Author: COSTA MIRADA, NÚRIA
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 APPLIED MATHEMATICS
Department: Department of Mathematics (MAT)
Mode: Normal
Deposit date: 08/03/2021
Reading date: 14/04/2021
Reading time: 10:00
Reading place: FME - Videoconferència e-meet: https://meet.google.com/ezh-ckis-phe
Thesis director: MORILLO BOSCH, MARIA PAZ
Committee:
     PRESIDENT: RÀFOLS SALVADOR, CARLA
     SECRETARI: HERRANZ SOTOCA, JAVIER
     VOCAL: GUASCH CASTELLÓ, SANDRA
Thesis abstract: This PhD thesis focuses on lattice-based cryptography and how to apply it to build post-quantum online voting systems. It is the result of the research done by the author at Scytl in close collaboration with Dr. Paz Morillo, from the Department of Applied Mathematics at UPC and Ramiro Martínez, PhD student. As part of her work at the electronic voting company Scytl, the author has participated in the design of several electronic voting systems as well as in their implementation, by providing support to the development team. Nevertheless, all these systems use standard and well-known cryptographic primitives, i.e., not lattice-based primitives, to ensure that the security requirements are fulfilled. Due to this, one of the main challenges of this PhD has been to start researching on a field which was not familiar to the author and contribute to its state of the art. This has allowed the company to enter the post-quantum world by participating in a project which aims to implement a lattice-based online voting system. The thesis has the following contents: an introduction to the lattice theory by describing some of its basic concepts and the computational problems in which the security of lattice-based cryptosystems relies. In this first part it is also described in detail those cryptosystems that are used as building blocks of three new protocols proposed in the thesis: a lattice-based coercion-resistant cast-as-intended protocol, a post-quantum mix-net and a fully post-quantum proof of a shuffle. The former is the lattice version of an existing protocol and allows the voter to check that the vote cast contains the selected voting options. The second and third protocols are the result of the research on lattice-based mix-nets. Two constructions are proposed: the first one allows to demonstrate that a mix-node has permuted and re-encrypted a list of RLWE ciphertexts without modifying them, but it cannot be considered fully post-quantum since the binding property of the commitment scheme relies on classical computational problems. The second one is fully post-quantum since all the cryptographic schemes used for building it, i.e., commitment scheme and zero-knowledge proofs, are based on lattices. Last but not least, for this second proposal a security definition and a proof of security are also provided. Finally, the last part of the thesis consists of building a post-quantum online voting system using as building blocks the protocols already presented and existing lattice-based constructions. This system is considered secure under quantum attacks and provides long-term privacy. It also guarantees vote anonymity, vote authenticity, vote integrity, individual verifiability and receipt-freeness. The algorithms involved in each phase are described in detail as well as the interaction among the participants. An implementation of this system is not given as part of this thesis although a lattice-based online voting system based on that is already being implemented at the company.

Author: KERIDOU, INA
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 POLYMERS AND BIOPOLYMERS
Department: Department of Chemical Engineering (EQ)
Mode: Temporary seizure
Deposit date: 16/02/2021
Reading date: 14/04/2021
Reading time: 11:30
Reading place: Aula A1.03 Edifici A EEBE - CAMPUS DIAGONAL BESOS - Av. d'Eduard Maristany, 16, 08930 Barcelona - videoconferència: https://meet.google.com/icx-eqyd-eab
Thesis director: PUIGGALI BELLALTA, JORGE | FRANCO GARCIA, MARIA LOURDES
Committee:
     PRESIDENT: MEAURIO ARRATE, EMILIANO
     SECRETARI: FERNANDEZ FRANCOS, XAVIER
     VOCAL: REINA LOZANO, JOSE ANTONIO
Thesis abstract: In the last decades, polymeric biomaterials, due to their advanced physical and mechanical properties, have been used in a vast variety of surgical and pharmaceutical applications. In this thesis, a study on crystallinity, properties, and degradability ofpoly-4-hydroxybutyrate (P4HB), commercially marketed as MonoMax® by B. Braun Surgical S.A.U. as an absorbable monofilament suture, and related polyesters is presented. ·Part of this work has been executed under the collaborative research project established between PSEP (Polímeros Sintéticos. Estructura y Propieda s) research group of Universitat Politécnica de Catalunya and B. Braun Surgical S.A.U. (Center of Excellence far Closur :Technologies) with the principal purpose of evolving ahd investigating polymeric systems with specific biomedical ápplications.This study covers different tapies related to P4HB such as (a) the physical, chemical, thermal and mechanical characterization;(b) the study of the crystallization kinetics; (c) the study of the degradation behavior of P4HB; and (d) the production of nanofibers by the electrospinning technique. Moreover, the work includes a study on blends of two different polyesters: PGA/PCL blends also produced employing the electrospinning technique and biphasic PLA/PA blends.Crystallization was studied under both isothermal and non-isothermal conditions using optical microscopy and differential scanning calorimetry. Furthermore, supplementary experiments performed in a synchrotron radiation facility provided us with further information about the lamellae morphology, crystal structure, and molecular orientation.Hydrolytic and enzymatic degradation of different matrices of P4HB was carried out in different buffered media. The hydrolytic degradation has been studied considerírig media of different pH values and temperatures. Enzymatic degradation has also been evatu ated at physiotogical conditions using two different lipases. The hydrolytic degradation mechanism differs from the enzymatic, where bulk degradation and a random éháin scission are characteristic of samples exposed to hydrolytic media, whereas surface erosion and successive removal of monomer units are charac!eristlc of samples exposed to enzymatic media. Far annealed fibers, small-angle X-ray diffraction studies revealed a supramolecular structure with two different types of !amellar stacks. The spherulitic morphology of the enzymatically degraded films was highlighted by the elimination of the amorphous regions.Nanofibers of PGA/PCL and P4HB were preparad using the electrospinning technique. The PGA/PCL nanofibers were also loaded with pharmacological drugs and Lised as a reinforcing agent of biodegradable polymer matrices. On the other hand, the biologicat performance of P4HB nanofibers was achieved with the incorporation of fibroblast growth factors. Far this purpose, wound healing assay for two different cell lines (e.g., epithelial and fibroblast) were studied.Finally, a study on the blends of PLA and Polyamide 6,1O was carried out to investigate the confinement effect of neighboring polymer domains on the phase separation and the structure and the influence of the disperse phase of polyamide in promotingPLA crystallization.

Author: AZNAR LUQUE, ARACELI
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 Applied Physics (FA)
Mode: Temporary seizure
Deposit date: 24/02/2021
Reading date: 15/04/2021
Reading time: 11:00
Reading place: Aula 1.6 Edifici A. EEBE - UPC DIAGONAL-BESÒS - videoconferencia: https://meet.google.com/xdg-tuvk-tjg
Thesis director: LLOVERAS MUNTANE, POL MARCEL | TAMARIT MUR, JOSE LUIS
Committee:
     PRESIDENT: VIVES SANTA EULÀLIA, EDUARD
     SECRETARI: MACOVEZ, ROBERTO
     VOCAL: GONZALEZ SILVEIRA, MARTA
Thesis abstract: Current refrigeration devices, based on vapour-compression cycles, employ refrigerants such as HFCs, which exhibit a global warming potential a thousand times higher than the one produced by CO2,. Furthermore, the increasing middle class, associated with their refrigeration needs, urges for research in new environmentally friendly refrigerant alternatives.Solid-state caloric effects have been proposed as potential alternatives to replace the vapour-compression refrigeration technologies. They may become giant under the cyclic application and removal of an external field which induces changes in entropy and temperature associated with the occurrence of a first-order phase transition. In this work we specifically focus on caloric effects driven by means of hydrostatic pressure (barocaloric effects, BCEs), which allow us to operate with powder compounds, avoiding fatigue upon cycling. Additionally, a wide variety of materials can be used with BC purposes, due to the possibility of working with powdered samples and to the emergence of BCE associated with any transition volume change.In this dissertation we carried out the study of the BC performance of a series of compounds belonging to four different material families: Plastic crystals (PC), hybrid organic-inorganic perovskites (HOIPs), magnetic alloys and a superionic conductor. The election of these materials is not arbitrary, but relies on several features which anticipate good BCEs, such as large transition entropy changes, pressure sensitivity of the transition temperature and small thermal hysteresis. The small hysteresis avoids losses related with the refrigeration cycle and ensures smaller pressures under which reversibility is observed (which at the same time enable smaller applied work to the refrigerant). Finally, other properties must also be taken into account when designing a refrigeration device: Density, thermal conductivity and costs of production. BCEs are determined by means of a combination of quasi-direct and indirect methods. Firstly, we conduct measurements of atmospheric pressure and high-pressure calorimetry (DSC and DTA, respectively), along with experiments of X-ray diffraction and dilatometry. Then, the isobaric entropy curves are constructed, from which by means of curves subtraction the BCEs can be obtained. Additionally, special attention has been put on reversibility, since cyclability is mandatory for a real refrigeration device. Among the family of PC, derivatives from adamantane (1- and 2-adamantanol) and neopentane (neopentylglycol, neopentyl alcohol, pentaglycerine, tris(hydroxymethyl)aminomethane and 2-amino-2-methyl-1,3-propanediol) have been studied. Results for reversible isothermal entropy changes reach colossal values between 300-500 JK-1kg-1 and 150-500 JK-1kg-1 for neopentane and adamantane derivatives, respectively. These values are associated with adiabatic temperature changes among 10-20 K for pressure changes of ~2.5 kbar.The studied HOIPs ([TMA](Mn(N3)3) and [TMA]2(NaFe(N3)6)) exhibit giant values of ~100 J K-1 kg-1 with temperature changes between 15-20 K for pressure changes of ~2 kbar. It is important to highlight the small pressure required in order to obtain reversibility for these compounds, which is about only ~0.1 kbar.Magnetic alloys MnCoGeB0.03, Mn3NiN, Mn3(Zn0.45In0.55)N and Ni50Mn31.5Ti18.5 have been analysed. Nonetheless, only MnCoGeB0.03 and Mn3(Zn0.45In0.55)N show reversibility. They exhibit ~25 J K-1 kg-1 and 4-10 K under pressure changes of ~3 kbar.Finally, AgI, the only superionic conductor studied in this dissertation, reaches ~50 J K-1 kg-1 and ~10 K under pressure changes of 2 kbar. These results become the most outstanding presented in this thesis when normalized by volume.Finally, several figures of merit are presented, in which the studied materials are put into comparison with each other and with other already reported compounds.

Author: SAEMISCH, LISA CHRISTIN
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: 10/03/2021
Reading date: 15/04/2021
Reading time: 15:00
Reading place: ICFO - Avda. Carl Friedrich Gauss, 3 - videoconferència: http://s.ic.fo/D0Qyj
Thesis director: VAN HULST, NIEK
Committee:
     PRESIDENT: NOVOTNY, LUKAS
     SECRETARI: GARCÍA PARAJO, MARÍA
     VOCAL: WERTZ, ESHTER ALEXANDRA
Thesis abstract: The interaction of light and matter is of crucial importance in fundamental science as well as in high-end technology.Ultimately, this concerns the interaction between a photon and a single quantum system, e.g. the absorption or emission of aphoton by a single molecule. At room temperature this interaction is very inefficient as the absorption cross-section of a molecule is small compared to the wavelength of light, which inhibits many photons from interacting and hence limits theabsorption, emission and scattering of a photon. An equivalent problem, and its solution, is found in our daily lives: small electric circuits (as found e.g. in our smartphones), which radiate very poorly by themselves, are linked to (radio) antennas toradiate and transfer information efficiently. Analogously, antennas working in the visible, so-called nanoantennas, are an effective tool to link matter and light. The strength of the coupling of a single molecule with a nanoantenna depends on many factors: the overlap of the antenna resonance and the molecular absorption/emission spectrum, the molecule¿s dipole orientation, the distance between molecule and nanoantenna, etc. Hence, strong interaction needs rather special conditions, which are hard to engineer. Moreover, to get a full interaction picture, a lot of single molecule encounters with different nanoantennas are needed - on one hand to make a statistically relevant statement including the many different factors and, on the other hand, to be able to observe the rare stronger interactions, that would have stayed hidden in experiments of only afew encounters. The central idea of this thesis is to statistically map and control the interactions of a very large number of single moleculeswith different tailored nanoantennas, to cover the landscape of interaction factors and thus extend the current knowledge of the mutual interaction. For this purpose, a home-built wide-field microscope is combined with a large array of lithographically fabricated nanoantennas, which are all probed by freely diffusing molecules. Thus in time millions of encounters are recorded in parallel.Chapter 2 introduces the necessary knowledge and methodology to understand the research work presented in chapters 3 to 5. Chapter 3 shows super-resolved nanoscale interaction maps of molecules and nanoantennas, linking the strength ofinteraction to the emission polarization and intensity of every encounter. Chapter 4 extends this approach by simultaneously recording the emission fluorescence and spectrum of every single molecule event, revealing strong spectral manipulation.Here, a suppression as well as an extreme enhancement of the vibrational sideband of the used molecule is observed.Additionally, the statistical mapping allows the freely diffusing molecules to encounter rare hotspots of extreme field intensities, enabling the observation of surface-enhanced Raman scattering.Finally, chapter 5 takes the first step in the direction of characterizing the interaction of molecule and nanoantenna with high sensitivity via phase measurements. Here, an interferometric wide-field microscope enables the measurement of the absolute phase of nanoparticles and demonstrates the distinction of different plasmonic and dielectric particles via their phase behavior. Furthermore, we implement a novel two-color excitation method, capable of rapidly identifying two types of nanoparticles in a single-shot image.

Author: COELLO DE PORTUGAL - MARTINEZ VAZQUEZ, JAIME MARIA
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 NUCLEAR AND IONISING RADIATION ENGINEERING
Department: Institute of Energy Technologies (INTE)
Mode: Normal
Deposit date: 17/03/2021
Reading date: pending
Reading time: pending
Reading place: pending
Thesis director: TOMAS GARCÍA, ROGELIO | KOUBYCHINE MERKULOV, YOURI ALEXANDROVICH
Committee:
     PRESIDENT: PEREZ RODRIGUEZ, FRANCISCO JOSE
     SECRETARI: CORTES ROSSELL, GUILLEM PERE
     VOCAL: DALENA, BARBARA
Thesis abstract: In order to increase the performance of particle colliders, it is crucial to make the beam sizes at the collision points as small as possible. This causes an increase of the beam size in the region surrounding the collision points thus enhancing the effect of magnetic errors. These errors must therefore be kept under tight control to ensure the performance and safety of the accelerator.The present thesis studies effects of the expected magnetic errors in the regions around the collision points on the beam optics that determine the beam size in the future High-Luminosity upgrade of the Large Hadron Collider (HL-LHC), a 27 km particle accelerator situated on the French-Swiss border near Geneva, Switzerland. It has become clear in recent years that in correcting the magnetic errors in this region a crucial requirement is an accurate measurement of the beam optics at the collision point. This thesis demonstrates that the technique used traditionally in recent years, called ¿K-modulation¿, is not accurate enough to ensure the performance of the HL-LHC and therefore alternative methods of performing this measurement must be studied.To perform these studies a new automatic optics correction tool has been developed and is presented in this thesis. This new tool allows faster and more systematic calculation of corrections of the magnetic errors around the interaction regions and has been successfully tested during commissioning and experiments in the LHC.Two complementary techniques are proposed in order to improve the accuracy of the determination of the beam sizes at the collision points, namely determining the minimum beam size near the collision point using the ¿phase-advance¿ of the beam oscillations around the accelerator and locating the position of this minimum, the ¿beam waist¿, by displacing it and maximising the collision rate characterized by the collider luminosity. In the thesis these techniques are studied theoretically, and the first results of their experimental validation performed in the LHC are presented.This push for smaller beam sizes at the collision points not only increases the beam sizes in sections around this point but also, though to lesser degree, in the arcs of the accelerator. These regions also become susceptible to smaller magnetic errors. As some regions of the accelerator do not count with adequate corrector magnets alternative solutions are needed. Here we present the first experimental results of an optics correction performed by traversing sextupoles with off-central beam in the LHC as a solution proposal. Another consequence of the growth of the beam sizes in the regions around the collision points is the eventual necessity for larger beam pipes. This is the case for HL-LHC where the magnetic lenses around the collision points are going to be replaced by new ones with the beam pipe of larger diameter. In order to keep the same magnetic strength though a new superconducting technology is going to be used to build these magnets. A downside of this novelty is that it is susceptible to a type of magnetic instability called ¿flux-jumps¿. In the thesis the effect of the flux-jumps on the beam sizes is studied theoretically and concrete predictions using measurements of this effect on the prototypes of the new magnets of the HL-LHC are given. The study is also extrapolated to the Future hadron-hadron Circular Collider (FCC-hh), a proposed 100 km circular collider, in which superconducting magnets of this type are expected to be installed all around its circumference.Finally, the thesis presents a summary of software developments performed during the previously mentioned studies, including a user interface to facilitate the use of the automatic correction tool, a new harmonic analysis program that replaces legacy code and many refactors and rewrites that have significantly eased the development of the optics measurements and corrections programs.