The case for negative senescence

Negative senescence is characterized by a decline in mortality with age after reproductive maturity, generally accompanied by an increase in fecundity. Hamilton (1966) ruled out negative senescence: we adumbrate the deficiencies of his model. We review empirical studies of various plants and some kinds of animals that may experience negative senescence and conclude that negative senescence may be widespread, especially in indeterminate-growth species for which size and fertility increase with age. We develop optimization models of life-history strategies that demonstrate that negative senescence is theoretically possible. More generally, our models contribute to understanding of the evolutionary and demographic forces that mold the agetrajectories of mortality, fertility and growth.

Conceptual design of a synchronous Mars telecommunications satellite

Future missions to Mars will require a communications system to link activities on the Martian surface with each other and with mission controllers on Earth. A conceptual design is presented for an aerosynchronous communications satellite to provide these links. The satellite provides the capability for voice, data/command, and video transmissions. The mission scenario assumed for the design is described, and a description of a single aerosynchronous satellite is explained. A viable spacecraft design is then presented. Communication band selection and channel allocation are discussed. The communications system conceptual design is presented along with the trades used in sizing each of the required antennas. Also, the analyses used to develop the supporting subsystem designs are described as is the communications impact on each subsystem design

An Assessment Instrument of Technological Literacies in Makerspaces and FabLabs

Background As the maker movement is increasingly adopted into K‐12 schools, students are developing new competences in exploration and fabrication technologies. This study assesses learning with these technologies in K‐12 makerspaces and FabLabs. Purpose Our study describes the iterative process of developing an assessment instrument for this new technological literacy, the Exploration and Fabrication Technologies Instrument, and presents findings from implementations at five schools in three countries. Our index is generalizable and psychometrically sound, and permits comparison between student confidence and performance. Design/Method Our evaluation of distinct technology skills separates general computing, information and communication technology (ICT), and exploration and fabrication technologies (EFTs) into nonoverlapping areas of technological expertise required to perform their respective sets of tasks. The instrument also tracks student confidence in EFT skills and assesses how that confidence relates to actual task performance. Results Exploration and fabrication technologies constitute a new and distinct set of technology literacies arising from fabrication settings. The EFT instrument compares students\u27 self‐reported confidence with their performance on complex design tasks and demonstrates that, for students, exposure to general computing and ICT tools differs from exposure to EFT tools. Conclusion The EFT instrument captures a new and distinct set of technology literacies that arise within fabrication settings and are independent of both general computing and digital content production skills

The Impact of Tree Planting Program Governance Structure on Tree Survivorship and Vigor: A Case Study using the Massachusetts Greening the Gateway Cities Program

Trees in urban neighborhoods benefit residents by reducing building energy costs, providing cleaner air, decreasing surface runoff, and improving quality of life. However, tree canopy cover is not evenly distributed across neighborhoods in many mid-sized American cities which leads to higher air and surface temperatures, and increased energy bills for residents who are the most economically vulnerable. The state of Massachusetts (USA) created the Greening the Gateway Cities (GGC) program to increase tree canopy cover by 10% in post-industrial, midsized cities with lower educational attainment and lower income than state averages. The study posed two questions: what is the governance structure of the GGC program? How successful is the program using annual survivorship and vigor of the trees? This research examines the GGC program as a case study for a governance structure that fosters connections between the city, community and residents can create the social and environmental infrastructure to support increased tree canopy in urban neighborhoods. Data was collected in four gateway cities in Massachusetts: Chicopee, Fall River, Holyoke and Chelsea. 49 residents who received trees as part of the program were interviewed as well as two DCR foresters, three city planners, one head of the city’s community maintenance (Department of Public Works), and two paid staff and three volunteers of community partners. These interviews informed the creation of a governance framework for the GGC program. Tree survivorship, annual mortality and vigor of 3459 trees were used to measure the initial success of the planting program and to forecast potential benefits to residents. Results show how the GGC planting program can produce increased sense of ownership between cities, communities and individuals in the planting zones. The governance model, with an emphasis on stewardship, showed high rates of annual survivorship (~96.5%), low annual mortality rates (~3.5%) and average vigor rating of 1.5 (1 being healthy, 5 being dead)

Mathematical modelling reveals differential effects of erythropoietin on proliferation and lineage commitment of human hematopoietic progenitors in early erythroid culture

Erythropoietin is essential for the production of mature erythroid cells, promoting both proliferation and survival. Whether erythropoietin and other cytokines can influence lineage commitment of hematopoietic stem and progenitor cells is of significant interest. To study lineage restriction of the common myeloid progenitor to the megakaryocyte/erythroid progenitor of peripheral blood CD34(+) cells, we have shown that the cell surface protein CD36 identifies the earliest lineage restricted megakaryocyte/erythroid progenitor. Using this marker and carboxyfluorescein succinimidyl ester to track cell divisions in vitro, we have developed a mathematical model that accurately predicts population dynamics of erythroid culture. Parameters derived from the modeling of cultures without added erythropoietin indicate that the rate of lineage restriction is not affected by erythropoietin. By contrast, megakaryocyte/erythroid progenitor proliferation is sensitive to erythropoietin from the time that CD36 first appears at the cell surface. These results shed new light on the role of erythropoietin in erythropoiesis and provide a powerful tool for further study of hematopoietic progenitor lineage restriction and erythropoiesis

Competitive Orientations and Motives of Adult Sport and Exercise Participants

Participants in four different adult sport and exercise programs (running club, exercise classes, cardiac rehabilitation program, senior games) completed measures of competitive orientation and participation motivation. Our samples were older and more diverse than samples of previous research, and their competitive orientations and motives were similarly diverse. Multivariate analyses revealed gender and sample differences. Males were higher than females on competitiveness and win orientation, and runners were less win-oriented than other groups, but overall, all groups were similar to previous college-age samples in competitive orientation. Groups varied on specific motives, with females rating fitness, flexibility, affiliation, and appearance higher than males did. Generally, participants were diverse in orientations and motives, and positive about their participation. Research and conceptual models of sport orientation must extend beyond achievement motives to capture the diversity of adult participants. Program directors and instructors who offer activities and approaches to match this diversity will encourage wider participation and provide a more satisfying experience for more participants