Experiences with Problem-Based Learning: Virginia Initiative for Science Teaching and Achievement

The Virginia Initiative for Science Teaching and Achievement (VISTA) provides high-quality professional development for teachers and administrators to enhance the quality of their science instructional programs. One emphasis of this program is helping teachers learn to implement Problem-Based Learning in the elementary science classroom. Problem-Based Learning (PBL) has the potential to produce significant positive outcomes for students, such as increased student engagement, and opportunities for in-depth critical thinking [1]. Teachers find PBL challenging because it does take additional time for planning and material acquisition, but experience has shown that the benefits outweigh these challenges. Setting clear goals, identifying specific learning objectives, and developing big questions that tie these together help increase the success of the unit. Additionally, administrators can help teachers succeed in implementing a Problem-Based Learning unit by understanding the dynamic nature of the PBL environment, providing flexibility with unit pacing, and setting aside time for refining, reflection, and revision of the unit

Critical import supply elasticities and the ‘imports-as-market-discipline’ hypothesis

This paper formally examines the factors underlying how responsive imports must be to domestic prices (the ‘import supply elasticity’) in order to thwart an anticompetitive domestic price increase stemming from a merger––an issue that frequently arises in many antitrust reviews. Domestic firms face a fringe comprised of foreign firms who import their products into the domestic market. In the eyes of domestic consumers, these imports are viewed as imperfect substitutes in demand to the output produced by the domestic firms. The model is solved in terms of the ‘critical’ import supply elasticity that can then be used evaluate the ability of imports to constrain an anticompetitive price increase post-merger. Both general and linear demand specifications are considered. Numerical simulations are conducted to consider the magnitude of perturbations in the model’s exogenous parameters. Potential empirical extensions of the model are also considered.

Critical import supply elasticities and the ‘imports-as-market-discipline’ hypothesis

This paper formally examines the factors underlying how responsive imports must be to domestic prices (the ‘import supply elasticity’) in order to thwart an anticompetitive domestic price increase stemming from a merger––an issue that frequently arises in many antitrust reviews. Domestic firms face a fringe comprised of foreign firms who import their products into the domestic market. In the eyes of domestic consumers, these imports are viewed as imperfect substitutes in demand to the output produced by the domestic firms. The model is solved in terms of the ‘critical’ import supply elasticity that can then be used evaluate the ability of imports to constrain an anticompetitive price increase post-merger. Both general and linear demand specifications are considered. Numerical simulations are conducted to consider the magnitude of perturbations in the model’s exogenous parameters. Potential empirical extensions of the model are also considered.Competitive effects; Critical loss; Market definition; Import supply elasticity

Competition and cost pass-through in differentiated oligopolies

The impact that competition exerts on the incentives of firms to pass through reductions in their marginal costs is an important consideration in assessing the performance of alternate market structures. This paper examines the role of product differentiation on firm-specific and industry-wide pass-through rates. Relying on Shubik’s (1980) model of differentiated Cournot competition with linear demand, we show that there exists an initial critical range over which the firm-specific cost pass-through rate decreases in the number of firms. Beyond this range the rate continually increases – approaching 50 percent as the number of firms goes to infinity. This contrasts with a model of differentiated Bertrand competition in which cost pass through monotonically decreases in the number of firms. The disparate effects across the Cournot and Bertrand models are shown to stem from the influence of competition and product differentiation on the respective firm reaction functions. Suggestions for future empirical work based upon the models’ predictions and implications for antitrust policy are also discussed.Competitive effects; Oligopoly; Merger; Pass-through; Product differentiation

Contribution of thermal noise to the line width of Josephson radiation from superconducting point contacts

Contribution of thermal noise to line width of Josephson radiation from superconducting point contact

Pressure buildup during CO2 injection in brine aquifers using the Forchheimer equation

If geo-sequestration of CO2 is to be employed as a key emissions reduction method in the global effort to mitigate climate change, simple yet robust screening of the risks of disposal in brine aquifers will be needed. There has been significant development of simple analytical and semi-analytical techniques to support screening analysis and performance assessment for potential carbon sequestration sites. These techniques have generally been used to estimate the size of CO2 plumes for the purpose of leakage rate estimation. A common assumption has been that both the fluids and the geological formation are incompressible. Consequently, calculation of pressure distribution requires the specification of an arbitrary radius of influence. In this talk, a new similarity solution is derived using the method of matched asymptotic expansions. By allowing for slight compressibility in the fluids and formation, the solution improves on previous work by not requiring the specification of an arbitrary radius of influence. A large-time approximation of the solution is then extended to account for non-Darcy inertial effects using the Forchheimer equation. Both solutions are verified by comparison with finite difference solutions. The results show that inertial losses will often be comparable, and sometimes greater than, the viscous Darcy-like losses associated with the brine displacement, although this is strongly dependent on formation porosity and permeability

Self-Regulation in a Web-Based Course: A Case Study

Little is known about how successful students in Web-based courses self-regulate their learning. This descriptive case study used a social cognitive model of self-regulated learning (SRL) to investigate how six graduate students used and adapted traditional SRL strategies to complete tasks and cope with challenges in a Web-based technology course; it also explored motivational and environmental influences on strategy use. Primary data sources were three transcribed interviews with each of the students over the course of the semester, a transcribed interview with the course instructor, and the students’ reflective journals. Archived course documents, including transcripts of threaded discussions and student Web pages, were secondary data sources. Content analysis of the data indicated that these students used many traditional SRL strategies, but they also adapted planning, organization, environmental structuring, help seeking, monitoring, record keeping, and self-reflection strategies in ways that were unique to the Web-based learning environment. The data also suggested that important motivational influences on SRL strategy use—self-efficacy, goal orientation, interest, and attributions—were shaped largely by student successes in managing the technical and social environment of the course. Important environmental influences on SRL strategy use included instructor support, peer support, and course design. Implications for online course instructors and designers, and suggestions for future research are offered

Coal-shale interface detection system

A coal-shale interface detection system for use with coal cutting equipment consists of a reciprocating hammer on which an accelerometer is mounted to measure the impact of the hammer as it penetrates the ceiling or floor surface of a mine. A pair of reflectometers simultaneously view the same surface. The outputs of the accelerometer and reflectometers are detected and jointly registered to determine when an interface between coal and shale is being cut through

Pile Driving Adjacent to Municipal Drinking Water Storage Facility

An unexpected response occurred as piles were driven within 3 feet of the west wall of an existing municipal drinking water storage reservoir. Being located in a confined urban space, the expansion of the parking garage at a facility on the south end of Lake Michigan required the installation of 122 steel H-piles as close as 3 feet to the reservoir. Historically, structures on the site were supported on either shallow spread footings or H-piles driven to bedrock. At the contractor’s suggestion, considerable project savings were achieved by driving the H-piles to an extremely hard clay layer (“Chicago hardpan”) above the bedrock. Pressuremeter testing, and static and dynamic load testing of the H-piles were completed as part of the project testing program. Both the horizontal and vertical movements of the reservoir wall were monitored during pile driving. The paper presents the design parameter changes, static and dynamic pile testing, and vibration monitoring for construction of the multi-level parking structure adjacent to the 8 million gallon drinking water storage facility. The vertical movements of the tank’s west wall and the corrective actions taken after water began seeping from pre-existing cracks in the tanks wall are the focus of the case study

Studies on the Effects of Maintenance of Hamster Adrenals in Vitro

Whole adrenals of the young adult hamster were maintained in culture. In most of the experiments the organ was supported on lens paper, but, latterly, cellulose and gelatin sponge were used. The culture media employed were (1) Ringer\u27s Solution (no nutrient), and (2) a nutrient mixture consisting of modified Krebs-Ringer\u27s Solution, lactalbumen hydrolysate, yeast extract and horse serum. The maintenance period was up to seven days, and the culture medium was freshened regularly in certain cases. Organs were weighed at the beginning and end, and sometimes during maintenance. Histological appearance at termination was compared with that of a freshly extirpated adrenal. In absence of nutrient, weight remained constant for the first day of culture, decreased over the following two to three days, and then leveled off at about 60 percent of its initial value. By contrast, organs cultured in the nutrient medium showed quite random variations in weight. There appeared to be no correlation between maintenance of weight and histological preservation; in point of fact, all organs which were well preserved after more than one to two days in vitro had lost weight considerably. Histological criteria are discussed