Interactions Between Fire-Injured Trees and Insects in the Greater Yellowstone Area

After the 1988 Greater Yellowstone Area (GYA) fires, 24 permanent plots were established at 6 sites within 4 different burned areas. The purpose was to evaluate the effects of fire injury on susceptibility to insect attack and tree survival. Mensuration, fire injury, and insect attack data were collected on four species of burned conifers. By July 1991 76 percent of the 125 Douglas-fir had been infested by bark beetles and wood borers; 58 percent of the 151 lodgepole pine were infested; 82 percent of the 17 Engelmann spruce were infested; and 88 percent of the 17 subalpine fir were infested. Fire injury combined with subsequent insect attack resulted in death to 55 percent of the Douglas-fir, 69 percent of the lodgepole pine, 82 percent of the Engelmann spruce, and all of the subalpine fir

An Investigation on Cooling of CZT Co-Planar Grid Detectors

The effect of moderate cooling on CdZnTe semiconductor detectors has been studied for the COBRA experiment. Improvements in energy resolution and low energy threshold were observed and quantified as a function of temperature. Leakage currents are found to contribute typically $\sim$5 keV to the widths of photopeaks.Comment: 14 pages, 9 figures. Accepted for publication in Nuclear Inst. and Methods in Physics Research,

A new intense neutron generator and high-resolution detector for well logging applications

Advances in both ion source and gamma-ray detector technology at LBNL are being used to develop a new high-sensitivity neutron logging instrument. Up to 37 mA of current per 10-20 {mu}s pulse, 80-95% D{sup +}, has been produced by a 2 inch diameter pulsed multicusp ion source. A D-T neutron flux of 10{sup 9}-10{sup 10} n/s is projected from this data. CdZnTe is being developed as a possible gamma-ray detector because of its potential for good energy resolution and efficiency, and ability to operate at room temperature. 3-D time-dependent Monte Carlo calculations show the utility of this system for locating contaminants, especially chlorine-containing solvents, at remediation sites

Interplay between Coulomb Blockade and Resonant Tunneling studied by the Keldysh Green's Function Method

A theory of tunneling through a quantum dot is presented which enables us to study combined effects of Coulomb blockade and discrete energy spectrum of the dot. The expression of tunneling current is derived from the Keldysh Green's function method, and is shown to automatically satisfy the conservation at DC current of both junctions.Comment: 4 pages, 3 figures(mail if you need), use revtex.sty, error corrected, changed titl

Geometrically Induced Multiple Coulomb Blockade Gaps

We have theoretically investigated the transport properties of a ring-shaped array of small tunnel junctions, which is weakly coupled to the drain electrode. We have found that the long range interaction together with the semi-isolation of the array bring about the formation of stable standing configurations of electrons. The stable configurations break up during each transition from odd to even number of trapped electrons, leading to multiple Coulomb blockade gaps in the the $I-V$ characteristics of the system.Comment: 4 Pages (two-columns), 4 Figures, to be published in Physical Review Letter

Bark Beetle and Wood Borer Infestation in the Greater Yellowstone Area During Four Postfire Years

Extensive surveys of bark beetles and wood bores in the Greater Yellowstone area were conducted in 1991 through 1993. The study objectives were to determine the effect of delayed tree mortality following the 1988 fires on mosaics of fire-killed and green tree stands, the relationship between fire injury and subsequent infestation, and the effect of insect buildup in fire injured trees on infestation rates for uninjured trees. Surveys were conducted adjacent to roads, and plots wee selected randomly. In 1991, 321 plots were measured, 198 plots in 1992, and 127 plots in 1993. Insects killed 12.6 percent of the Douglas-fir, 17.9 percent of the lodgepole pine, 6.6 percent of the Engelmann spruce, 7.5 percent of the subalpine fire, and 2.8 percent of the whitebark pine. Delayed mortality attributed to fire injury accounted for more mortality than insects. Both types of mortality greatly altered the original fire-killed/green tree mosaics that were apparent immediately after the 1988 fires. Insect infestation was strongly and positively correlated with the percent of the basal circumference of the tree that was fire killed in the species, except in Engelmann spruce where infestation peaked in the middle fire-injury class. Infestation in Douglas-fir, lodgepole pine, and Engelmann spruce increased through 1992 then declined in 1993. Although it cannot be said with certainty that insects built up in fire-injured trees and then caused increased infestation of uninjured trees, the high level of infestation suggests this is the case

Non Equilibrium Electronic Distribution in Single Electron Devices

The electronic distribution in devices with sufficiently small diemnsions may not be in thermal equilibrium with their surroundings. Systems where the occupancies of electronic states are solely determined by tunneling processes are analyzed. It is shown that the effective temperature of the device may be higher, or lower, than that of its environment, depending on the applied voltage and the energy dependence of the tunneling rates. The I-V characteristics become asymmetric. Comparison with recent experiments is made

Theoretical analysis of quantum dynamics in 1D lattices: Wannier-Stark description

This papers presents a formalism describing the dynamics of a quantum particle in a one-dimensional tilted time-dependent lattice. The description uses the Wannier-Stark states, which are localized in each site of the lattice and provides a simple framework leading to fully-analytical developments. Particular attention is devoted to the case of a time-dependent potential, which results in a rich variety of quantum coherent dynamics is found.Comment: 8 pages, 6 figures, submitted to PR