Unfolding of phonetic information over time: a database of Dutch diphone perception

We present the results of a large-scale study on speech perception, assessing the number and type of perceptual hypotheses which listeners entertain about possible phoneme sequences in their language. Dutch listeners were asked to identify gated fragments of all 1179 diphones of Dutch, providing a total of 488,520 phoneme categorizations. The results manifest orderly uptake of acoustic information in the signal. Differences across phonemes in the rate at which fully correct recognition was achieved arose as a result of whether or not potential confusions could occur with other phonemes of the language (long with short vowels, affricates with their initial components, etc.). These data can be used to improve models of how acoustic-phonetic information is mapped onto the mental lexicon during speech comprehension.     

Structural disorder, octahedral coordination and two-dimensional ferromagnetism in anhydrous alums

The crystal structures of the triangular lattice, layered anhydrous alums KCr(SO₄)₂, RbCr(SO₄)₂ and KAl(SO₄)₂ are characterized by X-ray and neutron powder diffraction (NPD) at temperatures between 1.4 and 773 K. The compounds all crystallize in the space group , with octahedral coordination of the trivalent cations. In all cases, small amounts of disorder in the stacking of the triangular layers of corner sharing MO₆ octahedra and SO₄ tetrahedra is seen, with the MO₆−SO₄ network rotated in opposite directions between layers. The electron diffraction study of KCr(SO₄)₂ supports this model, which on an average can be taken to imply trigonal prismatic coordination for the M³⁺ ions; as was previously reported for the prototype anhydrous alum, KAl(SO₄)₂. The temperature-dependent magnetic susceptibilities for ACr(SO₄)₂ (A=K, Rb, Cs) indicate the presence of predominantly ferromagnetic interactions. Low-temperature powder neutron diffraction reveals that the magnetic ordering is ferromagnetic in-plane, with antiferromagnetic ordering between planes below 3 K.     

Structural and magnetic properties of pyrochlore solid solutions (Y,Lu)2Ti2−x(Nb,Ta)xO7±y

The synthesis and characterization of the pyrochlore solid solutions, Y₂Ti_2−xNb_xO_7−y, Lu₂Ti_2−xNb_xO_7−y, Y₂Ti_2−xTa_xO_7−y and Lu₂TiTaO_7−y (−0.4<y<0.5), is described. Synthesis at 1600 °C, and 10⁻⁵ Torr yields oxygen deficiency in all systems. All compounds are found to be paramagnetic and semiconducting, with the size of the local moments being less, in some cases substantially less, than the expected value for the number of nominally unpaired electrons present. Thermogravimetric analysis (TGA) shows that all compounds can be fully oxidized while retaining the pyrochlore structure, yielding oxygen rich pyrochlores as white powders. Powder neutron diffraction of Y₂TiNbO₇-based samples was done. Refinement of the data for oxygen deficient Y₂TiNbO_6.76 indicates the presence of a distribution of oxygen over the 8b and 48f sites. Refinement of the data for oxygen rich Y₂TiNbO_7.5 shows these sites to be completely filled, with an additional half filling of the 8a site. The magnetic and TGA data strongly suggest a preference for a Ti³⁺/(Nb,Ta)⁵⁺ combination, as opposed to Ti⁴⁺/(Nb,Ta)⁴⁺, in this pyrochlore family. In addition, the evidence clearly points to Ti³⁺ as the source of the localized moments, with no evidence for localized Nb⁴⁺ moments.