3,723 research outputs found
The Distribution and Prevalence of the Alfalfa Blotch Leafminer (Diptera: Agromyzidae) in Illinois
Surveys were made in 2001 and 2002 to determine the distribution and prevalence of the alfalfa blotch leafminer, Agromyza frontella (Diptera: Agromyzidae), and its primary parasitoids, Dacnusa dryas and Chrysocharis liriomyzae (Hymenoptera: Braconidae and Eulophidae, respectively), in Illinois. We collected 239 samples from alfalfa fields in the alfalfa-producing regions of Illinois. Samples from each site consisted of 20 cut stems and 10 sets of 10 sweeps in 2001, and 40 stems and 10 sets of 20 sweeps in 2002. Each trifoliate was examined for mining and pinholing injury, and the number of adult A. frontella, D. dryas, and C. liriomyzae per 10 sweeps was calculated for each site. We found that 16.3% of the sites were infested with A. frontella, and all infested fields were north of 39.95 N latitude. Although up to 95% of stems were injured at some sites, mean injury per stem never exceeded 12% of trifoliates. Maximum adult abundance was 8.1 adults per 10 sweeps. We did not detect D. dryas or C. liriomyzae in any of the sweep samples. Because of consistently low populations and the relatively slow rate of A. frontella’s spread in Illinois, we conclude that A. frontella is not a serious threat to alfalfa production in this state at this time
Distribution of an Exotic Pest, \u3ci\u3eAgromyza Frontella\u3c/i\u3e (Diptera: Agromyzidae), in Manitoba, Canada.
Agromyza frontella is an exotic alfalfa pest from Europe that was first detected in North America in 1968 and has since spread westward into Ontario and the north central United States. Informal surveys had detected A. frontella in Manitoba, but its distribution throughout this province was unknown. In 1998 we collected alfalfa stems to detect plant damage and sweep samples to detect adult A. frontella and the parasitoid Dacnusa dryas throughout the alfalfa growing region of Manitoba. In south central Manitoba, 100% of stems were damaged by A. frontella, and\u3e 100 adults/10 sweeps were recorded at several sites. In west central Manitoba, no plants were damaged and \u3c 10 adults/10 sweeps were observed. We believe this region to be near the western edge of A. frontella distribution. The most important introduced parasitoid of A. frontella, D. dryas, was not detected which suggests that D. dryas has not invaded Manitoba
On correlation between protein secondary structure, backbone bond angles, and side-chain orientations
We investigate the fine structure of the sp3 hybridized covalent bond
geometry that governs the tetrahedral architecture around the central
C carbon of a protein backbone, and for this we develop new
visualization techniques to analyze high resolution X-ray structures in Protein
Data Bank. We observe that there is a correlation between the deformations of
the ideal tetrahedral symmetry and the local secondary structure of the
protein. We propose a universal coarse grained energy function to describe the
ensuing side-chain geometry in terms of the C carbon orientations. The
energy function can model the side-chain geometry with a sub-atomic precision.
As an example we construct the C-C structure of HP35 chicken
villin headpiece. We obtain a configuration that deviates less than 0.4 \.A in
root-mean-square distance from the experimental X-ray structure
Elastic Energy and Phase Structure in a Continuous Spin Ising Chain with Applications to the Protein Folding Problem
We present a numerical Monte Carlo analysis of a continuos spin Ising chain
that can describe the statistical proterties of folded proteins. We find that
depending on the value of the Metropolis temperature, the model displays the
three known nontrivial phases of polymers: At low temperatures the model is in
a collapsed phase, at medium temperatures it is in a random walk phase, and at
high temperatures it enters the self-avoiding random walk phase. By
investigating the temperature dependence of the specific energy we confirm that
the transition between the collapsed phase and the random walk phase is a phase
transition, while the random walk phase and self-avoiding random walk phase are
separated from each other by a cross-over transition. We also compare the
predictions of the model to a phenomenological elastic energy formula, proposed
by Huang and Lei to describe folded proteins.Comment: 12 pages, 23 figures, RevTeX 4.
Aging dynamics of ferromagnetic and reentrant spin glass phases in stage-2 CuCCl graphite intercalation compound
Aging dynamics of a reentrant ferromagnet stage-2
CuCoCl graphite intercalation compound has been studied
using DC magnetic susceptibility. This compound undergoes successive
transitions at the transition temperatures ( K) and
( K). The relaxation rate exhibits a
characteristic peak at below . The peak time as a
function of temperature shows a local maximum around 5.5 K, reflecting a
frustrated nature of the ferromagnetic phase. It drastically increases with
decreasing temperature below . The spin configuration imprinted at the
stop and wait process at a stop temperature () during the
field-cooled aging protocol, becomes frozen on further cooling. On reheating,
the memory of the aging at is retrieved as an anomaly of the
thermoremnant magnetization at . These results indicate the occurrence
of the aging phenomena in the ferromagnetic phase () as well
as in the reentrant spin glass phase ().Comment: 9 pages, 9 figures; submitted to Physical Review
The Distribution and Prevalence of the Alfalfa Blotch Leafminer (Diptera: Agromyzidae) in Illinois
Surveys were made in 2001 and 2002 to determine the distribution and prevalence of the alfalfa blotch leafminer, Agromyza frontella (Diptera: Agromyzidae), and its primary parasitoids, Dacnusa dryas and Chrysocharis liriomyzae (Hymenoptera: Braconidae and Eulophidae, respectively), in Illinois. We collected 239 samples from alfalfa fields in the alfalfa-producing regions of Illinois. Samples from each site consisted of 20 cut stems and 10 sets of 10 sweeps in 2001, and 40 stems and 10 sets of 20 sweeps in 2002. Each trifoliate was examined for mining and pinholing injury, and the number of adult A. frontella, D. dryas, and C. liriomyzae per 10 sweeps was calculated for each site. We found that 16.3% of the sites were infested with A. frontella, and all infested fields were north of 39.95 N latitude. Although up to 95% of stems were injured at some sites, mean injury per stem never exceeded 12% of trifoliates. Maximum adult abundance was 8.1 adults per 10 sweeps. We did not detect D. dryas or C. liriomyzae in any of the sweep samples. Because of consistently low populations and the relatively slow rate of A. frontella’s spread in Illinois, we conclude that A. frontella is not a serious threat to alfalfa production in this state at this time
Distribution of an Exotic Pest, \u3ci\u3eAgromyza Frontella\u3c/i\u3e (Diptera: Agromyzidae), in Manitoba, Canada.
Agromyza frontella is an exotic alfalfa pest from Europe that was first detected in North America in 1968 and has since spread westward into Ontario and the north central United States. Informal surveys had detected A. frontella in Manitoba, but its distribution throughout this province was unknown. In 1998 we collected alfalfa stems to detect plant damage and sweep samples to detect adult A. frontella and the parasitoid Dacnusa dryas throughout the alfalfa growing region of Manitoba. In south central Manitoba, 100% of stems were damaged by A. frontella, and\u3e 100 adults/10 sweeps were recorded at several sites. In west central Manitoba, no plants were damaged and \u3c 10 adults/10 sweeps were observed. We believe this region to be near the western edge of A. frontella distribution. The most important introduced parasitoid of A. frontella, D. dryas, was not detected which suggests that D. dryas has not invaded Manitoba
Aging dynamics in reentrant ferromagnet: CuCoCl-FeCl graphite bi-intercalation compound
Aging dynamics of a reentrant ferromagnet
CuCoCl-FeCl graphite bi-intercalation compound has
been studied using AC and DC magnetic susceptibility. This compound undergoes
successive transitions at the transition temperatures ( K) and
( K). The relaxation rate exhibits a characteristic
peak at close to a wait time below , indicating that
the aging phenomena occur in both the reentrant spin glass (RSG) phase below
and the ferromagnetic (FM) phase between and . The
relaxation rate () in the FM phase
exhibits two peaks around and a time much shorter than under
the positive -shift aging, indicating a partial rejuvenation of domains. The
aging state in the FM phase is fragile against a weak magnetic-field
perturbation. The time () dependence of around is well approximated by a stretched exponential relaxation:
. The exponent depends on
, , and . The relaxation time () exhibits a
local maximum around 5 K, reflecting a chaotic nature of the FM phase. It
drastically increases with decreasing temperature below .Comment: 16 pages,16 figures, submitted to Physical Review
Kinetic hindrance during the initial oxidation of Pd(100) at ambient pressures
The oxidation of the Pd(100) surface at oxygen pressures in the 10^-6 to 10^3
mbar range and temperatures up to 1000 K has been studied in-situ by surface
x-ray diffraction (SXRD). The results provide direct structural information on
the phases present in the surface region and on the kinetics of the oxide
formation. Depending on the (T,p) environmental conditions we either observe a
thin sqrt(5) x sqrt(5) R27 surface oxide or the growth of a rough, poorly
ordered bulk oxide film of PdO predominantly with (001) orientation. By either
comparison to the surface phase diagram from first-principles atomistic
thermodynamics or by explicit time-resolved measurements we identify a strong
kinetic hindrance to the bulk oxide formation even at temperatures as high as
675 K.Comment: 4 pages including 4 figures, Related publications can be found at
http://www.fhi-berlin.mpg.de/th/paper.htm
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