Langevin dynamics modeling of the water diffusion tensor in partially aligned collagen networks

In this work, a Langevin dynamics model of the diffusion of water in articular cartilage was developed. Numerical simulations of the translational dynamics of water molecules and their interaction with collagen fibers were used to study the quantitative relationship between the organization of the collagen fiber network and the diffusion tensor of water in model cartilage. Langevin dynamics was used to simulate water diffusion in both ordered and partially disordered cartilage models. In addition, an analytical approach was developed to estimate the diffusion tensor for a network comprising a given distribution of fiber orientations. The key findings are that (1) an approximately linear relationship was observed between collagen volume fraction and the fractional anisotropy of the diffusion tensor in fiber networks of a given degree of alignment, (2) for any given fiber volume fraction, fractional anisotropy follows a fiber alignment dependency similar to the square of the second Legendre polynomial of cos(θ), with the minimum anisotropy occurring at approximately the magic angle (θMA), and (3) a decrease in the principal eigenvalue and an increase in the transverse eigenvalues is observed as the fiber orientation angle θ progresses from 0◦ to 90◦. The corresponding diffusion ellipsoids are prolate for θ < θMA, spherical for θ ≈ θMA, and oblate for θ > θMA. Expansion of the model to include discrimination between the combined effects of alignment disorder and collagen fiber volume fraction on the diffusion tensor is discussed.

Relative entropy rate based multiple hidden Markov Model Approximation

This paper proposes a novel relative entropy rate (RER) based approach for multiple HMM (MHMM) approximation of a class of discrete-time uncertain processes. Under different uncertainty assumptions, the model design problem is posed either as a min-max optimisation problem or stochastic minimisation problem on the RER between joint laws describing the state and output processes (rather than the more usual RER between output processes). A suitable filter is proposed for which performance results are established which bound conditional mean estimation performance and show that estimation performance improves as the RER is reduced. These filter consistency and convergence bounds are the first results characterising multiple HMM approximation performance and suggest that joint RER concepts provide a useful model selection criteria. The proposed model design process and MHMM filter are demonstrated on an important image processing dim-target detection problem.

Principal preparation and training : a look at China and its issues

Purpose: The purpose of this paper is to provide an understanding of principal preparation and training in China by providing a background discussion of principal preparation in a number of countries. As an illustration, it provides an overview of the curriculum used in the initial preparation of school principals at Beijing Normal University.-----Design/methodology/approach: The paper draws mainly on writing and research from China, Australia and the USA to explore principal preparation and training in China.-----Findings: In addition to providing a rich description of principal preparation in China, the paper's main findings comprise seven key challenges that confront China as it endeavours to provide quality principal preparation. These challenges include China's diversity and uneven social, cultural and educational development; limited resources in some regions throughout China; the place and importance of study tours for principal preparation; the teaching approach used to train principals; the process used for assessing principal learning during their training programs; the limited transfer of learning from the classroom to the school environment; and the timing of training for principals.-----Practical implications: Each of the challenges arising here raises important practical implications for developers of principal training programs.-----Originality/value: The paper paints a picture of principal preparation in China and raises a number of issues and challenges with which it continues to grapple. Of note is that China is not alone in facing some of these ongoing concerns.

Decentred optical axes and aberrations along principal visual field meridians

Suggestions that peripheral imagery may affect the development of refractive error have led to interest in the variation in refraction and aberration across the visual field. It is shown that, if the optical system of the eye is rotationally symmetric about an optical axis which does not coincide with the visual axis, measurements of refraction and aberration made along the horizontal and vertical meridians of the visual field will show asymmetry about the visual axis. The departures from symmetry are modelled for second-order aberrations, refractive components and third-order coma. These theoretical results are compared with practical measurements from the literature. The experimental data support the concept that departures from symmetry about the visual axis in the measurements of crossed-cylinder astigmatism J45 and J180 are largely explicable in terms of a decentred optical axis. Measurements of the mean sphere M suggest, however, that the retinal curvature must differ in the horizontal and vertical meridians.

Cost-effectiveness of a telephone-delivered intervention for physical activity and diet

Background: Given escalating rates of chronic disease, broad-reach and cost-effective interventions to increase physical activity and improve dietary intake are needed. The cost-effectiveness of a Telephone Counselling intervention to improve physical activity and diet, targeting adults with established chronic diseases in a low socio-economic area of a major Australian city was examined. Methodology/Principal Findings: A cost-effectiveness modelling study using data collected between February 2005 and November 2007 from a cluster-randomised trial that compared Telephone Counselling with a “Usual Care” (brief intervention) alternative. Economic outcomes were assessed using a state-transition Markov model, which predicted the progress of participants through five health states relating to physical activity and dietary improvement, for ten years after recruitment. The costs and health benefits of Telephone Counselling, Usual Care and an existing practice (Real Control) group were compared. Telephone Counselling compared to Usual Care was not cost-effective ($78,489 per quality adjusted life year gained). However, the Usual Care group did not represent existing practice and is not a useful comparator for decision making. Comparing Telephone Counselling outcomes to existing practice (Real Control), the intervention was found to be cost-effective ($29,375 per quality adjusted life year gained). Usual Care (brief intervention) compared to existing practice (Real Control) was also cost-effective ($12,153 per quality adjusted life year gained). Conclusions/Significance: This modelling study shows that a decision to adopt a Telephone Counselling program over existing practice (Real Control) is likely to be cost-effective. Choosing the ‘Usual Care’ brief intervention over existing practice (Real Control) shows a lower cost per quality adjusted life year, but the lack of supporting evidence for efficacy or sustainability is an important consideration for decision makers. The economics of behavioural approaches to improving health must be made explicit if decision makers are to be convinced that allocating resources toward such programs is worthwhile.

Thai word segmentation with hidden Markov Model and decision tree

The Thai written language is one of the languages that does not have word boundaries. In order to discover the meaning of the document, all texts must be separated into syllables, words, sentences, and paragraphs. This paper develops a novel method to segment the Thai text by combining a non-dictionary based technique with a dictionary-based technique. This method first applies the Thai language grammar rules to the text for identifying syllables. The hidden Markov model is then used for merging possible syllables into words. The identified words are verified with a lexical dictionary and a decision tree is employed to discover the words unidentified by the lexical dictionary. Documents used in the litigation process of Thai court proceedings have been used in experiments. The results which are segmented words, obtained by the proposed method outperform the results obtained by other existing methods.

An historical analysis of the development of thinking in the principal writings of Malcolm Knowles

Malcolm Shepherd Knowles was a key writer and theorist in the field of adult education in the United States. He died in 1997 and left a large legacy of books and journal articles. This thesis traced the development of his thinking over the 46-year period from 1950 to 1995. It examined the 25 works authored, co-authored, edited, reissued and revised by him during that period. The writings were scrutinised using a literature research methodology to expose the theoretical content, and a history of thought lens to identify and account for the development of major ideas. The methodology enabled a gradual unfolding of the history. A broadly-consistent and sequential pattern of thought focusing on the notion of andragogy emerged. The study revealed that after the initial phases of exploratory thinking, Knowles developed a practical-theoretical framework he believed could function as a comprehensive theory of adult learning. As his thinking progressed, his theory developed into a unified framework for human resource development and, later, into a model for the development of self-directed lifelong learners. The study traced the development of Knowles’ thinking through the phases of thought, identified the writings that belonged within each phase and produced a series of diagrammatic representations showing the evolution of his conceptual framework. The production of a history of the development of Knowles’ thought is the major outcome of the study. In addition to plotting the narrative sequence of thought-events, the history helps to explicate the factors and conditions that influenced Knowles’ thinking and to show the interrelationships between ideas. The study should help practitioners in their use and appreciation of Knowles’ works.