THE ROLE OF EXPIRATORY FLOW LIMITATION IN THE OXYGEN COST OF EXERCISE HYPERPNEA IN HIGHLY-TRAINED DISTANCE RUNNERS

There is an upper limitation to the flow rates achievable during exhalation. Once this limitation is reached (expiratory flow limitation; FLexp), such as that observed during intensive exercise, no further increase in expiratory flow is possible. During heavy to maximal exercise, a major consequence of FLexp may be an increased oxygen cost of breathing. To examine the effect of FLexp on respiratory muscle oxygen consumption (VO2RM) during maximal exercise, a sample of highly-trained male distance runners (n=18; O2 max = 74.28 ml·kg-1·min-1) completed an incremental exercise test to exhaustion on a treadmill. Based on flow-volume loop analysis, subjects were separated into two groups, flow-limited (FL) and non-flow limited (NFL). During a second visit, runners performed three separate trials of voluntary hyperpnea, matching exercise ventilation ( E) at 80%, 90%, and 100% of maximal exercise while standing on the treadmill. Respiratory muscle O2 consumption (VO2RM) was estimated during each voluntary hyperpnea trial. A one-tailed, independent samples t-test detected a significantly greater VO2RM in FL compared to NFL (P = 0.043). E at O2 max was also greater in FL vs. NFL (P = 0.029). No differences were found between expiratory reserve volume (ERV), tidal volume (VT), or breathing frequency (fb) during maximal exercise. When co-varying for E at O2 max, there was no significant difference in VO2RM between groups, suggesting that the greater oxygen cost of breathing in flow-limited individuals is a consequence of the greater VE and not due to differences in breathing mechanics associated with flow limitation.Submitted to the faculty of the University Graduate School in partial fulfillment of the requirements for the degree Master of Science in the Department of Kinesiology Indiana University August 12, 201

Riding Red Ink: Public Ownership of Mass Transit in Indianapolis

**Note** During the research process, IndyGo donated some of the resources cited within this paper to the Indiana Historical Society. That collection has not been archived yet. Further, IndyGo may have placed other documents (created during the time of public ownership) in the Indiana State Archives or the Indiana State Library.Indiana University-Purdue University Indianapolis (IUPUI)Today, most urban mass transit providers are publicly owned. Just a few decades ago, and for a majority of the history of mass transit, private owners provided transportation for communities. The decline of private ownership in Indianapolis resulted in transit crisis that pitted private owners against local government, riders and community groups. Advocates lambasted the private owners for their profit-first tactics, pointing to the dividends gained by the private owners. These owners, the Midland Transportation Corporation, also owned the mass transit companies in Milwaukee, Wisconsin and Louisville, Kentucky. Indianapolis politicians, residents and newspapers, all firmly conservative, hoped private owners could continue to operate Indianapolis Transit Systems without public assistance. The imminent failure prompted a discussion of the future of transportation in the city of Indianapolis. Community groups hoped the new public corporation would increase service for Indianapolis and not continue the skeleton system managed by the private owners. A storm of uncontrollable events prevented the robust expansion of the new public corporation and its lack of funding resulted in a continuing decline of service, much akin to the private owners that were abhorred by transit riders. Public ownership in Indianapolis revealed the importance of public ownership in the historiography of mass transportation and urban history. The regional investigation of Midland Transportation confirmed the notion of transit as a unique industry, both in its industrial relations and influence of the locality. The basic rationale for public ownership in Indianapolis would be the most important: the provision of public transportation for those unable to afford private transportation to obtain necessary services

The Effect of Variability on the Estimation of Quasar Black Hole Masses

We investigate the time-dependent variations of ultraviolet (UV) black hole mass estimates of quasars in the Sloan Digital Sky Survey (SDSS). From SDSS spectra of 615 high-redshift (1.69 < z < 4.75) quasars with spectra from two epochs, we estimate black hole masses, using a single-epoch technique which employs an additional, automated night-sky-line removal, and relies on UV continuum luminosity and CIV (1549A) emission line dispersion. Mass estimates show variations between epochs at about the 30% level for the sample as a whole. We determine that, for our full sample, measurement error in the line dispersion likely plays a larger role than the inherent variability, in terms of contributing to variations in mass estimates between epochs. However, we use the variations in quasars with r-band spectral signal-to-noise ratio greater than 15 to estimate that the contribution to these variations from inherent variability is roughly 20%. We conclude that these differences in black hole mass estimates between epochs indicate variability is not a large contributer to the current factor of two scatter between mass estimates derived from low- and high-ionization emission lines.Comment: 76 pages, 15 figures, 2 (long) tables; Accepted for publication in ApJ (November 10, 2007

Spectral Variability of Quasars in the Sloan Digital Sky Survey. II: The C IV Line

We examine the variability of the high-ionizaton C IV line in a sample of 105 quasars observed at multiple epochs by the Sloan Digital Sky Survey. We find a strong correlation between the change in the C IV line flux and the change in the line width, but no correlations between the change in flux and changes in line center and skewness. The relation between line flux change and line width change is consistent with a model in which a broad line base varies with greater amplitude than the line core. The objects studied here are more luminous and at higher redshift than those normally studied for variability, ranging in redshift from 1.65 to 4.00 and in absolute r-band magnitude from roughly -24 to -28. Using moment analysis line-fitting techniques, we measure line fluxes, centers, widths and skewnesses for the C IV line at two epochs for each object. The well-known Baldwin Effect is seen for these objects, with a slope beta = -0.22. The sample has a median intrinsic Baldwin Effect slope of beta = -0.85; the C IV lines in these high-luminosity quasars appear to be less responsive to continuum variations than those in lower luminosity AGN. Additionally, we find no evidence for variability of the well known blueshift of the C IV line with respect to the low-ionization Mg II line in the highest flux objects, indicating that this blueshift might be useful as a measure of orientation.Comment: 52 pages, 14 figures, accepted for publication in Ap

On the variability of quasars: a link between Eddington ratio and optical variability?

Repeat scans by the Sloan Digital Sky Survey (SDSS) of a 278 square degree stripe along the Celestial equator have yielded an average of over 10 observations each for nearly 8,000 spectroscopically confirmed quasars. Over 2500 of these quasars are in the redshift range such that the CIV emission line is visible in the SDSS spectrum. Utilising the width of these CIV lines and the luminosity of the nearby continuum, we estimate black hole masses for these objects. In an effort to isolate the effects of black hole mass and luminosity on the photometric variability of our dataset, we create several subsamples by binning in these two physical parameters. By comparing the ensemble structure functions of the quasars in these bins, we are able to reproduce the well-known anticorrelation between luminosity and variability, now showing that this anticorrelation is independent of the black hole mass. In addition, we find a correlation between variability and the mass of the central black hole. By combining these two relations, we identify the Eddington ratio as a possible driver of quasar variability, most likely due to differences in accretion efficiency.Comment: 13 pages, 5 figures, Accepted for publication in MNRA

Characteristic QSO Accretion Disk Temperatures from Spectroscopic Continuum Variability

Using Sloan Digital Sky Survey (SDSS) quasar spectra taken at multiple epochs, we find that the composite flux density differences in the rest frame wavelength range 1300-6000 AA can be fit by a standard thermal accretion disk model where the accretion rate has changed from one epoch to the next (without considering additional continuum emission components). The fit to the composite residual has two free parameters: a normalizing constant and the average characteristic temperature $\bar{T}^*$. In turn the characteristic temperature is dependent on the ratio of the mass accretion rate to the square of the black hole mass. We therefore conclude that most of the UV/optical variability may be due to processes involving the disk, and thus that a significant fraction of the UV/optical spectrum may come directly from the disk.Comment: 31 pages, 8 figure

A Quasar Catalog with Simultaneous UV, Optical and X-ray Observations by Swift

We have compiled a catalog of optically-selected quasars with simultaneous observations in UV/optical and X-ray bands by the Swift Gamma Ray Burst Explorer. Objects in this catalog are identified by matching the Swift pointings with the Sloan Digital Sky Survey Data Release 5 quasar catalog. The final catalog contains 843 objects, among which 637 have both UVOT and XRT observations and 354 of which are detected by both instruments. The overall X-ray detection rate is ~60% which rises to ~85% among sources with at least 10 ks of XRT exposure time. We construct the time-averaged spectral energy distribution for each of the 354 quasars using UVOT photometric measurements and XRT spectra. From model fits to these SEDs, we find that the big blue bump contributes about 0.3 dex to the quasar luminosity. We re-visit the alpha_ox-L_uv relation by selecting a clean sample with only type 1 radio-quiet quasars; the dispersion of this relation is reduced by at least 15% compared to studies that use non-simultaneous UV/optical and X-ray data. We only found a weak correlation between L/L_Edd and alpha_uv. We do not find significant correlations between alpha_x and alpha_ox, alpha_ox and alpha_uv, and alpha_x and Log L(0.3-10 keV). The correlations between alpha_uv and alpha_x, alpha_ox and alpha_x, alpha_ox and alpha_uv, L/L_Edd and alpha_x, and L/L_Edd and alpha_ox are stronger amongst low-redshift quasars, indicating that these correlations are likely driven by the changes of SED shape with accretion state.Comment: 63 pages, 22 figures, accepted by ApJ

Broad Absorption Line Variability in Repeat Quasar Observations from the Sloan Digital Sky Survey

We present a time-variability analysis of 29 broad absorption line quasars (BALQSOs) observed in two epochs by the Sloan Digital Sky Survey (SDSS). These spectra are selected from a larger sample of BALQSOs with multiple observations by virtue of exhibiting a broad CIV $\lambda$1549 absorption trough separated from the rest frame of the associated emission peak by more than 3600 km s$^{-1}$. Detached troughs facilitate higher precision variability measurements, since the measurement of the absorption in these objects is not complicated by variation in the emission line flux. We have undertaken a statistical analysis of these detached-trough BALQSO spectra to explore the relationships between BAL features that are seen to vary and the dynamics of emission from the quasar central engine. We have measured variability within our sample, which includes three strongly variable BALs. We have also verified that the statistical behavior of the overall sample agrees with current model predictions and previous studies of BAL variability. Specifically, we observe that the strongest BAL variability occurs among the smallest equivalent width features and at velocities exceeding 12,000 km s$^{-1}$, as predicted by recent disk-wind modeling.Comment: 11 pages, 7 figures. Accepted for publication in Ap

Spectral Variability of Quasars in the Sloan Digital Sky Survey. I: Wavelength Dependence

Sloan Digital Sky Survey (SDSS) repeat spectroscopic observations have resulted in multiple-epoch spectroscopy for roughly 2500 quasars observed more than 50 days apart. From this sample, we identify 315 quasars that have varied significantly between observations. We create an ensemble difference spectrum (bright phase minus faint phase) covering rest-frame wavelengths from 1000 to 6000 Angstroms. This average difference spectrum is bluer than the average single-epoch quasar spectrum; a power-law fit to the difference spectrum yields a spectral index alpha_lambda = -2.00, compared to an index of alpha_lambda = -1.35 for the single-epoch spectrum. The strongest emission lines vary only 30% as much as the continuum. Due to the lack of variability of the lines, measured photometric color is not always bluer in brighter phases, but depends on redshift and the filters used. Lastly, the difference spectrum is bluer than the ensemble quasar spectrum only for lambda_rest < 2500 Angstroms, indicating that the variability cannot result from a simple scaling of the average quasar spectrum.Comment: 47 pages, 14 figures, 3 tables, accepted for publication in Ap

The Ensemble Photometric Variability of ~25000 Quasars in the Sloan Digital Sky Survey

Using a sample of over 25000 spectroscopically confirmed quasars from the Sloan Digital Sky Survey, we show how quasar variability in the rest frame optical/UV regime depends upon rest frame time lag, luminosity, rest wavelength, redshift, the presence of radio and X-ray emission, and the presence of broad absorption line systems. The time dependence of variability (the structure function) is well-fit by a single power law on timescales from days to years. There is an anti-correlation of variability amplitude with rest wavelength, and quasars are systematically bluer when brighter at all redshifts. There is a strong anti-correlation of variability with quasar luminosity. There is also a significant positive correlation of variability amplitude with redshift, indicating evolution of the quasar population or the variability mechanism. We parameterize all of these relationships. Quasars with RASS X-ray detections are significantly more variable (at optical/UV wavelengths) than those without, and radio loud quasars are marginally more variable than their radio weak counterparts. We find no significant difference in the variability of quasars with and without broad absorption line troughs. Models involving multiple discrete events or gravitational microlensing are unlikely by themselves to account for the data. So-called accretion disk instability models are promising, but more quantitative predictions are needed.Comment: 41 pages, 21 figures, AASTeX, Accepted for publication in Ap