Partition coefficient of Ra in gypsum

A partition coefficient (λ) for Ra in gypsum was determined from coprecipitation experiment using oversaturation method. The λ-value derived for Ra was: λ _Ra = 0.32±0.15. Saturation state was estimated with the initial concentration of Ca and SO₄²⁻ in an experiment of the present study. Saturation index was calculated to be (0.49±0.02). This value was similar to those corresponds to analogous case where slow precipitation rate was kept in coprecipitation experiment for Sr in gypsum. Therefore, derived λ-value is thought to describe partition of Ra and Ca in solid phase and solution under an equilibrium condition without the effect of kinetic of precipitation. Determined λ-value was compared with those of other alkaline elements in sulfate minerals. The derived λ-value is smaller than that of Ra in barite and is similar to those of Sr in gypsum. This trend agrees with mechanical understanding for the size effect against partition coefficient.     

A study on the utilization of the Youden plot to evaluate proficiency test results

Methods of utilizing the Youden plot obtained from interlaboratory comparison tests are proposed. The Youden plot is a powerful tool for visually evaluating between- or within-laboratory errors. However, there are no generally applicable methods to indicate the anomalies in the between- and the within-laboratory errors in qualitative terms. An evaluation frame was therefore developed in this study as an indication method. Moreover, the Youden plot is considered to be useful for visually assessing the comprehensive performance of laboratories using two types of results. Although the confidence ellipse has been proposed in ISO 13528:2005 for this purpose, robust determination of the parameters has not yet been implemented. In the present study, robust determination of one of the parameters, the correlation coefficient, was developed. Our proposals were analytically validated using two types of statistical models. In addition, the properties were evaluated through computational simulations. From the results obtained, it can be concluded that our proposals are practically applicable to actual interlaboratory comparison tests.     

A facile method for the preparation of α-methylene-γ-butyrolactones from tulip tissues by enzyme-mediated conversion

We developed a facile method of enzyme-mediated conversion of 6-tuliposide to α-methylene-γ-butyrolactone (tulipalin). We used a tuliposide-converting enzyme for the conversion of 6-tuliposides extracted from tulip tissues into the corresponding tulipalins in high yields within 2 h at pH 7.0. The resulting tulipalins were selectively extracted by using several organic solvents.     

Enhancement of gamma-ray radiolysis of carbon dioxide with the assistance of solid materials

This work is devoted to enhance gamma-ray radiolysis of CO₂ with the assistance of coexisting metal materials. It is found that lower energy electrons which are generated through interactions of γ-photons with the coexisting metal materials and ejected to CO₂ gas actually enhance decomposition of CO₂ to produce CO. The increment of CO production agrees well with the increment of the deposited energy in CO₂, given by the lower energy electrons emitted from the materials, which is calculated by a numerical simulations code MCNP. It is also suggested that the volumetric decomposition of CO₂ dominates the decomposition at the material’s surface.     

Isotropic transition of amphiphilic side-chain type liquid crystalline di-block copolymers

The effects of nitrogen (N₂) pressure on amphiphilic di-block copolymer, PEO₁₁₄-b-PMA(Az)₄₀, were investigated by scanning transitiometry. The isotropic transition temperature increased with the increase of pressure above 20 MPa. The hydrostatic pressure effects evaluated with the Clapeyron equation were smaller than the value obtained by mercury as a pressurizing medium because the amount of absorbed gas decreases the volume change at the isotropic transition.     

Synthesis of poly[2-(perfluorooctyl)ethyl acrylate-<Emphasis Type="Italic">co</Emphasis>-poly(ethylene glycol) methacrylate] and its control of enzyme activity in supercritical carbon dioxide

Poly[2-(perfluorooctyl)ethyl acrylate-co-poly(ethylene glycol) methacrylate], P(POA-co-PEGm) was prepared as a new surfactant for scCO₂. The random copolymer was obtained by the radical polymerization of 2-(perfluorooctyl)ethyl acrylate (POA) and poly(ethylene glycol) methacrylate (PEGm) in DMF. The molar ratio of the POA and PEGm units in the copolymer was POA/PEGm = 0.972/0.028 by ¹H NMR. The molecular weight and molecular weight distribution were estimated by size exclusion chromatography to be Mn = 133,000 and Mw/Mn = 8.25, respectively. It was suggested that the copolymer formed micellar aggregates with the cores of the PEGm chains in scCO₂, based on the analyses of the copolymer in hexafluorobenzene by ¹H NMR and dynamic light scattering. The copolymer was soluble in scCO₂ and had a cloud point at a much higher pressure than the critical pressure. It was found that the copolymer solubilized CO₂-insoluble proteins such as bovine serum albumin and subtilisin Carlsberg in scCO₂. The solubility of the copolymer was not influenced by the presence of the proteins; however, the solubility decreased in the presence of a small amount of water along with the protein. The activity of the subtilisin slightly decreased when only placed in scCO₂, whereas a marked decrease in the activity was observed for the subtilisin in the presence of the copolymer in scCO₂. The subtilisin activity decreased as the CO₂ pressure increased.     

Functionalization of a Single C−F Bond of Trifluoromethylarenes Assisted by an ortho-Silyl Group Using a Trityl-Based All-in-One Reagent with Ytterbium Triflate Catalyst

Catalytic thiolation and azidation of a single C−F bond of trifluoromethylarenes were achieved assisted by an ortho-silyl group with all-in-one reagents to generate a trityl cation and nucleophiles. The reactions catalyzed by ytterbium triflate efficiently afforded a wide variety of difluoromethylenes avoiding the further C−F bond cleavage, by virtue of the mild conditions without the generation of a Brønsted acid.