Collection of Yamato meteorites by the 35th Japanese Antarctic Research Expedition

The 35th Japanese Antarctic Research Expedition found 9 ordinary chondrites and 7 fragments around Camp 1 (latitude 71°32′49″S, longitude 35°24′07″E) located 5km westward from Massif C in the Yamato Mountains. In this area meteorites have not been collected previously. Meteorite surveys were also carried out along the route of the Camp migrations and around the Camp 3,although no meteorites were found. The chondrites examined microscopically may be classified into either H4 or H6 categories. The biggest chondrite (Yamato-9403) which is classified as H6 was examined magnetically

Paleomagnetic information from Lützow Holm, Rayner and Napier complexes in Enderby Land, East Antarctica

第3回極域科学シンポジウム/第32回極域地学シンポジウム 11月29日（木） 統計数理研究所 ３階セミナー

Magnetic fabric analysis of deformed rocks in the Riiser-Larsen Main Shear Zone, East Antarctica

Anisotropy of magnetic susceptibility (AMS) in deformed rocks in the Riiser-Larsen Main Shear Zone (RLMSZ) was analyzed in order to demonstrate the changes in rock magnetic properties due to deformation. Sixty-nine samples were collected at six sites from sheared gneisses and sheared dolerites. Experimental results of stepwise acquisition of isothermal remanence, demagnetization of a composite IRM and thermomagnetic measurement indicate the presence of Ti-poor titanomagnetite. Pyrrhotite also occurs characteristically in specimens with mylonitic textures. Magnetic foliations of AMS for the mylonite at three sites show good agreement with mylonitic foliation at each site. The mylonites showed enhancement of anisotropy degree from protoliths, indicating overprinting of the original magnetic fabrics. Their maximum susceptibility axes are well defined within each site, and dip about 50-60° northward. The magnetic lineation probably indicates the maximum stretching direction in the RLMSZ

Paleomagnetic Studies on Miocene Sequences of Hokutan and Tottori Groups in Southwest Japan: Implications for Middle Miocene Rotational Movement of Southwest Japan Block Associated with the Japan Sea Opening

Miocene sequences composed of volcanic rocks and overlying marine sediments distributing at the Japan Sea side of Southwest Japan have been considered to form related to the rifting and subsequent spreading of the Japan Sea back-arc basin in Miocene time. We performed paleomagnetic investigations on the sequences in the eastern San’in district, the Hokutan and Tottori Groups. Paleomagnetic analyses on samples from 33 sites indicated that characteristic magnetic components from five sites of volcanic rocks in the Hokutan Group and from four sites of marine sediments in the Tottori Group were regarded as primary components. An obtained paleomagnetic direction of the volcanic rocks has an easterly deflected declination (D = 23.9° ± 20.2°), while that of the marine sediments shows no significant deflection in declination (D = 17.8° ± 19.1°). Through the comparison with paleomagnetic data from the Miocene sequences in Southwest Japan, it is suggested that magnetic polarities of the volcanic and sedimentary sequences are assigned to C5Cn and C5Br-C5Bn, respectively, and that the eastern San’in district suffered a clockwise rotation of 24° at around 16 Ma after the early Miocene volcanic activity and before the middle Miocene marine transgression in the whole clockwise rotation process of Southwest Japan related to the Japan Sea opening

A mathematical model of Plasmodium falciparum transmission incorporating drug resistance: Simulations of the Solomon Islands situation

The Solomon Islands are known as a high endemic region of malaria. The resistance of Plasmodium falciparum to chloroquine has been confirmed since 1980 in the Solomon Islands, and the spread of chloroquine resistance is a big hurdle to malaria control. We have constructured the model for P. falciparum making allowance of chloroquine resistance. We distinguish the infection of resistance strains from that of sensitive strains in both the human and the vector populations. Since the overall parasite rate and the parasite rate of gametocytes for P.　falciparum are strongly dependent on age, the human population is divided into 7 age groups in the model. The epidemiological parameters are determined by malariological survey in northeastern Guadalcanal (Ishii et al.) and the sporozoite rate in vector population is assumed as 0.1% based on the entomological study (Harada et al.) Our study aims at estimating the effect of mass drug administration under the presence of drug-resistance and also analyzing the escalation of drug-resistance through the transmission model for P. falciparum which can deal with chloroquine resistance

Analysis of the effectiveness of control strategies against bioterrorist smallpox attacks by using Individual Based Model

We carried out simulations of various scenarios for bioterrorist attacks using smallpox occurring in a virtual area set up on the basis of the census of Okayama-city, Japan, which predict the effect of control strategies against bioterrorism and the loss scale. On simulating a smallpox epidemic, we followed the method of the Individual Based Model stochastically, which can treat the population in the virtual area as individuals. Individuals have personal information, behavior patterns, and interactions among social groups. We took into consideration the influence of residual immunity due to past vaccination. We considered Traced Vaccination (TV) and Mass Vaccination (MV) strategies against bioterrorism. We investigated the effect of TV and MV strategies on the suppression of smallpox epidemics. Consequently, the TV strategy was found to have higher effectiveness than the MV strategy

Collisional bending of the western Paleo-Kuril Arc deduced from paleomagnetic analysis and U–Pb age determination

The Paleo‐Kuril Arc in the eastern Hokkaido region of Japan, the westernmost part of the Kuril Arc in the northwestern Pacific region, shows a tectonic bent structure. This has been interpreted, using paleomagnetic data, to be the result of block rotations in the Paleo‐Kuril Arc. To understand the timing and origin of this tectonic bent structure in the Paleo‐Kuril arc‐trench system, paleomagnetic surveys and U–Pb radiometric dating were conducted in the Paleogene Urahoro Group, which is distributed in the Shiranuka‐hill region, eastern Hokkaido. The U–Pb radiometric dating indicated that the Urahoro Group was deposited at approximately 39 Ma. Paleomagnetic analysis of the Urahoro Group suggested that the Shiranuka‐hill region experienced a 28° clockwise rotation with respect to East Asia. The degree of clockwise rotation implied from the Urahoro Group is smaller than that of the underlying Lower Eocene Nemuro Group (62°) but larger than that of the overlying Onbetsu Group (−9°). It is thus suggested that the Shiranuka‐hill region experienced a clockwise rotation of approximately 34° between the deposition of the Nemuro and Urahoro Groups (50–39 Ma), and a 38° clockwise rotation between the deposition of the Urahoro and Onbetsu Groups (39–34 Ma). The origin of the curved tectonic belt of the Paleo‐Kuril Arc was previously explained by the opening of the Kuril Basin after 34 Ma. The age constraint for the rotational motion of the Shiranuka‐hill region in this study contradicts this hypothesis. Consequently, it is suggested that the process of arc–arc collision induced the bent structure of the western Paleo‐Kuril Arc

Global meta-analysis for controlling factors on carbon stable isotope ratios of lotic periphyton.

Carbon stable isotope ratios (δ(13)C) are widely used to trace resource transfer pathways, yet δ(13)C variation in freshwater autotrophs is not yet fully understood. We have analyzed data from 42 published studies, supplemented with some unpublished data, to show the determinants of lotic periphyton δ(13)C. At large spatial scales, we observed broad differences in periphyton δ(13)C among biomes and consistent longitudinal variation related to watershed area. Longitudinal increases in δ(13)C indicate the importance of in-stream processes on lotic carbon cycles and autotroph δ(13)C variation. At local spatial scales, periphyton δ(13)C was negatively related to canopy cover and water current velocity and positively related to chlorophyll a density. Autotroph δ(13)C varied among taxonomic groups. Cyanobacteria and red algae had significantly higher and lower δ(13)C than other taxa, respectively. A hierarchical model across spatial scales showed that local controls for periphyton δ(13)C were nested by regional controls, which suggested that productivity and CO(2) availability determine δ(13)C. Overall, our results reveal general patterns of periphyton δ(13)C and provide improved information for study design and the use of δ(13)C in isotopic mixing models in lotic food web studies