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Atomistic Insight into Ion Transport and Conductivity in Ga/Al-Substituted Li <sub/>7</sub> La <sub/>3</sub> Zr <sub/>2</sub> O <sub/>12</sub> Solid Electrolytes
摘要： Garnet-structured Li7La3Zr2O12 is a promising solid electrolyte for next-generation solid-state Li batteries. However, sufficiently fast Li-ion mobility required for battery applications only emerges at high temperatures, upon a phase transition to cubic structure. A well-known strategy to stabilize the cubic phase at room temperature relies on aliovalent substitution; in particular, the substitution of Li+ by Al3+ and Ga3+ ions. Yet, despite having the same formal charge, Ga3+ substitution yields higher conductivities (10?3 S/cm) than Al3+ (10?4 S/cm). The reason of such difference in ionic conductivity remains a mystery. Here we use molecular dynamic simulations and advanced sampling techniques to precisely unveil the atomistic origin of this phenomenon. Our results show that Li+ vacancies generated by Al3+ and Ga3+ substitution remain adjacent to Ga3+ and Al3+ ions, without contributing to the promotion of Li+ mobility. However, while Ga3+ ions tend to allow limited Li+ diffusion within their immediate surroundings, the less repulsive interactions associated with Al3+ ions lead to a complete blockage of neighboring Li+ diffusion paths. This effect is magnified at lower temperatures, and explains the higher conductivities observed for Ga-substituted systems. Overall this study provides a valuable insight into the fundamental ion transport mechanism in the bulk of Ga/Al-substituted Li7La3Zr2O12 and paves the way for rationalizing aliovalent substitution design strategies for enhancing ionic transport in these materials.
关键词： Li-ion conductivity/diffusion,enhanced sampling hybrid Monte Carlo,Molecular Dynamics,GSHMC,Ga/Al-substituted LLZO,Solid electrolytes
更新于2025-09-04 15:30:14
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Characterization of Retinal Functionality at Different Eccentricities in a Diurnal Rodent
摘要： Although the properties of the neurons of the visual system that process central and peripheral regions of the visual field have been widely researched in the visual cortex and the LGN, they have scarcely been documented for the retina. The retina is the first step in integrating optical signals, and despite considerable efforts to functionally characterize the different types of retinal ganglion cells (RGCs), a clear account of the particular functionality of cells with central vs. peripheral fields is still wanting. Here, we use electrophysiological recordings, gathered from retinas of the diurnal rodent Octodon degus, to show that RGCs with peripheral receptive fields (RF) are larger, faster, and have shorter transient responses. This translates into higher sensitivity at high temporal frequencies and a full frequency bandwidth when compared to RGCs with more central RF. We also observed that imbalances between ON and OFF cell populations are preserved with eccentricity. Finally, the high diversity of functional types of RGCs highlights the complexity of the computational strategies implemented in the early stages of visual processing, which could inspire the development of bio-inspired artificial systems.
关键词： retina,central vs. periphery,MEA,RGCs,spatiotemporal analysis,receptive field properties
更新于2025-09-04 15:30:14
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Designing of UCNPs@Bi@SiO2 Hybrid Theranostic Nanoplatforms for Simultaneous Multimodal Imaging and Photothermal Therapy
摘要： Herein, a novel multifunctional nanoplatform was designed towards multimodality imaging and photothermal therapy (PTT). It was found that Bi nanoparticles could grow in situ on the surface of NaYF4:20%Yb,2%Er@NaYF4:40%Yb@NaGdF4 core-shell nanoparticles (labeled as UCNPs). In this structure, UCNPs were mainly employed as upconversion luminescence (UCL) imaging agent, while the Bi nanoparticles worked as effective CT imaging and photothermal agent. Importantly, a dense SiO2 shell was employed to protect the Bi nanoparticles from oxidation, and it also endowed the nanoplatform with excellent hydrophilic ability. The effective UCL/CT imaging and PTT performances were emphasized by a series of in vivo experiments, which suggest that the integrated nanoplatform with imaging and therapy functions show great promise in the biomedical field.
关键词： Theranostic Nanoplatform,UCL imaging,CT imaging,Photothermal Therapy,UCNPs
更新于2025-09-04 15:30:14
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Surface-Mediated Processes for Energy Production and Conversion: Critical Considerations in Model System Design for DFT Calculations
摘要： Theoretical analysis of surface chemistry using Density Functional Theory (DFT) calculations has significantly contributed to our understanding of catalyzed processes related to energy production or consumption by providing performance descriptors, reaction mechanisms, and physical pictures of how electronic structure relates to catalytic reactivity. The identification of reactivity correlations within databases of DFT calculations has elucidated trends between active site composition (for metals, oxides, nitrides, phosphides, perovskites, etc.) or structure and catalytic reactivity or reactions including CO2 hydrogenation, NH3 synthesis, and the electrochemical oxygen evolution reaction (OER), among others. DFT calculations are now ubiquitously used in the analysis of catalytic processes due to the existence of easy to use software packages. It has become commonplace for publications to include combined experimental and theoretical treatment of a catalytic process, with the aim of providing a holistic picture of a reaction mechanism, an understanding of why materials exhibit their catalytic behaviors, or simply supporting inferences made from experimental measurements. While the combined approach is laudable, it is critical to recognize the challenges associated with using DFT calculations of model systems to understand experimental systems and how those challenges influence the conclusions derived from the calculations.
更新于2025-09-04 15:30:14
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Discordant Responses to MAPK Pathway Stimulation Include Axonal Growths in Adult Drosophila Photoreceptors
摘要： Wallenda (WND) is the Drosophila member of a conserved family of dual leucine-zipper kinases (DLK) active in both neuronal regeneration and degeneration. We examined the role of WND over-expression on sensory neuron morphology by driving WND in multiple subtypes of Drosophila photoreceptors. WND overexpression under control of the pan-retinal GAL4 driver GMR causes multiple photoreceptor defects including cell death, rhabdomere degeneration, and axonal sprouting. Individual photoreceptor subtypes were assayed using GAL4 drivers speci?c for each photoreceptor class. Many R7 and R8 cells exhibit axonal sprouting while some show cell degeneration. Delaying the onset of WND overexpression until 20 days of age showed that older adult R7 cells retain the ability to initiate new axon growth. R1–6 photoreceptor cells degenerate in response to WND expression and exhibit rhodopsin loss and rhabdomere degeneration. RNAi knockdown of the MAPK signaling components Kayak (KAY) and Hemipterous (HEP) attenuates the WND-induced loss of Rh1 rhodopsin. UAS-induced HEP expression is similar to WND expression, causing degeneration in R1–6 photoreceptors and axonal sprouting in R7 photoreceptors. These results demonstrate that WND in adult Drosophila photoreceptor cells acts through MAPK signaling activity with both regenerative and degenerative responses. These photoreceptors provide a tractable experimental model to reveal cellular mechanisms driving contradictory WND signaling responses.
关键词： degeneration,dual leucine kinase,Drosophila,axon regeneration,photoreceptors
更新于2025-09-04 15:30:14
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Security Authentication of Dual Chaotic Image Watermarking in Spatial Domain with Spatial and Frequency Domain Characteristics Analysis
摘要： This article presents an advanced dual chaotic watermarking scheme to improve information security. To ensure confidentiality in digital image transmission, a secure dual watermarking scheme is proposed by applying the chaotic logistic system and hyper-chaotic dynamical system. Chaotic watermarking was conducted in the spatial domain, where suboptimal secure hashing with a variable length was selected in preprocessing stages. The secret key was generated by the chaotic sequence for pixel shuffling using a chaotic logistic map, so that a controlled amount of distortion was inserted into the host digital image. Watermarking was proceeded after the chaotic watermark had been embedded into the shuffled image. To strengthen the security, the hyper-chaotic system was used to generate chaotic blocks for block scrambling in order to achieve dual chaotic watermarking. Characteristics analysis was conducted for multiple examples in both spatial and frequency domains. Potential effects induced by the chaotic driving parameter on processing time and integrity authentication of chaotic dual watermarking were also analyzed in detail.
关键词： hashing,information security,shuffling,hyper-chaotic system,scrambling,watermarking,logistic map
更新于2025-09-04 15:30:14
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Detachment Dynamics of Graphene Nanoribbons on Gold
摘要： Metal-surface physisorbed graphene nanoribbons (GNRs) constitute mobile nanocontacts whose interest is simultaneously mechanical, electronic, and tribological. Previous work showed that GNRs adsorbed on Au(111) generally slide smoothly and superlubrically owing to incommensurability of their structures. We address here the nanomechanics of detachment, such as realized when one end is picked up and lifted by an AFM cantilever. AFM nanomanipulations and molecular-dynamics (MD) simulations identify two successive regimes, characterized by (i) a progressively increasing local bending, accompanied by the smooth sliding of the adhered part, followed by (ii) a stick-slip dynamics involving sudden bending relaxation associated to intermittent jumps of the remaining adhered GNR segment and tail end. AFM measurements of the vertical force exhibit oscillations which, compared with MD simulations, can be associated to the successive detachment of individual GNR unit cells of length 0.42 nm. Extra modulations within one single period are caused by step-like advancements of the still-physisorbed part of the GNR. The sliding of the incommensurate moir′e pattern that accompanies the GNR lifting generally yields an additional long-period oscillation: while almost undetectable when the GNR is aligned in the standard “R30” orientation on Au(111), we predict that such feature should become prominent in the alternative rotated “R0” orientation on the same surface, or on a different surface, such as perhaps Ag(111).
关键词： molecular-dynamics simulations,gold,AFM,graphene nanoribbons,detachment dynamics
更新于2025-09-04 15:30:14
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Frequency Conversion in KTP Crystal and Its Isomorphs
摘要： We report the results of an analysis of the functional capabilities of the KTP crystal and its isomorphs for nonlinear-optical frequency conversion of all types of interactions in the transparency range of the crystal. The possibility of implementing angle, wavelength (frequency), and temperature-noncritical phase matching is shown.
关键词： temperature-noncritical mode,nonlinear crystals,frequency conversion,KTP and isomorphs,functional capabilities
更新于2025-09-04 15:30:14
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Monoisotopic Ensembles of Silicon-Vacancy Color Centers with Narrow-Line Luminescence in Homoepitaxial Diamond Layers Grown in H <sub/>2</sub> –CH <sub/>4</sub> – <sup> [ <i>x</i> ] </sup> SiH <sub/>4</sub> Gas Mixtures ( <i>x</i> = 28, 29, 30)
摘要： Silicon-vacancy (SiV?) color center in diamond is of high interest for applications in nanophotonics and quantum information technologies, as a single photon emitter with excellent spectral properties. To obtain spectrally identical SiV? emitters, we doped homoepitaxial diamond ?lms in situ with 28Si, 29Si, and 30Si isotopes using isotopically enriched (>99.9%) silane SiH4 gas added in H2?CH4 mixtures in the course of the microwave plasma-assisted chemical vapor deposition process. Zero-phonon line components as narrow as ～4.8 GHz were measured in both absorption and luminescence spectra for the monoisotopic SiV? ensembles with a concentration of a few parts per billion. We determined with high accuracy the Si isotopic energy shift of SiV? zero-phonon line. The SiV? emission intensity is shown to be easily controlled by the doped epi?lm thickness. Also, we identi?ed and characterized the localized single photon SiV? sources. The developed doping process opens a way to produce the SiV? emitter ensembles with energy con?ned in an extremely narrow range.
关键词： diamond,silicon-vacancy center,CVD synthesis,optical absorption,photoluminescence,doping,silicon isotope
更新于2025-09-04 15:30:14
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A Novel Multi-Exposure Image Fusion Method Based on Adaptive Patch Structure
摘要： Multi-exposure image fusion methods are often applied to the fusion of low-dynamic images that are taken from the same scene at different exposure levels. The fused images not only contain more color and detailed information, but also demonstrate the same real visual effects as the observation by the human eye. This paper proposes a novel multi-exposure image fusion (MEF) method based on adaptive patch structure. The proposed algorithm combines image cartoon-texture decomposition, image patch structure decomposition, and the structural similarity index to improve the local contrast of the image. Moreover, the proposed method can capture more detailed information of source images and produce more vivid high-dynamic-range (HDR) images. Speci?cally, image texture entropy values are used to evaluate image local information for adaptive selection of image patch size. The intermediate fused image is obtained by the proposed structure patch decomposition algorithm. Finally, the intermediate fused image is optimized by using the structural similarity index to obtain the ?nal fused HDR image. The results of comparative experiments show that the proposed method can obtain high-quality HDR images with better visual effects and more detailed information.
关键词： texture information entropy,adaptive selection,multi-exposure image fusion,patch structure decomposition
更新于2025-09-04 15:30:14