A microencapsulation approach to design microbial seed coatings to boost wheat seed germination and seedling growth under salt stress

IntroductionSalt stress in seed germination and early seedling growth is the greatest cause of crop loss in saline-alkali soils. Microbial seed coating is an effective way to promote plant growth and salt resistance, but these coatings suffer from poor seed adhesion and low survival rates under typical storage conditions.MethodsIn this study, the marine bacterium Pontibacter actiniarum DSM 19842 from kelp was isolated and microencapsulated with calcium alginate using the emulsion and internal gelation method.ResultsCompared to unencapsulated seeds, the spherical microcapsules demonstrated a bacterial encapsulation rate of 65.4% and survival rate increased by 22.4% at 25°C for 60 days. Under salt stress conditions, the seed germination percentage of microcapsule-embedded bacteria (M-Embed) was 90%, which was significantly increased by 17% compared to the germination percentage (73%) of no coating treatment (CK). Root growth was also significantly increased by coating with M-Embed. Chlorophyll, peroxidase, superoxide dismutase, catalase, proline, hydrogen peroxide and malondialdehyde levels indicated that the M-Embed had the best positive effects under salt stress conditions.DiscussionTherefore, embedding microorganisms in suitable capsule materials provides effective protection for the survival of the microorganism and this seed coating can alleviate salt stress in wheat. This process will benefit the development of sustainable agriculture in coastal regions with saline soils

Full-Space Wavefront Shaping of Broadband Vortex Beam with Switchable Terahertz Metasurface Based on Vanadium Dioxide

Currently, vortex beams are extensively utilized in the information transmission and storage of communication systems due to their additional degree of freedom. However, traditional terahertz metasurfaces only focus on the generation of narrowband vortex beams in reflection or transmission mode, which is unbeneficial for practical applications. Here, we propose and design terahertz metasurface unit cells composed of anisotropic Z-shaped metal structures, two dielectric layers, and a VO2 film layer. By utilizing the Pancharatnam–Berry phase theory, independent control of a full 2π phase over a wide frequency range can be achieved by rotating the unit cell. Moreover, the full-space mode (transmission and reflection) can also be implemented by utilizing the phase transition of VO2 film. Based on the convolution operation, three different terahertz metasurfaces are created to generate vortex beams with different wavefronts in full-space, such as deflected vortex beams, focused vortex beams, and non-diffraction vortex beams. Additionally, the divergences of these vortex beams are also analyzed. Therefore, our designed metasurfaces are capable of efficiently shaping the wavefronts of broadband vortex beams in full-space, making them promising applications for long-distance transmission, high integration, and large capacity in 6G terahertz communications

Terahertz Modulation and Ultrafast Characteristic of Two-Dimensional Lead Halide Perovskites

In recent years, two-dimensional (2D) halide perovskites have been widely used in solar cells and photoelectric devices due to their excellent photoelectric properties and high environmental stability. However, the terahertz (THz) and ultrafast responses of the 2D halide perovskites are seldom studied, limiting the developments and applications of tunable terahertz devices based on 2D perovskites. Here, 2D R-P type (PEA)2(MA)2Pb3I10 perovskite films are fabricated on quartz substrates by a one-step spin-coating process to study their THz and ultrafast characteristics. Based on our homemade ultrafast optical pump–THz probe (OPTP) system, the 2D perovskite film shows an intensity modulation depth of about 10% and an ultrafast relaxation time of about 3 ps at a pump power of 100 mW due to the quantum confinement effect. To further analyze the recombination mechanisms of the photogenerated carriers, a three-exponential function is used to fit the carrier decay processes, obtaining three different decay channels, originating from free carrier recombination, exciton recombination, and trap-assisted recombination, respectively. In addition, the photoconductor changes (∆σ) at different pump–probe delay times are also investigated using the Drude-Smith model, and a maximum difference of 600 S/m is obtained at τp = 0 ps for a pump power of 100 mW. Therefore, these results show that the 2D (PEA)2(MA)2Pb3I10 film has potential applications in high-performance tunable and ultrafast THz devices

Graphene-Modulated Terahertz Metasurfaces for Selective and Active Control of Dual-Band Electromagnetic Induced Reflection (EIR) Windows

Currently, metasurfaces (MSs) integrating with different active materials have been widely explored to actively manipulate the resonance intensity of multi-band electromagnetic induced transparency (EIT) windows. Unfortunately, these hybrid MSs can only realize the global control of multi-EIT windows rather than selective control. Here, a graphene-functionalized complementary terahertz MS, composed of a dipole slot and two graphene-integrated quadrupole slots with different sizes, is proposed to execute selective and active control of dual-band electromagnetic induced reflection (EIR) windows. In this structure, dual-band EIR windows arise from the destructive interference caused by the near field coupling between the bright dipole slot and dark quadrupole slot. By embedding graphene ribbons beneath two quadrupole slots, the resonance intensity of two windows can be selectively and actively modulated by adjusting Fermi energy of the corresponding graphene ribbons via electrostatic doping. The theoretical model and field distributions demonstrate that the active tuning behavior can be ascribed to the change in the damper factor of the corresponding dark mode. In addition, the active control of the group delay is further investigated to develop compact slow light devices. Therefore, the selective and active control scheme introduced here can offer new opportunities and platforms for designing multifunctional terahertz devices

Cosmogenic effects on chromium isotopes in meteorites

The ⁵³Mn-⁵³Cr short-lived radionuclide decay system is a powerful tool to investigate the timescales of early solar systemprocesses. A complication arises, however, from the fact that spallation and thermal/epithermal neutron capture processesinduced by cosmic rays can significantly alter ⁵³Cr/⁵²Cr ratios in solar system objects that have long exposure ages and high Fe/Cr ratios. Quantifying these cosmogenic effects helps constrain the cosmic ray exposure history of extraterrestrial samples.The isotopic shifts produced by cosmic ray irradiation also need to be corrected before the Cr isotope systematics can be usedas a dating tool and as a tracer of nucleosynthetic provenance. To investigate the impact of cosmogenic production on Cr, theCr isotopic compositions of 25 samples from 16 iron meteorites belonging to nine different chemical groups were measured.The measurements show that exposure to cosmic rays can cause large coupled excesses in ɛ⁵³Cr (-0.04 v 0.44 to +268.29 ± 0.14; 2SE)and ɛ⁵⁴Cr (+0.28 ± 0.72 to +1053.78 ± 0.72; 2SE) with a best fit line of ɛ⁵⁴Cr = (3.90 ± 0.03) x ɛ⁵³Cr. The magnitude of Cr isotopeproduction is controlled by various factors including the exposure age, the chemical composition (i.e., Cr concentrationand Ni/Fe ratio) and shielding conditions. Nevertheless, the correlation of ɛ⁵³Cr and ɛ⁵⁴Cr is independent of these factors,which provides an effective method to evaluate the cosmogenic contribution to ɛ⁵³Cr by monitoring the cosmogenic variations in ɛ⁵⁴ in meteoritic irons. The results are compared with modeling results that yield a slightly shallower slope of 3.6 ± 0.2. Modeling results for the olivine in stony meteorites yield a higher slope (~5.4). However, the previous estimated results forlunar samples (stony targets for comic ray irradiation) exhibit an observably shallower slope (~2.62). The reason for the dif-ferent slopes is that the production rates of different cosmogenic Cr isotopes in iron meteorites and lunar samples are in dif-ferent proportions. The differences may not be completely controlled by the higher thermal and epithermal neutron fluenciesin lunar samples than in iron meteorites, but instead may largely reflect different radiation geometry between the two. Morestudies are needed to solve this open question

Cellulose nanocrystals (CNCs) as hard templates for preparing mesoporous zeolite Y assemblies with high catalytic activity

Faujasite (FAU) Y zeolite assemblies with high mesoporosity (Sext = 347 m2 g−1 and Vmeso = 0.52 cm3 g−1) were synthesised using sustainable and economic cellulose nanocrystals (CNCs) via a template-directed synthesis method, i.e. CNCs-Y. In comparison with the control zeolite catalysts of the conventional microporous Y and carbon nanotube templated Y (CNTs-Y) zeolites, the resulting CNCs-Y demonstrated superior performance in catalytic dealkylation with excellent activity and longevity, as well as the anti-coking ability thanks to the exceptional mesoporous features of CNCs-Y zeolites. Thereby, the method and relevant CNCs-Y mesoporous zeolites based on the sustainable CNCs presented here have significant implications for being developed further for improving the sustainability of relevant catalytic processes such as fluid catalytic cracking (FCC).</p