排序方式: 共有37条查询结果,搜索用时 15 毫秒
1.
Frosch T Chan KL Wong HC Cabral JT Kazarian SG 《Langmuir : the ACS journal of surfaces and colloids》2010,26(24):19027-19032
Three-dimensional (3D) chemical information was obtained by means of a combination of two-dimensional attenuated total reflection Fourier transform infrared (ATR-FT-IR) imaging with a focal plane array detector and variable angle depth profiling. Since the penetration depth of the evanescent wave in ATR spectroscopy is not limited by diffraction, it was possible to resolve thin sandwiched polymer layers nondestructively within a stack of polymer layers. Chemical images were obtained from layers of different thickness of the laminate by moving a custom-made aperture to specific positions on the condenser lens of the ATR accessory. Sequences of absorption images detect the successive appearance of thin, buried layers of polybutylmethacrylate (d(PBMA) = 400 nm) and polycarbonate (d(TMPC) = 300 nm) in different depths of the stack of polymer layers. The depth resolution of variable-angle ATR-FT-IR imaging is sufficiently high to detect surface roughness at the interface between different polymer layers. Two different stacks of polymers with reordered sandwich-layers were imaged simultaneously, demonstrating the potential of variable angle ATR-FT-IR for 3D-imaging of a sample with xyz-heterogeneity, which can be a powerful analytical technique for materials science and biomedical research. 相似文献
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Methods to probe the molecular structure of living cells are of paramount importance in understanding drug interactions and environmental influences in these complex dynamical systems. The coupling of an acoustic levitation device with a micro-Raman spectrometer provides a direct molecular probe of cellular chemistry in a containerless environment minimizing signal attenuation and eliminating the affects of adhesion to walls and interfaces. We show that the Raman acoustic levitation spectroscopic (RALS) approach can be used to monitor the heme dynamics of a levitated 5 microL suspension of red blood cells and to detect hemozoin in malaria infected cells. The spectra obtained have an excellent signal-to-noise ratio and demonstrate for the first time the utility of the technique as a diagnostic and monitoring tool for minute sample volumes of living animal cells. 相似文献
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Deep UV resonance Raman micro-spectroscopy (lambda(exc) = 244 nm) was applied for a highly sensitive, selective, and gentle localization of the antimalarial quinine in situ in cinchona bark. The high potential of the method was demonstrated by the detection of small amounts of the alkaloid in the plant material without any further sample preparation, where conventional (non-resonant) Raman microscopy was unsuccessful due to a strong fluorescence background. The resonance Raman spectrum of cinchona bark corresponds well with that of quinine; it can be distinguished from its diastereomer quinidine via the mode at 831 cm(-1), which is shifted to 843 cm(-1) in the case of quinidine. This vibration involves a bending motion within the side chain around the chiral center of quinine. Vibrations belonging to the quinoline ring (important for its antimalarial activity in forming pi-pi-interactions to hemozoin) and the vinyl group are resonantly enhanced in the UV Raman spectra. A convincing mode assignment is derived by means of a combination of NIR Raman spectroscopy and DFT calculations. The Raman spectra of quinine in cinchona bark are modeled by considering a hydrous environment that causes a shift of the band at 1362 compared with 1371 cm(-1) in anhydrous quinine. This intense vibration is therefore sensitive to the presence of an aqueous environment and is assigned mostly to a stretching motion within the quinoline ring. The presented results nicely show the sensitivity of Raman spectroscopy to monitor subtle differences within the molecular structure and the influence of a biological relevant hydrous environment and trace low concentrated pharmaceutical relevant active agents in plant material. 相似文献
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R. Abela M. Daum G.H. Eaton R. Frosch B. Jost P.-R. Kettle E. Steiner 《Physics letters. [Part B]》1984,146(6):431-436
A new series of precision measurements of the muon momentum pμ+ in the decay π→μ+vμ at rest have been made using a magnetic spectrometer. The result is pμ+=(29.79139 ± 0.00083) MeV/c. The consequences of this value for the rest masses of the muon neutrino and of the charged pion are discussed. 相似文献
6.
Robert Keiner Martina Herrmann Kirsten Küsel Jürgen Popp Torsten Frosch 《Analytica chimica acta》2015
The comprehensive investigation of changes in N cycling has been challenging so far due to difficulties with measuring gases such as N2 and N2O simultaneously. In this study we introduce cavity enhanced Raman gas spectroscopy as a new analytical methodology for tracing the stepwise reduction of 15N-labelled nitrate by the denitrifying bacteria Pseudomonas stutzeri. The unique capabilities of Raman multi-gas analysis enabled real-time, continuous, and non-consumptive quantification of the relevant gases (14N2, 14N2O, O2, and CO2) and to trace the fate of 15N-labeled nitrate substrate (15N2, 15N2O) added to a P. stutzeri culture with one single measurement. Using this new methodology, we could quantify the kinetics of the formation and degradation for all gaseous compounds (educts and products) and thus study the reaction orders. The gas quantification was complemented with the analysis of nitrate and nitrite concentrations for the online monitoring of the total nitrogen element budget. The simultaneous quantification of all gases also enabled the contactless and sterile online acquisition of the pH changes in the P. stutzeri culture by the stoichiometry of the redox reactions during denitrification and the CO2-bicarbonate equilibrium. Continuous pH monitoring – without the need to insert an electrode into solution – elucidated e.g. an increase in the slope of the pH value coinciding with an accumulation of nitrite, which in turn led to a temporary accumulation of N2O, due to an inhibition of nitrous oxide reductase. Cavity enhanced Raman gas spectroscopy has a high potential for the assessment of denitrification processes and can contribute substantially to our understanding of nitrogen cycling in both natural and agricultural systems. 相似文献
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G.L. Borchert D. Anagnostopoulos M. Augsburger D. Belmiloud C. Castelli D. Chatellard M. Daum J.P. Egger P. El-Khoury M. Elble R. Frosch H. Gorke D. Gotta P. Hauser P. Indelicato K. Kirch S. Lenz N. Nelms K. Rashid O.W.B. Schult Th. Siems L.M. Simons 《Hyperfine Interactions》1998,114(1-4):157-164
Some time after its formation an exotic atom may be considered a hydrogen-like system consisting of a nucleus and an exotic
particle in a bound state. In this situation it is an ideal tool to study cascade properties, while for the innermost orbits
it can be used to probe the interaction with the nucleus. From an extended series of experiments using high resolution X-ray
spectroscopy for both aspects typical examples are reported and preliminary results are given: 1. To determine the complex
scattering length in
H the
hyperfine transitions have been measured. 2. To determine the pion mass the 5
4 transitions in
N have been studied. In all cases a major contribution to the uncertainty originates from the calibration. Therefore a new
method is proposed that will establish a universal set of high precision calibration lines for pionic, muonic and electronic
systems.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
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S. Hochberg V. K. La Mer J. Gicklhorn A. Nistler R. Collander N. P. Peskoff A. E. Wright A. Szegvàri Y. P. Liu T. P. Chou H. Y. Fang P. P. T. Sah L. Kofler G. Linck E. Köhler A. E. Sandström Ph. Groß H. Steiner F. Krauss E. A. Hauser C. J. Frosch S. Dushman H. A. Abramson L. S. Moyer A. Voet E. B. Grossman S. Komagata und G. E. van Gils 《Fresenius' Journal of Analytical Chemistry》1939,116(3-4):132-140
Ohne Zusammenfassung 相似文献
9.
C. Amsler F. Rudolf P. Weymuth L. Dubal G.H. Eaton R. Frosch S. Mango F. Požar 《Physics letters. [Part B]》1975,57(3):289-292
The P parameter for π+p scattering at 236.3 MeV has been measured between 50° and 146° c.m. with very low background using a butanol polarized proton target. The resulting D phases are in fair agreement with dispersion relation values. 相似文献
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A new setup for Raman spectroscopic wide-field imaging is presented. It combines the advantages of a fiber array based spectral translator with a tailor-made laser illumination system for high-quality Raman chemical imaging of sensitive biological samples. 相似文献