Hydrogen titanate (H 2 Ti 3 O 7 ) nanotubes (TNTs) have been synthesized by a one-step hydrothermal processing. Lactate oxidase (LOx) enzyme has been immobilized on the three-dimensional porous TNT network to make an electrochemical biosensor for lactate detection. Cyclic voltammetry and amperometry tests reveal that the LOx enzyme, which is supported on TNTs, maintains their substrate-specific catalytic activity. The nanotubes offer the pathway for direct electron transfer between the electrode surface and the active redox centers of LOx, which enables the biosensor to operate at a low working potential and to avoid the influence of the presence of O 2 on the amperometric current response. The biosensor exhibits a sensitivity of 0.24 μA cm −2 mM −1 , a 90% response time of 5 s, and a linear response in the range from 0.5 to 14 mM and the redox center of enzyme obviates the need of redox mediators for electrochemical enzymatic sensors, which is attractive for the development of reagentless biosensors.
We present a numerical study of nanosecond pulsed dielectric barrier discharge (DBD) actuator operating in quiescent air at atmospheric condition. Our study concentrates on plasma discharge induced fluid dynamics and on exploration of parametric space of interest for voltage pulse in an attempt to shed some light into elucidation of the mechanisms whereby the generated shock wave propagates through and affects the external flow. Specifically, a one-dimensional, self-similar, local ionization kinetic model recently developed to predict key parameters of nanosecond pulsed plasma discharge is coupled with the compressible Navier-Stokes equations possibly for the first time. Within the considered range of parameters of the plasma model which is justified for the modeling of surface nanosecond pulsed discharge at atmospheric pressure, our coupled method is able to provide satisfactory prediction of the shock structure generated by the actuator for comparison with experiment, not only in the qualitative shock wave shape but also in quantitative shock front displacement. We provide a comprehensive analysis of the gas heating, shock wave initiation and evolution processes. For example, the characteristic time of the rapid localized heating responsible for shock wave generation, which is yet to be quantified experimentally, is found to be ∼350 ns. We conduct a parametric investigation by varying the peak voltage from 10 kV to 50 kV and rise time from 5 ns to 150 ns. The pressure wave whose behavior is found to be dominated by input voltage amplitude, introduces highly transient, localized disturbance to the quiescent air. In addition, the vortex induced by the shock passage is relatively weak. The interplay of the induced flows by a few successive plasma discharges operating at continuous mode does not appear to be significant, especially at low voltage amplitude.
We show results on how the morphology of a ZnO layer can have a big impact on the random lasing threshold of the material. Plasma-enhanced chemical vapor deposition method is used to grow ZnO layers on sapphire substrates. The morphologies and structures of ZnO are observed to undergo transition when growth temperature decreases from 750 to 100 °C: the deposited ZnO changes from crystalline films to nanocrystalline films with columnarshaped grains, then to well-aligned ZnO nanorods, and finally to randomly oriented irregularshaped grains. ZnO nucleation and surface diffusion rates, coalescence between crystal grains, and preferential growth along c-axis play important roles in this transition from continuous films to nanorods. Random lasing properties of our ZnO films and nanorods are studied. The scattering ability of ZnO is critical to control the lasing properties. The lowest lasing thresholds are observed for ZnO films grown between 500 and 600 °C when the films have columnar-shaped grains and not at 750 °C when the ZnO layer has a continuous crystalline film. Calculations based on quasi-2D random lasing are consistent with the experimental results of lasing threshold measurements.
Porous and sub‐micrometer tubes made of textured GaN nanoparticles have been synthesized by an in situ chemical reaction and characterized by X‐ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and photoluminescence (PL) and Raman spectroscopies. The in situ reaction involves thermal decomposition and nitridation of 1D gallium oxyhydroxide (GaOOH) at temperatures in the range of 700–900 °C. The 1D shape of the precursor GaOOH is maintained in the resultant GaN tubes. The GaN nanocrystals (estimated to be about 15 nm in size) are found to be highly oriented with respect to each other in the tube structure, with the [110] GaN direction parallel to the tube axis. The growth mechanism of the tube structure has also been studied. β‐Ga2O3 is found to be an intermediate phase between the starting GaOOH precursor and the final GaN product. The growth mechanism involves decomposition of GaOOH, which produces β‐Ga2O3 tubes with hollow interiors, and nitridation of β‐Ga2O3, which leads to growth of textured GaN nanocrystals. Based on the growth mechanism, tubular structures with either quasi‐circular or rectangular cross section are selectively synthesized by controlling the heating rate and calcination temperature. This in situ chemical reaction method provides a new route for synthesizing 1D hollow nanostructures.
The antifatigue effects of the hot-water extract of longan (Dimocarpus longan Lour.) seeds were studied in mice. Longan seed polysaccharides were administered at doses of 50, 100, 200 and 400 mg/kg and antifatigue activity was evaluated using a swimming test, along with the determination of serum urea nitrogen, hepatic glycogen and blood lactic acid content. The results show that longan seed polysaccharides, in doses ranging from 50 to 100 mg/kg, extended swimming time, increased hepatic glycogen (p < 0.01, n = 10), reduced blood urea nitrogen (p < 0.01, n = 10) and decreased blood lactic acid (p < 0.01, n = 10) in the mice. Therefore longan seed polysaccharides may have potential as an antifatigue agent.
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