Run off Conditions on Rimming Power Law Fluids

The rimming ?ow of a power-law ?uid in the inner surface of a horizontal rotating cylinder is investigated. Exploiting the fact that the liquid layer is thin, the simplest lubrication theory is applied. The generalized run-off condition for the steady-state ?ow of the power-law liquid is derived. In the bounds implied by this condition, ?lm thickness admits a continuous solution. In the supercritical case when the mass of non-Newtonian liquid exceeds a certain value or the speed of rotation is less than an indicated limit, a discontinuous solution is possible and a hydraulic jump may occur in the steady-state regime. The location and height of the hydraulic jump for the power-law liquid is determined.

Specific and unspecific interactions in polar fluids in view of wideband dielectric far-infrared spectra

A simple molecular analytical theory of dielectric relaxation in strongly polar fluids is considered in terms of a semi- phenomenological approach. Theoretical spectra epsilon(v), a(v) of complex permittivity and absorption coefficient are fully determined by a form of intermolecular potential well, in which a dipole reorients. In a recent publication by VI. Gaiduk, O.F. Nielsen, and T.S. Perova [J. Molliq 95 (1002) 1-25] the wideband spectra of liquid H2O and D2O were described in terms of a composite model comprising the rectangular and the cosine squared potential wells. Much better results are achieved in this work, where the rectangular well is replaced by a well with a rounded bottom termed the hat-curved well. The spectrum of the auto-correlation function (ACF) is calculated for such a potential. The proposed theory of a composite model, comprising hat-curved and parabolic wells, is applied for liquid water. This model is capable for describing the Debye relaxation region, the second relaxation region in the submillimeter wavelength range, and the far infra-red (FIR) e(v), a(v) spectra, where an intense librational band and an additional weak band are placed, respectively, near 700 cm(-1) and 200 cm(-1). The latter band reflects the features of so-called specific (viz. directly related to H-bonds) interactions and the former band reflects the features of unspecific interactions. The physical mechanisms connected with these types of interactions are discussed in terms of two relevant types of water structure (types of molecular rotation). The proposed theory is also applied to a non-associated liquid in terms of one hat-curved potential well. (C) 2004 Elsevier B.V. All rights reserved.

Ascorbic acid in nasal and tracheobronchial airway lining fluids

Ascorbic acid (AA) is thought to be an important antioxidant in the respiratory tract, whose regulation is yet to be fully characterized. We investigated whether AA in respiratory tract lining fluids (RTLFs) can be augmented by oral supplementation with AA. Plasma, nasal lavage fluids (NLFs), induced sputum (IS), and saliva were analyzed for AA immediately before and 2 h after ingestion of 2 g of AA in 13 healthy subjects. Concentrations of AA (median and range) were 52.5 (16.0-88.5), 2.4 (0.18-4.66), 2.4 (0.18-6.00), and 0.55 (0.18-18.90) micromol/l, respectively. Two hours after ingestion of AA, plasma AA increased 2-fold (p = .004), NLF AA increased 3-fold (p = .039), but IS and saliva AA did not increase. As AA concentrations in saliva and tracheobronchial secretions were low compared with other common extracellular components (such as urate), we evaluated the fate of AA in these fluids. Addition of AA to freshly obtained saliva or IS resulted in rapid depletion, which could be largely prevented or reversed by sodium azide or dithiothreitol. These findings suggest that oxidant-producing systems in saliva and airway secretions, such as heme peroxidases and other oxidizing substances, rapidly consume AA. Whereas oral supplementation resulted in detectable increases of AA in NLFs, its levels in tracheobronchial lining fluid, as measured by IS, were unaffected and remained relatively low, suggesting that AA may play a less significant antioxidant role in this compartment as compared with most other extracellular compartments.

Computational challenges in atomic, molecular and optical physics

Six challenges are discussed. These are the laser-driven helium atom; the laser-driven hydrogen molecule and hydrogen molecular ion: electron scattering (with ionization) from one-electron atoms; the vibrational and rotational structure of molecules such as H-3(+) and water at their dissociation limits; laser- heated clusters; and quantum degeneracy and Bose-Einstein condensation. The first four concern fundamental few-body systems where use of high-performance computing (HPC) is currently making possible accurate modelling from first principles. This leads to reliable predictions and support for laboratory experiment as well as true understanding of the dynamics. Important aspects of these challenges addressable only via a terascale facility are set out. Such a facility makes the last two challenges in the above list meaningfully accessible for the first time, and the scientific interest together with the prospective role for HPC in these is emphasized.

The influence of compliant surfaces on bypass transition', Experiments in Fluids

The objective of the work was to investigate the effect of compliant surfaces on the receptivity and bypass transition of a boundary layer. Hot wire measurements in the pre-transitional and transitional boundary layers on nine different compliant and one rigid surface with identical geometries were made. The experiments were conducted in air and the compliant surfaces were manufactured from gelatine covered by a 10 lm protective PVC film. The laminar boundary layer profiles and growth rate results were the same for all the surfaces. However, the receptivity of the laminar boundary layer to freestream disturbances increased close to the leading edge of each compliant surface. Further downstream the majority of the compliant surfaces were successful in reducing the receptivity to a value below that for the rigid surface. The transition onset position on the compliant surfaces ranged from 3% downstream to 20% upstream of the rigid surface position. It was concluded that compliant surfaces with optimum properties can reduce receptivity and delay transition.