Characterisation and coagulation performance of polysilicate-ferric-zinc

A new type of coagulant, polysilicate-ferric-zinc (PSFZn) with different Fe/Zn molar ratios, was synthesised using water glass (industrial grade, w(SiO₂) = 21 mass %, ρ = 1.34 × 10³ kg m^?3, modulus = 3.2), FeSO₄ · 7H₂O, ZnSO₄, and NaClO₃ by way of co-polymerisation in the same (Fe + Zn)/Si molar ratio based on polysilicate-ferric (PSF). The effect of the Fe/Zn molar ratios on the morphology and structure was systematically investigated using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction (XRD) analysis. Three samples, namely PSFZn4, PSFZn1, and PSFZn0.25, represented Fe/Zn molar ratios of 4, 1, and 0.25, respectively, and were selected for a comparative study while a constant (Fe + Zn)/Si molar ratio equal to 1 was maintained. Accordingly, PSFZn was found to be a complex compound rather than a simple mixture of raw materials. With the decrease in Fe/Zn, a great change occurred in the surface morphology, from a tetrahedral cluster structure to a lamellar structure. The Fe—O and Fe—O—Si bonds were gradually replaced by Zn—O and Zn—O—Si. However, the crystalline peaks were more obvious with the increase in the number of zinc ions; hence the new polymer would be formed from iron, zinc, and polysilicate. In addition, the coagulation performance of PSFZn was investigated using a surface water sample. PSFZn4 exhibited a better coagulation performance than the other PSFZn coagulants. Additionally, the trends in changes in pH with different coagulation times after adding PSFZn were studied relative to PSF and FS. The replacement of zinc ions with iron ions could effectively counter the rapid decrease in pH. The effect of settling time on the coagulation efficiency was also investigated. PSFZn4 exhibited a better settlement performance than PSF and poly aluminium chloride (PAC). Hence, the partial substitution of zinc salt with iron salt not only addresses the inadequacies of iron salt but also improves the coagulation efficiency of zinc salt in water treatment.     

纳米镍钴铁氧体空心微球的制备与性能

以乙二醇为溶剂,氯化铁、氯化钴、氯化镍和醋酸铵为反应试剂,采用溶剂热法制备纳米Ni_xCo_1-xFe₂O₄(x=0、0.3、0.5、0.7、1)铁氧体空心微球,研究镍含量对铁氧体空心球的磁性与吸波性能的影响。借助X射线衍射仪(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、振动样品磁强计(VSM)和网络分析仪对试样的物相组成、微观形貌和电磁特性进行表征。结果表明制备的镍钴铁氧体为尖晶石结构,且形貌为空心球,粒径在200nm左右。当x=0时,镍钴铁氧体空心球饱和磁化强度最大为81.7emu·g^-1,反射损耗在1658.8MHz有最小值为-16.9dB。     

The synthesis of nebularine and its analogs via oxidative desulfuration in aqueous nitric acid

The synthesis of nebularine and its analogs has been achieved via oxidative desulfuration in H₂O for the first time. With 50% HNO₃ as an oxidant and solvent, 18 products were obtained in good yields (70%–94%). The oxidative desulfuration system could tolerate different functional groups including fluoro, chloro, amino, alkyl, allyl, ribosyl, deoxyribosyl, and arabinofuranosyl groups. More importantly, the drug nebularine could be obtained successfully on a 20 g scale, which made this route more attractive for industrial applications.     

普通化学教学改革与探索

结合近几年的普通化学教学实践,我们分析了普通化学教学实践过程中存在的一些问题,并提出了培养学生的创新能力,不断更新教学内容,将理论教学与实验教学相结合等几方面建议。     

FOX-7转晶行为的太赫兹光谱及理论计算研究

1, 1 -二氨基- 2, 2 -二硝基乙烯(FOX-7)是一款新型高能钝感炸药, 为了研究温度变化对其分子结构特性的影响, 利用太赫兹时域光谱技术对持续升温(298K→393 K)过程中FOX-7 在0.2—2.5 THz 频率范围内的吸收光谱进行了在线探测, 结果发现随着样品温度的升高, FOX-7 的吸收谱带发生变化, 于384 K 时出现一个新的吸收特征峰, 且该吸收峰的峰强逐渐升高. 基于密度泛函理论(DFT), 对样品在298 K 和393 K 温度下的晶体结构进行了小于2.5 THz 范围内吸收频谱的模拟计算, 完成了对FOX-7 两种晶型实验吸收特征峰的指认. 分析表明FOX-7 的分子结构会受温度的影响而发生改变, 互为异构晶型的基团表现出的振动模式不同, 温度384 K 时FOX-7 开始发生α→β 晶型转变, 且该晶型转变过程是可逆的, 新出现的1.12 THz 特征峰在393 K 时的振动是由—NO₂ 和—NH₂ 的摆动及各自的扭动所致.     

Multifunctional manganese carbonate microspheres with superparamagnetic and fluorescent properties: synthesis and biological application

Multifunctional manganese carbonate microspheres with superparamagnetic and fluorescent properties were fabricated and used as biological labels. The Fe(3)O(4)@MnCO(3) microspheres were synthesized by direct co-precipitation without any linker shell. The Fe(3)O(4)@MnCO(3) microspheres have uniform size distribution and rough surface, which provides a promising template for the assembly of polyelectrolytes (PEs) and CdTe quantum dots (QDs). A luminescent CdTe shell was observed in Fe(3)O(4)@MnCO(3)@PE-CdTe spheres by confocal fluorescence imaging. With excellent solubility in water and rough surfaces, the multifunctional microsphere offers a friendly microenvironment for immobilization of α-fetoprotein (AFP) antibodies (Ab(2)) to fabricate Fe(3)O(4)@MnCO(3)@PE-CdTe-Ab(2) architecture. By using the Fe(3)O(4) @MnCO(3)@PEs-CdTe-Ab(2) bioconjugate as a label, a promising and versatile platform for fluorescence imaging and electrochemical immunosensing of cancer biomarker AFP was developed. The prepared electrochemical immunosensor shows high sensitivity and selectivity with a detection limit of 0.3 pg mL(-1).     

单室固体氧化物燃料电池阴极材料La0.75Sr0.25Cr0.5Mn0.5O3的电化学性能研究

采用高温固相法制备了La0.75Sr0.25Cr0.5Mn0.5O3(LSCM)并利用XRD,SEM以及电化学阻抗谱(EIS)分别对粉体及电极进行研究。结果发现LSCM在C3H8-O2-N2混合气氛下能够保持很好的高温化学稳定性,且与电解质材料YSZ在1400℃空气气氛下不发生化学反应。电化学测试结果表明,阳极支撑型单室固体氧化物燃料电池Ni-YSZ|YSZ|LSCM在700℃、C3H8-O2-N2混合气氛下的短路电流密度达317 mA·cm-2,最大功率密度73 mW·cm-2。将LSCM与CGO形成梯度阴极,相同测试条件下,单室电池的短路电流密度为560 mA·cm-2,功率密度达到110 mW·cm-2,电池输出性能提高约50%。     

Electrochemical preparation and magnetic properties of submicron Co x Pb1−x dendrites

Magnetic dendrites of Co _x Pb_1−x were fabricated through potentiostatic electrochemical deposition on Cu substrates in boric acid solution at room temperature. The as-deposited dendrites were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), transmission electron microscopy (TEM), electrodeposition (ED), and energy dispersive X-ray spectroscopy (EDS). SEM results indicate that the Co _x Pb_1−x dendrites are highly symmetrical in structures. The diameters of the branches are about 50 ~ 200 nm, and the backbones are continuous with lengths up to about 10 μm. XRD patterns show that the as-deposited dendrites are solid solutions. The annealing treatment can result in the recrystallization of these metastable alloys into two separate phases. TEM, ED, and EDS results also reveal that the backbones and the branches of the dendrites are composed of different amounts of cobalt. Magnetic measurements confirm that the as-deposited Co _x Pb_1−x dendrites have a softly ferromagnetic behavior, and a small coercive force (about 80 Oe). Also the saturation magnetizations of the Co _x Pb_1−x dendrites decrease rapidly with the temperature increasing.     

Variable selection in a class of single-index models

In this paper we discuss variable selection in a class of single-index models in which we do not assume the error term as additive. Following the idea of sufficient dimension reduction, we first propose a unified method to recover the direction, then reformulate it under the least square framework. Differing from many other existing results associated with nonparametric smoothing methods for density function, the bandwidth selection in our proposed kernel function essentially has no impact on its root-n consistency or asymptotic normality. To select the important predictors, we suggest using the adaptive lasso method which is computationally efficient. Under some regularity conditions, the adaptive lasso method enjoys the oracle property in a general class of single-index models. In addition, the resulting estimation is shown to be asymptotically normal, which enables us to construct a confidence region for the estimated direction. The asymptotic results are augmented through comprehensive simulations, and illustrated by an analysis of air pollution data.     

周期脉冲作用下Logistic映射的复杂动力学行为及其分岔分析

研究了两种周期脉冲作用下Logistic映射的复杂动力学行为. 随着参数的变化, 该系统产生平衡解、周期解、混沌等现象, 且该系统可经级联倍周期分岔到达混沌. 通过构造Poincaré 映射, 对周期脉冲作用下Logistic映射进行了分岔分析. 最后基于Floquet理论揭示了该系统周期解的分岔机理. 关键词： Logistic映射 脉冲 周期解 分岔机理