A series of centrifuge model tests has been conducted to examine the behavior of laterally loaded pile groups in normally consolidated and overconsolidated kaolin clay. The pile groups have a symmetrical plan layout consisting of 2, 2ϫ2, 2ϫ3, 3ϫ3, and 4ϫ4 piles with a center-to-center spacing of three or five times the pile width. The piles are connected by a solid aluminum pile cap placed just above the ground level. The pile load test results are expressed in terms of lateral load-pile head displacement response of the pile group, load experienced by individual piles in the group, and bending moment profile along individual pile shafts. It is established that the pile group efficiency reduces significantly with increasing number of piles in a group. The tests also reveal the shadowing effect phenomenon in which the front piles experience larger load and bending moment than that of the trailing piles. The shadowing effect is most significant for the lead row piles and considerably less significant for subsequent rows of trailing piles. The approach adopted by many researchers of taking the average performance of piles in the same row is found to be inappropriate for the middle rows, of piles for large pile groups as the outer piles in the row carry significantly more load and experience considerably higher bending moment than those of the inner piles.

Through the injection of f-aequorin (a calcium-specific luminescent reporter), and the use of an imaging photon detector, transient localized elevations of free cytosolic calcium in the forming blastodisc (BD) and animal hemisphere cortex were visualized that correlated with ooplasmic segregation. The introduction of an appropriate concentration of the weak (KD = 1.5 micromol/L) calcium buffer 5,5'-dibromo-BAPTA results in the dissipation of these calcium domains, and inhibits cytoplasmic streaming and the subsequent formation of a BD at the animal pole. These inhibitory actions are dependent on the final cytosolic concentration of buffer within the egg: > or = 1.3 mmol/L blocks ooplasmic streaming; < 1.3 mmol/L eggs segregate normally. Injection of 5,5'-dimethyl-BAPTA (KD = 0.15 micromol/L) to a final concentration of 1.5 mmol/L as a control has no effect on ooplasmic streaming. These results suggest that localized domains of elevated free cytosolic calcium are essential for ooplasmic segregation in zebrafish. Furthermore, a hypothetical model is presented linking these calcium transients to the contraction of a cortically located actin microfilament network as a possible mechanism providing the driving force for segregation.

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The safe and economic use of mobile jack-up structures is still hindered by limited understanding of the installation of their large conical 'spudcan' footings in layered sand over clay sites. This paper addresses this by detailing experimentally observed bearing failure modes induced during the penetration of a spudcan through a layer of sand into underlying normally consolidated clay. Digital images were captured continuously by installing a half-spudcan against a transparent window, and analysed using a particle image velocimetry technique coupled with close-range photogrammetry correction. As the experiments were performed in a geotechnical centrifuge the observed mechanisms occurred in stress conditions of similar magnitude to the offshore case. The experimental evidence provides: (a) failure modes at different spudcan penetration depths; (b) the transitional failure mechanism at the event of peak bearing resistance; and (c) the changes in overall failure mechanism due to varying geometric and strength conditions of the layered soil. The results provide useful references for the development and validation of analytical or numerical solutions for this problem.