Sr and Pb isotopic composition of five USGS glasses (BHVO-2G, BIR-1G, BCR-2G, TB-1G, NKT-1G)   总被引：2，自引：0，他引：2  

Marlina Elburg  Pieter Vroon  Bas van der Wagt  Arnaud Tchalikian 《Chemical Geology》2005,223(4):196-207

Sr isotopic compositions and Rb / Sr ratios of three USGS glasses (BHVO-2G, BIR-1G, BCR-2G) are identical to those of the original USGS reference materials. NKT-1G and TB-1G give values of 0.70351 and 0.70558, respectively. Pb isotopic ratios were measured by the standard-sample bracketing technique on an MC-ICP-MS, which give results that are comparable in accuracy and reproducibility to double spike analyses. However, assessment of the reproducibility of the technique is hampered by inhomogeneous contamination of all USGS reference materials analysed. This contamination is likely to be the reason why the USGS glasses do not all have the same Pb isotopic composition as their unfused originals. Powdered glasses, distributed for characterisation of the glasses by bulk analytical techniques, do not all have the same Pb isotopic compositions as the solid glass material, and can therefore not be used for this purpose.  相似文献   

The importance and quality of governance in the Chilean wine industry     

Evert-Jan Visser  Peter de Langen 《GeoJournal》2006,65(3):177-197

The central theme of this paper is the issue of the governance of cooperation within the Chilean wine industry. The effects of the internationalization of this industry for the importance and the quality of governance of intra-cluster cooperation involving firms and other actors are analysed. Two questions stand central. First, what has been the relative importance of external and internal factors in improving the export performance of the Chilean wine industry over the past 20 years? Second, to what extent have collective actions and investments played a part in this growth, and what has been the quality of the various governance regimes dealing with the associated collective action problems? Empirical evidence suggests that world-market developments and upgrading efforts by individual wineries largely explain the good export performance of the Chilean wine industry until the year 2000. The evidence also shows that the industry’s success in world markets is stimulating cooperation between firms and other actors in areas where the industry needs to improve: marketing and promotion, internationalization, innovation and training. The enhanced cooperation has not only stimulated cluster development, but has also turned the quality of cluster governance into a central variable for future export growth. Nevertheless, several collective action problems await resolution before essential intra-cluster cooperation can develop. Overall, the evidence suggests that, in the case of the Chilean wine industry, industrial and cluster development do not automatically follow enhanced integration in world markets, but depend on the strategic skills of actors within the industry, in particular their ability to identify, prioritize, and realize collective investments while effectively managing the associated collective action problems. Internationalization stimulates firms to consider such investments, however, and provides them with an incentive to upgrade strategic skills at the local level as new opportunities arise and the pressure is there to exploit them in world markets.  相似文献   

Time series analysis of monthly mean data of temperature,salinity, nutrients,suspended matter,phyto- and zooplankton at eight locations on the northwest european shelf     

M. Visser  S. Batten  G. Becker  P. Bot  F. Colijn  P. Damm  D. Danielssen  D. Van den Eynde  L. FØyn  A. Frohse  G. Groeneveld  R. Laane  W. van Raaphorst  G. Radach  H. Schultz  J. Sündermann 《Ocean Dynamics》1996,48(3-4):299-323

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Definition of a Critical Confining Zone Using Surface Geophysical Methods     

Carol A. Eddy-Dilek  Brian B. Looney  Pieter Hoekstra  Norman Harthill  Mark Blohm  David R. Phillips 《Ground water》1997,35(3):451-462

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The European Gravity Field and Steady-State Ocean Circulation Explorer Satellite Mission Its Impact on Geophysics   总被引：1，自引：0，他引：1  

J. A. Johannessen  G. Balmino  C. Le Provost  R. Rummel  R. Sabadini  H. Sünkel  C.C. Tscherning  P. Visser  P. Woodworth  C. Hughes  P. Legrand  N. Sneeuw  F. Perosanz  M. Aguirre-Martinez  H. Rebhan  M. Drinkwater 《Surveys in Geophysics》2003,24(4):339-386

Current knowledge of the Earth's gravity field and its geoid, as derived from various observing techniques and sources, is incomplete. Within a reasonable time, substantial improvement will come by exploiting new approaches based on spaceborne gravity observation. Among these, the European Space Agency (ESA) Gravity field and steady-state Ocean Circulation Explorer (GOCE) satellite mission concept has been conceived and designed taking into account multi-disciplinary research objectives in solid Earth physics, oceanography and geodesy. Based on the unique capability of a gravity gradiometer combined with satellite-to-satellite high-low tracking techniques, an accurate and detailed global model of the Earth's gravity field and its corresponding geoid will be recovered. The importance of this is demonstrated by a series of realistic simulation experiments. In particular, the quantitative impact of the new and accurate gravity field and geoid is examined in studies of tectonic composition and motion, Glaciological Isostatic Adjustment, ocean mesoscale variability, water mass transport, and unification of height systems. Improved knowledge in each of these fields will also ensure the accumulation of new understanding of past and present sea-level changes.  相似文献   

Accuracy assessment of the monthly GRACE geoids based upon a simulation     

E. J. O. Schrama  P. N. A. M. Visser 《Journal of Geodesy》2007,81(1):67-80

The purpose of this paper is to demonstrate the effect of geophysical background model errors that affects temporal gravity solutions provided by the Gravity Recovery And Climate Experiment (GRACE). Initial performance estimates by Dickey et al. (1997) suggested a formal geoid RMS error better than 0.1 mm up to spherical harmonic degree 5. Now that the GRACE gravity models and data are available, it is evident that these original expectations were too optimistic. Our hypothesis is that this is partially explained by errors in geophysical background models that need to be applied in the GRACE data reduction, and that this effect was not considered by Dickey et al. (1997). We discuss the results of a closed-loop simulation, where satellite trajectory prediction software is used for the generation of GRACE range-rate data and GRACE orbit solutions with the help of the Global Positioning System (GPS). During the recovery step in our closed-loop simulation, we show that simulated nuisance signals (based on tide and air pressure model differences) map to a 0.7 mm geoid effect for periods longer than 3 months and to less than 0.4 mm for periods shorter than 3 months. The long-period geoid hydrology signal is at a level of 4.5 mm, while the short-period hydrology is at 0.25 mm. The long-period ocean bottom pressure (OBP) signal maps at 0.8 mm and for short periods it is 0.4 mm. We conclude that short-period effects are difficult to observe by GRACE and that long-period effects, like hydrology, are easier to recover than OBP variations.  相似文献   

A test case for anomalous fading correction in IRSL dating     

Jakob Wallinga  Adrie J.J. Bos  Pieter Dorenbos  Andrew S. Murray  Jeroen Schokker 《Quaternary Geochronology》2007,2(1-4):216-221

Infrared-stimulated luminescence (IRSL) dating of feldspars has the potential to date deposits beyond the age range of quartz optical (OSL) dating. Successful application of feldspar IRSL dating is, however, often precluded due to anomalous-fading, the tunnelling of electrons from one defect site to another. In this paper we test procedures proposed for anomalous-fading correction by comparing feldspar IRSL and quartz OSL dating results on a suite of samples from continental deposits from the southeastern Netherlands. We find that even after anomalous-fading correction IRSL ages underestimate the burial age of the deposits and argue that this may be a consequence of a dependency of anomalous fading rate on the dose rate and on the absorbed dose.  相似文献   

Tectonic discrimination of basalts with classification trees   总被引：5，自引：0，他引：5  

Pieter Vermeesch 《Geochimica et cosmochimica acta》2006,70(7):1839-1848

Traditionally, geochemical classification of basaltic rocks of unknown tectonic affinity has been performed by discrimination diagrams. Although easy to use, this method is fairly inaccurate because it only uses bi- or trivariate data. Furthermore, many popular discrimination diagrams are statistically not very rigorous because the decision boundaries are drawn by eye, and they ignore closure, thus violating the rules of compositional data analysis. Classification trees approximate the data space by a stepwise constant function, and are a more rigorous and potentially more effective way to determine tectonic affinity. Trees allow the simultaneous use of an unlimited number of geochemical features, while still permitting visualization by an easy-to-use, two-dimensional graph. Two classification trees are presented for the discrimination of basalts of mid-ocean ridge, ocean island, and island arc affinities. The first tree uses 51 major, minor, and trace elements and isotopic ratios and should be used for the classification of fresh basalt samples. A second tree only uses high field strength element analyses and isotopic ratios, and can also be used for basalts that have undergone alteration. The probability of successful classification is 89% for the first and 84% for the second tree, as determined by 10-fold cross-validation. Even though the trees presented in this paper use many geochemical features, it is not a problem if some of these are missing in the unknown sample. Classification trees solve this problem with surrogate variables, which give more or less the same decision as the primary variables. The advantages of the classification tree approach over discrimination diagrams are illustrated by a comparative test on a sample dataset of known tectonic affinities. Although arguably better than discrimination diagrams, classification trees are not perfect, and the limitations of the method are illustrated on a published dataset of basalts from the Pindos Basin (Greece).  相似文献   

A detailed post‐IR IRSL dating study of the Niuyangzigou loess site in northeastern China          下载免费PDF全文

Shuangwen Yi  Jan‐Pieter Buylaert  Andrew S. Murray  Huayu Lu  Christine Thiel  Lin Zeng 《Boreas: An International Journal of Quaternary Research》2016,45(4):644-657

In this study, we report standard quartz SAR OSL and post‐IR infrared (IR) stimulated luminescence (post‐IR IRSL; pIRIR₂₉₀) measurements made on sand‐sized quartz and K‐feldspar extracts from the loess‐palaeosol sequence at Niuyangzigou in northeastern China. The quartz OSL characteristics are satisfactory. Extensive pIRIR_50,290 dose recovery tests were performed by adding doses on top of the natural dose. We found that dose recovery ratios improve significantly when the test dose ranges between ~15 and ~80% of the total dose, and good dose recovery (within ±5% of unity) can be obtained up to ～800 Gy. Otherwise, the dose recovery ratio deviates from unity. The D_e values also depend on the test dose size and so we conclude that the effect of test dose size should be routinely considered in pIRIR dating. First IR stimulation plateau pIRIR₂₉₀ results are compared with multiple elevated temperature ‐pIRIR (MET‐pIRIR) data. It appears that the low temperature MET‐pIRIR data are strongly affected by poor dose recovery, but this is not the case for the pIRIR₂₉₀ results. Natural signal measurements at the highest (first IR) stimulation temperature on a sample expected to be in field saturation suggest that ~10% signal loss occurs in pIRIR signals. Long‐term laboratory bleaching experiments (>80 days) show that a constant (or very difficult to bleach) residual pIRIR₂₉₀ signal is reached after ~300 h, corresponding to a dose of 6.2±0.7 Gy. Quartz OSL and feldspar pIRIR_50,290 ages are in good agreement at least back to c. 70 ka. Beyond this the quartz ages begin to underestimate but the feldspar ages are in agreement with the expected Last Interglacial age palaeosol.  相似文献   

Numerical Analysis of the Effects of Wind and Sprayer Type on Spray Distribution in Different Orchard Training Systems     

Ashenafi T. Duga  Donald Dekeyser  Kris Ruysen  Dany Bylemans  David Nuyttens  Bart M. Nicolai  Pieter Verboven 《Boundary-Layer Meteorology》2015,157(3):517-535

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