Auditory discontinuities interact with categorization: implications for speech perception

Behavioral experiments with infants, adults, and nonhuman animals converge with neurophysiological findings to suggest that there is a discontinuity in auditory processing of stimulus components differing in onset time by about 20 ms. This discontinuity has been implicated as a basis for boundaries between speech categories distinguished by voice onset time (VOT). Here, it is investigated how this discontinuity interacts with the learning of novel perceptual categories. Adult listeners were trained to categorize nonspeech stimuli that mimicked certain temporal properties of VOT stimuli. One group of listeners learned categories with a boundary coincident with the perceptual discontinuity. Another group learned categories defined such that the perceptual discontinuity fell within a category. Listeners in the latter group required significantly more experience to reach criterion categorization performance. Evidence of interactions between the perceptual discontinuity and the learned categories extended to generalization tests as well. It has been hypothesized that languages make use of perceptual discontinuities to promote distinctiveness among sounds within a language inventory. The present data suggest that discontinuities interact with category learning. As such, "learnability" may play a predictive role in selection of language sound inventories.     

Fock space construction of the massless dipole field

We construct the Fock space representation of the free massless scalar dipole field in terms of creation and annihilation operators for the eigenvectors of the momentum operator. The Poincaré group is implemented unitarily only on a subspace of the full (positive metric) Hilbert space. The subspace possesses a hermitean, local, irreducible scalar field constructed out of the (non-hermitean) dipole field. Thus this subspace is a perfect candidate for a physical subspace of observable particles. We show that this possibility is however excluded by the fact that these particles interact with an external c-number source in a manner that violates unitarity. We illustrate our construction by applying it to the linearized Higgs model with external c-number source and examine the (non-trivial) dynamics of the dipole degrees of freedom in this case. An explicit separation of the physical degrees of freedom from the unphysical ones is presented for this interacting model.     

Computer-mediated reduction of spectral properties to molecular structures : General Design and Structural Building Blocks

A basic design is outlined for the conversion of the aggregate spectral properties of an organic compound of unknown structure to a set of compatible alternative molecular structures which is small in number anal exhaustive in scope. The process is built around a precisely defined unit of substructure. A procedure is described for the exhaustive generation of the set of these fragments from any specified group of elements and allowed valences. A versatile, user-friendly data-management system (FOCISS) provides a convenient means of manipulating these fragments and correlating their structure and properties. Extensive carbon-13 n.m.r. data are in place and applications of FOCISS to fragment-oriented searches are illustrated. The creation of a subset of chemically-stable fragments is also described.     

An efficient and versatile synthesis of β-alkylidene-α,α-disubstituted cyclopentanones

A direct, two step synthesis of specifically-substituted cyclopentanones utilizing α-alkoxy organolithium reagents is reported.     

Wavenumber mismatch of interacting modes in a plane wake

A technique is presented to examine the level of wavenumber mismatch between nonlinearly interacting components whose frequencies obey resonant matching conditions. Cross-correlation of the auto-bispectrum is used to quantify the level of mismatch, and the concept of bispectrum coherency is introduced to determine the confidence level in the wavenumber mismatch measurements. The results show that wavenumber mismatch of the order of one tenth of the fundamental wavenumber can exist between interacting triads whose frequencies obey resonance matching.     

Workshop on in‐situ studies of materials processing

More than eighty scientists from over ten different countries in Europe and America descended on Diamond Light Source in Oxfordshire to participate in the International Workshop on X-ray Spectroscopy of Magnetic Solids on June 10–21, 2010. The XRMS meetings have demonstrated to be a fruitful forum for informal discussion of recent results and future projects of synchrotron-radiation-based research on magnetism and also serve for the formation of new collaborations. The meetings are organized in sessions dedicated to specific scientific topics and experimental techniques. The absence of parallel sessions allows all the participants to take part in the discussion and to have a comprehensive view of the latest achievements and of the envisioned developments in the field. The previous meeting in the series was held last year at the synchrotron Soleil in St Aubin near Paris. The emerging new opportunities for magnetic spectroscopy, such as offered by the beamline for advanced dichroism experiments (BLADE), with its three intertwined assets of polarization, coherence, and time resolution, made it timely for the international community to convene at Diamond.