9,543 research outputs found

    Sagittal and Frontal Plane Knee Angular Jerk Effects During Prolonged Load Carriage

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    Introduction: Musculoskeletal injuries are a costly military problem that routinely occur during training. Quantifying smoothness of knee motion, or angular knee jerk, may be an effective measure to monitor injury risk during training, but to date, the effects of body borne load and prolonged locomotion on angular knee jerk are unknown. Purpose: This study sought to quantify angular knee jerk for frontal and sagittal plane motion during prolonged load carriage. Methods: Eighteen participants had peak and cost of angular jerk for frontal and sagittal plane knee motion quantified while they walked (1.3 m/s) 60-minutes with three body borne loads (0, 15, and 30 kg). Statistical Analysis: Peak and cost of angular jerk for sagittal and frontal plane knee motion of stance phase (0 % - 100%) were derived from motion capture and IMU data and submitted to a repeated measures linear model to test the main effects and interaction of load (0, 15, and 30 kg) and time (0, 15, 30, 45, and 60 min.). Two one sided t-tests (TOSTs) were used to compare the motion capture- and IMU-derived measures of angular jerk for sagittal and frontal plane knee motion. Results: For the motion capture-derived jerk measures, body borne load increased peak and cost of angular jerk for sagittal (p \u3c 0.001, p \u3c 0.001) and frontal (p \u3c 0.001, p \u3c 0.001) plane knee motion, while time increased jerk cost (p = 0.001) of frontal plane knee motion. While the IMU-derived jerk measures exhibited similar increases in peak and cost of angular jerk for sagittal (p \u3c 0.001, p \u3c 0.001) and frontal (p = 0.027, p \u3c 0.001) plane knee motion with addition of load, and in cost (p = 0.015) of angular jerk for frontal plane knee motion with time, they were not statistically equivalent to motion-capture derived measures (p \u3e 0.05). Conclusion: Prolonged load carriage may lead to jerkier knee motion and increased knee musculoskeletal injury risk. Specifically, the jerkier knee motions exhibited with the addition of body borne load and longer walking time may increase the joint loading that leads to greater knee musculoskeletal injury risk

    Elements of metacommunity structure of diatoms and macroinvertebrates within stream networks differing in environmental heterogeneity

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    Aim Idealized metacommunity structures (i.e. checkerboard, random, quasi-structures, nested, Clementsian, Gleasonian and evenly spaced) have recently gained increasing attention, but their relationships with environmental heterogeneity and how they vary with organism groups remain poorly understood. Here, we tested two main hypotheses: (a) gradient-driven patterns (Clementsian and Gleasonian) occur frequently in heterogeneous environments and (b) small organisms (here, diatoms) are more likely to exhibit gradient-driven patterns than large organisms (here, macroinvertebrates). Location Streams in three regions in China. Taxon Diatoms and macroinvertebrates. Methods The stream diatom and macroinvertebrate data, as well as the environmental data collected from the same set of sites were used to examine the idealized metacommunity structures via the elements of the metacommunity structure (EMS; coherence, turnover and boundary clumping) analysis in three regions. We extended the traditional EMS approach by ordering sites along known environmental gradients. Results We found that Clementsian structure with high degrees of coherence and turnover, and significantly positive clumping was typically observed in the high-heterogeneity regions, whereas randomness was prevalent in the low-heterogeneity region. Macroinvertebrates exhibited clearer Clementsian structures compared with diatoms, while diatoms showed more randomness compared with macroinvertebrates, indicating a stronger role of environmental filtering for macroinvertebrates than diatoms. In most cases, the results of the more novel EMS approach differed from the results of the traditional EMS technique. Main conclusions Our results suggested that the occurrence of different metacommunity structures may be related with the degree of regional environmental heterogeneity. However, diatom metacommunities were more random than those of macroinvertebrate, and such an unexpected result may result from different dispersal abilities between the two organism groups. In addition, we found that the novel EMS approach increased power in discerning metacommunity structure in comparison to the traditional EMS technique.peerReviewe

    Plan-based delivery composition in intelligent tutoring systems for introductory computer programming

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    In a shell system for the generation of intelligent tutoring systems, the instructional model that one applies should be variable independent of the content of instruction. In this article, a taxonomy of content elements is presented in order to define a relatively content-independent instructional planner for introductory programming ITS's; the taxonomy is based on the concepts of programming goals and programming plans. Deliveries may be composed by the instantiation of delivery templates with the content elements. Examples from two different instructional models illustrate the flexibility of this approach. All content in the examples is taken from a course in COMAL-80 turtle graphics

    A simplex of bound entangled multipartite qubit states

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    We construct a simplex for multipartite qubit states of even number n of qubits, which has the same geometry concerning separability, mixedness, kind of entanglement, amount of entanglement and nonlocality as the bipartite qubit states. We derive the entanglement of the class of states which can be described by only three real parameters with the help of a multipartite measure for all discrete systems. We prove that the bounds on this measure are optimal for the whole class of states and that it reveals that the states possess only n-partite entanglement and not e.g. bipartite entanglement. We then show that this n-partite entanglement can be increased by stochastic local operations and classical communication to the purest maximal entangled states. However, pure n-partite entanglement cannot be distilled, consequently all entangled states in the simplex are n-partite bound entangled. We study also Bell inequalities and find the same geometry as for bipartite qubits. Moreover, we show how the (hidden) nonlocality for all n-partite bound entangled states can be revealed.Comment: 11 pages, 4 figures; 2nd version changed considerably and a detailed derivation of the multipartite measure is include

    The role of diversification profiles and dyadic characteristics in the formation of technological alliances:Differences between exploitation and exploration in a low-tech industry

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    This paper posits that corporate and technological diversification of firms and their relatedness in terms of products and technologies will impact their propensity to form technological alliances. It argues that both higher levels of diversification and greater relatedness signal superior capabilities and available resources to prospective partners that will facilitate exploration and exploitation of technological assets in an alliance. These theoretical conjectures are tested using a dataset of all tire producers worldwide between 1985 and 1996 that combines detailed firm data on establishment, patenting, and alliance activities. The results indicate that complementarity in terms of corporate and technological diversification strategies, as well as partner characteristics (e.g., size, age, and technological capabilities) drive exploitation alliances. Moreover, firms with similar product portfolios are more likely to engage in exploitative interactions. In contrast, exploration alliances exhibit strong partner similarity across all firm characteristics. Both corporate and technological diversification have positive effects on firms’ propensity to engage in exploration, while technological distance has a negative nonlinear one.<br/

    Towards Innovative Healthcare Grid Solutions: ViroLab - A Virtual Laboratory for Infectious Diseases

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    With more rare and critical diseases, medical diagnoses and disease prevention constitutes one of the challenging and at the same time most difficult fields in modern health care. Using interdisciplinary approaches where different areas of research such as biology, chemistry, mathematics, and computer science meet together in order to analyze, understand and reconstruct complex medical processes, those projects typically achieve excellent research results but are inefficient and unfeasible for daily medical workflows. The EU funded project ViroLab should address this important issue by combining different scientists together into one project in order to design and develop a working platform for researchers and especially for doctors, which facilitates medical knowledge discovery and decision support for HIV drug resistance for daily clinical usage. In this paper, we will present the overall concept of the ViroLab project. The core functionalities will be described in detail and shall give the readers an idea of an innovative system for disease prevention, diagnosis and treatment based on integrated biomedical data and information on several levels

    Bowen-York Tensors

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    There is derived, for a conformally flat three-space, a family of linear second-order partial differential operators which send vectors into tracefree, symmetric two-tensors. These maps, which are parametrized by conformal Killing vectors on the three-space, are such that the divergence of the resulting tensor field depends only on the divergence of the original vector field. In particular these maps send source-free electric fields into TT-tensors. Moreover, if the original vector field is the Coulomb field on R3\{0}\mathbb{R}^3\backslash \lbrace0\rbrace, the resulting tensor fields on R3\{0}\mathbb{R}^3\backslash \lbrace0\rbrace are nothing but the family of TT-tensors originally written down by Bowen and York.Comment: 12 pages, Contribution to CQG Special Issue "A Spacetime Safari: Essays in Honour of Vincent Moncrief

    The export performance of emerging economy firms: the influence of firm capabilities and institutional environments

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    We advance a two-stage theoretical model which contends that the export performance of emerging economy firms (EEFs) will depend both upon their firm-specific capabilities and their home institutional environments. Specifically, we argue that EEFs will be more likely to export when facing more uncertainty at home from greater political instability, substantial informal competition, and high corruption. Furthermore, we hypothesize that firms’ export intensities will be contingent upon specialized internal capabilities such as a skilled workforce, top managerial experience, and access to external technologies. We test these hypotheses using a dataset of more than 16,000 firms from the four BRIC economies (i.e., Brazil, Russia, China and India). Our results confirm that political instability and informal competition have robust effects on the export propensity of EEFs, whilst export intensity is contingent upon the availability of skilled workers and access to external technologies via licensing
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