Azimuthal Seismic First-Arrival Tomography as a Proxy for Hydraulically Conductive Subsurface Fracture Networks

The Oak Ridge Field Research Center (ORFRC) was established by the Environmental Sciences Division (ESD) at the Oak Ridge National Laboratory (ORNL) in Oak Ridge, TN, in order to study the various biogeochemical processes involved in the remediation as well as natural attenuation of a large contaminant plume that is extant in the vicinity of the ORIFRC. A part of this work has been to characterize the movement of this groundwater/contaminant plume with the use of azimuthal seismic first-arrival tomography (ASFT). Within the general area of the ORIFRC, a 0-2 m layer of generally isotropic anthropogenic fill and unconsolidated soil overlies the deeper structural elements caused by the folding that formed the Valley and Ridge region of East Tennessee. Beneath this layer of fill, a fractured shale transition zone from saprolite to competent bedrock exists. It is suspected that this fracture network forms anisotropic flow conditions where contaminants exist beneath the surface layers. In an effort detect fracture-driven hydrologic anisotropy, we have collected surface SFT profiles at 10° intervals around a central point at the NT-2 site at ORNL. Each seismic survey consisted of a 96-channel survey with a 0.5 m offset, and shot points located at every fourth receiver along the line. The resultant tomograms were converted from XZ plane cross-sections to XY plane cross-sections. The resultant map-view velocity profiles showed a dramatic decrease in seismic isotropy with depth, as well as delineating the saprolite/bedrock transition zone at the NT-2 site. Two additional datasets have been collected approximately one half kilometer (Km-1 site) and one kilometer (Km-2 site) down valley from NT-2. Both of these datasets agree with the direction and degree of anisotropy present at the NT-2 site, and both were able delineate the transition between saprolite and competent bedrock, underscoring the efficacy and replicability of this experimental method. All of these datasets were compared to measured fracture set orientations in trenched saprolitic shale as well as measured hydrologic anisotropy with positive results in order to establish the accuracy of ASFT relative to conventional methods of hydrologic testing

Lobbyists as Imperfect Agents: Implications for Public Policy in a Pluralist System

Interest group pluralism presumes that public policy outcomes are determined principally through a contest for influence among organized pressure groups. Most interest groups, however, do not represent themselves in this process. Rather, they rely on professional lobbyists for representation, information, and advice. These lobbyists are agents with their own interests, and these interests may not align perfectly with those of their clients. This essay outlines this principal-agent problem and sketches its possible implications for policy outcomes. In particular, we hypothesize that the lobbyist-client agency problem may bias policy in favor of small homogeneous groups, may exacerbate status quo bias and lead to excessive attention to symbolic issues, may promote expansive delegations to administrative agencies, and may impede systematic reforms to the policy-making process

A spatially nonlinear generalised actuator disk model for the simulation of horizontal axis wind and tidal turbines

Efficient numerical simulation of renewable energy wind and tidal turbines is important for the layout of devices in farms. Computational Fluid Dynamics (CFD) approaches using blade geometry resolved models are computationally expensive. Therefore, most array models use source term representations of rotors, normally actuator disk, actuator line or blade element disk. Unfortunately, these methods rarely capture enough physics to accurately predict power and at the same time correctly characterise the wake velocity field and turbulent structures.This study describes a new Generalised Actuator Disk CFD model (GAD-CFD), that achieves the required accuracy for the simulation of horizontal axis wind and tidal turbines and their wakes. This new method combines a finite volume CFD code with additional source terms representing the rotor, including: correct consideration of losses along the foil by modification of the distribution of downwash; a concise downwash distribution computation; recognition that foil cross section varies along the length; dynamically changing Reynolds numbers and the application of a tip radius correction. Also reported are foil lift and drag coefficients and their variation with thickness, surface roughness and Reynolds number, which is necessary for the proper characterisation the whole rotor.The effectiveness of this approach is investigated and validated against two experiments, and demonstrates improvements over traditional source term methods, in particular the correct CFD approach to tip losses and consequent downstream wake prediction. This study provides confidence in application to both small scale flume studies and large scale array deployments in both the marine and wind environments

An enhanced disk averaged CFD model for the simulation of horizontal axis tidal turbines

Simulating fully resolved Horizontal Axis Tidal Turbine (HATT) geometry for a time period great enough to resolve a fully developed wake, and accurately predict power and thrust characteristics, is computationally very expensive. The BEM-CFD method is an enhanced actuator disk and is able to reduce the computational cost by simulating a time averaged downstream velocity field. Current implementations fall short of accurately determining tip losses, which are a function of the hydrofoil geometry. This work proposes a method of addressing this shortfall by modifying the angle of attack to conform to the constraints outlined in Prandtl's lifting line theory, i.e. the zero lift angle of attack at the hydrofoil tip. The revised model is compared to existing BEM-CFD methods and validated against experimental data. The revised BEM-CFD method presented in this work shows a significant improvement over previous BEM-CFD methods when predicting power and thrust. The coefficient of power is reduced from 0.57 (approx. 30% above experiment) to 0.44 (approx. 3% above experiment). An increase in turbulence intensity in the rotor region, in particular at the wake boundary, improves the recovery of the wake without the addition of empirical turbulence source terms. Good correlation with experimental results for power, thrust and wake prediction, is observed. The model may also be applied to wind turbines

Investigation of candidate biomarkers in Graves' disease and thyroid-associated ophthalmopathy

Thyroid-Associated Ophthalmopathy (TAO) is a debilitating inflammatory condition of the orbit occurring in 30-50% of Graves' Disease (GD) patients. It is not currently possible to predict which GD patients will develop TAO or the severity of their eventual ophthalmic manifestations. The aim of this thesis was to evaluate novel biomarkers for this purpose. I developed two immunoassays to detect serum antibodies to insulin-like growth factor-1 receptor (IGF-lR-Ab) in GD, TAO and healthy controls (HC). Assays were validated to measure commercial monoclonal IGF-lR-Ab but no study group differences, or correlation with clinical activity or severity, were noted with sera. Differential IGF-lR expression on peripheral blood CD4+ and CDS+ T lymphocyte memory subsets was observed, although without variance between groups. However, T cell differentiation was perturbed, with elevated proportions of naïve, and reduced cytokine-producing effector memory T cells, in GD and TAO compared to HC. Nuclear magnetic resonance-based serum metabolomic analysis differentiated GD and TAO subjects, and varying TAO clinical activity, with good uncorrected sensitivity and specificity. Distinguishing metabolites included lactate, isopropanol, methylguanidine and pyruvate. Collectively these data cast doubt on a simple model of IGF-lR-Ab being responsible for orbital inflammation in GD, but highlight the biomarker potential of metabolomics in TAO

The Diverse Infrared Properties of a Complete Sample of Star-Forming Dwarf Galaxies

We present mid-infrared Spitzer Space Telescope observations of a complete sample of star-forming dwarf galaxies selected from the KPNO International Spectroscopic Survey. The galaxies span a wide range in mid-infrared properties. Contrary to expectations, some of the galaxies emit strongly at 8 micron indicating the presence of hot dust and/or PAHs. The ratio of this mid-infrared dust emission to the stellar emission is compared with the galaxies' luminosity, star-formation rate, metallicity, and optical reddening. We find that the strength of the 8.0 micron dust emission to the stellar emission ratio is more strongly correlated with the star-formation rate than it is with the metallicity or the optical reddening in these systems. Nonetheless, there is a correlation between the 8.0 micron luminosity and metallicity. The slope of this luminosity-metallicity correlation is shallower than corresponding ones in the B-band and 3.6 micron. The precise nature of the 8.0 micron emission seen in these galaxies (i.e., PAH versus hot dust or some combination of the two) will require future study, including deep mid-IR spectroscopy.Comment: 14 pages, accepted Ap

Profound hypotony maculopathy in a first episode of bilateral idiopathic acute anterior uveitis

BACKGROUND: We report a case of a HLA-B27 negative patient presenting with severe, bilateral, idiopathic acute anterior uveitis with acute hypotony and hypotony maculopathy as their first uveitic episode. CASE PRESENTATION: Within a week of onset of her first episode of acute anterior uveitis, a 45 year-old Caucasian lady developed profound ocular hypotony with unrecordable intraocular pressures, reduced vision and choroidal folds. All investigations were negative. Uveitic hypotony responded slowly to corticosteroids – intravenous, oral and topical – with normalization of intraocular pressure and resolution of choroidal folds after two months. Anterior uveitis and hypotony have not returned with six months of follow-up. CONCLUSION: Bilateral, profound hypotony maculopathy may present acutely in idiopathic acute anterior uveitis, may be slow to respond to treatment and should be considered as a cause of vision loss in patients with this condition

Resonantly overcoming metal opacity

Copyright © 2013 American Institute of PhysicsThe near-perfect response of electrons in metals to low-frequency electromagnetic fields makes even a sub-skin-depth film almost completely opaque to microwave radiation. Here, it is experimentally demonstrated that by surrounding a ∼60 nm aluminium film with an array of thin resonant cavities, over 35% of the microwave radiation incident can be transmitted over a discrete set of narrow bands. This represents an enhancement of ∼1000 times over an isolated film and allows for a frequency selective screen with a thickness less than 1/70th of the operating wavelength that may be tuned through choice of resonant geometr