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To investigate an appropriate wind load design for buildings considering dynamic air density changes, classical extreme value and copula theories were utilized. Using wind speed, air temperature, and air pressure data from 123 meteorological stations in Shandong Province from 2004 to 2017, a joint probability distribution model was established for extreme wind speed and air density. The basic wind pressure was calculated for various conditional return periods. The results indicated that the Gumbel and Gaussian mixture model distributions performed well in extreme wind speed and air density fitting, respectively. The joint extreme wind speed and air density distribution exhibited a distinct bimodal pattern. The higher the wind speed was, the greater the air density for the same return conditional period. For the 10-year return period, the air density surpassed the standard air density, exceeding 1.30 kg/m3. The basic wind pressures under the different conditional return periods were more than 10% greater than those calculated from standard codes. Applying the air density based on the conditional return period in engineering design could enhance structural safety regionally. [ABSTRACT FROM AUTHOR]

As a frequent hazard, tropical cyclones have a great impact on the social and economic development of China, which is close to the origin of tropical cyclones in the western Pacific Ocean. The primary objective of this study was to construct a comprehensive risk assessment model for tropical cyclone hazards based on natural influencing factors, informing recommendations for hazard prevention and mitigation in affected regions. This research focused on tropical cyclones that made landfall in mainland China and Hainan from 1949 to 2023, utilizing hazard risk theory and classical extreme value theory. The wind speed and rainfall data during the peak cyclone periods (June to October) from 1997 to 2021 gathered from various meteorological stations, as well as altitude and vegetation cover data, were examined. Hierarchical analysis and ArcGIS spatial analysis methods were employed to study the characteristics of the spatiotemporal distribution of landfalling tropical cyclones and the comprehensive risk of tropical cyclone hazards, and the regions of China were delineated according to these methods. The results showed that, during the period from 1949 to 2023, the overall number of landfalling tropical cyclones decreased in a fluctuating manner, while the intensity of the cyclones increased. Furthermore, severe typhoons tended to occur more frequently in the summer than autumn with time, intensifying the challenge to resist short-term hazards. Moreover, the hazard-causing factors in areas affected by tropical cyclones displayed an increasing trend from north to south and from west to east. In detail, the regions sensitive to natural hazards were primarily located in the central part of Liaoning province, Tianjin, central and eastern Hebei province, Shandong province, eastern Henan province, central and northern Anhui province, Jiangsu province, and Shanghai, which are characterized by flat terrain and relatively low vegetation cover. Overall, the comprehensive risk of tropical cyclone hazards showed a geographical distribution that decreases from south to north and from east to west, with coastal cities in provinces such as Hainan, Guangdong, Guangxi, Fujian, and Zhejiang—including Haikou, Zhanjiang, Xiamen, Beihai, and Taizhou—exhibiting the highest levels of risk. [ABSTRACT FROM AUTHOR]

Quercetin, a flavonoid compound rich in hydroxyl groups, possesses antioxidant properties, whereas its poor water solubility limits its bioavailability. In pursuit of addressing the water solubility of quercetin and comprehending the impact of nanocrystal particle size on antioxidant efficacy, we prepared three different-sized quercetin nanocrystals, namely small (50 nm), medium (140 nm), and large (360 nm), using a nanosuspension method in this study. Within the in vitro setting, assessments employing solubility and radical scavenging assays revealed that quercetin nanocrystals displayed superior solubility (26, 21, and 13 fold corresponding to small, medium, and large particle sizes) and antioxidant performance compared to the coarse quercetin. Furthermore, quercetin nanocrystals of three particle sizes all demonstrated significant protection effects on the survival rate of H2O2-treated zebrafish at 72 h (77.78%, 73.33%, and 66.67% for small, medium, and large particle sizes, respectively), while the coarse quercetin group exhibited a low survival rate (53.3%) similar to the H2O2-treated group (47.8%). Moreover, all quercetin nanocrystals exhibited potent antioxidant capacity on both the antioxidants and enzymatic antioxidant system in H2O2-treated zebrafish to restore zebrafish to a normal state under oxidative stress. For instance, the levels of reactive oxygen species were reduced to 101.10%, 108.83%, and 109.77% of the normal levels for small, medium, and large particle-sized quercetin nanocrystals, respectively. In conclusion, quercetin nanocrystals demonstrated enhanced solubility, robust antioxidant capacity, and protective effects in zebrafish compared to coarse quercetin. [ABSTRACT FROM AUTHOR]

Melanin is a kind of dark insoluble pigment that can cause pigmentation and free-radical clearance, inducing melasma, freckles, and chloasma, affecting the quality of life of patients. Due to poor water solubility and low safety, the absorption of poorly water-soluble drugs is limited by the hinderance of a skin barrier. Therefore, it is necessary to develop new, safe, and highly efficient drugs to improve their transdermal absorption efficiency and thus to inhibit the production of melanin. To address these issues, we developed a new nicotinamide (NIC)-stabilized phloretin nanocrystals (PHL-NCs). First, NC technology significantly increased the solubility of PHL. The in vitro release results indicated that at 6 h, the dissolution of the PHL-NIC-NCs was 101.39% ± 2.40% and of the PHL-NCs was 84.92% ± 4.30%, while that of the physical mixture of the two drugs was only 64.43% ± 0.02%. Second, NIC acted not only as a stabilizer to enlarge the storage time of PHL-NIC-NCs (improved to 10-day in vitro stability) but also as a melanin transfer inhibitor to inhibit melanin production. Finally, we verified the melanin inhibition effect of PHL-NIC-NCs evaluated by the zebrafish model. It showed that 0.38 mM/L PHL-NIC-NCs have a lower tyrosinase activity at 62.97% ± 0.52% and have less melanin at 36.57% ± 0.44%. The inhibition effect of PHL-NCs and PHL-NIC-NCs was stronger compared to the positive control arbutin. In conclusion, the combination of NIC and PHL achieves better inhibition of tyrosinase and inhibition of melanin production through synergism. This will provide a direction to the subsequent development of melanin-inhibiting drugs and the combined use of pharmaceutical agents. [ABSTRACT FROM AUTHOR]