Bielefeld University

About: Bielefeld University is a education organization based out in Bielefeld, Nordrhein-Westfalen, Germany. It is known for research contribution in the topics: Population & Quantum chromodynamics. The organization has 10123 authors who have published 26576 publications receiving 728250 citations. The organization is also known as: University of Bielefeld & UNIVERSITAET BIELEFELD.

The memristive magnetic tunnel junction as a nanoscopic synapse-neuron system.

Abstract: Memristors cover a gap in the capabilities of basic electronic components by remembering the history of the applied electric potentials, and are considered to bring neuromorphic computers closer by imitating the performance of synapses.[1–3] We used memristive magnetic tunnel junctions[4,5] based on MgO to demonstrate that the synaptic functionality is complemented by neuron-like behavior in these nanoscopic devices. The synaptic functionality originates in a resistance change caused by a voltage-driven oxygen vacancy motion[6] within the MgO layer. The additional functionality provided by magnetic electrodes enabled a current-driven resistance modulation due to spin-transfer torque.[7] We showed that a phenomenon known as back-hopping[8–11] leads to repeated switching between two resistance levels accompanied by current spiking, which emulates neuronal behavior. As a result, this remarkably simple system, which is composed of two magnetic layers separated by an insulator, provides a sufficient basis for the fabrication of a complete neural network. According to a simple model, the human brain consists of a network of neurons, axons and synapses. Neurons exchange electrical impulses (i.e., spikes) along their axons, and synapses are the functionalized junctions between axons and neurons. The structure of the network is defined by the spatial arrangement of neurons and axons and by the strength of each synaptic connection. In this framework, one can equate the current configuration of the network with “knowledge” and its modulation with “learning”. In the conventional (Hebbian) concept of learning,[12] synaptic strength is modified by the coincident activity of presynaptic and postsynaptic neurons. In the past few years, a series of experiments has revealed a new picture. These studies suggest that instead of mere coincidence, the precise timing of presynaptic and postsynaptic spikes (i.e., spike-timing-dependent plasticity, STDP) plays a decisive role in determining the type of synaptic modification.[13,14] This modification can lead to a persistent increase or decrease in synaptic strength, commonly referred to as long-term potentiation (LTP) or long-term depression (LTD). Software inspired by neuronal networks is widely used for specific tasks, such as pattern recognition. In addition, hardware

Diversity policy, social dominance, and intergroup relations: predicting prejudice in changing social and political contexts.

Abstract: In contrast to authors of previous single-nation studies, we propose that supporting multiculturalism (MC) or assimilation (AS) is likely to have different effects in different countries, depending on the diversity policy in place in a particular country and the associated norms. A causal model of intergroup attitudes and behaviors, integrating both country-specific factors (attitudes and perceived norms related to a particular diversity policy) and general social-psychological determinants (social dominance orientation), was tested among participants from countries where the pro-diversity policy was independently classified as low, medium, or high (N = 1,232). Results showed that (a) anti-Muslim prejudice was significantly reduced when the pro-diversity policy was high; (b) countries differed strongly in perceived norms related to MC and AS, in ways consistent with the actual diversity policy in each country and regardless of participants' personal attitudes toward MC and AS; (c) as predicted, when these norms were salient, due to subtle priming, structural equation modeling with country included as a variable provided support for the proposed model, suggesting that the effect of country on prejudice can be successfully accounted by it; and (d) consistent with the claim that personal support for MC and AS played a different role in different countries, within-country mediation analyses provided evidence that personal attitudes toward AS mediated the effect of social dominance orientation on prejudice when pro-diversity policy was low, whereas personal attitudes toward MC was the mediator when pro-diversity policy was high. Thus, the critical variables shaping prejudice can vary across nations.