976 research outputs found
Food Security and the Federal Minimum Wage
This working paper, by William M. Rodgers III, Hanley S. Chiang, and Bruce W. Klein, estimates the extent to which increases in the U.S. federal minimum wage in October 1996 and September 1997 improved the ability of households to be food secure -- that is, to purchase for their members an adequate supply of nutritional and safe foods. First, the authors show that the two increases significantly altered the hourly wage distribution of householders (principal person in a household). The shifts were greatest among household heads that are minority, single parents, and household heads with no more than a high school diploma. Even after controlling for the link between the 1990s economic expansion and food security, the October 1996 and September 1997 increases in the federal minimum wage raised food security and reduced hunger, particularly in low-income households where householders had completed no more than a high school degree or were a single parent
Orderly Spanning Trees with Applications
We introduce and study the {\em orderly spanning trees} of plane graphs. This
algorithmic tool generalizes {\em canonical orderings}, which exist only for
triconnected plane graphs. Although not every plane graph admits an orderly
spanning tree, we provide an algorithm to compute an {\em orderly pair} for any
connected planar graph , consisting of a plane graph of , and an
orderly spanning tree of . We also present several applications of orderly
spanning trees: (1) a new constructive proof for Schnyder's Realizer Theorem,
(2) the first area-optimal 2-visibility drawing of , and (3) the best known
encodings of with O(1)-time query support. All algorithms in this paper run
in linear time.Comment: 25 pages, 7 figures, A preliminary version appeared in Proceedings of
the 12th Annual ACM-SIAM Symposium on Discrete Algorithms (SODA 2001),
Washington D.C., USA, January 7-9, 2001, pp. 506-51
(Mis)Labeled: The Challenge of Academic Capital Formation for Hmong American High School Students in an Urban Setting
The Model Minority Myth for Asians as a group disguises the challenges facing Hmong and other underrepresented Southeast Asian groups. Using the theoretical framework of Academic Capital Formation (ACF), this qualitative study examines the implications of the Model Minority Myth by focusing on the experiences and educational challenges of Hmong American high school students in an urban setting in the Midwest. Results from this study alludes to a bimodal pattern of achievement amongst the Asian American Pacific Islander community, emphasizing the importance of increasing visibility for underrepresented Southeast Asians, such as Hmong Americans, with regards to access to higher education
Classifying the mechanisms of electrochemical shock in ion-intercalation materials
“Electrochemical shock” – the electrochemical cycling-induced fracture of materials – contributes to impedance growth and performance degradation in ion-intercalation batteries, such as lithium-ion. Using a combination of micromechanical models and acoustic emission experiments, the mechanisms of electrochemical shock are identified, classified, and modeled in targeted model systems with different composition and microstructure. A particular emphasis is placed on mechanical degradation occurring in the first electrochemical cycle. Three distinct mechanisms of electrochemical shock are identified, and a fracture mechanics failure criterion is derived for each mechanism. In a given material system, crystal symmetry and phase-behavior determine the active mechanisms. A surprising result is that electrochemical shock in commercial lithium-storage materials occurs by mechanisms that are insensitive to the electrochemical cycling rate. This fundamental understanding of electrochemical shock leads naturally to practical design criteria for battery materials and microstructures that improve performance and energy storage efficiency. These microstructure and crystal chemical design criteria are demonstrated experimentally for spinel materials such as LiMn2O4 and LiMn1.5Ni0.5O4. A case study of LiMn1.5Ni0.5O4 is presented, in which small changes in composition that have negligible impact on electrochemical properties induce a significant change in phase behavior that allow electrochemical shock at relevant electrochemical cycling rates to be avoided. Although lithium-storage materials are used as model systems for experimental study, the physical phenomena are common to other ion-intercalation systems, including sodium- and magnesium-storage compounds
The Brightening of Re50N: Accretion Event or Dust Clearing?
The luminous Class I protostar HBC 494, embedded in the Orion A cloud, is
associated with a pair of reflection nebulae, Re50 and Re50N, which appeared
sometime between 1955 and 1979. We have found that a dramatic brightening of
Re50N has taken place sometime between 2006 and 2014. This could result if the
embedded source is undergoing a FUor eruption. However, the near-infrared
spectrum shows a featureless very red continuum, in contrast to the strong CO
bandhead absorption displayed by FUors. Such heavy veiling, and the high
luminosity of the protostar, is indicative of strong accretion but seemingly
not in the manner of typical FUors. We favor the alternative explanation that
the major brightening of Re50N and the simultaneous fading of Re50 is caused by
curtains of obscuring material that cast patterns of illumination and shadows
across the surface of the molecular cloud. This is likely occurring as an
outflow cavity surrounding the embedded protostar breaks through to the surface
of the molecular cloud. Several Herbig-Haro objects are found in the region.Comment: 8 pages, accepted by Ap
Using Clinical Decision Support to Maintain Medication and Problem Lists: A Pilot Study to Yield Higher Patient Safety
To Investigate Whether Clinical Decision Support that Automates the Matching of Ordered Drugs to Problems (Clinical Diagnoses) on the Problem List Can Enhance the Maintenance of Both Medication and Problem Lists in the Electronic Medical Record, We Designed a Clinical Decision Support System to Match Ordered Drugs on the Medication List and Ongoing Problems on the Problem List. We Evaluated the Capability and Performance of This Clinical Decision Support System in Medication-Problem Matching using Physician Expert Chart Audits to Match Ordered Drugs to Ongoing Clinical Problems. a Clinical Decision Support System Was Shown to Be Useful in Improving Medication-Problem Matches in 140 Randomly Selected Audited Patient Encounters in Three Inpatient Units. Enhanced Maintenance of Both the Medication and Problem Lists Can Permit the Exploitation of Advanced Decision Support Strategies that Yield Higher Patient Safety. © 2008 IEEE
The Light Curve of the Weakly-Accreting T Tauri Binary KH 15D from 2005-10: Insights into the Nature of its Protoplanetary Disk
Photometry of the unique pre-main sequence binary system KH 15D is presented,
spanning the years 2005-2010. This system has exhibited photometric variations
and eclipses over the last 50 years caused by a precessing circumbinary disk.
Advancement of the occulting edge across the binary orbit has continued and the
photospheres of both stars are now completely obscured at all times. The system
is now visible only by scattered light, and yet it continues to show a periodic
variation on the orbital cycle with an amplitude exceeding two magnitudes. This
variation, which depends only on the binary phase, has likely been present in
the data since at least 1995. It can, by itself, account for shoulders on the
light curve prior to ingress and following egress, obviating the need for
components of extant models such as a scattering halo around star A or forward
scattering from a fuzzy disk edge. A plausible source for the variable
scattering component is reflected light from the far side of a warped occulting
disk. We have detected color changes in V-I of several tenths of a magnitude to
both the blue and red that occur during times of minima. These may indicate the
presence of a third source of light (faint star) within the system, or a change
in the reflectance properties of the disk as the portion being illuminated
varies with the orbital motion of the stars. The data support a picture of the
circumbinary disk as a geometrically thin, optically thick layer of perhaps mm
or cm-sized particles that has been sculpted by the binary stars and possibly
other components into a decidedly nonplanar configuration. A simple (infinitely
sharp) knife-edge model does a good job of accounting for all of the recent
(2005-2010) occultation data.Comment: To appear in The Astronomical Journa
Multiyear On-orbit Calibration and Performance of Terra MODIS Thermal Emissive Bands
Since launch in December 1999, Terra MODIS has been making continuous Earth observations for more than seven years. It has produced a broad range of land, ocean, and atmospheric science data products for improvements in studies of global climate and environmental change. Among its 36 spectral bands, there are 20 reflective solar bands (RSB) and 16 thermal emissive bands (TEB). MODIS thermal emissive bands cover the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions with wavelengths from 3.7 to 14.4pm. They are calibrated on-orbit using an on-board blackbody (BB) with its temperature measured by a set of thermistors on a scan-by-scan basis. This paper will provide a brief overview of MODIS TEB calibration and characterization methodologies and illustrate on-board BB functions and TEB performance over more than seven years of on-orbit operation and calibration. Discussions will be focused on TEB detector short-term stability and noise characterization, and changes in long-term response (or system gain). Results show that Terra MODIS BB operation has been extremely stable since launch. When operated at its nominal controlled temperature of 290K, the BB temperature variation is typically less than +0.30mK on a scan-by-scan basis and there has been no time-dependent temperature drift. In addition to excellent short-term stability, most TEB detectors continue to meet or exceed their specified noise characterization requirements, thus enabling calibration accuracy and science data product quality to be maintained. Excluding the noisy detectors identified pre-launch and those that occurred post-launch, the changes in TEB responses have been less than 0.7% on an annual basis. The optical leak corrections applied to bands 32-36 have been effective and stable over the entire missio
Binaries in the Kuiper Belt
Binaries have played a crucial role many times in the history of modern
astronomy and are doing so again in the rapidly evolving exploration of the
Kuiper Belt. The large fraction of transneptunian objects that are binary or
multiple, 48 such systems are now known, has been an unanticipated windfall.
Separations and relative magnitudes measured in discovery images give important
information on the statistical properties of the binary population that can be
related to competing models of binary formation. Orbits, derived for 13
systems, provide a determination of the system mass. Masses can be used to
derive densities and albedos when an independent size measurement is available.
Angular momenta and relative sizes of the majority of binaries are consistent
with formation by dynamical capture. The small satellites of the largest
transneptunian objects, in contrast, are more likely formed from collisions.
Correlations of the fraction of binaries with different dynamical populations
or with other physical variables have the potential to constrain models of the
origin and evolution of the transneptunian population as a whole. Other means
of studying binaries have only begun to be exploited, including lightcurve,
color, and spectral data. Because of the several channels for obtaining unique
physical information, it is already clear that binaries will emerge as one of
the most useful tools for unraveling the many complexities of transneptunian
space.Comment: Accepted for inclusion in "The Kuiper Belt", University of Arizona
Press, Space Science Series Corrected references in Table
Factors predictive of acute renal failure and need for hemodialysis among ED patients with rhabdomyolysis
Objective: We assessed the primary causes of rhabdomyolysis, the factors associated with the
development of acute renal failure (ARF), and the need for hemodialysis (HD) among a series of
patients presenting to an urban emergency department with rhabdomyolysis.
Methods: A chart review between January 1992 and December 1995 was conducted of patients aged
18 years or older with a diagnosis of rhabdomyolysis and an initial serum creatine phosphokinase greater
than 1000 U/L. Patients were excluded if they had evidence of myocardial ischemia, cerebrovascular
insufficiency, or the development of rhabdomyolysis after hospitalization. Demographic information,
presumed causative factors, past medical history, medication usage, and laboratory data were collected.
Results: Ninety-seven patients (93 men, 4 women) were enrolled, with a mean age of 35.7 years. The
most common causes of rhabdomyolysis were cocaine (30), exercise (29), and immobilization (18).
Seventeen of 97 (17.5%) patients developed ARF; 8 patients (8.25%) needed HD. Several clinical and
laboratory factors were statistically associated with development of ARF and need for HD. The only
variable that was predictive of both ARF and need for HD in separate multivariate regression models was
the initial creatinine (Cr). Initial blood urea nitrogen also was predictive of the need for HD. No patient
developed ARF with an initial Cr less than 1.7 mg/dL.
Conclusion: Acute renal failure and need for HD are common complications of rhabdomyolysis. Except
for initial serum Cr and blood urea nitrogen, clinical and laboratory factors were not reliable predictors for
the development of ARF or need for HD.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/40388/1/Fernandez_Factors predictive of acute renal failure_2005.pd
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