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The validity of local thermodynamic equilibrium (LTE) in plasma is a long-term concern for laser-induced breakdown spectroscopy applications. In this paper, the spatial and temporal dependence of LTE deviation in picosecond laser-induced plasmas has been proved. A picosecond (∼20 ps) laser operated at 532 nm was used to ablate a silicon target to produce plasma at a pressure of 10−5 mbar. A general electron energy distribution function was used to provide access to the insight into population ratios of different energy levels for the spatially and temporally resolved optical emission intensity of laser-induced plasma. A precise temporal and spatial LTE boundary of plasma generated in picosecond laser ablation was obtained, and the results showed that only at delay times of 180–300 ns, the plasma away from the surface (>4 mm) is in LTE.

In Yb-Er co-doped upconversion (UC) nanomaterials, upconversion luminescence (UCL) can be modulated to generate multiband UCL emissions by changing the concentration of activator Er3+. Nonetheless, the effect of the Er3+ concentrations on the kinetics of these emissions is still unknown. We here study the single β-NaYF4:Yb3+/Er3+ microcrystal (MC) doped with different Er3+ concentrations by nanosecond time-resolved spectroscopy. Interestingly, different Er3+ doping concentrations exhibit different UCL emission bands and UCL response rates. At low Er3+ doping concentrations (1 mol%), multiband emission in β-NaYF4:Yb3+/Er3+ (20/1 mol%) MCs could not be observed and the response rate of UCL was slow (5–10 μs) in β-NaYF4:Yb3+/Er3+. Increasing the Er3+ doping concentration to 10 mol% can shorten the distance between Yb3+ ions and Er3+ ions, which promotes the energy transfer between them. β-NaYF4:Yb3+/Er3+ (20/10 mol%) can achieve obvious multiband UCL and a quick response rate (0.3 µs). However, a further increase in the Er doping concentration (80 mol%) makes MCs limited by the CR process and cannot achieve the four-photon UC process (4F5/2 → 2K13/2 and 2H9/2 → 2D5/2). Therefore, the result shows that changing the Er3+ doping concentration could control the energy flow between the different energy levels in Er3+, which could affect the response time and UCL emission of the Yb/Er doped rare earth materials. Our work can facilitate the development of fast-response optoelectronics, optical-sensing, and display industries.

Endoplasmic reticulum (ER) stress and the resulting neuronal cell damage have been implicated in the development and progression of Alzheimer's disease. Tunicamycin (TM) induces ER stress in vitro, and the protective effects of the carotenoid zeaxanthin against the effects of TM have recently been studied. Zeaxanthin has been shown to hold several beneficial health properties in human studies. The protective role of zeaxanthin against the toxic effects of TM has recently been studied for the first time. The present study investigated whether zeaxanthin protects SH-SYSY cells against TM-induced cell damage in vitro. Both pretreatment and post-treatment with zeaxanthin increased cell viability and suppressed lactate dehydrogenase release compared to levels in controls. Further, we found that zeaxanthin considerably ameliorated TM-induced cell damage by protecting the integrity of the mitochondrial membrane decreasing caspase-3 activity, and by reducing the apoptosis rate as well as the expression of the ER stress biomarker GRP78. Modulation of GRP78 may be one of the mechanisms by which zeaxanthin affects cell viability. Our results indicate a potential application of zeaxanthin in the development of new therapeutic drugs for the treatment of Alzheimer's disease. [ABSTRACT FROM AUTHOR]