The ability of Climacodon septentrionalis to immobilize and kill a mycophagous nematode (Aphelenchoides sp.) in vitro is described for the first time. Two isolates produced droplets (20–45 μm in diameter) that formed at the apices of tall, stalked, and branching secretory cells (700–1,500 μm tall). On 2% modified malt extract agar, nematodes became enveloped in the droplets, which restricted their ability to move and resulted in complete immobilization and death within several hours of contact. The rate of decomposition of the nematodes varied considerably, with most individuals persisting for weeks whereas others were degraded within several days and appeared to be colonized by dense hyphal growth. This study provides the first documentation of a non-agaricoid fungus producing secretory cells that are able to immobilize nematodes.

抄録全体を表示

The behavior of the soft clay grounds subjected to repeated loading is different from that subjected to sustained loading. The difference in settlement between these two loading patterns should be due to secondary compression over a long period of time. Consequently, soft clay grounds subjected to repeated loading tend to be more compressible than those subjected to sustained loading. Therefore, it is necessary for engineers to predict post-construction settlements under repeated loading. In this respect, the preloading is considered to be promising as a countermeasure to reduce the settlement of clay under repeated loading as well as under sustained loading. The effect of preloading on post-construction consolidation settlement of soft clay subjected to repeated loading after removal of a part of preload is investigated in the present paper. It has become clear that the settlement of a clay sample after preconsolidation is mainly affected by the amount of preload, the degree of consolidation due to the preload, the amount of permanent load and the amount of repeated load after removal of preload. The calculated settlement versus time relations using a method to estimate the amount of consolidation settlement of soft clay grounds subjected to repeated loading after removal of preloading were compared with the observed degree of consolidation as parameters of the intensities of preload and repeated load.

抄録全体を表示

A comparative study of the static and dynamic response of a slope is carried out, using the large deformation theory of the updated Lagrangian formulation and the conventional infinitesimal theory. In the static analysis, a strength reduction method proposed by one of the authors is used to evaluate the safety factor of the slope. It is found that by the large deformation theory, the safety factor is larger than that calculated by the infinitesimal theory, and this difference becomes large along with the reduction of elastic modulus. In the dynamic analysis, it is observed that the large deformation theory gives smaller sliding displacement and larger response acceleration than the infinitesimal approach. It is concluded that in many cases the large deformation approach gives more adequate solutions.

抄録全体を表示

Based on the concept "intermediate soil wedge" which is dependent on mobilized frictional resistance, a new theory has been developed for evaluating the seismic earth pressures against retaining walls under any condition between the active and passive states. For this theory, the seismic earth pressure is separated into four components according to their formation. New equations are proposed to determine the distribution, resultant and point of application for each component. An equivalent seismic coefficient is introduced to take into account non-uniform seismic acceleration distribution with depth. The equations place special emphasis on dependence of the seismic earth pressure on mode and level of wall movement. The equations can be reduced to the Mononobe-Okabe equation for the limiting conditions. Their applicability was confirmed by comparing the predictions with a number of previous model test results.

抄録全体を表示

During earthquakes, saturated loose sandy soils often liquefy, causing serious damage to buildings and underground structures. Various construction methods have been employed to stabilize these soils against liquefaction. The popular methods are those which increase their density. Vibration and impact methods are commonly employed, but these often pose a problem of noise and vibration in urban areas. Results of previous experiments have shown that Quick Lime Consolidated Briquettes (QCB), a soil stabilizer made of quicklime and cement placed to form cylinders, significantly increases resistance to liquefaction by utilizing the effects of water absorption, swelling, and hardening. In the present study, shaking table tests were performed to evaluate the earthquake resistance of soil treated with QCB. Results of these test showed that the response acceleration and excess pore water pressure in QCB-treated soils were scarcely affected by the excitation of 200 Gals. The soil settlement due to shaking was about one tenth of that for the untreated soil, proving the effectiveness of QCB during earthquakes.

抄録全体を表示

A finite element model capable of taking into account nonlinear hysteretic soil behavior is presented to study earthquake induced retaining wall movement. The model also accounts for increase in lateral stresses and settlement associated with grain slip caused by cyclic loads. The predictive capability of the proposed method is verified by comparing responses given by the model with those computed by another existing finite element model and also with responses recorded at the Cambridge centrifuge facility. The study reveals that the wall displacement can be substantially affected, among other factors, by the increase in lateral stresses due to grain slip and wall-soil friction. Care should be taken when selecting a constant value of wall-soil friction angle for the entire duration of excitation since structural changes can occur in the soil adjacent to the wall.

抄録全体を表示

In view of the significant role of the water film effect in flow failure for a liquefied sandy deposit, the mechanism of water film generation is numerically studied based on a 1-dimensional model test. The process of water film growth and decay can be simulated to a certain extent by a simple consolidation analysis, which indicates that only a small difference in permeability in layered sand is enough for a water film to develop. A 1 G shaking table test for a two-dimensional slope model with an arc of silt within a saturated sand is then addressed to discuss the dilatancy effect exerted in sheared sand during flow failure. It is possible that, once the water film is formed, the transmission of shear stress through it is interrupted, leaving the sand below free from the dilatancy ; this eventually allows the water film to stay without being absorbed during flow failure. The result of another shaking table test for a trapezoidal slope with horizontal silt seams indicate that water films beneath the seams enable the soil mass above them to laterally flow along water films very gently inclined even after shaking. If a silt seam breaks due to excessive pressure in the water film, it triggers re-liquefaction in the upper sand and leads to further instability.

抄録全体を表示

抄録全体を表示

Leakage of water due to internal erosion through a dam body or foundation is a major problem with fill-type dams. Recent case histories and research suggest that most cases of internal erosion are possibly triggered by hydraulic fracturing. However, the quantitative mechanism of hydraulic fracturing still remains to be solved. Therefore in-situ hydraulic fracture tests were carried out with a cheap, concise apparatus using boreholes dug in the soft clayey volcanic soil foundation of a low earth dam (Oyachi Dam) in Niigata Prefecture. Water was injected into the foundation through a perforated pipe by two methods : one was under a controlled injection pressure and the other was a controlled injection flow rate. In the former method, the relationship between flow rate and injection pressure was observed and it was found that a yield pressure or fracture pressure existed in all the tests. By repeating the injection test it was confirmed that once a crack is developed, it is very easily reopened by a water pressure a little higher than the earth pressure exerted on the crack. In the latter method, the relationship between injection pressure and time was observed and it was found that fracture pressure varied with flow rate. The boreholes were excavated to observe the development of fracture cracks and it was also found that the cracks had developed perpendicular to the borehole periphery, which means that fracture cracks were induced by tensile stress and denies the explanation that fractures are caused by shear failure.

抄録全体を表示

An empirical equation in use for estimating the pseudo-elastic shear modulus, G_f, of subsoil, associated with shear strains less than 0.001% is proposed in this paper. In a series of in-situ seismic cone tests performed nationwide, the profiles of both G_f and the in-situ void ratio, , with depth were successfully characterised at five sites, each comprising a soft clay layer deposited in the Holocene era. The database which comprised the original data from the field and laboratory tests, coupled with similar information on well-documented Holocene clay deposits in Europe, was statistically analyzed in attempts to determine a generalised relationship with which G_f of soft clay may be reasonably estimated only from routinely available borehole data; that is and the current geostatic effective overburden pressure, σ'_v. An empirical relationship, G_f=, 000 -√(σ'_v) (kPa), was derived from the statistical analysis applied to data from seven different clays worldwide, for which extended over a range between 1 and , and the overconsolidation ratio ranged roughly between 1 and 2. The applicability of the proposed relationship was evaluated for two case records, each in which the clay exhibited unusual behavior; i.., the undrained shear strength remained more or less constant with depth due to the existence of artesian pressure at one site, and, at the other, G_f decreased, whereas increased, with depth. It was demonstrated that even in these clay deposits exhibiting exceptional profiles, the proposed relationship was capable of predicting G_f with a reasonable accuracy by determining the profiles of and σ'_v with depth. In addition, the prediction when compared to G_max from carefully performed laboratory cyclic tests, yielded a better estimate of G_f from the in-situ seismic survey. Despite the fact that the empirical relationship was initially designated to estimate G_f of soft clays, it may be equally applicable to sandy deposits. This was verified by comparing it to similar, and well-established, relationships developed for sands. A case record as such is also described for a loose sand deposit at Higashi-Ohgishima in Tokyo Bay which was placed in 1960's by land reclamation.

抄録全体を表示

In this paper, consideration is given as to how to characterize depth-variation for the small-strain shear modulus of natural clay sedimentation, in a state of normal consolidation. A case study was carried out for a relatively uniform clay layer deposited in the Holocene era. Initially, the effects of both strain and in-situ stress levels on secant shear modulus were carefully examined in cyclic torsion shear tests using undisturbed samples, which were recovered at different depths in a test borehole. The range of shear strain examined was between 0.001% and 1%. Similar examination was made for a silty clay using reconstituted samples that were isotropically consolidated at different stress levels. On the basis of the results of these laboratory tests, together with the shear modulus from an in-situ seismic survey, the small-strain shear modulus was formulated in terms of the stress and strain levels, and linked also to undrained shear strength. Interactions of the small strain stiffness between in-situ and laboratory are discussed in depth with an attention paid to the existing aging effect in the original subsurface condition.

抄録全体を表示

Alfven resonance effects on the evolution of a magnetic island driven by an externally applied perturbation are investigated for rotating plasmas. The simulation results show the importance of Alfven resonance for obtaining a perturbed current profile and estimating a critical value of the external perturbation, beyond which the magnetic island grows rapidly. The nonlinear evolution of the externally driven magnetic island is also investigated at low and high viscosities ν. It is shown that the transition phase accompanying the secondary reconnection at the initial X-point in the driven magnetic island evolution occurs in low resistivity and viscosity plasmas.

抄録全体を表示

We screened the differentiation-inducing activities of 39 mushroom extracts from Akita prefecture, Japan, on the mouse osteoblastic cell line, MC3T3-1. Sixteen phosphate buffered saline (PBS), boiled PBS, 14 ethanol and 12 methanol extracts induced alkaline phosphatase (ALP) activities, an indicator of MC3T3-1 cell differentiation. The enzyme activities were markedly induced by extracts of Tricholoma auratum, and we isolated the active compound from methanol extracts of this mushroom. Physical data for the isolated active compound were identical to those for (,24R)-ergosta-,-diene-3β,,6β-triol (1). 1 induced ALP activities of MC3T3-1 cells and promoted cell proliferation. To investigate the relationships between the chemical structure and differentiation-inducing activity of the compound, ALP-inducing activities of MC3T3-1 cells by 1, ergosterol (2), ergocalciferol (3), cholesta-3β,,6β-triol (4), -dehydrocholesterol () and cholecalciferol (6) were tested. The enzyme activities of MC3T3-1 cells were increased 3.0-fold by 10 μM 1 and 2.4-fold by 10 μM 4. However, 2, 3, and 6 did not induce MC3T3-1 cell ALP activity at 0.1—10 μM. These results suggested that the OH groups at C- and/or C-6 of 1 and 4 played an important role in their differentiation-inducing activities on MC3T3-1 cells. Furthermore, 1 suppressed induction of MC3T3-1 cell apoptosis by serum starvation.

抄録全体を表示