The coexistence of gate-tunable superconducting, magnetic and topological orders in magic-angle twisted bilayer graphene provides opportunities for the creation of hybrid Josephson junctions. Here we ...report the fabrication of gate-defined symmetry-broken Josephson junctions in magic-angle twisted bilayer graphene, where the weak link is gate-tuned close to the correlated insulator state with a moiré filling factor of υ = -2. We observe a phase-shifted and asymmetric Fraunhofer pattern with a pronounced magnetic hysteresis. Our theoretical calculations of the junction weak link-with valley polarization and orbital magnetization-explain most of these unconventional features. The effects persist up to the critical temperature of 3.5 K, with magnetic hysteresis observed below 800 mK. We show how the combination of magnetization and its current-induced magnetization switching allows us to realise a programmable zero-field superconducting diode. Our results represent a major advance towards the creation of future superconducting quantum electronic devices.
Summary
The overuse of veterinary antibiotics in animal production and the subsequent land applications of manures contribute to the elevated antibiotic resistance in the soil environment. To ...minimize the risk of antibiotic resistance, it is important to understand the fate of antibiotics and the spread of antibiotic resistance genes (ARGs) from animal production systems to soil. In this paper, we review recent studies on veterinary antibiotic use, the concentrations of antibiotics and the abundance and diversity of AGRs in animal manures and in soil that receives manures or manure composts. The mechanisms of ARG dissemination in the environment are also discussed. Although we focus on China where around 3 billion tons of animal manures are produced and more than 84 000 tons of antibiotics are consumed annually in animal production industries, the problem is worldwide. Approximately 58% of the veterinary antibiotics consumed are excreted into the environment, more than half of which end up in the soil. The abundance of ARGs in manures can reach up to 10−1 of the 16S rRNA genes. Applications of manures or manure composts can enrich soil ARGs in at least three ways: (i) by the direct introduction of manure‐derived ARGs, (ii) by elevating the intrinsic soil ARGs and (iii) by imposing a selection of ARGs with the antibiotics in the manures. We also discuss the need for more stringent regulations on the use of veterinary antibiotics and future research directions on the mechanisms of antibiotic resistance and resistance management.
Highlights
Soil is a natural reservoir of antibiotics and antibiotic resistance genes (ARGs).
Manure applications introduce antibiotics and enrich soil ARGs through different mechanisms.
Horizontal gene transfer plays an important role in the spread of ARGs from manures.
More stringent regulations are needed to reduce the spread of ARG from animal sources.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The structural stability and the redox mechanism of Li-rich layered oxides (LLOs) are two very important aspects for high energy density. The former is related to the irreversible loss of lattice ...oxygen and capacity fading during cycling, while the latter determines the overall capacity of the materials. This paper aims at clarifying the factors governing the structural stability, the extra capacity and the redox mechanism of LLOs upon Li-removal. The results show that the structural stability against oxygen vacancy formation is improved with increasing M–O covalency, while it decreases with increasing d-shell electron number and with electrochemical extraction of lithium from the lattice. The redox mechanism of Li 2−x MO 3 electrodes formed by 3d metals or by heavier metals with a d 0 electronic configuration is related to the electron depletion from the oxygen lone-pairs (localized non-bonding O(2p) states) leading to an irreversible anionic redox ending with the reductive elimination of O 2 upon cycling. For these phases, long-term cycling is predicted to be very unlikely due to the irreversible loss of lattice oxygen upon charging. For the electrodes formed by 4d and 5d metals with intermediate d n electronic configurations, reversible cationic and anionic redox activities are predicted, therefore enabling reversible extra-capacities. The very different redox mechanisms exhibited by Li 2−x MO 3 electrodes are then linked to the delicate balance between the Coulomb repulsions ( U term) and the M–O bond covalency ( Δ term) through the general description of charge-transfer vs. Mott–Hubbard insulators. The present findings will provide a uniform guideline for tuning the band structures of Li 2 MO 3 phases and thus activating desired redox mechanisms, being beneficial for the design of high-energy density electrode materials for Li-ion battery applications.
The defining problem in frustrated quantum magnetism, the ground state of the nearest-neighbor S=1/2 antiferromagnetic Heisenberg model on the kagome lattice, has defied all theoretical and numerical ...methods employed to date. We apply the formalism of tensor-network states, specifically the method of projected entangled simplex states, which combines infinite system size with a correct accounting for multipartite entanglement. By studying the ground-state energy, the finite magnetic order appearing at finite tensor bond dimensions, and the effects of a next-nearest-neighbor coupling, we demonstrate that the ground state is a gapless spin liquid. We discuss the comparison with other numerical studies and the physical interpretation of this result.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
It’s whom you know that counts Xie, Y.
Science (American Association for the Advancement of Science),
03/2017, Volume:
355, Issue:
6329
Journal Article
Peer reviewed
Universalism-the evaluation of scientists' achievements based on merit alone rather than on functionally irrelevant factors (1-3)-has long been an unquestioned norm in science. Its existence is best ...illustrated by the reactions of outrage whenever a violation of universalism in science is exposed. For example, a study by Moss-Racusin et al. received a lot of attention in the scientific community because it found that when assessing application materials, science faculty rated students with male names as more competent than students who were otherwise identical but had been given female names (4). In a recent study, Fisman et al. (5) find evidence for favoritism in Chinese science: The election of membership to the two most prestigious scientific organizations, the Chinese Academy of Sciences (CAS) and the Chinese Academy of Engineering (CAE), appears to be influenced by "guanxi," or social network, as measured by hometown ties between candidates and selection committee members.
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BFBNIB, NMLJ, NUK, ODKLJ, PNG, SAZU, UL, UM, UPUK
Drylands are home to more than 38% of the world's population and are one of the most sensitive areas to climate change and human activities. This review describes recent progress in dryland climate ...change research. Recent findings indicate that the long‐term trend of the aridity index (AI) is mainly attributable to increased greenhouse gas emissions, while anthropogenic aerosols exert small effects but alter its attributions. Atmosphere‐land interactions determine the intensity of regional response. The largest warming during the last 100 years was observed over drylands and accounted for more than half of the continental warming. The global pattern and interdecadal variability of aridity changes are modulated by oceanic oscillations. The different phases of those oceanic oscillations induce significant changes in land‐sea and north‐south thermal contrasts, which affect the intensity of the westerlies and planetary waves and the blocking frequency, thereby altering global changes in temperature and precipitation. During 1948–2008, the drylands in the Americas became wetter due to enhanced westerlies, whereas the drylands in the Eastern Hemisphere became drier because of the weakened East Asian summer monsoon. Drylands as defined by the AI have expanded over the last 60 years and are projected to expand in the 21st century. The largest expansion of drylands has occurred in semiarid regions since the early 1960s. Dryland expansion will lead to reduced carbon sequestration and enhanced regional warming. The increasing aridity, enhanced warming, and rapidly growing population will exacerbate the risk of land degradation and desertification in the near future in developing countries.
Key Points
Drylands are one of the most sensitive areas to climate change and human activities
Attribution of major drivers and processes to dryland climate change has been summarized
Enhanced warming, increasing aridity, and expanding drylands pose a threat to developing countries
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper presents an improved algorithm for the bi-directional evolutionary structural optimization (BESO) method for topology optimization problems. The elemental sensitivity numbers are ...calculated from finite element analysis and then converted to the nodal sensitivity numbers in the design domain. A mesh-independency filter using nodal variables is introduced to determine the addition of elements and eliminate unnecessary structural details below a certain length scale in the design. To further enhance the convergence of the optimization process, the accuracy of elemental sensitivity numbers is improved by its historical information. The new approach is demonstrated by solving several compliance minimization problems and compared with the solid isotropic material with penalization (SIMP) method. Results show the effectiveness of the new BESO method in obtaining convergent and mesh-independent solutions.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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