Biology and ecology of Leptographium species and their vectos as components of loblolly pine decline

Loblolly pine (Pinus taeda L.) decline (LPD) has been present in upland sites of central Alabama since the 1960s. Symptoms of LPD (fine root deterioration, short chlorotic needles, sparse crowns, reduced radial growth) begin in the 30-40 yr age class, resulting in premature death at ages 35-50. Previously, declining loblolly was diagnosed as littleleaf disease (LLD); however, site conditions associated with LPD are different from LLD sites. Littleleaf disease only occurs on eroded, heavy clay soils and is secondarily associated with the fungus, Phytophthora cinnamomi. In contrast, LPD occurs on sandy, well-drained soils and is associated with Leptographium spp., as well as with root-feeding bark beetles and weevils. In the present study, 17 species (eleven newly reported) of subcortical root- and lower-stem feeding beetles were identified as vectors of Leptographium species, of which Hylastes salebrosus, H. tenuis, Hylobius pales and Pachylobius picivorus were statistically more abundant (F3,14=13.90, p=0.003) in LPD sites. Leptographium terebrantis, L. procerum, L. lundbergii, and L. serpens were isolated from the roots and insects. Pathogenicity studies suggested that L. lundbergii and L. serpens, fungi not previously reported in the U.S., were more virulent on loblolly pine. Spatial analysis correlated LPD to site and stand physical factors. Slope and aspect were the predominant predictive variables of LPD in central Alabama. Convexity and elevation were predictive only in combination with other topographical factors. These analyses have allowed the creation of LPD risk maps to accurately predict areas of loblolly decline, providing a vital new tool for managing southern forests for predetermined purposes

Symmetry Decomposition of Chaotic Dynamics

Discrete symmetries of dynamical flows give rise to relations between periodic orbits, reduce the dynamics to a fundamental domain, and lead to factorizations of zeta functions. These factorizations in turn reduce the labor and improve the convergence of cycle expansions for classical and quantum spectra associated with the flow. In this paper the general formalism is developed, with the $N$-disk pinball model used as a concrete example and a series of physically interesting cases worked out in detail.Comment: CYCLER Paper 93mar01

Echoes in classical dynamical systems

Echoes arise when external manipulations to a system induce a reversal of its time evolution that leads to a more or less perfect recovery of the initial state. We discuss the accuracy with which a cloud of trajectories returns to the initial state in classical dynamical systems that are exposed to additive noise and small differences in the equations of motion for forward and backward evolution. The cases of integrable and chaotic motion and small or large noise are studied in some detail and many different dynamical laws are identified. Experimental tests in 2-d flows that show chaotic advection are proposed.Comment: to be published in J. Phys.

High-temperature liquid-mercury cathodes for ion thrusters Quarterly progress report, 1 Dec. 1966 - 28 Feb. 1967

High temperature liquid mercury cathodes for ion thrusters - thermal design analysi

A method to find unstable periodic orbits for the diamagnetic Kepler Problem

A method to determine the admissibility of symbolic sequences and to find the unstable periodic orbits corresponding to allowed symbolic sequences for the diamagnetic Kepler problem is proposed by using the ordering of stable and unstable manifolds. By investigating the unstable periodic orbits up to length 6, a one to one correspondence between the unstable periodic orbits and their corresponding symbolic sequences is shown under the system symmetry decomposition

Semiclassical cross section correlations

We calculate within a semiclassical approximation the autocorrelation function of cross sections. The starting point is the semiclassical expression for the diagonal matrix elements of an operator. For general operators with a smooth classical limit the autocorrelation function of such matrix elements has two contributions with relative weights determined by classical dynamics. We show how the random matrix result can be obtained if the operator approaches a projector onto a single initial state. The expressions are verified in calculations for the kicked rotor.Comment: 6 pages, 2 figure

Cavity Light-Matter Entanglement through Quantum Fluctuations

The hybridization between light and matter forms the basis to achieve cavity control over quantum materials. In this work we investigate a cavity coupled to an XXZ quantum chain of interacting spinless fermions by numerically exact solutions and perturbative analytical expansions. We find two important effects: (i) Specific quantum fluctuations of the matter system play a pivotal role in achieving entanglement between light and matter; and (ii) in turn, light-matter entanglement is the key ingredient to modify electronic properties by the cavity. We hypothesize that quantum fluctuations of those matter operators to which the cavity modes couple are a general prerequisite for light-matter entanglement in the groundstate. Implications of our findings for light-matter-entangled phases, cavity-modified phase transitions in correlated systems, and measurement of light-matter entanglement through Kubo response functions are discussed

Semiclassical Quantization by Pade Approximant to Periodic Orbit Sums

Periodic orbit quantization requires an analytic continuation of non-convergent semiclassical trace formulae. We propose a method for semiclassical quantization based upon the Pade approximant to the periodic orbit sums. The Pade approximant allows the re-summation of the typically exponentially divergent periodic orbit terms. The technique does not depend on the existence of a symbolic dynamics and can be applied to both bound and open systems. Numerical results are presented for two different systems with chaotic and regular classical dynamics, viz. the three-disk scattering system and the circle billiard.Comment: 7 pages, 3 figures, submitted to Europhys. Let