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991.
A study on the relationship between iridium concentration in hen eggshell and iridium-enriched feed by NAA 总被引:1,自引:0,他引:1
Gaochuang Yang Xueying Mao Jinchun Wang Yali Lu Hong Ouyang Zhaohui Zhang Zhifang Chai 《Journal of Radioanalytical and Nuclear Chemistry》2001,247(3):567-570
Four hens were fed by adding ammonium hexachloroiridate into their forage. After two weeks, we measured the Ir concentration in three fractions (eggshell, albumen, egg yolk) of their eggs by instrumental neutron activation analysis (INAA). Ir was present in all the three parts of the eggs. Further, the highest concentration of Ir was found in the egg yolk fraction, about 10 times higher than that in the eggshell and albumen. Moreover, the longer the Ir-containing feed was used, the higher the Ir concentration in the egg fractions was. After 4-6 day feeding, the Ir concentration became stable. The experimental results indicated that the Ir concentration was about 2-7·10-10 g/g in the eggshell fraction compared to 5.6·10-7 g/g in feed. Therefore, we can estimate the ratio from the feed over the eggshell via gastrointestinal pathway to be about 0.08%. The new result is useful to evaluate the iridium-enriched eggshell fossils of dinosauria and to interpret the origin of the mass extinction of dinosauria at the end of Cretaceous. 相似文献
992.
固载蛋白A交联聚甲基丙烯酸缩水甘油酯连续床亲合色谱柱的制备及性能考察 总被引:5,自引:0,他引:5
采用沉淀聚法“原位”(in-situ)聚合合成了交联聚甲基丙烯酸缩水甘油酯连续床色谱柱,对其进行化学改性后,分别得到含有11个碳原子间隔臂以及不含间隔臂键合了蛋白A的高效亲合色谱柱。考察了这两种色谱介质的性能,结果表明含有间隔臂的介质有一定的疏水性;对传统制备蛋白配基的亲合色谱介质的合成路线进行了改进;采用不含间隔臂的亲合柱测定了人血浆中人免疫球蛋白G(HIgG)的含量,所测得的定量标准曲线线性相关系数达到0.999;考察了流速对合成的连续床色谱柱柱压的影响,当流速高达9.0mL/min时,柱压也仅为6.5MPa;采用pH梯度对HIgG的不同亚基进行了分离。 相似文献
993.
改性钛锆复合氧化物催化环己酮肟气相Beckmann重 排反应 总被引:6,自引:0,他引:6
制备了经SO4^2-,PO4^3-,MoO3,WO3和B2O3改性的钛锆复合氧化物(TiO2-ZrO2)催化剂,并用常压连续流动固定床微型反应器考察了它们对环己酮肟气相Beckmann重排反应制己内酰胺的催化性能。结果表明,在反应温度300℃时,B2O3/TiO2-ZrO2具有较高的己内酰胺选择性(97.0%)和收率(96.7%),且明显高于B2O3/TiO2和B2O3/ZrO2催化剂,用N2吸附和NH3-TPD,CO2-TPD等方法对催化剂的经表面积、孔容、孔分布和表面酸、碱性分别进行了测定,讨论了这些物化性能对催化剂活性、选择性和稳定性的影响。 相似文献
994.
995.
The cohesive interaction among polymer chains in a polyacrylamide (PAAm)–D2O solution has been studied by NMR relaxation. The NMR relaxation times of PAAm in the good solvent D2O were measured at different temperatures. The results show that the solution system has a high local viscosity and that its
relaxation characteristic is soft-solid-like. The temperature dependence of the relaxation behavior of the solution is obviously
different from that of ordinary polymer solutions. The difference lies in the relaxation behavior of the methylene protons
in the main chain of PAAm, as shown by analyzing the relaxation process with single exponential and biexponential decays.
As the temperature increases, the solvation is weakened, leading polymer chains to form curling coils, thus hindering the
movement of the methylene protons among the main chains. It can be expected from the existence of 80% fast-relaxing protons
that there are a zhigh number of entanglements among the polymer chains in PAAm solution. The information about entanglements
among the polymer chains can be deduced from the biexponential dependence of the spin–spin relaxation on the concentration
of the polymer solutions.
Received: 14 April 1999/Accepted in revised form: 12 October 1999 相似文献
996.
双金属氰化物配合物(DMC)催化剂的制备及表征 总被引:4,自引:0,他引:4
分别以乙二醇二甲醚,二乙二醇二乙和1,4-二氧六环为有机配体,制备了一系列双钓饵鹅的催化剂;用X射线衍射(XRD)和X射线光电子能谱(XPS)技术,研究了催化剂的晶相结构和表面状态。结果表明,钻以原料Zn3〖Co(CN6)【2.xh2O中的物种形式存在,在催化剂的制备过程中没有氧化还原反应发生,有机 本只与锌离子配位,这 与位作用破坏了Zn(2〗Co(CN)6〖2.12H2的晶体结构,催化剂的表面 相似文献
997.
2,7‐Diazapyrene is synthesized in three high‐yield steps from commercially available 1,4,5,8‐naphthalene tetracarboxylic dianhydride, which first reacts with concentrated ammonium hydroxide solution at room temperature to give 1,4,5,8‐naphthalenetetracarboxylic diimide (96%). The latter compound is subsequently reduced with borane in refluxing tetrahydrofuran to give 1,2,3,6,7,8‐hexahydro‐2,7‐diazapyrene (77%), which in turn is oxidized with manganese dioxide in refluxing benzene giving 2,7‐diazapyrene (71%). 相似文献
998.
This paper investigates the intensity tuning characteristics of a double
longitudinal modes He--Ne laser subjected to optical feedback. The intensity
undulations of the total light and the two modes are observed for different external
cavity length. Two modulations of the internal cavity length are performed. One is
only for the internal cavity length being modulated and the other is for both the
internal and the external cavity length being modulated. The undulation frequency of
the total light is found to be determined by the ratio of external cavity length to
internal cavity length in both modulations. When the external cavity length is
integral times of the internal cavity length, the fringe frequency of the total
light could be seven or even more times of that in conventional optical feedback. A
simple theoretical analysis is presented, which is in good agreement with the
experimental results. The potential use of the experimental results is also
discussed. 相似文献
999.
Based on the state equation of an ideal quantum gas, the regenerative loss of a
Stirling engine cycle working with an ideal quantum gas is calculated. Thermal
efficiency of the cycle is derived. Furthermore, under the condition of quantum
degeneracy, several special thermal efficiencies are discussed. Ratios of thermal
efficiencies versus the temperature ratio and volume ratio of the cycle are made. It
is found that the thermal efficiency of the cycle not only depends on high and low
temperatures but also on maximum and minimum volumes. In a classical gas state
the thermal efficiency of the cycle is equal to that of the Carnot cycle. In an ideal
quantum gas state the thermal efficiency of the cycle is smaller than that of the
Carnot cycle. This will be significant for deeper understanding of the gas Stirling
engine cycle. 相似文献
1000.
Summary: A facile and organic‐solvent‐free method for preparing thermoprocessable multiwalled carbon nanotube (MWCNT)‐filled thermoplastics is presented. MWCNTs are oxidized, neutralized, and then assembled with cationic soap‐free poly(methyl methacrylate) (PMMA) particles directly in water. The spontaneous electrostatic coupling between the negatively charged MWCNTs and positively charged PMMA particles, and the viscoelastic and thermomechanical behavior of the nanocomposites, are investigated. The electrostatic coupling interactions improve the dispersion of nanotubes and facilitate the formation of filler networks in the polymer matrix.