685 research outputs found
Remarks on the paper by A. De Visscher, "what does the g-index really measure?"
No full textAbstract: The author presents a different view on properties of impact measures than given in the paper of De Visscher (2011). He argues that a good impact measure works better when citations are concentrated rather than spread out over articles. The author also presents theoretical evidence that the g-index and the R-index can be close to the square root of the total number of citations, whereas this is not the case for the A-index. Here the author confirms an assertion of De Visscher
Balancing stress and recovery in sports
No full textTo reach elite level in sports, athletes have to start their intensive and time-consuming training at an early stage. The road to the top is a stressful one, not only due to the physiological stress of training, but also caused by psychological and social stress. In order to improve performance athletes continuously challenge their personal boundaries. This may lead to a local or general overload of the human body that results into injuries, illnesses and overtraining. Overtraining is characterized by an unexplained decrement in sport-specific performance and is often coupled with symptoms such as increased fatigue, poor concentration, disturbed mood, and altered eating and sleeping patterns. Full recovery may take months to years. Monitoring stress and recovery may help to optimize performance and prevent a local or general overload. Clinical measurements showed that mood state and hormonal responses to a double maximal exercise protocol provided valuable information to confirm the diagnosis of overtraining.
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Study of stochastic processes and RNA elasticity using optical tweezers
No full textOur main research project is to develop an experimental system to understand the ribosomes as molecular motors. For this purpose, we designed and developed the single molecule ribosome motility assay. In this thesis, we discuss the related steps which we have taken to develop this assay: the instrumentation and four experiments. In the introduction, we illustrate the current experimental scheme and show the preliminary data of the single molecule ribosome translation. In the first two chapters, we discuss two interesting experiments dealing with stochastic problems. In the first chapter, we introduce the idea that the noise can be reduced in certain conditions. We show that the noise can be really reduced but only if added fluctuations have to drive the input into states with reduced intrinsic noise. In the second chapter, we investigate two-state processes experimentally using a simple physical system in which a microscopic bead is trapped in a double-well potential. We discuss how we can control the characteristics of the escape process by adding a periodic force and illustrate the characteristics in terms of the residence time distribution and the escape phase. As last two chapters, we discuss the elastic and structural properties of homopolymeric RNA, polyadenylic acids (poly(A)), polycytidylic acids (poly(C)), and polyuridylic acids (poly(U)). First, we investigate the elastic property of poly(U) as a random coil. We find that the force-extension data is well predicted by a classic worm-like chain model at high Na⁺ concentrations, whereas at low such concentrations the introduction of a scale-dependent persistence length is required. As single-stranded helices, poly(A) and poly(C) are studied. We stretch the molecules to induce the conformational transition from folded states to unfolded states and use the elastically coupled two-state model to acquire their structural information (about 9 bases per turn and 8 bases per turn, for poly(A) and poly(C) respectively, at neutral pH and 500 mM [Na⁺]) and the free energy differences between two states (20 pN·nm for poly(A) and 17.5 pN·nm for poly(C))
Fire safety regulations for housing in Europe compared
No full textThere is still broad variety of systems of technical requirements for buildings in the various European countries, despite the existence of the Construction Products Directive of the European Union and the development of Euro Codes. The goals and topics are quite similar, but detailed study reveals considerable variety of functional requirements, performance requirements, and specifications, with inconsistency within the requirements of some countries.This article is based on the findings of comparative analysis of building regulations for housing in eight European countries, commissioned by the Dutch Ministry of Housing and intended to locate the Dutch Building Decree within the spectrum of regulations in other European countries. The project compares the systems of building control, the formulation of regulations, and the content of requirements for selected subjects and only for the domain of housing. Earlier (Visscher e. a. 2005) an article about the differences in the systems of formulation of regulations was published. This article focusses on the analysis of fire safety, which identifies several differences in both levels of requirements and strategies that may be significant in practice. It illustrates many impediments to harmonisation of the description of fire safety strategies.OTB Research Institut
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SgrAI Clustering on DNA
No full textSgrAI restriction enzymes bind to DNA at multiple sites and move to a central location on the molecule, forming a cluster. We qualitatively confirmed this behavior using a tethered particle motion assay and a DNA stretching assay using an optical trap. Quantitative analysis proved impossible due to the length of our DNA molecules and the large number of SgrAI binding sites. We recommend using a plasmid with a small number of binding sites for future experiments
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Five Years in Theoretical and Computational Chemistry: From H3+ to DNA
No full textThe research described in this dissertation concerns two fields of theoretical chemistry: Part I concerns applications of Density Functional Theory, and part II high accuracy calculations within the Born-Oppenheimer approximation using explicitly correlated Gaussian functions.In the first part, after a brief introduction to Density Functional Theory and Hartree Fock methods, the candidate's research in Density Functional Theory is described in two chapters. One treats the charge transport in B-DNA, specifically (GC) oligomers solvated by water. The second chapter treats the charge transfer between the Lithium atom and Fullerene-C in the endohedral complex Li@C. In both applications Density Functional Theory was the central quantum mechanical technique that allowed the approaching of such large molecular systems.In the second part of this dissertation, the candidate's development of a FORTRAN code using explicitly correlated Gaussian functions within the Born-Oppenheimer approximation is presented.Every item of the author's research during his graduate studies has been published in co-authorship with the author's scientific advisor and other collaborators in peer-reviewed journals. A total of 8 scientific articles and one letter have been published by the author while at The University of Arizona
Heart rate recovery during the Interval Shuttle Run Test in talented soccer players
No full textObjective: For soccer players, intermittent endurance capacity is important to reach professional level1. Several maximal tests during a season can increase the risk on injuries and it would therefore be beneficial to test players submaximal. The goal is to investigate whether the heart rate recovery (HRR) in the beginning of the Interval Shuttle Run Test (ISRT) predicts the final performance. Methods: Heart rate is registered (Polar team2 pro) in 18 talented soccer players (aged 17-19) participating in the ISRT2. Players are divided into two groups based on their performance (high vs. low) on the ISRT. HRR is determined as the difference between maximum heart rate during running periods and minimum heart rate in rest periods. Mean differences between groups in HRR during 2nd until 11th rest interval are statistically evaluated (t-test). Results: Differences in HRR were found between the two groups (p<0.05). Players with a high performance on the ISRT showed a significantly faster HRR (9.6 vs. 7.6 heart rate difference). Conclusion: Performance on ISRT seems associated with HRR. Faster HRR is promising to predict the final performance on ISRT. Practice implications: Submaximal ISRT with heart rate recording might be sufficient to determine intermittent endurance capacity of talented players. References: 1 Roescher C. R., Elferink-Gemser M. T., Huijgen B. C. H. & Visscher C. (2010). Soccer endurance development in professionals. International Journal of Sports Medicine, 31, 174 – 179 2 Lemmink K. A. P. M., Visscher C., Lambert M. I. & Lamberts R. (2004). The Interval Shuttle Run Test for intermittent sport players: evaluation of reliability. Journal of Strength and conditioning Research, 18, 821-82
Heart rate recovery during the Interval Shuttle Run Test in talented soccer players
No full textObjective: For soccer players, intermittent endurance capacity is important to reach professional level1. Several maximal tests during a season can increase the risk on injuries and it would therefore be beneficial to test players submaximal. The goal is to investigate whether the heart rate recovery (HRR) in the beginning of the Interval Shuttle Run Test (ISRT) predicts the final performance. Methods: Heart rate is registered (Polar team2 pro) in 18 talented soccer players (aged 17-19) participating in the ISRT2. Players are divided into two groups based on their performance (high vs. low) on the ISRT. HRR is determined as the difference between maximum heart rate during running periods and minimum heart rate in rest periods. Mean differences between groups in HRR during 2nd until 11th rest interval are statistically evaluated (t-test). Results: Differences in HRR were found between the two groups (p<0.05). Players with a high performance on the ISRT showed a significantly faster HRR (9.6 vs. 7.6 heart rate difference). Conclusion: Performance on ISRT seems associated with HRR. Faster HRR is promising to predict the final performance on ISRT. Practice implications: Submaximal ISRT with heart rate recording might be sufficient to determine intermittent endurance capacity of talented players. References: 1 Roescher C. R., Elferink-Gemser M. T., Huijgen B. C. H. & Visscher C. (2010). Soccer endurance development in professionals. International Journal of Sports Medicine, 31, 174 – 179 2 Lemmink K. A. P. M., Visscher C., Lambert M. I. & Lamberts R. (2004). The Interval Shuttle Run Test for intermittent sport players: evaluation of reliability. Journal of Strength and conditioning Research, 18, 821-82
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