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Design of a cast Al-based Al-Ni-Cr-Zr eutectic alloy with excellent high temperature mechanical properties
No full textThe present work reports the design of a cast ternary Al-3.8Ni-0.5Cr eutectic alloy for high-temperature applications with a minor Zr addition (0.15 at %). In the peak-aged condition (375 °C for 20 h), the alloy exhibited a hardness of 120 ± 3 HV and yield strengths of 355 ± 15, 225 ± 10, and 197 ± 8 MPa at 25, 200, and 250 °C, respectively. Notably, the alloy maintained a yield strength of 335 ± 25 MPa after long-term heat treatment at 375 °C for 100 h. The excellent microstructural stability and high-temperature strength are attributed to the presence of coherent and stable L1₂-ordered precipitates within the soft α-Al matrix of the eutectic phase. TEM weak-beam imaging revealed precipitate shearing via a planar dislocation glide mechanism, suggesting glide plane softening at 25 °C. Theoretical calculations predicted optimal strengthening from ordering, with peak strength achieved for precipitate sizes of ∼2.4 nm
On a function of Ramanujan twisted by a logarithm
No full textA two-term functional equation for an infinite series involving the digamma function and a logarithmic factor is derived. A modular relation on page 220 of Ramanujan's Lost Notebook as well as a corresponding recent result for the derivative of Deninger's function are two main ingredients in its derivation. An interesting integral H(x), which is of independent interest, plays a prominent role in our functional equation. Several alternative representations for H(x) are obtained
Unbalanced force emanating from stored elastic energy in granular packing: Fundamental insight from quasi-static DEM simulation
No full textUnbalanced force is poorly understood in discrete simulation of granular packing. During simulation of ‘wall friction test’ of granular iron ore, sharp peaks of unbalanced force were observed even during a quasi-static condition, contrary to the expected behavior. Particles having maximum unbalanced force were identified and the dynamic behavior of the particle and its neighborhood was thoroughly investigated (no explicit long range force was present in the simulation). It is inferred that the peaks occur due to storage of elastic energy within particles, followed by a sudden/gradual release. Finding of this article might have far reaching consequences in many disparate and diverse disciplines, such as Shear Transformation Zones (STZs) in metallic glasses, identifying tiny but non-trivial configurational changes at the onset of glass transition as well as for its relaxation behavior, origination of specific structural features (say, origin of stacking faults) in High Entropy Alloys (HEAs), kinetic instability induced symmetry breaking in granular media, Self-Organized Criticality (SOC) induced avalanching in granular systems etc. The unbalanced force index can turn out to be a very important metric for analyzing the configurational instability of those particulate ensemble for quasi-static and static conditions
Interaction-driven giant electrostatic modulation of ion permeation in atomically small capillaries
No full textManipulating the electrostatic double layer and tuning the conductance in nanofluidic systems at salt concentrations of 100 mM or higher has been a persistent challenge. The primary reasons are (i) the short electrostatic proximity length, ~3–10 Å, and (ii) difficulties in fabricating atomically small capillaries. Here, we successfully fabricate in-plane vermiculite laminates with transport heights of ~3–5 Å, which exhibit a cation selectivity close to 1 even at a 1000 mM concentration, suggesting an overlapping electrostatic double layer. For gate voltages from −2 V to +1 V, the K+-intercalated vermiculite shows a remarkable conductivity modulation exceeding 1400% at a 1000 mM KCl concentration. The gated ON/OFF ratio is mostly unaffected by the ion concentration (10–1000 mM), which confirms that the electrostatic double layer overlaps with the collective ion movement within the channel with reduced activation energy. In contrast, vermiculite laminates intercalated with Ca2+ and Al3+ ions display reduced conductance with increasing negative gate voltage, highlighting the importance of ion-specific gating effects under Å-scale confinement. Our findings contribute to a deeper understanding of electrostatic phenomena occurring in highly confined fluidic channels, opening the way to the exploration of the vast library of two-dimensional materials
Thank You to Our 2024 Reviewers
No full textOn behalf of the journal, AGU, and the scientific community, we, the editors of Earth's Future, are delighted to publish the names of the 1,061 peer reviewers who provided 1,642 reviews for our journal in 2024 (italicized names have contributed three or more reviews). Your diligent efforts to provide timely comments on our submissions have significantly improved the manuscripts and elevated the scientific rigor of future research. As a unique transdisciplinary journal, Earth's Future delves into the state of the planet and its inhabitants, sustainable and resilient societies, the science of the Anthropocene, and predictions of our shared future through research articles, reviews, and commentaries. In the face of observed and anticipated global environmental and climatic changes, the need for high-quality scientific theories, assessments, and projections about the future of our planet has never been more pressing. To safeguard research integrity in this crucial area, we rely on our reviewers' expertise and selfless cooperation. We extend our heartfelt thanks to each of the individuals listed below for their contributions to our journal and the broader scientific discourse. Your dedication is immensely appreciated
Testing for isospin symmetry breaking by combining isotope shift measurements with precise calculations in potassium
No full textPrecise evaluation of the isotope shift (IS) factors for seven low-lying potassium states is achieved using relativistic coupled-cluster theory. The energies of these states are compared with the experimental data to confirm the accuracy of wave functions calculated at different approximations and to highlight the significance of many-body and relativistic effects. Various methods are used to compute the IS factors, with the finite-field (FF) approach yielding results that align with observed and semiempirical data. This is attributed to orbital relaxation effects that are present naturally in the FF method but emerge only through perturbation in other methods. Using results from the FF approach, we review the mean-square-radius difference between 38mK and K39, which is combined with muonic atom x-ray spectroscopy and updated calculation of the nuclear polarizability effect to deduce the absolute radius of 38mK. Finally, we evaluate the isospin symmetry breaking (ISB) in the isotriplet by integrating the radius of 38mK with an updated radius of Ca38, concluding that the ISB is compatible with zero. This finding offers a stringent benchmark for nuclear models of ISB corrections in nuclear beta decay, which play a key role in determining the Vud matrix element
Multi-height Study of the Chromospheric Inverse Evershed Flow and its Association with Photospheric Flows
No full textWe analyzed the inverse Evershed flow (IEF) around a sunspot (NOAA 13131) using line scan observations in the Fe i 6173 Å and Ca ii 8542 Å spectral lines, complemented with data products from the Solar Dynamics Observatory's Helioseismic and Magnetic Imager. Line-of-sight (LOS) velocities were obtained for different bisector levels in both spectral lines. Additionally, the Ca ii 8542 Å spectra were inverted using the Non-LTE Inversion COde using the Lorien Engine (or NICOLE) to retrieve the temperature and velocity stratification over different layers of the lower solar atmosphere. The IEF evolved dynamically in time and with height in the solar atmosphere. The flow speed associated with the IEF channels was on the order of 8 km s−1 in the upper chromosphere, which decreased in the lower layers of the atmosphere. The flow was traced to the lower chromosphere in LOS velocity maps and the upper photosphere in intensity images. The temperature enhancements associated with the IEF were up to 300 K at log τ ≈ −2 and 800 K at log τ ≈ −6 near the end point of one channel. The overall appearance of the flow along the IEF channels seems consistent with a siphon flow model. We investigated the association of the IEF with the photospheric Evershed flow, but no obvious connection was found in our analysis. We also analyzed the effect of the IEF on moving magnetic features (MMF) selected near and away from IEF channels. MMFs moved radially outward with velocities in the 0.2-1 km s−1 range, with no apparent association with the IEF
