11,612 research outputs found
Investigation of Porcine Interferons as a metaphylactic intervention strategy against Classical Swine Fever Virus (CSFV)
Populations of Pear Thrips, \u3ci\u3eTaeniothrips Inconsequens\u3c/i\u3e (Thysanoptera: Thripidae) in Sugar Maple Stands in Vermont: 1989-2005
Development of an effective IPM strategy for pear thrips, Taeniothrips inconsequens (Uzel) (Thysanoptera: Thripidae), a pest of sugar maple, Acer saccharum Marshall, demands an understanding of their population fluctuations over time. Pear thrips populations were monitored using a standardized soil sampling method every fall from 1989 – 2005 in 14 counties of Vermont (U.S.). Data from individual sites were combined into north, central and south regions. High numbers of thrips emerged from soil sampled in 1989, 1990, 1993 and 2001, particularly in the north region (Washington, Lamoille, and Franklin counties). The central and south regions had lower pear thrips populations over all years. These results provide, for the first time, fundamental knowledge of pear thrips populations across a wide geographical area of Vermont and will assist in the design of suitable control strategies for pear thrips in the future
Anomalously large capacitance of a plane capacitor with a two-dimensional electron gas
In electronic devices where a two-dimensional electron gas (2DEG) comprises
one or both sides of a plane capacitor, the resulting capacitance can be
larger than the "geometric capacitance" determined by the physical
separation between electrodes. This larger capacitance is known to result
from the Coulomb correlations between individual electrons within the low
density 2DEG, which lead to a negative thermodynamic density of states
(negative compressibility). Experiments on such systems generally operate in
the regime where the average spacing between electrons in the 2DEG
is smaller than , and these experiments observe by only a few
percent. A recent experiment [1], however, has observed larger than
by almost 40% while operating in the regime . In this paper we argue
that at correlations between the electronic charge of opposite
electrodes become important. We develop a theory of the capacitance for the
full range of . We show that, in the absence of disorder, the capacitance
can be times larger than the geometric value, where is the
electron Bohr radius. Our results compare favorably with the experiment of Ref.
[1] without the use of adjustable parameters.Comment: 8 pages, 6 figures; revised discussion of the zero density limit;
some typos fixe
A model of large volumetric capacitance in graphene supercapacitors based on ion clustering
Electric double layer supercapacitors are promising devices for high-power
energy storage based on the reversible absorption of ions into porous,
conducting electrodes. Graphene is a particularly good candidate for the
electrode material in supercapacitors due to its high conductivity and large
surface area. In this paper we consider supercapacitor electrodes made from a
stack of graphene sheets with randomly-inserted "spacer" molecules. We show
that the large volumetric capacitances C > 100 F/cm^3 observed experimentally
can be understood as a result of collective intercalation of ions into the
graphene stack and the accompanying nonlinear screening by graphene electrons
that renormalizes the charge of the ion clusters.Comment: 13 pages, 5 figures; additional discussion and supporting
calculations adde
A Rich Population of X-ray Emitting Wolf-Rayet Stars in the Galactic Starburst Cluster Westerlund 1
Recent optical and IR studies have revealed that the heavily-reddened
starburst cluster Westerlund 1 (Wd 1) contains at least 22 Wolf-Rayet (WR)
stars, comprising the richest WR population of any galactic cluster. We present
results of a senstive Chandra X-ray observation of Wd 1 which detected 12 of
the 22 known WR stars and the mysterious emission line star W9. The fraction of
detected WN stars is nearly identical to that of WC stars. The WN stars WR-A
and WR-B as well as W9 are exceptionally luminous in X-rays and have similar
hard heavily-absorbed spectra with strong Si XIII and S XV emission lines. The
luminous high-temperature X-ray emission of these three stars is characteristic
of colliding wind binary systems but their binary status remains to be
determined. Spectral fits of the X-ray bright sources WR-A and W9 with
isothermal plane-parallel shock models require high absorption column densities
log N = 22.56 (cm) and yield characteristic shock temperatures
kT_shock ~ 3 keV (T ~ 35 MK).Comment: ApJL, 2006, in press (3 figures, 1 table
Hydrogenic Spin Quantum Computing in Silicon: A Digital Approach
We suggest an architecture for quantum computing with spin-pair encoded
qubits in silicon. Electron-nuclear spin-pairs are controlled by a dc magnetic
field and electrode-switched on and off hyperfine interaction. This digital
processing is insensitive to tuning errors and easy to model. Electron
shuttling between donors enables multi-qubit logic. These hydrogenic spin
qubits are transferable to nuclear spin-pairs, which have long coherence times,
and electron spin-pairs, which are ideally suited for measurement and
initialization. The architecture is scalable to highly parallel operation.Comment: 4 pages, 5 figures; refereed and published version with improved
introductio
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