Mouse Chromosome 11

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46996/1/335_2004_Article_BF00648429.pd

Physical and chemical characterization of Devonian gas shales. Eastern Gas Shale Project report No. 18. Final annual report

Quantitative mineralogical analyses for major minerals and qualitative analyses for trace minerals were made on 28 samples, all of which were analyzed chemically. Quartz grain-size distributions were measured on 28 samples. Physical tests made on several samples were hardness, density, point-load strength, directional-tensile strength, air permeability, directional-sonic velocity, and pore-size distribution. It was found that the clay mineral, kaolinite, was a major mineral in Well Core No. 20336, but no traces of kaolinite were formed in the Devonian shales of New York State. Both the point-load and directional-tensile strengths showed that the Devonian shales, in general, were stronger in the NW-SE direction than in the NE-SW direction. It was also observed that the shales were stronger with increasing quartz or silicon contents and weaker with increasing amounts of micaceous, disilicate minerals. As expected from previous work, the quartz grain-size distributions were skewed toward the larger sizes when the frequency curves were plotted linearly. An exhaustive analysis of all the data obtained was not attempted, since it was not a part of the contract

Evidence of Piezoelectric Resonance in Isolated Outer Hair Cells

Our results demonstrate high-frequency electrical resonances in outer hair cells (OHCs) exhibiting features analogous to classical piezoelectric transducers. The fundamental (first) resonance frequency averaged f(n) ∼ 13 kHz (Q ∼ 1.7). Higher-order resonances were also observed. To obtain these results, OHCs were positioned in a custom microchamber and subjected to stimulating electric fields along the axis of the cell (1–100 kHz, 4–16 mV/80 μm). Electrodes embedded in the side walls of the microchamber were used in a voltage-divider configuration to estimate the electrical admittance of the top portion of the cell-loaded chamber (containing the electromotile lateral wall) relative to the lower portion (containing the basal plasma membrane). This ratio exhibited resonance-like electrical tuning. Resonance was also detected independently using a secondary 1-MHz radio-frequency interrogation signal applied transversely across the cell diameter. The radio-frequency interrogation revealed changes in the transverse electric impedance modulated by the axial stimulus. Modulation of the transverse electric impedance was particularly pronounced near the resonant frequencies. OHCs used in our study were isolated from the apical region of the guinea pig cochlea, a region that responds exclusively to low-frequency acoustic stimuli. In this sense, electrical resonances we observed in vitro were at least an order of magnitude higher (ultrasonic) than the best physiological frequency of the same OHCs under acoustic stimuli in vivo. These resonance data further support the piezoelectric theory of OHC function, and implicate piezoelectricity in the broad-band electromechanical behavior of OHCs underlying mammalian cochlear function

The remarkable cochlear amplifier

International audienc