Spatial and temporal distributions of water temperature in aSargassum forest

The present study examined the influence of aSargassum forest on the spatial and temporal distributions of water temperature in a small cove on a time scale of the order of hours. Water temperature and algal density were measured along a fixed transect at the cove for almost 2 days. The measurements were carried out in May 1977 during the season of luxuriant seaweed growth, and in August during the season of little growth. The average standing crop per unit volume, named the spatial algal density, was employed as a means of expressing the growth condition of the seaweed forest along the transect. Using the spatial algal density and by analyzing water temperature distribution the following facts were revealed. The diurnal fluctuation of water temperature was influenced by theSargassum forest during the season of luxuriant growth, and the seaweed forest delayed the ascent and descent of water temperature, especially under its canopy, on a time scale of the order of hours, i.e., the temperature distribution patterns were influenced by the heights and densities of theSargassum forest during its season of luxuriant growth. It is thought that these phenomena are brought about by two effects: one is the absorption by the seaweed forest of short-wave radiation passing through the sea surface, and the other is the suppression of convection by the seaweed.     

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.     

Statistical distribution of building lot frontage: application for Tokyo downtown districts

The frontage of a building lot is the determinant factor of the residential environment. The statistical distribution of building lot frontages shows how the perimeters of urban blocks are shared by building lots for a given density of buildings and roads. For practitioners in urban planning, this is indispensable to identify potential districts which comprise a high percentage of building lots with narrow frontage after subdivision and to reconsider the appropriate criteria for the density of buildings and roads as residential environment indices. In the literature, however, the statistical distribution of building lot frontages and the density of buildings and roads has not been fully researched. In this paper, based on the empirical study in the downtown districts of Tokyo, it is found that (1) a log-normal distribution fits the observed distribution of building lot frontages better than a gamma distribution, which is the model of the size distribution of Poisson Voronoi cells on closed curves; (2) the statistical distribution of building lot frontages statistically follows a log-normal distribution, whose parameters are the gross building density, road density, average road width, the coefficient of variation of building lot frontage, and the ratio of the number of building lot frontages to the number of buildings; and (3) the values of the coefficient of variation of building lot frontages, and that of the ratio of the number of building lot frontages to that of buildings are approximately equal to 0.60 and 1.19, respectively.     

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.     

Biotic response of benthic foraminifera in Aso-kai lagoon,central Japan,to changes in terrestrial climate and ocean conditions (~AD 700–1600)

We investigated responses of shallow-water benthic foraminifera to changes in climate and ocean conditions, using sediment core ASC2 from Aso-kai lagoon, central Japan. Six AMS ¹⁴C dates reveal that the studied interval corresponds to sediments deposited from ~AD 700 to 1600. Sulfur content of the bulk sediment and multi-dimensional scaling (MDS) axis 1 of fossil benthic foraminifera indicate that the composition of the benthic foraminifera community was closely related to dissolved oxygen (DO) concentration in the hypolimnion. The sulfur content and MDS axis 1 also revealed two shifts over the 900-year interval. In the first phase (~AD 700–1250), the Shannon–Wiener Index (H′), E (S₂₀₀), evenness and rank abundance curve (RAC) kurtosis indicate a gradual deterioration in structure of the benthic foraminifera community. In that period, there are statistically significant correlations between the faunal composition (MDS axis 1) and faunal structure [Shannon–Wiener (H′), E (S₂₀₀), evenness and RAC kurtosis]. In the second phase (~AD 1250–1600), however, faunal composition and structure show no marked correspondence. Instead, abundance of benthic foraminifera fluctuated on a scale of ~200 years. Thus, a shift in the biotic response of benthic foraminifera in Aso-kai lagoon occurred in ca. AD 1250. Gradual deterioration of benthic foraminifera, with taxonomic losses, is consistent with declining DO in the first phase, possibly associated with the increasing influence of the Tsushima Warm Current. The possibility that closure of Aso-kai lagoon and development of the sand bar affected benthic foraminifera cannot, however, be ruled out. No corresponding response was observed in the second phase, during which there was no distinct taxonomic loss. Large variations in abundance, however, were a consequence of strength of the East Asian summer and winter monsoons. The shift in the biotic response of benthic foraminifera in Aso-kai lagoon during the period AD 700–1600 was apparently a result of changes in climate and ocean conditions on the East Asian continental margin.     

Seasonal changes in camera-based indices from an open canopy black spruce forest in Alaska,and comparison with indices from a closed canopy evergreen coniferous forest in Japan

Evaluation of the carbon, water, and energy balances in evergreen coniferous forests requires accurate in situ and satellite data regarding their spatio-temporal dynamics. Daily digital camera images can be used to determine the relationships among phenology, gross primary productivity (GPP), and meteorological parameters, and to ground-truth satellite observations. In this study, we examine the relationship between seasonal variations in camera-based canopy surface indices and eddy-covariance-based GPP derived from field studies in an Alaskan open canopy black spruce forest and in a Japanese closed canopy cedar forest. The ratio of the green digital number to the total digital number, hue, and GPP showed a bell-shaped seasonal profile at both sites. Canopy surface images for the black spruce forest and cedar forest mainly detected seasonal changes in vegetation on the floor of the forest and in the tree canopy, respectively. In contrast, the seasonal cycles of the ratios of the red and blue digital numbers to the total digital numbers differed between the two sites, possibly due to differences in forest structure and leaf color. These results suggest that forest structural characteristics, such as canopy openness and seasonal forest-floor changes, should be considered during continuous observations of phenology in evergreen coniferous forests.     

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).     

Galerkin boundary integral equation method for spontaneous rupture propagation problems: SH-case

We develop a Galerkin finite element boundary integral equation method (GaBIEM) for spontaneous rupture propagation problems for a planar fault embedded in a homogeneous full 2-D space. A 2-D antiplane rupture propagation problem, with a slip-weakening friction law, is simulated by the GaBIEM. This method allows one to eliminate the strong singularities from the integral representation of the traction, and to separate explicitly the expression for the traction into an instantaneous component; static and time-dependent components with weakly (logarithmic) singular kernels; and a dynamic component and a quasi-static component, with continuous, bounded, kernels. Simulated results throw light into the performance of the GaBIEM and highlight differences with respect to that of the traditional, collocation, boundary integral equation method (BIEM). Both methods converge with a power law with respect to grid size, with different exponents. There is no restriction on the CFL stability number for the GaBIEM since an implicit, unconditionally stable method is used for the time integration. The error of the approximation increases with the time step, as expected, and it can remain below that of the BIEM.     

Determination of Ti, K, Sm and Gd Values in Geological Survey of Japan Reference Materials by Prompt Gamma Neutron Activation Analysis

Prompt gamma neutron activation analysis was applied to the determination of the titanium, potassium, samarium and gadolinium contents of nine Geological Survey of Japan (GSJ) reference materials (JB-1, 1a, 2, 3; JA-1, 2, 3; JR-1, 2). Firstly, the values in JB-1 were determined by the standard addition method: pressed powder disks of JB-1 were used for neutron irradiation and gamma-ray measurements, after known quantities of standard reagents had been added. Secondly, the contents of eight other reference materials were determined by comparison methods using JB-1 as the comparative standard. The precision of analyses were obtained by replicate determinations on these samples. The relative standard deviation was generally less than 5%. For most samples, analysed values agreed well (< 5%) with the recommended values.     

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.