903 research outputs found
Characterization of Pallid Sturgeon (\u3ci\u3eScaphirhynchus albus\u3c/i\u3e) Spawning Habitat in the Lower Missouri River
Acipenseriformes (sturgeons and paddlefish) globally have declined throughout their range due to river fragmentation, habitat loss, overfishing, and degradation of water quality. In North America, pallid sturgeon (Scaphirhynchus albus) populations have experienced poor to no recruitment, or substantial levels of hybridization with the closely related shovelnose sturgeon (S. platorynchus). The Lower Missouri River is the only portion of the species’ range where successful reproduction and recruitment of genetically pure pallid sturgeon have been documented. This paper documents spawning habitat and behavior on the Lower Missouri River, which comprises over 1,300 km of unfragmented river habitat. The objective of this study was to determine spawning locations and describe habitat characteristics and environmental conditions (depth, water velocity, substrate, discharge, temperature, and turbidity) on the Lower Missouri River. We measured habitat characteristics for spawning events of ten telemetry-tagged female pallid sturgeon from 2008–2013 that occurred in discrete reaches distributed over hundreds of kilometers. These results show pallid sturgeon select deep and fast areas in or near the navigation channel along outside revetted banks for spawning. These habitats are deeper and faster than nearby river habitats within the surrounding river reach. Spawning patches have a mean depth of 6.6 m and a mean depth-averaged water-column velocity of 1.4 m per second. Substrates in spawning patches consist of coarse bank revetment, gravel, sand, and bedrock. Results indicate habitat used by pallid sturgeon for spawning is more common and widespread in the present-day channelized Lower Missouri River relative to the sparse and disperse coarse substrates available prior to channelization. Understanding the spawning habitats currently utilized on the Lower Missouri River and if they are functioning properly is important for improving habitat remediation measures aimed at increasing reproductive success. Recovery efforts for pallid sturgeon on the Missouri River, if successful, can provide guidance to sturgeon recovery on other river systems; particularly large, regulated, and channelized rivers
Universality of Quantum Entropy for Extreme Black Holes
We consider the extremal limit of a black hole geometry of the
Reissner-Nordstrom type and compute the quantum corrections to its entropy.
Universally, the limiting geometry is the direct product of two 2-dimensional
spaces and is characterized by just a few parameters. We argue that the quantum
corrections to the entropy of such extremal black holes due to a massless
scalar field have a universal behavior. We obtain explicitly the form of the
quantum entropy in this extremal limit as function of the parameters of the
limiting geometry. We generalize these results to black holes with toroidal or
higher genus horizon topologies. In general, the extreme quantum entropy is
completely determined by the spectral geometry of the horizon and in the
ultra-extreme case it is just a determinant of the 2-dimensional Laplacian. As
a byproduct of our considerations we obtain expressions for the quantum entropy
of black holes which are not of the Reissner-Nordstrom type: the extreme
dilaton and extreme Kerr-Newman black holes. In both cases the classical
Bekenstein-Hawking entropy is modified by logarithmic corrections.Comment: 18 pages, latex, no figures, minor changes, to appear in Nucl. Phys.
Four problems with global carbon markets: a critical review
This article offers a critique of global carbon markets and trading, with a special focus on the Clean Development Mechanism of the Kyoto Protocol. It explores
problems with the use of tradable permits to address climate change revolving around four areas: homogeneity, justice, gaming, and information. Homogeneity problems arise from the non-linear nature of climate change and sensitivity of emissions, which complicate attempts to calculate carbon offsets. Justice problems involve issues of dependency and the concentration of wealth among the rich, meaning carbon trading often counteracts attempts to reduce poverty. Gaming problems include pressures to promote high-volume, least-cost projects and the
consequences of emissions leakage. Information problems encompass transaction costs related to carbon trading and market participation and the comparatively weak institutional capacity of project evaluators
Constraints on the Geological History of the Karst System in Southern Missouri, U.S.A. Provided by Radiogenic, Cosmogenic and Physical/Chemical Characteristics of Doline Fill
Območje Ozarkov v južnem Missouriju gradijo predvsem karbonatne, morske, platformne kamnine paleozojske starosti. Teren, ki vsebuje obširen kras, predstavlja kopno že od poznega Paleozojka. Da bi bolje razumeli geološko zgodovino tega kraškega sistema, smo raziskali stratigrafske podatke ohranjene v zapolnitvi velike vrtače pri največjem izviru v okolici. Vzorci zapolnitve iz naravnih izdankov in iz vrtine so bili analizirani s termoluminiscenco (TL) in 10Be kozmogeno metodo. Fizikalno-kemijske značilnosti zapolnitve so bile določene vizualno, z rentgensko metodo in merjenjem velikosti delcev. Podatki vrtine kažejo, da je debelina alohtonega materiala, ki zapolnjuje vrtačo 36,3 m. Ta material prekriva podorne bloke in sedimente debeline vsaj 15,6 m. Glede na teksturo, strukturo in barvo delimo material, ki zapolnjuje vrtačo na 7 con. Analize 10Be koncentracij kažejo, da material za celotni stolpec zapolnitve izvira iz rezidualnega materiala iz srednjega (Illinoian) in zgornjega Pleistocena (Wisconsian). Rentgenske analize glin kažejo, da zapolnitev vrtače vsebuje enake količine kaolinita in illita, kar je skladno z zemeljskim preperevanjem.The Ozark Plateaus region of southern Missouri is underlain by dominantly carbonate marine platform rocks of Paleozoic age. The region has been sub-aerially exposed since the late Paleozoic and is characterized by extensive karst. To better understand the geologic history of this regional karst system, we examined the stratigraphic record preserved in the fill of a large doline near the largest spring in the region. Samples of fill from natural exposures and drill core were analyzed using thermoluminescence (TL) and 10Be cosmogenic techniques, and the physical/chemical characteristics of the fill material were determined by visual inspection, X-ray analyses, and grain-size measurements. Drill-hole data indicate that the allochthonous doline fill is 36.3 m thick and rests on at least 15.6 m of cave breakdown and sediment. The doline fill is divisible into 7 zones. Analysis of 10Be concentrations suggest that the entire doline fill was derived from local residuum during the middle (Illinoian) to late Pleistocene (Wisconsinan). X-ray diffraction analyses of clays throughout the doline fill indicate that they consist of nearly equal amounts of kaolinite and illite, consistent with terrestrial weathering.
T-infinity: The Dependency Inversion Principle for Rapid and Sustainable Multidisciplinary Software Development
The CFD Vision 2030 Study recommends that, NASA should develop and maintain an integrated simulation and software development infrastructure to enable rapid CFD technology maturation.... [S]oftware standards and interfaces must be emphasized and supported whenever possible, and open source models for noncritical technology components should be adopted. The current paper presents an approach to an open source development architecture, named T-infinity, for accelerated research in CFD leveraging the Dependency Inversion Principle to realize plugins that communicate through collections of functions without exposing internal data structures. Steady state flow visualization, mesh adaptation, fluid-structure interaction, and overset domain capabilities are demonstrated through compositions of plugins via standardized abstract interfaces without the need for source code dependencies between disciplines. Plugins interact through abstract interfaces thereby avoiding N 2 direct code-to-code data structure coupling where N is the number of codes. This plugin architecture enhances sustainable development by controlling the interaction between components to limit software complexity growth. The use of T-infinity abstract interfaces enables multidisciplinary application developers to leverage legacy applications alongside newly-developed capabilities. While rein, a description of interface details is deferred until the are more thoroughly tested and can be closed to modification
The Trans-Planckian Problem of Inflationary Cosmology
In most current models of inflation based on a weakly self-coupled scalar
matter field minimally coupled to gravity, the period of inflation lasts so
long that, at the beginning of the inflationary period, the physical
wavelengths of comoving scales which correspond to the present large-scale
structure of the Universe were smaller than the Planck length. Thus, the usual
computations of the spectrum of fluctuations in these models involve
extrapolating low energy physics (both in the matter and gravitational sector)
into regions where this physics is not applicable. In this paper we demonstrate
that the usual predictions of inflation for the spectrum of cosmological
fluctuations do indeed depend on the hidden assumptions about super-Planck
scale physics. We introduce a class of modified dispersion relations to mimic
possible effects of super-Planck scale physics, and show that in some cases
important deviations from the usual predictions of inflation are obtained. Some
implications of this result for the unification of fundamental physics and
early Universe cosmology are discussed.Comment: 16 pages, 2 figures. One important correction in the Corley/Jacobson
case with b_m>0 and some misprints corrected. Version published in PR
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