Allan Variance Analysis as Useful Tool to Determine Noise in Various Single-Molecule Setups

One limitation on the performance of optical traps is the noise inherently present in every setup. Therefore, it is the desire of most experimentalists to minimize and possibly eliminate noise from their optical trapping experiments. A step in this direction is to quantify the actual noise in the system and to evaluate how much each particular component contributes to the overall noise. For this purpose we present Allan variance analysis as a straightforward method. In particular, it allows for judging the impact of drift which gives rise to low-frequency noise, which is extremely difficult to pinpoint by other methods. We show how to determine the optimal sampling time for calibration, the optimal number of data points for a desired experiment, and we provide measurements of how much accuracy is gained by acquiring additional data points. Allan variances of both micrometer-sized spheres and asymmetric nanometer-sized rods are considered.Comment: 14 pages, 6 figures, presented at SPIE Optics+Photonics 2009 in San Diego, CA, US

Gesundheitsrelevantes Verhalten im Kontext. Eine international vergleichende Analyse des Einflusses von Umgebungsbedingungen auf das Gesundheitsverhalten von Kindern und Jugendlichen

Czerwinski F. Gesundheitsrelevantes Verhalten im Kontext. Eine international vergleichende Analyse des Einflusses von Umgebungsbedingungen auf das Gesundheitsverhalten von Kindern und Jugendlichen. Bielefeld: Universität Bielefeld; 2019.**Zusammenfassung** *Hintergrund:* Viele Weichen für die Gesundheit im Verlauf des Lebens werden in der Kindheit und Jugend gestellt. Dem gesundheitsrelevanten Verhalten in dieser Altersgruppe wird in der Forschung demnach eine große Aufmerksamkeit gewidmet. Die meisten Ansätze zur Erklärung dieses Verhaltensspektrums konzentrieren sich auf Merkmale des Individuums, wohingegen Merkmale der Lebenswelten junger Menschen häufig vernach-lässigt oder ignoriert werden. Hier setzt die vorliegende Arbeit an und analysiert Zusammenhänge zwischen drei Formen gesundheitsrelevanten Verhaltens (körperliche Aktivität, Tabak- und übermäßiger Alkoholkonsum) und Aspekten der familiären, schulischen und gesamtgesellschaftlichen Umwelt. Den theoretischen Rahmen bilden sozial-ökologische Modelle, die mit Elementen anderer theoretischer Ansätze angereichert werden. *Methodik:* Die Primärdaten dieser Arbeit stammen aus der „Health Behaviour in School-aged Children“ (HBSC)-Studie, die im Jahr 2009/2010 in insgesamt 43 Ländern in Europa und Nordamerika durchgeführt worden ist. Ergänzend zu den Angaben der befragten Schülerinnen und Schüler im Alter von 11-15 Jahren sind Informationen zu politischen und ökonomischen Merkmalen auf der nationalen Ebene aus diversen Datenquellen genutzt worden, um mithilfe von linearen und logistischen Mehrebenenmodellen Stärke und Richtung der Assoziationen zu bestimmen. *Ergebnisse:* Die Analysen zeigen, dass der größte Teil der Varianz aller drei Verhaltensweisen auf der individuellen Ebene liegt. Die beiden untersuchten Formen des Substanzkonsums sind stärker kontextabhängig als das Bewegungsverhalten und zeigen einen Varianzanteil von bis zu 26 % auf schulischer und nationaler Ebene. Darüber hinaus hängen einige der strukturellen Merkmale mit dem gesundheitsrelevanten Verhalten der Kinder und Jugendlichen zusammen. Besonders die Prävalenzen des entsprechenden Verhaltens unter den Mitschüler*innen und in der Gesamtbevölkerung zeigen sich konsistent als Korrelate. Die Modelle zeigen überdies viele geschlechtsspezifische Assoziationsmuster, bspw. hängt schulischer Stress nur bei Jungen mit einem erhöhten Risiko für Tabakkonsum zusammen, während Mädchen bei berichtetem Stress häufiger übermäßigen Alkoholkonsum angaben. *Diskussion:* Die erzielten Ergebnisse können einige neue Erkenntnisse zum Verständnis der drei Formen gesundheitsrelevanten Verhaltens von 11-15-Jährigen beisteuern. Sie könnten zudem unterstützend bei der Konzeptionierung und Evaluation geschlechtersensibler Interventionen genutzt werden, die neben Determinanten des individuellen Verhaltens auch strukturelle Merkmale auf verschiedenen Ebenen der Lebenswelt (Familie, Schule, Freunde, Gesellschaft) adressieren

The effects of social norms among peer groups on risk behavior: A multilevel approach to differentiate perceived and collective norms

Social norms have been found to be an important factor in individuals’ health and risk behaviors. Past research has typically addressed which social norms individuals perceive in their social environments (e.g., in their peer group). The present article explores normative social influences beyond such perceptions by applying a multilevel approach and differentiating between perceived norms at the individual level and collective norms at the group level. Data on norms and three road traffic risk behaviors (speeding, driving after drinking, and texting while driving) were obtained from a representative survey among young German car drivers (N = 311 anchor respondents) and their peer groups (overall N = 1,244). Multilevel modeling (MLM) revealed that beyond individual normative perceptions of peers’ behavior and approval, actual collective norms (peers’ actual risk behavior and attitudes) affect individuals’ risk behaviors. Findings are discussed with regard to theorizing normative influences on risk behavior and practical implications

Myxococcus xanthus gliding motors are elastically coupled to the substrate as predicted by the focal adhesion model of gliding motility

Myxococcus xanthus is a model organism for studying bacterial social behaviors due to its ability to form complex multi-cellular structures. Knowledge of M. xanthus surface gliding motility and the mechanisms that coordinate it are critically important to our understanding of collective cell behaviors. Although the mechanism of gliding motility is still under investigation, recent experiments suggest that there are two possible mechanisms underlying force production for cell motility: the focal adhesion mechanism and the helical rotor mechanism which differ in the biophysics of the cell-substrate interactions. Whereas the focal adhesion model predicts an elastic coupling, the helical rotor model predicts a viscous coupling. Using a combination of computational modeling, imaging, and force microscopy, we find evidence for elastic coupling in support of the focal adhesion model. Using a biophysical model of the M. xanthus cell, we investigated how the mechanical interactions between cells are affected by interactions with the substrate. Comparison of modeling results with experimental data for cell-cell collision events pointed to a strong, elastic attachment between the cell and substrate. These results are robust to variations in the mechanical and geometrical parameters of the model. We then directly measured the motor-substrate coupling by monitoring the motion of optically trapped beads and find that motor velocity decreases exponentially with opposing load. At high loads, motor velocity approaches zero velocity asymptotically and motors remain bound to beads indicating a strong, elastic attachment

Expanding the Health Information National Trends Survey Research Program Internationally to Examine Global Health Communication Trends: Comparing Health Information Seeking Behaviors in the U.S. and Germany

The Health Information National Trends Survey (HINTS) is a well-established U.S.-based research program administered by the National Cancer Institute to track the public access to and use of health information. This paper introduces a German research initiative, part of the International Studies to Investigate Global Health Information Trends (INSIGHTS) research consortium. This adaptation of the HINTS is important for initiating analyses of global health communication practices and comparing health information seeking behaviors (HISB) across nations to pinpoint potentials and challenges of health information provision and contribute to a deeper understanding of socio-contextual determinants of HISB. First cross-country comparisons revealed that the share of residents seeking for health information is high in the U.S. (80%) and Germany (74%), but different primary sources are used. Whereas a clear majority of U.S. residents chose the Internet to gather health information (74.9%), Germans most often turn to health professionals (48.0%). Socio-structural and health(care)-related predictors were found to contribute to the explanation of HISB in both countries, whereas information-related predictors were only relevant in Germany. The results indicate the need to engage in patient-provider communication to initiate HISB and to improve the access to information for residents with lower socio-economic backgrounds

Individual and school level correlates of moderate to vigorous physical activity among school-children in Germany - a multi-level analysis

Czerwinski F, Finne E, Kolip P, Bucksch J. Individual and school level correlates of moderate to vigorous physical activity among school-children in Germany - a multi-level analysis. BMC Public Health. 2015;15(1): 393.Background Young people spend half of their days in school, but evidence concerning the influence of school environment on the physical activity (PA) of pupils is still inconsistent. A better understanding of potential correlates of PA on the school-level and their possible interaction with individual aspects is needed to improve the development of more effective interventions. Methods We used data from the 2009/10 German Health Behaviour in School-aged Children study (HBSC)-sample (n=5,005 students aged 11–15 years) including self-reported moderate to vigorous intensity PA as well as a variety of biological, demographic and behavioral correlates and matched them with school-level data from the national school principals’ HBSC questionnaire. We analyzed the associations of individual- and school-level correlates with MVPA by gender-specific multi-level regression. Results Only a small share of the overall variation in student’s PA was attributable to the school-level. Consequently, the associations of individual-level correlates with PA were stronger than those of the school-level. Our analysis revealed significant associations of individual-level (i.e. age, consumption of softdrinks, overweight) as well as school-level correlates (i.e. the availability of a football ground and a swimming pool) with MVPA. We also observed some gender-specific findings especially for the school level correlates. Cross-level interactions between individual- and school-level were not apparent. Conclusions Our findings indicate the usefulness of applying an ecological framework to understand and explain complex health behaviors like PA. As we found gender-specific association it might be important to acknowledge that boys and girls have specific needs to be more physically active. Further research should also take other features/elements of the school environment and neighborhood as well as socio-cognitive correlates into account to advance the field

Single-molecule observations of topotecan-mediated TopIB activity at a unique DNA sequence

The rate of DNA supercoil removal by human topoisomerase IB (TopIB) is slowed down by the presence of the camptothecin class of antitumor drugs. By preventing religation, these drugs also prolong the lifetime of the covalent TopIB–DNA complex. Here, we use magnetic tweezers to measure the rate of supercoil removal by drug-bound TopIB at a single DNA sequence in real time. This is accomplished by covalently linking camptothecins to a triple helix-forming oligonucleotide that binds at one location on the DNA molecule monitored. Surprisingly, we find that the DNA dynamics with the TopIB–drug interaction restricted to a single DNA sequence are indistinguishable from the dynamics observed when the TopIB–drug interaction takes place at multiple sites. Specifically, the DNA sequence does not affect the instantaneous supercoil removal rate or the degree to which camptothecins increase the lifetime of the covalent complex. Our data suggest that sequence-dependent dynamics need not to be taken into account in efforts to develop novel camptothecins