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Fast and adaptive fractal tree-based path planning for programmable bevel tip steerable needles

© 2016 IEEE. Steerable needles are a promising technology for minimally invasive surgery, as they can provide access to difficult to reach locations while avoiding delicate anatomical regions. However, due to the unpredictable tissue deformation associated with needle insertion and the complexity of many surgical scenarios, a real-time path planning algorithm with high update frequency would be advantageous. Real-time path planning for nonholonomic systems is commonly used in a broad variety of fields, ranging from aerospace to submarine navigation. In this letter, we propose to take advantage of the architecture of graphics processing units (GPUs) to apply fractal theory and thus parallelize real-time path planning computation. This novel approach, termed adaptive fractal trees (AFT), allows for the creation of a database of paths covering the entire domain, which are dense, invariant, procedurally produced, adaptable in size, and present a recursive structure. The generated cache of paths can in turn be analyzed in parallel to determine the most suitable path in a fraction of a second. The ability to cope with nonholonomic constraints, as well as constraints in the space of states of any complexity or number, is intrinsic to the AFT approach, rendering it highly versatile. Three-dimensional (3-D) simulations applied to needle steering in neurosurgery show that our approach can successfully compute paths in real-time, enabling complex brain navigation

Multiple zero modes of the Dirac operator in three dimensions

One of the key properties of Dirac operators is the possibility of a degeneracy of zero modes. For the Abelian Dirac operator in three dimensions the construction of multiple zero modes has been sucessfully carried out only very recently. Here we generalise these results by discussing a much wider class of Dirac operators together with their zero modes. Further we show that those Dirac operators that do admit zero modes may be related to Hopf maps, where the Hopf index is related to the number of zero modes in a simple way.Comment: Latex file, 20 pages, no figure

Communication Networks and the adoption of three farn practices

The report commences with a discussion of the diffusion and adoption model, and illustrates some of the research observations and practical outcomes that have emerged in recent years, An overview of social network research is presented as a means of understanding communication exchanges and providing data relevant to the diffusion debate. The communication and adoption studies are then reported in three separate sections in the order they were conducted. (A map of the location of the survey areas is shown in Figure I ) . The objectives, survey method, results and a summary are presented for each study. A background to the dairy herd recording scheme is followed by an outline of the dairy industry itself. Two regions selected for the survey are discussed and compared. The soil conservation study commences with an overview of soil degradation problems, government involvement and policy, and technical solutions to these problems. Consideration is also given to the importance of the human element in soil conservation policy and extension. The Central Wheatbelt (pattern of settlement, landscape, soils, vegetation, climate and land use) is described as a region. Many soil conservation problems exist here that can be generalized to other regions. The minimum tillage enquiry first introduces the concept and technique of minimum tillage, its advantages and disadvantages. A history of the Jerramungup district, as well as details on physical aspects of the area and land use problems gives the setting of the study. Jerramungup (and the south coast region generally) is particularly prone to wind erosion and hence is valid area in which to study the diffusion of minimum tillage a technique which lessens wind erosion problems. A final discussion compares conclusions of each study. in each are are dealt with. the three adoption situations by examining the The extension situation and communication factors Conclusions and recommendations are provided

Farewell Daisy Bell

https://digitalcommons.library.umaine.edu/mmb-vp/5178/thumbnail.jp

Farmers\u27 use of agricultural information 1983

The Western Australian Department of Agriculture produces information for farmers which is disseminated through various mass media, The Australian Broadcasting Commission and commercial media outlets provide further agricultural information, In 1983 a telephone survey of cereal-sheep farmers was undertaken to determine what information sources were used by farmers, and how farmers used that information. A number of information processing factors were taken from communication research literature, These were accessibility and availability; surveillance and exposure; selection; storage and retrieval. From within this theoretical framework, information sources such as farming magazines, radio and television programmes were examined. Special attention was given to evaluating the performance of the following Department of Agriculture media: Farmnotes, Bulletins, Journal of Agriculture, Direct Mail Service, Agricultural Memos, Farming Today and radio broadcasts. There was considerable activity by farmers in surveillance, selection, storing and retrieving of information. It was found that the availability and exposure of Departmental media to farmers was high, except for the Journal of Agriculture, It is recommended that the form and content of the Journal be reviewed, and the circulation of this and other information sources be further increased. Revision of the little used Agdex filing system is also necessary. Other recommendations include: greater recognition of the role of the farm family in information processing, the provision of \u27entertaining\u27 agricultural television programmes for rural communities, and the need for farmer awareness of information storage and retrieval systems. Because the functions of the Direct Mail Service and Agricultural Memos were found to overlap, it is suggested that the use of these information sources could be studied further to test for redundancies in Departmental effort. It is also proposed that the Department should not commit itself to disseminating technical information through audio and video-tapes unless the effectiveness of these media can be demonstrated

T cell depleted hosts are uniquely susceptible to tolerance induced by non-professional APCs and mediated by IL-10 producing CD8+ T cells

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Modifying Teacher Behaviors to Promote Critical Thinking in K-12 Physical Education

This study examined four physical educators\u27 teaching behaviors before and after an intervention. The study was conducted over the span of three 15-week academic semesters. Phase 1 of the study involved videotaping the participants\u27 instruction prior to intervention. In Phase 2, participants were involved in two workshops planned to convey teaching strategies related to promoting critical thinking in physical education. In addition, participants and co-investigators team-taught three sample lessons focused on incorporating teaching behaviors attempting to foster critical thinking. Data collection was completed during Phase 3 by videotaping each teacher during one unit of instruction. A chi-square analysis of post-intervention data revealed that all four teachers\u27 observed instructional behaviors differed significantly from that expected. Results suggest that the intervention employed during Phase 2 was successful in helping teachers modify their instruction to promote critical thinking in physical education