Computer Simulations of Supercooled Liquids and Glasses

After a brief introduction to the dynamics of supercooled liquids, we discuss some of the advantages and drawbacks of computer simulations of such systems. Subsequently we present the results of computer simulations in which the dynamics of a fragile glass former, a binary Lennard-Jones system, is compared to the one of a strong glass former, SiO_2. This comparison gives evidence that the reason for the different temperature dependence of these two types of glass formers lies in the transport mechanism for the particles in the vicinity of T_c, the critical temperature of mode-coupling theory. Whereas the one of the fragile glass former is described very well by the ideal version of mode-coupling theory, the one for the strong glass former is dominated by activated processes. In the last part of the article we review some simulations of glass formers in which the dynamics below the glass transition temperature was investigated. We show that such simulations might help to establish a connection between systems with self generated disorder (e.g. structural glasses) and quenched disorder (e.g. spin glasses).Comment: 37 pages of Latex, 11 figures, to appear as a Topical Review article in J. Phys.: Condens. Matte

The Influence of Recovery and Training Phases on Body Composition, Peripheral Vascular Function and Immune System of Professional Soccer Players

Professional soccer players have a lengthy playing season, throughout which high levels of physical stress are maintained. The following recuperation period, before starting the next pre-season training phase, is generally considered short but sufficient to allow a decrease in these stress levels and therefore a reduction in the propensity for injury or musculoskeletal tissue damage. We hypothesised that these physical extremes influence the body composition, blood flow, and endothelial/immune function, but that the recuperation may be insufficient to allow a reduction of tissue stress damage. Ten professional football players were examined at the end of the playing season, at the end of the season intermission, and after the next pre-season endurance training. Peripheral blood flow and body composition were assessed using venous occlusion plethysmography and DEXA scanning respectively. In addition, selected inflammatory and immune parameters were analysed from blood samples. Following the recuperation period a significant decrease of lean body mass from 74.4±4.2 kg to 72.2±3.9 kg was observed, but an increase of fat mass from 10.3±5.6 kg to 11.1±5.4 kg, almost completely reversed the changes seen in the pre-season training phase. Remarkably, both resting and post-ischemic blood flow (7.3±3.4 and 26.0±6.3 ml/100 ml/min) respectively, were strongly reduced during the playing and training stress phases, but both parameters increased to normal levels (9.0±2.7 and 33.9±7.6 ml/100 ml/min) during the season intermission. Recovery was also characterized by rising levels of serum creatinine, granulocytes count, total IL-8, serum nitrate, ferritin, and bilirubin. These data suggest a compensated hypo-perfusion of muscle during the playing season, followed by an intramuscular ischemia/reperfusion syndrome during the recovery phase that is associated with muscle protein turnover and inflammatory endothelial reaction, as demonstrated by iNOS and HO-1 activation, as well as IL-8 release. The data provided from this study suggest that the immune system is not able to function fully during periods of high physical stress. The implications of this study are that recuperation should be carefully monitored in athletes who undergo intensive training over extended periods, but that these parameters may also prove useful for determining an individual's risk of tissue stress and possibly their susceptibility to progressive tissue damage or injury

Biological Earth observation with animal sensors.

Space-based tracking technology using low-cost miniature tags is now delivering data on fine-scale animal movement at near-global scale. Linked with remotely sensed environmental data, this offers a biological lens on habitat integrity and connectivity for conservation and human health; a global network of animal sentinels of environmen-tal change

Effects of carrying a pathogenic variant in the tyrosine hydroxylase gene on motivated action and valuation: A pilot study in family members with tyrosine hydroxylase deficiency

Contains fulltext : 218327.pdf (publisher's version ) (Open Access)Catecholamines (particularly dopamine) have long been implicated in motivation, learning and behavioural activation. Benign variants in dopamine-regulating genes have widely been linked to these processes as well, yet the cognitive effects of carrying pathogenic variants in the gene coding for tyrosine hydroxylase, which transforms tyrosine into dopamine’s direct precursor L-Dopa, have never been studied. Here, we assessed for the first time whether carriers of tyrosine hydroxylase deficiency (THD) show altered motivated action due to putative reductions in dopamine synthesis. To this end, we employed a motivational Go/NoGo learning task, which is sensitive to manipulations in dopamine function and compared 16 family members of THD patients with 20 education- and age-matched controls. In the first learning phase of this task, subjects learnt to make Go or NoGo responses to cues that predict reward vs. punishment. In the second transfer phase, the subjects were presented with pairs of cues and chose the one they preferred, in the absence of reinforcement. Cue valence strongly biased Go/NoGo responding in the learning phase, such that subjects made more Go responses to reward than punishment cues. The groups did not significantly differ in this motivational bias. However, the THD carriers exhibited a shift in preference from NoGo-to-Win to Go-to- Avoid cues relative to matched controls during the transfer phase. These results suggest that subjective valuation is altered in THD carriers, potentially due to catecholamine-dependent changes in reward expectations, whereas task performance was unaffected. This pilot study provides a first insight into the cognitive consequences of carrying pathogenic TH variants, focusing on alterations in the reward valuation system and motivational biases in action.Dissertation J.C. Swart, Radboud Universit