21,256 research outputs found

    On the Enforcement of a Class of Nonlinear Constraints on Petri Nets

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    International audienceThis paper focuses on the enforcement of nonlinear constraints in Petri nets. First, a supervisory structure is proposed for a nonlinear constraint. The proposed structure consists of added places and transitions. It controls the transitions in the net to be controlled only but does not change its states since there is no arc between the added transitions and the places in the original net. Second, an integer linear programming model is proposed to transform a nonlinear constraint to a minimal number of conjunc-tive linear constraints that have the same control performance as the nonlinear one. By using a place invariant based method, the obtained linear constraints can be easily enforced by a set of control places. The control places consist to a supervisor that can enforce the given nonlinear constraint. On condition that the admissible markings space of a nonlinear constraint is non-convex, another integer linear programming model is developed to obtain a minimal number of constraints whose disjunctions are equivalent to the nonlinear constraint. Finally, a number of examples are provided to demonstrate the proposed approach

    Comparative theoretical study of the Ag-MgO (100) and (110) interfaces

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    We have calculated the atomic and electronic structures of Ag-MgO(100) and (110) interfaces using a periodic (slab) model and an ab initio Hartree-Fock approach with a posteriori electron correlation corrections. The electronic structure information includes interatomic bond populations, effective charges, and multipole moments of ions. This information is analyzed in conjunction with the interface binding energy and the equilibrium distances for both interfaces for various coverages. There are significant differences between partly covered surfaces and surfaces with several layers of metal, and these can be understood in terms of electrostatics and the electron density changes.For complete monolayer (1:1) coverage of the perfect MgO(100) surface, the most favorable adsorption site energetically for the Ag atom is above the surface oxygen. However, for partial (1:4) coverage of the same surface, the binding energies are very close for all the three likely adsorption positions (Ag over O, Ag over Mg, Ag over a gap position),For a complete (1:1) Ag monolayer coverage of the perfect MgO(110) interface, the preferable Ag adsorption site is over the interatomic gap position, whereas for an Ag bilayer coverage the preferred Ag site is above the subsurface Mg2+ ion (the bridge site between two nearest surface O2- ions). In the case of 1:2 layer coverage, both sites are energetically equivalent. These two adhesion energies for the (110) substrate are by a factor of two to three larger than over other possible adsorption sites on perfect(110) or (100) surfaces.We compare our atomistic calculations for one to three Ag planes with those obtained by the shell model for 10 Ag planes and the Image Interaction Model addressing the case of thick metal layers. Qualitatively, our ab initio results agree well with many features of these models. The main charge redistributions are well in line with those expected from the Image Model. There is also broad agreement in regard to orders of magnitude of energies. (C) 1999 Elsevier Science B.V. All rights reserved

    EEG signals analysis using multiscale entropy for depth of anesthesia monitoring during surgery through artificial neural networks

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    In order to build a reliable index to monitor the depth of anesthesia (DOA), many algorithms have been proposed in recent years, one of which is sample entropy (SampEn), a commonly used and important tool to measure the regularity of data series. However, SampEn only estimates the complexity of signals on one time scale. In this study, a new approach is introduced using multiscale entropy (MSE) considering the structure information over different time scales. The entropy values over different time scales calculated through MSE are applied as the input data to train an artificial neural network (ANN) model using bispectral index (BIS) or expert assessment of conscious level (EACL) as the target. To test the performance of the new index's sensitivity to artifacts, we compared the results before and after filtration by multivariate empirical mode decomposition (MEMD). The new approach via ANN is utilized in real EEG signals collected from 26 patients before and after filtering by MEMD, respectively; the results show that is a higher correlation between index from the proposed approach and the gold standard compared with SampEn. Moreover, the proposed approach is more structurally robust to noise and artifacts which indicates that it can be used for monitoring the DOA more accurately.This research was financially supported by the Center for Dynamical Biomarkers and Translational Medicine, National Central University, Taiwan, which is sponsored by Ministry of Science and Technology (Grant no. MOST103-2911-I-008-001). Also, it was supported by National Chung-Shan Institute of Science & Technology in Taiwan (Grant nos. CSIST-095-V301 and CSIST-095-V302) and National Natural Science Foundation of China (Grant no. 51475342)

    Protective effect of nitric oxide against arsenic-induced oxidative damage in tall fescue leaves

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    Nitric oxide (NO) is a key molecule involved in many physiology processes. The effects of NO on alleviating arsenic-induced oxidative damage in tall fescue leaves were investigated. Arsenic (25 M) treatment induced significantly accumulation of reactive oxygen species (ROS) and led to serious lipid peroxidation in tall fescue leaves and the application of 100 M SNP before arsenic stress resulted in alleviated arsenic-induced electrolyte leakage and malondiadehyde (MDA) content in tall fescue leaves, the levels of hydrogen peroxide (H2O2) and superoxide radical (O2̅ ) were reduced as well. Moreover, the activities of superoxide dismutase (SOD), catalase (CAT) and ascorbate peroxidase (APX) increased in tall fescue leaves in presence of SNP under arsenic stress. This pattern was reversed by application of NO scavenger, 2-(4-carboxy-2-phenyl)-4,4,5,5-tetramethy-limidazoline-1-oxyl-3-oxide (PTIO) before arsenic treatment. Pronounced increases in endogenous NO production was found in plants after exposure to arsenic stress. The results suggested that arsenic stress elevated endogenous NO level and that NO might act as a signaling molecule to enhance antioxidant enzyme activities, further protecting against injuries caused by arsenic toxicity

    Circulating annexin A5 levels after atrial switch for transposition of the great arteries: relationship with ventricular deformation and geometry

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    Functional Assessment for Congenital Heart Disease

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    Truncated human endothelin receptor A produced by alternative splicing and its expression in melanoma

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    In this study, reverse transcriptase polymerase chain reaction was used to amplify human endothelin receptor A (ETA) and ETB receptor mRNA. A truncated ETA receptor transcript with exons 3 and 4 skipped was found. The skipping of these two exons results in 109 amino acids being deleted from the receptor. The truncated receptor was expressed in all tissues and cells examined, but the level of expression varied. In melanoma cell lines and melanoma tissues, the truncated receptor gene was the major species, whereas the wild-type ETA was predominant in other tissues. A 1.9-kb ETA transcript was identified in melanoma cell lines by Northern blot, which was much smaller than the transcript in heart and in other tissues reported previously (4.3 kb). The cDNA coding regions of the truncated and wild-type ETA receptors were stably transfected into Chinese hamster ovary (CHO) cells. The truncated ETA receptor-transfected CHO cells did not show binding affinity to endothelin 1 (ET-1) or endothelin 3 (ET-3). The function and biological significance of this truncated ETA receptor is not clear, but it may have regulatory roles for cell responses to ETs
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