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Two feeding trials were conducted to evaluate the influence of dietary curcumin level on fish meal replacement with poultry by-product (PBM) in a largemouth bass (Micropterus salmoides) diet. In trial I, the reference diet (R) contained 400 g/kg fish meal, and PBM replaced 60 and 80% of the fish meal (P16 and P8). In trial II, the diet containing 80 g/kg fish meal (P8) served as control (C), and curcumin was added at 5000 and 10000 mg/kg (C5 and C10), respectively. Replacement of fish meal with PBM significantly influenced feed intake, phosphorus retention efficiency (PRE), body lipid content, the ratio of fish meal consumption to fish production (RCP), and wastes of carbon and phosphorus but did not result in significant alternation in weight gain, feed conversion ratio (FCR), retention efficiencies of nitrogen (NRE), carbon (CRE) and energy (ERE), viscerosomatic index (VSI), hepatosomatic index (HSI), and body composition. The RCP, body lipid content, and phosphorus waste were higher in fish fed diet R than in fish fed diets P16 and P8. Curcumin supplementation influenced weight gain, feed intake, FCR, carbon waste, and RCP, but did not result in significant alternation in CRE, NRE, PRE, ERE, condition factor, VSI, HSI, body composition, and nitrogen and phosphorus wastes. The weight gain and feed intake were higher in fish fed diet C10 than in fish fed diet C, while the carbon waste was higher in fish fed diets C5 and C10 than in fish fed diet C. Overall, the minimum dietary fish meal level for largemouth bass could be dropped to 80 g/kg when PBM was used as an alternative ingredient, and 10000 mg/kg curcumin could obviously improve growth of fish fed diet containing 80 g/kg fish meal. [ABSTRACT FROM AUTHOR]

Raman spectroscopy is a widely practicable technique in gas analysis, but the application in simultaneous detection of multiple‐trace gas is still a challenge for its weak signal level. To extend the application of Raman gas analysis to detection of trace gas constituents, a closed parabolic sample cell proposed in our previous work is optimized by optical analysis and experimental verification. The optical analysis shows that for a parabolic reflector with rim diameter 6p (p, semi‐latus rectum), the collecting solid angle can be as large as 90% of full space (4π) and the power‐collecting efficiency can be as high as 80%. The variation of the Raman signal level with the position of collecting aperture and the parameter p of parabolic reflector was verified by the experimental results. At the optimized structure parameters, we get a signal‐to‐background ratio of 122 and a signal‐to‐noise ratio of 305 in the Raman spectra of ambient air with exposure time of 1 s. From the results of standard analytic gaseous samples, the limits of detection of 33 ppm‐bar for H2, 38 ppm‐bar for CO, 19 ppm‐bar for CH4, 27 ppm‐bar for C2H6, 23 ppm‐bar for C2H4, and 20 ppm‐bar for C2H2 were obtained with exposure time of 200 s. These results indicate that the parabolic sample cell is a competitive Raman collector, which showing good balance in signal enhancement and background level. [ABSTRACT FROM AUTHOR]

Revealing the mechanisms underlying soil microbial community assembly is a fundamental objective in molecular ecology. However, despite increasing body of research on overall microbial community assembly mechanisms, our understanding of subcommunity assembly mechanisms for different prokaryotic and fungal taxa remains limited. Here, soils were collected from more than 100 sites across southwestern China. Based on amplicon high‐throughput sequencing and iCAMP analysis, we determined the subcommunity assembly mechanisms for various microbial taxa. The results showed that dispersal limitation and homogenous selection were the primary drivers of soil microbial community assembly in this region. However, the subcommunity assembly mechanisms of different soil microbial taxa were highly variable. For instance, the contribution of homogenous selection to Crenarchaeota subcommunity assembly was 70%, but it was only around 10% for the subcommunity assembly of Actinomycetes, Gemmatimonadetes and Planctomycetes. The assembly of subcommunities including microbial taxa with higher occurrence frequencies, average relative abundance and network degrees, as well as wider niches tended to be more influenced by homogenizing dispersal and drift, but less affected by heterogeneous selection and dispersal limitation. The subcommunity assembly mechanisms also varied substantially among different functional guilds. Notably, the subcommunity assembly of diazotrophs, nitrifiers, saprotrophs and some pathogens were predominantly controlled by homogenous selection, while that of denitrifiers and fungal pathogens were mainly affected by stochastic processes such as drift. These findings provide novel insights into understanding soil microbial diversity maintenance mechanisms, and the analysis pipeline holds significant value for future research. [ABSTRACT FROM AUTHOR]

We design and numerically investigate a broadband tunable terahertz polarization converter based on graphene metamaterial. The converter presents a broad conversion band with high polarization conversion ratio (>0.95) in terahertz frequency over a bandwidth which is 25.8% of the central frequency. The converter can be dynamically tuned by varying the Fermi Energy of the graphene without changing the geometric structure. The converter shows high conversion ratio for a wide range of incident angles from 0 to 40°. By the scaling of the proposed structure, the broadband properties of the converter can be easily spread to other frequency. The proposed metamaterial offers an approach in the manipulation of the light polarization and has potential applications in imaging, sensing and communications. [ABSTRACT FROM AUTHOR]

A tunable external cavity diode laser (ECDL) system with narrow line-width emission at 410 nm is presented. Based on a commercially available laser diode and a Littrow arranged reflective holographic grating, a maximum output power over 500 mW with line-width of about 50 pm is achieved at the rated current. The power efficiency is over 85% and the threshold decreases over 20% compared to the free-running laser diode. Manual tuning range over 5 nm is achieved around threshold condition and over 2 nm at high injection currents up to 500 mA with side mode suppression ratio larger than 20 dB. [ABSTRACT FROM AUTHOR]

Grassland degradation seriously affects the health of our planet, thereby weakening the ability of grasslands to provide multiple ecosystem services. Soil microbes have been recognized as game changers in the succession of degraded lands; therefore, the determination of their responses to grassland degradation is crucial for restoring degraded grasslands. However, soil microbial responses to grassland degradation are still far from being well understood, especially for low-latitude meadows. Hence, this study was performed in one natural and two artificial degraded subalpine meadows in Southern China to identify the soil microbial responses to the degradation of low-latitude subalpine meadows. At each site, soils were collected from nondegraded, moderately degraded, and heavily degraded subalpine meadows. Soil microbial abundance and diversity were analyzed via real-time PCR and amplicon NovaSeq sequencing, respectively. We found that the degradation of subalpine meadows significantly decreased the concentrations of almost all of the soil nutrients and considerably changed soil pH and texture. We also found that soil microbes demonstrated almost consistent responses to the degradation of the natural and artificial subalpine meadows. Specifically, degradation did not affect soil microbial abundance but significantly changed microbial community profiles. The relative abundance of most plant growth-promoting microbial taxa significantly decreased with subalpine meadow degradation, whereas the microbial taxa that were adverse to plant health exhibited a reverse trend. Soil microbial richness was also significantly decreased by the heavy degradation of the subalpine meadows. Additionally, the heavy degradation of the subalpine meadows significantly decreased the complexity and stability of the microbial co-occurrence network. The aforementioned soil microbiome changes also showed the significant correlations with plant biomass. Collectively, the changes in the soil microbiome can be critical factors affecting the degradation of subalpine meadows, and the regulation of soil microbiome is a promising restoration strategy. • The heavy degradation of subalpine meadows decreased soil microbial richness. • The heavy degradation of subalpine meadows decreased microbial network stability. • Soil microbial abundance was unaffected by the subalpine meadow degradation. • Subalpine meadow degradation decreased plant growth-promoting microbial taxa. • Subalpine meadow degradation increased the microbial taxa adverse to plant health. [ABSTRACT FROM AUTHOR]

A stable external cavity diode laser coupled with volume Bragg grating for metastable argon atoms pumping is presented. The measured maximum output power of the continuous wave is 6.5 W when the spectral width (FWHM) is less than 21 pm around 811.53 nm and the power efficiency is 68%. The tuning range of the emission wavelength is bigger than 270 pm. The calculated deviation in relative absorption efficiency caused by the fluctuations of wavelength and power is less than 4%. [ABSTRACT FROM AUTHOR]