Can the visualization of rip currents prevent drowning accidents? Consideration of the effect of optimism bias

Drowning accidents at beach in Japan are caused by rip currents. To reduce these accidents, a new technology that can detect rip currents and notify beachgoers by using the Internet of Things (IoT) and Artificial Intelligence (AI) was proposed. However, studies on the effect of visualizing rip currents or considering the effect of optimism bias have not been conducted. This study investigates if visualization of rip currents might help in preventing drowning accidents, while considering the effect of optimism bias. The participants were 90 Japanese beachgoers. They were asked to answer questions based on their knowledge of the beach and rip currents, their optimism bias regarding rip currents, and awareness with or without visualization. The results of the analyses suggest that despite optimism bias, the visualization of rip currents increases the tendency of beachgoers to perceive and avoid rip currents. As described above, it was found that by visualizing the rip current, beachgoers were able to perceive and avoid rip currents. In addition, an understanding of rip currents is positively related to the intent to avoid rip currents even when rip currents are visualized. Therefore, it is necessary not only to enhance the avoidance tendency by visualizing rip currents, but also to further enhance knowledge of beachgoers to deepen the understanding of rip currents including the danger associated and methods to avoid them.

     

Trace-element zoning patterns in porphyroblastic garnets in low-T eclogites: Parameter optimization of the diffusion-limited REE-uptake model

Compositional zoning patterns of the major elements and REEs in prograde-zoned garnets whose Mg/(Mg + Fe) atomic ratios increase rimward have been widely used to understand the metamorphic P–T–t trajectories, and the diffusion-limited REE-uptake model is a promising way to interpret their growth rates and the REE diffusion kinetics in the low-temperature eclogite. In order to elucidate their growth kinetics with Skora et al.'s (2006) diffusion-limited REE uptake model for prograde-zoned garnets, we examine the trace-element zoning patterns of two prograde-zoned porphyroblastic garnets (~6 mm in size) in low-temperature eclogites from two different localities. Core-to-rim trace-element profiles in a garnet (prp_5–9alm_61–67sps_1–3grs_24–30) of a glaucophane-bearing epidote eclogite of Syros (Cyclades, Greece) are characterized by the presence of Y + HREE peaks in the mantle, which might be attributed to a continuous breakdown of the titanite to form rutile during the garnet growth. In contrast, those in a garnet (prp_4–7alm_61–68sps_3–10grs_23–24) extracted from a lawsonite-eclogite of the South Motagua Mélange (SMM) (Guatemala) have prominent central peaks of Y + HREEs. Although the REE profiles of both the garnets can be explained by the diffusion-limited uptake, their Mn profiles suggest that their growth-rate laws are different: i.e., diffusion-controlled (Syros) and interface-controlled (SMM). Prior to the model application, we optimize the number of the parameters as the garnet grows with the interface-controlled processes based on the growth Péclet number. In particular, we propose the ratio of the REE diffusivity in the eclogitic matrix to the garnet growth rate as the new parameter. Visualizing the values of the new parameters allows to readily understand the relationship between the REE profiles and the REE-diffusion/garnet-growth kinetics in low-T eclogite. Our model refinement leads to the simple quantitative characterization of core-to-rim REE profiles in garnet in low-temperature eclogites.     

Sedimentary Steryl Chlorin Esters (SCEs) and Other Photosynthetic Pigments as Indicators of Paleolimnological Change Over the Last 28,000 Years from the Buguldeika Saddle of Lake Baikal

Detailed depth profiles of photosynthetic pigments in a sediment core (G-12) collected at the BDP93 site, the Buguldeika saddle, of south Lake Baikal, along with depth profiles of total organic carbon (TOC) and biogenic silica, were studied to elucidate the temporal changes of phytoplankton assemblages in the lake during the past 28 kyr. In addition to the quantification of carotenoids by high-performance liquid chromatography with photodiode-array detection (HPLC-PDA), steryl chlorin esters (SCEs) were analyzed by HPLC-PDA, HPLC-mass spectrometry (LC-MS) and sterols in SCEs by gas chromatography–mass spectrometry (GC–MS) to enrich the taxonomical information on the phytoplankton composition. Allochthonous input of organic matter from the Selenga River resulted in the higher TOC contents in core G-12 than in a previously reported core (G-6) collected at another site from the southern basin. The poorer correlation in core G-12 than in G-6 between TOC and chlorophyll-a-originating pigments, which are indicative of autochthonous production, also indicated a significant allochthonous input at the site. The abundance of lutein among the carotenoids detected, and the good correlation of total chlorophyll a and b shows that green algae represented a significant portion of the phytoplankton, accompanying the diatoms at the G-12 site, after the last glacial period. The presence of cryptomonads and cyanobacteria were confirmed from marker carotenoids in the sediment core. GC–MS analysis of sterols in SCEs detected marker sterols of diatoms, green algae, chrysophytes and dinoflagellates. The depth profiles of the measured indicators gave consistent features for temporal changes in phytoplankton assemblage at the G-12 site of Lake Baikal after the last glacial maximum. Notably, the profile of a chrysophyte-specific sterol in SCEs was consistent with the reported distribution of chrysophyte cysts during the Holocene. The presence of phytoplankton, such as green algae, diatoms and chrysophytes, in Lake Baikal during the late last glacial period was indicated by the analysis of sterols in SCEs. Sedimentary carotenoids and sterols in SCEs were found to give complementary information about phytoplankton composition. These molecular indicators allow us to reconstruct past lake phytoplankton assemblages responding to environmental changes with a time resolution as high as age–depth relationship in sediments attainable at present.     

Petrographic features of a high-temperature granite just newly solidified magma at the Kakkonda geothermal field, Japan

A 3729-m-deep geothermal research well, WD-1a, provides us with a unique opportunity to study initial petrographic features of a high-temperature granite just after solidification of magma. The well succeeded in collecting three spot-cores of the Kakkonda Granite that is a pluton emplaced at a shallow depth and regarded as a heat source of the active Kakkonda geothermal system. The core samples were collected at the present formation temperatures of 370, 410 and over 500°C. These samples are granodiorite to tonalite consisting mainly of plagioclase, quartz, hornblende, biotite and K-feldspar. A sample collected at a formation temperature of over 500°C possesses the following remarkable petrographic features compared to the other two samples. Interstitial spaces are not completely sealed. K-feldspar exhibits no perthite by the exsolution of albite lamella. Quartz includes glassy melt inclusions without devitrification. Hornblende is less intensively altered to actinolite, and biotite is not altered. This study directly confirmed that perthite in K-feldspar is a recrystallization texture formed at 410–500°C based on a comparison of the in situ temperatures of the samples. Chemical compositions of minerals were analyzed to compare temperatures determined from geothermometers in several publications to the in situ temperatures of the samples.     

Three‐dimensional microstructure of samples recovered from asteroid 25143 Itokawa: Comparison with LL5 and LL6 chondrite particles

In this study, the three‐dimensional (3‐D) microstructure of 48 Itokawa regolith particles was examined by synchrotron microtomography at SPring‐8 during the preliminary examination of Hayabusa samples. Moreover, the 3‐D microstructure of particles collected from two LL6 chondrites (Ensisheim and Kilabo meteorites) and an LL5 chondrite (Tuxtuac meteorite) was investigated by the same method for comparison. The modal abundances of minerals, especially olivine, bulk density, porosity, and grain size are similar in all samples, including voids and cracks. These results show that the Itokawa particles, which are surface materials from the S‐type asteroid Itokawa, are consistent with the LL chondrite materials in terms of not only elemental and isotopic composition of the minerals but also 3‐D microstructure. However, we could not determine whether the Itokawa particles are purely LL5, LL6, or a mixture of the two. No difference between the particles collected from Rooms A and B of the sample chamber, corresponding to the sampling sequence of the spacecraft's second and first touchdowns, respectively, was detected because of the statistically small amount of particles from Room B.     

Assessment of nitrogen loading from the Kiso-Sansen Rivers into Ise Bay using stable isotopes

Concentrations of particulate organic nitrogen (PN), dissolved inorganic nitrogen (DIN), and their nitrogen isotope ratios (δ ¹⁵N) in the Kiso-Sansen Rivers were determined from monthly observations over the course of a year to assess variations in the form and sources of riverine nitrogen discharged into Ise Bay. The δ ¹⁵N values of NO₃ ⁻ observed in the Kiso-Sansen Rivers showed a logarithmic decreasing trend from 8 to 0‰, which varied with the river discharge, indicating mixing between point sources with high δ ¹⁵N and non-point sources with low δ ¹⁵N. The influence of isotope fractionation of in situ biogeochemical processes (mainly DIN assimilation by phytoplankton) on δ ¹⁵N of NO₃ ⁻ was negligible, because sufficient concentrations of NH₄ ⁺ for phytoplankton demand would inhibit the assimilation of NO₃ ⁻. A simple relationship between river discharge and δ ¹⁵N of NO₃ ⁻ showed that the fraction of total NO₃ ⁻ flux arising from point sources increased from 4.0–6.3% (1.1–1.8 tN day⁻¹) during higher discharge (>600 m³ s⁻¹) to 30.2–48.3% (2.6–4.1 tN day⁻¹) during lower discharge (<300 m³ s⁻¹). Riverine NO₃ ⁻ discharge from the Kiso-Sansen Rivers can explain 75% of the variations in surface NO₃ ⁻ at the head of Ise Bay over the year.     

Chlorinated hydrocarbons in the North Pacific and Indian Oceans

PCBs, DDT compounds and HCH isomers were detected in the air and surface waters of the North Pacific and Indian Oceans, including the Bering Sea, East China Sea, South China Sea, Bay of Bengal and the Arabian Sea. The general concentrations of each chlorinated hydrocarbon were as follows: water PCBs 0.1 to 1.0, DDT 0.01 to 1.0, HCH 1.0 to 10 ngl ^–1; air DDT 0.01 to 1.0, HCH 0.1 to 10 ng m^–3. PCB concentrations in surface waters were slightly lower than those of the North Atlantic and North Sea previously reported, while DDT concentrations in the air and water were higher. Remarkably high concentrations of DDT and HCH were found in the air off the western coast of India. Also in the Pacific site off Central America, a fairly high concentration of DDT was observed in an air sample. These data suggest that large amounts of DDT and HCH are being used in the tropical zone, especially in southern Asia. Furthermore, high concentrations were observed both in the air and water of the Northwest Pacific between 30°N and 40°N latitude. There is a possibility that both pesticides are not only still being used in lower latitude countries but also in the mid-latitude ones of the Asian continent excluding Japan. In addition to this atmospheric circulation may also contribute to the concentration of these pesticides in the mid-latitudinal zone.     

Investigation of cutting methods for small samples of Hayabusa and future sample return missions

We report the investigation of cutting methods for Hayabusa samples. The purpose of our study is to explore the possibility of applying multiple analyses to a single particle effectively. We investigated the cutting performance of a blade dicing saw, laser, focused ion beam (FIB), and physical breaking by microindenter. Cutting performance was examined by estimating the aspect ratio of the cut slit, i.e., depth over width of the slit. We also investigated the possible contamination and sample damage by cutting. The result of the investigation shows that we can cut the samples from <50 μm to 500 μm using those methods with aspect ratios from 10 to 20, although they would introduce some contamination or damage to the samples. Our investigations also provide an important basis for the analysis of samples obtained by future sample return missions.