Four polysaccharide fractions (P‐1: 71.40%, P‐2: 1.95%, P‐3: 1.14%, P‐4: 1.64%) were isolated from crude Polygonatum sibiricum polysaccharide (PSP), processed by water extraction, ethanol ...precipitation, and further separated with diethylaminoethyl cellulose‐52 anion‐exchange chromatography. Their molecular weights and monosaccharide compositions were characterized by high performance gel chromatography with evaporative light scattering detector and ultraviolet–visible detector. The antioxidant activity of four polysaccharides fractions were assessed by the electron transfer menchanism (DPPH, ferric reducing power, and ABST assays) and chelation of transition metals (Fe2+ and Cu2+ chelation ability). The highest content fraction P‐1 exhibited the lowest antioxidant activity, and the ranking of antioxidant capacity was P‐4 > P‐3 > P‐2 > PSP > P‐1. After processed by microwave‐assisted degradation, the molecular weight of P‐1 was decreased from 2.99 × 105 to 2.33 × 103 Da, while the antioxidant activity of degraded P‐1 was about eightfold higher than natural P‐1. These results indicated that the proposed microwave‐assisted degradation approach was an efficacious methodology to improve their bioactivity by lower the molecular weight of polysaccharides.
Practical Application
This study provided an environmentally friendly, convenient and efficient microwave‐assisted degradation technology to process the neutral polysaccharides from Polygonatum sibiricum. The results could be used for the development and utilization of various plant polysaccharides as a kind of food supplement in our daily life.
Vortex beam generators, especially for broadband working ones, are essential in recent communication systems, since it is believed to be a key to improve the channel capacity efficiently. However, ...available vortex beam generators surfer from narrow bands, low efficiencies as well as complex configurations. In this paper, we propose an ultra-broadband reflective Pancharatnam–Berry metasurface to generate the vortex beams within 12-18 GHz. The metasurface consists of 20×20 single-layered rotated reflective elements A Ku-band Archimedes spiral antenna is placed at the focal point of the PB metasurface as a feed source which is used to emit a right-handed circularly polarized wave. Then, the metasurface is fabricated, simulated, and measured. Numerical and experimental results coincided well, indicating that the proposed vortex beam generator demonstrated several improvements, including wideband working (12-18 GHz), high efficiency (75.76%), and simple fabrication. Our findings open up a new avenue for the design of high-performance broadband vortex beam generators.
We propose a high-gain transmitting lens antenna by employing layered phase-gradient metasurface (MS). The MS is engineered to focus the propagating plane wave to a point with high efficiency. An ...X-band patch antenna is placed at the focal point of the MS as a feed source, and then the quasi-spherical wave emitted by the source is transformed to plane wave. Due to the successful conversion of quasi-spherical wave to plane wave, the beam width of the patch antenna has been decreased 66° and the gain has been enhanced 11.6 dB. The proposed lens antenna not only opens up a new route for the applications of phase-gradient MS in microwave band, but also affords an alternative for high-gain antenna.
Multifunctional metasurface integrating different functions can significantly save the occupied space, although most of bifunctional metasurfaces reported to date only control the wave in either ...reflection or transmission regime. In this paper, we propose a scheme that allows one to independently control the reflection and transmission wavefront under orthogonal polarizations. For demonstration, we design a bifunctional metasurface that simultaneously realizes a diffusion reflection and a focusing transmission. The diffusion reflection is realized using a random phase distribution, which was implemented by randomly arranging two basic coding unit cells with the aid of an ergodic algorithm. Meanwhile, the hyperbolic phase distribution was designed to realize the focusing functionality in the transmission regime. To further show the potential applications, a high-gain lens antenna was designed by assembling the proposed metasurface with a proper feed. Both simulation and measurement results have been carried out, and the agreement between the two results demonstrates the validity of the performance as expected. The backward scattering can be reduced more than 5 dB within 6.4-10 GHz compared with the metallic plate. Moreover, the lens antenna has a gain of 20 dB (with around 13 dB enhancement in comparison with the bare feeding antenna) and an efficiency of 32.5%.
Magnesium (Mg)-deficiency is one of the most prevalent physiological disorders causing a reduction in Citrus yield and quality. 'Xuegan' (Citrus sinensis) seedlings were irrigated for 16 weeks with ...nutrient solution containing 2 mM (Mg-sufficiency) or 0 mM (Mg-deficiency) Mg(NO
)
. Thereafter, we investigated the Mg-deficient effects on gas exchange and chlorophyll a fluorescence in the upper and lower leaves, and Mg, reactive oxygen species (ROS) and methylglyoxal (MG) metabolisms in the roots, lower and upper leaves. The specific objectives were to corroborate the hypothesis that the responses of ROS and MG metabolisms to Mg-deficiency were greater in the lower leaves than those in the upper leaves, and different between the leaves and roots.
Mg level was higher in the Mg-deficient upper leaves than that in the Mg-deficient lower leaves. This might be responsible for the Mg-deficiency-induced larger alterations of all the measured parameters in the lower leaves than those in the upper leaves, but they showed similar change patterns between the Mg-deficient lower and upper leaves. Accordingly, Mg-deficiency increased greatly their differences between the lower and upper leaves. Most of parameters involved in ROS and MG metabolisms had similar variation trends and degrees between the Mg-deficient lower leaves and roots, but several parameters (namely glutathione S-transferase, sulfite reductase, ascorbate and dehydroascorbate) displayed the opposite variation trends. Obviously, differences existed in the Mg-deficiency-induced alterations of ROS and MG metabolisms between the lower leaves and roots. Although the activities of most antioxidant and sulfur metabolism-related enzymes and glyoxalase I and the level of reduced glutathione in the Mg-deficient leaves and roots and the level of ascorbate in the leaves were kept in higher levels, the levels of malonaldehyde and MG and/or electrolyte leakage were increased in the Mg-deficient lower and upper leaves and roots, especially in the Mg-deficient lower leaves and roots.
The ROS and MG detoxification systems as a whole did not provide sufficient detoxification capacity to prevent the Mg-deficiency-induced production and accumulation of ROS and MG, thus leading to lipid peroxidation and the loss of plasma membrane integrity, especially in the lower leaves and roots.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Lead halide perovskite (LHP) nanocrystals (NCs) have recently garnered enhanced development efforts from research disciplines owing to their superior optical and optoelectronic properties. These ...materials, however, are unlike conventional quantum dots, because they possess strong ionic character, labile ligand coverage, and overall stability issues. As a result, the system as a whole is highly dynamic and can be affected by slight changes of particle surface environment. Specifically, the surface ligand shell of LHP NCs has proven to play imperative roles throughout the lifetime of a LHP NC. Recent advances in engineering and understanding the roles of surface ligand shells from initial synthesis, through postsynthetic processing and device integration, finally to application performances of colloidal LHP NCs are covered here.
Lead halide perovskite nanocrystals possess labile ligand coverage, yielding a highly dynamic ligand system that can be affected by delicate changes in nanocrystal environment. As such, ligands play imperative roles throughout the lifetime of these ionic nanocrystals. Ligand roles in synthesis, postsynthetic processing, device integration, and application performance of lead halide perovskite nanocrystals are covered.
The human eye, which relies on a flexible and controllable lens to focus light onto the retina, has inspired many scientific researchers to understand better and imitate the biological vision system. ...However, real-time environmental adaptability presents an enormous challenge for artificial eye-like focusing systems. Inspired by the mechanism of eye accommodation, we propose a supervised-evolving learning algorithm and design a neuro-metasurface focusing system. Driven by on-site learning, the system exhibits a rapid response to ever-changing incident waves and surrounding environments without any human intervention. Adaptive focusing is achieved in several scenarios with multiple incident wave sources and scattering obstacles. Our work demonstrates the unprecedented potential for real-time, fast, and complex electromagnetic (EM) wave manipulation for various purposes, such as achromatic, beam shaping, 6 G communication, and intelligent imaging.
With the complexity of information tasks, the bipartite and tripartite entanglement can no longer meet our needs, and we need more entangled particles to process relativistic quantum information. In ...this paper, we study the genuine N-partite entanglement and distributed relationships for Dirac fields in the background of dilaton black holes. We present the general analytical expression including all physically accessible and inaccessible entanglement in curved spacetime. We find that the accessible N-partite entanglement exhibits irreversible decoherence as the increase of black hole’s dilaton, and on the other hand the inaccessible N-partite entanglement increases from zero monotonically or non-monotonically, depending on the relative numbers of the accessible to the inaccessible modes, which forms a sharp contrast with the cases of bipartite and tripartite entanglement where the inaccessible entanglement increase only monotonically. We also find two distributed relationships between accessible and inaccessible N-partite entanglement in curved spacetime. The results give us a new understanding of the Hawking radiation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Achieving multiple diversified functionalities in a single flat device is crucial for electromagnetic (EM) integration, but available efforts suffer the issues of device thickness, low efficiency, ...and restricted functionalities. Here, a general strategy to design high‐efficiency bifunctional devices based on metasurfaces composed by anisotropic meta‐atoms with polarization‐dependent phase responses is described. Based on the derived general criterions, two bifunctional metadevices, working in reflection and transmission modes, respectively, that can realize two distinct functionalities with very high efficiencies (≈90% in reflection geometry and ≈72% in transmission one) are designed and fabricated. Microwave experiments, including both far‐field and near‐field characterizations, are performed to demonstrate the predicted effects, which are in excellent agreement with numerical simulations. The findings in this study can motivate the realizations of high‐performance bifunctional metadevices in other frequency domains and with different functionalities, which are of crucial importance in EM integration.
A general strategy to design high‐efficiency bifunctional devices based on metasurfaces is proposed in this paper. As a proof of concept, it is experimentally demonstrated that two bifunctional metadevices working in reflection and transmission modes, respectively, can achieve two distinct functionalities (such as focusing and beam bending effect) with very high efficiency.
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