In this paper, we propose a new wavelet denoising method with edge preservation for digital images. Traditionally, most denoising methods assume additive Gaussian white noise or statistical models; however, we do not make such an assumption here. Briefly, the proposed method consists of a combination of dyadic lifting schemes and edge-preserving wavelet thresholding. The dyadic lifting schemes have free parameters, enabling us to construct filters that preserve important image features. Our method involves learning such free parameters based on some training images with and without noise. The learnt wavelet filters preserve important features of the original training image while removing noise from noisy images. We describe how to determine these parameters and the edge-preserving denoising algorithm in detail. Numerical image denoising experiments demonstrate the high performance of our method.

Electrochemical detection of ethylenebis(dithiocarbamic acid) manganese zinc complex (Manzeb), a widely used insecticide, by reductive desorption from Au(111) and Au(100) has been studied. Dithiocarbamate groups containing adlayer were formed on gold single-crystal electrodes by immersing into a Manzeb aqueous solution. The electrochemical responses and the adsorption amounts were evaluated based on the reductive desorption of sulfur species from the gold surface in alkaline solution. The detection limit for Manzeb depended on the modification time and the crystallographic orientation of gold. The limits of detection were 500 nM and 100 nM when a Au(111) electrode and a Au(100) electrode were used, respectively. The surface-enhanced infrared absorption spectra of Manzeb on a Au thin film electrode in its monolayer state showed that Manzeb was adsorbed on the substrate via the dithiocarbamate moiety and the long axis of ethylenebis(dithiocarbamate) dianion was almost perpendicular to the surface.

Sensitive electrochemical detection of nereistoxin (NEX), a widely used insecticide, by reductive desorption is studied. NEX is adsorbed onto a gold single-crystal electrode via its disulfide group to form a self-assembled monolayer (SAM), which shows a reductive desorption peak in alkaline solution. The detection limit depended on the modification time and the crystallographic orientation of Au. When a Au(111) electrode was used as a substrate, the limit of detection was 10 nM. This limit was decreased to 1 nM when a Au(100) electrode was used. The NEX-SAM on a Au(111) and Au(100) electrode also showed a characteristic reductive wave, which allowed NEX to be distinguished from other similar compounds such as aminoethanthiol, N-dimethylaminoethanthiol, and aminohexanethiol.

The adsorption of methylviologen dications (MV2+) on single‐crystalline Au electrodes in both H2SO4 and HClO4 was examined. MV2+ strongly interacted with sulfate and bisulfate anions adsorbed on the Au(111) electrode surface in 0.05 M H2SO4 under a controlled potential of 1.25 V vs. the reversible hydrogen electrode (RHE). A characteristic non‐Faradaic current was observed at 1.10 V vs. RHE. When adsorption of MV2+ was carried out in 0.1 M HClO4, the electrochemical response of MV2+ was less than that obtained in H2SO4. The results show that the formation of a highly ordered sulfate/bisulfate adlayer plays an important role in the formation of condensed MV2+ layers. Examination of polycrystalline Au and Au(100) electrodes revealed a poor electrochemical response due to the surface roughness of the Au substrate, but the electrochemical detection was applicable to polycrystalline Au electrodes. A systematic investigation of the structural dependency of viologen derivatives showed that molecular size is important for electrostatic interactions with a highly ordered sulfate/bisulfate adlayer. The findings of the present study demonstrate successful detection of MV2+ at a concentration of ≤1 pM with a non‐Faradaic current.

We studied the synthesis of 1,3-butadiene via the dehydration of crotyl alcohol (2-buten-1-ol) over solid acids. Crotyl alcohol conversion and butadiene selectivity were both 95 % or more over commercial silica _ alumina catalysts. However, a sudden decrease in catalytic activity was observed during the reaction. On the basis of the fact that the deactivated catalyst was regenerated by drying at 150-200 °C, it was revealed that the main cause of the catalyst deactivation was the adsorption of water formed during the reaction and not the coke formation. An analysis of the deactivated catalyst indicated that, since the formation of Al _ OH by the hydrolysis of the Al _ O _ Al bond increased the hydrophilicity of the catalyst surface, the adsorption of water on the catalyst surface was promoted, whereas that of crotyl alcohol was probably inhibited. Moreover, on the basis of the catalyst characterization, it was concluded that silica _ alumina catalysts with few silanol groups, few alumina-rich zones, and a low Si/Al ratio were preferable.