Strategies for model‐revision in a high school genetics classroom

Recent proposals to improve science education (e.g., AAAS, 1989; Rutherford & Ahlgren, 1990) have stressed the importance of providing high school students with a broad knowledge base consisting of a body of core concepts and theories. Science educators (Duschl, 1990; AAAS, 1989; Peterson & Jungck, 1988) have also argued that while concepts are an important part of any education, no student's scientific education can be considered complete without a complementary knowledge of the nature of science, including an understanding of the tentative nature of scientific knowledge and how it is constructed. In this paper we describe a science classroom in which students are given opportunities to construct and use scientific knowledge to solve realistic genetics problems, and suggest that allowing students to engage in the production of scientific knowledge can support science learning.     

An approach to measure distance between compositional diet estimates containing essential zeros

For many applications involving compositional data, it is necessary to establish a valid measure of distance, yet when essential zeros are present traditional distance measures are problematic. In quantitative fatty acid signature analysis (QFASA), compositional diet estimates are produced that often contain many zeros. In order to test for a difference in diet between two populations of predators using the QFASA diet estimates, a legitimate measure of distance for use in the test statistic is necessary. Since ecologists using QFASA must first select the potential species of prey in the predator's diet, the chosen measure of distance should be such that the distance between samples does not decrease as the number of species considered increases, a property known in general as subcompositional coherence. In this paper we compare three measures of distance for compositional data capable of handling zeros, but not satisfying some of the well-accepted principles of compositional data analysis. For compositional diet estimates, the most relevant of these is the property of subcompositionally coherence and we show that this property may be approximately satisfied. Based on the results of a simulation study and an application to real-life QFASA diet estimates of grey seals, we recommend the chi-square measure of distance.     

Apps-olutely Perfect! Apps to Support Common Core in the History/Social Studies Classroom

The inclusion of technology in the classroom is an increasingly important feature of effective instruction. The implementation of Common Core Standards in many states also requires teachers to consider new pedagogical strategies to support meaningful learning. This article explores the intersection between technology demands and curricular change by examining apps that can be used to support Common Core State Standards instruction in history/social studies. Specifically, the authors highlight several apps that they presented at a professional development workshop for six to twelve history/social studies teachers and discuss the teachers' feedback regarding the strengths and limitations of apps to support their instruction. Conclusions are drawn and recommendations for history/social studies teachers using apps in the classroom are provided.     

Sexual practices and the duration of last heterosexual encounter: findings from the Australian longitudinal study of health and relationships

This study investigated the association between sexual practices and duration of a sexual encounter. Using data from a population-based computer-assisted telephone survey of 8,656 Australians aged 16 to 64 years, four distinct patterns of sexual practices among respondents were found: "basic sexual encounter" (involving mainly kissing, cuddling, stroking one's partner and being stroked, and vaginal intercourse), "basic sexual encounter plus oral sex," "all assessed sexual practices" (all sexual behaviors included in the survey), and "mainly vaginal intercourse" (characterized by lower levels of kissing, cuddling, and stroking). For both men and women, respondents classified in the basic sexual encounter plus oral sex, and all assessed sexual practices clusters reported significantly longer durations than those in the basic sexual encounter group, whereas respondents in the mainly vaginal intercourse cluster reported shorter durations. These differences were found even after allowing for demographic differences in sexual duration-specifically, age and partner type of the most recent opposite-sex partner. These findings add to the understanding of what typically happens in a sexual encounter. Overall, longer sexual encounters appear to be associated with the inclusion of the least common sexual practices-namely, oral sex and self-stimulation.     

The Legacy of Lynching? An Empirical Replication and Conceptual Extension

Research shows enduring impacts of lynching on a variety of modern outcomes. For instance, Messner, Baller, and Zevenbergen found that lynching is associated with contemporary white-on-black homicide. We propose a model describing how events from the past can have effects on events in the present. Essential to our framework is the notion of social forces of “resistance” that can impede or facilitate the temporal transmission of collective memories. We test “indicators of resistance” that influence the transmission of a collective memory supportive of a “legacy of lynching.” Analyses reveal that the positive and significant association between lynching and white-on-black homicide observed by Messner et al. is attenuated and becomes statistically nonsignificant with the inclusion of these indicators. Our results suggest that the temporal transmission of a racist cultural schema manifested through lynching is more likely where resistance is low. These findings have implications for how researchers can study historical legacies.     

Learning about restoration of urban ecosystems: a case study integrating public participation,stormwater management,and ecological research

Restoration of ecosystem functions in urban environments is made challenging by 1) a public that often lacks understanding of ecological principles, 2) inadequate evidence of the effectiveness of restoration practices, and 3) difficulty integrating social and biophysical factors in studies of urban ecosystems. This paper describes a case study in which potential solutions to these challenges were explored. We facilitated collaborative learning through public participation in the design and implementation of an urban riparian buffer along a headwater stream in a neighborhood park, a process that was informed by ecological research. Learning outcomes were evaluated using surveys and qualitative assessment of discussion. Results indicated that participants’ knowledge about water quality problems associated with urbanization, stormwater, and nonpoint-source pollution increased, familiarity with stormwater management practices increased, and perceptions about the importance of stream ecosystem functions changed. In-stream monitoring of sediment delivery, as well as direct measurements of buffer infiltration capacity, provided early evidence of buffer effectiveness in prevention of sediment inputs to the stream and absorption of runoff from surrounding surfaces. This study provides a useful model for integration of collaborative learning through participation, ecological restoration, and ecological research in an urban setting. Elements deemed essential to success of this model included an opportunity for dialog focused on a specific natural feature, sustained interaction between participants and researchers, opportunities for hands-on participation by urban residents, and flexibility in restoration practice installation.     

Problems in the application of portfolio selection models

This paper discusses a number of problems which arise in the implementation of portfolio selection models. It is suggested that the effect of errors and biases in expected return forecasts can be reduced by using these forecasts to modify a prior distribution which leads to minimal trading activity. Efficient diversification across industry groups is hampered by the difficulties of predicting covariances. The use of a selection model through time raises the issues of revising forecasts and of the relationships upon which the appropriate investment horizon and portfolio turnover depend. Last, consideration is given to the conflicts which may exist between management objectives and the mean-variance criterion used by most models.     

Future state visioning—A powerful leadership process

The process of conceptualizing and implementing significant change in complex organizations can be aided greatly through ‘future state visioning’, a set of processes for determining what and where you want to be by a future date. After developing ideas about the nature of the future environment facing the organization and the stakeholders who will be significant at that time, executives can articulate the values and principles which should guide actions leading to the future state vision. Examples from three organizations are used to illustrate the steps for successful use of the future state visioning procedure.