1,776 research outputs found
A Study of Mentor Principal Training in Pennsylvania
Abstract
The purpose of this qualitative case study was to identify, investigate, and describe the espoused Pennsylvania Principal Mentoring Network (PPMN) training program and protocols for the principals who served as mentors for newly hired principals in Pennsylvania. This study posed three research questions: (1) what was the espoused training provided to mentor principals in Pennsylvania both prior to and during their mentoring experiences that prepared them to mentor newly hired principals?; (2) what were the program coordinators’ perspectives on the espoused training delivered by the PPMN for the respective mentors and to what degree was the training program the same or different through the term of each coordinator?; and (3) how does this espoused training compare and subsequently align to the competencies required of mentor principals highlighted in the research literature?
Through reviewing documents and conducting interviews, the author found that each principal mentor had participated in some form of mentor training. Each mentor principal had the opportunity to experience and access standard mentor training orientations, published newsletters and regional meetings, and the National Institute for School Leadership (NISL) five-day Instructional Leadership Institute’s condensed professional development series. The PPMN State Coordinators indicated that the PPMN attracted qualified mentor principals who modeled a results driven, research-based mentor training program. Throughout the existence of the PPMN, subtle changes to the mentor training program were identified but the focus, goals, and outcomes of the training remained intact.
The PPMN mentor training process had aligned fairly consistently to the research literature base and framework for this research study. Although minimal references to adult learning theory were found in this study, it is recommended that future mentor training programs strongly consider the efficacy of including this area within the scope and sequence of the training program. In addition, due to the unavailability of certain documents and no central repository for information, future research inquiries should be geared toward existing programs that are strongly organized and currently functioning
The Local Group: The Ultimate Deep Field
Near-field cosmology -- using detailed observations of the Local Group and
its environs to study wide-ranging questions in galaxy formation and dark
matter physics -- has become a mature and rich field over the past decade.
There are lingering concerns, however, that the relatively small size of the
present-day Local Group ( Mpc diameter) imposes insurmountable
sample-variance uncertainties, limiting its broader utility. We consider the
region spanned by the Local Group's progenitors at earlier times and show that
it reaches co-moving Mpc in linear size (a volume of ) at . This size at early cosmic epochs is large enough
to be representative in terms of the matter density and counts of dark matter
halos with . The Local
Group's stellar fossil record traces the cosmic evolution of galaxies with
(reaching
at ) over a region that is comparable to or larger than
the Hubble Ultra-Deep Field (HUDF) for the entire history of the Universe. It
is highly complementary to the HUDF, as it probes much fainter galaxies but
does not contain the intrinsically rarer, brighter sources that are detectable
in the HUDF. Archaeological studies in the Local Group also provide the ability
to trace the evolution of individual galaxies across time as opposed to
evaluating statistical connections between temporally distinct populations. In
the JWST era, resolved stellar populations will probe regions larger than the
HUDF and any deep JWST fields, further enhancing the value of near-field
cosmology.Comment: 6 pages, 5 figures; MNRAS Letters, in pres
A new paradigm in teaching large engineering mechanics courses
This study investigated the role of a new paradigm in teaching large introductory fundamental engineering mechanics courses that combines student-centered learning and supplemental student resources. The sample consisted of close to 5000 engineering students from Iowa State University.
Demographic characteristics in the study included students\u27 major, gender, performance in high school, and achievement and aptitude tests scores. Results of the study overwhelmingly showed that not only is there a difference between a class taught passively using the teacher-centered pedagogy and a class taught actively using the student-centered pedagogy, but also that the usage of the variety of student-centered pedagogies in statics of engineering is a significant predictor in student performance in mechanics of materials.
The principal focus of this work was to determine if the new paradigm was successful in improving student understanding of course concepts in statics of engineering. After evaluating the effects of several variables on students\u27 academic success, the results may provide important information for both faculty and researchers and present a convincing argument to those faculty interested in a reform but hesitant to abandon conventional teaching practices. By promoting a new paradigm, the potential for improving understanding of engineering fundamentals on a larger scale may be realized
The Mass Dependance of Satellite Quenching in Milky Way-like Halos
Using the Sloan Digital Sky Survey, we examine the quenching of satellite
galaxies around isolated Milky Way-like hosts in the local Universe. We find
that the efficiency of satellite quenching around isolated galaxies is low and
roughly constant over two orders of magnitude in satellite stellar mass
( = ), with only of systems
quenched as a result of environmental processes. While largely independent of
satellite stellar mass, satellite quenching does exhibit clear dependence on
the properties of the host. We show that satellites of passive hosts are
substantially more likely to be quenched than those of star-forming hosts, and
we present evidence that more massive halos quench their satellites more
efficiently. These results extend trends seen previously in more massive host
halos and for higher satellite masses. Taken together, it appears that galaxies
with stellar masses larger than about are uniformly
resistant to environmental quenching, with the relative harshness of the host
environment likely serving as the primary driver of satellite quenching. At
lower stellar masses (), however, observations of the Local
Group suggest that the vast majority of satellite galaxies are quenched,
potentially pointing towards a characteristic satellite mass scale below which
quenching efficiency increases dramatically.Comment: 14 pages, 8 figure
A Dichotomy in Satellite Quenching Around L* Galaxies
We examine the star formation properties of bright (~0.1 L*) satellites
around isolated ~L* hosts in the local Universe using spectroscopically
confirmed systems in the Sloan Digital Sky Survey DR7. Our selection method is
carefully designed with the aid of N-body simulations to avoid groups and
clusters. We find that satellites are significantly more likely to be quenched
than a stellar mass-matched sample of isolated galaxies. Remarkably, this
quenching occurs only for satellites of hosts that are themselves quenched:
while star formation is unaffected in the satellites of star-forming hosts,
satellites around quiescent hosts are more than twice as likely to be quenched
than stellar-mass matched field samples. One implication of this is that
whatever shuts down star formation in isolated, passive L* galaxies also plays
at least an indirect role in quenching star formation in their bright
satellites. The previously-reported tendency for "galactic conformity" in
color/morphology may be a by-product of this host-specific quenching dichotomy.
The S\'ersic indices of quenched satellites are statistically identical to
those of field galaxies with the same specific star formation rates, suggesting
that environmental and secular quenching give rise to the same morphological
structure. By studying the distribution of pairwise velocities between the
hosts and satellites, we find dynamical evidence that passive host galaxies
reside in dark matter halos that are ~45% more massive than those of
star-forming host galaxies of the same stellar mass. We emphasize that even
around passive hosts, the mere fact that galaxies become satellites does not
typically result in star formation quenching: we find that only ~30% of ~0.1 L*
galaxies that fall in from the field are quenched around passive hosts,
compared with ~0% around star forming hosts.Comment: 14 pages, 9 figure
Environmental Quenching of Low-Mass Field Galaxies
In the local Universe, there is a strong division in the star-forming
properties of low-mass galaxies, with star formation largely ubiquitous amongst
the field population while satellite systems are predominantly quenched. This
dichotomy implies that environmental processes play the dominant role in
suppressing star formation within this low-mass regime (). As shown by observations of the Local Volume,
however, there is a non-negligible population of passive systems in the field,
which challenges our understanding of quenching at low masses. By applying the
satellite quenching models of Fillingham et al. (2015) to subhalo populations
in the Exploring the Local Volume In Simulations (ELVIS) suite, we investigate
the role of environmental processes in quenching star formation within the
nearby field. Using model parameters that reproduce the satellite quenched
fraction in the Local Group, we predict a quenched fraction -- due solely to
environmental effects -- of within
of the Milky Way and M31. This is in good agreement with current observations
of the Local Volume and suggests that the majority of the passive field systems
observed at these distances are quenched via environmental mechanisms. Beyond
, however, dwarf galaxy quenching becomes difficult to explain
through an interaction with either the Milky Way or M31, such that more
isolated, field dwarfs may be self-quenched as a result of star-formation
feedback.Comment: 9 pages, 4 figures, MNRAS accepted version, comments welcome - RIP
Ducky...gone but never forgotte
Optimal partial-arcs in VMAT treatment planning
Purpose: To improve the delivery efficiency of VMAT by extending the recently
published VMAT treatment planning algorithm vmerge to automatically generate
optimal partial-arc plans.
Methods and materials: A high-quality initial plan is created by solving a
convex multicriteria optimization problem using 180 equi-spaced beams. This
initial plan is used to form a set of dose constraints, and a set of
partial-arc plans is created by searching the space of all possible partial-arc
plans that satisfy these constraints. For each partial-arc, an iterative
fluence map merging and sequencing algorithm (vmerge) is used to improve the
delivery efficiency. Merging continues as long as the dose quality is
maintained above a user-defined threshold. The final plan is selected as the
partial arc with the lowest treatment time. The complete algorithm is called
pmerge.
Results: Partial-arc plans are created using pmerge for a lung, liver and
prostate case, with final treatment times of 127, 245 and 147 seconds.
Treatment times using full arcs with vmerge are 211, 357 and 178 seconds. Dose
quality is maintained across the initial, vmerge, and pmerge plans to within 5%
of the mean doses to the critical organs-at-risk and with target coverage above
98%. Additionally, we find that the angular distribution of fluence in the
initial plans is predictive of the start and end angles of the optimal
partial-arc.
Conclusions: The pmerge algorithm is an extension to vmerge that
automatically finds the partial-arc plan that minimizes the treatment time.
VMAT delivery efficiency can be improved by employing partial-arcs without
compromising dose quality. Partial arcs are most applicable to cases with
non-centralized targets, where the time savings is greatest
Taking Care of Business in a Flash: Constraining the Timescale for Low-Mass Satellite Quenching with ELVIS
The vast majority of dwarf satellites orbiting the Milky Way and M31 are
quenched, while comparable galaxies in the field are gas-rich and star-forming.
Assuming that this dichotomy is driven by environmental quenching, we use the
ELVIS suite of N-body simulations to constrain the characteristic timescale
upon which satellites must quench following infall into the virial volumes of
their hosts. The high satellite quenched fraction observed in the Local Group
demands an extremely short quenching timescale (~ 2 Gyr) for dwarf satellites
in the mass range Mstar ~ 10^6-10^8 Msun. This quenching timescale is
significantly shorter than that required to explain the quenched fraction of
more massive satellites (~ 8 Gyr), both in the Local Group and in more massive
host halos, suggesting a dramatic change in the dominant satellite quenching
mechanism at Mstar < 10^8 Msun. Combining our work with the results of
complementary analyses in the literature, we conclude that the suppression of
star formation in massive satellites (Mstar ~ 10^8 - 10^11 Msun) is broadly
consistent with being driven by starvation, such that the satellite quenching
timescale corresponds to the cold gas depletion time. Below a critical stellar
mass scale of ~ 10^8 Msun, however, the required quenching times are much
shorter than the expected cold gas depletion times. Instead, quenching must act
on a timescale comparable to the dynamical time of the host halo. We posit that
ram-pressure stripping can naturally explain this behavior, with the critical
mass (of Mstar ~ 10^8 Msun) corresponding to halos with gravitational restoring
forces that are too weak to overcome the drag force encountered when moving
through an extended, hot circumgalactic medium.Comment: 12 pages, 6 figures; resubmitted to MNRAS after referee report
(August 25, 2015
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