A Detailed Analysis of a Cygnus Loop Shock-Cloud Interaction

The XA region of the Cygnus Loop is a complex zone of radiative and nonradiative shocks interacting with interstellar clouds. We combine five far ultraviolet spectral observations from the Hopkins Ultraviolet Telescope (HUT), a grid of 24 IUE spectra and a high-resolution longslit Halpha spectrum to study the spatial emission line variations across the region. These spectral data are placed in context using ground-based, optical emission line images of the region and a far-UV image obtained by the Ultraviolet Imaging Telescope (UIT). The presence of high-ionization ions (OVI, NV, CIV) indicates a shock velocity near 170 km/s while other diagnostics indicate v_shock=140 km/s. It is likely that a large range of shock velocities may exist at a spatial scale smaller than we are able to resolve. By comparing CIV 1550, CIII 977 and CIII] 1909, we explore resonance scattering across the region. We find that a significant column depth is present at all positions, including those not near bright optical/UV filaments. Analysis of the OVI doublet ratio suggests an average optical depth of about unity in that ion while flux measurements of [SiVIII] 1443 suggest a hot component in the region at just below 10^6K. Given the brightness of the OVI emission and the age of the interaction, we rule out the mixing layer interpretation of the UV emission. Furthermore, we formulate a picture of the XA region as the encounter of the blast wave with a finger of dense gas protruding inward from the pre-SN cavity.Comment: 21 pages, 9 figures, accepted by the Astronomical Journal, July 2001 Full resolution figures available at http://fuse.pha.jhu.edu/~danforth/xa

On the Significance of Absorption Features in HST/COS Data

We present empirical scaling relations for the significance of absorption features detected in medium resolution, far-UV spectra obtained with the Cosmic Origins Spectrograph (COS). These relations properly account for both the extended wings of the COS line spread function and the non-Poissonian noise properties of the data, which we characterize for the first time, and predict limiting equivalent widths that deviate from the empirical behavior by \leq 5% when the wavelength and Doppler parameter are in the ranges \lambda = 1150-1750 A and b > 10 km/s. We have tested a number of coaddition algorithms and find the noise properties of individual exposures to be closer to the Poissonian ideal than coadded data in all cases. For unresolved absorption lines, limiting equivalent widths for coadded data are 6% larger than limiting equivalent widths derived from individual exposures with the same signal-to-noise. This ratio scales with b-value for resolved absorption lines, with coadded data having a limiting equivalent width that is 25% larger than individual exposures when b \approx 150 km/s.Comment: 25 pages, 3 tables, 7 figures, accepted for publication in PAS

Farm Service Agency Direct Farm Loan Program Effectiveness Study

The three primary objectives of the Effectiveness Study are to: (1) identify groups being served by FSA direct farm loan programs, (2) examine the length of time borrowers remain in the programs and the proportion of borrowers who exit or 'graduate' from the programs, and (3) measure and identify ways of reducing loan subsidy rates. The study found that direct Farm Loan Programs (FLPs) appear to be serving their intended clientele. Recent FLP borrowers are more financially stressed than non-borrowers and would be generally considered as family farms. About 78 to 92 percent would qualify as small family farms using USDA's Small Farms Commission definition. FLP credit market penetration is relatively high among farms likely to be eligible for these credit programs, despite the fact that these programs represent a relatively small proportion of total outstanding agricultural debt. Increasing market penetration or the share of farms served by the program would require greater obligation funding and hence greater budgetary costs. Conversely, implementing more rigorous loan eligibility criteria would likely lower the number of operators receiving loans and hence loan loss occurrences and subsidy rates would likely fall. The majority of FSA Direct borrowers from FY 1994-1996 used FLPs as a transitional tool. At time of origination, FSA Direct borrowers had fewer years of farming experience than the farming population at large. More than half of these borrowers no longer had active FLP loans by the end of November 2004. So for the majority of borrowers, FLPs are not a lifetime credit source. FLPs are helping farmers move to commercial credit or aiding farmers who subsequently leave farming completely, as is common among U.S. farmers. Not surprisingly, farmers in stronger financial condition originating FSA Direct loans are more likely to exit and have fewer outstanding loans with FSA. FSA experiences higher loan loss rates than conventional agricultural lenders. This is to be expected because commercial lenders can be more selective in choosing borrowers and price loans to match risk profiles which FSA does not do. In essence, FSA's mission is to provide credit to riskier 'creditworthy' borrowers. The agency is accomplishing this goal. The natural consequence is that FSA loan loss rates are higher than for conventional lenders. Whether the current borrowers are too risky or should even riskier borrowers be included are policy questions. The analysis indicates that attempts to cut losses systematically would imply denying credit to some current borrowers.Agricultural Finance,