Modelling and analysis of bacterial tracks suggest an active reorientation mechanism in Rhodobacter sphaeroides

Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides. The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides. This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation.     

Detection of Axial Cracks in Pipes Using Focused Guided Waves

The implementation of synthetic guided wave focusing to locate axially aligned defects in pipes has been investigated. Results from both finite element computer models and experiments on real pipes are presented and the data show good agreement. Focusing is necessary to improve the reflection coefficient from axially aligned defects, as the signals are very weak. The Common Source Method (CSM) of synthetic focusing has been applied which makes it possible to apply focusing via post processing to previously collected data. The dependence of reflection coefficient on crack length was measured for both through thickness and part depth axially aligned defects, at a range of frequencies, using the torsional guided wave family. The results show that the reflection coefficient is approximately doubled when focusing is employed, compared to the sensitivity for unfocused fundamental torsional waves. However the sensitivity is still very low, so in practise this approach could only be used to find severe defects.     

Banana peel: an effective biosorbent for aflatoxins

This work reports the application of banana peel as a novel bioadsorbent for in vitro removal of five mycotoxins (aflatoxins (AFB1, AFB2, AFG1, AFG2) and ochratoxin A). The effect of operational parameters including initial pH, adsorbent dose, contact time and temperature were studied in batch adsorption experiments. Scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and point of zero charge (pH_pzc) analysis were used to characterise the adsorbent material. Aflatoxins’ adsorption equilibrium was achieved in 15 min, with highest adsorption at alkaline pH (6–8), while ochratoxin has not shown any significant adsorption due to surface charge repulsion. The experimental equilibrium data were tested by Langmuir, Freundlich and Hill isotherms. The Langmuir isotherm was found to be the best fitted model for aflatoxins, and the maximum monolayer coverage (Q₀) was determined to be 8.4, 9.5, 0.4 and 1.1 ng mg^?1 for AFB1, AFB2, AFG1 and AFG2 respectively. Thermodynamic parameters including changes in free energy (ΔG), enthalpy (ΔH) and entropy (ΔS) were determined for the four aflatoxins. Free energy change and enthalpy change demonstrated that the adsorption process was exothermic and spontaneous. Adsorption and desorption study at different pH further demonstrated that the sorption of toxins was strong enough to sustain pH changes that would be experienced in the gastrointestinal tract. This study suggests that biosorption of aflatoxins by dried banana peel may be an effective low-cost decontamination method for incorporation in animal feed diets.     

Geodesic Regression and the Theory of Least Squares on Riemannian Manifolds

This paper develops the theory of geodesic regression and least-squares estimation on Riemannian manifolds. Geodesic regression is a method for finding the relationship between a real-valued independent variable and a manifold-valued dependent random variable, where this relationship is modeled as a geodesic curve on the manifold. Least-squares estimation is formulated intrinsically as a minimization of the sum-of-squared geodesic distances of the data to the estimated model. Geodesic regression is a direct generalization of linear regression to the manifold setting, and it provides a simple parameterization of the estimated relationship as an initial point and velocity, analogous to the intercept and slope. A nonparametric permutation test for determining the significance of the trend is also given. For the case of symmetric spaces, two main theoretical results are established. First, conditions for existence and uniqueness of the least-squares problem are provided. Second, a maximum likelihood criteria is developed for a suitable definition of Gaussian errors on the manifold. While the method can be generally applied to data on any manifold, specific examples are given for a set of synthetically generated rotation data and an application to analyzing shape changes in the corpus callosum due to age.     

Knowledge risks in organizational networks: The practice perspective

This commentary paper aims to highlight issues associated with the supposed ability to transfer knowledge across networks. In response to the paper “Risks in Organizational Networks: An Exploratory Framework”, (Trkman and Desouza, 2012, pp. 1–17), we argue that the taken-for-granted assumption that knowledge is transferrable represents a risk in itself. We analyze knowledge in networks using a practice perspective – in turn we consider knowledge as enacted in social practices and as context-specific. In contrast with Trkman and Desouza’s paper, we argue that if knowledge is seen as enacted in practice, a framework that maps risks associated with knowledge transfer is limiting. We conclude that, since knowing in practice is emergent and not fully controllable, adopting a set of best practices on how to effectively transfer (or not) knowledge could itself be risky for managers who then believe that knowledge can be treated as a commodity and easily moved about a network.     

Trendof informatization development of analycal instruments

分析仪器和其他传统工业一样,正在信息技术的改造下,向微型化、智能化、自动化和网络化方向发展.分析仪器作为数据获得的源头技术,必将在信息技术发展中起到重要作用,将从被动转向主动,并促进信息技术的发展.分析工作者也将是未来物联网不可或缺的生力军.     

Continuous Improvement Methodology Applied to United Kingdom Academic Library Websites Via National Survey Results

This article analyzes the possibilities of applying Continuous Improvement principles to the management and maintenance of academic library websites. Current practice is mapped onto Continuous Improvement principles, with evidence distilled from a United Kingdom national survey of academic library web practitioners. The survey data informs a website organizational framework and operational model. The framework describes the setting within which library websites are managed, while the model focuses on library specific aspects to the management and development of their site.     

Enclothed cognition and hidden meanings in important Ottoman textiles

This paper illustrates how hidden details in garment design may reveal important clues about the motives of the wearer or designer that are of considerable cultural relevance. We suggest these hidden design features may reflect key psychological factors previously not considered. We illustrate this by doing a multilevel analysis of two important sixteenth century examples of Ottoman court clothing from the Topkapi Palace Museum. We show that these garments contain early examples of the use of “enclothed cognition” where the designs themselves are likely to have influenced the mind of the wearer. We suggest that the historical-social analysis of clothing may benefit from considering the concealed, as well as the explicit, psychologically relevant design features. We suggest that psychosocial interpretations of clothing may help further our understanding of textile and apparel design more generally, even within an historical context.     

Iosipescu shear deformation and fracture in model thermoplastic polyolefins

Shear deformation and fracture behaviors in polypropylene (PP)‐based model thermoplastic polyolefins (TPOs) were investigated with the Iosipescu shear test. The shear deformation process was monitored in situ via video camera to obtain experimental shear stress–strain curves of model TPOs. Shear fracture mechanisms were studied with optical microscopy and scanning electron microscopy. Macroscopically, the cracks in neat PP propagated along the maximum shear plane, which indicated that mode‐II shear failure existed in neat PP. Microscopically, it was shown that shear fracture initiated in the form of partial, discontinuous inclined microcracks that later coalesced and formed the final continuous crack. The incorporation of rubber in PP could transform the shear fracture process into a stretching process in the shear damage zone. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3201–3214, 2001     

Racial microaggressions and worldviews.

Comments by on an article entitled "Racial microaggression? How do you know?" by Rafael S. Harris Jr. (see record2008-05553-011). The author states that in our original article we asserted that the racial reality of POC was generally different from the racial reality of White Americans and that often times interpretations of situations and events are the result of worldviews or racial identity. When references are made to POC, or to “visible racial/ethnic groups,” reference is being made not only to the shared cultural characteristics, norms, values, and attitudes of the group (African American, Asian American, American Indian, and Latino/Hispanic American) but to a self-designation of racial identity formed from sociopolitical experiences of unequal social, economic, legal, and political power in U.S. society that are based on visible racial characteristics. (PsycINFO Database Record (c) 2010 APA, all rights reserved)