The effect of age and font size on reading text on handheld computers

Though there have been many studies of computer based text reading, only a few have considered the small screens of handheld computers. This paper presents an investigation into the effect of varying font size between 2 and 16 point on reading text on a handheld computer. By using both older and younger participants the possible effects of age were examined. Reading speed and accuracy were measured and subjective views of participants recorded. Objective results showed that there was little difference in reading performance above 6 point, but subjective comments from participants showed a preference for sizes in the middle range. We therefore suggest, for reading tasks, that designers of interfaces for mobile computers provide fonts in the range of 8-12 point to maximize readability for the widest range of users

Transmission of mitochondrial DNA following assisted reproduction and nuclear transfer

Review of the articleMitochondria are the organelles responsible for producing the majority of a cell's ATP and also play an essential role in gamete maturation and embryo development. ATP production within the mitochondria is dependent on proteins encoded by both the nuclear and the mitochondrial genomes, therefore co-ordination between the two genomes is vital for cell survival. To assist with this co-ordination, cells normally contain only one type of mitochondrial DNA (mtDNA) termed homoplasmy. Occasionally, however, two or more types of mtDNA are present termed heteroplasmy. This can result from a combination of mutant and wild-type mtDNA molecules or from a combination of wild-type mtDNA variants. As heteroplasmy can result in mitochondrial disease, various mechanisms exist in the natural fertilization process to ensure the maternal-only transmission of mtDNA and the maintenance of homoplasmy in future generations. However, there is now an increasing use of invasive oocyte reconstruction protocols, which tend to bypass mechanisms for the maintenance of homoplasmy, potentially resulting in the transmission of either form of mtDNA heteroplasmy. Indeed, heteroplasmy caused by combinations of wild-type variants has been reported following cytoplasmic transfer (CT) in the human and following nuclear transfer (NT) in various animal species. Other techniques, such as germinal vesicle transfer and pronuclei transfer, have been proposed as methods of preventing transmission of mitochondrial diseases to future generations. However, resulting embryos and offspring may contain mtDNA heteroplasmy, which itself could result in mitochondrial disease. It is therefore essential that uniparental transmission of mtDNA is ensured before these techniques are used therapeutically

Steering performance and dynamic complexity in a simulated underground mining vehicle

Research concerning the visuomotor control of steering suggests that some steering systems used in underground shuttle cars are not optimal. This research compared the performance of two groups of participants steering with a joystick interface through a simulated underground mine environment. The joystick employed either first-order or second-order control of heading. Results indicated poorer performance with second-order steering dynamics in the early stages of the experiment, which generally did not improve to levels observed in the first-order group. Poorer overall performance suggests that equipment manufacturers should reconsider the use of second-order steering dynamics in their vehicle designs. Alternately, simulation-based training technologies may have the potential to safely accelerate individual attainment of competence in the use of second-order steering systems

A Meta-Analysis of Performance under Thermal Stress

The goal of this work was to perform a quantitative review of temperature effects on human performance, with the aim of advancing both theory and practice. Meta-analytic methods were applied to the available literature on thermal stress and performance. Two-hundred-ninety-one references were collected resulting in forty-nine publications that met selection criteria. These studies provided 528 effect sizes. Analyses revealed an overall detrimental effect of temperature on performance. Effect-size for heat was comparable to that for cold temperatures. Temperature effects were task dependent, that is cognitive performance was least affected by thermal stress, while both psychomotor and perceptual task performance were degraded to a greater degree. Other moderating variables were identified and observed to influence the effect of thermal stress. Although the results clearly indicate more empirical research is necessary to achieve more accurate estimates, the current study provides initial effect-size estimates that should be considered when designing human-machine systems