4,857 research outputs found
Gallery of Planetary Nebula Spectra
We present the Gallery of Planetary Nebula Spectra now available at
http://oit.williams.edu/nebulae The website offers high-quality, moderate
resolution (~7-10 A FWHM) spectra of 128 Galactic planetary nebulae from
3600-9600 A, obtained by Kwitter, Henry, and colleagues with the Goldcam
spectrograph at the KPNO 2.1-m or with the RC spectrograph at the CTIO 1.5-m.
The master PN table contains atlas data and an image link. A selected object's
spectrum is displayed in a zoomable window; line identification templates are
provided. In addition to the spectra themselves, the website also contains a
brief discussion of PNe as astronomical objects and as contributors to our
understanding of stellar evolution. We envision that this website, which
concentrates a large amount of data in one place, will be of interest to a
variety of users: researchers might need to check the spectrum of a particular
object of interest; the non-specialist astronomer might simply be interested in
perusing such a collection of spectra; and finally, teachers of introductory
astronomy can use this database to illustrate basic principles of atomic
physics and radiation. To particularly encourage this last use, we have
developed two paper-and-pencil exercises to introduce beginning astronomy
students to the wealth of information that PN spectra contain.Comment: Two pages, two figures. Contributed paper to IAU Symp. 234,
``Planetary Nebulae in our Galaxy and Beyond.'
Climigration? Population and climate change in Arctic Alaska
Residents of towns and villages in Arctic Alaska live on “the front line of climate change.” Some communities face immediate threats from erosion and flooding associated with thawing permafrost, increasing river flows, and reduced sea ice protection of shorelines. The term climigration, referring to migration caused by climate change, originally was coined for these places. Although initial applications emphasized the need for government relocation policies, it has elsewhere been applied more broadly to encompass unplanned migration as well. Some historical movements have been attributed to climate change, but closer study tends to find multiple causes, making it difficult to quantify the climate contribution. Clearer attribution might come from comparisons of migration rates among places that are similar in most respects, apart from known climatic impacts. We apply this approach using annual 1990–2014 time series on 43 Arctic Alaska towns and villages. Within-community time plots show no indication of enhanced out-migration from the most at-risk communities. More formally, there is no significant difference between net migration rates of at-risk and other places, testing several alternative classifications. Although climigration is not detectable to date, growing risks make either planned or unplanned movements unavoidable in the near future
Reduce, Reuse, Recycle: Planetary Nebulae as Green Galactic Citizens
We review gas-phase abundances in PNe and describe their dual utility as
archives of original progenitor metallicity via the alpha elements, as well as
sources of processed material from nucleosynthesis during the star's evolution,
i.e., C, N, and s-process elements. We describe the analysis of PN spectra to
derive abundances and discuss the discrepancies that arise from different
choices at each step. Abundance results for the Milky Way and Magellanic Clouds
from various groups of investigators are presented; the observational results
are compared with theoretical predictions of AGB stellar yields. Finally, we
suggest areas where more work is needed to improve our abilities to determine
abundances in PNe.Comment: 8 pages, 7 figures, 1 table. Invited review presented at the IAU
Symposium No. 283, Planetary Nebulae: an Eye to the Futur
The Local Interstellar Ultraviolet Radiation Field
I have used the Hipparcos Input Catalog, together with Kurucz model stellar
atmospheres, and information on the strength of the interstellar extinction, to
create a model of the expected intensity and spectral distribution of the local
interstellar ultraviolet radiation field, under various assumptions concerning
the albedo a of the interstellar grains. (This ultraviolet radiation field is
of particular interest because of the fact that ultraviolet radiation is
capable of profoundly affecting the chemistry of the interstellar medium.) By
comparing my models with the observations, I am able to conclude that the
albedo a of the interstellar grains in the far ultraviolet is very low, perhaps
a = 0.1. I also advance arguments that my present determination of this albedo
is much more reliable than any of the many previous (and conflicting)
ultraviolet interstellar grain albedo determinations. Beyond this, I show that
the ultraviolet background radiation that is observed at high galactic
latitudes must be extragalactic in origin, as it cannot be backscatter of the
interstellar radiation field.Comment: Astrophysical Journal, in press; 9 figures + 16 text page
Increasing Doses of Intraoperative Hydromorphone Do Not Reduce Postoperative Pain
Introduction:
• Intermediate and long acting opioids are given intraoperatively to reduce pain during emergence from anesthesia.
• Recent evidence suggests that intraoperative opioids have inconsistent effects on nociception and pain in the immediate postoperative period.
• Multiple potent, short-acting opioids such as remifentanil, sufentanil and fentanyl have been shown to produce dose-related increases in pain scores and opioid consumption in the immediate postoperative recovery period.
• Intraoperative doses of longer acting opioids such as morphine and methadone6 have been shown to reduce pain scores and narcotic requirements in the immediate postoperative period.
• Hydromorphone is an intermediate duration narcotic which is commonly used intraoperatively but has not been studied for its potential to reduce pain in the immediate postoperative period
- …