Cosmic-ray-induced fission of heavy nuclides: Possible influence on apparent U-fission track ages of extraterrestrial samples

The rates of cosmic-ray-induced fission of U, Th, Bi, Pb, and Au in mineral samples as a function of burial depth in the lunar surface layer are calculated using the available experimental particle flux and cross section data. Theoretical correction factors are given for apparent fission track ages of extraterrestrial samples of different burial depths which were exposed to cosmic rays for various time fractions of their solidification age. Samples having typical lunar heavy element contents can yield apparent fission track ages which are too high by a factor of up to 13 due to cosmic-ray-induced fission. The interference may be neglected, if the ratio of exposure age to solidification age remains 5 × 10⁻³. The calculations show, that the induced fission of Bi, Pb, and Au which are known to have high meteoritic abundances may dominate spontaneous ²³⁸U-fission in long-time exposed meteorites of low U and Th contents.     

Studies on the thermoluminescence depth profile produced by 600-MeV protons in artificial lunar soil

The thermoluminescence (TL) of various plagioclase feldspars embedded in a thick target of 150 kg of artificial lunar soil was measured after a 600-MeV proton irradiation. No correlation was observed between the parameters of the characteristic feldspar glow peak and the anorthite contents. The relative TL sensitivities of the individual plagioclase variants were measured and found to be practically the same for⁶⁰Co-γ- and 600-MeV proton-irradiated samples.The TL intensity distribution within the target arrangement, converted to a 2π isotropic p-influx, resulted in an approximate TL depth profile of a thermally undisturbed lunar soil bomarded by galactic cosmic protons. The undisturbed TL intensity at a depth of 28 g/cm² (? 17 cm) decreased to 39% at a depth of 106 g/cm² (? 60 cm). For the evaluation of the temperature gradients by TL in lunar samples the experimental data at the sites of Taurus-Littrow and of Hadley-Rille yielded minimum depth intervals for sampling of ～ 20 cm and ～ 40 cm respectively, presuming an error of ± 15% in the TL determination. Certain aspects are seen by using the relation TL intensity/²²Na-activity ratio versus depth (thus representing the total ionization profile) to establish²²Na depth profiles.     

A GIS-based fire spread simulator integrating a simplified physical wildland fire model and a wind field model

??This article discusses the integration of two models, namely, the Physical Forest Fire Spread (PhFFS) and the High Definition Wind Model (HDWM), into a Geographical Information System-based interface. The resulting tool automates data acquisition, preprocesses spatial data, launches the aforementioned models and displays the corresponding results in a unique environment. Our implementation uses the Python language and Esri’s ArcPy library to extend the functionality of ArcMap 10.4. The PhFFS is a simplified 2D physical wildland fire spread model based on conservation equations, with convection and radiation as heat transfer mechanisms. It also includes some 3D effects. The HDWM arises from an asymptotic approximation of the Navier–Stokes equations, and provides a 3D wind velocity field in an air layer above the terrain surface. Both models can be run in standalone or coupled mode. Finally, the simulation of a real fire in Galicia (Spain) confirms that the tool developed is efficient and fully operational.     

Galileo Constellation Design

A significant effort has been carried out in Europe to define the European Global Navigation Satellite System (GNSS), named Galileo Satellites flying in Medium Earth Orbits (MEO) will compose the system (according to the most recent architecture definition baseline); a regional complement of geosynchronous satellites may be required to increase performances over Europe and maybe also to provide some specific communication services. Nominal medium performances are envisaged, but they will be increased by means of augmentation systems (local or wide area), or even by using simultaneously other GNSSs such as GPS. All the involved requirements make the design process quite complex. A powerful software tool, Elcano, has been developed for this purpose; its capabilities will be outlined, and the results of the design process will be presented. ? 2001 John Wiley & Sons, Inc.     

A climatic and environmental protection strategy,the road toward a sustainable future

This editorial essay conveys a clear message: The overuse of our fossil fuel resources especially in the North, and the overpopulation in many parts of the South, result in an unacceptable stress to Earth. This manifests itself in some of the most serious threats to mankind, such as global climatic change, environmental degradation, food shortage, hunger, poverty, and migration. It is the purpose of this editorial essay to make a contribution toward a reduction of some of these threats, notably those from climatic change. Specifically, I present a tractable climatic and environmental protection strategy which is designed to give concrete answers to such seemingly simple questions as: What has to be done? (This depends e.g. on the concentration stabilization objective of the Rio Climate Convention, and the global warming ceiling of the Enquete-Commission of the German Parliament). By whom does it have to be done? (This addresses the secret of a successful protection strategy which involves a fair burden sharing among the world's countries). When does it have to be done? (This discusses the problem of setting tractable, i.e. differentiated and binding emission targets). How can it be done? (This relates to individual countries, states, and municipalities. It is demonstrated for Germany how her commitment of a 25 to 30% CO₂ reduction by 2005 can be achieved.) Moreover, the question is addressed: How many people and how much fossil fuel use can our planet stand? The major result is that without self-restraint climate and ecosystem protection cannot be maintained, because it is incompatible with trends in the wasteful fossil fuel use in the North and strong population growth in the South. Finally, a plea is made to share responsibility on the road toward a sustainable future.     

A study on exposure ages of chondrites based on spallogenic 53Mn

Longlived spallogenic ⁵³Mn was determined in 36 individual chondrites. Combining our data with those available so far in literature (in total 91 ⁵³Mn-values of 61 individual stones) a ⁵³Mnproduction rate of 478 ± 84dpm/kg Fe was derived. Based on this figure it was possible to calculate ⁵³Mn-radiation ages for more than 30 stones with T_rad ≤ 10 × 10⁶ yr. A comparison of our results with the respective rare gas- and ²⁶Al-exposure ages (so far available) shows that in general a good agreement exists between ages calculated by these three different methods. Only in the case of ‘finds’, e.g. in Bondoc and some other stones of probably high terrestrial ages. partial losses of ⁵³Mn seem to have occurred. For well preserved objects the ⁵³Mn method is ideal for the estimation of terrestrial residence times.     

Beryllium abundance of meteorites determined by “non-destructive” photon activation

The beryllium content of 73 stony and 4 iron meteorites has been determined “non-destructively” by a newly developed sensitive low-level counting device. A fairly widespread beryllium content of stones ranging from 13 to 386 ppb was found. As expected from the lithophilic character of Be the 4 siderites contained < 8 ppb only. The resulting average chondritic abundance of 74 ppb Be is more than one order of magnitude lower than the cosmic abundance value adopted earlier by H.E. Suess and H.C. Urey (1956), but still about a factor of 2 higher than the value chosen by A.G.W. Cameron (1968). 10–15-g samples were taken in order to guarantee a rather good “mean”. For comparison the Be content of the U.S. Geological Survey basalt BCR-1 was determined in the same way to be 1.390 ± 0.006 ppm Be.