23,288 research outputs found
Neural mechanisms of response-preparation and inhibition in bilingual and monolingual children: Lateralized Readiness Potentials (LRPs) during a nonverbal Stroop task
Inhibitory control is a core executive function (EF) skill, thought to involve cognitive 'interference suppression' and motor 'response inhibition' sub-processes. A few studies have shown that early bilingualism shapes interference suppression but not response inhibition skills, however current behavioral measures do not fully allow us to disentangle these subcomponents. Lateralized Readiness Potentials (LRPs) are centroparietal event-related potentials (ERPs) that track motor response-preparations between stimulus-presentation and behavioral responses. We examine LRPs elicited during successful inhibitory control on a nonverbal Stroop task, in 6-8 year-old bilingual (n = 44) and monolingual (n = 48) children from comparable socio-economic backgrounds. Relative to monolinguals, bilinguals showed longer and stronger incorrect-response preparations, and a more mature pattern of correct-response preparation (shorter peak-latencies), underlying correct responses on Stroop-interference trials. Neural markers of response-inhibition were comparable between groups and no behavioral differences were found between-groups on the Stroop task. Results suggest group differences in underlying mechanisms of centroparietal motor-response preparation mechanisms in this age group, contrary to what has been shown using behavioral tasks previously. We discuss neural results in the context of speed-accuracy trade-offs. This is the first study to examine neural markers of motor-responses in bilingual children.Published versio
Quark and Gluon Tagging at the LHC
Being able to distinguish light-quark jets from gluon jets on an
event-by-event basis could significantly enhance the reach for many new physics
searches at the Large Hadron Collider. Through an exhaustive search of existing
and novel jet substructure observables, we find that a multivariate approach
can filter out over 95% of the gluon jets while keeping more than half of the
light-quark jets. Moreover, a combination of two simple variables, the charge
track multiplicity and the -weighted linear radial moment (girth), can
achieve similar results. While this pair appears very promising, our study is
only Monte Carlo based, and other discriminants may work better with real data
in a realistic experimental environment. To that end, we explore many other
observables constructed using different jet sizes and parameters, and highlight
those that deserve further theoretical and experimental scrutiny. Additional
information, including distributions of around 10,000 variables, can be found
on this website http://jets.physics.harvard.edu/qvg .Comment: 5 pages, 3 figures. v2 published versio
MMTF: The Maryland-Magellan Tunable Filter
This paper describes the Maryland-Magellan Tunable Filter (MMTF) on the
Magellan-Baade 6.5-meter telescope. MMTF is based on a 150-mm clear aperture
Fabry-Perot (FP) etalon that operates in low orders and provides transmission
bandpass and central wavelength adjustable from ~5 to ~15 A and from ~5000 to
over ~9200 A, respectively. It is installed in the Inamori Magellan Areal
Camera and Spectrograph (IMACS) and delivers an image quality of ~0.5" over a
field of view of 27' in diameter (monochromatic over ~10'). This versatile and
easy-to-operate instrument has been used over the past three years for a wide
variety of projects. This paper first reviews the basic principles of FP
tunable filters, then provides a detailed description of the hardware and
software associated with MMTF and the techniques developed to observe with this
instrument and reduce the data. The main lessons learned in the course of the
commissioning and implementation of MMTF are highlighted next, before
concluding with a brief outlook on the future of MMTF and of similar facilities
which are soon coming on line.Comment: 38 pages, 12 figures, 3 tables, now accepted for publication to the
Astronomical Journa
Searches For New Bosons Coupling To e-q Pairs At HERA And Other Colliders
The early observation at HERA of an excess of events compared to the
expectation from the Standard Model in very short distance
deep-inelastic scattering processes has renewed the interest in the search for
new physics which could manifest in electroweak-like interactions. New
preliminary results from the H1 and ZEUS experiments making use of all
available data are reviewed here, with an emphasis on the search for new
bosons possessing Yukawa couplings to lepton-quark pairs. The sensitivity of
HERA to leptoquarks, and to squarks of R-parity violating supersymmetry, is
confronted to existing indirect constraints from rare and forbidden
semi-leptonic decays, atomic parity violation and neutrinoless double-beta
decay, as well as to direct constraints from LEP and Tevatron colliders. The
HERA and Tevatron colliders are found to offer exciting prospects for new
physics, accessing yet unexplored domains of the mass-coupling plane. Possible
striking manifestation of explicit lepton flavour violation is also discussed.Comment: 27 pages, 16 figures. Proceedings of the WEIN'98 Symposium (June
1998
A Survey for Transient Astronomical Radio Emission at 611 MHz
We have constructed and operated the Survey for Transient Astronomical Radio
Emission (STARE) to detect transient astronomical radio emission at 611 MHz
originating from the sky over the northeastern United States. The system is
sensitive to transient events on timescales of 0.125 s to a few minutes, with a
typical zenith flux density detection threshold of approximately 27 kJy. During
18 months of around-the-clock observing with three geographically separated
instruments, we detected a total of 4,318,486 radio bursts. 99.9% of these
events were rejected as locally generated interference, determined by requiring
the simultaneous observation of an event at all three sites for it to be
identified as having an astronomical origin. The remaining 3,898 events have
been found to be associated with 99 solar radio bursts. These results
demonstrate the remarkably effective RFI rejection achieved by a coincidence
technique using precision timing (such as GPS clocks) at geographically
separated sites. The non-detection of extra-solar bursting or flaring radio
sources has improved the flux density sensitivity and timescale sensitivity
limits set by several similar experiments in the 1970s. We discuss the
consequences of these limits for the immediate solar neighborhood and the
discovery of previously unknown classes of sources. We also discuss other
possible uses for the large collection of 611 MHz monitoring data assembled by
STARE.Comment: 24 pages, 6 figures; to appear in PAS
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