University of Bedfordshire

About: University of Bedfordshire is a education organization based out in Luton, Bedford, United Kingdom. It is known for research contribution in the topics: Population & Social work. The organization has 3860 authors who have published 6079 publications receiving 143448 citations. The organization is also known as: University of Luton.

Rolling and sliding friction in compliant, lubricated contact

Abstract: Friction is investigated in a rolling-sliding, lubricated, steel ball on elastomer flat contact. Two different types of friction are identified: rolling friction, which results from the movement of the surfaces relative to the contact, and sliding or interfacial friction, which arises from relative motion of the two contacting surfaces. A novel experimental technique is described to measure these two types of friction simultaneously in a single test. This enables separate rolling and interfacial 'Stribeck-type' friction curves to be produced for Newtonian lubricants. These curves are compared with theoretical predictions of friction. The results show that rolling friction originates primarily from two sources: Poiseuille flow of lubricant in the contact and elastic hysteresis. There are also two main types of interfacial friction; due to Couette flow and solid surface adhesion. For compliant elastomer-on-steel contacts, rolling friction forms a significant proportion of the total friction even at quite high slide-roll ratios.

Dose-time relationships for elicitation of contact allergy to para-phenylenediamine.

Abstract: Skin-sensitizing chemicals exhibit dose-response relationships for the elicitation of contact dermatitis. Previously, considerable work has been carried out in which the elicitation of allergic skin reaction has been examined as a function of the applied concentration. However, the relationship between exposure time, dose and response has not been explored in any depth. The present work has extended our initial assessment of the relationship between both exposure time and concentration for para-phenylenediamine (PPD) in a group of 19 PPD-allergic volunteers. The results clearly demonstrate that a relationship exists between both exposure time and concentration. Positive responses to PPD were directly proportional to exposure time: at 5 min 16% responded; at 15 min, 38%; at 30 min, 50%; and at 120 min, 69%. A similar direct relationship was found between concentration of PPD and response: after 120 min, 22% of patients had responded to 0.01%, and 69% to 1% PPD. All exposures for 1 and 2 min were negative. Subsequent evaluation using repeated 5 min open application testing demonstrated a cumulative effect, as after 8 days 39% of the panel reacted, more than double the number that reacted to a single occluded 5-min treatment. It was noted that there was marked subject variability in exposure time and dose required to elicit an allergic response. These results are of relevance for the general interpretation of patch test data, especially with regard to risk assessment.

Relationships between macro and micro socio-cultural contexts: implications for the study of interactions in the mathematics classroom

Abstract: In this paper I attempt to clarify how the relationship between macro and micro social contexts has been addressed in the Vygotskian and Neo-Piagetian approaches to learning. For each approach I look at how key scholars (Cole, 1977; Perret-Clermont, Perret and Bell, 1991) come to view context as central to their theories of cognitive development. In order to illustrate my review of the dominant strands of empirical research I refer to studies that focus on the uses, learning and understanding of mathematics. I start the paper with the socio-cultural Vygotskian approach. This is closely associated with my own research into the relationship between culture and learning. Not surprisingly, I find biases in this body of research in terms of the macro and micro features of contexts which were analysed. In an attempt to gain insights into alternative ways of conceptualising these relationships I explore work which has adopted a socio-psychological approach. In the final part of the paper I discuss how these insights can be used to broaden our basis for studying interactions in the mathematics classroom and conclude by relating my ideas to new developments in socio-cultural theory.