Most organic polymeric materials have high flammability, for which the large amounts of smoke, toxic gases, heat, and melt drips produced during their burning cause immeasurable damages to human life ...and property every year. Despite some desirable results having been achieved by conventional flame‐retardant methods, their application is encountering more and more difficulties with the ever‐increasing high flame‐retardant requirements such as high flame‐retardant efficiency, great persistence, low release of heat, smoke, and toxic gases, and more importantly not deteriorating or even enhancing the overall properties of polymers. Under such condition, some advanced flame‐retardant methods have been developed in the past years based on “all‐in‐one” intumescence, nanotechnology, in situ reinforcement, intrinsic char formation, plasma treatment, biomimetic coatings, etc., which have provided potential solutions to the dilemma of conventional flame‐retardant methods. This review briefly outlines the development, application, and problems of conventional flame‐retardant methods, including bulk‐additive, bulk‐copolymerization, and surface treatment, and focuses on the raise, development, and potential application of advanced flame‐retardant methods. The future development of flame‐retardant methods is further discussed.
Flame‐retardant methods for polymeric materials are reviewed with particular focus on advanced flame‐retardant methods developed in recent years. Both the advantages and drawbacks of these methods are discussed, and prospects for the future development of flame‐retardant methods are presented. It is hoped that this review will guide the development of flame‐retardant polymeric materials.
Lightweight magnesium alloys are attractive as structural materials for improving energy efficiency in applications such as weight reduction of transportation vehicles. One major obstacle for ...widespread applications is the limited ductility of magnesium, which has been attributed to Formula: see text dislocations failing to accommodate plastic strain. We demonstrate, using in situ transmission electron microscope mechanical testing, that Formula: see text dislocations of various characters can accommodate considerable plasticity through gliding on pyramidal planes. We found that submicrometer-size magnesium samples exhibit high plasticity that is far greater than for their bulk counterparts. Small crystal size usually brings high stress, which in turn activates more Formula: see text dislocations in magnesium to accommodate plasticity, leading to both high strength and good plasticity.
The analysis points out that the current hydraulic pressure technology in coal mines faces challenges such as the inability to quickly and accurately adjust the output pressure and flow rate of ...fracturing pumps, the need to improve the remote safety monitoring effect, and the level of automation. An underground hydraulic fracturing automatic control system in coal mine has been designed. Based on the hydraulic fracturing technology and system composition in coal mines, it is clear that the key technologies of the control system include rapid and precise adjustment of the output flow and pressure of high-pressure and high flow fracturing pumps, remote high reliability and safety, high-speed real-time monitoring, one click start stop, and graphical analysis. Based on the KXH12 intrinsic safety controller as the core, combined with frequency converters, combination switches, monitoring hosts, electric valves and other equipment, as well as a dual line redundant communication scheme with fiber optic and CAN bus,
2D layered materials have sparked great interest from the perspective of basic physics and applied science in the past few years. Extraordinarily, many novel stacked structures that bring versatile ...properties and applications can be artificially assembled, as exemplified by vertical van der Waals (vdW) heterostructures, twisted multilayer 2D materials, hybrid dimensional structures, etc. Compared with the ordinary synthesis process, the stacking technique is a powerful strategy to achieve high‐quality and freely controlled 2D material stacked structures with atomic accuracy. This review highlights the most advanced stacking techniques involving the preparation, transfer, and stacking of high‐quality single crystal 2D materials. Apart from the 2D–2D stacked structures, 2D–0D, 2D–1D, and 2D–3D structures offer a prospective platform for the increasing application of 2D materials. The assembly strategy and physical properties of these stacked structures strongly depend on the factors in the stacking process, including the surface quality, angle control, and sample size. In addition, comparative analysis tables on the techniques involved are also available. The summary of these strategies and techniques will hopefully provide a valuable reference for relevant work.
2D stacked structures are being rapidly developed. However, the assembly and integration techniques of 2D material‐based devices are still subject to many restrictions, seriously hindering the design and development of new functional devices. As one of the most important aspects, 2D material stacking techniques are systematically summarized and analyzed in this review.
Abstract
The virulence factor database (VFDB, http://www.mgc.ac.cn/VFs/) is dedicated to presenting a comprehensive knowledge base and a versatile analysis platform for bacterial virulence factors ...(VFs). Recent developments in sequencing technologies have led to increasing demands to analyze potential VFs within microbiome data that always consist of many different bacteria. Nevertheless, the current classification of VFs from various pathogens is based on different schemes, which create a chaotic situation and form a barrier for the easy application of the VFDB dataset for future panbacterial metagenomic analyses. Therefore, based on extensive literature mining, we recently proposed a general category of bacterial VFs in the database and reorganized the VFDB dataset accordingly. Thus, all known bacterial VFs from 32 genera of common bacterial pathogens collected in the VFDB are well grouped into 14 basal categories along with over 100 subcategories in a hierarchical architecture. The new coherent and well-defined VFDB dataset will be feasible and applicable for future panbacterial analysis in terms of virulence factors. In addition, we introduced a redesigned JavaScript-independent web interface for the VFDB website to make the database readily accessible to all users with various client settings worldwide.
Two new species,
Liu,
and
Liu,
, are described from Hainan Island, China. Adult males and females of both species, including their genitalia, are figured and compared to closely related species.
High‐performance thermal insulating aerogels are attractive candidates for thermal protection in extreme environments. However, inorganic aerogels’ brittleness and poor machinability limit their ...applications, while organic aerogels suffer from severe strength degradation and structural collapse at high temperatures. Herein, for the first time, a thermo‐responsive self‐ceramifiable aerogel is demonstrated with exceptional strengthening and thermal insulation at high temperatures. This aerogel exhibits excellent toughness and processability like polymers under normal conditions but spontaneously transforms into high‐strength semi‐crystalline hard ceramics upon exposure to high temperatures. After prolonged thermal attack at 800 °C, the strength of the aerogels does not decrease but significantly increases several‐fold (from 0.739 to 2.726 MPa). The self‐ceramization behavior and mechanism of the aerogel are illustrated in detail. The unique self‐ceramifiable capacity enables aerogels to provide fire resistance, high‐strength support, and excellent thermal insulation at ultrahigh temperatures. Even with continuous burning at 1300 °C for 60 min, the 15 mm thick aerogel shows low backside temperature below 300 °C, crack‐free overall structure, and invariant porous morphology. This self‐ceramifiable aerogel opens up a new avenue for developing thermal‐protection materials with toughness, machinability, high strength, and thermal insulation in extreme environments.
A new thermo‐responsive self‐ceramifiable aerogel is for the first time reported with exceptional strengthening and thermal insulation at high temperatures. Under normal conditions, the aerogel exhibits excellent toughness and machinability. Upon exposure to high temperatures, the aerogel spontaneously and rapidly transforms into robust semi‐crystalline hard ceramics, thus leading to fire resistance, high strength, and thermal insulation in extreme environments.
Two and a half years into the COVID-19 pandemic, we have gained many insights into the human antibody response to the causative SARS-CoV-2 virus. In this Review, we summarize key observations of ...humoral immune responses in people with COVID-19, discuss key features of infection- and vaccine-induced neutralizing antibodies, and consider vaccine designs for inducing antibodies that are broadly protective against different variants of the SARS-CoV-2 virus.
The virulence factor database (VFDB, http://www.mgc.ac.cn/VFs/) is dedicated to providing up-to-date knowledge of virulence factors (VFs) of various bacterial pathogens. Since its inception the VFDB ...has served as a comprehensive repository of bacterial VFs for over a decade. The exponential growth in the amount of biological data is challenging to the current database in regard to big data analysis. We recently improved two aspects of the infrastructural dataset of VFDB: (i) removed the redundancy introduced by previous releases and generated two hierarchical datasets--one core dataset of experimentally verified VFs only and another full dataset including all known and predicted VFs and (ii) refined the gene annotation of the core dataset with controlled vocabularies. Our efforts enhanced the data quality of the VFDB and promoted the usability of the database in the big data era for the bioinformatic mining of the explosively growing data regarding bacterial VFs.
Turn-on/turn-off fluorescent probes for the selective detection of palladium ions in recent reports are compiled and their bottlenecks and future perspectives in the development of palladium sensors ...are discussed.
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•The first review on chemosensors for the detection of Pd ions.•Comprehensive information on the design and evaluation of fluorescent sensors.•Enhancement and quenching was achieved based on coordination and catalytic reactions.•Challenges as well as possible future research directions are presented.
Palladium is one of the important elements used in various industries, such as fuel cells, automobile, dental crowns and catalysts in drug synthesis. Its extensive use and waste produced have raised pollution emissions to water sources and soils, and have severe effects on plants, animals and humans. As a result, many methods have been developed to assess the levels of palladium in drug chemicals, food and crops. The dietary intake per person is limited to <15 μg day−1, as reported by the World Health Organization (WHO). This issue has led many researchers developing optical probes, hereafter fluorescent sensors, for the sensitive and selective detection of palladium, especially in the environmental and biological settings. The design of functionalized receptors that serve as palladium-selective chemosensors has gained great interest despite the difficulties associated with the similarities among the same group elements (especially platinum). This review provides a general overview of the recent research developments in fluorescent sensors, emphasizing on the structural features for designing fluorescent sensors for the selective detection of palladium ions. Because the number of chemosensors for palladium detection has grown in the past few years, this review was written to provide a comprehensive discussion of these types of sensors reported from 2000 to the present day. This review categorizes the palladium probes based on their sensing mechanisms or mode of interaction towards palladium ions, such as coordination, deallylation, depropargylation, hydrolysis, palladium induced aggregation, photo-induced electron transfer, Claisen rearrangement, CCN bond cleavage, oxidative cyclization and cross coupling reactions. The basic principles involved in the design of chemosensors for the selective analysis of palladium, problems and challenges in the field as well as possible future research directions are presented.
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