Multi-mode adaptive control strategy for a lower limb rehabilitation robot.

Different patients have different rehabilitation requirements. It is essential to ensure the safety and comfort of patients at different recovery stages during rehabilitation training. This study proposes a multi-mode adaptive control method to achieve a safe and compliant rehabilitation training strategy. First, patients' motion intention and motor ability are evaluated based on the average human-robot interaction force per task cycle. Second, three kinds of rehabilitation training modes-robot-dominant, patient-dominant, and safety-stop-are established, and the adaptive controller can dexterously switch between the three training modes. In the robot-dominant mode, based on the motion errors, the patient's motor ability, and motion intention, the controller can adaptively adjust its assistance level and impedance parameters to help patients complete rehabilitation tasks and encourage them to actively participate. In the patient-dominant mode, the controller only adjusts the training speed. When the trajectory error is too large, the controller switches to the safety-stop mode to ensure patient safety. The stabilities of the adaptive controller under three training modes are then proven using Lyapunov theory. Finally, the effectiveness of the multi-mode adaptive controller is verified by simulation results.

Novel green/red oxyfluoride phosphors with excellent optical properties for near-UV excited white light emitting diode.

Novel eye-sensitive Ba3Nb2O2F12(H2O)2:Tb3+ green and Ba3Nb2O2F12(H2O)2:Mn4+ red oxyfluoride phosphors with extremely strong absorption in the UV region were designed and synthesized by simple co-precipitation strategy. Particularly, Tb3+ ions were doped in this matrix for the first time, which greatly improves their absorption efficiency in the near ultraviolet region (367 nm) and emits sharp green light (544 nm). In addition, the Ba3Nb2O2F12(H2O)2:Mn4+ red phosphors have strong zero phonon line (ZPL) emission at 625 nm, which is conducive to improving the sensitivity of human eye and color purity. Meanwhile, the optical properties of the red phosphor are significantly enhanced via doping K+ cations as charge compensators. Crystal field environment and nephelauxetic effect of the as-prepared phosphors before and after K+ cation doping were systematically analyzed. Moreover, these synthesized red/green phosphors have good thermal stability and moisture resistance. Remarkably, the as-prepared Ba3Nb2O2F12(H2O)2:5%Mn4+ or K0.9Ba2.1Nb2O2F12(H2O)2:5%Mn4+ red phosphors can be directly mixed with the as-synthesized Ba3Nb2O2F12(H2O)2:13%Tb3+ green phosphor coating on 365 nm near-ultraviolet LED chip to package WLED devices with excellent electroluminescence performance. These findings are conducive to opening an avenue for screening the unique structure of optical materials.

Modulating electron density enable efficient cascade conversion from peroxymonosulfate to superoxide radical driven by electron-rich/poor dual sites.

The superoxide radical (•O2-)-mediated peroxymonosulfate (PMS)-based photo-Fenton-like reaction enables highly selective water decontamination. Nevertheless, the targeted construction of •O2--mediated photo-Fenton-like system has been challenging. Herein, we developed an electron-rich/-poor dual sites driven •O2--mediated cascade photo-Fenton-like system by modulating electron density. Experimental and theoretical results demonstrated that PMS was preferentially adsorbed on electron-poor Co site. This adsorption promoted O-O bond cleavage of PMS to generate hydrogen peroxide (H2O2), which then migrated to electron-rich O site to extract eg electrons for O-H bond cleavage, rather than competing with PMS for Co site. The developed versatile cascade reaction system could selectively eliminate contaminants with low n-octanol/water partition constants (KOW) and dissociation constants (pKa) and remarkably resist inorganics (Cl-, H2PO4- and NO3-), humic acid (HA) and even real water matrices (tap water and secondary effluent). This finding provided a novel and plausible strategy to accurately and efficiently generate •O2- for the selective water decontamination.

Molecular Motor-Driven Light-Controlled Logic-Gated K+ Channel for Cancer Cell Apoptosis.

Developing artificial ion transport systems, which process complicated information and step-wise regulate properties, is essential for deeply comprehending the subtle dynamic behaviors of natural channel proteins (NCPs). Here a photo-controlled logic-gated K+ channel based on single-chain random heteropolymers containing molecular motors, exhibiting multi-core processor-like properties to step-wise control ion transport is reported. Designed with oxygen, deoxygenation, and different wavelengths of light as input signals, complicated logical circuits comprising "YES", "AND", "OR" and "NOT" gate components are established. Implementing these logical circuits with K+ transport efficiencies as output signals, multiple state transitions including "ON", "Partially OFF" and "Totally OFF" in liposomes and cancer cells are realized, further causing step-wise anticancer treatments. Dramatic K+ efflux in the "ON" state (decrease by 50% within 7 min) significantly induces cancer cell apoptosis. This integrated logic-gated strategy will be expanded toward understanding the delicate mechanism underlying NCPs and treating cancer or other diseases is expected.

Optical enhancement of highly efficient organic-inorganic oxyfluoride red phosphors via the cation co-doping strategy.

Herein, a new organic cationic matrix [N(CH3)4]3MoO3F3 suitable for Mn4+ doping was constructed. Due to the large steric hindrance of N[CH3]4+ (TMA), charge compensation defects can be effectively prevented in the heterovalent Mn4+-doping process, and a high IQE (91.05%) was obtained. Through the cation co-doping strategy, Mg2+/Zn2+/Li+ cations were introduced into the Mo6+ cationic site, which improved the crystallinity of the matrix and reduced energy losses, so as to improve luminescence intensity, QE, thermal stability, water stability and other spectral properties. Meanwhile, [N(CH3)4]2TiF6:Mn4+ phosphors with the same TMA organic cation and equivalent Mn4+ doping were synthesized for comparison, and the effects of the Mg2+ cation co-doping strategy on the spectral properties of phosphors with different matrix types (fluoride/oxyfluoride) and substitution types (equivalent/non-equivalent) were analyzed. These findings provide the basis for the preparation of new luminescent materials. Furthermore, according to the optical properties exhibited by these phosphors, they are packaged into WLED devices with excellent photoelectric properties, which are suitable for indoor lighting and display fields.

Spin state-dependent in-situ photo-Fenton-like transformation from oxygen molecule towards singlet oxygen for selective water decontamination.

The development of 1O2-dominanted selective decontamination for water purification was hampered by extra H2O2 consumption and poor 1O2 generation. Herein, we proposed the reconstruction of Fe spin state using near-range N atom and long-range N vacancies to enable efficient generation of H2O2 and sequential activation of H2O2 into 1O2 after visible-light irradiation. Theoretical and experimental results revealed that medium-spin Fe(III) strengthened O2 adsorption, penetrated eg electrons to antibonding p-orbital of oxygen, and lowered the free energy of O2 activation, enabling the oxygen protonation for H2O2 generation. Thereafter, the electrons of H2O2 could be extracted by low-spin Fe(III) and rapidly converted into 1O2 in a nonradical path. The developed 1O2-dominated in-situ photo-Fenton-like system had an excellent pH universality and anti-interference to inorganic ions, dissolved organic matter, and even real water matrixes (e.g., tap water and secondary effluent). This work provided a novel insight for sustainable and efficient 1O2 generation, which motivated the development of new-generation selective water treatment technology.

Light-controlled artificial transmembrane signal transduction for 'ON/OFF'-switchable transphosphorylation of an RNA model substrate.

Inspired by nature, it is of significant importance to design and construct biomimetic signaling systems to mimic natural signal transduction. Herein, we report an azobenzene/α-cyclodextrin (α-CD)-based signal transduction system with three functional modules: a light-responsive headgroup, lipid-anchored group, pro-catalyst tailgroup. The transducer can be inserted into the vesicular membrane to trigger the transmembrane translocation of molecules under the activation of light, forming a ribonuclease-like effector site and leading to the transphosphorylation of the RNA model substrate inside the vesicles. Moreover, the transphosphorylation process can be reversibly turned 'ON/OFF' over multiple cycles by the activation and deactivation of the pro-catalyst. This artificial photo-controlled signal transduction successfully constructs a signal responsive catalysis system across the membrane to utilize light to reversibly control the internal transphosphorylation process of an RNA model substrate, which might provide a new strategy for future design to utilize exogenous signals for implementing endogenous enzyme manipulation and gene regulation.

Adaptive control of a class of time-varying nonlinear systems via immersion and invariance.

This paper addresses the adaptive control of a class of time-varying nonlinear systems. Under the framework of Immersion and Invariance (I&I) adaptive control, a set of sufficient conditions is obtained to stabilize the concerned time-varying nonlinear systems. It is shown that the presented controller can also be utilized to complete tracking control for a class of nonholonomic constraint systems if the desired trajectories satisfy certain conditions. The effectiveness of the new adaptive controller is demonstrated by some numerical simulations on a nonholonomic mobile robot.

Flexible Single-Chain-Heteropolymer-Derived Transmembrane Ion Channels with High K+ Selectivity and Tunable pH-Gated Characteristics.

A series of single-chain random heteropolymer (RHP)-derived artificial ion channels with both high K+ selectivity and controllable pH-gated behaviors were fabricated by a facile "one-pot" polymerization method. The benzo-18-crown-6 moieties appended on lateral chains of RHPs can form ion-permeable nanopores and transport K+ over Na+ through the lipid bilayers. The ion permeation selectivity was significantly enhanced by incorporating a cholesterol group to serve as a membrane anchor. Interestingly, similar to natural gated protein channels, on-off switchable characteristics were also realized by integrating an additional acid-sensitive alkylamine group into the RHP-derived channel. The unique design strategies have endowed the RHP-derived ion channels with facile synthetic procedures, desirable membrane compatibility, high K+ selectivity, and tunable pH-gated properties. This work provides an entry point for future design of novel functional nanochannels.

An Adaptive Time-Varying Impedance Controller for Manipulators.

Aiming at the situation that the structural parameters of the general manipulators are uncertain, a time-varying impedance controller based on model reference adaptive control (MRAC) is proposed in this article. The proposed controller does not need to use acceleration-based feedback or to measure external loads and can tolerate considerable structure parameter errors. The global uniform asymptotic stability of the time-varying closed-loop system is analyzed, and a selection approach for control parameters is presented. It is demonstrated that, by using the proposed control parameter selection approach, the closed-loop system under the adaptive controller is equivalent to an existing result. The feasibility of the presented controller for the general manipulators is demonstrated by some numerical simulations.

Supramolecularly regulated artificial transmembrane signal transduction for 'ON/OFF'-switchable enzyme catalysis.

An artificial signal transduction model with a supramolecular recognition headgroup, a membrane anchoring group, and a pro-enzyme catalysis endgroup was constructed. The transmembrane translocation of the transducer can be reversibly regulated by competitive host-guest complexations as an input signal to control an enzyme reaction inside the lipid vesicles.

A case of unilateral pulmonary oedema associated with severe acute mitral regurgitation.

A 44-year-old woman presented to the emergency department with sudden chest tightness and breathlessness, and a chest X-ray revealed unilateral pulmonary oedema (UPO). Colour Doppler echocardiography showed that the leaflet prolapsed with severe regurgitation, and the regurgitant jet tended to blow rightward within the left atrium. With the assistance of mechanical ventilation and venoarterial extracorporeal membrane oxygenation, the patient underwent mitral valve replacement. UPO is easily misdiagnosed, which leads to delays in treatment. Therefore, accurate diagnosis and immediate treatment are crucial.

Unimolecular Helix-Based Transmembrane Nanochannel with a Smallest Luminal Cavity of 1 Å Expressing High Proton Selectivity and Transport Activity.

Natural protein channels have evolved with exquisite structures to transport ions selectively and rapidly. Learning from nature to construct biomimetic artificial channels is always challenging. Herein we present a unimolecular transmembrane proton channel by quinoline-derived helix, which exhibited highly selective and ultrafast proton transport behaviors. This helix-based channel possesses a small luminal cavity of 1 Å in diameter, which could efficiently reject the permeation of cations, anions or water molecules but only permits the translocation of protons owing to the size effect. The proton flow rate exceeded 107 H+ s-1 channel-1 and reached the same magnitude with gramicidin A. Mechanism investigation revealed that the directionally arrayed NH-chain inside the synthetic channel played a pivotal role during the proton flux. This work not only presented a helix-based channel with the smallest observable nanopore, but also unveiled an unexplored pathway for realizing efficient transport of protons via the consecutive NH-chain.

Biocompatible Diselenide-Containing Protein Hydrogels with Effective Visible-Light-Initiated Self-Healing Properties.

Smart hydrogels are typical functional soft materials, but their functional and mechanical properties are compromised upon micro- or macro-mechanical damage. In contrast, hydrogels with self-healing properties overcome this limitation. Herein, a dual dynamic bind, cross-linked, self-healing protein hydrogel is prepared, based on Schiff base bonds and diselenide bonds. The Schiff base bond is a typical dynamic covalent bond and the diselenide bond is an emerging dynamic covalent bond with a visible light response, which gives the resulting hydrogel a dual response in visible light and a desirable self-healing ability. The diselenide-containing protein hydrogels were biocompatible due to the fact that their main component was protein. In addition, the hydrogels loaded with glucose oxidase (GOx) could be transformed into sols in glucose solution due to the sensitive response of the diselenide bonds to the generated hydrogen peroxide (H2O2) by enzymatic catalysis. This work demonstrated a diselenide-containing protein hydrogel that could efficiently self-heal up to nearly 100% without compromising their mechanical properties under visible light at room temperature.

Biomimetic Cascade Polymer Nanoreactors for Starvation and Photodynamic Cancer Therapy.

The selective disruption of nutritional supplements and the metabolic routes of cancer cells offer a promising opportunity for more efficient cancer therapeutics. Herein, a biomimetic cascade polymer nanoreactor (GOx/CAT-NC) was fabricated by encapsulating glucose oxidase (GOx) and catalase (CAT) in a porphyrin polymer nanocapsule for combined starvation and photodynamic anticancer therapy. Internalized by cancer cells, the GOx/CAT-NCs facilitate microenvironmental oxidation by catalyzing endogenous H2O2 to form O2, thereby accelerating intracellular glucose catabolism and enhancing cytotoxic singlet oxygen (1O2) production with infrared irradiation. The GOx/CAT-NCs have demonstrated synergistic advantages in long-term starvation therapy and powerful photodynamic therapy (PDT) in cancer treatment, which inhibits tumor cells at more than twice the rate of starvation therapy alone. The biomimetic polymer nanoreactor will further contribute to the advancement of complementary modes of spatiotemporal control of cancer therapy.

Comparing dark- and photo-Fenton-like degradation of emerging pollutant over photo-switchable Bi2WO6/CuFe2O4: Investigation on dominant reactive oxidation species.

The extensive use of tetracycline hydrochloride (TCH) poses a threat to human health and the aquatic environment. Here, magnetic p-n Bi2WO6/CuFe2O4 catalyst was fabricated to efficiently remove TCH. The obtained Bi2WO6/CuFe2O4 exhibited 92.1% TCH degradation efficiency and 50.7% and 35.1% mineralization performance for TCH and raw secondary effluent from a wastewater treatment plant in a photo-Fenton-like system, respectively. The remarkable performance was attributed to the fact that photogenerated electrons accelerated the Fe(III)/Fe(II) and Cu(II)/Cu(I) conversion for the Fenton-like reaction between Fe(II)/Cu(I) and H2O2, thereby generating abundant •OH for pollutant oxidation. Various environmental factors including H2O2 concentration, initial pH, catalyst dosage, TCH concentration and inorganic ions were explored. The reactive oxidation species (ROS) quenching results and electron spin resonance (ESR) spectra confirmed that •O2- and •OH were responsible for the dark and photo-Fenton-like systems, respectively. The degradation mechanisms and pathways of TCH were proposed, and the toxicity of products was evaluated. This work contributes a highly efficient and environmentally friendly catalyst and provides a clear mechanistic explanation for the removal of antibiotic pollutants in environmental remediation.

Template-Free Self-Assembly of Two-Dimensional Polymers into Nano/Microstructured Materials.

In the past few decades, enormous efforts have been made to synthesize covalent polymer nano/microstructured materials with specific morphologies, due to the relationship between their structures and functions. Up to now, the formation of most of these structures often requires either templates or preorganization in order to construct a specific structure before, and then the subsequent removal of previous templates to form a desired structure, on account of the lack of "self-error-correcting" properties of reversible interactions in polymers. The above processes are time-consuming and tedious. A template-free, self-assembled strategy as a "bottom-up" route to fabricate well-defined nano/microstructures remains a challenge. Herein, we introduce the recent progress in template-free, self-assembled nano/microstructures formed by covalent two-dimensional (2D) polymers, such as polymer capsules, polymer films, polymer tubes and polymer rings.

Efficient photoactivation of peroxymonosulfate by Z-scheme nitrogen-defect-rich NiCo2O4/g-C3N4 for rapid emerging pollutants degradation.

Limited peroxymonosulfate (PMS, HSO4-) activation efficiency resulted from slow metal reduction has been a challenge in visible-light (vis) assisted sulfate radical-based oxidation. Herein, a Z-scheme photocatalyst composed of nitrogen-defect-rich graphitic carbon nitride nanosheets embedded with nickel cobaltate nanoparticles (NiCo2O4/g-C3N4-Nvac) was elaborately designed to accelerate Ni(III)/Ni(II) and Co(III)/Co(II) cycles for PMS activation in PMS/vis system. The NiCo2O4/g-C3N4-Nvac exhibited remarkable enhancement with a tetracycline hydrochloride (TCH) degradation rate constant (0.1168 min-1), higher than those of NiCo2O4/g-C3N4 (0.0724 min-1) and g-C3N4 (0.0233 min-1), respectively. Also, the removal efficiencies of 95.5%, 94.2%, 98.0% and 91.4% for carbamazepine, 4-chlorophenol, atrazine and p-nitrophenol were achieved within 30 min, respectively. Theoretical and experimental results suggested that nitrogen (N) vacancies modulated electric structure to build Z-scheme-charge-transfer platform for rapid reduction of Ni(III) and Co(III), thereby accelerating PMS activation for remarkable removal of emerging pollutants. NiCo2O4/g-C3N4-Nvac exhibited excellent stability and corresponding electrical energy per order (EE/O) in different water matrix was evaluated. Additionally, TCH degradation behavior, pathways and toxicity of products were analyzed, respectively. This work provided an novel paradigm to design the efficient photo-activator of PMS for environmental remediation.

Dynamically Tunable Ultrathin Protein Membranes for Controlled Molecular Separation.

Developing the ultrathin membranes for high-performance separation still faces the challenge of both high permeance and selectivity. Herein, a large-area protein membrane was fabricated by the interfacial self-assembly of bovine serum albumin (BSA) and surfactants at the oil/water interface of emulsions. Benefiting from the ultrathin thickness and unique protein-surrounded tortuous channels, the membrane displays ultrahigh permeation flux and selective sieving capability for various molecules ranging from small dye molecules to proteins based on a dual filtration mechanism. More importantly, the rejection precision can also be reversibly regulated by the folding/unfolding transition of proteins to control the effective pore size of transport channels, even under a pressure-driven condition. This dynamically tunable ultrathin protein membrane combines the advantages of high permeance, selectivity, controllability, recyclability, and mechanical stability, which may create new opportunities for advanced applications in extended fields.

Difunctionalized pillar[5]arene-based polymer nanosheets for photodynamic therapy of Staphylococcus aureus infection.

Bacterial infections pose severe threats to global public health security. Developing antibacterial agents with both high efficiency and safety to handle this problem has become a top priority. Here, highly stable and effective polymer nanosheets have been constructed by the covalent co-assembly of a pillar[5]arene derivative and metalloporphyrin for photodynamic antibacterial therapy (PDAT). The monolayer nanosheets are strongly positively charged and thus capable of binding with Staphylococcus aureus (SA) through electrostatic interactions. Additionally, the nanosheets can be activated to generate reactive oxygen species (ROS) under white-light irradiation, and exhibit satisfactory antibacterial performance towards SA. More importantly, cell viability assays demonstrate that the nanosheets show little to no cytotoxicity impact on mammalian cells even when the concentrations are much higher than those employed in the antibacterial studies. The above results suggest that the polymer nanosheets could be an effective antibacterial agent to overcome bacterial infections and hold a broad range of potential applications in real life.