Exchange Reactions between Alkanethiolates and Alkaneselenols on Au{111}

When alkanethiolate self-assembled monolayers on Au{111} are exchanged with alkaneselenols from solution, replacement of thiolates by selenols is rapid and complete, and is well described by perimeter-dependent island growth kinetics. The monolayer structures change as selenolate coverage increases, from being epitaxial and consistent with the initial thiolate structure to being characteristic of selenolate monolayer structures. At room temperature and at positive sample bias in scanning tunneling microscopy, the selenolate-gold attachment is labile, and molecules exchange positions with neighboring thiolates. The scanning tunneling microscope probe can be used to induce these place-exchange reactions

Sympathy, Opacity and Palatalization in English

This paper examines Palatalization in English to discuss the issue of opacity. The paper shows that English Palatalization involves opacity and thus poses challenge to mainstream Optimality Theory (Prince and Smolensky 1993). In derivational terms, Palatalization in English requires intermediate representations, neither input nor output. The intermediate representations cannot be directly managed by output-oriented Optimality Theory (OT). This paper argues that McCarthy's (1997) Sympathy Theory, which assumes a constraint termed selector and a constraint regulating the relation between a failed, sympathetic candidate and an optimal candiate, is the most successful theory available to settle the opacity problem observed in English Palatalization.Supported by the Grant for the Reform of University Education under the BK21 Project of SNU

An Analysis of Embedding Impedance for Q-Band Waveguide Gunn Oscillator With Resonance Post

The oscillation frequency tuning range of waveguide Gunn oscillator and its stability depend sensitively on the dimensions of the resonator. Therefore the embedding impedances with the various dimensions of the resonator for Q-band (33~50 GHz) Gunn oscillator are calculated by using HFSS (High Frequency Structure Simulator). In this paper the comparisons between theoretical results of embedding impedances as a function of frequency and that of experimental results are described. And the oscillation frequency range could be predicted by using the theoretical evaluation methods which were proposed in this paper. It shows that post size has an effect on the frequency tuning characteristics of Gunn oscillator

Comparison of numerical schemes for improved prediction model of fecal indicator bacteria in a riverine system

Different numerical schemes for the fate and transport models of fecal indicator bacteria (FIB) were used to predict the concentration of FIB in a creek, which were then compared to a steady state model (QUAL2E). Escherichia coli (EC) and enterococci bacteria (ENT) were selected as representative FIB to compare the model performance under different flow and weather conditions in the Gwangju Creek in Korea. The results revealed that model accuracy of the forward time centered space (FTCS) scheme is the highest compared to the upstream, Dufort-Frankel, Crank-Nicolson methods and steady state model (QUAL2E) under dry weather conditions. In wet weather conditions, however, the upstream scheme shows the best performance among the five models. The upstream scheme thus represented a potential method for predicting the fate and transport of FIB originating from nonpoint sources during the rainy season. This study demonstrates that prediction results could vary in response to different numerical schemes and that the amount of discrepancy between the observed and predicted results can be quite significant. We expect that this study could be applied to the water quality forecasting system as a real time management in near future.clos