Comparative performance of disposable soft contact lenses.

A short-term clinical study was undertaken to compare and evaluate the fit and clinical behaviour of eight disposable hydrogel contact lenses. Thirty subjects were enrolled in a 1-day, randomised, double-masked study. The lenses compared were Vistakon Acuvue (8.80), Vistakon Surevue (8.80), Aspect Frequency-55, Bausch & Lomb Medalist (SeeQuence 2), Ciba Focus (8.90), Lunelle Rythmic, Pilkington Barnes Hind Precision-Wand Wesley Jessen Freshlook. Three of the eight designs, Acuvue (86.7%), Precision-UV (86.7%) and Frequency-55 (90%), achieved relatively high levels of fitting success. The Rythmic lenses achieved the lowest success rate (70%) showing significantly greater downward decentration than the other designs. Although all the lenses were designed to fit a wide variety of eyes, they exhibited widely varying fitting characteristics. Some were more successful than others. The study shows that it is necessary for practitioners to utilise a range of lens designs in order to fit satisfactorily the typical contact lens population.     

Internal biasing by δ-doping for low-voltage, high-bandwidthquantum-well optical modulators

Optical intensity modulators must exhibit low-voltage operation, low insertion loss, high contrast ratio and high electrical bandwidth. Electroabsorption calculations for semiconductor quantum wells predict that internal biasing by strategic δ-doping can produce greatly improved low-voltage operation in waveguide or normal-incidence modulators, for a specified insertion loss and contrast ratio, without compromising electrical bandwidth. Growth of strategically δ-doped electrorefractive intensity modulators is shown computationally to be insensitive to nonreproducibility in layer growth. Internal biasing by strategic doping is of potential value across the whole range of modulator applications     

Virgin Queen Mandibular Gland Signals of Apis mellifera capensis Change with Age and Affect Honeybee Worker Responses

The mandibular gland secretions of Apis mellifera capensis virgin queens were analyzed by gas chromatography–mass spectroscopy. Changes in the patterns of the mandibular gland volatiles of A. m. capensis virgin queens were followed from emergence until 14-d old. Ontogenetic changes in the mandibular gland secretions were largely quantitative in nature, delineating the age categories (global R = 0.612, P = 0.001), except for 7- and 14-d-old queens, which cannot be separated on their mandibular gland profiles (P = 0.2). (E)-9-Oxodec-2-enoic acid (9ODA) contributes most and most consistently to the dissimilarity between groups as well as the similarity within groups. Worker reactions to introduced virgin queens of various ages were recorded. Workers showed a significant increase in hostile reactions as queens aged (r = 0.615, N = 20, P < 0.05). Consequently, worker reactions and relative 9ODA production exhibit a positive queen age-dependent response.     

Nonisothermal crystallization kinetics and stability of leucite and kalsilite from K2O-Al2O3-SiO2 glasses

The crystallization mechanisms and elemental stability of leucite and kalsilite formed from K₂O-Al₂O₃-SiO₂ glasses were investigated by X-ray powder diffraction (XRD), X-ray fluorescence (XRF), Raman spectroscopy and differential scanning calorimetry (DSC). Glass samples with compositions along the leucite-kalsilite tie-line were produced by melt processing and were then heat-treated at 850, 950, and 1250°C for times ranging from 5 minutes to 1000 hours. Kalsilite is an unstable phase that behaves as an intermediate precursor to leucite. Crystalline materials in which kalsilite is the major phase lose potassium upon prolonged heat treatment (1000 hours at 1250°C), in contrast to those with leucite, in which little or no compositional alteration is detected. The formation of leucite from stoichiometric kalsilite is accompanied by the formation of potassium-doped alumina. The activation energies for leucite and kalsilite crystallization, determined via application of the Kissinger equation to thermal analysis data, were 579 and 548 kJ/mol, respectively. Finally, production of pure leucite can be achieved with more favorable crystallization kinetics when starting with off-stoichiometric compositions.     

Progress towards the development of a model for predicting human reliability

A methodology for predicting the probability of human task reliability during a task sequence is described. The method is based on a probabilistic performance requirement–resource consumption model. This enables error-promoting conditions in accident scenarios to be modelled explicitly and a time-dependent probability of error to be estimated. Particular attention is paid to modelling success arising from underlying human learning processes and the impact of limited resources. The paper describes the principles of the method together with an example related to safety and risk of a diver in the wreck scenario. © 1998 John Wiley & Sons, Ltd.     

Angle dependent optical properties of polymer films with a biomimetic anti-reflecting surface replicated from cylindrical and tapered nanoporous alumina

Anodic porous alumina nanostructures have been fabricated with tapered and cylindrical pores with a spacing of 100 and 200 nm and depth of 180-500 nm. The porous nanostructures were replicated into polymer films to create a moth-eye anti-reflecting surface by a roll-to-roll UV replication process. The angle dependent optical transmission of the resulting polymer films exhibited up to a 2% increase in transmission at a normal angle and up to a 5% increase in transmission at a 70° angle of incidence to an equivalent film with a surface replicated from polished aluminum. No significant difference was observed between the optical performance of moth-eye surfaces formed from cylindrical and tapered nano-pores.     

Stability to thermal treatment of dipeptidyl peptidase-IV inhibitory activity of a boarfish (Capros aper) protein hydrolysate when incorporated into tomato-based products

Biofunctional peptide ingredients should retain their stability following standard processing operations in food-based delivery vehicles. A boarfish protein hydrolysate, exhibiting anti-diabetic activity, was subjected to a range of thermal treatments following incorporation into tomato-based soup and juice products. The dipeptidyl peptidase-IV (DPP-IV) inhibitory activity and peptide profile of the hydrolysate within the products were assessed before and after thermal treatment. The treatments applied had no effect on the DPP-IV inhibitory activity or peptide profile of the protein hydrolysate. The heat-treated (90 °C × 1 min and 121 °C × 42 s) juice-fortified beverage had microbial counts within the acceptable limits for consumption when stored at 4 °C for 30 days. Furthermore, the hydrolysate within the beverage products was resistant to simulated gastrointestinal digestion (SGID) regardless of whether it was heat- or non-heat-treated, or stored for 30 days at 4 °C. Therefore, tomato-based beverages are suitable delivery vehicles for biofunctional peptide ingredients.     

Boarfish (Capros aper) protein hydrolysate has potent insulinotropic and GLP-1 secretory activity in vitro and acute glucose lowering effects in mice

The anti-diabetic actions of a boarfish protein hydrolysate (BPH) were investigated in cultured cells and mice. A boarfish (Capros aper) muscle protein hydrolysate was generated using the enzymes Alcalase 2.4 L and Flavourzyme 500 L. Furthermore, the BPH was subjected to simulated gastrointestinal digestion (SGID). BPH and SGID samples (0.01–2.5 mg mL⁻¹) were tested in vitro for DPP-IV inhibition and insulin and GLP-1 secretory activity from BRIN-BD11 and GLUTag cells, respectively. The BPH and SGID samples, caused a dose-dependent increase (4.2 to 5.3-fold, P < 0.001) in insulin secretion from BRIN-BD11 cells and inhibited DPP-IV activity (IC₅₀ 1.18 ± 0.04 and 1.21 ± 0.04 mg mL⁻¹), respectively. The SGID sample produced a 1.3-fold (P < 0.01) increase in GLP-1 secretion. An oral glucose tolerance test (OGTT) was conducted in healthy mice (n = 8), with or without BPH (50 mg/kg bodyweight). BPH mediated an increase in plasma insulin levels (AUC_{(0–120 min),} P < 0.05) and a consequent reduction in blood glucose concentration (P < 0.01), after OGTT in mice versus controls. The BPH showed potent anti-diabetic actions in cells and improved glucose tolerance in mice.     

Enhanced electrorefraction in symmetric narrow coupled quantumwells

The quadratic electrooptic coefficient of narrow symmetric-coupled GaAs-Al_0.2Ga_0.8As quantum wells has been measured for light having a range of detuned wavelengths with TE polarization and is found to be 2-3 times larger than that of single quantum wells equivalent overall width