Tetsuya Matsuno

Multichannel taste sensor using electric potential changes in lipid membranes

A taste sensor with a multichannel electrode was developed by using lipid membranes as a transducer of taste substances. The sensor can detect the taste in a similar manner to the human gustatory sensation by response patterns of electric potential to taste substances. The sensitivity, reproducibility and durability were superior to those of humans. The same taste as that elicited by some commercial aqueous drink was reproduced by making aqueous solution mixed from four kinds of basic taste substances, the concentrations of which were determined so that the electric-potential pattern of this mixed solution could agree well with the pattern by the drink. Different brands of beer were easily distinguished by the electric-potential patterns.

Discrimination of Taste of Amino Acids with a Multichannel Taste Sensor

Taste of amino acids was studied using a multichannel taste sensor with lipid membranes as the transducer of taste substances. The study on taste of amino acids has drawn much attention so far because each of them elicits complicated mixed taste. The response of the sensor to amino acids was compared with results of panel tests, and response potentials from the eight membranes were transformed to terms representing five basic tastes by multiple linear regression. This expression of five basic tastes reproduced human taste sensation very well. The taste was expressed more quantitatively by assuming new channels, which are represented by multiplication of the response potentials of the original channels. This new set of channels implies the existence of processes involving the nervous system which is connected with taste cells.

DC susceptibility of type-II superconductors in field-cooled processes

Abstract The DC susceptibility of oxide superconducting specimens in the field-cooled process has been experimentally found to depend not only on the applied DC magnetic field but also on the size of the specimens. The DC susceptibility is calculated using the critical state model in which the diamagnetism and the flux-pinning effect of superconductors are taken into account. It is shown that the saturated value of the DC susceptibility at sufficiently low temperatures, i.e., the so-called Meissner fraction, decreases with increasing DC field and/or increasing specimen size.

Study of astringency and pungency with multichannel taste sensor made of lipid membranes

Abstract Pungent and astringent substances have been studied using a multichannel taste sensor. The electric-potential pattern made up of eight outputs from the membranes of the sensor has information about taste quality and intensity. Pungent substances including capsaicin, piperine and allyl isothiocyanate have no effect on the electric potentials of the liquid membranes. On the other hand, astringent substances such as catechin, tannic acid, chlorogenic acid and gallic acid change the potentials remarkably. A principal-component analysis of the patterns in electric-potential change caused by the taste substances reveals that the taste quality of astringency is located between bitterness and sourness. A model for astringency is presented.

Oscillations of electrical potential along a root of a higher plant

Higher plants exhibit an oscillation of electrical potential near the surface along the root. The oscillation was studied with the aid of both the usual intracellular microelectrode technique and the extracellular multielectrode technique, the latter making it possible to measure simultaneously electrical potentials along the root. It was found that the oscillation of extracellular surface potential showed the largest amplitude in the elongation region, and the phase of the oscillation in this region differed by 180 degrees from that in the mature region, where the oscillation appeared coherent. The measurement of the intracellular electrical potential suggested the existence of oscillatory components localized to the parenchyma/xylem interface in the elongation region. A theoretical analysis based on an electrical circuit network described the above-mentioned behavior. It was shown that the oscillation was propagated along the root over several centimeters without substantial decay in the mature region.

A theory of thermal-fluctuation-induced depinning line in weakly pinning high-Tc superconductors

Abstract The expression for the thermal-fluctuation-induced depinning line, T = TP (Be), is derived theoretically for weakly pinning high-Tc superconductors. In the derivation, it is shown that the thermal displacement of pinned fluxoids, uth reduces the critical current density as J c = J c0 ( − 〈u 2 th 〉/d 2 p ) 3 2 , where J c0 is the critical current density in the absence of u th and d p is the effective half width of the summed-up pinning potential. Then T p (itB e) is determined as the temperature at which Jc becomes zero due to the increase of 〈u2th〉 with the increase of T in the external flux density of Be. The relation of Tp(Be) with the irreversibility line of Ti(Be) and the flux melting line of Tm(Be) is also discussed.

Early Gravi-Electrical Responses in Bean Epicotyls

The relationship between gravitropism and surface electrical potentials was studied using etiolated epicotyls of adzuki bean (Phaseolus angularis). Early downward curvature (or transient positive gravitropic response) was observed about 1 min after gravistimulation. The downward curvature was closely related to the speed of the subsequent upward curvature. Surface electrical potentials decreased cooperatively in a limited region on the upper side within only 0.5 to 2 min. This is the earliest event found so far to follow gravistimulation of intact epicotyls. The rapid change in the potential had a high correlation with the early downward curvature and also the subsequent negative gravitropism. It is suggested that the rapid potential change plays an important role in gravity perception.

Critical current density of superconducting NbTa tapes in a longitudinal magnetic field

Abstract It is empirically known that the superconducting critical current density is much larger in a longitudinal field geometry than in a transverse one. Flux cutting and flux pinning have been considered as two possible reasons for the origin of large longitudinal critical current density. Critical current density in superconducting NbTa tapes with normal precipitates was measured in this field geometry in a wide range of pinning strength in order to investigate this problem. Critical current density depended strongly on the pinning strength and increased with increasing pinning strength. This result insists that flux pinning dominates in the determination of critical current density. If the cutting threshold exists, it is estimated to be quite small from extrapolation of the present results to the limit of weak pinning. This value is compared with the theoretical estimate of the cutting threshold.

On the magnetic field dependence of critical current density in single crystals of high-Tc superconductors

Abstract The critical current density, Jc, is discussed theoretically to explain the exponential dependence of Jc on the flux density, B, given typically by Jc∝exp( −B B 0 (T) ), which has been widely observed for single crystals of high-Tc superconductors in an external magnetic field parallel to the crystal c-axis. It is pointed out that Jc shows an exponential-type dependence, Jc∝exp( −ƒf(B, T) ), when the tilt modulus, C44, of fluxoids shows a remarkable softening for higher values of the wave number. It is also shown that the present expression of Jc is reduced to the observed B dependence of ƒ(B, T)⋍ B B 0 (T) by taking account of th e effects of the layered crystal structure on C44 and the correlation length, l44.

Proximity Effect on Flux Pinning Strength in Superconducting Nb-Ti with Thin α-Ti Ribbons

It has been found by Lee et al. that the critical temperature reduces monotonically, while the critical current density first increases and is followed by a decrease, according as the diameter of superconducting multifilamentary Nb-Ti wire is decreased. This behavior is mainly caused by the proximity effect between superconducting matrix and normal α -Ti ribbons that becomes more remarkable as the thicknesses of two regions become smaller. The critical temperature and the elementary pinning strength of α -Ti ribbons are theoretically estimated by solving the phenomenological Ginzburg-Landau equations for multilayered structure with superconducting and normal layers. The critical current density is calculated from a statistic summation of the elementary pinning forces. The obtained critical temperature decreases monotonically, while the critical current density increases, with decreasing thicknesses of the two layers. The decrease in JC observed by Lee et al. is considered to result from constriction of superconducting layers by heavy cold work.