Students’ images of two-variable functions and their graphs

This paper presents a conceptual analysis for students’ images of graphs and their extension to graphs of two-variable functions. We use the conceptual analysis, based on quantitative and covariational reasoning, to construct a hypothetical learning trajectory (HLT) for how students might generalize their understanding of graphs of one-variable functions to graphs of two-variable functions. To evaluate the viability of this learning trajectory, we use data from two teaching experiments based on tasks intended to support development of the schemes in the HLT. We focus on the schemes that two students developed in these teaching experiments and discuss their relationship to the original HLT. We close by considering the role of covariational reasoning in generalization, consider other ways in which students might come to conceptualize graphs of two-variable functions, and discuss implications for instruction.     

Caregiver instability and early life changes among infants reported to the child welfare system

This study describes the extent of caregiver instability (defined as a new placement for 1 week or longer in a different household and/or with a new caregiver) in a nationally representative sample of infants, followed for 5–7 years. Data were drawn from the National Survey of Child and Adolescent Well-Being (NSCAW), a longitudinal study of 5,501 children investigated for child maltreatment. The analysis sample was restricted to 1,196 infants. Overall, 85.6% of children who were infants at the time of the index maltreatment experienced at least one caregiver instability event during their first 2 years of life. Caregiver instability was associated with the child having a chronic health condition and the caregiver being older than 40 years of age at baseline. The levels of instability reported in this study from infancy to school entry are extremely high. Children with more risk factors were significantly more likely to experience caregiver instability than children with fewer risk factors. The repeated loss of a young child's primary caregiver or unavailable, neglectful care can be experienced as traumatic. Some evidence-based programs that are designed to work with young maltreated children can make a substantial positive difference in the lives of vulnerable infants.     

Basic Research-Reference Material

Audiovisual Market Place 1978: A Multimedia Guide (431 pp.—$21.50, paper)

Fine Arts Market Place edited by Paul Cumnings (403 pp.—$19.95, paper)

Photography Market Place edited by Fred W. McDarrah (502 pp.—$15.50, paper)

Keith A. Larson's Public Relations, the Edward L. Bernaypes and the American Scene: A Bibliography (Westwood, Mass.: F.W. Faxon Co. "Useful Reference Series No. 114"—$25.00)

Ching-Chih Chen's Scientific and Technical Information Sources, (Cambridge, Mass.: MIT Press, 1977—$24.95)

Book Dealers in North America: A Directory of Dealers in Secondhand and Antiquarian Books in Canada and the United States of America (London: Sheppard Press, updated every four-five years—inquire on price)     

Broadcasting

TALK RADIO AND THE AMERICAN DREAM by Murray B, Levin (Lexington, MA: Lexington Books, 1987—$22.00)

WHO SHOT THE SHERIFF? THE RISE AND FALL OF THE TELEVISION WESTERN by J. Fred MacDonald (New York: Praeger, 1987—$29.95)

LIVE TV: AN INSIDE LOOK AT DIRECTING AND PRODUCING by Tony Verna (Stoneham, MA: Focal Press, 1987—$22.95)

TV CAREERS BEHIND THE SCREEN by Jane Blanksteen and Avi Odeni (New York: John Wiley, 1987—$12.95, paper)

THE BROADCASTER'S DICTIONARY by James R. McDonald (Windriver Books, Box 481, Broomfield, CT 80020—$20.00 incl. postage, paper)

Three recent publications by the National Association of Broadcasters (Publications Dept., 1771 N St. NW. Washington, DC 20036)

TELECOMMUNICATIONS MANAGEMENT: THE BROADCAST &; CABLE INDUSTRIES by Barry L. Sherman (New York: McGraw-Hill, 1987—$29.95)

CHANNELS OF DISCOURSE: TELEVISION AND CONTEMPORARY CRITICISM edited by Robert C. Allen (Chapel Hill: University of North Carolina Press, 1987—$25.00/7.95)

THE HOUR OF TELEVISION: CRITICAL APPROACHES by N.D. Batra (Metuchen, NJ: Scarecrow Press. 1987—$29.50)     

Radio

RADIO: A REFERENCE GUIDE by Thomas Allen Greenfield (Westport, CT: Greenwood Press, 1989—$39.95, ISBN 0-313-22276-2)

THE RADIO STATION by Michael Keith and Joseph Krause (Stoneham, MA: Focal Press, 1989—$24.95, paper, ISBN 0-240-80028-1)

PROGRAMMING RADIO TO WTN IN THE NEW AMERICA by John Parikhal and David Oakes (1989—$40.00 but $20 to NAB/BEA members, paper, ISBN 0-89324-062-1)

PROFITING FROM RADIO RATINGS: A MANUAL FOR RADIO MANAGERS, SALES MANAGERS AND PROGRAMMERS by James E. Fletcher (1989—$40.00 but $20 to NAB/BEA members, paper, ISBN 0-89324-065-6)

DEVELOPING AN EFFECTIVE MARKETING PLAN: A WORKING GUIDE FOR RADIO BROADCASTERS by John Geason and John Sutherland (1989—$20.00, paper, ISBN 0-89324-066-4)

AMERICAN RADIO SPRING 1989 by James H. Duncan, Jr. (Duncan's American Radio, Box 90284, Indianapolis, IN 46290—$79.00, paper)     

Bundling in Cable Television: A Pedagogical Note With a Policy Option

Bundling can be a pricing mechanism by which monopolists capture economic surplus from consumers.We suggest that given the cost structure of media markets, channel bundling in the cable and satellite market could also emerge in a competitive environment. A la carte channel pricing on cable television may or may not increase consumer welfare and could decrease total welfare. Because bundling may create other problems, policymakers may consider allowing cable and satellite networks to sell packages of channel space to viewers at a given price, allowing viewers to choose which channels they want in their packages. We term this option quasi-bundling.     

Starting up the News: The Impact of Venture Capital on the Digital News Media Ecosystem

ABSTRACT

Venture capital funding is an increasingly common yet understudied management model in the rapidly changing market of news media. Drawing on scholarship in media management and entrepreneurship, this study applies a community ecology framework to analyze the relationship between venture capital funding and digital news media firms. In doing so, this work explores the interaction between legacy news media firms and new entrants as they struggle for scarce resources and seek to grow in the face of rapid change. A dataset tracking funding activity of legacy and startup news media firms is used to analyze resource allocation within the digital news media ecosystem. Results of the analyses provide insights for news media management by furthering understanding regarding venture capital funding models and the generative mechanisms that help drive growth. Specifically, findings highlight the importance of cross-sector engagement and the tension between firm age and position for growth in the digital news media ecosystem.