Mechanism for spatial organization in quantum dot self-assembly

Inspired by experimental observations of spatially ordered growth hillocks on the (001) surfaces of natural graphite crystals, a mechanism for spatial organization in quantum dotself-assembly is proposed. The regular arrangement of steps from a screw dislocation-generated growth spiral provides the overall template for such ordering. An ordered array of quantum dots may be formed or nucleated from impurities driven to the step corners by diffusion and by their interactions with the spiral’s steps and kinks. Kinetic Monte Carlo simulation of a solid-on-solid model supports the feasibility of such a mechanism

Streaming Algorithm for Euler Characteristic Curves of Multidimensional Images

We present an efficient algorithm to compute Euler characteristic curves of gray scale images of arbitrary dimension. In various applications the Euler characteristic curve is used as a descriptor of an image. Our algorithm is the first streaming algorithm for Euler characteristic curves. The usage of streaming removes the necessity to store the entire image in RAM. Experiments show that our implementation handles terabyte scale images on commodity hardware. Due to lock-free parallelism, it scales well with the number of processor cores. Our software---CHUNKYEuler---is available as open source on Bitbucket. Additionally, we put the concept of the Euler characteristic curve in the wider context of computational topology. In particular, we explain the connection with persistence diagrams

The Associations Between Park Environments and Park Use in Southern US Communities

Purpose To document park use and park and neighborhood environment characteristics in rural communities, and to examine the relationship between park characteristics and park use. Methods The System for Observing Play and Recreation in Communities measured use in 42 target areas across 6 community parks in May 2010 and October 2010. Direct observation instruments were used to assess park and neighborhood environment characteristics. Logistic regression was used to determine the relationship between the condition, number of amenities, and number of incivilities in a target area with target area use. Findings Ninety‐seven people were observed across all parks during May 2010 data collection and 116 people during October 2010 data collection. Low park quality index scores and unfavorable neighborhood environment characteristics were observed. There was a significant positive association between number of incivilities in a target area and target area use (OR = 1.91; 95% CI: 1.09‐3.38; P = .03). Conclusions The number of people observed using the parks in this study was low, and it was considerably less than the number observed in other studies. The objective park and neighborhood environment characteristics documented in this study provide a more comprehensive understanding of parks than other studies. Further examining the complex relationship between park and neighborhood environment characteristics and park use is important, as it can inform park administrators and city planners of characteristics that are best able to attract visitors.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/108592/1/jrh12071.pd

Computational Topology Techniques for Characterizing Time-Series Data

Topological data analysis (TDA), while abstract, allows a characterization of time-series data obtained from nonlinear and complex dynamical systems. Though it is surprising that such an abstract measure of structure - counting pieces and holes - could be useful for real-world data, TDA lets us compare different systems, and even do membership testing or change-point detection. However, TDA is computationally expensive and involves a number of free parameters. This complexity can be obviated by coarse-graining, using a construct called the witness complex. The parametric dependence gives rise to the concept of persistent homology: how shape changes with scale. Its results allow us to distinguish time-series data from different systems - e.g., the same note played on different musical instruments.Comment: 12 pages, 6 Figures, 1 Table, The Sixteenth International Symposium on Intelligent Data Analysis (IDA 2017

Optimal topological simplification of discrete functions on surfaces

We solve the problem of minimizing the number of critical points among all functions on a surface within a prescribed distance {\delta} from a given input function. The result is achieved by establishing a connection between discrete Morse theory and persistent homology. Our method completely removes homological noise with persistence less than 2{\delta}, constructively proving the tightness of a lower bound on the number of critical points given by the stability theorem of persistent homology in dimension two for any input function. We also show that an optimal solution can be computed in linear time after persistence pairs have been computed.Comment: 27 pages, 8 figure

The Electronic Community Park Audit Tool (eCPAT): Exploring the Use of Mobile Technology for Youth Empowerment and Advocacy for Healthy Community Policy, Systems, and Environmental Change

Empowering and engaging youth in advocacy and participatory action research (PAR) for healthy community environments is an emerging approach to reducing the childhood obesity epidemic. Technology is a promising strategy for engaging youth in such efforts. The Community Park Audit Tool (CPAT) is user-friendly tool for evaluating the ability of parks to promote youth physical activity. Recently an electronic version of the tool (eCPAT) was developed and validated. The purpose of this study was to explore the use of eCPAT mobile technology on youth empowerment and advocacy. This study examined tool usability, youths' technology access, use, and readiness for PAR efforts, effectiveness of mobile technology on youth empowerment and advocacy, interaction effects between tool format and regular technology use, and tool format preferences. Youth ages 11–18 years were recruited and randomized into one of three study conditions: Control (no audit), paper (CPAT), and mobile technology (eCPAT). Intervention youth completed two park audits using assigned format. A subsample of youth in the Control group completed both CPAT and eCPAT audits for comparison. Independent samples t-tests and MANCOVAs explored differences in post-project levels of tool usability and empowerment and advocacy scores between groups. Multivariate linear regression analysis explored the interaction between Control, Paper, or eCPAT group membership and mean technology use in predicting empowerment and advocacy. Youth (n = 124) completed pre and post surveys. The majority of youth had access to technology (smartphone 77.4%, tablet/iPad 67.7%). Youth used mobile technology at least once a day to use apps (M = 7.8, SD = 3.2), browse the web (M = 6.3, SD = 3.3), and search for information (M = 6.3, SD = 3.5). Youth were also ready and willing to use technology for PAR (M = 3.42–3.59). No main or interaction effects were found for post-project levels of youth empowerment or advocacy. However, the eCPAT tool had high usability scores, was better liked, and was preferred by youth over paper-pencil methods. Mobile technologies are ubiquitous and a preferred strategy among youth for engagement in community change. Future studies should explore mobile technology as a potential strategy for engaging youth in ongoing PAR efforts to achieve successful engagement and advocacy in community healthy environmental change

Advanced homology computation of digital volumes via cell complexes

Given a 3D binary voxel-based digital object V, an algorithm for computing homological information for V via a polyhedral cell complex is designed. By homological information we understand not only Betti numbers, representative cycles of homology classes and homological classification of cycles but also the computation of homology numbers related additional algebraic structures defined on homology (coproduct in homology, product in cohomology, (co)homology operations,...). The algorithm is mainly based on the following facts: a) a local 3D-polyhedrization of any 2×2×2 configuration of mutually 26-adjacent black voxels providing a coherent cell complex at global level; b) a description of the homology of a digital volume as an algebraic-gradient vector field on the cell complex (see Discrete Morse Theory [5], AT-model method [7,5]). Saving this vector field, we go further obtaining homological information at no extra time processing cost

Worldwide trends in mortality from biliary tract malignancies

BACKGROUND: Intrahepatic cholangiocarcinomas are malignant tumors arising from the intrahepatic biliary tract. The pathogenesis of these tumors remains unknown. Although there is a marked global variation in prevalence, some recent studies have suggested an increase in mortality from intrahepatic cholangiocarcinoma in several regions of low endemicity. As the study of mortality trends may yield clues to possible etiological factors, we analyzed worldwide time trends in mortality from biliary tract malignancies. METHODS: Annual age-standardized rates for individual countries were compiled for deaths from biliary tract malignancies using the WHO database. These data were used to analyze gender and site-specific trends in mortality rates. RESULTS: An increasing trend for mortality from intrahepatic cholangiocarcinoma was noted in most countries. The average estimated annual percentage change (EAPC) in mortality rates for males was 6.9 ± 1.5, and for females was 5.1 ± 1.0. Increased mortality rates were observed in all geographic regions. Within Europe, increases were higher in Western Europe than in Central or Northern Europe. In contrast, mortality rates for extrahepatic biliary tract malignancies showed a decreasing trend in most countries, with an overall average EAPC of -0.3 ± 0.4 for males, but -1.3 ± 0.4 for females. CONCLUSIONS: There has been a marked global increase in mortality from intrahepatic, but not extra-hepatic, biliary tract malignancies

A Novel Plaque Enriched Long Noncoding RNA in Atherosclerotic Macrophage Regulation (PELATON)

Objective: Long noncoding RNAs (lncRNAs) are an emergent class of molecules with diverse functional roles, widely expressed in human physiology and disease. Although some lncRNAs have been identified in cardiovascular disease, their potential as novel targets in the prevention of atherosclerosis is unknown. We set out to discover important lncRNAs in unstable plaque and gain insight into their functional relevance. Approach and Results: Analysis of RNA sequencing previously performed on stable and unstable atherosclerotic plaque identified a panel of 47 differentially regulated lncRNAs. We focused on LINC01272, a lncRNA upregulated in unstable plaque previously detected in inflammatory bowel disease, which we termed PELATON (plaque enriched lncRNA in atherosclerotic and inflammatory bowel macrophage regulation). Here, we demonstrate that PELATON is highly monocyte- and macrophage-specific across vascular cell types, and almost entirely nuclear by cellular fractionation (90%-98%). In situ hybridization confirmed enrichment of PELATON in areas of plaque inflammation, colocalizing with macrophages around the shoulders and necrotic core of human plaque sections. Consistent with its nuclear localization, and despite containing a predicted open reading frame, PELATON did not demonstrate any protein-coding potential in vitro. Functionally, knockdown of PELATON significantly reduced phagocytosis, lipid uptake and reactive oxygen species production in high-content analysis, with a significant reduction in phagocytosis independently validated. Furthermore, CD36, a key mediator of phagocytic oxLDL (oxidized low-density lipoprotein) uptake was significantly reduced with PELATON knockdown. Conclusions: PELATON is a nuclear expressed, monocyte- and macrophage-specific lncRNA, upregulated in unstable atherosclerotic plaque. Knockdown of PELATON affects cellular functions associated with plaque progression