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Examples of image blurring
Published in Mario Bertero, Patrizia Boccacci, Christine De Mol, Introduction to Inverse Problems in Imaging, 2021
Mario Bertero, Patrizia Boccacci, Christine De Mol
An optical microscope is a system that uses visible light and lenses to magnify images of small samples. Most microscopes used nowadays in biology are based on the physical phenomenon of fluorescence: the specimen (cells or living tissues) is stained by fluorophores, fluorescent chemical compounds that can re-emit light upon excitation by a light source, for instance a laser. The illuminating light has a specific wavelength and its absorption by the fluorophores causes the nearly simultaneous emission of light with a longer wavelength (Stokes shift). Therefore, in the case of fluorescence microscopy, the object f(0)(x) is the distribution of the fluorophores within the biological specimen (see, for instance, [33] for a very brief and synthetic account of fluorescence microscopy for users of image deconvolution).
Introduction to Biological Light Microscopy
Published in Jay L. Nadeau, Introduction to Experimental Biophysics, 2017
Jay L. Nadeau, Michael W. Davidson
The value of ε shows only absorptivity and tells nothing about emission. The quantum yield Q of a fluorochrome or fluorophore represents a quantitative measure of fluorescence emission efficiency and is expressed as the ratio of the number of photons emitted to the number of photons absorbed (Figure 7.16b). Quantum yields typically range between a value of 0 and 1, and fluorescent molecules commonly employed as probes in microscopy have quantum yields ranging from very low (0.05 or less) to almost 1. The easiest way to determine quantum yield is to compare the integrated fluorescence intensity I of a solution of the fluorophore with that of a reference fluorophore of known quantum yield (“R”). Both fluorophores should be within their linear absorbance range, and both the absorbance and emission spectra should be measured. Then the relative quantum yield is given by
Nanostructure Evaluation of Ionic Liquid Aggregates by Spectroscopy
Published in Sarhan M. Musa, Nanoscale Spectroscopy with Applications, 2018
Clarissa P. Frizzo, Aniele Z. Tier, Izabelle M. Gindri, Lilian Buriol, Marcos A. Villetti, Nilo Zanatta, Marcos A.P. Martins
Fluorescence is the emission of radiation (ultraviolet (UV), vis, or infrared) from any substance and occurs in electronically excited states (Lakowicz et al. 2006). Fluorophore is a fluorescent chemical compound that absorbs energy at a specific wavelength and then reemits it at a different, although equally specific, one. The amount and wavelength of the emitted energy depend on both the fluorophore and the chemical environment of the fluorophore (Sauer et al. 2011). In excited singlet states, the electron in the excited orbital is paired (by opposite spin) to the second electron in the ground-state orbital. Consequently, the return to the ground state is spin allowed and occurs rapidly by emission of a photon (Lakowicz et al. 2006). As a simple rule, the energetically favored electron promotion will be from the highest occupied molecular orbital (HOMO), usually the singlet ground state (S0), to the lowest unoccupied molecular orbital (LUMO), and the resulting species is called the singlet excited state (S1). Compounds that absorb in the vis region of the spectrum (these compounds have color) generally have some weakly bound or delocalized electrons and normally comprehend several combined aromatic groups (plane or cyclic molecules) with several π bonds. In these systems, the energy difference between the lowest LUMO and the HOMO corresponds to the quantum energies in the vis region (Sauer et al. 2011). Compounds that emit in the vis region are of interest in the fluorescence spectroscopy. The schematic representation of the fluorescence method is shown in Figure 6.22.
Determination of mercury (II) in water samples by fluorescence using a dansyl chloride immobilized glass slide
Published in Instrumentation Science & Technology, 2020
Imran Muhammad, Turghun Muhammad, Amina Hoji, Xiaoxia Yang, Aziguli Yigaimu
Among the strategies, immobilization fluorophores provide several advantages for sensors that include reversibility, reproducibility, and easy implementation into devices.[13] Many small organic molecules have been reported to be fluorophores for Hg2+ such as rhodamine,[14,15] pyrene,[16,17] naphthalimide,[18] bispyrenyl,[19] terphenyl,[20,21] naphthylthiourea,[22] and isocoumarins.[23] Among the fluorophores, dansyl chloride is favored due to its well-known microenvironment sensitivity and selective response to Hg2+.
Coherence-enhanced diffusion filtering applied to partially-ordered fluids
Published in Molecular Physics, 2020
Perry W. Ellis, Jyothishraj Nambisan, Alberto Fernandez-Nieves
Fluorescence is an inelastic process where a material absorbs and then re-emits light; the initial absorption excites a singlet state in the material which then decays via photon emission [17]. The absorption and emission are characterised by their respective spectra, with the peak in the emission spectrum occurring at a longer wavelength than the peak in the absorption spectrum. As a historical aside, the realisation that this process consists of both absorption and emission of light is attributed to Stokes, as is the name ‘fluorescence’ itself [18,19]. This is the reason that the difference in the peak of the excitation and emission spectra for a given fluorophore is known as the ‘Stokes shift’ [17]. A standard epifluoresence setup takes advantage of this with a dichroic mirror and pair of band-pass filters centred on the peaks in the excitation and emission spectra, with no overlap in the transmitted wavelengths of the filters. Consequently, the light passed by these filters is referred to as the excitation light and emission light, respectively. The dichroic mirror typically reflects the excitation light and passes the emission light. Thus, the sample can be illuminated by the excitation light, exciting the fluorophores in the sample, with only the emission light collected on the detector, typically a CCD camera. Imaging the active nematic with such a setup results in signal coming from only the fluorescently labelled microtubules, clearly revealing the nematic structure, as shown in the example image in Figure 1(D). This is a wide-field technique, meaning that even though only a specific plane in the sample is in focus, light from out of focus planes can still reach the detector.