Species-specific effect of particle viscosity and particle-phase reactions on the formation of secondary organic aerosol.

Secondary organic aerosol (SOA) is a major component of atmospheric fine particulate matter. Both particle viscosity and particle-phase chemistry play a crucial role in the formation and evolution of SOA; however, our understanding on how these two factors together with gas-phase chemistry collectively determine the formation of SOA is still limited. Here we developed a kinetic aerosol multilayer model coupled with gas-phase and particle-phase chemistry to simulate SOA formation. We take the atmospherically important α-pinene + OH oxidation system as an example application of the model. The simulations show that although the particle viscosity has negligible to small influences on the total SOA mass concentration, it strongly changes the concentration and distribution of individual compounds within the particle. This complicated effect of particle viscosity on SOA formation is a combined result of inhibited condensation or evaporation of specific organics due to slowed particle-phase diffusion. Furthermore, the particle-phase reactions alter the volatility and abundance of specific compounds and exacerbate their non-uniform distribution in highly viscous particles. Our results highlight an important species-specific effect of particle viscosity and particle-phase chemistry on SOA formation and demonstrate the capability of our model for quantifying such complicated effects on SOA formation and evolution.

Effect of Xuefu Zhuyu Decoction Pretreatment on Myocardium in Sepsis Rats.

Xuefu Zhuyu Decoction (XFZYD), the classical recipe for promoting blood circulation by removing blood stasis, has been used in China for a long history clinically. XFZYD has been found to improve cardiac function through reducing inflammation. However, the effect of XFZYD on myocardial apoptosis remains unclear. Herein, we investigated the mechanism of XFZYD preconditioning on myocardial injury in sepsis rats. The rats were treated with XFZYD one week, followed with intraperitoneal injection of lipopolysaccharide (LPS: 10 mg/kg) to induce sepsis. Pretreatment with XFZYD could reverse the effects of LPS-induced decreased mean arterial pressure (MAP) and increased heart rate (HR). XFZYD decreased the levels of malondialdehyde (MDA), superoxide dismutase (SOD), tumor necrosis factor-α (TNF-α), interleukin-1ß (IL-1ß), and interleukin-6 (IL-6) in serum or in heart. TUNEL staining revealed that the apoptotic index of XFZYD was significantly lower compared with the LPS group (P<0.05). Western blot results showed that the high doses of pretreatment XFZYD group can reduce the Bax expression of myocardial tissue in rats (P<0.05, P<0.01). The expression of Bcl-2 in XFZYD group was significantly higher than that in the LPS group (P<0.01), while the expression of caspase-3 in treatment group was significantly lower than that in the LPS group only after 12 h modeling (P<0.01). In addition, caspase-3 activity in rat cardiomyocytes of XFZYD-treated animals was significantly decreased. These findings suggest that pretreatment with XFZYD exerts a protective effect in the myocardium of septic rats by inhibiting myocardial cell apoptosis and antioxidation.