540 research outputs found
Bark Beetle-Fire Associations in the Greater Yellowstone Area
The large forest fires in and around Yellowstone National Park in 1988 bring up many ecological questions, including the role of bark beetles. Bark beetles may contribute to fuel buildup over the years preceding a fire, resulting in stand replacement fires. Fire is important to the survival of seral tree species and bark beetles that reproduce in them. Without fire, seral species are ultimately replaced by climax species. Following fire, bark- and wood-boring beetles respond to fire-injured trees. Because of synchrony of the fires and life cycles of the beetles, beetle infestation in 1988 was not observed in fire-injured trees. However, endemic populations of beetles, beetle infestation in 1988 was not observed in fire-injured trees. However, endemic populations of beetles, upon emergence in 1989, infested large numbers of fire-injured trees. Of the trees examined in each species, 28 to 65 percent were infested by bark beetles: Pinus contora (28 percent) by Ips pini:; Pseudotsuga menziesii (32 percent) by Dendroctonus pseudotsugae; Picea engelmannii (65 percent) by Dendroctonus rufipennis; and Abies lasiocarpa (35 percent) by Buprestidae and Cerambycidae. Most trees infested by bark beetles had 50 percent or more of their basal circumference killed by fire. Bark beetle populations probably will increase in the remaining fire-injured trees
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
anti-Tricyclo[4.2.1.12,5]deca-3,7-diene-9-endo,10-endo-diol
The title compound, C10H12O2, was synthesized as a candidate for further functionalization. The asymmetric unit comprises two independent molecules, both of which are situated on a center of symmetry. Both molecules are involved in a network of hydrogen bonding, with each alcohol group participating in one hydrogen bond as a donor and in a second hydrogen bond as an acceptor
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
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
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
A Search for various Double Beta Decay Modes of Cd, Te and Zn Isotopes
Various double beta decay modes of Cd, Zn and Te isotopes are explored with
the help of CdTe and CdZnTe semiconductor detectors. The data set is splitted
in an energy range below 1 MeV having a statistics of 134.5 gd and one
above 1 MeV resulting in 532 gd. No signals were observed in all
channels under investigation. New improved limits for the neutrinoless double
beta decay of Zn70 of (90% CL), the longest
standing limit of all double beta isotopes, and 0EC of Te120 of
(90% CL) are given. For the first time a
limit on the half-life of the 2ECEC of Te of (90% CL) is obtained. In addition, limits on 2ECEC for ground
state transitions of Cd106, Cd108 and Zn64 are improved. The obtained results
even under rough background conditions show the reliability of CdTe
semiconductor detectors for rare nuclear decay searches.Comment: Extended introduction and summar
Charge Solitons in 1-D Arrays of Serially Coupled Josephson Junctions
We study a 1-D array of Josephson coupled superconducting grains with kinetic
inductance which dominates over the Josephson inductance. In this limit the
dynamics of excess Cooper pairs in the array is described in terms of charge
solitons, created by polarization of the grains. We analyze the dynamics of
these topological excitations, which are dual to the fluxons in a long
Josephson junction, using the continuum sine-Gordon model. We find that their
classical relativistic motion leads to saturation branches in the I-V
characteristic of the array. We then discuss the semi-classical quantization of
the charge soliton, and show that it is consistent with the large kinetic
inductance of the array. We study the dynamics of a quantum charge soliton in a
ring-shaped array biased by an external flux through its center. If the
dephasing length of the quantum charge soliton is larger than the circumference
of the array, quantum phenomena like persistent current and coherent current
oscillations are expected. As the characteristic width of the charge soliton is
of the order of 100 microns, it is a macroscopic quantum object. We discuss the
dephasing mechanisms which can suppress the quantum behaviour of the charge
soliton.Comment: 26 pages, LaTex, 7 Postscript figure
Fluctuation theorem for currents and Schnakenberg network theory
A fluctuation theorem is proved for the macroscopic currents of a system in a
nonequilibrium steady state, by using Schnakenberg network theory. The theorem
can be applied, in particular, in reaction systems where the affinities or
thermodynamic forces are defined globally in terms of the cycles of the graph
associated with the stochastic process describing the time evolution.Comment: new version : 16 pages, 1 figure, to be published in Journal of
Statistical Physic
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