Dipòsit Digital de la Universitat de Barcelona
El Dipòsit Digital de la Universitat de Barcelona és el repositori institucional que conté en format digital els materials derivats de l'activitat docent, investigadora i institucional de la comunitat universitària.
Enviaments recents
Treball de fi de grauEnergy loss of atmospheric muons and the Bethe–Bloch formula(2026-06) Bestard Navarro, Elsa; Torres Rincón, Juan M. ; Fernández Varea, José MaríaThe stopping power of atmospheric muons in silicon is studied by combining the Bethe-Bloch formalism with a semiconductor detector called MiniPix. The Bethe–Bloch formula was implemented numerically, correctly reproducing the characteristic energy loss regimes. The energy calibration was performed using the γ emission lines from a source of 241Am (59.54 keV and 26.34 keV). During a 15-hour acquisition period, 267 muon candidates were identified and selected for their linearity and track length. A numerical inversion of the Bethe–Bloch function was applied to reconstruct the energies of the muons from the measured stopping power values. The energies were found to be systematically underestimated, attributed to the geometric incompatibility between γ-based calibration and the extended charge deposition profile of muon tracks. Although a quantitative comparison with the Bethe–Bloch prediction could not be achieved, the tracks recorded are qualitatively consistent with the expected behavior of the muons, validating the detection methodology.- Treball de fi de grauNanoscale Diffusion Regimes of Amyloid-β Studied by Liquid-Phase TEM(2026-06) Benito Carayol, Adrià; Ruiz Pérez, Eloisa LorenaThis project studies the diffusion regimes of misfolded proteins amyloid-β-42 (Aβ-42) aggregates observed by liquid-TEM. Videos acquired using this technique were analysed to reconstruct particle trajectories and thus quantify their dynamic behaviour at the nanometric scale. Due to the low contrast of these protein samples, the videos were preprocessed by normalisation, clipping, Gaussian filtering, and averaging of consecutive frames. Then, regions of interest were selected, and particle tracking was performed to obtain their trajectories. From these trajectories, the mean squared displacement (MSD) was calculated and fitted using a power law to determine the diffusion exponent α. Large aggregates of diameters circa 100nm yielded α ∼ 0 and therefore they showed negligible translational mobility while for small oligomers of diameter circa 8nm the exponent α ∼ 1 showing a behaviour compatible with normal Brownian diffusion.
- Treball de fi de grauNuclear Matter at Finite Temperature(2026-06) Bañuelos Sánchez, Arnau; Centelles Aixalà, MarioIn this work, we compute the equation of state of hot nuclear matter and study how thermodynamic quantities such as the entropy, free energy, and pressure evolve with temperature as functions of density. We also analyse the role of isospin asymmetry, showing how the relative neutron and proton content influences the stiffness of the equation of state and the saturation properties of the system. In addition, the free symmetry energy is evaluated as a measure of the isospin dependence of nuclear matter.
- Treball de fi de grauCosmic Censorship Violation at Large D(2026-06) Arias Aranda, Guillem; Luna i Perelló, RaimonIn this work, the Large-D limit of General Relativity is used as a framework to investigate violations of weak cosmic censorship and ultimately to reproduce the results of [3, 4]. In this limit, Einstein’s equations simplify allowing gravitational dynamics to be described in terms of collective fields. A dimensional reduction is performed in order to work with spacetimes of an arbitrary number of dimensions. We study the stability of different objects in this limit and numerical simulations do show that, for sufficiently high angular momentum, there are no stable stationary black hole solutions in the theory. Finally, we provide evidence for a violation of weak cosmic censorship by simulating the collision of two boosted black holes.
- ArticleMetabolic Screening of Gut Microbiota by Fourier-Transform Infrared Spectroscopy(American Chemical Society, 2026-06-12) Sayol Altarriba, Anna; Aira Gómez, Andrea; Martín-López, Eva; Villasante, Anna; Albarracín, Rosa; Faneca, Joana; Pitart, Cristina; Roca Subirà, Ignasi; Casals Mercadal, Gregori; Marco Colás, Santiago; Villanueva Cañas, José Luis; Casals Pascual, ClimentShort-chain fatty acids (SCFAs) are bacterial metabolites with crucial roles in host homeostasis and immune system modulation. Given their benefits, they have been proposed as markers of healthy microbiota. However, accurate SCFA quantification typically requires gas chromatography coupled with mass spectrometry (GC-MS), which is time-consuming, expensive, and requires specialized personnel and equipment, limiting its routine use for stool quality assessment in clinical contexts. In this initial feasibility study, we explored the use of Fourier transform infrared (FT-IR) spectroscopy as a rapid metabolic screening approach for stool samples. Analysis of SCFA-associated spectral windows enhanced discrimination between healthy and dysbiotic stool samples with <em>Clostridioides difficile</em> infection using principal component analysis. FT-IR is not intended to replace GC-MS for precise SCFA quantification but rather to provide a rapid screening of metabolically relevant differences. Although additional validation is still needed, the present study provides a robust proof-of-concept demonstrating the feasibility of applying FT-IR spectroscopy to clinical stool samples. Combined with the widespread availability of this technology in most hospitals, these advantages highlight its potential for future development as a tool for routine screening in clinical laboratories.