8,814 research outputs found
Response to comments on "Differential Sensitivity to Human Communication in Dogs, Wolves, and Human Infants."
The comments by Fiset and Marshall-Pescini et al. raise important methodological issues and propose alternative accounts for our finding of perseverative search errors in dogs. Not denying that attentional processes and local enhancement are involved in such object search tasks, we provide here new evidence and argue that dogsâ behavior is affected by a combination of factors, including specific susceptibility to human communicative signals
The direct evaluation of attosecond chirp from a streaking measurement
We derive an analytical expression, from classical electron trajectories in a
laser field, that relates the breadth of a streaked photoelectron spectrum to
the group-delay dispersion of an isolated attosecond pulse. Based on this
analytical expression, we introduce a simple, efficient and robust procedure to
instantly extract the attosecond pulse's chirp from the streaking measurement.Comment: 4 figure
X,Y,Z-Waves: Extended Structures in Nonlinear Lattices
Motivated by recent experimental and theoretical results on optical X-waves,
we propose a new type of waveforms in 2D and 3D discrete media -- multi-legged
extended nonlinear structures (ENS), built as arrays of lattice solitons (tiles
or stones, in the 2D and 3D cases, respectively). First, we study the stability
of the tiles and stones analytically, and then extend them numerically to
complete ENS forms for both 2D and 3D lattices. The predicted patterns are
relevant to a variety of physical settings, such as Bose-Einstein condensates
in deep optical lattices, lattices built of microresonators, photorefractive
crystals with optically induced lattices (in the 2D case) and others.Comment: 4 pages, 4 figure
Baryon Asymmetry of the Universe without Boltzmann or Kadanoff-Baym
We present a formalism that allows the computation of the baryon asymmetry of
the universe from first principles of statistical physics and quantum field
theory that is applicable to certain types of beyond the Standard Model physics
(such as the neutrino Minimal Standard Model -- MSM) and does not require
the solution of Boltzmann or Kadanoff-Baym equations. The formalism works if a
thermal bath of Standard Model particles is very weakly coupled to a new sector
(sterile neutrinos in the MSM case) that is out-of-equilibrium. The key
point that allows a computation without kinetic equations is that the number of
sterile neutrinos produced during the relevant cosmological period remains
small. In such a case, it is possible to expand the formal solution of the von
Neumann equation perturbatively and obtain a master formula for the lepton
asymmetry expressed in terms of non-equilibrium Wightman functions. The master
formula neatly separates CP-violating contributions from finite temperature
correlation functions and satisfies all three Sakharov conditions. These
correlation functions can then be evaluated perturbatively; the validity of the
perturbative expansion depends on the parameters of the model considered. Here
we choose a toy model (containing only two active and two sterile neutrinos) to
illustrate the use of the formalism, but it could be applied to other models.Comment: 26 pages, 10 figure
Universal Heat Conduction in YBa_2Cu_3O_6.9
The thermal conductivity of YBa_2Cu_3O_6.9 was measured at low temperatures
in untwinned single crystals with concentrations of Zn impurities from 0 to 3%
of Cu. A linear term kappa_0/T = 0.19 mW/K^2.cm is clearly resolved as T -> 0,
and found to be virtually independent of Zn concentration. The existence of
this residual normal fluid strongly validates the basic theory of transport in
unconventional superconductors. Moreover, the observed universal behavior is in
quantitative agreement with calculations for a gap function of d-wave symmetry.Comment: Latex file, 4 pages, 3 EPS figures, to appear in Physical Review
Letter
Experimental phase diagram of moving vortices
In the mixed state of type II superconductors, vortices penetrate the sample
and form a correlated system due to the screening of supercurrents around them.
Interestingly, we can study this correlated system as a function of density and
driving force. The density, for instance, is controlled by the magnetic field,
B, whereas a current density j acts as a driving force F=jxB on all vortices.
The free motion of vortices is inhibited by the presence of an underlying
potential, which tends to pin the vortices. Hence, to minimize the pinning
strength we studied a superconducting glass in which the depinning current is
10 to 1000 times smaller than in previous studies, which enables us to map out
the complete phase diagram in this new regime. The diagram is obtained as a
function of B, driving current and temperature and led a remarkable set of new
results, which includes a huge peak effect, an additional reentrant depinning
phase and a driving force induced pinning phase.Comment: 4 page
Exact Soliton-like Solutions of the Radial Gross-Pitaevskii Equation
We construct exact ring soliton-like solutions of the cylindrically symmetric
(i.e., radial) Gross- Pitaevskii equation with a potential, using the
similarity transformation method. Depending on the choice of the allowed free
functions, the solutions can take the form of stationary dark or bright rings
whose time dependence is in the phase dynamics only, or oscillating and
bouncing solutions, related to the second Painlev\'e transcendent. In each case
the potential can be chosen to be time-independent.Comment: 8 pages, 7 figures. Version 2: stability analysis of the dark
solutio
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Competition Climbing as Serious Leisure
Serious Leisure has received considerable attention in the leisure research for the past forty years. Building on recent efforts to operationalize serious leisure constructs, this study examined the relationship between serious leisure characteristics and rewards in the context of indoor competition climbing, a sport recognized as a potential serious leisure pursuit. The purposes of the study were to validate the 18-item Serious Leisure Inventory Measure (SLIM) as well as the three-factor model of serious leisure proposed by previous researchers. A national sample of 646 indoor competition climbers completed a 59-item survey. Results suggest partial validation of the 18-Item SLIM and a three factor model of serious leisure characteristics and rewards. Serious leisure characteristics significantly, positively contributed to personal and social rewards in the structural model, confirming the relationships and distinctions between these constructs. Further replication and validation of the 18-Item SLIM with different populations is recommended
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Measuring Self-Reported Fidelity in Experiential Education: Exploring the Effectiveness of the Facilitator Characteristics and Program Contributions Scale
Social science researchers have called for evidenced based practices when implementing, delivering, and evaluating programs. One important component of these practices is to monitor program implementation. However, in experiential education and more broadly the social sciences this process is rarely assessed or evaluated; when it is assessed it is frequently resource intensive. As such, program providers have needed an implementation measurement approach more conducive to low-resource organizations. This paper introduces a self-report mechanism to measure facilitator characteristics that contribute to delivering a program as designed. A Confirmatory Factor Analysis of 121 program facilitator responses to the Facilitator Characteristics and Program Contributions Scale (FCPC) indicated that the FCPC is a valid and reliable measure of facilitator characteristics and their pro-fidelity beliefs, and thus may be a promising alternative to other resource intensive approaches to implementation assessment
Angular position of nodes in the superconducting gap of YBCO
The thermal conductivity of a YBCO single crystal has been studied as a
function of the relative orientation of the crystal axes and a magnetic field
rotating in the Cu-O planes. Measurements were carried out at several
temperatures below T_c and at a fixed field of 30 kOe. A four-fold symmetry
characteristic of a superconducting gap with nodes at odd multiples of 45
degrees in k-space was resolved. Experiments were performed to exclude a
possible macroscopic origin for such a four-fold symmetry such as sample shape
or anisotropic pinning. Our results impose an upper limit of 10% on the weight
of the s-wave component of the essentially d-wave superconducting order
parameter of YBCO.Comment: 10 pages, 4 figure
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