Transient breathing dynamics during extinction of dissipative solitons in mode‑locked fiber lasers

The utilization of the dispersive Fourier transformation approach has enabled comprehensive observation of the birth process of dissipative solitons in fiber lasers.However,there is still a dearth of deep understanding regarding the extinction process of dissipative solitons.In this study,we have utilized a combination of experimental and numerical techniques to thoroughly examine the breathing dynamics of dissipative solitons during the extinction process in an Er-doped mode-locked fiber laser.The results demonstrate that the transient breathing dynamics have a substantial impact on the extinction stage of both steady-state and breathing-state dissipative solitons.The duration of transient breathing exhibits a high degree of sensitivity to variations in pump power.Numerical simulations are utilized to produce analogous breathing dynamics within the framework of a model that integrates equations characterizing the population inversion in a mode-locked laser.These results corroborate the role of Q-switching instability in the onset of breathing oscillations.Furthermore,these findings offer new possibilities for the advancement of various operational frameworks for ultrafast lasers.

Mercury enrichment in Brassica napus in response to elevated atmospheric mercury concentrations

Mercury enrichment in response to elevated atmospheric mercury concentrations in the organs of rape （Brassica napus） was investigated using an open top chamber fumigation experiment and a soil mercury enriched cultivation experiment. Results indicate that the mercury concentration in leaves and stems showed a significant variation under different concentrations of mercury in atmospheric and soil experiments while the concentration of mercury in roots, seeds and seed coats showed no significant variation under different atmospheric mercury concentrations. Using the function relation established by the experiment, results for atmospheric mercury sources in -rape field biomass showed that atmospheric sources accounted for at least 81.81% of mercury in rape leaves and 32.29% of mercury in the stems. Therefore, mercury in the aboveground biomass predominantly derives from the absorption of atmospheric mercury.

Cysteine-enhanced reductive degradation of nitrobenzene using nano-sized zero-valent iron by accelerated electron transfer

As an aliphatic amino acid,cysteine(CYS)is diffuse in the living cells of plants and animals.However,little is known of its role in the reactivity of nano-sized zero-valent iron(NZVI)in the degradation of pollutants.This study shows that the introduction of CYS to the NZVI system can help improve the efficiency of reduction,with 30%more efficient degradation and a reaction rate constant nine times higher when nitrobenzene(NB)is used as probe compound.The rates of degradation of NB were positively correlated with the range of concentrations of CYS from 0 to 10 mmol/L.The introduction of CYS increased the maximum concentration of Fe(Ⅲ)by 12 times and that of Fe(II)by four times in this system.A comparison of systems featuring only CYS or Fe(Ⅱ)showed that the direct reduction of NB was not the main factor influencing its CYS-stimulated removal.The reduction in the concentration of CYS was accompanied by the generation of cystine(CY,the oxidized form of cysteine),and both eventually became stable.The introduction of CY also enhanced NB degradation due to NZVI,accompanied by the regeneration of CYS.This supports the claim that CYS can accelerate electron transfer from NZVI to NB,thus enhancing the efficiency of degradation of NB.