23 research outputs found
Examining EdD Dissertations in Practice: The Carnegie Project on the Education Doctorate
In 2007, 25 colleges and schools of education (Phase I) came together under the aegis of the Carnegie Project on the Education Doctorate (CPED) to transform doctoral education for education practitioners. A challenging aspect of the reform of the educational doctorate is the role and design of the dissertation or Dissertation in Practice. In response to consortium concerns, members of the CPED Dissertation in Practice Awards Committee conducted this action research study to examine the format and design of Dissertations in Practice submitted by (re) designed programs. Data were gathered with an online survey, interviews, analyses of 25 Dissertations in Practice submitted in 2013 to the Committee. Results indicated few changes occurred in the final product, despite evidence of change in the Dissertation in Practice process. Findings contribute to debates about the distinctive nature of EdDs (and of professional doctorates generally) as distinct from PhDs, and how about the key criteria for demonstrating ânew knowledge to solve significant problems of practiceâ are demonstrated through the dissertation submission
Chandra Cluster Cosmology Project II: Samples and X-ray Data Reduction
We discuss the measurements of the galaxy cluster mass functions at z=~0.05
and z=~0.5 using high-quality Chandra observations of samples derived from the
ROSAT PSPC All-Sky and 400deg^2 surveys. We provide a full reference for the
data analysis procedures, present updated calibration of relations between the
total cluster mass and its X-ray indicators (T_X, Mgas, and Y_X) based on a
subsample of low-z relaxed clusters, and present a first measurement of the
evolving L_X-Mtot relation (with Mtot estimated from Y_X) obtained from a
well-defined statistically complete cluster sample and with appropriate
corrections for the Malmquist bias applied. Finally, we present the derived
cluster mass functions, estimate the systematic uncertainties in this
measurement, and discuss the calculation of the likelihood function. We
confidently measure the evolution in the cluster comoving number density at a
fixed mass threshold, e.g., by a factor of 5.0 +- 1.2 at M_500=2.5e14 h^-1 Msun
between z=0 and 0.5. This evolution reflects the growth of density
perturbations and can be used for the cosmological constraints complementing
those from the distance-redshift relation.Comment: ApJ in press (Feb 10, 2009 issue); replacement to match accepted
version, includes revisions in response to referee's and community comment
The Observed Growth of Massive Galaxy Clusters II: X-ray Scaling Relations
(Abridged) This is the second in a series of papers in which we derive
simultaneous constraints on cosmology and X-ray scaling relations using
observations of massive, X-ray flux-selected galaxy clusters. The data set
consists of 238 clusters drawn from the ROSAT All-Sky Survey with 0.1-2.4 keV
luminosities >2.5e44 erg/second, and incorporates extensive follow-up
observations using the Chandra X-ray Observatory. Our analysis accounts
self-consistently for all selection effects, covariances and systematic
uncertainties. Here we describe the reduction of the follow-up X-ray
observations, present results on the cluster scaling relations, and discuss
their implications. Our constraints on the luminosity-mass and temperature-mass
relations, measured within r_500, lead to three important results. First, the
data support the conclusion that excess heating of the intracluster medium has
altered its thermodynamic state from that expected in a simple, gravitationally
dominated system; however, this excess heating is primarily limited to the
central regions of clusters (r<0.15r_500). Second, the intrinsic scatter in the
center-excised luminosity-mass relation is remarkably small, being undetected
at the <10% level in current data; for the hot, massive clusters under
investigation, this scatter is smaller than in either the temperature-mass or
Y_X-mass relations (10-15%). Third, the evolution with redshift of the scaling
relations is consistent with the predictions of simple, self-similar models of
gravitational collapse, indicating that the mechanism responsible for heating
the central regions of clusters was in operation before redshift 0.5 (the limit
of our data) and that its effects on global cluster properties have not evolved
strongly since then.Comment: 25 pages, 7 figures, 14 tables. v3: final version (typographic
corrections). Results can be downloaded at
https://www.stanford.edu/group/xoc/papers/xlf2009.htm
The gas distribution in the outer regions of galaxy clusters
We present the analysis of a local (z = 0.04 - 0.2) sample of 31 galaxy
clusters with the aim of measuring the density of the X-ray emitting gas in
cluster outskirts. We compare our results with numerical simulations to set
constraints on the azimuthal symmetry and gas clumping in the outer regions of
galaxy clusters. We exploit the large field-of-view and low instrumental
background of ROSAT/PSPC to trace the density of the intracluster gas out to
the virial radius. We perform a stacking of the density profiles to detect a
signal beyond r200 and measure the typical density and scatter in cluster
outskirts. We also compute the azimuthal scatter of the profiles with respect
to the mean value to look for deviations from spherical symmetry. Finally, we
compare our average density and scatter profiles with the results of numerical
simulations. As opposed to some recent Suzaku results, and confirming previous
evidence from ROSAT and Chandra, we observe a steepening of the density
profiles beyond \sim r500. Comparing our density profiles with simulations, we
find that non-radiative runs predict too steep density profiles, whereas runs
including additional physics and/or treating gas clumping are in better
agreement with the observed gas distribution. We report for the first time the
high-confidence detection of a systematic difference between cool-core and
non-cool core clusters beyond \sim 0.3r200, which we explain by a different
distribution of the gas in the two classes. Beyond \sim r500, galaxy clusters
deviate significantly from spherical symmetry, with only little differences
between relaxed and disturbed systems. We find good agreement between the
observed and predicted scatter profiles, but only when the 1% densest clumps
are filtered out in the simulations. [Abridged]Comment: The data for the average profiles and individual clusters can be
downloaded at:
http://www.isdc.unige.ch/~deckert/newsite/The_Planck_ROSAT_project.htm
Enrichment and Pre-Heating in Intragroup Gas from Galactic Outflows
We examine metal and entropy content in galaxy groups having T_X~0.5-2 keV in
cosmological hydrodynamic simulations. Our simulations include a
well-constrained prescription for galactic outflows following momentum-driven
wind scalings, and a sophisticated chemical evolution model. Our simulation
with no outflows reproduces observed iron abundances in X-ray emitting gas, but
the oxygen abundance is too low; including outflows yields iron and oxygen
abundances in good agreement with data. X-ray measures of [O/Fe] primarily
reflect metal distribution mechanisms into hot gas, not the ratio of Type Ia to
Type II supernovae within the group. Iron abundance increases by x2 from z=1-0
independent of group size, consistent with that seen in clusters, while [O/Fe]
drops by ~30%. Core entropy versus temperature is elevated over self-similar
predictions regardless of outflows due to radiative cooling removing
low-entropy gas, but outflows provide an additional entropy contribution below
1 keV. This results in a noticeable break in the L_X-T_X relation below 1 keV,
as observed. Importantly, outflows serve to reduce the stellar content of
groups to observed levels. Radial profiles from simulations are in broad
agreement with observations, but there remain non-trivial discrepancies that
may reflect an excess of late-time star formation in central group galaxies in
our simulations. Our model with outflows suggests a connection between physical
processes of galaxy formation and both pre-heating and enrichment in intragroup
gas, though more definitive conclusions must await a model that simultaneously
suppresses cooling flows as observed.Comment: 16 pages, MNRAS, accepted versio
Cosmology with clusters of galaxies
In this Chapter I review the role that galaxy clusters play as tools to
constrain cosmological parameters. I will concentrate mostly on the application
of the mass function of galaxy clusters, while other methods, such as that
based on the baryon fraction, are covered by other Chapters of the book. Since
most of the cosmological applications of galaxy clusters rely on precise
measurements of their masses, a substantial part of my Lectures concentrates on
the different methods that have been applied so far to weight galaxy clusters.
I provide in Section 2 a short introduction to the basics of cosmic structure
formation. In Section 3 I describe the Press--Schechter (PS) formalism to
derive the cosmological mass function, then discussing extensions of the PS
approach and the most recent calibrations from N--body simulations. In Section
4 I review the methods to build samples of galaxy clusters at different
wavelengths. Section 5 is devoted to the discussion of different methods to
derive cluster masses. In Section 6 I describe the cosmological constraints,
which have been obtained so far by tracing the cluster mass function with a
variety of methods. Finally, I describe in Section 7 the future perspectives
for cosmology with galaxy clusters and the challenges for clusters to keep
playing an important role in the era of precision cosmology.Comment: 49 pages, 19 figures, Lectures for 2005 Guillermo Haro Summer School
on Clusters, to appear in "Lecture notes in Physics" (Springer
Mentoring among scientists :implications for interpersonal relationships within a formal mentoring program /by Bryan D. Maughan.
This study sheds an optimistic light on the future of the technology workforce. Effective mentors facilitate knowledge transfer and succession planning by applying interpersonal relationship principles found in transformational leadership, mentorship, and learnership. Mentors who incorporate such principles develop a cultural ambience where caring is obvious and learning is optimized. In such a culture the immediate application of knowledge becomes a natural outgrowth in which those relationships produce the most beneficial outcomes for the prot{acute}eg{acute}e, mentor, and organization. Results of this study indicate that the degree of success will be influenced by the deeper implications of interpersonal relationships and the developmental process of adult learning. Mentoring is fundamentally a leadership and learnership activity which is done in relationship. To build an enduring research and development community, mentors should become aware of and active in their understanding of how learning happens and how interpersonal relationships underpin the reception and retention of knowledge. To develop an effective mentorship requires an operational definition which includes the necessity of relationship development. Invitations to become a part of an organization and accept and retain knowledge are extended tacitly through character, intelligence, and caring attitudes, but there is something deeper that determines the degree of knowledge that will be captured and retained. Tacitly, mentors communicate in ways that either undermine or bolster strategies and skills meant to improve leadership development and knowledge management. Training specific to the development of healthy interpersonal relationships can help manage tacit knowledge and achieve the results mentoring promises.Thesis (Ph. D., Education)--University of Idaho, April 2007