In this article, we demonstrate transition-metal-catalyzed olefin metathesis as a simple, effective method for healing polymers via dynamic exchange of strong carbon–carbon double bonds. Upon ...introducing a very low level of the Grubbs’ second-generation Ru metathesis catalyst into cross-linked polybutadiene (PBD) network, the material self-heals effectively at various conditions under moderate pressures. In sharp contrast, catalyst-free control samples with identical network topology and cross-linking density show minimal healing. The healing efficiency of the materials was carefully investigated under different concentrations of the Ru catalyst, compression pressures, and temperatures. It is demonstrated for the first time that a bulk polymer could effectively heal via dynamic covalent bond formation at sub-ambient temperature. The Ru-loaded PBD samples not only heal well with themselves but also with control samples without any catalyst. Furthermore, a completely Ru-free PBD network can heal effectively upon simply applying a very small amount of Ru catalyst only at the fracture surface. The simplicity and effectiveness of this self-healing approach make it potentially applicable to a wide range of olefin-containing polymers.
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IJS, KILJ, NUK, PNG, UL, UM
Covalently cross-linked polymers have many technological applications for their excellent properties, but they suffer from the lack of processability and adaptive properties. We report a simple, ...efficient method of generating adaptive cross-linked polymers via olefin metathesis. By introducing a very low level of the Grubbs’ second-generation Ru metathesis catalyst, a chemically cross-linked polybutadiene network becomes malleable at room temperature while retaining its insolubility. The stress relaxation capability increases with increasing level of catalyst loading. In sharp contrast, catalyst-free control samples with identical network topology and cross-linking density do not show any adaptive properties. This chemistry should offer a possibility to combine the dimensional stability and solvent resistance of cross-linked polymers and the processability/adaptibility of thermoplastics.
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Abstract
Intrinsically and fully stretchable active-matrix-driven displays are an important element to skin electronics that can be applied to many emerging fields, such as wearable electronics, ...consumer electronics and biomedical devices. Here, we show for the first time a fully stretchable active-matrix-driven organic light-emitting electrochemical cell array. Briefly, it is comprised of a stretchable light-emitting electrochemical cell array driven by a solution-processed, vertically integrated stretchable organic thin-film transistor active-matrix, which is enabled by the development of chemically-orthogonal and intrinsically stretchable dielectric materials. Our resulting active-matrix-driven organic light-emitting electrochemical cell array can be readily bent, twisted and stretched without affecting its device performance. When mounted on skin, the array can tolerate to repeated cycles at 30% strain. This work demonstrates the feasibility of skin-applicable displays and lays the foundation for further materials development.
In this study, we explored the hourly extreme rainfall over the Pearl River Delta metropolitan region (PRDMR) by performing a statistical analysis on a 10‐year hourly precipitation dataset combined ...with the fifth generation of ECMWF atmospheric hourly reanalysis (ERA‐5) and half‐hourly FengYun‐2 geostationary satellite observations during the pre‐summer rainy season from 2008 to 2017. Results showed that hourly extreme rainfall events over the PRDMR increased at a significant pace during the most recent 10 years, which frequently occurred during the early morning (0400–0900 local standard time LST; UTC + 8 hr) and afternoon (1300–1800 LST) over the central urban district and 100‐km downstream area. Comparative analysis of the meteorological conditions between the two peak periods revealed that the hourly extreme rainfall events over the PRDMR during the pre‐summer rainy season were overall prefrontal rainstorms that occurred under the influence of dominant south‐westerlies and weak easterly backflows of warm‐moist air at lower atmospheres. The hot plumes rooted at the urban surface may be the key local environmental factors responsible for generating hourly heavy rainfall over the PRDMR. Given favourable large‐scale conditions, the interaction of urban heat island effects with sea breezes and mountain‐valley breezes can promote convection by altering the thermodynamic and dynamic structures around the PRDMR. By comparison, the hourly extreme rainfall events that occurred during morning periods over the PRDMR were more sensitive to moderate to strong wind shear at the lower planetary boundary layer, whereas those that occurred during afternoon periods were more likely to occur in the presence of an environment with high conditional instability.
In response to global warming, the frequency of extreme rainfall has experienced significant increases and is expected to continue increasing in the future. As the biggest and most populous metropolitan area in China, the Pearl River Delta Metropolitan Region (PRDMR) experienced a fast growth of the extreme rainfall frequency at a speed of two events every one rainy season during year 2008–2017. They prefer to occur during morning and afternoon over the central urban district and its 100‐km downstream.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Tropopause‐penetrating convection (or “overshooting convection” OC) is defined as a meso‐to‐microscale stratosphere–troposphere exchange process caused by deep convection. OC plays an important role ...in stratosphere–troposphere exchange and in producing turbulence. Compared with the tropics, the characteristics of OC in the extratropics are poorly understood. To this end, a high‐resolution and objective satellite‐based OC identification and classification algorithm was developed. In the algorithm, a machine learning method was utilized to derive tropopause height directly from satellite observations to ensure a high level of consistency between tropopause and cloud top height variations. By studying the climatology of OCs, including geographic distribution, vertical extent, and seasonal and diurnal variation, as well as their linkage with turbulence in the extratropics in 2018 based on Fengyun‐4A geostationary meteorological satellite data, it was found that most OCs in the extratropics have relatively shallow vertical extents and are more likely to occur over complex topography within the cyclonic curvature side of subtropical jets near the exit region, with a total frequency lower than 0.2%. They showed significant seasonal and diurnal variation. OCs in the Northern Hemisphere occurred most frequently during spring and summer and peak in the afternoon, while those in the Southern Hemisphere were more likely to occur in winter and spring, and with the highest likelihood in the early morning. Typical synoptic conditions for the occurrence of OCs in the mid–high latitudes of the Northern Hemisphere in the summer months included low‐level easterly flows, increased moisture symmetric instability, upper cold trough (or cold vortex), and a subtropical westerly jet. Under this large‐scale flow pattern, moderate‐to‐greater turbulence was often found to occur within or about 200 km away from the core convective area. The stronger the penetrating convection, the greater the probability of moderate‐to‐greater turbulence.
A flowchart of Geostationary‐satellite‐based (GEOsat) overshooting convection identification algorithm.
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Evolutionarily conserved DDB1‐and CUL4‐associated factor 13 (DCAF13) is a recently discovered substrate receptor for the cullin RING‐finger ubiquitin ligase 4 (CRL4) E3 ubiquitin ligase that ...regulates cell cycle progression. DCAF13 is overexpressed in many cancers, although its role in breast cancer is currently elusive. In this study we demonstrate that DCAF13 is overexpressed in human breast cancer and that its overexpression closely correlates with poor prognosis, suggesting that DCAF13 may serve as a diagnostic marker and therapeutic target. We knocked down DCAF13 in breast cancer cell lines using CRISPR/Cas9 and found that DCAF13 deletion markedly reduced breast cancer cell proliferation, clone formation, and migration both in vitro and in vivo. In addition, DCAF13 deletion promoted breast cancer cell apoptosis and senescence, and induced cell cycle arrest in the G1/S phase. Genome‐wide RNAseq analysis and western blotting revealed that loss of DCAF13 resulted in both mRNA and protein accumulation of p53 apoptosis effector related to PMP22 (PERP). Knockdown of PERP partially reversed the hampered cell proliferation induced by DCAF13 knockdown. Co‐immunoprecipitation assays revealed that DCAF13 and DNA damage‐binding protein 1 (DDB1) directly interact with PERP. Overexpression of DDB1 significantly increased PERP polyubiquitination, suggesting that CRL4DCAF13 E3 ligase targets PERP for ubiquitination and proteasomal degradation. In conclusion, DCAF13 and the downstream effector PERP occupy key roles in breast cancer proliferation and potentially serve as prognostics and therapeutic targets.
DCAF13 is overexpressed in breast cancer and its overexpression closely correlates with the poor prognosis. DCAF13 deletion markedly decreased breast cancer cell proliferation, clone formation, and migration both in vitro and in vivo.DCAF13 promotes breast cancer cell proliferation by inhibiting the expression of PERP.
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pH‐dependent peptide biomaterials hold tremendous potential for cell delivery and tissue engineering. However, identification of responsive self‐assembling sequences with specified secondary ...structure remains a challenge. In this work, An experimental procedure based on the one‐bead one‐compound (OBOC) combinatorial library is developed to rapidly screen self‐assembling β‐sheet peptides at neutral aqueous solution (pH 7.5) and disassemble at weak acidic condition (pH 6.5). Using the hydrophobic fluorescent molecule thioflavin T (ThT) as a probe, resin beads displaying self‐assembling peptides show fluorescence under pH 7.5 due to the insertion of ThT into the hydrophobic domain, and are further cultured in pH 6.5 solution. The beads with extinguished fluorescence are selected. Three heptapeptides are identified that can self‐assemble into nanofibers or nanoparticles at pH 7.5 and disassemble at pH 6.5. P1 (LVEFRHY) shows a rapid acid response and morphology transformation with pH modulation. Changes in the charges of histidine and hydrophobic phenyl motif of phenylalanine may play important roles in the formation of pH‐responsive β‐sheet nanofiber. This high‐throughput screening method provides an efficient way to identify pH‐dependent β‐sheet self‐assembling peptide and gain insights into structural design of such nanomaterials.
High‐throughput one‐bead one‐compound (OBOC）screening strategy enables identification of pH‐dependent self‐assembling peptides with β‐sheet structure, providing insight into interactions between histidine and phenylalanine in the rational design of pH‐dependent biomaterials.
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AbstractNon-Gaussian processes beset many aspects of structural engineering analysis. To estimate non-Gaussian processes, various third-order Hermite polynomial models have been proposed and widely ...applied. Different forms of expressions have been proposed for hardening and softening processes in existing Hermite polynomial models, which makes them inconvenient to implement. Furthermore, these models are either too simple to ensure accurate results or too complicated to implement conveniently. Thus, a unified third-order Hermite polynomial model that achieves a good balance between accuracy and convenience for both hardening and softening processes is proposed in this study. Explicit expressions for translations of the marginal distributions between the non-Gaussian and Gaussian processes using the proposed Hermite polynomial model are deduced, and the applicable ranges are provided. The accuracy of the proposed model is demonstrated by comparing the coefficients and estimated moments with those obtained from the moment-matching method. Furthermore, the application of the proposed model in evaluating first passage probability, analyzing fatigue damage, and estimating peak factors of non-Gaussian wind pressure coefficient histories is demonstrated with numerical and practical examples.
With increasing concerns about noise pollution, the pursuit of highly dependable piezoelectric acoustic sensors for real‐time noise monitoring has come to the forefront of scientific research. ...Lead‐based perovskite piezoelectric films, exemplified by lead zirconate titanate Pb(Zr,Ti)O3 (PZT), surpass traditional piezoelectric materials such as ZnO and AlN in their piezoelectric properties, promising substantial advancements in next‐generation acoustic sensor technologies. However, the toxic nature of lead in PZT materials poses formidable environmental and human health risks. In an unprecedented breakthrough, it presents the pioneering development of an environmentally benign lead‐free piezoelectric Micro‐Electro‐Mechanical System (MEMS) acoustic sensor based on potassium sodium niobate (K,Na)NbO3 (KNN) film. High‐quality textured 3 µm‐thick KNN film is successfully integrated into commercially used Si substrate, rendering exceptional piezoelectricity (transverse piezoelectric coefficients e31* of ≈8.5 C m−2) with satisfactory thermal stability. The atomic‐scale Z‐contrast imaging and piezoresponse force microscopy characterizations reveal that the outstanding piezoresponse originates from the local coexistence of multiple phases and the enhancement of extrinsic piezoelectric contributions from in‐plane polarization anisotropy. Finite element simulation is employed to design the triangular cantilever structure and annular diaphragm structure, each corresponding to different operating bandwidths. The resultant MEMS acoustic sensors stand out with outstanding acoustic performance (the high sensitivity and expansive receiving field of view), which are attributed to the microstructural engineering at multi‐length scales for the excellent piezoelectric properties of KNN film. These features enable sensitive acoustic monitoring in various environments, including large‐scale power grids and urban traffic.
Engineering the microstructure across multi‐length scales in potassium sodium niobate enhances the functionality of piezoelectric acoustic sensors. This pioneering approach sets a precedent for utilizing lead‐free ferroelectric films in MEMS devices, opening avenues in diverse applications encompassing noise monitoring, nondestructive detection, and hearing aids technologies.
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A highly selective, efficient and practical method for synthesizing primary alcohols was presented. By using cheap Fe(BF4)2 ⋅ 6H2O and /tris2‐(diphenylphosphino)phenylphosphine (L1) as catalysts with ...formic acid as hydrogen source, a variety of primary alcohols bearing versatile functional groups could be obtained from both alkyl‐ and aryl‐substituted epoxides under mild conditions.
Highly selective and efficient synthesis of primary alcohols from epoxides could be achieved under mild conditions by iron catalysis, this process used formic acid as hydrogen source and was suitable for both alkyl‐ and aryl‐substituted epoxides.
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