A flash photolysis resonance fluorescence investigation of the reactions of Oxygen O(3P) atoms with aliphatic ethers and diethers in the gas phase

Rate constants for the gas phase reCedex 2, Franceactions of O(³P) atoms with a series of symmetric aliphatic ethers have been determined using the flash photolysis resonance fluorescence technique over the temperature range 240–400 K. The Arrhenius parameters derived from these data are (in units of cm³ molecule ^?1 s^?1): The error limits are two standard deviations derived from the least-squares fit. Rate constants for several other ethers were determined only at 298 K. The values obtained were (in units of 10^?14 cm³ molecule^?1 s^?1): tetrahydrofuran (37.5 ± 1.1); 1,4?dioxane 1(6.81 ± 0.46); diethoxymethane (40.4 ± 1.8); ethyl -t-butyl ether (37.0 ± 1.3); and methyl-t-amylether (57.3 ± 2.3).     

Ein invariantes Vektorraumfeld auf einem reduktiven,lokal-symmetrischen homogenen Raum ist involutorisch

Ohne Zusammenfassung     

Certified reference materials for the quality control of environmental analysis within the standards,measurements and testing programme (formerly BCR)

A great number of analyses is performed every year, the results of which are used for many purposes, e.g. the quality of goods and food, the status of quality of the environment or the health of patients. The accuracy of these results is a prerequisite for a good interpretation of the data obtained. One of the most powerful tool for achieving quality control of chemical analysis is to use reference materials (RMs) and certified reference materials (CRMs). These materials are necessary for one or more of the following items: method validation (CRMs), monitoring of the state of statistical control (RMs), samples in inter-comparisons (RMs), etc. The requirements and use of RMs and CRMs in chemical analysis are described, with special emphasis on environmental analysis, and some examples of environmental materials currently in production within the Standards, Measurements and Testing Programme (formerly BCR) of the European Commission are given.     

Effective conductivity and skew Brownian motion

We consider heat conduction in a periodic body which is composed of finitely many different components. The effective conductivity is represented in terms of skew Brownian motion. The representation formula is a fluctuation-dissipation relation. The dissipation term in this formula is related to the transmission of heat through the surface separating the different components of the body; it is described by the skew reflections of Brownian motion at these surfaces. The problems caused by the discontinuity of the microscopic conductivity are handled in the framework of Dirichlet forms.     

Pinning of an interface by a weak potential

We prove that in a two-dimensional Gaussian SOS model with a small attractive potential the height of the interface remains bounded no matter how small the potential is; this is in sharp contrast with the free situation in which the interface height diverges logarithmically in the thermodynamic limit.     

Approaches toward the synthesis of 2,5-disubstituted-1,3-thiazolidines

Synthetic approaches for new 2,5-disubstituted-1,3-thiazolidines are described. Steric and electronic effects of the N-substituent of the thiazolidine ring represent the major parameter in the rearrangement process. The nmr studies demonstrate that N-unsubstituted 2,5-disubstituted-1,3-thiazolidines exist as epimeric mixture, while the corresponding N-acetylated analogues exist as a conformer mixture.     

Modules with scalar product

The divergent scalar product of some nonnormalizable states in one dimension is redefined by an extension of the domain of c-numbers.