Sample pretreatment for the determination of gamma emitting nuclides in dry radioactive waste using a dry ashing and high-performance microwave digestion system

A sample pretreatment procedure for the dry radioactive waste such as paper, cotton, vinyl, and plastic generated from nuclear power plants (NPPs) was established to determine the activity concentrations of ⁶⁰Co and ¹³⁷Cs. Because the volatility of cesium is temperature-dependent, the heating temperature was examined from 300 to 650 °C. Although the cesium was not volatile until 500, 450 °C was selected to save time. Cesium with a paper towel and a planchet of stainless steel were quantitatively recovered at 450 °C. The produced ash was completely dissolved with 10 mL of HNO₃, 4 mL of HCl, and 0.25 mL of HF in a high-performance microwave digestion system using a nova high temperature rotor at 250 °C for 90 min until 0.2 g was reached. This procedure was applied to low and intermediate level radioactive wastes generated from NPPs.     

Soluble and transparent polyimides from unsymmetrical diamine containing two trifluoromethyl groups

A new unsymmetrical diamine monomer containing two trifluoromethyl (CF₃) groups is prepared from 2‐bromo‐5‐nitro‐1,3‐bis(trifluoromethyl)benzene. The monomer is polymerized with typical dianhydrides, in this case PMDA, BPDA, BTDA, ODPA, and 6‐FDA, using a one‐pot synthetic method to obtain corresponding polyimides. All of the prepared polyimides are readily soluble in many organic solvents and can be solution‐cast into transparent, flexible, and tough films. These films have a UV–vis absorption cut‐off wavelength at 340–375 nm and light transparencies of 87–91% at a wavelength of 550 nm. Incorporation of two CF₃ groups unsymmetrically into rigid polyimides improves their solubility and transparencies without decreasing their physical properties. The polymers exhibit high thermal stability with 5% weight loss at temperatures ranging from 534 to 593 °C in nitrogen and from 519 to 568 °C in air, and high glass transition temperatures (T_g) above > 300 °C depending on their molecular structures. They also have a coefficient of thermal expansion (CTE) value of 46–69 ppm/°C. In addition, they show low refractive indices in the range of 1.535–1.602 at a wavelength of 633 nm due to the unsymmetrical incorporation effect of the two CF₃ groups. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4413–4422     

A spectral boundary integral method for inviscid water waves in a finite domain

In this paper, we show how the spectral formulation of Baker, Meiron and Orszag can be used to solve for waves on water of infinite depth confined between two flat, vertical walls, and also how it can be modified to take into account water of finite depth with a spatially varying bottom. In each case, we use Chebyshev polynomials as the basis of our representation of the solution and filtering to remove spurious high‐frequency modes. We show that spectral accuracy can be achieved until wave breaking, plunging or wall impingment occurs in two model problems. Copyright © 2016 John Wiley & Sons, Ltd.     

Analysis of mandipropamid residual levels through systematic method optimization against the matrix complexity of sesame leaves using HPLC/UVD

An analytical method was developed to detect mandipropamid residues in sesame leaves using high‐performance liquid chromatography–ultraviolet detection. Samples were extracted with acetonitrile and were prepurified using a solid‐phase extraction (SPE) cartridge with an additional dispersive‐SPE (d‐SPE) sorbent application. The method was validated using an external calibration curve prepared using pure solvent. The linearity was excellent with determination coefficient = 1. The limits of detection and quantification were 0.003 and 0.01 mg/kg, respectively. Recoveries at three spiking levels – 0.1, 0.5, and 1.0 mg/kg – were in the range 80.3–90.7% with relative standard deviations <2%. This method was applied to field‐treated samples collected from two different areas, Gwangju and Muan, in the Republic of Korea and the half‐lives were similar, 5.10 and 5.41 days, respectively. The pre‐harvest residue limit was also predicted for both sites. The proposed method is sensitive and able to quantify trace amounts of mandipropamid in leafy vegetables. The combination of SPE and d‐SPE effectively removed the matrix components in sesame leaves. Copyright © 2015 John Wiley & Sons, Ltd.     

A combination of solid‐phase extraction and dispersive solid‐phase extraction effectively reduces the matrix interference in liquid chromatography–ultraviolet detection during pyraclostrobin analysis in perilla leaves

Perilla leaves contain many interfering substances; thus, it is difficult to protect the analytes during identification and integration. Furthermore, increasing the amount of sample to lower the detection limit worsens the situation. To overcome this problem, we established a new method using a combination of solid‐phase extraction and dispersive solid‐phase extraction to analyze pyraclostrobin in perilla leaves by liquid chromatography with ultraviolet absorbance detection. The target compound was quantitated by external calibration with a good determination coefficient (R² = 0.997). The method was validated (in triplicate) with three fortification levels, and 79.06– 89.10% of the target compound was recovered with a relative standard deviation <4. The limits of detection and quantification were 0.0033 and 0.01 mg/kg, respectively. The method was successfully applied to field samples collected from two different areas at Gwangju and Muan. The decline in the resiudue concentrations was best ascribed to a first‐order kinetic model with half‐lives of 5.7 and 4.6 days. The variation between the patterns was attributed to humidity. Copyright © 2015 John Wiley & Sons, Ltd.     

Crystallization behavior of P(EN‐co‐ET) copolyesters: Crystallization kinetics and morphology revealed by DSC,time‐resolved SAXS analysis,and TEM

The crystallization kinetics and morphology of PEN/PET copolyesters were investigated using differential scanning calorimetry (DSC), time‐resolved small‐angle X‐ray scattering (TR‐SAXS), and transmission electron microscopy (TEM). The Avrami exponents obtained using DSC were approximately 3 for homo PEN and 4 for all the copolyesters. The 3‐parameter Avrami model was successfully fitted to the invariants with respect to the time obtained from TR‐SAXS, and the exponent values were similar to those obtained from DSC. Moreover, the Avrami rate constants obtained from TR‐SAXS showed marked temperature‐sensitive decreases in all samples, like those obtained from DSC. This indicates that not only could changes in morphological parameters be obtained from the analysis of TR‐SAXS data but also crystallization kinetics. The changes in the morphological parameters determined from the SAXS data indicate that the minor components, dimethyl terephthalate (DMT) segments, are rejected into the amorphous phase during crystallization. In the TEM study, copolyesters crystallized at temperature above 240 °C grew into both the α‐ and β‐form, although 240 °C is the optimum condition for the β‐form crystal. © 2005 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 43: 805–816, 2005     

Influence of ionic association on the nonisothermal crystallization kinetics of sodium sulfonate poly(butylene succinate) ionomers

We evaluated the relationship between the ionic substituents and nonisothermal crystallization behavior in poly(butylene succinate) (PBS) ionomers, synthesized by the introduction of sulfonated dimethyl fumarate (SDMF) with sodium sulfonate. In addition, we investigated the effect of sodium ions on the molecular structure of the PBS backbone by solid‐state ²³Na NMR analysis. Sodium ion aggregates (multiplets) was predominately created with the ionic group concentration, and melt rheology and dynamic melt analysis results showed that multiplet formation induced not only remarkable heterogeneity, but also a high degree of clustering in the PBS chains. At low ionic group concentration, well dispersed multiplets behaved as effective nuclei during the crystallization of the PBS ionomer and accelerated the rate of crystallization. As ionic group concentration grew higher, crystallization rates decreased due to hindered chain mobility by clusters consisting of numerous multiplets. A combined Ozawa and Avrami equation proved to be more effective than the Ozawa equation in describing the nonisothermal crystallization kinetics of PBS and its ionomers. The observed nucleation activity indicates that the nonisothermal crystallization rate is not directly proportional to the ionic group concentration. Superior nucleation activity was observed in PBS ionomer containing 1 mol % SDMF. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 925–937, 2008     

Palladium(II)‐Catalyzed Tandem Synthesis of Acenes Using Carboxylic Acids as Traceless Directing Groups

A straightforward synthetic strategy for generating useful anthracene derivatives was developed involving palladium(II)‐catalyzed tandem transformation with carboxylic acids as traceless directing groups. Carboxyl‐directed C‐H alkenylation, carboxyl‐directed secondary C‐H activation and rollover, intramolecular C?C bond formation, and decarboxylative aromatization are proposed as the key steps in the tandem reaction pathway. This novel synthetic route utilizes a broad range of substrates and provides a convenient synthetic tool that allows access to acenes.