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Evidence for Magma-Crust interaction recorded in Xenopumice from Harrat Rahat, Saudi Arabia
No full textThe term “xenopumice” describes a pumice-like xenolith of low density, frothy, highly vesiculated, partially molten, silicic crustal material found in mafic volcanic eruption products that usually serves as an indicator of magma-crust interaction. In this study we describe the occurrence of xenopumice in Quaternary eruption sequences at Harrat Rahat, in Saudi Arabia. Harrat Rahat is an intraplate volcanic field, whose last eruption was in 1256C.E. in proximity to the city of Al-Madinah, and is characterized by a range of volcanic products from basalts to trachyte. This chemical variation found in the volcanic field, has been suggested to be reflective of closed system fractional crystallization with little to no crustal influences. To examine whether xenopumice samples collected indicate crustal assimilation and the extent to which open system processes play a role in the compositional diversity of Harrat Rahat magmas, we analyzed the mineralogy, textural features, whole-rock geochemistry and oxygen isotopes of a set of xenopumice samples and their host basalts. Their subalkaline character with high Si-contents, enriched but variable trace element contents and elevated δ18O (>9.8 ‰) values exclude a plutonic cumulate or lower crustal origin for the xenopumice. Instead, their chemistry and textures overlap with metamorphosed granites of upper Arabian crust and/or (meta-)sedimentary rocks of the Proterozoic Arabian Shield. The δ18O-isotopes of host basaltic magmas (5.1 to 6 ‰) document assimilation of xenopumice material by magmas in some cases. The xenopumices found are an indicator of magma-crust interaction in upper crustal magma reservoirs, emphasizing the importance of evaluating the role of crustal assimilation in the Saudi Arabian Harrats.We are grateful to J. Follmann and I. Zivadinovic, both KAUST for their help in field. Further we like to thank Mario Thöner, GEOMAR Kiel for his assistance at the microprobe. We like to thank H. Murcia and an anonymous reviewer for constructive and helpful feedback and S. Cronin for editorial handling of the manuscript.
This work was supported by KAUST Baseline Grant awarded to F.M. van der Zwan
Falling Walls, WWW, Modern AI, and the Future of the Universe
No full textAround 1990, the Berlin Wall came down, the WWW was born at
CERN, mobile phones became popular, self-driving cars appeared
in traffic, and modern AI based on very deep artificial neural networks emerged, including the principles behind the G, P, and T
in ChatGPT. I place these events in the history of the universe
since the Big Bang, and discuss what’s next: not just AI behind the
screen in the virtual world, but real AI for real robots in the real
world, connected through a WWW of machines. Intelligent (but
not necessarily super-intelligent) robots that can learn to operate
the tools and machines operated by humans can also build (and
repair when needed) more of their own kind. This will culminate in
life-like, self-replicating and self-improving machine civilisations,
which represent the ultimate form of upscaling, and will shape the
long-term future of the entire cosmos. The wonderful short-term
side effect is that our AI will continue to make people’s lives longer,
healthier and easie
Finite Element Formulations for Maxwell's Eigenvalue Problem Using Continuous Lagrangian Interpolations
No full textWe consider nodal-based Lagrangian interpolations for the finite element approximation of the Maxwell eigenvalue problem. The first approach introduced is a standard Galerkin method on Powell–Sabin meshes, which has recently been shown to yield convergent approximations in two dimensions, whereas the other two are stabilized formulations that can be motivated by a variational multiscale approach. For the latter, a mixed formulation equivalent to the original problem is used, in which the operator has a saddle point structure. The Lagrange multiplier introduced to enforce the divergence constraint vanishes in an appropriate functional setting. The first stabilized method consists of an augmented formulation including a mesh dependent term that can be regarded as the Laplacian of the divergence constraint multiplier. The second formulation is based on orthogonal projections, which can be recast as a residual based stabilization technique. We rely on the classical spectral theory to analyze the approximating methods for the eigenproblem. The stability and convergence aspects are inherited from the associated source problems together with an assumption which is discussed numerically. We investigate the performance of the proposed formulations and provide some convergence results validating the theoretical ones for several benchmark tests, including ones with smooth and singular solutions.Ramon Codina acknowledges the support received from the ICREA Acad\u00E8mia Research Program of the Catalan Government. Daniele Boffi is member of INdAM research group GNCS
STP: single-cell partition for subcellular spatially-resolved transcriptomics
No full textSpatially-resolved transcriptomics (SRT) technologies now allow exploration of gene expression with spatial context. Recent advances achieving subcellular resolution provide richer data but also introduce challenges, such as aggregating subcellular spots into individual cells, which is a task distinct from traditional deconvolution. Existing methods often grid SRT data into predefined squares, which is unrealistic for accurately capturing cellular boundaries. We propose a method, STP, that integrates subcellular SRT data with nuclei-stained images to partition individual cells. STP first segments nuclei and maps their masks onto the SRT data, then uses a simulated-annealing-inspired approach to expand nuclear boundaries to the full cellular level. Evaluated on subcellular SRT datasets from Drosophila embryos at multiple developmental stages and from mouse embryos with a large field-of-view, STP demonstrated accurate single-cell partitioning, unveiling significant spatial tissue patterns and identifying undetected cell types beyond previous methods.H.L. and X.G. were supported by the King Abdullah University of Science and Technology (KAUST) Office of Research Administration (ORA) under Award No REI/1/5234-01-01, REI/1/5414-01-01, REI/1/5289-01-01, REI/1/5404-01-01, REI/1/5992-01-01, URF/1/4663-01-01, Center of Excellence for Smart Health (KCSH), under award number 5932, and Center of Excellence on Generative AI, under award number 5940. Q.H. and Y.H. were supported by the Shenzhen Science and Technology Innovation Program (Grant No. KQTD20180411143432337, China) and Shenzhen Key Laboratory of Gene Regulation and Systems Biology (Grant No. ZDSYS20200811144002008) (to Y.H. and Q.H.), Shenzhen Medical Research Fund (Grant No. D2401016 to Y.H.), Guangdong Basic and Applied Basic Research Foundation (Grant No. 2024A1515012343 to Q.H.), and the National Natural Science Foundation of China (Grant No. 32100684 to Q.H.). Computational resources and experimental facilities were supported by the Center for Computational Science and Engineering and the Core Research Facilities at Southern University of Science and Technology. Z.Q. was supported by Heilongjiang Provincial Key Research and Development Plan 2023ZX02C10, 2023ZXJ02C03, and Jiangsu Provincial Key Research and Development Plan BE2023081. H.X. was supported in part by the National Key R&D Program of China (Grant No.2023YFF0725001), in part by the National Natural Science Foundation of China (Grant No.92370204), in part by the guangdong Basic and Applied Basic Research Foundation (Grant No.2023B1515120057) in part by Guangzhou-HKUST(GZ) Joint Funding Program (Grant No.2023A03J0008), Education Bureau of Guangzhou Municipality
Beyond phase boundaries: atomic mechanisms governing structure and property variations in (K, Na)NbO3-based ferroelectrics
No full textChemical dopants-induced phase boundary engineering has boosted electrical properties of (K, Na)NbO3-based piezoceramics, yet the underlying mechanisms governing these improvements remain unclear. Here, we elucidate these mechanisms through comprehensive multi-scale structural analysis (atomic-to-nanoscale-to-mesoscale) on two representative solid-solutions, namely (K, Na, Li)NbO3 and (K, Na)NbO3-(Bi0.5Na0.5)ZrO3. By utilizing neutron pair distribution function analysis, scanning transmission electron microscope, first-principle calculations, and phase-field simulations, our results reveal distinct atomic-scale mechanism underlying phase boundary engineering. In (K, Na, Li)NbO3, convergent off-center displacements of Li atoms induce an interplay between displacive and order-disorder phase transition; while in (K, Na)NbO3-(Bi0.5Na0.5)ZrO3, divergent off-center displacements of Bi atoms trigger a predominant order-disorder type phase transition. These atomic-scale structural characteristics directly correlate with mesoscopic ferroelectric domains and ultimately determine macroscopic electrical properties. This work elucidates the role of chemical dopants in phase boundary engineering from a multi-scale perspective, establishing a framework for designing lead-free piezoceramics with enhanced electrical properties and advancing the development of eco-friendly piezoceramics.This work is supported by the National Natural Science Foundation of China [Grant Nos. 12204327 (X.L.) and U23A20567 (J.W.)], the Natural Science Foundation of Sichuan Province [Grant Nos. 2023NSFSC0967 (X.L.) and 2024NSFJQ0025 (J.W.)], the Sichuan University postdoctoral interdisciplinary Innovation Fund [Grant No. 1082204112L76 (J.W.)], and the Fundamental Research Funds for the Central Universities [(J.W.)]. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory [Grant No. IPTS-30510 for POWGEN and NOMAD instruments (A.P.)]. Dr. Yueliang Gu at SSRF is appreciated for helping collect the synchrotron data. The authors thank Ms. Hui Wang and Mr. Xi Wu (both from the Analytical & Testing Center of Sichuan University) for conducting the FE-SEM and ICP-OES measurements, respectively
Liquid-State NMR Spectroscopy for Battery Electrolyte Design
No full textElectrolytes transport ions and maintain interfacial stability, thus playing a pivotal role in determining battery performance. Liquid-state nuclear magnetic resonance (ls-NMR) spectroscopy has emerged as a powerful tool to elucidate the underlying electrolyte chemistry. However, the testing protocols and analysis criteria have not been fully standardized. In addition, the correlations between spectroscopic results and electrolyte chemistry are complex and poorly characterized. Therefore, it is imperative to clarify the principles of ls-NMR spectroscopy and the roles it can play in improving our mechanistic understanding of liquid battery electrolytes. In this Perspective, several emerging ls-NMR techniques are categorized and discussed, with an emphasis on visualizing the solvation effect, ion dynamics, and intermolecular interactions in liquid electrolytes. We demonstrate how ls-NMR spectroscopy can be used to understand electrolyte chemistry and expedite electrolyte design for emerging battery technologies.The research reported in this publication was supported by King Abdullah University of Science and Technology (KAUST) – Center of Excellence for Renewable Energy and Storage Technologies (CREST) under award number 5937
CCDC 2481432: Experimental Crystal Structure Determination :
No full textAn entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures
Iron Phosphate Nanomaterials for Photocatalytic Degradation of Tetracycline Hydrochloride
No full textFour different phosphorous precursors [H3PO4, (NH4)H2PO4, (NH4)2HPO4, and (NH4)3PO4] were utilized to study their influence on the physicochemical characteristics and photocatalytic performance of iron phosphate (FeP) nanomaterials. Among the synthesized samples, FeP-H3 photocatalyst synthesized using H3PO4 exhibited superior photocatalytic performance for degradation of aqueous tetracycline hydrochloride (TCH) solution under visible light. The investigation of the influence of photocatalytic reaction conditions revealed that the degradation efficiency of TCH in 5 h was 72% when the dosage of FeP-H3 catalyst was 120 mg/L; the initial concentration of TCH solution was 15 mg/L; and the initial pH of 10. The phosphorus precursor shows multiple effects on the physicochemical properties of FeP nanomaterial. It is revealed that the FeP-H3 sample possesses highly crystalline FeP nanosheets with high surface area and low bandgap, resulting in the fast capture of photogenerated electrons and the following generation of O2− radicals. The [PO4]3−and [─OH] groups adsorbed on the surface of FeP can further assist negative electrostatic field, which enhances the separation of photogenerated e−-h+ pairs, whereby the h+ species improve the generation of photoreactive OH radicals. Furthermore, the photocatalytic performance of FeP nanomaterials for degradation of TCH was optimized
Ultrastructure of astrocytes using volume electron microscopy: A scoping review.
No full textThe morphological features of astrocytes are crucial for brain homeostasis, synaptic activity and structural support, yet remain poorly quantified. As a result of the nanometre-sized cross-section of neuropil astrocytic processes, electron microscopy (EM) is the only technique availabe to date capable of revealing their finest morphologies. Volume EM (vEM) techniques, such as serial block-face or focused ion beam scanning EM, enable high-resolution imaging of large fields and allow more extensive 3-D model analyses, revealing new astrocytic morphological features. This scoping review aims to summarize the state of the art of astrocyte ultrastructural analysis. This review included 45 of 439 non-duplicated articles from a Pubmed search, categorizing studies by research focus, animal models, brain region, vEM techniques and segmentation methods. By answering classical questions such as volume, surface area, branching complexity and synaptic ensheathment reported in the literature, this work is a valuable resource for scientists working on structural biology or computational neuroscience
