Experimental research on the residual magnetization of a rare-earth permanent magnet for a cryogenic undulator

The magnetic properties of commercial polycrystalline Nd2Fe14B (N50M,N45H,N40SH,N35EH) and Sm2Co17(XG30/20,XG26/25,XG22/20) magnets at cryogenic temperatures were tested by using a comprehensive physical properties measurement system (PPMS). The results show that the spin tilt temperature Tst of Nd2Fe14B magnets is closely related to intrinsic coercivity Hci , N50M and N45H with smaller Hci show a residual magnetization jump at 235K and 225K, respectively. For Sm2Co17 magnets, in 50-300 K, with temperature decreasing, residual magnetization Mrc shows a nearly linear increase, while in 10-50 K, Mrc has little change. The research results provide a reference for cryogenic undulators and other high-precision cryogenic devices.     

黄酮类化合物抗鼠肝微粒体脂质过氧化作用的结构与活性关系

黄酮类化合物具有多种药理作用 .由于该类化合物种类多 ,生物活性差别大 ,研究其抗氧化活性与结构的关系 ,将为寻找活性更强的黄酮类物质提供依据 .研究表明 [1] ,黄酮类化合物抗氧化活性与下列结构因素有关 :黄酮母核上的羟基数目及位置 ;B环上是否有邻二羟基 ;C环 2 ,3位是否有双键结构 ,4位是否有羰基结构 ;3 ,5位是否存在羟基 .由于不同研究者所研究的黄酮结构差异较大 ,目前所得到的抗氧化作用的构效关系并不十分一致 ,上述关系也不能全面概括黄酮类抗氧化作用的构效关系 .黄酮类化合物抗氧化活性不仅与其结构有关 ,还与氧自由基的种…     

微波辅助一步合成2-取代吲哚

微波辐射下以取代苯胺1, 2-溴芳基乙酮2为原料, 在无催化剂条件下一步合成了一系列2-取代吲哚3. 该方法具操作简单、反应时间短、产率高等特点.     

四种天然槲皮素-3-糖苷的合成

以芦丁为原料, 经苄基化、酸水解得到关键中间体3′,4′,7-O-三苄基槲皮素(3), 3与相应的1-溴代乙酰糖在四丁基溴化铵催化下在氯仿-0.25 mol•L^－1 K₂CO₃溶液中缩合成相应的糖苷, 脱去保护基得天然槲皮素3-糖苷类化合物 1a～1d. 其结构经IR, ¹H NMR, MS及元素分析确证.     

β分泌酶抑制剂的药效团模型研究

选择活性跨越0.002至25 μmol•L－1的4类共25个β分泌酶抑制剂作为训练集, 使用Catalyst软件包构建出药效团模型, 并通过对药效团的有效性分析, 筛选得到的最佳模型(correlCorrel＝0.969, Config＝16.32, Δcost＝62.422)由一个环芳香性、一个疏水中心、一个正电荷中心和一个氢键供体组成. 并用其它209个抑制剂组成测试集对模型进行验证, 结果表明该模型显示出较强的预测能力, 能够为进一步的数据库搜索, 寻找新型的β分泌酶抑制剂先导物提供依据.     

Synthesis of 2-cyclohexenone derivatives via gold(I)-catalyzed hydrative cyclization of 1,6-diynes

The gold(I) complex (MeAuPPh3) was found to be a highly effective catalyst for the hydrative cyclization of 1,6-diynes to form the corresponding 3-methyl hex-2-enone derivatives with good to excellent yield. The proposed mechanism is described.     

The randomly organized structure of urban ground bus-transport networks in China

In this paper, the evolution dynamical properties of four topological urban ground bus-transport networks (BTNs) in China are empirically researched. As the statistical results of some common used measurements show that there are large fluctuations because of small sample sizes to induce some indistinct conclusions, and there are even incorrect BTN structure pictures as positive degree relation of the adjacent vertices in those BTNs though they are actually uncorrelated at all, i.e., exhibiting “pseudo positive connectivity correction”. Thus in order to uncover the randomly organized architecture of BTNs, new measurements of the average sum of the nearest-neighbors’ degree-degree correlation D_nn(k), and the degree average edges among the nearest-neighbors L(k) are proposed. The obtained results of two new measurements do reflect that the considered BTNs are organized randomly. In this point, those empirical results provide one new framework for a more realistic BTN model, which will capture the underlying evolution principles of a BTN in the geographical topology.     

Synthesis,Crystal Structure and Photophysical Properties of Cu（Ⅰ） Complexes Containing 2,5-Bis（pyridyl）-1,3,4-oxadiazole

Four novel Cu(Ⅰ) complexes,[Cu(o-PYO)(PPh3)2]BF4(1),[Cu(o-PYO)(DPEphos)]BF4(2),[Cu2 (o-PYO)(PPh3)3(CH3CN)](BF4)2(3) and [Cu2(o-PYO)(DPEphos)2 ](BF4)2(4) (o-PYO=2,5bis(pyridyl)-1,3,4-oxadiazole,PPh 3=triphenylphosphine,DPEphos=bis(2-(diphenylphosphanyl)phenyl)ether),have been synthesized and characterized by 1 H NMR,elemental analysis and single-crystal X-ray diffraction.The central cuprous ions in all complexes are surrounded by N and P atoms to form a distorted tetrahedral geometry,although one of the cuprous ions in complex 3 is coordinated by a PPh3 and an acetonitrile molecule due to the steric hindrance and weak coordination ability from monodentate PPh3 ligand.The UV-vis absorption spectra in CH2Cl2 show the characteristic metal-to-ligand charge transfer (MLCT) absorption bands in the region of 360-480nm.Four Cu(I) complexes exhibit yellow to orange-red phosphorescence with the emission maximum at 572,577,562 and 597nm,respectively in the solid state.     

上海光源低温波荡器永磁铁在低温下的磁特性研究

用综合物性测量系统测试了国产Nd₂Fe₁₄B (N50M)永磁铁在低温下(10–300 K)的M-H和M-T. 获得了N50M剩磁B_r和内禀矫顽力H_ci在低温下的变化图, 对其取向度和三维磁化强度进行了分析研究. 结果表明, N50M在80–150 K发生强烈自旋再取向效应, B_r在120–130 K出现峰值, H_ci随温度下降呈线性增加. 在130 K, B_r和H_ci分别比常温(300 K)增加15.6%和220%, 达到1.65 T和3638 kA/m. 在150–300 K, 随温度下降, N50M宏观取向度与外磁场均匀性逐步改善, 但在80–235 K, 微观外磁场均匀性恶化.实验研究发现, 235 K附近, N50M垂直取向方向呈现“剩余磁化强度跳跃”. 研究结果为上海光源Ⅱ期低温波荡器及其他高精度低温永磁仪器与设备的物理设计提供了参考. 关键词： 低温波荡器 2Fe₁₄B永磁铁')" href="#">Nd₂Fe₁₄B永磁铁 低温 磁特性     

Synthesis and cytotoxicity of indolopyrrolemaleimides

A series of indolopyrrolemaleimides have been synthesized and evaluated for their cytotoxicity in vitro against human leukemia cell line and four human solid cancer cell lines. Some of the compounds showed high or mediate activity against the lines. 6dc is the most promising compound among them. The inhibition toward topoisomerase I was also studied.