3,903 research outputs found
Crossing MGLS with the Middle Grades Research Agenda: A Guide for Researchers
For the past several years, leaders in middle grades education research have strengthened their call for more methodologically robust quantitative research to address important questions in the field. Recently, two important routes towards addressing this call have emerged: the Middle Grades Longitudinal Study from the National Center for Education Statistics, and a new research agenda from the Middle Level Education Research Special Interest Group of the American Educational Research Association. In this paper, we conduct a content analysis of the items in the forthcoming longitudinal study in light of the extant research agenda. Results indicate that research questions in eight sections of the agenda are moderately to well-addressed by the data, and that the longitudinal study will provide rich contextual data related to many others. The concurrent emergence of the research agenda and this data offers an opportunity for the research community to engage in high-level quantitative research with a middle grades lens to inform future policy. The item-by-item crosswalk available for download (scroll down for link below) provides guidance for researchers using the Middle Grades Longitudinal Study data to address questions from the research agenda
Another Flattened Dark Halo: Plar Ring Galaxy A0136-0801
Knowledge of the shape of dark matter halos is critical to our understanding
of galaxy formation, dynamics, and of the nature of dark matter itself. Polar
ring galaxies (PRGs) --- early-type galaxies defined by their outer rings of
gas, dust and stars on orbits nearly perpendicular to those of the central host
--- provide a rare probe of the vertical-to-radial axis ratio of dark halos. We present a Fabry-Perot velocity field for the H
gas in the kinematically-confirmed PRG \gal. By comparing ring orbits evolved
in a generalized mass model to the observed ring velocity field and morphology
of \gal, we conclude that and rule out a spherical geometry.Comment: uuencoded gz-compressed file with figures include
Rocket exhaust plume computer program improvement. Volume 1: Summary: Method of characteristics nozzle and plume programs
A summary is presented of the various documents that discuss and describe the computer programs and analysis techniques which are available for rocket nozzle and exhaust plume calculations. The basic method of characteristics program is discussed, along with such auxiliary programs as the plume impingement program, the plot program and the thermochemical properties program
Empirical Study of Simulated Two-planet Microlensing Event
We undertake the first study of two-planet microlensing models recovered from
simulations of microlensing events generated by realistic multi-planet systems
in which 292 planetary events including 16 two-planet events were detected from
6690 simulated light curves. We find that when two planets are recovered, their
parameters are usually close to those of the two planets in the system most
responsible for the perturbations. However, in one of the 16 examples, the
apparent mass of both detected planets was more than doubled by the unmodeled
influence of a third, massive planet. This fraction is larger than, but
statistically consistent with, the roughly 1.5% rate of serious mass errors due
to unmodeled planetary companions for the 274 cases from the same simulation in
which a single planet is recovered. We conjecture that an analogous effect due
to unmodeled stellar companions may occur more frequently. For seven out of 23
cases in which two planets in the system would have been detected separately,
only one planet was recovered because the perturbations due to the two planets
had similar forms. This is a small fraction (7/274) of all recovered
single-planet models, but almost a third of all events that might plausibly
have led to two-planet models. Still, in these cases, the recovered planet
tends to have parameters similar to one of the two real planets most
responsible for the anomaly.Comment: 21 pages, 9 figures, 2 tables; submitted to ApJ; for a short video
introducing the key results, see https://www.youtube.com/watch?v=qhK4a6sbfO
Computational Identification of Four Spliceosomal snRNAs from the Deep-Branching Eukaryote Giardia intestinalis
Funding: Marsden Fund New Zealand Allan Wilson Centre The funders had no role in study design, data collection and analysis, decision to publish, or
preparation of the manuscript.RNAs processing other RNAs is very general in eukaryotes, but is not clear to what extent it is ancestral to eukaryotes. Here
we focus on pre-mRNA splicing, one of the most important RNA-processing mechanisms in eukaryotes. In most eukaryotes
splicing is predominantly catalysed by the major spliceosome complex, which consists of five uridine-rich small nuclear
RNAs (U-snRNAs) and over 200 proteins in humans. Three major spliceosomal introns have been found experimentally in
Giardia; one Giardia U-snRNA (U5) and a number of spliceosomal proteins have also been identified. However, because of
the low sequence similarity between the Giardia ncRNAs and those of other eukaryotes, the other U-snRNAs of Giardia had
not been found. Using two computational methods, candidates for Giardia U1, U2, U4 and U6 snRNAs were identified in this
study and shown by RT-PCR to be expressed. We found that identifying a U2 candidate helped identify U6 and U4 based on
interactions between them. Secondary structural modelling of the Giardia U-snRNA candidates revealed typical features of
eukaryotic U-snRNAs. We demonstrate a successful approach to combine computational and experimental methods to
identify expected ncRNAs in a highly divergent protist genome. Our findings reinforce the conclusion that spliceosomal
small-nuclear RNAs existed in the last common ancestor of eukaryotes
Thermophysical Phenomena in Metal Additive Manufacturing by Selective Laser Melting: Fundamentals, Modeling, Simulation and Experimentation
Among the many additive manufacturing (AM) processes for metallic materials,
selective laser melting (SLM) is arguably the most versatile in terms of its
potential to realize complex geometries along with tailored microstructure.
However, the complexity of the SLM process, and the need for predictive
relation of powder and process parameters to the part properties, demands
further development of computational and experimental methods. This review
addresses the fundamental physical phenomena of SLM, with a special emphasis on
the associated thermal behavior. Simulation and experimental methods are
discussed according to three primary categories. First, macroscopic approaches
aim to answer questions at the component level and consider for example the
determination of residual stresses or dimensional distortion effects prevalent
in SLM. Second, mesoscopic approaches focus on the detection of defects such as
excessive surface roughness, residual porosity or inclusions that occur at the
mesoscopic length scale of individual powder particles. Third, microscopic
approaches investigate the metallurgical microstructure evolution resulting
from the high temperature gradients and extreme heating and cooling rates
induced by the SLM process. Consideration of physical phenomena on all of these
three length scales is mandatory to establish the understanding needed to
realize high part quality in many applications, and to fully exploit the
potential of SLM and related metal AM processes
Comparing families of dynamic causal models
Mathematical models of scientific data can be formally compared using Bayesian model evidence. Previous applications in the biological sciences have mainly focussed on model selection in which one first selects the model with the highest evidence and then makes inferences based on the parameters of that model. This βbest modelβ approach is very useful but can become brittle if there are a large number of models to compare, and if different subjects use different models. To overcome this shortcoming we propose the combination of two further approaches: (i) family level inference and (ii) Bayesian model averaging within families. Family level inference removes uncertainty about aspects of model structure other than the characteristic of interest. For example: What are the inputs to the system? Is processing serial or parallel? Is it linear or nonlinear? Is it mediated by a single, crucial connection? We apply Bayesian model averaging within families to provide inferences about parameters that are independent of further assumptions about model structure. We illustrate the methods using Dynamic Causal Models of brain imaging data
Playing the odds in clinical decision making: lessons from berry aneurysms undetected by magnetic resonance angiography
No description supplie
Conservation Evaluation of Howell's Triteleia, Triteleia howellii, an Endangered Lily in Canada
In Canada, Triteleia howellii is restricted to Quercus garryana stands and grass-dominated meadows on southeastern Vancouver Island in southwestern British Columbia. Nine sites have been confirmed in recent years while three other sites are considered extirpated. These Canadian sites represent the northern range limits of T. howellii. Threats to existing populations vary in intensity. Although most populations are protected to a certain extent from direct habitat destruction, introduced species pose a serious potential threat to the continued existence of most populations. Managing sites for T. howellii is difficult because little information is available regarding the general biology of this species
Conservation Evaluation of the Small-flowered Tonella, Tonella tenella, in Canada
In Canada, the Small-flowered Tonella, Tonella tenella, is restricted to the west side of Saltspring Island in the Gulf Islands of southwestern British Columbia. This population represents the northern limits of the species which is disjunct from its main range in southern Washington (Columbia River gorge), through Oregon to central California. In British Columbia, Tonella tenella is associated with rock outcrops and dry, steep, sparsely forested talus slopes at elevations of 50 to 300 m. The population on Saltspring Island is on private property and not directly imperilled at this time. There is, however, a potential for housing development in the future on this waterfront site, thus the authors consider the species endangered
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