ESR isochron dating analyses at Bau de l'Aubesier,Provence, France: Clues to U uptake in fossil teeth     

Bonnie A.B. Blackwell  Anne R. Skinner  Joel I.B. Blickstein  Serge Lebel  Helen Y.M. Leung 《Geoarchaeology》2001,16(7):719-761

At Bau de l'Aubesier, Provence, Mousterian artifacts and human teeth occur in inhomogeneous (“lumpy”) sedimentary deposits that include bone and tooth fragments and extensive burnt horizons. Electron spin resonance (ESR) isochron analyses of mammal teeth, which use multiple subsamples with different U concentrations, can measure the external dose rate experienced by the tooth regardless of reworking and sedimentary dose rate changes. Isochron analyses do depend on the U uptake model assumed, but can also identify teeth that have experienced secondary U uptake or leaching. Using 11 teeth from six archaeological layers, the isochrons demonstrate that at least three teeth have experienced secondary uptake. For eight teeth, the U uptake has apparently not followed strictly early (EU), linear (LU), or recent uptake (RU), but more closely approximates LU‐RU. Comparing volumetrically averaged sedimentary geochemistry with thermoluminescent dosimetry suggests that fossil tissues in the sediment have also experienced LU‐RU uptake. LU‐RU uptake can explain standard ESR ages that underestimate the true fossil age. © 2001 John Wiley & Sons, Inc.  相似文献   

The impact of different rainfall products on landscape modelling simulations     

Christopher J. Skinner  Nadav Peleg  Niall Quinn  Tom J. Coulthard  Peter Molnar  Jim Freer 《地球表面变化过程与地形》2020,45(11):2512-2523

Rainfall products can contain significantly different spatiotemporal estimates, depending on their underlying data and final constructed resolution. Commonly used products, such as rain gauges, rain gauge networks, and weather radar, differ in their information content regarding intensities, spatial variability, and natural climatic variability, therefore producing different estimates. Landscape evolution models (LEMs) simulate the geomorphic changes in landscapes, and current models can simulate timeframes from event level to millions of years and some use rainfall inputs to drive them. However, the impact of different rainfall products on LEM outputs has never been considered. This study uses the STREAP rainfall generator, calibrated using commonly used rainfall observation products, to produce longer rainfall records than the observations to drive the CAESAR-Lisflood LEM to examine how differences in rainfall products affect simulated landscapes. The results show that the simulation of changes to basin geomorphology is sensitive to the differences between rainfall products, with these differences expressed linearly in discharges but non-linearly in sediment yields. Furthermore, when applied over a 1500-year period, large differences in the simulated long profiles were observed, with the simulations producing greater sediment yields showing erosion extending further downstream. This suggests that the choice of rainfall product to drive LEMs has a large impact on the final simulated landscapes. The combination of rainfall generator model and LEMs represents a potentially powerful method for assessing the impacts of rainfall product differences on landscapes and their short- and long-term evolution. © 2020 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd  相似文献   

Modelling the dust and gas outflows from IRC+10 216 -- I. Ground-based and airborne observations     

C. J. Skinner †  K. Justtanont ‡  A. G. G. M. Tielens  A. L. Betz  R. T. Boreiko  F. Baas 《Monthly notices of the Royal Astronomical Society》1999,302(2):293-304

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Large ground surface temperature changes of the last three centuries inferred from borehole temperatures in the Southern Canadian Prairies, Saskatchewan   总被引：1，自引：0，他引：1  

Jacek A. Majorowicz  Jan Safanda  Robert N. Harris  Walter R. Skinner 《Global and Planetary Change》1999,20(4):715

New temperature logs in wells located in the grassland ecozone in the Southern Canadian Prairies in Saskatchewan, where surface disturbance is considered minor, show a large curvature in the upper 100 m. The character of this curvature is consistent with ground surface temperature (GST) warming in the 20th century. Repetition of precise temperature logs in southern Saskatchewan (years 1986 and 1997) shows the conductive nature of warming of the subsurface sediments. The magnitude of surface temperature change during that time (11 years) is high (0.3–0.4°C). To assess the conductive nature of temperature variations at the grassland surface interface, several precise air and soil temperature time series in the southern Canadian Prairies (1965–1995) were analyzed. The combined anomalies correlated at 0.85. Application of the functional space inversion (FSI) technique with the borehole temperature logs and site-specific lithology indicates a warming to date of approximately 2.5°C since a minimum in the late 18th century to mid 19th century. This warming represents an approximate increase from 4°C around 1850 to 6.5°C today. The significance of this record is that it suggests almost half of the warming occurred prior to 1900, before dramatic build up of atmospheric green house gases. This result correlates well with the proxy record of climatic change further to the north, beyond the Arctic Circle [Overpeck, J., Hughen, K., Hardy, D., Bradley, R., Case, R., Douglas, M., Finney, B., Gajewski, K., Jacoby, G., Jennings, A., Lamourex, S., Lasca, A., MacDonald, G., Moore, J., Retelle, M., Smith, S., Wolfe, A., Zielinski, G., 1997. Arctic environmental change of the last four centuries, Science 278, 1251–1256.].  相似文献   

Gamma Ray Fresnel Lenses – Why Not?     

G. K. Skinner 《Experimental Astronomy》2005,20(1-3):289-298

Fresnel lenses offer the possibility of concentrating the flux of X-rays or gamma-rays flux falling on a geometric area of many square metres onto a focal point which need only be a millimetre or so in diameter (and which may even be very much smaller). They can do so with an efficiency that can approach 100%, and yet they are easily fabricated and have no special alignment requirements. Fresnel lenses can offer diffraction-limited angular resolution, even in a domain where that limit corresponds to less than a micro second of arc.Given all these highly desirable attributes, it is natural to ask why Fresnel gamma ray lenses are not already being used, or at least why there is not yet any mission that plans to use the technology. Possible reasons (apart from the obvious one that nobody thought of doing so) include the narrow bandwidth of simple Fresnel lenses, their very long focal length, and the problems of target finding. It is argued that none of these is a ‘show stopper’ and that this technique should be seriously considered for nuclear astrophysics.  相似文献   

Brightness of the O₂ atmospheric bands in the daytime thermosphere     

W.R. Skinner  P.B. Hays 《Planetary and Space Science》1985,33(1):17-22

The Fabry-Perot interferometer on Dynamics Explorer 2 was used as a low sensitivity photometer to study the O₂ Atmospheric A band during the daytime. A study of the brightness of the emission showed that the assumed source of O₂(b¹Σ_g⁺) in the thermosphere, O(¹D), can account for the observed intensity up to about 250 km but with a significantly different scale height. This combined with an enhanced brightness above this altitude suggests an additional source for this emission.  相似文献   

Techniques for the analysis of data from coded-mask X-ray telescopes     

G. K. Skinner  T. J. Ponman  A. P. Hammersley  C. J. Eyles 《Astrophysics and Space Science》1987,136(2):337-349

Several techniques useful in the analysis of data from coded-mask telescopes are presented. Methods of handling changes in the instrument pointing direction are reviewed and ways of using FFT techniques to do the deconvolution considered. Emphasis is on techniques for optimally-coded systems, but it is shown that the range of systems included in this class can be extended through the new concept of partial cycle averaging.  相似文献   

Microbes all around     

Skinner HC  Banfield JF 《Geotimes》1997,42(8):16-19

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Geographies of care: A commentary     

Christine Milligan  Sarah Atkinson  Mark Skinner  Janine Wiles 《New Zealand geographer》2007,63(2):135-140

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Social and environmental regulation in rural China: bringing the changing role of local government into focus     

Mark W. Skinner  Richard G. Kuhn 《Geoforum》2003,34(2):267-281

China’s rapid economic growth following the 1978 reforms has resulted in significant economic, social and environmental change. These reforms and their outcomes have been subjected to considerable scrutiny. However, relatively little research has been directed towards the relationship between the changing role of local government, which has itself been subject to substantial restructuring, and the local mediation of the social and environmental impacts of rapid economic growth. This paper investigates the local manifestation of social and environmental change in Zhejiang Province. In particular, it considers the changing role of local government in the regulatory process, and features a case study of Huzhou Municipality. A synthesis of the factual knowledge and perceptions of 48 key-informants from government and public institutions and rural industries is used as the platform for an analysis of the changing nature of local regulation with respect to the provision of key public services (health care and education) and environmental protection (water pollution control). The results reveal the ability of local government to selectively implement national and provincial policies in light of local priorities, which is taken as indicative of the emergence of local agency within local development processes. The case study suggests a need to re-evaluate conventional wisdom on the absence of autonomy at local levels of government in China, particularly as it relates to the continued devolution of administrative responsibility and the emergence of increasingly powerful economic interests.  相似文献