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The function of proteins depends on their correct structure and proper dynamics. Understanding the dynamics of target proteins facilitates drug design and development. However, dynamic information is often hidden in the spatial structure of proteins. It is important but difficult to identify the specific residues that play a decisive role in protein dynamics. Here, we report that a critical glycine residue (Gly463) dominates the motion of threonyl-tRNA synthetase (ThrRS) and the sensitivity of the enzyme to antibiotics. Obafluorin (OB), a natural antibiotic, is a novel covalent inhibitor of ThrRS. The binding of OB induces a large conformational change in ThrRS. Through five crystal structures, biochemical and biophysical analyses, and computational simulations, we found that Gly463 plays an important role in the dynamics of ThrRS. Mutating this flexible residue into more rigid residues did not damage the enzyme's three-dimensional structure but significantly improved the thermal stability of the enzyme and suppressed its ability to change conformation. These mutations cause resistance of ThrRS to antibiotics that are conformationally selective, such as OB and borrelidin. This work not only elucidates the molecular mechanism of the self-resistance of OB-producing Pseudomonas fluorescens but also emphasizes the importance of backbone kinetics for aminoacyl-tRNA synthetase-targeting drug development. Crystal structures and molecular dynamics simulations reveal that a critical glycine residue dominates the motion of threonyl-tRNA synthetase and the sensitivity of the enzyme to conformation selective inhibitors. [ABSTRACT FROM AUTHOR]

Aminoacyl-tRNA synthetases (aaRSs) play a central role in the translation of genetic code, serving as attractive drug targets. Within this family, the lysyl-tRNA synthetase (LysRS) constitutes a promising antimalarial target. ASP3026, an anaplastic lymphoma kinase (ALK) inhibitor was recently identified as a novel Plasmodium falciparum LysRS (PfLysRS) inhibitor. Here, based on cocrystal structures and biochemical experiments, we developed a series of ASP3026 analogues to improve the selectivity and potency of LysRS inhibition. The leading compound 36 showed a dissociation constant of 15.9 nM with PfLysRS. The inhibitory efficacy on PfLysRS and parasites has been enhanced. Covalent attachment of l-lysine to compound 36 resulted in compound 36K3, which exhibited further increased inhibitory activity against PfLysRS but significantly decreased activity against ALK. However, its inhibitory activity against parasites did not improve, suggesting potential future optimization directions. This study presents a new example of derivatization of kinase inhibitors repurposed to inhibit aaRS. Using a combination of biochemical and structural approaches, the authors demonstrate that derivatization of kinase inhibitors can yield new repurposed anti-malarial drugs that specifically target Plasmodium falciparum Lysine-tRNA synthetase. [ABSTRACT FROM AUTHOR]

In this paper, we extend Open-set Semantic Segmentation (OSS) into a new image segmentation task called Generalized Open-set Semantic Segmentation (GOSS). Previously, with well-known OSS, the intelligent agents only detect unknown regions without further processing, limiting their perception capacity of the environment. It stands to reason that further analysis of the detected unknown pixels would be beneficial for agents' decision-making. Therefore, we propose GOSS, which holistically unifies the abilities of two well-defined segmentation tasks, i.e. OSS and generic segmentation. Specifically, GOSS classifies pixels as belonging to known classes, and clusters (or groups) of pixels of unknown class are labelled as such. We propose a metric that balances the pixel classification and clustering aspects to evaluate this newly expanded task. Moreover, we build benchmark tests on existing datasets and propose neural architectures as baselines. Our experiments on multiple benchmarks demonstrate the effectiveness of our baselines. Code is made available at https://github.com/JHome1/GOSS_Segmentor. [ABSTRACT FROM AUTHOR]

The discharge corrosion of glass fiber reinforced epoxy resin rods is considered as a primary factor in the fracture of composites insulators. Therefore, studying the discharge corrosion of epoxy resin is meaningful. In this study, Electrochemical Impedance Spectroscopy (EIS) in conjunction with Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) are applied to evaluate the microstructure evaluation and water diffusion of epoxy resin under corona discharge. Polar groups including N–H, N–C bonds and aromatic nitro-compounds are generated, leading to decrease of water contact angle. Blisters are generated on the surface after corona treatment, likely induced by overheating, and their dimensions increase with treatment time. After 6 h treatment, micro-cracks are observed on surface of blisters. EIS diagrams showed two time constant at middle frequencies attributing to surface blisters and inner structure defects after corona treatment. The water diffusion coefficient of corona treated samples increases from 0.11 × 10−11 cm2s−1 to 72.89 × 10−11 cm2s−1 along with porosity upgraded to 1000 times to virgin sample, as treatment time prolongs. The generation of polar groups, micro-cracks, and development of structure defects from surface to deeper position accelerate water diffusion in epoxy resin. The process of blistering on the surface of epoxy resin under corona discharge gradually leads to structure defects, resulting in increased porosity and loss of barrier properties. [ABSTRACT FROM AUTHOR]

This document is a correction notice for an article titled "GOSS: towards generalized open-set semantic segmentation" published in the journal Visual Computer. The correction addresses mistakes in the article, including incorrect email addresses for the authors and errors in Figures 1, 3, and 4. The corrected addresses and figures are provided, and electronic supplementary material is added. The article discusses the tasks of image segmentation and introduces the framework of the baseline and GOSS Segmentor for pixel classification and clustering. Visualized segmentation results from the GOSS Segmentor are also presented. The original article has been corrected. [Extracted from the article]

Cross-modality pedestrian image matching, which entails the matching of visible and infrared images, is a vital area in person re-identification (reID) due to its potential to facilitate person retrieval across a spectrum of lighting conditions. Despite its importance, this task presents considerable challenges stemming from two significant areas: cross-modality discrepancies due to the different imaging principles of spectrum cameras and within-class variations caused by the diverse viewpoints of large-scale distributed surveillance cameras. Unfortunately, the existing literature provides limited insights into effectively mitigating these issues, signifying a crucial research gap. In response to this, the present paper makes two primary contributions. First, we conduct a comprehensive study of training methodologies and subsequently present a strong baseline network designed specifically to address the complexities of the visible-infrared person reID task. This strong baseline network is paramount to the advancement of the field and to ensure the fair evaluation of algorithmic effectiveness. Second, we propose the Cross-Modality Contrastive Learning (CMCL) scheme, a novel approach to address the cross-modality discrepancies and enhance the quality of image embeddings across both modalities. CMCL incorporates intra-modality and inter-modality contrastive loss components, designed to improve the matching quality across the modalities. Thorough experiments show the superior performance of the baseline network, and the proposed CMCL can further bring performance over the baselines, outperforming the state-of-the-art methods considerably. [ABSTRACT FROM AUTHOR]

Embedding data in hyperbolic spaces has proven beneficial for many advanced machine learning applications. However, working in hyperbolic spaces is not without difficulties as a result of its curved geometry (e.g., computing the Fréchet mean of a set of points requires an iterative algorithm). In Euclidean spaces, one can resort to kernel machines that not only enjoy rich theoretical properties but that can also lead to superior representational power (e.g., infinite-width neural networks). In this paper, we introduce valid kernel functions for hyperbolic representations. This brings in two major advantages, 1. kernelization will pave the way to seamlessly benefit the representational power from kernel machines in conjunction with hyperbolic embeddings, and 2. the rich structure of the Hilbert spaces associated with kernel machines enables us to simplify various operations involving hyperbolic data. That said, identifying valid kernel functions on curved spaces is not straightforward and is indeed considered an open problem in the learning community. Our work addresses this gap and develops several positive definite kernels in hyperbolic spaces (modeled by a Poincaré ball), the proposed kernels include the rich universal ones (e.g., Poincaré RBF kernel), or realize the multiple kernel learning scheme (e.g., Poincaré radial kernel). We comprehensively study the proposed kernels on a variety of challenging tasks including few-shot learning, zero-shot learning, person re-identification, deep metric learning, knowledge distillation and self-supervised learning. The consistent performance gain over different tasks shows the benefits of the kernelization for hyperbolic representations. [ABSTRACT FROM AUTHOR]

In this paper, a new four-dimensional hyperchaotic system that has better unpredictability, more complex dynamic behavior, and a larger key space is proposed. The initial chaos value is calculated by using the Secure Hash Algorithm-512 (SHA-512) function, and the hyperchaotic sequence is then used as the key stream to encrypt the original image through pixel scrambling and pixel diffusion. The experimental results show that the image encryption algorithm has a strong ability to resist exhaustive attacks, statistical attacks and plaintext attacks. [ABSTRACT FROM AUTHOR]

Many researchers have devoted themselves to studying image encryption based on chaotic system and have made significant strides in research in recent decades. This paper first combs and summarizes the development of the current image encryption algorithm. Then, the classification of chaotic system is described, and representative work and the latest achievements regarding image encryption algorithms based on chaotic system are analysed, expounding their advantages and disadvantages. Finally, we discuss future research directions and development trends in image encryption algorithms based on chaotic system. [ABSTRACT FROM AUTHOR]

In this work, a series of iso-structural eulyite-type Ba3Yb(PO4)3:Tb3+ solid solution phosphors were synthesized via high-temperature solid-phase method. The corresponding unit cell structure, luminescence properties, thermal stability, and chromaticity coordinates of the as-obtained phosphors were systematically investigated. The crystal structure of Ba3Yb(PO4)3:Tb3+ was refined by GSAS program, which indicates the oxygen ions in Ba3Yb(PO4)3 are disordered at one C3 site, and the oxygen atoms are distributed at two sites. Under 378 nm ultraviolet excitation, the emission peak of Ba3Yb(PO4)3:Tb3+ appears in the range of 450–650 nm, and a characteristic green emission peak appears at 542 nm. Moreover, the luminous intensity of the Ba3Yb(PO4)3:14 at.% Tb3+ sample at 160 °C is 87.7% at room temperature, and the quantum yield is 55.8%, which reveals good thermal stability. Our results suggest that the Ba3Yb(PO4)3:Tb3+ phosphors are promising high-efficiency green light conversion materials for UV-LED applications. [ABSTRACT FROM AUTHOR]

Aminoacyl-tRNA synthetases (AARSs), a family of essential protein synthesis enzymes, are attractive targets for drug development. Although several different types of AARS inhibitors have been identified, AARS covalent inhibitors have not been reported. Here we present five unusual crystal structures showing that threonyl-tRNA synthetase (ThrRS) is covalently inhibited by a natural product, obafluorin (OB). The residue forming a covalent bond with OB is a tyrosine in ThrRS active center, which is not commonly modified by covalent inhibitors. The two hydroxyl groups on the o-diphenol moiety of OB form two coordination bonds with the conserved zinc ion in the active center of ThrRS. Therefore, the β-lactone structure of OB can undergo ester exchange reaction with the phenolic group of the adjacent tyrosine to form a covalent bond between the compound and the enzyme, and allow its nitrobenzene structure to occupy the binding site of tRNA. In addition, when this tyrosine was replaced by a lysine or even a weakly nucleophilic arginine, similar bonds could also be formed. Our report of the mechanism of a class of AARS covalent inhibitor targeting multiple amino acid residues could facilitate approaches to drug discovery for cancer and infectious diseases. Structures of E. coli threonyl-tRNA synthetase in complex with natural product obafluorin (OB) reveal that OB is a unique covalent inhibitor. [ABSTRACT FROM AUTHOR]

Polyacrylonitrile (PAN)-based carbon fibers are widely used as reinforcement materials and heating elements for their excellent mechanical and electric heating properties. But fiber oxidation at high temperature can easily cause electric heating device failure. Herein, the electrothermal effect of the carbon fiber modified by graphene epoxy resin coating was investigated, and the mechanism of electrothermal enhancement of the fiber was explored by detailed analysis of the surface structure and finite element simulation. The results showed that graphene coating and sintering under N2 environment have effective protective effects on the carbon fiber, which greatly improves the electrothermal performance of the carbon fiber. Graphene coating-modified carbon fibers reached about 35°C at 3 V within 20 s, and the equilibrium temperature is about 21% higher than that of the pristine carbon fiber. At the same time, in 20 electric heating and cooling tests at 5 V, the electric temperature can quickly reach 82°C with good stability. Further simulation showed that the electrothermal performance may be enhanced by the current accumulation caused by the surface defect structure of modified carbon fibers. The modification method of graphene coating on carbon fiber surface presented in this paper is simple and easy to control and has great potential to be applied to industrial and civil electric heating equipment. [ABSTRACT FROM AUTHOR]

To address the problems of existing image encryption algorithms based on chaotic systems, such as the weak resistance to attack, the unstable performance of the chaotic system, and the small size of the key space, a new block image encryption algorithm based on a new hyperchaotic system and generative adversarial networks (GANs) is proposed in this paper. First, a new hyperchaotic system with an improved chaotic dynamic performance and key space is designed. Then, to ensure the security and efficiency of whole-image block encryption, the new hyperchaotic system is combined with the nonlinear parallel processing mechanism of the neural network, key stream, generative adversarial networks and an improved generalized Feistel structure to scramble and diffuse the plaintext image at the pixel level to obtain the ciphertext image. The experimental results show that the proposed encryption algorithm has a large key space, high security and robustness and resistance to common attacks. At the same time, the proposed method provides a new idea for the combination of chaotic systems and neural networks in image encryption. [ABSTRACT FROM AUTHOR]

The evolutionary necessity of aminoacyl-tRNA synthetases being associated into complex is unknown. Human lysyl-tRNA synthetase (LysRS) is one component of the multi-tRNA synthetase complex (MSC), which is not only critical for protein translation but also involved in multiple cellular pathways such as immune response, cell migration, etc. Here, combined with crystallography, CRISPR/Cas9-based genome editing, biochemistry, and cell biology analyses, we show that the structures of LysRSs from metazoan are more dynamic than those from single-celled organisms. Without the presence of MSC scaffold proteins, such as aminoacyl-tRNA synthetase complex-interacting multifunctional protein 2 (AIMP2), human LysRS is free from the MSC. The interaction with AIMP2 stabilizes the closed conformation of LysRS, thereby protects the essential aminoacylation activity under stressed conditions. Deleting AIMP2 from the human embryonic kidney 293 cells leads to retardation in cell growth in nutrient deficient mediums. Together, these results suggest that the evolutionary emergence of the MSC in metazoan might be to protect the aminoacyl-tRNA synthetase components from being modified or recruited for use in other cellular pathways. [ABSTRACT FROM AUTHOR]

Nafion composite membranes with various amounts of sulfonated multi-walled carbon nanotubes (Su-CNTs) were prepared either in or without a strong magnetic field. Interestingly, it is found that being recast in a strong magnetic field, the tensile strength at break and proton conductivity of Su-CNTs/Nafion composite membranes parallel to the magnetic field direction were higher than those perpendicular to magnetic field. Remarkably, such anisotropic mechanical property and proton conductivity of Su-CNTs/Nafion composite membranes strongly depend on water uptake and temperature, in particular the content of Su-CNTs. Quite a different dependence of the proton conductivity of the composite membranes on Su-CNT content, relative humidities and temperatures is well explained for the anisotropic proton conductivity of the Su-CNTs/Nafion membrane recast in a strong magnetic field, which is attributed to the preferential proton transporting along ionic water channels mainly coalesced by the orientated Su-CNTs at a specific water uptake. For Nafion composite membranes with 5 wt.% Su-CNTs, the proton conductivity along the direction of treating magnetic field approaches to 0.216 S/cm, which is ∼ 46% higher than that perpendicular to the magnetic field at 95 ∘ C. The present work provides a deep insight of the humidity and temperature dependence of proton conductivity of Su-CNTs/Nafion composite membranes and a new strategy for fabrication proton exchange membranes with high proton conductivity as well as good mechanical property. [ABSTRACT FROM AUTHOR]

Fumed silica (FS)-filled polydimethylsiloxane (PDMS) composite is widely used as the external insulating material in power grid. The function of PDMS composite is to keep the core of an insulation device being dry by preventing the permeation of outside water. To study water diffusion in PDMS composite helps to shed light upon the failure mechanism of the insulation devices. In this paper, positron annihilation lifetime spectroscopy (PALS) and electrochemical impedance spectroscopy (EIS) were applied to study the FS/PDMS interface structure and water diffusion in PDMS composite. It is found that the FS has two basic existing states in PDMS matrix: dispersed state and percolated state, and the percolation threshold of FS is fitted to be 6.0 wt.%. In the dispersed state, the FS particles are randomly dispersed in PDMS matrix. The values of τ 3 remain stable, being approximately 1.0 ns, indicating no overlaps of the FS/PDMS interfaces. Moreover, water cannot diffuse through the sample after corona aging. In the percolated state, the FS particles are tightly packed in the PDMS matrix. The values of τ 3 decrease with the weight fraction of FS, suggesting the overlapping of the FS/PDMS interfaces. As the FS percolates in sample bulk, these overlapped FS/PDMS interfaces provide continuous diffusion tunnels for water, thus resulting in failure of the composite after corona aging. It is found that polarization and discharge of the electrons at FS/PDMS interface under corona discharge is the main mechanism that leads to the failure of the composite bulk. [ABSTRACT FROM AUTHOR]

Silicone rubber is widely used in power grids, electronics and aerospace, because of its hydrophobicity, high flexibility, etc. However, it is susceptible to some environmental chemical factors, such as NO2 and ozone, which can induce chain scission, the generation of defects and the ingress of water. In this work, we systematically studied the microstructure variations and water diffusion behavior of high-temperature vulcanized (HTV) silicone rubber after NO2-induced oxidative damage. Microstructure evolution in silicone rubber was investigated by positron annihilation lifetime spectroscopy (PALS). The results show that the oxidation of NO2 significantly degrades organic matrices, which induces the decrease of crosslinking degree and the formation of defects compared to virgin samples. The water transportation was evaluated by electrochemical impedance spectroscopy (EIS), which showed that the diffusion coefficient, under the NO2 concentration of 28.75 mg L−1, is 106 times that of virgin sample with a water uptake of 31%. Particularly, when the concentration reaches the critical value around 17.25 mg L−1, the diffusion coefficient and water uptake increase sharply, and the calculated average porosity of samples also dramatically increases by 4 orders of magnitude. These indicate the formation of more nano- and micron holes, serving as a pointer for percolation of defects in silicone rubber bulk. The study of microstructure variations and water transportation can help us to understand the aging mechanism, design reasonable composite polymer materials and prevent the damage of chemical contact. [ABSTRACT FROM AUTHOR]

Aminoacyl-tRNA synthetases (aaRSs) are ubiquitously expressed, essential enzymes, synthesizing aminoacyl-tRNAs for protein synthesis. Functional defects of aaRSs frequently cause various human disorders. Human KARS encodes both cytosolic and mitochondrial lysyl-tRNA synthetases (LysRSs). Previously, two mutations (c.1129G>A and c.517T>C) were identified that led to hearing impairment; however, the underlying biochemical mechanism is unclear. In the present study, we found that the two mutations have no impact on the incorporation of LysRS into the multiple-synthetase complex in the cytosol, but affect the cytosolic LysRS level, its tertiary structure, and cytosolic tRNA aminoacylation in vitro. As for mitochondrial translation, the two mutations have little effect on the steady-state level, mitochondrial targeting, and tRNA binding affinity of mitochondrial LysRS. However, they exhibit striking differences in charging mitochondrial tRNALys, with the c.517T>C mutant being completely deficient in vitro and in vivo. We constructed two yeast genetic models, which are powerful tools to test the in vivo aminoacylation activity of KARS mutations at both the cytosolic and mitochondrial levels. Overall, our data provided biochemical insights into the potentially molecular pathological mechanism of KARS c.1129G>A and c.517T>C mutations and provided yeast genetic bases to investigate other KARS mutations in the future. [ABSTRACT FROM AUTHOR]

Selective growth of cocatalyst on the surface of photocatalyst has been attracted considerable attention due to their efficient charges transfer property. In this study, the robust NiS modified graphitic carbon nitride (g-C3N4) hybrids were successfully synthesized by a facile surface photochemical deposition process. The structure and composition characterization results revealed that the NiS is highly dispersed loading on the surface of g-C3N4 nanosheets, and the NiS/g-C3N4 hybrids possess large surface areas and excellent optical properties. Under the visible light illumination, the NiS/g-C3N4 hybrids with 1.0% weight content of NiS cocatalyst exhibits the highest hydrogen evolution rate of 1346.1 μmol h−1 g−1 with an apparent quantum efficiency (AQE) of 7.67%. On the basis of photoluminescence (PL) spectra and photoelectrochemical methodology, the photocatalytic hydrogen evolution mechanism was proposed. The results demonstrated that the excellent activity arises from the strong electronic coupling, highly efficient charges separation and migration. This work demonstrates a facile photochemical deposition method to consciously construct the robust two-dimensional (2D) hybrids, so as to realize accurate deposition of cocatalyst and efficient migration of photo-generated carriers. [ABSTRACT FROM AUTHOR]

In this paper, Bi2O3 samples were prepared by a hydrothermal way. The effects of microstructure on the electrochemical properties of Bi2O3 samples were studied by adjusting hydrothermal time of synthesization (2, 6, 10, 14, and 18 h) to control the microstructure. The structure, morphology, specific surface, and chemical environment of Bi2O3 were characterized by XRD, SEM, BET, and XPS. XRD patterns revealed that all diffraction peaks intensity increased with the increase of reaction time and it indicates that a higher crystallization had taken place. However, continuous improvements in electrochemical properties of the samples were not found with enhancement of the crystallinity. The specific capacitance decreases with the increase of crystalline grain size. From the SEM results, as the hydrothermal time increases, it is obvious that the sample particles agglomerate to flakes and then to flowers. The sample of Bi2O3 with a hydrothermal time of 10 h exhibited a high specific capacitance (980 F g−1 at 1 A g−1), excellent capacity retention (86.9% from 1 to 20 A g−1), and a good cycle stability (85.2% at 5 A g−1 after 1000 cycles). The significance of this work is that it is possible to boost the electrochemical properties of the samples by controlling the microstructures, including reducing the crystalline grain size and maintaining a proper morphology of Bi2O3 particles. [ABSTRACT FROM AUTHOR]

Slow positron beam was applied to study the depth profile structure of the virgin and the aged high-temperature vulcanized silicone rubber (HTV). Scanning electron microscope (SEM) images show that the surface of virgin sample is smooth, while the outdoor aged samples are all rough. According to the S(E) curves obtained by slow positron beam, in a depth of more than 1 μm, the S parameter of the sample aged at low-potential side keeps the same value with the virgin one; while the S values of the highpotential side aged sample remain rather low in a depth of about 5 μm. Thermo gravimetric analysis (TGA) results show that the sample in high potential side contains more inorganic constituents than that of other samples. The results are attributed to the strong electric field induced corona aging at high potential side of the composite insulator. [ABSTRACT FROM AUTHOR]

Polyamide thin film composite reverse osmosis membranes on porous polysulfone support were prepared using m-phenylenediamine, trimesoyl chloride and dimethyl sulfoxide (DMSO) with various contents as precursors via an interfacial polymerization. The membrane with heterogeneous multilayer structure was depth-profiled by positron annihilation lifetime spectroscopy based on a pulsed slow positron beam and the thickness of the polyamide active layer can be estimated through fitting the results of depth dependence of o-Ps intensity. The free volume characteristics in the polyamide selective layer of the membranes were evaluated and were correlated with the permeation properties. With increasing DMSO content, mean free volume size (VFV) was enlarged, which was responsible for the enhanced water and sodium chloride permeation. However, the salt rejection was significantly decreased with a slight increase in the VFV around a critical value of 88.0 Å3, which was the average size of hydrated sodium and chloride ions. It was well interpreted for that the broadened free volume distribution enables an amount of larger free volumes to be involved in the salt permeation, although little change in VFV was found. [ABSTRACT FROM AUTHOR]

A novel proton conductor has been designed by the surface immobilization of protonated polyimidazolium monolayer on titanate nanotubes (TiNTs) through a polymer brush strategy. 2,2′-Azobis(2-methylpropionitrile) (AIBN)-type initiators are first attached to TiNTs followed by a free radical polymerization of protonated 1-vinylimidazole (VyImBF4) on the surface. The chemical structure of the resulting poly(VyImBF4)-modified TiNTs is verified by Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS). TGA curve indicates their good thermal stability. The maximum proton conductivity achieves 6.74 × 10−4 S cm−1 at 200 °C under dry condition and 3.60 × 10−2 S cm−1 at 120 °C under 100% humidity, respectively, when the polymerization is carried out under a polymerization time of 3 h and an immobilized initiator concentration of approximately 42.4 mmol L−1. The proposed preparation of poly(VyImBF4)-modified TiNTs would give a new idea for the design of other ion conductors. [ABSTRACT FROM AUTHOR]

Acrylate-terminated poly(lactic acid) (DPLA) was synthesized by polycondensation, using lactic acid, polyalcohol and acrylic acid as the raw materials. The prepolymer products in each process were characterized by FT-IR, 1H-NMR, GPC and DSC. DPLAs were then formulated with reactive diluent and diphenyl ketone as photoinitiator and photopolymerized into film(FPLA). Thermal stability and degradation properties of the UV curing PLA film were studied. The results showed that the structures of prepolymer and the performances of the film could be adjusted by changing the types and content of the branching agent polyalcohol. After crosslinking modification, the degradation rate of FPLA was reduced and FPLA had better thermal stability than the pure PLA. [ABSTRACT FROM AUTHOR]

Silicone rubber is widely used as the housing material of composite insulator for outdoor high-voltage insulation. However, corona-induced aging in silicone rubber contributes to the ingress of water or moisture, which finally leads to fracture of a composite insulator. To investigate water transportation in silicone rubber helps to shed light upon the insulator fracture mechanism. In this work, water transportation behaviors in silicone rubber treated by different applied voltages of corona discharge were systematically studied using electrochemical impedance spectroscopy (EIS). Low voltages (3, 4 kV) of corona treatments result in growing value of fθmin in Bode phase angle, indicative of severer degree of surface delamination. After 5 kV of corona treatment, water can finally diffuse through the silicone rubber, and then induces double-layer capacitance (Cdl) and the charge transfer resistance (Rct) in EIS spectra. For high-voltage (≥6kV) corona-exposed samples, great number of surface cracks are observed, and then Warburg impedance appears in EIS spectra on initial period of immersion, suggesting a direct water transportation process. The polar groups generated in silicone rubber during corona exposure also facilitate this water diffusion process. Calculated water diffusion coefficients show a sharp increase between 5 and 6 kV, which serves as an indicator for percolation of cracks or defects in bulk of silicone rubber. [ABSTRACT FROM AUTHOR]

CeO and FeO co-modified titanate nanosheet (FeO/CeO@TNS) was prepared by one-pot hydrothermal method; the photocatalyst exhibited large surface area with CeO and FeO particles well dispersed on the surface. The results of XRD, BET, and Raman proved that the CeO and FeO introduced in the TNS influenced its structure evolution from 3D to 2D. The modification resulted in a shift of the absorption edge toward a longer wavelength and the band gap reduced to 2.87 eV. The three-component systems performed excellent photocatalytic activity and cycle stability on phenol and methyl blue (MB) solution under sunlight; nearly total phenol and MB were degraded in dozens of minutes. And the reaction rate constant ( K) of FeO/CeO@TNS on phenol degradation was 1.77, 3.25, 4.88, and 13-fold of FeO@TNS, CeO@TNS, bare TNS, and P25, respectively. The enhanced photocatalytic activity could be ascribed to the efficient separation of photogenerated pairs through the formation of tandem n-n-n heterojunction among the three-component systems. This work will be useful for the design of other tandem n-n-n heterojunction photocatalytic systems for application in energy conversion and environmental remediation. [ABSTRACT FROM AUTHOR]

Polylactide (PLA)/polyurethane (PU) composites were prepared by reactive blending method with in-situ formation of PU particles via the reaction between polyester polyol (PPG) and toluene-2,4-diisocyanate (TDI). The interfacial compatibility and adhesion between the PLA and PU phases were greatly improved by the reaction of the terminal hydroxyl groups of PLA and N=C=O groups of TDI forming graft copolymer, as confirmed by FTIR spectroscopy. The elongation at break and notch impact strength of PLA/PU composites increased considerably with increasing PU content, and the tensile strength of PLA/PU composites decreased slightly compared with that of pure PLA. The excellent interfacial adhesion, dispersed PU elastomeric particles acting as stress concentration areas and the triggering of large matrix shearing yielding and many fibrils by internal cavitation were the main mechanical toughening mechanisms. [ABSTRACT FROM AUTHOR]

We investigated the aging effect on the chemical structure of silicone rubber composite materials under outdoor environment. The variations of low molecular weight siloxanes in silicone rubber were probed by gas chromatography-mass spectrometry during the degradation process. The experimental results indicate that a series of cyclic siloxanes exist in both the virgin and aged silicone rubber samples, while the additional low molecular weight siloxanes (hexamethyl cyclotrisiloxane) only appear in the aged samples. Meanwhile, the total amounts of low molecular weight siloxanes in the aged samples are much less than those in the virgin ones. The loss of low molecular weight siloxanes is induced by the chain scission and depolymerization. [ABSTRACT FROM AUTHOR]

A series of holmium-doped TiO2-based nanosheet (Ho-TNS) photocatalysts with different Ho/Ti molar ratios were prepared via a simple hydrothermal method. The photocatalysts were characterized by field-emission scanning electron microscope, high-resolution transmission electron microscope, X-ray diffraction (XRD), Raman Spectroscopy, X-ray photoemission spectroscopy, nitrogen adsorption-desorption isotherm measurement, ultraviolet-visible light diffuse reflectance spectra (DRS), and fluorescence spectra (FL). The TEM images of Ho-TNS exhibit clearly sheet-like structures and existence of the (201) plane of H2Ti3O7. The increased (101) peak intensity in XRD spectrum and the enhanced Eg mode (141 cm-1) in Raman spectrum indicate that Ho doping has obvious influence on the formation and structure of Ho-TNS, which can be explained by the formation of Ho-O-Ti bonds. With the doping ratio (Ho/Ti molar ratio) increasing from 0 to 2.0 %, the absorption edge shifts to a longer wavelength, and the band-gap of photocatalysts reduces from 3.18 to 3.07 eV. The decline of FL intensity implies that the photocatalysts with higher Ho content have higher electron-hole separation efficiency. However, after Ho doping, the surface structure of specimens is significantly altered, which will lead to the specific surface areas and adsorption capacity decrease. Under the combined effect of the variables, the photocatalyst with a doping ratio of 1.0 % reaches the best photoactivity, which is 1.90-fold and 12.38-fold higher compared with undoped TNS and P25 under visible light, respectively. The high photoactivity of the prepared Ho-TNS indicates that it may be useful for dealing with wastewater. [ABSTRACT FROM AUTHOR]

Lysyl-tRNA synthetase (KRS), a protein synthesis enzyme in the cytosol, relocates to the plasma membrane after a laminin signal and stabilizes a 67-kDa laminin receptor (67LR) that is implicated in cancer metastasis; however, its potential as an antimetastatic therapeutic target has not been explored. We found that the small compound BC-K-YH16899, which binds KRS, impinged on the interaction of KRS with 67LR and suppressed metastasis in three different mouse models. The compound inhibited the KRS-67LR interaction in two ways. First, it directly blocked the association between KRS and 67LR. Second, it suppressed the dynamic movement of the N-terminal extension of KRS and reduced membrane localization of KRS. However, it did not affect the catalytic activity of KRS. Our results suggest that specific modulation of a cancer-related KRS-67LR interaction may offer a way to control metastasis while avoiding the toxicities associated with inhibition of the normal functions of KRS. [ABSTRACT FROM AUTHOR]

TiO2-based nanostructures usually possess excellent photochemical properties. However, the relationship between their dimensionality and photocatalytic activity was rarely investigated. In this study, a series of TiO2-based nanostructures in various dimensionalities (such as nanosheets, nanotubes) were obtained by hydrothermal treatment of P25, and the process of structural evolution was also systematically investigated by TEM, BET, Raman, and XRD analysis. Much higher rate constant (3.7 × 10min) for the degradation of rhodamine B was found for nanosheets, comparing with those of three-dimensional P25 nanoparticles (0.59 × 10 min) and one-dimensional nanotubes (0.85 × 10 min). It is found that the hydrothermally prepared TiO2-based nanosheets possess small thickness (ca. 5 nm) and plentiful surface hydroxyl groups, and the reason why TiO2-based nanosheets possess superior photocatalytic activity is also discussed in detail from the microstructure and surface chemical states. In addition, TiO2-based nanosheets exhibit good reusability in the cyclic experiments, implying a potential application for photocatalytic degradation of organic pollutants. [ABSTRACT FROM AUTHOR]

Nitrogen-doped titanium dioxide (TiO) nanotube arrays were synthesized by anodization in ethylene glycol electrolyte and annealing in ammonia at 500 °C. Detailed analysis showed that the nitrogen-doped titania nanotubes were pure anatase of ordered structure, with a crystallite size of 8.5 nm. The doping nitrogen atoms were induced on the interstitial sites and substitutional sites and the ratio of oxygen vacancies increased to 27.15 %, resulting in an add-on peak in the absorption spectrum and extended the absorption from 387 to 618 nm. The photocatalytic activity of the nitrogen-doped TiO nanotubes was evaluated by photocatalytic degradation of methyl blue under visible light irradiation. Significant improvement of photocatalytic activity under visible light irradiation was observed. We assumed the nitrogen doping induced the effect produced by nitrogen atoms, Ti cations and oxygen vacancies and the size effect of the TiO crystallite should be responsible for the effective photocatalytic activity. [ABSTRACT FROM AUTHOR]

mong the known covalent damages that can occur spontaneously to proteins, the formation of isoaspartyl linkages through deamidation of asparagines and isomerization of aspartates may be one of the most rapid forms under conditions of physiological pH and temperature. The protein l-isoaspartyl methyltransferase (PIMT) is thought to recognize l-isoaspartyl residues and repair this kind of damaged proteins. Curiously, there is a potential functional difference between bacterial and mammalian PIMTs. Herein, we present the crystal structure of Escherichia coli PIMT ( EcPIMT) at a resolution of 1.8 Å. The enzyme we investigated was able to remain bound to its product S-adenosylhomocysteine (SAH) during crystallization. Analysis indicates that the high affinity of EcPIMT for SAH might lead to the lower activity of the enzyme. [ABSTRACT FROM AUTHOR]

Large-scale, well-aligned, and oriented ZnS nanorod arrays were fabricated by a novel and original template-free hydrothermal method. The ZnS nanorods were grown on the pulse-plating Zn nanocrystallines along a certain Zn crystalline direction. It was found that reaction factors such as hydrothermal reaction time, zinc source, and sulfide source concentration in the precursor solution, the acid–base property of the precursor solution, and the substrate where ZnS nanorod arrays were grown greatly influence the morphology of the final products. The growth mechanism of ZnS nanorod arrays was also studied. Pulse-plating Zn nanocrystallines were found to be essential for the growth of ZnS nanorod arrays. These ZnS nanorod arrays could be theoretically fabricated on almost any raw base plate as long as Zn nanocrystallines could be pulse-plated on it. Therefore, the as-synthesized ZnS nanorod array might be one of the promising candidates for field-emission or sensitive nanomaterials in the future. [ABSTRACT FROM AUTHOR]

The radiation effect of neutrons in a reactor on polyurethane was studied. The gases produced by irradiated samples were analyzed by gas chromatography, and the dynamic mechanical and compression properties of the samples were also studied. The positron annihilation lifetime of irradiated samples was measured at room temperature in vacuum. The experimental results indicate that gas chromatography is a powerful tool to quantitatively analyze the gas products from neutron-irradiated polyurethane and characterizes the chemical changes in the sample. And the changes in microstructure determined from the PAL correlate well with the measurements of the mechanical properties by dynamic mechanical analysis (DMA). [ABSTRACT FROM AUTHOR]

Signal transduction systems enable organisms to monitor their external environments and accordingly adjust the cellular processes. In mast cells, the second messenger Ap4A binds to the histidine triad nucleotide-binding protein 1 (HINT1), disrupts its interaction with the microphthalmia-associated transcription factor (MITF), and eventually activates the transcription of genes downstream of MITF in response to immunostimulation. How the HINT1 protein recognizes and is regulated by Ap4A remain unclear. Here, using eight crystal structures, biochemical experiments, negative stain electron microscopy, and cellular experiments, we report that Ap4A specifically polymerizes HINT1 in solution and in activated rat basophilic leukemia cells. The polymerization interface overlaps with the area on HINT1 for MITF interaction, suggesting a possible competitive mechanism to release MITF for transcriptional activation. The mechanism depends precisely on the length of the phosphodiester linkage of Ap4A. These results highlight a direct polymerization signaling mechanism by the second messenger. The second messenger Ap4A contributes to mast cell activation by interacting with HINT1 but the molecular mechanism is not fully understood. Here, the authors show that Ap4A regulates downstream signaling by polymerizing HINT1 and provide insights into how specificity over other second messengers is achieved. [ABSTRACT FROM AUTHOR]

Aminoacyl-tRNA synthetases (AARSs) catalyze an early step in protein synthesis, but also regulate diverse physiological processes in animal cells. These include angiogenesis, and human threonyl-tRNA synthetase (TARS) represents a potent pro-angiogenic AARS. Angiogenesis stimulation can be blocked by the macrolide antibiotic borrelidin (BN), which exhibits a broad spectrum toxicity that has discouraged deeper investigation. Recently, a less toxic variant (BC194) was identified that potently inhibits angiogenesis. Employing biochemical, cell biological, and biophysical approaches, we demonstrate that the toxicity of BN and its derivatives is linked to its competition with the threonine substrate at the molecular level, which stimulates amino acid starvation and apoptosis. By separating toxicity from the inhibition of angiogenesis, a direct role for TARS in vascular development in the zebrafish could be demonstrated. Bioengineered natural products are thus useful tools in unmasking the cryptic functions of conventional enzymes in the regulation of complex processes in higher metazoans. [ABSTRACT FROM AUTHOR]