1,649 research outputs found

    From Statehouse to Schoolhouse: Anti-Bullying Policy Efforts in U.S. States and School Districts

    Get PDF
    In 2011, 29.5 percent of U.S. public school districts didn't have anti-bullying policies, including many districts in states that require them, according to a report published by GLSEN. In states with such mandates, 26.3 percent of districts didn't have local policies. The report shows the gap that can emerge between the intentions of a law and the effectiveness of its implementation via policy and regulations

    Weak Gravitational Lensing and Cluster Mass Estimates

    Get PDF
    Hierarchical theories of structure formation predict that clusters of galaxies should be embedded in a web like structure, with filaments emanating from them to large distances. The amount of mass contained within such filaments near a cluster can be comparable to the collapsed mass of the cluster itself. Diffuse infalling material also contains a large amount of mass. Both these components can contribute to the cluster weak lensing signal. This ``projection bias'' is maximized if a filament lies close to the line-of-sight to a cluster. Using large--scale numerical simulations of structure formation in a cosmological constant dominated cold dark matter model, we show that the projected mass typically exceeds the actual mass by several tens of percent. This effect is significant for attempts to estimate cluster masses through weak lensing observations, and will affect weak lensing surveys aimed at constructing the cluster mass function.Comment: 4 pages, 3 figures. LaTeX2e, uses emulateapj.sty and onecolfloat.sty. To be submitted to the Astrophysical Journal Letter

    Forests

    Get PDF
    The Anthropocene draws attention to how humans have increasingly shaped forests in the past, how forest loss and forest planting play a key role in today’s climate emergency, and how we think about forests and forest stewardship in the future. In this handbook entry I review the human moulding of forests, both constructive and destructive, since prehistoric times and suggest a conceptualization that explicitly incorporates human elements among the many processes constituting forests

    Forest transitions: a new conceptual scheme

    Get PDF
    “Forest transitions” have recently received much attention, particularly in the hope that the historical transitions from net deforestation to forest recovery documented in several temperate countries might be repro- duced in tropical countries. The analysis of forest transitions, however, has struggled with questions of forest definition and has at times focussed purely on tree cover, irrespective of tree types (e.g. native forest or exotic plantations). Furthermore, it has paid little attention to how categories and definitions of forest are used to polit- ical effect or shape how forest change is viewed. In this paper, I propose a new heuristic model to address these lacunae, building on a conception of forests as distinct socio-ecological relationships between people, trees, and other actors that maintain and threaten the forest. The model draws on selected work in the forest transition, land change science, and critical social science literatures. It explicitly forces analysts to see forests as much more than a land cover statistic, particularly as it internalizes consideration of forest characteristics and the dif- ferential ways in which forests are produced and thought about. The new heuristic model distinguishes between four component forest transitions: transitions in quantitative forest cover (FT1); in characteristics like species composition or density (FT2); in the ecological, socio-economic, and political processes and relationships that constitute particular forests (FT3); and in forest ideologies, discourses, and stories (FT4). The four are inter- linked; the third category emerges as the linchpin. An analysis of forest transformations requires attention to diverse social and ecological processes, to power-laden official categories and classifications, and to the dis- courses and tropes by which people interpret these changes. Diverse examples are used to illustrate the model components and highlight the utility of considering the four categories of forest transitions

    Violent Relaxation of Indistinguishable Objects and Neutrino Hot Dark Matter in Clusters of Galaxies

    Get PDF
    The statistical mechanical investigation of violent relaxation (Lynden-Bell 1967) is extended to indistinguishable objects. It is found that, coincidentally, the equilibrium distribution is the same as that obtained for classical objects. For massive neutrinos, the Tremaine \& Gunn (1979) phase space bound is revisited and reinterpretated as the limit indicating the onset of degeneracy related to the coarse-grained phase space distribution. In the context of one of the currently most popular cosmological models, the Cold and Hot Dark Matter (CHDM) model (Primack et al. 1995), the onset of degeneracy may be of importance in the core region of clusters of galaxies. Degeneracy allows the neutrino HDM density to exceed the limit imposed by the Tremaine \& Gunn (1979) bound while accounting for the phase space bound.Comment: AASTeX, 16 pages, 2 EPS figures, uses aas2pp4.sty. Accepted by ApJ Letter

    The political ecology of weeds : a scalar approach to landscape transformations

    Get PDF
    How do plants that move and spread across landscapes become branded as weeds and thereby objects of contention and control? We outline a political ecology approach that builds on a Lefebvrian understanding of the production of space, identifying three scalar moments that make plants into 'weeds' in different spatial contexts and landscapes. The three moments are: the operational scale, which relates to empirical phenomena in nature and society; the observational scale, which defines formal concepts of these phenomena and their implicit or explicit 'biopower' across institutional and spatial categories; and the interpretive scale, which is communicated through stories and actions expressing human feelings or concerns regarding the phenomena and processes of socio-spatial change. Together, these three scalar moments interact to produce a political ecology of landscape transformation, where biophysical and socio-cultural processes of daily life encounter formal categories and modes of control as well as emotive and normative expectations in shaping landscapes. Using three exemplar 'weeds' - acacia, lantana and ambrosia - our political ecology approach to landscape transformations shows that weeds do not act alone and that invasives are not inherently bad organisms. Humans and weeds go together; plants take advantage of spaces and opportunities that we create. Human desires for preserving certain social values in landscapes in contradiction to actual transformations is often at the heart of definitions of and conflicts over weeds or invasives

    Political ecology and resilience: competing interdisciplinarities?

    Get PDF
    Both “political ecology” and “resilience” (or socio-ecological systems) are research approaches that explicitly claim to be inter- or even post-disciplinary. Both of these “interdisciplines” are currently dominant in academic study of society-environment interactions, engaging sizeable communities of students and scholars drawn from a range of traditional disciplines. Both approaches seeks to facilitate the kinds of boundary crossings that are crucial at the interface of nature and society, leading to new insights and knowledge, and to solving problems that are not contained within the boundaries. Yet there are inevitably pressures to “discipline” the new “interdisciplines”. In the case of political ecology and resilience, each has separate intellectual traditions, with some fundamental differences in purpose, in epistemology, in explanatory tools, and in ideology – illustrating that there are multiple ways of being interdisciplinary. This chapter explores these differences and reflects on the meaning of interdisciplinarity
    corecore