Search

With the increasing global demand for net-zero carbon emissions, actions to address climate change have gained momentum among policymakers and the public. The urgent need for a sustainable economy is underscored by the mounting waste crisis in landfills and oceans. However, the proliferation of distributed electronic devices poses a significant challenge due to the resulting electronic waste. To combat this issue, the development of sustainable and environmentally friendly materials for these devices is imperative. Cellulose, an abundant and CO2-neutral substance with a long history of diverse applications, holds great potential. By integrating electrically interactive components with cellulosic materials, innovative biobased composites have been created, enabling the fabrication of bulk electroactive paper and the establishment of new, potentially more sustainable manufacturing processes for electronic devices. This review explores recent advances in bulk electroactive paper, including the fundamental interactions between its constituents, manufacturing techniques, and large-scale applications in the field of electronics. Furthermore, it addresses the importance and challenges of scaling up production of electroactive paper, highlighting the need for further research and development. [ABSTRACT FROM AUTHOR]

We review recent contributions to the modeling of democratic backsliding. We organize these theories according to (a) the source of constraints on the executive (vertical or horizontal restrainers) and (b) the target of backsliding (electoral manipulation or executive aggrandizement), and then use these concepts to build a scaffold for a meta-model of democratic backsliding. This meta-model allows us to describe and compare the premises and insights of this scholarship. We further apply our two-dimensional classification to more than 30 empirical papers and show how these theories can guide research design. We conclude by highlighting open issues for future research. [ABSTRACT FROM AUTHOR]

Despite lignin having long been viewed as an impediment to the processing of biomass for the production of paper, biofuels, and high-value chemicals, the valorization of lignin to fuels, chemicals, and materials is now clearly recognized as a critical element for the lignocellulosic bioeconomy. However, the intended application for lignin will likely require a preferred lignin composition and form. To that end, effective lignin valorization will require the integration of plant biology, providing optimal feedstocks, with chemical process engineering, providing efficient lignin transformations. Recent advances in our understanding of lignin biosynthesis have shown that lignin structure is extremely diverse and potentially tunable, while simultaneous developments in lignin refining have resulted in the development of several processes that are more agnostic to lignin composition. Here, we review the interface between in planta lignin design and lignin processing and discuss the advances necessary for lignin valorization to become a feature of advanced biorefining. [ABSTRACT FROM AUTHOR]

Rotating-disk flows were first considered by von Kármán in a seminal paper in 1921, where boundary layers in general were discussed and, in two of the nine sections, results for the laminar and turbulent boundary layers over a rotating disk were presented. It was not until in 1955 that flow visualization discovered the existence of stationary cross-flow vortices on the disk prior to the transition to turbulence. The rotating disk can be seen as a special case of rotating cones, and recent research has shown that broad cones behave similarly to disks, whereas sharp cones are susceptible to a different type of instability. Here, we provide a review of the major developments since von Kármán's work from 100 years ago, regarding instability, transition, and turbulence in the boundary layers, and we include some analysis not previously published. [ABSTRACT FROM AUTHOR]

This article argues that conflict rather than consensus defines the history of African American political thought. Its seminal figures have pursued justice along different and diverging lines—including advocating reformist, realist, and nationalist paths. While there is agreement that white supremacy is a form of social, economic, and political domination that should be eradicated, there is disagreement regarding its nature, effects, and resilience. This variance in judgments and inferences regarding the foundations and consequences of white supremacy leads to different accounts of social change, diverging strategic advice for realizing that change, and conflicting political theories. To press this claim, I consider the conflicting political visions of Booker T. Washington (1856–1915), W.E.B. Du Bois (1868–1963), and Marcus Garvey (1887–1940). [ABSTRACT FROM AUTHOR]

It has long been argued that only humans could produce and understand language. But now, for the first time, artificial language models (LMs) achieve this feat. Here we survey the new purchase LMs are providing on the question of how language is implemented in the brain. We discuss why, a priori, LMs might be expected to share similarities with the human language system. We then summarize evidence that LMs represent linguistic information similarly enough to humans to enable relatively accurate brain encoding and decoding during language processing. Finally, we examine which LM properties—their architecture, task performance, or training—are critical for capturing human neural responses to language and review studies using LMs as in silico model organisms for testing hypotheses about language. These ongoing investigations bring us closer to understanding the representations and processes that underlie our ability to comprehend sentences and express thoughts in language. [ABSTRACT FROM AUTHOR]

The hippocampus is critical for memory and spatial navigation. The ability to map novel environments, as well as more abstract conceptual relationships, is fundamental to the cognitive flexibility that humans and other animals require to survive in a dynamic world. In this review, we survey recent advances in our understanding of how this flexibility is implemented anatomically and functionally by hippocampal circuitry, during both active exploration (online) and rest (offline). We discuss the advantages and limitations of spike timing–dependent plasticity and the more recently discovered behavioral timescale synaptic plasticity in supporting distinct learning modes in the hippocampus. Finally, we suggest complementary roles for these plasticity types in explaining many-shot and single-shot learning in the hippocampus and discuss how these rules could work together to support the learning of cognitive maps. [ABSTRACT FROM AUTHOR]

This review highlights major developments and milestones during the early days of numerical simulation of turbulent flows and its use to increase our understanding of turbulence phenomena. The period covered starts with the first simulations of decaying homogeneous isotropic turbulence in 1971–1972 and ends about 25 years later. Some earlier history of the progress in weather prediction is included if relevant. Only direct simulation, in which all scales of turbulence are accounted for explicitly, and large-eddy simulation, in which the effect of the smaller scales is modeled, are discussed. The method by which all scales are modeled, Reynolds-averaged Navier–Stokes, is not covered. [ABSTRACT FROM AUTHOR]

Observations that resolve nearby galaxies into individual regions across multiple phases of the gas–star formation–feedback "matter cycle" have provided a sharp new view of molecular clouds, star-formation efficiencies, timescales for region evolution, and stellar feedback. We synthesize these results, covering aspects relevant to the interpretation of observables, and conclude the following: The observed cloud-scale molecular gas surface density, line width, and internal pressure all reflect the large-scale galactic environment while also appearing mostly consistent with properties of a turbulent medium strongly affected by self-gravity. Cloud-scale data allow for statistical inference of both evolutionary and physical timescales. These suggest a period of cloud collapse on the order of the free-fall or turbulent crossing time (∼10–30 Myr) followed by forming massive stars and subsequent rapid (≲5 Myr) gas clearing after the onset of star formation. The star-formation efficiency per free-fall time is well determined over thousands of individual regions at εff ≈ 0.5−0.3+0.7%. The role of stellar feedback is now measured using multiple observational approaches. The net yield is constrained by the requirement to support the vertical weight of the galaxy disk. Meanwhile, the short gas-clearing timescales suggest a large role for presupernova feedback in cloud disruption. This leaves the supernovae free to exert a large influence on the larger galaxy, including stirring turbulence, launching galactic-scale winds, and carving superbubbles. [ABSTRACT FROM AUTHOR]

Human interest in the possibility of other worlds in the Universe has existed for over two millennia. In recent centuries, this question has been translated into the following terms: Are there planetary systems linked to stars other than the Sun? Developments in astronomical instrumentation have transformed this philosophical dream into a new, vibrant chapter in astronomy. This article describes my journey that started over 40 years ago with the exploration of the dynamics of our Galaxy, that brought astonishing scientific progress to which my collaborators and I have contributed, and eventually led to the amazing discovery of the plurality of worlds. [ABSTRACT FROM AUTHOR]

This review covers the techniques, observations, and inferences of solar flare spectroscopy. It is not a spectroscopist's view of solar flares but rather a solar flare physicist's view of spectroscopy. Spectroscopy is carried out across the electromagnetic spectrum, but this review emphasizes the optical to soft X-ray part of the spectrum and discusses results from spectroscopy applied to the preflare, impulsive, and gradual phases, as well as a few highlights from modeling. The main spectroscopic signatures of the preflare phase are line broadening in optically thin ultraviolet to soft X-ray lines and small Doppler shifts in active region filaments that are becoming unstable. In the impulsive phase, fast upflows of heated plasma into the corona and slow downflows of cooler chromospheric plasma take place at the sites of strong chromospheric energy deposition. Radiation-hydrodynamic modeling of optically thick spectral lines gives a picture of an impulsive-phase chromosphere with a dense, heated layer deep in the atmosphere and an overlying, downward moving condensation that is partially optically thin. Gradual-phase observations show us the heated coronal plasma cooling and draining but also provide evidence for ongoing slow energy input and slow upflows in other locations. Interesting hints of non-Maxwellian and nonequilibrium plasmas have been found, along with possible evidence of plasma turbulence from line broadening. [ABSTRACT FROM AUTHOR]

The chemical compositions of stars encode the history of the universe and are thus fundamental for advancing our knowledge of astrophysics and cosmology. However, measurements of elemental abundance ratios, and our interpretations of them, strongly depend on the physical assumptions that dictate the generation of synthetic stellar spectra. Three-dimensional radiation-hydrodynamic (3D RHD) box-in-a-star simulations of stellar atmospheres offer a more realistic representation of surface convection occurring in late-type stars than do traditional one-dimensional (1D) hydrostatic models. As evident from a multitude of observational tests, the coupling of 3D RHD models with line formation in nonlocal thermodynamic equilibrium (non-LTE) today provides a solid foundation for abundance analysis for many elements. This review describes the ongoing and transformational work to advance the state of the art and replace 1D LTE spectrum synthesis with its 3D non-LTE counterpart. In summary: 3D and non-LTE effects are intricately coupled, and consistent modeling thereof is necessary for high-precision abundances; such modeling is currently feasible for individual elements in large surveys. Mean 3D (〈3D〉) models are not adequate as substitutes. The solar abundance debate is presently dominated by choices and systematic uncertainties that are not specific to 3D non-LTE modeling. 3D non-LTE abundance corrections have a profound impact on our understanding of FGK-type stars, exoplanets, and the nucleosynthetic origins of the elements. [ABSTRACT FROM AUTHOR]

M dwarfs dominate the stellar population, accounting for three of every four stars, the nearest of which is Proxima Centauri, the closest destination beyond our Solar System. These cool stars span large ranges in luminosities (one ten-thousandth to 6% L⊙) and temperatures (2,100–3,900 K) and have spectra dominated by absorption bands of titanium oxide (TiO) and, for the latest spectral types, vanadium oxide (VO). They have masses that span 0.075 to 0.61 M⊙, a factor of eight, which is comparable with a spread in masses for dwarf types mid-B through K. Unlike these more massive stars, in the age of the Universe no M dwarfs have evolved in any significant way. M dwarf systems are multiple roughly one-quarter of the time, with the closest binaries found in orbits that have been circularized via tides for orbital periods of about one week. Unlike any other type of main sequence star, there is a gap in the distribution of M dwarfs near masses of 0.35 M⊙ that pinpoints the separation of partially and fully convective stars, yet both types of M dwarfs are often active, showing both Hα in emission and flares. Many planets are found orbiting M dwarfs, and most of them are terrestrial or neptunian in size, rather than jovian, yet much more work remains to be done to characterize the exoplanet population. Overall, the Solar Neighborhood is dominated by M dwarfs that are likely orbited by many small, as yet unseen, planets—some of which may harbor life very near to that in our Solar System: M dwarfs account for three of every four stars. M dwarf counts increase all the way to the end of the main sequence. M dwarfs are partially radiative at high masses and fully convective at low masses. [ABSTRACT FROM AUTHOR]

Galactic winds shape the stellar, gas, and metal content of galaxies. To quantify their impact, we must understand their physics. We review potential wind-driving mechanisms and observed wind properties, with a focus on the warm ionized and hot X-ray-emitting gas. Energy and momentum injection by supernovae (SNe), cosmic rays, radiation pressure, and magnetic fields are considered in the light of observations: Emission and absorption line measurements of cool/warm gas provide our best physical diagnostics of galactic outflows. The critical unsolved problem is how to accelerate cool gas to the high velocities observed. Although conclusive evidence for no one mechanism exists, the momentum, energy, and mass-loading budgets observed compare well with theory. A model in which star formation provides a force ∼L/c, where L is the bolometric luminosity, and cool gas is pushed out of the galaxy's gravitational potential, compares well with available data. The wind power is ∼0.1 of that provided by SNe. The very hot X-ray-emitting phase may be a (or the) prime mover. Momentum and energy exchange between the hot and cooler phases is critical to the gas dynamics. Gaps in our observational knowledge include the hot gas kinematics and the size and structure of the outflows probed with UV absorption lines. Simulations are needed to more fully understand mixing, cloud–radiation, cloud–cosmic ray, andcloud–hot wind interactions, the collective effects of star clusters, and both distributed andclustered SNe. Observational works should seek secondary correlations in the wind data thatprovide evidence for specific mechanisms and compare spectroscopy with the column density–velocity results from theory. [ABSTRACT FROM AUTHOR]

Adequate micronutrient intake and status are global public health goals. Vitamin and mineral deficiencies are widespread and known to impair health and survival across the life stages. However, knowledge of molecular effects, metabolic pathways, biological responses to variation in micronutrient nutriture, and abilities to assess populations for micronutrient deficiencies and their pathology remain lacking. Rapidly evolving methodological capabilities in genomics, epigenomics, proteomics, and metabolomics offer unparalleled opportunities for the nutrition research community to link micronutrient exposure to cellular health; discover new, arguably essential micronutrients of microbial origin; and integrate methods of molecular biology, epidemiology, and intervention trials to develop novel approaches to assess and prevent micronutrient deficiencies in populations. In this review article, we offer new terminology to specify nutritional application of multiomic approaches and encourage collaboration across the basic to public health sciences to advance micronutrient deficiency prevention. [ABSTRACT FROM AUTHOR]

A seminal report, released in 2001 by the Institute of Medicine, spurred research on the design, implementation, and evaluation of multilevel interventions targeting obesity and related behaviors. By addressing social and environmental factors that support positive health behavior change, interventions that include multiple levels of influence (e.g., individual, social, structural) aim to bolster effectiveness and, ultimately, public health impact. With more than 20 years of multilevel obesity intervention research to draw from, this review was informed by published reviews (n = 51) and identified intervention trials (n = 103), inclusive of all ages and countries, to elucidate key learnings about the state of the science. This review provides a critical appraisal of the scientific literature related to multilevel obesity interventions and includes a description of their effectiveness on adiposity outcomes and prominent characteristics (e.g., population, setting, levels). Key objectives for future research are recommended to advance innovations to improve population health and reduce obesity. [ABSTRACT FROM AUTHOR]

Diet, a modifiable risk factor, plays a pivotal role in most diseases, from cardiovascular disease to type 2 diabetes mellitus, cancer, and obesity. However, our understanding of the mechanistic role of the chemical compounds found in food remains incomplete. In this review, we explore the "dark matter" of nutrition, going beyond the macro- and micronutrients documented by national databases to unveil the exceptional chemical diversity of food composition. We also discuss the need to explore the impact of each compound in the presence of associated chemicals and relevant food sources and describe the tools that will allow us to do so. Finally, we discuss the role of network medicine in understanding the mechanism of action of each food molecule. Overall, we illustrate the important role of network science and artificial intelligence in our ability to reveal nutrition's multifaceted role in health and disease. [ABSTRACT FROM AUTHOR]

Food and nonalcoholic beverage marketing is implicated in poor diet and obesity in children. The rapid growth and proliferation of digital marketing has resulted in dramatic changes to advertising practices and children's exposure. The constantly evolving and data-driven nature of digital food marketing presents substantial challenges for researchers seeking to quantify the impact on children and for policymakers tasked with designing and implementing restrictive policies. We outline the latest evidence on children's experience of the contemporary digital food marketing ecosystem, conceptual frameworks guiding digital food marketing research, the impact of digital food marketing on dietary outcomes, and the methods used to determine impact, and we consider the key research and policy challenges and priorities for the field. Recent methodological and policy developments represent opportunities to apply novel and innovative solutions to address this complex issue, which could drive meaningful improvements in children's dietary health. [ABSTRACT FROM AUTHOR]

I started my journey as a nutrition scholar in 1974 when I began PhD studies at Cornell University. My journey has been rich with opportunity. I engaged in research on diet-related risks for cardiovascular diseases, diabetes, and cancer, partly motivated by my strong commitment to addressing health disparities affecting Black Americans. Obesity became my major focus and would eventually involve both US and global lenses. This focus was also linked to other dietary intake issues and health disparities and drew on knowledge I had gained in my prior study and practice of social work. I positioned myself as a bridge builder across nutrition, epidemiology, and public health, advocating for certain new ways of thinking and acting in these spheres and in the academy itself. Life skills honed during my formative years living within racially segregated contexts have been critical to any successes I have achieved. [ABSTRACT FROM AUTHOR]

Humans require energy to sustain their daily activities throughout their lives. This narrative review aims to (a) summarize principles and methods for studying human energy expenditure, (b) discuss the main determinants of energy expenditure, and (c) discuss the changes in energy expenditure throughout the human life course. Total daily energy expenditure is mainly composed of resting energy expenditure, physical activity energy expenditure, and the thermic effect of food. Total daily energy expenditure and its components are estimated using variations of the indirect calorimetry method. The relative contributions of organs and tissues determine the energy expenditure under different physiological conditions. Evidence shows that energy expenditure varies along the human life course, at least in part due to changes in body composition, the mass and specific metabolic rates of organs and tissues, and levels of physical activity. This information is crucial to estimate human energy requirements for maintaining health throughout the life course. [ABSTRACT FROM AUTHOR]

Over the last decades, surgical complication rates have fallen drastically. With the introduction of new surgical techniques coupled with specific evidence-based perioperative care protocols, patients today run half the risk of complications compared with traditional care. Many patients who in previous years needed weeks of hospital care now recover and can leave in days. These remarkable improvements are achieved by using nutritional stress-reducing care elements for the surgical patient that reduce metabolic stress and allow for the return of gut function. This new approach to nutritional care and how it is delivered as an integral part of enhancing recovery after surgery are outlined in this review. We also summarize the new and increased understanding of the effects of the routes of delivering nutrition and the role of the gut, as well as the current recommendations for artificial nutritional support. [ABSTRACT FROM AUTHOR]

Approximately five million children die each year from preventable causes, including respiratory infections, diarrhea, and malaria. Roughly half of those deaths are attributable to undernutrition, including micronutrient deficiencies (MNDs). The influence of infection on micronutrient status is well established: The inflammatory response to pathogens triggers anorexia, while pathogens and the immune response can both alter nutrient absorption and cause nutrient losses. We review the roles of vitamin A, vitamin D, iron, zinc, and selenium in the immune system, which act in the regulation of molecular- or cellular-level host defenses, directly affecting pathogens or protecting against oxidative stress or inflammation. We further summarize high-quality evidence regarding the synergistic or antagonistic interactions between MNDs, pathogens, and morbidity or mortality relevant to child health in low- and middle-income countries. We conclude with a discussion of gaps in the literature and future directions for multidisciplinary research on the interactions of MNDs, infection, and inflammation. [ABSTRACT FROM AUTHOR]