Tonotopy of cochlear hair cell biophysics (excl. mechanotransduction)

The cochlea is tonotopically organised to ensure that the auditory nerve fibres can be frequency coded in an orderly manner. In part the mechanism depends on the structural and mechanical organisation of the cochlea but it also requires that the individual cells have an organised expression of ionic channels in the basolateral membrane. This short review will discuss evidence for several distributions of K+ and other channels along the cochlea in both mammalian and non-mammalian hearing organs. It will also describe how the gradients are set up and address the question of whether OHCs contribute uniformly to mammalian cochlear tuning

Next-to-next-to-leading order O(αs4){\cal O}(\alpha_s^4) results for heavy quark pair production in quark--antiquark collisions: The one-loop squared contributions

We calculate the next-to-next-to-leading order ${\cal O}(\alpha_s^4)$ one-loop squared corrections to the production of heavy quark pairs in quark-antiquark annihilations. These are part of the next-to-next-to-leading order ${\cal O}(\alpha_s^4)$ radiative QCD corrections to this process. Our results, with the full mass dependence retained, are presented in a closed and very compact form, in the dimensional regularization scheme. We have found very intriguing factorization properties for the finite part of the amplitudes.Comment: 12 pages, 2 figures, electronic results file, abbreviation NNLO in Title and Abstract expanded, Summary expanded, reference updated, version to appear in Phys.Rev.

One-loop amplitudes for four-point functions with two external massive quarks and two external massless partons up to O(epsilon^2)

We present complete analytical ${\mathcal O}(\epsilon^2)$ results on the one-loop amplitudes relevant for the NNLO quark-parton model description of the hadroproduction of heavy quarks as given by the so-called loop-by-loop contributions. All results of the perturbative calculation are given in the dimensional regularization scheme. These one-loop amplitudes can also be used as input in the determination of the corresponding NNLO cross sections for heavy flavor photoproduction, and in photon-photon reactions.Comment: 25 pages, 6 figures in the text, Revtex, one reference added, minor improvements in the text, to appear in Phys.Rev.

Effective Discharge for Suspended Sediment Transport in Streams of the Saskatchewan River Basin

Effective discharge for suspended sediment load was determined for 21 sites in the Saskatchewan River basin at which sediment records range from 5 to 29 years in length. The drainage areas for these streams ranges from 10 to over 300,000 km2. The sediment discharge histograms have a variety of forms ranging from the classic unimodal form in which the peak occurs at discharges with a duration of 1–3% to those in which the effective discharge is the extreme event of record and cases in which a single effective discharge is difficult to define. The percentage duration of the effective-discharge ranges from less than 0.1% to over 15%, a greater range than previously has been reported. There is an obvious tendency for the percentage duration of the effective discharge to increase with drainage area and hence downstream through the drainage system

Atom detection and photon production in a scalable, open, optical microcavity

A microfabricated Fabry-Perot optical resonator has been used for atom detection and photon production with less than 1 atom on average in the cavity mode. Our cavity design combines the intrinsic scalability of microfabrication processes with direct coupling of the cavity field to single-mode optical waveguides or fibers. The presence of the atom is seen through changes in both the intensity and the noise characteristics of probe light reflected from the cavity input mirror. An excitation laser passing transversely through the cavity triggers photon emission into the cavity mode and hence into the single-mode fiber. These are first steps towards building an optical microcavity network on an atom chip for applications in quantum information processing.Comment: 4 pages, 4 figures. A typographical error in the published paper has been corrected (equation of the corrected normalized variance, page 3, 2nd paragraph

Spatial and Temporal Patterns of Suspended-Sediment Yield in the Saskatchewan River Basin

Long-term suspended-sediment concentration and load records are available for 23 Water Survey of Canada sediment-monitoring stations in the Saskatchewan River basin, where the drainage areas range from 10 to over 300 000 km2. Mean annual sediment yield is greatest in the western Alberta Plains along the Oldman and Red Deer rivers (over 100 t km−2 year−1) and tends to increase downstream along the North and South Saskatchewan rivers until major reservoirs in Saskatchewan intervene. Average sediment concentration shows a pattern of variation similar to that of yield. Temporal aspects of suspended-sediment transport vary along the drainage network. The range and skewness of the yield–duration and concentration–duration curves are greater in the intermediate-size basins close to the Rocky Mountains and in two small basins with Prairie sources than they are in the large Prairie streams with mountain sources and the glacier-fed upper North Saskatchewan River. Similarly, infrequent flows transport a larger proportion of the annual load in the smaller Foothills and western Plains basins than in the large Prairie streams because of differences in drainage area and discharge regime

Innocence and nostalgia in conversation analysis: the dynamic relations of tape and transcript

This paper attempts an analysis of some of the methodological practices of Conversation Analysis (CA); in particular, tape recording and transcription. The paper starts from the observation that, in the CA literature, these practices, and the analytic objects they create (the tape and the transcript), are accorded different treatment: simply put, for CA the tape is a "realist" object, while the transcript is a "constructivist" one. The significance of this difference is explored through an analysis of the dynamics of CA practice. We argue that the "constructivist transcript" is premised on an understanding of CA as predominantly concerned with maximising its "analytic utility": a concern of one distinct temporal stage of CA work: that of the "innocent" apprehension of objects in the "first time through". The "realist tape", in contrast, is based on a different aspect of the work of CA: its quest for greater "evidential utility", achieved by the "nostalgic" revisiting of previously produced objects for purposes of checking them against each other; work done in the "next time through". We further argue that both the ontology and the epistemology of CA's objects are changed in any next time encounter. We conclude with a cautionary speculation on the currently-projected, transcript-free, digital future of CA

Outer Hair Cells and Electromotility

Outer hair cells (OHCs) of the mammalian cochlea behave like actuators: they feed energy into the cochlear partition and determine the overall mechanics of hearing. They do this by generating voltage-dependent axial forces. The resulting change in the cell length, observed by microscopy, has been termed “electromotility.” The mechanism of force generation OHCs can be traced to a specific protein, prestin, a member of a superfamily SLC26 of transporters. This short review will identify some of the more recent findings on prestin. Although the tertiary structure of prestin has yet to be determined, results from the presence of its homologs in nonmammalian species suggest a possible conformation in mammalian OHCs, how it can act like a transport protein, and how it may have evolved

Transformative Geomorphic Research Using Laboratory Experimentation

Laboratory experiments in geomorphology is the theme of the 46th annual Binghamton Geomorphology Symposium (BGS). While geomorphic research historically has been dominated by field-based endeavors, laboratory experimentation has emerged as an important methodological approach to study these phenomena, employed primarily to address issues related to scale and the analytical treatment of the geomorphic processes. It is contended here that geomorphic laboratory experiments have resulted in transformative research. Several examples drawn from the fluvial and aeolian research communities are offered as testament to this belief, and these select transformative endeavors often share very similar attributes. The 46th BGS will focus on eight broad themes within laboratory experimentation, and a strong and diverse group of scientists have been assembled to speak authoritatively on these topics, featuring several high-profile projects worldwide. This special issue of the journal Geomorphology represents a collection of the papers written in support of this symposium

The Thermal Stability of Mass-Loaded Flows

We present a linear stability analysis of a flow undergoing conductively-driven mass-loading from embedded clouds. We find that mass-loading damps isobaric and isentropic perturbations, and in this regard is similar to the effect of thermal conduction, but is much more pronounced where many embedded clumps exist. The stabilizing influence of mass-loading is wavelength independent against isobaric (condensing) perturbations, but wavelength dependent against isentropic (wave-like) perturbations. We derive equations for the degree of mass-loading needed to stabilize such perturbations. We have also made 1D numerical simulations of a mass-loaded radiative shock and demonstrated the damping of the overstability when mass-loading is rapid enough.Comment: 4 pages, 1 figure, to be published in A&