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220 results on '"Kokubun T"'

12. Skill-level based examination of forearm muscle activation associated with efficient wrist and finger movements during typing

Author

Akira Kobayashi, Kanemura N, Kokubun T, Ito T, Y. Matsumoto, Yoshida M, and Funakoshi H

Subjects
medicine.medical_specialty, medicine.diagnostic_test, business.industry, Index finger, Electromyography, Kinematics, Wrist, Motion capture, body regions, medicine.anatomical_structure, Physical medicine and rehabilitation, Forearm, medicine, Finger joint, Typing, business
Abstract

Background Musculoskeletal disorders caused by computer use are associated with socio-economic problems. Reducing the biomechanical loading caused by hand movements could reduce the occurrence of such disorders. However, most participants recruited for past experimental studies had a certain level of typing skill, and differences in the biomechanical loading of those with different typing skills have not been examined. This study aimed to quantify the relationship between the movements of the wrist and finger joints and the loading on the forearm muscles and to clarify the differences between typists of different skill levels. Methods A 3D motion capture system measured wrist and index finger joint movements, and surface electromyography measured muscle activities for the right hand during a typing task. We compared wrist and finger joint movements and forearm muscle loading during typing, keystroke time, and key release time between skilled and unskilled typists. Findings Skilled typists move their wrists and fingers faster with less muscle activity during typing, the active tension of their finger flexor muscles during keystrokes are high, and they have higher mechanical stresses on the finger flexor tendons during keystrokes. Unskilled typists develop strategies to prevent excessive stiffness in their wrist joints when making keystrokes. They are expected to have a higher cumulative loading on the extensor muscles of the wrist during key release. Interpretation Biomechanical loading in typing skill is different, which may make it possible to predict disability. This could provide information on the changes in physical parameters and environments to prevent disability.

Published
2021

32. Quantifying the metabolic cost to an Antarctic liverwort of responding to an abrupt increase in UVB radiation exposure

Author

Snell, Katherine R.S., Kokubun, T., Griffiths, H., Convey, Peter, Hodgson, Dominic, Newsham, Kevin K., Snell, Katherine R.S., Kokubun, T., Griffiths, H., Convey, Peter, Hodgson, Dominic, and Newsham, Kevin K.

Abstract

We quantified the metabolic cost to the Antarctic leafy liverwort Cephaloziella varians of responding to an abrupt increase in ultraviolet B (UVB) radiation exposure in the natural environment at Rothera Point on the western Antarctic Peninsula (67 degrees 34'S, 68 degrees 07'W). The liverwort was protected from exposure to UVB radiation for 44 days with screens containing Mylar polyester, after which time its thalli, which are normally black in colour, had become green owing to reduced concentrations of an anthocyanidin, identified here as riccionidin A, in thallus tips. Thalli were then exposed to an abrupt increase in UVB radiation by removing the screens. The thalli became visibly darker within 48 h of the screens being removed, resynthesizing riccionidin A to the same concentration as that present in thalli outside screens during this period. Chlorophyll fluorescence measurements indicated that nonphotochemical quenching was higher in the thalli formerly under the screens than in those not previously covered with screens, but that F-v/F-m and photochemical quenching were the same in the two groups of thalli. We used data from aqueous phase oxygen electrode measurements to calculate an estimate for carbon fixation by C. varians during the 48 h after the screens were removed. Assuming a photosynthetic quotient for Antarctic bryophytes of 1, these analyses indicated that the minimum weight of carbon used to synthesize riccionidin A was equivalent to 1.85% of the carbon fixed by thalli during the 48 h after the abrupt increase in UVB radiation exposure.

Published
2009

33. Taxonomy of Calicium victorianum (F. Wilson) Tibell (Caliciaceae, Lecanorales), a lichenized ascomycete new to Europe

Author

Aguirre-Hudson, B., Kokubun, T., Spooner, B., Tibell, Leif, Aguirre-Hudson, B., Kokubun, T., Spooner, B., and Tibell, Leif

Abstract

The morphological features and chemical compounds found in the first European collection of Calicium victorianum are compared with type material from Australia of C. piperatum F. Wilson. The phylogenetic relationships of the species are discussed by comparing its nuclear rDNA ITS 1-5.8S-ITS2 with that of other species of Calicium.

Published
2007
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