5,381 research outputs found
The X-Ray Position and Infrared Counterpart of the Eclipsing X-Ray Pulsar OAO 1657-415
We have measured the precise position of the 38-s eclipsing X-ray pulsar OAO
1657-415 with the Chandra X-Ray Observatory: RA = 17h00m48.90s, Dec =
-41d39m21.6s, equninox J2000, error radius = 0.5 arcsec. Based on the
previously measured pulsar mass function and X-ray eclipse duration, this
10.4-d high-mass X-ray binary is believed to contain a B supergiant companion.
Deep optical imaging of the field did not detect any stars at the Chandra
source position, setting a limit of V>23. However, near-IR imaging revealed a
relatively bright star (J=14.1, H=11.9, K_s=10.7) coincident with the Chandra
position, and we identify this star as the IR counterpart of OAO 1657-415. The
IR colors and magnitudes and the optical non-detections for this star are all
consistent with a highly reddened B supergiant (A_V= 20.4 +/- 1.3) at a
distance of 6.4 +/- 1.5 kpc. This implies an X-ray luminosity of 3e36 erg/s
(2-10 keV). IR spectroscopy can verify the spectral type of the companion and
measure its radial velocity curve, yielding a neutron star mass measurement.Comment: 4 pages. ApJ in press (Vol. 573, July 10 issue
The Missions and Camino Real of Baja California: A Binational View
From the end of the seventeenth century through the early nineteenth century, missionaries from the Jesuit, Franciscan, and Dominican orders founded numerous missions in Baja California. In this article we introduce readers in Alta California to these missions, which along with El Camino Real de las Californias, were the most important institutions used by the Spanish Crown to colonize the Pacific coast of North America
Professional Development for the Integration of Engineering in High School STEM Classrooms
Science, Technology, Engineering, and Mathematics (STEM) education in the U.S. is in transition. The recently published A Framework for K-12 Science Education: Practices, Crosscutting Concepts, and Core Ideas as well as the Next Generation Science Standards are responsive to this call and clearly articulate a vision that includes engineering practices as key components. This shift presents significant challenges to school districts owing to a stark lack of research-based engineering-focused instructional materials and corresponding teacher professional development. The purpose of this study was to investigate the impact of a professional development program on high school STEM teachersâ ability to enact design-based pedagogical practices associated with the pre-selected engineering design curriculum (INSPIRES Engineering in Healthcare: A Heart-Lung System Case Study). Data were generated through evaluation of teacher practice using the Reformed Teaching Observation Protocol (RTOP). Findings demonstrated that RTOP scores were statistically significant
Non-relativistic Maxwell-Chern-Simons Vortices
The non-relativistic Maxwell-Chern-Simons model recently introduced by Manton
is shown to admit self-dual vortex solutions with non-zero electric field. The
interrelated ``geometric'' and ``hidden'' symmetries are explained. The theory
is also extended to (non-relativistic) spinors. A relativistic, self-dual
model, whose non-relativistic limit is the Manton model is also presented. The
relation to previous work is discussed.Comment: 20 pages plain TeX. Revised: minor errors corrected and symmetries
explained in a clearer way. Version as will appear in Ann. Phys. (N.Y.
A culture-based entrepreneurship program: Impact on student interest in business ownership
This paper reports the results of a study that examined the impact of a culture-based entrepreneurship study abroad program on interest in business ownership. Forty-three students were asked to complete a pre and post program questionnaire that asked about their understanding of a variety of program activities and to gauge their interest in starting a business. Almost no similar research has been reported in the literature. Pre- and postprogram mean rankings of the variables are reported The results indicated that post-program mean rankings tend to be higher than pre-program mean rankings. Twelve of the post-program mean values are significantly different from pre-program mean values. Logit regression analysis indicated that the culture variable was positively associated with interest in starting a business while the Spanish business and entrepreneurial skills, and program structure variables were negatively associated with business ownership. The results of this study may be of interest to educators involved in developing entrepreneurship and study abroad courses and programs. The study may be of special interest to those involved in developing integrative entrepreneurship programs
Effect of Defoliation Frequency and Severity during Winter on Herbage Regrowth and WaterâSoluble Carbohydrate Content of Perennial Ryegrass (\u3cem\u3eLolium perenne\u3c/em\u3e L.) Dominant Swards
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