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Recently, single-particle cryo-electron microscopy (cryo-EM) has become an indispensable method for determining macromolecular structures at high resolution to deeply explore the relevant molecular mechanism. Its recent breakthrough is mainly because of the rapid advances in hardware and image processing algorithms, especially machine learning. As an essential support of single-particle cryo-EM, machine learning has powered many aspects of structure determination and greatly promoted its development. In this article, we provide a systematic review of the applications of machine learning in this field. Our review begins with a brief introduction of single-particle cryo-EM, followed by the specific tasks and challenges of its image processing. Then, focusing on the workflow of structure determination, we describe relevant machine learning algorithms and applications at different steps, including particle picking, 2-D clustering, 3-D reconstruction, and other steps. As different tasks exhibit distinct characteristics, we introduce the evaluation metrics for each task and summarize their dynamics of technology development. Finally, we discuss the open issues and potential trends in this promising field.

Most organic polymeric materials have high flammability, for which the large amounts of smoke, toxic gases, heat, and melt drips produced during their burning are causing immeasurable damages to human life and property every year. Despite some desirable results have 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 provided potential solution 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. This article is protected by copyright. All rights reserved.

Frequent oil spills have caused severe environmental and ecological damage. Effective cleanup has become a complex challenge owing to the poor flowability of viscous crude oils. The current method of solar heating to reduce the viscosity of heavy oil is only suitable during sunny days, while the use of Joule heating is limited by the risk of direct exposure to high-voltage electricity. Herein, we demonstrate a noncontact electromagnetic induction and solar dual-heating sponge for the quick, safe, and energy-saving cleanup of ultrahigh-viscosity heavy oil. The resulting sponge with magnetic, conductive, and hydrophobic properties can be rapidly heated to absorb heavy oil under alternating magnetic fields, solar irradiation, or both of these conditions. By constructing theoretical models and fitting the actual data, an in-depth analysis of induction and solar heating processes is carried out. The sponge has excellent resilience and stability, indicating its reusability, fast and continuous adsorption (16.17 g in 10 s), and large capacity (75-81 g/g, the highest value ever) for soft asphalt (a highly viscous crude oil). This work provides a new noncontact dual-heating strategy for heavy oil cleanup, in which absorbents use induction heating during an emergency and then switch to partial or full solar heating to save energy in sunny conditions. ENVIRONMENTAL IMPLICATION: Heavy oils stranded on the beach or floating on water can kill underwater plants by blocking sunlight, or trap water birds and other animals. Heavy oil also contains aromatic substances that are toxic to aquatic organisms. Although oil spills near shallow water cannot be cleaned up by fences or other machinery, an oil adsorbent can deal with this problem. However, common adsorbents cannot effectively absorb high-viscosity oils, such as heavy oil. In this paper, an induction and solar dual-heating sponge is developed for the effective cleanup of high-viscosity oil.

A label-free, rapid response colorimetric aptasensor for sensitive detection of chloramphenicol (CAP) was proposed, which was based on the strategy of ssDNA-modified gold nanoparticle (AuNP) aggregation assisted by lanthanum (La3+) ions. The AuNPs generated a color change that could be monitored in the red, green, and blue and analyzed by the smartphone imaging app. La3+, as a trigger agent, strongly combined with the phosphate groups of the surface of ssDNA-AuNPs probe, which helps create AuNP aggregation and the color change of AuNPs from red to blue. On the contrary, when mixing with CAP, the aptamer (Apt) bound to CAP to form a rigid structure of the Apt-CAP complex, and La3+ attached to the phosphate groups of the complex, which prevented the aptamer from binding to the surface of the AuNPs. As a result, the color of the AuNPs changed to violet-red. Finally, UV-vis absorption spectroscopy and the smartphone imaging app were employed to determine CAP with a lower detection limit of 7.65 nM and 5.88 nM, respectively. The proposed strategy featuring high selectivity and strong anti-interference ability for detection of CAP in practical samples was achieved. It is worth mentioning that the simple and portable colorimetric aptasensor will be used for facilitating on-site detection of food samples.

As typical anisotropic materials combining the entropy elasticity of an elastomer with the self-organization of rigid mesogens, liquid crystalline elastomers (LCEs) possess the emerging application...

Upon heating, polyesters decompose to small molecules and release flammable volatiles and toxic gases, primarily through chain scission of their ester linkages, and therefore exhibit poor fire-safety properties, thus restricting their applications. Reported herein is an end-group-capturing effect of (bis)oxazoline groups, generated from the thermal rearrangement of the N-(2-hydroxyphenyl)phthalimide (HPI) moiety which was incorporated into the polyester chain by copolymerization. These copolyesters, as a result, exhibit high efficiency in retarding decomposition by capturing the decomposed products, particularly for the carbonyl-terminated fragments, thus increasing the fire-safety properties, such as self-extinguishing, anti-dripping, and inhibiting heat release and smoke production. The successful application of this method in both semi-aromatic and aliphatic polyesters provide promising perspectives to designing versatile fire-safe polymers.

Copper is widely used in many applications due to its excellent electric conductivity, processing ductility and corrosion resistance. However, poor hardness and low strength are the major limitations of copper in many fields. Herein, we report a high-performance copper matrix composites prepared by powder metallurgy. The copper matrix composites were prepared by mixed acid treatment, molecular-level method, ball milling and spark plasma sintering (SPS) process. The fabrication, microstructure, mechanical properties and electrical conductivity of the composites were investigated. The results show that nano-Al2O3 can act as an active mixing agent to disperse CNTs in copper powders and increase the adhesion between CNTs and copper matrix in composites. Additionally, the uniform dispersion of Al2O3 and CNTs can restrict the grain growth and form a strong bonding interface. Thus, the synthesized Cu-1.5CNTs-0.5Al2O3 composite displays the highest comprehensive performance, such as 131 HV hardness, 345 MPa ultimate tensile strength, 324 MPa yield strength, 13.8% elongation, and 50.6 MS/m (87.2%IACS) electrical conductivity. This work provides a feasible way to prepare high-performance copper matrix composites.

Background Breast cancer is the most common cancer among women worldwide, and approximately 70% of breast cancers are hormone receptor-positive and express estrogen receptor-α (ERα) or/and progesterone receptor. ERα has been identified to promote the growth of primary breast cancer, however, it can also antagonize signaling pathways that lead to epithelial-mesenchymal transition (EMT), including transforming growth factor-β (TGF-β) signaling. miRNA alteration or dysfunction is involved in cancer development and progression. Although miR-1271 has identified as a tumor suppressor in various cancers, the role of miR-1271 in breast cancer is still limited. Methods The effect of miR-1271 on breast cancer progression was investigated both in vitro and in vivo. The EMT-related protein expression levels and localization were analyzed by western blotting and immunofluorescence, respectively. Chromatin immunoprecipitation and dual-luciferase reporter assays were used to validate the regulation of ERα-miR-1271-SNAI2 feedback loop. Results miR-1271 suppresses breast cancer progression and EMT phenotype both in vitro and in vivo by targeting SNAI2. Estrogen reverses TGF-β-induced EMT in a miR-1271 dependent manner. Furthermore, ERα transactivates the miR-1271 expression and is also transcriptionally repressed by SNAI2. Conclusions Our data uncover the ERα-miR-1271-SNAI2 feedback loop and provide a mechanism to explain the TGF-β network in breast cancer progression. Electronic supplementary material The online version of this article (10.1186/s13046-019-1112-4) contains supplementary material, which is available to authorized users.

The remodelling of structural and functional neurovascular unit (NVU) becomes a central therapeutic strategy after cerebral ischaemic stroke. In the present study, we investigated the effect of combined therapy of sodium ferulate (SF), n‐butylidenephthalide (BP) and adipose‐derived stromal cells (ADSCs) to ameliorate the injured NVU in the photochemically induced thrombotic stroke in rats. After solely or combined treatment, the neovascularization, activation of astrocytes, neurogenesis, expressions of vascular endothelial growth factor (VEGF) and claudin‐5 were assessed by immunohistochemical or immunofluorescence staining. In order to uncover the underlying mechanism of therapeutic effect, signalling of protein kinase B/mammalian target of rapamycin (AKT/mTOR), extracellular signal‐regulated kinase 1/2 (ERK1/2), and Notch1 in infarct zone were analysed by western blot. 18F‐2‐deoxy‐glucose/positron emission tomography, magnetic resonance imaging, Evans blue staining were employed to evaluate the glucose metabolism, cerebral blood flow (CBF), and brain‐blood barrier (BBB) permeability, respectively. The results showed that combined treatment increased the neovascularization, neurogenesis, and VEGF secretion, modulated the astrocyte activation, enhanced the regional CBF, and glucose metabolism, as well as reduced BBB permeability and promoted claudin‐5 expression, indicating the restoration of structure and function of NVU. The activation of ERK1/2 and Notch1 pathways and inhibition of AKT/mTOR pathway might be involved in the therapeutic mechanism. In summary, we have demonstrated that combined ADSCs with SF and BP, targeting the NVU remodelling, is a potential treatment for ischaemic stroke. These results may provide valuable information for developing future combined cellular and pharmacological therapeutic strategy for ischaemic stroke.

A novel and efficient light-controlled colorimetric assay for the quantification and detection of nitroreductase (NTR) was constructed based on p-aminophenol (pAP)-catalyzed and nicotinamide adenine dinucleotide (NADH)-mediated generation of AgNPs. Due to the hydrolysis of p-nitrophenol by NTR in the presence of NADH, the hydrolysis product can be used as a catalyst to catalyze the reduction of Ag+ by NADH under the light. As the concentration of NTR increases, the value of absorbance at ca. 400 nm (A400) decreases and the color of the solution turns from brown to bright yellow. A linear correlation was obtained between A400 and the NTR concentration in the range from 1-50 μg mL-1 and the limit of detection (LOD) is 0.27 μg mL-1. The detection system does not respond to other common biological molecules due to the specificity of enzymes and the effect of the nitroreductase inhibitor on the NTR activity was also tested. Finally, we applied the assay to determine NTR in human serum samples by spiking different concentrations of NTR with a recovery of 85.2%-92.5%.

Concentration-dependent photoluminescence carbon dots (CDs) have been successfully synthesized through the one-step hydrothermal treatment of o-phthalic acid and ethylenediamine. The CDs possessed higher fluorescence quantum yield, up to 39.22%, exhibiting distinguished optical property, water solubility, and stability. The CDs that emit strong blue-green fluorescence can visually identify and determine tetracycline (TC), oxytetracycline (OTC), and chlortetracycline (CTC). TC quenched the fluorescence of CDs at 500 nm owing to the inner filter effect; OTC behaved similarly, but the emission wavelength of CDs was red-shifted to 515 nm. Inversely, once CTC was introduced to CDs solution, the fluorescence increased and the emission peak was blue-shifted to 450 nm. Bandgap transition and electrostatic interaction were proposed to be the mechanisms for the detection of OTC and CTC by CDs. Wide linear relationships were established for TC, OTC, and CTC with the limits of detection to be 50 nM, 36 nM, and 373 nM, respectively. Furthermore, the nanoscale probe constructed by this system has been applied to detect tetracyclines (TCs) in complex samples with satisfying recoveries (93.2–114%) and was designed as a portable test strip sensor for visually on-site TCs of honey sample screening. Accordingly, the preparation process of the nano fluorescent probe is simple and environmentally friendly, and the probe has a specific recognition ability for tetracyclines. The synthesized CDs in this work provide a new orientation for fast, effective, and visual real-time detection of tetracycline in actual samples.

A high-frequency equivalent circuit modeling method is proposed, which can model the overvoltage sensor called Current Transformers (CTs). The proposed method uses the formula, which is based on the electromagnetic resonance, to get the high-frequency equivalent circuit. Then the magnitude of overvoltage can be reconstructed according to the last-screen current and high-frequency equivalent circuit. It is important to rebuild overvoltage, which can effectively assess the insulation risk and ensure the safe operation of the power grid. In this paper, the correctness of the proposed high-frequency equivalent circuit is verified by a simulation model, the conclusion is given by numerical results. while the measurement results show that by fitting the parameters of the equivalent circuit, the admittance of the Current Transformers can be obtained.

Gold nanoparticles (AuNPs) catalyze the mild reaction between the weak reducing agent kojic acid (KA) and silver ions (Ag+) to form Au@Ag bimetallic NPs by the combination of the intrinsic catalysis with plasmonic properties This is proposed as a novel optical assay to determine the tyrosinase (TYRase) concentration. The nanoparticles have been characterized by UV-vis spectroscopy, transmission electron microscope (TEM) images, and X-ray photoelectron spectroscopy (XPS). The sensing mechanism is based on the fact that KA binds to TYRase by chelating with dicopper active site of TYRase and the introduction of TYRase restrains the Au@Ag bimetallic NP formation by the precedent binding with KA. A clear color variation from yellow to pink and UV-vis spectral changes are observed at the optimal wavelength of 410 nm. The assay works in the range 0.13~0.73 U mL−1 with a detection limit (LOD) of 0.019 U mL−1. The impact from matrix interfering substances including glucose, uric acid, common oxidases, and amino acids is negligible. The applicability is demonstrated by quantitative determination of TYRase in human serum samples with 74 to 89% recovery and RSD less than 4.0%, which accords with the level for bio-sample analysis.

A simple but efficient colorimetric assay was developed for the detection and quantification of acid phosphatase (ACP) using a smartphone. This strategy is based on target-controlled iodine-mediated etching of gold nanorods (AuNRs). Due to effective hydrolysis of the substrate pyrophosphate (PPi) by ACP, chelated Cu2+ with PPi was released, which promoted the redox reaction with an iodide ion (I−), leading to the formation of I3−. As the etching agent of AuNRs, I3− caused a blueshift of the localized surface plasmon resonance peak and, more importantly, an observable color change. The vivid colors were recorded with a smartphone camera and directly analyzed using an image-processing app. On the basis of the direct correlation between ACP concentration and the etching degree of AuNRs as well as color change, this smartphone nanocolorimetry technique showed a good linear response toward ACP over the range of 0–15.0 U/L, with a detection limit of 0.97 U/L. Using the standard addition method, the practical applicability of the proposed smartphone-based assay was successfully demonstrated by determining ACP in human serum samples, with results consistent with those obtained by UV-Vis spectrophotometry.

Accurate imaging of soft tissues is one of the ultimate goals in biomedical imaging. Different imaging modalities can improve their disadvantages, and promote the imaging ability. However, once an imaging agent has been prepared, it is usually hard to adjust it according to the actual needs. Herein, we developed a supramolecular brush polymer (SBP) as a versatile imaging agent platform. The SBP platform (SBPP) is constructed by the intermolecular inclusion complexation of bridged tris(β-cyclodextrin) (1) with Mn(III)-porphyrin-bearing poly(ethylene glycol) (PEG) side chains (Mn(III)-TPP), and can further bind other functional groups by host–guest interactions of cyclodextrin and adamantine. The SBPP is characterized by UV/vis absorption spectroscopy, NMR, dynamic light scattering (DLS), atomic force microscopy (AFM) and transmission electron microscopy (TEM). We demonstrated that this SBPP not only has no cellular toxicity against NIH 3T3 cells in in vitro cell experiments, but it also shows an efficient enhanced T1 relaxivity in in vitro MR imaging experiments. When used as multifunctional imaging agents, different imaging probes and/or targeting agents can be introduced to this SBPP as needed through simple host–guest interactions. In in vitro imaging experiments, it shows accurate imaging of different kinds of cancer cells by choosing on-demand targeting agents. These results suggest a promising strategy for engineering multifunctional imaging agents with SBPs.

High-performance and multifunctional epoxy resins (EPs) are of great use in the booming electric & electronic and 5G fields, however their fabrication shows huge challenges. Herein, through a facile strategy by simply incorporating a functional molecule DPI (phosphaphenanthrene polyethylenimine), which possessed a unique structure with hyperbranched polyethyleneimine as flexible inner core and phosphaphenanthrene groups as rigid outer shell, a high-performance and multifunctional epoxy resin was successfully fabricated. The hyperbranched rigid-flexible structure of DPI endowed the resultant thermoset EP-DPI with superb mechanical performance and high glass transition temperature, for which, at a low DPI content (≤4 wt%), EP-DPI exhibited 160%, 40%, and 31% improvement in impact toughness, tensile strength, and flexural strength compared with neat EP. At the same time, the good compatibility between DPI and the EP matrix enabled EP-DPI to be highly transparent, and the aromatic phosphorus structure endowed EP-DPI with excellent UV-shielding effect in the UV-A band. The dielectric performance of EP-DPI was enhanced due to the unique structure of DPI and its interaction with the EP matrix. Furthermore, the phosphaphenanthrene groups endowed EP-DPI with excellent anti-ignition, self-extinguishing, and low heat release during combustion. This work opens up a new strategy for developing novel high-performance and multifunctional EPs with potential versatile applications.

At present, developing a flame-retardant unit to solve the flammability and melt-dripping of poly(ethylene terephthalate) (PET) still is a key issue. To endow PET with good flame retardancy and low smoke releasing, a third monomer, N, N′-bis(2-hydroxyethyl)-biphenyl-3,4,3′,4′-tetracarboxylic diimide (BPDI) containing biphenyl biimide and without any traditional flame-retardant elements, is synthesized and incorporated to the main chain of PET to obtain the P(ET-co-BP)n copolyester via melt polymerization. The thermal stability, combustion and pyrolysis behaviors of the obtained copolyesters have been well investigated. Thermogravimetric analysis (TGA) results demonstrate that introducing BPDI into PET obviously improves its thermal stability and the forming ability of char residue. LOI, vertical UL-94 and cone calorimeter measurements have been applied to investigate the combustion behaviors of P(ET-co-BP)n. The results prove that P(ET-co-BP)n copolyesters containing biphenyl biimide show better fire safety, reflected by lower fire growth rate (FIGRA) and low smoke production. SEM and Raman results suggest that the char layers of P(ET-co-BP)n become denser and mainly consist of polyaromatic species with small and uniform microstructures. The pyrolysis behaviors of the copolyesters are investigated by Py-GC/MS, and the results showed that the biphenyl biimide structure units can lead to rearrangement reactions at high temperature, ultimately forming the phenanthrene ring structures during combustion. Without traditional flame-retardant elements like halogen and phosphorus, this novel PET copolyester is environmentally friendly and more safety.

To improve the flame retardant efficiency of aromatic Schiff base (BA), and adjust the crosslinking temperature of imine groups, a cyano group, an electron-drawing group has been introduced into the chemical structure of aromatic Schiff base to obtain a third monomer for poly(ethylene terephthalate) (PET), named as dimethyl-5-[(2-cyanobenzylidene)amino]-isophthalate (CBAA). Thermogravimetry-differential scanning calorimetry (TG-DSC) and dynamic rheological results prove that the PET-based copolyester containing CBAA (CBAAnPETs) can cross-link at higher temperature than that containing BA, which will not affect the preparing and processing of PET. DSC and wide angle x-ray diffraction (WAXD) results demonstrate CBAAnPETs remain good crystallization ability. Owing to the two types of cross-linking reactions, i. e. the reactions between Schiff base ( CH N-) and cyano group (-C≡N), and among -CH N- units, CBAA plays an important role in solid phase as well as gaseous phase endowing CBAAnPETs with excellent flame retardancy. With a low CBAA content (only 6.7 mol%), the copolyesters self-extinguish in 5 s with no melt drips in UL-94 vertical test, and its LOI value also increases to 31.0%. The peak heat release rate and total smoke release of the copolyesters obtained from cone calorimetry also observably decrease.

To characterize the dry and wet deposition of atmospheric trace elements in urban Beijing, both active and passive samplers were used to collect bulk and wet sedimentation samples between May 2014 and April 2015.The concentrations of 19 trace elements (Na, Mg, Al, K, Ca, V, Cr, Mn, Fe, Cu, Zn, As, Se, Mo, Cd, Sb, Tl, Th, and U) in the samples were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results show that the concentrations of metals in bulk deposition samples[7160.68 μg·L

The achievement of both robust fire-safety and mechanical properties is of vital requirement for carbon fiber (CF) composites. To this end, a facile interfacial strategy for fabricating flame-retardant carbon fibers decorated by bio-based polyelectrolyte complexes (PEC) consisting of chitosan (CH) and ammonium polyphosphate (APP) was developed, and its corresponding fire-retarded epoxy resin composites (EP/(PEC@CF)) without any other additional flame retardants were prepared. The decorated CFs were characterized by SEMEDX, XPS and XRD, indicating that the flame-retardant PEC coating was successfully constructed on the surface of CF. Thanks to the nitrogen- and phosphorous-containing PEC, the resulting composites exhibited excellent flame retardancy as the limiting oxygen index (LOI) increased from 31.0% of EP/CF to 40.5% and UL-94 V-0 rating was achieved with only 8.1 wt% PEC. EP/(PEC8.1@CF) also performed well in cone calorimetry with the decrease of peak-heat release rate (PHRR) and smoke production rate (SPR) by 50.0% and 30.4%, respectively, and the value of fire growth rate (FIGRA) was also reduced to 3.41 kW·m–2·s–1 from 4.84 kW·m–2·s–1, suggesting a considerably enhanced fire safety. Furthermore, SEM images of the burning residues revealed that the PEC coating exhibited the dominant flame-retardant activity in condensed phase via the formation of compact phosphorus-rich char. In addition, the impact strength of the composite was improved, together with no obvious deterioration of flexural properties and glass transition temperature. Taking advantage of the features, the PEC-decorated carbon fibers and the relevant composites fabricated by the cost-effective and facile strategy would bring more chances for widespread applications.

Hypoxia refers to the lack of oxygen supply to cells or tissues. The overexpression of nitroreductase has been shown to be closely related to the degree of hypoxia, which leads to the level of nitroreductase (NTR) being used as an indicator of hypoxia. We reported a facile visual detection of NTR based on the aggregation of gold and silver alloy nanoparticles. Compared with gold nanoparticles (AuNPs), the aggregation behavior of Au80Ag20 NPs caused a more prominent color change. Copper ions (Cu2+) can be rapidly reduced by nicotinamide adenine dinucleotide (NADH) under the catalysis of Au80Ag20 NPs. But NADH is consumed as an electron donor during the catalytic reduction reaction of p-nitrophenol (pNP) by NTR. A decrease of NADH amount results in the aggregation of Au80Ag20 NPs by the excess Cu2+ and different aggregation degrees of Au80Ag20 NPs lead to observable color change. A linear correlation of A600/A505 = 0.0285 [NTR]+0.361 (R2 = 0.980) was obtained with a limit of detection (LOD) of 0.23 μg/mL for UV–vis spectrophotometer. For visual detection, the values of R/B against the concentration of NTR obtains a calibration curve of R/B = −0.031 [NTR]+ 1.54 (R2 = 0.985) with a LOD of 0.76 μg/mL, which is of the same order of magnitude as the UV–vis spectrophotometer analysis. As a comparison, Au80Ag20 NPs was replaced by several different composition nanoparticles (Au NPs, Au70Ag30 NPs, Au50Ag50 NPs) to be a chromogenic substrate, and the results suggest the Au80Ag20 NPs is the most sensitive substrate in our assay. Selectivity tests showed that the detection system did not respond to other common substances, and the reaction mechanism was verified by inhibitor research. Finally, the assay was used on the human serum samples with spiking NTR, and the recovery rates of this assay with UV–vis spectrophotometer were basically consistent with RGB analysis.

Biomass-derived aerogels have received extensive attention as potential thermal management materials for energy-efficient buildings. However, it remains a huge challenge to fabricate a fully bio-based aerogel with excellent mechanical property, flame retardancy, and low thermal conductivity. Herein, we demonstrate a novel and facile strategy to manufacture a fully biomass-based aerogel from naturally abundant ammonium alginate (AL) and phytic acid (PA), in which PA acting as both flame retardant and cross-linking components constructs a strong network with AL matrix. Consequently, the resultant biomass aerogel with a low density of 0.052 g/cm3 exhibits ultrahigh mechanical modulus (25.1 ± 3.1 MPa) and specific modulus (440.4 ± 54.4 MPa cm3·g−1), much superior to those of biomass aerogels ever reported. Due to the existence of the uniform three-dimensional porous network, the biomass aerogels exhibit low thermal conductivity (34–38 mW/m·K) and excellent thermal insulation performances. Further, the introduction of PA endows the aerogel with high flame retardancy (limiting oxygen index value of 57%, UL-94 V-0 rating, and extremely low heat release), while the biodegradability of the materials keeps at a high level with a biodegradation rate of 91.43%. Combining with the advantages of mechanically strong property, high flame retardancy, excellent thermal insulation, and biodegradation, the aerogel of this work provides a new strategy to fabricate thermal insulation materials with high environmental safety.

We report a green, reliable and single-step colorimetric assay for tyrosinase (Tyr) using the silver nanoparticles (AgNPs) as the signal readout. With the aid of light as the catalyst, kojic acid can rapidly reduce Ag+ ions and stablize the produced AgNPs. While uopn addition of Tyr during the synthesis of AgNPs, Tyr can effectively interrupt the formation of AgNPs due to its preferential combination with kojic acid, eventually leading to color fading and signal decrease of AgNPs solution. The presented method shows a good linear response toward Tyr over the range 0.5–4 u/mL with low detection limit of 0.117 u/mL. Common coexisting substances including metal ions, amino acids and biomacromolecules exert no effect on the determination of Tyr. This colorimetric sensor was successfully employed to quantify Tyr in human serum samples.

The use of conventional flame-retardant elements such as Cl, Br, P for carbon-based polymers usually leads to the deterioration of smoke and toxic gas release, and possesses serious environmental and ecological issues. Herein, we proposed a facile strategy to largely improve the flame-retardant efficiency of an eco-friendly flame-retardant method. By simply tailoring the substitution position of the functional polymerization monomer, the corresponding copolymer exhibited extremely high flame retardancy, including a 59% lower peak heat release rate (pHRR), a 48% lower smoke density, a high limiting oxygen index (LOI) of 30%, and passed the UL-94 V-0 rating without dripping. More importantly, the para-substitution copolymer showed a much higher flame-retardant efficiency than the meta-substitution copolymer, for which the monomer content needed for UL-94 V-0 rating, high LOI value, and low smoke and toxic gas release largely decreased by 25%. The detailed mechanism and the different performance between the two copolymers were comprehensively investigated. The results first confirmed the “end-group-capturing” mechanism, then revealed that the different flame-retardant efficiency was owing to the different thermal rearrangement capability of the two functional monomers. The molecular-level mechanism revealed here provided a novel thinking for designing flame-retardant polymers.

Conventional methods of improving the flame retardancy of PA 6 usually involve the sacrifice of mechanical properties, which is unfavorable for the practical application. Herein, two Schiff-base containing phosphonate oligomers PSA and POSC, were designed and used as novel flame retardants for PA 6. The PA 6-PSA20 composite involving P-Ph structure achieved a LOI value of 27% and UL-94 V-0 rating, while the PA 6-POSC20 composite involving P-O-Ph structure achieved a higher LOI value of 32% but a UL-94 V-2 rating. The PA 6-POSC composites also exhibited better heat-suppression effect than the PA 6-PSA composites. The different flame-retardant mechanism of these two flame retardants were comprehensively studied via Raman spectra, XPS, FTIR, TG-IR and Py-GC/MS. Additionally, the PA 6 composites all exhibited great processability and largely retained mechanical properties. This work proposed an efficient route for preparing flame-retardant polyamide composite with excellent overall performance.

Semi-aromatic polyamides (SaPAs) combining each advantages of aliphatic and aromatic polyamides received ever-increasing development in both academia and industrial circles. In this work, four kinds of SaPAs with fluorenyl pendent and different length of aliphatic spacers, named P–FPB, P–FPH, P–FPO and P–FPD respectively, were designed and synthesized via the aromatic nucleophilic substitution (SNAr) polycondensation. The effects of both the rigid pendent and flexible methylene (4, 6, 8, 10) spacers on the comprehensive properties of the SaPAs were comprehensively investigated. At the presence of the rigid fluorenyl pendent and the intermolecular π–π stacking thereof, the resulting SaPAs exhibited enhanced glass transition temperature (Tg), thermal stability, solubility in typical organic solvents and mechanical properties compared with the commercially available 6T based SaPa. Also with increasing the number of the methylene units of the SaPAs, their Tg, Vicat softening temperature, tensile strength and modulus gradually decreased; while the initial decomposition temperature and impact strength anomalously increased. Rheological investigations and solubility tests further confirmed that the resulting SaPAs were suitable for processing either in melt or in solution. In addition, these polyamides displayed favorable dielectric properties for potential availability in electric and electronic applications.

Pseudocrossocheilus bamaensis is endemic to the upstream of Xijiang River, Guangxi, China and its natural population has been declining due to overfishing and habitat destruction. Here, we first report the complete mitogenome of this species, which is 16,594 bp in length, containing 13 protein-coding genes, 22 tRNA genes, two rRNA genes, as well as a putative light strand origin of replication (OL) and a putative control region (D-loop). The overall base composition is 31.8% of A, 15.7% of G, 26.8% of T and 25.7% of C, with a high A + T content (58.6%). Phylogenetic analysis suggests that P. bamaensis is closely related to Ptychidio jordani and Rectoris posehensis. These results will contribute to the molecular evolution and phylogenetic research of Labeoninae and further protection of its fish species.

In this paper, the 2X method is used to extract the components parameters, and the 2X method is been verified by using simulation models. Meanwhile, we compare the de-embedding results under two different through standards, which are based on composite standard and through standard respectively. The conclusion is that the extraction based on through standard is more accurate.

Background Shengui Sansheng Pulvis (SSP) has about 300 years history used for stroke treatment, and evidences suggest it has beneficial effects on neuro-angiogenesis and cerebral energy metabolic amelioration post-stroke. However, its protective action and mechanisms on blood-brain barrier (BBB) is still unknown. Purpose Based on multiple neuroprotective properties of vasoactive intestinal peptide (VIP) in neurological disorders, we investigate if SSP maintaining BBB integrity is associated with VIP pathway in rat permanent middle cerebral artery occlusion (MCAo) model. Methods Three doses of SSP extraction were administered orally. Evaluations of motor and balance abilities and detection of brain edema were performed, and BBB permeability were assessed by Evans blue (EB) staining. Primary brain microvascular endothelial cells (BMECs) were subjected to oxygen-glucose deprivation, and incubated with high dose SSP drug-containing serum and VIP-antagonist respectively. Transendothelial electrical resistance (TEER) assay and Tetramethylrhodamine isothiocyanate (TRITC)-dextran (4.4 kDa) and fluorescein isothiocyanate (FITC)-dextran (70 kDa) were used to evaluate the features of paracellular junction. Western blot detected the expressions of Claudin-5, ZO-1, Occludin and VE-cadherin, matrix metalloproteinase (MMP) 2/9 and VIP receptors 1/2, and immunofluorescence staining tested VIP and Claudin-5 expressions. Results Our results show that SSP significantly reduces EB infiltration in dose-dependent manner in vivo and attenuates TRITC- dextran and FITC-dextran diffusion in vitro, and strengthens endothelial junctional complexes as represented by decreasing Claudin-5, ZO-1, Occludin and VE-cadherin degradations and MMP 2/9 expression, as well as promoting TEER in BMECs after ischemia. Moreover, it suggests that SSP notably enhances VIP and its receptors 1/2 expressions. VIP-antagonist exacerbates paracellular barrier of BMECs, while the result is reversed after incubation with high dose SSP drug-containing serum. Additionally, SSP also improve brain edema and motor and balance abilities after ischemic stroke. Conclusions we firstly demonstrate that the ameliorated efficacy of SSP on BBB permeability is related to the enhancements of VIP and its receptors, suggesting SSP might be an effective therapeutic agent on maintaining BBB integrity post-stroke.

A colorimetric assay is described for determination of cytosine-rich ssDNA at physiological pH values. The working principle is based on (a) Ag(I) ion-induced formation of an i-motif structure, and (b) glucose oxidase-controlled growth of gold nanoparticles (AuNPs). The combination between Ag+ and cytosine-rich DNA can modulate the generation of H2O2 resulting from enzyme catalyzed glucose oxidation. Depending on the amount of H2O2 formed, the solution containing the AuNPs will turn red in the presence of cytosine-rich ssDNA but blue in the absence of such DNA if Ag+ is added before the formation of the red AuNPs. Upon addition of C-DNA at different concentrations, the peak shift (Δλ) of the AuNP solution relative to the SPR peak position (560 nm) in the absence of C-DNA is taken as the signal readout. The method shows a good linear response toward C-DNA over the range 10–200 nM with a detection limit of 2.7 nM. It may also be performed visually. The photometric assay is highly sensitive, specific, and rapid. The method is particularly attractive in terms of applications such as in human serum analysis, a colorimetric logic gate, and the calculation of binding constants for the interaction between Ag+ and glucose oxidase (GOx), and between Ag+ and cytosine-rich ssDNAs.

Breast cancer is the most common malignant tumor and the main cause of cancer-associated mortality in females worldwide. Long non-coding RNAs (lncRNAs) have been reported to play vital roles in breast cancer development and progression; however, our understanding of most lncRNAs in breast cancer is still limited. In this study, we demonstrated that small nucleolar RNA host gene 5 (SNHG5) promotes breast cancer cell proliferation both in vitro and in vivo, and depletion of SNHG5 significantly led to cell-cycle arrest at G1 phase. Accumulating evidence has shown that many lncRNA transcripts could function as competing endogenous RNAs (ceRNAs) by competitively binding common microRNAs (miRNAs). We found that SNHG5 acts as a sponge for miR-154-5p, reducing its ability to repress proliferating cell nuclear antigen (PCNA). SNHG5 promoted breast cancer proliferation and cell-cycle progression by upregulation of PCNA expression. Clinically, we observed an increased SNHG5 expression in breast cancer, whereas miR-154-5p was decreased in breast cancer tissues compared with the adjacent normal breast tissues. Furthermore, the SNHG5 expression was significantly negatively correlated with miR-154-5p expression. Taken together, our data uncover the SNHG5-miR-154-5p-PCNA axis and provide a novel mechanism to explain breast cancer proliferation., Graphical Abstract

In order to find attack patterns from a large number of redundant alert logs, build multi-step attack scenarios, and eliminate the false alerts of the alert logs, this paper proposes a new multi-step attack scenario construction model, which is divided into two parts: offline mode and online mode. In the offline mode, the known real attack alert log is used to train the neural network for removing error alerts, and eventually to generate a Bayesian network attack graph by alert aggregation processing and causal association attack sequence. In the online mode, a large number of online alert logs are used to update the neural network and the Bayesian network attack graph generated by the previous offline mode, so that the iterative attack graph is more complete and accurate. In the end, we extract a variety of multi-step attack scenarios from the Bayesian network attack graph to achieve the purpose of eliminating false alerts in the redundant IDS alert logs. In order to verify the validity of the algorithm, we use the DARPA 2000 dataset to test, and the results show that the algorithm has higher accuracy.

Lateral root (LR) formation and development play a vital role in plant development by permitting the establishment of branched root systems. It is well known that nutrient availability controls LR development. Moreover, LR development is fine-tuned by a myriad of hormonal signals. Many transcription factors (TFs) participate in LR development. Here, we discuss the TFs involved in the nitrate and auxin signaling pathways and how these function in the regulation of LR formation and development in chrysanthemum. AtTCP20 is a plant-specific TF, which can modulate LR development in response to nitrate. The roles of CmTCP20 in LR development were identified by overexpression in chrysanthemum and heterologous expression in Arabidopsis. Overexpression of CmTCP20 significantly increased the number and average length of LRs compared with the wild type in chrysanthemum and Arabidopsis. We also found that CmTCP20 positively influenced auxin accumulation in the LRs at least partly by improving auxin biosynthesis, transport and response, thereby promoting LR development. Moreover, we found that CmTCP20 interacts with an auxin response factor, CmARF8, which also can be induced by nitrate and combined to proximal sites in the upstream promoter region of CmCYCB1;1 to positively regulate the cell cycle. The CmTCP20-CmARF8 heterodimer links nitrate and auxin signaling and converts cell-cycle signals to regulate LR initiation and growth.

Conventional methods to improve the flame retardancy of polymeric materials usually involve the use of flame-retardant elements such as Cl, Br and P, however, their use may bring more smoke and toxic gases hazards, and more importantly, cause non-negligible environmental and ecological problems. In this work, we put forward a novel green strategy that eliminates the use of any conventional flame-retardant elements to improve the flame retardancy by incorporating a synergistically cross-linkable structure (named PN) containing phenylacetylene and phenylimide groups. The resulting PN copolymer exhibited an excellent 55% lower smoke release rate and 68% lower heat release rate than the pure polymer, as well as a high LOI value of 32% and UL-94 V-0 rating with excellent anti-dripping performance. TG-DSC, rheological and FTIR results proved the high cross-linking ability of the PN copolymer due to the synergistic cross-linking effect between the “imide-isoimide” rearrangement of phenylimide and the “self-cross-linking” of phenylacetylene. The SEM, Raman and Py-GC/MS results further upheld the condensed phase flame-retardant mechanism. This eco-friendly synergistic cross-linking strategy provided new perspective for the design and synthesis of polymeric materials with excellent flame retardancy, great anti-dripping performance, and low release of heat, smoke, and toxic gas.

Despite the excellent overall performance, the application of polyesters is severely restricted by their inherently high flammability. Although many gratifying results have been achieved through different fire-safety methods, customization is still needed for every specific polymer, thus a generally applicable method is highly desired. Herein, we developed an eco-friendly and general fire-safety method for semi-aromatic polyesters based on the “end-group-capturing” concept. The functional monomer was chemically incorporated into the main chains of a series of semi-aromatic polyesters with similar structures (i.e., polyethylene terephthalate (PET), polytrimethylene terephthalate (PTT) and polybutylene terephthalate (PBT)), and the specific contribution of the fire-safety method was investigated comprehensively. The results showed that the fire safety of all the copolyesters were efficiently improved, while interestingly, the fire safety gradually declined with the increase of the methylene group numbers in their molecular chains. The reason behind this phenomenon was comprehensively studied by both theoretical calculation and experiments. The increasing cyclization tendency of the copolyesters derived from the increase of the methylene group numbers was proved to be responsible for the decrease of the fire safety. The successful application and in-depth mechanism revealed here provide theoretical supports for the development of novel fire-safety polymeric materials.

An approach to fabricate sintered copper with high green strength and high sintered density using nonaqueous gelcasting technology is presented in this study. The effects of various gelcasting processing parameters such as monomer content, monomer/crosslinker ratio, initiator content, dispersant dosage, and temperature on the flexural strength of dried green bodies and the relative density of sintered bodies were studied to obtain better microstructures and properties. The appropriate process parameters obtained for copper gelcasting are as follows: monomer content, 20vol%–30vol% (based on the total volume of reagents); monomer/crosslinker ratio, 10:1 to 20:1; initiator content, 3vol%–4vol% (based on the volume of the monomer); dispersant dosage, 1.5wt%–2.5wt% (based on the mass of the copper powder); and reaction temperature, 65–75°C.

The Chinese white wax scale insect, Ericerus pela, can survive at extremely low temperatures, and some overwintering individuals exhibit supercooling at temperatures below -30°C. To investigate the deep supercooling ability of E. pela, transcriptomic and proteomic analyses were performed to delineate the major gene and protein families responsible for the deep supercooling ability of overwintering females. Gene Ontology (GO) classification and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis indicated that genes involved in the mitogen-activated protein kinase, calcium, and PI3K-Akt signaling pathways and pathways associated with the biosynthesis of soluble sugars, sugar alcohols and free amino acids were dominant. Proteins responsible for low-temperature stress, such as cold acclimation proteins, glycerol biosynthesis-related enzymes and heat shock proteins (HSPs) were identified. However, no antifreeze proteins (AFPs) were identified through sequence similarity search methods. A random forest approach identified 388 putative AFPs in the proteome. The AFP gene ep-afp was expressed in Escherichia coli, and the expressed protein exhibited a thermal hysteresis activity of 0.97°C, suggesting its potential role in the deep supercooling ability of E. pela.

Several kinds of novel flame-retardant-free and thermo-crosslinkable epoxy resins (EPs) containing azobenzene or/and phenylacetylene groups have been synthesized and characterized, and the flame retardant properties as a result of thermal crosslinking during combustion were investigated in detail. Crosslinking behaviors were tested by simultaneous thermogravimetry–differential scanning calorimetry (TGA–DSC). Thermal stabilities were investigated by thermogravimetric analysis (TGA). Flame retardance of the resulting EPs was evaluated through LOI tests, and combustion behaviors were studied via cone calorimetry and micro-combustion calorimetry (MCC), which further confirmed that flame retardance of these EPs was significantly improved, despite the absence of conventional flame retardant. Py–GC/MS analysis was used to investigate the degradation mechanism of these epoxy resins, and the results confirmed that the flame-retardant activity of epoxy resins mainly took effect in the condensed phase. The chemical constitution of the char layers were investigated by XPS and Raman spectrum. The co-crosslinking behavior between azobenzene and phenylacetylene groups was predicted and confirmed, which led to the most compact char layer, therefore resulted in the best flame retardance of these EPs.

The whispering-gallery mode microlasers with the merits of small size and low power consumption are suitable for chip-based photonic integration. In this paper, the nonlinear dynamics for microdisk laser subject to optical injection is investigated for potential applications including photonic microwave generation and improved modulation characteristics. The four-wave mixing, period-one and period-two oscillations, and optical injection locking states are investigated based on the lasing spectra and generated microwave for a 10-μm-radius directional emission microdisk laser. Furthermore, direct modulation bandwidth enhancement from 5.6 to 17.6 GHz is observed for the injection-locked microdisk laser biased at 7 mA. The results reveal the necessity of further explore toward the potential applications of microdisk lasers under optical injection in photonic integrated chip.

Aiming to develop high performance flame-retardant epoxy resin (EP), a novel phosphorus-containing semi-aromatic polyester named poly[4,4′-bis(6-hydroxyhexyloxy)biphenyl 9,10-dihydro-10-[2,3-di(hydroxycarbonyl)propyl]-phosphaphenanthrene-10-oxide] (PBHDDP) was synthesized and employed as a multi-functional additive for EP with simultaneously flame retardation and mechanical enhancement. Appropriate thermodynamic compatibility between PBHDDP and the EP network made no phase separation occurred in the process of curing reaction. Compared with neat EP, the resultant EP thermoset containing barely 2.5 phr (2.44 wt%) of PBHDDP exhibited superior mechanical properties with 20.3% and 149% increase in tensile and impact strengths, respectively. Simultaneously, as increasing the content of PBHDDP, flame retardancy of the thermosets enhanced obviously as evidenced by the elevated anti-ignition and self-extinguishing performance, along with the reduced combustion rate and heat release. Whereas, obvious sacrifice of either transparency, glass transition temperature or thermal stability was absent. The exploration of this novel state-of-art that simultaneously improved the mechanical properties and flame retardancy of EP thermosets at a relatively low content of a single-component multi-functional additive provided a powerful basis for the technologies and potential industrial applications.

In this paper, we obtain the existence of non-planar circular homographic solutions and non-circular homographic solutions of the (2 + N)- and (3 + N)-body problems of the Lennard-Jones system. These results show the essential difference between the Lennard-Jones potential and the Newton’s potential of universal gravitation.

Based on the specialty orientation of Polymer Materials and Engineering in Beijing Institute of Graphic Communication (BIGC), this paper proposed the specific purpose, significance and basic principle on the course construction of Progress in Polymer. The basic content of curriculum construction mainly contain the lecture material construction, classroom teaching, practice and examination forms. The overall goal of this course is to train students with an international perspective and suitable to the economic and social development demands.

Microwave generation based on the nonlinear dynamics of a microsquare laser subject to optical injection is proposed and demonstrated experimentally. The nonlinear dynamics are illustrated and analyzed based on the lasing spectra under the optical injection with different detuning frequencies. The microwave signal related to the oscillation of carrier density is directly measured from the electrode of the microsquare laser. The generated microwave power versus the microwave frequency is in agreement with small signal modulation response curve. The results provide a possible approach to the on-chip integrated photonic microwave source.

Highly stable inclusion complexes between cyclodextrin (CD) and guest molecules form due to their host–guest interaction. Polymer systems based on the complexes have been extensively reported in recent years. In this review, we highlight some recent advances from polymer systems with adamantane (Ada), azobenzene (Azo), ferrocene (Fc) and so on as guest molecules in terms of their synthesis, properties and functions. Various polymer topologies ranging from linear, branched, comb-like and hyper-branched are discussed in detail. In addition, the related systems with environmental stimuli-responsiveness and their potential applications are also presented.