Synthesis of cyclophanes with planar and helical chirality

Novel helical macrocyclic imines derived from planar chiral [2.2]paracyclophane were synthesized. The chiroptical properties of the enantiopure compounds were investigated and their absolute configurations were assigned.     

金属材料疲劳损伤检测的非线性声学方法*

金属材料的疲劳损伤有前期、后期两个阶段,前期疲劳损伤主要来源于位错,而随着疲劳程度的不断加深,位错密度也不断的增加,这将导致疲劳后期微裂纹的产生。这两个阶段产生声学非线性效应的机理不同,分别用位错模型、微裂纹模型对其产生非线性效应的机理进行了阐述,并对不同阶段的疲劳试样进行了相关实验研究。实验结果表明:对于材料早期疲劳损伤,随着疲劳程度的增加,其接收声波信号中的非线性谐波成分越来越显著,并且随着激励电压的增加,非线性效应更加明显,因此可用接收信号中的谐波激发情况来评估材料的早期疲劳损伤程度。而对于材料疲劳后期出现微裂纹后,其产生的非线性与早期疲劳损伤相比,谐波成分更加丰富,并且随激励电压的增加谐波幅度增加明显,可据此来判断材料中的疲劳损伤阶段。     

固体氧化物燃料电池运行初期电化学性能演变机制

固体氧化物燃料电池(solid oxide fuel cell,SOFC)是一种清洁高效的发电装置,其运行中的性能衰减受到众多因素的影响,如何分辨这些因素的贡献、并在此基础上确定衰减的主导因素,对于更有针对性地提升SOFC的运行寿命至关重要.广泛的测试结果表明,SOFC的电化学性能在运行初期(约前100 h)会发生最为...     

Wnt/β-catenin signaling stimulates the self-renewal of conjunctival stem cells and promotes corneal conjunctivalization

Limbal stem cell deficiency causes conjunctivalization characterized by the covering of the corneal surface with conjunctival epithelium. However, the driving force for the encroachment of these conjunctival cells is unclear. Conjunctival stem cells are bipotent stem cells that can proliferate and differentiate into conjunctival epithelial cells and goblet cells to maintain regeneration of the conjunctival epithelium. Here, we show a robust proliferative response of conjunctival stem cells and upregulation of Wnt2b and Wnt3a gene expression in the conjunctivae of mice with induced limbal stem cell deficiency. Topical application of the Wnt/β-catenin signaling activator CHIR resulted in increased proliferation of ΔNp63α-positive stem cells in the basal layers of the bulbar and forniceal conjunctivae and enhanced invasion of conjunctival epithelial and goblet cells into the corneal surface. We also found that in cultures of stem cells isolated from the human conjunctiva, Wnt/β-catenin pathway activation improved the expansion of the ΔNp63α/ABCG2 double-positive cell population by promoting the proliferation and preventing the differentiation of these cells. These expanded stem cells formed a stratified epithelium containing goblet cells under airlift culture conditions. Our data reveal that Wnt/β-catenin signaling contributes to the pathological process of limbal stem cell deficiency by promoting the self-renewal of conjunctival stem cells and suggest that these cells are a driving force in corneal conjunctivalization.Subject terms: Self-renewal, Stem-cell research, Experimental models of disease     

Towards Better Sinomenine-Type Drugs to Treat Rheumatoid Arthritis: Molecular Mechanisms and Structural Modification

Sinomenine is the main component of the vine Sinomenium acutum. It was first isolated in the early 1920s and has since attracted special interest as a potential anti-rheumatoid arthritis (RA) agent, owing to its successful application in traditional Chinese medicine for the treatment of neuralgia and rheumatoid diseases. In the past few decades, significant advances have broadened our understanding of the molecular mechanisms through which sinomenine treats RA, as well as the structural modifications necessary for improved pharmacological activity. In this review, we summarize up-to-date reports on the pharmacological properties of sinomenine in RA treatment, document their underlying mechanisms, and provide an overview of promising sinomenine derivatives as potential RA drug therapies.     

Development of a simultaneous quantification method of imatinib and sunitinib and their main metabolites and its application in patients with gastrointestinal stromal tumor

Correlations between plasma concentrations of imatinib and sunitinib with efficacy and toxicity have been established. It is crucial to develop a sensitive and precise method for determining the plasma concentrations of imatinib and sunitinib, along with their active metabolites, to facilitate therapeutic drug monitoring and individualized therapy. Plasma samples were separated on an Agilent ZORBAX SB-C₁₈ chromatographic column using gradient elution. Quantification was performed using a mass spectrometer equipped with electrospray ionization in multiple reaction monitoring. The analysis time was 18 min per run, with all analytes and internal standards eluting within 8 min. The calibration range was 25–4000 ng/mL for imatinib, 5–800 ng/mL for N-desmethyl imatinib (CGP74588), and 2.5–400 ng/mL for sunitinib and N-desethyl sunitinib (SU12662). Intra- and inter-assay precision were both below 15%, and accuracy ranged between 90.0% and 101.9%. The method was successfully applied to determine blood samples from 120 patients with gastrointestinal stromal tumors who received imatinib (n = 115) and sunitinib (n = 5). It has been validated as linear, accurate, precise, and robust, making it suitable for therapeutic drug monitoring of imatinib and sunitinib in routine clinical practice.     

Modulating the Reaction Configuration by Breaking the Structural Symmetry of Active Sites for Efficient Photocatalytic Reduction of Low-concentration CO2

Photocatalytic conversion of low-concentration CO₂ is considered as a promising way to simultaneously mitigate the environmental and energy issues. However, the weak CO₂ adsorption and tough CO₂ activation process seriously compromise the CO production, due to the chemical inertness of CO₂ molecule and the formed fragile metal-C/O bond. Herein, we designed and fabricated oxygen vacancy contained Co₃O₄ hollow nanoparticles on ordered macroporous N-doped carbon framework (Vo−HCo₃O₄/OMNC) towards photoreduction of low-concentration CO₂. In situ spectra and ab initio molecular dynamics simulations reveal that the constructed oxygen vacancy is able to break the local structural symmetry of Co−O−Co sites. The formation of asymmetric active site switches the CO₂ configuration from a single-site linear model to a multiple-sites bending one with a highly stable configuration, enhancing the binding and structural polarization of CO₂ molecules. As a result, Vo−HCo₃O₄/OMNC shows unprecedent activity in the photocatalytic conversion of low-concentration CO₂ (10 % CO₂/Ar) under laboratory light source or even natural sunlight, affording a syngas yield of 337.8 or 95.2 mmol g⁻¹ h⁻¹, respectively, with an apparent quantum yield up to 4.2 %.     

Solvent-derived Fluorinated Secondary Interphase for Reversible Zn-graphite Dual-ion Batteries

The irreversibility of anion intercalation-deintercalation is a fundamental issue in determining the cycling stability of a dual-ion battery (DIB). In this work, we demonstrate that using a partially fluorinated carbonate solvent can drive a beneficial fluorinated secondary interphase layer formation. Such layer facilitates reversible anion (de−)intercalation processes by impeding solvent molecule co-intercalation and the associated graphite exfoliation. The enhanced reversibility of anion transport contributes to the overall cycling stability for a Zn-graphite DIB—a high Coulombic efficiency of 98.5 % after 800 cycles, with an attractive discharge capacity of 156 mAh g⁻¹ and a mid-point discharge voltage of ≈1.7 V (at 0.1 A g⁻¹). In addition, the formed fluorinated secondary interphase suppresses the self-discharge behavior, preserving 29 times of the capacity retention rate compared to the battery with a commonly used carbonate solvent, after standing for 24 hours. This work provides a simple and effective strategy for addressing the critical challenges in graphite-based DIBs and contributes to fundamental understanding to help accelerate their practical application.     

High-Porosity Metal-Organic Framework Glasses

We report a synthetic strategy to link titanium-oxo (Ti-oxo) clusters into metal-organic framework (MOF) glasses with high porosity though the carboxylate linkage. A new series of MOF glasses was synthesized by evaporation of solution containing Ti-oxo clusters Ti₁₆O₁₆(OEt)₃₂, linkers, and m-cresol. The formation of carboxylate linkages between the Ti-oxo clusters and the carboxylate linkers was confirmed by Fourier-transform infrared (FT-IR) spectroscopy. The structural integrity of the Ti-oxo clusters within the glasses was evidenced by both X-ray absorption near edge structure (XANES) and ¹⁷O magic-angle spinning (MAS) NMR. After ligand exchange and activation, the fumarate-linked MOF glass, termed Ti-Fum, showed a N₂ Brunauer–Emmett–Teller (BET) surface areas of 923 m² g⁻¹, nearly three times as high as the phenolate-linked MOF glass with the highest BET surface area prior to this report.     

Construction of ion-conductive dual-channels by P(EA-co-AALi)-based gel electrolytes for high-performance lithium metal batteries

Journal of Solid State Electrochemistry - As people possess more safety conscious, the issue of electrolytes is attracting concern. The gel polymer electrolyte offers high ionic conductivity,...