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Long‐Term Stability and Oxidation of Ferroelectric AlScN Devices : An Operando Hard X‐ray Photoelectron Spectroscopy Study
No full textAluminum scandium nitride (Al1− xScxN) is a promising material for ferroelectric devices due to its large remanent polarization, scalability, and compatibility with semiconductor technology. By doping AlN with Sc, the bonds in the polar AlN structure are weakened, which enables ferroelectric switching below the dielectric breakdown field. However, one disadvantage of Sc doping is that it increases the material's tendency toward oxidation. Herein, the oxidation process of tungsten‐capped and uncapped Al0.83Sc0.17N thin films is investigated by hard X‐ray photoelectron spectroscopy (HAXPES). The samples is exposed to air for either 2 weeks or 6 months. HAXPES spectra indicate the replacement of nitrogen by oxygen and the tendency of oxygen to favor oxidation with Sc rather than Al. The appearance of an N 2 spectral feature thus can be directly related to the oxidation process. An oxidation model that mimics these spectroscopic results of the element‐specific oxidation processes within Al1− xScxN is presented. Finally, in operando HAXPES data of uncapped and capped AlScN‐capacitor stacks are interpreted using the proposed model.publishe
Mechanistic insights into the formation of hydroxides with unconventional coordination environments to achieve their cost-effective synthesis
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Scientific uptake in United Nations Security Council debates on climate change and security
No full textConcerns about adverse security implications of climate change have fostered a booming research agenda and have also gained increasing traction in international political fora, such as the United Nations Security Council (UNSC). To what extent do policy discourses and decisions reflect the scientific understanding of the problem? Here, we assess evidence on uptake of scientific research on climate change and violent conflict in high-level UNSC debates, 2007–2022. We show that UNSC member states increasingly acknowledge climate-conflict risks as real but context-dependent, consistent with recent academic literature on the topic. Even so, views remain divided among prominent Council members, blocking progress on this matter. Explicit engagement with science on climate change and conflict, which might have helped resolve disagreements, remains rare and partly selective. We highlight challenges and opportunities for the scientific community to improve the perceived relevance and accessibility of research to stakeholders and strengthen science-policy interaction.publishe
Bridging Realities in a Heartbeat : How Integrating Heartbeat Signals Supports Collaboration in Mixed Reality
No full textMixed Reality (MR) has great potential for remote collaboration, as remote users can be integrated with co-located users while facilitating similar richness in verbal and nonverbal communication, comprising gestures, facial expressions, voice, and body posture. However, current approaches mostly neglect more subtle cues, like physiological signals, which have been shown to be relevant during social interactions. We propose that physiological signals, such as heartbeats, should be integrated into virtual user representations to facilitate more effective remote collaboration in MR. In this work, we discuss the integration of heartbeats specifically, to enrich embodied interactions across the MR continuum, further bridging the gap between co-located and remote collaboration in MR. In addition, we identify key challenges and propose future research directions to support this vision.accepte
Detecting random bifurcations via rigorous enclosures of large deviations rate functions
No full textThe main goal of this work is to provide a description of transitions from uniform to non-uniform snychronization in diffusions based on large deviation estimates for finite time Lyapunov exponents. These can be characterized in terms of moment Lyapunov exponents which are principal eigenvalues of the generator of the tilted (Feynman–Kac) semigroup. Using a computer assisted proof, we demonstrate how to determine these eigenvalues and investigate the rate function which is the Legendre–Fenchel transform of the moment Lyapunov function. We apply our results to two case studies: the pitchfork bifurcation and a two-dimensional toy model, also considering the transition to a positive asymptotic Lyapunov exponent.publishe
The Alarming Consequences of Workforce Reductions at the FDA, EPA, NIH and CDC in the United States
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Stronger femtosecond excitation causes slower electron-phonon coupling in silicon
No full textElectron-hole pairs in semiconductors are essential for solar cells and fast electronic circuitry, but the competition between carrier transport and relaxation into heat limits the efficiency and speed. Here we use ultrafast electron diffraction with terahertz pulse compression to measure the electron-phonon decay rate in single-crystal silicon as a function of laser excitation strength. We find that the excited electrons relax slower into phonons for higher carrier densities. The electron-phonon scattering rate changes in a nonlinear way from 400 fs at ∼2×1020/cm3 to 1.2 ps at ∼4×1020/cm3. These results indicate that a hot electron gas quenches the scattering into phonons in a temperature-dependent way. Ultrafast electronic circuitry of silicon should therefore work faster and provide higher bandwidths at lower carrier densities.publishe
Morphology and ultrastructure of external sense organs of Drosophila larvae
No full textSensory perception is the ability through which an organism is able to process sensory stimuli from the environment. This stimulus is transmitted from the peripheral sensory organs to the central nervous system, where it is interpreted. Drosophila melanogaster larvae possess peripheral sense organs on their head, thoracic, and abdominal segments. These are specialized to receive diverse environmental information, such as olfactory, gustatory, temperature or mechanosensory signals. In this work, we complete the description of the morphology of external larval sensilla and provide a comprehensive map of the ultrastructure of the different types of sensilla that comprise them. This was achieved by 3D electron microscopic analysis of partial and whole body volumes, which contain high-resolution and complete three-dimensional data of the anatomy of the sensilla and adjacent ganglia.Our analysis revealed three main types of sensilla on thoracic and abdominal segments: the papilla sensillum, the hair sensillum and the knob sensillum. They occur solitary or organized in compound sensilla such as the thoracic keilin’s organ or the terminal sensory cones. We present a spatial map defining these sensilla by their position on thoracic and abdominal segments. Further, we identify and name the sensilla at the larval head and the last fused abdominal segments. We show that mechanosensation dominates in the larval peripheral nervous system, as most sensilla have corresponding structural properties. The result of this work, the construction of a complete structural and neuronal map of the external larval sensilla, provides the basis for following molecular and functional studies to understand which sensory strategies the Drosophila larva employs to orient itself in its natural environment.publishe
On the forward–backward method with nonmonotone linesearch for infinite-dimensional nonsmooth nonconvex problems
No full textThis paper provides a comprehensive study of the nonmonotone forward–backward splitting (FBS) method for solving a class of nonsmooth composite problems in Hilbert spaces. The objective function is the sum of a Fréchet differentiable (not necessarily convex) function and a proper lower semicontinuous convex (not necessarily smooth) function. These problems appear, for example, frequently in the context of optimal control of nonlinear partial differential equations (PDEs) with nonsmooth sparsity-promoting cost functionals. We discuss the convergence and complexity of FBS equipped with the nonmonotone linesearch under different conditions. In particular, R-linear convergence will be derived under quadratic growth-type conditions. We also investigate the applicability of the algorithm to problems governed by PDEs. Numerical experiments are also given that justify our theoretical findings.publishe
Palaeogenomic inference of biodiversity dynamics across Quaternary timescales
No full textBiodiversity is essential for the resilience and stability of life, yet it is highly dynamic and has continuously evolved throughout Earth’s history. The biodiversity concept encompasses three hierarchical levels of equal importance to fundamental ecological processes: diversity at the ecosystem, species and genetic levels. The current biodiversity crisis calls for an urgent need to understand the causes and consequences of widespread diversity losses at all three levels. Breakthroughs in palaeogenomics have increased the ecological and temporal scales on which we can use genomic information to study past biodiversity, reaching as far back as the Early Pleistocene. In this Review, we explore the possibilities and limitations of using palaeogenomics for studying all aspects of biodiversity. We explore how incorporating palaeogenomics into biodiversity research can provide clues about ecosystem composition, trophic interactions, species distributions, adaptation, evolution and extinction through time, in response to natural processes and as a consequence of human impact. We report how palaeogenomics can be applied to address a wide range of topics across all three hierarchical levels of biodiversity, and we show how advances within the field are making palaeogenomics an invaluable tool for understanding past and present declines in biodiversity, and in helping to predict future losses.publishe