Linear sums of two composition operators on the Fock space

Linear sums of two composition operators of the multi-dimensional Fock space are studied. We show that such an operator is bounded only when both composition operators in the sum are bounded. So, cancelation phenomenon is not possible on the Fock space, in contrast to what have been known on other well-known function spaces over the unit disk. We also show the analogues for compactness and for membership in the Schatten classes. For linear sums of more than two composition operators the investigation is left open.     

Projections for harmonic Bergman spaces and applications

On the setting of general bounded smooth domains in , we construct L¹-bounded nonorthogonal projections and obtain related reproducing formulas for the harmonic Bergman spaces. In addition, we show that those projections satisfy Sobolev L^p-estimates of any order even for p=1. Among applications are Gleason's problems for the harmonic Bergman-Sobolev and (little) Bloch functions on star-shaped domains with strong reference points.     

A new ergostane-type cholesterol biosynthesis inhibitor isolated from Hormoconis resinae

A new ergostane-type steroid, 3β-hydroxy-1,11-dioxo-ergosta-8,24(28)-diene-4α-carboxylic acid (1) was isolated from the mold Hormoconis resinae as a cholesterol biosynthesis inhibitor in the Chang liver cell. The absolute stereostructure of 1 was established based on the spectroscopic analyses and modified Mosher's method.     

Ionic strength-controlled virtual area of mesoporous platinum electrode

Mesoporous electrodes provide an unusual opportunity to observe the dramatic transition of the electrochemical potential distribution in vicinity to mesoporous surfaces as the ionic strength varies. The experimental results were in accordance with what the classical Gouy-Chapman theory predicts on the basis of the correlation between Debye length (kappa-1) and the diameter of mesopores. Using the phenomenon that the electrochemically effective area of mesoporous electrode depends on the ionic strength, the faradaic current density of dioxygen reduction could be controlled by the electrolyte concentration.     

Existence of intramolecular triplet excimer of bis(9-fluorenyl)methane: phosphorescence and delayed fluorescence spectroscopic and ab initio studies

A concerted computational and experimental study has been undertaken to probe the conformational structure and excited-state dynamics of bis(9-fluorenyl)methane (BFM). We have observed that the relative intensity of the delayed excimer fluorescence of BFM is greatly enhanced in comparison with that of the normal fluorescence. This is presumably because the relative concentration of the triplet excimer is enhanced in comparison with the singlet excimer. B3LYP DFT/6-31G(d) calculations indicate that the sandwich conformer of BFM in the singlet ground state is unstable, whereas that in the triplet excited state has a bound state, being very slightly higher in internal and Gibbs free energies than that of the lowest state of the near-orthogonal conformer.     

Numerical design of electrical-mechanical traps

We present a coupled immersed interface method-boundary element method (IIM-BEM) numerical technique that predicts the behaviour of deformable cells under the effect of both hydrodynamic and electrical forces. This technique is applied to the study of a hybrid electrical-mechanical trap for single-cell trapping. We report on the effect of different combinations of electrode positions and mechanical properties of the trap on the maximum loading and unloading Reynolds numbers. We also report on the effect that cells moving with the flow have on cells which have been already trapped in a cavity.     

A new constitutive model for monodispersed suspensions of spheres at high concentrations

We describe a constitutive model for monodispersed concentrated suspensions of spheres at high volume fractions. In this model the motion of a pair of generic spheres is represented by that of a pair of force-free and torque-free spheres tumbling along with the flow. The interaction with the surrounding spheres is modelled by an anisotropic diffusion process. Viscometric and elongational properties of the model are obtained by a Brownian dynamic simulation. Received: 24 September 1998 Accepted: 1 December 1998     

The evolution of a detonation wave in a variable cross-sectional chamber

A two-dimensional numerical simulation has been performed to study the interaction of a gaseous detonation wave with obliquely inclined surfaces in a variable cross-sectional chamber. The weighted essentially non-oscillatory (WENO) numerical scheme with a relatively low resolution grid is employed. A detailed elementary chemical reaction model with 9 species and 19 elementary reactions is used for a stoichiometric oxy-hydrogen mixture diluted with argon. In this work, we study the effect of area expansion and contraction on the main/gross features of the detonation cellular structures in the presence of detonation reflection, diffraction and localized explosion. The result shows that there exists a transition region as the detonation wave propagates through the converging/diverging chamber. Within the transition region, the initial regular detonation cells become distorted and irregular before they re-obtain their regularity. While the ultimate regular cell size and the length of the transition region are strongly affected by the converging/diverging angle, the width/length ratio of the cells is fairly independent of it. A localized explosion near the wall is found as the detonation wave propagates in the diverging chamber.      

Use of DES in mildly separated internal flow: dimples in a turbulent channel

Detached eddy simulation (DES) is investigated as a means to study an array of shallow dimples with depth to diameter ratios of 1.5% and 5% in a turbulent channel. The DES captures large-scale flow features relatively well, but is unable to predict skin friction accurately due to flow modelling near the wall. The current work instead relies on the accuracy of DES to predict large-scale flow features, as well as its well-documented reliability in predicting flow separation regions to support the proposed mechanism that dimples reduce drag by introducing spanwise flow components near the wall through the addition of streamwise vorticity. Profiles of the turbulent energy budget show the stabilising effect of the dimples on the flow. The presence of flow separation however modulates the net drag reduction. Increasing the Reynolds number can reduce the size of the separated region and experiments show that this increases the overall drag reduction.