56 research outputs found
Three-dimensional metamaterials with an ultra-high effective refractive index over broad bandwidth
The authors introduce a general mechanism, based on electrostatic and
magnetostatic considerations, for designing three-dimensional isotopic
metamaterials that possess an enhanced refractive index over an extremely large
frequency range. The mechanism allows nearly independent control of effective
electric permittivity and magnetic permeability without the use of resonant
elements
Spontaneous generation and active manipulation of real-space optical vortex
Optical vortices host the orbital nature of photons, which offers an extra
degree of freedom in photonic applications. Unlike vortices in other physical
entities, optical vortices require structural singularities, which restrict
their abilities in terms of dynamic and interactive characteristics. In this
study, we present the spontaneous generation and external magnetic
field-induced manipulation of an optical vortex and antivortex. A
gradient-thickness optical cavity (GTOC) consisting of an Al/SiO2/Ni/SiO2
multilayer structure realised the distinct transition between the trivial and
non-trivial topological phases, depending on the magneto-optic effects of the
Ni layer. In the non-trivial topological phase, the mathematical singularities
generating the optical vortex and antivortex pair in the reflected light
existed in the generalised parameter space of the thicknesses of the top and
bottom SiO2 layers, which is bijective to the real space of the GTOC. Coupled
with the magnetisation, the optical vortex and antivortex in the GTOC
experienced an effective spin-orbit interaction and showed topology-dependent
dynamics under external magnetic fields. We expect that field-induced
engineering of optical vortices will pave the way for the study of topological
photonic interactions and their applications.Comment: 22 pages, 4 figure
Comment on "Amplified emission and lasing in photonic time crystals"
Lyubarov et al. (Research Articles, 22 July 2022, p. 425) claim that the
spontaneous emission rate of an atom vanishes at the momentum gap edges of
photonic Floquet media. We show that their theoretical prediction is based on
assumptions that result in misleading interpretations on the spontaneous
emission rate in photonic Floquet media
Translocation of residual ethoprophos and tricyclazole from soil to spinach
The dissipation of ethoprophos and tricyclazole in soil and their translocation tendency to spinach were investigated. Prior to field trials, the analytical method for the determination of these pesticide residues was optimized and validated on soil and spinach. The field trial was conducted under greenhouse conditions for two different pretreatment periods with the pesticides. After treating with pesticides 30 (PBI-30) and 60 days (PBI-60) before seeding, soil samples were collected on different days for the dissipation study of soil. Spinach samples were harvested from the soil, and 50% and 100% mature spinach samples were collected. The initial amounts of ethoprophos residue in the PBI-60 and PBI-30 soils were 0.21 and 2.74 mg/kg, respectively, and these both decreased to less than 0.01 mg/kg on the day of spinach harvest. Similar initial residues of tricyclazole were observed in the PBI-60 (0.87 mg/kg) and PBI-30 soils (0.84 mg/kg), and these decreased to 0.44 and 0.34 mg/kg, respectively. The half-lives of ethoprophos in the soils were calculated as 7.6 and 4.8 days, respectively, while relatively long half-lives of 36.5 and 77.0 days were calculated for tricyclazole. According to the pesticide residue amounts in the spinach, the translocation rate from the soil to the spinach was determined. In the case of ethoprophos, the residual amount was already rapidly degraded in the soil, and the translocation rate could not be confirmed. On the other hand, for tricyclazole, it was confirmed that 1.19 to 1.61% of the residual amount in soil was transferred to spinach. According to these results, safe management guidelines for tricyclazole in soil were suggested considering the maximum residue limit on spinach.This work was supported by the Rural Development Administration (PJ0152772020)
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