Effect of waveform of ac voltage on the morphology and crystallinity of electrochemically assembled platinum nanowires.

Here we present electrochemically grown ultrathin platinum nanowires and demonstrate that their morphology and crystalline structure can be tuned by the waveform of the alternating voltage applied to the microelectrodes. The structure of the nanowires was analyzed by scanning and transmission electron microscopy. The voltage signal, applied to grow the nanowires, consisted of several Fourier components of a square-shaped wave. We observed that, depending on the number of Fourier components, the morphology of the nanowires changed from branched dendritic-like patterns to straight wires and the wire crystallinity changed from polycrystalline to highly oriented growth with the [111] direction of platinum crystallites along the nanowire axis. We propose a simple model to explain this intriguing observation.

Human melody singing by bullfinches (Pyrrhula pyrrula) gives hints about a cognitive note sequence processing.

We studied human melody perception and production in a songbird in the light of current concepts from the cognitive neuroscience of music. Bullfinches are the species best known for learning melodies from human teachers. The study is based on the historical data of 15 bullfinches, raised by 3 different human tutors and studied later by Jürgen Nicolai (JN) in the period 1967-1975. These hand-raised bullfinches learned human folk melodies (sequences of 20-50 notes) accurately. The tutoring was interactive and variable, starting before fledging and JN continued it later throughout the birds' lives. All 15 bullfinches learned to sing alternately melody modules with JN (alternate singing). We focus on the aspects of note sequencing and timing studying song variability when singing the learned melody alone and the accuracy of listening-singing interactions during alternatively singing with JN by analyzing song recordings of 5 different males. The following results were obtained as follows: (1) Sequencing: The note sequence variability when singing alone suggests that the bullfinches retrieve the note sequence from the memory as different sets of note groups (=modules), as chunks (sensu Miller in Psychol Rev 63:81-87, 1956). (2) Auditory-motor interactions, the coupling of listening and singing the human melody: Alternate singing provides insights into the bird's brain melody processing from listening to the actually whistled part of the human melody by JN to the bird's own accurately singing the consecutive parts. We document how variable and correctly bullfinches and JN alternated in their singing the note sequences. Alternate singing demonstrates that melody-singing bullfinches did not only follow attentively the just whistled note contribution of the human by auditory feedback, but also could synchronously anticipate singing the consecutive part of the learned melody. These data suggest that both listening and singing may depend on a single learned human melody representation (=coupling between perception and production).