111 research outputs found

    New acoustic system for continuous measurement of river discharge and water temperature

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    AbstractIn many cases, river discharge is indirectly estimated from water level or streamflow velocity near the water surface. However, these methods have limited applicability. In this study, an innovative system, the fluvial acoustic tomography system (FATS), was used for continuous discharge measurement. Transducers with a central frequency of 30 kHz were installed diagonally across the river. The system's significant functions include accurate measurement of the travel time of the transmission signal using a GPS clock and the attainment of a high signal-to-noise ratio as a result of modulation of the signal by the 10th order M-sequence. In addition, FATS is small and lightweight, and its power consumption is low. Operating in unsteady streamflow, FATS successfully measured the cross-sectional average velocity. The agreement between FATS and acoustic Doppler current profilers (ADCPs) on water discharge was satisfactory. Moreover, the temporal variation of the cross-sectional average temperature deduced from the sound speed of FATS was similar to that measured by a temperature sensor near the bank

    Instability Phenomenon in Dip-Coating Process for Self-Assembly of Fine Particles and Design Countermeasures

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    The self-assembly of fine particles is a promising process for the production of nano-structures. In this process, aqueous suspension is often used. The spreading of the suspension on the substrate is a complex phenomenon that sometimes causes problems of instability. This paper discusses the instability phenomenon and proposes countermeasures from various aspects. It was found that special attention should be paid to the pattern design of site-selective assembly. Finally, complex structures made of particles of different sizes and materials are shown to demonstrate the improved stability after repeated dip-coating

    Self-assembly of Fine Particles Applied to the Production of Antireflective Surfaces

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    We introduce a new fabrication process for antireflective structured surfaces. A 4-inch silicon wafer was dipped in a suspension of 300-nm-diameter silica particles dispersed in a toluene solution. When the wafer was drawn out of the suspension, a hexagonally packed monolayer structure of particles self-assembled on almost the complete wafer surface. Due to the simple process, this could be applied to micro- and nano-patterning. The self-assembled silica particles worked as a mask for the subsequent reactive ion etching. An array of nanometer-sized pits could be fabricated since the regions that correspond to the small gaps between particles were selectively etched off. As etching progressed, the pits became deeper and combined with neighboring pits due to side-etching to produce an array of cone-like structures. We investigated the effect of etching conditions on antireflection properties, and the optimum shape was a nano-cone with height and spacing of 500 nm and 300 nm, respectively. This nano-structured surface was prepared on a 30 × 10-nm area. The reflectivity of the surface was reduced 97% for wavelengths in the range 400-700 nm

    Design of Structured Surfaces for Directional Mobility of Droplets

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    This paper deals with the directional mobility of droplets on structured surfaces. Structured surfaces were micro-patterned with rectangular lines and spaces of varying pitch and height in the sub-millimeter range. The material used was polydimethylsiloxane, which is hydrophobic and wettable by oil. First, we studied the effect of the structural design on the sliding angle of pure water or oil through experiments. For pure water droplets, we found that a wider pitch enhanced the directionality. On the other hand, oil droplets spread along the groove because of their low surface tension and strong capillary force. The directionality of the sliding angle of oil droplets was larger than that of pure water, especially when the groove was narrower and deeper. Second, we poured a large amount of liquid on the structure and evaluated the removal rate on the tilted surface. We found that a parallel structure enhanced the liquid mobility for both pure water and oil

    Defective function of GABA-containing synaptic vesicles in mice lacking the AP-3B clathrin adaptor

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    AP-3 is a member of the adaptor protein (AP) complex family that regulates the vesicular transport of cargo proteins in the secretory and endocytic pathways. There are two isoforms of AP-3: the ubiquitously expressed AP-3A and the neuron-specific AP-3B. Although the physiological role of AP-3A has recently been elucidated, that of AP-3B remains unsolved. To address this question, we generated mice lacking μ3B, a subunit of AP-3B. μ3B−/− mice suffered from spontaneous epileptic seizures. Morphological abnormalities were observed at synapses in these mice. Biochemical studies demonstrated the impairment of γ-aminobutyric acid (GABA) release because of, at least in part, the reduction of vesicular GABA transporter in μ3B−/− mice. This facilitated the induction of long-term potentiation in the hippocampus and the abnormal propagation of neuronal excitability via the temporoammonic pathway. Thus, AP-3B plays a critical role in the normal formation and function of a subset of synaptic vesicles. This work adds a new aspect to the pathogenesis of epilepsy

    The 3D structures and temporal variations of typhoon-driven coastal upwelling are mapped by data assimilation of travel-time data into Princeton Ocean Model (POM)

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    Data are grouped into three: First group: coastal acoustic tomography data obtained at acoustic stations H1, H2, H3 and H5, located at the periphery of the bay. (1) travel time difference data proportional to path-average current velocity (2) travel time summation data proportional to path-average sound speed (temperature) Second group: temperature array data obtained at the raft station near Nino-shima Island. The 5-min interval temperature are obtained at depths 0, 2, 4, 7, 10 and 15 m. Third group: CTD (conductivity-temperature-depth) data obtained at 10 stations (C1-C10) distributed over the bay. One-time CTD casts were done during 11:00-13:00 of September 18, 2013. Data were sampled at a 0.1-m interval at each station.Data Time Period: From September 11 to 23 GeoLocation: Hiroshima, JAPAN Dataset Progress Status: complete Use Limitations: No limitation Funding Reference: JST A-STEP program (AS242Z01178H

    船舶搭載型ADCPによる対馬海流の流向流速計測

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