Recovery of entire shocked samples in a range of pressure from ~100 GPa to Hugoniot elastic limit

We carried out laser shock experiments and wholly recovered shocked olivine and quartz samples. We investigated the petrographic features based on optical micrographs of sliced samples and found that each recovered sample comprises three regions, I (optically dark), II (opaque), and III (transparent). Scanning electron microscopy combined with electron backscattered diffraction shows that there are no crystal features in the region I; the materials in the region I have once melted. Moreover, numerical calculations performed with the iSALE shock physics code suggest that the boundary between regions II and III corresponds to Hugoniot elastic limit (HEL). Thus, we succeeded in the recovery of the entire shocked samples experienced over a wide range of pressures from HEL (~10 GPa) to melting pressure (~100 GPa) in a hierarchical order.     

Strain partitioning between the Suruga Trough and the Zenisu Thrust: Neogene to present tectonic evolution in the onland and offshore Tokai district, Japan

The Tokai district in central Japan is located close to the convergent boundary between the Philippine Sea and Eurasian plates, and has experienced not only repeated large interplate earthquakes but also intense aseismic movement. In this paper, the spatial and temporal tectonic evolution of the Tokai district, particularly around the Omaezaki area, is discussed to assess whether the district has been and will be active or inactive. According to a geological survey, the horizontal crustal shortening strain can imply the hypothetical tectonic model that the area has been getting less active and the strain rate since the Neogene can be calculated as 12% and 2×10⁻⁶%/year, respectively. The present interseismic horizontal crustal strain and strain rate around the Omaezaki area are approximately 4×10⁻⁷% and 4×10⁻⁹%/year. By comparing these rates, the decrease since Neogene can imply the hypothetical tectonic model that the area has been getting less active influenced by the strain partitioning between the Suruga Trough and the Zenisu Thrust.     

Inland penetration of the sea breeze over the suburban area of Tokyo

Observational results of the structure of the sea breeze over the urban and suburban areas of Tokyo for four summer days are presented.On two of these days, the inland penetration of the sea breeze front could be clearly traced. In one case, the sea breeze was first observed along the shores of Tokyo Bay around 0900 JST, and propagated in three hours through the Tokyo City area, the width of which is about 20 km. It then advanced inland at a rate of 16 km h^–1. Prior to the arrival of the sea breeze at the suburban site, the mixing height had remained at about 600 m for four hours. With the arrival of the sea breeze front, accompanied by an abrupt change in wind speed and direction, the mixing height increased sharply to 1700 m. It is suggested that this behavior and the structure of the front are intensified due to the urban effect, or the difference in the thermal characteristics between the urban and rural areas.On the days without a sea breeze front, the land breeze system during the early morning was less intense, allowing the sea breeze to develop simultaneously with the inland valley wind and easily form a large-scale local wind system during the morning hours. In both cases, the vertical motion accompanying the local wind system works as a feedback mechanism to control the local winds by modifying the thermal and pressure fields.     

Mathematical Derivation of Spatially-Averaged Momentum Equations for an Urban Canopy Model Using Underlying Concepts of the Immersed Boundary Method

We propose a new approach to derive spatially-averaged momentum equations for an urban canopy model that resolves buildings vertically and not horizontally. First, in order to mathematically describe the actual momentum field as a completely continuous field, the underling concepts of the immersed boundary method are employed, where we assume that (i) the entire simulation space, including that occupied by buildings, is filled with a fluid, and (ii) an external body force field exists that reduces the wind speed to zero at all positions coinciding with the space occupied by the buildings. Then, in order to obtain the required spatially-averaged momentum equations in a self-consistent manner, a spatial-averaging operation is applied to the Navier–Stokes equations that include a term representing the external force field. The applied spatial-averaging operation is equivalent to the conventional spatial filtering operation used in large-eddy simulations. To examine the significance of the subgrid-scale (SGS) stresses of the spatially-averaged momentum equations, a numerical simulation is performed for a flow around a regular array of cubical blocks with a grid resolution that is sufficient to resolve the blocks. By estimating the individual terms in the spatially-averaged momentum equations using the simulation results, we show that the SGS stresses contribute significantly to the spatially-averaged momentum budget, and therefore they should not be neglected in urban canopy modelling.     

1-Gbps VLBI, The First Detection of Fringes

We report on the detection of VLBI fringes from quasars by a new VLBI system operating at 1 Gbps (1024 Mbits-per-second). Newly developed 1024 Msps (mega sample-per-second) AD samplers and 1024 Mbps recorders were used for the observations. A correlator with external buffers was used for the 1024 Mbps correlation processing of the tapes data.Our new VLBI system enabled 1024 Mbps VLBI, and this allowed the sampling of a 512 MHz bandwidth from a radio telescope receiver. This is the highest sampling speed ever used for VLBI, and the widest bandwidth used for VLBI observation. Initial sensitivity as evaluated by SNR comparison with earlier VLBI systems produced results to matched the expanded bandwidth. In our first observations, simultaneous optical fibre linked real-time VLBI observations were made to check the validity of data and precisely detemine the clock offsets among the radio telescopes.     

On the possibility of a geocoronal contribution to the celestial soft X-ray background

The possibility is investigated that a significant fraction of the X-ray background in the energy range 0.2–0.28 keV originates in the geocorona through bremsstrahlung. It is concluded that the geocoronal flux must be substantial at some times and the possibility exists that an observable geocoronal background exists at all times. The existing data on the soft X-ray background is found to be compatible with the hypothesis of a geocoronal component.     

Statistical study of Am stars in spectroscopic binary systems

Using the Am components in spectroscopic binaries, the region of metallicism in the (logm, logR) diagram is statistically discussed. The metallic-line characteristics appear in a slightly evolved stage near the Main Sequence within a belt characterized by logg=3.8–4.2, for which the radiiR/R =1.5–2.7. The distribution in the diagram indicates that appreciable differences should exist in the abundances as well as in the mixing lengths of the atmospheres of the Am components.Synchronism between rotation and revolution for the Am components is discussed, and it is clearly found that the synchronism holds accurately for the Am binaries with periods less than about six days, but for those with periods between six and ten days some Am components corotate and some do not, perhaps depending upon their ages.Using the Am spectroscopic binaries with periods less than twelve days, we find that the excess of metallicity is statistically correlated with the rotational velocity; and it is confirmed that the metallicity grossly decreases with increasing rotational velocity. If the effect of a non-Am secondary component is eliminated from a [m ₁]-value for the combined light, the correlation between metallicity excess and rotational velocity for the Am components only should approach [m ₁]/V (km s^–1)=–0.00077.     

Diurnal variability of thermospheric N and NO

A model for diurnal variations of neutral and ionic nitrogen compounds in the thermosphere is reconstructed on the basis of a new photochemical aspect on N(²D), together with new observations of the NO density. The NO density so far measured must be reduced by a factor 2, due to a revision of the fluorescence coefficient for the NO γ-band airglow. Incorporating the quenching reaction of N(²D) with O in the model calculation results in a reduction of the NO density at heights as low as 100 km. These two effects are combined to lead to an evaluation that the N(²D) quantum yield for various possible reactions is as large as 0.9. A smaller rate coefficient for the quenching reaction than that measured in the laboratory, i.e. 1.0 × 10^?12cm³sec^?1 is favourable for the recent NO observation in the early morning, as well as the observed emission rates of the 5200 A airglow from N(²D) The present model predicts a significant day-to-night variation of N and NO densities at heights above 100 km. Below 100 km, the NO density is fairly stable because of its long chemical time constant. Since the rate coefficient for the conversion of N(⁴S) to NO is highly temperature dependent, the relative population of N(⁴S) and NO is very sensitive to the thermospheric temperature variation. Large variations of both N(⁴S) and NO densities due to the temperature change could occur especially at night. The model is in good agreement with the NO observations so far available in low and middle latitudes, as well as the N observation by the use of a rocket in the twilight.     

Concentrations of trace elements in muscle of sturgeons in the Caspian Sea

Concentrations of 21 trace elements were determined in muscle of beluga (Huso huso), Persian sturgeon (Acipenser persicus), Russian sturgeon (Acipenser gueldenstaedtii), ship sturgeon (Acipenser nudiventris) and stellate sturgeon (Acipenser stellatus) collected from coastal regions of Azerbaijan, Iran, Kazakhstan and Turkmenistan, surrounding the Caspian Sea during 2000-2001. Concentrations of Mn, Co, Cu, Mo, Sn, Hg, Pb and Bi in the muscle were apparently different among the five species of sturgeons. Especially, beluga showed the highest concentrations of Hg, Pb and Mn in all the five species. In addition, more than half of the individuals of beluga exceeded the guideline level (0.3 microg/g wet wt.) of Hg for food in UK. However, V, Cr, Zn, Ga, Rb, Sr and Ba concentrations were similar among five sturgeons. Growth-dependent increase in Hg in beluga, Cu in Persian sturgeon, and Zn in Russian sturgeon were observed, whereas V, Mn, Co, Cu, Ga, Sr, Mo, Sn, Hg and Bi concentrations in Persian sturgeon, Pb in ship sturgeon, and Cr, Mn, and Rb in stellate sturgeon were negatively correlated with body length. All species of sturgeon in Azerbaijan showed the highest concentration of Sr and the lowest concentration of Rb, while the five sturgeons from Iran showed opposite trends. Concentration of V, which is present in oil, in sturgeons in the Caspian Sea was considerably lower than that of fish from Kuwait, but was comparable to that of Cambodia and the Gulf and Gulf of Oman. To our knowledge, this study provides the first extensive data on multielemental accumulation in sturgeons of the Caspian Sea.     

Air-sea CO<Subscript>2</Subscript> flux by eddy covariance technique in the equatorial Indian Ocean

Direct measurements of the air-sea CO₂ flux by the eddy covariance technique were carried out in the equatorial Indian Ocean. The turbulent flux observation system was installed at the top of the foremast of the R/V MIRAI, thus minimizing dynamical and thermal effects of the ship body. During the turbulent flux runs around the two stations, the vessel was steered into the wind at constant speed. The power spectra of the temperature or water vapor density fluctuations followed the Kolmogorov −5/3 power law, although that of the CO₂ density fluctuation showed white noise in the high frequency range. However, the cospectrum of the vertical wind velocity and CO₂ density was well matched with those of the vertical velocity and temperature or water vapor density in this frequency range, and the CO₂ white noise did not influence the CO₂ flux. The raw CO₂ fluxes due to the turbulent transport showed a sink from the air to the ocean, and had almost the same value as the source CO₂ fluxes due to the mean vertical flow, corrected by the sensible and latent heat fluxes (called the Webb correction). The total CO₂ fluxes including the Webb correction terms showed a source from the ocean to the air, and were larger than the bulk CO₂ fluxes estimated using the gas transfer velocity by mass balance techniques.