Alloying anodes such as silicon are promising electrode materials for next‐generation high energy density lithium‐ion batteries because of their ability to reversibly incorporate a high concentration ...of Li atoms. However, alloying anodes usually exhibit a short cycle life due to the extreme volumetric and structural changes that occur during lithium insertion/extraction; these transformations cause mechanical fracture and exacerbate side reactions. To solve these problems, there has recently been significant attention devoted to creating silicon nanostructures that can accommodate the lithiation‐induced strain and thus exhibit high Coulombic efficiency and long cycle life. In parallel, many experiments and simulations have been conducted in an effort to understand the details of volumetric expansion, fracture, mechanical stress evolution, and structural changes in silicon nanostructures. The fundamental materials knowledge gained from these studies has provided guidance for designing optimized Si electrode structures and has also shed light on the factors that control large‐volume change solid‐state reactions. In this paper, we review various fundamental studies that have been conducted to understand structural and volumetric changes, stress evolution, mechanical properties, and fracture behavior of nanostructured Si anodes for lithium‐ion batteries and compare the reaction process of Si to other novel anode materials.
Due to its extremely high theoretical lithium storage capacity, silicon is an attractive anode material for next‐generation lithium‐ion batteries. However, complex volume changes and phase transformations during the lithium‐silicon reaction can lead to capacity decay with cycling. In this review, we discuss fundamental studies that have been conducted to understand volume changes, phase transformations, stress evolution, mechanical properties, and fracture behavior of nanostructured Si anodes for lithium‐ion batteries.
The recent availability of shale gas has led to a renewed interest in C-H bond activation as the first step towards the synthesis of fuels and fine chemicals. Heterogeneous catalysts based on Ni and ...Pt can perform this chemistry, but deactivate easily due to coke formation. Cu-based catalysts are not practical due to high C-H activation barriers, but their weaker binding to adsorbates offers resilience to coking. Using Pt/Cu single-atom alloys (SAAs), we examine C-H activation in a number of systems including methyl groups, methane and butane using a combination of simulations, surface science and catalysis studies. We find that Pt/Cu SAAs activate C-H bonds more efficiently than Cu, are stable for days under realistic operating conditions, and avoid the problem of coking typically encountered with Pt. Pt/Cu SAAs therefore offer a new approach to coke-resistant C-H activation chemistry, with the added economic benefit that the precious metal is diluted at the atomic limit.
Measuring Well-Being Lee, Matthew T; Kubzansky, Laura D; VanderWeele, Tyler J
05/2021
eBook
This edited volume explores conceptual and practical challenges in measuring well-being. Given the bewildering array of measures available and ambiguity regarding when and how to measure particular ...aspects of well-being, knowledge in the field can be difficult to reconcile. Representing numerous disciplines including psychology, economics, sociology, statistics, public health, theology, and philosophy, contributors consider the philosophical and theological traditions on happiness, well-being, and the good life, as well as recent empirical research on well-being and its measurement. Leveraging insights across diverse disciplines, they explore how research can help make sense of the proliferation of different measures and concepts while also proposing new ideas to advance the field. Some chapters engage with philosophical and theological traditions on happiness, well-being, and the good life; some evaluate recent empirical research on well-being and consider how measurement requirements may vary by context and purpose; and others more explicitly integrate methods and synthesize knowledge across disciplines. The final section offers a lively dialogue about a set of recommendations for measuring well-being derived from a consensus of the contributors. Collectively, the chapters provide insight into how scholars might engage beyond disciplinary boundaries and contribute to advances in conceptualizing and measuring well-being. Bringing together work from across often siloed disciplines will provide important insight regarding how people can transcend unhealthy patterns of both individual behavior and social organization in order to pursue the good life and build better societies.
Despite progress in solid-state battery engineering, our understanding of the chemo-mechanical phenomena that govern electrochemical behaviour and stability at solid-solid interfaces remains limited ...compared to at solid-liquid interfaces. Here, we use operando synchrotron X-ray computed microtomography to investigate the evolution of lithium/solid-state electrolyte interfaces during battery cycling, revealing how the complex interplay among void formation, interphase growth and volumetric changes determines cell behaviour. Void formation during lithium stripping is directly visualized in symmetric cells, and the loss of contact that drives current constriction at the interface between lithium and the solid-state electrolyte (Li
SnP
S
) is quantified and found to be the primary cause of cell failure. The interphase is found to be redox-active upon charge, and global volume changes occur owing to partial molar volume mismatches at either electrode. These results provide insight into how chemo-mechanical phenomena can affect cell performance, thus facilitating the development of solid-state batteries.
Silicon is one of the most attractive anode materials for use in Li-ion batteries due to its ∼10 times higher specific capacity than existing graphite anodes. However, up to 400% volume expansion ...during reaction with Li causes particle pulverization and fracture, which results in rapid capacity fading. Although Si nanomaterials have shown improvements in electrochemical performance, there is limited understanding of how volume expansion takes place. Here, we study the shape and volume changes of crystalline Si nanopillars with different orientations upon first lithiation and discover anomalous behavior. Upon lithiation, the initially circular cross sections of nanopillars with ⟨100⟩, ⟨110⟩, and ⟨111⟩ axial orientations expand into cross, ellipse, and hexagonal shapes, respectively. We explain this by identifying a high-speed lithium ion diffusion channel along the ⟨110⟩ direction, which causes preferential volume expansion along this direction. Surprisingly, the ⟨111⟩ and ⟨100⟩ nanopillars shrink in height after partial lithiation, while ⟨110⟩ nanopillars increase in height. The length contraction is suggested to be due to a collapse of the {111} planes early in the lithiation process. These results give new insight into the Si volume change process and could help in designing better battery anodes.
A hallmark symptom of many anxiety disorders, and multiple neuropsychiatric disorders more broadly, is generalization of fearful responses to non-fearful stimuli. Anxiety disorders are often comorbid ...with cardiovascular diseases. One established, and modifiable, risk factor for cardiovascular diseases is salt intake. Yet, investigations into how excess salt consumption affects anxiety-relevant behaviors remains little explored. Moreover, no studies have yet assessed how high salt intake influences generalization of fear. Here, we used adult C57BL/6J mice of both sexes to evaluate the influence of two or six weeks of high salt consumption (4.0% NaCl), compared to controls (0.4% NaCl), on contextual fear acquisition, expression, and generalization. Further, we measured osmotic and physiological stress by quantifying serum osmolality and corticosterone levels, respectively. Consuming excess salt did not influence contextual fear acquisition nor discrimination between the context used for training and a novel, neutral context when training occurred 48 prior to testing. However, when a four week delay between training and testing was employed to induce natural fear generalization processes, we found that high salt intake selectively increases contextual fear generalization in females, but the same diet reduces contextual fear generalization in males. These sex-specific effects were independent of any changes in serum osmolality nor corticosterone levels, suggesting the behavioral shifts are a consequence of more subtle, neurophysiologic changes. This is the first evidence of salt consumption influencing contextual fear generalization, and adds information about sex-specific effects of salt that are largely missing from current literature.
We report on molecular analyses of baseline tumor samples from the phase 3 JAVELIN Renal 101 trial (n = 886; NCT02684006 ), which demonstrated significantly prolonged progression-free survival (PFS) ...with first-line avelumab + axitinib versus sunitinib in advanced renal cell carcinoma (aRCC). We found that neither expression of the commonly assessed biomarker programmed cell death ligand 1 (PD-L1) nor tumor mutational burden differentiated PFS in either study arm. Similarly, the presence of FcɣR single nucleotide polymorphisms was unimpactful. We identified important biological features associated with differential PFS between the treatment arms, including new immunomodulatory and angiogenesis gene expression signatures (GESs), previously undescribed mutational profiles and their corresponding GESs, and several HLA types. These findings provide insight into the determinants of response to combined PD-1/PD-L1 and angiogenic pathway inhibition and may aid in the development of strategies for improved patient care in aRCC.
To utilize high-capacity Si anodes in next-generation Li-ion batteries, the physical and chemical transformations during the Li–Si reaction must be better understood. Here, in situ transmission ...electron microscopy is used to observe the lithiation/delithiation of amorphous Si nanospheres; amorphous Si is an important anode material that has been less studied than crystalline Si. Unexpectedly, the experiments reveal that the first lithiation occurs via a two-phase mechanism, which is contrary to previous understanding and has important consequences for mechanical stress evolution during lithiation. On the basis of kinetics measurements, this behavior is suggested to be due to the rate-limiting effect of Si–Si bond breaking. In addition, the results show that amorphous Si has more favorable kinetics and fracture behavior when reacting with Li than does crystalline Si, making it advantageous to use in battery electrodes. Amorphous spheres up to 870 nm in diameter do not fracture upon lithiation; this is much larger than the 150 nm critical fracture diameter previously identified for crystalline Si spheres.
Although DNA methylation is commonly invoked as a mechanism for transcriptional repression, the extent to which it actively silences transcription factor (TF) occupancy sites in vivo is unknown. To ...study the role of DNA methylation in the active modulation of TF binding, we quantified the effect of DNA methylation depletion on the genomic occupancy patterns of CTCF, an abundant TF with known methylation sensitivity that is capable of autonomous binding to its target sites in chromatin. Here, we show that the vast majority (>98.5%) of the tens of thousands of unoccupied, methylated CTCF recognition sequences remain unbound upon abrogation of DNA methylation. The small fraction of sites that show methylation-dependent binding in vivo are in turn characterized by highly variable CTCF occupancy across cell types. Our results suggest that DNA methylation is not a primary groundskeeper of genomic TF landscapes, but rather a specialized mechanism for stabilizing intrinsically labile sites.
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•Most CTCF binding in vivo is unaltered by genomic abrogation of DNA methylation•A limited set of CTCF sites from other cell lineages is methylation sensitive•Methylation-sensitive CTCF sites are highly variable across cell types•Key sequence and chromatin features predict methylation sensitivity of CTCF binding
Alterations of DNA methylation in malignancy and development are frequently interpreted as affecting transcriptional activity. Maurano et al. find that, upon genomic abrogation of DNA methylation, binding of the canonically methylation-sensitive transcriptional regulator CTCF is largely unaffected. Their results suggest that a limited set of methylation-sensitive CTCF sites are variable across cell types and that key sequence and chromatin features predict methylation sensitivity of CTCF binding.
Rapid progress has been made in realizing battery electrode materials with high capacity and long-term cyclability in the past decade. However, low first-cycle Coulombic efficiency as a result of the ...formation of a solid electrolyte interphase and Li trapping at the anodes, remains unresolved. Here we report LixSi-Li2O core-shell nanoparticles as an excellent prelithiation reagent with high specific capacity to compensate the first-cycle capacity loss. These nanoparticles are produced via a one-step thermal alloying process. LixSi-Li2O core-shell nanoparticles are processible in a slurry and exhibit high capacity under dry-air conditions with the protection of a Li2O passivation shell, indicating that these nanoparticles are potentially compatible with industrial battery fabrication processes. Both Si and graphite anodes are successfully prelithiated with these nanoparticles to achieve high first-cycle Coulombic efficiencies of 94% to >100%. The LixSi-Li2O core-shell nanoparticles enable the practical implementation of high-performance electrode materials in lithium-ion batteries.
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