Large scale simulation of watershed mass transport – a case study of Tsengwen reservoir watershed

The Tenth International Symposium on Mitigation of Geo-disasters in Asia Matsue Symposium Place: Shimane Civil Center, Matsue Date: 8 October 2012We present the large scale simulation of watershed mass transport, including landslide, debris-flow and sediment transport. A case study of Tsengwen reservoir watershed under the extreme rainfall triggered by typhoon Morakot is simulated for verification. This approach starts with volume-area relationship formula with inventory method to predict temporal and regional landslide volume production and distribution. Then, debris flow model, Debris-2D, is used to simulate the mass transport of debris-flow from hillslope to fluvial channel. Finally a sediment transport model, NETSTARS, is used for hydraulic and sediment routing in river and reservoir. The integrated simulation for the whole watershed gives a very good agreement with the temporal variation of sediment concentration recorded at the very downstream location

Experimental study of seismo-acoustic frequency and flow velocity of debris flow

Seismo-acoustic wave radiated from debris flows motion is one of the main properties used for its monitoring and detection. Understanding the Seismo-acoustic wave using geophone recordings may give us great insight into the physical process of debris flows such as flow velocity and flow rate. To connect the seismo acoustic observation to the debris flows motion, vibration signal recorded from fixed geophones were analysed. In this study, a small-scale granular flow of volume 0.2 m3 consisting of material with average particle diameter 3.34 mm was simulated in a hydraulic flume with cross section of 0.5 m X 0.5 m through granular bed to simulate the debris flow. A series of three-axis geophones were buried along channel bed to record the vibrations produced by granular flows. The discrete Fourier transform was used to decompose vibrations into frequency spectrum and the weighted non-linear least square regression was adopted to isolate the dominant frequency functions and peak frequency. Meanwhile, the physical parameters including front profile, surface velocity, flow depth and discharge were tracked through video recordings and were compared with respect to isolated peak frequency. Assuming the radiated peak frequency in the moving granular flow is within 20-50 Hz and normally distributed, the isolated peak frequency shift in the fixed geophone location was analysed with the tracked flow parameters. Results shows that the peak frequency shift seems to have a non-linear relation with the surface velocity

Debris flow seismo-acoustic wave in a finite layer waveguide

The seismo-acoustic wave detection is a popular method to detect debris flows. It has been successfully used in different early warning systems worldwide. However, more information is embedded in the signals related to flow conditions. This research uses theoretical derivation to connect signals with debris flow propagation speed. We assume debris flow generates seismo-acoustic stress acting on a river bed and the seismo-acoustic waves propagate in a finite layer waveguide below the channel. Then, the propagation of seismo-acoustic stress was solved with the elastic wave equations along the channel. For any fixed point in this waveguide, the frequency of the recording signal can be translated as a function of debris flow propagation speed and seismo-acoustic wave velocity. The result shows that there is a Doppler-like property for a recorded signal where debris flow propagation speed can cause a frequency shift. This result also indicates that different superior frequency bands would be recorded from different media

A Broadband Superabsorber at Optical Frequencies: Design and Demonstration

Metasurface based super absorbers exhibit near unity absorbance. While the absorption peak can be tuned by the geometry/size of the sub-wavelength resonator, broadband absorption can be obtained by placing multiple resonators of various size or shapes in a unit cell. Metal dispersion hinders high performance broadband absorption at optical frequencies and careful designing is essential to achieve good structures. We propose a novel analytical framework for designing a broadband super absorber which is much faster than the time consuming full wave simulations that are employed so far. Analytical expressions are derived for the wavelength dependency of the design parameters, which are then used in the optimization of broadband absorption. Numerical simulations report an average polarization-independent absorption of ~97 in the 450 to 950 nm spectral region with a near unity absorption (99.36) in the 500 to 850 nm region. Experimentally, we demonstrate an average absorption over 98 in the 450 to 950 nm spectral region at 20 degree incident angle The designed super absorber is polarization insensitive and has a weak launch angle dependency. The proposed framework simplifies the design process and provides a quicker optimal solution for high performance broadband super absorbers

High-Throughput Screening of Australian Marine Organism Extracts for Bioactive Molecules Affecting the Cellular Storage of Neutral Lipids

Mammalian cells store excess fatty acids as neutral lipids in specialised organelles called lipid droplets (LDs). Using a simple cell-based assay and open-source software we established a high throughput screen for LD formation in A431 cells in order to identify small bioactive molecules affecting lipid storage. Screening an n-butanol extract library from Australian marine organisms we identified 114 extracts that produced either an increase or a decrease in LD formation in fatty acid-treated A431 cells with varying degrees of cytotoxicity. We selected for further analysis a non-cytotoxic extract derived from the genus Spongia (Heterofibria). Solvent partitioning, HPLC fractionation and spectroscopic analysis (NMR, MS) identified a family of related molecules within this extract with unique structural features, a subset of which reduced LD formation. We selected one of these molecules, heterofibrin A1, for more detailed cellular analysis. Inhibition of LD biogenesis by heterofibrin A1 was observed in both A431 cells and AML12 hepatocytes. The activity of heterofibrin A1 was dose dependent with 20 µM inhibiting LD formation and triglyceride accumulation by ∼50% in the presence of 50 µM oleic acid. Using a fluorescent fatty acid analogue we found that heterofibrin A1 significantly reduces the intracellular accumulation of fatty acids and results in the formation of distinct fatty acid metabolites in both cultured cells and in embryos of the zebrafish Danio rerio. In summary we have shown using readily accessible software and a relatively simple assay system that we can identify and isolate bioactive molecules from marine extracts, which affect the formation of LDs and the metabolism of fatty acids both in vitro and in vivo

Graphene-Based Nanocomposites for Energy Storage

Since the first report of using micromechanical cleavage method to produce graphene sheets in 2004, graphene/graphene-based nanocomposites have attracted wide attention both for fundamental aspects as well as applications in advanced energy storage and conversion systems. In comparison to other materials, graphene-based nanostructured materials have unique 2D structure, high electronic mobility, exceptional electronic and thermal conductivities, excellent optical transmittance, good mechanical strength, and ultrahigh surface area. Therefore, they are considered as attractive materials for hydrogen (H2) storage and high-performance electrochemical energy storage devices, such as supercapacitors, rechargeable lithium (Li)-ion batteries, Li–sulfur batteries, Li–air batteries, sodium (Na)-ion batteries, Na–air batteries, zinc (Zn)–air batteries, and vanadium redox flow batteries (VRFB), etc., as they can improve the efficiency, capacity, gravimetric energy/power densities, and cycle life of these energy storage devices. In this article, recent progress reported on the synthesis and fabrication of graphene nanocomposite materials for applications in these aforementioned various energy storage systems is reviewed. Importantly, the prospects and future challenges in both scalable manufacturing and more energy storage-related applications are discussed

RNF185, a Novel Mitochondrial Ubiquitin E3 Ligase, Regulates Autophagy through Interaction with BNIP1

Autophagy is an evolutionarily conserved catabolic process that allows recycling of cytoplasmic organelles, such as mitochondria, to offer a bioenergetically efficient pathway for cell survival. Considerable progress has been made in characterizing mitochondrial autophagy. However, the dedicated ubiquitin E3 ligases targeting mitochondria for autophagy have not been revealed. Here we show that human RNF185 is a mitochondrial ubiquitin E3 ligase that regulates selective mitochondrial autophagy in cultured cells. The two C-terminal transmembrane domains of human RNF185 mediate its localization to mitochondrial outer membrane. RNF185 stimulates LC3II accumulation and the formation of autophagolysosomes in human cell lines. We further identified the Bcl-2 family protein BNIP1 as one of the substrates for RNF185. Human BNIP1 colocalizes with RNF185 at mitochondria and is polyubiquitinated by RNF185 through K63-based ubiquitin linkage in vivo. The polyubiquitinated BNIP1 is capable of recruiting autophagy receptor p62, which simultaneously binds both ubiquitin and LC3 to link ubiquitination and autophagy. Our study might reveal a novel RNF185-mediated mechanism for modulating mitochondrial homeostasis through autophagy