965 research outputs found
Scattering functions of knotted ring polymers
We discuss the scattering function of a Gaussian random polygon with N nodes
under a given topological constraint through simulation. We obtain the Kratky
plot of a Gaussian polygon of N=200 having a fixed knot for some different
knots such as the trivial, trefoil and figure-eight knots. We find that some
characteristic properties of the different Kratky plots are consistent with the
distinct values of the mean square radius of gyration for Gaussian polygons
with the different knots.Comment: 4pages, 3figures, 3table
Search for long-lived states in antiprotonic lithium
The spectrum of the (L_i^3 + p-bar + 2e) four-body system was calculated in
an adiabatic approach. The two-electron energies were approximated by a sum of
two single-electron effective charge two-center energies as suggested in [6].
While the structure of the spectrum does not exclude the existence of
long-lived states, their experimental observability is still to be clarified
Electron and Photon Energy Deposition in Universe
We consider energy deposition of high energy electrons and photons in
universe. We carry out detailed calculations of fractions of the initial energy
of the injected electron or photon which are used to heat, ionize and excite
background plasma in the early universe for various ionization states and
redshifts.Comment: 21 pages, 12 figure
Convergent variational calculation of positronium-hydrogen-atom scattering lengths
We present a convergent variational basis-set calculational scheme for
elastic scattering of positronium atom by hydrogen atom in S wave. Highly
correlated trial functions with appropriate symmetry are needed for achieving
convergence. We report convergent results for scattering lengths in atomic
units for both singlet () and triplet () states.Comment: 11 pages, 1 postscript figure, Accepted in J. Phys. B (Letter
S-, P- and D-wave resonances in positronium-sodium and positronium-potassium scattering
Scattering of positronium (Ps) by sodium and potassium atoms has been
investigated employing a three-Ps-state coupled-channel model with Ps(1s,2s,2p)
states using a time-reversal-symmetric regularized electron-exchange model
potential fitted to reproduce accurate theoretical results for PsNa and PsK
binding energies. We find a narrow S-wave singlet resonance at 4.58 eV of width
0.002 eV in the Ps-Na system and at 4.77 eV of width 0.003 eV in the Ps-K
system. Singlet P-wave resonances in both systems are found at 5.07 eV of width
0.3 eV. Singlet D-wave structures are found at 5.3 eV in both systems. We also
report results for elastic and Ps-excitation cross sections for Ps scattering
by Na and K.Comment: 9 pages, 5 figures, Accepted in Journal of Physics
Suppression of High Transverse Momentum Spectra in Au+Au Collisions at RHIC
Au+Au, A GeV measurements at RHIC, obtained with the PHENIX,
STAR, PHOBOS and BRAHMS detectors, have all indicated a suppression of neutral
pion production, relative to an appropriately normalized NN level. For central
collisions and vanishing pseudo-rapidity these experiments exhibit suppression
in charged meson production, especially at medium to large transverse momenta.
In the PHENIX experiment similar behavior has been reported for
spectra.
In a recent work on the simpler D+Au interaction, to be considered perhaps as
a tune-up for Au+Au, we reported on a pre-hadronic cascade mechanism which
explains the mixed observation of moderately reduced suppression at
higher pseudo-rapidity as well as the Cronin enhancement at mid-rapidity. Here
we present the extension of this work to the more massive ion-ion collisions.
Our major thesis is that much of the suppression is generated in a late stage
cascade of colourless pre-hadrons produced after an initial short-lived
coloured phase. We present a pQCD argument to justify this approach and to
estimate the time duration of this initial phase. Of essential
importance is the brevity in time of the coloured phase existence relative to
that of the strongly interacting pre-hadron phase. The split into two phases is
of course not sharp in time, but adequate for treating the suppression of
moderate and high mesons.Comment: 19 pages, 10 figure
Semi-Classical Description of Antiproton Capture on Atomic Helium
A semi-classical, many-body atomic model incorporating a momentum-dependent
Heisenberg core to stabilize atomic electrons is used to study antiproton
capture on Helium. Details of the antiproton collisions leading to eventual
capture are presented, including the energy and angular momentum states of
incident antiprotons which result in capture via single or double electron
ionization, i.e. into [He or He], and the
distribution of energy and angular momentum states following the Auger cascade.
These final states are discussed in light of recently reported, anomalously
long-lived antiproton states observed in liquid He.Comment: 15 pages, 9 figures may be obtained from authors, Revte
A Simple Empirically Motivated Template for the Unresolved Thermal Sunyaev-Zeldovich Effect
We develop a model for the power spectrum of unresolved clusters of galaxies
arising from the thermal Sunyaev-Zeldovich (tSZ) effect. The model is based on
a'universal' gas pressure profile constrained by X-ray observations and
includes a parameter to describe departures from self-similar evolution. The
model is consistent with recent Planck observations of the tSZ effect for X-ray
clusters with redshifts z<1 and reproduces the low amplitude for the tSZ
inferred from recent ground based observations. By adjusting two free
parameters, we are able to reproduce the tSZ power spectra from recent
numerical simulations to an accuracy that is well within theoretical
uncertainties. Our model provides a simple, empirically motivated tSZ template
that may be useful for the analysis of new experiments such as Planck.Comment: 6 pages 4 figure
Metacognitive scaffolding boosts cognitive and neural benefits following executive attention training in children
Version of Record online: 25 October 2018Interventions including social scaffolding and metacognitive strategies have been used in
educational settings to promote cognition. In addition, increasing evidence shows that
computerized process-based
training enhances cognitive skills. However, no prior studies
have examined the effect of combining these two training strategies. The goal of this
study was to test the combined effect of metacognitive scaffolding and computer-based
training of executive attention in a sample of typically developing preschoolers at the
cognitive and brain levels. Compared to children in the regular training protocol and an
untrained active control group, children in the metacognitive group showed larger gains
on intelligence and significant increases on an electrophysiological index associated with
conflict processing. Moreover, changes in the conflict-related
brain activity predicted
gains in intelligence in the metacognitive scaffolding group. These results suggest that
metacognitive scaffolding boosts the influence of process-based
training on cognitive
efficiency and brain plasticity related to executive attention.Secretaría de Estado de Investigación,
Desarrollo e Innovación, Grant/Award
Number: PSI2014-55833-
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