217 research outputs found
A filled duration illusion in music: Effects of metrical subdivision on the perception and production of beat tempo.
This study replicates and extends previous findings suggesting that metrical
subdivision slows the perceived beat tempo (Repp, 2008). Here, musically trained participants produced the
subdivisions themselves and were found to speed up, thus compensating for the
perceived slowing. This was shown in a synchronization-continuation paradigm
(Experiment 1) and in a reproduction task (Experiment 2a). Participants also
judged the tempo of a subdivided sequence as being slower than that of a
preceding simple beat sequence (Experiment 2b). Experiment 2 also included
nonmusician participants, with similar results. Tempo measurements of famous
pianists’ recordings of two variation movements from Beethoven sonatas revealed
a strong tendency to play the first variation (subdivided beats) faster than the
theme (mostly simple beats). A similar tendency was found in musicians’
laboratory performances of a simple theme and variations, despite instruc-tions
to keep the tempo constant (Experiment 3a). When playing melodic sequences in
which only one of three beats per measure was subdivided, musicians tended to
play these beats faster and to perceive them as longer than adjacent beats, and
they played the whole sequence faster than a sequence without any subdivisions
(Experiments 3b and 3c). The results amply demonstrate a filled duration
illusion in rhythm perception and music performance: Intervals
containing events seem longer than empty intervals and thus must be shortened to
be perceived as equal in duration
Atomic Hole Doping of Graphene
Graphene is an excellent candidate for the next generation of electronic
materials due to the strict two-dimensionality of its electronic structure as
well as the extremely high carrier mobility. A prerequisite for the development
of graphene based electronics is the reliable control of the type and density
of the charge carriers by external (gate) and internal (doping) means. While
gating has been successfully demonstrated for graphene flakes and epitaxial
graphene on silicon carbide, the development of reliable chemical doping
methods turns out to be a real challenge. In particular hole doping is an
unsolved issue. So far it has only been achieved with reactive molecular
adsorbates, which are largely incompatible with any device technology. Here we
show by angle-resolved photoemission spectroscopy that atomic doping of an
epitaxial graphene layer on a silicon carbide substrate with bismuth, antimony
or gold presents effective means of p-type doping. Not only is the atomic
doping the method of choice for the internal control of the carrier density. In
combination with the intrinsic n-type character of epitaxial graphene on SiC,
the charge carriers can be tuned from electrons to holes, without affecting the
conical band structure
Strong polarization-induced reduction of addition energies in single-molecule nanojunctions
We address polarization-induced renormalization of molecular levels in
solid-state based single-molecule transistors and focus on an organic conjugate
molecule where a surprisingly large reduction of the addition energy has been
observed. We have developed a scheme that combines a self-consistent solution
of a quantum chemical calculation with a realistic description of the screening
environment. Our results indeed show a large reduction, and we explain this to
be a consequence of both (a) a reduction of the electrostatic molecular
charging energy and (b) polarization induced level shifts of the HOMO and LUMO
levels. Finally, we calculate the charge stability diagram and explain at a
qualitative level general features observed experimentally.Comment: 9 pages, 5 figure
Recommended from our members
Cue properties change timing strategies in group movement synchronisation
To maintain synchrony in group activities, each individual within the group must continuously correct their movements to remain in time with the temporal cues available. Cues might originate from one or more members of the group. Current research suggests that when synchronising movements, individuals optimise their performance in terms of minimising variability of timing errors (asynchronies) between external cues and their own movements. However, the cost of this is an increase in the timing variability of their own movements. Here we investigate whether an individual’s timing strategy changes according to the task, in a group scenario. To investigate this, we employed a novel paradigm that positioned six individuals to form two chains with common origin and termination on the circumference of a circle. We found that participants with access to timing cues from only one other member used a strategy to minimise their asynchrony variance. In contrast, the participant at the common termination of the two chains, who was required to integrate timing cues from two members, used a strategy that minimised movement variability. We conclude that humans are able to flexibly switch timekeeping strategies to maintain task demands and thus optimise the temporal performance of their movements
Quantum transport through STM-lifted single PTCDA molecules
Using a scanning tunneling microscope we have measured the quantum
conductance through a PTCDA molecule for different configurations of the
tip-molecule-surface junction. A peculiar conductance resonance arises at the
Fermi level for certain tip to surface distances. We have relaxed the molecular
junction coordinates and calculated transport by means of the Landauer/Keldysh
approach. The zero bias transmission calculated for fixed tip positions in
lateral dimensions but different tip substrate distances show a clear shift and
sharpening of the molecular chemisorption level on increasing the STM-surface
distance, in agreement with experiment.Comment: accepted for publication in Applied Physics
Green function techniques in the treatment of quantum transport at the molecular scale
The theoretical investigation of charge (and spin) transport at nanometer
length scales requires the use of advanced and powerful techniques able to deal
with the dynamical properties of the relevant physical systems, to explicitly
include out-of-equilibrium situations typical for electrical/heat transport as
well as to take into account interaction effects in a systematic way.
Equilibrium Green function techniques and their extension to non-equilibrium
situations via the Keldysh formalism build one of the pillars of current
state-of-the-art approaches to quantum transport which have been implemented in
both model Hamiltonian formulations and first-principle methodologies. We offer
a tutorial overview of the applications of Green functions to deal with some
fundamental aspects of charge transport at the nanoscale, mainly focusing on
applications to model Hamiltonian formulations.Comment: Tutorial review, LaTeX, 129 pages, 41 figures, 300 references,
submitted to Springer series "Lecture Notes in Physics
Synthesis and characterization of triangulene
Triangulene, the smallest triplet-ground-state polybenzenoid (also known as Clar's hydrocarbon), has been an enigmatic molecule ever since its existence was first hypothesized1. Despite containing an even number of carbons (22, in six fused benzene rings), it is not possible to draw Kekulé-style resonant structures for the whole molecule: any attempt results in two unpaired valence electrons2. Synthesis and characterization of unsubstituted triangulene has not been achieved because of its extreme reactivity1, although the addition of substituents has allowed the stabilization and synthesis of the triangulene core3, 4 and verification of the triplet ground state via electron paramagnetic resonance measurements5. Here we show the on-surface generation of unsubstituted triangulene that consists of six fused benzene rings. The tip of a combined scanning tunnelling and atomic force microscope (STM/AFM) was used to dehydrogenate precursor molecules. STM measurements in combination with density functional theory (DFT) calculations confirmed that triangulene keeps its free-molecule properties on the surface, whereas AFM measurements resolved its planar, threefold symmetric molecular structure. The unique topology of such non-Kekulé hydrocarbons results in open-shell π-conjugated graphene fragments6 that give rise to high-spin ground states, potentially useful in organic spintronic devices7, 8. Our generation method renders manifold experiments possible to investigate triangulene and related open-shell fragments at the single-molecule level
Long-Range Correlation in Synchronization and Syncopation Tapping: A Linear Phase Correction Model
We propose in this paper a model for accounting for the increase in long-range correlations observed in asynchrony series in syncopation tapping, as compared with synchronization tapping. Our model is an extension of the linear phase correction model for synchronization tapping. We suppose that the timekeeper represents a fractal source in the system, and that a process of estimation of the half-period of the metronome, obeying a random-walk dynamics, combines with the linear phase correction process. Comparing experimental and simulated series, we show that our model allows accounting for the experimentally observed pattern of serial dependence. This model complete previous modeling solutions proposed for self-paced and synchronization tapping, for a unifying framework of event-based timing
Modeling, analyzing, and synthesizing expressive piano performance with graphical models
FMLP- and TNF-stimulated monoclonal Lym-1 antibody-dependent lysis of B lymphoblastoid tumour targets by neutrophils
- …