FCT: DF - Dissertações de Mestrado
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- New algorithms for pigmentation abnormalities detection in human skinPublication . Silva, Liliana Cristina dos Santos; Vieira, Pedro; Pinto, Pedro; Silva, PedroDetecting and localising regions of hyperpigmentation on facial skin is a challenging task in dermatology. These lesions are often diffuse and irregular, making them difficult to detect and track over time. Accurate localisation and classification of these regions are crucial for dermatological assessments and for companies like PhD Trials®, which evaluate the efficacy of topical products. The ability to extract precise detection metrics can significantly enhance the evaluation of treatment effectiveness, providing deeper insights into skin response. This dissertation presents a deep learning approach for developing a robust automatic object detection system for brownish hyperpigmentation on facial skin. Several pre- trained models, including YOLO and Faster R-CNN, were explored, along with different frameworks such as MATLAB and Detectron2. The proposed solution employs transfer learning to fine-tune these models with a custom dataset, optimising them for detecting and distinguishing lentigines from nevi. The research further extends the utility of these models by integrating segmentation using Otsu’s method, which enabled the delineation of the regions of interest and the extraction of monitoring metrics for each detected area, offering a more comprehensive evaluation of skin health. The results show that this solution outperforms PhD Trials®’ current software, providing superior detection and enhanced usability. The tool facilitates more reliable analyses in studies involving topical treatments, which are valuable for both clinical and cosmetic evaluations. Its ability to work with high-resolution camera images, not just dermoscopic ones, makes it suitable for broader clinical use, including telemedicine. This advancement represents a significant contribution to dermatological research and the development of AI-driven skin analysis tools.
- Mimicking animal behavior: Implementing reinforcement learning strategies on a wireless robotPublication . Pereira, Francisco Bastos; Marques, Hugo; Vieira, Pedro; McNamee, DanielAnimals constantly modify their behavior based on the outcomes of previous experiences; a process we commonly call learning. This work seeks to replicate certain biological learning processes in a mobile robotic platform, as the study of this processes in both biological and artificial systems has long been a subject of interest in neuroscience and robotics. In particular, the research focuses on operant conditioning, a learning mechanism in which an agent’s behavior is shaped by associating actions with a reinforcement, or punishment stimuli. In the mammalian brain, the basal ganglia is believed to play a key role in this process, implementing a kind of reinforcement learning framework that guides behavior through dopaminergic signals from the midbrain. To explore these principles, the study will utilize a wireless mobile robot developed at the Champalimaud Foundation. The robot will be trained to chase or avoid “objects” according to whether these have previously provided positive or negative feedback. These "objects" consist of images projected onto the ground by a ceiling-mounted projector and detected by the robot using a wireless camera. The ultimate objective is for the robot to learn associations between visual inputs and behavioral responses, ensuring it moves towards rewarding stimuli while avoiding negative ones. Throughout the project, we implement Reinforcement Learning techniques, specifically Temporal-Difference Learning. The programming of the robot as well as the experimental platform will is done by using Python and Bonsai, a reactive-based visual programming language, capable of naturally handling asynchronous streams of data.
- LOW TOTAL ELECTRON YIELD N-DOPED GRAPHENE COATINGS PRODUCED BY ELECTROPHORETIC DEPOSITIONPublication . Guerreiro, Pedro Miguel Alves; Bundaleski, NenadLow secondary electron emission (SEE) materials have gained significant attention in recent years, particularly in aerospace technologies, such as RF devices for satellite communications, and in fundamental particle physics studies. In high-intensity particle accelerators such as the High Luminosity Large Hadron Collider (HL-LHC) at CERN, materials with low SEE are crucial for mitigating electron cloud formation, thereby enabling higher maximum beam intensities, improved thermal conditions, and more reliable experimental results. This phenomenon results from the multipacting effect: electrons are generated either through ionization of the residual gas or via the photoelectric effect induced by synchrotron radiation. These high-energy electrons subsequently collide with the accelerator walls, producing secondary electrons. The electric field, produced by the bunches of positive particles, accelerates these secondary electrons, triggering a localized avalanche. The most common strategy to reduce the electron cloud formation is to coat the inner walls of accelerators with low Total Electron Yield (TEY) materials. Graphene is a promising candidate due to its inherently low SEE and surface roughness, which further reduces TEY. Recent studies revealed that nitrogen doping into graphene can lower its Secondary Electron Yield (SEY) even further, while also mitigating aging effects caused by repeated exposure to air. In this project, N-doped graphene free-standing powder was deposited onto metallic substrates, similar to those used as accelerator inner walls, using electrophoretic deposition (EPD). This technique was chosen for its ability to preserve the material’s original properties while offering a simple and cost-effective deposition method. Following the sample preparation, X-ray Photoelectron Spectroscopy (XPS) was used to characterize the samples in terms of surface chemical composition, while TEY measurements were performed. This allowed the identification of optimal deposition parameters and enabled the establishment of correlations between material characteristics and the TEY performance.
- ENCAPSULAMENTO DE UM INIBIDOR DE REPARAÇÃO DE ADN EM LIPOSSOMAS PARA TRATAMENTO DO CANCROPublication . Oliveira, Inês Alexandra dos Santos; Raposo, Maria de Fátima; Vieira, TâniaNeste trabalho pretendeu-se aprimorar o conhecimento de um tratamento inovador ba- seado na inibição de reparação do ácido desoxirribonucleico (ADN) através da utilização develiparib, uma molécula inibidora de uma proteína de reparação de ADN a Poli (ADP-ribose) Polimerase-1 (PARP1). Para tal, as moléculas de veliparib foram encapsuladas em lipossomas para que a entrega deste inibidor às células cancerígenas seja mais eficaz. Para se avaliar o efeito do inibidor e do inibidor encapsulado foram realizados estudos de citotoxicidade e fo- totoxicidade em duas linhagens de células. No desenvolvimento deste projeto as moléculas develiparib foram encapsuladas em lipossomas que foram preparadas a partir da mistura de 1,2- dipalmitoil-sn-glicero fosfocolina (DPPC) com 1,2 – dipalmitoil-sn-glicero-3-fosfoglicerol (DPPG). As soluções aquosas de veliparib e as emulsões de veliparib encapsulado em liposso- mas de diferentes concentrações, foram utilizadas em ensaios in vitro de citotoxicidade da molécula de veliparib em células cancerígenas denominadas de carcinoma de células escamo- sas (MET-1) e em células não cancerígenas de queratinócitos (HaCaT) e estudos de fototoxici- dade irradiadas com UV. Estes testes permitiram analisar a viabilidade celular após a exposição a diferentes concentrações do fármaco e o impacto da radiação UV na resposta celular. Os resultados indicam que o veliparib encapsulado em lipossomas é citotóxico nas células MET-1 e ao mesmo tempo reduz efeitos adversos nas células HaCaT sugerindo maior seletividade do tratamento. Estes resultados demonstram que esta abordagem pode reduzir a toxicidade nos tecidos saudáveis, melhorar a qualidade de vida dos pacientes e oferecer outra perspetiva de terapia anticancerígena.
- Evaluating the Potential of Gold-coated Nanodiamonds as Radiosensitizers to Enhance the Effectiveness of Radiation TherapyPublication . Alves, Gil Duarte Cabrita Dias; Belchior, Ana; Cruz, JoãoCancer remains one of the leading causes of death worldwide, demanding continuous advancements in therapeutic strategies. Radiotherapy is a widely used treatment modality, but its effectiveness is often limited by radioresistant cancer cells and collateral damage to healthy tissues. To address this issue, radiosensitizers have emerged as a promising solution to enhance the effectiveness of radiotherapy by locally increasing the radiation- induced damage to cancer cells, while minimizing harm to the surrounding healthy tissues. In this context, gold nanoparticles have demonstrated a considerable radiosensitizing potential, while nanodiamonds have been explored for their fluorescence properties. Accordingly, recent investigations suggest that by combining these materials into gold- coated nanodiamonds (NDAus), it may be possible to integrate radiosensitization with bioimaging, enabling theranostic applications. In this study, the radiosensitizing potential of NDAus was assessed in lung cancer cells exposed to 𝛾-rays, X-rays and protons, delivered by a cobalt-60 irradiator, a clinical photon beam and a Van de Graaff accelerator, respectively. The cell survival response was evaluated using clonogenic assays, while fluorescence microscopy was employed to investigate mechanisms of DNA damage and repair, reactive oxygen species production and lipid droplets formation. Results demonstrated a predominant radiosensitizing effect at an NDAus concentration of 10 𝜇g/mL under X-ray irradiation, with significant cell effects observed in the DNA damage and repair dynamics, as well as in the reactive oxygen species levels. This work was distinguished with the Young Investigator Award at the 49𝑡 ℎ conference of the European Radiation Research Society and was presented orally at both this meeting and the 11𝑡 ℎ Congress of Proteção Contra Radiações dos Países de Língua Portuguesa. Addi- tionally, the work was further discussed in the PIANOFORTE intensive course “Particle Irradiation: Molecular, Cellular and Tissue Effects”.
- Nuclear analytical techniques applied to determine black smokers’ plumes physicochemical propertiesPublication . Carmo, Mariana Custódio do; Cruz , João; Raposo, Maria de FátimaThe demand for Critical Raw Materials (CRM) is expected to grow significantly, driven by the need to reduce greenhouse gas emissions and mitigate climate change. The use of low-carbon energy technologies is essential, including electric vehicle batteries, wind turbines, and solar panels. All of these rely on CRM such as Lithium, Cobalt, and Rare Earth Elements (REE). Black Smokers are chimneys naturally formed on the ocean floor, releasing plumes of super-heated, mineral-rich water that precipitate near the formation. Some companies are already seeking to exploit these minerals by collecting fragments from the seabed around the chimneys; however, such practices can have devastating consequences for marine life. In this work, the physicochemical properties of Black Smoker rocks were studied using nuclear analytical techniques such as Particle-Induced X-Ray Emission (PIXE), Particle- Induced Gamma Ray Emission (PIGE), and Elastic Backscattering Spectrometry (EBS) to better understand the minerals they release. The results are promising, as several valuable elements, including some REE, were identified. Building on this knowledge, we propose and test a methodology to recover materials released by Black Smokers using functionalized surfaces capable of adsorbing specific minerals. These surfaces were created and tested for Au and Eu, and their adsorption efficiency was evaluated, showing encouraging results. This study provides a first step towards a sustainable strategy for recovering CRM from hydrothermal vent systems, while highlighting the need to optimize adsorption efficiency and assess large-scale applicability.
- Light fragment detection using Resistive Plate Chambers Contribution to GSI experiment G249Publication . Copeto, Pedro David Arsénio; Redondo, Daniel; Cruz, JoãoThis thesis presents the development, simulation, and experimental application of recon- struction methods for light fragment detection using a Resistive Plate Chamber (RPC) in the framework of the R3B collaboration at GSI. The work is carried out in the context of experiment G249, which investigates the structure of the neutron-rich nucleus 25F via quasi-free scattering. A central part of the thesis is the development of multidimensional fitting (MDF) functions within the R3BRoot framework, designed to reconstruct physical quantities from detector observables. Simulated datasets were used to train the MDF models with input from the FOOT tracking detectors, the GLAD dipole magnet, and the RPC. Functions were validated in Geant4-based simulations, achieving high predictive accuracy with uncertainties down to 10−3, demonstrating robustness under realistic detector resolutions. Simulations were also performed to estimate the fragment composition reaching the RPC, identifying deuterons, tritons, and alpha particles as dominant contributions. The RPC performance during the G249 beam time was evaluated. Key results include a time resolution of 38 ps, efficiency of ∼93% close to expectations, and identification of problematic strips affecting calibration. Preliminary applications of the MDF method to real data showed promising results for p/Q but poorer resolution for A/Q, attributed to ongoing detector calibration. Overall, this work highlights the RPC’s potential to evolve from a proton and timing detector to an active fragment reconstruction device, extending its role within R3B and at FAIR.
- Relativistic effects in mesonsPublication . Valverde, Vasco Mata Nascimento Gomes; Stadler, Alfred; Biernat, Elmar; Guerra, MauroMost mesons consist of a quark and an antiquark, bound together by the strong interac- tion. These bound states can be remarkably well described by the nonrelativistic Cornell potential, which is the sum of one-gluon-exchange potential term and a linear confin- ing potential term. In order to describe the observed masses of mesons with different quantum numbers, the inclusion of spin-dependent relativistic corrections is required. Most quark model calculations solve a Schrödinger equation with the Cornell potential in coordinate space, with spin-dependent corrections usually included perturbatively, whereas spin-independent relativistic corrections are often omitted. Momentum-space calculations, on the other hand, are rare due to difficulties imposed by the presence of singularities in the kernel of the integral equations. A new method for treating these sin- gularities in the kernel enables the application of standard numerical solution techniques like the Nyström method to solve the resulting eigenvalue equation. In this work we de- velop a nonperturbative momentum-space treatment of the first-order relativistic correc- tions to the Cornell potential, employing the Nyström method as the numerical solution. The spin-dependent interactions produce spectra with smoothly converging eigenvalues and well-behaved wave functions. Some spin-independent terms still present numerical challenges, in particular for lighter mesons. Nevertheless, the methods presented here establish a viable approach to handling relativistic corrections to the Cornell potential in momentum space, paving the way for future studies. The research work described in this dissertation was carried out in accordance with the norms established in the ethics code of Universidade Nova de Lisboa. The work described and the material presented in this dissertation, with the exceptions clearly indicated, constitute original work carried out by the author.
- Integrating Wearable Technology with METHIS Digital Platform for Enhanced Chronic Disease ManagementPublication . Santos, Maria Matilde Nascimento Ramos Martins dos; Lapão, LuísWith the ageing of the global population, the need for services that aim at increasing quality of life has increased exponentially. An ageing population faces a greater number of individuals with chronic diseases, a large percentage of whom suffer from multimorbidity. Patients with multimorbidity constitute a greater allocation of resources, time, and money, as they have a greater need to consult with their doctors and use the available health services. This puts pressure on Primary Health Care, which is responsible for monitoring and managing chronically ill patients. One way to combat this problem is to provide digital health systems with real-time monitoring of patients’ health parameters. This empowers patients to manage their health and incites professionals to make evidence-based decisions that rely on relevant information. This project presents a system for monitoring each individual’s daily number of steps and heart rate recorded using a smartband. The data collected is sent to the METHIS Digital Platform, a multimorbidity management system that aims to promote patient involvement and direct communication with healthcare providers. Participants in a pilot study revealed that they felt motivated to increase their daily step count when confronted with the number displayed on the device. Similarly, doctors and nurses validated that the information collected improves the continuous monitoring of patients with multimorbidity. In conclusion, the incorporation of real-time monitoring facilitated by wearable tech- nology in this project represents a significant stride toward enhancing the quality of information pertinent to healthcare decision-making processes. By utilizing wearable devices in conjunction with the METHIS Digital Platform, this approach fosters heightened precision and expediency in health data acquisition, thereby equipping healthcare practitioners and patients with invaluable insights for judicious management of chronic conditions.
- Production, characterization and in vitro evaluation of a ternary dermal skin substitutePublication . Marques, Diana Mendes; Silva, Jorge; Vieira, TâniaSkin wounds heal through a series of complex physiological processes triggered by injury to restore homeostasis. In developed countries, it is estimated that 1–2% of individuals will experience a chronic, non-healing wound at some point in their lives, presenting a significant global health challenge. Treating such injuries remains clinically difficult, as existing skin substitutes fail to promote the regeneration of extensively damaged skin. Limitations such as rapid degradation and the inability to fully replicate native tissue structure and function have driven researchers to explore improved solutions. In this study, four different hydrogels were developed using chitosan (CS), bovine gelatin (GEL), and hyaluronic acid (HA) in different combinations: CS-GEL, CS-HA, GEL-HA and CS-GEL-HA. Crosslinking was performed using EDC/NHS, followed by NaOH treatment to enhance stability. The hydrogels were characterized in terms of their morphology using Scanning Electron Microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), water retention, swelling behaviour and degradation rates. Biocompatibility was assessed through cytotoxicity tests, while their potential for skin regeneration was evaluated by examining fibroblast adhesion and proliferation. The incorporation of the three polymerswas employed to achieve a composition resembling the extracellular matrix. The findings suggest that some hydrogels have potential as wound healing biomaterials due to their ability to maintain hydration, support fibroblast proliferation, and resist rapid degradation. Future studies will focus on optimizing the hydrogel formulation to enhance mechanical properties and investigating their performance in vivo wound healing models.