Effect of Multiple Layered Vegetation on the Velocity Distribution of Flow in an Open Channel

Vegetation of various heights widely co-exists in natural rivers and wetlands, where the ecological environment and flow process are affected by the riparian vegetation, which has drawn great attention in river engineering and aquatic environmental management. Majority of studies in the past have been mainly focused on the understanding of flow through vegetation of single-layered vegetation. However, in natural riverine environments, mixing vegetation with different heights often occurs in natural rivers, which have a different effect on the flow than the single-layered vegetation does. In a flow condition under multiple layered vegetation, it is limited known about the impact of such vegetation on the flow velocity of channel, which is pre-requisite for many problems in river engineering and environmental management. In this paper, a novel experiment was designed to study the flow characteristics in an open-channel with vegetation of three different heights that exists on the channel bed, with a focus on the effect of the vegetation on the velocity distribution. Experiments were conducted in both partially submerged and fully submerged conditions. Three heights of dowels, 10, 15 and 20 cm, were used to mimic rigid vegetation in a staggered pattern for each type of dowel. Velocities at various locations across a section of channel were measured by Acoustic Doppler Velocimetry (ADV) and propeller velocimetry. Experimental results showed that the vertical velocity distribution is affected by vegetation heights. The results also revealed that the vegetation height have significant impact on the vertical distribution of velocity between and behind the vegetation. The vertical change of velocity behind TP (tall vegetation) and MP (medium vegetation) increases slowly beneath medium vegetation’s height (15cm) and then rapidly increases to the water surface. While the vertical change of velocity behind SP (short vegetation) and BP (blank space between vegetation) decreases a short amount beneath water height 5cm and increases rapidly to the water surface. Generally, the steamwise velocities at short vegetation zone and blank space are larger than tall vegetation zone and medium vegetation zone. These findings on the flow with multiple layered vegetation would be helpful for riparian management practices to maintain healthy ecological and habitat zones

Increased mitochondrial fission promotes autophagy and hepatocellular carcinoma cell survival through the ROS-modulated coordinated regulation of the NFKB and TP53 pathways

<p>Mitochondrial morphology is dynamically remodeled by fusion and fission in cells, and dysregulation of this process is closely implicated in tumorigenesis. However, the mechanism by which mitochondrial dynamics influence cancer cell survival is considerably less clear, especially in hepatocellular carcinoma (HCC). In this study, we systematically investigated the alteration of mitochondrial dynamics and its functional role in the regulation of autophagy and HCC cell survival. Furthermore, the underlying molecular mechanisms and therapeutic application were explored in depth. Mitochondrial fission was frequently upregulated in HCC tissues mainly due to an elevated expression ratio of DNM1L to MFN1, which significantly contributed to poor prognosis of HCC patients. Increased mitochondrial fission by forced expression of DNM1L or knockdown of MFN1 promoted the survival of HCC cells both in vitro and in vivo mainly by facilitating autophagy and inhibiting mitochondria-dependent apoptosis. We further demonstrated that the survival-promoting role of increased mitochondrial fission was mediated via elevated ROS production and subsequent activation of AKT, which facilitated MDM2-mediated TP53 degradation, and NFKBIA- and IKK-mediated transcriptional activity of NFKB in HCC cells. Also, a crosstalk between TP53 and NFKB pathways was involved in the regulation of mitochondrial fission-mediated cell survival. Moreover, treatment with mitochondrial division inhibitor-1 significantly suppressed tumor growth in an in vivo xenograft nude mice model. Our findings demonstrate that increased mitochondrial fission plays a critical role in regulation of HCC cell survival, which provides a strong evidence for this process as drug target in HCC treatment.</p