8,530 research outputs found
Some Caterpillars Frequently Mistaken for the European Corn Borer
The rapid advance westward of the European corn borer in 1926 has aroused the whole nation, particularly the corn belt states. New infestations were found all thru southern Michigan, across northern Ohio and into six counties in northeastern Indiana. An isolated infestation was discovered in Kankakee County, Illinois, only about 150 miles from Iowa.
A number of caterpillars occurring in Iowa are frequently mistaken for the Eropean corn borer. Some of these are of about the saine size and quite similar in color markings and general appear.ance, while others, even tho they are very different in appearance, cause injury which resembles somewhat the work of the European corn borer. This circular is issued . to acquaint farmers and Iowa people in general with the habits and characters of these caterpillars. By careful consideration of the larval descriptions, the time of appearance, and character of the injury, the European corn borer may be distinguished from most of the caterpillars discussed in this circular. The smartweed borer and the lotus borer are exceptions, because they so closely resemble the European corn borer that it requires an expert and a microscope to identify them with certainty
QED calculation of the n=1 and n=2 energy levels in He-like ions
We perform ab initio QED calculations of energy levels for the and
states of He-like ions with the nuclear charge in the range -100.
The complete set of two-electron QED corrections is evaluated to all orders in
the parameter \aZ. Uncalculated contributions to energy levels come through
orders \alpha^3 (\aZ)^2, \alpha^2 (\aZ)^7, and higher. The calculation
presented is the first treatment for excited states of He-like ions complete
through order \alpha^2 (\aZ)^4. A significant improvement in accuracy of
theoretical predictions is achieved, especially in the high- region.Comment: 23 pages, 5 figure
Controlling Screwworms
A new insect pest - the primary screwworm fly - has been moving into Iowa during recent summers to pester and kill some livestock. Two outbreaks were reported in June this year in southern Iowa and more may follow
Redshifted X-rays from the material accreting onto TW Hya: evidence of a low-latitude accretion spot
High resolution spectroscopy, providing constraints on plasma motions and
temperatures, is a powerful means to investigate the structure of accretion
streams in CTTS. In particular, the accretion shock region, where the accreting
material is heated to temperatures of a few MK as it continues its inward bulk
motion, can be probed by X-ray spectroscopy. To attempt to detect for the first
time the motion of this X-ray-emitting post-shock material, we searched for a
Doppler shift in the deep Chandra/HETGS observation of the CTTS TW Hya. This
test should unveil the nature of this X-ray emitting plasma component in CTTS,
and constrain the accretion stream geometry. We searched for a Doppler shift in
the X-ray emission from TW Hya with two different methods, by measuring the
position of a selected sample of emission lines, and by fitting the whole TW
Hya X-ray spectrum, allowing the line-of-sight velocity to vary. We found that
the plasma at T~2-4 MK has a line-of-sight velocity of 38.3+/-5.1 km/s with
respect to the stellar photosphere. This result definitively confirms that this
X-ray-emitting material originates in the post-shock region, at the base of the
accretion stream, and not in coronal structures. The comparison of the observed
velocity along the line of sight, 38.3+/-5.1 km/s, with the inferred intrinsic
velocity of the post shock of TW Hya, v_post~110-120 km/s, indicates that the
footpoints of the accretion streams on TW Hya are located at low latitudes on
the stellar surface. Our results indicate that complex magnetic field
geometries, such as that of TW Hya, permit low-latitude accretion spots.
Moreover, since on TW Hya the redshift of the soft X-ray emission is very
similar to that of the narrow component of the CIV resonance doublet at 1550
Ang, as found by Ardila et al. (2013), then the plasma at 2-4 MK and that at
0.1 MK likely originate in the same post-shock regions.Comment: Accepted for publication in Astronomy & Astrophysics; 2nd version
after language editor corrections; 16 pages, 8 figures, 6 table
Some Pattern Recognition Challenges in Data-Intensive Astronomy
We review some of the recent developments and challenges posed by the data
analysis in modern digital sky surveys, which are representative of the
information-rich astronomy in the context of Virtual Observatory. Illustrative
examples include the problems of an automated star-galaxy classification in
complex and heterogeneous panoramic imaging data sets, and an automated,
iterative, dynamical classification of transient events detected in synoptic
sky surveys. These problems offer good opportunities for productive
collaborations between astronomers and applied computer scientists and
statisticians, and are representative of the kind of challenges now present in
all data-intensive fields. We discuss briefly some emergent types of scalable
scientific data analysis systems with a broad applicability.Comment: 8 pages, compressed pdf file, figures downgraded in quality in order
to match the arXiv size limi
Long-range interactions of metastable helium atoms
Polarizabilities, dispersion coefficients, and long-range atom-surface
interaction potentials are calculated for the n=2 triplet and singlet states of
helium using highly accurate, variationally determined, wave functions.Comment: RevTeX, epsf, 4 fig
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