Hardware implementation of radial-basis neural networks with Gaussian activation functions on FPGA

Neural Computing and Applications - This article introduces a method for realizing the Gaussian activation function of radial-basis (RBF) neural networks with their hardware implementation on...     

Van der Waals SnSe2(1−x)S2x Alloys: Composition‐Dependent Bowing Coefficient and Electron–Phonon Interaction

The design of advanced functional materials with customized properties often requires the use of an alloy. This approach has been used for decades, but only recently to create van der Waals (vdW) alloys for applications in electronics, optoelectronics, and thermoelectrics. A route to engineering their physical properties is by mixing isoelectronic elements, as done for the SnSe_2(1?x)S_2x alloy. Here, by experiment and first‐principles modeling, it is shown that the value of x can be adjusted over a wide range, indicating good miscibility of the SnS₂ and SnSe₂ compounds. The x‐dependence of the indirect bandgap energy from E_ind = 1.20 eV for SnSe₂ to E_ind = 2.14 eV for SnS₂, corresponds to a large bowing coefficient b ≈ 1 eV, arising from volume deformation and charge exchange effects due to the different sizes and orbital energies of the S‐ and Se‐atoms. This also causes composition‐dependent phonon energy modes, electron–phonon interaction, and temperature dependence of E_ind. The alloys are exfoliable into thin layers with properties that depend on the composition, but only weakly on the layer thickness. This work shows that the electronic and vibrational properties of the SnSe_2(1?x)S_2x alloy and its thin layers provide a versatile platform for development and exploitation.     

卤化物钙钛矿射线探测器材料研究进展

卤化物钙钛矿由于具有高射线吸收系数、高载流子迁移率寿命乘积、可低温溶液法生长等特性, 有望突破传统高纯锗和碲锌镉探测器在成本、芯片兼容性和大尺寸成像等方面的制约, 成为新一代性能优异的室温射线探测材料。本文从卤化物钙钛矿材料的基本性质与射线探测原理出发, 介绍了2015年以来卤化物钙钛矿射线探测材料与器件的发展历程; 系统介绍了直接型射线探测器(强度、成像、能谱)及闪烁体探测器的最新研究成果; 分析了材料特性与器件结构对射线探测器性能的影响机制, 为今后更高效的卤化物钙钛矿射线探测器的开发提供参考。     

Stem Cell Therapy Enhances Motor Activity of Triceps Surae Muscle in Mice with Hereditary Peripheral Neuropathy

Impaired motor and sensory functions are the main features of Charcot–Marie–Tooth disease. Mesenchymal stem cell (MSCs) therapy is one of the possible treatments for this disease. It was assumed that MSCs therapy can improve the contractile properties of the triceps surae (TS) muscles in mice with hereditary peripheral neuropathy. Murine adipose-derived mesenchymal stromal cells (AD-MSCs) were obtained for transplantation into TS muscles of FVB-C-Tg(GFPU)5Nagy/J mice. Three months after AD-MSCs transplantation, animals were subjected to electrophysiological investigations. Parameters of TS muscle tension after intermittent high frequency electrical sciatic nerve stimulations were analyzed. It was found that force of TS muscle tension contraction in animals after AD-MSCs treatment was two-time higher than in untreated mice. Normalized values of force muscle contraction in different phases of electrical stimulation were 0.3 ± 0.01 vs. 0.18 ± 0.01 and 0.26 ± 0.03 vs. 0.13 ± 0.03 for treated and untreated animals, respectively. It is assumed that the two-fold increase in TS muscle strength was caused by stem cell therapy. Apparently, AD-MSCs therapy can promote nerve regeneration and partial restoration of muscle function, and thus can be a potential therapeutic agent for the treatment of peripheral neuropathies.     

Wavefront sensor based on the Talbot effect with the precorrected holographic grating

A holographic wavefront sensor based on the Talbot effect is proposed. Optical wavefronts are measured by sampling the light amplitude distribution with a two-dimensional (2D) precorrected holographic grating. The factors that allow changing an angular measurement range and a spatial resolution of the sensor are discussed. A comparative analysis with the Shack-Hartmann sensor is illustrated with some experimental results.     

Morphology and molecular orientation in sexithiophene and N,N′-bis (n-octyl)-dicyanoperylenediimide heterostructures

We report on the growth mode of N,N′-bis (n-octyl)-dicyanoperylenediimide (PDI-8CN₂) on sexithiophene (T6) thin films, studied with different structural, morphological and optical techniques. We aim to individuate the most favorable conditions for the realization of heterostructure devices. The crystalline quality was established by X-ray patterns and Atomic Force Microscopy (AFM) images, and found to be generally high. The anisotropic optical constants extracted from ellipsometry measurements shed light on the mean molecular orientation in the PDI-8CN₂ film. AFM images evidence two different growth modes: at T6 thickness less than 2 monolayers (ML), the growth of PDI-8CN₂ on T6 is favored with respect to SiO₂, while, at higher thickness (2-6 ML), the situation is reversed. An optimum T6 underlayer thickness of approximately 1 ML provides the best quality of PDI-8CN₂ layer corresponding to the highest island dimension, the highest molecular order parameter, and the lowest roughness. Spectrum broadening was observed for extinction coefficient of PDI-8CN₂ in the heterostructures, as compared with a sole material film, and explained by two effects: increase in molecular disorder and formation of charge transfer complexes.