Steady motion of 80-nm-size skyrmions in a 100-nm-wide track.

The current-driven movement of magnetic skyrmions along a nanostripe is essential for the advancement and functionality of a new category of spintronic devices resembling racetracks. Despite extensive research into skyrmion dynamics, experimental verification of current-induced motion of ultra-small skyrmions within an ultrathin nanostripe is still pending. Here, we unveil the motion of individual 80 nm-size skyrmions in an FeGe track with an ultrathin width of 100 nm. The skyrmions can move steadily along the track over a broad range of current densities by using controlled pulse durations of as low as 2 ns. The potential landscape, arising from the magnetic edge twists in such a geometrically confined system, introduces skyrmion inertia and ensures efficient motion with a vanishing skyrmion Hall angle. Our results showcase the steady motion of skyrmions in an ultrathin track, offering a practical pathway for implementing skyrmion-based spintronic devices.

Atomic scale disorder and reconstruction in bulk infinite-layer nickelates lacking superconductivity.

The recent discovery of superconductivity in infinite-layer nickelate films has sparked significant interest and expanded the realm of superconductors, in which the infinite-layer structure and proper chemical doping are both of the essence. Nonetheless, the reasons for the absence of superconductivity in bulk infinite-layer nickelates remain puzzling. Herein, we investigate atomic defects and electronic structures in bulk infinite-layer Nd0.8Sr0.2NiO2 using scanning transmission electron microscopy. Our observations reveal the presence of three-dimensional (3D) block-like structural domains resulting from intersecting defect structures, disrupting the continuity within crystal grains, which could be a crucial factor in giving rise to the insulating character and inhibiting the emergence of superconductivity. Moreover, the infinite-layer structure, without complete topotactic reduction, retains interstitial oxygen atoms on the Nd atomic plane in bulk nickelates, possibly further aggravating the local distortions of NiO2 planes and hindering the superconductivity. These findings shed light on the existence of structural and atomic defects in bulk nickelates and provide valuable insights into the influence of proper topotactic reduction and structural orders on superconductivity.

Effects of Resistance Exercise and Essential Amino Acid Intake on Muscle Quality, Myokine, and Inflammation Factors in Young Adult Males.

BACKGROUND: Recently, many studies have been devoted to discovering nutrients for exercise-like effects. Resistance exercise and the intake of essential amino acids (EAAs) are known to be factors that can affect muscle mass and strength improvement. The purpose of this study was to investigate changes in muscle quality, myokines, and inflammation in response to resistance exercise and EAA supplementation. METHODS: Thirty-four males volunteered to participate in this study. They were assigned to four groups: (1) placebo (CO), (2) resistance exercise (RE), (3) EAA supplementation, and (4) RE + EAA supplementation. Body composition, muscle quality, myokines, and inflammation were measured at baseline and four weeks after treatment. RESULTS: Lean body fat had decreased in both RE and RE + EAA groups. Lean body mass had increased in only the RE + EAA group. In all groups except for CO, irisin, myostatin A, and TNF-α levels had decreased. The grip strength of the right hand and trunk flexion peak torque increased in the RE group. The grip strength of the left hand, trunk flexion peak torque, and knee flexion peak torque of the left leg were increased in RE + EAA. CONCLUSIONS: RE, EAA, and RE + EAA could effectively improve the muscle quality, myokine, and inflammation factors of young adult males. This finding highlights the importance of resistance exercise and amino acid intake.

Stable skyrmion bundles at room temperature and zero magnetic field in a chiral magnet.

Topological spin textures are characterized by magnetic topological charges, Q, which govern their electromagnetic properties. Recent studies have achieved skyrmion bundles with arbitrary integer values of Q, opening possibilities for exploring topological spintronics based on Q. However, the realization of stable skyrmion bundles in chiral magnets at room temperature and zero magnetic field - the prerequisite for realistic device applications - has remained elusive. Here, through the combination of pulsed currents and reversed magnetic fields, we experimentally achieve skyrmion bundles with different integer Q values - reaching a maximum of 24 at above room temperature and zero magnetic field - in the chiral magnet Co8Zn10Mn2. We demonstrate the field-driven annihilation of high-Q bundles and present a phase diagram as a function of temperature and field. Our experimental findings are consistently corroborated by micromagnetic simulations, which reveal the nature of the skyrmion bundle as that of skyrmion tubes encircled by a fractional Hopfion.

Layer-Number-Dependent Magnetism in the Co-Doped van der Waals Ferromagnet Fe3GaTe2.

Recently, van der Waals (vdW) antiferromagnets have been proposed to be crucial for spintronics due to their favorable properties compared to ferromagnets, including robustness against magnetic perturbation and high frequencies of spin dynamics. High-performance and energy-efficient spin functionalities often depend on the current-driven manipulation and detection of spin states, highlighting the significance of two-dimensional metallic antiferromagnets, which have not been much explored due to the lack of suitable materials. Here, we report a new metallic vdW antiferromagnet obtained from the ferromagnet Fe3GaTe2 by cobalt (Co) doping. Through the layer-number-dependent Hall resistance and magnetoresistance measurements, an evident odd-even layer-number effect has been observed in its few-layered flakes, suggesting that it could host an A-type antiferromagnetic structure. This peculiar layer-number-dependent magnetism in Co-doped Fe3GaTe2 helps unravel the complex magnetic structures in such doped vdW magnets, and our finding will enrich material candidates and spin functionalities for spintronic applications.

Asymmetric Transfer Hydrogenation of 2-Substituted Quinoxalines with Regenerable Dihydrophenanthridine.

The asymmetric hydrogenation of quinoxalines represents one of the most efficient approaches for the synthesis of optically active tetrahyroquinoxalines. In this paper, we demonstrate a metal-free asymmetric transfer hydrogenation of 2-substituted quinoxalines with regenerable dihydrophenanthridine under H2 using a combination of chiral phosphoric acid and achiral borane as catalysts. A wide range of optically active 2-substituted tetrahydroquinoxalines were produced in high yields with ≤98% ee.

City-level livestock methane emissions in China from 2010 to 2020.

Livestock constitute the world's largest anthropogenic source of methane (CH4), providing high-protein food to humans but also causing notable climate risks. With rapid urbanization and increasing income levels in China, the livestock sector will face even higher emission pressures, which could jeopardize China's carbon neutrality target. To formulate targeted methane reduction measures, it is crucial to estimate historical and current emissions on fine geographical scales, considering the high spatial heterogeneity and temporal variability of livestock emissions. However, there is currently a lack of time-series data on city-level livestock methane emissions in China, despite the flourishing livestock industry and large amount of meat consumed. In this study, we constructed a city-level livestock methane emission inventory with dynamic spatial-temporal emission factors considering biological, management, and environmental factors from 2010 to 2020 in China. This inventory could serve as a basic database for related research and future methane mitigation policy formulation, given the population boom and dietary changes.

Thermal Stability of Skyrmion Tubes in Nanostructured Cuboids.

Magnetic skyrmions in bulk materials are typically regarded as two-dimensional structures. However, they also exhibit three-dimensional configurations, known as skyrmion tubes, that elongate and extend in-depth. Understanding the configurations and stabilization mechanism of skyrmion tubes is crucial for the development of advanced spintronic devices. However, the generation and annihilation of skyrmion tubes in confined geometries are still rarely reported. Here, we present direct imaging of skyrmion tubes in nanostructured cuboids of a chiral magnet FeGe using Lorentz transmission electron microscopy (TEM), while applying an in-plane magnetic field. It is observed that skyrmion tubes stabilize in a narrow field-temperature region near the Curie temperature (Tc). Through a field cooling process, metastable skyrmion tubes can exist in a larger region of the field-temperature diagram. Combining these experimental findings with micromagnetic simulations, we attribute these phenomena to energy differences and thermal fluctuations. Our results could promote topological spintronic devices based on skyrmion tubes.

Stereoselective Hydrosilylation of 1,2-Diketones Catalyzed by Chiral Frustrated Lewis Pairs.

The asymmetric reduction of 1,2-diketones for the synthesis of optically active 1,2-diols, especially 1,2-anti-diols, remains a formidable challenge. In this paper, we describe the first highly stereoselective hydrosilylation of unsymmetrical vicinal diketones with PhSiH3 by using a chiral frustrated Lewis pair (FLP) catalyst, giving a variety of 1,2-diaryl-1,2-anti-diols in high yields with excellent d.r. values and up to 97 % ee. The chiral FLP catalyst exhibits the ability to control regio-, diastereo- and enantioselectivites concurrently.

Synthesis of Tetrasubstituted Enamines through Borane-Catalyzed Hydrogenations.

This paper describes a B(C6F5)3-catalyzed hydrogenation of ß-substituted α,ß-unsaturated imines by using as low as 0.2 mol % catalyst. A variety of tetrasubstituted enamines were afforded in 95-99% yields. It provides an efficient and facile way without the need for column chromatography purification.

Asymmetric catalysis with FLPs.

Chiral catalysts play a crucial role in the realm of asymmetric catalysis. Since their breakthrough discovery in 2006, chiral frustrated Lewis pairs (FLPs) have risen as a novel catalyst category for a broad range of metal-free asymmetric reactions. This review provides an overview of the remarkable progress made in this field over the past 15 years. The design and synthesis of chiral FLPs and their applications in hydrogenation, hydrosilylation, transfer hydrogenation, and various other reactions are summarized and highlighted.

Room-Temperature Zero-Field kπ-Skyrmions and Their Field-Driven Evolutions in Chiral Nanodisks.

Target skyrmion, characterized by a central skyrmion surrounded by a series of concentric cylinder domains known as kπ-skyrmions (k ≥ 2), holds promise as a novel storage state in next-generation memories. However, target skyrmions comprising one or more concentric cylindrical domains have not been observed in chiral magnets, particularly at room temperature. In this study, we experimentally achieved kπ-skyrmions (k = 2, 3, and 4) with diameters of ∼220, 320, and 410 nm, respectively, and room-temperature stability under zero magnetic field by tightly confining these topological spin textures in ß-Mn-type Co8Zn10Mn2 nanodisks. The magnetic configurations and their field-driven evolutions were simultaneously investigated by using in situ off-axis electron holography. In combination with numerical simulations, we further investigated the dependence of kmax on the nanodisk diameter. These findings highlight the potential of kπ-skyrmions as information carriers and offer insights into manipulation of kπ-skyrmions in the future.

Asymmetric Hydrogenations of Acyclic α,ß-Unsaturated Ketones with Chiral Frustrated Lewis Pairs (FLPs).

In this paper, we demonstrate a metal-free asymmetric hydrogenation of acyclic α,ß-unsaturated ketones under the catalysis of a frustrated Lewis pair (FLP) comprising chiral oxazoline and achiral borane. A wide range of optically active α-substituted ketones were furnished in high yields with 26-85% ee's.

Wettability and Frictional Studies of PEEK Composites against Co-Cr Alloys with Surface Textures.

With the aim of promoting the qualities for total hip joint replacement, the wettability and tribological behaviors of PEEK composites pins with two sets of different fillers (PEEK/CF or PEEK/CF/PTFE/graphite) against Co-Cr alloy discs with five categories of surface textures (polished, orthogonal, spiral, r-θ, and orthogonal combined with spiral) were explored. It is revealed that the existence of CF in PEEK matrix increases the hydrophilicity in addition to the strength of PEEK, while the addition of PTFE increases the hydrophobicity of PEEK. The Co-Cr alloy discs with hydrophilic properties can be adjusted as hydrophobic, with the depth of textured grooves exceeding the critical sag height determined by the contact angle and the groove width. It can be concluded that PEEK/CF/PTFE/graphite composite has a lower wear rate than PEEK only reinforced with CF against Co-Cr alloy, both without surface texture and with shallow or deep grooves. The existence of shallow grooves on the disc surface could help the PEEK blends to achieve a steady friction against Co-Cr alloy in addition to collecting the worn debris. PEEK blend pins with 10 vol% CF, 10 vol% PTFE and 10 vol% graphite can achieve a lower friction coefficient of no more than 0.2 against Co-Cr alloy discs with shallow grooves around 3.5 µm in orthogonal or spiral textures.

Skyrmion-Bubble Bundles in an X-Type Sr2 Co2 Fe28 O46 Hexaferrite above Room Temperature.

Magnetic skyrmions are spin swirls that possess topological nontriviality and are considered particle-like entities. They are distinguished by an integer topological charge Q. The presence of skyrmion bundles provides an opportunity to explore the range of values for Q, which is crucial for the advancement of topological spintronic devices with multi-Q properties. In this study, a new material candidate, Sr2 Co2 Fe28 O46 hexaferrite of the X-type, which hosts small dipolar skyrmions at room temperature and above is presented. By exploiting reversed magnetic fields from metastable skyrmion bubbles at zero fields, skyrmion-bubble bundles with different interior skyrmion/bubble numbers, topological charges, and morphologies at room temperature are incorporated. These experimental findings are consistently supported by micromagnetic simulations. These results highlight the versatility of topological spin textures in centrosymmetric uniaxial magnets, thereby paving the way for the development of room-temperature topological spintronic devices with multi-Q characteristics.

City-level decoupling between livestock and crop production and its effect on fertilizer usage: Evidence from China.

China is one of the largest producers of livestock production and also with tremendous fertilizer consumption in crop production, regional decoupling between livestock and crop production often results in fertilizer overuse and environmental pollution. However, city-level coupling analysis between livestock and crop production is rare, and its impact on fertilizer usage also remains unclear. Here, we evaluated the nitrogen (N) nutrient supply from the livestock breeding sector and the N nutrient demand of cropland during the 2007-2020 period in a typical agricultural region in China. The city-level coupling degree of livestock and crop production and the effect on fertilizer usage were explored with spatial analysis and regression methods. Our results show that the province level has a relatively high coupling degree. However, significant spatial heterogeneity was found at the city level, especially in western Sichuan Province due to the highly unbalanced distribution of livestock and crop production, and this decoupling phenomenon may hinder fertilizer reduction. Furthermore, we reveal that technological development is not an effective way to achieve sustainable agriculture without other policy instruments, such as livestock spatial relocation, which must be considered when formulating crop-livestock integration policies. The findings expand city-level knowledge of the livestock-crop system and provide important implications for adjusting agricultural practices to realize sustainable agricultural development.

A hypernetwork-based urn model for explaining collective dynamics.

The topological characterization of complex systems has significantly contributed to our understanding of the principles of collective dynamics. However, the representation of general complex networks is not enough for explaining certain problems, such as collective actions. Considering the effectiveness of hypernetworks on modeling real-world complex networks, in this paper, we proposed a hypernetwork-based Pólya urn model that considers the effect of group identity. The mathematical deduction and simulation experiments show that social influence provides a strong imitation environment for individuals, which can prevent the dynamics from being self-correcting. Additionally, the unpredictability of the social system increases with growing social influence, and the effect of group identity can moderate market inequality caused by individual preference and social influence. The present work provides a modeling basis for a better understanding of the logic of collective dynamics.

High field magnetic transport measurements of FeGe thin plates.

Magnetic skyrmions have garnered considerable attention due to their topological properties and potential applications in information storage. These unique structures can be found in chiral magnets, including well-known compounds like MnSi and FeGe with a B20-type crystal structure. In this study, we utilized Lorentz transmission electron microscopy to investigate the influence of magnetic skyrmions on the Hall effect in FeGe under low magnetic fields. Additionally, we examined the magnetoresistance (MR) and Hall effect of FeGe under a high magnetic field of 28 T. Our findings reveal distinct mechanisms governing the MR at low and high temperatures. Notably, the anomalous Hall effect plays a significant role in the Hall resistivity observed at low magnetic fields. Meanwhile, the contribution of the skyrmion-induced topological Hall signal in the FeGe is ignorable. Furthermore, by employing a two-carrier model and fitting the carrier concentration of FeGe under high magnetic fields, we demonstrate a transition in the dominant carrier type from electrons to holes as the temperature increases. These results contribute to a deeper understanding of the intrinsic magnetic properties of FeGe.