10,976 research outputs found

    Optimal or antagonistic? muscle force solutions in the lower limb

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    Provides evidence of the appropriateness of different muscle force distribution protocols in a musculoskeletal model of the lower limb

    Vague Concept

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    Terminus

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    Effect of current corrugations on the stability of the tearing mode

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    The generation of zonal magnetic fields in laboratory fusion plasmas is predicted by theoretical and numerical models and was recently observed experimentally. It is shown that the modification of the current density gradient associated with such corrugations can significantly affect the stability of the tearing mode. A simple scaling law is derived that predicts the impact of small stationary current corrugations on the stability parameter Δ′\Delta'. The described destabilization mechanism can provide an explanation for the trigger of the Neoclassical Tearing Mode (NTM) in plasmas without significant MHD activity.Comment: Accepted to Physics of Plasma

    Multilevel Models of Krypton for the Application to Stepwise Ionization Relaxation Processes

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    A four step model and two five step models of krypton are developed for application to stepwise ionization relaxation. The four step model is preferred out of practical and economical grounds. The corresponding rate equations for collisional excitation and ionization are given assuming ladder climbing for the electrons. Selected results of an application of the model to ionization relaxation in shock waves are reported

    Colloquium: Atomic spin chains on surfaces

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    In the present Colloquium, we focus on the properties of 1-D magnetic systems on solid surfaces. From the emulation of 1-D quantum phases to the potential realization of Majorana edge states, spin chains are unique systems to study. The advent of scanning tunnelling microscope (STM) based techniques has permitted us to engineer spin chains in an atom-by-atom fashion via atom manipulation and to access their spin states on the ultimate atomic scale. Here, we present the current state of research on spin correlations and dynamics of atomic spin chains as studied by the STM. After a brief review of the main properties of spin chains on solid surfaces, we classify spin chains according to the coupling of their magnetic moments with the holding substrate. This classification scheme takes into account that the nature and lifetimes of the spin-chain excitation intrinsically depend on the holding substrate. We first show the interest of using insulating layers on metals, which generally results in an increase in the spin state's lifetimes such that their quantized nature gets evident and they are individually accessible. Next, we show that the use of semiconductor substrates promises additional control through the tunable electron density via doping. When the coupling to the substrate is increased for spin chains on metals, the substrate conduction electron mediated interactions can lead to emergent exotic phases of the coupled spin chain-substrate conduction electron system. A particularly interesting example is furnished by superconductors. Magnetic impurities induce states in the superconducting gap. Due to the extended nature of the spin chain, the in-gap states develop into bands that can lead to the emergence of 1-D topological superconductivity and, consequently to the appearance of Majorana edge states

    Genetic differentiation and phylogenetic relationships among six Abies species from European and Turkish areas

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    The phylogenetic relationships of the Abies species in European and Turkish regions have frequently been an object of controversial conclusions. Therefore, we compared the genetic structures of 21 populations belonging to six Abies species which are native to  entral, eastern and south-eastern European regions and  different areas in the Turkey (Asia minor). We used the allele frequency distribution of five isozyme gene locialready showing a high discriminatory power to assess the genetic differentiation among the Abies populations. The UPGMA-dendrogram based on genetic distances showed a clear discrimination between the Turkish Abies species and A. alba from Europe. The particular allele frequency distributions at the isozyme loci PGI-A and 6PGDH-Aconfirmed a great genetic dissimilarity between A. alba and the Turkish Abies species.These results contradict the phylogenetic relationships of the Abies species postulated inother studies
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