1,609 research outputs found

    Searching for plasticity in dissociated cortical cultures on multi-electrode arrays

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    We attempted to induce functional plasticity in dense cultures of cortical cells using stimulation through extracellular electrodes embedded in the culture dish substrate (multi-electrode arrays, or MEAs). We looked for plasticity expressed in changes in spontaneous burst patterns, and in array-wide response patterns to electrical stimuli, following several induction protocols related to those used in the literature, as well as some novel ones. Experiments were performed with spontaneous culture-wide bursting suppressed by either distributed electrical stimulation or by elevated extracellular magnesium concentrations as well as with spontaneous bursting untreated. Changes concomitant with induction were no larger in magnitude than changes that occurred spontaneously, except in one novel protocol in which spontaneous bursts were quieted using distributed electrical stimulation

    The Joint Archives Quarterly, Volume 02.04: Winter 1991

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    The Joint Archives Quarterly, Volume 04.03: Fall 1992

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    The Joint Archives Quarterly, Volume 03.01: Spring 1991

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    Spin-mediated dissipation and frequency shifts of a cantilever at milliKelvin temperatures

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    We measure the dissipation and frequency shift of a magnetically coupled cantilever in the vicinity of a silicon chip, down to 2525 mK. The dissipation and frequency shift originates from the interaction with the unpaired electrons, associated with the dangling bonds in the native oxide layer of the silicon, which form a two dimensional system of electron spins. We approach the sample with a 3.433.43 μ\mum-diameter magnetic particle attached to an ultrasoft cantilever, and measure the frequency shift and quality factor as a function of temperature and the distance. Using a recent theoretical analysis [J. M. de Voogd et al., arXiv:1508.07972 (2015)] of the dynamics of a system consisting of a spin and a magnetic resonator, we are able to fit the data and extract the relaxation time T1=0.39±0.08T_1=0.39\pm0.08 ms and spin density σ=0.14±0.01\sigma=0.14\pm0.01 spins per nm2^2. Our analysis shows that at temperatures ≤500\leq500 mK magnetic dissipation is an important source of non-contact friction.Comment: 5 pages, 3 figure

    The Joint Archives Quarterly, Volume 03.04: Winter 1992

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