Finite computable dimension and degrees of categoricity

We first give an example of a rigid structure of computable dimension 2 such that the unique isomorphism between two non-computably isomorphic computable copies has Turing degree strictly below ${\mathbf{0}}^{″}$, and not above ${\mathbf{0}}^{\prime }$. This gives a first example of a computable structure with a degree of categoricity that does not belong to an interval of the form $[{\mathbf{0}}^{(\alpha )},{\mathbf{0}}^{(\alpha +1)}]$ for any computable ordinal α. We then extend the technique to produce a rigid structure of computable dimension 3 such that if ${\mathbf{d}}_0$, ${\mathbf{d}}_1$, and ${\mathbf{d}}_2$ are the degrees of isomorphisms between distinct representatives of the three computable equivalence classes, then each ${\mathbf{d}}_i<{\mathbf{d}}_0\oplus {\mathbf{d}}_1\oplus {\mathbf{d}}_2$. The resulting structure is an example of a structure that has a degree of categoricity, but not strongly.     

First spin flipping of a stored spin-1 polarized beam

We recently studied spin flipping of a 270 MeV vertically polarized deuteron beam stored in the Indiana University Cyclotron Facility Cooler Ring. We adiabatically swept an rf solenoid's frequency through an rf-induced spin resonance and observed its effect on the deuterons' vector and tensor polarizations. After optimizing the resonance crossing rate and maximizing the solenoid's voltage, we measured a vector spin-flip efficiency of 94.2%+/-0.3%. We also found striking behavior of the spin-1 tensor polarization.     

Measurement of the absolute n p scattering differential cross section at 194 MeV

We describe a double-scattering experiment with a novel tagged neutron beam to measure differential cross sections for np backscattering to better than +/-2% absolute precision. The measurement focuses on angles and energies where the cross section magnitude and angle dependence constrain the charged pion-nucleon coupling constant, but existing data show serious discrepancies among themselves and with energy-dependent partial-wave analyses. The present results are in good accord with the partial-wave analyses, but deviate systematically from other recent measurements.     

Optically active tricarbonyl(cyclohexadienyl)iron(1+) salts: Synthetic equivalents to spatially directed organic cations

Optically active tricarbonyl (cyclohexdienyl)iron(1+) salts I, II and III are examples of olefin complexes with moleoular asymmetry due to coordination uith a transition metal. Their reactions serve to direct the eventual specific formation of a new chiral centre of known absolute configuration. The absolute configuration of the 2-methoxy-5-methyl salt I is defined its application to the asymmetric synthesis of λ-disubstituted cyclohexenones is described.     

Ribonucleosides and ribonucleotides derived from 5-acetyluracil

5-Acetyluridine has been obtained by condensing the trimethylsilyl derivative of 5-acetyluracil with 2,3,5-tri-O-benzoylribofuranosyl chloride and removing the blocking groups with sodium methoxide. Removal of the benzoyl groups was relatively slow; by the use of I molecular proportion of sodium methoxide at 20°, 5-acetyl-5′-O-benzoyluridine was obtained. Reduction of 5-acetyluridine with sodium borohydride gave 5-(1-hydroxyethyl)uridine. 5-Acetyl-2′,3′,-O-isopropylideneuridine upon phosphorylation and removal of the blocking group gave 5-acetyluridine 5′-phosphate which was converted via its morpholidate into 5-acetyluridine 5′-diphosphate. Attempts to polymerise this compound by means of polynucleotide phosphorylase were unsuccessful. The diphosphate acted as a weak inhibitor of the enzyme.     

The gauge in general relativity. II

The present paper and a companion work are intended as one possible realization of a non-customary gauge theory of general relativity-as set forth in only broad outline in an earlier work. In this first paper, it is found that both radar echo delay and the perihelion shift differ slightly from their customary expressions. Unfortunately, it is also found that the usual statement of the principle of equivalence does not hold in the present formulation. Finally, in the second paper, a single cosmological model is investigated that appears to be promising.This work forms part of a Ph.D. dissertation by L.S.