Physics at the [Formula: see text] linear collider.

A comprehensive review of physics at an [Formula: see text] linear collider in the energy range of [Formula: see text] GeV-3 TeV is presented in view of recent and expected LHC results, experiments from low-energy as well as astroparticle physics. The report focusses in particular on Higgs-boson, top-quark and electroweak precision physics, but also discusses several models of beyond the standard model physics such as supersymmetry, little Higgs models and extra gauge bosons. The connection to cosmology has been analysed as well.

Observation of polarized positrons from an undulator-based source.

An experiment (E166) at the Stanford Linear Accelerator Center has demonstrated a scheme in which a multi-GeV electron beam passed through a helical undulator to generate multi-MeV, circularly polarized photons which were then converted in a thin target to produce positrons (and electrons) with longitudinal polarization above 80% at 6 MeV. The results are in agreement with GEANT4 simulations that include the dominant polarization-dependent interactions of electrons, positrons, and photons in matter.

The distribution of spherical cells in the anteroventral cochlear nucleus of the guinea pig.

Several types of neuron are found in Nissl-stained sections of the anteroventral cochlear nucleus (AVCN). From these one group, the spherical cells (Osen, 1969), can be readily distinguished from the remaining small and multipolar forms. The rostral pole of the AVCN has previously been subdivided into the large and the small spherical cell areas (in several mammals). In the present study of the guinea pig AVCN, spatial distributions of cell density, size, and shape have been investigated. These have been used to test whether the subdivision made on the basis of morphological differences in the spherical cells is valid, or whether there is a gradual gradient in these features. This analysis has shown that although variations in cell size and shape are observed, the spherical cell area cannot be partitioned on these grounds. There is, however, a graded increase in spherical cell packing density towards the rostral pole of the AVCN, with proportionately fewer of the other cell types present.

Level dependence of psychophysical frequency resolution and auditory filter shape.

From gated tone thresholds measured in the presence of "comb-filtered" (sinusoidal energy spectrum) noise maskers, the shape of the "auditory filter" was estimated in five frequency regions, 0.5, 1, 2, 4, and 8 kHz, at a number of masker levels. The auditory filter shape became wider, asymmetrical, and shifted towards lower frequencies as the level increased, for filters with center frequencies in excess of 1 kHz. The assumptions inherent in the derivation of the filter functions are discussed, and it is concluded that the likely deviation from these assumptions (in particular, as a result of the generation of nonlinear distortion products) leads to only small errors in the shapes of the derived filter functions.

Quantitative investigation of the 'paired-click' method: some limitations and insights.

This paper examines analytically and by simulation a method described by Møller, (Møller, A.R. (1970): Acta Physiol. Scand. 78, 299-314) using click-pairs to characterize the linear component of a system which contains nonlinearities. Møller has used the method to obtain the filter function of the response of neural units in the peripheral auditory system. We show that exact solutions for the filter functions are obtained with this method only if the system nonlinearity is quadratic. The method offers approximate solutions for systems containing other even-order nonlinearities, since the resulting filter functions are 'contaminated' by higher-order terms.

Theoretical dependence of cochlear fibre discharge rate versus intensity function on frequency: evidence for basilar membrane nonlinearity?

The suggestion that the frequency dependence of the slope of the cochlear fibre discharge rate vs. intensity function is evidence for a frequency-dependent basilar-membrane nonlinearity, is challenged by a demonstration that such frequency dependence of slope can be derived from a model of the cochlea which involves only linear filters and memoryless, frequency-independent nonlinearities. Some of the shortcomings of both models are briefly discussed. A third type of model, involving feedback, is tentatively proposed, which might more parsimoniously explain neurophysiological results.