排序方式: 共有42条查询结果,搜索用时 15 毫秒
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Barbara Bojko Krzysztof Gorynski German Augusto Gomez-Rios Jan Matthias Knaak Tiago Machuca Vinzent Nikolaus Spetzler Erasmus Cudjoe Michael Hsin Marcelo Cypel Markus Selzner Mingyao Liu Shaf Keshavjee Janusz Pawliszyn 《Analytica chimica acta》2013
Metabolomics and biomarkers discovery are an integral part of bioanalysis. However, untargeted tissue analysis remains as the bottleneck of such studies due to the invasiveness of sample collection, as well as the laborious and time-consuming sample preparation protocols. In the current study, technology integrating in vivo sampling, sample preparation and global extraction of metabolites – solid phase microextraction was presented and evaluated during liver and lung transplantation in pig model. Sampling approaches, including selection of the probe, transportation, storage conditions and analyte coverage were discussed. The applicability of the method for metabolomics studies was demonstrated during lung transplantation experiments. 相似文献
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The preparation of cobalt nano-particles from a solution of Co(CO)3(NO) in n-decane under ultrasonication with a frequency of 20 kHz yielded cobalt particles of a size of ca. 5 nm. The presence of either silica or oleic acid in the solution reduced the particle size to ca. 3 and 2 nm, respectively. The resulting particle size is independent of the ultrasonication time, initial Co(CO)3(NO) concentration, ultrasound intensity and solution temperature. It is postulated that bubble collapse generates multiple nucleation sites resulting in the formation of cobalt particles with a rather uniform particle size distribution. 相似文献
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Effects of 3-amino-1,2,4-triazole on the inhibition of copper corrosion in acidic chloride solutions 总被引:1,自引:0,他引:1
Effects of 3-amino-1,2,4-triazole (ATA) on the inhibition of copper corrosion in 0.5 M HCl solutions have been studied using gravimetric, electrochemical, and Raman spectroscopy investigations. Weight-loss measurements after varied immersion periods revealed that the dissolution rate of copper decreased to a minimum, while the inhibition efficiency (zeta%) and consequently the degree of surface coverage (theta) increased with the presence of ATA and the increase of its concentration. Potentiodynamic polarization, chronoamperometric, and electrochemical impedance spectroscopy (EIS) measurements after 0, 24, and 48 h immersion of the copper electrode in the test solutions showed that the presence of ATA molecules significantly decreased cathodic, anodic, and corrosion (jcorr) currents and corrosion rates (Rcorr) and greatly increased polarization resistance (Rp), zeta%, and theta; this effect was increased on increasing the ATA content in the solution. Raman spectroscopy confirmed that ATA molecules strongly adsorbed onto the copper surface, blocking its active sites and preventing it from being corroded easily. 相似文献
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G. H. Kassier N. Erasmus K. Haupt I. Boshoff R. Siegmund S. M. M. Coelho H. Schwoerer 《Applied physics. B, Lasers and optics》2012,109(2):249-257
Temporally resolved observation of microscopic structural dynamics of solids with ultrafast electron diffraction (UED) requires extremely short pulsed, highly charged, monoenergetic electron beams with sufficient transverse coherence length of several unit cells of the investigated samples. However, Coulomb repulsion defeats these parameters in free propagation of an electron pulse initially bright on the photo cathode. We demonstrate a new electron pulse compressor design based on a simple and compact RF structure incorporating a pair of gallium arsenide photoconductive semiconductor switches that are triggered by femtosecond laser pulses, thereby providing a longitudinal voltage gradient of up to 20?V/ps. Our proof of principle experiment achieved compression of bunches containing 26,000 electrons to a duration of below 750?fs and a beam diameter of 300???m in the temporal and spatial focus of the device while maintaining the good beam collimation required for time resolved electron diffraction experiments. The simplicity of the compressor provides a strong incentive for its further development toward practical implementation in sub-relativistic UED experiments requiring the highest possible source brightness. 相似文献
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C. S. Erasmus H. W. Fesq E. J. D. Kable S. E. Rasmussen J. P. F. Sellschop 《Journal of Radioanalytical and Nuclear Chemistry》1977,39(1-2):323-334
The NIMROC reference materials NIM-D, NIM-G, NIM-L, NIM-N, NIM-P, and NIM-S and the precious metal ore PTO-1 have been analysed
using thermal and epithermal methods of instrumental neutron activation. The abundances of 40 major, minor and trace elements
are reported. The usefulness of the NIMROC reference materials is assessed in terms of the requirements of neutron activation
techniques. Of the seven reference materials, NIM-L is the most useful geochemical material for activation analysis. It contains
suitably high concentrations of most elements that can be determined. Inhomogeneity problems encountered in PTO-1 for some
elements give emphasis to the difficulty of selecting suitable geological material for ultra-trace elements where small quantities
of sample are used. 相似文献
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A general protocol for the Pd-catalyzed-arylation of nitroalkanes is described. Substituted aryl bromides as well as aryl chlorides can be coupled efficiently with a variety of nitroalkanes under mild conditions to selectively yield the monoarylated products. This method tolerates a number of functional groups including ketones, esters, and olefins. Notably, the arylation of nitroalkanes can be effected chemoselectively over ketone and ester arylation. 相似文献
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Hannen P Militzer HC Vogl EM Rampf FA 《Chemical communications (Cambridge, England)》2003,(17):2210-2211
We report the synthesis of new chiral monodentate phosphite ligands with a biphenyl backbone, the axial chirality of which is introduced early in the synthesis and locked by a chiral alkylenedioxy bridge. We also describe results obtained with these ligands in rhodium-catalysed asymmetric hydrogenation of various substrates. 相似文献
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Sekhar C. Ray Zikhona N. Tetana Rudolph Erasmus Way-Faung Pong Neil J. Coville 《Applied Physics A: Materials Science & Processing》2014,115(1):153-157
Carbon spheres (CSs) and low content nitrogen (2.5 and 3.5 at%) doped carbon spheres (NCSs) were synthesized by a pyrolysis process at 900 °C using $\mathrm{C}_{2}\mathrm{H}_{2}$ and CH3CN. The electronic structure and chemical bonding of CSs and NCSs were studied using Raman spectroscopy, valence-band photoemission spectroscopy (VBPES) and X-ray absorption near-edge structure spectroscopy (XANES). XANES spectroscopy showed the effect of carbon and nitrogen bonds and graphitic as well as pyridinic structures on the NCS structure. For the spheres VBPES showed the effect of nitrogen on the spectral shape of the density of states and confirmed the role played by the $\pi$ bonds in controlling the electronic and structural properties of the NCSs. VBPES also showed that both $\pi$ and $\sigma$ bands shift towards higher binding energies after N-doping which is consistent with the XANES data. The consistency of the spherical geometry, chemical purity, suitable electronic/bonding structure and the availability of macroscopic quantities of the N–CSs makes these spheres promising new materials for different applications. 相似文献