Recent Publications

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2017
Pessanha, S., M. Alves, J. M. Sampaio, J. P. Santos, M. L. Carvalho, and M. Guerra. "A novel portable energy dispersive X-ray fluorescence spectrometer with triaxial geometry." J. Inst. 12 (2017): P01014. Abstract
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2016
Sampaio, J. M., T. I. Madeira, M. Guerra, F. Parente, P. Indelicato, J. P. Santos, and J. P. Marques. "Relativistic calculations of K-, L- and M-shell X-ray production cross-sections by electron impact for Ne, Ar, Kr, Xe, Rn and Uuo." Journal of Quantitative Spectroscopy and Radiative Transfer 182 (2016): 87-93. AbstractWebsite

Journal of Quantitative Spectroscopy and Radiative Transfer, 182 + (2016) 87-93. doi:10.1016/j.jqsrt.2016.05.012

Rahangdale, H. V., D. Mitra, P. K. Das, S. De, M. Guerra, J. P. Santos, and S. Saha. "Spectroscopic investigations of L-shell ionization in heavy elements by electron impact." Journal of Quantitative Spectroscopy and Radiative Transfer 174 (2016): 79-87. AbstractWebsite

Journal of Quantitative Spectroscopy and Radiative Transfer, 174 + (2016) 79-87. doi:10.1016/j.jqsrt.2016.01.026

Amaro, Pedro, Filippo Fratini, Laleh Safari, Jorge Machado, Mauro Guerra, Paul Indelicato, and Jose Paulo Santos. "Relativistic evaluation of the two-photon decay of the metastable 1s22s2p 3P0 state in berylliumlike ions with an effective-potential model." Physical Review A 93 (2016): 032502-8. AbstractWebsite

The two-photon $1{s}^{2}2s2p\phantom{\rule{0.16em}{0ex}}{}^{3}{P}_{0}\ensuremath{\rightarrow}1{s}^{2}{s}^{2}\phantom{\rule{0.16em}{0ex}}{}^{1}{S}_{0}$ transition in berylliumlike ions is investigated theoretically within a fully relativistic framework and a second-order perturbation theory. We focus our analysis on how electron correlation, as well as the negative-energy spectrum, can affect the forbidden $E1M1$ decay rate. For this purpose, we include the electronic correlation via an effective local potential and within a single-configuration-state model. Due to its experimental interest, evaluations of decay rates are performed for berylliumlike xenon and uranium. We find that the negative-energy contribution can be neglected at the present level of accuracy in the evaluation of the decay rate. On the other hand, if contributions of electronic correlation are not carefully taken into account, it may change the lifetime of the metastable state by up to 20%. By performing a fully relativistic $jj$-coupling calculation, we find a decrease of the decay rate by two orders of magnitude compared to nonrelativistic $LS$-coupling calculations, for the selected heavy ions.

Sampaio, J. M., M. Guerra, F. Parente, T. I. Madeira, P. Indelicato, J. P. Santos, and J. P. Marques. "Calculations of photo-induced X-ray production cross-sections in the energy range 1–150 keV and average fluorescence yields for Zn, Cd and Hg." Atomic Data and Nuclear Data Tables 111-112 (2016): 67-86. AbstractWebsite

Atomic Data and Nuclear Data Tables, 111-112 (2016) 67-86. doi:10.1016/j.adt.2016.02.001

Ramos, I., I. M. Pataco, M. P. Mourinho, F. Lidon, F. Reboredo, M. F. Pessoa, M. L. Carvalho, J. P. Santos, and M. Guerra. "Elemental mapping of biofortified wheat grains using micro X-ray fluorescence." Spectrochimica Acta Part B: Atomic Spectroscopy 120 (2016): 30-36. AbstractWebsite

Spectrochimica Acta Part B: Atomic Spectroscopy, 120 (2016) 30-36. doi:10.1016/j.sab.2016.03.014

Guerra, M., C. Ferreira, M. L. Carvalho, J. P. Santos, and S. Pessanha. "Distribution of toxic elements in teeth treated with amalgam using μ-energy dispersive X-ray fluorescence." Spectrochimica Acta Part B: Atomic Spectroscopy 122 (2016): 114-117. AbstractWebsite

Spectrochimica Acta Part B: Atomic Spectroscopy, 122 (2016) 114-117. doi:10.1016/j.sab.2016.06.006

Guimarães, D., A. A. Dias, M. Carvalho, M. L. Carvalho, J. P. Santos, F. R. Henriques, F. Curate, and S. Pessanha. "Quantitative determinations and imaging in different structures of buried human bones from the XVIII-XIXth centuries by energy dispersive X-ray fluorescence – Postmortem evaluation." Talanta 155 (2016): 107-115. AbstractWebsite

Talanta, 155 + (2016) 107-115. doi:10.1016/j.talanta.2016.04.028

Lopes, A., A. Gabriel, J. Machado, P. Ribeiro, R. Gomes, Jo M. P. o Coelho, C. O. Silva, C. P. Reis, J. P. Santos, and P. Vieira. "Multiple Source Phototherapy in Breast Cancer: A Viability Study." In 9th International Conference on Biomedical Electronics and Devices, 247-250. SCITEPRESS - Science and and Technology Publications, 2016. Abstract
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2015
Marques, J. P., M. Guerra, F. Parente, J. P. Santos, P. Indelicato, and J. M. Sampaio. "K-shell width, fluorescence yield, and Kβ/ Kαintensity ratio calculation for Fe in the Dirac-Fock approach." Journal of Physics: Conference Series 635 (2015): 092094-2. AbstractWebsite
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Sampaio, J. M., M. Guerra, T. I. Madeira, F. Parente, P. Indelicato, J. P. Santos, and J. P. Marques. "Relativistic calculations of atomic parameters in Ununoctium." Journal of Physics: Conference Series 635 (2015): 092095-2. AbstractWebsite
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Rahangdale, H. V., D. Mitra, M. Guerra, J. P. Santos, and S. Saha. "Subshell resolved inner shell ionization cross-sections of High Z elements by electron impact." Journal of Physics: Conference Series 635 (2015): 052001-2. AbstractWebsite
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Sampaio, J. M., T. I. Madeira, M. Guerra, F. Parente, J. P. Santos, P. Indelicato, and J. P. Marques. "Dirac-Fock calculations of K−, L−, and M-shell fluorescence and Coster-Kronig yields for Ne, Ar, Kr, Xe, Rn, and Uuo." Physical Review A 91 (2015): 052507. AbstractWebsite
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Guerra, M., Th Stöhlker, P. Amaro, J. Machado, and J. P. Santos. "Electron impact ionization cross-sections for few-electron uranium ions." Journal of Physics B: Atomic, Molecular and Optical Physics 48 (2015): 1-5. AbstractWebsite

Journal of Physics B: Atomic, Molecular and Optical Physics, 48(2015) 144027. doi:10.1088/0953-4075/48/14/144027

Diepold, Marc, Luis M. P. Fernandes, Jorge Machado, Pedro Amaro, Marwan Abdou-Ahmed, Fernando D. Amaro, Aldo Antognini, François Biraben, Tzu-Ling Chen, Daniel S. Covita, Andreas J. Dax, Beatrice Franke, Sandrine Galtier, Andrea L. Gouvea, Johannes Götzfried, Thomas Graf, Theodor W. Hänsch, Malte Hildebrandt, Paul Indelicato, Lucile Julien, Klaus Kirch, Andreas Knecht, Franz Kottmann, Julian J. Krauth, Yi-Wei Liu, Cristina M. B. Monteiro, Françoise Mulhauser, Boris Naar, Tobias Nebel, François Nez, Jose Paulo Santos, Joaquim M. F. dos Santos, Karsten Schuhmann, Csilla I. Szabo, David Taqqu, João F. C. A. Veloso, Andreas Voss, Birgit Weichelt, and Randolf Pohl. "Improved x-ray detection and particle identification with avalanche photodiodes." Review of Scientific Instruments 86 (2015): 053102-7. AbstractWebsite
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Guerra, M., J. M. Sampaio, T. I. Madeira, F. Parente, P. Indelicato, J. P. Marques, J. P. Santos, J. Hoszowska, Cl J. Dousse, L. Loperetti, F. Zeeshan, M. Muller, R. Unterumsberger, and B. Beckhoff. "Theoretical and experimental determination of L-shell decay rates, line widths, and fluorescence yields in Ge." Physical Review A 92 (2015): 022507-9. AbstractWebsite
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Guerra, M., P. Amaro, J. Machado, and J. P. Santos. "Single differential electron impact ionization cross sections in the binary-encounter- Bethe approximation for the low binding energy regime." Journal of Physics B: Atomic, Molecular and Optical Physics 48 (2015): 1-9. AbstractWebsite

Journal of Physics B: Atomic, Molecular and Optical Physics, 48(2015) 185202. doi:10.1088/0953-4075/48/18/185202

Guerra, M., S. C. Pé-Leve Santos, A. M. E. Barroso, C. P. S. Fonseca, M. Eloy Cruz, P. Amaro, J. L. Figueirinhas, M. L. Carvalho, and J. P. Santos. "Spatially resolved determination of toxic trace elements in plants of Panasqueira mining region using micro X-ray fluorescence." Microscopy and Microanalysis 21 (2015): 54-55. AbstractWebsite
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Madeira, T. I., J. M. Sampaio, M. Guerra, F. Parente, P. Indelicato, J. P. Santos, and J. P. Marques. "Relativistic calculation of K-, L- and M-shell x-ray fluorescence yields for Ba." Physica Scripta 90 (2015): 1-3. AbstractWebsite

Physica Scripta, 90(2015) 054009. doi:10.1088/0031-8949/90/5/054009

Guerra, M., P. Amaro, J. Machado, and J. P. Santos. "Modified Binary-Encounter-Bethe Model for Electron Impact Ionization Cross Sections of Highly Charged Ions ." Journal of Physics: Conference Series 635 (2015): 052067. AbstractWebsite
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2014
Guimarães, D., J. P. Santos, M. L. Carvalho, M. S. Diniz, B. House, and V. M. Miller. "Analytical evidence of heterogeneous lead accumulation in the hypothalamic defence area and nucleus tractus solitarius." NeuroToxicology 44 (2014): 91-97. AbstractWebsite

Lead is a potent toxicant associated with adverse cardiovascular effects and hypertension in children. Yet, few studies have determined if autonomic dysfunction associated with lead exposure involves brain regions which regulate autonomic responses. Central autonomic nuclei such as the nucleus tractus solitarius (NTS) and hypothalamic defence area (HDA) may be particularly sensitive to lead infiltration because they are adjacent to ventricles and areas with semi-permeable blood-brain-barriers. To understand if autonomic nuclei are sensitive to lead accumulation Wistar rats were exposed to lead from the gestational period and lead levels were quantified in brain regions that regulate arterial pressure: the NTS and the HDA. Energy dispersive X-ray fluorescence (EDXRF) was used to quantify total brain lead levels and revealed no differences between exposed and control tissues; measured values were close to the detection limit (2μg/g). Electrothermal atomic absorption spectrometry (ETAAS) was also used, which has a greater sensitivity, to quantify lead. There was ∼2.1μg/g lead in the NTS and ∼3.1μg/g lead in the HDA of exposed rats, and no lead in the control rats. There were greater lead levels in the HDA (∼50%) as compared with the NTS. Pathology studies revealed more prominent lead granules in the HDA as compared with the NTS. Increased microglia and astrocyte activation was also noted in the NTS of lead exposed rats as compared with the HDA. Regional differences in neuro-inflammatory responses likely contribute to heterogeneous lead accumulation, with enhanced clearance of lead in the NTS. Future studies will resolve the mechanisms underpinning tissue-specific lead accumulation.

Guimarães, D., J. P. Santos, M. L. Carvalho, M. S. Diniz, B. House, and V. M. Miller. "Analytical evidence of heterogeneous lead accumulation in the hypothalamic defence area and nucleus tractus solitarius." NeuroToxicology 44 (2014): 91-97. AbstractWebsite

Lead is a potent toxicant associated with adverse cardiovascular effects and hypertension in children. Yet, few studies have determined if autonomic dysfunction associated with lead exposure involves brain regions which regulate autonomic responses. Central autonomic nuclei such as the nucleus tractus solitarius (NTS) and hypothalamic defence area (HDA) may be particularly sensitive to lead infiltration because they are adjacent to ventricles and areas with semi-permeable blood-brain-barriers. To understand if autonomic nuclei are sensitive to lead accumulation Wistar rats were exposed to lead from the gestational period and lead levels were quantified in brain regions that regulate arterial pressure: the NTS and the HDA. Energy dispersive X-ray fluorescence (EDXRF) was used to quantify total brain lead levels and revealed no differences between exposed and control tissues; measured values were close to the detection limit (2μg/g). Electrothermal atomic absorption spectrometry (ETAAS) was also used, which has a greater sensitivity, to quantify lead. There was ∼2.1μg/g lead in the NTS and ∼3.1μg/g lead in the HDA of exposed rats, and no lead in the control rats. There were greater lead levels in the HDA (∼50%) as compared with the NTS. Pathology studies revealed more prominent lead granules in the HDA as compared with the NTS. Increased microglia and astrocyte activation was also noted in the NTS of lead exposed rats as compared with the HDA. Regional differences in neuro-inflammatory responses likely contribute to heterogeneous lead accumulation, with enhanced clearance of lead in the NTS. Future studies will resolve the mechanisms underpinning tissue-specific lead accumulation.

Rahangdale, H. V., M. Guerra, P. K. Das, S. De, J. P. Santos, D. Mitra, and S. Saha. "Determination of subshell-resolved <span class="aps-inline-formula"><math><mi>L</mi></math></span>-shell-ionization cross sections of gold induced by 15–40-keV electrons." Physical Review A 89 (2014): 052708. AbstractWebsite
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Amaro, P., C. I. Szabo, S. Schlesser, A. Gumberidze, E. G. Kessler, A. Henins, E. O. Le Bigot, M. Trassinelli, J. M. Isac, P. Travers, M. Guerra, J. P. Santos, and P. Indelicato. "A vacuum double-crystal spectrometer for reference-free X-ray spectroscopy of highly charged ions." Radiation Physics and Chemistry 98 (2014): 132-149. AbstractWebsite

Radiation Physics and Chemistry, 98 + (2014) 132-149. doi:10.1016/j.radphyschem.2014.01.015

Rahangdale, H. V., M. Guerra, P. K. Das, S. De, J. P. Santos, D. Mitra, and S. Saha. "Determination of subshell-resolved <span class="aps-inline-formula"><math><mi>L</mi></math></span>-shell-ionization cross sections of gold induced by 15–40-keV electrons." Physical Review A 89 (2014): 052708. AbstractWebsite
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