Line features from Cygnus X-1 and the Crab nebula in the energy range 30–270 keV

A balloon-borne gemanium spectrometer was flown in an attempt to detect line-emission from Cyg X-1 and the Crab nebula in the energy range 30–270 keV. The experiment was carried out on 29–30 September, 1982. A line feature at 145 keV was observed from Cyg X-1. The intensity is (1.34±0.31)×10^–2 photons cm^–2 s^–1 and the width is 14.3 keV FWHM. From the Crab nebula, a weak line feature with 1.8 excess was found around 78 keV.     

Determination of Intraseasonal Variation of Precipitation Microphysics in the Southern Indian Ocean from Joss–Waldvogel Disdrometer Observation during the CINDY Field Campaign

To date, the intraseasonal variation of raindrop size distribution(DSD) in response to the Madden–Julian Oscillation(MJO) has been examined only over the Indonesian Maritime Continent, particularly in Sumatra. This paper presents the intraseasonal variation of DSD over the Indian Ocean during the Cooperative Indian Ocean experiment on Intraseasonal Variability in the Year 2011(CINDY 2011) field campaign. The DSDs determined using a Joss–Waldvogel disdrometer,which was installed on the roof of the anti-rolling system of the R/V Mirai during stationary observation(25 September to 30 November 2011) at(8°S, 80.5°E), were analyzed. The vertical structure of precipitation was revealed by Tropical Rainfall Measuring Mission Precipitation Radar(version 7) data. While the general features of vertical structures of precipitation observed during the CINDY and Sumatra observation are similar, the intraseasonal variation of the DSD in response to the MJO at each location is slightly different. The DSDs during the active phase of the MJO are slightly broader than those during the inactive phase, which is indicated by a larger mass-weighted mean diameter value. Furthermore, the radar reflectivity during the active MJO phase is greater than that during the inactive phase at the same rainfall rate. The microphysical processes that generate large-sized drops over the ocean appear to be more dominant during the active MJO phase, in contrast to the observations made on land(Sumatra). This finding is consistent with the characteristics of radar reflectivity below the freezing level, storm height, bright band height, cloud effective radius, and aerosol optical depth.     

Size distribution of urban blocks in the Tokyo Metropolitan Region: estimation by urban block density and road width on the basis of normative plane tessellation

The size distribution of urban blocks is important for the characterisation of urban block patterns and is known to follow several parametric statistical distributions. However, it has not previously been analysed on the basis of a normative plane tessellation and in terms of urban block density and mean road width. In this article, we formulate the size distribution of Voronoi cells using the gamma distribution estimated by urban block density and mean road width. We found that (1) both log-normal and gamma distributions can be good candidates for the size distribution of urban blocks at the scale of a region that consists of regular urban blocks and that has a uniform road width; and (2) the size distribution of urban blocks depends on the balance between pattern and width improvement effects. Based on one study region in Tokyo, if the pattern improvement effect is more prominent than the width improvement effect, the mode of urban block sizes tends to be larger than if it is not. These findings are expected to provide scientific support for urban planning (e.g. land readjustment projects).     

High-pressure and ultrahigh-temperature metamorphism at Komateri, northern Madurai Block, southern India

We report for the first time the evidence for prograde high-pressure (HP) metamorphism preceding a peak ultrahigh-temperature (UHT) event in the northernmost part of the Madurai Block in southern India. Mg–Al-rich Grt–Ged rocks from Komateri in Karur district contain poikiloblastic garnet with numerous multi-phase inclusions. Although most of the inclusion assemblages are composed of gedrite, quartz, and secondary biotite, rare staurolite + sapphirine and spinel + quartz are also present. The X_Mg (=Mg/[Fe+Mg]) of staurolite (0.45–0.49) is almost consistent with that reported previously from Namakkal district in the Palghat–Cauvery Shear Zone system (X_Mg = 0.51–0.52), north of the Madurai Block. The HP event was followed by peak UHT metamorphism at T = 880–1040 °C and P = 9.8–12.5 kbar as indicated by thermobarometric computations in the Grt–Ged rock and associated mafic granulite. Symplectic intergrowth of spinel (X_Mg = 0.50–0.59, ZnO < 1.7 wt.%) and quartz, a diagnostic indicator of UHT metamorphism, probably formed by decompression at UHT conditions. The rocks subsequently underwent retrograde metamorphism at T = 720–760 °C and P = 4.2–5.1 kbar. The P–T conditions and clockwise exhumation trajectory of the Komateri rocks, comparable to similar features recorded from the Palghat–Cauvery Shear Zone system, suggest that the Madurai Block and the Palghat–Cauvery Shear Zone system underwent similar HP and UHT metamorphic history probably related to the continent–continent collision during the final stage of amalgamation of Gondwana supercontinent.     

Landfill development in the urban fringe of Metro Manila

In low-lying areas of urban and suburban regions in Asia, the use of landfill has allowed urban land use to encroach onto watery landforms, such as back marshes, which were formerly used as rice fields. To improve understanding of the associations between land-use patterns and landfill development, we carried out a case study in the urban fringe of Metro Manila in the Philippines. We examined landfill volume derived from land-use change using GIS, and field surveyed qualitative aspects of the landfill used. We calculated the rate of application of landfill in low-lying housing development areas to be 5.0 × 10³ m³ km^?2 year^?1, most of which consisted of offsite disposal of construction waste or crushed rock produced by urban development and renewal on the adjoining uplands. The flow of fill material from offsite sources to onsite landfill development areas was on the basis of individual agreements between suppliers and developers.     

The development of Fe-nodules surrounding biological material mediated by microorganisms

Takashikozo is a phenomenon of Quaternary sediments in Japan. They are cylindrical Fe-oxyhydroxide nodules that form as plaques round plant roots, where Fe is preferentially concentrated to develop a solid wall. Structural features suggest that after the roots have decayed, the central space where the roots were situated acts as a flow path for oxidized water. Analysis of microbial 16S rDNA extracted from the nodules identified iron-oxidizing bacteria encrusted round the roots where they are the likely initiators of nodule formation. Direct microscopic observation revealed an accumulation of Fe-oxyhydroxides that fill the pore spaces and is also likely to be linked with the encrusting microbial colonies. Geological history and nanofossil evidence suggest that these Fe-nodules may have been buried at a depth of up to several tens of meters for at least 10⁵ years in reducing Quaternary sediments. Thus Fe-oxyhydroxide nodules that have formed in a geological environment at the interfaces between water and rock by microbial mediation can persist under reducing conditions. If this is the case, the phenomenon is significant as an analogue of post-closure conditions in radioactive waste repositories, since it could influence nuclide migration.     

Back-arc rifting in the Izu-Bonin Island Arc: Structural evolution of Hachijo and Aoga Shima Rifts

Abstract Multi- and single-channel seismic profiles are used to investigate the structural evolution of back-arc rifting in the intra-oceanic Izu-Bonin Arc. Hachijo and Aoga Shima Rifts, located west of the Izu-Bonin frontal arc, are bounded along-strike by structural and volcanic highs west of Kurose Hole, North Aoga Shima Caldera and Myojin Sho arc volcanoes. Zig-zag and curvilinear faults subdivide the rifts longitudinally into an arc margin (AM), inner rift, outer rift and proto-remnant arc margin (PRA). Hachijo Rift is 65 km long and 20–40 km wide. Aoga Shima Rift is 70 km long and up to 45 km wide. Large-offset border fault zones, with convex and concave dip slopes and uplifted rift flanks, occur along the east (AM) side of the Hachijo Rift and along the west (PRA) side of the Aoga Shima Rift. No cross-rift structures are observed at the transfer zone between these two regions; differential strain may be accommodated by interdigitating rift-parallel faults rather than by strike- or oblique-slip faults. In the Aoga Shima Rift, a 12 km long flank uplift, facing the flank uplift of the PRA, extends northeast from beneath the Myojin Knoll Caldera. Fore-arc sedimentary sequences onlap this uplift creating an unconformity that constrains rift onset to ～1-2Ma. Estimates of extension (～3km) and inferred age suggest that these rifts are in the early syn-rift stage of back-arc formation. A two-stage evolution of early back-arc structural evolution is proposed: initially, half-graben form with synthetically faulted, structural rollovers (ramping side of the half-graben) dipping towards zig-zagging large-offset border fault zones. The half-graben asymmetry alternates sides along-strike. The present ‘full-graben’ stage is dominated by rift-parallel hanging wall collapse and by antithetic faulting that concentrates subsidence in an inner rift. Structurally controlled back-arc magmatism occurs within the rift and PRA during both stages. Significant complications to this simple model occur in the Aoga Shima Rift where the east-dipping half-graben dips away from the flank uplift along the PRA. A linear zone of weakness caused by the greater temperatures and crustal thickness along the arc volcanic line controls the initial locus of rifting. Rifts are better developed between the arc edifices; intrusions may be accommodating extensional strain adjacent to the arc volcanoes. Pre-existing structures have little influence on rift evolution; the rifts cut across large structural and volcanic highs west of the North Aoga Shima Caldera and Aoga Shima. Large, rift-elongate volcanic ridges, usually extruded within the most extended inner rift between arc volcanoes, may be the precursors of sea floor spreading. As extension continues, the fissure ridges may become spreading cells and propagate toward the ends of the rifts (adjacent to the arc volcanoes), eventually coalescing with those in adjacent rift basins to form a continuous spreading centre. Analysis of the rift fault patterns suggests an extension direction of N80°E ± 10° that is orthogonal to the trend of the active volcanic arc (N10°W). The zig-zag pattern of border faults may indicate orthorhombic fault formation in response to this extension. Elongation of arc volcanic constructs may also be developed along one set of the possible orthorhombic orientations. Border fault formation may modify the regional stress field locally within the rift basin resulting in the formation of rift-parallel faults and emplacement of rift-parallel volcanic ridges. The border faults dip 45–55° near the surface and the majority of the basin subsidence is accommodated by only a few of these faults. Distinct border fault reflections decreases dips to only 30° at 2.5 km below the sea floor (possibly flattening to near horizontal at 2.8 km although the overlying rollover geometry shows a deeper detachment) suggesting that these rifting structures may be detached at extremely shallow crustal levels.     

Relationships between textural and photoluminescence spectral features of carbonado (natural polycrystalline diamond) and implications for its origin

Field Emission SEM (FESEM) textural observations, crystal size distribution (CSD) analyses, UV-excited luminescence imaging, and photoluminescence (PL) microspectroscopy excited by 488 nm laser were conducted on two texturally contrasting samples of carbonado, a kind of natural polycrystalline diamond from the Central African Republic (CAR). The investigated carbonado samples A and B show extremely different textures: sample A is made up of faceted crystals accompanied by abundant, small rectangular pores, whereas sample B has a granular texture with coarser crystals and scarce, large pores. Diamond crystals smaller than 2–3 µm are enriched in sample A but depleted in sample B. These textural features indicate that sample B diamonds were annealed under thermodynamically stable P–T conditions. The pore characteristics indicate that fluid permeability was higher for sample A than sample B. Photoluminescence (PL) spectra indicate that samples A and B correspond to Group A and B carbonados in the classification of Kagi et al. (1994), respectively, so that sample A reveals emissions from the H3 center without any N–V⁰ derived emission at 575 nm, whereas sample B shows emissions from the 3H center and the N–V⁰ defect. In addition, UV-excited luminescence images and photoluminescence spectra for sample B indicate that the rims of diamond crystals within several microns of a pore show luminescence features similar to those of Group AB carbonados (Kagi et al., 1994), indicating that this Group AB material was formed from Group B by irradiation from pore-filling, radioactive-element-bearing materials at a low temperature. The extent of the low-temperature irradiation is considered to depend on fluid permeability, and the Group A material was strongly irradiated due to its permeable texture whereas the Group B material was not significantly irradiated due to its less permeable granular texture. These results indicate that Group B carbonados have retained their original PL spectral features produced under high pressures and temperatures at mantle depths.     

Micro- and nano-inclusions in a superdeep diamond from São Luiz,Brazil

We report cloudy micro- and nano-inclusions in a superdeep diamond from São-Luiz, Brazil which contains inclusions of ferropericlase (Mg, Fe)O and former bridgmanite (Mg, Fe)SiO₃ and ringwoodite (Mg, Fe)₂SiO₄. Field emission-SEM and TEM observations showed that the cloudy inclusions were composed of euhedral micro-inclusions with grain sizes ranging from tens nanometers to submicrometers. Infrared absorption spectra of the cloudy inclusions showed that water, carbonate, and silicates were not major components of these micro- and nano-inclusions and suggested that the main constituent of the inclusions was infrared-inactive. Some inclusions were suggested to contain material with lower atomic numbers than that of carbon. Mineral phase of nano- and micro-inclusions is unclear at present. Microbeam X-ray fluorescence analysis clarified that the micro-inclusions contained transition metals (Cr, Mn, Fe, Co, Ni, Cu, Zn) possibly as metallic or sulfide phases. The cloudy inclusions provide an important information on the growth environment of superdeep diamonds in the transition zone or the lower mantle.     

Distribution pattern and morphochemical relationships of manganese nodules from the Central Indian Basin

In the Central Indian Basin manganese nodule abundance was variable in all sediment types. Mean abundance varied from 1.5 in calcareous ooze to 10.2 kg/m² in terrigenous-siliceous ooze sediments. Nodule grade and growth rates are positively correlated only up to 10 mm/My (million years), and grade shows no distinct relationship with abundance. Relationships between the morphochemical characteristics of the nodules and host sediment types are subtle. Both hydrogenetic and diagenetic nodules (with smooth and rough surfaces respectively) occur on almost all sediments, but in variable proportions. Thus, the overall distribution pattern shows that small nodules (<4-cm diameters) of lower grade (average value Ni+Cu+Co=1.21%) with smooth surfaces are more common on red clay, terrigenous, and terrigenous-siliceous ooze transition-zone sediments. By contrast, large nodules (>4-cm diameters) of higher grade (average value Ni+Cu+Co=1.80%) with rough surfaces are more prevalent on siliceous ooze, siliceous ooze-red clay, and calcareous ooze-red clay transition-zone sediments. This implies an enhanced supply of trace metals from pore waters to rough-surface nodules during early diagenesis.