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On the Study of Crystal Nucleation Via In Situ Optical Means: Scientific and Technical Advancements
No full textCrystal nucleation, a fundamental natural phenomenon, remains poorly understood at the microscopic level due to its heterogeneous and stochastic nature. Traditionally studied macroscopically, direct observation of its chemical structural evolution has been elusive. Understanding early crystallization stages is crucial for comprehensive insights into crystallization pathways and polymorph selection, significantly impacting material properties.
Despite their broad applicability, optical methods have limitations in studying crystal nucleation. This thesis introduces Single Crystal Nucleation Spectroscopy (SCNS), combining Raman microspectroscopy and Optical Trapping Induced Crystallization (OTIC), to study individual crystal nucleation events in situ. It highlights glycine's non-classical nucleation pathway via pre-nucleation aggregates and explores the effects of sodium chloride and deuteration on glycine polymorphism. Additionally, it presents the development of time-resolved Dynamic Light Scattering (DLS) microscopy to study the morphological evolution during crystallization, paving the way for further advancements in understanding the early stages of materials formation.</p
Time-of-day effect on adaptive immune responses and central nervous system autoimmunity
No full textCircadian rhythms are present in virtually all organisms and are evolutionarily conserved time-keeping mechanisms describing biological processes that oscillate in approximately 24-hour patterns. These rhythms are kept in synchrony by environmental cues and participate in the proper function of several physiological processes, among which are the innate and the adaptive immune system. Circadian rhythms are beneficial as they allow organisms to anticipate recurring events and to tune their behavioral response accordingly. With respect to immunity, these rhythms help the host to modulate its reactivity to times at which the probability of pathogen encounters may be highest. In addition, time-of-day-dependent activation of the immune system must be tightly controlled to trigger an efficient immune response without inducing side effects such as autoimmunity.
It is now widely accepted that time-of-day-dependent mechanisms can govern an acute immune response. However, we still do not understand why adaptive immune responses remain oscillatory over long periods of time. In the first part of this thesis, I demonstrate that the initial time of the challenge is key to shape the adaptive immune response for the ensuing several weeks. In particular, the time-of-day-dependent migration of dendritic cells generates oscillations in lymph node cellularity, which persists for weeks after the initial challenge and results in an increased likelihood of functional encounters between antigen-presenting dendritic cells and antigen-recognizing T cells. This is especially important in the context of immune responses to vaccination. Additionally, I show that rhythmic migration, activation, and function of different immune cells are required to create and maintain an efficient immune response over time.
However, immune responses are not always beneficial as is the case for an immune response directed against self, which can lead to autoimmunity. The second part of the thesis aims to decipher to what extent circadian rhythms are contributing to the development of experimental autoimmune encephalomyelitis (EAE), the most common mouse model of multiple sclerosis (MS). Using this model, I show a time-of-day dependent infiltration of immune cells into the central nervous system (CNS) during EAE development that is independent of disease severity. Interestingly, I observe a substantial increase in blood circulating CD11b+Ly6G+ cells before the appearance of symptoms associated with a switch in their phenotype. Altogether, these data suggest a potential contribution of CD11b+Ly6G+ leukocytes to early disease. Analysis of the mRNA levels in the spinal cord of EAE animals reveal a time-of-day dependent expression of both Cxcl1 and Cxcl2 chemokines responsible for the migration of monocytes and neutrophils, respectively. This study suggests the importance of circadian oscillations in cell infiltration in the central nervous system, as well as the importance of CD11b+Ly6G+ leukocytes in EAE development and identifies these cells as potential early biomarkers for diagnosis purposes and new therapeutic targets in MS patients.</p
The Impact of Climate Extremes on Dryland Ecosystems and Societies in Sub-Saharan Africa
No full textOver the past sixty years, land productivity in Africa has steadily declined, primarily due to climatic constraints that limit its full potential. With three-quarters of Africa's landmass being drylands spread across 46 out of 54 countries, the region is highly sensitive to climate and environmental challenges. This has led to severe and recurring climate extreme events, disproportionately affecting the livelihoods of the population, especially the poor. However, limited research and evidence exist on the magnitude of climate change outcomes and their impact on ecosystems, agriculture, and food production, as well as the response of individual households to these extreme events. The principle objective of this PhD thesis was to enhance our understanding of the impact of climate extremes on dryland ecosystems and society in sub-Saharan Africa (SSA), comprehensively examining various levels of impact. To achieve this, several methods were applied. First, by conducting a systematic scoping review at the continental scale, we compiled existing knowledge and identified gaps regarding trends and impacts of droughts in SSA. Next, an investigation was done on the influence of natural volcanic forcing and internal climate variability on one of the most extreme droughts that occurred during the 20th century in SSA; this analysis of the climatic impacts following the Mount Pinatubo eruption in 1991 also included identification of implications of this to geoengineering solutions of global warming. We then assessed the spatio-temporal characteristics of droughts in Tanzania, with a specific focus on examining their distribution and patterns over time. Lastly, by utilizing household panel survey data in Tanzania, I estimated the influence of climate extreme shocks on the decision of households among agro-pastoral communities to cope with droughts and heat and how market accessibility would facilitate.
The key findings of this study were: 1) extreme climate events such as droughts and heatwaves are intensifying over SSA and there is a demand for more empirical research on the continent especially to the underrepresented blocks such as central Africa, 2) stratospheric volcanic induced aerosols exacerbate droughts in SSA, implicating extreme caution for geoengineering solutions, 3) droughts have been significantly increasing in Tanzania over the past 61 years and the dry seasons are becoming drier while crop growing seasons have been impacted severely. This poses a major challenge to rain-fed agricultural schemes. Finally, 4) decisions of rural households to adapt to climate extremes rely on market accessibility as food consumption becomes constrained. All these findings have policy implication that, specificity will always remain to inform the details and therefore caution should be exercised in devising and implementing solutions to the climate crisis at any level, including solar radiation management to reduce warming.</p
Pond Biodiversity: Long-Term Dynamics and Benefits of Implementing Nature-based Solutions in Pondscapes
No full textPonds and pondscapes (i.e., networks of ponds in the landscape) are essential freshwater ecosystems that host a particularly rich biodiversity as well as deliver various Nature’s Contributions to People (NCPs), yet they have historically been dismissed as insignificant and have suffered from a lack of protection and study. In a context of global environmental change, it is crucial to monitor these ecosystems to know how they are faring and to guide conservation actions such as their protection, management, restoration and creation. This thesis investigated long-term trends in pond biodiversity and the benefits of implementing Nature-based Solutions (NbS) such as pond creation. Our results show a high resilience of pond species richness over time, in both high-elevation and lowland pondscapes, but also an important dynamism within metacommunities, with substantial species dispersal and turnover between habitats in lowland areas. This highlights the importance of conserving ponds on a landscape scale. Moreover, pond creation as NbS can offer great benefits to biodiversity as long as ponds are designed with this objective in mind, as evidenced by two case studies: i) the creation of flood management ponds in Scotland, and ii) the creation of diverse ponds for various purposes in the region of Geneva, Switzerland. To safeguard freshwater biodiversity and ecosystem services, it remains important to conserve pondscapes and to create ponds, as a way to compensate dramatic declines in habitat in past centuries
Réseau PartnerREC. Résultat d’une coconstruction entre patient‑e‑s partenaires et chercheur-se-s
No full textLe réseau PartnerREC des Hôpitaux universitaires de Genève a vu le jour afin de faciliter la collaboration entre les chercheur-ses et les patient-es partenaires dans tous les types de projets en recherche clinique, principalement ceux menés aux HUG. Il est le fruit d’une démarche de coconstruction débutée en 2019 par un groupe de médecins, chercheur-ses, membres de la Commission cantonale d’éthique de la recherche, une avocate et des patientes partenaires. Le réseau a mis en place 4 actions : a) la création d’un site internet destiné aux chercheur-ses et aux patient-es participant à des projets de recherche ; b) des conseils personnalisés pour accompagner les chercheur-ses dans leur démarche de partenariat ; c) une formation au partenariat en recherche, en collaboration avec des acteur-rices du partenariat en suisse romande et d) le développement de projets de recherche propres sur le partenariat patient-e en recherche.The PartnerREC network at the Geneva University Hospitals aims to facilitate the collaboration between researchers and patient partners in any type of clinical research, mainly those led at the HUG. It is the result of a coconstruction process initiated in 2019 by physicians, research professionals, cantonal research ethics committee members, a lawyer, and patient partners. The network implemented four initiatives: a) a website providing information to researchers and patients participating to research projects; b) personalized counseling for researchers to explore partnership opportunities in their own research projects; c) a training program related to patient partnership in research developed together with different partners in French-speaking Switzerland and d) its own research program on partnership in clinical research
Side Chain and Dimerization Influence on (Chir)Optical Properties of Cationic [4]Helicenes
No full textLes [4]hélicènes cationiques du type DMQA peuvent être obtenus énantiopurs et étudiés quant aux manières d’influencer leurs propriétés (chir)optiques. Une façon de le faire consiste à déformer leur squelette en variant les chaînes latérales, linéaires ou ramifiées. Ces composés ont été utilisés pour obtenir matériaux à propriétés (chir)optiques à l'état solide.
La dimérisation par couplage oxydant a été étudiée. Ce mécanisme repose sur la formation d'un radical dicationique qui agit comme électrophile. Les résultats sont différents en fonction du DMQA utilisé, linéaire ou ramifié, tant du point de vue synthétique que des propriétés.
Finalement, des molécules bis-fonctionnalisés ont été obtenues. A partir d'un de ces colorants, il pourrait être possible d'obtenir des oligomères reliés par des liaisons amide. Après nombreuses tentatives infructueuses pour obtenir cette liaison entre deux monomères monosubstitués, un protocole en présence de métaux en poudre a été identifié et utilisé pour obtenir des dimères homochiraux et hétérochiraux. </p
Comment décarboner notre système de santé : le cas du canton de Genève
No full textBien que performant, le système de santé suisse génère 6,7 % des émissions nationales de gaz à effet de serre. À Genève, notre étude a évalué pour la première fois son empreinte carbone à 436 831 tCO2e en 2022. Les hôpitaux (47 %) et les médicaments (58,6 %) en sont les principaux acteurs et sources d’émissions. Divers scénarios, incluant la promotion de la santé et la prévention, soulignent l’importance de mesures directes et indirectes pour réduire ces émissions de 70 % d’ici 2040. Ces approches sont adaptables aux autres systèmes de santé cantonaux.Although highly efficient, the Swiss healthcare system accounts for 6.7% of the country's greenhouse gas emissions. In Geneva, our study assessed its carbon footprint for the first time, estimating it at 436,831 tCO2e in 2022. Hospitals (47%) and medications (58.6%) are the main factors and sources of these emissions. Various scenarios, including health promotion and prevention, underscore the importance of direct and indirect measures to cut these emissions by 70% by 2040. These approaches are adaptable to other cantonal healthcare systems
Argument Structure in Mandarin Chinese: Voice Variants, Applicative Licensing, and Causative Constructions
No full textCette thèse s’inscrit dans le cadre théorique de la morphologie distribuée (Distributed Morphology), et examine la structure argumentale du mandarin à travers trois phénomènes syntaxiques majeurs : les alternances de voix, les constructions applicatives et les structures causatives. En mobilisant une approche comparative et formelle, l’étude met en lumière les mécanismes syntaxiques sous-jacents aux différentes configurations argumentales, en s’appuyant sur des données empiriques du mandarin moderne.
Le premier volet porte sur les alternances agent-patient et met en évidence des asymétries dans la réalisation syntaxique des arguments. Le deuxième volet explore le rôle des têtes applicatives dans la licence des arguments nonthématiques, en distinguant deux types de constructions applicatives en mandarin. Enfin, la dernière partie analyse les constructions causatives, en distinguant les causatives lexicales, analytiques et syntaxiques, et en soulignant les corrélations entre leurs propriétés morphosyntaxiques et leurs contraintes argumentales.
Ce travail contribue à une meilleure compréhension des relations entre structure argumentale et structure syntaxique dans les langues analytiques, et propose une perspective comparative sur des notions telles que la transitivité, la licence argumentale, et la hiérarchie fonctionnelle impliquant les projections Voice et Appl.</p
Les coordonnées juridiques du principe du Lotus
No full textThis contribution aims at discussing certain aspects of the so-called Lotus-Principle, which holds that absent an obligation under international law States enjoy a general freedom to act. The discussion turns first on the exact configuration of the principle within international law, for example in the context of determining at what point international law can be said to not contain a prohibition, the issue of strong and weak permissions, the territorial and extraterritorial reach of the freedom to act, etc. In the last part, a longer section dissects the commonalities and differences between two structurally closely related principles, namely the Lotus and the reserved domain (internal affairs)