection of random self-similar dendrites is constructed, and their Hausdorff dimension is calculated. Previous results determining this quantity for random self-similar structures have often relied on the scaling factors being bounded uniformly away from zero. However, using a percolative argument, and taking advantage of the tree-like structure of the sets considered here, it is shown that this condition is not necessary; a simple condition on the tail of the distribution of the scaling factors at zero is all that is assumed. The scaling factors of these recursively defined structures form what is known as a multiplicative cascade, and results about the height of this random object are also obtained. With important physical and probabilistic applications, the heat equation has justifiably received a substantial amount of attention in a variety of settings. For certain types of fractals, it has become clear that a key factor in estimating the heat kernel is the volume growth with respect to the resistance metric on the space. In particular, uniform polynomial volume growth, which occurs for many deterministic self-similar fractals, immediately implies uniform (on-diagonal) heat kernel behaviour. However, in the random fractal setting, this is frequently not the case, and volume fluctuations are often observed. Motivated by this, an analysis of how volume fluctuations lead to corresponding heat kernel fluctuations for measure-metric spaces equipped with a resistance form is conducted here. These results apply to the aforementioned random self-similar dendrites, amongst other examples. The continuum random tree (CRT) of Aldous is an important random example of a measure-metric space, and fits naturally into the framework of the previous paragraph. In this thesis, quenched (almost-sure) volume growth asymptotics for the CRT are deduced, which show that the behaviour in almost-every realisation is not uniform. Applying the results introduced above, these yield heat kernel bounds for the CRT, demonstrating that heat kernel fluctuations occur almost-surely. Finally, a new representation of the CRT as a random self-similar dendrite is presented.

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Svensson, Carl-Magnus. « Dynamics of spatially extended dendrites ». Thesis, University of Nottingham, 2009. http://eprints.nottingham.ac.uk/10788/.

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Dendrites are the most visually striking parts of neurons. Even so many neuron models are of point type and have no representation of space. In this thesis we will look at a range of neuronal models with the common property that we always include spatially extended dendrites. First we generalise Abbott’s “sum-over-trips” framework to include resonant currents. We also look at piece-wise linear (PWL) models and extend them to incorporate spatial structure in the form of dendrites. We look at the analytical construction of orbits for PWL models. By using both analytical and numerical Lyapunov exponent methods we explore phase space and in particular we look at mode-locked solutions. We will then construct the phase response curve (PRC) for a PWL system with compartmentally modelled dendrites. This sets us up so we can look at the effect of multiple PWL systems that are weakly coupled through gap junctions. We also attach a continuous dendrite to a PWL soma and investigate how the position of the gap junction influences network properties. After this we will present a short overview of neuronal plasticity with a special focus on the spatial effects. We also discuss attenuation of distal synaptic input and how this can be countered by dendritic democracy as this will become an integral part of our learning mechanisms. We will examine a number of different learning approaches including the tempotron and spike-time dependent plasticity. Here we will consider Poisson’s equation around a neural membrane. The membrane we focus on has Hodgkin-Huxley dynamics so we can study action potential propagation on the membrane. We present the Green’s function for the case of a one-dimensional membrane in a two-dimensional space. This will allow us to examine the action potential initiation and propagation in a multi-dimensional axon.

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Gudgel, Katherine Ann. « Growth of ammonium chloride dendrites ». Diss., The University of Arizona, 2001. http://hdl.handle.net/10150/289878.

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The ammonium chloride-water system has been used extensively as a transparent metal analog to model solidification in binary metal alloys. In this work, the growth rate and morphology of NH₄Cl dendrites grown from aqueous solutions were studied. Since an accurate knowledge of the materials parameters is essential to predicting the growth behavior, the equilibrium segregation coefficient was measured and a detailed analysis of the other NH₄Cl-H₂O materials properties cited in the literature was conducted. Isothermal experiments on bulk NH₄Cl-H₂O samples confirmed that the previously reported discontinuity in the growth rate as function of undercooling and associated transition from <100> oriented slowly growing dendrites to rapidly growing <111> dendrites are not artifacts of the sample geometry. Directional solidification experiments conducted to study the dendrite growth morphology revealed oscillations in both the growth rate and orientation. Results from these studies show that both the undercooling at which the <100> to <111> transition occurs and the peak velocity vary with composition. However, the observed shifts toward smaller apparent undercoolings and the narrowing of the oscillations at higher drive velocities result from changes in the local composition caused by the velocity and orientation dependencies of the partition coefficient. The oscillatory behavior of the <111> dendrites can be predicted using the residual <100> compositional field and the applied temperature gradient. By using an anisotropic segregation coefficient, the slow and fast growth rates can be separately modeled as a function of undercooling using the standard dendrite growth equations. While the transition to the <111> morphology can be attributed to the anisotropy in the k-value, several modifications need to be made to the existing dendritic growth models in order to describe the critical transition. Due to the complex relationships between the non-equilibrium segregation coefficient, composition, and growth rate, some of these modeling efforts have been left to future researchers. In addition to the inclusion of the overall anisotropy, our experiments indicate that the long-range compositional and thermal field effects must be incorporated into the dendrite growth models to explain the difference in growth rates of <111> Primary branches when <111> or <100> side-branches are present.

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Förstner, Friedrich. « The morphological identity of insect dendrites ». Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-129497.

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Jin, Xiaoming. « Dendritic development of GABAergic cortical interneurons revealed by biolistic transfection with GFP ». Morgantown, W. Va. : [West Virginia University Libraries], 2002. http://etd.wvu.edu/templates/showETD.cfm?recnum=2626.

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Thesis (Ph. D.)--West Virginia University, 2002.
Title from document title page. Document formatted into pages; contains vii, 218 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

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Nilson, James E. « Compartmental distribution of two cation chloride cotransporter types along starburst amacrine cell dendrites underlies the directional properties of these dendrites ». Thesis, Boston University, 2005. https://hdl.handle.net/2144/37167.

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Thesis (Ph.D.)--Boston University
PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you.
A fundamental aspect of vision is the ability to detect motion and to define its direction. In the retina, directionally selective ganglion cells respond to stimulus motion in a 'preferred' direction but respond little to stimulus motion in the opposite or 'null' direction. However despite nearly forty years of investigation, the precise cellular locus and underlying mechanisms of direction selective encoding have remained largely elusive. Recently, starburst amacrine cells, that are presynaptic to directionally selective ganglion cells, have been shown to provide direction specific inhibitory output to these ganglion cells. Therefore defining the biophysical properties specific to starburst amacrine cell dendrites will provide significant insight into the ability of visual systems to encode the direction of objects moving through an animal's visual field. Using a combination of intracellular filling of starburst amacrine cells and immunohistochemical localization of biophysically relevant molecules, we have examined how individual dendrites compute such motion. In order to define the relative degree and pattern of colocalization of these markers on filled dendrites we developed a new set of image acquisition and data analysis procedures that have allowed us to define the biophysical signature intrinsic to different portions of starburst amacrine cell dendrites. We have found that sodium-potassium-chloride cotransporter (NKCC2) and potassium-chloride cotransporter (KCC2) are expressed and differentially distributed on the proximal and distal dendritic compartments of starburst amacrine cells, respectively. The functional relevance of the anatomical distribution pattern of these cation-chloride-cotransporter types has been confirmed by others using physiological techniques. In summary, our studies provide a fundamental mechanism through which starburst amacrine cells define motion direction and transmit this information to directionally selective ganglions cells. In addition, our illumination of the basic concept of segregation of functional components to different dendritic compartments will likely prove to be an important theme of neuronal function throughout the nervous system.
2031-01-01

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Karam, Philippe Chucri. « Modeling passive and active mechanisms in motoneuron dendrites ». Thesis, Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/13713.

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George, Suma. « Simulink modeling and implementation of cmos dendrites using fpaa ». Thesis, Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44915.

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In this thesis, I have studied CMOS dendrites, implemented them on a reconfigurable analog platform and modeled them using MATLAB Simulink. The dendrite model was further used to build a computational model. I implemented a Hidden Markov Model (HMM) classifier to build a simple YES/NO wordspotter. I also discussed the inter-relation between neural systems, CMOS transistors and HMM networks. The physical principles behind the operation of silicon devices and biological structures are similar. Hence silicon devices can be used to emulate biological structures like dendrites. Dendrites are a branched, conductive medium which connect a neurons synapses to its soma. Dendrites were previously believed to be like wires in neural networks. However, recent research suggests that they have computational power. We can emulate dendrites using transistors in the Field Programmable Analog Array (FPAA). Our lab has built the Reconfigurable Analog Signal Processor (RASP) family of FPAAs which was used for the experiments. I analytically compared the mathematical model of dendrites to our model in silicon. The mathematical model based on the device physics of the silicon devices was then used to simulate dendrites in Simulink. An automated tool, sim2spice was then used to convert the Simulink model into a SPICE netlist, such that it can be implemented on a FPAA. This is an easier tool to use for DSP and Neuromorphic engineers who's primary areas of expertise isn't circuit design.

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Ou, Yimiao. « Molecular mechanisms controlling the arborization of dendrites in «Drosophila» ». Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=96940.

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The assembly and function of neural circuits depend on the patterned outgrowth, guidance and targeting of dendrites into appropriate territories during development. As a hallmark of any neuron, cell type-specific dendrite morphology has a crucial role in determining the sensory or synaptic input a neuron receives. Despite recent advances in exploring the molecular and cellular mechanisms that define dendritic architecture, our understanding of dendrite development is still far from complete. In this thesis research, I have taken a genetic screen approach and a candidate molecule approach to discover novel genes and mechanisms that are involved in dendrite morphogenesis, using Drosophila dendritic arborization (da) neurons as a model system. In three independent but related studies, my research led me to focus on 1) the nuclear receptor for the steroid hormone ecdysone (EcR), 2) the transcription factor Longitudinals Lacking (Lola) and 3) the cell surface recognition molecule Turtle (Tutl). I have found that these three different factors each regulate distinct aspects of dendritic arborization including dendrite branching, distribution and self-avoidance. Through their identification, expression patterns, and a characterization of their effects in loss-of-function and gain-of-function experiments, my findings provide novel insight into the regulatory networks that control dendrite morphogenesis.
L'élaboration et le fonctionnement harmonieux des circuits nerveux dépendent de la croissance des dendrites et de leur guidage et ciblage vers les territoires appropriés au cours du développement. La morphologie des dendrites sert de signe distinctif pour chaque neurone, et ainsi, joue un rôle crucial dans la détermination des différents influx (synaptiques ou sensoriels) que reçoit un neurone. Malgré de récentes avancées dans la compréhension des mécanismes moléculaires et cellulaires qui contrôlent l'architecture dendritique, notre connaissance du développement des dendrites reste encore incomplète. Mes travaux de recherche se sont attachés à découvrir de nouveaux gènes et mécanismes impliqués dans la morphogenèse dendritique. Dans ce but, j'ai choisi au cours de ma thèse deux méthodes d'étude: une approche par crible génétique et une approche par gènes candidats, que j'ai appliquées aux neurones appelés dendritic arborization (da) de la drosophile, mon modèle d'étude. Mes recherches m'ont permis de me concentrer sur trois molécules: 1) le récepteur nucléaire de l'hormone stéroïde ecdysone (EcR), 2) le facteur de transcription Longitudinals Lacking (Lola) et enfin, 3) la molécule de surface Turtle (Tutl). J'ai pu montrer que chacun de ces facteurs est implique dans des aspects distincts du processus de morphogenèse dendritique incluant le branchement, la distribution et l'auto-répulsion dendritiques. L'identification de ces molécules, la description de leurs patrons d'expression et la caractérisation des phénotypes associés à leurs pertes ou gains de fonctions, m'ont permis d'apporter de nouvelles connaissances des réseaux de régulation contrôlant la morphogenèse dendritique.

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Coutts, Emma Jayne. « The effect of noise in models of spiny dendrites ». Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2352.

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The dendritic tree provides the surface area for synaptic connections between the 100 billion neurons in the brain. 90% of excitatory synapses are made onto dendritic spines which are constantly changing shape and strength. This adaptation is believed to be an important factor in learning, memory and computations within the dendritic tree. The environment in which the neuron sits is inherently noisy due to the activity in nearby neurons and the stochastic nature of synaptic gating. Therefore the effects of noise is a very important aspect in any realistic model. This work provides a comprehensive study of two spiny dendrite models driven by different forms of noise in the spine dynamics or in the membrane voltage. We investigate the effect of the noise on signal propagation along the dendrite and how any correlation in the noise may affect this behaviour. We discover a difference in the results of the two models which suggests that the form of spine connectivity is important. We also show that both models have the capacity to act as a robust filter and that a branched structure can perform logic computations.

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Livres sur le sujet "Dendrites"

Greg, Stuart, Spruston Nelson et Häusser Michael, dir. Dendrites. 2^e éd. Oxford : Oxford University Press, 2007.

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Emoto, Kazuo, Rachel Wong, Eric Huang et Casper Hoogenraad, dir. Dendrites. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0.

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Greg, Stuart, Spruston Nelson et Häusser Michael, dir. Dendrites. Oxford : Oxford University Press, 1999.

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Dendritic spines. Cambridge, MA : MIT Press, 2009.

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A, Zhuravlëv V., dir. Physics of dendrites : Computational experiments. Singapore : World Scientific, 1994.

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Kupferman, Justine. Targeting Ion Channels to Distal Dendrites. [New York, N.Y.?] : [publisher not identified], 2013.

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R, Baylog Louis, dir. Dendritic spines biochemistry, modeling and properties. Hauppauge NY : Nova Science Publishers, 2009.

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Center, Langley Research, dir. Analytic theory for the selection of 2-D needle crystal at arbitrary Peclet number. Hampton, Va : National Aeronautics and Space Administration, Langley Research Center, 1989.

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Nova Scotian Institute of Science., dir. Dendrites and batrachians and reptiles of Nova Scotia. [Halifax, N.S : Nova Scotian Institute of Science, 1994.

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A, Hellawell, et United States. National Aeronautics and Space Administration., dir. Communications : Mechanical deformation of dendrites by fluid flow. [Washington, DC : National Aeronautics and Space Administration, 1996.

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Chapitres de livres sur le sujet "Dendrites"

Emoto, Kazuo, Rachel Wong, Eric Huang et Casper Hoogenraad. « Introduction ». Dans Dendrites, 3–6. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_1.

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Fuerst, Peter G. « Mosaics and Lamination in the Retina ». Dans Dendrites, 213–44. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_10.

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Wang, Yuan, et Edwin W. Rubel. « Modifying Dendritic Structure After Function ». Dans Dendrites, 245–70. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_11.

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Togashi, Kazuya, Hiroyuki Koizumi, Takahiro Kanamori et Kazuo Emoto. « Molecular Control of Dendritic Remodeling ». Dans Dendrites, 273–94. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_12.

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Cline, Hollis T. « Experience-Dependent Dendritic Arbor Development ». Dans Dendrites, 295–315. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_13.

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Katrancha, Sara Marie, et Anthony J. Koleske. « Dendrite Maintenance ». Dans Dendrites, 317–55. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_14.

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Iwasaki, Hirohide, Shinji Tanaka et Shigeo Okabe. « Molecular Assembly of Excitatory Synapses ». Dans Dendrites, 359–85. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_15.

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Bikbaev, Arthur, Maël Duménieu, Jeffrey Lopez-Rojas et Martin Heine. « Localising Receptors and Channels Across the Dendritic Arbour ». Dans Dendrites, 387–424. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_16.

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Chipman, Peter, et Yukiko Goda. « Adhesion Molecules in Synapse Assembly and Function ». Dans Dendrites, 425–65. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_17.

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Villa, Katherine L., et Elly Nedivi. « Excitatory and Inhibitory Synaptic Placement and Functional Implications ». Dans Dendrites, 467–87. Tokyo : Springer Japan, 2016. http://dx.doi.org/10.1007/978-4-431-56050-0_18.

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Actes de conférences sur le sujet "Dendrites"

Singh, P., V. Cozzolino, G. Galyon, R. Logan, K. Troccia, J. L. Hurd et P. Tsai. « Dendritic Growth Failure of a Mesa Diode ». Dans ISTFA 1997. ASM International, 1997. http://dx.doi.org/10.31399/asm.cp.istfa1997p0179.

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Abstract The time delayed failure of a mesa diode is explained on the basis of dendritic growth on the oxide passivated diode side walls. Lead dendrites nucleated at the p+ side Pb-Sn solder metallization and grew towards the n side metallization. The infinitesimal cross section area of the dendrites was not sufficient to allow them to directly affect the electrical behavior of the high voltage power diodes. However, the electric fields associated with the dendrites caused sharp band bending near the silicon-oxide interface leading to electron tunneling across the band gap at velocities high enough to cause impact ionization and ultimately the avalanche breakdown of the diode. Damage was confined to a narrow path on the diode side wall because of the limited influence of the electric field associated with the dendrite. The paper presents experimental details that led to the discovery of the dendrites. The observed failures are explained in the context of classical semiconductor physics and electrochemistry.

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« Dendrites Abstracts ». Dans 4th NAMASEN Training Workshop on Dendrites. Frontiers Media SA, 2014. http://dx.doi.org/10.3389/978-2-88919-341-7.

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Yoon, Ikroh, et Seungwon Shin. « Numerical Simulation of Multiple Seeds Interaction During Three-Dimensional Dendritic Solidification With Fluid Flow ». Dans ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18129.

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Most material of engineering interest undergoes solidification process from liquid to solid state which governs the microstructure of materials. Identifying the growth characteristic of the microstructure during the solidification process is essential to determine the physical properties of final product. Numerical simulation can provide valuable information during solidification process since heat and mass transfer associated with micro-structural growth of dendrite is in greatly small scale which is almost impossible to obtain by experiments. In real situations, dendrite tends to grow from multiple seeds as well as with external fluid flow. Growth characteristics of the dendrites will be greatly influenced by both external fluid convection and interaction between dendrites. In this paper, three-dimensional numerical simulation of multiple dendritic growth during solidification process with melt fluid convection is presented. The high-order Level Contour Reconstruction Method (LCRM), a hybrid form of Front-Tracking and Level-Set, is used to track the moving liquid-solid interface explicitly and sharp interface technique has been used to implement correct phase changing boundary conditions on the moving interface. To get the indicator function and the interface curvature more efficiently and accurately for three-dimensional simulation, we have generated the distance function directly from the interface. The method is validated by comparing with other numerical technique and showed good agreements. Three-dimensional results showed clear difference compared to two-dimensional simulation on growth behavior, especially with multiple seeds.

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Sekulic, Dusan P. « A Heuristic Thermodynamic Interpretation of a Mechanism Responsible for the Selection of Solidification Microstructures ». Dans ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39521.

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This paper offers a heuristic thermodynamic analysis of the selection of solidification microstructures formed during re-solidification of micro layers of molten metal driven by surface tension. This study explores empirical evidence obtained by performing a tightly controlled heating-dwell-cooling materials processing cycle that causes melting followed by re-solidification of micro layers of an Al + Si alloy in ultra high purity nitrogen. Identification of characteristic process parameters responsible for crystal pattern formation of the α-phase solid solution during associated rapid quench is discussed. The focus of the inquiry is ultimately directed toward solid solution dendrites population morphology. A transition from a scarce (even single or non existent) dendrite formation toward chaotically distributed α-phase dendrites imbedded in two-phase eutectic is identified. A heuristic approach has been established to interpret alpha phase dendrite pattern formation during solidification phenomena driven by entropy generation at the liquid-solid interfaces.

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Diepers, Hermann-J., Janin Eiken et Ingo Steinbach. « Is There a Difference Between Dendrites of a Binary or a Ternary Alloy ? Some Answers by Phase-Field Simulations ». Dans ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-32844.

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Dendritic growth is best understood for pure substances growing into a uniformly supercooled environment. Under certain assumptions the standard growth theory can be applied to the directional growth of dendrites in a binary alloy. To apply the theory to technical multicomponent alloys so called ‘binary equivalent’ or ‘pseudo-binary’ models have been proposed. The basic question of ‘Is there a difference between dendrites of a binary or ternary alloy?’ has only partially been answered. A phase-field model applied to a ternary Fe-C alloy with a third fictive component will be used in this paper to compare ternary and binary equivalent phase-field simulations focussing on different component diffusivities. Results for directional dendritic solidification indicate negligible and relevant differences with respect to micro-segregation and micro-structure.

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Rózsa, Balázs, Zoltán Szadai, Linda Judák, Balázs Chiovini, Gábor Juhász, Katalin Ócsai, Dénes Pálfi et al. « Imaging of dendrites and sparse interneuronal networks with 3D random access microscopy ». Dans Optics and the Brain. Washington, D.C. : Optica Publishing Group, 2023. http://dx.doi.org/10.1364/brain.2023.bw3b.6.

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Acousto-optical microscopy is a powerful tool to study spare networks and extensive dendritic arborization from the cortex of behaving animals. We used this novel approach for imaging dendrites and somata of sparse interneuron populations in a combination with auditory discrimination and detection tasks. Our results shed light of not yet known subcellular and network mechanisms from multiple brain regions.

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Jiang, Qian, Abhishek Deshpande et Abhijit Dasgupta. « Is the Heterogeneous Microstructure of SnAgCu (SAC) Solders Going to Pose a Challenge for Heterogeneous Integration ? » Dans ASME 2017 International Technical Conference and Exhibition on Packaging and Integration of Electronic and Photonic Microsystems collocated with the ASME 2017 Conference on Information Storage and Processing Systems. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/ipack2017-74133.

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The coarse heterogeneous microstructure of SAC alloys makes the behavior of interconnections highly sensitive to its geometric length-scale. Heterogeneous integration and the resulting increase in package complexity and miniaturization are making this scale-effect ever more important. This scale effect derives from the anisotropy of tin and the coarse multi-tiered microstructural heterogeneities in SAC solders. As a result, no two joints behave the same and every joint is unique depending on its specific microstructure. Product teams responsible for reliable heterogeneous integration have to ensure that they have adequate methods to deal with this variability. This paper highlights the multi-tiered microstructural morphology in SAC solders due to the solidification and crystallization process. At the highest tier in the joint microstructure are individual (highly anisotropic) grains that can be 100s of microns in size. At the next lower tier the primary heterogeneity is due to individual dendrites of pro-eutectic β tin, that can have lobes as large as 10–20 microns. At the next lower tier the characteristic heterogeneity is a eutectic mix of nanoscale Ag3Sn IMC particles dispersed in a Sn matrix. Researchers have long recognized that the grain morphology is extremely important to mechanical behavior of BGA solder joints because they are coarse-grained (i.e. there may be only a few anisotropic grains in each BGA solder joint). However, heterogeneous integration has now led to joints that are much smaller (less than 100 microns tall), thus making them of the same length-scale as individual tin dendrites within each grain. In other words, there may be just a few dendrites through the thickness of the joint. Unfortunately, very little attention has focused on SAC behavior at such a small length-scale. This study focuses on the effect of the tin-dendrite morphology on the effective behavior of SAC solder joints, using a combination of experiments and multi-tiered anisotropic models that combine dislocation nano-mechanics with composite micromechanics. The volume fraction of β-Sn dendrite within one crystal could vary from 20% to 80%, depending on the time and temperature above the liquidus temperature and the cooling rates. The effects of volume fraction and aspect ratio of Sn dendrites on the anisotropic steady-state creep rate of single crystal SAC specimen are examined. The objective of the study is to provide insights into the role that solder microstructural heterogeneity will play on package reliability in heterogeneous integration.

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Hutchinson, Zachary. « Artificial Dendrites : an Algorithm ». Dans 2020 IEEE Second International Conference on Cognitive Machine Intelligence (CogMI). IEEE, 2020. http://dx.doi.org/10.1109/cogmi50398.2020.00033.

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Guo, Taiming, Hongmin Li et G. X. Wang. « Development of Irregular Interface Morphology During Unidirectional Solidification of Succinonitrile ». Dans ASME 2003 Heat Transfer Summer Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/ht2003-47215.

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This paper reports an experimental investigation on irregular interface morphology patterns developed in thin-film unidirectional solidification of pure succinonitrile. Solidification experiments have been conducted under various temperature gradients and interface velocities. Several irregular patterns have been observed including titled dendrites, degenerate dendrites, and seaweed. It is found that as the temperature gradient increases, steady titled dendrites may evolve into degenerate dendrites and eventually to seaweed. With the same grain orientation, the irregular patterns may transform from one form to another as the growth condition changes. Observations demonstrate that normal dendrites exhibit a higher growth rate than seaweed pattern and would overgrow them. Irregular pattern may also become strongly dynamic and different patterns may evolve into each other during growth within the same experiment. These results should shed a light into the understanding of the interface morphology development during solidification.

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Plagge, Mark, Suma George Cardwell et Frances S. Chance. « Expressive Dendrites in Spiking Networks ». Dans 2024 Neuro Inspired Computational Elements Conference (NICE). IEEE, 2024. http://dx.doi.org/10.1109/nice61972.2024.10548485.

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Rapports d'organisations sur le sujet "Dendrites"

Wheeler, A. A., B. T. Murray et R. J. Schaefer. Computation of dendrites using a phase field model. Gaithersburg, MD : National Institute of Standards and Technology, 1992. http://dx.doi.org/10.6028/nist.ir.4894.

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Goodman, K. Copper Dendrites and Surface Engineering for Enhanced CO2 Reduction Research Report Paper. Office of Scientific and Technical Information (OSTI), mai 2021. http://dx.doi.org/10.2172/1784613.

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Uppuluri, Srinivas, Petar R. Dvornic, June W. Klimash, Peter I. Carver et Nora C. Tan. The Properties of Dendritic Polymers I : Generation 5 Poly(amidoamine) Dendrimers. Fort Belvoir, VA : Defense Technical Information Center, mai 1998. http://dx.doi.org/10.21236/ada346880.

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Allen, Jeffrey, Robert Moser, Zackery McClelland, Md Mohaiminul Islam et Ling Liu. Phase-field modeling of nonequilibrium solidification processes in additive manufacturing. Engineer Research and Development Center (U.S.), décembre 2021. http://dx.doi.org/10.21079/11681/42605.

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This project models dendrite growth during nonequilibrium solidification of binary alloys using the phase-field method (PFM). Understanding the dendrite formation processes is important because the microstructural features directly influence mechanical properties of the produced parts. An improved understanding of dendrite formation may inform design protocols to achieve optimized process parameters for controlled microstructures and enhanced properties of materials. To this end, this work implements a phase-field model to simulate directional solidification of binary alloys. For applications involving strong nonequilibrium effects, a modified antitrapping current model is incorporated to help eject solute into the liquid phase based on experimentally calibrated, velocity-dependent partitioning coefficient. Investigated allow systems include SCN, Si-As, and Ni-Nb. The SCN alloy is chosen to verify the computational method, and the other two are selected for a parametric study due to their different diffusion properties. The modified antitrapping current model is compared with the classical model in terms of predicted dendrite profiles, tip undercooling, and tip velocity. Solidification parameters—the cooling rate and the strength of anisotropy—are studied to reveal their influences on dendrite growth. Computational results demonstrate effectiveness of the PFM and the modified antitrapping current model in simulating rapid solidification with strong nonequilibrium at the interface.

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Uppuluri, Srinivas, Petar R. Dvornic, Nora C. Beck Tan et Gary Hagnauer. The Properties of Dendritic Polymers 2 : Generation Dependence of the Physical Properties of Poly(amidoamine) Dendrimers. Fort Belvoir, VA : Defense Technical Information Center, janvier 1999. http://dx.doi.org/10.21236/ada359423.

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Kenamond, Mark. Dendritic Paving Ideas. Office of Scientific and Technical Information (OSTI), décembre 2014. http://dx.doi.org/10.2172/1165179.

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Moore, Jeffrey S. Dendritic Materials Systems. Fort Belvoir, VA : Defense Technical Information Center, septembre 2003. http://dx.doi.org/10.21236/ada422098.

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Kenamond, Mark. (U) Dendritic Zoner Idea. Office of Scientific and Technical Information (OSTI), mai 2014. http://dx.doi.org/10.2172/1132544.

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Kumta, Prashant, Moni Datta et Oleg Velikokhatnyi. Engineering Approaches to Dendrite free Lithium Anodes. Office of Scientific and Technical Information (OSTI), mars 2021. http://dx.doi.org/10.2172/1772243.

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Kukowska Latallo, J. F., A. U. Bielinska, C. Chen, M. Rymaszewski et D. A. Tomalia. Gene Transfer Using StarburstTM Dendrimers. Fort Belvoir, VA : Defense Technical Information Center, janvier 1998. http://dx.doi.org/10.21236/ada406313.

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