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  • Author or Editor: Chin-tsai Lin x
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Abstract  

Chinese herbal medicine has recently become a hot research field internationally; an increasing number of pharmaceutical researchers and scientists have dedicated themselves to such research work. Based on papers in the American Journal of Chinese Medicine from 2002 to 2004, 60% of papers published in the journal were sponsored by different institutions in the authors’ countries. This fact indicates that researchers receive sponsorship for their work, and sponsors should pay more attention on the control of the researchers to use financial support more efficiency. This study applied Analytic Hierarchy Process, AHP to evaluating the performance of sponsored Chinese herbal medicine research, and this method can help sponsors weight evaluation elements without having to change the system of every category of research. To explain the process and application of AHP, a Taiwanese case study is presented. The analytical results presented in this study, provide a reference for institutes supporting research on Chinese Herbal Medicine.

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Summary  

Sorption of radionuclides onto surrounding rocks play an important role in retarding the migration of radionuclides from a radioactive waste repository. The sorption isotherm model is usually used to describe the sorption behaviors and assess the sorption potential of radionuclides on rock. However, most of the studies to investigate the feasibility of isotherm models for the sorption of radionuclides are based on the assumption that the sorption energy is uniform and homogeneously distributed on the sorbent surfaces. In this study, two heterogeneity-based isotherms, Langmuir-Freundlich isotherm model (LF) and generalized-Freundlich isotherm model (GF), were used for the evaluation of the sorption characteristics of cesium on the selected Taiwan tuff and basalt. The sorption experiments in this study were carried out by batch method, and the experimental data were modeled by LF and GF heterogeneity-based isotherm models. The results showed that both of the LF and GF models could fit the data more perfectly than the Langmuir model. The heterogeneity of sorption onto tuff and basalt could be well characterized by the LF and GF models by means of the calculation and plotting of the affinity spectrum. The results showed that the sorption surface of tuff is more heterogeneous and complex than that of basalts.

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Abstract  

Retardation factor (Rf) is the most frequently used indicator to describe the transport of radionuclides through geological substances. In this work, we compare the Rf values determined by four methods including direct experimental data, model fitting curve, integration technique and modeling at two relative concentration (C/C 0) 0.5 and 1.0 in a case study of Cs transport through crushed granite. A simple Q-test indicated all Rf values are valid at 96% confidence level. Meanwhile, the T-test demonstrated that the precision of Rf value is 4.21±0.39 at 90% and ±0.45 at 95% confidence level, which is about 9.3% and 10.7% of the average value of the Rf value. An uncertainty window of 10% is recommended in Rf value determination.

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Abstract  

We have examined the working diameter of capillary columns with diameter of 5, 7, 10 and 20 mm. These modified capillary columns were carefully filled with local Taiwan laterite (LTL). The porosity and density of these packed columns was 0.51±0.02 g/g and 1.27±0.05 g/cm3, respectively. The diffusion experiments were then carried out in synthetic groundwater with Cs loading of 0.1mM at room temperature. Experimental results have shown that the diffusion profiles of modified capillary columns fit Fick’s second law very well. This result revealed that the working diameter of a capillary column can be expanded to at least to 20 mm without affecting the validity of the derived diffusion coefficients. Among these columns, the ones with 5 mm diameter show the most consistent results of the derived K d, apparent and effective diffusion coefficients. Although the derived distribution and effective diffusion coefficients slightly decrease as the diameter of these columns increases due to the increase of the solid/liquid ratio. These values are still informative of the Cs diffusion in local Taiwan laterite. Moreover, our results clearly demonstrate the potential of using “modified capillary method” to study the diffusion behaviors of concerned radionuclide because columns with large diameter enable the filling with more versatile geological substances.

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Summary  

To provide comprehensive information for assessing the safety of geological disposal of radioactive waste, the additivity of sorption properties during different reaction times for various bentonite/quartz sand mixtures was investigated. Se and Cs were the nuclides of interest. Synthetic seawater (SW) was employed as the liquid phase tosimulate the possible groundwater conditions while the disposal site is an island area. Batch sorption experiments were conducted to measure the distribution ratio, R d. Regardless of whether Cs and Se were used, the additivityat the reaction time of 7 and 14 days was better than that of 28 and 56 days.Interactions between bentonite and quartz sand might occur in synthesized seawater in reactions beyond 14 days. Under the experimental conditions,the additivity equation could be corrected by the composition ratio and reaction time. Long-term prediction of the R dby short term batch sorption experiments would be helpful while assessing buffer materials mixed by bentonite and quartz sand.

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Abstract  

In this study, batch and through-diffusion experiments have been performed in order to determine the distribution coefficients (K d), apparent diffusion coefficients (D a) and retardation factor (Rf), respectively. Both apparent and effective diffusion coefficient (D a and D e) of Cs were obtained by accumulative concentration method developed by Crank (1975). In addition, a non-reactive radionuclide, HTO, was initially conducted in through-diffusion experiment for assessing the ability of radionuclide retardation. The distribution coefficients (K d) obtained by batch tests in 14 days under aerobic and anaerobic systems were 2.06 and 3.52 ml/g. Moreover, it is found in through-diffusion test that Rf = 4.12 and 4.40 and K d = 0.97 and 1.06 of Cs did not have an obvious discrepancy in a length/diameter/ (L/D) ratio of 0.44 and 1.78. However, Rf and K d revealed a larger difference in an L/D ratio closing to 1 due to the geometric change of one-dimension diffusive hypothesis. Therefore, it demonstrates that Rf and K d obtained by through-diffusion experiments only could be achieved at a lower or larger L/D ratio and would be reliable for long-term performance assessment.

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Abstract  

In this present work, the kinetic reaction constants including the forward (kf, Cs adsorption onto granite) and backward (kb, Cs desorption from granite) rate constants of Cs on granite were determined by fitting the experimental data from both adsorption and desorption experiments with a pseudo first-order reaction model. In the case of Cs adsorption, both forward and backward rate constants are consistent with one another as Cs loading less than 0.1 mM. In contrast, both forward and backward reaction constants from desorption experiment dramatically increase as the Cs loading increases. Rearrangement of these desorption data by linearization technique, a notable instantaneous desorption process appears, which profoundly influences the determination of the rate constants. Based on our fitting results, the rate constants including both forward and backward reactions determined from Cs adsorption onto granite are much suitable to represent the adsorption behavior, in which the recommended values are of 0.42 and 0.03 h−1, respectively.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Yi-Lin Jan, Tsing-Hai Wang, Ming-Hsu Li, Shih-Chin Tsai, Yuan-Yaw Wei, Chun-Nan Hsu, and Shi-Ping Teng

Abstract  

A good understanding of the migration of selenite, Se(IV), through deep granitic layers depends on a good understanding of the geochemistry of these layers. Chemical sequential extraction is applied herein to evaluate the ability of granite to adsorb Se(IV) in DW, GW and SW systems. The experimental results indicate that the removal of crystalline Fe oxides reduces the adsorption of Se(IV), suggesting its importance in granite. The normalized concentrations of Se(IV) adsorbed onto crystalline Fe oxides is approximately 0.0301, 0.0330 and 0.0335 mole Se(IV) adsorbed/mole of Fe in DW, GW and SW systems. Kinetic adsorption experiments are conducted to elucidate the results of the chemical sequential extraction. Both the treated and the untreated granite take the same time to reach their equilibrium, suggesting that crystalline Fe oxides dominate the adsorption of Se(IV). Meanwhile, the one-site model suffices to simulate the kinetics of adsorption.

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