Observation of Spin-Dependent Charge Symmetry Breaking in ΛN Interaction: Gamma-Ray Spectroscopy of _{Λ}^{4}He

The energy spacing between the spin-doublet bound state of _{Λ}^{4}He(1^{+},0^{+}) was determined to be 1406±2±2  keV, by measuring γ rays for the 1^{+}→0^{+} transition with a high efficiency germanium detector array in coincidence with the ^{4}He(K^{-},π^{-})_{Λ}^{4}He reaction at J-PARC. In comparison to the corresponding energy spacing in the mirror hypernucleus _{Λ}^{4}H, the present result clearly indicates the existence of charge symmetry breaking (CSB) in ΛN interaction. By combining the energy spacings with the known ground-state binding energies, it is also found that the CSB effect is large in the 0^{+} ground state but is vanishingly small in the 1^{+} excited state, demonstrating that the ΛN CSB interaction has spin dependence.

Accumulation of accident-derived radiocesium in lake and coastal sediments at 300-700 km distance from Fukushima area

The accumulation of accident-derived radiocesium was investigated in nine water bodies located 300-700 km from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP). (134)Cs from the accident was detected in surface sediment of five water bodies. The (134)Cs concentration, corrected to the time of the accident in 2011, was generally lower than that of (137)Cs, and its spatial pattern does not fully correspond to that of (137)Cs. These results suggest that radiocesium derived from both FDNPP and past global fallout can be separately observed and that the contributions of both sources are non-uniform within these sites. The (134)Cs inventory in surface sediments is smaller than its deposition, suggesting that almost all deposited (134)Cs remains within the catchment and/or a part has been discharged from the saline and brackish water bodies.

Transport of Particulate Organic Matter and Dissolved Organic Matter from Land to Ocean in Hokkaido, Japan

Both ?14C, ?13C for the particulate organic matter (POM) and 3-Dimensional Excitation and Emission Matrix spectroscopy (3D-EEM) for the dissolved organic matter (DOM) were used to study transport behavior from land to ocean in Hokkaido, Japan. The ?14C values of the Tokachi POC (particulate organic carbon) show similar variations to Ishikari. However, the variation range of the Tokachi of ?14C is smaller than that of the Ishikari POC. ?13C values for the Ishikari showed larger variation range than those of the Tokachi. The POC during spring snow-melting for the Ishikari and in autumn during heavy rain fall for the Tokachi were distinctive in the correlations of POC, ?14C, and ?13C.There were two different pathways in the correlations of POC content, ?14C, and water discharge for both river systems. The significant pathway during snow-melting found in the Ishikari and at autumn during heavy rain fall for the Tokachi. The Tokachi and the Ishikari River showed similar variations patterns of dissolved organic carbon (DOC) concentrations and relative fluorescence intensity (RFI). The run-off point of DOC and FA-like materials is similar to POC. Therefore, characteristics and export of POC and DOC may be controlled by water discharge in small rivers in sub-arctic zone. The both rivers showed averaged POC flux from 1.43~1.51 ¥ 1010 g/yr, DOC flux of 0.98~2.32 ¥ 1010 g/yr, and fulvic-like materials-carbon (FAC) flux of 0.70~1.22 ¥ 1010 g/yr. The percentages of POC, DOC, and FAC flux in two rivers during snow-melting and heavy rainfall were 78~95% and 25~ 42 %, respectively. The watersheds of the Ishikari and Tokachi are important in transport of POC from land to ocean, especially during snow-melting and heavy rain event. DOI: http://dx.doi.org/10.3329/dujs.v63i1.21768 Dhaka Univ. J. Sci. 63(1): 47-51, 2015 (January)

Delivery mechanism of (134)Cs and (137)Cs in seawater off the Sanriku Coast, Japan, following the Fukushima Dai-ichi NPP accident

To assess the delivery mechanism of radiocesium emitted from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), we examined vertical profiles of (134)Cs, (137)Cs, and (228)Ra concentrations and the (228)Ra/(226)Ra ratio in the water columns off the Sanriku Coast in the northwestern Pacific Ocean, in July 2012, along with their surface lateral variations in July 2009. Radiocesium concentrations exhibited maximum peaks (3-5 mBq/L for (134)Cs) at depths of 100-200 m, accompanied by high (228)Ra concentrations (0.6-0.8 mBq/L) in comparison with shallower depths (∼0.4 mBq/L). Taking the circulation patterns of currents in the area into account, it was inferred that radioactive depositions were supplied to the (228)Ra-rich Tsugaru Warm Current Water (TWCW) in the offshore area of the Sanriku Coast following the FDNPP accident, and that after the spring of 2011, this water (∼26.5σθ) was covered by lower density surface water, which helped intrude its way to depths of 100-200 m.

Isotopic Pu, Am and Cm signatures in environmental samples contaminated by the Fukushima Dai-ichi Nuclear Power Plant accident

Dust samples from the sides of roads (black substances) have been collected together with litter and soil samples at more than 100 sites contaminated heavily in the 20-km exclusion zones around Fukushima Dai-ichi Nuclear Power Plant (FDNPP) (Minamisoma City, and Namie, Futaba and Okuma Towns), in Iitate Village located from 25 to 45 km northwest of the plant and in southern areas from the plant. Isotopes of Pu, Am and Cm have been measured in the samples to evaluate their total releases into the environment from the FDNPP and to get the isotopic compositions among these nuclides. For black substances and litter samples, in addition to Pu isotopes, (241)Am, (242)Cm and (243,244)Cm were determined for most of samples examined, while for soil samples, only Pu isotopes were determined. The results provided a coherent data set on (239,240)Pu inventories and isotopic composition among these transuranic nuclides. When these activity ratios were compared with those for fuel core inventories in the FDNPP accident estimated by a group at JAEA, except (239,240)Pu/(137)Cs activity ratios, fairly good agreements were found, indicating that transuranic nuclides, probably in the forms of fine particles, were released into the environment without their large fractionations. The obtained data may lead to more accurate information about the on-site situation (e.g., burn-up, conditions of fuel during the release phase, etc.), which would be difficult to get otherwise, and more detailed information on the dispersion and deposition processes of transuranic nuclides and the behavior of these nuclides in the environment.

Trans fatty acids exacerbate dextran sodium sulphate-induced colitis by promoting the up-regulation of macrophage-derived proinflammatory cytokines involved in T helper 17 cell polarization

Numerous reports have shown that a diet containing large amounts of trans fatty acids (TFAs) is a major risk factor for metabolic disorders. Although recent studies have shown that TFAs promote intestinal inflammation, the underlying mechanisms are unknown. In this study, we examined the effects of dietary fat containing TFAs on dextran sodium sulphate (DSS)-induced colitis. C57 BL/6 mice were fed a diet containing 1·3% TFAs (mainly C16:1, C18:1, C18:2, C20:1, C20:2 and C22:1), and then colitis was induced with 1·5% DSS. Colonic damage was assessed, and the mRNA levels of proinflammatory cytokines and major regulators of T cell differentiation were measured. The TFA diet reduced survival and exacerbated histological damage in mice administered DSS compared with those fed a TFA-free diet. The TFA diet significantly elevated interleukin (IL)-6, IL-12p40, IL-23p19 and retinoic acid-related orphan receptor (ROR)γt mRNA levels in the colons of DSS-treated animals. Moreover, IL-17A mRNA levels were elevated significantly by the TFA diet, with or without DSS treatment. We also examined the expression of proinflammatory cytokines in lipopolysaccharide (LPS)-stimulated RAW264.7 cells and peritoneal macrophages. These cells were exposed to TFAs (linoelaidic acid or elaidic acid) with or without LPS and the mRNA levels of various cytokines were measured. IL-23p19 mRNA levels were increased significantly by TFAs in the absence of LPS. Cytokine expression was also higher in LPS-stimulated cells exposed to TFAs than in unexposed LPS-stimulated cells. Collectively, our results suggest that TFAs exacerbate colonic inflammation by promoting Th17 polarization and by up-regulating the expression of proinflammatory cytokines in the inflamed colonic mucosa.

228Ra/226Ra ratio and 7Be concentration in the Sea of Japan as indicators for water transport: comparison with migration pattern of Fukushima Dai-ichi NPP-derived 134Cs and 137Cs

To assess the migration patterns of radiocesium emitted from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP), we analyzed (228)Ra/(226)Ra ratios and (7)Be concentrations and compared them with (134)Cs and (137)Cs concentrations in seawater samples collected within the Sea of Japan before and after the FDNPP accident (i.e., during the period 2007-2012) using low-background γ-spectrometry. The (228)Ra/(226)Ra ratios in surface waters exhibited lateral and seasonal variations, reflecting the flow patterns of surface water. This indicates the transport patterns of the FDNPP-derived radiocesium by surface water. Cosmogenic (7)Be (half-life: 53.3 d) exhibited markedly high concentrations (5-10 mBq/L) at depths shallower than 50 m, with concentrations decreasing steeply (0.2-2 mBq/L) at depths of 50-250 m. The distribution of (7)Be concentrations suggests that the downward delivery of the FDNPP-derived radiocesium to below 50 m depth was negligible for a few months prior to its removal from the Sea of Japan.

Transport behavior of particulate organic matter in river water during snow melting in the Ishikari, Tokachi, Teshio and Kushiro Rivers, Japan

Both ?14C and ?13C were used to study the transport behavior of particulate organic matter (POM) in the Ishikari, Tokachi, Teshio and Kushiro rivers in Japan. Water samples were collected once a month in April and May in 2004 and 2005 during snow melting. Positive correlations were found between ?14C and particulate organic carbon (POC) content. Negative correlations were found between ?14C and increased water level. These results indicate that the river systems showed similar transportation behavior during snow melting because of the variation of water level and water discharge. DOI: http://dx.doi.org/10.3329/jasbs.v38i2.15597 J. Asiat. Soc. Bangladesh, Sci. 38(2): 163-173, December 2012

Observation of the (Λ)(7)He hypernucleus by the (e, e'K+) reaction

An experiment with a newly developed high-resolution kaon spectrometer and a scattered electron spectrometer with a novel configuration was performed in Hall C at Jefferson Lab. The ground state of a neutron-rich hypernucleus, (Λ)(7)He, was observed for the first time with the (e, e'K+) reaction with an energy resolution of ~0.6 MeV. This resolution is the best reported to date for hypernuclear reaction spectroscopy. The (Λ)(7)He binding energy supplies the last missing information of the A = 7, T = 1 hypernuclear isotriplet, providing a new input for the charge symmetry breaking effect of the ΛN potential.

134Cs and 137Cs activities in coastal seawater along Northern Sanriku and Tsugaru Strait, northeastern Japan, after Fukushima Dai-ichi Nuclear Power Plant accident

A total of 37 seawater samples were collected at 10 sites along the coastline of the Northern Sanriku and Tsugaru Strait, 250-450 km north of the Fukushima Dai-ichi Nuclear Power Plant in April-December 2009 and May-June 2011, and analyzed for (134)Cs and (137)Cs activities using low-background γ-spectrometry. The (134)Cs and (137)Cs activities measured in these samples in May 2011 were found to be 2-3 mBq/L and 2.5-4 mBq/L, respectively. By June, these values had decreased by 25-45%/month and 5-30%/month, respectively. These results can be plausibly explained by surface infusion of these isotopes into the sea by atmospheric transport from Fukushima and their subsequent reduction by water migration to off-shore and deeper regions.

Lateral variation of 134Cs and 137Cs concentrations in surface seawater in and around the Japan Sea after the Fukushima Dai-ichi Nuclear Power Plant accident

A total of 82 surface seawater samples was collected in the Japan Sea and the southwestern Okhotsk Sea before and after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident. Analysis of (134)Cs and (137)Cs concentrations using low-background γ-spectrometry revealed that the (137)Cs concentration of the samples collected in June 2011 was 1.5-2.8mBq/L, which is approximately 1-2 times higher than the pre-accident (137)Cs level, while the (134)Cs concentration was less than detectable to 1mBq/L. In addition to (134)Cs being clearly detected (∼1mBq/L), (137)Cs concentration in water samples from the northeastern Japan Sea (2-2.8mBq/L) was also higher than that from the coast in the southwestern Japan Sea (∼1.5mBq/L). These higher concentrations in the northeastern Japan Sea could be ascribed to the atmospheric transport of nuclides from the FDNPP as aerosols and subsequent transport and dilution after delivery to the sea surface.