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Centre of Physics and Technological Research
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Study of Low-energy Electron Collisions with Molecules of Biological Relevance
Publication . Loupas, Alexandra Cristina Rodrigues; Gorfinkiel, Jimena; Limão-Vieira, Paulo
This thesis is focused on the application of the R-matrix method, as implemented in the
UKRmol and UKRmol+ suites, to study low-energy electron collisions with three medium-sized
molecules of biological relevance: para-benzoquinone, thiophene and alanine. Our goals for
all the targets are mainly three: (i) to identify and characterize respective resonances; (ii) to
calculate elastic and inelastic integral and elastic differential cross sections; and (iii) compare
our results with the literature. To do so, we use several scattering models, choosing the most
suitable on the basis of the characteristics being investigated: Static Exchange, Static Exchange
plus Polarization and/or Close-Coupling approximation.
Specially at higher energies, we find an unexpectedly large number of resonances for the
three targets, most of them of core-excited and core-excited shape character. We compare our
results with other calculations and/or experiments in the literature, but the absence of detailed
experimental results for many targets at these energies precludes a meaningful comparison.
Nonetheless, three scenarios are then obtained: in the first one, for para-benzoquinone, the
agreement with previous results is satisfactory; in the second, for thiophene, is excellent; and
finally, for alanine, there is not much prior information on the literature to make decisive conclusions.
This work was all published in peer-reviewed journals.
Study of the Effects of Cold Atmospheric Plasmas on Skin Cancer Cells
Publication . Pereira, Sara Raquel Gemelgo; Venceslau, Susana; Ribeiro, Paulo
Cold atmospheric plasmas (CAPs) are a specific type of non-thermal plasmas mainly composed of reactive oxygen and nitrogen species (ROS and RNS, respectively), UV radiation and charged particles. In the last years, liquids treated by CAPs (indirect CAPs treatments) have attracted attention in oncology due to its ability to destroy cancer cells with an effectiveness similar to direct irradiation of cells by CAPs. Moreover, these indirect treatments offer the advantage of avoiding the effects of UV radiation and of the electrical fields present in plasmas being their effects mainly dependent on the reactive species produced in CAPs treated medium. To better understand the mechanisms behind the interaction between CAPs, treated medium and cells, in this work, a plasma jet device was engineered for study the vulnerability of four human cell lines (SCC-15, Met-1, HaCat, and HGF-1) to the culture medium previously exposed to CAPs. Besides that, also the characterization of the liquids exposed to plasma was done, by quantification of the concentration of H2O2, nitrate, and nitrite, using colorimetric assays and ion chromatography, respectively. To prove that the effects of exposure to CAPs are dependent on the used device, mass spectrometry studies were carried out in order to compare the spectra obtained using the developed device with that of the kINPen09. Based on this study, it was possible to investigate the oxidation of thiol groups of a cysteine solution. Cysteine was chosen since it is an amino acid that acts as a biomarker of oxidative damage. To complete these results, the study of phenol degradation and the addition of scavengers to the treated medium were also evaluated. According to the obtained results it could be observed that the cancer cell lines (SCC-15 and Met-1) in study are more sensitive to the liquids treated by CAPs than the non-cancer ones (HGF-1 and HaCat). The CAPs effects, in the case of the developed jet, seem to be mainly related to the mechanisms induced by RNS species, while in treatments performed using kINPen09, a higher oxidation rate was observed, due to the high concentration of ROS species, mainly H2O2.
Liposomes encapsulating catechins: a biophysical approach for skin cancer therapy
Publication . Pires, Ana Filipa Soares; Raposo, Maria de Fátima
Every year, a large number of skin cancer cases caused by a prolonged ultraviolet
radiation exposure, are diagnosed around the world. Epigallocatechin–3–
gallate (EGCG) derived from green tea leaves, display protective effect against
oxidative stress which reduce the risk of contracting skin cancer. However, frequently,
the antioxidant and anti–inflammatory activities of EGCG in are compromised
because this molecule is extremely unstable and rapidly degraded in
physiological conditions. Considering these issues, the main goal of this thesis
was developed a stable liposomal nanocarrier for topical/transdermal delivery of
EGCG, firstly, to increase its bioavailability and, secondly, to offer an desirable
skin protection against harmful effects of UV radiation. Primarily, the molecular
mechanisms between EGCG and different phospholipids were studied using
Langmuir experiments, revealling the affinity and localization of EGCG on each
lipidic membrane, which according to the results depends on the molecular organization
of lipidic monolayer (functional groups anchored at headgroup) and of
the degree of protonation of EGCG. EGCG establishes electrostatic and hydrogenbonding
interactions with zwitterionic (DMPC, DPPC) and anionic (DPPG and
DPPS) phospholipids, which condense the monolayers and alter the membrane’s
potential and compressibility. Regarding the irradiation experiments, the results
indicated that EGCG efficiently slows down the oxidant events in monolayers and
in lipid bilayers, which were produced by blue and ultraviolet radiation exposure,
respectively. Lastly, the nanofibers meshes containing EGCG-loaded liposomes
are biocompatible, support human fibroblasts adhesion and scavenge the oxidant
species generated by UV radiation, which guarantees a higher cell survival.
Highly efficient side-pumped solar laser with enhanced tracking-error compensation capacity
Publication . Tibúrcio, Bruno D.; Liang, Dawei; Almeida, Joana; Garcia, Dário; Vistas, Cláudia R.; Morais, Paulo J.; CeFITec – Centro de Física e Investigação Tecnológica; DF – Departamento de Física; Elsevier Science B.V., Amsterdam.
We report here a significant numerical improvement in side-pumped solar laser collection efficiency and solar-to-laser conversion efficiency, with an enhanced tracking error compensation capacity. Two side-pumped configurations, a single-rod and a dual-rod scheme were studied. The former pumped a thick laser rod with the full collection area of a parabolic mirror and the latter pumped two thin laser rods simultaneously, each rod being pumped by half of the collection area of the same concentrator. Both configurations were composed of a fused silica aspheric lens and a 2D-shaped-semicylindrical pump cavity, within which the Nd:YAG rods were mounted, allowing a tight focusing of the concentrated solar pump power from the focal spot of the heliostat–parabolic mirror solar energy collection and concentration system and an efficient pumping to the laser crystals. 42.70 W continuous-wave multimode solar laser power, corresponding to 27.37 W/m2 collection efficiency, and 3.26% solar-to-laser power conversion efficiency were numerically calculated for the single-rod scheme, being 1.55 and 1.34 times, respectively, higher than the previous state-of-the-art experimental records of side-pumped solar laser. For the dual-rod scheme, 37.72 W multimode solar laser power, corresponding to 24.18 W/m2 collection efficiency, and 2.88% solar-to-laser power conversion efficiency were numerically obtained, being 1.37 and 1.19 times, respectively, more than the previous record in side-pumping configurations. More importantly, largely enhanced brightness figure of merit, thermal performance and tracking error compensation capacity were attained by the dual-rod scheme, as compared to that of the single-rod scheme.
Thermally stimulated desorption optical fiber-based interrogation system
Publication . Raposo, Maria; Xavier, Carlota; Monteiro, Catarina; Silva, Susana; Frazão, Orlando; Zagalo, Paulo; Ribeiro, Paulo António; DF – Departamento de Física; CeFITec – Centro de Física e Investigação Tecnológica; MDPI - Multidisciplinary Digital Publishing Institute
Thin graphene oxide (GO) film layers are being widely used as sensing layers in different types of electrical and optical sensor devices. GO layers are particularly popular because of their tuned interface reflectivity. The stability of GO layers is fundamental for sensor device reliability, particularly in complex aqueous environments such as wastewater. In this work, the stability of GO layers in layer-by-layer (LbL) films of polyethyleneimine (PEI) and GO was investigated. The results led to the following conclusions: PEI/GO films grow linearly with the number of bilayers as long as the adsorption time is kept constant; the adsorption kinetics of a GO layer follow the behavior of the adsorption of polyelectrolytes; and the interaction associated with the growth of these films is of the ionic type since the desorption activation energy has a value of 119 ± 17 kJ/mol. Therefore, it is possible to conclude that PEI/GO films are suitable for application in optical fiber sensor devices; most importantly, an optical fiber-based interrogation setup can easily be adapted to investigate in situ desorption via a thermally stimulated process. In addition, it is possible to draw inferences about film stability in solution in a fast, reliable way when compared with the traditional ones.
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Entidade financiadora
Fundação para a Ciência e a Tecnologia
Programa de financiamento
6817 - DCRRNI ID
Número da atribuição
UID/FIS/00068/2019