207 research outputs found
Natural attenuation of Fukushima-derived radiocesium in soils due to its vertical and lateral migration
Processes of vertical and lateral migration lead to gradual reduction in contamination of catchment soil, particularly its top layer. The reduction can be considered as natural attenuation. This, in turn, results in a gradual decrease of radiocesium activity concentrations in the surface runoff and river water, in both dissolved and particulate forms. The purpose of this research is to study the dynamics of Fukushima-derived radiocesium in undisturbed soils and floodplain deposits exposed to erosion and sedimentation during floods. Combined observations of radiocesium vertical distribution in soil and sediment deposition on artificial lawn-grass mats on the Niida River floodplain allowed us to estimate both annual mean sediment accumulation rates and maximum sedimentation rates corresponding to an extreme flood event during Tropical Storm Etau, 6-11 September 2015. Dose rates were reduced considerably for floodplain sections with high sedimentation because the top soil layer with high radionuclide contamination was eroded and/or buried under cleaner fresh sediments produced mostly due to bank erosion and sediments movements. Rate constants of natural attenuation on the sites of the Takase River and floodplain of Niida River was found to be in range 0.2-0.4 year-1. For the site in the lower reach of the Niida River, collimated shield dose readings from soil surfaces slightly increased during the period of observation from February to July 2016. Generally, due to more precipitation, steeper slopes, higher temperatures and increased biological activities in soils, self-purification of radioactive contamination in Fukushima associated with vertical and lateral radionuclide migration is faster than in Chernobyl. In many cases, monitored natural attenuation along with appropriate restrictions seems to be optimal option for water remediation in Fukushima contaminated areas
Research and management challenges following soil and landscape decontamination at the onset of the reopening of the Difficult-to-Return Zone, Fukushima (Japan)
Twelve years after the nuclear accident that occurred at the
Fukushima Dai-ichi Nuclear Power Plant (FDNPP) in March 2011, radiocesium
contamination (with a large dominance of 137Cs, with a 30-year
half-life) remains a major concern in various municipalities of north-eastern
Japan. The Japanese authorities completed an unprecedented soil
decontamination programme in residential and cultivated areas affected by
the main radioactive plume (8953 km2). They implemented a
complex remediation programme scheme to remediate soils that are fundamental
to life on Earth, relying on different decision rules depending on the waste
type, its contamination level and its region of origin, after delineating
different zones exposed to contrasted radiation rates. The central objective
was not to expose local inhabitants to radioactive doses exceeding 1 mSv yr−1 in addition to the natural levels. At the onset of the full
reopening of the Difficult-to-Return Zone (DTRZ) in spring 2023, the current review
provides an update of a previous synthesis published in 2019
(Evrard et al., 2019). Although this ambitious soil remediation
and reconstruction programme has almost been completed in the 12 municipalities
of Fukushima Prefecture in which an evacuation order was imposed in at least
one neighbourhood in 2011, from the 147 443 inhabitants who lived there
before the accident, only 29.9 % of them had returned by 2020. Waste
generated by decontamination and tsunami cleaning/demolition work is planned
to have been fully transported to (interim) storage facilities by the end of
2023. The cost of the operations conducted between 2011 and 2020 for the
so-called “nuclear recovery” operations (including decontamination) was
estimated by the Board of Audit of Japan in 2023 as JPY 6122.3 billion
(∼ EUR 44 billion). Decontamination of cropland was shown to
have impacted soil fertility, and potassium fertilisation is recommended to
limit the transfer of residual radiocesium to new crops. In forests that
cover 71 % of the surface area of Fukushima Prefecture and that were
not targeted by remediation, radiocesium is now found in the upper mineral
layer of the soil in a quasi-equilibrium state. Nevertheless, 137Cs
concentrations in forest products (including wood for heating and
construction, wild plants, wildlife game, mushrooms) often keep exceeding
the threshold values authorised in Japan, which prohibits their exploitation
in the area affected by the main plume. Radionuclides from forests were shown
to be exported in dissolved and particle-bound forms to downstream river
systems and floodplains, although multiple monitoring records showed the
continuous decrease in radiocesium concentrations in both river water and
sediment across the main plume between 2011 and 2021. Fish contamination is now
generally found to be below the threshold limits although reputational damage
remains a major concern for local fishing communities. The remobilisation of
radiocesium from sediment accumulated in reservoirs of the region is also of
potential concern as it may lead to secondary contamination of fish or
irrigation waters supplied to decontaminated fields. Overall, this synthesis
demonstrates the need to continue monitoring post-accidental radiocesium
transfer in these environments and to keep sharing data in order to refine
our predictive understanding of radiocesium mobility and consolidate the
tools available to model contaminant transfer in ecosystems. In forests in
particular, novel countermeasures and wood uses remain to be developed and
tested. Furthermore, the hydrologic connectivity between soils under
different ecosystems greatly influences long-term radiocesium
transport. The consequences of extreme phenomena (e.g. typhoons, forest
fires) that may become more frequent in the future as a result of global
change in these contaminated environments should be further anticipated.</p
Planet Sensitivity from Combined Ground- and Space-based Microlensing Observations
To move one step forward toward a Galactic distribution of planets, we
present the first planet sensitivity analysis for microlensing events with
simultaneous observations from space and the ground. We present this analysis
for two such events, OGLE-2014-BLG-0939 and OGLE-2014-BLG-0124, which both show
substantial planet sensitivity even though neither of them reached high
magnification. This suggests that an ensemble of low to moderate magnification
events can also yield significant planet sensitivity and therefore probability
to detect planets. The implications of our results to the ongoing and future
space-based microlensing experiments to measure the Galactic distribution of
planets are discussed.Comment: 10 pages, 5 figures, 1 table; ApJ in pres
Characterisation of a recombinant β-xylosidase (xylA) from Aspergillus oryzae expressed in Pichia pastoris
β-xylosidases catalyse the hydrolysis of short chain xylooligosaccharides from their non-reducing ends into xylose. In this study we report the heterologous expression of Aspergillus oryzae β-xylosidase (XylA) in Pichia pastoris under the control of the glyceraldehyde-3-phosphate dehydrogenase promoter. The recombinant enzyme was optimally active at 55°C and pH 4.5 with Km and Vmax values of 1.0 mM and 250 μmol min−1 mg−1 respectively against 4-nitrophenyl β-xylopyranoside. Xylose was a competitive inhibitor with a Ki of 2.72 mM, whereas fructose was an uncompetitive inhibitor reducing substrate binding affinity (Km) and conversion efficiency (Vmax). The enzyme was characterised to be an exo-cutting enzyme releasing xylose from the non-reducing ends of β-1,4 linked xylooligosaccharides (X2, X3 and X4). Catalytic conversion of X2, X3 and X4 decreased (Vmax and kcat) with increasing chain length
Suppression of Cellular Transformation by Poly (A) Binding Protein Interacting Protein 2 (Paip2)
Controlling translation is crucial for the homeostasis of a cell. Its deregulation can facilitate the development and progression of many diseases including cancer. Poly (A) binding protein interacting protein 2 (Paip2) inhibits efficient initiation of translation by impairing formation of the necessary closed loop of mRNA. The over production of Paip2 in the presence of a constitutively active form of hRasV12 can reduce colony formation in a semi-solid matrix and focus formation on a cell monolayer. The ability of Paip2 to bind to Pabp is required to suppress the transformed phenotype mediated by hRasV12. These observations indicate that Paip2 is able to function as a tumor suppressor
A novel xylan degrading β-D-xylosidase: purification and biochemical characterization
Aspergillus ochraceus, a thermotolerant fungus isolated in Brazil from decomposing materials, produced an extracellular b-xylosidase that was purified using DEAE-cellulose ion exchange chromatography, Sephadex G-100 and Biogel P-60 gel filtration. b-xylosidase is a
glycoprotein (39 % carbohydrate content) and has a molecular mass of 137 kDa by SDS-PAGE, with optimal temperature and pH at 70 C and 3.0–5.5, respectively.b-xylosidase was stable in acidic pH (3.0–6.0) and 70 C for 1 h. The enzyme was activated by 5 mM MnCl2 (28 %)and MgCl2 (20 %) salts. The b-xylosidase produced by A. ochraceus preferentially hydrolyzed p-nitrophenyl-b- D-xylopyranoside, exhibiting apparent Km and Vmax values of 0.66 mM and 39 U (mg protein)-1 respectively, and to a lesser extent p-nitrophenyl-b-D-glucopyranoside. The enzyme was able to hydrolyze xylan from different sources,suggesting a novel b-D-xylosidase that degrades xylan.
HPLC analysis revealed xylans of different compositions which allowed explaining the differences in specificity observed by b-xylosidase. TLC confirmed the capacity.This work was supported by the Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP), and the Conselho de Desenvolvimento Científico e Tecnológico (CNPq). J. A. J. and M. L. T. M. P are Research Fellows of CNPq. M. M. was a recipient of a FAPESP fellowship and this work is part of her Doctoral Thesis. It is also part of the project SISBIOTA CNPq: 563260/2010-6 and FAPESP: 2010/52322-3
Generation of Germline-Competent Rat Induced Pluripotent Stem Cells
Recent progress in rat pluripotent stem cell technology has been remarkable. Particularly salient is the demonstration that embryonic stem cells (ESCs) in the rat (rESCs) can contribute to germline transmission, permitting generation of gene-modified rats as is now done using mouse ESCs (mESCs) or mouse induced pluripotent stem cells (iPSCs; miPSCs). However, determinations of whether rat iPSCs (riPSCs) can contribute to germ cells are not published. Here we report the germline competency of riPSCs.We generated riPSCs by transducing three mouse reprogramming factors (Oct3/4, Klf4, and Sox2) into rat somatic cells, followed by culture in the presence of exogenous rat leukemia inhibitory factor (rLIF) and small molecules that specifically inhibit GSK3, MEK, and FGF receptor tyrosine kinases. We found that, like rESCs, our riPSCs can contribute to germline transmission. Furthermore we found, by immunostaining of testis from mouse-rat interspecific chimeras with antibody against mouse vasa homolog, that riPSCs can contribute to embryonic development with chimera formation in mice (rat-mouse interspecific chimeras) and to interspecific germlines.Our data clearly demonstrate that using only three reprogramming factors (Oct3/4, Klf4, and Sox2) rat somatic cells can be reprogrammed into a ground state. Our generated riPSCs exhibited germline transmission in either rat-rat intraspecific or mouse-rat interspecific chimeras
Comparison of Corneal Safety and Intraocular Pressure?Lowering Effect of Tafluprost Ophthalmic Solution with Other Prostaglandin Ophthalmic Solutions
Purpose: The benzalkonium chloride (BAK) content of tafluprost ophthalmic solution (TaprosR: tafluprost) has been reduced to balance corneal safety and preservative effectiveness (old formulation: 0.01%; new formulation: 0.001%). However, no reports have been published on its clinical effect. Therefore, we conducted a clinical research study to compare the safety of BAK-reduced tafluprost on the ocular surface with other prostaglandin ophthalmic solutions. Methods: This clinical study included 28 glaucoma patients (28 eyes) with a treatment history of latanoprost ophthalmic solution (XalatanR) or travoprost ophthalmic solution (Travatan Z R), who presented with corneal epithelial disorders. The subjects were switched to BAK-reduced tafluprost, and its effect on the ocular surface was examined after 1 and 2 months of treatment [using fluorescein staining score, hyperemia, tear film breakup time, and intraocular pressure (IOP) lowering]. Results: In all analyzed subjects (N=27), the fluorescein staining score was significantly improved after switching to BAK-reduced tafluprost (P<0.0001). Conversely, the IOP-lowering effect was not notably changed. The subjects switched from latanoprost (n=10) showed significant improvement in fluorescein staining score (P<0.05) as well as in IOP lowering (P<0.01). The subjects switched from travoprost (n=17) also showed significant improvement in fluorescein staining score (P<0.001), but without a significant change in IOP lowering. Conclusions: Tafluprost with reduced BAK has potential as a superior antiglaucoma drug, not only for its IOP-lowering effect, but also for its good corneal safety profile
Computerized tomography angiography in preoperative assessment of intravenous leiomyomatosis extending to inferior vena cava and heart
- …