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At night, honey bees pass through a physiological state that is similar to mammalian sleep. Like sleep in mammals, sleep-like behaviour in honey bees is an active process. This is expressed most clearly in these insects by spontaneous antennal movements which appear at irregular intervals throughout the night and interrupt episodes of antennal immobility. Here we present a newly developed video technique for the continuous recording of the position and movements of the bee's antennae. The same technique was used to record head inclination and ventilatory movements. Despite the constancy of the ambient temperature, the magnitudes of antennae-related parameters, as well as head inclination and ventilatory cycle duration, displayed dynamic unimodal time-courses which exhibited a high degree of temporal covariance. The similarity between these time-courses and the nightly time-course of the reaction threshold for a sensory stimulus, investigated previously, indicates that, in honey bees, deepest "sleep" and least ventilatory activity occur at the same time (in the 7th hour of the rest phase).

Abstract-This paper introduces new polarimetric algorithms for generating 3-D images and estimating scattering mechanisms from polarimetric multibaseline (MB) interferometric synthetic aperture radar (SAR) measurements. First, an MB interferometric SAR signal model is generalized to the fully polarimetric configuration, establishing the notion of polarimetric reflectivity. Subsequently, polarimetric beamforming, Capon, and MUSIC methods that determine optimal polarization combinations for height estimation are developed. These new techniques allow for extracting the height of reflectors, the associated scattering mechanisms, and the polarimetric (pseudo)reflectivities. By means of polarimetric dual-baseline interferometric SAR observations of an urban environment, the performance of the conceived algorithms is examined in detail. Producing 3-D images of a building layover, the quality of the approaches is compared in terms of refined resolution and lowered side lobes. Furthermore, the scattering processes occurring in urban scenes are investigated thoroughly by analyzing the optimal reflection types. The algorithms are validated using dual-baseline polarimetric SAR interferometric data at L-band acquired by German Aerospace Center's experimental SAR system over Dresden city.

SUMMAR Y Rest at night in forager honey bees (Apis mellifera) meets essential criteria of sleep. This paper reports the effect of a 12-h total sleep deprivation (SD) by forced activity on the behaviour of these animals. The behaviour of sleep-deprived animals is compared with that of control animals under LD [periodic alternation between light (L) and darkness (D)] 12 : 12 hours. SD for 12 h during the first D period resulted in a significant difference with respect to the parameter Ôhourly amount of antennal immobilityÕ between sleep-deprived and control animals during the remaining L and D periods. This difference did not occur in the L period following the deprivation night, but rather it became obvious at the beginning of the following D period. The increase of the amount of antennal immobility in sleep-deprived bees was accompanied by an increase of the duration of episodes of antennal immobility. Moreover, the latency from Ôlights offÕ to the first episode of antennal immobility lasting 20 s or longer (Ôdeep sleep latencyÕ) tended to be shorter in sleep-deprived than in control animals. Disturbing the bees during the day (L period) did not result in such differences between disturbed and control animals. Highest reaction thresholds in sleeping honey bees occur during long episodes of antennal immobility. We therefore conclude that honey bees compensate a sleep deficit by intensification (deepening) of the sleep process and thus that sleep in honey bees, like that in other arthropods and mammals, is controlled by regulatory mechanisms.k e y w o r d s antennal immobility, behavioural sleep, honey bee, sleep deprivation INTRODUCTIONThe biological significance of sleep is still largely unknown.Comparative sleep research attempts to answer this fundamental question by comparing the sleep of as many species as possible with that of humans. This approach is based on the assumption that -during sleep -processes occur which are of vital importance for the performance and survival of the organism. If this assumption is correct, one would expect that sleep appeared early on in evolution, long before the development of birds and mammals. In 1983, two independent publications led to the conclusion that sleep-like states exist in insects (Kaiser and Steiner-Kaiser 1983;Tobler 1983). Knowledge of the sleep process in insects, e.g. the honey bee, is fundamental to the search for generally valid principles about sleep. This is the genuine approach of comparative physiology, the field to which comparative sleep research belongs. On the basis of the results from detailed electrophysiological, electromyographical and behavioural investigations, Kaiser (1988) concluded that, during the night, honey bees experience a process that is similar to mammalian sleep. High reaction thresholds are one crucial feature of sleep. Honey bees fulfil this criterion both at the level of individual neurones of the visual system (Kaiser 1983;Kaiser and Steiner-Kaiser 1983) as well as at the behavioural level (Kaiser 1988). Highest thresholds in ...