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51.
Hopmans EC Kienhuis MV Rattray JE Jaeschke A Schouten S Damsté JS 《Rapid communications in mass spectrometry : RCM》2006,20(14):2099-2103
Ladderane lipids, containing three or five linearly concatenated cyclobutane moieties, are considered to be unique biomarkers for the process of anaerobic ammonium oxidation, an important link in the oceanic nitrogen cycle. Due to the thermal lability of the strained cyclobutane moieties, the ladderane lipids are difficult to analyze by gas chromatography. A method combining high-performance liquid chromatography coupled to positive ion atmospheric pressure chemical ionization tandem mass spectrometry (HPLC/APCI-MS/MS) was developed for the analysis of the most abundant ladderane lipids, occurring as fatty acids and ether-bound to glycerol. Detection was achieved by selective reaction monitoring of four specific fragmentations per ladderane lipid. Detection limits of 30-35 pg injected on-column and a linear response (r(2) > 0.99) over nearly 3 orders of magnitude were achieved for all compounds. Using this method, these unique ladderane lipids were for the first time identified in a surface sediment from the Gullmarsfjorden, in concentrations ranging from 1.1-5.5 ng/g for the ladderane fatty acids and of 0.7 ng/g for the monoether. It is foreseen that this method will allow the investigation of the occurrence of anaerobic ammonium oxidation in natural settings in much greater detail than before. 相似文献
52.
van Werven JR Marsman HA Nederveen AJ ten Kate FJ van Gulik TM Stoker J 《Magnetic resonance imaging》2012,30(1):112-121
Purpose
To investigate the feasibility of in vivo assessment of hepatic lipid composition using 3.0-T proton magnetic resonance spectroscopy (1H-MRS) in a steatotic rat model and compare it to histopathological and biochemical assessment.Materials and Methods
Hepatic steatosis was induced by feeding rats with a methionine/choline-deficient (MCD) diet for 1, 2, 3, 5 or 7 weeks (n=5 per group). At the end of the diet period, 1H-MRS of the liver was performed, and rats were sacrificed for histopathological and biochemical assessment of the liver. Spectra were acquired in a single voxel (1.2 cc) using a point-resolved spectroscopic sequence with TE/TR=35/2000 ms and 64 signal acquisitions. From the MR spectra, peak area ratios were calculated to estimate hepatic lipid composition.Results
During MCD diet periods, hepatic steatosis significantly increased on histopathology (P<.001). The 1H-MRS measurements of total hepatic fat content [1.3/(1.3+4.65) ppm] correlated strongly with histological macrovesicular hepatic steatosis (r=0.93, P<.001) and with the biochemical total hepatic fatty acids (r=0.94, P<.001). Total unsaturated fatty acids [TUFA, 5.4/(1.3+4.65) ppm] estimated with 1H-MRS strongly correlated with the biochemical unsaturated fatty acids (r=0.90, P<.001). Polyunsaturated fatty acids [PUFA, 2.8/(1.3+4.65) ppm] estimated with 1H-MRS strongly correlated with biochemical PUFA (r=0.91, P<.001). The proportion of total unsaturated fatty acids relative to the amount of total fatty acids (rTUFA, 5.4/1.3ppm) measured with 1H-MRS strongly correlated with the biochemical amount of unsaturated relative to total hepatic fatty acids (r=0.81, P<.001). The proportion of PUFA relative to the amount of total fatty acids (rPUFA, 2.8/1.3 ppm) measured with 1H-MRS correlated with the biochemical amount of PUFA relative to total fatty acids (r=0.59, P=0.005,) and with the biochemical amount of omega-6 PUFA relative to total fatty acids (r=0.73, P<.001).PUFA at 1H-MRS correlated with the histopathologically assessed degree of lobular inflammation in the liver (r=0.57, P=.001).Conclusion
3.0T 1H-MRS is able to measure poly- and unsaturated hepatic fatty acids and this strongly correlates with biochemical assessment. This study provides evidence that 3.0-T 1H-MRS is a noninvasive technique to assess hepatic lipid composition. 相似文献53.
de Boer T Meulman E Meijering H Wieling J Dogterom P Lass H 《Biomedical chromatography : BMC》2012,26(2):156-165
The development and validation of methods for determining concentrations of the antipsychotic drug asenapine (ASE) and three of its metabolites [N-desmethylasenapine (DMA), asenapine-N(+) -glucuronide (ASG) and 11-O-sulfate-asenapine (OSA)] in human plasma using LC-MS/MS with automated solid-phase extraction is described. The three assessment methods in human plasma were found to be acceptable for quantification in the ranges 0.0250-20.0 ng/mL (ASE), 0.0500-20.0 ng/mL (DMA and OSA) and 0.250-50.0 ng/mL (ASG). 相似文献
54.
Benaskar F Engels V Rebrov EV Patil NG Meuldijk J Thüne PC Magusin PC Mezari B Hessel V Hulshof LA Hensen EJ Wheatley AE Schouten JC 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(6):1800-1810
New routes for the preparation of highly active TiO(2)-supported Cu and CuZn catalysts have been developed for C-O coupling reactions. Slurries of a titania precursor were dip-coated onto glass beads to obtain either structured mesoporous or non-porous titania thin films. The Cu and CuZn nanoparticles, synthesized using a reduction by solvent method, were deposited onto calcined films to obtain a Cu loading of 2 wt%. The catalysts were characterized by inductively coupled plasma (ICP) spectroscopy, temperature-programmed oxidation/reduction (TPO/TPR) techniques, (63)Cu nuclear magnetic resonance (NMR) spectroscopy, X-ray diffraction (XRD), scanning and transmission electron microscopy (S/TEM-EDX) and X-ray photo-electron spectroscopy (XPS). The activity and stability of the catalysts obtained have been studied in the C-O Ullmann coupling of 4-chloropyridine and potassium phenolate. The titania-supported nanoparticles retained catalyst activity for up to 12 h. However, catalyst deactivation was observed for longer operation times due to oxidation of the Cu nanoparticles. The oxidation rate could be significantly reduced over the CuZn/TiO(2) catalytic films due to the presence of Zn. The 4-phenoxypyridine yield was 64% on the Cu/nonporous TiO(2) at 120 °C. The highest product yield of 84% was obtained on the Cu/mesoporous TiO(2) at 140 °C, corresponding to an initial reaction rate of 104 mmol g(cat) (-1) s(-1). The activation energy on the Cu/mesoporous TiO(2) catalyst was found to be (144±5) kJ mol(-1), which is close to the value obtained for the reaction over unsupported CuZn nanoparticles (123±3 kJ mol(-1)) and almost twice the value observed over the catalysts deposited onto the non-porous TiO(2) support (75±2 kJ mol(-1)). 相似文献
55.
56.
Jaap Top 《Indagationes Mathematicae》2003,14(2):275-283
57.
H. van Gemerden C. Davids Harry H. Tolkamp Wayland R. Swain Jaap Dorgelo 《Journal of Radioanalytical and Nuclear Chemistry》1995,195(2):371-371
List of participants 相似文献
58.
Robert Kreiter Mariëlle D. A. Rietkerk Ben C. Bonekamp Henk M. van Veen Vadim G. Kessler Jaap F. Vente 《Journal of Sol-Gel Science and Technology》2008,48(1-2):203-211
Zirconia and titania nanoparticle sols were prepared, using either ligand-based precursor stabilization or acid stabilization routes. These sols were used to prepare microporous coatings on γ-alumina substrates. The acetylacetonate-based particles have very small hydrodynamic diameters (1–2 nm), which lead to sol intrusion into the supports. As a result no appropriate membrane layer was formed. A microemulsion-based zirconia sol leads to a membrane that was selective in pervaporation dehydration of a water/n-butanol mixture. An optimized membrane showed stable separation performance for 120 days with a high selectivity toward water. Permporometry and gas permeation results on a titania membrane based on an acid-stabilized sol not only show microporosity, but also a significant contribution from defect flow. 相似文献
59.
Jaap W. Deckers 《Accreditation and quality assurance》2004,10(1-2):37-40
The clinical management of patients with acute ischaemic syndromes continues to evolve. It is therefore useful to review the most common categories of such patients, with specific emphasis on the contribution of some well-known laboratory assessments. Key questions on diagnosis, prognosis and medical quality are discussed.Presented at the 9th Conference on Quality in the Spotlight, 18–19 March 2004, Antwerp, Belgium 相似文献
60.