气隙式热开关传热特性研究

本文介绍了一种新型低温热开关的工作原理.考虑到热开关充人的气体在连续介质区和自由分子状态的传热以及肋片沿轴向的导热对热开关的传热特性进行了详细的理论分析.建立了该种热开关传热的理论模型.给出了肋片的厚度、长度、气隙宽度、外壳壁厚与导通热导之间的关系曲线以及气体压强、外壳厚度与关断热导之间的关系曲线.     

基片偏压对MCECR溅射硬碳膜特性的影响

采用封闭式电子回旋共振(MCECR)氩等离子体溅射碳靶的方法在硅片上沉积了高质量的硬碳膜, 膜层厚度约40 nm. 使用X射线光电子能谱仪(XPS)和高分辨率透射电子显微镜(HRTEM)分析了碳膜结构,并用POD摩擦磨损仪测试了碳膜的摩擦磨损特性,用纳米压入仪测试了碳膜的纳米硬度.详细研究了基片偏压对碳膜的结构、摩擦磨损特性以及纳米硬度的影响,得到了最佳基片偏压.     

A new compound from the fruit of Amorpha fruticosa and activity against acetaminophen-induced hepatotoxicity

A new isoflavone was obstained from the medicinal herb Amorpha fruticosa.It was elucidated asbenzopyran-12-one,1,4,10,11- tetrahydro-6′-[8′-(hydroxymethyl)ethenyl]-2,3-dimethoxy-8′-O-β-D-glucopyranosyl-O-α-D-arabinoside by spectroscopic methods including UV,IR,1D NMR and 2D NMR techniques.And the activity against acetaminophen-induced hepatotoxicity of this compound was also studied,and found this compound can protect liver obviously from hepatotoxicity induced by acetaminophen (AAP).     

Furofuran lignans and alkaloids from Clinacanthus nutans

One new furofuran lignan 2-methoxy-9β-hydroxydiasesamin (1), and four analogues (2–5), together with eight alkaloids (6–13), were isolated from the ethanol extract of the aerial part of Clinacanthus nutans. Their structures were elucidated by the detailed analysis of comprehensive spectroscopic data. All the compounds were isolated from the genus of Clinacanthus for the first time. In addition, lignans isolated from C. nutans was reported for the first time. Compound 1 exhibited modest activity against three human tumor cell lines Hela, MCF-7, and A549, with IC₅₀ values of 68.55, 60.00, and 59.17 μM, respectively.     

A new flavanone glycoside isolated from Tournefortia sibirica

A new flavanone glycoside, (2S)-dihydrooroxylin A 7-O-[β-D-apiosyl(1→2)]-β-D-glucoside (1), and four known compounds (2–5) were isolated from Tournefortia sibirica L. The chemical structures of these compounds were determined by 1?D and 2?D NMR and HR-ESI-MS spectra, and results were compared with data from the literature. These five compounds (1–5) were isolated from the family Boraginaceae for the first time. Anti-inflammatory effects of compounds (1–5) were evaluated in terms of inhibition of production of NO, TNF-α, and IL-6 in LPS-induced RAW 264.7 cells.     

Bifunctional probe for Cu2+/Al3+ based on a diarylethene with a 4, 5-[bis-(5-ethylacetate-yl)-2-thienyl]-1H-imidazole unit

A new asymmetric perfluordiarylethene (1O) was synthesized using 4, 5-[bis-(5-ethylacetate-yl)-2-thienyl]-1H-imidazole as a functional group. 1O exhibited favorable reversible cyclization and cycloreversion reactions upon alternating irradiation with UV and visible light. Both of its open- and closed-ring isomers were found to be highly selective towards Cu²⁺ with significant absorption and color changes, which could be used as a ‘naked-eye’ colorimetric sensor for Cu²⁺ detection. Upon exposure to acid, its fluorescence dramatically enhanced by 14-fold with a color change from dark to bright cyan due to the formation of the protonated compound. Moreover, 1O showed obvious fluorescence “turn-on” signal response towards Al³⁺, and the detection limit for Al³⁺ was determined to be 4.8 × 10^?9 mol L^?1. Based on the fluorescence signals of 1O, a combinational stimuli logic circuit were designed by using the fluorescence intensity as the output signal with the inputs of lights, Al³⁺ and EDTA. Finally, 1O could be used as a biological probe for detecting intracellular Al³⁺ in a physiological environmental.     

A bifunctional probe for Al3+ and Zn2+ based on diarylethene with an ethylimidazo[2,1-b]thiazole-6-hydrazide unit

A new diarylethene with ethylimidazo[2,1-b]thiazole-6-hydrazide unit was synthesized, and its photochromic and fluorescent behaviors have been systematically investigated by the stimulation of lights and metal ions in methanol. This new diarylethene exhibited high selectivity and sensitivity toward Al³⁺ and Zn²⁺. The addition of Al³⁺ and Zn²⁺ displayed excellent colorimetric response behaviour with the concomitant color change from colorless to yellow, which could be easily observed by the naked eye. Upon addition of Al³⁺, the fluorescence intensity was enhanced by 180–fold and the emission peak of 1O–Al³⁺ blue-shifted by 15?nm accompanied with a color change from colorless to bright blue. In contrast, when stimulated with Zn²⁺, its fluorescence intensity was enhanced by 35–fold and the emission peak of 1O–Zn²⁺ red-shifted by 16?nm with an evident color change from black to bright green. The LOD for Al³⁺ and Zn²⁺ were determined to be 2.97?×?10^?9?mol?L^?1 and 5.98?×?10^?9?mol?L^?1, respectively. Moreover, a logic circuit was constructed with the fluorescence intensity as the output signal responding to the light and chemical species as the inputs.     

Detecting Single‐Molecule Dynamics on Lipid Membranes with Quenchers‐in‐a‐Liposome FRET

Tracking membrane‐interacting molecules and visualizing their conformational dynamics are key to understanding their functions. It is, however, challenging to accurately probe the positions of a molecule relative to a membrane. Herein, a single‐molecule method, termed LipoFRET, is reported to assess interplay between molecules and liposomes. It takes advantage of FRET between a single fluorophore attached to a biomolecule and many quenchers in a liposome. This method was used to characterize interactions between α‐synuclein (α‐syn) and membranes. These results revealed that the N‐terminus of α‐syn inserts into the membrane and spontaneously transitions between different depths. In contrast, the C‐terminal tail of α‐syn is regulated by calcium ions and floats in solution in two conformations. LipoFRET is a powerful tool to investigate membrane‐interacting biomolecules with sub‐nanometer precision at the single‐molecule level.     

Characterization and on‐line adjustment of the sagittal‐bent Laue crystal profile

The sagittal‐bent Laue monochromator can provide an ideal way to focus high‐energy X‐ray beams. However, the anticlastic curvature induced by sagittal bending has a great influence on the crystal performance. Thus, characterizing the bent‐crystal shape is very important for predicting the performance of the bent‐crystal monochromator. In this paper the crystal profile is measured by off‐line optical metrology and on‐line X‐ray experiments. The off‐line results showed that the bent‐crystal surface could be well fitted to a saddle surface apart from a redundant cubic term which was related to the different couples applied on the crystal. On‐line characterization of the meridional and the sagittal radius of the bent crystal includes double‐crystal topography and ray‐tracing measurement. In addition, the double‐crystal topography experiment could be used as a quick diagnostic method for the bending condition adjustment. The sagittal radius of the bent crystal was characterized through a ray‐tracing experiment by using a particularly designed tungsten mask. Moreover, rocking curves under different bending conditions were measured as well. The results were highly consistent with analytical results derived from the elastic theory. Furthermore, radii along different vertical positions under various bending conditions were measured and showed a quadratic relationship between the vertical positions and the meridional radii.     

Heterogeneous oxidization of graphene nanosheets damages membrane

Graphene-based materials exhibit unique properties that have been sought to utilize for various potential applications. Many studies suggest that graphene-based materials can be cytotoxic, which may be attributed to destructive effects on cell membranes.However, there still are conflicting results regarding interactions between graphene-based materials and lipid membranes. Here,through cryo-electron microscopy(Cryo-EM) and dye-leakage experiments along with in silico methods, we found that graphene oxide nanosheets induce significant membrane damage, while the effect of pristine graphene is negligible. We revealed the importance of heterogeneous oxidization of graphene-based nanosheets in damaging vesicle membranes. Moreover, that not only the oxidization degree but also the oxidization loci and membrane tension play important roles in the cytotoxicity of the graphene-based nanosheets.