Publications by authors named "Seiya Nagao"

38 Publications

The input-output balance of microplastics derived from coated fertilizer in paddy fields and the timing of their discharge during the irrigation season.

Chemosphere 2021 Sep 15;279:130574. Epub 2021 Apr 15.

School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo, 169-8555, Japan.

Polymer-based microcapsules derived from coated fertilizers are not recovered after use. Therefore, they are a source of microplastics to the agricultural lands and coastal areas of Japan. In this study, we investigated the input-output balance of microcapsules in three paddy fields and the timing of microcapsule discharge from the fields with the aim of developing effective techniques to reduce microcapsule discharge. Microcapsules were discharged from the paddy fields primarily during puddling, when the weir plate was overflowed, and when surface drainage was implemented. About 50% of the total discharge during the irrigation period occurred during puddling, which is a process for leveling paddy fields. Therefore, contamination of the surrounding environment by microcapsules from paddy fields can be effectively reduced by preventing the release of microplastics from paddy fields during puddling. We also showed that the total microcapsule discharge cannot be controlled solely by irrigation water management, such as by adjusting the height of the weir plate. We found that about 0.067-0.076% of the total number of microcapsules accumulated in the soil of the paddy fields was discharged during the irrigation season in 2020. Furthermore, 70% of the microcapsules discharged from one field in 2020 had resided in the soil for at least two years. The use as fertilizer coatings of biodegradable polymers that would degrade completely in the soil within a few years could therefore substantially reduce the amount of microplastics released into the ocean from agricultural fields, and their development is thus urgently needed.
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http://dx.doi.org/10.1016/j.chemosphere.2021.130574DOI Listing
September 2021

Development of a gel-in-oil emulsion as a transdermal drug delivery system for successful delivery of growth factors.

J Biosci Bioeng 2021 Jul 18;132(1):95-101. Epub 2021 Apr 18.

Department of Chemical Engineering, Faculty of Engineering, Graduate School, Kyushu University, 744 Motooka, Nishi-ku, Fukuoka 819-0395, Japan. Electronic address:

Growth factors (GFs) are indispensable in regenerative medicine because of their high effectiveness. However, as GFs degenerate easily, the development of a suitable carrier with improved stability for GFs is necessary. In this study, we developed a gel-in-oil (G/O) emulsion technology for the transdermal delivery of growth factors. Nanogel particles prepared with heparin-immobilized gelatin that can bind growth factors were dispersed in isopropyl myristate. The particle size of the G/O emulsion could be controlled by changing the surfactant concentration, volume ratio of the water phase to the oil phase, and gelatin concentration. In vitro skin penetration studies showed better penetration through the stratum corneum of fluorescent proteins containing G/O emulsions than of the aqueous solution of GF. Similarly, an in vivo study showed an angiogenesis-inducing effect after transdermal application of GF-immobilized G/O emulsion. Angiogenesis in mice was confirmed owing to both an increased blood vessel network and higher hemoglobin content in the blood. Therefore, the G/O emulsion could be a promising carrier for GFs with better stability and can effectively deliver GFs at the target site.
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http://dx.doi.org/10.1016/j.jbiosc.2021.03.015DOI Listing
July 2021

Characteristics and unique sources of polycyclic aromatic hydrocarbons and nitro-polycyclic aromatic hydrocarbons in PM2.5 at a highland background site in northwestern China.

Environ Pollut 2021 Apr 18;274:116527. Epub 2021 Jan 18.

Institute of Nature and Environmental Technology, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan; Institute of Medical, Pharmaceutical and Health Sciences, Kanazawa University, Kakuma-machi, Kanazawa, 920-1192, Japan. Electronic address:

Polycyclic aromatic hydrocarbons (PAHs) and nitro-PAHs (NPAHs) in PM were first observed at a background site (Yuzhong site: YZ site) in the northwestern highlands of China in five seasonal campaigns. Compared with major northwestern cities, PAHs and NPAHs at the YZ site were at a lower level but showed consistent seasonal differences. The PAH and NPAH concentrations peaked in the winter campaigns, which were 36.11 ± 6.54 ng/m and 418.11 ± 123.55 pg/m, respectively, in winter campaign 1 and 28.97 ± 10.07 ng/m and 226.89 ± 133.54 pg/m, respectively, in winter campaign 2. These values were approximately a dozen times larger those in other campaigns. The diagnostic ratios indicate that vehicle emissions were the primary source of the PAHs throughout the five campaigns, and coal and biomass combustion also contributed during the winter, summer, and fall campaigns. Among NPAHs, 2-nitrofluoranthene and 2-nitropyrene were generated through OH radical-initiated reactions during atmospheric transport, while 1-nitropyrene came from combustion sources. There is an observation worth pondering, which is that the ratio between pyrene and fluoranthene increased abnormally in the spring and fall campaigns, which is presumably caused by the burning of Tibetan barley straw in the northwestern highlands. The backward trajectories over Tibetan areas in Qinghai and southwestern Gansu are consistent with this hypothesis. In addition, this study reported for the first time that the burning of Tibetan barley straw has become a seasonal contributor to air pollution in northwestern China and is participating in the atmospheric transport of air pollutants driven by the monsoon in East Asia, which urgently requires further research.
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http://dx.doi.org/10.1016/j.envpol.2021.116527DOI Listing
April 2021

Accumulation of microcapsules derived from coated fertilizer in paddy fields.

Chemosphere 2021 Mar 7;267:129185. Epub 2020 Dec 7.

School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo, 169-8555, Japan.

Japanese agriculture uses large amounts of plastics. Fertilizer-containing plastic microcapsules with a diameter of 2-5 mm ("coated fertilizer") are not recovered after use, and after diffusion of the fertilizer components these microcapsules are found in large quantities, not only on agricultural land but also along the coast of Japan. Here, we investigated the accumulation of microcapsules derived from coated fertilizer in 19 paddy fields. Microcapsules were detected in all of the paddy fields surveyed, at concentrations in the range of 6-369 mg/kg (mean 144 mg/kg)-much higher than the concentrations of microplastics in farmlands in other countries. There was no difference in mean microcapsule concentration between sampling sites with continuous rice cultivation and those with crop rotation, but that of a paddy field that had never received coated fertilizer was significantly lower. Examination of the spatial distribution of microcapsules in one paddy field showed that there was a hot spot with a high concentration near the drainage outlet. This was likely due to the strong influence of irrigation water flowing from the water inlet to the drainage outlet. The amount of microcapsules accumulated in Japanese paddy fields, as estimated from our results, and the amount applied to the fields, as estimated from the statistics, were almost equivalent. Therefore, most of the microcapsules that have already been applied to paddy fields may continue to accumulate. The impact of these high concentrations of microcapsules on the soil environment needs to be assessed.
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http://dx.doi.org/10.1016/j.chemosphere.2020.129185DOI Listing
March 2021

The role of coated fertilizer used in paddy fields as a source of microplastics in the marine environment.

Mar Pollut Bull 2020 Dec 6;161(Pt B):111727. Epub 2020 Oct 6.

School of Creative Science and Engineering, Waseda University, 3-4-1 Okubo, Shinjuku, Tokyo 169-8555, Japan.

Fixed-point and multi-point field survey was conducted to determine the actual contamination of the Japanese coast by microcapsules derived from coated fertilizers. The results indicated that the amount of microcapsules increased during the irrigation season (9423-74,869 pieces/m) and decreased in the non-irrigation season (77-1471 pieces/m). Microcapsules accounted for 90% of all microplastics sampled during the irrigation season. The lack of correlation between the area of agricultural land in the watershed and the microcapsule density on the coast suggested that the density of microcapsules on the coast was not only dependent on the total load to the ocean, but also on topographic and meteorological conditions. More than 90% of the microcapsules collected from the shoreline were made of polyethylene. Scanning electron microscopic observation of the surface of the microcapsules revealed that portions of the microcapsules were removed as secondary microplastics in the process of migration to the ocean.
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http://dx.doi.org/10.1016/j.marpolbul.2020.111727DOI Listing
December 2020

Circulation paths of Cs in seawater southwest of Japan in 2018 and 2019.

J Environ Radioact 2020 Nov 8;223-224:106382. Epub 2020 Sep 8.

Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Nomi, Ishikawa, 923-1224, Japan.

The spatial variations of low-level Cs concentrations (activities) in seawater off the Japanese Archipelago, particularly in the eastern East China Sea (ECS), in 2018 and 2019 were examined. The Cs concentrations, decay-corrected to the date of the Fukushima Dai-ichi Nuclear Power Plant accident, in seawaters were 0.5-2.0 mBq/L. High Cs concentrations (1.1-2.0 mBq/L) of the Kuroshio Current subsurface water (densities of 25-26σ) in the eastern ECS could indicated the contribution of the subtropical mode water from the Pacific Ocean side, and total column inventories were 330-426 Bq/m. In contrast, as indicated by the same Cs concentration level at the surface of the eastern ECS and Sea of Japan, larger portions of the subsurface waters remained in the ECS and Yellow Sea side in response to the existence of the shallow Tsushima Strait.
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http://dx.doi.org/10.1016/j.jenvrad.2020.106382DOI Listing
November 2020

Desorption Behavior of Fukushima-derived Radiocesium in Sand Collected from Yotsukura Beach in Fukushima Prefecture.

Anal Sci 2020 ;36(5):569-575

Woods Hole Oceanographic Institution.

Beach sand samples were collected along a coastal area 32 km south of the Fukushima Daiichi Nuclear Power Plant (FDNPP) in Fukushima Prefecture, Japan, 5 years after the FDNPP accident. Desorption experiments were performed on the sand samples using seawater in a batch experimental system to understand the forms of existence of radiocesium in sand and their desorption behavior in a coastal environment. The percentage of radiocesium desorption decreased exponentially with an increase in the number of desorption experiments for the four sand samples, with Cs radioactivity from 16 to 1077 Bq kg at surface and deeper layers from three sites. Total desorption percentage ranged from 19 to 58% in 12 desorption experiments. The results indicate that the weak adsorption varies with the sampling sites and their depth layer. To understand the desorption behavior of radiocesium in the sand samples, the desorption experiments were performed for a sand sample by using natural and artificial seawater, and NaCl solution in the presence and absence of KCl. The Cs desorption from the sand collected at a depth of 100 - 105 cm from the ground surface (Cs radioactivity 1052 ± 25 Bq kg) was 0.1% by ultrapure water, 3.7% by 1/4 seawater and 7.1% by 1/2 seawater, 2.2% by 470 mM NaCl solution (corresponding to a similar concentration of seawater) and 10 - 12% by seawater, artificial seawater and 470 mM NaCl + 8 mM KCl solution. These results indicate that about 10% of radiocesium adsorbed on the sand is mainly desorbed by ion exchange of potassium ion in seawater, though the concentration of major cation, or sodium ion, in seawater makes a small contribution on Cs desorption from the sand samples.
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http://dx.doi.org/10.2116/analsci.19SBP08DOI Listing
January 2021

Interannual Survey on Polycyclic Aromatic Hydrocarbons (PAHs) in Seawater of North Nanao Bay, Ishikawa, Japan, from 2015 to 2018: Sources, Pathways and Ecological Risk Assessment.

Int J Environ Res Public Health 2020 02 1;17(3). Epub 2020 Feb 1.

Division of Material Chemistry, Graduate School of Natural Science and Technology, Kanazawa University, Kanazawa 920-1192, Japan.

To improve the understanding of the emission sources and pathways of polycyclic aromatic hydrocarbons (PAHs) in the coastal environments of remote areas, their particulate and dissolved concentrations were analyzed on a monthly basis from 2015 to 2018 in surface waters of Nanao Bay, Japan. The concentration of the targeted 13 species of PAHs on the United States Environmental Protection Agency (USEPA) priority pollutant list in dissolved and particle phases were separately analyzed by high-performance liquid chromatography (HPLC) coupled to a fluorescence detector. Particulate and dissolved PAHs had average concentrations of 0.72 ng∙L and 0.95 ng∙L, respectively. While most of the samples were lower than 1 ng∙L, abnormally high levels up to 10 ng∙L were observed in the winter of 2017-2018 for particulate PAHs. Based on the isomer ratios of Flu to Flu plus Pyr, it was possible to determine that the pyrogenic loads were greater than the petrogenic loads in all but four out of 86 samples. The predominant environmental pathway for PAHs in winter was determined to be long-range atmospheric transportation fed by the East Asian winter monsoon, while for the summer, local sources were more relevant. By the risk quotients method, it was determined that PAHs in surface seawater presented a very low risk to marine life during the interannual survey.
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http://dx.doi.org/10.3390/ijerph17030904DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7038190PMC
February 2020

Temporal Variations of Polycyclic Aromatic Hydrocarbons in the Seawater at Tsukumo Bay, Noto Peninsula, Japan, during 2014-2018.

Int J Environ Res Public Health 2020 01 30;17(3). Epub 2020 Jan 30.

Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa 920-1192, Japan.

Concentrations of phase-partitioning 13 polycyclic aromatic hydrocarbons (PAHs) in seawater were investigated in the Tsukumo Bay, Noto Peninsula, Japan, during 2014-2018, to improve the understanding of the environmental behavior of PAHs in the coastal areas of the Japan Sea. Total PAH (particulate plus dissolved) concentrations in surface seawater were in the range 0.24-2.20 ng L (mean 0.89 ng L), an order of magnitude lower than the mean values observed in the Japan Sea in 2008 and 2010. Although the PAH contamination levels during 2014-2018 were significantly lower than those in the East China Sea, the levels increased from 2014 to 2017 and were maintained at the higher level during 2017-2018. The main sources of particulate and dissolved PAHs during 2014-2018 were combustion products, of which the former were more influenced by liquid fossil-fuel combustion and the latter by biomass or coal combustion. The increase in particulate PAH concentrations in October-December during 2014-2018 was due to the impact of PAH-rich airmasses transported from the East Asian landmass in the northwesterly winter monsoon winds. The increase in dissolved PAH levels during July-September in 2014, 2016, 2017, and 2018 indicates that the Tsukumo Bay is possibly impacted by the PAH-rich summer continental shelf water transported by the Coastal Branch of the Tsushima Warm Current, which flows into the Japan Sea from the East China Sea.
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http://dx.doi.org/10.3390/ijerph17030873DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7037195PMC
January 2020

A nano-sized gel-in-oil suspension for transcutaneous protein delivery.

Int J Pharm 2019 Aug 2;567:118495. Epub 2019 Jul 2.

Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan; Division of Biotechnology, Center for Future Chemistry, Kyushu University, Japan. Electronic address:

We developed a new oil-based delivery system for transdermal protein delivery, a gel-in-oil (G/O) nanosuspension, where gelatin-based hydrogel was coated with hydrophobic surfactants. The high entrapment efficiency of a model protein, phycocyanin (PC), into nano-sized gelatin hydrogel particles was achieved. Spectroscopic evaluation of PC suggested that the G/O nanosuspension could retain the functional form of PC in isopropyl myristate. In vitro skin permeation studies showed that the G/O nanosuspension facilitated the delivery of PC through the stratum corneum of Yucatan micropig skin.
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http://dx.doi.org/10.1016/j.ijpharm.2019.118495DOI Listing
August 2019

Low levels of Fukushima Dai-ichi NPP-derived radiocesium in marine products from coastal areas in the Sea of Japan (2012-2017).

Appl Radiat Isot 2019 Mar 28;145:187-192. Epub 2018 Dec 28.

Low Level Radioactivity Laboratory, Kanazawa University, Wake O-24, Nomi, Ishikawa 923-1224, Japan.

Radiocesium concentrations in marine biota in coastal areas of the Sea of Japan were < ~0.005-0.02 Bq/kg-wet and ~0.01-0.18 Bq/kg-wet for Cs and Cs, respectively (2012-2017). The biota-seawater concentration factors were ~25-100, which approximately agreed with those of Cs recorded before FDNPP accident. The low levels of Cs in marine biota were likely taken up from ambient seawaters. The total of radiocesium concentrations is now equivalent to that in the 1990s based on the ambient water data.
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http://dx.doi.org/10.1016/j.apradiso.2018.12.029DOI Listing
March 2019

Radiocesium dynamics in the aquatic ecosystem of Lake Onuma on Mt. Akagi following the Fukushima Dai-ichi Nuclear Power Plant accident.

Sci Total Environ 2018 May 13;622-623:1153-1164. Epub 2017 Dec 13.

Low Level Radioactivity Laboratory, Kanazawa University, Japan.

Understanding ecosystem dynamics of radionuclides is necessary to ensure effective management for food safety. The Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident on March 11, 2011 released large amounts of radiocesium (Cs and Cs) and contaminated the environment across eastern Japan. In this study, we aimed to elucidate the temporal dynamics of Cs in the aquatic ecosystem of Lake Onuma on Mt. Akagi. The effective ecological half-life (T) of Cs in fishes, western waterweed (Elodea nuttallii), seston (phytoplankton and zooplankton), and lake water was estimated using survey data of Cs concentration collected from 2011 to 2016, and single- and two-component decay function models (SDM and TDM, respectively). The decay processes of Cs concentrations in wakasagi (Hypomesus nipponensis), pale chub (Zacco platypus), phytoplankton, and total Cs concentrations of the water column (WC) in the lake were well suited by the TDMs. The T in the fast component of the TDMs in these samples ranged from 0.49 to 0.74years. The T in the slow component of the TDMs could converge towards the physical half-life of Cs. Nearly five and a half years after the FDNPP accident, we concluded that Cs concentrations approached a state of dynamic equilibrium between some aquatic organisms (wakasagi, pale chub, and phytoplankton) and the environment (lake water). However, the decay processes of Cs concentrations in Japanese dace (Tribolodon hakonensis), western waterweed, zooplankton, and particulate- and dissolved-forms in the WC were better predicted for the SDM. The total Cs concentrations in inflowing river and spring waters were one to two orders of magnitude lower than lake water under normal flow conditions. However, particulate Cs contamination level in the river water was high after heavy rains. Overall, Cs contamination levels have significantly decreased in Lake Onuma, but monitoring surveys should be continued for further understanding of the reduction processes.
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http://dx.doi.org/10.1016/j.scitotenv.2017.12.017DOI Listing
May 2018

Vertical profiles of Fukushima Dai-ichi NPP-derived radiocesium concentrations in the waters of the southwestern Okhotsk Sea (2011-2017).

J Environ Radioact 2018 Dec 1;192:580-586. Epub 2018 May 1.

Low Level Radioactivity Laboratory, Kanazawa University, Wake O-24, Nomi, Ishikawa, 923-1224, Japan.

We examined the vertical Cs and Cs concentration profiles in the southwestern Okhotsk Sea in 2011, 2013, and 2017. In June 2011, atmospheric deposition-derived Cs from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) was detected at depths of 0-200 m (0.06-0.6 mBq/L). In July 2013, Cs detected at depths of 100-200 m (∼0.05 mBq/L) was ascribed to the transport of low-level Cs-contaminated water and/or the convection of radioactive depositions (<0.03 mBq/L at depths of 0-50 m). In July 2017, Cs was detected in water samples at depths above 300 m (0.03-0.05 mBq/L), and the inventory, decay-corrected to the FDNPP accident date, exhibited its maximum value (85 Bq/m) during this period. Combining temperature-salinity data with the concentrations of global fallout-derived Cs led to a plausible explanation for this observation, which is a consequence of re-entry of FDNPP-derived radiocesium through the Kuril Strait from the northwestern North Pacific Ocean to the Okhotsk Sea and subsequent mixing with the south Okhotsk subsurface layer until 2017.
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http://dx.doi.org/10.1016/j.jenvrad.2018.04.021DOI Listing
December 2018

Radiocesium distribution in aggregate-size fractions of cropland and forest soils affected by the Fukushima nuclear accident.

Chemosphere 2018 Aug 18;205:147-155. Epub 2018 Apr 18.

Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Ishikawa 923-1224, Japan.

The Fukushima Daiichi nuclear power plant accident caused serious radiocesium (Cs) contamination in soils in a range of terrestrial ecosystems. It is well documented that the interaction of Cs with soil constituents, particularly clay minerals, in surface soil layers exerts strong control on the behavior of this radionuclide in the environment; however, there is little understanding of how soil aggregation-the binding of soil particles together into aggregates-can affect the mobility and bioavailability of Cs in soils. To explore this, soil samples were collected at seven sites under different land-use conditions in Fukushima and were separated into four aggregate-size fractions: clay-sized (<2 μm); silt-sized (2-20 μm); sand-sized (20-212 μm); and macroaggregates (212-2000 μm). The fractions were then analyzed for Cs content and extractability and mineral composition. In forest soils, aggregate formation was significant, and 69%-83% of Cs was associated with macroaggregates and sand-sized aggregates. In contrast, there was less aggregation in agricultural field soils, and approximately 80% of Cs was in the clay- and silt-sized fractions. Across all sites, the Cs extractability was higher in the sand-sized aggregate fractions than in the clay-sized fractions. Mineralogical analysis showed that, in most soils, clay minerals (vermiculite and kaolinite) were present even in the larger-sized aggregate fractions. These results demonstrate that larger-sized aggregates are a significant reservoir of potentially mobile and bioavailable Cs in organic-rich (forest and orchard) soils. Our study suggests that soil aggregation reduces the mobility of particle-associated Cs through erosion and resuspension and also enhances the bioavailability of Cs in soils.
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http://dx.doi.org/10.1016/j.chemosphere.2018.04.092DOI Listing
August 2018

Radiocesium in seawater, sediments, and marine megabenthic species in coastal waters off Fukushima in 2012-2016, after the 2011 nuclear disaster.

Mar Environ Res 2018 Jun 30;137:206-224. Epub 2018 Mar 30.

Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa, Ishikawa 920-1192 Japan.

In bottom-sediment samples collected in 2012 from a coastal strip (∼30 km × 120 km) off the Fukushima Daiichi Nuclear Power Plant (FDNPP), radiocesium activity concentrations were generally higher south of the FDNPP, with high activity concentration patches in the north. In periodic surveys conducted at nearshore sites during 2012-2016, no clear temporal trends were observed in radiocesium activity concentrations in seawater or bottom sediment, and activity concentrations were higher in fish than in invertebrates. During 2012-2014, radiocesium activity concentrations tended to decrease in fish, but during 2012-2013 in the south, some increases were observed. Radiocesium activity concentrations were significantly higher in some fish (e.g., Okamejei kenojei) directly offshore and south of the FDNPP than in the north. Activity concentrations in fish stomach contents were significantly correlated with those in muscle tissue, suggesting that the consumption of contaminated prey contributed greatly to radiocesium contamination in demersal fish.
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http://dx.doi.org/10.1016/j.marenvres.2018.03.014DOI Listing
June 2018

Unexpected source of Fukushima-derived radiocesium to the coastal ocean of Japan.

Proc Natl Acad Sci U S A 2017 10 2;114(42):11092-11096. Epub 2017 Oct 2.

Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Kanazawa 920-1192, Japan.

There are 440 operational nuclear reactors in the world, with approximately one-half situated along the coastline. This includes the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), which experienced multiple reactor meltdowns in March 2011 followed by the release of radioactivity to the marine environment. While surface inputs to the ocean via atmospheric deposition and rivers are usually well monitored after a nuclear accident, no study has focused on subterranean pathways. During our study period, we found the highest cesium-137 (Cs) levels (up to 23,000 Bq⋅m) outside of the FDNPP site not in the ocean, rivers, or potable groundwater, but in groundwater beneath sand beaches over tens of kilometers away from the FDNPP. Here, we present evidence of a previously unknown, ongoing source of Fukushima-derived Cs to the coastal ocean. We postulate that these beach sands were contaminated in 2011 through wave- and tide-driven exchange and sorption of highly radioactive Cs from seawater. Subsequent desorption of Cs and fluid exchange from the beach sands was quantified using naturally occurring radium isotopes. This estimated ocean Cs source (0.6 TBq⋅y) is of similar magnitude as the ongoing releases of Cs from the FDNPP site for 2013-2016, as well as the input of Fukushima-derived dissolved Cs via rivers. Although this ongoing source is not at present a public health issue for Japan, the release of Cs of this type and scale needs to be considered in nuclear power plant monitoring and scenarios involving future accidents.
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http://dx.doi.org/10.1073/pnas.1708659114DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5651766PMC
October 2017

Desorption of radioactive cesium by seawater from the suspended particles in river water.

Chemosphere 2017 Oct 17;185:806-815. Epub 2017 Jul 17.

Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 1-1 Katahira, 2-chome, Aoba-ku, Sendai 980-8577, Japan.

In 2011, the accident at the Fukushima-Daiichi nuclear power plant dispersed radioactive cesium throughout the environment, contaminating the land, rivers, and sea. Suspended particles containing clay minerals are the transportation medium for radioactive cesium from rivers to the ocean because cesium is strongly adsorbed between the layers of clay minerals, forming inner sphere complexes. In this study, the adsorption and desorption behaviors of radioactive cesium from suspended clay particles in river water have been investigated. The radioactive cesium adsorption and desorption experiments were performed with two kinds of suspended particulate using a batch method with Cs tracers. In the cesium adsorption treatment performed before the desorption experiments, simulated river water having a total cesium concentration ([Cs]) of 1.3 nM (10 mol/L) was used. The desorption experiments were mainly conducted at a solid-to-liquid ratio of 0.17 g/L. The desorption agents were natural seawater collected at 10 km north of the Fukushima-Daiichi nuclear power plant, artificial seawater, solutions of NaCl, KCl, NHCl, and CsCl, and ultrapure water. The desorption behavior, which depends on the preloaded cesium concentration in the suspended particles, was also investigated. Based on the cesium desorption experiments using suspended particles, which contained about 1000 ng/g loaded cesium, the order of cesium desorption ratios for each desorption agent was determined as 1 M NaCl (80%) > 470 mM NaCl (65%) > 1 M KCl (30%) ≈ seawater (natural seawater and Daigo artificial seawater) > 1 M NHCl (20%) > 1 M CsCl (15%) ≫ ultrapure water (2%). Moreover, an interesting result was obtained: The desorption ratio in the 470 mM NaCl solution was much higher than that in seawater, even though the Na concentrations were identical. These results indicate that the cesium desorption mechanism is not a simple ion exchange reaction but is strongly related to structural changes in the clay minerals in the suspended particles. Hydrated Na ions expand the interlayer distance of the clay minerals, resulting in the facile desorption of cesium; in contrast, dehydrated K ions reduce the interlayer distance and inhibit the desorption of cesium. In conclusion, the desorption of cesium from the suspended particles is controlled by the presence of sodium and potassium ions and the preloaded cesium concentration in the suspended particles.
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http://dx.doi.org/10.1016/j.chemosphere.2017.07.078DOI Listing
October 2017

Hybrid procedure combining clip on wrapping and stent placement for ruptured supraclinoid blood blister-like aneurysm of the internal carotid artery.

Clin Case Rep 2017 Mar 3;5(3):285-289. Epub 2017 Feb 3.

Department of Neurosurgery Kawasaki Saiwai Hospital 31-27, Omiya-cho, Saiwai-ku, Kawasaki Kanagawa Japan.

Blood blister-like aneurysms of the supraclinoid portion of the internal carotid artery are rare, fragile, and thin-walled lesions with a higher rate of rebleeding. Our case underwent a hybrid procedure combining direct surgical and endovascular approach.
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http://dx.doi.org/10.1002/ccr3.799DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5331233PMC
March 2017

Fractionation of radiocesium in soil, sediments, and aquatic organisms in Lake Onuma of Mt. Akagi, Gunma Prefecture using sequential extraction.

Sci Total Environ 2017 Jan 2;575:1247-1254. Epub 2016 Oct 2.

Low Level Radioactivity Laboratory, Kanazawa University, Japan.

The Fukushima Daiichi Nuclear Power Plant (FDNPP) accident has resulted in the contamination of the environment in Gunma Prefecture with radioisotope cesium (radio-Cs, Cs and Cs). Concentrations of radio-Cs >500Bqkg were found in wakasagi (Hypomesus nipponensis) in Lake Onuma at the top of Mount (Mt.) Akagi in August 2011. To explain the mechanism of this contamination, monitoring studies have been conducted around Lake Onuma by measuring radio-Cs concentrations in samples of fish, aquatic plants, plankton, lake water, lake sediments, and surrounding soil. The leachability of radio-Cs was evaluated using sequential extraction by Tessier et al. The total concentration of radio-Cs in Lake Onuma ecosystems decreased gradually with time. In the brown forest soil, radio-Cs concentrations of 2000 to 6000Bqkg were detected. The abundance ratio of the easy-elution form (exchangeable and carbonate forms) in the samples was <10%. The concentrations in phytoplankton samples were 3-6 times higher than those in wakasagi samples. The ratios of easy-elution forms increased by the rank in the food chain; 37% in phytoplankton, 78% in zooplankton, and 97% in wakasagi. It is likely that the lower ratio of the easy-elution form in phytoplankton is related to the adsorption of radio-Cs on suspended substances in the lake, as suggested by the analyses of aluminum and titanium in the phytoplankton, zooplankton, and wakasagi samples. The high concentrations of radio-Cs in wakasagi would be related also to the characteristics of closed mountain lakes.
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http://dx.doi.org/10.1016/j.scitotenv.2016.09.205DOI Listing
January 2017

Physicochemical and ion-binding properties of highly aliphatic humic substances extracted from deep sedimentary groundwater.

Environ Sci Process Impacts 2015 Aug 13;17(8):1386-95. Epub 2015 Jul 13.

Nuclear Professional School, School of Engineering, The University of Tokyo, 2-22 Shirakata Shirane, Tokai-mura, Ibaraki, 319-1188, Japan.

Humic substances (HSs) are ubiquitous in various aquatic systems and play important roles in many geochemical processes. There is increasing evidence of the presence of HSs in deep groundwater; nevertheless, their ion binding properties are largely unknown. In this study we investigated the physicochemical and ion-binding properties of humic and fulvic acids extracted from deep sedimentary groundwater. The binding isotherms of protons (H(+)) and copper (Cu(2+)) were measured by potentiometry and fitted to the NICA-Donnan model, and the obtained parameters were compared with the generic parameters of the model, which are the average parameters for HSs from surface environments. The deep groundwater HSs were different from surface HSs, having high aliphaticities, high sulfur contents, and small molecular sizes. Their amounts of acidic functional groups were comparable to or slightly larger than those of surface HSs; however, the magnitude of Cu(2+) binding to the deep groundwater HSs was smaller. The NICA-Donnan model attributed this to the binding of Cu(2+) to chemically homogeneous low affinity sites, which presumably consist of carboxylic groups, via mono-dentate coordination at relatively low pH. The binding mode tended to shift to multi-dentate coordination with carboxylic groups and more heterogeneous alcoholic/phenolic groups at higher pH. X-ray absorption spectroscopy also revealed that Cu(2+) binds to O/N containing functional groups and to a lesser extent S containing functional groups as its divalent from. This study shows the particularity of the deep groundwater HSs in terms of their physicochemical and ion-binding properties, compared with surface HSs.
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http://dx.doi.org/10.1039/c5em00176eDOI Listing
August 2015

Biogeochemical signals from deep microbial life in terrestrial crust.

PLoS One 2014 17;9(12):e113063. Epub 2014 Dec 17.

Japan Atomic Energy Agency, 1-64 Yamanouchi, Akiyo-cho, Mizunami, Gifu 509-6132, Japan.

In contrast to the deep subseafloor biosphere, a volumetrically vast and stable habitat for microbial life in the terrestrial crust remains poorly explored. For the long-term sustainability of a crustal biome, high-energy fluxes derived from hydrothermal circulation and water radiolysis in uranium-enriched rocks are seemingly essential. However, the crustal habitability depending on a low supply of energy is unknown. We present multi-isotopic evidence of microbially mediated sulfate reduction in a granitic aquifer, a representative of the terrestrial crust habitat. Deep meteoric groundwater was collected from underground boreholes drilled into Cretaceous Toki granite (central Japan). A large sulfur isotopic fractionation of 20-60‰ diagnostic to microbial sulfate reduction is associated with the investigated groundwater containing sulfate below 0.2 mM. In contrast, a small carbon isotopic fractionation (<30‰) is not indicative of methanogenesis. Except for 2011, the concentrations of H2 ranged mostly from 1 to 5 nM, which is also consistent with an aquifer where a terminal electron accepting process is dominantly controlled by ongoing sulfate reduction. High isotopic ratios of mantle-derived 3He relative to radiogenic 4He in groundwater and the flux of H2 along adjacent faults suggest that, in addition to low concentrations of organic matter (<70 µM), H2 from deeper sources might partly fuel metabolic activities. Our results demonstrate that the deep biosphere in the terrestrial crust is metabolically active and playing a crucial role in the formation of reducing groundwater even under low-energy fluxes.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0113063PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4269445PMC
September 2015

Spatial variations of low levels of ¹³⁴Cs and ¹³⁷Cs in seawaters within the Sea of Japan after the Fukushima Dai-ichi Nuclear Power Plant accident.

Appl Radiat Isot 2013 Nov 28;81:340-3. Epub 2013 Mar 28.

Low Level Radioactivity Laboratory, Kanazawa University, Nomi, Ishikawa 923-1224, Japan.

Our method based on low background γ-spectrometry enabled the measurement of low radiocesium concentrations in only 20 L of seawater. In May 2011 after deposition of radiocesium, (134)Cs concentration in surface water within the Sea of Japan was confirmed to be significantly small (<0.1-1 mBq/L) by the method. The concentration was not detected (<0.1 mBq/L) below 50 m depth. The Fukushima-derived radiocesium migrated from the surface water of the Sea of Japan without advection to below the thermocline.
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http://dx.doi.org/10.1016/j.apradiso.2013.03.084DOI Listing
November 2013

Deposition records in lake sediments in western Japan of radioactive Cs from the Fukushima Dai-ichi nuclear power plant accident.

Appl Radiat Isot 2013 Nov 26;81:366-70. Epub 2013 Mar 26.

Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, O 24 Wake, Nomi, Ishikawa 923-1224, Japan.

Sediment trap observations of lakes in western Japan before and after Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident indicate that changes in the radioactive Cs discharge are influenced by fluctuations in precipitation and geomorphological conditions in each catchment. Contributions of FDNPP-derived (134,137)Cs to the sediment decreased from 19-48% to 10-15% within a few months, implying that the major transport processes of FDNPP-derived (134,137)Cs have changed from direct fallout to transport by soil particles.
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http://dx.doi.org/10.1016/j.apradiso.2013.03.073DOI Listing
November 2013

Syringomyelia associated with Paget disease of the skull.

Neurol Med Chir (Tokyo) 2013 ;53(2):115-8

Department of Neurosurgery, Faculty of Medicine, University of Toyama, Toyama, Japan.

A 38-year-old man presented with a rare case of syringomyelia associated with Paget disease of the skull. Syringosubarachnoid (SS) shunting was performed. We speculate that deformation of the skull secondary to Paget disease caused narrowing of the foramen magnum with progressive impairment of the cerebrospinal fluid circulation, which led to syringomyelia and neurological symptoms. SS shunting is safe, effective, and technically simple, so may be a useful initial treatment for syringomyelia associated with Paget disease of the skull.
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http://dx.doi.org/10.2176/nmc.53.115DOI Listing
January 2014

Comparison of the vertical distributions of Fukushima nuclear accident radiocesium in soil before and after the first rainy season, with physicochemical and mineralogical interpretations.

Sci Total Environ 2013 Mar 5;447:301-14. Epub 2013 Feb 5.

Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Tokai-mura, Ibaraki 319-1195, Japan.

Effect of intense rainfall on the distribution of Fukushima-accident-derived (137)Cs in soil was examined. Inventories and vertical distributions of (137)Cs in soils were determined at 15 locations (including croplands, grasslands, and forests) in Fukushima city in the post-rainy season, approximately 4.5months after the accident, and were compared with those in the pre-rainy season determined in our former study. The (137)Cs inventory levels scarcely changed between points in time spanning the first rainy season after the accident. Moreover, the majority of (137)Cs remained stored in the aboveground vegetation and in the upper 5cm of soil layer at undisturbed locations in the post-rainy season. A more quantitative analysis with the characterization of the vertical profile of (137)Cs using the relaxation length confirmed that the vertical profile was almost unchanged at most locations. Accordingly, it is concluded that rainfall during the rainy season had a limited effect on (137)Cs distribution in the soil, indicating the very low mobility. Chemical extraction of (137)Cs from selected soil samples indicated that (137)Cs in the soil was barely water soluble, and even the fraction extracted with 1M ammonium acetate was only approximately 10%. This further supports the low mobility of (137)Cs in our soils. Soil mineralogical analyses, which included the identification of clay minerals, suggested that smectite and mica could lower the exchangeable fraction of (137)Cs. However, no direct relationship was obtained between mineral composition and (137)Cs retention in the upper soil layer. In contrast, positive correlations were observed between (137)Cs extractability and soil properties such as pH, organic matter content, finer-sized particle content, and cation-exchange capacity. These results suggest that the mineralogical effect on the firm fixation of (137)Cs on soil constituents may be masked by the non-specific adsorption offered by the physicochemical properties of the soils.
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http://dx.doi.org/10.1016/j.scitotenv.2012.12.087DOI Listing
March 2013

Factors affecting vertical distribution of Fukushima accident-derived radiocesium in soil under different land-use conditions.

Sci Total Environ 2012 Aug 15;431:392-401. Epub 2012 Jun 15.

Nuclear Science and Engineering Directorate, Japan Atomic Energy Agency, Ibaraki 319-1195, Japan.

The Fukushima Dai-ichi nuclear power plant accident in Japan, triggered by a big earthquake and the resulting tsunami on 11 March 2011, caused a substantial release of radiocesium ((137)Cs and (134)Cs) and a subsequent contamination of soils in a range of terrestrial ecosystems. Identifying factors and processes affecting radiocesium retention in these soils is essential to predict how the deposited radiocesium will migrate through the soil profile and to other biological components. We investigated vertical distributions of radiocesium and physicochemical properties in soils (to 20 cm depth) at 15 locations under different land-use types (croplands, grasslands, and forests) within a 2 km × 2 km mesh area in Fukushima city. The total (137)Cs inventory deposited onto and into soil was similar (58.4±9.6 kBq m(-2)) between the three different land-use types. However, aboveground litter layer at the forest sites and herbaceous vegetation at the non-forested sites contributed differently to the total (137)Cs inventory. At the forest sites, 50-91% of the total inventory was observed in the litter layer. The aboveground vegetation contribution was in contrast smaller (<35%) at the other sites. Another remarkable difference was found in vertical distribution of (137)Cs in mineral soil layers; (137)Cs penetrated deeper in the forest soil profiles than in the non-forested soil profiles. We quantified (137)Cs retention at surface soil layers, and showed that higher (137)Cs retention can be explained in part by larger amounts of silt- and clay-sized particles in the layers. More importantly, the (137)Cs retention highly and negatively correlated with soil organic carbon content divided by clay content across all land-use types. The results suggest that organic matter inhibits strong adsorption of (137)Cs on clay minerals in surface soil layers, and as a result affects the vertical distribution and thus the mobility of (137)Cs in soil, particularly in the forest ecosystems.
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http://dx.doi.org/10.1016/j.scitotenv.2012.05.041DOI Listing
August 2012

Influence of halogen substituents on the catalytic oxidation of 2,4,6-halogenated phenols by Fe(III)-tetrakis(p-hydroxyphenyl) porphyrins and potassium monopersulfate.

Molecules 2011 Dec 22;17(1):48-60. Epub 2011 Dec 22.

Laboratory of Chemical Resources, Division of Sustainable Resources Engineering, Graduate School of Engineering, Hokkaido University, Sapporo 060-8628, Japan.

The influence of halogen substituents on the catalytic oxidation of 2,4,6-trihalogenated phenols (TrXPs) by iron(III)-porphyrin/KHSO₅ catalytic systems was investigated. Iron(III)-5,10,15,20-tetrakis(p-hydroxyphenyl)porphyrin (FeTHP) and its supported variants were employed, where the supported catalysts were synthesized by introducing FeTHP into hydroquinone-derived humic acids via formaldehyde poly-condensation. F (TrFP), Cl (TrCP), Br (TrBP) and I (TrIP) were examined as halogen substituents for TrXPs. Although the supported catalysts significantly enhanced the degradation and dehalogenation of TrFP and TrCP, the oxidation of TrBP and TrIP was not enhanced, compared to the FeTHP catalytic system. These results indicate that the degree of oxidation of TrXPs is strongly dependent on the types of halogen substituent. The order of dehalogenation levels for halogen substituents in TrXPs was F > Cl > Br > I, consistent with their order of electronegativity. The electronegativity of a halogen substituent affects the nucleophilicity of the carbon to which it is attached. The levels of oxidation products in the reaction mixtures were analyzed by GC/MS after extraction with n-hexane. The most abundant dimer product from TrFP via 2,6-difluoroquinone is consistent with a scenario where TrXP, with a more electronegative halogen substituent, is readily oxidized, while less electronegative halogen substituents are oxidized less readily by iron(III)-porphyrin/KHSO₅ catalytic systems.
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http://dx.doi.org/10.3390/molecules17010048DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6268336PMC
December 2011

Clear cell meningioma with histologically aggressive appearance and clinically aggressive behavior: a case report.

Neuropathology 2012 Aug 14;32(4):415-9. Epub 2011 Nov 14.

Laboratory of Pathology, Department of Neurosurgery, Faculty of Medicine, University of Toyama, Toyama University Hospital, and Toyama Cyber Knife Center, Toyama, Japan.

Clear cell meningioma (CCM) is an uncommon variant of meningioma, corresponding to WHO grade II. We present a case of CCM with histologically aggressive appearance and clinically aggressive behavior. The tumor demonstrated rapid regrowth and brain metastasis. The histological progression from the ordinal CCM to the atypical area and higher MIB-1 index was observed. We assume that the short time of recurrence and metastasis may result from atypical histological features in our case. If the CCM has a histologically aggressive appearance as in our case, we suggest that postoperative adjuvant radiotherapy should be performed despite total resection of the tumor.
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http://dx.doi.org/10.1111/j.1440-1789.2011.01272.xDOI Listing
August 2012

Spatial variations of 226Ra, 228Ra, 137Cs, and 228Th activities in the southwestern Okhotsk Sea.

J Environ Radioact 2012 Feb 6;104:75-80. Epub 2011 Oct 6.

Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Nomi, Ishikawa 923-1224, Japan.

We collected 14 water column seawater samples in the southwestern Okhotsk Sea and 7 surface samples around the northern area of Hokkaido Island, Northern Japan, and employed low-background γ-spectrometry with convenient minimal radiochemical processing to determine the activities of (226)Ra (half-life t(1/2)=1600 y), (228)Ra (5.75 y), (137)Cs (30.2 y), and (228)Th (1.91 y) in the samples. Activities of (226)Ra (~2.3 mBq/L), (228)Ra (~0.7 mBq/L), and (137)Cs (~1 mBq/L) of surface waters on the Okhotsk Sea side show notable differences from those on the Japan Sea side (Soya Warm Current Water; SWCW) (~1.5 mBq/L; 1.5-2 mBq/L; 1.4-1.6 mBq/L), indicating their different origins and lateral mixing patterns. All of these nuclides exhibit unique vertical profiles; activities of soluble (226)Ra, (228)Ra, (137)Cs, and reactive (228)Th exhibit small variations from 50 to 500 m depth ((226)Ra, ~2.2 mBq/L; (228)Ra, ~0.4 mBq/L; (137)Cs, ~1 mBq/L; (228)Th, ~0.13 mBq/L). These profiles can be explained by the convective mixing of surface water such as the East Sakhalin Current Water (ESCW) to this layer.
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http://dx.doi.org/10.1016/j.jenvrad.2011.09.007DOI Listing
February 2012

Carbon isotope composition of dissolved humic and fulvic acids in the Tokachi River system.

Radiat Prot Dosimetry 2011 Jul 22;146(1-3):322-5. Epub 2011 Apr 22.

Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology, Kanazawa University, Wake, Nomi, Ishikawa 923-1224, Japan.

This study reports carbon isotopic ratios (Δ(14)C and δ(13)C) of dissolved humic and fulvic acids in the Tokachi River system, northern Japan. These acids have a refractory feature and they represent the largest fraction of dissolved organic matter in aquatic environments. The acids were isolated using the XAD extraction method from river water samples collected at three sites (on the upper and lower Tokachi River, and from one of its tributaries) in June 2004 and 2005. δ(13)C values were -27.8 to -26.9 ‰ for humic and fulvic acids. On the other hand, the Δ(14)C values ranged from -247 to +26 ‰ and the average values were -170 ± 79 ‰ for humic acid and -44 ± 73 ‰ for fulvic acid. The difference was attributed to the residence time of fulvic acid in the watershed being shorter than that of humic acid. The large variation suggested that humic substances have a different pathway in each watershed environment.
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http://dx.doi.org/10.1093/rpd/ncr180DOI Listing
July 2011
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