Andrei Utkin - Academia.edu (original) (raw)

Papers by Andrei Utkin

Estuarine Coastal and Shelf Science, Mar 1, 2021

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.

Frontiers in Environmental Science, Aug 24, 2022

Emerging pollutants impose a high degree of stress on marine ecosystems, compromising valuable re... more Emerging pollutants impose a high degree of stress on marine ecosystems, compromising valuable resources, the planet and human health. Pharmaceutical residues often reach marine ecosystems, and their input is directly related to human activities. Fluoxetine is an antidepressant, and one of the most prescribed selective serotonin reuptake inhibitors globally and has been detected in aquatic ecosystems in concentrations up to 40 μg L −1. The present study aims to evaluate the impact of fluoxetine ecotoxicity on the photochemistry, energy metabolism and enzyme activity of Ulva lactuca exposed to environmentally relevant concentrations (0.3, 0.6, 20, 40, and 80 μg L −1). Exogenous fluoxetine exposure induced negative impacts on U. lactuca photochemistry, namely on photosystem II antennae grouping and energy fluxes. These impacts included increased oxidative stress and elevated enzymatic activity of ascorbate peroxidase and glutathione reductase. Lipid content increased and the altered levels of key fatty acids such as hexadecadienoic (C16:2) and linoleic (C18:2) acids revealed strong correlations with fluoxetine concentrations tested. Multivariate analyses reinforced the oxidative stress and chlorophyll a fluorescence-derived traits as efficient biomarkers for future toxicology studies.

Optics and Spectroscopy, Jul 1, 2010

... 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.

Lecture Notes in Computer Science, 2018

In this work we propose a multi-population genetic algorithm for tree-shaped network design probl... more In this work we propose a multi-population genetic algorithm for tree-shaped network design problems using random keys. Recent literature on finding optimal spanning trees suggests the use of genetic algorithms. Furthermore, random keys encoding has been proved efficient at dealing with problems where the relative order of tasks is important. Here we propose to use random keys for encoding trees. The topology of these trees is restricted, since no path from the root vertex to any other vertex may have more than a pre-defined number of arcs. In addition, the problems under consideration also exhibit the characteristic of flows. Therefore, we want to find a minimum cost tree satisfying all demand vertices and the pre-defined number of arcs. The contributions of this paper are twofold: on one hand we address a new problem, which is an extension of the well known NP-hard hop-constrained MST problem since we also consider determining arc flows such that vertices requirements are met at minimum cost and the cost functions considered include a fixed cost component and a nonlinear flow routing component; on the other hand, we propose a new genetic algorithm to efficiently find solutions to this problem.

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.

Wiley-VCH Verlag GmbH & Co. KGaA eBooks, Oct 4, 2013

Journal of the Optical Society of America, Mar 15, 2012

A model of steady-state X-shaped wave generation by a superluminal (supersonic) point-like source... more A model of steady-state X-shaped wave generation by a superluminal (supersonic) point-like source infinitely moving along a straight line is extended to a more realistic causal scenario of a source pulse launched at time zero and propagating rectilinearly at constant superluminal speed. In the case of infinitely short (delta) pulse, the new model yields an analytical solution, corresponding to the propagation-invariant Xshaped wave clipped by a droplet-shaped support, which perpetually expands along the propagation and transversal directions, thus tending the droplet-shaped wave to the X-shaped one.

Agricultural Water Management, 2016

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.

International Journal of Wildland Fire, 2004

The problem of eye safety in lidar-assisted wildland fire detection and investigation is consider... more The problem of eye safety in lidar-assisted wildland fire detection and investigation is considered as a problem of reduction of the hazard range within which the laser beam is dangerous for direct eye exposure. The dependence of this hazard range on the lidar characteristics is examined and possible eye-safety measures discussed. The potential of one of the cheapest ways of providing eye safety, which is based on placing the lidar in an elevated position and using a 1064-nm laser beam with increased divergence, is also investigated experimentally. It is demonstrated that a lidar system operating with wider beams maintains its ability to detect smoke plumes efficiently. Providing eye-safe conditions allows scanning of the internal 3D structure of smoke plumes in the vicinity of fire plots. Examples are given as layer-by-layer smoke concentration plots on the topographic map.

Neural Processing Letters, Jun 1, 2004

The automatic recognition of smoke signatures in lidar signals collected during very small-scale ... more The automatic recognition of smoke signatures in lidar signals collected during very small-scale experimental forest fires using neural-network algorithms was studied. An algorithm for pre-processing of raw lidar signals is proposed, which selects suspicious backscattering peaks and makes them unbiased and scale independent. The resulting patterns can be successfully classified as corresponding to alarm or no-alarm conditions by a neural-network algorithm based on a simple one-neuron structure (perceptron). In the case of an alarm, the pre-processing algorithm provides the location of the smoke plume. Five algorithms selected from the literature, and one that was specially developed, all with learning rate adaptation, were used for training the perceptron. Their efficiencies and statistical properties were compared. The best perceptron classifier presented an efficiency of 97% in the classification of smoke-signature patterns and a false alarm rate of 0.9%.