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We discuss results of a superposed epoch analysis of dipolarization fronts, rapid (δt < 30 s), high‐amplitude (δBz > 10 nT) increases in the northward magnetic field component, observed during six Time History of Events and Macroscale Interactions during Substorms (THEMIS) conjunction events. All six fronts propagated earthward; time delays at multiple probes were used to determine their propagation velocity. We define typical magnetic and electric field and plasma parameter variations during dipolarization front crossings and estimate their characteristic gradient scales. The study reveals (1) a rapid 50% decrease in plasma density and ion pressure, (2) a factor of 2–3 increase in high‐energy (30–200 keV) electron flux and electron temperature, and (3) transient enhancements of ∼5 mV/m in duskward and earthward electric field components. Gradient scales of magnetic field, plasma density, and particle flux were found to be comparable to the ion thermal gyroradius. Current densities associated with the Bz increase are, on average, 20 nA/m2, 5–7 times larger than the current density in the cross‐tail current sheet. Because j · E > 0, the dipolarization fronts are kinetic‐scale dissipative regions with Joule heating rates of 10% of the total bursty bulk flow energy. Key Points Superposed epoch analysis of THEMIS dipolarization front events Common pattern in field and particle variations during front crossings Particle energization and energetic plasma transport

Synthesizing metals with extremely small (nanoscale) grain sizes makes for much stronger materials. However, very small–grained materials start to coarsen at relatively low temperatures, wiping out their most desirable properties. Zhou et al. discovered a way to avoid this problem by mechanically grinding copper and nickel at liquid nitrogen temperatures. The processing method creates low-angle grain boundaries between the nanograins, which promotes thermal stability. Science , this issue p. 526 Low-temperature plastic deformation creates nanoscale metals more resilient to higher-temperature grain coarsening. The limitation of nanograined materials is their strong tendency to coarsen at elevated temperatures. As grain size decreases into the nanoscale, grain coarsening occurs at much lower temperatures, as low as ambient temperatures for some metals. We discovered that nanometer-sized grains in pure copper and nickel produced from plastic deformation at low temperatures exhibit notable thermal stability below a critical grain size. The instability temperature rises substantially at smaller grain sizes, and the nanograins remain stable even above the recrystallization temperatures of coarse grains. The inherent thermal stability of nanograins originates from an autonomous grain boundary evolution to low-energy states due to activation of partial dislocations in plastic deformation.

Fusarium is a genus of filamentous fungi that includes species that cause devastating diseases in major staple crops, such as wheat, maize, rice, and barley, resulting in severe yield losses and mycotoxin contamination of infected grains. Phenamacril is a novel fungicide that is considered environmentally benign due to its exceptional specificity; it inhibits the ATPase activity of the sole class I myosin of only a subset of Fusarium species including the major plant pathogens F. graminearum, F. asiaticum and F. fujikuroi. To understand the underlying mechanisms of inhibition, species specificity, and resistance mutations, we have determined the crystal structure of phenamacril-bound F. graminearum myosin I. Phenamacril binds in the actin-binding cleft in a new allosteric pocket that contains the central residue of the regulatory Switch 2 loop and that is collapsed in the structure of a myosin with closed actin-binding cleft, suggesting that pocket occupancy blocks cleft closure. We have further identified a single, transferable phenamacril-binding residue found exclusively in phenamacril-sensitive myosins to confer phenamacril selectivity.

Arrestins comprise a family of signal regulators of G-protein-coupled receptors (GPCRs), which include arrestins 1 to 4. While arrestins 1 and 4 are visual arrestins dedicated to rhodopsin, arrestins 2 and 3 (Arr2 and Arr3) are β-arrestins known to regulate many nonvisual GPCRs. The dynamic and promiscuous coupling of Arr2 to nonvisual GPCRs has posed technical challenges to tackle the basis of arrestin binding to GPCRs. Here we report the structure of Arr2 in complex with neurotensin receptor 1 (NTSR1), which reveals an overall assembly that is strikingly different from the visual arrestin–rhodopsin complex by a 90° rotation of Arr2 relative to the receptor. In this new configuration, intracellular loop 3 (ICL3) and transmembrane helix 6 (TM6) of the receptor are oriented toward the N-terminal domain of the arrestin, making it possible for GPCRs that lack the C-terminal tail to couple Arr2 through their ICL3. Molecular dynamics simulation and crosslinking data further support the assembly of the Arr2‒NTSR1 complex. Sequence analysis and homology modeling suggest that the Arr2‒NTSR1 complex structure may provide an alternative template for modeling arrestin–GPCR interactions.

The latest discovery of high temperature superconductivity near 80 K in La 3 Ni 2 O 7 under high pressure has attracted much attention. Many proposals are put forth to understand the origin of superconductivity. The determination of electronic structures is a prerequisite to establish theories to understand superconductivity in nickelates but is still lacking. Here we report our direct measurement of the electronic structures of La 3 Ni 2 O 7 by high-resolution angle-resolved photoemission spectroscopy. The Fermi surface and band structures of La 3 Ni 2 O 7 are observed and compared with the band structure calculations. Strong electron correlations are revealed which are orbital- and momentum-dependent. A flat band is formed from the Ni-3d z 2 orbitals around the zone corner which is ~ 50 meV below the Fermi level and exhibits the strongest electron correlation. In many theoretical proposals, this band is expected to play the dominant role in generating superconductivity in La 3 Ni 2 O 7 . Our observations provide key experimental information to understand the electronic structure and origin of high temperature superconductivity in La 3 Ni 2 O 7 . Recently, superconductivity near 80 K was observed in La3Ni2O7 under high pressure, but the mechanism is debated. Here the authors report angle-resolved photoemission spectroscopy measurements under ambient pressure, revealing flat bands with strong electronic correlations that could be linked to superconductivity.

Astrophysical and space plasmas are inherently multi-scale in nature. Identifying the mechanisms responsible for transporting energy across different physical scales is an essential step in modeling the dynamics of these plasmas and their associated astrophysical and space systems. Traditionally, these mechanisms are examined within an electron-single ion framework, even in the presence of multiple ion species. This simplification is justified by the dominance of a single ion species in most observations. In this work, we present measurements from the Magnetospheric Multiscale mission in Earth’s magnetosphere that challenge this paradigm. Data analysis reveals that hydrogen and helium ions, which commonly coexist, behave differently in ion-scale waves, with hydrogen ions responding more like electrons and helium ions behaving more like ions. These differential responses then induce interactions between the two ion species, exciting lower-hybrid electrostatic waves and consequently driving energy cascading from the ion scale down to the lower-hybrid scale. This process remains efficient even when helium ions are present in very minor quantities. Our observations, therefore, provide direct experimental evidence for cross-scale energy transfer processes in plasmas through multiple-ion interactions. The study provides observational evidence of energy transfer in space plasmas, showing hydrogen and helium ions interact differently with ion-scale waves. Despite helium’s low abundance, they show their interaction can excite electrostatic waves, facilitating energy transfer across scales and challenging traditional models.

SummaryA meta-analysis of observational studies was conducted to assess the relationship between overweight/obesity and vertebral fractures in older adults. We found that overweight was related to a decreased risk of vertebral fractures in female and non-Asian populations, while obesity failed to be associated with vertebral fracture risks based on the present data.IntroductionRecent investigations suggest that the influence of overweight/obesity on fracture risks is site-specific, while conflicting data were reported related to vertebral fracture. This meta-analysis was performed to qualitatively assess the relationship between overweight/obesity and the risk of vertebral fracture.MethodsMEDLINE, Web of Science, Embase, and Cochrane were searched for relevant observational articles assessing the vertebral fracture risk of the overweight or obese population compared to normal population. Two independent reviewers conducted data extraction and quality assessment. Relative risks (RR) and 95% confidence intervals (CI) were pooled using a random effect model.ResultsEleven studies including 1,078,094 participants were extracted from 1645 records. Pooled RR showed that decreased risk of vertebral fractures was observed in the overweight older adults (RR: 1.16; 95% CI: 1.07–1.26; I2: 51.8%), but not in the obese populations (RR: 0.98; 95% CI: 0.82–1.17; I2: 92.1%). In the subgroup analysis, we found a significant inverse association between overweight and risk of vertebral fracture in women (RR: 0.92; 95% CI: 0.85–1.00; I2: 0.0%), non-Asian areas (RR: 0.89; 95% CI: 0.80–0.99; I2: 40.7%), sample size > 2000 (RR: 0.87; 95% CI: 0.80–0.94; I2: 4.9%), and quality score > 7 (RR: 0.87; 95% CI: 0.79–0.95; I2: 21.9%). Furthermore, pooled studies of sample size > 2000 (RR: 0.66; 95% CI: 0.76, 0.89; I2: 52.1%) and quality score > 7 (RR: 0.75; 95% CI: 0.62, 0.91; I2: 68.1%) showed that the people with obesity had a significantly lower prevalence of vertebral fracture.ConclusionsOverweight aged adults tend to have a lower vertebral fracture risk. When gender and ethnicity were taken into consideration, the inverse relationship between overweight and vertebral fracture risk were only observed in female and non-Asian populations. Besides, there is insufficient data to conclude the relationship between obesity and the risk of vertebral fractures, and thus, further studies are needed.

The independent control of two magnetic electrodes and spin-coherent transport in magnetic tunnel junctions are strictly required for tunneling magnetoresistance, while junctions with only one ferromagnetic electrode exhibit tunneling anisotropic magnetoresistance dependent on the anisotropic density of states with no room temperature performance so far. Here, we report an alternative approach to obtaining tunneling anisotropic magnetoresistance in α′-FeRh-based junctions driven by the magnetic phase transition of α′-FeRh and resultantly large variation of the density of states in the vicinity of MgO tunneling barrier, referred to as phase transition tunneling anisotropic magnetoresistance. The junctions with only one α′-FeRh magnetic electrode show a magnetoresistance ratio up to 20% at room temperature. Both the polarity and magnitude of the phase transition tunneling anisotropic magnetoresistance can be modulated by interfacial engineering at the α′-FeRh/MgO interface. Besides the fundamental significance, our finding might add a different dimension to magnetic random access memory and antiferromagnet spintronics. Tunneling anisotropic magnetoresistance is promising for next generation memory devices but limited by the low efficiency and functioning temperature. Here the authors achieved 20% tunneling anisotropic magnetoresistance at room temperature in magnetic tunnel junctions with one α′-FeRh magnetic electrode.

We report on the evolving ion distributions associated with the arrival of an earthward propagating dipolarization front in the near‐Earth magnetotail using Time History of Events and Macroscale Interactions during Substorms (THEMIS). Ion distributions exhibit steady duskward anisotropy well before the front arrival, suggesting thin current sheet formation at ∼11 RE, during the growth phase of a moderate geomagnetic substorm. As the dipolarization front moves closer, an additional, earthward streaming ion population appears, resulting in an earthward velocity moment. This population eventually overwhelms the preexisting duskward anisotropy and merges with the earthward convecting bulk flow once the dipolarization front arrives. Test‐particle simulations show that the observed ion evolution is consistent with a picture of ions reflected and accelerated by the approaching front and moving ahead of it.

Large-scale, highly integrated and low-power-consuming hardware is becoming progressively more important for realizing optical neural networks (ONNs) capable of advanced optical computing. Traditional experimental implementations need N 2 units such as Mach-Zehnder interferometers (MZIs) for an input dimension N to realize typical computing operations (convolutions and matrix multiplication), resulting in limited scalability and consuming excessive power. Here, we propose the integrated diffractive optical network for implementing parallel Fourier transforms, convolution operations and application-specific optical computing using two ultracompact diffractive cells (Fourier transform operation) and only N MZIs. The footprint and energy consumption scales linearly with the input data dimension, instead of the quadratic scaling in the traditional ONN framework. A ~10-fold reduction in both footprint and energy consumption, as well as equal high accuracy with previous MZI-based ONNs was experimentally achieved for computations performed on the MNIST and Fashion-MNIST datasets. The integrated diffractive optical network (IDNN) chip demonstrates a promising avenue towards scalable and low-power-consumption optical computational chips for optical-artificial-intelligence. Here, we propose the integrated diffractive optical network for implementing parallel Fourier transforms, convolution operations and application-specific optical computing with reduced footprint and energy consumption.