(

3H

) Tobramycin was used as a probe to determine the relationship between the structure of aminoglycoside antibiotics and their ability to remove this drug from its higher affinity binding site on the ribosome. The dissacharide moieties (neamine, tobramine, gentamine) appeared to have a common binding site, whereas the kanosamine, garosamine and ribose moieties determined the specificity of this binding. Amikacin and butikacin behaved in an anomalous manner in spite of their close structural relationship to tobramycin.

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The mechanism of wave-induced instability in a permeable seabed have been studied for more than two decades. The distinction between shear failure and liquefaction, however, has not been clearly defined. This paper presents a fundamental study on the differences in two failure modes for a fully saturated seabed of both finite and infinite thickness. The wave-induced effective stresses and pore pressure, obtained from an analytical solution of Biot's pore-elastic consolidation theory, were employed to examine the failure modes under a two-dimensional plane strain condition. A case study is presented to examine the failure modes with respect to several parameters, such as excess pore pressure, seepage flow, seepage force, failure areas and stress path in the seabed. The conclusions obtained from this study were as follows ; () the thickness of a permeable seabed affects the pore pressure and effective stress response to ocean waves and the failure mode of the seabed, (2) either a liquefaction or shear failure, or both, occur in the seabed, even in the saturated seabed, () the Mohr-Coulomb's failure criterion, when combined with elastic stresses, can not be employed to estimate the liquefaction failure in the seabed, (4) the liquefaction can be evaluated by a criterion in terms of the excess pore pressure, (5) The liquefied zone in the seabed is significantly different from the shear failure zone. The shape beneath the seabed surface for the former is almost identical to the contour where the upward seepage flow is concentrated.

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The objective of this article is to propose and evaluate a sliding-block model to deal with very large displacements of slopes when a horizontal earthquake is applied. The slip surface consists of two inclinations on which full shear resistance is mobilized. Internal shearing exists along a sub-plane that intersects the angle between the two sub-planes that form the external slip surface. The ratio of the distance moved along the two external sub-planes depends on the inclination of the internal sub-plane. If there is a water table line, undrained conditions are assumed during motion and total stress analysis is performed. The governing equations of motion are formulated, analytical solutions are obtained for some cases, and back-analysis of four well-documented slides is performed.

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This paper is concerned with an extension of a rotational limit equilibrium method for determining the permanent displacements of slopes under seismic excitation. In the proposed procedure, the sliding mass is treated as a rigid rotating body defined by a log spiral trace. Permanent displacements are obtained by double-integration of the equation of motion in a manner similar to Newmark's translational sliding block method. The seismic slope stability analysis is based on the rotational (variational) limit equilibrium approach. This stability analysis was verified with dynamic experimental results obtained from centrifuge model testing. A series of parametric studies was conducted on"unstable"slopes, investigating the effects of soil properties and characteristics of excitation on the magnitude of permanent displacements. The higher the frictional angle, the smaller the permanent displacement of the slope is. Low excitation frequency yields larger slope displacement if the excitation is extended for the same time period of time. The effect of frequency becomes less distinct when a larger value of yield seismic coefficient is used. The proposed procedures produce a rational criterion to evaluate the seismic performance of simple slopes. This criterion is based on permanent displacement limit rather than factor of safety alone.

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The activities of tobramycin derivatives acetylated and ethylated on the '-N, 2'-N and -N positions were examined. The MICs of these derivatives against tobramycin sensitive strains indicated that 2'-N-ethylated and '-N-ethylated derivatives have a fairly good activity, and confirmed that the -N position is the most important one for antibiotic activity since -N derivatives were less active. The MICs of these derivatives against tobramycin resistant strains, and their inactivation by tobramycin modifying enzymes were examined. These results showed that 2'-N or '-N ethylation protects the drug against inactivation by AAC(2') or AAC('), respectively, and 2'-N-ethyltobramycin and '-N-ethyltobramycin were active against strains containing these modifying enzymes. On the other hand, -N ethylation protects the drug against inactivation by AAC() but -N-ethyl tobramycin does not inhibit strains containing this enzyme.

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In the 1993 Kushiro-oki Earthquake of Richter magnitude ., simultaneous recording of earthquake motions was successfully made at the ground surface and at a depth of 77 meters in a dense saturated sand deposit. The peak horizontal acceleration was 0.47 g on the ground surface and 0.21 g at a depth of 77 meters. The acceleration record at the ground surface showed a distinctive ground response, which consisted of a cyclic motion having a period of about .5 seconds overlain by a spike at each peak of the motion. In order to study the mechanism of this peculiar ground response, effective stress analysis was conducted on the dense saturated sand deposit. The model used for this study was a strain space multiple mechanism model, which takes into account the effect of principal stress axis rotation. The recorded earthquake motion at a depth of 77 meters was used as the input earthquake motion for the analysis. Sampling after in-situ freezing was done in order to evaluate the properties of the sand. The results of the analysis indicated that the observed ground response was due to the effect of dilatancy of sand, which plays a significant role in the response of the dense saturated sand deposits during strong earthquake motions.

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The curvatures and subsequent bending imposed to piles by the surrounding soil during the passage of seismic waves is studied. This type of bending develops even in the absence of a superstructure and is referred to as "kinematic" bending, to distinguish it from pile bending generated from inertia forces in the superstructure (termed "inertial" bending). Although kinematic bending may be severe in the presence of sharp stiffness discontinuities in the profile and may lead to damage, it has received little attention by engineers. The scope of this paper is threefold : () to review some existing design methods ; (2) to present an improved analytical model for estimating kinematic pile bending moments at an interface between two thick soil layers under dynamic SH-wave excitation ; and () to propose a simplified analysis procedure to be used for designing piles against kinematic loading. To this end, a dimensionless bending strain parameter (instead of the commonly-used bending moment) and a strain transmissibility function relating pile bending strain and corresponding soil shear strain are introduced. The two indices provide insight into the physics of the problem which is often obscured by the use of bending moments. Results from the model are in good agreement with more rigorous solutions. Numerical examples are presented.

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The dynamic response of large-diameter end-bearing cylindrical shafts is studied. First, the popular plane-strain model of Novak is reviewed and its limitations are discussed. An improved model is then developed which, while retaining the simplicity of the original model, accounts for the third dimension by considering the normal and shear stresses acting on the upper and lower faces of a horizontal soil slice. These stresses are incorporated in the analysis by impleminting a dynamic Vlasov-Leontiev approximation based on integrating the governing equations over the thickness of the soil layer. It is shown that this operation leads to a set of elastodynamic equations which are similar to those in the plane-strain model, yet properly incorporate the salient -D effects. Explicit closed-form solutions are obtained for : (i) the dynamic soil reaction along the shaft ; (ii) the dynamic impedance of the shaft ; (iii) the displacement field in the soil ; and (iv) the dynamic interaction factors between neighboring shafts. Both vertical and lateral oscillations are analyzed for single and grouped shafts. Results are presented in terms of dimensionless graphs which highlight the importance of soil-foundation interaction on the response. It is shown that the proposed model avoids the limitations of the plane strain model.

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An analytical measure was developed so that the permanent displacement/deformation caused by seismic subsoil liquefaction can be predicted. Since the effects of topography on displacement is important, a three-dimensional analysis was developed which can fully consider the topography. Moreover, the loss of resistance in the surface unliquefied crust undergoing a tensile stress was taken into account. The empirical interpolation of the lateral displacement along the vertical axis helped reduce the amount of computation. Consequently, a finite-element two-dimensional analysis which is equivalent to a three-dimensional calculation was developed. The displacement obtained by the proposed method is the maximum possible to minimize the potential energy of the subsoil. By comparing the calculated displacement with the observation, the predicted displacement was to some extent greater than the observation. Hence, a dynamic analysis in the time domain, which was also developed by the authors, is necessary for a better matching between prediction and observation. In contrast, the direction of displacement was correctly predicted by the present analysis.

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Liquefaction susceptibility is the measure of a soil's ability to liquefy during earthquakes. Conventionally, liquefaction susceptibility is determined from soil properties and a subjective knowledge of the geologic conditions. There are many uncertainties in this approach because of the subjectivity in evaluating many important factors. An expert is required if the evaluation is to be performed with confidence. The application of fuzzy set theory is proposed to improve this process. The intent was to develop a method of evaluating liquefaction susceptibility that included factors usually evaluated only by an expert. The method could then be used by engineers with little experience with liquefaction. This new approach incorporates expert opinion of the importance of the subjective factors known to affect liquefaction. The engineer inputs the soil profile using linguistic descriptions which are then processed using the theory of fuzzy sets. The resulting fuzzy sets are interpreted by defining the Fuzzy Liquefaction Susceptibility Index (FLSI), a number which can be plotted and contoured to produce a map of liquefaction susceptibility. The new approach was tested by mapping the liquefaction susceptibility of Charleston, South Carolina, and comparing with other published results generated from conventional analysis. The results were quite comparable, indicating the potential for the new method to evaluate liquefaction susceptibility. The new technique is useful in creating maps of relative liquefaction hazard that can be used in municipal planning.

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This paper concerns with the mechanism of the permanent lateral displacement of ground induced by seismic liquefaction. The present study consists of three series of shaking table tests of both large and small scales. The test results demonstrated that the ground movement occurs in the same direction as that of the total head gradient as defined in hydraulics, while a large shear distortion occurs in the liquefied sand. The horizontal displacement in a liquefied layer was found to be null at the bottom and maximal at the ground water table. It was also observed that the surface unliquefied layer, if any, moved together with the liquefied subsoil without slip. The influence exerted by a global topography should not be neglected, although the local ground condition is important as well. The effect of the seismic inertia force is not important as compared with that of the gravity force. With these findings, it is suggested that the liquefied sand undergoing lateral displacement behaves similar to liquid. This idea seems to help predict the extent of the permanent displacement of the liquefied ground.

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By employing an undrained cyclic loading ring-shear apparatus, a series of tests to reproduce the dynamic behavior of the Nikawa landslide induced by the January 17, 1995 Hyogoken-Nambu earthquake, is conducted. The test sample is Osaka-group coarse sandy soil taken from the landslide. The initial stress condition acting on a soil element in the sliding surface is applied to the sample. Based on the seismic records monitored at the JR Takarazuka Station, the input seismic wave is synthesized to reproduce the seismic stress acting on the sliding surface. The test results show that the soil failed due to the dynamic loading of the earthquake. The most important results are the excess pore water pressure generation and the acceleration of shear displacement continuing after the main shock. Combined with the grain crushing at the shear zone and the volume reduction in the drained constant-speed ring-shear test, the mechanism of this landslide is interpreted as, shear displacement causing grain crushing in the shear zone and volume reduction, and then resulting in a localized liquefaction phenomenon, "sliding-surface liquefaction". This geotechnical simulation test provides a reasonable interpretation of this highly mobile landslide.

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In this paper, centrifuge shaking table tests were conducted in order to understand the performance of seawalls during a seismic event. The model tests showed that the displacement of the caisson was much affected by the seaward shear deformation of the sand seabed beneath it during shaking. It was also confirmed that an armored embankment played an important role in the displacement of the caisson during shaking. Based on these test results, a two-dimensional DEM-FEM coupled analysis method was newly developed to numerically predict the deformation of seawalls covered with armored embankments during earthquakes. The movements of the armor units were calculated by DE analysis and deformations of the caisson, rubble mound, sand seabed and backfill were calculated by FE analysis considering the non-linearity of the soil materials based on the effective stress. Dynamic interaction was taken into account by delivering the nodal displacements of the finite elements or the nodal forces converted from the contact forces through the imaginary distinct elements defined at the boundaries between the DE and FE domain. The applicability of this method to the prediction of the deformation of seawalls was verified through numerical simulations of the centrifuge model test.

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Seismic records obtained from a seismometer array located in downtown Tokyo Japan for about ten years were inversely analyzed to estimate the dynamic soil parameters. Due to the illposed nature of the problem, the simple and often used "least square method" does not properly estimate the parameters. The Extended Bayesian Method combined with the Akaike Bayesian Information Criterion was introduced to overcome this difficulty. The results obtained were compared with dynamic triaxial test results obtained at the time of the seismometer installation. The shear moduli agree quite well with the estimated results, however the damping ratios estimated are slightly higher than the ones obtained in the laboratory.

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This paper concerns the stability against overturning of the caissons on rubble mound subjected to wave loading. A theoretical discussion is first made of the stability of a leaning caisson during wave loading, as a single degree-of-freedom system. The expression for the lower bound of driving moments sufficient to overturn a given caisson is derived. A review is then made of the damages induced to a composite breakwater, which consisted of two adjoining Stretches and C with slightly different sizes of caissons. Attention is called for the observation that most of the caissons in Stretch were overturned, whereas no caissons in Stretch C were brought into overturning. This fact is examined in detail in the light of the theory of overturning, making it possible to estimate the destructive wave heights that are compatible with the observed patterns of damage in Stretches and C of the composite breakwater.

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Stress wave theory is applied to open-ended pipe piles to clarify the effects of soil plug on the behaviour of piles during driving and static loading. Measured field data and various numerical models are reviewed ; methods are presented to calculate wave propagation in both the pile and the soil plug ; modelling is presented which takes into account the interaction between the soil plug and the pile ; also presented is simplified method to estimate the loadsettlement relation of the pipe pile in static loading. By correlating observed and calculated values in two analytical cases, the authors demonstrate that incorporation of the soil plug (modelled as a series of masses and springs) is required to correctly predict pile behaviour during driving and static loading.

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Man-made islands have recently been considered as possible new construction sites for a variety of facilities. The performance of the seawalls bounding these islands when subjected to seismic loading is an important aspect of design. To obtain data on the performance of such structures when founded on a medium dense sand seabed and supported by an armored embankment, a series of large scale centrifuge models were tested at the University of California, Davis. The concrete caisson within the seawall was found to settle, displace laterally and rotate slightly away from the backfill. However, the deformations were limited, and global failure of the structure did not occur despite base accelerations of up to 0. g. The model accelerations were amplified up through the substratum and caisson during relatively small events, but were strongly attenuated during the larger events. Zones containing high excess pore pressures were generally located towards the top of the sand fill forming the island, and in the seabed below the toe of the armored embankment. These zones grew progressively larger as the event magnitude increased, and accordingly the times for pore pressure dissipation to occur lengthened with increasing event magnitude.

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