Shigeru Aoki

Intelligent bridge maintenance system using MEMS and network technology

A protype of Remote Intelligent Monitoring System (RIMS) was developed for intelligent bridge and infrastructure maintenance. It consists of MEMS sensor, micro-controller with buffer memory and Ethernet controller. Each component is carefully chosen. In the software, TCP/IP and http are adopted in the communication part. The RIMS prototype is a small and relatively inexpensive. It was installed to measure the acceleration of a light pole and its effectiveness was demonstrated.

Field evidence for bioluminescent signaling in the pony fish, Leiognathus elongatus

Luminescence of the pony fish, Leiognathus elongatus, was observed in the natural environment during nighttime diving. The light was emitted from the lateroventral portion of the body, as bright rectangular-shaped luminescence patches turned on and off periodically. Luminescent fish had a distinct clear patch on the flank through which light was emitted, whereas non-luminous fish did not have such a clear patch. Both luminous and non-luminous fish were found within a shoal, where non-luminous individuals were chased by luminous ones. From previous morphological studies, the luminous and non-luminous individuals are likely to be male and female, respectively. Our observations provide field evidence that the luminescence functions as intraspecific communications in L. elongatus.

Nitrogen-flow in the rotifer Brachionus rotundiformis and its significance in mass cultures

The nitrogen budget in the rotifer Brachionus rotundiformis wasmeasured by the stable-isotope technique. The budget was estimatedusing the difference in the turnover time between egestion andexcretion. The rotifer was fed on the algae Nannochloropsiswhich was labeled with 15N as a tracer. The turnover time ofegestion and excretion were 20 min and 2.5 hours, respectively. Where77% of the ingested nitrogen was egested, and of the assimilated23%, 18% were devoted to growth and 5% to excretion.As for the unassimilated nitrogen egested as faeces, it recycled tothe rotifer through bacteriovory. When the algae provided as foodwere almost fully consumed, bacteriovory became dominant. Thethreshold occurred when the concentration of algae in the culture wasbetween 1.5 and 0.5 million cells of Nannochloropsis per ml. Ina chemostat operated with un-limited food condition, bacterialnitrogen corresponding to 20% of algal feeding, was consumed by therotifer.In a semi-continuous mass culture where food condition was limited,bacteriovory was more effective in supporting the rotiferreproduction. It contributed to the extremely high nitrogen recoveryfrom the provided foods (algae and oil-yeast) to the harvestedrotifers. The rapid and large nitrogen outflow from rotifersaccelerated the propagation of edible bacteria and can explain thestrange paradox observed in the culture; daily supply of foods didnot cover the sum of growth and excretion.It is not too exaggerated to state that the rotifer mass culture issupported by bacteria. The future strategy for maintenance of masscultures should consider this aspect.

Establishment of shell growth analysis technique of juvenile Manila clam Ruditapes philippinarum : semidiurnal shell increment formation

The conventional acetate peel method was modified to analyze the shell growth pattern of juvenile Manila clam Ruditapes philippinarum as small as 2 mm in shell length (SL). In the outer shell layer along the axis of maximum growth, two types of growth increments were observed: distinct increments and indistinct increments, which, respectively, do and do not continue to the middle shell layer. The distinct increments were found to be formed every two days in intertidal and shallow subtidal zones by field enclosure experiments of juveniles with datum points marked with alizarin complexone. Growth patterns of juveniles (12 mm SL) collected from the Seaside Park of Yokohama in Tokyo Bay were analyzed to confirm the modified method. Mean daily shell growth rate from April to July 2005 ranged 120–142 μm/day, which was reasonable as compared with previous studies. It was impossible to backcalculate the growth to the settlement size (i.e. 0.2 mm SL) because of erosion of the outer shell surface, and the smallest backcalculated minimum shell length was 0.8 mm. Fluctuations in daily growth rate were high, ranging 29–315 μm/day, and did not show a clear two-weekly rhythm.

Excretion of bis(tri‐n‐butyltin)oxide and triphenyltin chloride from CARP

Excretion of bis(tri‐n‐butyltin)oxide ((Bu3Sn)2O) and triphenyltin chloride (Ph3SnCl) from carp was studied in clean water for 3 days after bioconcentration of these compounds in the test tank for 7 days. The concentrations of (Bu3Sn)2O and Ph3SnCl in muscle decreased, but those in viscera (liver, kidney and gallbladder) did not change during the 3 days excretion experiment. The excretion rate constants were 0.40 day‐1 for (Bu3Sn)2O and 0.50 day‐1 for Ph3SnCl assuming their processes to be first‐order kinetics.