Dynamics Analysis of Neuron Bursting under the Modulation of Periodic Stimulation

A nonsmooth neuron model with periodic excitation which can reproduce spiking and bursting behavior of cortical neurons is investigated in this paper. Based on nonsmooth bifurcation analysis, the mechanism of the bursting behavior induced by slow-changing periodical stimulation as well as the associated evolution with the variation of the stimulation is explored. The modulating character of the external excitation and the effect of the bifurcation occurring at the switching boundary of the vector field are presented

Monolayer heterojunction interactive hydrogels for high-freedom 4D shape reconfiguration by two-photon polymerization

Mimicking natural botanical/zoological systems has revolutionarily inspired four-dimensional (4D) hydrogel robotics, interactive actuators/machines, automatic biomedical devices, and self-adaptive photonics. The controllable high-freedom shape reconfiguration holds the key to satisfying the ever-increasing demands. However, miniaturized biocompatible 4D hydrogels remain rigorously stifled due to current approach/material limits. In this research, we spatiotemporally program micro/nano (μ/n) hydrogels through a heterojunction geometric strategy in femtosecond laser direct writing (fsLDW). Polyethylene incorporated N-isopropylacrylamide as programmable interactive materials here. Dynamic chiral torsion, site-specific mutation, anisotropic deformation, selective structural coloration of hydrogel nanowire, and spontaneous self-repairing as reusable μ/n robotics were identified. Hydrogel-materialized monolayer nanowires operate as the most fundamental block at nanometric accuracy to promise high freedom reconfiguration and high force-to-weight ratio/bending curvature under tight topological control. Taking use of this biomimetic fsLDW, we spatiotemporally constructed several in/out-plane self-driven hydrogel grippers, diverse 2D-to-3D transforming from the same monolayer shape, responsive photonic crystal, and self-clenched fists at μ/n scale. Predictably, the geometry-modulable hydrogels would open new access to massively-reproducible robotics, actuators/sensors for microenvironments, or lab-on-chip devices

Characterization Method for 3D Substructure of Nuclear Cell Based on Orthogonal Phase Images

A set of optical models associated with blood cells are introduced in this paper. All of these models are made up of different parts possessing symmetries. The wrapped phase images as well as the unwrapped ones from two orthogonal directions related to some of these models are obtained by simulation technique. Because the phase mutation occurs on the boundary between nucleus and cytoplasm as well as on the boundary between cytoplasm and environment medium, the equation of inflexion curve is introduced to describe the size, morphology, and substructure of the nuclear cell based on the analysis of the phase features of the model. Furthermore, a mononuclear cell model is discussed as an example to verify this method. The simulation result shows that characterization with inflexion curve based on orthogonal phase images could describe the substructure of the cells availably, which may provide a new way to identify the typical biological cells quickly without scanning

Simulation and Experimental Study of Terahertz Wave Transmission Characteristics Based on Periodic Metal Open Resonant Ring Structures

Different open resonant ring structures with substrate of polyimide were designed. The transmission characteristics of the structures for terahertz wave were investigated by simulation and experiment. The results show that the transmission peak of the structures moves to high frequency with increase of thickness of the metal layer. With increase of substrate thickness, the transmission peak moved to low frequency and the transmissivity decreased. The influence of number of “C” shape open resonant rings in the unit structure on the transmission characteristics of terahertz wave was also studied. It is found that when the number of “C” shape open resonant rings increases from one to two, more transmission peaks appeared in the frequency of 0.2–2 THz. The transmissivity of the designed structures was tested by terahertz time-domain spectrometer (THz-TDS). The experimental results showed good agreement to the simulation results

Silver Clusters as Robust Nodes and π–<i>A</i>ctivation Sites for the Construction of Heterogeneous Catalysts for the Cycloaddition of Propargylamines

The use and transformation of carbon dioxide as a C1 source into valuable chemical products using cheap industrial chemicals under mild reaction conditions fulfill the requirements of atom economy in the chemical industry. In this paper, two new silver-cluster-based frameworks were synthesized by incorporating thiourea on the backbone of the tripodal ligands. Given their large pores, high density of catalytic sites, and appropriate coordination geometries, these heterogeneous materials could be used as high-efficiency π-activation catalysts in the atom-economical cycloaddition of propargylamines with carbon dioxide. The loading of 0.1 mol % catalysts enabled the almost complete transformation of the propargylamines into oxazolidinones at atmospheric pressure and room temperature. DFT calculations show significant charge accumulation regions with π* symmetry on C atoms associated with the acetylene bond along the Ag–C directions and charge depletion regions with σ symmetry along the C–C direction, further supporting the important role of silver-cluster-based catalysts in π* activation of substrates for subsequent reactions with approaching CO₂. The crystallinity of the frameworks allowed the structure of the encapsulated substrates and the interactions of the CC bonds in the active intermediates to be clearly observed. The recyclability and high turnover number of the cycloaddition reaction demonstrate the broad potential applications of these designed materials as π-activation catalysts for practical applications in the chemical industry