The locomotor activity of Acheta domesticus in light–dark (LD) cycles became more synchronous, i.e. it had a smaller variance around the mean, as the concentration of melatonin in drinking water increased. The ratio of night activity to total activity was increased and the acrophase was delayed by melatonin drinking. Bouts of activity also decreased in LD cycles as the concentration of melatonin increased. The number of activity bouts in the free-running rhythm in DD, however, was not influenced by the melatonin concentration. The most apparent effect of melatonin on the activity in LD cycles seems to be the elimination of day-time activity. Not only did melatonin eliminate day-time activity to give a better synchronization in LD cycles but it also affected the free-running rhythm, which tended to be more synchronized, i.e. the activity became more concentrated, as the concentration of melatonin increased. The amplitude of free-running rhythms also increased as the melatonin concentration increased, even at 100 μg melatonin/ml, though the amplitude in DD was lower than that in LD cycles.

The role of the compound eyes in entrainment of the circadian activity rhythm was examined in Protophormia terraenovae (Diptera: Calliphoridae). In intact females, the freerunning period of the rhythm under constant darkness was about 25.0h. The rhythm entrained to light–dark (LD) cycles with activity restricted to the photophase. When the compound eyes were completely covered with silver paint and black synthetic resin paint, the rhythm freeran under LD cycles with the photophase of intensities 1.4×10−3 as well as 1.4W/m2. Control flies showed complete entrainment. When the compound eyes and ocelli were surgically removed, the rhythm freeran under 1.4×10−3W/m2 LD cycles but entrained to 1.4W/m2 LD cycles. Flies subjected to a sham operation, in which the ocelli were removed, showed complete entrainment to LD cycles. When the compound eyes were removed and then the operated region was covered with the paint, some flies showed entrainment while others showed freerunning rhythm under 1.4W/m2 LD cycles. The results show that P. terraenovae uses both extraretinal and retinal pathways for rhythm entrainment, and that the extraretinal receptors receive light passing principally through the compound eyes. It appears that entrainment is mediated primarily by signals from the retinal receptors at low light intensities.

Abstract The phase of locomotor activity of the onion fly, Delia antiqua, in LD12:12 advanced at a low temperature (20°C) as compared with that at a high temperature (25°C). The free-running period (τ) in constant darkness (DD) at 20°C became shorter than that at 25°C, suggesting that the phase advance of locomotor activity in LD cycles at 20°C was caused by the decrease in τ. In constant light (LL), the locomotor activity was arrhythmic at a constant temperature. In both DD and LL, the locomotor activity was entrained to a 12 hr 25°C:12 hr 20°C temperature cycle; the activity occurred in the thermophase and its peak delayed with age. However, the delay in LL was smaller than that in DD. At a cycle of 12 hr cool (20°C) light and 12 hr warm (25°C) dark, the fly showed a similar activity pattern to that in LD 12:12 at a constant temperature (20°C or 25°C); the activity occurred in the light phase. This suggests that LD cycle is a stronger zeitgeber than a temperature cycle to entrain the locomotor activity of D. antiqua.

The phase of locomotor activity of the onion fly, Delia antiqua, in L (400 lux) L-dim (1.0 lux) cycles delayed as compared with that in LD cycles. The free-running period (tau) in constant dim light (LdimLdim) was longer than that in constant darkness (DD), suggesting that the phase delay of locomotor activity in LL,, cycle was caused by the increase in tau. At LdimD 12:12 in which the light intensity of the photophase was 1.0 lux, the locomotor activity free-ran with the period shorter than 24 hr until about week 2 after eclosion but thereafter entrained to LdimD in spite of tau might become longer than 24 hr. This suggests that the flies may become more sensitive to light intensity with age.

At photoperiods longer than 8h per 24h, adults of the day-active onion fly Delia antiqua showed a major peak of locomotor activity in the late photophase and also bursts of activity induced by lights-on or lights-off. At shorter photoperiods the activity peaks fused. After transfer from long photoperiods to constant darkness (DD), the rhythm free-ran, but only the major peak persisted. This suggests that only the major peak is controlled by the circadian pacemaker. At long photoperiods, the daily phase of the major peak occurred progressively later with age. As a result, the activity at short photoperiods often shifted from photophase to scotophase in old flies. The free-running period (τ) also changed with age; τ was shorter than 24h until 14–20 days after eclosion and thereafter became longer, but a few individuals repeated changes in τ. The phase delay of locomotor activity with age in D. antiqua would be attributable to the increase in τ.

This paper summarizes the theory and practice of geosynthetic reinforcement of fills over extremely soft ground in Japan. Emphasis is placed on artificially reclaimed soft ground composed of marine soils which are characterized by high water contents and low shear strengths. The use of geosynthetics facilitates the movement of construction equipment and the placement of fill. The bearing capacity of the ground is improved by using high strength geosynthetics. Classical bearing capacity theory, cable theory combined with modulus of subgrade reaction theory, and plate theory are found to be useful in designing embankments on soft ground. The empirical parameters used in these theories are available for most projects. The unique geotechnical conditions of the soft ground typically inhibit the construction procedures specified in the design. The experience gained from past geosynthetic reinforced fill projects, one of which is highlighted in the paper, facilitates the improvement of fill placement and spreading techniques on soft ground.

Japan has a 400 years' history of shallow sea reclamation for new land. However, the application of Soil Mechanics Engineering to reclamation started just recently. In reclamation works, two types of fill–material, the pit sand and the dredged seabed soil, are generally employed. The water content of dredged soil used as fill–material is rather high due to the intrusion of seawater while dredging and as a result, an extremely soft ground is made–up. As such there arise the problems of insufficient bearing capacity and subsidence of the reclaimed ground. Some measures for ground improvement are required to solve these problems. This paper deals with the technology on reclamation, seabed dredging, revetment construction, the problems of reclaimed ground as viewed from Soil Mechanics Engineering and their solutions. These are discussed together with Japan's unique nature of technological development in the field of reclamation engineering.