Understanding the friction mechanisms between the human finger and flat contacting surfaces in moist conditions

Human hands sweat in different circumstances and the presence of sweat can alter the friction between the hand and contacting surface. It is, therefore, important to understand how hand moisture varies between people, during different activities and the effect of this on friction. In this study, a survey of fingertip moisture was done. Friction tests were then carried out to investigate the effect of moisture. Moisture was added to the surface of the finger, the finger was soaked in water, and water was added to the counter-surface; the friction of the contact was then measured. It was found that the friction increased, up until a certain level of moisture and then decreased. The increase in friction has previously been explained by viscous shearing, water absorption and capillary adhesion. The results from the experiments enabled the mechanisms to be investigated analytically. This study found that water absorption is the principle mechanism responsible for the increase in friction, followed by capillary adhesion, although it was not conclusively proved that this contributes significantly. Both these mechanisms increase friction by increasing the area of contact and therefore adhesion. Viscous shearing in the liquid bridges has negligible effect. There are, however, many limitations in the modelling that need further exploration

Skin friction at the interface between hands and sports equipment

The friction between the finger pad/palm and items of sports equipment strongly influences how well an athlete is able to perform. It not only determines how well equipment can be gripped and manipulated, but also how the equipment feels to use and the perceived level of performance. In this paper various fundamental aspects of finger pad friction are reviewed, including the effects of applied force, skin moisture, material, surface texture etc., and the influence that they have on friction mechanisms such as adhesion, deformation, interlocking and hysteresis. A number of applied case studies are then outlined. The first is rugby balls and the effect the ball surface pimple pattern has on friction. Initially high speed video was used to establish how the hand interacts with a ball. Friction tests were then carried out with different hand conditions and pimple patterns and the link between friction and pass accuracy was explored. The second study relates to friction modifiers used in sports such as rock climbing and athletics. These can be affected by hand and environmental conditions so a focus was placed on tests with moist hands or wet surfaces. Finally Frisbee interactions were investigated. The impact of loss of feel as a result of wearing gloves was studied to see if any improvements in wet conditions with gloves were offset by the reduced feedback from the Frisbee interface. The fundamentals of skin tribology can play a key role in developing optimised sports equipment, gaps still exist, however, in the understanding and modelling of surface texture and how important feel/comfort are, which are both important for sports equipment design

An assessment of the performance of grip enhancing agents used in sports applications

The performances of four grip enhancing agents, powdered and liquid chalk, rosin and Venice turpentine, were assessed using a bespoke finger friction rig and compared against an agent-free finger. The effectiveness of these agents was measured in dry, damp and wet conditions, to simulate the different environments in which the agents are used. The tests were first done on a polished steel surface and then the powdered and liquid chalk and agent-free finger were tested on sandstone. The tests on the steel showed that in a dry condition, only the Venice turpentine significantly increased the coefficient of friction, compared to no application of agent, with the rosin and powdered chalk actually decreasing the coefficient of friction. It is thought that the reduction in the coefficient of friction is caused by the solid particles acting as a lubricant between the two surfaces. When the fingers were wet, only the granular powder-based agents increased the coefficient of friction. This is because the Venice turpentine cannot adhere well to a wet finger, and therefore is not as effective. When the surface is wet, there is very little difference between the agents due to the water separating the finger surface from the steel. The tests on the sandstone showed no real difference between the lubricants or the different conditions, except for the dry, chalk-free finger, which had a decreased coefficient of friction due to the lubricating properties of the sandstone particles. These results highlight that the use of grip enhancing agents should take into account the moisture in the contact, as in dry conditions, the grip may be optimum when there is no agent used. It also shows that in different sports, different grip enhancing agents should be used

Human finger contact with small, triangular ridged surfaces

Ridges are often added to surfaces to improve grip of objects such as sports equipment, kitchen utensils, assistive technology, etc. Although considerable work has been carried out to study finger friction generally, not much attention has been paid to understanding and modelling the effects of surface texture. Previous studies indicate that at low roughness values friction decreases as roughness increases, but then a sharp increase is seen after a threshold level of roughness is reached. This is thought to be due to interlocking. In this study an analytical model was developed to analyse the different mechanisms of friction of a fingerpad sliding against triangular-ridged surfaces that incorporated adhesion, interlocking and hysteresis. Modelling was compared with experimental results from tests on five different triangular-ridged surfaces, manufactured from aluminium, brass and steel. Model and experiment compared well. The study showed that at low ridge height and width the friction was dominated by adhesion. However, above a ridge height of 42.5 μm, interlocking friction starts to contribute greatly to the overall friction. Then at a height of 250 μm, a noticeable contribution from hysteresis, of up to 20% of the total friction, is observed

Revealing microhabitat requirements of an endangered specialist lizard with LiDAR

A central principle of threatened species management is the requirement for detailed understanding of species habitat requirements. Difficult terrain or cryptic behaviour can, however, make the study of habitat or microhabitat requirements difficult, calling for innovative data collection techniques. We used high-resolution terrestrial LiDAR imaging to develop three-dimensional models of log piles, quantifying the structural characteristics linked with occupancy of an endangered cryptic reptile, the western spiny-tailed skink (Egernia stokesii badia). Inhabited log piles were generally taller with smaller entrance hollows and a wider main log, had more high-hanging branches, fewer low-hanging branches, more mid- and understorey cover, and lower maximum canopy height. Significant characteristics linked with occupancy were longer log piles, an average of three logs, less canopy cover, and the presence of overhanging vegetation, likely relating to colony segregation, thermoregulatory requirements, and foraging opportunities. In addition to optimising translocation site selection, understanding microhabitat specificity of E. s. badia will help inform a range of management objectives, such as targeted monitoring and invasive predator control. There are also diverse opportunities for the application of this technology to a wide variety of future ecological studies and wildlife management initiatives pertaining to a range of cryptic, understudied taxa

Revealing microhabitat requirements of an endangered specialist lizard with LiDAR

A central principle of threatened species management is the requirement for detailed understanding of species habitat requirements. Difcult terrain or cryptic behaviour can, however, make the study of habitat or microhabitat requirements difcult, calling for innovative data collection techniques. We used high-resolution terrestrial LiDAR imaging to develop three-dimensional models of log piles, quantifying the structural characteristics linked with occupancy of an endangered cryptic reptile, the western spiny-tailed skink (Egernia stokesii badia). Inhabited log piles were generally taller with smaller entrance hollows and a wider main log, had more high-hanging branches, fewer low-hanging branches, more mid- and understorey cover, and lower maximum canopy height. Signifcant characteristics linked with occupancy were longer log piles, an average of three logs, less canopy cover, and the presence of overhanging vegetation, likely relating to colony segregation, thermoregulatory requirements, and foraging opportunities. In addition to optimising translocation site selection, understanding microhabitat specifcity of E. s. badia will help inform a range of management objectives, such as targeted monitoring and invasive predator control. There are also diverse opportunities for the application of this technology to a wide variety of future ecological studies and wildlife management initiatives pertaining to a range of cryptic, understudied taxa.Holly S. Bradley, Michael D. Craig, Adam T. Cross, SeanTomlinson, Michael J. Bamford, Philip W. Batema

Predators in a mining landscape: Threats to a behaviourally unique, endangered lizard

First published: 09 June 2022Patchy resource distribution can cluster predator activity around areas of the highest productivity in ecosystems. For the endangered Western Spiny-tailed Skink (Egernia stokesii badia) in Western Australia, the log piles that they permanently inhabit in an otherwise patchy, arid landscape, represent a potentially reliable, high abundance food source for predators. Not only are encounter rates by potential predators of E. s. badia likely to be influenced by vegetation structure at the micro habitat scale but also E. s. badia occurs in a region where minesites and associated infrastructure, such as landfill sites, likely concentrate generalist predators (e.g. Feral Cats and corvids). We assessed the influence of the presence of coarse woody debris (CWD) and distance to the land-fill on predator behaviour towards E. s. badia through plasticine model experiments, unbounded point count bird surveys and camera trapping. We found that CWD inhabited byE. s. badia attracted a greater relative activity of corvids compared with uninhabited CWD, or control sites without CWD. The relative activity of corvids and predatory birds combined increased with decreasing distance from the landfill. Preferential hunting by corvids at CWD inhabited byE. s. badia compared to both uninhabited CWD and open sites suggests that inhabited CWD may be targeted by generalist predators in the region, and that adaptive management may be required for species conservation around active mining areas.Holly S. Bradley, Michael D. Craig, Sean Tomlinson, Adam T. Cross, Michael J. Bamford, Philip W. Batema

Disease consequences of higher adiposity uncoupled from its adverse metabolic effects using Mendelian randomisation

Background:Some individuals living with obesity may be relatively metabolically healthy, whilst others suffer from multiple conditions that may be linked to adverse metabolic effects or other factors. The extent to which the adverse metabolic component of obesity contributes to disease compared to the non-metabolic components is often uncertain. We aimed to use Mendelian randomisation (MR) and specific genetic variants to separately test the causal roles of higher adiposity with and without its adverse metabolic effects on diseases.Methods:We selected 37 chronic diseases associated with obesity and genetic variants associated with different aspects of excess weight. These genetic variants included those associated with metabolically ‘favourable adiposity’ (FA) and ‘unfavourable adiposity’ (UFA) that are both associated with higher adiposity but with opposite effects on metabolic risk. We used these variants and two sample MR to test the effects on the chronic diseases.Results:MR identified two sets of diseases. First, 11 conditions where the metabolic effect of higher adiposity is the likely primary cause of the disease. Here, MR with the FA and UFA genetics showed opposing effects on risk of disease: coronary artery disease, peripheral artery disease, hypertension, stroke, type 2 diabetes, polycystic ovary syndrome, heart failure, atrial fibrillation, chronic kidney disease, renal cancer, and gout. Second, 9 conditions where the non-metabolic effects of excess weight (e.g. mechanical effect) are likely a cause. Here, MR with the FA genetics, despite leading to lower metabolic risk, and MR with the UFA genetics, both indicated higher disease risk: osteoarthritis, rheumatoid arthritis, osteoporosis, gastro-oesophageal reflux disease, gallstones, adult-onset asthma, psoriasis, deep vein thrombosis, and venous thromboembolism.Conclusions:Our results assist in understanding the consequences of higher adiposity uncoupled from its adverse metabolic effects, including the risks to individuals with high body mass index who may be relatively metabolically healthy.Funding:Diabetes UK, UK Medical Research Council, World Cancer Research Fund, National Cancer Institute

Disease consequences of higher adiposity uncoupled from its adverse metabolic effects using Mendelian randomisation

Background:Some individuals living with obesity may be relatively metabolically healthy, whilst others suffer from multiple conditions that may be linked to adverse metabolic effects or other factors. The extent to which the adverse metabolic component of obesity contributes to disease compared to the non-metabolic components is often uncertain. We aimed to use Mendelian randomisation (MR) and specific genetic variants to separately test the causal roles of higher adiposity with and without its adverse metabolic effects on diseases.Methods:We selected 37 chronic diseases associated with obesity and genetic variants associated with different aspects of excess weight. These genetic variants included those associated with metabolically ‘favourable adiposity’ (FA) and ‘unfavourable adiposity’ (UFA) that are both associated with higher adiposity but with opposite effects on metabolic risk. We used these variants and two sample MR to test the effects on the chronic diseases.Results:MR identified two sets of diseases. First, 11 conditions where the metabolic effect of higher adiposity is the likely primary cause of the disease. Here, MR with the FA and UFA genetics showed opposing effects on risk of disease: coronary artery disease, peripheral artery disease, hypertension, stroke, type 2 diabetes, polycystic ovary syndrome, heart failure, atrial fibrillation, chronic kidney disease, renal cancer, and gout. Second, 9 conditions where the non-metabolic effects of excess weight (e.g. mechanical effect) are likely a cause. Here, MR with the FA genetics, despite leading to lower metabolic risk, and MR with the UFA genetics, both indicated higher disease risk: osteoarthritis, rheumatoid arthritis, osteoporosis, gastro-oesophageal reflux disease, gallstones, adult-onset asthma, psoriasis, deep vein thrombosis, and venous thromboembolism.Conclusions:Our results assist in understanding the consequences of higher adiposity uncoupled from its adverse metabolic effects, including the risks to individuals with high body mass index who may be relatively metabolically healthy.Funding:Diabetes UK, UK Medical Research Council, World Cancer Research Fund, National Cancer Institute

The Japanese model in retrospective : industrial strategies, corporate Japan and the 'hollowing out' of Japanese industry

This article provides a retrospective look at the Japanese model of industrial development. This model combined an institutional approach to production based around the Japanese Firm (Aoki's, J-mode) and strategic state intervention in industry by the Japanese Ministry of International Trade and Industry (MITI). For a long period, the alignment of state and corporate interests appeared to match the wider public interest as the Japanese economy prospered. However, since the early 1990s, the global ambitions of the corporate sector have contributed to a significant 'hollowing out' of Japan's industrial base. As the world today looks for a new direction in economic management, we suggest the Japanese model provides policy-makers with a salutary lesson in tying the wider public interest with those of the corporate sector