Seasonal changes in the mesozooplankton biomass and community structure in subarctic and subtropical time-series stations in the western North Pacific

Seasonal changes in mesozooplankton biomass and their community structures were observed at time-series stations K2 (subarctic) and S1 (subtropical) in the western North Pacific Ocean. At K2, the maximum biomass was observed during the spring when primary productivity was still low. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 1.39 (day) and 2.49 (night) g C m^?2 and 4.00 (day) and 3.63 (night) g C m^?2, respectively. Mesozooplankton vertical distribution was bimodal and mesopelagic peak was observed in a 200- to 300-m layer; it mainly comprised dormant copepods. Copepods predominated in most sampling layers, but euphausiids were dominant at the surface during the night. At S1, the maximum biomass was observed during the spring and the peak timing of biomass followed those of chlorophyll a and primary productivity. The annual mean biomasses in the euphotic and 200- to 1000-m layers were 0.10 (day) and 0.21 (night) g C m^?2 and 0.47 (day) and 0.26 (night) g C m^?2, respectively. Copepods were dominant in most sampling layers, but their mean proportion was lower than that in K2. Mesozooplankton community characteristics at both sites were compared with those at other time-series stations in the North Pacific and with each other. The annual mean primary productivities and sinking POC fluxes were equivalent at both sites; however, mesozooplankton biomasses were higher at K2 than at S1. The difference of biomasses was probably caused by differences of individual carbon losses, population turnover rates, and trophic structures of communities between the two sites.     

The role of crabs (Macrophthalmus japonicus) burrows on organic carbon cycle in estuarine tidal flat,Japan

The objective of this study is to elucidate the burrow structure and to clarify the role of burrows in material cycle in the tidal flat. In our work, we focused on the dominant species in muddy tidal flat, crab Macrophthalmus japonicus.Burrow structure of Macrophthalmus japonicus was investigated on a Katsuura river tidal flat in Tokushima prefecture, Japan, using in situ resin casting. Sampling was conducted in August 2006, and a total of 48 burrow casts were obtained. Burrows consisted mainly of J-shaped structures (98%) while the rest belonged to U-shaped structures (2%). The maximum measured burrow volume was 120 cm³ and wall surface area was 224 cm², while maximum burrow length and depth were 23.2 cm and 16.5 cm, respectively. Burrow volume and surface area were strongly correlated with carapace width of M. japonicus. Investigation of the individual number of M. japonicus in 13 quadrats (50 × 50 × 20 cm) was conducted using 2 mm sieve. The number of M. japonicus was 15–31 ind./m². Using cohort analysis we estimated that surface area of burrows was 0.07–0.15 m²/m².CO₂ emission rate was measured at the surface sediment during the period from June to December 2008. Results varied from 13.8 ± 2.2 to 49.4 ± 3.2 mg CO₂/m²/h, and organic carbon decomposition was 3.8 ± 0.6–13.5 ± 0.9 mg C/m²/h. This leads the increase of organic carbon decomposition by 1.1 times, because of the expansion of the tidal flat surface area by burrowing activity. Organic carbon decomposition in burrow walls therefore contributed to organic matter decomposition in the tidal flat. These results indicated that in situ activities of Macrophthalmus japonicus significantly influence the material cycle and it is important to consider the existence of burrow in order to understand the fluxes of materials and to evaluate the purification function of the tidal flat.     

Is bacteriophage φX174 DNA a message from an extraterrestrial intelligence?

We speculate that a simple biological system carrying a message and capable of self-replication in suitable environments may be one possible channel for interstellar communication. A preliminary experiment was performed to test the hypothesis that phage φC174 DNA carries a message from an advanced civilization.     

Viscosity measurements of hydrous rhyolitic melts using the fiber elongation method

We have devised a new, simple and easy technique to measure the viscosity of hydrous silicate melts by combining an autoclave for melt hydration and the fiber elongation method for viscosity measurement. Using this, we measured the viscosity of hydrous rhyolitic melts whose water content ranges from 0.02 to 0.58 wt%. We observed a drastic decrease in viscosity against water content: 0.1 wt% water decreases the viscosity about an order of magnitude. Even when the water content is only 0.02 wt%, the viscosity decreased about half an order of magnitude. These results clearly demonstrate that the effect of water on viscosity should not be ignored even when it occurs as a trace constituent. We compared our experimental data with those derived from a non-Arrhenian viscosity model, which is considered to be applicable to calc-alkaline samples. This model succeeded in expressing the viscosity variation against water content but was unable to accurately predict the measured viscosity of liquids.Editorial responsibility: D. Dingwell     

Landslides in Sado Island of Japan: Part I. Case studies, monitoring techniques and environmental considerations

A sufficient knowledge on the kinematics and development of landslides helps to adopt proper measures that can be used to protect slopes and the environment in general. This can be achieved by adequate monitoring programs. This paper presents the findings of intensive monitoring activities carried out on Shiidomari and Katanoo landslides found in Sado Island of Japan. More than one year of observation of the two landslides allowed defining some peculiar futures of their kinematics and style of development. The problem of slope instability in the two areas is generally accredited to various factors. But, both landslides were triggered by heavy rainfalls and snowmelt. Because of the outline of the area and the presence of relict topographic features, the Shiidomari landslide is considered to be a large-scale reactivation of old slope failures. The Katanoo landslide is, however, a first-time case. Geophysical investigations and drilling activities in Shiidomari indicated the presence of two slip planes. The deepest (80–100 m) of these is controlled by existing lineaments. Monitoring data suggests that the body of the landslide has subsided as much as 1.16 m just below the main scarp, but a centimeter in the central region. The toe sector also experienced a significant amount of subsidence, but this was counter-balanced by an uplift on the opposite side of the landslide. Hence, the landslide seems not any more active along the deepest slip surface, although it may extend upward and define a series of shallow shear planes around the crown. In the case of Katanoo, the landform characteristics, differential weathering, the road cut and groundwater fluctuations appeared to contribute much to determine the exact location of the landslide. Extensional cracks that preceded the landslide can be related to heavy rainfalls and the cold and warm cycles thereafter. Subsurface investigations and monitoring works indicated that the landslide has two slide blocks with different slip planes. During the observation period, the upper part of the landslide responded more effectively to rainfall and snowmelt than the middle and lower sections. The corresponding movements, however, appeared to settle about three months after failure. There were also little strain transmissions in boreholes and no significant change in the characteristics of the landslide. The kinematics of deformation of many of the slopes in Sado Island resembles that of Shiidomari landslide. But mass movements along highways and mountain roads are usually similar to Katanoo. Landslides of the type like Shiidomari may not show sudden and drastic failures, but are usually long lasting and can reactivate repeatedly along new, shallow shear planes. Monitoring works and long-term supervisions in these types of landslides are useful to identify impending failures and take the right measures before they brought about large-scale destruction to the environment.     

Evolution and effect of the stress concentration and rock failure in the deep multi-seam coal mining

Supports crushing accident occasionally occurs in the protected seam exploitation of deep multi-seam coal mining structure and results in adverse effect to the production. To prevent its recurrence in a newly developed working field, a 3D numerical extraction model was built based on the geologic and mining conditions of Jining coal mine to evolve the changes, state and characteristics of the reconstructed vertical and lateral stress in rock interlayer after protective seam exploitation. Stress release and increase zones of this mining structure were separated. Mining-induced localized stress concentration and the interlayer rock failure behavior were explored. The action of concentrated stress on the hydraulic supports in protected seam was discussed upon the major stress redistribution. Using the infinitesimal strain method, a mechanical model was created to further explore, from the vertical and lateral directions, the cause and mechanism of localized stress concentration and rock failure behavior in rock interlayer. The field investigation was finally performed to verify the numerical and mechanical results, and the essential control measures were proposed to prevent this accident. Key findings of this study bring some new insights into the deep multi-seam coal extraction and help to promote a more reliable underground mining.     

Experimental and Numerical Investigations of Ground Deformation Using Chemical Grouting for Pipeline Foundation

Based on experimental and numerical investigations, the present paper focuses on under ground scope (UGS) chemical grouting method that can actually improve the pipeline surrounding foundation to solve pipeline saggy damage. According to the experimental results, a solution-type injection material could make lager soil deformation, using less total slurry amount than suspension-type injection material. Therefore, a suspension-type injection material with shorter gel time is more suitable for the UGS method, making it more effective to reinforce the pipeline foundation and restore pipelines. The results of some patterns of injection tests revealed relationship between the behavior of the grouting material and the deformation of the soil. It is found that the material can be injected into a foundation by fracture grouting if the permeation coefficient is lower than 1.00 × 10⁻³ mm/s. The situation was analyzed by using 2-D finite element method analysis software Phase2, and the analysis result proposes that the real data and simulation data are nearly the same in impermeable soil. Furthermore, even if the construction object is permeable soil, it can also be become impermeable soil by two phases grouting: soil improvement grouting and restoration grouting.     

An Application of Hydraulic Tomography to a Large‐Scale Fractured Granite Site,Mizunami, Japan

While hydraulic tomography (HT) is a mature aquifer characterization technology, its applications to characterize hydrogeology of kilometer‐scale fault and fracture zones are rare. This paper sequentially analyzes datasets from two new pumping tests as well as those from two previous pumping tests analyzed by Illman et al. (2009) at a fractured granite site in Mizunami, Japan. Results of this analysis show that datasets from two previous pumping tests at one side of a fault zone as used in the previous study led to inaccurate mapping of fracture and fault zones. Inclusion of the datasets from the two new pumping tests (one of which was conducted on the other side of the fault) yields locations of the fault zone consistent with those based on geological mapping. The new datasets also produce a detailed image of the irregular fault zone, which is not available from geological investigation alone and the previous study. As a result, we conclude that if prior knowledge about geological structures at a field site is considered during the design of HT surveys, valuable non‐redundant datasets about the fracture and fault zones can be collected. Only with these non‐redundant data sets, can HT then be a viable and robust tool for delineating fracture and fault distributions over kilometer scales, even when only a limited number of boreholes are available. In essence, this paper proves that HT is a new tool for geologists, geophysicists, and engineers for mapping large‐scale fracture and fault zone distributions.     

Propagation characteristics of hydromagnetic waves in a cold plasma mixed with a hot plasma and right-hand polarized Pc1 and Pc5

Propagation characteristics of hydromagnetic waves in a cold plasma mixed with a hot plasma under a uniform static magnetic field are investigated. The existence of cold plasma seriously affects the polarization properties of the waves. The results are applied to the interpretation of Pcl and Pc5 with righthand polarizations guided along the geomagnetic field line.     

Landslide susceptibility mapping using GIS-based weighted linear combination,the case in Tsugawa area of Agano River,Niigata Prefecture,Japan

A spatial database of 791 landslides is analyzed using GIS to map landslide susceptibility in Tsugawa area of Agano River. Data from six landslide-controlling parameters namely lithology, slope gradient, aspect, elevation, and plan and profile curvatures are coded and inserted into the GIS. Later, an index-based approach is adopted both to put the various classes of the six parameters in order of their significance to the process of landsliding and weigh the impact of one parameter against another. Applying primary and secondary-level weights, a continuous scale of numerical indices is obtained with which the study area is divided into five classes of landslide susceptibility. Slope gradient and elevation are found to be important to delineate flatlands that will in no way be subjected to slope failure. The area which is at high scale of susceptibility lies on mid-slope mountains where relatively weak rocks such as sandstone, mudstone and tuff are outcropping as one unit.