Quantification of spatial structure of human proximal tibial bone biopsies using 3D measures of complexity

Changes in trabecular bone composition during development of osteoporosis are used as a model for bone loss in microgravity conditions during a space flight. Symbolic dynamics and measures of complexity are proposed and applied to assess quantitatively the structural composition of bone tissue from 3D data sets of human tibia bone biopsies acquired by a micro-CT scanner. In order to justify the newly proposed approach, the measures of complexity of the bone architecture were compared with the results of traditional 2D bone histomorphometry. The proposed technique is able to quantify the structural loss of the bone tissue and may help to diagnose and to monitor changes in bone structure of patients on Earth as well as of the space-flying personnel.     

High energy cosmic ray nuclei results on Ulysses: 1. Mission overview

The cosmic ray flux observed with the Kiel Electron Telescope on board the ULYSSES spaceprobe varies with solar activity as well as with heliospheric position. Determination of the latitudinal gradients requires a careful analysis of the influences of the current sheet tilt angle, the number of major solar flares, interplanetary shocks and interaction regions evolving in the expanding solar wind. In this paper we concentrate on nuclei with rigidity above 1 GV. We discuss the effects of the variable solar activity in the declining phase of the present solar cycle and the variation with radial distance as a basis for separating latitudinal effects. We show that during this phase of the solar cycle modulation of GV nuclei is ordered by temporal evolution, radial distance and negligible latitudinal effects even at latitudes between 30° and 50° South.     

Hard X-ray balloon observations of compact galactic and extragalactic X-ray sources

A balloon program in hard X-ray astronomy (20–200 keV) is jointly pursued by the Astronomisches Institut der Universität Tübingen (AIT) and the Max Planck-Institute für Extraterrestrische Physik in Garching (MPE). Since 1973 nine successful balloon flights have been performed from Texas and Australia. Here results on Centaurus A and on several galactic binary X-ray sources are summarized. In particular the high energy photon spectrum of Hercules X-1 and the evidence for the cyclotron line feature which was discovered by us in 1976 is reviewed.     

Infrared spectrometry of Venus from “Venera-15” and “Venera-16”

Fourier spectrometers for the investigation of infrared spectra of Venus were installed on the recent Soviet orbiters “Venera-15” and “Venera-16”. Many spectra with reliable absolute calibration were obtained in the 280–1500 cm^?1 region with a spectral resolution of 5 cm^?1 (ground based processing) and about 7 cm^?1 (preoprocessed on board) and a spatial resolution of about 100 km at the Venusian cloud top level. Bands of CO₂, H₂O, H₂SO₄ and SO₂ are identified. The 15 μm-CO₂- fundamental band was used for retrieval of altitude dependent temperature profiles. There are significant differences in the cloud structure above 60 km for distinct regions of Venus, demonstrated by differences in the spectra.     

Interrelation between KOSI experiments and comet nucleus sampling

In situ observations of comet Halley yielded information on the nucleus and its environment. These measurements are related to properties of and processes at the nucleus by theoretical modelling and by simulation experiments in the laboratory. The objective of the KOSI (Kometensimulation) experiments is to study in detail processes which occur near the surface of ice-dust mixtures under irradiation by light, like heat transport into the sample, chemical fractionation of sample material, emission of gases, and others. The KOSI experiments are carried out at the large space simulation chamber in Köln. By providing an in-depth understanding of potential cometary processes the results from the KOSI experiments are relevant to any comet nucleus sample return mission.     

The inner heliosphere from solar minimum to solar maximum: Short- and long-term variations in the energetic particle population

Between 1975 and 1983 HELIOS 1 scanned the interplanetary medium between 0.3 and 1 AU 31 times. The observed variations in the differential and integral flux of protons and helium nuclei in the energy range from 4 to >50 MeV/n are characterized by large temporal changes in the intensities, moderate changes in the energy spectrum and changes in the gradient below the detection level (60%). During solar minimum conditions recurrent disturbances are caused mainly by corotating interaction regions. The onset of solar activity near the end of 1977, characterized by a large number of solar events, is accompanied by a monotonous decrease of galactic cosmic radiation. The successive reduction of the cosmic ray intensity to the level of solar maximum is discussed in view of the role of large transient disturbances as compared to processes as diffusion, convection, adiabatic energy losses and drifts.     

The flux of interstellar dust observed by Ulysses and Galileo

Interstellar dust detected by the dust sensor onboard Ulysses was first identified after the Jupiter flyby when the spacecraft's trajectory changed dramatically (Grün et al., 1994). Here we report on two years of Ulysses post-Jupiter data covering the range of ecliptic latitudes from 0° to –54° and distances from 5.4 to 3.2 AU. We find that, over this time period, the flux of interstellar dust particles with a mean mass of 3·10^–13 g stays nearly constant at about 1·10^–4, m^–2 s^–1 ( sr)^–1, with both ecliptic latitude and heliocentric distance.Also presented are 20 months of measurements from the identical dust sensor onboard the Galileo spacecraft which moved along an in-ecliptic orbit from 1.0 to 4.2 AU. From the impact direction and speeds of the measured dust particles we conclude that Galileo almost certainly sensed interstellar dust outside 2.8 AU; interstellar particles may also account for part of the flux seen between 1 and 2.8 AU.