503,911 research outputs found
Analysis of the vertex with the light-cone QCD sum rules
In this article, we analyze the vertex with the light-cone QCD
sum rules. The strong coupling constant is an important
parameter in evaluating the charmonium absorption cross sections in searching
for the quark-gluon plasmas. Our numerical value for the is
consistent with the prediction of the effective SU(4) symmetry and vector meson
dominance theory.Comment: 6 pages, 1 figure, revised versio
Congener Host Selection by the Pre-Dispersal Seed Predator, \u3ci\u3eApion Rostrum\u3c/i\u3e (Coleoptera: Apionidae)
Apion rostrum Say (Coleoptera: Apionidae) is the major seed predator of the wild indigo congeners, Baptisia alba and B. bracteata in the Russell Kirt Tallgrass Prairie, a reconstructed prairie located at College of DuPage, Illinois. This study, conducted during 2006, investigated factors attracting A. rostrum to each congener. The two Baptisia differ in developmental period, stature, and patterns of dispersion. B. bracteata flowers and initiates pods usually along a single raceme during late spring, and is a shorter plant that grows in clusters. In contrast, B. alba flowers and initiates pods beginning a month after B. bracteata, produces a tall central raceme with often several satellite racemes, and does not grow in dense clusters. Mating and ovipositing A. rostrum were observed on B. bracteata during the first half of June, and with greater abundance on B. alba from early June through mid July. Results of stepwise multiple regression showed a positive relationship of weevil counts per plant to raceme counts per cluster for B. bracteata and to inflated pod counts per plant for B. alba. The developmental synchrony between A. rostrum and pods of B. alba is evidence of a closer evolutionary relationship than the seed predator has with B. bracteata. This can explain the greater number of reproductive weevils seen on B. alba as well as the higher levels of pod infestations
Optimal Control for Holonomic and Nonholonomic Mechanical Systems with Symmetry and Lagrangian Reduction
In this paper we establish necessary conditions for optimal control using the ideas of Lagrangian reduction in the sense of reduction under a symmetry group. The techniques developed
here are designed for Lagrangian mechanical control systems with symmetry. The benefit of such
an approach is that it makes use of the special structure of the system, especially its symmetry
structure and thus it leads rather directly to the desired conclusions for such systems.
Lagrangian reduction can do in one step what one can alternatively do by applying the
Pontryagin Maximum Principle followed by an application of Poisson reduction. The idea of
using Lagrangian reduction in the sense of symmetry reduction was also obtained by Bloch and
Crouch [1995a,b] in a somewhat different context and the general idea is closely related to those
in Montgomery [1990] and Vershik and Gershkovich [1994]. Here we develop this idea further
and apply it to some known examples, such as optimal control on Lie groups and principal
bundles (such as the ball and plate problem) and reorientation examples with zero angular
momentum (such as the satellite with moveable masses). However, one of our main goals is to
extend the method to the case of nonholonomic systems with a nontrivial momentum equation in
the context of the work of Bloch, Krishnaprasad, Marsden and Murray [1995]. The snakeboard
is used to illustrate the method
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