Mechanoelectrical transduction of adult outer hair cells studied in a gerbil hemicochlea

Sensory receptor cells of the mammalian cochlea are morphologically and functionally dichotomized. Inner hair cells transmit auditory information to the brain, whereas outer hair cells (OHC) amplify the mechanical signal, which is then transduced by inner hair cells. Amplification by OHCs is probably mediated by their somatic motility in a mechanical feedback process. OHC motility in vivo is thought to be driven by the cell's receptor potential. The first steps towards the generation of the receptor potential are the deflection of the stereociliary bundle, and the subsequent flow of transducer current through the mechanosensitive transducer channels located at their tips. Quantitative relations between transducer currents and basilar membrane displacements are lacking, as well as their variation along the cochlear length. To address this, we simultaneously recorded OHC transducer currents (or receptor potentials) and basilar membrane motion in an excised and bisected cochlea, the hemicochlea. This preparation permits recordings from adult OHCs at various cochlear locations while the basilar membrane is mechanically stimulated. Furthermore, the stereocilia are deflected by the same means of stimulation as in vivo. Here we show that asymmetrical transducer currents and receptor potentials are significantly larger than previously thought, they possess a highly restricted dynamic range and strongly depend on cochlear location.     

Copper oxide superconductors: sharp-mode coupling in high-Tc superconductors

In conventional superconductivity, sharp phonon modes (oscillations in the crystal lattice) are exchanged between electrons within a Cooper pair, enabling superconductivity. A critical question in the study of copper oxides with high critical transition temperature (Tc) is whether such sharp modes (which may be more general, including, for example, magnetic oscillations) also play a critical role in the pairing and hence the superconductivity. Hwang et al. report evidence that sharp modes (either phononic or magnetic in origin) are not important for superconductivity in these materials, but we show here that their conclusions are undermined by the insensitivity of their experiment to a crucial physical effect.     

Room-temperature ferromagnetic nanotubes controlled by electron or hole doping

Nanotubes and nanowires with both elemental (carbon or silicon) and multi-element compositions (such as compound semiconductors or oxides), and exhibiting electronic properties ranging from metallic to semiconducting, are being extensively investigated for use in device structures designed to control electron charge. However, another important degree of freedom--electron spin, the control of which underlies the operation of 'spintronic' devices--has been much less explored. This is probably due to the relative paucity of nanometre-scale ferromagnetic building blocks (in which electron spins are naturally aligned) from which spin-polarized electrons can be injected. Here we describe nanotubes of vanadium oxide (VO(x)), formed by controllable self-assembly, that are ferromagnetic at room temperature. The as-formed nanotubes are transformed from spin-frustrated semiconductors to ferromagnets by doping with either electrons or holes, potentially offering a route to spin control in nanotube-based heterostructures.     

Monoenergetic beams of relativistic electrons from intense laser-plasma interactions

High-power lasers that fit into a university-scale laboratory can now reach focused intensities of more than 10(19) W cm(-2) at high repetition rates. Such lasers are capable of producing beams of energetic electrons, protons and gamma-rays. Relativistic electrons are generated through the breaking of large-amplitude relativistic plasma waves created in the wake of the laser pulse as it propagates through a plasma, or through a direct interaction between the laser field and the electrons in the plasma. However, the electron beams produced from previous laser-plasma experiments have a large energy spread, limiting their use for potential applications. Here we report high-resolution energy measurements of the electron beams produced from intense laser-plasma interactions, showing that--under particular plasma conditions--it is possible to generate beams of relativistic electrons with low divergence and a small energy spread (less than three per cent). The monoenergetic features were observed in the electron energy spectrum for plasma densities just above a threshold required for breaking of the plasma wave. These features were observed consistently in the electron spectrum, although the energy of the beam was observed to vary from shot to shot. If the issue of energy reproducibility can be addressed, it should be possible to generate ultrashort monoenergetic electron bunches of tunable energy, holding great promise for the future development of 'table-top' particle accelerators.     

Electrolytic reduction of mixed solid oxides in molten salts for energy efficient production of the TiNi alloy

Fast and energy efficient technologies for material production are essential for the sustainable develop- ment of human society. The TiNi alloy is an important intelligent material[1], having high abrasive resistance, superior elasticity and good shape me…     

Collagen proteins in rats on long-term tyrosine diet

Zusammenfassung Bei Ratten wurde nach 12monatlicher Diät mit 5% 1-Tyrosin eine Alkaptonurie hervorgerufen. Die histologische Prüfung ergab eine Übersättigung mit der Homogentisinsäure, eine verringerte Aktivität der Oxidase der Homogentisinsäure in der Leber und deren massive Ausscheidung im Harn.     

Die Konstitution des Phthalylharnstoffs

Summary On the basis of experimental evidence, it is proved that phthalyl urea has the structure II, and not structure I, proposed byPiutti and generally accepted by other investigators.     

The cloacal gland complex of the Japanese quail

Résumé Chez les cailles japonaises, le complexe glandulaire du cloaque est en fait localisé dans la lèvre dorsale du cloaque et non de l'anus. Il existe un complexe glandulaire similaire et très petit du côté ventral. La glande active se colore intensément avec le réactif périodique «acide Schiff», avec la fuchsine aldéhyde, avec le bleu d'alciane et métachromatiquement avec le bleu de toluidine. Ceci indique la présence d'une sécrétion de glycomucoprotéines. Le liquide transparent sécrété est transformé en masse blanche mousseuse au contact des bactériesE. coli etProteus mirabilis, présentes en quantités équivalentes dans le proctodeum. Les gaz émis consistent probablement en H₂ et CO₂, ce dernier peut agir comme tampon et stabiliser le pH de la sécrétion autour de la valeur 6,5.

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This work was supported by U.S.P.H.S. grant No. ES 00054, Support for Toxicology Center, and by NASA research grant No. NGR 05-004-028.