A comparison of head and manual control for a position-control pursuit tracking task

Head control was compared with manual control in a pursuit tracking task involving proportional controlled-element dynamics. An integrated control/display system was used to explore tracking effectiveness in horizontal and vertical axes tracked singly and concurrently. Compared with manual tracking, head tracking resulted in a 50 percent greater rms error score, lower pilot gain, greater high-frequency phase lag and greater low-frequency remnant. These differences were statistically significant, but differences between horizontal- and vertical-axis tracking and between 1- and 2-axis tracking were generally small and not highly significant. Manual tracking results were matched with the optimal control model using pilot-related parameters typical of those found in previous manual control studies. Head tracking performance was predicted with good accuracy using the manual tracking model plus a model for head/neck response dynamics obtained from the literature

A model of primitive streak initiation in the chick embryo

Initiation of the primitive streak in avian embryos provides a well-studied example of a pattern-forming event that displays a striking capacity for regulation. The mechanisms underlying the regulative properties are, however, poorly understood and are not easily accounted for by traditional models of pattern formation, such as reaction–diffusion models. In this paper, we propose a new activator–inhibitor model for streak initiation. We show that the model is consistent with experimental observations, both in its pattern-forming properties and in its ability to form these patterns on the correct time-scales for biologically realistic parameter values. A key component of the model is a travelling wave of inhibition. We present a mathematical analysis of the speed of such waves in both diffusive and juxtacrine relay systems. We use the streak initiation model to make testable predictions. By varying parameters of the model, two very different types of patterning can be obtained, suggesting that our model may be applicable to other processes in addition to streak initiation

Weighted network modules

The inclusion of link weights into the analysis of network properties allows a deeper insight into the (often overlapping) modular structure of real-world webs. We introduce a clustering algorithm (CPMw, Clique Percolation Method with weights) for weighted networks based on the concept of percolating k-cliques with high enough intensity. The algorithm allows overlaps between the modules. First, we give detailed analytical and numerical results about the critical point of weighted k-clique percolation on (weighted) Erdos-Renyi graphs. Then, for a scientist collaboration web and a stock correlation graph we compute three-link weight correlations and with the CPMw the weighted modules. After reshuffling link weights in both networks and computing the same quantities for the randomised control graphs as well, we show that groups of 3 or more strong links prefer to cluster together in both original graphs.Comment: 19 pages, 7 figure

\u3ci\u3eMedicine Meets Virtual Reality 17\u3c/i\u3e

Chapter, A Virtual Reality Training Program for Improvement of Robotic Surgical Skills, co-authored by Mukul Mukherjee and Nicholas Stergiou, UNO faculty members. Chapter, Consistency of Performance of Robot-Assisted Surgical Tasks in Virtual Reality, co-authored by Mukul Mukherjee and Nicholas Stergiou, UNO faculty members. The 17th annual Medicine Meets Virtual Reality (MMVR17) was held January 19-22, 2009, in Long Beach, CA, USA. The conference is well established as a forum for emerging data-centered technologies for medical care and education. Each year, it brings together an international community of computer scientists and engineers, physicians and surgeons, medical educators and students, military medicine specialists and biomedical futurists. MMVR emphasizes inter-disciplinary collaboration in the development of more efficient and effective physician training and patient care. The MMVR17 proceedings collect 108 papers by conference lecture and poster presenters. These papers cover recent developments in biomedical simulation and modeling, visualization and data fusion, haptics, robotics, sensors and other related information-based technologies. Key applications include medical education and surgical training, clinical diagnosis and therapy, physical rehabilitation, psychological assessment, telemedicine and more. From initial vision and prototypes, through assessment and validation, to clinical and academic utilization and commercialization - MMVR explores the state-of-the-art and looks toward healthcare’s future. The proceedings volume will interest physicians, surgeons and other medical professionals interested in emerging and future tools for diagnosis and therapy; educators responsible for training the next generation of doctors and scientists; IT and medical device engineers creating state-of-the-art and next-generation simulation, imaging, robotics and communication systems; data technologists creating systems for gathering, processing and distributing medical intelligence; military medicine specialists addressing the challenges of warfare and defense health needs; and biomedical futurists and investors who want to understand where the field is headed.https://digitalcommons.unomaha.edu/facultybooks/1233/thumbnail.jp

Large Magellanic Cloud Planetary Nebula Morphology: Probing Stellar Populations and Evolution

Planetary Nebulae (PNe) in the Large Magellanic Cloud (LMC) offer the unique opportunity to study both the Population and evolution of low- and intermediate-mass stars, by means of the morphological type of the nebula. Using observations from our LMC PN morphological survey, and including images available in the HST Data Archive, and published chemical abundances, we find that asymmetry in PNe is strongly correlated with a younger stellar Population, as indicated by the abundance of elements that are unaltered by stellar evolution (Ne, Ar, S). While similar results have been obtained for Galactic PNe, this is the first demonstration of the relationship for extra-galactic PNe. We also examine the relation between morphology and abundance of the products of stellar evolution. We found that asymmetric PNe have higher nitrogen and lower carbon abundances than symmetric PNe. Our two main results are broadly consistent with the predictions of stellar evolution if the progenitors of asymmetric PNe have on average larger masses than the progenitors of symmetric PNe. The results bear on the question of formation mechanisms for asymmetric PNe, specifically, that the genesis of PNe structure should relate strongly to the Population type, and by inference the mass, of the progenitor star, and less strongly on whether the central star is a member of a close binary system.Comment: The Astrophysical Journal Letters, in press 4 figure

The pleasures and perils of inheritance

Facing death, reflecting on one’s legacies (material and ethical, personal and political) and the legal and interpersonal attempts to resolve or prevent inheritance conflicts, all bring to the fore constructions of memory and identity, intergenerational relations, and the complexities of doing and undoing family and kinship. Consequently, drawing attention to inheritance, keeping sight of it, and bringing it into play is a useful piece of the puzzle of ageing across a range of disciplines and this article provides an overview of some of the key themes in this emerging field

Strength in diversity: enhancing learning in vocationally-orientated, master's level courses

Postgraduate education in geography, especially at the Master’s level, is undergoing significant changes in the developed world. There is an expansion of vocationally-oriented degree programmes, increasing recruitment of international students, integration of work place skills, and the engagement of non-traditional postgraduate students as departments respond to policies for a more ‘inclusive’ higher education. This paper sets the context by outlining some programmatic changes in selected countries (Australia, the UK, and the USA). We briefly reflect on how postgraduate ‘bars’ or ‘levels’ are defined and explore in detail what ‘diversity’ or ‘heterogeneity’ means in these new postgraduate settings. The paper then explores some examples of practice drawn from our own experiences, whilst recognising that relevance will vary in other contexts. Finally we consider how diversity can be harnessed as a strength that has potential to enhance taught elements of contemporary postgraduate education in and beyond the discipline