Nonpoint Source Abatement Costs in the Kentucky River Watershed

A growing share of water pollution in the U.S. can be attributed to nonpoint sources (USEPA 2002). Some of this trend can be attributed to declining point source (PS) emissions as a result of regulation under the Clean Water Act (CWA). However, fertilizer-intensive practices used to improve agricultural productivity over recent decades have also increased nitrate loads and resulted in water quality impairments. Nonpoint source (NPS) pollution from agricultural practices is generally exempt from federal regulation. However, some voluntary programs allow point sources subject to the CWA’s effluent limitations to meet their standards by purchasing offset credits reflecting reductions in NPS discharges to the same waters (USEPA 2004). Such water quality trading (WQT) programs have been implemented in a number of states to reduce pollution abatement costs (Breetz et al 2004). In this setting, NPS supply pollution abatement when they implement best management practices (BMP) that reduce nutrient loads, and the cost of BMPs form a supply curve for credits. WQT programs are supported by the EPA as an important means for efficiently pursuing water quality goals (USEPA 2003a). Among the BMPs available for water quality management, riparian buffer strips have proven effective in mitigating the movement of nutrients and other pollutants into surface waters (Qiu et al 2006). Estimates of riparian buffer costs would be valuable for developing policy related to WQT and other conservation programs. This paper estimates the annual costs of buffer strips in six counties in the Lower Kentucky River Basin, as part of a project evaluating the feasibility of WQT programs in that area.Environmental Economics and Policy,

Predicting Student Sensitivity to Tuition and Financial Aid

Over the last two decades, a substantial body of research has examined student responsiveness to tuition increases and financial aid offers in postsecondary educational decisions (see, for example, Heller, 1997; Leslie and Brinkman, 1988). Another major research interest in higher education literature is student behavior in choosing a postsecondary educational institution (see, for example, Hossler, Braxton, and Coopersmith, 1989; Paulsen, 1990). As the costs of postsecondary education have risen, policy analysts and scholars have paid increasing attention to the impact of tuition costs and student financial aid on access to postsecondary education, college matriculation decisions, and subsequent student persistence in postsecondary education (McPherson and Shapiro, 1991, 1998; Mumper, 1996; St. John, 1990a, 1990b; St. John, Starkey, Paulsen and Mbaduagha, 1995; Weiler, 1996). Institutional policy-makers are concerned about student recruitment and enrollment on the one hand and institutional financial health on the other, while state and federal policy-makers are worried about the effective use of public funds to meet national interests such as access, choice, and attainment in postsecondary education. Policy analysts and higher education researchers have recently become concerned about whether students attend college and which schools students attend, because the postsecondary destinations of students are related to student educational attainment and career development (Hearn, 1988, 1991; Pascarella and Terenzini, 1991). Thus, from a social equity perspective, college tuition and financial aid have become serious policy issues. It is believed that the influence of perceived college tuition rates and financial aid availability becomes important during student college choice process and reaches the highest level in the senior year of high school (Hossler and Gallagher, 1987; Hossler, Schmit, and Vesper, 1999). However, not until the last few years has research on the impact of college tuition and financial aid been linked with models of student college choice. Savoca (1990) integrated price impact into her research on student application behaviors to college and concluded that this integration would result in estimating student price responsiveness more accurately. Meanwhile, recent research implies that tuition pricing and financial aid offers exert different impacts on student postsecondary participation decisions (St. John and Starkey, 1995). The purpose of this study is to identify the predictors of student sensitivity to college tuition and financial aid and to differentiate the impacts of these predictors on student price sensitivity in the student college choice process

Modal response and frequency shift of the cantilever in a noncontact atomic force microscope

The force-sensing cantilever in a noncontact atomic force microscope is a continuous system with infinite number of eigenmodes. Although the frequently used point mass model was found sufficient in many cases, its conditions for validity and the insights on how higher eigen-modes could affect the selection of operation parameters were not established. In this letter, we formulate the cantilever motion using modal response analysis, a powerful means enabling an efficient numerical solution and a first order analytical solution. The origins and impacts of the higher eigenfrequency oscillation are then investigated, which sheds lights on achieving optimal imaging conditions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87824/2/183506_1.pd

Two-Component Structure of the Hbeta Broad-Line Region in Quasars. I. Evidence from Spectral Principal Component Analysis

We report on a spectral principal component analysis (SPCA) of a sample of 816 quasars, selected to have small Fe II velocity shifts with spectral coverage in the rest wavelength range 3500--5500 \AA. The sample is explicitly designed to mitigate spurious effects on SPCA induced by Fe II velocity shifts. We improve the algorithm of SPCA in the literature and introduce a new quantity, \emph{the fractional-contribution spectrum}, that effectively identifies the emission features encoded in each eigenspectrum. The first eigenspectrum clearly records the power-law continuum and very broad Balmer emission lines. Narrow emission lines dominate the second eigenspectrum. The third eigenspectrum represents the Fe II emission and a component of the Balmer lines with kinematically similar intermediate velocity widths. Correlations between the weights of the eigenspectra and parametric measurements of line strength and continuum slope confirm the above interpretation for the eigenspectra. Monte Carlo simulations demonstrate the validity of our method to recognize cross talk in SPCA and firmly rule out a single-component model for broad Hbeta. We also present the results of SPCA for four other samples that contain quasars in bins of larger Fe II velocity shift; similar eigenspectra are obtained. We propose that the Hbeta-emitting region has two kinematically distinct components: one with very large velocities whose strength correlates with the continuum shape, and another with more modest, intermediate velocities that is closely coupled to the gas that gives rise to Fe II emission.Comment: 22 pages, 17 figures, accepted for publication in The Astrophysical Journa

Impacts of indoor surface finishes on bacterial viability.

Microbes in indoor environments are constantly being exposed to antimicrobial surface finishes. Many are rendered non-viable after spending extended periods of time under low-moisture, low-nutrient surface conditions, regardless of whether those surfaces have been amended with antimicrobial chemicals. However, some microorganisms remain viable even after prolonged exposure to these hostile conditions. Work with specific model pathogens makes it difficult to draw general conclusions about how chemical and physical properties of surfaces affect microbes. Here, we explore the survival of a synthetic community of non-model microorganisms isolated from built environments following exposure to three chemically and physically distinct surface finishes. Our findings demonstrated the differences in bacterial survival associated with three chemically and physically distinct materials. Alkaline clay surfaces select for an alkaliphilic bacterium, Kocuria rosea, whereas acidic mold-resistant paint favors Bacillus timonensis, a Gram-negative spore-forming bacterium that also survives on antimicrobial surfaces after 24 hours of exposure. Additionally, antibiotic-resistant Pantoea allii did not exhibit prolonged retention on antimicrobial surfaces. Our controlled microcosm experiment integrates measurement of indoor chemistry and microbiology to elucidate the complex biochemical interactions that influence the indoor microbiome

Outflows from active galactic nuclei: The BLR-NLR metallicity correlation

The metallicity of active galactic nuclei (AGNs), which can be measured by emission line ratios in their broad and narrow line regions (BLRs and NLRs), provides invaluable information about the physical connection between the different components of AGNs. From the archival databases of the International Ultraviolet Explorer, the Hubble Space Telescope and the Sloan Digital Sky Survey, we have assembled the largest sample available of AGNs which have adequate spectra in both the optical and ultraviolet bands to measure the narrow line ratio [N II]/H{\alpha} and also, in the same objects, the broad-line N V/C IV ratio. These permit the measurement of the metallicities in the NLRs and BLRs in the same objects. We find that neither the BLR nor the NLR metallicity correlate with black hole masses or Eddington ratios, but there is a strong correlation between NLR and BLR metallicities. This metallicity correlation implies that outflows from BLRs carry metal-rich gas to NLRs at characteristic radial distances of ~ 1.0 kiloparsec. This chemical connection provides evidence for a kinetic feedback of the outflows to their hosts. Metals transported into the NLR enhance the cooling of the ISM in this region, leading to local star formation after the AGNs turn to narrow line LINERs. This post-AGN star formation is predicted to be observable as an excess continuum emission from the host galaxies in the near infrared and ultraviolet, which needs to be further explored.Comment: 19 pages, 13 figures, 3 tables. Accepted for publication at MNRA

An Augmented Subspace Based Adaptive Proper Orthogonal Decomposition Method for Time Dependent Partial Differential Equations

In this paper, we propose an augmented subspace based adaptive proper orthogonal decomposition (POD) method for solving the time dependent partial differential equations. By augmenting the POD subspace with some auxiliary modes, we obtain an augmented subspace. We use the difference between the approximation obtained in this augmented subspace and that obtained in the original POD subspace to construct an error indicator, by which we obtain a general framework for augmented subspace based adaptive POD method. We then provide two strategies to obtain some specific augmented subspaces, the random vector based augmented subspace and the coarse-grid approximations based augmented subspace. We apply our new method to two typical 3D advection-diffusion equations with the advection being the Kolmogorov flow and the ABC flow. Numerical results show that our method is more efficient than the existing adaptive POD methods, especially for the advection dominated models.Comment: 28 pages, 4 figures, 7 table

Analysis of the limiting spectral distribution of large dimensional General information-plus-noise type matrices

In this paper, we derive the analytical behavior of the limiting spectral distribution of non-central covariance matrices of the "general information-plus-noise" type, as studied in [14]. Through the equation defining its Stieltjes transform, it is shown that the limiting distribution has a continuous derivative away from zero, the derivative being analytic wherever it is positive, and we show the determination criterion for its support. We also extend the result in [14] to allow for all possible ratios of row to column of the underlying random matrix

Exact Separation of Eigenvalues of Large Dimensional Noncentral Sample Covariance Matrices

Let \bbB_n =\frac{1}{n}(\bbR_n + \bbT^{1/2}_n \bbX_n)(\bbR_n + \bbT^{1/2}_n \bbX_n)^* where \bbX_n is a $p \times n$ matrix with independent standardized random variables, \bbR_n is a $p \times n$ non-random matrix, representing the information, and \bbT_{n} is a $p \times p$ non-random nonnegative definite Hermitian matrix. Under some conditions on \bbR_n \bbR_n^* and \bbT_n , it has been proved that for any closed interval outside the support of the limit spectral distribution, with probability one there will be no eigenvalues falling in this interval for all $p$ sufficiently large. The purpose of this paper is to carry on with the study of the support of the limit spectral distribution, and we show that there is an exact separation phenomenon: with probability one, the proper number of eigenvalues lie on either side of these intervals