A new model of a mobility aid for the blind was designed using microprocessor and ultrasonic devices. This mobility aid was evaluated based on psychophysical experiments. In this model, a downswept FM ultrasound signal is emitted from a transmitting array with broad directional characteristics in order to detect obstacles. The ultrasound reflections from the obstacles are picked up by a two-channel receiver. The frequency of the emitted ultrasound is swept from 70 to 40 kHz within 1 ms, so it has almost the same characteristics as the ultrasound a bat produces for echolocation. The frequency of the reflected ultrasound wave is down converted by about 50:1 by using a microcomputer with A/D and D/A converters. These audible waves are then presented binaurally through earphones. In this method obstacles may be perceived as localized sound images corresponding to the direction and the size of the obstacles. From the results of psychophysical experiments, it was found that downswept FM ultrasound was superior for the recognition of small obstacles compared to other ultrasonic schemes. With it a blind person can recognize a 1-mm-diameter wire. It was also proved that the blind could discriminate between several obstacles at the same time without any virtual images. This mobility aid, modeled after the bat's echolocation system, is very effective at detecting small obstacles placed in front of the head.

A ganglioside-stimulated protein phosphorylation system was discovered in plasma membrane fractions of human neuroblastoma cells (GOTO). Gangliosides (GQ1b, GT1a, GT1b, GD1a, GD1b, GD3, and GM1) could stimulate this system. GQ1b showed the most effective stimulation among these gangliosides. The substrate specificity was rather broad. Not only some (de novo) proteins of the membranes but also purified histones and tubulin were phosphate-acceptable. This protein phosphorylation system specifically depended upon Ca2+ (optimum concentration: 50-100 microM). The optimum pH was 7.0-7.5. GQ1b/Ca2+ could not directly activate well known protein kinases (Ca2+/phospholipid-activated protein kinase, Ca2+/calmodulin-activated protein kinase, and cyclic nucleotide-dependent protein kinases). Furthermore, GQ1b could replace neither phospholipids nor calmodulin. Thus, an unknown, new type of protein kinase(s) may be involved in this system. Alternatively, GQ1b may activate some known protein kinase(s) in cooperation with another unknown factor which may be removed during the preparation of the partially purified known protein kinase used in this experiment.

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Katuhira 2-1-1, Aohu-ku, Sendui 980-8577, Jupun phone/fax +81-22-217-5553, ohno@nec.tohokx.ucjpModem information technology utilizes the charge degree of freedom of electrons to process inforrnatmn in semiconductors and the spin degree of freedom for mass storage of information in magnetic materials New fmchonalities are expected from semiconductor devices that make use of both charge and spin degrees of keedom in semiconductors. Carrier-induced ferromagnetism in transition metal doped 111-V compounds offers integration of ferromagnetism with the existing aonmagnetic 111-V heterostrucbxes These aructures allow us to explore spin-dependent phenomena in semiconductor heteroshuctures, which may lead us to a new form of electron~cs, spmtronics, where both the spin and charge degrees of freedom play cntical roles [ 13 Here, 1 review the recent development in the field of HI-V ferromagnetism and spin-dependent phenomena in its heterostructures A mean-field theory based on exchange between carrier spin and Mn spin is shown to be capable of explaining the ferromagnetic transition temperatures, strain-dependent easy axis, and peculiar temperature dependence of magnehc circular dicrhosm, when realistic band structure IS incorporated [23 Magnetichonmagnetic trilayer structures based on 111-V's have been shown to exhibit spm-dependent scattenng, tunnel magnetoresistance as well as interlayer coupling due to the carrier polarization [3] Electncal spin injection across a ferromagnetdnonmagnetic heterojunctlon and into an InGaAs quantum well (QW> has been demonstrated using ferromagnetic (Ga,Mn)As as a source of spin polarized carriers [4] Electncal electron spin injection has also been realized in a spin Esah diode structure [SI By the use of insulating-gate field-effect transistor structures, we can electrically switch the ferromagnetic phaqe transition [6] We are thus b e p " to learn how to control and utilize the spin degree of freedom in semiconductors Routes to room temperature ferromagnetism by realizing new surface stabilized ferromagnehc compounds compatible with semiconductor heterostmctures will also be discussed [7] References [I] H Ohno, Scrence, 281,95 I (1998), J Mag Mag Materials, 200, I 10 (1 999) [2]

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