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A photonic technique for microwave frequency measurement based on stimulated Brillouin scattering (SBS) with low measurement error and large measurement range is demonstrated. In the scheme, an optical phase modulator is employed and the intensity balance between the two sidebands of the phase‐modulated signal is broken by use of SBS in a fibre. The frequency measurement is achieved by detecting the existence of a microwave signal after photoelectric detection of the phase modulated signal. The measurement error is experimentally shown to be 50 MHz in a narrow measuring range of ∼1 GHz and 100 MHz in a wide range of 20 GHz. [ABSTRACT FROM AUTHOR]

Cyanobacterial blooms can impair drinking water quality due to the concomitant extracellular organic matter (EOM). As copper is often applied as an algicide, cyanobacteria may experience copper stress. However, it remains uncertain whether algal growth compensation occurs and how EOM characteristics change in response to copper stress. This study investigated the changes in growth conditions, photosynthetic capacity, and EOM characteristics of M. aeruginosa under copper stress. In all copper treatments, M. aeruginosa experienced a growth inhibition stage followed by a growth compensation stage. Notably, although chlorophyll-a fluorescence parameters dropped to zero immediately following high-intensity copper stress (0.2 and 0.5 mg/L), they later recovered to levels exceeding those of the control, indicating that photosystem II was not destroyed by copper stress. Copper stress influenced the dissolved organic carbon (DOC) content, polysaccharides, proteins, excitation–emission matrix spectra, hydrophobicity, and molecular weight (MW) distribution of EOM, with the effects varying based on stress intensity and growth stage. Principal component analysis revealed a correlation between the chlorophyll-a fluorescence parameters and EOM characteristics. These results imply that copper may not be an ideal algicide. Further research is needed to explore the dynamic response of EOM characteristics to environmental stress. [Display omitted] • Compensatory growth of M. aeruginosa was confirmed following exposure to copper stress. • Post-copper stress, M. aeruginosa 's chlorophyll-a fluorescence surpassed control. • Low copper concentration (0.05 mg/L) enhance short- and long-term EOM content. • EOM characteristics of M. aeruginosa varied with copper stress intensity and the specific growth stage. [ABSTRACT FROM AUTHOR]

A photonic approach for generating radio frequency (RF) chirped and non-chirped waveforms with reconfigurable envelope and high fidelity is proposed and experimentally demonstrated based on frequency-to-time mapping (FTM). A space light modulator based pulse shaper is used for spectral shaping. To make full use of the available bandwidth of the pulse shaper, the output of an amplified mode-locked laser is used as a broadband optical source. A feedback scheme is proposed to compensate the absence of the amplified spontaneous emission spectrum in frequency-to-time mapping. Based on the spectrum compensated FTM, chirped and non-chirped waveforms with different envelopes and high fidelity are experimentally generated. [ABSTRACT FROM AUTHOR]

• Study the co-oxidation behavior of methanol on ammonia in supercritical water. • The synergy between kinetics and thermal actions of methanol on ammonia. • Examine the influence of reaction conditions and the formation of nitrate. • Compare methanol and isopropanol by positive effect and exothermic behavior. The co-oxidation behavior of methanol on ammonia in supercritical water was investigated in a continuous tubular reactor under a range of methanol concentration (10–800 mmol/L), ammonia concentration (50–400 mmol/L), oxidation coefficient (1.05–1.7) and preheating temperature of 400 and 415 °C. Calculation based on a mechanism-based model for supercritical water oxidation of methanol/ammonia showed that the synergy between the kinetics action to supply radicals and the thermal action to elevate the reaction temperature of methanol would improve the efficient decomposition of ammonia at relatively moderate reaction conditions. Specifically, near complete conversion of ammonia (97.5%) can be achieved at [CH 3 OH] 0 = 800 mmol/L, preheating temperature of 415 °C and oxidation coefficient of 1.5. The influence of reaction conditions on the co-oxidation behavior and the formation of nitrate were examined experimentally. Methanol and isopropanol served as the auxiliary fuel for ammonia were compared by the positive effect and exothermic performance, which reached that methanol was superior to isopropanol. [ABSTRACT FROM AUTHOR]