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Abstract  

A simple operation mode to determine the apparent activation energy E a is introduced. E a can be determined with a double-curve method by using a constant reaction rate (CRR) approach of Hi-Res TG. The most appropriate mechanism function f(α) and frequency factor A are determined by a single-curve method when the activation energies provided by the two methods are in good agreement with each other. The deacetylation of EVA copolymer has been used for illustration. Advantages of the CRR are discussed.

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Abstract  

A total reflection X-ray fluorescence (TXRF) analyzer with a special structure is described. Its short X-ray path (about 15 cm) resulted in a high sensitivity, low power consumption and small volume. The structure with double total reflection path is suitable for easy change of exciting source to cover a large element range. The minimum detection limit (MDL) of 6 pg for Co under Cu exciting source and 22 pg for Sr under Mo tube. Some significant works were done, such as the detemination of sulfur content in fuel oils, the non-destructive analysis of an ancient bronze utensil and the regular analysis of tap water.

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The thermal stability of lithium-ion battery cathode could substantially affect the safety of lithium-ion battery. In order to disclose the decomposition kinetics of charged LiCoO2 used in lithium ion batteries, thermogravimetric analyzer (TG) and C80 microcalorimeter were employed in this study. Four stages of mass losses were detected by TG and one main exothermic process was detected by C80 microcalorimeter for the charged LiCoO2. The chemical reaction kinetics is supposed to fit by an Arrhenius law, and then the activation energy is calculated as E a=148.87 and 88.87 kJ mol−1 based on TG and C80 data, respectively.

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Abstract  

In this paper studies on the oscillation regularity of the classical B–Z reaction system, and the calorimetric curves of the reaction system measured at three temperatures, 25, 27 and 29°C are described. A new way is presented for studying the regularity properties of chemical oscillation phenomena from the viewpoint of reaction heat effects.

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Abstract  

It is proposed to use 14 MeV neutrons tagged by the associated particle neutron time-of-flight technique (APnTOF) to identify the fillers of unexploded ordnances (UXO) by characterizing their carbon, nitrogen and oxygen contents. To facilitate the design and construction of a prototype system, a preliminary simulation model was developed, using the Geant4 toolkit. This work established the toolkit environment for (a) generating tagged neutrons, (b) their transport and interactions within a sample to induce emission and detection of characteristic gamma-rays, and (c) 2D and 3D-image reconstruction of the interrogated object using the neutron and gamma-ray time-of-flight information. Using the modeling, this article demonstrates the novelty of the tagged-neutron approach for extracting useful signals with high signal-to-background discrimination of an object-of-interest from that of its environment. Simulations indicated that an UXO filled with the RDX explosive, hexogen (C3H6O6N6), can be identified to a depth of 20 cm when buried in soil.

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Summary  

Cyanocobalamin (CNCbl), a kind of vitamin B12 (cobalamin, Cbl), which has a special binding capability to rapid dividing cells and proliferating tissue, especially tumors, has been modified and labeled by 99mTc. The optimal labeling condition was determined, and the biodistribution of 99mTc-DTPA-b-CNCbl both in normal mice and TA2 mice bearing MA891 mammary tumors were studied. 99mTc-DTPA-b-CNCbl showed low uptake and rapid clearance in nontarget tissues, and renal excretion. About 40% of uptake at 1 hour remained in the tumor at 12 hours p.i. The satisfying ratio of T/NT was acquired at 6 hours p.i.

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Abstract  

The migration of 237Np in an undisturbed Chinese loess column was investigated by direct γ-ray method. The column was taken from a field test site and installed in a laboratory simulation hall. Radionuclide 237Np in the form of neptunium nitrate, mixed with quartz, was introduced into the column and covered with loess. Artificial rainfall was applied to the column for about 3 years and, the counting rates of 237Np in the column from 56 to 616 days at different vertical positions were detected with a γ-ray detection system. Based on the counting rates of 237Np in the simulation column at different vertical positions and the distance from the source layer, the relationship of the mass center of 237Np in the column at different experimental periods to the experimental time was established, C m = 0.36 log(t)-2.75. Here C m is the mass center of 237Np in the column, cm, and t is the experimental time in days. Based on this relationship, the mass center of 237Np for the 1,073-day experiment was predicted and compared to that obtained with the final destructive method. The good agreement between the prediction and the experimental values indicates that the direct γ-ray method could be used to predict the migration of strongly adsorbed radionuclides such as 237Np in environmental media with the help of laboratory simulation columns.

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Abstract  

TA/MS (thermal analysis coupled with mass spectrometry) was applied to the pyrolysis of Chinese coals with different ranks. A total of 13 Chinese coals were investigated. The samples were deliberately chosen to represent the 13 types of Chinese coals according to the Chinese coal classification system. The experiments were carried out in an argon atmosphere with a flow rate of 150 ml min-1. The samples were heated from 40 up to 1200C with a constant heating rate of 10 k min-1. The main evolved pyrolysis products were identified through the on-line recorded mass spectra. The thermal and evolution behavior was compared between the coals. The results showed a strong thermal and evaluation behavior dependence on the coal rank. Different aliphatic fragments and also some aromatic substances, which are of environmental concern (BTX, PAHs), were found to be released depending on the different types of coal.

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Abstract  

Heat capacities of both the ingot-like and melt-spun Al-Sr alloys have been measured through the temperature range 373 to 1060 K using differential scanning calorimetry. The experimental results show that rapid solidification has a slight effect on the temperature dependence of the heat capacities of the Al-Sr alloys. The heat capacities of the melt-spun Al-Sr alloys increase more slowly than those of the ingot-like alloys with increasing temperature from 373 to 900 K. Furthermore, the effect of rapid solidification on the heat capacities becomes more obvious with increasing Sr concentration in the Al-Sr alloys. The data of the heat capacities between 373 and 900 K have been fitted with the least square method and a linear dependence on temperature was assumed for that temperature range.

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Abstract  

The thermal dehydration of La[Co(CN)6]⋅5H2O proceeded through at least three stages from the temperature range of30~230C, and an abrupt mass loss occurred around 350C and the perovskite type oxide,LaCoO3 was obtained at 1000C. After dehydration, the color of the anhydride changed from white to pale blue around 230C and furthermore, the color changed to blue around 290C. These color changes were discussed on the basis of the changes of coordination structures around Co ions. In La[Co(CN)6]⋅5H2O, Co3+ ions lie at the center of the Oh crystal field consisted of six CN ions. However, in the pale blue specimen, Co3+ ions were situated in the center of D4h crystal field which was distorted the Oh one by lengthening of the trans CN ions along z-axis. In the blue specimen, Co3+ ions were reduced to Co2+ ions which were situated in the Td crystal field formed by four CNions as [Co(CN)4]2–.

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