β Cephei stars from a photometric point of view

This is an observational review, with an emphasis on photometric data and their interpretation. Two lists are presented, one containing β Cephei stars, and the other, β Cephei suspects. These lists then serve as a basis for discussing such topics as the location of β Cephei stars in the observational and theoretical H-R diagrams, the evolutionary state of these stars, the period-luminosity and period-luminosity-color relations, and observational identification of pulsation modes. The paper also includes references to recent work connected with the theoretical discovery that an opacity mechanism is responsible for the excitation of β Cephei-star pulsations. Finally, observational programs for verifying the consequences of this discovery are suggested.     

Simulation considers the human factors

Human factors aspects of flight simulation design at McDonnell Douglas are considered. Modeling approaches are examined and testing with pilots and cockpits is described.     

Total solar and spectral irradiance variations from solar cycles 21 to 23

Total solar and UV irradiances have been measured from various space platforms for more than two decades. More recently, observations of the “Variability of solar IRradiance and Gravity Oscillations” (VIRGO) experiment on SOHO provided information about spectral irradiance variations in the near-UV at 402 nm, visible at 500 nm, and near-IR at 862 nm. Analyses based on these space-borne irradiance measurements have convinced the skeptics that solar irradiance at various wavelengths and in the entire spectrum is changing with the waxing and waning solar activity. The main goal of this paper is to review the short- and long-term variations in total solar and spectral irradiances and their relation to the evolution of magnetic fields from solar cycles 21 to 23.     

Did life exist on Mars? Search for organic and inorganic signatures, one of the goals for “SAM” (sample analysis at Mars)

Observation of Mars shows signs of a past Earth-like climate, and, in that case, there is no objection to the possible development of life, in the underground or at the surface, as in the terrestrial primitive biosphere. Sample analysis at Mars (SAM) is an experiment which may be proposed for atmospheric, ground and underground in situ measurements. One of its goals is to bring direct or indirect information on the possibility for life to have developed on Mars, and to detect traces of past or present biological activity. With this aim, it focuses on the detection of organic molecules: volatile organics are extracted from the sample by simple heating, whereas refractory molecules are made analyzable (i.e. volatile), using derivatization technique or fragmentation by pyrolysis. Gaseous mixtures thus obtained are analyzed by gas chromatography associated to mass spectrometry. Beyond organics, carbonates and other salts are associated to the dense and moist atmosphere necessary to the development of life, and might have formed and accumulated in some places on Mars. They represent another target for SAM. Heating of the samples allows the analysis of structural gases of these minerals (CO₂ from carbonates, etc.), enabling to identify them. We also show, in this paper, that it may be possible to discriminate between abiotic minerals, and minerals (shells, etc.) created by living organisms.     

A space radiation shielding model of the Martian radiation environment experiment (MARIE)

The 2001 Mars Odyssey spacecraft was launched towards Mars on April 7, 2001. Onboard the spacecraft is the Martian radiation environment experiment (MARIE), which is designed to measure the background radiation environment due to galactic cosmic rays (GCR) and solar protons in the 20–500 MeV/n energy range. We present an approach for developing a space radiation-shielding model of the spacecraft that includes the MARIE instrument in the current mapping phase orientation. A discussion is presented describing the development and methodology used to construct the shielding model. For a given GCR model environment, using the current MARIE shielding model and the high-energy particle transport codes, dose rate values are compared with MARIE measurements during the early mapping phase in Mars orbit. The results show good agreement between the model calculations and the MARIE measurements as presented for the March 2002 dataset.     

Cold resistance and metabolic activity of lichens below 0°C

Laboratory measurements show that lichens are extremely tolerant of freezing stress and of low-temperature exposure. Metabolic activity recovered quickly after severe and extended cold treatment. Experimental results demonstrate also that CO₂ exchange is already active at around −20°C. The psychrophilic character of polar lichen species is demonstrated by optimum temperatures for net photosynthesis between 0 and 15°C. In situ measurements show that lichens begin photosynthesizing below 0°C if the dry thalli receive fresh snow. The lowest temperature measured in active lichens was −17°C at a continental Antarctic site. The fine structure and the hydration state of photobiont and mycobiont cells were studied by low-temperature scanning electron microscopy (LTSEM) of frozen hydrated specimens. Water potentials of the frozen system are in the range of or even higher than those allowing dry lichens to start photosynthesis by water vapor uptake at +10°C. The great success of lichens in polar and high alpine regions gives evidence of their physiological adaptation to low temperatures. In general lichens are able to persist through glacial periods, but extended snow cover and glaciation are limiting factors.     

CME-geometry and cosmic-ray anisotropy observed by a prototype muon detector network

We analyze the cosmic-ray anisotropy observed by a prototype network of muon detectors during geomagnetic storms associated with coronal mass ejections (CMEs). The network currently consists of multidirectional surface muon detectors at Nagoya (Japan) and Hobart (Australia), together with a prototype detector at São Martinho (Brazil) which has been in operation since March, 2001. In this report, we analyze the anisotropy recorded in both the muon detector and neutron monitor (the Spaceship Earth) networks and find significant enhancements of cosmic-ray anisotropy during geomagnetic storms. Following the analysis by Bieber and Evenson [Bieber, J.W., Evenson, P. CME geometry in relation to cosmic ray anisotropy. Geophys. Res. Lett. 25 (1998) 2955–2958] for the neutron monitor data at 10 GeV, we also derive cosmic-ray density gradients from muon data at higher-energy (50 GeV), possibly reflecting the larger-scale geometry of CMEs causing geomagnetic storms. We particularly find in some events the anisotropy enhancement clearly starting prior to the storm onset in both the muon and neutron data. This is the first result of the CME-geometry derived from simultaneous observations of the anisotropy with networks of multidirectional muon detectors and neutron monitors.     

Waves on the subsolar ionopause of venus

The subsolar ionopause of Venus is expected to be stable to both the Kelvin-Helmholtz and flute instabilities. However, magnetic profiles obtained in the subsolar region indicate that the surface of the ionopause contains large amplitude corrugations, perhaps incipient flux ropes. A possible mechanism for destabilizing the boundary is suggested by the observation that the ion density does not drop abruptly at the ionopause but continues to decrease smoothly into the magnetosheath.     

Origin of organic matter in the protosolar nebula and in comets.

Comet organics are traced to their origin in interstellar space. Possible sources of comet organics from solar nebula chemistry are briefly discussed. The infrared spectra of interstellar dust are compared with spectra of solar (space) irradiated laboratory organic residues and with meteorites. The spectra compare very favorably. The atomic composition of first generation laboratory organic residues compares favorably with that of comet Halley organics if divided into appropriate "volatile" (less refractory) and "refractory" (more refractory) complex organics.     

Optical search for gamma-ray bursts

The preliminary results from optical search for light pulses associated with gamma ray bursts by means of the Czechoslovak Fireball Network plate collection at the Ondřejov observatory are given. Optical monitoring represents more than 7700 hours, but no real optical counterpart was found. Problems associated with the optical search for gamma ray bursts are discussed.