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High sensitivity biomimetic accelerometer model using amplifying mechanism of stereocilia
No full textA biomimetic mechanical model of the negative stiffness and adaptation mechanism of stereocilia bundle
No full text
High sensitivity biomimetic accelerometer model using amplifying mechanism of stereocilia
No full textA mechanical mimicry of the negative stiffness and adaptation mechanism of stereocilia bundle.
No full textStereocilia is a mechanotransducer that change external mechanical stimuli into electrical signal and has high sensitivity over a broad dynamic range, which is design conflict of the conventional inertia sensor and accelerometer. The mechanism of the retained high sensitivity was hypothesized as an interplay between the negative stiffness and adaptation. The adaptation shifts the nonlinear high sensitivity region toward the operation region of the stereocilia bundle. In this study, we developed a biomimetic mechanical model of stereocilia to demonstrate the interplay between the negative stiffness and the adaptation mechanism. The model consists of an inverted pendulum supported by pivot spring and a fixed bar which represent a pair of adjacent stereocilia. The magnet pairs are attached to pendulum and fixed bar each other to emulate ion channel’s gating force. The magnet on the fixed bar connected to a stepping motor to move the magnet side-to-side which demonstrate readjustment of tip-link tension by slipping down and climbing up of adaptation molecular motors of stereocilia. A displacement clamping equipment which consists of a uniaxial force sensor and actuator was used to measure the mechanical stiffness of the model. Experimental data from mechanical model showed the negative stiffness region near the equilibrium position and shifted the high sensitivity region with the progress of adaptation. Spontaneous oscillation which produced by the interplay between negative stiffness and adaptation mechanism also observed. The results demonstrate that the negative stiffness and adaptation mechanism was mechanically produced by the combination of repulsive force and its continuous readjustment. The change of model parameters of biomimetic mechanical system such as spring stiffness, magnetic force, and adaptation motor speed provided us better understanding of nature’s inertia sensing mechanism
Mechanical modelling of vestibular hair cell’s amplifying mechanism.
No full textINTRODUCTION: Vestibular hair cell is the basic sensory unit of nature’s inertia sensor. It has high sensitivity over broad dynamic range by combination of negative stiffness and adaptation mechanism.[1][2] To examine these biophysical mechanisms with a mechanical point of view[3], we developed a mechanical model of vestibular hair cell. We measure the system response and stiffness and observe similar characteristics with hair cell. This results help to better understanding of vestibular hair cell function.
METHODS: A mechanical model of stereocilia on hair cell consists of two inverted pendulums that demonstrate a pair of adjacent stereocilia. To make negative stiffness which induced by a transduction channels’ sudden opening, use pair of magnet which make repulsive force. Adaptation mechanism is mimicked by using stepping motor similar with molecular motor on stereocilia. Stiffness and temporal response was measured using force sensor and motion capture system.
RESULTS: Similar results from physiological stereocilia were observed. Negative stiffness region was observed near the origin and this region was shifted as motor made magnet moving side-to-side. And the spontaneous oscillation which known to induced by the interplay of the negative stiffness and the adaptation of the stereocilia also observed. Parameter study of the model well demonstrated the role of each system component.
CONCLUSIONS: Integration of adaptation and negative stiffness mechanism of hair cell was mechanically mimicked by two inverted pendulums and interacting moving magnet pair controlled by stepping motor and results is similar to the physiological measurement.
ACKNOWLEDGEMENTS: The work was supported by the Pioneer Research Program fund of the
Ministry of Education, Science and Technology.
Fig.1 Mechanical model of hair cell and force-displacement relation & time response of vestibular hair cell model.
REFERENCES
1. P.Martin. et al. PNAS. Vol.97, No.22, pp.12026-12031. 2000.
2. Peter G. Gillespie & Richard G. Walker. NATURE, Vol.413, 13. 2001.
3. Koeun Lim, Sukyung Park. Journal of Biomechanics. 42, 2158-2164. 2009
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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