Precipitation of authigenic uranium in suboxic continental margin sediments from the Okinawa Trough

Concentrations of U and Th isotopes in Okinawa Trough and East China Sea sediment cores were determined by isotope dilution inductively coupled plasma-mass spectrometry (ID-ICP-MS) to investigate the behavior of redox sensitive uranium in suboxic hemipelagic sediments and determine their significance in oceanic uranium balance. ²³⁸U concentrations and ²³⁸U/²³²Th activity ratios in the East China Sea sediments showed no remarkable variation with depth. However, ²³⁸U and ²³⁸U/²³²Th ratios in the Okinawa Trough sediments were low in the surface oxidizing layer but increased where the suboxic condition was encountered. The distribution profiles of ²³⁰Th and ²³²Th concentrations were relatively constant with depth in both the Okinawa Trough and East China Sea sediment cores. These results suggested that there has been post-depositional precipitation of authigenic uranium within the suboxic Okinawa Trough sediment column. The post-depositional precipitation rates of authigenic uranium were estimated to be 47 ± 5 to >62 ± 8 ng cm⁻² yr⁻¹; these rates were comparable to those previously reported for several anoxic sediments. A mechanism controlling precipitation of uranium may be the downward diffusion of uranium U(VI), reduction to U(IV) and finally precipitation onto the solid phase. The accumulation rate of uranium for the Okinawa Trough sediments was approximately eight times higher than the world average rate reported for suboxic sediments. This removal of uranium in the oceanic budget increases the importance of the suboxic sediment sink.     

The inventory and chemical characterization of dissolved proteins in oceanic waters

One-dimensional sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and high resolution two-dimensional electrophoresis (2-DE) were applied to separate protein molecules in dissolved organic matter (DOM) from oceanic waters. Results were: (1) The 2-DE distinguished a total of 412 protein spots in 10 samples from five water columns over the Pacific, although fewer than 30 proteins were resolved as bands from the identical samples by SDS-PAGE. (2) Major and ubiquitous protein bands (34 and 39 kDa proteins) on the SDS-PAGE gel were resolved into horizontally spread arrays (trains) of spots on the 2-DE gels, indicating that these bands were a mixture of protein species that have the same molecular weight (MW) but different isoelectric points (pIs). (3) Proteins that exhibited such electrophoretic patterns on the 2-DE gels were glycosylated with variable linkages between the sugar and polypeptide chains. (4) N-terminal amino-acid sequencing demonstrated that individual spots within each train of spots had identical N-terminal amino-acid sequences.The N-terminal amino-acid sequences of the 39 and 34 kDa glycoprotein spots in samples collected at different sites were also identical. Protein isoforms with the same amino-acid sequence but different glycosylation profiles, termed glycoforms, were often observed on the 2-DE gel. Thirty-one and 24 spots on the 2-DE gels were glycoforms of two glycoproteins with MWs of 39 and 34 kDa, respectively; they were one protein species. The glycoforms of the 39 kDa protein were identified as a low molecular weight alkaline phosphatase (L-AP) of Pseudomonas aeruginosa PAO1 by a homology search through five amino-acid sequence databases. The present and earlier work indicates that all identified source organisms of dissolved proteins belong to the Pseudomonas group. We propose the hypothesis that proteins associated with membrane vesicles liberated from a minor member of the bacterioplankton assemblage, the marine Pseudomonas group, are one of the important sources of dissolved proteins in oceanic waters. This hypothesis may apply to the source pathway and survival not only of proteins and also to the universally occurring bacterial peptidoglycan and lipopolysaccharide components in DOM.     

Detection of Vibrio (Listonella) Anguillarum Porin Homologue Proteins and Their Source Bacteria from Coastal Seawater

The molecular distribution of dissolved proteins in seawater from coastal marine environments in Uranouchi Bay, Kochi Prefecture, is first reported in this article. Occurrence of bacteria-derived dissolved proteins and their source bacteria were examined using a probe of the antibody (anti-Omp35La) against a porin outer membrane protein (Omp35La) of the fish pathogenic bacterium Vibrio (Listonella) anguillarum. The electrophoretograms of dissolved proteins from coastal seawater showed a large number of discrete and individual proteins overlapped each other over a wide range of molecular masses indicating active processes in coastal environments in transferring proteins from organisms to the inanimate dissolved protein pool. Among the dissolved proteins, 37 kDa- and 18 kDa-proteins reacted with the Omp35La. In order to isolate the source bacteria of such dissolved proteins, bacteria from seawater and diseased fish were screened by colony Western blotting with anti-Omp35La. The reactive strains were further examined in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE)/Western blotting to verify the presence of Omp35La homologues among the outer membrane proteins of such strains. Outer membrane proteins reacting with anti-Omp35La were detected in only 4 strains of the 129 strains that were positive in the colony Western blotting. The level of possible source bacteria of 37 kDa- and 18 kDa-dissolved proteins was suggested to be 5–6 orders of magnitude lower than the total bacterial count. The present study leads us to hypothesize that a minor portion of the bacterial assemblage is responsible for the dissolved proteins in the coastal waters.     

Capability of the penetrator seismometer system for lunar seismic event observation

We developed a seismometer system for a hard landing “penetrator” probe in the course of the former Japanese LUNAR-A project to deploy new seismic stations on the Moon. The penetrator seismometer system (PSS) consists of two short-period sensor components, a two-axis gimbal mechanism for orientation, and measurement electronics. To carry out seismic observations on the Moon using the penetrator, the seismometer system has to function properly in a lunar environment after a hard landing (impact acceleration of about 8000 G), and requires a signal-to-noise ratio to detect lunar seismic events. We evaluated whether the PSS could satisfactorily observe seismic events on the Moon by investigating the frequency response, noise level, and response to ground motion of our instrument in a simulated lunar environment after a simulated impact test. Our results indicate that the newly developed seismometer system can function properly after impact and is sensitive enough to detect seismic events on the Moon. Using this PSS, new seismic data from the Moon can be obtained during future lunar missions.     

On Huynen's decomposition of a Kennaugh matrix

For some special case, Huynen's decomposition cannot be used to extract a desired target from an average Kennaugh matrix. In this paper, the authors modify Huynen's method for overcoming its disadvantage, based on a simple transform of a Kennaugh matrix. Using an example, the effectiveness of the modified method is validated.     

Redeposition of volcaniclastic sediments by a tsunami 4600 years ago at Kushima City,south-eastern Kyushu,Japan

The Hyuga-nada Sea, south-eastern Kyushu, Japan, is located between a strong (Nankai Trough) and a weak interplate coupling zone (Ryukyu Trench). Over the past 400 years this area has only experienced Magnitude 7·5 earthquakes or smaller and associated small-scale tsunamis. However, this short historical record most likely does not include the full range of high magnitude, low frequency giant earthquakes that might have occurred in the region. Thus, it is still unclear whether giant earthquakes and their associated tsunamis have occurred in this region. This paper reports on a prehistoric tsunami deposit discovered in a coastal lowland in south-eastern Kyushu facing the Hyuga-nada Sea. There is a reddish-brown pumiceous layer preserved in a non-marine, organic-rich mud sequence obtained from onshore sediment cores. This layer is recognized as the ca 4600 year old Kirishima-Miike tephra (that is now placed around 4500 years ago) sourced from Mount Kirishima, southern Kyushu. Another whitish pumiceous layer is evident below the Kirishima-Miike tephra in almost all of the sediment cores. A relatively high percentage of marine and brackish diatoms is recorded within this lower pumiceous layer (but not in the surrounding muds or in the overlying Kirishima-Miike tephra), indicating a marine or beach sediment source. Plant material obtained from organic-rich mud immediately below the event layer was dated to ca 4430 to 4710 cal yr bp , providing a limiting-maximum age for this marine incursion event. The presence of marine diatoms below the event layer is probably explained by pre-seismic subsidence. An absence of the resting spore of the planktonic brackish diatom Cheatoceros and the appearance of the freshwater diatom Eunotia serra immediately above the event layer probably represents a marked change to a relatively low-salinity environment. Assuming that there were no significant local geomorphological changes, such as drainage obstruction caused by formation of a new barrier spit, it is considered that co-seismic or immediate post-seismic uplift are the most likely explanations for this notable environmental change. Based on the crustal movements noted before and after the marine incursion, this event is interpreted here as an earthquake-generated tsunami. Moreover, because of these notable seismic crustal movements the tsunamigenic earthquake probably occurred immediately offshore of the study site.     

Ephemeral landform development following rapid coastal uplift in the southern orogen of Taiwan

Newly emerged landscapes above sea level are characterized by rapidly evolving geomorphic systems where the initial fluvial pattern adapts to a former submarine topography. Such an early formed fluvial system establishes drainage basins and unstable landforms that characterize high topographic asymmetry which are prone to fast removal or reorganization. Transitional landscapes might form depositional systems as lakes or ponds that subsequently are incised, captured and incorporated into drainage basins. In this study we focus on the recently emerged Hengchun Peninsula to survey its paleoenvironment evolution. Three drillings performed in the Gangkou basin with fieldwork revealed several indicators that reconstructed stages of the landscape reorganization. The major finding shows an ephemeral large lake in the central part of the Hengchun Peninsula that was drained to the Pacific c. 6000 bp . The lake belonged to an ephemeral lakeland that was created after the emergence of the peninsula. Currently, several areas as relict landforms indicate this stage of topography evolution that through high rates of incision and subsequent captures, transforms into drainage basins. Furthermore, two drillings show brackish waters at the present estuary of the Gangkou basin. These two different paleoenvironments today build one system – Gangkou catchment. Long-term uplift rates show that a hanging wall of the Hengchun Fault plays a significant role in the creation of a lakeland by tilting the peninsula's surface. The tilt impacts on asymmetrical emergence of the peninsula and catchment development. Our study shows that a new geomorphic system might create depositional ephemeral landforms (lakes) that represent phases of early topography evolution after emergence above a sea level that are subjected to instantaneous rearrangement and evolves through large-scale phases before it reaches a topographic steady-state.     

The Crab Nebula's dynamical age as measured from its northern filamentary jet

We present a deep [O  iii ]λλ4959,5007 image of the northern filamentary jet in the Crab Nebula taken with the 8.2-m Subaru telescope. Using this image and an image taken with the Kitt Peak National Observatory (KPNO) 4-m in 1988, we have computed proper motions for 35 locations in the jet. The results suggest that when compared to the main body of the remnant, the jet experienced less outward acceleration from the central pulsar's rapidly expanding synchrotron nebula. The jet's apparent expansion rate yields an undecelerated explosion date for the Crab Nebula of 1055 ± 24 CE, a date much closer to the appearance of the historic 1054 CE guest star than the 1120–1140 CE dates estimated in previous studies using filaments located within the remnant's main nebula. Our proper motion measurements suggest the jet likely formed during the 1054 supernova explosion and represents the remnant's highest velocity knots possibly associated with a suspected N–S bipolar outflow from the supernova explosion.     

Structurally preserved Zamites bayeri Kvaček from the Coniacian Kashima Formation (Yezo Group) of Hokkaido,Japan

A permineralized frond from the Coniacian Kashima Formation (Yezo Group) of Hokkaido, Japan, is identified as Zamites bayeri based on leaf shape, transverse orientation of stomata, papillate epidermal surface, and hollow subsurface bodies formed only on the abaxial epidermis. The specimen has an articulation at the base of the leaflet from which the leaflet was detached by means of an abscission zone. This finding suggests that Z. bayeri has compound leaves that are functionally equivalent to a twig bearing simple leaves. This functional conversion is often found in extant compound-leaved ferns or cycads growing in infertile conditions; thus Z. bayeri might have lived in a similar habitat. Leaflet articulation is also found in other Zamites species including the type species of the genus, whereas it is unknown in other bennettitalean foliar morphogenera. The rachis of the specimen has a columnar vascular bundle, which is common in bennettitalean foliage.