Analysis and conservation of modern modeling materials found in Auguste Rodin's sculptures

Prior to the exhibition Portrait-making, Rodin and his models (2009), the Rodin museum wanted to restore two busts of Hanako and Clemenceau. Interestingly, these two sculptures contain pieces of modern modeling materials (MMMs) invented at the end of the nineteenth century as an alternative to clay or waxes. The poor state of conservation of the two portraits made any handling and exhibition impossible. Accordingly, the purpose of this article is twofold: to contribute to technical art history and conservation. Elemental and chemical analyses were done on samples from 12 sculptures (SEM–EDX, FTIR, GC–MS, GC–FID, XRD, synchrotron-based µXRF, µXANES, and µFTIR) aimed at identifying the composition of MMMs used by Rodin on plaster sculptures and establishing hypotheses about the origins of their degradation. This thorough study of their composition and degradation was necessary to implement an appropriate restoration plan. The development of conservation protocols adapted to such materials is rarely documented. Different tests were performed on mock-ups (pH, solubility, adhesion, consolidation, and cleaning). In particular, a protocol based on laser cleaning was developed and successfully applied to remove superficial dust and crusts so that the sculptures regained their original aspect.     

新兴的数字化革命:打造图书馆员的领导力

香港大学图书馆领导研修班是为现任和未来图书馆领导而设的密集式培训班,预计参加者主要为现任或未来的馆长或助理馆长.研修班将采用英语作为主要讲授语言另辅以部分中文翻译,采取让学员透过一系列主题讲学、个案研究、小组活动及互动讨论的方式向其它馆员和资讯业专家学习.     

Dynamics of the basketball shot with application to the free throw

A completely general three-dimensional dynamic model is presented for the motion of basketball shots that may contact the rim, the backboard, the bridge between the rim and board, and possibly the board and the bridge simultaneously. Non-linear ordinary differential equations with six degrees of freedom describe the ball angular velocity and ball centre position. The model includes radial ball compliance and damping and contains five sub-models: purely gravitational flight, and ball-rim, ball-bridge, ball-board, and ball-bridge-board contact. Each contact sub-model has both slipping and non-slipping motions. Switching between the sub-models depends on the reaction force at, and velocity of, the contact point. Although the model can be used to study shots from any point on the court, we here use it to study the sets of free throw release angle, velocity, angular velocity, and lateral deviation angle that result in success (capture), as well as underhand free throws and those using an under-inflated ball. Free throw shots with larger backspin, lower inflation pressures, and underhand release conditions are shown to result in larger capture percentages.     

Success in elite cycling: A prospective and retrospective analysis of race results

The development of peak performances is a main research focus in sports science. It is unclear how many former top junior athletes achieve success in the elite class later. The aim of the present study was to examine the careers of athletes who participated in major junior or adult/elite cycling events using prospective and retrospective analysis of competition results. The official results of major junior (age < or = 18 years) and elite (age > 18 years) cycling races from 1980 to 2004 were analysed. Age-related aspects, career lengths, and success were compared between riders who presented results in both junior and elite races (JUNIOR ELITE) and riders who had no junior race results (ELITE ONLY). Altogether, 27,454 results of 8004 athletes from 108 countries were collected. We found that 29.4% of the elite athletes had participated in junior World Championships, and that 34% of the participants in junior World Championships later participated in major elite competitions. JUNIOR ELITE athletes are significantly more successful in several cycling disciplines and have their first and last elite result at a younger age than ELITE ONLY athletes. No difference was found in career lengths. The data presented here emphasize the importance of long-term training programmes in the development of peak performance in cycling.     

The distance-time relationship over a century of running Olympic performances: A limit on the critical speed concept

We analyse the evolution of the slope (critical speed) and the y-intercept (anaerobic distance capacity) of the linear distance-time relationship over a century of Olympic running performances. The distance-time relationship of each Olympic Games (1920-2004) was plotted using the performances in the 800-, 1500- and 5000-m track events. Values for critical speed and anaerobic distance capacity were determined by linear modelling. Mean performances for the 800, 1500 and 5000 m were 104.9 +/- 1.5 s (1.4%), 217.2 +/- 2.8 s (1.3%) and 808.9 +/- 18.4 s (2.3%), respectively. Critical speed improved during the first three-quarters of the twentieth century to reach a plateau in 1984. This is in accordance with the literature (Peronnet & Thibault, 1989) and suggests that "human aerobic endurance" has improved within the century (+13.4%) and tends to stabilize. Anaerobic distance capacity was highly variable over the century (coefficient of variation = 9.4%) and did not show a linear improvement over the years as has previously been suggested (Peronnet & Thibault, 1989). This could be due to an artefact in the application of the two-parameter model to only three Olympic performances. A limitation to the use of this linear mathematical model to fit physiological data may have been demonstrated.     

Physical and metabolic demands of training and match-play in the elite football player

In soccer, the players perform intermittent work. Despite the players performing low-intensity activities for more than 70% of the game, heart rate and body temperature measurements suggest that the average oxygen uptake for elite soccer players is around 70% of maximum (VO(2max). This may be partly explained by the 150 - 250 brief intense actions a top-class player performs during a game, which also indicates that the rates of creatine phosphate (CP) utilization and glycolysis are frequently high during a game. Muscle glycogen is probably the most important substrate for energy production, and fatigue towards the end of a game may be related to depletion of glycogen in some muscle fibres. Blood free-fatty acids (FFAs) increase progressively during a game, partly compensating for the progressive lowering of muscle glycogen. Fatigue also occurs temporarily during matches, but it is still unclear what causes the reduced ability to perform maximally. There are major individual differences in the physical demands of players during a game related to physical capacity and tactical role in the team. These differences should be taken into account when planning the training and nutritional strategies of top-class players, who require a significant energy intake during a week.