Prioritizing your time (1996)

Think of time as one of the tools that you have available to reach your goals. As with many tools, if you want to use time effectively, it may require some training (or retraining), determination and practice

Using graphical and pictorial representations to teach introductory astronomy students about the detection of extrasolar planets via gravitational microlensing

The detection and study of extrasolar planets is an exciting and thriving field in modern astrophysics, and an increasingly popular topic in introductory astronomy courses. One detection method relies on searching for stars whose light has been gravitationally microlensed by an extrasolar planet. In order to facilitate instructors' abilities to bring this interesting mix of general relativity and extrasolar planet detection into the introductory astronomy classroom, we have developed a new Lecture-Tutorial, "Detecting Exoplanets with Gravitational Microlensing." In this paper, we describe how this new Lecture-Tutorial's representations of astrophysical phenomena, which we selected and created based on theoretically motivated considerations of their pedagogical affordances, are used to help introductory astronomy students develop more expert-like reasoning abilities.Comment: 10 pages, 10 figures, accepted for publication in the American Journal of Physic

Answering Complex Questions as We Make Headway on Annual Grasses and Fire

Annual grasses challenge our ability to meet forage production and plant community conservation objectives. Direct competition, potential mutualism, and shortened fire return interval interplay resulting in complexity of how to meet challenges we face. Bromus tectorum presents challenges to sagebrush dominated plant communities with shortened fire return intervals and the advancing invasion of Ventenata dubia poses threats to forage production through competitive interactions that may involve mutualism to enhance V. dubia’s invasion of annual and perennial grass dominated plant communities. Use of fuel breaks can reduce the extent of fires and their proper function hinges on their reduced plant biomass in contrast to surrounding vegetation to improve fire fighting ability. Reducing annual grass biomass within fuel breaks reduces fuel continuity and shortens the duration of dry vegetation. Indaziflam and imazapic are two herbicide active ingredients that allow control of annual grasses within fuel breaks and sagebrush plant communities. Aerial application of these herbicides allows us to match control actions to the scope of the problem. These herbicides can also reduce competition from annual grasses, allowing increased cover and diversity of native plant communities. Removal or reduction of annual grasses has improved plant species diversity and forage production

A New Lecture-Tutorial for Teaching about Molecular Excitations and Synchrotron Radiation

Light and spectroscopy are among the most important and frequently taught topics in introductory, college-level, general education astronomy courses. This is due to the fact that the vast majority of observational data studied by astronomers arrives at Earth in the form of light. While there are many processes by which matter can emit and absorb light, Astro 101 courses typically limit their instruction to the Bohr model of the atom and electron energy level transitions. In this paper, we report on the development of a new Lecture-Tutorial to help students learn about other processes that are responsible for the emission and absorption of light, namely molecular rotations, molecular vibrations, and the acceleration of charged particles by magnetic fields.Comment: 13 pages, 7 figures Accepted for publication in The Physics Teache

Characteristics of Some Fruiting Plant Species in Northwest Arkansas, and the Avian Assemblages that Feed on Them

Fruits continue to be recognized as an important food source for birds in temperate areas, particularly during the fall migration period. More than 20 species of plants producing fleshy fruits are found in the Arkansas Ozarks. However, only a few of these appear to be important resources for birds during the fall migration period (August - October). Among those are sassafras (Sassafras albidum), gray-backed grape (Vitis cinerea), black cherry (Prunus serotina), hercules club (Araliaspinosa) and pokeweed (Phytolacca americana). Over the past 4 years, we have documented the physical and nutritional characteristics of those fruits and taken observational data on the assemblages of birds eating them. It appears that avian species assemblages feeding on fruits are partially determined by the physical and nutritional contents of those fruits. Sassafras is extremely lipid-rich and higher in caloric content than the other species of fruits. It appears to be eaten almost exclusively by larger birds, perhaps be due to the large size of its fruits, which may exceed gape width of many smaller bird species. Prunus and Vitis are also eaten by a large number of avian species. Phytolacca was eaten only by a small number of primarily resident bird species and often persisted into the winter. Reasons for this pattern are not clear, as it was relatively similar to the other fruits inmost characteristics. Aralia was seen being eaten by only a few species of birds but is less common than the other species, and its small fruits may not be as attractive as those of the other species. Compared to other places in the east, there appear to be a relatively low number of migratory frugivorous birds in northwestern Arkansas. Overall, there were very few species noted at any fruiting plants, and a large proportion of the total assemblage of birds was comprised of resident species

Flight-based chemical characterization of biomass burning aerosols within two prescribed burn smoke plumes

Biomass burning represents a major global source of aerosols impacting direct radiative forcing and cloud properties. Thus, the goal of a number of current studies involves developing a better understanding of how the chemical composition and mixing state of biomass burning aerosols evolve during atmospheric aging processes. During the Ice in Clouds Experiment-Layer Clouds (ICE-L) in the fall of 2007, smoke plumes from two small Wyoming Bureau of Land Management prescribed burns were measured by on-line aerosol instrumentation aboard a C-130 aircraft, providing a detailed chemical characterization of the particles. After ~2–4 min of aging, submicron smoke particles, produced primarily from sagebrush combustion, consisted predominantly of organics by mass, but were comprised primarily of internal mixtures of organic carbon, elemental carbon, potassium chloride, and potassium sulfate. Significantly, the fresh biomass burning particles contained minor mass fractions of nitrate and sulfate, suggesting that hygroscopic material is incorporated very near or at the point of emission. The mass fractions of ammonium, sulfate, and nitrate increased with aging up to ~81–88 min and resulted in acidic particles. Decreasing black carbon mass concentrations occurred due to dilution of the plume. Increases in the fraction of oxygenated organic carbon and the presence of dicarboxylic acids, in particular, were observed with aging. Cloud condensation nuclei measurements suggested all particles >100 nm were active at 0.5% water supersaturation in the smoke plumes, confirming the relatively high hygroscopicity of the freshly emitted particles. For immersion/condensation freezing, ice nuclei measurements at −32 °C suggested activation of ~0.03–0.07% of the particles with diameters greater than 500 nm