Ru@SiO2 core–shell structured nanospheres have been prepared via a one-pot synthetic route in a NP-5/cyclohexane reverse micelle system and characterized by XRD, SEM, TEM, N2 adsorption–desorption, ...and H2 temperature programmed desorption. The characterized results show that ultrafine Ru nanoparticles (NPs) of around 2 nm are effectively embedded in the center of well-proportioned spherical and porous silica nanospheres (∼25 nm in diameter). Interestingly, the number of Ru NPs increases inside the spherical particles of SiO2 as the increase of Ru loading. The as-synthesized Ru@SiO2 exhibits high catalytic activity and good durability for hydrogen generation from the aqueous of ammonia borane (AB) complex under ambient atmosphere at room temperature. The hydrolysis activation energy of Ru@SiO2 was estimated to be about 38.2 kJ mol−1, which is lower than most of the reported activation energy values for the same reaction using many different Ru-based and other noble metal containing catalysts, indicating the superior catalytic performance of these core–shell structured nanospheres.
•Ru@SiO2 core–shell NPs are synthesized via a simple one-pot synthetic route.•Ultrafine Ru NPs (∼2 nm) embedded in well-proportioned SiO2 nanospheres (∼25 nm).•Ru@SiO2 shows a high activity and good durability for H2 generation from NH3BH3.•The measured activation energy 38.2 kJ mol−1 is lower than most of the reported values.
Abstract
Wild teas are valuable genetic resources for studying domestication and breeding. Here we report the assembly of a high-quality chromosome-scale reference genome for an ancient tea tree. The ...further RNA sequencing of 217 diverse tea accessions clarifies the pedigree of tea cultivars and reveals key contributors in the breeding of Chinese tea. Candidate genes associated with flavonoid biosynthesis are identified by genome-wide association study. Specifically, diverse allelic function of
CsANR
,
CsF3’5’H
and
CsMYB5
is verified by transient overexpression and enzymatic assays, providing comprehensive insights into the biosynthesis of catechins, the most important bioactive compounds in tea plants. The inconspicuous differentiation between ancient trees and cultivars at both genetic and metabolic levels implies that tea may not have undergone long-term artificial directional selection in terms of flavor-related metabolites. These genomic resources provide evolutionary insight into tea plants and lay the foundation for better understanding the biosynthesis of beneficial natural compounds.
The interfacial recombination at the perovskite/hole conductor interface generally results in significant energy losses in inverted perovskite solar cells (PSCs) with a p–i–n device architecture. ...Herein, a chemical bridge is built at the interface of poly(triarylamine) (PTAA)/perovskites by using 3-(1-pyridinio)-1-propanesulfonate (PPS) molecules to minimize interfacial recombination of charge carriers. Extensively theoretical calculations and experimental studies reveal that the pyridine of PPS molecule and the phenyl group of PTAA could be chemically coupled through π–π stacking, and the sulfonate at the other end of PPS molecule could anchor perovskites through a strong SO···Pb coordination bond. The chemical bridge structure significantly suppresses charge carrier recombination at the interface of PTAA/perovskites. Meanwhile, after incorporation of PPS molecules as an additive in the perovskites to effectively passivate surface defects of perovskites, an efficiency of up to 21.7% with negligible hysteresis is achieved for inverted PSCs.
Continual semantic segmentation (CSS) aims to learn new tasks sequentially and extract object(s) and stuff represented by pixel-level maps of new categories while preserving the original segmentation ...capabilities even when the old class data is absent. Current CSS methods typically preserve the capacities of segmenting old classes via knowledge distillation, which encounters the limitations of insufficient utilization of the semantic knowledge, i.e., only distilling the last layer of the feature encoder, and the semantic shift of background caused by directly distilling the entire feature map of the decoder. In this paper, we propose a novel CCS method based on scale-hybrid distillation and knowledge disentangling to address these limitations. Firstly, we propose a scale-hybrid group semantic distillation (SGD) method for encoding, which transfers the multi-scale knowledge from the old model’s feature encoder with group pooling refinement to improve the stability of new models. Then, the knowledge disentangling distillation (KDD) method for decoding is proposed to distillate feature maps with the guidance of the old class regions and reduce incorrect guides from old models towards better plasticity. Extensive experiments are conducted on the Pascal VOC and ADE20K datasets. Competitive performance compared with other state-of-the-art methods demonstrates the effectiveness of our proposed method.
Calciphylaxis, a rapidly progressive and potentially life-threatening vascular calcification syndrome that clinically presents with persistently painful, ulcerative, or necrotizing skin lesions in ...multiple parts of the body, is predominantly observed in patients treated with dialysis. Early diagnosis of calciphylaxis is a key measure for reducing high disability and mortality. At present, there is no unified diagnostic standard for calciphylaxis, and there is a lack of effective early screening strategies. This paper summarized and discussed the diagnostic accuracy of calciphylaxis based on the latest research worldwide. We propose a modified strategy for the early diagnosis of calciphylaxis, which is suitable for dialysis patients to help clinicians better identify such disease and improve prognosis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
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•3D MnCo2O4@MnMoO4 CSNs on NF have been constructed.•The CSNs were built by growing MnMoO4 nanosheets onto MnCo2O4 NAs.•Such CSNs exhibit a high specific capacity of 885 C g−1 at ...3 A g−1.•95% capacitance retention are be achieved after 5000 cycles at 10 A g−1.•The assembled ASC delivers an energy density of 49.4 W h kg−1 at 815 W kg−1.
Rational design and fabrication of core-shell nanoarrays (CSNs) with distinctive architectures and desirable capacitive performances are believed to be a promising and challenging strategy toward advanced electrode materials for supercapacitors (SCs). In this work, we report a two-step synthesis of three-dimensional (3D) MnCo2O4 nanosheets@MnMoO4 nanosheets CSNs on Ni foam (NF), which are constructed by vertically growing MnMoO4 nanosheets onto interconnected MnCo2O4 nanosheets arrays (NAs). Such MnCo2O4@MnMoO4 CSNs can make full use of its unique 3D architecture and the synergistic effect between MnCo2O4 and MnMoO4. Therefore, the prepared MnCo2O4@MnMoO4 CSNs, as a binder-free electrode for SCs, demonstrate a significantly enhanced specific capacity (885 C g−1 at 3 A g−1), higher rate capability (629 C g−1 at 30 A g−1), and better cycling stability (95% capacitance retention after 5000 cycles at 10 A g−1) compared with the single MnCo2O4 or MnMoO4 NAs electrode. Moreover, the assembled asymmetric SC cell (ASC) based on MnCo2O4@MnMoO4//activated carbon (AC) also exhibits a specific capacity (222 C g−1 at 1 A g−1) and an energy density (49.4 W h kg−1 at 815 W kg−1), indicating a promising practical application for the prepared MnCo2O4@MnMoO4 CSNs in high-performance SCs.
Interfacial charge recombination occurring at the interface between a colloidal quantum dot (CQD) solid and the electron collecting layer (ECL) in CQD solar cells significantly affects the charge ...carrier collection, therefore limiting the device photovoltaic performance. In this work CQD solar cells with an improved performance are reported by employing MgZnO as a buffer layer (BL) with tunable electronic energy levels in the solar cells to reduce interfacial charge recombination and hence improve the solar cell photovoltaic performance. The effect of the BL on the solar cell performance is experimentally investigated and compared to theoretical calculations. Incorporation of a BL with favorable electronic energy levels forming a suitable band alignment with the CQD layer in solar cells diminishes the interfacial charge recombination and an increased photovoltage can be obtained. A CQD solar cell with a BL shows a power conversion efficiency of up to 9.3%, compared to that of 8.2% for a solar cell without any BLs. The unsealed solar cells are also rather stable under ambient conditions both in the dark and under continuous illumination. This work suggests that a MgZnO BL with energy level tunability provides a potential strategy to improve the interfacial properties of CQD photovoltaic devices.
A novel multifrequency printed monopole antenna applied to both WLAN and WiMAX systems is proposed in this letter. The antenna structure is simple, and the size is 34×18 mm 2 . The proposed ...microstrip-fed antenna mainly comprises a fork-shaped strip that is etched on a modified rectangular ring and a rectangular-defected ground plane. To experimentally analyze the characteristics of this antenna, the design, fabrication, and measurement have been completed. Good antenna performances have been obtained.
The aim of this study is to investigate the thermal decomposition and combustion characteristics of electric wire under different oxygen concentrations and external radiations. Fire propagation ...apparatus was used, and the thermal decomposition, limit oxygen concentration, ignition time, mass loss rate, and heat release rate are discussed. It was found that under nitrogen atmosphere, higher external heat flux promoted the thermal decomposition. The mass loss rate of decomposition exhibited a linear behavior versus radiant heat flux. The limit oxygen concentration was linearly reduced with increasing external heat flux. For the combustion process, the ignition time decreased while the mass loss rate increased with the increasing oxygen concentration and external heat flux. The wire sample used in this study is proved to be thermally thin and the increase rate of the mass loss rate reduced under high external heat flux. The peak heat release rate increases with oxygen concentration under low external heat flux. While under high external heat flux, the peak heat release rate first increaseed and then decreaseed with oxygen concentration due to the effect of increasing heat blockage effect.
Organo-metal halide perovskites (OMHPs) are materials with attractive properties for optoelectronics. They made a recent introduction in the photovoltaics world by methylammonium (MA) lead triiodide ...and show remarkably improved charge separation capabilities when chloride and bromide are added. Here we show how halide substitution in OMHPs with the nominal composition CH3NH3PbI2X, where X is I, Br, or Cl, influences the morphology, charge quantum yield, and local interaction with the organic MA cation. X-ray diffraction and photoluminescence data demonstrate that halide substitution affects the local structure in the OMHPs with separate MAPbI3 and MAPbCl3 phases. Raman spectroscopies as well as theoretical vibration calculations reveal that this at the same time delocalizes the charge to the MA cation, which can liberate the vibrational movement of the MA cation, leading to a more adaptive organic phase. The resonance Raman effect together with quantum chemical calculations is utilized to analyze the change in charge transfer mechanism upon electronic excitation and gives important clues for the mechanism of the much improved photovoltage and photocurrent also seen in the solar cell performance for the materials when chloride compounds are included in the preparation.
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