Preparation and Measurement of Cassiterite for Sn Isotope Analysis          下载免费PDF全文

Ryan Mathur  Wayne Powell  Andrea Mason  Linda Godfrey  Junming Yao  Mark E. Baker 《Geostandards and Geoanalytical Research》2017,41(4):701-707

Increased interest in the fractionation of Sn isotopes has led to the development of several techniques for preparing cassiterite (SnO₂, the primary ore of Sn) for isotopic analysis. Two distinct methods have been applied in recent isotopic studies of cassiterite: (a) reduction to tin metal with potassium cyanide (KCN) at high temperature (800 °C), with subsequent dissolution in HCl, and (b) reduction to a Sn solution with hydriodic acid (HI) at low temperature (100 °C). This study compares the effectiveness and accuracy of these two methods and contributes additional methodological details. The KCN method consistently yielded more Sn (> 70% in comparison with < 5%), does not appear to fractionate Sn isotopes at high temperatures over a 2‐hour period and produced consistent Sn isotope values at flux mass ratios of ≥ 4:1 (flux to mineral) with a minimum reduction time of 40 min. By means of a distillation experiment, it was demonstrated that HI could volatilise Sn, explaining the consistently low yields by this method. Furthermore, the distillation generated Sn vapour, which is up to 0.38‰ per mass unit different from the starting material, the largest induced Sn fractionation reported to date. Accordingly, the HI method is not recommended for cassiterite preparation for Sn isotopic analysis.  相似文献   

Emerging fisheries,emerging fishery interactions with sea turtles: A case study of the large-mesh gillnet fishery for flounder in Pamlico Sound,North Carolina,USA     

Barbie L. Byrd  Aleta A. Hohn  Matthew H. Godfrey 《Marine Policy》2011

Emerging fisheries and changes in fishery practices are not always readily apparent, nor are their impacts on non-target species such as seabirds, sea turtles, and marine mammals. Data from several different sources led managers to discover high rates of sea turtle bycatch in an inshore large-mesh gillnet fishery in North Carolina, USA, particularly the emerging deep-water gillnet fishery. This paper reviews the history of how increased numbers of observed stranded sea turtles in 1999 led to the discovery that turtles were becoming entangled in the large-mesh gillnet fishery in Pamlico Sound, North Carolina. It also demonstrates how a variety of data sets from fisheries observers, aerial surveys, and fisheries statistics programs contributed to shaping management of the large-mesh gillnet fishery in Pamlico Sound to decrease turtle bycatch and now point towards the need of additional assessment of gillnet bycatch in other parts of North Carolina. Finally, potential approaches are discussed for a more timely detection of future fishery conflicts and development of a plan to reduce otherwise inevitable bycatch and disruptions to fishing effort.  相似文献   

Mineralogical and Geochemical Constraints on the Sediment Sources of Late Stone Age Pottery from the Birimi Site,Northern Ghana     

J. Victor Owen  Joanna L. Casey  John D. Greenough  Dorothy Godfrey‐Smith 《Geoarchaeology》2013,28(4):394-411

The mineralogy and bulk chemical compositions of 15 Kintampo (Late Stone Age) potsherds from the Birimi site on the Gambaga Escarpment and eight samples of local sediment were determined with the intent of characterizing these wares and identifying the material used in their manufacture. Sediment from clay pits still used by potters north of the escarpment contains iron‐rich laterite clasts (100 × XFeO_t = 100 × FeO_t/[FeO_t + Al₂O₃ + SiO₂] ≥10). Sedimentary clasts in stream sediments are relatively siliceous and iron‐poor (100 × XFeO_t < 10). Bulk geochemical data together with the compositions of lithic clasts (laterite, siltstone/sandstone) link the pottery to sediment sources, including escarpment sediments not presently used by Ghanaian potters. Fresh granite clasts found in some of the sherds were not found in the analyzed sediment samples, although some of their distinctive mineralogical constituents (e.g., variably barian alkali feldspar) are present. The analytical data suggest that pots found at Birimi were made locally by mixing escarpment sediment with clay and stream sediment brought in from below the escarpment. This contrasts with present‐day practice, whereby the pots themselves are imported. The place where Birimi pottery was made and the outcrop source of aluminous sediment (mudstone with an “escarpment” trace element signature) used in these wares, however, remain unidentified. © 2013 Wiley Periodicals, Inc.  相似文献   

A search for propylene oxide and glycine in Sagittarius B2 (LMH) and Orion     

M. R. Cunningham  P. A. Jones  P. D. Godfrey  D. M. Cragg  I. Bains  M. G. Burton  P. Calisse  N. H. M. Crighton  S. J. Curran  T. M. Davis  J. T. Dempsey  B. Fulton  M. G. Hidas  T. Hill  L. Kedziora-Chudczer  V. Minier  M. B. Pracy  C. Purcell  J. Shobbrook  T. Travouillon 《Monthly notices of the Royal Astronomical Society》2007,376(3):1201-1210

We have used the Mopra Telescope to search for glycine and the simple chiral molecule propylene oxide in the Sgr B2 (LMH) and Orion KL, in the 3-mm band. We have not detected either species, but have been able to put sensitive upper limits on the abundances of both molecules. The 3σ upper limits derived for glycine conformer I are  3.7 × 10¹⁴ cm⁻²  in both Orion-KL and Sgr B2 (LMH), comparable to the reported detections of conformer I by Kuan et al. However, as our values are 3σ upper limits rather than detections we conclude that this weighs against confirming the detection of Kuan et al. We find upper limits for the glycine II column density of  7.7 × 10¹² cm⁻²  in both Orion-KL and Sgr B2 (LMH), in agreement with the results of Combes et al. The results presented here show that glycine conformer II is not present in the extended gas at the levels detected by Kuan et al. for conformer I. Our ATCA results have ruled out the detection of glycine (both conformers I and II) in the compact hot core of the LMH at the levels reported, so we conclude that it is unlikely that Kuan et al. have detected glycine in either Sgr B2 or Orion-KL. We find upper limits for propylene oxide abundance of  3.0 × 10¹⁴ cm⁻²  in Orion-KL and  6.7 × 10¹⁴ cm⁻²  in Sgr B2 (LMH). We have detected fourteen features in Sgr B2 and four features in Orion-KL which have not previously been reported in the interstellar medium, but have not been able to plausibly assign these transitions to any carrier.  相似文献   

Centralization and marginalization: The Chinese banking industry in reform   总被引：1，自引：0，他引：1  

Godfrey Yeung  Canfei He  Hao Liu 《Applied geography (Sevenoaks, England)》2012,32(2):854-867

Based on the distribution patterns of the sub-branches and saving outlets of the Industrial and Commercial Bank of China and the Bank of China in prefectural cities in China between 2001 and 2009, this paper examines how these two Chinese state-owned commercial banks may centralize their operations and thus lead to the possible marginalization of the provision of basic banking services to low value-added customers. The restructuring of SOCBs may not result in high levels of layoff due to the state’s objectives of minimizing both operational costs and political risks. When the politically sensitive issue of (un)employment is not taken into account, the more economically developed cities with larger populations and the more developed telecommunication facilities experience a higher level of centralization of their banking operations. The centralization of banking operations in China is, however, not always at the expense of savings outlets, despite the merging of savings outlets with sub-branches in various Chinese cities. There is circumstantial evidence to suggest the convergence thesis is not applicable to the banking industry in China, which is different from the conventional argument in financial geography that the centralization and marginalization of banking operations are two sides of the same coin as in the restructuring of the Anglo-American banking industries. This difference could be due to the hybrid ownership structures of state-owned commercial banks in China where the boundaries between public and private property rights are blurred.  相似文献   

International trade and industrial dynamics: Geographical and structural dimensions of Chinese and Sino-EU merchandise trade   总被引：1，自引：0，他引：1  

Li LiMichael Dunford  Godfrey Yeung 《Applied geography (Sevenoaks, England)》2012,32(1):130-142

This paper draws on trade data to examine the degree of upgrading of China’s trade structure with the world as a whole and in particular with the European Union (EU). More specifically it examines the evolution of the industrial structure of China’s trade with the world and with the EU between 1996 and 2008 and of the underlying dynamic indicators of revealed comparative advantage. This method of analysing China’s industrial structure provides clear evidence of upgrading into more advanced industries without at present losing significant competitive advantage in industries employing unskilled workers. The examination of revealed comparative advantage indices for world and Sino-EU trade also indicates an increasingly high degree of interdependence between the EU and China between 1996 and 2008. The EU (especially Germany, the UK, and France) is China’s most important export market, though it is also much more important as a market for China’s exports than the EU is as a supplier for China. China’s consequent trade surplus with the EU has gradually shifted from textiles and clothing to machinery and furniture. Further investigation reveals that the complementary Sino-EU bilateral trade is moving towards intra-industry trade at the 4-digit level of HS (Harmonization System) commodity classification. Although China is still a ‘global sweatshop’ with a strong specialization in labour-intensive commodities produced for economically developed countries (by importing machinery, raw materials and exporting processed goods), there are signs of technological upgrading in number of selected sectors in China, noticeably electronics, computers and telecommunications equipment. China’s reliance of imports of minerals indicates however that energy and resource security could be an important constraint on China’s long-term economic development.  相似文献   

Geo-political genetics: Claiming the commons through species mapping     

Lisa M. Campbell  Matthew H. Godfrey 《Geoforum》2010,41(6):897-907

Genetic techniques are increasingly employed in the field of conservation biology; our understanding of sea turtle biology, and particularly of sea turtle migrations and population structures, has increased through genetic analyses that ‘match’ turtles found in various and often widely distributed habitats (e.g. nesting beaches, foraging grounds, migratory corridors). This relatively recent technological development has implications for how sea turtles are conceived, both as resources and as objects of conservation. Traditionally, sea turtle populations have been identified with nesting beaches, and most conservation efforts have been focused on these discrete geographic locations and undertaken by the state. The more complete understanding of relationships among turtles found in geographically disparate areas, achieved via genetic analysis, can take conservation beyond the beaches and territorial waters of individual states; foraging populations can now be linked to nesting populations sometimes hundreds of kilometers distant. In this paper, we explore the implications of genetic analysis for sea turtle conservation, the scale at which it is undertaken, and the variety of actors with competing interests in it. We focus on the case of hawksbill sea turtles in the Caribbean, where genetic data are invoked in conservation conflicts. We are particularly interested in the way genetic data can support the scaling-up of sea turtle conservation, creating new ‘conservation territories,’ and we draw on political ecology and common pool resource theory to explore the implications thereof.  相似文献   

The Mount Cameroon 1959 compound lava flow field: morphology, petrography and geochemistry     

Manga S. Njome  Cheo E. Suh  R. Stephen J. Sparks  Samuel N. Ayonghe  J. Godfrey Fitton 《Swiss Journal of Geoscience》2008,101(1):85-98

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Land-use and land tenure explain spatial and temporal patterns in terrestrial net primary productivity (NPP) in Southern Africa     

Godfrey Pachavo  Amon Murwira 《国际地球制图》2013,28(6):671-687

Net primary productivity (NPP) is an important indicator of ecosystem health and its estimation and understanding of factors determining its spatial and temporal variations is critical. It is important to note that biophysical factors and human induced factors are interlinked in determining NPP patterns. Nevertheless, it is difficult to consider some aspects of human management systems in relation to NPP variations on a global scale analysis than on a local scale analysis. In this study, we tested the hypothesis that, at the local scale, particularly in highly intensive systems, land-use/land tenure types influence NPP variations by altering the biophysical conditions of the land. We estimated NPP between 2000 and 2009 using MODIS data and used ANOVA to test the abovementioned hypotheses. Results showed that NPP significantly (p < 0.05) varied by land-use/land tenure type. We also found that biophysical factors remained essential in explaining NPP variations even at local scales. These results exhibit the intricacies that exist between the biophysical and human-induced factors in explaining NPP variations within ecological landscapes.  相似文献   

A Search for biomolecules in Sagittarius B2 (LMH) with the Australia Telescope Compact Array   总被引：1，自引：0，他引：1  

P. A. Jones  M. R. Cunningham  P. D. Godfrey  D. M. Cragg 《Monthly notices of the Royal Astronomical Society》2007,374(2):579-589

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