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91.
The isotope content of ethane formed by pyrolysis of the complex (Me2PPh)2PtMe3I and its deuterated derivatives shows that the reaction is both intramolecular and first order with respect to substrate and gives the activation parameter ΔH3 = 129 ± 5 kJ · mol?1. 相似文献
92.
Stefania Principe Job J.M.H. van Bragt Cristina Longo Rianne de Vries Peter J. Sterk Nicola Scichilone Susanne J.H. Vijverberg Anke H. Maitland-van der Zee 《Molecules (Basel, Switzerland)》2021,26(5)
Breath analysis using eNose technology can be used to discriminate between asthma and COPD patients, but it remains unclear whether results are influenced by smoking status. We aim to study whether eNose can discriminate between ever- vs. never-smokers and smoking <24 vs. >24 h before the exhaled breath, and if smoking can be considered a confounder that influences eNose results. We performed a cross-sectional analysis in adults with asthma or chronic obstructive pulmonary disease (COPD), and healthy controls. Ever-smokers were defined as patients with current or past smoking habits. eNose measurements were performed by using the SpiroNose. The principal component (PC) described the eNose signals, and linear discriminant analysis determined if PCs classified ever-smokers vs. never-smokers and smoking <24 vs. >24 h. The area under the receiver–operator characteristic curve (AUC) assessed the accuracy of the models. We selected 593 ever-smokers (167 smoked <24 h before measurement) and 303 never-smokers and measured the exhaled breath profiles of discriminated ever- and never-smokers (AUC: 0.74; 95% CI: 0.66–0.81), and no cigarette consumption <24h (AUC 0.54, 95% CI: 0.43–0.65). In healthy controls, the eNose did not discriminate between ever or never-smokers (AUC 0.54; 95% CI: 0.49–0.60) and recent cigarette consumption (AUC 0.60; 95% CI: 0.50–0.69). The eNose could distinguish between ever and never-smokers in asthma and COPD patients, but not recent smokers. Recent smoking is not a confounding factor of eNose breath profiles. 相似文献
93.
Jack E. Baldwin Timothy D. W. Claridge Andrew J. Culshaw Florian A. Heupel Victor Lee David R. Spring Roger C. Whitehead Robert J. Boughtflower Ian M. Mutton Richard J. Upton 《Angewandte Chemie (International ed. in English)》1998,37(19):2661-2663
The biomimetic synthesis of a pentacyclic alkaloid (keramaphidin B, 1 ), an intermediate in the biogenetic pathway to the manzamine alkaloids, has been achieved. Compound 1 was formed by an intramolecular Diels–Alder reaction of macrocycle 2 in buffer followed by reduction with NaBH4. This reaction provides the first direct expeimental evidence for the authors' biosynthetic hypothesis. 相似文献
94.
95.
Titan, the largest moon of Saturn, is enveloped in a reddish brown organic haze. Titan haze is presumed to be formed from methane and nitrogen (CH(4) and N(2)) in Titan's upper atmosphere through energetic photochemistry and particle bombardment. Though Titan haze has been directly investigated using methods including the Cassini mission, its formation mechanism and the contributing chemical structures and prebiotic potential are still not well developed. We report here the structural investigation of the (13)C and (15)N labeled, simulated Titan haze aerosol (tholin) by solution-state NMR. The one-dimensional (1)H, (13)C, and (15)N NMR spectra and decoupling experiments indicate that the tholin sample contains amine, nitrile, imine, and N-heteroaromatic compounds of tremendous import in understanding complex organic chemistry in anaerobic, extraterrestrial environments. 相似文献
96.
It is consistent with the measurement of θ13∼0.15 by Daya Bay to suppose that, in addition to being unitary, the neutrino mixing matrix is also almost Hermitian, and thereby only a small perturbation from diag(+1,−1,−1) in a suitable basis. We suggest this possibility simply as an easily falsifiable ansatz, as well as to offer a potentially useful means of organizing the experimental data. We explore the phenomenological implications of this ansatz and parametrize one type of deviation from the leading order relation |Ve3|≈|Vτ1|. We also emphasize the group-invariant angle between orthogonal matrices as a means of comparing to data. The discussion is purely phenomenological, without any attempt to derive the condition V†≈V from a fundamental theory. 相似文献
97.
Computed tomography (CT) has the potential to greatly enhance our understanding of the turbulent flow structures, the combustion
chemistry, and the interactions between the two, which challenge us in our attempts to understand and model the details of
turbulent combustion. Here, we present high-resolution and fully three-dimensional measurements of the flame surface of a
turbulent reacting flow. The CT-reconstructed images show the flame front, at a single instant in time, of a turbulent, premixed
propane/air flame. The significance of this powerful experimental tool is to provide new insight into turbulent combustion,
allowing for the development of cleaner burning, higher power, and more efficient combustors. 相似文献
98.
Zachary D. Reed Brent Sperling Roger D. van Zee James R. Whetstone Keith A. Gillis Joseph T. Hodges 《Applied physics. B, Lasers and optics》2014,117(2):645-657
We have developed a portable photoacoustic spectrometer that offers routine, precise and accurate measurements of the molar concentration of atmospheric carbon. The temperature-controlled spectrometer continuously samples dried atmospheric air and employs an intensity-modulated distributed feedback laser and fiber amplifier operating near 1.57 µm. For measurements of carbon dioxide in air, we demonstrate a measurement precision (60-s averaging time) of 0.15 µmol mol?1 and achieve a standard uncertainty of 0.8 µmol mol?1 by calibrating the analyzer response in terms of certified gas mixtures. We also investigate how water vapor affects the photoacoustic signal by promoting collisional relaxation of the carbon dioxide. 相似文献
99.
Profiling and semiquantitative analysis of the cell surface proteome in human mesenchymal stem cells
Sang Kwang Lee Jae Ho Kim Sung-Soo Kim Taewook Kang Nam Hyun Park Kyung-Hoon Kwon Sang Sook Lee Zee Won Lee Hae young Suh-Kim Kun Cho Su Yeoung Yun Ji Young Han Jong Shin Yoo Hyun Joo An Young Mok Park 《Analytical and bioanalytical chemistry》2013,405(16):5501-5517
Mulitpotent mesenchymal stem cells (MSCs) derived from human bone marrow are promising candidates for the development of cell therapeutic strategies. MSC surface protein profiles provide novel biological knowledge concerning the proliferation and differentiation of these cells, including the potential for identifying therapeutic targets. Basic fibroblast growth factor (bFGF) affects cell surface proteins, which are associated with increased growth rate, differentiation potential, as well as morphological changes of MSCs in vitro. Cell surface proteins were isolated using a biotinylation-mediated method and identified using a combination of one-dimensional sodium dodecyl sulfate–polyacrylamide gel electrophoresis and mass spectrometry. The resulting gel lines were cut into 20 bands and digested with trypsin. Each tryptic fragment was analyzed by liquid chromatography–electrospray ionization tandem mass spectrometry. Proteins were identified using the Mascot search program and the International Protein Index human database. Noble MSC surface proteins (n?=?1,001) were identified from cells cultured either with (n?=?857) or without (n?=?667) bFGF-containing medium in three independent experiments. The proteins were classified using FatiGO to elucidate their function. We also confirmed the proteomics results using Western blotting and immunofluorescence microscopic analysis. The nature of the proteins identified makes it clear that MSCs express a wide variety of signaling molecules, including those related to cell differentiation. Among the latter proteins, four Ras-related Rab proteins, laminin-R, and three 14-3-3 proteins that were fractionated from MSCs cultured on bFGF-containing medium are implicated in bFGF-induced signal transduction of MSCs. Consequently, these finding provide insight into the understanding of the surface proteome of human MSCs. Figure
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100.
Alexander P. Boichenko Natalia Govorukhina Ate G. J. van der Zee Rainer Bischoff 《Journal of separation science》2013,36(21-22):3463-3470
Proteome profiling of crude serum is a challenging task due to the wide dynamic range of protein concentrations and the presence of high‐abundance proteins, which cover >90% of the total protein mass in serum. Peptide fractionation on strong cation exchange, weak anion exchange in the electrostatic repulsion hydrophilic interaction chromatography (ERLIC) mode, RP C18 at pH 2.5 (low pH), fused‐core fluorinated at pH 2.5, and RP C18 at pH 9.7 (high pH) stationary phases resulted in two to three times more identified proteins and three to four times more identified peptides in comparison with 1D nanoChip‐LC–MS/MS quadrupole TOF analysis (45 proteins, 185 peptides). The largest number of peptides and proteins was identified after prefractionation in the ERLIC mode due to the more uniform distribution of peptides among the collected fractions and on the RP column at high pH due to the high efficiency of RP separations and the complementary selectivity of both techniques to low‐pH RP chromatography. A 3D separation scheme combining ERLIC, high‐pH RP, and low‐pH nanoChip‐LC–MS/MS for crude serum proteome profiling resulted in the identification of 208 proteins and 1088 peptides with the lowest reported concentration of 11 ng/mL for heat shock protein 74. 相似文献