Evidence for an anisotropic contribution to 3 J FF from the 19F N.M.R. spectrum of hexafluorocyclopropane dissolved in a nematic phase

Analysis of the fluorine N.M.R. spectrum of a sample of hexafluorocyclopropane dissolved in p-ethoxybenzylidene-p-n-butylaniline (EBBA) has given the magnitudes and relative signs of three anisotropic and three isotropic coupling constants. The anisotropic couplings ² T _FF and ³ T _FF(cis) appear to be entirely dipolar in origin, whereas the value of ³ T _FF(trans) can be considered as 86 per cent dipolar, the remaining 14 per cent being attributed to an anisotropy in the electron-coupled spin-spin interaction.     

Fourth-order finite difference methods for three-dimensional general linear elliptic problems with variable coefficients

In this article, we give a simple method for deriving finite difference schemes on a uniform cubic grid. We consider a general, three-dimensional, second-order, linear, elliptic partial differential equation with variable coefficients. We derive two simple fourth-order schemes. When the coefficients of the second-order mixed derivatives are equal to zero, the fourth-order scheme requires only 19 grid points. When the coefficients of the mixed derivatives are not equal to zero and the coefficients of U_xx, U_yy, and U_zz are equal, we require the 27 points of the cubic grid. Numerical examples are given to demonstrate the performance of the two schemes derived. There does not exist a fourth-order scheme involving 27 grid points for the general case.     

Cyclisation reactions of bis-protected guanidines

The cyclisation of N-allyl- and N-homoallylguanidines using DMDO or I₂/K₂CO₂ leading to novel heterocycles is reported.     

A dynamical model for gravitation

A gravitational model is proposed that relates the terrestrially measured value of the gravitational constantG directly to the density and angular velocity of the galaxy. The model indicates a constant scalar value forG within most regions of our galaxy, but predicts thatG will be different in other galaxies and zero in intergalactic space. The model offers explanations for galactic cluster stability, discrepancies in terrestrial measurements ofG, and atomic particle stability. The model also provides a causal relationship between strong, electromagnetic, weak, and gravitational interactions. The two postulates required for the proposed model reduce to two assumptions made in GRT in regions whereG is constant; these postulates are consistent with the existence of a 2.7 K blackbody background radiation.     

Platinum-195 NMR studies of Pt(LL)2 (LL = −S2PR2, −S2P(OR)2, −S2CNR2) and their derivatives with phosphorus containing ligands

Platinum-195 NMR spectra have been recorded for CH₂Cl₂ solutions of a range of Pt(LL)₂ (LL = ^?S₂PR₂, ^?S₂P(OR)₂, ^?S₂CNR₂) and their derivatives with phosphorus containing ligands. Platinum chemical shifts cover a range of almost 2000 ppm.