Preparation of ion exchange membranes by preirradiation induced grafting of styrene/divinylbenzene into crosslinked PTFE films and successive sulfonation

Ion exchange membranes (IEMs) were prepared by preirradiation induced grafting of styrene with or without divinylbenzene (DVB) into crosslinked polytetrafluoroethylene (RX‐PTFE) films and successively sulfonated by chlorosulfonic acid. The effects of the DVB concentration and solvent on the kinetic of the graft polymerization were studied. The ion exchange capacity (IEC) values of the prepared membranes ranging from 1.5 to 2.8 mequiv/g were obtained. The degree of swelling increased with the increase in the degree of grafting, while higher crosslinking density of both the RX‐PTFE matrices and the grafts suppressed the degree of swelling. The chemical stabilities of the IEMs were tested by recording the weight of the membranes being soaked in hot H₂O₂ solutions. The weight‐time curves of the prepared membranes showed one‐step quick decrease due to the decomposition of the poly(styrene‐sulfonic acid) (PSSA) grafts. Higher crosslinking density in both the RX‐PTFE matrices and the grafts improved the chemical stability of the IEMs. The ionic conductivity of the IEMs increases with the increase in the IEC values. The IEMs with IEC values higher than 2.2 mequiv/g hold the higher ionic conductivity than that of Nafion® 112 membrane. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3587–3599, 2006     

Analytical method of cereulide in processed cereal-based foods and milk powder by LC-MS/MS

An LC-MS/MS method for analysis of cereulide, an emetic toxin produced by Bacillus cereus, was developed. Cereulide was extracted from samples, fried rice, pan-fried noodles, red bean paste and baby formula, with methanol and purified using Oasis HLB cartridges. LC separation was performed on a C18 column with a mixture of formic acid solution and methanol containing ammonium formate as a mobile phase, and the mass spectrometer was operated in the positive electrospray ionization mode. Performance evaluation showed that trueness was higher than 70% and repeatability and reproducibility were within 10%. The limits of quantification were lower than 1 μg/kg.     

KRAS/BRAF Analysis in Ovarian Low-Grade Serous Carcinoma Having Synchronous All Pathological Precursor Regions

Ovarian low-grade serous carcinoma is thought to begin as a serous cystadenoma or adenofibroma that progresses in a slow stepwise fashion. Among the low-grade serous carcinomas, there is a high frequency of activating mutations in the KRAS or BRAF genes; however, it remains unclear as to how these mutations contribute to tumor progression. This is the first report to track the histopathological progression of serous adenofibroma to low-grade serous carcinoma. Each stage was individually analyzed by pathological and molecular genetic methods to determine what differences occur between the distinct stages of progression.     

Inkjet Aerosol Generator as Monodisperse Particle Number Standard

The AIST-inkjet aerosol generator (IAG) can generate highly monodisperse solid or liquid aerosol particles in the particle diameter range from 0.3 to 20 μm at precisely known particle generation rates. The device has been developed for evaluating the counting efficiencies of optical and condensation particle counters. Particle generation efficiency of the IAG is defined as the number of aerosol particles generated by one voltage pulse sent to an inkjet head. The 95% confidence interval of the efficiency were 0.998 ± 0.006 within the 0.4 to 10 μm particle diameter range. The efficiencies remained close to unity when the droplet generation rates were within 20–500 s^?1 and 100–900 s^?1 using ultrapure-water and isopropyl alcohol (IPA) as the solvent of the inkjet solution, respectively. The operating aerosol flowrate range of the IAG is currently 0.5 and 1.0 L/min. The coefficients of variations (C.V.) of the size distributions were 2 to 3% indicating the generated particles were highly monodisperse. The generated particle sizes were defined as the volume equivalent diameter, D_ve. The uncertainty analysis on the factors affecting D_ve indicated that 95% confidence interval of the D_ve is expected to be ±5%. The uncertainty of D_ve was entirely caused by the uncertainty of the average mass of a droplet. The reproducibility of particle sizes within 0.5 to 10 μm was evaluated using an aerodynamic particle sizer. The C.V. of the measured particle sizes were less than 6% and 4% when NaCl particles and ionic liquid droplets were generated, respectively.

Copyright 2014 American Association for Aerosol Research     

Chemical Shifts of Silicon X-ray Photoelectron Spectra by Polymerization Structures of Silicates

The binding energy of Si 2 p electrons and the kinetic energy of the Si(KLL) X-ray-excited state were measured by using X-ray photoelectron spectroscopy (XPS) and X-ray Auger electron spectroscopy (XAES), respectively, for silicates with SiO₄ tetrahedra of various polymerization types. The resulting Si 2 p XPS binding energies varied from 101.3 eV in merwinite (monomeric structure) to 103.4 eV in quartz and cristobalite (three-dimensional framework structure). A clear chemical-shift relation was observed, relating the polymerization structures of SiO₄ tetrahedra to the plots of their Si 2 p XPS binding energy versus the kinetic energy of their Si(KLL) XAES spectra. Thus, the structural state of the surface silicates in various substances can be deduced from this chemical-shift relationship.     

Stress corrosion cracking of copper in swollen bentonite simulating nuclear waste disposal environment

Stress corrosion cracking (SCC) of pure copper in bentonite clay was examined using a slow strain rate test (SSRT). Bentonite was swollen with pure water or aqueous solutions containing NH₃ of 5 and 10 mM. Thick corrosion films and particulate deposits were formed on the copper surface after the SSRT. Typical tarnish rupture-type SCC occurred on pure copper in swollen bentonite with and without NH₃. The crack propagation rate was enhanced by NH₃. It is confirmed that a thick oxide layer was formed on copper during plastic deformation, resulting in tarnish crack-type SCC. Many particulate deposits observed on the surface were formed due to the rapid dissolution of Cu²⁺ ions to form porous CuO at local deformed sites, regardless of the SCC occurrence.