252 research outputs found
Recommended from our members
Empirical Analyses and Connectionist Modeling of Real-Time Human Image Understanding
Running head: IMPROVING STUDENT ACHIEVEMENT 1 A Systems-based Synthesis of Research Related to Improving Students ’ Academic Performance
This paper addresses the issue of school improvement by looking to research on both the variables that should be the focus of school improvement efforts as well as factors that make it more likely that the organization will actually implement research findings. Issues of transformational leadership, instructional leadership, and high functioning teams are addressed; Hattie’s (2009) review of over 800 meta-analyses of variables related to school achievement is the primary source of identifying classroom and school variables that can be addressed by educators. As developed nations move out of the industrial age into the information/conceptual age, there is an ongoing debate about how to best prepare children and youth for adult success in the twenty-first century (Huitt, 1999b, 2007). While there is a consensus that schools should play a major role in this process, there is less agreement about exactly what that role should be. Some believe that the primary focus of schools should be academic preparation of students (Hirsch, 1987, 1996; Tienken, & Wilson, 2001), that classroom teachers are primarily responsible for student academic achievement (Darling-Hammond, 2000), and schools should efficiently and effectively organize themselves towards that task (Engelmann & Carnine, 1991). These effort
A Spectacular H Complex in Virgo: Evidence for a Collision Between M86 and NGC 4438 and Implications for Collisional ISM Heating of Ellipticals
Deep wide-field H+[NII] imaging around the Virgo cluster giant
elliptical galaxy M86 reveals a highly complex and disturbed ISM/ICM. The most
striking feature is a set of H filaments which clearly connect M86 with
the nearby disturbed spiral NGC 4438 (23=120 kpc projected away), providing
strong evidence for a previously unrecognized collision between them.
Spectroscopy of selected regions show a fairly smooth velocity gradient between
M86 and NGC 4438, consistent with the collision scenario. Such a collision
would impart significant energy into the ISM of M86, probably heating the gas
and acting to prevent the gas from cooling to form stars. We propose that cool
gas stripped from NGC 4438 during the collision and deposited in its wake is
heated by shocks, ram pressure drag, or thermal conduction, producing most of
the H filaments. Some H filaments are associated with the
well-known ridge of bright X-ray emission to the NW of the nucleus, suggesting
that the collision is responsible for peculiarities of M86 previously ascribed
to other effects. M86 is radio-quiet, thus AGN heating is unlikely to play a
significant role. The M86 system has implications for understanding the role of
gravitational interactions in the heating of the ISM in ellipticals, and how
collisions in clusters transform galaxies.Comment: 6 pages, 2 figures. For high-resolution images, see
http://www.astro.yale.edu/tal/research/index.htm
Chandra Observations of the Interacting NGC 4410 Galaxy Group
We present high resolution X-ray imaging data from the ACIS-S instrument on
the Chandra telescope of the nearby interacting galaxy group NGC 4410. Four
galaxies in the inner portion of this group are clearly detected by Chandra,
including the peculiar low luminosity radio galaxy NGC 4410A. In addition to a
nuclear point source, NGC 4410A contains diffuse X-ray emission, including an
X-ray ridge extending out to about 12" (6 kpc) to the northwest of the nucleus.
This ridge is coincident with an arc of optical emission-line gas, which has
previously been shown to have optical line ratios consistent with shock
ionization. This structure may be due to an expanding superbubble of hot gas
caused by supernovae and stellar winds or by the active nucleus. The Chandra
observations also show four or five possible compact ultra-luminous X-ray (ULX)
sources (L(x) >= 10^39 erg/s) associated with NGC 4410A. At least one of these
candidate ULXs appears to have a radio counterpart, suggesting that it may be
due to an X-ray binary with a stellar-mass black hole, rather than an
intermediate mass black hole. In addition, a faint diffuse intragroup X-ray
component has been detected between the galaxies (L(x) ~ 10^41 erg/s). This
supports the hypothesis that the NGC 4410 group is in the process of evolving
via mergers from a spiral-dominated group (which typically have no
X-ray-emitting intragroup gas) to an elliptical-dominated group (which often
have a substantial intragroup medium).Comment: 27 pages, 14 figures; Accepted by Astronomical Journal; color images
at http://www.etsu.edu/physics/bsmith/research/n4410.htm
The Two-dimensional XMM-Newton Group Survey: z<0.012 groups
We present the results of the 2-dimensional XMM-Newton Group Survey (2dXGS),
an archival study of nearby galaxy groups. In this paper we consider eleven
nearby systems (z<0.012) in Mulchaey et al. (2003), which span a broad range in
X-ray luminosity from 10^40 to 10^43 ergs/s. We measure the iron abundance and
temperature distribution in these systems and derive pressure and entropy maps.
We find statistically significant evidence for structure in the entropy and
pressure of the gas component of seven groups on the 10-20% level. The
XMM-Newton data for the three groups with best statistics also suggest patchy
metalicity distributions within the central 20--50 kpc of the brightest group
galaxy, probed with 2-10 kpc resolution. This provides insights into the
processes associated with thermalization of the stellar mass loss. Analysis of
the global properties of the groups reveals a subclass of X-ray faint groups,
which are characterized by both higher entropy and lower pressure. We suggest
that the merger history of the central elliptical is responsible for both the
source and the observed thermodynamical properties of the hot gas of the X-ray
faint groups.Comment: 18 pages, ApJ, 646, 143, 200
Properties of the H-alpha-emitting Circumstellar Regions of Be Stars
Long-baseline interferometric observations obtained with the Navy Prototype
Optical Interferometer of the H-alpha-emitting envelopes of the Be stars eta
Tauri and beta Canis Minoris are presented. For compatibility with the
previously published interferometric results in the literature of other Be
stars, circularly symmetric and elliptical Gaussian models were fitted to the
calibrated H-alpha observations. The models are sufficient in characterizing
the angular distribution of the H-alpha-emitting circumstellar material
associated with these Be stars. To study the correlations between the various
model parameters and the stellar properties, the model parameters for eta Tau
and beta CMi were combined with data for other Be stars from the literature.
After accounting for the different distances to the sources and stellar
continuum flux levels, it was possible to study the relationship between the
net H-alpha emission and the physical extent of the H-alpha-emitting
circumstellar region. A clear dependence of the net H-alpha emission on the
linear size of the emitting region is demonstrated and these results are
consistent with an optically thick line emission that is directly proportional
to the effective area of the emitting disk. Within the small sample of stars
considered in this analysis, no clear dependence on the spectral type or
stellar rotation is found, although the results do suggest that hotter stars
might have more extended H-alpha-emitting regions.Comment: 24 pages, 16 figures, accepted for publication in Ap
Minimally Invasive Mitral Valve Surgery III: Training and Robotic-Assisted Approaches.
Minimally invasive mitral valve operations are increasingly common in the United States, but robotic-assisted approaches have not been widely adopted for a variety of reasons. This expert opinion reviews the state of the art and defines best practices, training, and techniques for developing a successful robotics program
Minimally Invasive Mitral Valve Surgery I: Patient Selection, Evaluation, and Planning.
Widespread adoption of minimally invasive mitral valve repair and replacement may be fostered by practice consensus and standardization. This expert opinion, first of a 3-part series, outlines current best practices in patient evaluation and selection for minimally invasive mitral valve procedures, and discusses preoperative planning for cannulation and myocardial protection
Minimally Invasive Mitral Valve Surgery II: Surgical Technique and Postoperative Management.
Techniques for minimally invasive mitral valve repair and replacement continue to evolve. This expert opinion, the second of a 3-part series, outlines current best practices for nonrobotic, minimally invasive mitral valve procedures, and for postoperative care after minimally invasive mitral valve surgery
1957 Ruby Yearbook
A digitized copy of the 1957 Ruby, the Ursinus College yearbook.https://digitalcommons.ursinus.edu/ruby/1060/thumbnail.jp
- …