2,005 research outputs found
Encouraging the perceptual underdog: positive affective priming of nonpreferred local–global processes
Two experiments examined affective priming of global and local perception. Participants attempted to detect a target that might be present as either a global or a local shape. Verbal primes were used in 1 experiment, and pictorial primes were used in the other. In both experiments, positive primes led to improved performance on the nonpreferred dimension. For participants exhibiting global precedence, detection of local targets was significantly improved, whereas for participants exhibiting local precedence, detection of global targets was significantly improved. The results provide support for an interpretation of the effects of positive affective priming in terms of increased perceptual flexibility
On the existence of finite-energy lumps in classic field theories
We show how the existence of non-trivial finite-energy time-dependent
classical lumps is restricted by a generalized virial theorem. For simple model
Lagrangians, bounds on energies follow.Comment: 4 pages, 1 figure; substantial change
Probing lepton flavour violation in scattering and conversion on nucleons
We study lepton flavour-violating interactions which could result in the
-lepton production in the scattering or in
conversion on nucleons at high energies. Phenomenological bounds on the
strength of interactions are extracted from
the combined result of the NOMAD and CHORUS experiments on searching for
oscillations. Some of these bounds supersede limits
from rare decays. We also propose a ``missing energy'' type experiment
searching for conversion on nucleons. The experiment can be
performed at a present accelerator or at a future neutrino factory.Comment: 13 pages, 4 figure
Percutaneous pulmonary valve implantation in humans - Results in 59 consecutive patients
Background - Right ventricular outflow tract (RVOT) reconstruction with valved conduits in infancy and childhood leads to reintervention for pulmonary regurgitation and stenosis in later life.Methods and Results - Patients with pulmonary regurgitation with or without stenosis after repair of congenital heart disease had percutaneous pulmonary valve implantation (PPVI). Mortality, hemodynamic improvement, freedom from explantation, and subjective and objective changes in exercise tolerance were end points. PPVI was performed successfully in 58 patients, 32 male, with a median age of 16 years and median weight of 56 kg. The majority had a variant of tetralogy of Fallot (n = 36), or transposition of the great arteries, ventricular septal defect with pulmonary stenosis (n = 8). The right ventricular (RV) pressure (64.4 +/- 17.2 to 50.4 +/- 14 mm Hg, P < 0.001), RVOT gradient (33 +/- 24.6 to 19.5 +/- 15.3, P < 0.001), and pulmonary regurgitation ( PR) (grade 2 of greater before, none greater than grade 2 after, P < 0.001) decreased significantly after PPVI. MRI showed significant reduction in PR fraction (21 +/- 13% versus 3 +/- 4%, P < 0.001) and in RV end-diastolic volume (EDV) (94 +/- 28 versus 82 +/- 24 mL (.) beat(-1) (.) m(-2), P < 0.001) and a significant increase in left ventricular EDV ( 64 +/- 12 versus 71 +/- 13 mL (.) beat(-1.) m(-2), P = 0.005) and effective RV stroke volume ( 37 +/- 7 versus 42 +/- 9 mL (.) beat(-1) (.) m(-2), P = 0.006) in 28 patients (age 19 +/- 8 years). A further 16 subjects, on metabolic exercise testing, showed significant improvement in V(O2)max (26 +/- 7 versus 29 +/- 6 mL (.) kg(-1) (.) min(-1), P < 0.001). There was no mortality.Conclusions - PPVI is feasible at low risk, with quantifiable improvement in MRI-defined ventricular parameters and pulmonary regurgitation, and results in subjective and objective improvement in exercise capacity
Charged Particle Multiplicity in Diffractive Deep Inelastic Scattering
The recent data from H1 Collaboration on hadron multiplicity in diffractive
DIS has been studied in the framework of perturbative QCD as a function of
invariant diffractive mass. The formulas obtained explain the observed excess
of particle production in diffractive DIS relative to that in DIS and
annihilation. It is shown that the results are sensitive to the quark--gluon
structure of the Pomeron. Namely, the data say in favour of a super-hard gluon
distribution at the initial scale.Comment: 12 pages, 3 figures; to be published in Phys. Rev.
Time-based selection in complex displays : visual marking does not occur in multi-element asynchronous dynamic (MAD) search
In visual search, a preview benefit occurs when half of the distractor items (the preview set) are presented before the remaining distractor items and the target (the search set). Separating the display across time allows participants to prioritize the search set, leading to increased search efficiency. To date, such time-based selection has been examined using relatively simple types of search displays. However, recent research has shown that when displays better mimic real-world scenes by including a combination of stationary, moving and luminance-changing items (Multi-element Asynchronous Dynamic [MAD] displays), previous search principles reported in the literature no longer apply. In the current work, we examined time-base selection in MAD search conditions. Overall the findings illustrated an advantage for processing new items based on overall RTs but no advantage in terms of search rates. In the absence of a speed–accuracy trade-off no preview benefit emerged when using more complex MAD stimuli
Small-x behavior of the structure function F_2 and its slope partial ln(F_2)/partial ln(1/x) for "frozen" and analytic strong-coupling constants
Using the leading-twist approximation of the Wilson operator product
expansion with "frozen" and analytic versions of the strong-coupling constant,
we show that the Bessel-inspired behavior of the structure function F_2 and its
slope\break partial ln(F_2)/partial ln(1/x) at small values of x, obtained for
a flat initial condition in the DGLAP evolution equations, leads to good
agreement with experimental data of deep-inelastic scattering at DESY HERA.Comment: new curves added to Figs. 1 and 2, minor changes to the text,
accepted for publication in Phys. Lett.
Quark fragmentation functions in a diquark model for proton and hyperon production
A simple quark-diquark model for nucleon and structure is used to
calculate leading twist light-cone fragmentation functions for a quark to
inclusively decay into P or . The parameters of the model are
determined by fitting to the known deep-inelastic structure functions of the
nucleon. When evolved from the initial to the final scale, the calculated
fragmentation functions are in remarkable agreement (for ) with those
extracted from partially inclusive and experiments at high
energies. Predictions are made, using no additional parameters, for
longitudinally and transversely polarized quarks to fragment into p or
.Comment: 15 pages, latex, figures may be obtained by writing to
hafsa%png-qau%[email protected]
Shafranov's virial theorem and magnetic plasma confinement
Shafranov's virial theorem implies that nontrivial magnetohydrodynamical
equilibrium configurations must be supported by externally supplied currents.
Here we extend the virial theorem to field theory, where it relates to
Derrick's scaling argument on soliton stability. We then employ virial
arguments to investigate a realistic field theory model of a two-component
plasma, and conclude that stable localized solitons can exist in the bulk of a
finite density plasma. These solitons entail a nontrivial electric field which
implies that purely magnetohydrodynamical arguments are insufficient for
describing stable, nontrivial structures within the bulk of a plasma.Comment: 9 pages no figure
Novel features of diffraction at the LHC
Interest and problems in the studies of diffraction at LHC are highlighted.
Predictions for the global characteristics of proton-proton interactions at the
LHC energy are given. Potential discoveries of the antishadow scattering mode
and diffractive scattering conjugated with high-- jets are discussed.Comment: 10 pages, 7 figures, journal version, 1 figure added, extended
introductio
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