Reproduced neuron-like excitability and bursting synchronization of memristive Josephson junctions loaded inductor.

Employing electronic component including memristor and Josephson junction to mimic biological neuron or synapse has elicited intense research in recent years. Neurons described by nonlinear oscillators can exhibit complex electrical activities. Josephson junctions are excellent candidates for neuron-inspired components because of their physical properties with low energy costs and high efficiency. In this paper, we revisit a prior work on memristive Josephson junction (MJJ) to identify the dynamical mechanisms to mimic neuron-like excitability and spiking. The inductive memristive Josephson junction (L-MJJ) model is further developed by adding an inductor with internal resistor. It is found that the L-MJJ model can reproduce square-wave bursting of the classical neuronal model from the neurodynamics point of view. The coupling L-MJJ oscillators can achieve in-phase and antiphase bursting synchronization similar with nonlinear coupling neurons. From the framework of nonlinear dynamics theory, this work aspires to build effective bridge between superconducting physics and theoretical neuroscience. Obtained results confirm the potential feasibility of this junction in designing a neuron-inspired computation to explore dynamics of larger-scale neuromorphic network.

Physical approach of a neuron model with memristive membranes.

The membrane potential of a neuron is mainly controlled by the gradient distribution of electromagnetic field and concentration diversity between intracellular and extracellular ions. Without considering the thickness and material property, the electric characteristic of cell membrane is described by a capacitive variable and output voltage in an equivalent neural circuit. The flexible property of cell membrane enables controllability of endomembrane and outer membrane, and the capacitive properties and gradient field can be approached by double membranes connected by a memristor in an equivalent neural circuit. In this work, two capacitors connected by a memristor are used to mimic the physical property of two-layer membranes, and an inductive channel is added to the neural circuit. A biophysical neuron is obtained and the energy characteristic, dynamics, self-adaption is discussed, respectively. Coherence resonance and mode selection in adaptive way are detected under noisy excitation. The distribution of average energy function is effective to predict the appearance of coherence resonance. An adaptive law is proposed to control the capacitive parameters, and the controllability of cell membrane under external stimulus can be explained in theoretical way. The neuron with memristive membranes explains the self-adaptive mechanism of parameter changes and mode transition from energy viewpoint.

Research on innovative mechanisms of financial agglomeration enabling green coordinated development in the Yangtze River Delta of China.

Exploring innovative mechanisms for financial agglomeration affecting the green coordinated development of China's Yangtze River Delta is important for the city to take advantage of financial and innovative resources to promote high-quality green development. Using panel data from 41 cities in the Yangtze River Delta region from 2003 to 2019, the intermediate effects model and spatial Durbin model are conducted to deeply explore the impact of financial agglomeration on coordinated green development and the intermediary role of innovation. Results show that, first, financial agglomeration can drive green technology innovation to significantly improve the coordinated development of "production greening - social optimization - environmental protection deepening". Second, financial agglomeration significantly improves the green coordinated development in neighboring areas through inter-city innovative spatial connections, and the spatial spillover effect tends to decay with the critical point of the maximum impact range at 240 km. Third, the intermediate mechanism of green technology innovation performs well in the high-level financial agglomeration and financial capital agglomeration areas. The Banking and securities industries are the leading factors in financial capital agglomeration. Low-level financial agglomeration and financial personnel agglomeration cannot play the "driving green" role of the innovation mechanism.

Research on the impact of financial agglomeration on the coordinated development of urban ecological green: based on the empirical comparison of four metropolitan areas in the Yangtze River Delta of China.

As key carriers of new urbanization, metropolitan areas should pay more attention to the green and coordinated development of economy, society, and environment. Finance is an important tool to support China's high-quality development. Exploring the key dynamics and mechanisms of financial agglomeration for a green and coordinated development is important to obtain strategic support for the green development of the Yangtze River Delta metropolitan area. Using panel data of 25 prefecture-level cities in the four major metropolitan areas of the Yangtze River Delta region from 2003 to 2019, a Dubin model of three types of spatial weight matrices is constructed to explore the impact of financial agglomeration on coordinated ecological green development. Results show that, first, the positive local and neighborhood effects of financial agglomeration on the coordinated ecological green development are mainly reflected in the Hefei, Hangzhou, and Shanghai metropolitan areas and that the intensity of such effect decreases sequentially. Information transfer and technology correlation are important mechanisms to improve the local effect of financial agglomeration, and the neighborhood effect varies from one metropolitan area to another. Second, in addition to the adverse impact of the concentration of financial personnel on the ecological green integration, the agglomeration of securities, banking, and insurance industries can release "green driving potential energy," and the intensity of contribution gradually weakens. Third, the financial agglomeration of Shanghai exerts the strongest radiation effect, those of Nanjing and Hangzhou respectively demonstrate a "U"-shaped and inverted "U"-shaped impact, and that of Hefei does not play a role.

Transition between multimode oscillations in a loaded hair bundle.

In this paper, we study the dynamics of an autonomous system for a hair bundle subject to mechanical load. We demonstrated the spontaneous oscillations that arise owing to interactions between the linear stiffness and the adapting stiffness. It is found that by varying the linear stiffness, the system can induce a weakly chaotic attractor in a certain region where the stable periodic orbit is infinitely close to a parabolic curve composed of unstable equilibrium points. By altering the adapting stiffness associated with the calcium concentration, the system is able to trigger the transition from the bistable resting state, through a pair of symmetric Hopf bifurcation, into the bistable limit cycle, even to the chaotic attractor. At a negative adapting stiffness, the system exhibits a double-scroll chaotic attractor. According to the method of qualitative theory of fast-slow decomposition, the trajectory of a double-scroll chaotic attractor in the whole system depends upon the symmetric fold/fold bifurcation in a fast system. Furthermore, the control of the adapting stiffness in the improved system with two slow variables can trigger a new transition from the bistable resting state into the chaotic attractor, even to the hyperchaotic attractor by observing the Lyapunov exponent.

Calculation of Hamilton energy and control of dynamical systems with different types of attractors.

Strange attractors can be observed in chaotic and hyperchaotic systems. Most of the dynamical systems hold a finite number of attractors, while some chaotic systems can be controlled to present an infinite number of attractors by generating infinite equilibria. Chaos can also be triggered in some dynamical systems that can present hidden attractors, and the attractors in these dynamical systems find no equilibria and the basin of attraction is not connected with any equilibrium (the equilibria position meets certain restriction function). In this paper, Hamilton energy is calculated on the chaotic systems with different types of attractors, and energy modulation is used to control the chaos in these systems. The potential mechanism could be that negative feedback in energy can suppress the phase space and oscillating behaviors, and thus, the chaotic, periodical oscillators can be controlled. It could be effective to control other chaotic, hyperchaotic and even periodical oscillating systems as well.

Chitosan-based nanoparticles for improved anticancer efficacy and bioavailability of mifepristone.

In addition to its well-known abortifacient effect, mifepristone (MIF) has been used as an anticancer drug for various cancers in many studies with an in-depth understanding of the mechanism of action. However, application of MIF is limited by its poor water solubility and low oral bioavailability. In this work, we developed a drug delivery system based on chitosan nanoparticles (CNs) to improve its bioavailability and anticancer activity. The MIF-loaded chitosan nanoparticles (MCNs) were prepared by convenient ionic gelation techniques between chitosan (Cs) and tripolyphosphate (TPP). The preparation conditions, including Cs concentration, TPP concentration, Cs/MIF mass ratio, and pH value of the TPP solution, were optimized to gain better encapsulation efficiency (EE) and drug loading capacity (DL). MCNs prepared with the optimum conditions resulted in spherical particles with an average size of 200 nm. FTIR and XRD spectra verified that MIF was successfully encapsulated in CNs. The EE and DL of MCNs determined by HPLC were 86.6% and 43.3%, respectively. The in vitro release kinetics demonstrated that MIF was released from CNs in a sustained-release manner. Compared with free MIF, MCNs demonstrated increased anticancer activity in several cancer cell lines. Pharmacokinetic studies in male rats that were orally administered MCNs showed a 3.2-fold increase in the area under the curve from 0 to 24 h compared with free MIF. These results demonstrated that MCNs could be developed as a potential delivery system for MIF to improve its anticancer activity and bioavailability.

Model of electrical activity in cardiac tissue under electromagnetic induction.

Complex electrical activities in cardiac tissue can set up time-varying electromagnetic field. Magnetic flux is introduced into the Fitzhugh-Nagumo model to describe the effect of electromagnetic induction, and then memristor is used to realize the feedback of magnetic flux on the membrane potential in cardiac tissue. It is found that a spiral wave can be triggered and developed by setting specific initials in the media, that is to say, the media still support the survival of standing spiral waves under electromagnetic induction. Furthermore, electromagnetic radiation is considered on this model as external stimuli, it is found that spiral waves encounter breakup and turbulent electrical activities are observed, and it can give guidance to understand the occurrence of sudden heart disorder subjected to heavily electromagnetic radiation.

Synthesis and Biological Evaluation of Novel Ursolic acid Derivatives as Potential Anticancer Prodrugs.

Ursolic acid (UA) is a natural product which has been shown to possess a wide range of pharmacological activities, in particular those with anticancer activity. In this study, 13 novel ursolic acid derivatives were designed and synthesized in an attempt to further improve compound potency. The structures of the newly synthesized compounds were confirmed using mass spectrometry, infrared spectroscopy, and (1) H NMR. The ability of the UA derivatives to inhibit cell growth was assayed against both various tumor cell lines and a non-pathogenic cell line, HELF. Analysis of theoretical toxicity risks for all derivatives was performed using OSIRIS and indicated that the majority of compounds would present moderate to low risks. Pharmacological results indicated that the majority of the derivatives were more potent growth inhibitors than UA. In particular, 5b demonstrated IC50 values ranging from 4.09 ± 0.27 to 7.78 ± 0.43 µm against 12 different tumor cell lines. Flow cytometry analysis indicated that 5b induced G0/G1 arrest in three of these cell lines. These results were validated by structural docking studies, which confirmed that UA could bind to cyclins D1 (Cyc D1) and cyclin-dependent kinases (CDK6), the key regulators of G0/G1 transition in cell cycle, while the piperazine moiety of 5b could bind with glucokinase (GK), glucose transporter 1 (GLUT1), and ATPase, which are the main proteins involved in cancer cell metabolism. Acridine orange/ethidium bromide staining confirmed that 5b was capable of inducing apoptosis and decreasing cell viability in a dose-dependent manner.