Dendritic Size Research Articles

Enhanced tribological performance of laser directed energy deposited Inconel 625 achieved through laser surface remelting

Inconel 625 (IN625) is an essential material for the manufacture of turbine blades and seals, aircraft ducting systems, engine components, and pressure valves. Laser Directed Energy Deposition (LDED) process has shown the potential to fabricate IN625 parts with superior mechanical properties and higher corrosion resistance when compared to those fabricated using conventional manufacturing techniques. However, the poor surface quality limits the practical application of LDED fabricated parts, especially in sectors that demand high tribological performance. To this end, this study focuses on improving the surface quality and tribological performance of LDED fabricated IN625 components using Laser Surface Remelting (LSR) as a postprocessing operation. The tribological performance was evaluated using a linear reciprocating ball-on-flat wear test setup. The surface roughness, remelting depth (RD), microstructure, hardness, and tribological performance (coefficient of friction and wear rate) of the remelted (RM) samples were compared with that of as-deposited (AD) samples. Microstructural characterization revealed that LSR resulted in grain refinement, reduced dendrite size, and primary dendritic arm spacing (PDAS). Laser scanning speed effects RD, dendrite size and PDAS via its effect on cooling rates. SEM + EDS analysis confirmed the presence of Laves phase in both AD and RM samples. XRD analysis of RM samples showed an increase in the amount of Laves phase. The refinement in microstructural features and the increased amount of Laves phase among the RM samples led to improvement in microhardness when compared to AD samples. Wear test results revealed a reduction in the coefficient of friction (COF) and wear rate after LSR with wear mechanism being either abrasive or delamination. Reduction in the size of dendrites and refinement in grain size are attributed to the enhanced tribological performance after LSR.

Effect of Welding Current on Mechanical Properties and Microstructure of Aluminium AA1135 Alloys by Gas Tungsten Arc Welding (GTAW)

Aluminium alloys have a wide range of applications in the defence and aerospace industry, including for the manufacture of fuel tanks. The welding Current and type of filler metal significantly affect the microstructure formed and the mechanical strength of metal joints. This study aimed to determine the effect of the kind of filler metal (ER5356 filler metal) and welding current (140 amperes, 160 amperes, and 180 amperes) on the mechanical properties and microstructural of aluminium alloys AA1135 by the GTAW welding process. The results showed that the dendrite size increased with increasing welding current. Furthermore, the micro-hardness of the weld metal shows a decreasing trend with increasing welding current. The maximum tensile strength was obtained at a current power of 160 amperes, and all specimens failed at HAZ. The fracture surface of tensile test observations using SEM showed brittle fracture for Er5356 filler metal specimens, while on the fracture surface of the base metal tensile test specimens, it was observed to show ductile fracture. Welding with a current strength of 180 amperes has met the standard acceptance criteria because no cracks were found on the face bend or the root bend specimen

Boron-induced microstructure evolution and mechanical properties of in situ Ti-based bulk metallic glass composites

The effect of boron(B) on the glass-forming ability (GFA), microstructure evolution and mechanical properties of (Ti48Zr20Nb12Cu5Be15)100-xBx bulk metallic glass composites (x = 0, 0.3, 0.5, 1.0 and 3.0 at. %) alloys was investigated. With increasing boron content to 0.3 at.%, the dendrite size is refiner than that of the other alloys, the B0.3 alloy presents good ductility and high strength at ambient temperature, which is mainly attributed to the strong interaction between dislocations, shear bands and the dendrite/glass interface. When the boron content is lower or higher than the critical value of 0.3 %, multiple slide steps decrease. Once the B content exceeds its maximum solid solubility, the phase instability of β-Ti dendrites and the glass matrix decreases, and more needle-like TiB2 phases and irregular block-like ZrB2 phases within and between the dendrites suppress the initiation of shear bands, resulting in brittle fracture.

Acoustic streaming and cavitation effect on microstructure evolution of Nb-Si-Ti alloy treated by ultrasound

Heat and mass transfer play a critical role in grain refinement by ultrasound treatment. In order to reveal the mechanism of ultrasonic in Nb-Si molten metal, a 3-D model was simulated on the acoustic, temperature and flow fields with different acoustic frequencies and displacement amplitudes by Comsol Multiphysics. Simulation results show that a new harmonic wave appears with frequency increasing, and the acoustic streaming effect is significant at 20 kHz. As the displacement amplitude increases from 10 μm to 20 μm, the maximum velocity varies from 0.01 m/s to 0.03 m/s. The distributions of three fields are dependent on frequency, and the displacement amplitude determines acoustic pressure value and fluid velocity. The displacement amplitude has a positive effect on the acoustic streaming effect improvement in the melt. In the UST ingots with different displacement amplitudes, the size of the broken dendrites decreases from 57.5 μm to 10 μm with the displacement amplitude lower than 16 μm, by 82.6%. γ-Nb5Si3 phase increases and the primary Nbss phases are elongated, coarsened and spheroidized with the increase of the displacement amplitudes. The simulation results of the flow directions can be verified by the elongated Nbss phase. The acoustic streaming effect promotes heat and mass transfer and the sluggish eutectoid reaction in Nb-Si-Ti alloy during the ultrasound treatment.

Elucidating the promoting mechanism of nitrogen in the columnar-to-equiaxed transition of steel ingot

Based on the behavior of heat and mass transfer ahead of the advancing columnar front, combined with the nucleation and growth of dendrites, as well as the blocking mechanism of columnar-to-equiaxed transition (CET), the promoting mechanism of nitrogen in the CET of steel ingot was elucidated. It was found that the CET moves from the center to the edge of the ingot as the nitrogen content increases, resulting in a decrease in the columnar dendrite zone and an increase in the equiaxed dendrite zone. The occurrence of this phenomenon can be attributed to two factors. On the one hand, an increase in nitrogen content leads to an increase in critical nucleation supercooling and incubation time of dendrites, causing a decrease in the number of dendrites nucleation. Additionally, the higher nitrogen content reduces the restriction effect of solute on the growth of columnar dendrites, leading to an increase in dendrite size. On the other hand, within the constitutional supercooling (CS) zone ahead of the advancing columnar front, both the CS and temperature gradient decrease with increasing nitrogen content, while the CS increases and the temperature gradient decreases with the distance from the advancing columnar front. Consequently, the nitrogen solute primarily influences the nucleation and growth of columnar and equiaxed dendrites, as well as the length, temperature gradient, and growth restriction factor Qc of the CS zone, resulting in changes in the heat and mass transfer behavior ahead of the advancing columnar front, thereby promoting CET.

Ischemia-reperfusion myocardial infarction induces remodeling of left cardiac-projecting stellate ganglia neurons.

Neurons in the stellate ganglion (SG) provide sympathetic innervation to the heart, brown adipose tissue (BAT), and other organs. Sympathetic innervation to the heart becomes hyperactive following myocardial infarction (MI). The impact of MI on the morphology of cardiac sympathetic neurons is not known, but we hypothesized that MI would stimulate increased cell and dendritic tree size in cardiac neurons. In this study, we examined the effects of ischemia-reperfusion MI on sympathetic neurons using dual retrograde tracing methods to allow detailed characterization of cardiac- and BAT-projecting neurons. Different fluorescently conjugated cholera toxin subunit B (CTb) tracers were injected into the pericardium and the interscapular BAT pads, respectively. Experimental animals received a 45-min occlusion of the left anterior descending coronary artery and controls received sham surgery. One week later, hearts were collected for assessment of MI infarct and SGs were collected for morphological or electrophysiological analysis. Cardiac-projecting SG neurons from MI mice had smaller cell bodies and shorter dendritic trees compared with sham animals, specifically on the left side ipsilateral to the MI. BAT-projecting neurons were not altered by MI, demonstrating the subpopulation specificity of the response. The normal size and distribution differences between BAT- and cardiac-projecting stellate ganglion neurons were not altered by MI. Patch-clamp recordings from cardiac-projecting left SG neurons revealed increased spontaneous excitatory postsynaptic currents despite the decrease in cell and dendritic tree size. Thus, increased dendritic tree size does not contribute to the enhanced sympathetic neural activity seen after MI.NEW & NOTEWORTHY Myocardial infarction (MI) causes structural and functional changes specifically in stellate ganglion neurons that project to the heart, but not in cells that project to brown adipose fat tissue.

Processing of Bimetallic Inconel 625-16Mo3 Steel Tube via Supercritical Bend: Study of the Mechanical Properties and Structure.

Incineration is currently the standard way of disposing of municipal waste. It uses components protected by high-temperature-resistant layers of materials, such as Inconel alloys. Therefore, the objective of the current paper is to study the mechanical properties and structure of a bimetallic Inconel 625-16Mo3 steel tube. The Inconel 625 layer was 3.5 mm thick and was applied to the surface of the tube with a wall thickness of 7 mm via the cold metal transfer method. The bimetallic tube was bent using a supercritical bend (d ≤ 0.7D). This paper is focused on the investigation of the material changes in the Inconel 625 layer areas influenced by the maximum tensile and compressive stresses after the bend. The change in layer thickness after the bend was evaluated and compared to the non-deformed tube. In addition, the local mechanical properties (nanohardness, Young modulus) across the indicated interfacial areas using quasistatic nanoindentation were investigated. Subsequently, a thorough microstructure observation was carried out in areas with maximum tensile and compressive stresses to determine changes in the morphology and size of dendrites related to the effect of tensile or compressive stresses induced by bending. It was found that the grain featured a stretched secondary dendrite axis in the area of tensile stress, but compressive stress imparted a prolongation of the primary dendrite axis.

Evaluation of aqueous-deficient and evaporative dry eye cases with confocal microscopy

Dry eye disease (DED) is an important health problem affecting hundreds of millions of people worldwide. In vivo confocal microscopy (IVCM) is a non-invasive imaging tool that can visualize ocular surface diseases. In this study, we aimed to evaluate corneal structures and inflammatory cells with IVCM in DED patients. The patients were divided into three subgroups: group 1, consisting of 22 patients with aqueous tear insufficiency; group 2, consisting of 21 patients with evaporative type DED; and group 3, consisting of 20 healthy patients. Imaging was performed with IVCM. The corneal epithelium, nerves, stroma, endothelial and inflammatory cells were compared between groups. There was a significant decrease in corneal epithelial cell density in cases with DED, and there was a significant increase in corneal basal epithelial cell density in the aqueous-deficient type. Keratocyte density was significantly increased in the aqueous-deficient type. A significant decrease in the number and density of sub-basal nerves was found in aqueous-deficient cases, and an increase was found in neural pilling and folding. Dendritic cell density, size, number and area were significantly increased in the aqueous-deficient type. There was also decreased corneal endothelial cell density in DED. We evaluated pathological changes in DED on the corneal surface by IVCM. This methodology is valuable in terms of objectively evaluating how the corneal surface is affected in accordance with disease severity and in predicting poor response to treatment.

Effects of submicron-sized TiC particles on the microstructure modification and mechanical properties of Al-Si-Mg alloy

The microstructure evolution and mechanical properties of Al-7Si-0.35Mg alloy with varied amounts of submicron-sized TiC particles addition were investigated. The results indicated that the TiC addition decreased the critical undercooling for α-Al nucleation and refined secondary dendritic arms and grain sizes, meanwhile the flaky eutectic phases were modified into fibrous morphology. With increasing TiC addition, the mechanical properties of aged composites were firstly increased and decreased with further addition. The composite with 0.3 wt% TiCP exhibited the optimal combination of mechanical properties, with simultaneously enhancements in ultimate tensile strength, 0.2 % yield strength, and elongation from 293 MPa, 220 MPa, and 7.7 % to 315 MPa, 240 MPa, and 16.3 %, respectively. These improvement in mechanical properties are mainly attributed to microstructure refinement and Si phase modification due to proper TiC addition. While a high content of TiC addition caused aggregation and resulted in the formation of coarsen undissolved Al-Mg-Si-Fe phase and needle-like Al-Si-Ti intermetallic compounds, as a result, the ductility and strength were decreased.

Detection, Analysis, and Behavior of Soft-Shorts in Solid-State Batteries

Lithium metal batteries face numerous challenges before being employed in practical energy storage systems. Chief among these is the suppression of lithium dendrites, which lead to cell shorting and thermal runaway. In the field of solid-state batteries, there is often talk of “soft-shorts”, where small lithium dendrites form, short, then disappear. However, there is no clear consensus on the definition of soft-shorts, how they behave, and what their presence means for solid electrolyte development. Here, we use composite polymer electrolytes as exemplary solid electrolytes to detect, analyze, and thoroughly describe the varied behavior of soft-shorts. We define soft-shorts and show quantitatively that both ionic and electronic current flow simultaneously in a soft-shorted cell. The amount of each current depends on dendrite size, which dictates the resistance to the electronic pathway as well as Joule heating of the thin metal filaments. This heating leads to the “burning out” of the dendrites, which is responsible for the rapid un-shorting of soft-shorted cells. We use computational modeling to quantify the dendrite properties and explain how this leads to the observed transient behavior. More persistent soft-shorts are analyzed with temperature-dependent, quantitative electrochemical impedance fitting, where it is shown that parallel ionic and electronic current paths present impedance data that can be misinterpreted without rigorous analysis. The advantages and disadvantages of several soft-short characterization techniques are discussed. In the end, we show that soft-shorts are diverse in nature and thus require diverse tools and keen eyes from researchers to avoid the over-selling of flawed materials for lithium metal batteries.

Solidification crack elimination in TIG welding of Al7075: Experimental investigation and modified RDG modelling

Although solidification crack susceptibility modelling has been a point of interest for many years in fusion welding of aluminum alloys, the underlying mechanism of solidification crack elimination is not yet fully understood. To contribute in closing this knowledge gap, the present study investigates and proposes a new modified Rappaz-Drezet-Gremaud (RDG) physical model in autogenous and heterogeneous TIG welding of Al7075 sheets. The core novelty of the new model is that it includes the shrinkage strain rate, which allows to better capture the effects of capillary pressure, coherency point, as well as final dendrite or grain size in the fusion zone. In agreement with the experimental results and previous models, the new model shows that the defining mechanism of eliminating solidification cracks in heterogeneous joints is the capacity of nanoparticles to initiate heterogeneous grain nucleation, altering the fusion zone grain morphology from dendritic to fine equiaxed, with only little impact of the resulting grain size. This leads to two main effects causing reduced solidification crack susceptibility: (1) a reduction in coherency point by about 15 % from 902 K to 879 K, which reduces strain accumulation on the coherent solid network; (2) a considerable increase in capillary pressure across the entire mushy zone, allowing to maintain the total pressure at void/liquid interfaces in the positive range, which prevents the growth of potentially formed voids between grains at any temperature during solidification. In contrast, dendrite widths below 68 μm are required to prevent solidification cracks in autogenous joints without TiC nanoparticles, indicating a greater role of grain refinement. Overall, the proposed model highlights the more determinant role of the temperature-dependent solidification shrinkage strain rate in solidification crack susceptibility as it is an order of magnitude greater compared to the temperature-independent thermal contraction strain rate that has been the main or sole focus of previous models.

Role of dendritic pendant sizes in the self-assembly of redox-responsive ferrocene-containing polymers to large compound micelles

Polymer self-assembly has attracted considerable attention for constructing interesting nanostructures. Dendronized polymers with a linear polymer backbone and dendritic wedges possess the potential to self-assemble into ordered nanostructures in solution. Herein, the self-assembly behaviors of dendronized ferrocenyl polymers are investigated in aqueous solution. After being oxidized with FeCl3·6H2O, dendronized ferrocenyl polymers form positively charged ferrocenium-containing polyelectrolytes to generate nano-objects in aqueous solution. In addition, the supramolecular polymers obtained from the host–guest interactions between ferrocenyl units and β-cyclodextrin are also able to form nano-objects in aqueous solution. Whereafter, both the oxidized and supramolecular polymers are used to encapsulate Rhodamine B, resulting in the cargo-loaded self-assembly. All self-assembly experiments demonstrate that the dendritic effects would drive ferrocenyl polymers to self-assemble from small micelles to large compound micelles. The ferrocenyl polymers with larger dendritic pendant sizes have a more obvious tendency to self-assemble into large compound micelles. The current work gives a chance to understand the self-assembly behaviors of dendronized polymers, which is expected to generate ordered nanostructures.

Impact of a pyridazine derivative on tripartite synapse ultrastructure in hippocampus: a three-dimensional analysis.

We previously discovered a pyridazine derivative compound series that can improve cognitive functions in mouse models of Alzheimer's disease. One of the advanced compounds from this series, LDN/OSU-0215111-M3, was selected as the preclinical development candidate. This compound activates local protein translation at the perisynaptic astrocytic process (PAP) and enhances synaptic plasticity sequentially. While biochemical evidence supports the hypothesis that the compound enhances the structural plasticity of the tripartite synapse, its direct structural impact has not been investigated. Volume electron microscopy was used to study the hippocampal tripartite synapse three-dimensional structure in 3-month-old wild-type FVB/NJ mice after LDN/OSU-0215111-M3 treatment. LDN/OSU-0215111-M3 increased the size of tertiary apical dendrites, the volume of mushroom spines, the proportion of mushroom spines containing spine apparatus, and alterations in the spine distribution across the surface area of tertiary dendrites. Compound also increased the number of the PAP interacting with the mushroom spines as well as the size of the PAP in contact with the spines. Furthermore, proteomic analysis of the isolated synaptic terminals indicated an increase in dendritic and synaptic proteins as well as suggested a possible involvement of the phospholipase D signaling pathway. To further validate that LDN/OSU-0215111-M3 altered synaptic function, electrophysiological studies showed increased long-term potentiation following compound treatment. This study provides direct evidence that pyridazine derivatives enhance the structural and functional plasticity of the tripartite synapse.

Endoplasmic Reticulum Exit Sites scale with somato-dendritic size in neurons.

Nervous systems exhibit dramatic diversity in cell morphology and size. How neurons regulate their biosynthetic and secretory machinery to support such diversity is not well understood. Endoplasmic reticulum exit sites (ERESs) are essential for maintaining secretory flux, and are required for normal dendrite development, but how neurons of different size regulate secretory capacity remains unknown. In Caenorhabditis elegans, we find that the ERES number is strongly correlated with the size of a neuron's dendritic arbor. The elaborately branched sensory neuron, PVD, has especially high ERES numbers. Asymmetric cell division provides PVD with a large initial cell size critical for rapid establishment of PVD's high ERES number before neurite outgrowth, and these ERESs are maintained throughout development. Maintenance of ERES number requires the cell fate transcription factor MEC-3, C. elegans TOR (ceTOR/let-363), and nutrient availability, with mec-3 and ceTOR/let-363 mutant PVDs both displaying reductions in ERES number, soma size, and dendrite size. Notably, mec-3 mutant animals exhibit reduced expression of a ceTOR/let-363 reporter in PVD, and starvation reduces ERES number and somato-dendritic size in a manner genetically redundant with ceTOR/let-363 perturbation. Our data suggest that both asymmetric cell division and nutrient sensing pathways regulate secretory capacities to support elaborate dendritic arbors.

Effect of rare earth Nd on the microstructural transformation and mechanical properties of 7xxx series aluminum alloys

Abstract Al–Zn–Mg–Cu–Zr aluminum alloys have shown promise as materials for drill pipes; however, their application temperature is limited to below 120°C. This study investigates the influence of incorporating the rare earth element Nd on the microstructure and mechanical properties of Al–Zn–Mg–Cu–Zr alloys. The microstructural evolution during casting, homogenization, hot deformation, and heat treatment processes is characterized using optical microscopy and scanning electron microscopy. The composition of the rare earth phase is determined through transmission electron microscopy (TEM). Furthermore, first-principles calculations are employed to determine the formation enthalpy, cohesive energy, shear modulus, bulk modulus, Young’s modulus, and Poisson’s ratio of bulk Al8Cu4Nd. The effect of Nd addition on the mechanical properties of the alloy is investigated through hardness and tensile testing. The results indicate that the addition of Nd significantly refines the grain and dendrite sizes of the alloy and effectively suppresses recrystallization behavior during hot extrusion and solution treatment. TEM observations reveal the presence of micrometer-sized blocky Al8Cu4Nd phases and nanometer-sized Al3Nd phases. The Al3Nd phases are located near dislocations, hindering dislocation movement and thus enhancing the alloy’s mechanical properties. First-principles calculations demonstrate that the bulk Al8Cu4Nd phase exhibits superior structural stability, deformation resistance, and brittle characteristics, which negatively impact the ductility of the alloy. The alloy with Nd addition can maintain a high hardness value for an extended period at high temperature, and the tensile strength of the alloy with 0.26 wt% Nd addition reaches 396.2 MPa at 120°C. These results indicate that the rare earth element Nd can improve the high-temperature mechanical properties of the alloy.

Microstructure Evolution of CET-Free Epitaxial Growth NiCoCrAlYTa Coating by Electron Beam Cladding

Some unavoidable factors in the operating environment could damage single-crystal components of nickel-based single-crystal superalloys. This work prepared an epitaxial growth NiCoCrAlYTa repaired coating without the columnar-to-equiaxed transition (CET) phenomenon on a nickel-based single-crystal superalloy by electron beam cladding. The microstructure of two cross-sections and two surfaces at different depths were characterized. Moreover, the formation mechanism of coating dendrite was revealed by studying the relationship between coating dendrite size, growth direction, and solidification rate. The microstructure evolution and crystal growth orientation of the coating were investigated. The microstructural investigation of the sample revealed that the dendrites’ orientations on the coating’s horizontal section were different, and its characteristics were highly visible on the surface of the coating. The crystal growth orientations of the coating on the vertical cross-section parallel/perpendicular to the scanning direction of the electron beam were also different. Moreover, the average primary dendrite arm spacing (PDAS) of the columnar dendrite in the different areas of the coating was different and increased from 2 μm to 4 μm. The oxidation resistance of the coating at 1000 °C was about three times higher than that of the substrate.

Models of Purkinje cell dendritic tree selection during early cerebellar development.

We investigate the relationship between primary dendrite selection of Purkinje cells and migration of their presynaptic partner granule cells during early cerebellar development. During postnatal development, each Purkinje cell grows more than three dendritic trees, from which a primary tree is selected for development, whereas the others completely retract. Experimental studies suggest that this selection process is coordinated by physical and synaptic interactions with granule cells, which undergo a massive migration at the same time. However, technical limitations hinder continuous experimental observation of multiple cell populations. To explore possible mechanisms underlying this selection process, we constructed a computational model using a new computational framework, NeuroDevSim. The study presents the first computational model that simultaneously simulates Purkinje cell growth and the dynamics of granule cell migrations during the first two postnatal weeks, allowing exploration of the role of physical and synaptic interactions upon dendritic selection. The model suggests that interaction with parallel fibers is important to establish the distinct planar morphology of Purkinje cell dendrites. Specific rules to select which dendritic trees to keep or retract result in larger winner trees with more synaptic contacts than using random selection. A rule based on afferent synaptic activity was less effective than rules based on dendritic size or numbers of synapses.

The RNA-binding protein NANOS1 controls hippocampal synaptogenesis.

Proteins from the NANOS family are conserved translational repressors with a well-known role in gonad development in both vertebrates and invertebrates. In addition, Drosophila Nanos controls neuron maturation and function, and rodent Nanos1 affects cortical neuron differentiation. Here we show that rat Nanos1 is expressed in hippocampal neurons and that the siRNA-mediated knockdown of Nanos1 impairs synaptogenesis. We found that both dendritic spine size and number were affected by Nanos1 KD. Dendritic spines were smaller and more numerous. Moreover, whereas in control neurons most dendritic PSD95 clusters contact pre-synaptic structures, a larger proportion of PSD95 clusters lacked a synapsin counterpart upon Nanos1 loss-of-function. Finally, Nanos1 KD impaired the induction of ARC typically triggered by neuron depolarization. These results expand our knowledge on the role of NANOS1 in CNS development and suggest that RNA regulation by NANOS1 governs hippocampal synaptogenesis.

Effect of stirring speed and temperature on the microstructure and mechanical properties of A356 alloy under vacuum

In this work, an effective method was proposed to purify aluminum alloy melt under stirring and vacuum. The formation mechanism of pore defects and their effects on the mechanical properties of A356 alloy were investigated. The results showed that compared with the untreated alloy, the mechanical properties of the purified A356 alloy were significantly improved. The purification parameters, including stirring speed and stirring temperature, had crucial effects on determining the size of dendrites and pores. The optimized stirring speed and stirring temperatures were 65 rpm and 730 °C, respectively. In this condition, grains with an average diameter of 279 μm and pores having an average diameter of 79.5 μm were obtained; the ultimate tensile strength, yield strength and elongation of the purified alloy reached 203.7 ± 4.3 MPa, 81.6 ± 3.3 MPa and 10.2 ± 0.5%, respectively. The variation in the microstructure and mechanical properties was associated with the bubble breakup mechanism, which accelerated the removal of bubbles in the melt during stirring in vacuum. Furthermore, the interaction between pore and solidified microstructure was also discussed.

Microgeometrical dendritic factors predict electrical decoupling between somatic and dendritic compartments in magnocellular neurosecretory neurons.

It is generally assumed that dendritic release of neuropeptides from magnocellular neurosecretory neurons (MNNs), a critical process involved in homeostatic functions, is an activity-dependent process that requires backpropagating action potentials (APs). Still, growing evidence indicates that dendritic release can occur in the absence of APs, and axonal APs have been shown to fail to evoke dendritic release. These inconsistencies strongly suggest that APs in MNNs may fail to backpropagating into dendrites. Here we tested whether simple factors of electrical signal attenuation could lead to effective decoupling between cell's body and dendritic release site within typical geometrical characteristics of MNN. We developed a family of linear mathematical models of MNNs and evaluated whether the somato-dendritic transfer of electrical signals is influenced by the geometrical characteristics. We determined the prerequisites for critically strong dendritic attenuation of the somatic input which are sufficient to explain the failure of APs initiated in the soma to backpropagating into dendritic compartments. Being measured in 100 μm from soma voltage attenuations down to 0.1 and 0.01 of the input value were chosen as the markers of electrical decoupling of dendritic sites from the soma, considering 0.1 insufficient for triggering dendritic spikes and 0.01 indistinguishable from background noise. The tested micro-geometrical factors were the dendritic stem diameter, varicosities, and size of peri-dendritic space limited by glial sheath wrapping. Varicosities increased the attenuation along homogeneous proximal dendrites by providing an increased current leak at the junction with the proximal dendritic section. The glial sheath wrapping a dendrite section promoted greater attenuation by increasing longitudinal resistance of the interstitial peri-dendritic space thus playing the insulating role. These decoupling effects were strengthened in the case of the dendritic stems with thinner diameters of and/or increased conductivity of the membrane. These micro-geometrical factors are biophysically realistic and predict electrical decoupling between somatic and dendritic compartments in MNNs.