1,950 research outputs found
Ambipolar charge injection and transport in a single pentacene monolayer island
Electrons and holes are locally injected in a single pentacene monolayer
island. The two-dimensional distribution and concentration of the injected
carriers are measured by electrical force microscopy. In crystalline monolayer
islands, both carriers are delocalized over the whole island. On disordered
monolayer, carriers stay localized at their injection point. These results
provide insight into the electronic properties, at the nanometer scale, of
organic monolayers governing performances of organic transistors and molecular
devices.Comment: To be published in Nano Letter
Where do people direct their attention while cycling? : A comparison of adults and children
Cycling in urban environments requires the ability to distinguish between relevant and irrelevant targets quickly and reliably, so that potential hazards can be anticipated and avoided. In two experiments, we investigated where adults and children direct their attention when viewing videos filmed from a cyclist's perspective. We wanted to see if there were any differences in the responses given by experienced adult cyclists, inexperienced adult cyclists, and child cyclists. In Experiment 1,16 adults (19-33 years) were asked to watch ten videos and to point out things they would pay attention to by tapping a touchscreen (pointed out locations). Afterwards, they were asked to explain their answers. In Experiment 2, 17 adults (19-34 years) and 17 children (11-12 years) performed the same task with the same ten videos, but they were not asked to explain their answers afterwards. The data sets from these two experiments were pooled, creating three groups: ten experienced adult cyclists, 23 inexperienced adult cyclists and 17 children. A total of 23 clearly visible, traffic-relevant targets (pre-specified targets) had previously been identified in the videos. We investigated whether the participants' pointed-out locations matched these targets (and if so, how fast they responded in pointing them out). We also investigated the number and vertical/horizontal dispersion of these pointed-out locations on the touchscreen. Adults pointed out more locations than children, especially pedestrians and cyclists. This result suggests that, while children focussed as well as adults on cars (arguably the most salient hazard), they were less able to identify other hazards (such as pedestrians or other cyclists). The children had also a larger vertical dispersion and a larger between-participant variation than the adults. Adults were faster at tapping the pre-specified targets and they missed them less often. Overall, the results suggest that 11-12 year old-cyclists have worse situation awareness in traffic than adults. (C) 2018 Published by Elsevier Ltd.Peer reviewe
Physical Study by Surface Characterizations of Sarin Sensor on the Basis of Chemically Functionalized Silicon Nanoribbon Field Effect Transistor
Surface characterizations of an organophosphorus (OP) gas detector based on
chemically functionalized silicon nanoribbon field-effect transistor (SiNR-FET)
were performed by Kelvin Probe Force Microscopy (KPFM) and ToF-SIMS, and
correlated with changes in the current-voltage characteristics of the devices.
KPFM measurements on FETs allow (i) to investigate the contact potential
difference (CPD) distribution of the polarized device as function of the gate
voltage and the exposure to OP traces and, (ii) to analyze the CPD hysteresis
associated to the presence of mobile ions on the surface. The CPD measured by
KPFM on the silicon nanoribbon was corrected due to side capacitance effects in
order to determine the real quantitative surface potential. Comparison with
macroscopic Kelvin probe (KP) experiments on larger surfaces was carried out.
These two approaches were quantitatively consistent. An important increase of
the CPD values (between + 399 mV and + 302 mV) was observed after the OP sensor
grafting, corresponding to a decrease of the work function, and a weaker
variation after exposure to OP (between - 14 mV and - 61 mV) was measured.
Molecular imaging by ToF-SIMS revealed OP presence after SiNR-FET exposure. The
OP molecules were essentially localized on the Si-NR confirming effectiveness
and selectivity of the OP sensor. A prototype was exposed to Sarin vapors and
succeeded in the detection of low vapor concentrations (40 ppm).Comment: Paper and supporting information, J. Phys. Chem. C, 201
Fruit scent and observer colour vision shape food-selection strategies in wild capuchin monkeys
The senses play critical roles in helping animals evaluate foods, including fruits that can change both in colour and scent during ripening to attract frugivores. Although numerous studies have assessed the impact of colour on fruit selection, comparatively little is known about fruit scent and how olfactory and visual data are integrated during foraging. We combine 25 months of behavioural data on 75 wild, white-faced capuchins (Cebus imitator) with measurements of fruit colours and scents from 18 dietary plant species. We show that frequency of fruit-directed olfactory behaviour is positively correlated with increases in the volume of fruit odours produced during ripening. Monkeys with red-green colour blindness sniffed fruits more often, indicating that increased reliance on olfaction is a behavioural strategy that mitigates decreased capacity to detect red-green colour contrast. These results demonstrate a complex interaction among fruit traits, sensory capacities and foraging strategies, which help explain variation in primate behaviour.https://www.nature.com/articles/s41467-019-10250-9Published versio
Prospects for high-z cluster detections with Planck, based on a follow-up of 28 candidates using MegaCam@CFHT
The Planck catalogue of SZ sources limits itself to a significance threshold
of 4.5 to ensure a low contamination rate by false cluster candidates. This
means that only the most massive clusters at redshift z>0.5, and in particular
z>0.7, are expected to enter into the catalogue, with a large number of systems
in that redshift regime being expected around and just below that threshold. In
this paper, we follow-up a sample of SZ sources from the Planck SZ catalogues
from 2013 and 2015. In the latter maps, we consider detections around and at
lower significance than the threshold adopted by the Planck Collaboration. To
keep the contamination rate low, our 28 candidates are chosen to have
significant WISE detections, in combination with non-detections in SDSS/DSS,
which effectively selects galaxy cluster candidates at redshifts .
By taking r- and z-band imaging with MegaCam@CFHT, we bridge the 4000A
rest-frame break over a significant redshift range, thus allowing accurate
redshift estimates of red-sequence cluster galaxies up to z~0.8. After
discussing the possibility that an overdensity of galaxies coincides -by
chance- with a Planck SZ detection, we confirm that 16 of the candidates have
likely optical counterparts to their SZ signals, 13 (6) of which have an
estimated redshift z>0.5 (z>0.7). The richnesses of these systems are generally
lower than expected given the halo masses estimated from the Planck maps.
However, when we follow a simplistic model to correct for Eddington bias in the
SZ halo mass proxy, the richnesses are consistent with a reference
mass-richness relation established for clusters detected at higher
significance. This illustrates the benefit of an optical follow-up, not only to
obtain redshift estimates, but also to provide an independent mass proxy that
is not based on the same data the clusters are detected with, and thus not
subject to Eddington bias.Comment: 13 pages, 7 figures. Accepted for publication in A&
Conductance switching at the nanoscale of diarylethene derivatives self-assembled monolayers on LaSrMnO
We report on the phosphonic acid route for the grafting of functional
molecules, optical switch (dithienylethene diphosphonic acid, DDA), on
La0.7Sr0.3MnO3 (LSMO). Compact self-assembled monolayers (SAMs) of DDA are
formed on LSMO as studied by topographic atomic force microscopy (AFM),
ellipsometry, water contact angle and X-ray photoemission spectroscopy (XPS).
The conducting AFM measurements show that the electrical conductance of
LSMO/DDA is about 3 decades below that of the bare LSMO substrate. Moreover,
the presence of the DDA SAM suppresses the known conductance switching of the
LSMO substrate that is induced by mechanical and/or bias constraints during
C-AFM measurements. A partial light-induced conductance switching between the
open and closed forms of the DDA is observed for the LSMO/DDA/C-AFM tip
molecular junctions (closed/open conductance ratio of about 8). We show that,
in the case of long-time exposition to UV light, this feature can be masked by
a non-reversible decrease (a factor of about 15) of the conductance of the LSMO
electrode.Comment: Full paper with supporting informatio
Cassini observations of ion and electron beams at Saturn and their relationship to infrared auroral arcs
We present Cassini Visual and Infrared Mapping Spectrometer observations of infrared auroral emissions from the noon sector of Saturn's ionosphere revealing multiple intense auroral arcs separated by dark regions poleward of the main oval. The arcs are interpreted as the ionospheric signatures of bursts of reconnection occurring at the dayside magnetopause. The auroral arcs were associated with upward field-aligned currents, the magnetic signatures of which were detected by Cassini at high planetary latitudes. Magnetic field and particle observations in the adjacent downward current regions showed upward bursts of 100–360 keV light ions in addition to energetic (hundreds of keV) electrons, which may have been scattered from upward accelerated beams carrying the downward currents. Broadband, upward propagating whistler waves were detected simultaneously with the ion beams. The acceleration of the light ions from low altitudes is attributed to wave-particle interactions in the downward current regions. Energetic (600 keV) oxygen ions were also detected, suggesting the presence of ambient oxygen at altitudes within the acceleration region. These simultaneous in situ and remote observations reveal the highly energetic magnetospheric dynamics driving some of Saturn's unusual auroral features. This is the first in situ identification of transient reconnection events at regions magnetically conjugate to Saturn's magnetopause
Connection between low energy effective Hamiltonians and energy level statistics
We study the level statistics of a non-integrable one dimensional interacting
fermionic system characterized by the GOE distribution. We calculate
numerically on a finite size system the level spacing distribution and
the Dyson-Mehta correlation. We observe that its low energy spectrum
follows rather the Poisson distribution, characteristic of an integrable
system, consistent with the fact that the low energy excitations of this system
are described by the Luttinger model. We propose this Random Matrix Theory
analysis as a probe for the existence and integrability of low energy effective
Hamiltonians for strongly correlated systems.Comment: REVTEX, 5 postscript figures at the end of the fil
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