Feedback control architecture and the bacterial chemotaxis network.

PMCID: PMC3088647This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.Bacteria move towards favourable and away from toxic environments by changing their swimming pattern. This response is regulated by the chemotaxis signalling pathway, which has an important feature: it uses feedback to 'reset' (adapt) the bacterial sensing ability, which allows the bacteria to sense a range of background environmental changes. The role of this feedback has been studied extensively in the simple chemotaxis pathway of Escherichia coli. However it has been recently found that the majority of bacteria have multiple chemotaxis homologues of the E. coli proteins, resulting in more complex pathways. In this paper we investigate the configuration and role of feedback in Rhodobacter sphaeroides, a bacterium containing multiple homologues of the chemotaxis proteins found in E. coli. Multiple proteins could produce different possible feedback configurations, each having different chemotactic performance qualities and levels of robustness to variations and uncertainties in biological parameters and to intracellular noise. We develop four models corresponding to different feedback configurations. Using a series of carefully designed experiments we discriminate between these models and invalidate three of them. When these models are examined in terms of robustness to noise and parametric uncertainties, we find that the non-invalidated model is superior to the others. Moreover, it has a 'cascade control' feedback architecture which is used extensively in engineering to improve system performance, including robustness. Given that the majority of bacteria are known to have multiple chemotaxis pathways, in this paper we show that some feedback architectures allow them to have better performance than others. In particular, cascade control may be an important feature in achieving robust functionality in more complex signalling pathways and in improving their performance

How students view the boundaries between their science and religious education concerning the origins of life and the universe

Internationally in secondary schools, lessons are typically taught by subject specialists, raising the question of how to accommodate teaching which bridges the sciences and humanities. This is the first study to look at how students make sense of the teaching they receive in two subjects (science and religious education) when one subject’s curriculum explicitly refers to cross-disciplinary study and the other does not. Interviews with 61 students in seven schools in England suggested that students perceive a permeable boundary between science and their learning in science lessons and also a permeable boundary between religion and their learning in RE lessons, yet perceive a firm boundary between science lessons and RE lessons. We concluded that it is unreasonable to expect students to transfer instruction about cross-disciplinary perspectives across such impermeable subject boundaries. Finally we consider the implications of these findings for the successful management of cross-disciplinary education

Children Will Follow Someone; Lead Them to Jesus - The Soil and the Sower

Children’s ministry is not school nor is it babysitting. It is getting on the path with our children and their families and assimilating God’s words into life. If kids do not follow Jesus when they are young, they are less likely to follow Him. Discover how we help children choose to follow Jesus, starting today

Children Will Follow Someone; Lead Them To Jesus - Prodigal Sons and Prodigal Brothers

Children’s ministry is not school nor is it babysitting. It is getting on the path with our children and their families and assimilating God’s words into life. If kids do not follow Jesus when they are young, they are less likely to follow Him. Discover how we help children choose to follow Jesus, starting today

Emotional Regulation and Resilience: Examining the Mediating Role of Rumination

The present study examined the mediating effect of rumination (brooding vs. reflective) in the correlation between emotional regulation (cognitive reappraisal vs. expressive suppression) and resilience. Three-hundred and twenty-five adult participants were recruited through Amazon Mechanical Turk to complete an online survey. A bivariate correlational analysis and four mediation analyses were conducted. In three of the four models, psychological rumination was found to have a significant indirect effect in the correlation between emotional regulation and resilience. The indirect effect of reflective rumination was not significant in the relationship between expressive suppression and resilience. A regression analysis was conducted in this case, and it was determined that expressive suppression and reflective rumination were significant predictors of resilience. The indirect effects were non-significant when positive and negative affect and perceived stress were included as covariates. Results are discussed with reference to necessary future directions of research into the underlying mechanisms of resilience and possible clinical interventions, as well as with reference to the limitations of the present study

Children Will Follow Someone; Lead Them to Jesus - New and Old Wineskins

Children’s ministry is not school nor is it babysitting. It is getting on the path with our children and their families and assimilating God’s words into life. If kids do not follow Jesus when they are young, they are less likely to follow Him. Discover how we help children choose to follow Jesus, starting today

Effects of space weathering on the Trojan asteroids

Thesis: S.B., Massachusetts Institute of Technology, Department of Earth, Atmospheric, and Planetary Sciences, 2002.Cataloged from PDF version of thesis. "The pagination in this thesis reflects how it was delivered to the Institute Archives and Special Collections. Thesis was submitted to the Institute Archives without all the required signatures"--Disclaimer Notice page.Includes bibliographical references (page 40).Trojan asteroids orbit at Jupiter's L4 and L5 points. They are included in the D-class of asteroids because of their steep spectral slope. According to spectra of other asteroid classes, the larger the diameter is of a D-class asteroid, the redder the asteroid should be in the visible spectrum. We examined a total of fifteen asteroids, five (from the SMASS 1 data set) were small, and ten (newly collected data) were large. The actual results did not match our expected results, most likely due to the large error bars and the small data set. Space weathering may affect Trojans in the same way as it does other asteroid classes. To know with certainty, further investigation is needed.by April A. Deet.S.B