Zeitschriftenartikel: „Fluorescence coefficients“

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Enderlein, Jörg. „Fluorescence correlation spectroscopy (IUPAC Technical Report)“. Pure and Applied Chemistry 85, Nr. 5 (02.04.2013): 999–1016. http://dx.doi.org/10.1351/pac-rep-11-11-17.

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We present an overview on the applicability of fluorescence correlation spectroscopy (FCS) for the accurate determination of translational diffusion coefficients and thus, via the Stokes–Einstein relation, of molecular size. We consider several of the most common sources of optical aberrations and their impact on the outcome of conventional FCS measurements. We describe also a new variant of FCS, dual-focus FCS, which is robust against most of the considered aberrations, and we report reference values of diffusion coefficients for several fluorescent dyes across the visible spectrum.

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Sarmento, M. J., S. N. Pinto, A. Coutinho, M. Prieto und F. Fernandes. „Accurate quantification of inter-domain partition coefficients in GUVs exhibiting lipid phase coexistence“. RSC Advances 6, Nr. 71 (2016): 66641–49. http://dx.doi.org/10.1039/c6ra13170k.

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Giant unilamellar vesicles (GUVs) with phase coexistence allow for the recovery of inter-domain partition coefficients (K_p) of fluorescent molecules through comparison of fluorescence intensities in each phase.

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Antony, Sumy, Jonathan C. Morris, Toby D. M. Bell, Tracey Brown, Leone Spiccia und Hugh H. Harris. „The H.G. Smith Award Article: Fluorescent Analogues of NAMI-A: Synthesis, Characterisation, Fluorescent Properties, and Preliminary Biological Studies in Human Lung Cancer Cells“. Australian Journal of Chemistry 67, Nr. 12 (2014): 1711. http://dx.doi.org/10.1071/ch14205.

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Two new fluorescent ruthenium(iii) complexes, namely 7-azaindolium trans-tetrachlorido(7-azaindole)(dimethylsulfoxide)ruthen(iii)ate (F1) and N-[histaminedihydrolium]-1,8-naphthalenecarboximidic trans-tetracholoro(dimethylsulfoxide)(N-[histaminedihydro]-1,8-naphthalenecarboximide)ruthen(iii)ate (F2) and their respective tetramethylammonium analogues (F3 and F4) are reported herein. The compounds were characterised by elemental analysis, mass spectrometry, UV-vis spectrophotometry, and fluorescence spectroscopy. Molar extinction coefficients (ϵmax) and fluorescence emission spectra were compared to evaluate the electronic properties of the synthesised fluorescent analogues, and hence their value as intracellular fluorescence probes. F3 and F4 were synthesised and characterised in order to eliminate fluorescence arising from the counter-cations in F1 and F2 and thus to obtain a fluorescence quantum yield that reflects only a contribution from the metal complex anion. Half-inhibitory concentrations (IC50) were determined for A549 cells exposed to the Ru complexes for 24 h: F3 (203 ± 26 μM) and F4 (185 ± 20 μM).

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Waharte, François, Karine Steenkeste, Romain Briandet und Marie-Pierre Fontaine-Aupart. „Diffusion Measurements inside Biofilms by Image-Based Fluorescence Recovery after Photobleaching (FRAP) Analysis with a Commercial Confocal Laser Scanning Microscope“. Applied and Environmental Microbiology 76, Nr. 17 (16.07.2010): 5860–69. http://dx.doi.org/10.1128/aem.00754-10.

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ABSTRACT Research about the reactional and structural dynamics of biofilms at the molecular level has made great strides, owing to efficient fluorescence imaging methods in terms of spatial resolution and fast acquisition time but also to noninvasive conditions of observation consistent with in situ biofilm studies. In addition to conventional fluorescence intensity imaging, the fluorescence recovery after photobleaching (FRAP) module can now be routinely implemented on commercial confocal laser scanning microscopes (CLSMs). This method allows measuring of local diffusion coefficients in biofilms and could become an alternative to fluorescence correlation spectroscopy (FCS). We present here an image-based FRAP protocol to improve the accuracy of FRAP measurements inside “live” biofilms and the corresponding analysis. An original kymogram representation allows control of the absence of perturbing bacterial movement during image acquisition. FRAP data analysis takes into account molecular diffusion during the bleach phase and uses the image information to extract molecular diffusion coefficients. The fluorescence spatial intensity profile analysis used here for the first time with biofilms is supported both by our own mathematical model and by a previously published one. This approach was validated to FRAP experiments on fluorescent-dextran diffusion inside Lactoccocus lactis and Stenotrophomonas maltophilia biofilms, and the results were compared to previously published FCS measurements.

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Buse, Ben, und Stuart Kearns. „Quantification of Olivine Using Fe Lα in Electron Probe Microanalysis (EPMA)“. Microscopy and Microanalysis 24, Nr. 1 (Februar 2018): 1–7. http://dx.doi.org/10.1017/s1431927618000041.

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AbstractQuantification of first series transition metal Lα X-rays is hampered by absorption and in some cases transition probabilities (fluorescence yields) varying with chemical bonding. Compound mass absorption coefficients for Fe Lα were measured in the olivine solid solution series [Forsterite (Mg2SiO4) to Fayalite (Fe2SiO4)] and the mass absorption coefficients for Fe Lα absorbed by Fe were calculated. The mass absorption coefficients vary systematically between Fo83 and Fo0. Using the measured mass absorption coefficients for both standard and unknown and by correcting for a systematic discrepancy, consistent with varying partial fluorescence yields, a good agreement between calculated k-ratios and measured k-ratios is achieved. The systematic variations allow quantification of unknown k-ratios. The described method of quantification requires modification of matrix correction routines to allow standards and unknowns to have different mass absorption coefficients, and to incorporate solid solution mass absorption coefficients and partial fluorescence yield corrections derived from regression of experimental data.

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Chandrasekaran, Vijayanand, Bhim Kafle, Aneesh Prabhakaran, Oded Heber, Michael Rappaport, Hilel Rubinstein, Dirk Schwalm, Yoni Toker und Daniel Zajfman. „Determination of Absolute Recurrent Fluorescence Rate Coefficients for C6–“. Journal of Physical Chemistry Letters 5, Nr. 23 (14.11.2014): 4078–82. http://dx.doi.org/10.1021/jz502100z.

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7

Unonius, L., und P. Suortti. „Mass attenuation coefficients of the elements Ti, V, Fe, Co, Ni, Cu and Zn for the K emission lines between 4.51 and 10.98 keV“. Journal of Applied Crystallography 22, Nr. 1 (01.02.1989): 46–52. http://dx.doi.org/10.1107/s0021889888010817.

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Mass attenuation coefficients of seven elements between atomic numbers 22 and 30 were measured at 20 X-ray energies between 4.5 and 11 keV. These energies correspond to fluorescence radiation excited by monochromatic Mo Kα radiation. The measurements were made on thin metal foils, which were spread flat and perpendicular to the beam scattered from the fluorescent sample. In this arrangement, the measured attenuation includes photoelectric absorption plus average elastic and inelastic scattering. The mass per unit area of a foil was determined by weighing and the impurity concentration by fluorescence analysis. The spectral lines corresponding to the components of the fluorescent radiation and those of the secondary radiation were resolved by the so-called singular value decomposition (SVD). The probable errors of the attenuation coefficients were typically 1%. The general agreement with previous experimental and theoretical values is good, but at low energies and at energies just above the absorption edges the present values are about 5% larger than theoretical values based on relativistic HFS (Hartree–Fock–Slater) calculations.

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8

Rousseau, Richard M. „Why The Fundamental Algorithm is So Fundamental“. Advances in X-ray Analysis 37 (1993): 639–46. http://dx.doi.org/10.1154/s0376030800016190.

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In X-ray fluorescence (XRF) analysis, one of the major problems is the correction for matrix effects (absorption and enhancement). One of the solutions proposed was the use of influence coefficients, which are numerical coefficients that correct for the effect of each matrix element on the analyte. For many years, these coefficients were considered as an empirical approach having little connection with X-ray fluorescence theory. They were considered useful only when no other alternative was available to solve the problem of matrix effect.

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Zhang, Zeshi, Elena Nadezhina und Kevin J. Wilkinson. „Quantifying Diffusion in a Biofilm ofStreptococcus mutans“. Antimicrobial Agents and Chemotherapy 55, Nr. 3 (28.12.2010): 1075–81. http://dx.doi.org/10.1128/aac.01329-10.

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ABSTRACTIn biofilms, diffusion may limit the chemical activity of nutrients, toxic compounds, and medicines. This study provides direct, noninvasive insight into the factors that will most effectively limit the transport of antibiotics and biocides in biofilms. Self-diffusion coefficients have been determined for a number of fluorescent probes in biofilms ofStreptococcus mutansusing fluorescence correlation spectroscopy. The effects of probe size and charge and the roles of biofilm pH, ionic strength, and heterogeneity were studied systematically. The relative diffusion coefficients (Din the biofilm divided by that in water) decreased with increasing probe size (3,000-molecular-weight [3K], 10K, 40K, 70K, and 2,000K dextrans). Studies using variably charged substrates (tetramethylrhodamine, Oregon Green, rhodamine B, and rhodamine 6G) showed that the self-diffusion coefficients decreased with an increasing negative charge of the fluorescent probes. No significant effect was observed for changes to the ionic strength (10−4to 10−1M) or pH (4 to 9) of the biofilm. Biofilm heterogeneity was responsible for variations of ca. one order of magnitude in the diffusion coefficients.

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Petrášek, Zdeněk, und Petra Schwille. „Precise Measurement of Diffusion Coefficients using Scanning Fluorescence Correlation Spectroscopy“. Biophysical Journal 94, Nr. 4 (Februar 2008): 1437–48. http://dx.doi.org/10.1529/biophysj.107.108811.

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11

Eisebitt, S., T. Böske, J. E. Rubensson und W. Eberhardt. „Determination of absorption coefficients for concentrated samples by fluorescence detection“. Physical Review B 47, Nr. 21 (01.06.1993): 14103–9. http://dx.doi.org/10.1103/physrevb.47.14103.

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Lamb, Don C., Andreas Schenk, Carlheinz R�cker und G. Ulrich Nienhaus. „Determining chemical rate coefficients using time-gated fluorescence correlation spectroscopy“. Journal of Physical Organic Chemistry 13, Nr. 10 (2000): 654–58. http://dx.doi.org/10.1002/1099-1395(200010)13:10<654::aid-poc294>3.0.co;2-s.

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13

Luschtinetz, Franziska, und Carsten Dosche. „Determination of micelle diffusion coefficients with fluorescence correlation spectroscopy (FCS)“. Journal of Colloid and Interface Science 338, Nr. 1 (Oktober 2009): 312–15. http://dx.doi.org/10.1016/j.jcis.2009.06.064.

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14

Lachance, Gerald R. „Correction procedures using influence coefficients in X-ray fluorescence spectrometry“. Spectrochimica Acta Part B: Atomic Spectroscopy 48, Nr. 3 (Februar 1993): 343–57. http://dx.doi.org/10.1016/0584-8547(93)80040-2.

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15

Hua, Younan, und C. T. Yap. „Calculation of Theoretical Alpha Coefficients for XRF Analysis of Major and Minor Elements in Iron-rich Geological Samples“. Zeitschrift für Naturforschung A 50, Nr. 9 (01.09.1995): 817–25. http://dx.doi.org/10.1515/zna-1995-0905.

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Abstract This paper introduces a method of calculating theorectical alpha coefficients for the X-ray fluorescence analysis of major and minor components in iron-rich samples. We choose a group of hypothetical standard samples whose average concentrations are those of the actual samples. The theoretical X-ray fluorescence relative intensities of the given components are calculated using the fundamental parameter NRLXRF program. We derived formulas from the Lachance-Traill equation and used these to calculate the basic, hybrid and modified alpha coefficients which are used respectively for the analysis of elements in compact specimens, oxides in compact specimens and oxides in diluted specimens. In order to use the theoretical alpha coefficients on-line, we also discuss the calculation of the alpha coefficients used in the D.J model.

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Han, Yesul, Jaeran Lee, Yumi Lee und Sok Won Kim. „Measurement of the Diffusion Coefficients of Fluorescence Beads and Quantum Dots by Using Fluorescence Correlation Spectroscopy“. Journal of the Korean Physical Society 59, Nr. 5(1) (15.11.2011): 3177–81. http://dx.doi.org/10.3938/jkps.59.3177.

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17

Braga, José, Joana M. P. Desterro und Maria Carmo-Fonseca. „Intracellular Macromolecular Mobility Measured by Fluorescence Recovery after Photobleaching with Confocal Laser Scanning Microscopes“. Molecular Biology of the Cell 15, Nr. 10 (Oktober 2004): 4749–60. http://dx.doi.org/10.1091/mbc.e04-06-0496.

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Fluorescence recovery after photobleaching (FRAP) is a widely used tool for estimating mobility parameters of fluorescently tagged molecules in cells. Despite the widespread use of confocal laser scanning microscopes (CLSMs) to perform photobleaching experiments, quantitative data analysis has been limited by lack of appropriate practical models. Here, we present a new approximate FRAP model for use on any standard CLSM. The main novelty of the method is that it takes into account diffusion of highly mobile molecules during the bleach phase. In fact, we show that by the time the first postbleach image is acquired in a CLSM a significant fluorescence recovery of fast-moving molecules has already taken place. The model was tested by generating simulated FRAP recovery curves for a wide range of diffusion coefficients and immobile fractions. The method was further validated by an experimental determination of the diffusion coefficient of fluorescent dextrans and green fluorescent protein. The new FRAP method was used to compare the mobility rates of fluorescent dextrans of 20, 40, 70, and 500 kDa in aqueous solution and in the nucleus of living HeLa cells. Diffusion coefficients were lower in the nucleoplasm, particularly for higher molecular weight dextrans. This is most likely caused by a sterical hindrance effect imposed by nuclear components. Decreasing the temperature from 37 to 22°C reduces the dextran diffusion rates by ∼30% in aqueous solution but has little effect on mobility in the nucleoplasm. This suggests that spatial constraints to diffusion of dextrans inside the nucleus are insensitive to temperature.

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Cortese, J. D., und C. Frieden. „Microheterogeneity of actin gels formed under controlled linear shear.“ Journal of Cell Biology 107, Nr. 4 (01.10.1988): 1477–87. http://dx.doi.org/10.1083/jcb.107.4.1477.

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The diffusion coefficients and fluorescence polarization properties of actin subjected to a known shear have been determined both during and after polymerization, using a modification of a cone-plate Wells-Brookfield rheometer that allows monitoring of samples with an epifluorescence microscope. Fluorescence polarization and fluorescence photobleaching recovery experiments using rhodamine-labeled actin as a tracer showed that under conditions of low shear (shear rates of 0.05 s-1), a spatial heterogeneity of polymerized actin was observed with respect to fluorescence intensity and the diffusion coefficients with actin mobility becoming quite variable in different regions of the sample. In addition, complex changes in fluorescence polarization were noted after stopping the shear. Actin filaments of controlled length were obtained using plasma gelsolin (gelsolin/actin molar ratios of 1:50 to 1:300). At ratios of 1:50, neither spatial heterogeneity nor changes in polarization were observed on subjecting the polymerized actin to shear. At ratios of approximately 1:100, a decrease on the intensity of fluorescence polarization occurs on stopping the shear. Longer filaments exhibit spatial micro-heterogeneity and complex changes in fluorescence polarization. In addition, at ratios of 1:100 or 1:300, the diffusion coefficient decreases as the total applied shear increased. This behavior is interpreted as bundling of filaments aligned under shear. We also find that the F-actin translational diffusion coefficients decrease as the total applied shear increases (shear rates between 0.05 and 12.66 s-1), as expected for a cumulative process. When chicken gizzard filamin was added to gelsolin-actin filaments (at filamin/actin molar ratios of 1:300 to 1:10), a similar decrease in the diffusion coefficients was observed for unsheared samples. Spatial microheterogeneity might be related to the effects of the shear field in the alignment of filaments, and the balance between a three-dimensional network and a microheterogeneous system (containing bundles or anisotropic phases) appears related to both shear and the presence of actin-binding proteins.

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Zhou, Kun, Jian Tian, Qiushi Zhang, Xiangxi Meng, Kun Yang und Qiushi Ren. „Simulation and quantitative analysis of fluorescence intensity distribution based on the Monte Carlo method“. Journal of Innovative Optical Health Sciences 08, Nr. 06 (27.10.2015): 1550038. http://dx.doi.org/10.1142/s1793545815500388.

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The Monte Carlo method is a versatile simulation algorithm to model the propagation of photons inside the biological tissues. It has been applied to the reconstruction of the fluorescence molecular tomography (FMT). However, such method suffers from low computational efficiency, and the time consumption is not desirable. One way to solve this problem is to introduce a priori knowledge which will facilitate iterative convergence. We presented an in vivo simulation environment for fluorescence molecular tomography (ISEFMT) using the Monte Carlo method to simulate the photon distribution of fluorescent objects and their sectional view in any direction quantitatively. A series of simulation experiments were carried out on different phantoms each with two fluorescent volumes to investigate the relationship among fluorescence intensity distribution and the excitation photon number, the locations and sizes of the fluorescence volumes, and the anisotropy coefficient. A significant principle was discovered, that along the direction of the excitation light, the fluorescent volume near the excitation point will provide shelter effect so that the energy of the fluorescent volume farther away from the excitation point is relatively lower. Through quantitative analysis, it was discovered that both the photon energy distribution on every cross section and the fluorescence intensity distributed in the two volumes exhibit exponential relationships. The two maximum positions in this distribution correspond to the centers of fluorescent volumes. Finally, we also explored the effect of the phantom coefficients on the exponential rule, and found out that the exponential rule still exists, only the coefficient of the exponential rule changed. Such results can be utilized in locating the positions of multiple fluorescent volumes in complicated FMT reconstruction involving multiple fluorescent volumes. Thus, a priori knowledge can be generalized, which would accelerate the reconstruction of FMT and even other images.

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Sniekers, Y. H., und C. C. van Donkelaar. „Determining Diffusion Coefficients in Inhomogeneous Tissues Using Fluorescence Recovery after Photobleaching“. Biophysical Journal 89, Nr. 2 (August 2005): 1302–7. http://dx.doi.org/10.1529/biophysj.104.053652.

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Pallix, Joan B., und Richard A. Copeland. „Measurement of catalytic recombination coefficients on quartz using laser-induced fluorescence“. Journal of Thermophysics and Heat Transfer 10, Nr. 2 (April 1996): 224–33. http://dx.doi.org/10.2514/3.779.

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Kitamura, Akira, und Masataka Kinjo. „Determination of diffusion coefficients in live cells using fluorescence recovery after photobleaching with wide-field fluorescence microscopy“. Biophysics and Physicobiology 15 (2018): 1–7. http://dx.doi.org/10.2142/biophysico.15.0_1.

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23

Veselovskii, Igor, Qiaoyun Hu, Philippe Goloub, Thierry Podvin, Marie Choël, Nicolas Visez und Mikhail Korenskiy. „Mie–Raman–fluorescence lidar observations of aerosols during pollen season in the north of France“. Atmospheric Measurement Techniques 14, Nr. 7 (02.07.2021): 4773–86. http://dx.doi.org/10.5194/amt-14-4773-2021.

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Abstract. The multiwavelength Mie–Raman–fluorescence lidar of the University of Lille has the capability to measure three aerosol backscattering coefficients, two extinction coefficients and three linear depolarization ratios, together with fluorescence backscattering at 466 nm. It was used to characterize aerosols during the pollen season in the north of France for the period March–June 2020. The results of observations demonstrate that the presence of pollen grains in aerosol mixture leads to an increase in the depolarization ratio. Moreover, the depolarization ratio exhibits a strong spectral dependence increasing with wavelength, which is expected for the mixture containing fine background aerosols with low depolarization and strongly depolarizing pollen grains. A high depolarization ratio correlates with the enhancement of the fluorescence backscattering, corroborating the presence of pollen grains. Obtained results demonstrate that simultaneous measurements of particle depolarization and fluorescence allows for the separation of dust, smoke particles and aerosol mixtures containing the pollen grains.

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Lachance, Gerald R. „Defining and Deriving Theoretical Influence Coefficients in XHF Spectrometry“. Advances in X-ray Analysis 31 (1987): 471–78. http://dx.doi.org/10.1154/s0376030800022321.

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AbstractThe concepts underlying the definition and calculation of fundamental influence coefficients and their role in the computation of derived coefficients in alpha-type algorithms are examined. The fundamental-parameter method initiated and continues to provide the basis for the steady progress in giving influence coefficients a sound theoretical status. New definitions of fundamental influence coefficients as the prorating of monochromatic coefficients on the basis of the intensities of each elementary contributions as a function of the total fluorescence intensity and of the intensity of the pure analyte are compared to the presently used approach of defining coefficients as a function of total absorption only.

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Pande, P., C. A. Trivedi und J. A. Jo. „Analysis of Fluorescence Lifetime Imaging Microscopy (FLIM) Data“. Methods of Information in Medicine 49, Nr. 05 (2010): 531–36. http://dx.doi.org/10.3414/me09-02-0046.

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Summary Objectives: A novel Fluorescence Lifetime Imaging Microscopy (FLIM) deconvolution method based on the linear expansion of fluorescence decays on a set of orthonormal Laguerre functions was recently proposed. The Laguerre deconvolution method applies linear least-square estimation to estimate the expansion coefficients of all pixel decays simultaneously, performing at least two orders of magnitude faster than the other algorithms. In the original Laguerre FLIM deconvolution implementation, however, the Laguerre parameter α is selected using a heuristic approach, making it unsuitable for online applications. Methods: In this study, we present a fully automated implementation of the Laguerre FLIM deconvolution, whereby the Laguerre parameter α is treated as a free parameter within a nonlinear least-squares optimization scheme. Results: The performance of this method has been successfully validated on simulated data, and experimental FLIM images of standard fluorescent dyes and endogenous tissue fluorescence. Conclusions: The main advantage of the proposed method is that it does not require any user intervention for tuning up the deconvolution process. Thus, we believe this method will facilitate the translation of FLIM to online applications, including real-time clinical diagnosis.

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Košovan, Peter, Filip Uhlík, Jitka Kuldová, Miroslav Štěpánek, Zuzana Limpouchová, Karel Procházka, Aleš Benda, Jana Humpolíčková und Martin Hof. „Monte Carlo simulation of fluorescence correlation spectroscopy data“. Collection of Czechoslovak Chemical Communications 76, Nr. 3 (2011): 207–22. http://dx.doi.org/10.1135/cccc2009526.

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We employed the Monte Carlo simulation methodology to emulate the diffusion of fluorescently labeled particles and understand the source of differences between values of diffusion coefficients (and consequently hydrodynamic radii) of fluorescently labeled nanoparticles measured by fluorescence correlation spectroscopy (FCS) and dynamic light scattering (DLS). We used the simulation program developed in our laboratory and studied the diffusion of spherical particles of different sizes, which are labeled on their surface. In this study, we focused on two complicating effects: (i) multiple labeling and (ii) rotational diffusion which affect the fluorescence signal from large particles and hinder the analysis of autocorrelation functions according to simple analytical models. We have shown that the fluorescence fluctuations can be well fitted using the analytical model for small point-like particles, but the obtained parameters deviate in some cases significantly from the real ones. It means that the current data treatment yields apparent values of diffusion coefficients and other parameters only and the interpretation of experimental results for systems of particles with sizes comparable to the size of the active illuminated volume requires great care and precaution.

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Ma, Yongmin, Herbert de Groot, Zudong Liu, Robert C. Hider und Frank Petrat. „Chelation and determination of labile iron in primary hepatocytes by pyridinone fluorescent probes“. Biochemical Journal 395, Nr. 1 (15.03.2006): 49–55. http://dx.doi.org/10.1042/bj20051496.

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A series of fluorescent iron chelators has been synthesized such that a fluorescent function is covalently linked to a 3-hydroxypyridin-4-one. In the present study, the fluorescent iron chelators were loaded into isolated rat hepatocytes. The intracellular fluorescence was not only quenched by an addition of a highly lipophilic 8-hydroxyquinoline–iron(III) complex but also was dequenched by the addition of an excess of the membrane-permeable iron chelator CP94 (1,2-diethyl-3-hydroxypyridin-4-one). The time course of uptake of iron and iron chelation in single, intact cells was recorded on-line by using digital fluorescence microscopy. Intracellular concentrations of various fluorescent iron chelators were determined by using a spectrofluorophotometer subsequent to lysis of probe-loaded cells and were found to depend on their partition coefficients; the more hydrophobic the compound, the higher the intracellular concentration. An ex situ calibration method was used to determine the chelatable iron pool of cultured rat hepatocytes. CP655 (7-diethylamino-N-[(5-hydroxy-6-methyl-4-oxo-1,4-dihydropyridin-3-yl)methyl]-N-methyl-2-oxo-2H-chromen-3-carboxamide), which is a moderately lipophilic fluorescent chelator, was found to be the most sensitive probe for monitoring chelatable iron, as determined by the intracellular fluorescence increase induced by the addition of CP94. The concentration of the intracellular chelatable iron pool in hepatocytes was determined by this probe to be 5.4±1.3 μM.

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Llovet, Xavier, Philippe T. Pinard, Erkki Heikinheimo, Seppo Louhenkilpi und Silvia Richter. „Electron Probe Microanalysis of Ni Silicides Using Ni-L X-Ray Lines“. Microscopy and Microanalysis 22, Nr. 6 (26.10.2016): 1233–43. http://dx.doi.org/10.1017/s1431927616011831.

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AbstractWe report electron probe microanalysis measurements on nickel silicides, Ni5Si2, Ni2Si, Ni3Si2, and NiSi, which were done in order to investigate anomalies that affect the analysis of such materials by using the Ni L3-M4,5line (Lα). Possible sources of systematic discrepancies between experimental data and theoretical predictions of Ni L3-M4,5k-ratios are examined, and special attention is paid to dependence of the Ni L3-M4,5k-ratios on mass-attenuation coefficients and partial fluorescence yields. Self-absorption X-ray spectra and empirical mass-attenuation coefficients were obtained for the considered materials from X-ray emission spectra and relative X-ray intensity measurements, respectively. It is shown that calculatedk-ratios with empirical mass attenuation coefficients and modified partial fluorescence yields give better agreement with experimental data, except at very low accelerating voltages. Alternatively, satisfactory agreement is also achieved by using the Ni L3-M1line (Lℓ) instead of the Ni L3-M4,5line.

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Vrebos, B. A. R., und P. A. Pella. „Uncertainties in mass absorption coefficients in fundamental parameter X-ray fluorescence analysis“. X-Ray Spectrometry 17, Nr. 1 (Februar 1988): 3–12. http://dx.doi.org/10.1002/xrs.1300170103.

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Sitko, Rafa? „Empirical coefficients models for x-ray fluorescence analysis of intermediate-thickness samples“. X-Ray Spectrometry 34, Nr. 1 (2004): 11–18. http://dx.doi.org/10.1002/xrs.778.

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31

Okada, T., Y. Kajiyama, H. Andou und M. Maeda. „Determination of diffusion coefficients of C2 radicals by laser induced fluorescence spectroscopy“. Applied Physics B Photophysics and Laser Chemistry 47, Nr. 2 (Oktober 1988): 191–93. http://dx.doi.org/10.1007/bf00684087.

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32

Nenninger, Anja, Giulia Mastroianni und Conrad W. Mullineaux. „Size Dependence of Protein Diffusion in the Cytoplasm of Escherichia coli“. Journal of Bacteriology 192, Nr. 18 (25.06.2010): 4535–40. http://dx.doi.org/10.1128/jb.00284-10.

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ABSTRACT Diffusion in the bacterial cytoplasm is regarded as the primary method of intracellular protein movement and must play a major role in controlling the rates of cell processes. A number of recent studies have used green fluorescent protein (GFP) tagging and fluorescence microscopy to probe the movement and distribution of proteins in the bacterial cytoplasm. However, the dynamic behavior of indigenous proteins must be controlled by a complex mixture of specific interactions, combined with the basic physical constraints imposed by the viscosity and macromolecular crowding of the cytoplasm. These factors are difficult to unravel in studies with indigenous proteins. To what extent the addition of a GFP tag might affect the movement of a protein through the cytoplasm has also remained unknown. To resolve these problems, we have carried out a systematic study of the size dependence of protein diffusion coefficients in the Escherichia coli cytoplasm, using engineered GFP multimers (from 2 to 6 covalently linked GFP molecules). Diffusion coefficients were measured using confocal fluorescence recovery after photobleaching (FRAP). At least up to 110 kDa (four linked GFP molecules), the diffusion coefficient varies with size roughly as would be predicted from the Einstein-Stokes equation for a classical (Newtonian) fluid. Thus, protein diffusion coefficients are predictable over this range. GFP tagging of proteins has little impact on the diffusion coefficient over this size range and therefore need not significantly perturb protein movement. Two indigenous E. coli proteins were used to show that their specific interactions within the cell are the main controllers of the diffusion rate.

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Pau, C. P., G. Patonay, C. W. Moss, D. Hollis, G. M. Carlone, B. D. Plikaytis und I. M. Warner. „Comparison of Flavobacterium and Sphingobacterium species by enzyme profiles, with use of pattern recognition of two-dimensional fluorescence data.“ Clinical Chemistry 33, Nr. 3 (01.03.1987): 377–80. http://dx.doi.org/10.1093/clinchem/33.3.377.

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Abstract Enzyme profiles of eight Flavobacterium species and one Sphingobacterium species were compared after using a two-dimensional fluorescence technique. Enzyme contents and corresponding activities were rapidly determined for whole-cell preparations after incubation with a mixture of preselected fluorogenic substrates. A two-dimensional fluorescence spectrum of the resulting product mixture, measured with a video fluorometer, provided a characteristic "fingerprint" for each organism. Comparison of fluorescent spectra was facilitated by a Fourier-transform-based pattern-recognition algorithm and by a clustering technique involving the Pearson product-moment correlation coefficient. F. multivorum, F. thalpophilum, and S. mizutae formed one cluster; F. indologenes, F. spiritivorum, F. odoratum, and F. balustinum formed a second. F. meningosepticum was intermediate between the first and second cluster, whereas F. breve was different from all other strains examined, based on their spectral dissimilarity indices and correlation coefficients.

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Sugunan, Sunish K., Matthew F. Paige und Ronald P. Steer. „Determination of oxygen permeabilities in thin polymer films using quenching of upconverted fluorescence in porphyrins“. Canadian Journal of Chemistry 89, Nr. 2 (Februar 2011): 195–202. http://dx.doi.org/10.1139/v10-095.

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Proof-of-principle is demonstrated for a method of measuring the oxygen diffusion properties of thin polymer films based on quenching of the delayed upconverted S2 fluorescence of Zn(II) meso-tetraphenylporphine (ZnTPP). Empirical oxygen diffusion coefficients and permeability coefficients for poly(vinyl alcohol) (PVA) have been computed using Stern–Volmer kinetics in the steady-state regime and a nonlinear gas solubility model in the time domain. Simplified dual-mode theory has been used to calculate crude theoretical oxygen permeability coefficients to compare with the experimental values. It is confirmed that oxygen permeability in the PVA matrix is controlled largely by the characteristics of the polymer matrix, particularly its water content and distribution.

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Shirshin, E. A., G. S. Budylin, N. Yu Grechischeva, V. V. Fadeev und I. V. Perminova. „Experimental evidence of incomplete fluorescence quenching of pyrene bound to humic substances: implications for Koc measurements“. Photochemical & Photobiological Sciences 15, Nr. 7 (2016): 889–95. http://dx.doi.org/10.1039/c6pp00052e.

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Fluorescence quenching (FQ) is extensively used for quantitative assessment of partition coefficients (K_OC) of polycyclic aromatic hydrocarbons (PAHs) to natural organic materials – humic substances (HS).

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Shaki, Hanieh, Alireza Khosravi und Kamaladin Gharanjig. „Novel self-coloured polymers based on new fluorescent naphthalimide derivatives: synthesis, characterisation and photophysical properties“. Pigment & Resin Technology 46, Nr. 3 (02.05.2017): 244–50. http://dx.doi.org/10.1108/prt-07-2016-0080.

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Purpose In this study, two novel fluorescent dyes, based on naphthalimide derivatives have been synthesised from acenaphthene as a starting material. The ability of the dyes to graft to polymer chain was then demonstrated. The novel synthesised dyes and self-coloured polymers were characterised by a variety of techniques. Design/methodology/approach The novel dyes were prepared through by halogenation, oxidation, imidation and amination reactions. All steps of these processes were monitored by thin layer chromatography. The fluorescent dyes and their intermediates were characterised by differential scanning calorimeter, fourier transform infrared spectroscopy (FTIR), Proton Nuclear Magnetic Resonance (1H-NMR) and carbon-13 nuclear magnetic resonance (13-CNMR) spectroscopic techniques. The molar extinction coefficients and absorption maximum wavelength were obtained by examining the dyes and polymer solutions in Dimethylformamide (DMF) and toluene solvents. The fluorescency of novel dyes and self-coloured polymers was evaluated. Their quantum yields and Stokes shift values were determined as DMF and toluene solutions. The percentage of the covalently bounded dyes into the polymer chain was calculated. Findings The characterisation of the synthesised dyes and self-coloured polymers verified their structural correctness. The results of reaction dyes with resin demonstrated that the dyes were covalently bonded to the chain of an acrylic polymer (resin) containing carboxylic acid groups giving self-coloured polymers. The extent of fluorescence of the synthesised dyes and their polymers showed that compounds containing functional amino group in C-4 position of naphthalimide ring have high fluorescence properties. Originality/value This study is original. Self-coloured polymers based on acrylic were synthesised by novel naphthalimide dyes with acrylic resin for the first time, successfully. The novel dyes and their self-coloured polymers exhibit good and acceptable fluorescent activity.

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Veselovskii, Igor, Qiaoyun Hu, Philippe Goloub, Thierry Podvin, Mikhail Korenskiy, Olivier Pujol, Oleg Dubovik und Anton Lopatin. „Combined use of Mie–Raman and fluorescence lidar observations for improving aerosol characterization: feasibility experiment“. Atmospheric Measurement Techniques 13, Nr. 12 (09.12.2020): 6691–701. http://dx.doi.org/10.5194/amt-13-6691-2020.

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Abstract. To study the feasibility of a fluorescence lidar for aerosol characterization, the fluorescence channel is added to the LILAS multiwavelength Mie–Raman lidar of Lille University, France. A part of the fluorescence spectrum induced by 355 nm laser radiation is selected by the interference filter of 44 nm bandwidth centered at 466 nm. Such an approach has proved to have high sensitivity, allowing fluorescence signals from weak aerosol layers to be detected and the fluorescence backscattering coefficient from the ratio of fluorescence and nitrogen Raman backscatters to be calculated. Observations were performed during the November 2019–February 2020 period. The fluorescence capacity (ratio of fluorescence to elastic backscattering coefficients), measured under conditions of low relative humidity, varied in a wide range, being the highest for the smoke and the lowest for the dust particles. The results presented also demonstrate that the fluorescence measurements can be used for monitoring the aerosol inside the cloud layers.

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Ang, Catharina Y. W., Wenhong Luo, Eugene B. Hansen, James P. Freemana und Harold C. Thompson. „Determination of Amoxicillin in Catfish and Salmon Tissues by Liquid Chromatography with Precolumn Formaldehyde Derivatization“. Journal of AOAC INTERNATIONAL 79, Nr. 2 (01.03.1996): 389–96. http://dx.doi.org/10.1093/jaoac/79.2.389.

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Abstract A liquid chromatographic (LC) method with fluorescence detection was developed for analysis of amoxicillin in catfish and salmon tissues. The tissue was extracted with phosphate buffer (pH 4.5), followed by trichloroacetic acid (TCA) precipitation of proteins and solid-phase (C18) extraction. Trace amounts of nonpolar interfering substances present after solid-phase extraction were removed by ether liquid-liquid extraction. The extract was reacted with formaldehyde and TCA at 100°C for 30 min. A fluorescent derivative was extracted with ether, concentrated, and analyzed by reversed phase LC with fluorescence detection. Average recoveries of amoxicillin spiked at 2.5-20 ppb were >80% for catfish and >75% for salmon muscle tissue, with coefficients of variation of <6%. Limits of detection (LOD) and quantitation (LOQ) for catfish tissue were 0.5 and 1.2 ppb, respectively. LOD and LOQ for salmon muscle tissue were 0.8 and 2.0 ppb, respectively.

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Chen, Songhua, Rui Luo, Xinyue Li, Meiyun He, Shanshan Fu und Jialiang Xu. „Aggregation Induced Emission and Nonlinear Optical Properties of an Intramolecular Charge-Transfer Compound“. Materials 14, Nr. 8 (11.04.2021): 1909. http://dx.doi.org/10.3390/ma14081909.

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Intramolecular charge transfer (ICT) compounds have attracted wide attention for their potential applications in optoelectronic materials and devices such as fluorescent sensors, dye-sensitized solar cells, organic light emitting diodes and nonlinear optics. In this work, we have synthesized a new ICT compound, dimethyl-[4-(7-nitro-benzo[1,2,5]thiadiazol-4-yl)-phenyl]-amine (BTN), and have fabricated it into low dimensional micro/nano structures with well-defined morphologies. These self-assembled nanostructures exhibit high efficiency solid state fluorescence via an aggregation induced emission mechanism, which overcomes the defect of fluorescence quenching caused by aggregation in the solid state of traditional luminescent materials. We also explored and studied the nonlinear optical properties of this material through the Z-scan method, and found that this material exhibits large third-order nonlinear absorption and refraction coefficients, which promises applications of the materials in the fields of nonlinear optics and optoelectronics.

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Gupta, Anjali, Thomas Korte, Andreas Herrmann und Thorsten Wohland. „Plasma membrane asymmetry of lipid organization: fluorescence lifetime microscopy and correlation spectroscopy analysis“. Journal of Lipid Research 61, Nr. 2 (19.12.2019): 252–66. http://dx.doi.org/10.1194/jlr.d119000364.

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A fundamental feature of the eukaryotic cell membrane is the asymmetric arrangement of lipids in its two leaflets. A cell invests significant energy to maintain this asymmetry and uses it to regulate important biological processes, such as apoptosis and vesiculation. The dynamic coupling of the inner or cytoplasmic and outer or exofacial leaflets is a challenging open question in membrane biology. Here, we combined fluorescence lifetime imaging microscopy (FLIM) with imaging total internal reflection fluorescence correlation spectroscopy (ITIR-FCS) to differentiate the dynamics and organization of the two leaflets of live mammalian cells. We characterized the biophysical properties of fluorescent analogs of phosphatidylcholine, sphingomyelin, and phosphatidylserine in the plasma membrane of two mammalian cell lines (CHO-K1 and RBL-2H3). Because of their specific transverse membrane distribution, these probes allowed leaflet-specific investigation of the plasma membrane. We compared the results of the two methods having different temporal and spatial resolution. Fluorescence lifetimes of fluorescent lipid analogs were in ranges characteristic for the liquid ordered phase in the outer leaflet and for the liquid disordered phase in the inner leaflet. The observation of a more fluid inner leaflet was supported by free diffusion in the inner leaflet, with high average diffusion coefficients. The liquid ordered phase in the outer leaflet was accompanied by slower diffusion and diffusion with intermittent transient trapping. Our results show that the combination of FLIM and ITIR-FCS with specific fluorescent lipid analogs is a powerful tool for investigating lateral and transbilayer characteristics of plasma membrane in live cell lines.

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Lau, Darryl, Shawn L. Hervey-Jumper, Susan Chang, Annette M. Molinaro, Michael W. McDermott, Joanna J. Phillips und Mitchel S. Berger. „A prospective Phase II clinical trial of 5-aminolevulinic acid to assess the correlation of intraoperative fluorescence intensity and degree of histologic cellularity during resection of high-grade gliomas“. Journal of Neurosurgery 124, Nr. 5 (Mai 2016): 1300–1309. http://dx.doi.org/10.3171/2015.5.jns1577.

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OBJECT There is evidence that 5-aminolevulinic acid (ALA) facilitates greater extent of resection and improves 6-month progression-free survival in patients with high-grade gliomas. But there remains a paucity of studies that have examined whether the intensity of ALA fluorescence correlates with tumor cellularity. Therefore, a Phase II clinical trial was undertaken to examine the correlation of intensity of ALA fluorescence with the degree of tumor cellularity. METHODS A single-center, prospective, single-arm, open-label Phase II clinical trial of ALA fluorescence-guided resection of high-grade gliomas (Grade III and IV) was held over a 43-month period (August 2010 to February 2014). ALA was administered at a dose of 20 mg/kg body weight. Intraoperative biopsies from resection cavities were collected. The biopsies were graded on a 4-point scale (0 to 3) based on ALA fluorescence intensity by the surgeon and independently based on tumor cellularity by a neuropathologist. The primary outcome of interest was the correlation of ALA fluorescence intensity to tumor cellularity. The secondary outcome of interest was ALA adverse events. Sensitivities, specificities, positive predictive values (PPVs), negative predictive values (NPVs), and Spearman correlation coefficients were calculated. RESULTS A total of 211 biopsies from 59 patients were included. Mean age was 53.3 years and 59.5% were male. The majority of biopsies were glioblastoma (GBM) (79.7%). Slightly more than half (52.5%) of all tumors were recurrent. ALA intensity of 3 correlated with presence of tumor 97.4% (PPV) of the time. However, absence of ALA fluorescence (intensity 0) correlated with the absence of tumor only 37.7% (NPV) of the time. For all tumor types, GBM, Grade III gliomas, and recurrent tumors, ALA intensity 3 correlated strongly with cellularity Grade 3; Spearman correlation coefficients (r) were 0.65, 0.66, 0.65, and 0.62, respectively. The specificity and PPV of ALA intensity 3 correlating with cellularity Grade 3 ranged from 95% to 100% and 86% to 100%, respectively. In biopsies without tumor (cellularity Grade 0), 35.4% still demonstrated ALA fluorescence. Of those biopsies, 90.9% contained abnormal brain tissue, characterized by reactive astrocytes, scattered atypical cells, or inflammation, and 8.1% had normal brain. In nonfluorescent (ALA intensity 0) biopsies, 62.3% had tumor cells present. The ALA-associated complication rate among the study cohort was 3.4%. CONCLUSIONS The PPV of utilizing the most robust ALA fluorescence intensity (lava-like orange) as a predictor of tumor presence is high. However, the NPV of utilizing the absence of fluorescence as an indicator of no tumor is poor. ALA intensity is a strong predictor for degree of tumor cellularity for the most fluorescent areas but less so for lower ALA intensities. Even in the absence of tumor cells, reactive changes may lead to ALA fluorescence.

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Wu, J., M. N. Pons und O. Potier. „Wastewater fingerprinting by UV-visible and synchronous fluorescence spectroscopy“. Water Science and Technology 53, Nr. 4-5 (01.02.2006): 449–56. http://dx.doi.org/10.2166/wst.2006.149.

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Municipal wastewater samples have been collected in three different types of community and fingerprinted by optical methods combining UV-visible spectrometry, synchronous fluorescence spectrometry and turbidity. Correlations, whose slope depends on the sampling location, were obtained between absorbance at 254 nm and the synchronous fluorescence intensity of peaks P1 (I366/316), P2 (I430/380) and P3 (I520/470). The corresponding correlation coefficients are larger than 0.75. Although related to urine as ammonia, the fluorescence intensity of P1 does not exhibit a strong correlation with this substance (correlation coefficient of approximately 0.6). All the measured parameters exhibit diurnal variation patterns related to human activities.

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Yechiel, E., und M. Edidin. „Micrometer-scale domains in fibroblast plasma membranes.“ Journal of Cell Biology 105, Nr. 2 (01.08.1987): 755–60. http://dx.doi.org/10.1083/jcb.105.2.755.

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We have used the technique of fluorescence photobleaching recovery to measure the lateral diffusion coefficients and the mobile fractions of a fluorescent lipid probe, 1-acyl-2-(12-[(7-nitro-2-1, 3-benzoxadiazol-4-yl)aminododecanoyl]) phosphatidylcholine (NBD-PC), and of labeled membrane proteins of human fibroblasts. Values for mobile fractions decrease monotonically with increasing size of the laser spot used for the measurements, over a range of 0.35-5.0 microns. Values for NBD-PC diffusion coefficients increase in part of this range to reach a plateau at larger laser spots. This variation is not an artifact of the measuring system, since the effects are not seen if diffusion of the probe is measured in liposomes. We also find that the distribution of diffusion coefficients measured with small laser spots is heterogeneous indicating that these small spots can sample different regions of the membrane. These regions appear to differ in protein concentration. Our data strongly indicate that fibroblast surface membranes consist of protein-rich domains approximately 1 micron in diameter, embedded in a relatively protein-poor lipid continuum. These features appear in photographs of labeled cell surfaces illuminated by the expanded laser beam.

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MORRISON, IAN E. G., CATHERINE M. ANDERSON, GEORGE N. GEORGIOU und RICHARD J. CHERRY. „Measuring diffusion coefficients of labelled particles on cell surfaces by digital fluorescence microscopy“. Biochemical Society Transactions 18, Nr. 5 (01.10.1990): 938. http://dx.doi.org/10.1042/bst0180938.

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Caruso, F., F. Grieser, A. Murphy, P. Thistlethwaite, R. Urquhart, M. Almgren und E. Wistus. „Determination of lateral diffusion coefficients in air-water monolayers by fluorescence quenching measurements“. Journal of the American Chemical Society 113, Nr. 13 (Juni 1991): 4838–43. http://dx.doi.org/10.1021/ja00013a019.

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46

Johnson, Robert G., und Stanley L. Fleming. „Energy-dispersive X-ray fluorescence analysis of massive sulfides using fundamental influence coefficients“. X-Ray Spectrometry 16, Nr. 4 (Juli 1987): 167–70. http://dx.doi.org/10.1002/xrs.1300160406.

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Sullivan, Kelley D., und Edward B. Brown. „Measuring Diffusion Coefficients in Confined Systems Via Multi-Photon Fluorescence Recovery after Photobleaching“. Biophysical Journal 98, Nr. 3 (Januar 2010): 578a. http://dx.doi.org/10.1016/j.bpj.2009.12.3143.

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Berberan-Santos, M. N. „The time dependence of rate coefficients and fluorescence anisotropy for non-delta production“. Journal of Luminescence 50, Nr. 2 (Juli 1991): 83–87. http://dx.doi.org/10.1016/0022-2313(91)90022-n.

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Pau, Chou-Pong, und Isiah M. Warner. „Evaluation of a Fourier-Transform-Based Pattern-Recognition Algorithm for Two-Dimensional Fluorescence Data“. Applied Spectroscopy 41, Nr. 3 (März 1987): 496–502. http://dx.doi.org/10.1366/0003702874448904.

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A pattern-recognition algorithm for two-dimensional fluorescence data previously reported is critically evaluated. The three spectral matching criteria—sum of the absolute value of the imaginary coefficients of the frequency-domain correlation function, sum of the absolute value of the real-negative coefficients of the frequency-domain correlation function, and the intervector distance between the abbreviated Fourier transforms of two spectra—are calculated. Spectra simulated with a computer as well as data acquired with a video fluorometer are examined. Results indicate that all three parameters are sensitive to changes in peak position, peak width, relative peak height, and intensity of background noises.

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Chenyakin, Yuri, Dagny A. Ullmann, Erin Evoy, Lindsay Renbaum-Wolff, Saeid Kamal und Allan K. Bertram. „Diffusion coefficients of organic molecules in sucrose–water solutions and comparison with Stokes–Einstein predictions“. Atmospheric Chemistry and Physics 17, Nr. 3 (15.02.2017): 2423–35. http://dx.doi.org/10.5194/acp-17-2423-2017.

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Abstract. The diffusion coefficients of organic species in secondary organic aerosol (SOA) particles are needed to predict the growth and reactivity of these particles in the atmosphere. Previously, viscosity measurements, along with the Stokes–Einstein relation, have been used to estimate the diffusion rates of organics within SOA particles or proxies of SOA particles. To test the Stokes–Einstein relation, we have measured the diffusion coefficients of three fluorescent organic dyes (fluorescein, rhodamine 6G and calcein) within sucrose–water solutions with varying water activity. Sucrose–water solutions were used as a proxy for SOA material found in the atmosphere. Diffusion coefficients were measured using fluorescence recovery after photobleaching. For the three dyes studied, the diffusion coefficients vary by 4–5 orders of magnitude as the water activity varied from 0.38 to 0.80, illustrating the sensitivity of the diffusion coefficients to the water content in the matrix. At the lowest water activity studied (0.38), the average diffusion coefficients were 1.9 × 10−13, 1.5 × 10−14 and 7.7 × 10−14 cm2 s−1 for fluorescein, rhodamine 6G and calcein, respectively. The measured diffusion coefficients were compared with predictions made using literature viscosities and the Stokes–Einstein relation. We found that at water activity ≥ 0.6 (which corresponds to a viscosity of ≤ 360 Pa s and Tg∕T ≤ 0.81), predicted diffusion rates agreed with measured diffusion rates within the experimental uncertainty (Tg represents the glass transition temperature and T is the temperature of the measurements). When the water activity was 0.38 (which corresponds to a viscosity of 3.3 × 106 Pa s and a Tg∕T of 0.94), the Stokes–Einstein relation underpredicted the diffusion coefficients of fluorescein, rhodamine 6G and calcein by a factor of 118 (minimum of 10 and maximum of 977), a factor of 17 (minimum of 3 and maximum of 104) and a factor of 70 (minimum of 8 and maximum of 494), respectively. This disagreement is significantly smaller than the disagreement observed when comparing measured and predicted diffusion coefficients of water in sucrose–water mixtures.

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