共查询到20条相似文献,搜索用时 31 毫秒
1.
2.
It is often desirable to selectively remove corrupting or uninteresting signals from complex NMR spectra without disturbing overlapping or nearby signals. For biofluids in particular, removal of solvent and urea signals is important for retaining quantitative accuracy in NMR‐based metabonomics. This article presents a novel algorithm for efficient filtering of unwanted signals using the filter diagonalization method (FDM). Unwanted signals are modeled in the time domain using FDM. This modeled signal is subtracted from the original free induction decay. The resulting corrected signal is then processed using established workflow. The algorithm is found to be reliable and fast. By eliminating large, broad, uninteresting signals, many spectra can be subjected to fully automated absolute value processing, allowing objective preparation of spectra for pattern recognition analysis. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
3.
Ke Jun TAN Yuan Fang LI Cheng Zhi HUANG Xue Lian LIU 《中国化学快报》2006,17(5):679-682
Resonance light scattering technique has been extensively applied in quantification of analyte, such as protein1, nucleic acid1, medicine1, and metallic ions2. Backscattering signals (BSS) has been generally applied in physics and biomedicine science3. Ho… 相似文献
4.
Polarization tuning of the interference of chirality-induced tensor components is used to simulate the suppression of diagonal peaks and amplification of cross peaks in femtosecond two-dimensional photon echo signals of excitons in a chiral porphyrin dimer. Superpositions of various tensor components which generate the optimized signals are constructed using a genetic learning algorithm. Exciton couplings and bath correlations may be extracted from these highly resolved signals. 相似文献
5.
Lung-Cheng Lin Hsin-Yi Wu Vincent Shin-Mu Tseng Lien-Chin Chen Yu-Chen Chang Pao-Chi Liao 《Journal of the American Society for Mass Spectrometry》2010,21(2):232-241
The tracing of metabolite signals in LC-MS data using stable isotope-labeled compounds has been described in the literature.
However, the filtering efficiency and confidence when mining metabolite signals in complex LC-MS datasets can be improved.
Here, we propose an additional statistical procedure to increase the compound-derived signal mining efficiency. This method
also provides a highly confident approach to screen out metabolite signals because the correlation of varying concentration
ratios of native/stable isotope-labeled compounds and their instrumental response ratio is used. An in-house computational
program [signal mining algorithm with isotope tracing (SMAIT)] was developed to perform the statistical procedure. To illustrate
the SMAIT concept and its effectiveness for mining metabolite signals in LC-MS data, the plasticizer, di-(2-ethylhexyl) phthalate
(DEHP), was used as an example. The statistical procedure effectively filtered 15 probable metabolite signals from 3617 peaks
in the LC-MS data. These probable metabolite signals were considered structurally related to DEHP. Results obtained here suggest
that the statistical procedure could be used to confidently facilitate the detection of probable metabolites from a compound-derived
precursor presented in a complex LC-MS dataset. 相似文献
6.
Significant improvements can be made in signal:noise ratios of transient signals arising in atomic-absorption spectroscopy by the use of resistor-capacitor damping. A suitable device is described and the effect it has on signals arising from instruments using analogue and digital forms of output is demonstrated. 相似文献
7.
Signal Formation in Laser-Enhanced Atomic Ionization Spectrometry with Laser Sampling into the Flame
The results of the observation of ionization signals in the laser-ablation sampling of solid samples into the flame were reported. The signals exhibited two maxima. The first, nonselective, maximum, which appeared immediately after the pulse of the volatilization laser, is due to thermions formed in the laser plasma. The second, selective (analytical), signal appeared after the pulse of the optical excitation laser. The nonselective signal may interfere with the detection of the analytical signal. The dependence of both signals on parameters such as the height of the cathode and the height of signal observation above the burner and the time delay between the laser pulses was studied. The optimal conditions for the detection of signals in laser-enhanced atomic ionization spectrometry were found. 相似文献
8.
Magnetic field decoupling experiments in the optically excited states of NO2 yield decoupling signals with a width of 10 to 40 mG. We attribute these signals to the non-rigidity of the excited molecule. 相似文献
9.
In present telecommunication networks, information transfer relies on the interplay of optical and electrical signals. Data are communicated optically but processed electronically. Methods to maintain the propagating signals solely at the optical level must be developed to overcome the transmission capacities and speed limits imposed by the electronic components. We have demonstrated that molecular switches can be used to gate optical signals in response to optical signals. We have realized a simple optical network consisting of three light sources, one cell containing a solution of three fluorescent molecules, one cell containing a solution of a three-state molecular switch and a detector. The light emitted by the three fluorophores is absorbed by the three states of the molecular switch. Using this simple operating principle, we have shown that multichannel digital transmission can be implemented on an ensemble of communicating molecules relying exclusively on the interplay of optical inputs and optical outputs. 相似文献
10.
F. Eigenmann 《Thermochimica Acta》2006,440(1):81-92
In thermoanalytical investigations the determination of the composition of the evolved gases is very important, especially when investigating decomposition processes or gas-solid reactions occurring in multi-component systems. The potential of simultaneous techniques, enabling the qualitative analysis of evolved species, such as TG-MS or TG-FTIR has been further improved by the introduction of the pulse thermal analysis (PulseTA®). This method provides a quantitative calibration by relating the mass spectrometric or FTIR signals to the injected quantity of probe gas.The influence of several experimental parameters such as concentration of the analyzed species, temperature and flow rate of the carrier gas on FTIR signals has been investigated. The reliability of quantifying FTIR signals was checked by relating them to the amount of evolved gases measured by thermogravimetry. In order to extend the opportunities for quantifying FTIR signals, the possibility of the injection of liquids into the carrier gas stream was studied. The linear dependence between the injected amount of liquids and the integral intensity of spectroscopic signals (peak area) enabled easy quantification of FTIR data. Systematic studies on a new method based on isothermal vaporization of liquids further widen the application range of in situ calibrations. 相似文献
11.
12.
Jiang Zhankui A. Persson L. Sturesson S. Svanberg 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,21(4):315-322
In the recently introduced high-contrast transmission version of saturated absorption laser spectroscopy, narrow signals are obtained from dense atomic samples subject to strong pumping. A study of possible systematic shifts of the signals in this domain of rather extreme experimental conditions was performed in order to assess the validity of spectroscopic data obtained with this technique. Certain signal components were found to be slightly shifted while others were not. Further, a theoretical study of the behaviour of overlapping signals in the high-contrast regime is presented. In particular, the question of whether structures buried under the natural linewidth could be resolved is addressed. 相似文献
13.
The use of variously-oriented film polarizers to reduce scattered light interference in fluorimetric analysis is reported. Single horizontally-oriented polarizers in the excitation beam (to obtain fluorescence spectra) or the emission beam (to obtain excitation spectra) are efficient at removing first-order Rayleigh scattered light signals. Crossed polarizers are necessary to remove substantial second-order signals. With the aid of polarizers, fluorimetric detection limits can be considerably improved, even when excitation and emission maxima are well separated, and when deproteinized blood plasma is analyzed. Polarizers are also effective in reducing scattered light signals from macromolecular solutes. 相似文献
14.
15.
Spectral assignments to the light emissions of fluorescent organic small molecules in aqueous medium
Spectrofluorometric identifications of artificial organic dyes have important environmental significance, but both scattered light signals and the fluorescence signals were twins in fluorospectroscopy, and the light scattering signals are always the interference sources of spectrofluorometry. In order to investigate the relationship between the light scattering and fluorescence in the spectrofluorometric measurements, herein we discuss the scattered light and fluorescence emission properties of organic small molecules (OSMs) using Lignin Pink (LP) in neutral medium as an example. With the help of UV-vis measurements, and starting from three-dimensional light emission measurements, scattered light and fluorescence emissions could be assigned. Investigations by increasing LP concentration showed that the light emission at 282.0 and 344.0 nm could be attributed to the resonance light scattering (RLS) signals and that at 420.0 and 570.0 nm are composed of both RLS and fluorescence emissions, respectively. UV-vis measurements showed that LP does not have the tendency of aggregation, and the strong RLS signals should be ascribed to the large hydrodynamic diameter of LP itself in aqueous medium, supported by dynamic light scattering (DLS) measurements. 相似文献
16.
The bystander effect is defined as the induction of cellular damage in unirradiated cells, induced by irradiated cells in the surrounding area. Our laboratory has previously identified that an environmentally relevant dose of UVA is able to induce the effect in human keratinocytes and fibroblasts, seen as reduced clonogenic survival. Here we report on our investigations into the periods over which the bystander signals are released by the irradiated cells and for how long unirradiated cells need to be exposed to them for the effect to be induced. Using a coincubation system we have identified that irradiated cells do not release the signals immediately following irradiation but have a time lag of over 24 h before levels are sufficient to induce the effect, with the signals being released for a minimum of 3 days following irradiation. We have also found that the recipient cells only require at most 24 h of exposure to these signals for induction of the effect. These data indicate that a single exposure to UVA can exert an effect for several days postirradiation, thus amplifying the deleterious effects of exposure. 相似文献
17.
Wang J Even MA Chen X Schmaier AH Waite JH Chen Z 《Journal of the American Chemical Society》2003,125(33):9914-9915
In this Communication, we demonstrate the novel observation that it is feasible to collect amide signals from polymer/protein solution interfaces in situ using sum frequency generation (SFG) vibrational spectroscopy. Such SFG amide signals allow for acquisition of more detailed molecular level information of entire interfacial protein structures. Proteins investigated include bovine serum albumin, mussel protein mefp-2, factor XIIa, and ubiquitin. Our studies indicate that different proteins generate different SFG amide signals at the polystyrene/protein solution interface, showing that they have different interfacial coverage, secondary structure, or orientation. 相似文献
18.
Temperature-dependent intensity data for two-photon excitation and second harmonic generation signals phase matched onto the polariton branches of the single a-exciton of naphthalene are presented. The data are shown be in quantitative agreement with the polariton fusion model which accounts for strong exciton-photon coupling. In this model the polariton scattering frequency and group velocity determine the branching ratios for the above signals. 相似文献
19.
《Tetrahedron: Asymmetry》2005,16(2):477-485
Analysis of glycosylation stereoselectivity in the synthesis of branched maltooligosaccharides is hampered by poor spectral dispersion due to the repetitive nature of the saccharide chain and overlap of sugar H-1 signals with benzylic proton signals from the typically used benzyl ether protecting groups. A suitably protected p-methoxyphenyl maltoside acceptor, when coupled with benzylated maltooligosaccharide donors, gives discrete aglycone 1H NMR signals that can be used to report on the stereoselectivity of 1,6-glycosylation reactions. 相似文献
20.
Dr. Jakob Thyr Prof. Tomas Edvinsson 《Angewandte Chemie (International ed. in English)》2023,62(43):e202219047
Micro-Raman spectroscopy is an important analytical tool in a large variety of science disciplines. The technique is suitable for both identification of chemical bonds and studying more detailed phenomena like molecular interactions, material strain, crystallinity, defects, and bond formations. Raman scattering has one major weakness however: it is a very low probability process. The weak signals require very sensitive detection systems, which leads to a high probability of picking up signals from origins other than the sample. This complicates the analysis of the results and increases the risk of misinterpreting data. This work provides an overview of the sources of spurious signals occurring in Raman spectra, including photoluminescence, cosmic rays, stray light, artefacts caused by spectrometer components, and signals from other compounds in or surrounding the sample. The origins of these false Raman peaks are explained and means to identify and counteract them are provided. 相似文献