3,541 research outputs found
Developmental Rate and Longevity of \u3ci\u3eIllinoia Pepperi\u3c/i\u3e (Homoptera: Aphididae) on Excised Blueberry Leaf Disks
The aphid Illinoia pepperi is the vector of blueberry shoestring virus, a serious disease of cultivated high bush blueberry. We present a laboratory study of the developmental rate of I. pepperi on excised blueberry leaf discs at different temperatures from 5 to 29°C. Growth rates were lowest at the upper temperature treatments (26 and 29°) and at 10°C. Growth rate and duration in degree-days for each life stage are presented as well as an overall regression equation for development. The lower developmental threshold was calculated at 3.4°C. The results are being used in a phenological management system and an epidemiological model for predicting spread of blueberry shoestring virus
An Investigation of the Relationships Among Various Language Skills of Freshman English Students at South Dakota State College
The primary objective of this study would be to determine the interrelationships of various language skills. For example, if one skill is more highly related at all others, we might suppose that is could be used as a “core” or pivotal area around which others would be taught. The minor objective of this study would be determine the degree of improvement among students in several skill areas. How much improvement was made? And in what areas did the students improve? However, it would probably be beyond the purpose of this study to offer adequate appraisals of the program
The Anderson model of localization: a challenge for modern eigenvalue methods
We present a comparative study of the application of modern eigenvalue
algorithms to an eigenvalue problem arising in quantum physics, namely, the
computation of a few interior eigenvalues and their associated eigenvectors for
the large, sparse, real, symmetric, and indefinite matrices of the Anderson
model of localization. We compare the Lanczos algorithm in the 1987
implementation of Cullum and Willoughby with the implicitly restarted Arnoldi
method coupled with polynomial and several shift-and-invert convergence
accelerators as well as with a sparse hybrid tridiagonalization method. We
demonstrate that for our problem the Lanczos implementation is faster and more
memory efficient than the other approaches. This seemingly innocuous problem
presents a major challenge for all modern eigenvalue algorithms.Comment: 16 LaTeX pages with 3 figures include
Empirically derived climate predictability over the extratropical northern hemisphere
International audienceA novel application of a technique developed from chaos theory is used in describing seasonal to interannual climate predictability over the Northern Hemisphere (NH). The technique is based on an empirical forecast scheme - local approximation in a reconstructed phase space - for time-series data. Data are monthly 500 hPa heights on a latitude-longitude grid covering the NH from 20° N to the equator. Predictability is estimated based on the linear correlation between actual and predicted heights averaged over a forecast range of one- to twelve.month lead. The method is capable of extracting the major climate signals on this time scale including ENSO and the North Atlantic Oscillation
Measurements with the Chandra X-Ray Observatory's flight contamination monitor
NASA's Chandra X-ray Observatory includes a Flight Contamination Monitor
(FCM), a system of 16 radioactive calibration sources mounted to the inside of
the Observatory's forward contamination cover. The purpose of the FCM is to
verify the ground-to-orbit transfer of the Chandra flux scale, through
comparison of data acquired during the ground calibration with those obtained
in orbit, immediately prior to opening the Observatory's sun-shade door. Here
we report results of these measurements, which place limits on the change in
mirror--detector system response and, hence, on any accumulation of molecular
contamination on the mirrors' iridium-coated surfaces.Comment: 7pages,8figures,for SPIE 4012, paper 7
CMB lensing and primordial squeezed non-Gaussianity
Squeezed primordial non-Gaussianity can strongly constrain early-universe
physics, but it can only be observed on the CMB after it has been
gravitationally lensed. We give a new simple non-perturbative prescription for
accurately calculating the effect of lensing on any squeezed primordial
bispectrum shape, and test it with simulations. We give the generalization to
polarization bispectra, and discuss the effect of lensing on the trispectrum.
We explain why neglecting the lensing smoothing effect does not significantly
bias estimators of local primordial non-Gaussianity, even though the change in
shape can be >~10%. We also show how tau_NL trispectrum estimators can be well
approximated by much simpler CMB temperature modulation estimators, and hence
that there is potentially a ~10-30% bias due to very large-scale lensing modes,
depending on the range of modulation scales included. Including dipole sky
modulations can halve the tau_NL error bar if kinematic effects can be
subtracted using known properties of the CMB temperature dipole. Lensing
effects on the g_NL trispectrum are small compared to the error bar. In
appendices we give the general result for lensing of any primordial bispectrum,
and show how any full-sky squeezed bispectrum can be decomposed into orthogonal
modes of distinct angular dependence.Comment: 22 pages, 6 figures; minor edits to match published versio
Latest results on Jovian disk X-rays from XMM-Newton
We present the results of a spectral study of the soft X-ray emission
(0.2-2.5 keV) from low-latitude (`disk') regions of Jupiter. The data were
obtained during two observing campaigns with XMM-Newton in April and November
2003. While the level of the emission remained approximately the same between
April and the first half of the November observation, the second part of the
latter shows an enhancement by about 40% in the 0.2-2.5 keV flux. A very
similar, and apparently correlated increase, in time and scale, was observed in
the solar X-ray and EUV flux.
The months of October and November 2003 saw a period of particularly intense
solar activity, which appears reflected in the behaviour of the soft X-rays
from Jupiter's disk. The X-ray spectra, from the XMM-Newton EPIC CCD cameras,
are all well fitted by a coronal model with temperatures in the range 0.4-0.5
keV, with additional line emission from Mg XI (1.35 keV) and Si XIII (1.86
keV): these are characteristic lines of solar X-ray spectra at maximum activity
and during flares.
The XMM-Newton observations lend further support to the theory that Jupiter's
disk X-ray emission is controlled by the Sun, and may be produced in large part
by scattering, elastic and fluorescent, of solar X-rays in the upper atmosphere
of the planet.Comment: 17 pages, 7 figures, accepted for publication in a special issue of
Planetary and Space Scienc
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