| 2. |
- Shard, A. G., et al.
(författare)
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Measuring Compositions in Organic Depth Profiling: Results from a VAMAS Interlaboratory Study
- 2015
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 119:33, s. 10784-10797
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Tidskriftsartikel (refereegranskat)abstract
- We report the results of a VAMAS (Versailles Project on Advanced Materials and Standards) interlaboratory study on the measurement of composition in organic depth profiling. Layered samples with known binary compositions of Irganox 1010 and either Irganox 1098 or Fmoc-pentafluoro-L-phenylalanine in each layer were manufactured in a single batch and distributed to more than 20 participating laboratories. The samples were analyzed using argon cluster ion sputtering and either X-ray photoelectron spectroscopy (XPS) or time-of-flight secondary ion mass spectrometry (ToF-SIMS) to generate depth profiles. Participants were asked to estimate the volume fractions in two of the layers and were provided with the compositions of all other layers. Participants using XPS provided volume fractions within 0.03 of the nominal values. Participants using ToF-SIMS either made no attempt, or used various methods that gave results ranging in error from 0.02 to over 0.10 in volume fraction, the latter representing a 50% relative error for a nominal volume fraction of 0.2. Error was predominantly caused by inadequacy in the ability to compensate for primary ion intensity variations and the matrix effect in SIMS. Matrix effects in these materials appear to be more pronounced as the number of atoms in both the primary analytical ion and the secondary ion increase. Using the participants' data we show that organic SIMS matrix effects can be measured and are remarkably consistent between instruments. We provide recommendations for identifying and compensating for matrix effects. Finally, we demonstrate, using a simple normalization method, that virtually all ToF-SIMS participants could have obtained estimates of volume fraction that were at least as accurate and consistent as XPS.
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| 3. |
- Pauly, Daniel, et al.
(författare)
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China's distant-water fisheries in the 21st century
- 2014
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Ingår i: Fish and Fisheries. - : Wiley. - 1467-2960 .- 1467-2979. ; 15:3, s. 474-488
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Tidskriftsartikel (refereegranskat)abstract
- We conservatively estimate the distant-water fleet catch of the People's Republic of China for 2000-2011, using a newly assembled database of reported occurrence of Chinese fishing vessels in various parts of the world and information on the annual catch by vessel type. Given the unreliability of official statistics, uncertainty of results was estimated through a regionally stratified Monte Carlo approach, which documents the presence and number of Chinese vessels in Exclusive Economic Zones and then multiplies these by the expected annual catch per vessel. We find that China, which over-reports its domestic catch, substantially under-reports the catch of its distant-water fleets. This catch, estimated at 4.6 million t year(-1) (95% central distribution, 3.4-6.1 million t year(-1)) from 2000 to 2011 (compared with an average of 368 000 t year(-1) reported by China to FAO), corresponds to an ex-vessel landed value of 8.93 billion year(-1) (95% central distribution, 6.3-12.3 billion). Chinese distant-water fleets extract the largest catch in African waters (3.1 million t year(-1), 95% central distribution, 2.0-4.4 million t), followed by Asia (1.0 million t year(-1), 0.56-1.5 million t), Oceania (198 000 t year(-1), 144 000-262 000 t), Central and South America (182 000 t year-1, 94 000299 000 t) and Antarctica (48 000 t year(-1), 8 000-129 000 t). The uncertainty of these estimates is relatively high, but several sources of inaccuracy could not be fully resolved given the constraints inherent in the underlying data and method, which also prevented us from distinguishing between legal and illegal catch.
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