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R Hayakawa

Publications and source records attributed to R Hayakawa.

At least 19 recordsLinked to original sources
PubMed2001

Critical behavior of nonlinear permittivity in the smectic-A phase of chiral liquid crystals.

We study the nonlinear permittivity of chiral liquid crystals in the smectic-A (Sm-A) phase near the ferroelectric smectic-C* (Sm-C*) phase and the smectic-C(*)(alpha) (Sm-C(*)(alpha)) phase theoretically and experimentally. The third-order nonlinear permittivity epsilon(3) shows the critical behavior with the exponent of four near the Sm-C* phase and its sign depends on the order of the phase transition. In the case of the Sm-A-Sm-C(*)(alpha) phase transition, the sign inversion of epsilon(3), presumably due to the large fluctuation of order parameter, is observed near the transition temperature.

Journal Article↗
PubMed2001

Electrophoretic microrheology in a dilute lamellar phase of a nonionic surfactant.

We measured the complex electrophoretic mobility mu(*)(omega) of nanometer-sized particles dispersed in a lyotropic lamellar phase, and observed two relaxation processes corresponding to the two characteristic lengths of lamellar structure. Faster relaxation is caused by the distortion field of lamellar phase induced by the colloidal particles, and slower relaxation is presumably due to the defects in lamellar structure. Since the dynamic transport property is strongly influenced by the microscopic circumstances as shown in this paper, this method is referred to as electrophoretic microrheology.

Journal Article↗
PubMed2001

Electro-optic response of a ferroelectric liquid crystal in thick free-standing films.

We study the electro-optic response of a ferroelectric liquid crystal in free-standing films as thick as the helical pitch. In the films thicker than about one pitch, two relaxation modes are observed in the frequency spectra. The relaxation frequency of the slower mode decreases when increasing the film thickness, while that of the faster mode, which appears at approximately 1 kHz, is almost independent of the film thickness. In thinner films, a single relaxation mode is observed at several hundred Hz. The obtained relaxation spectra are discussed in comparison to the theoretical spectra of the phase mode in a system of finite length along the helical axis calculated by Urbanc and Zeks [Phys. Rev. E 52, 3892 (1995)].

Journal Article↗
PubMed2000

Experimental study on skin sensitization potencies and cross-reactivities of hair-dye-related chemicals in guinea pigs.

In screening patch testing of hairdressers with occupational contact dermatitis, multiple positive reactions to hair dye-related chemicals, such as p-phenylenediamine (PPD), p-toluenediamine x 2HCl (PTD) and p-aminophenol (PAP), a fabric dye p-aminoazobenzene (PAB), and a tar dye Sudan III, were frequently encountered. To investigate individual skin sensitization potency and the cross-reactivities among above chemicals, a guinea pig maximization test with the above 5 chemicals was performed. In each group, 6 animals were induced with one of the chemicals at 0.1% concentration by intradermal injection and at 1.0% by topical application. The animals were challenged with all 5 chemicals in concentrations of dilution by 10 from 0.1% to 0.001%. Under the conditions of 0.1% challenges, similar sensitization potencies were observed in PPD (6/6), PTD (6/6), PAP (5/6) and PAB (6/6) groups, but no positive reactions were elicited in the Sudan III group. The cross-reactivities to PPD were confirmed in the animals challenged with PTD (6/6), PAP (6/6), PAB (6/6) and Sudan III (3/6). In the PTD-induced group, positive responses to cross-challenges were elicited by PPD (5/6), PAP (3/6), PAB (5/6) and Sudan III (1/6). The cross-reactivities to PAP were observed only with PPD (2/5) and PAB (5/5). PAB-induced animals responded only to PPD (1/6). The results indicate that all these chemicals except Sudan III are strong sensitizers. Their cross-reactivities are different in sensitized conditions, respectively. The cross-reactivities to PPD were higher than those to PTD, PAP and PAB.

Aminophenols↗
PubMed2000

4 cases of photocontact dermatitis due to ketoprofen.

We report 4 cases of photocontact dermatitis due to ketoprofen, a non-steroidal anti-inflammatory drug derived from propionic acid. We carried out a skin biopsy to examine the amount of ketoprofen in the eruptive skin. We investigated the cross-reactions between tiaprofenic acid, suprofen and ketoprofen by patch and photopatch testing. In case no. 1, 17 days after the discontinuance of Mohrus poultice (containing ketoprofen as an active ingredient), we detected ketoprofen 312.5 ng/g in the area of skin where the poultice was applied. All 4 cases reacted positively to the causative medicaments containing ketoprofen and ketoprofen 1% pet. 3 out of 4 cases reacted positively to tiaprofenic acid 1% pet. Only 1 case out of the ketoprofen and tiaprofenic acid positive cases reacted positively to suprofen 1% pet. Vehicles of patients' medicaments were negative in all 4 cases. We suspected that the key structure of the cross-reaction between ketoprofen and tiaprofenic acid and suprofen was the benzoyl radical.

Adult↗
PubMed2000

Results of patch testing with lavender oil in Japan.

We report the annual results of patch testing with lavender oil for a 9-year period from 1990 to 1998 in Japan. Using Finn Chambers and Scanpor tape, we performed 2-day closed patch testing with lavender oil 20% pet. on the upper back of each patient suspected of having cosmetic contact dermatitis. We compared the frequency of positive patch tests to lavender oil each year with those to other fragrances. We diagnosed contact allergy when patch test reactions were + or <+ at 1 day after removal. The positivity rate of lavender oil was 3.7% (0-13.9%) during the 9-year period from 1990 to 1998. The positivity rate of lavender oil increased suddenly in 1997. Recently, in Japan, there has been a trend for aromatherapy using lavender oil. With this trend, placing dried lavender flowers in pillows, drawers, cabinets, or rooms has become a new fashion. We asked patients who showed a positive reaction to lavender oil about their use of dried lavender flowers. We confirmed the use of dried lavender flowers in 5 cases out of 11 positive cases in 1997 and 8 out of 15 positive cases in 1998. We concluded that the increase in patch test positivity rates to lavender oil in 1997 and 1998 was due to the above fashion, rather than due to fragrances in cosmetic products.

Adolescent↗
PubMed2000

Generalizing the debye-Huckel equation in terms of density functional integral

We discuss the validity of generalized Debye-Huckel (GDH) equation proposed by Fisher et al. [B. P. Lee and M. E. Fisher, Phys. Rev. Lett. 76, 2906 (1996); Europhys. Lett. 39, 611 (1997); M. N. Tamashiro, Y. Levin, and M. C. Barbosa, Physica A 268, 24 (1999)], from the functional integral point of view. The GDH theory considers fluctuations around prescribed densities of positive and negative charges. Hence, we first formulate a density functional integral expression for the canonical system of Coulomb gas, and also demonstrate that this is a dual form to the sine-Gordon theory. Our formalism reveals the following: (i) The induced charge distribution around supposed density favors not only the cancellation of additional electrostatic potential like the original DH theory, but also the countervailing of chemical potential difference between imposed and equilibrium value. (ii) As a consequence apparent charge, absent in the GDH equation, comes out in our generalized equation. (iii) That is, the GDH equation holds only in special cases.

Journal Article↗
PubMed2000

Nonlinear dielectric relaxation spectroscopy of ferroelectric liquid crystals

The nonlinear dielectric relaxation spectra of ferroelectric liquid crystals (FLCs) have been studied in the chiral smectic-C phase. The linear and third-order nonlinear dielectric spectra show the relaxation corresponding to the fluctuation in the azimuthal angle of directors called the Goldstone mode. We calculated the nonlinear dielectric spectra of the Goldstone mode theoretically by the torque balance equation which describes the dynamics of FLCs under the electric field. The calculated spectra make good agreement with the measured ones. We also evaluated the material constants of FLCs from the best-fitted values of the linear and nonlinear dielectric increment and relaxation time.

Journal Article↗
PubMed1999

Field theoretical representation of the Hohenberg-Kohn free energy for fluids.

To go beyond Gaussian approximation to the Hohenberg-Kohn free energy playing the key role in the density functional theory (DFT), the density functional integral representation would be relevant, because the field theoretic approach to perturbative calculations becomes available. Then we first derive the associated Hamiltonian of the density functional, explicitly including the logarithmic entropy term, from the grand partition function expressed by configurational integrals. Moreover, two things are done so that the efficiency of the obtained form may be revealed: we demonstrate that this representation facilitates the field theoretic treatment of the perturbative calculation and, further, compare our perturbative formulation with that of the DFT.

Journal Article↗
PubMed1998

Fixed drug eruption due to amlexanox.

A 23-year-old woman developed allergic rhinitis in 1993. Her doctor prescribed for her Solfa (amlexanox 25 mg) and Lysozymen 90 (lysozyme chloride 90 mg) tablets. She took the tablets occasionally, whenever she developed allergic rhinitis. She noticed a macular erythema of about 3.5 cm wide on her buttocks in 1994, about 1 year after the initial prescription. We conducted a series of tests with the tablets. On patch testing, the patient had a positive reaction to Solfa 50% pet. on the eruptive area, but no such reaction on the non-eruptive area. Furthermore, on patch testing, she had no reaction to Lysozymen 90, 50% pet. on either the eruptive or the non-eruptive area. We also used open application test with Solfa 50% pet. to confirm the cause of her erythema.

Adult↗
PubMed1997

Immunosuppression by ultraviolet B rays via eyes in mice.

Irradiation by ultraviolet B (UV-B; 280-320 nm) initiates suppression of contact hypersensitivity. Immunosuppression was induced in C57BL/6N Crj mice by exposure of the dorsal skin or the eyes to a 10 kJ/m2 dose of UV-B radiation from 20SE sunlamps, followed by sensitization with 0.5% fluorescein isothiocyanate (FITC). The degree of immunosuppression induced by UV-B eye irradiation was equal to that induced by UV-B skin irradiation. When mice were irradiated with UV-B into the eyes after the optic nerve had been cut, systemic immunosuppression was not induced.

Animals↗