A physiological measure of shifting connections in the Rana pipiens retinotectal system

The retinotectal connections of developing Rana tadpoles and froglets have been studied using light-pipe techniques to directly assay the pattern of the projection from the retina to the tectum. The projection site of the retina surrounding the optic nerve head was determined at two different stages of development (late larval and metamorphic frog) on the same animal. Small electrolytic marker lesions were used to mark the tectal sites to which the optic nerve head projected at these two times. Comparison of the positions of the two lesions gives a direct measure of the shift in the projection during the interlesion time interval of one week. The results indicate a shift in the projection of 275 µm week–1 in late larval life. Previous work in Xenopus using the light-pipe techniques indicated a qualitatively similar shift during equivalent stages of development, but significantly smaller in magnitude. In the present study, topographic postsynaptic units could be recorded at all stages investigated, indicating functional synapses between the optic nerve fibres and the tectum. Thus, these studies offer evidence of a significant shift in the functional connection pattern of the amphibian retinotectal map during development, in agreement with the recent anatomical data from other laboratories on the Rana and goldfish visual system

Co-housing for stages of an aging Britain.

The use of diverse types of common interest or intentional communities has burgeoned over the past quarter century both in North America and in Europe, but especially in Scandinavia and the Netherlands. This paper will examine aspects of the particular legal environment for a nascent but growing CoHousing movement within the UK. Features of associated ownership, limitations on individuals’ land use through mutually binding contractual mechanisms and frameworks of positive mutual duties that characterise the legal documents used by or having potential utility for two different British CoHousing communities will be explored. The potential that emerging and adapted legal models of co-housing have for addressing issues arising from the housing and care needs of older people, especially older women and the attraction of CoHousing to families with children, will be discussed. Some potential future legal issues for UK CoHousing will be identified and its contribution to sustainable communities will be evaluated

The raising and feeding of red meat animals in the U.S. since 1945: A case study comparing Marxist crisis theories

Political economists have traditionally treated capitalist crisis as a central theoretical focus. Starting with Marx and Engels, Marxian political economists have viewed crisis as a necessary result of ordinary capitalist economic life. Recent Marxist scholars have argued that capitalist crisis is a predominant feature of contemporary capitalism... Non-Marxian political economists have also emphasized crisis in their work. Given the focus on crisis in political economy, and its particular prominence in Marxian theory, the current project centers around that theme. The objective is to systematically evaluate two competing Marxist theories of crisis, contrasting the Fundamentalist approach and its emphasis on the tendency for the rate of profit to fall with the Underconsumptionist perspective. Data from raising and feeding cows, calves, hogs, and pigs (the read meat industry) in the United States since 1945 will serve as a case study

Impacts And Dispersal Of Invasive Bivalves, Dreissena And Corbicula Spp., On Stream Benthic Communities

Asian clams (Corbicula spp.), zebra and quagga mussels (Dreisenna spp.) have invaded and spread throughout North American surface waters. Corbicula and Dreisenna species bio foul aquatic systems, occupy benthic substrates and degrade environments through shell deposition. I explored how Dreissena and Corbicula invasions affect benthic fish and macroinvertebrate communities, and examine how their impacts differ between urban and rural systems, and temperate and tropical climates. Macroinvertebrate and fish communities were evaluated at sites with increasing shell densities in the Rouge, and Huron rivers (MI, USA) using the United States Environmental Protection Agency’s Rapid Bioassessment Protocols (RBP). Urban and rural macroinvertebrate communities were compared by installing in situ colonization racks with Dreissena shell/cobble treatments of 100/0%, 75/25%, 25/75%, and 0/100% in urban and rural river reaches of the Rouge, Clinton and Huron rivers. I evaluated the impacts of Corbicula on macroinvertebrate communities in rivers in four climate regions including Michigan, Ohio, Georgia and Puerto Rico. All benthic community data was evaluated using water quality, diversity and habitat metrics. In the RBP assessment of the Rouge and Huron rivers, I found that that relative abundance of sensitive macroinvertebrates decreases as Dreissena shell densities increase in both rivers. Benthic fish were not significantly impacted as shell densities increased in either river. In rural reaches of the Huron River, fewer sensitive macroinvertebrate families colonized high density shell treatments when compared to cobble; conversely, macroinvertebrate community diversity was elevated in high shell densities when compared to low densities in urban reaches of all three rivers. The impact of increasing Corbicula population densities differed as macroinvertebrate diversity and evenness increased with population density in the temperate, Michigan climate and decreased as clam densities increased in tropical Puerto Rico. These findings indicate that bivalve invasions can have deleterious impacts on sensitive macroinvertebrates in urban and rural settings but can provide habitat for urban communities. Although temperate macroinvertebrates favor dense bivalve invasions in northern climates, declines in diversity and evenness in the south may foreshadow responses as surface water temperatures increase. This data could help management groups anticipate the impacts of invasive bivalves on native faunal communities

Positive Behavior Support Systems in a Rural West Texas Middle School

Positive Behavior Support (PBS) programs are being implemented in schools in the United States to support faculty, staff, and students. The purpose of this study was to evaluate a PBS system at a rural west Texas middle school to discover what improvements are necessary for district-wide implementation and sustainability. The study drew on Bandura\u27s social learning theory, which posits that people learn from each other through observation, imitation, and modeling. PBS systems provide the framework for exhibiting specific behavior expectations so students and teachers can get the most from their educational experiences. A program evaluation was completed using discipline data from 2008-2012 from the middle school, observations at the middle school, and archival campus improvement plan results from the campus needs assessment from 2012. The research instrument used to assess the information was a pre-established PBS evaluation system called the School-Wide Evaluation Tool (SET) designed for programmatic assessment. The SET assessment tool guided the evaluation of information gathered from 100 students, 15 teachers, and an administrative team survey to highlight the strengths and weaknesses of the PBS program in the school and district, identify necessary changes to improve its effectiveness, and determine how to best implement the system district-wide. These findings were used to inform a white paper outlining how to implement a successful program and how to maintain the program over time. This evaluation provided specific steps to strengthen each component of a PBS program to ensure school-wide application and sustainability. A positive social change is experienced by students, teachers, and parents by the enhancement of a PBS system that improves student behavior in the school and district

Paid and unpaid graduate internships: prevalence, quality and motivations at six months after graduation

Secondary analysis of the UK’s 2011/12 Destinations of Leavers from Higher Education survey reveals that many existing assumptions about graduate internships are questionable. This article proposes a reliable way of estimating the true extent of internships including those reported as ‘voluntary’ jobs: hidden internships. In doing so the article finds: 1) At six months after graduation, internships are a small feature of the UK graduate labour market, but significant in certain sectors; 2) Unpaid internships are much more prevalent than previously estimated, especially in these same sectors; and 3) Contrary to some public policy debate, unpaid internships appear, on balance, to be a residual option more likely to lead to underemployment and less favourable career development outcomes. Post-graduation internships appear less likely than pre-graduation work experiences to confer long-term employability advantages