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Volatiles are an important aspect of the flavor quality of tomato fruits. However, whether volatiles in tomato fruits respond to the regulation of exogenous methyl jasmonate (MeJA) remains unclear. In this study, four concentrations of MeJA (1, 10, 100 and 200 μmol/L) were sprayed on ‘Chaoyan 298’ tomatoes before harvest, and an equal volume of ultrapure water was used as the control. Ripe fruits were harvested and analyzed for the composition and content of volatile compounds by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS). Meanwhile, the optimal concentration of MeJA for improving the flavor quality of tomatoes was determined by multivariate statistical analysis. The results showed that a total of 71 volatile components were detected in the 5 groups, including 23 aldehydes, 17 alcohols, 8 ketones, 7 esters, 6 hydrocarbons and 10 other substances. Compared with the control group, exogenous application of MeJA increased the number and total amount of volatile compounds in tomato fruits, which increased first and then decreased with the increase in MeJA concentration, reaching the maximum value at 100 μmol/L MeJA concentration. Altogether 33 components were common to all groups, with the most abundant one being (Z)-3-hexen-1-ol. A total of 13 characteristic aroma components were identified in all tomato fruits, which mainly contributed to green, fruity and flowery notes. Overall, our results provide theoretical support that exogenous MeJA can improve that flavor quality of tomato fruits, which are conducive to further exploring the regulation mechanism of volatile compound biosynthesis in tomato fruits.

Manipulating electromagnetic (EM) waves by plasma-dielectric-plasma (PDP) waveguides or plasma array structures presents significant potential in microwave signal processing, such as filtering, signal delay, and EM enhancement or shielding. Owing to the simple structure and easy fabrication, the waveguide with a tooth-shaped resonator has been a strong candidate as a filtering device. Based on our previous work focusing on U-shaped filtering excited by PDP waveguides with a double-teeth structure, in this work, the formation mechanism of a U-shape filtering spectrum is systematically explored by transmission line theory (TLT) with proper field distributions. The results indicate that the U-shape spectrum consists of boundary edges and a filtering stopband. The boundary edges are attributed to Fano-type resonance, and the enhanced destructive interference from double teeth is responsible for the stopband. Such an approach shows a specific and clear mechanism for the generated U-shaped spectrum. In addition, the theoretical analysis of double teeth without Fano-type resonances is rigorously demonstrated using TLT, which significantly contributes to bandwidth modulation of stopband filtering in theory. These results contribute to the understanding of the formation mechanism of a U-shaped spectrum from a gap plasmon waveguide (such as PDP or metal-insulator-metal (MIM)) with tooth-shaped resonators, offering a feasible direction for the optimization of filtering properties, as well as offering significant parameters for subsequent experimental design. [ABSTRACT FROM AUTHOR]

Two kinds of fluorides are proposed innovatively to modulate the dielectric property of the plasma by reducing the electron density. There is a maximum of 74.41% electron density reduction after the fluorides are injected into the plasma at a magnitude of 1019 m−3, and the corresponding plasma frequency reduction is 49.42%. The fluorides proposed in this paper exhibit a wider modulation range, a faster modulation speed, and a longer maintenance time compared with SF6. The electromagnetic (EM) wave transmission characteristics in plasma are modulated correspondingly. The attenuation of S21 is reduced by 15.11–20.11 dB in 6–18 GHz, and an enhancement in the whole experimental frequency range is observed compared with SF6. The results of the paper can be applied in the mitigation of reentry vehicle's EM wave attenuation induced by the over-dense plasma sheath covering the vehicle. In addition, it also has a potential in broad applications of EM wave and plasma interactions. [ABSTRACT FROM AUTHOR]

The integrative design of scattering and radiation characteristics of antennas is of great practical significance for modern wireless communication. In this work, from the perspective of separate and cooperative modes, we comprehensively discussed the possibility of simultaneously and harmoniously implementing scattering suppression and radiation enhancement for an electrically small antenna by subwavelength plasmas. For the separate mode where the two functions are decoupled based on a two-layer structure, it is shown that an overdense–underdense core–shell density profile is preferred to achieve the optimal synergism between radiation enhancement and plasmonic-cloaking-induced invisibility, where the angular frequency of detecting waves (ωd) is supposed to be lower than that of communication signals (ωc). For the cooperative mode where the two functions are coupled within one plasma shell, the collaborative strategies between plasmonic-cloaking/Fano-resonance-induced invisibility and radiation enhancement are analyzed. The results show that the plasmonic-cloaking type requires ωd > ωc, while for the Fano-resonance type, ωd is larger/less than ωc when radiation enhancement is dominated by the symmetrically/asymmetrically coupled plasmon modes. Also, we provided clearer perspectives to distinguish the physical differences between plasmonic-cloaking and Fano-resonance-induced invisibility and between radiation enhancement underlying the two modes. Our results provide promising solutions for designing next-generation plasma-based tunable and intelligent stealth antennas. [ABSTRACT FROM AUTHOR]

The ground-based device, the Space Plasma Environment Research Facility (SPERF), is established for experimentally simulating magnetosphere plasma processes, with one of its major components, asymmetric reconnection experiment (AREX), for three-dimensional physics relevant to dayside asymmetric magnetopause reconnection. As an outstanding property of fast magnetic reconnection in collisionless plasmas, the Hall effect and its geometric features can be experimentally investigated in SPERF-AREX with various magnetic configurations related to different driven scenarios for simulating interplanetary magnetic field (IMF) conditions. In this work, the Hall effect and its geometric characteristics in such proposed experiments are numerically studied based on a Hall MHD model. The simulation results reveal that in the X-line geometry relevant to southward IMFs, the Hall field features in cross section perpendicular to the X-line are mostly analogous to typical two-dimensional Hall quadrupole structures, clearly an "anti-parallel reconnection" feature. In the separator (A-B null-line) geometry relevant to arbitrary IMF orientations, along the separator between magnetic nulls, the magnetic field configuration near a magnetic null also demonstrates the typical quadrupolar pattern. However, the pattern is distorted away (> 10 d i , here d i = c / ω p i is the ion inertial length) from the nulls, in a way similar to that in "component reconnection." Furthermore, the Hall effect induces a dawn-dusk asymmetry for both the X-line and the separator geometries. [ABSTRACT FROM AUTHOR]