A lithium superionic conductor.

Batteries are a key technology in modern society. They are used to power electric and hybrid electric vehicles and to store wind and solar energy in smart grids. Electrochemical devices with high energy and power densities can currently be powered only by batteries with organic liquid electrolytes. However, such batteries require relatively stringent safety precautions, making large-scale systems very complicated and expensive. The application of solid electrolytes is currently limited because they attain practically useful conductivities (10(-2) S cm(-1)) only at 50-80 °C, which is one order of magnitude lower than those of organic liquid electrolytes. Here, we report a lithium superionic conductor, Li(10)GeP(2)S(12) that has a new three-dimensional framework structure. It exhibits an extremely high lithium ionic conductivity of 12 mS cm(-1) at room temperature. This represents the highest conductivity achieved in a solid electrolyte, exceeding even those of liquid organic electrolytes. This new solid-state battery electrolyte has many advantages in terms of device fabrication (facile shaping, patterning and integration), stability (non-volatile), safety (non-explosive) and excellent electrochemical properties (high conductivity and wide potential window).

Ossicular resonance modes of the human middle ear for bone and air conduction.

The mean resonance frequency of the human middle ear under air conduction (AC) excitation is known to be around 0.8-1.2 kHz. However, studies suggest that the mean resonance frequency under bone conduction (BC) excitation is at a higher frequency around 1.5-2 kHz. To identify the cause for this difference, middle-ear responses to both AC and BC excitations were measured at the umbo and lateral process of the malleus using five human cadaver temporal bones. The resonance modes identified from these measurements, along with finite element analysis results, indicate the presence of two ossicular modes below 2 kHz. The dominant mode under AC excitation is the first mode, which typically occurs around 1.2 kHz and is characterized by a "hinging" ossicular motion, whereas the dominant mode under BC excitation is the second mode, which typically occurs around 1.7 kHz and is characterized by a "pivoting" ossicular motion. The results indicate that this second mode is responsible for the translational component in the malleus handle motion. The finding is also consistent with the hypothesis that a middle-ear structural resonance is responsible for the prominent peak seen at 1.5-2 kHz in BC limit data.

Inertial bone conduction: symmetric and anti-symmetric components.

Of the two pathways through which we hear, air conduction (AC) and bone conduction (BC), the fundamental mechanisms of the BC pathway remain poorly understood, despite their clinical significance. A finite element model of a human middle ear and cochlea was developed to gain insight into the mechanisms of BC hearing. The characteristics of various cochlear response quantities, including the basilar membrane (BM) vibration, oval-window (OW) and round-window (RW) volume velocities, and cochlear fluid pressures were examined for BC as well as AC excitations. These responses were tuned and validated against available experimental data from the literature. BC excitations were simulated in the form of rigid body vibrations of the surrounding bony structures in the x, y, and z orthogonal directions. The results show that the BM vibration characteristics are essentially invariant regardless of whether the excitation is via BC, independent of excitation direction, or via AC. This at first appeared surprising because the cochlear fluid pressures differ considerably depending on the excitation mode. Analysis reveals that the BM vibration responds only to the lower-magnitude anti-symmetric slow-wave cochlear fluid pressure component and not to the symmetric fast-wave pressure component, which dominates the magnitude of the total pressure field. This anti-symmetric fluid pressure is produced by the anti-symmetric component of the window volume velocities. As a result, the BM is effectively driven by the anti-symmetric component of the OW and RW volume velocities, irrespective of the type of excitation. Middle ear modifications that alter the anti-symmetric component of the OW and RW volume velocities corroborate this assertion. The current results provide further clarification of the mechanisms underlying Békésy's "paradoxical motion" concept.

Effects of ear-canal pressurization on middle-ear bone- and air-conduction responses.

In extremely loud noise environments, it is important to not only protect one's hearing against noise transmitted through the air-conduction (AC) pathway, but also through the bone-conduction (BC) pathways. Much of the energy transmitted through the BC pathways is concentrated in the mid-frequency range around 1.5-2 kHz, which is likely due to the structural resonance of the middle ear. One potential approach for mitigating this mid-frequency BC noise transmission is to introduce a positive or negative static pressure in the ear canal, which is known to reduce BC as well as AC hearing sensitivity. In the present study, middle-ear ossicular velocities at the umbo and stapes were measured using human cadaver temporal bones in response to both BC and AC excitations, while static air pressures of +/-400 mm H(2)O were applied in the ear canal. For the maximum negative pressure of -400 mm H(2)O, mean BC stapes-velocity reductions of about 5-8 dB were observed in the frequency range from 0.8 to 2.5 kHz, with a peak reduction of 8.6(+/-4.7)dB at 1.6 kHz. Finite-element analysis indicates that the peak BC-response reduction tends to be in the mid-frequency range because the middle-ear BC resonance, which is typically around 1.5-2 kHz, is suppressed by the pressure-induced stiffening of the middle-ear structure. The measured data also show that the BC responses are reduced more for negative static pressures than for positive static pressures. This may be attributable to a difference in the distribution of the stiffening among the middle-ear components depending on the polarity of the static pressure. The characteristics of the BC-response reductions are found to be largely consistent with the available psychoacoustic data, and are therefore indicative of the relative importance of the middle-ear mechanism in BC hearing.