18,678 research outputs found
The neural correlates of phonological short-term memory: A repetitive transcranial magnetic stimulation study
Neuropsychological reports and activation studies by means of positron emission tomography anti functional magnetic resonance imaging have suggested that the neural correlates of phonological short-term memory are located in the left hemisphere, with Brodmann's area (BA) 40 being, responsible for short-term storage and BA 44 for articulatory rehearsal. However, a careful review of the literature on the role of left BA 40 shows that the data are equivocal. We tested We hypotheses by means of repetitive transcranial magnetic stimulation (rTMS). Participants performed four tasks: two phonological judgements, thought to require only articulatory rehearsal Without the contribution of short-term storage digit span, which involves both short-term storage and articudlatory rehearsal: and a pattern span, this last heing the control task. The sites of stimulation were left BA 40. left BA 44 anti the electrode location V-W plus a baseline without TMS. Reaction times increased and accuracy decreased in the case of the phonological judgement and digit span after stimulation of both left sites, suggesting that BA 40, in addition to BA 44. is involved in phonological judgements. Possible explanations are discussed, namely, the possibility that (i) the neural correlates of rehearsal are not limited to BA and (ii) phonological judgements invlove processes other than rehearsal. We also consider the effects of using different tasks and responses to resolve some of the descrepancies in the literature
Constraining axion-nucleon coupling constants from measurements of effective Casimir pressure by means of micromachined oscillator
Stronger constraints on the pseudoscalar coupling constants of an axion to a
proton and a neutron are obtained from an indirect measurement of the effective
Casimir pressure between two Au-coated plates by means of micromechanical
torsional oscillator. For this purpose, the additional effective pressure due
to two-axion exchange is calculated. The role of boundary effects and the
validity region of the proximity force approximation in application to forces
of axion origin are determined. The obtained constraints are up to factors of
380 and 3.15 stronger than those found recently from other laboratory
experiments and are relevant to axion masses from eV to 15eV.Comment: 8 pages, 2 figures, 2 tables; several additions have been made in
accordance with version accepted for publication in Eur. Phys. J.
Evidences of evanescent Bloch waves in Phononic Crystals
We show both experimentally and theoretically the evanescent behaviour of
modes in the Band Gap (BG) of finite Phononic Crystal (PC). Based on
experimental and numerical data we obtain the imaginary part of the wave vector
in good agreement with the complex band structures obtained by the Extended
Plane Wave Expansion (EPWE). The calculated and measured acoustic field of a
localized mode out of the point defect inside the PC presents also evanescent
behaviour. The correct understanding of evanescent modes is fundamental for
designing narrow filters and wave guides based on Phononic Crystals with
defects.Comment: 8 pages, 3 figure
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