On Sums of Two Coprime k-th Powers(II)

For fixed k ≥ 3, let E_k(x) denote the error term of the sum ?_{n ￡ x}r_k(n)\sum_{n\le x}\rho_k(n) , where r_k(n) = ?_{n=|m|^k+|l|^k, g.c.d.(m,l)=1}\rho_k(n) = \sum_{n=|m|^k+|l|^k, g.c.d.(m,l)=1} 1. It is proved that if the Riemann hypothesis is true, then E₃(x) << x^331/1254+eE_3(x)\ll x^{331/1254+\varepsilon} , E₄(x) << x^37/184+eE_4(x)\ll x^{37/184+\varepsilon} . A short interval result is also obtained.     

一个除数问题的推广

本文推广了Ｒ．Ａ．Ｓｍｉｔｈ，Ｍ．Ｖ．Ｓｕｂｂａｒａｏ和Ｇ．Ｎｏｗａｋ所考虑的一个除数问题．令Ｓ＝｛（ａｉ，ｑｉ）｜ａｉ≤ｑｉ｝（ｒ≥３）．定义ｄ（ｎ；Ｓ）＝Σ（１）１，Σ（１）表示对满足ｎ＝ｍ１…ｍｒ，ｍｊ≡ａｊ（ｍｏｄｑｊ），ｊ＝１，２，…，ｒ的诸ｍｊ求和．我们求出了Σｎ≤ｘｄ（ｎ；Ｓ）的渐近公式，并得到了余项估计．     

离心泵蜗壳内部高粘油时均流动的LDV测量

本文用LDV测量了最优工况和小流量工况下，输送运动粘度为48mm2／s高粘油时，蜗壳第Ⅳ、Ⅵ和Ⅷ断面内的时均切向、径向速度。给出了角动量随半径的变化关系，并与输送粘度为1mm2／s水时的角动量进行了比较。     

Iron(Ⅱ) hydrides bearing a tetradentate PSNP ligand

Iron(II) hydrides bearing PSNP tetradentate ligand were synthesized and well characterized. The hydrido iron complex [2H(NCMe)](BF₄) is an extremely efficient catalyst for the hydroboration of aldehydes at room temperature.     

Amino‐Assisted Anchoring of CsPbBr3 Perovskite Quantum Dots on Porous g‐C3N4 for Enhanced Photocatalytic CO2 Reduction

Halide perovskite quantum dots (QDs) have great potential in photocatalytic applications if their low charge transportation efficiency and chemical instability can be overcome. To circumvent these obstacles, we anchored CsPbBr₃ QDs (CPB) on NH_x‐rich porous g‐C₃N₄ nanosheets (PCN) to construct the composite photocatalysts via N?Br chemical bonding. The 20 CPB‐PCN (20 wt % of QDs) photocatalyst exhibits good stability and an outstanding yield of 149 μmol h^?1 g^?1 in acetonitrile/water for photocatalytic reduction of CO₂ to CO under visible light irradiation, which is around 15 times higher than that of CsPbBr₃ QDs. This study opens up new possibilities of using halide perovskite QDs for photocatalytic application.     

硒对不同水体致癌因子诱发健康人微核的拮抗作用

采用微核检测技术，研究了亚硒酸钠对启东肝癌高发区不同类型饮用水诱发健康人外周血淋巴细胞微核的拮抗作用。结果表明：（１）各实验水体对细胞的毒性作用，宅沟水〉泯沟水〉自来水〉双蒸水。微核率随着实验水体剂量的增加而升高；（２）１ｍｇ／Ｌ的亚硒酸钠浓度对泯沟水，自来水诱发的微核效应有是显的抑制和／或拮抗作用，呈现明显的剂量－效应关系，提示肝癌高发区饮用水体中确存在与肝癌发病相关的致畸因子，补硒确有防与治原     

溶胶-凝胶法制备二元稀土掺杂(Sm2O3)0.04 (Gd2O3)0.06 Ce0.8O2-δ纳米粉体

以Sm2O3、Gd2O3与Ce2(CO3)3.nH2O为原料,采用Sol-Gel法制备了二元稀土掺杂(Sm2O3)0.04(Gd2O3)0.06Ce0.8O2.δ纳米粉体.测定了pH值对0.80Ce(OH)4·0.08Sm(OH)3·0.12Gd(OH)3水溶胶体系zeta电位的影响.pH值约为7.0时,体系的Zeta电位为0,即体系的等电点(IEP)为7.0.pH值为10.0时,Zeta电位达到最大值-18.5my,说明此时该体系的稳定性最好.DTA/TG热分析表明,0.80Ce(OH)4·0.08Sm(OH)3·0.12Gd(OH)3粉体的热分解温度约为232℃.由粉末XRD分析可知,经750℃焙烧的二元稀土掺杂CeO2粉末为立方萤石结构,说明Sm2O3与Gd2O3已完全固溶到CeO2中形成了CeO2基固溶体.由TEM照片可以看出,粉末具有良好的分散性,呈软团聚状态,粒径在5-10nm之间.经BET测试计算的平均颗粒尺寸为11nm,与TEM结果是一致的.     

SYNTHESIS, STRUCTURE AND ELECTRICAL PROPERTIES OF POLY(PHENYLENE VINYLENE) FILM DOPED WITH FERRIC CHLORIDE

Poly(phenylene vinylene) (PPV) film was synthesized via a soluble precursor poly-mer. Strong fluorescence at 500-600nm was observed in both precursor and PPV film.Room-temperature conductivity of PPV film doped with FeCl_3 depends on the eliminationtemperature, the concentration of FeCl_3 and doping time. The maximum conductivity ofdoped PPV at room-temperature can reach about 40 S·cm~(-1). The temperature depen-dence of conductivity was controlled by 1D-VRH (1 Dimension Variable Range Hopping)model with T_0 value of 3.9×10~3 K. Non-Ohmic conductivity resulting from Schottky effectwas observed and the value of converted voltage from Ohmic region into non-Ohmic regionat the current-voltage characteristic was found to be dependent upon the work function ofelectrodes.     

L-聚乳酸/低分子量壳聚糖共混膜的制备和特性

二甲基亚砜(DMSO)作为共溶刺，将两种极性不同的生物医用高分子L-聚乳酸(PLLA)与低分子量壳聚糖混合在一起．扫描电镜(SEM)研究结果表明两种组分共混时存在着明显的相分离．当壳聚糖含量在2％以内时，壳聚糖相在共混膜中呈现空心圆状的图案，空心圆的直径为几微米．PLLA用DMSO溶解后，在重新干燥的过程中，PLLA的堆积结构会发生变化，它的玻璃化转变温度由55.5℃变为34℃．共混膜中混入的壳聚糖含量在2％以内时，在保持的聚乳酸的力学性能的同时。可以降低聚乳酸的接触角。改善聚乳酸的亲水性．     

Transition metal-free tandem pyridinyl–allyl–allyl cross-coupling reaction

A transition metal-free, direct one-pot domino allylation reaction of 2-pyridinyl Grignard reagents with polysubstituted allyl chlorides for the regioselective synthesis of pyridinyl-substituted 1,5-diene derivatives has been disclosed. The reaction presumably proceeded through the coupling of polysubstituted allyl chloride to 2-PyMgX, which was in situ generated from 2-bromopyridine with i-PrMgCl·LiCl.