First-principles kinetic modeling in heterogeneous catalysis: an industrial perspective on best-practice, gaps and needs

Electronic structure calculations have emerged as a key contributor in modern heterogeneous catalysis research, though their application in chemical reaction engineering remains largely limited to academia. This perspective aims at encouraging the judicious use of first-principles kinetic models in industrial settings based on a critical discussion of present-day best practices, identifying existing gaps, and defining where further progress is needed

Per capita interactions and stress tolerance drive stress-induced changes in biodiversity effects on ecosystem functions

Environmental stress changes the relationship between biodiversity and ecosystem functions, but the underlying mechanisms are poorly understood. Because species interactions shape biodiversity-ecosystem functioning relationships, changes in per capita interactions under stress (as predicted by the stress gradient hypothesis) can be an important driver of stress-induced changes in these relationships. To test this hypothesis, we measure productivity in microalgae communities along a diversity and herbicide gradient. On the basis of additive partitioning and a mechanistic community model, we demonstrate that changes in per capita interactions do not explain effects of herbicide stress on the biodiversity-productivity relationship. Instead, assuming that the per capita interactions remain unaffected by stress, causing species densities to only change through differences in stress tolerance, suffices to predict the stress-induced changes in the biodiversity-productivity relationship and community composition. We discuss how our findings set the stage for developing theory on how environmental stress changes biodiversity effects on ecosystem functions

Hydrogen radical additions to unsaturated hydrocarbons and the reverse β-scission reactions: modeling of activation energies and pre-exponential factors

The group additivity method for Arrhenius parameters is applied to. hydrogen-addition to alkenes and alkynes and the reverse beta-scission reactions, an important famliy of reactions in thermal processes based on radical chemistry. A consistent set of group additive values for 33 groups is derived to calculate the activation energy and pre-exponential factor for a broad range of hydrogen addition reactions. Thee;group additive values are determined from CBS-QB3 ab-initio-calculated rate coefficients. A mean factor of deviation of only two between CBS-QB3 and experimental rate coefficients for seven reactions in the range 300-1000 K is found. Tunneling. coefficients for these reactions were found to be significant;below 400 K and a correlation accounting for tunneling is presented. Application of the obtained group additive values to predict the kinetics for a set of 11 additions and beta-scissions yields rate coefficients within a factor of 3.5 of the CBS-QB3 results except for two beta-scissions with severe steric effects. The mean factor of deviation with respect to experimental rate coefficients of 2.0 shows that the group additive method with tunneling corrections can accurately predict the kinetics and is at least as accurate as the most commonly used density functional methods. The constructed group additive model can hence be applied to predict the kinetics of hydrogen radical additions for a broad range of unsaturated compounds

Arkansas Soil Fertility Studies 1998

Rapid technological changes in crop management and production require that the research efforts also be presented in an expeditious manner. The contributions of soil fertility and fertilizers are major production factors in all Arkansas crops. The studies contained within will allow producers to compare their practices with the university’s research efforts. Additionally, soil test data and fertilizer sales are presented to allow comparisons among years, crops, and other areas within Arkansas

Consumer perception and behaviour towards tropical fruits in Belgium

Increased health consciousness and growing importance consumers attach to fruit in the diet lead to an increasing demand for various tropical fruits in Europe. Also food industries are making greater use of novel tropical fruits to meet the growing interest in innovations in healthy food products. The introduction of food products with novel tropical fruits in Europe can only be successful if consumers’ demand are taken into consideration. This PhD gains insight in perceptions and consumption behaviour among Belgian consumers towards tropical fruits that are not yet common on European markets. Findings indicate that consumers have a positive attitude towards tropical fruit consumption. Pleasure seeking, together with consumers’ beliefs that tropical fruits and their products are healthy, nutritious, special and attractive, form the major drivers. Taste is predominant, whereas unfamiliarity with tropical fruits and the perceived high acquisition prices form the main barriers for purchase and consumption. Tropical fruit juices are considered intrinsically healthy. Additional information about health-related benefits through the use of claims is not seen as a persuasive tool for their purchase. Nevertheless, claims seem to influence consumers’ behaviour, particularly when the ‘claim-carrier’ combination is optimal. Fruit juices with açaí may have a potential for successful commercialisation on the West-European market. Indications are the current trend of healthy eating habits, açaí’s nutritional properties, and the existence of processing industries and a well-developed market in the country of production. However, besides shortcomings on the supply side, unfamiliarity with açaí and its flavour, as well as the incomplete knowledge of its nutritional profile, may hamper its introduction. This research indicates that consumers may be willing to accept açaí fruit juices, but only up to a certain açaí concentration. Açaí fruit juices do not benefit much from providing additional health information. The findings indicate that purchase behaviour is most notably driven by sensory pleasure and less by perceived health benefits. The obtained findings are pertinent to different actors along the tropical fruit chain. The study stresses the importance for further research, focussing on 1) consumer segmentation, 2) familiarity, 3) nutrient profiles, 4) nutrition and health claims, and 5) sustainability issues