The kagome Heisenberg antiferromagnet is a leading candidate in the search for a spin system with a quantum spin-liquid ground state. The nature of its ground state remains a matter of active debate. ...We conducted oxygen-17 single-crystal nuclear magnetic resonance (NMR) measurements of the spin-1/2 kagome lattice in herbertsmithite ZnCu₃(OH)₆Cl₂, which is known to exhibit a spinon continuum in the spin excitation spectrum. We demonstrated that the intrinsic local spin susceptibility χkagome, deduced from the oxygen-17 NMR frequency shift, asymptotes to zero below temperatures of 0.03J, where J ∼ 200 kelvin is the copper-copper superexchange interaction. Combined with the magnetic field dependence of χkagome that we observed at low temperatures, these results imply that the kagome Heisenberg antiferromagnet has a spin-liquid ground state with a finite gap.
Host–guest complexation between calix5arene and aggregation‐induced emission luminogen (AIEgen) can significantly turn off both the energy dissipation pathways of intersystem crossing and thermal ...deactivation, enabling the absorbed excitation energy to mostly focus on fluorescence emission. The co‐assembly of calix5arene amphiphiles and AIEgens affords highly emissive supramolecular AIE nanodots thanks to their interaction severely restricting the intramolecular motion of AIEgens, which also show negligible generation of cytotoxic reactive oxygen species. In vivo studies with a peritoneal carcinomatosis‐bearing mouse model indicate that such supramolecular AIE dots have rather low in vivo side toxicity and can serve as a superior fluorescent bioprobe for ultrasensitive fluorescence image‐guided cancer surgery.
Calix5arene‐based supramolecular AIE nanodots were synthesized with high quantum yields in water by virtue of the host–guest complexation. The absorbed excitation energy was mostly focused on fluorescence emission, leading to an ultrahigh signal‐to‐background ratio in fluorescence‐image‐guided cancer surgery.
The application of conventional metal–organic frameworks (MOFs) as electrode materials in supercapacitors is largely hindered by their conventionally poor electrical conductivity. This study reports ...the fabrication of conductive MOF nanowire arrays (NWAs) and the application of them as the sole electrode material for solid‐state supercapacitors. By taking advantage of the nanostructure and making full use of the high porosity and excellent conductivity, the MOF NWAs in solid‐state supercapacitor show the highest areal capacitance and best rate performance of all reported MOF materials for supercapacitors, which is even comparable to most carbon materials.
Conductive metal–organic framework (MOF) nanowire arrays (NWAs) are prepared as the sole electrode material for solid‐state supercapacitors. By taking advantage of their nanostructure and making full use of the high porosity and excellent conductivity, the MOF NWAs in the solid‐state supercapacitor show the highest areal capacitance and best rate performance of all reported MOF materials.
Lip language is an effective method of voice-off communication in daily life for people with vocal cord lesions and laryngeal and lingual injuries without occupying the hands. Collection and ...interpretation of lip language is challenging. Here, we propose the concept of a novel lip-language decoding system with self-powered, low-cost, contact and flexible triboelectric sensors and a well-trained dilated recurrent neural network model based on prototype learning. The structural principle and electrical properties of the flexible sensors are measured and analysed. Lip motions for selected vowels, words, phrases, silent speech and voice speech are collected and compared. The prototype learning model reaches a test accuracy of 94.5% in training 20 classes with 100 samples each. The applications, such as identity recognition to unlock a gate, directional control of a toy car and lip-motion to speech conversion, work well and demonstrate great feasibility and potential. Our work presents a promising way to help people lacking a voice live a convenient life with barrier-free communication and boost their happiness, enriches the diversity of lip-language translation systems and will have potential value in many applications.
Transition metal phosphides exhibit promising catalytic performance for the hydrogen evolution reaction (HER); however their surface structure evolution during electrochemical operation has rarely ...been studied. In this work, we investigate the surface reconstruction of CoP nanosheets by an
electrochemical activation method. After remodeling, CoP nanosheets experience an irreversible and significant evolution of the morphology and composition, and low-valence Co complexes consisting of Co(OH)
species are formed on the surface of CoP nanosheets, and they largely accelerate the dissociation of water. Benefiting from the synergistic effect of CoP and Co(OH)
, the working electrode shows a remarkably enhanced HER activity of 100 mV at 10 mA cm
with a Tafel slope of 76 mV dec
, which is better than that of most transition metal phosphide catalysts. This work would provide a deep understanding of surface reconstruction and a novel perspective for rational design of high performance transition metal phosphide electrocatalysts for water related electrolysis.
Fe−N−C electrocatalysts have been demonstrated to be the most promising substitutes for benchmark Pt/C catalysts for the oxygen reduction reaction (ORR). Herein, we report that N‐doped carbon ...materials with trace amounts of iron (0–0.08 wt. %) show excellent ORR activity and durability comparable and even superior to those of Pt/C in both alkaline and acidic media without significant contribution by the metal sites. Such an N‐doped carbon (denoted as N‐HPCs) features a hollow and hierarchically porous architecture, and more importantly, a noncovalently bonded N‐deficient/N‐rich heterostructure providing the active sites for oxygen adsorption and activation owing to the efficient electron transfer between the layers. The primary Zn‐air battery using N‐HPCs as the cathode delivers a much higher power density of 158 mW cm−2, and the maximum power density in the H2−O2 fuel cell reaches 486 mW cm−2, which is comparable to and even better than those using conventional Fe−N−C catalysts at cathodes.
An N‐doped hollow and hierarchically porous carbon nanocage catalyst having a noncovalently bonded N‐deficient/N‐rich layered heterostructure exhibits excellent ORR performance in both alkaline and acidic media without significant contributions by negligble amounts of Fe (0–0.08 wt.%) owing to the intermolecular charge‐transfer and accelerated electron/mass transfer in the hierarchically porous structure.
Human fingers possess stable high sensitivity and a wide range of tactile perception, attributed to the gradient microstructure and the interlocking collagen fiber on the skin's surface. However, ...challenges persist in achieving simultaneous enhancement of multiple functionalities in artificial skin. Inspired by the unique structure of the skin, a two‐step process involving ion diffusion‐induced and strong‐weak topological crosslinking is synergistically employed to fabricate a bilayer gradient hydrogel. Zn2+ initially diffuses to induce the formation of weak bonds, imparting elasticity. Subsequently, Fe3+/Zn2+ diffusion constructs a strong‐weak topologically crosslinked network, enhancing the toughness of the gel while reducing the brittleness associated with robust bonds. Due to its distinctive design, the gel employs an adaptive energy dissipation strategy subjected to large and small stress, ensuring high sensitivity (3.31 kPa−1, 0–2 kPa), wide sensing range (0.4–40.6 kPa), and exceptional stability (500 cycles). This flexible approach enables programmable design in three dimensions, including ion diffusion type, direction, and shape. This gel can detect the gentle brushing of feathers and human body movements. It utilizes significant differences generated by magnitudes of stress to perform binary information encryption. This study introduces a novel strategy for preparing skin‐like gels, offering promising potential for expanding their applications in complex scenarios.
The flexible network induced by weak Zn2+ diffusion undergoes simultaneous sacrifice and reconstruction when subjected to loading, endowing a bilayer gradient gel with high sensitivity. Through strong‐weak Fe3+/Zn2+ dual‐ion diffusion, a topological cross‐linked network is constructed, and the robust coordination imparts a wide detection range. Weak bonds, serving as a buffer, alleviate hysteresis induced by the fracture of brittle bonds.
The experimental realization of quantum spin liquids is a long-sought goal in physics, as they represent new states of matter. Quantum spin liquids cannot be described by the broken symmetries ...associated with conventional ground states. In fact, the interacting magnetic moments in these systems do not order, but are highly entangled with one another over long ranges. Spin liquids have a prominent role in theories describing high-transition-temperature superconductors, and the topological properties of these states may have applications in quantum information. A key feature of spin liquids is that they support exotic spin excitations carrying fractional quantum numbers. However, detailed measurements of these 'fractionalized excitations' have been lacking. Here we report neutron scattering measurements on single-crystal samples of the spin-1/2 kagome-lattice antiferromagnet ZnCu(3)(OD)(6)Cl(2) (also called herbertsmithite), which provide striking evidence for this characteristic feature of spin liquids. At low temperatures, we find that the spin excitations form a continuum, in contrast to the conventional spin waves expected in ordered antiferromagnets. The observation of such a continuum is noteworthy because, so far, this signature of fractional spin excitations has been observed only in one-dimensional systems. The results also serve as a hallmark of the quantum spin-liquid state in herbertsmithite.
Traditional artificial skin gels often only focuses on a single perspective and overlooks the necessity of multidimensional synergistic design for sensitivity enhancement. To address these problems, ...the innovative introduction of dual solvents on the surface of polyacrylamide/sodium alginate gel induces to the transformation of supramolecular interactions including ion coordination, crystalline alcohol, and phase separation, synergistically achieving adjustable wrinkle wavelengths (304.2 ± 19.9 to 2393.5 ± 95.9 µm) and modulated chemical compositions with tunable moduli (87.5 ± 3.3 to 157.6 ± 3.7 kPa). This flexible strategy allows the construction of long‐range ordered wrinkled microstructures of three‐dimensional surfaces and complex morphologies. Meanwhile, the bridge effect induced by crystalline alcohols directs the insertion of ethanol molecules into the polymer chains, effectively reducing intramolecular friction. Benefiting from the small wavelength and low modulus dominated by crystalline alcohol, the wrinkled gel exhibits extremely high sensitivity of 164 kPa−1 (<0.5 kPa) and wide detection range (44.3 kPa). The wrinkled gel remains stable high sensitive to detect micro‐ and large stress, tactile perception, and human motion behaviors. This work proposes a new strategy for constructing highly sensitive bioinspired skin from multiple dimensions, showing broad application prospects in the fields of bioengineering and behavioral cognition.
The bridge effect exhibited by dual solvent‐induced crystalline alcohols can effectively reduce the modulus of the hard shell and maintain a long‐range ordered wrinkled surface, synergistically achieving optimal sensitivity and wide detection range. Additionally, it facilitates the anchoring of ethanol within the gel system, leading to reduced intramolecular friction and improved stability.
Evidence about COVID-19 on cardiac injury is inconsistent.
We aimed to summarize available data on severity differences in acute cardiac injury and acute cardiac injury with mortality during the ...COVID-19 outbreak.
We performed a systematic literature search across Pubmed, Embase and pre-print from December 1, 2019 to March 27, 2020, to identify all observational studies that reported cardiac specific biomarkers (troponin, creatine kinase–MB fraction, myoglobin, or NT-proBNP) during COVID-19 infection. We extracted data on patient demographics, infection severity, comorbidity history, and biomarkers during COVID-19 infection. Where possible, data were pooled for meta-analysis with standard (SMD) or weighted (WMD) mean difference and corresponding 95% confidence intervals (CI).
We included 4189 confirmed COVID-19 infected patients from 28 studies. More severe COVID-19 infection is associated with higher mean troponin (SMD 0.53, 95% CI 0.30 to 0.75, p < 0.001), with a similar trend for creatine kinase–MB, myoglobin, and NT-proBNP. Acute cardiac injury was more frequent in those with severe, compared to milder, disease (risk ratio 5.99, 3.04 to 11.80; p < 0.001). Meta regression suggested that cardiac injury biomarker differences of severity are related to history of hypertension (p = 0.030). Also COVID19-related cardiac injury is associated with higher mortality (summary risk ratio 3.85, 2.13 to 6.96; p < 0.001). hsTnI and NT-proBNP levels increased during the course of hospitalization only in non-survivors.
The severity of COVID-19 is associated with acute cardiac injury, and acute cardiac injury is associated with death. Cardiac injury biomarkers mainly increase in non-survivors. This highlights the need to effectively monitor heart health to prevent myocarditis in patients infected with COVID-19.
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