A simple model for the optical Bu modes inAV-BVI-CVII compounds

The eigenvalues of the optical modes of theAV-BVI-CVII compounds SbSI, SbSeI, BiSI, BiSeI, BiSBr, BiSeBr, and SbSBr in the paraelectric phase and the polarizationE c are calculated by use of a simple model fitted by the observed transverse mode frequencies. For the low-frequency mode theAV and theBVI ions are shown to vibrate simultaneously against theCVII ions. For the high-frequency mode the motion of theCVII ions is almost absent and theAV ions vibrate against theBVI ions.     

Nonlinear acoustics in the pant hoots of common chimpanzees (Pan troglodytes): vocalizing at the edge

Common chimpanzee (Pan troglodytes) "pant hoots" are multi-call events that build from quiet, consistently harmonic introductory sounds to loud, screamlike "climax" calls with acoustic irregularities known as "nonlinear phenomena" (NLP). Two possible functions of NLP in climax calls are to increase direct auditory impact on listeners and to signal physical condition. These possibilities were addressed by comparing climax calls from 12 wild chimpanzee males with "screams" and pant hoot "introduction" calls from the same individuals. Climax calls that included NLP were found to have higher fundamental frequencies (F0s) than introduction or climax calls that were purely harmonic. NLP onsets within climax calls were also specifically associated with local F0 maxima, suggesting vocalizers are vibrating their vocal folds at the upper limits of stability. Furthermore, climax calls showed far fewer NLP than did screams recorded from the same individuals, while showing equivalent or higher F0 values. Overall, the results are consistent with the hypothesis that the relative prevalence of NLP is a signal of physical condition, with callers "vocalizing at the edge" of regular, stable production while producing few NLP. The results are discussed in light of the initial hypotheses.     

Infrared Lattice Vibrations in NaGaO2

Infrared reflectivity spectra of NaGaO₂ samples prepared from powdered material are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹. An analysis of the spectra with the Kramers-Kronig method reveals 16 vibrational modes. From a comparison of the results for NaGaO₂ with previous measurements on the isostructural compound LiGaO₂ conclusions are made with regard to the Ga–O and Na–O bond related vibrational modes.     

Infrared lattice vibrations of CdIn2Se4

Infrared reflectivity spectra of CdIn₂Se₄ single crystals are measured at room temperature in the wavenumber range from 180 to 4000 cm⁻¹ for the polarization directions E ⟂ c and E ‖[112]. The spectra reveal two vibrational modes with nearly the same frequencies for both polarization directions. The frequencies of the modes with highest energy compare well with the corresponding mode frequencies in ZnIn₂Se₄, CuInSe₂ and AgInSe₂. It is concluded that these modes are sphalerite-like in nature and that their frequencies are essentially determined by the properties of the In Se bond.     

A Bifunctional Lewis Acidic Spacer in Self-Assembled Molecular Stairs and Ladders

Depending on the stoichiometry , diindacycle 1 and pyrazine in THF reversibly form a stair- or a ladderlike self-organized coordination polymer. In both cases, the building blocks are assembled at angles close to 90°.