Princeton University

Significant technology maturation efforts are underway by privately funded fusion startups with the goal to demonstrate mature HTS magnet technology. To support the private sector development effort and the DOE milestone based program, a U.S. Fusion Magnet Community Workshop was held on March 14-15, 2023 in Princeton, NJ. This was the first U.S. community workshop focused on fusion magnet technologies aimed at determining the structure and technical direction for a public program designed to complement the private fusion industry landscape. Based on the wide range of different contributions, a set of general themes and fusion magnet R&D needs were identified and discussed. Feedback received to the workshop charge questions highlighted critical magnet R&D gaps such as availability of existing large cable and coil test facilities, a magnet education program that can generate a trained and essential workforce by leveraging R&D capabilities of universities, U.S. national labs, and fusion industry. Other opportunities synergistic and complementary with high energy physics, high field magnets that are open for a broad range of science drivers. The defined R&D gaps underpin the need for a mid-term and long-term public program in fusion magnet development, which reflects the purpose of the workshop in developing the rationale and consent for such a base program. A self-consistent, fusion specific U.S. fusion magnet program will complement and de-risk fusion pilot plants (FPPs) of promising magnetic configurations developed by private companies on a timeline consistent with the NASEM report on bringing fusion to the U.S. grid. We describe the magnet challenges presented and R&D needs discussed in the workshop. These challenges and R&D needs provide focus for the development of U.S. mid-term and long term roadmaps on enabling HTS for high field fusion.

High current density cables are needed for the engineering design of potentially low cost, simpler geometry high temperature superconducting (HTS) magnets in the promising magnetic configurations as a fusion pilot plant (FPP) option. Significant technology maturation efforts are underway by privately funded startups with the goal to demonstrate mature HTS magnet technology. Test results, however, indicate critical engineering issues remain to be addressed to meet performance goals, and demonstrate HTS coil operation repeatability and reliability. To this end, exploring and enabling multiple viable conductor and cable options is vital. Partnering with a private fusion startup and manufacturers of superconducting strands and cables, Princeton Plasma Physics Laboratory (PPPL) is exploring and seeking to de-risk the aggressive high field approach presently targeted by others. Our main objective is to develop, test and calibrate novel high current density cables for a broad deployment of affordable and reliable coils using Bi-2212 conductors. If successful, such a project will provide technical feasibility for promising FPP configurations including spherical tokamaks (ST) and compact stellarators. We aim at the state-of-the-art Bi-2212 cable technologies toward a current density of 100 A/mm2 at 16 T and 4.2 K-10 K operation for low cost, simpler geometry toroidal field (TF) coils for compact stellarators developed by fusion startup companies on a timeline consistent with the FPP initiatives and beyond.

Traditional air-coupled inductors are usually limited to two phases. This paper presents the concept of multiphase 3-D polyhedron air-coupled inductors – termed “origami inductors” – formed by folding planar windings on modular surfaces into symmetric 3-D structures, which enables symmetric air-coupling of more than two phases. The air-coupled origami inductors, unlike traditional multiphase coupled inductors, do not need a magnetic core and can operate at high frequencies. Compared to discrete air-core inductors, the origami inductors can be easily transported and assembled and can offer reduced size, smaller current ripple, and faster transient due to dc and ac flux cancellation. Models are developed to quantify the performance benefits of the origami inductor. A tetrahedron-shaped four-phase origami inductor was designed and through FEM simulations, its reduced volume was verified. The origami inductor was also tested as a part of a 5 V input, 12 V output, 80 W four-phase interleaved dc-dc boost converter, switching between frequencies ranging from 1 MHz to 5 MHz, to verify its operational effectiveness.

This letter presents a simplified dc-bias injection circuit utilizing a voltage mirror transformer configured in a unique way for improved equipment applicability and measurement accuracy. A mirror transformer can minimize the impact of the reflected actuation voltages on the dc source and improve the quality of the dc-bias injection. By combining the dc-bias and ac actuation current, the traditional three-winding dc-bias measurement setup was simplified with improved accuracy and reduced equipment complexity. The dc-bias injection circuit was implemented as a part of a highly automated data acquisition system designed for fast and accurate characterization of power magnetic materials under a wide range of operating conditions.

Phytoplankton stoichiometry modulates the interaction between carbon, nitrogen and phosphorus cycles. Environmentally driven variations in phytoplankton C:N:P can alter biogeochemical cycling compared to expectations under fixed ratios. In fact, the assumption of fixed C:N:P has been linked to Earth System Model (ESM) biases and potential misrepresentation of responses to future change. Here we integrate key elements of the Adaptive Trait Optimization Model (ATOM) for phytoplankton stoichiometry with the Carbon, Ocean Biogeochemistry and Lower Trophics (COBALT) ocean biogeochemical model. Within a series of global ocean‐ice‐ecosystem retrospective simulations, ATOM‐COBALT reproduced observations of phytoplankton N:P, and compared to static ratios, exhibited reduced phytoplankton P‐limitation, enhanced N‐fixation, and increased low‐latitude export, improving consistency with observations and highlighting the biogeochemical implications of dynamic N:P. We applied ATOM‐COBALT to explore the impacts of different physiological mechanisms hypothesized to underlie N:P variation, finding that two mechanisms together drove the observed patterns: proportionality of P‐rich ribosomes in phytoplankton cells to growth rates and reductions in P‐storage during scarcity. A third mechanism which linked temperature with phytoplankton biomass allocations to non‐ribosomal proteins, led only to relatively modest impacts because this mechanism decreased the temperature dependence of phytoplankton growth rates, compensating for changes in N:P. We find that there are quantitative response differences that associate distinctive biogeochemical footprints with each mechanism, which are most apparent in highly productive low‐latitude regions. These results suggest that variable phytoplankton N:P makes phytoplankton productivity and export resilient to environmental changes, and support further research on the physiological and environmental drivers of phytoplankton stoichiometry and biogeochemical role.

Phonons play a crucial role in many properties of solid-state systems, and it is expected that topological phonons may lead to rich and unconventional physics. On the basis of the existing phonon materials databases, we have compiled a catalog of topological phonon bands for more than 10,000 three-dimensional crystalline materials. Using topological quantum chemistry, we calculated the band representations, compatibility relations, and band topologies of each isolated set of phonon bands for the materials in the phonon databases. Additionally, we calculated the real-space invariants for all the topologically trivial bands and classified them as atomic or obstructed atomic bands. We have selected more than 1000 “ideal” nontrivial phonon materials to motivate future experiments. The datasets were used to build the Topological Phonon Database.

To fully understand how the human brain works, knowledge of its structure at high resolution is needed. Presented here is a computationally intensive reconstruction of the ultrastructure of a cubic millimeter of human temporal cortex that was surgically removed to gain access to an underlying epileptic focus. It contains about 57,000 cells, about 230 millimeters of blood vessels, and about 150 million synapses and comprises 1.4 petabytes. Our analysis showed that glia outnumber neurons 2:1, oligodendrocytes were the most common cell, deep layer excitatory neurons could be classified on the basis of dendritic orientation, and among thousands of weak connections to each neuron, there exist rare powerful axonal inputs of up to 50 synapses. Further studies using this resource may bring valuable insights into the mysteries of the human brain.

Editors of the Journal of Geophysical Research—Earth Surface express their appreciation to those who served as peer reviewers for the journal in 2023.

In magnetic fusion devices, error field (EF) sources, spurious magnetic field perturbations, need to be identified and corrected for safe and stable (disruption-free) tokamak operation. Within Work Package Tokamak Exploitation RT04, a series of studies have been carried out to test the portability of the novel non-disruptive method, designed and tested in DIII-D (Paz-Soldan et al 2022 Nucl. Fusion 62 126007), and to perform an assessment of model-based EF control strategies towards their applicability in ITER. In this paper, the lessons learned, the physical mechanism behind the magnetic island healing, which relies on enhanced viscous torque that acts against the static electro-magnetic torque, and the main control achievements are reported, together with the first design of the asynchronous EF correction current/density controller for ITER.

Atmospheric rivers (ARs) are characterized by intense lower tropospheric plumes of moisture transport that are frequently responsible for midlatitude wind and precipitation extremes. The prediction of ARs on subseasonal timescales is currently at a low level of skill, reflecting a need to improve our understanding of their underlying sources of predictability. Based on hindcast experiments from the Seamless System for Prediction and Earth System Research (SPEAR) at the Geophysical Fluid Dynamics Laboratory, we evaluate the global subseasonal prediction skill of wintertime AR statistics. Overall, the results from SPEAR are comparable to the European Centre for Medium-Range Weather Forecasts (ECMWF). Higher forecast skill is detected for strong AR activities than weak AR activities, despite that the occurrence frequency for weak ARs exceeds that of strong ARs. Importantly, we assess the sources of predictability and find that three most predictable modes of ARs in the North Pacific sector can be interpreted as arising from the influence of the El Niño–Southern Oscillation, the Pacific North American and the Arctic Oscillation patterns. Subseasonal AR forecast skill in western North America is modulated by different phases of these modes of large-scale seasonal variability highlighting the potential windows of opportunity for subseasonal AR forecasting.

A novel metric that describes the vulnerability of the measurements in power systems to data integrity attacks is proposed. The new metric, coined vulnerability index (VuIx), leverages information theoretic measures to assess the attack effect in terms of the fundamental limits of the disruption and detection tradeoff. The result of computing the VuIx of the measurements in the system yields an ordering of their vulnerability based on the degree of exposure to data integrity attacks. This new framework is used to assess the measurement vulnerability of IEEE 9‐bus and 30‐bus test systems and it is observed that power injection measurements are significantly more vulnerable to data integrity attacks than power flow measurements. A detailed numerical evaluation of the VuIx values for IEEE test systems is provided.

Iron(Fe)-doped -nickel oxyhydroxide (-NiOOH) is a highly active, noble-metal-free electrocatalyst for the oxygen evolution reaction (OER), with the latter being the bottleneck in electrochemical water splitting for sustainable hydrogen production....

The emergence of quasiparticles in quantum many-body systems underlies the rich phenomenology in many strongly interacting materials. In the context of doped Mott insulators, magnetic polarons are quasiparticles that usually arise from an interplay between the kinetic energy of doped charge carriers and superexchange spin interactions1–8. However, in kinetically frustrated lattices, itinerant spin polarons—bound states of a dopant and a spin flip—have been theoretically predicted even in the absence of superexchange coupling9–14. Despite their important role in the theory of kinetic magnetism, a microscopic observation of these polarons is lacking. Here we directly image itinerant spin polarons in a triangular-lattice Hubbard system realized with ultracold atoms, revealing enhanced antiferromagnetic correlations in the local environment of a hole dopant. In contrast, around a charge dopant, we find ferromagnetic correlations, a manifestation of the elusive Nagaoka effect15,16. We study the evolution of these correlations with interactions and doping, and use higher-order correlation functions to further elucidate the relative contributions of superexchange and kinetic mechanisms. The robustness of itinerant spin polarons at high temperature paves the way for exploring potential mechanisms for hole pairing and superconductivity in frustrated systems10,11. Furthermore, our work provides microscopic insights into related phenomena in triangular-lattice moiré materials17–20.

The nucleus is highly organized, such that factors involved in the transcription and processing of distinct classes of RNA are confined within specific nuclear bodies1,2. One example is the nuclear speckle, which is defined by high concentrations of protein and noncoding RNA regulators of pre-mRNA splicing³. What functional role, if any, speckles might play in the process of mRNA splicing is unclear4,5. Here we show that genes localized near nuclear speckles display higher spliceosome concentrations, increased spliceosome binding to their pre-mRNAs and higher co-transcriptional splicing levels than genes that are located farther from nuclear speckles. Gene organization around nuclear speckles is dynamic between cell types, and changes in speckle proximity lead to differences in splicing efficiency. Finally, directed recruitment of a pre-mRNA to nuclear speckles is sufficient to increase mRNA splicing levels. Together, our results integrate the long-standing observations of nuclear speckles with the biochemistry of mRNA splicing and demonstrate a crucial role for dynamic three-dimensional spatial organization of genomic DNA in driving spliceosome concentrations and controlling the efficiency of mRNA splicing.

Antarctic meltwater discharge has been largely emphasized for its potential role in climate change mitigation, not only by reducing global warming, but also by stabilizing the Atlantic Meridional Overturning Circulation (AMOC). Despite the tremendous impact of the AMOC on the climate system, its temporal evolution in response to the meltwater remains poorly understood. Here, we investigate the meltwater impacts on the AMOC based on the GFDL CM2.1 experiments and discover its fast weakening and slow strengthening to the Antarctic meltwater discharge. Cold ocean surface caused by meltwater spread throughout the globe and eventually strengthened the AMOC. However, in the early stages, the tropical temperature response could stimulate the Rossby wave teleconnection, modulating atmospheric circulation in the North Atlantic, and weakening convection and even the AMOC. This counterintuitive evolution implies a potential destabilizing effect of Antarctic meltwater, underscoring the importance of the atmospheric dynamics in the interaction between the two poles.

Plain Language Summary The ocean plays a central role in Earth's climate system as a major reservoir of heat. Understanding how ocean heat content (OHC) changed in the past is therefore key to unraveling the history of global climate. Xenon, krypton, and nitrogen trapped in ice core air bubbles offer a means of reconstructing past OHC, because changes in global ocean temperature affect the solubilities of these gases in seawater, leading to corresponding changes in their atmospheric abundances. For example, a colder ocean can hold more xenon, meaning less xenon resides in the atmosphere. However, these gases in the ocean today are slightly out of equilibrium with the atmosphere (i.e., they are undersaturated), and it remains unclear to what extent this disequilibrium could have changed in the past. We carried out global atmosphere‐ocean model simulations, finding that undersaturation was likely reduced in the Last Glacial Maximum (LGM), a colder era of global climate ∼20,000 years ago. Our analysis suggests that a small component of the additional xenon in the colder LGM ocean arose from this change in air‐sea disequilibrium. After accounting for this effect, ice core noble gas measurements suggest a slightly warmer LGM ocean than previously thought.

Unlike unitary dynamics, measurements of a subsystem can induce long-range entanglement via quantum teleportation. The amount of measurement-induced entanglement or mutual information depends jointly on the measurement basis and the entanglement structure of the state (before measurement), and has operational significance for whether the state is a resource for measurement-based quantum computing, as well as for the computational complexity of simulating the state using quantum or classical computers. In this paper, we examine entropic measures of measurement-induced entanglement (MIE) and information (MII) for the ground states of quantum many-body systems in one and two spatial dimensions. From numerical and analytic analysis of a variety of models encompassing critical points, quantum Hall states, string-net topological orders, and Fermi liquids, we identify universal features of the long-distance structure of MIE and MII that depend only on the underlying phase or critical universality class of the state. We argue that, whereas in 1D the leading contributions to long-range MIE and MII are universal, in 2D, the existence of a teleportation transition for finite-depth circuits implies that trivial 2D states can exhibit long-range MIE, and the universal features lie in subleading corrections. We introduce modified MIE measures that directly extract these universal contributions. As a corollary, we show that the leading contributions to strange correlators, used to numerically identify topological phases, are in fact nonuniversal in two or more dimensions, and explain how our modified constructions enable one to isolate universal components. We discuss the implications of these results for classical- and quantum- computational simulation of quantum materials.

Introduction/Aims To better understand the disease burden faced by individuals with Duchenne muscular dystrophy (DMD) of all ages and elucidate potential targets for therapeutics, this study determined the prevalence and relative importance of symptoms experienced by individuals with DMD and identified factors associated with a higher disease burden. Methods We conducted qualitative interviews with individuals with DMD and caregivers of individuals with DMD to identify potential symptoms of importance to those living with DMD. We subsequently performed a cross‐sectional study to assess which symptoms have the highest prevalence and importance in DMD and to determine which factors are associated with a higher disease burden. Results Thirty‐nine individuals, aged 11 years and above, provided 3262 quotes regarding the symptomatic burden of DMD. Two hundred participants (87 individuals with DMD and 113 caregivers) participated in a subsequent cross‐sectional study. Individuals with DMD identified limitations with mobility or walking (100%), inability to do activities (98.9%), trouble getting around (97.6%), and leg weakness (97.6%) as the most prevalent and life altering symptomatic themes in DMD. The symptomatic themes with the highest prevalence, as reported by caregivers on behalf of those with DMD for whom they care, were limitations with mobility or walking (90.3%), leg weakness (89.2%), and emotional issues (79.6%). Steroid/glucocorticoid use (e.g., prednisone or deflazacort) was associated with a lower level of disease burden in DMD. Discussion There are many symptomatic themes that contribute to disease burden in individuals with DMD. These symptoms are identified by both individuals with DMD and their caregivers and have a variable level of importance and prevalence in the DMD population.

Hong Kong has historically been the epicenter of the global shark fin trade. Despite this legacy, recent public outreach campaigns highlighting the effects of consumption on marine ecosystems have precipitated shifts in the market. Fish maw and sea cucumber have emerged as substitutes in wildlife markets, marking an understudied phenomenon from urban geographical perspectives. This article investigates the transitional nature of social value systems underpinning Hong Kong's marine wildlife market through interviews with retailers, conservation organizations, and government officials, as well as visual surveys of market displays. Hong Kong's marine wildlife market, this article contends, brings into sharp relief how transitions in social value systems that substitute one type of non-fungible wildlife commodity for others can amplify biodiversity loss and reproduce expressions of social difference in urban space. The article illuminates how social value systems embedded in urban wildlife markets are related to human health, aging, gifting, and relationship building. Furthermore, it analyzes how the possession, consumption, and display of high-value wildlife commodities in cities reflects classed and gendered forms of social difference. The article further examines the challenges of regulating the market and shaping public values and actions in the face of escalating global biodiversity loss.

Increasing snow accumulation over the Antarctic Ice Sheet may mitigate future sea level rise. However, current estimates of mitigation potential are poorly constrained due to limited records of past variability. We present an annually resolved reconstruction of Antarctic snow accumulation from 1801 to 2000 CE, employing a paleoclimate data assimilation methodology to integrate ice core records with a multi‐model ensemble of climate simulations. Our reconstruction correlates well with instrumental reanalysis, and we find that Antarctic accumulation rates increased over the 20th‐century, resulting in a modest amount (∼1 mm) of sea level mitigation. Mitigation is primarily driven by an accelerating trend since around 1970. Our results contrast with previous mitigation estimates of ∼10–12 mm; this discrepancy is due to poorly constrained baseline estimates of 19th‐century accumulation in East Antarctica. Our reconstruction suggests that the uncertainty of future sea level mitigation from increasing Antarctic accumulation has been underestimated.