Stability of aqueous films between bubbles. Part 1. The effect of speed on bubble coalescence in purified water and simple electrolyte solutions

Film thinning experiments have been conducted with aqueous films between two air phases in a thin film pressure balance. The films are free of added surfactant but simple NaCl electrolyte is added in some experiments. Initially the experiments begin with a comparatively large volume of water in a cylindrical capillary tube a few millimeters in diameter, and by withdrawing water from the center of the tube the two bounding menisci are drawn together at a prescribed rate. Thismodels two air bubbles approaching at a controlled speed. In pure water, the results show three regimes of behavior depending on the approach speed; at slow speed (<1 μm/s) it is possible to form a flat film of pure water, ∼100 nm thick, that is stabilized indefinitely by disjoining pressure due to repulsive double-layer interactions between naturally charged air/water interfaces. The data are consistent with a surface potential of -57mV on the bubble surfaces. At intermediate approach speed (∼1-150 μm/s), the films are transiently stable due to hydrodynamic drainage effects, and bubble coalescence is delayed by ∼10-100 s. At approach speeds greater than ∼150 μm/s, the hydrodynamic resistance appears to become negligible, and the bubbles coalesce without any measurable delay. Explanations for these observations are presented that take into account Derjaguin-Landau-Verwey-Overbeek and Marangoni effects entering through disjoining pressure, surface mobility, and hydrodynamic flow regimes in thin film drainage. In particular, it is argued that the dramatic reduction in hydrodynamic resistance is a transition from viscosity-controlled drainage to inertia-controlled drainage associated with a change from immobile to mobile air/water interfaces on increasing the speed of approach of two bubbles. A simple model is developed that accounts for the boundaries between different film stability or coalescence regimes. Predictions of the model are consistent with the data, and the effects of adding electrolyte can be explained. In particular, addition of electrolyte at high concentration inhibits the near-instantaneous coalescence phenomenon, thereby contributing to increased foam film stability at high approach speeds, as reported in previous literature. This work highlights the significance of bubble approach speed as well as electrolyte concentration in affecting bubble coalescence.

Effect of gender on thermal comfort in multicultural public places

The city and the urban environment became extremely important in the daily lives of the increasing number of urban populations across the world. Urban research acknowledges that planning urban places should be responsive to the diversity of population. The aim of this paper is to analyse the results of thermal comfort study in the outdoor urban places. The location has been monitored regarding standard comfort variables: air temperature, humidity, wind speed, and globe temperature. The quantitative assessment of comfort conditions was combined with a questionnaire of pedestrians’ thermal comfort perception. In this paper, the analysis of observed thermal sensation with regard to gender and cultural background concerning the sensitivity of different groups to heat and cold is presented.

Effect of temperature on anaerobic fermentation of banana stem residue

Anaerobic fermentation experiments were conducted on banana (pseudo) stem residue to study the relationship between fermentation temperature and gas production yield and gas production rate, and methane content. Based on fixed dry matter concentration, inoculum concentration and fermentation time, different temperatures, i.e. 25, 30, 35, 40°C were selected and formed four experimental groups. Four levels of single factor tests were conducted to optimize temperature parameter for anaerobic fermentation of banana stem residue. The results showed that the daily gas yield of banana stem residue reached the maximum value of 36.8L on the fourth day at 35°C, and the average gas yield was 5.03L/d. The total gas yield was 402.3L, while the maximum methane content was 61.2% in the whole fermentation process. The results indicated that the comprehensive effect was best at 35°C in anaerobic fermentation of banana stem residue.

Effect of adrenaline on glucose kinetics during exercise in adrenalectomised humans

1. The role of adrenaline in regulating hepatic glucose production and muscle glucose uptake during exercise was examined in six adrenaline deficient, bilaterally adrenalectomised humans. Six sex and age matched healthy individuals served as controls (CON).

2. Adrenalectomised subjects cycled for 45 min at 68 ± 1% maximum pulmonary Oμ uptake (VOμ,max), followed by 15 min at 84 ± 2% VOμ,max without (−ADR) or with (+ADR) adrenaline infusion, which elevated plasma adrenaline levels (45 min, 4·49 ± 0·69 nmol l¢; 60 min, 12·41 ± 1·80 nmol l¢; means ± s.e.m.). Glucose kinetics were measured using [3_ÅH]glucose.

3. Euglycaemia was maintained during exercise in CON and −ADR, whilst in +ADR plasma glucose was elevated. The exercise induced increase in hepatic glucose production was similar in +ADR and −ADR; however, adrenaline infusion augmented the rise in hepatic glucose production early in exercise. Glucose uptake increased during exercise in +ADR and −ADR, but was lower and metabolic clearance rate was reduced in +ADR.

4. During exercise noradrenaline and glucagon concentrations increased, and insulin and cortisol concentrations decreased, but plasma levels were similar between trials. Adrenaline infusion suppressed growth hormone and elevated plasma free fatty acids, glycerol and lactate. Alanine and â_hydroxybutyrate levels were similar between trials.

5. The results demonstrate that glucose homeostasis was maintained during exercise in adrenalectomised subjects. Adrenaline does not appear to play a major role in matching hepatic glucose production to the increase in glucose clearance. In contrast, adrenaline infusion results in a mismatch by simultaneously enhancing hepatic glucose production and inhibiting glucose clearance.

The effect of particles on twins and magnesium

This dataset includes orientation from xray diffraction, electron diffraction, and microstructural characterisation. Some transmission electronmicroscopy is also included.

A prospective study of the effect of education on non-compliant behaviour in contact lens wear

The contact lens practitioner and patient present a specific case for the study of non-compliance in areas such as hygiene, solution use, appointment attendance and wearing times. Education is one of the factors thought to influence compliance among patients in general health care situations and contact lens practitioners are encouraged to educate patients in the care and maintenance of contact lenses. A prospective, randomized, controlled and double masked study was performed to assess the effect of a‘compliance enhancement strategy’ on levels of compliance among contact lens wearers over twelve months. Eighty experienced contact lens patients were randomly allocated to two experimental groups. A standard level of contact lens instruction was applied to the first group and in addition the compliance enhancement strategy was applied to patients assigned to the second group. The strategy consisted of extra education for patients using a video, booklets, posters, a checklist and a health care contract. Patients were given free supplies of RelMu multipurpose solution and Medalist 38 soft contact lenses IBausch and Lomb, Rochester. New York). Compliance levels were assessed at a twelve month aftercare appointment by demonstration and questionnaire. The results indicate that the compliance enhancement strategy had little significant effect on the compliance levels of the patients to whom it was applied. The population of contact lens wearers were generally very compliant and the contact lenses and care regimen were clinically successful. The possibility that the assessment of non–compliance was not adequately sensitive to highlight small differences in non-compliant, behaviour is discussed. The standard level of eduction applied to this sample of contact lens patients was adequate to ensure generally high levels of compliance with the simple care and maintenance regimen recommended.

Effect of aluminum on the corrosion resistance of low-alloy steel in 10wt% sulfuric acid solution

The aqueous corrosion behavior of low-alloy steel with aluminum contents was examined in a 10 wt% H₂SO₄ (pH 0.13) solution using electrochemical techniques and surface analyses. The corrosion resistance of the new alloy steel was evaluated in terms of electrochemical parameters, such as passive current density, film, and charge transfer resistances. The results showed that a high Al content in the steel imparted better passivation behavior resulting in a lower corrosion rate. It related to the enrichment of iron carbonate and hydrocarbon by the dissolution of the carbide phase.