The Federal Minimum Wage, Political Thought and Citizenship

Several questions about the minimum wage have not been answered adequately by scholars. The wage’s origins, its reasons for federal passage, the roots of its decline, and its future prospects are all up for debate in the current literature. This paper weighs in on these questions, hoping to improve the debate surrounding them. In the process, the importance of linking the wage to citizenship becomes clear. As the political thought of the issue has moved away from conceiving of minimum wages as tools for reaffirming the status of low wage workers, support for the wage, and its monetary value, has declined. The need for a more responsible scholarship about the minimum wage, one without ideologically biased preconceptions, is also addressed

Variance Analysis of Unevenly Spaced Time Series Data

We have investigated the effect of uneven data spacing on the computation of delta (sub chi)(gamma). Evenly spaced simulated data sets were generated for noise processes ranging from white phase modulation (PM) to random walk frequency modulation (FM). Delta(sub chi)(gamma) was then calculated for each noise type. Data were subsequently removed from each simulated data set using typical two-way satellite time and frequency transfer (TWSTFT) data patterns to create two unevenly spaced sets with average intervals of 2.8 and 3.6 days. Delta(sub chi)(gamma) was then calculated for each sparse data set using two different approaches. First the missing data points were replaced by linear interpolation and delta (sub chi)(gamma) calculated from this now full data set. The second approach ignored the fact that the data were unevenly spaced and calculated delta(sub chi)(gamma) as if the data were equally spaced with average spacing of 2.8 or 3.6 days. Both approaches have advantages and disadvantages, and techniques are presented for correcting errors caused by uneven data spacing in typical TWSTFT data sets

Rapidly solidified titanium alloys by melt overflow

A pilot plant scale furnace was designed and constructed for casting titanium alloy strips. The furnace combines plasma arc skull melting techniques with melt overflow rapid solidification technology. A mathematical model of the melting and casting process was developed. The furnace cast strip of a suitable length and width for use with honeycomb structures. Titanium alloys Ti-6Al-4V and Ti-14Al-21 Nb were successfully cast into strips. The strips were evaluated by optical metallography, microhardness measurements, chemical analysis, and cold rolling

Spot activity of the RS Canum Venaticorum star σ Geminorum

Aims. We model the photometry of RS CVn star σ Geminorum to obtain new information on the changes of the surface starspot distribution, that is, activity cycles, differential rotation, and active longitudes. Methods. We used the previously published continuous period search (CPS) method to analyse V-band differential photometry obtained between the years 1987 and 2010 with the T3 0.4 m Automated Telescope at the Fairborn Observatory. The CPS method divides data into short subsets and then models the light-curves with Fourier-models of variable orders and provides estimates of the mean magnitude, amplitude, period, and light-curve minima. These light-curve parameters are then analysed for signs of activity cycles, differential rotation and active longitudes. Results. We confirm the presence of two previously found stable active longitudes, synchronised with the orbital period Porb = 1960, and found eight events where the active longitudes are disrupted. The epochs of the primary light-curve minima rotate with a shorter period Pmin,1 = 1947 than the orbital motion. If the variations in the photometric rotation period were to be caused by differential rotation, this would give a differential rotation coefficient of α ≥ 0.103. Conclusions. The presence of two slightly different periods of active regions may indicate a superposition of two dynamo modes, one stationary in the orbital frame and the other one propagating in the azimuthal direction. Our estimate of the differential rotation is much higher than previous results. However, simulations show that this may be caused by insufficient sampling in our data

Spot activity of LQ Hydra from photometry between 1988 and 2011

Aims. We investigate the spot activity of the young magnetically active main sequence star LQ Hya. Our aims are to identify possible active longitudes, estimate the differential rotation, and study long and short term changes in the activity. Methods. Our analysis is based on 24 years of Johnson V-band photometry of LQ Hya obtained with the T3 0.4 m Automated Telescope at the Fairborn Observatory. We use the previously published continuous period search (CPS) method to model the evolution of the light curve of LQ Hya. The CPS fits a Fourier series model to short overlapping subsets of data. This enables us to monitor the evolution of the light curve and thus the spot configuration of the star with a higher time resolution. Results. We find seasonal variability in the mean level and amplitude of the light curve of LQ Hya. The variability of the light curve amplitude seems not to be cyclic, but the long-term variations in the mean magnitude may be indicative of an approximately 13 year cycle. However, because of the limited length of the observed time series, it is not yet possible to determine whether this structure really represents an activity cycle. Based on fluctuations of the light curve period, we estimate the differential rotation of the star to be small, and the star is potentially very close to a rigid rotator. We search for active longitudes from the inferred epochs of the light curve minima. We find that on time scales up to six months there are typically one or two relatively stable active areas on the star with limited phase migration. On the other hand, on time scales longer than one year, no stable active longitudes have been present except for the period between 2003 and 2009 and possibly also some time before 1995. Neither do we find any signs of flip-flops with a regular period. The mean time scale of change of the light curve during the observation period is determined to be of the same order of magnitude as the estimated convective turnover time for the star

Time series analysis of V815 Herculis photometry between 1984 and 1998

As a case study of the solar-stellar connection, we have analysed a prolonged time series of BV photometry of the chromospherically active binary V815 Her . The surface differential rotation in the rapidly rotating G5{v} primary caused changes of 4.6% in the seasonal photometric rotation periods. This would imply a differential rotation coefficient of k = 0.184, if the rotation of the starspots follows the solar law of differential rotation and the activity is confined within the same latitudinal range as in the Sun, having k = 0.189 and the spectral-type of G2{v}. Our analysis of the primary and secondary minima of the seasonal light curves indicated that the regions of stronger activity have concentrated on one active longitude, which has maintained a constant rotation period of 1.d79244 for about 14 years. No regular activity cycle was detected in the mean brightness changes of V815 Her

ETDs in Lock-Down: Trends, Analyses and Faculty Perspectives on ETD Embargoes

Owen, Terry, Timothy Hackman and Thomas Harrod. 2009. “ETDs in Lock-Down: Trends, Analyses and Faculty Perspectives on ETD Embargoes.” ETD 2009: 12th International Symposium on Electronic Theses and Dissertations, Pittsburgh, PA, June 10-13, 2009. Also available at http://conferences.library.pitt.edu/ocs/viewabstract.php?id=679&cf=7.Since September 2006, graduate students at the University of Maryland have had the option of restricting access to their ETD in the university’s digital repository (DRUM) for either a one- or six-year period. Embargo requests must be approved by the student’s faculty advisor and submitted to the Graduate School prior to uploading the ETD. Since the beginning of the program, an average of 32% of the ETDs that have been submitted each semester have been embargoed. While Engineering has the largest number of embargoes (150), Chemical and Life Sciences has the greatest percentage (54%), followed closely by Agriculture and Natural Resources (51%) and Business (47%). The College of Arts and Humanities, specifically the English Department, has the largest number of six-year embargoes (75). Faculty advisors who had approved at least one embargo request since 2006 were surveyed to gain insight into their perspectives on publicly available ETDs and ascertain their reasons for approving embargo requests. In general, faculty advisors indicated that they approve ETDs without attempting to change the students’ choice of embargo period, indicating that the student plays a major role in deciding whether or not to embargo their ETD. In addition, faculty stated that the primary reason for approving embargoes was to protect opportunities for future publication. While the percentage of embargoes has remained relatively constant each semester, our goal is to decrease the number of embargoes by educating faculty and students on the benefits of making their research widely available. We are working with the Graduate School and library faculty to develop a scholarly communications program that not only educates faculty and graduate students about the consequences of embargoes, but also makes them more aware of open access issues in general

From convective stellar dynamo simulations to Zeeman-Doppler images

Zeeman-Doppler imaging (ZDI) is used to reconstruct the surface magnetic field of late-type stars from high resolution spectropolarimetric observations. The results are usually described in terms of characteristics of the field topology, i.e. poloidality vs. toroidality and axi-symmetry vs. non-axisymmetry in addition to the field strength. We want to test how well these characteristics are preserved when applying the ZDI method on simulated data, i.e. how accurately the field topology is preserved and to what extent stellar parameters influence the reconstruction. We use published magnetic field data from direct numerical MHD simulations. These have variable rotation rates, and hence represent different levels of activity, of an otherwise Sun-like setup. Our ZDI reconstruction is based on spherical harmonics expansion. By comparing the original values to those of the reconstructed images, we study the ability to reconstruct the surface magnetic field in terms of various characteristics of the field. The main large-scale features are reasonably well recovered, but the strength of the recovered magnetic field is just a fraction of the original input. The quality of the reconstruction shows clear correlations with the data quality. Furthermore, there are some spurious dependencies between stellar parameters and the characteristics of the field. Our study uncovers some limits of ZDI. Firstly, the recovered field strength will generally be lower than the "real" value as smaller structures with opposite polarities will be blurred in the inversion. Secondly, the axisymmetry is overestimated. The poloidality vs. toroidality is better recovered. The reconstruction works better for a stronger field and faster rotation velocity. Still, the ZDI method works surprisingly well even for a weaker field and slow rotation, provided the data has a high signal-to-noise and good rotation phase coverage.Comment: 12 pages, 21 figures, A&A, in press, abstract shortene

Shapes of stellar activity cycles

Context.Magnetic activity cycles are an important phenomenon both in the Sun and other stars. The shape of the solar cycle is commonly characterised by a fast rise and a slower decline, but not much attention has been paid to the shape of cycles in other stars. Aims.Our aim is to study whether the asymmetric shape of the solar cycle is common in other stars as well, and compare the cycle asymmetry to other stellar parameters. We also study the differences in the shape of the solar cycle, depending on the activity indicator that is used. The observations are also compared to simulated activity cycles. Methods.We used the chromospheric Ca II H&K data from the Mount Wilson Observatory HK Project. In this data set, we identified 47 individual cycles from 18 stars. We used the statistical skewness of a cycle as a measure of its asymmetry, and compared this to other stellar parameters. A similar analysis has been performed for magnetic cycles extracted from direct numerical magnetohydrodynamic simulations of solar-type convection zones. Results.The shape of the solar cycle (fast rise and slower decline) is common in other stars as well, although the Sun seems to have particularly asymmetric cycles. Cycle-to-cycle variations are large, but the average shape of a cycle is still fairly well represented by a sinusoid, although this does not take its asymmetry into account. We find only slight correlations between the cycle asymmetry and other stellar parameters. There are large differences in the shape of the solar cycle, depending on the activity indicator that is used. The simulated cycles differ in the symmetry of global simulations that cover the full longitudinal range and are therefore capable of exciting non-axisymmetric large-scale dynamo modes, and wedge simulations that cover a partial extent in longitude, where only axisymmetric large-scale modes are possible. The former preferentially produce positive and the latter negative skewness.Peer reviewe

Starspots due to large-scale vortices in rotating turbulent convection

We study the generation of large-scale vortices in rotating turbulent convection by means of Cartesian direct numerical simulations. We find that for sufficiently rapid rotation, cyclonic structures on a scale large in comparison to that of the convective eddies, emerge, provided that the fluid Reynolds number exceeds a critical value. For slower rotation, cool cyclonic vortices are preferred, whereas for rapid rotation, warm anti-cyclonic vortices are favored. In some runs in the intermediate regime both types of cyclones co-exist for thousands of convective turnover times. The temperature contrast between the vortices and the surrounding atmosphere is of the order of five per cent. We relate the simulation results to observations of rapidly rotating late-type stars that are known to exhibit large high-latitude spots from Doppler imaging. In many cases, cool spots are accompanied with spotted regions with temperatures higher than the average. In this paper, we investigate a scenario according to which the spots observed in the temperature maps could have a non-magnetic origin due to large-scale vortices in the convection zones of the stars.Comment: 8 pages, 8 figures, version published in ApJ. Version with higher resolution figures can be found at http://www.helsinki.fi/~kapyla/publ.htm