425 research outputs found
Geometric Theory of the Recursion Operators for the Generalized Zakharov-Shabat System in Pole Gauge on the Algebra sl(n,C)
We consider the recursion operator approach to the soliton equations related
to the generalized Zakharov-Shabat system on the algebra sl(n,C) in pole gauge
both in the general position and in the presence of reductions. We present the
recursion operators and discuss their geometric meaning as conjugate to
Nijenhuis tensors for a Poisson-Nijenhuis structure defined on the manifold of
potentials
Impact of age and race on outcomes of a program to prevent excess weight gain and disordered eating in adolescent girls
Interpersonal psychotherapy (IPT) prevents weight gain and reduces loss-of-control (LOC)-eating in adults. However, IPT was not superior to health-education (HE) for preventing excess weight gain and reducing LOC-eating over 1-year in adolescent girls at risk for excess weight gain and eating disorders. Limited data suggest that older and non-White youth may be especially responsive to IPT. In secondary analyses, we examined if age or race moderated weight and LOC-eating outcomes. The 113 participants (12–17 years; 56.6% White) from the original trial were re-contacted 3 years later for assessment. At baseline and follow-up visits through 3 years, we assessed BMI, adiposity by dual energy X-ray absorptiometry, and LOC-eating presence. In linear mixed models, baseline age moderated 3-year BMI outcome; older girls in IPT had the lowest 3-year BMI gain compared to younger girls in IPT and all girls in HE, p = 0.04. A similar pattern was observed for adiposity. Race moderated 3-year LOC-eating; non-White girls in IPT were most likely to abstain from LOC-eating at 3 years compared to all other girls, p = 0.04. This hypothesis-generating analysis suggests future studies should determine if IPT is especially efficacious at reducing LOC-eating in older, non-White adolescents
Fast Two-Robot Disk Evacuation with Wireless Communication
In the fast evacuation problem, we study the path planning problem for two
robots who want to minimize the worst-case evacuation time on the unit disk.
The robots are initially placed at the center of the disk. In order to
evacuate, they need to reach an unknown point, the exit, on the boundary of the
disk. Once one of the robots finds the exit, it will instantaneously notify the
other agent, who will make a beeline to it.
The problem has been studied for robots with the same speed~\cite{s1}. We
study a more general case where one robot has speed and the other has speed
. We provide optimal evacuation strategies in the case that by showing matching upper and lower bounds on the
worst-case evacuation time. For , we show (non-matching)
upper and lower bounds on the evacuation time with a ratio less than .
Moreover, we demonstrate that a generalization of the two-robot search strategy
from~\cite{s1} is outperformed by our proposed strategies for any .Comment: 18 pages, 10 figure
The Generalised Zakharov-Shabat System and the Gauge Group Action
The generalized Zakharov-Shabat systems with complex-valued non-regular
Cartan elements and the systems studied by Caudrey, Beals and Coifman (CBC
systems) and their gauge equivalent are studied. This study includes: the
properties of fundamental analytical solutions (FAS) for the gauge-equivalent
to CBC systems and the minimal set of scattering data; the description of the
class of nonlinear evolutionary equations, solvable by the inverse scattering
method, and the recursion operator, related to such systems; the hierarchies of
Hamiltonian structures. The results are illustrated on the example of the
multi-component nonlinear Schrodinger (MNLS) equations and the corresponding
gauge-equivalent multi-component Heisenberg ferromagnetic (MHF) type models,
related to so(5;C) algebra.Comment: 17 pages, 1 figure, LaTeX. arXiv admin note: substantial text overlap
with arXiv:0710.330
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