Sensitivity of a tucuxi (Sotalia fluviatilis guianensis) to airborne sound

Auditory systems of cetaceans are considered highly specialized for underwater sound processing, whereas the extent of their hearing capacity in air is still a point of issue. In this study, the sensitivity to airborne sound in a male tucuxi (Sotalia fluviatilis guianensis) was tested by means of a go/no go response paradigm. Auditory thresholds were obtained from 2 to 31.5 kHz. Compared to the hearing thresholds of other dolphins as well as of amphibian mammals, the sensitivity to airborne sound of the test subject is low from 2 to 8 kHz, with the highest threshold at 4 kHz. Thresholds at 16 and 31.5 kHz reveal a sharp increase in hearing sensitivity. Thus, although not obtained in this study, the upper aerial hearing limit is in the ultrasonic range. A comparison of the present data with the underwater audiogram of the same test subject referred to sound intensity indicates that the sensitivity of Sotalia to underwater sound is generally better than to airborne sound.     

Dopant-modulated pair interaction in cuprate superconductors

A comparison of recent experimental STM data with single-impurity and many-impurity Bogoliubov-de Gennes calculations strongly suggests that random out-of-plane dopant atoms in cuprates modulate the pair interaction locally. This type of disorder is crucial to understanding the nanoscale electronic inhomogeneity observed in BSCCO-2212, and can reproduce observed correlations between the positions of impurity atoms and various aspects of the local density of states such as the gap magnitude and the height of the coherence peaks. Our results imply that each dopant atom modulates the pair interaction on a length scale of order one lattice constant.     

Weak measurements with arbitrary probe states

The exact conditions on valid probe states for weak measurements are derived. It is demonstrated that weak measurements can be performed with any probe state with vanishing probability current density. This condition is found both for weak measurements of noncommuting observables and for c-number observables. In addition, the interaction between object and probe must be sufficiently weak. Strange weak values can be observed also with mixed probe states, but not for c-number observables.     

Stopping power in insulators and metals without charge exchange

The slowing-down process of pointlike charged particles in matter has been investigated by measuring the stopping power for antiprotons in materials of qualitatively very different nature. Whereas the velocity-proportional stopping power observed for metal-like targets such as aluminum over a wide energy range of 1-50 keV is in agreement with expectations, it is surprising that the same velocity dependence is seen for a large band-gap insulator such as LiF. The validity of these observations is supported by several measurements with protons and several checks of the target properties. The observations call for both a qualitative explanation and a quantitative theoretical model.     

Mott transition and suppression of orbital fluctuations in orthorhombic 3d1 perovskites

Using t(2g) Wannier functions, a low-energy Hamiltonian is derived for orthorhombic 3d(1) transition-metal oxides. Electronic correlations are treated with a new implementation of dynamical mean-field theory for noncubic systems. Good agreement with photoemission data is obtained. The interplay of correlation effects and cation covalency (GdFeO3-type distortions) is found to suppress orbital fluctuations in LaTiO3 and even more in YTiO3, and to favor the transition to the insulating state.     

Proper use of certified reference materials?

Certified reference materials (CRMs) are important quality assurance tools in the laboratory. It is, however, not certain they are always used properly. Several guidelines are available on the use of CRMs, but appear to be mostly unknown. The users thus get very little help on the way to proper use. Many of the problems with CRMs are well known, but that does not mean they have disappeared. Better use of CRMs will require the involvement of producers and analytical societies, e.g. the AOAC. Editors of international analytical journals could have a great influence on how CRM results and other QA data are treated in publications.     

Microwave-assisted group-transfer cyclization of organotellurium compounds

Primary- and secondary-alkyl aryl tellurides, prepared by arenetellurolate ring-opening of epoxides/ O-allylation, were found to undergo rapid (3-10 min) group-transfer cyclization to afford tetrahydrofuran derivatives in 60-74% yield when heated in a microwave cavity at 250 degrees C in ethylene glycol or at 180 degrees C in water. To go to completion, similar transformations had previously required extended photolysis in refluxing benzene containing a substantial amount of hexabutylditin. The only drawback of the microwave-assisted process was the loss in diastereoselectivity which is a consequence of the higher reaction temperature. Substitution in the Te-aryl moiety of the secondary-alkyl aryl tellurides (4-OMe, 4-H, 4-CF(3)) did not affect the outcome of the group-transfer reaction in ethylene glycol. However, at lower temperature, using water as a solvent, the CF(3) derivative failed to react. The microwave-assisted group-transfer cyclization was extended to benzylic but not to primary- and secondary-alkyl phenyl selenides.     

Monitoring nanoparticle formation during laser ablation of graphite in an atmospheric-pressure ambient

Excimer laser ablation of highly oriented pyrolytic graphite (HOPG) was performed at atmospheric pressure in an N₂ and in an air ambient. During the ablation, nanoparticles condensed from the material ejecta, and their size distribution was monitored in the gas phase by a Differential Mobility Analyzer (DMA) in combination with a Condensation Particle Counter (CPC). Size distributions obtained at different laser repetition rates revealed that the interaction between subsequent laser pulses and formed particles became significant above 15 Hz. This interaction resulted in laser heating, leading to considerable evaporation and a decrease in the size of the particles. X-ray photoelectron spectroscopy revealed that approximately 8% nitrogen was incorporated into the CN_x particles generated in the N₂ ambient, and that the nitrogen was mostly bonded to sp³-hybridized carbon. Monodisperse particles were also deposited and were analyzed by means of Raman spectroscopy to monitor size-induced effects. PACS 81.07.-b; 61.46.+w; 79.70.+q