To evaluate possible risk factors for recurrence after primary resection of ileocolic Crohn's disease, the clinical course of 48 consecutive patients operated on over a 27-year period were reviewed. Median follow-up was 10 years (range, 3-27 years). The probability of not having a recurrence and the probability of not undergoing a second resection were 0.476 (+/- 0.191, 95% confidence limits) and 0.701 (+/- 0.180), respectively, after 10 years. None of the possible risk factors examined--sex, age at the primary resection, length of preoperative history, length of bowel involvement, failure of preoperative medical treatment, and residual microscopic disease at resections lines--significantly influenced the risk of recurrent disease (P greater than 0.05, log-rank test); however, there was a trend towards a higher risk of recurrence for the patients who had received medical treatment preoperatively. In the present study it was not possible to identify any factors that influenced the risk of recurrence.

The free radicals CH3, SiH3, GeH3, and SnH3 have been produced in a krypton matrix at 4.2°K by γ irradiation of the matrix containing dilute concentrations of CH4, SiH4, GeH4, and SnH4. The electron spin resonances indicate free or restricted rotation for all the radicals in the matrix. Observed anisotropies in g show that SiH3, GeH3, and SnH3execute restricted rotation about an axis perpendicular to the symmetry axis. From the observed values for the rotating radicals, the axially symmetric principal g values for the static radicals are derived as follows: for SiH3, g∥ = 2.003, g⊥ = 2.007; for GeH3, g∥ = 2.003, g⊥ = 2.017; for SnH3, g∥ = 2.003, g⊥ = 2.025. Hyperfine structure caused by 29Si is observed for SiH3 with isotropic coupling constant Af = 266 G and anisotropic coupling Aμ = 24 G. These couplings reveal 22% scharacter in the orbital of the unpaired electron, which indicates that the radical is nonplanar with bond angles of 110.6°. Probably GeH3 and SnH3 are also nonplanar. The magnitudes of the isotropic proton couplings are: 23, 8.1, 15, and 26 G, respectively, for CH3, SiH3, GeH3, and SnH3. The coupling of SiH3 is probably negative like that for CH3, but that of GeH3 and of SnH3 may be positive.

Free radicals produced by 'Y irradiation of PHa and of AsHa in dilute solution in a krypton matrix at 4.2°K have been studied with electron spin resonance. For the PHa solution, PH2 radicals as well as Hand P atoms were observed. For the AsHa solutions, only H and As atoms were observed. For the PH2 radicals, the observed ESR constants are: A/(alp) =80 G, A/(H) =18 G, and g=2.0087. For the P atoms, A/(alp) = 30.5 G and g=2.0027. For the As atoms, A/(75As) = 11.2 G and g= 1.9975. From the P and H couplings it is concluded that the P bonding orbitals of PH2 are SP2 hybrids with 27% s character. From the line shapes it is concluded that the PH2 radical rotates in the krypton matrix.

The microwave spectra of the CD3 species and of seven monosubstituted isotopic species of CH3CH=C=O have been examined, and a complete structure of methylketene has been obtained by the substitution method. The structural parameters found are: C=O=1.171, C=C=1.306, C–C=1.518, C–H (vinyl)=1.083, and C–H (methyl)=1.083 or 1.11 Å (see text). The ketene group is linear, and the methyl group is staggered, ∠CCC=122.6°, ∠C(1)C(2)H(2)=113.7°, and ∠HCH=109.9° or 108.8°. The barrier splittings were used to determine the value of the barrier to hindered rotation and the angle between the methyl-axis and the principal-axis system for each of the monosubstituted species; V3=1177±20 cal/mole. The dipole moment of methylketene was measured on the 21,2→31,3transition, yielding μa=1.755, μb=0.35, μ=1.79 D.