NO2 gas sensor has been constructed using reduced graphene oxide-ZnO nanoparticles (ZnO-rGO) hybrids as sensing materials. Most importantly, the sensor exhibits higher sensitivity, shorter response ...time and recovery time than those of the sensor based on rGO, indicating that the sensing performances for NO2 sensing operating at room temperature have been enhanced by introduction of ZnO nanoparticles into rGO matrix.
The temporal and spatial control of natural systems has aroused great interest for the creation of synthetic mimics. By using boronic ester based dynamic covalent chemistry and coupling it with an ...internal pH feedback system, we have developed a new chemically fueled reaction network for non‐equilibrium supramolecular chiral G‐quadruplex hydrogels with programmable lifetimes from minutes, to hours, to days, as well as high transparency and conductivity, excellent injectability, and rapid self‐healing properties. The system can be controlled by the kinetically controlled in situ formation and dissociation of dynamic boronic ester bonds between the cis‐diol of guanosine (G) and 5‐fluorobenzoxaborole (B) in the presence of chemical fuels (KOH and 1,3‐propanesultone), thereby leading to a precipitate‐solution‐gel‐precipitate cycle under non‐equilibrium conditions. A combined experimental‐computational approach showed the underlying mechanism of the non‐equilibrium self‐assembly involves aggregation and disaggregation of right‐handed helical G‐quadruplex superstructures. The proposed dynamic boronic ester‐based non‐equilibrium self‐assembly strategy offers a new option to design next‐generation adaptive and interactive smart materials.
The temporal and spatial control of natural systems has aroused great interest for the creation of synthetic mimics. Herein, a dynamic boronic ester based non‐equilibrium self‐assembly strategy has enabled the creation of programmable and transient supramolecular chiral G‐quadruplex hydrogels with tunable lifetimes from minutes, to hours, to days, as well as high transparency and conductivity, excellent injectability, and self‐healing properties.
Abstract
CRISPR/Cas9 is a programmable genome editing tool widely used for biological applications and engineered Cas9s have increased discrimination against off-target cleavage compared with ...wild-type Streptococcus pyogenes (SpCas9) in vivo. To understand the basis for improved discrimination against off-target DNA containing important mismatches at the distal end of the guide RNA, we performed kinetic analyses on the high-fidelity (Cas9-HF1) and hyper-accurate (HypaCas9) engineered Cas9 variants. We show that DNA cleavage is impaired by more than 100- fold for the high-fidelity variants. The high-fidelity variants improve discrimination by slowing the observed rate of cleavage without increasing the rate of DNA rewinding and release. The kinetic partitioning favors release rather than cleavage of a bound off-target substrate only because the cleavage rate is so low. Further improvement in discrimination may require engineering increased rates of dissociation of off-target DNA.
A stable aqueous dispersion of reduced graphene oxide (rGO) has been prepared by the chemical reduction of graphene oxide with the use of benzylamine as a reducing and stabilizing agent. Raman ...spectroscopy, and X-ray photoelectron spectroscopy were used to characterize the resulting rGO. The rGO could be decorated with Ag nanoparticles (AgNPs) by direct adsorption of preformed, negatively-charged AgNPs. It was found that the resulting hybrid exhibits good catalytic activity toward the reduction of hydrogen peroxide, leading to an enzymeless sensor with a fast amperometric response time of less than 2
s. The linear detection range is estimated to be from 100
μM to 100
mM (
r
=
0.999), and the detection limit is estimated to be 31.3
μM at a signal-to-noise ratio of 3.
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•A highly adsorptive magnetic biochar was prepared using K2FeO4 in one-step.•Oxygen containing groups were simultaneously introduced with single phase ɤ-Fe2O3.•In situ generation of ...oxygen containing groups benefited to capturing ɤ-Fe2O3.•Both ɤ-Fe2O3 and biochar matrix contributed to adsorption of Cr(VI).•The magnetic biochar exhibited 209.64 mg/g maximum adsorption capability.
Magnetic biochar was usually prepared using ferrous and ferric compounds as precursor of magnetic medium. Ferrate, which could be an internal oxidative modifier, was less explored for preparing magnetic biochar. Here, a magnetic biochar was prepared through K2FeO4-promoted pyrolysis of pomelo peel for adsorption of hexavalent chromium. Oxygen-containing groups and single phase ɤ-Fe2O3 were simultaneously introduced into biochar matrix at 300 °C. The magnetic biochar exhibited 209.64 mg/g maximum adsorption capability at 45 °C, outperformed the best magnetic biochar with 142.86 mg/g maximum adsorption capability at 40 °C in the literature. Moreover, a good magnetism was obtained, facilitating separation of the magnetic biochar from aqueous solution by a magnet. The removal of hexavalent chromium was contributed to the hybrid adsorption of ɤ-Fe2O3 and biochar matrix by reduction, electrostatic interaction and complexation. This method was attractive, required neither extra modifiers nor multiple operations for preparation of highly adsorptive magnetic biochar.
In this paper, an integrated production and distribution problem for perishable products is presented, which is an NP hard problem where a single machine, multi-customers, and homogenous vehicles ...with capacity constraints are considered. The objective is to minimize the total order weighted delivery time to measure the customer service level, by making two interacted decisions, production scheduling and vehicle routing, simultaneously. An integrated mathematical model is built, and the validity is measured by the linear programming software CPLEX by solving the small-size instances. An improved large neighborhood search algorithm is designed to address the problem. Firstly, a two-stage algorithm is constructed to generate the initial solution, which determines the order production sequence according to the given vehicle routing. Secondly, several removal/insertion heuristics are applied to enlarge the search space of neighbor solutions. Then, a local search algorithm is designed to improve the neighbor solutions, which further generates more chances to find the optimal solution. For comparison purposes, a genetic algorithm developed in a related problem is employed to solve this problem. The computational results show that the proposed improved large neighborhood search algorithm can provide higher quality solutions than the genetic algorithm.
Hierarchical structured CoP/CNFs composite composed of 1D carbon nanofibers and 2D CoP nanosheets was successfully synthesized and explored as a high-efficiency bifunctional electrocatalyst for ...overall splitting water.
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•CoP/CNFs composites with 1D/2D hierarchical structure were constructed.•The CoP/CNFs were explored as bifunctional eletrocatalysts for both OER and HER.•The CoP/CNFs composite exhibited potential application in overall water splitting.
The design of efficient, stable, and economical electrocatalysts for oxygen and hydrogen evolution reaction (OER and HER) is a major challenge for overall water splitting. Herein, a hierarchical structured CoP/carbon nanofibers (CNFs) composite was successfully synthesized and its potential application as a high-efficiency bifunctional electrocatalyst for overall splitting water was evaluated. The synergetic effect of two-dimensional (2D) CoP nanosheets and one-dimensional (1D) CNFs endowed the CoP/CNFs composites with abundant active sites and rapid electron and mass transport pathways, and thereby significantly improved the electrocatalytic performances. The optimized CoP/CNFs delivered a current density of 10 mA cm−2 at low overpotential of 325 mV for OER and 225 mV for HER. In the overall water splitting, CoP/CNFs achieved a low potential of 1.65 V at 10 mA cm−2. The facile strategy provided in the present work can facilitate the design and development of multifunctional non-noble metal catalysts for energy applications.
Polyamines are ubiquitous in almost all biological entities and involved in various crucial physiological processes. They are also closely associated with the onset and progression of many diseases. ...Polyaminopathies are a group of rare genetic disorders caused by alterations in the function of proteins within the polyamine metabolism network. Although the identified polyaminopathies are all rare diseases at present, they are genetically heritable, rendering high risks not only to the carriers but also to their descendants. Meanwhile, more polyaminopathic patients might be discovered with the increasing accessibility of gene sequencing. This review aims to provide a comprehensive overview of the structural variations of mutated proteins in current polyaminopathies, in addition to their causative genes, types of mutations, clinical symptoms, and therapeutic approaches. We focus on analyzing how alterations in protein structure lead to protein dysfunction, thereby facilitating the onset of diseases. We hope this review will offer valuable insights and references for the future clinical diagnosis and precision treatment of polyaminopathies.
With the ongoing development and improvement of deep learning technology, autonomous vehicles (AVs) have made tremendous progress in recent years. Despite its great potential, AV supported by deep ...learning technology still faces numerous security threats, which prevent AV from being putting into large-scale practice. Aiming at this challenging situation, in this paper, we would like to exploit two attacks against deep learning algorithms in traffic sign recognition system by leveraging particle swarm optimization. Specifically, we first exploit the PAPSO (poisoning attack with particle swarm optimization) which focuses on the training process of the deep learning algorithms in the traffic sign recognition system, i.e., the attacker injects crafted samples into the training dataset, causing a reduction in classification accuracy of the traffic sign recognition system. Then, we also explore the EAPSO (evasion attack with particle swarm optimization) which on the other hand focuses on the interference process of the deep learning algorithms, i.e., the attacker adds some hardly perceptible perturbations to the targeted test sample, leading to a misclassification on it. Extensive experiments are conducted to shed light on the effectiveness of our attacks, and some corresponding defense strategies are also presented.
Short-term plasticity and long-term plasticity of bio-synapse are thought to underpin critical physiological functions in neural circuits. In this letter, we vividly emulated the short-term and ...long-term synaptic functions in a single Cu/a-Si/Pt memristor. By controlling the injection quantity of Cu cations into the a-Si layer, the device showed volatile and non-volatile resistive switching behaviors. Owing to the unique characteristics of Cu/a-Si/Pt device, the short-term synaptic functions, i.e., short-term potentiation, pair-pulse facilitation, and long-term functions, i.e., long-term potentiation/depression, spike-timing-dependent plasticity, were mimicked in the memristor successfully. Furthermore, the transition from short-term memory to long-term memory of the device was also observed under repeated stimuli. The experimental results confirm that the Cu/a-Si/Pt memristor with various synaptic behaviors has a potential application in the brain-inspired computing systems.
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