The study of reaction centers and of the primary and associated reactions of photosynthesis by means of absorption difference spectrophotometry: a commentary on ‘Reversible changes in bacteriochlorophyll in purple bacteria upon illumination’ by L.N.M. Duysens, W.J. Huiskamp, J.J. Vos and J.M. van der Hart Biochim. Biophys. Acta 19 (1956) 188–190

Duysens, L.N.M.

doi:10.1016/s0006-3002(89)80034-4

Cited by 30 publications

(31 citation statements)

References 11 publications

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“…Figure 3 illustrates such a comparison. Here, the solid curves correspond to the calculations using formulas (4), (5), and (7) and the symbols correspond to the formulas of [2]. Figure 3a shows that the difference of coefficients C k obtained using the two methods is no greater than 5%.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, we may conclude that the method of this work is in reasonable agreement with the Monte Carlo calculations. The advantages of expressions (4), (5), and (7) are related to the analytical character of calculations that allow simple variations in length L, angle ϑ, and the physical quantity that is corrected using the corresponding coefficient. Formulas of [2] are valid under certain conditions (the length is fixed (L = ∞), the inclusions are uniformly distributed along the directions), and the calculated results are presented only for coefficients C k and C ef .…”

Section: Resultsmentioning

confidence: 99%

“…Various shapes and orientations of inclusions relative to the incident beam are possible. Regular objects are rare in nature, and objects in radiation transfer problems are often approximated using cylinders (blood vessels of biological tissues [1][2][3] and erythrocytes [4]), spheres (algae in water [5]), paraboloids (cumulus clouds in atmosphere [6]), and parallelepipeds (snow surface [7]). Light propagation in such media differs from the propagation under uniform distribution of the same amount of material, since the presence of inclusions implies the presence of pores or holes in which radiation does not interact with medium [8,9].…”

Section: Introductionmentioning

confidence: 99%

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Effect of scattering and absorbing inclusions in dispersive medium on the optical parameters of an elementary volume

Barun

Иванов

2015

Opt. Spectrosc.

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A problem of the relationship of phenomenological optical parameters of dispersive medium that contains inclusions with arbitrary shape and the parameters of such inclusions is theoretically solved in the approximation of 1D scattering phase function. It is demonstrated that the desired relationships can be represented in terms of several correction coefficients. In the presence of local inclusions, the scattering and absorption coefficients of the medium generally decrease relative to the corresponding coefficients of the uniform spatial distribution of the same amount of the dispersive material. Under certain conditions, an increase in the forward scattering of the medium with an increase in the size of inclusions can be obtained. Physical reasons for such a behavior of the phenomenological parameters are discussed, and analytical expressions for the above relationships are derived. The theoretical expressions are applied in various problems of biomedical optics in which optical characteristics of multicomponent biological tissues must be determined using the known spectral and geometrical characteristics of components. The results can be used by researchers who study light scattering in various natural and artificial media (e.g., biological tissues and sea water) that contain local scattering inclusions.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of scattering and absorbing inclusions in dispersive medium on the optical parameters of an elementary volume

Barun

Иванов

2015

Opt. Spectrosc.

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“…This is used only for large particles in a thin layer. The sizes of particles must be much larger than the wavelength and their amount must be very small [6], or no "bolt ing" will occur [7]. This model is hardly suited for solutions of macromolecules, aggregates of molecules, most colloids, and small suspensions.…”

Section: Introductionmentioning

confidence: 99%

Tyndall’s hypochromism in suspensions

et al. 2015

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Passage of light through a suspension is accompanied by a competition of processes of absorption and scattering for each individual particle. As a result, a hypochromism phenomenon (a decrease in the extinction coefficient) takes place. The hypochromism value increases with the growth of a particle sizes or its refractive index. Since Tyndall's light scattering in a suspension where the size of every particle is consid erably larger than the wavelength weakly depends on the wavelength, the absorption (or excitation) spectrum is almost uniformly attenuated. A simple method for determination of the true extinction coefficients of the absorption and excitation spectra of diluted suspensions which have no multiple light scattering is proposed. Experimental data on the spectra of hemoglobin in erythrocytes, actinomycin in DNA, and flavines in mito chondria are discussed.

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“…Equation (3) defines C + and C − , which are related to phototaxis toward the right (+) and left (−) directions. Here, we consider that the intensity of light scattered from the cells is proportional in the number density and decays with the distance |x -y|, which is based on Lambert-Beer law [19]. The average number density in space is given by…”

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confidence: 99%

Localized Bioconvection ofEuglenaCaused by Phototaxis in the Lateral Direction

et al. 2011

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Euglena, a swimming micro-organism, exhibited a characteristic bioconvection that was localized at the center of a sealed chamber under bright illumination to induce negative phototaxis. This localized pattern consisted of high-density spots, in which convection was found. These observations were reproduced by a mathematical model that was based on the phototaxis of individual cells in both the vertical and lateral directions. Our results indicate that this convection is maintained by upward swimming, as with general bioconvection, and the localization originates from lateral phototaxis.

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Cited by 30 publications

References 11 publications

Effect of scattering and absorbing inclusions in dispersive medium on the optical parameters of an elementary volume

Effect of scattering and absorbing inclusions in dispersive medium on the optical parameters of an elementary volume

Tyndall’s hypochromism in suspensions

Localized Bioconvection ofEuglenaCaused by Phototaxis in the Lateral Direction

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