Biomedical subjects

N Nishihara

Publications and source records attributed to N Nishihara.

7 recordsLinked to original sources

PubMed2004

Productivity and fatigue.

UNLABELLED: In studying productivity, effects of environmental factors have focused only on performance. However, previous studies of the impact of the environment upon performance of mental tasks generally conclude that productivity research is somewhat confusing because the results are sometimes conflicting. In experiments, subjects may be highly motivated for a short time period, so it is very difficult to find differences in performance. In this paper, our research group used new methods to evaluate the factors affecting productivity. Not only task performance but also parameters of fatigue were investigated. Three subjective experiments using these evaluation methods to investigate the effect of productivity are summarized. PRACTICAL IMPLICATIONS: This paper introduces interesting new methods for evaluation of people's fatigue.

Adult↗

PubMed2001

Relation of acoustical parameters with and without audiences in concert halls and a simple method for simulating the occupied state.

Five acoustical parameters-reverberation time RT, early decay time EDT, clarity C80, strength G, and interaural cross-correlation coefficient IACC-were measured using identical procedures with and without audiences in six concert and opera halls. Reverberation times without audiences were measured in 15 additional halls using the same measuring techniques as for the six halls above, but for full occupancy the data were taken from musical stop chords at symphonic concerts. This paper shows that in all halls (1) the occupied RT can be predicted from the unoccupied RT using a linear regression equation, y = a - b exp(x), within acceptable limits, at low- and mid-frequencies. It is also shown for the six halls that (2) occupied C80's are predicted accurately from unoccupied values by the newly proposed equation; (3) G's with and without audiences are highly correlated by a first degree linear regression equation; and (4) IACCs have nearly the same value in both occupied and unoccupied halls. As a separate subject, the successful use of a cloth covering for seats in a concert or opera hall to simulate the occupied condition has been developed.

Acoustics↗

PubMed2001

Mechanism of sound absorption by seated audience in halls.

Four methods are explored for predicting the reverberation times in fully occupied halls for music as related to the sound absorption by their audiences. The methods for providing audience absorptions include two that use reverberation chambers, namely, the ISO 354 method (and other similar standards) (ISO) and Kath and Kuhl's method (K & K) [Acustica 15, 127-131 (1965)], and two that use average data from halls, i.e., Beranek's method (COH) [Concert and Opera Halls: How They Sound (Acoustical Society of America, Melville, NY, 1996)], and the average audience power-per-seat absorption which in practice is multiplied by the number of seats (AA). These methods are applied to the calculation of reverberation times in six existing halls, fully occupied, and the results were compared with actual measurements. The COH method was best for predictions over the entire frequency range. The K & K method showed the highest accuracy at mid-frequencies. Both the ISO and the K & K methods yielded wide differences for the measurements in the 125- and 250-Hz bands. The AA method was as good as the COH method when the measurements for the six halls were averaged, but showed a wide spread in the predictions around the average because it does not consider the degree of upholstering of the seats. It was hypothecated by the authors that the principal reasons for the ISO and K & K discrepancies at low frequencies were (a) differences between the degree of sound diffusion in actual halls and that in reverberation chambers, and (b) lack of information on the mechanisms of absorption of sound by people seated side-by-side in rows, particularly for near-grazing incidence sound fields. First, this article explores the sound diffusivity in a reverberation chamber and in the halls using CAD models. A probability density function of the incident angles of the sound rays that impinge on the audiences is defined and was measured for each case. Using a unique method, the sound absorption coefficient of each portion of the body and chair in a seated audience was determined in an anechoic chamber as a function of the incident angle of a sound wave. With adjustments from these findings, the K & K method can be made to equal the COH method in accuracy at all frequencies. Its forte is that it can be used for the determination of the sound absorption of occupied chairs from measurements of a limited number in a reverberation chamber.

Journal Article↗

PubMed2000

Flow cytometry as a strategy to study the endosymbiosis of algae in Paramecium bursaria.

BACKGROUND: The stable symbiotic association between Paramecium bursaria and algae is of interest to study such mechanisms in biology as recognition, specificity, infection, and regulation. The combination of algae-free strains of P. bursaria, which have been recently established by treating their stocks of green paramecia with herbicide paraquat (Hosoya et al.: Zool Sci 12: 807-810, 1995), with the cloned symbiotic algae isolated from P. bursaria (Nishihara et al.: Protoplasma 203: 91-99, 1998), provides an excellent clue to gain fundamental understanding of these phenomena. METHODS: Flow cytometry and light microscopy have been employed to characterize the algal cells after they have been released from the paramecia by ultrasonic treatment. Algal optical properties such as light scattering and endogenous chlorophyll fluorescence intensity have been monitored for symbiotic and free-living strains, and strains at stages of interaction with a host. RESULTS: Neither algal morphology nor chlorophyll content has been found to be altered by sonication of green paramecia. This fact allows to interpret in adequate degree changes in the optical properties of symbiont that just has been released from the association with a host (decreased forward light scatter and chlorophyll fluorescence signals). Optical characterization of both symbiotic and free-living algal strains with respect to their ability to establish symbioses with P. bursaria showed that chlorophyll content per cell volume seems to be a valuable factor for predicting a favorable symbiotic relationship between P. bursaria and algae. CONCLUSIONS: Flow cytometry combined with algae-free paramecia and cloned symbiotic algae identifies algal populations that may be recognized by host cells for the establishment of symbioses.

Animals↗

PubMed2000

Acoustical design of the Tokyo Opera City (TOC) concert hall, Japan

The Tokyo Opera City concert hall seats 1632, volume 15 300 m3, and reverberation time, with audience and orchestra, 1.95 s. As part of the design process, measurements on CAD computer and 1:10 wooden models of the hall and full-sized materials samples were conducted over a 5-yr. period. The hall in plan is rectangular. The ceiling is a distorted pyramid, with its peak 28 m above the main floor and nearer the stage than the rear of the hall. This unique shape was analyzed on the models so that all interior surfaces combine to distribute sources on the stage uniformly over the seating areas and to yield optimum values for reverberation time (RT), early decay time (EDT), interaural cross-correlation coefficient (IACCE3), bass ratio (BR), initial-time-delay gap (ITDG), strength (G), and sound diffusion index (SDI) [for definitions see L. Beranek, Concert and Opera Halls: How They Sound (Acoustical Society of America, Woodbury, NY, 1996)]. On the long ceiling facing the stage, Schroeder QRD diffusers provide diffusion, eliminate a possible echo, and strengthen lateral reflections. Performers and critics judge the acoustics excellent.

Journal Article↗

PubMed1999

Microtubule-dependent movement of symbiotic algae and granules in Paramecium bursaria.

Paramecia demonstrate rotational cytoplasmic streaming, in which some cytoplasmic granules and organelles, including symbiotic algae, flow in a constant direction. To elucidate the mechanism of this streaming, we examined the effects of cytochalasins (cytochalasin B and D, and dihydrocytochalasin B) and nocodazole, which are reagents affecting microfilament and microtubule networks, respectively, in the cell. In previous reports, paramecia have been compressed with a coverslip to facilitate observation of cytoplasmic streaming. Here we found that the cytoplasmic streaming of paramecia was suppressed by such compression and then observed the process without compression in this work. In the presence of cytochalasins, cytoplasmic streaming was not affected. In contrast, treatment with nocodazole (10 microg/ml) resulted in discontinuation of cytoplasmic streaming in paramecia. Immunofluorescent microscopic observations by confocal microscopy revealed that the number of intracellular microtubules in nocodazole-treated cells was markedly decreased compared to that of controls. Electron microscopic observations confirmed the decrease. These results suggest that cytoplasmic microtubules play an important role in the cytoplasmic streaming of paramecia.

Animals↗

PubMed1984

Surgical treatment of cervical spondylotic myelopathy complicating athetoid cerebral palsy.

Operative treatment was performed in nine patients with cervical spondylotic myelopathy complicating athetoid cerebral palsy. The first two patients were treated by laminectomy, and the other seven by anterior interbody fusion. The symptoms in both the laminectomy patients improved after operation, but became worse again when cervical instability developed; they then had to have an anterior fusion in addition. In six of the seven patients who had primary anterior fusion a halo-cast (or a halo-vest) was used to keep the cervical spine immobile, and good bony fusion was obtained with satisfactory results. However, in one patient no halo apparatus was used, bony union did not occur and the radiculopathy reappeared. In cervical myelopathy complicating athetoid cerebral palsy laminectomy is contra-indicated; anterior fusion combined with a halo apparatus is, however, satisfactory.

Adult↗