Effect of hydrolysis degree of hydrolyzed polyacrylamide grafted carboxymethyl cellulose on dye removal efficiency

In this present work, a series of hydrolyzed polyacrylamide grafted carboxymethyl cellulose (CMC-g-HPAM) was prepared. The structure and solution properties of CMC-g-HPAM were characterized by FTIR, ¹H-NMR, elemental analysis and zeta potential measurements. The graft copolymers were applied as flocculants to remove methylene blue (MB), a cationic dye, from aqueous solutions. In comparison with its precursors, carboxymethyl cellulose (CMC) and polyacrylamide CMC-g-PAM, CMC-g-HPAM exhibited higher removal efficiencies. Furthermore, the flocculation performance of the copolymers was significantly improved with the increase of the hydrolysis degree, and the MB removal efficiency was more than 90 % when the hydrolysis degree of CMC-g-HPAM was higher than 80 %. More importantly, image analysis in combination with fractal theory demonstrated that the graft copolymers could produce notably denser and larger flocs, which was of great significance in practical water treatment. The improved flocculation performance was ascribed to both charge neutralization and bridging effects.     

Preparation and characterization of oxidized regenerated cellulose film for hemostasis and the effect of blood on its surface

Hemostatic effects of oxidized regenerated cellulose (ORC) are well-known but its mechanism has never been demonstrated clearly. Since thrombus formation is a kind of surface phenomenon, we changed the morphology of cellulose to form a kind of membrane with ionic liquid as solution, and also we prepared ORC films with nitrogen dioxide(NO₂)/carbon tetrachloride(CCl₄) oxidation system reacting for 16, 40, 64 and 88 h, respectively. FTIR and NMR spectra showed that NO₂/CCl₄ oxidation system had a high selectivity on hydroxyl group at C6 of regenerated cellulose. With the oxidation time prolonging, the carboxyl content was enhanced and the DP was reduced. The XPS results suggested that a new carboxyl bond was formed due to the increasing of oxygen content. From contact angle analysis, the wettability of blood on the ORC film surface was better than that of the regenerated cellulose film, which was beneficial for the blood to spread. SEM photographs showed that the ORC film oxidized for 40 h could adsorb and activate more platelets and erythrocytes. Hemostatic evaluation and enzyme-linked immunosorbent assay indicated that the ORC film had a dramatic hemostatic performance, and the products of platelets release reaction, activated platelets glycoprotein and activated clotting enzymes were increased simultaneously. Moreover, the possible mechanism of the hemostasis for ORC film was discussed.     

Li+掺杂对Y2SiO5:Pr3+上转换发光性能影响

采用溶胶-凝胶法制备Li+掺杂改性的Y2SiO5:Pr3+上转换发光材料,考察了Li+掺杂对样品晶型及发光性能的影响。采用XRD,DSC-TGA,FS对所制备的材料进行表征,结果表明Li+掺入浓度在7%～8%(摩尔分数)之间会引起Y2SiO5晶体类型由X1型转变为X2型,且Li+掺入后样品转晶型温度由950℃降至800℃;样品经800℃煅烧处理后以X1型Y2SiO5为主相,850℃煅烧处理后以X2型Y2SiO5为主相;Li+掺入同时会提高Y2SiO5:Pr3+材料的上转换发光强度,Li+最佳掺杂浓度为10%,对于双掺杂Pr3+,Li+:Y2SiO5体系中Pr3+最佳掺杂浓度为1.2%。     

Eu（TTA）3AA-NBR/PVP同轴超细纤维的制备及荧光性能研究

用同轴静电纺丝制备了含有稀土铕配合物(Eu(TTA)3AA)的芯-壳结构的丁腈橡胶/聚乙烯吡咯烷酮(NBR/PVP)超细荧光纤维。考察了在外层PVP纺丝参数不变的情况下,改变芯层丁腈橡胶纺丝液的纺丝速度、Eu(TTA)3AA含量等对纤维形貌的影响。通过研究Eu(TTA)3AA-NBR/PVP同轴超细纤维中Eu(TTA)3AA微观结构、含量与纤维的荧光性能之间的关系,发现在同轴纤维形成过程中由于溶剂的快速挥发可使Eu(TTA)3AA形成无定形结构,进而在纤维中形成分子簇级别的分散,在Eu(TTA)3AA含量为30%时,同轴纤维比Eu(TTA)3AA粉末的荧光强度提高了2倍。     

二维柱坐标系辐射输运方程保球对称的离散纵标格式

 离散纵标格式是计算辐射输运方程的常用格式之一. 但是, 传统的离散纵标格式求解二维柱坐标系辐射输运方程模拟一维球对称问题时, 会出现明显的非对称现象, 球对称性被破坏. 针对该问题, 本文分析了传统离散纵标格式不能够保持球对称性的原因, 提出了空间基于柱坐标系、方向基于球坐标系的辐射输运方程, 并对该方程设计了新的离散纵标格式, 从理论上证明了当空间网格取球对称剖分时该离散格式能够保持一维球对称性的充分必要条件. 通过对真空球区域辐射输运、与物质耦合辐射输运等球对称算例的数值模拟, 验证了该格式的保球对称性, 球对称误差能够达到机器精度. 非对称辐射驱动模型以及非对称网格剖分条件下的数值模拟等算例也取得了较好的结果.     

Edge Flips in Surface Meshes

Little theoretical work has been done on edge flips in surface meshes despite their popular usage in graphics and solid modeling to improve mesh equality. We propose the class of \((\varepsilon ,\alpha )\)-meshes of a surface that satisfy several properties: the vertex set is an \(\varepsilon \)-sample of the surface, the triangle angles are no smaller than a constant \(\alpha \), some triangle has a good normal, and the mesh is homeomorphic to the surface. We believe that many surface meshes encountered in practice are \((\varepsilon ,\alpha )\)-meshes or close to being one. We prove that flipping the appropriate edges can smooth a dense \((\varepsilon ,\alpha )\)-mesh by making the triangle normals better approximations of the surface normals and the dihedral angles closer to \(\pi \). Moreover, the edge flips can be performed in time linear in the number of vertices. This helps to explain the effectiveness of edge flips as observed in practice and in our experiments. A corollary of our techniques is that, in \(\mathbb {R}^2\), every triangulation with a constant lower bound on the angles can be flipped in linear time to the Delaunay triangulation.     

Enantioselective sulfenylation of α-nitroesters catalyzed by diarylprolinols

The organocatalytic sulfenylation of α-nitroesters mediated by diaryl-l-prolinols was developed. A range of α-sulfenylated α-nitroesters were obtained in good yields with moderate to good enantioselectivities.     

A Low‐dimensional Viologen/Iodoargentate Hybrid [(BV)2­(Ag5I9)]n: Structure,Properties, and Theoretical Study

A new low‐dimensional benzyl viologen/iodoargentate hybrid, [(BV)₂(Ag₅I₉)]_n ( 1 ) (BV²⁺ = benzyl viologen) was prepared. In 1 , (Ag₆I₉)_n^2– chain exhibits a new type of one‐dimensional chain constructed from vertex‐sharing of Ag₅I₁₀ units, and its two‐dimensional layer structure was constructed from C–H ··· I hydrogen bonds. Strong luminescence at 404 nm can be detected in 1 . DFT calculation suggests that 1 displays a reduced bandgap, which is led by a more dispersed LUMO band of BV²⁺ compared with MV²⁺ in [MV(Ag₂I₄)]_n.     

One‐Pot Synthesis of Highly Substituted Polyheteroaromatic Compounds by Rhodium(III)‐Catalyzed Multiple C?H Activation and Annulation

A new method for the synthesis of highly substituted naphthyridine‐based polyheteroaromatic compounds in high yields proceeds through rhodium(III)‐catalyzed multiple C H bond cleavage and C C and C N bond formation in a one‐pot process. Such highly substituted polyheteroaromatic compounds have attracted much attention because of their unique π‐conjugation, which make them suitable materials for organic semiconductors and luminescent materials. Furthermore, a possible mechanism, which involves multiple chelation‐assisted ortho C H activation, alkyne insertion, and reductive elimination, is proposed for this transformation.