Intraannual variability of sea level around Tosa Bay

Through analysis of monthly in situ hydrographic, tide gauge, altimetry and Kuroshio axis data for the years 1993–2001, the intraannual variability of sea level around Tosa Bay, Japan, with periods of 2–12 months is examined together with the intraannual variability of the Kuroshio south of the bay. It is shown that the intraannual variation of steric height on the slope in Tosa Bay can account for that of sea level at the coast around the bay as well as on this slope. It is found that the steric height (or sea level) variation on the slope in this bay is mainly controlled by the subsurface thermal variation correlated with the Kuroshio variation off Cape Ashizuri, the western edge of Tosa Bay. That is, when the nearshore Kuroshio velocity south of the cape is intensified [weakened] concurrently with the northward [southward] displacement of the current axis, temperature in an entire water column decreases [increases] simultaneously, mainly due to the upward [downward] displacement of isotherms, coincident with that of the main thermocline. It follows that the steric height (or sea level) decreases [increases].     

Circulation and Material Transport in Suo-Nada during Spring and Summer

An attempt was made to reproduce the circulation pattern in Suo-Nada, Japan during spring and summer season in order to elucidate the water exchange mechanism in the basin. Two hydrographic surveys at the end of each season were conducted covering the entire Suo-Nada area. A three-dimensional hydrodynamic Princeton Ocean Model (POM) was used to compute the current resulting from the observed density and wind field. During spring, a very pronounced counter clockwise gyre is situated near the opening of the basin. This is replaced by a clockwise circulation which seemed to occupy the whole domain during summer. Within each season, however, the vertical distribution of current does not show any remarkable differences, indicating the dominance of horizontal current and a very weak estuarine flow. These observational and numerical results were used to estimate the remnant function and the corresponding average residence time of permanently dissolved matter (PDM) and transformable matter (TM). The results revealed a small difference in the average residence times of materials within each season but a large seasonal variability between spring and summer. Furthermore, calculations based on climatological density fields have indicated a similar trend of variation between the seasonal values of average residence times. This revised version was published online in July 2006 with corrections to the Cover Date.     

Tidal pump at the shelf edge

Material transport through the shelf edge to the deep ocean determines the fate of particulate matter generated in productive coastal seas. In stratified estuaries, onshore flow in the bottom layer generally keeps particulate matter generated in the upper layer and settled down to the bottom layer within the estuaries. AT the shelf edge of Tokyo Bay under the condition of average onshore flow in the bottom layer, we observed higher vertical sediment flux during ebb than flood tidal currents. The on-shelf and off-shelf differences in turbulent mixing and water depth mainly cause such difference in sediment flux. We propose to call this export process of particulate matter the tidal pump at the shelf edge.     

藻酸双酯钠对蛋白激酶A活性的影响

大鼠肝脏经匀浆、硫酸铵盐析和DEAE-纤维素柱层析,得到部分纯化的Ⅰ型和Ⅱ型蛋白激酶A。将两型酶制剂在体外分别与藻酸双酯钠孵育,藻酸双酯钠对两型酶的活性均有剂量依赖性抑制作用。     

Baroclinic eddies south of Cheju Island in the East China Sea

The detailed structures of baroclinic eddies, that is, an anticlockwise circulation in the upper layer and a clockwise one in the lower layer south of Cheju Island in the East China Sea have been revealed by intensive field observation. Such baroclinic eddies are accompanied by the southward spreading of the Yellow Sea Bottom Cold Water.     

Distribution and sources of organic carbon, nitrogen and their isotopes in sediments of the subtropical Pearl River estuary and adjacent shelf, Southern China

The isotopic composition (δ¹³C and δ¹⁵N) and organic carbon (OC) and total nitrogen (TN, organic plus inorganic) content of 37 carbonate-free surficial sediments of the subtropical Pearl River estuary and the adjacent shelf of South China Sea (SCS) was determined. The δ¹³C values indicate that the sediment organic material is a mixture from two sources, terrestrial and marine. Several of the sediments have extremely low (< 4) OC / TN ratios, which could be due to low OC contents and/or to a significant fraction of the TN present as inorganic nitrogen adsorbed on clays. In general, the spatial patterns of OC, TN, δ¹³C and δ¹⁵N are similar. Values are low at the river mouth and on the western coast, suggesting proportionally greater accumulation of terrestrial particulate organic matter relative to marine phytodetritus, which is limited by low productivity in the turbid plume of the Pearl River. Algal-derived organic carbon (al-OC) content is estimated to be low (≤ 0.06%) at the river mouth and higher (up to 0.57%) on the adjacent inner shelf based on a mixing model of end members.     

Flare event statistics on UV Ceti-type stars

A statistical study of 228 flares on the three UV Ceti-type stars, i.e., YZ CMi, AD Leo, and EV Lac, is presented. Observations were gathered by Ichimura and Shimizu over a total monitoring time of 907 hours distributed over 18 years (1971 to 1988). Period analysis of flare activity was performed, and no periodicity was detected on the three stars for either the flare number rate or the energy rate in time-scales ranging from a year up to 14 years. Average colour of flares at peak was (U-B)=–0.98±0.17 and (B-V)=0.05±0.13. Cumulative number distributions of flare event time-integrated energies were solved by a least-squares method on a log-log plot for a power-law function to get both the constant of and the gradient , which were found to be similar among the three stars. The gradient showed that rare large flare events radiate most of the energy released by all the flare events in the monitoring time. The flare number rate and energy rate are similar if the power-law distributions are extended up to a specific maximum energy. In reality, the Kolmogorov-Smirnov test showed that the observed cumulative number distributions of flare event energy were not necessarily a power-law function. The monte-Carlo simulation, however, indicates that the monitoring time and/or the patrol observation time interval may not be long enough to get the average flare number rate and energy rate, especially at the upper energy limits which are statistically unreliable.     

Buoyancy-driven perturbations in a rapidly rotating,electrically conducting fluid: part II – dynamo action

The helicity, electromotive force and α-effect produced in a homogeneous, rapidly rotating, electrically conducting fluid by an isolated source of buoyancy at small Elsasser number are calculated, visualized and analyzed. Due to physical symmetries of the system, the integrals of helicity and electromotive force over all space are zero. However, each has a significant non-zero value when integrated over the cross section of the Taylor column. The local α-effect is found to be significantly anisotropic; it is strongest when the applied magnetic field is toroidal and the resulting EMF is parallel to the applied field.     

Effects of the undecomposed layer and semi-decomposed layer of Quercus variabilis litter on the soil erosion process and the eroded sediment particle size distribution

Simulated rainfall experiments were performed on bare, undecomposed litter layer and semi-decomposed litter layer slopes with litter biomasses of 0, 50, 100 and 150 g m⁻², respectively, to evaluate the effect of the undecomposed layer and semi-decomposed layer of Quercus variabilis litter on the soil erosion process and the particle size distribution of eroded sediment. The undecomposed layer and semi-decomposed layer of litter reduced the runoff rate by 10.91–27.04% and 12.91–36.05%, respectively, and the erosion rate by 13.35–40.98% and 17.16–59.46%, respectively. The percentage of smaller particles (clay and fine silt particles) decreased and the percentage of larger particles (coarse silt and sand particles) increased with an increased rainfall duration on all treated slopes, while the extent of the eroded sediment particle content varied among the treated slopes with the rainfall duration, with bare slopes exhibiting the largest variability, followed by undecomposed litter layer slopes and finally semi-decomposed litter layer slopes. The clay and sand particles were transported as aggregates, and fine silt and coarse silt particles were transported as primary particles. Compared with the original soil, sediment eroded from all treated slopes was mainly enriched in smaller particles. Furthermore, the loss of the smaller particles from the undecomposed litter layer slopes was lower than that from the semi-decomposed litter layer slopes, indicating that the undecomposed litter layer alleviated soil coarsening to some extent. The findings from this study improve our understanding of how litter regulates slope erosion and provide a reference for effectively controlling soil erosion.