Short Dendrites Research Articles

Interaction between PCB-Cu corrosion and electrochemical migration under the Coupling of electric field and thin liquid film

An in-situ monitoring and observation experimental setup was designed in the coupled environment of a thin liquid film and an electric field. The interactive development of PCB-Cu corrosion and electromigration under different bias voltages, salt concentrations, and liquid-film thicknesses was investigated, and an interactive model was proposed. The results showed that electromigration of copper was dominant at a high voltage of 3 V, whereas corrosion occurred without salt deposition at a low voltage of 1 V. The growth rate of the dendrites decreased with increasing liquid film thickness. In the presence of 1 g/m2 of NaCl, dendrite growth was absent because corrosion precipitation occurred before dendrite formation, thereby hindering the migration of copper ions. At a higher NaCl deposition density of 10 g/m2, the electromigration of copper became dominant, resulting in the formation of many short dendrites, evenly distributed on the cathode at a low voltage of 1 V. These observations are consistent with the results of the in-situ current monitoring tests.

Dermoscopy and reflectance confocal microscopy finding of different anatomic sites of Langerhans cell histiocytosis.

Recognizing Langerhans cell histiocytosis (LCH) might be a challenge due to its rarity. Reflectance confocal microscopy (RCM) and dermoscopy were emergent promising non-invasive technique as auxiliary tools in diagnosis of different skin conditions. However, the RCM and dermoscopic features of LCH had been less investigated. To reveal the common RCM and dermoscopic features of LCH. Forty cases of LCH were retrospectively analyzed according to age, locations, clinical, RCM, and dermoscopic features from September 2016 to December 2022. To reveal the differences and common in clinical, RCM, and dermoscopic features that occur in different anatomic location. In the study, sites of predilection include the trunk 31/40 (77.5%), extremity 21/40 (52.5%), face 14/40 (35%), scalp 11/40 (27.5%), vulvar 4/40 (10%), and nail 2/40 (5%). All LCHs had the common RCM features. There were significant differences in clinical and dermoscopic features for age and lesion anatomic site. The common dermoscopic features for scalp, face, trunk, and extremity were the erythematous scaly rash, purplish-red globules or patches, scar-like streaks with ectatic vessels. While the features for nail LCH were purpuric striae, onycholysis and purulent scaly rash, and the erosive erythematous plaque and purulent scaly rash for vulvar LCH. The common RCM features of all LCH showed a focal highly reflective dense image in the surface keratin layer, epidermis architectural disarray, obscuration of dermo-epidermal junction, numerous polygonal, large, medium reflective, short dendrites cells in the epidermis, and dermis. All LCH involving the vulvar and nail did not manifest skin lesions. RCM and dermoscopy showed promising value for diagnosis and differentiation of LCH.

Lithium Metal Anode Using Fluorination on Iron Powder for Lithium Metal Batteries

High-energy-density batteries have been gaining considerable attentions in renewable energy, and Li metal anodes are potential candidates for developing such batteries. Therefore, many attempts were carried out to find alternative ways to use Li by mixing it with tiny metal powders or impregnating the porous media. However, most materials used in battery fabrication are lithiophobic to molten Li; hence, infusion of Li into porous structures or powders with an intrinsically lithiophobic surface presents challenges in developing Li metal batteries. Optimizing and improving molten Li's wettability is one approach to address this. Herein, we propose an efficient and straightforward direct fluorination method for achieving an ultra-lithiophilic fluoride layer on the surface of the Fe powder. Fluorination of Fe powders resulted in a remarkable increase in the wettability of molten Li by a growth of Fe-F layer on the surface of Fe powder. This layer was lithiophilic and showed high wettability. Moreover, an anode prepared using fluorinated Fe-Li metal showed no evidence of short circuits or dendrite formation after the cycle test at 0.1 and 0.2 mA cm-2. In contrast, a pure Li anode and pristine Fe powder showed unstable charge-discharge characteristics in cycle tests. The proposed fluorination is the most practical and straightforward method among those reported. Thus, the proposed method will further develop rechargeable lithium-metal battery technology.

A mathematical study of the efficacy of possible negative feedback pathways involved in neuronal polarization

Neuronal polarization, a process wherein nascent neurons develop a single long axon and multiple short dendrites, can occur within in vitro cell cultures without environmental cues. This is an apparently random process in which one of several short processes, called neurites, grows to become long, while the others remain short. In this study, we propose a minimum model for neurite growth, which involves bistability and random excitations reflecting actin waves. Positive feedback is needed to produce the bistability, while negative feedback is required to ensure that no more than one neurite wins the winner-takes-all contest. By applying the negative feedback to different aspects of the neurite growth process, we demonstrate that targeting the negative feedback to the excitation amplitude results in the most persistent polarization. Also, we demonstrate that there are optimal ranges of values for the neurite count, and for the excitation rate and amplitude that best maintain the polarization. Finally, we show that a previously published model for neuronal polarization based on competition for limited resources shares key features with our best-performing minimal model: bistability and negative feedback targeted to the size of random excitations.

Deposition of hard solid-lubricating composite coating on Ti-6Al-4V alloy with enhanced mechanical, corrosion, and electrical discharge wear properties

In the present work, a hard solid-lubricating clad layer has been developed on Ti-6Al-4V substrate by pre-placed powder TIG cladding technique to enhance the mechanical, corrosion and electrical discharge wear properties. The combining effect of Ti, Ni, and Si coating powders with different % of La2O3 in the N2 environment has been studied. The phase analysis detects peaks of both hard (NiTi, TiO2, and TiAlN) and solid lubricating (LaNi5 and Si3N4) phases. The sub-surface analysis shows defect-free cladding with good metallurgical bonds and refined microstructure near the interfacial zone. Mainly short and long dendrite, fish-bone-like, lamellar and short needle-like microstructures are observed. Two times higher microhardness in the range of 578.51 ± 13.99 HV0.5 (Sample S4) – 603.56 ± 9.66 HV0.5 (Sample S1) is observed. Mechanical wear analysis reveals a rigorous decrease in the coefficient of friction which is 14.5 times much better than titanium substrate. The prominent mechanism for mechanical wear is a combination of abrasion (Sample S1 and S2) with adhesion (Sample S3 and S4) with the lowest and highest wear rate of 63.92 ± 8.34 mm3 N−1 m−1 (Sample S4) and 154.52 ± 13.27 mm3 N−1 m−1 (Sample S1) respectively. The corrosion rate is found much lower than titanium substrate. The chance of the electrical discharge wear reduced to 81.90 % which is much better than titanium substrate. These results demonstrate that fabricated coating on Ti-6Al-4V substrate can be used in any of the mechanical, corrosion, and electrical discharge wear environments.

High stability of solid electrolyte interphase in lithium metal batteries enabled by direct fluorination on metal iron powder

Multiple studies attempted mixing Li with microparticle metal powders or using it to impregnate a porous media to utilize for thermal batteries. The infusion of Li into porous structures or powders is challenging as most materials used in battery fabrication are lithiophobic to molten Li. Optimizing and improving the wettability of molten Li is one approach to address this. Herein, we propose an efficient and facile direct fluorination method for achieving an ultra-lithiophilic fluoride layer on the surface of a Fe powder. Fluorination of Fe powders resulted in a significant increase in the wettability of molten Li by growing a Fe-F layer on the surface of the Fe powder. This layer was lithiophilic and showed good wettability. An anode prepared using fluorinated Fe-Li metal showed no evidence of short circuits or dendrite formation after a cycle test at 0.2 mA cm−2. Both a pure Li anode and pristine Fe powder showed unstable charge–discharge characteristics when used as an anode in cycle tests. This proposed method will further develop rechargeable lithium-metal battery technology.

Inhibition of Forebrain Microglia Ameliorates Non‐alcoholic Fatty Liver Disease During Obesity

Non‐alcoholic fatty liver disease (NAFLD), characterized by increased hepatic triglycerides (i.e. steatosis), leads to an increased risk for type II diabetes, cardiovascular disease and obesity‐related mortality. Accumulating data points to central nervous system (CNS) alterations as a NAFLD contributor. In this context, we have recently shown that pharmacological inhibition of microglia, the resident immune cells of the brain, attenuates NAFLD during obesity. However, the brain regions involved in this microglial driven steatosis remains unknown. The forebrain subfornical organ (SFO), a circumventricular nucleus situated outside of the blood‐brain‐barrier, has recently been suggested to be critical in NAFLD. Based on this, we hypothesized that SFO microglia activation contributes to hepatic steatosis during obesity. To investigate this, we used a common murine model of diet‐induced NAFLD where male C57Bl/6J mice were fed a high fat diet (HFD, 60% kCal fat) or normal chow for 11 weeks, starting at 6 weeks of age. Immunohistochemistry for ionized calcium‐binding adapter molecule 1 (Iba1) revealed SFO microglia activation following HFD feeding (1.0±0.01 vs 1.4±0.15, relative Iba1 intensity, normal chow vs HFD, p<0.05, n=7). 3‐dimensional analysis further indicated that HFD feeding was associated with a shift to an activated SFO microglia morphology, including decreased branching complexity and shorter dendrites (e.g. branch #/dendrite: 3.1±0.2 vs 2.5±0.1, normal chow vs HFD, p<0.05, n=5/group, 203‐364 microglia/animal). Building upon this, we employed a chemogenetic strategy to selectively inhibit SFO microglia. HFD or normal chow male mice underwent SFO stereotaxic delivery of a designer receptors exclusively activated by designer drugs inhibitory construct targeted to microglia via the CD68 promoter (pAAV‐CD68‐hM4Gi‐mCherry). Following surgical recovery, the pharmacological ligand clozapine‐N‐oxide (CNO; 3 mg/kg i.p.) was administered once daily over 3 days to inhibit SFO microglia. Saline served as a control (n=7–11/group). Short‐term inhibition of SFO microglia did not alter body weight (43±1 vs 42±2 g, HFD saline vs CNO, p>0.05) and food intake in normal chow or HFD fed mice. Similarly, indirect calorimetry evaluations revealed no change in oxygen consumption, respiratory exchange ratio, or energy expenditure in either diet group during SFO microglia inhibition (e.g. energy expenditure: 0.49±0.01 vs 0.49±0.01 kcal/hr, HFD saline vs CNO, p>0.05). Regional adiposity including visceral, subcutaneous, and brown adipose mass was also not different between CNO and saline treated animals. However, histological examination (Oil Red O staining) revealed widespread hepatic lipid accumulation in HFD fed mice (0.4±0.1 vs 36.2±5.5 %stained area; normal chow saline vs HFD saline, p<0.05), which was reduced by ~49% following 3‐day SFO microglia inhibition (18.4±5.4 %stained area, HFD CNO, p<0.05 vs HFD saline). This decline in hepatic steatosis in response to SFO microglia inhibition was further confirmed with liver triglyceride measurements. In line with the direct association of NAFLD and type II diabetes, inhibition of SFO microglia also resulted in a reduction in fed blood glucose levels in obese mice (229±24 vs 182±9 mg/dl, HFD saline vs CNO, p=0.05). Collectively, these results indicate that SFO microglia activation is a critical contributor to hepatic steatosis during obesity.

Simulation Study on Internal Short Circuits in a Li-Ion Battery Depending on the Sizes, Quantities, and Locations of Li Dendrites

The internal short circuit caused by the Li dendrite is well known to be a major cause for fire or explosion accidents involving state-of-the-art lithium-ion batteries (LIBs). However, post-mortem analysis cannot identify the most probable cause, which is initially embedded in the cell, because the original structure of the cell totally collapses after the accident. Thus, multiphysics modeling and simulation must be an effective solution to investigate the effect of a specific cause in a variety of conditions. Herein, we reported an electrochemical-thermal model to simulate the internal short circuit depending on Li dendrite’s sizes (1, 3, 5, 7, and 9 μm), quantities (1–9), relative locations (0, 25, 50, 100, and 150 μm), and external temperature (−10, 10, 30, and 50°C). Through monitoring the temperature change affected by the joule and reaction heats for each case, we suggested critical conditions that led to unavoidable thermal runaway. Thus, this model can be a steppingstone in understanding the correlation between internal short circuits and Li dendrites.

Mapping of folic acid in the children brainstem.

Using highly specific antisera, the neuroanatomical distribution of folic acid (FA) and retinoic acid (RA) has been studied for the first time in the children brainstem. Neither immunoreactive structures containing RA nor immunoreactive fibers containing FA were found. FA-immunoreactive perikarya (fusiform, small/medium in size, one short dendrite) were only found in the pons in three regions: central gray, reticular formation, and locus coeruleus. The number of cell bodies decreased with age. In the first case studied (2 years), a moderate density of cell bodies was observed in the central gray and reticular formation, whereas a low density was found in the locus coeruleus. In the second case (6 years), a low density of these perikarya was observed in the central gray, reticular formation, and locus coeruleus. In the third case (7 years), a low density of FA-immunoreactive cell bodies was found in the central gray and reticular formation, whereas in the locus coeruleus no immunoreactive cell bodies were observed. The distribution of FA in the central nervous system of humans and monkeys is different and, in addition, in these species the vitamin was located in different parts of the nerve cells. The restricted distribution of FA suggests that the vitamin is involved in specific physiological mechanisms.

Microstructure and magnetic properties of Nd-Fe-B permanent magnets produced by laser powder bed fusion

Additive manufacturing of Nd-Fe-B is a novel approach for the fabrication of permanent magnets. We present an analysis of the magnetic properties and microstructure of Nd-Fe-B permanent magnets, which were produced by laser powder bed fusion (LPBF). By optimization of processing parameters for the Nd-lean powder coercivity of 921 kA/m (1.16 T), remanence of 0.63 T and maximum energy product of 63 kJ/m3 are achieved without the addition of further Nd-rich low-melting alloys or any other post treatment. Thereby, remanence and maximum energy product represent the highest reported values for additively manufactured permanent magnets. The impact of area energy density EA on the magnetic properties is discussed. The isotropic microstructure consists of short Nd2Fe14B dendrites at the melt pool boundaries and globular sub-micron sized grains in the melt pool interior. After LPBF of the Nd-lean powder no evidence of α-Fe is found in the microstructure.

Ultrastructure of chemosensory tarsal tip-pore sensilla of Argiope spp. Audouin, 1826 (Chelicerata: Araneae: Araneidae).

While chemical communication has been investigated intensively in vertebrates and insects, relatively little is known about the sensory world of spiders despite the fact that chemical cues play a key role in natural and sexual selection in this group. In insects, olfaction is performed with wall-pore and gustation with tip-pore sensilla. Since spiders possess tip-pore sensilla only, it is unclear how they accomplish olfaction. We scrutinized the ultrastructure of the trichoid tip-pore sensilla of the orb weaving spider Argiope bruennichi-a common Palearctic species the males of which are known to be attracted by female sex pheromone. We also investigated the congener Argiope blanda. We examined whether the tip-pore sensilla differ in ultrastructure depending on sex and their position on the tarsi of walking legs of which only the distal parts are in contact with the substrate. We hypothesized as yet undetected differences in ultrastructure that suggest gustatory versus olfactory functions. All tarsal tip-pore sensilla of both species exhibit characters typical of contact-chemoreceptors, such as (a) the presence of a pore at the tip of the sensillum shaft, (b) 2-22 uniciliated chemoreceptive cells with elongated and unbranched dendrites reaching up to the tip-pore, (c) two integrated mechanoreceptive cells with short dendrites and large tubular bodies attached to the sensillum shaft's base, and (d) a socket structure with suspension fibres that render the sensillum shaft flexible. The newly found third mechanoreceptive cell attached to the proximal end of the peridendritic shaft cylinder by a small tubular body was likely overlooked in previous studies. The organization of tarsal tip-pore sensilla did not differ depending on the position on the tarsus nor between the sexes. As no wall-pore sensilla were detected, we discuss the probability that a single type of sensillum performs both gustation and olfaction in spiders.

Prenatal sevoflurane exposure causes neuronal excitatory/inhibitory imbalance in the prefrontal cortex and neurofunctional abnormality in rats

The balance of excitatory and inhibitory neurons in the central nervous system is critical for maintaining brain function and sevoflurane, a general anesthetic and an GABA receptor modulator, may change the balance of excitatory and inhibitory neurons in the cortex during early brain development. Herein, we investigated whether prenatal sevoflurane exposure (PSE) disturbs cortical neuronal development and brain function. Pregnant rats at the gestational day 14.5 were subjected to sevoflurane exposure at 3.0% for 3 h and their offspring were studied thereafter. We found a significant increase of parvalbumin-positive neurons, vesicular GABA transporter (VGAT) and GAD67 expression, and GABA neurotransmitter, and a significant decrease of vesicular glutamate transporter 1 (VGLUT1) expression and glutamate in the medial prefrontal cortex (mPFC) of offspring. Pyramidal neurons showed atrophy with shorter dendrites, less branches and lower spine density visualized by Golgi stain and a decrease of excitability with the increased miniature inhibitory postsynaptic current (mIPSC) frequency and amplitude, the decreased miniature excitatory postsynaptic current (mEPSC) frequency and excitation/inhibition (E/I) ratio using whole-cell recording in offspring. There was a significant increase of inhibitory synapse in the mPFC detected by electron microscopy. Furthermore, PSE animals showed hypo-excitatory phenotype including depression-like behaviors and learning deficits. Thus, our studies provide novel evidence that PSE causes the persisted imbalance of excitatory and inhibitory neurons in the mPFC, and this is very likely the mechanisms of the sevoflurane-induced brain functional abnormalities.

Neurotoxic effects of phenytoin on primary culture of hippocampal neurons: Neural development retardation

ObjectivesIons are key regulators of the morphogenesis, dendritogenesis and development of neurons therefore drugs that perturb ion homeostasis are associated with high risk of mental retardation, intellectual disability and even abortion of fetus. Phenytoin (PHT) is an antiepileptic drug which regulates ion influx especially Ca2+ and Na+ and widely prescribed to pregnant women suffer from epilepsy. This study aimed to investigate neurodevelopmental features of primary culture of hippocampal cells such as morphology, dendritogenesis, cytotoxicity and cell death in the presence and absence of PHT. MethodsPrimary culture of hippocampal neurons from neonatal rat was treated by 25 and 50 μg/ml of PHT and morphological development was evaluated during the 14 days. Arborization of neurons during the time was monitored by light microscopy. MTT assay and lactate dehydrogenase (LDH) penetrating test also assessed PHT imposed cytotoxicity. ResultsOur results confirmed high dose of PHT could cause excessive cell death in neural cells. PHT exposing causes morphological abnormalities in hippocampal neurons such as shrieked cell body or thick and short dendrite. PHT also prevents branching of dendrites and induces LDH leakage that refers to cytotoxicity. DiscussionBy considering the Ca2+ and Na+ important roles in cell development process, PHT affect neural shape and arborization rate. It could retard neural development and lead neurons to the cell death. PHT is an anticonvulsant that prescribed to pregnant women so could disrupt brain development and increase the risk of mental retardation in newborn children.

Microstructure and Property of In-Situ TiC Reinforced Co-Based Composite Coatings by Laser Cladding

In order to improve the wear resistance of Co-based alloy coatings, in-situ TiC reinforced Co-based composite coatings were prepared on 45 steel surface by laser cladding Co-based alloy, Ti and C powders. The effect of (Ti + C) addition on the microstructure and wear resistance of in-situ TiC reinforced Co-based composite coatings was investigated systematically. The results showed that TiC and Co3Ti phases were detected in the in-situ TiC reinforced Co-based composite coatings, besides γ-Co and Cr23C6. The in-situ TiC reinforced Co-based composite coatings was mainly composed of planar crystals in the binding zone, dendrites in the bottom and equiaxed crystals in the upper. With the increase of (Ti + C) addition, the number of short rod-like dendrites and equiaxed crystals was gradually increased, the microstructure was more fine and uniform. The microhardness of the composite coatings was improved gradually, and the maximum improvement in the microhardness was 35.7%, for 30.0 wt.% (Ti + C) addition. The mass loss of the composite coatings was firstly reduced and then increased, the lowest value was 10.5 mg for 20.0 wt.% (Ti + C) addition, which was 59.7% of that of Co-based alloy coatings, and the wear mechanism of the composite coatings after adding (Ti + C) was the abrasive wear. These results indicated that adding (Ti + C) had a significant influence on the properties of the composite coatings, and were consistent with the calculated results of applied multivariate statistical analysis.

Nonpyramidal neurons in the primate basolateral amygdala: A Golgi study in the baboon (Papio cynocephalus) and long-tailed macaque (Macaca fascicularis).

Nonpyramidal GABAergic interneurons in the basolateral nuclear complex (BNC) of the amygdala are critical for the regulation of emotion. Remarkably, there have been no Golgi studies of these neurons in nonhuman primates. Therefore, in the present study we investigated the morphology of nonpyramidal neurons (NPNs) in the BNC of the baboon and monkey using the Golgi technique. NPNs were scattered throughout all nuclei of the BNC and had aspiny or spine-sparse dendrites. NPNs were morphologically heterogeneous and could be divided into small, medium, large, and giant types based on the size of their somata. NPNs could be further divided on the basis of their somatodendritic morphology into four types: multipolar, bitufted, bipolar, and irregular. NPN axons, when stained, formed dense local arborizations that overlapped their dendritic fields to varying extents. These axons always exhibited varying numbers of varicosities representing axon terminals. Three specialized NPN subtypes were recognized because of their unique anatomical features: axo-axonic cells, neurogliaform cells, and giant cells. The axons of axo-axonic cells formed "axonal cartridges," with clustered varicosities that contacted the axon initial segments of pyramidal neurons (PNs). Neurogliaform cells had small somata and numerous short dendrites that formed a dense dendritic arborization; they also exhibited a very dense axonal arborization that overlapped the dendritic field. Giant cells had very large irregular somata and long, thick dendrites; their distal dendrites often branched extensively and had long appendages. In general, the NPNs of the baboon and monkey BNC, including the specialized subtypes, were similar to those of rodents.

Influence of carbon dioxide shielding gas on microstructure and corrosion property of welds

AbstractThe microstructures and corrosion properties of weld joints are studied during 10 kW high power fiber laser welding of 304 stainless steel with shielding gases of 100 % argon, 80 % argon containing 20 % carbon dioxide and 100 % carbon dioxide, respectively. As the content of carbon dioxide in argon shielding gas increases from 0 % to 20 % then to 100 % during 10 kW high power fibre laser welding, the interdendritic δ‐ferrite in weld joints changes from lathy, short strip and trivial structures to thick‐long strip with short secondary dendrite arms then to skeletal‐network structure. Oxide inclusions, observed in 100 % carbon dioxide shielded weld, promote the formation of the skeletal‐network structure of δ‐ferrite and the homogenization of chromium and nickel in weld joint. The 100 % argon shielded weld joint has a highest initial corrosion current density, the 80 % argon containing 20 % carbon dioxide shielded weld has a lowest pitting potential, while the 100 % carbon dioxide shielded weld has a highest initial corrosion potential. The microstructures and element distribution play important role in determining the corrosion properties of the weld joints.

Structural and molecular correlates of cognitive aging in the rat

Aging is associated with cognitive decline. Herein, we studied a large cohort of old age and young adult male rats and confirmed that, as a group, old rats display poorer spatial learning and behavioral flexibility than younger adults. Surprisingly, when animals were clustered as good and bad performers, our data revealed that while in younger animals better cognitive performance was associated with longer dendritic trees and increased levels of synaptic markers in the hippocampus and prefrontal cortex, the opposite was found in the older group, in which better performance was associated with shorter dendrites and lower levels of synaptic markers. Additionally, in old, but not young individuals, worse performance correlated with increased levels of BDNF and the autophagy substrate p62, but decreased levels of the autophagy complex protein LC3. In summary, while for younger individuals “bigger is better”, “smaller is better” is a more appropriate aphorism for older subjects.

Developmental pattern and structural factors of dendritic survival in cerebellar granule cells in vivo

Granule cells (GCs) in the cerebellar cortex are important for sparse encoding of afferent sensorimotor information. Modeling studies show that GCs can perform their function most effectively when they have four dendrites. Indeed, mature GCs have four short dendrites on average, each terminating in a claw-like ending that receives both excitatory and inhibitory inputs. Immature GCs, however, have significantly more dendrites—all without claws. How these redundant dendrites are refined during development is largely unclear. Here, we used in vivo time-lapse imaging and immunohistochemistry to study developmental refinement of GC dendritic arbors and its relation to synapse formation. We found that while the formation of dendritic claws stabilized the dendrites, the selection of surviving dendrites was made before claw formation, and longer immature dendrites had a significantly higher chance of survival than shorter dendrites. Using immunohistochemistry, we show that glutamatergic and GABAergic synapses are transiently formed on immature GC dendrites, and the number of GABAergic, but not glutamatergic, synapses correlates with the length of immature dendrites. Together, these results suggest a potential role of transient GABAergic synapses on dendritic selection and show that preselected dendrites are stabilized by the formation of dendritic claws—the site of mature synapses.

Dendritic Pt shells coated on concave Pd nanocrystals: synthesis and use as electrocatalysts for acidic oxygen reduction reaction

A simple method to prepare a dendritic Pt-shell coating on concave Pd nanoparticles (NPs) was successfully developed. In this study, tuning the Pt precursor concentration in the reaction mixture allowed control over the length of the outer Pt dendrites, enclosed by (211) high-index facets or (110) facets were performed. The concave Pd NPs covered by short Pt dendrites (Pd/S-Pt) and long Pt dendrites (Pd/L-Pt) were applied as catalysts for the oxygen reduction reaction (ORR) in 0.1 M HClO4 electrolyte solution. Pd/S-Pt with (211) facets had higher specific activity (0.106 mA cm−2) than that of Pd/L-Pt with (110) facets (0.066 mA cm−2) or commercial Pt/C (0.076 mA cm−2). Additionally, the accelerated durability test (ADT) results revealed that the decay for the ORR kinetic current catalysed by Pd/S-Pt was 28.21%, which was smaller than that of Pt/C (58.15%). Thus, Pd/S-Pt was effective for catalysis of the ORR.

Effects of Polymer Coatings on Electrodeposited Lithium Metal.

The electrodeposition of lithium metal is a key process in next-generation, high energy density storage devices. However, the high reactivity of the lithium metal causes short cycling lifetimes and dendrite growth that can pose a serious safety issue. Recently, a number of approaches have been pursued to stabilize the lithium metal-electrolyte interface, including soft polymeric coatings that have shown the ability to enable high-rate and high-capacity lithium metal cycling, but a clear understanding of how to design and modify these coatings has not yet been established. In this work, we studied the effects of several polymers with systematically varied chemical and mechanical properties as coatings on the lithium metal anode. By examining the early stages of lithium metal deposition, we determine that the morphology of the lithium particles is strongly influenced by the chemistry of the polymer coating. We have identified polymer dielectric constant and surface energy as two key descriptors of the lithium deposit size. Low surface energy polymers were found to promote larger deposits with smaller surface areas. This may be explained by a reduced interaction between the coating and the lithium surface and thus an increase in the interfacial energy. On the other hand, high dielectric constant polymers were found to increase the exchange current and gave larger lithium deposits due to the decreased overpotentials at a fixed current density. We also observed that the thickness of the polymer coating should be optimized for each individual polymer. Furthermore, polymer reactivity was found to strongly influence the Coulombic efficiency. Overall, this work offers new fundamental insights into lithium electrodeposition processes and provides direction for the design of new polymer coatings to better stabilize the lithium metal anode.