Spectral analysis of environmental microplastic polyethylene (PE) using average spectra

In this study, microplastic samples from surface seawater of Tokyo Bay were collected, polyethylene (PE) microplastics were used to calculate carbonyl index (CI), and average spectra of PE were analyzed and compared with a previous study applying agitation during chemical treatment. It was found that PE and polypropylene (PP) were the predominant polymer type in the samples. Among PE samples, fragments were the most commonly observed shape, with white being the dominant color. Deviations were found in the average spectra among different shapes and colors when compared to the standard PE spectrum. A comparison of the average spectra between the two datasets suggests that pronounced peaks related to oxidation are most likely resulted from agitation during the chemical treatment. Additionally, it was found a closer spectral resemblance between the sample spectra and the spectrum of standard sample of oxidized PE (PEOx) than with the standard PE spectrum, suggesting that using the oxidized PE as a reference spectrum might be more effective for identification. These findings highlight the complex factors affecting the spectral properties of microplastics and highlight the importance of understanding these variations to enhance the accuracy of microplastic identification workflows and understanding of environmental fate of microplastics.

A beaker method for determination of microplastic concentration by micro-Raman spectroscopy

Fourier-transform infrared (FT-IR) spectroscopy method for measuring small microplastic (SMP) concentration in marine environment is time-consuming and labor-intensive due to sample pre-treatment. In contrast, Raman spectroscopy is less influenced by water and can directly measure SMP samples in water, making it a more efficient method to measure SMP concentration. Therefore, a method that can directly estimate the concentration of SMPs in water was developed, and the relationship between SMP concentration and experimental Raman spectra were established by testing with standard polyethylene (PE) samples. It was found that average spectra acquired in water solution could reflect characteristic peaks of the plastic after baseline correction. Further investigation found that there is a significant functional relationship between correlation coefficient of sample spectra and the concentration of PE particles, and such relationship can be modelled by Langmuir model. The empirical functional relationships can be used to estimate SMP concentrations by measuring average Raman spectra. The developed methodology is helpful for developing rapid SMP identification and monitoring methods in a more complex manner.•A method of directly measuring MP concentration in water is proposed.•Experimental procedures are provided.•Data analysis methods are outlined.

The pretreatment method in marine organisms and sediment for microplastics analysis by FTIR using "Cylindrical microplastics fractionator"

For the detection of microplastics (MPs) in aquatic biota using Fourier transform infrared spectroscopy (FTIR), the ability to remove organic matter (OM) in pretreatment steps is essential to increase the time efficiency of MPs measurement and method uniformity. In principle, decreasing OM can be achieved by increasing the number of pretreatment steps. However, MPs are lost in proportion to the number of transfers between each step. Therefore, we have created a "Cylindrical MPs Fractionator" composed of commercially available materials. This container allows for a six-step pretreatment process that is designed to increase the removal capacity of OM with only one transfer to prevent the loss of MPs.•Biological or sediment samples are placed in the extractor and subjected to chemical treatment and density separation.•Residues containing MPs are obtained on filters by vacuum filtration.•After additional chemical treatment of the obtained residue, the components of the residue are identified by microscopic FTIR.This method removed 99.3% of OM and recovered 88.5% of MPs. The presenting method confirmed that this can be used with the same process for 11 organisms and sediments from estuarine ecosystem in Japan as models.

Accessing the intrinsic factors of carbonyl index of microplastics: Physical and spectral properties, baseline correction, calculation methods, and their interdependence

Carbonyl index (CI) is a measure of the degradation status of microplastics. While many studies address environmental factors of microplastic degradation, intrinsic factors like physical properties, spectral properties, baseline correction, and CI calculation methods are less explored. This research focused on these aspects using surface seawater samples. We found that color and shape have limited dependence on particle size or signal-to-noise ratio (SNR). Baseline correction can significantly alter CI values, with the direction of the shift depending on the methods used. Additionally, most CI values before and after baseline correction and those calculated using different methods tend to be strongly correlated. Using the selected CI calculation methods, we found that CI values varied significantly by shape and color. CI's relation to the similarity between the sample and its pristine form suggests an alternative degradation measure. Our findings emphasize the need for standardized CI calculation methods.

Challenges of Raman spectra to estimate carbonyl index of microplastics: A case study with environmental samples from sea surface

This study investigates the feasibility of using the carbonyl index (CI) derived from Raman spectra as an indicator of plastic degradation and its relationship with the CI calculated from Fourier transform infrared (FTIR) spectra, using microplastic samples of polyethylene (PE) from surface seawater. Multiple methods were used to calculate the CI values of FTIR spectra, while proposed methods were used to calculate the corresponding CI values of Raman spectra. Some significant relations between FTIR CI and Raman CI were observed. However, small R2 values suggest weak functional relationships, which can be attributed to the low signal-to-noise ratio (SNR) of Raman spectra. These results highlight the challenges of establishing a functional relationship between FTIR CI and Raman CI, including challenges such as the uniformity of Raman spectra, determining optimal Raman measurement parameters, selecting appropriate peaks for Raman CI calculation, deciding on spectral processing methods, and addressing the interdependence of these issues.

Coumarin 6 staining method to detect microplastics

Microplastics have contaminated the ocean in large quantities and are widely distributed throughout the world. Thus, our understanding of the concentration of microplastics in various environments should be increased. However, current methods to detect microplastics require considerable effort and expensive equipment. In this study, we developed a fluorescence staining technique using coumarin 6 and examined its effectiveness. A mixture of acetone and ethanol was used as the solvent, and 10 different types of plastics were able to be stained with coumarin 6. The fluorescence peak for coumarin 6 staining was approximately 500 nm for each plastic type. The optimal immersion time and coumarin 6 concentration for staining were determined to be 60 min and 1 mg L-1, respectively. Using this technique, we were able to stain all of the microplastics obtained from samples collected in Tokyo Bay seawater.

Microplastic pollution in the gastrointestinal tract of giant river catfish Sperata seenghala (Sykes, 1839) from the Meghna River, Bangladesh

Freshwater rivers are considered the major route for microplastics (MPs), yet limited studies have been reported on MPs in freshwater river fish, especially in Bangladesh. This research reveals the intake of MPs by the giant river catfish Sperata seenghala, collected from the Meghna River, which is the only outlet of the Ganges-Brahmaputra River. Three locations, namely, Chandpur Sadar, Bhola Sadar, and Char Fasson, along the Meghna River, were selected in order to investigate the gastrointestinal tracts (GIT) of the fish. Ninety percent (n=27) of fish (n=30) were contaminated, with fragment-shaped MPs (65%) as the most abundant among the four types. A total of 179 MP particles were detected using micro-Fourier transformed infrared spectroscopy (μ-FTIR), with an average of 5.96 ± 1.32 MP particles per fish. Among the four size groups, the highest proportion of MPs (54%) occurred in the 45-100 μm group; the dominant color among the seven color groups was white (30%). The highest quantity of MPs was found in the relatively densely populated Chandpur Sadar region. Polypropylene-polyethylene copolymer (PP-PE, 23%) was proportionally dominant among the 15 types. No significant relationship was found between the total number of observed MPs and the GIT weight. This study will help us to understand MP pollution in S. seenghala that may transmit to the human body through the food chain.

Development of automated microplastic identification workflow for Raman micro-imaging and evaluation of the uncertainties during micro-imaging

In this study, an automated identification workflow for Raman micro-imaging (RMI) was developed, and the performance was evaluated by artificial samples of microplastic (MP) microsphere with different sizes and types. Theoretical detection rate and estimated particle size were derived and compared with experimental data. Results show that the proposed workflow can identify plastic types and estimate the size of the MP microspheres under different conditions for most cases. However, size of laser spot and discrepancy between sample surface and focal plane can influence RMI results in two ways. Firstly, small particles are more likely to be detected. Secondly, estimated sizes of particles are more likely to be overestimated. The derived uncertainties can serve as a reference for future experimental design and further investigation of more complex situations. The workflow is accessible online, and interested researchers can adjust the parameter values as necessary to suit their specific circumstances.

A double sliding-window method for baseline correction and noise estimation for Raman spectra of microplastics

When measuring microplastics of environmental samples, additives and attachment of biological materials may result in strong fluorescence in Raman spectra, which increases difficulty for imaging, identification, and quantification. Although there are several baseline correction methods available, user intervention is usually needed, which is not feasible for automated processes. In current study, a double sliding-window (DSW) method was proposed to estimate the baseline and standard deviation of noise. Simulated spectra and experimental spectra were used to evaluate the performance in comparison with two popular and widely used methods. Validation with simulated spectra and spectra of environmental samples showed that DSW method can accurately estimate the standard deviation of spectral noise. DSW method also showed better performance than compared methods when handling spectra of low signal-to-noise ratio (SNR) and elevated baselines. Therefore, DSW method is a useful approach for preprocessing Raman spectra of environmental samples and automated processes.

Comparative evaluation of the carbonyl index of microplastics around the Japan coast

The carbonyl index (CI) of polyethylene and polypropylene microplastics (MPs) (2950 particles) collected in coastal waters around Japan was investigated. The CI of MPs was calculated by the specified area under band technique. The mean MP CI in all samples (regardless of shape and color) was 0.69 ± 0.34 and 0.70 ± 0.34 for polyethylene and polypropylene, respectively, and there was no significant difference in the color or shape of the MPs. The polyethylene, white, and fragment MPs CI was negatively (p < 0.05) correlated with the major length of the MPs. Large MPs with relatively little deterioration were distributed along the west coast of the Sea of Japan, whereas small MPs were distributed along the east coast. Our findings of this gradual change in the deterioration of MPs, based on geographical distribution, are in accordance with literature CI-size and MP degradation hypotheses.

Microplastics pollution in the river Karnaphuli: a preliminary study on a tidal confluence river in the southeast coast of Bangladesh

Bangladesh is a deltaic country in Asia, and its riverine systems ultimately drain into the Bay of Bengal. Plastic is a severe environmental issue for coastal-marine ecosystems due to the indiscriminate usage and discarding of plastic items in the upstream river that eventually find their route into the Bay of Bengal. Microplastics (MPs) are widespread pollutants in almost all environmental compartments, including aquatic environments. This study aimed to quantify and understand the distribution of microplastics in surface water and sediments of the river Karnaphuli, a tidal confluence river adjacent to the Chattogram seaport city of Bangladesh, a highly inhabited and industrial area on the southeast coast of the Bay of Bengal. A manta trawl net (300-µm mesh size) was used to collect surface water samples, while an Ekman dredge was used to collect sediment samples. The concentrations of microplastics in the surface water of the river Karnaphuli during late monsoon, winter, and early summer were recorded to be 120,111.11, 152,222.22, and 164,444.44 items/km², respectively, while in sediments, those were recorded to be 103.83, 137.50, and 103.67 items/kg, respectively. A higher abundance of microplastics was observed in downstream surface water (228,888.88 items/km²) and sediments (164.17 items/kg). Smaller sizes (0.3 to 0.5 mm) of microplastics were predominant, fibers or threads were the frequent types, and black was the most common color in the river Karnaphuli. The Fourier transform infrared analysis revealed that polyethylene terephthalate (surface water: 22%, sediments: 19%), polyamide (surface water: 15%, sediments: 13%), polyethylene (surface water: 12%, sediments: 18%), polystyrene (surface water: 13%, sediments: 11%), and alkyd resin (surface water: 13%, sediments: 10%) were the most prevalent polymers in the river Karnaphuli. Moreover, there was a moderate positive correlation between MPs abundance in surface water and sediments. Therefore, improved long-term research (in different seasons with horizontal and vertical monitoring) is necessary in order to accurately determine the flux of microplastics from the river Karnaphuli to the Bay of Bengal.

Contamination of sea surface water offshore the Tokai region and Tokyo Bay in Japan by small microplastics

A nested double neuston net was prepared and used to collect samples from the surface of coastal waters around Japan to obtain information about the properties of both small microplastics (SMPs; <350 μm) and large microplastics (LMPs; >350 μm). The SMP concentrations ranged from 1000 to 5900 pieces m^-3 in the open ocean and averaged approximately 3000 pieces m^-3 in the inner part of Tokyo Bay. The SMP concentrations were around 20-60 times greater than the LMP concentrations. By analyzing the seawater, we obtained a microplastic size distribution that spanned 50-5000 μm. The LMPs mainly comprised packaging-related plastics, such as polyethylene (PE) and polypropylene, while the SMPs were dominated by paint-related plastics. SMPs derived from packaging materials (e.g., PE) may have gradually sank down from the sea surface when they were smaller than 600 μm.

Contamination of sea urchin Mesocentrotus nudus by radiocesium released during the Fukushima Daiichi Nuclear Power Plant accident

Countless marine organisms were polluted with radioactive materials that were dispersed when the Fukushima Daiichi Nuclear Power Plant (FDNPP) was damaged in 2011 by the Great East Japan Earthquake. The aim of this study was to determine the degree to which marine herbivorous sea urchins, Mesocentrotus nudus, were contaminated with radiocesium because of the accident. We collected samples of sea urchins from four locations in Fukushima prefecture (at the coast and offshore from the Yotsukura and Ena stations) and investigated how the ¹³⁷Cs activity concentrations changed. The biological half-life (T_bio) of ¹³⁷Cs in the individual sea urchins was between 121 and 157 days. The ecological half-life (T_eco) of ¹³⁷Cs was 181–423 days and was high in places close to the FDNPP. The T_eco values in the sea urchins were longer than previously reported. The results infer that the food sources of the sea urchins around the Fukushima coast strongly influenced their uptake of ¹³⁷Cs.

First Application of Mass Measurements with the Rare-RI Ring Reveals the Solar r-Process Abundance Trend at A=122 and A=123

The Rare-RI Ring (R3) is a recently commissioned cyclotronlike storage ring mass spectrometer dedicated to mass measurements of exotic nuclei far from stability at Radioactive Isotope Beam Factory (RIBF) in RIKEN. The first application of mass measurement using the R3 mass spectrometer at RIBF is reported. Rare isotopes produced at RIBF-^{127}Sn, ^{126}In, ^{125}Cd, ^{124}Ag, ^{123}Pd-were injected in R3. Masses of ^{126}In, ^{125}Cd, and ^{123}Pd were measured whereby the mass uncertainty of ^{123}Pd was improved. This is the first reported measurement with a new storage ring mass spectrometry technique realized at a heavy-ion cyclotron and employing individual injection of the preidentified rare nuclei. The latter is essential for the future mass measurements of the rarest isotopes produced at RIBF. The impact of the new ^{123}Pd result on the solar r-process abundances in a neutron star merger event is investigated by performing reaction network calculations of 20 trajectories with varying electron fraction Y_{e}. It is found that the neutron capture cross section on ^{123}Pd increases by a factor of 2.2 and β-delayed neutron emission probability, P_{1  n}, of ^{123}Rh increases by 14%. The neutron capture cross section on ^{122}Pd decreases by a factor of 2.6 leading to pileup of material at A=122, thus reproducing the trend of the solar r-process abundances. The trend of the two-neutron separation energies (S_{2n}) was investigated for the Pd isotopic chain. The new mass measurement with improved uncertainty excludes large changes of the S_{2n} value at N=77. Such large increase of the S_{2n} values before N=82 was proposed as an alternative to the quenching of the N=82 shell gap to reproduce r-process abundances in the mass region of A=112-124.

Determining the appropriate number of particles on a filter to allow small microplastics to be analyzed by microscopy

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Appropriate number of particles for small plastic particle analysis was determined.

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Numerical experiments to determine particle distributions on a filter were performed.

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Particle number for a 99% isolation ratio was determined.

The concentrations of small microplastics (diameter < 350 µm) on filters are usually determined by microscopy or micro Fourier-transform infrared spectroscopy. The presence of too many particles on a filter will cause the measured number of particles and particle sizes to be incorrect because of overlapping particles. In this study, the appropriate quantity of particles on a filter to allow effective particle analysis to be performed was determined by performing numerical experiments. The larger the number of particles and the larger the particles, the smaller the proportion of isolated particles. An isolation ratio of 99% requires a particle density on the filter of 1.28 particles mm⁻² if the particle size is 50 µm or of 0.351 particles mm⁻² if the particle size is 100 µm.•

Appropriate number of particles for small plastic particle analysis was determined.

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Numerical experiments to determine particle distributions on a filter were performed.

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Particle number for a 99% isolation ratio was determined.

Bayesian inference of ion velocity distribution function from laser-induced fluorescence spectra

The velocity distribution function is a statistical description that connects particle kinetics and macroscopic parameters in many-body systems. Laser-induced fluorescence (LIF) spectroscopy is utilized to measure the local velocity distribution function in spatially inhomogeneous plasmas. However, the analytic form of such a function for the system of interest is not always clear under the intricate factors in non-equilibrium states. Here, we propose a novel approach to select the valid form of the velocity distribution function based on Bayesian statistics. We formulate the Bayesian inference of ion velocity distribution function and apply it to LIF spectra locally observed at several positions in a linear magnetized plasma. We demonstrate evaluating the spatial inhomogeneity by verifying each analytic form of the local velocity distribution function. Our approach is widely applicable to experimentally establish the velocity distribution function in plasmas and fluids, including gases and liquids.

Reevaluation of microplastics identification based on Neuston net survey data

To verify data accuracy regarding microplastics (MPs), the effects of chemical preprocessing and optical identification with Fourier transform infrared spectroscopy (FTIR) were examined using survey data. We aimed to clarify the cause of overestimation of the number concentration of MPs without FTIR by focusing on shape types. The proportion of fragments (foam) decreased (increased) after FTIR analysis. Although significant difference was found in terms of the size distribution of fragments (after FTIR > before FTIR), no such difference was found with regard to foam. These findings indicate that impurities categorized as fragments via visual confirmation, especially those measuring <1000 μm, were removed using the FTIR technique. Although previous studies recommended the use of data on MPs measuring >1000 μm, this threshold should be applied only to fragments and not to foam.

Inclusion of shape parameters increases the accuracy of 3D models for microplastics mass quantification

As microplastics may bring about adverse effects on living organisms, it is important to establish more precise quantification approaches to better understand their dynamics. One method to determine the concentration of microplastics is to estimate their mass using three-dimensional (3D) models, but its accuracy is not well known. In this study, we evaluated the shape of the particles and verified the accuracy of a 3D model-based mass estimation using samples from a tidal flat facing Tokyo Bay. The particle shape evaluation suggested that the microplastics were flat and irregular in shape; based on these data, we created two types of models to estimate their mass. As a result, an accuracy of mass estimation by our model was higher than other models that consider the slenderness and flatness of particles. The optimization of mass estimation methods based on 3D models may improve the reliability of microplastic evaluation in monitoring studies.

Radiocesium concentrations in shallow water sediments (Matsukawa-ura Lagoon, Fukushima, Japan) from a compact NaI(Tl) scintillation spectrometer

We collected continuous sedimentary ¹³⁷Cs concentration data from a shallow fishery ground (Matsukawa-ura Lagoon, Fukushima, Japan) in 2016 using a new compact underwater NaI(Tl) scintillation spectrometer and a quantitative technique. ¹³⁷Cs concentrations in sediments were low (approx. 40 Bq/kg DW) at the lagoon mouth and high (641.2 Bq/kg DW) at the head of the lagoon. Some areas of locally elevated ¹³⁷Cs concentrations (>500 Bq/kg DW) were also found.

Microplastics on the sea surface of the semi-closed Tokyo Bay

Microplastics (MPs) pollution surveys were conducted in Tokyo Bay using neuston nets (May 2019 and January 2020). Although the pollution level in Tokyo Bay was high (3.98 pcs/m³, May), it was lower than reported in other semi-closed bays because of differences in the Enclosed Index. It was found that polyethylene fragments dominated the retrieved MPs; the mode of MPs size was 800 μm. As MPs abundance in rivers had the same seasonality as found in the inner bay, rivers were considered the main source of MPs. The seawater residence time is shorter than the time required for the density of MPs to become greater than that of seawater; therefore, it was considered that MPs are transported out of the bay instead of sinking. MPs were aggregated into a convergence zone by residual currents (the thermohaline front) in May (January). These findings will improve understanding of MPs pollution in other bays.

Changes in radioactive cesium concentrations from 2011 to 2017 in Fukushima coastal sediments and relative contributions of radioactive cesium-bearing microparticles

Sedimentary cesium-137 concentrations around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were measured from 2011 to 2017 at eight stations. Although high values were observed until 2013, decreasing trends were observed at the surface sediments of seven stations. We isolated 25 radioactive Cs-bearing microparticles (CsMPs; 1.0-5385 Bq per particle). The contribution ratio of CsMPs to each sample ranged from 4.1% to 99.5% (median 58.8%), with the contribution ratio of the CsMPs in the southern part of the FDNPP was low compared to that from the northern part. In the southern part of the FDNPP, small CsMPs that could not be isolated in this study were present in large quantities immediately after the accident, and gradually diffused away and/or were dissolved over time. In contrast, the CsMPs in the northern part of the FDNPP have most likely accumulated over time, as suggested by the silty nature of the sediments there.

Swelling of Doubly Magic ^{48}Ca Core in Ca Isotopes beyond N=28

Interaction cross sections for ^{42-51}Ca on a carbon target at 280  MeV/nucleon have been measured for the first time. The neutron number dependence of derived root-mean-square matter radii shows a significant increase beyond the neutron magic number N=28. Furthermore, this enhancement of matter radii is much larger than that of the previously measured charge radii, indicating a novel growth in neutron skin thickness. A simple examination based on the Fermi-type distribution, and mean field calculations point out that this anomalous enhancement of the nuclear size beyond N=28 results from an enlargement of the core by a sudden increase in the surface diffuseness of the neutron density distribution, which implies the swelling of the bare ^{48}Ca core in Ca isotopes beyond N=28.

Spatial variation in sedimentary radioactive cesium concentrations in Tokyo Bay following the Fukushima Daiichi Nuclear Power Plant accident

Cesium-137 concentrations in sediment (¹³⁷Cs) at Tokyo Bay were measured at 26 stations during 2017. Average ¹³⁷Cs concentrations at the Arakawa river mouth (117 ± 46 Bq kg^-1) were approximately six times higher than those of the other stations in the bay (20 ± 16 Bq kg^-1). There were radiocesium-bearing microparticles in the bay sediment as well as in suspended matter of Fukushima coastal waters. Radioactivity of radiocesium-bearing microparticles was estimated to be 0.12 Bq. However, the contributions of radiocesium-bearing microparticles to each ¹³⁷Cs concentration of the bulk sample were low; 3% was the maximum. The ¹³⁷Cs inventory in sediment at the entire bay was 0.67 TBq, showing that a large amount of ¹³⁷Cs was supplied to the bay from the river following the Fukushima Daiichi Nuclear Power Plant accident. Approximately 9.2% of the ¹³⁷Cs which was fallout in the drainage basin has already flowed into the bay from the watershed, which is approximately 3.2 times higher than that of a previous estimate.

Temporal Variation of Radionuclide Contamination of Marine Plants on the Fukushima Coast after the East Japan Nuclear Disaster

As a result of the Great East Japan Earthquake and associated tsunami in March 2011, the Fukushima Daiichi Nuclear Power Plant (FDNPP) released a large amount of radioactive material into the environment, resulting in contamination of many marine organisms. In this study, 15 marine algal species and a seagrass species were collected from the sublittoral zone of the Iwaki Coast of Fukushima Prefecture from May 2012 to June 2015 and analyzed for variations in ^110mAg, ¹³⁴Cs, and ¹³⁷Cs over time. The results indicated that (1) ^110mAg, ¹³⁴Cs, and ¹³⁷Cs were present in all marine plants collected in May 2012, (2) the concentration of ^110mAg in the seagrass Phyllospadix iwatensis decreased significantly over time while the ecological half-life of ^110mAg in P. iwatensis was longer at locations closer to the FDNPP, and (3) the ^110mAg/¹³⁷Cs radioactivity ratio of P. iwatensis was remarkably high until 2015, indicating that detectable ^110mAg was present in the coastal environment 4 years after the accident. The concentration of ^110mAg in P. iwatensis was higher than those in other marine algae, demonstrating a species-specific mechanism of accumulation.

A trial of in situ and static measurements of levels of radioactive cesium 137 on shallow rugged reefs lying close to the coastline of Fukushima

With the use of an in situ and static method for gamma-ray measurements, levels of radioactive cesium 137 on shallow rugged reefs which lie between 37.3° N and 37.4° N, from the coastline of Fukushima to 141.06° E, at a depth of around 10 m were surveyed for the first time from May 2016 to December 2017. To confirm the contact between the detector and a surface of rock, we used a fact that potassium containing minerals are abundant and uniformly distributed in the area, and thus the strength of the photoelectric peak of natural radioactive potassium 40 is nearly constant over the area. We have found that the levels of radioactive cesium 137 varied from point to point within a range from 1 × 10⁴ Bq/m² to 6 × 10⁴ Bq/m².

Abstract P3-09-04: Possible role of p53/Mieap-regulated mitochondrial quality control as a tumor suppressor in human breast cancer

[Background] In sporadic breast cancers, the most important gene is p53, given that it is a tumor suppressor gene and mutated in greater than 50% of human cancers. According to previous reports, p53 is also mutated in approximately 20–40% of breast cancers. Recent data from the cancer genome atlas (TCGA) revealed that 37% of breast cancer specimens had alterations in p53-particularly, 72% in (human epidermal growth factor) HER2-rich and 80% of basal-like breast cancer cases—indicating that it is a critical driver of tumor development even in breast cancer. p53 is clinically very important not only because of its high mutation rate but also because mutation is associated with more aggressive disease and worse overall survival. Mitochondria-eating protein (Mieap) is a p53-target gene that plays an important role in mitochondrial quality control. Mieap has been reported to have a critical role in tumorsuppression of colorectal cancer. Here, we investigated the role of Mieap as a tumorsuppressor in breast cancer. [Marerial and methods] We overexpressed Mieap using the constructed adenovirus in breast cancer cell lines such as MCF-7, SK-BR-3, and MDA-MB-231 cells. The percentages of cells in different cell cycle phases (subG1, G1, S, and G2/M) were determined using FACS analysis and also caspase activities (Caspase, 3/7, 9) were measured. Cleaved PARP, which is a marker of cells undergoing apoptosis, was detected by western blot. For in vivo experiments, we examined the expression of Mieap using surgical specimens (invasive ductal carcinomas (IDCs): 75, ductal carcinoma in situ (DCIS): 27, fibroadenomas (FAs): 18) by immunohistochemistry. Next, we performed methylation-specific PCR (MSP) for Mieap, NIX, and BNIP3 promoters and p53-mutation search using 46 samples that were cryopreserved, among 75 IDC cases used for immunohistochemistry. These studies were approved by the central ethics committee of Gifu University.[Results] The enforced-expression of exogenous Mieap in breast cancer cells induced caspase-dependent apoptosis, with activation of both caspase-3/7 and caspase-9. Immunohistochemistry revealed endogenous Mieap in the cytoplasm in 24/75 (32%) invasive ductal carcinomas (IDCs), 15/27 (55.6%) cases of ductal carcinoma in situ (DCIS), and 16/18 (88.9%) fibroadenomas (FAs) (IDC vs DCIS; p = 0.0389, DCIS vs FA; p = 0.0234, IDC vs FA; p &lt; 0.0001). In IDCs, the Mieap promoter was methylated in 6/46 (13%) cases whereas p53 was mutated in 6/46 (13%) cases. Therefore, the p53/Mieap-regulated mitochondrial quality control pathway was inactivated in 12/46 IDCs (26.1%). Interestingly, all of the tumors derived from the 12 patients with the Mieap-promoter methylation or p53 mutation pathologically exhibited more aggressive and malignant phenotype of breast cancers, resulting in significantly shorter disease-free survival (DFS) (p = 0.021). [Conclusion]These results indicate that p53/Mieap-regulated mitochondrial quality control has a critical role in tumor suppression of breast cancer, possibly in part, through mitochondrial apoptotic pathway.

Citation Format: Futamura M, Gaowa S, Arakawa H, Yoshida K. Possible role of p53/Mieap-regulated mitochondrial quality control as a tumor suppressor in human breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-09-04.

INVESTIGATION OF A PRACTICAL PATIENT DOSE INDEX FOR ASSESSMENT OF PATIENT ORGAN DOSE FROM CONE-BEAM COMPUTED TOMOGRAPHY IN RADIATION THERAPY USING A MONTE CARLO SIMULATION

The purpose of this study was to investigate a practical patient dose index for assessing the patient organ dose from a cone-beam computed tomography (CBCT) scan by comparing eight dose indices, i.e. CTDI100, CTDIIEC, CTDI∞, midpoint doses f(0)PMMA for a cylindrical polymethyl methacrylate (PMMA) phantom, f(0)Ap for an anthropomorphic phantom and f(0)Pat for a prostate cancer patient, as well as the conventional size specific dose estimations (SSDEconv) and modified SSDE (SSDEmod), with organ dose for the prostate (ODprost) obtained via Monte Carlo (MC) simulation. The ODprost was the reference dose used to find the practical dose index at the center of the pelvic region of a prostate cancer patient. The smallest error rate with respect to the ODprost of 19.3 mGy (reference) among eight dose indices was 5% for f(0)Pat. The practical patient dose index was the f(0)Pat, which showed the smallest error with respect to the reference dose.

Radioactive cesium concentrations in coastal suspended matter after the Fukushima nuclear accident

Radioactive cesium concentrations in the suspended matter of the coastal waters around the Fukushima Daiichi Nuclear Power Plant (FDNPP) were investigated between January 2014 and August 2015. The concentrations of radioactive cesium in the suspended matter were two orders higher in magnitude than those determined in the sediment. In addition, we discovered highly radioactive Cs particles in the suspended matter using autoradiography. The geometrical average radioactivity of particles was estimated to be 0.6 Bq at maximum and 0.2 Bq on average. The contribution ratio of highly radioactive Cs particles to each sample ranged from 13 to 54%, and was 36% on average. A major part of the radioactive Cs concentration in the suspended matter around the FDNPP was strongly influenced by the highly radioactive particles. The subsequent resuspension of highly radioactive Cs particles has been suggested as a possible reason for the delay in radioactive Cs depuration from benthic biota.

The effects of sediment transport on temporal variation in radiocesium concentrations in very shallow water off the southern coast of Fukushima, Japan

We studied the very shallow coastal water off Iwaki City, Fukushima Prefecture, and investigated: (1) temporal variation in ¹³⁷Cs concentrations; (2) particle-size distribution of sediments; and (3) the effect on variation by waves, component-fractionated concentration of radiocesium and mineral composition at three sampling stations (Yotsukura, Ena rocky reef and Ena sandy station). There was a decline in ¹³⁷Cs concentrations in sediment samples at all sampling stations between 425 and 1173 days after the accident. All stations had fluctuations in ¹³⁷Cs concentrations between 425 and 800 days. At Ena sandy station and Ena rocky reef stations the declines in ¹³⁷Cs concentrations slowed from about 800 days after the accident. Fluctuations in particle median diameters were seen, as well as in ¹³⁷Cs concentrations. At Yotsukura, where the fluctuation in median diameter was small, a constant decrease in ¹³⁷Cs concentrations was observed. We considered that bioturbation may contribute the constant decrease. At Ena sandy station, where the fluctuation of the median diameter was large, the fluctuation in ¹³⁷Cs concentrations was also large. The movement of sediments was evaluated by the Shields parameter, and results indicated that at any station where the sediment was moved more frequently, the fluctuation in ¹³⁷Cs concentrations was also large. The highly contaminated small particles moved from our stations due to wave action between 425 and 800 days after the accident. The remaining relatively large particles might contribute to the slowing down in reduction of ¹³⁷Cs concentrations from 800 days after the accident. However, the ¹³⁷Cs concentrations in sediments in very shallow water off the southern coast of Fukushima may continue to decline over time.

Distribution of hydrocarbons in seabed sediments derived from tsunami-spilled oil in Kesennuma Bay, Japan

As a result of the 2011 Great East Japan earthquake, about 11,000kL of fuel oil was spilled into Kesennuma Bay, Miyagi Prefecture. This oil either accumulated in seabed sediments or was burned in a marine fire on the sea surface. We investigated spatial and temporal variations in the concentrations of oil and hydrocarbons. The maximum concentrations of n-hexane extract (NHE), total petroleum hydrocarbon (TPH), and polycyclic aromatic hydrocarbons (PAHs) in the sediments in 2012 were 8000, 1200, and 16.2mg/kg (DW), respectively. NHE and TPH concentrations were high in the inner and west bay, and PAHs concentrations were high in the east bay. NHE and PAH concentrations didn't change; however, TPH concentrations decreased significantly with time. The total NHE in the sediment across the whole bay was estimated at 1685kL and there was still about 13% of the original amount in the sediment in December 2014.

Note: Optimization of magnifying a polarization angle with Littrow layout blazed gratings

Magnification of a polarization angle with Littrow layout gratings has been developed. High magnification with a factor of 7.7 using two gratings in Littrow layout was experimentally proved. The magnification range was investigated by calculation at a wavelength of 10.6 μm. The method can be applied for a high magnification factor >30. Larger groove numbers and smaller blaze angles are suitable for the large magnification. Statistical fluctuation of the diffracted polarization angle is compared with that of the incident polarization angle.

A Concept of Cross-Ferroic Plasma Turbulence

The variety of scalar and vector fields in laboratory and nature plasmas is formed by plasma turbulence. Drift-wave fluctuations, driven by density gradients in magnetized plasmas, are known to relax the density gradient while they can generate flows. On the other hand, the sheared flow in the direction of magnetic fields causes Kelvin-Helmholtz type instabilities, which mix particle and momentum. These different types of fluctuations coexist in laboratory and nature, so that the multiple mechanisms for structural formation exist in extremely non-equilibrium plasmas. Here we report the discovery of a new order in plasma turbulence, in which chained structure formation is realized by cross-interaction between inhomogeneities of scalar and vector fields. The concept of cross-ferroic turbulence is developed, and the causal relation in the multiple mechanisms behind structural formation is identified, by measuring the relaxation rate and dissipation power caused by the complex turbulence-driven flux.

Effects of sediment influx on the settlement and survival of canopy-forming macrophytes

Kelp forests on coastal rocky shores are negatively impacted by sudden sediment loads that can occur with storms and floods. Using laboratory experiments, we studied the effects of sediment deposition on the survival of the large brown alga Eisenia bicyclis juveniles (zoospores and gametophytes) to quantify the potential impacts of particulate matter on kelp forests. The zoospore adhesion rate and the gametophyte survival and growth rates all declined markedly with increasing sediment load, particularly with smaller particle diameter. Using experimental results, we derived an equation to calculate the rate of initial kelp depletion with sediment load based on the quantity and size distribution of sediment particles. The equation enabled the estimation of E. bicyclis depletion rates in the field by measurement of particle quantity and diameter distribution of sediments on the reef substrate.

Biological half-life of radioactive cesium in Japanese rockfish Sebastes cheni contaminated by the Fukushima Daiichi nuclear power plant accident

Since the Fukushima accident in March 2011 the concentration of radioactive cesium in Japanese rockfish (Sebastes cheni) has been decreasing slower than other fish species. The aim of this study was therefore to investigate the possibility of slow elimination rate (i.e., relatively longer Tb) as one of the reasons for the slow decrease in (137)Cs concentrations in Japanese rockfish (S. cheni). To do this, we reared twenty-three individuals of this species for a period of about 1 year, during which time we measured the (137)Cs concentrations and γ-ray spectra 14 times by using a high-efficiency NaI(Tl) scintillator. We then examined the relationship between the (137)Cs concentrations and the total length of each individual. We estimated the biological half-life (Tb, day) for each individual using the total number of (137)Cs counts in the energy region, and examined the effects of total length and (137)Cs concentration on Tb by generalized linear model (GLM). We also examined the effect of sex, total length, seawater temperature, and the (137)Cs concentration of seawater on temporal changes in the (137)Cs count reduction rate by GLM. There was no clear relationship between the corrected whole-body (137)Cs concentrations and the total length in females, however there was a significant positive correlation between these two variables in males. The difference between males and females may be attributable to variation in the degree of dilution because of variable growth of individuals, and suggests that the (137)Cs concentrations of small individuals may be greatly diluted because of faster growth. However, there was no significant difference in Tb between sexes. The mean Tb (±SD) in all individuals was 269 (±39) days; this Tb value is 2.7-5.4 times longer than past Tb values (marine fish: 50-100 days), and is thought to be one of the reasons for the slower decrease in (137)Cs concentrations in this species than other fish species on the coast of Fukushima. The GLM showed significant effects of both total length and (137)Cs concentration on Tb, which may reflect a reduction in the metabolic rate with increased body size (i.e., aging) and gradient of concentration against seawater. The GLM also showed a significant positive effect of seawater temperature on the reduction rate of the (137)Cs counts (D, day(-1)). Therefore, D was clearly related to seasonal variations in the temperature of seawater, and this relationship may be attributable to changes in the metabolic rate that are controlled by variations in the seawater temperature. From these measurements, we examined the processes that control reductions in (137)Cs radioactivity.

Note: Magnification of a polarization angle with a Littrow layout brazed grating

A new method to magnify a small polarization angle with brazed gratings has been developed. In the method, difference in diffraction efficiency for S and P polarization components is used. The magnification dependence on the incident angle can be small by arranging the grating in Littrow layout. A magnification with a factor ~2.7 has been demonstrated for a 10.6 μm CO2 laser beam as expected from a calculation. The method is applicable in many polarimetry fields.

Natural course of dissecting vertebrobasilar artery aneurysms without stroke

BACKGROUND AND PURPOSE

The natural history and therapeutic management of dissecting vertebrobasilar aneurysms without ischemic or hemorrhagic stroke (nonstroke dissecting vertebrobasilar aneurysms) are not well-established. We conservatively followed patients with nonstroke dissecting vertebrobasilar aneurysms and evaluated the factors related to clinical and morphologic deterioration.

MATERIALS AND METHODS

One hundred thirteen patients were enrolled and divided by clinical presentation at diagnosis: asymptomatic (group 1, n = 52), pain only (group 2, n = 56), and mass effect (group 3, n = 5). Patients were conservatively managed without intervention and antithrombotic therapy. Clinical outcomes and morphologic changes were analyzed.

RESULTS

A total of 113 patients who were diagnosed with nonstroke dissecting vertebrobasilar aneurysm had a mean follow-up of 2.9 years (range, 27 days to 8 years). Throughout that period, 1 patient in group 1 (1.9%) and 1 patient in group 2 (1.8%) showed clinical deterioration due to mass effect, and 1 patient in group 3 (20%) developed ischemic stroke followed by subarachnoid hemorrhage. Most patients (97.3%) were clinically unchanged. Three patients who had clinical deterioration showed aneurysm enlargement (P < .001). Aneurysms remained morphologically unchanged in 91 patients (80.5%). Aneurysm enlargement was seen in 5 patients (4.4%); risk of enlargement was significantly associated with either maximum diameter (hazard ratio = 1.30; 95% CI, 1.11-11.52; P = .001) or aneurysm ≥10 mm (hazard ratio = 18.0; 95% CI, 1.95-167; P = .011).

CONCLUSIONS

The natural course of these lesions suggests that acute intervention is not always required and close follow-up without antithrombotic therapy is reasonable. Patients with symptoms due to mass effect or aneurysms of >10 mm may require treatment.

Validation and initial application of a semiautomatic aneurysm measurement software: a tool for assessing volumetric packing attenuation

BACKGROUND AND PURPOSE

Precise aneurysm measurements and volume embolization ratios are essential for long-term durability of endovascular coil embolization. We evaluated the accuracy of newly developed semiautomatic cerebral aneurysm measurement software, NeuroVision, and explored the value of volume embolization ratio in the prediction of re-treatment.

MATERIALS AND METHODS

We compared software-derived volume measurements of 4 silicone aneurysm models with those calculated with an approximation formula and ground truth values (validation study). We used NeuroVision to retrospectively evaluate outcomes of 100 unruptured aneurysms (97 patients) treated with embolization (clinical study). Aneurysm size (height, width, and neck), volume, and volume embolization ratios were calculated for 3 groups (stable, recanalization, and re-treatment) and were compared.

RESULTS

This validation study illustrated higher accuracy of NeuroVision in computing aneurysm volume compared with an approximation formula: percentage absolute errors were 4.50% ± 3.18% and 23.07% ± 17.60%, with maximal percentage absolute errors of 8.99% and 45.63%, respectively. Of 100 unruptured aneurysms, 20 recanalized and 12 were re-treated. Average volume embolization ratios of stable and re-treated aneurysms were 24.88% ± 5.91% and 20.50% ± 4.06%, respectively (P ≤ .01). The optimal volume embolization ratio cutoff point for re-treatment was < 19.15%, at which the Youden index was 0.50 (sensitivity, 58.33%; specificity, 87.50%; area under the receiver operating characteristic curve, 0.74).

CONCLUSIONS

The NeuroVision software provided accurate aneurysm volume measurements and may be a useful standardized tool to measure aneurysm size and volume, especially for multicenter clinical studies. Volume embolization ratio may be a valuable predictor of aneurysm occlusion changes.

'I-shaped' sign in the upper mediastinum: a novel potential marker for antenatal diagnosis of d-transposition of the great arteries

OBJECTIVES

To investigate the 'I-shaped' sign as a novel echocardiographic marker for antenatal diagnosis of d-transposition of the great arteries (dTGA) in routine cardiac examination, and to compare its prevalence in fetuses with dTGA, those with other congenital heart diseases (CHDs) and those with normal structural hearts.

METHODS

This retrospective evaluation involved 1134 fetuses undergoing echocardiography to screen for CHD over a 4-year period. I-shaped sign was defined as the characteristic appearance of the aortic arch, resembling the letter 'I', from the most anterior to the most posterior point of the descending aorta visible in the three vessels and trachea view. The frequency of this sign was evaluated in cases with dTGA, those with other cardiac defects and those with normal cardiac structures.

RESULTS

CHD was diagnosed in 671 (59.1%) cases, of which 31 (4.6%) had dTGA. I-shaped sign was observed in 30/31 (96.8%) cases of dTGA, compared with 31/640 (4.8%) cases with other cardiac anomalies, which included single ventricle with pulmonary atresia or severe pulmonary stenosis, hypoplastic left heart syndrome with aortic atresia, corrected transposition of the great arteries, and double outlet right ventricle with malposition of the great arteries. I-shaped sign was detected significantly more frequently in the dTGA group compared with the normal group and with the other CHDs group (both P < 0.001) and had 96.8% sensitivity and 97.1% specificity for diagnosis of dTGA. Importantly, I-shaped sign was never observed in fetuses with structurally normal hearts.

CONCLUSIONS

Detection on echocardiography of an extremely long vessel with a marked I-shape should raise suspicion of cardiac anomaly, especially dTGA. This marker may therefore aid in the prenatal diagnosis of dTGA during routine ultrasound examination.

Justification of unruptured intracranial aneurysm repair: a single-center experience

BACKGROUND AND PURPOSE

Whether to treat UIAs is controversial. The aim of the study was to compare the clinical outcome of patients with UIAs who were either treated conservatively or preventively.

MATERIALS AND METHODS

Patients with UIAs referred to our institution were prospectively enrolled in the study. Data collected included baseline characteristics, aneurysmal features, and procedural and follow-up information. Preventive treatment was recommended if the aneurysm was larger than 5 mm and was considered safely treatable. Endovascular surgery was the first-line therapy if the aneurysmal shape was appropriate for coiling.

RESULTS

From January 2003 through April 2008, a total of 879 patients with 1110 UIAs were enrolled; 325 patients with 369 UIAs (mean size, 7.8 mm) were treated (treatment group), and 603 patients with 741 UIAs (mean size, 4.4 mm) were managed conservatively (observation group). Mean follow-up was 692.5 days (1405.5 person-years). In the observation group, 26 aneurysms (3.5%) had ruptured (1.8% per year; 1405.5 person-years), 10 patients died, and 7 were disabled (mRS, 3-6: 2.8%). Aneurysmal size was a significant risk factor for rupture (P = .001). The treatment group included aneurysms treated either with coiling (n=315), clipping (n=32), or a combined approach (n=9); 1 patient died, and 3 were disabled (mRS, 3-6: 1.2%). Therapeutic intervention was equal (UIAs of all sizes) or superior (UIAs > 5 mm; P = .025) to conservative management.

CONCLUSIONS

Treatment of UIAs was justified in aneurysms larger than 5 mm, and EVS can be safely applied to nearly 90% of UIAs.

Development of a novel telomerase assay using the PPDK-luciferin-luciferase detection system

Telomerase participates in malignant transformation or immortalization of cells, and has attracted attention as an anticancer drug screening and diagnostic tumor marker. We developed a novel telomerase assay called the PPDK-luciferin-luciferase system bioluminescence assay (PLLBA) using pyruvate phosphate dikinase (PPDK). In this assay, pyrophosphate produced by the telomerase reaction and polymerase chain reaction (PCR) is converted to ATP by PPDK, and ATP is detected by the firefly luciferin-luciferase reaction. In this work, telomerase substrate was obtained in accordance with the telomeric repeat amplification protocol (TRAP). Telomerase-positive (500 cells/assay), -inactive (heated for 10 min at 85 °C) and -negative (only Chaps lysis buffer) samples were used. As a result, the findings clearly showed that the signal-to-noise (S/N) ratio of the positive cells was 39.5. After the telomerase reaction and PCR, PLLBA was completed ~ 120 s later. A high level of reproducibility was obtained with - coefficient of variation (CV) of 4.1% (positive cells). The detection limit for cells using telomerase was one cell per assay. This assay for telomerase activity was also shown to be adaptable to human cancer-derived cell lines.

Shift in apparent contrast of disc at Secchi disc depth in coastal sea areas

The relationship between Secchi disc depth and amount of suspended material in seawater varies depending on the particular marine area. To identify the cause of this dependence, we calculated the apparent contrast (C (SD)) at each Secchi disc depth in different coastal sea areas. When the turbidity from the surface to the Secchi disc depth was uniform, the C (SD) was distributed in the range of 1.3 to 0.001 for a Secchi disc depth (Z (SD)) of 2-18 m. Z (SD) tended to decrease as C (SD) became larger. The dominant wavelength for the sea color was 475-500 nm for a Secchi disc depth of 13-18 m, and 500-575 nm for a Z(SD) of 2-6 m, shifting to longer wavelengths as the Secchi disc depth increased. That is, when Z (SD) decreased, the dominant wavelength of the sea color, and the C (SD) increased simultaneously. This phenomenon seems to occur because the contrast threshold for the human eye is higher at longer wavelengths. In other words, the contrast threshold is visibly indistinguishable when the apparent contrast in ocean waters with low Secchi disc depths is high. This phenomenon occurs because the human eye is affected by the color of the sea.

Identification of errors in the electron density measurements of a tangential interferometer∕polarimeter system during a tokamak discharge

A new method for the comparative verification of electron density measurements obtained with a tangential interferometer and a polarimeter during a discharge is proposed. The possible errors associated with the interferometer and polarimeter are classified by the time required for their identification. Based on the characteristics of the errors, the fringe shift error of the interferometer and the low-frequency noise of the polarimeter were identified and corrected for the JT-60U tangential interferometer∕polarimeter system.