369 research outputs found
Impairment of spatial cognitive function with preservation of verbal performance during spatial disorientation
Spatial disorientation, which is responsible for up to 30% of aircraft accidents causes impairment of cognitive function which may further compromise a pilot's ability to think his way out of the situation and regain control [1,]. The functional-anatomical separation of spatial and verbal processing [10,11] raises the possibility of selective interference between the task of resolving spatial disorientation and the ability to perform concurrent spatial, as opposed to verbal, secondary tasks. We report for the first time a degradation of spatial task performance with preservation of verbal performance when subjects in a simulator are disoriented by conflict between self- motion and visual flow in the view of the external environment
Numerical Study of Competing Spin-Glass and Ferromagnetic Order
Two and three dimensional random Ising models with a Gaussian distribution of
couplings with variance and non-vanishing mean value are studied
using the zero-temperature domain-wall renormalization group (DWRG). The DWRG
trajectories in the () plane after rescaling can be collapsed on two
curves: one for and other for . In the first case
the DWRG flows are toward the ferromagnetic fixed point both in two and three
dimensions while in the second case flows are towards a paramagnetic fixed
point and spin-glass fixed point in two and three dimensions respectively. No
evidence for an extra phase is found.Comment: a bit more data is taken, 5 pages, 4 eps figures included, to appear
in PR
Absolute differential cross sections for the electron impact excitation of the 12S → 22S + 22P levels of atomic hydrogen at 50 and 100 eV
Absolute experimental differential cross sections for the electron impact excitation of the 12S → 22S + 22P levels of H at 50 and 100 eV incident energy are obtained using an application of the method of mixtures and available accurate He (n = 2) experimental electron impact excitation differential cross sections. The determination of the number density composition of the mixed beam is made from energy loss measurements of the mixed beam at 200 eV and 25° scattering angle using accurate H and He theoretical differential cross sections obtained from the distorted-wave Born approximation [D. H. Madison (private communication)] and convergent close coupling [I. Bray and A. Stelbovics, Phys. Rev. A 46, 6995 (1992); D. V. Fursa and I. Bray, Phys. Rev. A 52, 1279 (1995)]
Exponents appearing in heterogeneous reaction-diffusion models in one dimension
We study the following 1D two-species reaction diffusion model : there is a
small concentration of B-particles with diffusion constant in an
homogenous background of W-particles with diffusion constant ; two
W-particles of the majority species either coagulate ()
or annihilate () with the respective
probabilities and ; a B-particle and a
W-particle annihilate () with probability 1. The
exponent describing the asymptotic time decay of
the minority B-species concentration can be viewed as a generalization of the
exponent of persistent spins in the zero-temperature Glauber dynamics of the 1D
-state Potts model starting from a random initial condition : the
W-particles represent domain walls, and the exponent
characterizes the time decay of the probability that a diffusive "spectator"
does not meet a domain wall up to time . We extend the methods introduced by
Derrida, Hakim and Pasquier ({\em Phys. Rev. Lett.} {\bf 75} 751 (1995); Saclay
preprint T96/013, to appear in {\em J. Stat. Phys.} (1996)) for the problem of
persistent spins, to compute the exponent in perturbation
at first order in for arbitrary and at first order in
for arbitrary .Comment: 29 pages. The three figures are not included, but are available upon
reques
Dynamics of an Unbounded Interface Between Ordered Phases
We investigate the evolution of a single unbounded interface between ordered
phases in two-dimensional Ising ferromagnets that are endowed with
single-spin-flip zero-temperature Glauber dynamics. We examine specifically the
cases where the interface initially has either one or two corners. In both
examples, the interface evolves to a limiting self-similar form. We apply the
continuum time-dependent Ginzburg-Landau equation and a microscopic approach to
calculate the interface shape. For the single corner system, we also discuss a
correspondence between the interface and the Young tableau that represents the
partition of the integers.Comment: 9 pages, 11 figures, 2-column revtex4 format. V2: references added
and discussion section expanded slightly. Final version for PRE. V3: A few
small additional editorial change
Exploring Triadic Family Relationship Profiles and Their Implications for Adolescents’ Early Substance Initiation
This study examined combinations of warmth and hostility in mother-father-adolescent triadic relationships when adolescents were in 6th grade and associations with adolescent middle school substance initiation. We conducted a latent profile analysis with a sample of 687 two-parent families (52.4% of adolescents were female, mean age = 11.27 at 6th grade). These analyses revealed five profiles of triadic relationships, labeled as: cohesive families (46%, high warmth and low hostility in all three dyads), compensatory families (24%, low interparental warmth but high parent-adolescent warmth), disengaged families (13%, average to low warmth and hostility in three dyads), distressed families (9%, high hostility and low warmth in all three dyads), and conflictual families (8%, high hostility and average warmth in all three dyads). There were significant differences across triadic relationship profiles in rate of alcohol initiation during middle school. Specifically, adolescents in distressed families and conflictual families initiated alcohol at higher rates than adolescents in other types of families. Cohesive families and compensatory families initiated alcohol at the lowest rates among all five types of families. Similar patterns appeared for drunkenness and cigarettes. Implications for family-based interventions to decrease adolescent substance use and future research directions are discussed
Nature of the Spin-glass State in the Three-dimensional Gauge Glass
We present results from simulations of the gauge glass model in three
dimensions using the parallel tempering Monte Carlo technique. Critical
fluctuations should not affect the data since we equilibrate down to low
temperatures, for moderate sizes. Our results are qualitatively consistent with
earlier work on the three and four dimensional Edwards-Anderson Ising spin
glass. We find that large scale excitations cost only a finite amount of energy
in the thermodynamic limit, and that those excitations have a surface whose
fractal dimension is less than the space dimension, consistent with a scenario
proposed by Krzakala and Martin, and Palassini and Young.Comment: 5 pages, 7 figure
Ultrametricity in 3D Edwards-Anderson spin glasses
We perform an accurate test of Ultrametricity in the aging dynamics of the
three dimensional Edwards-Anderson spin glass. Our method consists in
considering the evolution in parallel of two identical systems constrained to
have fixed overlap. This turns out to be a particularly efficient way to study
the geometrical relations between configurations at distant large times. Our
findings strongly hint towards dynamical ultrametricity in spin glasses, while
this is absent in simpler aging systems with domain growth dynamics. A recently
developed theory of linear response in glassy systems allows to infer that
dynamical ultrametricity implies the same property at the level of equilibrium
states.Comment: 4 pages, 5 figure
The Chiral Phase Transition in Dissipative Dynamics
Numerical simulations of the chiral phase transition in the (3+1)dimensional
O(4)-model are presented. The evolutions of the chiral field follow purely
dissipative dynamics, starting from random chirally symmetric initial
configurations down to the true vacuum with spontaneously broken symmetry. The
model stabilizes topological textures which are formed together with domains of
disoriented chiral condensate (DCC) during the roll-down phase. The classically
evolving field acts as source for the emission of pions and mesons.
The exponents of power laws for the growth of angular correlations and for
emission rates are extracted. Fluctuations in the abundance ratios for neutral
and charged pions are compared with those for uncorrelated sources as potential
signature for the chiral phase transition after heavy-ion collisions. It is
found that the presence of stabilizing textures (baryons and antibaryons)
prevents sufficiently rapid growth of DCC-domain size, so observability of
anomalous tails in the abundance ratios is unlikely. However, the transient
formation of growing DCC domains causes sizable broadening of the distributions
as compared to the statistical widths of generic sources.Comment: 28 pages, 8 figure
Disordered Environments in Spatial Games
The Prisoner's dilemma is the main game theoretical framework in which the
onset and maintainance of cooperation in biological populations is studied. In
the spatial version of the model, we study the robustness of cooperation in
heterogeneous ecosystems in spatial evolutionary games by considering site
diluted lattices. The main result is that due to disorder, the fraction of
cooperators in the population is enhanced. Moreover, the system presents a
dynamical transition at , separating a region with spatial chaos from
one with localized, stable groups of cooperators.Comment: 6 pages, 5 figure
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