ALBERT

Description: IntroductionThe evolution of Antarctica and the Antarctic Ocean is vital to understanding the growth and breakup of super continent Gondwana. The reconstruction models of Gondwana have been established by many authors using geophysical data set as well as geological data (e.g. Norton and Sclater, 1978). The area around Syowa Station, the Japanese Antarctic wintering Station in Lützow- Holm Bay, is considered to be a junction of Africa, India, Madagascar, and Antarctic continents from the reconstruction models of Gondwana. Therefore this area is a key to investigate the formation and fragmentation of Gondwana. However, the tectonic evolution is still speculative because geological evidence is limited to a few isolated outcrops and the coverage with geophysical surveys in this area is poor.Joint Japanese-German airborne geophysical surveys around Syowa Station had been conducted in January 2006 during the 47th Japanese Antarctic Research Expedition to reveal tectonic evolution of the area around Syowa Station. The observation lines are shown in Figure 1.Data The airborne geophysical surveys had been made along almost N-S observation lines with spacing of about 20 km. Ice radar measurements had been carried out onshore area and ice thickness data are obtained. Bed rock topography are estimated using RAMP surface elevation data set. Magnetic and gravity measurements had been conducted both onshore and offshore areas. Magnetic anomalies are determined after correcting diurnal geomagnetic variations at Syowa Station. Precise positions of the aircraft are determined using DGPS techniques and free-air gravity anomalies are also obtained. Those data are girded and plotted using GMT software (Wessel and Smith, 1998).ResultsThe results of bed rock topography, gravity and magnetic anomalies are shown in Figures 2, 3 and 4, respectively. Characteristic features possibly related to the tectonic evolution from the results are summarized as followings.. Large negative gravity anomalies are observed along the Shirase Glacier (A in Figure 3) and those almost correspond to deep bed rock topography. Two sets of positive and negative gravity anomalies are shown along ocean-continental transition (B in Figure 3). However, magnetic anomalies along ocean-continental transition indicate only one set. NW-SE trending positive magnetic anomalies are observed between 40°E and 43°E near Antarctic continental margin (A in Figure 4). Those almost correspond to the transitional zone from Amphibolite to Granulite faces in the Lützow-Holm Complex. NE-SW trending magnetic anomalies in offshore area possibly indicate magnetic anomaly lineations (B in Figure 4). Positive magnetic anomalies surrounded by negative ones are observed around Cape Hinode (C in Figure 4). DiscussionLarge negative gravity anomalies and deep bed topography along the Shirase Glacier (A in Figure 4) possibly indicate major geological boundaries. It has been inferred that the peak metamorphic grade of the Lützow-Holm Complex progressively increases in a southwestern direction from amphibolite-facies to granulite-facies conditions and higher metamorphic grade are observed near the Shirase Glacier (Hiroi et al., 1983). Therefore large negative gravity anomalies and deep bed topography along the Shirase Glacier most likely delineate southwestern boundary of the Lützow-Holm Complex.Characteristic magnetic anomaly features around Cape Hinode (C in Figure 5) may indicate an allochthonous unit in the Lützow-Holm Complex. The main orogenic activities of the Lützow-Holm Complex took place during the Latest Proterozoic ro Early Paleozoic times. However, older rocks around 1000 Ma were documented at Cape Hinode within the Lützow-Holm Complex (Shiraishi et al., 1994). Magnetic anomaly data will provide new constraints for constructing tectonic evolution model in this area.NE-SW trending magnetic anomalies (B in Figure 5) possibly represent M sequence magnetic anomaly lineations. ENE-WSW and E-W magnetic anomaly lineation trends, possibly belonging to the Mesozoic magnetic anomaly lineation sequence, accompanied by the NW-SE and NNW-SSE trending fracture zones are deduced from vector magnetic anomalies just seaward of the continental slope of Antarctica to the east of Gunnerus Ridge (Nogi et al. 1996). NE-SW trending magnetic anomalies show similar strikes of magnetic anomalies from vector magnetic anomalies. Two sets of positive and negative gravity along ocean-continental transition (B in Figure 4) possibly reflect initial breakup conditions of Gondwana. Magnetic anomalies along ocean-continental transition do not show two sets of positive and negative magnetic anomalies. However, possible magnetic anomaly lineation trends in this area are almost parallel to the trends of gravity anomalies along ocean-continental transition and those imply that the direction of initial extension are normal to present coast line of Antarctica in this area. Two sets of positive and negative gravity along ocean-continental transition may suggest initial extension of Gondwana breakup.ConclusionsThe outline of ice thickness, bed rock topography, gravity and magnetic anomaly results in the area around Syowa Station are shown. Characteristic features from the results are indicated and discussed. These results provide new constraints on the tectonic evolution in the area a junction of Africa, India, Madagascar, and Antarctic continents of Gondwana. Further data analysis are carrying out and detailed discussion will be made based on those results.

Description: The area around Syowa Station, the Japanese Antarctic wintering Station in Lützow-Holm Bay, is a key area to investigate the formation of Gondwana, because this area is considered to be a junction of Africa, India, Madagascar, and Antarctic continents from the reconstruction model of Gondwana. However, the tectonic evolution is still speculative because geological evidence is limited to a few isolated outcrops and the coverage with geophysical surveys in this area is poor. Joint Japanese-German airborne geophysical surveys around Syowa Station had been conducted in January 2006 during the 47th Japanese Antarctic Research Expedition to reveal the tectonic evolution related to Gondwana formation and breakup in this area. Ice radar, magnetic, and gravity data are obtained using the AWI owned, Dornier aircraft (Polar-2). The airborne geophysical surveys had been made along almost N-S observation lines with spacing of about 20 km.Several characteristic features possibly related to the tectonic evolution of Gondwana are inferred from magnetic and gravity anomaly maps as well as bedrock topography. Large negative gravity anomalies are observed along the Shirase Glacier and those almost correspond to deep bed rock topography. This structure most likely delineate southwestern boundary of the Lützow-Holm Complex. Northeastern boundary of the Lützow-Holm Complex is also deduced from magnetic and gravity anomalies. Moreover, Lützow-Holm Complex seems to be divided into three segments by the boundaries with almost ENE-WSW strike. These structures may reflect tectonic movements of the post collision. Positive magnetic anomalies surrounded by negative ones are also observed around Cape Hinode within the Lützow-Holm Complex. These data will provide new constraints for constructing tectonic evolution model in this area.

Description: The evolution of Antarctica and the Antarctic Ocean is vital to understanding the growth and breakup of super continent Gondwana. The area around Syowa Station, the Japanese Antarctic wintering Station in L_tzow-Holm Bay, is considered to be a junction of Africa, India, Madagascar, and Antarctic continents from the reconstruction model of Gondwana. Therefore this area is a key to investigate the formation and fragmentation of Gondwana. However, the tectonic evolution is still speculative because geological evidence is limited to a few isolated outcrops and the coverage with geophysical surveys in this area is poor. To reveal the tectonic evolution related to Gondwana formation and breakup in this area, joint Japanese-German airborne geophysical surveys around Syowa Station had been conducted in January 2006 during the 47th Japanese Antarctic Research Expedition. Ice radar, magnetic, and gravity data are obtained onshore and offshore areas using the AWI owned Polar2, a fixed wing Dornier aircraft (Do228-101) on skis. We present preliminary results of magnetic, gravity, and ice thickness (bed rock topography) measurements around Syowa Station obtained by the airborne geophysical survey 2006 and discuss the tectonic evolution in this area.

Description: The area around Syowa Station, the Japanese Antarctic wintering station in Lützow-Holm Bay, is widely considered to a junction of the continents of Africa, India, Madagascar, and Antarctica, according to a reconstruction model of Gondwana that considers the suture between East and West Gondwana. This area is therefore key investigating the formation of Gondwana. To reveal the tectonic evolution that contributed to Gondwana's formation in this area, joint Japanese-German airborne geophysical surveys were conducted around Syowa Station in January 2006 during the 47th Japanese Antarctic Research Expedition, from 67°S to 73°S latitude and from 35°E to 45°E longitude. Ice radar, magnetic, and gravity data were obtained from onshore areas. Several characteristic features that are possibly related to the tectonic evolution of Gondwana were inferred, primarily from magnetic anomalies, as well as from gravity anomalies and bedrock topography. The boundaries of the Lützow- Holm Complex, the Yamato-Belgica Complex, and the Western Rayner Complex are defined, but the inland extension of the boundary between the Lützow-Holm and the Yamato-Belgica Complexes is unknown south of 71°S. The main geological structural trends of the Lützow-Holm Complex derived from magnetic anomalies are NW-SE and are concordant with the geological results in the coastal region. However, nearly NE-SW-trending magnetic anomalies cut across the NW-SW magnetic anomaly trends, and NE-SW right lateral strike-slip faults were deduced from the magnetic and the gravity anomaly data of the Lützow-Holm Complex. The Lützow-Holm Complex was sub-divided into four blocks based on the estimated strike-slip faults. These strike-slip faults may have been generated during a younger stage of Pan-African orogeny, after the formation of NW-SE-striking geological structures. Cape Hinode, which is considered an allochthonous unit in the Lützow-Holm Complex according to its surface geology, may have originated from the Rayner Complex and been transported by right lateral strike-slip motions. These results provide new constraints on the tectonic evolution of Gondwana during the Pan-African orogeny.

Description: The area around Syowa Station, the Japanese Antarctic station in Lutzow-Holm Bay, is widely considered to be a junction of the Africa, India, Madagascar, and Antarctic continents, according to the reconstruction model of Gondwana. This area is key to investigating the formation of Gondwana. Joint Japanese-German airborne geophysical surveys were conducted around Syowa Station in January 2006 to reveal the tectonic evolution contributing to the formation of Gondwana in this area. Ice radar, magnetic, and gravity data were obtained from onshore areas. Several characteristic features that may be related to the tectonic evolution of Gondwana were inferred primarily from magnetic anomalies and from gravity anomalies and bedrock topography. The boundaries of the Lutzow-Holm Complex, the Yamato-Belgica Complex, and the Western Rayner Complex are defined, but the inland extension of the boundary between the Lutzow-Holm and the Yamato-Belgica Complexes is unknown south of 71S. The main geological structural trends of the Lutzow-Holm Complex derived from magnetic anomalies are NW-SE and are concordant with the geological results in the coastal region. However, nearly NE-SW-trending magnetic anomalies cut across the NW-SW magnetic anomaly trends, and the NE-SW right lateral strike-slip faults are deduced from the magnetic and the gravity anomaly data in the Lutzow-Holm Complex. The Lutzow-Holm Complex is divided into four blocks based on the estimated strike-slip faults. The strike-slip faults were possibly generated during a younger stage of Pan-African orogeny, after the formation of NW-SE-striking geological structures. These results provide new constraints for the formation of Gondwana.

Description: Axon branching is remodeled by sensory-evoked and spontaneous neuronal activity. However, the underlying molecular mechanism is largely unknown. Here, we demonstrate that the netrin family member netrin-4 (NTN4) contributes to activity-dependent thalamocortical (TC) axon branching. In the postnatal developmental stages of rodents, ntn4 expression was abundant in and around the...

Description: Since the initial discovery of hydrothermal vents in 1977, these ‘extreme’ chemosynthetic systems have been a focus of interdisciplinary research. The Okinawa Trough (OT), located in the semi-enclosed East China Sea between the Eurasian continent and the Ryukyu arc, hosts more than 20 known vent sites but all within a relatively narrow depth range (600–1880 m). Depth is a significant factor in determining fluid temperature and chemistry, as well as biological composition. However, due to the narrow depth range of known sites, the actual influence of depth here has been poorly resolved. Here, the Yokosuka site (2190 m), the first OT vent exceeding 2000 m depth is reported. A highly active hydrothermal vent site centred around four active vent chimneys reaching 364°C in temperature, it is the hottest in the OT. Notable Cl depletion (130 mM) and both high H 2 and CH 4 concentrations (approx. 10 mM) probably result from subcritical phase separation and thermal decomposition of sedimentary organic matter. Microbiota and fauna were generally similar to other sites in the OT, although with some different characteristics. In terms of microbiota, the H 2 -rich vent fluids in Neuschwanstein chimney resulted in the dominance of hydrogenotrophic chemolithoautotrophs such as Thioreductor and Desulfobacterium . For fauna, the dominance of the deep-sea mussel Bathymodiolus aduloides is surprising given other nearby vent sites are usually dominated by B. platifrons and/or B. japonicus , and a sponge field in the periphery dominated by Poecilosclerida is unusual for OT vents. Our insights from the Yokosuka site implies that although the distribution of animal species may be linked to depth, the constraint is perhaps not water pressure and resulting chemical properties of the vent fluid but instead physical properties of the surrounding seawater. The potential significance of these preliminary results and prospect for future research on this unique site are discussed.

Description: A dual-pipe-type microreactor was applied to the formation of nanoparticles at a very rapid reaction rate. As a representative example, zirconia particles were produced by supplying zirconium tetrabutoxide solutes and alcohol/water mixtures. The effects of the solvent and alcohol types and the residence time on the particle properties were examined. Zirconia particles were produced and grown in an inner fluid, and no precipitation of particles was observed at the wall in the outer fluid. When ethanol was used as a solvent for diluting water, the zirconia particles had a sharp narrow size distribution that could not be attained by means of a conventional batch method. The mean particle size was successfully controlled in the range of 4–600 nm merely by changing the mean residence time and the concentrations of zirconium tetrabutoxide and water in the presence of a dispersant, polyethyleneimine. Experiments were performed to form zirconia fine particles using a concentric microreactor with an axle dual pipe. The particle size of zirconia particles was controlled by changing the mean residence time and the concentrations of zirconium tetrabutoxide and water in the presence of a dispersant. Primary nucleation and particle growth can be independently and precisely controlled.