O-17 NMR spectra of ring compounds. Correlation of 17O and 13C methyl substitution parameters

The ¹⁷O NMR spectra of 22 1,3-dioxanes, four exanes, four 4-heterooxanes, four tetrahydrofurans and four 1,3-dioxolanes have been recorded and methyl substitution parameters determined for the 1,3-dioxanes. The parameters, including γ_a, correlate linearly with corresponding ₁₃C parameters for methyloxanes.     

Multiple periodic solutions for a nonlinear suspension bridge equation

We investigate nonlinear oscillations in a fourth-order partialdifferential equation which models a suspension bridge. Previouswork establishes multiple periodic solutions when a parameterexceeds a certain eigenvalue. In this paper, we use Leray-Schauderdegree theory to prove that if the parameter is increased further,beyond a second eigenvalue, then additional solutions are created.     

Operation of a superthermal ultra-cold neutron source and the storage of ultra-cold neutrons in superfluid Helium4

We report the first successful operation of a superthermal UCN source and the observation of the storage of Ultra-Cold Neutrons in superfluid Helium⁴ at Temperatures in the range 0.5–1.15K. From the observations we obtain the total cross section for UCN scattering by superfluid Helium. The temperature dependence of the total cross section is found to be consistent with calculations which include the effects of phonon absorption and phonon and roton scattering.     

Synthesis and properties of polyimidazopyrrolones

The preparation of polyimidazopyrrolones by three general synthetic methods has been presented. The effects of structure, conversion temperature, and conversion environment were determined. The polyimidazopyrrolones were shown to retain useful mechanical properties at elevated temperatures, after severe chemical treatment and after unusually high exposure to ionizing radiation. Thermogravimetric analysis of the polymers indicated the effect of structure on oxidative stability was relatively minor; furthermore, the relative stabilities of a series of eight polymers in air were not directly comparable to the order of stability in a vacuum environment.     

Rediscovering cobalt's surface chemistry

Cobalt is an active metal for a variety of commercially and environmentally significant heterogeneously catalysed processes. Despite its importance, Co's surface chemistry is less studied compared to other key industrial catalyst metals. This stems in part from the difficulties associated with single crystal preparation and stability. Recent advances in scanning probe microscopy have enabled the atomic scale study of the structural, electronic, and magnetic properties of well-defined Co nanoparticles on metal substrates. Such systems offer an excellent platform to investigate the adsorption, diffusion, dissociation, and reaction of catalytically relevant molecules. Here we discuss the current understanding of metal-supported Co nanoparticles, review the limited literature on molecular adsorption, and suggest ways that they can be used to explore Co's rich surface chemistry. Our discussion is accompanied by new high resolution scanning tunnelling microscopy data from our group, which illustrate some of the interesting properties of these complex systems.     

Possibleπ(h 11 2/3 g 7 2/−1 ) states in144Nd

High spin states of the nucleus¹⁴⁴Nd have been studied using the techniques of gamma-ray spectroscopy and the¹³⁰Te(¹⁸O,4n) reaction at 85 MeV. It is suggested that a sequence of states having J=17–24 arises from the coupling of the h ₁ ^2/3 g ₇ ^2–1 proton configuration to the f ₇ ^2/2 and f_7/2h_9/2 neutron configurations.This work was supported by the National Science Foundation and the State of Florida.     

A Linear Risk Model

A special structure optimization model is presented which includes many of the single variable risk problems that are encountered in operational problems. A risk function is assumed which is a piece-wise linear function of some random variable whose distribution is known; one seeks the value of the decision variable which minimizes expected risk. In this paper are presented the necessary and sufficient conditions for this optimization for random variables which are either continuously or discretely distributed. The important special case of a continuous risk function is discussed; multiple risk problems with a joint constraint are analyzed; and the change in policy for a small change in the distribution of the random variable is investigated. Examples illustrate the application of the model.     

Alpha 1-acid glycoprotein high-performance liquid chromatography column (EnantioPAC) as a screening tool for protein binding

An attempt was made to correlate retention behavior on a high-performance liquid chromatographic (HPLC) system employing an immobilized alpha 1-acid glycoprotein (AAG) column with AAG binding behavior for various compounds. Protein binding was assessed by propranolol displacement studies in an equilibrium dialysis system using isolated AAG. HPLC retention behavior poorly correlated with propranolol displacement from AAG. This system is not suitable for use as a screening tool for AAG affinity.