SASAKI, Y. 1992. Resolution of resistivity tomography inferred from numerical simulation. Geophysical Prospecting 40,453-463.Some factors affecting the resolution and accuracy of resistivity tomography are examined using numerical simulation. The inversion method used is based on smoothnessconstrained least-squares and finite-element methods. An appropriate block discretization is obtained by dividing the target region into square blocks of size equal to half the minimum electrode spacing. While the effect of the damping factor on the resolution is significant, the resolution is not very sensitive to Gaussian noise as long as the damping factor is properly chosen, according to the noise level. The issue of choosing an optimum electrode array should be considered at the planning stage of a survey.When the instrumental accuracy is high, the dipole-dipole array is more suitable for resolving complex structures than the pole-pole array. The pole-dipole array gives somewhat less resolution than the dipole-dipole array but yields greater signal strength; thus, the poledipole array may be a good compromise between resolution and signal strength. The effect of an inhomogeneity located outside the target region may be very small if block discretization is done so as to represent the resistivity variations in both the target and outside regions.

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This paper describes 2-D joint inversion of MT and dipole-dipole resistivity data with the emphasis on the computer algorithm. The algorithm produces a 2-D model composed of a large number of rectangular blocks, each of which has constant resistivity. The solutions to two forward problems are based on the finiteelement method. The computation time for the partial derivatives of MT responses is reduced by using the reciprocity relation and the concept of a fictitious source. The smoothness-constrained least-squares method, together with the modified Gram-Schmidt method, is also used to stabilize the solution and avoid spurious resistivity features. Synthetic and field data examples show that the 2-D joint inversion can be effective for improving the resolution attained by the 2-D interpretation of a single kind of data set.

With the increased availability of faster computers, it is now practical to employ numerical modeling techniques to invert resistivity data for 3-D structure. Full and approximate 3-D inversion methods using the finite‐element solution for the forward problem have been developed. Both methods use reciprocity for efficient evaluations of the partial derivatives of apparent resistivity with respect to model resistivities. In the approximate method, the partial derivatives are approximated by those for a homogeneous half‐space, and thus the computation time and memory requirement are further reduced. The methods are applied to synthetic data sets from 3-D models to illustrate their effectiveness. They give a good approximation of the actual 3-D structure after several iterations in practical situations where the effects of model inadequacy and topography exist. Comparisons of numerical examples show that the full inversion method gives a better resolution, particularly for the near‐surface features, than does the approximate method. Since the full derivatives are more sensitive to local features of resistivity variations than are the approximate derivatives, the resolution of the full method may be further improved when the finite‐element solutions are performed more accurately and more efficiently.

Ta N is a very promising photocatalyst for solar water splitting because of its wide spectrum solar energy utilization up to 600 nm and suitable energy band position straddling the water splitting redox reactions. However, its development has long been impeded by poor compatibility with electrolytes. Herein, we demonstrate a simple sputtering-nitridation process to fabricate high-performance Ta N film photoanodes owing to successful synthesis of the vital TaO precursors. An effective GaN coating strategy is developed to remarkably stabilize Ta N by forming a crystalline nitride-on-nitride structure with an improved nitride/electrolyte interface. A stable, high photocurrent density of 8 mA cm was obtained with a CoPi/GaN/Ta N photoanode at 1.2 V under simulated sunlight, with O and H generated at a Faraday efficiency of unity over 12 h. Our vapor-phase deposition method can be used to fabricate high-performance (oxy)nitrides for practical photoelectrochemical applications.

Photoelectrochemical water splitting is regarded as ap romising approacht ot he production of hydrogen, and the development of efficient photoelectrodes is one aspect of realizing practical systems.I nt his work, transparent Ta 3 N 5 photoanodes were fabricated on n-type GaN/sapphire substrates to promote O 2 evolution in tandem with aphotocathode, to realize overall water splitting.F ollowing the incorporation of an underlying GaN layer,aphotocurrent of 6.3 mA cm À2 was achieved at 1.23 Vvs. areversible hydrogen electrode.The transparency of Ta 3 N 5 to wavelengths longer than 600 nm allowed incoming solar light to be transmitted to aC uInSe 2 (CIS), whicha bsorbs up to 1100 nm. As tand-alone tandem cell with as erially-connected dual-CIS unit terminated with aP t/Ni electrode was thus constructed for H 2 evolution. This tandem cell exhibited as olar-to-hydrogen energy conversion efficiency greater than 7% at the initial stage of the reaction.Hydrogen generation from water utilizing solar energy is one of the most promising means of producing hydrogen as ac lean, transportable and renewable energy. [1] In addition, overall water splitting using photoelectrochemical (PEC) cells is regarded as ap referable method of converting solar energy to obtain hydrogen. Atypical PEC cell is composed of ap hotoanode and ap hotocathode that are electrically connected to one another and immersed in an aqueous electrolyte solution. [2] Thes olar-to-hydrogen energy conversion efficiency(STH) of aPEC cell is maximized by adjusting the light-receiving area and the common operational potential of both photoelectrodes in order to balance the photocurrent from each. [1a, 2c, 3] AP EC cell having at andem configuration in conjunction with as tacked structure,i ncorporating af ront side transparent photoelectrode along with asecond photoelectrode that responds to the light transmitted through the front side photoelectrode,could potentially allow efficient water splitting. [4] Thed evelopment of transparent photoelectrodes is thus ap rerequisite for constructing such devices.PEC water splitting using Ta 3 N 5 -based photoanodes has been extensively investigated because the band structure of this material is well-suited to water splitting. [5] Liu et al. demonstrated that aT a 3 N 5 -based photoanode can generate ac urrent density of 12.1 mA cm À2 at 1.23 Vv s. ar eversible hydrogen electrode (RHE) under simulated sunlight. [6] This value is close to the theoretical limiting current density under 1s un illumination (12.9 mA cm À2 )e stimated from the band gap of Ta 3 N 5 .O ur own group has previously reported that ap hotoanode based on aT a 3 N 5 thin film prepared on aT a metal substrate can produce 7.5 mA cm À2 at 1.23 Vv s. RHE under simulated sunlight. [7] To date,t here have been few reports of PEC oxygen evolution using transparent Ta 3 N 5 -based photoanodes.H ajibabaei et al. recently reported at ransparent Ta 3 N 5 photoanode prepared on aT a-doped TiO 2 -coated SiO 2 (Ta-TiO 2 / SiO 2 )s ubstrate. [8] This Ta 3 N 5 /Ta-TiO ...

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Leukocytosis in tobacco smokers has been well recognized; however, the exact cause has not been elucidated. To test the hypothesis that tobacco nicotine stimulates neutrophils in the respiratory tract to produce IL-8, which causes neutrophilia in vivo, we examined whether nicotine induces neutrophil-IL-8 production in vitro; the causative role of NF-kappaB in its production, in association with the possible production of reactive oxygen intermediates that activate NF-kappaB; and the nicotinic acetylcholine receptors (nAChRs) involved in IL-8 production. Nicotine stimulated neutrophils to produce IL-8 in both time- and concentration-dependent manners with a 50% effective concentration of 1.89 mM. A degradation of IkappaB-alpha/beta proteins and an activity of NF-kappaB p65 and p50 were enhanced following nicotine treatment. The synthesis of superoxide and the oxidation of dihydrorhodamine 123 (DHR) were also enhanced. The NOS inhibitor, nomega-Nitro-l-arginine methyl ester, prevented nicotine-induced IL-8 production, with an entire abrogation of DHR oxidation, IkappaB degradation, and NF-kappaB activity. Neutrophils spontaneously produced NO whose production was not increased, but rather decreased by nicotine stimulation, suggesting that superoxide, produced by nicotine, generates peroxynitrite by reacting with preformed NO, which enhances the NF-kappaB activity, thereby producing IL-8. The nAChRs seemed to be involved in IL-8 production. In smokers, blood IL-8 levels were significantly higher than those in nonsmokers. In conclusion, nicotine stimulates neutrophil-IL-8 production via nAChR by generating peroxynitrite and subsequent NF-kappaB activation, and the IL-8 appears to contribute to leukocytosis in tobacco smokers.