University of Maryland, Baltimore County

About: University of Maryland, Baltimore County is a education organization based out in Baltimore, Maryland, United States. It is known for research contribution in the topics: Population & Galaxy. The organization has 8749 authors who have published 20843 publications receiving 795706 citations. The organization is also known as: UMBC.

Automated stress detection using keystroke and linguistic features: An exploratory study

Abstract: Monitoring of cognitive and physical function is central to the care of people with or at risk for various health conditions, but existing solutions rely on intrusive methods that are inadequate for continuous tracking. Less intrusive techniques that facilitate more accurate and frequent monitoring of the status of cognitive or physical function become increasingly desirable as the population ages and lifespan increases. Since the number of seniors using computers continues to grow dramatically, a method that exploits normal daily computer interactions is attractive. This research explores the possibility of detecting cognitive and physical stress by monitoring keyboard interactions with the eventual goal of detecting acute or gradual changes in cognitive and physical function. Researchers have already attributed a certain amount of variability and ''drift'' in an individual's typing pattern to situational factors as well as stress, but this phenomenon has not been explored adequately. In an attempt to detect changes in typing associated with stress, this research analyzes keystroke and linguistic features of spontaneously generated text. Results show that it is possible to classify cognitive and physical stress conditions relative to non-stress conditions based on keystroke and linguistic features with accuracy rates comparable to those currently obtained using affective computing methods. The proposed approach is attractive because it requires no additional hardware, is unobtrusive, is adaptable to individual users, and is of very low cost. This research demonstrates the potential of exploiting continuous monitoring of keyboard interactions to support the early detection of changes in cognitive and physical function.

The causal connection between disc and power-law variability in hard state black hole X-ray binaries

Abstract: We use the XMM–Newton EPIC-pn instrument in timing mode to extend spectral time-lag studies of hard state black hole X-ray binaries into the soft X-ray band. We show that variations of the disc blackbody emission substantially lead variations in the power-law emission, by tenths of a second on variability time-scales of seconds or longer. The large lags cannot be explained by Compton scattering but are consistent with time delays due to viscous propagation of mass accretion fluctuations in the disc. However, on time-scales less than a second the disc lags the power-law variations by a few milliseconds, consistent with the disc variations being dominated by X-ray heating by the power law, with the short lag corresponding to the light traveltime between the power-law emitting region and the disc. Our results indicate that instabilities in the accretion disc are responsible for continuum variability on time-scales of seconds or longer and probably also on shorter time-scales.

The Ionized Gas and Nuclear Environment in NGC 3783. IV. Variability and Modeling of the 900 Kilosecond Chandra Spectrum

Abstract: We present a detailed spectral analysis of the data obtained from NGC 3783 during the period 2000-2001 using Chandra. The data were split in various ways to look for time- and luminosity-dependent spectral variations. This analysis, along with the measured equivalent widths of a large number of X-ray lines and photoionization calculations, lead us to the following results and conclusions. (1) NGC 3783 fluctuated in luminosity by a factor of ~1.5 during individual observations (most of which were of 170 ks duration). These fluctuations were not associated with significant spectral variations. (2) On a longer timescale (20-120 days), we found the source to exhibit two very different spectral shapes. The main difference between these can be well-described by the appearance (in the "high state") and disappearance (in the "low state") of a spectral component that dominates the underlying continuum at the longest wavelengths. Contrary to the case in other objects, the spectral variations are not related to the brightening or the fading of the continuum at short wavelengths in any simple way. NGC 3783 seems to be the first active galactic nucleus (AGN) to show this unusual behavior. (3) The appearance of the soft continuum component is consistent with being the only spectral variation, and there is no need to invoke changes in the opacity of the absorbers lying along the line of sight. Indeed, we find that all the absorption lines that can be reliably measured have the same equivalent widths (within the observational uncertainties) during high and low states. (4) Photoionization modeling indicates that a combination of three ionized absorbers, each split into two kinematic components, can explain the strengths of almost all the absorption lines and bound-free edges. These three components span a large range of ionization and have total column of about 4 × 1022 cm-2. Moreover, all three components are thermally stable and seem to have the same gas pressure. Thus, all three may coexist in the same volume of space. This is the first detection of such a multicomponent, equilibrium gas in an AGN. (5) The only real discrepancy between our model and the observations concerns the range of wavelengths absorbed by the iron M-shell UTA feature. This most likely arises as the result of our underestimation of the poorly known dielectronic recombination rates appropriate for these ions. We also note a small discrepancy in the calculated column density of O VI and discuss its possible origin. (6) The lower limit on the distance of the absorbing gas in NGC 3783 is between 0.2 and 3.2 pc, depending on the component of ionized gas considered. The assumption of pressure equilibrium imposes an upper limit of about 25 pc on the distance of the least-ionized component from the central source.

The Returns of a Community College Education: Evidence From the National Education Longitudinal Survey

Abstract: Using the 2000 follow-up of the National Education Longitudinal Survey, the authors estimated earnings effects of a community college education. Previous research relied on data collected from students enrolled 20 or 30 years ago. Because the labor market and community colleges have changed dramatically since then, the authors provide an update by studying students enrolled in the 1990s. They found substantial evidence that a community college education has positive effects on earnings among young workers. This effect was larger for annual earnings than for hourly wages. Earnings benefits accrued both to those who failed to earn a credential and to those who earned an associate degree. The current results are similar to estimates for earlier cohorts. The stability of the wage advantage of a community college education during a period of growing enrollment provides evidence of a growing relative demand for a community college over a high school education.