Sensitive Determination of Carbohydrates by Fluorimetric Method with Ce(IV) and Sodium Triphosphate

A new simple and sensitive fluorimetric method for the determination of carbohydrates is described. The method is based on the reaction between carbohydrates and Ce(IV) in the presence of sulfuric acid. All the reductive carbohydrates can be detected indirectly by the fluorescence of Ce(III) produced. The addition of sodium triphate enhances the sensitivity of the method by more than 10-folds. Under optimum conditions, an excellent linear relationship was obtained between the fluorescence intensity and the concentration of carbohydrates. The limits of detection lie in the range of 9.3 x 10(-10) - 1.3 x 10(-9) mol/L. As compared to the normal fluorimetric method, the proposed method is faster and more sensitive.     

EXAFS研究Ni-B和Ni-Ce-B超细非晶态合金的退火晶化

采用同步辐射EXAFS技术定量地研究化学还原法制备的Ni-B和Ni-Ce-B超细非晶态合金中Ni原子的局域环境结构随退火温度升高而产生的变化,结果表明,对于Ni-B和Ni-Ce-B超细非晶态合金初始样品：Ni-Ni最邻近配位壳层的平均键长RNi-Ni、配位数N、热无序σT、结构无序σs分别为0．275nm,11.9.0.0069nm,0.034nm;0.276nm,12.4,0.0067nm,0.035nm,Ni-B最邻近配位壳层的RNi-B,N, σT,σs分别为0．215nm,2.7,0.0055nm,0.0048nm;0.214nm,2.0,0.0058nm,0.0042nm,Ni-Ni配位的σs很大,是其σT的4－5倍,比Ni－B配位的σs大近一个数量级,在300℃退火后,Ni－B样品开始发生晶化生成晶态Ni3B,其RNi-Ni和σs分别为0．254nm和0．011nm,σs降低近2倍;而．3％原子比的Ce掺入后使Ni-Ce-B超细非晶态合金的晶化温度升高100℃左右。在500℃退火后,Ni－B样品的结构参数与Ni箔的相近,但Ni-Ce-B样品中的Ni-Ni配位的σs仍为0．0073nm,Ni-B配位的N为1．2,表明稀土元素Ce（以CeO2)显著增强了Ni与B的相互作用,且同时使退火晶化成的Ni晶结构产生畸变。     

CexTi1-xO2复合氧化物的结构及负载CuO对NO还原性能研究

采用共沉淀法制备了不同摩尔比(x=0,0.1,0.2～0.9,1.0)的CexTi1-xO2复合氧化物,考察了CuO/CexTi1-xO2对NO+CO反应的活性,并用BET,TPR和XRD等技术对各试样进行了表征。结果表明,试样的结构和还原特性随焙烧温度变化而变化。XRD检测表明,x值从0.1增加到0.5时,650℃焙烧的试样已形成了CeTi2O6物相,且主要以无定形状态存在;试样经800℃焙烧后晶化完全;x>0.6时,一些TiO2已经进入了CeO2晶格,形成了Ce Ti固溶体。催化剂活性评价表明CuO/CexTi1-xO2(650℃)对NO+CO反应具有较好的活性,其活性随x值变化而变化。TPR及XRD结果表明CuO与CeTi2O6之间存在很强的相互作用,CeTi2O6物相的形成使CuO的还原峰温由380℃提前到200℃,而CuO的存在又促进CeTi2O6的还原峰温从600℃提前至200～300℃。     

Ce∶LuAG闪烁晶体的生长研究

Ce∶LuAG晶体是一种性能优良的闪烁材料,但采用提拉法生长Ce∶LuAG时,经常出现开裂和包裹物缺陷。本文通过理论与实践相结合的方式分析了温度梯度、提拉速度、晶体旋转速度和热应变等因素对晶体产生缺陷的影响,并提出了解决办法,给出了适合生长优质Ce∶LuAG晶体的工艺参数:熔体上方温度梯度在5 ℃/mm左右,放肩角度在30°~60°,提拉速度1.0~1.5 mm/h,晶体旋转速度15~25 r/min。最后成功生长出直径30 mm、等径长50 mm质量较为完好的Ce∶LuAG单晶,晶体内核心面积小。     

ChemInform Abstract: Intermetallic Compounds Ce4Ru3Ga3 and La3Ru2Ga2 with Crystal Structures of New Types.

Ce₄Ru₃Ga₃ (I) and La₃Ru₂Ga₂ (II) are synthesized by arc melting of the elements under Ar followed by annealing (873 K, 30 d).     

Ion beam mixing induced by electronic energy deposition in Fe-Si multilayers

Abstract

Spectroscopic properties of Ce³⁺ ions in GdAlO₃ crystal are presented. At least three Ce³⁺ nonequivalent centres (multisites) are present in this crystal. Energy transfer from the Ce³⁺ main in the UV emitting centres to the Ce³⁺ green emitting centres is observed. Ce³⁺ fluorescence decays are either fast (1.5–20 ns) or slower due to complicated processes of energy transfer and migration (Ce³⁺)_i → (Gd³⁺)_n-steps → (Ce³⁺)_j (energy transfer through Gd³⁺ sublattice).     

The chemical potential for the inhomogeneous electron liquid in terms of its kinetic and potential parts with special consideration of the surface potential step and BCS-BEC crossover

The chemical potential μ of a many-body system is valuable since it carries fingerprints of phase changes. Here, we summarize results for μ for a three-dimensional electron liquid in terms of average kinetic and potential energies per particle. The difference between μ and the energy per particle is found to be exactly the electrostatic potential step at the surface. We also present calculations for an integrable one-dimensional many-body system with delta function interactions, exhibiting a BCS-BEC crossover. It is shown that in the BCS regime the chemical potential can be expressed solely in terms of the ground-state energy per particle. A brief discussion is also included of the strong coupling BEC limit.