A new ent-norabietant diterpenoid from roots of Euphorbia lathyris L.

A new highly oxidized ent-norabietane diterpenoid named lathyrisol A (1) was isolated from roots of Euphorbia lathyris L. The structure and absolute configuration of 1 were elucidated on the basis of data obtained by HRESIMS, NMR, and the Cu-Kα radiation X-ray diffraction analysis. This compound is the first example of naturally occurring norabietane diterpenoid with an exocyclic olefin at the C-4 position.     

TDPAC and emission Mössbauer spectroscopy of99Ru in YBa2Cu3O7−x

The hyperfine interactions of⁹⁹Ru(⁹⁹Rh) in YBa₂Cu₃O_7–x withx<0.2 andx1 were studied by means of TDPAC and emission Mössbauer spectroscopy. The superconductor YBa₂Cu₃O_7–x withx<0.2 was prepared by conventional heat treatment in oxygen, the semiconductor withx1 by heating the superconductor under a reduced pressure. The TDPAC and Mössbauer measurements show that Ru ions exclusively occupy the Cu-1 site, which forms one-dimensional Cu-O chains in the orthorhombic phase.     

Defect-fluorite oxides: Ln (Eu and Gd) Mössbauer study coupled with new defect-crystal-chemistry model

A recently proposed lattice-parameter (a ₀(ss)) model for parent fluorite-type MO₂-LnO_1.5 solid solutions (M^4?+? ?=? Ce and Th; Ln^3?+? ?=? lanthanide) has been extended to more complex LnO_1.5-stabilized zirconia (hafnia) (M^4?+? ?=? Zr(Hf)) with pyrochlore-type ordering and its-associated broad a ₀(ss) hump, using key Ln (Eu and Gd)-Mössbauer and related local-structure data.     

Nonlocal stress field of interface dislocations

Summary The basic theory of nonlocal elasticity is stated with emphasis on the difference between the nonlocal theory and classical continuum mechanics. The concept of Nonlocal Interface Residual (NIR) is introduced in nonlocal theory. With the concept of NIR and the nonlocal constitutive equation, we calculate nonlocal stresses due to an edge dislocation on the interface of bi-materials. The nonlocal stress distribution along an interface is quite different from the classical one. Instead of the singularity in the dislocation core, nonlocal stress gives a finite value in the core. A maximum of the stress is also found near the dislocation core. Received 27 May 1997; accepted for publication 1 July 1997     

Weak isoscalar response of 11B

Weak-interaction responses of ¹¹B were studied by measuring the ¹¹B(³He, t) and ¹¹B(p, p′) reactions. Obtained nuclear transition matrix elements B(GT), B(στ), and B(σ) were compared with the shell-model calculations. The shell-model calculations, which explained the isovector parts B(GT) and B(στ) reasonably well if the quenching factors of 0.5–0.7 were taken into account, did not describe the isoscalar part B(σ).     

Estimating the sizes of surface cracks based on Hall element measurements of the leakage magnetic field and a dipole model of a crack

A method is proposed for estimating the sizes of surface cracks in magnetic materials. The method is based on applying a magnetic field, then determining the leakage magnetic field in the vicinity of a crack by moving a Hall element on the surface of the material along one or two scanning lines crossing the crack, and measuring the corresponding Hall voltage distribution. A dipole model of a crack is utilized, in which a surface crack is considered as being full of magnetic dipoles aligned parallel to the applied field, and whose density varies linearly along the depth of the crack. Analytical expressions are derived for the z-component of the intensity of the leakage magnetic field, and for the measured Hall voltage in the vicinity of a crack with an arbitrary cross-section along its long axis when it is perpendicular to the applied field. The crack sizes and the parameters of the distribution of magnetic dipoles along the crack depth are computed by crack inversion, which represents a regression for the Hall voltage distribution. A variable theoretical Hall voltage distribution is fitted to the measured Hall voltage distribution by minimizing the corresponding RMS error, which gives the unknown parameters at the end of the minimization. Hall voltage distributions are measured on ferromagnetic steel samples containing one artificial surface crack. Some crack inversions are performed for estimating the maximum crack depth and the crack width of cracks with rectangular and isosceles triangular cross-sections along the long crack axis. The accuracy of these crack inversions increases by utilizing either Hall voltage distributions measured along only one of the scanning lines, instead of along both scanning lines, or by using more precisely measured Hall voltage distributions. The fast and accurate estimation of the maximum crack depth and the crack width by such crack inversions could be important for pipeline inspection. Other crack inversions are performed for determining the cross-section along the long axis of the investigated cracks with satisfactory results. Received: 2 March 2001 / Accepted: 10 April 2001 / Published online: 25 July 2001