Uranium-lead isotope systematics and apparent ages of zircons and other minerals in precambrian granitic rocks,Granite Mountains,Wyoming

Zircon suites from the two main types of granite in the Granite Mountains, Wyoming, yielded concordia-intercept ages of 2,640±20 m.y. for a red, foliated granite (granite of Long Creek Mountain) and 2,595±40 m.y. for the much larger mass of the granite of Lankin Dome. These ages are statistically distinct (40±20 m.y. difference) and are consistent with observed chemical and textural differences. The lower intercepts of the zircon chords of 50±40 and 100+ 75 m.y. for the granite of Long Creek Mountain and granite of Lankin Dome, respectively, are not consistent with reasonable continuous diffusion lead-loss curves but do correspond well with the known (Laramide) time of uplift of the rocks. Epidote, zircon, and apatite from silicified and epidotized zones in the granites all record at least one postcrystallization disturbance in addition to the Laramide event and do not define a unique age of silicification and epidotization. The lower limit of 2,500 m.y. provided by the least disturbed epidote, however, suggests that these rocks were probably formed by deuteric processes shortly after emplacement of the granite of the Lankin Dome. The earlier of the two disturbances that affected the minerals of the silicified-epidotized rock can be bracketed between 1,350 and 2,240 m.y. ago and is probably the same event that lowered mineral K-Ar and ages in the region.Zircon suites from both types of granite show well-defined linear correlations among U content, common-Pb content, and degree of discordance. One of the zircon suites has an extremely high common-Pb content (up to 180 ppm) and exhibits a component of radiogenic-Pb loss that is apparently unrelated to radiation damage.     

Zur Funkortung bei weit von einander entfernten Sendern

Zusammenfassung Es wird in dem vorliegenden Aufsatz gezeigt, wie man auf Grund der Funkpeilungen dreier weit voneinander entfernter Sender ohne Benutzung von Karten und Tafeln die geographischen Koordinaten seines Standortes geometrisch exakt konstruieren kann.

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Radio direction finding with the aid of three widely spaced wireless transmitters

Summary The present paper shows how to plot the geographical coordinates of a certain position in a geometrically exact manner with the aid of radio bearings of three widely-spaced transmitters without using charts or tables.

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Relèvement radiogoniométrique à l'aide de trois émetteurs à grande distance l'un de l'autre

Résumé L'article suivant décrit de quelle manière on peut dessiner exactement au sens de la géométrie les coordonnées géographiques d'une certaine position en se servant du relèvement radiogoniométrique de trois émetteurs installés à grande distance l'un de l'autre sans y employer des cartes marines ou des tables.

     

Assessment of Cyto‐ and Genotoxic Effects of a Variety of Chemicals Using Saccharomyces cerevisiae

Saccharomyces cerevisiae as the most simple eukaryotic organism is broadly accepted as a laboratory model organism. For the detection of potential toxic effects of pure compounds and complex composed samples like wastewater a miniaturised short‐term in vitro cyto‐ and genotoxicity screening assay was developed. The assay based on genetically modified S. cerevisiae cells deleted in the prominent drug efflux transporters Pdr5, Snq2, and Yor1 that facilitate pleiotropic drug resistance. The yeast strain devoid of these proteins that mediate the efflux of structurally diverse hydrophobic compounds exhibited an increased sensitivity to a variety of organic compounds. The DNA damage inducible RAD54 promoter fused to a yeast optimized derivative of the GFP (green fluorescent protein) gene from the jelly fish Aequorea victoria served as an indicator of DNA damage in this strain. Various pure compounds including the direct‐acting genotoxins methyl‐N‐nitro‐N‐nitrosoguanidine (MNNG), 4‐nitroquinoline‐N‐oxide (4‐NQO), methyl methanesulfonate (MMS) and hydroxyurea as well as the heavy metals cadmium and chromium(VI), the insecticide lindane and the central nervous system stimulant caffeine were tested exhibiting dose dependent induction of green fluorescence. All compounds were in parallel examined for chronic toxicity. A bioassay detecting simultaneously geno‐ and cytotoxic effects of potential toxicants in a single assay can be an important tool with a variety of applications in environmental monitoring and aquatic ecotoxicology. By partial automation and miniaturisation to microtitration scale this bioassay enables sensitive and fast biomonitoring for a multitude of samples.     

The “Mediterraneanization” of the climate in Mediterranean countries —a cause of the unstable ecobudget

Changes of accumulation, pedogenesis and vertical erosion for the last nearly 20 000 years in connexion with periods of warm and cold climates can be proved for Mediterranean areas. The climate of Mediterranean areas became more arid for the last nearly 5 000 years. Geomorphological processes in Mediterranean areas concur with geomorphological processes in N Africa. Substantial sediments formerly marked as “historical fills” are of natural origin. Pollen analytical observations about forest formations confirm the distinction of holocene sediments: older strata of natural origin and younger layers of anthropogenic origin. Maccia and phrygana in Mediterranean areas stand for a degradation of forest caused by man. They provide eminently efficient protection of the soil cover. This poses an important question: Is afforestation, esp. in mountain areas, ecologically and economically advisable?     

Geotechnical characterization and rockfall simulation of a slope: a practical case study from South Tyrol (Italy)

Rockfalls occur often along the state road SS241 Val d'Ega in the Val d'Ega Valley (South Tyrol, Italy). In order to protect the road and the traffic, stabilization works are necessary. Detailed geological and geomorphologic mapping along structural and geomechanic sections was carried out, and experimental rockfall trails were examined on the slope above the state road between km 3.550 and 3.830. Rockfall simulation, rock mass classification and an interpretation of field data, especially concerning joints, wrapped up the investigations. They helped find the specific need for stabilization work and its positioning along the slope. The stabilization works were completed on February 2002. Another important aspect concerns ongoing geotechnical investigations and stabilization works urgently realised during autumn 1999.

This paper is a practical approach in solving rockfall problems along public roads. It should be considered as a workbook for university personnel and also for professional geologists.     

<Emphasis Type="Italic">Phragmites</Emphasis> and environmental management: A question of values

For a common, widespread, and familiar plant,Phragmites australis engenders an enormous level of scientific controversy and emotional conflict. In parts of the world,Phragmites is an important component of healthy ecosystems and an integral (if now minor) contributor to human economies. In other places it is an invading, unfriendly, and ugly weed. To some scientists and environmentalists,Phragmites is an indicator of and key factor in landscape degradation and habitat deterioration. To others, it is a valiant remnant of nature, providing a relatively rich ecology where there might otherwise be only barren and eroding ground. Our review of the literature leads us to conclude thatPhragmites is simply a biological entity. It is not inherently good or bad, since its evolution, biology, and ecology do not give it a value. The controversy overPhragmites, its role in the ecosystem, and the need for and intensity of management efforts are all artifacts of human perspectives. Effective, consistent management decisions (for either control or enhancement ofPhragmites) can only be made on the basis of site-specific scientific findings, a consideration of technologies with their needed level-of-effort, and explicit exposition of the human values driving the management options. We present a simple decision model to illustrate the interaction of these management components forPhragmites in the environment.