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Martin Gutowski Jonathan M. Bull Timothy J. Henstock Tom Hiller Paul R. White 《Applied Acoustics》2008,69(3):262-271
Chirp sub-bottom profilers are marine acoustic devices that use a known and repeatable frequency-modulated source signature to produce vertical seismic reflection cross-sections of the sub-seabed. Here a 3D Chirp system is described that operates in the frequency range of 1.5-13 kHz, to produce a three-dimensional image of the sub-seabed, with typical penetration of 10-30 m and decimetric horizontal and vertical resolution. The system design incorporates a rigid frame that contains the Chirp source array together with 60 receiver elements, with positioning provided by an integrated real-time-kinematic (RTK) global positioning system (GPS). The system can be surface towed from a small survey vessel and can be applied to targets of marine geological, engineering, archaeological and defence interest. Data acquisition and processing are described for a case study which images a buried engineering structure in the Port of Southampton. 相似文献
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Niels M. B. Smeets Tom G. T. Jansen Timo J. J. Sciarone Johan P. A. Heuts Jan Meuldijk Alex M. Van Herk 《Journal of polymer science. Part A, Polymer chemistry》2010,48(5):1038-1048
The effect a Co(II) based catalytic chain transfer agent (CCTA) has on the course of the polymerization and the product properties of an emulsion polymerization is governed by the intrinsic activity and the partitioning behavior of the catalyst. The effect on the conversion time history, the molecular weight distribution and the particle size distribution is evaluated in batch emulsion polymerization of methyl methacrylate for three different CCTAs, which cover a range of intrinsic activities and partitioning behaviors. It was demonstrated that radical desorption from the particle phase to the aqueous phase preceded by chain transfer is the main kinetic event controlling the course of the polymerization and the product properties in terms of the particle size distribution. The experimental results show that the aqueous phase solubility of the CCTA is the key parameter controlling the course of the polymerization and the particle size distribution. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1038–1048, 2010 相似文献
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Emilie Combet Tom Preston Kenneth E. L. McColl 《Rapid communications in mass spectrometry : RCM》2010,24(5):529-534
Nitrite has long been considered a potential pre‐carcinogen for gastric cancer. Acidification of salivary nitrite, derived from dietary nitrate, produces nitrosative species such as NOSCN, NO+ and N2O3, which can form potentially carcinogenic N‐nitroso compounds. Ascorbic acid inhibits nitrosation by converting the nitrosative species into nitric oxide (NO). However, NO diffuses rapidly to adjacent lipids, where it reacts with oxygen to reform nitrosative species. Nitrosation has been studied in vitro in aqueous systems and less frequently in organic systems; however, there is a need to investigate acid‐catalysed nitrosation in a system combining aqueous and lipid environments, hence providing a physiologically relevant model. Here, we describe a two‐phase system, which can be used as a tool to understand acid‐catalysed nitrosation. Using gas chromatography/ion trap tandem mass spectrometry, we investigated the nitrosation of secondary amines as a function of the lipid phase composition and reaction mixing. An increased interface surface area was a driver for nitrosation, while incorporation of unsaturated fatty acids affected morpholine and piperidine nitrosation differently. Linoleic acid methyl esters did not affect morpholine nitrosation and only had a limited effect on N‐nitrosopiperidine formation, while incorporation of free linoleic acid to the lipid phase significantly reduced N‐nitrosopiperidine formation, but increased N‐nitrosomorpholine formation at low levels. The mechanisms driving these effects are thought to involve amine partitioning, polarity and unsaturated fatty acids acting as scavengers of nitrosating species, findings relevant to the nitrosative chemistry occurring in the stomach, where the gastric acid meets a range of dietary fats which are emulsified during digestion. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Tom Bohman 《Proceedings of the American Mathematical Society》2003,131(11):3559-3569
This paper contains a construction for independent sets in the powers of odd cycles. It follows from this construction that the limit as goes to infinity of is zero, where is the Shannon capacity of the graph .