5,789 research outputs found

    The Molecular Mechanism of Seed Physical Dormancy in Legume Forage

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    Legume forage seeds have evolved a specific dormancy trait, physical dormancy, to inhibit germination until favorable conditions appear. Physical dormancy is an adaptive trait that widely exists in higher plants and plays a vital role in maintaining natural seed banks. This kind of dormancy is caused by a waterimpermeable layer that blocks water and oxygen from the surrounding environment. The outermost cuticle of the seed coat is critical for establishing seed physical dormancy. The molecular mechanism underlying physical dormancy remains largely elusive. Using Medicago (Medicago truncatula) as a model, we set up the legume plant to study seed physical dormancy. Our studies suggest that a class II KNOTTED-like homeobox (KNOXII) gene, KNOX4 is a transcription factor critical for controlling hardseededness. We reported the function of a seed coat β-ketoacyl-CoA synthase, KCS12. kcs12 mutant seeds lost physical dormancy and were able to absorb water without scarification treatment. Chemical analysis revealed that concentrations of C24:0 lipid polyester monomers are significantly decreased in knox4 and kcs12mutant seeds, indicating that both genes are critical to cuticle formation in the seed coat. These findings define a molecular mechanism by which KNOX4 and KCS12 control formation of the seed coat and seed physical dormancy. More mutant identification are performed to understand more about the mechanism of physical dormancy and legume forage improvement, like in alfalfa

    Nitrogen-Mediated Graphene Oxide Enables Highly Efficient Proton Transfer

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    Two-dimensional (2D) graphene and graphene oxide (GO) offer great potential as a new type of cost-efficient proton-exchange membranes (PEM) for electrochemical devices. However, fundamental issues of proton transfer mechanism via 2D membranes are unclear and the transfer barrier for perfect graphene are too high for practical application. Using ab initio molecular dynamic simulations, we screened the proton transfer barrier for different un-doped and nitrogen doped GO membranes, and clarified the corresponding transfer mechanisms. More significantly, we further identify that N-mediated GO can be built into a highly efficient PEM with a proton transfer rate of seven orders of magnitude higher than an un-doped case via. a proton relay mechanism between a ketone-like oxygen and a pyridine-like nitrogen across the vacancy site. The N-doped 2D GO is also impermeable to small molecules, and hence a highly efficient PEM for practical applications

    Cognitive Principles in Robust Multimodal Interpretation

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    Multimodal conversational interfaces provide a natural means for users to communicate with computer systems through multiple modalities such as speech and gesture. To build effective multimodal interfaces, automated interpretation of user multimodal inputs is important. Inspired by the previous investigation on cognitive status in multimodal human machine interaction, we have developed a greedy algorithm for interpreting user referring expressions (i.e., multimodal reference resolution). This algorithm incorporates the cognitive principles of Conversational Implicature and Givenness Hierarchy and applies constraints from various sources (e.g., temporal, semantic, and contextual) to resolve references. Our empirical results have shown the advantage of this algorithm in efficiently resolving a variety of user references. Because of its simplicity and generality, this approach has the potential to improve the robustness of multimodal input interpretation

    Some integral inequalities on time scales

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    In this paper, some new integral inequalities on time scales are presented by using elementarily analytic methods in calculus of time scales.Comment: 8 page

    Analysis of RTN signals in Resistive-Switching RAM device and its correlation with device operations

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    Filament rupture/restoration induced by movement of defects, e.g. oxygen ions/vacancies, is considered as the switching mechanism in HfO2 RRAM. However, details of filament alteration during switching are still speculative, due to the limitations of existing experiment-based probing techniques, impeding its understanding. In this work, for the first time, an RTN-based defect tracking technique is developed for RRAM devices, which can monitor the movements of defects and statistically provide their spatial and energy profiles. The critical filament region is experimentally identified and its alteration is observed and correlated with switching operations under various operation conditions. This provides a useful tool for further development of RRAM technology

    Bearing angle based cooperative source localization

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    © 2014 IEEE. This paper deals with the cooperative source localization problem with the goal of having an accurate estimate of the coordinate of the source cooperatively by a group of unicycle-type mobile agents. Neither absolute positioning information nor a common sense of direction is shared by the agents. Each agent gets its estimate about the source's coordinate in its own local frame based on the bearing measurements about its neighbors (that may or may not include the source) together with its own linear and angular speed information. A continuous time estimation scheme and a distributed fusion scheme are proposed for this goal such that the source's relative coordinate can be estimated at any time by each agent no matter whether it can directly detect the source or not. The globally asymptotic convergence of the estimation scheme and the fusion scheme is rigorously analyzed. Simulation results are also provided to verify the effectiveness of the proposed algorithms
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