364 research outputs found

    Synchronized single electron emission from dynamical quantum dots

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    We study synchronized quantized charge pumping through several dynamical quantum dots (QDs) driven by a single time modulated gate signal. We show that the main obstacle for synchronization being the lack of uniformity can be overcome by operating the QDs in the decay cascade regime. We discuss the mechanism responsible for lifting the stringent uniformity requirements. This enhanced functionality of dynamical QDs might find applications in nanoelectronics and quantum metrology.Comment: 4 pages, 3 figures, submitted to AP

    Elastic precession of electronic spin states in interacting integer quantum Hall edge channels

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    We consider the effect of Coulomb interactions in the propagation of electrons, prepared in arbitrary spin states, on chiral edge channels in the integer quantum Hall regime. Electrons are injected and detected at the same energy at different locations of the Hall bar, which is modeled as a chiral Tomonaga-Luttinger liquid. The current is computed perturbatively in the tunneling amplitudes, within a non-crossing approximation using exact solutions of the interacting Green's functions. In the case of different channel velocities, the spin precession effect is evaluated, and the role of interaction parameters and wavevectors is discussed.Comment: 5 pages, 3 figure

    A quantized current source with mesoscopic feedback

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    We study a mesoscopic circuit of two quantized current sources, realized by non-adiabatic single- electron pumps connected in series with a small micron-sized island in between. We find that quantum transport through the second pump can be locked onto the quantized current of the first one by a feedback due to charging of the mesoscopic island. This is confirmed by a measurement of the charge variation on the island using a nearby charge detector. Finally, the charge feedback signal clearly evidences loading into excited states of the dynamic quantum dot during single-electron pump operation

    Vertex similarity in networks

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    We consider methods for quantifying the similarity of vertices in networks. We propose a measure of similarity based on the concept that two vertices are similar if their immediate neighbors in the network are themselves similar. This leads to a self-consistent matrix formulation of similarity that can be evaluated iteratively using only a knowledge of the adjacency matrix of the network. We test our similarity measure on computer-generated networks for which the expected results are known, and on a number of real-world networks

    Reliability of the running vertical jump test in female team sport athletes

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    Injury rates to the lower limb have increased over the past 40 years, coinciding with increases in female sport participation rates. Sport specific tests such as the running vertical jump (RVJ) are utilised for injury risk profiling, however the test-retest reliability is unknown. Objectives: The aim of this study was to investigate the test-retest reliability of the thorax, pelvis and lower limb joint angular kinematics and kinetics for the RVJ test in female team sport athletes. Design: Three-dimensional motion capture with force plate integration was utilised as participants performed five trials on each limb on three separate days. Setting: Testing occurred in a biomechanics laboratory. Participants: Thirty-four females (Australian Rules Football = 15, Netball = 12, Soccer = 7) participated in this study. Main Outcome Measures: Intraclass correlation coefficients (ICC), effect sizes and typical errors (TE) of segment and joint angular kinematics and kinetics were calculated. Results: Poor to excellent reliability (ICC = −0.12 – 0.92), small to large effect sizes (0.00–0.90) and TE (0.02–289.24) were observed across segment and joint angular kinematics and kinetics. Conclusions: The RVJ test is recommended when analysing ground reaction forces and joint angular kinematics in female team sport athletes

    A systematic review on the diagnosis of pediatric bacterial pneumonia: When gold is bronze

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    Background: In developing countries, pneumonia is one of the leading causes of death in children under five years of age and hence timely and accurate diagnosis is critical. In North America, pneumonia is also a common source of childhood morbidity and occasionally mortality. Clinicians traditionally have used the chest radiograph as the gold standard in the diagnosis of pneumonia, but they are becoming increasingly aware that it is not ideal. Numerous studies have shown that chest radiography findings lack precision in defining the etiology of childhood pneumonia. There is no single test that reliably distinguishes bacterial from non-bacterial causes. These factors have resulted in clinicians historically using a combination of physical signs and chest radiographs as a \u27gold standard\u27, though this combination of tests has been shown to be imperfect for diagnosis and assigning treatment. The objectives of this systematic review are to: 1) identify and categorize studies that have used single or multiple tests as a gold standard for assessing accuracy of other tests, and 2) given the \u27gold standard\u27 used, determine the accuracy of these other tests for diagnosing childhood bacterial pneumonia. Methods and Findings: Search strategies were developed using a combination of subject headings and keywords adapted for 18 electronic bibliographic databases from inception to May 2008. Published studies were included if they: 1) included children one month to 18 years of age, 2) provided sufficient data regarding diagnostic accuracy to construct a 2×2 table, and 3) assessed the accuracy of one or more index tests as compared with other test(s) used as a \u27gold standard\u27. The literature search revealed 5,989 references of which 256 were screened for inclusion, resulting in 25 studies that satisfied all inclusion criteria. The studies examined a range of bacterium types and assessed the accuracy of several combinations of diagnostic tests. Eleven different gold standards were studied in the 25 included studies. Criterion validity was calculated for fourteen different index tests using eleven different gold standards. The most common gold standard utilized was blood culture tests used in six studies. Fourteen different tests were measured as index tests. PCT was the most common measured in five studies each with a different gold standard. Conclusions: We have found that studies assessing the diagnostic accuracy of clinical, radiological, and laboratory tests for bacterial childhood pneumonia have used a heterogeneous group of gold standards, and found, at least in part because of this, that index tests have widely different accuracies. These findings highlight the need for identifying a widely accepted gold standard for diagnosis of bacterial pneumonia in children. © 2010 Lynch et al

    Correlated multiplexity and connectivity of multiplex random networks

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    Nodes in a complex networked system often engage in more than one type of interactions among them; they form a multiplex network with multiple types of links. In real-world complex systems, a node's degree for one type of links and that for the other are not randomly distributed but correlated, which we term correlated multiplexity. In this paper we study a simple model of multiplex random networks and demonstrate that the correlated multiplexity can drastically affect the properties of giant component in the network. Specifically, when the degrees of a node for different interactions in a duplex Erdos-Renyi network are maximally correlated, the network contains the giant component for any nonzero link densities. In contrast, when the degrees of a node are maximally anti-correlated, the emergence of giant component is significantly delayed, yet the entire network becomes connected into a single component at a finite link density. We also discuss the mixing patterns and the cases with imperfect correlated multiplexity.Comment: Revised version, 12 pages, 6 figure

    Cardiovascular disease risk marker responses to breaking up prolonged sedentary time in individuals with paraplegia: the Spinal Cord Injury Move More (SCIMM) randomised crossover laboratory trial protocol

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    Introduction: Sedentary behaviour is a distinct risk factor for cardiovascular disease (CVD) and could partly explain the increased prevalence of CVD in people with spinal cord injury (SCI). Interrupting prolonged sitting periods with regular short bouts of walking acutely suppresses postprandial glucose and lipids in able-bodied individuals. However, the acute CVD risk marker response to breaking up prolonged sedentary time in people with SCI has not been investigated. Methods and analysis: A randomised two-condition laboratory crossover trial will compare: 1) breaking up prolonged sedentary time with 2 min moderate-intensity arm crank activity every 20 min, with 2) uninterrupted prolonged sedentary time (control) in people with SCI. Outcomes will include acute effects on postprandial glucose, insulin, lipids and blood pressure. Blood samples will be collected and blood pressure measured at regular intervals during each 5.5 h condition. Ethics and dissemination: This study was approved by the Cambridge South NHS Research Ethics Committee. This research will help determine if breaking up prolonged sedentary time could be effective in lowering CVD risk in people with SCI. The findings of the research will be published in a peer review journal and disseminated to relevant user groups. Trial registration: The study is registered as a clinical trial on the ISRCTN register (trial ID: ISRCTN51868437)

    A comparison of game-play characteristics between elite youth and senior Australian National Rugby League competitions

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    Objectives: To compare game-play characteristics between elite youth and senior Australian National Rugby League (NRL) competitions. Design: Longitudinal observational. Methods: The dataset consisted of 12 team performance indicators (e.g., ‘all runs’, ‘offloads’ and ‘tackles’) extracted from all 2016 national under 20 (U20) competition (elite youth; n = 372 observations) and National Rugby League (NRL) (elite senior; n = 378 observations) matches. Data was classified according to competition (Two levels: U20 and NRL) and modelled using two techniques. Firstly, non-metric multidimensional scaling resolved multivariate competition (dis)similarity, visualised using a two-dimensional ordination. Secondly, a conditional interference (CI) classification tree was grown to reveal the performance indicators most capable of explaining competition level. Results: Non-metric multidimensional scaling revealed high competition dissimilarity, with U20 and NRL teams orienting distinctive positions on the first dimension of the ordination surface. Five team performance indicators were retained within the CI tree (‘all runs’, ‘tackle breaks’, ‘tackles’, ‘missed tackles’, and ‘kicks’), which correctly classified 79% of the U20 observations and 93% of the NRL observations. Conclusions: Multivariate differences between elite youth and senior rugby league competitions were identified. Specifically, NRL game-play was classified by a greater number of ‘all runs’, and ‘tackles’ and a lower number of ‘missed tackles’ relative to the U20 competition. Given the national U20 competition is purported to assist with the development of prospective NRL players, junior coaches may consider training interventions that primarily aid the tackling capacities of players. This may subsequently assist with talent development and player progression in Australian rugby league
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