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In this paper, a comparison is made of the evolution of turbulence in oscillatory channel flows with a zero-mean velocity in two and three dimensions, using the numerical technique of the lattice Boltzmann method. The results confirm a primary two-dimensional instability. Evidence is shown of a secondary, viscous three-dimensional instability mechanism acting in the oscillatory boundary layer, which is consistent with experimental observations.

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Correctional facilities have become collection and containment centres for HIV-seropositive individuals. This is due to factors that affect incarceration in general: past criminal behaviour, age and crime type. In addition, the sex trade industry, intravenous drug use and community instability are likely factors affecting this particular population. The objective of this study was to determine whether HIV-positive offenders have higher rates of rearrest than HIV-negative offenders. A sample of HIV-positive offenders (n = 57) were seen for mental health evaluation at the King County Correctional Facility (KCCF) in Seattle Washington. They were compared to a historical sample (n = 254) of HIV-negative individuals also from the KCCF. After three months, 50% of both samples had been rearrested. Using the log rank test in Kaplan-Meier survival analysis, statistical difference in the relative risk of rearrest occurred for the HIV-positive group (logrank = 0.03). Statistical adjustment for mental illness, age, race, ethnicity, substance abuse history and past criminal history did not affect rearrest significantly. Nonetheless, HIV-positive individuals who presented with mental health needs appeared to be significantly more vulnerable to rearrest after the first three months of release into the community.

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Responsive hydrophobically associating polymers can in many ways be considered to be analogous to proteins in their ability to form compact molecules with a defined secondary structure, and hence, functionality. These molecules are characterized by the presence of alternating charged and hydrophobic groups. The balance between charge repulsion and hydrophobic interactions is sensitive to environmental pH and therefore changes in pH produce controllable conformational changes. The change from a charged extended chain to a collapsed uncharged coil structure is sometimes referred to as hypercoiling behaviour and enables the polymer to act as a simple switch between an 'on' and 'off' state. The purpose of this review is to illustrate the structure and behaviour of polymers that exhibit hypercoiling behaviour and to highlight their potential pharmaceutical applications, which in terms of drug delivery is likely to be related to their surface behaviour and solubilizing activity.

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PURPOSE: To investigate the ex vivo wettability of Etafilcon A contact lenses over an eight hour period of wear and observe the influence of surfactant pre-treatment. METHODS: Etafilcon A hydrogel lenses, comprising poly[2-hydroxyethyl methacrylate-co-methacrylic acid] and 58% water, were soaked for 12 hours in either 0.9% saline (control) or a 1% aqueous solution of poloxamine 1107 (treated). The advancing and receding contact angles were subsequently determined ex vivo after various periods of wear in six adapted contact lens wearers using a single-blind, randomised protocol. Contact angles were measured with a dynamic contact angle tensiometer, using the Wilhelmy plate technique. Patient comfort scores were recorded and the static surface tensions of the probe fluids assessed. RESULTS: Control lenses exhibited no change in wetting angles over time, indicating a lack of surface modification by components within the tear film. Treated lenses exhibited a significantly reduced advancing angle (p < 0.001) and hysteresis angle (p < 0.001) when compared with control lenses. In addition, treated lenses were consistently rated as being more comfortable than control lenses (p = 0.04). CONCLUSIONS: This study has shown clearly that new Etafilcon A lenses do not exhibit significant changes in wettability during the initial four hour wearing period. Pre-treatment of such lenses with a polymeric surfactant results in wetting of the lenses due to the adsorption of surfactant. The surfactant is retained by the lens for at least eight hours of wear, resulting in significant improvements in subjective comfort, especially over the first 30 minutes of wear.

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A simple, non-invasive technique has been developed for assessment of the stability of the pre-corneal tear film. Changes are observed in the reflection of a grid pattern from the tear film surface. Breaks in the tear film appear as random discontinuities in the grid image. Using this non-invasive technique the stability of the pre-corneal tear film was assessed in nine normal subjects and twelve established dry-eye patients. The non-invasive tear film break-up time (NIBUT) of the dry-eye patients was on average only 25% to 32% of normal values. The non-invasive technique provides an alternative approach to diagnosing non-wetting disorders as well as a means of evaluating the efficacy of artificial tear solutions.

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Non-invasive tear film break-up time (NIBUT) was measured in nine normal subjects to investigate the effect of fluorescein instillation of tear film stability. It was found that fluorescein instillation reduced the tear film stability in the treated group, compared with the control group (P less than 0.05). It is, therefore likely that the tear film stability may be greater than had hitherto been suggested by the fluorescein method.

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The concentrations 5-hydroxytryptamine, noradrenaline, their precursors and metabolites have been determined in three regions of mouse brain following gonadectomy; the rates of depletion of 5-hydroxytryptamine and noradrenaline following synthesis blockade have also been examined. Previous investigations have shown that gonadectomy results in changes in hypothalamic catecholamine metabolism; this report shows that changes are not confined to the hypothalamic area and suggests that the effects in other areas of the brain may contribute to the increased incidence of mental disturbances in man when hormone levels are drastically altered. Gonadectomy results in reduced 5-hydroxytryptamine and 5-hydroxyindoleacetic acid concentrations in all regions of the mouse brain. Normetanephrine concentrations are significantly increased and the rate of depletion of noradrenaline from the brain following synthesis blockade is markedly accelerated following gonadectomy; this suggests that circulating steroid sex hormones may exert a stabilising effect on brain catecholamine stores.

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The formation of dansyl derivatives of amino acids, 5-hydroxyindoleacetic acid and histamine, and their separation on polyamide plates provided a reliable and sensitive method for studying circadian changes in single pineal and pituitary glands of the rat. There appears to be no correlation between the circadian changes in concentrations of these substances in the pineal and pituitary glands. Chronically administered D-amphetamine altered the circadian rhythms of five amino acids in the pituitary, including the putative transmitters taurine, glycine, and glutamate; in the pineal gland only the rhythmical changes of lysine and 5-hydroxyindoleacetic acid were affected.

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