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Biomedical subjects

K Ohgushi

Publications and source records attributed to K Ohgushi.

12 recordsLinked to original sources
PubMed2005

Anomalous magnetic properties near the spin-flop bicritical point in Mn(2)AS(4) (A = Si and Ge).

The magnetic properties of the single crystalline Mn(2)AS(4) (A = Si and Ge) with an olivine structure, which are the uniaxially anisotropic antiferromagnets (the b axis as an easy axis), were investigated. Near the Néel temperature, both compounds exhibit the contrastive magnetic responses along the c axis, namely, the spontaneous weak ferromagnetism in A = Si and the significant enhancement of the differential susceptibility (dM/dH) under the small magnetic field in A = Ge. When A = Ge, we also observed the evolution of dM/dH along the axis at low temperatures. We discuss these phenomena on the basis of the magnetic field-temperature (H-T) phase diagram with the spin-flop bicritical point (H(BP), T(BP). The role of the thermal or quantum fluctuation was stressed.

Journal Article↗
PubMed2005

General features of photoinduced spin dynamics in ferromagnetic and ferrimagnetic compounds.

Ultrafast photoinduced spin dynamics has been investigated by time-resolved magneto-optical Kerr spectroscopy for various ferromagnetic and ferrimagnetic compounds: FeCr2S4, CoCr2S4, CuCr2Se4, CdCr2Se4, La0.6Sr0.4MnO3, and SrRuO3. The temporal demagnetization process, which is observed commonly for all the compounds, essentially consists of two components: One is an instantaneous change which originates perhaps from multiple emissions of magnetic excitations during nonradiative decay of photoexcited carriers, and the other is a delayed response due to thermalization of the spin system. The time constant of the delayed change depends strongly on materials and is scaled with the magnetocrystalline anisotropy, indicating that spin-orbit coupling is a dominant interaction for this process.

Journal Article↗
PubMed1993

Audibility of partials in inharmonic complex tones.

These experiments examined the ability of musically trained subjects to hear out individual partials in complex tones with partials uniformly spaced on a scale related to the equivalent rectangular bandwidth (ERB) of the auditory filter. ERB spacings of 0.75, 1.0, 1.25, 1.5, and 2 were used, and the central component always had a frequency of 1000 Hz. All components had a level of 65 dB SPL. On each trial, subjects heard a pure tone (the "probe") followed by a complex tone. The probe was close in frequency to one of the partials in the complex, but was mistuned downward by 4.5% on half the trials (at random) and mistuned upward by 4.5% on the other half. The task of the subject was to indicate whether the probe was higher or lower in frequency than the nearest partial in the complex. The partial that was "probed" varied randomly from trial to trial. Scores for the highest and lowest components in the complexes were generally high (> 90%) for component spacings greater than 1 ERB, but worsened somewhat for ERB spacings of 0.75 and 1.0. Scores for the inner components were close to chance level at 0.75-ERB spacing, and improved progressively as the ERB spacing was increased from 1 to 2 ERBs. For ERB spacings of 1.25 or less, the scores did not change smoothly with component frequency; marked irregularities were observed, as well as systematic errors. An explanation for these is suggested in terms of irregularities in the middle ear transfer function. Performance for the inner components tended to be worse for component frequencies above 1000 Hz than below 1000 Hz. It is suggested that this happens because the pitches of partials are partly coded in the time patterns of neural impulses (phase locking), and the precision of phase locking deteriorates progressively with increasing frequency above 1000 Hz. The auditory filter shapes of the subjects were measured for a center frequency of 1000 Hz, using the notched noise method. One subject had a broader auditory filter than the other three subjects, and this same subject generally had more difficulty in hearing out partials from complex tones than the other subjects.

Acoustic Stimulation↗
PubMed1991

[Hairy cell leukemia expressing SIgM+, SIgG-, CD11b+ and CD21+ and accompanying lymphadenopathy without splenomegaly].

Hairy cell leukemia (HCL) expressing both surface monocytoid antigen and IgM (kappa) was reported. A 62-year-old male was admitted to our hospital in September 21, 1989 because of leukocytosis. Physical examinations showed axillary and inguinal lymphadenopathy but no hepato-splenomegaly. The leukocyte count was 12,600/microliters with 73% of abnormal cells like large lymphocytes which had abundant cytoplasm and hairy appearance under phase microscopy. They had ruffles with microvilli under electron microscope. Bone marrow puncture showed normocellular marrow with 71.2% of abnormal cells similar to the peripheral blood. Surface markers were CD11b+, CD21+, HLA-DR+, Tac- and IgM (kappa). They were positive for ++acid phosphatase staining, but negative for peroxidase and tartrate-resistant acid phosphatase staining. He was diagnosed as Japanese type HCL. HCL expressing both surface monocytoid antigen and IgM is rare and the clinical features of our case are compared with those reported in Japan.

Antigens, Differentiation, B-Lymphocyte↗
PubMed1987

Perceptual components of pitch: spatial representation using a multidimensional scaling technique.

Paired comparison experiments were carried out on the pitch of 18 computer-generated complex tones synthesized by slight modification of the frequency structure of Shepard's endless scale sounds. The results were analyzed by a multidimensional scaling technique, and simple helixes were obtained in which two components of pitch (tone height and tone chroma) were represented. Some individual differences in perception of pitch were observed according to the weight that the subject gives to each component.

Humans↗
PubMed1983

The relationship between the cross-correlation coefficient of two-channel acoustic signals and sound image quality.

In order to investigate sound image quality, white and bandlimited noises with various cross-correlation coefficients are reproduced from two loudspeakers placed in anechoic or echoic chambers. Subjects are asked to make similarity judgments and some subjective evaluations of pairs of the noises. The experimental data are analyzed by Kruskal's multidimensional scaling (MDS) program. The analysis of the experimental data shows the following: (1) sound image quality depends mostly on the width and the distance of the sound image, (2) the width of the sound image depends on the absolute value of the cross-correlation coefficient, (3) the distance of the sound image depends on the cross-correlation coefficient itself, (4) with respect to physical and psychological factors governing sound image quality, there is no fundamental difference between anechoic and echoic chambers.

Acoustic Stimulation↗
PubMed1978

On the role of spatial and temporal cues in the perception of the pitch of complex tones.

This paper describes a new approach to pitch perception. It focuses attention on the slight difference between the pitch of complex tone and the pitch of a pure tone with the same (fundamental) frequency. This approach is based on the assumption that pitch perception is based on both spatial and temporal cue analysis. In this study, the values provided by the temporal cue are calculated from physiological data from the auditory nerve fibers. The possible ratios of the pitch of complex tones relative to the pitch of pure tones at various frequencies are predicted. Psychophysical experimental results strongly support this prediction. In addition, another experiment suggests that the above psychophysical effect is not based upon a mutual masking effect in the spatial domain.

Cues↗
PubMed1978

Directional sensitivity in cat of collicular auditory neurons to FM sound.

Directional sensitivity for FM sound was compared between two types of FM sound, a linear FM and a "Step" FM digitally synthesized to contain 28 steady short tones with half-overlap in time between every successive pair, simulating the formant transitions of speech. There seemed to be no difference in the response of the cat collicular neuron in directionality of the units for ascending vs descending frequencies. As far as we have examined, no FM-sensitive neurons were observed which were specifically responsive to particular FM components in a stimulus.

Acoustic Stimulation↗
PubMed1977

Collagen biochemistry of the two layers of carious dentin.

The amino acid composition and intermolecular cross links of collagen fibers in the two layers of carious dentin, differentiated by a 0.5% basic fuchsin-propylene glycol-stain, were biochemically investigated. No difference in the pattern of amino acid composition of collagen fibers was found between the first and second layers of carious dentin and the sound dentin. However, obvious differences in the intermolecular cross links of collagen fibers were found between the three layers. Namely, compared with the sound dentin, the second layer of carious dentin had decreased cross links and increased precursors. This change is considered to be reversible. Contrastingly, in the first layer, both the cross links and the precursors remarkably decreased. In addition, the hexitollysines (protein-saccharide compounds probably related to bacterial metabolism) were found and several peaks of unknown materials appeared. This indicates irreversible destruction of cross-linkage in the first layer of carious dentin.

Amino Acids↗