Relationship Between Structure and Coordination Strength of N and N,O-Hybrid Donor Ligands with Trivalent Lanthanides

ABSTRACT

To effectively separate lanthanides (Ln(III)) from actinides (An(III)), symmetrical 2,2′-bipyridyl (Bpy), 1,10-phenanthroline (Phen), and unsymmetrical N-methyl-N-tolyl-1,10-phenanthroline-2-carboxamide (MeTol-PTA) were investigated. According to the crystal structures and EXAFS experiments, the decreasing ionic radius from light to heavy Ln led to decreases in the Ln–N (Bpy) and Ln–N (Phen) distances, while log β simply increased due to the electrostatic interaction and the order of Ln–O (MeTol-PTA) < Ln–N (Bpy, Phen) < Ln–N (MeTol-PTA) was obtained. This indicated that the bulky phenanthroline moiety of MeTol-PTA may not allow N (MeTol-PTA) to come close to Ln. Consequently, the log β of MeTol-PTA exhibited a local maximum (around Nd).     

Determination of Precise Unit-Cell Parameters of the α-Tricalcium Phosphate Ca3(PO4)2 Through High-Resolution Synchrotron Powder Diffraction

Unit-cell parameters of the α-tricalcium phosphate [TCP; Ca₃(PO₄)₂] were investigated using high-resolution synchrotron powder diffraction and the Rietveld method. The diffraction experiment was conducted at 29°C at the BL-15XU experimental station of SPring-8, Japan. Precise unit-cell parameters of the α-TCP were obtained; a =12.87271 (9), b =27.28034(8), c =15.21275(12) Å, α=γ=90°, and β=126.2078(4)°. The calculated density of α-TCP (2.8677 g/cm³) is smaller than that of β-TCP, indicating the "looser" structure of α-TCP.     

Effect of oxygen potential on the sintering behavior of MgO-based heterogeneous fuels containing (Pu, Am)O2−x

The effect of oxygen potential on the sintering behavior of MgO-based heterogeneous fuels containing (Pu, Am)O_2−x was experimentally investigated. Sintering tests in various atmospheres, i.e. air, moisturized 4%H₂-Ar, and 4%H₂-Ar atmosphere, were carried out. The sintering behavior was found to be significantly affected by the oxygen potential in the sintering atmosphere. The sintered density decreased with decreasing oxygen potential. The (Pu, Am)O_2−x phase sintered in a reductive atmosphere had hypostoichiometry. The aggregates of the (Pu, Am)O_2−x phase sintered in the reductive atmosphere grew, in comparison with those in the oxidizing one. The sintering mechanism was discussed in terms of the difference in sintering behavior of (Pu, Am)O_2−x and MgO.     

Chemical reaction kinetics dataset of Cs-I-B-Mo-O-H system for evaluation of fission product chemistry under LWR severe accident conditions

In order to improve LWR source term under severe accident conditions, the first version of a fission product chemistry database named ‘ECUME’ was developed. The ECUME is intended to include several datasets of major chemical reactions and their effective kinetic constants for representative severe accident sequences. It is expected that the ECUME can serve as a fundamental basis from which fission product chemical models can be elaborated for use in the severe accident analysis codes. The implemented chemical reactions in the first version were those for representative gas species in Cs-I-B-Mo-O-H system from 300 to 3000 K. The chemical reaction kinetic constants were evaluated from either literature data or calculated values using ab-initio calculations. The sample chemical reaction calculation using the presently constructed dataset showed meaningful kinetics effects at 1000 K. Comparison of the chemical equilibrium compositions by using the dataset with those by chemical equilibrium calculations has shown rather good consistency for the representative Cs-I-B-Mo-O-H species. From these results, it was concluded that the present dataset should be useful to evaluate fission product chemistry in Cs-I-B-Mo-O-H system under LWR severe accident conditions, where kinetics effects should be considered.     

Detection and Quantitation of Left-to-Right Shunts from Radionuclide Angiocardiography Using the Homomorphic Deconvolution Technique

The homomorphic filtering method is described for the detection and quantitation of left-to-right shunts from radionuclide angiocardiography. First, the method is investigated theoreticatly and numerically using a realistic model with systemic recirculation. It is demonstrated that even in a noisy situation the shunt flow fraction can be relatively well estimated, if only the characteristics of the fiters used are suitable. Second, the method is applied to real data, i.e., the pulmonary time-activity curves from radionucUde anglocardiography. The presence or absence of a left-to-right shunt is determined using the ratio AT/MTT. The pulmonary-to-systemic flow ratios calculated from the areas of the two decomposed curves are compared with those from oximetry at cardiac catheterization. Good agreement between the Qp/Qs ratios calculated by oximetry and radionucUide angiocardiography is obtained.     

Micro machining for control of wettability with surface topography

A micro fabrication is presented to manufacture hydrophobic surfaces with micro-scale structures. Hydrophobicity is controlled with the shape and the alignment of micro pillars in the structure. The structures are manufactured in large areas at high production rates in the following processes: (1) the structure is fabricated on a tool by focused ion beam sputtering; (2) the reverse structure is formed on a metal plate by incremental stamping using the structured tool; and (3) the structure is transferred onto plastic plates by molding. A consecutive stamping is also proposed to fabricate several structures on a surface accurately with a structured tool, in which the moving pitch of the structured tool is numerically controlled. The effect of the surface topography on hydrophobicity is discussed with measuring contact angles on the structured surfaces in the water droplet tests. Hydrophobicity on the plastic plate is associated with the solid fraction on the structured surface based on the Cassie–Baxter model. A larger contact angle is observed for a smaller solid fraction of the surface.     

Power characteristics of unsteadily forward–reverse rotating impellers in an unbaffled aerated agitated vessel

Power characteristics of an unbaffled aerated agitated vessel with unsteadily forward‐reverse rotating impellers, ie a new type of gas–liquid agitator named ‘AJITER’, treating viscous Newtonian liquids were studied experimentally. Measurements were first made on the agitation torque, ie the torque on the drive shaft on which forward–reverse rotating impellers with four delta‐type blades were attached, and the data obtained were analyzed by fitting them to an equation consisting of two terms with respect to the resistance of the fluid, one due to viscous drag and the other due to added moment of inertia. The effects of operating conditions and physical properties of liquids on the drag and added moment of inertia coefficients were then evaluated, and empirical relationships which estimate values of these coefficients, useful to predict the unsteady behavior and magnitude of agitation torque, were presented. Furthermore, equations were developed for estimating the average and maximum power consumptions as a function of the drag and added moment of inertia coefficients. Prediction of respective power levels in AJITER by these equations was also discussed. © 2001 Society of Chemical Industry     

Synergistic effect of Pt or Pd and perovskite oxide for water gas shift reaction

The water gas shift (WGS) reaction over Pt and Pd catalysts supported on various perovskite oxides has been investigated at 573 K without catalyst pretreatment. The Pt and Pd catalysts on LaCoO₃ support showed high catalytic activity. Interaction between Pt or Pd and the support is considered to promote the WGS reaction: Pt/LaCoO₃ had high initial activity but deactivated immediately; Pd/LaCoO₃ was less active than Pt/LaCoO₃, but had superior stability. Catalysts were characterized using XRD, STEM, XPS, and H₂-temperature programmed reduction (TPR). Results of this study showed that reduction of the support decreased the CO conversion on Pt/LaCoO₃. On the other hand, Pd/LaCoO₃ showed stable activity for the WGS reaction. Therefore, Pd was added to Pt/LaCoO₃ for stabilizing the catalyst activity, and 0.5 wt.% Pd/1 wt.% Pt/LaCoO₃ catalyst showed higher activity and stability.