742 research outputs found

    The Model of the Low Rate Telemetry Communication System for Matlab-Simulink

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    This article is dedicated to the model of low rate telemetry system, which has been developed for Matlab-Simulink environment. The purpose of this model is a research of the low rate telemetry transmission reliability in those cases where the modulation scheme carrier-subcarrier is used. This modulation scheme is widely used in case of the interplanetary spacecrafts. The main purpose of the model is a research of the effects of AWGN and phase noise especially for very low value of Eb/N0. Effects can be evaluated for the whole transmission system or for its components parts. The model described is very versatile and it can be easily modified or expanded

    The Low Rate Telemetry Transmission Simulator

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    The presented paper is dedicated to the low rate telemetry transmission simulator. The basic concept of the system uses the carrier (DSB) and subcarrier (BPSK). The research is focused on the AWGN and carrier phase noise influence. Presented system can be extended with the described carrier phase noise model. In this paper, some issues related to the described model are also discussed. For example, the relation between bit error rate for uncoded bit stream and bit stream with differential coding, which is used in the model. Authors prove the using of Costas loops for very low energy per bit to noise power spectral density ratio. The influence of additive white Gaussian noise and phase noise is also investigated

    Application of product dioids for dead token detection in interval P-time event graphs

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    Linear description of interval P-time event graphs using a product idempotent semiring is proposed and applied to dead token detection. The dependence of dead token on initial condition is studied using residuation theory. Finally, the relationship with the spectral theory of matrices over product semirings is discusse

    The Increase of Epidermal Imidazoleacrylic Acid Following Insolation

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    It has been confirmed, by electron microscopy, that suction blisters detach the epidermis at the dermo-epidermal junction. Inter- and intracellular vacuolization was observed in some of the specimens. On the basis of a study comprising 15 subjects (12 males and 3 females), it was concluded that urocanic acid in the epidermis (suction blister skin) of the upper arm increased 9–11 days following insolation in comparison with specimens situated at an exactly symmetrical site of the control (non-irradiated) arm. This difference was significant in terms of ÎŒg urocanic acid per mg dry weight at a 95% level of probability and in terms of ÎŒg per cm2 of blister base at a 99% level (t-test for paired values). In two of the subjects other time intervals after insolation were also studied and an increase of epidermal urocanic acid level was noted. Dry weights of epidermis (mg per cm2) on the irradiated and control side (9–11 days following insolation) did not differ significantly in the group of 15 subjects. Significant increase due to insolation was only demonstrated when the values were divided by control values obtained for the respective arms 2 months before the experiment. Histidine ammonia-lyase activity was estimated in 8 subjects. The increase on the irradiated side on the 9–11th day after unilateral insolation was not significant

    Modeling sea-salt aerosols in the atmosphere: 2. Atmospheric concentrations and fluxes

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    Atmospheric sea-salt aerosol concentrations are studied using both long-term observations and model simulations of Na+ at seven stations around the globe. Good agreement is achieved between observations and model predictions in the northern hemisphere. A stronger seasonal variation occurs in the high-latitude North Atlantic than in regions close to the equator and in high-latitude southern hemisphere. Generally, concentrations are higher for both boreal and austral winters. With the model, the production flux and removal flux at the atmosphere-ocean interface was calculated and used to estimate the global sea-salt budget. The flux also shows seasonal variation similar to that of sea-salt concentration. Depending on the geographic location, the model predicts that dry deposition accounts for 60–70% of the total sea-salt removed from the atmosphere while in-cloud and below-cloud precipitation scavenging accounts for about 1% and 28–39% of the remainder, respectively. The total amount of sea-salt aerosols emitted from the world oceans to the atmosphere is estimated to be in the vicinity of 1.17×1016 g yr−1. Approximately 99% of the sea-salt aerosol mass generated by wind falls back to the sea with about 1–2% remaining in the atmosphere to be exported from the original grid square (300×300 km). Only a small portion of that exported (∌4%) is associated with submicron particles that are likely to undergo long-range transport

    Dendritic Spine Shape Analysis: A Clustering Perspective

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    Functional properties of neurons are strongly coupled with their morphology. Changes in neuronal activity alter morphological characteristics of dendritic spines. First step towards understanding the structure-function relationship is to group spines into main spine classes reported in the literature. Shape analysis of dendritic spines can help neuroscientists understand the underlying relationships. Due to unavailability of reliable automated tools, this analysis is currently performed manually which is a time-intensive and subjective task. Several studies on spine shape classification have been reported in the literature, however, there is an on-going debate on whether distinct spine shape classes exist or whether spines should be modeled through a continuum of shape variations. Another challenge is the subjectivity and bias that is introduced due to the supervised nature of classification approaches. In this paper, we aim to address these issues by presenting a clustering perspective. In this context, clustering may serve both confirmation of known patterns and discovery of new ones. We perform cluster analysis on two-photon microscopic images of spines using morphological, shape, and appearance based features and gain insights into the spine shape analysis problem. We use histogram of oriented gradients (HOG), disjunctive normal shape models (DNSM), morphological features, and intensity profile based features for cluster analysis. We use x-means to perform cluster analysis that selects the number of clusters automatically using the Bayesian information criterion (BIC). For all features, this analysis produces 4 clusters and we observe the formation of at least one cluster consisting of spines which are difficult to be assigned to a known class. This observation supports the argument of intermediate shape types.Comment: Accepted for BioImageComputing workshop at ECCV 201

    (Quantum) Space-Time as a Statistical Geometry of Fuzzy Lumps and the Connection with Random Metric Spaces

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    We develop a kind of pregeometry consisting of a web of overlapping fuzzy lumps which interact with each other. The individual lumps are understood as certain closely entangled subgraphs (cliques) in a dynamically evolving network which, in a certain approximation, can be visualized as a time-dependent random graph. This strand of ideas is merged with another one, deriving from ideas, developed some time ago by Menger et al, that is, the concept of probabilistic- or random metric spaces, representing a natural extension of the metrical continuum into a more microscopic regime. It is our general goal to find a better adapted geometric environment for the description of microphysics. In this sense one may it also view as a dynamical randomisation of the causal-set framework developed by e.g. Sorkin et al. In doing this we incorporate, as a perhaps new aspect, various concepts from fuzzy set theory.Comment: 25 pages, Latex, no figures, some references added, some minor changes added relating to previous wor

    Recurrent intestinal metaplasia after radiofrequency ablation for Barrett’s esophagus: endoscopic findings and anatomic location

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    Radiofrequency ablation (RFA) is a safe and effective treatment for Barrett’s esophagus (BE) that results in high rates of complete eradication of intestinal metaplasia (CEIM). However, recurrence is common after CEIM and surveillance endoscopy is recommended. Neither the anatomic location nor the endoscopic appearance of these recurrences is well described

    Prospects for measuring the gravitational free-fall of antihydrogen with emulsion detectors

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    The main goal of the AEgIS experiment at CERN is to test the weak equivalence principle for antimatter. AEgIS will measure the free-fall of an antihydrogen beam traversing a moir\'e deflectometer. The goal is to determine the gravitational acceleration g for antihydrogen with an initial relative accuracy of 1% by using an emulsion detector combined with a silicon micro-strip detector to measure the time of flight. Nuclear emulsions can measure the annihilation vertex of antihydrogen atoms with a precision of about 1 - 2 microns r.m.s. We present here results for emulsion detectors operated in vacuum using low energy antiprotons from the CERN antiproton decelerator. We compare with Monte Carlo simulations, and discuss the impact on the AEgIS project.Comment: 20 pages, 16 figures, 3 table

    Development and evaluation of a clinical algorithm to monitor patients on antiretrovirals in resource-limited settings using adherence, clinical and CD4 cell count criteria

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    <p>Abstract</p> <p>Background</p> <p>Routine viral load monitoring of patients on antiretroviral therapy (ART) is not affordable in most resource-limited settings.</p> <p>Methods</p> <p>A cross-sectional study of 496 Ugandans established on ART was performed at the Infectious Diseases Institute, Kampala, Uganda. Adherence, clinical and laboratory parameters were assessed for their relationship with viral failure by multivariate logistic regression. A clinical algorithm using targeted viral load testing was constructed to identify patients for second-line ART. This algorithm was compared with the World Health Organization (WHO) guidelines, which use clinical and immunological criteria to identify failure in the absence of viral load testing.</p> <p>Results</p> <p>Forty-nine (10%) had a viral load of >400 copies/mL and 39 (8%) had a viral load of >1000 copies/mL. An algorithm combining adherence failure (interruption >2 days) and CD4 failure (30% fall from peak) had a sensitivity of 67% for a viral load of >1000 copies/mL, a specificity of 82%, and identified 22% of patients for viral load testing. Sensitivity of the WHO-based algorithm was 31%, specificity was 87%, and would result in 14% of those with viral suppression (<400 copies/mL) being switched inappropriately to second-line ART.</p> <p>Conclusion</p> <p>Algorithms using adherence, clinical and CD4 criteria may better allocate viral load testing, reduce the number of patients continued on failing ART, and limit the development of resistance.</p
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