There and back again: a holographic journey towards black-hole microstates

The microscopic interpretation of the Bekenstein-Hawking entropy is still an open challenge in theoretical physics. Supersymmetric indices and holography, turn out to be major tools to improve our knowledge. In the first part of this thesis, using a Bethe Ansatz formulation, we compute the large $N$ limit of the superconformal index with arbitrary chemical potentials for all charges and angular momenta, for generic 4d $\mathcal{N}=1$ conformal theories with a holographic dual. We conjecture and bring evidence that a particular universal Bethe vacuum dominates the index at large $N$. For $\mathcal{N}=4$ super-Yang-Mills, this contribution correctly leads to the entropy of BPS Kerr-Newman black holes in AdS$_5 \times S^5$ for arbitrary values of the conserved charges, completing the derivation of their microstates. We also consider theories dual to AdS$_5 \times \mathrm{SE}_5$, where SE$_5$ is a Sasaki-Einstein manifold. We first check our results against the so-called universal black hole. We then explicitly construct the near-horizon geometry of BPS Kerr-Newman black holes in AdS$_5 \times T^{1,1}$, charged under the baryonic symmetry of the conifold theory, and with equal angular momenta. We compute their entropy using the attractor mechanism and find complete agreement with the field theory predictions. For BPS black holes with an AdS$_2$ factor at the horizon, the black-hole microstates can be seen as ground states of a dual 1d theory. In the second part of this dissertation, we construct an \cN=2 supersymmetric gauged 1d model by starting from the 3d \cN=2 Chern-Simons matter theory holographically dual to massive type IIA string theory on AdS$_4 \times S^6$, and Kaluza-Klein reducing it on $S^2$ with a background dual to the asymptotics of static dyonic BPS black holes in AdS$_4$. The background involves a choice of gauge fluxes, that we fix via a saddle-point analysis of the 3d topologically twisted index at large $N$. The ground-state degeneracy of the effective quantum mechanics reproduces the entropy of BPS black holes, and we expect its low-lying spectrum to contain information about near-extremal horizons. Interestingly, the model has a large number of statistically-distributed couplings, reminiscent of SYK-like models

Nutritional status in hospitalized patients: prevalence, déterminants and impact on hospital stay, mortality and costs

Undernutrition is a frequent condition among hospitalized patients, leading to increased morbidity, mortality, length of hospital stay, and health costs. However, few studies have reported undernutrition prevalence and its management in Switzerland. Indeed, very little information exists for Switzerland regarding the factors associated with undernutrition and its impact on health outcomes and health costs. This project thus aimed to better characterize the prevalence, determinants, management, and consequences of undernutrition among hospitalized patients in Switzerland. To achieve this, five studies were conducted: one literature review, two cross-sectional studies, one diagnostic accuracy study, and one trend analysis. The initial literature review showed that in Europe, undernutrition represents a considerable economic burden, representing as much as 10% of total national health expenditures. The first cross-sectional study was conducted in the Lausanne university hospital and showed that three out of five hospitalized patients are ‘at-risk’ of undernutrition, but only half of them were nutritionally managed; the study also showed that nutritionally ‘at-risk’ patients had higher in- hospital mortality and costs, while their reimbursement rates were lower. Further, the diagnostic accuracy study showed that, despite a good specificity (87%), undernutrition-related codes in hospital discharge data had low sensitivity (43%) and positive predictive values (28%), thus precluding adequate evaluation of prevalence rates of undernutrition. The second cross-sectional analysis focused on hospital discharge data for whole Switzerland; it showed considerable regional variations regarding the reporting of undernutrition and its management, highlighting the absence of standardized procedures for the whole country. Analysis of hospital discharge data for whole Switzerland for the period 1998-2014 showed a several-fold increase in the prevalence of reported undernutrition-related codes (e.g. from 0.18% to 2.13% in Ticino and from 0.23% to 5.63% in Mittelland). Nevertheless, in 2014, still 40% of hospitalizations with an undernutrition-related code had no indication of nutritional management. Overall, this project provided some important information regarding the prevalence, determinants, and impact of undernutrition in Swiss hospitals. The results will hopefully serve as reference for future intervention studies. -- La dénutrition est une condition fréquente parmi les patients hospitalisés, augmentant la morbi-mortalité, la durée du sàjour, et les coûts de la santé. Peu d’études se sont intéressées à la prévalence de la dénutrition et sa prise en charge en Suisse. En fait, il existe très peu d’information concernant les déterminants de la dénutrition et ses conséquences sur la santé et les coûts. L’objectif de ce travail était de mieux caractériser la prévalence, les déterminants, la prise en charge et les conséquences de la dénutrition parmi les patients hospitalisés en Suisse. Pour ce faire, cinq études ont été conduites : une revue de la littérature, deux études transversales, une étude diagnostique et une analyse temporelle. La revue de la littérature a montré qu’en Europe la dénutrition représente un coût financier considérable, pouvant aller jusqu’à 10% des dépenses nationales de santé. La première étude transversale a été conduite à l’hôpital universitaire de Lausanne et a montré que trois patients sur cinq étaient à risque de dénutrition, mais que seulement la moitié bénéficiait d’une prise en charge. Cette étude a également montré que les patients à risque avaient une plus grande mortalité intra-hospitalière et coûtaient plus cher, alors que les taux de remboursement étaient moindres. Par ailleurs, l’étude diagnostique a montré que le codage de la dénutrition avait une bonne spécificité (87%) mais une mauvaise sensibilité (43%) et une valeur prédictive positive faible (28%), ce qui limite l’estimation de la prévalence de la dénutrition par l’utilisation des codes. La seconde étude transversale a porté sur les données de la statistique hospitalière suisse ; elle a montré de grandes disparités régionales concernant le codage et la prise en charge de la dénutrition, dues à l’absence de recommandations au niveau national. Finalement, l’analyse temporelle de la statistique hospitalière suisse pour la période 1998-2014 a montré une augmentation considérable de la fréquence des codes de dénutrition (de 0.18% à 2.13% au Tessin et de 0.23% a 5.63% an Mittelland). Néanmoins, en 2014, encore 40% des hospitalisations ayant un code de dénutrition n’avaient pas de code associé à une intervention nutritionnelle. Dans l’ensemble, ce travail a permis d’obtenir des données concernant la prévalence, les déterminants et l’impact de la dénutrition dans les hôpitaux suisses. Nous espérons que ces résultats pourront servir de référence pour de futures études d’intervention

A Quadratic Boost Converter Suitable for Fuel Cell-Powered Electric Vehicles

This study presents a non-inverting transformer-lessBoost converter with a higher voltage conversion ratio, resultingin quadratic growth of the output voltage with modest incrementsin the duty cycle rate. The continuous input current of thisconverter simplifies the input filter design and enhances fuelcells’ lifetime and stability. Additionally, compared to existingarchitectures, this converter reduces the voltage and currentstresses on semiconductor components, making it a promisingalternative to other quadratic Boost converters. As a result, thistopology appears to be a viable alternative for the remainingquadratic Boost converters. The inclusion of common-groundswitches, which eliminate the need for additional components forgate driver isolation, is one of the main features that make thistopology distinct. As a result, the converter fabrication cost andsize are reduced. The proposed converter’s steady-state analysis isthoroughly explained. Stresses placed on semiconductor devices.Then, a meaningful comparison between the proposed circuitand its counterparts is provided to understand this converter’sunique attributes

Investigating the Effect of Variations in Irrigation Water Price on Cropping Pattern and Gross Margin under Uncertainty (Case Study: Khorasan Razavi)

Water shortage crisis is an issue that has led to drastic changes in different agricultural policies, especially in arid and semi-arid areas. Uncertainty in the amount of resources, e.g. water, used for agricultural production entails risk for farmers' income and cropping pattern changes. In the present study, the robust optimization model was used for optimal allocation of arable lands of Khorasan Razavi Province under uncertainty. During the allocation, the effect of water input price variations on total gross margin and cropping pattern was considered. It was found that under certain data, both parameters of total gross margin and total acreage are more than uncertain data. Given that water price variations resulted in tangible changes in wheat acreage, it is recommended to adopt appropriate policies to reduce its production risk

Prospective association between adherence to the Mediterranean diet and hepatic steatosis: the Swiss CoLaus cohort study

Objective: The Mediterranean diet has been promoted as a healthy dietary pattern, but whether the Mediterranean diet may help to prevent hepatic steatosis is not clear. This study aimed to evaluate the prospective association between adherence to the Mediterranean diet and risk of hepatic steatosis. Design: Population-based prospective cohort study. Setting: The Swiss CoLaus Study. Participants: We evaluated 2288 adults (65.4% women, aged 55.8±10.0 years) without hepatic steatosis at first follow-up in 2009–2012. Adherence to the Mediterranean diet was scaled as the Mediterranean diet score (MDS) based on the Mediterranean diet pyramid ascertained with responses to Food Frequency Questionnaires. Outcome measures: New onset of hepatic steatosis was ascertained by two indices separately: the Fatty Liver Index (FLI, ≥60 points) and the non-alcoholic fatty liver disease (NAFLD) score (≥−0.640 points). Prospective associations between adherence to the Mediterranean diet and risk of hepatic steatosis were quantified using Poisson regression. Results: During a mean 5.3 years of follow-up, hepatic steatosis was ascertained in 153 (6.7%) participants by FLI criteria and in 208 (9.1%) by NAFLD score. After multivariable adjustment, higher adherence to MDS was associated with lower risk of hepatic steatosis based on FLI: risk ratio 0.84 (95% CI 0.73 to 0.96) per 1 SD of MDS; 0.85 (0.73 to 0.99) adjusted for BMI; and 0.85 (0.71 to 1.02) adjusted for both BMI and waist circumference. When using NAFLD score, no significant association was found between MDS and risk of hepatic steatosis (0.95 (0.83 to 1.09)). Conclusion: A potential role of the Mediterranean diet in the prevention of hepatic steatosis is suggested by the inverse association observed between adherence to the Mediterranean diet and incidence of hepatic steatosis based on the FLI. The inconsistency of this association when hepatic steatosis was assessed by NAFLD score points to the need for accurate population-level assessment of fatty liver and its physiological markers

Description of Ultra-Processed Food Intake in a Swiss Population-Based Sample of Adults Aged 18 to 75 Years.

Ultra-processed foods (UPFs) are associated with lower diet quality and several non-communicable diseases. Their consumption varies between countries/regions of the world. We aimed to describe the consumption of UPFs in adults aged 18-75 years living in Switzerland. We analysed data from the national food consumption survey conducted among 2085 participants aged 18 to 75 years. Foods and beverages resulting from two 24-h recalls were classified as UPFs or non-UPFs according to the NOVA classification, categorized into 18 food groups, and linked to the Swiss Food Composition Database. Overall, the median energy intake [P25-P75] from UPFs was 587 kcal/day [364-885] or 28.7% [19.9-38.9] of the total energy intake (TEI). The median intake of UPFs relative to TEI was higher among young participants (<30 years, p = 0.001) and those living in the German-speaking part of Switzerland (p = 0.002). The food groups providing the most ultra-processed calories were confectionary, cakes & biscuits (39.5% of total UPF kcal); meat, fish & eggs (14.9%); cereal products, legumes & potatoes (12.5%), and juices & soft drinks (8.0%). UPFs provided a large proportion of sugars (39.3% of total sugar intake), saturated fatty acids (32.8%), and total fats (31.8%) while providing less than 20% of dietary fibre. Consumption of UPFs accounted for nearly a third of the total calories consumed in Switzerland. Public health strategies to reduce UPF consumption should target sugary foods/beverages and processed meat

Superconformal indices at large N and the entropy of AdS5 x SE5 black holes

The large N limit of the four-dimensional superconformal index was computed and successfully compared to the entropy of a class of AdS5 black holes only in the particular case of equal angular momenta. Using the Bethe ansatz formulation, we compute the index at large N with arbitrary chemical potentials for all charges and angular momenta, for general four-dimensional conformal theories with a holographic dual. We conjecture and bring some evidence that a particular universal contribution to the sum over Bethe vacua dominates the index at large N. For SYM, this contribution correctly leads to the entropy of BPS Kerr-Newman black holes in AdS5 x S5 for arbitrary values of the conserved charges, thus completing the microscopic derivation of their microstates. We also consider theories dual to AdS5 x SE5, where SE5 is a Sasaki-Einstein manifold. We first check our results against the so-called universal black hole. We then explicitly construct the near-horizon geometry of BPS Kerr-Newman black holes in AdS5 T^{1,1}, charged under the baryonic symmetry of the conifold theory and with equal angular momenta. We compute the entropy of these black holes using the attractor mechanism and find complete agreement with the field theory predictions

Causal and associational language in observational health research: a systematic evaluation

We estimated the degree to which language used in the high profile medical/public health/epidemiology literature implied causality using language linking exposures to outcomes and action recommendations; examined disconnects between language and recommendations; identified the most common linking phrases; and estimated how strongly linking phrases imply causality. We searched and screened for 1,170 articles from 18 high-profile journals (65 per journal) published from 2010-2019. Based on written framing and systematic guidance, three reviewers rated the degree of causality implied in abstracts and full text for exposure/outcome linking language and action recommendations. Reviewers rated the causal implication of exposure/outcome linking language as None (no causal implication) in 13.8%, Weak 34.2%, Moderate 33.2%, and Strong 18.7% of abstracts. The implied causality of action recommendations was higher than the implied causality of linking sentences for 44.5% or commensurate for 40.3% of articles. The most common linking word in abstracts was “associate” (45.7%). Reviewer’s ratings of linking word roots were highly heterogeneous; over half of reviewers rated “association” as having at least some causal implication. This research undercuts the assumption that avoiding “causal” words leads to clarity of interpretation in medical research