Different age response of zircon and monazite during the tectono-metamorphic evolution of a high grade paragneiss from the Ruhla Crystalline Complex,central Germany   总被引：5，自引：0，他引：5  

Armin?ZehEmail author  Ian?S.?Williams  Helene?Br?tz  Ian?L.?Millar 《Contributions to Mineralogy and Petrology》2003,145(6):691-706

Results of TIMS, SIMS and SEM analyses show that zircon and monazite in a high-grade paragneiss of the Ruhla Crystalline Complex, central Germany, were formed and/or altered during different stages of a tectono-metamorphic history between Early Devonian and Permian times. Detrital zircon cores of >460 Ma place an older limit on the age of anatexis, and show that the paragneiss sequence contains rocks at least as young as early Cambrian. Metamorphic zircon growth commenced at ~365 Ma, peaking at ~360–355 Ma at the same time that granite dykes were emplaced. In contrast, monazite in the paragneiss preserves little record of the metamorphic peak. Most monazite grains grew or were recrystallised in the Lower Carboniferous at ~339 Ma, contemporaneous with the emplacement of voluminous diorite and granite bodies. These intrusions and related tectonics caused some of the high-U zircon overgrowths to undergo moderate to severe Pb loss. A second Pb loss event, between 300 and 280 Ma, can be related to Late Carboniferous/Early Permian large-scale block faulting.Editorial responsibility: J. Hoefs  相似文献   

Ultra-High Resolution Nitrate in Polar Ice as Indicator of Past Solar Activity   总被引：3，自引：0，他引：3  

Gisela Dreschhoff  Edward J. Zeller 《Solar physics》1998,177(1-2):365-374

Ionization in the polar atmosphere causes the formation of nitrate compounds, which are frozen out and incorporated into the layers of the polar ice sheets. From a 122-m ice core collected in 1992 on the central Greenland ice sheet, it has been possible to examine a solar signal in a ultra-high resolution record of nitrate concentrations. The sequence extends over a period of 415 years at a temporal resolution of no less than one analysis per month (total number of samples 7776 resulting from 1.5 cm sampling along the entire core). This type of measurement reveals major nitrate anomalies which are thought to result from the injection of individual solar proton events into the winter polar stratosphere. For this reason, the large nitrate anomalies provide the possibility to delineate a signal of solar activity well beyond the known geophysical records.  相似文献   

Hydrothermal gases offshore Milos Island, Greece   总被引：3，自引：0，他引：3  

Reiner Botz  Doris Stüben  Gisela Winckler  Reinhold Bayer  Manfred Schmitt  Eckhard Faber 《Chemical Geology》1996,130(3-4):161-173

Hydrothermal fluids emerge from the seafloor of Paleohori Bay on Milos. The gases in these fluids contain mostly CO₂ but CH₄ concentrations up to 2% are present. The stable carbon isotopic composition of the CO₂ (near 0%) indicates an inorganic carbon source (dissociation of underlying marine carbonates). The carbon and hydrogen isotopes of most CH₄ samples are enriched in the heavy species (δ¹³C = −9.4 to −17.8‰; δD = −102 to −189‰) which is believed to be characteristic for an abiogenic production of CH₄ by CO₂-reduction (Fischer-Tropsch reactions). Depletions in the deuterium content of three CH₄ samples (to −377%) are probably caused by unknown subsurface rock alteration processes. Secondary hydrogen isotope exchange processes between methane, hydrogen and water are most likely responsible for calculated unrealistic methane formation temperatures.

We show that excess helium, slightly enriched in ³He, is present in the hydrothermal fluids emerging the seafloor of Paleohori Bay. When the isotopic ratio of the excess component is calculated a ³He/⁴He_excess of 3.6 · 10⁻⁶ is obtained: This indicates that the excess component consists of about one third of mantle helium and two thirds of radiogenic helium. We infer that the mantle-derived component has been strongly diluted by radiogenic helium during the ascent of the fluids to the surface.  相似文献   

A multi-site campaign on the long period variable subdwarf b star PG 1627+017     

Suzanna Randall  Gilles Fontaine  Elizabeth Green  Dave Kilkenny  Lisa Crause  Oliver Cordes  Simon O’Toole  Lázló Kiss  Bi-Qing For  Pierre-Olivier Quirion 《Astrophysics and Space Science》2004,291(3-4):465-471

We report on the outcome of the first major multi-site campaign on a long-period variable subdwarf B star. The target PG 1627+017 was observed for a total of 334 h during April/May/June 2003 from the lynchpin observatory at Mt. Bigelow, Arizona, with important contributions coming from co-observations at SAAO, Calar Alto and Siding Spring. Preliminary analysis indicates the presence of 8–10 probable periods in the range ～4500 to ～8900 s with relative amplitudes between 0.1 and 0.5%;. The range over which the periods are found is in qualitative agreement with theoretical predictions and the number of periods found shows potential for an in-depth asteroseismological analysis. Multi-colour observations show that the relative amplitudes of pulsation are larger in the U-band than in the R, which again is in agreement with theory. However, more multi-colour observations are needed to be able to make statements at the quantitative level.  相似文献   

Economic drivers of migration and climate change in LDCs     

Helene Bie Lilleør  Katleen Van den Broeck 《Global Environmental Change》2011

Environmental migration is a topic which has given rise to widespread debate and gloomy predictions about the state of the world in 2050, but where rigorous research and empirical evidence are unfortunately in short supply. In this paper, we review the existing research on and empirical evidence of how climate change and climate variability in Less Developed Countries (LDCs) affects two main drivers of migration identified by migration models in the economic literature, namely income level differentials between origin and destination areas and income variability in origin areas, and how they in turn affect migration. We find that there are serious gaps in both the economic and the environmental literature that render it impossible to make sound and robust predictions of how climate change and increased climate variability will affect the economic migration drivers, and of how these in turn may change existing migration patterns. There are some empirical indications that income differentials may increase due to lower income levels in the origin areas of LDCs, but virtually no evidence exists of the effects of climate change or increased climate variability on income variability. Furthermore, although a negative relationship between migration and rainfall has been established by many researchers, there is only very limited evidence as to what drives it. A clearer picture of the driving force behind the link between rainfall and migration would greatly benefit policymaking in this area.  相似文献   

Cytochrome P450 1A1 expression in cetacean skin biopsies from the Indian Ocean     

Jauniaux T  Farnir F  Fontaine M  Kiszka J  Sarlet M  Coignoul F 《Marine pollution bulletin》2011,62(6):1317-1319

The study describes cytochrome P450 1A1 (CYPA1) expression in the skin of different cetacean species (Megaptera novaeangliae, n = 15; Stenella attenuata, n = 7 and Stenella longirostris, n = 24) from the Mozambique Channel island of Mayotte. Immunohistochemical examination was performed with a monoclonal antibody against scup cytochrome CYPA1. The sex was determined using a molecular approach consisting in the genotyping sex-specific genes. CYPA1 was detected at the junction between epidermis and blubber on dolphins only, mostly in the endothelial cells. Similar observation was obtained in the dermis of one M. novaeangliae. Immunohistochemical slides were scored to evaluate the expression of the CYPA1 and a higher expression was observed in S. longirostris, suggesting a higher exposure to pollutants for this species. The difference of expression between sexes was not significant.  相似文献   

Reply to Reimer and Mossman. Comment on “Trace-element characteristics of different pyrite types in Mesoarchaean to Palaeoproterozoic placer deposits” by Koglin et al. (<Emphasis Type="Italic">Mineralium Deposita</Emphasis> 42: 259–280, 2010)     

Nikola Koglin  Hartwig E. Frimmel  W. E. Lawrie Minter  Helene Brätz 《Mineralium Deposita》2011,46(7):839-840

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Place,gender and the appeal of video lottery terminal gambling: unpacking a focus group study of Montreal youth     

Dana Helene Wilson  Nancy A. Ross 《GeoJournal》2011,76(2):123-138

Youth gambling has become an important public health issue in Canada and elsewhere owing to the known associations between gambling and delinquency, family dysfunction and suicide. Modern electronic and virtual gambling activities like video lottery terminals (VLTs) may have particular appeal to youth who have been raised in social environments that are increasingly dependent on information and communication technologies. The main objective of the study was to explore why youth gamble and what makes gambling activities like VLTs popular to youth in the places where youth live, study and play. The research is framed within a population health perspective that recognizes the role of social and physical environments in influencing health-related behaviours. Group discussions were conducted with youth to explore the popularity and appeal of gambling and VLTs, and how gambling fits into the daily routines of youth and the spaces they occupy. Methodologically, this research was conscious of responding to calls in the literature to analyze focus groups as an interactive group process rather a collection of individual responses, and to exercise analytic rigour by explicitly making the research team’s positionality and the data collection process transparent. Group discussions revealed gender differences in the appeal of particular gambling activities with young males being more likely to discuss poker, dice, sports-betting and online gambling as exciting social activities, while females described lottery and scratch (instant win) tickets as fun solitary activities. Substantive results point to the need for interventions to address social aspects of gambling that appeal, in particular, to young males potentially through increased provision of healthier alternatives to social engagement and greater attention to young people’s use of space.  相似文献   

Re-testing the JET-X Flight Module No. 2 at the PANTER facility     

Daniele Spiga  Gianpiero Tagliaferri  Paolo Soffitta  Oberto Citterio  Stefano Basso  Ronaldo Bellazzini  Alessandro Brez  Wolfgang Burkert  Vadim Burwitz  Enrico Costa  Luca de Ruvo  Ettore Del Monte  Sergio Fabiani  Gisela Hartner  Benedikt Menz  Massimo Minuti  Fabio Muleri  Giovanni Pareschi  Michele Pinchera  Alda Rubini  Carmelo Sgrò  Gloria Spandre 《Experimental Astronomy》2014,37(1):37-53

The Joint European X-ray Telescope (JET-X) was the core instrument of the Russian Spectrum-X- γ space observatory. It consisted of two identical soft X-ray (0.3–10 keV) telescopes with focusing optical modules having a measured angular resolution of nearly 15 arcsec. Soon after the payload completion, the mission was cancelled and the two optical flight modules (FM) were brought to the Brera Astronomical Observatory where they had been manufactured. After 16 years of storage, we have utilized the JET-X FM2 to test at the PANTER X-ray facility a prototype of a novel X-ray polarimetric telescope, using a Gas Pixel Detector (GPD) with polarimetric capabilities in the focal plane of the FM2. The GPD was developed by a collaboration between INFN-Pisa and INAF-IAPS. In the first phase of the test campaign, we have re-tested the FM2 at PANTER to have an up-to-date characterization in terms of angular resolution and effective area, while in the second part of the test the GPD has been placed in the focal plane of the FM2. In this paper we report the results of the tests of the sole FM2, using an unpolarized X-ray source, comparing the results with the calibration done in 1996.  相似文献   

Evidence of individual solar proton events in Antarctic snow   总被引：1，自引：0，他引：1  

Gisela A. M. Dreschhoff  Edward J. Zeller 《Solar physics》1990,127(2):333-346

The high-resolution nitrate analyses of a snow sequence in Antarctica reveals clear evidence that the snow contains a chemical record of ionization from charged particles incident upon the upper atmosphere of the Earth. The Antarctic continent acts as a cold trap that effectively freezes out this signal and retains it in the stratigraphy of the ice shelves and the continental ice sheet. The signal that we measure results from the ionization of nitrogen and oxygen, the two primary constituents of the Earth's atmosphere, which subsequently react to form oxides of nitrogen. A large portion of the nitrogen oxides produced are ultimately oxidized to nitric acid and incorporated in snow crystals together with nitrates from tropospheric sources that also contribute to the general background. The nitrate concentration in a firn core was measured in Antarctica by ultraviolet spectrophotometry under tightly controlled experimental procedures. Based on uninterrupted, high-resolution sampling, variations in nitrate concentration were found to average about 53% (one standard deviation) of the mean concentration for the entire core. Short pulses of high nitrate concentration were found to show a variance of up to 11 standard deviations above the mean. At the series mean, the precision of analysis is better than 2%.The firn core was drilled by hand to a depth of 21.7 m corresponding to 62 years and including more than 5 solar cycles. The time series that resulted from a total of 1393 individual analyses shows a statistically significant modulation of the background signal that is clearly tracable to solar activity. Several anomalously large concentration peaks were observed that have been dated and found to correlate with the major solar proton events of August 1972, July 1946, and the white-light flare of July 1928.  相似文献