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Abstract The recharge oscillator (RO) is a simple mathematical model of the El Niño Southern Oscillation (ENSO). In its original form, it is based on two ordinary differential equations that describe the evolution of equatorial Pacific sea surface temperature and oceanic heat content. These equations make use of physical principles that operate in nature: (a) the air‐sea interaction loop known as the Bjerknes feedback, (b) a delayed oceanic feedback arising from the slow oceanic response to winds within the equatorial band, (c) state‐dependent stochastic forcing from fast wind variations known as westerly wind bursts (WWBs), and (d) nonlinearities such as those related to deep atmospheric convection and oceanic advection. These elements can be combined at different levels of RO complexity. The RO reproduces ENSO key properties in observations and climate models: its amplitude, dominant timescale, seasonality, and warm/cold phases amplitude asymmetry. We discuss the RO in the context of timely research questions. First, the RO can be extended to account for ENSO pattern diversity (with events that either peak in the central or eastern Pacific). Second, the core RO hypothesis that ENSO is governed by tropical Pacific dynamics is discussed from the perspective of influences from other basins. Finally, we discuss the RO relevance for studying ENSO response to climate change, and underline that accounting for ENSO diversity, nonlinearities, and better links of RO parameters to the long term mean state are important research avenues. We end by proposing important RO‐based research problems. 

ABSTRACT We present determinations of the gas-phase and stellar metallicities of a sample of 65 star-forming galaxies at $$z \simeq 3.5$$ using rest-frame far-ultraviolet (FUV) spectroscopy from the VANDELS survey in combination with follow-up rest-frame optical spectroscopy from VLT/KMOS and Keck/MOSFIRE. We infer gas-phase oxygen abundances ($$Z_{\mathrm{g}}$$; tracing O/H) via strong optical nebular lines and stellar iron abundances ($$Z_{\star }$$; tracing Fe/H) from full spectral fitting to the FUV continuum. Our sample spans the stellar mass range $$8.5 \lt \mathrm{log}(M_{\star }/\mathrm{M}_{\odot }) \lt 10.5$$ and shows clear evidence for both a stellar and gas-phase mass-metallicity relation (MZR). We find that our O and Fe abundance estimates both exhibit a similar mass-dependence, such that $$\mathrm{Fe/H}\propto M_{\star }^{0.30\pm 0.11}$$ and $$\mathrm{O/H}\propto M_{\star }^{0.32\pm 0.09}$$. At fixed $$M_{\star }$$ we find that, relative to their solar values, O abundances are systematically larger than Fe abundances (i.e. α-enhancement). We estimate an average enhancement of $$\mathrm{(O/Fe)} = 2.65 \pm 0.16 \times \mathrm{(O/Fe)_\odot }$$ which appears to be independent of $$M_{\star }$$. We employ analytic chemical evolution models to place a constraint on the strength of galactic-level outflows via the mass-outflow factor ($$\eta$$). We show that outflow efficiencies that scale as $$\eta \propto M_{\star }^{-0.32}$$ can simultaneously explain the functional form of of the stellar and gas-phase MZR, as well as the degree of α-enhancement at fixed Fe/H. Our results add further evidence to support a picture in which α-enhanced abundance ratios are ubiquitous in high-redshift star-forming galaxies, as expected for young systems whose interstellar medium is primarily enriched by core-collapse supernovae. 

Polypropylene (PP) and its composites are one of the hardest to directly join with metals due to their inherent chemical incompatibility. This paper presents a simple, efficient, and cost-effective method for joining PP composite to aluminum alloy in spot welding configuration by seeding the functional groups via an insert layer of PA6 thin film without requiring surface or material pre-treatment. The resulting joint loading capacity is shown to be sufficiently high to consistently develop failures in PP substrates in lap shear tensile tests away from the bonded area. Joint interface microstructure features are examined in detail. Bonding mechanisms are then described based on the detailed observations obtained in this study. 

Abstract The Electron-Ion Collider (EIC), a state-of-the-art facility for studying the strong force, is expected to begin commissioning its first experiments in 2028. This is an opportune time for artificial intelligence (AI) to be included from the start at this facility and in all phases that lead up to the experiments. The second annual workshop organized by the AI4EIC working group, which recently took place, centered on exploring all current and prospective application areas of AI for the EIC. This workshop is not only beneficial for the EIC, but also provides valuable insights for the newly established ePIC collaboration at EIC. This paper summarizes the different activities and R&D projects covered across the sessions of the workshop and provides an overview of the goals, approaches and strategies regarding AI/ML in the EIC community, as well as cutting-edge techniques currently studied in other experiments. 

ABSTRACT Extremely elongated, conducting dust particles (also known as metallic ‘needles’ or ‘whiskers’) are seen in carbonaceous chondrites and in samples brought back from the Itokawa asteroid. Their formation in protostellar nebulae and subsequent injection into the interstellar medium have been demonstrated, both experimentally and theoretically. Metallic needles have been suggested to explain a wide variety of astrophysical phenomena, ranging from the mid-infrared interstellar extinction at $$\sim \,$$3–8$$\, {\rm \mu m}$$ to the thermalization of starlight to generate the cosmic microwave background. To validate (or invalidate) these suggestions, an accurate knowledge of the optics (e.g. the amplitude and the wavelength dependence of the absorption cross sections) of metallic needles is crucial. Here we calculate the absorption cross sections of iron needles of various aspect ratios over a wide wavelength range, by exploiting the discrete dipole approximation, the most powerful technique for rigorously calculating the optics of irregular or nonspherical grains. Our calculations support the earlier findings that the antenna theory and the Rayleigh approximation, which are often taken to approximate the optical properties of metallic needles, are indeed inapplicable. 

We propose a new Scaled Population (SP) based arithmetic computation approach that achieves considerable improvements over existing stochastic computing (SC) techniques. First, SP arithmetic introduces scaling operations that significantly reduce the numerical errors as compared to SC. Experiments show accuracy improvements of a single multiplication and addition operation by 6.3X and 4X, respectively. Secondly, SP arithmetic erases the inherent serialization associated with stochastic computing, thereby significantly improves the computational delays. We design each of the operations of SP arithmetic to take O(1) gate delays, and eliminate the need of serially iterating over the bits of the population vector. Our SP approach improves the area, delay and power compared with conventional stochastic computing on an FPGA-based implementation. We also apply our SP scheme on a handwritten digit recognition application (MNIST), improving the recognition accuracy by 32.79% compared to SC.