2,609 research outputs found
LEXTALE_CH: A quick, character-based proficiency test for Mandarin Chinese
Research in second language acquisition suggests that objective performance-based assessments may provide more reliable and valid measures of second language proficiency than subjective self-ratings. To measure proficiency in English as a second language, a quick, vocabulary-based test called LexTALE (Lexical Test for Advanced Learners of English) was developed and shown to be able to differentiate between various levels of English proficiency. Following in the line of adaptations of this test for other languages, we created a character-based adaptation for Mandarin Chinese: LEXTALE_CH. In this paper, we discuss the development and validation of LEXTALE_CH in detail. In short, LEXTALE_CH can discriminate between high and low levels of Mandarin proficiency and is sensitive to the significant differences in vocabulary size between native speakers and second language learners of Mandarin; further, it takes only a few minutes to administer and is simple to score, making it a practical tool for low-stakes estimation of Mandarin proficiency.http://www.lingref.com/bucld/42/BUCLD42-09.pdfPublished versio
Perception of nonnative tonal contrasts by Mandarin-English and English-Mandarin sequential bilinguals
This study examined the role of acquisition order and crosslinguistic similarity in influencing transfer at the initial stage of perceptually acquiring a tonal third language (L3). Perception of tones in Yoruba and Thai was tested in adult sequential bilinguals representing three different first (L1) and second language (L2) backgrounds: L1 Mandarin-L2 English (MEBs), L1 English-L2 Mandarin (EMBs), and L1 English-L2 intonational/non-tonal (EIBs). MEBs outperformed EMBs and EIBs in discriminating L3 tonal contrasts in both languages, while EMBs showed a small advantage over EIBs on Yoruba. All groups showed better overall discrimination in Thai than Yoruba, but group differences were more robust in Yoruba. MEBsâ and EMBsâ poor discrimination of certain L3 contrasts was further reflected in the L3 tones being perceived as similar to the same Mandarin tone; however, EIBs, with no knowledge of Mandarin, showed many of the same similarity judgments. These findings thus suggest that L1 tonal experience has a particularly facilitative effect in L3 tone perception, but there is also a facilitative effect of L2 tonal experience. Further, crosslinguistic perceptual similarity between L1/L2 and L3 tones, as well as acoustic similarity between different L3 tones, play a significant role at this early stage of L3 tone acquisition.Published versio
Anisotropy and oblique total transmission at a planar negative-index interface
We show that a class of negative index (n) materials has interesting
anisotropic optical properties, manifest in the effective refraction index that
can be positive, negative, or purely imaginary under different incidence
conditions. With dispersion taken into account, reflection at a planar
negative-index interface exhibits frequency selective total oblique
transmission that is distinct from the Brewster effect.
Finite-difference-time-domain simulation of realistic negative-n structures
confirms the analytic results based on effective indices.Comment: to appear in Phys. Rev.
When a typical jumper skips:Itineraries and staging habitats used by Red Knots (<i>Calidris canutus piersmai</i>) migrating between northwest Australia and the New Siberian Islands
The ecological reasons for variation in avian migration, with some populations migrating across thousands of kilometres between breeding and non-breeding areas with one or few refuelling stops, in contrast to others that stop more often, remain to be pinned down. Red Knots Calidris canutus are a textbook example of a shorebird species that makes long migrations with only a few stops. Recognizing that such behaviours are not necessarily species-specific but determined by ecological context, we here provide a description of the migrations of a relatively recently described subspecies (piersmai). Based on data from tagging of Red Knots on the terminal non-breeding grounds in northwest Australia with 4.5- and 2.5-g solar-powered Platform Terminal Transmitters (PTTs) and 1.0-g geolocators, we obtained information on 19 route-records of 17 individuals, resulting in seven complete return migrations. We confirm published evidence that Red Knots of the piersmai subspecies migrate from NW Australia and breed on the New Siberian Islands in the Russian Arctic and that they stage along the coasts of southeastern Asia, especially in the northern Yellow Sea in China. Red Knots arrived on the tundra breeding grounds from 8 June onwards. Southward departures mainly occurred in the last week of July and the first week of August. We documented six non-stop flights of over c. 5000 km (with a maximum of 6500 km, lasting 6.6 days). Nevertheless, rather than staging at a single location for multiple weeks halfway during migration, piersmai-knots made several stops of up to a week. This was especially evident during northward migration, when birds often stopped along the way in southeast Asia and 'hugged' the coast of China, thus flying an additional 1000-1500 km compared with the shortest possible (great circle route) flights between NW Australia and the Yellow Sea. The birds staged longest in areas in northern China, along the shores of Bohai Bay and upper Liaodong Bay, where the bivalve Potamocorbula laevis, known as a particularly suitable food for Red Knots, was present. The use of multiple food-rich stopping sites during northward migration by piersmai is atypical among subspecies of Red Knots. Although piersmai apparently has the benefit of multiple suitable stopping areas along the flyway, it is a subspecies in decline and their mortality away from the NW Australian non-breeding grounds has been elevated
Derivation of the Effective Chiral Lagrangian for Pseudoscalar Mesons from QCD
We formally derive the chiral Lagrangian for low lying pseudoscalar mesons
from the first principles of QCD considering the contributions from the normal
part of the theory without taking approximations. The derivation is based on
the standard generating functional of QCD in the path integral formalism. The
gluon-field integration is formally carried out by expressing the result in
terms of physical Green's functions of the gluon. To integrate over the
quark-field, we introduce a bilocal auxiliary field Phi(x,y) representing the
mesons. We then develop a consistent way of extracting the local pseudoscalar
degree of freedom U(x) in Phi(x,y) and integrating out the rest degrees of
freedom such that the complete pseudoscalar degree of freedom resides in U(x).
With certain techniques, we work out the explicit U(x)-dependence of the
effective action up to the p^4-terms in the momentum expansion, which leads to
the desired chiral Lagrangian in which all the coefficients contributed from
the normal part of the theory are expressed in terms of certain Green's
functions in QCD. Together with the existing QCD formulae for the anomaly
contributions, the present results leads to the complete QCD definition of the
coefficients in the chiral Lagrangian. The relation between the present QCD
definition of the p^2-order coefficient F_0^2 and the well-known approximate
result given by Pagels and Stokar is discussed.Comment: 16 pages in RevTex, some typos are corrected, version for publication
in Phys. Rev.
Segregation of In to dislocations in InGaN.
Dislocations are one-dimensional topological defects that occur frequently in functional thin film materials and that are known to degrade the performance of InxGa1-xN-based optoelectronic devices. Here, we show that large local deviations in alloy composition and atomic structure are expected to occur in and around dislocation cores in InxGa(1-x)N alloy thin films. We present energy-dispersive X-ray spectroscopy data supporting this result. The methods presented here are also widely applicable for predicting composition fluctuations associated with strain fields in other inorganic functional material thin films.This work was funded in part by the Cambridge Commonwealth trust, St. Johnâs College and
the EPSRC. SKR is funded through the Cambridge-India Partnership Fund and Indian Institute
of Technology Bombay via a scholarship. MAM acknowledges support from the Royal Society
through a University Research Fellowship. Additional support was provided by the EPSRC
through the UK National Facility for Aberration-Corrected STEM (SuperSTEM). The Titan 80-
200kV ChemiSTEMTM was funded through HM Government (UK) and is associated with the
capabilities of the University of Manchester Nuclear Manufacturing (NUMAN) capabilities. SJH
acknowledges funding from the Defence Treat Reduction Agency (DTRA) USA (grant number
HDTRA1-12-1-0013).This is the accepted manuscript. The final version is available at http://pubs.acs.org/doi/abs/10.1021/nl5036513
Journal Staff
We present the first measurements of the differential cross section d sigma/dp(T)(gamma) for the production of an isolated photon in association with at least two b-quark jets. The measurements consider photons with rapidities vertical bar y(gamma)vertical bar < 1.0 and transverse momenta 30 < p(T)(gamma) < 200 GeV. The b-quark jets are required to have p(T)(jet) > 15 GeVand vertical bar y(jet)vertical bar < 1.5. The ratio of differential production cross sections for gamma + 2 b-jets to gamma + b-jet as a function of p(T)(gamma) is also presented. The results are based on the proton-antiproton collision data at root s = 1.96 TeV collected with the D0 detector at the Fermilab Tevatron Collider. The measured cross sections and their ratios are compared to the next- to- leading order perturbative QCD calculations as well as predictions based on the k(T)- factorization approach and those from the sherpa and pythia Monte Carlo event generators
Measurement of the top quark mass using the matrix element technique in dilepton final states
We present a measurement of the top quark mass in ppÂŻ collisions at a center-of-mass energy of 1.96 TeV at the Fermilab Tevatron collider. The data were collected by the D0 experiment corresponding to an integrated luminosity of 9.7ââfbâ1. The matrix element technique is applied to ttÂŻ events in the final state containing leptons (electrons or muons) with high transverse momenta and at least two jets. The calibration of the jet energy scale determined in the lepton+jets final state of ttÂŻ decays is applied to jet energies. This correction provides a substantial reduction in systematic uncertainties. We obtain a top quark mass of mt=173.93±1.84ââGeV
Measurement of Leptonic Asymmetries and Top Quark Polarization in ttbar Production
We present measurements of lepton (l) angular distributions in ttbar -> W+ b
W- b -> l+ nu b l- nubar bbar decays produced in ppbar collisions at a
center-of-mass energy of sqrt(s)=1.96TeV, where l is an electron or muon. Using
data corresponding to an integrated luminosity of 5.4fb^-1, collected with the
D0 detector at the Fermilab Collider, we find that the angular distributions of
l- relative to anti-protons and l+ relative to protons are in agreement with
each other. Combining the two distributions and correcting for detector
acceptance we obtain the forward-backward asymmetry A^l_FB = (5.8 +- 5.1(stat)
+- 1.3(syst))%, compared to the standard model prediction of A^l_FB (predicted)
= (4.7 +- 0.1)%. This result is further combined with the measurement based on
the analysis of the l+jets final state to obtain A^l_FB = (11.8 +- 3.2)%.
Furthermore, we present a first study of the top-quark polarization.Comment: submitted versio
Measurement of the semileptonic charge asymmetry in B0 meson mixing with the D0 detector
We present a measurement of the semileptonic mixing asymmetry for B0 mesons,
a^d_{sl}, using two independent decay channels: B0 -> mu+D-X, with D- ->
K+pi-pi-; and B0 -> mu+D*-X, with D*- -> antiD0 pi-, antiD0 -> K+pi- (and
charge conjugate processes). We use a data sample corresponding to 10.4 fb^{-1}
of ppbar collisions at sqrt(s) = 1.96 TeV, collected with the D0 experiment at
the Fermilab Tevatron collider. We extract the charge asymmetries in these two
channels as a function of the visible proper decay length (VPDL) of the B0
meson, correct for detector-related asymmetries using data-driven methods, and
account for dilution from charge-symmetric processes using Monte Carlo
simulation. The final measurement combines four signal VPDL regions for each
channel, yielding a^d_{sl} = [0.68 \pm 0.45 \text{(stat.)} \pm 0.14
\text{(syst.)}]%. This is the single most precise measurement of this
parameter, with uncertainties smaller than the current world average of B
factory measurements.Comment: Version includes minor textual changes following peer review by
journal, most notably the updating of Ref. [21] to reflect the most recent
publicatio
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