σ-Phase in Lean Duplex Stainless Steel Sheets

The precipitation kinetics of secondary phases in two austeno-ferritic lean duplex stainless steels (lean DSS) were examined after aging the materials at 800 °C. Owing to the instability of ferrite, all DSS are known to be sensitive to solid-state phase transformations in the critical temperature range 600-1,000 °C and different secondary phases may form, depending on composition and microstructure. The performed thermodynamic simulations revealed the proneness to the precipitation of such phases also have been done in lean DSS, but only information on the equilibrium microstructures were achieved. Therefore, the materials were aged at various times, in order to verify the simulations and determine the precipitation kinetics. The occurred structural modifications were observed and quantified by scanning electron microscope and X-ray diffraction measurements, determining phase type, composition and volumetric fraction. At 800 °C, grade 2101 was found to be only affected by Cr₂N nitrides precipitation, whereas a significant amount of σ-phase was found to form in LDX 2404 for treatment longer than 1 h, almost totally replacing ferrite after 50 h. Up to now, the intermetallic σ-phase has been observed only in the high alloyed DSS, and the unexpected precipitation in grade 2404 highlighted that the increased content of molybdenum in this steel might be considered as determinant for the formation.     

Syntheses and characterisation of electrically conductive and fluorescent poly[3-(ω-bromoalkyl)thiophenes]

A novel series of functionalized polythiophenes incorporating 3-(ω-bromoalkyl) pendants were synthesized by chemical oxidative polymerization using FeCl₃ and characterized using FT-IR, UV–Vis absorption spectroscopy, fluorescence emission spectroscopy, conductivity measurements and thermal analyses. These polymers attained a maximum electrical conductivity between 4.7 and 8.4 S cm⁻¹ upon doping with iodine and have a fluorescence quantum yield of up to 11.1% with respect to quinine sulfate. The influence of the terminal ω-bromine substituent as of the length of the alkyl pendant on electrical conductivity, spectral behavior and thermal stability is discussed.     

雌激素对培养大鼠皮质神经元细胞β淀粉样蛋白(25-35)损伤的保护作用

目的: 研究雌激素对β 淀粉样蛋白(β-amyloidprotein, Aβ) 诱导的大鼠神经细胞损伤的影响。方法: 通过相差倒置显微镜、Giemsa 染色及乳酸脱氢酶(lactate dehydrohenase, LDH) 释放率的测定。观察17β-雌二醇(17β-estradiol, 17β-E2) 对Aβ(25-35) 诱导的大鼠皮质神经元细胞损伤的影响。结果: Aβ(25-35) 可以诱导大鼠皮质神经元细胞损伤, 17β-E2 预处理48 h 显著抑制Aβ(25-35) 诱导的大鼠皮质神经元细胞损伤。结论: Aβ 对大鼠皮质神经元细胞有毒性作用, 雌激素可以抑制Aβ 诱导的大鼠皮质神经元细胞损伤, 雌激素具有神经保护作用。