Public display of deposited theses

DOCTORAL DEGREE IN AUTOMATIC CONTROL, ROBOTICS AND VISION

• LAPLAZA GALINDO, JAVIER: Human motion and intention prediction/detection for human-robot collaboration
  
  Author: LAPLAZA GALINDO, JAVIER
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN AUTOMATIC CONTROL, ROBOTICS AND VISION
  Department: Institute of Industrial and Control Engineering (IOC)
  Mode: Normal
  Deposit date: 29/10/2024
  Deposit END date: 12/11/2024
  Thesis director: SANFELIU CORTES, ALBERTO | MORENO NOGUER, FRANCESC D'ASSIS
  Thesis abstract: This doctoral thesis develops and evaluates advanced human motion prediction models to improve human-robot interactions in handover and harvesting tasks. The research creates three unique datasets and utilizes pose detection algorithms and RGBD cameras for 3D reconstruction of human skeletons.A deep learning model based on Attention and Graph Convolutional Networks (GCN) is proposed to enhance prediction accuracy by integrating the robot’s end effector position. The research shows greater accuracy when considering the approach and pre-contact phases separately.Additionally, by including obstacles and human intentions in the models, prediction accuracy improves further, and a user study confirms this enhances interaction quality in terms of sociability, naturalness, and comfort. The thesis also investigates body gestures as a communication channel, finding users prefer gesture-based communication over traditional methods.In summary, the research significantly contributes to human-robot interaction by providing robust datasets and advanced prediction models, enhancing the naturalness and effectiveness of collaborative tasks.
  

DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS

• ZENG, MING: Barocaloric and multicaloric effects under hydrostatic pressure and electric field
  
  Author: ZENG, MING
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTATIONAL AND APPLIED PHYSICS
  Department: Department of Physics (FIS)
  Mode: Normal
  Deposit date: 05/11/2024
  Deposit END date: 18/11/2024
  Thesis director: LLOVERAS MUNTANE, POL MARCEL | TAMARIT MUR, JOSE LUIS
  Thesis abstract: At present, HFC refrigerants with a global warming potential of thousands of times that of CO2, are widely used in air conditioners and, refrigerators. Due to lack of maintenance and poor management, and low or moderate efficiencies, cooling devices contribute to approximately 8% of total greenhouse gas emissions. Given the increasing global warming, it is urgent to find new cooling technologies with low carbon emissions. Cooling methods based on solid-state caloric effects (adiabatic temperature changes ∆T and isothermal entropy changes ∆S) driven by external fields have been proposed as an environmentally friendly alternative to today's gas compression equipment. This thesis focus on caloric effects driven by hydrostatic pressure (barocaloric, BC) and/or electric field (electrocaloric, EC) near first-order phase transitions. In particular, BC effects have been investigated in different material families: Inorganic salts, Mn-based antiperovskites, superionic plastic crystals, and melting of stearic acid encapsulated in metal–organic frameworks (MOFs). Multicaloric effects were also investigated under simultaneous application of pressure and electric field on Lead Scandium Tantalate (PbSc0.5Ta0.5O3, PST). For this purpose, standard and modulated differential scanning calorimetry, and differential thermal analysis under different applied pressure and/or electric field were performed on the mentioned materials. The obtained data were combined with temperature-dependent volume data to construct the isofield entropy curves from which the caloric effects were calculated using the quasi-direct method. Concerning antiperovskite manganese nitrides: Mn3Cu1 – xSnxN, giant inverse BC effects were obtained. Interestingly, all these samples exhibit reversible|∆S| > 20 J K−1 kg−1 at pressures below 100 MPa thanks to a hysteresis lower than 1 K, which is minimized at the equiatomic composition x=0.5. Concerning LiCB11H12, this compound exhibits a high-temperature phase that combines superionic conductivity and orientational molecular disorder which appears above a phase transition with colossal latent heat. In that case, we obtained outstanding conventional reversible |∆S| 200 J K−1 kg−1 and |∆T| 10 K, respectively ∆p 100 MPa, which increase up to |∆S| 280 J K−1 kg−1 and |∆T| 32 K, respectively, under the applied pressure of only ∆p 230 MPa. Concerning MIL−101 (Cr)−NH2+x% stearic acid (SA) system, that with x = 80% SA displays |∆T| 25 K and |∆S| 550 J K−1 kg−1 under ∆p 200 MPa. These results suggest that MOFs can be used as suitable solid framework for encapsulation of non-solid high-performance BC materials. Finally, the multicaloric effects in the prototypical ferroelectric PST have also been studied. Unprecedented calorimetry experiments under simultaneous electric fields E up to around 7 kV cm−1 and hydrostatic pressures p up to 400 MPa were conducted across the ferroelectric transition on PST. The so far unexplored 3-dimensional phase diagram T(p,E) was obtained and analyzed. It was demonstrated that multicaloric effects may provide opportunities that cannot be achieved by monocaloric effects, such as tuning or expansion of temperature ranges and efficiency improvement. This research has demonstrated the feasibility, novelty, and impact of multicaloric effects under p and E, thus opening up a new area of caloric effects that should provide new physical insights on the wide family of ferroelectrics.
  

DOCTORAL DEGREE IN COMPUTING

• MOLINA LÓPEZ, ELENA: Advanced Interaction in Immersive Analytics Systems for Molecular Visualizations
  
  Author: MOLINA LÓPEZ, ELENA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN COMPUTING
  Department: Department of Computer Science (CS)
  Mode: Normal
  Deposit date: 07/11/2024
  Deposit END date: 20/11/2024
  Thesis director: VÁZQUEZ ALCOCER, PERE PAU
  Thesis abstract: The rapid evolution of computational technologies and data processing algorithms has led to an unprecedented increase in data generation across various fields, including economics, social sciences, medicine, and particularly in the biological data realm, which is the focus of this thesis. This surge necessitates the development of innovative methods for data analysis and visualization, particularly in immersive environments such as Virtual Reality (VR), Augmented Reality (AR), and Mixed Reality (MR). These technologies offer unique opportunities for interactive exploration of complex datasets that present great challenges. For instance, the accurate representation of scientific data, especially those like molecular structures with three-dimensional (3D) components that create complex scenes with a high number of components and occlusion, is enhanced by these tools that preserve spatial relationships and provide contextual representations, therefore helping in the understanding of these structures in a 3D environment. This thesis aims to address the challenges associated with visualizing and interacting with complex molecular models. The research focuses on two primary areas: enhancing the perception of 2D data visualizations in immersive environments and developing advanced interaction techniques for 3D molecular data. Specifically, the thesis investigates effective design strategies for 2D charts such as Violin plots and Heatmaps, and introduces novel methods for precise selection and manipulation of molecular structures, with a particular emphasis on DNA and protein models. By leveraging immersive analytics, the research demonstrates improved comprehension and decision-making capabilities through more interactive and immersive data exploration tools.Key objectives include advice for the design of effective 2D charts within 3D environments, the development of advanced interaction techniques for complex scenes with protein structures in VR, and a prototype application for the 3D visualization of chromatin models. These advancements enhance our ability to analyze and interpret complex biological data, paving the way for more effective scientific research and discovery.In conclusion, this thesis provides significant insights into the integration of data visualization and interaction techniques within immersive environments, offering a foundation for future research and applications in various scientific domains.
  

DOCTORAL DEGREE IN CONSTRUCTION ENGINEERING

• MENDUIÑA MONTERO, RAUL: Estudio teórico y experimental del refuerzo mediante recrecido de encepados rígidos de hormigón armado
  
  Author: MENDUIÑA MONTERO, RAUL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN CONSTRUCTION ENGINEERING
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 25/10/2024
  Deposit END date: 08/11/2024
  Thesis director: BAIRÁN GARCÍA, JESÚS MIGUEL | MARI BERNAT, ANTONIO RICARDO
  Thesis abstract: The need to strengthen foundations in existing structures has become increasingly important, driven by the aging of constructions and the growing demand for enhanced structural capacity, whether due to changes in use or updates to regulatory standards. In the case of rigid RC foundations, these often behave as D-regions, areas where stress and deformations do not follow a linear pattern and require specialized design approaches. While numerous studies have focused on the reinforcement of B-regions, research addressing the behavior of D-regions, such as rigid foundations, remains limited. This thesis addresses this gap by analyzing the behavior and reinforcement techniques through the enlargement of rigid reinforced concrete pile caps, a solution that increases their structural capacity. Special emphasis is made on the application of the Strut-and-Tie Method (STM), an approach particularly suited for D-regions, as it simplifies the non-linear behavior of stresses in these areas, facilitating the understanding of the structural mechanisms involved.The research combines a comprehensive literature review with an experimental campaign, in which reinforcement of rigid RC pile caps through enlargement was evaluated. The experimental tests and Non-Linear Finite Element Analysis (NLFEA) helped study the structural behavior of the pile caps in different configurations. The analysis of the results shows that enlargement is an effective technique to improve the structural capacity of foundations, although its success depends on factors such as the quality of the joints between the new and existing concrete and, to a lesser extent, the arrangement of secondary reinforcement. Additionally, the behavior in the Serviceability Limit State (SLS) was analyzed, and strut-and-tie models were proposed, with concrete ties whose tension varies with the evolution of crack widths. These models are capable of coherently explaining the behavior observed experimentally across the entire load range.Following the presentation of the experimental results, different design methodologies are compared, and the use of STM for reinforced pile caps is proposed, with a particular focus on verifying the struts crossing the joints between the original and enlarged sections. The findings are not only applicable to various structural scenarios but also establish a solid foundation for future research on the reinforcement of D-regions, making a significant contribution to the preservation and enhancement of existing structures.
  

DOCTORAL DEGREE IN ELECTRICAL ENGINEERING

• DAKIC, JOVANA: Tools for analysis of novel concepts of transmission systems for offshore wind power plants
  
  Author: DAKIC, JOVANA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ELECTRICAL ENGINEERING
  Department: Department of Electrical Engineering (DEE)
  Mode: Normal
  Deposit date: 04/11/2024
  Deposit END date: 15/11/2024
  Thesis director: GOMIS BELLMUNT, ORIOL | CHEAH MAÑÉ, MARC
  Thesis abstract: Achieving the goals set forth by the Paris Agreement requires to cut global greenhouse gas emissions in half by 2030. Significant portions of high-emission technologies should be substituted with zero- or low-carbon alternatives in less than six years. Expanding renewable energy is crucial for transitioning to a sustainable energy landscape. Currently, the offshore wind industry stands at the brink of significant expansion, regarded as an efficient energy source due to high wind speeds at sea, great consistency, and lack of physical interference that are common on land or from human-made structures. In addition, the notable technological advances in wind turbine size and power ratings lead to an increase in volume of projects and investments.On the other side, the new connections of numerous inverters to the grid bring fast changing rules in the grid codes and challenge the development time line. Also, the high inflation rates affect the project costs and decelerate the energy transition.Early-phase planning of offshore wind projects is one of the primary steps that facilitates overcoming the challenges mentioned earlier. The benefit stands in developing a digital model of a potential wind power plant project to be able to anticipate future conditions and plan on a global scale. Therefore, this thesis focuses on determining cost effective solutions of transmission systems for integration of offshore wind power plants. A tool is developed to enable a thorough evaluation of key technical and financial characteristics of different type of transmission configurations and assessment of viability. Firstly, the focus is the optimal design of High Voltage Alternating Current (HVAC) systems, by including minimization of the cost with a special emphasis on benefits of installing a mid-cable reactor. The well-known rivalry between using HVAC and High Voltage Direct Current (HVDC) systems is analysed in detail for a range of offshore wind power plant rated powers and distances from the shore. Further on, the tool is expanded with the possibility to design the system to achieve grid code reactive power compliance. In addition, the offshore wind power plant is modelled more in detail, therefore maximum contribution of the wind turbines to the transmission system are studied. The collaboration with Vatenfall enabled application and validation of the tool based on data from existing and future projects.Finally, design of a novel transmission system including Low Frequency Alternating Current (LFAC) technology is investigated. The consequence of low frequency on the sizing and cost of the system is explained, while including a range of non-standard frequencies. Moreover, the comparison and break-even distance of all three technologies are presented.
  

DOCTORAL DEGREE IN ELECTRONIC ENGINEERING

• GON MEDAILLE, AXEL: Advanced characterization and modelling of innovative low-dimensional materials for solar cells applications
  
  Author: GON MEDAILLE, AXEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ELECTRONIC ENGINEERING
  Department: Department of Electronic Engineering (EEL)
  Mode: Normal
  Deposit date: 05/11/2024
  Deposit END date: 18/11/2024
  Thesis director: SAUCEDO SILVA, EDGARDO ADEMAR | JEHL, ZACHARIE VICTOR SAMUEL NATHANAEL
  Thesis abstract: Energy transition keeps its course while new materials keep emerging promising better impact on environment. Among those materials, Q-1D chalco-halides materials using Bi and Sb, S, Se and I, Br, giving rise to wide combinations of materials. Most of them present the unique feature of a Pnma crystallographic structure allowing them to grow alongside one preferential direction, giving them optoelectronic properties highly seeked for PV applications, in particular for thin film solar cells. So far, Sb2Se3 has been the most investigated material within this class of material with an efficiency up until now of XX% in substrate configuration under AM1.5 spectrum illumination. Indeed, Sb2Se3 presenting the same crystallographic structure, is well-known within the PV community. However, despite having promising results over the past years, Sb2Se3-based solar cells reached a bottleneck in terms of efficiency. More generally, Q-1D chalco-halides materials either lack or do not have characterization data due to their recent emergence or re-emergence for some materials.This thesis will intend to address Sb2Se3 bottlenecks and present some solutions to allow Sb2Se3-based and other Q-1D chalco-halides solar cells to reach new heights through device modelling, present advanced characterization results from other Q-1D chalco-halides materials such as BiSeBr & SbSeI. Finally, the use of a novel material: Ti3C2Tx MXenes as selective contact suitable for those absorbers is also presented in this thesis. Firstly, a brief introduction of Sb2Se3 modelling parameters as well as BiSeBr & SbSeI results from by Raman spectroscopy and Time – Resolved Photoluminescence (TRPL) characterization are presented. A multi-wavelength investigation done by Raman spectroscopy coupled with novel Density Function Theory (DFT) are presented, giving information regarding the composition of the materials and the impact of the synthesis method for BiSeBr & SbSeI. Additionally, TRPL measurements highlighted the carriers’ dynamics and provide hints towards defects status of those materials. Altogether, this information helped to determine the potential of those new material as photo-absorber according to new figure of merit. Secondly, an emphasis is put on the device modelling using SCAPS-1D software and previous references to generate a qualitative model of Sb2Se3/CdS solar cells in substrate configuration to then design 2 numerical solutions to tackle the current bottlenecks experienced by the PV community. Those numerical solutions enable Sb2Se3 devices to reach 10.7% in efficiency by either implementing an ultrathin Al2O3 oxide intercalated between Sb2Se3 and CdS or operating a partial surface sulfurization on Sb2Se3 layer. Then, a simplified structure including only BiSeBr and 2 selective contacts was generated to pinpoint requirements from an electrical point of view. Although, due to software limitations, optical consideration is lacking to determine accurately suitable selective contacts, first approximations were determined through those simulations.Lastly, we develop the use of another novel material: MXenes Ti3C2Tx as a potential selective contact for Sb2Se3-based solar cells. Besides their wide range of deposition techniques and application, MXenes properties can be modulated alongside their synthesis. Initially, we perform materials characterization through Raman spectroscopy and X-Rays Diffraction (XRD) while changing intercalating agent and post deposition treatment (PDT) parameters to highlight this modulating feature. Then, we synthetized devices with Ti3C2Tx as hole transport layer (HTL) and Sb2Se3 as absorber. To improve carrier extraction, Se was incorporated on Ti3C2Tx layer under different PDT configurations. While PV performances were still poor compared to reference device without Ti3C2Tx some parameters presented some improvements upon Se incorporation onto Ti3C2Tx surface.
  
• JIMENEZ ARGUIJO, ALEX: Advanced strategies for the defect management in high efficiency kesterite solar cells
  
  Author: JIMENEZ ARGUIJO, ALEX
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ELECTRONIC ENGINEERING
  Department: Department of Electronic Engineering (EEL)
  Mode: Article-based thesis
  Deposit date: 24/10/2024
  Deposit END date: 07/11/2024
  Thesis director: SAUCEDO SILVA, EDGARDO ADEMAR | GIRALDO MUÑOZ, SERGIO
  Thesis abstract: Kesterite-based solar cells represent a promising avenue towards sustainable energy production due to their reliance on abundant, low-toxicity materials, aligning with global initiatives to minimize environmental impact and enhance energy security. This thesis contributes significantly to the field by advancing the understanding and efficiency of kesterite solar cells through innovative defect management strategies and the development of high-performance devices.The research initially focuses on developing a comprehensive and realistic model of kesterite solar cells, which is pivotal in bridging the theoretical predictions with experimental results, providing a robust framework for the analysis of the efficiency limitations and identifying avenues for enhancement. By incorporating a realistic depiction on the influence of defects on the device performance, this model sets a new benchmark for the assessment and optimization of thin-film solar cells. The innovative approaches for defect control within kesterite materials are central to the thesis. The research demonstrates that through precise defect control by an induced electric field or transient doping with small atoms, such as hydrogen and lithium, it is possible to significantly modulate the defect structure of kesterite absorbers. These modifications lead to the decoupling majority carrier density from minority carrier lifetime, effectively enhancing the performance and efficiency of the solar cells. These approaches not only improve the electrical properties of the material but also provides a method to systematically address the intrinsic limitations of kesterite semiconductors.Moreover, the thesis presents advancements in the synthesis and processing of kesterite solar cells, employing techniques such as solution processing, doping, and interface passivation. These methods have been shown to considerably improve the compositional uniformity and optoelectronic properties of the materials, driving the efficiencies closer to those required for commercial viability. Notably, the development of solution-processed kesterite solar cells emerge as a scalable and environmentally benign method, indicating a significant step towards the industrialization of this photovoltaic technology.The thesis concludes that the strategies and methodologies developed herein substantially enhance the understanding and performance of kesterite solar cells. The findings underscore the potential of these materials in the transition to renewable energy sources, highlighting their role in promoting a sustainable future. With further refinement and optimization, kesterite solar cells could play a critical role in the global energy landscape, offering a viable, cost-effective, and environmentally sustainable solution to meet the growing energy demands.In summary, the work presented in this thesis exemplifies a significant advance in the field of photovoltaics, offering practical solutions and novel insights that pave the way for further research and development towards achieving high-efficiency, sustainable solar energy techniques.
  
• JIMENEZ GUERRA, MAYKEL: Innovative bulk and interfaces management on Q-1D Sb2Se3 based solar cells
  
  Author: JIMENEZ GUERRA, MAYKEL
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ELECTRONIC ENGINEERING
  Department: Department of Electronic Engineering (EEL)
  Mode: Normal
  Deposit date: 31/10/2024
  Deposit END date: 14/11/2024
  Thesis director: SAUCEDO SILVA, EDGARDO ADEMAR | SÁNCHEZ GONZÁLEZ, YUDANIA
  Thesis abstract: This thesis investigated antimony Q-1D (Sb)-based solar cells as a promising alternative for sustainable energy generation, addressing critical challenges related to material properties, interfaces, and device architecture. Innovative strategies were developed to optimize optoelectronic properties and improve conversion efficiency, focusing on Sb2Se3, but including also preliminary studies on the Sb2(S,Se)3 solid solution, as well as exploring cadmium-free (Cd-free) materials as electron selective transport layers (ETL).A major achievement was the optimization of the Sb2Se3/CdS interface using chemical etching techniques, such as KCN treatment, which increased the average efficiency of solar cells from 4% to 5%, reaching 5.3% in the best-performing sub-cell. These treatments not only enhanced surface passivation but also altered surface polarity, resulting in the formation of a "buried junction" that improved the fill factor and overall energy conversion efficiency.High-pressure thermal annealings proved effective in enhancing crystal quality by increasing grain size, promoting preferred crystal orientations, and reducing defect density, which enabled a 5.8% efficiency using a new co-evaporation method. These findings demonstrate the feasibility of these techniques to improve device performance and reproducibility.Cadmium-free or significantly Cd-reduced configurations were explored to reduce environmental impact, achieving an efficiency of 6.6% in superstrate-configuration devices based on Sb2(S,Se)3, approaching the 7.6% benchmark achieved with CdS. In the substrate configuration, a Cd-free Sb2Se3 cell reached an efficiency of 5.2%, surpassing the 4.8% achieved with CdS, highlighting the potential of alternative materials to replace cadmium.Despite the progress made, several challenges remain, such as ensuring the stability of Sb2Se3 interfaces under operational conditions and optimizing new materials like SbSeI and SbSeBr. Improving the scalability of fabrication processes and the cost-effectiveness of new treatments are also key areas for future research. The results of this thesis provide a solid foundation for developing more efficient and sustainable Sb2Se3-based solar cells, emphasizing the importance of continued innovation in materials science and device engineering to overcome the remaining challenges and advance toward more scalable and efficient photovoltaic technologies.
  

DOCTORAL DEGREE IN ENVIRONMENTAL ENGINEERING

• ALTAMIRA ALGARRA, BEATRIZ: Bioplastic production by cyanobacteria-rich microbiomes. From field samples to productive cultures
  
  Author: ALTAMIRA ALGARRA, BEATRIZ
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN ENVIRONMENTAL ENGINEERING
  Department: Department of Civil and Environmental Engineering (DECA)
  Mode: Normal
  Deposit date: 05/11/2024
  Deposit END date: 18/11/2024
  Thesis director: GARCIA SERRANO, JOAN | GONZALEZ FLO, EVA
  Thesis abstract: Biobased and biodegradable, like polyhydroxyalkanoates (PHAs), offer an alternative to petroleum-based plastics by reducing energy use and mitigating plastic waste. Among PHAs, polyhydroxybutyrate (PHB) is the most extensively studied, but its high production costs make it essential to explore novel production systems, like cyanobacteria. In addition, in the seek for exploring cost-effective strategies regarding PHB synthesis, the use of cyanobacteria rich microbiomes, or mixed cultures - a diverse microbial culture comprising various cyanobacterial strains and other microorganisms - is a strong option. However, research on cyanobacteria microbiomes for PHB production is relatively scarce.The present PhD thesis aims to contribute to this research gap by exploring the potential of cyanobacteria-enriched microbiomes, detailing the entire experimental process from field sample collection to the development of productive microbiomes in 3 liters (L) photobioreactors (PBRs). Additionally, it is also intended to provide fundamental insights to improve the production PHB process. To achieve the objective, seven samples were collected from different locations to obtain various microbiomes. A low concentration of phosphorus (0.2 mg·L⁻¹) was applied to promote the dominance of cyanobacteria. In an initial experiment to optimize PHB production, three factors were evaluated: organic carbon supplementation, inorganic carbon supplementation, and light cycles. The results showed that the addition of organic carbon, in the form of acetate, increased PHB production in all samples, reaching up to 14 % PHB in dry cell weight (dcw).In the attempt to develop a methodology to successfully obtain a productive photosynthetic microbiome, the operating mode in regards to nutrients, temperature, light, and carbon supplementation was evaluated in a 3 L PBR under non-sterile conditions. A two-stage approach was developed consisting in alternating seven days for biomass growth and seven days for PHB accumulation. During accumulation phase, acetate supplementation (600 mg·L⁻¹) combined with exposure to darkness resulted in different PHB yields across microbiomes. Of the seven microbiomes analysed, two stood out for their high PHB production, reaching peaks of 28 % and 37 %dcw, some of the highest levels reported in cyanobacteria. Three other microbiomes maintained sustained but lower production (12-15% dcw PHB), while the remaining two showed very low production (<5% dcw PHB) due to the presence of non-PHB-producing organisms, such as green algae. Analysis of 16S rRNA and gene expression revealed that the high PHB levels were associated with the overexpression of the phaC gene, responsible for PHB synthesis, and glgp1, involved in glycogen catabolism, indicating a relationship between the two metabolic pathways. Low PHB production was linked to the overexpression of the gltA gene, which diverts resources toward the Krebs cycle, away from PHB synthesis.Microscopy techniques successfully confirmed the presence of PHB granules within cyanobacteria cells. Further validation of the accumulated polymer as PHB was achieved through Raman spectroscopy, Fourier-transform infrared spectroscopy, and proton nuclear magnetic resonance.Finally, simultaneous production of up to 205 mg·L⁻¹ exopolyssacharides (EPS) and 12 %dcw PHB was achieved in a 3 L PBR. Notably, the presence of uronic acid in the EPS promoted biomass flocculation. Overall, this thesis tries to demonstrate the feasibility of using cyanobacteria rich microbiomes for long-term PHB production in a non-sterile system. The research provides valuable insights into the metabolic pathways involved and the microbial community contributing to the process, offering a multidisciplinary approach for optimizing cultivation factors and bringing this promising technology closer to pilot scale-up, paving the way for more sustainable and cost-effective bioplastic manufacturing technology.
  

DOCTORAL DEGREE IN PHOTONICS

• NOWAKOWSKI, KRYSTIAN: Graphene-based Moiré superlattices under opto-electronic spotlight: Bloch oscillations, single photon detection, and polarization-resolved photocurrents
  
  Author: NOWAKOWSKI, KRYSTIAN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 07/11/2024
  Deposit END date: 20/11/2024
  Thesis director: KOPPENS, FRANK
  Committee:
       PRESIDENT: POLINI, MARCO
       SECRETARI: RUBIO VERDÚ, CARMEN
       VOCAL: TIELROOIJ, KLAAS-JAN
  Thesis abstract: In the last two decades, two-dimensional (2D) materials have captivated the scientific community thanks to their surprising characteristics and technological potential. Significant advancements in the understanding of their properties have opened up promises of applications in the electronics, photonics, sensing, and energy sectors. One of the most unprecedented prospects is the ability to freely combine various 2D materials into heterostructures. The 2D layers can be twisted with respect to each other, enabling a novel tuning mechanism in the solid-state physics toolbox. Introducing a few-degree angle between the layers can create a superlattice structure because of the moiré effect, allowing one to tune the material band structure. Graphene-based moiré superlattices have become a focal point of research in recent years, facilitating the design of many exotic phenomena and effectively bridging the fields of strongly correlated electrons, 2D materials, and topological physics. Optical measurements of these materials were non-existent at the inception of this thesis, prompting the investigation presented herein.In the first part of this thesis, the initial goal was to understand the photoresponse mechanisms of these materials using optoelectronic techniques in the mid-IR wavelength range. Our study reveals a nontrivial polarization-dependent photocurrent response in graphene-based materials. This response can significantly affect the measured signals and exhibit complex spatial patterns. A novel approach was developed to extract spatial maps of polarization-dependent components.One potential responsible mechanism is the bulk photovoltage effect (BPVE) response. BPVEs are second-order photocurrent generation mechanisms that are intricately connected to the quantum geometric tensor, reflecting the phase of the electron wavefunctions and distances between quantum states. Measuring BPVEs can provide insights into the underlying quantum nature of electronic states in moiré materials. We discuss role BPVEs in our results and the potential artifacts that can mimic it as well as the methodology and insights that are fundamental for discerning these different contributions.In the second part of this thesis, we report the discovery of negative differential conductance (NDC) in the high-bias regime in bilayer graphene aligned with hexagonal boron nitride. The NDC probably arises from Bloch oscillation-like mechanisms enabled by a folded band structure of the \moire superlattice. From the NDC we engineer a bi-stable state and demonstrate its sensitivity to single photons. This moire single photon detector (MSPD) can operate at wavelengths from 675 nm to 11.3 um (and beyond) and up to temperatures of 20 K, a combination that remains elusive in the single-photon detector field. The design is compact, CMOS-compatible, and array-integrable, presenting exciting opportunities for upscaling. This is the first observation of Bloch oscillations in a 2D system, enabling the entire arsenal of highly versatile experimental methods suited to these material platforms. We introduce spatially resolved photocurrent measurements as a pioneering technique for visualizing the Bloch oscillation regions. This advancement could lead to new high-frequency electronics and optoelectronic applications in addition to single-photon detection.This thesis lays the groundwork for further exploration of BPVE effects and high-bias phenomena in moiré superlattices and promising breakthroughs in Bloch oscillations, 2D optoelectronics, and photodetector technologies. These findings significantly advance our understanding of both the applied and fundamental physics in these systems, while also introducing crucial methodological innovations for future research in optoelectronics and photodetection.
  
• VINCENT, STEPHY: Solution Processed Colloidal Quantum Dot-Based Short Wave Infrared Light Emitters
  
  Author: VINCENT, STEPHY
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN PHOTONICS
  Department: Institute of Photonic Sciences (ICFO)
  Mode: Normal
  Deposit date: 25/10/2024
  Deposit END date: 08/11/2024
  Thesis director: KONSTANTATOS, GERASIMOS
  Committee:
       PRESIDENT: ANTHOPOULOS, THOMAS
       SECRETARI: BURGUES CEBALLOS, IGNASI
       VOCAL: CHRISTODOULOU, SOTIRIOS
  Thesis abstract: Shortwave infrared (SWIR) light sources are highly significant due to their ability to interact with molecular bonds and penetrate materials with reduced scattering and absorption. These properties make SWIR light exceptionally valuable across diverse applications, including spectroscopic analysis, non-invasive biomedical imaging, food and agriculture, and environmental monitoring. However, traditional SWIR sources tend to be bulky, inefficient, and characterized by high bulb temperatures, prolonged warm-up times, limited dimming capabilities, relatively short lifespans, and high costs. This has resulted in an increasing demand for more efficient, compact, and cost-effective alternatives.Solution-processed colloidal quantum dots (CQDs) are promising candidates for advanced SWIR light sources due to their wavelength tunability, high photoluminescence quantum yield (PLQY), and cost-effective synthesis. While CQD-based light sources are well-established in the visible range, there is a need for further development of SWIR emitters. This thesis addresses this gap by utilizing CQDs to create efficient, flexible SWIR light emitters through a simplified and cost-effective fabrication method.We developed SWIR light emitters with an emission wavelength of around 1350 nm using the down-conversion (DC) technique, where lead sulfide (PbS) quantum dots (QDs) absorb high-energy photons and emit lower-energy SWIR photons. Down-conversion using QDs addresses certain drawbacks of conventional phosphor-converted LEDs based on lanthanides or transition metal ions, such as the need for complex fabrication processes involving high-temperature sintering or annealing, limited emission band tunability, and challenges in supporting pulsed operations. We used binary blends of large-bandgap matrix QDs and small-bandgap emitter QDs, as they are reported to improve the PLQY.Initially, flexible DC films were fabricated on PET substrates via solid-state ligand exchange (SSLE) and spin coating, with various ligands, including 3-Mercaptopropionic Acid (MPA), combinations of Zinc Iodide (ZnI2) and MPA, and combinations of 1-Ethyl-3-methylimidazolium Iodide (EMII) and MPA, studied. The best performance was achieved using MPA as the ligand, and selectively exciting the emitter QDs proved more efficient than exciting both matrix and emitter QDs. The DC film treated with MPA, when excited by a 980 nm LED produced a SWIR power density of 0.19 mW mm⁻². Despite these promising results, spin coating was found to be inefficient and labor-intensive, necessitating a more scalable method.To address this, we developed an alternative fabrication method using ethyl cellulose (EC) polymer, where oleic acid-capped QDs are mixed with EC to form flexible QD-EC composites. This approach is industrially adaptable, reduces QD usage by a factor of 20, eliminates wastage, and requires less manual effort than the SSLE process. It also allows for scalable fabrication of DC films in any size or shape. The maximum SWIR power density achieved for a DC film with OA-capped PbS QDs, without ligand modification, was 0.18 mW mm⁻² .To further enhance efficiency, we applied solution-phase ligand exchange (SPLE) using 1-dodecanethiol (DDthiol) to improve surface passivation and reduce non-radiative recombination. DC films made with DDthiol-treated PbS QDs demonstrated a three-fold increase in SWIR power output and reduced efficiency roll-off by 37% at higher excitation power, compared to films with oleic acid (OA)-capped QDs. The best-performing film, composed of DDthiol-treated matrix QDs and OA-capped emitter QDs, achieved a maximum SWIR power density of 0.54 mW mm⁻² . This methodology was further extended to develop SWIR light sources emitting at 1470 nm. In summary, we developed efficient and flexible SWIR light sources using solution-processed CQDs through a cost-effective and scalable fabrication method by overcoming the limitations of conventional sources.
  

DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS

• CARRASCO RIBELLES, LUCÍA AMALIA: Multimorbidity and frailty trajectories and explainable prediction models for health-related outcomes using longitudinal electronic health records of the ageing Catalan population
  
  Author: CARRASCO RIBELLES, LUCÍA AMALIA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Normal
  Deposit date: 07/11/2024
  Deposit END date: 20/11/2024
  Thesis director: CABRERA BEAN, MARGARITA ASUNCION | VIOLÁN FORS, CONCEPCIÓN
  Thesis abstract: As life expectancy rises, people over 65 years old become a larger proportion of the population. However, longer life expectancy does not imply healthy ageing. Older individuals are more likely to develop multiple chronic diseases and other disabling conditions such as frailty. These conditions not only reduce quality of life but also place significant demands on an already strained healthcare system. This thesis aimed to 1) enhance understanding of the relationship and progression of frailty and multimorbidity, 2) study how frailty modifies multimorbidity patterns and trajectories, and 3) develop explainable predictive models using longitudinal electronic health records (EHRs). All the studies focused on three outcomes: all-cause mortality, nursing home admission, and home care need. Utilising SIDIAP, the primary care EHR database in Catalonia, enabled the development of large, population-based longitudinal studies with greater generalisability and the application of more sophisticated analytical techniques. This thesis yielded several important findings and recommendations. Firstly, it was demonstrated how the characterisation of multimorbidity and frailty and their impact on health-related outcomes evolves with age. The accumulation of diseases increases the likelihood of death, but older individuals with fewer diseases and more frailty-related deficits are more likely to require specialised care. Therefore, treatment plans should be tailored based not only on age but also on the specific characterisation of the patient at any given time. Secondly, the study found that multimorbidity patterns and trajectories are modified when frailty is considered, improving their predictive power for some health-related outcomes. Thus, future research on multimorbidity in older populations should integrate frailty information. Thirdly, a predictive model that addressed the technical challenges of longitudinal EHRs and incorporated mechanisms to enhance transparency was developed and called ARIADNEhr. During ARIADNEhr's development, it was found that increased model complexity does not necessarily improve discriminability but does enhance the clinical plausibility of the resulting attention maps. This model generally outperformed others using cross-sectional data. Additionally, the model's performance was validated with an external population, specifically in the UK with the CPRD database. This thesis exemplifies the transfer of advanced analytical techniques, such as clustering and deep learning, to the health field, supported by rigorous validation to ensure reliability. It offers valuable insights for future studies on the ageing population, emphasising the need for having access to longitudinal, high-quality data such as that from primary care. The findings aim to improve treatment penalisation, enhance patients' quality of life, and reduce costs for the national healthcare system.
  
• WANG, YIAN: Detection and Dynamic Update of Landslide Deformation in Plateau Reservoir Area Using Time Series InSAR
  
  Author: WANG, YIAN
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN SIGNAL THEORY AND COMMUNICATIONS
  Department: Department of Signal Theory and Communications (TSC)
  Mode: Change of supervisor + Article-based thesis
  Deposit date: 31/10/2024
  Deposit END date: 14/11/2024
  Thesis director: MALLORQUI FRANQUET, JORDI JOAN | GONG, JIANYA
  Thesis abstract: Spaceborne radar interferometry (InSAR) has shown significant advantages in extracting surface deformation information of landslides. However, the steep terrain, dense vegetation coverage, and rapidly changing meteorological conditions in complex reservoir areas pose substantial challenges to the application of time-series InSAR technology for landslide deformation detection and dynamic monitoring. Therefore, achieving reliable, efficient, and high-precision InSAR-based landslide deformation detection and dynamic updates in complex mountainous regions has become a research hotspot in the fields of radar remote sensing and engineering geology. This paper addresses the aforementioned challenges and conducts theoretical algorithm development and applied research, with the main research contents and contributions including the following:1) InSAR Applicability Estimation Method for Landslide Detection.2) Sequential Optimization Method for Distributed Scatterer Polarimetric Interferometric Phase. 3)Tropospheric Delay Phase Correction for Mountainous InSAR Considering Spatial Heterogeneity. 4) Automatic Detection and Dynamic Cataloging Method for Large-Scale Active Landslides Using InSAR.
  

DOCTORAL DEGREE IN URBANISM

• FIALLO CARDONA, GLORIA CAROLINA: INTERACCIONES LÍQUIDAS. Dibujar el agua de la ciudad de Bogotá
  
  Author: FIALLO CARDONA, GLORIA CAROLINA
  Thesis file: (contact the Doctoral School to confirm you have a valid doctoral degree and to get the link to the thesis)
  Programme: DOCTORAL DEGREE IN URBANISM
  Department: Department of Urbanism, Territory and Landscape (DUTP)
  Mode: Normal
  Deposit date: 24/10/2024
  Deposit END date: 07/11/2024
  Thesis director: SABATE BEL, JOAQUIN | PESOA MARCILLA, MELISA
  Thesis abstract: Bogotá, located in a lacustrine savanna surrounded by páramos and wetlands, has been shaped throughout its history by its relationship with water. From the muisca camellones to modern urbanization processes, the city has integrated rivers, canals, and streams into its urban fabric. Water, “sie,” has been the subject of study from various disciplines, highlighting its environmental, economic, and social significance. However, the traditional approach in Bogotá has focused on water supply and risk control, often leading to overexploitation of the resource and a reductionist representation on maps, where water is depicted as a simple blue line, disconnected from its context, resulting in a loss of environmental quality.In light of the current climate crisis, it is imperative to reexamine the relationship between water and territory with a more holistic and sensitive approach, especially from an environmental perspective. This research is based on the hypothesis that Bogotá acts as an interface between páramos and wetlands, revealing the need for new interpretations of how water interacts with the territory. The main objective is to explain the interactions between water and the city of Bogotá, shedding light on the role of water in the city through two epistemological approaches: water as a subject of rights and as a network agent.The thesis uses hydrocartographies, combining data analysis techniques with interpretative drawings and empirical observations to provide a comprehensive view of the different representations of water and its influence on territorial configuration. The proposed trans-scalar and multidimensional approach allows questioning traditional analyses and exploring new solutions based on an understanding of water’s natural cycles.We conclude that in Bogotá, water acts as a dynamic agent in the spatial dialogue between the urban environment and bodies of water, redefining boundaries through a trans-scalar approach that challenges traditional limits and proposes a more harmonious integration of territorial components. Since no cartography is definitive and each representation reflects processes in constant flux, the study suggests a new way of appreciating the territory’s attributes, promoting a reconciliation between water and the city while emphasizing the constancy of change, the fluidity. This deeper understanding highlights the need to adapt urban planning to consider water not only as a static resource but as a subject of rights and an agent in constant influence over urban development. The vision of Bogotá as a city of wetlands, interacting with páramos and basins, would make water dynamics visible in urban planning, challenging territorial models that have ignored its presence.