Crystal structures of some niobium and tantalum oxides. VII. K4+5xTa16−xO42 (x ≈ 0.3)

K_4+5xTa_16?xO₄₂ crystallizes in the hexagonal system with unit-cell dimensions (from single-crystal data) a = 9.085(6), c = 12.254(8) Å and space group $\text{P6}{}_3\text{mcm}\text{, Z = 1}$. The structure was solved by Patterson and Fourier techniques and refinement by full-matrix least-squares methods using 271 reflections, measured by counter techniques, with I ? 3.5 σ (I), resulted in an R of 0.060 (R_w = 0.051). The structure consists of units of six octahedra, edge- and corner-shared to one another, that are linked by corner sharing through a single octahedron. This structure provided the “key” to other structures in the K₂O:Ta₂O₅ and Rb₂O:Nb₂O₅ systems. Its significance in this respect is discussed.     

Direct decays from superdeformed states in 192Pb observed using time-correlated gamma-ray spectroscopy

Correlations of decays above and below isomeric states in the normally deformed minimum of 192Pb have been used to identify discrete transitions in the decay of the superdeformed (SD) band. The data establish the absolute excitation energy of the lowest observed SD level as 4.425 MeV. Extrapolation to the bandhead indicates that the excitation energy of the superdeformed well in 192Pb is 0.5 MeV lower than in the heavier isotope 194Pb. The results confirm the trend to decreasing excitation energy with decreasing neutron number predicted by both a macroscopic Strutinsky method approach and microscopic mean field calculations.     

Organometallic complexes containing the bridging group N,N′-o-phenylenebis(salicylideneimine); crystal and molecular structure of μ-N,N′-o-phenylenebis(salicylideneiminato)bis(2-C,N-acetophenoneoximepalladium(II))

The reactions of the conjugate base of (methylmethoxycarbene)pentacarbonylchromium(0) with epoxides and with methyl bromoacetate give alkylated carbene complexes which cannot be obtained by previous synthetic routes.     

Minimum dissipative relaxed states in toroidal plasmas

Relaxation of toroidal discharges is described by the principle of minimum energy dissipation together with the constraint of conserved global helicity. The resulting Euler-Lagrange equation is solved in toroidal coordinates for an axisymmetric torus by expressing the solutions in terms of Chandrasekhar-Kendall (C-K) eigenfunctions analytically continued in the complex domain. The C-K eigenfunctions are obtained as hypergeometric functions that are solutions of scalar Helmholtz equation in toroidal coordinates in the large aspect-ratio approximation. Equilibria are constructed by assuming the current to vanish at the edge of plasma. For the m=0, n=0 (m and n are the poloidal and toroidal mode numbers respectively) relaxed states, the magnetic field, current, q (safety factor) and pressure profiles are calculated for a given value of aspect-ratio of the torus and for different values of the eigenvalue λ _{r 0}. The new feature of the present model is that solutions allow for both tokamak as well as RFP-like behaviour with increase in the values of λ _{r 0}, which is related directly to volt-sec in the experiment.