A new floating emulator for the flux-controlled memristor is introduced in this paper. The proposed emulator circuit is very simple and consists of only two current feedback operational amplifiers ...(CFOAs), two analog multipliers, three resistors, and two capacitors. The emulator can be configured as an incremental or decremental type memristor by using an additional switch. The mathematical model of the emulator is derived to characterize its behavior. The hysteresis behavior of the emulator is discussed in detail, showing that the pinched hysteresis loops in v-i plane depend not only on the amplitude-to-frequency ratio of the exciting signal but also on the time constant of the emulator circuit itself. Experimental tests are provided to validate the emulator’s workability.
Islet transplantation has shown promise as a curative therapy for type 1 diabetes (T1D). However, the side effects of systemic immunosuppression and limited long‐term viability of engrafted islets, ...together with the scarcity of donor organs, highlight an urgent need for the development of new, improved, and safer cell‐replacement strategies. Induction of local immunotolerance to prevent allo‐rejection against islets and stem cell derived β cells has the potential to improve graft function and broaden the applicability of cellular therapy while minimizing adverse effects of systemic immunosuppression. In this mini review, recent developments in non‐encapsulation, local immunomodulatory approaches for T1D cell replacement therapies, including islet/β cell modification, immunomodulatory biomaterial platforms, and co‐transplantation of immunomodulatory cells are discussed. Key advantages and remaining challenges in translating such technologies to clinical settings are identified. Although many of the studies discussed are preliminary, the growing interest in the field has led to the exploration of new combinatorial strategies involving cellular engineering, immunotherapy, and novel biomaterials. Such interdisciplinary research will undoubtedly accelerate the development of therapies that can benefit the whole T1D population.
An overview of different local immunomodulatory approaches in β cell replacement therapies is provided. Strategies in islet/β cell modification with immunomodulatory proteins immobilized on the cell surface or released to the local microenvironment, biomaterial platforms presenting or delivering immunomodulatory signals, and co‐transplantation of immunomodulatory cells are discussed.
Hydrogels have long been explored as attractive materials for biomedical applications given their outstanding biocompatibility, high water content, and versatile fabrication platforms into materials ...with different physiochemical properties and geometries. Nonetheless, conventional hydrogels suffer from weak mechanical properties, restricting their use in persistent load‐bearing applications often required of materials used in medical settings. Thus, the fabrication of mechanically robust hydrogels that can prolong the lifetime of clinically suitable materials under uncompromising in vivo conditions is of great interest. This review focuses on design considerations and strategies to construct such tough hydrogels. Several promising advances in the proposed use of specialty tough hydrogels for soft actuators, drug delivery vehicles, adhesives, coatings, and in tissue engineering settings are highlighted. While challenges remain before these specialty tough hydrogels will be deemed translationally acceptable for clinical applications, promising preliminary results undoubtedly spur great hope in the potential impact this embryonic research field can have on the biomedical community.
Design strategies to construct tough hydrogels are outlined here, and promising advances in their use for soft actuators, drug delivery vehicles, adhesives, coatings, and in tissue engineering are highlighted. Translating promising research to clinical settings remains challenging but further advancements in the field will undoubtedly positively impact the biomedical community.
A fully integrated cross-coupled charge pump circuit with a new clock scheme has been presented in this paper. The new clock scheme ensures that all NMOS pre-charge transistors are turned off when ...the voltages of main clock signals are high. Notably, all PMOS transfer transistors will be turned off when the voltages of the main clock signals are low. As a result, the charge pump eliminates all of the reversion power loss and reduces the ripple voltage. The proposed charge pump has a better performance even in scenarios where the main clock signals are mismatched. The proposed charge pump circuit was simulated using spectre in the TSMC 0.18 µm CMOS process. The simulation results show that the proposed charge pump circuit has a high voltage conversion efficiency and low ripple voltage.
The self-assembly of gyroid-forming diblock copolymers confined in cylindrical geometry is studied using a combination of computer simulations and experiments. The simulations, based on a system ...qualitatively representative of poly(styrene-b-isoprene), are performed with cylindrical nanopores of different diameter (D) and surface selectivity. The effects of the pore size and surface selectivity on morphology are systematically investigated. Different morphological sequences are predicted for two gyroid-forming diblock copolymers. The experiments are carried out on two gyroid-forming poly(styrene-b-dimethylsiloxane) block copolymer samples confined in the core of continuous core−shell nanofibers of different diameters, which are obtained by a coaxial two-fluid electrospinning technique. The internal microphase-separated morphologies of these fibers are investigated by transmission electron microscopy (TEM). Both simulations and experiments demonstrate that a rich variety of structures spontaneously form for the gyroid-forming diblock copolymers, depending on the conditions of cylindrical confinement. Many of these confinement-induced structures are quite different from those of cylinder-forming or lamella-forming block copolymers. Simulations further show that these structures depend sensitively on the block copolymer composition, surface selectivity, and the ratio D/L 0 where L 0 is the period of the equilibrium gyroid phase. While the simulation and experimental systems are representative of different chemistries, the morphological predictions of simulations are qualitatively consistent with the experimental observations.
Despite the promise of RNA interference (RNAi) therapeutics, progress toward the clinic has been slowed by the difficulty of delivering short interfering RNA (siRNA) into cellular targets within the ...body. Nearly all siRNA delivery vehicles developed to date employ a single cationic or ionizable material. In order to increase the material space available for development of siRNA delivery therapeutics, this study examined the possibility of using binary combinations of ionizable lipid-like materials to synergistically achieve gene silencing. Interestingly, it was found that ineffective single lipid-like materials could be formulated together in a single delivery vehicle to induce near-complete knockdown of firefly luciferase and factor VII in HeLa cells and in mice, respectively. Microscopy experiments suggested that synergistic action resulted when combining materials that respectively mediated cellular uptake and endosomal escape, two important steps in the delivery process. Together, the data indicate that formulating lipid-like materials in combination can significantly improve siRNA delivery outcomes while increasing the material space available for therapeutic development. It is anticipated that this binary formulation strategy could be applicable to any siRNA delivery material in any target cell population that utilizes the two-step endosomal delivery pathway.
A library of cationic polymers, poly(beta‐amino alcohols) with a great chemical diversity are synthesized using combinatorial polymerization. These polymers, when immobilized on a surface, ...drastically affect the behavior of monocyte/macrophage cells in vitro and early inflammatory reactions in vivo. Certain polymers are found capable of mitigating the foreign‐body responses.
The brain is a complex network system in which a large number of neurons are widely connected to each other and transmit signals to each other. The memory characteristic of memristors makes them ...suitable for simulating neuronal synapses with plasticity. In this paper, a memristor is used to simulate a synapse, a discrete small-world neuronal network is constructed based on Rulkov neurons and its dynamical behavior is explored. We explore the influence of system parameters on the dynamical behaviors of the discrete small-world network, and the system shows a variety of firing patterns such as spiking firing and triangular burst firing when the neuronal parameter α is changed. The results of a numerical simulation based on Matlab show that the network topology can affect the synchronous firing behavior of the neuronal network, and the higher the reconnection probability and number of the nearest neurons, the more significant the synchronization state of the neurons. In addition, by increasing the coupling strength of memristor synapses, synchronization performance is promoted. The results of this paper can boost research into complex neuronal networks coupled with memristor synapses and further promote the development of neuroscience.
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