| 1. |
- Wosinski, Tadeusz, et al.
(författare)
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Domain-wall induced magneto-resistive memory in ferromagnetic (Ga, Mn) As nanostructures
- 2008
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Ingår i: JOURNAL OF MATERIALS SCIENCE-MATERIALS IN ELECTRONICS. - : Springer Science and Business Media LLC. - 0957-4522 .- 1573-482X. ; 19, s. 111-114
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Konferensbidrag (refereegranskat)abstract
- Novel magneto-resistive memory effect is demonstrated, which appears in lithographically patterned Y-shaped, three-terminal nanostructures, consisting of three nanowires joined in one point, formed in the epitaxial layer of a ferromagnetic (Ga, Mn) As semiconductor. The effect, in which the zero-field resistance of a pair of nanowires depends on the direction of the previously applied magnetic field, results from a rearrangement of magnetic domain walls, contributing an extra resistance, between different pairs of nanowires in the structure. Two-state behaviour of the nanostructure resistance provides its usefulness for applications in non-volatile memory devices.
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| 2. |
- Andrearczyk, Tomasz, et al.
(författare)
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Remnant magnetoresistance effect at the intersection of two ferromagnetic (Ga,Mn)As nanowires
- 2011
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Ingår i: Physica Status Solidi. B: Basic Research. - : Wiley. - 0370-1972. ; 248:7, s. 1587-1591
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Tidskriftsartikel (refereegranskat)abstract
- Cross-like nanostructures composed of two perpendicular ferromagnetic (Ga,Mn)As nanowires were fabricated using electron-beam lithography patterning. Nanostructures of different orientations with respect to the crystallographic axes of the parent (Ga,Mn)As epitaxial layer were studied. Electrical resistance of individual nanowires as a function of applied magnetic field were investigated at low temperatures. Low-field magnetoresistance (MR) of the nanowires exhibits hysteresis-like behaviour and related remnant resistance in zero magnetic field. These effects are explained in terms of magnetic domain walls (DWs) pinned at the wires intersection, which contribute to the wire resistance. The DW resistivity, which depends on the degree of spin misalignment in the wall, has been determined to be of the order of 1 Omega mu m(2). High-field MR has, in turn, allowed determining the lithography-induced anisotropy field for the nanowires of different crystallographic orientations. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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| 3. |
- Lindström, Sivert, et al.
(författare)
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Feedforward and recurrent inhibitory receptive fields of principal cells in the cats dorsal lateral geniculate nucleus
- 2011
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Ingår i: PFLUGERS ARCHIV-EUROPEAN JOURNAL OF PHYSIOLOGY. - : Springer Science Business Media. - 0031-6768 .- 1432-2013. ; 461:2, s. 277-294
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Tidskriftsartikel (refereegranskat)abstract
- Principal cells in the dorsal lateral geniculate nucleus receive both feedforward and recurrent inhibition. Despite many years of study, the receptive field structure of these inhibitory mechanisms has not been determined. Here, we have used intracellular recordings in vivo to differentiate between the two types of inhibition and map their respective receptive fields. The feedforward inhibition of a principal cell originates from the same type of retinal ganglion cells as its excitation, while the recurrent inhibition is provided by both on- and off-centre cells. Both inhibitory effects are strongest at the centre of the excitatory receptive field. The diameter of the feedforward inhibitory field is two times larger, and the recurrent two to four times larger than the excitatory field centre. The inhibitory circuitry is similar for X and Y principal cells.
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| 4. |
- Nersisyan, Syune, et al.
(författare)
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Cholinergic and Noradrenergic Modulation of Corticothalamic Synaptic Input From Layer 6 to the Posteromedial Thalamic Nucleus in the Rat
- 2021
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Ingår i: Frontiers in Neural Circuits. - : Frontiers Media S.A.. - 1662-5110. ; 15
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Tidskriftsartikel (refereegranskat)abstract
- Cholinergic and noradrenergic neuromodulation of the synaptic transmission from cortical layer 6 of the primary somatosensory cortex to neurons in the posteromedial thalamic nucleus (PoM) was studied using an in vitro slice preparation from young rats. Cholinergic agonist carbachol substantially decreased the amplitudes of consecutive excitatory postsynaptic potentials (EPSPs) evoked by a 20 Hz five pulse train. The decreased amplitude effect was counteracted by a parallel increase of synaptic frequency-dependent facilitation. We found this modulation to be mediated by muscarinic acetylcholine receptors. In the presence of carbachol the amplitudes of the postsynaptic potentials showed a higher trial-to-trial coefficient of variation (CV), which suggested a presynaptic site of action for the modulation. To substantiate this finding, we measured the failure rate of the excitatory postsynaptic currents in PoM cells evoked by "pseudominimal" stimulation of corticothalamic input. A higher failure-rate in the presence of carbachol indicated decreased probability of transmitter release at the synapse. Activation of the noradrenergic modulatory system that was mimicked by application of norepinephrine did not affect the amplitude of the first EPSP evoked in the five-pulse train, but later EPSPs were diminished. This indicated a decrease of the synaptic frequency-dependent facilitation. Treatment with noradrenergic alpha-2 agonist clonidine, alpha-1 agonist phenylephrine, or beta-receptor agonist isoproterenol showed that the modulation may partly rely on alpha-2 adrenergic receptors. CV analysis did not suggest a presynaptic action of norepinephrine. We conclude that cholinergic and noradrenergic modulation act as different variable dynamic controls for the corticothalamic mechanism of the frequency-dependent facilitation in PoM.
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| 5. |
- Nersisyan, Syune, et al.
(författare)
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Cholinergic modulation of synaptic properties of cortical layer VI input to posteromedial thalamic nucleus of the rat investigated in vitro
- 2012
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Ingår i: Acta Neurobiologiae Experimentalis. - 0065-1400 .- 1689-0035. ; 72:4, s. 461-467
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Tidskriftsartikel (refereegranskat)abstract
- The second order somatosensory thalamic nucleus (posteromedial nucleus, PoM) receives excitatory projection from layer VI of somatosensory cortex. While it is known that layer VI cortical input to first order, ventrobasal nucleus (VB) is modulated by cholinergic projections from the brainstem, no such data exists concerning the PoM nucleus. In order to study if layer VI corticothalamic transmission to PoM is also modulated we used patch-clamp recording in thalamocortical slices from the rat's brain. Excitatory postsynaptic potentials (EPSPs) were evoked in PoM cells by trains of 5 electrical pulses at 20 Hz frequency applied to corticothalamic fibers. After carbachol was applied to mimic activation of the cholinergic neuromodulatory system corticothalamic EPSP amplitudes were reduced, while facilitation of EPSP amplitudes was enhanced for each next pulse in the series. Such cholinergic control of layer VI corticothalamic synapses in PoM may be used as gain modulator for the transfer of the peripheral sensory information to the cortex.
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