Not so presto? Outcomes of sluggish prestin in outer hair cells

Prestin (SLC26A5), a protein essential for the sensitivity of the mammalian ear, was so named from \emph{presto}. The assumption was that this membrane protein supports fast movement of outer hair cells (OHCs) that matches the mammalian hearing range, up to 20 kHz in general and beyond, depending on the species. \emph{In vitro} data from isolated OHCs appeared to be consistent with such frequencies. However, some recent reports cast doubts on this assumption, suggesting that the intrinsic transition rates of this protein are much lower, about 3 kHz for guinea pigs, not covering the auditory frequency range of the animal. Recent \emph{in vivo} data also show that the amplitude of OHC motion rolls off well below the best frequency of the location. The present report examines whether or not these resent observations are compatible with the physiological function of OHCs by using simple piezoelectric models.Comment: 12 pages, 3 figures, to be presented at Mechanics of Hearing Workshop at Helsing{\o}r, Denmar

How Close Should the Outer Hair Cell RC Roll-Off Frequency Be to the Characteristic Frequency?

AbstractRecent experiments have shown a much larger conductance in outer hair cells, the central components of the mammalian cochlear amplifier. The report used only the cell's linear capacitance, which together with increased conductance, raised the cell's RC corner frequency so that voltage-dependent motility was better able to amplify high-frequency sounds. We construct transfer functions for a simple model of a high characteristic frequency (CF) local cochlear resonance. These show that voltage roll-off does not occur above the RC corner. Instead, it is countered by high-pass filtering that is intrinsic to the mammal's electromechanical resonance. Thus, the RC corner of a short outer hair cell used for high-frequency amplification does not have to be close to the CF, but depending on the drag, raised only above 0.1 CF. This high-pass filter, built in to the mammalian amplifier, allows for sharp frequency selectivity at very high CF

Clicktivism Sebagai Dramaturgi Di Media Sosial

Media sosial adalah salah satu medium online yang paling banyak digunakan saat ini dengan angka pengguna yang terus meningkat dari tahun ke tahun. Media sosial dipercaya telah membawa bentuk baru dalam dunia komunikasi, termasuk sosiologi komunikasi. Di Indonesia dan beberapa negara lainnya, penggunaan media sosial dalam sebuah aktivisme telah menjadi hal yang lumrah. Aktivisme suatu gerakan sosial menggunakan fitur-fitur yang terdapat dalam media sosial untuk mencari anggota/relawan dan mendukung penyebaran awareness dari gerakan agar menyebar luas (viral). Dengan tujuan tersebut, aktivisme dalam suatu gerakan sosial rentan berubah menjadi clicktivism, yaitu kemauan untuk menunjukkan kepedulian dari suatu gerakan sosial melalui aktivitas di dunia maya (click), tetapi tidak diimbangi dengan pengorbanan yang berarti (action) dalam membuat suatu Perubahan sosial di dunia nyata. Banyaknya clicktivism yang terjadi di media sosial seakan memberi peluang bagi pelaku (clicktivist) untuk memanfaatkan aktivitas tersebut sebagai upaya unjuk diri, seperti yang dijelaskan dalam konsep dramaturgi oleh Erving Goffman (1959). Penelitian bertujuan untuk mengetahui makna dan gagasan-gagasan clicktivist yang menjadikan clicktivism sebagai dramaturgi di media sosial. Penelitian ini menggunakan model penelitian deskriptif kualitatif dengan menggunakan metode analisis semiotika oleh Roland Barthes (1957). Teknik pengumpulan data dilakukan dengan studi dokumentasi, yaitu dengan mengumpulkan beberapa post di media sosial tentang gerakan Ice Bucket Challenge pada Agustus 2014. Data kemudian diinterpretasi menggunakan konsep analisis mitos dalam studi semiotika Barthes. Hasil penelitian menunjukkan bahwa clicktivist menggunakan aksi dalam gerakan Ice Bucket Challenge sebagai upaya untuk menampilkan diri, seperti yang dijelaskan Goffman dalam konsep dramaturgi. Clicktivist menggunakan front stage untuk mempercantik tampilan dirinya melalui aksi yang dilakukan, atau pakaian dan atribut yang dikenakan. Clicktivist juga menggunakan impression management agar dipersepsikan secara positif oleh penonton sesuai dengan gambaran/image ideal dirinya. Impression management ditunjukkan melalui pakaian/atribut yang dikenakan, juga dari dialog dan gesture yang ditampilkan clicktivist. Sedangkan back stage merupakan fakta-fakta yang terdapat dalam aksi Ice Bucket Challenge yang dilakukan clicktivist. Fakta ini seringkali tidak sesuai dengan apa yang diungkapkan clicktivist pada front stage-ny

Self-similar solution of a nonsteady problem of nonisothermal vapour condensation on a droplet growing in diffusion regime

This paper presents a mathematically exact self-similar solution to the joint nonsteady problems of vapour diffusion towards a droplet growing in a vapour-gas medium and of removal of heat released by a droplet into a vapour-gas medium during vapour condensation. An equation for the temperature of the droplet is obtained; and it is only at that temperature that the self-similar solution exists. This equation requires the constancy of the droplet temperature and even defines it unambiguously throughout the whole period of the droplet growth. In the case of strong display of heat effects, when the droplet growth rate decreases significantly, the equation for the temperature of the droplet is solved analytically. It is shown that the obtained temperature fully coincides with the one that settles in the droplet simultaneously with the settlement of its diffusion regime of growth. At the obtained temperature of the droplet the interrelated nonsteady vapour concentration and temperature profiles of the vapour-gas medium around the droplet are expressed in terms of initial (prior to the nucleation of the droplet) parameters of the vapour-gas medium. The same parameters are used to formulate the law in accordance with which the droplet is growing in diffusion regime, and also to define the time that passes after the nucleation of the droplet till the settlement of diffusion regime of droplet growth, when the squared radius of the droplet becomes proportionate to time. For the sake of completeness the case of weak display of heat effects is been studied.Comment: 12 pages, 4 figure

Heterogeneous condensation in dense media

The theoretical description of the heterogeneous nucleation kinetics is presented. This description takes into account the perturbation of the vapor phase initiated by the growing droplets. The form of the density profile around the growing droplet is analyzed which leads to some special approximations. Then the process of nucleation in the whole system is described. As the result all main characteristics of the process are determined analytically.Comment: 50 pages, LATE