3,693 research outputs found
Habituation to novel visual vestibular environments with special reference to space flight
The etiology of space motion sickness and the underlying physiological mechanisms associated with spatial orientation in a space environment were investigated. Human psychophysical experiments were used as the basis for the research concerning the interaction of visual and vestibular cues in the development of motion sickness. Particular emphasis is placed on the conflict theory in terms of explaining these interactions. Research on the plasticity of the vestibulo-ocular reflex is discussed
Random skew plane partitions with a piecewise periodic back wall
Random skew plane partitions of large size distributed according to an
appropriately scaled Schur process develop limit shapes. In the present work we
consider the limit of large random skew plane partitions where the inner
boundary approaches a piecewise linear curve with non-lattice slopes,
describing the limit shape and the local fluctuations in various regions. This
analysis is fairly similar to that in [OR2], but we do find some new behavior.
For instance, the boundary of the limit shape is now a single smooth (not
algebraic) curve, whereas the boundary in [OR2] is singular. We also observe
the bead process introduced in [B] appearing in the asymptotics at the top of
the limit shape.Comment: 24 pages. This version to appear in Annales Henri Poincar
M.I.T./Canadian Vestibular Experiments on the Spacelab-1 Mission. Part 1: Sensory Adaptation to Weightlessness and Readaptation to One-G: An Overview
Experiments on human spatial orientation were conducted on four crewmembers of Space Shuttle Spacelab Mission 1. The conceptual background of the project, the relationship among the experiments, and their relevance to a 'sensory reinterpretation hypothesis' are presented. Detailed experiment procedures and results are presented in the accompanying papers in this series. The overall findings are discussed as they pertain to the following aspects of hypothesized sensory reinterpretation in weightlessness: (1) utricular otolith afferent signals are reinterpreted as indicating head translation rather than tilt, (2) sensitivity of reflex responses to footward acceleration is reduced, and (3) increased weighting is given to visual and tactile cues in orientation perception and posture control. Results suggest increased weighting of visual cues and reduced weighting of graviceptor signals in weightlessness
Super-rough phase of the random-phase sine-Gordon model: Two-loop results
We consider the two-dimensional random-phase sine-Gordon and study the
vicinity of its glass transition temperature , in an expansion in small
, where denotes the temperature. We derive
renormalization group equations in cubic order in the anharmonicity, and show
that they contain two universal invariants. Using them we obtain that the
correlation function in the super-rough phase for temperature behaves
at large distances as , where the amplitude
is a universal function of temperature
. This result differs at
two-loop order, i.e., , from the prediction based on
results from the "nearly conformal" field theory of a related fermion model. We
also obtain the correction-to-scaling exponent.Comment: 34 page
Vacancy localization in the square dimer model
We study the classical dimer model on a square lattice with a single vacancy
by developing a graph-theoretic classification of the set of all configurations
which extends the spanning tree formulation of close-packed dimers. With this
formalism, we can address the question of the possible motion of the vacancy
induced by dimer slidings. We find a probability 57/4-10Sqrt[2] for the vacancy
to be strictly jammed in an infinite system. More generally, the size
distribution of the domain accessible to the vacancy is characterized by a
power law decay with exponent 9/8. On a finite system, the probability that a
vacancy in the bulk can reach the boundary falls off as a power law of the
system size with exponent 1/4. The resultant weak localization of vacancies
still allows for unbounded diffusion, characterized by a diffusion exponent
that we relate to that of diffusion on spanning trees. We also implement
numerical simulations of the model with both free and periodic boundary
conditions.Comment: 35 pages, 24 figures. Improved version with one added figure (figure
9), a shift s->s+1 in the definition of the tree size, and minor correction
Exact solution of the six-vertex model with domain wall boundary condition. Critical line between ferroelectric and disordered phases
This is a continuation of the papers [4] of Bleher and Fokin and [5] of
Bleher and Liechty, in which the large asymptotics is obtained for the
partition function of the six-vertex model with domain wall boundary
conditions in the disordered and ferroelectric phases, respectively. In the
present paper we obtain the large asymptotics of on the critical line
between these two phases.Comment: 22 pages, 6 figures, to appear in the Journal of Statistical Physic
Eccentric lamellar keratolimbal grafts harvested with a manually guided microkeratome
Background: To perform lamellar keratolimbal allograft transplantation in a one- step procedure with a single graft, we investigated the feasibility of harvesting eccentric lamellar keratolimbal grafts from conventionally processed corneoscleral buttons using a manually guided microkeratome in conjunction with an artificial anterior chamber system. Methods: We used the Moria LSK- One microkeratome and the automated lamellar therapeutic keratoplasty ( ALTK) system ( Antony, France). Ten human donor eyes were used to obtain single- piece lamellar keratolimbal grafts. Specimens were processed for light and electron microscopy. Results: Eccentric keratolimbal grafts could be obtained from all human donor buttons. Grafts include a crescent- shaped limbal and a large corneal portion. No visible damage to the limbal region was discernible. Conclusion: Our data show that the LSK- One microkeratome in conjunction with the ALTK system allows harvesting eccentric keratolimbal grafts from donor corneoscleral buttons. Copyright (c) 2007 S. Karger AG, Basel
The symbiotic star CH Cygni â II. The ejecta from the 1998-2000 active phase
We present Hubble Space Telescope (HST) imaging, a Very Large Array (VLA) radio map (4.74 GHz), optical high-resolution (echelle) spectroscopy and UBV photoelectric photometry of the symbiotic star CH Cyg obtained during its 1998â2000 active phase. The HST imaging, taken during eclipse, shows the central stars are embedded in a nebula extending to 620 ± 150 au for a distance of 270 ± 66 pc. The inner nebula is strongly influenced by the onset of activity and associated outflow in 1998. The surface brightness contours of the contemporaneous radio VLA observation agree well with HST images. Photometric observations of the broad 1999 U-minimum suggest that it is due to the eclipse of the active hot component by the giant on the long-period (14.5 yr) outer orbit. We also find that the onset of the 1998 and the 1992 active periods occur at the same orbital phase of the inner binary. Spectroscopic observations reveal two types of outflow from the active star: a high-velocity (>1200 km sâ1) hot star wind sporadically alternating with a more massive outflow indicated by P-Cygni-like profiles. We present evidence connecting the extended nebulosity with the high-velocity shocked outflow, and hence the activity in the central binary
Testing the Principle of Equivalence by Solar Neutrinos
We discuss the possibility of testing the principle of equivalence with solar
neutrinos. If there exists a violation of the equivalence principle quarks and
leptons with different flavors may not universally couple with gravity. The
method we discuss employs a quantum mechanical phenomenon of neutrino
oscillation to probe into the non-universality of the gravitational couplings
of neutrinos. We develop an appropriate formalism to deal with neutrino
propagation under the weak gravitational fields of the sun in the presence of
the flavor mixing. We point out that solar neutrino observation by the next
generation water Cherenkov detectors can improve the existing bound on
violation of the equivalence principle by 3-4 orders of magnitude if the
nonadiabatic Mikheyev-Smirnov-Wolfenstein mechanism is the solution to the
solar neutrino problem.Comment: Latex, 17 pages + 6 uuencoded postscript figures, KEK-TH-396,
TMUP-HEL-9402 (unnecessary one reference was removed
Monte Carlo study of the hull distribution for the q=1 Brauer model
We study a special case of the Brauer model in which every path of the model
has weight q=1. The model has been studied before as a solvable lattice model
and can be viewed as a Lorentz lattice gas. The paths of the model are also
called self-avoiding trails. We consider the model in a triangle with boundary
conditions such that one of the trails must cross the triangle from a corner to
the opposite side. Motivated by similarities between this model, SLE(6) and
critical percolation, we investigate the distribution of the hull generated by
this trail (the set of points on or surrounded by the trail) up to the hitting
time of the side of the triangle opposite the starting point. Our Monte Carlo
results are consistent with the hypothesis that for system size tending to
infinity, the hull distribution is the same as that of a Brownian motion with
perpendicular reflection on the boundary.Comment: 21 pages, 9 figure
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