Silicon IC models brain activity

Article Abstract:

Researchers at MIT, Lucent Technologies and the Institute of Neuroformatics in Zurich, Switzerland have demonstrated a new, biologically-inspired IC that uses transistors to mimic brain cells. The device has 17 silicon 'neurons' arranged in a ring and making positive-feedback connections to themselves and each other. When an excitatory neuron receives a significant external input, it amplifies it and passes it to its neighbors; inhibitory subcircuits work to squelch current output from other neurons. Adjusting the gain on the neurons modifies the amplitude but does not alter the number of neurons that respond, precisely mimicking gain field modulation, a phenomenon already observed in living brains. The new circuit's success is due largely to careful balancing of the feedbacks among the neurons; if there is too much or too little inhibitory feedback the circuit will not respond or will exploded into the electronic equivalent of epilepsy.

Science & research, Computer networks, Technology development, Neural networks, Neural network

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A single-electron transistor

Article Abstract:

Massachusetts Institute of Technology (MIT, Cambridge, MA) researchers Marc A. Kastner and Udi Meirav and IBM's Thomas J. Watson Research Center (Yorktown Heights, NY) researcher Shalom J. Wind developed a new transistor that turns on and off through the addition or subtraction of a single electron. The transistor consists of a heavily doped gallium-arsenide (GaAs) substrate surfaced by a layer of insulating aluminum-GaAs and topped by a thin layer of lightly doped GaAs. The top layer has an electrode at either end of a transistor with a gate between that allows electrons to pass through when a voltage is applied to the gate. The entry of electrons into the channel forces the current up or down, effectively turning the transistor on or off. The researchers can control the exact number of electrons entering the channel to achieve the desired state.

Commercial physical research, Noncommercial research organizations, International Business Machines Corp., IBM, Industrial research, Product introduction, Research and Development, Gallium Arsenide Semiconductor, Scientific Research, New Technique, Transistor

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Christian Antenor-Habazac: under the volcano

Article Abstract:

A brief profile of Institute de Physique du Globe de Paris engineer, who explores volcanoes, is presented.

Executive changes & profiles, Officials and employees, Brief biography, Habazac, Christian Antenor

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