Hydrolytic degradation data from a wide variety of experiments on Estane 5703, a commercial poly(ester urethane), are modeled with an AAC2 mechanism of reversible esterification and hydrolysis together with a cluster model for water concentration. The experimental conditions spanned a range of temperatures from 21 to 95 °C, relative humidities from 0 to 100%, times up to more than 30 years, and different initial molecular weights and acidities. In addition, the experiments were performed in several different laboratories with a number of different instruments and techniques. All the experimental data, both for molecular weight and acidity, are modeled with a single set of concentration‐independent rate coefficients, and the kinetic model fits the data well and constitutes a robust model of the hydrolytic degradation of this polymer. The results also show that ester hydrolysis is the dominant cause of the molecular weight loss of Estane 5703 in indoor storage at ambient temperatures and humidities. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 1136–1151, 2003

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Publication costs assisted by Chevron Research CompanyA reinvestigation of isolated hydroxyl groups on silica surfaces shows the 3750-cm-l SiOH band to be structureless and asymmetric, for wafers prepared a t pressures _<200,000 lb/in.2. Band peak positions vary linearly with temperature with a temperature coefficient of 0.0176 cm-l/deg. The log of the band halfwidths varies linearly with 1/T above -100'. Hydroxyl group rotational activation energies are about 0.9 kcal/mol. Identical surface environments have been found for hydroxyl groups on two different silicas (Cab-0-Si1 and Aerosil) by the precise spectroscopic measurements reported here. * Address correspondence t o this author a t the Jet PropulsionLaboratory, Pasadena, Calif. 91103. observed in the OH region. More recently, Van ( k~+ &~r t and coworkers claim to have resolved the OH absorption

Abstract. The wflow_sbm hydrologic model, recently released by Deltares, as part of the Wflow.jl (v0.6.1) modelling framework is being used to better understand and potentially address multiple operational and water resources planning challenges from catchment scale, national scale to continental and global scale. Wflow.jl is a free and open-source distributed hydrologic modelling framework written in the Julia programming language. The development of wflow_sbm, the model structure, equations and functionalitities are described in detail, including example applications of wflow_sbm. The wflow_sbm model aims to strike a balance between low-resolution, low-complexity and high-resolution, high-complexity hydrologic models. Most wflow_sbm parameters are based on physical characteristics or processes and at the same time wflow_sbm has a runtime performance well suited for large-scale high-resolution model applications. Wflow_sbm models can be set a priori for any catchment with the Python tool HydroMT-Wflow based on globally available datasets and through the use of point-scale (pedo)transfer functions and suitable upscaling rules and generally results in a satisfactory (0.4 ≥ Kling-Gupta Efficiency (KGE) < 0.7) to good (KGE ≥ 0.7) performance a-priori (without further tuning). Wflow_sbm includes relevant hydrologic processes as glacier and snow processes, evapotranspiration processes, unsaturated zone dynamics, (shallow) groundwater and surface flow routing including lakes and reservoirs. Further planned developments include improvements on the computational efficiency and flexibility of the routing scheme, implementation of a water demand and allocation module for water resources modelling, the addition of a deep groundwater concept and distributed computing with a focus on multi-node parallelism.