This article studies the planning problem for a robot residing in partially unknown environments under signal temporal logic (STL) specifications, where most of the existing planning methods using ...STL rely on a fully known environment. In many practical scenarios, however, robots do not have prior information of all the obstacles. In this article, a novel two-phase planning method, i.e., offline exploration followed by online planning, is proposed to efficiently synthesize paths that satisfy STL tasks. In the offline exploration phase, a rapidly exploring random tree* (RRT*) is grown from task regions under the guidance of timed transducers, which guarantees that the resultant paths satisfy the task specifications. In the online phase, the path with minimum cost in RRT* is determined when an initial configuration is assigned. This path is then set as the reference of the time elastic band algorithm, which modifies the path until it has no collisions with obstacles. It is shown that the online computational burden is reduced, and collisions with unknown obstacles are avoided by using the proposed planning framework. The effectiveness and superiority of the proposed method are demonstrated in simulations and real-world experiments.
MicroRNA (miRNA) play a vital role in the pathological development of many diseases. It is considered to be the diagnosis and potential biomarkers of prognosis. Herein, we proposed Bis-enzyme cascade ...Platform by combining T7 RNA polymerase and CRISPR-Cas12a (BPTC) for a miRNA detection. In the proposed BPTC, the RNA to DNA conversion ability of phi29 amplification and trans-cleavage of CRISPR-Cas12a are combined. The target miRNA can be amplified after binding to the recognizer ssDNA, and then transcribed the CRISPR-derived RNA (crRNA) by T7 RNA polymerase. The produced crRNA can thereby be assembled by CRISPR-Cas12a and recognized with its target dsDNA, thus triggered its trans-cleavage towards surrounding fluorescent reporters, labeled with a fluorophore and a corresponding quenching group. Based on the bis-enzyme cascade system, the biosensor shows highly sensitivity and excellent specificity. Moreover, this study provided a novel all-in-one detect strategy for miRNA and may open a new idea for the design of CRISR-Cas-based miRNA biosensing platforms.
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•A bis-enzyme cascade CRISPR-Cas12a platform for miRNA.•The biosensor can achieve “All-in-one” detection for miRNA.•The biosensor can realize fast and convenient detection of miRNA.
The single-phase cascaded H-bridge (CHB) inverter can realize module-level MPPT. Its multilevel output voltage can reduce the volume of filter inductance and avoid using the power frequency ...transformer. Therefore, the single-phase CHB inverter has a significant advantage in household photovoltaic (PV) power generation. However, due to the change of illumination conditions or damage to PV panels, the output power of H-bridges (HBs) will be unbalanced and result in the HBs with higher output power being overmodulated, affecting the stable operation of the CHB system and the quality of grid current. In this article, a control strategy is proposed to extend the operation range of the single-phase CHB inverter. The modulation strategy and reference power of each HB are adjusted according to the HB modulation index to achieve the whole operation range power matching. Compared with the existing methods, the proposed strategy further expands the operation range of the single-phase CHB inverter and ensures the full utilization of the power transmission capacity of the system on the premise of stable operation and grid current quality. The simulation and experiment verify the effectiveness of the proposed strategy.
The design and synthesis of efficient and earth-abundant nonprecious metal electrocatalyst for oxygen evolution reaction (OER) plays a vital role in electrocatalytic water splitting. Here, amorphous ...NiFe layered double hydroxide (LDH) nanosheets deposited on Fe doped Ni3S2 nano-ridges (Fe-Ni3S2 @NiFe LDH) are successfully synthesized through a simple hydrothermal-electrodeposition method and are applied as OER electrocatalysts. In addition, benefiting from the abundant electroactive sites, electronic effect induced by Fe-doping and synergistic effect between NiFe LDH and Fe-Ni3S2, the as-prepared Fe-Ni3S2 @NiFe LDH heterogeneous catalyst can exhibit excellent OER performance in 1.0 M KOH solution. Fe-Ni3S2 @NiFe LDH only reach an overpotential of 192 mV at the current density of 10 mA cm− 2 with a Tafel slope of 43.1 mV dec−1. Notably, as-obtained Fe-Ni3S2 @NiFe LDH electrocatalyst only requires a low overpotential of 217 mV to achieve a current density of 50 mA cm− 2. And Fe-Ni3S2 @NiFe LDH also exhibits excellent durability at 50 mA cm−2 in 1.0 M KOH at room temperature. This study provides a feasible approach for the design of highly efficient earth-abundant nonprecious metal electrocatalysts for OER.
Three-dimensional architecture Fe-Ni3S2 @NiFe LDH heterojunctions are successfully fabricated by hydrothermal and electrodeposition methods. Fe-Ni3S2 @NiFe LDH heterojunctions can be used as high efficient and stable electrocatalysts for oxygen evolution reaction. Display omitted
•Three-dimensional Fe-Ni3S2@NiFe LDH heterojunctions were constructed by hydrothermal and electrodeposition methods.•Fe-Ni3S2@NiFe LDH exhibits remarkable OER activity and stability.•The Fe-Ni3S2@NiFe LDH is based on non-noble metals and shows better performance than RuO2.
CRISPR-Cas systems have been employed to detect a large variety of pathogenic microorganisms by simply changing the guide RNA sequence. However, these platforms usually rely on nucleic acid ...extraction and amplification to achieve good sensitivity. Herein, we developed a new platform for the highly specific and sensitive detection of live staphylococcus aureus (S. aureus) based on an Aptamer-based Cas14a1 Biosensor (ACasB), without the need for nucleic acid extraction or amplification. First, the S. aureus specific aptamer was hybrid with a blocker DNA. After the live S. aureus was added, the blocker can be released upon bacteria-aptamer binding. Finally, the released blocker can activate Cas14a1 protein by binding with the sgRNA to generate a change of fluorescent intensity. The ACasB indicates high specificity and sensitivity: it can directly distinguish 400 CFU/ml live S. aureus cells. Comparable to qPCR, the Cas14a1-aptamer biosensor can detect S. aureus with 100% accuracy in complex samples. Therefore, this ACasB for the on-site detection of live S. aureus can broaden its applications in food safety and environmental monitoring.
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The grid-connected inverter is the vital energy conversion device in renewable energy power generation. With the increasing installed capacity of renewable energy, the grid presents characteristics ...of weak grids with large grid impedance. In general, the inverter often obtains grid synchronization information by the phase-locked loop (PLL) and to suppress the background harmonic and amplitude disturbance of grid voltage, the grid voltage feedforward (GVF) control is also needed. However, previous researches revealed that the PLL and the GVF would shape the quadrature-axis (<inline-formula> <tex-math notation="LaTeX">\boldsymbol {q} </tex-math></inline-formula>-axis) output impedance of the inverter into a negative resistance in the low-frequency band, and this would be responsible for the instability of the inverter under a weak grid. To resolve this instability issue, this article proposes an impedance controller for reshaping the <inline-formula> <tex-math notation="LaTeX">\boldsymbol {q} </tex-math></inline-formula>-axis impedance into a positive resistance in the low-frequency band, which eliminates the negative effect introduced by the PLL and the GVF; therefore, the inverter will operate under very weak grids. Moreover, the proposed control strategy is only for <inline-formula> <tex-math notation="LaTeX">\boldsymbol {q} </tex-math></inline-formula>-axis impedance reshaping, and it does not affect the output characteristics of <inline-formula> <tex-math notation="LaTeX">\boldsymbol {d} </tex-math></inline-formula>-axis, thus ensuring the ability of the inverter to suppress background harmonics and amplitude disturbance of the grid voltage. The conclusions are verified by experimental results.
Due to the advantages of renewable, low pollution and wide distribution of biomass resources, it is selected as the electrode material for supercapacitors. For carbon-based electrode materials, ...specific surface area and pore structure have a great influence. Exploring and summarizing the influence of activation on pore structure will greatly broaden this field. Based on the activation mechanism of activator, this paper summarizes the latest progress of biomass activation applied to supercapacitors, including traditional physical and chemical activation methods and non-traditional methods such as biological activation method, self-activation method, template assisted activation method and green activator activation. Finally, the challenges, strategies and prospects for the future development of biomass-derived carbon material activation are pointed out. In summary, this review will help researchers choose appropriate strategies to design biomass-derived carbon electrode materials for supercapacitors, thereby promoting the application of biomass materials.
The pore structure and multi-level distribution largely determine the electrochemical performance of electrode materials, so it is of great significance to summarize the law of activation effect. In this paper, from two aspects of traditional activation and unconventional activation, with activator as the breakthrough point, the chemical reaction in the activation process is pointed out, and the complete process of pore formation in the activation process is expounded. Display omitted
The actual role of coronavirus disease 2019 (COVID-19) in brain damage has been increasingly reported, necessitating a meta-analysis to collate and summarize the inconsistent findings from functional ...imaging and voxel-based morphometry (VBM) studies. A comprehensive voxel-wise meta-analysis of the whole brain was conducted to identify alterations in functional activity and gray matter volume (GMV) between COVID-19 patients and healthy controls (HCs) by using Seed-based d Mapping software. We included 15 functional imaging studies (484 patients with COVID-19, 534 HCs) and 9 VBM studies (449 patients with COVID-19, 388 HCs) in the analysis. Overall, patients with COVID-19 exhibited decreased functional activity in the right superior temporal gyrus (STG) (extending to the right middle and inferior temporal gyrus, insula, and temporal pole TP), left insula, right orbitofrontal cortex (OFC) (extending to the right olfactory cortex), and left cerebellum compared to HCs. For VBM, patients with COVID-19, relative to HCs, showed decreased GMV in the bilateral anterior cingulate cortex/medial prefrontal cortex (extending to the bilateral OFC), and left cerebellum, and increased GMV in the bilateral amygdala (extending to the bilateral hippocampus, STG, TP, MTG, and right striatum). Moreover, overlapping analysis revealed that patients with COVID-19 exhibited both decreased functional activity and increased GMV in the right TP (extending to the right STG). The multimodal meta-analysis suggests that brain changes of function and structure in the temporal lobe, OFC and cerebellum, and functional or structural alterations in the insula and the limbic system in COVID-19. These findings contribute to a better understanding of the pathophysiology of brain alterations in COVID-19.
This first large-scale multimodal meta-analysis collates existing neuroimaging studies and provides voxel-wise functional and structural whole-brain abnormalities in COVID-19. Findings of this meta-analysis provide valuable insights into the dynamic brain changes (from infection to recovery) and offer further explanations for the pathophysiological basis of brain alterations in COVID-19.
•This is the first multimodal neuroimaging meta-analysis identifying brain functional and structural alterations in individuals with COVID-19 infection.•The multimodal meta-analysis revealed overlapping functional and structural changes in the right STG.•The current study found dynamic brain functional and structural changes over time (from infection to recovery) after COVID-19 infection.•Correlations between older age and reduction of brain functional activity in the right orbitofrontal cortex and insula were identified in COVID-19.
•Three multi-element co-doped carbon dots (CDs) were synthesized for the first time by solvothermal carbonization of ternary/quaternary mixtures.•By studying the effects of metal ion doping on the ...properties of CDs, we found that the presence of valence electrons in P, W, and Hf ions can promote the electron transfer between metal ions and CDs, leading to the formation of radiative electron recombination and holes on the surface of CDs, which makes the material exhibit excellent physicochemical properties.•Comparing the physicochemical properties, biodistribution, and pharmacokinetics of the three materials, we found that P, W, and Hf co-doped CDs-1 exhibited intense and stable dual-emission fluorescence and excellent QYs, and outstanding fluorescence and CT dual-mode imaging properties of OS models.
Osteosarcoma (OS), the most common pediatric malignant bone tumor, has been stagnant in its current treatment status due to its highly heterogeneous, aggressive, and lethal nature. Herein, we developed multi-element charge-transfer co-doped carbon dots (CDs) as dual-mode contrast agents for OS models using hydrothermal carbonization. The obtained P, W co-doped CDs, P, W, Hf co-doped CDs-1, and P, W, Hf co-doped CDs-2 have high long-wavelength quantum yields (16.5, 27.3, and 14.2%) in N, N-dimethylformamide solution, which can be attributed to the presence of valence electrons in the doped metal ions or metal hydrochloride, which promotes the radiative recombination of electrons and the formation of holes. Moreover, P, W, Hf co-doped CDs-1 exhibited higher biocompatibility, good 143B cell imaging, and fluorescence/CT high contrast imaging performance in Balb/C tumor-bearing mice compared to P, W co-doped CDs, and P, W, Hf co-doped CDs-2. In addition, the biodistribution and pharmacokinetic results further indicate that P, W, Hf co-doped CDs-1 has apparent advantages in imaging tracking and biosafety of OS and has excellent potential as a dual-mode imaging contrast agent.
