9,798 research outputs found
The Role of Opacities in Stellar Pulsation
We examine the role of opacities in stellar pulsation with reference to
Cepheids and RR Lyraes, and examine the effect of augmented opacities on the
theoretical pulsation light curves in key temperature ranges. The temperature
ranges are provided by recent experimental and theoretical work that have
suggested that the iron opacities have been considerably underestimated. For
Cepheids, we find that the augmented opacities have noticeable effects in
certain period ranges (around ) even though there is a
degeneracy with mixing length. We also find significant effects in theoretical
models of B-star pulsators.Comment: 6 pages, 3 Figures, Proceeding for the "Workshop on Astrophysical
Opacities
Chandra Observation of an X-ray Flare at Saturn: Evidence for Direct Solar Control on Saturn's Disk X-ray Emissions
Saturn was observed by Chandra ACIS-S on 20 and 26-27 January 2004 for one
full Saturn rotation (10.7 hr) at each epoch. We report here the first
observation of an X-ray flare from Saturn's non-auroral (low-latitude) disk,
which is seen in direct response to an M6-class flare emanating from a sunspot
that was clearly visible from both Saturn and Earth. Saturn's disk X-ray
emissions are found to be variable on time scales of hours to weeks to months,
and correlated with solar F10.7 cm flux. Unlike Jupiter, X-rays from Saturn's
polar (auroral) region have characteristics similar to those from its disk.
This report, combined with earlier studies, establishes that disk X-ray
emissions of the giant planets Saturn and Jupiter are directly regulated by
processes happening on the Sun. We suggest that these emissions could be
monitored to study X-ray flaring from solar active regions when they are on the
far side and not visible to Near-Earth space weather satellites.Comment: Total 12 pages including 4 figure
Research Notes : United States : Measured and predicted yield response of soybeans to simulated acid rain
Modern soybean cultivars in the U.S. are highly related within the northern and within the southern maturity groups and they trace their genetic constitution to a small number of ancestral lines. On the other hand, there is much less genetic relationship between northern cultivars and southern cultivars. Examples of this can be seen in Figure 1, which shows the ancestral relationships among selected lines and cultivars developed from the northern and southern germplasm pools, respectively
Irradiation of benzene molecules by ion-induced and light-induced intense fields
Benzene, with its sea of delocalized -electrons in the valence orbitals,
is identified as an example of a class of molecules that enable establishment
of the correspondence between intense ion-induced and laser-light-induced
fields in experiments that probe ionization dynamics in temporal regimes
spanning the attosecond and picosecond ranges.Comment: 4 ps figure
Recurrent pneumomediastinum in a patient with rheumatoid arthritis
Recurrent pneumomediastinum in a patient with rheumatoid arthritis. H. Bhardwaj, B. Bhardwaj, P.V. Carlile. Spontaneous pneumomediastinum (SPM); also known as mediastinal emphysema, is a rare and usually benign self-resolving appearance of extraluminal air in the mediastinum without any underlying trigger. This is an uncommon disorder mostly seen in the young males and classic clinical presentation is with chest pain, dyspnea, cough and appearance of subcutaneous emphysema. Although several connective tissue disorders have been reported in association with SPM, it is a rare occurrence in rheumatoid arthritis (RA) with only small number of cases reported in literature. We report a 69 years old male with RA who developed recurrent asymptomatic episodes of SPM detected over a period of one year. The recurrent but benign episodes of SPM in this patient reestablish the usual uncomplicated course of this unusual clinical entity even in the rare recurrent cases
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