Leveling transparency via situated intermediary learning objectives (SILOs)

When designers set out to create a mathematics learning activity, they have a fair sense of its objectives: students will understand a concept and master relevant procedural skills. In reform-oriented activities, students first engage in concrete situations, wherein they achieve situated, intermediary learning objectives (SILOs), and only then they rearticulate their solutions formally. We define SILOs as heuristics learners devise to accommodate contingencies in an evolving problem space, e.g., monitoring and repairing manipulable structures so that they model with fidelity a source situation. Students achieve SILOs through problem-solving with media, instructors orient toward SILOs via discursive solicitation, and designers articulate SILOs via analyzing implementation data. We describe the emergence of three SILOs in developing the activity Giant Steps for Algebra. Whereas the notion of SILOs emerged spontaneously as a framework to organize a system of practice, i.e. our collaborative design, it aligns with phenomenological theory of knowledge as instrumented action

Apollo experience report: The AN/ARD-17 direction finding system

This report contains a statement of the operational philosophy and requirements leading to the development of the AN/ARD-17 direction-finding system. The technical problems encountered and the solutions devised in the AN/ARD-17 development are discussed. An evaluation of the system under actual operational conditions is included

IRS Scan-mapping of the Wasp-waist Nebula (IRAS 16253–2429). I. Derivation of Shock Conditions from H_2 Emission and Discovery of 11.3 μm PAH Absorption

The outflow driven by the Class 0 protostar, IRAS 16253–2429, is associated with bipolar cavities visible in scattered mid-infrared light, which we refer to as the Wasp-Waist Nebula. InfraRed Spectometer (IRS) scan mapping with the Spitzer Space Telescope of a ~1' × 2' area centered on the protostar was carried out. The outflow is imaged in six pure rotational (0-0 S(2) through 0-0 S(7)) H_2 lines, revealing a distinct, S-shaped morphology in all maps. A source map in the 11.3 μm polycyclic aromatic hydrocarbon (PAH) feature is presented in which the protostellar envelope appears in absorption. This is the first detection of absorption in the 11.3 μm PAH feature. Spatially resolved excitation analysis of positions in the blue- and redshifted outflow lobes, with extinction-corrections determined from archival Spitzer 8 μm imaging, shows remarkably constant temperatures of ~1000 K in the shocked gas. The radiated luminosity in the observed H_2 transitions is found to be 1.94 ± 0.05 × 10^(–5) L_⊙ in the redshifted lobe and 1.86 ± 0.04 × 10^(–5) L_⊙ in the blueshifted lobe. These values are comparable to the mechanical luminosity of the flow. By contrast, the mass of hot (T ~ 1000 K) H_2 gas is 7.95 ± 0.19 × 10^(–7) M_⊙ in the redshifted lobe and 5.78 ± 0.17 × 10^(–7) M_⊙ in the blueshifted lobe. This is just a tiny fraction, of order 10^(–3), of the gas in the cold (30 K), swept-up gas mass derived from millimeter CO observations. The H_2 ortho/para ratio of 3:1 found at all mapped points in this flow suggests previous passages of shocks through the gas. Comparison of the H_2 data with detailed shock models of Wilgenbus et al. shows the emitting gas is passing through Jump (J-type) shocks. Pre-shock densities of 10^4 cm^(–3)≤ n _H ≤ 10^5 cm^(–3) are inferred for the redshifted lobe and n _H ≤ 10^3 cm^(–3) for the blueshifted lobe. Shock velocities are 5 km s^(–1) ≤ v_s ≤ 10 km s^(–1) for the redshifted gas and v_s = 10 km s^(–1) for the blueshifted gas. Initial transverse (to the shock) magnetic field strengths for the redshifted lobe are in the range 10-32 μG, and just 3 μG for the blueshifted lobe. A cookbook for using the CUBISM contributed software for IRS spectral mapping data is presented in the Appendix

Automated land-use mapping from spacecraft data

The author has identified the following significant results. In response to the need for a faster, more economical means of producing land use maps, this study evaluated the suitability of using ERTS-1 computer compatible tape (CCT) data as a basis for automatic mapping. Significant findings are: (1) automatic classification accuracy greater than 90% is achieved on categories of deep and shallow water, tended grass, rangeland, extractive (bare earth), urban, forest land, and nonforested wet lands; (2) computer-generated printouts by target class provide a quantitative measure of land use; and (3) the generation of map overlays showing land use from ERTS-1 CCTs offers a significant breakthrough in the rate at which land use maps are generated. Rather than uncorrected classified imagery or computer line printer outputs, the processing results in geometrically-corrected computer-driven pen drawing of land categories, drawn on a transparent material at a scale specified by the operator. These map overlays are economically produced and provide an efficient means of rapidly updating maps showing land use

Spatial and Temporal Variation in the Aquatic Invertebrate Community Structure of Rock Pools Along the Penobscot River, Maine

Pools of water that form in the fissures and depressions of rock outcrops, known as rock pools, are fairly common aquatic habitats that can easily be found along the rocky banks of many of Maine’s major rivers. In general, rock pools and the aquatic invertebrates inhabiting them have received little research attention and, though ubiquitous, have never been studied in Maine. My research addressed this knowledge gap by surveying 40 rock pools at four sites along the Penobscot River in Maine. The rock pools themselves had highly variable environmental characteristics and differed across sites and over time, especially in hydroperiod. They contained surprisingly abundant and diverse communities, totaling 71 invertebrate taxa across 16 orders. The non-biting midge Dicrotendipes and the biting midge Dasyhelea were the most abundant genera. Community composition differed significantly between sites in June, largely associated with differences in pool size, hydroperiod, influence of the adjacent river, and food resources. However, over the course of the summer, communities across sites became more similar to each other, likely due to the combination of phenologically-driven life histories for some taxa and the loss of stress-intolerant taxa. I also conducted an experiment in which I artificially extended rock pool hydroperiods to determine the independent effect of hydroperiod on invertebrate community structure. I hypothesized that pools with longer hydroperiods would contain more diverse and abundant invertebrate communities and that pools with longer hydroperiods would contain more long-lived taxa, such as Odonata and Coleoptera. To test this hypothesis, I prevented ten rock pools from desiccating by adding deionized water to them and left ten rock pools to naturally dry. Hydroperiod was not a significant driver of overall invertebrate abundance or richness and was only important in determining the individual abundance of one of five taxa collected in the experiment. Pool volume, location on the rock outcrop, and water chemistry (pH and conductivity) were the significant factors determining community structure. This suggests that the effect of hydroperiod observed in my survey and in other rock pool surveys may be confounded by pool size and by environmental variables mediated by hydroperiod

Anti-urbanism in Culture and in the Adventist Church: Advocacy and Action for Urban Ministry In the Twentieth Century—Part 2

This article explores the response within the Seventh-day Adventist Church after Ellen G. White’s death to the dual emphases in her writings on the city and rural living. On one hand she strongly encouraged large Adventist institutions and families raising children to locate out of the cities. This was because of the advantages natural surroundings have on physical, emotional, and spiritual wellbeing, and to shield children and young adults from the evils and temptations of the city. While she recognized the evils in the city and God’s impending judgments, she aggressively pushed church leaders to take a more active role in evangelizing the cities, precisely because of their great need. The church was slow to respond to her plea for greater mission to the cities during her lifetime. Once she passed away, the gains made in city mission during her lifetime were gradually lost. Leadership focused on foreign missions but work in the cities seem to have fallen by the wayside, being replaced with a drive for all Adventists to move to the country. This paper’s focus is on the period from the 1910 through the 1990s