We extend our hybrid linear-method/accelerated-descent variational Monte Carlo optimization approach to excited states and investigate its efficacy in double excitations. In addition to showing a superior statistical efficiency when compared to the linear method, our tests on small molecules show good energetic agreement with benchmark methods. We also demonstrate the ability to treat double excitations in systems that are too large for a full treatment by using selected configuration interaction methods via an application to 4-aminobenzonitrile. Finally, we investigate the stability of state-specific variance optimization against collapse to other states' variance minima and find that symmetry, Ansatz quality, and sample size all have roles to play in achieving stability.

In this work, we investigated several titanates with lepidocrocite-type structures (general formula AxTi1-yMyO4, with A = Na and M = Li or Mg), having potential utility as anode materials for sodium-ion batteries. First-principles calculations were used to determine key battery metrics, including potential profiles, structural changes during sodiation, and sodium diffusion energy barriers for several compositions, and were compared to experimental results. Site limitations were found to be critical determinants of the gravimetric capacities, which are also affected both by the stacking arrangement of the corrugated layers and the identity of M (Li or Mg). To explain the experimentally observed lattice parameter changes observed as a function of the state of charge, it was necessary to assume the participation of water/solvent during the sodium intercalation process. Sodium diffusion barriers were also found to vary as a function of state of charge and diffusion direction, with a spread of 0.06-1.3 eV at low sodium contents, narrowing to 0.3-0.5 eV at higher sodium contents. Based on these results, strategies for selecting and improving the performance of these electrode materials are suggested.

Abstract: The evolution of seed size may be influenced by intrinsic attributes of populations, such as mating system and extrinsic factors, such as climate. Several hypotheses propose that the evolution of self‐fertilization from an outcrossing progenitor will be accompanied by a reduction in seed size, but this prediction has not been rigorously tested. Many studies report that the mean seed size of populations or taxa is associated with long‐term climate conditions. Here, we examined the effects on seed size of both mating system and climate within a single genus. In the California wildflower genus, Clarkia (Onagraceae), we sampled seeds from 58 populations representing three pairs of sister taxa; each pair included a predominantly outcrossing and a facultatively selfing taxon. We then examined the independent effects on population mean seed size of mating system, elevation, long‐term (30‐year) climate conditions, and climate anomalies (the deviation between conditions in the year of collection and the long‐term mean), focusing on maximum monthly temperature (Tmax), cumulative moisture deficit and cumulative precipitation (PPT) during Clarkia's growing season (fall, winter and spring). In each taxon pair, the selfing taxon had smaller seeds than the outcrosser. Local, long‐term (1921–1980 and 1981–2000) mean Tmax, PPT and elevation were independently and negatively associated with seed size. Long‐term means for Tmax and PPT explain geographical variation in seed size better than climate anomalies in the year of collection. Synthesis. We corroborated two key hypotheses concerning the drivers of geographical variation in mean seed size. Small seeds in Clarkia co‐evolve with selfing (although the mechanism remains elusive) and in response to chronically warm and wet conditions. The effect of long‐term mean precipitation on seed size differs qualitatively from the effect of precipitation anomalies; relatively large seeds are produced in populations experiencing wetter‐than‐normal years. Ongoing climate change may therefore generate conflicting selection on seed size in Clarkia: intensifying drought is likely to lead to an evolutionary increase in seed size due to its effects on seedling survivorship, while climate‐driven declines in pollinators or selection favouring more rapid reproduction may promote the evolution of self‐pollination, facilitating the evolution of smaller seeds.

Tailoring electron transfer dynamics across solid-liquid interfaces is fundamental to the interconversion of electrical and chemical energy. Stacking atomically thin layers with a small azimuthal misorientation to produce moiré superlattices enables the controlled engineering of electronic band structures and the formation of extremely flat electronic bands. Here, we report a strong twist-angle dependence of heterogeneous charge transfer kinetics at twisted bilayer graphene electrodes with the greatest enhancement observed near the 'magic angle' (~1.1°). This effect is driven by the angle-dependent tuning of moiré-derived flat bands that modulate electron transfer processes with the solution-phase redox couple. Combined experimental and computational analysis reveals that the variation in electrochemical activity with moiré angle is controlled by a structural relaxation of the moiré superlattice at twist angles of <2°, and 'topological defect' AA stacking regions, where flat bands are localized, produce a large anomalous local electrochemical enhancement that cannot be accounted for by the elevated local density of states alone.

Background

Metastases to the skin are found with increased frequency at certain sites, such as the scalp, but the biological factors that influence this distribution are not understood.

Objective

We aimed to compare the proportional frequency of metastases at various cutaneous locations with the immunologic microenvironments at those sites.

Methods

We retrospectively identified all biopsy specimens of cutaneous metastases diagnosed at our institution from 1991 to 2014 (n = 1984) and mapped their anatomic distribution while controlling for regional surface area. Using a separate, mapped cohort of normal-appearing skin samples (n = 140), we measured the density of regulatory T cells, CD4(+) effector T cells, and CD8(+) T cells by flow cytometry.

Results

Per unit surface area, cutaneous metastases arise most commonly on the head and neck, followed by the trunk, upper extremities, and lower extremities, respectively. Sites with more frequent metastases tend to contain a greater density of regulatory T cells and a lower proportion of CD8(+) T cells (P < .05).

Limitations

Immunologic factors were only assessed in control tissue and were not measured from patients with metastatic disease in this correlative single-center study.

Conclusion

The distribution of cutaneous metastases follows the distribution of regulatory and effector T cells in skin. Further studies are required to prove a mechanistic association between local immunologic factors and the development of cutaneous metastases.

Moiré superlattices formed by twisting trilayers of graphene are a useful model for studying correlated electron behaviour and offer several advantages over their formative bilayer analogues, including a more diverse collection of correlated phases and more robust superconductivity. Spontaneous structural relaxation alters the behaviour of moiré superlattices considerably and has been suggested to play an important role in the relative stability of superconductivity in trilayers. Here we use an interferometric four-dimensional scanning transmission electron microscopy approach to directly probe the local graphene layer alignment over a wide range of trilayer graphene structures. Our results inform a thorough understanding of how reconstruction modulates the local lattice symmetries crucial for establishing correlated phases in twisted graphene trilayers, evincing a relaxed structure that is markedly different from that proposed previously.