25年ぶりに相模湾で発生した円石藻Gephyrocapsa oceanicaによるブルーム

Coccolithophore is one type of phytoplankton that forms calcium carbonate plates called coccoliths, and is relatively diverse with about 200 species in the worldʼs oceans. Coccoliths accumulate in massive calcareous deposits on the sea floor that serve as a sedimentary buffer of ocean chemistry and are also a major long-term carbon storage that has a significant impact on the global carbon cycle and climate. Coccolithophores are also a major producer of dimethyl sulfide (DMS) that is the dominant precursor for cloud condensation nuclei in the marine atmosphere; DMS emissions decrease solar radiation due to increasing cloud cover. Coccolithophores play an important role in biogeochemical cycles in the ocean by influencing the oceanic uptake of atmospheric carbon dioxide, and producing calcium carbonate sediments and DMS. Coccolithophores often bloom on massive scales. Around the Japan archipelago, coccolithophore blooms have also been reported; a Gephyrocapsa oceanica bloom in Tokyo Bay and Sagami Bay (1995) and Hakata Bay (2004, 2007, 2008), and a Emiliania huxleyi bloom in Suruga Bay (2007). In mid-May 2020, a massive bloom of coccolithophores were observed in Sagami Bay, Japan, possibly for the first time in 25 years. The bloom was initially observed by the JAXA, GCOM-C ocean color remote sensing satellite “Shikisai” capturing a vast emerald green reflectance image in the bay. Researchers who received the report immediately conducted in situ observations, and found that coccolithophores caused the massive bloom. Coccolithophore is a common yet elusive group in the waters around Japan, and there has only been one report of a bloom observation in Sagami Bay. This study shows the characteristics of the coccolithophore bloom observed in Sagami Bay in 2020 and also reports on the marine environment during the bloom. Water temperature, salinity, nutrients, chlorophyll a, and cell density were collected from field samples. Satellite ocean color data was provided by “Shikisai”. Satellite images on May 13 and 17 in 2020 show that the bloom spread counterclockwise due to counterclockwise coastal currents in Sagami Bay. The species, Gephyrocapsa oceanica, was confirmed using light microscopy and a scanning electron microscope, and was the same species that occurred in 1995. Chlorophyll a concentration and cell density at the surface were 1.2 μg L-1 and 9.0×103 cells mL-1, respectively. NO2- and NO3-concentrations at the surface during the bloom were 0.10 μmol L-1 and 1.83 μmol L-1, respectively, which were relatively higher than previous years. The results suggest that one of the causes of coccolithophore bloom is the relatively high concentration of inorganic nitrogen. Previous studies of prokaryotic and eukaryotic community structure in the coastal areas of Sagami Bay using genetic analysis have reported occurrence of haptophytes and the occurrence of coccolithophores throughout the year. These results suggest that coccolithophores are frequently present in Sagami Bay and form massive blooms in a short time period if environmental conditions are favorable. Further investigation including culture experiments are needed to resolve the details and specific causes

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Results of radiotherapy for lung cancer patients

The results of radiotherapy were investigated in 49 patients with lung cancer admitted to the Department of Radiology, Okayama University Hospital. Of the 26 patients not undergoing surgery, the one-year survival rate was 100% in the stage I patients, 55% in the stage Ⅲ patients and 56% in the stage Ⅳ patients, and the two-year survival rate was 50% in the stage I patients, 0% in the stage Ⅲ patients and 9% in the stage Ⅳ patients. A significant difference in survival between patients irradiated with over 60 Gy and patients irradiated with less than 60 Gy was recognized among those not undergoing surgery. However, with respect to the frequency of local recurrence and distant metastases, a correlation with the irradiated dose was not demonstrated. Local recurrence and distant metastases were not observed in 5 of 6 patients who received preventive irradiation after curative surgery was conducted. Concerning 11 patients after non-curative surgery, local recurrence and distant metastases were recognized in 3 of them, and 7 of them showed a favourable outcome brought about by the irradiation after surgery as expected. In 6 patients with local recurrence after surgery, the survival period after radiotherapy was less than 13 months