Synchrotron X-ray analysis of norbergite, Mg2.98Fe0.01Ti0.02Si0.99O4(OH0.31F1.69) structure at high pressure up to 8.2?GPa

The natural norbergite, Mg_2.98Fe_0.01Ti_0.02Si_0.99O₄(OH_0.31F_1.69) is examined by synchrotron X-ray diffraction analysis at pressures up to 8.2 GPa. The measured linear compressibilities of the crystallographic axes are β _a  = 2.18(4) × 10⁻³, β _b  = 2.93(7) × 10⁻³, and β _c  = 2.77(7) × 10⁻³ (GPa⁻¹), respectively and the calculated isothermal bulk modulus of the norbergite is K _T = 113(2) GPa based on the Birch–Murnaghan equation of state assuming a pressure derivative of K′ = 4. The crystal structures of norbergite are refined at room temperature and pressures of 4.7, 6.3, and 8.2 GPa, yielding R values for the structure refinements of 4.6, 5.3, and 5.3%, respectively. The bulk moduli of the polyhedral sites are 293(15) GPa for the tetrahedron, 106(5) GPa for the M2 octahedron, 113(2) GPa for the M3 octahedron, and 113(3) GPa for the total void space. The bulk modulus exhibits a good linear correlation with the filling factor for polyhedral sites in structures of the humite minerals and forsterite, reflecting the Si⁴⁺ + 4O²⁻ ⇔ □ + 4(OH, F)⁻ substitution in the humite minerals. Moreover, two simply linear trends were observed in the relationship between bulk modulus and packing index for natural minerals and dense hydrous magnesium silicate minerals. This relationship would reflect that the differences in compression mechanism were involved with hydrogen bonding in these minerals. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Rapid and Simple Measurement of H2 Emission from Active Faults Using Compact Sampling Equipments

Smaller equipment has been developed for sampling and measuring H₂ in fault zones. A considerable volume of hydrogen emission, suggesting the presence of fluid paths along fault zones, was detected within a 1‐h simple field procedure at an active fault in Central Japan, the Atotsugawa Fault. The equipment enabled measurements in a thin fault gouge with a thickness of 10 mm; this led to pervasive sampling from small fault zones hosted in harder rocks. A rapid evaluation of the spatio‐temporal heterogeneity of hydrogen emissions along the faults, using the present method, would increase knowledge of fluid circulation around faults.     

Rocket observation of the EUV images of a solar flare and active regions

Images of a flare and active regions were obtained in the extreme ultraviolet emission lines such as CIII 977 Å, Ne VIII 770 Å, and HI L, and hydrogen Lyman continua with a spatial resolution of less than ten seconds of arc together with one-dimensional scanning at 1650 Å. A microchannel plate was used as a detector, and pointing accuracy was, for about half of the observation time, around 0.5 arc sec.The relationship between the shape of the flare and the structure of the photospheric magnetic field is discussed. A map of the electron temperature distribution derived from the intensity ratio of the Lyman continua at 880 Å and 815 Å showed a lower temperature in regions of higher activity. A very small geometrical thickness of 50–500 m in the C III emitting region of the flare was found. And the layer emitting the continuum in 1650 Å is shown to be at a temperature of 5300 K in the flare and 4700 K in active regions.     

Observations of Flares and Active Regions from Yohkoh, and Magnetodynamic Models Explaining Them

We discuss here some of the new aspects about solar flares and active regions found by the Solar X-ray Satellite Yohkoh, by taking advantage of the wider dynamic range and higher cadence observations with higher spatial resolution compared with the previous satellites. Those new aspects have lead us to new ways of understandings, with contradictions to the previous views about flares and active regions that are widely conceived for a long time. We give some models that explain those newly revealed observational results. This revised version was published online in July 2006 with corrections to the Cover Date.     

Studies on a very flare-active δ group: Peculiar δ spot evolution and inferred subsurface magnetic rope structure

The complex subsurface magnetic rope structure of a very flare-active isolated group (McMath 13043, July 1974) is studied by means of high-resolution evolutionary data from BBSO magnetic and velocity data. This group showed unusually fast evolution accompanied by a number of intense flares occurring on the neutral line of a spot, and provided an excellent opportunity to study the inherent relation of flare occurrence to changes of the magnetic configuration. We first examine the abnormal evolution of this group started by formation of a large, compact, reversed spot by squeezing of multipoles. The configuration was deformed by penetration into the opposite polarity umbra and its subsequent disappearance, decaying by rapid shear motions. Strong transverse fields over 4000 G were detected in the penumbrae and some umbral components.Combining these data with the August 1972 region, the evolution of these isolated groups is shown to decompose into two flare-associated elementary modes: (A) shearing produced by spot growth and (B) reduction of shear as spots disappear. We propose a model of an emerging twisted magnetic knot to explain the two modes and apply realistically to the present evolution. The inferred magnetic topological structure of this region consists of tightly twisted (sheet-like) knots and a long-winding twisted rope with an internally reversed loop and a hooked bottom struture. Their consecutive emergences are suggested to explain the abnormal evolution of this 5 group. This result indicates that the origin of the concentrated flare activity in these isolated groups may be traced to internal magnetic activity responsible for forming anomalous magnetic ropes.The author died on January 2, 1990. This paper, prepared for publication at the time of his death, was edited by Professor H. Zirin.     

A sediment trap experiment in Funka Bay, Japan: “upward flux” of particulate matter in seawater

Sediment trap experiments were carried out ten times in one year (1977) at three depths in Funka Bay. The material obtained in the traps was analyzed for metals, organic elements and radionuclides, together with the suspended matter in the overlying water column. Two groups with extremely different downward fluxes were found, a group with a small flux increasing with depth, and another with a large flux that is rather constant with depth and is observed only in winter. The flux in winter, and sometimes in the bottom layer below the summer thermocline was larger than the net sedimentation rate for total dry matter or for each chemical constituent. The flux was also larger than the net removal flux for ²³⁴Th. A most striking fact is that the specific activity of short-lived ²³⁴Th did not decrease in winter, indicating that the large flux in winter was not caused by the re-suspension of old bottom sediments. The concentration of suspended matter in winter was not much greater than that in other seasons. These results suggest that the downward flux observed in sediment trap experiments is not a net removal rate and that there must be an upward particulate flux in the bay.     

Gram Stain Index (GSI) of Bacterial and Archaeal Cells in the Natural Microbial Communities of Slightly and Extremely Saline Environments

The use of GSI (Gram Stain Index) was studied for natural microbial cells in slightly and extremely saline environments. The GSI spectra of archaeal cells in an extremely saline environment showed unique profiles, different from those of Bacteria. These profiles can be applied for structural analysis of the microbial communities in aquatic environments.     

Citrate-dithionite-bicarbonate extractable phosphorus (CDB-P) pool in the suspended and surface sediments of the tidal flat area in inner Ariake Bay,Japan

CDB-P (phosphorus extractable by the citrate-dithionite-bicarbonate extraction procedure) was used as the indicator of bio-available inorganic P in the suspended and surface sediments in the inner part of Ariake Bay. The CDB-P pool of suspended and surface sediments in the tidal flat area was estimated to be 10 ton and 90 ton, respectively (total of 100 ton), which corresponds to 1.5 times the average dissolved inorganic phosphorus standing stock. During the summer periods of hypoxia, the CDB-P concentration in the surface sediments decreased with the decline of Eh, losing 43–47% of the CDB-P observed in April. These results suggest that the phosphorus dynamics have been affected by the decrease of resuspended sediment concentrations brought about by the reduction of the tidal currents and phosphate release from the surface sediments during frequently occurring summer hypoxia events.     

Clay Minerals and Geotechnical Index Properties of Marine Clays in East Asia

Clay mineral composition and geotechnical index properties of marine clays collected from Singapore, Korea, and Japan were investigated, and the correlation of clay mineral composition with the consistency limits and activity of the clays was examined. Predominant clay minerals were kaolinite for Singapore clay, kaolinite, vermiculite, and illite for Pusan clay, and smectite for Hachirogata and Ariake clay from Japan. The activity of clay indicates that Singapore clay is classified as normal or inactive, Pusan clay as normal, and Hachirogata and Ariake clays mostly as active. Significant positive correlations were found between smectite percentage in bulk soil and the liquid and plastic limits of the clays.     

Growth and mortality of larval and juvenile Japanese seaperch Lateolabrax japonicus in relation to seasonal changes in temperature and prey abundance in the Chikugo estuary

Japanese seaperch Lateolabrax japonicus migrate from Ariake Bay to the estuarine turbidity maximum (ETM) zone of the Chikugo River and inhabit there through the post-migration period (15–20 mm in standard length). The feeding, growth and mortality during the post-migration period of Japanese seaperch were analyzed in relation to seasonal changes in temperature and prey concentration. Larvae and juveniles were collected from ten sampling stations at 4–7 day intervals from 24 February to 24 April 2005 in the Chikugo estuary. Based on the otolith microstructure analysis the sampled fish were divided into nine cohorts, each cohort covering a 5 day hatch date period (22 December 2004 to 4 February 2005). The growth coefficient (G, day⁻¹) was higher and the mortality coefficient (M, day⁻¹) was lower in the later cohorts. The ratio of G to M as an index of stage-specific survival during the post-migration period significantly increased as the season progressed and exceeded 1.0 in the last cohort examined. Variability in abundance of the major prey organism, Sinocalanus sinensis, had a significant effect on the Japanese seaperch ingestion rate. Increase in temperature and spring bloom of S. sinensis is concluded to provide the later cohorts with a higher survival probability through increasing ingestion and growth rates during their post-migration period in spring 2005.