Astaxanthin Isomers: A Comprehensive Review of Isomerization Methods and Analytic Techniques.

The presence of multiple conjugated double bonds and chiral carbon atoms endows astaxanthin with geometric and optical isomers, and these isomers widely exist in biological sources, food processing, and in vivo absorption. However, there remains no systematic summary of astaxanthin isomers regarding isomerization methods and analytic techniques. To address this need, this Review focuses on a comprehensive analysis of Z-isomerization methods of astaxanthin, including solvent system, catalyst, and heat treatment. Comparatively, high-efficiency and health-friendly methods are more conducive to put into practical use, such as food-grade solvents and food-component catalysts. In addition, we outline the recent advances in analysis techniques of astaxanthin isomers, as well as the structural characteristics reflected by various methods (e.g., HPLC, NMR, FTIR, and RS). Furthermore, we summarized the related research on the safety evaluation of astaxanthin isomers. Finally, future trends and barriers in Z-transformation and analysis of astaxanthin isomers are also discussed.

Recent advances in health benefits and bioavailability of dietary astaxanthin and its isomers.

Astaxanthin, a xanthophyll carotenoid, has attracted considerable attention owing to its unique molecular structure and excellent antioxidant properties. Due to its structural particularity, it has many geometrical and optical isomers in the diet; Interestingly, the human body has considerable quantity of Z- and optical isomers despite the intake of E- and (3S,3'S) isomers. However, there remains no systematic analysis and summary of astaxanthin and its isomers regarding health benefits and bioavailability. To address this need, this review details the latest research progress of biological activities related to oxidative damage, and these effects are more obvious in Z- and (3S,3'S)-isomers from the existing research. In addition, we outline a comprehensive analysis of the bioavailability of dietary astaxanthin and its isomers from the perspective of transporter-mediated process (e.g. SR-BI, CD36). Further nvestigation of astaxanthin and its isomers is expected to improve human health and promote their applications in future healthcare-related products.

A Comparative Study on Evolutionary Multi-objective Optimization Algorithms Estimating Surface Duct.

The problem of atmospheric duct inversion is usually solved as a single objective optimization problem. Based on ground-based Global Positioning System (GPS) phase delay and propagation loss, this paper develops a multi-objective method including the effect of source frequency and receiving antenna height. The diversity and convergence of solution sets are evaluated for seven multi-objective evolutionary algorithms with three performance metrics: Hypervolume (HV), Inverted Generational Distance (IGD), and the averaged Hausdorff distance (Δ2). The inversion results are compared with the simulation results, and the experimental comparison is conducted on three groups of test situations. The results demonstrate that the ranking of algorithm performance varies because of the different methods used to calculate performance metrics. Moreover, when the algorithms show overwhelming performance using performance metrics, the inversion result is not more close to the real value. In the comparison of computational experiments, it was found that, as the retrieved parameter dimension increases, the inversion result becomes more unstable. When the observed data are sufficient, the inversion result seems to be improved.

Observations of Turbulence in Free Atmosphere by Balloon-Borne Sensors.

In recent years, Thorpe analysis has been used to retrieve the characteristics of turbulence in free atmosphere from balloon-borne sensor data. However, previous studies have mainly focused on the mid-high latitude region, and this method is still rarely applied at heights above 30 km, especially above 35 km. Therefore, seven sets of upper air (>35 km) sounding data from the Changsha Sounding Station (28°12' N, 113°05' E), China are analyzed with Thorpe analysis in this article. It is noted that, in the troposphere, Thorpe analysis can better retrieve the turbulence distribution and the corresponding turbulence parameters. Also, because of the thicker troposphere at low latitudes, the values of the Thorpe scale L T and turbulent energy dissipation rate ε remain greater in a larger height range. In the stratosphere below the height of 35 km, the obtained ε is higher, and Thorpe analysis can only be used to analyze the characteristics of large-scale turbulence. In the stratosphere at a height of 35⁻40 km, because of the interference of sensor noise, Thorpe analysis can only help to retrieve the rough distribution position of large-scale turbulence, while it can hardly help with the calculation of the turbulence parameters.