827 research outputs found
Echo spectroscopy of bulk Bogoliubov excitations in trapped Bose-Einstein condensates
We propose and demonstrate an echo method to reduce the inhomogeneous
linewidth of Bogoliubov excitations, in a harmonically-trapped Bose-Einstein
condensate. Our proposal includes the transfer of excitations with momentum +q
to -q using a double two photon Bragg process, in which a substantial reduction
of the inhomogeneous broadening is calculated. Furthermore, we predict an
enhancement in the method's efficiency for low momentum due to many-body
effects. The echo can also be implemented by using a four photon process, as is
demonstrated experimentally.Comment: 4 pages, 5 figure
ERPs and task effects in the auditory processing of gender agreement and semantics in French
We investigated task effects on violation ERP responses to Noun-Adjective gender
mismatches and lexical/conceptual semantic mismatches in a combined auditory/visual
paradigm in French. Participants listened to sentences while viewing pictures of objects.
This paradigm was designed to investigate language processing in special populations (e.g.,
children) who may not be able to read or to provide stable behavioral judgment data. Our
main goal was to determine how ERP responses to our target violations might differ
depending on whether participants performed a judgment task (Task) versus listening for
comprehension (No-Task). Characterizing the influence of the presence versus absence of
judgment tasks on violation ERP responses allows us to meaningfully interpret data obtained
using this paradigm without a behavioral task and relate them to judgment-based paradigms
in the ERP literature. We replicated previously observed ERP patterns for semantic and
gender mismatches, and found that the task especially affected the later P600 component
The temporal dynamics of inflected word recognition: a masked ERP priming study of French verbs
Morphological aspects of human language processing have been suggested by some to be
reducible to the combination of orthographic and semantic effects, while others propose that
morphological structure is represented separately from semantics and orthography and
involves distinct neuro-cognitive processing mechanisms. Here we used event-related brain
potentials (ERPs) to investigate semantic, morphological and formal (orthographic)
processing conjointly in a masked priming paradigm. We directly compared morphological to
both semantic and formal/orthographic priming (shared letters) on verbs. Masked priming
was used to reduce strategic effects related to prime perception and to suppress semantic
priming effects. The three types of priming led to distinct ERP and behavioural patterns:
semantic priming was not found, while formal and morphological priming resulted in
diverging ERP patterns. These results are consistent with models of lexical processing that
make reference to morphological structure. We discuss how they fit in with the existing
literature and how unresolved issues could be addressed in further studies
Near-Field Scanning Microwave Microscopy: Measuring Local Microwave Properties and Electric Field Distributions
We describe the near-field microwave microscopy of microwave devices on a
length scale much smaller than the wavelength used for imaging. Our microscope
can be operated in two possible configurations, allowing a quantitative study
of either material properties or local electric fields.Comment: 4 pages, 8 figures, minor corrections to text and 2 figure
Low Power Superconducting Microwave Applications and Microwave Microscopy
We briefly review some non-accelerator high-frequency applications of
superconductors. These include the use of high-Tc superconductors in front-end
band-pass filters in cellular telephone base stations, the High Temperature
Superconductor Space Experiment, and high-speed digital electronics. We also
present an overview of our work on a novel form of near-field scanning
microscopy at microwave frequencies. This form of microscopy can be used to
investigate the microwave properties of metals and dielectrics on length scales
as small as 1 mm. With this microscope we have demonstrated quantitative
imaging of sheet resistance and topography at microwave frequencies. An
examination of the local microwave response of the surface of a heat-treated
bulk Nb sample is also presented.Comment: 11 pages, including 6 figures. Presented at the Eight Workshop on RF
Superconductivity. To appear in Particle Accelerator
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