127 research outputs found
Rate Determining Factors in Protein Model Structures
Previous research has shown a strong correlation of protein folding rates to
the native state geometry, yet a complete explanation for this dependence is
still lacking. Here we study the rate-geometry relationship with a simple
statistical physics model, and focus on two classes of model geometries,
representing ideal parallel and antiparallel structures. We find that the
logarithm of the rate shows an almost perfect linear correlation with the
"absolute contact order", but the slope depends on the particular class
considered. We discuss these findings in the light of experimental results.Comment: 4 pages, 2 figure
Unbalanced Langmuir kinetics affects TASEP dynamical transitions: mean-field theory
In a previous study we developed a mean-field theory of dynamical transitions
for the totally-asymmetric simple-exclusion process (TASEP) with open
boundaries and Langmuir kinetics, in the so-called balanced regime,
characterized by equal binding and unbinding rates. Here we show that simply
including the possibility of unbalanced rates gives rise to an unexpectedly
richer dynamical phase diagram. In particular, the current work predicts an
unusual type of dynamical transition, which exhibits certain similarities with
first-order phase transitions of equilibrium systems. We also point out that
different types of dynamical transition are accompanied by different structural
changes in the (mean-field) relaxation spectrum.Comment: 32 pages, 8 figure
Immunogenicity and effectiveness of virosomal adjuvanted vaccines against influenza: a brief review of their utility in the elderly population
The World Health Organisation (WHO) estimates that seasonal influenza affects approximately 5-15% of the population on an annual basis and these outbreaks are responsible for significant morbidity and mortality resulting in increased hospital admissions. Annual vaccination remains the main public health strategy for containing influenza. Inactivated influenza vaccines offer a great deal of protection against influenza but these vaccines are not optimal for older adults due to their waning immunity and other factors affecting immunogenicity. Virosomes, stimulate the immune system in a similar way as a natural infection and studies have shown that the virosomal adjuvanted influenza vaccine is immunogenic and safe in different population groups including: the elderly, children and immunocompromised subjects. Currently available data suggest improved immunogenicity of the virosomal adjuvanted vaccine in the elderly and in subjects without protective antibody as compared to conventional vaccines
Measuring movement fluency during the sit-to-walk task
Restoring movement fluency is a key focus for physical rehabilitation; it's measurement, however, lacks objectivity. The purpose of this study was to find whether measurable movement fluency variables differed between groups of adults with different movement abilities whilst performing the sit-to-walk (STW) movement. The movement fluency variables were: (1) hesitation during movement (reduction in forward velocity of the centre of mass; CoM), (2) coordination (percentage of temporal overlap of joint rotations) and (3) smoothness (number of inflections in the CoM jerk signal)
Optimality in Self-Organized Molecular Sorting
We introduce a simple physical picture to explain the process of molecular sorting, whereby specific proteins are concentrated and distilled into submicrometric lipid vesicles in eukaryotic cells. To this purpose, we formulate a model based on the coupling of spontaneous molecular aggregation with vesicle nucleation. Its implications are studied by means of a phenomenological theory describing the diffusion of molecules toward multiple sorting centers that grow due to molecule absorption and are extracted when they reach a sufficiently large size. The predictions of the theory are compared with numerical simulations of a lattice-gas realization of the model and with experimental observations. The efficiency of the distillation process is found to be optimal for intermediate aggregation rates, where the density of sorted molecules is minimal and the process obeys simple scaling laws. Quantitative measures of endocytic sorting performed in primary endothelial cells are compatible with the hypothesis that these optimal conditions are realized in living cells
Metabolic power in hurling with respect to position and halves of match-play.
The current investigation compared the metabolic power and energetic characteristics in team sports with respect to positional lines and halves of match-play. Global positioning system (GPS) technology data were collected from 22 elite competitive hurling matches over a 3-season period. A total of 250 complete match-files were recorded with players split into positional groups of full-back; half-back; midfield; half-forward; full-forward. Raw GPS data were exported into a customized spreadsheet that provided estimations of metabolic power and speed variables across match-play events (average metabolic power [Pmet], high metabolic load distance [HMLD], total distance, relative distance, high-speed distance, maximal speed, accelerations, and deceleration). Pmet, HMLD, total, relative and high-speed distance were 8.9 ± 1.6 W·kg-1, 1457 ± 349 m, 7506 ± 1364 m, 107 ± 20 m·min-1 and 1169 ± 260 m respectively. Half-backs, midfielders and half-forwards outperformed full-backs (Effect Size [ES] = 1.03, 1.22 and 2.07 respectively), and full-forwards in Pmet (Effect Size [ES] = 1.70, 2.07 and 1.28 respectively), and HMLD (full-backs: ES = -1.23, -1.37 and -0.84 respectively, and full-forwards: ES = -1.77, -2.00 and -1.38 respectively). Half-backs (ES = -0.60), midfielders (ES = -0.81), and half-forwards (ES = -0.74) experienced a second-half temporal decrement in HMLD. The current investigation demonstrates that metabolic power may increase our understanding of the match-play demands placed on elite hurling players. Coaches may utilize these findings to construct training drills that replicate match-play demands
Individual-environment interactions in swimming: The smallest unit for analysing the emergence of coordination dynamics in performance?
Displacement in competitive swimming is highly dependent on fluid characteristics,
since athletes use these properties to propel themselves. It is essential for sport
scientists and practitioners to clearly identify the interactions that emerge between
each individual swimmer and properties of an aquatic environment. Traditionally, the
two protagonists in these interactions have been studied separately. Determining the
impact of each swimmerâs movements on fluid flow, and vice versa, is a major
challenge. Classic biomechanical research approaches have focused on swimmersâ
actions, decomposing stroke characteristics for analysis, without exploring
perturbations to fluid flows. Conversely, fluid mechanics research has sought to
record fluid behaviours, isolated from the constraints of competitive swimming
environments (e.g. analyses in two-dimensions, fluid flows passively studied on
mannequins or robot effectors). With improvements in technology, however, recent
investigations have focused on the emergent circular couplings between swimmersâ
movements and fluid dynamics. Here, we provide insights into concepts and tools that
can explain these on-going dynamical interactions in competitive swimming within
the theoretical framework of ecological dynamics
Pacing and Decision Making in Sport and Exercise: The Roles of Perception and Action in the Regulation of Exercise Intensity
In pursuit of optimal performance, athletes and physical exercisers alike have to make decisions about how and when to invest their energy. The process of pacing has been associated with the goal-directed regulation of exercise intensity across an exercise bout. The current review explores divergent views on understanding underlying mechanisms of decision making in pacing. Current pacing literature provides a wide range of aspects that might be involved in the determination of an athlete's pacing strategy, but lacks in explaining how perception and action are coupled in establishing behaviour. In contrast, decision-making literature rooted in the understanding that perception and action are coupled provides refreshing perspectives on explaining the mechanisms that underlie natural interactive behaviour. Contrary to the assumption of behaviour that is managed by a higher-order governor that passively constructs internal representations of the world, an ecological approach is considered. According to this approach, knowledge is rooted in the direct experience of meaningful environmental objects and events in individual environmental processes. To assist a neuropsychological explanation of decision making in exercise regulation, the relevance of the affordance competition hypothesis is explored. By considering pacing as a behavioural expression of continuous decision making, new insights on underlying mechanisms in pacing and optimal performance can be developed. © 2014 Springer International Publishing Switzerland
- âŠ