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• The radiation induced static mode degradation (SMD) was discovered and studied. • The threshold of SMD could be related with the composition of active fiber and increases with the increase of Ce. • When the Ce concentration increased by 35.5%, SMD threshold rose by 16% at most. We report on an experimental investigation of radiation induced static mode degradation in Yb-Ce co-doped pulsed fiber amplifiers. For investigating the impact of irradiation on beam quality, radiation-darkened fibers were irradiated by gamma rays. The laser properties of three types of fibers were investigated. With the pump power increased, static mode degradation appeared: M2 factor raised significantly and the output beam profile transformed from LP 01 into LP 11 shape without high-frequency component. The threshold of static mode degradation decreased with irradiation dose, and related to Yb-Ce co-doped fiber compositions. The doping of Ce benefits to the improvement of the static mode degradation threshold: in the case of the Ce concentration increasing by 35.5%, SMD threshold rose by 16% at most. [ABSTRACT FROM AUTHOR]

• The contribution of oyster reefs characteristics to the omnivorous fish intestinal microbiota was distinct. • Microbial communities in the oyster reefs and fish intestines showed various predictive functions and unique core indicators. • The microbial diversity in sediments were significantly higher than that in intestines. The habitats of oyster reefs had played various ecological services functions, as an important means of marine ecological restoration and fishery resources conservation, which had been widely used worldwide. And the characteristics of microbial communities would be inevitably affected by habitat of oyster reefs. The aim of this study was to reveal the relationship between oyster reefs and the intestinal microbiota of fish (Takifugu ocellatus , Acanthopagrus latus , Clupanodon thrissa , and Mugil cephalus). Here, based on 16S rRNA sequencing, this research analyzed the microbial communities of fishes gut in the oyster reefs from the most crucial estuary economic zone in Southern China. It was significantly lower that the bacterial alpha-diversity in the fish intestines than in the sediments of oyster reefs. The non-metric multidimensional scaling (NMDS) and analysis of similarities (ANOSIM) results showed that intestines microbiota of T. ocellatus and A. latus were more homologous to sediments microbiota, but intestines microbiota of C. thrissa and M. cephalus were more similar to the water microbiota. There were obvious differences in the contribution of oyster reefs habitat to intestinal microorganisms of four fishes. Source tracking analysis as well reached the similar conclusion. For instance, contribution of water to T. ocellatus and A. latus was lesser than sediments, which was related to their benthic habits. Based on the differences in microbial community compositions, the functional prediction analysis had demonstrated that special functional pathways and independent core indicators had been formed separately from oyster reefs and fish intestines. Overall, these findings highlighted the characteristics of microbial diversity and functions from the omnivorous fish living in oyster reefs habitats. This research proposed new insights into the function of oyster reefs habitats, which have enriched the ecological service value of oyster reefs from microbial ecology and provided a reference for the application of oyster reefs habitats in other estuaries. [ABSTRACT FROM AUTHOR]

• We first presented all-fiber cascaded combiners for ARM beam laser with a flattop central beam. The cascaded combiners are consist of a 3×1 combiner and a (6+1)×1 combiner in series. • By selecting appropriate structural parameters of the cascaded combiners, the first 3 × 1 combiner can form a multi-mode laser beam, which is input to the center port of the second (6 + 1) × 1 combiner to obtain an ARM beam with a uniformly distributed central beam. • The cascaded combiners yield an 8.8 kW central output laser with a transmission efficiency of 96.2 % and M2 factor of 5.24, as well as a ring output laser with an average efficiency higher than 98 %. An all-fiber structure that obtains an adjustable-ring mode (ARM) beam with a uniformly distributed central beam is put forward for the first time based on the beam combining technology. This structure is all-fiber cascaded combiners consisting of a 3 × 1 combiner and a (6 + 1) × 1 combiner in series. A multi-mode fiber with core diameter of 50 µm acts as the connective fiber, transmitting the combined laser of the first 3 × 1 combiner into the center guide core of the output fiber by the well-designed (6 + 1) × 1 combiner. Through the independent transmission of the center and ring beams, an 8.8 kW uniformly distributed central output laser with a transmission efficiency of 96.2 % and M2 of 5.24 is obtained by the cascaded combiners. The feasibility of ARM laser beam with a 10 kW-level flattop central beam provides a new approach for high-power laser welding. [ABSTRACT FROM AUTHOR]

• Present the first experimental results about the relationship between the Modal degradation (MD) and stimulated Brillouin scattering (SBS) in high-power continuous-wave (CW) narrow-linewidth (NL) linearly polarized fiber amplifiers. • For the first time, the time-frequency domain information analysis is added to the SBS and MD phenomena in the experiment, and the relationship between SBS and MD is completely studied in combination with the beam quality analyzer. • A near-diffraction-limited output beam without MI is achieved up to 760 W with M2 x = 1.09 and M2 y = 1.08, and polarization extinction ratio (PER) > 19 dB. In our high-power continuous-wave (CW) narrow-linewidth linearly polarized master oscillator power amplifier (MOPA) system, the mode degradation (MD) induced by stimulated Brillouin scattering (SBS) was observed. In the experiments, the beam quality maintained LP01 mode until the onset of SBS, and significantly deteriorated with the surging of SBS. Once the method of suppressing SBS was implemented, such as linewidth broadening and polarization extinction ratio (PER) weakening of the seed laser, the output laser mode recovered to fundamental mode, revealing the MD effect was evidently mitigated. Meanwhile, the associated relationship between MD and SBS was also investigated based on the analysis of spectrum, oscilloscope, and beam quality. [ABSTRACT FROM AUTHOR]

• A multi-dimensional functional space was built to visualize the functional structure. • The functional structure and trait composition of fish in the PRE vary seasonally. • The CWM traits were mainly affected by temperature, DO, chlorophyll-a, and depth. Estuaries are one of the most important ecosystems with high biological productivity. They connect freshwater and marine ecosystems, and the fish community assemblages face intense environmental changes, so estuarine fish communities have unique ecological characteristics. With the increase of human activities and the discharge of pollutants, the pressure on the ecosystem of the Pearl River Estuary (PRE) is intensifying, and its ecosystem functions and services are inevitably affected. To better understand the functional structure of the fish community in the PRE and its response to environmental changes, we analyzed the trait composition of the community and its relationships to environmental factors based on 10 functional traits of 130 fish species collected in the PRE during the summer and winter of 2020–2021. In addition, we built a multi-dimensional functional space to visualize the overall functional structure of the PRE and explore the seasonal variation of the selected traits in the functional space. Our findings suggest that the functional traits of the fish communities in the PRE were mainly affected by temperature, dissolved oxygen, chlorophyll-a, and depth. Among them, the effects of dissolved oxygen, temperature, and chlorophyll-a on CWM traits were reflected in seasonal differences, while the effects of depth were reflected in spatial differences. We also found the main trait categories that occupied the most functional space and contributed the most to the seasonal differences in functional space. The results of this study are significant for understanding the seasonal variation of the functional structure in the PRE and how environmental gradients drive the functional traits of fish communities, and also provide insights for effective ecosystem-based management in the PRE. [ABSTRACT FROM AUTHOR]

• The stochastic pulses and temporal optical rogue waves (RWs) behavior are observed and investigated in the high power short-cavity Yb-doped random fiber laser (YDRFL) for the first time. • The record output power without the stimulated Raman scattering (SRS) is promoted to 26.6 W in the YDRFL with the Ge-doped fiber (GDF) length of 120 m. • The experimental results manifest that the proportion of RWs depends on the GDF length and can also affect the stability of output lasing and the M2 factor distribution. • The experimental phenomenons display that the multiple high order SRS stokes lights and the visible light radiations are generated in the YDRFL with shorter GDF length. • The research results reveal that achieving the relative stable output power requires the greater pump power for the shorter GDF length. A high power short-cavity random fiber laser employing the gain mechanism of the Yb-doped fiber and the half-open cavity structure and the temporal optical rogue waves (RWs) behavior are observed and investigated in the paper. The record output power without the stimulated Raman scattering (SRS) is promoted to 26.6 W in the Yb-doped random fiber lasers (YDRFL) with the Ge-doped fiber (GDF) length of 120 m. The stochastic pulses and temporal optical RWs are observed and demonstrated in the short cavity YDRFL for the first time. It is found that the proportion of RWs depends on the GDF length and can also affect the stability of output lasing and the M2 factor distribution. The M2 factor distribution demonstrated a special longitudinal mode instability phenomenon. The experimental phenomenons display that the multiple high order SRS stokes lights and the visible light radiations are generated by the soliton self-frequency shift and Cherenkov radiation in the YDRFL with shorter GDF length. The research results reveal that achieving the relative stable output power requires the greater pump power for the shorter GDF length, although decreasing the GDF length will promote the maximum output power of the YDRFL without the SRS. [ABSTRACT FROM AUTHOR]