Symmetry in quantum theory: Implications for the convexity formalism, the measurement problem, and hidden variables

Symmetries are introduced into the convexity approach to physics. This allows one to make connections between classical and quantum theories by exploiting the properties of quantum mechanics on phase space. The measurement problem is discussed and many of the known no-go theorems are shown not to apply. Finally, hidden variable theories exhibiting these physical symmetries are shown to have a certain required group structure, if they exist at all.     

Molecular modeling of the intestinal bile acid carrier: A comparative molecular field analysis study

A structure–binding activity relationship for the intestinal bile acidtransporter has been developed using data from a series of bile acid analogsin a comparative molecular field analysis (CoMFA). The studied compoundsconsisted of a series of bile acid–peptide conjugates, withmodifications at the 24 position of the cholic acid sterol nucleus, andcompounds with slight modifications at the 3, 7, and 12 positions. For theCoMFA study, these compounds were divided into a training set and a test set,comprising 25 and 5 molecules, respectively. The best three-dimensionalquantitative structure–activity relationship model found rationalizesthe steric and electrostatic factors which modulate affinity to the bile acidcarrier with a cross-validated, conventional and predictive r²of 0.63, 0.96, and 0.69, respectively, indicating a good predictive model forcarrier affinity. Binding is facilitated by positioning an electronegativemoiety at the 24–27 position, and also by steric bulk at the end of theside chain. The model suggests substitutions at positions 3, 7, 12, and 24that could lead to new substrates with reasonable affinity for the carrier.     

Emission Mössbauer study of the interface between a cobalt substrate and a polyimide coating

The emission Mössbauer technique is used to study the chemical structure of the interphase formed between a cobalt substrate and a polyimide coating. The results are interpreted to indicate that the coating is bonded to the cobalt substrate by means of carboxylate bonds with Co²⁺ ions in the oxide film at the interface.     

Can an Attractive Potential Increase the Pressure of an Ideal Electron Gas?

We examine the intuitive, classical idea that an interactive system involving commonly used attractive potentials should always have a pressure which is less than that of an ideal Fermi gas. We find that quantum effects are of crucial importance and that, while this idea is normally correct, under certain circumstances, the pressure can exceed that of the ideal Fermi gas.     

CLP-type data validation guidelines for neutron activation analysis

Neutron activation analysis data quality must be validated to serve evidentiary purposes for environmental restoration and health protection projects. This paper gives a basis for determining the technical validity of neutron activation analysis data.     

First separation and characterization of cis and trans 1,2-bisaryloxy perfluorocyclobutanes

4-Bromotrifluorovinyloxybenzene (4-Br-TFVE) undergoes cyclodimerization upon heating at 150 °C affording cis and trans isomers of 1,2-bis(4-bromophenoxy)hexafluorocylcobutane. Stereoisomers were separated by selective crystallization, confirmed by single crystal X-ray, and further characterized by NMR. Remarkable difference in the solid state structures include aryl to aryl dihedral angles of 12° for the trans isomer and 88° for the cis isomer. Polymers containing roughly equal amounts of cis and trans fused perfluorocyclobutyl (PFCB) rings should be expected to have low crystallinity due to the marked difference in the two unit cells as is observed.     

Ab initio calculation of the heats of formation of CF3OH and CF2O

The heats of formation of the trifluoromethanol (CF₃OH) and carbonic difluoride (CF₂O) molecules are calculated with theoretical methods of demonstrated high accuracy. The results are used to assess the accuracy of the reported value of the heat of formation of CF₂O and to provide an accurate estimate for CF₃OH. The implications of these results for atmospheric chemistry are discussed.