3,155 research outputs found
A Case Study in Data Sharing: 211 Helplink and the AIRS XSD
The Coordinated Assistance Network (CAN) helps communities prepare for and respond to disasters. The ability to exchange upâtoâdate information about resources and clients is central to effective response. To facilitate the exchange of resource data, CAN has been working with information & referral organizations, namely 2â1â1s, to ensure that their existing data about community services may be easily and quickly shared with CAN in the event of disaster. CAN has been working with 211 Helplink (San Francisco, California) to develop an exchange using the data standard developed by the Alliance of Information and Referral Systems, AIRS XSD 2.07. The data exchange has failed. The University of Nebraska Public Policy Center and the University of NebraskaâLincoln Department of Computer Science and Engineering agreed to analyze the exports, determine the failure points, and make recommendations for this and future data exchanges
Possible Cosmological Implications of the Quark-Hadron Phase Transition
We study the quark-hadron phase transition within an effective model of QCD,
and find that in a reasonable range of the main parameters of the model, bodies
with quark content between and 10 solar masses can have been formed
in the early universe. In addition, we show that a significant amount of
entropy is released during the transition. This may imply the existence of a
higher baryon number density than what is usually expected at temperatures
above the QCD scale. The cosmological QCD transition may then provide a natural
way for decreasing the high baryon asymmetry created by an Affleck-Dine like
mechanism down to the value required by primordial nucleosynthesis.Comment: 19 pages, LaTeX, 5 Postscript figures included. Submitted to Journal
of Physics
On the nucleon self-energy in nuclear matter
We consider the nucleon self-energy in nuclear matter in the absence of Pauli
blocking. It is evaluated using the partial-wave analysis of scattering
data. Our results are compared with that of a realistic calculation to estimate
the effect of this blocking. It is also possible to use our results as a check
on the realistic calculations.Comment: 6 pages, 2 figure
Predicting the effects of climate change on freshwater cyanobacterial blooms requires consideration of the complete cyanobacterial life cycle
To date, most research on cyanobacterial blooms in freshwater lakes has focused on the pelagic life stage. However, examining the complete cyanobacterial life cycleâincluding benthic life stagesâmay be needed to accurately predict future bloom dynamics. The current expectation, derived from the pelagic life stage, is that blooms will continue to increase due to the warmer temperatures and stronger stratification associated with climate change. However, stratification and mixing have contrasting effects on different life stages: while pelagic cyanobacteria benefit from strong stratification and are adversely affected by mixing, benthic stages can benefit from increased mixing. The net effects of these potentially counteracting processes are not yet known, since most aquatic ecosystem models do not incorporate benthic stages and few empirical studies have tracked the complete life cycle over multiple years. Moreover, for many regions, climate models project both stronger stratification and increased storm-induced mixing in the coming decades; the net effects of those physical processes, even on the pelagic life stage, are not yet understood. We therefore recommend an integrated research agenda to study the dual effects of stratification and mixing on the complete cyanobacterial life cycleâboth benthic and pelagic stagesâusing models, field observations and experiments
Three-pion exchange: a gap in the nucleon-nucleon potential
The leading contribution to the three-pion exchange nucleon-nucleon potential
is calculated in the framework of chiral symmetry. It has pseudoscalar and
axial components and is dominated by the former, which has a range of about 1.5
fm and tends to enhance the OPEP. The strength of this force does not depend on
the pion mass and hence it survives in the chiral limit.Comment: 20 pages, 5 figures, 1 tabl
1953 oil and gas well drilling statistics
Includes The development of underground storage in Ohio, by J.J. Schmidt, K.C. Cottingham and Rotary vs cable tool drilling in Ohio, by Robert L. Alkire
Nucleon-Meson Coupling Constants and Form Factors in the Quark Model
We demonstrate the calculation of the coupling constants and form factors
required by effective hadron lagrangians using the quark model. These relations
follow from equating expressions for strong transition amplitudes in the two
approaches. As examples we derive the NNm nucleon-meson coupling constants and
form factors for m = pi, eta, eta', sigma, a_0, omega and rho, using harmonic
oscillator quark model meson and baryon wavefunctions and the 3P0 decay model;
this is a first step towards deriving a quark-based model of the NN force at
all separations. This technique should be useful in the application of
effective lagrangians to processes in which the lack of data precludes the
direct determination of coupling constants and form factors from experiment.Comment: 7 pages, 4 figures, 1 tabl
Collaborative Understanding of Cyanobacteria in Lake Ecosystems
We describe a collaboration between mathematicians and ecologists studying the cyanobacterium Gloeotrichia echinulata and its possible role in eutrophication of New England lakes. The mathematics includes compartmental modeling, differential equations, difference equations, and testing models against high-frequency data. The ecology includes observation, field sampling, and parameter estimation based on observed data and the related literature. Mathematically and ecologically, a collaboration like this progresses in ways it never would have if either group worked alone
Cyanobacteria as biological drivers of Lake Nitrogen and Phosphorus Cycling
Here we draw attention to the potential for pelagic bloomâforming cyanobacteria to have substantial effects on nutrient cycling and ecosystem resilience across a wide range of lakes. Specifically, we hypothesize that cyanobacterial blooms can influence lake nutrient cycling, resilience, and regime shifts by tapping into pools of nitrogen (N) and phosphorus (P) not usually accessible to phytoplankton. The ability of many cyanobacterial taxa to fix dissolved N2 gas is a wellâknown potential source of N, but some taxa can also access pools of P in sediments and bottom waters. Both of these nutrients can be released to the water column via leakage or mortality, thereby increasing nutrient availability for other phytoplankton and microbes. Moreover, cyanobacterial blooms are not restricted to high nutrient (eutrophic) lakes: blooms also occur in lakes with low nutrient concentrations, suggesting that changes in nutrient cycling and ecosystem resilience mediated by cyanobacteria could affect lakes across a gradient of nutrient concentrations. We used a simple model of coupled N and P cycles to explore the effects of cyanobacteria on nutrient dynamics and resilience. Consistent with our hypothesis, parameters reflecting cyanobacterial modification of N and P cycling alter the number, location, and/or stability of model equilibria. In particular, the model demonstrates that blooms of cyanobacteria in lowânutrient conditions can facilitate a shift to the highânutrient state by reducing the resilience of the lowânutrient state. This suggests that cyanobacterial blooms warrant attention as potential drivers of the transition from a lowânutrient, clearâwater regime to a highânutrient, turbidâwater regime, a prediction of particular concern given that such blooms are reported to be increasing in many regions of the world due in part to global climate change
Spatial and Temporal Variability in Recruitment of the Cyanobacterium Gloeotrichia echinulata in an Oligotrophic Lake
Recruitment from dormant stages in the benthos can provide a critically important inoculum for surface populations of phytoplankton, including bloom-forming cyanobacteria. For example, water-column populations of the large (1â3-mm diameter) colonial cyanobacterium Gloeotrichia echinulata (Smith) P. Richter can be strongly subsidized by benthic recruitment. Therefore, understanding controls on recruitment is essential to an investigation of the factors controlling Gloeotrichiablooms, which are increasing in low-nutrient lakes across northeastern North America. We quantified surface abundances and recruitment from littoral sediments at multiple near-shore sampling sites in oligotrophic Lake Sunapee, New Hampshire, USA, during the summers of 2005â2012 and used this data setâthe longest known record of cyanobacterial recruitmentâto investigate potential drivers of interannual differences in Gloeotrichia recruitment. We found extensive spatiotemporal variability in recruitment. Recruitment was higher at some sites than others, and within seasons, recruitment into replicate traps at the same site was generally more similar than recruitment at different sites. These data suggest that local factors, such as substrate quality or the size of the seed bank, may be important controls on recruitment. Benthic recruitment probably accounted forGloeotrichia recruitment may be related to regional climatic variability
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