New approach to quantum corrections in synchrotron radiation

Owing to a recent controversy over the importance of the second-order quantum corrections to the power spectrum of synchrotron radiation, we here reexamine this question by using a proper time method to calculate the forward Compton scattering of a real photon on a spin-0 charged particle in external magnetic fields. This approach, aside from being the simplest method found so far, has the feature that it resembles the classical procedure so that the quantum corrections can be identified at every stage of the computation. The option of being able to perform first the angular integration before doing the proper time integral enables us to simplify the calculation and to obtain the quantum corrections unambiguously. We find that the criterion for the quantum corrections to be important is the same as that found more than two decades ago.     

The Constituents of the Bark of Armand Pine

Twenty three compounds were isolated from the bark of Pinus armandii. These compounds include nine serratenes (1-9), a norserratenone 10, eight phenols 11-18, two flavonoids 19-20, one lignan 21, a diterpene 22 and a novel triterpendiol acetonide 23. Their structures were determined from their physical and spectral properties.     

Magnetoacoustic effect in non-degenerate semiconductors

The effect of ultrasonic waves propagating at an angle ? relative to the direction of a magnetic field in nondegenerate semiconductors such as n-type InSb has been studied by using a quantum treatment which is valid at high frequencies and in strong magnetic fields. Numerical results show that both the absorption coefficient and the change in the sound velocity depend on the direction of the propagation of ultrasonic waves relative to the magnetic field.     

Polarization in Pseudoscalar Meson Photoproduction

Two problems of current interest in the use of polarization observables for pseudoscalar meson photoproduction to probe the basic dynamics are discussed. The first one concerns the extraction of the ratio of electric quadrupole to magnetic dipole transition strengths in the photo-excitation of the . The predictions of various models are compared with the recent LEGS and MAMI data obtained with polarized photon beams. The second one is a proposal by Saghai and Tabakin to use the nodal structure of spin observables to unveil underlying dynamics in the production process. We demonstrate with the example of at photon energy that the assumption of multipole truncation, which enters into their nodal analysis, is questionable. Received October 11, 1997; revised February 16, 1998; accepted for publication March 6, 1998     

Hybrid-conventional finite element for gradient-dependent plasticity

The hybrid-conventional finite element method is applied to the analysis of quasi-static, gradient-dependent elastoplastic problems in solid mechanics. The stresses within the element domain and the displacements on the boundary are simultaneously and independently approximated using Trefftz constraints, which lead to boundary integrals. The plastic multipliers are conventionally approximated with regard to C₀ continuity of the multiplier field of the gradient-dependent plasticity. The finite element formulation is derived using a Galerkin-weighted residual approach. The plastic boundary conditions are examined and plastic radiations are set to zero on the plastic boundaries. The effectiveness of the present method is demonstrated with three numerical applications.     

Ferroelectric liquid crystal materials synthesized from 2(S)-[2(S)-methylbutyloxy]propanol

A new chiral alcohol, 2(S)-[2(S)-methylbutyloxy]propanol (3), containing two chiral centres has been synthesized from ethyl lactate and (S)-1-iodo-2-methylbutane. It was used as a chiral building block for the preparation of ferroelectric liquid crystal materials. Several of the new materials exhibit an enantiotropic S*_c phase with a wide temperature range. The results indicate that the molecular structure of 3 is useful for synthesizing ferroelectric liquid crystal materials.     

Comparison of three solvers for viscoelastic fluid flow problems

The computational efficiency of three numerical schemes has been examined for the solution of a linearized system of equations resulting from the finite element discretization of a viscoelastic fluid flow problem. The first scheme is a modified frontal solver, which solves the linear system of equations directly. The other two, one based on a biconjugate gradient stabilized (BiCGStab) method and another based on a generalized minimal residual (GMRES) method, are iterative schemes. The stick-slip problem and the four-to-one contraction problem were analyzed and the viscoelastic fluid was assumed to obey the Oldroyd-B model. The two iterative schemes are superior to the direct scheme in terms of CPU time consumed and the BiCGStab scheme is even faster than the GMRES scheme. The range of convergence for both iterative schemes is compatible with that of the direct scheme.     

Towards Bounding Complexity of a Minimal Model

We give some effectivity results in birational geometry. We provide an upper bound on the rational constant in Rationality Theorem in terms of certain intersection numbers, under an additional condition on the variety that it admits a divisorial contraction. One consequence is an explicit bound on the number of certain extremal rays. Our main result tries to construct from a given set of ample divisors H _j on X with their intersection numbers b _i , a certain set of ample divisors L _j on X' or X ⁺ where X' or X ⁺ arises from a contraction or a flip,such that the corresponding intersection numbers of L _j are uniformly bounded in terms of b _i and the index of X. This gives a bound on the projective degree of a minimal model in special case.