Voluntary Web-Based Self-Assessment Quiz Use Improves Exam Performance, Especially for Learners with Low Prior Knowledge

We examined students’ voluntary use of digital self-assessment quizzes as a resource for learning in a large anatomy and physiology lecture course. Students (N = 238) could use 16 chapter quizzes and four analogous unit quizzes to rehearse and self-assess knowledge. Repeated use was uncommon (12%), as was lack of use (13%). Most students (75%) engaged in occasional use of self-assessment quiz items. Exam performance differed between repeated use (84%), occasional use (76%), and no use (72%) groups. Differences were greater among students who lacked prior knowledge of course topics. Quiz use improved performance more for low prior knowledge students, and differences increased over the semester. Overall, repeated users significantly outperformed occasional users (+7.5%) and non users (+11.9%) on course examshttps://digitalscholarship.unlv.edu/btp_expo/1023/thumbnail.jp

A Plan of Farm Organization for Hill Land Farms in Southeastern Ohio

Exact date of bulletin unknown.PDF pages: 2

Mitotic instability in benomyl-resistant transformants of a fluffy strain of Neurospora crassa

The isolation of the beta-tubulin gene from a benomyl-resistant Neurospora crassa strain (Orbach et al. 1986 Mol. Cell. Biol. 6:2452-2461) has provided a dominant selectable marker usable in transformation experiments with N. crassa

The size distribution of magnetic bright points derived from Hinode/SOT observations

Context. Magnetic Bright Points (MBPs) are small-scale magnetic features in the solar photosphere. They may be a possible source of coronal heating by rapid footpoint motions that cause magnetohydrodynamical waves. The number and size distribution are of vital importance in estimating the small scale-magnetic-field energy. Aims. The size distribution of MBPs is derived for G-band images acquired by the Hinode/SOT instrument. Methods. For identification purposes, a new automated segmentation and identification algorithm was developed. Results. For a sampling of 0.108 arcsec/pixel, we derived a mean diameter of (218 +- 48) km for the MBPs. For the full resolved data set with a sampling of 0.054 arcsec/pixel, the size distribution shifted to a mean diameter of (166 +- 31) km. The determined diameters are consistent with earlier published values. The shift is most probably due to the different spatial sampling. Conclusions. We conclude that the smallest magnetic elements in the solar photosphere cannot yet be resolved by G-band observations. The influence of discretisation effects (sampling) has also not yet been investigated sufficiently.Comment: Astronomy and Astrophysics, Volume 498, Issue 1, 2009, pp.289-29

The formation and disintegration of magnetic bright points observed by Sunrise/IMaX

The evolution of the physical parameters of magnetic bright points (MBPs) located in the quiet Sun (mainly in the interwork) during their lifetime is studied. First we concentrate on the detailed description of the magnetic field evolution of three MBPs. This reveals that individual features follow different, generally complex, and rather dynamic scenarios of evolution. Next we apply statistical methods on roughly 200 observed MBP evolutionary tracks. MBPs are found to be formed by the strengthening of an equipartition field patch, which initially exhibits a moderate downflow. During the evolution, strong downdrafts with an average velocity of 2.4 km/s set in. These flows, taken together with the concurrent strengthening of the field, suggest that we are witnessing the occurrence of convective collapses in these features, although only 30% of them reach kG field strengths. This fraction might turn out to be larger when the new 4 m class solar telescopes are operational as observations of MBPs with current state of the art instrumentation could still be suffering from resolution limitations. Finally, when the bright point disappears (although the magnetic field often continues to exist) the magnetic field strength has dropped to the equipartition level and is generally somewhat weaker than at the beginning of the MBP's evolution. Noteworthy is that in about 10% of the cases we observe in the vicinity of the downflows small-scale strong (exceeding 2 km/s) intergranular upflows related spatially and temporally to these downflows.Comment: 19 pages, 13 figures; final version published in "The Astrophysical Journal

New mutants of Neurospora crassa highly resistant to the microtubule inhibitor benomyl

Mutants of N. crassa highly resistant to benomyl with respect to hyphal growth were obtained by mutagenizing wild type strain St. Lawrence 74A or mutant Bml 511(r) which is moderately resistant to the fungicide. One of these, strain E1-91 that has a mutation mapping at the Bml (beta-tubulin) locus, showed temporary sensitivity to the benzimidazole

Physiological implications of natural versus induced arousal from torpor

During the hibernation season, animals oscillate between periods of torpor and periods of interbout arousal (IBA). During torpor, body temperature is often near 0° C and metabolism is severely depressed. Oxygen consumption, a proxy for aerobic metabolism, may fall to 1% of active values. Many physiological processes including cardiovascular, respiratory, and cellular functions nearly cease. During the IBA, euthermic body temperature is restored and most systemic and cellular processes function at fully active levels. The transition period between these two physiologically dissimilar states is called arousal. The rate of rewarming (RRW) during arousal was previously expected to progressively increase until a euthermic set point was approached. However, my data contradict this expectation. I monitored the body temperature (Tb) of goldenmantled ground squirrels (Spermophilus lateralis) housed at 4, 8, 12, and 16° C during natural arousals. The various housing temperatures facilitate manipulation of torpid Tb, since torpid Tb is usually within 1° C of ambient temperature (Ta). The maximum RRW, the time required to reach a maximum RRW, and the relative time index all demonstrated negative relationships with Ta. The Tb corresponding to maximal RRW demonstrated a positive relationship with Ta. One parameter was independent of ambient temperature. Squirrels reached maximal RRW when they had generated 30 to 40% of the heat required to reach a euthermic Tb. These data suggest that arousal is more constrained than expected and that both time and temperature influence the RRW. Much hibernation research involving arousal has been conduced on animals that were induced to arouse prematurely. Natural arousal from torpor occursspontaneously with highly predictable timing. However, animals can also be induced to arouse prematurely in response to various disturbances. While many investigations have used natural and induced arousals synonymously, direct comparisons of these two types of arousal have been lacking. I addressed the question of whether natural and prematurely induced arousals are the same. I compared the effects of ambient temperature on the dynamics of natural versus induced arousals. Arousal duration, maximum rewarming rate, and the variance associated with increases in body temperature increased during induced arousals. Prematurely inducing arousal also decreased the duration of the interbout aroused (IBA) period, and the responsiveness to the induced arousal stimulus was influenced by torpor duration. The metabolic cost of natural versus induced arousal from torpor was also investigated. Metabolic activity was estimated through indirect calorimetry and assays of metabolites in blood plasma. Although initial rates of oxygen consumption were comparable for natural and induced arousal, initial rates of carbon dioxide production and respiratory quotient values were significantly reduced during induced arousal. Plasma lactate levels were significantly elevated during induced arousal whereas glucose and free fatty acids levels were similar. Previous work has indicated oxidative stress and elevated antioxidant defenses during hibernation. However, the effectiveness of these defenses has not been as well characterized. Indicators of oxidative damage to lipids and proteins in heart, liver, kidney, and brain tissues were measured to investigate potential oxidative damage to cellular macromolecules. Lipid peroxidation products and protein carbonyl levels were low in all tissues for both types of arousal. Thus, hibernators appear to be well protected against oxidative damage. Arousal was once regarded as a sole effort to rewarm as quickly as possible, thereby facilitating conservation of energy stores. However, data indicate that arousal is a more constrained process where animals regularly experience less than maximal rewarming rates. Further, prematurely inducing arousal alters key aspects of the rewarming process as well as metabolic activity. Considering these differences, I recommend that careful consideration be given to experimental design and data interpretation when arousing animals are utilized

Spin Gap in the Single Spin-1/2 Chain Cuprate Sr1.9_{1.9}Ca0.1_{0.1}CuO3_3

We report $^{63}$Cu nuclear magnetic resonance and muon spin rotation measurements on the S=1/2 antiferromagnetic Heisenberg spin chain compound Sr$_{1.9}$Ca$_{0.1}$CuO$_3$. An exponentially decreasing spin-lattice relaxation rate 1/T$_1$ indicates the opening of a spin gap. This behavior is very similar to what has been observed for the cognate zigzag spin chain compound Sr$_{0.9}$Ca$_{0.1}$CuO$_2$, and confirms that the occurrence of a spin gap upon Ca doping is independent of the interchain exchange coupling $J'$. Our results therefore generally prove the appearance of a spin gap in an antiferromagnetic Heisenberg spin chain induced by a local bond disorder of the intrachain exchange coupling $J$. A low temperature upturn of 1/T$_1$ evidences growing magnetic correlations. However, zero field muon spin rotation measurements down to 1.5 K confirm the absence of magnetic order in this compound which is most likely suppressed by the opening of the spin gap.Comment: 5 pages, 4 figure

Thermodynamic modeling of solder melting and solidification for proposed squishbot design

Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Cataloged from PDF version of thesis.Includes bibliographical references (p. 52).This thesis develops a thermodynamic simulation of the melting and solidification of a substance resting on a surface. The simulation was created in an effort to develop a single actuator joint locking and unlocking mechanism for Squishbot. The Squishbot is a proposed robot that has the ability to climb walls and change shape in order to gain entry into normally inaccessible areas. By using COMSOL Multiphysics, a simple model was developed and tested. Under these conditions, the solder melting phase transition took 2.25 seconds to melt and 2.65 seconds to solidify. These results, as well as observations about the behavior of the program's numerical solver, seem to suggest that the proposed joint locking system is feasible. A framework is laid out to proceed with improved and more specific models for use as an optimization tool.by Robert Utz.S.B

High Speed Lunar Navigation for Crewed and Remotely Piloted Vehicles

Increased navigation speed is desirable for lunar rovers, whether autonomous, crewed or remotely operated, but is hampered by the low gravity, high contrast lighting and rough terrain. We describe lidar based navigation system deployed on NASA's K10 autonomous rover and to increase the terrain hazard situational awareness of the Lunar Electric Rover crew