3,915 research outputs found

    Experiment K-6-08. Biochemical and histochemical observations of vastus medialis

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    Muscles of the hindlimb in the rat have been used to demonstrate the effects of unloading in weightlessness and in animal models used to mimic weightlessness. The vastus medialis (VM) is discussed here. Samples were obtained from rats exposed to weightlessness for 12 days in Cosmos 1887 (Experiment K-6-08, coordinated by Dr. V.S. Oganov). The principal objective of this study was to ascertain if the vastus medialis responded to 12 days of microgravity exposure. The loss in muscle mass is greatest, -43 percent, when comparing F vs B, and least, -13 percent, when comparing F vs. V. Taken at face value these differences may be misleading. Due to the variability of the muscle weight in the basal group, these muscle mass losses may be exaggerated. In terms of percent water, there were no differences between the flight and the control groups. In spite of the limited sample, researchers conclude that muscle mass changes in the VM are not significant. Although some of the morphological parameters suggest a small degree of atrophy in the vastus medialis, the biochemical analyses (protein, RNA and DNA) suggest that these may be minimal and functionally nonsignificant. The relatively similar CS and LDH activities of VM from F and various control groups, as well as the lack of difference in LPL activity between F and S rats, suggests that there is little or no effect on the oxidative or glycolytic function of this muscle. Since the VM is chiefly a mixed fast twitch muscle, these metabolic indices of energy production are relatively unchanged. The results of VM studies are in agreement with previous observations of another type II fast twitch muscle, the EDL, from SL-3 rats which did not respond markedly to weightlessness and whole body suspension

    Robustness and Enhancement of Neural Synchronization by Activity-Dependent Coupling

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    We study the synchronization of two model neurons coupled through a synapse having an activity-dependent strength. Our synapse follows the rules of Spike-Timing Dependent Plasticity (STDP). We show that this plasticity of the coupling between neurons produces enlarged frequency locking zones and results in synchronization that is more rapid and much more robust against noise than classical synchronization arising from connections with constant strength. We also present a simple discrete map model that demonstrates the generality of the phenomenon.Comment: 4 pages, accepted for publication in PR

    Locally Trivial W*-Bundles

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    We prove that a tracially continuous W∗^*-bundle M\mathcal{M} over a compact Hausdorff space XX with all fibres isomorphic to the hyperfinite II1_1-factor R\mathcal{R} that is locally trivial already has to be globally trivial. The proof uses the contractibility of the automorphism group Aut(R)\mathrm{Aut}({\mathcal{R}}) shown by Popa and Takesaki. There is no restriction on the covering dimension of XX.Comment: 20 pages, this version will be published in the International Journal of Mathematic

    Radical news? Immigrants’ television use, acculturation challenges, and support for terrorism

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    Previous research shows that acculturation challenges predict immigrants’ support for terrorism. Here, we acknowledge the central role of mass media use in the acculturation process. We investigate whether immigrants who infrequently use ethnic and host country media, a possible indicator or driver of marginalisation, report higher sympathy with terrorism than frequent media users. We further examine if those who prefer ethnic over host country media, which might reflect or facilitate disengagement from the host society, support terrorism more strongly. To address these research questions, we conducted secondary analyses of a public opinion poll of Muslim immigrants resident in the United Kingdom (N = 880). Focusing on immigrants’ use of ethnic and host country television channels, latent class analysis identified four groups: Frequent and Infrequent Media Users as well as Ethnic and Host Country Media Users. Overall sympathy with terrorism was low. Contesting our hypothesis, Frequent Media Users supported terrorist action more than Infrequent Media Users. Ethnic Media Users also expressed higher sympathy with terrorism than Host Country Media Users. Findings emphasise the dynamic interplay between media use and acculturation challenges; they further suggest strategies to reduce immigrants’ support for terrorism

    Construction of Parseval wavelets from redundant filter systems

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    We consider wavelets in L^2(R^d) which have generalized multiresolutions. This means that the initial resolution subspace V_0 in L^2(R^d) is not singly generated. As a result, the representation of the integer lattice Z^d restricted to V_0 has a nontrivial multiplicity function. We show how the corresponding analysis and synthesis for these wavelets can be understood in terms of unitary-matrix-valued functions on a torus acting on a certain vector bundle. Specifically, we show how the wavelet functions on R^d can be constructed directly from the generalized wavelet filters.Comment: 34 pages, AMS-LaTeX ("amsproc" document class) v2 changes minor typos in Sections 1 and 4, v3 adds a number of references on GMRA theory and wavelet multiplicity analysis; v4 adds material on pages 2, 3, 5 and 10, and two more reference
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