Some applications of Henkin quantifiers

We show how to approximate a Henkin formula by first order formulas. This method of approximation is then applied to problems of axiomatizing classes of structures. Dedicated to the memory of Abraham Robinson. The author is an Alfred P. Sloan Fellow.     

Copper and iron interactions with angiotensin-converting enzyme inhibitors. A study by fast-atom bombardment tandem mass spectrometry

Fast atom bombardment, combined with high-energy collision-induced tandem mass spectrometry, has been used to investigate gas-phase metal-ion interactions with captopril, enalaprilat and lisinopril, all angiotensin-converting enzyme inhibitors.Suggestions for the location of metal-binding sites are presented. For captopril, metal binding occurs most likely at both the sulphur and the nitrogen atom. For enalaprilat and lisinopril, binding preferably occurs at the amine nitrogen. Copyright 1999 John Wiley & Sons, Ltd.     

The inter-and intramolecular addition of aromatic ketone triplets to quadricyclenes: Comparison with the corresponding reactivities of norbornadiene,methylenenorbornene, methylenenorbornane and norbornene

Irradiation of acetophenone or benzophenone in the presence of norbornadiene or quadricyclene gives 1: 1-adducts. These arise via reaction of the ketone triplet with the quadricyclene. Similar reactivity is exhibited in an intramolecular sense by 7-phenacylnorbornadiene and the corresponding quadricyclene. Addition of triplet benzophenone to 5-methylene norbornene is regiospecific in contrast to expectations based on a comparison of the reactivities of 2-methylenenorbornane and norbornene. The possibility is raised that, in contrast to the simple olefins and the quadricyclenes, exciplexes formed by reaction of the rigid homoconjugated dienes with the triplet ketone are endo orientated with participation of both double bounds.     

Hanf numbers for fragments of ℶ h (A)

We describe an ordinalh(A) which plays a key role in the model theory of the admissible fragmentL _A . In particular, the Hanf number ofL _A is ℶh(A) IfL _A isL _κ=ω wherecf(k)>ω thenh(A) can be characterized as the least ordinal which is notH(k ⁺)-recursive. Financial support received from NSF Grant GP-23114 Financial support received from NSF Grant GP-23114 and the A. P. Sloan Foundation     

Characterization of crude oils using fluorescence lifetime data

The average fluorescence lifetimes of nine North Sea crude oils with API gravities of between 20 and 51 were measured using a modular, filter based, instrument developed in-house. Two pulsed light emitting diode (LED) excitation sources (460 and 510 nm) were used to excite fluorescence, the lifetime of which was measured at a range of emission wavelengths. Fluorescence lifetimes were found to vary from 1.8 to 8.2 ns with confidence intervals of +/- 0.11 ns. The average lifetimes at all emission wavelengths were linearly correlated with API gravity and with aromatic concentration with the best results being obtained with the 460 nm excitation source. Predictive models with an accuracy of +/- 7.6 API degrees were generated using partial least-squares methods from average fluorescence lifetimes measured at an emission wavelength of 500 nm using 460 nm excitation. A better correlation was found between the aromatic concentration of the oils and the ratio of the average fluorescence lifetimes at measured at 550 and 650 nm using 460 nm excitation. This led to a quantitative model with an accuracy of +/- 5.4% for aromatic concentration.