Strange-metal phenomena often develop at the border of antiferromagnetic order in strongly correlated metals1. Previous work established that they can originate from the fluctuations anchored by the ...quantum-critical point associated with a continuous quantum phase transition out of the antiferromagnetic order2–4. What is still unclear is how these phenomena can be associated with a potential new phase of matter at zero temperature. Here, we show that magnetic frustration of the 4f local moments in the distorted kagome intermetallic compound cerium palladium aluminium gives rise to such a paramagnetic quantum-critical phase. Our discovery motivates a design principle for strongly correlated metallic states with unconventional excitations.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Pore structure of shale was studied from fractal perspective.•Shales samples with higher TOC have greater fractal dimension.•Micropores have a greater impact on fractal dimension than mesopores and ...macropores.•Shale samples with a higher fractal dimension have greater adsorption capacity.
Nanopore structure greatly affects gas adsorption and transport in shales. Such structures in shale samples from the Lower Cambrian strata of the Sichuan Basin of China have been investigated using X-ray diffraction, total organic carbon content (TOC) tests, porosity and permeability tests, nitrogen adsorption, and methane adsorption experiments. Fractal dimensions were obtained from the nitrogen adsorption data using the Frenkel–Halsey–Hill method. The relationships between TOC, clay minerals, pore structure parameters and fractal dimension have been investigated. Based on the physical description of the fractal surfaces, the impact of fractal dimension on adsorption capacity has also been discussed. The results showed that the shale samples had fractal geometries with fractal dimensions ranging from 2.68 to 2.83. The organic matter is a controlling factor on fractal dimension, shown by positive correlation between TOC and fractal dimension. Fractal dimension increases with increasing surface area and pore volume, and also increases with decreasing pore diameter because of the complicated pore structure. Micropores have a greater impact on fractal dimension than mesopores and macropores. A negative correlation between fractal dimension and permeability was observed, especially for shales with high TOC and micropores counts. The fractal dimension can be used to evaluate adsorption capacity. Shale samples with larger fractal dimensions have higher methane adsorption capacity. Fractal analysis leads to a better understanding of the pore structure and adsorption capacity of a shale gas reservoir.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Mitofusin-2 (MFN2) is a dynamin-like GTPase that plays a central role in regulating mitochondrial fusion and cell metabolism. Mutations in MFN2 cause the neurodegenerative disease Charcot-Marie-Tooth ...type 2A (CMT2A). The molecular basis underlying the physiological and pathological relevance of MFN2 is unclear. Here, we present crystal structures of truncated human MFN2 in different nucleotide-loading states. Unlike other dynamin superfamily members including MFN1, MFN2 forms sustained dimers even after GTP hydrolysis via the GTPase domain (G) interface, which accounts for its high membrane-tethering efficiency. The biochemical discrepancy between human MFN2 and MFN1 largely derives from a primate-only single amino acid variance. MFN2 and MFN1 can form heterodimers via the G interface in a nucleotide-dependent manner. CMT2A-related mutations, mapping to different functional zones of MFN2, lead to changes in GTP hydrolysis and homo/hetero-association ability. Our study provides fundamental insight into how mitofusins mediate mitochondrial fusion and the ways their disruptions cause disease.
Variable screening methods have been shown to be effective in dimension reduction under the ultra-high dimensional setting. Most existing screening methods are designed to rank the predictors ...according to their individual contributions to the response. As a result, variables that are marginally independent but jointly dependent with the response could be missed. In this work, we propose a new framework for variable screening, random subspace ensemble (RaSE), which works by evaluating the quality of random subspaces that may cover multiple predictors. This new screening framework can be naturally combined with any subspace evaluation criterion, which leads to an array of screening methods. The framework is capable to identify signals with no marginal effect or with high-order interaction effects. It is shown to enjoy the sure screening property and rank consistency. We also develop an iterative version of RaSE screening with theoretical support. Extensive simulation studies and real-data analysis show the effectiveness of the new screening framework.
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BFBNIB, GIS, IJS, KISLJ, NUK, PNG, UL, UM, UPUK
Capillary electrochromatography, which combined the high selectivity of high‐performance liquid chromatography and the high separation efficiency of capillary electrophoresis, is an attractive ...separation tool. In this review, the developments on monolithic and open tubular capillary electrochromatography during 2017 to August 2019 are summarized. Considering the development of novel stationary phases is the most active research field in capillary electrochromatography, monolithic capillary electrochromatography is classified according to the polymer‐based and hybrid monolithic columns, while open‐tubular capillary electrochromatography is categorized by cyclodextrin, silica, polymer, nanomaterials, microporous materials, and biomaterials‐based open tubular columns.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Tunability and stability in the electrical properties of 2D semiconductors pave the way for their practical applications in logic devices. A robust layered indium selenide (InSe) field‐effect ...transistor (FET) with superior controlled stability is demonstrated by depositing an indium (In) doping layer. The optimized InSe FETs deliver an unprecedented high electron mobility up to 3700 cm2 V−1 s−1 at room temperature, which can be retained with 60% after 1 month. Further insight into the evolution of the position of the Fermi level and the microscopic device structure with different In thicknesses demonstrates an enhanced electron‐doping behavior at the In/InSe interface. Furthermore, the contact resistance is also improved through the In insertion between InSe and Au electrodes, which coincides with the analysis of the low‐frequency noise. The carrier fluctuation is attributed to the dominance of the phonon scattering events, which agrees with the observation of the temperature‐dependent mobility. Finally, the flexible functionalities of the logic‐circuit applications, for instance, inverter and not‐and (NAND)/not‐or (NOR) gates, are determined with these surface‐doping InSe FETs, which establish a paradigm for 2D‐based materials to overcome the bottleneck in the development of electronic devices.
A robust layered indium selenide (InSe) field‐effect transistor (FET) with superior high mobility (3700 cm2 V−1 s−1 at room temperature) is demonstrated by depositing an indium doping layer. With tunable carrier transport, the surface‐doped InSe FETs present flexible operations to realize various logic circuits, such as inverters and not‐or and not‐and gates.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Ordered and flexible porous frameworks with solution processability are highly desirable to fabricate continuous and large‐scale membranes for the efficient gas separation. Herein, the first ...microporous hydrogen‐bonded organic framework (HOF) membrane has been fabricated by an optimized solution‐processing technique. The framework exhibits the superior stability because of the abundant hydrogen bonds and strong π–π interactions. Thanks to the flexible HOF structure, the membrane possesses the unprecedented pressure‐responsive H2/N2 separation performance. Furthermore, the scratched membrane can be healed by the treatment of solvent vapor, achieving the recovery of separation performance.
Press to separate: A hydrogen‐bonded organic framework membrane has been fabricated by simple solution‐processing techniques. It shows pressure‐responsive gas separation performance.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Supported metal nanostructures are the most widely used type of heterogeneous catalyst in industrial processes. The size of metal particles is a key factor in determining the performance of such ...catalysts. In particular, because low-coordinated metal atoms often function as the catalytically active sites, the specific activity per metal atom usually increases with decreasing size of the metal particles. However, the surface free energy of metals increases significantly with decreasing particle size, promoting aggregation of small clusters. Using an appropriate support material that strongly interacts with the metal species prevents this aggregation, creating stable, finely dispersed metal clusters with a high catalytic activity, an approach industry has used for a long time. Nevertheless, practical supported metal catalysts are inhomogeneous and usually consist of a mixture of sizes from nanoparticles to subnanometer clusters. Such heterogeneity not only reduces the metal atom efficiency but also frequently leads to undesired side reactions. It also makes it extremely difficult, if not impossible, to uniquely identify and control the active sites of interest. The ultimate small-size limit for metal particles is the single-atom catalyst (SAC), which contains isolated metal atoms singly dispersed on supports. SACs maximize the efficiency of metal atom use, which is particularly important for supported noble metal catalysts. Moreover, with well-defined and uniform single-atom dispersion, SACs offer great potential for achieving high activity and selectivity. In this Account, we highlight recent advances in preparation, characterization, and catalytic performance of SACs, with a focus on single atoms anchored to metal oxides, metal surfaces, and graphene. We discuss experimental and theoretical studies for a variety of reactions, including oxidation, water gas shift, and hydrogenation. We describe advances in understanding the spatial arrangements and electronic properties of single atoms, as well as their interactions with the support. Single metal atoms on support surfaces provide a unique opportunity to tune active sites and optimize the activity, selectivity, and stability of heterogeneous catalysts, offering the potential for applications in a variety of industrial chemical reactions.
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IJS, KILJ, NUK, PNG, UL, UM
Primates interact with the world by exploring visual objects; they seek opportunities to view novel objects even when these have no extrinsic reward value. How the brain controls this novelty seeking ...is unknown. Here we show that novelty seeking in monkeys is regulated by the zona incerta (ZI). As monkeys made eye movements to familiar objects to trigger an opportunity to view novel objects, many ZI neurons were preferentially activated by predictions of novel objects before the gaze shift. Low-intensity ZI stimulation facilitated gaze shifts, whereas ZI inactivation reduced novelty seeking. ZI-dependent novelty seeking was not regulated by neurons in the lateral habenula or by many dopamine neurons in the substantia nigra, traditionally associated with reward seeking. But the anterior ventral medial temporal cortex, an area important for object vision and memory, was a prominent source of novelty predictions. These data uncover a functional pathway in the primate brain that regulates novelty seeking.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
A novel single-fed low-cost wideband and high-gain slotted cavity antenna based on substrate integrated waveguide (SIW) technology using high-order cavity modes is demonstrated in this paper. ...High-order resonant modes (TE130, TE310, TE330) inside the cavity are simply excited by a coaxial probe which is located at the center of the antenna. Energy is coupled out of the cavity by a 3 × 3 slot array etched on the top surface of the cavity. Two antennas with different polarizations are designed and tested. Measured results show that the linearly polarized prototype achieves an impedance bandwidth (|S 11 | <; -10 dB) of > 26% (28 to 36.6 GHz), and a 1-dB gain bandwidth of 14.1% (30.3 to 34.9 GHz). In addition, a measured maximum gain of 13.8 dBi and radiation efficiency of 92% are obtained. To generate circularly polarized radiation, a rotated dipole array is placed in front of the proposed linearly polarized antenna. Measured results show that the circularly polarized antenna exhibits a common bandwidth (10-dB return loss bandwidth, 3-dB axial ratio bandwidth, and 1-dB gain bandwidth) of 11%.
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