Breakdown of linear dielectric theory for the interaction between hydrated ions and graphene

Many vital processes taking place in electrolytes, such as nanoparticle self-assembly, water purification, and the operation of aqueous supercapacitors, rely on the precise many-body interactions between surfaces and ions in water. Here we study the interaction between a hydrated ion and a charge-neutral graphene layer using atomistic molecular dynamics simulations. For small separations, the ion–graphene repulsion is of nonelectrostatic nature, and for intermediate separations, van der Waals attraction becomes important. Contrary to prevailing theory, we show that nonlinear and tensorial dielectric effects become non-negligible close to surfaces, even for monovalent ions. This breakdown of standard isotropic linear dielectric theory has important consequences for the understanding and modeling of charged objects at surfaces

Water Dielectric Effects in Planar Confinement

We investigate the dielectric profile of water confined between two planar polar walls using atomistic molecular dynamics simulations. For a water slab thickness below 1 nm the dielectric response is highly asymmetric: while the parallel component slightly increases compared to bulk, the perpendicular one decreases drastically due to anticorrelated polarization of neighboring water molecules. We demonstrate the importance of the dielectric contribution due to flexible polar headgroups and derive an effective dielectric tensorial box model suitable for coarse-grained electrostatic modeling

Universal and Nonuniversal Aspects of Electrostatics in Aqueous Nanoconfinement

Dielectric water properties, which significantly change in confinement, determine electrostatic interactions and thereby influence all molecular forces and chemical reactions. We present comparative simulations of water between graphene sheets, decanol monolayers, and phospholipid and glycolipid bilayers. Generally, dielectric profiles strongly differ in perpendicular and parallel surface directions and for large surface separation decay to the bulk value 1-2 nm away from the surface. Polar surface groups enhance the local interfacial dielectric response and for phospholipid bilayers induce a giant parallel contribution. A mapping on a box model with asymptotically determined effective water layer widths demonstrates that the perpendicular effective dielectric constant for all systems decreases for confinement below a nanometer, while the parallel one stays rather constant. The confinement-dependent perpendicular effective dielectric constant for graphene is in agreement with experimental data only if the effective water layer width is suitably adjusted. The interactions between two charges at small separation depend on the product of parallel and perpendicular effective water dielectric components; for large separation the interactions depend on the confining medium. For metallic confining media the interactions at large separation decay exponentially with a decay length that depends on the ratio of the effective parallel and perpendicular water dielectric components

Global burden of 369 diseases and injuries in 204 countries and territories, 1990–2019: a systematic analysis for the Global Burden of Disease Study 2019

Background: In an era of shifting global agendas and expanded emphasis on non-communicable diseases and injuries along with communicable diseases, sound evidence on trends by cause at the national level is essential. The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) provides a systematic scientific assessment of published, publicly available, and contributed data on incidence, prevalence, and mortality for a mutually exclusive and collectively exhaustive list of diseases and injuries. Methods: GBD estimates incidence, prevalence, mortality, years of life lost (YLLs), years lived with disability (YLDs), and disability-adjusted life-years (DALYs) due to 369 diseases and injuries, for two sexes, and for 204 countries and territories. Input data were extracted from censuses, household surveys, civil registration and vital statistics, disease registries, health service use, air pollution monitors, satellite imaging, disease notifications, and other sources. Cause-specific death rates and cause fractions were calculated using the Cause of Death Ensemble model and spatiotemporal Gaussian process regression. Cause-specific deaths were adjusted to match the total all-cause deaths calculated as part of the GBD population, fertility, and mortality estimates. Deaths were multiplied by standard life expectancy at each age to calculate YLLs. A Bayesian meta-regression modelling tool, DisMod-MR 2.1, was used to ensure consistency between incidence, prevalence, remission, excess mortality, and cause-specific mortality for most causes. Prevalence estimates were multiplied by disability weights for mutually exclusive sequelae of diseases and injuries to calculate YLDs. We considered results in the context of the Socio-demographic Index (SDI), a composite indicator of income per capita, years of schooling, and fertility rate in females younger than 25 years. Uncertainty intervals (UIs) were generated for every metric using the 25th and 975th ordered 1000 draw values of the posterior distribution. Findings: Global health has steadily improved over the past 30 years as measured by age-standardised DALY rates. After taking into account population growth and ageing, the absolute number of DALYs has remained stable. Since 2010, the pace of decline in global age-standardised DALY rates has accelerated in age groups younger than 50 years compared with the 1990–2010 time period, with the greatest annualised rate of decline occurring in the 0–9-year age group. Six infectious diseases were among the top ten causes of DALYs in children younger than 10 years in 2019: lower respiratory infections (ranked second), diarrhoeal diseases (third), malaria (fifth), meningitis (sixth), whooping cough (ninth), and sexually transmitted infections (which, in this age group, is fully accounted for by congenital syphilis; ranked tenth). In adolescents aged 10–24 years, three injury causes were among the top causes of DALYs: road injuries (ranked first), self-harm (third), and interpersonal violence (fifth). Five of the causes that were in the top ten for ages 10–24 years were also in the top ten in the 25–49-year age group: road injuries (ranked first), HIV/AIDS (second), low back pain (fourth), headache disorders (fifth), and depressive disorders (sixth). In 2019, ischaemic heart disease and stroke were the top-ranked causes of DALYs in both the 50–74-year and 75-years-and-older age groups. Since 1990, there has been a marked shift towards a greater proportion of burden due to YLDs from non-communicable diseases and injuries. In 2019, there were 11 countries where non-communicable disease and injury YLDs constituted more than half of all disease burden. Decreases in age-standardised DALY rates have accelerated over the past decade in countries at the lower end of the SDI range, while improvements have started to stagnate or even reverse in countries with higher SDI. Interpretation: As disability becomes an increasingly large component of disease burden and a larger component of health expenditure, greater research and developm nt investment is needed to identify new, more effective intervention strategies. With a rapidly ageing global population, the demands on health services to deal with disabling outcomes, which increase with age, will require policy makers to anticipate these changes. The mix of universal and more geographically specific influences on health reinforces the need for regular reporting on population health in detail and by underlying cause to help decision makers to identify success stories of disease control to emulate, as well as opportunities to improve. Funding: Bill & Melinda Gates Foundation. © 2020 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licens

Global burden of 288 causes of death and life expectancy decomposition in 204 countries and territories and 811 subnational locations, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BACKGROUND Regular, detailed reporting on population health by underlying cause of death is fundamental for public health decision making. Cause-specific estimates of mortality and the subsequent effects on life expectancy worldwide are valuable metrics to gauge progress in reducing mortality rates. These estimates are particularly important following large-scale mortality spikes, such as the COVID-19 pandemic. When systematically analysed, mortality rates and life expectancy allow comparisons of the consequences of causes of death globally and over time, providing a nuanced understanding of the effect of these causes on global populations. METHODS The Global Burden of Diseases, Injuries, and Risk Factors Study (GBD) 2021 cause-of-death analysis estimated mortality and years of life lost (YLLs) from 288 causes of death by age-sex-location-year in 204 countries and territories and 811 subnational locations for each year from 1990 until 2021. The analysis used 56 604 data sources, including data from vital registration and verbal autopsy as well as surveys, censuses, surveillance systems, and cancer registries, among others. As with previous GBD rounds, cause-specific death rates for most causes were estimated using the Cause of Death Ensemble model-a modelling tool developed for GBD to assess the out-of-sample predictive validity of different statistical models and covariate permutations and combine those results to produce cause-specific mortality estimates-with alternative strategies adapted to model causes with insufficient data, substantial changes in reporting over the study period, or unusual epidemiology. YLLs were computed as the product of the number of deaths for each cause-age-sex-location-year and the standard life expectancy at each age. As part of the modelling process, uncertainty intervals (UIs) were generated using the 2·5th and 97·5th percentiles from a 1000-draw distribution for each metric. We decomposed life expectancy by cause of death, location, and year to show cause-specific effects on life expectancy from 1990 to 2021. We also used the coefficient of variation and the fraction of population affected by 90% of deaths to highlight concentrations of mortality. Findings are reported in counts and age-standardised rates. Methodological improvements for cause-of-death estimates in GBD 2021 include the expansion of under-5-years age group to include four new age groups, enhanced methods to account for stochastic variation of sparse data, and the inclusion of COVID-19 and other pandemic-related mortality-which includes excess mortality associated with the pandemic, excluding COVID-19, lower respiratory infections, measles, malaria, and pertussis. For this analysis, 199 new country-years of vital registration cause-of-death data, 5 country-years of surveillance data, 21 country-years of verbal autopsy data, and 94 country-years of other data types were added to those used in previous GBD rounds. FINDINGS The leading causes of age-standardised deaths globally were the same in 2019 as they were in 1990; in descending order, these were, ischaemic heart disease, stroke, chronic obstructive pulmonary disease, and lower respiratory infections. In 2021, however, COVID-19 replaced stroke as the second-leading age-standardised cause of death, with 94·0 deaths (95% UI 89·2-100·0) per 100 000 population. The COVID-19 pandemic shifted the rankings of the leading five causes, lowering stroke to the third-leading and chronic obstructive pulmonary disease to the fourth-leading position. In 2021, the highest age-standardised death rates from COVID-19 occurred in sub-Saharan Africa (271·0 deaths [250·1-290·7] per 100 000 population) and Latin America and the Caribbean (195·4 deaths [182·1-211·4] per 100 000 population). The lowest age-standardised death rates from COVID-19 were in the high-income super-region (48·1 deaths [47·4-48·8] per 100 000 population) and southeast Asia, east Asia, and Oceania (23·2 deaths [16·3-37·2] per 100 000 population). Globally, life expectancy steadily improved between 1990 and 2019 for 18 of the 22 investigated causes. Decomposition of global and regional life expectancy showed the positive effect that reductions in deaths from enteric infections, lower respiratory infections, stroke, and neonatal deaths, among others have contributed to improved survival over the study period. However, a net reduction of 1·6 years occurred in global life expectancy between 2019 and 2021, primarily due to increased death rates from COVID-19 and other pandemic-related mortality. Life expectancy was highly variable between super-regions over the study period, with southeast Asia, east Asia, and Oceania gaining 8·3 years (6·7-9·9) overall, while having the smallest reduction in life expectancy due to COVID-19 (0·4 years). The largest reduction in life expectancy due to COVID-19 occurred in Latin America and the Caribbean (3·6 years). Additionally, 53 of the 288 causes of death were highly concentrated in locations with less than 50% of the global population as of 2021, and these causes of death became progressively more concentrated since 1990, when only 44 causes showed this pattern. The concentration phenomenon is discussed heuristically with respect to enteric and lower respiratory infections, malaria, HIV/AIDS, neonatal disorders, tuberculosis, and measles. INTERPRETATION Long-standing gains in life expectancy and reductions in many of the leading causes of death have been disrupted by the COVID-19 pandemic, the adverse effects of which were spread unevenly among populations. Despite the pandemic, there has been continued progress in combatting several notable causes of death, leading to improved global life expectancy over the study period. Each of the seven GBD super-regions showed an overall improvement from 1990 and 2021, obscuring the negative effect in the years of the pandemic. Additionally, our findings regarding regional variation in causes of death driving increases in life expectancy hold clear policy utility. Analyses of shifting mortality trends reveal that several causes, once widespread globally, are now increasingly concentrated geographically. These changes in mortality concentration, alongside further investigation of changing risks, interventions, and relevant policy, present an important opportunity to deepen our understanding of mortality-reduction strategies. Examining patterns in mortality concentration might reveal areas where successful public health interventions have been implemented. Translating these successes to locations where certain causes of death remain entrenched can inform policies that work to improve life expectancy for people everywhere. FUNDING Bill & Melinda Gates Foundation

Global, regional, and national burden of disorders affecting the nervous system, 1990–2021: a systematic analysis for the Global Burden of Disease Study 2021

BackgroundDisorders affecting the nervous system are diverse and include neurodevelopmental disorders, late-life neurodegeneration, and newly emergent conditions, such as cognitive impairment following COVID-19. Previous publications from the Global Burden of Disease, Injuries, and Risk Factor Study estimated the burden of 15 neurological conditions in 2015 and 2016, but these analyses did not include neurodevelopmental disorders, as defined by the International Classification of Diseases (ICD)-11, or a subset of cases of congenital, neonatal, and infectious conditions that cause neurological damage. Here, we estimate nervous system health loss caused by 37 unique conditions and their associated risk factors globally, regionally, and nationally from 1990 to 2021.MethodsWe estimated mortality, prevalence, years lived with disability (YLDs), years of life lost (YLLs), and disability-adjusted life-years (DALYs), with corresponding 95% uncertainty intervals (UIs), by age and sex in 204 countries and territories, from 1990 to 2021. We included morbidity and deaths due to neurological conditions, for which health loss is directly due to damage to the CNS or peripheral nervous system. We also isolated neurological health loss from conditions for which nervous system morbidity is a consequence, but not the primary feature, including a subset of congenital conditions (ie, chromosomal anomalies and congenital birth defects), neonatal conditions (ie, jaundice, preterm birth, and sepsis), infectious diseases (ie, COVID-19, cystic echinococcosis, malaria, syphilis, and Zika virus disease), and diabetic neuropathy. By conducting a sequela-level analysis of the health outcomes for these conditions, only cases where nervous system damage occurred were included, and YLDs were recalculated to isolate the non-fatal burden directly attributable to nervous system health loss. A comorbidity correction was used to calculate total prevalence of all conditions that affect the nervous system combined.FindingsGlobally, the 37 conditions affecting the nervous system were collectively ranked as the leading group cause of DALYs in 2021 (443 million, 95% UI 378–521), affecting 3·40 billion (3·20–3·62) individuals (43·1%, 40·5–45·9 of the global population); global DALY counts attributed to these conditions increased by 18·2% (8·7–26·7) between 1990 and 2021. Age-standardised rates of deaths per 100 000 people attributed to these conditions decreased from 1990 to 2021 by 33·6% (27·6–38·8), and age-standardised rates of DALYs attributed to these conditions decreased by 27·0% (21·5–32·4). Age-standardised prevalence was almost stable, with a change of 1·5% (0·7–2·4). The ten conditions with the highest age-standardised DALYs in 2021 were stroke, neonatal encephalopathy, migraine, Alzheimer's disease and other dementias, diabetic neuropathy, meningitis, epilepsy, neurological complications due to preterm birth, autism spectrum disorder, and nervous system cancer.InterpretationAs the leading cause of overall disease burden in the world, with increasing global DALY counts, effective prevention, treatment, and rehabilitation strategies for disorders affecting the nervous system are needed

Einfluss von Wasser auf die Wechselwirkung und Reibung zwischen polaren Oberflächen

The effects of water on the interaction and friction between surfaces are important both in biological and technological systems. For a quantitative description, the molecular details require modeling of all relevant degrees of freedom. The aim of this work is to obtain atomistic information from Molecular Dynamics simulations and incorporate them into continuum models, which are extended where necessary. Throughout this work we study interactions between water-separated surfaces, which requires control of the water chemical potential. First, we study the dielectric properties of water confined between flexible polar groups, which reveals a highly asymmetric behavior at separations below 1 nm: while the component of the dielectric permittivity parallel to the surface slightly increases compared to bulk, the perpendicular one drastically decreases due to the anti-correlated polarization of neighboring water molecules. The obtained molecular information is incorporated into a tensorial box-model suitable for coarse-grained electrostatic modeling. Second, we investigate the origin of the overwhelmingly repulsive hydration force that universally acts between hydrated surfaces. We model the indirect, water--mediated forces in terms of a Landau--Ginzburg free energy and obtain all phenomenological parameters from the simulations. We find that polarization related order parameters quantitatively describe the decay length of the indirect pressures, but only account for about ten percent of the amplitude, which we attribute to effects that are not captured within the one-dimensional mean-field model. Contributions from other order parameters are negligible. Third, we compare the pressure as a function of separation between uncharged and charged surfaces with neutralizing counterions. At separations larger than 0.5 nm and at low surface charge, we find that the continuum Poisson--Boltzmann model accounts for the additional pressures. For small separations, the ion--surface repulsion is dominating. Our simulations at controlled chemical potential offer the possibility to investigate such effects in explicit water for the first time. Last, we study the shear friction between polar surfaces in the linear response regime at low shearing velocity, which is the relevant regime for typical biological applications. With decreasing water film thickness we find three consecutive friction regimes: For thick films friction is governed by bulk water viscosity. At separations of about a nanometer the highly viscous interfacial water layers dominate and increase the surface friction, while at the transition to the dry friction limit interfacial slip sets in. We construct a confinement-dependent friction model which accounts for the additive friction contributions from bulk-like water, interfacial water layers and slip on arbitrary lengthscales.Der Einfluss von Wasser auf die Wechselwirkung und Reibung zwischen Oberflächen ist relevant in biologischen und technischen Systemen. Um diese quantitativ zu beschreiben, müssen auf molekularer Ebene alle relevanten Freiheitsgrade berücksichtigt werden. Ziel dieser Arbeit ist die Extraktion der Information auf atomarer Ebene aus Molekül\\-dynamik\\-si\\-mu\\-la\\-tio\\-nen und deren Einbindung in Kontinuumsmodelle, die wir gegebenenfalls erweitern. Diese Arbeit behandelt die Wechselwirkung zwischen Oberflächen in Wasser, wobei stets das chemische Potential von Wasser kontrolliert werden muss. Zunächst beschäftigt sich die Arbeit mit den dielektrischen Eigenschaften von Wasser zwischen polaren Kopfgruppen. Bei Abständen unter 1 nm ist die Komponente parallel zur Oberfläche etwas größer als in reinem Wasser, wogegen die senkrechte Komponente durch die anti-korrelierte Polarisierung benachbarter Wasser reduziert wird. Aus den dielektrischen Profilen berechnen wir ein Boxmodell, das sich zur effektiven elektrostatischen Modellierung eignet. Im zweiten Teil befassen wir uns mit dem Ursprung der extrem starken Hydrationsrepulsion, die generell zwischen hydratisierten Oberflächen wirkt. Wir beschreiben die indirekten, durch Wasser vermittelten Kräfte mit einer Landau--Ginzburg Freien Energie und leiten die phänomenologischen Parameter aus Simulationsdaten ab. Ordnungsparameter, die auf der Polarisierung basieren, liefern quantitativ die korrekte Länge, auf welcher der indirekte Druck abfällt, erklären jedoch nur zehn Prozent des Drucks, was wir auf Effekte zurückführen, die sich nicht in der eindimensionalen Näherung beschreiben lassen. Andere Ordnungsparameter liefern einen viel kleineren Beitrag. Das dritte Kapitel befasst sich mit Druck-Abstands-Kurven für neutrale und geladene Oberflächen, die durch Gegenionen neutralisiert werden. Bei Abständen über 0.5 nm und kleinen Ladungsdichten beschreibt das Poisson--Boltzmann--Modell die zusätzlichen Drücke. Für kleine Abstände dominiert die Repulsion zwischen Ionen und Oberfläche. Unsere Simulationen unter Berücksichtigung des chemischen Potentials von Wasser ermögli\\-chen erstmals die Analyse solcher Effekte in explizitem Wasser. Zuletzt betrachten wir die Scherkraft zwischen polaren Oberflächen im linearen Bereich bei kleinen Schergeschwindigkeiten, was typischen biologischen Situationen entspricht. Mit abnehmender Wasserschichtdicke treten drei Regimes auf: Die Viskosität von purem Wasser beschreibt große Abstände. Unterhalb eines Nanometers dominieren die hoch\\-viskosen Grenzschichten und erhöhen die Reibung. Beim Übergang zur trockenen Reibung kommt es zu Schlupf. Mit einem abstandsabhängigen Modell beschreiben wir die drei additiven Beiträge auf beliebigen Längenskalen

Electronic screening using a virtual Thomas-Fermi fluid for predicting wetting and phase transitions of ionic liquids at metal surfaces

Of relevance to energy storage, electrochemistry and catalysis, ionic and dipolar liquids display unexpected behaviours-especially in confinement. Beyond adsorption, over-screening and crowding effects, experiments have highlighted novel phenomena, such as unconventional screening and the impact of the electronic nature-metallic versus insulating - of the confining surface. Such behaviours, which challenge existing frameworks, highlight the need for tools to fully embrace the properties of confined liquids. Here we introduce a novel approach that involves electronic screening while capturing molecular aspects of interfacial fluids. Although available strategies consider perfect metal or insulator surfaces, we build on the Thomas-Fermi formalism to develop an effective approach that deals with any imperfect metal between these asymptotes. Our approach describes electrostatic interactions within the metal through a 'virtual' Thomas-Fermi fluid of charged particles, whose Debye length sets the screening length $\lambda$. We show that this method captures the electrostatic interaction decay and electrochemical behaviour on varying $\lambda$. By applying this strategy to an ionic liquid, we unveil a wetting transition on switching from insulating to metallic conditions

Dispersion truncation affects the phase behavior of bulk and confined fluids: Coexistence, adsorption, and criticality

International audienceWe present molecular simulations of bulk and confined Lennard-Jones fluids to asses the effect of dispersion truncation through a simple spherical cutoff. The latter is well corrected on a mean field level for bulk fluids if the cutoff distance is larger than about three molecular diameters. In confinement, however, there is no general analytical treatment and thus the truncated and shifted Lennard-Jones potential has to be employed, with drastic consequences on the bulk critical temperature, vapor/liquid coexistence pressure and surface tension. We show using Grand-Canonical Monte-Carlo simulations of nitrogen adsorption in amorphous silica nanopores that the choice of the cutoff significantly modifies the pressure at which capillary condensation occurs and compute the capillary critical temperature in terms of a first order transition between an adsorbed film and filled pores