Biomedical subjects

Y Masumoto

Publications and source records attributed to Y Masumoto.

At least 19 recordsLinked to original sources

PubMed2005

Direct observation of the electron spin relaxation induced by nuclei in quantum dots.

We have studied the electron spin relaxation in semiconductor InAs/GaAs quantum dots by time-resolved optical spectroscopy. The average spin polarization of the electrons in an ensemble of p-doped quantum dots decays down to 1/3 of its initial value with a characteristic time T(Delta) approximately 500 ps, which is attributed to the hyperfine interaction with randomly oriented nuclear spins. We show that this efficient electron spin relaxation mechanism can be suppressed by an external magnetic field as small as 100 mT.

Journal Article↗

PubMed2001

Fluorescence intermittency in self-assembled InP quantum dots.

Fluorescence intermittency in InP self-assembled dots is investigated by means of far field imaging and single dot spectroscopy. Based on our observation that blinking dots are found in the vicinity of scratches and the blinking frequency is drastically enhanced under a near-infrared laser irradiation, we attribute the origin of the fluorescence intermittency to a local electric field due to a carrier trapped at a deep localized center in the Ga0.5In0.5P matrix. The validity of this explanation is confirmed by a thermal activation-type behavior of the switching rate and artificial reproduction of the blinking phenomenon by an external electric field.

Journal Article↗

PubMed2001

[Effects of carbocisteine on airway inflammation and related events in SO2-exposed rats].

Airway inflammation leads to secretion of abnormal mucous glycoprotein and ciliary injury. To investigate the possible usefulness of carbocisteine against airway inflammation and events related to it, we conducted a study in SO2-exposed rats of the effects of carbocisteine and ambroxol, as an active control drug, on components of mucous glycoprotein (fucose, sialic acid and protein) in bronchoalveolar lavage fluid (BALF); on infiltration and activation of inflammatory cells in BALF; on tracheal and bronchial-ciliary lesions; and on cAMP levels in tracheal and alveolar tissues. Carbocisteine inhibited or improved all SO2-induced changes tested, and dosages of 125 and 250 mg/kg b.i.d. reduced fucose, sialic acid and protein contents, inflammatory cells (as markers of inflammation), free radicals, and elastase activity in BALF, and suppressed the development of ciliary lesions of the tracheal and bronchial mucosa, while ambroxol (10 mg/kg b.i.d.) showed no such effects. In addition, carbocisteine improved cAMP levels in the tracheal and alveolar tissues. These results indicate that carbocisteine is able to prevent the development of inflammation-related respiratory disease in this rat model, and that this remission of airway inflammation may be associated with carbocisteine-induced normalization of cAMP levels in tracheal and alveolar tissues as well as with its mucoregulant and anti-inflammatory effects. In conclusion, carbocisteine has a unique mucoregulant action and inhibits SO2-induced airway inflammation in a manner different from that of ambroxol.

Ambroxol↗

PubMed2000

Effect on electroencephalogram of chewing flavored gum.

The objective of the present study was to evaluate the effect on the electroencephalogram (EEG) of a chewing gum with and without our prepared new flavor. Electroencephalograms were obtained after the following three tests: chewing pure gumbase with sucrose (standard gumbase), chewing flavored standard gum and the inhalation of flavored aromatic oil. As the control, we used the pre-stimulus control EEG record without a stimulus. We examined the relationship between the pre-stimulus control record and the post-stimulus record using the changes of power in four bands. Chewing the standard gumbase led to an increase in the alpha wave and a decrease in the beta wave. Chewing the flavored standard gum and inhaling the flavored aromatic oil each increased the alpha and beta waves. In addition, chewing the flavored standard gum led to a change in the ratio of theta wave in the frontal area. The difference in the theta, alpha and beta bands in chewing gum with and without the added flavor suggested that the flavor as well as chewing could induce concentration with a harmonious high arousal state in brain function.

Adult↗

PubMed1999

Effects of three principal constituents in chewing gum on electroencephalographic activity.

The effects of three principal constituents (sugar, spearmint, and gumbase) in chewing gum on EEG findings in 20 normal subjects were investigated. After they chewed the gumbase, theta activity decreased significantly at Fp2, O1, T3, T4, F4, P3, and Pz; alpha activity increased significantly at O1 and decreased significantly at Fpl, and beta activity increased significantly at Fpl, Fp2, O1, T3, T4, P3 and Pz. After they inhaled the spearmint, alpha activity decreased significantly at 02, F3, P4, and Fz, and beta increased significantly at 02, F3, P4, and Fz. The mean frequency of the alpha band was significantly higher than after 1 min at rest without inhalation. After the subjects chewed the gumbase with sucrose, theta activity increased at Fp2 and Fz; alpha activity increased significantly at T3; and beta activity decreased significantly at Fpl, Fp2, F4, P3, P4, Fz, and Pz. The mean frequency of the alpha band was significantly lower than after 1 min at rest without it at almost all the positions. These results suggest that the gumbase with sucrose induced relaxed concentration effects while inhalation of spearmint induced arousal effects. The chewing of gumbase showed arousal tendency.

Adult↗

PubMed1998

Examination of the diagnostic value and estimation of the chaos phenomenon in masticatory movement using fractal dimension in patients with temporomandibular dysfunction syndrome.

The aim of this study was to estimate the chaos phenomenon (chaos) in masticatory movements using the fractal dimension (FD), and to examine the diagnostic value of the fractal dimension in comparing stomatognathic functional disturbances with normal stomatognathic function. The subjects were all high school students and included nine subjects presenting with acceptable normal occlusion, 18 subjects with TMJ dysfunction syndrome and seven subjects with tooth crowding. Masticatory movements were obtained during free, right side, and left side gum-chewing and were used to calculate the capacity dimension in the FD. Chaos in the masticatory movement was estimated by the FD saturated with some constant value to an increase of embedding dimension (approached a plateau). In the crowding group, the FD was also significantly high on the sagittal plane in comparison with the normal. In the patients with pain, the FD on the sagittal plane was significantly high. In the patients with pain and closed lock, the FD on the frontal plane was significantly high. However, in the patients with pain and with reduction of anterior disc displacement, the FD was significantly low on the horizontal plane. These findings suggest that chaos is present in masticatory movements and the difference in the FD are of diagnostic value in evaluation of the relationship between FD and stomatognathic functional disturbance.

Adolescent↗

PubMed1998

Spectral analysis of changes in electroencephalographic activity after the chewing of gum.

The present study aimed to examine the psychosomatic effect in the chewing of marketed gum using electroencephalogram (EEG) as an index. The EEG were taken in two sets: (i) a resting period before chewing (control recording) and a resting record (post-resting recording) for examining reproducibility; and (ii) a control recording and resting period after gum-chewing for 3 min (post-chewing recording). The ratio of each frequency band to the total frequency power, the mean frequency of the alpha band and laterality of the frequency power was calculated. In the examination of the reproducibility, no statistically significant differences were observed between control recording and post-resting recording in all indices. In the reflection of EEG after gum-chewing, there were no significant differences between control recording and the post-chewing recording. However, a significant interaction was observed among these indices by analysis of variance. In addition, the alpha power in the post-chewing recording was significantly higher than that in the control recording at almost all the positions. In conclusion, the intra-individual reproducibility of EEG was confirmed in the recording method. Furthermore, it was suggested that a significant interaction and a rising trend of the mean frequency of the alpha band after gum-chewing reflected 'arousal' psychosomatic responses by the chewing of marketed gum.

Adult↗

PubMed1996