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

Effects of applied pressure on hot-pressing of Beta-SiC

The effects of applied pressure on the densification during hot pressing of beta-SiC compacts were investigated. Beta-SiC powder is Starck made and has the average particle size of about 0.7 micrometer. Hot pressing experiments were carried out in graphite dies at temperatures of 1700 deg to 2300 deg C and at the pressures up to 1000 kg/sq cm. The compacts containing 1 weight percent B4C were examined. Sintered compacts were examined for microstructure and the Rockwell A-scale hardness was measured. The B4C addition was very effective to mitigate the hot pressing conditions. It is found that densification goes with the strengthening of the bonding and does not occur in particle deformation due to concentrated stress

Diffraction from Ordered States of Higher Multipoles

Possible ways of identification are discussed of an electronic order of higher multipoles such as octupoles and hexadecapoles. A particularly powerful method is resonant X-ray scattering (RXS) using quadrupolar resonance processes called E2.The characteristic azimuthal angle dependence of Ce$_{0.7}$La$_{0.3}$B$_6$ is interpreted as evidence of antiferro-octupole order. For PrRu$_4$P$_{12}$, eightfold pattern against azimuthal angle is predicted if its metal-insulator transition is a consequence of a hexadecapole order. In non-resonant superlattice Bragg scattering, hexadecapole contribution may also be identified because of absence of quadrupole component.Comment: Invited paper to be published in Proc. Hiroshima Workshop on Novel Functional Materials with Multinary Freedoms (Physica B, 2006

Role of p-f Hybridization in the Metal-Non-Metal Transition of PrRu4P12

Electronic state evolution in the metal-non-metal transition of PrRu4P12 has been studied by X-ray and polarized neutron diffraction experiments. It has been revealed that, in the low-temperature non-metallic phase, two inequivalent crystal-field (CF) schemes of Pr3+ 4f^2 electrons with Gamma_1 and Gamma_4^(2) ground states are located at Pr1 and Pr2 sites forming the bcc unit cell surrounded by the smaller and larger cubic Ru-ion sublattices, respectively. This modulated electronic state can be explained by the p-f hybridization mechanism taking two intermediate states of 4f^1 and 4f^3. The p-f hybridization effect plays an important role for the electronic energy gain in the metal-non-metal transition originated from the Fermi surface nesting.Comment: 5 pages, 5 figures. Accepted by J. Phys. Soc. Jp