299 research outputs found
Exploring the Use of Faded Worked Examples as a Problem Solving Approach for Underprepared Students
It is not uncommon for students to find themselves underprepared when entering a post secondary institution. In additional to lower levels of academic achievement, underprepared students may not be aware that they lack the skills needed to be successful and effectively acquire and process information. Because of this, students that enter post-secondary institutions underprepared often require more support in and out of the college classroom.
In computational based classes, such as math, engineering, chemistry or physics, this support often includes an introduction to effective problem solving strategies. This study introduced faded worked examples as a problem solving approach to students identified as mathematically underprepared in a college chemistry course. Faded worked examples are similar to worked examples but fade out steps for students to complete, allowing support within the problem solving approach as learning improves. The goal of this study was to explore students’ perceptions of this problem solving approach and their belief in its potential to enhance their learning, particularly with students identified as academically underprepared. Overall, students reported that faded worked examples enhanced their overall learning and problem solving abilities in chemistry and the step by step process allowed for a better understanding of the course material
CCD Photometry of the Globular Cluster M5. I. The Color-Magnitude Diagram and Luminosity Functions
We present new BVI photometry for the halo globular cluster M5, and examine
the B- and I-band luminosity functions (LFs), based on over 20,000 stars. We do
not see evidence in the LF of a ``subgiant excess'' or of a discrepancy in the
relative numbers of stars on the red-giant branch and main sequence, both of
which have been claimed in more metal-poor clusters. Inclusion of alpha-element
enhancements improves the agreement between the observed and predicted
positions of the ``red-giant bump''. Using the \Delta V_{TO}^{HB} method, we
conclude that the clusters M5, Palomar 5, M4, NGC 288, NGC 362, NGC 1261, NGC
1851 and NGC 2808 are the same age at the level of about 1.5 Gyr, with the
possible exception of NGC 288 (older by 3.5\pm 1.5 if the reddest NGC 288 HB
stars are on the zero-age horizontal branch). Even with NGC 288 set aside, the
large range in HB morphology in the remaining clusters appears to eliminate age
as the sole second parameter determining HB morphology in the case of constant
mass loss between RGB and HB. We are unable to chose between the two competing
values for M5's (absolute) metallicity: [Fe/H] = -1.40 (Zinn & West 1984) and
-1.17 (Sneden et al. 1992). This level of discrepancy has a signifcant effect
on the derivation of the distance modulus and absolute age of M5. From
theoretical isochrones and luminosity functions, we find an absolute age for M5
of 13.5 \pm 1 Gyr (internal error, assuming perfect models and no [M/H] error)
for the Zinn & West abundance scale and 11 \pm 1 Gyr for the higher abundance
value.Comment: AASTeX, 44 pages, uses amssym.sty, figures and tables only available
from http://ucowww.ucsc.edu/~erics/paper.html, ApJ, in pres
NGC 5128: The Giant Beneath
I review what we have learned about the old stellar population of NGC 5128,
the only large E galaxy close enough that we can currently observe individual
stars as faint as the horizontal branch. Although its galaxy type is still a
matter of debate for some, the uncertainties over distance are now largely
resolved; comparison of five stellar distance indicators gives d=3.8 +- 0.1
Mpc. The globular cluster system, which was once perplexingly invisible, is now
known to be predominantly old with a substantial metal-rich component. The GCS
total population and luminosity function are normal and the clusters follow the
same fundamental plane relation as those in the Milky Way and M31. Finally, the
halo out to at least ~7r_{eff} is dominated by metal-rich stars which are also
predominantly old, with age and metallicity tantalizingly similar to the
majority of globular clusters.Comment: PASA in pres
Evaluation of video-based linear depth inversion performance and applications using altimeters and hydrographic surveys in a wide range of environmental conditions
This paper is not subject to U.S. copyright. The definitive version was published in Coastal Engineering 136 (2018): 147-160, doi:10.1016/j.coastaleng.2018.01.003.The performance of a linear depth inversion algorithm, cBathy, applied to coastal video imagery was assessed using observations of water depth from vessel-based hydrographic surveys and in-situ altimeters for a wide range of wave conditions (0.3 < significant wave height < 4.3 m) on a sandy Atlantic Ocean beach near Duck, North Carolina. Comparisons of video-based cBathy bathymetry with surveyed bathymetry were similar to previous studies (root mean square error (RMSE) = 0.75 m, bias = −0.26 m). However, the cross-shore locations of the surfzone sandbar in video-derived bathymetry were biased onshore 18–40 m relative to the survey when offshore wave heights exceeded 1.2 m or were greater than half of the bar crest depth, and broke over the sandbar. The onshore bias was 3–4 m when wave heights were less than 0.8 m and were not breaking over the sandbar. Comparisons of video-derived seafloor elevations with in-situ altimeter data at three locations onshore of, near, and offshore of the surfzone sandbar over ∼1 year provide the first assessment of the cBathy technique over a wide range of wave conditions. In the outer surf zone, video-derived results were consistent with long-term patterns of bathymetric change (r2 = 0.64, RMSE = 0.26 m, bias = −0.01 m), particularly when wave heights were less than 1.2 m (r2 = 0.83). However, during storms when wave heights exceeded 3 m, video-based cBathy over-estimated the depth by up to 2 m. Near the sandbar, the sign of depth errors depended on the location relative to wave breaking, with video-based depths overestimated (underestimated) offshore (onshore) of wave breaking in the surfzone. Wave speeds estimated by video-based cBathy at the initiation of wave breaking often were twice the speeds predicted by linear theory, and up to three times faster than linear theory during storms. Estimated wave speeds were half as fast as linear theory predictions at the termination of wave breaking shoreward of the sandbar. These results suggest that video-based cBathy should not be used to track the migration of the surfzone sandbar using data when waves are breaking over the bar nor to quantify morphological evolution during storms. However, these results show that during low energy conditions, cBathy estimates could be used to quantify seasonal patterns of seafloor evolution.This research was funded by the U.S. Army Corps of Engineers Coastal Field Data Collection Program, the Deputy Assistant Secretary of the Army for Research and Technology under ERDC's research program titled “Force Projection Entry Operations, STO D.GRD.2015.34”, the U.S. Naval Research Laboratory base program from the Office of Naval Research, a Vannevar Bush Faculty Fellowship funded by the Assistant Secretary of Defense for Research and Engineering, and the National Science Foundation
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Sixteen years of bathymetry and waves at San Diego beaches.
Sustained, quantitative observations of nearshore waves and sand levels are essential for testing beach evolution models, but comprehensive datasets are relatively rare. We document beach profiles and concurrent waves monitored at three southern California beaches during 2001-2016. The beaches include offshore reefs, lagoon mouths, hard substrates, and cobble and sandy (medium-grained) sediments. The data span two energetic El Niño winters and four beach nourishments. Quarterly surveys of 165 total cross-shore transects (all sites) at 100 m alongshore spacing were made from the backbeach to 8 m depth. Monthly surveys of the subaerial beach were obtained at alongshore-oriented transects. The resulting dataset consists of (1) raw sand elevation data, (2) gridded elevations, (3) interpolated elevation maps with error estimates, (4) beach widths, subaerial and total sand volumes, (5) locations of hard substrate and beach nourishments, (6) water levels from a NOAA tide gauge (7) wave conditions from a buoy-driven regional wave model, and (8) time periods and reaches with alongshore uniform bathymetry, suitable for testing 1-dimensional beach profile change models
Oscillator Strengths for B-X, C-X, and E-X Transitions in Carbon Monoxide
Band oscillator strengths for electronic transitions in CO were obtained at
the Synchrotron Radiation Center of the University of Wisconsin-Madison. Our
focus was on transitions that are observed in interstellar spectra with the Far
Ultraviolet Spectroscopic Explorer; these transitions are also important in
studies of selective isotope photodissociation where fractionation among
isotopomers can occur. Absorption from the ground state (X ^1Sigma^+ v'' = 0)
to A ^1Pi (v'= 5), B ^1Sigma^+ (v' = 0, 1), C ^1Sigma^+ (v' = 0, 1), and E ^1Pi
(v' = 0) was measured. Fits to the A - X (5, 0) band, whose oscillator strength
is well known, yielded the necessary column density and excitation temperature.
These parameters were used in a least-squares fit of the observed profiles for
the transitions of interest to extract their band oscillator strengths. Our
oscillator strengths are in excellent agreement with results from recent
experiments using a variety of techniques. This agreement provides the basis
for a self-consistent set of f-values at far ultraviolet wavelengths for
studies of interstellar (and stellar) CO.Comment: 22 pages, 3 figures, ApJS (in press
The Age Dependent Luminosities of the Red Giant Branch Bump, Asymptotic Giant Branch Bump, and Horizontal Branch Red Clump
Color-magnitude diagrams of globular clusters often exhibit a prominent
horizontal branch (HB) and may also show features such as the red giant branch
(RGB) bump and the asymptotic giant branch (AGB) bump. Stellar evolution theory
predicts that the luminosities of these features will depend on the metallicity
and age of the cluster. We calculate theoretical lines of 2 to 12 Gyr constant
age RGB-bumps and AGB-bumps in the V(HB-Bump)--[Fe/H] diagram, which shows the
brightness difference between the bump and the HB as a function of metallicity.
In order to test the predictions, we identify giant branch bumps in new Hubble
Space Telescope color-magnitude diagrams for 8 SMC clusters. First, we conclude
that the SMC cluster bumps are RGB-bumps. The data for clusters younger than ~6
Gyr are in fair agreement the relative age dependent luminosities of the HB and
RGB-bump. The V(HB-Bump)--[Fe/H] data for clusters older then ~6 Gyr
demonstrate a less satisfactory agreement with our calculations. We conclude
that ~6 Gyr is a lower bound to the age of clusters for which the Galactic
globular cluster, age independent V(HB-Bump)--[Fe/H] calibration is valid.
Application of the V(HB-bump)--[Fe/H] diagram to stellar population studies is
discussed.Comment: Accepted for publication in the Astrophysical Journal, 30 pages,
Latex aaspp4.sty, including 7 postscript figure
High resolution near-IR spectra of NGC 6624 and NGC 6569
We present the first abundances analysis based on high-resolution infrared
(IR) echelle spectra of NGC 6569 and NGC 6624, two moderately reddened globular
clusters located in the outer bulge of the Galaxy. We find
[Fe/H]=-0.790.02 dex and [Fe/H]=-0.690.02 dex for NGC 6569 and NGC
6624, respectively and an average -elements enhancement of
+0.430.02 dex and +0.390.02 dex, consistent with previous
measurements on other metal-rich Bulge clusters. We measure accurate radial
velocities of and
and velocity dispersions of and for NGC 6569 and NGC 6624, respectively. Finally, we find very low
isotopics ratio (7 in NGC 6624 and 5 in NGC
6569), confirming the presence extra-mixing mechanisms during the red giant
branch evolution phase.Comment: 7 pages, 3 figures, accepted for publication on MNRA
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