Electrochemical activation of halogen bonding

International audienceIn the past, noncovalent interactions have been extensively studied by electrochemical methods. In this context, halogen bonding (XB) has been a long-time overlooked item in the toolbox of supramolecular chemistry. The article is treating electrochemical activation of XB in solution and at the solid–liquid interface. Key principles and recent work on the use of electrochemistry as a tool for detecting and controlling XB are reported. Different types of redox-switching XB are identified in the context of molecular recognition and detection. First evidence for XB promoted electron transfer reactions involving the activation of covalent bonds represents a completely new and emerging domain, ripe for exploration

Effects of complex movements on the brain as a result of increased decision-making

Non-linearity is considered to be an essential property of complex systems. The associated high sensitivity of the result on the constraints leads to fundamental problems of a system description based on variables selected in the reductionist tradition. The attempt to compensate the problems by averaging data leads to the neglect of the individual and the moment. However, both is of enormous importance for effective therapy, training, and learning. The theory of differential learning suggests an alternative approach to dealing with these problems. With constantly changing complex whole-body movements, extensive decisions are demanded from the learner, which lead to brain states through an overstraining of the working memory, as it were, as they are also known after mindfulness meditation

Acute effects of instructed and self-created variable rope skipping on EEG brain activity and heart rate variability

The influence of physical activity on brain and heart activity dependent on type and intensity of exercise is meanwhile widely accepted. Mainly cyclic exercises with longer duration formed the basis for showing the influence on either central nervous system or on heart metabolism. Effects of the variability of movement sequences on brain and heart have been studied only sparsely so far. This study investigated effects of three different motor learning approaches combined with a single bout of rope skipping exercises on the spontaneous electroencephalographic (EEG) brain activity, heart rate variability (HRV) and the rate of perceived exertion (RPE). Participants performed repetitive learning (RL) and two extremely variable rope skipping schedules according to the differential learning approach. Thereby one bout was characterized by instructed variable learning (DLi) and the other by self-created variable learning (DLc) in randomized order each on three consecutive days. The results show higher RPE after DLi and DLc than after RL. HRV analysis demonstrates significant changes in pre-post exercise comparison in all training approaches. No statistically significant differences between training schedules were identified. Slightly greater changes in HRV parameters were observed in both DL approaches indicating a higher activation of the sympathetic nervous system. EEG data reveals higher parietal alpha1 and temporal alpha2 power in RL compared to both DL schedules immediately post exercise. During the recovery of up to 30 minutes, RL shows higher temporal and occipital theta, temporal, parietal and occipital alpha, temporal and occipital beta and frontal beta3 power. In conclusion, already a single bout of 3 minutes of rope skipping can lead to brain states that are associated with being advantageous for cognitive learning. Combined with additional, cognitively demanding tasks in form of the DL approach, it seems to lead to an overload of the mental capacity, at least on the short term. Further research should fathom the reciprocal influence of cardiac and central-nervous strain in greater detail

Dynamic office environments improve brain activity and attentional performance mediated by increased motor activity

Current research demonstrates beneficial effects of physical activity on brain functions and cognitive performance. To date, less is known on the effects of movements that do not fall into the category of sports related aerobic or anaerobic exercise but involve gross motor movements. In previous studies, we found beneficial effects of dynamic working environments, i.e. environments that allow movements during cognitive task performance, on cognitive performance and the corresponding brain activity. The aim of the present study was to examine the effects of a dynamic and a static office environment on attentional and vigilance performance and on the corresponding EEG brain activation patterns. In a two-week intervention, participants worked either in a dynamic or a static office. In each intervention group, twelve subjects performed attentional and vigilance tasks. Spontaneous electroencephalographic (EEG) activity was measured on the first, and on the last experimental session continuously before, during, and immediately after each intervention session. EEG was recorded from nineteen electrodes. Results showed differences in EEG brain activity in the dynamic compared to the static office at the beginning as well as at the end of the intervention. EEG theta power was increased in the vigilance task in anterior regions, alpha power in central and parietal regions in the dynamic compared to the static office. Further, increases in beta activity in the attention and vigilance test were shown in the dynamic compared to the static office. Beta power was increased in frontal and central regions. Gamma power was increased in the d2-R test in frontal and central regions. After two weeks, the effects on brain activity increased for the attentional and the vigilance task in the dynamic office. Increased theta and alpha oscillations were obtained in anterior areas with increased activity in the beta and gamma bands in anterior and central areas in the dynamic compared to the static office. EEG oscillatory patterns indicate beneficial effects of dynamic office environments on attentional and vigilance performance that are mediated by increased motor activity. We discuss the obtained patterns of EEG oscillations in terms of the close interrelations between the attentional and the motor system

IDENTIFYING INDIVIDUAL MOVEMENT STYLES IN HIGH PERFORMANCE SPORTS BY MEANS OF SELF-ORGANIZING KOHONEN MAPS

INTRODUCTION: Although single case studies are common in more general oriented behavioral sciences (Yin 1988), they are still very rare in sports science. The still lasting preference of group studies in sports science is often connected with the assumption of ‚ideal techniques‘ in the investigated sports disciplin. Wether such an assumption is justifiable biomechanically, should have been investigated in this pilot-study by means of a pattern recognition approach. METHODS: The final throwing phase of 8 male and 19 female javelin throwers was filmed with two highspeed cameras threedimensionally. The male throwers were finalists of the world championship 1987 in Rome, whereas the female group consisted of 10 worldclass heptathletes and 19 javelin specialists with national and international level. From 2 female specialists 10 and 6 throwing trials were filmed in different competitions, respectively. The throwers movements were described physically complete by means of the main joint angles and its angular velocities. Kohonen maps were trained to project these highdimensional individual feature vectors to a low dimensional neuron output space. The euclidian distances between all trajectories in the neuron output space formed the basis for a cluster analysis (Bauer/Schöllhorn 1997). Beside the complete set of variables we seperated the movement into variables of the a) lower and upper body, b) left and right side, and c) angles and angular velocities. RESULTS AND DISCUSSION: The cluster analyses of all variable sets do not display any performance dependance. Clusters of male and female techniques are distinguishable only tendentious in the complete variable group. What we could identify in all sets of variables were the 10 and 6 trials of the two female specialists, respectively, within two seperated clusters. Although both athletes‘ throws had similar thrown distances (55m to 68m), they were not in the same cluster, but were seperated from the others completely. These clusters, even in the subgroups of variables, provide a clear indication for highly individual throwing techniques not only in the whole but also in upper and lower bodies movement as well as in the left and right side movement, and in the angle and angular velocity, respectively. CONCLUSION: The identification of individual throwing styles by means of a duration of 200ms leads to rethink the idea of ideal throwing techniques and its pure imitation in learning strategies. REFERENCES: Bauer, H. U. Schöllhorn, W. (1997). Self-Organizing Maps for the Analysis of Complex Movement Patterns. Neural Processing Letters 5, 193-199. Yin, R. K. (1988). Case Study Research. Newbury Park: Sage Publications. * We would like to acknowledge Dr.Menzel for providing the data