Dynamic Bayesian networks for the classification of spinning discs

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2004.Includes bibliographical references (p. 87-89).This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.This thesis considers issues for the application of particle filters to a class of nonlinear filtering and classification problems. Specifically, we study a prototype system of spinning discs. The system combines linear dynamics describing rotation with a nonlinear observation model determined by the disc pattern, which is parameterized by angle. A consequence of the nonlinear observation model is that the posterior state distribution of angle and spin-rate is multi-modal. This detail motivates the use of particle filtering. Practical issues that we consider when using particle filters are sample depletion and sample degeneracy, both of which lead to poor representations of the state distributions. Variance based resampling and regularization are common methods to mitigate sampling issues in particle filtering. We investigate these methods empirically for our prototype problem. Specific parameters of interest relating to these methods are the number of particles used to approximate the posterior distribution, quantitative methods for deciding when to resample, choice of regularization variance, the impact of measurement noise on all of these, and performance over time. A common issue, leading to inaccurate sample-based representations, is the case of relatively low measurement noise combined with an insufficient number of particles. Our empirical results show that for relatively smooth patterns (e.g. linear, cosine) particle filters were less susceptible to sampling issues than for patterns with higher frequency content. The goal of our experiments is to quantify the nature of these differences.by Aurora Clare Schmidt.M.Eng

Mixed methods evaluation of a primary eye care training programme for primary health workers in Morogoro Tanzania.

BACKGROUND: There are 285 million people with visual impairment (VI) worldwide including 39 million who are blind; 15 % of those with VI live in Africa, and around 80 % of VI is preventable or treatable with the right equipment, information and skills. The scarcity of human resources for eye health, particularly in Sub-Saharan Africa, is a key challenge towards achieving this goal. Therefore training primary health workers (PHW) in providing eye-care services has been seen by some authors as a way to improve access to eye-care services in remote communities. However, the package of interventions which could be effectively delivered for eye-care at the primary-care level or the set of skills and competencies that PHWs need has not yet been delineated. The aim of the study was to evaluate the effectiveness of a four day training programme of PHWs in primary eye-care conducted in Morogoro, Tanzania in 2010/2011. METHODS: A mixed methods study using pre- and immediate post-training knowledge assessment of 60 trainees, and in-depth face to face interviews with 20 PHWs and 8 service managers 2 to 3 years after the training. RESULTS: Pre-and immediate post-training assessments indicated improvement in health worker knowledge about eye-care in the short term. Qualitative investigations 2 to 3 years after the training showed that although staff could make the correct management decisions when presented with eye-health problems, they often could not make a correct diagnosis. PHWs and managers reported satisfaction with the content of the training but some of the less well qualified staff found it overwhelming. Theoretical teaching was appreciated by most participants but almost all suggested increasing the time spent on acquiring skills. The training manual was accepted by many and some improvements were recommended. All interviewed PHWs were keen to improve their skills and knowledge. Acquired skills and knowledge were used for identification, referral of patients and for eye-health promotion. CONCLUSION: The training program in Morogoro was considered by PHWs as broadly successful and satisfying in terms of content, methods and duration of training. However, any future programme needs to be considered within the context of strengthening wider health systems

Large-scale cross-societal examination of real-and minimal-group biases.

Peer reviewe

Thymic involution and rising disease incidence with age

For many cancer types, incidence rises rapidly with age as an apparent power law, supporting the idea that cancer is caused by a gradual accumulation of genetic mutations. Similarly, the incidence of many infectious diseases strongly increases with age. Here, combining data from immunology and epidemiology, we show that many of these dramatic age-related increases in incidence can be modeled based on immune system decline, rather than mutation accumulation. In humans, the thymus atrophies from infancy, resulting in an exponential decline in T cell production with a half-life of ∼16 years, which we use as the basis for a minimal mathematical model of disease incidence. Our model outperforms the power law model with the same number of fitting parameters in describing cancer incidence data across a wide spectrum of different cancers, and provides excellent fits to infectious disease data. This framework provides mechanistic insight into cancer emergence, suggesting that age-related decline in T cell output is a major risk factor

Critical residues involved in Toll-like receptor 4 activation by cationic lipid nanocarriers are not located at the lipopolysaccharide-binding interface.

DiC14-amidine is a cationic lipid that was originally designed as a lipid nanocarrier for nucleic acid transport, and turned out to be a Toll-like receptor 4 (TLR4) agonist as well. We found that while E. coli lipopolysaccharide (LPS) is a TLR4 agonist in all species, diC14-amidine nanoliposomes are full agonists for human, mouse and cat receptors but weak horse agonists. Taking advantage of this unusual species specificity, we used chimeric constructs based on the human and horse sequences and identified two regions in the human TLR4 that modulate the agonist activity of diC14-amidine. Interestingly, these regions lie outside the known LPS-binding domain. Competition experiments also support our hypothesis that diC14-amidine interacts primarily with TLR4 hydrophobic crevices located at the edges of the TLR4/TLR4* dimerization interface. We have characterized potential binding modes using molecular docking analysis and suggest that diC14-amidine nanoliposomes activate TLR4 by facilitating its dimerization in a process that is myeloid differentiation 2 (MD-2)-dependent and cluster of differentiation 14 (CD14)-independent. Our data suggest that TLR4 may be activated through binding at different anchoring points, expanding the repertoire of TLR4 ligands to non-MD-2-binding lipids.C.L. is a IEF Marie Curie Action Research Fellow (TLR4-CAT PIEF-GA-2012-326481) and would like to thank the Wiener-Anspach Foundation for financial support. K.L.I. was supported by a HBLB Veterinary Research Training scholarship. This work was supported by program grant support from the Wellcome Trust and the MRC to N.J.G and C.E.B.This is the final version of the article. It first appeared from Springer via http://dx.doi.org/10.1007/s00018-015-1915-

Expertise and the interpretation of computerized physiological data: implications for the design of computerized monitoring in neonatal intensive care

This paper presents the outcomes from a cognitive engineering project addressing the design problems of computerized monitoring in neonatal intensive care. Cognitive engineering is viewed, in this project, as a symbiosis between cognitive science and design practice. A range of methodologies has been used: interviews with neonatal staff, ward observations and experimental techniques. The results of these investigations are reported, focusing specifically on the differences between junior and senior physicians in their interpretation of monitored physiological data. It was found that the senior doctors made better use of the different knowledge sources available than the junior doctors. The senior doctors were able to identify more relevant physiological patterns and generated more and better inferences than did their junior colleagues. Expertise differences are discussed in the context of previous psychological research in medical expertise. Finally, the paper discusses the potential utility of these outcomes to inform the design of computerized decision support in neonatal intensive care