A Derivative-Free Mesh Optimization Algorithm for Mesh Quality Improvement and Untangling

We propose a derivative-free mesh optimization algorithm, which focuses on improving the worst element quality on the mesh. The mesh optimization problem is formulated as a min-max problem and solved by using a downhill simplex (amoeba) method, which computes only a function value without needing a derivative of Hessian of the objective function. Numerical results show that the proposed mesh optimization algorithm outperforms the existing mesh optimization algorithm in terms of improving the worst element quality and eliminating inverted elements on the mesh

Reversible intercalation of methyl viologen as a dicationic charge carrier in aqueous batteries.

The interactions between charge carriers and electrode structures represent one of the most important considerations in the search for new energy storage devices. Currently, ionic bonding dominates the battery chemistry. Here we report the reversible insertion of a large molecular dication, methyl viologen, into the crystal structure of an aromatic solid electrode, 3,4,9,10-perylenetetracarboxylic dianhydride. This is the largest insertion charge carrier when non-solvated ever reported for batteries; surprisingly, the kinetic properties of the (de)insertion of methyl viologen are excellent with 60% of capacity retained when the current rate is increased from 100 mA g-1 to 2000 mA g-1. Characterization reveals that the insertion of methyl viologen causes phase transformation of the organic host, and embodies guest-host chemical bonding. First-principles density functional theory calculations suggest strong guest-host interaction beyond the pure ionic bonding, where a large extent of covalency may exist. This study extends the boundary of battery chemistry to large molecular ions as charge carriers and also highlights the electrochemical assembly of a supramolecular system

Diffusion-free Grotthuss topochemistry for high-rate and long-life proton batteries

The design of Faradaic battery electrodes that exhibit high rate capability and long cycle life equivalent to those of the electrodes of electrical double-layer capacitors is a big challenge. Here we report a strategy to fill this performance gap using the concept of Grotthuss proton conduction, in which proton transfer takes place by means of concerted cleavage and formation of O-H bonds in a hydrogen-bonding network. We show that in a hydrated Prussian blue analogue (Turnbull's blue) the abundant lattice water molecules with a contiguous hydrogen-bonding network facilitate Grotthuss proton conduction during redox reactions. When using it as a battery electrode, we find high-rate behaviours at 4,000 C (380 Ag-1, 508 mA cm(-2)), and a long cycling life of 0.73 million cycles. These results for diffusion-free Grotthuss topochemistry of protons, in contrast to orthodox battery electrochemistry, which requires ion diffusion inside electrodes, indicate a potential direction to revolutionize electrochemical energy storage for high-power applications

25th annual computational neuroscience meeting: CNS-2016

The same neuron may play different functional roles in the neural circuits to which it belongs. For example, neurons in the Tritonia pedal ganglia may participate in variable phases of the swim motor rhythms [1]. While such neuronal functional variability is likely to play a major role the delivery of the functionality of neural systems, it is difficult to study it in most nervous systems. We work on the pyloric rhythm network of the crustacean stomatogastric ganglion (STG) [2]. Typically network models of the STG treat neurons of the same functional type as a single model neuron (e.g. PD neurons), assuming the same conductance parameters for these neurons and implying their synchronous firing [3, 4]. However, simultaneous recording of PD neurons shows differences between the timings of spikes of these neurons. This may indicate functional variability of these neurons. Here we modelled separately the two PD neurons of the STG in a multi-neuron model of the pyloric network. Our neuron models comply with known correlations between conductance parameters of ionic currents. Our results reproduce the experimental finding of increasing spike time distance between spikes originating from the two model PD neurons during their synchronised burst phase. The PD neuron with the larger calcium conductance generates its spikes before the other PD neuron. Larger potassium conductance values in the follower neuron imply longer delays between spikes, see Fig. 17.Neuromodulators change the conductance parameters of neurons and maintain the ratios of these parameters [5]. Our results show that such changes may shift the individual contribution of two PD neurons to the PD-phase of the pyloric rhythm altering their functionality within this rhythm. Our work paves the way towards an accessible experimental and computational framework for the analysis of the mechanisms and impact of functional variability of neurons within the neural circuits to which they belong

High-Energy Lithium-Sulfur Batteries and Non-Metallic Ion Aqueous Batteries: Integrating Experiment and Theoretical Modeling

Humanities have been craving more freedom and conveniences in whatever form. Carriages evolved to cars and ultimately to aircraft so that one can reach any place in the globe within a day. The mobile phone has enabled people to make a phone call without a need to find a phone booth, and laptops gave us conveniences to work outside of the office. Even with those benefits, people are still looking for more freedom by reducing the time of being connected to the charging stations to recharge batteries in your portable devices and even electrified transportations. To quench the thirst, a grand mission given to battery scientists is to boost up the energy density of batteries so that you can use your portable devices lengthy and drive farther without frequent charge. However, the current lithium-ion batteries (LIB) are facing capacity limitation due to the inherent Li storage performance of graphite and transition metal (TM) oxides. As a result, multiple promising Li-based chemistries were introduced during the past decade including lithium-sulfur (Li-S) batteries. Although those technologies promise more than five times of discharge capacity compared to that of state-of-the-art TM-based cathodes, their residence is still limited inside the laboratory due to the critical reasons that are usually being swept under the rug in academic-level researches. Not only the batteries for portable devices, but stationary batteries are also another important equipment to store electricity for household use and auxiliary power supply. As electricity has no shelf life, it translates into poor futuristic usage without proper storage devices albeit we feel it is ubiquitous these days. That is, the generation and consumption of electricity should come together, where the energy storage device is incongruous with the intermittency of the power generated from renewable sources. Pumped hydropower is a globally used method but a geographical requirement for the operation limits the wide applicability of it. Hence, rechargeable aqueous batteries, which are safe and cheap, are the best alternatives by ‘directly’ storing electricity while removing the location restriction and rendering us the time-independent options to utilize the resource. Especially, non-metallic charge carriers have not received attention as metal ions have been dominating the battery fields, which was deemed common sense. Here we suggest the possibility of using chemical waste to be utilized as the electrolyte source by showcasing prolonged rechargeable aqueous batteries using common acids as major electrolyte ingredients. To that end, high-energy Li-S batteries and cheap but safe aqueous batteries have been called for commercialization. Based on the purposes, different materials are applied for each type of battery, however, the all-encompassing underlying operation mechanism is more than similar: ‘chemical bonding’ of species inside the electrolyte and host electrode materials, which directly translates the performance of the electrochemical cells. Herein, this dissertation addresses three main topics. The first topic focuses on high-energy Li-S batteries towards a more practical-level under harsh conditions. In the first part, the synthesis of nano-sized ZnS crystals on the carbon/sulfur composites for better wettability of sulfur cathodes is introduced. In that work, we applied the facile coating method to the composite to enable the sulfur cathode work under the lean electrolyte regime, then its electrochemical performance and working chemistry are revealed. The second part describes a highly reversible lithium metal anode by introducing the secondary solvent, fluorinated ether, to be compatible with both anode and cathode for high gravimetric energy density Li-S batteries. The effect of co-solvent at the molecular level is studied to elucidate its chemical bonding between salts and solvents. Lastly, a full cell is tested under the practical level conditions, including lean electrolyte and the limited amount of anode that was not studied before. This information can be a good guideline for the development of feasible Li-S cells forward. The second topic presents theoretical modeling of non-metallic ion aqueous batteries. Here we used density functional theory (DFT) calculations to understand the unique chemical bonding between non-metal charge carriers and host materials. As stated before, simple acids were used as electrolytes and unexpected electrochemical performance was elucidated by exploring electron distribution via quantum chemistry-based modeling studies. We reveal proton, ammonium, and methyl viologen can be reversibly inserted via hydrogen bonds and exclusive host-guest interactions, where this finding can open a new avenue for the development of viable non-metallic ion aqueous batteries. The third part discusses integrating theoretical modeling with experimental results to distinguish the local Li environment in the layered LiMn0.5Ni0.5O2 for LIB cathode studies. We compared the experimental NMR spectrum and calculated NMR peaks based on particular TM orderings, where we can correlate the effect of annealing temperature in the experiment and composition of each TM arrangement. This information advises the new possibility of atomistic-scale interpretation by linking the DFT calculation and experimental NMR spectrum to comprehend the sub-nano scale world with confidence

Design of Tool Clamping Device Based on a Shape Memory Alloy

This paper describes a tool-clamping/unclamping mechanism for application of a micro-spindle. The mechanism is based on one-way shape memory effect and interference-fit. The corresponding mathematical models and a few considerable design parameters are mentioned in this paper. Especially, necessary conditions for the clamping and unclamping operation are investigated through finite element analysis. The analysis results show that the differences between the diametral deformations of the tool holder in high temperature and that in low temperature are increased according to amounts of the interference. Thus the less interference between the tool-holder and the ring, the less tolerance to allow the clamping and unclamping operation because the inner diameter of the tool holder in high temperature should be smaller than the diameter of the tool shank, and that in low temperature should be larger than the diameter of the tool shank. In addition, the design for maximization of clamping force are investigated based on finite element analysis. The results show that the more amounts of the interference, the more clamping force. As the result, the interference should be considered as a important factor to maximize the tool clamping force.clos

An ethyl methyl sulfone co-solvent eliminates macroscopic morphological instabilities of lithium metal anode

© 2019 The Royal Society of Chemistry. Lithium metal anodes suffer from a short cycle life, and the parasitic reactions of lithium with electrolytes are widely observed. Common sense is to avoid such reactions. Herein, we head in the opposite direction by using an oxidizing co-solvent, ethyl methyl sulfone, in the electrolyte, which addresses the 'dendrite' issue entirely, resulting in a dense and macroscopically smooth surface morphology of the plated lithium. However, a dendrite-free lithium metal anode does not necessarily exhibit a high coulombic efficiency

Suppressed prefrontal neuronal firing variability and impaired social representation in IRSp53-mutant mice

© 2022, Kim et al.Social deficit is a major feature of neuropsychiatric disorders, including autism spectrum disorders, schizophrenia, and attention-deficit/hyperactivity disorder, but its neural mechanisms remain unclear. Here, we examined neuronal discharge characteristics in the medial prefrontal cortex (mPFC) of IRSp53/Baiap2-mutant mice, which show social deficits, during social approach. We found a decrease in the proportion of IRSp53-mutant excitatory mPFC neurons encoding social information, but not that encoding non-social information. In addition, the firing activity of IRSp53-mutant neurons was less differential between social and non-social targets. IRSp53-mutant excitatory mPFC neurons displayed an increase in baseline neuronal firing, but decreases in the variability and dynamic range of firing as well as burst firing during social and non-social target approaches compared to wild-type controls. Treatment of memantine, an NMDA receptor antagonist that rescues social deficit in IRSp53-mutant mice, alleviates the reduced burst firing of IRSp53-mutant pyramidal mPFC neurons. These results suggest that suppressed neuronal activity dynamics and burst firing may underlie impaired cortical encoding of social information and social behaviors in IRSp53-mutant mice.11Nsciescopu

Excitatory synapses and gap junctions cooperate to improve Pv neuronal burst firing and cortical social cognition in Shank2-mutant mice

© 2021, The Author(s).NMDA receptor (NMDAR) and GABA neuronal dysfunctions are observed in animal models of autism spectrum disorders, but how these dysfunctions impair social cognition and behavior remains unclear. We report here that NMDARs in cortical parvalbumin (Pv)-positive interneurons cooperate with gap junctions to promote high-frequency (>80 Hz) Pv neuronal burst firing and social cognition. Shank2–/– mice, displaying improved sociability upon NMDAR activation, show impaired cortical social representation and inhibitory neuronal burst firing. Cortical Shank2–/– Pv neurons show decreased NMDAR activity, which suppresses the cooperation between NMDARs and gap junctions (GJs) for normal burst firing. Shank2–/– Pv neurons show compensatory increases in GJ activity that are not sufficient for social rescue. However, optogenetic boosting of Pv neuronal bursts, requiring GJs, rescues cortical social cognition in Shank2–/– mice, similar to the NMDAR-dependent social rescue. Therefore, NMDARs and gap junctions cooperate to promote cortical Pv neuronal bursts and social cognition.11Nsciescopu