1,916 research outputs found
In situ observations of ClO in the Antarctic: Evidence for chlorine catalyzed destruction of ozone
Results from a series of 12 ER-2 aircraft flights into the Antarctic polar vortex are summarized. These in situ data define the spatial and temporal distribution of ClO as the aircraft flew at an altitude of approx. 18 km from Punta Arenas (54 deg S latitude) to the base of the Palmer Peninsula (72 deg S latitude), executed a rapid descent to approx. 13 km, turned north and climbed bach to approximately 18 km, returning to Punta Arenas. A general pattern in the ClO distribution is reported: mixing ratios of approximately 10 ppt are found at altitude in the vicinity of 55 deg S increasing to 50 ppt at 60 degrees S. In the vicinity of 65 deg S latitude a steep gradient in the ClO mixing ratio is observed. At a fixed potential temperature, the ClO mixing ratio through this sharp transition increases by an order of magnitude within a very few degrees of latitude, thus defining the edge of the chemical containment vessel. From the edge of that containment vessel to the southern extension of the flights, 72 deg S, a dome of slowly increasing ClO best describes the distribution. Conclusion are drawn from the data
Improvements to the Indiana Geological Survey’s Petroleum Database Management System
This poster was presented at the 2011 Annual Meeting of the American Association of Petroleum Geologists, Eastern Section, in Arlington, Virginia, in September 2011.The Indiana Geological Survey’s Petroleum Database Management System (PDMS) is a web application that provides online access to petroleum-related geological information. Since its debut in 2004, the application has been widely used by the petroleum industry, academia, government agencies, and the general public. On June 6, 2011, a significantly enhanced version of the PDMS went online. New features include a robust search menu that permits elaborate queries of more than 74,000 petroleum wells, rapid and convenient online viewing and downloading of PDF-file well reports and both PDF- and TIFF-file geophysical and other well logs, and streamlined menus for easily accessing extensive well data. An interactive, context-driven web help explains every concept or term used.
The PDMS is organized in three main sections. The Well Tables Section includes such information as well location descriptions, completion zones, logs, operators, lease names, tests, reports, hydrocarbon shows, samples, cores, geologic formations and tops, and directional survey data. The Map Viewer Section contains many user-selectable layer options for showing well locations, petroleum fields, producing formations, aerial photographs, and topographic maps. Wells shown in the Map Viewer are hyperlinked to the Well Tables for easy access to the well data. The Fields and Production Section summarizes oil, natural gas, and gas storage field data, including historical oil production volumes in both tables and charts
Temporal trends and transport within and around the Antarctic polar vortex during the formation of the 1987 Antarctic ozone hole
During AAOE in 1987 an ER-2 high altitude aircraft made twelve flights out of Punta Arenas, Chile (53 S, 71 W) into the Antarctic polar vortex. The aircraft was fitted with fast response instruments for in situ measurements of many trace species including O3, ClO, BrO, NO sub y, NO, H2O, and N2O. Grab samples of long-lived tracers were also taken and a scanning microwave radiometer measured temperatures above and below the aircraft. Temperature, pressure, and wind measurements were also made on the flight tracks. Most of these flights were flown to 72 S, at a constant potential temperature, followed by a dip to a lower altitude and again assuming a sometimes different potential temperature for the return leg. The potential temperature chosen was 425 K (17 to 18 km) on 12 of the flight legs, and 5 of the flight legs were flown at 450 K (18 to 19 km). The remaining 7 legs of the 12 flights were not flown on constant potential temperature surfaces. Tracer data have been analyzed for temporal trends. Data from the ascents out of Punta Arenas, the constant potential temperature flight legs, and the dips within the vortex are used to compare tracer values inside and outside the vortex, both with respect to constant potential temperature and constant N2O. The time trend during the one-month period of August 23 through September 22, 1987, shows that ozone decreased by 50 percent or more at altitudes form 15 to 19 km. This trend is evident whether analyzed with respect to constant potential temperature or constant N2O. The trend analysis for ozone outside the vortex shows no downward trend during this period. The analysis for N2O at a constant potential temperature indicates no significant trend either inside or outside the vortex; however, a decrease in N2O with an increase in latitude is evident
Stellar Models with Enhanced Abundances of C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti, in Turn, at Constant Helium and Iron Abundances
Recent work has shown that most globular clusters have at least two
chemically distinct components, as well as cluster-to-cluster differences in
the mean [O/Fe], [Mg/Fe], and [Si/Fe] ratios at similar [Fe/H] values. In order
to investigate the implications of variations in the abundances of these and
other metals for H-R diagrams and predicted ages, grids of evolutionary
sequences have been computed for scaled solar and enhanced alpha-element
mixtures, and for mixtures in which the assumed [m/Fe] value for each of the
metals C, N, O, Ne, Na, Mg, Si, S, Ca, and Ti has been increased, in turn, by
0.4 dex at constant [Fe/H]. These tracks, together with isochrones for ages
from 6 to 14 Gyr, have been computed for -3.0 < [Fe/H] < -0.6, with helium
abundances Y = 0.25, 0.29, and 0.33 at each [Fe/H] value, using upgraded
versions of the Victoria stellar structure program and the Regina interpolation
code, respectively. Turnoff luminosity versus age relations from isochrones are
found to depend almost entirely on the importance of the CNO-cycle, and thereby
mainly on the abundance of oxygen. Since C, N, and O, as well as Ne and S, do
not contribute significantly to the opacities at low temperatures and
densities, variations in their abundances do not impact the Teff scale of red
giants. The latter is a strong function of the abundances of only Mg and Si
(and Fe, possibly to a lesser extent), because they are so abundant and because
they are strong sources of opacity at low temperatures. For these reasons, Mg
and Si also have important effects on the temperatures of main-sequence stars.
Due to their low abundances, Na, Ca, and Ti are of little consequence for
stellar models. The effects of varying the adopted solar metals mix and the
helium abundance at a fixed [Fe/H] are also briefly discussed.Comment: 27 pages, 18 figures; accepted and tentatively scheduled for
publication in ApJ, volume 755 (Aug 10, 2012 issue
Limits on the Optical Brightness of the Epsilon Eridani Dust Ring
The STIS/CCD camera on the {\em Hubble Space Telescope (HST)} was used to
take deep optical images near the K2V main-sequence star Eridani in
an attempt to find an optical counterpart of the dust ring previously imaged by
sub-mm observations. Upper limits for the optical brightness of the dust ring
are determined and discussed in the context of the scattered starlight expected
from plausible dust models. We find that, even if the dust is smoothly
distributed in symmetrical rings, the optical surface brightness of the dust,
as measured with the {\em HST}/STIS CCD clear aperture at 55 AU from the star,
cannot be brighter than about 25 STMAG/". This upper limit excludes some
solid grain models for the dust ring that can fit the IR and sub-mm data.
Magnitudes and positions for 59 discrete objects between 12.5" to 58"
from Eri are reported. Most if not all of these objects are likely
to be background stars and galaxies.Comment: Revision corrects author lis
K-shell photoionization of ground-state Li-like boron ions [B]: Experiment and Theory
Absolute cross sections for the K-shell photoionization of ground-state
Li-like boron [B(1s2s S)] ions were measured by employing the
ion-photon merged-beams technique at the Advanced Light Source synchrotron
radiation facility. The energy ranges 197.5--200.5 eV, 201.9--202.1 eV of the
[1s(2s\,2p)P]P and [1s(2s\,2p)P] P
resonances, respectively, were investigated using resolving powers of up to
17\,600. The energy range of the experiments was extended to about 238.2 eV
yielding energies of the most prominent
[1s(2\,n)]P resonances with an absolute accuracy
of the order of 130 ppm. The natural linewidths of the [1s(2s\,2p)P]
P and [1s(2s\,2p)P] P resonances were measured
to be meV and meV, respectively, which compare
favourably with theoretical results of 4.40 meV and 30.53 meV determined using
an intermediate coupling R-matrix method.Comment: 6 figures and 2 table
The MATHUSLA Test Stand
The rate of muons from LHC collisions reaching the surface above the
ATLAS interaction point is measured and compared with expected rates from
decays of and bosons and - and -quark jets. In addition, data
collected during periods without beams circulating in the LHC provide a
measurement of the background from cosmic ray inelastic backscattering that is
compared to simulation predictions. Data were recorded during 2018 in a 2.5
2.5 6.5~ active volume MATHUSLA test stand detector
unit consisting of two scintillator planes, one at the top and one at the
bottom, which defined the trigger, and six layers of RPCs between them, grouped
into three -measuring layers separated by 1.74 m from each other.
Triggers selecting both upward-going tracks and downward-going tracks were
used.Comment: 18 pages, 11 figures, 1 tabl
Spitzer/IRAC Limits to Planetary Companions of Fomalhaut and epsilon Eridani
Fomalhaut and epsilon Eridani are two young, nearby stars that possess
extended debris disks whose structures suggest the presence of perturbing
planetary objects. With its high sensitivity and stable point spread function,
Spitzer/IRAC is uniquely capable of detecting cool, Jupiter-like planetary
companions whose peak emission is predicted to occur near 4.5 um. We report on
deep IRAC imaging of these two stars, taken at 3.6 and 4.5 um using subarray
mode and in all four channels in wider-field full array mode. Observations
acquired at two different telescope roll angles allowed faint surrounding
objects to be separated from the stellar diffraction pattern. No companion
candidates were detected at the reported position of Fomalhaut b with 3 sigma
model-dependent mass upper limits of 3 MJ (for an age of 200 Myr). Around
epsilon Eridani we instead set a limit of 4 and <1 MJ (1 Gyr model age) at the
inner and outer edge of the sub-millimeter debris ring, respectively. These
results are consistent with non-detections in recent near-infrared imaging
searches, and set the strongest limits to date on the presence of planets
outside epsilon Eridani sub-millimeter ring.Comment: Accepted by The Astrophysical Journal. Request electronic-only plates
to M. Marengo ([email protected]
- …