5,267 research outputs found
A 20cm VLA Survey of Abell Clusters of Galaxies VI. Radio/Optical Luminosity Functions
From a statistically complete sample of 188 radio galaxies in Abell clusters,
we examine the radio/optical correlations, the FR I/II division, and the
univariate and bivariate luminosity functions. As suggested by Owen (1993), the
FR I/II division is shown to be a strong function of the optical luminosity of
the host galaxy (proportional to L_opt^2). This dependence is also seen in the
bivariate luminosity function, which suggests that the evolutionary tracks of
radio sources and/or the initial conditions in the source are governed by the
host galaxy properties. The probability for detecting radio emission increases
with optical luminosity. The optical dependence is clearly separated in the
integral luminosity functions which can be used as a constraint to models of FR
I radio power evolution. Additionally, the source counts from the integrated
univariate radio luminosity function (RLF) are consistent with our suggestion
in paper V that radio sources may be a transient phenomenon which occurs in all
elliptical galaxies at some time (or several times) over their lifetime. We
find no statistically significant differences in the luminosity functions
between rich cluster samples and radio sources not selected to reside in
clusters. These results suggest that all radio galaxies live in similar
environments in that the optical luminosity and the properties of the host
galaxy are the most important parameters which affect radio source formation
and evolution.Comment: 21 pages LaTeX, 3 tables, 12 figures. To appear in July 1996 A
Instructor perspectives on iteration during upper-division optics lab activities
Although developing proficiency with modeling is a nationally endorsed
learning outcome for upper-division undergraduate physics lab courses, no
corresponding research-based assessments exist. Our longterm goal is to develop
assessments of students' modeling ability that are relevant across multiple
upper-division lab contexts. To this end, we interviewed 19 instructors from 16
institutions about optics lab activities that incorporate photodiodes.
Interviews focused on how those activities were designed to engage students in
some aspects of modeling. We find that, according to many interviewees,
iteration is an important aspect of modeling. In addition, interviewees
described four distinct types of iteration: revising apparatuses, revising
models, revising data-taking procedures, and repeating data collection using
existing apparatuses and procedures. We provide examples of each type of
iteration, and discuss implications for the development of future modeling
assessments.Comment: 4 pages, 1 figure; under revie
Access to undergraduate research experiences at a large research university
The American Physical Society recently released a statement calling on all
university physics departments to provide or facilitate access to research
experiences for all undergraduate students. In response, we investigated the
current status of access to undergraduate research at University of Colorado
Boulder (CU), a large research institution where the number of undergraduate
physics majors outnumber faculty by roughly ten to one. We created and
administered two surveys within CU's Physics Department: one probed
undergraduate students' familiarity with, and participation in, research; the
other probed faculty members' experiences as research mentors to
undergraduates. We describe the development of these instruments, our results,
and our corresponding evidence-based recommendations for improving local access
to undergraduate research experiences. Reflecting on our work, we make several
connections to an institutional change framework and note how other
universities and colleges might adapt our process.Comment: 4 pages, 3 figures, 1 table; Submitted to 2015 PERC Proceeding
Student ownership of projects in an upper-division optics laboratory course: A multiple case study of successful experiences
We investigate students' sense of ownership of multiweek final projects in an
upper-division optics lab course. Using a multiple case study approach, we
describe three student projects in detail. Within-case analyses focused on
identifying key issues in each project, and constructing chronological
descriptions of those events. Cross-case analysis focused on identifying
emergent themes with respect to five dimensions of project ownership: student
agency, instructor mentorship, peer collaboration, interest and value, and
affective responses. Our within- and cross-case analyses yielded three major
findings. First, coupling division of labor with collective brainstorming can
help balance student agency, instructor mentorship, and peer collaboration.
Second, students' interest in the project and perceptions of its value can
increase over time; initial student interest in the project topic is not a
necessary condition for student ownership of the project. Third, student
ownership is characterized by a wide range of emotions that fluctuate as
students alternate between extended periods of struggle and moments of success
while working on their projects. These findings not only extend the literature
on student ownership into a new educational domain---namely, upper-division
physics labs---they also have concrete implications for the design of
experimental physics projects in courses for which student ownership is a
desired learning outcome. We describe the course and projects in sufficient
detail that others can adapt our results to their particular contexts.Comment: 22 pages, 3 tables, submitted to Phys. Rev. PE
Fixation of virgin lunar surface soil
Two systems are shown to be suitable for fixing loose particulate soils with a polymer film, without visually detectable disturbance of the soil particle spatial relationships. A two-component system is described, which uses a gas monomer condensible at the soil temperature and a gas phase catalyst acting to polymerize the monomer. A one-component system using a monomer which polymerizes spontaneously on and within the top few millimeters of the soil is also considered. The two-component system employs a simpler apparatus, but it operates over a narrower temperature range (approximately -40 to -10 C). Other two-component systems were identified which may operate at soil temperatures as high as +100 C, at relatively narrow temperature ranges of approximately 30 C. The one-component system was demonstrated to operate successfully with initial soil temperatures from -70 C or lower to +150 C
Upcycling Church: New Hope for Transforming Declining and Plateaued Churches
This article introduces new language and an alternative paradigm to the topic of revitalizing declining churches, which presents a transforming process for pastors, church leaders, denominational executives, and consultants to implement when coaching revitalizing churches. The biblical foundation for this writing is Jesus’ letter to the church of Sardis, recorded in Revelation 3:1–6. Five principles for upcycling a declining church are presented: embrace the crisis, answer the wakeup call, strengthen what remains, strengthen who remains, and return to spiritual roots
APPLICATIONS OF MASS SPECTROMETRY, MÖSSBAUER SPECTROMETRY AND OTHER PHYSICAL TECHNIQUES TO METAL CHELATE CHEMISTRY
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