INSIGHTS INTO GROUNDWATER FLOW PATHS IN AN INTENSIVELY MANAGED CRITICAL ZONE IN NEBRASKA

Glacier Creek, a groundwater-fed stream located in Glacier Creek Preserve (GCP) near Omaha, Nebraska, flows through restored tallgrass prairie and agricultural land (corn-soy rotation) draining a 4 km2 area. The 1 km wide watershed developed on Peoria Loess that overlies Sangamon age glacial till; Glacier Creek itself flows through the glacial till. Previous work concerning land use impacts on solute fluxes indicated a distinct distribution and flux of solutes through restored prairie and agricultural land. Inputs into the subsurface on agricultural land are slow and more concentrated but are diluted by precipitation along shallow flow paths to the north fork of Glacier Creek. In contrast, subsurface flow paths through the restored prairie are more rapid and deeper, leading to less concentrated water in the south fork of Glacier Creek. However, little is known about the subsurface stratigraphy and hydrogeology of the groundwater that provides year-round flow into Glacier Creek. Here we present the initial interpretation of a series of sediment cores and aquifer tests from the ridgetop, midslope, and foot slope topographic positions of agriculture and restored prairie. Sediment cores from the southern, restored prairie portion of GCP show loess overlying glacial till (identified by the appearance of gravel-sized rock fragments). The stratigraphy of the northern, agricultural portion of GCP is much more complex: while loess does overlie glacial till, there are also a series of sandy outwash deposits that cannot be correlated across the landscape. Under both land uses, the local groundwater table lies within the glacial till as referenced by water depth measurements in monitoring wells and gleyed sediments present in cores. Slug tests conducted in ridgetop and foot slope wells indicate that the saturated hydraulic conductivity of the sediments underlying the agricultural land range from two-fold to an order of magnitude greater than those underlying restored prairie, consistent with the presence of sandy layers that conduct water at a quicker rate. Furthermore, the higher flow rates explain why the north fork of Glacier Creek (draining agriculture) produces more water despite being a smaller portion of the watershed. Given these new findings, we modify our conceptual model of subsurface flow at GCP

LOMA: A fast method to generate efficient tagged-random primers despite amplification bias of random PCR on pathogens

10.1186/1471-2105-9-368BMC Bioinformatics9BBMI

Off-shell Behavior of the π ⁣− ⁣η\pi\!-\!\eta Mixing Amplitude

We extend a recent calculation of the momentum dependence of the $\rho-\omega$ mixing amplitude to the pseudoscalar sector. The $\pi\!-\!\eta$ mixing amplitude is calculated in a hadronic model where the mixing is driven by the neutron-proton mass difference. Closed-form analytic expressions are presented in terms of a few nucleon-meson parameters. The observed momentum dependence of the mixing amplitude is strong enough as to question earlier calculations of charge-symmetry-breaking observables based on the on-shell assumption. The momentum dependence of the $\pi\!-\!\eta$ amplitude is, however, practically identical to the one recently predicted for $\rho-\omega$ mixing. Hence, in this model, the ratio of pseudoscalar to vector mixing amplitudes is, to a good approximation, a constant solely determined from nucleon-meson coupling constants. Furthermore, by selecting these parameters in accordance with charge-symmetry-conserving data and SU(3)-flavor symmetry, we reproduce the momentum dependence of the $\pi\!-\!\eta$ mixing amplitude predicted from chiral perturbation theory. Alternatively, one can use chiral-perturbation-theory results to set stringent limits on the value of the $NN\eta$ coupling constant.Comment: 13 pages, Latex with Revtex, 3 postscript figures (not included) available on request, SCRI-03089

ConferenceXP-Powered I-MINDS: A Multiagent System for Intelligently Supporting Online Collaboration

In this paper, we describe a multiagent system designed for intelligently supporting online human collaboration, built on top of the ConferenceXP platform developed by Microsoft Research. Many current collaborative systems are passive in nature and do not provide active, intelligent support to users. A multiagent system can be used to track user behavior, perform automated tasks for humans, find optimal collaborative groups, and create and present helpful processed information based on data mining without detracting from the rest of the collaborative experience. Our ConferenceXP-powered I-MINDS application currently offers five different components for enhancing collaboration and sup-porting moderator decision making by giving each user a personal agent that works with other agents to further sup-port the entire system. These capabilities include two modes for group-based discussions, one for question/answer pairs between users and moderators, a search engine for retrieving tracked data, and a centralized classroom/team management system for quickly accessing user performance. CXP+I-MINDS has been successfully deployed to support an interactive business course where its intelligent activities assisted the professor in teaching, and we are working on delivering it to support a wireless classroom

Anharmonic parametric excitation in optical lattices

We study both experimentally and theoretically the losses induced by parametric excitation in far-off-resonance optical lattices. The atoms confined in a 1D sinusoidal lattice present an excitation spectrum and dynamics substantially different from those expected for a harmonic potential. We develop a model based on the actual atomic Hamiltonian in the lattice and we introduce semiempirically a broadening of the width of lattice energy bands which can physically arise from inhomogeneities and fluctuations of the lattice, and also from atomic collisions. The position and strength of the parametric resonances and the evolution of the number of trapped atoms are satisfactorily described by our model.Comment: 7 pages, 5 figure

Quark Coulomb Interactions and the Mass Difference of Mirror Nuclei

We study the Okamoto-Nolen-Schiffer (ONS) anomaly in the binding energy of mirror nuclei at high density by adding a single neutron or proton to a quark gluon plasma. In this high-density limit we find an anomaly equal to two-thirds of the Coulomb exchange energy of a proton. This effect is dominated by quark electromagnetic interactions---rather than by the up-down quark mass difference. At normal density we calculate the Coulomb energy of neutron matter using a string-flip quark model. We find a nonzero Coulomb energy because of the neutron's charged constituents. This effect could make a significant contribution to the ONS anomaly.Comment: 4 pages, 2 figs. sub. to Phys. Rev. Let

Conserved Charges in the Principal Chiral Model on a Supergroup

The classical principal chiral model in 1+1 dimensions with target space a compact Lie supergroup is investigated. It is shown how to construct a local conserved charge given an invariant tensor of the Lie superalgebra. We calculate the super-Poisson brackets of these currents and argue that they are finitely generated. We show how to derive an infinite number of local charges in involution. We demonstrate that these charges Poisson commute with the non-local charges of the model

Integrated, flexible, and rapid geophysical surveying

Aberdeen Proving Ground (APG), in the state of Maryland (Figure 1), is currently managing a comprehensive Installation Restoration Program involving more than 360 solid-waste managing units contained within 13 study areas. The Edgewood area and two landfills in the Aberdeen area appear on the National Priority List under the Comprehensive Environmental Response, Compensation, and Liability Act. Therefore, APG has entered into an interagency agreement with the US Environmental Protection Agency to address the listed areas. The West Branch of the Canal Creek area (Figure 1), located within the Edgewood area, is one of the areas that requires a Source Definition Study because there is an ongoing release of volatile organic compounds into the creek. A report prepared by EAI Corporation (1989) included a list of 29 potentially contaminated buildings in the Edgewood area. Sixteen of the buildings contain known contaminants, nine buildings contain unknown contaminants, and four of the buildings are potentially clean. The EAI report recommended that a sampling and monitoring program be established to verify contamination levels in and around each building. Thirteen of the potentially contaminated buildings are in the West Branch of the Canal Creek area and are potential sources of volatile organic compounds. Operations have ceased and the buildings have been abandoned, but processing equipment, sumps, drains, ventilation systems, and underground storage tanks remain. These appurtenances may contain liquid, solid, or vapor contaminants of unknown nature

Geophysics: Building E5481 decommissioning, Aberdeen Proving Ground

Building E5481 is one of ten potentially contaminated sites in the Canal Creek and Westwood areas of the Edgewood section of Aberdeen Proving Ground examined by a geophysical team from Argonne National Laboratory in April and May of 1992. Noninvasive geophysical surveys, including magnetics, electrical resistivity, and ground-penetrating radar, were conducted around the perimeter of the building to guide a sampling program prior to decommissioning and dismantling. The building is located on the northern margin of a landfill that was sited in a wetland. The large number of magnetic sources surrounding the building are believed to be contained in construction fill that had been used to raise the grade. The smaller anomalies, for the most part, are not imaged with ground radar or by electrical profiling. A conductive zone trending northwest to southeast across the site is spatially related to an old roadbed. Higher resistivity areas in the northeast and east are probably representive of background values. Three high-amplitude, positive, rectangular magnetic anomalies have unknown sources. The features do not have equivalent electrical signatures, nor are they seen with radar imaging

Generalized parton distributions and Deeply Virtual Compton Scattering in Color Glass Condensate model

Within the framework of the Color Glass Condensate model, we evaluate quark and gluon Generalized Parton Distributions (GPDs) and the cross section of Deeply Virtual Compton Scattering (DVCS) in the small-$x_{B}$ region. We demonstrate that the DVCS cross section becomes independent of energy in the limit of very small $x_{B}$, which clearly indicates saturation of the DVCS cross section. Our predictions for the GPDs and the DVCS cross section at high-energies can be tested at the future Electron-Ion Collider and in ultra-peripheral nucleus-nucleus collisions at the LHC.Comment: 20 pages, 8 Figure