Isolation and structures of eudesmanolides from Tanacetum cadmeum ssp. cadmeum

Eight sesquiterpene lactones, two coumarins, and two flavonoid derivatives were isolated from Tanacetum cadmeum (Boiss.) Heywood ssp. cadmeum. All compounds have been found previously in other plant species. The crystal structures of artesin and taurin are reported. Crystals of artesin (C₁₅H₂₂O₃) belong to the monoclinic space group P2₁: a = 8.300(1), b = 6.304(1), c = 13.118(2) Å, = 101.836(3)°, V = 671.8(2), Z = 2, R ₁ = 0.0291. Crystals of taurin belong to the monoclinic space group P2₁: a = 5.722(1), b = 8.279(2), c = 14.503(3) Å, = 90.025(1)° , V = 687.0(3), Z = 2, R ₁ = 0.0493. An investigation of the space group indicated a monoclinic system rather than orthorhombic.     

Application of combined Hartree-Fock-Roothaan theory to atoms with an arbitrary number of closed and open shells of any symmetry

The applicability of a combined open-shell Hartree-Fock theory of atomic-molecular and nuclear systems to the states of a single configuration which has the arbitrary symmetry of open shells is explicitly demonstrated by calculations based on the combined Hartree-Fock-Roothaan equations for atoms. As examples of an application of the combined theory using single-zeta Slater-type basis sets, the calculations have been performed for the lowest states of the lowest and excited electronic configurations of carbon and nitrogen atoms containing one-, two- and three-open shells. For the case of single-open shells for carbon and nitrogen atoms, the double-zeta basis-set calculations are also presented. The results of computer calculations for the orbitals, kinetic and total energies, linear combination coefficients and virial ratios are given.     

Propagators and renormalization transformations for lattice gauge theories. II

We continue the studies of the Paper I and extend the results of this paper to operators defined by restrictions on different scales, or by renormalization transformations of different orders.Research supported in part by the National Science Foundation under Grant PHY-82-03669     

Polaron effects on the energy levels of hydrogenic impurities in GaAs/Ga1−xAlxAs quantum well structures

The effect of electron phonon-coupling on the binding energies of impurities in GaAs/Ga_1?χAl_χAs quantum well structures is calculated. The correction becomes sizeable as the electron gets more deeply bound.     

Variation of the Kβ/Kα intensity ratios of Ti, V and Cr in halogen compounds versus excitation energy in the interval 5.5-12.1 keV

The K/K intensity ratios for Ti, V and Cr in halogen (F and Cl) compounds were investigated. Measurements were carried out at ten different energies in the 5.5-12.1 keV interval by using the secondary excitation method. K X-rays emitted by the samples were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. It was observed that the measured values are getting closer to the theoretical values with increasing excitation energy. Values obtained were compared with the theoretical ones for pure elements.     

Spaces of regular gauge field configurations on a lattice and gauge fixing conditions

We consider spaces of lattice gauge field configurations satisfying gauge invariant regularity conditions, and intersections of these spaces with a surface given by gauge fixing conditions. We prove that if these conditions are chosen properly then configurations belonging to the intersection are small and regular.Research supported in part by the National Science Foundation under Grant PHY-82-03669     

Generalized Pöschl-teller potential

From the point of view of the theory of differential equations, we present a four-parameter exactly solvable generalized Pöschl-Teller potential, related to the Jacobi polynomials, using the previously unconsidered equations.     

The He(I) and He(II) photoelectron spectra of bis (2,4,6-tri-t-butylphenyl)-diphosphene

Photoelectron spectra of the title compound have been obtained using various ionising radiations. The bands up to ～10 eV have been assigned with the aid of molecular-orbital calculations.     

Theoretical and FT-IR, FT-Raman studies of nipecotamide and its tautomers, isomers

The structure, conformers, energies and vibrational spectra of the important nipecotamide molecule have been characterized by FT-IR (mid-IR, far-IR), FT-Raman spectroscopy and by DFT calculations. The structure is optimized by B3LYP/6-311++G(d,p) calculations. All vibrational frequencies assigned in detail with the help of total energy distribution (TED). The calculated vibrational wavenumbers were compared with IR and Ra experimental data. In the most stable tautomer (NT-1), the piperidine ring adopts the chair conformation and the amide group is in the axial orientation and is stabilized by an intramolecular N-H…O hydrogen bond of 4.37 Å.