Effects of hypergravity on the development of cell number and asymmetry in fish brain nuclei.

Larval cichlid fish (Oreochromis mossambicus) siblings were subjected to 3 g hypergravity (hg) and total darkness for 21 days during development and subsequently processed for conventional histology. Further siblings reared at 1 g and alternating light/dark (12h:12h) conditions served as controls. Cell number counts of the visual Nucleus isthmi (Ni) versus the vestibular Nucleus magnocellularis (Nm) revealed that in experimental animals total cell number was decreased in the Ni, possibly due to retarded growth as a result of the lack of visual input whereas no effect was observed in the Nm. Calculating the percentual asymmetry in cell number (i.e., right vs. the left side of the brain), no effects of hg/darkness were seen in the Ni, whereas asymmetry was slightly increased in the Nm. Since the asymmetry of inner ear otoliths is decreased under hg, this finding may indicate efferent vestibular action of the CNS on the level of the Nm by means of a feedback mechanism.     

Calibration results obtained with Liulin-4 type dosimeters.

The Mobile Radiation Exposure Control System's (Liulin-4 type) main purpose is to monitor simultaneously the doses and fluxes at 4 independent places. It can also be used for personnel dosimetry. The system consists of 4 battery-operated 256-channel dosimeters-spectrometers. We describe results obtained during the calibrations of the spectrometers at the Cyclotron facilities of the University of Louvain, Belgium and of the National Institute of Radiological Sciences-STA, Chiba, Japan with protons of energies up to 70 MeV. The angular sensitivities of the devices are studied and compared with Monte-Carlo predictions. We also present the results obtained at the HIMAC accelerator with 500 MeV/u Fe ions and at the CERN high energy radiation reference fields. Records made during airplane flights are shown and compared with the predictions of the CARI-6 model.     

Analytic example of a Schweppe likelihood-ratio detector

A low-dimensional test problem with a known solution is used to verify various computer implementations of F.C. Schweppe's likelihood detector (1965). In this case a closed-form solution is provided for a Schweppe likelihood detector in terms of an intermediate Kalman filter, as utilized in its implementation, for detecting the presence of a two-state signal model in Gaussian white noise. The associated error probabilities are also evaluated following a procedure that utilizes optimized Chernoff-like bounds for a tight approximation. A methodology is demonstrated for appropriately setting the decision threshold for this example as a tradeoff against allowable observation time. By using this or similar examples, certain qualitative and quantitative aspects of the software implementation can be checked for conformance to anticipated behavior as an intermediate benchmark, prior to modular replacement of the various high-order matrices appropriate to the particular application     

Target State Estimation in a Multitarget Environment Using Multiple Sensors

An approach for target detection/state estimation that views theproblem as one of a finite state search over the target parameterspace is presented. This approach allows for a natural way toassociate different types of measurements, such as frequency andcoherence from multiple sensors, and also for dealing with multipletargets, dropouts, and clutter. We describe our model and present acomputationally efficient search algorithm for target detection andtarget state estimation in a multitarget environment based on thismodel. The results of a two-sensor, multitarget computer simulationare discussed.     

Singularities of Euler and Roll-Pitch-Yaw Representations

Euler and roll-pitch-yaw angles are routinely used to represent the orientation of rigid bodies in aerospace, navigation, and robotics because they minimize the dimensionality of the control problem.Both representations, however, introduce unwarranted mathematical singularities which are identified in this paper.Trajectory-tracking algorithms break down at singularities and cause loss of control. Since mathematical singularities do not reflect physical limitations of orientation, remedial measures can beimplemented in the controller.     

Gravity related research with fishes--perspectives in regard to the upcoming International Space Station, ISS.

During the entire evolution of life on Earth, the development of all organisms took place under constant gravity conditions, against which they achieved specific countermeasures for compensation and adaptation. On this background, it is still an open question to which extent altered gravity such as hypergravity (centrifuge) or microgravity (spaceflight) affects the normal individual development, either on the systemic level of the whole organism or on the level of individual organs or even single cells. The present review provides information on these questions, comprising gravistimulated effects on invertebrates and vertebrates (with the exception of mammals, since respective biomedically oriented reviews abound), focusing on developing fish as model systems, with special emphasis on the effect of altered gravity on the developing brain and vestibular system, comprising investigations on behaviour and plastic reactivities of the brain and inner ear. Clues and insights into the possible basic causes of space motion sickness-phenomena (SMS; a kinetosis) are provided as well as perspectives in regard to future work to be done including studies on the ISS concerning the analysis of gravistimulated effects on developmental issues (imprinting phase for graviperception?).     

Balloon observation of the 1983 solar eclipse in Indonesia

A balloon observation of the total solar eclipse on 11 June 1983 was carried out as a cooperative work between Japanese and Indonesian teams. The observation was a photo-polarimetry of the F corona in both visual and near-infrared regions.The balloon of 15,000-m³ with a payload of 150-kg was launched at 7^h13^m on 11 June from Watukosek Balloon Base in East Java. Observation at an altitude of 30.5-km was successfully made during the totality (11^h28～32^m) at a position of ～40-km east-south-east from Jogjakarta.As a preliminary result, an excess in infrared brightness has been found near the position of 3.8R_⊙ west from the sun, which may be due to thermal emission from a high-temperature dust cloud located around the sun.     

Particle simulation models for low frequency microinstabilities in a magnetic field

Several numerical plasma simulation models using particles are described which are appropriate for low frequency electrostatic and electromagnetic microinstabilities in a strong magnetic field. The model makes use of the guiding center drift approximations for the electrons while the ions are represented either as particles obeying the equation of motion with the full Lorentz force or a fluid which includes finite-Larmor-radius effects. These models are particularly useful for studying low frequency microinstabilities (ω ≲ ω_pi, Ω_i) propagating nearly perpendicular to an external magnetic field (k_⊥ ≫ k_∥).     

ROSAT observations of X-ray sources in globular clusters

We review the first observations of globular clusters obtained with the X-ray telescope on board of the ROSAT satellite. In the All-Sky Survey, all known bright sources and two new transient sources were detected. In addition a super-soft source was found in NGC5272. Concerning the dim sources, the survey suggests that those outside the core of ω Cen are not related to the cluster. The survey further improved by one or two magnitudes on many upper limits previously obtained by the HEAO-1 satellite. Pointed observations have improved the positional accuracy of a number of sources, and added to the number of known dim sources. In 47 Tuc, the known central source is resolved into 4 separate sources, which we argue are all soft X-ray transients. A comparison with observations of the old open cluster M67 leads us to suggest that some of the dim sources may be conglomerates of a large number of RS Can Ven type binaries.