Atmospheric resuspension of insoluble radioactive cesium-bearing particles found in the difficult-to-return area in Fukushima

The deposition of insoluble radiocesium-bearing microparticles (CsMPs), which were released from the Fukushima Daiichi Nuclear Power Plant (F1NPP) accident in March 2011, has resulted in the widespread contamination of eastern Japan. Obviously, these deposited insoluble CsMPs may become the secondary contamination sources by atmospheric migration or other environmental transferring process; however, the understanding of the transport mechanism remains non-elucidation, and the relevant evidence has not been directly provided. This study, for the first time, provides the direct evidence for the resuspension of these insoluble CsMPs to the atmosphere from (1) proximity of ¹³⁷Cs radioactivity and resemblance of the morphology and the elemental compositions of CsMPs in the samples of soil and aerosol derived from the same sampling site, (2) the special characteristics of the resuspended CsMPs of which the ratios of Na/Si, K/Si and/or Cs/Si were smaller than those from the initially released CsMPs collected at either long distance or near F1NPP, which can be ascribed to the slowly natural corrosion of CsMPs by the loss of the small amount of soluble contents in CsMPs, and (3) high CsMPs concentration of 10 granules/g in the surface soil of our sampling site and high resuspension frequency of CsMPs in spring when predominant suspended particles were soil dust. Specifically, 15 single CsMPs were successfully isolated from the aerosol filters collected by unmanned high-volume air samplers at a severely polluted area in Fukushima Prefecture, about 25 km away from F1NPP, from January 2015 to September 2019. The mean diameter of these CsMPs was 1.8 ± 0.5 μm, and the average ¹³⁷Cs radioactivity was 0.35 ± 0.23 Bq/granule. The contribution rate of the resuspended CsMPs to the atmospheric radiocesium was estimated from the ratio of ¹³⁷Cs radioactivity of a single CsMP to that of the aerosol filter to be of 23.9 ± 15.3%. There has been no considerable decreasing trend in the annual CsMP resuspension frequency

Investigation of the Chemical Characteristics of Individual Radioactive Microparticles Emitted from Reactor 1 by the Fukushima Daiichi Nuclear Power Plant Accident by Using Multiple Synchrotron Radiation X-ray Analyses

Seven radioactive particles were separated from a soil sample collected at the Northwest region of the Fukushima Daiichi Nuclear Power Plant (FDNPP). It has been pointed out that the soil is contaminated by radioactive materials emitted from reactor 1 of the FDNPP by the accident that occurred in March, 2011. The physical characteristics of these radioactive particles with –100 μm in diameter and non-uniform shape are clearly different from those of spherical microparticles, known as Cesium-balls, thought to be emitted from the FDNPP reactor 2. Three kinds of synchrotron radiation-based X-ray analyses (X-ray fluorescence analysis, X-ray absorption near edge structure analysis and X-ray diffraction analysis) were nondestructively applied to radioactive particles using a micro-focused X-ray beam at the SPring-8 to investigate their detailed chemical properties. Various elements related to fission products of nuclear fuel and components of the reactor were detected from the particles emitted from the FDNPP reactor 1 with an obvious heterogeneous elemental distribution. In particular, the chemical compositional feature of these particles was characterized by several elements (Sr, Ba etc.), which were easily volatilized in a reducing atmosphere. Although a main component of the particles was identified as silicate glass similar to the Cesium-balls, some crystalline materials were also found in microscopic regions containing Fe and other metallic elements. We concluded that these radioactive particles were emitted from reactor 1 to the atmosphere during 12th to 13th March, 2011. Our results suggest the fact that the nuclear fuel and the reactor vessels around the fuel were melted together at a very early stage of the accident. In addition, it was demonstrated that chemical compositional information of individual radioactive materials can be a new indicator as an alternative to the radioactive ratio to estimate the source of emissions

The methylation status of ASPP CpG island is changed in cancer cell lines retaining wild-type

原著Original ArticleThe p53 protein is one of the best-known tumor suppressors. Recently discovered ASPP1 and ASPP2 are specific activators of p53. To understand if ASPP inactivation offers a selective advantage to tumors that have wild-type p53, we measured the mRNA expression of ASPP1 and ASPP2 in tumor cell lines retaining wide-type p53. In addition, the CpG island methlyation status of ASPP1 gene and ASPP2 gene in the 5\u27-untranslated region was also investigated in order to understand the possible cause of abnormal expression of ASPP1 and ASPP2 in the tumor cell lines retaining wide-type p53. The data showed that mRNA expression of ASPP1 and ASPP2 is downregulated and CpG island tested is hypermethylated. These results indicated that ASPP CpG island aberrant methylation could be one molecular and genetic alteration in wild-type p53 tumors and one of the reasons that are responsible for the loss of ASPP activity

Collagen adhesion gene is associated with blood stream infections caused by methicillin-resistant Staphylococcus aureus

Objectives: Methicillin-resistant Staphylococcus aureus (MRSA) causes hospital- and community-acquired infections. It is not clear whether genetic characteristics of the bacteria contribute to disease pathogenesis in MRSA infection. We hypothesized that whole genome analysis of MRSA strains could reveal the key gene loci and/or the gene mutations that affect clinical manifestations of MRSA infection. Methods: Whole genome sequences (WGS) of MRSA of 154 strains were analyzed with respect to clinical manifestations and data. Further, we evaluated the association between clinical manifestations in MRSA infection and genomic information. Results: WGS revealed gene mutations that correlated with clinical manifestations of MRSA infection. Moreover, 12 mutations were selected as important mutations by Random Forest analysis. Cluster analysis revealed strains associated with a high frequency of bloodstream infection (BSI). Twenty seven out of 34 strains in this cluster caused BSI. These strains were all positive for collagen adhesion gene (cna) and have mutations in the locus, those were selected by Random Forest analysis. Univariate and multivariate analysis revealed that these gene mutations were the predictor for the incidence of BSI. Interestingly, mutant CNA protein showed lower attachment ability to collagen, suggesting that the mutant protein might contribute to the dissemination of bacteria. Conclusions: These findings suggest that the bacterial genotype affects the clinical characteristics of MRSA infection. (c) 2019 The Author(s). Published by Elsevier Ltd on behalf of International Society for Infectious Diseases

Dynamic intensity control system with RF-knockout slow-extraction in the HIMAC synchrotron

We have developed a dynamic beam intensity control system intended for use in three-dimensional pencil-beam scanning irradiation. In this system, which controls the spill structure and intensities of the beams extracted from the synchrotron, the amplitude of the RF-knockout is controlled using a 10 kHz response. Its amplitude modulation function is generated based on an analytical onedimensional model of the RF-knockout slow-extraction. Using feedback control of the proportional and integral controls, this system allows us to control the beam current dynamically in response to the request, as was experimentally verified in the HIMAC synchrotron. In this paper, we describe the system for controlling the amplitude modulation through the inclusion of feedback, and we provide some experimental results