The influence of defects in the crystal structure on helium diffusion in quartz

The solubility and diffusion of helium in quartz crystals are investigated as functions of the distribution and density of structural defects. The types of defects in the crystals are identified and their distribution over growth sectors is determined by x-ray diffraction topography and phase radiography with a synchrotron radiation source. The effective solubility and effective diffusion coefficients for helium in quartz are estimated from the experimental data on the amount of helium extracted from samples with different contents of defects. It is revealed that the effective diffusion coefficient of helium depends on the number of dislocations.     

Complexation between vanadium(V) and citrate: spectroscopic and structural characterization of a dinuclear vanadium(V) complex

Investigation of the aqueous coordination chemistry for citrate and vanadium(V) resulted in the isolation and characterization of a dinuclear vanadium(V) citrato complex (1) Na₂K₂[VO2(Hcit)]₂ · 9H₂O. Complex (1) is an intermediate between the fully deprotonated and diprotonated citrate vanadate. It may represent an early mobilized precursor in the biosynthesis of FeV-co, as well as a relevant model in the proton transport relay process between P-cluster pair to M-cluster pair. The complex has been characterized by elemental analyses and i.r. spectroscopy. Its i.r. spectra are consistent with a oxo-bridged dinuclear structure as revealed by a single crystal X-ray diffraction study.     

Air filter sterilization using a one atmosphere uniform glowdischarge plasma (the volfilter)

Two characteristics of microorganisms-extremely small size (0.01 to a few micrometers) and the ability to reproduce-hinder the effective filtration of bacteria and viruses from indoor air. The microorganisms captured by a filter in spite of their small size can reproduce in situ and be released into the airstream, giving rise to the “sick building syndrome”. The application of the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP) to a filter can address both these issues. At University of Tennessee at Knoxville, we have recently developed the “Volfilter”, a planar version of the OAUGDP produced by attaching strip electrodes to both sides of a sheet of dielectric filter material and energizing the electrodes with a high-voltage, low-frequency RF source. After the filter material removes microorganisms from the airstream, the OAUGD plasma kills the captured microorganisms. The combination of an appropriate filter material and periodic application of the OAUGDP results in an effective capture and sterilization device even for the smallest microorganisms and requires minimum maintenance. This paper will describe results obtained during the operation of a laboratory-scale “Volfilter” challenged by two kinds of microorganisms, S. aureus and the bacterial virus Phi X 174. An objective of this work is to demonstrate that a “Volfilter” exposed to a OAUGDP will have the number of captured microorganisms on its surface reduced by a factor of one million     

Physical Characterization of Acid-Doped Polyaniline

Polyaniline has been synthesized by the chemical and electrochemical oxidation of aniline. The conductivities increase by seven order of magnitude upon protonation. The IR absorption band near 1590 cm^?1 shifts to a lower frequency upon protonation. Visible spectra vary with the degree of protonation and the applied potential. Cyclic voltammetry indicates that polyaniline exists in several forms.     

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.