Lag Time、二氧化硫与啤酒新鲜度关系的研究

本文通过ESR测出的Lag Time指标来反映成品啤酒的EAP,研究了其与啤酒中二氧化硫及啤酒新鲜度感官得分的相关性,发现Lag Time与啤酒新鲜度得分、二氧化硫的含量呈正相关.外添加试验表明,添加二氧化硫的量与Lag Time几乎呈线性关系,验证了二氧化硫对啤酒抗老化起着关键作用.作者认为,在其它控制水平相对稳定的情况下,如何提高发酵过程的二氧化硫生成量、提高内源抗氧化力是延长啤酒保鲜期的重点.     

ESR Study of the Singlet Oxygen Quenching and Protective Activity of Trolox on the Photodecomposition of Riboflavin and Lumiflavin in Aqueous Buffer Solutions

ABSTRACT:  Singlet oxygen quenching activity of Trolox, a water-soluble derivative of tocopherol, was studied by electron spin resonance (ESR) spectroscopy in a buffer solution (pH 7.4) containing methylene blue (MB), 2,2,6,6-tetramethyl-4-piperidone (TMPD) after light illumination for 30 min. Trolox at the concentration of 125 μM quenched 89.1% singlet oxygen in the system. Trolox showed significantly higher singlet oxygen quenching activity than ascorbic acid in the buffer solution ( P  < 0.05). Riboflavin in phosphate buffer solutions was degraded very fast under fluorescent light illumination. The photodegradation rate of riboflavin at pH 8.5 was significantly higher than pHs 4.5 and 6.5 ( P  < 0.05). Lumiflavin was also degraded under the fluorescent light illumination, but its degradation rate was much lower than that of riboflavin under the same light intensity. Unlike riboflavin, the rate of lumiflavin photodegradation was the greatest at pH 4.5 and followed by pHs 6.5 and 8.5, in a decreasing order. Trolox greatly protected the photodegradation of riboflavin and lumiflavin. The protective activities of Trolox against the photodegradation of riboflavin and lumiflavin were also pH dependent. The treatments of 5 mM Trolox in the buffer solutions of pHs 8.5 and 6.5 exhibited 56.1% and 31.7% protection of riboflavin against degradation during 120 min light illumination, respectively. The treatments of Trolox at the concentrations of 1, 3, and 5 mM in the buffer of 6.5 exhibited 14.8%, 58.4%, and 81.4% protection of lumiflavin against degradation during 24 h light illumination, respectively.     

NRJ280B方型结晶器的研制

对电渣重熔用的方形结晶器的图纸设计、成形工装及制造进行了研究,在结构上使铜内衬由原来的两条焊缝改成一道焊缝,使结晶器的使用寿命提高了近1/3。     

静磁场下电渣重熔轴承钢的研究

在电渣重熔轴承钢的过程中施加与电流方向垂直的静磁场,研究了不同电流密度和磁感应强度对轴承钢重熔锭的凝固组织、非金属夹杂物、杂质元素含量和硬度的影响。结果表明:施加的静磁场形成电磁激振效应,能够显著细化金属熔滴,提高非金属夹杂物和杂质元素的去除效率;有利于降低枝晶间距获得细晶组织,降低合金元素的偏析;提高铸锭的力学性能,因此施加静磁场是强化电渣重熔过程的重要手段。     

Electron spin resonance of thin films of organic light-emitting material tris(8-hydroxyquinoline) aluminum doped by magnesium

We have successfully observed electron spin resonance (ESR) signals of radical anions in thin films of tris(8-hydroxyquinoline) aluminum (Alq₃), a compound widely used as electron transporting and luminescent layers in organic light-emitting diodes. To obtain definitely defined radical-anion states in Alq₃, we doped Alq₃ with Mg by co-evaporating these materials. The obtained g value and peak-to-peak ESR linewidth ΔH_pp of Alq₃ radical anions are 2.0030 and 2.19 mT, respectively. Theoretical g value and hyperfine interactions were calculated by density functional theory method, which are in good agreement with the experimental results. A quantitative evaluation of doping concentration was performed. We confirmed that doped charges are localized at deep trapping sites by the lineshape analysis and temperature dependence of the ESR signals. Morphological investigation using transmission electron microscopy clarified that the co-evaporated Mg atoms form clusters.     

电渣重熔钢液洁净度控制研究进展

电渣重熔工艺能够显著去除钢中的非金属夹杂物、降低钢中的总氧含量。本文阐述了电渣重熔过程中非金属夹杂物的去除机理、夹杂物成分和含量的控制以及电渣重熔过程中氧含量的控制,介绍了电渣重熔过程钢液洁净度控制的研究进展,提出了进一步提高电渣重熔过程钢液洁净度水平的研究方向。     

Electroslag remelting technologies and equipment—modern achievements and trends of development

More than 50 years have passed since the ESR commercialization.Main steps of the ESR technology and appropriate equipment,developing until now,will be outlined.The trends in development of ESR technology and equipment will be also discussed.A special attention will be paid to such applications as ESR of slab ingots for soknown "z-steel" manufacturing,hollow ingots and bimetal steel production.     

Inter-comparison study between human and cow teeth enamel for low dose measurement using ESR

Human and cow teeth enamel samples were separated and irradiated with γ-ray to study radiation-induced radicals as dosimetric material with electron spin resonance (ESR). The enamel spectrum is characterized by two main g-factors g|| = 1.9976 and g⊥ = 2.0019. The dosimetric signal for enamel at g = 2.0019 is ascribed to radicals. The dose response was studied in the range from 200 mGy to 2 Gy. Power dependence, energy dependence and thermal stability had been studied also to determine the optimum conditions for ESR measurements and stability of the signal at room temperature as well. Radical formation efficiency (G-value) of 0.44 ± 0.09 and 0.65 ± 0.13 was obtained for human enamel and cow enamel, respectively. The life time for human enamel and cow enamel were estimated from Arrhenius plot to be 1.1 × 10⁷ years and 7 × 10⁶ years, respectively. The activation energy for human enamel and cow enamel were also calculated from Arrhenius plot to be 1.23 eV and 1.15 eV, respectively. The dose conversion factors for enamel in water and air were calculated to be 0.901 D_water and 0.998 D_air. The combined and expanded uncertainties accompanying these measurements are ±5.79% and ±11.58%, respectively.     

Nickel versus cobalt catalysts for hydrogen production by ethanol steam reforming: Ni–Co–Zn–Al catalysts from hydrotalcite-like precursors

The urea hydrolysis method allowed to prepare well-crystallized Ni–Co–Zn–Al Layered Double Hydroxides to be used as precursors of mixed oxide catalysts for the Ethanol Steam Reforming (ESR) reaction. The calcination of the layered precursors gives rise to high surface area mixed oxides, being actually a mixture of a rock salt phase (NiO), a wurtzite phase (ZnO) and a spinel phase.     

Mechanism of vacuum-annealing defects and its effect on release behavior of hydrogen isotopes in Li2TiO3

Li₂TiO₃ is one of the most promising candidates among solid breeder materials. However, defects introduced into Li₂TiO₃ will act as the strong trapping sites for tritium. In the present study, mechanism of vacuum-annealing defects and its effect on release behavior of hydrogen isotopes in Li₂TiO₃ were investigated by means of X-ray diffraction, Raman spectroscopy, electron spin resonance and thermal desorption spectroscopy. The color of samples becomes dark blue and the defects were found to be introduced into Li₂TiO₃ when annealed in vacuum. This color change suggests the change from Ti⁴⁺ to Ti³⁺ due to decrease in oxygen content. The color recovers to white again after annealing in air. X-ray diffraction and Raman spectroscopy results indicate that there are no modifications on Li₂TiO₃ crystal phases, but on crystallinity. The main vacuum-annealing defects are E-centers and no other obvious types of defects were observed from electron spin resonance. Based on the experimental results, the production of defects by annealing in vacuum should be satisfied to the following conditions: (1) Li₂TiO₃ has been exposed in air more than 1 day; (2) Li₂TiO₃ must be annealed at the temperature higher than 300 °C; (3) Li₂TiO₃ should be annealed in vacuum lower than 10 Pa. E-centers formed under vacuum-annealing processes have considerable effects on release behavior of hydrogen isotopes investigated by thermal desorption spectroscopy and further should be considered in future fusion reactor. The present work gives some suggestions for future fusion reactors: (1) Li₂TiO₃ should be preserved in vacuum or kept from water vapor; (2) Li₂TiO₃ should be annealed at high temperature to remove the adsorbed water before loading into the facility, and must be finished within two days to avoid defects coming from reduction; (3) Li₂TiO₃ should be improved by adding more oxygen or other elements to refrain from defects introduced by reduction reaction.