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141.
Weiming Xu 《科学通报(英文版)》1997,42(4):282-282
Conclusions The results we obtained in the present investigations can be summarized as follows.
It can be concluded that the short-range chemical order plays a dominant role in this kind of magnetic order in this alloy.
Our results are favorable for the first picture given above which explains the mechanism of re-entrant spin glass behavior. 相似文献
1. | The sample is magnetically heterogeneous. Above Tc, the PM phase is dominant in the alloy. But in this temperature range, the M-Ba plot is still curved andthe external field dependence of the internal field was also observed in the in-field M?ssbauer measurements. It implies that there are magnetically coupled clusters in the sample. These clusters may behave superparamagnetically in the alloy. So they did not cause the change of the line width of the M?ssbauer spectra without external field. The magnetic moments of the clusters can be polarized by external field, which causes the curvature of M-Ba plot and the external field dependence of the internal field. |
2. | Below Tc, some PM phase persists down to 50 K at least. The clusters with very low Tc or even coupled antiferromagnetically at low temperatures are responsible for the PM phase in this temperature range. |
3. | At 50 K, the FM phase is dominant whereas some magnetic moments are coupled antiferromagnetically in the alloy. |
4. | At a freezing temperature of about 25 K, the re-entrant spin glass behavior can be observed in the alloy. |
142.
稀土磷酸盐发光材料的微波合成 总被引:5,自引:0,他引:5
稀土磷酸盐发光材料的微波合成徐文国,田一光,刘淼,刘海堂,方光华,庞文琴(吉林大学化学系,环境科学系,长春,130023)关键词微波合成,稀土磷酸盐,微晶玻璃,玻璃态,发光材料稀土磷酸盐发光材料的研究是当前材料科学的热门研究课题。它们一般通过高温固相... 相似文献
143.
Summary Methylbenzenes, pyridines and pyrazines were investigated on fused-silica and glass capillary columns coated with SE-30 and
PEG-40M/KF liquid phases, at two temperatures, 80° and 110°C. The contribution of the methylene groups to the partial molar
free sorption energy was determined for methylpyridines and pyrazines. Equations are proposed for the calculation of the retention
indices of methyl pyridines and pyrazines. These equations are based on the ortho- and α-effects of the methyl groups. The
predicted indices have been experimentally tested for six dimethyl- and trimethylpyridines, and four methylpyrazines. Good
accuracy of the calculation permits to use this method for the identification of methylpyridines and pyrazines in complex
mixtures.
Enlarged text of the paper presented at the Eighth International Symposium on Capillary Chromatography, Riva del Garda, Italy,
May 19–21, 1987. 相似文献
144.
As an alternative to acid pretreated UCON and FFAP capillaries for the analysis of wide-boiling free fatty acid mixtures, OV-1 : FFAP phase mixtures were used on high-temperature silylated inert glass capillary columns. The HETP-carrier gas velocity curves, peak asymmetry factors, coating efficiency, gas phase and stationary phase contributions to the mass transfer resistance were determined for various OV-1 : FFAP ratios. Mixed-phase capillaries showed optimum performance at a 2 : 1 OV-1 : FFAP ratio. The thermal and long-term stability of OV-1-stabilized FFAP columns surpassed those of the UCON and pure FFAP reference column used. 相似文献
145.
Different stationary phases were prepared by mixing a series of inorganic salts with dimethylsiloxane polymer (SE-30) and then tested by capillary gas chromatography. It was demonstrated that the polarity (as evaluated by measurement of Rohrschneider constants) of the mixed stationary phases, which is inferior or equal to that of a medium-polar OV-25 phases, reached even lower values than SE-30 alone. The influence of NaF, NaCl, NaBr, AgNO3, and other inorganic salts on the polarity of capillaries is reflected by a better resolution and shorter retention time of cis/trans isomers of fatty acid methyl esters (FAMES) as well as positional isomers of triglycerides. 相似文献
146.
Glass capillaries coated with Chirasil-Val, a chirally functionalised polysiloxane, are capable in principle of resolving all protein amino-acid enantiomers in a single run and within a short analysis time, thus allowing for example the quantitative amino acid determination by enantiomer labelling. The elution characteristics of the individual amino acids however are also dependent upon the chemical nature of the capillary wall surface, and a surface pretreatment is found to be necessary if all protein amino acids are to be analysed. Of the various methods of pretreatment tested, etching of borosilicate glass with gaseous HCl followed by deposition of colloidal silicic acid is considered to be the most suitable. 相似文献
147.
Structure determination of triglycerides according to their number of unsaturated fatty acids (N.U.F.A.) is more easily achieved after ozonolysis of their mixtures (fats and oils) than by capillary gas chromatographic analysis of the mixture as such. Analyses performed before and after ozonolysis of cocoa buttel, hazelnut oil, and a mixture of both fats illustrate the potential of this approach to the structure elucidation of triglycerides by chromatographic techniques. 相似文献
148.
After a brief introduction of the terms supercooling, amorphous solid state, glass transition and devitrification, the known ways of production of amorphous solid water are discussed. DSC experiments with quench cooled aqueous solutions show the phenomenon of glass transition and devitrification.This revised version was published online in November 2005 with corrections to the Cover Date. 相似文献
149.
早在六十年代,人们为了寻找较好的激光玻璃,曾对Sm~(3 )离子掺杂的玻璃中的光谱进行过研究。为了探寻新型的激光,发光玻璃,又进一步研究了Sm~(3 )在玻璃中的发光和敏化。我们以寻找一种高亮度,低成本的发光玻璃为目的,研究了基质玻璃组成,敏化离子及其浓度对Sm~(3 )发光性质的影响。 选择B_2O_3-BaO-M_mO_n(M_mO_n=Li_2O,Na_2O,K_2O,MgO,CaO,SrO)玻璃体系,所用原料的纯度皆为分析纯以上,用陶瓷坩埚在1250℃掺杂氧化钐(纯度均大于99%),玻璃的荧光谱和激发光谱,用MPF-4型荧光分光光度计测定。 相似文献
150.
We have encapsulated several hemoproteins in the sol-gel glass to catalyze the oxidation reaction of dibenzothiophene (model
for organic sulfur compounds in coal) with hydrogen peroxide. In addition to cytochrome c and myoglobin, which have previously
been encapsulated in sol-gel glasses, two other hemoproteins, horseradish peroxidase and bovine blood hemoglobin, have now
been successfully immobilized in sol-gel media with the retention of their spectroscopic properties. All four hemoproteins
studied also demonstrate similar catalytic activities toward the oxidation of dibenzothiophene as compared with the results
obtained with the proteins in solution. In the case of encapsulated cytochrome c, the more water-soluble S-oxide was obtained
with much higher selectivity over the less water-soluble sulfone (S-oxide/sulfone = 7.1) as compared to what was obtained
in the aqueous/organic medium (S-oxide/sulfone = 2.3). Because of the advantage of easy separation of the encapsulated proteins
from the liquid reaction mixture, it is clear from these studies that the immobilization of active hemoproteins in the solid
glass media could serve as more practical biocatalysts. 相似文献