SAXS and WAXD study of periodical structure for polyacrylonitrile fiber during coagulation

Small angle X‐ray scattering (SAXS) and wide angle X‐ray diffraction (WAXD) were adopted to investigate the formation and development of high order structure within polyacrylonitrile (PAN) precursor during coagulation. The scattering signal came from the microvoids and long period structure was separated reasonably by the analog computation method of decomposition of the one‐dimensional profile. Based on the established methodology, the statistic parameters of long period structure, such as length of the long period structure, crystalline region and amorphous region, were obtained by the analysis of correlation function. The results indicated that during the coagulation, the length of long period of the nascent coagulated fiber was 56.1 nm (meridional direction) and 35.6 nm (equatorial direction), respectively. The evolution of the long period during the coagulation was also discussed by combining WAXD data. With the processing of coagulation, the long period was decreased since the crystallinity increased. Copyright © 2014 John Wiley & Sons, Ltd.     

Effect of polyethylene glycol on the crystallization and impact properties of polylactide‐based blends

Polylactide (PLA) was plasticized by polyethylene glycols (PEGs) with five different molecular weights (M_w = 200–20,000 g/mol). The effects of content and molecular weight of PEG on the crystallization and impact properties of PLA were studied by wide‐angle X‐ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy, and V‐notched impact tests, respectively. The results revealed that PEG‐10,000 could significantly improve the crystallization capacity and impact toughness of PLA. When the PEG‐10,000 content ranged from 0 to 20 wt%, the increases in both V‐notched Izod and Charpy impact strengths of PLA/PEG‐10,000 blends were 206.10% and 137.25%, respectively. Meanwhile, the crystallinity of PLA/PEG‐10,000 blends increased from 3.95% to 43.42%. For 10 wt% PEG content, the crystallization and impact properties of PLA/PEG blends mainly depended upon PEG molecular weight. With increasing the M_w of PEG, the crystallinity and impact strength of PLA/PEG blends first decreased and then increased. The introduction of PEG reduced the intermolecular force and enhanced the mobility of PLA chains, thus improving the crystallization capacity and flexibility of PLA. Copyright © 2015 John Wiley & Sons, Ltd.     

酶注射式葡萄糖生物传感器建模方法研究

建立了酶注射式生物传感器的机理模型,并通过实验验证模型精确性.用传感器检测1和2 mg/mL葡萄糖溶液得到电压数据,通过数据拟合确定模型参数.将浓度值3 mg/mL带入模型得到预测曲线,再将其与传感器检测数据拟合后曲线进行比较,验证模型精确性.结果表明,参加反应的酶液米氏常数Km为1.97,数学模型与实际传感器工作模型相关系数(R2)为0.998.     

Microwave-assisted micro-solid-phase extraction for analysis of tetracycline antibiotics in environmental samples

In this study, a novel solid-liquid-solid extraction approach, which was termed ‘microwave-assisted micro-solid-phase extraction’ (MAE-μ-SPE), was developed. Target analytes were extracted from the sample into extraction solvent enhanced by microwave field, following adsorption by the adsorbent in the micro-solid-phase extraction device. Without any clean-up steps, the extracts were analysed by high performance liquid chromatography coupled with ultra-violet detector. The MAE-μ-SPE approach was developed for the extraction of four tetracycline antibiotics residues in environmental soil, sludge and atmospheric particulate matters. Variables affecting extraction procedures were systematically investigated. Low detection limits of 0.1–6.3 ng/g and low quantification limits of 0.33–20.7 ng/g were achieved under optimised conditions. The recoveries of antibiotics ranged from 70.6% to 110.5% with relative standard deviation of less than 15.1%. The predominance was showed when compared to conventional MAE and μ-SPE method. According to the results, MAE-μ-SPE was proved to be a simple and effective sample preparation method for the analysis of trace organic contaminants in environmental samples.     

镥晶体的绝热量热法测试和热力学函数

文章合成了Lu(NO₃)₃(C₂H₅O₂N)_4.H₂O,用红外和元素分析对其进行了表征。用高精度全自动绝热量热仪,测定了该配合物80-382 K温区的热容, 利用实验热容数据, 根据热容与焓、熵的热力学关系, 求出了配合物85-350 K温区内每隔5 K相对于298.15K的标准热力学函数(HT - H298.15)m和(ST - S298.15)m.在80-350 K温度区间内,配合物的热容随温度升高而增大,没有相转移点和热力学吸收峰的出现,该配合物在此温度区间内是稳定存在的。     

Four Metal Complexes Based on Bulky Imidazole Ligands: Solvothermal Syntheses,Crystal Structures,and Fluorescence Properties

In order to explore the influences of (de‐)protonation of the imidazole ring on the structural diversity of the resulting complexes, the imidazole‐based ligands 4, 5‐diphenylimidazole (Hdpi) and 1H‐phenanthro[9, 10‐d]imidazole (Hpi) were utilized as bulky building blocks to construct four complexes by solvothermal reactions, i.e. [Ag(Hdpi)₂](NO₃) · (H₂O) ( 1 ), [Cu(dpi)]_∞ ( 2 ), [Cu(Hpi)(NO₃)]_∞ ( 3 ), and [(H₂pi)(NO₃)] · H₂O ( 4 ). In complex 1 , two Hdpi ligands adopt a monodentate pattern and coordinate with one Ag^I ion to form a mononuclear unit, which is further connected by hydrogen bonds into a 1D supramolecular helix. The deprotonated dpi ligand of 2 acts in bidentate mode, and bridges Cu^I ions to afford a 1D chain. In 3 , the NO₃^– ion, acts as a monodentate bridging ligand and joins Cu^I ions to generate a 1D chain. The Hpi ligand employs a monodentate mode to bond with Cu^I ions of the 1D chain. 4 is protonated and two H₂pi nitrogen atoms are free of coordination. Interestingly, hydrogen bonds among the NO₃^– ion, the H₂pi ligand, and the water molecule yield a macro ring R⁴₄(14). The resulting structural diversity reveals that the (de‐)protonation of imidazole ring directly steers the coordination number of ligand, and thus causes a significant effect on the structure, especially the dimensionality. Furthermore, the solid‐state fluorescence properties of the free ligands and compounds 1 – 4 were studied at room temperature.     

Syntheses,Structures, and Magnetic Properties of Two Cobalt(II) Metal‐Organic Frameworks Based on Y‐shaped 3,5,4′‐Azobenzenetricarboxylic Acid and Different N‐donor Ligands

Two metal‐organic frameworks, [Co₂(ABTC)(bimh)(OH)] · 2H₂O ( 1 ) and [Co₃(ABTC)₂(dimb)₄]_n ( 2 ) [H₃ABTC = 3,4′,5‐azobenzenetricarboxylic acid, bimh = 1,1′‐(1,4‐hexanediy)bis(imidazole), dimb = 1,4‐bis(1H‐imidazol‐1‐yl)benzene], were prepared under solvothermal conditions and structurally characterized. Complex 1 demonstrates a complicated 3D (3,8)‐connected tfz‐d net with (4³)₂(4⁶.6¹⁷.8⁵) topology. The framework of 2 can be classified as a rare 3D (3,6,6)‐connected net with the Schäfli symbol of (4.6²)₂(4².6¹⁰.8³)(4⁴.6¹⁰.8), and exhibits an intriguing self‐penetrating motif. Meanwhile, the thermal stabilities and magnetic properties for 1 and 2 were also probed.     

Bioactive Trichothecenes Produced by the Myrothecium sp. QB‐1

Three new simple trichothecenes, 15‐acetyltrichoverrol B ( 3 ), 13′‐acetyltrichoverrin B ( 5 ), and 6′‐dehydroxytrichoverrin B ( 6 ), along with five known trichothecenes trichodermadienediol B ( 1 ), trichoverrol B ( 2 ), trichoverrin B ( 4 ), and roridins A ( 7 ) and D ( 8 ), have been isolated from the liquid culture of Myrothecium roridum (strain no. QB‐1). The structures of the new compounds were established by comprehensive analysis of 1D‐ and 2D‐NMR data. All the compounds were evaluated for antifungal activity, only compounds 7 and 8 showed significant antifungal activity against the tested fungi (MIC ranged from 10 to 5 μg/ml).     

Application of Löwdin's canonical orthogonalization method to the Slater‐type orbital configuration‐interaction basis set

We apply Löwdin's canonical orthogonalization method to investigate the linearly dependent problem arising from the variational calculation of atomic systems using Slater‐type orbital configuration‐interaction (STO‐CI) basis functions. With a specific arithmetic precision used in numerical computations, the nonorthogonal STO‐CI basis is easily linearly dependent when the number of basis functions is sufficiently large. We show that Löwdin's canonical orthogonalization method can successfully overcome such problem and simultaneously reduce the dimension of basis set. This is illustrated first through an S‐wave model He atom, and then the real two‐electron atoms in both the ground and excited states. In all of these calculations, the variational bound state energies of the two‐electron systems are obtained in reasonably high accuracy using over‐redundant STO‐CI bases, however, without using extended high‐precision technique. © 2015 Wiley Periodicals, Inc.