792 research outputs found
Exploring a new technique for comparing bilinguals’ L1 and L2 reading speed
Is it possible to tell whether bilinguals are able to read simple text in their two languages equally fluently? Is it thus possible to distinguish balanced bilinguals from unbalanced bilinguals with respect to reading fluency in their first language (L1) and second language (L2)? In this study, we avoided making direct comparisons between L1 and L2 reading speeds, comparing, instead, the amount of inhibition caused by a nonlinguistic, external factor (degraded text visibility). In two tasks, 32 university students read 20 target sentences in L1 Dutch and L2 English, each sentence appearing both in normal and in poorly readable font. Degraded font affected reading times substantially, more so in L2 than in L1, as predicted. However, it was not found that participants with higher L2 proficiency were less affected by degraded font in L2 reading than participants with lower L2 proficiency
Range of orbital angular momenta available for complete fusion between heavy ions
The same compound nucleus, 158Er, has been formed through three different entrance channels, with projectiles 16O, 40Ar and 84Kr. Excitation functions for reactions (HI, 5n) and (HI, 6n) are well fitted by statistical model calculations, provided that a certain window in orbital angular momentum should be taken in order to produce complete fusion in the case of Ar ions and Kr ions. Curiously enough, low l-waves should be avoided. It implies that, during the interaction leading to complete fusion, the energy dissipation by tangential friction should be rather large
Mesure de l'énergie des ions lourds par la méthode des protons projetés
Un dispositif destiné à la mesure de l'énergie des faisceaux d'ions lourds de 3 à 6 MeV/ uma a été construit. Le principe de la méthode est de mesurer l'énergie des protons projetés à zéro degré par collision élastique des ions incidents avec les noyaux d'hydrogène d'une cible de formvar. L'incertitude calculée sur l'énergie ainsi mesurée pour les ions lourds est de + 0,45 %. Des mesures faites sur des faisceaux de 19F et 40Ca d'énergie bien connue, accélérés par un Tandem MP, ont montré un écart maximum de 0,3 % entre les énergies réelles et mesurées. Le dispositif permet de contrôler ou calibrer des méthodes plus lourdes de détermination de l'énergie des ions lourds : déviation magnétique, temps de vol. Il se prête particulièrement bien à la mesure des pertes d'énergie d'ions lourds dans des ralentisseurs solides
Gain properties of dye-doped polymer thin films
Hybrid pumping appears as a promising compromise in order to reach the much
coveted goal of an electrically pumped organic laser. In such configuration the
organic material is optically pumped by an electrically pumped inorganic device
on chip. This engineering solution requires therefore an optimization of the
organic gain medium under optical pumping. Here, we report a detailed study of
the gain features of dye-doped polymer thin films. In particular we introduce
the gain efficiency , in order to facilitate comparison between different
materials and experimental conditions. The gain efficiency was measured with
various setups (pump-probe amplification, variable stripe length method, laser
thresholds) in order to study several factors which modify the actual gain of a
layer, namely the confinement factor, the pump polarization, the molecular
anisotropy, and the re-absorption. For instance, for a 600 nm thick 5 wt\% DCM
doped PMMA layer, the different experimental approaches give a consistent value
80 cm.MW. On the contrary, the usual model predicting the gain
from the characteristics of the material leads to an overestimation by two
orders of magnitude, which raises a serious problem in the design of actual
devices. In this context, we demonstrate the feasibility to infer the gain
efficiency from the laser threshold of well-calibrated devices. Besides,
temporal measurements at the picosecond scale were carried out to support the
analysis.Comment: 15 pages, 17 figure
A deep XMM-Newton X-ray observation of the Chamaeleon I dark cloud
Methods. The northern-eastern fringe of the Chameleon I dark cloud was
observed with XMM-Newton, revisiting a region observed with ROSAT 15 years ago.
Centered on the extended X-ray source CHXR49 we are able to resolve it into
three major contributing components and to analyse their spectral properties.
Furthermore, the deep exposure allows not only the detection of numerous,
previously unknown X-ray sources, but also the investigation of variability and
the study of the X-ray properties for the brighter targets in the field. We use
EPIC spectra, to determine X-ray brightness, coronal temperatures and emission
measures for these sources, compare the properties of classical and weak-line T
Tauri stars and make a comparison with results from the ROSAT observation.
Results. X-ray properties of T Tauri stars in Cha I are presented. The
XMM-Newton images resolve some previously blended X-ray sources, confirm
several possible ones and detect many new X-ray targets, resulting in the most
comprehensive list with 71 X-ray sources in the northern Cha I dark cloud. The
analysis of medium resolution spectra shows an overlapping distribution of
spectral properties for classical and weak-line T Tauri stars, with the X-ray
brighter stars having hotter coronae and a higher L_X/L_bol ratio. X-ray
luminosity correlates with bolometric luminosity, whereas the L_X/L_bol ratio
is slightly lower for the classical T Tauri stars. Large flares as well as a
low iron and a high neon abundance are found in both types of T Tauri stars.
Abundance pattern, plasma temperatures and emission measure distributions
during quiescent phases are attributed toa high level of magnetic activity as
the dominant source of their X-ray emission.Comment: 10 pages, 11 figures, accepted by A&
Direct observation of lithium metal dendrites with ceramic solid electrolyte
Dendrite formation, which could cause a battery short circuit, occurs in batteries that contain lithium metal anodes. In order to suppress dendrite growth, the use of electrolytes with a high shear modulus is suggested as an ionic conductive separator in batteries. One promising candidate for this application is Li7La3Zr2O12 (LLZO) because it has excellent mechanical properties and chemical stability. In this work, in situ scanning electron microscopy (SEM) technique was employed to monitor the interface behavior between lithium metal and LLZO electrolyte during cycling with pressure. Using the obtained SEM images, videos were created that show the inhomogeneous dissolution and deposition of lithium, which induce dendrite growth. The energy dispersive spectroscopy analyses of dendrites indicate the presence of Li, C, and O elements. Moreover, the cross-section mapping comparison of the LLZO shows the inhomogeneous distribution of La, Zr, and C after cycling that was caused by lithium loss near the Li electrode and possible side reactions. This work demonstrates the morphological and chemical evolution that occurs during cycling in a symmetrical Li–Li cell that contains LLZO. Although the superior mechanical properties of LLZO make it an excellent electrolyte candidate for batteries, the further improvement of the electrochemical stabilization of the garnet–lithium metal interface is suggested
Influence of the substrate-induced strain and irradiation disorder on the Peierls transition in TTF-TCNQ microdomains
The influence of the combined effects of substrate-induced strain, finite
size and electron irradiation-induced defects have been studied on individual
micron-sized domains of the organic charge transfer compound
tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) by temperature-dependent
conductivity and current-voltage measurements. The individual domains have been
isolated by focused ion beam etching and electrically contacted by focused ion
and electron beam induced deposition of metallic contacts. The
temperature-dependent conductivity follows a variable range hopping behavior
which shows a crossover of the exponent as the Peierls transition is
approached. The low temperature behavior is analyzed within the segmented rod
model of Fogler, Teber and Shklowskii, as originally developed for a
charge-ordered quasi one-dimensional electron crystal. The results are compared
with data obtained on as-grown and electron irradiated epitaxial TTF-TCNQ thin
films of the two-domain type
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