GeoTMI:Predicting quantum chemical property with easy-to-obtain geometry via positional denoising

As quantum chemical properties have a dependence on their geometries, graph neural networks (GNNs) using 3D geometric information have achieved high prediction accuracy in many tasks. However, they often require 3D geometries obtained from high-level quantum mechanical calculations, which are practically infeasible, limiting their applicability to real-world problems. To tackle this, we propose a new training framework, GeoTMI, that employs denoising process to predict properties accurately using easy-to-obtain geometries (corrupted versions of correct geometries, such as those obtained from low-level calculations). Our starting point was the idea that the correct geometry is the best description of the target property. Hence, to incorporate information of the correct, GeoTMI aims to maximize mutual information between three variables: the correct and the corrupted geometries and the property. GeoTMI also explicitly updates the corrupted input to approach the correct geometry as it passes through the GNN layers, contributing to more effective denoising. We investigated the performance of the proposed method using 3D GNNs for three prediction tasks: molecular properties, a chemical reaction property, and relaxed energy in a heterogeneous catalytic system. Our results showed consistent improvements in accuracy across various tasks, demonstrating the effectiveness and robustness of GeoTMI

Use of autotrophic sulfur-oxidizers to remove nitrate from bank filtrate in a permeable reactive barrier system

This study was conducted to evaluate the potential applicability of an in situ biological reactive barrier system to treat nitrate-contaminated bank filtrate. The reactive barrier consisted of sulfur granules as in electron donor and autotrophic sulfur-oxidizing bacteria as a biological component. Limestone was also used to provide alkalinity. The results showed that the autotrophic sulfur oxidizers were successfully colonized on the surfaces of the Sulfur particles and removed nitrate from synthetic bank filtrate. The sulfur-oxidizing activity continuously increased with time and then was maintained or slightly decreased after five days of column operation. Maximum nitrate removal efficiency and sulfur oxidation rate were observed at near neutral pH. Over 90% of the initial nitrate dissolved in synthetic bank filtrate was removed in all columns tested with some nitrite accumulation. However, nitrite accumulation was observed mainly during the initial operation period, and the concentration markedly diminished with time. The nitrite concentration in effluent was less than 2 mg-N/1 after 12 days of column operation. When influent nitrate concentrations were 30. 40. and 60 mg-N1 and sulfur content in column was 75% half-order autotrophic denitrification reaction rate constants were 31.73x10(-3). 33.3x10(-3). and 36.4x10(-3) mg(1/2)/1(1/2)min, respectively. Our data on the nitrate distribution profile along the column suggest that an appropriate wall thickness of a reactive barrier for autotrophic denitrification may be 30 cm when influent nitrate concentration is less than 60 mg-N/1. (C) 2003 Elsevier Ltd. All rights reserved.Financial support for this research was provided by Green Korea 21 Project and Brain Korea 21 Project. The authors would like to thank the Institute of Engineering Science at Seoul National University for invaluable technical assistance

Band Alignment at Au/MoS₂ Contacts: Thickness Dependence of Exfoliated Flakes

We investigated the surface potential (<i>V</i>_surf) of exfoliated MoS₂ flakes on bare and Au-coated SiO₂/Si substrates using Kelvin probe force microscopy. The <i>V</i>_surf of MoS₂ single layers was larger on the Au-coated substrates than on the bare substrates; our theoretical calculations indicate that this may be caused by the formation of a larger electric dipole at the MoS₂/Au interface leading to a modified band alignment. <i>V</i>_surf decreased as the thickness of the flakes increased until reaching the bulk value at a thickness of ∼20 nm (∼30 layers) on the bare and ∼80 nm (∼120 layers) on the Au-coated substrates, respectively. This thickness dependence of <i>V</i>_surf was attributed to electrostatic screening in the MoS₂ layers. Thus, a difference in the thickness at which the bulk <i>V</i>_surf appeared suggests that the underlying substrate has an effect on the electric-field screening length of the MoS₂ flakes. This work provides important insights to help understand and control the electrical properties of metal/MoS₂ contacts