Activity concept

Attempts have been made to apply the structure-activity concept (Hansch and Leo 1995) to environmental problems, and this has been successfully applied to the rates of hydrolysis of carbamate pesticides (Wolfe et al. 1978), and of esters of chlorinated carboxylic acids (Paris et al. 1984). This has been extended to correlating rates of biotransformation with the structure of the substrates and has been illustrated with a number of single-stage reactions. Clearly, this approach can be refined with the increased understanding of the structure and function of the relevant degradative enzymes. Some examples illustrate the application of this procedure ... 

Distance and timescales involved in the water activity concept... 

The previous comparison between first and second law methods may give the false impression that the latter should always be preferred. Second law methods can be unreliable, even if a sophisticated equation is used to fit the experimental data. The problem lies in the evaluation of the equilibrium constant, which must be defined in terms of the activities of reactants and products [ 1 ]. The activity concept... 

Degenhardt, A. et al., Preparative isolation of anthocyanins by high-speed countercurrent chromatography and application of the color activity concept to red wine. J. Agric. Food Chem. 48, 5812, 2000. 

Glycoside Synthesis Based on the Remote Activation Concept An Overview... 

The first generation of an O-unprotected glycosyl donor that could be activated based on the remote activation concept was exemplified by 2-pyridylthio p-D-glucopyranoside 1 [10], which could be easily prepared from acetobromoglucose [11]. Treatment of 1 with a variety of alcohols in the presence of mercuric nitrate in acetonitrile solution led, within a few minutes, to the corresponding O-glycosides, with isolated yields and a/p ratios varying from methanol (70 30, 95%), to 2-propanol (62 38 77%), and cyclohexanol (51 49, 75%) Scheme 2. Identical results were obtained when 2-pyrimidinylthio p-D-... 

Scheme 1 The design of glycosyl 2-pyridylcarbonate or glycosyl 2-thiopyridylcarbonate (TOP-CAT) donors based on the remote activation concept.

K. Koidc, M. Ohno, and S. Kobayashi, A new glycosylation reaction based on a remote activation concept Glycosyl 2-pyridinecarboxylate as a novel glycosyl donor. Tetrahedron Lett. 32 7065 (1991). 

As indicated above, the equilibrium partial vapor pressure of water defines its thermodynamic state. The thermodynamic state is usually described by use of the water activity concept, which defines water activity as aw — [pjpw Ir... 

T. Hofmann, Studies on the influence of the solvent on the contribution of single Maillard reaction products to the total color of browned pentose/alanine-solutions — a quantitative correlation by using the color activity concept, J. Agric. Food Chem., 1998, 46, 3912-3917. 

In accordance with the probabilistic nature of the biological activity concept, the most relevant methods for prediction of activity are those based on probabilistic theory and mathematical statistics, and the purpose of prediction is the complete relationship Pr(Doze) = P D). 

The object of this book is to provide an introduction to electrochemistry in its present state of development. An attempt has been made to explain the fundamentals of the subject as it stands today, devoting little or no space to the consideration of theories and arguments that have been discarded or greatly modified. In this way it is hoped that the reader will acquire the modern point of view in electrochemistry without being burdened by much that is obsolete. In the opinion of the writer, there have been four developments in the past two decades that have had an important influence on electrochemistry. They are the activity concept, the interionic attraction theory, the proton-transfer theory of acids and bases, and the consideration of electrode reactions as rate processes. These ideas have been incorporated into the structure of the book, with consequent simplification and clarification in the treatment of many aspects of electrochemistry. 

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