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Study of the immobilization of226Ra
I. Cement solidification of226Ra waste
Abstract
A study of the immobilization for226Ra waste has been carried out. Cement-based concrete was used as a matrix for the solidification of radium waste. The experimental results show that the cement mixture with water/cement between 0.46–0.54 has higher strengh (above 20 MPa), and the compressive strength was not reduced by addition of 1% barite or the radium waste (RaSO4) into the concrete solid.
Study of the immobilization of226Ra
II. Predictive model of radionuclide leaching behavior in a cement-based solid
Abstract
A three-dimensional leaching model was developed to describe the leaching of radionuclide from a cement-based concrete solid. The film mass transfer and interparticle diffusion were considered simultaneously. On the basis of the derived model the long-term behavior of radium-226 leaching from the waste solid has been quantitatively investigated.
Abstract
We have developed a thermogravimetric system (TG system) for condensable gas adsorption by modifying a standard thermogravimetric analyzer Cahn TG 2121 and performed isotherm measurements of water vapor adsorption on Fuji Davison type RD silica gel and ethanol vapor adsorption on Maxsorp II activated carbon. For the water vapor-silica gel data, our results compare favorably with the data reported by the manufacturer and those obtained from a volumetric method. This confirms the reliability of our TG system for adsorbents which do not swell significantly. In addition, our isotherm data also provide useful design information for the development of adsorption chillers.
Abstract
A radioactive multitracer solution obtained from the nuclear reaction of selenium with 25 MeV/nucleon40Ar ions was applied to the investigation of the trace elements behavior in feces and urine of mouse. The excretion rates of 23 elements, Na, K, Rb, Mg, Ca, Sr, Ga, As, Sc, V, Cr, Mn, Co, Fe, Zn, Y, Zr, Mo, Nb, Tc, Ru, Ag and In were simultaneously detected under strictly identical experimental conditions, in order to clarify the excretion behavior of the elements in mice. Fecal and urinary excretion rates of the elements in mice reached the highest value separately at 48 and 24 hours. The total excretion of Mo, Tc and Co within 96 hours were all larger, more than 60%. Accumulative excretion rates of Ca, Nb, Mg, Sr, V, Sc, Na, Cr, Fe, Ag, Mn and Zr were 60-30%. The total rates of Ru, K, As, Zn, Rb, Y, Ga and In were less than 30%, and low excretion. The main excretion pathway of Mo, Co, Mg, Fe and Ag was through urine, and Na, K, As and Rb were eliminated from the body also in urine. But fecal excretion of Tc, Nb, Sr, Y, Ru, and In were larger than urinary excretion, and Ca, Sc, Mn, Zr, Zn were eliminated from the body in feces.
Abstract
A novel thermokinetic research method for determination of the rate constant of a reaction taking place in a batch conduction calorimeter under isothermal conditions is proposed: the double-thermoanalytical curve method. The method needs only the characteristic time parameter t m, the peak height Δm at time t m and the peak area a*m after time t m for two thermoanalytical curves measured with different initial concentrations of the reactants: it conveniently calculates the rate constants. The thermokinetics of four reaction systems were studied with this method, and its validity was verified by the experimental results.
Abstract
A novel method for the determination of rate constants of reactions, the time-variable method, is proposed in this paper. The method needs only three time points (t), peak heights (
) and pre-peak areas (
), obtained from the measured thermoanalytical curve. It does not require the thermokinetic reaction to be completed. It utilizes data-processing on a computer to give the rate constants. Four reaction systems, including a first-order reaction, second-order reactions (with equal concentrations and with unequal concentrations) and a third-order reaction, were studied with this method. The method was validated and its theoretical basis was verified by the experimental results.
Abstract
Both calorimetric determination of displacement adsorption enthalpies ΔH and measurement of adsorbed amounts of lysozyme (Lyz) denatured by 1.8 mol L−1 guanidine hydrochloride (GuHCl) on a moderately hydrophobic packings at 298 K, pH 7.0 and various salt concentrations were carried out. Based on the thermodynamics of stoichiometric displacement theory (SDT) the fractions of thermodynamic functions, which related to four subprocesses of denatured protein refolding on the surface, were calculated and thermodynamic analysis that which one of the subprocesses plays major role for contribution to the thermodynamic fractions was made in detail. The moderately hydrophobic surface can provide denatured Lyz energy and make it gain more conformation with surface coverage or salt concentration increment. The displacement adsorptions of denatured Lyz onto PEG-600 surface are exothermic, more structure-ordered and enthalpy driven processes.
The effect of glucose on bovine serum albumin denatured aggregation kinetics at high concentration
The master plots method study by DSC
Abstract
The effect of glucose (0–15 mass%) on the kinetics of bovine serum albumin (BSA) denatured aggregation at high concentration in aqueous solution has been studied by differential scanning calorimetry. The observed denatured aggregation process was irreversible and could be characterized by a denaturation temperature (T m), apparent activation energy (E a), the approximate order of reaction, and pre-exponential factor (A). As the glucose concentration increased from 0 to 15 mass%, T m increased, E a also increased from 514.59409±6.61489 to 548.48611±7.81302 kJ mol−1, and A/s−1 increased from 1.24239E79 to 5.59975E83. The stabilization increased with an increasing concentration of glucose, which was attributed to its ability to alter protein denatured aggregation kinetics. The kinetic analysis was carried out using a composite procedure involving the iso-conversional method and the master plots method. The iso-conversional method indicated that denatured aggregation of BSA in the presence and absence of glucose should conform to single reaction model. The master plots method suggested that the simple order reaction model best describe the process. This study shows the combination of iso-conversional method and the master plots method can be used to quantitatively model the denatured aggregation mechanism of the BSA in the presence and absence of glucose.
Abstract
Calorimetric measurement of adsorption enthalpies of native lysozyme(Lyz) on a moderately hydrophobic surface at 25°C, pH 7.0 and various salt concentrations was performed. Based on the thermodynamics of stoichiometric displacement theory (SDT), we calculated the fractions of thermodynamic functions involving four subprocesses during a displacement adsorption process from the directly determined enthalpies in combination with adsorption isotherm measurements. The thermodynamic fractions reveal the relative degree of the four subprocesses for contributions to enthalpy, entropy and free energy. The results show that native Lyz adsorption on a moderately hydrophobic surface is an entropy driven process contributed mainly by conformational loss of adsorbed Lyz.
Different components of biodiversity may vary differently since species diversity was considered to be determined by resource availability but functional diversity was related to partitioning of niche space. Moreover, the harsh or benign conditions may result in different niche space partitioning by the coexisting species. For example, in harsh environments niche differentiation may be stronger resulting in higher functional diversity. In this study, we investigate species diversity and functional diversity along a south-to north-facing slope gradient with different resource availability in a sub-alpine meadow. Our results indicate that the patterns of species diversity and functional diversity are not consistent along this gradient. Both species richness and Shannon index of diversity increased, but functional diversity slightly decreased or changed a little from south-to north-facing slope. Moreover, these two components formed a quadratic relationship. Soil water content (SWC) was the limiting resource along this gradient. On one hand, it determined the species diversity; on the other hand, it also influenced functional diversity via affecting niche differentiation and species trait pool. In conclusion, functional diversity was determined by both species richness and niche differentiation with the influence of soil water content.
