3,495 research outputs found
Locally continuously perfect groups of homeomorphisms
The notion of a locally continuously perfect group is introduced and studied.
This notion generalizes locally smoothly perfect groups introduced by Haller
and Teichmann. Next, we prove that the path connected identity component of the
group of all homeomorphisms of a manifold is locally continuously perfect. The
case of equivariant homeomorphism group and other examples are also considered.Comment: 14 page
Aperiodic invariant continua for surface homeomorphisms
We prove that if a homeomorphism of a closed orientable surface S has no
wandering points and leaves invariant a compact, connected set K which contains
no periodic points, then either K=S and S is a torus, or is the
intersection of a decreasing sequence of annuli. A version for non-orientable
surfaces is given.Comment: 8 pages, to appear in Mathematische Zeitschrif
SELECTED ISSUES AND FEATURES OF UNDERGRADUATE INSTRUCTION IN AGRICULTURAL ECONOMICS
Teaching/Communication/Extension/Profession,
Comparison of the COBE FIRAS and DIRBE Calibrations
We compare the independent FIRAS and DIRBE observations from the COBE in the
wavelength range 100-300 microns. This cross calibration provides checks of
both data sets. The results show that the data sets are consistent within the
estimated gain and offset uncertainties of the two instruments. They show the
possibility of improving the gain and offset determination of DIRBE at 140 and
240 microns.Comment: Accepted for publication in the Astrophysical Journal 11 pages, plus
3 figures in separate postscript files. Figure 3 has three part
First synoptic analysis of volcanic degassing in Papua New Guinea
We report the first satellite-based survey of volcanic sulphur dioxide (SO2) degassing in Papua New Guinea, using Ozone Monitoring Instrument (OMI) data. OMI is sensitive to low-level passive degassing. These observations are useful for volcano monitoring, hazard assessment (particularly aviation hazard) and assessment of arc geochemical budgets and are of immense value in remote regions with little ground-based instrumentation, such as Papua New Guinea. We identify Bagana, Manam, Rabaul, Ulawun and Langila as the active sources of volcanic SO2 in Papua New Guinea, with Bagana being the largest source. We present an OMI SO2 time series for 2005â2008 and a total detected regional output of âŒ1.8 Ă 109 kg SO2. About 40% of emissions were released by major eruption events at Manam (January 2005), Bagana (June 2006) and Rabaul (October 2006). Over the past century however, we estimate that major explosive eruptions contribute <5% of the arc-scale SO2 emission budget. Ground-based DOAS measurements of SO2 degassing at five of Papua New Guinea's volcanoes are compared with our OMI observations. The total OMI SO2 output is only âŒ20% of the total extrapolated from DOAS, a discrepancy which we demonstrate is consistent with other volcanic arcs. Therefore, the true total regional SO2 output may be considerably higher than that detected by OMI. Uncertainties in the OMI SO2 data include the effects of in-plume chemical processing and dilution of SO2 prior to the satellite overpass, OMI's reduced sensitivity to low levels of SO2 in the planetary boundary layer and interference by meteorological clouds
Looking for Pure Rotational H_2 Emission from Protoplanetary Disks
We report on a limited search for pure-rotational molecular hydrogen emission
associated with young, pre-main-sequence stars. We looked for H_2 v=0 J = 3->1
and J = 4->2 emission in the mid-infrared using the Texas Echelon-Cross-Echelle
Spectrograph (TEXES) at NASA's 3m Infrared Telescope Facility. The high
spectral and spatial resolution of our observations lead to more stringent
limits on narrow line emission close to the source than previously achieved.
One star, AB Aur, shows a possible (2sigma) H_2 detection, but further
observations are required to make a confident statement. Our non-detections
suggest that a significant fraction, perhaps all, of previously reported H_2
emission towards these objects could be extended on scales of 5" or more.Comment: 14 pages including 2 figures. Accepted by ApJ Letter
Investigating the Behavior of Sedimentary Mercury (Hg) During BurialâRelated Thermal Maturation
Understanding the behavior of mercury (Hg) in organicârich sediments as they undergo thermal maturation is important, for example, because enrichment of Hg in sedimentary deposits has become a widely used proxy for volcanism from Large Igneous Provinces (LIPs). In this study, we evaluate the effects of such processes on sedimentary Hg concentrations by investigating a common stratigraphic interval in three drill cores with different levels of thermal maturity (immature, mature and postâmature) in Toarcian sediments (Posidonienschiefer Formation) from the Lower Saxony Basin, Germany. We present Hg concentrations, bulk organic geochemistry, and total sulfur data. Mercury concentrations in the mature and postâmature sediments are increased >2âfold relative to the immature material, which is greater than any potential differences in original Hg concentrations in the studied successions prior to burial. Organicâcarbon and hostârock mass loss during thermal maturation may have concentrated Hg in the mature sediments to some extent, provided Hg is considered effectively immobile. The increased Hg, TOCânormalized Hg, and TSânormalized Hg are most likely linked to the âclosed systemâ behavior of Hg in sedimentary basins and the relatively low temperatures (70â260°C) during maturation that resulted in limited Hg mobility. More speculatively, a certain degree of redistribution of Hg within the mature sediments is suggested by its enrichment in distinct stratigraphic levels. Regardless of the exact mechanisms at play, the elevated Hg concentrations in mature sediments amplify both Hg/TOC and Hg/TS, implying that thermal effects must be considered when using normalized Hg as a proxy for farâfield volcanic activity
Use of non-natal estuaries by migratory striped bass (Morone saxatilis) in summer
This paper is not subject to U.S. copyright. The definitive version was published in Fishery Bulletin 107 (2009): 329-338.For most migratory fish,
little is known about the location
and size of foraging areas or how
long individuals remain in foraging
areas, even though these attributes
may affect their growth, survival,
and impact on local prey. We tested
whether striped bass (Morone saxatilis
Walbaum), found in Massachusetts in
summer, were migratory, how long
they stayed in non-natal estuaries,
whether observed spatial patterns
differed from random model predictions,
whether fish returned to the
same area across multiple years, and
whether fishing effort could explain
recapture patterns. Anchor tags were
attached to striped bass that were
caught and released in Massachusetts
in 1999 and 2000, and recaptured
between 1999 and 2007. In
fall, tagged striped bass were caught
south of where they were released in
summer, confirming that fish were
coastal migrants. In the first summer,
77% and 100% of the recaptured fish
in the Great Marsh and along the
Massachusetts coast, respectively,
were caught in the same place where
they were released. About two thirds
of all fish recaptured near where they
were released were caught 2â7 years
after tagging. Our study shows that
smaller (400â500 mm total length)
striped bass migrate hundreds of
kilometers along the Atlantic Ocean
coast, cease their mobile lifestyle in
summer when they use a relatively
localized area for foraging (<20 km2),
and return to these same foraging
areas in subsequent years.This project was administered through the Massachusetts
Cooperative Fish and Wildlife Research Unit. The
Massachusetts Cooperative Fish and Wildlife Research
Unit is an association among the U.S. Geological Survey;
University of Massachusetts Department of Natural
Resources Conservation; Massachusetts Division of
Marine Fisheries; Massachusetts Division of Fisheries
and Wildlife, and the Wildlife Management Institute
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