Leader reputation and default in sovereign debt

This paper compares default incentives in competitive sovereign debt markets when leaders can be either democratically elected or dictators. When leaders can be replaced as in democracies, the incentives for repayment are mainly the ego rents from office and the possibility of getting a corrupt leader from replacement. In a dictatorship, on the other hand, the cost of not repaying loans is the permanent loss of reputation and the loss of future access to credit. There is a trade off between repayment and risk sharing. We show, counter-intuitively, that when ego rents are low, and value of reputation to dictators is high, then democracies repay more often and have lower risk premia than dictatorships

Global variation in diabetes diagnosis and prevalence based on fasting glucose and hemoglobin A1c

Fasting plasma glucose (FPG) and hemoglobin A1c (HbA1c) are both used to diagnose diabetes, but these measurements can identify different people as having diabetes. We used data from 117 population-based studies and quantified, in different world regions, the prevalence of diagnosed diabetes, and whether those who were previously undiagnosed and detected as having diabetes in survey screening, had elevated FPG, HbA1c or both. We developed prediction equations for estimating the probability that a person without previously diagnosed diabetes, and at a specific level of FPG, had elevated HbA1c, and vice versa. The age-standardized proportion of diabetes that was previously undiagnosed and detected in survey screening ranged from 30% in the high-income western region to 66% in south Asia. Among those with screen-detected diabetes with either test, the age-standardized proportion who had elevated levels of both FPG and HbA1c was 29-39% across regions; the remainder had discordant elevation of FPG or HbA1c. In most low- and middle-income regions, isolated elevated HbA1c was more common than isolated elevated FPG. In these regions, the use of FPG alone may delay diabetes diagnosis and underestimate diabetes prevalence. Our prediction equations help allocate finite resources for measuring HbA1c to reduce the global shortfall in diabetes diagnosis and surveillance

Worldwide trends in underweight and obesity from 1990 to 2022: a pooled analysis of 3663 population-representative studies with 222 million children, adolescents, and adults

Background Underweight and obesity are associated with adverse health outcomes throughout the life course. We estimated the individual and combined prevalence of underweight or thinness and obesity, and their changes, from 1990 to 2022 for adults and school-aged children and adolescents in 200 countries and territories. Methods We used data from 3663 population-based studies with 222 million participants that measured height and weight in representative samples of the general population. We used a Bayesian hierarchical model to estimate trends in the prevalence of different BMI categories, separately for adults (age ≥20 years) and school-aged children and adolescents (age 5–19 years), from 1990 to 2022 for 200 countries and territories. For adults, we report the individual and combined prevalence of underweight (BMI <18·5 kg/m2) and obesity (BMI ≥30 kg/m2). For schoolaged children and adolescents, we report thinness (BMI <2 SD below the median of the WHO growth reference) and obesity (BMI >2 SD above the median). Findings From 1990 to 2022, the combined prevalence of underweight and obesity in adults decreased in 11 countries (6%) for women and 17 (9%) for men with a posterior probability of at least 0·80 that the observed changes were true decreases. The combined prevalence increased in 162 countries (81%) for women and 140 countries (70%) for men with a posterior probability of at least 0·80. In 2022, the combined prevalence of underweight and obesity was highest in island nations in the Caribbean and Polynesia and Micronesia, and countries in the Middle East and north Africa. Obesity prevalence was higher than underweight with posterior probability of at least 0·80 in 177 countries (89%) for women and 145 (73%) for men in 2022, whereas the converse was true in 16 countries (8%) for women, and 39 (20%) for men. From 1990 to 2022, the combined prevalence of thinness and obesity decreased among girls in five countries (3%) and among boys in 15 countries (8%) with a posterior probability of at least 0·80, and increased among girls in 140 countries (70%) and boys in 137 countries (69%) with a posterior probability of at least 0·80. The countries with highest combined prevalence of thinness and obesity in school-aged children and adolescents in 2022 were in Polynesia and Micronesia and the Caribbean for both sexes, and Chile and Qatar for boys. Combined prevalence was also high in some countries in south Asia, such as India and Pakistan, where thinness remained prevalent despite having declined. In 2022, obesity in school-aged children and adolescents was more prevalent than thinness with a posterior probability of at least 0·80 among girls in 133 countries (67%) and boys in 125 countries (63%), whereas the converse was true in 35 countries (18%) and 42 countries (21%), respectively. In almost all countries for both adults and school-aged children and adolescents, the increases in double burden were driven by increases in obesity, and decreases in double burden by declining underweight or thinness. Interpretation The combined burden of underweight and obesity has increased in most countries, driven by an increase in obesity, while underweight and thinness remain prevalent in south Asia and parts of Africa. A healthy nutrition transition that enhances access to nutritious foods is needed to address the remaining burden of underweight while curbing and reversing the increase in obesit

K-stabilité et variétés kähleriennes avec classe transcendante

In this thesis we are interested in questions of geometric stability for constant scalar curvature Kähler (cscK) manifolds with transcendental cohomology class. As a starting point we develop generalized notions of K-stability, extending a classical picture for polarized manifolds due to G. Tian, S. Donaldson, and others, to the setting of arbitrary compact Kähler manifolds. We refer to these notions as cohomological K-stability. By contrast to the classical theory, this formalism allows us to treat stability questions for non-projective compact Kähler manifolds as well as projective manifolds endowed with non-rational polarizations. As a first main result and a fundamental tool in this thesis, we study subgeodesic rays associated to test configurations in our generalized sense, and establish formulas for the asymptotic slope of a certain family of energy functionals along these rays. This is related to the Deligne pairing construction in algebraic geometry, and covers many of the classical energy functionals in Kähler geometry (including Aubin's J-functional and the Mabuchi K-energy functional). In particular, this yields a natural potential-theoretic aproach to energy functional asymptotics in the theory of K-stability. Building on this foundation we establish a number of stability results for cscK manifolds: First, we show that cscK manifolds are K-semistable in our generalized sense, extending a result due to S. Donaldson in the projective setting. Assuming that the automorphism group is discrete we further show that K-stability is a necessary condition for existence of constant scalar curvature Kähler metrics on compact Kähler manifolds. More precisely, we prove that coercivity of the Mabuchi functional implies uniform K-stability, generalizing results of T. Mabuchi, J. Stoppa, R. Berman, R. Dervan as well as S. Boucksom, T. Hisamoto and M. Jonsson for polarized manifolds. This gives a new and more general proof of one direction of the Yau-Tian-Donaldson conjecture in this setting. The other direction (sufficiency of K-stability) is considered to be one of the most important open problems in Kähler geometry. We finally give some partial results in the case of compact Kähler manifolds admitting non-trivial holomorphic vector fields, discuss some further perspectives and applications of the theory of K-stability for compact Kähler manifolds with transcendental cohomology class, and ask some questions related to stability loci in the Kähler cone.Dans cette thèse nous étudions des questions de stabilité géométrique pour des variétés kähleriennes à courbure scalaire constante (cscK) avec classe de cohomologie transcendante. En tant que point de départ, nous introduisons des notions généralisées de K-stabilité, étendant une image classique introduite par G. Tian et S. Donaldson dans le cadre des variétés polarisées. Contrairement à la théorie classique, ce formalisme nous permet de traiter des questions de stabilité pour des variétés kähleriennes compactes non projectives ainsi que des variétés projectives munis de polarisations non rationnelles. Dans une première partie, nous étudions les rayons sous-géodésiques associés aux configurations tests dites cohomologiques, objets introduitent dans cette thèse. Nous établissons ainsi des formules fondamentales pour la pente asymptotique d'une famille de fonctionnelles d'énergie, le long de ces rayons géodésiques. Ceci est lié au couplage de Deligne en géométrie algébrique, et ce formalise permet en particulier de comprendre le comportement asymptotique d'un grand nombre de fonctionnelles d'énergie classiques en géométrie kählerienne, y compris la fonctionnelle d'Aubin-Mabuchi et la K-énergie. En particulier, ceci fournit une approche pluripotentielle naturelle pour étudier le comportement asymptotique des fonctionnelles d'énergie dans la théorie de K-stabilité. En s'appuyant sur cette première partie, nous démontrons ensuite un certain nombre de résultats de stabilité pour les variétés cscK. Tout d'abord, nous prouvons que les variétés cscK sont K-semistables dans notre sens généralisé, prolongeant ainsi un résultat dû à Donaldson dans le cadre projectif. En supposant que le groupe d'automorphisme est discret, nous montrons en outre que la K-stabilité est une condition nécessaire pour l'existence des métriques cscK sur des variétés kähleriennes compactes. Plus précisément, nous prouvons que la coercivité de la K-énergie implique la K-stabilité uniforme, ainsi généralisant des résultats de Mabuchi, Stoppa, Berman, Dervan et Boucksom-Hisamoto-Jonsson pour des variétés polarisées. Cela donne une preuve nouvelle et plus générale d'une direction de la conjecture Yau-Tian-Donaldson dans ce contexte. L'autre direction (suffisance de K-stabilité) est considérée comme l'un des problèmes ouverts les plus importants en géométrie kählerienne. Nous donnons enfin des résultats partiels dans le cas des variétés kähleriennes compactes qui admettent des champs de vecteurs holomorphes non triviaux. Nous discutons également autour des perspectives et applications de notre théorie de K-stabilité pour les variétés kähleriennes avec classe transcendante, notamment à l'étude des lieux de stabilité dans le cône de Kähler

K-stability and Kähler manifolds with transcendental cohomology class

Dans cette thèse nous étudions des questions de stabilité géométrique pour des variétés kähleriennes à courbure scalaire constante (cscK) avec classe de cohomologie transcendante. En tant que point de départ, nous introduisons des notions généralisées de K-stabilité, étendant une image classique introduite par G. Tian et S. Donaldson dans le cadre des variétés polarisées. Contrairement à la théorie classique, ce formalisme nous permet de traiter des questions de stabilité pour des variétés kähleriennes compactes non projectives ainsi que des variétés projectives munis de polarisations non rationnelles. Dans une première partie, nous étudions les rayons sous-géodésiques associés aux configurations tests dites cohomologiques, objets introduitent dans cette thèse. Nous établissons ainsi des formules fondamentales pour la pente asymptotique d'une famille de fonctionnelles d'énergie, le long de ces rayons géodésiques. Ceci est lié au couplage de Deligne en géométrie algébrique, et ce formalise permet en particulier de comprendre le comportement asymptotique d'un grand nombre de fonctionnelles d'énergie classiques en géométrie kählerienne, y compris la fonctionnelle d'Aubin-Mabuchi et la K-énergie. En particulier, ceci fournit une approche pluripotentielle naturelle pour étudier le comportement asymptotique des fonctionnelles d'énergie dans la théorie de K-stabilité. En s'appuyant sur cette première partie, nous démontrons ensuite un certain nombre de résultats de stabilité pour les variétés cscK. Tout d'abord, nous prouvons que les variétés cscK sont K-semistables dans notre sens généralisé, prolongeant ainsi un résultat dû à Donaldson dans le cadre projectif. En supposant que le groupe d'automorphisme est discret, nous montrons en outre que la K-stabilité est une condition nécessaire pour l'existence des métriques cscK sur des variétés kähleriennes compactes. Plus précisément, nous prouvons que la coercivité de la K-énergie implique la K-stabilité uniforme, ainsi généralisant des résultats de Mabuchi, Stoppa, Berman, Dervan et Boucksom-Hisamoto-Jonsson pour des variétés polarisées. Cela donne une preuve nouvelle et plus générale d'une direction de la conjecture Yau-Tian-Donaldson dans ce contexte. L'autre direction (suffisance de K-stabilité) est considérée comme l'un des problèmes ouverts les plus importants en géométrie kählerienne. Nous donnons enfin des résultats partiels dans le cas des variétés kähleriennes compactes qui admettent des champs de vecteurs holomorphes non triviaux. Nous discutons également autour des perspectives et applications de notre théorie de K-stabilité pour les variétés kähleriennes avec classe transcendante, notamment à l'étude des lieux de stabilité dans le cône de Kähler.In this thesis we are interested in questions of geometric stability for constant scalar curvature Kähler (cscK) manifolds with transcendental cohomology class. As a starting point we develop generalized notions of K-stability, extending a classical picture for polarized manifolds due to G. Tian, S. Donaldson, and others, to the setting of arbitrary compact Kähler manifolds. We refer to these notions as cohomological K-stability. By contrast to the classical theory, this formalism allows us to treat stability questions for non-projective compact Kähler manifolds as well as projective manifolds endowed with non-rational polarizations. As a first main result and a fundamental tool in this thesis, we study subgeodesic rays associated to test configurations in our generalized sense, and establish formulas for the asymptotic slope of a certain family of energy functionals along these rays. This is related to the Deligne pairing construction in algebraic geometry, and covers many of the classical energy functionals in Kähler geometry (including Aubin's J-functional and the Mabuchi K-energy functional). In particular, this yields a natural potential-theoretic aproach to energy functional asymptotics in the theory of K-stability. Building on this foundation we establish a number of stability results for cscK manifolds: First, we show that cscK manifolds are K-semistable in our generalized sense, extending a result due to S. Donaldson in the projective setting. Assuming that the automorphism group is discrete we further show that K-stability is a necessary condition for existence of constant scalar curvature Kähler metrics on compact Kähler manifolds. More precisely, we prove that coercivity of the Mabuchi functional implies uniform K-stability, generalizing results of T. Mabuchi, J. Stoppa, R. Berman, R. Dervan as well as S. Boucksom, T. Hisamoto and M. Jonsson for polarized manifolds. This gives a new and more general proof of one direction of the Yau-Tian-Donaldson conjecture in this setting. The other direction (sufficiency of K-stability) is considered to be one of the most important open problems in Kähler geometry. We finally give some partial results in the case of compact Kähler manifolds admitting non-trivial holomorphic vector fields, discuss some further perspectives and applications of the theory of K-stability for compact Kähler manifolds with transcendental cohomology class, and ask some questions related to stability loci in the Kähler cone

pH Dependence of γ‑Aminobutyric Acid Iontronic Transport

The organic electronic ion pump (OEIP) has been developed as an “iontronic” tool for delivery of biological signaling compounds. OEIPs rely on electrophoretically “pumping” charged compounds, either at neutral or shifted pH, through an ion-selective channel. Significant shifts in pH lead to an abundance of H⁺ or OH^–, which are delivered along with the intended substance. While this method has been used to transport various neurotransmitters, the role of pH has not been explored. Here we present an investigation of the role of pH on OEIP transport efficiency using the neurotransmitter γ-aminobutyric acid (GABA) as the model cationic delivery substance. GABA transport is evaluated at various pHs using electrical and chemical characterization and compared to molecular dynamics simulations, all of which agree that pH 3 is ideal for GABA transport. These results demonstrate a useful method for optimizing transport of other substances and thus broadening OEIP applications

Bariatric Surgery: Risks and Rewards

Context: Over 23 million Americans are afflicted with severe obesity, i.e. their body mass index (in kilograms per square meter) values exceed 35. Of even greater concern is the association of the adiposity with comorbidities such as diabetes, hypertension, cardiopulmonary failure, asthma, pseudotumor cerebri, infertility, and crippling arthritis