Energy-saving Way Research Articles

Predator detection and avoidance by lotic mayfly nymphs of different size.

We studied antipredatory responses of lotic mayfly (Baetis) nymphs in a factorial experiment with four levels of fish presence: (1) a freely foraging fish (the European minnow,Phoxinus phoxinus), (2) a constrained fish, (3) water from a fish stream, (4) water from a fishless stream. LargeBaetis nymphs drifted mainly during night-time in treatments involving either the chemical or actual presence of fish, whereas no diel periodicity was observed when the water was not conditioned with fish odour. The response was strongest when the fish was uncaged, which suggests that visual or hydrodynamic cues are needed in addition to chemical ones for an accurate assessment of predation risk. Fish presence had no effect on the drift rates of small nymphs. Instead, they increased their refuge use in the presence of a live fish. Chemical cues alone did not have any effect on the refuge use of any of theBaetis size classes. Our results indicate active drift entry by mayfly nymphs. Because predation pressure is spatially and temporally variable, nymphs must sample the environment in order to locate predator-free areas or areas with low predation risk. Drifting should be the most energy-saving way to do this. To avoid the risk from visually feeding fish, large individuals can sample safely (i.e. enter drift) only at night-time, while the small ones can also do this safely during the day. We suggest that, contrary to some earlier assumptions, mayfly drift is not a fixed prey response. Instead,Baetis nymphs are able to assess the prevailing predation pressure, and they adjust their foraging behaviour accordingly.

The new energy-saving way achieved by changing computer culture (saving energy by changing the computer room environment)

This paper describes how major savings of energy can be achieved by raising temperatures in computer rooms, this leading to a reduction in the power consumed by air-conditioners. For many years it has been thought that computer room temperatures should be set at a low level such as 23-24/spl deg/C when computers are in operation. The authors researched actual situations in computer rooms while also reviewing technical aspects and those of reliability with eight leading computer system manufacturers. The results led them to conclude that no problems would arise if the room temperature were increased to an upper limit of 28/spl deg/C. As far as this new way is concerned, trial estimations indicate that about 600 MW of demand could be saved within the service area of TEPCO if computer-using customers could be persuaded to raise computer room temperatures from the ordinary 23-24/spl deg/C to an upper limit of 28/spl deg/C. Furthermore, the authors also studied measures to improve the system of air-conditioning in computer rooms, as a result of which they presented and evaluated a new type of air conditioner which can offer much in saving of energy compared to conventional systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Long-term training in a choice reaction time task reveals different learning characteristics for the visual and auditory system

Among the vertebrates, birds and bats are capable of active flight. For active fliers soaring is considered to be the most energy-saving way to meet their needs, as energy is extracted from natural winds and converted into a potential or kinetic form. For example, seabirds (gulls) soar to move between roosting and foraging areas, whereas others with high wing loadings (auks, cormorants) can only soar in strong winds [1]. Until now bats were considered to be unable to use soaring flight, due to their wing construction and lack of convective air currents during nighttime [1]. In Madurai, India, we were able to observe emballonurid bats (Taphozous sp.) soaring at altitudes between 50 and 250 m. For two consecutive nights on August 3 and 4, 1990 a group of at least 15 animals used the smooth slope of Keelakuyilkudi hill (130 m high) and strong winds for slope-soaring. Individual bats were observed soaring at constant position for at least 0.5 h, interrupted only by sudden changes in altitude which were controlled by wing strokes. These flight maneuvers included turns, yawing, and rolling. Due to the nature of these maneuvers we suggest that these flight activities indicate the pursuit of prey. After these brief interludes the bats resumed soaring and remained motionless in the air. Therefore, the bats may use soaring in their search for prey insects which fly at high altitudes. The observations were made with binoculars by the light of a full moon and hazy sky. The genus of the bats was identified by wing contours as Taphozous [2]. As only two species of Taphozous occur in the Madurai area, the soaring bats were either T. melanopogon, T. nudiventris, or both. The two species are known to feed at high altitudes [2]. The bats started soaring at about 7.30 p.m., i.e., 0.5 h after fly-out time. For soaring the bats exploit the strong winds over the top of Keelakuyilkudi hill which usually prevail in summer during daytime and only cease around midnight. Further research is underway to investigate the exact energetic conditions and food resources of insectivorous bats at this altitude, as both species are known for their opportunistic feeding behavior [2].