Synthesis and characterization of polyethylene-like polyurethanes derived from long-chain, aliphatic α,ω-diols

Long-chain aliphatic α,ω-diols containing up to 32 consecutive methylene groups were synthesized by several methods and characterized. 1,22-Docosanediol HO-(CH₂)₂₂-OH and 1,32-dotriacontanediol HO-(CH₂)₃₂-OH both exhibited a solid-solid phase transition before melting. The α,ω-diols HO-(CH₂)_m-OH, where m=12, 22, or 32, were reacted in the melt with much shorter aliphatic α,ω-diisocyanates OCN-(CH₂)_n-NCO, where n=4, 6, 8, or 12, producing a series of linear, aliphatic, and increasingly polyethylene-like m,n-polyurethanes. Characterization (by DSC, TGA, and SAXS) of the m,n-polyurethane series showed that when the aliphatic segments were increased, and the hydrogen-bonding densities thus decreased, the polymers displayed physical and thermal properties (for example, solubility and melting temperature) typical of polyethylene.     

电子封装用环氧树脂的增韧和提高耐热性研究

用α,ω 二氯聚二甲基硅氧烷(DPS)或α 氯聚二甲基硅氧烷(CPS)来改性普通双酚A环氧树脂(BPAER)和四溴双酚A环氧树脂(TBBPAER),目标是制备出一系列可用于电子封装的高韧性高耐热性的环氧基料。通过对固化物的冲击强度、拉伸强度、断裂伸长率和玻璃化转变温度(Tg)以及断裂面形态的测定,探讨了改性方法、有机硅组成与含量等对材料性能的影响。结果表明,当m(BPAER)∶m(DPS)=100∶10时,树脂固化物的冲击强度达到30 5kJ/m2,拉伸强度达46 95MPa,断裂伸长率达到60 23%,Tg达到141 3℃;分别比未改性BPAER提高了19 7kJ/m2,1 69MPa,54 29%以及5 9℃。而当m(TBBPAER)∶m(CPS)=100∶10时,固化物的冲击强度达到17 2kJ/m2,拉伸强度达39 89MPa,断裂伸长率达到5 60%,Tg达到147 0℃;分别比未改性TBBPAER提高了12 8kJ/m2,28 26MPa,4 29%以及7 9℃。     

基于蕴涵算子族L-λ-R_0的模糊推理α-三I约束算法

提出了基于蕴涵算子族L-λ-R0的模糊推理的思想,这将有助于提高推理结果的可靠性。针对蕴涵算子族L-λ-R0给出了模糊推理的FMP模型及FMT模型的α-三I约束算法。     

α-MoO3/TiO2 core/shell nanorods: Controlled-synthesis and low-temperature gas sensing properties

Crystalline α-MoO₃/TiO₂ core/shell nanorods are fabricated by a hydrothermal method and subsequent annealing processes under H₂/Ar flow and in the ambient atmosphere. The shell layer is composed of crystalline TiO₂ particles with a diameter of 2-6 nm, and its thickness can be easily controlled in the range of 15-45 nm. The core/shell nanorods show enhanced sensing properties to ethanol vapor compared to bare α-MoO₃ nanorods. The sensing mechanism is different from that of other one-dimensional metal oxide core/shell nanostructures due to very weak response of TiO₂ nanoparticles to ethanol. The enhanced sensing properties can be explained by the change of type II heterojunction barrier formed at the interface between α-MoO₃ and TiO₂ in the different gas atmosphere. The present results demonstrate a novel sensing mechanism available for gas sensors with high performance.     

A label-free amperometric immunosensor based on horseradish peroxidase functionalized carbon nanotubes and bilayer gold nanoparticles

In this work, a novel label-free amperometric immunosensor has been constructed for detecting α-1-fetoprotein (AFP) based on nanocomposite of horseradish peroxidase (HRP) labeled carbon nanotubes (CNTs). First, the gold nanoparticles (AuNPs) were electrodeposited on the surface of the glass carbon electrode by electrochemical reduction of gold chloride tetrahydrate (HAuCl₄) to immobilize horseradish peroxidase labeled carbon nanotubes (HRP-CNTs). Then HRP-CNTs bioconjugate was immobilized on the surface of the electrodeposited AuNPs layer by the combination of forces (coordination and electrostatic force). Subsequently, it was immersed into gold colloidal nanoparticles (GNPs) solution, which was used to immobilize antibody biomolecules (anti-AFP). Enhanced sensitivity was obtained by using bioconjugates featuring HRP labeled (HRP-CNTs), which had lager specific surface area and good electronic catalysis (current response signal) compared to carbon nanotubes. Under optimized conditions, the linear ranges were from 0.2 to 200 ng mL⁻¹ with a detection limit of 0.067 ng mL⁻¹ (at an S/N of 3). The proposed immunosenor showed good precision, acceptable stability and reproducibility and could be used for the detection AFP in normal human serum, which provided a potential alternative tool for the detection of protein in clinical diagnosis.     

Rab7 and actin cytoskeleton participate during mobilization of β1EHFNR in fibronectin-stimulated Entamoeba histolyticatrophozoites

In vitro interaction of Entamoeba histolytica trophozoites with fibronectin (FN) induces redistribution of the amoebic fibronectin receptor (β1EhFNR). Trafficking of beta1 integrins is important for cell adhesion and migration in higher eukaryotes and requires the participation of Rab proteins. In E. histolytica, the machinery involved in integrin trafficking is not completely known. EhRab7 is a 24.5-kDa protein whose alignment with other Rab7 proteins demonstrated that it shared significant homology with Rab7 proteins from other organisms, including humans. Using different types of microscopy (fluorescence and confocal microscopy), it was established that Rab7 and the actin cytoskeleton participated in the mobilization of β1EhFNR in FN-stimulated trophozoites. β1EhFNR and Rab7 co-localized only in vesicular structures at 5 min, and at longer time (1 h), both co-localized in both plasma membrane and in vesicular structures; at the same time, Rab7 co-localized with specific actin structures (phagocytic vacuoles). At 5 h the β1EhFNR, Rab7, and actin co-localized at the plasma membrane, and only β1EhFNR and Rab7 decorated vesicles of different sizes. Actin and Rab7 co-localized in a cap-like structure at one end of the cell. Fluorescence resonance energy transfer and electron microscopy confirmed the close interaction between β1EhFNR and Rab7. Moreover, the use of a lysosome-specific marker (LysoTracker) and a Golgi-specific marker (NBD C(6)-ceramide) allowed us to establish that, at some point within the endocytic route, β1EhFNR and Rab7 co-localized within a lysosome-type organelle, but not a Golgi-like organelle, which indicated that this integrin-like molecule was returned to the plasma membrane via exocytic or secretory vesicles.     

非奇异H-矩阵的一个简捷判别定理

设A=(aij)∈Cn×n,若存在α∈(0,1),使■i∈N,有|aii|≥Rαi(A)S1-αi(A)成立,则称A为α链对角占优矩阵。利用α-链对角占优矩阵、不可约α-链对角占优矩阵、广义严格α-链对角占优矩阵等概念及性质,给出了非奇异H-矩阵的一个简捷判别定理。从而改进和推广了相应的一些结果,并给出相应的数值例子说明结果的有效性。     

黄河滩岸稳定性影响因素的敏感性分析

黄河滩岸的崩塌失稳将会对滩地和村庄造成严重冲蚀,甚至造成堤防冲决,对黄河滩岸稳定性及其影响因素的敏感性进行分析具有重要的工程实践意义.选择了影响滩岸稳定性较大的主要因素(土体凝聚力c、坡体内水头H和坡角α)进行分析.由c、H及α变化组成不同分析工况,采用边坡稳定性分析方法,分析了滩岸稳定性,并在此基础上研究了滩岸稳定性对c、H及α的敏感性.分析结果表明:在各种计算工况下,黄河滩岸是稳定的;c是影响滩岸坡体稳定性最强的因素,其敏感性随坡角及水头的增大而增强;H对滩岸坡体稳定性影响次之,其敏感性随坡角的增大而增大,随凝聚力的增大而减小;α对坡体稳定的敏感性相对较小,其随凝聚力的增大而减小,随水头的变化不明显.     

α-氰基丙烯酸酯生产新工艺

在反应器中使用甲醛水溶液与氰乙酸酯在催化剂及多功能复合助剂作用下,生成氰基丙烯酸乙酯的预聚物并使其从反应体系分离,然后置于解聚器中,使用有机溶剂(例如:苯、甲苯、二甲苯1,2-二氯乙烷1,3-二氯丙烷等)共沸脱水,脱溶剂,在高真空下解聚并精制,可获得质量好的α-氰基丙烯酸乙酯,其收率为75%以上。     

Can scanning near‐field optical microscopy be compared with confocal laser scanning microscopy? A preliminary study on α‐sarcoglycan and β1D‐integrin in human skeletal muscle

The dystrophin–glycoprotein complex and the vinculin–talin–integrin system constitute, together a protein machinery, called costameres. The dystrophin–glycoprotein complex contains, among other proteins, also dystrophin and the sarcoglycans subcomplex, proteins playing a key role in the pathogenesis of many muscular dystrophies and linking the cytoplasmic myofibrillar contractile elements to the signal transducing molecules of the extracellular matrix, also providing structural support to the sarcolemma. The vinculin–talin–integrin system connects some components of the extracellular matrix with intermediate filaments of desmin, forming transverse bridges between Z and M lines. In our previous reports we always studied these systems by confocal laser scanning microscopy (CLSM). In this paper we report on the first applications of optical near‐field fluorescence microscopy to the spatial localization of α‐sarcoglycan and β1D‐integrin in human skeletal muscle fibres in order to better compare and test the images obtained with conventional CLSM and with scanning near‐field optical microscopy (SNOM). In addition, the analysis of the surface morphology, and the comparison with the fluorescence map is put forward and analyzed for the first time on human muscle fibres. In aperture‐SNOM the sample is excited through the nanometre‐scale aperture produced at the apex of an optical fibre after tapering and subsequent metal coating. The acquisition of the topography map, simultaneously to the optical signal, by SNOM, permits to exactly overlap the fluorescence images obtained from the two consecutive scans needed for the double localization. Besides, the differences between the topography and the optical spatial patterns permit to assess the absence of artefacts in the fluorescence maps. Although the SNOM represented a good method of analysis, this technique remains a complementary method to the CLSM and it can be accepted in order to confirm the hypothesis advanced by CLSM.