Assessing and monitoring student progress in e-learning environments

E-learning has emerged as a form of pedagogy and as a delivery system with broad implications for meeting personnel needs nationally in special education. At present, it is important to make investments in research and development to ensure that this new pedagogy becomes fully developed and is appropriately applied. Assessment and monitoring of student progress in e-learning environments is an important element of this new form of pedagogy that requires research attention to maximize the effectiveness of e-learning when applied to teacher education. The authors draw upon their personal online teaching experience in addressing strategies for assessing student performance and using electronic portfolios in e-learning environments, both presented as integral aspects of e-learning instructional process. Perspectives from the literature and lessons learned from the authors’ own experience are shared.peerreviewe

The effect of limbic damage on the retention and performance of a runway response

Rats were trained to run a linear runway while hungry for food. Then they were tested for retention, continued performance levels, and extinction after recovery from bilateral damage of the hippocampus, the septal area, or the posterolateral neocortex. Retention losses were observed in animals which had hippocampal or neocortical destruction. Slower running speeds were found in animals with hippocampal destruction, while the running speeds of animals with septal area damage increased. Animals with hippocampal destruction and with septal area damage showed greater resistance to extinction than other groups of animals.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/33433/1/0000835.pd

Three Super-Earths Orbiting HD 7924

We report the discovery of two super-Earth mass planets orbiting the nearby K0.5 dwarf HD 7924 which was previously known to host one small planet. The new companions have masses of 7.9 and 6.4 M$_\oplus$, and orbital periods of 15.3 and 24.5 days. We perform a joint analysis of high-precision radial velocity data from Keck/HIRES and the new Automated Planet Finder Telescope (APF) to robustly detect three total planets in the system. We refine the ephemeris of the previously known planet using five years of new Keck data and high-cadence observations over the last 1.3 years with the APF. With this new ephemeris, we show that a previous transit search for the inner-most planet would have covered 70% of the predicted ingress or egress times. Photometric data collected over the last eight years using the Automated Photometric Telescope shows no evidence for transits of any of the planets, which would be detectable if the planets transit and their compositions are hydrogen-dominated. We detect a long-period signal that we interpret as the stellar magnetic activity cycle since it is strongly correlated with the Ca II H and K activity index. We also detect two additional short-period signals that we attribute to rotationally-modulated starspots and a one month alias. The high-cadence APF data help to distinguish between the true orbital periods and aliases caused by the window function of the Keck data. The planets orbiting HD 7924 are a local example of the compact, multi-planet systems that the Kepler Mission found in great abundance.Comment: Accepted to ApJ on 4/7/201

Comparison of Type II Endoleak Embolizations: Embolization of Endoleak Nidus Only versus Embolization of Endoleak Nidus and Branch Vessels

AbstractPurposeTo compare outcomes of type II endoleak embolization involving embolization of the endoleak nidus only vs embolization of the endoleak nidus and branch vessels in patients treated with endovascular repair of abdominal aortic aneurysms.Materials and MethodsTwenty-nine consecutive patients (mean age, 77.9 y; range, 63–88 y) with type II endoleak who underwent embolization from 2004 to 2015 were retrospectively reviewed. Patients were divided into 2 groups: embolization of endoleak nidus only (group A) and embolization of endoleak nidus and branch vessels (group B). Mean follow-up intervals were 20.5 months ± 14.7 in group A and 24.3 months ± 18.5 in group B. Outcomes were compared between groups by Mann–Whitney U and Pearson χ2 tests.ResultsMean interval from endovascular aneurysm repair to embolization was 47.6 months ± 42.9, and mean presentation time of endoleak before embolization was 23.1 months ± 25.8. Coils (n = 28) and liquid embolic agents (n = 23) were used for embolization. There were no significant differences in rates of residual endoleak (50% vs 53.8%; P = .96) or sac decrease/stabilization (62.5% vs 61.5%; P = .64). Procedure time and radiation exposure in group B (132.3 min ± 78.1; 232.4 Gy·cm2 ± 130.7) were greater than in group A (63.4 min ± 11.9; 61.5 Gy·cm2 ± 35.5; P < .01). There were no procedure-related complications.ConclusionsEmbolization of the endoleak nidus and branch vessels is not superior to embolization of only the nidus in terms of occlusion of type II endoleak and change in sac size despite requiring longer procedure times and resulting in greater patient radiation exposure

Some effects of hippocampal lesions on the behavior of mongolian gerbils

Adult male gerbils (Meriones unguiculatus) were subjected to one of three surgical procedures: aspiration of the hippocampus and overlying cortex, aspiration of the cortex overlying the hippocampus alone, or a sham operation. Hippocampal lesions increased the frequency of certain home cage behavior patterns (locomotion, rearing, sniffing and drinking), decreased the frequency of other patterns (sleeping/lying and shredding of nest materials) and left unchanged a third set of measures (alert inactivity, grooming and burrowing). In those cases where increments in occurrence of a given behavior were observed, there were lesion-induced shifts in frequency of initiation of certain behavior patterns (locomotion and sniffing) rather than in the duration of those patterns. This finding argues against a simple perservation view of the increment in frequency of these patterns. Lesion effects on reactivity to novel stimulation varied with the test procedure. Locomotor activity in an open field was enhanced, manipulatory and biting contacts with novel stimulus objects were reduced, and social reactions to unfamiliar visitor gerbils were relatively unaffected.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32726/1/0000094.pd

The Energy-Momentum Tensor for Cosmological Perturbations

We study the effective energy-momentum tensor (EMT) for cosmological perturbations and formulate the gravitational back-reaction problem in a gauge invariant manner. We analyze the explicit expressions for the EMT in the cases of scalar metric fluctuations and of gravitational waves and derive the resulting equations of state. The formalism is applied to investigate the back-reaction effects in chaotic inflation. We find that for long wavelength scalar and tensor perturbations, the effective energy density is negative and thus counteracts any pre-existing cosmological constant. For scalar perturbations during an epoch of inflation, the equation of state is de Sitter-like.Comment: 29 pages, LaTex; to appear in Phys. Rev.

HAT-P-50b, HAT-P-51b, HAT-P-52b, and HAT-P-53b: Three Transiting Hot Jupiters and a Transiting Hot Saturn From the HATNet Survey

We report the discovery and characterization of four transiting exoplanets by the HATNet survey. The planet HAT-P-50b has a mass of 1.35 M_J and a radius of 1.29 R_J, and orbits a bright (V = 11.8 mag) M = 1.27 M_sun, R = 1.70 R_sun star every P = 3.1220 days. The planet HAT-P-51b has a mass of 0.31 M_J and a radius of 1.29 R_J, and orbits a V = 13.4 mag, M = 0.98 M_sun, R = 1.04 R_sun star with a period of P = 4.2180 days. The planet HAT-P-52b has a mass of 0.82 M_J and a radius of 1.01 R_J, and orbits a V = 14.1 mag, M = 0.89 M_sun, R = 0.89 R_sun star with a period of P = 2.7536 days. The planet HAT-P-53b has a mass of 1.48 M_J and a radius of 1.32 R_J, and orbits a V = 13.7 mag, M = 1.09 M_sun, R = 1.21 R_sun star with a period of P = 1.9616 days. All four planets are consistent with having circular orbits and have masses and radii measured to better than 10% precision. The low stellar jitter and favorable R_P/R_star ratio for HAT-P-51 make it a promising target for measuring the Rossiter-McLaughlin effect for a Saturn-mass planet.Comment: Submitted to AJ. 20 pages, 9 figures, 5 tables. Data available at http://hatnet.org

KELT-11b: A Highly Inflated Sub-Saturn Exoplanet Transiting the V=8 Subgiant HD 93396

We report the discovery of a transiting exoplanet, KELT-11b, orbiting the bright ($V=8.0$) subgiant HD 93396. A global analysis of the system shows that the host star is an evolved subgiant star with $T_{\rm eff} = 5370\pm51$ K, $M_{*} = 1.438_{-0.052}^{+0.061} M_{\odot}$, $R_{*} = 2.72_{-0.17}^{+0.21} R_{\odot}$, log $g_*= 3.727_{-0.046}^{+0.040}$, and [Fe/H]$= 0.180\pm0.075$. The planet is a low-mass gas giant in a $P = 4.736529\pm0.00006$ day orbit, with $M_{P} = 0.195\pm0.018 M_J$, $R_{P}= 1.37_{-0.12}^{+0.15} R_J$, $\rho_{P} = 0.093_{-0.024}^{+0.028}$ g cm$^{-3}$, surface gravity log ${g_{P}} = 2.407_{-0.086}^{+0.080}$, and equilibrium temperature $T_{eq} = 1712_{-46}^{+51}$ K. KELT-11 is the brightest known transiting exoplanet host in the southern hemisphere by more than a magnitude, and is the 6th brightest transit host to date. The planet is one of the most inflated planets known, with an exceptionally large atmospheric scale height (2763 km), and an associated size of the expected atmospheric transmission signal of 5.6%. These attributes make the KELT-11 system a valuable target for follow-up and atmospheric characterization, and it promises to become one of the benchmark systems for the study of inflated exoplanets.Comment: 15 pages, Submitted to AAS Journal

Understanding the Impacts of Stellar Companions on Planet Formation and Evolution: A Survey of Stellar and Planetary Companions within 25 pc

We explore the impact of outer stellar companions on the occurrence rate of giant planets detected with radial velocities. We searched for stellar and planetary companions to a volume-limited sample of solar-type stars within 25 pc. Using adaptive optics imaging observations from the Lick 3 m and Palomar 200" Telescopes, we characterized the multiplicity of our sample stars, down to the bottom of the main sequence. With these data, we confirm field star multiplicity statistics from previous surveys. We additionally combined three decades of radial velocity (RV) data from the California Planet Search with newly collected RV data from Keck/HIRES and the Automated Planet Finder/Levy Spectrometer to search for planetary companions in these same systems. Using an updated catalog of both stellar and planetary companions, as well as detailed injection/recovery tests to determine our sensitivity and completeness, we measured the occurrence rate of planets among the single- and multiple-star systems. We found that planets with masses in the range of 0.1–10 M_J and with semimajor axes of 0.1–10 au have an occurrence rate of 0.18^(+0.04)_(−0.03) planets per star when they orbit single stars and an occurrence rate of 0.12 ± 0.04 planets per star when they orbit a star in a binary system. Breaking the sample down by the binary separation, we found that only one planet-hosting binary system had a binary separation 100 au and 0.04^(+0.04)_(−0.02) planets per star for binaries with separation a_B 100 au. Finally, we found evidence that giant planets in binary systems have a different semimajor-axis distribution than their counterparts in single-star systems. The planets in the single-star sample had a significantly higher occurrence rate outside of 1 au than inside 1 au by nearly 4σ, in line with expectations that giant planets are most common near the snow line. However, the planets in the wide binary systems did not follow this distribution, but rather had equivalent occurrence rates interior and exterior to 1 au. This may point to binary-mediated planet migration acting on our sample, even in binaries wider than 100 au

A Green Function for Metric Perturbations due to Cosmological Density Fluctuations

We study scalar perturbations to a Robertson-Walker cosmological metric in terms of a pseudo-Newtonian potential, which emerges naturally from the solution of the field equations. This potential is given in terms of a Green function for matter density fluctuations of arbitrary amplitude whose time and spatial dependence are assumed known. The results obtained span both the linearized and Newtonian limits, and do not explicitly depend on any kind of averaging procedure, but make the valid assumption that the global expansion rate is that of a Friedmann-Robertson-Walker model. In addition, we discuss the similarity to diffusive processes in the evolution of the potential, and possible applications.Comment: 19 pages, REVTeX. SU-ITP-9233, submitted to Physical Review