Effects of Porous Structure of the Auxiliary Electrode on the CO2 Sensing Properties of a NASICON-based Sensor

Structural effects of the auxiliary electrode layer on the CO_2 sensing properties of NASICON (Na_3Zr_2Si_2PO_) solid electrolyte sensors have been investigated. The sensor with a macroporous Li_2CO_3-BaCO_3-based auxiliary layer showed faster CO_2 response and recovery and a smaller EMF drift against a humidity change than those observed for the sensor equipped with a dense auxiliary layer. The CO_2 response of the present sensors was slightly larger than the theoretical one. This suggests the existence of some impurities capable of reacting with CO_2 in the auxiliary layer prepared in the present study.Nagasaki Symposium on Nano-Dynamics 2008 (NSND2008) 平成20年1月29日(火)於長崎大学 Poster Presentatio

Protective role of vascular endothelial growth factor in endotoxin-induced acute lung injury in mice

<p>Abstract</p> <p>Background</p> <p>Vascular endothelial growth factor (VEGF), a substance that stimulates new blood vessel formation, is an important survival factor for endothelial cells. Although overexpressed VEGF in the lung induces pulmonary edema with increased lung vascular permeability, the role of VEGF in the development of acute lung injury remains to be determined.</p> <p>Methods</p> <p>To evaluate the role of VEGF in the pathogenesis of acute lung injury, we first evaluated the effects of exogenous VEGF and VEGF blockade using monoclonal antibody on LPS-induced lung injury in mice. Using the lung specimens, we performed TUNEL staining to detect apoptotic cells and immunostaining to evaluate the expression of apoptosis-associated molecules, including caspase-3, Bax, apoptosis inducing factor (AIF), and cytochrome C. As a parameter of endothelial permeability, we measured the albumin transferred across human pulmonary artery endothelial cell (HPAEC) monolayers cultured on porous filters with various concentrations of VEGF. The effect of VEGF on apoptosis HPAECs was also examined by TUNEL staining and active caspase-3 immunoassay.</p> <p>Results</p> <p>Exogenous VEGF significantly decreased LPS-induced extravascular albumin leakage and edema formation. Treatment with anti-VEGF antibody significantly enhanced lung edema formation and neutrophil emigration after intratracheal LPS administration, whereas extravascular albumin leakage was not significantly changed by VEGF blockade. In lung pathology, pretreatment with VEGF significantly decreased the numbers of TUNEL positive cells and those with positive immunostaining of the pro-apoptotic molecules examined. VEGF attenuated the increases in the permeability of the HPAEC monolayer and the apoptosis of HPAECs induced by TNF-α and LPS. In addition, VEGF significantly reduced the levels of TNF-α- and LPS-induced active caspase-3 in HPAEC lysates.</p> <p>Conclusion</p> <p>These results suggest that VEGF suppresses the apoptosis induced by inflammatory stimuli and functions as a protective factor against acute lung injury.</p

Free-space optical channel estimation for physical layer security

We present experimental data on message transmission in a free-space optical (FSO) link at an eye-safe wavelength, using a testbed consisting of one sender and two receiver terminals, where the latter two are a legitimate receiver and an eavesdropper. The testbed allows us to emulate a typical scenario of physical-layer (PHY) security such as satellite-to-ground laser communications. We estimate information-theoretic metrics including secrecy rate, secrecy outage probability, and expected code lengths for given secrecy criteria based on observed channel statistics. We then discuss operation principles of secure message transmission under realistic fading conditions, and provide a guideline on a multi-layer security architecture by combining PHY security and upper-layer (algorithmic) security

Porous In2O3 powders prepared by ultrasonic-spray pyrolysis as a NO2-sensing material: Utilization of polymethylmethacrylate microspheres synthesized by ultrasonic-assisted emulsion polymerization as a template

NO2-sensing properties of porous In2O3 (pr-In2O3) powders prepared by ultrasonic-spray pyrolysis employing polymethylmethacrylate (PMMA) microspheres as a template has been investigated in this study. The PMMA microspheres were synthesized in water by ultrasonic-assisted emulsion polymerization employing methyl methacrylate monomer, sodium lauryl sulfate as a surfactant and ammonium persulfate as an initiator. The PMMA microspheres synthesized was quite uniform and the particle size was ca. 60.2 nm (measured by dynamic light scattering). The microstructure of pr-In2O3 powders prepared was largely dependent on the kind of In2O3 sources. The pr-In2O3 which was prepared from In(NO3)3 as an In 2O3 source (pr-In2O3(N)) consisted of submicron-sized spherical particles with welldeveloped spherical mesopores (several tens of nanometers in pore diameter) and each oxide wall among pores was constructed with meso-sized In2O3 particles connected continuously. On the other hand, the pr-In2O3 which was prepared from InCl3 as an In2O3 source (pr-In2 O3(Cl)) was composed of a large number of dispersed meso-sized particles and a few submicron-sized dense spherical particles. In contrast, the morphology of conventional In2O3 powder (c-In 2O3) prepared by ultrasonic-spray pyrolysis of PMMAfree In(NO3)3 aqueous solution as a reference was relatively dense and roughly spherical with a diameter of ca. 100-700 nm. The responses to 1.0 and 10ppm NO2 of pr-In2O3 sensors in air were much larger than those of a c-In2O3(N) sensor in the temperature range of less than 250°C and 300°C, respectively. In addition, the response and recovery speeds of both the pr-In2O 3 sensors were much faster than those of the c-In2O 3(N) sensor, because of the well-developed porous structure of the pr-In2O3 sensors

Effect of macrostructural control of an auxiliary layer on the CO2 sensing properties of NASICON-based gas sensors

Macrostructural effects of an auxiliary electrode on the CO2 gas sensing properties of NASICON (Na3Zr2Si2PO12) solid-electrolyte sensors were investigated. The sensor with a porous Li2CO3?BaCO3-based auxiliary layer (mp-Sensor), which was prepared by utilizing constituent metal acetates and polymethylmethacrylate microspheres as a template, showed faster CO2 response and recovery and smaller cross-response against humidity changes than those obtained with a dense auxiliary layer without pores (d-Sensor). The magnitude of CO2 response of mp-Sensor was slightly larger than the theoretical one, probably due to the existence of impurities which might have reacted with CO2 in the auxiliary layer. On the other hand, c-Sensor with a thicker and dense auxiliary layer, which was prepared by commercially available carbonates, showed smaller CO2 response and larger cross-response to humidity than mp-Sensor and d-Sensor. Thus, the use of the porous auxiliary layer prepared by constituent metal acetates was confirmed to be effective for improving the CO2 sensing properties along with the large CO2 response and small cross-response to humidity

NO2 sensing properties of macroporous In2O3-based powders fabricated by utilizing ultrasonic spray pyrolysis employing polymethylmethacrylate microspheres as a template

Macroporous (mp-) In2O3-based microspheres as a NO2 sensing material were prepared by the pyrolysis of atomized In(NO3)3 aqueous solutions containing polymethylmethacrylate (PMMA) microspheres (150 nm in diameter) as a template. Well-developed spherical macropores (less than 100 nm in diameter) reflecting the morphology of the PMMA microsphere templates could be formed in the In2O3-based microspheres. The introduction of macropores into In2O3-based microspheres was very effective in improving the NO2 response of their thick films fabricated on an alumina substrate equipped with interdigitated Pt electrodes (gap size: ca. 200 μm) by screen-printing. In addition, the addition of a little amount of SnO2 to the mp-In2O3 microspheres not only lowered the resistance in air but also improved the NO2 response. NO2 sensing properties of non-stacked microspheres of the mp-In2O3 mixed with SnO2 were also investigated by utilizing nano-gap Au electrodes (gap size: ca. 200 nm). The non-stacked microspheres showed fast response and recovery speeds to NO2, because of better diffusion capability of NO2

CO-sensing properties of a NASICON-based gas sensor attached with Pt mixed with Bi2O3 as a sensing electrode

NASICON (Na3Zr2Si2PO12)-based gas sensors capable of detecting various gases (CO2, NO2, Cl2, VOC and so on) have so far been developed by many researchers. In this study, planar-type gas sensors using a NASICON disc attached with Pt mixed with Bi2O3 as a sensing electrode (Pt(nBi2O3), n (0.01?30): the amount of Bi2O3 addition (wt%)) and Pt as a reference electrode were fabricated, and their sensing properties to CO and H2 were examined in the operating temperature range of 25?300 °C in dry and wet air. The sensors obtained were denoted as Pt(nBi2O3)/Pt. All Pt(nBi2O3)/Pt sensors fabricated responded to CO at all operating temperatures tested, and the magnitude of CO response increased with a decrease in the operating temperature. In addition, the magnitude of CO response largely depended on the additive amounts of Bi2O3 to the Pt sensing electrode. The increase in the additive amount of Bi2O3 to the Pt sensing electrode (0.01 ? n ? 1) enhanced markedly the magnitude of CO response, 90% response time and CO selectivity against H2. The Pt(1Bi2O3)/Pt sensor showed a linear relationship between the CO response and the logarithm of CO concentration (1?3000 ppm) in dry air at 25 °C and the CO selectivity against H2 was enhanced in wet air, in comparison with those observed in dry air. The interfacial layer, which was formed between the NASICON and the Pt(1Bi2O3) electrode, was suggested to play an important role in improving of the CO-sensing properties