Abstract The increasing uncontrolled development of human activities and consequent increase in t... more Abstract The increasing uncontrolled development of human activities and consequent increase in the production and release into the marine realm of potentially harmful substances highlights the need to develop efficient and high-throughput screening (HTS) tools. Bio-optical tools, such as laser-induced fluorescence (LIF) and pulse amplitude modulated (PAM) fluorometry, emerge as efficient non-invasive techniques for toxicophenomic evaluation in ecotoxicological trials. Both techniques generate large datasets that can be applied in multivariate analysis to evaluate canonical classification efficiency of the exposure types and levels to which photosynthetic organisms, such as diatoms, are subjected to. In the present work, marine diatom cultures were exposed to two trace elements known to have physiological roles and different toxicity ranges (Zn and Cu), and to two other trace elements without known metabolic functions and very different toxicological profiles (Cr and Hg). All the tested approaches were able to disentangle the control groups from the test groups. Moreover, the application of LIF raw-data showed that this technique had the higher classification efficiency, providing very good separation of the different doses applied of each trace element tested. Additionally, PAM chlorophyll fast induction kinetics raw data also produced good classification efficiencies and provided data that can be useful for interpreting the physiological shifts induced by trace element exposure. In sum, LIF and PAM techniques appear as completely non-invasive HTS techniques that, when applied together, produce a correct toxicophenomic classification and disentangle the physiological effects behind the observed phenomic changes. Therefore, they are worth to be included in future ecotoxicological assessment test protocols.
... The back scattering coefficient was calculated by Mie theory [32]. Following recommendations ... more ... The back scattering coefficient was calculated by Mie theory [32]. Following recommendations of Wiscombe [33] 1600 800 0 150 ... 4. J. Bösenberg, D. Brassington, and PC Simon, Instru ment Development for Atmospheric Research and Moni toring (Springer Verlag, Berlin, 1997). ...
Conference on Lasers and Electro-Optics Europe, 1996
We carry out calculations of the photon path statistical characteristics for homogeneous scatteri... more We carry out calculations of the photon path statistical characteristics for homogeneous scattering medium with the model bodies (inhomogeneities) which are akin to that of biological objects of real tomography investigations. Convenient approximation formulas for definition of the mean photon paths are constructed for both the time and frequency domains and different inhomogeneity types (inhomogeneous absorption, scattering, and refraction as well as inhomogeneities of the combined type). The possibility to represent the signal perturbations due to the macroinhomogeneities as an integral along the mean photon path is used to solve the tomography reconstruction problem. This enables us to reduce this problem to the set of simultaneous equations for the discrete distribution of the macroinhomogeneity characteristics. The optimum discretization scale is chosen on the basis of area across which the macroinhomogeneity characteristics are averaged (this area is defined by the values of the diffusion and refraction coefficients of the medium).
A system for semi-automated plant phenotyping is being developed in Portugal within the framework... more A system for semi-automated plant phenotyping is being developed in Portugal within the framework of the INTERPHENO project from the EU Programme "Portugal 2020." As a part of this activity, we tested two induced fluorescence techniques based on the laser and flashlamp excitation to facilitate the recognition of plants and photosynthetic state assessment based on the emission spectra.
Extension of the STTD (spacetime triangle diagram) technique - a powerful method of solving probl... more Extension of the STTD (spacetime triangle diagram) technique - a powerful method of solving problems related to generation and propagation of acoustic and electromagnetic signals (finite pulses) - to the case of wave motion within a sectorial waveguide is discussed. The paper shows how a general modal solution, which describes the wave-pulse generation by a source arbitrarily distributed within a sectoral horn, can be constructed for the Dirichlet or Neumann boundary conditions imposed on the horn walls. Providing an exact solution, readily implementable for particular sources using general software packages for scientific computing, the obtained integral formulas represent a powerful tool for analysis of pulsed wave propagation in the sectorial horn waveguides.
A model describing steady-state localized X-shaped field generation by a superluminal pointlike c... more A model describing steady-state localized X-shaped field generation by a superluminal pointlike charge (tachyon) infinitely moving along a straight line is extended to the case of a source current pulse of an arbitrary shape launched at time zero and propagating rectilinearly at constant superluminal speed. In the case of infinitely short (delta) pulse, the extended model yields an analytical solution, corresponding to the propagation-invariant X-shaped wave clipped by a droplet-shape support, infinitely expanding along both propagation and transversal directions, thus tending the droplet-shaped wave to the X-shaped one.
Time-domain investigation of formation of the laser-betatron radiation was carried out within the... more Time-domain investigation of formation of the laser-betatron radiation was carried out within the framework of a simple (toy) model of a two-component modulated line source current describing rectilinear propagation of the electron bunch perturbed by transverse oscillation in the co-propagating wakefield. Such an approach yields sufficiently general one-integral solution for the space-time structure of the emanated wave.
The STTD (spacetime triangle diagram) technique is applied for investigation of scalar and electr... more The STTD (spacetime triangle diagram) technique is applied for investigation of scalar and electromagnetic wave booms emanated by physically feasible pulsed line sources whose front travels faster than the wavefront. It is shown that a rough approximation of linearly growing source is sufficient for obtaining finite-amplitude wave-boom description everywhere outside the line of source-pulse trajectory.
Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to stud... more Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to study the photosynthetic efficiency of plants, under control or stress conditions. Compared to most protocols of pulse amplitude modulation (PAM) fluorometry, laser induced chlorophyll fluorescence (LIF) has the advantages of not requiring pulses to be delivered at close range, allowing the remote analysis of a great number of individual plants in a short period of time. Such analyses are extremely useful, for instance, when doing large phenotyping screens of Arabidopsis thaliana mutants or ecotypes. Water deficit is a major abiotic stress compromising plant growth and productivity. Arabidopsis has been adopted as the main model organism in plant sciences and it has been widely used in plant stress studies. However, reports on the applications of LIF techniques to this model plant are scarce. Here we report the use of LIF to investigate changes in chlorophyll a (Chl a) fluorescence signature under progressive drought of potted Arabidopsis plants (Slow Stress) and under fast dehydration of detached leaves (Fast Stress). Results show that the two dehydration methods cause distinct modifications on the red/far-red Chl a fluorescence ratio (F690/F730) and on the wavelengths of Chl a fluorescence maxima. These differences are likely related to distinct changes in water content, photosynthetic pigments, anthocyanins, fatty acid composition and other metabolic adaptations, which are differently regulated in Slow and Fast Stress. Of particular interest are Chl a emission fluorescence changes, which take place under progressive drought, before a substantial decrease in leaf water content. Additionally, no differences were found on LIF emission spectra between fully expanded and young leaves. However, the choice of leaf surface influenced fluorescence emission, with the abaxial surface displaying lower fluorescence and higher F690/F730 ratios. Results suggest that LIF is a fast and non-destructive tool suitable for high-throughput phenotyping of Arabidopsis under water deficit.
This work reports preliminary results of the application of the laser-induced fluorescence techni... more This work reports preliminary results of the application of the laser-induced fluorescence technique to ecotoxicological assessments. The research is focused on the investigation of manifestation of the trace-element stress in the fluorescence emission spectra of photosynthetic pigments in marine phototrophs.
Abstract The increasing uncontrolled development of human activities and consequent increase in t... more Abstract The increasing uncontrolled development of human activities and consequent increase in the production and release into the marine realm of potentially harmful substances highlights the need to develop efficient and high-throughput screening (HTS) tools. Bio-optical tools, such as laser-induced fluorescence (LIF) and pulse amplitude modulated (PAM) fluorometry, emerge as efficient non-invasive techniques for toxicophenomic evaluation in ecotoxicological trials. Both techniques generate large datasets that can be applied in multivariate analysis to evaluate canonical classification efficiency of the exposure types and levels to which photosynthetic organisms, such as diatoms, are subjected to. In the present work, marine diatom cultures were exposed to two trace elements known to have physiological roles and different toxicity ranges (Zn and Cu), and to two other trace elements without known metabolic functions and very different toxicological profiles (Cr and Hg). All the tested approaches were able to disentangle the control groups from the test groups. Moreover, the application of LIF raw-data showed that this technique had the higher classification efficiency, providing very good separation of the different doses applied of each trace element tested. Additionally, PAM chlorophyll fast induction kinetics raw data also produced good classification efficiencies and provided data that can be useful for interpreting the physiological shifts induced by trace element exposure. In sum, LIF and PAM techniques appear as completely non-invasive HTS techniques that, when applied together, produce a correct toxicophenomic classification and disentangle the physiological effects behind the observed phenomic changes. Therefore, they are worth to be included in future ecotoxicological assessment test protocols.
... The back scattering coefficient was calculated by Mie theory [32]. Following recommendations ... more ... The back scattering coefficient was calculated by Mie theory [32]. Following recommendations of Wiscombe [33] 1600 800 0 150 ... 4. J. Bösenberg, D. Brassington, and PC Simon, Instru ment Development for Atmospheric Research and Moni toring (Springer Verlag, Berlin, 1997). ...
Conference on Lasers and Electro-Optics Europe, 1996
We carry out calculations of the photon path statistical characteristics for homogeneous scatteri... more We carry out calculations of the photon path statistical characteristics for homogeneous scattering medium with the model bodies (inhomogeneities) which are akin to that of biological objects of real tomography investigations. Convenient approximation formulas for definition of the mean photon paths are constructed for both the time and frequency domains and different inhomogeneity types (inhomogeneous absorption, scattering, and refraction as well as inhomogeneities of the combined type). The possibility to represent the signal perturbations due to the macroinhomogeneities as an integral along the mean photon path is used to solve the tomography reconstruction problem. This enables us to reduce this problem to the set of simultaneous equations for the discrete distribution of the macroinhomogeneity characteristics. The optimum discretization scale is chosen on the basis of area across which the macroinhomogeneity characteristics are averaged (this area is defined by the values of the diffusion and refraction coefficients of the medium).
A system for semi-automated plant phenotyping is being developed in Portugal within the framework... more A system for semi-automated plant phenotyping is being developed in Portugal within the framework of the INTERPHENO project from the EU Programme "Portugal 2020." As a part of this activity, we tested two induced fluorescence techniques based on the laser and flashlamp excitation to facilitate the recognition of plants and photosynthetic state assessment based on the emission spectra.
Extension of the STTD (spacetime triangle diagram) technique - a powerful method of solving probl... more Extension of the STTD (spacetime triangle diagram) technique - a powerful method of solving problems related to generation and propagation of acoustic and electromagnetic signals (finite pulses) - to the case of wave motion within a sectorial waveguide is discussed. The paper shows how a general modal solution, which describes the wave-pulse generation by a source arbitrarily distributed within a sectoral horn, can be constructed for the Dirichlet or Neumann boundary conditions imposed on the horn walls. Providing an exact solution, readily implementable for particular sources using general software packages for scientific computing, the obtained integral formulas represent a powerful tool for analysis of pulsed wave propagation in the sectorial horn waveguides.
A model describing steady-state localized X-shaped field generation by a superluminal pointlike c... more A model describing steady-state localized X-shaped field generation by a superluminal pointlike charge (tachyon) infinitely moving along a straight line is extended to the case of a source current pulse of an arbitrary shape launched at time zero and propagating rectilinearly at constant superluminal speed. In the case of infinitely short (delta) pulse, the extended model yields an analytical solution, corresponding to the propagation-invariant X-shaped wave clipped by a droplet-shape support, infinitely expanding along both propagation and transversal directions, thus tending the droplet-shaped wave to the X-shaped one.
Time-domain investigation of formation of the laser-betatron radiation was carried out within the... more Time-domain investigation of formation of the laser-betatron radiation was carried out within the framework of a simple (toy) model of a two-component modulated line source current describing rectilinear propagation of the electron bunch perturbed by transverse oscillation in the co-propagating wakefield. Such an approach yields sufficiently general one-integral solution for the space-time structure of the emanated wave.
The STTD (spacetime triangle diagram) technique is applied for investigation of scalar and electr... more The STTD (spacetime triangle diagram) technique is applied for investigation of scalar and electromagnetic wave booms emanated by physically feasible pulsed line sources whose front travels faster than the wavefront. It is shown that a rough approximation of linearly growing source is sufficient for obtaining finite-amplitude wave-boom description everywhere outside the line of source-pulse trajectory.
Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to stud... more Chlorophyll fluorescence measurements have been widely applied as non-destructive methods to study the photosynthetic efficiency of plants, under control or stress conditions. Compared to most protocols of pulse amplitude modulation (PAM) fluorometry, laser induced chlorophyll fluorescence (LIF) has the advantages of not requiring pulses to be delivered at close range, allowing the remote analysis of a great number of individual plants in a short period of time. Such analyses are extremely useful, for instance, when doing large phenotyping screens of Arabidopsis thaliana mutants or ecotypes. Water deficit is a major abiotic stress compromising plant growth and productivity. Arabidopsis has been adopted as the main model organism in plant sciences and it has been widely used in plant stress studies. However, reports on the applications of LIF techniques to this model plant are scarce. Here we report the use of LIF to investigate changes in chlorophyll a (Chl a) fluorescence signature under progressive drought of potted Arabidopsis plants (Slow Stress) and under fast dehydration of detached leaves (Fast Stress). Results show that the two dehydration methods cause distinct modifications on the red/far-red Chl a fluorescence ratio (F690/F730) and on the wavelengths of Chl a fluorescence maxima. These differences are likely related to distinct changes in water content, photosynthetic pigments, anthocyanins, fatty acid composition and other metabolic adaptations, which are differently regulated in Slow and Fast Stress. Of particular interest are Chl a emission fluorescence changes, which take place under progressive drought, before a substantial decrease in leaf water content. Additionally, no differences were found on LIF emission spectra between fully expanded and young leaves. However, the choice of leaf surface influenced fluorescence emission, with the abaxial surface displaying lower fluorescence and higher F690/F730 ratios. Results suggest that LIF is a fast and non-destructive tool suitable for high-throughput phenotyping of Arabidopsis under water deficit.
This work reports preliminary results of the application of the laser-induced fluorescence techni... more This work reports preliminary results of the application of the laser-induced fluorescence technique to ecotoxicological assessments. The research is focused on the investigation of manifestation of the trace-element stress in the fluorescence emission spectra of photosynthetic pigments in marine phototrophs.
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