Atmospheric parameters and rotational velocities for a sample of Galactic B-type supergiants

High-resolution optical spectra of 57 Galactic B-type supergiant stars have been analysed to determine their rotational and macroturbulent velocities. In addition, their atmospheric parameters (effective temperature, surface gravity and microturbulent velocity) and surface nitrogen abundances have been estimated using a non-local thermodynamic equilibrium grid of model atmospheres. Comparisons of the projected rotational velocities have been made with the predictions of stellar evolutionary models and in general good agreement was found. However, for a small number of targets, their observed rotational velocities were significantly larger than predicted, although their nitrogen abundances were consistent with the rest of the sample. We conclude that binarity may have played a role in generating their large rotational velocities. No correlation was found between nitrogen abundances and the current projected rotational velocities. However, a correlation was found with the inferred projected rotational velocities of the main-sequence precursors of our supergiant sample. This correlation is again in agreement with the predictions of single star evolutionary models that incorporate rotational mixing. The origin of the macroturbulence and microturbulent velocity fields is discussed and our results support previous theoretical studies that link the former to subphotospheric convection and the latter to non-radial gravity mode oscillations. In addition, we have attempted to identify differential rotation in our most rapidly rotating targets.

Surface modification of poly(ε-caprolactone) using a dielectric barrier discharge in atmospheric pressure glow discharge mode

The role of roughening and functionalization processes involved in modifying the wettability of poly(e-caprolactone) (PCL) after treatment by an atmospheric pressure glow discharge plasma is discussed. The change in the ratio of Cdouble bond; length as m-dashO/C–O bonds is a significant factor influencing the wettability of PCL. As the contact angle decreases, the level of Cdouble bond; length as m-dashO bonds tends to rise. Surface roughness alterations are the driving force for lasting increases in wettability, while the surface functional species are shorter lived. We can approximate from ageing that the increase in wettability for PCL after plasma treatment is 55–60% due to roughening and 40–45% due to surface functionalization for the plasma device investigated.

Dielectric constant characterization using a numerical method for the microstrip ring resonator

A new method of dielectric-constant measurement is developed. The dielectric constant epsilon(r) RF/microwave substrate is extracted by combining the microstrip ring resonator measurement with Ansoft HFSS electromagnetic simulation software. The developed method has two advantages: (i) characterization of dielectric constant versus multiple frequency points, and (ii) compatibility with electronics design automation (EDA) software tools. This characterization method can reduce the design cycle of microwave circuits and devices. (C) 2004 Wiley Periodicals, Inc.